关键词: 多孔陶瓷, 硼酸铝晶须, 凝胶注模, 固相反应, 隔热材料

Abstract: In order to improve the strength and thermal insulating performance,porous aluminum borate ceramics were fabricated by tert-butyl alcohol-based gel casting combined with in situ solid state reaction technology with Al₂O₃ nanopowder and B₂O₃ micropowder as raw materials.Effects of aluminum/boron molar ratios (9∶2,9∶4 and 9∶6) and heat treatment temperatures (1 000,1 200,and 1 400 ℃) on the properties of porous aluminum borate ceramics were investigated.The findings are as follows.(1)Because B₂O₃ volatiles easily at high temperatures,excessive B₂O₃ is conducive to the formation of aluminum borate whiskers.However,too much B₂O₃ leads to the formation of over-thick aluminum borate whiskers,resulting in over-high density.(2)Low heat treatment temperatures are not suitable for the development of aluminum borate whiskers,resulting in low bulk density,while over-high heat treatment temperatures can lead to sintering densification between whiskers.(3)When the aluminum/boron molar ratio is 9∶4 and the heat treatment temperature is 1 200 ℃,the generated aluminum borate whiskers show a large length/diameter ratio and interlock with each other to form a three-dimensional network structure.The obtained porous aluminum borate ceramic exhibits low density (0.67 g·cm^-3),low thermal conductivity (0.141 W·m^-1·K^-1 at room temperature),and high cold compressive strength (6.23 MPa).

Key words: porous ceramics, aluminum borate crystal whisker, gel casting, solid state reaction, thermal insulation materials