Al掺杂对SiO_(2)气凝胶耐高温特性的影响研究

Effect of Al doping on the high-temperature resistance characteristics of SiO_(2) aerogels

SiO_(2)气凝胶具有成本低、制造工艺简单、化学性质稳定、密度小、超高比表面积等优点,是应用最广泛的高温保温隔热材料。以Si28和Si40为Si源,仲丁醇铝为Al源,乙醇为溶剂,采用酸碱催化、CO_(2)超临界干燥法制备了Al掺杂SiO_(2)气凝胶。结果表明:所得产品高温热处理后均为非晶态无定型结构,无掺杂SiO_(2)气凝胶线收缩率为24.34%,Al掺杂SiO_(2)气凝胶线收缩为14.05%,且在高温热处理后有较大的比表面积和孔体积,说明Al掺杂SiO_(2)气凝胶具有较好的耐高温性能和高温下的绝热性能,这是因为Al元素的掺入使气凝胶在形成过程中产生了很多细小的纳米空洞,热处理过程中Al-Si-O发生化学反应形成双金属氧化物,使气凝胶的氧化物骨架支撑力更强。

SiO_(2) aerogel has the advantages of low cost,simple manufacturing process,stable chemical properties,small density,and ultra-high specific surface area,etc.It is the most widely used high-temperature thermal insulation material.Al doped SiO_(2) aerogels were prepared by acid-base catalysis and CO_(2) supercritical drying method using Si28 and Si40 as Si sources,aluminium tri-sec-butoxide as Al source and ethanol as solvent.The results showed that the products obtained after high temperature heat treatment exhibited amorphous and non-crystalline structures.The linear shrinkage of undoped SiO_(2) aerogel was 24.34%,while that of Al-doped SiO_(2) aerogel was 14.05%,with a larger specific surface area and pore volume after high-temperature heat treatment,indicating that Al-doped SiO_(2) aerogel had a better high-temperature resistance and insulation performance at high temperatures.This was because the incorporation of Al element caused many fine nano cavities in the formation of aerogels.Furthermore,Al-Si-O reacted chemically to form bimetallic oxides during heat treatment,which made the support of oxide skeleton of the aerogels stronger.