硅气凝胶的制备、表征及其性能研究

【作者】 张利伟；

【导师】 关鲁雄；

【作者基本信息】 中南大学 ， 无机化学， 2011， 硕士

【摘要】 由于Si02气凝胶具有低密度、高比表面和高孔隙率的纳米多孔材料的优秀品质,使其在热学、力学、光学、电学、声学、催化剂及其药物载体等方面有着广阔的应用前景。本文以正硅酸乙酯(TEOS)为硅源,以N,N-二甲基甲酰胺(DMF),丙三醇(GLY),聚乙二醇(PEG400)为干燥控制化学添加剂(DCCA),以无水乙醇(EtOH)/六甲基二硅氮烷(HMDZ)/正己烷(Hexane)为溶剂交换与表面改性试剂,对Si02气凝胶合成中的“一步溶剂交换与表面改性”新工艺,首次进行了探索。实验中以气凝胶的稳定性、振实密度、接触角以及比表面(BET)等项目作为产品的性能指标；以傅立叶转换红外线光谱(FTIR)、X射线衍射(XRD)、热重-差示(TG-DSC)以及场发射扫描电镜(F-SEM)作为产品的结构指标；分别考察了DCCA的种类和用量、EtOH/HMDZ的摩尔比、HMDZ/Hexane的体积比等因素对产品的性能和结构的影响。并以产品对甲基橙和亚甲基蓝的吸附性能为标准,考察了Si02气凝胶的吸附应用性能。结果表明,溶胶凝胶一步溶剂交换与表面改性制备Si02气凝胶的最佳工艺条件为：以DMF为DCCA, n(DMF)/n(TEOS)和n(EtOH)/n(HMDZ)的最佳摩尔比分别为0.2和0.8,V(HMDZ)/V(Hexane)的最佳体积比为0.1。所得产品Si02气凝胶的密度为130kg/m3,比表面积为842.63m2/g,产品粒径约为15nm,孔径分布在2-150nm,并具有良好的疏水性能。在45℃条件下,产品对甲基橙的最大吸收率为18.5%；产品对亚甲基蓝的最大吸附率为98.8%。此外,本文还合成了六钛酸钾晶须掺杂Si02气凝胶,考察了不同掺杂量对产品结构和隔热性能的影响。结果表明,在不破坏Si02气凝胶原有微观结构掺杂量的前提下,随着掺杂量的增大,产品的隔热性能有所增强。综上所述,用“一步法”制备的Si02气凝胶性能优越,与“多步法”相当,但将生产周期从原来的6天缩减到4天,在保证质量的前提下有效的降低了能耗,减少了污染,节约了成本。为解决传统气凝胶制备工艺周期长,条件复杂的难问题,实现节能减排,提供了重要的理论依据。更多还原

【Abstract】 Silica aerogel has widely application prospects in thermology, mechanics, optics, electrics, acoustics and catalyst carriers, owning to its advantages of low density, high surface area and high porosity.In this paper, the new method of "one-step acid-base sol-gel pr ocess" was firstly explored in the synthesis of Silica aerogel, when Tetraethoxysilane was used as precusor of silica, dimethyl formamid e, glycerol and polyethylene glycol were as DCCA. ethanol/hexmeth ydisilazane/hexane were the reagents of one-step solvent exchange and surface modification process.The stability, tap density, contact angle and specific surface of aerogels were took as the main performance indexes of products. The structure and morphology of silica aerogels have been investigated by FTIR, XRD, TG-DSC, F-SEM, BET. The influence of the kinds and amounts of DCCA, EtOH/HMDZ molar ratio, HMDZ/Hexane volume ratio on the structures and properties of silica aerogels were also discussed, and the absorptivities of silica aerogels for were also investigated when took the adsorption performance of the product on methyl orange and methylene blue.The results showed that the aerogels had high surface area of 842.63m2/g when the molar ratio of DMF and TEOS was 0.2, the optimal molar ratio of ETOH and HMDZ was 0.8, and the volume ratio of HMDZ and Hexane was 0.1. the density of the aerogels with the high surface area was 130kg/m3, the diameter was about 15nm and the diameter of the pore sizes was in the range of 2～150nm, the aerogels also showed an excellent hydrophobic feature.The maximum absorptivity of product on methyl orange was 18.5% and the maximum absorptivity of products on methylene blue was 98.8% when the temperature was 45℃.Moreover, silica aerogels doped with K2Ti6O13 whiskers were also prepared, and the effects of doping amount on structure and heat-proof quality of product were also investigated. Results showed that the heat-proof quality of products was enhanced with doping amounts increasing on condition that the original microstructure of silica aerogel wasn’t destroyed.In conclusion, the performance of silica aerogel prepared with one-step method was superior than that prepared with multistep method, the production cycle was cut to four days from primary six days. The energy consumption was reduced, the pollution was decreased and the cost was saved in the premise of the guaranteeing quality. It also provided important theoretical basis for solving the problems of the long cycle and complex conditions of traditional aerogel preparation technology and realizing the advantages of energy saving and emission reduction.更多还原