温差电偶高温端接头W-BNi5-W-MoSi2-Si80Ge20的制备

Preparation of Thermocouple High Temperature End W-BNi5-W-MoSi-SiGe

温差电偶的制备是温差电技术理论转化为应用的核心环节。设计并制备出了硅锗合金温差电偶高温端电极接头。首先采用一步热压法制备出W-MoSi2-Si80Ge20,然后采用BNi5焊料焊接W-W,制备出W-BNi5-W-MoSi2-Si80Ge20高温端多层电极接头。对电极接头进行900℃下100h的高温加速实验。测试了电极接头在高温加速实验前后的接触电阻和剪切强度。采用SEM及EDS分析了电极接头在高温加速实验前后的界面形貌及元素分布。结果表明,制备的多层电极接头具有较佳的连接效果,连接后的接头接触电阻0.29mΩ·cm2,剪切强度15.6MPa,高温加速实验后接头性能恶化。SEM及EDS分析表明W-BNi5-W界面由于焊料和W热膨胀系数的差异,导致界面间产生缝隙,是接头性能恶化的主要原因,MoSi2能够有效阻挡W和Si80Ge20间的元素扩散,有利于维持硅锗合金热电性能。

The preparation of thermocouple is the core link of thermoelectric technology theory into application.The high-temperature end electrode connector of thermocouple of silicon-germanium alloy is designed and prepared.First,W-MoSi2-Si80Ge20 was prepared by one-step hot pressing method,and then W-W was soldered with BNi5 solder to prepare W-BNi5-W-MoSi2-Si80Ge20 high-temperature end multilayer electrode connector.The electrode joint was subjected to a high-temperature accelerated experiment at 900℃for 100 h.The contact resistance and shear strength of the electrode joint before and after the high temperature acceleration experiment were tested.SEM and EDS were used to analyze the interface morphology and element distribution of the electrode joints before and after the high temperature acceleration experiment.The results show that the prepared multi-layer electrode joint has better connection effect.The contact resistance of the joint after connection is 0.29 mΩ·cm2,the shear strength is 15.6 MPa,and the joint performance deteriorates after the high temperature acceleration test.SEM and EDS analysis show that the difference between the thermal expansion coefficients of solder and W at the W-BNi5-W interface leads to a gap between the interfaces,which is the main reason for the deterioration of the joint performance.MoSi2 can effectively block the diffusion of elements between W and Si80Ge20,which is conducive to maintaining the thermoelectric performance of silicon-germanium alloy.