Mechanical and thermal properties of spark plasma sintered Al2O3-graphene-SiC hybrid composites

Monolithic Al2O3 and Al2O3-graphene-SiC hybrid composites were prepared by spark plasma sintering (SPS) under vacuum atmosphere. The results show that the hybrid composites were almost completely dense (>97%). SiC content has a significant effect on the microstructure of the composites. With the increase of SiC content, the average grain size of alumina decreased gradually. The addition of SiC to alumina changed fracture mode from inter-granular fracture to mixed fracture mode of inter-granular fracture and trans-granular fracture. The Al2O3-0.4 wt%graphene-5 wt% SiC hybrid composite has the highest bending strength and hardness, which were 57% and 19.22% higher than those of the monolithic alumina, respectively. The room temperature (RT) thermal conductivity of the monolithic Al2O3 (25.5 W/m center dot K) was the highest. The thermal conductivity and thermal diffusivity coefficient of the composites decreased with the increase in temperature, while the specific heat of monolithic alumina and composites increased with the increase in temperature and additives. These properties were related to the microstructure of materials and the possible transport mechanisms were discussed.

Automated summary

Monolithic Al2O3 and Al2O3-graphene-SiC hybrid composites were prepared by spark plasma sintering (SPS) under vacuum atmosphere. The hybrid composites exhibited high density and the microstructure was significantly influenced by the SiC content. The addition of SiC changed the fracture mode from inter-granular fracture to a mixed mode. The Al2O3-0.4 wt%graphene-5 wt% SiC hybrid composite showed the highest bending strength and hardness, surpassing the monolithic alumina. The thermal properties of the composites were studied and correlated with the microstructure.