YAG (Y_(3)Al_(5)O_(12)) transparent ceramics have attractive application prospects for transparent armor protection modules because of their excellent light transmittance and anti-ballistic capability. Understanding t...YAG (Y_(3)Al_(5)O_(12)) transparent ceramics have attractive application prospects for transparent armor protection modules because of their excellent light transmittance and anti-ballistic capability. Understanding the fracture behavior and damage mechanism of YAG is necessary for armor design. To explore the damage characteristics of YAG under compression and tension, shock compression and shockless spalling experiments with soft recovery technique are conducted. The spall strength of YAG is obtained and the recovered samples are observed by CT and SEM. It is shown that the macroscopic damage characteristic of YAG under compression is vertical split cracks with oblique fine cracks distributed in the entire sample, while that under tension is horizontal transgranular cracks concentrated near the main spall surface. The cracks generated by macroscopic compression, tension and shear stress extend in similar tensile form at the microscale. The proportion of transgranular fractures on spall surfaces is higher than that of cracks induced by macroscopic compression. Meanwhile, higher loading rate and longer loading duration increase the transgranular fracture percentage.展开更多
Porous ceramics have been widely used in heat insulation,filtration,and as a catalyst carrier.Ceramics with high porosity and high strength are desired;however,this high porosity commonly results in low strength mater...Porous ceramics have been widely used in heat insulation,filtration,and as a catalyst carrier.Ceramics with high porosity and high strength are desired;however,this high porosity commonly results in low strength materials.In this study,porous alumina with high porosity and high strength was prepared by a popular direct foaming method based on particle-stabilized wet foam that used ammonium polyacrylate(PAA)and dodecyl trimethyl ammonium chloride(DTAC)as the dispersant and hydrophobic modifier,respectively.The effects of the dispersant and surfactant contents on the rheological properties of alumina slurries,stability of wet foams,and microstructure and mechanical properties of sintered ceramics were investigated.The microstructure of porous ceramics was regulated using wet foams to achieve high strength.For a given PAA content,the wet foams exhibited increasing stability with increasing DTAC content.The most stable wet foam was successfully obtained with 0.40 wt%PAA and 0.02 wt%DTAC.The corresponding porous alumina ceramics had a porosity of 82%,an average grain size of 0.7μm,and a compressive strength of 39 MPa.However,for a given DTAC content,the wet foams had decreasing stability with increasing PAA content.A possible mechanism to explain these results is analyzed.展开更多
Alumina-based foam ceramic filters were fabricated by using alumina,SiC,magnesia powder as major materials.It has been found that this ceramic filter has a uniform macrostructure for filtering molten metals.The influe...Alumina-based foam ceramic filters were fabricated by using alumina,SiC,magnesia powder as major materials.It has been found that this ceramic filter has a uniform macrostructure for filtering molten metals.The influences of SiC and magnesia content,the sintering temperatures on ceramic properties were discussed.Alumina-based foam ceramic filters containing 2.2 mass% magnesia and 7.6 mass% SiC has a compressive strength of 1.36 MPa and a thermal shock resistance of 5 times.Its main phases after 1 hour sintering at 1 500℃ consist of alumina,silicon carbide,spinel and mullite.展开更多
基金This work is funded by the National Natural Science Foundation of China(No.11772159)the NSAF Joint Fund(No.U1730101)the Fundamental Research Funds for the Central Universities(No.30917011104).
文摘YAG (Y_(3)Al_(5)O_(12)) transparent ceramics have attractive application prospects for transparent armor protection modules because of their excellent light transmittance and anti-ballistic capability. Understanding the fracture behavior and damage mechanism of YAG is necessary for armor design. To explore the damage characteristics of YAG under compression and tension, shock compression and shockless spalling experiments with soft recovery technique are conducted. The spall strength of YAG is obtained and the recovered samples are observed by CT and SEM. It is shown that the macroscopic damage characteristic of YAG under compression is vertical split cracks with oblique fine cracks distributed in the entire sample, while that under tension is horizontal transgranular cracks concentrated near the main spall surface. The cracks generated by macroscopic compression, tension and shear stress extend in similar tensile form at the microscale. The proportion of transgranular fractures on spall surfaces is higher than that of cracks induced by macroscopic compression. Meanwhile, higher loading rate and longer loading duration increase the transgranular fracture percentage.
基金supported by the National Natural Science Foundation of China(51602194 and 51772309)Science Foundation for Youth Scholar of State Key Laboratory of High Performance Ceramics and Superfine Microstructures(SKL201901).
文摘Porous ceramics have been widely used in heat insulation,filtration,and as a catalyst carrier.Ceramics with high porosity and high strength are desired;however,this high porosity commonly results in low strength materials.In this study,porous alumina with high porosity and high strength was prepared by a popular direct foaming method based on particle-stabilized wet foam that used ammonium polyacrylate(PAA)and dodecyl trimethyl ammonium chloride(DTAC)as the dispersant and hydrophobic modifier,respectively.The effects of the dispersant and surfactant contents on the rheological properties of alumina slurries,stability of wet foams,and microstructure and mechanical properties of sintered ceramics were investigated.The microstructure of porous ceramics was regulated using wet foams to achieve high strength.For a given PAA content,the wet foams exhibited increasing stability with increasing DTAC content.The most stable wet foam was successfully obtained with 0.40 wt%PAA and 0.02 wt%DTAC.The corresponding porous alumina ceramics had a porosity of 82%,an average grain size of 0.7μm,and a compressive strength of 39 MPa.However,for a given DTAC content,the wet foams had decreasing stability with increasing PAA content.A possible mechanism to explain these results is analyzed.
基金The project is supported by National Natural Science Foundation of China:50334030PhD Fund of Liaoning Province:20041010.
文摘Alumina-based foam ceramic filters were fabricated by using alumina,SiC,magnesia powder as major materials.It has been found that this ceramic filter has a uniform macrostructure for filtering molten metals.The influences of SiC and magnesia content,the sintering temperatures on ceramic properties were discussed.Alumina-based foam ceramic filters containing 2.2 mass% magnesia and 7.6 mass% SiC has a compressive strength of 1.36 MPa and a thermal shock resistance of 5 times.Its main phases after 1 hour sintering at 1 500℃ consist of alumina,silicon carbide,spinel and mullite.
基金National Natural Science Foundation of China (52032011)State Key Laboratory of New Ceramic and Fine Processing Tsinghua University (KF 202007)Youth Fund of China Building Materials Academy (ZD-16)。
