PREPARATION, MICROSTRUCTURE AND PROPERTIES OF MGSIN2 CERAMICS

The synthesis of MgSiN2 powder, starting from the metal nitrides, is described. The powder is resistant against oxidation in air up to 800-degrees-C. From the prepared powder full dense MgSiN2 ceramics can be sintered at 1550-degrees-C. The samples were sintered in a closed Mo vessel to prevent evaporation of magnesium nitride. Phase composition, chemical properties and the mechanical properties of the as-prepared ceramics are described. The ceramics are oxidation resistant in air at least up to 920-degrees-C. The thermal conductivity at room temperature is estimated at 17 W/m K. A reasonable strength of 270 MPa and a rather good fracture toughness of about 4.3 M Pa m1/2 are obtained. A hardness of about 15 GPa and a Young's modulus of 235 GPa have been measured. Considerable improvement in properties is expected when the processing conditions, well within reach, are optimised.