The Research On Measurement Of Linear Expansion Coefficient For Materials With Laser Interferometric Dilatomete

With the development and of the science, science and technology in competition is behaved as comprehensive science abilities. The research on the expansion coefficient for material is the basic of the science research and the foundation of the Innovation, so it is more and more emphasized in our country. Under the National Fifteen Great Research Project----"The Research on creating Our Country's measurement technology of the heat physical property Standards System", this paper is completed in the NIM (National Institute of Metrology). This paper is mainly improved and perfected the dilatometer by the experiment , and do some research of theory and experiment studies on experimental equipment,experimental methods and the theory of the expansion coefficient.on the basis of the laser interferometric dilatometer for measuring linear expansion coefficient which is designed by NIM, improved and perfected the dilatometer and achieved measuring the linear expansion coefficient for material over the temperature ranging from 240K to 1200K by this dilatometer.The performance of the new device has been examined by testing the reference materials SRM731,SRM738 and silicon in different temperature. In order to analyze the reliability of the result, we analyzed the influence factors of the result. And the standard uncertainty at room temperature is 3.4×10^-2(K=2).In the experiment we heat the sample to the target temperature in a quick speed, the results showed that for SRM 738 and SRM 731, the length change of the sample is behind the temperature change; for silicon, the length change of the sample keeps up with the temperature change. The SRM 738 and SRM 731 sample are suits of the dynamic proceess of thermal expansion.By heat the silicon sample in a very slow speed to make the length change of the sample keep up with the temperature change, and measures the linear expansion coefficient of silicon. The measurement result agrees with the values measured by normal heating methods of the relative deviation less than 1%, the thermal expansion of silicon is suit of the typical theory of the thermal expansion.By the research of this works, we have developed a high accuracy laser interferometric dilatometer to measure linear expansion coefficient. And the dilatometer has high precise, can measure wide temperature range.