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defects boost graphitization for highly conductive graphene films

National Science Review 2023年第7期10卷 172-182页

作者： Qing Zhang Qinwei Wei Kun Huang Zhibo Liu Wei Ma Zehui Zhang Yanfeng Zhang Hui-Ming Cheng Wencai Ren Shenyang National Laboratory for Materials Science Institute of Metal Research Chinese Academy of Sciences School of Materials Science and Engineering University of Science and Technology of China School of Materials Science and Engineering Peking University Shenzhen Institute of Advanced Technology Chinese Academy of Sciences

Fabricating highly crystalline macroscopic films with extraordinary electrical and thermal conductivities from graphene sheets is essential for applications in electronics,telecommunications and thermal management.High-temperature graphitization is the only method known to date for the crystallization of all types of carbon materials,where defects are gradually removed with increasing temperature.However,when using graphene materials as precursors,including graphene oxide,reduced graphene oxide and pristine graphene,even lengthy graphitization at 3000℃ can only produce graphene films with small grain sizes and abundant structural disorders,which limit their conductivities.Here,we show that high-temperature defects substantially accelerate the grain growth and ordering of graphene films during graphitization,enabling ideal AB stacking as well as a 100-fold,64-fold and 28-fold improvement in grain size,electrical conductivity and thermal conductivity,respectively,between 2000℃ and 3000℃.This process is realized by nitrogen doping,which retards the lattice restoration of defective graphene,retaining abundant defects such as vacancies,dislocations and grain boundaries in graphene films at a high temperature.With this approach,a highly ordered crystalline graphene film similar to highly oriented pyrolytic graphite is fabricated,with electrical and thermal conductivities(～2.0×104S cm-1;～1.7×103W m-1K-1) that are improved by about 6-and 2-fold,respectively,compared to those of the graphene films fabricated by graphene oxide.Such graphene film also exhibits a superhigh electromagnetic interference shielding effectiveness of ～90 dB at a thickness of 10 μm,outperforming all the synthetic materials of comparable thickness including MXene films.This work not only paves the way for the te chnological application of highly conductive graphene films but also provides a general strategy to efficiently improve the synthesis and properties of other carbon materials such as graphene fibers,carbon nanotube fibers,carbon fibers,polym

关键词： graphene film defects graphitization electrical and thermal conductivity thermal management and EMI shielding

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defects and doping engineering towards high performance lead-free or lead-less perovskite solar cells

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Journal of Energy Chemistry 2022年第5期31卷 420-438页

作者： Wenying Cao Zhaosheng Hu Zhenhua Lin Xing Guo Jie Su Jingjing Chang Yue Hao State Key Discipline Laboratory of Wide Band Gap Semiconductor Technology School of MicroelectronicsXidian UniversityXi’an 710071ShaanxiChina Advanced Interdisciplinary Research Center for Flexible Electronics Xidian UniversityXi’an 710071ShaanxiChina

Up to now, perovskite solar cells(PSCs) have reached a certified 25.5% efficiency. As a promising photo-electric material, the metal halide perovskite possesses many outstanding properties such as tunable bandgap, long diffusion length, high absorption coefficient and carrier mobility. In spite of these remarkable properties, defects are inevitable during the solution processing. Therefore, many efforts have been made to reduce defects in perovskite films and thus improve the performance of devices. Among them,substitution or doping engineering is one of the most studied methods. Meanwhile, due to the poor stability of the organic-inorganic hybrid perovskite and the toxicity of Pb-based perovskite materials, all inorganic perovskite and lead-less or lead-free perovskite have emerged as promising materials. Here,we focus on the defect engineering especially substitutions on different sites in an ABX_(3) structure. The particular attention is devoted towards lead-less or lead-free perovskites, and we discuss several common elements or groups used to partially replace Pb^(2+). It is noted that proper elemental doping at different sites is an important guarantee for obtaining high-performance lead-less or lead-free PSCs.

关键词： Perovskite defects Doping engineering Lead-free Lead-less Solar cells

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defects Engineering with Multiple Dimensions in Thermoelectric Materials

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Research 2020年第1期2020卷 1898-1920页

作者： Chenxi Zhao Zhou Li Tianjiao Fan Chong Xiao Yi Xie Hefei National Laboratory for Physical Sciences at Microscale CAS Center for Excellence in NanoscienceUniversity of Science&Technology of ChinaHefeiAnhui 230026China Institute of Energy Hefei Comprehensive National Science CenterHefeiAnhui 230031China

Going through decades of development,great progress in both theory and experiment has been achieved in thermoelectric materials.With the growing enhancement in thermoelectric performance,it is also companied with the complexation of defects induced in the materials.0D point defects,1D linear defects,2D planar defects,and 3D bulk defects have all been induced in thermoelectric materials for the optimization of thermoelectric performance.Considering the distinct characteristics of each type of defects,in-depth understanding of their roles in the thermoelectric transport process is of vital importance.In this paper,we classify and summarize the defect-related physical effects on both band structure and transport behavior of carriers and phonons when inducing different types of defects.Recent achievements in experimental characterization and theoretical simulation of defects are also summarized for accurately determining the type of defects serving for the design of thermoelectric materials.Finally,based on the current theoretical and experimental achievements,strategies engaged with multiple dimensional defects are reviewed for thermoelectric performance optimization.

关键词： materials defects defects

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The Impact of Pregnancy Termination before 28 Weeks of Gestation on the Overall Prevalence of Birth defects-Shaanxi Province,China,2014-2020

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China CDC weekly 2022年第43期4卷 967-973页

作者： Min Li Le Zhang Lu Gan Zhiwen Li Northwest Women’s and Children's Hospital Xi’an CityShaanxi ProvinceChina Institute of Reproductive and Child Health Peking UniversityBeijingChina Key Laboratory of Reproductive Health National Health Commission of the People’s Republic of ChinaBeijingChina

Introduction:The prevalence of birth defects(BDs)at≥28 gestational weeks in China has declined significantly in recent years.However,a few studies have implied that the prevalence is underestimated due to pregnancies with severe BDs often being terminated before 28 weeks of gestation.This study sought to contribute to this data conflict by determining the total prevalence of BDs throughout the entirety of pregnancies,depicting the epidemiological distribution of BDs in Shaanxi Province,and examining the impact of pregnancy termination before 28 weeks of gestation on overall BD prevalence.Methods:Based on data extracted from the provincial Birth defects Surveillance Network in Shaanxi Province,from 2014 to 2020,the trends of 18 frequent,major BDs at any gestational age were analysed.Results:The total prevalence of BDs throughout pregnancy in Shaanxi Province increased significantly from 2014 to 2020,partly due to the inclusion of slight congenital heart diseases.It was also shown that the prevalence of all major types of BD had been previously underestimated,particularly severe external BDs,anywhere from 10%to 100%due to the previous sole measurement of terminations after 28 gestational weeks.Neural tube defects,however,remained one of the top five BDs with the highest total prevalence.Conclusions:The exclusion of pregnancy terminationsdefects.To estimate the true population-level prevalence of BD better,the current BD surveillance system should include pregnancy terminations before 28 weeks of gestation.

关键词： termination Impact defects

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Built defects of homogeneous junction to enhance the lithium storage capacity of niobium pentoxide materials

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Journal of Energy Chemistry 2024年第5期92卷 730-737页

作者： Huibin Ding Yang Luo Zihan Song Cong Chen Kai Feng Xiaofei Yang Hongzhang Zhang Xianfeng Li Division of Energy Storage National Laboratory for Clean EnergyDalian Institute of Chemical PhysicsChinese Academy of SciencesDalian 116023LiaoningChina University of Chinese Academy of Sciences Beijing 100049China College of Chemistry&Engineering Yantai UniversityYantai 264005ShandongChina

Niobium pentoxide(Nb_(2)O_(5))is deemed one of the promising anode materials for lithium-ion batteries(LIBs)for its outstanding intrinsic fast Li-(de)intercalation kinetics.The specific capacity,however,is still limited,because the(de)intercalation of excessive Li-ions brings the undesired stress to damage Nb_(2)O_(5) crystals.To increase the capacity of Nb_(2)O_(5) and alleviate the lattice distortion caused by stress,numerous homogeneous H-and M-phases junction interfaces were proposed to produce coercive stress within theNb_(2)O_(5)crystals.Such interfaces bring about rich oxygen vacancies with structural shrinkage tendency,which pre-generate coercive stress to resist the expansion stress caused by excessive Li-ions intercalation.Therefore,the synthesized Nb_(2)O_(5) achieves the highest lithium storage capacity of 315 mA h g−1 to date,and exhibits high-rate performance(118 mA h g^(-1) at 20 C)as well as excellent cycling stability(138 mA h g^(-1) at 10 C after 600 cycles).

关键词： Niobiumpent oxide Homojunction polycrystalline defects Oxygen vacancy

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RuO_(2)-PdO nanowire networks with rich interfaces and defects supported on carbon toward the efficient alkaline hydrogen oxidation reaction

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能源化学:英文版 2023年第8期83卷 255-263,I0008页

作者： Yuanyuan Cong Fanchao Meng Haibin Wang Di Dou Qiuping Zhao Chunlei Li Ningshuang Zhang Junying Tian School of Petrochemical Technology Lanzhou University of TechnologyLanzhou 730050GansuChina Key Laboratory of Low Carbon Energy and Chemical Engineering of Gansu Province Lanzhou University of TechnologyLanzhou 730050GansuChina

Interfacial engineering is a promising approach for enhancing electrochemical performance,but rich and efficient interfacial active sites remain a challenge in fabrication.Herein,RuO_(2)-PdO heterostructure nanowire networks(NWs) with rich interfaces and defects supported on carbon(RuO_(2)-PdO NWs/C) for alkaline hydrogen oxidation reaction(HOR) was formed by a seed induction-oriented attachment-thermal treatment method for the first time.As expected,the RuO_(2)-PdO NWs/C(72.8% Ru atomic content in metal) exhibits an excellent activity in alkaline HOR with a mass specific exchange current density(jo,m) of 1061 A gRuPd-1,which is 3.1 times of commercial Pt/C and better than most of the reported nonPt noble metal HOR electrocatalysts.Even at the high potential(~0.5 V vs.RHE) or the presence of CO(5 vol%),the RuO_(2)-PdO NWs/C still effectively catalyzes the alkaline HOR.Structure/electrochemical analysis and theoretical calculations reveal that the interfaces between RuO_(2) and PdO act as the active sites.The electronic interactions between the two species and the rich defects for the interfacial active sites weaken the adsorption of Had,also strengthen the adsorption of OHad,and accelerate the alkaline HOR process.Moreover,OHadon RuO_(2) can spillover to the interfaces,keeping the RuO_(2)-PdO NWs/C with the stable current density at higher potential and high resistance to CO poisoning.

关键词： Hydrogen oxidation reaction Heterostructure Nanowire networks defects Interfacial active sites

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Pore defects in a nickel-based superalloy with high Ti content

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Progress in Natural Science:Materials International 2022年第4期32卷 456-462页

作者： Puying Shi Wenliang Xu Baoquan Fu Jin Liu Jianing Zhang Kaixuan Wang Xianghong Liu Western Superconducting Technologies Co. Ltd. School of Mechanical Engineering Xi'an Jiaotong University

Pores are uncommon defects in superalloy bars, which deserve to be investigated. In this work, a type of pore defect within GH4710 nickel-based superalloy was investigated by 3D X-ray imaging method combined with metallographic analysis. 3D X-ray imaging was used for locating and visualizing the defects in the alloy. The 3D Xray imaging result of the defects showed a good agreement with the defect anatomical morphologies. It was observed that the pore defect was accompanied by MC carbides, micro-crack, and non-metallic inclusions. The origin of pore defect was attributed to the shrinkage pores, inclusion and the complex precipitates. The analysis showed that the pore defects in GH4710 alloy was associated with strong micro-segregation and complex phase precipitation during solidification, induced by the high weight content of Ti and C in the alloy.

关键词： Ni-based superalloy defects 3D X-ray imaging High Ti content

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Analysis of element loss, densification, and defects in laser-based powder-bed fusion of magnesium alloy WE43

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Journal of Magnesium and Alloys 2022年第8期10卷 2118-2136页

作者： Faridreza Attarzadeh Ebrahim Asadi Department of Mechanical Engineering The University of MemphisMemphisTN 38152United States

It is well known that laser-based powder-bed fusion(L-PBF) additive manufacturing of magnesium(Mg) and its alloys is associated with high Mg loss due to vaporization(MgLoss) and high incidence of many types of defects in the manufactured parts/samples. Despite this,MgLoss, densification, and defect characteristics have not been holistically considered in the determination of the optimal values of L-PBF processing parameters for Mg and its alloys. This study presents a combined modeling and experimental approach applied for a widely used Mg alloy(WE43) to address this shortcoming in the literature. First, an experimentally calibrated model is proposed to determine MgLoss as a function of the L-PBF processing parameters. The model couples the temperature profile using a double ellipsoidal heat source with a Langmuir vaporization model and is calibrated using the width of the single-track L-PBF process and the measured Mglossusing inductively coupled plasma mass spectrometry(ICP-MS). Second, the densification of the samples is determined using a modification of the Archimedes method that considers the amount of MgLossin the calculation of the relative density. Third, a comprehensive and quantitative study is conducted on the relationships between the characteristics of porosity defects and the L-PBF processing parameters. Finally, the optimized L-PBF processing parameters are determined by considering the MgLoss, densification, and the characteristics of defects. The present study yields 0.23 wt.% MgLosscompared to 2 wt.% MgLossthat was reported in the previous studies. Furthermore, more than 99.5% densification is achieved while only ~2% and ~0.5% of the total defects are characterized as keyhole and lack of fusion defects, respectively.

关键词： WE43 magnesium alloy Additive manufacturing Powder-bed fusion Mg loss Vaporization defects

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Assembly of 3D-printed Ti scaffold and free vascularized fibula using a customized Ti plate for the reconstruction of mandibular defects

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Bio-Design and Manufacturing 2022年第2期5卷 424-429页

作者： Chiyang Zhong Yixuan Zhao Hongyu Xing Qingguo Lai Runqi Xue Tianxiang Song Xiaopeng Tang Kaiwen Zhu Yanwei Deng Department of Oral and Maxillofacial Surgery The Second HospitalCheeloo College of MedicineShandong UniversityJinan 250033China School of Stomatology Cheeloo College of MedicineShandong UniversityJinan 250012China School of Mechanical and Electronic Engineering Shandong Jianzhu UniversityJinan 250101China Research Center of 3D Printing in Stomatology of Shandong University Jinan 250012China

Introduction Mandibular segmental defects result in significant cosmetic and functional deficiencies.Meanwhile,the reconstruction of both the contour and function of the mandible is a challenging task.At present,autologous vascularized fibula transplantation is the most common method to reconstruct a mandible with long-span defects[1].

关键词： fibula mandibular defects

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In situ generated layered NiFe-LDH/MOF heterostructure nanosheet arrays with abundant defects for efficient alkaline and seawater oxidation

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Nano Research 2023年第7期16卷 8945-8952页

作者： Manjie Xiao Can Wu Jiawei Zhu Chengtian Zhang Yan Li Jiahui Lyu Weihao Zeng Haiwen Li Lei Chen Shichun Mu State Key Laboratory of Advanced Technology for Materials Synthesis and Processing Wuhan University of TechnologyWuhan 430070China Foshan Xianhu Laboratory Foshan 528200China Science and Technology Institute of Advanced Technology Wuhan 430051China Hefei General Machinery Research Institute Hefei 230031China

As the main limiting step of overall water splitting,oxygen evolution reaction(OER)is urgent to be enhanced by developing efficient catalysts to promote the process of electrolytic water.Based on theoretical analysis,the Ni-metal-organic framework(Ni-MOF)and NiFe-layered double hydroxide(NiFe-LDH)(NiFe-LDH/MOF)heterostructure can optimize the energy barrier of the OER process and decrease the adsorption energy of oxygen-containing intermediates,effectively accelerating the OER kinetics.Accordingly,layered NiFe-LDH/MOF heterostructures are in situ constructed through a facile two-step reaction process,with substantial oxygen defects and lattice defects that further improve the catalytic performance.As a result,only 208 and 275 mV OER overpotentials are needed for NiFe-LDH/MOF to drive the current densities of 20 and 100 mA·cm^(-2)in 1 M KOH solutions,and even maintain catalytic stability of 100 h at 20 mA·cm^(-2).When applied to seawater oxidation,only 235 and 307 mV OER overpotentials are required to achieve the current densities of 20 and 100 mA·cm^(-2),respectively,with almost no attenuation for 100 h stability test at 20 mA·cm^(-2),all better than commercial RuO_(2).This work provides the theoretical and experimental basis and a new idea for efficiently driving fresh water and seawater cracking by heterostructure and defect coupling design toward catalysts.

关键词： oxygen evolution reaction defects seawater electrolysis catalyst

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