Study on preparation and properties of SiO2 high efficiency energy saving aerogel thermal insulation materials
Using N,N-dimethylformamide as desiccant,SiO2 aerogel thermal insulation materials were prepared by atmospheric drying method.The effects of the molar ratio of tetraethyl orthosilicate and water on the mor-phology,phase structure,pore size distribution,mechanical properties and thermal conductivity of SiO2 aerogel were studied.The results showed that the SiO2 aerogel thermal insulation material was a typical amorphous structure with ordered mesoporous channels.With the increase of the molar ratio of water,the ordered degree of the pore structure of the aerogel gradually increased,and the macro morphology was more complete and com-pact.The porous grid structure of the aerogel prepared by the molar ratio of n(TEOS)∶n(water)=1∶30 was the most compact.With the increase of water mole ratio,the specific surface area and compressive strength of SiO2 aerogel first increased and then decreased,and the thermal conductivity first decreased and then increased.When the molar ratio n(TEOS)∶n(water)=1∶30,the maximum specific surface area of the aerogel was 441 m2/g,the corresponding pore volume was 0.414 cm3/g,the pore size distribution is 3.75 nm,the maximum com-pressive strength was 29.79 kPa,and the minimum thermal conductivity was 0.022 W/(m·K).The thermal insulation performance was optimal.SiO2 aerogels were hydrophobic modified with TMCS and n-hexane.When the volume ratio of n(TMCS)∶n(n-hexane)=1∶10,the contact angle of the surface of SiO2 aerogels reached the maximum value of 139.6°.The hydrophobic property was the best and the thermal stability was also improved.
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