Textured surfaces are widely used in engineering components as they can improve tribological properties of sliding contacts, while the detailed behaviors of nanoscale reciprocating sliding contacts of textured surface...Textured surfaces are widely used in engineering components as they can improve tribological properties of sliding contacts, while the detailed behaviors of nanoscale reciprocating sliding contacts of textured surfaces are still lack of study. By using multiscale method, two dimensional nanoscale reciprocating sliding contacts of textured surfaces are investigated. The influence of indentation depth, texture shape, texture spacing, and tip radius on the average friction forces and the running-in stages is studied. The results show that the lowest indentation depth can make all the four textured surfaces reach steady state. Surfaces with right-angled trapezoid textures on the right side are better for reducing the running-in stage, and surfaces with right-angled trapezoid textures on the left side are better to reduce wear. Compared with other textured surfaces, the total average friction forces can be reduced by 82.94%–91.49% for the case of the contact between the tip with radius R = 60rand the isosceles trapezoid textured surface. Besides,the total average friction forces increase with the tip radii due to that bigger tip will induce higher contact areas. This research proposes a detailed study on nanoscale reciprocating sliding contacts of textured surfaces, to contribute to design textured surfaces, reduce friction and wear.展开更多
Studies on surface wettability have received tremendous interest due to their potential applications in research and industrial processes. One of the strategies to tune surface wettability is modifying surface topogra...Studies on surface wettability have received tremendous interest due to their potential applications in research and industrial processes. One of the strategies to tune surface wettability is modifying surface topography at micro-and nanoscales. In this research, periodic micro-and nanostructures were patterned on several polymer surfaces by ultra-precision single point diamond turning to investigate the relationships between surface topographies at the micro-and nanoscales and their surface wettability. This research revealed that single-point diamond turning could be used to enhance the wettability of a variety of polymers, including polyvinyl chloride(PVC), polyethylene 1000(PE1000), polypropylene copolymer(PP) and polytetrafluoroethylene(PFTE), which cannot be processed by conventional semiconductor-based manufacturing processes. Materials exhibiting common wettability properties(θ≈ 90°) changed to exhibit "superhydrophobic" behavior(θ > 150°). Compared with the size of the structures, the aspect ratio of the void space between micro-and nanostructures has a strong impact on surface wettability.展开更多
Contact electrification(CE)is a pretty common phenomenon,but still is poorly understood.The long-standing controversy over the mechanisms of CE related to polymers is particularly intense due to their complexity.In th...Contact electrification(CE)is a pretty common phenomenon,but still is poorly understood.The long-standing controversy over the mechanisms of CE related to polymers is particularly intense due to their complexity.In this paper,the CE between metals and polymers is systematically studied,which shows the evolution of surfaces is accompanied by variations of CE outputs.The variations of CE charge quantity are closely related to the creep and deformation of the polymer and metal surfaces.Then the relationship between CE and polymer structures is put forward,which is essentially determined by the electronegativity of elements and the functional groups in the polymers.The effects of load and contact frequency on the CE process and outputs are also investigated,indicating the increase of CE charge quantity with load and frequency.Material transfer from polymer to metal is observed during CE while electrons transfer from metal to polymer,both of which are believed to have an influence on each other.The findings advance our understanding of the mechanism of CE between metal and polymers,and provides insights into the performance of CE-based application in various conditions,which sheds light on the design and optimization of CE-based energy harvest and self-powered sensing devices.展开更多
Cu-Zn, Cu-Zn-Sn, Cu-Zn-Ni alloys were melted by vacuum smelter. The effect factors to the surface free energy of the alloys such as chemical composition, crystal structure and surface crystal lattice distortion etc. w...Cu-Zn, Cu-Zn-Sn, Cu-Zn-Ni alloys were melted by vacuum smelter. The effect factors to the surface free energy of the alloys such as chemical composition, crystal structure and surface crystal lattice distortion etc. were investigated by OCA30 automatic contact angle test instrument, metallography microscope and XRD instrument etc. Results suggests: adding alloy element to Cu may increase its surface free energy, and the more kinds of alloy elements are added, the more surface free energy increases; the alloy element Sn an increase the surface free energy of Cu-Zn alloy; Cu-Zn alloy with fir-tree crystal structure, great phase discrepancy and obvious composition aliquation has greater surface free energy; Cu-Zn alloy with compounds and serious surface crystal lattice distortion has greater surface free energy.展开更多
Membrane proteins are an important kind of proteins embedded in the membranes of cells and play crucial roles in living organisms, such as ion channels,transporters, receptors. Because it is difficult to determinate t...Membrane proteins are an important kind of proteins embedded in the membranes of cells and play crucial roles in living organisms, such as ion channels,transporters, receptors. Because it is difficult to determinate the membrane protein's structure by wet-lab experiments,accurate and fast amino acid sequence-based computational methods are highly desired. In this paper, we report an online prediction tool called Mem Brain, whose input is the amino acid sequence. Mem Brain consists of specialized modules for predicting transmembrane helices, residue–residue contacts and relative accessible surface area of a-helical membrane proteins. Mem Brain achieves aprediction accuracy of 97.9% of ATMH, 87.1% of AP,3.2 ± 3.0 of N-score, 3.1 ± 2.8 of C-score. Mem BrainContact obtains 62%/64.1% prediction accuracy on training and independent dataset on top L/5 contact prediction,respectively. And Mem Brain-Rasa achieves Pearson correlation coefficient of 0.733 and its mean absolute error of13.593. These prediction results provide valuable hints for revealing the structure and function of membrane proteins.Mem Brain web server is free for academic use and available at www.csbio.sjtu.edu.cn/bioinf/Mem Brain/.展开更多
Most copper current collectors for commercial lithium-ion batteries(LIBs)are smooth copper foils,which cannot form a stable and effective combination with electrode slurry.They are likely to deform or fall off after l...Most copper current collectors for commercial lithium-ion batteries(LIBs)are smooth copper foils,which cannot form a stable and effective combination with electrode slurry.They are likely to deform or fall off after long-term operation,resulting in a sharp decline in battery performance.What is worse is that this condition inevitably causes internal short circuits and thus brings about security risks.In this study,a process route of fabricating the functional surface structures on the surface of a copper collector for LIBs by twice-crisscross micro-plowing(TCMP)is proposed,which provides a new idea and an efficient method to solve the above problems from the perspective of manufacturing.The finite element simulation of TCMP combined with the cutting force test and morphological characterization is conducted to verify the forming mechanism of the surface structures on a copper sheet and its relationship with the processing parameters.The influence of several key processing parameters on the surface characteristics of the copper sheet is comprehensively explored.A series of functions is tested to obtain the optimal parameters for performance improvement of the current collector.Results show that the structured copper sheet with the cutting distance of 250μm,cutting depth of 80μm,and cutting crossing angle of 90°enables the best surface features of the current collector;the contact angle reaches 0°,the slurry retention rate is up to 89.2%,and the friction coefficient reaches 0.074.The battery using the as-prepared structured copper sheet as the current collector produces a specific capacity of 318.6 mAh/g after 50 cycles at a current density of 0.2 C,which is 132.7%higher than the one based on a smooth surface.The capacity reversibility of the sample with the new current collector is much better than that of the traditional samples,yielding a lower impedance.展开更多
Plasma immersion ion implantation(PIII) was used to fabricate micro/nano structures on monocrystalline Si surfaces with different ratios of mixed gases(SF_6/O_2). The micro/nano structures on the surfaces of the sampl...Plasma immersion ion implantation(PIII) was used to fabricate micro/nano structures on monocrystalline Si surfaces with different ratios of mixed gases(SF_6/O_2). The micro/nano structures on the surfaces of the sample were characterized by scanning electron microscopy(SEM) and atomic force microscopy(AFM). The results showed that with increasing ratio of mixed gases(SF_6/O_2), the height of the micro/nano structures first increased and then decreased. Contact-angle measurements indicated that the surfaces' micro/nano structures have an obvious effect on the contact-angle, and could cause a change in surface wettability. The theoretical analysis of contact-angle showed that the Wenzel and Cassie theories cannot predict the contact-angle of a roughened surface accurately, and should be corrected for practical applications using an actual model. Moreover, the contact-angle first increased and then decreased with increasing ratio of mixed gases(SF_6/O_2), which is in accordance with the change of the height of micro/nano structures.展开更多
基金Supported by National Natural Science Foundation of China(Grant Nos.51675429,51205313)Fundamental Research Funds for the Central Universities,China(Grant No.3102014JCS05009)the 111 Project,China(Grant No.B13044)
文摘Textured surfaces are widely used in engineering components as they can improve tribological properties of sliding contacts, while the detailed behaviors of nanoscale reciprocating sliding contacts of textured surfaces are still lack of study. By using multiscale method, two dimensional nanoscale reciprocating sliding contacts of textured surfaces are investigated. The influence of indentation depth, texture shape, texture spacing, and tip radius on the average friction forces and the running-in stages is studied. The results show that the lowest indentation depth can make all the four textured surfaces reach steady state. Surfaces with right-angled trapezoid textures on the right side are better for reducing the running-in stage, and surfaces with right-angled trapezoid textures on the left side are better to reduce wear. Compared with other textured surfaces, the total average friction forces can be reduced by 82.94%–91.49% for the case of the contact between the tip with radius R = 60rand the isosceles trapezoid textured surface. Besides,the total average friction forces increase with the tip radii due to that bigger tip will induce higher contact areas. This research proposes a detailed study on nanoscale reciprocating sliding contacts of textured surfaces, to contribute to design textured surfaces, reduce friction and wear.
基金financial support from Heriot-Watt University (Edinburgh)the Engineering and Physical Sciences Research Council (EP/K018345/1) for this study
文摘Studies on surface wettability have received tremendous interest due to their potential applications in research and industrial processes. One of the strategies to tune surface wettability is modifying surface topography at micro-and nanoscales. In this research, periodic micro-and nanostructures were patterned on several polymer surfaces by ultra-precision single point diamond turning to investigate the relationships between surface topographies at the micro-and nanoscales and their surface wettability. This research revealed that single-point diamond turning could be used to enhance the wettability of a variety of polymers, including polyvinyl chloride(PVC), polyethylene 1000(PE1000), polypropylene copolymer(PP) and polytetrafluoroethylene(PFTE), which cannot be processed by conventional semiconductor-based manufacturing processes. Materials exhibiting common wettability properties(θ≈ 90°) changed to exhibit "superhydrophobic" behavior(θ > 150°). Compared with the size of the structures, the aspect ratio of the void space between micro-and nanostructures has a strong impact on surface wettability.
基金supported by the National Natural Science Foundation of China(Grant Nos.52075249,51505217,51435008,and 51705247)。
文摘Contact electrification(CE)is a pretty common phenomenon,but still is poorly understood.The long-standing controversy over the mechanisms of CE related to polymers is particularly intense due to their complexity.In this paper,the CE between metals and polymers is systematically studied,which shows the evolution of surfaces is accompanied by variations of CE outputs.The variations of CE charge quantity are closely related to the creep and deformation of the polymer and metal surfaces.Then the relationship between CE and polymer structures is put forward,which is essentially determined by the electronegativity of elements and the functional groups in the polymers.The effects of load and contact frequency on the CE process and outputs are also investigated,indicating the increase of CE charge quantity with load and frequency.Material transfer from polymer to metal is observed during CE while electrons transfer from metal to polymer,both of which are believed to have an influence on each other.The findings advance our understanding of the mechanism of CE between metal and polymers,and provides insights into the performance of CE-based application in various conditions,which sheds light on the design and optimization of CE-based energy harvest and self-powered sensing devices.
基金This work was financially supported by the Key Technologies R&D Programme of Tianjin (06YFGZGX02400).
文摘Cu-Zn, Cu-Zn-Sn, Cu-Zn-Ni alloys were melted by vacuum smelter. The effect factors to the surface free energy of the alloys such as chemical composition, crystal structure and surface crystal lattice distortion etc. were investigated by OCA30 automatic contact angle test instrument, metallography microscope and XRD instrument etc. Results suggests: adding alloy element to Cu may increase its surface free energy, and the more kinds of alloy elements are added, the more surface free energy increases; the alloy element Sn an increase the surface free energy of Cu-Zn alloy; Cu-Zn alloy with fir-tree crystal structure, great phase discrepancy and obvious composition aliquation has greater surface free energy; Cu-Zn alloy with compounds and serious surface crystal lattice distortion has greater surface free energy.
基金supported by the National Natural Science Foundation of China(Nos.61671288,91530321,61603161)Science and Technology Commission of Shanghai Municipality(Nos.16JC1404300,17JC1403500,16ZR1448700)
文摘Membrane proteins are an important kind of proteins embedded in the membranes of cells and play crucial roles in living organisms, such as ion channels,transporters, receptors. Because it is difficult to determinate the membrane protein's structure by wet-lab experiments,accurate and fast amino acid sequence-based computational methods are highly desired. In this paper, we report an online prediction tool called Mem Brain, whose input is the amino acid sequence. Mem Brain consists of specialized modules for predicting transmembrane helices, residue–residue contacts and relative accessible surface area of a-helical membrane proteins. Mem Brain achieves aprediction accuracy of 97.9% of ATMH, 87.1% of AP,3.2 ± 3.0 of N-score, 3.1 ± 2.8 of C-score. Mem BrainContact obtains 62%/64.1% prediction accuracy on training and independent dataset on top L/5 contact prediction,respectively. And Mem Brain-Rasa achieves Pearson correlation coefficient of 0.733 and its mean absolute error of13.593. These prediction results provide valuable hints for revealing the structure and function of membrane proteins.Mem Brain web server is free for academic use and available at www.csbio.sjtu.edu.cn/bioinf/Mem Brain/.
基金the support from National Natural Science Foundation of China(No.51975218)Natural Science Foundation of Guangdong Province(No.2021A1515010642)+1 种基金Science and Technology Plan Program of Guangdong Province(No.2021A0505110002)S&T Innovation Projects of Zhuhai City(ZH01110405180034PWC).
文摘Most copper current collectors for commercial lithium-ion batteries(LIBs)are smooth copper foils,which cannot form a stable and effective combination with electrode slurry.They are likely to deform or fall off after long-term operation,resulting in a sharp decline in battery performance.What is worse is that this condition inevitably causes internal short circuits and thus brings about security risks.In this study,a process route of fabricating the functional surface structures on the surface of a copper collector for LIBs by twice-crisscross micro-plowing(TCMP)is proposed,which provides a new idea and an efficient method to solve the above problems from the perspective of manufacturing.The finite element simulation of TCMP combined with the cutting force test and morphological characterization is conducted to verify the forming mechanism of the surface structures on a copper sheet and its relationship with the processing parameters.The influence of several key processing parameters on the surface characteristics of the copper sheet is comprehensively explored.A series of functions is tested to obtain the optimal parameters for performance improvement of the current collector.Results show that the structured copper sheet with the cutting distance of 250μm,cutting depth of 80μm,and cutting crossing angle of 90°enables the best surface features of the current collector;the contact angle reaches 0°,the slurry retention rate is up to 89.2%,and the friction coefficient reaches 0.074.The battery using the as-prepared structured copper sheet as the current collector produces a specific capacity of 318.6 mAh/g after 50 cycles at a current density of 0.2 C,which is 132.7%higher than the one based on a smooth surface.The capacity reversibility of the sample with the new current collector is much better than that of the traditional samples,yielding a lower impedance.
基金financially supported by NSFC Project(Grant No.51376022)
文摘Plasma immersion ion implantation(PIII) was used to fabricate micro/nano structures on monocrystalline Si surfaces with different ratios of mixed gases(SF_6/O_2). The micro/nano structures on the surfaces of the sample were characterized by scanning electron microscopy(SEM) and atomic force microscopy(AFM). The results showed that with increasing ratio of mixed gases(SF_6/O_2), the height of the micro/nano structures first increased and then decreased. Contact-angle measurements indicated that the surfaces' micro/nano structures have an obvious effect on the contact-angle, and could cause a change in surface wettability. The theoretical analysis of contact-angle showed that the Wenzel and Cassie theories cannot predict the contact-angle of a roughened surface accurately, and should be corrected for practical applications using an actual model. Moreover, the contact-angle first increased and then decreased with increasing ratio of mixed gases(SF_6/O_2), which is in accordance with the change of the height of micro/nano structures.
