Sol-Gel Preparation Technology And Characterization Of Alumina And Zirconia Aerogels

Aerogel is listed as one of the top ten popular science and technology.It is known as the versatile new material that can change the world.Because of the excellent features,aerogel has a very good application in many ways.Especially in the field of insulation,good thermal conductivity with excellent thermal stability,so it plays an important role in a variety of special window insulation system.However,the industrial application of aerogel is restrained because of the low strength and easy to break of the alumina,zirconia aerogels.And the high temperature phase reaction and sintering will affect the high temperature properties of aerogels.In this paper,Crack-free,monolithic alumina and zirconia aerogels were prepared by a sol-gel method with supercritical drying technique,and the effects of synthesis parameters on the phase stability and morphological characteristic of aerogels were discussed.The main conclusions are drawn as the following:(1)In this paper,with Sec-butyl alcohol aluminum as the main raw material and the mixed solution of water and ethanol were as reaction medium and formamide was added as dry chemical control agent.The white,crack-free,monolithic alumina aerogel was synthesized by sol-gel technology and supercritical drying technique.The surface area of alumina aerogel was 10 m2/g after heated at 1200?.(2)SiO2-Al2O3 aerogel was synthesized by the addition of tetraethoxysilane(TEOS).There were still no collapse and microcrack in the aerogel after the temperature rising from room temperature to 1200?.When the molar ratio of Al/Si is 8:1,the aerogel could have best thermally stable property.The surface area can maintain 100 m2/g after heated at 1200?.The microstructure of aerogel is changed by the addition of silica,the particles sintering and phase transformation were suppressed.(3)Yttria-stabilized zirconia aerogel are successfully obtained by sol-gel technology and supercritical drying technique.There were still no collapse and microcrack in the aerogel after the temperature rising from room temperature to 1200?.The addition of a small amount of yttrium resulted in a significant suppression of phase transformation from tetragonal phase to monoclinic phase.The higher thermal stability was achieved by the addition of 8 wt%yttrium,the transformation from tetragonal phase to monoclinic phase did not take place after heat-treated at 1000?for 2 h.(4)Through the study of RE2O3(RE=La,Ce,Gd,Yb)co-doped Yttria-stabilized zirconia aerogel,the kinds of rare earth element are of crucial importance for the phase structure of aerogel.The result shows that YSZ doped with larger cations should have higher thermal stability.In this paper,RE(RE=La,Ce,Gd,Yb)-YSZ aerogels are successfully synthesized.The thermal stability of La-YSZ aerogel is greater than others.And the transformation from tetragonal phase to monoclinic phase is still restrained in La-YSZ aerogel even after heat-treated at 1300? for 2h.