The Preparation And Characterization Of Alumina Aerogel Composites

Al2O3 aerogel is a porous,low density,monolithic,nanometer material,and its continuous network structure can be controlled and tailored at the nanometer scale.Alumina aerogels have a large specific surface area and excellent high temperature stability,and have wide application prospects in high temperature resistant materials and high temperature catalysis.However,pure alumina aerogels,directly dried from wet gel,generally have poor mechanical properties and tend to break into fragments.In this thesis,alumina aerogel was modified by addition of GO,and wet gel samples were prepared by sol-gel method and hydrothermal method respectively.Then the alumina aerogel composites with porous would be obtained through organic solvent sublimation drying and freeze drying.The detailed results are as follows:Firstly,we investigated the effects of experimental parameters on the structure of GO/Al2O3 aerogels during sol-gel preparation process.When the volume of GO solution was increased,the gel time of the sol was increased under the constant volume of alcohol and GO solution;With the increase of the amount of PO,the gel time of the sol become shorter and the specific surface area of the sample changed with the addition of PO.When n(PO):n(Al)=10,the specific surface area of the sample is the largest,reaching 444.18 m2/g;When the concentration of GO solution is low,the shrinkage rate of the sample is large.To the contrary,the mechanical strength of the sample is low and easy to break.Secondly,the influence of various experimental parameters on the structure and morphology of the alumina aerogels during hydrothermal synthesis process.When pH value increased from acidic to alkaline,the morphology of alumina also changed,from flake to three-dimensional tufted,to sea urchin shaped particles,and finally to a one-dimensional acicular state of aggregation;Crystal structures appeared only when the temperature was above 180 ℃.The morphology of alumina aerogels changed with the increase of the temperature;After reduction of GO,alumina crystal of composite aerogels,prepared under different pH conditions,all tends to transform to nanofibrous structure.