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Journal of Materials Science & Technology 2023年第1期132卷 201-212页

作者： D.D.Zhang J.Kuang H.Xue J.Y.Zhang g.liu J.Sun State Key Laboratory for Mechanical Behavior of Materials Xi’an Jiaotong UniversityXi’an 710049China

In this work,we designed a novel NiCoCr-based medium-entropy alloy(MEA)strengthened by coher-ent L12-nanoparticles,i.e.,(NiCoCr)92 Al 6 Ta 2(at.%).The strengthening and deformation mechanisms of the material and the coarsening kinetics of the coherent precipitates were systematically investigated.The results indicated that giant precipitation hardening and its synergy with other strengthening contributors confer on the aged material a yield strength as high as 1.0 gPa.Moreover,a unique particle-features-dependent plasticity mechanism was revealed in this alloy.That is,the alloy with a lower volume frac-tion,denser distribution,and finer particles mainly deformed by dislocation planar slip,otherwise,stack-faults-mediated plasticity was favored,rationalized by the cooperative/competitive effect of stack-fault energy,spatial confinement,and applied stress.Furthermore,the coarsening behavior of precipitate fol-lowed a modified Lifshitz-Slyozov-Wagner(LSW)model,and the nanoparticles displayed remarkably su-perior thermal stability compared to most traditional superalloys and reported multicomponent alloys.The superb coarsening resistance of precipitate originated from the coupled effect of intrinsic sluggish diffusion in multi-principal alloys and the dual-roles of Ta species as a precipitate stabilizer.This work provides a new pathway to develop strong-yet-ductile multicomponent alloys as promising candidates for high-temperature applications.

关键词： Medium-entropy alloy Mechanical properties Precipitation hardening Deformation mechanisms Coarsening kinetics

Enhancing the high-temperature creep properties of Mo alloys via nanosized La_(2)O_(3) particle addition

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Journal of Materials Science & Technology 2022年第35期130卷 53-63页

作者： P.M.Cheng C.Yang P.Zhang J.Y.Zhang H.Wang J.Kuang g.liu J.Sun State Key Laboratory for Mechanical Behavior of Materials Xi’an Jiaotong UniversityXi’an 710049China School of Mechanical Engineering Chengdu UniversityChengdu 610106China

Molybdenum(Mo) alloys with different La_(2)O_(3)particle additions(0.6,0.9,1.5 wt.%) were prepared by powder metallurgy to investigate the effect of La_(2)O_(3)particles on microstructural evolution and creep behavior of the alloy.Pure Mo,annealed at 1500℃ for 1 h,presented a fully recrystallized microstructure characterized by equiaxed grains.The alloys doped with La_(2)O_(3)particles(Mo-La_(2)O_(3)alloys),on the other hand,exhibited fibrous grains elongated in the rolling direction of the plate.In contrast to the shape of the grains,the average grain size of the alloys was found to be insensitive to the addition of La_(2)O_(3)particles.Nanosized La_(2)O_(3)particles with diameters ranging from 65 to 75 nm were distributed within the grain interior.Tensile creep tests showed that dislocation creep was the predominant deformation mode at intermediate creep rate(10^(-7)s^(-1)-10^(-4)s^(-1)) in the present alloys.The creep stress exponent and activation energy were found to decrease with increasing temperature,particularly within the low creep rate regime(greater apparent stress exponent and activation energy than pure Mo.A creep constitutive model based on the interaction between particles and dislocations was utilized to rationalize the nanoparticle-improved creep behavior.It was demonstrated that low relaxed efficiency of dislocation line energy,which is responsible for an enhanced climb resistance of dislocations,is the major creep strengthening mechanism in the Mo-La_(2)O_(3)alloys.In addition,the area reduction and creep fracture mode of the Mo-La_(2)O_(3)alloys were found to be a function of the creep rate and temperature,which can be explained by the effect of the two parameters on the creep and fracture mechanisms.

关键词： Mo alloys Nanosized particles Creep strength Deformation and fracture

Unusual He-ion irradiation strengthening and inverse layer thickness-dependent strain rate sensitivity in transformable high-entropy alloy/metal nanolaminates:A comparison of Fe_(50)Mn_(30)Co_(10)Cr_(10)/Cu vs Fe_(50)Mn_(30)Co_(10)Ni_(10)/Cu

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Journal of Materials Science & Technology 2022年第21期116卷 199-213页

作者： Y.F.Zhao H.H.Chen D.D.Zhang J.Y.Zhang Y.Q.Wang K.Wu g.liu J.Sun State Key Laboratory for Mechanical Behavior of Materials Xi’an Jiaotong UniversityXi’an 710049China

In this work,we prepare transformable HEA/Cu nanolaminates(NLs)with equal individual layer thick-ness(h)by the magnetron sputtering technique,i.e.,Fe_(50)Mn_(30)Co_(10)Cr_(10)/Cu and Fe_(50)Mn_(30)Co_(10)Ni_(10)/Cu,and comparatively study He-ion irradiation effects on their microstructure and mechanical properties.It ap-pears that the as-deposited HEA/Cu NLs manifest two size h-dependent hardness regimes(i.e.,increased hardness at small h and hardness plateau at large h),while the He-implanted ones exhibit monotonically increased hardness.Contrary to the fashion that smaller h renders less irradiation hardening in bimetal NLs,the Fe_(50)Mn_(30)Co_(10)Cr_(10)/Cu NLs manifest the trend that smaller h leads to greater irradiation hard-ening.By contrast,the Fe_(50)Mn_(30)Co_(10)Ni_(10)/Cu NLs exhibit the maximum irradiation hardening at a critical h=50 nm.Below this critical size,smaller h results in lower radiation hardening(similar to bimetal NLs),while above this size,smaller h results in greater radiation hardening(similar to Fe_(50)Mn_(30)Co_(10)Cr_(10)/Cu NLs).Moreover,these transformable HEA/Cu NLs display inverse h-dependent strain rate sensitivity(SRS m)before and after He-ion irradiation.Nevertheless,compared with as-deposited samples,the irradi-ated Fe_(50)Mn_(30)Co_(10)Cr_(10)/Cu NLs display reduced SRS,while the irradiated Fe_(50)Mn_(30)Co_(10)Ni_(10)/Cu NLs dis-play enhanced SRS.Such unusual size-dependent irradiation strengthening and inverse h effect on SRS in irradiated samples were rationalized by considering the blocking effects of He bubbles on dislocation nucleation and motion,i.e.,dislocations shearing or bypassing He bubbles.

关键词： High entropy alloy/metal nanolaminates Interfaces Irradiation hardening Strain rate sensitivity Size effects

Designing hetero-structured ultra-strong and ductile Zr-2.5Nb alloys:Utilizing the grain size-dependent martensite transformation during quenching

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Journal of Materials Science & Technology 2022年第30期125卷 198-211页

作者： S.Y.liu J.Y.Zhang J.Kuang X.Y.Bao D.D.Zhang C.L.Zhang J.K.Yang g.liu J.Sun State Key Laboratory for Mechanical Behavior of Materials Xi’an Jiaotong UniversityXi’an 710049China

To further improve the service performance of Zr-2.5Nb alloy worked as pressure tubes in pressurized heavy water reactors,more investigation about the microstructure and thermomechanical processing route of Zr-2.5Nb alloy need to be conducted.In this work,a hetero-structured Zr-2.5Nb alloy was prepared by applying a novel technique.Microstructure analysis reveals that the alloy exhibits a grain sizedependent martensite substructure transition during post-rolling quenching.The hetero-structure consists of equiaxed primaryαgrains and the lamellae groups containing both parallelα’dislocation martensite andα’twin martensite.Compared with the previously reported Zr-Nb alloys,the present Zr-2.5Nb alloys manifest the highest yield strength(∼710 MPa),together with a high ultimate tensile strength(∼844 MPa)and good ductility(∼17.1%).The enhanced mechanical properties are found to arise from the properly controlled fraction/size of the two types of martensite,which not only significantly strengthens the alloy but also contributes to a stronger strain hardening.A model based on the grain-size-dependent critical resolved shear stress for dislocation slip and twinning has been proposed to explain theα’martensite substructures transition at a critical grain size dc=3.3μm.Below this size,the critical resolved shear stress(CRSS)for twinning is higher than that for theslip.Thus,theα’dislocation martensite is more favorable to form.Otherwise,theα’twin martensite would exhibit a high activity.The present work indicates that making use of the grain size-dependent martensite transformation to tailor the heterostructure in Zr alloys is an effective strategy to overcome the strength–ductility trade-off in the material.

关键词： Zr-Nb alloys Heterogeneous structure Martensitic transformation grain size Strength

Effectiveness and safety of acupuncture in treatment of pregnancyrelated symptoms:a systematic review and Meta-analysis

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Journal of Traditional Chinese Medicine 2024年第1期44卷 16-26页

作者： liu Tingting.liu Tongou liu Mingfu School of Traditional Chinese Medicine Clinical Medicine Hubei University of Traditional Chinese MedicineWuhan 430000China First Clinical College of Hubei University of Traditional Chinese Medicine Wuhan 430000China Department of Acupuncture and Tuina Affiliated Hospital of Hubei University of Traditional Chinese MedicineHubei Provincial Hospital of Traditional Chinese MedicineWuhan 430000China

OBJECTIVE:To systematically evaluate the efficacy and safety of acupuncture(AM)in the treatment of pregnancyrelated symptoms such as acute vomiting during pregnancy.METHODS:We comprehensively searched the available literature up to November 2021,including Pub Med,Embase,Cochrane Library,Chinese Biomedical Literature Database,and China National Knowledge Infrastructure Database,for randomized controlled trials(RCTs)on AM for the treatment of severe vomiting,insomnia,pharyngeal and pelvic pain,mood abnormalities,and dyspepsia during pregnancy.RESULTS:Sixteen RCTs with a cumulative sample size of 1178 cases were included.Of these,964 patients were included in the Meta-analysis.The Meta-analysis results showed that AM was more efficient than Western medicine in treating discomfort during pregnancy[odds ratio(OR)=1.19,95%confidence interval(CI)(1.11,1.28),Pgroup in improving the visual analog scale scores[standard mean difference(SMD)=0.62,95%CI(0.53,0.71),Pgroup in improving Numerical Rating Scale(NRS)symptom scores[OR=7.31,95%CI(3.36,15.94),Pgnificant difference in adverse effects between the AM and sham-AM groups and the analgesic drug group[OR=0.70,95%CI(0.39,1.28),P=0.25],but the treatment and control groups had mild adverse effects with a low incidence.CONCLUSIONS:AM is more effective than other treatments or pharmacotherapy alone in the treatment of pregnancy-related symptoms,and is relatively safe.However,the quality of the included trials was rather poor,and high-quality studies are required to confirm our findings.

关键词： acupuncture pregnancy nausea vomiting sleep initiation and maintenance disorders low back pain pelvic pain mood abnormalities Meta-analysis systematic review

Removal of Cr(Ⅵ)by glutaraldehyde-crosslinked chitosan encapsulating microscale zero-valent iron:Synthesis,mechanism,and longevity

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Journal of Environmental Sciences 2024年第8期142卷 115-128页

作者： Yijun Duan Fang.liu Xiang.liu Miao Li School of Environment Tsinghua UniversityBeijing 100084China Transportation Institute of Inner Mongolia University Hohhot 010070China

Microscale zero-valent iron(mZVI)has shown great potential for groundwater Cr(Ⅵ)remediation.However,low Cr(Ⅵ)removal capacity caused by passivation restricted the wide use of mZVI.We prepared mZVI/gCS by encapsulating mZVI in a porous glutaraldehydecrosslinked chitosan matrix,and the formation of the passivation layer was alleviated by reducing the contact between zero-valent iron particles.The average pore diameter of mZVI/gCS was 8.775 nm,which confirmed the mesoporous characteristic of this material.Results of batch experiments demonstrated that mZVI/gCS exhibited high Cr(Ⅵ)removal efficiency in a wide range of pH(2-10)and temperature(5-35℃).Common groundwater coexisting ions slightly affected m ZVI/gCS.The material showed great reusability,and the average Cr(Ⅵ)removal efficiency was 90.41%during eight cycles.In this study,we also conducted kinetics and isotherms analysis.Pseudo-second-order model was the most matched kinetics model.The Cr(Ⅵ)adsorption process was fitted by both Langmuir and Freundlich isotherms models,and the maximum Langmuir adsorption capacity of m ZVI/gCS reached243.63 mg/g,which is higher than the adsorption capacities of materials reported in most of the previous studies.Notably,the column capacity for Cr(Ⅵ)removal of a mZVI/gCS-packed column was 6.4 times higher than that of a mZVI-packed column in a 50-day experiment.Therefore,mZVI/gCS with a porous structure effectively relieved passivation problems of mZVI and showed practical application prospects as groundwater Cr(Ⅵ)remediation material with practical application prospects.

关键词： Chitosan glutaraldehyde mZVI Cr(Ⅵ) groundwater

Frequency Regulation of VSC-MTDC System with Offshore Wind Farms

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Journal of Modern Power Systems and Clean Energy 2024年第1期12卷 275-286页

作者： Haoyu liu Chongru liu North China Electric Power University Beijing 102206China

Frequency regulation of voltage source converter-based multi-terminal high-voltage direct current(VSC-MTDC)system with offshore wind farms enhances the frequency stability by compensating the power for a disturbed AC system.However,it is difficult to reasonably allocate frequency-regulation resources due to a lack of coordination mechanisms between wind farms and the MTDC system.Moreover,it is difficult for the frequency control of the wind farms to manage changes in wind speed;and the risk of wind-turbine stalls is high.Thus,based on the kinetic energy of wind turbines and the power margin of the converters,the frequency-regulation capability of wind turbines is evaluated,and a dynamic frequency-support scheme considering the real-time frequency-support capability of the wind turbines and system frequency evolution is proposed to improve the frequency-support performance.A power adaptation technique at variable wind speeds is developed;the active power in the frequency-support stage and restoration stage is switched according to the wind speed.A hierarchical zoning frequency-regulation scheme is designed to use the frequency-regulation resources of different links in the MTDC system with wind farms.The simulation results show that the novel frequency-regulation strategy maintains frequency stability with wind-speed changes and avoids multiple frequency dips.

关键词： Wind generation voltage source converter-based multi-terminal high-voltage direct current(VSC-MTDC) frequency regulation cooperative control adaptive control variable wind speed

Characteristics and sources of peroxyacetyl nitrate(PAN)in the rural North China Plain:Results from1-year continuous observations

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Journal of Environmental Sciences 2024年第4期138卷 719-731页

作者： Xin liu Xiaowei He Chenglong Zhang Yifei Song Shuyang Xie Chengtang.liu Pengfei liu Yuanyuan Zhang Yujing Mu Junfeng.liu Research Center for Eco-Environmental Sciences Chinese Academy of SciencesBeijing 100085China University of Chinese Academy of Sciences Beijing 100049China

Peroxyacetyl nitrate(PAN)is an important photochemical pollutant in the troposphere,whereas long-term measurements are scarce in rural areas in North China Plain(NCP),resulting in unclear seasonal variations and sources of PAN in rural NCP.In this study,we conducted a 1-year observation of PAN during 2021-2022 at the rural NCP site.The average concentrations of PAN were 1.10,0.75,0.65,and 0.88 ppbv in spring,summer,autumn,and winter,respectively,with a 1-year average of 0.81±0.60 ppbv.Calculations indicate that the loss of PAN through thermal decomposition in summer accounts for 43.2% of the total formed PAN,which is an important reason for the low concentration of PAN in summer.We speculate that since the correlation between PAN and O_(3) in winter is significantly lower than that in other seasons,the observed regional transport of PAN cannot be ignored in winter.Through budget analysis,regional transport accounted for 12.8% and 55.9% of the observed PAN on the spring and winter pollution days,respectively,which showed that regional transport played key roles during the photochemical pollution of the rural NCP in winter.The potential source contribution function revealed that the transported PAN mainly comes from southern Hebei in spring.In winter,the transported PAN was mainly from Langfang,Hengshui,and southern Beijing.Our findings may aid in understanding PAN variations in different seasons in rural areas and highlight the impact of regional transport on the PAN budget.

关键词： Photochemical pollution Peroxyacetyl nitrate(PAN) Seasonal variations Regional transport Rural area

Dual effect of Cu on the Al3Sc nanoprecipitate coarsening

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Journal of Materials Science & Technology 2020年第2期37卷 38-45页

作者： Y.H.gao L.F.Cao J.Kuang J.Y.Zhang g.liu J.Sun State Key Laboratory for Mechanical Behavior of Materials Xi’an Jiaotong UniversityXi’an710049China International Joint Laboratory for Light Alloys(Ministry of Education) Chongqing UniversityChongqing 400044China

It is generally considered that the Al3Sc nanoprecipitates are highly thermal stable,mainly due to quite slow Sc diffusion in theα-Al matrix.In this paper,we demonstrate in an Al-Cu-Sc alloy that the Cu atoms have dual effect on the coarsening of Al3Sc nanoprecipitates.On the one hand,the Cu atoms with high diffusivity tend to accelerate the Al3Sc coarsening,which results from the Cu-promoted Sc diffusion.On the other hand,some Cu atoms will segregate at the Al3Sc/matrix interface,which further stabilizes the Al3Sc nanoprecipitates by reducing the interfacial energy.Competition between these two effects is tailored by temperature,which rationalizes the experimental findings that the coarsening kinetics of Al3Sc nanoprecipitate is greatly boosted at 300℃-overaging while significantly suppressed at 400℃-overaging.

关键词： Al alloys Precipitate coarsening Interfacial segregation Microstructural evolution

High-performance,stable CoNi LDH@Ni foam composite membrane with innovative peroxymonosulfate activation for 2,4-dichlorophenol destruction

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Journal of Environmental Sciences 2024年第7期141卷 235-248页

作者： Yu liu Weibao liu Xinrui gan Jiangwei Shang Xiuwen Cheng College of Chemistry and Environmental Science Xinjiang Laboratory of Phase Transitions and Microstructures of Condensed Matter PhysicsYili Normal UniversityYining 835000China Key Laboratory for Environmental Pollution Prediction and Control Gansu ProvinceCollege of Earth and Environmental SciencesLanzhou UniversityLanzhou 730000China

In this study,the cobalt-nickel layered double hydroxides(CoNi LDH)were synthesized with a variety of Co/Ni mass ratio,as CoxNiyLDHs.In comparison,Co1Ni3LDH presented the best peroxymonosulfate(PMS)activation efficiency for 2,4-dichlorophenol removal.Meanwhile,CoNi LDH@Nickel foam(CoNi LDH@NF)composite membrane was constructed for enhancing the stability of catalytic performance.Herein,CoNi LDH@NF-PMS system exerted high degradation efficiency of 99.22%within 90 min for 2,4-DCP when[PMS]_(0)=0.4 g/L,Co^(1)Ni^(3)LDH@NF=2 cm×2 cm(0.2 g/L),reaction temperature=298 K.For the surface morphology and structure of the catalyst,it was demonstrated that the CoNi LDH@NF composite membrane possessed abundant cavity structure,good specific surface area and sufficient active sites.Importantly,·OH,SO_(4)·^(-)and^(1)O_(2)played the primary role in the CoNi LDH@NF-PMS system for 2,4-DCP decomposition,which revealed the PMS activation mechanism in CoNi LDH@NF-PMS system.Hence,this study eliminated the stability and adaptability of CoNi LDH@NF composite membrane,proposing a new theoretical basis of PMS heterogeneous catalysts selection.

关键词： CoNi LDH@NF composite membrane Peroxymonosulfate 2,4-dichlorophenol Reactive radicals