| SiO2 aerogels is a kind of material of lightweight nano-porous network structure, with 0.003-0.5g/cm3 density,80%-99% porosity,500-1000m2/g specific surface area and 1-100nm pore and particle size. Its super-insulation property, due to slim nano-porous structure, makes such material have great application prospects. Currently, with the technology of supercritical drying, silica aerogels was made of TMOS and TEOS in domesitc and abroad. What with complex processing, time-consuming, inefficient, costly, toxic raw materials, dangerous process of supercritical drying, while lack of knowledge about the technology of supercritical drying under normal atmospheric pressure resulted in unsatisfied structural properties, and hydrophilic character of the unmodified, all of these hamper silica aerogels industrial application.The thesis studied the mesoporous material of silica aerogels with low density and high performance, made by the technology of drying under the normal atmospheric pressure, low-cost water glass as source material. The experiment studied the influence of indicators, it contained gelling system components ratio, gelling temperature, gelling system pH, the addition of formamide, wet gel aging, surface hydrophobic treatment,the process of making aerogel structure by the technology of drying under the normal atmospheric pressure and aerogel structure's natural density, tap density, aperture size and specific surface area. In the meanwhile, the theoretical result was compared with the actual one by the heat flow model which used the structure like a small ball and rodlike shape, and then theoretically analyzed and calculated. And the results ascertain the main factors of the thermal conductivity of Sol-Gel and built the relations between the tap density of Sol-Gel and thermal conductivity of Sol-Gel.The results showed that when the ratio of water glass and water was 1:3, sodium ion in Sol-Gel which was disposed by the exchange for amberite resin was reduced from 17.01% to 0.4%, the contents of sodium ion was obviously reduced; when the volume ratio between Silica acid and water which was disposed by the exchange of sodium ion was 30 ml:50ml and the temperature of gel was 40℃, the density of obtained Aerogel was the smallest and the performance was optimal; when the system pH is 5, the performance of the obtained Aerogel was topgallant, SiO2 composite aerogels obtained the most probable pore with the size of 10.76nm, and narrow pore distribution with the size of around 10nm; the gel time was increased after adding formamide, and the pore structure of aerogels became more well-proportioned after drying. When the addition of formamide was 1.5ml, BJH pore size distribution was mostly in 10nm, and the specific surface area was 610.6m2/g; the wet strength of the gel network structure was improved after using TEOS/ethanol solution on the wet gel aging treatment, it obtained the rule of influence about the specific surface area and the density between TEOS/ethanol concentration and aerogel structure. With 30%vol.of TEOS/ethanol solution of the wet gel aging treatment, massive and high specific surface area of silica aerogels materials can be obtained; use Chlorotrimethylsilane, n-hexane, isopropanol on the wet surface modification hydrophobic treatment, when TMCS and n-hexane molar ratio was 0.35, then the degree of hydrophobic of obtained aerogels was 43.95%. And infra-red spectrum(IR spectrum) showed the surface of aerogels grafted the hydrophobic group-CH3; select n-hexane as solvent medium, drying process to 50℃84h, 60℃72h, the density of aerogels obtained 0.14g/cm3, porosity was 93.7%, specific surface area 610.643m2/g, pore diameter 9.72nm, pore volume was 1.48ml/g. The adsorption isotherms curve was theⅣIsotherm in the IUPAC classification, which belongs to the typical mesoporous adsorption isotherms with the aperture size between 2nm and 5 nm; the thermal conductivity of silica aerogels was derivated deducedin theory and calculated by the heat flow model which used the structure like a small ball and rodlike shape, the result showed that the density is the key factor in the thermal conductivity of aerogels, and the material of silica agerogels with smaller thermal conductivity can be obtained by lowering its density.
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