Preparation of mullite-TiB₂-CNTs hybrid composite through spark plasma sintering

A near fully dense mullite-TiB₂-CNTs hybrid composite was prepared successfully trough spark plasma sintering. 1 wt%CNT and 10 wt%TiB₂ were mixed with nano-sized mullite powders using a high energy mixer mill. Spark plasma sintering was carried out at 1350 °C under the primary and final pressure of 10 MPa and 30 MPa, respectively. XRD results showed mullite and TiB₂ as dominant crystalline phases accompanied by tiny peaks of alumina. The microstructure of prepared composites demonstrated uniform distribution of TiB₂ reinforcements in mullite matrix without any pores and porosities as a result of near fully densified spark plasma sintered composite. The fracture surface of composite revealed a proper bonding of TiB₂ with mullite matrix and also areas with CNTs tunneling and superficies as a result of pulling-out phenomenon. The flexural strength of 531 ± 28 MPa, Vickers harness of 18.31 ± 0.3 GPa, and fracture toughness of 5.46 ± 0.12 MPa m^−1/2 were achieved for prepared composites as the measured mechanical properties.