Preparation And Properties Research Of Agarose-silica Composite Aerogels

Aerogel materials have great application prospects in the fields of sound insulation,adsorption,thermal insulation,construction and energy storage because of their low density,high specific surface area,low thermal conductivity,high porosity and low permittivity.However,its unique porous structure determines the poor mechanical properties of aerogels.In addition,the traditional inorganic oxide aerogels have poor mechanical properties and are difficult to be used in practical production in some fields.These problems limit the application of aerogel materials in daily life.Therefore,exploiting a more suitable method to prepare aerogels with excellent mechanical properties is of great significance to the practical application of aerogels.In this work,agarose-silica composite aerogel was taken as the research object,and the influence of isomorphic coating structure on the preparation and properties of composite aerogels and the influence of nanoscale interpenetrating network structure on the preparation and properties of composite aerogel were investigated.It is divided into the following three parts:（1）The agarose solution was cooled to gel,replaced by ethanol solvent and dried with supercritical CO₂ to prepare agarose aerogels with three-dimensional nanofibers network,and then the surface of the agarose gel skeleton was isomorphic covered with silica by CVD method.The coating layer was used to obtain agarose-silica composite aerogels,focusing on the effects of different concentrations of agarose on the properties of composite aerogels.（2）The agarose solution and oxidized cellulose were heated to dissolve,cool the gel,and then the agarose-cellulose composite aerogels were prepared by solvent replacement and supercritical CO₂ drying.Agarose-cellulose-silica composite aerogels were prepared by isomorphic coating with silica layer on agarose-cellulose nanofibers network by CVD method.Introducing cellulose nanofibers to further improve the mechanical properties of agarose-silica composite aerogels,and their performance and related mechanisms were discussed.（3）In order to optimize the preparation process of agarose-silica composite aerogel,a cheaper inorganic sodium silicate was used as the silicon source to remove sodium ions through cation exchange resin treatment to obtain a silicic acid solution,which was then directly mixed with agarose solution.The mixture was adjusted p H value to gel in situ,and finally constructing composite aerogels with an interpenetrating network structure by supercritical CO₂ drying.The properties and related mechanisms of the related samples were also discussed.