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Damage evolution and removal behaviors of GaN crystals involved in double-grits grinding

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International Journal of Extreme Manufacturing 2024年第2期6卷 469-484页

作者： Chen Li Yuxiu Hu Zongze Wei Chongjun Wu Yunfeng Peng Feihu Zhang Yanquan geng State Key Laboratory of Robotics and System(HIT) Harbin Institute of TechnologyHarbin 150001People’s Republic of China Key Laboratory of Microsystems and Microstructures Manufacturing(HIT) Harbin Institute of TechnologyHarbin 150001People’s Republic of China College of Mechanical Engineering Donghua UniversityShanghai 201620People’s Republic of China Department of Mechanical and Electrical Engineering Xiamen UniversityXiamen 361005People’s Republic of China

Elucidating the complex interactions between the work material and abrasives during grinding of gallium nitride(GaN)single crystals is an active and challenging research *** this study,molecular dynamics simulations were performed on double-grits interacted grinding of GaN crystals;and the grinding force,coefficient of friction,stress distribution,plastic damage behaviors,and abrasive damage were systematically *** results demonstrated that the interacted distance in both radial and transverse directions achieved better grinding quality than that in only one *** grinding force,grinding induced stress,subsurface damage depth,and abrasive wear increase as the transverse interacted distance ***,there was no clear correlation between the interaction distance and the number of atoms in the phase transition and dislocation *** interacted distances between abrasives can decrease grinding force,coefficient of friction,grinding induced stress,subsurface damage depth,and abrasive wear during the grinding *** results of grinding tests combined with cross-sectional transmission electron micrographs validated the simulated damage results,*** atoms,high-pressure phase transition,dislocations,stacking faults,and lattice *** results of this study will deepen our understanding of damage accumulation and material removal resulting from coupling between abrasives during grinding and can be used to develop a feasible approach to the wheel design of ordered abrasives.

关键词： grinding double-grits molecular dynamics damage material removal gallium nitride

High-performance Ti_(3)C_(2)T_(x)achieved by polyaniline intercalation and gelatinization as a high-energy cathode for zinc-ion capacitor

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Nano Research 2024年第6期17卷 5305-5316页

作者： Peng Liao ZiYu geng Xin Zhang Wenjie Yan Zenghui Qiu Haijun Xu College of Mathematics and Physics Beijing University of Chemical TechnologyBeijing 100029China

The actual manufacture of supercapacitors(SCs)is restricted by the inadequate energy density,and the energy density of devices can be properly promoted by assembling zinc-ion capacitors(ZICs)which used capacitive cathode and battery-type ***-dimensional(2D)MXene has brought great focuses in the electrode research on the foundation of large redox-active surface,but the specific capacitance is still affected by the tight stacking of ***_(3)C_(2)T_(x)@polyaniline(PANI)heterostructures are prepared by uniformly depositing the conductive polymer PANI nanorods as the intercalation agent into the external of Ti_(3)C_(2)T_(x)nanosheets to inhibit ***,by using graphene oxide(GO)-assisted low-temperature hydrothermal self-assembly manufacture,2D heterostructures are assembled into the three-dimensional(3D)porous crosslinked Ti_(3)C_(2)T_(x)@PANI-reduced graphene oxide(RGO)*** to the synergistic work of PANI nanorods,Ti_(3)C_(2)T_(X)nanosheets,and 3D crosslinking frameworks of RGO to match capacitive and battery effects,3D porous hierarchical Ti_(3)C_(2)T_(x)@PANI-RGO heterostructure hydrogels have rich ion transport channels,a large number of active sites,and excellent reaction *** is assembled by using Ti_(3)C_(2)T_(x)@PANI-RGO heterostructure hydrogels as cathodes and zinc foil as *** this work,Ti_(3)C_(2)T_(x)@PANI-RGO//Zn ZIC exhibits a wide working window(2.0 V),marked specific capacitance(589.89 F·g^(−1)at 0.5 A·g−1),salient energy density(327.71 Wh·kg^(−1)at 513.61 W·kg^(−1)and 192.20 Wh·kg^(−1)at 13,005.87 W·kg^(−1)),and durable cycling stability(97.87%capacitance retention after 10,000 cycles at 10 A·g^(−1)).This study emphasizes the device design of ZICs and the broad prospect of Ti_(3)C_(2)T_(x)-based hydrogels as viable cathodes for ZICs.

关键词： polyaniline(PANI) Ti_(3)C_(2)T_(x)@PANI heterostructure intercalation process three-dimensional(3D)porous hydrogel high energy density zinc-ion capacitor

Point defects in 2-D liquid crystals with a singular potential: Profiles and stability

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Science China Mathematics 2024年

作者： Zhiyuan geng Wei Wang Basque Center for Applied Mathematics School of Mathematical Sciences Zhejiang University

We study radial symmetric point defects with degreek2in the 2-D disk or R2in the Q-tensor framework with a singular bulk energy, which is defined by Bingham closure. First, we obtain the existence of solutions for the profiles of radial symmetric point defects with degreek2in the 2-D disk or R2. Then, we prove that the solution is stable for |k| = 1 and unstable for |k| > 1. Some identities are derived and utilized throughout the proof of existence and stability/instability.

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Investigation on cavitating turbulent flow for the twisted NACA66 hydrofoil using a PANS model with helicity modification

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Journal of Hydrodynamics 2024年第2期36卷 219-231页

作者： Chen geng Zhao-hui Qian Ke-xin Zheng Wei-xiang Ye Xian-wu Luo State Key Laboratory of Hydroscience cand Engineering Deparment of Energy and Power EngineeringTsinghua UniversityBeijing 100084China Institute of Nuclear and New Energy Technology Tsinghua UniversityBeijing 100084China

In the present paper,the unsteady cavitating turbulent flow over the twisted NACA66 hydrofoil is investigated based on an modified shear stress transfer k-ωpartially averaged Navier-Stokes(MSST PANS)model,i.e.,new MSST PANS(NMSST PANS)model,where the production term of kinetic energy in the turbulence model is modified with *** with the experimental data,cavitation evolution and its characteristic frequency are satisfactorily predicted by the proposed NMSST PANS *** is revealed that the interaction among the main flow,the reentrant jets,and sheet cavitation causes the formation of the primary shedding cavity near the mid-span and the secondary shedding cavity at each side of the twisted hydrofoil,and further induces the remarkable pressure gradient around shedding *** with the development of the primary and the secondary shedding cavities,the great pressure gradient associated with large cavity volume variation promotes the vortical flow generation and the spatial deformation of vortex structure during cavitation evolution,and results in the primary and the secondary U-type ***,dynamic mode decomposition(DMD)analysis is utilized to confirm the interaction among the main flow,the main reentrant jet and two side reentrant jets,and *** results indicate that the proposed NMSST PANS model is suitable to simulate the complicated cavitating turbulent flow for various engineering applications.

关键词： Cavitating turbulent flow partially averaged Navier-Stokes(PANS)model hydrofoil numerical simulation

Study on the dynamic mechanical properties of winding-block axial structure considering short circuit strain rate effect

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High Voltage 2024年第2期9卷 380-390页

作者： Xinyu Wang Ping Wang Jianghai geng Zikang Zhang Fangcheng Lü Shuguo Gao Hebei Provincial Key Laboratory of Power Transmission Equipment Security Defense North China Electric Power UniversityBaodingChina State Grid Hebei Electric Power Research Institute ShijiazhuangChina

Transformers may suffer multiple short-circuit impacts during long-term operation,and axial instability is one of the typical types of serious accidents caused by short-circuit *** axial instability form of the winding-block structure is analysed,and the dynamic solution of the winding short-circuit electromagnetic force is obtained by estab-lishing the three-dimensional magnetic-circuit-force multi-physical field coupling simulation *** influence of strain rate on the cushion block constitutive equation is corrected,and the modified model is verified by short-circuit impact test and quasi-static *** research results show that for 110 kV 31.5 MVA transformers,the maximum electromagnetic axial resultant force of winding is 363.16 kN,and the ultimate tilt force is 1214.2 *** pre-tightening force configuration is accordingly recom-mended to range from 363.16 to 608.28 kN,which is narrowed by 18.49%compared with the static calculation method;Meanwhile,adding a logarithmic strain rate correction term to the classical constitutive equation of the cushion block can achieve a good correction of the stress-strain relationship with the coefficient of determination above 0.99,and the cushion block has a larger elastic modulus under high strain rate *** research results provide an important theoretical reference for the axial stability structure of transformers.

关键词： axial correction structure

Recent progress in single crystal perovskite X-ray detectors

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Science China(Information Sciences) 2024年第3期67卷 5-19页

作者： Xiao LIU Jun REN Yu-Ang CHEN Xiangshun geng Dan XIE Tian-Ling REN School of Integrated Circuits Tsinghua University Beijing National Research Center for Information Science and Technology (BNRist)

Perovskites have attracted extensive attention as radiation detection material due to their long carrier diffusion length and lifetime, high absorption coefficient, and flexible manufacturing process. Compared with polycrystalline structures, single crystal perovskites improve the performance of optoelectronic devices due to their low defect state density, better photoelectric characteristics, and chemical ***, we review the recent progress of single crystal perovskite X-ray detectors. First, we briefly introduced the basic concepts, detection mechanisms, figure of merits of perovskite X-ray detectors, and the preparation methods of single crystal perovskites. Then, we summarized the significant advancements in single crystal perovskite X-ray detectors in recent times. Finally, we discussed the critical challenges and some practicable solutions for developing high-performance X-ray detectors.

关键词： single crystal perovskites carrier transport radiation detection X-ray detectors X-ray imaging

Nanostructured AlFeO_(3) thin films as a novel photoanode for photoelectrochemical water splitting

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Nano Research 2024年第3期17卷 1075-1085页

作者： Xin Sun Min Wang Qi geng Shuailin Chen Xiaojun Lv Xunlei Ding Meicheng Li State Key Laboratory of Alternate Electrical Power System with Renewable Energy Sources School of New EnergyNorth China Electric Power UniversityBeijing 102206China School of Mathematics and Physics North China Electric Power UniversityBeijing 102206China

The earth-abundant and robust aluminum ferrite,AlFeO_(3)(AFO),is mainly studied in the context of ***,we demonstrate that AFO can be used as a stable solar absorber in photoelectrochemical cells for solar water splitting,exhibiting attractive *** is the first report on the photoelectrochemical activity of *** thin-film photoelectrodes prepared by solution-processing methods are composed of vertically oriented thin nanosheets,featuring the rhombohedral symmetry(R3c)and n-type *** as-prepared AFO photoanodes generate a photocurrent density of+0.78 mA·cm^(-2) at 1.23 V *** hydrogen electrode(RHE)with the photocurrent _(onset) potential(U_(onset))close to the flat band potential of 0.5 V *** in the presence of hole ***,the U_(onset) of AFO for solar water splitting coincides with the flat band potential as well,which is rare in n-type inorganic *** also report other properties of AFO associated with photoelectrochemical *** films exhibit a band gap energy of 2.31 eV and positive band edges with low ***,the carrier lifetimes in AFO films are up to millisecond timescales under the mediation of defect *** on the photoelectrochemical behavior and optoelectronic properties,we believe that AFO has great potential for application in photoelectrochemical cells.

关键词： AlFeO_(3) photoanode nanosheets photoelectrochemistry onset potential

Interconnected microstructure and flexural behavior of Ti_(2)C-Ti composites with superior Young’s modulus

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International Journal of Minerals,Metallurgy and Materials 2024年第9期31卷 2088-2101页

作者： Fengbo Sun Rui Zhang Fanchao Meng Shuai Wang Lujun Huang Lin geng School of Materials Science and Engineering Harbin Institute of TechnologyHarbin 150001China Waikato Centre for Advanced Materials and Manufacturing School of EngineeringUniversity of WaikatoHamilton 3240New Zealand State Key Laboratory of Precision Welding&Joining of Materials and Structures Harbin Institute of TechnologyHarbin 150001China

To enhance the Young’s modulus(E)and strength of titanium alloys,we designed titanium matrix composites with intercon-nected microstructure based on the Hashin-Shtrikman *** to the results,the in-situ reaction yielded an interconnected microstructure composed of Ti_(2)C particles when the Ti_(2)C content reached 50vol%.With widths of 10 and 230 nm,the intraparticle Ti lamellae in the prepared composite exhibited a bimodal size distribution due to precipitation and the unreacted Ti phase within the grown Ti_(2)C *** composites with interconnected microstructure attained superior properties,including E of 174.3 GPa and ultimate flexural strength of 1014 *** with that of pure Ti,the E of the composite was increased by 55% due to the high Ti_(2)C content and interconnected *** outstanding strength resulted from the strong interfacial bonding,load-bearing capacity of interconnected Ti_(2)C particles,and bimodal intraparticle Ti lamellae,which minimized the average crack driving *** flexural tests revealed preferential crack initiation along the{001}cleavage plane and grain boundary of Ti_(2)C in the region with the highest tensile *** addition,the propagation can be efficiently inhibited by interparticle Ti grains,which prevented the brittle fracture of the composites.

关键词： titanium matrix composites titanium carbide interface Young’s modulus flexural behavior

Anthropogenic mineral generation and its potential resource supply:The case of niobium

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Science China Earth Sciences 2024年第8期67卷 2583-2591页

作者： Xianlai ZENG Moisés Gómez Mahmoud BAKRY Yong geng Jinhui LI School of Environment Tsinghua UniversityBeijing 100084China School of Environmental Science and Engineering Shanghai Jiao Tong UniversityShanghai 200240China School of International and Public Affairs Shanghai Jiao Tong UniversityShanghai 200030China

The strategy of carbon neutrality is reshaping the global landscape of resource flow and *** the final sink of geological minerals,the proliferated anthropogenic minerals,also called secondary resources,play an increasingly important role in resource supply *** is a critical metal that lacks full concern for its *** fundamental principle of niobium circularity is to recycle and maintain the material as close to the manufacturing process as *** we estimate the niobium-containing applications lost at their end-of-life,underscoring the imperative to minimize such ***,we elucidate the extraction processes for scrap and alloy quantities throughout the industry's *** from anticipated waste generated by the majority of niobium applications,a forecast indicates a potential loss of approximately 168 kt by 2090 in the absence of ***,with a recycling efficiency of 90%for niobium,the projected loss diminishes to approximately 16 *** delve into the significance of niobium's circular economy and explore various aspects that demand further investigation for a seamless transition from linear to circular practices.

关键词： Niobium Anthropogenic mineral Circular economy Recycling Sustainability

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