Preparation and sintering of nano Fe coated Si3N4 composite powders.

Fe/Si₃N₄ composite powder was synthesized by the heterogeneous precipitation-thermal reduction process, and then pressed into flakes under a pressure of 10 MPa. Flakes were sintered by pressureless and hot-pressing at 1 600 °C under 0.1 MPa N₂. The chemical composition, phases and microstructure of composite powder and sintered flakes were investigated by energy dispersive spectroscopy (EDS), X-ray diffraction (XRD), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The results show that the structure of composite powders is Si₃N₄ coated by nano Fe. The crystal phases of sintered flakes by pressureless are Fe(Si) compound, SiC and Si₃N₄. The crystal phases of the sintered samples by hot-pressing are Fe, Fe(Si) compound and Si₃N₄. It is found that crystal phases flakes obtained by pressureless and hot-pressing are very different. [ABSTRACT FROM AUTHOR]