溶胶-凝胶法制备纳米氢氧化铝溶胶

研究了利用铝酸钠溶液碳酸化产生的沉淀, 经胶溶作用制备出纳米氢氧化铝溶胶的过程. 分析了铝酸钠溶液滴加到大量碳酸氢钠溶液中时发生的反应. X射线衍射研究结果表明, 在纳米氢氧化铝溶胶制备过程中, 从无定形氢氧化铝沉淀到拟薄水铝石的晶型转变过程是氢氧化铝沉淀胶溶时溶解再析出的过程. 将碳酸氢钠加入到苛性比为1.7的铝酸钠溶液中, 中和至苛性比为1.3后, 溶液诱导期中的紫外光谱显示270 nm处的Al(OH)3-6吸收增强. 经与含铝原子六配位的晶体紫外光谱对比后表明, 在铝酸钠分解生成氢氧化铝的过程中, 其铝的配位结构从四配位转化为六配位. 拟薄水铝石溶胶粒子的形貌与胶溶所用的酸和分散剂有关.

Synthesis of Nano-Alumina Hydroxide Sol Using Sol-gel Method

The preparation process of nano-aluminum hydroxide sol by peptizing aluminum hydroxide precipitate produced via carbonation of sodium aluminate was investigated. The reaction, in which the sodium aluminate solution was dropwise added into abundant sodium bicarbonate solution, was analyzed. The XRD results indicated that the amorphous aluminum hydroxide precipitates transformed into pseudo-boehmite because the precipitates dissolved and recrystallized into pseudo-boehmite crystals during the sol preparation. Furthermore, the increase of absorption at 270 nm in the UV spectra indicated the presence of Al(OH)3-6 ion during the sodium aluminate solution with caustic ratio of 1.7 was neutralized to 1.3. Comparing with the absorption spectrum of the structure of six hydroxyl groups around Al atom, it could be concluded that the coordination numbers of Al atom with hydroxyl groups changed from four to six during the decomposition of sodium aluminate solution. Besides, the morphology of particles in the sol was also influenced by surfactants and acids used.