Development of the Remote Temperature Response Acquisition System and Its Data Processing for the Thermal Diffusivity Measurement at High Temperature

近年来，激光闪光法被用于测量各种无机物质在1000 K以上高温下的热扩散率和电导率。虽然所谓的双层技术在其数据处理中包括辐射传热，但传统热电偶获得的温度响应包含由闪烁的激光束和加热元件中诱导的振荡电场引起的样品挥发物质的电或电化学噪声。因此，本文开发了改进的红外锗探测器遥感数据采集系统，以获得无噪声的温度响应。该系统的数据处理也得到了发展，并通过对碳酸钠和硅酸钠的测量证实了它的实用性。特别是，该系统被发现是有效的样品含有挥发性成分。在1000 ~ 1673 K的温度范围内，用激光闪光法系统地测量了铁氧体钙的热扩散系数。采用对数法分析了后表面温升的初始短时间区域，减小了辐射热流和径向热流对热扩散系数的偏差。随着CaO含量的增加，铁氧体钙熔液的热扩散系数增大。这种行为与x射线衍射和粘度测量的结构数据表明的某种局部有序的形成是一致的。

The laser flash method have been recently employed for the measure-ment of thermal diffusivity and conductivity of various inorganic substances at high temperature above 1000 K. Although the so-called two-layered technique including radiative heat transfer in its data processing is well established, the temperature responses obtained by conventional thermocouples contain the electrical or electrochemical noises from volatized species of the sample by a flashed laser beam and oscillatory electric field induced in the heating element. Thus, the improved data acuisition system by remote sensing using a germanium infrared detector has been developed in this work to obtain the noise free temperature responses. The data processing of this new system has also been developed and its usefulness was confirmed by the measurements for sodium carbonates and sodium silicates. Particluarly, this system is found to be effective for the sample containing volatile components.Thermal diffusivities of calcium ferrites has been systematically measured by the laser flash method presently developed over the temperature range between 1000 and 1673 K. The logarithmic method analyzed the initial short time region of temerature rise of the back surface was used for reducing the deviation of thermal diffusivity by both radiation and radial heat flows. The thermal diffusivity of molten calcium ferrites was found to increase as the CaO content increases. This behaviour is consistent with the formation of a certain local ordering suggested from the structural data by x-ray diffracation and the viscosity measurements.