硅溶胶添加对氧化铝多孔陶瓷烧结性能的影响

Effect of silica sol addition on sintering properties of porous alumina ceramics

以煅烧α-Al_(2)O_(3)粉末为原料,硅溶胶为高温结合剂,羧甲基纤维素钠为成型黏结剂,通过混料、困料、模压成型、高温烧结等工序制备氧化铝多孔陶瓷,利用SEM和XRD对多孔陶瓷微观形貌和晶体结构进行测试,并对多孔陶瓷的线收缩率、体积密度、显气孔率和抗弯强度进行表征,系统地研究硅溶胶添加对氧化铝多孔陶瓷高温烧结特性的影响。结果表明:低温下硅溶胶的热解产物石英型SiO_(2)将氧化铝颗粒黏结起来,形成物理黏结,能提高多孔陶瓷的力学性能;烧结温度达1500℃时,SiO_(2)开始与氧化铝反应形成莫来石,莫来石结合相的生成使得氧化铝多孔陶瓷趋于致密,力学性能优异,抗弯强度可达(105.5±8.0) MPa;随烧结温度的升高莫来石生成量增多,导致氧化铝多孔陶瓷的体积膨胀,进而使得孔隙率增大,力学性能降低。烧结温度介于1400~1500℃之间时,可以得到微观结构合理、力学性能优异、孔隙率适中的氧化铝多孔陶瓷。

Porous alumina ceramics were prepared by using calcinedα-Al_(2)O_(3) as raw material,nano silica sol as high temperature binder and carboxymethy cellulose as molding binder with processes of mixing,aging,molding and sintering.The effect of silica sol addition on sintering properties was investigated by test method of SEM and XRD.The linear shrinkage,volume density,porosity and flexural strength were also tested.The results show that the quartz silicon dioxide which is pyrolysed product from silica sol could bond the alumina particles together to form porous ceramics and improve the mechanical properties.The essence of silica sol bonding is physical bonding.The silicon dioxide in the sol begins to react with alumina to form mullite when the sintering temperature reaches 1500℃,and the porous ceramics tend to be compact with excellence mechanical properties.The flexural strength is about(105.5±8.0)MPa.The content of mullite phase increases with sintering temperature.However,with much higher content of mullite generation,the porosity increases and the mechanical performance degrades.The porous alumina ceramics with excellence performance can be obtained when the sintering temperature is between 1400℃and 1500℃.