| Aerogel is a sort of nano porous material with many fancy characterizes, such as high porosity, high specific surface area, low density, and so on. It can be used as the catalyst and carrier, super thermal insulation material, particle trapping material, and adsorption material and target material of the inertial confinement fusion (ICF). Hence, aerogel has a promising application prospect in the fields of military, industry and civilian. In ICF experiment, aerogel with the property of low density and porosity is usually used to eliminate or decrease the fluid mechanic instability in the transportation process, homogenize the X-ray radiation, or used as an adsorption medium of liquid deuterium and tritium. Further more, aerogel, as an ICF target, should possess good processability, high environment stability and uniformity in structure and density.At present, SiO2 and its complex aerogel is one of the most used aerogels in ICF experiments. However, a lot of crucial technical problems appear widely in preparation of the low density aerogels, such as uncontrollability in sol-gel process, low mechanical strength, easy collapse in structure, poor forming and nonuniformity of microstructure. Hence, base on the investigation of relevant theories, farther improvement in preparation technology of aerogel, enhancement in material properties and reduction in production cost have been of intriguing interest in the field of aerogel study. This dissertation presents a detailed investigation in kinetics of sol-gel process and preparing process of low density SiO2 and its complex aerogels, and the block SiO2 aerogels with the densities range from 1.8 to 200mg/cm3 have been prepared successfully.In investigation of low density of SiO2 aerogels, this dissertation discussed the correlative mechanisms, sol formula and production procedure, and the low density SiO2 aerogels with good properties have been obtained. Based on the analysis results of dynamic characteristics in tetraethoxysilane (TEOS)-ethanol system, we found that gelation time increases in index as the density decreases, when the density of the target aerogel is lower than 10 mg/cm3, the system can not be gelatinized. Therefore we synthesized two kinds of novel precursors (poly ethoxyl silane, PES and octamethoxy polyhedral oligosilsesquioxane, OMOPOSS) and optimized the solvent system. Through the solvent substitution by dimethylformamide (DMF), acetonitrile (AN) and dimethyl sulfoxide (DMSO), the samples with the density lower than 3mg/cm3 was successfully achieved. In addition, in order to improve the production efficiency and yield of aerogel, a rapid preparation process based on the result of a mass of experiments was developed, and the preparing period of SiO2 aerogels was shortened to one tenth compared with that of the traditional method. The results of adsorption property and microstructure analysis indicated that aerogels prepared with different precursors have the same rule:the specific surface area of the sample presents the trend of first increase then decrease with the decrease of aerogel density, after that it tends to be steady. The hole-size of aerogel is smaller than 50 nm, and the main distribution arrangement is from 10nm to 20nm, which means the aerogel possesses the typical characteristic of mesopore.As for the research of the processability of low density SiO2 aerogel, we have investigated the effects of the microstructure, morphology and property of SiO2 aerogel by the process parameters of post-treatment method in mother liquor, sol-gel process and hydrophobical modification. We have employed post-treatment method in mother liquor and modification of in-situ toughening process to improve the hydrophobical property and the mechanical strength of SiO2 aerogel. In post-treatment process of mother liquor, we chose hexamethyldisilazane as a hydrophobic modification reagent to deal with the surface of aerogel, which lead a great improvement in anti-deliquescent property of aerogel. In the in-situ hydrophobic and toughening processes, the methyl triethoxysilane and TEOS are used as complex precursors to prepare SiO2 aerogel with excellent mechanical properties and environment stability. The analysis results of dynamic thermo-mechanical show that the SiO2 aerogel becomes elastic-plastic material from elastic-brittle material after modification process. Aerogels prepared by the two modification methods mentioned above exhibit excellent hydrophobicity. The contact angles are larger than 130°, and the largest angle is 151°. When the humidity is over 80% and the temperature is 50℃, the characteristics of aerogel would not be affected by humidity, and the environment stable period is longer than 60 days. As a conclusion, the stability and processability can meet the requirements to prepare ICF target.With respect to investigation of the doped SiO2 aerogels, this dissertation focused on the studies of the fabrication process, structure and properties of composite aerogels doped with metal particles, metallic oxides and metallic sulfide. We have investigated the principles and properties of Au-doped SiO2 aerogel which was prepared by in-situ reduction of Au on the surface of SiO2 sol by seeding method, and the Au nano particle doped SiO2 aerogel with the Au content range from 2.7% to 4.2% were firstly synthesized. Based on the same method, we prepared the Cu-doped SiO2 aerogel with the density from 90 to 110 mg/cm3, and the hole and framework sizes are all less than 100 nm. The highest doping quantity of Cu is more than 80 wt%, and the specific surface area of the corresponding complex aerogel ranges from 150 to 200m2/g. We have also investigated the preparation process of the GeO2/SiO2, Ta2O5/SiO2 composite aerogel with crosslinking co-polymerized framework by the generalized two-step and cohydrolysis method. The typical density of GeO2/SiO2 and Ta2O5/SiO2 aerogels is 3-30 mg/cm3 and 30-150mg/cm3 respectively. CdS film was deposited on the inner and external surface of SiO2 aerogel by the single-source CVD method under the atmospheric-pressure. When the flow of Ar is 1-3 L/min, CdS film is only deposited on the external surface. As the flow of Ar improves to 5L/min, there is no CdS film deposited. If the flow of Ar is controlled at 4 L/min, CdS film is deposited on the inner and external surface. The EDS results show that the thin film deposited on the inner and external surface of the SiO2 aerogel has the similar atom ratio (about 1:1) of sulfur and cadmium. The XRD results reveal that the CdS thin film deposited on the inner and external surface of SiO2 aerogel possesses the hexagonal crystal structure.
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