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  • 1.
    Abenayake, Himesha
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Materials Science and Engineering, Applied Material Science. Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Inorganic Chemistry.
    Additively Manufactured Rare Earth Free Permanent Magnets2023Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    It’s well known that MnAl(C) material consists of a metastable phase (τ) with promising ferromagnetic properties, produced either by controlled cooling from the high-temperature hexagonal ε-phase or rapid cooling that freezes the ε-phase followed by low-temperature annealing. Due to the high cooling rates involved, additive manufacturing (AM) especially selective laser melting (SLM), has been identified as a possible method to retain the high-temperature ε-phase, hence containing a potential capacity to produce permanent magnets upon low-temperature annealing. Moreover, the competency of additive manufacturing to address manufacturing design complexity, material scarcity and tailored properties, yields a great opportunity to produce permanent magnets with suitable magnetic properties for complex applications. This work provides a systematic study on three main aspects; development of printing parameters for improved relative density of as-printed MnAl(C) samples; investigation of the influence of scanning strategies on the crystallographic texture of as-printed and annealed samples; investigation of the influence of annealing time and temperature on τ-phase purity and magnetic properties. It was found that laser remelting (multiple laser exposure) combined with specific scanning strategies is a promising path to enhance the relative density of as-printed samples. Some specific scanning strategies were found to be capable of retaining relatively strong crystallographic textured ε-phase in as-printed samples. Following the annealing process for ε→τ transformation, only a partial transformation of crystallographic texture was observed. Characterization of annealed samples through XRD (x-ray diffraction) and phase fractions calculations through Rietveld refinement reveals that relatively short annealing times and low temperatures result in incomplete ε→τ transformation. In addition, longer annealing times and higher temperatures surpass the complete ε→τ transformation and lead to the formation of equilibrium phases subsequently reducing the magnetic performance. Furthermore, the experimental findings demonstrated a pronounced influence of higher carbon content in the powder, resulting in improved magnetic properties.

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    Additively Manufactured Rare Earth Free Permanent Magnets
  • 2.
    Afroze, Shammya
    et al.
    Univ Brunei Darussalam, Fac Integrated Technol, Jalan Tungku Link, BE-1410 Gadong, Brunei; Chalmers Univ Technol, Dept Chem & Chem Engn, SE-41296 Gothenburg, Sweden..
    Torino, Nico
    Chalmers Univ Technol, Dept Chem & Chem Engn, SE-41296 Gothenburg, Sweden..
    Reza, Md Sumon
    Univ Brunei Darussalam, Fac Integrated Technol, Jalan Tungku Link, BE-1410 Gadong, Brunei..
    Radenahmad, Nikdalila
    Univ Brunei Darussalam, Fac Integrated Technol, Jalan Tungku Link, BE-1410 Gadong, Brunei..
    Cheok, Quentin
    Univ Brunei Darussalam, Fac Integrated Technol, Jalan Tungku Link, BE-1410 Gadong, Brunei..
    Henry, Paul F.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Inorganic Chemistry. Rutherford Appleton Lab, ISIS Pulsed Neutron & Muon Facil, Harwell Campus, Didcot OX11 0QX, Oxon, England..
    Azad, Abul K.
    Univ Brunei Darussalam, Fac Integrated Technol, Jalan Tungku Link, BE-1410 Gadong, Brunei..
    Structure-conductivity relationship of PrBaMnMoO6-δ through in-situ measurements: A neutron diffraction study2021In: Ceramics International, ISSN 0272-8842, E-ISSN 1873-3956, Vol. 47, no 1, p. 541-546Article in journal (Refereed)
    Abstract [en]

    The structural and electrochemical properties of the double perovskite-type oxide, PrBaMnMoO6-δ, was investigated using neutron diffraction with in-situ conductivity measurement under a dry Argon atmosphere from 25 °C to 700 °C. A Rietveld refinement of the neutron diffraction data confirmed monoclinic symmetry in the P21/n space group. Rietveld refinement also confirms the unit cell parameters of a = 5.6567 (1) Å, b = 5.6065 (2) Å, c = 7.9344 (1) Å and β = 84.43° with reliable atomic positions and refinement factors (R-factors). Neutron diffraction data refinement shows two minor phases (< 5%), an orthorhombic AB2O5 type phase of PrMn2O5 in the Pbam (No. 32) space group with unit cell parameters, a = 7.9672 (1) Å, b = 8.9043 (2) Å and c = 5.8540 (1) Å and a scheelite phase of BaMoO4 in the tetragonal I41/a (88) space group with the unit cell parameters, a = b = 5.9522 (1) Å, and c = 12.3211 (2) Å. Morphological images revealed a porous and intertwined microstructure. In-situ conductivity measurement shows that the total conductivity of this material was 130.84 Scm−1 at 700 °C.

  • 3.
    Afroze, Shammya
    et al.
    Univ Brunei Darussalam, Fac Integrated Technol, Jalan Tungku Link, BE-1410 Bandar Seri Begawan, Brunei; Chalmers Univ Technol, Dept Chem & Chem Engn, SE-41296 Gothenburg, Sweden.
    Yilmaz, Duygu
    Chalmers Univ Technol, Dept Chem & Chem Engn, SE-41296 Gothenburg, Sweden.
    Reza, Md Sumon
    Univ Brunei Darussalam, Fac Integrated Technol, Jalan Tungku Link, BE-1410 Bandar Seri Begawan, Brunei.
    Henry, Paul F.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Inorganic Chemistry. Rutherford Appleton Lab, ISIS Pulsed Neutron & Muon Facil, Harwell Campus, Didcot OX11 0QX, Oxon, England.
    Cheok, Quentin
    Univ Brunei Darussalam, Fac Integrated Technol, Jalan Tungku Link, BE-1410 Bandar Seri Begawan, Brunei.
    Zaini, Juliana H.
    Univ Brunei Darussalam, Fac Integrated Technol, Jalan Tungku Link, BE-1410 Bandar Seri Begawan, Brunei.
    Azad, Abul K.
    Univ Brunei Darussalam, Fac Integrated Technol, Jalan Tungku Link, BE-1410 Bandar Seri Begawan, Brunei.
    Issakhov, Alibek
    Al Farabi Kazakh Natl Univ, Dept Math & Comp Modelling, Fac Mech & Math, Alma Ata, Kazakhstan.
    Sadeghzadeh, Milad
    Univ Tehran, Dept Renewable Energy & Environm Engn, Tehran, Iran.
    Investigation of Structural and Thermal Evolution in Novel Layered Perovskite NdSrMn2O5+δ via Neutron Powder Diffraction and Thermogravimetric Analysis2020In: International Journal of Chemical Engineering, ISSN 1687-806X, E-ISSN 1687-8078, Vol. 2020, article id 6642187Article in journal (Refereed)
    Abstract [en]

    Neutron diffraction is one of the best methods for structural analysis of a complex, layered perovskite material with low symmetry by accurately detecting the oxygen positions through octahedral tilting. In this research, the crystal structure of NdSrMn2O5+δ was identified through X-ray diffraction (XRD) and neutron powder diffraction (NPD) at room temperature (RT), which indicated the formation of a layered structure in orthorhombic symmetry in the Pmmm (no. 47) space group. Rietveld refinement of the neutron diffraction data has confirmed the orthorhombic symmetry with unit cell parameters (a = 3.8367 (1) Å, b = 3.8643 (2) Å, and c = 7.7126 (1) Å), atomic positions, and oxygen occupancy. Thermogravimetric analysis revealed the total weight loss of about 0.10% for 20–950°C temperature, which occurred mainly to create oxygen vacancies at high temperatures. Rietveld analyses concurred with the XRD and neutron data allowing correlation of occupancy factors of the oxygen sites.

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    FULLTEXT01
  • 4.
    Aguirre Castillo, José
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Inorganic Chemistry.
    Optimisation of the bottom stirring praxis in a LD-LBE converter: Investigations and tests on phosphorous removal, nitrogen as stirring gas, and slopping2015Independent thesis Advanced level (professional degree), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    The LD-process, called after the cities Linz and Donawitz, is used to convert pig iron into crude steel by blowing oxygen on top of the pig iron. A LD-LBE converter, Lance Bubbling Equilibrium, also stirs the melt trough a bottom stirring system.

    The bottom stirring in a LD-LBE converter is believed to have a positive effect alone on the phosphorous removal. Previous studies have shown that the temperature and slag composition are the main factors affecting phosphorus removal. Phosphorus binds to the slag easier at low temperature and to slag with certain levels of dissolved calcium (a process additive). Different praxes were tested and a better dephosphorisation was reached. The bottom stirrings effect on the dissolution of calcium additives is a possible explanation to the results and mechanisms presented in this study.

    The study also aimed to investigate the use of nitrogen as stirring gas instead of argon. Nitrogen is removed from the steel during the formation of carbon oxide gases. Nitrogen was used in varying amounts as stirring gas during the first half of the oxygen blow. It proved to be safe to use as long as there was a high content of carbon in the melt. However using nitrogen beyond half of the blow showed to be risky for nitrogen sensible steels; even in small amounts since there is not enough carbon left to degas the steel from nitrogen.

    Slopping happens when formed gas from the LD-process is trapped in the slag. The slag level rises and sometimes it floods the converter resulting in yield losses. The influence of the bottom stirring on slopping was studied, which resulted in the conclusion that slopping cannot be avoided by simply improving the bottom stirring.

    Although some verification studies remains to be done, if the suggestions based on the results of this thesis were employed, savings in the oxygen and stirring gas economies could be made. Not least improvements on the iron yield.

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  • 5.
    Ahlberg, Patrik
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Electronics.
    Johansson, Fredrik
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Condensed Matter Physics of Energy Materials.
    Zhang, Zhibin
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Electronics.
    Jansson, Ulf
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Inorganic Chemistry.
    Zhang, Shi-Li
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Electronics.
    Lindblad, Andreas
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Condensed Matter Physics of Energy Materials.
    Nyberg, Tomas
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Electronics.
    Defect formation in graphene during low-energy ion bombardment2016In: APL Materials, E-ISSN 2166-532X, Vol. 4, no 4, article id 046104Article in journal (Refereed)
    Abstract [en]

    This letter reports on a systematic investigation of sputter induced damage in graphene caused by low energy Ar+ ion bombardment. The integral numbers of ions per area (dose) as well as their energies are varied in the range of a few eV's up to 200 eV. The defects in the graphene are correlated to the dose/energy and different mechanisms for the defect formation are presented. The energetic bombardment associated with the conventional sputter deposition process is typically in the investigated energy range. However, during sputter deposition on graphene, the energetic particle bombardment potentially disrupts the crystallinity and consequently deteriorates its properties. One purpose with the present study is therefore to demonstrate the limits and possibilities with sputter deposition of thin films on graphene and to identify energy levels necessary to obtain defect free graphene during the sputter deposition process. Another purpose is to disclose the fundamental mechanisms responsible for defect formation in graphene for the studied energy range.

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  • 6.
    Ahlberg, Patrik
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Electronics.
    Nyberg, Tomas
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Electronics.
    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.
    Jansson, Ulf
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Inorganic Chemistry.
    Toward synthesis of oxide films on graphene with sputtering based processes2016In: Journal of Vacuum Science & Technology B, ISSN 1071-1023, E-ISSN 1520-8567, Vol. 34, no 4, article id 040605Article in journal (Refereed)
    Abstract [en]

    The impact of energetic particles associated with a sputter deposition process may introduce damage to single layer graphene films, making it challenging to apply this method when processing graphene. The challenge is even greater when oxygen is incorporated into the sputtering process as graphene can be readily oxidized. This work demonstrates a method of synthesizing ZnSn oxide on graphene without introducing an appreciable amount of defects into the underlying graphene. Moreover, the method is general and applicable to other oxides. The formation of ZnSn oxide is realized by sputter deposition of ZnSn followed by a postoxidation step. In order to prevent the underlying graphene from damage during the initial sputter deposition process, the substrate temperature is kept close to room temperature, and the processing pressure is kept high enough to effectively suppress energetic bombardment. Further, in the subsequent postannealing step, it is important not to exceed temperatures resulting in oxidation of the graphene. The authors conclude that postoxidation of ZnSn is satisfactorily performed at 300 degrees C in pure oxygen at reduced pressure. This process results in an oxidized ZnSn film while retaining the initial quality of the graphene film.

  • 7.
    Ahmed, Taha
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Structural Chemistry.
    Fondell, Mattis
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Inorganic Chemistry.
    Younesi, Reza
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Structural Chemistry.
    Donzel-Gargand, Olivier
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Materials Science and Engineering, Solar Cell Technology.
    Boman, Mats
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Inorganic Chemistry.
    Zhu, Jiefang
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Structural Chemistry.
    Preparation and characterisation of ZnO/Fe2O3 core–shell nanorodsManuscript (preprint) (Other academic)
    Abstract [en]

    ZnO is a widely used semiconductor photocatalyst. However, the bandgap of ZnO is too large to utilise visible light or solar energy. Therefore, ZnO can couple with a narrow band gap semiconductor that is a visible-light-responsive photocatalyst. ZnO can help with charge seperation through attracting electrons or holes from the other semiconductor. In this work, ZnO nanorods were electrodeposited on FTO glass, and then coated with ultrathin layer of Fe2O3 via ALD.

    SEM, TEM, XPS, Raman and UV-Vis spectroscopies were used to characterise the prepared samples. Raman shows that ALD-coated Fe2O3 is hematite (α-Fe2O3). The prepared ZnO/Fe2O3 shows photocatalytic activity of EBT degradation under visible light illumination. The synthetic strategy can also beextended to prepare other heterostructured photocatalysts.

  • 8.
    Ahmed, Taha
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Structural Chemistry.
    Thyr, Jakob
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Materials Science and Engineering, Solid State Physics.
    Naim Katea, Sarmad
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Inorganic Chemistry.
    Westin, Gunnar
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Inorganic Chemistry.
    Edvinsson, Tomas
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Inorganic Chemistry. Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Materials Science and Engineering, Solid State Physics. Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Structural Chemistry.
    Phonon–phonon and electron–phonon coupling in nano-dimensional ZnOManuscript (preprint) (Other academic)
    Abstract [en]

    Thermal losses through vibrational coupling are critical bottlenecks limiting several materials classes from reaching their full potential. Altering the phonon–phonon and electron–phonon coupling by controlled suppression of vibrational degrees of freedom through low-dimensionality are promising but still largely unexplored approaches. Here we report a detailed study of the first- and second-order Raman processes as a function of size for low-dimensional ZnO. Wurtzite ZnO nanoparticles were synthesised into 3D frameworks of ZnO crystallites, with tailored crystallite diameters from 10 nm to 150 nm and characterised by electron microscopy, X-ray diffraction and non-resonant and resonant Raman spectroscopy.

    We present a short derivation of how resonance Raman and the relation between the longitudinal optical (LO) phonons can be utilised to quantify the electron–phonon coupling, its merits, and limitations. Theoretical Raman response using density functional theory is corroborating the experimental data in assigning first- and second-order Raman modes. The Lyddane-Sachs-Teller equation was applied to the measured LO–TO split and revealed no change in the ratio between the static and high-frequency dielectric constant with changing ZnO dimension from 10 nm to 150 nm. The second-order Raman revealed a phonon–phonon coupling that generally increased with particle size and markedly so for differential modes. Resonance Raman showed the fundamental LO mode and the 2nd, 3rd, and 4th overtones. The intensity relation between the fundamental LO mode and its overtones enabled the extraction of the change in electron–phonon coupling via the Huang-Rhys parameter as a function of particle size, which showed an increase with particle size.

  • 9.
    Albertsson, Samuel
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Inorganic Chemistry.
    Metoder för tjockleksmätning av kopparoxidskikt på kopparkapslar, samt tillverkning av referensprover2022Independent thesis Advanced level (professional degree), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    Swedish Nuclear Fuel and Waste Management Company, SKB, main mission is to manage and take care of the Swedish nuclear waste. The method chosen is to store the waste far down in the ground in capsules made of copper, which needs to be intact for 100 thousands years. Friction stir welding is used to seal the capsules, which causes oxidation due to heat, but is avoided by using gas protection. If this protection fails, SKB needs to be able to measure the thickness of the oxide to be able to determine if there is too much oxygen in the capsules, which can cause problems in the long run by making the capsules disintegrate and leaking nuclear waste. In this work different methods that SKB can use to measure the thickness of the copperoxide are examined. To find a method for thickness measurements several methods were examined through literature (Spectral-reflectance, Terahertz Time-Domain Spectroscopy, Laser absorption and usage of color). One of these was tested in practice, which was spectral-reflectance. Reference samples were manufactured with known oxide thickness to be used for callibration and teseting of the chosen instrument. The spectral-reflectance measurements were performed on the samples from the work which gave results that agreed with ellipsometry measurements that were made to verify the thickness of the oxides. Since spectral-reflectance worked on the samples and it is a non-contact and non-destructive method, it was the chosen method to be suggested to SKB.

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  • 10.
    Alfakes, Boulos
    et al.
    Khalifa Univ Sci & Technol, LENS, Masdar Campus, Abu Dhabi 54224, U Arab Emirates.;Khalifa Univ Sci & Technol, Dept Mech & Mat Engn, Masdar Campus, Abu Dhabi 54224, U Arab Emirates..
    Garlisi, Corrado
    Khalifa Univ Sci & Technol, Dept Chem Engn, Masdar Campus, Abu Dhabi 54224, U Arab Emirates.;Khalifa Univ Sci & Technol, Res & Innovat CO2 & H2 RICH Ctr, POB 127788, Abu Dhabi, U Arab Emirates..
    Villegas, Juan
    New York Univ, Dept Elect & Comp Engn, Abu Dhabi 129118, U Arab Emirates..
    Al-Hagri, Abdulrahman
    Khalifa Univ Sci & Technol, LENS, Masdar Campus, Abu Dhabi 54224, U Arab Emirates.;Khalifa Univ Sci & Technol, Dept Mech & Mat Engn, Masdar Campus, Abu Dhabi 54224, U Arab Emirates..
    Tamalampudi, Srinivasa
    Khalifa Univ Sci & Technol, LENS, Masdar Campus, Abu Dhabi 54224, U Arab Emirates.;Khalifa Univ Sci & Technol, Dept Mech & Mat Engn, Masdar Campus, Abu Dhabi 54224, U Arab Emirates..
    Rajput, Nitul S.
    Khalifa Univ Sci & Technol, LENS, Masdar Campus, Abu Dhabi 54224, U Arab Emirates.;Khalifa Univ Sci & Technol, Dept Mech & Mat Engn, Masdar Campus, Abu Dhabi 54224, U Arab Emirates..
    Lu, Jin-You
    Khalifa Univ Sci & Technol, LENS, Masdar Campus, Abu Dhabi 54224, U Arab Emirates.;Khalifa Univ Sci & Technol, Dept Mech & Mat Engn, Masdar Campus, Abu Dhabi 54224, U Arab Emirates..
    Lewin, Erik
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Inorganic Chemistry.
    Sá, Jacinto
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Physical Chemistry. Polish Acad Sci, Inst Phys Chem, PL-01224 Warsaw, Poland..
    Almansouri, Ibraheem
    Khalifa Univ Sci & Technol, LENS, Masdar Campus, Abu Dhabi 54224, U Arab Emirates..
    Palmisano, Giovanni
    Khalifa Univ Sci & Technol, Dept Chem Engn, Masdar Campus, Abu Dhabi 54224, U Arab Emirates.;Khalifa Univ Sci & Technol, Res & Innovat CO2 & H2 RICH Ctr, POB 127788, Abu Dhabi, U Arab Emirates..
    Chiesa, Matteo
    Khalifa Univ Sci & Technol, LENS, Masdar Campus, Abu Dhabi 54224, U Arab Emirates.;Khalifa Univ Sci & Technol, Dept Mech & Mat Engn, Masdar Campus, Abu Dhabi 54224, U Arab Emirates.;UiT Arctic Univ Norway, Dept Phys & Technol, N-9037 Tromso, Norway..
    Enhanced photoelectrochemical performance of atomic layer deposited Hf-doped ZnO2020In: Surface & Coatings Technology, ISSN 0257-8972, E-ISSN 1879-3347, Vol. 385, article id 125352Article in journal (Refereed)
    Abstract [en]

    Generation of hydrogen using photoelectrochemical (PEC) water splitting has attracted researchers for the last two decades. Several materials have been utilized as a photoanode in a water splitting cell, including ZnO due to its abundance, low production cost and suitable electronic structure. Most research attempts focused on doping ZnO to tailor its properties for a specific application. In this work, atomic layer deposition (ALD) was used to precisely dope ZnO with hafnium (Hf) in order to enhance its PEC performance. The resultant doped materials showed a significant improvement in PEC efficiency compared to pristine ZnO, which is linked directly to Hf introduction revealed by detailed optical, structural and electrical analyses. The photocurrent obtained in the best performing Hf-doped sample (0.75 wt% Hf) was roughly threefold higher compared to the undoped ZnO. Electrochemical impedance spectroscopy (EIS) and open-circuit potential-decay (OCPD) measurements confirmed suppression in photocarriers' surface recombination in the doped films, which led to a more efficient PEC water oxidation. The enhanced PEC performance of Hf-doped ZnO and effectiveness of the used metal dopant are credited to the synergistic optimization of chemical composition, which enhanced the electrical, structural including morphological, and optical properties of the final material, making Hf-doping an attractive candidate for novel PEC electrodes.

  • 11.
    Almquist, Martin
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Division of Scientific Computing. Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Numerical Analysis.
    Mattsson, Ken
    Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Division of Scientific Computing. Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Numerical Analysis.
    Edvinsson, Tomas
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Inorganic Chemistry.
    High-fidelity numerical solution of the time-dependent Dirac equation2014In: Journal of Computational Physics, ISSN 0021-9991, E-ISSN 1090-2716, Vol. 262, p. 86-103Article in journal (Refereed)
  • 12.
    Almquist, Martin
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Division of Scientific Computing. Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Numerical Analysis.
    Mattsson, Ken
    Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Division of Scientific Computing. Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Numerical Analysis.
    Edvinsson, Tomas
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Inorganic Chemistry.
    Stable and accurate simulation of phenomena in relativistic quantum mechanics2013In: Proc. 11th International Conference on Mathematical and Numerical Aspects of Waves, Tunisia: ENIT , 2013, p. 213-214Conference paper (Other academic)
  • 13.
    Andersson, Claes-Henrik
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - BMC, Physical Organic Chemistry.
    Nyholm, Leif
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Inorganic Chemistry.
    Grennberg, Helena
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - BMC, Physical Organic Chemistry.
    Synthesis and characterization of a ferrocene-linked bis-fullerene[60] dumbbell2012In: Dalton Transactions, ISSN 1477-9226, E-ISSN 1477-9234, Vol. 41, no 8, p. 2374-2381Article in journal (Refereed)
    Abstract [en]

    A new [60]fullerene dumbbell consisting of two fulleropyrrolidines connected to a central ferrocene unit by amide linkages has been prepared and fully characterized by elemental analysis, 1H NMR, UV/Vis, fluorescence and mass spectrometry. The electrochemical properties as determined by cyclic voltammetry show ground state electronic communication between the ferrocene and the fullerene units. In addition, the preparaton of a ferrocene building block for an alternative linking approach is presented.

  • 14.
    Andersson, Edvin
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Structural Chemistry.
    Sångeland, Christofer
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Structural Chemistry.
    Berggren, Elin
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Condensed Matter Physics of Energy Materials.
    Johansson, Fredrik
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Inorganic Chemistry. Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy.
    Kühn, Danilo
    Lindblad, Andreas
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Condensed Matter Physics of Energy Materials.
    Mindemark, Jonas
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Polymer Chemistry. Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Structural Chemistry.
    Hahlin, Maria
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Structural Chemistry.
    Early-Stage Decomposition of Solid Polymer Electrolytes in Li-Metal Batteries2021In: Journal of Materials Chemistry, ISSN 0959-9428, E-ISSN 1364-5501, Vol. 9, no 39Article in journal (Refereed)
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  • 15.
    Andersson, Matilda
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Inorganic Chemistry.
    Högström, Jonas
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Inorganic Chemistry.
    Urbonaite, Sigita
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Structural Chemistry.
    Furlan, Andrej
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Inorganic Chemistry.
    Nyholm, Leif
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Inorganic Chemistry.
    Jansson, Ulf
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Inorganic Chemistry.
    Deposition and characterization of magnetron sputtered amorphous Cr-C films2012In: Vacuum, ISSN 0042-207X, E-ISSN 1879-2715, Vol. 86, no 9, p. 1408-1416Article in journal (Refereed)
    Abstract [en]

    Thin films in the Cr-C system with carbon content of 25-85 at.% have been deposited using non-reactive DC magnetron sputtering from elemental targets. Analyses with X-ray diffraction and transmission electron microscopy confirm that the films are completely amorphous. Also, annealing experiment show that the films had not crystallized at 500 degrees C. Furthermore, X-ray spectroscopy and Raman spectroscopy show that the films consist of two phases, an amorphous CrCx phase and an amorphous carbon (a-C) phase. The presence of two amorphous phases is also supported by the electrochemical analysis, which shows that oxidation of both chromium and carbon contributes to the total current in the passive region. The relative amounts of these amorphous phases influence the film properties. Typically, lower carbon content with less a-C phase leads to harder films with higher Young's modulus and lower resistivity. The results also show that both films have lower currents in the passive region compared to the uncoated 316L steel substrate. Finally, our results were compared with literature data from both reactively and non-reactively sputtered chromium carbide films. The comparison reveals that non-reactive sputtering tend to favour the formation of amorphous films and also influence e.g. the sp(2)/sp(3) ratio of the a-C phase. 

  • 16.
    Andersson, Matilda
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Inorganic Chemistry.
    Urbonaite, Sigita
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Structural Chemistry.
    Lewin, Erik
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Inorganic Chemistry.
    Jansson, Ulf
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Inorganic Chemistry.
    Magnetron sputtering of Zr-Si-C thin films2012In: Thin Solid Films, ISSN 0040-6090, E-ISSN 1879-2731, Vol. 520, no 20, p. 6375-6381Article in journal (Refereed)
    Abstract [en]

    The phase composition and chemical bonding of Zr-C and Zr-Si-C films deposited by magnetron sputtering has been studied. The results show that the binary Zr-C films at higher carbon contents form nanocrystallites of ZrC in an amorphous carbon matrix. The addition of Si induces a complete amorphization of the films above a critical concentration of about 15 at.%. X-ray diffraction and transmission electron microscopy confirm that the amorphous films contain no nanocrystallites and therefore can be described as truly amorphous carbides. The amorphous films are thermally stable but start to crystallize above 500 degrees C. Analysis of the chemical bonding with X-ray photoelectron spectroscopy suggests that the amorphous films exhibit a mixture of different chemical bonds such as Zr-C, Zr-Si and Si-C and that the electrical and mechanical properties are dependent on the distribution of these bonds. For higher carbon contents, strong Si-C bonds are formed in the amorphous Zr-Si-C films making them harder than the corresponding binary Zr-C films.

  • 17.
    Andersson, Mikael
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Inorganic Chemistry. NIST, NIST Ctr Neutron Res, Gaithersburg, MD 20899 USA.;Chalmers Univ Technol, Dept Chem & Chem Engn, SE-41296 Gothenburg, Sweden..
    Stavila, Vitalie
    Sandia Natl Labs, Energy Nanomat, Livermore, CA 94551 USA..
    Skripov, Alexander, V
    Russian Acad Sci, Ural Branch, Inst Met Phys, Ekaterinburg 620108, Russia..
    Dimitrievska, Mirjana
    NIST, NIST Ctr Neutron Res, Gaithersburg, MD 20899 USA.;Natl Renewable Energy Lab, Golden, CO 80401 USA.;Ecole Polytech Fed Lausanne, Inst Mat, Lab Semicond Mat, CH-1015 Lausanne, Switzerland..
    Psurek, Malgorzata T.
    NIST, NIST Ctr Neutron Res, Gaithersburg, MD 20899 USA.;Univ Maryland, Dept Chem, College Pk, MD 20742 USA..
    Leao, Juscelino B.
    NIST, NIST Ctr Neutron Res, Gaithersburg, MD 20899 USA..
    Babanova, Olga A.
    Russian Acad Sci, Ural Branch, Inst Met Phys, Ekaterinburg 620108, Russia..
    Skoryunov, Roman, V
    Russian Acad Sci, Ural Branch, Inst Met Phys, Ekaterinburg 620108, Russia..
    Soloninin, Alexei, V
    Russian Acad Sci, Ural Branch, Inst Met Phys, Ekaterinburg 620108, Russia..
    Karlsson, Maths
    Chalmers Univ Technol, Dept Chem & Chem Engn, SE-41296 Gothenburg, Sweden..
    Udovic, Terrence J.
    NIST, NIST Ctr Neutron Res, Gaithersburg, MD 20899 USA.;Univ Maryland, Dept Mat Sci & Engn, College Pk, MD 20742 USA..
    Promoting Persistent Superionic Conductivity in Sodium Monocarba-closo-dodecaborate NaCB11H12 via Confinement within Nanoporous Silica2021In: The Journal of Physical Chemistry C, ISSN 1932-7447, E-ISSN 1932-7455, Vol. 125, no 30, p. 16689-16699Article in journal (Refereed)
    Abstract [en]

    Superionic phases of bulk anhydrous salts based on large cluster-like polyhedral (carba)borate anions are generally stable only well above room temperature, rendering them unsuitable as solid-state electrolytes in energy-storage devices that typically operate at close to room temperature. To unlock their technological potential, strategies are needed to stabilize these superionic properties down to subambient temperatures. One such strategy involves altering the bulk properties by confinement within nanoporous insulators. In the current study, the unique structural and ion dynamical properties of an exemplary salt, NaCB11H12, nanodispersed within porous, high-surface-area silica via salt-solution infiltration were studied by differential scanning calorimetry, X-ray powder diffraction, neutron vibrational spectroscopy, nuclear magnetic resonance, quasielastic neutron scattering, and impedance spectroscopy. Combined results hint at the formation of a nanoconfined phase that is reminiscent of the high-temperature superionic phase of bulk NaCB11H12, with dynamically disordered CB11H12-anions exhibiting liquid-like reorientational mobilities. However, in contrast to this high-temperature bulk phase, the nanoconfined NaCB11H12 phase with rotationally fluid anions persists down to cryogenic temperatures. Moreover, the high anion mobilities promoted fast-cation diffusion, yielding Na+ superionic conductivities of similar to 0.3 mS/cm at room temperature, with higher values likely attainable via future optimization. It is expected that this successful strategy for conductivity enhancement could be applied as well to other related polyhedral (carba)borate-based salts. Thus, these results present a new route to effectively utilize these types of superionic salts as solid-state electrolytes in future battery applications.

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  • 18.
    Andersson, Sara
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Inorganic Chemistry.
    Förutsättningar att utforma stationsbatterier i vattenkraftverk med Li-jonteknik2015Independent thesis Advanced level (professional degree), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    In hydropower plants it is necessary to always have local power supply. Therefore, the plants are equipped with batteries as stationary back up power. Vattenfall Vattenkraft is using lead acid batteries but has been investigating alternatives to replace them. The aim of this study is to investigate the potential of using Li-ion technology as back up power.

    The study showed that Li-ion batteries have many qualities. The Li-ion technology will decrease the space and maintenance demand. The technology also eliminates many of the personal safety risks that lead acid batteries may cause. Unfortunately overcharging or overheating the Li-ion battery may result in fire or explosion. Those risks are reduced by an electronic battery management system and mechanical protection.

    The result from the cost comparison between the two battery technologies showed that the maintenance costs decreases with 70 % when using Li-ion battery. The purchase cost of Li-ion batteries is almost three times higher compared to lead acid batteries. But prices will probably drop drastically in the coming years.

    According to this study Li-ion has great potential to replace the lead acid battery.  Vattenfall Vattenkraft should wait until the technology develops further and prices decrease before any larger installations are made. But small installations should be considered in order to get more experience of the technology.

     

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  • 19.
    Andersson, Y
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Inorganic Chemistry.
    Rundqvist, S
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Inorganic Chemistry.
    Beckman, O
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Lundgren, L
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Nordblad, P
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Properties of Fe2 P crystals prepared from a liquid copper medium1978In: Physica status solidi. A, Applied research, ISSN 0031-8965, E-ISSN 1521-396X, Vol. 49, no 2, p. K153-K156Article in journal (Refereed)
  • 20.
    Araujo, Rafael
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Theory. Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Materials Science and Engineering, Solid State Physics. Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström.
    Edvinsson, Tomas
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Inorganic Chemistry. Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Materials Science and Engineering, Solid State Physics. Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Structural Chemistry.
    N-2 adsorption on high-entropy alloy surfaces: unveiling the role of local environments2023In: Journal of Materials Chemistry A, ISSN 2050-7488, E-ISSN 2050-7496, Vol. 11, no 24, p. 12973-12983Article in journal (Refereed)
    Abstract [en]

    Developing highly active catalysts to electrochemically reduce N-2 to NH3 under ambient conditions is challenging but bears the promise of using ammonia as a potential energy vector in sustainable energy technology. One of the scientific challenges concerns the inertness of N-2 emanating from the highly stable triple bonds and the lack of dipole moments, making N-2 fixation on catalytic surfaces difficult. Another critical challenge is that electrons are more prone to reduce hydrogen than N-2 at the surface, forming a scaling relationship where the reduction ability of the catalyst most often benefits hydrogen reduction instead of nitrogen reduction. Here we show that high-entropy alloys (HEA) - a new class of catalysts with vast compositional and structural possibilities, can enhance N-2 fixation. More specifically, we investigate the role of the local environment in the first and second solvation shell of the adsorbing elements in the bond strength between the dinitrogen molecules and the HEA surfaces. Density functional theory using a Bayesian error estimation functional and vdW interactions is employed to clarify the properties dictating the local bonding. The results show that although the main property calibrating the N-2 bond strength is the d-band centers of the adsorbing elements, the value of the d-band centers of the adsorbing elements is further regulated by their local environment, mainly from the elements in the first solvation shell due to electron donor-acceptor interactions. Therefore, there exists a first solvation shell effect of the adsorbing elements on the bond strength between N-2 molecules and the surface of HEAs. The results show that apart from the direct active site, the indirect relation adds further modulation abilities where the local interactions with a breath of metallic elements could be used in HEAs to engineer specific surface environments. This is utilized here to form a strategy for delivering higher bond strength with the N-2 molecules, mitigating the fixation issue. The analysis is corroborated by correlation analysis of the properties affecting the interaction, thus forming a solid framework of the model, easily extendable to other chemical reactions and surface interaction problems.

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  • 21.
    Asfaw, Habtom D.
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Structural Chemistry.
    Younesi, Reza
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Structural Chemistry.
    Valvo, Mario
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Structural Chemistry.
    Maibach, Julia
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Structural Chemistry.
    Ångström, Jonas
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Structural Chemistry.
    Tai, Cheuk-Wai
    Bacsik, Zoltan
    Sahlberg, Martin
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Inorganic Chemistry.
    Nyholm, Leif
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Inorganic Chemistry.
    Edström, Kristina
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Structural Chemistry.
    Boosting the thermal stability of emulsion–templated polymers via sulfonation: an efficient synthetic route to hierarchically porous carbon foams2016In: ChemistrySelect, ISSN 2365-6549, Vol. 1, no 4, p. 784-792Article in journal (Refereed)
    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.

  • 22.
    Asfaw, Habtom Desta
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Structural Chemistry.
    Kotronia, Antonia
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Structural Chemistry.
    Tai, Cheuk-Wai
    Stockholm Univ, Dept Mat & Environm Chem, Arrhenius laboratory, Stockholm, Sweden.
    Nyholm, Leif
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Inorganic Chemistry.
    Edström, Kristina
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Structural Chemistry.
    Tailoring the Microstructure and Electrochemical Performance of 3D Microbattery Electrodes Based on Carbon Foams2019In: Energy Technology, ISSN 2194-4288, E-ISSN 2194-4296, Vol. 7, no 10, article id UNSP 1900797Article in journal (Refereed)
    Abstract [en]

    Three‐dimensional (3D) carbon electrodes with suitable microstructural features and stable electrochemical performance are required for practical applications in 3D lithium (Li)‐ion batteries. Herein, the optimization of the microstructures and electrochemical performances of carbon electrodes derived from emulsion‐templated polymer foams are dealt with. Exploiting the rheological properties of the emulsion precursors, carbon foams with variable void sizes and specific surface areas are obtained. Carbon foams with an average void size of around 3.8 μm are produced, and improvements are observed both in the coulombic efficiency and the cyclability of the carbon foam electrodes synthesized at 2200 °C. A stable areal capacity of up to 1.22 mAh cm−2 (108 mAh g−1) is achieved at a current density of 50 μA cm−2. In addition, the areal capacity remains almost unaltered, i.e., 1.03 mAh cm−2 (91 mAh g−1), although the cycling current density increases to 500 μA cm−2 indicating that the materials are promising for power demanding applications.

  • 23.
    Asfaw, Habtom Desta
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Structural Chemistry.
    Roberts, Matthew R.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström.
    Tai, Cheuk-Wai
    Stockholm University.
    Younesi, Reza
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Structural Chemistry. DTU.
    Valvo, Mario
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Structural Chemistry.
    Nyholm, Leif
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Inorganic Chemistry.
    Edström, Kristina
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Structural Chemistry.
    Nanosized LiFePO4-decorated emulsion-templated carbon foam for 3D micro batteries: a study of structure and electrochemical performance2014In: Nanoscale, ISSN 2040-3364, E-ISSN 2040-3372, Vol. 6, no 15, p. 8804-8813Article in journal (Refereed)
    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.

  • 24.
    Asfaw, Habtom Desta
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Structural Chemistry.
    Tai, Cheuk-Wai
    Stockholm University.
    Nyholm, Leif
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Inorganic Chemistry.
    Edström, Kristina
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Structural Chemistry.
    Emulsion-templated graphitic carbon foams with optimum porosity for 3D Li-ion microbatteriesManuscript (preprint) (Other academic)
  • 25.
    Asfaw, Habtom Desta
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Structural Chemistry.
    Tai, Cheuk-Wai
    Stockholm Univ, Arrhenius Lab, Dept Mat & Environm Chem, S-10691 Stockholm, Sweden..
    Nyholm, Leif
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Inorganic Chemistry.
    Edström, Kristina
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Structural Chemistry.
    Over-Stoichiometric NbO2 Nanoparticles for a High Energy and Power Density Lithium Microbattery2017In: ChemNanoMat, E-ISSN 2199-692X, Vol. 3, no 9, p. 646-655Article in journal (Refereed)
    Abstract [en]

    Effective utilization of active materials in microbatteries can be enhanced by rational design of the electrodes. There is an increasing trend of using 3D electrodes that are coated in nanosized active materials to boost both energy and power densities. This article focuses on the fabrication of 3D electrodes based on monolithic carbon foams coated in over-stoichiometric NbO2 nanoparticles. The electrodes exhibit remarkable energy and power densities at various current densities when tested in lithium microbatteries. An areal capacity of around 0.7mAhcm(-2) and energy density up to 45mWhcm(-3) have been achieved. More than half of the areal capacity can be accessed at a current density of about 11mAcm(-2), with the corresponding energy and power densities being 21mWhcm(-3) and 1349mWcm(-3). These values are comparable to those of microsupercapacitors containing carbon and MnO2 nanomaterials. Furthermore, the electrochemical reversibility improves progressively upon cycling along with substantial increase in the charge transfer kinetics of the electrode. Based on impedance analyses almost a fourfold decrease in the charge transfer resistance has been observed over 25 cycles. Such enhancement of the electronic properties of NbO2 can account for the high electrochemical rate performance of the 3D electrodes.

  • 26.
    Asfaw, Habtom Desta
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Structural Chemistry.
    Tai, Cheuk-Wai
    Stockholm University.
    Nyholm, Leif
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Inorganic Chemistry.
    Edström, Kristina
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Structural Chemistry.
    Surface-oxidized NbO2 nanoparticles for high performance lithium microbatteriesManuscript (preprint) (Other academic)
  • 27.
    Backe, Kalle
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Inorganic Chemistry.
    Functionalization of graphene for biosensor-applications2014Independent thesis Advanced level (professional degree), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    This project investigates the interaction of water with graphene and graphane. It also examines how the functionalization with polystyrene will affect the surfaces and their interaction with water. This study is completely theoretical and is performed with the simulating and modeling software called Materials Studio from Accelrys, Inc. Calculations are done with CASTEP, Dmol3 and Forcite. It is important to gain a deep understanding about the interactions between graphene (or graphane) surfaces and the water that is attached to it, since these materials are of a large interest for biosensor applications.

    The conclusion is that graphane (compared to graphene) is more susceptible to functionalization with styrene. This is most probably due to the sp3 hybridization of the C atoms, so one has to hydrogenate the graphene surface to make it more functionalizable. The graphane surface are also more hydrophilic than graphene. However, by functionalization with styrene it is possible to make both surfaces more hydrophilic and thus more suitable for biological system. Further investigations need to be done in order to validate these results.

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  • 28.
    Barker, Paul Michael
    et al.
    Laboratory for Nanoscale Materials Science, Empa, Dübendorf, Switzerland.
    Konstantinidis, Stephanos
    Chimie des Interactions Plasma-Surface (ChIPS), Université de Mons, Belgium.
    Lewin, Erik
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Inorganic Chemistry.
    Britun, Nikolay
    Chimie des Interactions Plasma-Surface (ChIPS), Université de Mons, Belgium.
    Patscheider, Jörg
    Laboratory for Nanoscale Materials Science, Empa, Dübendorf, Switzerland.
    An investigation of c-HiPIMS discharges during titanium deposition2014In: Surface & Coatings Technology, ISSN 0257-8972, E-ISSN 1879-3347, Vol. 258, p. 631-638Article in journal (Refereed)
    Abstract [en]

    Abstract A modified version of high power impulse magnetron sputtering (HiPIMS) has been used to deposit titanium films at higher deposition rates than for conventional HiPIMS whilst maintaining similar pulse voltages and peak currents. This process, named chopped-HiPIMS (c-HiPIMS) utilises pulses decomposed into several short single pulses instead of single HiPIMS pulses. Experiments show that manipulating the pulse sequence during c-HiPIMS, i.e. the tÎŒon and tÎŒoff times (explained in the glossary) allows for an increase of the deposition rate; increases of up to 150% are reported here for selected conditions. Further, deposition rates higher than those measured using direct current magnetron sputtering are also shown. Investigations by optical emission and optical absorption spectroscopy at the substrate show that the increase of deposition rate is not a consequence of different ion concentrations arriving at the substrate when changing the micro-pulse-off times of c-HiPIMS. Thus alternative reasons for the enhanced deposition rate during c-HiPIMS deposition of metal films are discussed. It is demonstrated that film micro-structure maintains the void free, dense nature typically demonstrated by HiPIMS deposited coatings whilst at enhanced deposition rates. Thus c-HiPIMS allows for the preparation of dense films with the benefit of faster growth rates.

  • 29. Barker, Paul Michael
    et al.
    Lewin, Erik
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Inorganic Chemistry.
    Patscheider, Jorg
    Modified high power impulse magnetron sputtering process for increased deposition rate of titanium2013In: Journal of Vacuum Science & Technology. A. Vacuum, Surfaces, and Films, ISSN 0734-2101, E-ISSN 1520-8559, Vol. 31, no 6, p. 060604-Article in journal (Refereed)
    Abstract [en]

    A modified version of high power impulse magnetron sputtering (HiPIMS) has been used to deposit titanium films at higher deposition rates than for conventional HiPIMS while maintaining similar pulse voltages and peak currents. In the present study, additional control parameters are explored through the chopping of the HiPIMS pulse into a pulse sequence. Experiments show that the use of sequences allows for an increase of the deposition rate of more than 45% compared to conventional HiPIMS. The increase in deposition rate is ascribed to a combination of reduced gas rarefaction effects, prevention of sustained self-sputtering, and a relaxation of ion trapping.

  • 30.
    Bayani, Amirhossein
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Inorganic Chemistry.
    Kishore, M. R. Ashwin
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Inorganic Chemistry.
    Larsson, Karin
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Inorganic Chemistry.
    The influence by substrate morphology on the Rashba band splitting in graphene2020In: Results in Physics, ISSN 2211-3797, Vol. 17, article id 103065Article in journal (Refereed)
    Abstract [en]

    The influence of substrate morphology on the Rashba band splitting at the Dirac point of graphene, has been theoretically investigated. More specifically, the possibility for this splitting to be caused by spin–orbit coupling (with the heavy metal substrate) was of a special interest to study. The model system consisted of a 4H-SiC (0 0 0 1)/graphene interface, with an intercalated metal layer (Ag and Au, respectively). These intercalating metal layers were built with two different types of morphologies; either flat or buckled (with different buckling positions). The results show that depending on the position of the buckled metal atom, the size of the bandgap and band splitting (at the Dirac point of graphene) will either increase (or decrease). Moreover, the enlargement of the buckling size was also shown to affect the electronic properties of graphene (i.e., by increasing the bandgap). The sizes of the bandgaps and band splitting for the different intercalating metals (Ag and Au), were also found to be different. Spin-projected band structures was also implemented in the present study, with the purpose to show the spin-texture of graphene. It was thereby shown that the spins pined to the x and y spin components for most of the cases.

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  • 31.
    Bayani, Amirhossein
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Inorganic Chemistry.
    Larsson, Karin
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Inorganic Chemistry.
    Intercalation of Au Atoms into SiC(0001)/Buffer Interfaces: A First-Principles Density Functional Theory Study2020In: ACS Omega, E-ISSN 2470-1343, Vol. 5, no 24, p. 14842-14846Article in journal (Refereed)
    Abstract [en]

    The process of Au intercalation into a SiC/buffer interface has been theoretically investigated here by using density functional theory (DFT) and the nudged elastic band (NEB) method. Energy barriers were at first calculated (using NEB) for the transfer of an Au atom through a free-standing graphene sheet. The graphene sheet was either of a nondefect character or with a defect in the form of an enlarged hexagonal carbon ring. Defects in the form of single and double vacancies were also considered. Besides giving a qualitative prediction of the relative energy barriers for the corresponding SiC/buffer interfaces, some of the graphene calculations also proved evidence of energy minima close to the graphene sheet. The most stable Au positions within the SiC/buffer interface were, therefore, calculated by performing geometry optimization with Au in the vicinity of the buffer layer. Based on these NEB and DFT calculations, two factors were observed to have a great influence on the Au intercalation process: (i) energy barrier and (ii) preferential bonding of Au to the radical C atoms at the edges of the vacancies. The energy barriers were considerably smaller in the presence of vacancies. However, the Au atoms preferred to bind to the edge atoms of these vacancies when approaching the buffer layer. It can thereby be concluded that the Au intercalation will only occur for a nondefect buffer layer when using high temperature and/or by using high-energy impacts by Au atoms. For this type of Au intercalation, the buffer layer will become completely detached from the SiC surface, forming a single layer of graphene with an intact Dirac point.

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  • 32.
    Bayani, Amirhossein
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Inorganic Chemistry.
    Larsson, Karin
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Inorganic Chemistry.
    The morphology of an intercalated Au layer with its effect on the Dirac point of graphene2020In: Scientific Reports, E-ISSN 2045-2322, Vol. 10, no 1Article in journal (Refereed)
    Abstract [en]

    This is a theoretical investigation where Density Functional Theory (DFT) has been used in studying the phenomenon of Au intercalation within the 4H-SiC/graphene interface. The electronic structure of some carefully chosen morphologies of the Au layer has then been of special interest to study. One of these specific Au morphologies is of a more hypothetical nature, whilst the others are, from an experimental point of view, realistic ones. The latter ones were also found to be energetically stable. Band structure calculations showed that intercalated Au layers with morphologies different from a planar Au layer will induce a band gap at the Dirac point of graphene (with up to 174 meV for the morphologies studied in the present work). It should here be mentioned that this bandgap size is four times larger than the energy of thermal motion at room temperature (26 meV). These findings reveal that a wide bandgap at the Dirac point of graphene comes from an inhomogeneous staggered potential on the Au layer, which non-uniformly breaks the sublattice symmetry. The presence of spin-orbit (SO) interactions have also been included in the present study, with the purpose to find out if SO will create a bandgap and/or band splitting of graphene.

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  • 33.
    Bayrak Pehlivan, Ilknur
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Materials Science and Engineering, Solid State Physics.
    Saguì, Nicole A.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Materials Science and Engineering.
    Oscarsson, Johan
    Solibro Res AB, Vallvagen 5, S-75651 Uppsala, Sweden.
    Qiu, Zhen
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Materials Science and Engineering, Solid State Physics. KTH Royal Inst Technol, Dept Chem Engn, SE-10044 Stockholm, Sweden.
    Zwaygardt, Walter
    Forschungszentrum Julich, Inst Energy & Climate Res, IEK 14 Electrochem Proc Engn, D-52425 Julich, Germany.
    Lee, Minoh
    Forschungszentrum Julich, Inst Energy & Climate Res, IEK 14 Photovolta, D-52425 Julich, Germany.
    Mueller, Martin
    Forschungszentrum Juelich GmbH, Institute of Energy and Climate Research, IEK-14: Electrochemical Process Engineering, 52425 Juelich, Germany .
    Haas, Stefan
    Forschungszentrum Julich, Inst Energy & Climate Res, IEK 14 Photovolta, D-52425 Julich, Germany.
    Stolt, Lars
    Solibro Res AB, Vallvagen 5, S-75651 Uppsala, Sweden.
    Edoff, Marika
    Uppsala Univ, Solid State Elect, Dept Mat Sci & Engn, Box 534, S-75121 Uppsala, Sweden.
    Edvinsson, Tomas
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Inorganic Chemistry. Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Materials Science and Engineering, Solid State Physics.
    Scalable and thermally-integrated solar water-splitting modules using Ag-doped Cu(In,Ga)Se-2 and NiFe layered double hydroxide nanocatalysts2022In: Journal of Materials Chemistry A, ISSN 2050-7488, E-ISSN 2050-7496, Vol. 10, no 22, p. 12079-12091Article in journal (Refereed)
    Abstract [en]

    Photovoltaic (PV) electrolysis is an important and powerful technology for environmentally-friendly fuel production based on solar energy. By directly coupling solar cell materials to electrochemical systems to perform water electrolysis, solar energy can be converted into hydrogen fuel utilizing locally-generated heat and avoid losses from DC-DC convertors and power grid transmission. Although there have been significant contributions to the photoelectrochemical and PV-electrolysis field using isolated laboratory cells, the capacity to upscale and retain high levels of efficiency in larger modules remains a critical issue for widespread use and application. In this study, we develop thermally-integrated, solar-driven water-splitting device modules using AgCu(In,Ga)Se-2 (ACIGS) and an alkaline electrolyzer system with NiFe-layered double hydroxide (LDH) nanocatalysts with devices of 82-100 cm(2) area. The Ga-content in the ACIGS solar cells is tuned to achieve an optimal voltage for the catalyst system, and the average efficiencies and durability of the PV-electrolyzer were tested in up to seven-day indoor and 21 day outdoor operations. We achieved a solar-to-hydrogen (STH) module efficiency of 13.4% from gas volume measurements for the system with a six-cell CIGS-electrolyzer module with an active area of 82.3 cm(2) and a 17.27% PV module efficiency under 100 mW cm(-2) illumination, and thus 77% electricity-to-hydrogen efficiency at one full sun. Outdoor tests under mid-Europeen winter conditions exhibited an STH efficiency between 10 and 11% after the initial activation at the installation site in Julich, Germany, in December 2020, despite challenging outdoor-test weather conditions, including sub-zero temperatures.

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  • 34.
    BECKMAN, O
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    LUNDGREN, L
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    NORDBLAD, P
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    SANDLUND, L
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    SVEDLINDH, P
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    LUNDSTROM, T
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Inorganic Chemistry.
    RUNDQVIST, S
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Inorganic Chemistry.
    SPECIFIC-HEAT AND MAGNETIC-SUSCEPTIBILITY OF SINGLE-PHASE YBA2CU3O71987In: Physics Letters A, ISSN 0375-9601, E-ISSN 1873-2429, Vol. 125, p. 425-428Article in journal (Refereed)
  • 35.
    BECKMAN, O
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    LUNDGREN, L
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    NORDBLAD, P
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    SVEDLINDH, P
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    TORNE, A
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    ANDERSSON, Y
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Inorganic Chemistry.
    RUNDQVIST, S
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Inorganic Chemistry.
    SPECIFIC-HEAT OF THE FERROMAGNET FE2P1982In: Physica scripta. T, ISSN 0281-1847, Vol. 25, p. 679-681Article in journal (Refereed)
  • 36.
    Ben-Akiva, Elana
    et al.
    Johns Hopkins Univ, Sch Med, Dept Biomed Engn, Baltimore, MD 21231 USA.;Johns Hopkins Univ, Sch Med, Translat Tissue Engn Ctr, Baltimore, MD 21231 USA.;Johns Hopkins Univ, Sch Med, Inst NanoBioTechnol, Baltimore, MD 21231 USA.;Sidney Kimmel Comprehens Canc Ctr, Bloomberg Kimmel Inst Canc Immunotherapy, Baltimore, MD 21287 USA..
    Karlsson, Johan
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Inorganic Chemistry. Johns Hopkins Univ, Sch Med, Dept Biomed Engn, Baltimore, MD 21231 USA; Johns Hopkins Univ, Sch Med, Translat Tissue Engn Ctr, Baltimore, MD 21231 USA; Johns Hopkins Univ, Sch Med, Inst NanoBioTechnol, Baltimore, MD 21231 USA.
    Hemmati, Shayan
    Johns Hopkins Univ, Sch Med, Dept Biomed Engn, Baltimore, MD 21231 USA.;Johns Hopkins Univ, Sch Med, Translat Tissue Engn Ctr, Baltimore, MD 21231 USA.;Johns Hopkins Univ, Sch Med, Inst NanoBioTechnol, Baltimore, MD 21231 USA..
    Yu, Hongzhe
    Johns Hopkins Univ, Sch Med, Dept Biomed Engn, Baltimore, MD 21231 USA.;Johns Hopkins Univ, Sch Med, Translat Tissue Engn Ctr, Baltimore, MD 21231 USA.;Johns Hopkins Univ, Sch Med, Inst NanoBioTechnol, Baltimore, MD 21231 USA..
    Tzeng, Stephany Y.
    Johns Hopkins Univ, Sch Med, Dept Biomed Engn, Baltimore, MD 21231 USA.;Johns Hopkins Univ, Sch Med, Translat Tissue Engn Ctr, Baltimore, MD 21231 USA.;Johns Hopkins Univ, Sch Med, Inst NanoBioTechnol, Baltimore, MD 21231 USA..
    Pardoll, Drew M.
    Sidney Kimmel Comprehens Canc Ctr, Bloomberg Kimmel Inst Canc Immunotherapy, Baltimore, MD 21287 USA.;Johns Hopkins Univ, Sch Med, Dept Oncol, Baltimore, MD 21231 USA.;Johns Hopkins Univ, Sch Med, Dept Med, Baltimore, MD 21231 USA.;Johns Hopkins Univ, Sch Med, Dept Pathol, Baltimore, MD 21231 USA.;Johns Hopkins Univ, Sch Med, Dept Mol Biol & Genet, Baltimore, MD 21231 USA..
    Green, Jordan J.
    Johns Hopkins Univ, Sch Med, Dept Biomed Engn, Baltimore, MD 21231 USA.;Johns Hopkins Univ, Sch Med, Translat Tissue Engn Ctr, Baltimore, MD 21231 USA.;Johns Hopkins Univ, Sch Med, Inst NanoBioTechnol, Baltimore, MD 21231 USA.;Sidney Kimmel Comprehens Canc Ctr, Bloomberg Kimmel Inst Canc Immunotherapy, Baltimore, MD 21287 USA.;Johns Hopkins Univ, Sch Med, Dept Oncol, Baltimore, MD 21231 USA.;Johns Hopkins Univ, Dept Mat Sci & Engn, Baltimore, MD 21231 USA.;Johns Hopkins Univ, Dept Chem & Biomol Engn, Baltimore, MD 21231 USA.;Johns Hopkins Univ, Sch Med, Dept Ophthalmol, Baltimore, MD 21231 USA.;Johns Hopkins Univ, Sch Med, Dept Neurosurg, Baltimore, MD 21231 USA..
    Biodegradable lipophilic polymeric mRNA nanoparticles for ligand-free targeting of splenic dendritic cells for cancer vaccination2023In: Proceedings of the National Academy of Sciences of the United States of America, ISSN 0027-8424, E-ISSN 1091-6490, Vol. 120, no 26, article id E2301606120Article in journal (Refereed)
    Abstract [en]

    Nanoparticle (NP) -based mRNA cancer vaccines hold great promise to realize person-alized cancer treatments. To advance this technology requires delivery formulations for efficient intracellular delivery to antigen-presenting cells. We developed a class of bioreducible lipophilic poly(beta- amino ester) nanocarriers with quadpolymer architec-ture. The platform is agnostic to the mRNA sequence, with one -step self-assembly allow-ing for delivery of multiple antigen-encoding mRNAs as well as codelivery of nucleic acid-based adjuvants. We examined structure-function relationships for NP-mediated mRNA delivery to dendritic cells (DCs) and identified that a lipid subunit of the pol-ymer structure was critical. Following intravenous administration, the engineered NP design facilitated targeted delivery to the spleen and preferential transfection of DCs without the need for surface functionalization with targeting ligands. Treatment with engineered NPs codelivering antigen-encoding mRNA and toll -like receptor agonist adjuvants led to robust antigen-specific CD8+ T cell responses, resulting in efficient antitumor therapy in in vivo models of murine melanoma and colon adenocarcinoma.

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  • 37. Benesperi, Iacopo
    et al.
    Michaels, Hannes
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Physical Chemistry.
    Edvinsson, Tomas
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Inorganic Chemistry. Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Materials Science and Engineering, Solid State Physics.
    Pavone, Michele
    Probert, Michael R.
    Waddell, Paul
    Muñoz-García, Ana Belén
    Freitag, Marina
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Physical Chemistry.
    Dynamic dimer copper coordination redox shuttles2022In: Chem, ISSN 2451-9308, E-ISSN 2451-9294, Vol. 8, no 2, p. 439-449Article in journal (Refereed)
    Abstract [en]

    Summary Conventional redox mediators based on metal coordination complexes undergo electron transfer through the change in oxidation state of the metal center. However, electron transfer kinetics are offset toward preferred oxidation states when preorganized ligands constrain the reorganization of the coordination sphere. In contrast, we report here on dimeric copper(II/I) redox couples, wherein the extent of oxidation/reduction of two metal centers dictates the dynamic formation of dimer and monomer complexes: the dimeric (Cu(I))2 transitions to monomers of Cu(II). The bis(thiazole/pyrrole)-bipyridine tetradentate ligands stabilize both oxidation states of the unique redox systems. The dynamic dimer redox mediators offer a viable two-electron redox mechanism to develop efficient hybrid solar cells through inhibited recombination and rapid charge transport. Density functional theory calculations reveal inner reorganization energies for single-electron transfer as low as 0.27 eV, marking the dimeric complexes superior redox systems over single complexes as liquid and potentially solid-state electrolytes.

  • 38.
    Berastegui, Pedro
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Inorganic Chemistry.
    Riekehr, Lars
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Inorganic Chemistry.
    Jansson, Ulf
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Inorganic Chemistry.
    Magnetron Sputtering of Nanolaminated Cr2AlB22020In: Coatings, ISSN 2079-6412, Vol. 10, no 8, article id 735Article in journal (Refereed)
    Abstract [en]

    A ternary Cr(2)AlB(2)phase was deposited as a film using magnetron sputtering. Its anisotropic structure displays both structural and chemical similarities with the nanolaminated MAX phases (M(n+1)AX(n)(n = 1-3) where M usually is an early transition metal, A is typically an element in group 13-14 and X is C or N), and can be described as CrB slabs separated by layers of Al. Combinatorial sputtering was used to optimise the sputtering process parameters for films with the Cr(2)AlB(2)composition. The influences of substrate, temperature and composition were studied using X-ray diffraction, X-ray photoelectron spectroscopy and electron microscopy. Films deposited at room temperature were X-ray amorphous but crystalline films could be deposited on MgO substrates at 680 degrees C using a composite Al-B, Cr and Al targets. X-ray diffraction analyses showed that the phase composition and texture of the films was strongly dependent on the chemical composition. Films with several phases or with a single Cr(2)AlB(2)phase could be deposited, but an additional Al target was required to compensate for a loss of Al at the high deposition temperatures used in this study. The microstructure evolution during film growth was strongly dependent on composition, with a change in texture in Al-rich films from a preferred [010] orientation to a [100]/[001] orientation. A model based on Al desorption from the surface of the growing grains is proposed to explain the texture variations.

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  • 39.
    Berastegui, Pedro
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Inorganic Chemistry.
    Tai, Cheuk-Wai
    Stockholm University.
    Valvo, Mario
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Structural Chemistry.
    Electrochemical reactions of AgFeO2 as negative electrode in Li- and Na-ion batteries2018In: Journal of Power Sources, ISSN 0378-7753, E-ISSN 1873-2755, Vol. 401, p. 386-396Article in journal (Refereed)
    Abstract [en]

    AgFeO2 nanoparticles synthesized via precipitation at room temperature are investigated in Li- and Na-ion cells through electrode coatings with an alginate binder. The electrochemical reactions of AgFeO2 with Li+ and Na+ions, as well as its role as alternative negative electrode in these cell systems are carefully evaluated. Initial Li uptake causes irreversible amorphization of the AgFeO2 structure with concomitant formation of Ag0 nanoparticles. Further Li incorporation results in conversion into Fe0 nanoparticles and Li2O, together with Li-alloying of these Ag0 clusters. Similar mechanisms are also found upon Na uptake, although such processes are hindered by overpotentials, the capacity and reversibility of the reactions with Na+ ions being not comparablewith those of their Li+ counterparts. The behaviour of AgFeO2 at low potentials vs. Li+/Li displays a synergic pseudo-capacitive charge storage overlapping Li-Ag alloying/de-alloying. This feature is exploited in full cells having deeply lithiated AgFeO2 and LiFePO4 as negative and positive electrodes, respectively. These environmentally friendly iron-based full cells exhibit attractive cycle performances with ≈80% capacity retention after 1000 cycles without any electrolyte additive, average round trip efficiency of ≈89% and operational voltage of 3.0 V combined with built-in pseudo-capacitive characteristics that enable high cycling rates up to≈25C.

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  • 40.
    Berg, Camilla
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Inorganic Chemistry.
    Influence of Magnesium in theFormation of Phosphate Spheres: A simple method for the fabrication of sphericalparticles of calcium and magnesium phosphate2017Independent thesis Advanced level (professional degree), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    Calcium phosphates and recently also magnesium phosphates, are used for medical applications, due to their biocompatibility and bioactivity. These properites makes spherical particles of calcium and magnesium phosphate suitable for carrier materials for drug delivery applications. By creating porous and/or hollow particles itis possible to load the particles with a drug and control therelease of the active substance.

    In this work, an ion-induced method for the synthesis of spherical calcium and magnesium phosphates was developed. A simple precipitation reaction was used, where substituting magnesium ions could replace the function of templates, such as surfactants or micelles, to induce the formation of spheres of a certain size and morphology.

    Experimental results showed that magnesium had an inhibitory effect on the nucleation and crystal growth of calcium phosphates. By using substituting ions as a structural regulator, it was possible to alter the size, morphology and phase composition of the spheres. At low magnesium concentrations, the spheres had a smooth surface andwere between 200 nanometer to 1 micrometer in diameter and composed of hydroxyapatite and/or magnesium-substituted beta-TCP. At higher magnesium concentrations, the spheres were about 10-50 micrometer with a rough, flaky surface. Results also proved that calcium ionshave the same effect on the crystallisation and self-assembly of magnesium phosphates. Apart from the magnesium concentration, reaction temperature proved to have a high influence on the sphereformation, whereas Ca/P ratio and reaction times above three hours did not affect the sphere formation to the same extent.

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  • 41.
    Berglund, Sigrid
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Physical Chemistry.
    Bassy, Clara
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Pharmacy, Department of Pharmaceutical Biosciences. Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Physical Chemistry.
    Kaya, Ibrahim
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Pharmacy, Department of Pharmaceutical Biosciences.
    Andrén, Per E.
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Pharmacy, Department of Pharmaceutical Biosciences, MMS, Medical Mass Spectrometry. Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Pharmacy, Department of Medicinal Chemistry. Uppsala University, Science for Life Laboratory, SciLifeLab.
    Shtender, Vitalii
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Inorganic Chemistry. Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Materials Science and Engineering, Applied Material Science.
    Lasagna, Mauricio
    Department of Biochemistry and Biphysics, Texas A&M University.
    Tommos, Cecilia
    Department of Biochemistry and Biphysics, Texas A&M University.
    Magnuson, Ann
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Physical Chemistry. Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Photochemistry and Molecular Science, Molecular Biomimetics. Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Photochemistry and Molecular Science, Chemical Physics. Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Photochemistry and Molecular Science, Molecular Biomimetics. Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Molecular Biomimetics.
    Glover, Starla
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Physical Chemistry.
    Hydrogen production by a fully de novo enzyme2024Manuscript (preprint) (Other academic)
    Abstract [en]

    Molecular catalysts based on abundant elements that function in neutral water represent an essential component of sustainable hydrogen production. Artificial hydrogenases based on protein-inorganic hybrids have emerged as an intriguing class of catalysts for this purpose. We have prepared a novel artificial hydrogenase based on cobaloxime bound to a de novo three alpha-helical protein, α3C, via a pyridyl-based unnatural amino acid. The functionalized de novo protein was characterised by UV-visible, CD, and EPR spectroscopy, as well as MALDI spectrometry, which confirmed the presence and ligation of cobaloxime to the protein. The new de novo protein produced hydrogen under electrochemical, photochemical and reductive chemical conditions in neutral water solution. A change in hydrogen evolution capability of the de novo enzyme compared with native cobaloxime was observed, with turnover numbers around 80% of that of cobaloxime, and hydrogen evolution rates of 40% of that of cobaloxime. We discuss these findings in the context of existing literature, how our study contributes important information about the functionality of cobaloxime as hydrogen evolving catalysts in protein environments, and the feasibility of using de novo proteins for developent into artificial metalloenzymes. Small de novo proteins as enzyme scaffolds have the potential to function as upscalable bioinspired catalysts thanks to their efficient atom economy, and the findings presented here show that these types of novel enzymes are a possible product. 

  • 42.
    Bericat Vadell, Robert
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Physical Chemistry.
    Sekar, Pandiaraj
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström.
    Patehebieke, Yeersen
    Univ Gothenburg, Dept Chem & Mol Biol, Kemivagen 10, S-41258 Gothenburg, Sweden..
    Zou, Xianshao
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Physical Chemistry.
    Kaul, Nidhi
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Physical Chemistry.
    Broqvist, Peter
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Structural Chemistry.
    Lindblad, Rebecka
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Physical Chemistry. Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Inorganic Chemistry. Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy.
    Lindblad, Andreas
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Inorganic Chemistry. Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Condensed Matter Physics of Energy Materials.
    Arkhypchuk, Anna I.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Molecular Biomimetics. Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Synthetic Molecular Chemistry.
    Walletin, Carl-Johan
    Univ Gothenburg, Dept Chem & Mol Biol, Kemivagen 10, S-41258 Gothenburg, Sweden..
    Sá, Jacinto
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Physical Chemistry. Polish Acad Sci, Inst Phys Chem, Marcina Kasprzaka 44-52, PL-01224 Warsaw, Poland..
    Single-electron transfer reactions on surface-modified gold plasmons2023In: Materials Today Chemistry, E-ISSN 2468-5194, Vol. 34, article id 101783Article in journal (Refereed)
    Abstract [en]

    Photoredox catalysis's relevance in organic synthesis research and innovation will increase in the coming decades. However, the processes rely almost exclusively on expensive noble metal complexes, most notably iridium complexes, to absorb light and transfer a single charge to a substrate or a catalyst to initiate cascade transformations. Light-triggered plasmon resonances generate a non-Fermi-Dirac energy distribution with many hot carriers that decay in similar to 1 ps. Their ultrafast relaxation makes performing single electron transfer (SET) transformations challenging. Herein, a novel photosystem is proposed based on surface-modified gold nanoparticles (aka plasmon "molecularization"), which improved charge separation and, more importantly, enabled SET reactions, expanding the portfolio of photocatalysts available for photoredox catalysis. The photosystem was made into an electrode, permitting its use in photoelectrochemical arrangements that leverage electro- and photo-chemical approaches' benefits and chemical engineering solutions, helping the synthetic chemistry efforts towards greener synthesis and synthesis of more complex structures on a scale.

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  • 43.
    Blom, Tobias
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    Jafri, Hassan
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    Widenkvist, Erika
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Inorganic Chemistry.
    Jansson, Ulf
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Inorganic Chemistry.
    Grennberg, Helena
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Biochemistry and Organic Chemistry.
    Quinlan, R A
    Holloway, B C
    Leifer, Klaus
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    An In-Situ Prepared Nano-Manipulator Tip for Electrical Characterization of Free Standing Graphene Like Sheets Inside a Focused Ion Beam/Scanning Electron Microscope2011In: Journal of Nanoelectronics and Optoelectronics, ISSN 1555-130X, E-ISSN 1555-1318, Vol. 6, no 2, p. 162-168Article in journal (Refereed)
    Abstract [en]

    Although contacting and moving atoms has been demonstrated using probe techniques, for many nano-objects, a fast and reproducible nano-probe technique is needed to acquire a large number of electrical measurements on nano-objects that are often similar but not the identical. Nano-manipulators have become a common tool in many scanning electron microscopes (SEM) and focussed ion beam devices (FIB). They can be rapidly and reproducibly moved from one nano-object to another. In this work we present a procedure to obtain reproducible electrical measurements of nano- to micron-sized objects by using a sharp, tungsten tip with well defined surface properties. The tip is a part of a manipulator and is sharpened in-situ by using the gallium ion beam inside a focused ion beam/scanning electron microscope (FIB/SEM). The contact resistance between a Au surface and the tip is 70 kΩ before the sharpening procedure and 10 Ω after sharpening. The leakage current of the total set-up of 10pA makes it possible to measure currents through a variety of nano-objects. This measurement technique is applied to measure the resistance of as grown, water treated and two HCl treated carbon nanosheets (CNS). These CNS vary in size and morphology. Using this nano-contacting set-up, we could obtain measurements of more than 400 different CNS. The obtained histograms allow us to observe a clear decrease of the resistance between original and 3 hour acid treated CNSs. We observe that longer periods of exposure of the CNS to the HCl do not further modify the resistance.

  • 44.
    Boll, T.
    et al.
    Chalmers, Dept Appl Phys, SE-41296 Gothenburg, Sweden..
    Thuvander, M.
    Chalmers, Dept Appl Phys, SE-41296 Gothenburg, Sweden..
    Koch, S.
    Chalmers, Dept Appl Phys, SE-41296 Gothenburg, Sweden..
    Wagner, J. N.
    Karlsruhe Inst Technol, KNMF, DE-76344 Eggenstein Leopoldshafen, Germany..
    Nedfors, N.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström.
    Jansson, Ulf
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Inorganic Chemistry.
    Stiller, K.
    Chalmers, Dept Appl Phys, SE-41296 Gothenburg, Sweden..
    An APT investigation of an amorphous Cr-B-C thin film2015In: Ultramicroscopy, ISSN 0304-3991, E-ISSN 1879-2723, Vol. 159, p. 217-222Article in journal (Refereed)
    Abstract [en]

    A magnetron sputtered amorphous Cr-B-C thin film was investigated by means of atom probe tomography (APT). The film is constituted of two phases; a Cr-rich phase present as a few nanometer large regions embedded in a Cr-poor phase (tissue phase). The Cr-rich regions form columnar chains oriented parallel to the growth direction of the film. It was found that the Cr-rich regions have a higher B:C ratio than the Cr-poor regions. The composition of the phases was determined as approximately 35Cr-33B-30C and 15Cr-40B-42C (at%), respectively. The results suggest that this type of nanocomposite films has a more complex structure than previously anticipated, which may have an importance for the mechanical and electrical properties.

  • 45.
    Boman, Mats
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Inorganic Chemistry.
    Berger, Rolf
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Inorganic Chemistry.
    Andersson, Yvonne
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Inorganic Chemistry.
    Hahlin, Maria
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström.
    Björefors, Fredrik
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Structural Chemistry.
    Gustafsson, Torbjörn
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Structural Chemistry.
    Ottosson, Mikael
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Inorganic Chemistry.
    Corrosion of copper in water free from molecular oxygen2014In: Corrosion Engineering, Science and Technology, ISSN 1478-422X, E-ISSN 1743-2782, Vol. 49, no 6, p. 431-434Article in journal (Refereed)
    Abstract [en]

    The possibility of copper reacting with O-2-free water has been investigated by analysis of primary corrosion products, as well as by monitoring gas pressure change by time, in long term experiments for up to 6 months in a glove box environment. We establish hydrogen production, but being of the same magnitude irrespective whether copper is present or not. Although low, the hydrogen production rate is considerably larger than what would directly correspond to the amount of analysed copper oxidation products. Our analyses encompass the changes to the surface cleaned copper (99.9999%), the water phase and the Duran glass in contact with the water (ppt quality). We have used very sensitive methods (XPS, AES, ICP-MS, XRF) while keeping contamination risks to a minimum. We conclude that the oxidation rate of copper is very low, yielding only parts of a monolayer of Cu2O after 6 months of exposure at 50 degrees C together with an accompanying very low concentration of copper species (4-5 mu g L-1) in the water phase.

  • 46.
    Borg, Sebastian
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Inorganic Chemistry.
    Synthetic bone grafts for treatment of femoral head necrosis2017Independent thesis Advanced level (professional degree), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    Necrosis of the femoral head is a relatively common medical condition that radically

    decrease the quality of life for the patient. Left untreated it could lead to destruction

    of the hip joint. A common treatment is using bone autografts, also called bone chips.

    However, in the last decades synthetic bone grafts have become a very interesting

    alternative. This thesis had two aims; to evaulate how porous hydroxyapatite grafts

    with varied pore size could be produced by different size of the porogen and to

    create two-phase cements which would form pores in situ by using a dissolvable

    phase of calcium sulfate hemihydrate. The phase composition, morphology, porosity

    and pore size distribution were characterized with x-ray diffraction, scanning electron

    microscopy and micro-computed tomography. It was found that hydroxyapatite

    granules could be produced and it was possible to vary their pore size to some extent

    by changing the size of the porogen. At physiological temperature, pores were formed

    in the two-phase cements from one week and onwards.

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  • 47.
    Borisov, Vladislav
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Theory.
    Xu, Qichen
    KTH Royal Inst Technol, AlbaNova Univ Ctr, Sch Engn Sci, Dept Appl Phys, SE-10691 Stockholm, Sweden.;KTH Royal Inst Technol, SeRC Swedish Sci Res Ctr, SE-10044 Stockholm, Sweden..
    Ntallis, Nikolaos
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Theory.
    Clulow, Rebecca
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Inorganic Chemistry.
    Shtender, Vitalii
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Inorganic Chemistry.
    Cedervall, Johan
    Stockholm Univ, Dept Mat & Environm Chem, SE-10691 Stockholm, Sweden..
    Sahlberg, Martin
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Inorganic Chemistry.
    Wikfeldt, Kjartan Thor
    KTH Royal Inst Technol, PDC Ctr High Performance Comp, SE-10044 Stockholm, Sweden..
    Thonig, Danny
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Theory. Örebro Univ, Sch Sci & Technol, SE-70182 Örebro, Sweden..
    Pereiro, Manuel
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Theory.
    Bergman, Anders
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Theory.
    Delin, Anna
    KTH Royal Inst Technol, AlbaNova Univ Ctr, Sch Engn Sci, Dept Appl Phys, SE-10691 Stockholm, Sweden.;KTH Royal Inst Technol, SeRC Swedish Sci Res Ctr, SE-10044 Stockholm, Sweden..
    Eriksson, Olle
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Theory. Örebro Univ, Sch Sci & Technol, SE-70182 Örebro, Sweden..
    Tuning skyrmions in B20 compounds by 4d and 5d doping2022In: Physical Review Materials, E-ISSN 2475-9953, Vol. 6, no 8, article id 084401Article in journal (Refereed)
    Abstract [en]

    Skyrmion stabilization in novel magnetic systems with the B20 crystal structure is reported here, primarily based on theoretical results. The focus is on the effect of alloying on the 3d sublattice of the B20 structure by substitution of heavier 4d and 5d elements, with the ambition to tune the spin-orbit coupling and its influence on magnetic interactions. State-of-the-art methods based on density functional theory are used to calculate both isotropic and anisotropic exchange interactions. Significant enhancement of the Dzyaloshinskii-Moriya interaction is reported for 5d-doped FeSi and CoSi, accompanied by a large modification of the spin stiffness and spiralization. Micromagnetic simulations coupled to atomistic spin-dynamics and ab initio magnetic interactions reveal the spin-spiral nature of the magnetic ground state and field-induced skyrmions for all these systems. Especially small skyrmions similar to 50 nm are predicted for Co0.75Os0.25Si, compared to similar to 148 nm for Fe0.75Co0.25Si. Convex-hull analysis suggests that all B20 compounds considered here are structurally stable at elevated temperatures and should be possible to synthesize. This prediction is confirmed experimentally by synthesis and structural analysis of the Ru-doped CoSi systems discussed here, both in powder and in single-crystal forms.

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  • 48.
    Boström, Hanna
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Inorganic Chemistry. Univ Oxford, Dept Chem, Inorgan Chem Lab, South Pk Rd, Oxford OX1 3QR, England.
    Tilts and shifts in molecular perovskites2020In: CrystEngComm, ISSN 1466-8033, E-ISSN 1466-8033, Vol. 22, no 5, p. 961-968Article in journal (Refereed)
    Abstract [en]

    Molecular perovskites have attracted widespread research attention for their diverse properties. Like inorganic perovskites, these systems are susceptible to displacive phase transitions of rigid octahedra. This study investigates the prevalence of the accessible rigid unit modes-conventional and unconventional tilts and columnar shifts-in the classes of molecular perovskites. Formate-based compounds prefer conventional tilting, as a result of its anti-anti binding mode. Azides, hypophosphites, and dicyanamides show a propensity for unconventional tilts and shifts, which relates to their flexible binding geometries.

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  • 49.
    Boström, Hanna
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Inorganic Chemistry. Max Planck Inst Solid State Res, Heisenbergstr 1, D-70569 Stuttgart, Germany..
    Brant, William
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Structural Chemistry.
    Octahedral tilting in Prussian blue analogues2022In: Journal of Materials Chemistry C, ISSN 2050-7526, E-ISSN 2050-7534, Vol. 10, no 37, p. 13690-13699Article in journal (Refereed)
    Abstract [en]

    Octahedral tilting is key to the structure and functionality of perovskites. We present a metastudy of published literature showing how these distortions manifest in the related Prussian blue analogues (PBAs): cyanide versions of double perovskites with formula AM[M '(CN)(6)](1-y)(y)center dot nH(2)O (A = alkali metal, M and M ' = transition metals, = vacancy/defect). Tilts are favoured by high values of x if A = Na or K, whereas the transition metals play a less important role. External hydrostatic pressure induces tilt transitions nearly irrespective of the stoichiometry, whereas thermal transitions are only reported for x > 1. Interstitial water can alter the transitions induced by a different stimulus, but (de)hydration per se does not lead to tilts. Finally, the implications for rational design of critical functionality-including improper ferroelectricity and electrochemical performance-are discussed. The results are integral for a fundamental understanding of phase transitions and for the development of functional materials based on PBAs.

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  • 50.
    Boström, Hanna
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Inorganic Chemistry. Max Planck Inst Solid State Res, D-70569 Stuttgart, Germany.;Uppsala Univ, Angstrom Lab, Dept Inorgan Chem, SE-75121 Uppsala, Sweden.;Univ Oxford, Dept Chem, Oxford OX1 3QR, England..
    Collings, Ines E.
    EMPA Swiss Fed Labs Mat Sci & Technol, Ctr Xray Analyt, CH-8600 Dubendorf, Switzerland..
    Daisenberger, Dominik
    Diamond Light Source Ltd, Didcot OX11 0DE, Oxon, England..
    Ridley, Christopher J.
    Rutherford Appleton Lab, ISIS Neutron & Muon Source, Didcot OX11 0QX, Oxon, England..
    Funnell, Nicholas P.
    Rutherford Appleton Lab, ISIS Neutron & Muon Source, Didcot OX11 0QX, Oxon, England..
    Cairns, Andrew B.
    Imperial Coll London, Dept Mat, London SW7 2AZ, England.;Imperial Coll London, London Ctr Nanotechnol, London SW7 2AZ, England..
    Probing the Influence of Defects, Hydration, and Composition on Prussian Blue Analogues with Pressure2021In: Journal of the American Chemical Society, ISSN 0002-7863, E-ISSN 1520-5126, Vol. 143, no 9, p. 3544-3554Article in journal (Refereed)
    Abstract [en]

    The vast compositional space of Prussian blue analogues (PBAs), formula A(x)M[M'(CN)(6)](y)center dot nH(2)O, allows for a diverse range of functionality. Yet, the interplay between composition and physical properties-e.g., flexibility and propensity for phase transitions-is still largely unknown, despite its fundamental and industrial relevance. Here we use variable-pressure X-ray and neutron diffraction to explore how key structural features, i.e., defects, hydration, and composition, influence the compressibility and phase behavior of PBAs. Defects enhance the flexibility, manifesting as a remarkably low bulk modulus (B-0 approximate to 6 GPa) for defective PBAs. Interstitial water increases B-0 and enables a pressure-induced phase transition in defective systems. Conversely, hydration does not alter the compressibility of stoichiometric MnPt(CN)(6), but changes the high-pressure phase transitions, suggesting an interplay between low-energy distortions. AMnCo(CN)(6) (A(I) = Rb, Cs) transition from F (4) over bar 3m to P (4) over bar n2 upon compression due to octahedral tilting, and the critical pressure can be tuned by the A-site cation. At 1 GPa, the symmetry of Rb0.87Mn[Co(CN)(6)](0.91) is further lowered to the polar space group Pn by an improper ferroelectric mechanism. These fundamental insights aim to facilitate the rational design of PBAs for applications within a wide range of fields.

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