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Interface-enhanced thermoelectric output power in crn/SrTiO_(3-x) heterostructure

Journal of Energy Chemistry 2022年第1期31卷 16-22,I0002页

作者： Xueying Wan Xiaowei Lu Lin Sun Mingyu Chen Na Ta Wei Liu Qi Chen Liwei Chen Jian He Peng Jiang Xinhe Bao State Key Laboratory of Catalysis CAS Center for Excellence in NanoscienceDalian Institute of Chemical PhysicsChinese Academy of SciencesDalian 116023LiaoningChina University of Chinese Academy of Sciences Beijing 100049China Dalian National Laboratory for Clean Energy Dalian Institute of Chemical PhysicsChinese Academy of SciencesDalian 116023LiaoningChina i-Lab Suzhou Institute of Nano-Tech and Nano-BionicsChinese Academy of SciencesSuzhou 215123jiangsuChina Department of Physics and Astronomy Clemson UniversityClemson 29634-0978USA

Thermoelectric devices enable direct conversion between thermal and electrical energy.Recent studies have indicated that the thin film/substrate heterostructure is effective in achieving high thermoelectric performance via decoupling the Seebeck coefficient and electrical conductivity otherwise adversely inter-dependent in homogenous bulk materials.However,the mechanism underlying the thin film/substrate heterostructure thermoelectricity remains unclear.In addition,the power output of the thin film/substrate heterostructure is limited to the nanowatt scale to date,falling short of the practical application requirement.Here,we fabricated the crn/SrTiO_(3-x) heterostructures with high thermoelectric output power and outstanding thermal stability.By varying the crn film thickness and the reduction degree of crn/SrTiO_(3-x) substrate,the optimized power output and the power density have respectively reached 276μWand 10^(8) mW/cm^(2) for the 30 nm crn film on a highly reduced surface of crn/SrTiO_(3-x) under a temperature difference of 300 K.The performance enhancement is attributed to the crn/crn/SrTiO_(3-x) heterointerface,corroborated by the band bending as revealed by the scanning Kelvin probe microscopy.These results will stimulate further research efforts towards interface thermoelectrics.

关键词： SrTi0_(3-x) crn Heterostructure Interface thermoelectrics Thin film

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Throughput Enhancement for NOMA Systems Using Intelligent Reflecting Surfaces

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Computers, Materials & Continua 2022年第12期73卷 5233-5244页

作者： Raed Alhamad Hatem Boujemaa Information Technology Department Saudi Electronic UniversityRiaydhSaudi Arabia UCAR-SUPCOM-COSIM Ariana2083Tunisia

In this article,we optimize the powers associated to Non Orthogonal Multiple Access(NOMA)users,sensing and harvesting duration for Cognitive Radio Networks(crn).The secondary source harvests energy from node A signal.Then,it senses the channel to detect primary source.Then,the secondary source transmits a signal that is reflected by Intelligent Reflecting Surfaces(IRS)so that all reflections have a zero phase at any user.A set Ii of reflectors are associated to user Ui.The use ofM=Mi=512,256,128,64,32,16,8 reflectors per user offers 45,42,39,36,33,30,27 dB gain vs.the absence of IRS.We also suggest the use of IRS in energy harvesting.The use P=8 reflectors for energy harvesting and M=Mi=8 reflectors per user for data communications offers 7 and 38 dB gain vs.one IRSM=Mi=8 and the absence of IRS.The use of P=16 reflectors for energy harvesting and M=Mi=8 reflectors per user for data communications offers 9 and 42 dB gain vs.one IRS M=Mi=8 and the absence of IRS.

关键词： crn NOMA spectrum sensing energy harvesting throughput maximization

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NOMA with Adaptive Transmit Power Using Intelligent Reflecting Surfaces

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Computer Systems Science & Engineering 2023年第5期45卷 2059-2070页

作者： Raed Alhamad Hatem Boujemaa Information Technology Department Saudi Electronic UniversityRiaydhSaudi Arabia University of Carthage SUPCOM-COSIMAriana2083Tunisia

In this article,we use Intelligent Reflecting Surfaces(IRS)to improve the throughput of Non Orthogonal Multiple Access(NOMA)with Adaptive Transmit Power(ATP).The results are valid for Cognitive Radio Networks(crn)where secondary source adapts its power to generate low interference at primary receiver.In all previous studies,IRS were implemented with fixed transmit power and previous results are not valid when the power of the secondary source is adaptive.In crn,secondary nodes are allowed to transmit over the same band as primary users since they adapt their power to minimize the generated interference.Each NOMA user has a subset of dedicated reflectors.At any NOMA user,all IRS reflections have the same phase.crn-NOMA using IRS offers 7,13,20 dB gain vs.crn-NOMAwithout IRS for N=8,16,32 reflectors.We also evaluate the effects of primary interference.The results are valid for any number of NOMA users,Quadrature Amplitude Modulation(QAM)and Rayleigh channels.

关键词： IRS 6G crn NOMA adaptive transmit power(ATP)

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Tribological behavior of crn-coated Cr–Mo–V steels used as die materials

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International Journal of Minerals,Metallurgy and Materials 2017年第12期24卷 1394-1402页

作者： Gulsah Aktas Celik Seyda Polat S.Hakan Atapek Kocaeli University Faculty of EngineeringDepartment of Metallurgical and Materials EngineeringUmuttepe Campus41380 KocaeliTurkey

DIN 1.2343 and 1.2367 steels are commonly used as die materials in aluminum extrusion, and single/duplex/multi-coatings enhance their surface properties. The design of an appropriate substrate/coating system is important for improving the tribological performance of these steels under service conditions because the load-carrying capacity of the system can be increased by decreasing the plastic deformation of the substrate. In this study, the tribological behavior of crn-coated Cr–Mo–V steels(DIN 1.2343, 1.2367, and 1.2999 grades) was investigated using different setups and tribological pairs at room and elevated temperatures. The aim of this study was to reveal the wear resistance of a suggested system(1.2999/crn) not yet studied and to understand both the wear and the failure characteristics of coated systems. The results showed that(i) among the steels studied, the DIN 1.2999 grade steel exhibited the lowest friction coefficient because it had the highest load-carrying capacity as a result of secondary hardening at elevated temperatures;(ii) at room temperature, both abrasive tracks and adhesive layers were observed on the worn surfaces; and(iii) a combination of chemical reactions and progressive oxidation caused aluminum adhesion on the worn surface, and the detachment of droplets and microcracking were the characteristic damage mechanisms at high temperatures.

关键词： Cr–Mo–V steels crn coating aluminum extrusion tribological behavior

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Effects of Bias Voltage on the Structure and Mechanical Properties of Thick crn Coatings Deposited by Mid-Frequency Magnetron Sputtering

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Plasma Science and Technology 2009年第1期11卷 38-41页

作者：容双全何俊王红军田灿鑫郭立平付德君 Accelerator Lab Department of PhysicsKey Laboratory of Acoustic and Photonic Materials and Devices of Ministry of EducationWuhan University Accelerator Lab Department of PhysicsKey Laboratory of Acoustic and Photonic Materials and Devices of Ministry of EducationWuhan University

Thick crn coatings were deposited on Si （111） substrates by electron source assisted mid-frequency magnetron sputtering working at 40 kHz. The deposition rate, structure, and microhardness of the coatings were strongly influenced by the negative bias voltage （Vb）. The deposition rate reached 8.96 μm/h at a Vb of -150 V. X-ray diffraction measurement revealed strong crn （200） orientation for films prepared at low bias voltages. At a high bias voltage of Vb less than -25 V both crn （200） and （111） were observed. Large and homogeneous grains were observed by both atomic force microscopy and scanning electron microscopy in samples prepared under optimal conditions. The samples exhibited a fibrous microstructure for a low bias voltage and a columnar structure for VD less than -150 V.

关键词： crn middle-frequency magnetron sputtering bias voltage

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Tribological properties of crn coating deposited on 20CrMo against tin bronze

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Science China(Technological Sciences) 2018年第11期61卷 1713-1722页

作者： LIU JiLiang LIAO RiDong XIE GuoXin XIANG JianHua LUO Jun LIAO Bin LIU QingYi School of Mechanical Engineering Beijing Institute of TechnologyBeiiing 100081China Beijing Liang Xin Technology Co. Ltd.Beijing 100081China State Key Laboratory of Tribology Tsinghua UniversityBeijing 100084China Beijing Radiation Center Beijing 100875China College of Nuclear Science and Technology Beijing Normal UniversityBeijing 100875China State Key Laboratory of Engine Reliability Weichai Power Co.Ltd.Weifang 261001China

A crn coating was deposited on the piston pin material 20CrMo. The tribological properties of 20CrMo and crn coating against tin bronze QSn7-0.2 were compared by pin-on-disk tests under dry friction and oil lubrication, respectively. The cross-sectional morphologies and structures of the coating were characterized through scanning electron microscopy and X-ray diffraction. The hardness, elastic modulus, and adhesion strength of the coating were tested through nano-hardness and scratch tests. The wear tracks were tested with an optical profilometer, and wear volume was calculated. Under dry friction conditions, the crn coating exhibited a significantly stable friction coefficient and a relatively lower wear rate against QSn7-0.2 at various temperatures compared with 20CrMo. The wear rate decreased by 98.5% at 700°C. Under poly-alpha-olefine lubrication, the crn coating reduced the load effect on the friction coefficient. Under engine oil 5 W40 lubrication, the crn coating improved the tribological properties under high speed and heavy load conditions. Simultaneously, the crn coating changed the friction and heat flow with increasing temperature.

关键词： crn coating tribological properties piston pin friction coefficient wear rate

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Microstructure and Mechanical Properties of crn Films Deposited by Inductively Coupled Plasma Enhanced Radio Frequency Magnetron Sputtering

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Plasma Science and Technology 2008年第3期10卷 340-343页

作者：刘峰孟月东任兆杏舒兴胜 Institute of Plasma Physics Chinese Academy of Sciences Hefei 230031 China

crn films have been synthesized on Si（100） wafer by inductively coupled plasma （ICP）-enhanced radio frequency （RF） magnetron sputtering. The effects of ICP power on microstructure, crystal orientation, nanohardness and stress of the crn films have been investigated. With the increase of ICP power, the current density at substrate increases and the films exhibit denser structure, while the DC self-bias of target and the deposition rate of films decrease. The films change from crystal structure to amorphous structure with the increase of ICP power. The measured nanohardness and the compressive stress of films reach the topmost at ICP power of 150 W and 200 W, respectively. The mechanical properties of films show strong dependence on the crystalline structure and the density influenced by the ICP power.

关键词： inductively coupled plasma （ICP） RF magnetron sputtering crn microstructure nanohardness stress

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Structural,electronic,and magnetic properties of crn under high pressure

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Chinese Physics B 2011年第7期20卷 356-361页

作者：蔺何曾雉 Key Laboratory of Materials Physics Institute of Solid State PhysicsChinese Academy of Sciences Institute of Applied Chemistry Xinjiang University Graduate University of the Chinese Academy of Sciences

The structural, electronic and magnetic properties of crn under high pressure are investigated by first-principles calculations. The antiferromagnetic orthorhombic structure is identified to be the preferred ground state structure. It possesses a bulk modulus of 252.8 GPa and the nonzero magnetic moment of 2.33 μB per Cr ion, which agree well with the experimental results. crn undergoes structural and magnetic transitions from an antiferromagnetic rocksalt structure to a non-magnetic Pnma phase at 132 GPa. Under compression, the magnetic moment of the Cr ion reduces rapidly near the equilibrium and phase transition point, and the distribution of the density of states is broadened, but the form of overlap between the orbitals of Cr d and N p remains unchanged. The broadening of the band induces spin flipping, which consequently results in the smaller magnetic moment of the Cr ion.

关键词： crn pressure electronic property magnetic property

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Tribological Properties of crn Coated H13 Grade Tool Steel

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Journal of Iron and Steel Research(International) 2014年第2期21卷 240-245页

作者： Erdem Atar zgür Alpaslan zgür elik Hüseyin imenoglu Department of Materials Science and Engineering Gebze Institute of Technology Small and Medium Sized Enterprises Development Organization Metallurgical and Materials Engineering Department Istanbul Technical University

The characteristics of crn coated martensitic H13 grade tool steels were studied. crn coatings were depos- ited by the arc physical vapor deposition （PVD） before and after the pulse plasma nitriding of the samples. The PVD and plasma nitriding techniques were applied in relevant workshops by following the commercial practice parameters. Experimental results showed that crn coating deposited on the nitrided surfaces exhibited superior scratch and wear resistances as compared to that deposited on the original martensitic surface.

关键词： crn coating nitriding PVD tool steel wear

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A Novel Duplex Low-temperature Chromizing Process at 500℃

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Journal of Materials Science & Technology 2007年第6期23卷 823-827页

作者： Huiliang CAO Cuilan WU Jiangwen LIU Chengping LUO Ganfeng ZOU School of Mechanical Engineering South China University of Technology Guangzhou 510641 China College of Materials Science and Engineering Hunan University Changsha 410082 China

An optimized low-temperature chromizing process at 500℃ was realized on a plain medium-carbon steel with 0.45 wt pct carbon via a duplex chromizing process which consists of a precursor plasma nitriding, and a followed salt bath thermoreactive deposition and diffusion （TRD） chromizing process. crn layer with a thin diffusion layer underneath was formed. The duplex chromizing process was studied by optical microscopy （OM）, scanning electron microscopy （SEM）, energy dispersive X-ray spectroscopy （EDS）, X-ray diffraction （XRD）, and transmission electron microscopy （TEM）. It was found that the chromizing speed at 500℃ was successfully enhanced by adding more Cr-Fe powders into the salt bath, and the crn layer formed at the cost of the prior nitride compound layer. A crn layer with average 8.1/~m in thickness and 1382 HV0.01 in microhardness was formed on the substrate by duplex chromizing at 500℃ for 24 h. Further more, the crn layer consisted of nanocrystalline crn grains.

关键词： Chromizing Plasma nitriding Thermoreactive deposition and diffusion （TRD） crn

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