方形γ-MnOOH单晶的水热法制备

Synthesis of Prismatic Single Crystal γ-MnOOH

在150℃水热条件下,用HMnO_4氧化Mn(CH_3COO)_2,制备出了方形γ-MnOOH单晶.反应过程中使用HMnO_4为氧化剂,不引入任何金属阳离子杂质.通过XRD、SEM、TEM、HRTEM、TG等方法研究发现,γ-MnOOH单晶的形成经过两个主要阶段:(1)反应初期生成γ-MnO_2晶须;(2)在水热系统中,晶须按照吸附生长机理生长,由于各个晶面的表面能的不同,(111)晶面首先快速生长,再沿其他方向生长,形成方形γ-MnOOH单晶.反应时间是影响晶体形态的主要因素.TG结果证明γ-MnOOH单晶在350℃下开始转化成MnO_2.

Prismatic single crystal γ-MnOOH was synthesized by a hydrothermal method through oxidizing Mn（CH3COO）2 with HMnO4 at 150℃. The advantage of oxidizing agent HMnO4 is that no other metallic ions coming into the product structures. The synthesized samples were characterized by XRD, SEM, TEM, HRTEM and TG. It is found that the formation process of single crystal γ-MnOOH includes two primary evolution stages： （1） the γ-MnOOH whiskers are initially formed, and （2） the whiskers grow to prismatic single crystal γ-MnOOH by an adsorption-growth process, （111） plane grows faster than other planes, because the surface energy of each crystal plane is different, the different growth rate makes the whiskers changed to prismatic crystal. The hydrothermal reaction time is the major factor that influences crystal morphology. TG results show that the single crystal γ-MnOOH is transferred to MnO2 at 350℃.