Preparation And Properties Of Silica Aerogels And Their Insulation Materials

Silica aerogel is a highly crosslinked porous network material with a gas-filled interior and the most representative aerogel material.Silica aerogels have played an important role in the fields of thermal,optical,environmental protection,electricity,and catalyst carriers due to their high specific surface area,high porosity,low thermal conductivity,and low density.However,there are still major challenges in its preparation and application,such as how to optimally prepare aerogel under normal pressure conditions,while maintaining its porous network structure while maintaining its appearance;how to prepare aerogel composite fiber Insulation material solves the problem of aerogel felt powder,so that its insulation material can be widely used in the building insulation industry.In view of the current research situation,this thesis focuses on the problems of atmospheric pressure preparation and composite application of silica aerogel,designing different contrast experiments,seeking to use the shortest time and the most convenient and environmentally friendly way under normal pressure conditions.Method for preparing silica aerogel and preparing aerogel felt composite with excellent mechanical properties and thermal insulation properties without powder.The main findings are as follows:?1?By controlling different variables:silicon source,raw material ratio,catalyst,post-treatment conditions and drying temperature,different sets of comparative experiments were designed to perform a series of characterization of the prepared silica aerogel products.Judging its appearance,performance and other conditions.The specific properties of aerogels were tested by means of SEM,BET,TG,thermal conductivity measurement,etc.,and the best preparation conditions for preparing aerogels were obtained?ethyl orthosilicate is the source of silicon,raw material ratio nEthyl orthosilicate:nanhydrous ethanol:nwater=1:7:3,1 M diluted hydrochloric acid and 0.5 M diluted ammonia as the acid-base catalyst,the post-treatment step temperature is 50?,the solvent is n-hexane,the surface modifier It is trimethylchlorosilane,and the atmospheric drying conditions are:80? 3 h,120? 6 h.?,so that the obtained aerogel products can ensure the integrity and performance at the same time,and the process is shortened and the cost is reduced.The best aerogel has a high specific surface area of 851.7 m²/g,good thermal stability?13% mass loss rate?,low density?0.13 g/cm³?,low thermal conductivity?16.0 mW/m·K?and maximum 9.00 g/g of organic solvent adsorption capacity and other advantages.?2?Due to the brittleness of pure silica aerogel,in order to enhance its mechanical properties,glass fiber mat?Nanjing Debile and Weifang Youxin Fe?was used in situ to bond with silica aerogel to successfully prepare composite thermal insulation material..The structure and properties of the aerogel felt composite were also investigated by varying the variables in the process of preparing the composite?fiber mat,raw material ratio,catalyst,bonding mode,post-treatment conditions,and drying temperature?.The optimum preparation conditions are as follows:Nanjing Debeili and Weifang Youxin felt are fiber mats,raw material ratio n _{Ethyl orthosilicate}:n_{anhydrous ethanol}:n_water=1:7:3,impregnation method"gas and felt",1 M diluted hydrochloric acid and 0.5 M diluted ammonia water are acid-base catalysts,the post-treatment step temperature is 50?,the solvent is n-hexane,the surface modifier is trimethylchlorosilane,and the atmospheric pressure drying condition is:80? for 2h,80 Maintain at ?90? for 2 h.Finally,it has excellent mechanical properties?compressive strength of 827 kPa when compressed at room temperature of 20%?,good thermal stability at high temperature?loss rate of 8%?,low density?0.23 g/cm³?,superhydrophobic Composite insulation material?water contact angle>150°?,good thermal insulation performance?thermal conductivity 20.4 mW/m·K?and maximum organic solvent adsorption capacity of 3.55 g/g,showing its in the field of thermal insulation Application potential.The preparation process of silica aerogel under normal pressure and the formulation of hydrophobic silica aerogel composite fiber felt insulation material provided by this thesis provide reference for the application of aerogel in the field of building insulation materials.