微米级硫酸钙晶须的制备

Preparation of Calcium Sulfate Whisker in Micrometer Scale

为了制备分布均一、具有较好光滑性和长径比的微米结构二水硫酸钙(CaSO4.2H2O)晶须,在室温条件下,以CaCl2和(NH4)2SO4为主要原料,通过一步超声反应制备出具有比较理想结构的微米级二水硫酸钙晶须。研究发现,在硫酸钙晶须生成过程中无水乙醇的量起着非常重要的作用,过多、过少的无水乙醇都不利于生成目标产物。CTAB的量对于二水硫酸钙晶须的长径比大小具有较大的调控作用。当无水乙醇的量为20mL,CTAB的浓度为0.9mmol/L,超声时间为1h时可以制备较理想的目标产物。120℃热处理2h晶须变碎,结果与热重结果相一致。与一般的晶体制备不同的是陈化时间对硫酸钙晶须的长径比无影响。通过X射线粉末衍射和热重分析分别对产物的结构和热稳定性进行了表征。结合实验简单探讨了二水硫酸钙晶须生成的机理,从中发现了制备较高长径比的二水硫酸钙晶须的一些规律。

CaSO4·2H2O whiskers in micrometer scale were prepared with CaCl2 and （ NH4 ） 2SO4 as the main raw materials via an ultrasonic process at room temperature. The product with better smoothness and higher aspect ratio was obtained. The method is friendly with environment and simple in manipulation under mild conditions. The effects of volume of anhydrous alcohol, concentration of hexadecyltrimethylammonium bromide （CTAB）, ultrasonic time, heat-treatment and aging time on the morphology and size of CaSO4·2H2O were investigated in details. It has been found that the volume of anhydrous alcohol is important to the growth of CaSO4·2H2O whiskers. Anhydrous alcohol with excessive or insufficient volume is unfavorable to the preparation of the target product and the aspect ratio of CaSO4·2H2O whiskers is controlled by the concentration of CTAB. When the volume of anhydrous alcohol is 20 mL, the concentration of CTAB is 0. 9 mmol/L and ultrasonic time is 1 h, the target product was prepared. The whisker became shiver, which coincide with the results of TG. Different from the general preparation process of inorganic compounds, aging time has no influ- ence on the aspect ratio of CaSO4 whisker. The structure and thermostability of the product were characterized by X-ray diffraction and thermal gravimetric analysis, respectively. The growth mechanism of CaSO4·2H2O whiskers is discussed simply according to the experiment result. Some regulative rules of preparing CaSO4·2H2O whisker with high aspect ratio have been obtained.