大长径比硫酸钙晶须的制备及形貌研究

以天然石膏为原料采用水热法制备半水硫酸钙晶须，SEM观察晶须形貌及分析长径比。考察了外加剂、原料粒度、水热温度、pH值、初始料浆浓度、水热时间对硫酸钙晶须形貌影响。结果表明:外加剂提高了天然石膏在水中的溶解度；原料粒度会影响天然石膏的溶解速率，粒度越小溶液越容易达到过饱和状态；水热温度在 < 100 ℃时较难生成硫酸钙晶须；溶液pH值可改变溶液离子质量分数，随着pH值升高晶须平均直径逐渐减小，同时会导致外加剂失效；料浆浓度越高，晶须生长空间越小，溶液体系离子迁移速度降低。在原料粒度4 μm、料浆浓度5%、CuCl₂ 1.5%（相对于天然石膏质量）、水热温度120 ℃、pH=5.3、水热时间140 min的条件下，制备出平均直径1~2 μm、长径比达160的半水硫酸钙晶须。 

Study on the Preparation and Morphology of Large Aspect Ratio Calcium Sulfate Whisker

Natural gypsum was used as raw material in airtight reactor to prepare hemihydrate calcium sulfate whiskers by hydrothermal method, and SEM was utilized to observe the morphology and aspect ratio. The additive, particle size, hydrothermal temperature, pH, initial slurry concentration and hydrothermal time on the morphology of calcium sulfate whisker were investigated. The results showed that additive increased the solubility of natural gypsum in solution; particle size of raw material affected the dissolution rate of natural gypsum, smaller particles easily reached the supersaturated sate; it's difficult to turn into calcium sulfate whisker when hydrothermal temperature was less than 100 ℃; pH of solution can change the mass fraction of ion, and as pH increased the average diameter of whisker gradually decreased, along with being invalid of the additive of CuCl₂; the higher slurry concentration was, the smaller the space of whisker growth was and the slower ion transport rate was. The optimum conditions for the preparation were as follows: the diameter of raw material was 4 μm with the slurry concentration at 5%, the content of copper chloride was 1.5%, temperature was 120 ℃, pH=5.3, and reaction time was 140 minutes. Then, the calcium sulfate whisker of average diameter 1~2 μm, aspect ratio 160 were obtained.