The Experts below are selected from a list of 303 Experts worldwide ranked by ideXlab platform
Z.f. Yue - One of the best experts on this subject based on the ideXlab platform.
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Atomic simulation of void location effect on the void growth in nickel-based single crystal
Computational Materials Science, 2019Co-Authors: Junbiao Wang, Junhao Liang, Z.x. Wen, Z.f. YueAbstract:Abstract Void growth in metallic materials are strongly affected by local microstructure. The location of defect produces a great influence on the mechanical properties of material, especially if defect occurs at the interface. Considering the complex microstructure of nickel-based single crystal, the Ni, Ni3Al and Ni/Ni3Al interface model were established to analyze the expansion dynamics of void using molecular dynamics (MD) method. The expansion behavior of void shows that a/6〈1 1 2〉 Shockley Partial dislocations initially nucleates on the free surface of void during the stretching of Ni and Ni3Al model. Whereas, dislocations nucleate from the interface of Ni/Ni3Al interface model. Evolution of void suggested that the plasticity deformation is dominated by movable Shockley Partial dislocations and immovable Stair-rod dislocations. Void size effect analysis revealed that the larger void radius is, the smaller yield stress and Young’s modulus are. The mechanical properties of Ni/Ni3Al interface model were controlled by the interaction between void and interface.
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Atomistic simulation analysis of the effects of void interaction on void growth and coalescence in a metallic system
Current Applied Physics, 2018Co-Authors: Z.x. Wen, Junbiao Wang, Wu Yunwu, K.j. Zhou, Z.f. YueAbstract:Abstract Material deformation caused by the interaction between defects is a significant factor of material fracture failure. The present study employs molecular dynamics simulations of single-void and double-void crystalline Ni atomic systems to investigate inter-void interactions. Furthermore, simulations showing the evolution of dislocations for three different crystallographic orientations are conducted to study the void growth and coalescence. The simulations also consider the effect of the radius of the secondary void on dislocation evolution. The results show that double-void systems are more prone to yield than single-void systems. Further microstructural analysis indicates that the interaction between voids is realized by dislocation reactions. The simulation results of the dislocation evolution of the three orientations reveal that a relationship exists between the evolution of the dislocation density and the stress-strain curve. At the initial stage of dislocation, the dislocation grows slowly, and consists of Shockley Partial dislocation. The dislocation growth rate then increases significantly in the sharply declining stage of the stress-strain curve, where most of dislocations are Shockley Partial dislocation. Analysis of the dislocation length during the overall simulation indicates that the dislocation length of the [110] orientation is the longest, followed by that of the [111] orientation and the [100] orientation, which has the shortest dislocation length.
I. Belabbas - One of the best experts on this subject based on the ideXlab platform.
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Recombination of Shockley Partial dislocations by electron beam irradiation in wurtzite GaN
Journal of Applied Physics, 2019Co-Authors: I. Belabbas, I. G. Vasileiadis, J. Moneta, Julita Smalc-koziorowska, G. P. DimitrakopulosAbstract:Dissociated a-type screw dislocations in gallium nitride, comprising pairs of 30° Shockley Partial dislocations separated by I2 basal stacking faults, were observed by aberration-corrected high resolution transmission electron microscopy (HRTEM). HRTEM image simulations, in conjunction with density functional theory calculations, led to the identification of the core structures of the Shockley Partials. Both Partials were found to belong to the glide set rather than the shuffle one, while the core with gallium polarity is reconstructed, but the one with nitrogen polarity is not. During in situ irradiation by the electron beam, the I2 stacking fault ribbon was found to shrink, ultimately leading to a remerging of the two Partials. This reversal of the dissociation reaction was attributed to recombination enhanced dislocation glide, whereby the Shockley Partial with nitrogen polarity was identified to be the mobile one. A possible model explaining this mobility is proposed comprising a local modification of the dislocation's electronic structure due to the presence of nitrogen vacancies at its core.Dissociated a-type screw dislocations in gallium nitride, comprising pairs of 30° Shockley Partial dislocations separated by I2 basal stacking faults, were observed by aberration-corrected high resolution transmission electron microscopy (HRTEM). HRTEM image simulations, in conjunction with density functional theory calculations, led to the identification of the core structures of the Shockley Partials. Both Partials were found to belong to the glide set rather than the shuffle one, while the core with gallium polarity is reconstructed, but the one with nitrogen polarity is not. During in situ irradiation by the electron beam, the I2 stacking fault ribbon was found to shrink, ultimately leading to a remerging of the two Partials. This reversal of the dissociation reaction was attributed to recombination enhanced dislocation glide, whereby the Shockley Partial with nitrogen polarity was identified to be the mobile one. A possible model explaining this mobility is proposed comprising a local modification of...
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energetics of the 30 Shockley Partial dislocation in wurtzite gan
Superlattices and Microstructures, 2006Co-Authors: I. Belabbas, G. P. Dimitrakopulos, J Kioseoglou, A Bere, J Chen, Ph Komninou, P Ruterana, G NouetAbstract:Abstract In the present work, we have investigated the relative energy of different core configurations of the 30∘ Shockley Partial dislocation in wurtzite GaN. By using a modified Stillinger–Weber potential, we have carried out large scale calculations on models containing many thousands of atoms. Both glide and shuffle configurations have been considered within the two core polarities (Ga, N). Similarly to what was reported for conventional semiconductors, our calculations showed that the reconstructed glide configurations are energetically favoured over the shuffle ones.
Yi Chen - One of the best experts on this subject based on the ideXlab platform.
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Determination of the Core-structure of Shockley Partial Dislocations in 4H-SiC
MRS Online Proceedings Library, 2008Co-Authors: Yi Chen, Ning Zhang, Xianrong Huang, Joshua D. Caldwell, Kendrick X. Liu, Robert E. Stahlbush, Michael DudleyAbstract:Synchrotron x-ray topographs taken using basal plane reflections indicate that the electron-hole recombination activated Shockley Partial dislocations in 4 H silicon carbide bipolar devices appear as either white stripes with dark contrast bands at both edges or dark lines. In situ electroluminescence observations indicated that the mobile Partial dislocations correspond to the white stripes in synchrotron x-ray topographs, while immobile Partial dislocations correspond to the dark lines. Computer simulation based on ray-tracing principle indicates that the contrast variation of the Partial dislocations in x-ray topography is determined by the position of the extra atomic half planes associated with the Partial dislocations lying along their Peierls valley directions. The chemical structure of the Shockley Partial dislocations can be subsequently determined unambiguously and non-destructively.
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Synchrotron X-Ray Topographic Studies of Recombination Activated Shockley Partial Dislocations in 4H-Silicon Carbide Epitaxial Layers
Materials Science Forum, 2008Co-Authors: Yi Chen, Ning Zhang, Xianrong Huang, Joshua D. Caldwell, Kendrick X. Liu, Michael Dudley, Robert E. StahlbushAbstract:Electron-hole recombination activated Shockley Partial dislocations bounding expanding stacking faults and their interactions with threading dislocations have been studied in 4H-SiC epitaxial layers using synchrotron x-ray topography. The bounding Partials appear as white stripes or narrow dark lines in back-reflection X-ray topographs recorded using the basal plane reflections. Such contrast variations are attributable to the defocusing/focusing of the diffracted X-rays due to the edge component of the Partial dislocations, which creates a convex/concave distortion of the basal planes. Simulation results based on the ray-tracing principle confirm our argument. The sign of the Partial dislocations can be subsequently determined.
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Observations of the influence of threading dislocations on the recombination enhanced Partial dislocation glide in 4H-silicon carbide epitaxial layers
Applied Physics Letters, 2007Co-Authors: Yi Chen, Kendrick X. Liu, M. Dudley, R. E. StahlbushAbstract:Electron-hole recombination enhanced glide of Shockley Partial dislocations bounding expanding stacking faults and their interactions with threading dislocations have been studied in 4H- silicon carbide epitaxial layers. The mobile silicon-core Shockley Partial dislocations bounding the stacking faults are observed to cut through threading edge dislocations, leaving no trailing dislocation segments in their wake. When the Shockley Partial dislocations interact with threading screw dislocations, 30° Partial dislocation dipoles are initially deposited in their wake. These Partial dislocation dipoles quickly and spontaneously snap into screw orientation whereupon they cross slip and annihilate, leaving a prismatic stacking fault on the (21¯1¯0) plane.
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Interaction between Recombination Enhanced Dislocation Glide Process Activated Basal Stacking Faults and Threading Dislocations in 4H-Silicon Carbide Epitaxial Layers
MRS Proceedings, 2007Co-Authors: Yi Chen, Kendrick X. Liu, Michael Dudley, Robert E. StahlbushAbstract:AbstractElectron-hole recombination enhanced glide of Shockley Partial dislocations bounding expanding stacking faults and their interactions with threading dislocations in 4H silicon carbide epitaxial layers have been studied using synchrotron white beam X-ray topography and in situ electroluminescence. The mobile silicon-core Shockley Partial dislocations bounding the stacking faults are able to cut through threading edge dislocations leaving no trailing dislocation segments in their wake. However, when the Shockley Partial dislocations interact with threading screw dislocations, trailing 30o Partial dislocation dipoles are initially deposited in their wake due to the pinning effect of the threading screw dislocations. These dipoles spontaneously snap into their screw orientation, regardless the normally immobile carbon-core Shockley Partial dislocation components in the dipoles. They subsequently cross slip and annihilate, leaving a prismatic stacking fault in (2-1-10) plane with the displacement vector 1/3[01-10].
R. E. Stahlbush - One of the best experts on this subject based on the ideXlab platform.
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Observations of the influence of threading dislocations on the recombination enhanced Partial dislocation glide in 4H-silicon carbide epitaxial layers
Applied Physics Letters, 2007Co-Authors: Yi Chen, Kendrick X. Liu, M. Dudley, R. E. StahlbushAbstract:Electron-hole recombination enhanced glide of Shockley Partial dislocations bounding expanding stacking faults and their interactions with threading dislocations have been studied in 4H- silicon carbide epitaxial layers. The mobile silicon-core Shockley Partial dislocations bounding the stacking faults are observed to cut through threading edge dislocations, leaving no trailing dislocation segments in their wake. When the Shockley Partial dislocations interact with threading screw dislocations, 30° Partial dislocation dipoles are initially deposited in their wake. These Partial dislocation dipoles quickly and spontaneously snap into screw orientation whereupon they cross slip and annihilate, leaving a prismatic stacking fault on the (21¯1¯0) plane.
Z.x. Wen - One of the best experts on this subject based on the ideXlab platform.
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Atomic simulation of void location effect on the void growth in nickel-based single crystal
Computational Materials Science, 2019Co-Authors: Junbiao Wang, Junhao Liang, Z.x. Wen, Z.f. YueAbstract:Abstract Void growth in metallic materials are strongly affected by local microstructure. The location of defect produces a great influence on the mechanical properties of material, especially if defect occurs at the interface. Considering the complex microstructure of nickel-based single crystal, the Ni, Ni3Al and Ni/Ni3Al interface model were established to analyze the expansion dynamics of void using molecular dynamics (MD) method. The expansion behavior of void shows that a/6〈1 1 2〉 Shockley Partial dislocations initially nucleates on the free surface of void during the stretching of Ni and Ni3Al model. Whereas, dislocations nucleate from the interface of Ni/Ni3Al interface model. Evolution of void suggested that the plasticity deformation is dominated by movable Shockley Partial dislocations and immovable Stair-rod dislocations. Void size effect analysis revealed that the larger void radius is, the smaller yield stress and Young’s modulus are. The mechanical properties of Ni/Ni3Al interface model were controlled by the interaction between void and interface.
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Atomistic simulation analysis of the effects of void interaction on void growth and coalescence in a metallic system
Current Applied Physics, 2018Co-Authors: Z.x. Wen, Junbiao Wang, Wu Yunwu, K.j. Zhou, Z.f. YueAbstract:Abstract Material deformation caused by the interaction between defects is a significant factor of material fracture failure. The present study employs molecular dynamics simulations of single-void and double-void crystalline Ni atomic systems to investigate inter-void interactions. Furthermore, simulations showing the evolution of dislocations for three different crystallographic orientations are conducted to study the void growth and coalescence. The simulations also consider the effect of the radius of the secondary void on dislocation evolution. The results show that double-void systems are more prone to yield than single-void systems. Further microstructural analysis indicates that the interaction between voids is realized by dislocation reactions. The simulation results of the dislocation evolution of the three orientations reveal that a relationship exists between the evolution of the dislocation density and the stress-strain curve. At the initial stage of dislocation, the dislocation grows slowly, and consists of Shockley Partial dislocation. The dislocation growth rate then increases significantly in the sharply declining stage of the stress-strain curve, where most of dislocations are Shockley Partial dislocation. Analysis of the dislocation length during the overall simulation indicates that the dislocation length of the [110] orientation is the longest, followed by that of the [111] orientation and the [100] orientation, which has the shortest dislocation length.