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Dense dislocations induced ductile SnTe thermoelectric semiconductor over a wide range of temperatures

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Journal of Materials Science & technology 2023年第13期144卷 213-218页

作者： Houjiang Yang Xiege Huang Bo Duan Luoqi Wu Hongtao Wang Xiaobin Feng Maoyuan Jiang Guodong Li Ling Zhou Pengcheng Zhai Qingjie Zhang Hubei Key laboratory of Theory and application of advanced Materials Mechanics Wuhan University of TechnologyWuhan 430070China State Key laboratory of advanced technology for Materials Synthesis and Processing Wuhan University of TechnologyWuhan 430070China

Most inorganic thermoelectric semiconductors are intrinsically brittle,restricting the application of ther-moelectric materials.Therefore,developing ductile thermoelectric materials is crucial to thermoelectric technology applications.In this work,single-phase SnTe bulks with dense dislocations were prepared by melting quenching combined with spark plasma sintering.The resulting SnTe thermoelectric materials exhibited a large compressive strain of∼7.5%at room temperature,originating from high-density pre-existing mobile dislocations.The initiation of localized slip bands and preferred slip system were also identified by first-principles simulation.Detail microstructural characterizations reveal that the thermal activated dislocation emission and migration lead to higher compressive strains at intermediate tem-peratures.At 673 K,the deformation mechanism changed from dislocation mediated to grain boundary mediated plasticity,resulting in an ultra-high compressive strain of∼42%.In sum,new insights into the mechanical behavior of SnTe thermoelectric material over a wide range of temperatures were provided.This work offers the dislocation engineering strategy to design ductile thermoelectric materials for flexi-ble electronics and energy systems.

关键词： SnTe Ductile thermoelectric materials Deformation mechanism Dislocation engineering

The Shock Response and Spall Mechanism of Mg-Al-Zn Alloy:Molecular Dynamics Study

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Acta Mechanica Solida Sinica 2022年第3期35卷 495-503页

作者： Xiaoyue Yang Shuang Xu Lisheng Liu Hubei Key laboratory of Theory and application of advanced Materials Mechanics Wuhan University of TechnologyWuhan 430070China State Key laboratory of advanced technology for Materials Synthesis and Processing Wuhan University of TechnologyWuhan 430070China

Shock responses of Mg-Al-Zn alloy are investigated by the molecular dynamics(MD)method.The wave propagation,plastic deformation behavior and failure mechanism along the[0001]and[1010]orientations are analyzed.For both orientations,simulation results show that the shock wave has an obvious double-wave structure(plastic-elastic)under a piston velocity of 1200 m/s.A higher Hugoniot elastic limit(HEL)is observed for[0001]-oriented shock.When the shock pressure is along the[1010]direction,the distance between plastic and elastic waves is closer,and higher dislocation density and more twins are observed.Moreover,the spall strength for[1010]-oriented shock is predicted to be higher.In addition,the wave interactions,HEL and spall strength predicted for Mg-Al-Zn alloy are compared with the experimental results and MD simulation results of Mg single crystal in the literature.It is concluded that the shock performance of Mg-Al-Zn is better than that of Mg single crystal.

关键词： Mg-Al-Zn Shock compression Molecular dynamics Hugoniot elastic limit Spall strength

Effect of Ag Addition on Microstructure,Mechanical and Corrosion Properties of Mg-Nd-Zn-Zr Alloy for Orthopedic application

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Acta Metallurgica Sinica(English Letters) 2023年第2期36卷 295-309页

作者： Yu-Jin Nie Jian-Wei Dai Xiao-Bo Zhang School of Materials Science and Engineering Nanjing Institute of TechnologyNanjing211167China Jiangsu Key laboratory of advanced Structural Materials and application technology Nanjing211167China

The as-extruded Mg-3Nd-0.2Zn-0.4Zr-xAg(x=0,0.2,0.5,1 wt%)alloys were prepared for biomedical applications.Scanning electron microscope,electron backscattered diffraction,X-ray diffraction,tensile test machine,electrochemical workstation,and immersion experiments were used to study microstructures,mechanical properties,and corrosion behavior of the as-extruded alloys.The results indicate that the microstructures of all the as-extruded alloys are composed of coarse undynamic recrystallized grains,fine equiaxed recrystallized grains,and precipitated phases.Ag element plays a positive role in promoting dynamic recrystallization and grain refinement.And during the extrusion,all the four alloys generate a //ED fiber texture.With the increase of Ag element,the volume fraction of Mg_(12)Nd phase increases and then decreases slightly.By increasing Ag addition,both yield strength and ultimate tensile strength of the as-extruded alloys reduce first and then improve,and the elongation improves gradually from 9.4 to 12.7%.More importantly,the addition of Ag accelerates corrosion of the as-extruded alloys in simulated body fluid,and all the as-extruded alloys show uniform corrosion mode.

关键词： Magnesium alloy Hot extrusion Mechanical properties Corrosion resistance

Stress corrosion cracking of magnesium alloys:A review

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镁合金学报(英文) 2023年第6期11卷 1906-1930页

作者： Jiahao Jiang Xue Geng Xiaobo Zhang School of Materials Science and Engineering Nanjing Institute of TechnologyNanjing 211167China Jiangsu Key laboratory of advanced Structural Materials and application technology Nanjing 211167China

Magnesium(Mg)alloys have been widely used in automobile,aviation,computer,and other fields due to their lightweight,high specific strength and stiffness,low pollution,and good electromagnetic shielding performance.However,the chemical stability of Mg alloys is poor,especially in the corrosive medium environment with high stress corrosion sensitivity,which causes sudden damage to structural components and restricts their application field.In recent years,owing to the increasing failure rate of engineering structures caused by stress corrosion of Mg alloys,it has become necessary to understand and pay more attention to the stress corrosion cracking(SCC)behavior of Mg alloys.In this paper,the SCC mechanisms and test methods of Mg alloys have been summarized.The recent research progress on SCC of Mg alloys has been reviewed from the aspects of alloying,preparation process,surface modification,corrosive medium,and strain rate.More importantly,future research trends in the field of SCC of Mg alloys have also been proposed.

关键词： Magnesium alloys Stress corrosion cracking Alloying Preparation process Corrosion media Surface treatment

Effects of Nd on microstructure and mechanical properties of as-cast Mg-12Gd-2Zn-xNd-0.4Zr alloys with stacking faults

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International Journal of Minerals,Metallurgy and Materials 2022年第8期29卷 1570-1577页

作者： Lixin Hong Rongxiang Wang Xiaobo Zhang School of Materials Science and Engineering Nanjing Institute of TechnologyNanjing 211167China Jiangsu Key laboratory of advanced Structural Materials and application technology Nanjing 211167China

In order to study the effects of Nd addition on microstructure and mechanical properties of Mg-Gd-Zn-Zr alloys,the microstruc-ture and mechanical properties of the as-cast Mg-12Gd-2Zn-xNd-0.4Zr(x=0,0.5wt%,and 1wt%)alloys were investigated by using optical microscope,scanning electron microscope,X-ray diffractometer,nano indentation tester,microhardness tester,and tensile testing machine.The results show that the microstructures mainly consist ofα-Mg matrix,eutectic phase,and stacking faults.The addition of Nd plays a significant role in grain refinement and uniform microstructure.The tensile yield strength and microhardness increase but the compression yield strength decreases with increasing Nd addition,leading to weakening tension-compression yield asymmetry in reverse of the Mg-12Gd-2Zn-xNd-0.4Zr alloys.The highest ultimate tensile strength(194 MPa)and ultimate compression strength(397 MPa)are obtained with 1wt%Nd addition of the alloy.

关键词： magnesium alloy neodymium microstructure stacking fault mechanical properties

Mechanochromism of polyurethane based on folding-unfolding of cyano-substituted oligo(p-phenylene)vinylene dimer

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Frontiers of Materials Science 2023年第2期17卷 169-180页

作者： Na Zhang Xiang-Yu Ma Shun Li Yu-Xin Zhang Chen Lv Zheng-Peng Mao Zi-Yi Dou Tai-Sheng Wang School of Materials Science and Engineering Nanjing Institute of TechnologyNanjing 211167China Jiangsu Key laboratory of advanced Structural Materials and application technology Nanjing 211167China

The incorporation of mechanophores,motifs that transform mechanical stimulus into chemical reaction or optical variation,allows creating materials with stressresponsive properties.The most widely used mechanophore generally features a weak bond,but its cleavage is typical an irreversible process.Here,we showed that this problem can be solved by folding–unfolding of a molecular tweezer.We systematically studied the mechanochromic properties of polyurethanes with cyano-substituted oligo(p-phenylene)vinylene(COP)tweezer(DPU).As a control experiment,a class of polyurethanes containing only a single COP moiety(MPU)was also prepared.The DPU showed prominent mechanochromic properties,due to the intramolecular folding–unfolding of COP tweezer under mechanical stimulus.The process was efficient,reversible and optical detectable.However,due to the disability to form either intramolecular folding or intermolecular aggregation,the MPU sample was mechanical inert.

关键词： mechanochromism molecular tweezer folding-unfolding cyanosubstituted oligo(p-phenylene)vinylene polyurethane

Flexible and transparent graphene/silver-nanowires composite ?lm for high electromagnetic interference shielding effectiveness

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Science Bulletin 2019年第8期64卷 540-546页

作者： Ning Zhang Zhe Wang Rongguo Song Qianlong Wang Hongye Chen Bin Zhang Haifei Lv Zhi Wu Daping He Hubei Engineering Research Center of RF-Microwave technology and application School of Science Wuhan University of Technology Shenzhen Institute of advanced Graphene application and technology (SIAGAT)

Herein, an efficient approach to prepare flexible, transparent, and lightweight films based on graphene nanosheets(GNS) and silver nanowires(AgNWs) for high electromagnetic interference(EMI) shielding effectiveness(SE) has been explained. High-conductive GNS were fabricated by liquid phase stripping and composited with AgNWs by a two-step spin-coating method. Owing to the high transparency, good conductivity, and homogeneous distribution of both GNS and AgNWs, the obtained GNS/AgNWs film exhibits superb EMI SE and light transmittance, yielding a significantly high EMI SE up to 26 dB in both Ku-band and K-band and light transmittance higher than 78.4%. Moreover, this GNS/AgNWs film shows good flexibility and excellent structural stability. The obtained flexible, light and transparent film could have a great potential for transparent EMI shielding and smart electronics.

关键词： Flexibility Transparent Electromagnetic interference shielding Graphene Silver nanowires

具有多孔微结构的高导电石墨烯组装膜及其自支撑式超低功率应变传感器应用

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Science Bulletin 2020年第16期65卷 1363-1370,M0004页

作者：王哲李鹏宋荣国钱伟周煌王乾龙王永曾显词任琳晏石林木士春何大平 Hubei Engineering Research Center of RF-Microwave technology and application.School of Science Wuhan University of TechnologyWuhan 430070China Hubei Key laboratory of Theory and application of advanced Materials Mechanics School of ScienceWuhan University of TechnologyWuhan 430070China State Key laboratory of advanced technology for Materials Synthesis and Processing Wuhan University of TechnologyWuhan 430070China

石墨烯由于其优越的机械性能和高导电性,成为构造高性能应变传感器的理想材料.然而,在将石墨烯组装成宏观材料的过程中,其电导率显著降低.而且,繁琐的制备过程阻碍了石墨烯应变传感器的应用.本文介绍了一种通过高温热处理法制备的具有... 详细信息

石墨烯由于其优越的机械性能和高导电性,成为构造高性能应变传感器的理想材料.然而,在将石墨烯组装成宏观材料的过程中,其电导率显著降低.而且,繁琐的制备过程阻碍了石墨烯应变传感器的应用.本文介绍了一种通过高温热处理法制备的具有多孔微结构和高导电率的自支撑式石墨烯组装膜(GAF).GAF表现出良好的热稳定性.就应变传感器敏感材料的电导率而言,GAF高于绝大多数报道的碳纳米管和石墨烯等先进碳材料.这些优点使GAF应变传感器可以用于检测气流和声音振动,并实现超低功耗.与大多数已报道的应变传感器相比,GAF应变传感器无需任何柔性基底,大大简化了制备过程.此外,本文还研究了GAF用作压力传感器且功率可低至~4.7μW.这项工作为制备具有超低功耗的先进传感器以及开发节能的柔性电子设备提供了新的思路.

关键词：应变传感器超低功耗压力传感器多孔微结构石墨烯柔性电子柔性基底高温热处理

Research on Tibetan Speech Recognition Based on the Am-do Dialect

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Computers, Materials & Continua 2022年第12期73卷 4897-4907页

作者： Kuntharrgyal Khysru Jianguo Wei Jianwu Dang Key laboratory of Artificial Intelligence application technology State Ethnic Affairs Commission Qinghai Minzu UniversityXining810007China Tianjin Key laboratory of Cognitive Computing and application Tianjin UniversityTianjin300072China Japan advanced Institute of Science and technology IshikawaJapan

In China,Tibetan is usually divided into three major dialects:the Am-do,Khams and Lhasa dialects.The Am-do dialect evolved from ancient Tibetan and is a local variant of modern Tibetan.Although this dialect has its own specific historical and social conditions and development,there have been different degrees of communication with other ethnic groups,but all the abovementioned dialects developed from the same language:Tibetan.This paper uses the particularity of Tibetan suffixes in pronunciation and proposes a lexicon for the Am-do language,which optimizes the problems existing in previous research.Audio data of the Am-do dialect are expanded by data augmentation technology combining noise and reverberation,and the morphological characteristics and characteristics of the Tibetan language are further considered.According to the particularity of Tibetan grammar,grammatical features are used to optimize grammatical relationships and are combined with a language model,and the Am-do dialect is scored and rescored.Experimental results show that compared with the baseline,our proposed new lexicon and data augmentation technology yields a relative increase of approximately 3%in character error rates(CERs)and a relative increase of 3%-19%in the recognition rate of acoustic models and language models.

关键词： Am-do dialect acoustic model language model rescoring