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Al2O3 supported hybrid Pd-CeO2 colloidal spheres and its enhanced catalytic performances for methane combustion

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Journal of Rare earths 2019年第7期37卷 714-719页

作者： Xinwei Yang Chenhao Du Yanglong Guo Yun Guo Li Wang Yunsong Wang Wangcheng Zhan Key Laboratory for Advanced Materials and Research Institute of Industrial Catalysis School of Chemistry and Molecular EngineeringEast China University of Science and TechnologyShanghai 200237China Sinopec Shanghai Research Institute of Petrochemical Technology Shanghai 201208China

Fabrication of novel nano-catalyst with improved activity and stability has been a hot topic in heterogeneous catalysis. Herein a novel approach was designed to synthesize Pd-CeO2 colloidal assembled spheres(CASs) in one-pot fashion. The Pd clusters were encompassed by the CeO2 nanocrystals with a high dispersity. Based on this hybrid structure, the Pd/ceria interface area can be greatly improved. After Pd-CeO2 CASs was supported on γ-Al2O3, its catalytic activity for CH4 combustion was evaluated. The result shows that Al2O3 supported Pd-CeO2 CASs exhibits an improved catalytic activity and stability,compared to the Pd/CeO2 catalyst prepared by impregnation method. The results of several characterization techniques indicate that the enhanced catalytic activity of Al2O3 supported Pd-CeO2 CASs can be attributed to the more interfacial Pd-O-Ce species and the more surface active oxygen species.

关键词： CeO2 Interface area Methane combustion Stability Rare earths

Phase constitutions,growth pattern and mechanical properties of Mg-1.4Gd-1.2Y-xZn-0.15Zr(at%) alloys

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Journal of Rare earths 2020年第3期38卷 315-323页

作者： Dongjie Chen Yongjun Li Kui Zhang Xinggang Li Minglong Ma Guoliang Shi Jiawei Yuan Ting Li State Key Laboratory of Nonferrous Metals and Process GRINM Group Co.Ltd. Beijing 100088 China GRIMAT Engineering Institute Co. Ltd. Beijing 101407 China General Research Institute for Nonferrous Metals Beijing 100088 China National Center of Analysis and Testing for Nonferrous Metals and Electronic Materials GRINM Group Co.Ltd. Beijing 100088 China Guobiao(Beijing)Testing&Certification Co. Ltd. Beijing 100088 China

The effects of minor Zn(0.2 at%,0.4 at%,0.6 at%) on the microstructures and mechanical properties of Mg-1.4 Gd-1.2 Y-0.15 Zr(at%) alloys were systematically *** reveal that increasing Zn content leads to the increase of the intergranular phases and the change of their composition from Mg24(Gd,Y)5 phase and(Mg,Zn)3(Gd,Y) phase to 18 R-LPSO phase and(Mg,Zn)3(Gd,Y) ***24(Gd,Y)5 phase is body-centered cubic structure and shares the same lattice constant with Mg24Y5 while(Mg,Zn)3(Gd,Y)phase is face-centered cubic structure with lattice constant of 0.72 nm,slightly lower than Mg3Gd.18RLPSO structure is identified to be monoclinic with c-axis not strictly vertical to the bottom surface but93.5°.The growth patterns of intergranular phases change from the divorced growth to coupled growth as compositions ***,the mechanical performance improves with Zn rising,ascribed to the decrease of brittle phases at grain boundaries and the increase of LPSO structure phases.

关键词： Mg-Gd-Y-Zn alloy Long period stacking ordered(LPSO) Phase growth Mechanical properties Rare earths

Surface exsolution and local atomic structure of amorphous CeTiO_x

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Journal of Rare earths 2019年第2期37卷 160-165页

作者： Seung-Hyeon Jo Soonok Kim Jiseung Ryu Dae-Seung Cho Bora Jeong Heesoo Lee Department of Materials Science and Engineering Pusan National University Department of Naval Architecture & Ocean Engineering Pusan National University Green Materials & Processes Group Ulsan Regional Division Korea Institute of Industrial Technology

We made precipitated nano-ceria(~5 nm) on the surface of the catalyst by heat treatment of Cesupersaturated amorphous CeTiOxto improve the oxygen storage properties of CeO_2. The catalysts were prepared by sol-gel methods and TiO_2 nanoparticles were preferentially generated as a core material to form selective Ce-supersaturated structure on the catalyst surface. Reaction temperature and amount of doping element are optimized to induce selective crystallization of CeO_2. Cee Ce(2 nd shell)bond around 0.38 nm of Ce L3-edge extended X-ray absorption fine structure is reduced and nanostructure of precipitated ceria on the surface is observed by HREM. The catalyst is present as amorphous with precipitated nano-CeO_2 on the surface. The de-NOxefficiency of the catalyst, which has precipitated CeO_2, improves by ~50% owing to the simultaneous reactions of the nano CeO_2 and the amorphous CeTiO_x.

关键词： Ce-Ti oxide Exsolution Amorphous catalyst Local atomic structure De-NO_x efficiency Rare earths

Single phase A2B7-type La-Mg-Ni alloy with improved electrochemical properties prepared by melt-spinning and annealing

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Journal of Rare earths 2019年第12期37卷 1305-1311页

作者： Yiming Li Zhuocheng Liu Guofang Zhang Yanghuan Zhang Huiping Ren Key Laboratory of Integrated Exploitation of Bayan Obo Multi-Metal Resources Inner Mongolia University of Science and Technology

La-Mg-Ni alloys were prepared by melt-spinning with different cooling rates and followed by *** of the cooling rate leads to refinement of the grains size and increasing of the abundance of *** is favorable to formation of the A2 B7-type phase and promotes the discharge capacity,cycling stability and high rate discharge ability of the as-spun *** constitution of the annealed alloys is found to be closely related to the microstructure of the as-spun alloys.A single phase A2 B7-type microstructure is obtained in the annealed alloy which is attributed to the lower abundance of the LaNis of the original alloy spun with lower cooling *** of the single phase A2 B7-type microstructure is also ascribed to the isolated and homogeneous distribution of the morphology of the as-spun *** single phase alloy presents higher discharge capacity and better cycling stability compared with other annealed alloys.

关键词： La-Mg-Ni electrode alloys Melt-spinning Annealing Single phase microstructure Electrochemical properties Rare earths

Temperature sensing behavior of Tm^3+:1G4(a),1G4(b) in oxyfluoride glass ceramics containing BaYbxY1-xF5 nanocrystals

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Journal of Rare earths 2020年第4期38卷 356-361页

作者： Rui Zhu Ke Zhang Congcong Zhu Zhencai Li Qiuhong Min Dacheng Zhou Jianbei Qiu College of Materials Science and Engineering Kunming University of Science and TechnologyKunming 650093China

Tm3+-doped transparent oxyfluoride glass ceramics containing BaYbxY((1-x))F5 nanocrystals were prepared via high temperature solid phase melting method,of which up-conversion emission is achieved by the Yb3+-mediated energy transfer *** required photon number of Tm3+ions emissions in BaYbxY(1-x)F5 nanocrystals was calculated through the luminescence spectra,revealing the strong dependence of energy transfer mechanism on Yb3+ions ***,based on the fluore scence intensity ratio technology,the effect of different energy transfer mechanism on the temperature sensitivity was investigated by the temperature-dependent luminescence intensity of thermally coupled energy levels of Tm3+:1G4(a),1G4(b).The obtained sensitivity decreases with the increase of Yb3+ions content,which is mainly attributed to the changes in photon absorption process of Tm^3+:1G4(b).

关键词： Tm^3+ BaYbxY(1-x)F5 Glass ceramics Up-conversion luminescence Temperature sensing Rare earths

Corrosion behavior of Ce-doped Ni-10Cu-11Fe-6Al(wt%) inert anode in molten CaCl_2 salt

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Journal of Rare earths 2019年第2期37卷 218-224页

作者： Mehdi Alzamani Kourosh Jafarzadeh Arash Fattah-alhosseini Malek Ashtar University of Technology Department of Materials Engineering Bu-Ali Sina University

In this research the effect of cerium dopingon corrosion behavior of Ni-10 Cu-11 Fe-6 Al(wt%) alloy as a novel inert anode in titanium electrolytic production was investigated. The samples, including un-doped and Ce-doped nickel-based alloys, were prepared using vacuum induction melting(VIM) process and then exposed to the electrolysis in molten calcium chloride at 900C at à1.6 V versus graphite reference electrode for different immersion time. The surface and cross-section of the samples were characterized using scanning electron microscopy(SEM), and their electrochemical behavior was investigated by electrochemical impedance spectroscopy(EIS). The results show that the un-doped samples have greater number of voids and porosities as compared to that of the 0.0064 wt% Ce-doped samples(as the optimum content of cerium in the alloy). Thus, the nickel-based alloy becomes less sensitive to the pitting by addition of cerium. The corrosion penetration depth reaches about 244 mm after 16 h of electrolysis in the un-doped sample, while was approximately 103 mm for the 0.0064 wt% Ce-doped sample, which is an indication that the corrosion penetration depth decreases by adding small amounts of Ce.

关键词： Ni-10Cu-11Fe-6Al Ce doping Corrosion behavior Molten CaCl2 salt Nickel-based alloy Rare earths

Controllable synthesis of Eu3+ ions doped Zn（OH）F and ZnO micro-structures:Phase,morphology and luminescence property

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Journal of Rare earths 2019年第9期37卷 955-960,I0003页

作者： Zhiyuan Chen Jingbin Huang Yanyan Wang Dan Yue Zhenling Wang Jingyang Niu Henan Key Laboratory of Polyoxometalate Chemistry College of Chemistry and Chemical EngineeringHenan UniversityKaifeng 475004China College of Chemistry and Molecular Engineering Zhengzhou UniversityZhengzhou 450001China Henan Key Laboratory of Rare Earth Functional Materials Zhoukou Normal UniversityZhoukou 466001China

Eu3+ions doped Zn(OH)F and ZnO micro-structures with specific morphologies were synthesized by a simple hydrothermal method only through altering the addition amount of NH4F and hexamethylenetetramine(HMT).The phase structure,morphology and luminescence properties of the as-prepared samples were characterized by X-ray powder diffraction(XRD),scanning electron microscopy(SEM),transmission electron microscopy(TEM),photoluminescence(PL)spectra and *** results indicate that the obtained Zn(OH)F:Eu^3+samples possess net-like and dandelion-like morphologies,which have an identical orthorhombic phase *** is found that the addition amount of raw materials such as NH4F and HMT plays a critical role for the formation of Zn(OH)F:Eu^3+.If the addition amounts of NH4F or HMT are reduced by half,the hexagonal ZnO:Eu^3+sample with peanut-like morphology can be *** the excitation of UV light,both the as-prepared Zn(OH)F:Eu^3+and ZnO:Eu^3+samples exhibit the characteristic emission of the doped Eu^3+.

关键词： Eu3+ions Doping Zn(OH)F ZnO Luminescence Rare earths

Preparation of La2O3 by ion-exchange membrane electrolysis of LaCl3 aqueous solution

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Journal of Rare earths 2019年第9期37卷 1009-1014,I0005页

作者： Deliang Meng Qiuyue Zhao Xijuan Pan Ting’an Zhang Key Laboratory of Ecological Metallurgy of Multi-Metal Intergrown Ores of Ministry of Education School of MetallurgyNortheastern University

The ion-exchange membrane electrolysis technology was applied inventively in the preparation of lanthanum hydroxide,after calcination,lanthanum oxide was obtained *** effect of the concentration of lanthanum chlo ride solution on electrolytic product was mainly *** phase composition,micro morphology,particle size and chlorine content of the product were characterized,*** the conditions of this work,the product that forms by electrolysis of LaCl3 aqueous solution directly is La(OH)*** the initial concentration of LaCl3 changes from 0.1 to 0.5 mol/L,the current efficiency of La(OH)3 increases from 60%to 85%,the product roasted at 800℃for 1.5 h is La2O3,whose median particle size(D50)is 10-20μm,the mass fraction of chloride ion is less than 0.02 wt%.Additio nally,the prepared La2O3 particles are porous and non-spherical particle s,which are composed of small crystals with sheet structure.

关键词： Lanthanum chloride Membrane electrolysis Lanthanum hydroxide Lanthanum oxide Current efficiency Rare earths

Energy transfer and cross-relaxation induced multicolor upconversion emissions in Er^3+/Tm^3+/Yb^3+ doped double perovskite La2ZnTiO6 phosphors

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Journal of Rare earths 2020年第2期38卷 130-138页

作者： Youfusheng Wu Fengqin Lai Bin Liu Zhibiao Li Tongxiang Liang Yaochun Qiang Jianhui Huang Xinyu Ye Weixiong You School of Material Science and Engineering Jiangxi University of Science and TechnologyGanzhou 341000China Key Laboratory of Rare Earth Luminescence Materials and Devices of Jiangxi Province Ganzhou 341000China School of Metallurgy and Chemistry Engineering Jiangxi University of Science and TechnologyGanzhou 341000China

Investigation on the bright and stable upconversion(UC)phosphors with multicolor emissions is fundamental and significant for the frontier applications of display and tempe rature *** re,dive rse emitting colors with blue,cyan and yellowish green,which are caused by the energy transfer and crossrelaxation processes,are obtained by altering Er^3+,Tm^3+and Yb^3+concentrations in Er3+singly,Er^3+-Tm^3+-Yb^3+co-and tri-doped double perovskite La2ZnTiO6(LZT)phosphors synthesized by a simple solid-state *** addition,excellent infrared emission at 801 nm located at"first biological windo w"is collected in Tm^3+-Yb^3+co-doped ***,the temperature sensing properties based on the thermally coupled levels((^2H11/2)/(^4S3/2))of Er3+ions were analyzed from 298 to 573 K of LZT:0.15 Er^3+/0.10 Yb^3+phosphor,demonstrating that the maximal sensitivity value is about56×10^-4 K^-1 at 448 *** these results imply that this kind of UC material has potential applications in display,bioimaging and optical device.

关键词： Upconversion Double perovskite Color-tunable Multiple applications Rare earths