KDP晶体的高温热行为及其热脱水反应动力学研究

Investigation on High Temperature Behavior and Thermal Dehydration Kinetics of KDP Crystal

采用热重（TG-DTA）、定压比热（Cp）和原位高温红外反射光谱等热分析手段研究了四方相KDP晶体室温至260℃之间的高温热行为。实验发现：KDP晶体在183℃附近并未发生四方相到单斜相的相变或发生脱水反应;且晶体于207-210℃左右开始分解,随温度上升,分解过程分为三个阶段。第一个分解阶段出现P2O2-7基团的吸收峰,意味着第一阶段的分解朝着K4P2O7的方向进行;第二阶段是第一阶段产生的中间态产物继续分解的过程;第三个分解阶段为前两个过程的继续分解,最终KDP完全分解为KPO3。通过Kissinger法,根据热重数据计算了KDP在260℃前两个明显的分解过程的动力学参数,其热脱水活化能分别为101.7 J·mol^-1和112.4 J·mol^-1。

The high temperature behavior of tetrahedral phase of KDP crystal was depicted by using thermo gravimetry-differential thermal analysis,specific heat and in-situ infrared reflective spectra over the temperature range from room temperature to 260 ℃,respectively. The experimental results show that no phase transition from tetragonal to monoclinic or dehydration occurrs near 183 ℃,and the dehydration begins at 207-210 ℃. The dehydration undergoes three alterations as temperature increasing. In the first alteration,new peaks in representation of P2O2-7appear which means dehydration occurrs in the direction to K4P2O7. The second alteration is the continuous decomposition of the intermediates. The last alteration is the continuous decomposition of the intermediates yielded in the second stage and translates to KPO3 ultimately. Based on the Kissinger method,the thermal dehydration kinetics of KDP crystal is calculated in terms of the TG data and the active energy are acquired for 101. 7 J ·mol- 1and 112. 4 J·mol- 1,respectively.