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A semi-analytical approach for calculating the equilibrium structure and radial breathing mode frequency of single-walled carbon nanotubes

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Acta Mechanica Sinica 2016年第6期32卷 1075-1087页

作者： j.gong L.Thompson G.Li Department of Mechanical Engineering Clemson University

A semi-analytical model for determining the equilibrium configuration and the radial breathing mode (RBM) frequency of single-wall carbon nanotubes (CNTs) is presented. By taking advantage of the symmetry characteristics, a CNT structure is represented by five independent variables. A line search optimization procedure is employed to determine the equilibrium values of these variables by minimizing the potential energy. With the equilibrium configuration obtained, the semi-analytical model enables an efficient calculation of the RBM frequency of the CNTs. The radius and radial breathing mode frequency results obtained from the semi-analytical approach are compared with those from molecular dynamics (MD) and ab initio calculations. The results demonstrate that the semi-analytical approach offers an efficient and accurate way to determine the equilibrium structure and radial breathing mode frequency of CNTs.

关键词： Carbon nanotubes Equilibrium structure Radial breathing mode frequency

Modeling flow in naturally fractured reservoirs： effect of fracture aperture distribution on dominant sub-network for flow

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Petroleum Science 2017年第1期14卷 138-154页

作者： j. gong W. R. Rossen Department of Geoscience and Engineering Delft University of Technology 2628 CN Delft The Netherlands

Fracture network connectivity and aperture （or conductivity） distribution are two crucial features controlling flow behavior of naturally fractured reservoirs. The effect of connectivity on flow properties is well documented. In this paper, however, we focus here on the influence of fracture aperture distribution. We model a two dimensional fractured reservoir in which the matrix is impermeable and the fractures are well connected. The fractures obey a power-law length distribution, as observed in natural fracture networks. For the aperture distribution, since the information from subsurface fracture networks is limited, we test a number of cases： log-normal distributions （from narrow to broad）, power-law distributions （from narrow to broad）, and one case where the aperture is pro- portional to the fracture length. We find that even a well- connected fracture network can behave like a much sparser network when the aperture distribution is broad enough （c~ 〈 2 for power-law aperture distributions and σ ≥ 0.4 for log-normal aperture distributions）. Specifically, most fractures can be eliminated leaving the remaining dominant sub-network with 90% of the permeability of the original fracture network. We determine how broad the aperture distribution must be to approach this behavior and the dependence of the dominant sub-network on the parameters of the aperture distribution. We also explore whether one can identify the dominant sub-network without doing flow calculations.

关键词： Naturally fractured reservoir Non-uniformflow Effective permeability Percolation Waterflood

Preparation and Characterization of Multilayered Al/Fe-Mo-Si-B Alloy with Nanostructure

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journal of Materials Science & Technology 1996年第2期12卷 114-118页

作者： Yao, B gong, j Geng, YZ Min, CZ Xing, ZM Wang, AM Ding, BZ Hu, ZQ CHINESE ACAD SCI INST MET RESNATL KEY LAB RSASHENYANG 110015PEOPLES R CHINA

The bulk multilayered Al/Fe-Mo-Si-B alloy with nanostructure was prepared by annealing the alternate layers consisting of metal Al and amorphous (Fe-0.99,Mo-0.01)(78)Si9B13 alloy ribbons for 30 min at 873 K under pressure of 3 similar to 5.5 GPa. The structures and grain sizes of the Fe-Mo Si-B nanocrystalline alloy were measured and analyzed. It was found that the pressure could restrain the growth of the grains and influence the formation of phases. The dependence of grain sizes for alpha-Fe(Mo,Si) and Fe2B on pressure was given. The morphologies of Al/Fe-Mo-Si-B nanocrystalline alloy interfaces were observed by SEM. Two interfacial phases formed at various pressures were established by TEM and EDAX, and an unknown Fe-rich one with nanostructure was also observed. The dependence of the interfacial phases on pressure and its formation and growth mechanism were discussed.

关键词： Nanostructured materials

3-D FINITE ELEMENT ANALYSIS OF THE EFFECT OF WELDING RESIDUAL STRESS ON HYDROGEN DIFFUSION IN HYDROGEN CONTAINED ENVIRONMENT

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Acta Metallurgica Sinica(English Letters) 2007年第5期20卷 347-354页

作者： W.C. jiang j.M. gong j.Q. Tang H. Chen S.T. Tu College of Mechanical and Power Engineering Nanjing University of Technology Nanjing 210009 China

The hydrogen distribution of 16MnR steel weldment in hydrogen contained environment was calculated using the finite element method （ FEM）. The effect of welding residual stress on hydrogen diffusion has been discussed using a 3-D sequential coupling finite element analysis procedure complied by Abaqus code. The hydrogen diffusion coefficient in weld metal, the heat affected zone （HAZ）, and the base metal of the 16MnR steel weldment were measured using the electrochemical permeation technique. The hydrogen diffusion without the effect of stress was also calculated and compared. Owing to the existence of welding residual stress, the hydrogen concentration was obviously increased and the hydrogen wouM diffuse and accumulate in the higher stress region.

关键词： 16MnR steel hydrogen diffusion welding residual stress finite element analysis

Oxidation Performance and Interdiffusion Behaviour of two MCrAlY Coatings on a Fourth-Generation Single-Crystal Superalloy

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Acta Metallurgica Sinica(English Letters) 2022年第4期35卷 679-692页

作者： K.j.Tan j.j.Liang X.G.Wang X.P.Tao j.gong C.Sun Y.Z.Zhou X.F.Sun Institute of Metal Research Chinese Academy of SciencesShenyang 110016China School of Materials Science and Engineering University of Science and Technology of ChinaShenyang 110016China

The oxidation behaviour of a fourth-generation single-crystal superalloy without coating and with two types of MCrAlY coatings at 1140℃was *** results showed that both coatings greatly improved the oxidation resistance of the superalloy,and the addition of Hf further improved the oxidation resistance by pinning the oxide layer into the *** and after oxidation,obvious Cr and Al interdiffusion was *** Cr diffusion induces the precipitation of a topologically close-packed phase,while the diffusion of Al affects the structure of theγ/γ’phase,the solubility of refractory elements,and the formation of an interdiffusion zone.

关键词： Superalloys Metal coatings Oxidation Electron probe microanalyser(EPMA) Element diffusion

Microstructural evolution and mechanical properties of NiCrAlYSi+NiAl/cBN abrasive coating coated superalloy during cyclic oxidation

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journal of Materials Science & Technology 2021年第12期71卷 44-54页

作者： Y.D.Liu j.Sun W.Li W.S.Gu Z.L.Pei j.gong C.Sun School of Materials Science and Engineering University of Science and Technology of China72 Wenhua RoadShenyang 110016China Institute of Metal Research Chinese Academy of Sciences72 Wenhua RoadShenyang 110016China Advanced Research Institute for Multidisciplinary Science Qilu University of Technology(Shandong Academy of Sciences)3501 Daxue RoadJinan 250353China

Cyclic oxidation behavior of Ni Cr Al YSi+Ni Al/c BN abrasive coating at 900°C and the mechanical properties of the coating-substrate system were *** indicated that elemental interdiffusion occurred between the coating and substrate,which caused the formation of interdiffusion zone(IDZ)and secondary reaction zone(SRZ)during aluminization,while their compositions and structures changed with *** N interfacial layer formed at c BN/metallic matrix interface during aluminization,while it transformed into multilayer oxides during *** to the microstructural evolution of these interfaces,the fracture behavior and bending toughness of the system changed greatly during three-point bending ***,the damage mechanisms were discussed.

关键词： Abrasive coating Cyclic oxidation TEM Interface Superalloy

Multimedia model of atrazine in plant-soil-groundwater system with a fugacity approach

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journal of Environmental Sciences 2001年第4期13卷 466-471页

作者： Ye, C.-m. Lei, Z.-f. Wang, X.-j. gong, A.-j. Zheng, H.-h. Res. Cntr. Eco-Environmental Sci. Chinese Academy of Sciences Beijing 100085 China

The application of atrazine in China during the last ten years has led to some environmental problems. In this paper, the multimedia model of atrazine in soil-plant-groundwater system at Baiyangdian Lake area in Northern China was established using a fugacity approach, and verified with observed values. The model involved 7 environmental compartments which are air, groundwater, soil, corn roots, corn stem, corn leaf and kernel of corn. The results showed that the relative errors between calculated and observed values have a mean value of 24.7%, the highest value is 48% and the lowest value is 1.4%. All these values indicated that this multimedia model can be used to simulate the environmental fate of atrazine. Both the calculated and observed values of concentrations of atrazine in plant compartments are in the following order: in corn roots > in corn stem > in kernel of corn > in corn leaf, it exhibited a good regularity. The prediction results indicated that concentrations of atrazine in the groundwater and kernel of corn will override the limitation of 3 μg/L and 0.05 mg/kg respectively.

关键词： Concentration (process) Error detection Groundwater Lakes Plants (botany) Soils

Micro injection of metallic glasses parts under ultrasonic vibration

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journal of Materials Science & Technology 2017年第7期33卷 703-707页

作者： X.Liang j.Ma X.Y.Wu B.Xu F.gong j.G.Lei T.j.Peng R.Cheng Guangdong Provincial Key Laboratory ofMicro/Nano Optomechatronics Engineering College of Mechatronics and Control and Engineering Shenzhen University Shenzhen 518060 China Shenzhen ESUN Exhibition Company Limited Shenzhen 518048. China

This work investigates the evolution of structure and mechanical performance of metallic glasses（MGs）under a proposed rapid forming approach. Through the unique ultrasonic-assisted micro injection method, micro MGs parts with fine dimensional accuracy were successfully fabricated. The temperature during the micro injection is higher than the glass transition temperature and lower than the crystallization temperature. Differential scanning calorimeter curve and X-ray diffraction pattern show that the MGs micro parts keep the amorphous nature after the ultrasonic-assisted micro injection. Our results propose a novel route for the fast forming of MGs and have promising applications in the rapid fabrication of micro scale products and devices.

关键词： Metallic glasses Micro injection Ultrasonic vibration

Magnetic Properties and Coercivity of MnGa Films Deposited on Different Substrates

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journal of Materials Science & Technology 2017年第3期33卷 291-294页

作者： j.N.Feng W.Liu W.j.gong X.G.Zhao D.Kim C.j.Choi Z.D.Zhang Shenyang National Laboratory for Materials Science Institute of Metal Research Chinese Academy of Sciences Powder and Ceramics Division Korea Institute of Materials Science

MnGa films were grown by magnetron sputtering on thermally oxidized Si（Si/SiO2） and glass substrates. Films grown on single-crystal Si（100） substrate with different underlayers were prepared for comparison. It is found that the Si/SiO2 substrate is more suitable for growing high-coercivity MnGa films than the glass substrate, which is the result of the isolated-island-like growth. A coercivity of 9.7 kOe can be achieved for the 10 nm MnGa films grown on Si/SiO2 substrate at substrate temperature TS of 450 °*** experimental conditions are specified by changing the thickness of the MnGa films and the temperature of the substrates.

关键词： Atomic force microscopy Coercivity Magnetic properties Magnetron sputtering Thin film