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Promoting hybrid twins structure to reduce yield asymmetry of rolled AZ31 plates by combining side-rolling and torsion

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镁合金学报(英文) 2023年第6期11卷 2096-2105页

作者： Bo Song Meng Wang Ruolan Shi Zhiwen Du Ning Guo Fang Wang Shengfeng Guo school of Materials and energy Southwest UniversityChongqingChina

In this work,an as-rolled AZ31 square bar with c-axis//ND(normal direction)texture was used.Side-rolling and reciprocating torsion were performed to treat the bar.Microstructure evolution and tensile-compressive properties were investigated in detail.Initial rolled AZ31 bar exhibits a large yield asymmetry along the rolling direction(RD).Reciprocating torsion can generate extension twins to introduce twin boundaries and twin-texture.The twin structure can reduce yield asymmetry.However,only limited regions in the rolled AZ31 bar can be twinned during torsion.Pre-side-rolling along the transverse direction(TD)can generate two texture components(c-axis//TD texture and c-axis//ND texture)by introducing profuse{10–12}twins.Such dual texture components help increase the regions which are favorable for twinning during torsion.Finally,combining side-rolling and reciprocating torsion generates hybrid{10–12}twins structure on the entire cross-section,resulting in a remarkably low yield asymmetry.The relevant mechanisms were discussed in detail.

关键词： AZ31 Square section Torsion Hybrid twins Orientation Yield asymmetry

Ionization Engineering of Hydrogels Enables Highly Efficient Salt‑Impeded Solar Evaporation and Night‑Time Electricity Harvesting

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Nano-Micro Letters 2024年第1期16卷 131-146页

作者： Nan He Haonan Wang Haotian Zhang Bo Jiang Dawei Tang Lin Li School of Energy and Power Engineering Key Laboratory of Ocean Energy Utilization and Energy Conservation of Ministry of EducationDalian University of TechnologyDalian 116024People’s Republic of China

Interfacial solar evaporation holds immense potential for brine desalination with low carbon footprints and high energy utilization.Hydrogels,as a tunable material platform from the molecular level to the macroscopic scale,have been considered the most promising candidate for solar evaporation.However,the simultaneous achievement of high evaporation efficiency and satisfactory tolerance to salt ions in brine remains a challenging scientific bottleneck,restricting the widespread application.Herein,we report ionization engineering,which endows polymer chains of hydrogels with electronegativity for impeding salt ions and activating water molecules,fundamentally overcoming the hydrogel salt-impeded challenge and dramatically expediting water evaporating in brine.The sodium dodecyl benzene sulfonate-modified carbon black is chosen as the solar absorbers.The hydrogel reaches a ground-breaking evaporation rate of 2.9 kg m−2 h−1 in 20 wt%brine with 95.6%efficiency under one sun irradiation,surpassing most of the reported literature.More notably,such a hydrogel-based evaporator enables extracting clean water from oversaturated salt solutions and maintains durability under different high-strength deformation or a 15-day continuous operation.Meantime,on the basis of the cation selectivity induced by the electronegativity,we first propose an all-day system that evaporates during the day and generates salinity-gradient electricity using waste-evaporated brine at night,anticipating pioneer a new opportunity for all-day resource-generating systems in fields of freshwater and electricity.

关键词： Solar evaporation Hydrogel evaporators Salt impeding Ionization engineering Cyclic vapor-electricity generation

带挡板的预混氢/空气燃料微型燃烧室的热性能优化

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Journal of Central South University 2023年第12期30卷 4285-4298页

作者：莫淞涵李玉强袁文华 School of Energy Science and Engineering Central South UniversityChangsha 410083China school of Mechanical and energy Engineering Shaoyang UniversityShaoyang 422000China

微燃烧室是微热光伏系统(MTPV)的重要组成部件。本研究中提出了一种能提高热性能的新型平板式带挡板的氢气/空气预混微型燃烧室,该燃烧室提升了平均壁温和理论辐射效率等性能,考虑了壁温均匀性,并优化了内置挡板的材料、数量、长度、厚... 详细信息

微燃烧室是微热光伏系统(MTPV)的重要组成部件。本研究中提出了一种能提高热性能的新型平板式带挡板的氢气/空气预混微型燃烧室,该燃烧室提升了平均壁温和理论辐射效率等性能,考虑了壁温均匀性,并优化了内置挡板的材料、数量、长度、厚度和布局等关键参数。研究结果表明,引入不锈钢材料的水平挡板将导致平均壁温明显升高约150 K,同时还能改善壁温分布使其更均匀。在考虑燃烧室和挡板的材料时,本文评估了不锈钢、氧化铝陶瓷、碳化硅和石英四种材料,其中不锈钢表现出最高的平均壁温和理论辐射效率,而碳化硅表现出最均匀的壁温。当微型燃烧室配备的挡板参数为:数量N=3,长度L=13.5 mm,厚度t=0.3 mm时,实现了最佳的热性能。值得注意的是,当微燃烧室内的挡板为以上结构参数时适合集群布局,这可以实现平均壁温、理论辐射效率和均匀性的更大改进。

关键词：微热光伏系统微型燃烧器热性能挡板优化

Texture development and tensile properties of Mg?Yb binary alloys during hot extrusion and subsequent annealing

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Journal of Magnesium and Alloys 2022年第1期10卷 267-283页

作者： Lu Li Cuncai Zhang Hao Lv Chunrong Liu Zhuozhang Wen Jingwen Jiang school of Materials and energy Southwest UniversityChongqingChina

Ytterbium(Yb)containing magnesium alloys have aroused extensive interest due to their excellent mechanical properties after thermomechanical processing and heat treatment.Unfortunately,the sole effect of Yb addition on the microstructure and mechanical properties of pure Mg matrix remains uncertain to date.In this work,the effects of Yb concentration on the texture development and tensile properties of pure Mg matrix during hot extrusion and the subsequent annealing were systematically investigated.The results revealed that the constitutional supercooling induced by Yb addition refined the as-cast microstructure but exerted a negligible effect on the original columnar grain morphology.When extruded at 300°C,the dynamic recrystallization(DRX)process was considerably retarded.The in-grain misorientation axes(IGMA)analysis combined with TEM observation indicated that non-basal slips operated with increasing Yb concentration.Specifically,the prismaticslip should be robustly activated in Mg-1.0 Yb extrudate,promoting the formation of the texture with{10?10}plane normal to the extrusion direction(ED),while for the Mg?2.0 Yb counterpart,the increased activity of pyramidalslip and the relaxation of basal/dislocations generated an ED-tilted texture component.The preferential grain growth dominated the subsequent annealing texture development at 400°C when a comparable grain size was achieved.An obvious ED-tilted texture intensity with the peak aroundwas observed in Mg-2.0 Yb alloy,which was primarily caused by grains with the basal orientation vanished and with the non-basal orientations intensified due to a higher concentration of Yb solute.Favored by the grain refinement,the Mg-2.0 Yb extrudate exhibited a high tensile yield strength of 304±3.5 MPa,while the subsequently annealed counterpart presented a favorable elongation to failure of 14.8±1.2%,which mainly due to the homogeneous grain structure,weak ED-tilted texture,and dissolution of coarse phases after high-temperature annealing.

关键词： Magnesium alloy Ytterbium Texture development Tensile properties

ZnO Additive Boosts Charging Speed and Cycling Stability of Electrolytic Zn–Mn Batteries

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Nano-Micro Letters 2024年第4期16卷 293-304页

作者： Jin Wu Yang Tang Haohang Xu Guandie Ma Jinhong Jiang Changpeng Xian Maowen Xu Shu‑Juan Bao Hao Chen Institute for Clean energy&Advanced Materials School of Materials and EnergySouthwest UniversityChongqing 400715People’s Republic of China

Electrolytic aqueous zinc-manganese(Zn–Mn) batteries have the advantage of high discharge voltage and high capacity due to two-electron reactions. However, the pitfall of electrolytic Zn–Mn batteries is the sluggish deposition reaction kinetics of manganese oxide during the charge process and short cycle life. We show that, incorporating ZnO electrolyte additive can form a neutral and highly viscous gel-like electrolyte and render a new form of electrolytic Zn–Mn batteries with significantly improved charging capabilities. Specifically, the ZnO gel-like electrolyte activates the zinc sulfate hydroxide hydrate assisted Mn^(2+) deposition reaction and induces phase and structure change of the deposited manganese oxide(Zn_(2)Mn_(3)O_8·H_(2)O nanorods array), resulting in a significant enhancement of the charge capability and discharge efficiency. The charge capacity increases to 2.5 mAh cm^(-2) after 1 h constant-voltage charging at 2.0 V vs. Zn/Zn^(2+), and the capacity can retain for up to 2000 cycles with negligible attenuation. This research lays the foundation for the advancement of electrolytic Zn–Mn batteries with enhanced charging capability.

关键词： Electrolytic aqueous zinc-manganese batteries Electrolyte pH value ZnO electrolyte additive Fast constant-voltage charging ability

Tetraphenylethene-based hole transporting material for highly efficient and stable perovskite solar cells

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Science China Chemistry 2024年第6期67卷 2009-2015页

作者： Peng Wang Pei Yuan Chenghao Ge Rongjun Zhao Lin Xie Yong Hua school of Materials and energy Yunnan UniversityKunming650091China

2,2,7,7-Tetrakis-(N,N-di-p-methoxyphenylamine)-9,9-spirobifluorene(Spiro-OMeTAD)has been identified as the most widely used and effective hole transporting material(HTM)in perovskite solar cells(PSCs).However,the complicated multistep synthesis and low intrinsic hole mobility of Spiro-OMe TAD limit its commercialized application.Therefore,developing highly efficient HTMs with less synthetic steps becomes increasingly important.Moreover,understanding hot carriers transfer dynamics at the interface of perovskite layer and hole transport layer is crucial for further enhancing PSCs performance towards Shockley-Queisser limit,which still lacks full investigation to date.Herein,a new HTM based on tetraphenylethene(WP1)was successfully synthesized by a simple one-step reaction process.It was found that WP1-based HTM exhibits more matched energy level,higher hole mobility and conductivity than those of the control Spiro-OMe TAD.The femtosecond transient absorption results reveal that the transfer rate of hot holes in perovskite/WP1 sample is four times higher than that of perovskite/Spiro-OMeTAD,thereby helping enhance the device performance.Consequently,the efficiency of PSCs is enhanced to 24.04%(WP1)from 22.85%(Spiro-OMeTAD).Moreover,the un-encapsulated device prepared with WP1 exhibits better long-term stability,retaining 87%of its initial PCE value after storing for 72 days under air environment,while the reference device shows76%of its initial value.This work indicates that simple tetraphenylethene-based organic small molecule could be a very promising HTM candidate for highly efficient PSCs,and gives some significant insights for understanding intrinsic hot carriers transfer dynamics in device.

关键词： tetraphenylethene hole transporting material perovskite solar cells mobility hot carrier

Teacher-Student Training Approach Using an Adaptive Gain Mask for LSTM-Based Speech Enhancement in the Airborne Noise Environment

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Chinese Journal of Electronics 2023年第4期32卷 882-895页

作者： HUANG Ping WU Yafeng school of Power and energy Northwestern Polytechnical University

Research on speech enhancement algorithms in the airborne environment is of great significance to the security of airborne systems. Recently, the research focus of speech enhancement has turned from conventional unsupervised algorithms, like the log minimum mean square error estimator(log-MMSE), to the state-ofthe-art masking-based long short-term memory(LSTM)method. However, each method has its characteristics and limitations, so they cannot always handle noise well. Besides, the requirements of clean speech and noise data for training a supervised speech enhancement model are difficult to satisfy in the real-world airborne environment.Therefore, in this work, to fully utilize the advantages of those two different methods without any data restrictions,we propose a novel adaptive gain mask(AGM) based teacher-student training approach for speech enhancement. In our method, the AGM, as a robust learning target for the student model, is devised by incorporating the estimated ideal ratio mask from the teacher model into the procedure of the log-MMSE approach. To get an appropriate tradeoff between the two methods, we adaptively update the AGM using a recursive weighting coefficient. Experiments on the real airborne data show that the proposed AGM-based method outperforms other baselines in terms of all essential objective metrics evaluated in this paper.

关键词： Adaptive ideal mask Teacher-student learning Long short-term memory (LSTM) Speech enhancement

Preparation of chitosan and citric acid crosslinked membrane and its application in quasi-solid supercapacitors

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Rare Metals 2023年第2期42卷 430-437页

作者： Hao-Hang Xu Liang Yue Yang Tang Fan Liu Hong-Jiu Zhu Shu-Juan Bao Institute for Clean energy&Advanced Materials School of Materials and EnergySouthwest UniversityChongqing400715China

Quasi-solid electrolytes promote the development of safe and flexible energy storage devices.In this work,a chitosan and citric acid crosslinked membrane is prepared by a freeze-thaw cross-linking method,in which the chemical crosslinking of chitosan and citric acid increase the viscoelastic behavior of the polymer membrane,and the freeze-thaw assist freeze drying process to create abundant interconnected open-pores and three-dimensional(3D)network.Due to the good viscoelasticity,excellent electrolyte loading capacity(596%)and high ion conductivity(7.7×10^(-3)S·cm^(-)1),as quasi-solid electrolyte,our proposed chitosan and citric acid crosslinked membrane helps ZnICCFT-ZnSO4lAC hybrid supercapacitor to delivers wide operating voltage,high specific capacity of 100.5 F·g^(-1)and stable cycle life(93%after1000 cycles),which suggests that our proposed freezethaw assisted freeze drying method has great potential in designing quasi-solid state electrolyte for energy storage device.

关键词： Quasi-solid electrolyte Chitosan Freeze-thaw Hybrid supercapacitor

Characterization of size-resolved effective density of atmospheric particles in an urban atmosphere in Southern China

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Journal of Environmental Sciences 2024年第7期141卷 194-204页

作者： Tingting Xie Liming Cao Jinyi Zheng Peng Xuan Xiaofeng Huang Laboratory of Atmospheric Observation Supersite School of Environment and EnergyPeking University Shenzhen Graduate SchoolShenzhen 518055China

Effective density(ρ_(eff))is one of the most important physical properties of atmospheric particles,providing important references in exploring the emissions and aging processes of fresh particles.In this study,a combined system of differential mobility analyzer,centrifugal particle mass analyzer,and condensation particle counter was used to periodically measure theρ_(eff)of atmospheric particles in Shenzhen from Oct.2021 to Jan.2022.Results showed that theρ_(eff)of particles with various size presented a bimodal distribution,which could be divided into main density(ρ_(m),main peak,corresponding to relatively dense particles after aging)and sub density(ρ_(s),sub peak,corresponding to fresh particles).The occurrence frequencies ofρ_(s)of particles with diameters of 50 and 80 nm were less than 20%,but were as high as about 40%of that with diameters from 120 to 350 nm.Theρ_(m)showed increasing trend with the size of particles,whileρ_(s)decreased as the increasing of the size of particles.Theρ_(eff)on pollution day varied significantly with chemical compositions.The increasing of the proportion of sulfate could promote the increasing ofρ_(eff),while black carbon and organic matter caused opposite effects,which may be related to various factors,including the difference of the material density and morphology of various chemical components.Theρ_(eff)of 50,80 and 120 nm particles decreased considerably during the new particle formation event,indicating that organic condensation was an important contributor to new particle growth.

关键词： DMA-CPMA-CPC Effective density Main/sub density Size distribution