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Influence of Zr and Mn additions on microstructure and properties of Mg-2.5wt%Cu-Xwt%Zn(X=2.5,5 and 6.5)alloys

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International Journal of Minerals,Metallurgy and Materials 2022年第9期29卷 1733-1745页

作者： A.V.Koltygin V.E.Bazhenov I.V.Plisetskaya V.A.Bautin A.I.Bazlov N.Y.Tabachkova O.O.Voropaeva A.A.Komissarov V.D.Belov Foundry Department National University of Science and Technology(MISiS)Moscow 119049Russia Department of Metallurgy Steel New Production Technologies and Protection of MetalsNational University of Science and Technology(MISiS)Moscow 119049Russia laboratory of Advanced Green Materials National University of Science and Technology(MISiS)Moscow 119049Russia Department of Materials Science of Semiconductors and dielectrics National University of Science and Technology(MISiS)Moscow 119049Russia Fianit laboratory(Laser Materials and Technology Research Center at GPI) Prokhorov General Physics Institute RASMoscow 119991Russia laboratory of Hybrid Nanostructured Materials National University of Science and Technology(MISiS)Moscow 119049Russia laboratory of Medical Bioresorption and Bioresistance Moscow State University of Medicine and DentistryMoscow 127473Russia

This work studied the effects of adding Zr and Mn in amounts less than 1wt%on the microstructure,mechanical properties,casting properties,and corrosion resistance of Mg-Zn-Cu alloys containing 2.5wt%Cu and 2.5wt%-6.5wt%*** hardness and electrical conductivity measurements were used to find an optimal heat treatment schedule with the best mechanical *** has been established that Zr significantly increases the yield strength of the alloys due to a strong grain refinement ***,the presence of Mn and Zr has a detrimental effect on alloy’s elongation at *** was shown that the precipitation of the Mg_(2)Cu cathodic phase in the alloy structure negatively affects the corrosion ***,the addition of Mn decreases the corrosion rate of the investigated *** best combination of the mechanical,casting,and corrosion properties were achieved in the alloys containing 2.5wt%Cu and 5wt%***,the Mn or Zr addition can improve the properties of the alloys;for example,the addition of Mn or Zr increases the fluidity of the alloys.

关键词： magnesium alloy Mg-Zn-Cu casting alloy Mn addition Zr addition

二维钙钛矿氧化物高κ电介质用于高性能光电晶体管（英文）

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Science Bulletin 2024年第13期 2001-2003页

作者：刘忠范 Center for Nanochemistry Beijing Science and Engineering Center for Nanocarbons Beijing National Laboratory for Molecular Sciences College of Chemistry and Molecular Engineering Peking University Technology Innovation Center of Graphene Metrology and Standardization for State Market Regulation Beijing Graphene Institute

Field-effect transistors are essential components of modern electronics. Nowadays, the continued scaling of electronic and optoelectronic devices is bringing silicon-based technologies close to their physical limits, causing issues such as short-channel effects[1]. Two-dimensional (2D) semiconductors provide an attractive solution for transistors to extend Moore’s law because of their ultrathin thickness and immunity to short-channel effects [2]. To fulfill the potential of 2D semiconductors, gate dielectrics need to be simultaneously engineered to build future 2D-material-based transistors. Gate insulators with high dielectric constants (κ) exhibit lower equivalent oxide thickness, which can ensure efficient gate control over channels and low gate leakage [3]. Therefore,tremendous efforts have been made in searching for novel high-κdielectrics.

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Synthesis of Ag@Al_2O_3 Core-shell Structure Nanoparticles and Their Enhancement Effect on Dielectric Properties for Ag@Al_2O_3/Polyimide Nanocomposites

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Journal of Wuhan University of Technology(Materials Science) 2015年第1期30卷 47-50页

作者：翁凌 YAN Liwen LI Hongxia XIA Qianshan LIU Lizhu Key laboratory of Engineering dielectrics and Its Application Ministry of Education Harbin University of Science and Technology School of Materials Science and Engineering Harbin University of Science and Technology

A novel core-shell structure Ag@Al2O3 nano-particles were synthesized and doped into polyimide as conductive fillers to prepare the composite films with high dielectric properties and low dielectric loss. The morphology and structures of the Ag@Al2O3 nano-particles were characterized by transmission electron microscopy （TEM）, X-ray diffraction （XRD）, and UV-visible spectroscopy. All the results proved that the Ag@Al2O3 nano-parficles had a typical core-shell structure, for the Ag particles were coated by Al2O3 shell and the average sizes ofAg@Al2O3 particles were between 30 to 150 nm. The as-prepared Ag@Al2O3 nanoparticles were doped into the polyimide with different mass fractions to fabricate the Ag@Al2O3/PI composite films via in-situ polymerization process. SEM analysis of composite films showed that the Ag@Al2O3 nano- particles homogeneously dispersed in polyimide matrix with nanoseale. As dielectric materials for electronic packaging systems, the Ag@Al2O3/PI composites exhibited appropriate mechanical properties and erthaneed dielectric properties, including greatly enhanced dielectric constant and just a slight increase in dielectric loss. These improvements were attributed to the core-shell structure of fillers and their fine dispersion in the PI matrix.

关键词： core-shell structure polyimide nanocomposites dielectrics

Theoretical Studies on Dielectric Breakdown Strength Increasing Mechanism of SF6 and Its Potential Alternative Gases

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Chemical Research in Chinese Universities 2015年第1期31卷 123-129页

作者： ZHANG Hui SHANG Yan CHEN Qingguo HAN Baozhong Key laboratory of Engineering dielectrics and Its Application of Ministry of Education College of Chemical and Environmental Engineering Harbin University of Science and Technology Harbin 150080 P. R. China

A theoretical investigation on the dielectric insulation mechanism of sulfur hexafluoride（SF6） and its potential alternative gases at the atomic and molecular levels was made. The electronic structures of the molecules of them were calculated at the B3LYP/6-31 11＋G（d,p） level. The HOMO-LUMO energy gaps, ionization potentials, electron affinities, and dipole moments of the studied molecules at the ground state were obtained. The 11 isomerization reactions, with the harmonic vibration frequencies of the equilibrium geometries and the minimum energy path by the intrinsic reaction coordinate theory, were also obtained at the same level. The results show that the insulation gas, with the larger HOMO-LUMO energy gap, the higher ionization potential and the stronger electron affinity, can increase the dielectric breakdown strength efficiently, which is in good agreement with the available experimental finding. We suggested that the molecule with isomerization reaction occurring can dissipate the energy of hot electrons availably, which is favorable to the dielectric breakdown strength increasing for the SF6 potential alternative gas.

关键词： Dielectric breakdown strength Sulfur hexafluoride Transition state Mechanism

Fabrication of polymeric-Laponite composite hollow microspheres via LBL assembly

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Chinese Chemical Letters 2017年第2期28卷 367-371页

作者： Wei Deng Hua-Chao Guo Guo-An Li Cheng-You Kan Key laboratory of Engineering dielectrics and Its Application Ministry of Education School of Material Science and Engineering Harbin University of Science and Technology Key laboratory of Advanced Materials of Ministry of Education Department of Chemical Engineering Tsinghua University

Hollow structure microspheres with composite polymeric-Laponite shells were prepared by electrostatic self-assembly of Laponite on the polymeric hollow microspheres in this *** multilayer hydrophilic core/hydrophobic shell polymer latex particles containing carboxyl groups inside were first synthesized via seeded emulsion polymerization,followed by alkali treatment,generating polymeric hollow ***,polyethyleneimine（PEI） and Laponite were alternately electrostatic adsorbed on the prepared polymeric hollow microspheres to form polymeric-Laponite composite hollow *** was indicated that the morphology of alkali-treated microspheres could be tuned through simply altering the dosage of alkali used in the post-treatment *** with the increasing of the coating layers,the zeta potential of microspheres absorbed PEI or Laponite approximately tended to be constant respectively,and the thickness of Laponite layer around the hollow microspheres increased clearly,getting more uniform and ***,the corresponding polymeric-Laponite hollow microspheres showed high pressure resistance ability compared to the polymeric hollow microspheres.

关键词： Composite microspheres Hollow structure Laponite Osmotic swelling LBL assembly

600 Mesh Silicon Carbide Corona Protection Varnish with EPOXY/OMMT Nano-composite Adhesive

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Journal of Wuhan University of Technology(Materials Science) 2016年第4期31卷 818-822页

作者：胡春秀 ZHAO Yingnan HOU Haibo ZHANG Xiaohong Harbin Research Institute of Large Electric Machinery Harbin 150040 China Key laboratory of Engineering dielectrics and Its Application Harbin University of Science and Technology Harbin 150080 China

A new corona protection varnish was prepared by using epoxy/montmorillonite nanocomposite and pure epoxy resin as adhesives *** adhesive with different amounts of organic montmorillonite（OMMT） was mixed with 1200 mesh silicon carbide（Si C） by different weight *** surface states of the varnishes with various adhesives were observed by powerful optical *** properties of the varnishes were analyzed during the enduring time under 5kV/cm DC,such as the relation of change in nonlinear coefficient,natural surface resistivity,and surface temperature *** results showed that the amounts of OMMT had little effect on the natural surface resistance of the varnish but had important influence on the nonlinear property of the *** the range of the OMMT content was 2wt% to 6wt%,the nonlinear coefficient of all materials with epoxy/OMMT nano-composite adhesive was higher than that with pure epoxy resin *** surface temperature of the varnish with epoxy/OMMT nanocomposite adhesive was all lower than that with the pure epoxy resin adhesive under high electrical field strength.

关键词： adhesive epoxy Corona resin carbide spacing paint polyester fluctuation powerful

Relaxor antiferroelectric-relaxor ferroelectric crossover in NaNbO_(3)-based lead-free ceramics for high-efficiency large-capacitive energy storage

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Chinese Chemical Letters 2024年第7期35卷 465-469页

作者： Shuangliang Xie Yuyue Chen Qing He Liang Chen Jikun Yang Shiqing Deng Yimei Zhu He Qi School of Materials Science and Engineering University of Science and Technology BeijingBeijing 100083China Beijing Advanced Innovation Center for Materials Genome Engineering Department of Physical ChemistryUniversity of Science and Technology BeijingBeijing 100083China School of Mathematics and Physics University of Science and Technology BeijingBeijing 100083China Department of Condensed Matter Physics and Materials Science Brookhaven National LaboratoryUptonNew York 11973United States

Relaxor ferroic dielectrics have garnered increasing attention in the past decade as promising materials for energy *** them,relaxor antiferroelectrics(AFEs)and relaxor ferroelectrics(FEs)have shown great promise in term of high energy storage density and efficiency,*** this study,a unique phase transition from relaxor AFE to relaxor FE was achieved for the first time by introducing strong-ferroelectricity BaTiO_(3)into NaNbO_(3)-BiFeO_(3)system,leading to an evolution from AFE R hierarchical nanodomains to FE polar nanoregions.A novel medium state,consisting of relaxor AFE and relaxor FE,was identified in the crossover of 0.88NaNbO_(3)–0.07BiFeO_(3)–0.05BaTiO_(3)ceramic,exhibiting a distinctive core-shell grain structure due to the composition *** harnessing the advantages of high energy storage density from relaxor AFE and large efficiency from relaxor FE,the ceramic showcased excellent overall energy storage *** achieved a substantial recoverable energy storage density W_(rec)~13.1 J/cm^(3)and an ultrahigh efficiencyη~88.9%.These remarkable values shattered the trade-off relationship typically observed in most dielectric capacitors between W_(rec)andη.The findings of this study provide valuable insights for the design of ceramic capacitors with enhanced performance,specifically targeting the development of next generation pulse power devices.

关键词： Relaxor ferroelectric Antiferroelectric Core-shell Energy storage High efficiency

Spoof surface plasmons resonance effect and tunable electric response of improved metamaterial in the terahertz regime

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Chinese Physics B 2015年第12期24卷 483-487页

作者：王玥张丽颖梅金硕张文超童一静 Department of Electrical Science and Technology Harbin University of Science and Technology Key laboratory of Engineering dielectrics and Its Application Ministry of EducationHarbin University of Science and Technology School of Engineering and Applied Science George Washington University

We propose an improved design and numerical study of an optimized tunable plasmonics artificial material resonator in the terahertz regime. We demonstrate that tunability can be realized with a transmission intensity as much as - 61% in the lower frequency resonance, which is implemented through the effect of photoconductive switching under *** the higher frequency resonance, we show that spoof surface plasmons along the interface of metal/dielectric provide new types of electromagnetic resonances. Our approach opens up possibilities for the interface of metamaterial and plasmonics to be applied to optically tunable THz switching.

关键词： surface plasmons metamaterials terahertz resonance

Preparation and Characterization of Multi Shape ZnO/PVDF Composite Materials

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Journal of Wuhan University of Technology(Materials Science) 2017年第4期32卷 958-962页

作者：翁凌 JU Peihai LI Hongxia YAN Liwen LIU Lizhu Key laboratory of Engineering dielectrics and Its Application Ministry of Education Harbin University of Science and Technology Harbin 150080 China School of Materials Science and Engineering Harbin University of Science and Technology Harbin 150040 China

Two different morphologies of ZnO（lotus-shaped, rod-shaped） and ZnO/PVDF composite materials were prepared. The morphologies of ZnO and composite materials were characterized by scanning electron microscopy（SEM） and transmission electron microscopy（TEM）. Fourier transform infrared spectroscopy（FT-IR）, thermal gravimetry（TG）, and X-ray diffraction（XRD） were also used to characterize the chemical structures and phase composites of ZnO and ZnO/PVDF composite materials. Breakdown voltage, dielectric constant and dielectric loss of ZnO/PVDF composite materials were also tested. Microstructure analysis showed that ZnO nanoparticles dispersed uniformly in the matrix. And the dielectric constant expresses a significantly improvement while the dielectric loss and breakdown voltage expresses no significant change. Moreover, dielectric constant keeps an improvement tendency with increasing content of ZnO.

关键词： polyvinylidene fluoride(PVDF) zinc oxide(ZnO) composite materials morphology dielectric properties