β型四钼酸铵的制备及结晶过程

来源期刊：中南大学学报(自然科学版)2001年第2期

论文作者：吴争平 尹周澜 陈启元 张平民

文章页码：135 - 138

关键词：四钼酸铵;结晶;热力学分析;动力学分析

Key words：ammonium tetramolybdate; crystallization; analysis of thermodynamics; analysis of dynamics

摘    要：研究了用晶种生长法制备β型四钼酸铵的方法.其制备分2步进行:首先用酸沉法制备四钼酸铵;再以酸沉法制得的四钼酸铵为原料,氨浸后用晶种法制备β型四钼酸铵,其包含2个相关过程(一是晶核的生成过程,控制pH值为1.2;二是晶核的长大过程,控制pH值为2~3).对2种结晶进行差热及热重分析,结果表明用酸沉法制得的为α型四钼酸铵,用晶种法制得的晶体为β型四钼酸铵.用晶种法制得的结晶的晶体形貌与用酸沉法制得结晶的晶体形貌相比,颗粒较大且均匀.对四钼酸铵的结晶过程进行了热力学分析和动力学分析,说明结晶反应自发进行的趋势很强,速度也较快.此外,初步探讨了四钼酸铵结晶过程机理和晶型的控制,阐明了晶体生长速度的大小对实际晶体的影响.

Abstract: The ammonium β-tetramolybdate was prepared and the preparing process included two courses: preparing amonium tetramolybdate bythe method of acidified deposition; and preparing ammonium β-tetramolybdate bythe method o seeded decomposition. The second course included two processes: one was born of crystal seeds(pH=1.2), the other as growth of crystal seeds(pH=2~3). The TGA and DTA proved that the crystal was ammonium α-tetramolybdate prepared by the method of acidified deposition and was ammonium β-tetramolybdate prepared by the method of seeded decomposition. The thermodynamics and the dynamics of the process were analyzed. The mechanism of crystallization process and the control of the crystalline were discussed simply in this paper.