Development of two types of high temperature calorimeters

For heat capacity measurement of ceramic materials at high temperatures above 1500 K, two new calorimeters, i.e. a high speed cooling calorimeter and an advanced-direct heating pulse calorimeter, have been developed in our laboratory. The high speed cooling calorimeter is assembled of an induction heating furnace, a paraboloidal mirror and a high speed six-wavelength pyrometer. In this calorimeter, the heat capacity is determined from the cooling rate of a sample dropped from the induction heating furnace. As a simulation of a dropped specimen, two different experiments on transient modes were made using a calibrated tungsten lamp in the temperature range 2060–2180 K: (1) by changing temperature with time (cooling curve measurement), and (2) by changing the position of a tungsten lamp vertically at constant temperature. Both results show reliability of this calorimeter at high temperatures. The advanced direct heating pulse calorimeter is a re-designed and re-constructed apparatus of the direct heating pulse calorimeter previously developed in our laboratory to increase the measuring temperature for the heat capacity up to 2000 K. By the improvement of a new vacuum vessel, molybdenum thermal insulator and tantalum heating wire, heat capacity and electrical conductivity of graphite could be measured up to 1750 K.