Fluoride doped SiC/Si3N4 composite as a high thermal conductive material with enhanced mechanical properties

Silicon nitride (Si3N4) based composites have been extensively studied and widely used in industrial applications. Herein, SiC/Si3N4 composites were prepared through hot press sintering at 1700 degrees C under nitrogen (N-2) atmosphere. Fluoride additives (AIF(3) and MgF2) were used to reduce lattice oxygen content, which can affect the bulk density and a source to increase the porosity of the composite. Experimental results revealed that the chemical compatibility between silicon carbide (SiC) and Si3N4 matrix under high temperature sintering could be effectively improved by integrating SiC/Si3N4 ceramics interphase. The X-ray diffraction (XRD) and scanning electron microscopy (SEM) results indicate that a complete transformation of a to beta-Si3N4 and intergranular behavior of material occurred, which revealed that the phase transformation was unaffected by the addition of SiC. Furthermore, the enhanced crystallization degree and a strong interfacial effect of the SiC/Si3N4 composites enabled to obtain a significant increase in thermal conductivity (90.67-145.66 W/mK), fracture toughness (8.52-10.3 MPa m(0.5)) and Vickers hardness (1849-2125 HV).