溶胶-凝胶法制备莫来石纤维过程中MgO的影响

Effect of Magnesium Oxide on Preparation of Mullite Fibers via Sol-Gel Method

以异丙醇铝、硝酸铝、正硅酸乙酯为原料,采用溶胶-凝胶法制备莫来石纤维,利用扫描电镜、TGA分析仪、X射线衍射仪、红外光谱等分析仪器,研究了莫来石纤维的形成过程。MgO添加剂通过硝酸镁分解导入。XRD和IR分析结果表明,最终纤维产物主晶相为莫来石,MgO的加入可以显著降低凝胶纤维转化为莫来石纤维的温度,加入质量分数为1%的MgO可以使莫来石析晶温度降低100℃。通过扫描电镜观察纤维形貌发现,当MgO加入量较低时,纤维表面光滑且直径约为20μm,无明显缺陷,但是加入量过多会影响成品纤维的表面形貌。综合考虑,适宜的MgO质量分数为1%,既可降低莫来石析晶温度,又可获得形貌良好的莫来石纤维。

Mullite fibers were prepared from aqueous solution of aluminum nitrate, aluminum isopropoxide and tetraethylorthosilicate by sol-gel method. The formation of mullite fibers was studied by scanning electron microscope, TGA analysis, X-ray diffraction, and IR spectra. MgO was introduced into the fibers by adding Mg（NOa）2. Mullite crystallization temperature decreased by 100 ℃ with the presence of MgO（wvgo = 1%） and the main crystalline phase of the as-prepared fiber was mullite as observed by XRD and IR. As shown by SEM, the fibers had a diameter about 20 μm and smooth surface without obvious defects with low amount of MgO, while overdose of MgO affected the surface morphology. Taken together, adding w=1% MgO could both reduce the mullite crystallization temperature and obtain mullite fibers with good surface at low temperature.