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Mechanistic investigation on Ce addition in tuning recrystallization behavior and mechanical property of Mg alloy

Journal of Materials Science & Technology 2023年第1期132卷 1-17页

作者： J.r.Li D.S.Xie z.r.zeng B.Song H.B.Xie r.S.Pei H.C.Pan Y.P.ren G.W.Qin Key Laboratory for Anisotropy and Texture of Materials(Ministry of Education) College of Materials Science and EngineeringNortheastern UniversityShenyang110819China College of Engineering and Computer Science Australian National UniversityACT 2601Australia School of Materials and Energy Southwest UniversityChongqing 400715China Institute for Physical Metallurgy and Materials Physics RWTH Aachen UniversityAachen 52062Germany

Constructing bimodal grain structure is a promising approach to achieve the high strength-ductility syn-ergy in Mg *** of bimodal grain is closely related to the dynamic and/or static recrystal-lization process,which has not been fully understood in the typical Mg-rE based *** this work,it is claimed for the first time that the minor Ce addition(∼0.3 wt%)into Mg matrix significantly pro-motes the pyramidaland non-basaldislocations at the early stage of extrusion,which con-sequently enhances the formation of sub-grain boundaries via the movement and recovery of pyramidal II-type*** this stage,fine sub-grain lamellae are widely observed predominantly due to the low migration rate of sub-grain boundary caused by the limited mobility of*** the later stage,the sub-grains continuously transform into dynamic recrystallized(DrXed)grains that have10¯10Taylor axis and also strong fiber texture,indicating substantial activation of pyramidal II-type*** low mobility ofdislocations,accompanied with the solute drag from grain boundary(GB)segregation and pinning from nano-phases,cause a sluggish DrX process and thus a bimodal microstructure with ultra-fined DrXed grains,∼0.51μ*** resultant texture hardening and grain refinement hardening effects,originated from bimodal microstructure,result in a yield strength of∼352 MPa,which is exceptional in Mg-Ce dilute *** work clarifies the critical role of Ce addition in tuning recrystallization behavior and mechanical property of magnesium,and can also shed light on designing the other high-performance Mg alloys.

关键词： Mg alloys recrystallization behavior Mechanical property Pyramidal dislocation Thermal stability

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Electron localization of H_2^+ in a dc electric field

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Chinese Physics B 2017年第1期26卷 170-175页

作者： z M Jia z N zeng W T Tang r X Li State Key Laboratory of High Field Laser Physics Shanghai Institute of Optics and Fine Mechanics Chinese Academy of Sciences Shanghai 201800 China Signal and Information Processing Jingchu University of Technology Jingmen 448000 China

A dc electric field is utilized to steer the electron motion after the molecular ion H2-＋ is excited by an ultrashort ultraviolet laser pulse. The numerical simulation shows that the electron localization distribution and the dissociation control ratio are dependent on the polarization direction and amplitude of the dc electric field. Most electrons of the dissociation state move opposite to the dc electric field and stabilize at the dressed-up potential well, for the dressed-down well is occupied by the electrons of the 1 sσg state.

关键词： dissociation localization time dependent Schrdinger equation Coulomb potential ultraviolet laser pulse

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Inactivation, reactivation and regrowth of indigenous bacteria in reclaimed water after chlorine disinfection of a municipal wastewater treatment plant

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Journal of Environmental Sciences 2013年第7期25卷 1319-1325页

作者： Dan Li Siyu zeng April z. Gu Miao He Hanchang Shi Environmental Simulation and Pollution Control State Key Joint Laboratory School of Environment Tsinghua University Department of Civil and Environmental Engineering Northeastern University

Disinfection of reclaimed water prior to reuse is important to prevent the transmission of pathogens. Chlorine is a widely utilized disinfectant and as such is a leading contender for disinfection of reclaimed water. To understand the risks of chlorination resulting from the potential selection of pathogenic bacteria, the inactivation, reactivation and regrowth rates of indigenous bacteria were investigated in reclaimed water after chlorine disinfection. Inactivation of total coliforms, Enterococcus and Salmonella showed linear correlations, with constants of 0.1384, 0.1624 and 0.057 L/（mg·min） and r 2 of 0.7617, 0.8316 and 0.845, respectively. However, inactivation of total viable cells by measurement of metabolic activity typically showed a linear correlation at lower chlorine dose （0-22 （mg·min）/L）, and a trailing region with chlorine dose increasing from 22 to 69 （mg·min）/L. reactivation and regrowth of bacteria were most likely to occur after exposure to lower chlorine doses, and extents of reactivation decreased gradually with increasing chlorine dose. In contrast to total coliforms and Enterococcus, Salmonella had a high level of regrowth and reactivation, and still had 2% regrowth even after chlorination of 69 （mg·min）/L and 24 hr storage. The bacterial compositions were also significantly altered by chlorination and storage of reclaimed water, and the ratio of Salmonella was significantly increased from 0.001% to 0.045% after chlorination of 69 （mg·min）/L and 24 hr storage. These trends indicated that chlorination contributes to the selection of chlorine-resistant pathogenic bacteria, and regrowth of pathogenic bacteria after chlorination in reclaimed water with a long retention time could threaten public health security during wastewater reuse.

关键词： inactivation regrowth reactivation indigenous bacteria reclaimed water

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Determination of strain-dependent soil water retention characteristics from gradation curve

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Journal of rock Mechanics and Geotechnical Engineering 2020年第6期12卷 1356-1360页

作者： Min Wang GNPande Stan Pietruszczak z.X.zeng zienkiewicz Centre for Computational Engineering Swansea UniversitySwanseaSA18ENUK Civil Engineering McMaster UniversityHamiltonOntarioL8S 4L8Canada École des Ponts ParisTech Champs-sur-MarneMarne-la-Vallée77455France

The importance of soil water retention characteristics in modelling the hydro-mechanical response of unsaturated soils has been well recognised by many investigators in recent *** of strain-dependent soil water retention curve(SWrC)is likely to be extraordinarily *** first two authors have recently shown that SWrC can be computed from the gradation curve and the calculation result is consistent with the experimental results obtained from pressure plate *** this paper,based on a hypothesis related to change in the pore size distribution(POSD)due to volumetric strain of soil skeleton,a method to compute strain-dependent SWrC is *** is found that at initial degrees of saturation higher than 0.8,the influence of volumetric strain may be marginal whilst at initial degrees of saturation lower than 0.8,its influence is likely to be *** all cases,the gradation curve of the soil affects the SWrC.

关键词： Soil water retention curve(SWrC) Gradation curve Pore size distribution(POSD) Unsaturated soil

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Evaluation of the infectivity,gene and antigenicity persistence of rotaviruses by free chlorine disinfection

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Journal of Environmental Sciences 2011年第10期23卷 1691-1698页

作者： Dan Li April z. Gu Siyu zeng Wan Yang Miao He Hanchang Shi Environmental Simulation and Pollution Control （ESPC） State Key Joint Laboratory School of Environment Tsinghua University Beijing 100084 China Department of Civil and Environmental Engineering Northeastern University Boston MA 02115 USA

The effects of free chlorine disinfection of tap water and wastewater effluents on the infectivity, gene integrity and surface antigens of rotaviruses were evaluated by a bench-scale chlorine disinfection experiments. Plaque assays, integrated cell culture-quantitative rT- PCr （ICC-rT-qPCr）, rT-qPCr, and enzyme-linked immunosorbent assays （ELISA）, respectively, were used to assess the influence of the disinfectant on virus infectivity as well as genetic and antigenic integrity of simian rotavirus SA11 as a surrogate for human rotaviruses. The ICC-rT-qPCr was able to detect rotaviruses survival from chlorine disinfection at chlorine dose up to 20 mg/L （60 min contact）, which suggested a required chlorine dose of 5 folds （from 1 to 5 mg/L） higher than that indicated by the plaque assay to achieve 1.8 log10 reductions in tap water with 60 rain exposing. The VP7 gene was more resistant than the infectivity and existed at chlorine dose up to 20 mg/L （60 min contact）, while the antigencity was undetectable with chlorine dose more than 5 mg/L （60 min contact）. The water quality also impacted the inactivation efficiencies, and rotaviruses have a relatively higher resistant in secondary effluents than in the tap water under the same chlorine disinfection treatments. This study indicated that rotaviruses have a higher infectivity, gene and antigencity resistance to chlorine than that previously indicated by plaque assay only, which seemed to underestimate the resistance of rotaviruses to chlorine and the risk of rotaviruses in environments. Present results also suggested that re-evaluation of resistance of other waterborne viruses after disinfections by more sensitive infectivity detection method （such as ICC-rT-qPCr） may be necessary, to determine the adequate disinfectant doses required for the inactivation of waterborne viruses.

关键词： rotaviruses free chlorine disinfection infectivity genes antigenicity ICC-rT-qPCr

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Improving the hard magnetic properties by intragrain pinning for Ta doped nanocrystalline Ce-Fe-B alloys

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Journal of Materials Science & Technology 2019年第9期35卷 1877-1885页

作者： J.S.zhang W. Li X.F. Liao H.Y. Yu L.z. zhao H.X. zeng D.r. Peng z.W. Liu School of Materials Science and Engineering South China University of TechnologyGuangzhou510640China Innovative Center for Advanced Materials (ICAM) Hangzhou Dianzi UniversityHangzhou310012China

To develop Ce based permanent magnets with high performance/cost ratio, Ta doping is was employed to enhance the magnetic performance of Ce-Fe-B alloys. For melt spun Cei7Fe78-xTaxB6 (x = 0-1) alloys, the coercivity Hc increases from 439 to 553 kA/m with increasing x value from 0 to 0.75. Microstructure characterizations indicate that Ta doping is helpful for grain refinement. A second phase of TaB2 is observed in Ce17Fe77.25Tao.75B6 alloy, which acts as the pinning center of the magnetic domains, resulting in the change of coercivity mechanism from nucleation type to nucleation +pinning type. The micromagnetic simulation confirms that non-magnetic particles within hard magnetic phase can increase the demagnetization field around them and it is crucial for preventing the further magnetization reverse by pinning effect. Take the advantage of Ta doping for enhancing the coercivity, Ce content of Ce-Fe-B alloy can be further cut down to increase the remanence Jr due to the reduced volume fraction of CeFe2 phase and increased Fe/Ce ratio. As a result, a good combination of magnetic properties with Hc = 514 kA/m, Jr = 0.49 T, and the maximum energy product (BH)max = 36 kJ/m^3 have been obtained in Ce15Fe79.25Tao.75B6 alloy. It is expected that the present work can serve as a useful reference for designing new permanent magnetic materials with low-cost.

关键词： Melt-spinning Permanent magnets Second phase Coercivity mechanism Thermal stability

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MICrOSTrUCTUrE AND ELECTrOCHEMICAL CHArACTErISTICS OF zr_(0.9)Ti_(0.1)(Ni_(1.1)Mn_(0.7)V_(0.2))_x METAL HYDrIDE ELECTrODE

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Acta Metallurgica Sinica(English Letters) 2003年第3期16卷 192-196页

作者： S.M.Han M.S.zhao Y.z.zeng Department of Environmental and Chemical Engineering Yanshan University Qinhuangdao 066004China Key Laboratory of Rare Earth Chemistry and PhysicsChangchun Institute of Applied Chemistry The Chinese Academy of SciencesChangchun 130022 ChinaDepartment of Environmental and Chemical Engineering Yanshan University Qinhuangdao 066004China Key Laboratory of Rare Earth Chemistry and PhysicsChangchun Institute of Applied Chemistry The Chinese Academy of SciencesChangchun 130022 ChinaDepartment of Environmental and Chemical Engineering Yanshan UniversityQinhuangdo 066004 China

The crystal structure, the phase composition and the electrochemical characteristics of zr0.9Ti0.1(Ni1.1Mn0.7V0.2)x (x=0.90, 0.95, 1.00, 1.05) alloys were investigated by means of XrD, SEM, EDS and electrochemical measurements. It was shown that all alloys are multiphase with C15 Laves phase as a main phase along with C14 phase and some secondary phases. And the amounts of the C14 phase and secondary phases in the four alloys increases with decreasing x. The results indicated that the various stoichiometric ratios have great effects on the electrochemical characteristics such as the maximum discharge capacity, discharge rate capability and self-discharge properties etc. for zr0.9Ti0.1(Ni1.1Mn0.7 V0.2)X (x=0.90, 0.95, 1.00, 1.05) alloys. The hyper-stoichiometric zr0.9 Ti0.1(N1.1Mn0.7 V0.20)1.05 exhibits the maximum discharge capacity of 332mAh-g-1. The C14 phase and secondary phases seems to improve discharge rate capability of the alloys.

关键词： metal hydride electrode microstructure electrochemical characteristics non-stoichiometric ratio

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ATOMIzATION CAUSED BY BOTTOM FLOW ENErGY DISSIPATION

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Journal of Hydrodynamics 2001年第1期13卷 23-27页

作者： Hu, M.L. Liang, z.C. zeng, Y.H. Wuhan Univ. of Hydraulic and Electr. Wuhan 430072 China

Bottom flow energy dissipation is one of the common energy dissipation methods for flood-releasing structures with high water head. Measures of this energy dissipation depend mainly on the turbulent action of hydraulic jump. In this paper, the physical process and the calculating methods of the atomization caused by bottom flow energy dissipation were studied, the computation models of atomization quantity for the self-aerated flow in overflow and hydraulic jump regions are presented, and the main results are of theoretical and practical significance for the hydraulic and electric engineering.

关键词： Energy dissipation Hydraulic jump Hydrodynamics

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Microstructural evolution of aluminum alloy during friction stir welding under different tool rotation rates and cooling conditions

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Journal of Materials Science & Technology 2019年第6期35卷 972-981页

作者： X.H. zeng P. Xue L.H. Wu D.r. Ni B.L. Xiao K.S. Wang z.Y. Ma Shenyang National Laboratory for Materials Science Institute of Metal Research Chinese Academy of Sciences Shenyang 110016 China University of Chinese Academy of Sciences Beijing 100049 China School of Metallurgical Engineering Xi'an University of Architecture and Technology Xi'an 710055 China

The microstructural evolution during friction stir welding(FSW) has long been studied only using one single welding parameter. Conclusions were usually made based on the final microstructure observation and hence were one-sided. In this study, we used the "take-action" technique to freeze the microstructure of an Al-Mg-Si alloy during FSW, and then systematically investigated the microstructures along the material flow path under different tool rotation rates and cooling conditions. A universal characteristic of the microstructural evolution including four stages was identified, i.e. dynamic recovery(DrV), dislocation multiplication, new grain formation and grain growth. However, the dynamic recrystallization(DrX)mechanisms in FSW depended on the welding condition. For the air cooling condition, the DrX mechanisms were related to continuous DrX associated with subgrain rotation and geometric DrX at high and low rotation rates, respectively. Under the water cooling condition, we found a new DrX mechanism associated with the progressive lattice rotation resulting from the pinning of the second-phase *** on the analyses of the influencing factors of grain refinement, it was clearly demonstrated that the delay of DrV and DrX was the efficient method to refine the grains during FSW. Besides, ultra-high strain rate and a short duration at high temperatures were the key factors to produce an ultrafine-grained material.

关键词： Aluminum alloys Grain refinement Dynamic recrystallization Severe plastic deformation Friction stir welding

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Effects of Growth Temperature on Structural and Electrical Properties of Li-N-H Codoped znO

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Journal of Materials Science & Technology 2013年第2期29卷 154-156页

作者： Y.F. Lu z.z. Ye L.P. zhu Y.J. zeng J.Y. Huang B.H. zhao State Key Laboratory of Silicon Materials Department of Materials Science and Engineering Zhejiang University

Effects of growth temperature on the structural and electrical properties of Li-N-H codoped znO thin films grown by DC reactive magnetron sputtering were investigated. Scanning electron microscopy and X-ray diffraction results showed that increasing growth temperature could improve the crystalline quality. But Hall measurement results showed that growth temperature had a nonlinear influence on the electrical property. The variation of electrical properties with the growth temperature was found to be related to the activated concentration of N in znO and the evaporation of Li during the growth process, derived from the Hall measurement and the second ion mass spectroscopy measurement.

关键词： znO Codoped Growth temperature Structural property Electrical property

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