Study On The Preparation Of Cordierite Powder Via Non-hydrolytic Sol-Gel Method

Cordierite powders were prepared via non-hydrolytic sol-gel method.The effect of aluminum source category,adding time of magnesium source,the kinds of solvents and the way of gelatin and magnesium acetate tetrahydrate dehydration on synthesis of cordierite powder have been systematically investigated by DTA-TG,XRD,FT-IR,SEM when cordierite powder were prepared via non-hydrolytic sol-gel method.On this basis,the root of the effect of magnesium source types on the synthesis of cordierite powder and the phase transition process of gel during the heat treatment have been further studied.The experimental results indicated that the phase transition of cordierite precursor gel prepared by non-hydrolytic sol-gel method in the heat treatment process when under the condition of not adding mineralizer is:the amorphous cordierite began to transform into?-cordierite at 900?simultaneously accompanied by a small amount of magnesium aluminum spinel phase.?-cordierite turn into?-cordierite at 1050?.?-cordierite was obtained at 1200?via the further reaction of very small amount of spinel and amorphous silica.Compared with anhydrous magnesium chloride and ethanol magnesium,magnesium acetate is more beneficial to low temperature synthesis of cordierite for magnesium acetate could further occur non-hydrolytic condensation reaction with precursor to form Mg-O-Al and Mg-O-Si bond.It is more profitable to synthesize cordierite when introduce magnesium acetate after aluminum,silicon condensation reaction;Gelation played a significant role in the synthesis of cordierite under the condition of auxiliary pressure field and dispersion effect of cordierite powder is significantly improved via the gelation process.Cordierite powders were prepared under the condition of adding mineralizer and its sintering properties were studied in order to further reduce the synthesis temperature of?-cordierite powder on the basis of above.The phase transition process of gel which added mineralizing agent during the heat treatment and the effect of mineralizer category,the adding amount of mineralizer,adding time of mineralizing agent on synthesis of cordierite powder have been systematically researched by DTA-TG,XRD,FT-IR,SEM,universal testing machine,thermal expansion meter and the mechanism of optimal agent mineralization borate reducing the synthesis temperature of?-cordierite powder was discussed.The experimental results shows that the phase transition of cordierite precursor gel prepared by non-hydrolytic sol-gel method in the heat treatment process when under the condition of adding mineralizer is:amorphous cordierite directly turn into?-cordierite phase at900?.The introduction of boric acid enhanced the Mg-O-Al,Mg-O-Si and Al-O-Si bond of gel compared to the lithium fluoride and ammonium dihydrogen phosphate.Simultaneously limited solid solution were formed due to boron ions entering into the crystal lattice of?-cordierite at a high temperature,which promoted lower of synthesis temperature of?-cordierite together with the formation of liquid phase.The optimum adding amount of boric acid?molar ratio of boric acid to TEOS?is 0.3.The synthetic effect of?-cordierite is better when boric acid was introduced simultaneously with magnesium source or after aluminum,silicon precursor product further condensation with magnesium source than it was introduced before aluminum and silicon occurring condensation reaction.When the sintering temperature is 1425?,the bending strength of cordierite ceramic reaches a maximum of120.71 MPa and its expansion coefficient is 1.636×10^-6/?.