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Fu, Le
Publications (10 of 13) Show all publications
Chen, S., Abdel-Magied, A. F., Fu, L., Jonsson, M. & Forsberg, K. (2019). Incorporation of strontium and europium in crystals of a-calcium isosaccharinate. Journal of Hazardous Materials, 364, 309-316
Open this publication in new window or tab >>Incorporation of strontium and europium in crystals of a-calcium isosaccharinate
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2019 (English)In: Journal of Hazardous Materials, ISSN 0304-3894, E-ISSN 1873-3336, Vol. 364, p. 309-316Article in journal (Refereed) Published
Abstract [en]

The final repository for short-lived, low and intermediate level radioactive waste in Sweden is built to act as a passive repository. Already within a few years after closure water will penetrate the repository and conditions of high alkalinity (pH 10.5-13.5) and low temperature (< 7 degrees C) will prevail. The mobility of radionuclides in the repository is dependent on the radionuclides distribution between solid and liquid phases. In the present work the incorporation of strontium (II) and europium (III) in alpha-calcium isosaccharinate (ISA) under alkaline conditions (pH similar to 10) at 5 degrees C and 50 degrees C have been studied. The results show that strontium and europium are incorporated into alpha-Ca(ISA)(2) when crystallized both at 5 degrees C and 50 degrees C. Europium is incorporated to a greater extent than strontium. The highest incorporation of europium and strontium at 5 degrees C rendered the phase compositions Ca0.986Eu0.014(ISA)(2) (2.4% of Eu(ISA)(3) by mass) and Ca0.98Sr0.02(ISA)(2) (2.2% of Sr(ISA)(2) by mass). XPS spectra show that both trivalent and divalent Eu coexist in the Eu incorporated samples. Strontium ions were found to retard the elongated growth of the Ca(ISA)(2) crystals. The incorporation of Sr2+ and Eu3+ into the solid phase of Ca(ISA)(2) is expected to contribute to a decreased mobility of these ions in the repository.

Place, publisher, year, edition, pages
ELSEVIER SCIENCE BV, 2019
Keywords
Mobility, Radionuclides, Isosaccharinate, Precipitation
National Category
Physical Chemistry
Identifiers
urn:nbn:se:uu:diva-372867 (URN)10.1016/j.jhazmat.2018.10.001 (DOI)000452926500034 ()30384240 (PubMedID)
Funder
Swedish Radiation Safety Authority, SSM2016-2126
Available from: 2019-01-10 Created: 2019-01-10 Last updated: 2019-01-10Bibliographically approved
Fu, L., Xiong, Y., Carlsson, G., Palmer, M., Örn, S., Zhu, W., . . . Xia, W. (2018). Biodegradable Si3N4 bioceramic sintered with Sr, Mg and Si for spinal fusion: Surface characterization and biological evaluation. Applied Materials Today, 12, 260-275
Open this publication in new window or tab >>Biodegradable Si3N4 bioceramic sintered with Sr, Mg and Si for spinal fusion: Surface characterization and biological evaluation
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2018 (English)In: Applied Materials Today, ISSN 2352-9407, Vol. 12, p. 260-275Article in journal (Refereed) Published
Abstract [en]

Silicon nitride (Si3N4) is an industrial ceramic used in spinal fusion and maxillofacial reconstructionbecause of its excellent mechanical properties and good biocompatibility. This study compares the sur-face properties, apatite formation ability, bacterial infection, cell-biomaterial interactions, and in vivotoxicity (zebrafish) of newly developed Si3N4 bioceramics (sintered with bioactive sintering additivesSrO, MgO and SiO2) with two standard biomaterials; titanium (Ti) and traditional Si3N4 bioceramics (sin-tered with standard sintering additives Al2O3 and Y2O3). In general, Si3N4 bioceramics (both the newlydeveloped and the traditional) displayed less in vitro bacterial affinity than Ti, which may arise fromdifferences in the surface properties between these two types of material. The newly developed Si3N4bioceramics developed lower biofilm coverage and thinner biofilm, compared to traditional Si3N4 bioce-ramics. The effects of ionic dissolution products (leach) on proliferation and differentiation of MC3T3-E1cell were also investigated. Ionic dissolution products containing moderate amount of Sr, Mg and Siions (approximately 4.72 mg/L, 3.26 mg/L and 3.67 mg/L, respectively) stimulated osteoblast prolifera-tion during the first 2 days in culture. Interestingly, ionic dissolution products from the traditional Si3N4bioceramics that contained small amount of Si and Y ions achieved the greatest stimulatory effect foralkaline phosphatase activity after 7 days culture. The toxicity of ionic dissolution products was investi-gated in a putative developmental biology model: zebrafish (Danio rerio). No toxicity, or developmentalabnormalities, was observed in zebrafish embryos exposed to ionic dissolution products, for up to 144 hpost fertilization. These newly developed Si3N4 bioceramics with bioactive sintering additives show greatpotential as orthopedic implants, for applications such as spinal fusion cages. Future work will focus onevaluation of the newly developed Si3N4 bioceramics using a large animal model.

Keywords
Si3N4 bioceramic, Spinal fusion, Biocompatibility, Bioactive ions, Zebrafish
National Category
Medical Materials
Identifiers
urn:nbn:se:uu:diva-356522 (URN)10.1016/j.apmt.2018.06.002 (DOI)000443213700023 ()
Funder
Carl Tryggers foundation
Available from: 2018-07-30 Created: 2018-07-30 Last updated: 2019-06-26Bibliographically approved
Fu, L. (2018). Spark plasma sintered ZrO2-SiO2 glass ceramics and Si3N4 bioceramics. (Doctoral dissertation). Uppsala: Acta Universitatis Upsaliensis
Open this publication in new window or tab >>Spark plasma sintered ZrO2-SiO2 glass ceramics and Si3N4 bioceramics
2018 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

This thesis focuses on elaboration and characterization of two types of bioceramics: one is ZrO2-SiO2 nanocrystalline glass ceramic (NCGC) for dental application. The goal is to develop new ZrO2-SiO2 NCGCs with a combination of high strength and high translucency; the other is biodegradable Si3N4 ceramics for spinal fusion. This project aims to improve the osteointergration property of Si3N4 ceramics. Translucent glass ceramics typically suffer from impaired mechanical properties, compared to full-ceramics. We presented a method of obtaining ZrO2-SiO2 NCGCs, with a microstructure of monocrystalline ZrO2 nanoparticles (NPs), embedded in an amorphous SiO2 matrix. Raw powders containing different ZrO2 contents were prepared by the sol-gel method, followed by the spark plasma sintering (SPS). The NCGC with a composition of 35%ZrO2-65%SiO2 (molar ratio, 35Zr) was transparent. Tetragonal ZrO2 NPs were spherical with a diameter of 20–40 nm. The average flexural strength of 35Zr NCGC was 234 MPa. To improve the flexural strength, NCGCs with compositions of 45%ZrO2-55%SiO2 (45Zr), 55%ZrO2-45%SiO2 (55Zr), 65%ZrO2-35%SiO2 (65Zr) were also elaborated. All NCGCs showed high translucency. The flexural strength of the NCGCs significantly increased with the increase of ZrO2 content, achieving as high as 1014 MPa for 65Zr NCGC.  ZrO2 NPs in 65Zr NCGC were ellipsoidal and had a core-shell structure with a thin Zr/Si interfacial layer as the shell. Some of the ZrO2 NPs were connected and formed ZrOnanofibers. Moreover, the ZrOnanofibers were orderly stacked in short-range to form the 3D nano-architecture. The high flexural strength of the 65Zr NCGC mainly originates from synergistic strengthening effects of the thin Zr/Si interfacial layer and 3D stacked nano-architecture. Regarding biodegradable Si3N4 bioceramics, we used a ternary sintering additive of SrO, MgO and SiO2.   The mechanical properties of the developed Si3N4 bioceramics were comparable to those of traditional Si3N4 ceramics. Sr2+, Mg2+, and Si4+ ions released from the intergranular glass phase after immersion in solution, indicating that the developed Si3N4 bioceramics showed certain biodegradable ability. These ions enhanced the proliferation and differentiation of preosteoblasts. Meanwhile, the ionic dissolution products did not show any toxic effects to the development or physiology of zebrafish embryos.

Place, publisher, year, edition, pages
Uppsala: Acta Universitatis Upsaliensis, 2018. p. 70
Series
Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Science and Technology, ISSN 1651-6214 ; 1710
Keywords
ZrO2-SiO2 glass ceramic, high-strength, translucency, 3D nano-architecture, Si3N4 bioceramic, biodegradable, spark plasma sintering
National Category
Ceramics
Research subject
Materials Science
Identifiers
urn:nbn:se:uu:diva-357128 (URN)978-91-513-0419-9 (ISBN)
Public defence
2018-10-10, Häggsalen, 10132, Ångström, Lägerhyddsvägen 1, Uppsala, 09:00 (English)
Opponent
Supervisors
Funder
Carl Tryggers foundation
Available from: 2018-09-18 Created: 2018-08-12 Last updated: 2018-10-02
Fu, L., Engqvist, H. & Xia, W. (2018). Spark plasma sintering of biodegradable Si3N4 bioceramic with Sr, Mg and Si as sintering additives for spinal fusion. Journal of the European Ceramic Society, 38(4), 2110-2119
Open this publication in new window or tab >>Spark plasma sintering of biodegradable Si3N4 bioceramic with Sr, Mg and Si as sintering additives for spinal fusion
2018 (English)In: Journal of the European Ceramic Society, ISSN 0955-2219, E-ISSN 1873-619X, Vol. 38, no 4, p. 2110-2119Article in journal (Refereed) Published
Abstract [en]

Silicon nitride (Si3N4) bioceramics with standard sintering additives (Al2O3 and Y2O3) are used in spinal fusion. Alternative Si3N4 bioceramics with biologically beneficial sintering additives could lead to improved osseoin- tegrative properties. The aim of this study is to obtain dense and strong Si3N4 bioceramics by using SrO, MgO and SiO2 as sintering additives, and evaluate the effect of these sintering additives on microstructures and properties of Si3N4 bioceramics. Raw powders with 10 wt% and 18 wt% sintering additives were sintered by spark plasma sintering. Samples sintered at 1750 °C, with an applied pressure of 60 MPa and a holding time of 3 min, showed the highest content of β-Si3N4 (94.9%). The mechanical properties of the developed Si3N4 bio- ceramics are comparable to the mechanical properties of currently used structural Si3N4 ceramics sintered with standard sintering additives (Al2O3 and Y2O3). The highest flexural strength of the developed Si3N4 bioceramics reached 1079 MPa. Ion release results showed that Sr2+,Mg2+ and Si4+ ions kept leaching out within 10 days’ immersion. The degradable Si3N4 bioceramics with adequate strength and biologically beneficial sintering ad- ditives show the promise for load bearing biomedical applications, such as spinal fusion.

National Category
Natural Sciences Engineering and Technology
Identifiers
urn:nbn:se:uu:diva-331879 (URN)10.1016/j.jeurceramsoc.2017.10.003 (DOI)000424716700136 ()
Funder
Carl Tryggers foundation
Available from: 2017-10-19 Created: 2017-10-19 Last updated: 2018-08-12Bibliographically approved
Fu, L., Xie, L., Fu, W., Hu, S., Zhang, Z., Leifer, K., . . . Xia, W. (2018). Ultrastrong translucent glass ceramic with nanocrystalline, biomimetic structure. Nano letters (Print), 18(11), 7146-7154
Open this publication in new window or tab >>Ultrastrong translucent glass ceramic with nanocrystalline, biomimetic structure
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2018 (English)In: Nano letters (Print), ISSN 1530-6984, E-ISSN 1530-6992, Vol. 18, no 11, p. 7146-7154Article in journal (Refereed) Published
Abstract [en]

Transparent/translucent glass ceramics (GCs) have broad applications in biomedicine, armor, energy, and constructions. However, GCs with improved optical properties typically suffer from impaired mechanical properties, compared to traditional sintered full-ceramics. We present a method of obtaining high-strength, translucent GCs by preparing ZrO2-SiO2 nanocrystalline glass ceramics (NCGCs), with a microstructure of monocrystalline ZrO2 nanoparticles (NPs), embedded in an amorphous SiO2 matrix. The ZrO2-SiO2 NCGC with a composition of 65%ZrO2-35%SiO2 (molar ratio, 65Zr) achieved an average flexural strength of 1 GPa. This is one of the highest flexural strength values ever reported for GCs. ZrO2 NPs have a core-shell structure, and the shell is a thin (2–3 nm) amorphous Zr/Si interfacial layer that provides strong bonding between the ZrO2 NPs and SiO2 matrix. The diffusion of Si atoms into the ZrO2 NPs forms a Zr-O-Si superlattice. Electron tomography results show that some of the ZrO2 NPs are connected in one direction, forming in situ ZrO2 nanofibers (with length of ~500 nm), and that the ZrO2 nanofibers are stacked in an ordered way in all three dimensions. The nano-architecture of the ZrO2 nanofibers mimics the architecture of mineralized collagen fibril in cortical bone. Strong interface bonding enables efficient load transfer from the SiO2 matrix to the 3D nano-architecture built by ZrO2 nanofibers and NPs, and the 3D nano-architecture carries the majority of the external load. These two factors synergistically contribute to the high strength of the 65Zr NCGC. This study deepens our fundamental understanding of the microstructure-mechanical strength relationship, which could guide the design and manufacture of other high-strength, translucent GCs.

Keywords
glass ceramic, translucency, high strength, biomimetic structure, 3D nano-architecture
National Category
Nano Technology
Identifiers
urn:nbn:se:uu:diva-356884 (URN)10.1021/acs.nanolett.8b03220 (DOI)000451102100065 ()30335389 (PubMedID)
Funder
Carl Tryggers foundation
Note

Le Fu and Ling Xie contributed to this work equally and are co-first authors

Available from: 2018-08-08 Created: 2018-08-08 Last updated: 2018-12-21Bibliographically approved
Xia, W., Fu, L. & Engqvist, H. (2017). Critical cracking thickness of calcium phosphates biomimetic coating: Verification via a Singh-Tirumkudulu model. Ceramics International, 43, 15729-15734
Open this publication in new window or tab >>Critical cracking thickness of calcium phosphates biomimetic coating: Verification via a Singh-Tirumkudulu model
2017 (English)In: Ceramics International, ISSN 0272-8842, E-ISSN 1873-3956, Vol. 43, p. 15729-15734Article in journal (Refereed) Published
Abstract [en]

Despite the many advantages of biomimetic calcium phosphates (CaPs) coatings, there is a troublesome problem of low cohesion in the coatings. The low cohesion originates from the absence of bonding between CaP crystals, leading to cracks during drying of the coatings. In this study, based on a simplified Singh-Tirumkudulu model, the critical cracking thickness (CCT) of biomimetic CaPs coatings has been calculated. CaPs crystal size is the key factor influencing the CCT, except for the particle's shear modulus. Biomimetic CaPs coatings with different thickness have been prepared by soaking Ti substrates with a transition layer of TiO2 (rutile) in Dulbecco's phosphate buffer saline solution (DPBS) for 1, 2, 4 and 6 weeks. The morphology, thickness, and whether cracks formed or not were evaluated by SEM. The simplified Singh and Tirumkudulu model has been verified in terms of our experimental results and data obtained from previous literatures. Via dedicated experiments and calculations it is concluded that a thickness of about approximately 2 gm is the critical value for a crack-free CaPs coating given that the CaPs crystal size is smaller than 100 nm. The model could be used in the future design of crack-free biomimetic coatings.

National Category
Medical Materials
Identifiers
urn:nbn:se:uu:diva-330143 (URN)10.1016/j.ceramint.2017.08.134 (DOI)000413175300158 ()
Available from: 2017-09-26 Created: 2017-09-26 Last updated: 2018-02-05Bibliographically approved
Fu, L., Engqvist, H. & Xia, W. (2017). Highly translucent and strong ZrO2-SiO2 nanocrystalline glass ceramic prepared by sol-gel method and spark plasma sintering with fine 3D microstructure for dental restoration. Journal of the European Ceramic Society, 37(13), 4067-4081
Open this publication in new window or tab >>Highly translucent and strong ZrO2-SiO2 nanocrystalline glass ceramic prepared by sol-gel method and spark plasma sintering with fine 3D microstructure for dental restoration
2017 (English)In: Journal of the European Ceramic Society, ISSN 0955-2219, E-ISSN 1873-619X, Vol. 37, no 13, p. 4067-4081Article in journal (Refereed) Published
Abstract [en]

Balance of better mechanical strength and good translucency for dental restorative materials is always a challenge. A translucent glass ceramic/ceramic with improved mechanical properties or a strong glass ceramic/ceramic with good translucency would therefore be interesting for dental application. Nanocrystalline glass ceramics (NCGC) attract a lot attention because of their superior optical and mechanical properties. This study aims to obtain ZrO2-SiO2 nanocrystalline glass-ceramic that possesses high mechanical strength as well as excellent translucency by controlling the content, size, and connection of nanocrystalline ZrO2 in a ZrO2-SiO2 glass-ceramic material. Toward this end, well-homogenized nano powders with three different compositions, 45%ZrO2-55%SiO2 (molar ratio, 45Zr), 55%ZrO2-45%SiO2 (55Zr), and 65%ZrO2-35%SiO2 (65Zr), were synthesized, followed by a fast sintering process. Highly translucent nanocrystalline glass ceramics composed of tetragonal ZrO2 were obtained. Samples with high zirconia content showed that the structure of the skeleton was predominately built by nano-sized ellipsoidal ZrO2 particles bonded by grain boundaries, with amorphous SiO2 filling the voids between the ZrO2 particles. The achieved flexural strength measured by piston-on-three-ball test was as high as 1014 MPa. To our knowledge, this is one of the highest flexural strength values of glass ceramics ever reported, which is higher than transparent zirconia and alumina ceramics. The 3D structure of nanocrystalline zirconia in silica matrix did enhance the flexural strength of the NCGC. The results of this study suggest that the new ZrO2-SiO2 NCGC has great potential of using as dental restoration.

Keywords
Nanocrystalline glass ceramics, ZrO2-SiO2, Translucency, High strength, 3D microstructure
National Category
Ceramics
Identifiers
urn:nbn:se:uu:diva-360206 (URN)10.1016/j.jeurceramsoc.2017.05.039 (DOI)000404704800027 ()
Funder
Carl Tryggers foundation
Available from: 2018-09-13 Created: 2018-09-13 Last updated: 2018-09-13Bibliographically approved
Fu, L., Unosson, E., Wu, C., Grandfield, K., Chang, J., Engqvist, H. & Xia, W. (2016). Spark plasma sintering consolidated transparent ZrO2- SiO2 glass ceramic containing nano-sized ZrO2 spheres. In: : . Paper presented at ICC6 International Congress on Ceramics.
Open this publication in new window or tab >>Spark plasma sintering consolidated transparent ZrO2- SiO2 glass ceramic containing nano-sized ZrO2 spheres
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2016 (English)Conference paper, Poster (with or without abstract) (Refereed)
National Category
Medical Materials
Identifiers
urn:nbn:se:uu:diva-284200 (URN)
External cooperation:
Conference
ICC6 International Congress on Ceramics
Available from: 2016-04-15 Created: 2016-04-15 Last updated: 2018-02-08
Fu, L., Wu, C., Grandfield, K., Unosson, E., Chang, J., Engqvist, H. & Xia, W. (2016). Transparent single crystalline ZrO2-SiO2 glass nanoceramic sintered by SPS. Journal of the European Ceramic Society, 36(14), 3487-3494
Open this publication in new window or tab >>Transparent single crystalline ZrO2-SiO2 glass nanoceramic sintered by SPS
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2016 (English)In: Journal of the European Ceramic Society, ISSN 0955-2219, E-ISSN 1873-619X, Vol. 36, no 14, p. 3487-3494Article in journal (Refereed) Published
Abstract [en]

Transparent ZrO2-SiO2 glass ceramics show potential for application in the dental industry. The application of this material prepared by a sol-gel method was hindered by the difficulties in obtaining large dimension samples. Spark plasma sintering (SPS) offers the possibility of achieving transparent ZrO2-SiO2 glass ceramics. In this study, a ZrO2-SiO2 powder was prepared by the sol-gel method and subsequently sintered by SPS. Varied sintering temperatures and pressures were explored to achieve better mechanical strength and transparency. TEM results showed single crystalline ZrO2 spherical nanocrystals (approximately 20 nm) homogenously embedded in the SiO2 matrix. Tetragonal ZrO2 was the only crystalline phase in all specimens. With sintering conditions of 1200 degrees C and 30 MPa, a glass ceramic with fracture toughness of 4.13 MPa was obtained. This value is similar to the commercial dental glass ceramic of IPS e.max (R) Press. The studied transparent glass ceramic with high transparency and moderate mechanical strength shows promise for dental application.

Keywords
ZrO2-SiO2, Single crystalline spheres, Transparent glass ceramic, SPS, Sol-gel
National Category
Materials Engineering
Identifiers
urn:nbn:se:uu:diva-301007 (URN)10.1016/j.jeurceramsoc.2016.05.016 (DOI)000379888400029 ()
External cooperation:
Funder
Carl Tryggers foundation
Available from: 2016-08-17 Created: 2016-08-17 Last updated: 2018-08-12Bibliographically approved
Cai, Y., Pujari-Palmer, S., Gururaj, S., Fu, L., Chen, S., Engqvist, H., . . . Xia, W. (2016). Utilization of Translucent Hydroxyapatite Nano-Ceramics as a Bio-Window Material. Nano Advances, 1, 45-49
Open this publication in new window or tab >>Utilization of Translucent Hydroxyapatite Nano-Ceramics as a Bio-Window Material
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2016 (English)In: Nano Advances, Vol. 1, p. 45-49Article in journal (Refereed) Published
Abstract [en]

Bioceramic materials are importantlyused in the field ofhard tissue engineering. The direct detection of cell response is almost impossible for mostof bioceramics due to theiropaqueness. Thus,the live tracking of cell behavior cannot be performedon these ceramics. In this study, we proposea strategy thatdirect observation of cell growth through hydroxyapatite (HA)ceramics can be realized by employing a translucent hydroxyapatite (tHA) nano-ceramic. We obtained MC3T3 preosteoblast cells and cultured them in the presence of tHA for up to 7 days. The results show that MC3T3cells were able to be seen through the tHA. In addition, live fluorescent staining confirmed that the MC3T3 cells were viable throughout the culture time period. The findings reveal the as-fabricated tHA nano-ceramics can bepotentialas a bio-window material for cell adhesion and proliferation.

National Category
Nano Technology
Identifiers
urn:nbn:se:uu:diva-277119 (URN)
Available from: 2016-02-17 Created: 2016-02-17 Last updated: 2018-02-08Bibliographically approved
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