溶胶-凝胶-喷雾干燥法制备超细Al_2O_3-SiO_2二元粉体材料

Study on Al_2O_3-SiO_2 binary powder materials prepared by sol-gel and spray drying methods

以硝酸铝(Al(NO3)3·9H2O)和正硅酸乙酯(TEOS)为原料,采用溶胶-凝胶(Sol-Gel)技术并结合喷雾干燥(SPD)技术制得超细Al2O3-SiO2二元复合粉体材料,并分别于400℃、800℃、1000℃、1150℃和1200℃煅烧2 h;采用全自动比表面积与孔隙率分析仪、TEM、TG-DSC及XRD等仪器研究了热处理温度、pH值(分别为5.5、7和8)以及干燥方法对粉体材料的表面性能、显微形貌、物相组成及Al2O3-SiO2二元系晶体转变过程的影响.结果表明:由Sol-Gel-SPD制备的超细Al2O3-SiO2二元粉体材料的比表面积＞448 m2·g-1,而经1200℃煅烧2 h后所得的超细莫来石的比表面积34.05m2·g-1;TG-DSC分析表明:采用Sol-Gel-SPD制得的Al2O3-SiO2二元粉体材料的质量损失主要发生在500℃之前;XRD分析表明:粉体试样的开始莫来石化温度为1000℃,铝硅尖晶石(6Al2O3·SiO2)与非晶态SiO2在1150～1200℃完全转化为莫来石;比较不同pH值试样经1200℃煅烧后的TEM照片发现,当pH=7时,得到的超细莫来石粉体粒径最小,为50 nm.

Ultrafine mullite powders were prepared by calcinating the AlO3-SiO2 binary composite powders （at 400℃,800℃, 1000℃ , 1150℃ and 1200℃ for 2 h respectively） obtained by sol-gel and spray dryng methods,using Al（ NO3）3·9H2O and TEOS as starting materials. TG- DSC,XRD,TEM and BET were used to study the effects of calcinating temperature,pH value （5.5,7 and 8 ）and drying method on the thermal behavior as welt as the change of phase structure, specific surface area, particle size and morphology of the mullite precursor powders. The results showed that the specific surface area of the ultrafine Al2O3 - SiO2 binary composite powders was 448 m^2 · g^ -1 above and that of the completely mullitization powders by calcinating precursors at 1200℃ for 2 h was keeping at 34.05 m^2 · g^-1. TG - DSC results showed that the mass loss of the Al2O3 - SiO2 binary composite powders mainly happened before 500℃ and XRD results showed that the initial mullitization temperature was 1000℃ . By going through transition phases of aluminium - silicon spinel and amorphous SiO2 ,the precursor powders transformed to mullite at 1150 - 1200℃ . TEM photos of specimens with different pH values showed that ultrafine mullite powders with smallest particle of 50 nm were obtained with pH =7.