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Stability and chirality effect on twist formation of collapsed double wall carbon nanotubes

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中国有色金属学会会刊：英文版 2006年第B02期16卷 776-779页

作者：肖建亮刘彬黄永刚黄克智俞敏峰 department of Engineering MechanicsTsinghua University Beijing 100084China department of mechanical and Industrial engineeringuniversity of Illinois at Urbana-Champaign UrbanaIL 61801USA

This study is to reveal the effect of interlayer lattice registry on the formation of collapsed double wall carbon nanotubes (DWCNTs). It is found that collapsed carbon nanotubes can be energetically unstable, metastable or stable, depending mainly on the diameter of the CNT. A fully collapsed DWCNT can adopt different structural morphologies, such as a straight ribbon, a warping ribbon or a twisted ribbon, depending on the chirality of the CNT, which is similar to single wall carbon nanotubes (SWCNTs). Different from SWCNTs, this study also shows some unique phenomena in the formation of collapsed DWCNTs. A fully collapsed DWCNT can have different combinations of the interlayer lattice registry effect within the inner and outer tube, thus the outer tube can influence the formation of the collapsed CNT via lattice registry effect, sometimes even dominates the twist of the CNT.

关键词：双壁碳纳米管扭曲形成稳定性手性效应倒塌

Experimental investigation of laser surface processing of flexure silicon nitride ceramic

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Transactions of Nonferrous Metals Society of China 2006年第S2期 558-565页

作者： A.P.MALSHE P．H．MCCLUSKEY department of mechanical engineeringuniversity of arkansas FayettevilleAR 72701USA Technology & Solutions Division Caterpillar Inc. PeoriaIL 61629USA

A continuous wave carbon dioxide (CO2) laser (λ=10.6μm) was employed to treat the surface of Si3N4 MOR (modulus of rupture) bars. The effects of the CO2 laser process on physical and mechanical properties of ground Si3N4 samples were investigated. Scanning electron microscopy (SEM) analysis shows that the area occupied by cavities and fracture is decreased by about 49.4% after laser treatments. Cross-sectional metallography results indicate that the secondary YSiAlON phase in the Si3N4 ceramic is softened/melted and flowed into the defects. Four-point bending tests show that the flexural strength of the treated samples is improved to 10.9%. Fractographic analysis show that the fracture origins move from the surface to subsurface. It is concluded that laser surface processing have significant effects on fracture behavior of flexure Si3N4 ceramic.

关键词： Si3N4 silicon nitride ceramic laser surface processing surface integrity flexural strength fracture origin

Tribological behavior of polydopamine/polytetrafluoroethylene coating on laser textured stainless steel with Hilbert curves

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Friction 2023年第7期11卷 1307-1319页

作者： Firuze SOLTANI-KORDSHULI Nathaniel HARRIS Min ZOU department of mechanical Engineering University of ArkansasFayetteville AR 72701USA Center for Advanced Surface Engineering University of ArkansasFayetteville AR 72701USA

Shallow Hilbert curve patterns with easily programmable texture density were selected for laser texturing of stainless steel *** different texture path segment lengths(12 and 24 μm)and four different laser power percentages(5%,10%,15%,and 20%)were *** textured and smooth substrates were coated with thin polydopamine/polytetrafluoroethylene(PDA/PTFE)coatings for tribological property *** effects of texture density(texture area coverage)and laser power on the durability and friction of the coated surfaces were *** texturing the substrates improved the coating durability up to 25 times,reduced the friction coefficient,and prevented coating global *** textures fabricated with a laser power of 15%and a texture path segment length of 12 μm yielded the best coating *** textures provided the interlocking for the PTFE coating and thus prevented its global ***,the PTFE inside the texture grooves replenished the solid lubricant worn away in the wear track and prolonged the coating wear life.

关键词： polytetrafluoroethylene(PTFE) coating durability laser texturing Hilbert curve stainless steel

Process simulation and analysis of carbon capture with an aqueous mixture of ionic liquid and monoethanolamine solvent

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International Journal of Coal Science & Technology 2017年第1期4卷 25-32页

作者： Baptiste Zacchello Eni Oko Meihong Wang Aloui Fethi department of mechanical and Energetics School ofEngineering ENSIAME 59313 Valenciennes France department of Chemical and Biological engineeringuniversity of Sheffield Sheffield SI 3JD UK

This study investigated the prospect of using aqueous mixture of 1-butylpyridinium tetrafluoroborate （[Bpy][BF4]） ionic liquid （IL） and monoethanolamine （MEA） as solvent in post-combustion CO2 capture （PCC） process. This is done by analysis of the process through modelling and simulation. In literature, reported PCC models with a mixture of IL and MEA solvent were developed using equilibrium-based mass transfer approach. In contrast, the model in this study is developed using rate-based mass transfer approach in Aspen Plus. From the results, the mixed aqueous solvent with 5-30 wt% IL and 30 wt% MEA showed 7%-9% and 12%-27% less specific regeneration energy and solvent circulation rate respectively compared to commonly used 30 wt% MEA solvent. It is concluded that the ｜L concentration （wt%） in the solvent blend have significant impact on specific regeneration energy and solvent circulation rate. This study is a starting point for further research on technical and economic analysis of PCC process with aqueous blend of IL and MEA as solvent.

关键词： Rate-based mass transfer Process simulation Post-combustion CO2 capture Ionic liquid (IL) Monoethanolamine (MEA)

Friction anisotropy dependence on lattice orientation of graphene

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Science China(Physics,Mechanics & Astronomy) 2014年第4期57卷 663-667页

作者： ZHANG Yu LIU LianQing XI Ning WANG YueChao DONG ZaiLi WEJINYA Uchechukwu C State Key Laboratory of Robotics Shenyang Institute of Automation Chinese Academy of Sciences University of Chinese Academy of Sciences department of mechanical and Biomedical Engineering City University of HongKong department of mechanical Engineering University of ArkansasFayetteville Arkansas 72701 USA

The observation of friction anisotropy on graphene by friction measurement at atomic scale has been reported in this ***-scale friction measurement revealed friction anisotropy with a periodicity of 60°,which is consistent with the hexagonal periodicity of the *** experiments and theory show that the value of the friction force is related to the graphene lattice orientation,and the friction force along armchair orientation is also larger than the one along zigzag *** results will play a critical role in the use of graphene to manufacture nanoscale devices.

关键词： graphene friction anisotropic lattice orientation

Localized CO2 laser bonding process for MEMS packaging

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Transactions of Nonferrous Metals Society of China 2006年第S2期 577-581页

作者： A．P.MALSHE S．CUNNINGHAM A．MORRIS department of mechanical engineeringuniversity of arkansas Fayetteville AR 72701USA wiSpry Inc.Irvine CA 92618USA wiSpry Inc.Cary NC 27513 USA

The packaging poses a critical challenge for commercialization of MEMS products. Major problems with the packaging process include degraded reliability caused by the excess stress due to thermal mismatch and altered performance of the MEMS device after packaging caused by thermal exposure. The localized laser bonding technique for ceramic MEMS packaging to address above-mentioned challenges was investigated. A continuous wave CO2 laser was used to locally heat sealing material for ceramic MEMS package lid to substrate bonding. To determine the laser power density and scanning speed, finite element analysis thermal models were constructed to simulate the localized laser bonding process. Further, the effect of external pressure at sealing ring on the bonding formation was studied. Pull testing results show that the scanning speed and external pressure have significant influence on the pull strength at the bonding interface. Cross-sectional microscopy of the bonding interface indicates that the packages bonded with relatively low scanning speed and external pressure conditions have higher bonding quality. This research demonstrates the potential of localized laser bonding process for ceramic MEMS packaging.

关键词： localized laser bonding MEMS packaging FEA mechanical pull tests cross-sectional microscopy

Raman analysis of chemisorbed tribofilm for metal-on-polyethylene hip joint prostheses

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Biosurface and Biotribology 2021年第1期7卷 1-11页

作者： Risha Rufaqua Martin Vrbka Dušan Hemzal Dipankar Choudhury David Rebenda Ivan Křupka Martin Hartl Faculty of mechanical Engineering Brno University of TechnologyBrnoCzech Republic department of Condensed Matter Physics Faculty of ScienceMasaryk UniversityBrnoCzech Republic Nano Mechanics and Tribology Laboratory Department of Mechanical EngineeringUniversity of ArkansasFayettevilleArkansasUSA

The biochemical reaction during the formation of lubricant film the in case of a cobalt-chromium ball on an ultrahigh-molecular weight polyethylene cup was *** types of model synovial fluids and hyaluronic acid(HA)at physiologic concentrations were used in the *** coefficient of friction was measured using a pendulum hip simulator,and Raman spectroscopy was used to perceive chemical reactions between the synovial fluid and implant *** spectra evidenced that the three model fluids and HA chemisorbed onto the cobalt-chromium ***α-helix structure of the model fluid components was detected on the surface of the prosthesis.

关键词： material surface experiment

Experimental investigation of laser surface processing of flexure silicon nitride ceramic

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中国有色金属学会会刊：英文版 2006年第B02期16卷 558-565页

作者： SUN Li A. P. MALSHE JIANG Wen-ping P. H. MCCLUSKEY department of mechanical Engineering University of Arkansas Fayetteville AR 72701 USA Technology ＆ Solutions Division Caterpillar Inc. Peoria IL 61629 USA

关键词：氮化硅陶瓷激光表面处理实验研究挠曲强度物理性质

Fabrication and characteristic detection of graphene nanoelectrodes

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Science China(Technological Sciences) 2014年第10期57卷 1950-1955页

作者： XIE ShuangXi LIU ZengLei JIAO NianDong TUNG Steve LIU LianQing State Key Laboratory of Robotics Shenyang Institute of Automation Chinese Academy of Sciences University of Chinese Academy of Sciences department of mechanical Engineering University of Arkansas

Graphene has the advantages of high electrical conductivity,high heat conductivity,and low noise,which makes it a potential option for integrated circuits interconnection and *** this paper,we present a novel fabrication method for graphene nanoeletrodes with ***,graphene grown by chemical vapor deposition(CVD)is assembled to a chip with ***,an atomic force microscopy(AFM)based mechanical cutting method is developed to cut the graphene into nanoribbons and nanoeletrodes with *** the electronic property of a single nanodot is characterized using the garphene nanoelectrodes,demonstrating the effectiveness of the graphene *** fabricated graphene nanoeletrode pairs can be used as probes to detect single molecule in micro-environment,and show an attractive prospect for future molecular electronics applications.

关键词： atomic force microscopy graphene nanoelectrodes nanogap molecular electronics