用差热分析测定玻璃析晶过程的核化速率曲线

THE DETERMINATION OF NUCLEATION RATE CURVE IN THE CRYSTALLIZATION PROCESS OF GLASSES FROM DTA TECHNIQUE

本方法通过对玻璃试样 DTA 数据的处理,改进了玻璃晶化过程中成核速率随温度变化曲线的测定方法。此法比用光学显微镜,对试样中可见晶粒进行计数的传统方法,更快速而简便。本实验确认,Li_2O·2SiO_2玻璃的成核速率曲线(I-T)和晶体生长速度曲线(U-T)不重叠。该系统的 DTA 曲线中,晶体放热峰的高度δT可看成是试样中晶核数量的大小。实验还证明,在确定成核温度范围和成核速率达最大值的最佳温度方面,峰高δT随温度变化的曲线可以代替成核速率 I 随温度变化的曲线。由固体相变理论推出的结论,证明了本实验方法的可行性。

A method for determining the nucleation rate curve varying with the temperature in the crystallization process of glasses was developed by treating the data of glass samples from Differential Thermal Analysis(DTA),which is more rapid and easier than the classi- cal method by counting the visible crystal particles in the glass samples under optical micro- scope.It was confirmed in this experiment that for the Li_2O·2SiO_2 glass system,whose nucleation rate curve(I-T)and crystal growth rate curve(U-T)are separate,the peak height(δT)of crystal exothermic peak in the DTA curve can be considered the magnitude of the number of nuclei in the glass samples.It was also confirmed that the curve of δT va- rying with the temperature can substitute for the curve of nucleation rate(I)varying with the temperature,in terms of determining the nucleation temperature range and the optimal temperature,where the nucleation rate reaches the largest.The feasibility of the experimental method was verified by the deduction of the theory of the phase transforma- tion in solids.