高温超強度Si3N4-SiCナノ複合材料

概要

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Effects of nano-size dispersions on mechanical properties such as hardness, fracture toughness and strength were investigated for the Si3N4-SiC nanocomposite system. The Si3N, -SiC nanocomposites were fabricated by hot-pressing the mixtures of amorphous Si-C-N precursor powder with various C/N ratio and sintering additives. Transmisson electron microscopic observation indicated that the Sic particles less than approximately 0.1μm in diameter were dispersed whithin the Si3N4, matrix grains. No apparent impurity phases was observed at the intertfaces of Si3N4 and Sic. The grain morphology of Si3N4 was strongly influenced by the Sic dispersion, indicating that the formation of elongated and equiaxed Si3N4 grains was acceralated at the lower and higher SiC volume fractions, respectively. As expected from this change of grain morphology, the fracture toughness and strength were showed the maxmima, 155OMPa and 6.5MPam1/2, at the certain volume fraction of SiC. The high-temperature strength was also improved by the Sic dispersion and the high strength of over 1GPa was observed even at 1400°C.
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