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Friction 2022年第1期10卷 142-158页

作者： Zonglin PAN Qinzhao ZHOU Pengfei WANG dongfeng diao Institute of Nanosurface Science and Engineering(INSE) Guangdong Provincial Key Laboratory of Micro/Nano Optomechatronics EngineeringShenzhen UniversityShenzhen 518060China

Reducing the friction force between the commercial archwire and bracket during the orthodontic treatment in general dental practice has attracted worldwide interest.An investigation on the friction and wear behaviors of the uncoated and carbon film coated stainless steel archwires running against stainless steel brackets was systematically conducted.The carbon films were prepared at substrate bias voltages from+5 to+50 V using an electron cyclotron resonance plasma sputtering system.With increasing substrate bias voltage,local microstructures of the carbon films evolved from amorphous carbon to graphene nanocrystallites.Both static and stable friction coefficients of the archwire-bracket contacts sliding in dry and wet(artificial saliva)conditions decreased with the deposition of carbon films on the archwires.Low friction coefficient of 0.12 was achieved in artificial saliva environment for the graphene sheets embedded carbon(GSEC)film coated archwire.Deterioration of the friction behavior of the GSEC film coated archwire occurred after immersion of the archwire in artificial saliva solution for different periods before friction test.However,moderate friction coefficient of less than 0.30 sustained after 30 days immersion periods.The low friction mechanism is clarified to be the formation of salivary adsorbed layer and graphene sheets containing tribofilm on the contact interfaces.The robust low friction and low wear performances of the GSEC film coated archwires make them good candidates for clinical orthodontic treatment applications.

关键词： friction steel wear

Current-carrying friction in carbon coated ball bearing

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摩擦:英文版 2023年第11期11卷 2008-2020页

作者： Peidong XUE Cheng CHEN Xue FAN dongfeng diao Institute of Nanosurface Science and Engineering(INSE) Guangdong Provincial Key Laboratory of Micro/Nano Optomechatronics EngineeringShenzhen UniversityShenzhen 518060China College of Physics and Optoelectronic Engineering Shenzhen UniversityShenzhen 518060China

In this work,we proposed a method for coating the whole surfaces of bearing balls uniformly by carbon film with a rotatable ball clamp.We studied the carbon/carbon friction with a self-designed currentcarrying ball bearing friction test system.A notable and instant friction force drop of 28%and significant carbon film wear alleviation were found when currents were applied.By using TEM-,SEM-,and EDS-analysis,special carbon stacks with a mixture of large wear particles and oxide were found in the wear areas under current applied condition.We elucidated the current-carrying friction mechanisms as follows:(1)wear particles formation;(2)wear particles charged by tribomicroplasma;(3)formation of surface passivated carbon stacks under electric force;(4)sliding between passivated carbon surfaces.This work may facilitate the development of novel solid-lubricated ball bearings and lay some foundations for current-carrying rolling friction.

关键词： current-carrying friction carbon film ball bearing carbon stack

Superhydrophobic,photo-sterilize,and reusable mask based on graphene nanosheet-embedded carbon(GNEC)film

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Nano Research 2021年第4期14卷 1110-1115页

作者： Zezhou Lin Zheng Wang Xi Zhang dongfeng diao Institute of Nanosurface Science and Engineering Guangdong Provincial Key Laboratory of Micro/Nano Optomechatronics EngineeringShenzhen UniversityShenzhen 518060China Shenzhen Anhio Medical Technology Co. LtdShenzhen 518110China

The 2019 coronavirus disease(COVID-19)has affected more than 200 countries.Wearing masks can effectively cut off the virus spreading route since the coronavirus is mainly spreading by respiratory droplets.However,the common surgical masks cannot be reused,resulting in the increasing economic and resource consumption around the world.Herein,we report a superhydrophobic,photo-sterilize,and reusable mask based on graphene nanosheet-embedded carbon(GNEC)film,with high-density edges of standing structured graphene nanosheets.The GNEC mask exhibits an excellent hydrophobic ability(water contact angle:157.9°)and an outstanding filtration efficiency with 100%bacterial filtration efficiency(BFE).In addition,the GNEC mask shows the prominent photo-sterilize performance,heating up to 110℃quickly under the solar illumination.These high performances may facilitate the combat against the COVID-19 outbreaks,while the reusable masks help reducing the economic and resource consumption.

关键词： COVID-19 graphene nanosheet superhydrophobic photo-sterilize

Direct fabrication of flexible tensile sensors enabled by polariton energy transfer based on graphene nanosheet films

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Nanotechnology and Precision Engineering 2023年第1期6卷 1-11页

作者： Xi Zhang Junchi Ma Wenhao Huang Jichen Zhang Chaoyang Lyu Yu Zhang Bo Wen Xin Wang Jing Ye dongfeng diao College of Mechatronics and Control Engineering Shenzhen UniversityShenzhen 518060China Research Center of Medical Plasma Technology Shenzhen UniversityShenzhen 518060China Shenzhen Milebot Robotics Co. Ltd.Shenzhen 518060China

A fundamental problem in the direct manufacturing of flexible devices is the low melting temperature of flexible substrates,which hinders the development of flexible electronics.Proposed here is an electron-cyclotron-resonance sputtering system that can batch-fabricate devices directly on flexible substrates under a low temperature by virtue of the polariton energy transfer between the plasma and the material.Flexible graphene nanosheet-embedded carbon(F-GNEC)films are manufactured directly on polyimide,polyethylene terephthalate,and polydimethylsiloxane,and how the substrate bias(electron energy),microwave power(plasma flux and energy),and magnetic field(electron flux)affect the nanostructure of the F-GNEC films is investigated,indicating that electron energy and flux contribute to the formation of standing graphene nanosheets in the film.The films have good uniformity of distribution in a large size(17 mm×17 mm),and tensile and angle sensors with a high gauge factor(0.92)and fast response(50 ms)for a machine hand are obtained by virtue of the unique nanostructure of the F-GNEC film.This work sheds light on the quantum manufacturing of carbon sensors and its applications for intelligent machine hands and virtual-reality technology.

关键词： Direct flexible fabrication Graphene nanosheets film Polariton energy transfer Flexible sensor Quantum manufacturing

Frictional behavior of nanostructured carbon films

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Friction 2013年第1期1卷 63-71页

作者： dongfeng diao Chao WANG Xue FAN Key Laboratory of Education Ministry for Modern Design and Rotor-Bearing System School of Mechanical EngineeringXi'an Jiaotong UniversityXi'an 710049China Nanosurface Science and Engineering Research Institute Shenzhen UniversityShenzhen 518060China

We propose a new path for preparing nanostructured carbon films(NCFs)by using electron cyclotron resonance(ECR)plasma sputtering with ion-electron hybrid irradiation for controlling the frictional behavior.The frictional behavior of the NCF was measured by using a pin-on-disk tribometer with a nanoprobe displacement sensor,and the transition curves of the friction coefficient and microdisplacement of the NCFs were examined.The friction mechanism was discussed by transmission electron microscopy(TEM)observation on the wear track.From the results,we found a new method to prepare NCFs,which has the potential to achieve low friction at the early stage of sliding contact.In addition,the technology of ECR plasma with ion-electron hybrid irradiation provides a new vision to rebuild a nanostructured surface from an original surface for controlling the frictional behavior.

关键词： friction nanostructured carbon film(NCF) electron cyclotron resonance(ECR) ion-electron hybrid irradiation

Machine learning accelerated DFT research on platinum-modified amorphous alloy surface catalysts

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Chinese Chemical Letters 2023年第5期34卷 645-649页

作者： Xi Zhang Kangpu Li Bo Wen Jiang Ma dongfeng diao Institute of Nanosurface Science and Engineering Guangdong Provincial Key Laboratory of Micro/NanoShenzhen UniversityShenzhen 518060China College of Mechatronics and Control Engineering Shenzhen UniversityShenzhen 518060China Research Center of Medical Plasma Technology Shenzhen UniversityShenzhen 518060China

Pt-modified amorphous alloy(Pt@PdNiCuP)catalyst exhibits excellent electro-catalytic activity and high experimental durability for hydrogen evolution reaction(HER).However,the physical origin of the catalytically active remains unclear.In this paper,we constructed a distance contribution descriptor(DCD)for the feature engineering of machine learning(ML)potential,and calculated the Gibbs free energies(ΔGH)of 46,000*H binding sites on the Pt@Pd Ni Cu P surface by ML-accelerated density functional theory(DFT).The relationship betweenΔGHand DCD revealed that in the H-Pt distance region of 2.0-2.5 A where the parabolic tail and disordered scatters coexist,the H-metal bonding configuration is mainly the bridge-or hollow-bonding type.The contribution analysis of DCD indicates that the joint effect of Pt,Pd and Ni atoms determines the catalytical behavior of amorphous alloy,which agrees well with experimental results.By counting atomic percentages in different energy intervals,we obtained the atomic ratio for the best catalytic performance(Pt:Pd:Ni:Cu:P=0.33:0.17:0.155:0.16:0.185).Projected density of states(PDOS)show that H 1s orbital,Pt 5d orbital,and Pd 4d orbital form a bonding state at-2 e V.These results provide new ideas for designing more active amorphous alloy catalysts.

关键词： Hydrogen evolution reaction Amorphous alloy Density functional theory Machine learning

Bone-inspired(GNEC/HAPAAm)hydrogel with fatigue-resistance for use in underwater robots and highly piezoresistive sensors

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Microsystems & Nanoengineering 2023年第4期9卷 57-67页

作者： Chaoyang Lyu Bo Wen Yangzhen Bai Daning Luo Xin Wang Qingfeng Zhang Chenyang Xing Tiantian Kong dongfeng diao Xi Zhang Institute of Nanosurface Science and Engineering Guangdong Provincial Key Laboratory of Micro/Nano Optomechatronics EngineeringShenzhen University518060 ShenzhenChina Research Center of Medical Plasma Technology Shenzhen University518060 ShenzhenChina Key Laboratory of Optoelectronic Devices and Systems of Ministry of Education College of Physics and Optoelectronic EngineeringShenzhen University518060 ShenzhenChina Department of Biomedical Engineering School of MedicineShenzhen University518000 ShenzhenChina

A novel bone-inspired fatigue-resistant hydrogel with excellent mechanical and piezoresistive properties was developed,and it exhibited great potential as a load and strain sensor for underwater robotics and daily monitoring.The hydrogel was created by using the high edge density and aspect ratio of graphene nanosheet-embedded carbon(GNEC)nanomaterials to form a three-dimensional conductive network and prevent the expansion of microcracks in the hydrogel system.Multiscale progressive enhancement of the organic hydrogels(micrometer scale)was realized with inorganic graphene nanosheets(nanometer scale).The graphene nanocrystals inside the GNEC film exhibited good electron transport properties,and the increased distances between the graphene nanocrystals inside the GNEC film caused by external forces increased the resistance,so the hydrogel was highly sensitive and suitable for connection to a loop for sensing applications.The hydrogels obtained in this work exhibited excellent mechanical properties,such as tensile properties(strain up to 1685%)and strengths(stresses up to 171 kPa),that make them suitable for use as elastic retraction devices in robotics and provide high sensitivities(150 ms)for daily human monitoring.

关键词： fatigue resistance underwater

Abrasive Wear Mechanisms of Sand Particles Intruding into ATM Roller-scraper Tribosystem

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Chinese Journal of Mechanical Engineering 2011年第5期24卷 905-910页

作者： WU Tonghai diao dongfeng FANG Liang Theory of Lubrication and Bearing Institute Xi＇an Jiaotong University Xi＇an 710049 China Post-doctoral Research Center of Material Science and Engineering Xi＇an Jiaotong University Xi＇an 710049 China

The roller-scraper tribosystem of automatic teller machine（ATM） plays an important role in reliable cash requests.However,the abrasive wear of the polymer tribosystem becomes a prominent problem when operating in sandy environment.The wear behavior of the tribosystem in a simulated sandy environment has been experimentally studied previously.However the abrasive wear mechanism of roller-scraper tribosystems is still unknown to new design.The wear rates of polymer rollers were examined comprehensively and several jumping variations were found in the full data extent.Three wear stages were classified by the magnitude of wear rates,and different dominant wear mechanisms corresponding with different particle diameter were found by examining the worn surfaces.Accordingly a presumption was proposed that wear mechanisms in different stages were correlated with sand particles of different diameter.In a verification experiment,three typical wear mechanisms including cutting,ploughing,and wedging were found corresponding with different wear stages by scanning electron microscope（SEM） examination.A theoretical analysis was carried out with a simplified sphere particle intrusion model and the transfer conditions for different wear mechanisms were studied referring to the slip-field theory.As a main result,three typical wear models versus friction coefficient of particle/roller,and particle radius were mapped with variant hardness of the polymer roller and ratio of contact shear stress to bulk shear stress.The result illuminated the abrasive wear mechanism during particle intrusion.Particularly,the critical transition conditions gave the basis for improving the wear performance of roller-scraper tribosystems in a sandy environment.

关键词： tribosystem,abrasive wear,mechanism

Numerical Analysis on Nanoparticles-laden Gas Film Thrust Bearing

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Chinese Journal of Mechanical Engineering 2013年第4期26卷 675-679页

作者： YANG Zhiru diao dongfeng YANG Lei Key Laboratory of Education Ministry for Modern Design and Rotor-Bearing System Xi'an Jiaotong University Institute of Nanosurface Science and Engineering (INSE) Shenzhen University

Nanoparticles can be taken as additives and added into various fluids to improve their lubricating performances. At present, researches in this area are mainly concentrated on the improvement effects of nanoparticles on the lubricating performances of liquid such as oil and water. Nanoparticles will also affect gas lubrication, but few related studies have been reported. Nanoparticles-laden gas film (NLGF) is formed when adding nanoparticles into gas bearing. Then, the lubricating performances of gas bearing including pressure distribution and load-carrying capacity will change. The variations of pressure distribution and load-carrying capacity in nanoparticles-laden gas film thrust bearing are investigated by numerical method. Taking account of the compressibility of gas and the interactions between gas and nanoparticles, a computational fluid dynamics model based on Navier-Stokes equations is applied to simulate the NLGF flow. The effects of inlet nanoparticles volume fraction and orifice radius on film pressure distribution and load-carrying capacity of the NLGF are calculated. The numerical calculation results show that both of the film land pressure and the maximum film pressure both increase when the nanoparticles are added into gas bearing, and the film pressures increase with the rising of the inlet nanoparticles volume fraction. The nanoparticles have an enhancement effect on load-carrying capacity of the studied bearing, and the enhancement effect becomes greater as the film thickness decrease. Therefore, nanoparticles can effectively improve the lubricating performance of gas bearing. The proposed research provides a theoretical basis for the design of new-type nanoparticles-laden gas film bearings.

关键词： load-carrying capacity pressure distribution nanoparticles-laden gas film computational fluid dynamics

Critical Maximum Contact Pressure for Yielding in Hard Coating under Sliding Contact

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稀有金属材料与工程 2012年第S1期41卷 239-242页

作者： Zhang Pengyu diao dongfeng Wang Zhanjiang Xi An Jiao Tong Univ Sch Mech Engn Key Lab Educ Minist Modern Design & Rotor Bearing Xian 710049 Peoples R China Chongqing Univ State Key Lab Mech Transmiss Chongqing 400030 Peoples R China

In order to design the best combination of the coating and the substrate for preventing the yield,the semi-analytical method(SAM)was used to analyze the von Mises stress distributions in the contact system,and calculate the critical maximum contact pressure for yielding at the interface and surface in hard coating under both normal and tangential loads on three-dimensional elastic half space.From the results,it can be concluded that,to obtain a higher maximum critical contact pressure for the yield at the interface,increasing the substrate hardness and the ratio value of the coating thickness to the Hertzian contact radius(t/a0)is more effective when t/a0 is larger than 0.5 while increasing the substrate hardness or making the friction coefficient smaller is better when t/a0 is very small;to prevent yielding at the surface,choosing a relatively lower friction system or increasing the yield strength ratio of the coating to the substrate(Yf/Yb)will be effective.

关键词： hard coating sliding contact contact pressure three-dimension yield semi-analytical method