| 1. |
- Wei, Zhu, et al.
(författare)
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Injectable and assembled 3D solid structure for free-to-fixed shape in bone reconstruction
- 2020
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Ingår i: Applied Materials Today. - : Elsevier BV. - 2352-9407. ; 21
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Tidskriftsartikel (refereegranskat)abstract
- There is a gap between injectable and scaffold-like bioceramics. Injectable bioactive materials, such as bone cement and hydrogel, are good for minimized surgery, but the extremely low porosity and small pore size limited enhanced bone repair and regeneration. Macroporous bioceramic scaffolds are used because of the controlled pore size and porosity, but not injectable. It's a challenge of preparation of an injectable macroporous ceramic scaffold for minimized bone reconstruction. By using the reversible setting reaction of calcium sulfate and combining a dual setting system with magnesium silicate hydrate, the injectable and assembled 3D porous bioceramic scaffold has been successfully developed. The content of amorphous magnesium silicate hydrate in the dual setting system affected the mechanical strength and degradation. The porous structure could be controlled by the size of granules. The granules can also be used for the fabrication of porous materials with varied shapes and customized structures by using a simple injection process. The biological testing showed good biocompatibility and in vitro osteogenesis. By using the femoral lateral condyle defect model, we can see the granules could be injected into the defect and formed a rigid porous structure in situ, and further presented better new bone formation compared with autologous bone chips. Briefly, we demonstrated the first injectable 3D solid porous ceramic structure for minimized bone repair and free-form shaping.
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| 2. |
- Berg, Camilla
(författare)
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Ceramic Core–Shell Particles : Synthesis and Use within Dentistry
- 2021
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Dentin hypersensitivity is one of the most prevalent conditions related to oral health, affecting a large share of the adult population. Shortcomings with the available treatment options are related to non-ideal particle sizes and degradation properties. An improved clinical outcome could possibly be obtained using a bioactive occluding agent that can offer a high, continuous release of ions, as well as having a particle size that allows for penetration into the dentin tubules. The work in this thesis focused on the development and investigation of a synthesis approach for calcium phosphate core–shell particles and the use of those in the treatment of dentin hypersensitivity. The overall aim was to increase the knowledge about the synthesis and to evaluate the in vitro performance of amorphous calcium magnesium phosphate (ACMP) particles when used as an occluding agent. The synthesis of the core-shell particles was based on precipitation reactions in aqueous solutions and the synthesized materials were studied in terms of morphological, structural, and compositional aspects. Resulting particles had diameters ranging from 400 nm–1. 5 µm (depending on reaction conditions), with morphologies and structures that were shown to correlate with the ionic radius and the concentration of the substituting ion. This insight resulted in the possibility to control the outcome of the reaction and to extend the synthesis to other alkaline earth phosphates. The mechanism of formation was suggested to be the simultaneous precipitation of primary nanoparticles (NPs) and the formation of gas bubbles that could function as soft templates.A study of the degradation properties together with a series of in vitro studies, using a dentin-disc model, indicated that the ACMP particles may be a promising candidate for clinical use. The material was shown to offer a rapid and continuous release of Ca2+, Mg2+, and phosphate, aiding surface, as well as intratubular occlusion and mineralization. Additional use of a fluoride toothpaste resulted in incorporation of F– in the mineralized material. This could enhance the in vivo performance due to the known benefits of including F– in dental tissues, e.g. decreased solubility. The ACMP particles were, furthermore, shown to be more efficient in terms of degree of occlusion when compared to other similar products available on the market. The intratubular mineralization was additionally mitigating the effect of an acid attack, which is of importance for a long-lasting effect in clinical use.
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| 3. |
- Cheng, Kaiyuan, et al.
(författare)
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Injectable tricalcium phosphate/calcium sulfate granule enhances bone repair by reversible setting reaction
- 2021
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Ingår i: Biochemical and Biophysical Research Communications - BBRC. - : Elsevier. - 0006-291X .- 1090-2104. ; 557, s. 151-158
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Tidskriftsartikel (refereegranskat)abstract
- Towards repairing bone defects, calcium sulfate and calcium phosphate cement have been recognized as promising bone grafts. However, the current bone cements are generally lack of proper porosity for cell migration and new tissue formation. On the other hand, porous scaffold cannot be delivered by injection, which limits its use its clinical use. Herein, we develop a novel tricalcium phosphate/calcium sulfate granule to overcome the limitations of injectable cements and traditional scaffolds. The biocompatible granule underwent in situ self-setting to form scaffold with porous structure after injection. It con-tributes to calcium deposition and upregulation of osteogenic genes of mesenchymal stem cells in a time-dependent manner. Within three months, cavitary bone defects of distal rabbit femurs implanted the granules exhibited better bone formation than those with those implanted with autologous bone.
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| 4. |
- Bai, Xuan, et al.
(författare)
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Sequential macrophage transition facilitates endogenous bone regeneration induced by Zn-doped porous microcrystalline bioactive glass
- 2021
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Ingår i: Journal of materials chemistry. B. - : Royal Society of Chemistry. - 2050-750X .- 2050-7518. ; 9:12, s. 2885-2898
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Tidskriftsartikel (refereegranskat)abstract
- Macrophages play an important role in the immune microenvironment during bone healing, and sequential macrophage phenotypic transition could achieve superior osteogenic outcomes. Microcrystalline bioactive glasses (MCBGs) with osteoimmunomodulatory effects show potential in bone tissue regeneration. Zinc (Zn) has been approved to coordinate innate and adaptive immunity. Therefore, in this study, different amounts of ZnO were incorporated into microcrystalline bioactive glass to improve its immunomodulatory ability. The effect of Zn-MCBG ionic extracts on macrophage transition was studied, and the 5Zn-MCBG extracts could orchestrate sequential M1-to-M2 macrophage transition and promote the expression of proinflammatory and anti-inflammatory genes and cytokine expression to induce human bone marrow stromal cells (hBMSCs) osteogenic differentiation in vitro. Macroporous Zn-MCBG scaffolds containing mesopores were fabricated and showed good cell adhesion and feasible apatite formation when immersed in SBF in vitro. Furthermore, a rat calvarial defect model was used to confirm that the Zn-MCBG scaffold could modulate macrophage phenotypic transition and create a desirable osteogenic microenvironment to promote osteogenesis in vivo.
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| 5. |
- Bang, Le T., et al.
(författare)
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Synthesis and assessment of metallic ion migration through a novel calcium carbonate coating for biomedical implants
- 2020
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Ingår i: Journal of Biomedical Materials Research. Part B - Applied biomaterials. - : Wiley. - 1552-4973 .- 1552-4981. ; 108:2, s. 429-438
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Tidskriftsartikel (refereegranskat)abstract
- Titanium (Ti) implants are commonly regarded as well accepted by the body. However, metal ion release is still a cause for concern. A small decrease in pH, which can be caused by inflammation, may produce a large increase in the corrosion rate of Ti implants. Coating the alloy with a buffer layer could have a significant protective effect. In this study, a calcium carbonate coating was developed on commercially pure Ti and a Ti-6Al-4V alloy through a hydrothermal treatment of previously NaOH-treated surfaces in calcium-citric acid chelate complexes. The results showed that a superstructured calcite coating layer formed on the Ti substrate after treatment at 170 degrees C for 3 hr. The coating was approx. 1 mu m thick and covered the substrate surface uniformly. When prolonging the hydrothermal treatment from 5 hr to 24 hr, the rhombohedral structure of calcite was observed in addition to the superstructure of calcite. Dissolution test results showed no significant differences in solution pH between the coated- and un-coated samples. However, the CaCO3 coating reduced by approx. 2-5 times the Ti and V ion release from the substrate as compared to the uncoated material, at pH 4. CaCO3 and hydroxyapatite (HA) coatings gave nonsignificant effects at neutral pH although the HA coating showed a trend for better results at the longer time points. The reduction in metal ion release from the substrate and the buffering ability of the CaCO3 coating encourage further studies on this coating for clinical applications.
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| 6. |
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| 7. |
- Berg, Camilla, et al.
(författare)
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Comparative study of technologies for tubule occlusion and treatment of dentin hypersensitivity
- 2021
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Ingår i: Journal of Functional Biomaterials. - : MDPI. - 2079-4983. ; 12:2
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Tidskriftsartikel (refereegranskat)abstract
- This study aimed to evaluate the occluding/remineralization performance and resistance to acid attacks of the mineralization layer formed by a tooth-desensitizing gel containing amorphous calcium magnesium phosphate (ACMP) particles and compare it to six other desensitizing products available on the market. Similar comprehensive studies are few and there is especially a lack of studies that are up to date. A dentin-disc model was used for in vitro evaluation of the desensitizing toothpastes/gels. Application of the products was performed twice daily for seven days. One set of specimens were evaluated using scanning electron microscopy (SEM) directly after the final treatment and another set was evaluated after an acid challenge, exposing specimens to 2 wt% citric acid. The ACMP desensitizing gel was the only product resulting in complete occlusion by the formation of mineralized material on the dentin surface and inside the tubules. Particle deposition was dominant after treatment with the other desensitizing products, with little or no mineralization, resulting in partial occlusion only. Sensodyne Repair & Protect and Oral-B Pro-Expert showed the highest resistance toward acid attacks. Material inside the tubules remained relatively unaffected by acid attacks in all specimens. The results in this study indicated a great variability among the occluding agents in terms of occlusion and acid resistance of the mineralization layer. The high degree of occlusion and intra-tubular mineralization that could mitigate the effect of acid solubilization indicate that the ACMP desensitizing gel may be a superior option for the treatment of dentin hypersensitivity.
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| 8. |
- F. Abdel-Magied, Ahmed, et al.
(författare)
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Magnetic metal-organic frameworks for efficient removal of cadmium(II), and lead(II) from aqueous solution
- 2022
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Ingår i: Journal of Environmental Chemical Engineering. - : Elsevier BV. - 2213-2929 .- 2213-3437. ; 10:3
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Tidskriftsartikel (refereegranskat)abstract
- Efficient and convenient methods for the removal of toxic heavy metal ions especially Cd(II) and Pb(II) from aqueous solutions is of great importance due to their serious threat to public health and the ecological system. In this study, two magnetic metal-organic frameworks (namely: Fe3O4@ZIF-8, and Fe3O4@UiO-66–NH2) were synthesized, fully characterized, and applied for the adsorption of Cd(II) and Pb(II) from aqueous solutions. The adsorption efficiencies for the prepared nanocomposites are strongly dependent on the pH of the aqueous solution. The maximum adsorption capacities of Fe3O4@UiO-66–NH2, and Fe3O4@ZIF-8 at pH 6.0 were calculated to be 714.3 mg·g−, and 370 mg·g−1 for Cd(II), respectively, and 833.3 mg·g−1, and 666.7 mg·g−1 for Pb(II), respectively. The adsorption process follows a pseudo-second-order model and fit the Langmuir isotherm model. Moreover, the thermodynamic studies revealed that the adsorption process is endothermic, and spontaneous in nature. A plausible adsorption mechanism was discussed in detail. The magnetic adsorbents: Fe3O4@ZIF-8, and Fe3O4@UiO-66–NH2 showed excellent reusability, maintaining the same efficiency for at least four consecutive cycles. These results reveal the potential use of magnetic Fe3O4@ZIF-8, and Fe3O4@UiO-66–NH2 as efficient adsorbents in removing Cd(II) and Pb(II) from aqueous solutions.
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| 9. |
- Fu, Le, et al.
(författare)
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Doping of tantalum, niobium, and hafnium in a translucent ZrO2-SiO2 nanocrystalline glass-ceramic
- 2022
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Ingår i: Journal of the European Ceramic Society. - : Elsevier. - 0955-2219 .- 1873-619X. ; 42:4, s. 1731-1742
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Tidskriftsartikel (refereegranskat)abstract
- The addition of dopant(s) is an effective strategy to regulate the microstructure and properties of ZrO2-based ceramics. In this study, we investigated the effects of ternary element alloying, namely tantalum (Ta), niobium (Nb), and hafnium (Hf) elements, on the microstructure and transformability of ZrO2 nanocrystallites in a ZrO2SiO2 nanocrystalline glass-ceramic (NCGC) during sintering and thermal treatments. The ternary dopants enhanced the transformability of tetragonal ZrO2 (t-ZrO2) nanocrystallites during sintering, i.e., the dopants acted as t-ZrO2 destabilizer. The Ta, Nb and Hf elements dissolved in ZrO2 nanocrystallites, forming ZrO2 solid solution. Meanwhile, lamella nanotwins were formed within many ZrO2 nanocrystallites. No obvious segregation of dopants was detected at ZrO2 grain boundaries. t-ZrO2 and monoclinic (m) ZrO2 nanocrystallites were metastable in thermal treatments process, with "t" to "m" and the reverse "m" to "t" polymorphic transformation occurred simultaneously. Meanwhile, t-ZrO2 and m-ZrO2 nanocrystallites had a great tendency to grow larger during thermal treatments.
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| 10. |
- Fu, Le, et al.
(författare)
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Enhanced Bacteriostatic Properties of Ti Alloys by Surface Nitriding
- 2023
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Ingår i: Biomedical Materials & Devices. - : Springer Nature. - 2731-4812 .- 2731-4820. ; 1, s. 760-771
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Tidskriftsartikel (refereegranskat)abstract
- Surface nitriding has been widely used to improve the surface physicochemical properties of Ti alloys. However, the currently utilized surface nitriding methods, such as laser nitriding, typically require expensive and complicated instruments, which makes surface nitriding a less cost-effective process. Meanwhile, the antibacterial properties of surface-nitrided Ti alloy implants have not been evaluated. Thereafter, in this study, we were aiming to develop an effective, simple, and cost-effective surface nitriding strategy to enhance the antimicrobial properties of Ti alloy implants. The surface nitriding strategy was realized by wet-chemical etching and thermal treatment at controlled conditions. Results showed that the above surface modification treatments exerted significant effects on the phase composition and morphology of the newly formed phases on the surface of Ti samples. Crystalline TiN and TiO2 formed after treatments. Meanwhile, amorphous nitrides and oxynitride were also presented on the sample surfaces. The surface-modified Ti samples showed a bacterial inhibition effect compared with the non-treated Ti ones, and the bacterial inhibition effect was attributed to the released ammonia species from the surface of Ti samples. The surface modification strategy shows promise to improve the bacteriostatic property of Ti implants in dental and orthopedic fields.
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| 11. |
- Fu, Le, et al.
(författare)
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Fabrication of mechanically robust nanoporous ZrSiO4 ceramics at low temperature with a low doping level of Mn dopant
- 2024
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Ingår i: International Journal of Applied Ceramic Technology. - : John Wiley & Sons. - 1546-542X .- 1744-7402. ; 21:3, s. 1954-1964
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Tidskriftsartikel (refereegranskat)abstract
- Zircon (ZrSiO4) ceramics have been widely used in many fields due to their excellent physical and chemical properties. However, ZrSiO4 ceramics typically possess moderately low mechanical properties, which hinders their wider application. Meanwhile, elevated temperatures (similar to 1500 degrees C) are required to obtain high-purity synthetic ZrSiO4 ceramics, which is time- and energy-consuming. In the present study, we prepared mechanically robust ZrSiO4 ceramics at low temperature (similar to 1170 degrees C) with a low doping level of Mn dopant (<2 mol%). The ZrSiO4 ceramic processed by hot isostatic pressing with .5 mol% Mn dopant achieved the highest flexural strength (512 MPa), elastic modulus (341 GPa), and nanohardness (20.8 GPa). These values are significantly higher than conventional ZrSiO4 ceramics. The strengthening mechanisms of the prepared ZrSiO4 ceramics were attributed to the formation of homogeneously-distributed nanopores due to incomplete densification and submicron ZrSiO4 grains (similar to 300 nm). The nanopores avoided stress concentration and deflected microcracks during loading, and the submicron ZrSiO4 grains endowed the ZrSiO4 ceramics with grain refinement strengthening. The results reported in this study would offer guidance to fabricate mechanically robust ZrSiO4 ceramics at low temperatures with a low doping level of dopant.
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| 12. |
- Fu, Le, et al.
(författare)
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Far from equilibrium ultrafast high-temperature sintering of ZrO2-SiO2 nanocrystalline glass-ceramics
- 2023
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Ingår i: Journal of The American Ceramic Society. - : John Wiley & Sons. - 0002-7820 .- 1551-2916. ; 106:7, s. 4005-4012
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Tidskriftsartikel (refereegranskat)abstract
- Ultrafast high-temperature sintering (UHS) is a novel sintering technique with ultrashort firing cycles (e.g., a few tens of seconds). The feasibility of UHS has been validated on several ceramics and metals; however, its potential in consolidating glass-ceramics has not yet been demonstrated. In this work, an optimized carbon-free UHS was utilized to prepare ZrO2-SiO2 nanocrystalline glass-ceramics (NCGCs). The phase composition, grain size, densification behavior, and microstructures of NCGCs prepared by UHS were investigated and compared with those of samples sintered by pressureless sintering. Results showed that NCGCs with a high relative density (similar to 95%) can be obtained within similar to 50 s discharge time by UHS. The UHS processing not only hindered the formation of ZrSiO4 and cristobalite but also enhanced the stabilization of t-ZrO2. Meanwhile, owing to the ultrashort firing cycles, the UHS technology allowed the NCGCs to be consolidated in a far from equilibrium state. The NCGCs showed a microstructure of spherical monocrystalline ZrO2 nanocrystallites embedded in an amorphous SiO2 matrix.
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| 13. |
- Fu, Le, et al.
(författare)
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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
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Ingår i: Journal of the European Ceramic Society. - : Elsevier BV. - 0955-2219 .- 1873-619X. ; 37, s. 4067-4081
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Tidskriftsartikel (refereegranskat)abstract
- Balance of better mechanical strength and good translucency for dental restorative materials is alwaysa challenge. A translucent glass ceramic/ceramic with improved mechanical properties or a strongglass 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 andmechanical properties. This study aims to obtain ZrO2-SiO2 nanocrystalline glass-ceramic that possesseshigh mechanical strength as well as excellent translucency by controlling the content, size, and connectionof 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 withhigh zirconia content showed that the structure of the skeleton was predominately built by nano-sizedellipsoidal ZrO2 particles bonded by grain boundaries, with amorphous SiO2 filling the voids betweenthe ZrO2 particles. The achieved flexural strength measured by piston-on-three-ball test was as high as1014 MPa. To our knowledge, this is one of the highest flexural strength values of glass ceramics everreported, which is higher than transparent zirconia and alumina ceramics. The 3D structure of nanocrys-talline zirconia in silica matrix did enhance the flexural strength of the NCGC. The results of this studysuggest that the new ZrO2-SiO2 NCGC has great potential of using as dental restoration.
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| 14. |
- Fu, Le, et al.
(författare)
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Liquid-phase sintering of ZrO2-based nanocrystalline glass-ceramics achieved by multielement co-doping
- 2023
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Ingår i: Journal of The American Ceramic Society. - : John Wiley & Sons. - 0002-7820 .- 1551-2916. ; 106:4, s. 2702-2715
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Tidskriftsartikel (refereegranskat)abstract
- Liquid-phase sintering (LPS) is an effective pathway to assist the densification of ceramics. However, it has seldom been used to densify glass-ceramics. In the present study, a multielement co-doping strategy has been utilized to achieve LPS of a ZrO2-SiO2 nanocrystalline glass-ceramic. Compared with undoped samples densified by solid-state sintering, doping of equimolar Al, Y, and Ca promoted the densification of the glass-ceramic at lower temperatures with a faster densification rate. Ternary doping enhanced coarsening of ZrO2 nanocrystallites during sintering and annealing. The distribution of dopants was carefully observed with X-ray energy-dispersive spectrometry technique in scanning electron transmission microscopy mode. Results showed that the three dopants showed different distribution behaviors. After sintering, Y dopants were predominately distributed in ZrO2 nanocrystallites, whereas parts of Al and Ca dopants were distributed in ZrO2 nanocrystallites and part of them co-segregated at the ZrO2/SiO2 heterointerfaces. Meanwhile, the segregation of Ca dopant at some intergranular films among ZrO2 nanocrystallites was observed. Redistribution of dopants did not occur during annealing.
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| 15. |
- Fu, Le, et al.
(författare)
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Microstructure of rapidly-quenched ZrO2-SiO2 glass-ceramics fabricated by container-less aerodynamic levitation technology
- 2023
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Ingår i: Journal of The American Ceramic Society. - : John Wiley & Sons. - 0002-7820 .- 1551-2916. ; 106:4, s. 2635-2651
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Tidskriftsartikel (refereegranskat)abstract
- In this work, an aerodynamic levitation technology (ALT) was utilized to prepare ZrO2-SiO2 glass-ceramics with two different ZrO2 contents, that is, 35 mol% and 50 mol%. The glass-ceramics were partially melted at similar to 2000 degrees C or fully melted at similar to 3000 degrees C by ALT, followed by rapid quenching to obtain spherical glass-ceramic beads. The phase compositions and microstructures of the glass-ceramics were characterized. Crystallization of ZrO2 occurred during the solidification process and ZrO2 content, processing temperature, and the addition of yttrium (3 mol%) affected the crystalline phase of ZrO2. No ZrSiO4 or crystalline SiO2 were formed during the solidification process and the glass-ceramics were away from thermodynamic equilibrium due to rapid quenching. The glass-ceramics showed a microstructure of irregular-shaped ZrO2 micro-aggregates embedded in an amorphous SiO2 matrix, with lamellar twins and lattice defects formed within ZrO2 crystals. For samples prepared at similar to 3000 degrees C, a liquid-liquid phase separation occurred in the melt, which eventually resulted in the formation of large and irregular-shaped ZrO2 aggregates. In comparison, for samples prepared at similar to 2000 degrees C, pre-existed ZrO2 crystals formed during heating acted as nucleation sites during the cooling process, followed by grain growth to form large ZrO2 aggregates. Solidification and microstructure formation mechanisms were proposed to elucidate the solidification process during rapid cooling and the microstructure of the glass-ceramics obtained.
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| 16. |
- Fu, Le, et al.
(författare)
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New insights into the formation mechanism of zircon in a ZrO2-SiO2 nanocrystalline glass-ceramic : A TEM study
- 2022
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Ingår i: Ceramics International. - : Elsevier. - 0272-8842 .- 1873-3956. ; 48:18, s. 27097-27105
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Tidskriftsartikel (refereegranskat)abstract
- We have previously observed that doping of Ca ions was beneficial to the formation of zircon (ZrSiO4). It is well known that synthetic ZrSiO4 is typically formed via a solid-state reaction between ZrO2 and SiO2, in which the interfaces between the reactant and resultant play an important role. However, the interfaces are lacking detailed microstructural observation. This follow-up study aims at exploring the formation mechanism of ZrSiO4 by inspecting the interfaces at the nano and atomic scales with TEM techniques. Results demonstrated that ZrSiO4 was formed in the Ca-doped sample after sintering at 1200 ?, whereas, no ZrSiO4 was formed in the undoped sample even after sintering at 1230 ?. The Ca-doped sample consisted of a continuous ZrSiO4 matrix with dispersed ZrO2 nanocrystallites. Doping of Ca ions promoted the formation of ZrSiO4 by causing lattice distortion and oxygen vacancies in ZrO2 lattices. Thin amorphous grain boundary complexions were found between ZrO2 nanocrystallites and between ZrO2 and ZrSiO4 crystallites. These amorphous complexions acted as reaction sites and an intermediate metastable state for the solid-state reaction. A detailed formation mechanism of ZrSiO4 at the nanometer scale and atomic scale has been proposed.
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| 17. |
- Fu, Le, et al.
(författare)
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Observation of yttrium oxide segregation in a ZrO2-SiO2 glass-ceramic at nanometer dimensions
- 2020
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Ingår i: Journal of The American Ceramic Society. - : WILEY. - 0002-7820 .- 1551-2916. ; 103:12, s. 7147-7158
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Tidskriftsartikel (refereegranskat)abstract
- Dopant segregation at grain boundaries (GBs) in ceramics has been widely reported, while whether similar segregation behavior occurs in glass-ceramics remains unknown. The distribution of dopant in glass-ceramics may be totally different due to the existence of glass phase. This study examines the distribution of Y3+ ions in a ZrO2-SiO2 glass-ceramic. Two samples were prepared by hot pressing, yttrium oxide-doped, and undoped 65 mol% ZrO2-35 mol% SiO2 nanocrystalline glass-ceramics (NCGCs). The NCGCs had the same microstructure, that is, ZrO2 nanoparticles (NPs) embedded in an amorphous SiO2 matrix. XRD results showed that the undoped NCGC was composed of 20.9 wt% (weight percentage) monoclinic ZrO2 (m-ZrO2) and 79.1 wt% tetragonal ZrO2 (t-ZrO2), while the yttrium oxide-doped NCGC was composed of 9.6 wt% m-ZrO2 and 90.4 wt% t-ZrO2. X-ray energy-dispersive spectrometry (EDS) results in scanning electron transmission microscopy (STEM) mode demonstrated that Y3+ ions segregated both on the surface of ZrO2 NPs and within the thin intergranular glass film (with a thickness of approximately 7 angstrom) between ZrO2 NPs in the yttrium oxide-doped NCGC. Interestingly, no obvious Y signals were detected in the amorphous SiO2 matrix. Density functional theory calculation results showed that Y3+ ions had a strong segregation tendency in the GB area and the segregation of Y3+ ions increased the work of separation of GB layer. These findings provide new understanding of the segregation behavior of dopant in glass-ceramics, which may offer useful guidance for other researchers to tailor the properties of glass-ceramics through GB engineering.
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| 18. |
- Fu, Le, et al.
(författare)
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Size-driven phase transformation and microstructure evolution of ZrO2 nanocrystallites associated with thermal treatments
- 2021
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Ingår i: Journal of the European Ceramic Society. - : Elsevier. - 0955-2219 .- 1873-619X. ; 41:11, s. 5624-5633
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Tidskriftsartikel (refereegranskat)abstract
- Thermal stability of nanocrystallites plays an important role in the manufacturing and application of nanocrystalline ceramics/glass-ceramics. This study explores the effects of thermal treatments on the microstructures of two ZrO2-SiO2 nanocrystalline glass-ceramics (NCGCs), an undoped one and a yttria-doped one. The two assintered NCGCs were composed of tetragonal (t) and monoclinic (m) ZrO2 nanocrystallites, and SiO2 component was amorphous. t-ZrO2 and m-ZrO2 nanocrystallites were metastable during thermal treatment. The content of m-ZrO2 in the undoped ZrO2-SiO2 NCGC first increased after thermal treating at 850 degrees C for 5 h, then decreased after thermal treating at and above 950 degrees C. After thermal treating at 1250 degrees C for 5 h, t-ZrO2 nanocrystallites experienced a rapid phase transformation during cooling, resulting the formation of 88.6 vol% m-ZrO2. Sizedriven phase transformation was utilized to explain the metastability of t-ZrO2 and m-ZrO2 nanocrystallites. In contrast, the content of m-ZrO2 in the yttria-doped ZrO2-SiO2 NCGC continuously decreased with the increase of thermal treatment temperature. The addition of yttria improved the phase stability of t-ZrO2 up to at least 1250 degrees C. Crystallite size of both t-ZrO2 and m-ZrO2 nanocrystallites increased with the increase of thermal treatment temperature in the two NCGCs. The presence of residual thermal stress in the as-sintered NCGCs changed the lattice spacing of t-ZrO2 and m-ZrO2 nanocrystallites, and the stress can be released after thermal treatment. Thermal treatment exerts significant influences on the microstructure of ZrO2-SiO2 NCGCs.
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| 19. |
- Fu, Le, et al.
(författare)
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Structural integrity and damage of glass-ceramics after He ion irradiation : Insights from ZrO2-SiO2 nanocrystalline glass-ceramics
- 2023
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Ingår i: Journal of the European Ceramic Society. - : Elsevier. - 0955-2219 .- 1873-619X. ; 43:6, s. 2624-2633
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Tidskriftsartikel (refereegranskat)abstract
- Developing new radiation-resistant materials and understanding the structural damages caused by radiation are persistent goals of material scientists. Here, we report on the structural integrity and damage to ZrO2-SiO2 nanocrystalline glass-ceramics after radiation with 1.4 MeV He ions at three different fluences: 1.0 x 1016 ions/ cm2 (low), 5.0 x 1016 ions/cm2 (moderate), and 1.0 x 1017 ions/cm2 (high) at 500 degrees C. Grazing incident X-ray diffraction shows the tetragonal-ZrO2 to monoclinic-ZrO2 phase transformation induced by microstrain from the irradiation. The addition of yttrium indicated tetragonal-ZrO2 stabilization effect during irradiation. The irra-diated glass-ceramics show a Raman signal-enhancement effect probably related to the electronic structure changes of the amorphous SiO2 component in the glass-ceramics. The formation of microcracks and lattice de-fects within ZrO2 nanocrystallites is the main structural damage caused by irradiation. There was no observable amorphization of ZrO2 nanocrystallites due to irradiation. No obvious He bubbles were detected, either. The formation of microcracks results in a decrease of in the nanohardness of the glass-ceramics. The results provide fundamental experimental data to understand the structural integrity and damage caused by radiation, which could be useful to design radiation-resistant nanocrystalline glass-ceramics for extremely radioactive environments.
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| 20. |
- Fu, L., et al.
(författare)
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Three-Dimensional Insights into Interfacial Segregation at the Atomic Scale in a Nanocrystalline Glass-Ceramic
- 2021
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Ingår i: Nano Letters. - : American Chemical Society (ACS). - 1530-6984 .- 1530-6992. ; 21:16, s. 6898-6906
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Tidskriftsartikel (refereegranskat)abstract
- The distribution of dopant atoms plays a key role in the effectiveness of doping, thereby requiring delicate characterizations. In this study, we found that energy-dispersive X-ray spectroscopy (EDX) and electron energy loss spectroscopy (EELS) techniques in scanning transmission electron microscopy (STEM) were not adequate to reveal the distribution of yttrium and the chemical composition of the ZrO2/SiO2 heterophase interface in an yttrium-doped ZrO2-SiO2 nanocrystalline glass-ceramic. Atom probe tomography (APT) is rarely utilized to characterize ceramics due to some inherent difficulties. However, we successfully revealed the three-dimensional distribution of ZrO2 nanocrystallites and SiO2 matrix at the atomic scale with APT under optimized and well-controlled conditions. We also found that the ZrO2 nanocrystallites had a special core-shell structure, with a thin Zr/Si interfacial layer as a shell and a ZrO2 solid solution as a core. Yttrium dopants showed interfacial segregation at both ZrO2 grain boundaries and the ZrO2/SiO2 heterophase interfaces.
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| 21. |
- Fu, Le, et al.
(författare)
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Understanding microstructure-mechanical properties relationship in ZrO2-SiO2 nanocrystalline glass-ceramics : The effect of ZrO2 content
- 2022
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Ingår i: Materials Science & Engineering. - : Elsevier. - 0921-5093 .- 1873-4936. ; 840
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Tidskriftsartikel (refereegranskat)abstract
- The content of crystalline phase plays a significant role in manipulating the microstructure and mechanical properties of glass-ceramics. This study aims at exploring the optimum content of crystalline phase in ZrO2-SiO2 nanocrystalline glass-ceramics (NCGCs) in terms of obtaining the highest mechanical properties. To this end, the mechanical properties of ZrO2-SiO2 NCGCs with 70 mol%, 75 mol%, 80 mol% ZrO2 were tested and compared with those of the previously prepared NCGCs with ZrO2 content ranging from 35 mol% to 65 mol%. Results showed that 65 mol% was the optimum content of ZrO2 in terms of obtaining the highest flexural strength. The flexural strength of NCGCs with ZrO2 content over 65 mol% was lower than that of the NCGCs with 65 mol% ZrO2. This was because the NCGC with 65 mol% ZrO2 had a homogenous microstructure, with ZrO2 nano crystallites homogeneously distributed in an amorphous SiO2 matrix. Whereas, when ZrO2 content was increased to 75 mol%, ZrO2 nanocrystallites were not homogeneously distributed in the SiO2 matrix anymore. The formation of SiO2 "holes/canyon " due to ZrO2 grain coalescence resulted in the decrease of flexural strength. The fracture mechanism and wear properties of the NCGCs were also investigated.
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| 22. |
- Ghajeri, Farnaz
(författare)
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Nanostructured Ceramics - Synthesis and Understanding
- 2022
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- During the last years, nanostructured ceramics have been favored for use in the industry due to their beneficial properties. For example, calcium phosphate ceramics with their biocompatible and bioactive characteristics are beneficial in biomedicine. On the other hand, silica-based nanoporous materials with large specific surface areas are efficient in adsorption applications. In such materials, the structure is the basis for efficiency in the mentioned applications. This investigation was conducted to understand the structure and its relation to the synthesis process. Two types of materials were investigated: silica-based nanoporous materials under the family name of Quartzene® and calcium phosphate ceramics. We have used different analysis methods, e.g., electron microscopy, nitrogen adsorption, and x-ray diffraction, to characterize the materials and understand the structure. We observed that similar synthesis processes could lead to different structures that were efficient for different applications, e.g., adsorption. The relation between the structure of Quartzene® and its efficiency in the adsorption application is discussed. Various factors (e.g., cleaning method and the storage time/conditions) influenced the resulting structures. Calcium phosphates were produced in aqueous solutions, and the effect of residual ions combined with various reaction temperatures and time was studied. We observed that the combination of residual ions and varying reaction temperature and time could influence the formation of the intermediate phase, octacalcium phosphate (OCP), and dicalcium phosphate dihydrate (DCPD), and particle size when the starting ion concentrations were fixed. High reaction temperature (60 °C) induced OCP and higher precipitation efficiency. For future investigation, fine-tuning the synthesis process is recommended to enhance the structure of the materials suitable for industrial use.
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| 23. |
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| 24. |
- Ghajeri, Farnaz, et al.
(författare)
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The Influence of Residuals Combining Temperature and Reaction Time on Calcium Phosphate Transformation in a Precipitation Process
- 2022
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Ingår i: Journal of Functional Biomaterials. - : MDPI. - 2079-4983. ; 13:1
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Tidskriftsartikel (refereegranskat)abstract
- Precipitation is one of the most common processes to synthesize hydroxyapatite, which is the human body’s mineral forming bone and teeth, and the golden bioceramic material for bone repair. Generally, the washing step is important in the precipitation method to remove the residuals in solution and to stabilize the phase transformation. However, the influence of residuals in combination with the reaction temperature and time, on calcium phosphate formation, is not well studied. This could help us with a better understanding of the typical synthesis process. We used a fixed starting ion concentration and pH in our study and did not adjust it during the reaction. XRD, FTIR, ICP-OES, and SEM have been used to analyze the samples. The results showed that combining residuals with both reaction temperature and time can significantly influence calcium phosphate formation and transformation. Dicalcium phosphate dihydrate formation and transformation are sensitive to temperature. Increasing temperature (60◦C) can inhibit the formation of acidic calcium phosphate or transform it to other phases, and further the particle size. It was also observed that high reaction temperature (60◦C) results in higher precipitation efficiency than room temperature. A low ion concentration combining reaction temperature and time could still significantly influence the calcium phosphate transformation during the drying. © 2022 by the authors.
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| 25. |
- Katsaros, Ioannis, et al.
(författare)
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Antiviral Properties of Oxidized Silicon Nitride Against SARS-CoV-2
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Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
- The spread of SARS-CoV-2 led to a global pandemic that caused several million deaths. The severity of this pandemic created challenges for scientists worldwide regarding the prevention of the spread of COVID-19, the disease the virus causes. While the use of personal protective equipment and social distancing limited the spread of the virus, high transmission rates were noted. A solution to the issue of viral spread can be partially given by the utilization of antiviral materials for long-term protection against pathogens on environmental surfaces. To this end, nitrides are materials of high interest due to their proven efficiency in inactivating bacteria and viruses. Silicon nitride (Si3N4) is a ceramic material that possesses an inactivation mechanism termed ‘catch and kill’. In this study we hypothesized that a surface-modified Si3N4 material whose hydrophilicity has been increased through a heat treatment could lead to high attachment and inactivation of SARS-CoV-2 virions. Si3N4 powders were oxidized, characterized and the inactivation of SARS-CoV-2 by them was tested. The results showed that oxidized Si3N4 was highly effective in binding and inactivating SARS-CoV-2 after as little as one minute of contact and can be used to inhibit the spread of COVID-19 under certain circumstances.
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