碱性条件下钛石膏晶须生长工艺及机理分析

以工业副产钛石膏为原料,氢氧化钙饱和溶液为溶剂,七水硫酸镁为晶型助长剂,采用水热法制备α-半水硫酸钙晶须。研究了碱性环境下反应温度、反应时间、浆料固液比、晶型助长剂用量、体系总体积以及体系pH值对α-半水硫酸钙晶须产率及形貌的影响,分析了晶须的生长机理。结果表明在碱性水热环境中,钛石膏先转变为α-半水硫酸钙,再逐渐依附于既有晶须生长,形成粗大的晶须,在较优的工艺条件下,α-半水硫酸钙晶须产率可达71.6%,晶须表面光滑,长径比为70。

Whiskers Growth and Mechanism Analysis by Titanium Gypsum under Alkaline Conditions

The α-calcium sulfate hemihydrate whiskers were prepared by hydrothermal method with titanium gypsum as raw material, calcium hydroxide saturated solution as solvent and magnesium sulfate heptahydrate as crystal promoter. The effects of reaction temperature, reaction time, solid-liquid ratio of slurry, content of crystal promoter and volume of calcium hydroxide solution on the yield and morphology of α-calcium sulfate hemihydrate whiskers were investigated, the growth mechanism of whiskers was clarified, too. The results show that in alkaline hydrothermal environment, titanium gypsum first transforms into α-calcium sulfate hemihydrate and then grows into whiskers. Adhering to the existing whiskers is an important way of whisker growth. When the solid-liquid ratio of slurry is 1∶12, the temperature is 120 ℃, the reaction time is 8 h, and the content of crystal promoter is 6%, the α-calcium sulfate hemihydrate whisker has high yield and excellent performance. The whiskers yield with smooth surface can reach 71.6%, and the mean aspect ratio is 70.