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

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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.