Critical pressure for weakening of size-induced stiffness in spinel-structure Si3N4 nanocrystals
نویسندگان
چکیده
We demonstrate that the compressibility of spinel Si3N4 nanocrystals increases when the pressure is raised above ;40 GPa. Si3N4 nanocrystals initially exhibit an extremely high bulk modulus of 685~45! GPa. But, above 40 GPa, the bulk modulus is reduced to 415~10! GPa. Thus, a critical pressure of ;40 GPa was determined that signifies the onset of size-induced weakening of elastic stiffness in nanocrystalline Si3N4 . Enhanced surface energy contributions to the shell layers of nanoparticles and the resulting effect on the corresponding large d-spacing planes are used to explain the observed phenomenon. Upon decompression, the bulk modulus of the Si3N4 spinel remained at its lower value of 415 GPa. This study provides a reasonable explanation for the different compressibility properties of numerous nanocrystals. © 2003 American Institute of Physics. @DOI: 10.1063/1.1618365#
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