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Electrocatalysis of Oxygen Evolution Reaction on Ti/SnO_2+RuO_2+MnO_2/MnO_2 Electrode in Sulfuric Acid Solution

Chemical Research in Chinese Universities 2001年第3期17卷 287-292页

作者： LIANG Zhen-hai FAN Cai-mei SUN Yan-ping Laboratory of Electrochemical Engineering Research College of Chemical EngineeringTaiyuan University of TechnologyTaiyuan 030024P.R.China

The Ti-Supported MnO_2 electrode was modified by introducing SnO_2+RuO_2+MnO_2 as an intermediate layer into the Ti/MnO_2 interface. The anodic polarization curves were measured at various temperatures ranging from 30 to 80℃ and the activation energy for the oxygen evolution reaction was evaluated. The experimental activation energy increased linearly with increasing the overpotential. The activation energy at the equilibrium potential was linearly correlated with the difference between the crystal field stabilization energies of Mn^(4+) at initial state and Mn^(4+) at transition state. The electrocatalysis characteristics of the anode were discussed by means of the mechanism of the substitution reaction of the ligand(S_N1 and S_N2) and molecular orbital theory. The results show that the anode has better electrocatalystic characteristics.

关键词： Ti/SnO2+RuO2+MnO2/MnO2 anode Electroeatalysis Activation energy crystal field theory Molecular Orbital theory

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Electromagnetic wave absorbing properties of TMCs(TM=Ti,Zr,Hf,Nb and Ta)and high entropy(Ti0.2Zr0.2Hf0.2Nb0.2Ta0.2)C

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Journal of Materials Science & Technology 2021年第15期74卷 105-118页

作者： Yanchun Zhou Biao Zhao Heng Chen Huimin Xiang Fu-Zi Dai Shijiang Wu Wei Xu Science and Technology on Advanced Functional Composite Laboratory Aerospace Research Institute of Materials&Processing TechnologyBeijing100076China Henan Key Laboratory of Aeronautical Materials and Application Technology School of Material Science and EngineeringZhengzhou University of AeronauticsZhengzhou450046China Key Laboratory of Advanced Ceramics and Machining Technology of Ministry of Education School of Materials Science and EngineeringTianjin UniversityTianjin300072China Zibo Firstar New Material Incoqjorated Co.Ltd. Zibo255000China Shanghai Chenhua Science and Technology Coloration Ltd. Shanghai201804China

Electromagnetic wave(EMW)absorbing materials play a vital role in modern communication and information processing technologies to inhibit information leakage and prevent possible damages to environment and human bodies.Currently,most of EMW absorbing materials are either composites of two or more phases or in the form of nanosheets,nanowires or nanofibers in order to enhance the EMW absorption performance through dielectric loss,magnetic loss and dielectric/magnetic loss coupling.However,the combination of complex shapes/multi phases and nanosizes may compound the difficulties of materials processing,composition and interfaces control as well as performance maintenance during service.Thus,searching for single phase materials with good stability and superior EMW absorbing properties is appealing.To achieve this goal,the EMW absorbing properties of transition metal carbides TMCs(TM=Ti,Zr,Hf,Nb and Ta)and high entropy(Ti_(0.2)Zr_(0.2)Hf_(0.2)Nb_(0.2)Ta_(0.2))C which belong to ultrahigh temperature ceramics,were investigated in this work.Due to the good electrical conductivity and splitting of d orbitals into lower energy t2glevel and higher energy eglevel in TMC6octahedral arrangement,TMCs(TM=Ti,Zr,Hf,Nb and Ta)exhibit good EMW absorbing properties.Especially,Hf C and Ta C exhibit superior EMW absorbing properties.The minimum reflection loss(RLmin)value of Hf C is-55.8 d B at 6.0 GHz with the thickness of 3.8 mm and the effective absorption bandwidth(E_(AB))is 6.0 GHz from 12.0 to 18.0 GHz at thickness of 1.9 mm;the RL_(minvalue)of Ta C reaches-41.1 d B at 16.2 GHz with a thickness of 2.0 mm and the EABis 6.1 GHz with a thickness of 2.2 mm.Intriguingly,the electromagnetic parameters,i.e.,complex permittivity and permeability are tunable by forming single phase solid solution or high entropy(Ti_(0.2)Zr_(0.2)Hf_(0.2)Nb_(0.2)Ta_(0.2))C.The R_(Lminvalue)of high entropy(Ti_(0.2)Zr_(0.2)Hf_(0.2)Nb_(0.2)Ta_(0.2))C is-38.5 d B at 9.5 GHz with the thickness of 1.9 mm,and the EABis 2.3 GHz(from 11.3 to 13.6 GHz)at thickness o

关键词： Transition metal carbides High entropy ceramics Microwave absorption Electromagnetic parameters Electronic structure crystal field theory

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Investigation on Spin Hamiltonian Parameters for Tetragonal Ytterbium Center in Lutetium Orthovanadate

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Journal of Rare Earths 2007年第S1期25卷 541-543页

作者：董会宁帅欣关鸣刘俊 Institute of Applied Physics Chongqing University of Posts and Telecommunications

Rare earth doped orthovanadate crystal LuVO4∶Yb3+ shows high power laser applications because of the low quantum defect and the high thermal conductivity. Since electronic paramagnetic resonance (EPR) is a powerful tool to analyze the electronic properties and the local structures of paramagnetic impurity centers in crystals, the EPR spectra of the Yb3+ centers in LuVO4 crystal were measured recently. However, the above experimental results have not been theoretically interpreted. In this work, The EPR g factors and the hyperfine structure constants of 171Yb3+ and 173Yb3+ isotopes in LuVO4 crystal were theoretically studied from the perturbation formulae of the spin Hamiltonian parameters for 4f13 ion in tetragonal symmetry. The needed crystal parameters were obtained from the superposition model and the local structure of the studied system. The calculated results were in reasonable agreement with the observed values.

关键词： ytterbium orthovanadate electronic paramagnetic resonance superposition model crystal field theory rare earths

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