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(1) Sol-gel method was used to prepare homogeneous silicon dioxide aerogels with pore structure. The effects of the ratio of silicon source, pH value, reaction time and the effect of different supercritical fluids on the structure of silica aerogels were investigated. The gel process can be divided into acid-base two-step catalytic method. First, the silicon source is hydrolyzed under acidic conditions to form precursor sol (only low crosslinking oligomer can be formed under acidic conditions). Then, the sols undergo rapid polycondensation under the action of their own amino groups, forming clusters of larger size until a cluster-aggregate-gel is formed throughout the container. When the gel is just formed, the strength is low and the aging process is required to increase its strength, so the aging process is also generally considered to be a continuation of the gelation process. After the gel is formed, the monomer or oligomer in the solution phase of the pores will continue to be connected to the network and crosslinked with the formed gel network. At the same time, some small clusters on the gel skeleton network will dissolve again Polycondensation reaction, the Gibbs free energy principle that they will be deposited in the neck of the skeleton particles between the region, resulting in the network gradually coarsening smooth, thereby enhancing the strength of the gel. After solvent displacement, the sample was dried with supercritical drying to obtain a silicon dioxide aerogel sample. 

(2) On the basis of the previous step, the sample was gelated and immersed in chlorobenzene containing polyethylene of different molecular weight. So that polystyrene attached to the silicon dioxide skeleton, aging for some time, solvent exchange, the supercritical drying to get the sample.

 

 

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