纳米孔硅气凝胶的制备工艺对组织结构和物理性能的影响作用.doc

摘 要
 
SiO2气凝胶是一类轻质介孔材料，具有超低密度、高孔隙率、高比表面积和低热导率等特点，在许多领域具有潜在的应用前景。目前国内外多以正硅酸甲酯、正硅酸乙酯为硅源、以超临界干燥工艺制备SiO2气凝胶，其制备工艺过程复杂，耗能费时，成本昂贵，原料有一定的毒性，超临界高温高压干燥存在较大的危险性。而SiO2气凝胶常压干燥制备技术研究较少，且制备出SiO2气凝胶性绝热能与超临界干燥法相比较差。同时未改性的SiO2气凝胶亲水疏油。这些问题限制了SiO2气凝胶材料的发展与应用。
本论文研究以水玻璃为硅源，常压干燥制备低密度、高性能的介孔SiO2气凝胶材料，试验研究了：凝胶体系pH、甲酰胺的添加、湿凝胶的老化、表面疏水处理以及常压低温干燥工艺对气凝胶制备过程及所制备气凝胶的自然密度、振实密度、孔径大小和比表面积等指标的影响。试验结果表明：当体系pH为5时，所得气凝胶的性能最佳；当甲酰胺的添加量为1.5ml时，孔径大小分布范围大都在10nm左右，比表面积为610.6m2/g；当用30%的正硅酸乙酯/乙醇溶液对湿凝胶进行老化处理时，能够得到块状、高比表面积的二氧化硅气凝胶材料；利用三甲基氯硅烷和正己烷的混合溶液对湿凝胶进行表面疏水修饰处理，TMCS与孔洞中水的摩尔比为0.35时，所得气凝胶的疏水度为43.95%；选用正己烷做为溶剂替换介质，干燥工艺为50℃84h，60℃72h时，所得气凝胶的密度为0.14g/cm3，孔隙率为93.7%，比表面积为610.643m2/g，孔直径为9.72nm。

关键词：SiO2气凝胶，水玻璃，制备工艺，性能

Abstract

Silica aerogels are a class of light mesoporous materials with low density, high porosity,high surface area and low thermal conductivity. Because of their unique properties, silica aerogels have great potential application future in many fields. Currently, with the technology of supercritical drying , silica aerogels was made of TMOS and TEOS in domesitc and abroad. Because the process of the made tehchnology was very complex, time-consuming,inefficient and costly, and the raw was toxic, and the technology of supercritical drying was dangerous, however, the technology of drying under the normal altmospheric pressure was still lack, the structure of the property of silica aerogels was not compared with that by using the technology of supercritical drying, meanwhile, unmodified silica aerogels was hydrophilic,which limited the current industrial application of silica aerogels materials.
The thesis studied the mesoporous material of silica aerogels with low denisty and high performance which source was low-cost water glass and that was made by the technology of drying under the normal altmospheric pressure. The expriment studied the influence of indicators, it contained gelling system pH, the addition of formamide, wet gel aging, surface hydrophobic treatment ,the process of mading aerogel structure by the technology of drying under the normal altmospheric pressure and aerogel structure’s natural denisty, tap density, aperture size and specific surface area. The results showed that when the system pH is 5, the performance of the obtained Aerogel was topgallant； When the addtion of formamide was 1.5ml, BJH pore size distribution was mostly in 10nm, and the specific surface area was 610.6m2/ g; With 30%vol.of TEOS/ethanol solution of the wet gel aging treatment, massive and high specific surface area of silica aerogels materials can be obtained; using Chlorotrimethylsilane and n-hexane on the wet surface modification hydrophobic treatment, When TMCS and n-hexane molar ratio was 0.35, the degree of hydrophobic of obtained aerogels was 43.95%. using n-hexane as solvent medium, drying process to 50 ℃ 84h, 60 ℃ 72h, the density of aerogels obtained 0.14g/cm3, porosity was 93.7%, specific surface area 610.643m2/g, pore diameter 9.72nm.

KEY WORDS: silica aerogel, water glass, preparation technology，performance

目  录
第一章  绪论 1
1.1 前言 1
1.2 气凝胶绝热材料发展及研究现状 2
1.2.1 国外研究现状 2
1.2.2 国内研究现状 3
1.3 论文研究目的意义及研究内容 3
1.3.1 论文研究的目的和意义 3
1.3.2 论文研究的主要内容 4
第二章  实验部分 5
2.1 实验材料及实验设备 5
2.1.1 实验材料 5
2.1.2 实验设备 5
2.2 实验方案 6
2.2.1 SiO2气凝胶制备工艺 6
2.2.2 凝胶工艺参数影响试验 7
2.2.3 老化工艺试验 7
2.2.4表面修饰试验 7
2.2.5 化学干燥剂添加量试验 8
2.2.6 干燥工艺试验 8
2.2.7检测方法 8
第三章  结果分析与讨论 9
3.1 pH值对气凝胶密度、凝胶时间及微观结构的影响 9
3.2 老化工艺对气凝胶性能的影响 11
3.3 表面修饰对气凝胶性能的影响 12
3.4 DCCA添加量对气凝胶性能的影响 14
3.5 常压低温干燥工艺对气凝胶性能的影响 17
结论 19
参考文献 21