Study On The Preparation Of Al₂TiO₅ Powder Via Nonhydrolytic Sol-Gel Route Using Alcohols As Oxygen Donor

Aluminum titanate powder has been synthesized at low temperature of 750℃bysolvent-free nonhydrolytic sol-gel route using titanium tetrachloride and anhydrousaluminum trichloride as precursors and anhydrous alcohols as oxygen donors. A Chinesepatent (ZL 200610005316.5) has been got for the innovative result. On the baisi of thestudy, aluminum titanate powder with more excellent sintering properties has beenprepared via the pressure field assisted nonhydrolytic sol-gel method. The effects ofprocess factors on low temperature synthensis of Al₂TiO₅ have been studied by means ofXRD, FE-SEM, BET, and so on. The results show that stoichiometrically used as oxygendonor for synthesizing Al₂TiO₅ by solvent-free nonhydrolytic sol-gel route ethanol is themost effective oxygen donor and next comes isoropanol and n-butyl alcohol,successively. However, the pressure field assisted nonhydrolytic sol-gel route leads to thepoppsite result. Meanwhile, the appropriate choose of precursor addition order can makethinner the solvation layer of chloroalkoxides and accelerate the gel reaction, accordingly.Althougth raising reaction temperature and prolonging heating time of gel reaction canimprove the effect of Al₂TiO₅ synthesis, too high pre-reaction temperature gives rise tobad result of synthesis.The nonhydrolytic sol-gel reaction mechanism and its phase transformation duringheat treatment have been investigated by means of FT-IR, DTA-TG. It is discovered thatAl-O-Ti bond, formed in the nonhydrolytic sol-gel route, causes the amorphous gel tocrystallize directly into Al₂TiO₅ with phase transformation heat releasing. It is theseheterocondensation bonds that play the key role in the low temperature synthesis ofAl₂TiO₅. However, the Al-O-Ti bond is difficult to occur in the hydrolytic sol-gel process.As a result, the hydrolytic gel undergos the crystallization of rutile andα-Al₂O₃, whichreact on each other to synthesize Al₂TiO₅ through their solid state diffusion. This is anendothermal process, and its synthesis temperature is above 1300℃.Compared with solid state reaction, hydrolysis sol-gel method and solvent-freenonhydrolytic sol-gel, the pressure field assisted nonhydrolytic sol-gel method resulted inthe Al₂TiO₅ powder with best sintering property. The bending strength of the sinteredAl₂TiO₅ body is as high as 16.6 MPa and its thermal expansion coefficient only 0.77×10^-6/℃.