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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

Targeted Double Negative Properties in Silver/Silica Random Metamaterials by Precise Control of Microstructures

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Research 2019年第1期2019卷 1226-1236页

作者： Peitao Xie Zidong Zhang Zhongyang Wang Kai Sun runhua fan College of Ocean Science and Engineering Shanghai Maritime UniversityShanghai 201306China Key Laboratory for Liquid-Solid Structural Evolution and Processing of Materials(Ministry of Education) Shandong UniversityJinan 250061China

Te mechanism of negative permittivity/permeability is still unclear in the random metamaterials,where the precise control of microstructure and electromagnetic properties is also a challenge due to its random *** silver was introduced into porous SiO_(2) microsphere matrix by a self-assemble and template method to construct the random *** distribution of silver was restricted among the interstices of SiO_(2) microspheres,which lead to the precise regulation of electrical percolation(from hoping to Drude-type conductivity)with increasing silver *** permittivity came from the plasma-like behavior of silver network,and its value and frequency dispersion were further adjusted by Lorentz-type dielectric *** this process,the frequency of epsilon-near-zero(ENZ)could be adjusted *** permeability was well explained by the magnetic response of eddy current in silver *** calculation results indicated that negative permeability has a linear relation with ω^(0.5),showing a relaxation-type spectrum,diferent from the“magnetic plasma”of periodic *** simulations demonstrated that negative permittivity materials and ENZ materials,with the advantage of enhanced absorption(40dB)and intelligent frequency selection even in a thin thickness(0.1 mm),could have potentials for electromagnetic attenuation and *** work provides a clear physical image for the theoretical explanation of negative permittivity and negative permeability in random metamaterials,as well as a novel strategy to precisely control the microstructure of random metamaterials.

关键词： silver permittivity precise

Moisture-proof and Enhanced Effect of Inorganic Coating on Porous Si_3N_4 Ceramic

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Journal of Wuhan University of Technology(Materials Science) 2015年第2期30卷 311-314页

作者：程传兵 fan runhua WANG Chonghai WANG Hongsheng ZHOU Changling 刘福田 School of Materials Science and Engineering The University of Jinan Key Laboratory for Liquid-Solid Structural Evolution and Processing of Materials (Ministry of Education) Shandong University Shandong Research&Design Institute of Industrial Ceramics

Inorganic coating was fabricated on the surface of the porous Si3N4 ceramic by polymer derived（PD） and spraying technology, via using vinyl-polysilazane（PSN-1） as a preceramic polymer and Si3N4 and lithium aluminosilicate（LAS） powders as fillers. The phase and microstructure of the coatings were analyzed by X-ray diffraction（XRD） analysis and scanning electron microscopy（SEM）, respectively. The effect of the coatings on mechanical property and humidity resistance of the porous Si3N4 ceramic was investigated. The experimental results showed that we successfully fabricated the uniform and dense coating which preferably combined with the substrate upon the addition of fillers. The bending strength of the porous Si3N4 ceramic sprayed the coating increased by more than 18%, and the surface hardness increased by 1.7 times. The apparent porosity of the materials reduced by an average of 97.7%, and water absorption was below 0.5%. Therefore, the prepared coating with preferable density had an obviously moisture-proof and enhanced effect on the porous Si3N4 ceramic.

关键词： inorganic coating Si3N4 ceramic moisture-proof and enhanced coating polymer derived radome

Epsilon-negative BaTiO_(3)/Cu composites with high thermal conductivity and yet low electrical conductivity

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Journal of Materiomics 2020年第1期6卷 145-151页

作者： Zhongyang Wang Kai Sun Peitao Xie Yao Liu Qilin Gu runhua fan John Wang College of Ocean Science and Engineering Shanghai Maritime UniversityShanghai201306China Key Laboratory for Liquid-Solid Structural Evolution and Processing of Materials(Ministry of Education) Shandong UniversityJinan250061China Department of Materials Science and Engineering National University of Singapore117574Singapore State Key Laboratory of Bio-fibers and Eco-textiles Institute of Biochemical EngineeringCollege of Materials Science and EngineeringQingdao UniversityQingdao266071China

Epsilon-negative materials with high thermal conductivity and low electrical conductivity are of great importance for high power microwave *** this work,BaTiO_(3)/Cu composites,as a class of epsilonnegative materials,are rationally designed to achieve a high thermal conductivity yet maintaining the electrical insulative *** permittivity behavior induced by dielectric resonance and plasma oscillation is observed in these BaTiO_(3)/Cu composites,which can be explained by the Lorentz and Drude model *** outstanding absorption ability is achieved near the zero-cross point of the *** from the positive temperature coefficient of resistance and the weak temperature dependence of thermal conductivity in BaTiO_(3)/Cu composites,sample containing 22.3 vol% of Cu content exhibits a thermal conductivity of up to 17.7 W/(m·k)and an electrical conductivity down to 0.0022(Ω cm)^(-1) at 150℃.Therefore,BaTiO_(3)/Cu composite is a promising candidate for applications in electromagnetic attenuation and thermal management.

关键词： BaTiO_(3)/Cu composite Negative permittivity Percolation Thermal conductivity Electrical conductivity

Flexible and biocompatible poly(vinyl alcohol)/multi-walled carbon nanotubes hydrogels with epsilon-near-zero properties

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Journal of Materials Science & Technology 2022年第36期131卷 91-99页

作者： Jiahong Tian runhua fan Zheng Zhang Yang Li Haikun Wu Pengtao Yang Peitao Xie Wenxin Duan Chun-Sing Lee College of Ocean Science and Engineering Shanghai Maritime UniversityShanghai 201306China Department of Applied Mathematics The Hong Kong Polytechnic UniversityHong KongChina Department of Chemistry City University of Hong KongHong KongChina Hong Kong Branch of National Precious Metals Material Engineering Research Centre City University of Hong KongHong KongChina State Key Laboratory of Bio-Fibers and Eco-Textiles Institute of Biochemical Engineering College of Materials Science and EngineeringQingdao UniversityQingdao 266071China

Epsilon-near-zero(ENZ)material has been a research hotspot in recent years due to unique physical properties such as inverse Doppler effect and negative refractive index,showing great potentials in the fields of flexible electronics,wearable devices,sensors,*** ENZ materials are mostly reported at visible,infrared and terahertz wavelengths,while the report about ENZ materials at radio frequency is *** this work,flexible and biocompatible poly(vinyl alcohol)/multi-walled carbon nanotubes(PVA/MWCNTs)hydrogels,which were successfully fabricated by an environmentally friendly method,were used as ENZ materials at radio frequency for the first *** experiments proved that the experimental process and products are green,environmentally friendly and *** microstructure,crystalline structure,chemical composition and dielectric properties were *** different water states,which were free water molecules and bound water molecules,coexisted in these PVA/MWCNTs hydrogels and accounted for about 37.5 wt%and 15.9 wt%respectively by analyzing the thermogravimetric analysis *** the MWCNTs content reached 12 wt%and 15 wt%,the continuous conductive MWCNTs network was formed in the hydrogel,and ENZ phenomenon was observed at about 760 k Hz and 580 k Hz respectively,which was attributed to the interband *** the flexibility and non-toxicity of PVA/MWCNTs hydrogels,the ENZ properties of this structure at the radio frequency can be well used in wearable invisibility cloak,flexible electronics,skin sensors and other wearable devices.

关键词： Epsilon-near-zero Hydrogels Biocompatibility Negative permittivity

Negative permittivity derived from inductive characteristic in the percolating Cu/EP metacomposites

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Journal of Materials Science & Technology 2019年第11期35卷 2463-2469页

作者： Kai Sun Jiahao Xin Yaping Li Zhongyang Wang Qing Hou Xiaofeng Li Xinfeng Wu runhua fan Kwang Leong Choy College of Ocean Science and Engineering Shanghai Maritime UniversityShanghai201306China Key Laboratory for Liquid-Solid Structural Evolution and Processing of Materials(Ministry of Education) Shandong UniversityJinan250061China Department of Materials Science and Engineering National University of SingaporeSingapore119077Singapore Department of Chemistry University College LondonLondonWC1H 0AJUK UCL Institute for Materials Discovery University College LondonLondonWC1E 7JEUK

Recently,increasing attention has been concentrated on negative permittivity with the development of the emerging metamaterials composed of periodic array ***,taking facile preparation into consideration,it is important to achieve negative permittivity behavior based on materials'intrinsic properties rather than their artificially periodic *** this paper,we proposed to fabricate the percolating composites with copper dispersed in epoxy(EP)resin by a polymerization method to realize the negative permittivity *** Cu content in the composites reached to 80 wt%,the conductivity abruptly went up by three orders of magnitudes,suggesting a percolation *** the percolation threshold,the conductivity spectra conform to Jonscher's power law;when the Cu/EP composites reached to percolating state,the conductivity gradually reduced in high frequency region due to the skin *** is indicated that the conductive mechanism changed from hopping conduction to electron *** addition,the permittivity did not increase monotonously with the increase of Cu content in the vicinity of percolation threshold,due to the presence of leakage ***,the negative permittivity conforming to Drude model was observed above the percolation *** investigation revealed that there was a constitutive relationship between the permittivity and the *** conductive fillers are slightly above the percolation threshold,the inductive characteristic derived from conductive percolating network leads to the negative *** epsilon-negative materials can potentially be applied in novel electrical devices,such as high-power microwave filters,stacked capacitors,negative capacitance field effect transistors and coil-free *** addition,the design strategy based on percolating composites provides an approach to epsilon-negative materials.

关键词： Negative permittivity Epsilon-negative materials Percolating composites Metacomposites Metamaterials

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负介材料:超材料的分支

中国材料进展 2019年第4期38卷 313-318页

作者：范润华上海海事大学海洋科学与工程学院材料系上海201306 山东大学材料液固结构演变与加工教育部重点实验室山东济南250061

介电常数是材料的基本物性参数之一,其值一直被认为正。受超材料的负物性参数启发,作者研究组提出导体/绝缘体随机复合探索常规材料的"超常"性质,建立了负介材料的原理框架和构筑策略,形成了有别于其它超材料的一个特色分支。对于导体/... 详细信息

介电常数是材料的基本物性参数之一,其值一直被认为正。受超材料的负物性参数启发,作者研究组提出导体/绝缘体随机复合探索常规材料的"超常"性质,建立了负介材料的原理框架和构筑策略,形成了有别于其它超材料的一个特色分支。对于导体/绝缘体复合材料,导电相含量超过但仍然接近逾渗阈值情况下,绝缘基体中连通的导电相成为电感(L)功能体,射频等离振荡这一自由电子集体行为导致负介电;孤立的导电相则作为电容(C)功能体,并通过LC谐振影响负介电行为。逾渗复合材料为负介性能调控提供了丰富的手段,导电相可以是金属、碳材料等不同类别,可以是颗粒、纤维、片层等不同形貌;绝缘体可以是树脂,也可以是陶瓷。相对于主要建立在阵列结构基础上的超材料,负介材料是一个补充,丰富了超材料的内涵。负介材料为电容器和电感器、微波吸收和衰减、天线等领域的选材用材提供了新的思路。

关键词：超材料介电常数微波吸收电容器电介质

Effect of Fast Multiple Rotation Rolling on Microstructure and Properties of Ti6Al4V Alloy

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Journal of Shanghai Jiaotong university(Science) 2023年第2期28卷 264-269页

作者：杨晓洁常雪婷范润华 College of Ocean Science and Engineering Shanghai Maritime UniversityShanghai 201306China Shandong Institute for Product Quality Inspection Jinan 250100China

Using fast multiple rotation rolling(FMRR),a nanostructure layer was fabricated on the surface of Ti6Al4V *** microstructure of the surface layer was investigated using optical microscopy,transmission electron microscopy,scanning electron microscopy,and X-ray *** results indicated that a nanostructured layer,with an average grain size of 72—83 nm,was obtained in the top surface layer,when the FMRR duration was 15 *** the average grain size further reduced to 24—37 nm when the treatment duration increased to 45 *** density dislocations,twins,and stacking faults were observed in the top surface *** microhardness of FMRR specimen,compared with original specimen,was significantly increased.A uniform,continuous and thicker compound layer was obtained in the top surface of FMRR sample,and the diffusion speed of N atom in the top surface layer was *** treatment provides corrosion improvement.

关键词： fast multiple rotation rolling(FMRR) nanostructure layer Ti6Al4V alloy high density dislocation plasma nitriding low temperature

Effect of ECAP Pass Number on Mechanical Properties of2Al2 Al Alloy

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Journal of Wuhan University of Technology(Materials Science) 2008年第1期23卷 71-73页

作者：毕见强 Key lab of Material Liquid Structure and Heredity Education Ministry Key Lab of Engineering Ceramics of Shandong Province Shandong University

2A12 Al alloy was suffered from equal-channel angular pressing（ECAP） in this experiment. The influence of ECAP pass number on ultimate strength（UTS）, hardness and elongation was studied. The results show that during ECAP the number of sample passing through the channels is very important for mechanical properties and microstructure refinement. ECAP not only increases their plasticity and hardness but also leads to refined grain. But the elongation reduces from 17.5% tol 1.8 % after 1 pass ECAP, then almost tends to be unchanged with the increasing of pass number. The value of ultimate strength of 2A12 Al alloy increases by 135%, hardness by 51%, and ultra fine grains of about 200 nm can be observed after 8 passes.

关键词： ECAP ultra-fine grain materials Al alloy 2A 12 mechanical properties