Centrifugal slip casting in prefabricated template was used to prepare open-cell Al2O3 foams. Aqueous α- Al2O3 slurries with up to 50% solid contents (volume fraction) were prepared. The sedimentation of slurries dur...Centrifugal slip casting in prefabricated template was used to prepare open-cell Al2O3 foams. Aqueous α- Al2O3 slurries with up to 50% solid contents (volume fraction) were prepared. The sedimentation of slurries during centrifugation was discussed with respect to the hydronamic conditions at large particle concentrations. The effect of solid contents on mass segregation was observed. Segregation phenomena were hindered for slurries with high solid loadings exceeding 50% (volume fraction). The dried and sintered behaviors of samples were analyzed. The cell struts in green bodies had good particles packing and showed high green density (63.4% theory density). After sintered at 1500 ℃, the cell struts of final products had high sintered density (98.8% theory density) and homogeneous microstructure. The porosity of final products is 75.6%展开更多
Compositionally graded composite of alumina-20%zirconia (volume fraction) was fabricated by using centrifugal casting incorporated with relatively thin slip. An EPMA analysis exhibited a nearly linear variation of the...Compositionally graded composite of alumina-20%zirconia (volume fraction) was fabricated by using centrifugal casting incorporated with relatively thin slip. An EPMA analysis exhibited a nearly linear variation of the alumina/zirconia ratio along the centrifugal direction; zirconia tended to accumulate in the bottom section, while alumina in the top section. Such a graded structure exhibited a considerably higher flexural strength when the alumina rich surface was subjected to a tensile stress than compositionally uniform composite of the same average composition. Fracture toughness measurement across the specimen thickness by indentation method revealed that the crack lengths along the vertical and horizontal directions were different. The anisotropy of the fracture toughness was accounted for by the variation of the residual stress across the specimen thickness.展开更多
文摘Centrifugal slip casting in prefabricated template was used to prepare open-cell Al2O3 foams. Aqueous α- Al2O3 slurries with up to 50% solid contents (volume fraction) were prepared. The sedimentation of slurries during centrifugation was discussed with respect to the hydronamic conditions at large particle concentrations. The effect of solid contents on mass segregation was observed. Segregation phenomena were hindered for slurries with high solid loadings exceeding 50% (volume fraction). The dried and sintered behaviors of samples were analyzed. The cell struts in green bodies had good particles packing and showed high green density (63.4% theory density). After sintered at 1500 ℃, the cell struts of final products had high sintered density (98.8% theory density) and homogeneous microstructure. The porosity of final products is 75.6%
文摘Compositionally graded composite of alumina-20%zirconia (volume fraction) was fabricated by using centrifugal casting incorporated with relatively thin slip. An EPMA analysis exhibited a nearly linear variation of the alumina/zirconia ratio along the centrifugal direction; zirconia tended to accumulate in the bottom section, while alumina in the top section. Such a graded structure exhibited a considerably higher flexural strength when the alumina rich surface was subjected to a tensile stress than compositionally uniform composite of the same average composition. Fracture toughness measurement across the specimen thickness by indentation method revealed that the crack lengths along the vertical and horizontal directions were different. The anisotropy of the fracture toughness was accounted for by the variation of the residual stress across the specimen thickness.
