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摘要
以正硅酸乙酯为原料,去离子水和无水乙醇为溶剂,盐酸和氨水为催化剂,通过酸/碱两步溶胶-凝胶法制得SiO2醇凝胶,经过老化、溶剂置换等后续工艺,在亚临界条件下干燥制备了块状SiO2气凝胶,并对其干燥机理进行分析。采用XRD、SEM、TEM、BET、FT-IR及DSC-TG等手段对样品进行了表征。结果表明,当干燥温度为220℃、干燥压力为3.5MPa时,制备的样品性能最佳,该样品气凝胶为无定型结构,表观密度为0.221g/cm3,比表面积达973.68m2/g,孔容为2.1cm3/g。经过600℃高温煅烧3h前后对比,孔型和孔径分布基本无变化,比表面积仍高达850.59m2/g,孔容为1.6cm3/g。本研究采用亚临界干燥方法,大大简化了气凝胶的干燥工艺,制备的气凝胶开裂收缩小,透明度高,有较好的热稳定性。
Abstract
SiO2 monolithic aerogels were prepared by the two-step sol-gel and gel aging and solvent replacement method at subcritical condition using tetraethyl orthosilicate as raw material,deionized water and anhydrous ethanol as solvent,and HCl and NH4OH as hydrolysis and condensation cataysts.The drying mechanism was analyzed.The structural properties of SiO2 aerogels samples were characterized by means of XRD,SEM,TEM,BET,FT-IR and DSC-TG,etc.The results shown that the prepared sample had the best performance when the drying temperature was 220℃ and the drying pressure was 3.5MPa.The sample had an amorphous structure with the apparent density of 0.221g/cm3 and specific surface area of 973.68m2/g.The capacity was 2.1cm3/g.After the high temperature calcination at 600℃ for 3h,the pore shape and pore size distribution were basically unchanged,the specific surface area was still as high as 850.59m2/g,and the pore volume was 1.6cm3/g.The subcritical drying method used in this study greatly simplifies the aerogel drying process,and the prepared aerogel had small cracking shrinkage,high transparency and good thermal stability.
关键词
SiO2气凝胶
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亚临界干燥
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热稳定性
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干燥机理
Key words
SiO2 aerogel
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subcritical drying
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thermal stability
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drying mechanism
亚临界干燥法制备透明SiO2气凝胶及干燥机理分析[J].
化工新型材料, 2020, 48(2): 157-162 DOI:
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基金资助
国家重点研发计划项目(2016YFC0700804);国家自然科学基金(51562008)
