三段控温固定点炉复现铝凝固点研究

Study on the Realization of Aluminum Freezing Point in the Three-zone Temperature Controlled Fixed Point Furnace

固定点炉垂直温场均匀性是影响ITS-90国际温标固定点温坪质量的重要因素。为了提高铝凝固温坪的复现水平,设计了三段控温固定点炉,利用金属外壳铝固定点容器,研究了垂直温场均匀性及其影响因素;在此基础上,采用连续热流密度法高精度复现了铝凝固点。实验结果表明:通过调整上部、中部、下部炉温的设置,可改善固定点炉温场均匀性,铝凝固温坪4 h内的温度变化在1 m K以内;此外,在实验条件下,高纯铝相变的过冷度约为0.14℃。

The vertical temperature uniformity of the fixed-point furnace is an important factor affecting the plateau quality of the fixed-points of the International Temperature Scale of 1990( ITS-90). In order to improve the reproducibility of the aluminum freezing point,a three-zone temperature-controlled fixed-point furnace was designed,and the aluminum fixed point cell with a metal shell was used to study the vertical temperature uniformity and its influencing factors. On this basis,the continuous heat flux method was adopted to precisely realize the aluminum freezing point. The experimental results show that the temperature uniformity can be improved by adjusting the settings of the top,middle,and bottom furnace temperatures,and the temperature stability of the freezing plateau within 4 hours is less than 1 mK. The phase transition supercooling of the high purity aluminum is approximately 0. 14 ℃ under the experimental conditions.