Abstract

Sintering ceramics involves neck formation, densification and eventually grain growth. A simplified model is developed to describe the effects of pore fraction, average grain size and the contact area between particles due to neck formation on the thermal conductivity of the green or partially sintered ceramic. Laser flash measurements on green bodies of alumina powders with different average particle sizes reveal similar thermal conductivity values close to 0.5 Wm−1K−1, corresponding to thermal resistances for equivalent planes of contacts in the range 10-7 to 2 10-6 m2KW−1. BET specific surface area measurements were then used to estimate the contact area due to neck formation in partially sintered alumina ceramics fired from 400 °C to 1200 °C. As predicted by the model, there is a strong increase in thermal conductivity. Such information is relevant as input data for numerical modelling of the green body behaviour during thermal treatment.

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