| 1. |
- Liu, Leifeng, et al.
(författare)
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Self-supported yttria-stabilized zirconia mesocrystals with tunable mesopores prepared by a chemi-thermal process
- 2019
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Ingår i: Journal of Materiomics. - : Elsevier BV. - 2352-8478 .- 2352-8486. ; 5:3, s. 350-356
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Tidskriftsartikel (refereegranskat)abstract
- Mesoporous mesocrystals are highly desired in catalysis, energy storage, medical and many other applications, but most of synthesis strategies involve the usage of costly chemicals and complicated synthesis routes, which impede the commercialization of such materials. During the sintering of dense ceramics, coarsening is an undesirable phenomenon which causes the growth of the grains as well as the pores hence hinders the densification, however, coarsening is desired in the sintering of porous ceramics to expand the pore sizes while retaining the total pore volume. Here we report a chemi-thermal process, during which nanocrystallite aggregates were synthesized by hydrothermal process and then converted to the product by sintering. Through this strategy, we synthesized mesoporous self-supported mesocrystals of yttria-stabilized zirconia with tunable pore size and the process was then scaled-up to industrial production. The thermal conductivity measurement shows that the mesoporous powder is a good thermal isolator. The monolith pellets can be obtained by SPS sintering under high pressure and the mesoporosity is retained in the monolith pellets. This work features facile and scalable process as well as low cost raw chemicals making it highly desirable in industrial applications.
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| 2. |
- Li, Duan, et al.
(författare)
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Dense and strong ZrO2 ceramics fully densified in <15 min
- 2019
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Ingår i: Advances in Applied Ceramics. - : Informa UK Limited. - 1743-6753 .- 1743-6761. ; 118:1-2, s. 23-29
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Tidskriftsartikel (refereegranskat)abstract
- Crack-free zirconia ceramics were consolidated via sintering by intense thermal radiation (SITR) approach at 1600–1700°C for 3–5 min. The resulted ceramic bulks can achieve a relative density up to 99.6% with a grain size of 300–1200 nm. Their bending strength, Vickers hardness and indentation toughness values are up to 1244 ± 139 MPa, 13.3 ± 0.3 GPa and 5.5 ± 0.1 MPa m1/2, respectively. Quantitative Raman and XRD analysis show the presence of minor m phase on the natural surface (<7%), fracture surface (<10%) and indentation areas (<15%). It reveals that the SITR method is efficient for rapidly manufacturing zirconia ceramics with desired density, fine grained microstructure and good mechanical properties that are strongly demanded in dental applications.
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| 3. |
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| 4. |
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| 5. |
- Liu, Yihong, et al.
(författare)
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Self-glazed zirconia reducing the wear to tooth enamel
- 2016
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Ingår i: Journal of the European Ceramic Society. - : Elsevier BV. - 0955-2219 .- 1873-619X. ; 36:12, s. 2889-2894
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Tidskriftsartikel (refereegranskat)abstract
- The wear behaviors of a newly developed grade of self-glazed zirconia against the enamel of freshly extracted teeth were investigated under simulated oral stresses and chemical environment. It was revealed that an inherently formed enamel-like surface on self-glazed zirconia that is very smooth on micrometer scale yet with nanoscale roughness has almost the same frictional coefficient against tooth enamel as the well-polished zirconia surface. The wear scars observed on the worn surface of enamel against self-glazed zirconia and well-polished zirconia surface revealed that in both cases fatigue wear is the dominating wear mechanism. It was concluded that the friction and wear performances of both the well-polished and self-glazed zirconia ceramics against natural enamel were very similar, which bears a very strong implication for the clinical safe use of the full contour zirconia restorations, yet the self-glazed zirconia provides sufficiently improved aesthetic appearance that ensures its potential for direct clinical uses.
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| 6. |
- Olsén, Jon, 1983-, et al.
(författare)
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Tailoring hierarchical structures in selective laser melted materials
- 2017
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Ingår i: IOP Conference Series. - : Institute of Physics (IOP).
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Konferensbidrag (refereegranskat)abstract
- With selective laser melting the potential to manufacture a wide variety of geometries from different materials has presented itself. Interest in this technology keeps growing every year, and with that growth a deeper understanding of the process and resulting materials is urgently needed. In this paper we present a short overview of the structural elements that appear during selective laser melting, and explain how to tailor them to achieve specific structures and material properties. Melt-pools, texture and grains, subgrain cells, and inclusions are the elements discussed herein, and tailoring of these elements can have effects on density, and corrosion resistance, as well as mechanical properties in general.
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| 7. |
- Shen, Zhijian, et al.
(författare)
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Fractography of self-glazed zirconia with improved reliability
- 2017
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Ingår i: Journal of the European Ceramic Society. - : Elsevier BV. - 0955-2219 .- 1873-619X. ; 37:14, s. 4339-4345
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Tidskriftsartikel (refereegranskat)abstract
- The fractography of a new grade of zirconia ceramics, known as self-glazed zirconia, was investigated. The as-sintered intact top surface was made with superior smoothness that mimicked the optical appearances of the natural teeth enamel. The beneath surface opposite to this was made hierarchically rough with microscopic pits of the size up to 60. μm together with grain-level roughness of about 2. μm. The three-point bending test of the samples made with the hierarchically rough surface being tensile one demonstrated an average bending strength of 1120. ±. 70. MPa and a Weibull modulus of as high as 18 ascribed to the improved structural homogeneity. Surface topography was found the main origins of crack initiation leading to fracture. The observed unusually predominant transgranular fracture mode of submicron-sized grains disclosed a possible toughening mechanism of disassembling of mesocrystalline grains that differs significantly from the commonly quoted phase transformation toughening of this category of ceramics.
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| 8. |
- Yuan, Bo, et al.
(författare)
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Fabrication and microstructure of porous SiC ceramics with Al2O3 and CeO2 as sintering additives
- 2016
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Ingår i: Ceramics International. - : Elsevier BV. - 0272-8842 .- 1873-3956. ; 42:11, s. 12613-12616
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Tidskriftsartikel (refereegranskat)abstract
- In the present study, porous silicon carbide ceramics were prepared via spark plasma sintering at relatively low temperatures using Al2O3 and CeO2 as sintering additives. Sacrificial template was selected as the pore forming mechanism, and gelcasting was used to fix the slurry in a short time. The evolution process of the microstructures during different steps was observed by SEM. The influence of the sintering temperature and sintering additives on the shrinkage and porosity of the samples was studied. The microstructures of different samples were characterized, and the mechanical properties were also evaluated.
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| 9. |
- Afewerki, Samson, et al.
(författare)
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Highly Enantioselective Control of Dynamic Cascade Transformations by Dual Catalysis : Asymmetric Synthesis of Polysubstituted Spirocyclic Oxindoles
- 2015
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Ingår i: ACS Catalysis. - : American Chemical Society (ACS). - 2155-5435. ; 5:2, s. 1266-1272
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Tidskriftsartikel (refereegranskat)abstract
- The highly enantioselective (up to >99.5:0.5 er) synthesis of polysubstituted spirocyclic oxindoles with four new contiguous stereocenters, including the spiro all-carbon quaternary center, is disclosed. It is accomplished by the highly stereoselective control of a dynamic conjugate/intramolecular allylic alkylation relay sequence based on the synergistic cooperation of metal and chiral amine catalysts in which the careful selection of organic Nand, metal complex, and chiral amine is essential. The intermolecular C-C bond-forming step occurred only when both the metal and chiral amine catalysts were present.
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| 10. |
- Chen, Xiaozong, et al.
(författare)
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Preparation of nano-sized Bi2Te3 thermoelectric material powders by cryogenic grinding
- 2012
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Ingår i: Progress in Natural Science. - : Elsevier BV. - 1002-0071 .- 1745-5391. ; 22:3, s. 201-206
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Tidskriftsartikel (refereegranskat)abstract
- A novel method for rapid preparation of Bi2Te3 nano-sized powders with an average particle size of about 7nm was developed. A starting powder mixture consisting of Bi2Te3 coarse particles of similar to 5mm was ground using cryogenic grinding in the liquid nitrogen. For comparison, the conventional high-energy ball milling was used to prepare the Bi2Te3 nano-sized powders. Sintering properties of as-prepared powders was investigated by spark plasma sintering (SPS). The effects of the preparation procedure on the crystallinity, morphology and structure were examined by X-ray diffraction (XRD) and transmission electron microscopy (TEM). It was found that Bi2Te3 was not transformed into a non-equilibrium amorphous phase or decomposed during the cryogenic grinding process, and as-prepared nano-powders possessed excellent sinterability. This technique might also be applicable to other thermoelectric materials.
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