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  • 1.
    Abdulkareem Najm Al-Saedi, Ahmed
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Materials Science and Engineering.
    Hedenfeldt, Anders
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Materials Science and Engineering.
    García, Andrea
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Materials Science and Engineering.
    Kron, Anna-Karin
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Materials Science and Engineering.
    Bergström, Cornelia
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Materials Science and Engineering.
    Källkvist, Lova
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Materials Science and Engineering.
    Analysis of Resin Impregnated Non-woven: In collaboration with Hitachi Energy2022Independent thesis Basic level (degree of Bachelor), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    High voltage bushings are the most critical components of power transformers. A common material used in bushings is resin impregnated paper (RIP). Hitachi Energy is investigating whether this can be replaced with a new material, resin impregnated non-woven (RIN). One of the main reasons is that non-woven is less prone to absorb moisture compared to paper. Thus, for design purposes the mechanical, thermal and absorption properties of RIN have been studied and compared to RIP. The mechanical properties were tested by tensile and bending tests at room temperature and 80 ℃, showing that RIN has a lower elastic modulus and tensile strength than RIP at both temperatures. However, it was demonstrated that RIN does not retain its elongation at break and elasticity properties at elevated temperatures. The bending test showed no significant differences in flexural properties for RIN between room and high temperature. The thermal properties were studied with the transient plane source method (TPS) showing that both RIN and RIP had a higher specific heat capacity than pure epoxy. The thermal conductivity of the materials will be measured and included later. Lastly, the water absorption test was performed in order to provide information about the suitability of the materials used in bushings. For this different methods were used; water immersion andwater vapor testing. The immersion test showed that non-woven is more water resistant than paper and that the composites only absorb a small amount of water. No useful information was achieved from the water vapor test due to limited testing time. The results demonstrate the promising potential of RIN in bushings.

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  • 2.
    Afshar, Reza
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Materials Science and Engineering.
    Size effect on mechanical properties of wood in transverse direction2022Conference paper (Refereed)
  • 3.
    Afshar, Reza
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Materials Science and Engineering, Applied Mechanics. Uppsala University.
    Alavyoon, Navid
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Materials Science and Engineering, Applied Mechanics.
    Ahlgren, A
    Swedish National Maritime and Transport Museums, the Vasa Museum, Stockholm, Sweden.
    Gamstedt, E. Kristofer
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Materials Science and Engineering, Applied Mechanics.
    Full scale finite element modelling and analysis of the 17th-century warship vasa: A methodological approach and preliminary results2021In: Engineering structures, ISSN 0141-0296, E-ISSN 1873-7323, Vol. 231, no 111765Article in journal (Refereed)
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  • 4.
    André, Benny
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    Nanocomposites for Use in Sliding Electrical Contacts2011Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    In this thesis nanocomposite materials for use in high performance electrical contacts are tested. Self mating silver as coatings on cupper substrates are the most used material combination in power connectors today. In this work two new concepts were tested. The first one was to change one of the mating surfaces to a hard thin coating and keep the other surface made of silver. Tested coatings were nanocomposites with hard carbides in a matrix of amorphous carbon. TiC/a-C and  Ti-Ni-C/a-C were tested both electrically and tribologically. The total amount of carbon and the amount of carbon matrix was important, both for the electrical and the tribological properties. The Ti-Ni-C coating also showed that substituting Ti in TiC with the weak carbide former Ni changed the stability of the carbides. The substitution resulted in more a-C matrix and less C in the carbides. Thin coatings of nc-TiC/a-C and  Ti-Ni-C/a-C showed high potential as material candidates for use in electrical contacts.

    The other tested concept was to modify the used silver instead of replacing it. This was done by embedding nanoparticles of solid lubricant IF-WS2 in the silver. The results from reciprocating sliding displayed low friction and high wear resistance. The modified silver surfaces lasted for 8000 strokes with a friction of about 0.3 while at the same time allowing for a low contact resistance. The results for surfaces of pure silver coating displayed a friction of 0.8-1.2 and that the silver was worn through already after 300 strokes.

    A new method to investigate inherent hardness and residual stress of thin coatings, on complex geometries or in small areas, was also developed. An ion beam was used to create stress free coating as free standing micro pillars. Hardness measured on the pillars and on as-deposited coating were then used to calculate the residual stress in the coatings.

    List of papers
    1. Industrialisation Study of Nanocomposite nc-TiC/a-C Coatings for Electrical Contact Applications
    Open this publication in new window or tab >>Industrialisation Study of Nanocomposite nc-TiC/a-C Coatings for Electrical Contact Applications
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    2009 (English)In: Plasma Processes and Polymers, ISSN 1612-8850, Vol. 6, no S1, p. S928-S934Article in journal (Refereed) Published
    Abstract [en]

    Nanocomposite nc-TiC/a-C coatings were prepared by non-reactive magnetron sputtering in industrial scale equipment, under varying deposition conditions in order to investigate upscaling and possible industrialisation. The coatings were found to have similar microstructure and performance compared to previous laboratory scale experiments. The samples were characterised with XRD, XPS and SEM as well with ball-on-disc, nanoindentation and electrical measurements. Coatings containing a small fraction of a-C matrix phase were found to have promising both electrical properties (rho < 400 mu Omega cm and contact resistances down to 0.34 m Omega at 40 N) and tribological properties (f < 0.3 for 10 000 laps).

    Place, publisher, year, edition, pages
    WILEY-VCH Verlag GmbH & Co, 2009
    Keywords
    conductivity, inorganic materials, nanocomposites, thin films, tribology
    National Category
    Chemical Sciences Inorganic Chemistry Engineering and Technology
    Research subject
    Inorganic Chemistry; Chemistry with specialization in Inorganic Chemistry
    Identifiers
    urn:nbn:se:uu:diva-109022 (URN)10.1002/ppap.200932303 (DOI)000272302900178 ()
    Available from: 2009-10-07 Created: 2009-10-07 Last updated: 2016-04-14
    2. Synthesis, structure and properties of Ni-alloyed TiCx-based thin films
    Open this publication in new window or tab >>Synthesis, structure and properties of Ni-alloyed TiCx-based thin films
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    2010 (English)In: Journal of Materials Chemistry, ISSN 0959-9428, E-ISSN 1364-5501, Vol. 20, no 28, p. 5950-5960Article in journal (Refereed) Published
    Abstract [en]

    By using non-reactive sputter deposition at low temperatures metastable solid solution phases in the Ti–Ni–C system were synthesized. Produced thin films were either single phase carbides or nanocomposite of nanocrystalline carbide and amorphous C. In the Ni-containing samples a supersaturated solid solution phase (Ti1−xNix)Cy was identified, and was present either as single phase or in a nanocomposite with amorphous C. By modification of the chemical stability of the carbide phase, the addition of Ni was found to strongly promote the formation of amorphous carbon phase in the coatings. Samples have been microstructurally analyzed using X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and transmission electron microscopy (TEM). Mechanical properties have been evaluated through nanoindentation and pin-on-disc measurements; electrical properties were determined by measurement of the resistivity and the contact resistance. Alloyed nanocomposite coatings were also found to exhibit enhanced tribological and electrical properties, with a decreased resistivity and friction. This makes these thin films very interesting for application in sliding electrical contacts. The mechanisms responsible for the reductions remain to be determined.

    National Category
    Inorganic Chemistry Engineering and Technology
    Research subject
    Chemistry with specialization in Inorganic Chemistry
    Identifiers
    urn:nbn:se:uu:diva-109034 (URN)10.1039/c0jm00592d (DOI)000279565900025 ()
    Available from: 2009-10-08 Created: 2009-10-08 Last updated: 2022-01-28Bibliographically approved
    3. Friction and contact resistance of nanocomposite Ti-Ni-C coatings
    Open this publication in new window or tab >>Friction and contact resistance of nanocomposite Ti-Ni-C coatings
    2011 (English)In: Wear, ISSN 0043-1648, E-ISSN 1873-2577, Vol. 270, no 9-10, p. 555-566Article in journal (Refereed) Published
    Abstract [en]

    Ceramic nanocomposite coatings in the Ti-Ni-C were deposited using PVD and studied with respect to tribological properties and contact resistance. It was shown that coatings could be deposited combining of a low contact resistance and a low friction coefficient against silver, making them suitable for use in high performance electrical contacts.Nine coatings with different amounts of C and Ni were deposited. Coatings on flat Ni plated copper substrates were tested in a tribological ball-on-disc setup against ball bearing steel balls. Depending on primarily the amount of carbon the coatings showed very different friction coefficient and wear rate. The coatings were also deposited on cylindrical Ni plated copper substrates. Using geometrically identical silver plated cylinders as counter surface these were evaluated in a test setup better resembling a real life electrical contact. For most coatings a low electrical contact resistance was measured. The evolution of friction coefficient and contact resistance was correlated to wear marks and contact tracks, with their generated tribofilms, as examined after testing using electron microscopy, Raman spectroscopy and X-ray photoelectron spectroscopy.

    Keywords
    TiC, TiNiC, Friction, Tribofilm, Electrical contacts, Contact resistance
    National Category
    Inorganic Chemistry Engineering and Technology
    Research subject
    Inorganic Chemistry; Engineering Science with specialization in Materials Science
    Identifiers
    urn:nbn:se:uu:diva-109425 (URN)10.1016/j.wear.2010.12.006 (DOI)000290132500001 ()
    Available from: 2009-10-15 Created: 2009-10-15 Last updated: 2022-01-28
    4. Nanoindentation on micro pillars for determination of intrincic hardness and residual stress in coatings deposited on complex geometries
    Open this publication in new window or tab >>Nanoindentation on micro pillars for determination of intrincic hardness and residual stress in coatings deposited on complex geometries
    (English)Manuscript (preprint) (Other academic)
    Keywords
    nanoindentation, hardness, residual stress, focused ion beam, coating, PVD
    National Category
    Materials Engineering Other Materials Engineering
    Research subject
    Materials Science; Engineering Science with specialization in Tribo Materials; Engineering Science with specialization in Materials Science
    Identifiers
    urn:nbn:se:uu:diva-160807 (URN)
    Available from: 2011-10-31 Created: 2011-10-31 Last updated: 2016-04-22
    5. Performance and Tribofilm Formation of a Low-Friction Coating Incorporating Inorganic Fullerene Like Nano-Particles
    Open this publication in new window or tab >>Performance and Tribofilm Formation of a Low-Friction Coating Incorporating Inorganic Fullerene Like Nano-Particles
    2012 (English)In: Surface & Coatings Technology, ISSN 0257-8972, E-ISSN 1879-3347, Vol. 206, no 8-9, p. 2325-2329Article in journal (Refereed) Published
    Abstract [en]

    A new tribological coating with potential as a coating for components for low-friction applications is tested and compared to three, state of the art, commercial low-friction PVD coatings. The new coating is an electrodeposited coating composed by a Ni-P matrix incorporating fullerene like nanoparticles of WS2. The performance of the new coating is compared with three reference coatings in a ball-on-disc setup. The tribological tests involved ball bearing steel balls slid on coated discs, under different conditions of humidity and also with or without oil lubrication. Both mating surfaces were closely investigated in a scanning electron microscope and the low-friction tribofilms formed were further analysed. The correlations found between coefficient of friction, surface roughness of the wear scar, tribofilm formation and contact conditions are discussed. The new coating exhibits a very low coefficient of friction at low humidity, a behaviour closely resembling that of the MoS2-based commercial reference, whereas the carbon based PVD coatings tested exhibit the reversed dependence of humidity. The low-friction behaviour of the new coating is correlated to the formation of a WS2 tribofilm with a superficial alignment of the basal planes parallel to the sliding direction. When lubricated with a base oil, the beneficial tribofilm is not formed and the coefficient of friction is much higher. The results show that even though the coating is an electrodeposited coating it can compete with state of the art commercial PVD coatings.

    Keywords
    Friction, Wear, Tungsten disulphide, Nanoparticles, Fullerene, Tribofilm
    National Category
    Materials Engineering
    Research subject
    Engineering Science with specialization in Tribo Materials; Engineering Science with specialization in Materials Science
    Identifiers
    urn:nbn:se:uu:diva-160806 (URN)10.1016/j.surfcoat.2011.10.012 (DOI)000300458500038 ()
    Available from: 2011-10-31 Created: 2011-10-31 Last updated: 2017-12-08
    6. Enhancing silver through embedding of fullerene like WS2 for sliding electrical contacts
    Open this publication in new window or tab >>Enhancing silver through embedding of fullerene like WS2 for sliding electrical contacts
    (English)Manuscript (preprint) (Other academic)
    Keywords
    friction, wear, electrical, contacts, tungsten, disulfide, silver
    National Category
    Materials Engineering Composite Science and Engineering Other Materials Engineering
    Research subject
    Materials Science; Engineering Science with specialization in Materials Science; Engineering Science with specialization in Tribo Materials
    Identifiers
    urn:nbn:se:uu:diva-160808 (URN)
    Available from: 2011-11-01 Created: 2011-11-01 Last updated: 2012-05-08
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  • 5.
    André, Benny
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    Kassman-Rudolphi, Åsa
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    Wiklund, Urban
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    Enhancing silver through embedding of fullerene like WS2 for sliding electrical contactsManuscript (preprint) (Other academic)
  • 6.
    Asfaw, Habtom Desta
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Structural Chemistry.
    Multifunctional Carbon Foams by Emulsion Templating: Synthesis, Microstructure, and 3D Li-ion Microbatteries2017Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    Carbon foams are among the existing electrode designs proposed for use in 3D Li-ion microbatteries. For such electrodes to find applications in practical microbatteries, however, their void sizes, specific surface areas and pore volumes need be optimized. This thesis concerns the synthesis of highly porous carbon foams and their multifunctional applications in 3D microbatteries. The carbon foams are derived from polymers that are obtained by polymerizing high internal phase water-in-oil emulsions (HIPEs).

    In general, the carbonization of the sulfonated polymers yielded hierarchically porous structures with void sizes ranging from 2 to 35 µm and a BET specific surface area as high as 630 m2 g-1. Thermogravimetric and spectroscopic evidence indicated that the sulfonic acid groups, introduced during sulfonation, transformed above 250 oC to thioether (-C-S-) crosslinks which were responsible for the thermal stability and charring tendency of the polymer precursors. Depending on the preparation of the HIPEs, the specific surface areas and void-size distributions were observed to vary considerably. In addition, the pyrolysis temperature could also affect the microstructures, the degree of graphitization, and the surface chemistry of the carbon foams.

    Various potential applications were explored for the bespoke carbon foams. First, their use as freestanding active materials in 3D microbatteries was studied. The carbon foams obtained at 700 to 1500 oC suffered from significant irreversible capacity loss during the initial discharge. In an effort to alleviate this drawback, the pyrolysis temperature was raised to 2200 oC. The resulting carbon foams were observed to deliver high, stable areal capacities over several cycles. Secondly, the possibility of using these structures as 3D current collectors for various active materials was investigated in-depth. As a proof-of-concept demonstration, positive active materials like polyaniline and LiFePO4 were deposited on the 3D architectures by means of electrodeposition and sol-gel approach, respectively. In both cases, the composite electrodes exhibited reasonably high cyclability and rate performance at different current densities. The syntheses of niobium and molybdenum oxides and their potential application as electrodes in microbatteries were also studied. In such applications, the carbon foams served dual purposes as 3D scaffolds and as reducing reactants in the carbothermal reduction process. Finally, a facile method of coating carbon substrates with oxide nanosheets was developed. The approach involved the exfoliation of crystalline VO2 to prepare dispersions of hydrated V2O5, which were subsequently cast onto CNT paper to form oxide films of different thicknesses.

    List of papers
    1. Boosting the thermal stability of emulsion–templated polymers via sulfonation: an efficient synthetic route to hierarchically porous carbon foams
    Open this publication in new window or tab >>Boosting the thermal stability of emulsion–templated polymers via sulfonation: an efficient synthetic route to hierarchically porous carbon foams
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    2016 (English)In: ChemistrySelect, ISSN 2365-6549, Vol. 1, no 4, p. 784-792Article in journal (Refereed) Published
    Abstract [en]

    Hierarchically porous carbon foams with specific surface areas exceeding 600 m2 g−1 can be derived from polystyrene foams that are synthesized via water-in-oil emulsion templating. However, most styrene-based polymers lack strong crosslinks and are degraded to volatile products when heated above 400 oC. A common strategy employed to avert depolymerization is to introduce potential crosslinking sites such as sulfonic acids by sulfonating the polymers. This article unravels the thermal and chemical processes leading up to the conversion of sulfonated high internal phase emulsion polystyrenes (polyHIPEs) to sulfur containing carbon foams. During pyrolysis, the sulfonic acid groups (-SO3H) are transformed to sulfone (-C-SO2-C-) and then to thioether (-C−S-C-) crosslinks. These chemical transformations have been monitored using spectroscopic techniques: in situ IR, Raman, X-ray photoelectron and X-ray absorption near edge structure spectroscopy. Based on thermal analyses, the formation of thioether links is associated with increased thermal stability and thus a substantial decrease in volatilization of the polymers.

    Keywords
    Emulsion-templated polymer, sulfonation, pyrolysis, spectroscopy, carbon foam
    National Category
    Materials Chemistry
    Research subject
    Chemistry with specialization in Materials Chemistry
    Identifiers
    urn:nbn:se:uu:diva-283174 (URN)10.1002/slct.201600139 (DOI)000395395900026 ()
    Projects
    3D microbatteries
    Available from: 2016-04-11 Created: 2016-04-11 Last updated: 2017-10-30Bibliographically approved
    2. Emulsion-templated bicontinuous carbon network electrodes for use in 3D microstructured batteries
    Open this publication in new window or tab >>Emulsion-templated bicontinuous carbon network electrodes for use in 3D microstructured batteries
    2013 (English)In: Journal of Materials Chemistry, ISSN 0959-9428, E-ISSN 1364-5501, Vol. 1, no 44, p. 13750-13758Article in journal (Refereed) Published
    Abstract [en]

    High surface area carbon foams were prepared and characterized for use in 3D structured batteries. Twopotential applications exist for these foams: firstly as an anode and secondly as a current collector supportfor electrode materials. The preparation of the carbon foams by pyrolysis of a high internal phase emulsionpolymer (polyHIPE) resulted in structures with cage sizes of 25 mm and a surface area enhancement pergeometric area of approximately 90 times, close to the optimal configuration for a 3D microstructuredbattery support. The structure was probed using XPS, SEM, BET, XRD and Raman techniques; revealingthat the foams were composed of a disordered carbon with a pore size in the <100 nm range resultingin a BET measured surface area of 433 m2 g-1. A reversible capacity exceeding 3.5 mA h cm2 at acurrent density of 0.37 mA cm-2 was achieved. SEM images of the foams after 50 cycles showed thatthe structure suffered no degradation. Furthermore, the foams were tested as a current collector bydepositing a layer of polyaniline cathode over their surface. High footprint area capacities of500 mA h cm-2 were seen in the voltage range 3.8 to 2.5 V vs. Li and a reasonable rate performancewas observed.

    Place, publisher, year, edition, pages
    United Kingdom: , 2013
    Keywords
    Carbon foam, High internal phase emulsion polymer, microbattery, 3D microbattery, Lithium ion
    National Category
    Chemical Sciences Materials Chemistry
    Research subject
    Materials Science; Chemistry; Materials Science; Physical Chemistry
    Identifiers
    urn:nbn:se:uu:diva-210659 (URN)10.1039/C3TA12680C (DOI)000326463400009 ()
    Projects
    STEM-VR-Microbattery
    Funder
    Swedish Energy AgencySwedish Research Council
    Available from: 2013-11-12 Created: 2013-11-12 Last updated: 2017-12-06Bibliographically approved
    3. Emulsion-templated graphitic carbon foams with optimum porosity for 3D Li-ion microbatteries
    Open this publication in new window or tab >>Emulsion-templated graphitic carbon foams with optimum porosity for 3D Li-ion microbatteries
    (English)Manuscript (preprint) (Other academic)
    Keywords
    carbon, foam, graphitic, anode, three-dimensional, microbattery, lithium
    National Category
    Polymer Technologies Chemical Process Engineering Materials Chemistry Polymer Chemistry Inorganic Chemistry Physical Chemistry
    Identifiers
    urn:nbn:se:uu:diva-312893 (URN)
    Funder
    Swedish Research Council, 2012–4681StandUp
    Available from: 2017-01-14 Created: 2017-01-14 Last updated: 2017-12-30
    4. Nanosized LiFePO4-decorated emulsion-templated carbon foam for 3D micro batteries: a study of structure and electrochemical performance
    Open this publication in new window or tab >>Nanosized LiFePO4-decorated emulsion-templated carbon foam for 3D micro batteries: a study of structure and electrochemical performance
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    2014 (English)In: Nanoscale, ISSN 2040-3364, E-ISSN 2040-3372, Vol. 6, no 15, p. 8804-8813Article in journal (Refereed) Published
    Abstract [en]

    In this article, we report a novel 3D composite cathode fabricated from LiFePO4 nanoparticles deposited conformally on emulsion-templated carbon foam by a sol–gel method. The carbon foam is synthesized via a facile and scalable method which involves the carbonization of a high internal phase emulsion (polyHIPE) polymer template. Various techniques (XRD, SEM, TEM and electrochemical methods) are used to fully characterize the porous electrode and confirm the distribution and morphology of the cathode active material. The major benefits of the carbon foam used in our work are closely connected with its high surface area and the plenty of space suitable for sequential coating with battery components. After coating with a cathode material (LiFePO4nanoparticles), the 3D electrode presents a hierarchically structured electrode in which a porous layer of the cathode material is deposited on the rigid and bicontinuous carbon foam. The composite electrodes exhibit impressive cyclability and rate performance at different current densities affirming their importance as viable power sources in miniature devices. Footprint area capacities of 1.72 mA h cm−2 at 0.1 mA cm−2 (lowest rate) and 1.1 mA h cm−2 at 6 mA cm−2(highest rate) are obtained when the cells are cycled in the range 2.8 to 4.0 V vs. lithium.

    Place, publisher, year, edition, pages
    Royal Society of Chemistry: , 2014
    National Category
    Physical Chemistry Polymer Chemistry Materials Chemistry Inorganic Chemistry
    Identifiers
    urn:nbn:se:uu:diva-228630 (URN)10.1039/C4NR01682C (DOI)000339861500051 ()
    Projects
    STEM-VR-Microbattery
    Available from: 2014-07-18 Created: 2014-07-18 Last updated: 2017-12-05Bibliographically approved
    5. Surface-oxidized NbO2 nanoparticles for high performance lithium microbatteries
    Open this publication in new window or tab >>Surface-oxidized NbO2 nanoparticles for high performance lithium microbatteries
    (English)Manuscript (preprint) (Other academic)
    Keywords
    niobium, oxide, nanoparticle, power, energy, carbon, foam, lithium, microbattery
    National Category
    Natural Sciences Inorganic Chemistry Materials Chemistry Physical Chemistry Condensed Matter Physics Materials Engineering Chemical Engineering
    Research subject
    Chemistry with specialization in Materials Chemistry
    Identifiers
    urn:nbn:se:uu:diva-312894 (URN)
    Projects
    3D Lithium-ion microbattery
    Funder
    Swedish Research Council, 2012–4681StandUp
    Available from: 2017-01-14 Created: 2017-01-14 Last updated: 2017-12-30
    6. A one-step water based strategy for synthesizing hydrated vanadium pentoxide nanosheets from VO2(B) as free-standing electrodes for lithium battery applications
    Open this publication in new window or tab >>A one-step water based strategy for synthesizing hydrated vanadium pentoxide nanosheets from VO2(B) as free-standing electrodes for lithium battery applications
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    2016 (English)In: Journal of Materials Chemistry A, ISSN 2050-7488, Vol. 4, no 46, p. 17988-18001Article in journal (Refereed) Published
    Abstract [en]

    The synthesis of two dimensional (2D) materials from transition metal oxides, chalcogenides, and carbides mostly involve multiple exfoliation steps in which hazardous solvents and reagents are used. In this study, hydrated vanadium pentoxide (V2O5[middle dot]nH2O) nanosheets with a thickness of a few nanometers were prepared via a facile environmentally friendly water based exfoliation technique. The exfoliation process involved refluxing the precursor, vanadium dioxide (VO2(B)), in water for a few days at 60 [degree]C. The proposed exfoliation mechanism is based on the intercalation/insertion of water molecules into the VO2(B) crystals and the subsequent cleavage of the covalent bonds holding the layers of VO2(B) together. The thermal and chemical analyses showed that the approximate chemical composition of the nanosheets is H0.4V2O5[middle dot]0.55H2O, and the percentage of VV content to that of VIV in the nanosheets is about 80(3)% to 20(3)%. The exfoliated aqueous suspension of the V2O5[middle dot]0.55H2O nanosheets was successfully deposited onto multi-walled carbon nanotube (MW-CNT) paper to form free-standing electrodes with a thickness of the V2O5[middle dot]0.55H2O layer ranging between 45 and 4 [small mu ]m. A series of electrochemical tests were conducted on the electrodes to determine the cyclability and rate capability of lithium insertion into V2O5[middle dot]0.55H2O nanosheets. The electrodes with the thinnest active material coating ([similar]4 [small mu ]m) delivered gravimetric capacities of up to 480 and 280 mA h g-1 when cycled at current densities of 10 and 200 mA g-1, respectively.

    Keywords
    2D materials, vanadium oxides, free-standing, battery, lithium
    National Category
    Materials Chemistry
    Identifiers
    urn:nbn:se:uu:diva-311357 (URN)10.1039/C6TA06571F (DOI)000388505400010 ()
    Funder
    Swedish Research Council, 2012-4681Swedish Energy AgencyBerzelii Centre EXSELENTStandUp
    Available from: 2016-12-24 Created: 2016-12-24 Last updated: 2022-03-21
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  • 7.
    Bayrak Pehlivan, İlknur
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Functionalization of polymer electrolytes for electrochromic windows2013Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    Saving energy in buildings is of great importance because about 30 to 40 % of the energy in the world is used in buildings. An electrochromic window (ECW), which makes it possible to regulate the inflow of visible light and solar energy into buildings, is a promising technology providing a reduction in energy consumption in buildings along with indoor comfort. A polymer electrolyte is positioned at the center of multi-layer structure of an ECW and plays a significant role in the working of the ECW.

    In this study, polyethyleneimine: lithium (bis(trifluoromethane)sulfonimide (PEI:LiTFSI)-based polymer electrolytes were characterized by using dielectric/impedance spectroscopy, differential scanning calorimetry, viscosity recording, optical spectroscopy, and electrochromic measurements.

    In the first part of the study, PEI:LiTFSI electrolytes were characterized at various salt concentrations and temperatures. Temperature dependence of viscosity and ionic conductivity of the electrolytes followed Arrhenius behavior. The viscosity was modeled by the Bingham plastic equation. Molar conductivity, glass transition temperature, viscosity, Walden product, and iso-viscosity conductivity analysis showed effects of segmental flexibility, ion pairs, and mobility on the conductivity. A connection between ionic conductivity and ion-pair relaxation was seen by means of (i) the Barton-Nakajima-Namikawa relation, (ii) activation energies of the bulk relaxation, and ionic conduction and (iii) comparing two equivalent circuit models, containing different types of Havriliak-Negami elements, for the bulk response.

    In the second part, nanocomposite PEI:LiTFSI electrolytes with SiO2, In2O3, and In2O3:Sn (ITO) were examined. Adding SiO2 to the PEI:LiTFSI enhanced the ionic conductivity by an order of magnitude without any degradation of the optical properties. The effect of segmental flexibility and free ion concentration on the conduction in the presence of SiO2 is discussed. The PEI:LiTFSI:ITO electrolytes had high haze-free luminous transmittance and strong near-infrared absorption without diminished ionic conductivity. Ionic conductivity and optical clarity did not deteriorate for the PEI:LiTFSI:In2O3 and the PEI:LiTFSI:SiO2:ITO electrolytes.

    Finally, propylene carbonate (PC) and ethylene carbonate (EC) were added to PEI:LiTFSI in order to perform electrochromic measurements. ITO and SiO2 were added to the PEI:LiTFSI:PC:EC and to a proprietary electrolyte. The nanocomposite electrolytes were tested for ECWs with the configuration of the ECWs being plastic/ITO/WO3/polymer electrolyte/NiO (or IrO2)/ITO/plastic. It was seen that adding nanoparticles to polymer electrolytes can improve the coloring/bleaching dynamics of the ECWs.

    From this study, we show that nanocomposite polymer electrolytes can add new functionalities as well as enhancement in ECW applications.

    List of papers
    1. PEI-LiTFSI electrolytes for electrochromic devices: Characterization by differential scanning calorimetry and viscosity measurements
    Open this publication in new window or tab >>PEI-LiTFSI electrolytes for electrochromic devices: Characterization by differential scanning calorimetry and viscosity measurements
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    2010 (English)In: Solar Energy Materials and Solar Cells, ISSN 0927-0248, E-ISSN 1879-3398, Vol. 94, no 12, p. 2399-2404Article in journal (Refereed) Published
    Abstract [en]

    Polymer electrolytes containing poly(ethylene imine) (PEI) and lithium bis(trifluoromethylsulfonyl) imide (LiTFSI) can serve as model electrolytes for electrochromic devices. Such electrolytes were characterized by differential scanning calorimetry, conductivity, and viscosity measurements. The glass transition temperature (T-g) and viscosity of the PEI-LiTESI electrolytes have minima at a [N]:[Li] ratio of 100:1. Both T-g and viscosity increased at high salt concentrations. The temperature dependences of ionic conductivity and viscosity followed an Arrhenius equation with parameters depending only weakly on the salt concentration. The fluid behavior of the electrolytes could be reconciled with the Bingham plastic model with parameters being functions of salt concentration.

    Keywords
    Polymer electrolyte, Electrochromic, Smart window, PEI, DSC, Viscosity
    National Category
    Chemical Sciences Engineering and Technology
    Identifiers
    urn:nbn:se:uu:diva-135307 (URN)10.1016/j.solmat.2010.08.025 (DOI)000283959500066 ()
    Available from: 2011-09-21 Created: 2010-12-06 Last updated: 2017-12-11Bibliographically approved
    2. Ion conduction of branched polyethyleneimine-lithium bis(trifluoromethylsulfonyl) imide electrolytes
    Open this publication in new window or tab >>Ion conduction of branched polyethyleneimine-lithium bis(trifluoromethylsulfonyl) imide electrolytes
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    2011 (English)In: Electrochimica Acta, ISSN 0013-4686, E-ISSN 1873-3859, Vol. 57, p. 201-206Article in journal (Refereed) Published
    Abstract [en]

    Ionic conductivity of polymer electrolytes containing branched poly (ethylene imine) (BPEI) and lithium bis(trifluoromethyl sulfonyl)imide (LiTFSI) was measured between temperatures of 20 and 70◦C and molar ratios of 20:1 and 400:1. The electrolytes were characterized by impedance spectroscopy, differential scanning calorimetry, and viscosity measurements. At room temperature, the maximum conductivity was 2×10−6 S/cm at a molar ratio of 50:1. The molar conductivity of the electrolytes displayed first a minimum and then a maximum upon increasing salt concentration. A proportionality of molar conductivity to segmental mobility was seen from glass transition temperature and viscosity measurements. Analysis of the Walden product and isoviscosity conductivity showed that the percentage of ions bound in ion pairs increased at low concentrations below 0.1 mol/kg. The average dipole moment decreased with salt concentration. The temperature dependence of the ionic conductivity showed an Arrhenius behavior.

    Keywords
    Ionic conductivity, Poly (ethylene imine), Arrhenius behavior, Walden rule, Ion pairing
    National Category
    Other Materials Engineering
    Research subject
    Chemistry with specialization in Polymer Chemistry; Engineering Science with specialization in Solid State Physics
    Identifiers
    urn:nbn:se:uu:diva-163443 (URN)10.1016/j.electacta.2011.04.040 (DOI)000298463900029 ()
    Available from: 2011-12-12 Created: 2011-12-12 Last updated: 2017-12-08Bibliographically approved
    3. Ionic relaxation in polyethyleneimine-lithium bis(trifluoromethylsulfonyl) imide polymer electrolytes
    Open this publication in new window or tab >>Ionic relaxation in polyethyleneimine-lithium bis(trifluoromethylsulfonyl) imide polymer electrolytes
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    2010 (English)In: Journal of Applied Physics, ISSN 0021-8979, E-ISSN 1089-7550, Vol. 108, no 7, p. 074102-Article in journal (Refereed) Published
    Abstract [en]

    Polymer electrolytes containing polyethyleneimine and different concentrations of lithium bis(trifluoromethylsulfonyl) imide were investigated by impedance spectroscopy at different temperatures. Two equivalent circuit models were compared for the bulk impedance response. The first one includes a conductive Havriliak-Negami (HN) element which represents ionic conductivity and ion pair relaxation in a single process, and the second model includes a dielectric HN element, which represents ion pair relaxation, in parallel with ion conductivity. Comparison of the two circuit models showed that the quality of the fit was similar and in some cases better for the conductive model. The experimental data follow the Barton-Nakajima-Namikawa relation, which relates the ion conductivity and the parameters of the relaxation. This indicates that ion conductivity and ion pair relaxation are two parts of the same process and should be described by the conductive model.

    National Category
    Physical Sciences Engineering and Technology
    Identifiers
    urn:nbn:se:uu:diva-133611 (URN)10.1063/1.3490133 (DOI)000283222200101 ()
    Available from: 2011-09-21 Created: 2010-11-11 Last updated: 2017-12-12Bibliographically approved
    4. [PEI-SiO2]:[LiTFSI] nanocomposite polymer electrolytes: Ion conduction and optical properties
    Open this publication in new window or tab >>[PEI-SiO2]:[LiTFSI] nanocomposite polymer electrolytes: Ion conduction and optical properties
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    2012 (English)In: Solar Energy Materials and Solar Cells, ISSN 0927-0248, E-ISSN 1879-3398, Vol. 98, p. 465-471Article in journal (Refereed) Published
    Abstract [en]

    Ion conductivity and optical properties were investigated for polymer electrolytes based on poly (ethyleneimine) and lithium bis(trifluoromethylsulfonyl)imide and also containing up to 9 wt.% of 7-nm-diameter SiO2 nanoparticles. The [N]:[Li] molar ratio was kept constant at 50:1. Impedance measurements were performed in the frequency range 10(-2)-10(7) Hz and between the temperatures 20 and 70 degrees C with an applied ac voltage of 1 V. Spectrophotometric data of total and diffuse transmittance were taken between the wavelengths 300 and 2500 nm. The bulk impedance was fitted to a conductive Havriliak-Negami circuit model. The ion conductivity increased monotonically for increasing SiO2 contents: specifically its room temperature value went from 8.5 x 10(-7) S/cm without nanoparticles to 3.8 x 10(-5) S/cm for 8 wt.% of SiO2 while the diffuse transmittance remained at similar to 1% so that optical clarity prevailed.

    Keywords
    Polymer electrolyte, Nanocomposite, PEI, LiTFSI, SiO2
    National Category
    Engineering and Technology
    Research subject
    Engineering Science with specialization in Solid State Physics
    Identifiers
    urn:nbn:se:uu:diva-171404 (URN)10.1016/j.solmat.2011.11.021 (DOI)000300536500065 ()
    Available from: 2012-03-20 Created: 2012-03-19 Last updated: 2017-12-07Bibliographically approved
    5. Ion conduction mechanism of nanocomposite polymer electrolytes comprised of polyethyleneimine–lithium bis(trifluoromethylsulfonyl)imide and silica
    Open this publication in new window or tab >>Ion conduction mechanism of nanocomposite polymer electrolytes comprised of polyethyleneimine–lithium bis(trifluoromethylsulfonyl)imide and silica
    2014 (English)In: Electrochimica Acta, ISSN 0013-4686, E-ISSN 1873-3859, Vol. 119, p. 164-168Article in journal (Refereed) Published
    National Category
    Nano Technology
    Research subject
    Engineering Science with specialization in Solid State Physics
    Identifiers
    urn:nbn:se:uu:diva-204451 (URN)10.1016/j.electacta.2013.12.032 (DOI)000335877000023 ()
    Available from: 2013-08-05 Created: 2013-08-05 Last updated: 2017-12-06Bibliographically approved
    6. A polymer electrolyte with high luminous transmittance and low solar throughput: Polyethyleneimine-lithium bis(trifluoromethylsulfonyl) imide with In2O3:Sn nanocrystals
    Open this publication in new window or tab >>A polymer electrolyte with high luminous transmittance and low solar throughput: Polyethyleneimine-lithium bis(trifluoromethylsulfonyl) imide with In2O3:Sn nanocrystals
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    2012 (English)In: Applied Physics Letters, ISSN 0003-6951, E-ISSN 1077-3118, Vol. 100, no 24, p. 241902-Article in journal (Refereed) Published
    Abstract [en]

    Chemically prepared similar to 13-nm-diameter nanocrystals of In2O3:Sn were included in a polyethyleneiminelithium bis(trifluoromethylsulfonyl) imide electrolyte and yielded high haze-free luminous transmittance and strong near-infrared absorption without deteriorated ionic conductivity. The optical properties could be reconciled with effective medium theory, representing the In2O3:Sn as a free electron plasma with tin ions screened according to the random phase approximation corrected for electron exchange. This type of polymer electrolyte is of large interest for opto-ionic devices such as laminated electrochromic smart windows.

    National Category
    Physical Sciences Engineering and Technology
    Research subject
    Engineering Science with specialization in Solid State Physics
    Identifiers
    urn:nbn:se:uu:diva-178647 (URN)10.1063/1.4728994 (DOI)000305269200024 ()
    Available from: 2012-08-02 Created: 2012-08-01 Last updated: 2017-12-07Bibliographically approved
    7. Electrochromic Devices with Polymer Electrolytes Functionalized by SiO2 and In2O3:Sn Nanoparticles: Rapid Coloring/Bleaching Dynamics and Strong Near-Infrared Absorption
    Open this publication in new window or tab >>Electrochromic Devices with Polymer Electrolytes Functionalized by SiO2 and In2O3:Sn Nanoparticles: Rapid Coloring/Bleaching Dynamics and Strong Near-Infrared Absorption
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    2014 (English)In: Solar Energy Materials and Solar Cells, ISSN 0927-0248, E-ISSN 1879-3398, Vol. 126, p. 241-247Article in journal (Refereed) Published
    Abstract [en]

    We studied the optical properties and coloring/bleaching dynamics of electrochromic devices based on tungsten oxide and nickel oxide and incorporating polymer electrolytes functionalized by adding about one percent of nanoparticles of SiO2 (fumed silica) or In2O3:Sn. SiO2 improved the coloring/bleaching dynamics and In2O3:Sn quenched the near-infrared transmittance. Both of these effects can be important in electrochromic smart windows, and our results point at the advantage of a polymer laminated construction over a monolithic one.

    National Category
    Nano Technology
    Research subject
    Engineering Science with specialization in Solid State Physics
    Identifiers
    urn:nbn:se:uu:diva-204448 (URN)10.1016/j.solmat.2013.06.010 (DOI)000338395100035 ()
    Conference
    10th International Meeting on Electrochromism (IME), Holland, MI, August 12-16, 2012
    Available from: 2013-08-05 Created: 2013-08-05 Last updated: 2017-12-06Bibliographically approved
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  • 8.
    Bengtsson, Rhodel
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Materials Science and Engineering, Applied Mechanics.
    Afshar, Reza
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Materials Science and Engineering, Applied Mechanics.
    Gamstedt, E. Kristofer
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Materials Science and Engineering, Applied Mechanics.
    A basic orthotropic viscoelastic model for composite and wood materials considering available experimental data and time-dependent Poisson's ratios2020In: IOP Conference Series: Materials Science and Engineering, ISSN 1757-8981, E-ISSN 1757-899X, Vol. 942, article id 012021Article in journal (Refereed)
    Abstract [en]

    Long-term deformation in creep is of significant engineering importance. For anisotropic materials, such as wood, composites and reinforced concrete, creep testing in several axial directions including shear is necessary to obtain a creep model which is able to predict deformation in the basic orthotropic case. Such a full set of experimental data is generally not available, and simplifying assumptions are typically made to conceive a useful 3D model. These assumptions should preferably be made based on the material behaviour and sound engineering arguments. This problem appears to be addressed in many different ways and sometimes the assumptions are not well justified. In the present study, we examine 3D creep of wood and composite materials. Particular emphasis is made on explaining the choices made in developing the model, considering practicality, incomplete material data and the specific behaviour of wood and composites. An orthotropic linear viscoelastic model is implemented as a material model in a commercial FE software. The constitutive equations are derived in the 1D case using a hereditary approach, then later generalized to the 3D formulation. Guidelines are shown how to implement it into the FE software to predict creep of components and structures. Although the model itself is conventional, the effect of considering time-dependent Poisson's ratios is investigated here, as well an optimization approach when inserting inevitably asymmetric experimental creep data into the model. As far as the authors know, creep of wooden materials have not been defined using this approach before. The model of interest is calibrated against experimental data. Examples using experimental results from solid wood data and a unidirectional fiber composite are demonstrated. The results show that the model is able to capture the orthotropic behaviour adequately. Orthotropy requires symmetry of the creep compliance matrix, which typically is not the case experimentally. It is shown that in rendering the matrix symmetric, one needs to decide which direction is more important. It is also shown that the frequently employed assumption of constant Poisson's ratios should be made with caution.

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  • 9.
    Bengtsson, Rhodel
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Materials Science and Engineering, Applied Mechanics.
    Afshar, Reza
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Materials Science and Engineering, Applied Mechanics.
    Gamstedt, E. Kristofer
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Materials Science and Engineering, Applied Mechanics.
    An applicable orthotropic creep model for wood materials and composites2022In: Wood Science and Technology, ISSN 0043-7719, E-ISSN 1432-5225, Vol. 56, no 6, p. 1585-1604Article in journal (Refereed)
    Abstract [en]

    Despite the engineering importance of creep of composite materials and other fibrous anisotropic load-carrying materials like wood, there is an apparent lack in useful experimental data in 3D. Proposed creep models are generally not commensurate with realistic data from experimental characterization. In the present study, an orthotropic linear viscoelastic model is presented and examined on its performance of predicting the time-dependent nature of wood and composite materials. The constitutive equations are presented using the hereditary approach. A clear description of the finite element implementation of the material model is given. Since constant Poisson's ratios are a common assumption for viscoelastic composites due to lack of data, this study presents the effects of time-dependent Poisson's ratio in the study. The model is calibrated against inevitably asymmetric experimental creep data using an optimization approach. With time-dependent Poisson's ratios, the results show that the model is able to simultaneously capture the time-dependent behaviour in three material axis of orthotropic materials such as European beech wood and a fibre-reinforced composite. However, a relatively poor match was found when the Poisson's ratios were set to be constant. Thus, the frequently employed assumption of constant Poisson's ratios should be made with caution.

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  • 10.
    Bengtsson, Rhodel
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Materials Science and Engineering.
    Afshar, Reza
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Materials Science and Engineering.
    Mousavi, Mahmoud
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Materials Science and Engineering.
    Gamstedt, Kristofer
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Materials Science and Engineering.
    Evaluating viscoelastic shearproperties in clear wood via off-axis compression testing and digital image correlation2022Conference paper (Refereed)
  • 11.
    Bengtsson, Rhodel
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Materials Science and Engineering, Applied Mechanics. Uppsala University.
    Florisson, Sara
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Materials Science and Engineering, Applied Mechanics.
    Afshar, Reza
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Materials Science and Engineering, Applied Mechanics.
    Mousavi, Mahmoud
    Van Blokland, Joran
    Department of Forest Biomaterials and Technology, SLU.
    Gamstedt, Kristofer
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Materials Science and Engineering, Applied Mechanics.
    Comparison of measured creep in a wooden beam with finite element predictions based on orthotropic viscoelastic material modelManuscript (preprint) (Other academic)
    Abstract [en]

    Creep is of concern for long-term deformations of wooden structures. Since wood is anisotropic and creeps in several material directions, it may not be sufficient to include only axial creep along the grain even for deformations in beam-like components. A bottle-neck is that creep characterisation in all material directions is both costly and complicated. Multiscale modelling from cell-wall creep including the main contributing features (density, ray content, microfibrillar angle) can contribute to fill to complete material models for wood creep. In the present study, we have chosen a four-point bending test of a Norway spruce beam to represent a loaded wooden component in a structure.  Digital image correlation was used to gather data on strain and displacement fields during the creep test. The experimental results were compared with finite element predictions based on a 3D orthotropic viscoelastic model obtained by multiscale homogenisation. There was generally good agreement in the strain fields between the finite element simulations and experimental observations. However, the numerical predictions exhibits slightly greater stiffness in terms of displacement, suggesting the need for further refinement of the multiscale model or a combination of materials creep charactrisation and multiscale modelling.

  • 12.
    Bengtsson, Rhodel
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Materials Science and Engineering, Applied Mechanics. Uppsala University.
    Gamstedt, Kristofer
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Materials Science and Engineering, Applied Mechanics.
    Florisson, Sara
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Materials Science and Engineering, Applied Mechanics.
    Bernhoff, Hans
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Electrical Engineering, Electricity.
    Feasiblity of wooden towers for offshore wind turbines: Creep and fatigue predictionsManuscript (preprint) (Other academic)
    Abstract [en]

    Long-term experiences with vertical axis wind turbines constructed with wood are positive, and show that wood towers are a viable alternative to conventional steel towers on land. Wood is a renewable material in contrast to steel and concrete and could steer a more sustainable use of raw material for future wind farms. The obvious drawback of moisture-induced softening and degradation in off-shore settings can be mitigated by efficiently sealing the tower using a barrier coating. In that case, fatigue sensitivity and creep deformations are the main design concerns. In this paper through finite element simulations of a floating tilted vertical-axis wind turbine, it was shown that fatigue issues can be resolved with proper design of the mast and the blade joints keeping the stress concentrations at bay. The numerical results also indicated that creep displacements are negligible. The review and calculations reinforce the assumption that the fast developments seen in timber high-rise building can also be expected for off-shore wind turbine towers. 

  • 13.
    Bengtsson, Rhodel
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Materials Science and Engineering.
    Mousavi, Mahmoud
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Materials Science and Engineering.
    Afshar, Reza
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Materials Science and Engineering.
    Gamstedt, Kristofer
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Materials Science and Engineering.
    Parametric study on moisture-dependent wood cell structures with periodic boundary conditions2022Conference paper (Refereed)
  • 14.
    Benz, Kerstin
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Materials Science and Engineering.
    End-of-life wind blade recycling through thermal process2023Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    Renewable energy production with wind turbines has been rising in the last 30 years and it is a crucial technology, which is necessary for the energy transition. As sustainable as the energy production of wind turbines is, the waste management of the blade material is not. Most of the blades end up on a landfill or get incinerated. There are different types of recycling methods, but the most commonly used is to shred the fibers into little pieces and reusing them for filler material in the concrete industry. This approach does not actually split up the blade material into its components but it is more of a downcycling. In this thesis, a new type of pyrolysis will be looked into, which splits up the blade material into its components namely glass fibers and plastic using molten salt. This process would make the glass fiber industry more sustainable by introducing a recycled glass fiber with minimal loss in quality. In a first step, the blade material will be examined more closely with a thermogravimetric analysis to find out what kind of plastic it is and what temperature would be necessary to pyrolyze it. This information will be used to conduct an experiment in a molten salt solution and determine the necessary reaction time and temperature. This data will be used to compare the costs of this method with shredding the material and the conventional pyrolysis. From the thermogravimetric analysis, it was possible to determine that the type of plastic used in this turbine was made out of epoxy. The maximum degredation of this material occurred at 380 ◦C. Not many experiments could be conducted in order to find the optimal conditions for the pyrolysis process due to difficulties with the furnace. Nevertheless, one sample was successfully pyrolyzed at a temperature of 400 ◦C with a residence time of 15 minutes. With the current market conditions in the recycled glass fibers industry, this product would be too expensive and the demand would be too little. However, the market is expected to grow in the next couple years due to rising interests in circular economy and governments introducing regulations. Nevertheless, it is necessary to increase the efficiency of the molten salt pyrolysis in order to be applicable to a bigger scale. More experiments should be conducted with cheaper molten salt in order to sink the costs of the process. 

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  • 15. Bergeon, Louis
    et al.
    Bengtsson, Rhodel
    Afshar, Reza
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Materials Science and Engineering.
    Shear creep experiment on wood2022Conference paper (Refereed)
  • 16.
    Bergman, Oskar
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Materials Science and Engineering.
    Stenerhag, Klara
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Materials Science and Engineering.
    Strömberg, Nicole
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Materials Science and Engineering.
    Gille, Katja
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Materials Science and Engineering.
    Material Selection for Revolutionary new Electric Motor Type2023Independent thesis Basic level (degree of Bachelor), 10 credits / 15 HE creditsStudent thesis
  • 17.
    Bohlin, Johannes
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Materials Science and Engineering, Applied Material Science.
    Lifetime prediction of a polymeric propellant binder using the Arrhenius approach2021Independent thesis Advanced level (professional degree), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    The thermal-oxidative degradation of a crosslinked hydroxy-terminated polybutadiene (HTPB)/cycloaliphatic diisocyanate (H12MDI) based polymer, which is commonly used as a polymeric binder in propellants, is investigated at temperatures from 95°C to 125°C with the aim of estimating the lifetime of the material in storage conditions (20°C) using the Arrhenius approach. Furthermore, the effect of antioxidants and to a lesser extent plasticizer on the degradation process was also studied. Diffusion-limited oxidation (DLO) was theoretically modelled and DLO conditions were estimated by gathering oxygen permeability and consumption data from similar studies. It was concluded that DLO-effects might be present at the highest experiment temperature (125°C) depending on the actual properties of the material investigated. The mechanical degradation was monitored by conducting tensile tests in a DMA apparatus and photographs using a microscope was taken to examine potential DLO effects. The degradation process of the stabilized polymer (with antioxidant) did not showcase Arrhenius behaviour, which was confirmed by the failure to construct a satisfactory mastercurve. This was most likely due to loss of antioxidants, resulting in autocatalytic oxidation(acceleration of the oxidation process). However, the induction period of the stabilized polymer showcased Arrhenius behaviour in the temperature region 95-125°C with an ~E_a = 90 kJ/mol. If the activation energy E_a is assumed to remain constant, the lifetime at ambient temperature (20°C) is predicted to be approximately 176 Years for a 2mm thick sample. However, this is probably an overestimation since curvature in the Arrhenius plot has been observed for many rubber materials in the lower temperature region. Assuming the E_a drops from ~90 kJ/mol to~71 kJ/mol, a more conservative lifetime prediction of 58 Years was estimated.

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  • 18.
    Bojestig, Eric
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    Adhesion of CVD coatings on new cemeted carbides2016Independent thesis Advanced level (professional degree), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    Steel turning inserts cemented carbides have a binder phase consisting of cobalt (Co). However, in recent years a study from the United States National Toxicity Program (NTP) found that cobalt powder is carcinogenic upon inhalation. The European Union's REACH have therefore also classified cobalt powder as carcinogenic upon inhalation. The worldwide search to find a replacement has therefore lately intensified. It is important that the alternative binder phase has no negative effects on the properties of the insert. In this thesis the adhesion between a multilayer ceramic chemical vapor deposition (CVD) coating and a cemented carbide with the alternative binder phases consisting of iron (Fe), nickel (Ni) and cobalt (Co) has been studied.

    First of all, the fracture surfaces showed that the CVD coating was able to grow on all cemented carbides, regardless of which binder phase. To evaluate the adhesion, scratch tests were performed on all samples. The results from the scratch tests were not as expected. No chipping of the coating down to the cemented carbide occurred on any of the samples and the samples with the hardest cemented carbide did not get the highest critical load, which it should according to the literature if all other parameters were the same. Instead the sample with the binder phase consisting of 73 wt% iron and 27 wt% nickel had the highest critical load. This is thought to be due to that during the scratch test the binder phase in this cemented carbide would most likely transform into deformation martensite.

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  • 19.
    Borg, Erik
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    New Impact test method for rock drill inserts2018Independent thesis Advanced level (professional degree), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    This work has been performed at the Applied Materials ScienceDivision at The Ångström Laboratory in collaboration with SandvikMining AB. The project is part of the joint research programmeCoFree.In this work, the problem of finding an impact test method forcemented carbide rock drill inserts is considered. A suitable testmethod is required to benchmark alternative binder cemented carbidesagainst today’s cobalt based grades. The developed test method isbased on a Charpy pendulum arrangement and utilizes, as in rockdrilling, impact of cylindrical bars to achieve the high impact forcesufficient to fracture the rock drill inserts. The impact issymmetrical with two inserts facing each other, which proves to be anefficient way of damaging the inserts. To gain more informationregarding the force and pulse duration, the history of the impact isrecorded with the use of strain gauges. The measured force curvesfrom repeated tests are typically very similar, a strong indicationthat the test loads the buttons in a well-defined, repeatable way.Also, quasi-static loading of the insert is present in the impactwhich agrees to the results from a static compression test. Thisindicates that the inserts are subjected to quasi-static loading,rather than dynamic loading.A single impact test procedure was developed in this work. Thismethodology proved capable of differentiating the impact performanceof two different button cemented carbide grades. Hence, the test canbe used in the future as a benchmark test. It is however necessary toobtain statistical evidence. The impact performance was measured byobserving cracks produced in the impact contact zone with the aid ofan optical microscope with 85x objective. Radial cracks are veryoften found, often forming a cross around the contact zone. Whenlarge button chippings occur due to the impact loading, a very clearsudden drop in the measured force pulse is seen. This is however notseen for impacts that only produces cracks.

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  • 20.
    Chatterjee, Sanjukta
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy.
    Structural and Physical Effects of Carbon Nanofillers in Thermoplastic and Thermosetting Polymer Systems2012Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    Ever since the discovery of carbon nano materials like carbon nanotube (CNT) and graphene, this class of materials has gained significant attention due to their exotic properties. The principle idea of my present research project is to understand the novel improvements induced in polymer matrices with inclusion of the nanofillers. This thesis is thematically divided into three parts.

    In the first part we introduce principle materials that we use for preparation of composites. Methods of nanofiller preparation and different nanocomposites as previously reported in literature are discussed to formulate the basis of our study. Different dispersion techniques are discussed which facilitate uniform nanofiller distribution. A variety of experimental methods are described which were employed to investigate the structure and properties of the composites.

    In the second part we discuss in details polyamide-12 (PA12) composites using CNT and graphene as fillers. A marked improvement is recorded in the toughness of the films with incorporation of CNT, dispersed in PA12 using a surfactant. Electrical percolation is also achieved in the otherwise insulating matrix. With PA-12 fibers we explored the effect of fiber processing and CNT incorporation in the mechanical properties. Extensive wide angle x-ray diffraction was carried out to interpret the structural modifications brought about by CNT in the matrix.

    The final part of the thesis deals with a thermosetting polymer, epoxy composites. CNT, Graphene and also a mixture of the two nanofillers were used as reinforcing agents. Appreciable improvement was recorded in the mechanical properties, electrical and thermal conductivity of the composites. Detailed optical and electron microscopy was carried out to get a vivid idea of the micro-structure and dispersion.

    The presented work demonstrates the significant ability of carbon nanofillers to reinforce polymer matrices enhancing their mechanical, electrical and thermal properties and opening a wide horizon for a variety of applications.

    List of papers
    1. Improvement of toughness and electrical properties of epoxy composites with carbon nanotubes prepared by industrially relevant processes
    Open this publication in new window or tab >>Improvement of toughness and electrical properties of epoxy composites with carbon nanotubes prepared by industrially relevant processes
    Show others...
    2011 (English)In: Nanotechnology, ISSN 0957-4484, E-ISSN 1361-6528, Vol. 22, no 12, p. 125702-Article in journal (Refereed) Published
    Abstract [en]

    The addition of carbon nanotubes (CNTs) to polymeric matrices or master batches has thepotential to provide composites with novel properties. However, composites with a uniformdispersion of CNTs have proved to be difficult to manufacture, especially at an industrial scale.This paper reports on processing methods that overcome problems related to the control andreproducibility of dispersions. By using a high pressure homogenizer and a three-rollcalendaring mill in combination, CNT reinforced epoxies were fabricated by mould castingwith a well dispersed nanofiller content from 0.1 to 2 wt%. The influence of the nano-carbonreinforcements on toughness and electrical properties of the CNT/epoxies was studied. Asubstantial increase of all mechanical properties already appeared at the lowest CNT content of0.1 wt%, but further raising the nanofiller concentration only led to moderate further changes.The most significant enhancement was obtained for fracture toughness, reaching up to 82%.The low percolation thresholds were confirmed by electrical conductivity measurements on thesame composites yielding a threshold value of only about 0.01 wt%. As corroborated by athorough microscopic analysis of the composites, mechanical and electrical enhancement pointsto the formation of an interconnected network of agglomerated CNTs.

    Keywords
    CNT, Epoxy
    National Category
    Composite Science and Engineering
    Research subject
    Materials Science
    Identifiers
    urn:nbn:se:uu:diva-169989 (URN)10.1088/0957-4484/22/12/125702 (DOI)
    Available from: 2012-03-13 Created: 2012-03-07 Last updated: 2017-12-07Bibliographically approved
    2. Comparing carbon nanotubes and graphene nanoplatelets as reinforcements in polyamide 12 composites
    Open this publication in new window or tab >>Comparing carbon nanotubes and graphene nanoplatelets as reinforcements in polyamide 12 composites
    2011 (English)In: Nanotechnology, ISSN 0957-4484, E-ISSN 1361-6528, Vol. 22, no 27, p. 275714-Article in journal (Refereed) Published
    Abstract [en]

    We investigate the influence of nanofillers including carbon nanotubes (CNTs) and graphene nanoplatelets on a thermoplastic engineering polymer, polyamide 12 (PA12). The comparison between these two important nanofillers as to how they influence the structure and properties of the polymer is systematically studied. The polymer–nanofiller composites were prepared using a twin-screw micro-extruder and the composite was thereafter hot pressed into thin films. The structure (using wide angle x-ray diffraction and differential scanning calorimetry) and properties (through tensile testing and conductivity measurement) of the thin films have been investigated. The composites incorporating surfactant showed the best CNT distribution and dispersion, causing an improvement of up to 80% in the toughness modulus over pure PA12. Electrical percolation could also be achieved at nanofiller concentrations of 1 to 2 wt%. In this study we observed that CNT fillers bring about more pronounced improvements in PA12 compared to graphene nanoplatelets, as far as mechanical and electrical properties are concerned.

    Keywords
    CNT, Polymer composite, Graphene
    National Category
    Condensed Matter Physics
    Identifiers
    urn:nbn:se:uu:diva-168031 (URN)10.1088/0957-4484/22/27/275714 (DOI)
    Available from: 2012-02-06 Created: 2012-02-03 Last updated: 2017-12-08Bibliographically approved
    3. Investigation of crystalline and tensile properties of carbon nanotube-filled polyamide-12 fibers melt-spun by industry-related processes
    Open this publication in new window or tab >>Investigation of crystalline and tensile properties of carbon nanotube-filled polyamide-12 fibers melt-spun by industry-related processes
    2012 (English)In: Journal of Engineered Fibers and Fabrics, E-ISSN 1558-9250, Vol. 7, no 3Article in journal (Refereed) Published
    Abstract [en]

    The paper addresses the influence of carbon nanotubes (CNT) on the structure and mechanical properties of high tensile strength thermoplasticpolymer fibers. Polyamide (PA) fibers with different draw ratios, with and without CNTs as fillers, and having mechanical properties close to industrial standards were spun in a pilot melt spinning plant. The morphology of the fibers was investigated using optical microscopy, nuclear magnetic resonance (NMR) and 2-D wide angle x-ray diffraction (WAXD). Differential scanning calorimetry (DSC) was carried out to get an estimation of the crystallinity. For a concise interpretation of the results of tensile measurements performed on the fibers, a parameter was developed to account for the detrimental influence of polymer extrusion on their mechanical properties. CNTs seem to act as sites for the growth of un-oriented crystalline domains converted from oriented regions, without yielding a mechanical reinforcing effect.

    National Category
    Composite Science and Engineering
    Identifiers
    urn:nbn:se:uu:diva-169990 (URN)
    Available from: 2012-03-13 Created: 2012-03-07 Last updated: 2023-10-04Bibliographically approved
    4. Mechanical reinforcement and thermal conductivity in expanded graphene nanoplatelets reinforced epoxy composites
    Open this publication in new window or tab >>Mechanical reinforcement and thermal conductivity in expanded graphene nanoplatelets reinforced epoxy composites
    Show others...
    2012 (English)In: Chemical Physics Letters, ISSN 0009-2614, E-ISSN 1873-4448, Vol. 531, p. 6-10Article in journal (Refereed) Published
    Abstract [en]

    Influence of reinforcements on mechanical and thermal properties of graphene nanoplatelets/epoxy com-posites is investigated. Amine functionalized expanded graphene nanoplatelets (EGNPs) were dispersed within epoxy resins using high-pressure processor followed by three roll milling. Functionality on the EGNPs was confirmed with FTIR and micro-Raman spectroscopy. Bending and nano-mechanical testingwas performed on the composites. Incorporation of EGNPs improved the flexural modulus and hardness of the composite and increased fracture toughness by up to 60%. Marked improvement was observed inthermal conductivity of the composites reaching 36% at 2 wt.% loading. Functionalized EGNPs exhibited significant improvements indicating favorable interaction at EGNPs/polymer interface.

    National Category
    Composite Science and Engineering
    Identifiers
    urn:nbn:se:uu:diva-169994 (URN)10.1016/j.cplett.2012.02.006 (DOI)
    Available from: 2012-03-13 Created: 2012-03-07 Last updated: 2017-12-07Bibliographically approved
    5. The size and synergy effects of graphene nanoplatelets andcarbon nanotubes in mechanical properties of epoxy composites.
    Open this publication in new window or tab >>The size and synergy effects of graphene nanoplatelets andcarbon nanotubes in mechanical properties of epoxy composites.
    (English)Manuscript (preprint) (Other academic)
    Abstract [en]

    We study mechanical reinforcement in a widely used epoxy matrix with the addition of graphenenanoplatelets (GnPs) and various mixture ratios of carbon nanotubes (CNTs) withGnPs. Two different dimensions of GnPs were used with flake sizes of 5 mm and 25 mm toinvestigate the influence of nanofiller size on the composite properties. In the GnP reinforcedcomposites, the bigger flakes showed greater reinforcement at all GnP concentrations. The influenceof size on properties is significant as bigger flakes actively control the failure mechanismsin the composite. In the mixture samples, highest CNT content (9:1) showed significantimprovement in fracture toughness of 76 %. For composites with mixtures of CNTs andGnPs, the CNT:GnP ratio is an interesting factor significantly influencing the properties ofthe epoxy matrix. The combination of high aspect ratio of CNTs and larger surface area ofGnPs contribute to the synergistic effect of the CNT-GnP hybrid samples. Thermal conductivityconsistently increases with the incorporation of GnPs in the matrix. Transmission electronmicroscopy (TEM) images confirm the uniform nanofiller dispersion achieved in thecomposites with GnP. For the hybrid samples the CNTs are seen to align themselves on theGnP flakes creating an inter-connected strong nanofiller network in the matrix. The homogenousnanofiller dispersions have been achieved by high shear calendaring which is a methodcapable of being industrially scaled up.

    National Category
    Composite Science and Engineering
    Identifiers
    urn:nbn:se:uu:diva-171572 (URN)
    Available from: 2012-03-22 Created: 2012-03-21 Last updated: 2012-04-13Bibliographically approved
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  • 21.
    Chatterjee, Sanjukta
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy.
    The size and synergy effects of graphene nanoplatelets andcarbon nanotubes in mechanical properties of epoxy composites.Manuscript (preprint) (Other academic)
    Abstract [en]

    We study mechanical reinforcement in a widely used epoxy matrix with the addition of graphenenanoplatelets (GnPs) and various mixture ratios of carbon nanotubes (CNTs) withGnPs. Two different dimensions of GnPs were used with flake sizes of 5 mm and 25 mm toinvestigate the influence of nanofiller size on the composite properties. In the GnP reinforcedcomposites, the bigger flakes showed greater reinforcement at all GnP concentrations. The influenceof size on properties is significant as bigger flakes actively control the failure mechanismsin the composite. In the mixture samples, highest CNT content (9:1) showed significantimprovement in fracture toughness of 76 %. For composites with mixtures of CNTs andGnPs, the CNT:GnP ratio is an interesting factor significantly influencing the properties ofthe epoxy matrix. The combination of high aspect ratio of CNTs and larger surface area ofGnPs contribute to the synergistic effect of the CNT-GnP hybrid samples. Thermal conductivityconsistently increases with the incorporation of GnPs in the matrix. Transmission electronmicroscopy (TEM) images confirm the uniform nanofiller dispersion achieved in thecomposites with GnP. For the hybrid samples the CNTs are seen to align themselves on theGnP flakes creating an inter-connected strong nanofiller network in the matrix. The homogenousnanofiller dispersions have been achieved by high shear calendaring which is a methodcapable of being industrially scaled up.

  • 22. Chatterjee, Sanjukta
    et al.
    Reifler, F A
    Chu, B T T
    Hufenus, R
    Investigation of crystalline and tensile properties of carbon nanotube-filled polyamide-12 fibers melt-spun by industry-related processes2012In: Journal of Engineered Fibers and Fabrics, E-ISSN 1558-9250, Vol. 7, no 3Article in journal (Refereed)
    Abstract [en]

    The paper addresses the influence of carbon nanotubes (CNT) on the structure and mechanical properties of high tensile strength thermoplasticpolymer fibers. Polyamide (PA) fibers with different draw ratios, with and without CNTs as fillers, and having mechanical properties close to industrial standards were spun in a pilot melt spinning plant. The morphology of the fibers was investigated using optical microscopy, nuclear magnetic resonance (NMR) and 2-D wide angle x-ray diffraction (WAXD). Differential scanning calorimetry (DSC) was carried out to get an estimation of the crystallinity. For a concise interpretation of the results of tensile measurements performed on the fibers, a parameter was developed to account for the detrimental influence of polymer extrusion on their mechanical properties. CNTs seem to act as sites for the growth of un-oriented crystalline domains converted from oriented regions, without yielding a mechanical reinforcing effect.

    Download full text (pdf)
    fulltext
  • 23. Chatterjee, Sanjukta
    et al.
    Wang, J W
    Kuo, W S
    Tai, N H
    Salzmann, C
    Li, W L
    Hollertz, R
    Nüesch, F A
    Chu, B T T
    Mechanical reinforcement and thermal conductivity in expanded graphene nanoplatelets reinforced epoxy composites2012In: Chemical Physics Letters, ISSN 0009-2614, E-ISSN 1873-4448, Vol. 531, p. 6-10Article in journal (Refereed)
    Abstract [en]

    Influence of reinforcements on mechanical and thermal properties of graphene nanoplatelets/epoxy com-posites is investigated. Amine functionalized expanded graphene nanoplatelets (EGNPs) were dispersed within epoxy resins using high-pressure processor followed by three roll milling. Functionality on the EGNPs was confirmed with FTIR and micro-Raman spectroscopy. Bending and nano-mechanical testingwas performed on the composites. Incorporation of EGNPs improved the flexural modulus and hardness of the composite and increased fracture toughness by up to 60%. Marked improvement was observed inthermal conductivity of the composites reaching 36% at 2 wt.% loading. Functionalized EGNPs exhibited significant improvements indicating favorable interaction at EGNPs/polymer interface.

  • 24. Dong, Zhiyun
    et al.
    Wu, Dan
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Materials Science and Engineering, Applied Material Science.
    Engqvist, Håkan
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Materials Science and Engineering, Applied Material Science.
    Luo, Jun
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Materials Science and Engineering, Applied Material Science. Sichuan University.
    Persson, Cecilia
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Materials Science and Engineering, Applied Material Science.
    Silk fibroin hydrogels induced and reinforced by acidic calcium phosphate: A simple way of producing bioactive and drug-loadable composites for biomedical applications2021In: International Journal of Biological Macromolecules, ISSN 0141-8130, E-ISSN 1879-0003, Vol. 193, p. 433-440Article in journal (Refereed)
    Abstract [en]

    Silk fibroin (SF) hydrogels have attracted extensive interest in biomedical applications due to their biocompatibility and wide availability. However, their generally poor mechanical properties limit their utility. Here, injectable, ready-to-use SF-based composites, simultaneously induced and reinforced by acidic calcium phosphates, were prepared via a dual-paste system requiring no complex chemical/physical treatment. The composite was formed by mixing a monocalcium phosphate monohydrate paste with a β-tricalcium phosphate/SF paste. The conformational transition of SF in an acidic environment forms continuous networks, and the acidic calcium phosphate, brushite and monetite, formed simultaneously in the networks during mixing. The composites displayed a partly elastomeric compression behavior, with mechanical properties increasing with an increasing calcium phosphate and β-sheet content at the lower calcium phosphate contents evaluated (22.2–36.4 wt%). While the stiffness was still relatively low, the materials presented a high elasticity and ductility, and no failure at stresses in the range of failure stresses of trabecular bone. Furthermore, the calcium phosphate confers bioactivity to the material, and the composites with a promising in vitro cell response also showed potential as drug vehicles, using vancomycin as a model drug. These dual-paste systems exhibit potential utility in biomedical applications, such as bone void fillers and drug vehicles.

  • 25.
    Ek Fliesberg, Linda
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Materials Science and Engineering, Applied Material Science.
    Linné, Beatrice
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Materials Science and Engineering, Applied Material Science.
    Framställning av magnetisk polymerkomposit: Stålpulverfylld epoxi med magnetiska egenskaper2021Independent thesis Basic level (professional degree), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    To compete with other manufacturing companies in the market, product design and manufacturing methods need to be improved constantly. To save time and money, there is an advantage if there is a manufacturing plan in place before designing the final product. Composites have been used worldwide for over 6,000 years and their use is expected to increase in the future. Composites offer advantages in product design and manufacturing since it can be adapted to the intended purpose. 

    The purpose of the project is to determine whether it is possible to produce a magnetic polymer composite with a sufficiently high magnetism to lift a specific weight. The purpose is fulfilled through practical executions together with a literature study to find out which materials were most suitable for the application. The polymer composites were tested in magnetic tests to see if a sufficiently high magnetism was obtained to lift the specific weight. 

    Two steel powders, differing in particle structure and density, were mixed with an epoxy as a binder and then cast in two different moulds with a depth of 2 mm and 4 mm. The proportions of the steel powder were tested from 50% up to 97%. The result showed that sufficiently high magnetism to lift the intended weight was reached at a concentration of steel powder between 85% - 97%. The composites did not exhibit the necessary magnetic capacity to function in the intended application and therefore further tests with a magnetic material with higher relative permeability are proposed.

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    Examensarbete
  • 26.
    Espadas Escalante, Juan José
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Mechanics. Uppsala University.
    On numerical analyses of woven composite laminates: Homogenization, damage and fracture2019Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    This dissertation analyzes various mechanical properties of textile reinforced composite laminates.

    The dissertation is based on a total of six published works, which are essentially numerical, although experimental elements are available. The numerical methods used are based on high-resolution finite element models in combination with sophisticated phase-field theories for brittle fracture. A key result is that important mechanical properties in engineering applications, such as fracture or damage resistance, can be substantially affected by the arrangement of the constituent materials at the meso level.

    List of papers
    1. A phase-field model for strength and fracture analyses of fiber-reinforced composites
    Open this publication in new window or tab >>A phase-field model for strength and fracture analyses of fiber-reinforced composites
    2019 (English)In: Composites Science And Technology, ISSN 0266-3538, E-ISSN 1879-1050, Vol. 174, p. 58-67Article in journal (Refereed) Published
    Abstract [en]

    A phase-field model for brittle fracture is proposed and evaluated for strength and fracture analyses of composites. In addition to the elastic properties, this approach makes use of only the fracture toughness and the strength of the material. The capability of the method is shown in analyses of composites at two scales. In laminates, strengths of notched laminates are estimated, including hole size effects. In a lamina, cracks developed in both transverse tension and compression are analyzed and compared to other numerical methods in the literature. The effects of a spectral and a hydrostatic-deviatoric decomposition of the strain energy density, two variants often used in phase-field formulations, are studied. It is shown that the choice of the decomposition affects the fracture development. Results are compared to experiments and simulations in the literature showing the capabilities of the phase-field approach.

    Place, publisher, year, edition, pages
    Elsevier, 2019
    Keywords
    Computational mechanics, Strength, Fracture, Finite element analysis (FEA)
    National Category
    Composite Science and Engineering
    Identifiers
    urn:nbn:se:uu:diva-368254 (URN)10.1016/j.compscitech.2018.10.031 (DOI)000469407500008 ()
    Available from: 2018-12-03 Created: 2018-12-03 Last updated: 2019-07-05Bibliographically approved
    2. A study on the influence of boundary conditions in computational homogenization of periodic structures with application to woven composites
    Open this publication in new window or tab >>A study on the influence of boundary conditions in computational homogenization of periodic structures with application to woven composites
    2017 (English)In: Composite structures, ISSN 0263-8223, E-ISSN 1879-1085, Vol. 160, p. 529-537Article in journal (Refereed) Published
    Abstract [en]

    The influence of boundary conditions (BCs) in the estimation of elastic properties of periodic structures is investigated using computational homogenization with special focus on planar structures. Uniform displacement, uniform traction, periodic, in-plane periodic and a proposed mix of periodic and traction BCs are used. First, the effect of the BCs is demonstrated in structures with one-, two- and three-dimensional periodicity. Mixed BCs are shown to most accurately represent the behavior of layered structures with a small number of repeating unit cells. Then, BCs are imposed on a twill woven composite architecture. Special attention is devoted to investigate the sensitivity of the estimated properties with respect to the BCs and to show differences when considering a single lamina or a laminate. High sensitivity of the in-plane extensional modulus and Poisson's ratio with respect to the type of BCs is found. Moreover, it is shown that the mix of BCs and in-plane periodic BCs are capable to represent an experimental strain field.

    Keywords
    Computational homogenization, Mixed boundary conditions, Heterogeneous structures, Elastic properties, Woven composites, Finite element method
    National Category
    Composite Science and Engineering
    Identifiers
    urn:nbn:se:uu:diva-359307 (URN)10.1016/j.compstruct.2016.10.082 (DOI)000390470300044 ()
    Available from: 2018-08-31 Created: 2018-08-31 Last updated: 2019-07-05Bibliographically approved
    3. The effect of free-edges and layer shifting on intralaminar and interlaminar stresses in woven composites
    Open this publication in new window or tab >>The effect of free-edges and layer shifting on intralaminar and interlaminar stresses in woven composites
    2018 (English)In: Composite structures, ISSN 0263-8223, E-ISSN 1879-1085, Vol. 185, p. 212-220Article in journal (Refereed) Published
    Abstract [en]

    The free-edge effects and relative layer shifting in the interlaminar and intralaminar stresses of plain woven composite laminates under uniaxial extension is investigated numerically using a finite element approach. A computational framework of the free-edge problem for periodic structures with finite width is applied to woven laminates. First, two-layered laminates with three different shifting configurations are studied considering repeating unit cells simulating finite and infinite width. For each configuration, two different widths are considered by trimming the model at different locations in order to investigate different free-edge effects. Then, two four-layered laminates with no shifting and a maximum shifting configuration are analyzed to illustrate the effect of neighboring layers in the stresses. For each shifting configuration, different delamination mechanisms are expected. When considering more layers, it is found that the stacking configuration affects the state of stress and the free-edge effects depending on the shifting. In general, a different behavior than that of unidirectional tape laminates is found, since the interlaminar and intralaminar stresses can be higher than those generated at the free-edges. Particularly, for the maximum shifting configuration results are in agreement with experimental results in the literature where no debonding between yarns was observed at the free-edges.

    Keywords
    Woven composites, Finite element method, Intralaminar stresses, Interlaminar stresses, Free-edge effects, Multiscale modeling
    National Category
    Applied Mechanics
    Identifiers
    urn:nbn:se:uu:diva-341485 (URN)10.1016/j.compstruct.2017.11.014 (DOI)000418961000018 ()
    Available from: 2018-02-28 Created: 2018-02-28 Last updated: 2019-07-05Bibliographically approved
    4. A study of induced delamination and failure in woven composite laminates subject to short-beam shear testing
    Open this publication in new window or tab >>A study of induced delamination and failure in woven composite laminates subject to short-beam shear testing
    2019 (English)In: Engineering Fracture Mechanics, ISSN 0013-7944, E-ISSN 1873-7315, Vol. 205, p. 359-369Article in journal (Refereed) Published
    Abstract [en]

    Failure in woven composite laminates subject to global shear load is studied. Laminates are manufactured, tested and analyzed using X-ray computed tomography, scanning electron microscopy and finite element models. It is found that the stress distribution along the thickness direction is dependent on the layer shifting that alters different yarn interactions, which in turn, affects delamination and failure onset A suggested failure mechanism is in agreement with experimental observations.

    National Category
    Applied Mechanics
    Identifiers
    urn:nbn:se:uu:diva-368250 (URN)10.1016/j.engfracmech.2018.10.015 (DOI)000453766000026 ()
    Available from: 2018-12-03 Created: 2018-12-03 Last updated: 2019-07-05Bibliographically approved
    5. Analysis of the Influence of Layer Shifting on the Elastic Response and Damage Nucleation and Growth in Woven Composite Laminates
    Open this publication in new window or tab >>Analysis of the Influence of Layer Shifting on the Elastic Response and Damage Nucleation and Growth in Woven Composite Laminates
    2018 (English)In: NASA Technical MemorandumsArticle in journal (Refereed) Published
    National Category
    Engineering and Technology
    Identifiers
    urn:nbn:se:uu:diva-368253 (URN)
    Available from: 2018-12-03 Created: 2018-12-03 Last updated: 2019-07-05
    6. Mesoscale analysis of the transverse cracking kinetics in woven composite laminates using a phase-field fracture theory
    Open this publication in new window or tab >>Mesoscale analysis of the transverse cracking kinetics in woven composite laminates using a phase-field fracture theory
    2019 (English)In: Engineering Fracture Mechanics, ISSN 0013-7944, E-ISSN 1873-7315, Vol. 216, article id 106523Article in journal (Refereed) Published
    Abstract [en]

    A phase-field approach to fracture is used to simulate transverse cracking kinetics in composite laminates. First, a typical unidirectional tape laminate is modeled and the transverse cracking evolution with the consequent reduction in the in-plane modulus of elasticity is estimated. Then, a four-layered plain weave composite is modeled using different layer shifting configurations. Predictions in the transverse cracking evolution become improved as the shifting configuration of the laminate model become closer to experimental observations. Simulations predict that some cracks do not form perpendicularly to the loading direction, as it has been observed experimentally in similar locations. Only the fracture toughness and the in situ transverse strength of the ply are required without prior knowledge of the position of the cracks or an ad hoc criterion for crack evolution. All the simulations are compared qualitatively and quantitatively to experiments published elsewhere.

    Keywords
    Composites, Fibre reinforced materials, Fracture mechanics, Damage mechanics, Crack growth
    National Category
    Applied Mechanics
    Research subject
    Engineering science with specialization in Applied Mechanics
    Identifiers
    urn:nbn:se:uu:diva-388533 (URN)10.1016/j.engfracmech.2019.106523 (DOI)000477573000028 ()
    Available from: 2019-07-01 Created: 2019-07-01 Last updated: 2019-09-20Bibliographically approved
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  • 27.
    Espadas-Escalante, Juan José
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Mechanics.
    Bednarcyk, Brett A.
    NASA, Glenn Res Ctr, Cleveland, OH 44135 USA.
    Pineda, Evan J.
    NASA, Glenn Res Ctr, Cleveland, OH 44135 USA.
    Isaksson, Per
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Mechanics.
    Modeling the influence of layer shifting on the properties and nonlinear response of woven composites subject to continuum damage2019In: Composite structures, ISSN 0263-8223, E-ISSN 1879-1085, Vol. 220, p. 539-549Article in journal (Refereed)
    Abstract [en]

    The influence of relative layer shifting on the elastic and damage response of plain weave composite laminates is analyzed using a continuum damage mechanics approach in combination with the finite element method. First, the homogenized properties of the woven composite as a function of the number of layers and of layer shifting are presented. Next, the damage development in various shifting configurations is studied using different damage constitutive models for the matrix and the fiber bundles. It is shown that the impact of layer shifting on both the elastic response and the nonlinear damage response is significant. Most notably, the model captures changes in the damage mechanisms within the woven composite that occur due to layer shifting, resulting in stiffer, more brittle behavior, which has been shown experimentally in the literature. Model results in the linear and nonlinear regimes are shown to be consistent with both an independent analytical model and reported experiments.

  • 28.
    Espadas-Escalante, Juan José
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Mechanics.
    van Dijk, Nico P.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Mechanics.
    Isaksson, Per
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Mechanics.
    A phase-field model for strength and fracture analyses of fiber-reinforced composites2019In: Composites Science And Technology, ISSN 0266-3538, E-ISSN 1879-1050, Vol. 174, p. 58-67Article in journal (Refereed)
    Abstract [en]

    A phase-field model for brittle fracture is proposed and evaluated for strength and fracture analyses of composites. In addition to the elastic properties, this approach makes use of only the fracture toughness and the strength of the material. The capability of the method is shown in analyses of composites at two scales. In laminates, strengths of notched laminates are estimated, including hole size effects. In a lamina, cracks developed in both transverse tension and compression are analyzed and compared to other numerical methods in the literature. The effects of a spectral and a hydrostatic-deviatoric decomposition of the strain energy density, two variants often used in phase-field formulations, are studied. It is shown that the choice of the decomposition affects the fracture development. Results are compared to experiments and simulations in the literature showing the capabilities of the phase-field approach.

  • 29.
    Espadas-Escalante, Juan José
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Mechanics.
    van Dijk, Nico P.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Mechanics.
    Isaksson, Per
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Mechanics.
    A study on the influence of boundary conditions in computational homogenization of periodic structures with application to woven composites2017In: Composite structures, ISSN 0263-8223, E-ISSN 1879-1085, Vol. 160, p. 529-537Article in journal (Refereed)
    Abstract [en]

    The influence of boundary conditions (BCs) in the estimation of elastic properties of periodic structures is investigated using computational homogenization with special focus on planar structures. Uniform displacement, uniform traction, periodic, in-plane periodic and a proposed mix of periodic and traction BCs are used. First, the effect of the BCs is demonstrated in structures with one-, two- and three-dimensional periodicity. Mixed BCs are shown to most accurately represent the behavior of layered structures with a small number of repeating unit cells. Then, BCs are imposed on a twill woven composite architecture. Special attention is devoted to investigate the sensitivity of the estimated properties with respect to the BCs and to show differences when considering a single lamina or a laminate. High sensitivity of the in-plane extensional modulus and Poisson's ratio with respect to the type of BCs is found. Moreover, it is shown that the mix of BCs and in-plane periodic BCs are capable to represent an experimental strain field.

  • 30.
    Graf Brolund, Åke
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Materials Science and Engineering, Applied Mechanics.
    Beccau, Edvin
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Materials Science and Engineering, Applied Mechanics.
    Optimization of composite materials in 2D2023Independent thesis Basic level (degree of Bachelor), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    Composites are a useful type of material due to their ability to be created for specific applications. On the other hand composites often leads to a challenging optimization problem. Since composites often consists of more than two constituent materials it can be challenging to distribute the constituent materials in order to fulfill a certain mechanical property. The goal of this report is to construct an algorithm to optimize mechanical properties for a composite. The geometry of the composite is a 2-dimensional square with a pre-crack. The mechanical properties that the algoritm seeks to optimize is toughness and minimized stress in the crack tip. The results shows that the algoritm can be used in order to redistribute the constituent materials in order to improve a mechanical property.

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  • 31.
    Hartwig, Marie
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Materials Science and Engineering, Applied Mechanics.
    Gamstedt, E. Kristofer
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Materials Science and Engineering, Applied Mechanics.
    On the composite design of wood branches leading to improved bending strength2020In: IOP Conference Series: Materials Science and Engineering, ISSN 1757-8981, E-ISSN 1757-899X, Vol. 942, article id 012008Article in journal (Refereed)
    Abstract [en]

    Wooden branches are designed to carry large bending moments, and so are longer composite structures, e.g. rotor blades for wind turbines. Being a natural fibrous composite material, wood is made from relatively simple biopolymer building blocks. In this preliminary work, we describe the composition and structure of softwood branches, including 3D images from X-ray computed tomography. The main difference in branch structure compared with other wood tissues is the reaction wood formed on the compressive side in e.g. spruce and pine. A simple beam is used to show that maximum bending moment is multiplied several times solely from the reaction wood. This is noteworthy, since chemical composition of the reaction wood does not differ significantly from the rest of the wood. The tissue gradients in the branch resulting from variation in density, microfibrillar angle and cell geometry contribute to the strength improvements. In composite structures, sandwich design is used to improve the load carrying capacity. From a general perspective, also local features as found in wood, such as smooth gradients and controlled cellular structure, could be further explored to improve bending strength in engineered composite materials.

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  • 32. Hollertz, R
    et al.
    Chatterjee, Sanjukta
    Guttmann, H
    Geiger, T
    Nüesch, F A
    Chu, B T T
    Improvement of toughness and electrical properties of epoxy composites with carbon nanotubes prepared by industrially relevant processes2011In: Nanotechnology, ISSN 0957-4484, E-ISSN 1361-6528, Vol. 22, no 12, p. 125702-Article in journal (Refereed)
    Abstract [en]

    The addition of carbon nanotubes (CNTs) to polymeric matrices or master batches has thepotential to provide composites with novel properties. However, composites with a uniformdispersion of CNTs have proved to be difficult to manufacture, especially at an industrial scale.This paper reports on processing methods that overcome problems related to the control andreproducibility of dispersions. By using a high pressure homogenizer and a three-rollcalendaring mill in combination, CNT reinforced epoxies were fabricated by mould castingwith a well dispersed nanofiller content from 0.1 to 2 wt%. The influence of the nano-carbonreinforcements on toughness and electrical properties of the CNT/epoxies was studied. Asubstantial increase of all mechanical properties already appeared at the lowest CNT content of0.1 wt%, but further raising the nanofiller concentration only led to moderate further changes.The most significant enhancement was obtained for fracture toughness, reaching up to 82%.The low percolation thresholds were confirmed by electrical conductivity measurements on thesame composites yielding a threshold value of only about 0.01 wt%. As corroborated by athorough microscopic analysis of the composites, mechanical and electrical enhancement pointsto the formation of an interconnected network of agglomerated CNTs.

  • 33.
    Holmgren, Jonna
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Materials Science and Engineering, Applied Material Science.
    Heinrichs, Jannica
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Materials Science and Engineering, Applied Material Science.
    Kassman Rudolphi, Åsa
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Materials Science and Engineering, Applied Material Science.
    Jacobson, Staffan
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Materials Science and Engineering, Applied Material Science.
    Strategies for revealing deformation and wear mechanisms of polymer composites by combining scanning electron microscopy, energy dispersive x‐ray spectroscopy and cross‐section techniques—Exemplified by glass fiber reinforced poly‐phenylene‐sulphide2023In: Journal of Applied Polymer Science, ISSN 0021-8995, E-ISSN 1097-4628, Vol. 141, no 9, article id e55027Article in journal (Refereed)
    Abstract [en]

    Polymers and polymer composites are frequently used in tribological applications. However, their use is often limited by excessive wear or plastic deformation, therefore research and development aiming to improve the materials is ongoing. Tribological evaluations of polymer composites often study the friction coefficient and wear rate for different types, sizes and amounts of fillers. But rarely are any mechanisms presented. Although polymer materials differ from metals, the techniques typically used for metal components, for example, scanning electron microscopy (SEM) and energy dispersive x-ray spectroscopy (EDS), can be adapted to polymer materials, to achieve more informative SEM micrographs and EDS analyses. The aim of this article is to present useful analysis strategies, from sample preparation and selection of viewing angles, to selection of instrument settings and detector types. The strategies are exemplified by analysis of poly-phenylene-sulphide filled with glass fiber, evaluated against steel in a reciprocating ball-on-flat test set-up. This article takes its starting point with the worn surfaces, and subsequently analyze them using SEM and EDS. A selection of cross section preparation techniques, analysis parameters and microscopy settings are presented and discussed. By combining these techniques and settings, the observation of a strongly modified surface layer, as well as sub-surface plastic deformation and imbedded wear particles, is facilitated.

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  • 34.
    Holmgren, Jonna
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    Kassman Rudolphi, Åsa
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    Friction and wear studies of some PEEK materials2014In: 16th Nordic Symposium on Tribology (NORDTRIB), 2014Conference paper (Other academic)
  • 35.
    Holmgren Lind, Jonna
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    Kassman Rudolphi, Åsa
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    Effect of PTFE on the tribological behaviour of PPS with glass fiber2014In: 1st International conference on polymer tribology (PolyTrib), 2014Conference paper (Other academic)
  • 36.
    Huc, Sabina
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Mechanics. Univ Boras, Fac Text Engn & Business, S-50190 Boras, Sweden.
    Hozjan, Tomaz
    Univ Ljubljana, Fac Civil & Geodet Engn, Ljubljana 1000, Slovenia.
    Svensson, Staffan
    Univ Boras, Fac Text Engn & Business, S-50190 Boras, Sweden.
    Rheological behavior of wood in stress relaxation under compression2018In: Wood Science and Technology, ISSN 0043-7719, E-ISSN 1432-5225, Vol. 52, no 3, p. 793-808Article in journal (Refereed)
    Abstract [en]

    Rheological behavior of wood under uniaxial compression along and perpendicular to the grain in constant environment was examined. Tests with constant deformation rate until failure and stress relaxation tests with constant deformation applied stepwise were carried out. The experimental results of stress relaxation showed nonlinear material behavior over time that got more prominent under high deformation levels. Considerable amount of stress relaxed during applying the deformation. Wood experienced greater stress relaxation along the grain than perpendicular to it. Three rheological models for orthotropic material were calibrated to the experimentally determined stress-time curves in longitudinal and transverse directions simultaneously. Small deformation levels assuming linear strains were accounted for in the models. Required elastic material parameters were determined from the tests with constant deformation rate. A model including the highest number of viscoelastic material parameters was the most successful in predicting stress relaxation of wood under stepwise deformation. Modeling indicated that wood behavior was very close to linear viscoelastic in relaxation under small deformation. The obtained material parameters made the model suitable for predicting rheological behavior of wood comprehensively, under sustained deformation or load in constant conditions.

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  • 37.
    Huc, Sabina
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Mechanics. Univ Boras, Fac Text Engn & Business, SE-50190 Boras, Sweden.
    Svensson, Staffan
    Univ Boras, Fac Text Engn & Business, SE-50190 Boras, Sweden.
    Influence of grain direction on the time-dependent behavior of wood analyzed by a 3D rheological model: A mathematical consideration2018In: Holzforschung, ISSN 0018-3830, E-ISSN 1437-434X, Vol. 72, no 10, p. 889-897Article in journal (Refereed)
    Abstract [en]

    A three-dimensional (3D) rheological model for an orthotropic material subjected to sustained load or deformation under constant climate has been mathematically formulated. The elastic and viscoelastic compliance matrices are symmetric, where the mathematical derivation of the latter is shown. The model is linear and requires constant numerical values for the elastic and viscoelastic material parameters. The model's ability to predict the natural time-dependent response in three material directions simultaneously is demonstrated on a Douglas fir (Pseudotsuga menziesii) specimen subjected to a constant uniaxial tensile load. The material extends in a longitudinal direction and contracts in the transverse directions with time. The required material parameters are taken from the literature when possible, otherwise they are assumed. Furthermore, the influence of misalignment between the directions of observation and wood material directions on induced time-dependent strains is analyzed. The analyses show that the misalignment has a large effect on the material behavior. In some cases, the specimen under constant uniaxial tension even extends in the perpendicular transverse direction with time. The obtained results clearly demonstrate the high importance of considering the alignment of material directions precisely in order to be able to interpret the time-dependent behavior of wood correctly.

  • 38.
    Hägglund, Carl
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Electronics. Department of Applied Physics, Chalmers University of Technology.
    Apell, Peter S.
    Department of Applied Physics, Chalmers University of Technology.
    Kasemo, Bengt
    Department of Applied Physics, Chalmers University of Technology.
    Maximized optical absorption in ultrathin films and its application to plasmon-based two-dimensional photovoltaics2010In: Nano letters (Print), ISSN 1530-6984, E-ISSN 1530-6992, Vol. 10, no 8, p. 3135-3141Article in journal (Refereed)
  • 39.
    Hägglund, Carl
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Electronics. Chalmers University of Technology.
    Apell, S. P.
    Chalmers University of Technology.
    Resource efficient plasmon-based 2D-photovoltaics with reflective support2010In: Optics Express, E-ISSN 1094-4087, Vol. 18, no S3, p. A343-A356Article in journal (Refereed)
  • 40.
    Isaksson, Per
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Mechanics.
    Carlsson, L. A.
    Florida Atlantic Univ, Dept Mech Engn, Boca Raton, FL 33431 USA..
    Analysis of the out-of-plane compression and shear response of paper-based web-core sandwiches subject to large deformation2017In: Composite structures, ISSN 0263-8223, E-ISSN 1879-1085, Vol. 159, p. 96-109Article in journal (Refereed)
    Abstract [en]

    The mechanical response of three different structural core sandwich panels in out-of-plane compression and shear has been analyzed. Specific core shapes examined are arc-tangent, wavy trapezoidal and hemispherical. Unit cells consisting of representative elements of the core attached to face sheets were selected for analysis. Both face sheets and core were assumed made from paper. Finite element analysis employing large deformation and rotations and orthotropic elastic-plastic behavior was used. The results show that the arc-tangent and trapezoidal cores are prone to collapse by extensive bending and buckling, whereas the hemispherical core behaved more stably in compression and shear. Core sheets with a hemispherical shape were prepared from copy paper sheets in a specially designed forming machine. Sandwich test specimens were prepared from this core and tested in out-of-plane compression, and the load-displacement response was compared to predictions from finite element simulations. The experimental and finite element results were consistent.

  • 41.
    Jansson, Jessica
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Polymer Chemistry.
    Termoelaster i kompositkrut: En möjlig ersättning till nitrocellulosa2016Independent thesis Advanced level (professional degree), 20 credits / 30 HE creditsStudent thesis
    Abstract [sv]

    Sedan människor började använda energetiska material har risken för oönskade explosioner alltid varit ett problem. Många produktionsanläggningar och förråd har förstörts på grund av oönskad antändning energetiska material. Idag är nitrocellulosa en komponent i de flesta kanonkrut. En negativ egenskap hos nitrocellulosa är att den bryts ner över tid och eftersom det är en naturprodukt så kommer det alltid att finnas en viss skillnad mellan olika batcher. Genom att ersätta nitrocellulosa med en produkt som inte bryts ner men som fortfarande ger liknande övriga egenskaper kan kanonkrutssäkerheten öka. Termoelaster undersöktes då de är smältbara och tåliga. Smältpunkt och glastransitionstemperaturen bestämdes med differentiell svepkalorimetri, viskositeten mättes vid flera temperaturer med en reometer och mekaniska egenskaper utvärderades i en dragprovningsmaskin. De två mest lovande polymererna blandades sedan med hexamin som är ett inert material för att simulera ett kompositkrut. Agglomerering av hexamin undveks genom tillsats av små mängder pyrogen kiseldioxid. Fyllnadsgraden i systemet nådde 70 viktprocent hexamin i en polymer. Kompositmaterialen dragprovades och resultaten jämfördes med motsvarande data för två nitrocellulosabaserat krut. Kompositmaterialen hade lägre brottgräns än det ena nitrocellulosabaserade krutet men högre brottgräns än det andra nitrocellulosabaserade krutet. Kompositmaterialen hade högre E-modul än det nitrocellulosabaserade krutet men lägre brottöjning. Resultaten är lovande och visar att termoelasterna har stor potential att användas i kompositkrut. Med fortsatt undersökning och optimering av kompositmaterialen kan ett säkrare alternativ till nitrocellulosa skapas.

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  • 42.
    Jeong, Seung Hee
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Microsystems Technology. Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Electronics.
    Soft Intelligence: Liquids Matter in Compliant Microsystems2016Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    Soft matter, here, liquids and polymers, have adaptability to a surrounding geometry. They intrinsically have advantageous characteristics from a mechanical perspective, such as flowing and wetting on surrounding surfaces, giving compliant, conformal and deformable behavior. From the behavior of soft matter for heterogeneous surfaces, compliant structures can be engineered as embedded liquid microstructures or patterned liquid microsystems for emerging compliant microsystems.

    Recently, skin electronics and soft robotics have been initiated as potential applications that can provide soft interfaces and interactions for a human-machine interface. To meet the design parameters, developing soft material engineering aimed at tuning material properties and smart processing techniques proper to them are to be highly encouraged. As promising candidates, Ga-based liquid alloys and silicone-based elastomers have been widely applied to proof-of-concept compliant structures.

    In this thesis, the liquid alloy was employed as a soft and stretchable electrical and thermal conductor (resistor), interconnect and filler in an elastomer structure. Printing-based liquid alloy patterning techniques have been developed with a batch-type, parallel processing scheme. As a simple solution, tape transfer masking was combined with a liquid alloy spraying technique, which provides robust processability. Silicone elastomers could be tunable for multi-functional building blocks by liquid or liquid-like soft solid inclusions. The liquid alloy and a polymer additive were introduced to the silicone elastomer by a simple mixing process. Heterogeneous material microstructures in elastomer networks successfully changed mechanical, thermal and surface properties.

    To realize a compliant microsystem, these ideas have in practice been useful in designing and fabricating soft and stretchable systems. Many different designs of the microsystems have been fabricated with the developed techniques and materials, and successfully evaluated under dynamic conditions. The compliant microsystems work as basic components to build up a whole system with soft materials and a processing technology for our emerging society.

    List of papers
    1. Liquid alloy printing of microfluidic stretchable electronics
    Open this publication in new window or tab >>Liquid alloy printing of microfluidic stretchable electronics
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    2012 (English)In: Lab on a Chip, ISSN 1473-0197, E-ISSN 1473-0189, Vol. 22, no 12, p. 4657-4664Article in journal (Refereed) Published
    Abstract [en]

    Recently, microfluidic stretchable electronics has attracted great interest from academia since conductive liquids allow for larger cross-sections when stretched and hence low resistance at longer lengths. However, as a serial process it has suffered from low throughput, and a parallel processing technology is needed for more complex systems and production at low costs. In this work, we demonstrate such a technology to implement microfluidic electronics by stencil printing of a liquid alloy onto a semi-cured polydimethylsiloxane (PDMS) substrate, assembly of rigid active components, encapsulation by pouring uncured PDMS on-top and subsequent curing. The printing showed resolution of 200 mm and linear resistance increase of the liquid conductors when elongated up to 60%. No significant change of resistance was shown for a circuit with one LED after 1000 times of cycling between a 0% and an elongation of 60% every 2 s. A radio frequency identity (RFID) tag was demonstrated using the developed technology, showing that good performance could be maintained well into the radio frequency (RF) range.

    Place, publisher, year, edition, pages
    Royal society of chemistry, 2012
    Keywords
    liquid alloy, printing, stretchable electronics, wireless communication
    National Category
    Electrical Engineering, Electronic Engineering, Information Engineering Other Materials Engineering
    Research subject
    Engineering Science with specialization in Microsystems Technology; Engineering Science with specialization in Electronics
    Identifiers
    urn:nbn:se:uu:diva-183278 (URN)10.1039/C2LC40628D (DOI)000310865200010 ()
    Available from: 2012-10-23 Created: 2012-10-23 Last updated: 2017-12-07Bibliographically approved
    2. Adhesive transfer soft lithography: low-cost and flexible rapid prototyping of microfluidic devices, Micro and Nanosystems
    Open this publication in new window or tab >>Adhesive transfer soft lithography: low-cost and flexible rapid prototyping of microfluidic devices, Micro and Nanosystems
    2014 (English)In: micro and nanosystems, ISSN 1876-4037, Vol. 6, p. 42-49Article in journal (Refereed) Published
    Abstract [en]

    A simple and low-cost approach was proposed for prototyping PDMS based microfluidic devices by transferringadhesive film microstructures onto a flexible substrate as a mould for PDMS replicas. The microstructures were engravedon an adhesive coated film using a commercial cutting plotter and then transferred (or laminated) onto a flexiblesubstrate, allowing for engraved isolated patterns. The proposed technique was demonstrated by a hydrodynamic focusingmicrofluidic device, having splitting and re-combining sheath channels. The whole processing could be finished within 1h in a normal laboratory environment. This approach offers an easy, flexible and rapid prototyping of microfluidic andlab-on-a-chip devices to users without expertise in microfabrication. In addition, by minimizing the use of chemicals, theprocess becomes more environmentally friendly than conventional photolithography based micro-fabrication techniques.

    Place, publisher, year, edition, pages
    Bentham Science Publishers, 2014
    Keywords
    liquid alloy, printing, soft lithography, rapid prototyping
    National Category
    Other Engineering and Technologies
    Research subject
    Engineering Science with specialization in Microsystems Technology
    Identifiers
    urn:nbn:se:uu:diva-239241 (URN)
    Available from: 2014-12-19 Created: 2014-12-19 Last updated: 2016-04-22
    3. Tape Transfer Printing of a Liquid Metal Alloy for Stretchable RF Electronics
    Open this publication in new window or tab >>Tape Transfer Printing of a Liquid Metal Alloy for Stretchable RF Electronics
    2014 (English)In: Sensors, E-ISSN 1424-8220, Vol. 14, no 9, p. 16311-16321Article in journal (Refereed) Published
    Abstract [en]

    In order to make conductors with large cross sections for low impedance radio frequency (RF) electronics, while still retaining high stretchability, liquid-alloy-based microfluidic stretchable electronics offers stretchable electronic systems the unique opportunity to combine various sensors on our bodies or organs with high-quality wireless communication with the external world (devices/systems), without sacrificing enhanced user comfort. This microfluidic approach, based on printed circuit board technology, allows large area processing of large cross section conductors and robust contacts, which can handle a lot of stretching between the embedded rigid active components and the surrounding system. Although it provides such benefits, further development is needed to realize its potential as a high throughput, cost-effective process technology. In this paper, tape transfer printing is proposed to supply a rapid prototyping batch process at low cost, albeit at a low resolution of 150 mu m. In particular, isolated patterns can be obtained in a simple one-step process. Finally, a stretchable radio frequency identification (RFID) tag is demonstrated. The measured results show the robustness of the hybrid integrated system when the tag is stretched at 50% for 3000 cycles.

    Keywords
    tape transfer printing, liquid metal alloy, microfluidic stretchable electronics, stretchable RF electronics, radio frequency identification (RFID) tag
    National Category
    Electrical Engineering, Electronic Engineering, Information Engineering
    Identifiers
    urn:nbn:se:uu:diva-237588 (URN)10.3390/s140916311 (DOI)000343106600041 ()
    Available from: 2014-12-05 Created: 2014-12-03 Last updated: 2022-02-10Bibliographically approved
    4. Tape transfer atomization patterning of liquid alloys for microfluidic stretchable wireless power transfer
    Open this publication in new window or tab >>Tape transfer atomization patterning of liquid alloys for microfluidic stretchable wireless power transfer
    2015 (English)In: Scientific Reports, E-ISSN 2045-2322, Vol. 5, p. 8419-Article in journal (Refereed) Published
    Abstract [en]

    Stretchable electronics offers unsurpassed mechanical compliance on complex or soft surfaces like the human skin and organs. To fully exploit this great advantage, an autonomous system with a self-powered energy source has been sought for. Here, we present a new technology to pattern liquid alloys on soft substrates, targeting at fabrication of a hybrid-integrated power source in microfluidic stretchable electronics. By atomized spraying of a liquid alloy onto a soft surface with a tape transferred adhesive mask, a universal fabrication process is provided for high quality patterns of liquid conductors in a meter scale. With the developed multilayer fabrication technique, a microfluidic stretchable wireless power transfer device with an integrated LED was demonstrated, which could survive cycling between 0% and 25% strain over 1,000 times.

    National Category
    Mechanical Engineering
    Research subject
    Engineering Science with specialization in Microsystems Technology
    Identifiers
    urn:nbn:se:uu:diva-247504 (URN)10.1038/srep08419 (DOI)000349245600018 ()25673261 (PubMedID)
    Available from: 2015-03-19 Created: 2015-03-19 Last updated: 2022-09-15Bibliographically approved
    5. Stretchable wireless power transfer with a liquid alloy coil
    Open this publication in new window or tab >>Stretchable wireless power transfer with a liquid alloy coil
    2015 (English)In: Micro Electro Mechanical Systems (MEMS), 2015 28th IEEE International Conference on, 2015, p. 1137-1140Conference paper, Published paper (Refereed)
    Abstract [en]

    An integrated stretchable wireless power transfer device was demonstrated by packaging rigid electronic chips onto a liquid alloy coil patterned on a half-cured polydimethylsiloxane (PDMS) surface. To obtain low enough resistance, the long liquid alloy coil with a large cross section was made with a tape transfer masking followed by spray deposition of the liquid alloy. The measured results indicated the wireless power transfer efficiency reached 10% at 140 kHz and good performance under 25% overall strain. Different sizes of liquid alloy coils and a soft magnetic composite core were tested to improve the efficiency of the system.

    Series
    Proceedings IEEE Micro Electro Mechanical Systems, ISSN 1084-6999
    Keywords
    Liquid alloy, Stretchable electronics, Wireless power transfer, Smart system integration
    National Category
    Engineering and Technology
    Research subject
    Materials Science
    Identifiers
    urn:nbn:se:uu:diva-265529 (URN)10.1109/MEMSYS.2015.7051165 (DOI)000370382900296 ()978-1-4799-7955-4 (ISBN)
    Conference
    Micro Electro Mechanical Systems (MEMS), 2015 28th IEEE International Conference on, Estoril, January 18-22, 2015
    Available from: 2015-10-31 Created: 2015-10-31 Last updated: 2016-04-21Bibliographically approved
    6. Mechanically Stretchable and Electrically Insulating Thermal Elastomer Composite by Liquid Alloy Droplet Embedment
    Open this publication in new window or tab >>Mechanically Stretchable and Electrically Insulating Thermal Elastomer Composite by Liquid Alloy Droplet Embedment
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    2015 (English)In: Scientific Reports, E-ISSN 2045-2322, Vol. 5, article id 18257Article in journal (Refereed) Published
    Abstract [en]

    Stretchable electronics and soft robotics have shown unsurpassed features, inheriting remarkable functions from stretchable and soft materials. Electrically conductive and mechanically stretchable materials based on composites have been widely studied for stretchable electronics as electrical conductors using various combinations of materials. However, thermally tunable and stretchable materials, which have high potential in soft and stretchable thermal devices as interface or packaging materials, have not been sufficiently studied. Here, a mechanically stretchable and electrically insulating thermal elastomer composite is demonstrated, which can be easily processed for device fabrication. A liquid alloy is embedded as liquid droplet fillers in an elastomer matrix to achieve softness and stretchability. This new elastomer composite is expected useful to enhance thermal response or efficiency of soft and stretchable thermal devices or systems. The thermal elastomer composites demonstrate advantages such as thermal interface and packaging layers with thermal shrink films in transient and steady-state cases and a stretchable temperature sensor.

    National Category
    Textile, Rubber and Polymeric Materials Mechanical Engineering
    Identifiers
    urn:nbn:se:uu:diva-272055 (URN)10.1038/srep18257 (DOI)000366451800001 ()26671673 (PubMedID)
    Funder
    Swedish Research Council, 621-2010-5443 621-2014-5596Swedish Foundation for Strategic Research , EM11-0002 SE13-0061
    Available from: 2016-01-12 Created: 2016-01-11 Last updated: 2022-09-15Bibliographically approved
    7. PDMS-Based Elastomer Tuned Soft, Stretchable, and Sticky for epidermal electronics
    Open this publication in new window or tab >>PDMS-Based Elastomer Tuned Soft, Stretchable, and Sticky for epidermal electronics
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    2016 (English)In: Advanced Materials, ISSN 0935-9648, E-ISSN 1521-4095, Vol. 28, no 28, p. 5830-5836Article in journal (Refereed) Published
    Abstract [en]

    Targeting good user experiences, softness and stretchability are essential features for epidermal devices in body signal monitoring and body area stimulation. A highly soft, stretchable and sticky polydimethylsiloxane based elastomer (S3-PDMS) is achieved by a simple process with a widely used siloxane precursors, the properties of which are tuned by adding small fractions of an amine-based polymer, ethoxylated polyethylenimine (EPEI). This allows formation of a thick unobstrusive patch and may ease implementation of epidermal electronics in wearable healthcare applications. 

    Keywords
    Adhesion, Compliance, Elongation at break, Epidermal electronics, PDMS-based elastomer tuning
    National Category
    Textile, Rubber and Polymeric Materials Applied Mechanics Polymer Chemistry
    Research subject
    Engineering Science with specialization in Materials Science
    Identifiers
    urn:nbn:se:uu:diva-281212 (URN)10.1002/adma.201505372 (DOI)000382400900004 ()
    Funder
    Swedish Research Council, 2010-5443
    Available from: 2016-03-21 Created: 2016-03-21 Last updated: 2017-11-30Bibliographically approved
    8. Stretchable thermoelectric generators metallized with liquid alloy
    Open this publication in new window or tab >>Stretchable thermoelectric generators metallized with liquid alloy
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    2017 (English)In: ACS Applied Materials and Interfaces, ISSN 1944-8244, E-ISSN 1944-8252, Vol. 9, no 18, p. 15791-15797Article in journal (Refereed) Published
    Abstract [en]

    Conventional thermoelectric generators (TEGs) are normally hard, rigid, and flat. However, most objects have curvy surfaces, which require soft and even stretchable TEGs for maximizing efficiency of thermal energy harvesting. Here, soft and stretchable TEGs using conventional rigid Bi2Te3 pellets metallized with a liquid alloy is reported. The fabrication is implemented by means of a tailored layer-by-layer fabrication process. The STEGs exhibit an output power density of 40.6 mu W/cm(2) at room temperature. The STEGs are operational after being mechanically stretched-and-released more than 1000 times, thanks to the compliant contact between the liquid alloy interconnects and the rigid pellets. The demonstrated interconnect scheme will provide a new route to the development of soft and stretchable energy-harvesting avenues for a variety of emerging electronic applications.

    National Category
    Energy Engineering Textile, Rubber and Polymeric Materials Other Engineering and Technologies not elsewhere specified
    Identifiers
    urn:nbn:se:uu:diva-281213 (URN)10.1021/acsami.7b04752 (DOI)000401307100064 ()28453282 (PubMedID)
    Funder
    Swedish Foundation for Strategic Research , EM11-0002, SE13-0061Swedish Research Council, 621-2014-5596
    Available from: 2016-03-21 Created: 2016-03-21 Last updated: 2017-07-04Bibliographically approved
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  • 43.
    Jeong, Seung Hee
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Microsystems Technology.
    Chen, Si
    Chalmers University of Technology.
    Huo, Jinxing
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Mechanics.
    Gravier, Laurent
    University of Applied Sciences and Arts Western Switzerland.
    Gamstedt, Erik Kristofer
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Mechanics.
    Liu, Johan
    Chalmers University of Technology.
    Zhang, Shi-Li
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Electronics.
    Zhang, Zhi-Bin
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Electronics.
    Wu, Zhigang
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Microsystems Technology. Huazhong Univ Sci & Technol, State Key Lab Digital Mfg Equipment & Technol, Wuhan, Peoples R China.
    Hjort, Klas
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Microsystems Technology.
    Thermal Elastomer Composites for Soft Transducers2015Conference paper (Refereed)
    Abstract [en]

    There is a need for thermal elastomer composites (TEC) which are stretchable, electrically insulating and easily processablefor soft and stretchable sensor or actuator systems as a thermal conductor or heat spreader at an interface or in a package.A novel TEC was made by embedding a gallium based liquid alloy (Galinstan) as a droplet in polydimethylsiloxane (PDMS,Elastosil RT 601) matrix with a high speed mechanical mixing process.

  • 44.
    Joffre, Thomas
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    Miettinen, Arttu
    Wernersson, Erik L. G.
    Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Division of Visual Information and Interaction. Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Computerized Image Analysis and Human-Computer Interaction.
    Isaksson, Per
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Mechanics.
    Gamstedt, E. Kristofer
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Mechanics.
    Effects of defects on the tensile strength of short-fibre composite materials2014In: Mechanics of materials, ISSN 0167-6636, E-ISSN 1872-7743, Vol. 75, p. 125-134Article in journal (Refereed)
  • 45.
    Joffre, Thomas
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    Wernersson, Erik L. G.
    Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Division of Visual Information and Interaction. Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Computerized Image Analysis and Human-Computer Interaction.
    Miettinen, Arttu
    Luengo Hendriks, Cris L.
    Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Division of Visual Information and Interaction. Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Computerized Image Analysis and Human-Computer Interaction.
    Gamstedt, E. Kristofer
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Mechanics.
    Swelling of cellulose fibres in composite materials: Constraint effects of the surrounding matrix2013In: Composites Science And Technology, ISSN 0266-3538, E-ISSN 1879-1050, Vol. 74, p. 52-59Article in journal (Refereed)
  • 46.
    Jung, Jiyoung
    et al.
    Korea Adv Inst Sci & Technol KAIST, Dept Mech Engn, 291 Daehak Ro, Daejeon 34141, South Korea..
    Jeong, Seung Hee
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Materials Science and Engineering, Microsystems Technology.
    Hjort, Klas
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Materials Science and Engineering, Microsystems Technology.
    Ryu, Seunghwa
    Korea Adv Inst Sci & Technol KAIST, Dept Mech Engn, 291 Daehak Ro, Daejeon 34141, South Korea..
    Investigation of thermal conductivity for liquid metal composites using the micromechanics-based mean-field homogenization theory2020In: Soft Matter, ISSN 1744-683X, E-ISSN 1744-6848, Vol. 16, no 25, p. 5840-5847Article in journal (Refereed)
    Abstract [en]

    For the facile use of liquid metal composites (LMCs) for soft, stretchable and thermal systems, it is crucial to understand and predict the thermal conductivity of the composites as a function of liquid metal (LM) volume fraction and applied strain. In this study, we investigated the effective thermal conductivity of LMCs based on various mean-field homogenization frameworks including Eshelby, MoriTanaka, differential and double inclusion methods. The double inclusion model turned out to make the prediction closest to the experimental results in a wide range of LM volume fractions. Interestingly, we found that the theoretical models based on the assumption of ideal LM dispersion and zero interfacial resistance underestimated the thermal conductivity compared to the experimental results in a low volume fraction regime. By considering the accompanied variations in the LM inclusion's aspect ratios under a typical size distribution of inclusions (Bmm), the change of effective thermal conductivity was predicted under a uniaxial 300% tensile strain. Our study will deepen the understanding of the thermal properties of LMCs and support the designs of stretchable thermal interfaces and packaging with LMCs in the future.

  • 47.
    Kilic, Nuzhet I.
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Materials Science and Engineering, Microsystems Technology. Department of Applied Physics, Biomedical and X-ray Physics, KTH Royal Institute of Technology, SE 10691 Stockholm, Sweden.
    Saladino, Giovanni M.
    Department of Applied Physics, Biomedical and X-ray Physics, KTH Royal Institute of Technology, SE 10691 Stockholm, Sweden.
    Johansson, Sofia
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Materials Science and Engineering, Microsystems Technology. Uppsala University, Science for Life Laboratory, SciLifeLab.
    Shen, Rickard
    Kanthal AB, SE 73427 Hallstahammar, Sweden.
    McDorman, Cacie
    Alleima Advanced Materials, Palm Coast, Florida 32164, United States.
    Toprak, Muhammet S.
    Department of Applied Physics, Biomedical and X-ray Physics, KTH Royal Institute of Technology, SE 10691 Stockholm, Sweden.
    Johansson, Stefan
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Materials Science and Engineering, Microsystems Technology.
    Two-Photon Polymerization Printing with High Metal Nanoparticle Loading2023In: ACS Applied Materials and Interfaces, ISSN 1944-8244, E-ISSN 1944-8252, Vol. 15, no 42, p. 49794-49804Article in journal (Refereed)
    Abstract [en]

    Two-photon polymerization (2PP) is an efficient technique to achieve high-resolution, three-dimensional (3D)-printed complex structures. However, it is restricted to photocurable monomer combinations, thus presenting constraints when aiming at attaining functionally active resist formulations and structures. In this context, metal nanoparticle (NP) integration as an additive can enable functionality and pave the way to more dedicated applications. Challenges lay on the maximum NP concentrations that can be incorporated into photocurable resist formulations due to the laser-triggered interactions, which primarily originate from laser scattering and absorption, as well as the limited dispersibility threshold. In this study, we propose an approach to address these two constraints by integrating metallic Rh NPs formed ex situ, purposely designed for this scope. The absence of surface plasmon resonance (SPR) within the visible and near-infrared spectra, coupled with the limited absorption value measured at the laser operating wavelength (780 nm), significantly limits the laser-induced interactions. Moreover, the dispersibility threshold is increased by engineering the NP surface to be compatible with the photocurable resin, permitting us to achieve concentrations of up to 2 wt %, which, to our knowledge, is significantly higher than the previously reported limit (or threshold) for embedded metal NPs. Another distinctive advantage of employing Rh NPs is their role as promising contrast agents for X-ray fluorescence (XRF) bioimaging. We demonstrated the presence of Rh NPs within the whole 2PP-printed structure and emphasized the potential use of NP-loaded 3D-printed nanostructures for medical devices.

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  • 48.
    Källquist, Ida
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Structural Chemistry.
    Lithium titanium oxide materials for hybrid supercapacitor applications2016Independent thesis Advanced level (professional degree), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    The objective of this thesis was to investigate the suitability of some different Li4Ti5O12 materials as a negative electrode in hybrid supercapacitors. A hybrid supercapacitor is a combination of a battery and an electric double-layer capacitor that uses both a battery material and a capacitor material in the same device. The target for these combination devices is to bridge the performance gap between batteries and capacitors and enable both high energy and power density. To achieve this, materials with high capacity as well as high rate capability are needed. To improve the rate of the commonly slow battery materials nanosizing has been found to be an effective solution.

    This study shows that Li4Ti5O12 has a significantly higher experimental capacity than the most common capacitor material, activated carbon. The capacity remained high even at high discharge rates due to a successful nanostructuring that increased the accessibility of the material and shortened the diffusion distance for the ions, leading to a much improved power performance compared with the bulk material. The use of a nanostructured Li4Ti5O12 material in a hybrid device together with activated carbon was estimated to double the energy density compared to an electric double-layer capacitor and maintain the same good power performance. To further increase the energy density also improved materials for the positive electrode should be investigated.

  • 49.
    Larsson, Niklas
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    Gradient formation in cemented carbides with 85Ni:15Fe-binder phase2015Independent thesis Advanced level (professional degree), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    In today’s inserts used for metal cutting the binder phase consists of cobalt (Co).However, EU’s REACH programme and the U.S’s National Toxicity Programme(NTP) classified Co as toxic/carcinogenic. Therefore, there is a strong need toinvestigate alternative binder phases. This thesis covers sintering and characterisationof cemented carbide with a binder phase consisting of nickel (Ni) and iron (Fe) withthe composition of 85Ni:15Fe. The aim was to study the gradient formation of turninginsert and find sintering processes to achieve a gradient structure with the targetedthickness of 26 microns.

    Simulations in ThermoCalc provided a suitable composition and a starting point forsintering parameters. The influences of sintering process parameters, such as holdingtime, temperature and counter pressure on the formation of the gradient zone wereinvestigated. Hot isostatic pressing (HIP) sintering was done in order to study thegradient formation as well as to reduce the porosity when needed. Sintered insertswere analysed by light optical microscopy.

    It was found that there are at least three possible ways to control the formation ofthe gradient: sintering in vacuum with a holding time of 20 min at 1450°C, sintering at1450°C with a counter pressure of 5 mbar nitrogen, and sintering with a counterpressure of 11.5 mbar followed by a double sinter-hip with 55 bar argon atmosphere.However, only the last process fulfilled the microstructure criteria in terms ofporosity and binder phase distribution. It is clear that the formation of gradient zonesin 85Ni:15Fe can be predicted, however calculations and simulations need to beoptimized in order to get more accurate results.

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    Gradient formation in cemented carbides with 85Ni:15Fe-binder phase
  • 50.
    Laskar, Partha
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström.
    Varghese, Oommen P.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Macromolecular Chemistry.
    Shastri, V. Prasad
    Univ Freiburg, Inst Macromol Chem, D-79104 Freiburg, Germany.;Univ Freiburg, BIOSS Ctr Biol Signalling Studies, D-79104 Freiburg, Germany..
    Advances in Intracellular and On-Surface Polymerization in Living Cells: Implications for Nanobiomedicines2023In: Advanced NanoBiomed Research, ISSN 2699-9307, Vol. 3, no 8, article id 2200174Article, review/survey (Refereed)
    Abstract [en]

    The cellular environment offers some unique features to carry out polymerizations under controlled conditions. Polymerization of monomers in cellular compartments and on the surface of living organisms holds much promise in the engineering of biofunctional synthetic polymers for sensing and probing cell behavior and of late has received significant interest. This effort lies at the interface of synthetic biology and polymer chemistry and can pave the way for innovative solutions to many existing challenges in healthcare, environment, energy, and the study of the "origin of life". Herein, recent advances in controlled polymerization strategies for intracellular and surface of living cells are presented with a particular emphasis on nanobiomedicines. Furthermore, polymerization strategies, cytocompatible monomer structures, compatible cell lines and microorganisms, nature of stimulus, catalysts, along with specific polymerization conditions to produce non-natural biofunctional polymers that can undergo polymerization-induced self-assembly within and onto the living cells are presented in detail. Furthermore, the review offers a window into the future of such novel emerging synthetic bionano systems in biomedical sciences.

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