【作者】 张伟娜；

【导师】 李云辉；

【作者基本信息】 长春理工大学 ， 无机化学， 2007， 硕士

【摘要】 SiO₂气凝胶是目前世界上最轻的固体材料，由于其特殊的网络结构使其具有很多独特的性能，在所有固体材料中它的隔热性最好、声传播速率最低且孔隙率较高等，因此具有广泛的应用价值。 本文研究了各因素对其不同性能的影响，并采用四因素三水平的正交实验，“一步”溶胶-凝胶和“两步”溶胶-凝胶两种方法，对其最佳制备条件进行了研究。而制备疏水性气凝胶又是解决常压干燥过程中体积收缩和开裂的关键，本文采用共前驱体法和衍生法两种方法对其疏水改性进行了研究。 结果表明“两步法”比“一步法”所得SiO₂气凝胶性能更好，衍生法疏水改性后的样品性能比共前驱体法所得样品性能好，且更适合常压下干燥。 本文用两步溶胶-凝胶法以三甲基氯硅烷（TMCS）为化学结构、表面修饰剂通过衍生法制备出了疏水性二氧化硅气凝胶，并用XRD、SEM、ED、TEM、IR、DTA-TG等测试方法对其结构、形貌及化学组成进行了分析。结果表明：该样品为热稳定性较高的非晶、多孔、轻质、高比表面积的纳米材料，密度平均为134.3kg·cm^-3、BET比表面积为729m²·g^-1、孔隙率约为99％、平均孔径为10nm；所得样品纯度较高，组成样品连续网络结构的粒子呈球形且分散均匀，平均粒径约为5nm。由IR、DTA-TG图谱和接触角（120°）可看出以TMCS修饰后的气凝胶表面疏水基团—CH₃取代了亲水基团-OH，实现了块状疏水性SiO₂气凝胶的常压干燥制备。更多还原

【Abstract】 Recently, silica aerogels are the lightest solid material. The silica aerogels have many unique properties owing to their special structure, such as they have the best properties in thermal insulation, the lowest sound velocities and have the higher porosity in all solid materials and so on. So they have many extensive applied values.The influences of each factor on their different properties had been studied in this dissertation. The orthogonal experiment was designed by using four factors and three levels, selecting two methods: one-step sol-gel and two-step sol-gel to study their optimal prepared conditions. But the key of shrinkage and crack when drying at ambient pressure was the preparation of hydrophobic silica aerogels. Hydrophobic modification had been studied by two methods: co-precursor and derivatization methods.The results showed that the properties of silica aerogels which produced by two-step sol-gel method were better than those produced by one-step sol-gel method. The properties of the samples which were modified by derivatization method were better than those modified by co-precursor method, and those were more suitable to be dryed under ambient pressure.In this dissertation hydrophobic silica aerogels had been prepared by two-step sol-gel method with trimethylchlorosilane（TMCS） as the structural surface chemical modification via derivatization method. The XRD,SEM, ED, TEM,IR and DTA-TG analysis were used to observe the structure, the surface morphology and the chemical composites of the samples. The results showed that the samples were non-crystallized, porous and light nanometer materials with higher thermal stability and higher specific surface area. And their average density was 134.3 kg·cm^3-, BET specific surface area was 729 m²·g^-1, porosity was 99% approximately, average pore diameter was 10nm. The obtained samples had higher purity. The particles which constituted the continual net structure of aerogels were spherical with average diameter 5nm, and the particles dispersed evenly. The IR, DTA-TG spectrogram and contact angle（120°） had indicated that the hydrophobic group methyl had substituted hydrophilic group hydroxyl on the structure and surface of aerogels modified by TMCS. The preparation of bulk hydrophilic silica aerogels dried at ambient pressure had been realized.更多还原