Catalytic nitridation preparation of high-performance Si3N4(w)-SiC composite using Fe2O3 nano-particle catalyst: Experimental and DFT studies

The complete conversion from Si into Si3N4 was achieved after 2 h nitridation at 1400 °C by using in-situ formed Fe2O3 nano-particles (NPs) as a catalyst. Such a synthesis condition was remarkably milder than that (>1450 °C for many hours) required by the conventional Si nitridation method. Density functional theory (DFT) calculations suggest that Fe2O3 catalyst accelerates the Si nitridation via weakening the bond strength of absorbed N2 molecule. Furthermore, Si3N4(w)-SiC composites prepared by the present catalytic nitridation method showed excellent high-temperature properties including modulus of rupture (MOR of 29.9 MPa at 1400 °C), thermal shock resistance (residual MOR percentage of 50% at ΔT = 1300 °C), as well as good oxidation resistance and cryolite corrosion resistance against molten cryolite. It can be concluded that, Fe2O3 NPs not only greatly accelerated the Si nitridation and Si3N4 formation, but also facilitated the epitaxial growth of reinforcement phase of Si3N4 whisker in the Si3N4(w)-SiC composites.