纳米多孔材料隔热性能的研究

发布时间：2018-05-16 06:46

  本文选题：纳米孔 + 气凝胶　； 参考：《辽宁科技大学》2015年硕士论文

【摘要】：化石能源的日益枯竭及其在使用过程中引发的环境污染正在迫使人们越来越倾向于合理高效地利用有限的自然资源,隔热技术就是实现资源高效利用的重要手段。近年来,纳米技术不断进步,所获材料的应用领域也在不断拓新。纳米多孔材料的孔隙处于纳米尺度,因此表现出优异的热绝缘性能,是高性能隔热材料领域的研究热点。本文首先考察了基于超临界干燥工艺和一种非超临界干燥工艺合成的SiO2气凝胶的主要性质,对比了两种工艺条件下所获气凝胶材料的多孔网络结构,及其对于材料热隔离能力的影响。然后按照经典的合成路线分别制备了具有二维六方结构相的SBA-15,MCM-41以及具有三维体心立方结构的SBA-16介孔分子筛材料,对以上分子筛材料的晶体结构、微观形貌以及孔结构参数进行了表征,着重考查它们的隔热性能,为拓展纳米多孔性质分子筛材料的应用领域提供一定可参考的实验数据。最后,采用有限元分析方法对钢包温度场进行数值模拟,分析了纳米多孔保温隔热层对钢液温度和包衬传热情形的影响。通过以上各方面的研究,获得的主要研究结果如下:(1)尽管共沸蒸馏干燥工艺可使气凝胶颗粒表面产生疏水效应,所获气凝胶材料与超临界干燥工艺获得的气凝胶材料同属非晶态,且两者的氮气吸附曲线也表明均属于IV型,但是前者归属于典型的H2类型,整体表现为不完好的介孔特性;而后者则更倾向于H1型,说明通过超临界干燥的气凝胶内部的介孔孔径较为均匀统一,其集中分布在2~40nm范围内。纳米孔隙微观结构上的差异导致后者具有较低的导热系数,常温下和200℃时分别仅为0.020/0.033 W·m-1·K-1。(2)SBA-15分子筛呈长1μm、宽0.5μm且粒径均匀的短棒状,其内部介孔孔道具有很高的一级定向和较为规则二级取向定向。MCM-41分子筛则为不规整的短棒状和颗粒状,而采用EISA路线合成的SBA-16分子筛呈粒度约为1μm的“单晶”多面体状,表现出仅在介观尺度上有序。氮气吸附测试表明,二维六方结构相的SBA-15和MCM-41分子筛由BJH模型计算得到的孔径分别集中分布在8~12nm之间和2~4nm之间,以SBA-16分子筛为代表的三维体心立方结构介孔材料的孔道窗口只有约4nm,三种材料的平均孔径依次为7.47、3.53和5.29nm。其中,MCM-41分子筛具有最低的常温导热系数,仅为0.043 W·m-1·K-1。(3)将10mm厚的纳米多孔隔热材料用作钢包保温层,相比于无保温层和采用常规隔热材料作为保温层的钢包,在钢水静置15min后,可使钢水温度分别提高6.82℃和3.12℃,将钢水的温降速率降低至0.1938℃·min-1,同时将钢壳外壁温度降低了约113℃。
[Abstract]:The depletion of fossil energy and the environmental pollution caused by the use of fossil energy are forcing people to make more and more rational and efficient use of limited natural resources. Thermal insulation technology is an important means to achieve efficient use of resources. In recent years, nanotechnology continues to progress, the application of materials are also constantly expanding. The pores of nano-porous materials are in nanometer scale, so they exhibit excellent thermal insulation performance and are the research hotspot in the field of high performance thermal insulation materials. In this paper, the main properties of SiO2 aerogels based on supercritical drying process and a non-supercritical drying process are investigated, and the porous network structure of aerogel materials obtained under two conditions is compared. And its influence on thermal isolation ability of materials. Then, SBA-15MCM-41 with two-dimensional hexagonal structure and SBA-16 mesoporous molecular sieve with three-dimensional body-centered cubic structure were prepared according to the classical synthesis route. The microstructure and pore structure parameters were characterized with emphasis on their thermal insulation properties. The experimental data can be used to expand the application field of nano-porous molecular sieve materials. Finally, the finite element method is used to simulate the temperature field of ladle, and the influence of nano-porous thermal insulation layer on the temperature of liquid steel and the heat transfer of ladle lining is analyzed. The main results obtained from the above studies are as follows: 1) although azeotropic distillation and drying process can cause hydrophobic effect on aerogel particle surface, The aerogel materials obtained by supercritical drying process belong to amorphous state, and their nitrogen adsorption curves also show that they belong to type IV, but the former belongs to the typical H2 type, and the whole aerogel material exhibits imperfect mesoporous properties. The latter is more inclined to H1, indicating that the mesoporous pore size of the aerogel by supercritical drying is uniform and concentrated in the range of 2~40nm. The difference in the microstructure of the nano-pore leads to the lower thermal conductivity of the latter, which is only 0.020 / 0.033 W / m ~ (-1) K-1.(2)SBA-15 molecular sieve at room temperature and 200 鈩，

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