摘要：气凝胶是一种固体材料，它由超微粒子组成的。气凝胶的特点是粒径小、比表面积高和密度低。这使得气凝胶催化剂的活性和选择性远远高于常规催化剂,并且气凝胶还可减少副反应发生。最早，气凝胶主要用于工业应用，比如将乙酸转化为丙酮、将丙酸转化为二乙基丙酮等。总体来讲，气凝胶的性能和制备过程上，人们已经取得不错的研究成果，然而气凝胶获得广泛应用还有如下问题：74616
1）超临界干燥工艺成本高和危险性大，但传统方法制备的凝胶比表面积低；
2）制备工艺复杂，生产成本高，无法工业化生产，需进一步改进气凝胶的制备方法。
综上，本实验研究的意义在于：寻找较好的溶胶-凝胶法制备气凝胶的实验条件，研究反应的温度、时间、原料的用量等实验因素。
本文用醋酸乙烯酯为添加剂，仲丁醇铝为Al2O3前驱体，经溶胶-凝胶法和常压干燥制备Al2O3气凝胶；优化模板剂使用量、仲丁醇铝和水的比例等制备工艺参数；用XRD和物理吸附对合成的材料进行表征。在常压干燥装置中，控制溶剂挥发速率，研究其对所制备气凝胶密度的影响获得凝胶原位质量和体积变化，推测凝胶结构破坏机理，以便优化Al2O3气凝胶制备的条件。
毕业论文关键词：气凝胶；溶胶凝胶法；常压干燥；凝胶结构
Synthesis of Al2O3 aerogels by addition of polyvinyl alcohol modified with acetaloacetate
Abstract：Aerogel is a solid material consisting of ultrafine particles。 Aerogel is characterized by small particle size, high specific surface area and low density。 This allows the activity and selectivity of the aerogel catalyst to be much higher than that of the conventional catalyst, and the aerogels also reduce side effects。 The earliest, aerogel is mainly used for industrial applications, such as acetic acid into acetone, propionic acid into diethy acetone and so on。In general, the performance and preparation process of aerogel, people have made good research results, but the widespread use of aerogel there are the following questions:
1) supercritical drying process cost is high and the risk is large, but the traditional method of preparation of gel specific surface area is low;
2) preparation process is complex, the production cost is too high, can not be industrialized production, need to further improve the preparation of aerogel。
In summary, the significance of this experimental study is to find a better sol-gel method for the preparation of aerogel experimental conditions, to study the reaction temperature, time, the amount of raw materials and other experimental factors。
In this paper, Al2O3 aerogel was prepared by sol-gel method and atmospheric pressure drying with acetaloacetate-modified polyvinyl alcohol as a template, and aluminum tri-butoxide as a Al2O3 precursor。 XRD and physical adsorption were used to characterize the synthesized materials。 The amount of templating agent used, the ratio of water to the preparation process parameters were optimized。 In situ mass and volume changes of gels in the atmospheric pressure drying device were investigated to control solvent evaporation rate and its impact on the density of the aerogels obtained and the mechanism of gel structure damage to optimize conditions for the preparation of Al2O3 aerogels。
Keywords: aerogel,；sol gel method,；atmospheric pressure drying,；gel structure
目录
1 绪论 1
1。1气凝胶简介 1
1。2气凝胶的分类 2
1。3气凝胶的特性 3
1。4气凝胶的应用 4
1。4。1气凝胶应用的优势 改性聚醋酸乙烯酯为添加剂合成气凝胶的研究:http://www.youerw.com/cailiao/lunwen_85258.html