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Crystallographic orientation effect on cutting-based single atomic layer removal

Wenkun XIE, Fengzhou FANG

《机械工程前沿（英文）》 2020年 第15卷 第4期   页码 631-644 doi: 10.1007/s11465-020-0599-x

摘要： The ever-increasing requirements for the scalable manufacturing of atomic-scale devices emphasize the significance of developing atomic-scale manufacturing technology. The mechanism of a single atomic layer removal in cutting is the key basic theoretical foundation for atomic-scale mechanical cutting. Material anisotropy is among the key decisive factors that could not be neglected in cutting at such a scale. In the present study, the crystallographic orientation effect on the cutting-based single atomic layer removal of monocrystalline copper is investigated by molecular dynamics simulation. When undeformed chip thickness is in the atomic scale, two kinds of single atomic layer removal mechanisms exist in cutting-based single atomic layer removal, namely, dislocation motion and extrusion, due to the differing atomic structures on different crystallographic planes. On close-packed crystallographic plane, the material removal is dominated by the shear stress-driven dislocation motion, whereas on non-close packed crystallographic planes, extrusion-dominated material removal dominates. To obtain an atomic, defect-free processed surface, the cutting needs to be conducted on the close-packed crystallographic planes of monocrystalline copper.

关键词： ACSM     single atomic layer removal mechanism     crystallographic orientation effect     mechanical cutting     Manufacturing III    

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Ionic strength directed self-assembled polyelectrolyte single-bilayer membrane for low-pressure nanofiltration

《化学科学与工程前沿（英文）》 2022年 第16卷 第5期   页码 699-708 doi: 10.1007/s11705-021-2093-3

摘要： Layer-by-layer assembly is a versatile technique for fabricating nanofiltration membranes, where multiple layers of polyelectrolytes are usually required to achieve reasonable separation performance. In this work, an ionic strength directed self-assembly procedure is described for the preparation of nanofiltration membranes consisting of only a single bilayer of poly(diallyldimethylammoniumchloride) and poly(sodium-4-styrenesulfoate). The influence of background ionic strength as well as membrane substrate properties on the formation of single-bilayer membranes are systematically evaluated. Such a simplified polyelectrolyte deposition procedure results in membranes having outstanding separation performance with permeating flux of 14.2 ± 1.5 L∙m–2∙h–1∙bar–1 and Na2SO4 rejection of 97.1% ± 0.8% under a low applied pressure of 1 bar. These results surpass the ones for conventional multilayered polyelectrolyte membranes. This work encompasses an investigation of ionic strength induced coiling of the polyelectrolyte chains and emphasizes the interplay between-polyelectrolyte chain configuration and substrate pore profile. It thus introduces a new concept on the control of membrane fabrication process toward high performance nanofiltration.

关键词： layer-by-layer self-assembly     single bilayer     nanofiltration membrane     desalination    

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Molecular dynamics investigation of mechanical properties of single-layer phagraphene

Ali Hossein Nezhad SHIRAZI

《结构与土木工程前沿（英文）》 2019年 第13卷 第2期   页码 495-503 doi: 10.1007/s11709-018-0492-4

摘要： Phagraphene is a very attractive two-dimensional (2D) full carbon allotrope with very interesting mechanical, electronic, optical, and thermal properties. The objective of this study is to investigate the mechanical properties of this new graphene like 2D material. In this work, mechanical properties of phagraphene have been studied not only in the defect-free form, but also with the critical defect of line cracks, using the classical molecular dynamics simulations. Our study shows that the pristine phagraphene in zigzag direction experience a ductile behavior under uniaxial tensile loading and the nanosheet in this direction are less sensitive to temperature changes as compared to the armchair direction. We studied different crack lengths to explore the influence of defects on the mechanical properties of phagraphene. We also investigated the temperature effect on the mechanical properties of pristine and defective phagraphene. Our classical atomistic simulation results confirm that larger cracks can reduce the strength of the phagraphene. Moreover, it was shown the temperature has a considerable weakening effect on the tensile strength of phagraphene. The results of this study may be useful for the design of nano-devices using the phagraphene.

关键词： phaqraphene     mechanical properties     crack propaqation     molecular dynamics     thermal effects    

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Hierarchical fractal structure of perfect single-layer graphene

T. Zhang, K. Ding

《机械工程前沿（英文）》 2013年 第8卷 第4期   页码 371-382 doi: 10.1007/s11465-013-0279-1

摘要：

The atomic lattice structure of perfect single-layer graphene that can actually be regarded as a kind of hierarchical fractal structure from the perspective of fractal geometry was studied for the first time. Three novel and special discoveries on hierarchical fractal structure and sets were unveiled upon examination of the regular crystal lattices of the single-layer graphene. The interior fractal-type structure was discovered to be the fifth space-filling curve from physical realm. Two efficient methods for calculating the fractal dimension of this fresh member was also provided. The outer boundary curve had a fractal dimension equal to one, and a multi-fractal structure from a naturally existing material was found for the first time. A series of strict self-similar hexagons comprised a rotating fractal set. These hexagons slewed at a constant counterclockwise angle of 19.1° when observed from one level to the next higher level. From the perspective of fractal geometry, these pioneering discoveries added three new members to the existing regular fractal structures and sets. A fundamental example of a multi-fractal structure was also presented.

关键词： hierarchical fractal structure     fractal dimension     the fifth space-filling curve     multi-fractal structure    

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Numerical studies of dynamic behavior of liquid film on single-layer wire mesh with different wettabilities

《化学科学与工程前沿（英文）》   页码 1672-1680 doi: 10.1007/s11705-022-2205-8

摘要： Droplet impacting on the stainless steel wire mesh is very common in chemical devices, like a rotating packed bed. Surface wettability of wire mesh significantly affects the liquid flow pattern and liquid dispersion performance. However, the effect of surface wettability on the impaction phenomena at microscale such as liquid film is still unknown. In this work, the dynamic behavior of liquid film on the surface of wire mesh was analyzed by computational fluid dynamics simulation. The dynamic behavior of liquid film on the surface of wire mesh can be divided into the following three steps: (1) spreading step; (2) shrinkage process; (3) stabilizing or disappearing step. Effects of surface wettability, as well as operating conditions, on wetting area and liquid film thickness were studied. Compared to the hydrophilic wire mesh, the final wetting area of hydrophobic wire mesh is zero in most cases. The average liquid film thickness on the surface of hydrophilic wire mesh is 30.02–77.29 μm, and that of hydrophobic wire mesh is 41.76–237.37 μm. This work provided a basic understanding of liquid film flow at microscale on the surface with various surface wettabilities, which can be guiding the packing optimization and design.

关键词： stainless steel wire mesh     computational fluid dynamics     surface wettability     liquid film     impacting    

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Fabrication and mechanical properties of single-wall carbon nanotubes and hyperbranched diazonium salt

LI Xinyang, FAN Pengwei, TUO Xinlin, WANG Xiaogong

《化学科学与工程前沿（英文）》 2008年 第2卷 第3期   页码 286-290 doi: 10.1007/s11705-008-0058-4

摘要： Acidized single-wall carbon nanotubes (SWNTs) were fabricated into multilayers with a hyperbranched azobenzene-containing polymeric diazonium salt (PDAS) using the layer-by-layer adsorption technique. The fabrication process, multilayer thickness variation, multilayer surface morphology and the interaction between SWNTs and PDAS were monitored by UV-Vis absorption spectroscopy, optical ellipsometry, Atomic Force Microscopy, Scanning Electron Microscopy and Raman spectroscopy. Moreover, the nanomechanical properties of the multilayer films were measured by nanoindentation. All results show that SWNTs and PDAS can be fabricated into multilayers based on the cooperation of electrostatic absorption and chemical cross-linkage between SWNTs and PDAS. Further, this cooperation endows the SWNT/PDAS multilayer films with outstanding nanomechanical properties. The hardness and modulus are about 2.0GPa and 10.0GPa, respectively. Finally, the SWNT/PDAS multilayer film can be peeled off to be a free-standing film.

关键词： PDAS     layer-by-layer     interaction     cooperation     single-wall    

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Influence of damages on static behavior of single-layer cable net supported glass curtain wall: full-scale

Gang SHI, Yongjiu SHI, Yuanqing WANG, Yongzhi ZUO, Xiaohao SHI, Zaoyang GUO,

《结构与土木工程前沿（英文）》 2010年 第4卷 第3期   页码 383-395 doi: 10.1007/s11709-010-0074-6

摘要： The single-layer cable net supported glass curtain wall has been applied in many building structures all over the world. In service, it will inevitably be subject to various damages. To study the influence of such damages on the static behavior of the single-layer cable net supported glass curtain wall, a full-scale model with the outside outline size of 4.85 m × 4.85 m and 4 × 4 grids is designed and tested. Two kinds of damages that are the cable prestress loss and cable anchorage end failure are led into the structure model during the test, and their influence has been investigated. The stiffness contribution of glass panels to the single-layer cable net supported glass curtain wall structure with or without damages and its change have been tested and analyzed. The results show that the maximum change rate of nodal deflection is 13.78% for the damage of cable prestress loss, while the change rate of nodal deflection is between 7% and 22% for the damage of cable anchorage end failure. The influence degree of the damages depends on the ratio of the structure initial stress stiffness change caused by damages to the total stiffness of the structure. The stiffness contribution of glass panels increases with the load increase. Under the same loading condition, the stiffness contribution of glass panels to the damaged structure is greater than that to the intact structure. The stiffness contribution of glass panels reduces the effect of the damages on the structural displacement and the cable tension force, but the glass panel could break if its stiffness contribution is too large.

关键词： single-layer plane cable net supported glass curtain wall     damage     cable prestress loss     cable anchorage end failure     stiffness contribution of glass panels    

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Thermal performance of a single-layer packed metal pebble-bed exposed to high energy fluxes

Shengchun ZHANG, Zhifeng WANG, Hui BIAN, Pingrui HUANG

《能源前沿（英文）》 2021年 第15卷 第2期   页码 513-528 doi: 10.1007/s11708-019-0638-7

摘要： It is difficult to accurately measure the temperature of the falling particle receiver since thermocouples may directly be exposed to the solar flux. This study analyzes the thermal performance of a packed bed receiver using large metal spheres to minimize the measurement error of particle temperature with the sphere temperature reaching more than 700°C in experiments in a solar furnace and a solar simulator. The numerical models of a single sphere and multiple spheres are verified by the experiments. The multiple spheres model includes calculations of the external incidence, view factors, and heat transfer. The effects of parameters on the temperature variations of the spheres, the transient thermal efficiency, and the temperature uniformity are investigated, such as the ambient temperature, particle thermal conductivity, energy flux, sphere diameter, and sphere emissivity. When the convection is not considered, the results show that the sphere emissivity has a significant influence on the transient thermal efficiency and that the temperature uniformity is strongly affected by the energy flux, sphere diameter, and sphere emissivity. As the emissivity increases from 0.5 to 0.9, the transient thermal efficiency and the average temperature variance increase from 53.5% to 75.7% and from 14.3% to 27.1% at 3.9 min, respectively. The average temperature variance decreases from 29.7% to 9.3% at 2.2 min with the sphere diameter increasing from 28.57 mm to 50 mm. As the dimensionless energy flux increases from 0.8 to 1.2, the average temperature variance increases from 13.4% to 26.6% at 3.4 min.

关键词： packed bed     solar thermal power plants     high heat fluxes     radiative heat transfer    

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Phosphorene: Current status, challenges and opportunities

Anandarup Goswami, Manoj B. Gawande

《化学科学与工程前沿（英文）》 2019年 第13卷 第2期   页码 296-309 doi: 10.1007/s11705-018-1783-y

摘要： The field of 2-dimensional (2D) materials has witnessed a sharp growth since its inception and can majorly be attributed to the substantial technical and scientific developments, leading to significant improvements in their syntheses, characterization and applications. In the list of 2D materials, the relatively newer addition is phosphorene, which ideally consists of a single layer of black phosphorous. Keeping in mind the past, and ongoing research activities, this short account offers a brief overview of the present status and the associated challenges in the field of phosphorene-related research, with special emphasis on their syntheses, properties, applications and future opportunities.

关键词： phosphorene     black phosphorous     anisotropy     single layer     thermoelectric     chemical vapor deposition     catalysis     battery     supercapacitor    

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Chemically reactive solute transfer in a boundary layer slip flow along a stretching cylinder

Swati Mukhopadhyay

《化学科学与工程前沿（英文）》 2011年 第5卷 第3期   页码 385-391 doi: 10.1007/s11705-011-1101-4

摘要： This paper presents the distribution of a solute undergoing a first order chemical reaction in an axisymmetric laminar boundary layer flow along a stretching cylinder. Velocity slip condition at the boundary is used instead of no-slip condition. Similarity transformations are used to convert the partial differential equations corresponding to momentum and concentration into highly nonlinear ordinary differential equations. Numerical solutions of these equations are obtained by the shooting method. The velocity decreases with increasing slip parameter. The skin friction as well as the mass transfer rate at the surface is larger for a cylinder than for a flat plate.

关键词： boundary layer     stretching cylinder     partial slip     mass transfer     similarity solution    

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Modeling nanostructured catalyst layer in PEMFC and catalyst utilization

Jiejing ZHANG, Pengzhen CAO, Li XU, Yuxin WANG

《化学科学与工程前沿（英文）》 2011年 第5卷 第3期   页码 297-302 doi: 10.1007/s11705-011-1201-1

摘要： A lattice model of the nanoscaled catalyst layer structure in proton exchange membrane fuel cells (PEMFC) was established by Monte Carlo method. The model takes into account all the four components in a typical PEMFC catalyst layer: platinum (Pt), carbon, ionomer and pore. The elemental voxels in the lattice were set fine enough so that each average sized Pt particulate in Pt/C catalyst can be represented. Catalyst utilization in the modeled catalyst layer was calculated by counting up the number of facets of Pt voxels where “three phase contact” are met. The effects of some factors, including porosity, ionomer content, Pt/C particle size and Pt weight percentage in the Pt/C catalyst, on catalyst utilization were investigated and discussed.

关键词： catalyst layer     PEM fuel cell     lattice model     Monte Carlo method     catalyst utilization    

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Effect of a less permeable stronger soil layer on the stability of non-homogeneous unsaturated slopes

Nabarun DEY, Aniruddha SENGUPTA

《结构与土木工程前沿（英文）》 2020年 第14卷 第6期   页码 1462-1475 doi: 10.1007/s11709-020-0674-8

摘要： Slope failure occurs due to an increase in the saturation level and a subsequent decrease in matric suction in unsaturated soil. This paper presents the results of a series of centrifuge experiments and numerical analyses on a 55° inclined unsaturated sandy slope with less permeable, stronger silty sand layer inclusion within it. It is observed that a less permeable, stronger silty sand layer in an otherwise homogeneous sandy soil slope hinders the infiltration of water. The water content of the slope just above the stronger layer increases significantly, compared to elsewhere. No shear band is found to initiate in a homogeneous sandy soil slope, whereas for a non-homogeneous slope, they initiate just above the less pervious, stronger layer. A discontinuity of the shear zone is also observed for the case of a non-homogeneous soil slope. The factor of safety of a non-homogeneous, unsaturated soil slope decreases because of the less permeable, stronger layer. It decreases significantly if this less permeable, stronger soil layer is located near the toe of the slope.

关键词： non-homogeneous slope     stronger soil layer     factor of safety     centrifuge model test     unsaturated soils    

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存在信道状态估计误差的最大比合并/选择合并分集技术在单输入多输出窃密系统中的遍历保密容量分析 Article

Hui ZHAO, You-yu TAN, Gao-feng PAN, Yun-fei CHEN

《信息与电子工程前沿（英文）》 2017年 第18卷 第4期   页码 578-590 doi: 10.1631/FITEE.1500430

摘要： 在物理层中，本文研究了存在信道估计误差的最大比合并/选择合并的保密容量性能。在一个单输入多输出窃密信道中，信源向一个装备M根接收天线并采用最大比合并/选择合并技术处理多径信号的信宿发送保密信息。与此同时，一个窃密者装备N根接收天线并采用最大比合并/选择合并技术来提高窃密的成功率。我们分别推导了两种情况下遍历保密容量的精确和近似闭式表达式：（1）最大比合并带有信道估计误差；（2）选择合并带有信道延迟。此外，本文得到了高信噪比斜率和高信噪比功率补偿两个重要的参数，它们在高信噪比条件下决定了遍历保密容量。最后，本文通过仿真分析验证了所得到的闭式表达式的准确性。

关键词： 遍历保密容量，最大比合并，加权误差，物理层保密，选择合并，单输入多输出    

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Numerical investigation of the effectiveness of effusion cooling for plane multi-layer systems with different

Dieter BOHN, Robert KREWINKEL

《能源前沿（英文）》 2009年 第3卷 第4期   页码 406-413 doi: 10.1007/s11708-009-0041-x

摘要： Within Collaborative Research Center (SFB) 561 “Thermally Highly Loaded, Porous and Cooled Multi-Layer Systems for Combined Cycle Power Plants” at RWTH Aachen University, an effusion-cooled multi-layer plate configuration is investigated numerically by the application of a three-dimensional in-house fluid flow and heat transfer solver, CHTflow. CHTflow is a conjugate code, which yields information on the temperature distribution in the solid body. This enables a detailed discussion of the effects of a change in materials. The geometrical set-up and the fluid flow conditions derive from modern gas turbine combustion chambers and bladings. Within the SFB, two different multi-layer systems, one consisting of substrate made of CMSX-4 (a single-crystal super-alloy), an MCrAlY-bondoat and a ZrO thermal barrier coating (TBC), and the other consisting of a NiAl-alloy and a graded bondcoat/TBC, have been investigated. The grading will increase the life-span of the TBC as it can better compensate the different thermal expansion coefficients of different materials. The main focus in this study is on the different substrate materials, because the thermal conductivity of the NiAl is considerably higher than that of CMSX-4, which leads to different temperature profiles in the components. The numerical grid for the simulations contains the coolant supply (plenum), the solid body for the conjugate calculations, and the main flow area on the plate. The effusion-cooling is realized by finest drilled shaped holes with a diameter of 0.2mm. The investigation is concentrated on a cooling hole geometry with a laterally widened fan-shaped outlet, contoured throughout, and one without lateral widening that is only shaped in the TBC-region of the system. Two blowing ratios, =0.28 and =0.48, are investigated, both for a hot gas Mach number of 0.25. The results for the lower blowing ratio and the fully contoured hole are discussed as well as those of the higher blowing ratio and the non-laterally widened hole. These represent two characteristic cases.

关键词： conjugate calculation     effectiveness of effusion cooling     multi-layer systems     CMSX-4     NiAl-FG75    

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The influence of manufacturing parameters and adding support layer on the properties of Zirfon

Li XU,Yue YU,Wei LI,Yan YOU,Wei XU,Shaoxing ZHANG

《化学科学与工程前沿（英文）》 2014年 第8卷 第3期   页码 295-305 doi: 10.1007/s11705-014-1433-y

摘要： The composite separator comprising of polysulfone and zirconia was prepared by phase inversion precipitation technique. The influence of manufacturing parameters on its properties was investigated, and the results show that the manufacturing parameters affect the ionic resistance and maximum pore size significantly. A modified composite separator with a support layer was prepared to enhance the tensile strength of separator. By adding support layer, the tensile strength of the separator increases from 1.85 MPa to 13.66 MPa. In order to evaluate the practical applicability of the composite separator, a small-scale industrial electrolytic experiment was conducted to investigate the changes of cell voltage, gas purity and separator stability. The results show that the modified composite separator has a smaller cell voltage and a higher H purity than the asbestos separator, and are promising material for industrial hydrogen production.

关键词： separator     alkaline water electrolysis     manufacturing parameters     support layer    

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标题 作者 时间 类型 操作

Crystallographic orientation effect on cutting-based single atomic layer removal

Wenkun XIE, Fengzhou FANG

期刊论文

Ionic strength directed self-assembled polyelectrolyte single-bilayer membrane for low-pressure nanofiltration

期刊论文

Molecular dynamics investigation of mechanical properties of single-layer phagraphene

Ali Hossein Nezhad SHIRAZI

期刊论文

Hierarchical fractal structure of perfect single-layer graphene

T. Zhang, K. Ding

期刊论文

Numerical studies of dynamic behavior of liquid film on single-layer wire mesh with different wettabilities

期刊论文

Fabrication and mechanical properties of single-wall carbon nanotubes and hyperbranched diazonium salt

LI Xinyang, FAN Pengwei, TUO Xinlin, WANG Xiaogong

期刊论文

Influence of damages on static behavior of single-layer cable net supported glass curtain wall: full-scale

Gang SHI, Yongjiu SHI, Yuanqing WANG, Yongzhi ZUO, Xiaohao SHI, Zaoyang GUO,

期刊论文

Thermal performance of a single-layer packed metal pebble-bed exposed to high energy fluxes

Shengchun ZHANG, Zhifeng WANG, Hui BIAN, Pingrui HUANG

期刊论文

Phosphorene: Current status, challenges and opportunities

Anandarup Goswami, Manoj B. Gawande

期刊论文

Chemically reactive solute transfer in a boundary layer slip flow along a stretching cylinder

Swati Mukhopadhyay

期刊论文

Modeling nanostructured catalyst layer in PEMFC and catalyst utilization

Jiejing ZHANG, Pengzhen CAO, Li XU, Yuxin WANG

期刊论文

Effect of a less permeable stronger soil layer on the stability of non-homogeneous unsaturated slopes

Nabarun DEY, Aniruddha SENGUPTA

期刊论文

存在信道状态估计误差的最大比合并/选择合并分集技术在单输入多输出窃密系统中的遍历保密容量分析

Hui ZHAO, You-yu TAN, Gao-feng PAN, Yun-fei CHEN

期刊论文

Numerical investigation of the effectiveness of effusion cooling for plane multi-layer systems with different

Dieter BOHN, Robert KREWINKEL

期刊论文

The influence of manufacturing parameters and adding support layer on the properties of Zirfon

Li XU,Yue YU,Wei LI,Yan YOU,Wei XU,Shaoxing ZHANG

期刊论文