不同原料凝胶注模制备莫来石陶瓷的结构与性能

Microstructure and properties of mullite ceramics prepared by gelcasting process with different raw materials

分别以溶胶-凝胶法制备的莫来石粉末和分析纯级氧化铝/氧化硅混合粉末为原料,经过凝胶注模成形后,在1 400~1 600℃温度下无压烧结,制备莫来石陶瓷,研究原料种类及烧结温度对莫来石陶瓷的显微结构、力学性能和抗热震性能的影响。结果表明:以溶胶-凝胶法制得的莫来石粉末为原料时,随烧结温度升高,陶瓷的密度和抗弯强度都是先升高后降低,烧结温度为1 500℃时,材料的密度和抗弯强度最高,分别为3.13 g/cm^3和155.85MPa,经过5次1 400℃?100℃沸水间热震后抗弯强度保留率达54.99%。以氧化铝/氧化硅混合粉末为原料时,起始烧结温度降低,1 400℃下烧结的陶瓷即具有较高的密度和抗弯强度,分别为3.01 g/cm^3和106.40 MPa,热震后的抗弯强度保留率为77.80%。抗弯强度随烧结温度升高而下降,烧结温度为1 600℃时抗弯强度下降至74.21MPa。

The mullite ceramics were fabricated by gelcasting method and pressless sintering using mullite powder prepared by sol-gel or a mixture of analyzed alumina and silica powders as raw materials.The effects of raw materials and sintering temperatures on microstructures,flexural strength and thermal shock resistance of the mullite ceramics were investigated.The results show that the bend strength of mullite ceramics increases first and then decreases with increasing temperature when the mullite powder prepared by sol-gel method is used as raw material.The highest density of3.13g/cm3and flexural strength of155.85MPa are obtained after1500℃sintering.After5times of1400℃?100℃thermal shock,the bend strength retention rate reaches54.99%.When using Al2O3and SiO2mixture powder as raw materials,the starting sintering temperature decreases.The ceramics with higher density of3.01g/cm3and the bend strength of106.40MPa can be obtained at only1400℃sintering temperature.The bend strength decreases with increasing temperature,and reaches a minimum of74.21MPa when the sintering temperature is1600℃.The bend strength retention rate is77.80%after thermal shock.