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MXene Hollow Spheres Supported by a C–Co Exoskeleton Grow MWCNTs for Efficient Microwave Absorption

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Nano-Micro Letters 2024年第6期16卷 76-94页

作者： Ze Wu Xiuli Tan Jianqiao Wang Youqiang Xing Peng Huang Bingjue Li Lei Liu school of Mechanical engineering Southeast UniversityNanjing 211189People’s Republic of China

High-performance microwave absorption(MA) materials must be studied immediately since electromagnetic pollution has become a problem that cannot be disregarded. A straightforward composite material, comprising hollow MXene spheres loaded with C–Co frameworks, was prepared to develop multiwalled carbon nanotubes(MWCNTs). A high impedance and suitable morphology were guaranteed by the C–Co exoskeleton, the attenuation ability was provided by the MWCNTs endoskeleton, and the material performance was greatly enhanced by the layered core–shell structure. When the thickness was only 2.04 mm, the effective absorption bandwidth was 5.67 GHz, and the minimum reflection loss(RLmin) was-70.70 d B. At a thickness of 1.861 mm, the sample calcined at 700 ℃ had a RLmin of-63.25 d B. All samples performed well with a reduced filler ratio of 15 wt%. This paper provides a method for making lightweight core–shell composite MA materials with magnetoelectric synergy.

关键词： MXene C-Co skeleton MWCNTs Microwave absorption

Steric hindrance modulation of hexaazatribenzanthraquinone isomers for high-capacity and wide-temperature-range aqueous proton battery

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National Science Review 2024年第4期11卷 271-282页

作者： Mingsheng Yang Yuxin Hao Bei Wang Yan Wang Liping Zheng Rui Li Huige Ma Xinyu Wang Xiaoming Jing Hongwei Li Mengxiao Li Zhihui Wang Yujie Dai Guangcun Shan Mingjun Hu Jun Luo Jun Yang school of Materials Science and engineering Beihang University Beijing Institute of Nanoenergy &Nanosystems Chinese Academy of Sciences Center on Nanoenergy Research School of Physical Science & TechnologyGuangxi University school of Chemistry and Chemical engineering Center on Nanoenergy Research Guangxi University school of Instrumentation Science and Opto-electronics engineering Beihang University ShenSi Lab Shenzhen Institute for Advanced StudyUniversity of Electronic Science and Technology of China

Organic materials with rich active sites are good candidates of high-capacity anodes in aqueous batteries,but commonly low utilization of active sites limits their capacity.Herein,two isomers,symmetric and asymmetric hexaazatribenzanthraquinone（s-HATBAQ and a-HATBAQ）,with rich active sites have been synthesized in a controllable manner.It has been revealed for the first time that a sulfuric acid catalyst can facilitate the stereoselective formation of s-HATBAQ.Attributed to the reduced steric hindrance in favor of proton insertion as well as the amorphous structure conducive to electrochemical dynamics,s-HATBAQ exhibits 1.5 times larger specific capacity than a-HATBAQ.Consequently,the electrode of s-HATBAQ with50% reduced graphene oxide（s-HATBAQ-50%rGO） delivers a record high specific capacity of405 mAh g-1in H2SO4electrolyte.Moreover,the assembled MnO2//s-HATBAQ-50%rGO aqueous proton full batteries show an exceptional cycling stability at 25℃ and can maintain ～92% capacity after1000 cycles at 0.5 A g-1at-80℃.This work demonstrates the controllable synthesis of isomers,showcases a wide-temperature-range prototype proton battery and highlights the significance of precise mole cular structure modulation in organic energy storage.

关键词： stereoisomers steric effect aqueous battery super cycling stability ultra-low temperature proton battery

Laser-assisted direct roller imprinting of large-area microstructured optical surfaces

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Microsystems & Nanoengineering 2024年第1期10卷 257-266页

作者： Keisuke Nagato Ken Takahashi Yuki Yajima Masayuki Nakao Department of Mechanical engineering Graduate School of EngineeringThe University of Tokyo7-3-1 HongoBunkyo-kuTokyo 113-8656Japan

In this study,a high-throughput fabrication method called laser-assisted direct roller imprinting(LADRI)was developed to lower the cost of nanoimprinting large-area polymer films and to address problems associated with nanoimprinting,namely,microstructural damage and precision in flatness of entire film.With LADRI,the laser directly heats the microstructured surface of the roller mold,which heats and melts the surface of a polymethyl methacrylate(PMMA)film to replicate the microstructures on the mold rapidly.In this study,the effects of laser power density,scanning speed,size of the microstructures,and contact pressure on the replication speed were investigated experimentally.The replication speed increased as the power and scanning speed increased.However,because the film required heating until it filled the entire depth of the microstructure,an appropriate replication speed was necessary.This result was supported by simulation of the temperature distribution inside the mold and the PMMA using transient heat conduction analyses.To demonstrate the applications of LADRI,two different optical surfaces were replicated:an antireflection(AR)structure with conical structures sized several hundred nanometers and a lightextraction structure with a microlens array(MLA)comprising 10μm lenses,for display and illumination,respectively.The replication degree of the MLA was governed by the contact pressure.Polymer flow simulation indicated that the heat conduction and flow speeds of the melted PMMA surface were comparable within several tens of micrometers.In addition,the reflectivity of the AR structure decreased from 4 to 0.5%,and the light intensity of the light-extraction structure increased by a factor of 1.47.

关键词： microstructure roller conduction

Tackling the proton limit under industrial electrochemical CO_(2)reduction by a local proton shuttle

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Carbon Energy 2024年第4期6卷 233-243页

作者： Tianye Shao Kang Yang Sheng Chen Min Zheng Ying Zhang Qiang Li Jingjing Duan MIIT Key Laboratory of Thermal Control of Electronic Equipment School of Energy and Power EngineeringSchool of Chemistry and Chemical EngineeringNanjing University of Science and TechnologyNanjingChina school of Chemical engineering and Advanced Materials The University of AdelaideAdelaideSouth AustraliaAustralia

Industrial CO_(2)electroreduction has received tremendous attentions for resolution of the current energy and environmental crisis,but its performance is greatly limited by mass transport at high current density.In this work,an ion‐polymer‐modified gas‐diffusion electrode is used to tackle this proton limit.It is found that gas diffusion electrode‐Nafion shows an impressive performance of 75.2%Faradaic efficiency in multicarbon products at an industrial current density of 1.16 A/cm^(2).Significantly,in‐depth electrochemical characterizations combined with in situ Raman have been used to determine the full workflow of protons,and it is found that HCO_(3)^(−)acts as a proton pool near the reaction environment,and HCO_(3)^(−)and H_(3)O^(+)are local proton donors that interact with the proton shuttle−SO_(3)^(−)from Nafion.With rich proton hopping sites that decrease the activation energy,a“Grotthuss”mechanism for proton transport in the above system has been identified rather than the“Vehicle”mechanism with a higher energy barrier.Therefore,this work could be very useful in terms of the achievement of industrial CO_(2)reduction fundamentally and practically.

关键词： industrial CO_(2)electroreduction proton donor proton pool proton shuttle proton transport mechanism

Review of tribological properties of nanoparticle-based lubricants and their hybrids and composites

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Friction 2024年第4期12卷 569-590页

作者： Ye Zar Ni HTWE Aws.S.AL-JANABI Yasmin WADZER Hussin MAMAT Ku NOORYASMIN school of Materials&Mineral Resources engineering Universiti Sains Malaysia(Engineering Campus)Nibong Tebal 14300Malaysia school of Aerospace engineering Universiti Sains Malaysia(Engineering Campus)Nibong Tebal 14300Malaysia Universiti Sains Malaysia

Due to their encouraging results,nanolubricants have been revolutionary in the field of lubrication.The degree,to which the new material may improve the tribology,energy savings,and durability,is a crucial consideration for any new additive to a conventional lubricant.The results of the earlier research on carbon,metal,metal oxide,and their composites and hybrid nanolubricants as well as their effects on tribology,are summarized in this review paper.The most popular measuring methodologies,the tribology results for lubricants with an oil base,biodegradable base,and a water base,as well as the reasons that explain these tribological advancements,are all included in this study.Finally,prospects for more study in this area are emphasized.

关键词： nanolubricants tribology carbon metal metal oxide hybrid

Performance Improvement of Two-Phase Steam Ejector based on CFD Techniques,Response Surface Methodology and Genetic Algorithm

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Journal of Thermal Science 2024年第2期33卷 675-695页

作者： ZHANG Hao ZHAO Hongxia ZHANG Xiuao ZENG Hongxuan DENG Jianqiang school of Energy and Power engineering Shandong UniversityJi’nan250061China school of Chemical engineering and Technology Xi’an Jiaotong UniversityXi’an710049China

The steam ejector is a crucial component in the waste heat recovery system.Its performance determines the amount of recovered heat and system efficiency.However,poor ejector performance has always been the main bottleneck for system applications.Therefore,this study proposes an optimization methodology to improve the steam ejector's performance by utilizing computational fluid dynamics(CFD) techniques,response surface methodology(RSM),and genetic algorithm(GA).Firstly,a homogeneous equilibrium model(HEM) was established to simulate the two-phase flow in the steam ejector.Then,the orthogonal test was presented to the screening of the key decision variables that have a significant impact on the entrainment ratio(ER).Next,the RSM was used to fit a response surface regression model(RSRM).Meanwhile,the effect of the interaction of geometric parameters on the performance of the steam ejector was revealed.Finally,GA was employed to solve the RSRM's global optimal ER value.The results show that the RSRM exhibits a good fit for ER(R^(2)=0.997).After RSM and GA optimization,the maximum ejector efficiency is 27.94%,which is 48.38% higher than the initial ejector of 18.83%.Furthermore,the optimized ejector efficiency is increased by 46.4% on average under off-design conditions.Overall,the results reveal that the combination of CFD,RSM,and GA presents excellent reliability and feasibility in the optimization design of a two-phase steam ejector.

关键词： two-phase steam ejector optimization methodology CFD techniques response surface methodology genetic algorithm homogeneous equilibrium model

Prediction of collapse process and tipping points for mutualistic and competitive networks with k-core method

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Chinese Physics B 2024年第5期33卷 173-180页

作者：段东立毕菲菲李思凡吴成星吕长春蔡志强 school of Information and Control engineering Xi'an University of Architecture and TechnologyXi'an 710311China school of Mechanical engineering Northwestern Polytechnical UniversityXi'an 710072China

Ecosystems generally have the self-adapting ability to resist various external pressures or disturbances,which is always called resilience.However,once the external disturbances exceed the tipping points of the system resilience,the consequences would be catastrophic,and eventually lead the ecosystem to complete collapse.We capture the collapse process of ecosystems represented by plant-pollinator networks with the k-core nested structural method,and find that a sufficiently weak interaction strength or a sufficiently large competition weight can cause the structure of the ecosystem to collapse from its smallest k-core towards its largest k-core.Then we give the tipping points of structure and dynamic collapse of the entire system from the one-dimensional dynamic function of the ecosystem.Our work provides an intuitive and precise description of the dynamic process of ecosystem collapse under multiple interactions,and provides theoretical insights into further avoiding the occurrence of ecosystem collapse.

关键词： complex networks tipping points dimension reduction k-core

Boosting cycling stability by regulating surface oxygen vacancies of LNMO by rapid calcination

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Nano Research 2024年第4期17卷 2671-2677页

作者： Haoran Jiang Cuihua Zeng Wei Zhu Jiawei Luo Zhedong Liu Jingchao Zhang Rui Liu Yunhua Xu Yanan Chen Wenbin Hu school of Materials Science and engineering Tianjin UniversityTianjin 300072China school of Materials Science and engineering Shandong University of Science and TechnologyQingdao 266590China

Spinel LiNi_(0.5-x)Mn_(1.5+x)O_(4)(LNMO)has attracted intensive interest for lithium-ion battery due to its high voltage and high energy density.However,severe capacity fade attributed to unstable surface structure has hampered its commercialization.Oxygen vacancies(OVs)tend to occur in the surface of the material and lead to surface structure reconstruction,which deteriorates the battery performance during electrochemical cycling.Here,we utilize high-temperature-shock(HTS)method to synthesize LNMO materials with fewer surface OVs.Rapid calcination drives lower surface OVs concentration,reducing the content of Mn^(3+)and surface reconstruction layers,which is beneficial to obtain a stable crystal structure.The LNMO material synthesized by HTS method delivers an initial capacity of 127 mAh·g^(-1) at 0.1 C and capacity retention of 81.6%after 300 cycles at 1 C,and exhibits excellent performance at low temperature.

关键词： ultrafast synthesis oxygen vacancy LiNi_(0.5-x)Mn_(1.5+x)O_(4)(LNMO)cathode high-temperature-shock lithium-ion batteries

One dimensional CeO_(2) nanorods/poly(ethylene oxide) solid composite electrolyte for all-solid-state lithium-ion batteries

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Journal of Rare Earths 2024年第3期42卷 570-577,I0005页

作者： Yudi Guo Erqing Zhao Xiaofang Zhao Shuailei Liu school of Chemistry and Materials engineering Xinxiang UniversityXinxiang453003China school of Chemistry and Chemical engineering Henan Institute of Science and TechnologyXinxiang453003China

The research of poly(ethylene oxide)(PEO)-based solid composite electrolyte with high ionic conductivity and excellent interfacial stability is the key to the development of all-solid-state lithium-ion batteries(ASSLIBs). Herein, uniform nanorod structured CeO_(2) fillers were controllably synthesized by electrospinning, which were subsequently filled into PEO polymer to prepare CeO_(2)/PEO solid composite electrolyte. The addition of CeO_(2) nanorods can reduce both the glass transition temperature and the melting point of PEO polymer, and also interact with PEO and lithium bis(trifluoromethanesulphonyl)imide(LITFSI) by Lewis acid—base reaction. Therefore, the solid composite electrolyte exhibits a high ionic conductivity of 4.52 × 10^(-4)S/cm, a wide electrochemical stability window of about 4.8 V, and a good interfacial stability with Li at 55℃. Moreover, the LiFePO_4/Li ASSLIB divulges the discharging specific capacity of 165, 162, 156 and 146 mA,h/g at 0.2, 0.5, 1 and 2 C, respectively, and achieves the capacity retention of 90.3% after 150 cycles at 0.5 C. Consequently, one dimensional CeO_(2) nanorods can be considered as an alternative filler for polymeric solid electrolyte.

关键词： Poly(ethylene oxide) Solid composite electrolyte CeO_(2)nanorods Ionic conductivity Rare earths