pH值对溶胶-凝胶法制备莫来石纳米粉体微观形貌的影响(英文)

Effect of Precursor pH on One-dimensional Growth of Mullite Prepared by Sol-Gel Method with WO_3 Catalyst

以氧化钨为催化剂,利用溶胶-凝胶方法制备了具有高长径比的一维莫来石纳米粉体.研究表明,溶胶前驱体的pH值对氧化钨的催化作用有重要的影响.只有当溶胶前驱体的pH值小于7时,才能形成AlWO4生长模板引导一维莫来石颗粒的形成.随着溶胶前驱体pH值的逐渐升高,前驱体的化学均匀度降低,导致γ-Al2O3形成温度升高,WO3在生成AlWO4之前已经大量挥发.生长模板的缺失使莫来石粉体的微观形貌从各向异性向各向同性发展.

One-dimensional mullite particles were synthesized by sol-gel method from hydrous aluminum chloride （AlCl3·6H2O） and tetraethoxysilane （TEOS） as raw materials and WO3 as catalyst. WO3 had a desired effect on the anisotropic growth of mullite particles by forming aluminum tungstate （AlWO4） as growth template at low temperature, which was greatly dependent on the precursor pH. NMR results indicate that the pH during gelation can highly influence the homogeneity of precursor, mullite formation and microstructural features. One-dimensional mullite particles are significant only when the precursor pH is lower than 7. Morphology of the mullite particles synthesized with pH≥7 transforms from anisotropy to isotropy and platelike.