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主管单位 中华人民共和国
工业和信息化部
主办单位 中国材料研究学会
哈尔滨工业大学
主编 苑世剑 国际刊号ISSN 1005-0299 国内刊号CN 23-1345/TB

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引用本文:廖进军,高朋召,徐凛,冯坚.热负载条件对SiO2气凝胶组成及微观结构的影响[J].材料科学与工艺,2018,26(5):33-39.DOI:10.11951/j.issn.1005-0299.20170343.
LIAO Jinjun,GAO Pengzhao,XU Lin,FENG Jian.Influence of heating loading conditions on the composition and microstructure of SiO2 aerogel[J].Materials Science and Technology,2018,26(5):33-39.DOI:10.11951/j.issn.1005-0299.20170343.
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热负载条件对SiO2气凝胶组成及微观结构的影响
廖进军1,高朋召1,徐凛2,冯坚2
(1.湖南大学 材料科学与工程学院,长沙 410082;2.新型陶瓷纤维与复合材料重点实验室(国防科技大学),长沙 410082)
摘要:
通过阶梯升温并结合傅里叶变换红外光谱(FT-IR)、X射线光电子能谱(XPS)、扫描电子显微镜(SEM)和透射电子显微镜(TEM)等表征手段,研究了不同温度所得SiO2气凝胶的组成和微观结构,在程序升温条件下通过TG-DTG曲线和无模式函数法研究了SiO2气凝胶热重行为的变化.结果表明:SiO2气凝胶主要由7~9 nm球状颗粒构成类线形团簇,进而以团簇为骨架构成三维网络多孔结构;阶梯升温下,随着热处理温度的升高,气凝胶中Si—O—Si基团的摩尔分数逐渐增加,Si—OH和Si—OC2H5的摩尔分数逐渐降低,1 073 K时Si—OH基本消失,但存在6.59%的Si—OC2H5基团;气凝胶颗粒逐渐长大,部分骨架坍塌,温度达到1 273 K时,颗粒长大至约50 nm,团簇彻底消失,材料发生明显烧结.程序升温下,升温速率越高,气凝胶的热稳定性越好;材料的失重过程分为3个阶段:当反应转化率α < 30%时,主要发生硅羟基(Si—OH)间的缩合;当30% < α < 70%时,主要是硅羟基(Si—OH)与/或硅乙氧基(Si—OC2H5)之间的缩合;当α>70%时,主要是硅乙氧基(Si—OC2H5)之间的缩合.
关键词:  SiO2气凝胶  热负载条件  热稳定性  微观结构  反应机理
DOI:10.11951/j.issn.1005-0299.20170343
分类号:TB321
文献标识码:A
基金项目:国家自然科学基金资助项目(51372078).
Influence of heating loading conditions on the composition and microstructure of SiO2 aerogel
LIAO Jinjun1, GAO Pengzhao1, XU Lin2, FENG Jian2
(1.College of Materials Science and Engineering, Hunan University, Changsha 410082, China; 2. Key Laboratory of New Ceramic Fibers and Composites (National University of Defense Technology), Changsha 410082, China)
Abstract:
Composition and microstructure of SiO2 aerogels treated at different temperatures were studied using the ladder-elevating temperature combined with FT-IR, XPS, SEM, and TEM. The change of thermogravimetric behavior of SiO2 aerogels under temperature-programmed conditions was investigated using TG-DTG curve and model-free kinetics. Results showed that SiO2 aerogel was mainly composed of spherical particles ranged between 7 and 9 nm. These particles formed the class alignment clusters, which continued to work as skeletons to from a three-dimensional network porous structure. Under ladder-elevating temperature condition, with the increase of treatment temperatures, content of Si—O—Si group increased while that of Si—OH and Si—OC2H5 groups both decreased. When the temperature reached 1 073 K, Si—OH group almost disappeared and content of Si—OC2H5 group decreased to 6.59%. Nanoparticles in SiO2 aerogel grew slowly, resulting in the collapse of skeletons. When the temperature rose to 1 273 K, the particle size grew about 50 nm, clusters disappeared completely, and SiO2 aerogels sintered obviously. Under temperature-programmed condition, the faster the heating rate, the better the thermal stability of SiO2 aerogel. The weight-loss process of SiO2 aerogel was mainly divided into three steps: when α < 30%, the weight-loss process was controlled via condensation reaction between Si—OH; when 30% < α < 70%, it was mainly controlled via the condensation reaction between Si—OH and/or Si—OC2H5; when α>70%, it was mainly controlled via condensation reaction of Si—OC2H5.
Key words:  SiO2 aerogel  thermal loading condition  thermal stability  microstructure  reaction mechanism

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