热处理对二氧化硅干凝胶组织结构的影响

Effect of Heat Treatment on Texture and Structure of Silica Xerogels

气凝胶是一种低密度纳米多孔非晶态材料,具有连续无规则网络结构,其纳米尺度的颗粒及孔隙分布,使其具有很多独特的性质。利用溶胶-凝胶酸碱二步催化法和常压干燥法制备了结构完整的SiO2干凝胶。采用DTA-TG,XRD,SEM和IR等实验手段,对SiO2干凝胶在室温以及300,600,900,1200℃四个热处理温度下的组织结构进行了对比和分析。结果表明,粘性流造成干凝胶的烧结。热处理后,材料颗粒变大,孔隙缩小,材料发生收缩,并在高温下变得坚硬致密。

Aerogels are new low density nano-porous non-crystalline solid materials,and have continuous random network structure.Because of nano-size granules and distribution of nano-pore,aerogels have lots of particular properties.Two-step acid-base catalyzed silica xerogels were prepared through sol-gel and ambient pressure drying.Texture and structure of silica xerogels were contrasted and analyzed at room temperature,300,600,900℃ and 1200℃ by means of DTA-TG,XRD, SEM and IR.The results showed that the viscous flow leaded to thermal sintering of silica xerogles.After heat treatment,grains grew at the same time the pores reduced.Materials,which had Si-O-Si short chain structure,shrank and became stiff and compact under the high temperature.