Reinforcement of mullite matrix with multi-walled carbon nanotubes

Dense multi-walled carbon nanotubes (MWNTs)-mullite ceramic matrix composites were firstly prepared by hot pressure sintering with MWNTs, Al2O3 and SiO2 powders as starting materials. It was found that when the sample was sintered at 1600 °C, the addition of 5 volume percent MWNTs led to 10% increase in bending strength and 78% increase in fracture toughness, respectively, compared with the monolithic mullite. The reinforcement mechanism was discussed based on the microstructure investigation. The broken nanotubes and pullout of MWNTs at interfaces are efficient in transferring the load from the mullite matrix to the nanotubes, leading to the improvement of the mechanical properties.