Development Of Gallium-Based Alloy Fixed Point And Research On Temperature Assignment Method

In order to improve the infrared remote sensing high precision measurement level,developing the secondary fixed point suitable for infrared remote sensing temperature measurement range has become an important method to improve the accuracy of on-orbit temperature calibration.Aiming at the temperature range(190 K-350 K)involved In the field of infrared remote sensin,in this paper,combined with heat transfer and mechanical analysis,designed and optimized the alloy fixed point,and the perfusion of gallium based eutectic fixation points(Ga-In,Ga-Sn,Ga-Zn)and Bi-In-Sn ternary alloy fix points was completed.At the same time,in order to obtain better phase transition temperature plateau,the characteristics of eutectic point transformation were studied,and proposed the premelting method to preprocess the ternary alloy fix points,to improve the reproducibility of fixed point phase transition plateau.The main research work and achievements are shown below:(1)Based on the size of alloy fixed point cell,successfully developed a new gallium-based eutectic fixed point container to solve the problem of thermometer well fracture caused by thermal stress of gallium metal,and accomplished high-precision reproduction of the alloy fixed point.Problem-based the eutectic point segregation in the process of phase transition,the eutectic phase transition plateau curve is more inclined than pure metal plateau,based on the Bi-In-Sn ternary alloy fixed point,analysed the pre-melt,pre-heat temperature,pre-melt temperature,melting temperature and the the premelt extent influence on phase temperature plateau,to provide theoretical basis about fixed temperature plateau optimization.(2)Study on the phase transition temperature evaluation methods,and three methods,namely inflection point method,run-off point method and histogram method,were selected for comparative analysis,providing a reasonable and accurate method for the performance evaluation of fixed points.The reproducibility of the fixed points of Ga-In,Ga-Sn,Ga-Zn and Bi-In-Sn are 0.15 m K,0.15 m K,0.45 m K and 1.25 m K.The results show that the fixed points all have good reproducibility,and the inflection point method is more suitable for the fixed point transformation temperature of the alloy in this experiment.Use the highest level temperature measurement system to assignment the fixed point,and the uncertainty evaluation of fixed points was completed according to the uncertainty evaluation method defined by CCT.(3)Use comsol simulation software to verify the feasibility of the new galliumbased eutectic fixed-point cell,research the change of thermal stress caused by gallium metal due to its heat shrinkage and cold expansion characteristics on the quartz thermometer well in the cooling process,compare the heat leakage of the two containers,and verify it through experiments.The method of increasing immersion depth is proposed to reduce heat leakage effect,which provides a technical basis for the improved design of fixed point vessel.