Preparation Of Alumina Aerogels And Composite Materials Materials Assisted By Polymeric Complexing Agent

Alumina aerogels not only have the general properties of aerogels,but also own the properties of higher thermal stability and strength.Therefore,the alumina aerogels have great potential applicants in insulation,high temperature catalysis and so on.When we prepare the alumina aerogels,the quality of alumina sol is the key factor to affect the final products we will get.In the traditional preparation process,the prepared alumina sols have the problems such as low concentration of aluminum ion,easy to precipitate or high cost of precursor?for aluminum alkoxide?.These restricts the application of alumina aerogesl.In this study,a modified polyvinyl alcohol is prepared to obtain a polymer complexing agent,then is used to prepar the alumina sols with AlCl₃·6H₂O.The prepared sols have some advantages such as high aluminum ion concentration,high stability and uniform dispersion.The aerogel products have excellent performance,such as high specific surface area,high porosity and high strength.In addition,by doping sepiolite nanofibers and montmorillonite,the properties of alumium aerogels are optimized and the characteristics of phase composition,specific surface and strength of alumium aerogels are investigatedIn this paper,the modification method of polyvinyl alcohol is carried out and there are some studies about the modified polyvinyl alcohol with different molecular weight effort on alumina aerogels.At the same time,a series of sepiolite doped alumina aerogels and montmorillonite doped alumina aerogels are prepared by dispersing sepiolite nanofibers or montmorillonite nanoscale in the alumina sols.Its structure,strength,dispersibility and other properties are investigated.The main conclusions are as follows:?1?High-density alumina aerogels are prepared by using AlCl₃·6H₂O as precursor with a amount of modified polyvinyl alcohol.The experimental results show that a small amount of modified polyvinyl alcohol could not form the alumina gel,while too much modified polyvinyl alcohol result in gels cracking.The excellent alumina aerogel structure is obtained by adding the appropriate amount of modified PVA.The specific surface of aluminum aerogel can reach up to 593 m²/g,at the same time it remains 143 m²/g after heat treatment of1000°C,and the highest Young's modulus is 8.81MPa.?2?The alumina-sepiolite aerogels are made by doping modified sepiolite in aluminum sols.The specific surface can reach to 280 m²/g after dring,and 171m²/g after heat treatment of 1000?.The liner shrinkage is only 4.1%after heat treatment of 1000?.Its bending strain can reach up to 6.8%??3?Based on alumina sol we made above,self-made exfoliated montmorillonite as adding nanoscale,alumina aerogels with a higher density are then prepared.The specific surface is up to 327 m²/g,and 326 m²/g after heat treatment of 400?.