Single Mo center supported on N-doped black phosphorus is predicted to be a compelling highly efficient and durable catalyst for electrochemical N2 fixation by density functional theory calculations.
Using density functional theory calculations, we compute the edge energies and stresses for edges of SiC and BN nanoribbons, and the boundary energies and stresses for domain boundaries of graphene-BN superlattices. SiC and BN armchair nanoribbons show pronounced edge relaxations, which obliterate the threefold oscillatory behavior of the edge stress reported for graphene. Our calculations show small boundary stresses in graphene-BN superlattices, suggesting that such domain boundaries will not experience severe deformation. We have also found that the C-terminated and Si-terminated zigzag edges in SiC nanoribbons have different compressive stresses which results in different rippling behavior of these edges.
Fatigue crack growth rates have been experimentally determined for the superalloy GH2036 (in Chinese series) at an elevated temperature of 550 °C under pure low cycle fatigue (LCF) and combined high and low cycle fatigue (CCF) loading conditions by establishing a CCF test rig and using cornernotched specimens. These studies reveal decelerated crack growth rates under CCF loading compared to pure LCF loading , and crack propagation accelerates as the dwell time prolongs. Then the mechanism of fatigue crack growth at different loadings has been discussed by using scanning electron microscope (SEM) analyses of the fracture surface.
Combining atomistic simulations and continuum modeling, we studied dislocation shielding of a nanocrack in monolayer graphene under mode-I loading. Different crack-dislocation configurations were constructed and the shielding effects on the threshold stress intensity for crack propagation were examined. Excellent agreement between simulation results and linear-elastic fracture mechanics (LEFM) predictions was achieved. As the separation between the crack-tip and dislocation, that is, rR, varies (with respect to the crack size a), the shielding effect exhibits two different dependences on rR, scaling as 1/rR 1/2 for rR/a ≪ 1 (near-tip), whereas 1/rR for rR/a ≫ 1 (far-field), respectively. Particularly, the far-field 1/rR scaling was shown to be a direct manifestation of the stress field of dislocation in graphene. Our work presents a systematic study of nanoscale crackdislocation interactions in graphene, providing valuable information on defect engineering of graphene.
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