Preparation of mullite/B4C composites: A comparative study on the effect of heating methods

Abstract The present study investigated preparation of the mullite/B 4 C composites through microwave and spark plasma sintering processes. A high-energy ball mill was used to mix the nono-sized mullite and B 4 C powders in ethanol media for 10 min. The mixed nano-sized powders were pelletized and sintered by microwave (MW) and spark plasma sintering (SPS) processes at 1500 and 1300 °C, respectively. The XRD results revealed the reactions between mullite and B 4 C, and also the formation of SiC, Al 2 O 3 , Si phases in SPS sintered sample. The identified crystalline phases in the microwave sintered sample were mullite and B 4 C. Samples sintered in SPS reached almost full density and showed improved mechanical properties (the hardness of 16.29 ± 0.2 GPa, bending strength of 348 ± 21 MPa and fracture toughness of 3.01 ± 0.18 MPa m −1/2 ) than those sintered in microwave. The microstructural investigations showed the formation of needle-like mullite at some areas of sample sintered in SPS with a uniform distribution of B 4 C in mullite matrix alongside pore-free microstructure. The microstructure of microwave sintered sample contained a large number of pores.