Yttria nanocrystalline powder doped with 9% lanthanum was synthesized by co-precipitation method using ammonia for pH adjusting. After calcinations, finer particles with narrow distribution and large surface area were...Yttria nanocrystalline powder doped with 9% lanthanum was synthesized by co-precipitation method using ammonia for pH adjusting. After calcinations, finer particles with narrow distribution and large surface area were obtained. After dry pressing, samples were sintered at 1500℃―1700℃ for 4 h in vacuum to produce transparent polycrystalline ceramics with uniform grains. Samples with 9 mol% lanthanum were transparent in visible light after being sintered at 1500℃ for 4 h. The grain sizes increased with lanthanum doping compared with those of pure yttria transparent ceramic sintered at the same conditions. Relative density of the transparent ceramic was 99.7%. The in-line transmittance was 73% at 580 nm wavelength after milling and polishing.展开更多
MWCNTS/SiC composites were fabricated by aqueous tape casting. High solid content (50 vol%) SiC slurries with sintering additives and multi-wall carbon nanotubes (MWCNTs) as reinforcements were prepared using Tetramet...MWCNTS/SiC composites were fabricated by aqueous tape casting. High solid content (50 vol%) SiC slurries with sintering additives and multi-wall carbon nanotubes (MWCNTs) as reinforcements were prepared using Tetramethylammonium hydroxide as the dispersant. The stability of MWCNTs/SiC slur-ries was studied and characterized in terms of zeta potential and rheology measurements. The relative density of the composite was about 98% after hot-pressing at 1850℃ (at 25 MPa in Ar for 30 min). The hardness of the composites decreased with the increase in MWCNTs content. The flexural strength and the fracture toughness were 742.17 MPa and 4.63 MPa·m1/2, respectively when the MWCNTs content was 0.25 wt%. Further increase in MWCNTs content to 0.50 wt% did not lead to the increase in mechanical properties. Most of MWCNTs were found to be located at SiC grain boundaries and the pull out of the MWCNTs was observed.展开更多
基金Supported by the Shanghai Science and Technology Committee(Grant No.07DJ14001)State Key Laboratory of High Performance Ceramics and Superfine Microstructures
文摘Yttria nanocrystalline powder doped with 9% lanthanum was synthesized by co-precipitation method using ammonia for pH adjusting. After calcinations, finer particles with narrow distribution and large surface area were obtained. After dry pressing, samples were sintered at 1500℃―1700℃ for 4 h in vacuum to produce transparent polycrystalline ceramics with uniform grains. Samples with 9 mol% lanthanum were transparent in visible light after being sintered at 1500℃ for 4 h. The grain sizes increased with lanthanum doping compared with those of pure yttria transparent ceramic sintered at the same conditions. Relative density of the transparent ceramic was 99.7%. The in-line transmittance was 73% at 580 nm wavelength after milling and polishing.
基金Supported by the Shanghai Key Program for Basic Research (Grant No. 06JC14071)
文摘MWCNTS/SiC composites were fabricated by aqueous tape casting. High solid content (50 vol%) SiC slurries with sintering additives and multi-wall carbon nanotubes (MWCNTs) as reinforcements were prepared using Tetramethylammonium hydroxide as the dispersant. The stability of MWCNTs/SiC slur-ries was studied and characterized in terms of zeta potential and rheology measurements. The relative density of the composite was about 98% after hot-pressing at 1850℃ (at 25 MPa in Ar for 30 min). The hardness of the composites decreased with the increase in MWCNTs content. The flexural strength and the fracture toughness were 742.17 MPa and 4.63 MPa·m1/2, respectively when the MWCNTs content was 0.25 wt%. Further increase in MWCNTs content to 0.50 wt% did not lead to the increase in mechanical properties. Most of MWCNTs were found to be located at SiC grain boundaries and the pull out of the MWCNTs was observed.
