R-curve behaviour and microstructure of sintered silicon nitride
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R-curves for two in situ reinforced silicon nitrides A and B, of different microstructures, were characterized using indentation-crack growth measurements. Silicon nitride B, with its coarser microstructure and 8 MPa m1/2 toughness, showed higher resistance to crack growth and more damage tolerance than silicon nitride A, with its finer microstructure and 7 MPa m1/2 toughness. However, silicon nitride A showed a higher Weibull modulus than that of silicon nitride B due to the relatively narrow critical grain-size distribution. These results suggest that a coarse microstructure with narrow flaw-size distribution is beneficial to toughening, damage tolerance, and reliability.
KeywordsPolymer Silicon Microstructure Nitride High Resistance
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