Current views on thermal conductivity and diffusivity measurements of oxide melts at high temperature
Abstract There have been various attempts to measure thermal conductivity of relatively low conductive materials such as oxides and nitrides, at high temperature. However, their accuracy was not sufficient to allow quantitative discussion mainly because of experimental difficulties, particularly at sample temperature above 1000 K, for several reasons. For example, the radiative heat flow is known to play a significant role at higher temperature, but the separation of such a component from the measured heat flows has only been established recently. An attempt will be made in this paper to review current information on thermal conductivity measurement of oxide melts at high temperature above 1000 K. Thus, this review is primarily concerned with the several methods for determining thermal conductivity of high temperature melts including their respective merits and demerits. A new laser-flash method proposed in the early 1960's has received much attention for determining thermal conductivity of high temperature melts and is an even better technique than the conventional techniques such as the hot-wire method. Although some advantages of the laser-flash method are readily apparent, major progress has been obtained only in the last few years and new information is now available. Therefore, it will be the authors' intention to provide the principle and the new data processing for the laser-flash method, including some selected examples of its application to determining thermal conductivity of oxide melts at high temperature. The relevant significant quantities such as the radiative heat transfer coefficient are also discussed, in order to facilitate the understanding of the present status of fundamentals and the powerful link between physical constants such as the reflective index of sample material and the required formulae for determining thermal conductivity of high temperature melts by the laser-flash method.