A HIGH-TEMPERATURE SYSTEM BASED ON THE LASER FLASH METHOD TO MEASURE THE THERMAL-DIFFUSIVITY OF MELTS

A high-temperature measuring system has been developed to undertake me asurements of thermal diffusivity and specific hear up to 1900 K. The overall design allows measurements on solids to be undertaken using th e accepted standard techniques and analytical procedures. The specific design for molten materials and especially slags is based on the diff erential threelayer technique utilizing a special cell which can be ac comodated in the system. In this method, the liquid specimen is sandwi ched between an upper inner platinum crucible and a lower outer platin um crucible, to provide a three-layered sandwich. A laser pulse irradi ates the surface of the upper platinum crucible and the temperature re sponse of the surface of the lower platinum crucible is observed. For the purpose of accurate measurement of specimen thickness at the measu ring temperature, two runs are performed in which the thicknesses are l and l+Delta l, where I is unknown but Delta l can be set accurately with a built-in micrometer. The thermal diffusivity is obtained throug h a curve-fitting method by a personal computer using a three-layer an alysis with a correction for the radiative component based on the tran sparent body assumption. Following verification of the basic performan ce, using solids of known properties and water and ethanol, a continuo us casting mixture has been evaluated. The initial results on the flui ds are in good agreement with those in the literature.