ATOMISTIC UNDERSTANDING OF THE PARTICLE CLUSTERING AND PARTICLE SIZE EFFECT ON THE ROOM TEMPERATURE STRENGTH OF SIC-SI3N4 NANOCOMPOSITES

作者：Tomar Vikas^*; Samvedi Vikas; Kim Han Sung

来源：International Journal for Multiscale Computational Engineering, 2010, 8(5): 463-472.

• nanocomposites
• molecular dynamics
• mechanical strength

Experimentally obtained silicon carbide (SiC)-silicon nitride (Si3N4) nanocomposites have SiC particles with circular cross section placed in a Si3N4 matrix, either along grain boundaries (GBs) or in intergranular positions. It has been observed that by a controlled manipulation of the SiC particle clustering and sizes, mechanical strength of such nanocomposites could be tailored. In the present investigation, 3D molecular dynamics (MD) analyses of SiC-Si3N4 nanocomposite deformation are performed in order to understand the related underlying mechanisms. Analyses reveal that the second-phase particles act as significant stress raisers in the case of a single-crystalline Si3N4 phase matrix reducing the mechanical strength by a factor of 1.8 with higher particle size causing larger reduction in peak strength. However, the particle's presence does not have any effect on the mechanical strength of a bicrystalline Si3N4 phase matrix. The deformation mechanism consists of considerable ductile shearing at the SiC-Si3N4 interfaces in all microstructures. The presence of an initial crack has very little effect on the overall mechanical strength, indicating the presence of flaw tolerance at the length scale of the analyses. An examination of the effect of particle clustering together in a Si3N4 phase matrix showed that particle clusters with larger particle size result in higher reduction in mechanical strength. Overall, MD analyses confirm that the strengthening of the nanocomposite owing to SiC second-phase particles is a strong function of particle size, particle placement along GBs, and particle clustering.

• 出版日期2010