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Photoinduced self-stability mechanism of CdS photocatalyst:The dependence of photocorrosion and H_(2)-evolution performance

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Journal of Materials Science & Technology 2022年第26期121卷 19-27页

作者： Yuxiao chen wei Zhong Feng chen Ping wang Jiajie fan Huogen Yu School of Chemistry Chemical Engineering and Life Sciencesand State Key Laboratory of Silicate Materials for ArchitecturesWuhan University of TechnologyWuhan 430070China Laboratory of Solar Fuel Faculty of Materials Science and ChemistryChina University of GeosciencesWuhan 430070China School of Materials Science and Engineering Zhengzhou UniversityZhengzhou 450002China

CdS photocorrosion is one of the most important factors that greatly affect the photocatalytic H_(2)-production rate and long-time ***,the reported works about CdS photocorrosion are mainly focused on the surface oxidation by photogenerated holes,while the possible reduction of lattice Cd^(2+) by photogenerated electrons is usually *** this work,the lattice Cd^(2+) reduction by photogenerated electrons during CdS photocorrosion were carefully investigated to reveal its potential effect on the microstructure change and photocatalytic H_(2)-production performance of CdS photocatalyst based on the two typical Na_(2)S-Na_(2)SO_(3) and lactic acid H_(2)-evolution *** was found that many isolated metallic Cd nanoparticles(5–50 nm)were produced on the CdS surface in the Na_(2)S-Na_(2)SO_(3) system,causing its serious destroy of CdS surface and a gradually decreased photocatalytic activity,while only a metallic Cd layer(2-3 nm)is homogeneously coated on the CdS surface in the lactic acid system,leading to an increased H-evolution *** fact,once a certain amount of metallic Cd was produced on the CdS surface,the resulting CdS-Cd composites can present a stable photocatalytic H_(2)-production activity and excellent stability for the final CdS-Cd ***,a photoinduced self-stability mechanism of CdS photocatalyst has been proposed,namely,the spontaneously produced metallic Cd contributes to the transformation of unstable CdS into stable CdS-Cd structure,with the simultaneous realization of final stable H_(2)-evolution performance.

关键词： Photocatalysis H_(2)evolution CdS Photocorrosion Self-stability

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Modeling and Experimental Analysis of Roughness Effect on Ultrasonic Nondestructive Evaluation of Micro-crack

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Chinese Journal of Mechanical Engineering 2021年第6期34卷 126-137页

作者： Zhe wang Zhichao fan Xuedong chen Yihua Kang Jingwei cheng wei chen National Safety Engineering Technology Research Center for Pressure Vessels and Pipeline Hefei General Machinery Research Institute Co.LtdHefei230031China State Key Lab of Digital Manufacturing Equipment&Technology Huazhong University of Science and TechnologyWuhan430074China

A high-precision evaluation of ultrasonic detection sensitivity for a micro-crack can be restricted by a corroded rough surface when the surface microtopography is of the same order of magnitude as the crack *** this study,a back-surface micro-crack is considered as a research target.A roughness-modified ultrasonic testing model for micro-cracks is established based on a multi-Gaussian beam model and the principle of phase-screen *** echo signals of micro-cracks and noises corresponding to different rough front surfaces and rough back surfaces are obtained based on a reference reflector signal acquired from a two-dimensional simulation *** compari-son between the analytical and numerical models shows that the responses of micro-cracks under the effects of dif-ferent corroded rough surfaces can be accurately *** numerical and analytical results show that the echo signal amplitude of the micro-crack decreases significantly with an increase in roughness,whereas the noise ampli-tude slightly ***,the effect of the rough front surface on the echo signal of the micro-crack is greater than that of the rough back *** the root-mean-square(RMS)height of the surface microtopography is less than 15μm,the two rough surfaces have less influence on the echo signals detected by a focused transducer with a frequency of 5 MHz and diameter of 6 mm.A method for predicting and evaluating the detection accuracy of micro-cracks under different rough surfaces is proposed by combining the theoretical model and a finite element ***,a series of rough surface samples containing different micro-cracks are fabricated to experimentally validate the evaluation method.

关键词： Surface roughness Micro-crack Ultrasonic testing model Detection accuracy Evaluation method

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Effect of Microstructures on Elevated-Temperature Wear Resistance of a Hot Working Die Steel

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Journal of Iron and Steel Research International 2011年第10期18卷 47-53页

作者： wei min-xian wang Shu-qi wang Lan chen Kang-min School of Materials Science and Engineering Jiangsu University Zhenjiang 212013 Jiangsu China

Elevated-temperature wear tests under atmospheric conditions at 400 ℃ were performed for a hot working die steel H21 on a pin-on-disk wear tester. The phase and morphology of worn surfaces were examined using XRD and SEM, and the relation of wear resistance to tempered microstructures was studied for H21 steel. XRD patterns exhibit that oxidative wear is a predominated wear mechanism with Fe3O4 and Fe2O3 on worn surfaces. It is found that with increasing normal load, obvious plastic deformation of substrate appears on worn surfaces. Microstructures start to affect apparently wear resistance of the steel with an increase of load. Under loads of 50--100 N, wear losses of steel retain low values and relatively approach for steels with various microstructures. As loads are increased to 150--200 N, wear losses of steel start to increase obviously and present apparent difference for steel with various microstructures. Wear resistance is found to increase in the sequence as follows., tempered sorbite, tempered martensite, tempered troostite without secondary hardening and tempered troostite with secondary hardening or upcoming one. Higher strength and microstructural stability are required for steels with excellent wear resistance.

关键词： steel heat treatment microstructure wear wear resistance

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Progress on RE2O3-Mo/W matrix secondary emitter materials

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Science China(Technological Sciences) 2017年第10期60卷 1439-1446页

作者： wang JinShu DONG LiRan LIU wei YANG fan chen ShuQun School of Materials Science and Engineering Beijing University of Technology Beijing 100124 China

Two types of secondary emitter materials, the rare earth oxides(RE_2O_3) doped Mo cermet cathodes and the Y_2O_3-W matrix pressed cathode, are introduced in this paper. According to the calculation results, Y_2O_3 exhibits the best secondary emission property among Y_2O_3,La_2O_3,CeO_2 and Lu_2O_3. The rare earth oxides co-doped Mo cathodes in which Y_2O_3 is the main active substance exhibit better secondary emission property than single RE_2O_3 doped Mo cathode. The results obtained by the Monte-Carlo calculation method show that the secondary electron emission property is strongly related to the grain size of the cathode. The decreasing of the grain size reduces the positive charge effect of the rare earth oxide due to the electrons supplement from the metal to the rare earth oxide, whereby the secondary electrons are easier to escape into the vacuum. Y_2O_3 is introduced into Ba-W cathode to fabricate a pressed Y_2O_3-W matrix dispenser cathode. The result indicates that the secondary emission yield of the Ba-W cathode increases from 2.13 to 3.51 by adding Y_2O_3, and the thermionic emission current density(J_0) could reach 4.18 A/cm^2 at 1050 ℃b.

关键词： rare earth oxide molybdenum tungsten cathode

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Hydrothermal synthesis of manganese oxide encapsulated multiporous carbon nanofibers for supercapacitors

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Nano Research 2016年第9期9卷 2672-2680页

作者： Haiyan wang Jiang Deng Yiqing chen fan Xu Zhongzhe wei Yong wang Advanced Materials and Catalysis Group ZJU-NHU United R&D CenterCenter for Chemistry of High-Performance and Novel MaterialsDepartment of ChemistryZhejiang UniversityHangzhou 310028China

Hydrothermal carbonization (HTC) of biomass to produce one-dimensional carbon materials with hierarchical pores is of significant importance. Here, we fabricate composites of MnOx-encapsulated multiporous carbon nanofibers (M-MCNFs) from naturally available carbohydrates through a dopamine-assisted HTC/ templating process. The introduction of dopamine aids in the formation of the morphology of carbon nanofibers (CNFs) by enhancing the interactions between the hard-templates and carbohydrates. The chosen cryptomelane hard-templates, which are superior to traditional hard-templates, are converted into Mn3O4nanoparticles embedded in multiporous CNFs (MCNFs), eliminating the need for tedious post deposition procedures to introduce redox active sites. Hence, the obtained hybrids with large surface areas, hierarchical pores, and unique structures show great potential in supercapacitors. This economic and sustainable strategy paves a new way for synthesizing MCNFs and metal oxide-encapsulated MCNFs composites from biomass. [Figure not available: see fulltext.] © 2016, Tsinghua University Press and Springer-Verlag Berlin Heidelberg.

关键词： hydrothermal carbonization multiporous carbon nanofiber manganese oxide encapsulated supercapacitor

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Ternary layered boride MoAlB:A novel thermo-regulation microwave absorbing ceramic material

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Journal of Advanced Ceramics 2024年第5期13卷 699-710页

作者： Zhangjue wang fan Zhang Nannan wang wei Li Yongqiang chen Hailong wang Rui Zhang Yanqiu Zhu Bingbing fan School of Material Science and Engineering Zhengzhou UniversityZhengzhou 450001China Henan Academy of Sciences Zhengzhou 450046China State Key Laboratory of Featured Metal Materials and Life Cycle Safety for Composite Structures MOE Key Laboratory of New Processing Technology for Nonferrous Metals MaterialsSchool of ResourcesEnvironment and MaterialsGuangxi UniversityNanning 530004China Department of Materials and Earth Sciences Technical University of DarmstadtDarmstadt 64287Germany School of Material Science and Engineering Luoyang Institute of Science and TechnologyLuoyang 471023China Department of Engineering Faculty of EnvironmentScience and EconomyUniversity of ExeterExeter EX44QFUK

In the context of the fifth-generation(5G)smart era,the demand for electromagnetic wave(EMW)-absorbing materials has become increasingly prominent,so it is necessary to explore promising candidate *** work focuses on the exploration of the material absorbing properties of a MoAlB MAB(MAB represents a promising group of alternatives,where M stands for a transition metal,A typically denotes Al,and B is boron)phase ***,the first-principles calculations were performed to reveal the unique crystal and layered structure of the MoAlB ceramics and to predict their potential for use as an EMW absorption ***,a series of MoAlB ceramics were synthesized at temperatures ranging from 800 to 1300℃,and the influence of temperature on the phase compositions and microstructures of the obtained MoAlB ceramics was characterized and ***,the practical EMW absorption performance of the prepared MoAlB ceramics was evaluated via a combination of experiments and radar cross-sectional *** MoAlB sample synthesized at 900℃ exhibits superior EMW absorption performance,achieving an impressive minimum reflection loss(RL)of−50.33 *** unique layered structure and good electrical conductivity of the MoAlB samples are the main reasons for their enhanced wave absorption performance,which provides interfacial polarization and multiple dielectric loss ***,this study not only contributes to the understanding of the preparation of MoAlB materials but also provides potential guidance for their utilization in the realm of electromagnetic wave absorption.

关键词： MoAlB electronic band structure electromagnetic wave(EMW)absorption layered ternary boride density of states

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Space view of the decadal variation for typical air pollutants in the Pearl River Delta （PRD） region in China

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Frontiers of Environmental Science & Engineering 2016年第5期10卷 129-142页

作者： Zifeng wang min SHAO Liangfu chen minghui TAO Liuju ZHONG Duohong chen Meng fan Yang wang Xinhui wang State Key Laboratory of Remote Sensing Science Jointly Sponsored by Institute of Remote Sensing and Digital Earth of Chinese Academy of Sciences and Beijing Normal University Beijing 100101 China College of Environmental Sciences and Engineering Peking University Beijing 100876 China Guangdong Environmental Monitoring Center Guangzhou 510308 China

The Pearl River Delta （PRD） is one of the most industrialized, urbanized and populated regions in China, and thus has been long suffering from severe air pollutions. Space data provide a unique perspective for investigating the atmospheric environment at a regional scale. By utilizing multiple satellite retrievals from 2005 to 2013, this study presented, for the first time, the spatial patterns and temporal trends of typical air pollutants over PRD and its vicinity. As viewed from space, aerosol optical depth （AOD）, NO2 and SO2 all had their higher values at the central part of PRD, and showed clear descending gradients as moving to the outskirt of this region. As to the inter-annual variation, all these pollutants had decreasing trends in PRD during the study period, which generally agreed with the relevant in situ measurements. However, the satellite retrievals differed from ground measurements when addressing NO2 and SO2 in the vicinity of PRD. This work also provides the inter-comparison among PRD and three other metropolitan clusters in China： PRD had relatively high AOD, moderate NO2 and low SO2 levels, and it was the only region achieving the effective reduction of NO2 and SO2 during last decade. Unlike the previous three pollutants, HCHO observed by satellite showed very special patterns： it had a relatively homogeneous spatial distribution over both of PRD and its vicinity, and presented an opposite increasing trend from 2005 to 2010. Moreover, PRD had the highest HCHO level among all the metropolitan clusters, hinting a considerable contribution of biogenic origins of HCHO in PRD.

关键词： The Pearl River Delta (PRD) Satellite monitoring Regional air quality Long-term trend HCHO

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The pitch-catch nonlinear ultrasonic imaging techniques for structural health monitoring

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Science China(Technological Sciences) 2021年第12期64卷 2608-2617页

作者： chenG Jingwei DRINKWATER Bruce W. chen XueDong fan ZhiChao chen wei wang Zhe National Safety Engineering Technology Research Centre for Pressure Vessels and Pipelines Hefei General Machinery Research Institute Co.Ltd.Hefei 230031China Department of Mechanical Engineering University of BristolBristol BS81TRUnited Kingdom

Nonlinear ultrasonic imaging techniques in pulse-echo configuration have recently shown their potential to allow the effective separation of nonlinear and linear features in a nonlinear *** this study,two ultrasonic phased arrays are implemented to produce an image of elastic nonlinearity through the parallel-sequential subtraction of the coherently scattered components in the through-transmission acoustic field at the transmission or subharmonic *** parallel mode,a physical focus at each pixel is achieved by firing the transmitters with a predefined delay *** sequential mode,each transmitter is fired in sequence and all the receivers are employed to capture the data *** full matrix captured data can be post-processed and focused synthetically at the target *** images of parallel focusing and sequential focusing are expected to be linearly identical and hence any differences remained on the subtracted image can be related to the nonlinearities arising from the ***,the imaging metric here is defined as the difference between parallel and sequentially focused amplitudes obtained from forward coherently scattered fields at each target ***,the negative influences due to the instrumentation nonlinearities are investigated by studying the remaining relative phase and amplitude at undamaged pixels.A compensation method is implemented to suppress these noises,significantly enhancing the selectivity of nonlinear scattering *** proposed techniques are then implemented to monitor fatigue crack growth in order to explore the capability of these methods as measures of elastic nonlinearity induced by different sizes of small closed *** promising results suggest that nonlinear imaging can be used to monitor crack growth and improve the detectability at early stages.

关键词： pitch-catch coherent measurement nonlinear imaging fatigue crack monitoring ultrasonic phased array nonlinearities decoupling

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Influence of mandrel-cores filling on size effect of cross-section distortion of bimetallic thin-walled composite bending tube

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Chinese Journal of Aeronautics 2023年第3期36卷 421-435页

作者： Yingxia ZHU Miaomiao WAN wei chen Yun wang Wenbin TU fan XU School of Mechanical Engineering Jiangsu UniversityZhenjiang 212013China School of Mechanical Engineering Guilin University of Aerospace TechnologyGuilin 541004China

Two new size factors of cross-section hollow coefficient and bending degree are introduced to reveal the size effect of bending forming of bimetallic composite *** coefficient and bending degree can limit the commonly used bent tube to the size description range of(0,2.00).The evolution laws of the cross-section distortion forms in the hollow coefficient-bending degree interval are revealed as well as the action of the mandrel-cores on the size *** show the mandrel-cores filling can expand the forming limit of the bent tube,but also bring two other forming defects of wrinkle and *** identification factor(hollow coefficient multiply bending degree)provides a method for querying the cross-section distortion forms of all composite bending *** the identification factor interval(0,1.00),the distribution area of bending forming defects of the composite tube is *** thin-walled composite bending tube collapses when identification factor in(0,0.39),wrinkles when identification factor in[0.39,0.50),and ruptures when identification factor in[0.50,1.00).The mathematical model of size effect is derived,by which the average cross-section distortion rate is found to distribute like a radial leaf in the hollow coefficient-bending degree qualified forming *** best forming zone is hollow coefficient 0.46-0.68,and bending degree 0.25-0.47.

关键词： Bending Bimetallic composite tube Cross-section distortion Size factor Size effect Mandrel

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A Stiffness Variable Passive Compliance Device with Reconfigurable Elastic Inner Skeleton and Origami Shell

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Chinese Journal of Mechanical Engineering 2020年第5期33卷 75-87页

作者： Zhuang Zhang Genliang chen weicheng fan wei Yan Lingyu Kong Hao wang Shanghai Key Laboratory of Digital Manufacture for Thin‑walled Structures Shanghai Jiao Tong UniversityShanghai 200240China State Key Laboratory of Mechanical System and Vibration Shanghai Jiao Tong UniversityShanghai 200240China Intelligent Robot Research Center Zhejiang LabHangzhou 311100China

Devices with variable stiffness are drawing more and more attention with the growing interests of human-robot interaction,wearable robotics,rehabilitation robotics,*** this paper,the authors report on the design,analysis and experiments of a stiffness variable passive compliant device whose structure is a combination of a reconfigurable elastic inner skeleton and an origami *** main concept of the reconfigurable skeleton is to have two elastic trapezoid four-bar linkages arranged in *** stiffness variation generates from the passive deflection of the elastic limbs and is realized by actively switching the arrangement of the leaf springs and the passive joints in a fast,simple and straightforward *** kinetostatics and the compliance of the device are analyzed based on an efficient approach to the large deflection problem of the elastic links.A prototype is fabricated to conduct experiments for the assessment of the proposed *** results show that the prototype possesses relatively low stiffness under the compliant status and high stiffness under the stiff status with a status switching speed around 80 ms.

关键词： Variable stiffness Passive compliance device Reconfigurable skeleton Origami shell

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