DTA试验体系的热时间常数RC_S及最小分离温度L的测定方法

Determination Method of Thermal Time Constant RC_s and Least Separation Temperature L of DTA System

本文用6种型号的8台差热分析仪(DYA)做了铟、铅、锌、聚乙烯的熔融过程及结晶草酸钙和一水硫酸铜脱水过程的DTA试验。利用Gray的DTA曲线方程和反应终点指数衰减关系,测定了从出峰到峰顶的时间t_(max)及描述DTA曲线拖尾程度的热时间常数RC_S,由此可算出用以定量描述分辩率优劣的L值。在相同条件下,t_(max)值越小,峰的起始边越陡;RC_S越小,则拖尾程度越轻,因而峰宽变窄,L值减小,相邻两峰的分离就好。所以t_(tmx),RC_S和L是表征DTA仪器的三个重要指标。

The melting processes of pure indium,zinc,lead,polyethylene and dehydration of crystal calcium oxalate(CaC_2O_4·H_2O)and cupric sulphate monohydrate(CuSO_4·H_2O)were carried out with.eight DTA apparatus.According to the equation of the DTA curve and the exponential declination of the curve after the reaction end point,which are proposed by Gray,the t_(max) and the thermal time constant RC_s are determined,thus the least separation temperature L is calculated out. In the same condition,the lower the t_(max),the steeper the starting line of the peak;the smaller the RC_s,the more the tailing.When T_(ma) and RC_s arc small,L is decreased,i c.the peak width becomes narrower and the separation of adjacent peaks is better.Therefore,the T_(max),RC_s and L are three important indications of the performance of a DTA apparatus.