Enhanced Creep Resistant Silicon-Nitride-Based Nanocomposite
Silicon nitride–silicon carbide nanocomposite has been prepared by an in situ method that utilizes C+SiO2 carbo-thermal reduction during the sintering process. The developed material is nearly defect free and consists of a silicon nitride matrix with an average grain size of approximately 200 nm with inter- and intra-granular SiC particles with sizes of approximately 150 and 40 nm, respectively. The creep behavior was investigated in bending at temperatures from 1200° to 1450°C, under stresses ranking from 50 to 150 MPa in air. The stress exponents are in the interval from 0.8 to 1.28 and the apparent activation energy is 480 kJ/mol. A significantly enhanced creep resistance was achieved by the incorporation of SiC nanoparticles into the matrix. This is because of a change of the microstructure and grain boundary chemistry leading to a change of creep mechanism and creep rate.
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