Thermal diffusivity of kaolinite–mullite ceramic matrix composite with silicon nitride nanoparticle filler

• Silicon nitride nanopowder was inserted into a mullite matrix composite.
• Increasing sintering temperature up to 1200 °C produces higher thermal diffusivity for pure mullite.
• Silicon nitride nanopowder suppresses thermal diffusivity of the composites at 1200 °C sintering temperature.
• Low thermal diffusivity suggests pore formation but FESEM image indicate glass-like morphology within the composites.
• Silicon nitride nanopowder could cause heat transfer interruption within the composite, thus resulting in low thermal diffusivity values.

Thermal diffusivity of mullite fused ceramics was determined from room temperature up to 500 °C at intervals of 100 °C. The ceramic material was formed by combining kaolinite as the matrix and silicon nitride as the filler powder. The ceramics were sintered at 1000 °C, 1100 °C, and 1200 °C to study the structural differences. Thermal diffusivity data showed that the addition of silicon nitride affects the composites heat flow and this behavior is noticeable at 1100 °C and 1200 °C samples. The thermal diffusivity data was plotted on 1000/T graph to demonstrate a linear relation for filler effects of silicon nitride on the mullite matrix. Additions of 25% and 30% silicon nitride sintered at 1200 °C exhibited thermal diffusivity values lower than pure mullite crystal at 0.55–0.45 mm2/s. These values suggest that heat conduction across the system was interrupted by silicon nitride nanoparticle additions via micropore formations. These samples have potential applications for high temperature thermal insulation.