检索结果-南通市图书馆

Suppressing thermal quenching via defect passivation for efficient quasi-2D perovskite light-emitting diodes

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Light(Science & Applications) 2022年第4期11卷 644-653页

作者： Dezhong Zhang Yunxing Fu Hongmei Zhan Chenyang Zhao Xiang Gao Chuanjiang Qin Lixiang Wang State Key Laboratory of Polymer Physics and Chemistry Changchun Institute of Applied ChemistryChinese Academy of SciencesChangchun 130022China School of Applied Chemistry and Engineering University of Science and Technology of ChinaHefei 230026China

Emission thermal quenching is commonly observed in quasi-2D perovskite emitters,which causes the severe drop in luminescence eficiency for the quasi-2D perovskite light-emitting diodes(Pel EDs)during practical operations.However,this issue is often neglected and rarely studied,and the root cause of the thermal quenching has not been completely revealed now.Here,we develop a passivation strategy via the 2,7-dibromo-9,9-bis(3'-diethoxylphosphorylpropyl-fluorene to investigate and suppress the thermal quenching.The agent can effectively passivate coordination-unsaturated Pb2+defects of both surface and bulk of the flm without affecting the perovskite crysaliation,which helps to more truly demonstrate the important role of defects in thermal quenching.And our results reveal the root cause that the quenching will be strengthened by the defect promoted exciton-phonon coupling.Ultimately,the PeL EDs with defect passivation achieve an improved external quantum efficiengy(EQE)over 22%and doubled operation lifetime at room temperature,and can maintain about 85%of the initial EQE at 85℃,much higher than 17%of the control device.These findings provide an important basis for fabricating practical PeLEDs for lighting and displays.

关键词： thermal defect quenching

Kinetics of hydrogen peroxide quenching following UV/H_(2)O_(2)advanced oxidation by thiosulfate,bisulfite,and chlorine in drinking water treatment

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Frontiers of Environmental Science & Engineering 2023年第12期17卷 59-69页

作者： Tianyi Chen Lizbeth Taylor-Edmonds Susan Andrews Ron Hofmann Department of Civil and Mineral Engineering University of TorontoTorontoOntario M5S 1A4Canada

Residual H_(2)O_(2)from UV/H_(2)O_(2)treatment can be quenched by thiosulfate,bisulfite,and chlorine,but the kinetics of these reactions have not been reported under the full range of practical conditions.In this study,the rates of H_(2)O_(2)quenching by these compounds were compared in different water matrices,temperatures,pH,and when using different forms of bisulfite and chlorine.In general,it was confirmed that thiosulfate would be too slow to serve as a quenching agent in most practical scenarios.At pH 7-8.5,chlorine tends to quench H_(2)O_(2)more than 20 times faster than bisulfite in the various conditions tested.An important observation was that in lightly-buffered water(e.g.,alkalinity of 20 mg/L as CaCO_(3)),the form of chlorine can have a large impact on quenching rate,with gaseous chlorine slowing the reaction due to its lowering of the pH,and hypochlorite having the opposite effect.These impacts will become less significant when water buffer capacity(i.e.,alkalinity)increases(e.g.,to 80 mg/L as CaCO_(3)).In addition,water temperature should be considered as the time required to quench H_(2)O_(2)by chlorine at 4℃is up to 3 times longer than at 20℃.

关键词： UV/H_(2)O_(2) H_(2)O_(2) quenching Chlorine type Water alkalinity Temperature

Influence of quenching medium on the dendrite morphology,hardness,and tribological behaviour of cast Cu-Ni-Sn spinodal alloy for defence application

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Defence Technology（防务技术） 2023年第12期30卷 83-100页

作者： Bipin Sankar Karthik V Shankar Vamu Sunil Hemanth Kashyap S Nikhil Nair Adarsh A.Nair Abhinav P M Department of Mechanical Engineering Amrita Vishwa VidyapeethamAmritapuriIndia

Cu-Ni-Sn spinodal alloys(Spinodal bronze)are potential materials with robust applications in components associated with defence applications like bearings,propellers,bushes,and shafts of heavily loaded aircraft,off-road vehicles,and warships.This paper presents a comparative study using water,Brine solution,and SAE 40 oil as the quenching media in regular bronze(Cu-6Sn)and spinodal bronze(Cu-9Ni-6Sn)alloys.Morphological analysis was conducted by optical microscopy,transmission electron microscopy(TEM),and X-ray diffraction technique(XRD)on bronze and spinodal bronze samples immersed in the three different quenching media to understand the grain size and hardness values better.Tribological analysis was performed to analyze the effect of quenching media on the wear aspects of bronze and spinodal bronze samples.The hardness value of the brine-aged spinodal bronze samples was as high as 320 Hv,and the grain size was very low in the range of 60μm.A quantitative comparison between brine-aged regular bronze and brine-aged spinodal bronze showed that the hardness(Hv)was almost 80%higher for brine-aged spinodal bronze.Further,the grain size was approximately 30%finer for spinodal bronze when compared with regular bronze.When the load was increased in spinodal bronze samples,there was an initial dip in wear rate followed by a marginal increase.There was a steady increase in friction coefficient with a rise in load for brine-aged regular bronze and spinodal bronze samples.These results indicate that brine solution is the most effective quenching medium for cast Cu-Ni-Sn spinodal alloys.

关键词： quenching Water Brine SAE 40 oil Grain size Hardness Wear rate Spinodal decomposition CuSn Spinodal alloy CuNiSn

Effect of quenching residual stress on precipitation behaviour of 7085 aluminium alloy

在线全文

学校读者我要写书评

暂无评论

Journal of Materials Science & Technology 2023年第1期132卷 154-165页

作者： Jin Liu Zhiyong Du Jinlong Su Jie Tang Fulin Jiang Dingfa Fu Jie Teng Hui Zhang College of Materials Science and Engineering Hunan UniversityChangsha 410082China

The quenching-induced residual stress in ultrahigh strength Al-Zn-Mg-Cu alloys has a great influence on their precipitation behaviour in subsequent heat treatment and the properties of the final products.In the present work,the cladding quenching method was employed for 7085 Al alloy slabs to tailor different quenching residual stresses.Then the effects of quenching residual stress on the precipitation behaviour of the 7085 Al alloy were investigated through finite element analysis,residual stress and hardness distri-bution measurements and microstructural examinations.The results indicate that the reduction in resid-ual stress increases with increasing cladding layer thickness.For a cladding layer thickness in the range of 1-1.4 mm,the residual stress is almost eliminated.The hardness at the surface of the aged sample with a large compressive residual stress is decreased,while the hardness at the centre of the sample with a large tensile residual stress is increased.The hardness is approximately identical between the aged sam-ples with little or no residual stress.The elastic lattice distortion caused by residual stress is found to promote the nucleation of precipitates during the artificial ageing process.The in-depth mechanisms for the effect of quenching residual stress on the precipitation of 7085 Al alloy are also discussed.

关键词： Aluminium alloy quenching Residual stress Precipitation Finite element method

quenching residual stress distributions in aluminum alloy plates with different dimensions

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Rare Metals 2019年第11期38卷 1051-1061页

作者： Ya-Nan Li Yong-An Zhang Xi-Wu Li Zhi-Hui Li Guo-Jun Wang Long-Bing Jin Shu-Hui Huang Bai-Qing Xiong State Key Laboratory of Nonferrous Metals and Process General Research Institute for Nonferrous MetalsBeijing 100088China Northeast Light Alloy Co. Ltd.Harbin 150060China

Finite element method(FEM) simulations were employed to investigate the quenching residual stress distributions of 7085 aluminum alloy plates.The effect of dimensional variation on the quenching residual stress distributions was studied and discussed by using models with different dimensions(length,width,and thickness).The accuracy and efficiency of the models were verified by other numerical examples.The order of the dimension effects on the quenching residual stress distributions is:thickness> width=length.The maximum tensile stress and compressive stress increase from 33 to 190 and 39 to 270 MPa,respectively,as the thickness increases from 30 to 150 mm.The ultimate maximum tensile stress(about190 MPa) is equivalent to half of the quenching yield strength at 20℃,while the ultimate maximum compressive stress(about 300 MPa) is equivalent to 80 % of the quenching yield strength at 20℃.There are stress fluctuations at the edge of the large plate both in rolling and in transverse directions.The ratio of the fluctuation region along the rolling direction and transverse direction increases as the thickness increases,while it decreases as the length or width increases.The actual length of the fluctuation region is almost a constant value for the plates with a thickness of 115 mm(about 500 mm in length and 300 mm in width).

关键词： Aluminum alloy quenching residual stress Dimension effects Finite element method

quenching AND AGEING BEHAVIORS OF Mg-Li-Zn ALLOY

在线全文

学校读者我要写书评

暂无评论

中国有色金属学会会刊：英文版 1997年第3期7卷 41-45页

作者： Le, Qichi Gui, Jianzhong Liu, Hanwu Northeastern Univ Shenyang China

ＱＵＥＮＣＨＩＮＧＡＮＤＡＧＥＩＮＧＢＥＨＡＶＩＯＲＳＯＦＭｇＬｉＺｎＡＬＬＯＹ①ＬｅＱｉｃｈｉ，ＣｕｉＪｉａｎｚｈｏｎｇ，ＬｉｕＨａｎｗｕＤｅｐａｒｔｍｅｎｔｏｆＭｅｔａｌＦｏｒｍｉｎｇ，ＳｃｈｏｌｏｆＭａｔｅ... 详细信息

ＱＵＥＮＣＨＩＮＧＡＮＤＡＧＥＩＮＧＢＥＨＡＶＩＯＲＳＯＦＭｇＬｉＺｎＡＬＬＯＹ①ＬｅＱｉｃｈｉ，ＣｕｉＪｉａｎｚｈｏｎｇ，ＬｉｕＨａｎｗｕＤｅｐａｒｔｍｅｎｔｏｆＭｅｔａｌＦｏｒｍｉｎｇ，ＳｃｈｏｌｏｆＭａｔｅｒｉａｌａｎｄＭｅｔａｌｕｒｇｙ，...

关键词： Mg Li Zn quenching ageing

Internal OH^(-)induced cascade quenching of upconversio n luminesce nee in NaYF4:Yb/Er nanocrystals

在线全文

学校读者我要写书评

暂无评论

Light(Science & Applications) 2021年第6期10卷 1078-1087页

作者： Yansong Feng Zhi Li Qiqing Li Jun Yuan Langping Tu Lixin Ning Hong Zhang van't Hoff Institute for Molecular Sciences University of AmsterdamScience Park 9041098XH AmsterdamThe Netherlands. State Key Laboratory of Explosion Science and Technology School of Mechatronical EngineeringBeijing Institute of TechnologyBeijing 100081China. Anhui Key Laboratory of Optoelectronic Materials Science and Technology Department of PhysicsAnhui Normal University241000 WuhuChina. State Key Laboratory of Luminescenee and Applications Changchun Institute of OpticsFine Mechanics and PhysicsChinese Academy of SciencesChangchun 130033 JilinChina

Internal hydroxyl impurity is known as one of the main detrimental factors affecting the upconversion(UC)efficiency of upconversion luminescence(UCL)nanomaterials.Different from surface"ligand-related emission quenching which can be effectively diminished by,e.g.,core"shell structure,internal hydroxyl is easy to be introduced in synthesis but difficult to be quantified and controlled.Therefore,it becomes an obstacle to fully understand the relevant UC mechanism and improve UC efficiency of nanomaterials.Here we report a progress in quantifying and large-range adjustment of the internal hydroxyl impurity in NaYF4 nanocrystals.By combining the spectroscopy study and model simulation,we have quantitatively unraveled the microscopic in teractions underlying UCL que nching between internal hydroxyl and the sensitizers and activators,respectively.Furthermore,the internal hydroxyl-involved UC dynamical process is interpreted with a vivid concept of"Survivor effect" i.e.;the shorter the migration path of an excited state,the larger the possibility of its surviving from hydroxyl-induced quenchi ng.Apart from the consist ent experimental results,this concept can be further evidenced by Monte Carlo simulation,which monitors the variation of energy migration step distribution before and after the hydroxyl introduction.The new quantitative insights shall promote the construction of highly efficient UC materials.

关键词： materials. quenching excited

quenching rates for heat equations with coupled singular nonlinear boundary flux

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Science China Mathematics 2008年第9期51卷 1631-1643页

作者： ZHENG SiNing SONG XianFa Department of Applied Mathematics Dalian University of TechnologyDalian 116024China Department of Mathematics China University of Mining and Technology(Beijing)Beijing 100083China

We study finite time quenching for heat equations coupled via singular nonlinear bound-ary flux. A criterion is proposed to identify the simultaneous and non-simultaneous quenchings. In particular, three kinds of simultaneous quenching rates are obtained for different nonlinear exponent re-gions and appropriate initial data. This extends an original work by Pablo, Quir′os and Rossi for a heat system with coupled inner absorption terms subject to homogeneous Neumann boundary conditions.

关键词： quenching simultaneous quenching non-simultaneous quenching quenching rate heat equation singular nonlinear boundary flux

Microstructural evolution of GCr15 steel during austenitizing and quenching considering C and Cr content

在线全文

学校读者我要写书评

暂无评论

Journal of Central South University 2016年第10期23卷 2492-2499页

作者：刘青龙钱东升魏文婷 School of Materials Science and Engineering Wuhan University of Technology Hubei Key Laboratory of Advanced Technology for Automotive Components School of Automotive Engineering Wuhan University of Technology

Microstructural evolution of GCr15 steels with different C and Cr contents during austenitizing and quenching was studied. Thermodynamic analysis of cementite dissolution was implied to obtain the critical temperature. The coordination number x in Fe_xCr_(3-x)C and the volume fraction of undissolved cementite were computed according to element conservation and equilibrium phase diagram. The M_S(martensite transformation temperature) was calculated by using empirical formula. The retained austenite content was calculated with further consideration of quenching temperature. The results showed that the coordination number and the undissolved cementite content were promoted by the austenitizing temperature and carbon content of the steel. Increasing Cr element reduced the coordination number.GCr15 steels with different components had nearly the same M_S when austenitization at 830 °C to 860 °C. The interaction of C and Cr complicated the evolution of M_S and retained austenite content. The results were in good agreement with the literature, which could guide to obtain specified retained austenite and/or carbides.

关键词： GCr15 steel austenitization quenching thermodynamic calculation kinetics