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.
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