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Composition-dependent structural characteristics and mechanical properties of amorphous SiBCN ceramics by ab-initio calculations

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Journal of Advanced Ceramics 2023年第5期12卷 984-1000页

作者： Yuchen liu Yu Zhou Dechang Jia Zhihua Yang Wenjiu Duan Daxin li shuzhou li Ralf Riedel Bin liu Institute for Advanced Ceramics School of Materials Science and EngineeringHarbin Institute of TechnologyHarbin 150001China School of Materials Science and Engineering Shanghai UniversityShanghai 200444China Tsinghua Shenzhen International Graduate School Tsinghua UniversityShenzhen 518055China School of Materials Science and Engineering Nanyang Technological UniversitySingapore 639798Singapore Institut für Materialwissenschaft Technische Universität DarmstadtDarmstadt D-64287Germany

The atomic structural features and the mechanical properties of amorphous silicoboron carbonitride ceramics with 13 different compositions in the Si–BN–C phase diagram are investigated employing ab-initio calculations.Both chemical bonds and local structures within the amorphous network relate to the elemental composition.The distribution of nine types of chemical bonds is composition-dependent,where the B–C,Si–N,Si–C,and B–N bonds hold a large proportion for all compositions.Si prefers to be tetrahedrally coordinated,while B and N prefer sp^(2)-like trigonal coordination.In the case of C,the tetrahedral coordination is predominant at relatively low C contents,while the trigonal coordination is found to be the main feature with the increasing C content.Such local structural characteristics greatly influence the mechanical properties of SiBCN ceramics.Among the studied amorphous ceramics,SiB_(2)C_(3)N_(2) and SiB_(3)C_(2)N_(3) with low Si contents and moderate C and/or BN contents have high elastic moduli,high tensile/shear strengths,and good debonding capability.The increment of Si,C,and BN contents on this basis results in the decrease of mechanical properties.The increasing Si content leads to the increment of Si-contained bonds that reduce the bond strength of SiBCN ceramics,while the latter two cases are attributed to the raise of sp^(2)-like trigonal configuration of C and BN.These discoveries are expected to guide the composition-tailored optimization of SiBCN ceramics.

关键词： ultra-high-temperature ceramics density functional theory(DFT) amorphous structure mechanical properties

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Melting mechanisms of Pt-based multimetallic spherical nanoparticles by molecular dynamics simulation

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稀有金属：英文版 2023年第2期42卷 406-417页

作者： Chun-Yu Cheng Yuan-Yuan Guo Yi-Ming Zou Amanda Jiamin Ong Alfred ling Yoong Tok shuzhou li School of Materials Science and Engineering Nanyang Technological UniversitySingapore639798Singapore

The melting mechanisms of Pt-based multimetallic nanoparticles(NPs)are important to help determine their optimal melting processes.To understand the melting and coalescence behaviors of heterogeneous NPs(Pd-Pt NPs)with various sizes and compositions,molecular dynamics(MD)simulation was employed.The MD results for larger Pd-Pt NPs with an effective diameter of4.6-7.8 nm show that PtPd alloy can form at Pd/Pt interface before Pd NP melted completely,while for Pt-core/Pdshell NP and Pd-core/Pt-shell NP,PtPd alloy formed only after Pd portion melted completely.For smaller Pd-Pt NPs with an effective diameter of 2.5-4.0 nm,PdPt alloy is not formed until both Pd and Pt NPs melted completely.Besides,the coalescence process of Pd-Pt NPs depends on the melting temperature of Pt NP when Pt composition is higher than 20 at%.Furthermore,the melting mechanisms of Pd/Pt/Ir trimetallic NPs are investigated.A two-step melting process occurs in Pd-Pt-Ir NPs and Ir-core/Ptshell/Pd-shell NP,and the melting sequence of Pd-core/Ptshell/Ir-shell NP and Pt-core/Pd-shell/Ir-shell NP is different from Pd/Pt bimetallic NPs.

关键词： Molecular dynamics(MD) Melting mechanism Pt-based Multimetallic Heterogeneous structure

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Molecule functionalization to facilitate electrocatalytic oxygen reduction on graphdiyne

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Journal of Energy Chemistry 2022年第2期31卷 141-148页

作者： Huiying Yao Yasong Zhao Nailiang Yang Wei Hao Hu Zhao shuzhou li Jia Zhu lin Shen Weihai Fang College of Chemistry Key Laboratory of Theoretical&Computational Photochemistry of Ministry of EducationBeijing Normal UniversityBeijing 100875China State Key Laboratory of Biochemical Engineering Institute of Process EngineeringChinese Academy of SciencesBeijing 100190China School of Materials Science and Engineering Nanyang Technological University50 Nanyang Avenue639798Singapore Department of Physics Beijing Normal UniversityBeijing 100875China Laboratory of Theoretical and Computational Nanoscience CAS Center for Excellence in NanoscienceNational Center for Nanoscience and TechnologyChinese Academy of SciencesBeijing 100190China

Chemical doping is verified to be a promising strategy to regulate local electron distribution and further promote the poor intrinsic catalytic activity of graphdiyne.However,the current doping approach still faces problems such as precise doping for creating active sites and the destruction of graphdiyne skeleton calling for high temperature.Here,we achieved charge redistribution on graphdiyne surface through molecule functionalization.A p-type molecule–F4 TCNQ(2,3,5,6-tetrafluoro-7,7,8,8-tetracyanoquinodime thane)was introduced and the site-defined functionalization was accomplished.Theoretical calculations showed that the charge transfer ability is improved and graphdiyne becomes positively charged.The oxygen reduction electrocatalysis was conducted as a proof of principle,where the electronic states of sp hybridized C active site was tuned toward favorable reaction intermediates’adsorption.Such work from both theoretical prediction and experimental validation,found that molecule functionalization is effective to promote the electrocatalytic oxygen reduction,which creates new possibilities for graphdiyne’s applications in different electrochemical reactions.

关键词： Graphdiyne F4TCNQ Density functional calculations Electronic structure Oxygen reduction reaction

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内陆复杂风电场风速垂直外推模型研究

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中国电力 2024年第5期57卷 232-239页

作者：胡锐武书洲李永华乔加飞华北电力大学能源动力与机械工程学院河北保定071066 国家能源集团新能源技术研究院有限公司北京102209

陆上风能资源评估中风电机组的轮毂高度大于测风塔高度,忽略大气稳定度影响与地表粗糙度变化,风切变指数受地面地形和地貌因素的影响,且在外推到轮毂高度处时,风速难以精确预测。综合考虑了Monin Obukhov相似理论与动力学粗糙度最小二... 详细信息

陆上风能资源评估中风电机组的轮毂高度大于测风塔高度,忽略大气稳定度影响与地表粗糙度变化,风切变指数受地面地形和地貌因素的影响,且在外推到轮毂高度处时,风速难以精确预测。综合考虑了Monin Obukhov相似理论与动力学粗糙度最小二乘法计算模型,建立一种基于大气热稳定性在中性条件下的拟合方法。首先,评估了风切变指数在不同地点的空间分布和与大气稳定度变化之间的相关影响;其次,以2个不同地貌下陆上风电场的实测数据为基础,与常用的综合切变外推轮毂高度风速的计算方案相比较,结果表明:风切变指数日变化与大气稳定性日变化存在一定的相关性,新型外推风速模型计算方法能更加准确地评估目标高度风速的垂直分布变化。

关键词：风能大气稳定度风切变指数幂律公式

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Accurate machine learning models based on small dataset of energetic materials through spatial matrix featurization methods

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Journal of Energy Chemistry 2021年第12期30卷 364-375,I0009页

作者： Chao Chen Danyang liu Siyan Deng lixiang Zhong Serene Hay Yee Chan shuzhou li Huey Hoon Hng School of Materials Science and Engineering Nanyang Technological University50 Nanyang AvenueSingapore 639798Singapore

A large database is desired for machine learning(ML) technology to make accurate predictions of materials physicochemical properties based on their molecular structure.When a large database is not available,the development of proper featurization method based on physicochemical nature of target proprieties can improve the predictive power of ML models with a smaller database.In this work,we show that two new featurization methods,volume occupation spatial matrix and heat contribution spatial matrix,can improve the accuracy in predicting energetic materials' crystal density(ρ_(crystal)) and solid phase enthalpy of formation(H_(f,solid)) using a database containing 451 energetic molecules.Their mean absolute errors are reduced from 0.048 g/cm~3 and 24.67 kcal/mol to 0.035 g/cm~3 and 9.66 kcal/mol,respectively.By leave-one-out-cross-validation,the newly developed ML models can be used to determine the performance of most kinds of energetic materials except cubanes.Our ML models are applied to predict ρ_(crystal) and H_(f,solid) of CHON-based molecules of the 150 million sized PubChem database,and screened out 56 candidates with competitive detonation performance and reasonable chemical structures.With further improvement in future,spatial matrices have the potential of becoming multifunctional ML simulation tools that could provide even better predictions in wider fields of materials science.

关键词： Small database machine learning Energetic materials screening Spatial matrix featurization method Crystal density Formation enthalpy n-Body interactions

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Perovskite-transition metal dichalcogenides heterostructures: recent advances and future perspectives

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Opto-Electronic Science 2022年第8期1卷 1-40页

作者： Ahmed Elbanna Ksenia Chaykun Yulia Lekina Yuanda liu Benny Febriansyah shuzhou li Jisheng Pan Ze Xiang Shen Jinghua Teng Institute of Materials Research and Engineering Agency for ScienceTechnology and Research(A*STAR)2 Fusionopolis WaySingapore 138634Singapore Division of Physics and Applied Physics School of Physical and Mathematical SciencesNanyang Technological University50 Nanyang AvenueSingapore 637371Singapore Interdisciplinary Graduate Program Energy Research Institute@NTUNanyang Technological University50 Nanyang AvenueSingapore 639798Singapore The Photonics Institute and Center for Disruptive Photonic Technologies Nanyang Technological University50 Nanyang AvenueSingapore 639798 Singapore School of Materials Science and Engineering Nanyang Technological University50 Nanyang AvenueSingapore 639798Singapore Berkeley Educational Alliance for Research in Singapore(BEARS) Ltd.1 CREATE WaySingapore 138602Singapore.

Transition metal dichalcogenides(TMDs)and perovskites are among the most attractive and widely investigated semiconductors in the recent decade.They are promising materials for various applications,such as photodetection,solar energy harvesting,light emission,and many others.Combining these materials to form heterostructures can enrich the already fascinating properties and bring up new phenomena and opportunities.Work in this field is growing rapidly in both fundamental studies and device applications.Here,we review the recent findings in the perovskite-TMD heterostructures and give our perspectives on the future development of this promising field.The fundamental properties of the perovskites,TMDs,and their heterostructures are discussed first,followed by a summary of the synthesis methods of the perovskites and TMDs and the approaches to obtain high-quality interfaces.Particular attention is paid to the TMD-perovskite heterostructures that have been applied in solar cells and photodetectors with notable performance improvement.Finally through our analysis,we propose an outline on further fundamental studies and the promising applications of perovskite-TMD heterostructures.

关键词： transition metal dichalcogenides perovskites heterostructures photodetectors solar cells 2D materials

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An in-situ spectroscopy investigation of alkali metal interaction mechanism with the imide functional group

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Nano Research 2020年第12期13卷 3224-3229页

作者： Xu lian Zhirui Ma Zhonghan Zhang Jinlin Yang Shuo Sun Chengding Gu Yuan liu Honghe Ding Jun Hu Xu Cao Junfa Zhu shuzhou li Wei Chen Department of Chemistry National University of SingaporeSingapore117543Singapore Centre for Advanced 2D Materials National University of SingaporeSingapore117546Singapore School of Materials Science and Engineering Nanyang Technological UniversitySingapore639798Singapore National University of Singapore(Suzhou)Research Institute Suzhou215123China Joint School of National University of Singapore and Tianjin University International Campus of Tianjin UniversityFuzhou350207China National Synchrotron Radiation Laboratory Department of Chemical PhysicsUniversity of Science and Technology of ChinaHefei230029China Department of Physics National University of SingaporeSingapore117542Singapore

Organic anode materials have attracted considerable interest owing to their high tunability by adopting various active functional groups.However,the interaction mechanisms between the alkali metals and the active functional groups in host materials have been rarely studied systematically.Here,a widely used organic semiconductor of perylene-3,4,9,10-tetracarboxylic diimide(PTCDI)was selected as a model system to investigate how alkali metals interact with imide functional groups and induce changes in chemical and electronic structures of PTCDI.The interaction at the alkali/PTCDI interface was probed by in-situ X-ray photoelectron spectroscopy(XPS),ultraviolet photoelectron spectroscopy(UPS),synchrotron-based near edge X-ray absorption fine structure(NEXAFS),and corroborated by density functional theory(DFT)calculations.Our results indicate that the alkali metal replaces the hydrogen atoms in the imide group and interact with the imide nitrogen of PTCDI.Electron transfer induced gap states and downward band-bending like effects are identified on the alkali-deposited PTCDI surface.It was found that Na shows a stronger electron transfer effect than li.Such a model study of alkali insertion/intercalation in PTCDI gives insights for the exploration of the potential host materials for alkali storage applications.

关键词： perylene-3,4,9,10-tetracarboxylic diimide(PTCDI) lithium storage organic anode imide electron transfer

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What Drives Chinese Firms'Export Sophistication?A Perspective from the Rise of Minimum Wages

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China & World Economy 2022年第2期30卷 28-59页

作者： Xiaoping li shuzhou Peng Wei-Chiao Huang Qian Zhou Economics School Zhongnan University of Economics and LawChina Department of Economics Western Michigan UniversityUS.

This paper re-examines the driving factors behind the upgrading of China s export sophistication.Based on county-level minimum wages and firm-level export data for 2000-2013,this paper finds that the labor cost shocks caused by rising minimum wages have a significant positive impact on Chinese firms'export sophistication.Channel tests show that the positive effect of rising minimum wages on firms'export sophistication derives from the exit of less sophisticated products and the reallocation of the relative share of surviving products,rather than introducing new highly sophisticated products.Heterogeneity analysis reveals that rising minimum wages have a greater impact on export sophistication for low-wage firms,domestic firms,and labor-intensive firms.This paper has implications for developing countries regarding the transition from a low-cost labor trade model to a sophistication-driven trade model.

关键词： Chinese firms export sophistication minimum wages

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超高效液相色谱-串联质谱法快速测定凉皮汤料中5种罂粟壳生物碱

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现代疾病预防控制 2024年第1期35卷 15-19页

作者：王书舟李俊玲张宇王冬梅安阳市疾病预防控制中心河南安阳455000

目的建立超高效液相色谱-串联质谱法快速测定凉皮汤料中5种罂粟壳生物碱的方法。方法精确称量样品后加入乙腈涡旋混匀,加入无水醋酸钠和无水硫酸镁辅助提取后离心,上清液经乙二胺-N-丙基硅烷粉末净化,HIliC色谱柱分离,多反应监测模式... 详细信息

目的建立超高效液相色谱-串联质谱法快速测定凉皮汤料中5种罂粟壳生物碱的方法。方法精确称量样品后加入乙腈涡旋混匀,加入无水醋酸钠和无水硫酸镁辅助提取后离心,上清液经乙二胺-N-丙基硅烷粉末净化,HIliC色谱柱分离,多反应监测模式下测定,外标法定量。结果罂粟碱、那可丁、蒂巴因在0.05~2.0 ng/mL,吗啡、可待因在0.25~10.0 ng/mL范围内线性关系良好,相关系数均大于0.999 0,检出限为0.03μg/kg(罂粟碱、那可丁、蒂巴因)和0.15μg/kg(吗啡、可待因),加标回收率为81.3%~98.6%,相对标准偏差为2.1%~4.9%。结论该方法前处理简单高效,经济科学,灵敏度高,准确度好,适用于批量凉皮汤料中罂粟壳生物碱的快速准确测定。

关键词：超高效液相色谱-串联质谱法罂粟壳生物碱凉皮汤料

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基于B/S架构的国产化指控系统告警框架

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工业控制计算机 2024年第5期37卷 124-125,128页

作者：李树洲石畅钱丰王元双孙华刘军军胡亚威赵智男中国电子科技集团公司第二十八研究所江苏南京210007

以JavaScript、C++作为开发语言,以达梦作为数据库工具,构建了一个基于B/S架构的国产化指控系统告警框架。框架对各告警事件的类型、等级、阈值进行收集、统计,并在此基础上实现了各类型告警事件统一的前台展现,支持告警记录的查询、筛... 详细信息

以JavaScript、C++作为开发语言,以达梦作为数据库工具,构建了一个基于B/S架构的国产化指控系统告警框架。框架对各告警事件的类型、等级、阈值进行收集、统计,并在此基础上实现了各类型告警事件统一的前台展现,支持告警记录的查询、筛选,提供后续的事件处置接口。框架统一集成的方式在减少开发人员工作量的同时,也有利于指控人员对各类告警事件进行查阅、管理。

关键词：告警事件 B/S 国产化框架统一管理

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