溶胶-凝胶法制备的莫来石先驱体的相变研究

Transformation Study of Sol-gel Precursors of Mullite

通过正硅酸乙酯和异丙醇铝醇盐在氨水中的水解制备莫来石先驱体凝胶,然后在120℃烘箱中干燥,并研磨制得干凝胶粉末。对干凝胶粉末进行差热分析,并采用XRD分析法研究了凝胶粉经不同温度处理后的相态。结果表明,无定形凝胶在加热过程中,依次析出立方γ-Al2O3、六方α-Al2O3,并最终转变为正交晶莫来石。所制凝胶转变为莫来石晶体的相变温度位于1100～1200℃之间。

A precursor gel with stoichiometric mullite composition (Al 2O 3 ∶SiO 2=3∶2) was prepared by alkoxide hydrolysis of tetraethoxysilane (TEOS) and aluminum isopropoxide (Al(OC 3H 7) 3) in amine solution The mixture was then gelled in a 120℃ oven for 18h and ground into powders Some of the powders were calcined at 500℃,1000℃,1100℃ and 1200℃ respectively for 2h for study The formation of mullite (3Al 2O 3·2SiO 2) from these sol gel derived precursor powders was studied using differential thermal analysis (DTA) and X ray diffraction (XRD) method It is concluded that, with the increase of temperature , the phases precipitated from the noncrystalline gel are successively cubic gamma Al 2O 3, hexagonal alpha Al 2O 3, and orthorombic mullite As confirmed by the experimental results,the prepared gel powder can be transformed into mullite at a temperature as low as 1100~1200℃