Self-reinforced Si 3N 4 ceramics fabricated using Si 3N 4 produced by self-propagating high temperature synthesis

Abstract

Silicon nitride has played a prominent role among the structural ceramics, and it is one of the few ceramic materials currently used in structural applications such as cutting tools, turbochargers for car engines, and various components for gas turbines. These developments have been possible due to its oxidation resistance, high strength and low thermal expansion coefficient, which in combination with its moderately high thermal conductivity affords an excellent behavior under thermal shock. For further applications of this material in structural components, however, two main limitations, fracture resistance and cost, must be overcome. In the present work the authors present a new route to obtain high toughness silicon nitride with a bimodal microstructure using silicon nitride powder obtained by self-propagating high-temperature synthesis (SHS). The cost of this powder is between one fourth to one fifth that of the standard silicon nitride powder used, and in addition, the powder contains the seeding {beta}-Si{sub 3}N{sub 4} single crystal particles which lead to the development of a bimodal microstructure during sintering.