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Doped ceramics of indium oxides for negative permittivity materials in MHz-kHz frequency regions

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Journal of Materials Science & Technology 2021年第2期61卷 125-131页

作者： guohua fan Zhongyang Wang Kai Sun Yao Liu Runhua fan Key Laboratory fo r Liquid-Solid Structural Evolution and Processing of Materials(Ministry of Education) Shandong UniversityJinan 250061China College of Ocean Science and Engineering Shanghai Maritime UniversityShanghai 201306China

Negative permittivity has been widely studied in various metamaterials and percolating composites, of which the anomalous dielectric behavior was attributed to critical structural properties of building ***, mono-phase ceramics of indium tin oxides(ITO) were sintered for epsilon-negative materials in MHz-k Hz frequency regions. Electrical conductivity and complex permittivity were analyzed with DrudeLorentz oscillator model. Carriers’ characters were measured based on Hall effect and the magnitude and frequency dispersion of negative permittivity were mainly determined by carrier ***-dependent dielectric properties further proved the epsilon-negative behaviors were closely associated with free carriers’ collective responses. It’s found that negative permittivity of ITO ceramics was mainly caused by plasma oscillations of free carriers, while the dielectric loss was mainly attributed to conduction loss. Negative permittivity realized here was related to materials intrinsic nature and this work preliminarily determined the mechanism of negative permittivity in doped ceramics from the perspective of carriers.

关键词： Tin-doped indium oxides Negative permittivity n-type carriers Plasma oscillation

Defect-induced insulator-metal transition and negative permittivity in La_(1-x)Ba_(x)CoO_(3)perovskite structure

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Journal of Materials Science & Technology 2022年第17期112卷 77-84页

作者： Zaixin Wei Zhongyang Wang Ciqun Xu guohua fan Xiaoting Song Yao Liu Runhua fan Key Laboratory for Liquid-Solid Structural Evolution and Processing of Materials Ministry of Education Shandong UniversityJinan 250061China State Key Lab of Metal Matrix Composites School of Materials Science and EngineeringShanghai Jiao Tong UniversityShanghai 200240China Department of Engineering Mathematics University of BristolBristol BS81TWUnited Kingdom College of Ocean Science and Engineering Shanghai Maritime UniversityShanghai 201306China

The development of negative permittivity materials in multifunctional applications requests expansion of their operating frequency and improvement of stability of negative *** electron density is beneficial to reduce plasma frequency so that negative permittivity is achieved in kHz *** permittivity achieved by percolating composites is restricted in practicality due to its instability nature at high *** achieve temperature-stable negative permittivity in kHz region,monophase La_(1-x)Ba_(x)CoO_(3)ceramics were prepared,and the transition from dielectric to metal was elaborated in the perspective of electrical conductivity and negative *** plasma-like negative permittivity is attained in kHz region,which is interpreted by the collective oscillation of low electron *** temperature-stable negative permittivity is based on the fact that the plasmonic state will not be undermined at high *** addition,zero-crossing behavior of real permittivity is observed in La_(0.9)Ba_(0.1)CoO_(3)sample,which provides a promising alternative to designing epsilon-near-zero *** work makes the La_(1-x)Ba_(x)CoO_(3)system a source material for achieving effective negative permittivity.

关键词： La_(1-x)Ba_(x)CoO_(3)ceramics Insulator-metal transition Negative permittivity Electrical conductivity temperature stability

Effect of Pressure on the Solidification Behavior and Mechanical Properties of SiCp/Al-Mg Composites

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Journal of Wuhan University of Technology(Materials Science) 2013年第2期28卷 274-278页

作者：张宏伟耿林 fan guohua SUN Yuan School of Materials Science and Engineering Harbin Institute of Technology Institute of Metal Research Chinese Academy of Sciences

SiCp/A1-Mg metal matrix composites were manufactured by semi-solid stirring technique. The composites were remelted and then solidified under different pressures to study the solidification behavior of composites by differential thermal analysis, scanning electron microscopy, and transmission electron microscopy. The experimental results show that SiCp reinforcements can not act as heterogeneous nucleation sites for c^（A1）, and an interfacial layer composed of MgA1204 spinel and Si-rich phase existed at A1/SiCp interface. The undercooling of the matrix alloy was improved by the pressure applied, resulting in the grain of matrix alloy refining. The X-ray diffraction pattern of composites testified that the matrix alloy exhibited a certain preferred orientation during solidification. In addition, with increasing the pressure for solidification, the pored defects in the composites decreased, while the relative density, hardness and compressive strength increased. Therefore, the microstructure and mechanical properties of the composites were improved by pressure placed during the solidification of SiCp/A1-Mg composites.

关键词： MMCs nucleation solidification behavior microstructure mechanical properties

Micro Defects Evolution of Nickel-Based Single Crystal Superalloys during Shear Deformation:A Molecular Dynamics Study

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Acta Metallurgica Sinica(English Letters) 2023年第12期36卷 2089-2099页

作者： Peng Zhang Ming Chen Qiang Zhu Linfu Zhang guohua fan Heyong Qin Qiang Tian National Key Laboratory for Precision Hot Processing of Metals Harbin Institute of TechnologyHarbin 150001China School of Materials Science and Engineering Harbin Institute of TechnologyWeihai 264209China Key Laboratory for Light-Weight Materials Nanjing Tech UniversityNanjing 211816China Central Iron&Steel Research Institute Group Beijing 100081China

Nickel-based single crystal superalloys have become the main structural materials of the aero-engines due to excellent high-temperature *** micro defects evolution of nickel-based single crystal superalloys under shear deformation was investigated by molecular dynamics(MD)simulations in the present *** is found that the interfacial dislocations decompose into Shockley dislocations under low shear stress,resulting in the plastic deformation of the Ni *** initial plastic deformation of the Ni3Al phase is caused by Shockley dislocations cutting into the Ni3Al *** following deformation from low temperature to medium temperature is controlled by dislocation slip,but the deformation at high temperature is *** is also found that the microvoid evolution can be divided into void growth and coalescence during shear *** microvoid could prevent dislocation entanglement,accelerate dislocation decomposition,and promote earlier plastic deformation under relatively low temperatures.

关键词： Nickel-based single crystal superalloys Micro defects evolution Molecular dynamics simulation Shear deformation

Recent Progress of Synchrotron X-Ray Imaging and Diffraction on the Solidification and Deformation Behavior of Metallic Materials

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Acta Metallurgica Sinica(English Letters) 2022年第1期35卷 3-24页

作者： Youhong Peng Kesong Miao Wei Sun Chenglu Liu Hao Wu Lin Geng guohua fan School of Materials Science and Engineering Harbin Institute of TechnologyHarbin150001China School of Engineering Xi’an Jiaotong-Liverpool UniversitySuzhou215123China Key Laboratory for Light-Weight Materials Nanjing Tech UniversityNanjing211816China

Characterizing the microstructure and deformation mechanism associated with the performances and properties of metallic materials is of great importance in understanding the microstructure-property *** past few decades have witnessed the rapid development of characterization techniques from optical microscopy to electron microscopy,although these conventional methods are generally limited to the sample surface because of the intrinsic opaque nature of metallic *** synchrotron radiation(SR)facilities can produce X-rays with strong penetrability and high spatiotemporal resolution,and thereby enabling the non-destructive visualization of full-field structural information in three *** endeavors were devoted to the 3 rd generation SR over the past three decades,in which X-ray beams have been focused down to 100 *** this paper,recent progresses on SR-related characterization technologies were reviewed,with particular emphases on the fundamentals of synchrotron X-ray imaging and synchrotron X-ray diffraction,as well as their applications in the in situ observations of material preparation(e.g.,in situ dendrite growth during solidification)and service under extreme environment(e.g.,in situ mechanics).Future innovations toward next-generation SR and newly emerging SRbased technologies such as dark-field X-ray microscopy and Bragg coherent X-ray diffraction imaging were also advocated.

关键词： Synchrotron radiation Synchrotron X-ray imaging Synchrotron X-ray diffraction Metallic alloys

Unexpected de-twinning of strongly-textured Ti mediated by local stress

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Journal of Materials Science & Technology 2022年第30期125卷 231-237页

作者： Kesong Miao Meng Huang Yiping Xia Hao Wu Qing Liu guohua fan Key Laboratory for Light-weight Materials Nanjing Tech UniversityNanjing 211816China School of Materials Science and Engineering Harbin Institute of TechnologyHarbin 150001China

As one of the heterostructures,the layered structure has attracted extensive research interests as it could regulate the deformation mechanisms[1-3].A remarkable combination of strength and ductility has been achieved in layered metals,including CuCu[4-6],Cu-Ni[7],Cu-Al[8,9],Cu-Ti[10],Ti-Ti[11,12],and Ti-Al[13-15].During deformation,mechanical mismatch(discrepancies of yield strength,work hardening,etc.)between component layers leads to mutual constraints,which generates local stress and local strain that deviate from the applied counterparts[16-18].As a result,the activation of additional deformation mechanisms is promoted in layered metals,such as slip systems with low Schmid factor or high critical resolved shear stress[19,20].

关键词： stress deformation strength

Green carbonization of waste coffee grounds into porous C/Fe hybrids for broadband and high-efficiency microwave absorption

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Journal of Materials Science & Technology 2024年第3期170卷 1-10页

作者： Xin Wen Cui Li Hui Liu guohua fan Yanan Tang Chuncheng Hao Lili Ma Pingan Song Institute of Advanced Electrical Materials College of Materials Science and EngineeringQingdao University of Science and TechnologyQingdao 266042China Center for Future Materials University of Southern QueenslandSpringfieldQLD 4300Australia School of Agriculture and Environmental Science University of Southern QueenslandSpringfieldQLD 4300Australia

Recently great effort s have been focused on designing high-performance microwave absorbers using sustainable biomass resources,but there remains a lack of green and efficient fabrication ***,inspired by natural porous character of biomass waste,we demonstrated a green one-step route to convert waste coffee grounds into porous C/Fe hybrids,and further explored their potential applications for broadband and high-efficiency microwave *** this design,the WCG-20-750(incorporated 20 wt%Fe(C_(5)H_(7)O_(2))_(3)catalyst and carbonized at 750℃)exhibited porous microstructure with the highest char yield of 55.45 wt%.Furthermore,the as-prepared C/Fe hybrids from WCG-20-750 displayed excellent microwave absorption ***,the minimum reflection loss(RL_(min))reached to-52.86 dB and the widest effective absorption bandwidth(EAB)was 6.40 GHz at the thickness of 3.0 *** work provides an economically viable and environmentally friendly strategy to convert biomass wastes into value-added microwave absorbers,ultimately making contributions to the upcycling of renewable biomass resources and the fostering of sustainable environment.

关键词： Waste recycling Microwave absorption Green carbonization Porous carbon Biomass

Effects of the layer thickness ratio on the enhanced ductility of laminated aluminum

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Journal of Materials Science & Technology 2022年第16期111卷 256-267页

作者： Yiping Xia Hao Wu Kesong Miao Xuewen Li Chao Xu Lin Geng Honglan Xie guohua fan School of Materials Science and Engineering Harbin Institute of TechnologyHarbin 150001China Key Laboratory for Light-weight Materials Nanjing Tech UniversityNanjing 211816China Shanghai Synchrotron Radiation Facility Shanghai Institute of High Energy Applied PhysicsShanghai 200000China

The layered structural parameters have been reported to be critical for tuning the tensile properties of laminated ***,we investigated the effects of the thickness ratio(rc/f)of coarse-grained layers(CLs)to fine-grained layers(FLs)on the enhanced ductility of the laminated *** local strain evolution demonstrates that the strain delocalization ability of laminated Al is improved with the decrease of rc/*** interfacial strain gradients,which can produce extra work hardening,gradually approach and cover the CLs with the rc/fdecreasing,explaining the trend of uniform elongation in laminated Al with various rc/*** integrated fracture morphology characterization reveals that the increase of the rc/fleads to an improvement in the tolerance of the interfacial microcracks,which is corresponding to the variation of fracture elongation in the laminated ***,there is an evident transition of transverse propagation path of interfacial microcracks from the CLs to FLs with increasing the rc/*** on a geometrical criterion of microcracks connectivity,the preferential transverse propagation path of interfacial microcracks in these laminated Al was *** calculation based on this criterion also predicted the critical rc/fcorresponding to the optimal combination of strength and fracture *** work deepens the understanding of the role of structural parameters of laminated metals in achieving the strength and ductility synergy.

关键词： Layered structure Structural parameter Digital image correlation Crack propagation

Micro Hierarchical Structure and Mechanical Property of Sparrow Hawk (Accipiter nisus) Feather Shaf

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Computer Modeling in Engineering & Sciences 2021年第5期127卷 705-720页

作者： Yichen Lu Zongning Chen Enyu Guo Xiangqing Kong Huijun Kang Yanjin Xu Rengeng Li guohua fan Tongmin Wang Key Laboratory of Solidification Control and Digital Preparation Technology(Liaoning Province) School of Materials Science and EngineeringDalian University of TechnologyDalian116024China School of Civil Engineering Liaoning University of TechnologyJinzhou121001China AVIC Manufacturing Technology Institute Beijing100024China Key Laboratory for Light-Weight Materials Nanjing Tech UniversityNanjing211816China

In this study,the real 3D model of the feather shaft that is composed of medulla and cortex is characterized by X-ray computer tomography,and the structural features are quantitatively *** and tensile tests are conducted to evaluate the mechanical performance of the feather shaft and cortex at different *** analysis of the 3D model shows that the medulla accounts for∼70%of the shaft volume and exhibits a closed-cell foam-like structure,with a porosity of 59%.The cells in the medulla show dodecahedron and decahedron morphology and have an equivalent diameter of∼30μ*** axial compression,the presence of medulla enhances the shaft ***,the combined effect of the medulla and cortex increases the buckling strength of the middle and distal shaft by 77%and 141%,respectively,compared to the calculated value of the shaft using linear mixed *** tensile properties of the cortex along the shaft axis are anisotropic because of the different fiber *** the fiber orientation gradually becomes uniform in the axial direction,the Young’s modulus and tensile strength of the cortex on the dorsal gradually increase from calamus to the distal shaft,and the fracture mode changes from tortuous fracture to V-shaped *** cortex on the lateral shows the opposite trend,that is the distal shaft becomes weaker due to fiber tangles.

关键词： Biomechanics feather shaft structure mechanical properties tomography