Formation of self-reinforced microstructure by the control of starting phase in liquid-phase sintered silicon carbide ceramics

摘要

Silicon carbide (SiC) has been studied as a potentially important structural ceramic due to its excellent resistance to oxidation and corrosion, high-temperature strength, thermal shock resistance, high wear resistance and good thermal conductivity. Therefore, it is being developed for possible uses in heat engines, heat exchangers, mechanical seals and other components. However, a disadvantage has been its low fracture toughness (3-4 MParn1/2) [1]. Recently, many scientists have reported that sintered silicon nitride containing rod-like grains, the so-called self-reinforced or in .yto-reinforced silicon nitride, has high fracture toughness due to mechanisms such as crack deflection, microcracking, and grain pull-out and bridging actions [2-5]. In silicon carbide ceramics, a number of attempts have recently been made to improve its low fracture toughness by control of the microstructure during sintering or annealing, for example toughening by heterophase dispersion or by nanocomposite formation [6-9]. One way of obtaining the microstructure of heterophase dispersion in silicon carbide ceramics is by using liquid-phase sintering and the phase transformation of β-+ a during sintering or heat treatment after sintering [9-11].