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Investigations on femtosecond laser-induced surface modification and periodic micropatterning with anti-friction properties on Ti6Al4V titanium alloy

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Chinese Journal of Aeronautics 2022年第4期35卷 521-537页

作者： Xinlei PAN Weifeng HE Zhenbing CAI Xuede WANG Ping LIU Sihai LUO Liucheng ZHOU Science and Technology on Plasma Dynamics Laboratory Air Force Engineering UniversityXi'an 710038China Institute of Aeronautics Engine School of Mechanical EngineeringXi'an Jiao tong UniversityXi'an 710049China Tribology Research Institute Key Lab of Advanced Technologies of MaterialsSouthwest Jiao-tong UniversityChengdu 610031China

Titanium alloys have a wide application in aerospace industries as it has greater strength and low density, but it has poor tribological properties. To improve its friction and wear performance, in present work, a femtosecond laser is used to directly irradiate the Ti6Al4V titanium alloy surface in air conditioning, which results in localized ablation and the formation of periodic microstructures but also a strong pressure wave, propagating the material inside. Through the optimization of processing parameters, surface modification and periodic micropatterning with effective anti-friction properties were successfully induced on the surface. After a treatment of femtosecond laser-induced surface modification(FsLSM), the surface microhardness was improved by 16.6% and compressive residual stress reached-746 MPa. Besides, laser-induced periodic surface structures(LIPSS) with a titanium oxide outer coating were fabricated uniformly on the titanium alloy surface. Rotary ball-on-disk wear experiments revealed that the average coefficient of friction(COF) and wear mass loss of the specimen with Fs LSM treatment were largely reduced by 68.9% and 90% as compared to that of untreated specimens, respectively. It was analyzed that the reason for the remarkable wear resistance was attributed to the comprehensive action of the generation of LIPSS, the titanium oxide outer coating, high amplitude compressive residual stress and gradient grain size distribution on the subsurface during the laser surface treatment. Since the findings here are broadly applicable to a wide spectrum of engineering metals and alloys, the present results offer unique pathways to enhancing the tribological performance of materials.

关键词： Femtosecond laser-induced surface modification laser-induced periodic surface structures Microstructure Titanium alloys Tribological performance

surface Micro-Nano structures on GaN Thin Films induced by 355 nm Nanosecond laser Irradiation

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激光与光电子学进展 2023年第7期60卷 196-202页

作者： Gu Yonggang Niu Jian Yang Jian Dong Fang Xu Hongxing School of Physics and Technology Wuhan UniversityWuhan 430072HubeiChina State Key Laboratory of Precision Spectroscopy East China Normal UniversityShanghai 200062China The Institute of Technological Sciences Wuhan UniversityWuhan 430072HubeiChina

Gallium nitride(GaN)has widespread applications in the semiconductor industry because of its desirable optoelectronic *** fabrication of surface structures on GaN thin films can effectively modify their optical and electrical properties,providing additional degrees of freedom for controlling GaN-based *** with lithography-based techniques,laser processing is maskless and much more *** paper shows how surface micronano structures can be produced on GaN thin films using 355 nm nanosecond laser *** effects of the laser pulse energy,number of pulses,and polarization direction were *** was found that distinct micro-nano structures were formed under different irradiation conditions,and their geometries and elemental compositions were *** results indicate that different types of surface micro-nano structures can be produced on GaN thin films in a controllable manner using 355 nm nanosecond laser *** results of our study provide valuable guidance for the surface modification of GaN-based optoelectronic devices.

关键词： gallium nitride thin films nanosecond laser micro-nano structures laser-induced periodic surface structures

laser-induced periodic surface structured electrodes with 45% energy saving in electrochemical fuel generation through field localization

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Opto-Electronic Advances 2022年第11期5卷 29-44页

作者： Chaudry Sajed Saraj Subhash C.Singh Gopal Verma Rahul A Rajan Wei Li Chunlei Guo GPL Photonics Lab State Key Laboratory of Applied OpticsChangchun Institute of OpticsFine Mechanics and PhysicsChinese Academy of SciencesChangchun 130033China University of Chinese Academy of Sciences(UCAS) Beijing 100049China The Institute of Optics University of RochesterRochesterNY 14627USA

Electrochemical oxidation/reduction of radicals is a green and environmentally friendly approach to generating *** reactions,however,suffer from sluggish kinetics due to a low local concentration of radicals around the electrocatalyst.A large applied electrode potential can enhance the fuel generation efficiency via enhancing the radical concentration around the electrocatalyst sites,but this comes at the cost of ***,we report about a~45%saving in energy to achieve an electrochemical hydrogen generation rate of 3×10^(16) molecules cm^(–2)s^(–1)(current density:10 mA/cm^(2))through localized electric field-induced enhancement in the reagent concentration(LEFIRC)at laser-induced periodic surface structured(LIPSS)*** finite element model is used to simulate the spatial distribution of the electric field to understand the effects of LIPSS geometric parameters in field *** the LIPSS patterned electrodes are used as substrates to support Pt/C and RuO_(2) electrocatalysts,the η_(10) overpotentials for HER and OER are decreased by 40.4 and 25%,***,the capability of the LIPSS-patterned electrodes to operate at significantly reduced energy is also demonstrated in a range of electrolytes,including alkaline,acidic,neutral,and ***,when two LIPSS patterned electrodes were assembled as the anode and cathode into a cell,it requires 330 mVs of lower electric potential with enhanced stability over a similar cell made of pristine electrodes to drive a current density of 10 mA/cm^(2).This work demonstrates a physical and versatile approach of electrode surface patterning to boost electrocatalytic fuel generation performance and can be applied to any metal and semiconductor catalysts for a range of electrochemical reactions.

关键词： electric field localization hotspot formation laser-induced periodic surface structures electrochemical fuel generation overall water splitting

Large-area straight,regular periodic surface structures produced on fused silica by the interference of two femtosecond laser beams through cylindrical lens

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Opto-Electronic Advances 2021年第12期4卷 34-42页

作者： Long Chen Kaiqiang Cao Yanli Li Jukun Liu Shian Zhang Donghai Feng Zhenrong Sun Tianqing Jia State Key Laboratory of Precision Spectroscopy School of Physics and Electronic ScienceEast China Normal UniversityShanghai 200062China Collaborative Innovation Center of Extreme Optics Shanxi UniversityTaiyuan 030006China.

Inhomogeneity and low efficiency are two important factors that limit the application of laser-induced periodic surface structures(LIPSSs),especially on glass *** this study,two-beam interference(TBI)of femtosecond lasers was used to produce large-area straight LIPSSs on fused silica using cylindrical *** with those produced us-ing a single circular or cylindrical lens,the LIPSSs produced by TBI are much straighter and more *** on the laser fluence and scanning velocity,LIPSSs with grating-like or spaced LIPSSs are produced on the fused silica *** structural colors are blue,green,and red,and only green and red,***-like LIPSS patterns oriented in different directions are obtained and exhibit bright and vivid colors,indicating potential applications in surface coloring and anti-counterfeiting logos.

关键词： laser-induced periodic surface structures two-beam interference structural coloring fused silica cylindrical lens