Study on the Improvement of Accuracy for the Measurement of Thermophysical Properties at High Temperature by a Singgle Rectangular Pulse Heating Method

工业的各个领域都需要新材料的热物性信息。其中一位作者提出了一种方便的矩形脉冲加热测量导热系数和比热的方法。在该方法中，考虑了置于真空高温下的有限圆盘试件的所有表面的热辐射损失。当样品各表面的发射率相同时，散热损失随环境温度的升高而增大，随样品的热扩散率和比热的增大而减小。因此，如果在高温下对陶瓷等低热电性能材料进行测量，辐射损耗会很大。因此，发射率的不确定性引起的误差似乎是不可避免的。本研究的目的是研究样品上涂层在1600K以下的发射率与温度的关系，以提高发射率的测量精度。发射率测量技术是通过比较样品和保持相同温度的黑体炉的辐射度来实现的。对四种耐热涂层进行了测试。结果表明，在800-1600K温度范围内，碳化硅喷涂层没有出现涂层与试件的分离现象，涂层的温度依赖性很小。在此基础上，利用矩形脉冲加热装置测量了喷镀碳化硅的镍砖和镁砖的热扩散率和比热。人们认识到，目前的测量方法存在一些差异，认识到现在的测量方法与以前的使用碳黑涂层的方法有一些不同，并提高了准确度。

The information on thermophysical properties of new materials are required in vatious fields of industry. One of the authers presented a convenient measuring method of thermal conductivity and specific heat by a single rectanguar pulse heating. In this method, the thermal rdiation losses from all the surfaces of a finite disk specimen which is set in a vacuum high temperature furmace are taken into account. If the eemissivities are same on the all surfaces of the specimen, the rafiation heat loss increases with ambient temperature increase and decreases with thermal diffusivity and specific heat of the specimen increase. Therefore, if the measurement on a material having low thermal vonfuctivity as ceramics was carried out at high temerature tange, the rdiation loss will be large. So, the errors caused by uncertainty of the emissivity seem to be unavoidable. The obhjective of this study is to investigate the temperature dependence of the emissivity of the coatings on the specimen at high temperature up to 1600 k, and to improve the accuracy of the measurement.The technique of the emissivity measurement is based on comparing radiance from the specimen and a blackbody furnace keeping the same temperature. Four kinds of heat resisting coats were examined. It was found that no separation of coating from the specimen appeared and the temperature dependence was rather fiat in the 800-1600 k for SiC spray coating. Then, the thermal diffusivity and specific heat were measured on nickel and magnesia brick with SiC spray coating by the single rectangular pulse heating rechnigue. It was recognised that there were some differences between the present measuremeent recognized that there were some differences between the present measuremeent and the former one using carbon black coating, and improvement of the accuracy.