熔盐法制备锌铝尖晶石粉体及其反应机理

Preparation and Reaction Mechanism of Zinc Aluminate Spinel Powders by Molten Salt Method

以Al2(SO4)3·18H2O和ZnO为原料、Na2SO4为熔盐,采用熔盐法合成了锌铝尖晶石粉体,研究了熔盐用量、合成温度和保温时间对合成锌铝尖晶石的影响,分析熔盐法合成锌铝尖晶石的反应机理,及合成产物的物相组成及微观形貌,采用TG-DSC对比分析不加熔盐和加10%(质量分数)Na2SO4熔盐2个体系的不同反应过程。结果表明:以Na2SO4为熔盐,加入量10%,焙烧温度1 000℃、保温时间3 h时可以合成高纯锌铝尖晶石粉体;熔盐法合成的锌铝尖晶石晶体大部分呈六棱柱状,少部分呈八面体结构,晶体尺寸100~200 nm;加入Na2SO4可使体系在较低的温度下生成锌铝尖晶石,在液相环境中锌铝尖石生成主要遵循"模板合成"反应机理,小部分遵循"溶解-沉淀"反应机理。

A zinc aluminate spinel powder was prepared by a molten salt method using Al2(SO4)3·18H2O, ZnO as raw material and Na2SO4 as a flux of molten salt. The influences of molten salt amount, synthesis temperature and soaking time on the synthesis performance of zinc aluminate spinel powder were investigated. The growth mechanism, phase composition and microstructure of synthesized product were analyzed. The reaction processes of two systems without and with 10%(in mass fraction) molten salt Na2SO4 were investigated by thermogravimetry and differential scanning analysis. The results indicate that a pure zinc aluminate spinel powder can be obtained at 1 000 ℃ for 3 h when Na2SO4 is used as a molten salt at the amount of 10%. Most of the synthesized zinc aluminate spinel crystals are a hexagonal prism shape, a small part is octahedral shape and the crystalline sizes are 100-200 nm. Zinc aluminate spinel can be synthesized at a lower temperature in the presence of Na2SO4 as a molten salt. In liquid phase environment, the formation of zinc aluminate spinel is principally controlled via template synthesis reactions, and secondarily controlled via dissolution-precipitation reactions.