In Situ Investigation of Debinding of Non-Oxide Ceramic

Abstract

Binder removal in small and large green compacts of AlN ceramic was investigated by combining different in situ measuring techniques. Dimensional changes, wetting behaviour and weight loss were measured by a thermooptical measuring device (TOM). Thermal diffusivity was measured by the laser-flash technique and evolved gas species were identified by FTIR analysis. The properties of the binder changed with increasing temperature. Wetting properties drastically improved between 150°C and 350°C. The activation energy for the rate determining step of binder decomposition was derived from weight loss data using the kinetic field method. It was 180 kJ/Mol up to a temperature of 350°C, where it strongly increased. The binder enhanced thermal conductivity of the green compacts – especially in the last stage of binder removal - which was explained by its location in the vicinity of the contacts between the AlN particles. With large samples and high heating rate a superposition of weight loss reactions which could be clearly separated in other experiments was observed. This was attributed to the effect of the high partial pressure of evolved gases in the pore system of the green compacts.