126 results on '"Qing-Xiang Pei"'
Search Results
102. Mechanical properties of methyl functionalized graphene: a molecular dynamics study
- Author
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Qing-Xiang Pei, Vivek B. Shenoy, and Yong-Wei Zhang
- Subjects
Materials science ,Graphene ,Mechanical Engineering ,Drop (liquid) ,Radical ,Bioengineering ,General Chemistry ,law.invention ,Molecular dynamics ,Mechanics of Materials ,law ,Ultimate tensile strength ,Perpendicular ,Surface modification ,General Materials Science ,Electrical and Electronic Engineering ,Composite material ,Elastic modulus - Abstract
Molecular dynamics simulations have been performed to study the mechanical properties of methyl (CH(3)) functionalized graphene. It is found that the mechanical properties of functionalized graphene greatly depend on the location, distribution and coverage of CH(3) radicals on graphene. Surface functionalization exhibits a much stronger influence on the mechanical properties than edge functionalization. For patterned functionalization on graphene surfaces, the radicals arranged in lines perpendicular to the tensile direction lead to larger strength deterioration than those parallel to the tensile direction. For random functionalization, the elastic modulus of graphene decreases gradually with increasing CH(3) coverage, while both the strength and fracture strain show a sharp drop at low coverage. When CH(3) coverage reaches saturation, the elastic modulus, strength and fracture strain of graphene drop by as much as 18%, 43% and 47%, respectively.
- Published
- 2010
103. Molecular-dynamics studies of competitive replacement in peptide-nanotube assembly for control of drug release
- Author
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Yuan Cheng, Huajian Gao, and Qing-Xiang Pei
- Subjects
Nanotubes, Peptide ,Nanotube ,Materials science ,Bioengineering ,Nanotechnology ,Peptide ,Carbon nanotube ,law.invention ,symbols.namesake ,Molecular dynamics ,law ,General Materials Science ,Electrical and Electronic Engineering ,Peptide sequence ,chemistry.chemical_classification ,Drug Carriers ,Mechanical Engineering ,General Chemistry ,Kinetics ,chemistry ,Pharmaceutical Preparations ,Mechanics of Materials ,Drug delivery ,symbols ,Biophysics ,van der Waals force ,Drug carrier ,Protein Binding - Abstract
We report molecular-dynamics simulation of carbon-nanotube-based drug delivery and release systems. We show that a peptide encapsulated inside or attached to the outer surface of a carbon nanotube can be released by another nanotube through a competitive replacement process. Energy analysis reveals that the van der Waals interaction plays the key role in this process, and the potential well between two nanotubes drives the competitive replacement. We further show that competitive replacement is a basic principle which may be generally explored for drug release. For example, one type of peptide can be used to replace/release another type of peptide, depending on the difference in their affinity for the nanotube. The effects of the peptide sequence and the nanotube size on the drug release process are also studied in this paper.
- Published
- 2009
104. Study of Materials Deformation in Nanometric Cutting by Large-scale Molecular Dynamics Simulations
- Author
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Chun Lu, Qing-Xiang Pei, HP Lee, and Yong-Wei Zhang
- Subjects
Length scale ,Materials science ,Nano Express ,Scale (ratio) ,Nanochemistry ,Nanotechnology ,Nanometric cutting ,Mechanics ,Molecular dynamics ,Deformation (meteorology) ,Condensed Matter Physics ,Condensed Matter::Materials Science ,Materials Science(all) ,lcsh:TA401-492 ,Materials deformation ,lcsh:Materials of engineering and construction. Mechanics of materials ,General Materials Science ,Dislocation ,Large-scale simulation ,Embedded atom model ,Morse potential - Abstract
Nanometric cutting involves materials removal and deformation evolution in the surface at nanometer scale. At this length scale, atomistic simulation is a very useful tool to study the cutting process. In this study, large-scale molecular dynamics (MD) simulations with the model size up to 10 millions atoms have been performed to study three-dimensional nanometric cutting of copper. The EAM potential and Morse potential are used, respectively, to compute the interaction between workpiece atoms and the interactions between workpiece atoms and tool atoms. The material behavior, surface and subsurface deformation, dislocation movement, and cutting forces during the cutting processes are studied. We show that the MD simulation model of nanometric cutting has to be large enough to eliminate the boundary effect. Moreover, the cutting speed and the cutting depth have to be considered in determining a suitable model size for the MD simulations. We have observed that the nanometric cutting process is accompanied with complex material deformation, dislocation formation, and movement. We find that as the cutting depth decreases, the tangential cutting force decreases faster than the normal cutting force. The simulation results reveal that as the cutting depth decreases, the specific cutting force increases, i.e., “size effect” exists in nanometric cutting.
- Published
- 2009
105. Method of Examining Surface Cracks on Monocrystalline Silicon
- Author
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Feng Zhou Fang, Yu Chan Liu, Qing Xiang Pei, and Xiao Tang Hu
- Published
- 2007
106. Thermal transport behavior of polycrystalline graphene: A molecular dynamics study
- Author
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Zhili Dong, Yong-Wei Zhang, P. H. Wu, Xiangjun Liu, S.S. Quek, Guibin Zhang, Zhen-Dong Sha, Qing-Xiang Pei, and School of Materials Science & Engineering
- Subjects
Materials science ,Graphene ,General Physics and Astronomy ,Nanotechnology ,Science::Physics [DRNTU] ,Grain size ,law.invention ,Molecular dynamics ,Thermal conductivity ,law ,Ultimate tensile strength ,Thermal ,Crystallite ,Composite material ,Graphene nanoribbons - Abstract
The thermal transport behavior of polycrystalline graphene is studied using molecular dynamics simulations, with focus on the effects of grain size, tensile strain, and temperature on the thermal conductivity. All the simulation samples have the same overall dimensions of 30 × 30 nm with average grain sizes ranging from 2.5 to 12.5 nm. It is found that polycrystalline graphene exhibits a significant reduction in thermal conductivity compared to single-crystalline graphene, and the smaller the grain size is, the more the thermal conductivity drops. The thermal conductivity of polycrystalline graphene with average grain size of 2.5 nm is only about 20% of single-crystalline graphene. However, the thermal conductivity of polycrystalline graphene is less sensitive to both the applied strain and temperature than that of single-crystalline graphene. The underlying mechanisms for the differences in thermal behavior are examined and discussed. These findings are important for the thermal management of graphene-based devices. Published version
- Published
- 2014
107. THREE-DIMENSIONAL FINITE ELEMENT STUDY OF THE ELASTIC FIELDS IN QUANTUM DOT STRUCTURES
- Author
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Qing-Xiang Pei and Chun Lu
- Subjects
Physics ,Classical mechanics ,Quantum dot ,Finite element study - Published
- 2002
108. Temperature and strain-rate dependent fracture strength of graphynes
- Author
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Yingyan Zhang, YuanTong Gu, Qing-Xiang Pei, and Yiu-Wing Mai
- Subjects
Materials science ,Acoustics and Ultrasonics ,Strain (chemistry) ,Graphene ,Modulus ,Strain rate ,Condensed Matter Physics ,Surfaces, Coatings and Films ,Electronic, Optical and Magnetic Materials ,law.invention ,Graphyne ,Molecular dynamics ,Flexural strength ,law ,Composite material ,Deformation (engineering) - Abstract
Graphyne is an allotrope of graphene. The mechanical properties of graphynes (α-, β-, γ- and 6,6,12-graphynes) under uniaxial tension deformation at different temperatures and strain rates are studied using molecular dynamics simulations. It is found that graphynes are more sensitive to temperature changes than graphene in terms of fracture strength and Young's modulus. The temperature sensitivity of the different graphynes is proportionally related to the percentage of acetylenic linkages in their structures, with the α-graphyne (having 100% of acetylenic linkages) being most sensitive to temperature. For the same graphyne, temperature exerts a more pronounced effect on the Young's modulus than fracture strength, which is different from that of graphene. The mechanical properties of graphynes are also sensitive to strain rate, in particular at higher temperatures.
- Published
- 2014
109. On the notch sensitivity of CuZr nanoglass
- Author
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Qing-Xiang Pei, Yong-Wei Zhang, Zhen-Dong Sha, T. J. Wang, Zishun Liu, Hui Pan, and Linchun He
- Subjects
Shear (sheet metal) ,Materials science ,Metallurgy ,Nucleation ,General Physics and Astronomy ,Superplasticity ,Shear matrix ,Deformation (engineering) ,Composite material ,Shear band ,Grain size ,Stress concentration - Abstract
Recently, nanoglass (NG) was found to exhibit a surprising homogeneous superplastic deformation behavior. However, how the presence of notch affects its mechanical properties remains unexplored. Here, we perform molecular dynamics simulations on a superplastic Cu50Zr50 NG containing a pre-existing notch under tensile loading, with focus on the notch sensitivity. Our results show that when the notch size is smaller than or comparable to the average grain size (d), the NG still exhibits a superplastic deformation and shows notch-insensitivity. When the notch size is larger than d, however, the NG fails by localized shear banding emanating from the notch root and shows notch-sensitivity. The origin of this transition arises from the competition between the shear band nucleation induced by the stress concentration at the notch root and the growth of shear transformation zones distributed in the glass-glass interfaces. Our results provide useful guidelines for the design and engineering of NG with notch for st...
- Published
- 2014
110. Effects of temperature and strain rate on the mechanical properties of silicene
- Author
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Yingyan Zhang, Qing-Xiang Pei, Yong-Wei Zhang, and Zhen-Dong Sha
- Subjects
Materials science ,Silicon ,Graphene ,Silicene ,General Physics and Astronomy ,chemistry.chemical_element ,Young's modulus ,Strain rate ,law.invention ,symbols.namesake ,Fracture toughness ,chemistry ,Flexural strength ,law ,Ultimate tensile strength ,symbols ,Composite material - Abstract
Silicene, a graphene-like two-dimensional silicon, has attracted great attention due to its fascinating electronic properties similar to graphene and its compatibility with existing semiconducting technology. So far, the effects of temperature and strain rate on its mechanical properties remain unexplored. We investigate the mechanical properties of silicene under uniaxial tensile deformation by using molecular dynamics simulations. We find that the fracture strength and fracture strain of silicene are much higher than those of bulk silicon, though the Young's modulus of silicene is lower than that of bulk silicon. An increase in temperature decreases the fracture strength and fracture strain of silicene significantly, while an increase in strain rate enhances them slightly. The fracture process of silicene is also studied and brittle fracture behavior is observed in the simulations.
- Published
- 2014
111. Phonon thermal conductivity of monolayer MoS2 sheet and nanoribbons
- Author
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Xiangjun Liu, Yong-Wei Zhang, Qing-Xiang Pei, and Gang Zhang
- Subjects
Materials science ,Thermal conductivity ,Physics and Astronomy (miscellaneous) ,Condensed matter physics ,Graphene ,law ,Seebeck coefficient ,Thermoelectric effect ,Monolayer ,Thermal conduction ,Thermoelectric materials ,Graphene nanoribbons ,law.invention - Abstract
We investigated the thermal conduction of monolayer MoS2 sheet and nanoribbons using molecular dynamics simulations. Room temperature thermal conductivity of monolayer MoS2 is found to be 1.35 W/mK, which is three orders of magnitude lower than that of graphene. In contrast to the remarkable size effect observed in graphene nanoribbons, the thermal conductivity of MoS2 nanoribbons is insensitive to width (3–16 nm), length (4–111 nm), and the type of edge, which are explained by the local heat flux analysis and phonon scattering mechanisms. The low thermal conductivity together with reported high Seebeck coefficient opens up the possibility to realize MoS2-based two-dimensional thermoelectric devices.
- Published
- 2013
112. A molecular dynamics investigation on mechanical properties of hydrogenated graphynes
- Author
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Chien Ming Wang, Qing-Xiang Pei, Yingyan Zhang, Yong-Wei Zhang, and Yuan Cheng
- Subjects
Materials science ,Hydrogen ,Hexagonal crystal system ,General Physics and Astronomy ,Modulus ,chemistry.chemical_element ,Young's modulus ,Fracture mechanics ,Graphyne ,symbols.namesake ,Molecular dynamics ,chemistry ,Ultimate tensile strength ,symbols ,Organic chemistry ,Composite material - Abstract
Graphyne, a new type of carbon allotropes, has attracted considerable attention in recent years. Using molecular dynamics simulations, we investigate the mechanical properties of four different graphynes (α-, β-, γ-, and 6,6,12-graphynes) functionalized with hydrogen. The simulations results show that hydrogenation can greatly deteriorate the mechanical properties of the graphynes. For the different graphynes with 100% H-coverage, the reduction in fracture stress depends on the percentage of acetylenic linkages in the graphyne structures: The more the acetylenic linkages, the larger the reduction. For the same graphyne, the reduction in fracture stress depends on the hydrogenation location, distribution, and coverage. Hydrogenation on the acetylenic linkages causes a larger reduction in fracture stress than that on the hexagonal rings. A line hydrogenation perpendicular to the tensile direction leads to a larger reduction in fracture stress than that when the line hydrogenation is parallel to the tensile direction. For random hydrogenation, the fracture stress and Young's modulus decrease rapidly at low H-coverage (
- Published
- 2013
113. On the notch sensitivity of CuZr metallic glasses
- Author
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Zhen-Dong Sha, V. Sorkin, Paulo S. Branicio, Yong-Wei Zhang, Huajian Gao, and Qing-Xiang Pei
- Subjects
Amorphous metal ,Materials science ,Physics and Astronomy (miscellaneous) ,Ultimate tensile strength ,Zirconium alloy ,Metallurgy ,Nucleation ,Material failure theory ,Composite material ,Critical value ,Shear band ,Stress concentration - Abstract
Atomistic simulations are performed to study the effects of size and shape of a superficial or internal notch on the strength and failure mechanism of CuZr metallic glass (MG) under tensile loading. Our results show that plastic deformation originating at the notch root reduces the stress concentration there and leads to a notch-insensitive normalized tensile strength. The notch, however, dictates the failure location as the plastic zone at the notch root serves as a nucleation site for shear band (SB) formation. It is shown that when the plastic zone size reaches a critical value, a SB starts to propagate from the notch root across the entire sample, causing the material failure. These results provide useful guidelines for the design, testing, and engineering of MG for structural applications.
- Published
- 2013
114. Large-scale molecular dynamics simulations of wear in diamond-like carbon at the nanoscale
- Author
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David J. Srolovitz, Qing-Xiang Pei, Yong-Wei Zhang, Zhen-Dong Sha, V. Sorkin, and Paulo S. Branicio
- Subjects
Normal load ,Molecular dynamics ,Materials science ,Physics and Astronomy (miscellaneous) ,Shear (geology) ,Diamond-like carbon ,Chemical bond ,Friction force ,Nanostructured materials ,Composite material ,human activities ,Nanoscopic scale - Abstract
We perform large-scale molecular dynamics simulations on diamond-like carbon to study wear mechanism and law at the nanoscale. Our simulations show that material loss during sliding varies linearly with normal load and sliding distance, consistent with Archard's law. Our simulations also show that the number of chemical bonds across the contact interface during sliding correlates well with friction force, but not with material loss, indicating that friction and wear follow different mechanisms. Our analysis reveals the following wear mechanism: the shear traction causes mass accumulation at the trailing end of contact, which is then lost by a cluster detachment process.
- Published
- 2013
115. Tuning the thermal conductivity of silicene with tensile strain and isotopic doping: A molecular dynamics study
- Author
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Vivek B. Shenoy, Zhen-Dong Sha, Yong-Wei Zhang, and Qing-Xiang Pei
- Subjects
Materials science ,Condensed matter physics ,Silicon ,Silicene ,Graphene ,Superlattice ,Doping ,General Physics and Astronomy ,chemistry.chemical_element ,law.invention ,Condensed Matter::Materials Science ,Thermal conductivity ,chemistry ,law ,Thermoelectric effect ,Monolayer - Abstract
Silicene is a monolayer of silicon atoms arranged in honeycomb lattice similar to graphene. We study the thermal transport in silicene by using non-equilibrium molecular dynamics simulations. We focus on the effects of tensile strain and isotopic doping on the thermal conductivity, in order to tune the thermal conductivity of silicene. We find that the thermal conductivity of silicene, which is shown to be only about 20% of that of bulk silicon, increases at small tensile strains but decreases at large strains. We also find that isotopic doping of silicene results in a U-shaped change of the thermal conductivity for the isotope concentration varying from 0% to 100%. We further show that ordered doping (isotope superlattice) leads to a much larger reduction in thermal conductivity than random doping. Our findings are important for the thermal management in silicene-based electronic devices and for thermoelectric applications of silicene.
- Published
- 2013
116. Mechanical properties of graphynes under tension: A molecular dynamics study
- Author
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Qing-Xiang Pei, Yingyan Zhang, and Chen Wang
- Subjects
Materials science ,Physics and Astronomy (miscellaneous) ,Graphene ,Modulus ,Young's modulus ,law.invention ,Graphyne ,symbols.namesake ,Molecular dynamics ,law ,Chemical physics ,Computational chemistry ,symbols ,Single bond ,Elastic modulus - Abstract
Graphyne is the allotrope of graphene. In this letter, four different graphynes (α, β, γ, and 6,6,12-graphenes) are investigated by molecular dynamics simulations to explore their mechanical properties and failure mechanisms. It is found that the presence of the acetylenic linkages in graphynes leads to a significant reduction in fracture stress and Young’s modulus with the degree of reduction being proportional to the percentage of the linkages. This deterioration in mechanical properties stems from the low atom density in graphynes and weak single bonds in the acetylenic linkages where the facture is initiated.
- Published
- 2012
117. Carbon isotope doping induced interfacial thermal resistance and thermal rectification in graphene
- Author
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Zhen-Dong Sha, Vivek B. Shenoy, Yong-Wei Zhang, and Qing-Xiang Pei
- Subjects
Materials science ,Physics and Astronomy (miscellaneous) ,Graphene ,Thermal resistance ,Doping ,Analytical chemistry ,Physics::Optics ,Condensed Matter::Mesoscopic Systems and Quantum Hall Effect ,Thermal conduction ,law.invention ,Condensed Matter::Materials Science ,Thermal conductivity ,Rectification ,law ,Chemical physics ,Isotopes of carbon ,Interfacial thermal resistance - Abstract
We investigate the thermal transport properties of carbon isotope doped graphene using nonequilibrium molecular dynamics simulations. We find that the interfacial thermal resistance between graphene and the isotope atoms causes severe reduction in thermal conductivity of the doped graphene. Furthermore, we find that thermal rectification occurs in the interface. Tensile strain leads to an increase in the interfacial thermal resistance and thermal rectification, while increasing temperature decreases these parameters. We calculate the phonon spectra and find that the thermal rectification is associated with the overlap areas in the phonon spectra.
- Published
- 2012
118. Molecular dynamics study on DNA oligonucleotide translocation through carbon nanotubes
- Author
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Huajian Gao, C. G. Lim, Qing-Xiang Pei, and Yuan Cheng
- Subjects
Models, Molecular ,Materials science ,Field (physics) ,Nanotubes, Carbon ,Oligonucleotide ,DNA, Single-Stranded ,Water ,General Physics and Astronomy ,Nanotechnology ,Carbon nanotube ,Gravitational acceleration ,law.invention ,Kinetics ,chemistry.chemical_compound ,Molecular dynamics ,Oligodeoxyribonucleotides ,chemistry ,Gravitational field ,Chemical physics ,law ,Nucleic Acid Conformation ,A-DNA ,Physical and Theoretical Chemistry ,DNA ,Gravitation - Abstract
Molecular dynamics simulations are performed to study the translocation of a DNA oligonucleotide in a carbon nanotube (CNT) channel consisting of CNTs of two different diameters. A strong gravitational acceleration field is applied to the DNA molecule and water solvent as an external driving force for the translocation. It is observed that both the CNT channel size and the strength of gravitational field have significant influence on the DNA translocation process. It is found that the DNA oligonucleotide is unable to pass through the (8,8) CNT even under strong gravitational fields, which extends previous finding that DNA cannot be self-inserted into a (8,8) CNT. It is shown that the DNA can pass through the (10,10)-(12,12) and (12,12)-(14,14) CNTs with stronger gravitational field resulting in faster translocation. The translocation time tau is found to follow the inverse power law relationship with the gravitational acceleration a as tau approximately a(-1.21). The energetic analysis of the translocation process shows that there is an energy barrier for DNA translocation into the (10,10) tube from the (14,14) tube, which is in contrast to previous report that DNA can be self-inserted into a (10,10) tube from outside the CNT. This difference with previous report shows that the dynamic behavior of DNA translocation inside a CNT channel is quite different from that of DNA translocation into a CNT from outside the CNT.
- Published
- 2008
119. Recent progress of additive manufactured Ti-6Al-4V by electron beam melting
- Author
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Wang, P., Sharon Nai, M. L., Tan, X., Vastola, G., Raghavan, S., Sin, W. J., Tor, S. B., Qing-Xiang Pei, and Wei, J.
120. Mechanical properties and failure behaviour of graphene/silicene/graphene heterostructures.
- Author
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Jing-Yang Chung, Viacheslav Sorkin, Qing-Xiang Pei, Cheng-Hsin Chiu, and Yong-Wei Zhang
- Subjects
ELECTRIC properties of graphene ,DYNAMIC simulation ,HETEROSTRUCTURES - Abstract
Van der Waals heterostructures based on graphene and other 2D materials have attracted great attention recently. In this study, the mechanical properties and failure behaviour of a graphene/silicene/graphene heterostructure are investigated using molecular dynamics simulations. We find that by sandwiching silicene in-between two graphene layers, both ultimate tensile strength and Young’s modulus of the heterostructure increase approximately by a factor of 10 compared with those of stand-alone silicene. By examining the fracture process of the heterostructure, we find that graphene and silicene exhibit quite different fracture behaviour. While graphene undergoes cleavage through its zigzag edge only, silicene can cleave through both its zigzag and armchair edges. In addition, we study the effects of temperature and strain rate on the mechanical properties of the heterostructure and find that an increase in temperature results in a decrease in its mechanical strength and stiffness, while an increase in strain rate leads to an increase in its mechanical strength without significant changes in its stiffness. We further explore the failure mechanism and show that the temperature and strain-rate dependent fracture stress can be accurately described by the kinetic theory of fracture. Our findings provide a deep insight into the mechanical properties and failure mechanism of graphene/silicene heterostructures. [ABSTRACT FROM AUTHOR]
- Published
- 2017
- Full Text
- View/download PDF
121. Interfacial thermal conductance in multilayer graphene/phosphorene heterostructure.
- Author
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Ying-Yan Zhang, Qing-Xiang Pei, Yiu-Wing Mai, and Siu-Kai Lai
- Subjects
- *
NANOELECTROMECHANICAL systems , *HETEROSTRUCTURES , *PHOSPHORENE - Abstract
Vertical integration of 2D materials has recently appeared as an effective method for the design of novel nano-scale devices. Using non-equilibrium molecular dynamics simulations, we study the interfacial thermal transport property of graphene/phosphorene heterostructures where phosphorene is sandwiched in between graphene. Various modulation techniques are thoroughly explored. We found that the interfacial thermal conductance at the interface of graphene and phosphorene can be enhanced significantly by using vacancy defects, hydrogenation and cross-plane compressive strain. By contrast, the reduction in the interfacial thermal conductance can be achieved by using cross-plane tensile strain. Our results provide important guidelines for manipulating the thermal transport in graphene/phosphorene based-nano-devices. [ABSTRACT FROM AUTHOR]
- Published
- 2016
- Full Text
- View/download PDF
122. Atomic vacancies significantly degrade the mechanical properties of phosphorene.
- Author
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Zhen-Dong Sha, Qing-Xiang Pei, Ying-Yan Zhang, and Yong-Wei Zhang
- Subjects
- *
PHOSPHORENE , *TEMPERATURE , *THERMAL properties , *MOLECULAR physics , *PHOSPHORUS - Abstract
Due to low formation energies, it is very easy to create atomic defects in phosphorene during its fabrication process. How these atomic defects affect its mechanical behavior, however, remain unknown. Here, we report on a systematic study of the effect of atomic vacancies on the mechanical properties and failure behavior of phosphorene using molecular dynamics simulations. It is found that atomic vacancies induce local stress concentration and cause early bond-breaking, leading to a significant degradation of the mechanical properties of the material. More specifically, a 2% concentration of randomly distributed mono-vacancies is able to reduce the fracture strength by ∼40%. An increase in temperature from 10 to 400 K can further deteriorate the fracture strength by ∼60%. The fracture strength of defective phosphorene is also found to be affected by defect distribution. When the defects are patterned in a line, the reduction in fracture strength greatly depends on the tilt angle and the loading direction. Furthermore, we find that di-vacancies cause an even larger reduction in fracture strength than mono-vacancies when the loading is in an armchair direction. These findings provide important guidelines for the structural design of phosphorene in future applications. [ABSTRACT FROM AUTHOR]
- Published
- 2016
- Full Text
- View/download PDF
123. Mechanical properties and fracture behavior of single-layer phosphorene at finite temperatures.
- Author
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Zhen-Dong Sha, Qing-Xiang Pei, Zhiwei Ding, Jin-Wu Jiang, and Yong-Wei Zhang
- Subjects
- *
PHOSPHORENE , *MECHANICAL behavior of materials , *CRACK propagation (Fracture mechanics) , *GRAPHENE , *MOLECULAR dynamics , *AXIAL loads , *HIGH temperatures - Abstract
Phosphorene, a new two-dimensional (2D) material beyond graphene, has attracted great attention in recent years due to its superior physical and electrical properties. However, compared to graphene and other 2D materials, phosphorene has a relatively low Young’s modulus and fracture strength, which may limit its applications due to possible structure failures. For the mechanical reliability of future phosphorene-based nanodevices, it is necessary to have a deep understanding of the mechanical properties and fracture behaviors of phosphorene. Previous studies on the mechanical properties of phosphorene were based on first principles calculations at 0 K. In this work, we employ molecular dynamics simulations to explore the mechanical properties and fracture behaviors of phosphorene at finite temperatures. It is found that temperature has a significant effect on the mechanical properties of phosphorene. The fracture strength and strain reduce by more than 65% when the temperature increases from 0 K to 450 K. Moreover, the fracture strength and strain in the zigzag direction is more sensitive to the temperature rise than that in the armchair direction. More interestingly, the failure crack propagates preferably along the groove in the puckered structure when uniaxial tension is applied in the armchair direction. In contrast, when the uniaxial tension is applied in the zigzag direction, multiple cracks are observed with rough fracture surfaces. Our present work provides useful information about the mechanical properties and failure behaviors of phosphorene at finite temperatures. [ABSTRACT FROM AUTHOR]
- Published
- 2015
- Full Text
- View/download PDF
124. Friction between silicon and diamond at the nanoscale.
- Author
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Lichun Bai, Zhen-Dong Sha, Narasimalu Srikanth, Qing-Xiang Pei, Xu Wang, David J Srolovitz, and Kun Zhou
- Subjects
FRICTION ,SILICON ,DIAMONDS ,NANOSTRUCTURED materials ,MOLECULAR dynamics ,COVALENT bonds - Abstract
This work investigates the nanoscale friction between diamond-structure silicon (Si) and diamond via molecular dynamics simulation. The interaction between the interfaces is considered as strong covalent bonds. The effects of load, sliding velocity, temperature and lattice orientation are investigated. Results show that the friction can be divided into two stages: the static friction and the kinetic friction. During the static friction stage, the load, lattice orientation and temperature dramatically affects the friction by changing the elastic limit of Si. Large elastic deformation is induced in the Si block, which eventually leads to the formation of a thin layer of amorphous Si near the Si-diamond interface and thus the beginning of the kinetic friction stage. During the kinetic friction stage, only temperature and velocity have an effect on the friction. The investigation of the microstructural evolution of Si demonstrated that the kinetic friction can be categorized into two modes (stick-slip and smooth sliding) depending on the temperature of the fracture region. [ABSTRACT FROM AUTHOR]
- Published
- 2015
- Full Text
- View/download PDF
125. In-plane and cross-plane thermal conductivities of molybdenum disulfide.
- Author
-
Zhiwei Ding, Jin-Wu Jiang, Qing-Xiang Pei, and Yong-Wei Zhang
- Subjects
MOLYBDENUM disilicide ,THERMAL conductivity ,PHONON scattering ,MOLECULAR dynamics ,MONOMOLECULAR films ,BAND gaps - Abstract
We investigate the in-plane and cross-plane thermal conductivities of molybdenum disulfide (MoS
2 ) using non-equilibrium molecular dynamics simulations. We find that the in-plane thermal conductivity of monolayer MoS2 is about 19.76 W mK−1 . Interestingly, the in-plane thermal conductivity of multilayer MoS2 is insensitive to the number of layers, which is in strong contrast to the in-plane thermal conductivity of graphene where the interlayer interaction strongly affects the in-plane thermal conductivity. This layer number insensitivity is attributable to the finite energy gap in the phonon spectrum of MoS2 , which makes the phonon–phonon scattering channel almost unchanged with increasing layer number. For the cross-plane thermal transport, we find that the cross-plane thermal conductivity of multilayer MoS2 can be effectively tuned by applying cross-plane strain. More specifically, a 10% cross-plane compressive strain can enhance the thermal conductivity by a factor of 10, while a 5% cross-plane tensile strain can reduce the thermal conductivity by 90%. Our findings are important for thermal management in MoS2 based nanodevices and for thermoelectric applications of MoS2 . [ABSTRACT FROM AUTHOR]- Published
- 2015
- Full Text
- View/download PDF
126. Temperature and strain-rate dependent fracture strength of graphynes.
- Author
-
Ying-Yan Zhang, Qing-Xiang Pei, Yiu-Wing Mai, and Yuan-Tong Gu
- Subjects
- *
MECHANICAL properties of metals , *STRAIN rate , *ALLOTROPY , *GRAPHENE , *MOLECULAR dynamics - Abstract
Graphyne is an allotrope of graphene. The mechanical properties of graphynes (α-, β-, γ- and 6,6,12-graphynes) under uniaxial tension deformation at different temperatures and strain rates are studied using molecular dynamics simulations. It is found that graphynes are more sensitive to temperature changes than graphene in terms of fracture strength and Young's modulus. The temperature sensitivity of the different graphynes is proportionally related to the percentage of acetylenic linkages in their structures, with the α-graphyne (having 100% of acetylenic linkages) being most sensitive to temperature. For the same graphyne, temperature exerts a more pronounced effect on the Young's modulus than fracture strength, which is different from that of graphene. The mechanical properties of graphynes are also sensitive to strain rate, in particular at higher temperatures. [ABSTRACT FROM AUTHOR]
- Published
- 2014
- Full Text
- View/download PDF
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