高强度氧化地铝气凝胶复合材料的制备研究

发布时间：2018-02-27 10:14

  本文关键词： 氧化铝气凝胶 凹凸棒土(ATP) 强度　出处：《东南大学》2015年硕士论文　论文类型：学位论文

【摘要】：氧化铝气凝胶除具有一般气凝胶的基本性质,还具有优异的高温稳定性,是制备耐高温隔热材料的理想材料。但目前报导得到的氧化铝气凝胶材料普遍存在强度低、力学性能差的缺点,这严重制约了其实际应用。凹凸棒土(ATP)是种具有独特的层链状晶体结构的含水富镁铝硅酸盐粘土矿物,具有优异的吸附性、填充性及热稳定性等。鉴于其独特的结构和稳定的物理化学性质,本文采用凹凸棒土作为增强体,常压直接干燥制备高强度氧化铝气凝胶。首先,实验从水(H2O)和乙醇(EtOH)用量比例、环氧丙烷(PO)用量以及ATP加入方式几个方面优化了实验工艺。通过观察和借助相关表征,最终确定H2O:EtOH=3:7vol,环氧丙烷用量为n(Al):n(PO)=1:8,ATP添加方式为制备成稳定的ATP悬浮液后再添加到氧化铝溶胶,效果最佳。其次,研究了ATP用量对A1203气凝胶复合材料力学等性能的影响。研究结果表明：加入ATP后,气凝胶复合材料的表观密度略微下降,基体密度大幅下降；各含量的ATP/Al2O3气凝胶复合材料的抗压强度均高于纯A1203气凝胶的抗压强度,且抗压强度随ATP用量增加呈先快速增后缓慢减小的趋势,ATP(26.09wt%)/Al2O3气凝胶复合材料的抗压强度高达74.55MPa,较纯A1203气凝胶的抗压强度(26.74MPa)增强了近3倍；加入ATP后气凝胶复合材料的隔热性能变的更好。最后,探索了ATP对氧化铝气凝胶力学性能的增强机制,选用常压干燥方法制备A1203气凝胶和ATP/Al2O3气凝胶复合材料分别从相组成、微观形貌、比表面状况以及热稳定性等方面着手比较分析。通过SEM和TEM分析表明ATP晶束在复合材料中作为骨架存在,使氧化铝颗粒附着并蔓延生长成三维网络结构,从而起到提高气凝胶复合材料的力学性能；通过分析不同温度下材料的比表面积和孔结构参数,表明ATP可以有效的抑制氧化铝颗粒的烧结,使氧化铝气凝胶更有利于在高温下使用,如添加ATP后热处理温度从500℃.升高到900℃时,气凝胶比表面积损失从43.94%降低到34.37%,孔容积损失从48%降低到7.34%;通过XRD、FT-IR、TGA分析,发现氧化铝相仍保持原有的晶型、分子结构,说明ATP的加入不会破坏氧化铝气凝胶一些基本性质,如用作催化剂及催化剂载体的性质和热稳定性等。
[Abstract]:Alumina aerogels not only have the basic properties of general aerogels, but also have excellent high temperature stability. The disadvantages of poor mechanical properties seriously restrict its practical application. Attapulgite ATP is a kind of water rich magnesium-rich aluminosilicate clay mineral with unique layer chain crystal structure which has excellent adsorbability. In view of its unique structure and stable physical and chemical properties, this paper uses attapulgite as reinforcements to prepare high strength alumina aerogels by direct drying at atmospheric pressure. The experimental process was optimized in terms of the ratio of H 2O and EtOH, the amount of propoxypropane oxide and the addition of ATP. Finally, it was determined that the best way of adding H _ 2O: EtOH3: 7voland propylene oxide to alumina sol was to prepare stable ATP suspensions and then add them to alumina sol. The effect of ATP content on mechanical properties of A1203 aerogel composite was studied. The results showed that the apparent density of aerogel composite decreased slightly and the matrix density decreased significantly after adding ATP. The compressive strength of ATP/Al2O3 aerogel composites with different contents was higher than that of pure A1203 aerogels. The compressive strength of ATP / Al _ 2O _ 3 aerogel composites increased rapidly first and then decreased slowly with the increase of ATP content. The compressive strength of the composite was as high as 74.55 MPA, which was nearly three times higher than that of pure A1203 aerogel. After the addition of ATP, the thermal insulation properties of the aerogel composites became better. Finally, the enhancement mechanism of ATP on the aerogel properties of alumina was explored. A1203 aerogel and ATP/Al2O3 aerogel composites were prepared by atmospheric pressure drying method. SEM and TEM analysis show that the ATP crystal beam exists as a skeleton in the composites, which makes the alumina particles adhere and grow into a three-dimensional network structure. By analyzing the specific surface area and pore structure parameters of the aerogel composites at different temperatures, it is shown that ATP can effectively inhibit the sintering of alumina particles. The alumina aerogel is more suitable for use at high temperature, such as the heat treatment temperature after adding ATP from 500 鈩，

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