| 1. |
- Liu, Leifeng, et al.
(författare)
-
Self-supported yttria-stabilized zirconia mesocrystals with tunable mesopores prepared by a chemi-thermal process
- 2019
-
Ingår i: Journal of Materiomics. - : Elsevier BV. - 2352-8478 .- 2352-8486. ; 5:3, s. 350-356
-
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.
|
|
| 2. |
- Chen, Jinhan, et al.
(författare)
-
The effect of hot isostatic pressing on thermal conductivity of additively manufactured pure tungsten
- 2020
-
Ingår i: International journal of refractory metals & hard materials. - : Elsevier BV. - 0263-4368. ; 87
-
Tidskriftsartikel (refereegranskat)abstract
- The crack-healing behaviors and microstructure evolution of pure tungsten produced by laser powder bed fusion (LPBF) were studied and compared before and after post hot isostatic pressing (post-HIP) treatment. An average thermal conductivity of 133 W.m(-1).K-1 at room temperature (RT) was obtained after HIP, which was 16% higher than that of as-built sample (115 W.m(-1).K-1). Although the HIP process had little effect on density, it resulted in a large grain size of > 300 mu m accompanied by a decrease in dislocation density and crack healing, which led to a substantial improvement of thermal conductivity of pure tungsten. The positive correlation between relative density and thermal conductivity of as-built tungsten was reported.
|
|
| 3. |
- Li, Duan, et al.
(författare)
-
Dense and strong ZrO2 ceramics fully densified in <15 min
- 2019
-
Ingår i: Advances in Applied Ceramics. - : Informa UK Limited. - 1743-6753 .- 1743-6761. ; 118:1-2, s. 23-29
-
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.
|
|
| 4. |
|
|
| 5. |
|
|
| 6. |
- Liu, Xihe, et al.
(författare)
-
CNT-reinforced AlSi10Mg composite by selective laser melting : microstructural and mechanical properties
- 2019
-
Ingår i: Materials Science and Technology. - : Informa UK Limited. - 0267-0836 .- 1743-2847. ; 35:9, s. 1038-1045
-
Tidskriftsartikel (refereegranskat)abstract
- Carbon nanotube (CNT)-AlSi10Mg composites were fabricated by selective laser melting (SLM). The influence of CNTs on the density, microstructure, and strength of SLM CNT-AlSi10Mg composites was investigated. The addition of CNTs over 0.1 wt-% significantly damaged the density due to the high surface energy of the CNTs. The network Si eutectic had no significant difference in either the SLM AlSi10Mg alloy or the CNT-AlSi10Mg composite. Reserved CNTs with a short scale were observed in the SLM CNT(0.5 wt-%)-AlSi10Mg composite. The ultimate tensile strength of the 0.05 wt-% CNT-AlSi10Mg composite was 441.2 +/- 0.9 MPa, which was higher than that of AlSi10Mg alloy. The grain boundary strengthening played an important role in the reinforcement of CNT-AlSi10Mg composite because of the refined grain.
|
|
| 7. |
- Liu, Xihe, et al.
(författare)
-
Microstructure of selective laser melted AlSi10Mg alloy
- 2019
-
Ingår i: Materials & design. - : Elsevier BV. - 0264-1275 .- 1873-4197. ; 168
-
Tidskriftsartikel (refereegranskat)abstract
- The influence of laser power during selective laser melting (SLM) on the grain morphology and texture component in AlSi10Mg alloy has been investigated, using electron backscattered diffraction (EBSD). Both equiaxed and columnar grainswere observed. The formation of equiaxed grainswas attributed to the huge thermal gradient on the border of melt pool and the columnar to equiaxed transition (CET) occurred in front of the columnar grains. The grain size of lowlaser power samplewas found smaller than that of higher ones. A fine pseudoeutectic structure, in which Si existed as fibrous, was observed because of the high cooling rate. This paper, from a new angle, explained the formations of three different zones across the melt pool, which were differentiated by the morphology of Si phase. The three zones correspond to the three temperature zones, whichwere divided by liquidus and solidus temperature, during the heating by laser beam. The coarse zones are formed by reheating the basic metal to semi-solid state when the temperature is lower than the liquidus temperature but higher than the solidus temperature.
|
|
| 8. |
- Liu, Xihe, et al.
(författare)
-
Morphological Development of Sub-Grain Cellular/Bands Microstructures in Selective Laser Melting
- 2019
-
Ingår i: Materials. - : MDPI AG. - 1996-1944. ; 12:8
-
Tidskriftsartikel (refereegranskat)abstract
- In this paper, single-layer and bulk 316 L selective laser melting (SLM) experiments were conducted, fine submicron-scale geometric symmetrical cellular (hexagonal, pentagonal and square), elongated cellular and bands solidification morphologies were found in the laser-melt top surface. Meanwhile, morphological developed sub-grain patterns with quasi-hexagonal cellular, elongated cellular and bands structures (size similar to 1 m) coexisting inside one single macro-solidified grain were also identified. This demonstrated the transitions from quasi-hexagonal-cells to elongated cells/bands, and transitions reverse, occurred in the whole bulk under some circumstances during SLM. Based on the experimental realities, these morphologies are formed by the local convection and Benard instabilities in front of the solid/liquid interface (so-called mushy zones) affected by intricate temperature and surface tension gradients. Quasi-hexagonal cellular convective fields are then superimposed on macro-grain solidification to form the sub-grain patterns and micro-segregations. This explanation seems reasonable and is unifying as it can be expanded to other eutectic alloys with face center cubic (FCC) prevenient phase prepared by SLM, e.g., the Al-Si and Co-Cr-Mo systems.
|
|
| 9. |
- Liu, Yihong, et al.
(författare)
-
Failure Modes and Fracture Origins of Porcelain Veneers on Bilayer Dental Crowns
- 2014
-
Ingår i: International Journal of Prosthodontics. - : Quintessence Publishing. - 0893-2174 .- 1139-9791. ; 27:2, s. 147-150
-
Tidskriftsartikel (refereegranskat)abstract
- The aims of this study were to determine the fracture origins and crack paths in the porcelain of clinically failed bilayer ceramic restorations and to reveal the correlation between the porcelain failures and material properties. Three clinically failed crowns of each material (bilayer zirconia crowns, galvano-ceramic crowns, and porcelain-fused-to-metal crowns) were collected and underwent failure analysis. The fractures found in porcelain veneers showed several characteristics including wear, Hertzian cone crack, chipping off, and delamination. The results indicated that the fracture origins and features of the porcelain in bilayer ceramic restorations might be affected by the rigidity of core materials and thickness of copings.
|
|
| 10. |
- Liu, Yihong, et al.
(författare)
-
Self-glazed zirconia reducing the wear to tooth enamel
- 2016
-
Ingår i: Journal of the European Ceramic Society. - : Elsevier BV. - 0955-2219 .- 1873-619X. ; 36:12, s. 2889-2894
-
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.
|
|
