基于Scheil方程的微量杂质对锌凝固点相变温度影响的评估方法  

Estimation Method of the Effect on the Transition Temperature of the Trace Impurities in Freezing Point of Zinc Based on the Scheil Equation

作　　者：孙建平[1] 邓小龙[2] 张金涛[1] 

机构地区：[1]中国计量科学研究院,北京100029 [2]北京科技大学,北京100083

出　　处：《计量学报》2015年第2期136-140,共5页Acta Metrologica Sinica

摘　　要：微量杂质是影响ITS-90国际温标定义固定点复现的最主要的不确定度来源。从凝固理论出发，建立基于Scheil方程的评估微量杂质对凝固点相变温度影响的数学模型，以国家温度基准中的锌凝固点为对象，利用最小二乘拟合法拟合实验数据评估了杂质对其相变温度的影响，并通过化学分析对该方法的有效性进行了验证，结果表明，全部杂质综合结果使相变温度增加0．56 mK，化学分析结果中Ag及Cu在锌中存在一定量级证明该方法的有效性，该方法相对于SIE与OME方法具有较好的应用前景。Trace impurities in the defining fixed-point metals are usually the most significant source of uncertainty inthe realization of ITS-90. A mathematical model is built based on the Scheil equation from the solidification theory toestimate the trace impurities effect on the phase transition temperature of freezing point. The national primary standards oftemperature of the fixed point of zinc is studied, the least squares method is used to fit experimental data to estimate theimpurities effect on the phase transition temperature. The validity of this method would be proved by chemical analysis. Theresults show that the phase transition temperature of the zinc freezing point is 0. 56 mK higher than the phase transitiontemperature of the ideal pure zinc since the impurities present, and the higher concentrations of the Ag and Cu in the zincprove the validity of this method. The foreground of application of this method is better than SIE and OME methods.

关 键 词：计量学 国际90温标 Scheil方程 锌凝固点 微量杂质 相变温度 

分 类 号：TB942[一般工业技术—计量学]