Study On Preparation And Properties Of Silica Aerogelat Atmospheric Pressure

Aerogel is a highly cross-linked porous network structure material,its nanoporous network structure is filled with a large amount of gaseous dispersion medium,and has the characteristics of high porosity and nano-scale pore size,which can effectively inhibit convection,conduction and radiation heat transfer.It is one of the most potential thermal insulation materials,which possesses important implications for reducing energy consumption.Silica（SiO₂）aerogel has their inherent brittleness,hydrophilicity,volume shrinkage,expensive and cumbersome preparation processes,and long preparation cycles,which greatly limit their application fields.Based on the above research status,this paper studies the properties of SiO₂aerogel from the aspects of normal pressure preparation process,strength,hydrophobicity,thermal insulation,etc.The main research work is as follows:1.Methyltrimethoxysilane（MTMS）was selected as the silicon source precursor,and the control variable method was used to optimize the process conditions in the preparation process,thereby determining the optimal process for the preparation of SiO₂aerogel at atmospheric pressure.When the MTMS:ethanol:water volume ratio is5:10:15,the hydrolysis p H=3,the condensation p H=8,cetyltrimethylammonium bromide（CTAB）is selected as the surfactant in the preparation process,the addition amount is 0.1 g,and the gelation temperature is 45°C,the comprehensive performance of the optimized sample is better.Relevant tests show that the gel time is19 min,the shrinkage rate is 19.56%,the density is 0.0987 g/cm³,the porosity is95.51%,and the thermal conductivity is 36.5 m W/（m·K）.The contact angle and compressive rebound tests show that the SiO₂aerogel has good hydrophobic and mechanical properties.2.The MAPTMS-SiO₂aerogel was successfully prepared by blending3-（methacryloyloxy）propyltrimethoxysilane（MAPTMS）with the silicon source precursor.MAPTMS acts as cross-linked molecular bridged silicon secondary particles to form a bead-like structure and improve the volume shrinkage,density,compressive strength and thermal conductivity of SiO₂aerogels.The research shows that when the optimum addition amount of MAPTMS is 8%,the gel time of MAPTMS-SiO₂aerogel is 31min,the shrinkage rate is 15.97%,the density is 0.1122g/cm³,the porosity is 94.89%,and the thermal conductivity is 33.5 m W/（m·K）.Its contact angle is further improved to 130.3°,which is better than that of unmodified SiO₂aerogel（123.6°）.The results of the compression rebound test show that the maximum compressive strength reaches 2.95 k Pa,which is about 20%higher than that of the unmodified SiO₂aerogel.3.The styrene monomer was introduced as the polymer reinforcement phase,and the polymer was introduced on the surface of the SiO₂particles to form a coating layer.The styrene reinforced SiO₂aerogel was successfully prepared by in-situ polymerization.The research shows that when the optimum addition amount of styrene monomer is 10%,the gel time of the aerogel is 50min,the shrinkage rate is15.78%,the density is 0.159 g/cm³,the porosity is 92.77%,and the thermal conductivity is 38.5 m W/（m·K）.The contact angle is further improved to 135.6°,which is better than that of MAPTMS-modified SiO₂aerogel.Compression rebound test results show that the maximum compressive strength reaches 3.5 k Pa,which is about 17%higher than that of MAPTMS-SiO₂aerogel.Thermogravimetric test results showed that the addition of styrene did not reduce the thermal stability of the aerogel.