Structural, electronic properties and enhancement of electrical polarization in Er{sub 2}NiMnO{sub 6}/La{sub 2}NiMnO{sub 6} superlattice by first-principles calculations

Energy Technology Data Exchange (ETDEWEB)

Lu, Haipeng; Deng, Longjiang [National Engineering Research Center of Electromagnetic Radiation Control Materials, University of Electronic Science and Technology of China, Chengdu, Sichuan, 610054 (China); State Key Laboratory of Electronic Thin Films and Integrated Devices, University of Electronic Science and Technology of China, Chengdu, Sichuan, 610054 (China); Sun, Xun, E-mail: sunxunphy@hotmail.com; Hou, Zhihua; Yang, Wen; Wang, Siyuan; Xie, Jianliang [State Key Laboratory of Electronic Thin Films and Integrated Devices, University of Electronic Science and Technology of China, Chengdu, Sichuan, 610054 (China)

2016-03-15

Employing first-principles calculations, structural, electronic properties of new multiferroic material Er{sub 2}NiMnO{sub 6}/La{sub 2}NiMnO{sub 6} perovskite superlattice are investigated. This structure is computed as monoclinic phase with obvious distortion. The average in-plane anti-phase rotation angle, average out-of-plane in-phase rotation angle and other microscopic features are reported in this paper. Ni and Mn are found in this superlattice that stay high spin states. These microscopic properties play important roles in multiferroic properties. Based on these microscopic features, the relationship between the direction of spontaneous polarization and the order of substitution in neighboring A-O layers is explained. Finally, we try to enhance the electrical polarization magnitude by 32% by altering the previous superlattice as LaEr{sub 2}NiMnO{sub 7} structure. Our results show that both repulsion force of A site rare earth ions and the arrangement of B site ions can exert influences on spontaneous polarization.

Facile synthesis of MnO2/rGO/Ni composite foam with excellent pseudocapacitive behavior for supercapacitors

International Nuclear Information System (INIS)

Sun, Youyi; Zhang, Wenhui; Li, Diansen; Gao, Li; Hou, Chunlin; Zhang, Yinghe; Liu, Yaqing

2015-01-01

In this study, the MnO 2 /reduced graphene oxide/Ni (MnO 2 /rGO/Ni) composite foam as a binder-free supercapacitor electrode was prepared by a facile method. The rGO film has been firstly coated on the skeletons of Ni foam current collectors by chemical deposition method and that have been used as substrates for preparation of a novel three dimensional rGO/Ni composite foam-supported porous MnO 2 film by the hydrothermal method. The structure of MnO 2 /rGO/Ni composite foam was characterized by Raman spectra, IR spectra and Scanning electron microscopy. It indicated that the high-quality rGO film have been coated on skeletons of Ni foam current collectors and the MnO 2 film had a 3D network microstructure, consisting of interlaced nanosheets. Furthermore, the binder-free MnO 2 /rGO/Ni composite foam electrode has been characterized by the cyclic voltammetry, galvanostatic charge/discharge and electrochemical impedance spectra. It exhibited excellent pseudocapacitive behavior with specific capacitance of 479.0 F/g. The capacitance could retain about 83.5% after 1000 charge–discharge cycles. This simple synthetic approach provides a convenient route for the large scale preparation of 3D porous MnO 2 /rGO/Ni composite foam for lots of applications in future. - Graphical abstract: The MnO 2 /rGO/Ni composite foam was prepared by a facile method as shown in Fig. 1 and the unique structure of composite foam was suited to be a binder-free supercapacitor electrode due to low resistance, 3D network and porous structure. - Highlights: • The MnO 2 /rGO directly grown on Ni foam was firstly reported. • The MnO 2 /rGO/Ni composite foam was prepared by a facile method. • The MnO 2 /graphene/Ni composite foam as a binder-free supercapacitor electrode exhibited excellent pseudocapacitive behavior

MnO2/multiwall carbon nanotube/Ni-foam hybrid electrode for electrochemical capacitor

Science.gov (United States)

Chen, L. H.; Li, L.; Qian, W. J.; Dong, C. K.

2018-01-01

The ternary composites of manganese dioxide/multiwall carbon nanotube/Ni-foam (MnO2/MWNT/Ni-foam) for supercapacitors were fabricated via a hydrothermal method after direct growth of MWNTs on the Ni-foam. The structural properties of the electrodes were characterized by SEM and TEM. The electrode exhibited excellent electrochemical properties from the investigation based on the three-electrode setup. Low contact resistance Rs of about 0.291 Ω between MnO2/MWNT and Ni-foam was reached benefited from the direct growth structure. High capacitance of 355.1 F/g at the current density of 2 A/g was achieved, with good capacitive response at high current density. The MnO2/MWNT/Ni-foam electrode exhibits good stability performance after 2000 cycles at a current of 40 mA.

Behavior and mechanism of Ni(II) uptake on MnO2 by a combination of macroscopic and EXAFS investigation

International Nuclear Information System (INIS)

Guodong Sheng; Jiang Sheng; Shitong Yang; Ju Hu; Xiangke Wang

2011-01-01

The effects of pH, ionic strength, competing ions and initial metal concentrations on the uptake behavior and mechanism of radioactive Ni(II) onto MnO 2 was investigated using a combination of classical macroscopic methods and the extended X-ray absorption fine structure (EXAFS) spectroscopy technique. The results indicated that the uptake of Ni(II) on MnO 2 is obviously dependent on pH but independent of ionic strength, which suggested that the uptake of Ni(II) onto MnO 2 is attributed to an inner-sphere surface complex rather than an outer-sphere surface complex. EXAFS analysis shows that the hydrated Ni(II) is adsorbed through six-fold coordination with an average Ni-O interatomic distance of 2.04 ± 0.01 A. It can be inferred from the EXAFS analysis that the inner-sphere surface complex of Ni(II) onto MnO 2 is involved in both edge-sharing and corner-sharing linkages. Both the macroscopic uptake data and the molecular level evidence of Ni(II) surface speciation at the MnO 2 -water interfaces should be factored into better prediction of the bioavailability and mobility of Ni(II) in soil and water environment. (author)

Facile synthesis of MnO{sub 2}/rGO/Ni composite foam with excellent pseudocapacitive behavior for supercapacitors

Energy Technology Data Exchange (ETDEWEB)

Sun, Youyi; Zhang, Wenhui [Research Center for Engineering Technology of Polymeric Composites of Shanxi Province, North University of China, Taiyuan 030051 (China); Li, Diansen [Key Laboratory of Bio-Inspired Energy Materials and Devices, School of Chemistry and Environment, Beijing University of Aeronautics and Astronautics, Beijing 100191 (China); Gao, Li; Hou, Chunlin [Research Center for Engineering Technology of Polymeric Composites of Shanxi Province, North University of China, Taiyuan 030051 (China); Zhang, Yinghe [International Center for Science and Engineering, Waseda University, Shinjuku-ku, Tokyo 169-8555 (Japan); Liu, Yaqing, E-mail: lyqzgz2010@163.com [Research Center for Engineering Technology of Polymeric Composites of Shanxi Province, North University of China, Taiyuan 030051 (China)

2015-11-15

In this study, the MnO{sub 2}/reduced graphene oxide/Ni (MnO{sub 2}/rGO/Ni) composite foam as a binder-free supercapacitor electrode was prepared by a facile method. The rGO film has been firstly coated on the skeletons of Ni foam current collectors by chemical deposition method and that have been used as substrates for preparation of a novel three dimensional rGO/Ni composite foam-supported porous MnO{sub 2} film by the hydrothermal method. The structure of MnO{sub 2}/rGO/Ni composite foam was characterized by Raman spectra, IR spectra and Scanning electron microscopy. It indicated that the high-quality rGO film have been coated on skeletons of Ni foam current collectors and the MnO{sub 2} film had a 3D network microstructure, consisting of interlaced nanosheets. Furthermore, the binder-free MnO{sub 2}/rGO/Ni composite foam electrode has been characterized by the cyclic voltammetry, galvanostatic charge/discharge and electrochemical impedance spectra. It exhibited excellent pseudocapacitive behavior with specific capacitance of 479.0 F/g. The capacitance could retain about 83.5% after 1000 charge–discharge cycles. This simple synthetic approach provides a convenient route for the large scale preparation of 3D porous MnO{sub 2}/rGO/Ni composite foam for lots of applications in future. - Graphical abstract: The MnO{sub 2}/rGO/Ni composite foam was prepared by a facile method as shown in Fig. 1 and the unique structure of composite foam was suited to be a binder-free supercapacitor electrode due to low resistance, 3D network and porous structure. - Highlights: • The MnO{sub 2}/rGO directly grown on Ni foam was firstly reported. • The MnO{sub 2}/rGO/Ni composite foam was prepared by a facile method. • The MnO{sub 2}/graphene/Ni composite foam as a binder-free supercapacitor electrode exhibited excellent pseudocapacitive behavior.

Electrochemically active MnO{sub 2} coated Li{sub 1.2}Ni{sub 0.18}Co{sub 0.04}Mn{sub 0.58}O{sub 2} cathode with highly improved initial coulombic efficiency

Energy Technology Data Exchange (ETDEWEB)

Jin, Yanling; Xu, Youlong, E-mail: ylxu@mail.xjtu.edu.cn; Sun, Xiaofei; Xiong, Lilong; Mao, Shengchun

2016-10-30

Highlights: • MnO{sub 2} was used to coat lithium-rich layered oxide Li{sub 1.2}Ni{sub 0.18}Co{sub 0.04}Mn{sub 0.58}O{sub 2}. • MnO{sub 2} is electrochemically active and became spinel phase after cycles. • MnO{sub 2}-coated material shows noticeably improved initial coulombic efficiency. • Specific capacities and rate performances could also be enhanced by MnO{sub 2} coating. - Abstract: Lithium-rich layered oxide is known to be one of the most promising positive electrode materials for lithium ion batteries due to its large capacity and high energy density. However, low initial coulombic efficiency is currently an urgent problem hindering its practical application. In this work, electrochemically active MnO{sub 2} coating was used to improve the coulombic efficiency of Li{sub 1.2}Ni{sub 0.18}Co{sub 0.04}Mn{sub 0.58}O{sub 2}. Firstly, the pristine material was synthesized via co-precipitation following by solid-state calcination. Then MnO{sub 2}-coated Li{sub 1.2}Ni{sub 0.18}Co{sub 0.04}Mn{sub 0.58}O{sub 2} was prepared by heat treatment of the mixture of pristine powder and manganese nitrate. During first discharging, lithium ions can intercalate into not only the delithiated Li{sub 1.2}Ni{sub 0.18}Co{sub 0.04}Mn{sub 0.58}O{sub 2} but also the MnO{sub 2} coating, thus noticeably improves the coulombic efficiency and discharge capacity. The initial efficiency is enhanced from 61.2% (pristine) to 84.4%, 88.8% and 95.4%, respectively, for 10 wt.%, 15 wt.% and 20 wt.% MnO{sub 2} coated Li{sub 1.2}Ni{sub 0.18}Co{sub 0.04}Mn{sub 0.58}O{sub 2} at 20 mA g{sup −1}. Furthermore, the 15 wt.% MnO{sub 2} coated sample delivers an initial discharge capacity as high as 294.4 mAh g{sup −1}.

Synthesis of NiO@MnO_2 core/shell nanocomposites for supercapacitor application

International Nuclear Information System (INIS)

Chen, Junjiao; Huang, Ying; Li, Chao; Chen, Xuefang; Zhang, Xiang

2016-01-01

Graphical abstract: - Highlights: • MnO_2 nanosheets were grown on the surface of porous NiO microtube. • The NiO@MnO_2 nanocomposite exhibits excellent cycle performance. • The nanocomposite exhibits specific capacitance of 266.7 F g"−"1 at 0.5 A g"−"1. - Abstract: In this work, NiO@MnO_2 core/shell nanocomposites were fabricated by a two-step method. The morphology and structure of the nanocomposites were characterized by scanning electron microscopy, transmission electron microscopy, X-ray photoelectron spectroscopy, X-ray diffraction analysis and thermal gravity analysis. In addition, the supercapacitive performances were examined by cyclic voltammogram (CV), galvanostatic charge–discharge and electrochemical impedance spectroscopy (EIS). The electrochemical results indicate that the composite exhibits a specific capacitance of 266.7 F g"−"1 at 0.5 A g"−"1 and excellent cycling stability (81.7% retention after 2000 cycles at 1 A g"−"1). Therefore, this wok offers meaningful reference for supercpacitor applications in the future.

Hierarchical 3D NiFe2O4@MnO2 core-shell nanosheet arrays on Ni foam for high-performance asymmetric supercapacitors.

Science.gov (United States)

Zhang, Xinyang; Zhang, Ziqing; Sun, Shuanggan; Sun, Qiushi; Liu, Xiaoyang

2018-02-13

Hierarchical NiFe 2 O 4 @MnO 2 core-shell nanosheet arrays (NSAs) were synthesized on Ni foam as an integrated electrode for supercapacitors, using a facile two-step hydrothermal method followed by calcination treatment. The NiFe 2 O 4 nanosheets were designed as the core and ultrathin MnO 2 nanoflakes as the shell, creating a unique three-dimensional (3D) hierarchical electrode on Ni foam. The composite electrode exhibited remarkable electrochemical performance with a high specific capacitance of 1391 F g -1 at a current density of 2 mA cm -2 and long cycling stability at a high current density of 10 mA cm -2 (only 11.4% loss after 3000 cycles). Additionally, an asymmetric supercapacitor (ASC) device was fabricated with a NiFe 2 O 4 @MnO 2 composite as the positive electrode material and activated carbon (AC) as the negative one. The ASC device exhibited a high energy density (45.2 W h kg -1 ) at a power density of 174 W kg -1 , and an excellent cycling stability over 3000 cycles with 92.5% capacitance retention. The remarkable electrochemical performance demonstrated its great potential as a promising candidate for high-performance supercapacitors.

2D water layer enclathrated between Mn(II)-Ni(CN)4 coordination frameworks

International Nuclear Information System (INIS)

Ray, Ambarish; Bhowmick, Indrani; Sheldrick, William S.; Jana, Atish Dipankar; Ali, Mahammed

2009-01-01

A [Ni(CN) 4 ] 2- based two-dimensional Mn(II) coordination polymer {Mn(H 2 O) 2 [NiCN] 4 .4H 2 O}, in which the coordination layers are stacked on top of each other sandwiching 2D water layer of boat-shaped hexagonal water clusters has been synthesized. The complex exhibits high thermal decomposition temperature and reversible water absorption, which were clearly demonstrated by thermal and PXRD studies on the parent and rehydrated complex after dehydration. - Abstract: A coordination polymer, {Mn(H 2 O) 2 [NiCN] 4 .4H 2 O} n , showed that the coordination layers are stacked on top of each other sandwiching 2D ice layer of boat-shaped hexagonal water clusters . Display Omitted

Density functional theory study on the structures, electronic and magnetic properties of the MFe3n‑1O4n (n = 1–3) (M=Mn, Co and Ni) clusters

Science.gov (United States)

Li, Zhi; Zhao, Zhen; Wang, Qi; Yin, Xi-tao

2018-04-01

The structures, electronic and magnetic properties of the MFe3n‑1O4n (n = 1–3) (M=Mn, Co and Ni) clusters are obtained by using the GGA-PBE functional. The results found that the CoFe3n‑1O4n (n = 1–3) clusters are more stable than the corresponding NiFe3n‑1O4n and MnFe3n‑1O4n clusters. The NiFe2O4, MnFe5O8 and CoFe5O8 clusters have higher kinetic stability than their neighbors. The average magnetic moments of MFe3n‑1O4n (n = 1–3) (M=Mn, Co and Ni) clusters are successively: NiFe3n‑1O4n > CoFe3n‑1O4n > MnFe3n‑1O4n. For NiFe3n‑1O4n and CoFe3n‑1O4n clusters, the average magnetic moments are decreased with the cluster size increasing while for MnFe3n‑1O4n, the opposite situation is occur. The difference of 3d orbital electrons of M (M=Mn, Co and Ni) atoms influence the magnetic properties of MFe3n‑1O4n clusters.

Self-assembled decanuclear Na(I)2Mn(II)4Mn(III)4 complexes: from discrete clusters to 1-D and 2-D structures, with the Mn(II)4Mn(III)4 unit displaying a large spin ground state and probable SMM behaviour.

Science.gov (United States)

Langley, Stuart K; Chilton, Nicholas F; Moubaraki, Boujemaa; Murray, Keith S

2011-12-07

The synthesis, magnetic characterization and X-ray crystal structures are reported for five new manganese compounds, [Mn(III)(teaH(2))(sal)]·(1/2)H(2)O (1), [Na(I)(2)Mn(II)(4)Mn(III)(4)(teaH)(6)(sal)(4)(N(3))(2)(MeOH)(4)]·6MeOH (2), [Na(I)(2)Mn(II)(4)Mn(III)(4)(teaH)(6)(sal)(4)(N(3))(2)(MeOH)(2)](n)·7MeOH (3), [Na(I)(2)Mn(II)(4)Mn(III)(4)(teaH)(6)(sal)(4)(N(3))(2)(MeOH)(2)](n)·2MeOH·Et(2)O (4) and [K(I)(2)Mn(II)(4)Mn(III)(4)(teaH)(6)(sal)(4)(N(3))(2)(H(2)O)(2)](n)·5MeOH (5). Complex 1 is a mononuclear compound, formed via the reaction of Mn(NO(3))(2)·4H(2)O, triethanolamine (teaH(3)) and salicylic acid (salH(2)) in a basic methanolic solution. Compound 2 is a mixed-valent hetero-metallic cluster made up of a Mn(8)Na(2) decanuclear core and is formed via the reaction of sodium azide (NaN(3)) with 1. Compounds 3-5 are isolated as 1- or 2-D coordination polymers, each containing the decanuclear Mn(8)M(2) (M = Na(+) or K(+)) core building block as the repeating unit. Compound 3 is isolated when 1 is reacted with NaN(3) over a very short reaction time and forms a 1-D coordination polymer. Each unit displays inter-cluster bridges via the O-atoms of teaH(2-) ligands bonding to the sodium ions of an adjacent cluster. Increasing the reaction time appears to drive the formation of 4 which forms 2-D polymeric sheets and is a packing polymorph of 3. The addition of KMnO(4) and NaN(3) to 1 resulted in compound 5, which also forms a 1-D coordination polymer of the decanuclear core unit. The 1-D chains are now linked via inter-cluster potassium and salicylate bridges. Solid state DC susceptibility measurements were performed on compounds 1-5. The data for 1 are as expected for an S = 2 Mn(III) ion, with the isothermal M vs. H data being fitted by matrix diagonalization methods to give values of g and the axial (D) and rhombic (E) zero field splitting parameters of 2.02, -2.70 cm(-1) and 0.36 cm(-1) respectively. The data for 2-5, each with an identical Mn(II)(4)Mn(III)(4

Three-Dimensional NiCo2O4@MnMoO4 Core-Shell Nanoarrays for High-Performance Asymmetric Supercapacitors.

Science.gov (United States)

Yuan, Yuliang; Wang, Weicheng; Yang, Jie; Tang, Haichao; Ye, Zhizhen; Zeng, Yujia; Lu, Jianguo

2017-10-10

Design of new materials with sophisticated nanostructure has been proven to be an efficient strategy to improve their properties in many applications. Herein, we demonstrate the successful combination of high electron conductive materials of NiCo 2 O 4 with high capacitance materials of MnMoO 4 by forming a core-shell nanostructure. The NiCo 2 O 4 @MnMoO 4 core-shell nanoarrays (CSNAs) electrode possesses high capacitance of 1169 F g -1 (4.24 F cm -2 ) at a current density of 2.5 mA cm -2 , obviously larger than the pristine NiCo 2 O 4 electrode. The asymmetric supercapacitors (ASCs), assembled with NiCo 2 O 4 @MnMoO 4 CSNAs as binder-free cathode and active carbon (AC) as anode, exhibit high energy density of 15 Wh kg -1 and high power density of 6734 W kg -1 . Cycle performance of NiCo 2 O 4 @MnMoO 4 CSNAs//AC ASCs, conducted at current density of 20 mA cm -2 , remain 96.45% of the initial capacitance after 10,000 cycles, demonstrating its excellent long-term cycle stability. Kinetically decoupled analysis reveals that the capacitive capacitance is dominant in the total capacitance of NiCo 2 O 4 @MnMoO 4 CSNAs electrode, which may be the reason for ultra long cycle stability of ASCs. Our assembled button ASC can easily light up a red LED for 30 min and a green LED for 10 min after being charged for 30 s. The remarkable electrochemical performance of NiCo 2 O 4 @MnMoO 4 CSNAs//AC ASCs is attributed to its enhanced surface area, abundant electroactive sites, facile electrolyte infiltration into the 3D NiCo 2 O 4 @MnMnO 4 nanoarrays and fast electron and ion transport path.

Synthesis of NiO@MnO{sub 2} core/shell nanocomposites for supercapacitor application

Energy Technology Data Exchange (ETDEWEB)

Chen, Junjiao; Huang, Ying, E-mail: chenjunjiao001@163.com; Li, Chao; Chen, Xuefang; Zhang, Xiang

2016-01-01

Graphical abstract: - Highlights: • MnO{sub 2} nanosheets were grown on the surface of porous NiO microtube. • The NiO@MnO{sub 2} nanocomposite exhibits excellent cycle performance. • The nanocomposite exhibits specific capacitance of 266.7 F g{sup −1} at 0.5 A g{sup −1}. - Abstract: In this work, NiO@MnO{sub 2} core/shell nanocomposites were fabricated by a two-step method. The morphology and structure of the nanocomposites were characterized by scanning electron microscopy, transmission electron microscopy, X-ray photoelectron spectroscopy, X-ray diffraction analysis and thermal gravity analysis. In addition, the supercapacitive performances were examined by cyclic voltammogram (CV), galvanostatic charge–discharge and electrochemical impedance spectroscopy (EIS). The electrochemical results indicate that the composite exhibits a specific capacitance of 266.7 F g{sup −1} at 0.5 A g{sup −1} and excellent cycling stability (81.7% retention after 2000 cycles at 1 A g{sup −1}). Therefore, this wok offers meaningful reference for supercpacitor applications in the future.

Oxygen storage capacity and structural properties of Ni-doped LaMnO3 perovskites

International Nuclear Information System (INIS)

Ran, Rui; Wu, Xiaodong; Weng, Duan; Fan, Jun

2013-01-01

Graphical abstract: Dynamic OSC of (a) fresh and (b) aged LaMn 1−x Ni x O 3 perovskites (0.1 Hz). Aged condition: 1050 °C, 5 h, 7% steam in air. The LaMn 1−x Ni x O 3 perovskites exhibit considerable dynamic OSC in comparison to CeO 2 –ZrO 2 (CZ), even after 1050 °C hydrothermal ageing for 5 h. Highlights: •Ni-doped LaMnO 3 perovskites exhibit very large dynamic OSC and high oxygen storage rate. •Mn 4+ is favourable to the releasable oxygen. •Doping of Ni ions increase the Mn 4+ content and the oxygen vacancies. •Doping of Ni ions reduce the BO 6 distortion in the LaMnO 3 perovskites. -- Abstract: A series of Ni doped LaMnO 3 perovskites were prepared by a sol–gel method as oxygen storage materials. Powder X-ray diffraction (XRD), X-ray adsorption fine structure (XAFS), oxygen storage capacity (OSC) and H 2 -temperature program reduction (TPR) measurements were performed to investigate the OSC of the perovskites as well as the effects of Ni on the structural properties. The results showed that the Ni-doped LaMnO 3 perovskite exhibited very large dynamic OSC and high oxygen release rate, which provided a possibility to serve as an oxygen storage material candidate in three-way catalysts. The available oxygen species below 500 °C primarily originated from the redox reaction between Mn 4+ and Mn 3+ , and the more Mn 4+ were favourable to the releasable oxygen. The doping of appropriate Ni ions promoted the OSC of the LaMnO 3 perovskites by increasing the Mn 4+ content and adjusting the structural defects. On the other hand, the doped Ni ions could make the BO 6 distortion disappearing in the LaMnO 3 perovskites to reduce the lattice oxygen activity

Porous Hollow Superlattice NiMn2O4/NiCo2O4 Mesocrystals as a Highly Reversible Anode Material for Lithium-Ion Batteries

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Lingjun Li

2018-05-01

Full Text Available As a promising high-capacity anode material for Li-ion batteries, NiMn2O4 always suffers from the poor intrinsic conductivity and the architectural collapse originating from the volume expansion during cycle. Herein, a combined structure and architecture modulation is proposed to tackle concurrently the two handicaps, via a facile and well-controlled solvothermal approach to synthesize NiMn2O4/NiCo2O4 mesocrystals with superlattice structure and hollow multi-porous architecture. It is demonstrated that the obtained NiCo1.5Mn0.5O4 sample is made up of a new mixed-phase NiMn2O4/NiCo2O4 compound system, with a high charge capacity of 532.2 mAh g−1 with 90.4% capacity retention after 100 cycles at a current density of 1 A g−1. The enhanced electrochemical performance can be attributed to the synergistic effects of the superlattice structure and the hollow multi-porous architecture of the NiMn2O4/NiCo2O4 compound. The superlattice structure can improve ionic conductivity to enhance charge transport kinetics of the bulk material, while the hollow multi-porous architecture can provide enough void spaces to alleviate the architectural change during cycling, and shorten the lithium ions diffusion and electron-transportation distances.

Freeze drying synthesis of LiNi0.5Mn0.5O2 cathode materials

International Nuclear Information System (INIS)

Shlyakhtin, O.A.; Yoon, Young Soo; Choi, Sun Hee; Oh, Young-Jei

2004-01-01

The influence of several processing conditions on the phase formation and electrochemical performance of LiNi 0.5 Mn 0.5 O 2 powders, obtained by freeze drying method, is studied. Thermal processing in pellets at maximum heating rate promotes better crystallographic ordering of hexagonal LiNi 0.5 Mn 0.5 O 2 and maximum capacity values irrespectively of chemical composition of the precursor. Instead, intense mechanical processing of precursors exerts considerable negative effect on the electrochemical performance. Cathode materials containing superstoichiometric amount of lithium (Li 1.3 Mn 0.5 Ni 0.5 O 2+δ ) demonstrate reversible capacity values up to 190 mAh/g between 2.5 and 4.6 V

Facile dip coating processed 3D MnO2-graphene nanosheets/MWNT-Ni foam composites for electrochemical supercapacitors

International Nuclear Information System (INIS)

Kong, Shuying; Cheng, Kui; Ouyang, Tian; Gao, Yinyi; Ye, Ke; Wang, Guiling; Cao, Dianxue

2017-01-01

Carbon materials, especially graphene nanosheets (GNS) and/or multi-walled carbon nanotube (MWNT), have been widely used as electrode materials for supercapacitor due to their advantages of higher specific surface area and electronic conductivity, but the relatively low specific capacitance thus results in low energy density hindering their large applications. On the contrary, MnO 2 exhibits higher energy density but poor electrical conductivity. In order to obtain high performance supercapacitor electrode, here, combining the advantages of these materials, we have designed a facile two-step strategy to prepare 3D MnO 2 -GNS-MWNT-Ni foam (MnO 2 -GM-Ni) electrode. First, GNS and MWNT is wrapped on the surface of Ni foam (GM-Ni) via a “dip & dry” method by using an organic dye as a co-dispersant. Then, by using this 3D GM-Ni as substrate, MnO 2 nanoflakes are in-situ supporting on the surface of GNS and MWNT through a hydrothermal reaction. The specific capacitances of MnO 2 -GM-Ni electrode reach as high as 470.5 F g −1 at 1 A g −1 . Furthermore, we have successfully fabricated an asymmetric supercapacitor with MnO 2 -GM-Ni and GM-Ni as the positive and negative electrodes, respectively. The MnO 2 -GM-Ni//GM-Ni asymmetric supercapacitor exhibits a maximum energy density of 35.3 Wh kg −1 at a power density of 426 W kg −1 and also a favorable cycling performance that 83.8% capacitance retention after 5000 cycles. These results show manageable and high-performance which offer promising future for practical applications.

Strongly reduced band gap in NiMn2O4 due to cation exchange

International Nuclear Information System (INIS)

Huang, Jhih-Rong; Hsu, Han; Cheng, Ching

2014-01-01

NiMn 2 O 4 is extensively used as a basis material for temperature sensors due to its negative temperature coefficient of resistance (NTCR), which is commonly attributed to the hopping mechanism involving coexisting octahedral-site Mn 4+ and Mn 3+ . Using density-functional theory + Hubbard U calculations, we identify a ferrimagnetic inverse spinel phase as the collinear ground state of NiMn 2 O 4 . By a 12.5% cation exchange, a mixed phase with slightly higher energy can be constructed, accompanied by the formation of an impurity-like band in the original 1 eV band gap. This impurity-like band reduces the gap to 0.35 eV, suggesting a possible source of NTCR. - Highlights: • Density functional based calculations were used to study collinear phase of NiMn 2 O 4 . • The ground-state structure is a ferrimagnetic inverse spinel phase. • The tetrahedral and octahedral Mn cations have ferromagnetic interactions. • A 12.5% cation exchange introduces an impurity-like band in the original 1 eV gap. • The 0.35 eV gap suggests a source of negative temperature coefficient of resistance

Structure and electrochemical impedance of LiNi_xMn_2_-_xO_4

International Nuclear Information System (INIS)

Ta Anh Tan; Nguyen Si Hieu; Le Ha Chi; Pham Duy Long; Dang Tran Chien; Le Dinh Trong

2016-01-01

Ni-substitution spinel LiNi_xMn_2_-_xO_4 (x = 0, 0.1, 0.2) materials were synthesized by the sol--gel method. The structure and morphology of the samples were characterized by the X-ray diffraction (XRD) and the scanning electron microscopy. The ac conduction of the materials was investigated by electrochemical impedance spectroscopy (EIS) measurements. The refinement results showed that the substitution of Ni decreased the lattice constant and Mn--O distance, while increased Li--O bond length and 16c octahedral volume. The EIS results confirmed the decrease of conductivity with increasing Ni substitution content. Based on XRD and EIS results, the relationship between the crystal structure and electrochemical behavior of the materials was discussed and explained. (author)

Hierarchical α-MnO2 nanowires@Ni1-x Mnx Oy nanoflakes core-shell nanostructures for supercapacitors.

Science.gov (United States)

Wang, Hsin-Yi; Xiao, Fang-Xing; Yu, Le; Liu, Bin; Lou, Xiong Wen David

2014-08-13

A facile two-step solution-phase method has been developed for the preparation of hierarchical α-MnO2 nanowires@Ni1-x Mnx Oy nanoflakes core-shell nanostructures. Ultralong α-MnO2 nanowires were synthesized by a hydrothermal method in the first step. Subsequently, Ni1-x Mnx Oy nanoflakes were grown on α-MnO2 nanowires to form core-shell nanostructures using chemical bath deposition followed by thermal annealing. Both solution-phase methods can be easily scaled up for mass production. We have evaluated their application in supercapacitors. The ultralong one-dimensional (1D) α-MnO2 nanowires in hierarchical core-shell nanostructures offer a stable and efficient backbone for charge transport; while the two-dimensional (2D) Ni1-x Mnx Oy nanoflakes on α-MnO2 nanowires provide high accessible surface to ions in the electrolyte. These beneficial features enable the electrode with high capacitance and reliable stability. The capacitance of the core-shell α-MnO2 @Ni1-x Mnx Oy nanostructures (x = 0.75) is as high as 657 F g(-1) at a current density of 250 mA g(-1) , and stable charging-discharging cycling over 1000 times at a current density of 2000 mA g(-1) has been realized. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Influence of bismuth on the magnetic and electrical properties of La2MnNiO6 .IAEA.ATOMS

International Nuclear Information System (INIS)

Nautiyal, Pranjal; Motin Seikh, Md.; Pralong, V.; Kundu, Asish K.

2013-01-01

In this study, we report the ambient pressure and low temperature synthesis of ordered perovskite La 2−x Bi x Mn 1+y Ni 1−y O 6 with high bismuth content. Keeping y=0, we are able to substitute La by Bi up to x=0.4 i.e. 20% of La. However, 50% La could be replaced by Bi for y=0.5 without any impurity phases. Interestingly, these compounds remain ferromagnetic with the Curie temperature T C of 255 and 75 K for La 1.6 Bi 0.4 MnNiO 6 and LaBiMn 1.5 Ni 0.5 O 6 compositions, respectively. Moreover, these Bi-substituted phases become more conducting, three order of magnitude higher, at room temperature compared to the parent La 2 MnNiO 6 phase. - Highlights: • Synthesis of bismuth based perovskite at ambient pressure and low temperature with 50% Bi-doped phase. • Magnetic interactions between Mn and Ni ions have been proposed clearly for the doped phases • The band gap energy in the samples have been determined to explain their higher conductivity

Coating effect of LiFePO4 and Al2O3 on Li1.2Mn0.54Ni0.13Co0.13O2 cathode surface for lithium ion batteries

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Seteni, Bonani; Rapulenyane, Nomasonto; Ngila, Jane Catherine; Mpelane, Siyasanga; Luo, Hongze

2017-06-01

Lithium-manganese-rich cathode material Li1.2Mn0.54Ni0.13Co0.13O2 is prepared by combustion method, and then coated with nano-sized LiFePO4 and nano-sized Al2O3 particles via a wet chemical process. The as-prepared Li1.2Mn0.54Ni0.13Co0.13O2, LiFePO4-coated Li1.2Mn0.54Ni0.13Co0.13O2 and Al2O3-coated Li1.2Mn0.54Ni0.13Co0.13O2 are characterized by X-ray diffraction, scanning electron microscopy and transmission electron microscopy. The scanning electron microscopy shows the agglomeration of the materials and their nanoparticle size ∼100 nm. The transmission electron microscopy confirms that LiFePO4 forms a rough mat-like surface and Al2O3 remain as islandic particles on the surface of the Li1.2Mn0.54Ni0.13Co0.13O2 material. The Li1.2Mn0.54Ni0.13Co0.13O2 coated with LiFePO4 and Li1.2Mn0.54Ni0.13Co0.13O2 coated with Al2O3 exhibits improved electrochemical performance. The initial discharge capacity is enhanced to 267 mAhg-1 after the LiFePO4 coating and 285 mAhg-1 after the Al2O3 coating compared to the as-prepared Li1.2Mn0.54Ni0.13Co0.13O2 material that has an initial discharge capacity of 243 mAhg-1. Galvanostatic charge-discharge tests at C/10 display longer activation of Li2MnO3 phase and higher capacity retention of 88% after 20 cycles for Li1.2Mn0.54Ni0.13Co0.13O2-LiFePO4 compared to Li1.2Mn0.54Ni0.13Co0.13O2-Al2O3 of 80% after 20 cycles and LMNC of 80% after 20 cycles. Meanwhile Li1.2Mn0.54Ni0.13Co0.13O2-LiFePO4 also shows higher rate capability compared to Li1.2Mn0.54Ni0.13Co0.13O2-Al2O3.

Mechanisms responsible for two possible electrochemical reactions in Li1.2Ni0.13Mn0.54Co0.13O2 used for lithium ion batteries

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Konishi, Hiroaki; Hirano, Tatsumi; Takamatsu, Daiko; Gunji, Akira; Feng, Xiaoliang; Furutsuki, Sho; Okumura, Takefumi; Terada, Shohei; Tamura, Kazuhisa

2018-02-01

Two electrochemical reactions are possible in regard to Li1.2Ni0.13Mn0.54Co0.13O2 (0.5Li2MnO3-0.5LiNi0.33Mn0.33Co0.33O2), viz, Li2MnO3-like and LiNi0.33Mn0.33Co0.33O2-like reactions. The open circuit potential (OCP) and changes in crystal structure during the charge-discharge process of Li1.2Ni0.13Mn0.54Co0.13O2 were investigated to clarify the mechanism responsible for the two reactions. Li2MnO3 and LiNi0.33Mn0.33Co0.33O2 were separately prepared for the investigation, and the OCPs and crystal structures in these cathodes were measured and then compared with those for Li1.2Ni0.13Mn0.54Co0.13O2. The results obtained using X-ray diffraction (XRD) indicated that two phases existed in Li1.2Ni0.13Mn0.54Co0.13O2. The changes in crystal structure of the two phases during the charge-discharge process were similar to those in Li2MnO3 and LiNi0.33Mn0.33Co0.33O2. This indicated that two phases, viz, Li2MnO3-like and LiNi0.33Mn0.33Co0.33O2-like, existed in Li1.2Ni0.13Mn0.54Co0.13O2. Li2MnO3-like, LiNi0.33Mn0.33Co0.33O2-like, and Li2MnO3-like phases were found to contribute mainly to electrochemical reactions in the low, middle, and high state of charge (SOC) ranges during the charge process from the results obtained using XRD and electrochemical measurements carried out on Li1.2Ni0.13Mn0.54Co0.13O2. In contrast, the Li2MnO3-like and LiNi0.33Mn0.33Co0.33O2-like phases mainly contributed to electrochemical reactions in the low and high SOC ranges during the discharge process. Furthermore, the high polarization and potential decay during the charge-discharge cycling of Li1.2Ni0.13Mn0.54Co0.13O2 were mainly attributed to the Li2MnO3-like phase.

Enhanced electrochemical performance of Ti substituted P2-Na2/3Ni1/4Mn3/4O2 cathode material for sodium ion batteries

International Nuclear Information System (INIS)

Zhao, Wenwen; Tanaka, Akinobu; Momosaki, Kyoko; Yamamoto, Shinji; Zhang, Fabi; Guo, Qixin; Noguchi, Hideyuki

2015-01-01

Highlights: • Ti substituted P2-Na 2/3 Ni 1/4 Mn 3/4 O 2 cathode was synthesized. • Structural and electrochemical properties of Na 2/3 Ni 1/4 Ti x Mn 3/4-x O 2 were studied. • Ti substituted cathodes exhibit enhanced cycleability and rate performance. • Ti substitution has impact on stabilizing the P2 structure during cycling. -- Abstract: Ti substituted P2-Na 2/3 Ni 1/4 Mn 3/4 O 2 cathode material with the composition of Na 2/3 Ni 1/4 Ti x Mn 3/4-x O 2 has been synthesized by solid state method. The influence of Ti substitution for Mn on the structure, morphology and electrochemical performances of P2-Na 2/3 Ni 1/4 Mn 3/4 O 2 has been investigated. X-ray diffraction (XRD) results of Ti substituted sample show that they exhibit same diffraction patterns as those of pristine P2-Na 2/3 Ni 1/4 Mn 3/4 O 2 . Progressive change in the lattice parameters of Ti substituted samples suggests that Mn was successfully substituted by Ti. In contrast to P2-Na 2/3 Ni 1/4 Mn 3/4 O 2 which shows step-type voltage profiles, Ti substituted samples show sloping voltage profiles. Drastic capacity fade occurred for P2-Na 2/3 Ni 1/4 Mn 3/4 O 2 cathode, while Ti substituted cathodes still show high capacity retention over 92% after 25 cycles at the voltage range of 2.0-4.3 V. Even cycled at high upper cut-off voltage of 4.5 V, Ti=0.20 sample can deliver a reversible capacity of 140 mAhg −1 with the capacity retention over 92% after 25 cycles. Furthermore, Ti substituted cathodes exhibit enhanced rate capability over pristine P2-Na 2/3 Ni 1/4 Mn 3/4 O 2 cathode. Comparison of the Ex-situ XRD results of the cycled P2-Na 2/3 Ni 1/4 Mn 3/4 O 2 and its substituted samples provides evidence that the improved electrochemical performance of Ti substituted cathodes would be attributed to the stabilization of the structure with Ti substitution

Crystalline structure of the manganites solid solution RE(Me,MnO₃, (RE=Gd,Er; Me=Ni,Co

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Peña, O.

2009-08-01

Full Text Available The structural properties of the manganites solid solution RE(Me,MnO₃, RE=Er,Gd, have been studied by X-ray diffraction and electric measurements. Powders were prepared by solid state reaction between the component oxides. Incorporation of Ni²⁺ or Co²⁺ on the lattice in the Mn sites leads to changes in the parameters and symmetry of the perovskite or hexagonal compounds GdMnO₃ and ErMnO₃ respectively. The phase transitions depend on the amount of substituted Jahn-Teller Mn³⁺ cations, and, therefore, of the cooperative Jahn-Teller interaction weakness. Solid solutions based on GdMnO₃ perovskite compound change from O’-type to O-type orthorhombic perovskite symmetry when the Mn³⁺ cation amount decreases, because of the progressive substitution for Ni, Co. This transition occurs for lower amount of Ni²⁺ than for Co²⁺ cation. The Er-based solid solutions showed a different behaviour. For Ni²⁺ and Co²⁺ incorporation there are changes from hexagonal ErMnO₃-type lattice to perovskite-type symmetry, for 20 at% and 30 at% respectively of substituting cations. The resultant perovskites crystallised directly in the O-type orthorhombic perovskite structure. The steric influence seems to play a secondary role, such as it can be deduced of the small variation of the Goldschmidt tolerance factor, t, for perovskite structure.

Las propiedades estructurales de las soluciones sólidas RE(Me,MnO₃, RE=Gd,Er, Me=Ni,Co, han sido estudiadas por difracción de rayos X, (DRX y medidas eléctricas. Las fases se sintetizaron por reacción en estado sólido entre los óxidos componentes. La incorporación de los cationes Ni²⁺ y Co^2+,3+ en la red en lugar de Mn lleva a cambios en los parámetros de red y en la simetría de la perovskita, GdMnO₃ o del compuesto hexagonal ErMnO

Solid state opto-impedance of LiNiVO4 and LiMn2O4

International Nuclear Information System (INIS)

Kalyani, P; Sivasubramanian, S; Prabhu, S Naveen; Ragavendran, K; Kalaiselvi, N; Ranganathan, N G; Madhu, S; SundaraRaj, A; Manoharan, S P; Jagannathan, R

2005-01-01

Spinel type LiMn 2 O 4 and inverse spinel LiNiVO 4 systems serve as standard cathode materials or potential cathode systems for application in high energy density lithium-ion batteries. Upon photo-excitation using UV radiation of energy ∼5 eV, the LiNiVO 4 system shows significant modification in the solid state impedance pattern while the LiMn 2 O 4 system does not. This study has revealed a significant difference in the opto-impedance pattern for LiNiVO 4 with respect to LiMn 2 O 4 , which may be due to the different electronic processes involved. An attempt has been made to study this behaviour from the solid-state viewpoint

Three-dimensional sandwich-structured NiMn2O4@reduced graphene oxide nanocomposites for highly reversible Li-ion battery anodes

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Huang, Jiarui; Wang, Wei; Lin, Xirong; Gu, Cuiping; Liu, Jinyun

2018-02-01

A sandwich-structured NiMn2O4@reduced graphene oxide (NiMn2O4@rGO) nanocomposite consisting of ultrathin NiMn2O4 sheets uniformly anchored on both sides of a three-dimensional (3D) porous rGO is presented. The NiMn2O4@rGO nanocomposites prepared through a dipping process combining with a hydrothermal method show a good electrochemical performance including a high reversible capability of 1384 mAh g-1 at 1000 mA g-1 over 1620 cycles, and an superior rate performance. Thus, a full cell consisting of a commercial LiCoO2 cathode and the NiMn2O4@rGO anode delivers a stable capacity of about 1046 mAh g-1 (anode basis) after cycling at 50 mA g-1 for 60 times. It is demonstrated that the 3D porous composite structure accommodates the volume change during the Li+ insertion/extraction process and facilitates the rapid transport of ions and electrons. The high performance would enable the presented NiMn2O4@rGO nanocomposite a promising anode candidate for practical applications in Li-ion batteries.

Detailed studies of a high-capacity electrode material for rechargeable batteries, Li2MnO3-LiCo(1/3)Ni(1/3)Mn(1/3)O2.

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Yabuuchi, Naoaki; Yoshii, Kazuhiro; Myung, Seung-Taek; Nakai, Izumi; Komaba, Shinichi

2011-03-30

Lithium-excess manganese layered oxides, which are commonly described by the chemical formula zLi(2)MnO(3)-(1-z)LiMeO(2) (Me = Co, Ni, Mn, etc.), are of great importance as positive electrode materials for rechargeable lithium batteries. In this Article, Li(x)Co(0.13)Ni(0.13)Mn(0.54)O(2-δ) samples are prepared from Li(1.2)Ni(0.13)Co(0.13)Mn(0.54)O(2) (or 0.5Li(2)MnO(3)-0.5LiCo(1/3)Ni(1/3)Mn(1/3)O(2)) by an electrochemical oxidation/reduction process in an electrochemical cell to study a reaction mechanism in detail before and after charging across a voltage plateau at 4.5 V vs Li/Li(+). Changes of the bulk and surface structures are examined by synchrotron X-ray diffraction (SXRD), X-ray absorption spectroscopy (XAS), X-ray photoelectron spectroscopy (XPS), and time-of-flight secondary ion mass spectroscopy (SIMS). SXRD data show that simultaneous oxygen and lithium removal at the voltage plateau upon initial charge causes the structural rearrangement, including a cation migration process from metal to lithium layers, which is also supported by XAS. This is consistent with the mechanism proposed in the literature related to the Li-excess manganese layered oxides. Oxygen removal associated with the initial charge on the high voltage plateau causes oxygen molecule generation in the electrochemical cells. The oxygen molecules in the cell are electrochemically reduced in the subsequent discharge below 3.0 V, leading to the extra capacity. Surface analysis confirms the formation of the oxygen containing species, such as lithium carbonate, which accumulates on the electrode surface. The oxygen containing species are electrochemically decomposed upon second charge above 4.0 V. The results suggest that, in addition to the conventional transition metal redox reactions, at least some of the reversible capacity for the Li-excess manganese layered oxides originates from the electrochemical redox reaction of the oxygen molecules at the electrode surface.

Facile synthesis of hierarchical Co3O4@MnO2 core-shell arrays on Ni foam for asymmetric supercapacitors

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Huang, Ming; Zhang, Yuxin; Li, Fei; Zhang, Lili; Wen, Zhiyu; Liu, Qing

2014-04-01

Hierarchical Co3O4@MnO2 core-shell arrays on Ni foam have been fabricated by a facile hydrothermal approach and further investigated as the electrode for high-performance supercapacitors. Owing to the high conductivity of the well-defined mesoporous Co3O4 nanowire arrays in combination with the large surface area provided by the ultrathin MnO2 nanosheets, the unique designed Co3O4@MnO2 core-shell arrays on Ni foam have exhibited a high specific capacitance (560 F g-1 at a current density of 0.2 A g-1), good rate capability, and excellent cycling stability (95% capacitance retention after 5000 cycles). An asymmetric supercapacitor with Co3O4@MnO2 core-shell nanostructure as the positive electrode and activated microwave exfoliated graphite oxide activated graphene (MEGO) as the negative electrode yielded an energy density of 17.7 Wh kg-1 and a maximum power density of 158 kW kg-1. The rational design of the unique core-shell array architectures demonstrated in this work provides a new and facile approach to fabricate high-performance electrode for supercapacitors.

Facile Synthesis of Free-Standing NiO/MnO2 Core-Shell Nanoflakes on Carbon Cloth for Flexible Supercapacitors.

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Xi, Shuang; Zhu, Yinlong; Yang, Yutu; Jiang, Shulan; Tang, Zirong

2017-12-01

Free-standing NiO/MnO 2 core-shell nanoflake structure was deposited on flexible carbon cloth (CC) used as electrode for high-performance supercapacitor (SC). The NiO core was grown directly on CC by hydrothermal process and the following annealing treatment. MnO 2 thin film was then covered on NiO structures via a self-limiting process in aqueous solution of 0.5 M KMnO 4 and 0.5 M Na 2 SO 4 with a carbon layer serving as the sacrificial layer. Both the core and shell materials are good pseudocapacitive materials, the compounds of binary metal oxides can provide the synergistic effect of all individual constituents, and thus enhance the performance of SC electrode. The obtained CC/NiO/MnO 2 heterostructure was directly used as SC electrodes, showing an enhanced electrochemical performance including areal capacitance of 316.37 mF/cm 2 and special gravimetric capacitance of 204.3 F/g at the scan rate of 50 mV/s. The electrode also shows excellent cycling stability, which retains 89% of its initial discharge capacitance after 2200 cycles with >97% Coulombic efficiency. The synthesized binder-free hierarchical composite electrode with superior electrochemical properties demonstrates enormous potential in the application of flexible SCs.

Synthesis of 0.3Li2MnO3·0.7LiNi1/3Co1/3Mn1/3O2 cathode materials using 3-D urchin-like MnO2 as precursor for high performance lithium ion battery

International Nuclear Information System (INIS)

Zhao, Chenhao; Hu, Zhibiao; Zhou, Yunlong; Fang, Shuzhen; Cai, Shaohan

2015-01-01

In the paper, we report synthesis of lithium rich layered oxide 0.3Li 2 MnO 3 ·0.7LiNi 1/3 Co 1/3 Mn 1/3 O 2 by using an urchin-like MnO 2 as precursor. The influences of calcination temperatures on the structures and electrochemical performances of as-prepared materials are systematically studied. The results show that the obtained sample can partially retain the morphology of urchin-like precursor especially at low temperature, and a higher calcination temperature helps to improve the layered structure and particle size. As lithium ion battery cathodes, the 750 °C sample with the size of 100–200 nm reveals an optimal electrochemical performance. The initial discharge capacity of 234.6 mAh g −1 with high Coulombic efficiency of 84.6 % can be reached at 0.1C within 2.0–4.7 V. After 50 cycles, the capacity retention can reach 90.2 % at 0.5C. Even at high current density of 5C, the sample also shows a stable discharge capacity of 120.5 mAh g −1 . Anyways, the urchin-like MnO 2 directed route is suitable to prepare 0.3Li 2 MnO 3 ·0.7LiNi 1/3 Co 1/3 Mn 1/3 O 2 as lithium ion battery cathode

Core/shell structure NiCo2O4@MnCo2O4 nanofibers fabricated by different temperatures for high-performance supercapacitors

Science.gov (United States)

Wang, Qing; Qin, Xuefeng; Jiang, Pengcheng; Dai, Jianfeng; Li, Weixue; Gao, Haoran

2018-03-01

Core/shell structure NiCo2O4@MnCo2O4 nanofibers (NiCo2O4@MnCo2O4 NFs) were prepared by a facile co-electrospinning method and heat treatment. The composites annealed at 500 °C have a complete, continuously obvious core/shell structure, and clear interface of composites with good morphology, while annealed at 600 °C were stacked on each other and were unable to sustain three-dimensional network structures and 700 °C calcination have completely lost one-dimensional structure. The core NiCo2O4 is about 70 nm in diameter and the MnCo2O4 shell behaves a thickness about 60 nm. When investigated as an electrode material for supercapacitors, the NiCo2O4@MnCo2O4 NFs annealed at 500 °C exihibited the specific capacitance of 463 F g-1 (0.926 F cm-2) at 1 A g-1, higher than that annealed at 600 °C 362 F g-1, 1 A g-1 (0.724 F cm-2, 1 A g-1) and 700 °C 283 F g-1, 1 A g-1 (0.566 F cm-2, 1 A g-1). These results suggest that core/shell NiCo2O4@MnCo2O4 NFs annealed at 500 °C have formed a good morphology with continuously complete core/shell structure which lead to good properties would be potential electrodes for supercapacitors.

Investigation on the electrochemical activation process of Li1.20Ni0.32Co0.004Mn0.476O2

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Daichun Tang

2014-08-01

Full Text Available The lithium-rich layered oxides are one of the most attractive cathode materials for lithium-ion batteries. Here, two types of Li1.20Ni0.32Co0.004Mn0.476O2 were synthesized using Li2CO3 and LiOH as lithium sources. An electrochemical activation process occurs in Li1.2Ni0.32Co0.004Mn0.476O2 prepared from Li2CO3 (LLO-1, while no obvious activation in Li1.2Ni0.32Co0.004Mn0.476O2 prepared from LiOH (LLO-2 is observed. Via advanced scanning transmission electron microscopy (STEM, we found that Li2MnO3-like structure is rich in the surface region of LLO-2. The study provides a direct explanation for the electrochemical activation of lithium-rich materials. The sample with more LiMO2-like phase at the surface region shows a better cycling performance. It is likely that more LiMO2-like phase at the surface region could stabilize the interface and improve the cycling performance of the Li-rich cathode materials.

Use of MnO2 and MnO2 SiO2 for sorbing of Sr-90 from liquid rad waste

International Nuclear Information System (INIS)

Subiarto; Las, Thamzil; Aan BH, Martin; Utomo, Cahyo Hari

1998-01-01

The synthesis of MnO 2 adsorbent and MnO 2 -SiO 2 composite has been done. MnO 2 synthesis is done by the reaction of KMnO 4 , Mn(NO 3 ) 2 .4H 2 O and Na 2 S 2 O 4 ( MnO 2 -A, MnO 2 -B, and MnO 2 -T ). MnO 2 . SiO 2 is made from KMnO 4 , Na 2 SiO 3 , and H 2 O 2 . The result obtained show the best Sr-90 sorption by MnO 2 -A with Kd = 2085.63 ml/g, by MnO 2 -L with Kd = 755.09 ml/g, and by MnO 2 - SiO 2 composite with Kd = 1466.51 ml/g. From this result, we can conclude that MnO 2 -SiO 2 can be expanded for Sr-90 sorption from liquid radioactive waste. (author)

NiO and Fe/Mn in Fo-rich olivines from OIB, MORB, and mantle peridotites

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Li, H.; Baker, M.; Hofmann, A. E.; Clague, D.; Stolper, E.

2006-12-01

Olivines from mantle peridotites have a narrow range of NiO (0.36±0.03 [1σ] wt%), but NiO of olivines in basalts suggest NiO in mantle olivines is actually more variable: e.g., Hawaiian phenocrysts (Fo>90) have NiO >0.55%, and olivines from continental flood basalts can have >0.5% NiO. At the other end of the spectrum, some basaltic suites (e.g., Iceland, MORBs) have Fo>90 olivines with NiO >0.2%. Partial melting calculations on peridotites show it is difficult to generate liquids that crystallize Fo>90 olivines with >0.4% NiO without resorting to complex processes. Hypotheses to explain the variability of NiO in mantle-derived olivines include (1) reaction of peridotite with silica-rich melts of eclogite results in decreasing modal abundance of olivine and increasing NiO in olivine [1,2]; (2) magmas with NiO-rich olivines come from sources enriched in NiO due to a core-derived component [3]. [4] proposed that high Fe/Mn of Hawaiian vs. Icelandic and MORB lavas reflect a core-derived component in their sources. Possible core incorporation is poorly constrained but FeO and NiO are expected to increase by such processes, leading to correlations between NiO and Fe/Mn in mantle rocks with significant core-derived components. We present high-precision analyses of Fo-rich olivines from OIBs, MORBs, komatiites, and mantle peridotites, focusing on NiO contents and Fe/Mn ratios. Our goal is to test hypotheses to explain elevated NiO of Fo-rich olivines in basalts. Olivines are Fo85.1-93.4; more were analyzed, but we focused on this range to avoid complications due to decreasing NiO in olivine with crystallization. Errors (1σ) are 0.01 wt% in NiO and 1.5 in Fe/Mn (wt). Our data show several features: (1) NiO contents and Fe/Mn ratios of Fo>88 olivines are positively correlated, with the low end of the trend (NiO ~0.23%, Fe/Mn ~61) defined by MORB and Iceland and the high end of the trend (NiO ~0.55%, Fe/Mn ~80) by Reunion and Hawaii. Between these end points, there is a

Comparative Investigation of 0.5Li2MnO3·0.5LiNi0.5Co0.2Mn0.3O2 Cathode Materials Synthesized by Using Different Lithium Sources

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Peng-Bo Wang

2018-05-01

Full Text Available Lithium-rich manganese-based cathode materials has been attracted enormous interests as one of the most promising candidates of cathode materials for next-generation lithium ion batteries because of its high theoretic capacity and low cost. In this study, 0.5Li2MnO3·0.5LiNi0.5Co0.2Mn0.3O2 materials are synthesized through a solid-state reaction by using different lithium sources, and the synthesis process and the reaction mechanism are investigated in detail. The morphology, structure, and electrochemical performances of the material synthesized by using LiOH·H2O, Li2CO3, and CH3COOLi·2H2O have been analyzed by using Thermo gravimetric analysis (TGA, X-ray diffraction (XRD, Scanning electron microscope (SEM, Transmission electron microscope (TEM, X-ray photoelectron spectroscopy (XPS, and electrochemical measurements. The 0.5Li2MnO3·0.5LiNi0.5Co0.2Mn0.3O2 material prepared by using LiOH·H2O displays uniform morphology with nano particle and stable layer structure so that it suppresses the first cycle irreversible reaction and structure transfer, and it delivers the best electrochemical performance. The results indicate that LiOH·H2O is the best choice for the synthesis of the 0.5Li2MnO3·0.5LiNi0.5Co0.2Mn0.3O2 material.

Anion Redox Chemistry in the Cobalt Free 3d Transition Metal Oxide Intercalation Electrode Li[Li0.2Ni0.2Mn0.6]O2.

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Luo, Kun; Roberts, Matthew R; Guerrini, Niccoló; Tapia-Ruiz, Nuria; Hao, Rong; Massel, Felix; Pickup, David M; Ramos, Silvia; Liu, Yi-Sheng; Guo, Jinghua; Chadwick, Alan V; Duda, Laurent C; Bruce, Peter G

2016-09-07

Conventional intercalation cathodes for lithium batteries store charge in redox reactions associated with the transition metal cations, e.g., Mn(3+/4+) in LiMn2O4, and this limits the energy storage of Li-ion batteries. Compounds such as Li[Li0.2Ni0.2Mn0.6]O2 exhibit a capacity to store charge in excess of the transition metal redox reactions. The additional capacity occurs at and above 4.5 V versus Li(+)/Li. The capacity at 4.5 V is dominated by oxidation of the O(2-) anions accounting for ∼0.43 e(-)/formula unit, with an additional 0.06 e(-)/formula unit being associated with O loss from the lattice. In contrast, the capacity above 4.5 V is mainly O loss, ∼0.08 e(-)/formula. The O redox reaction involves the formation of localized hole states on O during charge, which are located on O coordinated by (Mn(4+)/Li(+)). The results have been obtained by combining operando electrochemical mass spec on (18)O labeled Li[Li0.2Ni0.2Mn0.6]O2 with XANES, soft X-ray spectroscopy, resonant inelastic X-ray spectroscopy, and Raman spectroscopy. Finally the general features of O redox are described with discussion about the role of comparatively ionic (less covalent) 3d metal-oxygen interaction on anion redox in lithium rich cathode materials.

Hierarchical ZnO@MnO2 Core-Shell Pillar Arrays on Ni Foam for Binder-Free Supercapacitor Electrodes

KAUST Repository

Huang, Ming; Li, Fei; Zhao, Xiao Li; Luo, Da; You, Xue Qiu; Zhang, Yu Xin; Li, Gang

2015-01-01

© 2014 Elsevier Ltd. All rights reserved. Hierarchical ZnO@MnO2 core-shell pillar arrays on Ni foam have been fabricated by a facile two-step hydrothermal approach and further investigated as the binder-free electrode for supercapacitors. The core-shell hybrid nanostructure is achieved by decorating ultrathin self-standing MnO2 nanosheets on ZnO pillar arrays grown radically on Nickel foam. This unique well-designed binder-free electrode exhibits a high specific capacitance (423.5 F g-1 at a current density of 0.5 A g-1), and excellent cycling stability (92% capacitance retention after 3000 cycles). The improved electrochemical results show that the ZnO@MnO2 core-shell nanostructure electrode is promising for high-performance supercapacitors. The facile design of the unique core-shell array architectures provides a new and effective approach to fabricate high-performance binder-free electrode for supercapacitors.

Effect of Fe substitution at the Ni and Mn sites on the magnetic properties of Ni50Mn35In15 Heusler alloys

International Nuclear Information System (INIS)

Halder, Madhumita; Suresh, K.G.

2015-01-01

The structural and magnetic properties of Ni 48 Fe 2 Mn 35 In 15 and Ni 50 Mn 34 FeIn 15 Heusler alloys have been investigated. At room temperature, Ni 48 Fe 2 Mn 35 In 15 has L2 1 cubic structure, whereas Ni 50 Mn 34 FeIn 15 shows a two-phase structure due to the martensitic transition. In the case of Ni 48 Fe 2 Mn 35 In 15 , there is only one magnetic transition at 316 K with no martensitic transition. However, in Ni 50 Mn 34 FeIn 15 , we observe the martensitic transition at about 280 K. The Curie temperatures for austenite and martensite phases are 314 and 200 K, respectively. The maximum magnetic entropy changes are found to be 5.5 and 4.5 J kg −1 K −1 for Ni 48 Fe 2 Mn 35 In 15 and Ni 50 Mn 34 FeIn 15 , respectively, for 50 kOe. Ni 50 Mn 34 FeIn 15 exhibits exchange bias behavior, with a bias field of 130 Oe at 5 K. Both the alloys satisfy the empirical relation between the martensitic transition and the valence electron concentration (e/a) ratio. - Highlights: • Structural and magnetic properties of Ni 48 Fe 2 Mn 35 In 15 and Ni 50 Mn 34 FeIn 15 Heusler alloys have been investigated. • Ni 48 Fe 2 Mn 35 In 15 does not undergo a martensitic transition, whereas Ni 50 Mn 34 FeIn 15 shows martensitic transition. • Ni 50 Mn 34 FeIn 15 alloy exhibits exchange bias behavior. • Both alloys satisfy the empirical relation between martensitic transition and valence electron concentration (e/a)

Study of the crystallographic and magnetic properties of cubic manganite spinels NiMn{sub 2}O{sub 4}; Etude des proprietes cristallographiques et magnetiques des manganites spinelles cubiques NiMn{sub 2}O{sub 4}

Energy Technology Data Exchange (ETDEWEB)

Boucher, B [Commissariat a l' Energie Atomique, Saclay (France). Centre d' Etudes Nucleaires

1969-07-01

We study the variation of the crystallographic properties (inversion degree, position parameters and short range order) of the cubic spinel Mn{sub {nu}}Ni{sub 1-{nu}}[Mn{sub 2{nu}}Ni{sub {nu}}]O{sub 4}, as a function of the thermal treatment applied to the sample. {nu} lies between 0. 74 and 0. 93; the slower the sample is cooled the more inverse it is. We show, in a molecular field theory, that a system of three magnetic sublattices can afford a 'star' configuration. We establish the conditions of stability of such a structure and its evolution as a function of temperature is foreseen. Neutron diffraction measurements show that the magnetic structure of NiMn{sub 2}O{sub 4} at 4.2 K is a 'star' configuration and that with increasing temperature it becomes a collinear structure in agreement with the theory. Furthermore, we find an anomaly in the value of specific heat at the transition temperature between 'star' and collinear structures. (author) [French] On etudie la variation des proprietes cristallographiques (inversion, parametre de position, ordre a courte distance) du spinelle cubique Mn{sub {nu}}Ni{sub 1-{nu}}[Mn{sub 2{nu}}Ni{sub {nu}}]O{sub 4}, en fonction du traitement thermique que subit l'echantillon, {nu} est compris entre 0,74 et 0,93; plus le corps est refroidi lentement, plus il est inverse. On montre, dans le cadre d'une theorie de champ moleculaire, qu'un systeme a trois sous-reseaux magnetiques peut presenter une configuration en ''etoile''. On etablit les conditions de stabilite d'une telle structure et on prevoit son evolution en fonction de la temperature. Les mesures de diffraction de neutrons montrent que la structure magnetique de NiMn{sub 2}O{sub 4} a 4,2 K est du type ''en etoile'' et qu'elle evolue en fonction de la temperature vers une structure colineaire comme le prevoit la theorie. De plus on observe une anomalie de chaleur specifique a la temperature de la transition entre la structure ''en etoile'' et la structure colineaire. (auteur)

Effect of different MnO{sub 2} precursors on the electrochemical properties of spinel LiNi{sub 0.5}Mn{sub 1.5}O{sub 4} cathode active materials for high-voltage lithium ion batteries

Energy Technology Data Exchange (ETDEWEB)

Ma, Ye, E-mail: mayetju@tju.edu.cn [Department of Applied Chemistry, School of Chemical Engineering and Technology, Tianjin University, Tianjin 300072 (China); Collaborative Innovation Center of Chemical Science and Engineering, Tianjin (China); Tang, Haoqing [Department of Applied Chemistry, School of Chemical Engineering and Technology, Tianjin University, Tianjin 300072 (China); Tang, Zhiyuan, E-mail: zytang46@163.com [Department of Applied Chemistry, School of Chemical Engineering and Technology, Tianjin University, Tianjin 300072 (China); Collaborative Innovation Center of Chemical Science and Engineering, Tianjin (China); Mao, Wenfeng [Department of Applied Chemistry, School of Chemical Engineering and Technology, Tianjin University, Tianjin 300072 (China); Zhang, Xinhe [McNair Technology Company Limited, Dongguan, Guangdong 523700 (China)

2016-11-15

Highlights: • Synthesis of spinel LNMO via a facile template method. • The specific morphology of LNMO is closely related to that of MnO{sub 2} precursor. • LNMO using NH{sub 4}HCO{sub 3} as precipitant exhibits superior electrochemical performance. - Abstract: LiNi{sub 0.5}Mn{sub 1.5}O{sub 4} (LNMO) cathode materials with different morphologies are prepared via a facile template method using various MnO{sub 2} precursors. The structures, morphologies and electrochemical properties of the as-prepared LiNi{sub 0.5}Mn{sub 1.5}O{sub 4} samples are tested by various physical and electrochemical methods. The results of characterization show that the spinel LNMO cathode materials have good crystal structure and the MnO{sub 2} precursors have no effect on the final products. Moreover, the specific morphology of LNMO is closely related to that of MnO{sub 2} precursor, and further influence the electrochemical performance. In addition, the LNMO sample using NH{sub 4}HCO{sub 3} as precipitant exhibits excellent rate capability and cyclic stability in all as-prepared samples. Cycled at 0.5 and 1 C, the discharge capacities of LNMO cathode active particles using NH{sub 4}HCO{sub 3} as precipitant are 110.6 and 102.2 after 200 charge–discharge cycles, respectively, which are the largest compared with the LNMO using (NH{sub 4}){sub 2}S{sub 2}O{sub 8} and KMnO{sub 4} as oxidants.

Boosting Bifunctional Oxygen Electrocatalysis with 3D Graphene Aerogel-Supported Ni/MnO Particles.

Science.gov (United States)

Fu, Gengtao; Yan, Xiaoxiao; Chen, Yifan; Xu, Lin; Sun, Dongmei; Lee, Jong-Min; Tang, Yawen

2018-02-01

Electrocatalysts for oxygen-reduction and oxygen-evolution reactions (ORR and OER) are crucial for metal-air batteries, where more costly Pt- and Ir/Ru-based materials are the benchmark catalysts for ORR and OER, respectively. Herein, for the first time Ni is combined with MnO species, and a 3D porous graphene aerogel-supported Ni/MnO (Ni-MnO/rGO aerogel) bifunctional catalyst is prepared via a facile and scalable hydrogel route. The synthetic strategy depends on the formation of a graphene oxide (GO) crosslinked poly(vinyl alcohol) hydrogel that allows for the efficient capture of highly active Ni/MnO particles after pyrolysis. Remarkably, the resulting Ni-MnO/rGO aerogels exhibit superior bifunctional catalytic performance for both ORR and OER in an alkaline electrolyte, which can compete with the previously reported bifunctional electrocatalysts. The MnO mainly contributes to the high activity for the ORR, while metallic Ni is responsible for the excellent OER activity. Moreover, such bifunctional catalyst can endow the homemade Zn-air battery with better power density, specific capacity, and cycling stability than mixed Pt/C + RuO 2 catalysts, demonstrating its potential feasibility in practical application of rechargeable metal-air batteries. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Nickel permanganate as a precursor in the synthesis of a NiMn2O4 spinel

International Nuclear Information System (INIS)

Schmidt, Jorge A.; Sagua, Aurora E.; Bazan, Julio C.; Prat, Maria R.; Braganza, Maria E.; Moran, Emilio

2005-01-01

The present study describes the preparation, characterization, and thermal decomposition of the compound Ni(MnO 4 ) 2 .xH 2 O, which was synthesized by a coprecipitation method at a low temperature. The role of this compound as a precursor in the synthesis of a Ni-Mn spinel was determined via X-ray, TG-DTA, electron diffraction, and EDAX measurements

Magnetic properties of Ni(II)-Mn(III) LDHs

Energy Technology Data Exchange (ETDEWEB)

Giovannelli, F., E-mail: fabien.giovannelli@univ-tours.fr [LEMA, UMR 6157 CNRS-CEA, Universite Francois Rabelais, 3 place Jean Jaures, 41029 Blois (France); Zaghrioui, M.; Autret-Lambert, C. [LEMA, UMR 6157 CNRS-CEA, Universite Francois Rabelais, 3 place Jean Jaures, 41029 Blois (France); Delorme, F.; Seron, A. [BRGM, 3 Avenue Claude Guillemin, BP 36009, 45060 Orleans Cedex 2 (France); Chartier, T.; Pignon, B. [LEMA, UMR 6157 CNRS-CEA, Universite Francois Rabelais, 3 place Jean Jaures, 41029 Blois (France)

2012-11-15

The synthesis of Ni{sub 1-x}Mn{sub x}(OH){sub 2}(CO{sub 3}){sub x/2}{center_dot}nH{sub 2}O Layered Double Hydroxides (LDHs) for x = 0.2, 0.25 and 0.33, their characterisation by electron microscopy, X-ray diffraction and their magnetic properties are reported in this study. When x increases, the crystallinity of the nanoparticles is improved. The low temperature magnetic behaviour of these compounds is characteristic of the competition between in plane ferromagnetic and interlayer antiferromagnetic interactions. The ferromagnetism is due to in plane Ni cations interaction and decreases when manganese content increases (Tc decreases from 26 to 15 K when x increases from 0.2 to 0.33). It was found that the substitution of Ni by Mn ions favours the in plane antiferromagnetic order. This study demonstrates that magnetic interactions occur in LDH with non magnetic interlayer anions. -- Highlights: Black-Right-Pointing-Pointer The synthesis of Ni{sub 1-x}Mn{sub x}(OH){sub 2}(CO{sub 3}){sub x/2}{center_dot}nH{sub 2}O Layered Double Hydroxides have been performed. Black-Right-Pointing-Pointer The low temperature magnetic behaviour of these compounds has been studied. Black-Right-Pointing-Pointer The substitution of Ni by Mn ions favours the in plane antiferromagnetic order.

Highly efficient alkane oxidation catalyzed by [Mn(V)(N)(CN)4](2-). Evidence for [Mn(VII)(N)(O)(CN)4](2-) as an active intermediate.

Science.gov (United States)

Ma, Li; Pan, Yi; Man, Wai-Lun; Kwong, Hoi-Ki; Lam, William W Y; Chen, Gui; Lau, Kai-Chung; Lau, Tai-Chu

2014-05-28

The oxidation of various alkanes catalyzed by [Mn(V)(N)(CN)4](2-) using various terminal oxidants at room temperature has been investigated. Excellent yields of alcohols and ketones (>95%) are obtained using H2O2 as oxidant and CF3CH2OH as solvent. Good yields (>80%) are also obtained using (NH4)2[Ce(NO3)6] in CF3CH2OH/H2O. Kinetic isotope effects (KIEs) are determined by using an equimolar mixture of cyclohexane (c-C6H12) and cyclohexane-d12 (c-C6D12) as substrate. The KIEs are 3.1 ± 0.3 and 3.6 ± 0.2 for oxidation by H2O2 and Ce(IV), respectively. On the other hand, the rate constants for the formation of products using c-C6H12 or c-C6D12 as single substrate are the same. These results are consistent with initial rate-limiting formation of an active intermediate between [Mn(N)(CN)4](2-) and H2O2 or Ce(IV), followed by H-atom abstraction from cyclohexane by the active intermediate. When PhCH2C(CH3)2OOH (MPPH) is used as oxidant for the oxidation of c-C6H12, the major products are c-C6H11OH, c-C6H10O, and PhCH2C(CH3)2OH (MPPOH), suggesting heterolytic cleavage of MPPH to generate a Mn═O intermediate. In the reaction of H2O2 with [Mn(N)(CN)4](2-) in CF3CH2OH, a peak at m/z 628.1 was observed in the electrospray ionization mass spectrometry, which is assigned to the solvated manganese nitrido oxo species, (PPh4)[Mn(N)(O)(CN)4](-)·CF3CH2OH. On the basis of the experimental results the proposed mechanism for catalytic alkane oxidation by [Mn(V)(N)(CN)4](2-)/ROOH involves initial rate-limiting O-atom transfer from ROOH to [Mn(N)(CN)4](2-) to generate a manganese(VII) nitrido oxo active species, [Mn(VII)(N)(O)(CN)4](2-), which then oxidizes alkanes (R'H) via a H-atom abstraction/O-rebound mechanism. The proposed mechanism is also supported by density functional theory calculations.

Electrochemical Properties of Hydrogen-Storage Alloys ZrMn{sub 2}Ni{sub x} and ZrMnNi{sub 1+x} for Ni-MH Secondary Battery

Energy Technology Data Exchange (ETDEWEB)

Park, Hye Ryoung [Faculty of Applied Chemistry, Chonnam National University, Kwangju (Korea); Kwon, Ik Hyun [Automobile High-Technology Research Institute, Division of Advanced Materials Engineering, Chonbuk National University, Chonju (Korea)

2001-04-01

In order to improve the performance of AB{sub 2}-type hydrogen-storage alloys for Ni-MH secondary battery, AB{sub 2}-type alloys, ZrMn{sub 2}Ni{sub x}(x=0.0, 0.3, 0.6, 0.9 and 1.2) and ZrMnNi{sub 1+x}(x=0.0, 0.1, 0.2, 0.3 and 0.4) were prepared as the Zr-Mn-Ni three component alloys. The hydrogen-storage and the electrochemical properties were investigated. The C14 Laves phase formed in all alloys of ZrMn{sub 2}Ni{sub x}(x=0.0 {approx} 1.2). The equilibrium plateau pressure of the alloy, ZrMn{sub 2}Ni{sub 0.6}-H{sub 2} system, was about 0.5 atm at 30 degree C. Among these alloys, ZrMn{sub 2}Ni{sub 0.6} was the easiest to activate, and it had the largest discharge capacity as well as the best cycling performance. The C14 Laves phase also formed in all alloys of ZrMnNi{sub 1+x}(x=0.0 {approx} 0.4). The equilibrium plateau pressure of the alloy, ZrMnNi{sub 1.0}-H{sub 2} system, was about 0.45 atm at 30 degree C. Among these alloys, ZrMnNi{sub 1.0} was the easiest to activate, taking only 3 charge-discharge cycles, and it had the largest discharge capacity of 42 mAh/g. Among these alloys, ZrMn{sub 2}Ni{sub x}(x=0.0 {approx} 1.2) and ZrMnNi{sub 1+x}(x=0.0 {approx} 0.4), ZrMnNi{sub 1.0} had the largest discharge capacity (maximum value of 42 mAh/g), and it showed the fastest activation and good cycling performance. 23 refs., 4 figs., 2 tabs.

Investigation of positive electrode materials based on MnO2 for lithium batteries

International Nuclear Information System (INIS)

Le, My Loan Phung; Lam, Thi Xuan Binh; Pham, Quoc Trung; Nguyen, Thi Phuong Thoa

2011-01-01

Various composite materials of MnO 2 /C have been synthesized by electrochemical deposition and then used for the synthesis of lithium manganese oxide (LiMn 2 O 4 ) spinel as a cathode material for lithium ion batteries. The structure and electrochemical properties of electrode materials based on MnO 2 /C, spinel LiMn 2 O 4 and doped spinel LiNi 0.5 Mn 1.5 O 4 have been studied. The influence of synthesis conditions on the structural and electrochemical properties of synthesized materials was investigated by x-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electronic microscopy (TEM) and charge–discharge experiments. Some of the studied materials exhibit good performance of cycling and discharge capacity

Composites Li2MnO3·LiMn1/3Ni1/3Co1/3O2: Optimized synthesis and applications as advanced high-voltage cathode for batteries working at elevated temperatures

International Nuclear Information System (INIS)

Yu Chuang; Li Guangshe; Guan Xiangfeng; Zheng Jing; Li Liping; Chen Tianwen

2012-01-01

Highlights: ► Composites xLi 2 MnO 3 ·(1 − x)LiMn 1/3 Ni 1/3 Co 1/3 O 2 (x = 0.1–0.4) were prepared by a novel two-step molten-salt route. ► Structure and chemical compositions of the composites were optimized to show an optimum electrochemical property. ► Composite electrode 0.3Li 2 MnO 3 ·0.7LiMn 1/3 Ni 1/3 Co 1/3 O 2 exhibited an excellent electrochemical performance at elevated temperature of 45.4 °C. ► Electrode kinetics of composites was uncovered for the excellent electrochemical performance at elevated temperature. - Abstract: This work reports on the optimized preparation of a series of composites xLi 2 MnO 3 ·(1 − x)LiMn 1/3 Ni 1/3 Co 1/3 O 2 (x = 0.1–0.4) with an aim to find an advanced high-voltage cathode for lithium-ion batteries that can work at elevated temperatures. Developing a two-step molten-salt method leads to composites with a layered-type structure, showing a particle size distribution ranging from 350 to 450 nm. The composites are featured by oxidation states stabilized as Mn 4+ , Ni 2+ , and Co 3+ , and by lattice occupation of Li + in both transition-metal layers and lithium layer of LiMn 1/3 Ni 1/3 Co 1/3 O 2 . When acting as a cathode of lithium-ion batteries, the composite at x = 0.3 shows an optimum electrochemical performance as characterized by a discharge capacity of 120 mAh g −1 at a high current density of 500 mA g −1 and a capacity retention of 64% after 20 cycles. Surprisingly, this electrochemical performance is significantly improved at elevated temperatures. Namely, discharge capacity is increased to 140.4 mAh g −1 at a high current density of 500 mA g −1 , while average capacity decay rate becomes very small to 0.76%. These excellent performance is explained in terms of the dramatically improved lithium-ion diffusions in both electrode and surface films at elevated temperatures.

Local atomic characterization of LiCo1/3Ni1/3Mn1/3O2 cathode material

International Nuclear Information System (INIS)

Nedoseykina, Tatiana; Kim, Sung-Soo; Nitta, Yoshiaki

2006-01-01

Co, Ni and Mn K-edge XAFS investigation of LiCo 1/3 Ni 1/3 Mn 1/3 O 2 as alternative cathode material to commercially used LiCoO 2 in lithium rechargeable battery has been performed. Parameters of a local atomic structure such as radii of metal-oxygen and metal-metal coordination shells and disorder in those shells have been determined. It has been found that the radius of the first coordination shell (metal-oxygen) as well as a local disorder in the second shell (metal-metal) around each of the 3d-metals are in a good agreement with obtained for superlattice model of √3 x √3] R30 o type in triangular lattice of sites by first principle calculation. Other parameters of the local atomic structure around Co, Ni and Mn atoms do not provide evidence for presence of superstructure in LiCo 1/3 Ni 1/3 Mn 1/3 O 2

A new rechargeable lithium-ion battery with a xLi2MnO3.(1 - x) LiMn0.4Ni0.4Co0.2O2 cathode and a hard carbon anode

International Nuclear Information System (INIS)

Liu Jinlong; Wang Jie; Xia Yongyao

2011-01-01

Highlights: → A new type of battery with 0.4Li 2 MnO 3 0.6LiMn 0.4 Ni 0.4 Co 0.2 O 2 and hard carbon was proposed. → The irreversible capacity encountered at both electrodes, can be counterbalanced each other. → The battery delivers capacities of 105 mAh g -1 and specific energies of 315 Wh kg -1 . - Abstract: We reported a new type of rechargeable lithium-ion battery consisting of a structurally integrated 0.4Li 2 MnO 3 .0.6LiMnNi 0.4 Co 0.2 O 2 cathode and a hard carbon anode. The drawback of the high irreversible capacity loss of both electrodes, occurring at the first charge/discharge process, can be counterbalanced each other. The battery shows good reversibility with a sloping voltage from 1.5 V to 4.5 V and delivers a capacity of 105 mA h g -1 and a specific energy of 315 W h kg -1 based on the total weight of the both active electrode materials.

Spin reversal in Gd(Me,MnO3 (Me = Co, Ni

Directory of Open Access Journals (Sweden)

Gutiérrez, D.

2004-06-01

Full Text Available Partial substitution of the rare-earth by calcium at the cationic site of the ABO3 perovskites may show extraordinary effects of spin reversal due to a negative polarization between the rare-earth and the manganese networks, as it occurs in the solid solution Gd1‑xCaxMnO3. We present herein similar effects in gadolinium perovskites of the Gd(Me,MnO3 type, in which the manganese sublattice has been partially substituted by transition metal elements Me, leaving the gadolinium network intact. The spin reversal phenomena is observed at a critical concentration of x(Me = 1/3, which implies an optimum number of pairs Mn3+-Mn4+. Néel temperatures of 48 and 67 K are obtained for Me = Co and Ni, respectively, at the optimum concentration of substituent. A comparison between these different solid solutions allows us to generalize the interpretation of two interacting magnetic sublattices : a Mn-based ferromagnetic one and a negatively-aligned gadolinium network.La sustitución parcial del lantánido por el elemento calcio en el sitio catiónico (sitio A de la perovskita ABO3 puede dar lugar a efectos importantes ligados a una inversión del espín. Dicha inversión se debe a una interacción negativa entre la tierra rara y la subred de manganeso, tal como ocurre en la solución solida Gd1-xCaxMnO3. Se presentan en este trabajo efectos similares que ocurren en las perovskitas de gadolinio de fórmula Gd(Me,MnO3, en las cuales la subred de manganeso (sitio B ha sido reemplazada parcialmente por otros metales de transición Me, dejando intacta la subred de gadolinio. Se observa el fenómeno de inversión de espín para una concentración crítica x(Me = 1/3, para la cual se logra una cantidad óptima de pares Mn3+‑Mn4+. Para esta concentración crítica se observan temperaturas de Néel antiferromagnéticas del orden de 48 y 67 K, respectivamente para Me = Co y Ni. Un análisis comparativo entre estos diferentes sistemas permite generalizar la

M(II)-dipyridylamide-based coordination frameworks (M=Mn, Co, Ni): Structural transformation

Energy Technology Data Exchange (ETDEWEB)

Tzeng, Biing-Chiau; Selvam, TamilSelvi; Tsai, Miao-Hsin

2016-11-15

A series of 1-D double-zigzag (([M(papx){sub 2}(H{sub 2}O){sub 2}](ClO{sub 4}){sub 2}){sub n}; M=Mn, x=s (1), x=o (3); M=Co, x=s (4), x=o (5); M=Ni, x=s (6), x=o (7)) and 2-D polyrotaxane ([Mn(paps){sub 2}(ClO{sub 4}){sub 2}]{sub n} (2)) frameworks were synthesized by reactions of M(ClO{sub 4}){sub 2} (M=Mn, Co, and Ni) with papx (paps, N,N’-bis(pyridylcarbonyl)-4,4’-diaminodiphenylthioether; papo, N,N’-bis(pyridylcarbonyl)-4,4’-diaminodiphenyl ether), which have been isolated and structurally characterized by X-ray diffraction. Based on powder X-ray diffraction (PXRD) experiments, heating the double-zigzag frameworks underwent structural transformation to give the respective polyrotaxane ones. Moreover, grinding the solid samples of the respective polyrotaxanes in the presence of moisture also resulted in the total conversion to the original double-zigzag frameworks. In this study, we have successfully extended studies to Mn{sup II}, Co{sup II}, and Ni{sup II} frameworks from the previous Zn{sup II}, Cd{sup II}, and Cu{sup II} ones, and interestingly such structural transformation is able to be proven experimentally by powder and single-crystal X-ray diffraction studies as well. - Graphical abstract: 1-D double-zigzag and 2-D polyrotaxane frameworks of M(II)-papx (x=s, o; M=Mn, Co, Ni) frameworks can be interconverted by heating and grinding in the presence of moiture, and such structural transformation has be proven experimentally by powder and single-crystal X-ray diffraction studies.

Effects of lithium-active manganese trioxide coating on the structural and electrochemical characteristics of LiNi_0_._5Co_0_._2Mn_0_._3O_2 as cathode materials for lithium ion battery

International Nuclear Information System (INIS)

Li, Lingjun; Yao, Qi; Chen, Zhaoyong; Song, Liubin; Xie, Tian; Zhu, Huali; Duan, Junfei; Zhang, Kaili

2015-01-01

Li_2MnO_3-coated LiNi_0_._5Co_0_._2Mn_0_._3O_2 materials are successfully synthesized by sol–gel method. The effects of various pH values and Li_2MnO_3 contents on the structural and electrochemical properties of LiNi_0_._5Co_0_._2Mn_0_._3O_2 cathode materials are systematically investigated, respectively. Scanning electron microscope, transmission electron microscope and energy dispersive spectrometer confirm that the particles of LiNi_0_._5Co_0_._2Mn_0_._3O_2 are completely coated by crystalline Li_2MnO_3 phase. Electrochemical tests show that suitable Li_2MnO_3-coated samples exhibit higher rate capacity and better cycling performance than those of the pristine one. This improvement can be attributed to the synergetic contribution from the neutral pH value and appropriate Li_2MnO_3 amount. The neutral pH environment can protect the core material from damaging during the coating process and is conducive to relieving the rapid moisture uptaking problem of LiNi_0_._5Co_0_._2Mn_0_._3O_2. While, suitable Li_2MnO_3 coating can protect the bulk from directly contacting the electrolyte and offer a fast Li"+ diffusion path at the interface of bulk and electrolyte. - Graphical abstract: The 5% Li_2MnO_3-coated LiNi_0_._5Co_0_._2Mn_0_._3O_2 sample, modified at pH 6, exhibits a conformal and amorphous coating layer before calcination. After been sintered at 880 °C for 5 h, the sample shows Li_2MnO_3 crystalline surface, as well as superior electrochemical performance. - Highlights: • Li_2MnO_3-coated LiNi_0_._5Co_0_._2Mn_0_._3O_2 is prepared by sol–gel method. • Neutral pH environment can protect NMC from damaging during the coating process. • Li_2MnO_3 coating enhances the pristine at high cyclability and rate properties. • Suitable Li_2MnO_3 modification results in better Li"+ diffusion coefficient. • The 5% Li_2MnO_3-coated sample exhibits the best electrochemical performance.

Production of hydrogen with methane decomposition using Ni-Mn/Ce-ZrO{sub 2} catalysts; Produccion de hidrogeno via descomposicion de metano mediante catalizadores de Ni-Mn/Ce-ZrO{sub 2}

Energy Technology Data Exchange (ETDEWEB)

Diaz, C; Hernandez-Pichardo, M L; Valenzuela, M A [Instituto Politecnico Nacional-ESIQIE, Mexico, D.F. (Mexico); Del Angel, P; Montoya de la Fuente, J.A. [Instituto Mexicano del Petroleo, Mexico, D.F. (Mexico)

2009-09-15

The catalytic decomposition of methane makes it possible to obtain CO and CO{sub 2} free hydrogen, which is a desirable characteristic for fuel cell applications. In addition, this method simultaneously obtains diverse carbon nanostructures with a large variety of applications. This work prepared catalysts with different Ni contents supported by Ce-Zr mixed oxides and doped with manganese to promote activity. The supports were synthesized with surfactant-assisted coprecipitation. The Ni and Mn deposits were performed using conventional impregnation for evaluation in the methane decomposition catalyst at 500 degrees Celsius. It was observed that with the incorporation of 1% of Mn into the Ni0 active phase, the conversion of methane into hydrogen and carbon nanostructures increased. The results of reduction at the programmed temperature indicate that the addition of Mn enables the formation of different NiO{sub x} species, increasing dispersion and the degree of reduction to Ni0. Analyses with electron and transmission microscopy show the formation of distinct species of carbon, including nanotubes, nanofibers and concentric onion-like structures, as well as a significant formation of encapsulated Ni0 particles. [Spanish] La descomposicion catalitica de metano permite la obtencion de hidrogeno libre de CO y CO{sub 2}, lo cual es una caracteristica deseable para su aplicacion en celdas de combustible. Ademas, por esta ruta, simultaneamente se obtienen diversas nanoestructuras de carbono con una gran variedad de aplicaciones. En este trabajo se prepararon catalizadores con diferentes contenidos de Ni soportados en oxidos mixtos Ce-Zr y se doparon con manganeso como promotor de actividad. Los soportes se sintetizaron por coprecipitacion asistida por surfactante y el deposito del Ni y del Mn se efectuo por impregnacion convencional para su evaluacion en la descomposicion catalitica de metano a 500 grados centigrados. Se observo que mediante la incorporacion de 1% de Mn a

Influence of Ga vacancies, Mn and O impurities on the ferromagnetic properties of GaN micro- and nanostructures

Science.gov (United States)

Guzmán, G.; Escudero, R.; Silva, R.; Herrera, M.

2018-04-01

We present a study of the influence of gallium vacancy (VGa) point defects on the ferromagnetic properties of GaN:Mn and GaN:Mn,O micro- and nanostructures. Results demonstrate that the generation of these point defects enhances the ferromagnetic signal of GaN:Mn microstructures, while incorporation of oxygen as an impurity inhibits this property. XPS measurements revealed that Mn impurities in ferromagnetic GaN:Mn samples mainly exhibit a valence state of 2+. Cathodoluminescence (CL) spectra from Mn-doped GaN samples displayed emissions centered at about 1.97 eV, attributed to transitions between the 4T1-6A1 states of the Mn2+ d orbitals, and emissions centered at 2.45 and 2.9 eV, associated with the presence of VGa. CL measurements also revealed a blue shift of the GaN band-edge emission generated by the expansion of the wurtzite lattice due to Mn incorporation, which was confirmed by XRD measurements. These latter measurements also revealed an amorphization of GaN:Mn due to the incorporation of oxygen as impurities. The GaN:Mn samples were synthesized by thermal evaporation of GaN and MnCO3 powders onto Ni0.8Cr0.2/Si(100) in a horizontal furnace operated at low vacuum. The residual air inside the system was used as a source of oxygen during the synthesis of Mn and O co-doped GaN nanostructures. Mn and O impurities were incorporated into the nanostructures at different concentrations by varying the growth temperature. Energy Dispersive Spectroscopy, XRD, and XPS measurements confirmed that the obtained samples predominantly consisted of GaN.

Preparation of mesoporous MnO2/C catalyst for n-hexyl acetate synthesis

International Nuclear Information System (INIS)

Yang Zeheng; Pan Yanmei; Mei Zhousheng; Zhang Weixin

2012-01-01

A mesoporous MnO 2 /C composite was prepared by impregnating self-made porous carbon spheres with manganese nitrate aqueous solution and subsequently reacting with KMnO 4 aqueous solution. It was characterized with X-ray photoelectron spectroscopy (XPS), transmission electron microscopy (TEM), field emission scanning electron microscopy (FESEM), the Brunauer-Emmett-Teller (BET) surface area and the Barrett-Joyner-Halenda (BJH) pore size distribution. The as-prepared mesoporous MnO 2 /C composite was used as catalyst for the synthesis of n-hexyl acetate, and the effects of MnO 2 loading and esterification reaction parameters on the esterification rate were investigated. The results prove that MnO 2 loading has a significant effect on the catalytic activity and that the mesoporous MnO 2 /C composite exhibits high catalytic activity with an esterification rate of 96.42% under the conditions below: MnO 2 loading (73.09 wt%), catalyst dosage (0.1% in total weight), acetic acid/n-hexanol molar ratio (2:1), reaction temperature (130 °C) and reaction time (5 h).

Onset of phase separation in the double perovskite oxide mn>2mn>MnNiO>6mn>

Energy Technology Data Exchange (ETDEWEB)

Spurgeon, Steven R.; Sushko, Peter V.; Devaraj, Arun; Du, Yingge; Droubay, Timothy; Chambers, Scott A.

2018-04-01

Identification of kinetic and thermodynamic factors that control crystal nucleation and growth represents a central challenge in materials synthesis. Here we report that apparently defect-free growth of La2MnNiO6 (LMNO) thin films supported on SrTiO3 (STO) proceeds up to 1–5 nm, after which it is disrupted by precipitation of NiO phases. Local geometric phase analysis and ensemble-averaged x-ray reciprocal space mapping show no change in the film strain away from the interface, indicating that mechanisms other than strain relaxation induce the formation of the NiO phases. Ab initio simulations suggest that the electrostatic potential build-up associated with the polarity mismatch at the film-substrate interface promotes the formation of oxygen vacancies with increasing thickness. In turn, oxygen deficiency promotes the formation of Ni-rich regions, which points to the built-in potential as an additional factor that contributes to the NiO precipitation mechanisms. These results suggest that the precipitate-free region could be extended further by either incorporating dopants that suppress the built-in potential or by increasing the oxygen fugacity in order to suppress the formation of oxygen vacancies.

Phase equilibria and stability of the B2 phase in the Ni-Mn-Al and Co-Mn-Al systems

International Nuclear Information System (INIS)

Kainuma, R.; Ise, M.; Ishikawa, K.; Ohnuma, I.; Ishida, K.

1998-01-01

The phase equilibria and ordering reactions in the composition region up to 50 at.% Al have been investigated in the Ni-Mn-Al and Co-Mn-Al systems at temperatures in the interval 850-1200 C mainly by the diffusion couple method. The compositions of the γ (A1: fcc-Ni, -Co, γ-Mn), γ' (L1 2 : Ni 3 Al), β (B2: NiAl, CoAl, NiMn), β-Mn (A13: β-Mn type), δ-Mn (A2: bcc-Mn) and ε (A3: hcp-(Mn, Al)) phases in equilibrium and the critical boundaries of the A2/B2 continuous ordering transition in the bcc phase region have been determined. It is shown that in the Mn-rich portion of the ternary systems both continuous and discontinuous A2 to B2 ordering transitions exist. The A2+B2 two-phase region in the isothermal sections has a lenticular shape and exists over a wide temperature range. The phase equilibria between the γ, γ', β, β-Mn, δ-Mn and ε phases are presented and the stability of the ordered bcc aluminides is discussed. (orig.)

Synthesis and characterization of composites HoMn_1_-_x(Ni,Co)_xO_3

International Nuclear Information System (INIS)

Santos, Cassio Morilla dos

2011-01-01

In this work was accomplished the synthesis process and structural and magnetic characterization of HoMn_1_-_X(Ni,Co)_XO_3 compounds of perovskite structure. The samples synthesis were performed through modified polymeric precursor method. After synthesis and solvent removal, the polymer resin formed was treated at 350 deg C/4h for organic constituents removal, followed by heating treatment at 500 deg C/4h and 900 deg C/20h to obtain the crystalline phase. For structural characterization, it was used D10B-XPD beam line of Laboratorio Nacional de Luz Sincrotron (LNLS), where X-rays wavelengths below cobalt, manganese and nickel absorption edge, were used. The formation of HoNi_0_._5_0Mn_0_._5_0O_3, HoCo_0_._5_0Mn_0_._5_0O_3 and HoNi_0_._2_5Co_0_._2_5Mn_0_._5_0O_3 phases were observed by X-ray diffraction technique. By Rietveld refinement method for sample HoNi_0_._2_5Co_0_._2_5Mn_0_._5_0O_3, it was determined that cobalt and nickel had similar occupations at the top and bottom of unit cell, while the manganese preferentially occupied plan 002. The magnetic response of samples was studied through magnetization curves according to the temperature function and the applied magnetic field. The ZFC curves showed a paramagnetic response associated to holmium magnetic moment, and ferromagnetism, antiferromagnetism and ferrimagnetism coexistence, due to sublattices formed by transition metals. The FC curves evidenced the spin reversal phenomenon, associated to the interaction between the sublattice formed by transition metals with sublattices formed by rare-earth, considering a mechanism of antiferromagnetic exchange interaction. (author)

Ferro- to antiferromagnetic crossover angle in diphenoxido- and carboxylato-bridged trinuclear Ni(II)₂-Mn(II) complexes: experimental observations and theoretical rationalization.

Science.gov (United States)

Seth, Piya; Figuerola, Albert; Jover, Jesús; Ruiz, Eliseo; Ghosh, Ashutosh

2014-09-02

Three new trinuclear heterometallic Ni(II)-Mn(II) complexes have been synthesized using a [NiL] metalloligand, where H2L = N,N'-bis(salicylidene)-1,3-propanediamine. The complexes [(NiL)2Mn(OCnn)2(CH3OH)2]·CH3OH (1), [(NiL)2Mn(OPh)2(CH3OH)2][(NiL)2Mn(OPh)2]·H2O (2), and [(NiL)2Mn(OSal)2(CH3OH)2]·2[NiL] (3) (where OCnn = cinnamate, OPh = phenylacetate, OSal = salicylate) have been structurally characterized. In all three complexes, in addition to the double phenoxido bridge, the two terminal Ni(II) atoms are linked to the central Mn(II) by means of a syn-syn bridging carboxylate, giving rise to a linear structure. Complexes 1 and 2 with Ni-O-Mn angles of 97.24 and 96.43°, respectively, exhibit ferromagnetic interactions (J(Ni-Mn) = +1.38 and +0.50 cm(-1), respectively), whereas 3 is antiferromagnetic (J(Ni-Mn) = -0.24 cm(-1)), having an Ni-O-Mn angle of 98.51°. DFT calculations indicate that there is a clear magneto-structural correlation between the Ni-O-Mn angle and J(Ni-Mn) values, which is in agreement with the experimental results.

Mn-substituted perovskites RECoxMn1-xO3: a comparison between magnetic properties of LaCoxMn1-xO3 and GdCoxMn1-xO3

Directory of Open Access Journals (Sweden)

Barahona, P.

2008-08-01

Full Text Available Cooperative phenomena constitute important mechanisms to explain the magnetic properties of the perovskite manganites REMnO3, in which the rare-earth and/or Mn is partially replaced by divalent elements. In this way, the manganese ion changes its valence state (Mn3+ Mn4+, triggering strong magnetic interactions. In this work we describe the case of GdCoxMn1-xO3 (0.0 ≤ x ≤ 1.0 for which the antiferromagnetic interaction between the Gd sublattice and the Mn/Co network leads to a reversal of the magnetic moment at low temperature. No inversion is observed for the LaCoxMn1-xO3 series, in which the ordering temperature may attain a maximum of 235 K for LaCo0.50Mn0.50O3, while it is only 120 K for similar Co/Mn ratio in the case of GdCo0.50Mn0.50O3. Magnetic properties are described in terms of two regimes: one, for x 3 manganite and another one, for x > 0.5, when Mn substitutes Co in the GdCoO3 cobaltite, while the magnetic interactions are maximized at x(Co = 0.50. This hypothesis is discussed in terms of the respective oxidation states of both manganese (Mn3+ / Mn4+ and cobalt (Co2+ / Co3+.El fenómeno cooperativo constituye un importante mecanismo para explicar las propiedades magnéticas de las perovskitas manganitas TRMnO3, en las que el catión de tierra rara, TR, y/o el catión Mn3+ son parcialmente reemplazados por cationes divalentes. Por esta vía el ión de manganeso cambia de estado de valencia (Mn3+ Mn4+, generando fuertes interacciones magnéticas. En el presente trabajo se describe el caso de las soluciones sólidas GdCoxMn1-xO3 (0.0 ≤ x ≤ 1.0 para las que la interacción antiferromagnética entre la subred del Gd3+ y la red Mn/Co lleva a una inversión del momento magnético a baja temperatura. No se ha observado inversión para la serie LaCoxMn1-xO3, en que la temperatura de orden puede alcanzar un máximo de 235K para LaCo0.50Mn0.50O3, mientras que en el caso de GdCo0.50Mn0.50O3, en que sí se observa inversión, la

In Situ Growth of MnO2 Nanosheets on N-Doped Carbon Nanotubes Derived from Polypyrrole Tubes for Supercapacitors.

Science.gov (United States)

Ou, Xu; Li, Qi; Xu, Dan; Guo, Jiangna; Yan, Feng

2018-03-02

Nitrogen-doped porous carbon nanotubes@MnO 2 (N-CNTs@MnO 2 ) nanocomposites are prepared through the in situ growth of MnO 2 nanosheets on N-CNTs derived from polypyrrole nanotubes (PNTs). Benefiting from the synergistic effects between N-CNTs (high conductivity and N doping level) and MnO 2 nanosheets (high theoretical capacity), the as-prepared N-CNTs@MnO 2 -800 nanocomposites show a specific capacitance of 219 F g -1 at a current density of 1.0 A g -1 , which is higher than that of pure MnO 2 nanosheets (128 F g -1 ) and PNTs (42 F g -1 ) in 0.5 m Na 2 SO 4 solution. Meanwhile, the capacitance retention of 86.8 % (after 1000 cycles at 10 A g -1 ) indicates an excellent electrochemical performance of N-CNTs@MnO 2 prepared in this work. © 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Electrochemical performance of co-doped Li1.2Mn0.6Ni0.2O2 cathode materials

CSIR Research Space (South Africa)

David, K

2013-04-01

Full Text Available The composite material has a xLi2MnO3·(1-x)LiMO2 (M = Mn, Co, Ni) structure has been considered as one of the most promising cathode materials for advanced lithium-ion batteries due to their low-cost and high capacity (> 200 mAh g−1) between 4.8 V...

Ce3+ doping into 0.6Li2MnO3·0.4LiNi0.5Co0.2Mn0.3O2 as cathode material for Li-ion batteries applied in new energy vehicle

Science.gov (United States)

Peng, Han; Yao, Linxiao; Zhang, Ming

2018-06-01

The pristine Li1.20[Mn0.52Ni0.20Co0.08]O2 and Ce3+-doped Li1.20[Mn0.50Ni0.20Co0.08Ce0.02]O2 cathode materials have been synthesized by using the typical sol-gel method. The XRD, SEM, ICP-OES and galvanostatic charge-discharge tests were carried out to study the influence of Ce3+ doping on the crystal structural, morphology and electrochemical properties of Li1.20Mn0.54Ni0.13Co0.13O2. The XRD result revealed the Ce3+ doping modification could decrease the cation mixing degree. The galvanostatic charge-discharge tests results showed that the sample after Ce3+ doping demonstrated the smaller irreversible capacity loss, more stable cyclic performance and better rate capacity than those of the pristine one.

Solid state opto-impedance of LiNiVO{sub 4} and LiMn{sub 2}O{sub 4}

Energy Technology Data Exchange (ETDEWEB)

Kalyani, P; Sivasubramanian, S; Prabhu, S Naveen; Ragavendran, K; Kalaiselvi, N; Ranganathan, N G; Madhu, S; SundaraRaj, A; Manoharan, S P; Jagannathan, R [Central Electrochemical Research Institute, Karaikudi-630006, Tamil Nadu (India)

2005-04-07

Spinel type LiMn{sub 2}O{sub 4} and inverse spinel LiNiVO{sub 4} systems serve as standard cathode materials or potential cathode systems for application in high energy density lithium-ion batteries. Upon photo-excitation using UV radiation of energy {approx}5 eV, the LiNiVO{sub 4} system shows significant modification in the solid state impedance pattern while the LiMn{sub 2}O{sub 4} system does not. This study has revealed a significant difference in the opto-impedance pattern for LiNiVO{sub 4} with respect to LiMn{sub 2}O{sub 4}, which may be due to the different electronic processes involved. An attempt has been made to study this behaviour from the solid-state viewpoint.

Low-temperature molar heat capacities and entropies of MnO2 (pyrolusite), Mn3O4 (hausmanite), and Mn2O3 (bixbyite)

Science.gov (United States)

Robie, R.A.; Hemingway, B.S.

1985-01-01

Pyrolusite (MnO2), hausmanite (Mn3O4), and bixbyite (Mn2O3), are important ore minerals of manganese and accurate values for their thermodynamic properties are desirable to understand better the {p(O2), T} conditions of their formation. To provide accurate values for the entropies of these important manganese minerals, we have measured their heat capacities between approximately 5 and 380 K using a fully automatic adiabatically-shielded calorimeter. All three minerals are paramagnetic above 100 K and become antiferromagnetic or ferrimagnetic at lower temperatures. This transition is expressed by a sharp ??-type anomaly in Cpmo for each compound with Ne??el temperatures TN of (92.2??0.2), (43.1??0.2), and (79.45??0.05) K for MnO2, Mn3O4, and Mn2O3, respectively. In addition, at T ??? 308 K, Mn2O3 undergoes a crystallographic transition, from orthorhombic (at low temperatures) to cubic. A significant thermal effect is associated with this change. Hausmanite is ferrimagnetic below TN and in addition to the normal ??-shape of the heat-capacity maxima in MnO2 and Mn2O3, it has a second rounded maximum at 40.5 K. The origin of this subsidiary bump in the heat capacity is unknown but may be related to a similar "anomalous bump" in the curve of magnetization against temperature at about 39 K observed by Dwight and Menyuk.(1) At 298.15 K the standard molar entropies of MnO2, Mn3O4, and Mn2O3, are (52.75??0.07), (164.1??0.2), and (113.7??0.2) J??K-1??mol-1, respectively. Our value for Mn3O4 is greater than that adopted in the National Bureau of Standards tables(2) by 14 per cent. ?? 1985.

Study of the crystallographic and magnetic properties of cubic manganite spinels NiMn2O4

International Nuclear Information System (INIS)

Boucher, B.

1969-01-01

We study the variation of the crystallographic properties (inversion degree, position parameters and short range order) of the cubic spinel Mn ν Ni 1-ν [Mn 2ν Ni ν ]O 4 , as a function of the thermal treatment applied to the sample. ν lies between 0. 74 and 0. 93; the slower the sample is cooled the more inverse it is. We show, in a molecular field theory, that a system of three magnetic sublattices can afford a 'star' configuration. We establish the conditions of stability of such a structure and its evolution as a function of temperature is foreseen. Neutron diffraction measurements show that the magnetic structure of NiMn 2 O 4 at 4.2 K is a 'star' configuration and that with increasing temperature it becomes a collinear structure in agreement with the theory. Furthermore, we find an anomaly in the value of specific heat at the transition temperature between 'star' and collinear structures. (author) [fr

Rietveld refinement of the orthorhombic Pbca structures of Rb2CdSi5O12, Cs2MnSiO5O12, Cs2CoSi5O12 and Cs2NiSi5O12 leucites by synchrotron X-ray powder diffraction

International Nuclear Information System (INIS)

Bell, A.M.T.; Henderson, C.M.B.

1996-01-01

Analysis of high-resolution synchrotron X-ray powder diffraction patterns for hydrothermally synthesized Rb 2 CdSi 5 O 12 and Cs 2 MnSi 5 O 12 leucite analogues, and dry-synthesized Cs 2 CoSi 5 O 12 and Cs 2 NiSi 5 O 12 leucite analogues showed that they have an orthorhombic Pbca structure. The structures have been refined by the Rietveld method, showing that the tetrahedrally coordinated atoms (Si, Cd, Mn, Co and Ni) are ordered on separate sites. The Cs 2 MnSi 5 O 12 , Cs 2 CoSi 5 O 12 and Cs 2 NiSi 5 O 12 leucite samples are unusual in containing SiO 4 tetrahedra which are more distorted, on average, than the larger MnO 4 , CoO 4 and NiO 4 tetrahedra. The JCPDS file numbers for Rb 2 CdSi 5 O 12 , Cs 2 MnSi 5 O 12 and Cs 2 CoSi 5 O 12 are 46-1491, 46-1492 and 46-1493, respectively. (orig.)

Effect of Nb and F Co-doping on Li1.2Mn0.54Ni0.13Co0.13O2 Cathode Material for High-Performance Lithium-Ion Batteries

Directory of Open Access Journals (Sweden)

Lei Ming

2018-04-01

Full Text Available The Li1.2Mn0.54−xNbxCo0.13Ni0.13O2−6xF6x (x = 0, 0.01, 0.03, 0.05 is prepared by traditional solid-phase method, and the Nb and F ions are successfully doped into Mn and O sites of layered materials Li1.2Mn0.54Co0.13Ni0.13O2, respectively. The incorporating Nb ion in Mn site can effectively restrain the migration of transition metal ions during long-term cycling, and keep the stability of the crystal structure. The Li1.2Mn0.54−xNbxCo0.13Ni0.13O2−6xF6x shows suppressed voltage fade and higher capacity retention of 98.1% after 200 cycles at rate of 1 C. The replacement of O2− by the strongly electronegative F− is beneficial for suppressed the structure change of Li2MnO3 from the eliminating of oxygen in initial charge process. Therefore, the initial coulombic efficiency of doped Li1.2Mn0.54−xNbxCo0.13Ni0.13O2−6xF6x gets improved, which is higher than that of pure Li1.2Mn0.54Co0.13Ni0.13O2. In addition, the Nb and F co-doping can effectively enhance the transfer of lithium-ion and electrons, and thus improving rate performance.

Electrochemical reaction mechanisms under various charge-discharge operating conditions for Li1.2Ni0.13Mn0.54Co0.13O2 in a lithium-ion battery

Science.gov (United States)

Konishi, Hiroaki; Hirano, Tatsumi; Takamatsu, Daiko; Gunji, Akira; Feng, Xiaoliang; Furutsuki, Sho; Okumura, Takefumi; Terada, Shohei; Tamura, Kazuhisa

2018-06-01

The potential in each state of charge (SOC) during charging of Li1.2Ni0.13Mn0.54Co0.13O2 is higher than that during discharging. In other words, the potential hysteresis occurs between charging and discharging. Furthermore, the potential in each SOC changes according to the charge-discharge operating conditions, indicating that the charge-discharge reaction mechanism is also affected. To clarify the effect of charge-discharge operating conditions on the electrochemical reaction, Li1.2Ni0.13Mn0.54Co0.13O2 was charged and discharged under various charge-discharge operating ranges, and open-circuit potential (OCP), crystal structure, and oxidation states of the transition metals were evaluated by electrochemical measurement, X-ray diffraction (XRD), and X-ray absorption fine structure (XAFS). These results indicate that OCP, lattice parameters, and oxidation states of the transition metals of Li1.2Ni0.13Mn0.54Co0.13O2 in each SOC are not constant. The XRD results indicate that two phases, namely, LiNi0.33Mn0.33Co0.33O2-like and Li2MnO3-like, exist in Li1.2Ni0.13Mn0.54Co0.13O2. For the LiNi0.33Mn0.33Co0.33O2-like phase, the relationship between OCP, lattice parameters, and oxidation states of the transition metals in each SOC is not affected by the charge-discharge operating conditions, indicating that extraction and insertion of lithium ions for the LiNi0.33Mn0.33Co0.33O2-like phase progresses at almost the same potential. Although the extraction and insertion of lithium ions for the Li2MnO3-like phase progresses at almost the same potential in the low-SOC region, the OCP and lattice parameter in each SOC in the high-SOC region are not constant. Therefore, the extraction of lithium ions from the Li2MnO3-like phase in the high-SOC region causes the potential hysteresis of Li1.2Ni0.13Mn0.54Co0.13O2.

XPS and EELS characterization of Mn{sub 2}SiO{sub 4}, MnSiO{sub 3} and MnAl{sub 2}O{sub 4}

Energy Technology Data Exchange (ETDEWEB)

Grosvenor, A.P., E-mail: andrew.grosvenor@usask.ca [Department of Chemistry, University of Saskatchewan, Saskatoon, SK S7N 5C9 (Canada); Bellhouse, E.M., E-mail: erika.bellhouse@arcelormittal.com [Global R & D—Hamilton, ArcelorMittal Dofasco, 1330 Burlington St. E, Hamilton, ON L8N 3J5 (Canada); Korinek, A., E-mail: korinek@mcmaster.ca [Canadian Centre for Electron Microscopy, Brockhouse Institute for Materials Research, McMaster University, 1280 Main St. W., Hamilton, ON L8S 4M1 (Canada); Bugnet, M., E-mail: bugnetm@mcmaster.ca [Canadian Centre for Electron Microscopy, Brockhouse Institute for Materials Research, McMaster University, 1280 Main St. W., Hamilton, ON L8S 4M1 (Canada); McDermid, J.R., E-mail: mcdermid@mcmaster.ca [Steel Research Centre, McMaster University, 1280 Main St. W., Hamilton, ON L8S 4M1 (Canada)

2016-08-30

Graphical abstract: XPS and EELS spectra were acquired from Mn2Al2O4, MnSiO3 and Mn2SiO4 standards and unique features identified that will allow unambiguous identification of these compounds when studying the selective oxidation of advanced steels. - Highlights: • Mn2Al2O4, MnSiO3 and Mn2SiO4 standards were synthesized and characterized using both XPS and EELS. • Unique features in both the XPS high resolution and EELS spectra were identified for all compounds. • The spectra can be used to identify these compounds when studying the selective oxidation of steels. - Abstract: X-ray Photoelectron Spectroscopy (XPS) and Electron Energy Loss Spectroscopy (EELS) are strong candidate techniques for characterizing steel surfaces and substrate-coating interfaces when investigating the selective oxidation and reactive wetting of advanced high strength steels (AHSS) during the continuous galvanizing process. However, unambiguous identification of ternary oxides such as Mn{sub 2}SiO{sub 4}, MnSiO{sub 3}, and MnAl{sub 2}O{sub 4} by XPS or EELS, which can play a significant role in substrate reactive wetting, is difficult due to the lack of fully characterized standards in the literature. To resolve this issue, samples of Mn{sub 2}SiO{sub 4}, MnSiO{sub 3} and MnAl{sub 2}O{sub 4} were synthesized and characterized by XPS and EELS. The unique features of the XPS and EELS spectra for the Mn{sub 2}SiO{sub 4}, MnSiO{sub 3} and MnAl{sub 2}O{sub 4} standards were successfully derived, thereby allowing investigators to fully differentiate and identify these oxides at the surface and subsurface of Mn, Si and Al alloyed AHSS using these techniques.

Novel manganate Cs{sub 23}Mn{sub 16}O{sub 28} containing two different types of quasi one-dimensional polyanions, {sup 1}{sub ∞}[MnO{sub 2}]{sub n} and unique {sup 1}{sub ∞}[Mn{sub 3}O{sub 5}]{sub n}

Energy Technology Data Exchange (ETDEWEB)

Nuss, Juergen; Jansen, Martin [Max-Planck-Institut fuer Festkoerperforschung, Stuttgart (Germany); Senaris-Rodriguez, Maria A. [Dept. Quimica, Facultad de Ciencias, Universidad de A Coruna (Spain); Klemenz, Sebastian [Max-Planck-Institut fuer Chemische Physik fester Stoffe, Dresden (Germany)

2017-11-17

Cs{sub 23}Mn{sub 16}O{sub 23} was synthesized via the azide/nitrate route from mixtures of Mn{sub 2}O{sub 3}, CsNO{sub 3}, and CsN{sub 3}. This manganese(II/III) mixed-valent oxide, which contains only one Mn{sup 3+} besides 15 Mn{sup 2+} cations, was studied by single-crystal X-ray diffraction and magnetic susceptibility measurements. Its crystal structure [P anti 1, Z = 1, a = 1114.26(2), b = 1185.53(2), c = 1205.39(2) pm, α = 70.596(1), β = 80.377(2), γ = 83.072(2) , R{sub 1} = 0.033] is based on a honeycomb-like arrangement of cesium atoms, providing the space for two different types of one-dimensional polyoxomanganate anions, illustrated by the syntax Cs{sub 23}[MnO{sub 2}]{sub 4}[Mn{sub 3}O{sub 5}]{sub 4}. Magnetic susceptibility measurements indicate dominant antiferromagnetic intra-chain interactions present already at ambient temperature and long range inter-chain magnetic ordering at 11 K. (copyright 2017 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

Characterization and Catalytic Activity of Mn-Co/TiO2 Catalysts for NO Oxidation to NO2 at Low Temperature

Directory of Open Access Journals (Sweden)

Lu Qiu

2016-01-01

Full Text Available A series of Mn-Co/TiO2 catalysts were prepared by wet impregnation method and evaluated for the oxidation of NO to NO2. The effects of Co amounts and calcination temperature on NO oxidation were investigated in detail. The catalytic oxidation ability in the temperature range of 403–473 K was obviously improved by doping cobalt into Mn/TiO2. These samples were characterized by nitrogen adsorption-desorption, X-ray diffraction (XRD, X-ray photoelectron spectroscopy (XPS, transmission electron microscope (TEM and hydrogen temperature programmed reduction (H2-TPR. The results indicated that the formation of dispersed Co3O4·CoMnO3 mixed oxides through synergistic interaction between Mn-O and Co-O was directly responsible for the enhanced activities towards NO oxidation at low temperatures. Doping of Co enhanced Mn4+ formation and increased chemical adsorbed oxygen amounts, which also accelerated NO oxidation.

Synthesis of highly efficient Mn2O3 catalysts for CO oxidation derived from Mn-MIL-100

Science.gov (United States)

Zhang, Xiaodong; Li, Hongxin; Hou, Fulin; Yang, Yang; Dong, Han; Liu, Ning; Wang, Yuxin; Cui, Lifeng

2017-07-01

In this work, metal-organic frameworks (MOFs) Mn-MIL-100 were first prepared, which were next used as templates to obtain the irregular porous Mn2O3 cubes through calcination with air at different temperature. The catalysts were characterized by N2 adsorption-desorption, X-ray diffraction (XRD), scanning electron microscope (SEM), transmission electron microscopy (TEM), H2-temperature program reduction (H2-TPR) and X-ray photoelectron spectroscopic (XPS). The catalytic activity for CO oxidation over Mn2O3 catalysts was investigated. It was found that calcination temperature had a strong effect on the structure and catalytic activity of Mn2O3 catalyst. Mn2O3 catalyst obtained by calcined at 700 °C (Mn2O3-700) showed a smaller specific surface area, but displayed a high catalytic activity and excellent stability with a complete CO conversion temperature (T98) of 240 °C, which was attributed to the unique structure, a high quantity of surface active oxygen species, smaller particle size, oxygen vacancies and good low temperature reduction behavior. The effect of water vapor on catalytic activity was also examined. The introduction of water vapor to the feedstock induced a positive effect on CO oxidation over Mn2O3-700 catalyst. Furthermore, no obvious drop is observed in activity over catalysts even in the presence of water vapor during 48 h.

Tuning the magnetocaloric properties of La0.7Ca0.3MnO3 manganites through Ni-doping

Science.gov (United States)

Gómez, A.; Chavarriaga, E.; Supelano, I.; Parra, C. A.; Morán, O.

2018-04-01

The effect of Ni2+ doping on the magnetic and magnetocaloric properties of La0.7Ca0.3MnO3 manganites synthesized via the auto-combustion method is reported. The aim of studying Ni2+-substituted La0.7Ca0.3Mn1 - xNixO3 (x = 0 , 0.02 , 0.07, and 0.1) manganites was to explore the possibility of increasing the operating temperature range for the magnetocaloric effect through tuning of the magnetic transition temperature. X-ray diffraction analysis confirmed the phase purity of the synthesized samples. The substitution of Mn3+ ions by Ni2+ ions in the La0.7Ca0.3MnO3 lattice was also corroborated through this technique. The dependence of the magnetization on the temperature reveals that all the compositions exhibit a well-defined ferromagnetic to paramagnetic transition near the Curie temperature. A systematic decrease in the values of the Curie temperature is clearly observed upon Ni2+ doping. Probably the replacement of Mn3+ by Ni2+ ions in the La0.7Ca0.3MnO3 lattice weakens the Mn3+-O-Mn4+ double exchange interaction, which leads to a decrease in the transition temperature and the magnetic moment in the samples. By using Arrott plots, it was found that the phase transition from ferromagnetic to paramagnetic is second order. The maximum magnetic entropy changes observed for the x = 0 , 0.02 , 0.07, and 0.1 composites was 0.85, 0.77, 0.63, and 0.59 J/kg K, respectively, under a magnetic field of 1.5 T. In general, it was verified that the magnetic entropy change achieved for La0.7Ca0.3Mn1 - xNixO3 manganites synthesized via the auto-combustion method is higher than those reported for other manganites with comparable Ni2+-doping levels synthesized via standard solid state reaction. The addition of Ni2+ increases the value of the relative cooling power as compared to that of the parent compound. The highest value of this parameter (∼60 J/kg) is found for a Ni-doping level of 2% around 230 K in a field of 1.5 T.

A study of the phase transition and magnetocaloric effect in multiferroic La{sub 2}MnNiO{sub 6} single crystals

Energy Technology Data Exchange (ETDEWEB)

Balli, M., E-mail: mohamed.balli@usherbrooke.ca; Jandl, S. [Regroupement québécois sur les matériaux de pointe, Département de physique, Université de Sherbrooke, Quebec J1K 2R1 (Canada); Fournier, P. [Regroupement québécois sur les matériaux de pointe, Département de physique, Université de Sherbrooke, Quebec J1K 2R1 (Canada); Canadian Institute for Advanced Research, Toronto, Ontario M5G 1Z8 (Canada); Gospodinov, M. M. [Institute of Solid State Physics, Bulgarian Academy of Science, Sofia 1184 (Bulgaria)

2014-05-07

Magnetic and magnetocaloric properties of single crystal double perovskite La{sub 2}MnNiO{sub 6} have been investigated in details. Its ordered phase with a high Curie temperature (T{sub C} = 280 K) exhibits a significant refrigerant capacity around room temperature. A model based on the mean field theory approximation has been used in order to quantify the magnetic and magnetocaloric properties in the ordered La{sub 2}MnNiO{sub 6}. The magnetization and entropy changes were satisfactorily simulated as a function of temperature and magnetic field. On the other hand, the presence of cationic disorder in La{sub 2}MnNiO{sub 6} phases allows to shift the Curie point to low temperature without a significant change in the magnetocaloric performance.

Characterization of High Dose Mn, Fe, and Ni implantation into p-GaN

CERN Document Server

Pearton, S J; Thaler, G; Abernathy, C R; Theodoropoulou, N; Hebard, A F; Chu, S N G; Wilson, R G; Zavada, J M; Polyakov, A Y; Osinsky, A V; Norris, P E; Chow, P P; Wowchack, A M; Hove, J M V; Park, Y D

2002-01-01

The magnetization of p-GaN or p-AlGaN/GaN superlattices was measured after implantation with high doses (3-5x10 sup 1 sup 6 cm sup - sup 2) of Mn, Fe, or Ni and subsequent annealing at 700-1000 deg. C. The samples showed ferromagnetic contributions below temperatures ranging from 190-250 K for Mn to 45-185 K for Ni and 80-250 K for Fe. The use of superlattices to enhance the hole concentration did not produce any change in ferromagnetic ordering temperature. No secondary phase formation was observed by x-ray diffraction, transmission electron microscopy, or selected area diffraction pattern analysis for the doses we employed.

Dopant driven tunability of dielectric relaxation in MxCo(1-x)Fe2O4 (M: Zn2+, Mn2+, Ni2+) nano-ferrites

Science.gov (United States)

Datt, Gopal; Abhyankar, A. C.

2017-07-01

Nano-ferrites with tunable dielectric and magnetic properties are highly desirable in modern electronics industries. This work reports the effect of ferromagnetic (Ni), anti-ferromagnetic (Mn), and non-magnetic (Zn) substitution on cobalt-ferrites' dielectric and magnetic properties. The Rietveld analysis of XRD data and the Raman spectroscopic study reveals that all the samples are crystallized in the Fd-3m space group. The T2g Raman mode was observed to split into branches, which is due to the presence of different cations (with different vibrational frequencies) at crystallographic A and B-sites. The magnetization study shows that the MnCoFe2O4 sample has the highest saturation magnetization of 87 emu/g, which is attributed to the presence of Mn2+ cations at the B-site with a magnetic moment of 5 μB. The dielectric permittivity of these nanoparticles (NPs) obeys the modified Debye model, which is further supported by Cole-Cole plots. The dielectric constant of MnCoFe2O4 ferrite is found to be one order higher than that of the other two ferrites. The increased bond length of the Mn2+-O2- bond along with the enhanced d-d electron transition between Mn 2 +/Co 2 +⇋Fe 3 + cations at the B-site are found to be the main contributing factors for the enhanced dielectric constant of MnCoFe2O4 ferrite. We find evidence of variable-range hopping of localized polarons in these ferrite NPs. The activation energy, hopping range, and density of states N (" separators="|EF ), of these polarons were calculated using Motts' 1/4th law. The estimated activation energies of these polarons at 300 K were found to be 288 meV, 426 meV, and 410 meV, respectively, for the MnCoFe2O4, NiCoFe2O4, and ZnCoFe2O4 ferrite NPs, while the hopping range of these polarons were found to be 27.14 Å, 11.66 Å, and 8.17 Å, respectively. Observation of a low dielectric loss of ˜0.04, in the frequency range of 0.1-1 MHz, in these NPs makes them potential candidates for energy harvesting devices in

Preparation and Characterization of Mn/N Co-Doped TiO2 Loaded on Wood-Based Activated Carbon Fiber and Its Visible Light Photodegradation

Directory of Open Access Journals (Sweden)

Xiaojun Ma

2015-09-01

Full Text Available Using MnSO4·H2O as manganese source and urea as nitrogen source, Mn/N co-doped TiO2 loaded on wood-based activated carbon fiber (Mn/Ti-N-WACF was prepared by sol–gel method. Mn/Ti-N-WACF with different Mn doping contents was characterized by scanning electron microscopy, X-ray diffraction (XRD and X-ray photoelectron spectroscopies (XPS, and ultraviolet-visible spectrophotometer. Results showed that the loading rate of TiO2 in Mn/Ti-N-WACF was improved by Mn/N co-doping. After calcination at 450 °C, the degree of crystallinity of TiO2 was reduced due to Mn/N co-doption in the resulting Mn/Ti-N-WACF samples, but the TiO2 crystal phase was not changed. XPS spectra revealed that some Ti4+ ions from the TiO2 lattice of Mn/Ti-N-WACF system were substituted by doped Mn. Moreover, new bonds formed within N–Ti–N and Ti–N–O because of the doped N that substituted some oxygen atoms in the TiO2 lattice. Notably, the degradation rate of methylene blue for Mn/Ti-N-WACF was improved because of the co-doped Mn/N under visible-light irradiation.

Martensitic transformation and magnetic properties of manganese-rich Ni-Mn-In and Ni-Mn-Sn Heusler alloys

International Nuclear Information System (INIS)

Krenke, T.

2007-01-01

In the present work, the martensitic transition and the magnetic properties of Manganese rich Ni 50 Mn 50-x Sn x and Ni 50 Mn 50-y In y alloys with 5 at%≤x(y)≤25 at% were investigated. Calorimetry, X-ray and neutron diffraction, magnetization, and strain measurements were performed on polycrystalline samples. It was shown that alloys close to the stoichiometric composition Ni 50 Mn 25 Sn 25 and Ni 50 Mn 25 Sn 25 do not exhibit a structural transition on lowering of the temperature, whereas alloys with x≤15 at% Tin and y≤16 at% Indium transform martensitically. The structural transition temperatures increase linearly with decreasing Tin or Indium content. The crystal structures of the low temperature martensite are modulated as well as unmodulated. Alloys with compositions close to stoichiometry are dominated by ferromagnetic interactions, whereas those close to the binary composition Ni 50 Mn 50 order antiferromagnetically. Ferromagnetic order and structural instability coexist in a narrow composition range between 13 at%≤x≤15 at% and 15 at%≤x≤16 at% for Ni 50 Mn 50-x Sn x and Ni 50 Mn 50-y In y respectively. As a consequence, interesting magnetoelastic effects are observed. The Ni 50 Mn 34 In 16 alloy shows a magnetic field-induced structural transition, whereby application of an external magnetic field in the martensitic state stabilizes the high temperature L2 1 structure. Evidence for this was given by neutron diffraction experiments in external magnetic fields. Moreover, the structural transition temperatures of this alloy show large magnetic field dependencies. By use of calorimetry, M(T), and strain measurements, changes in M s up to -11 K/Tesla are observed. Such large values have, until now, not been observed in Heusler alloys. Since during transformation the volume changes reversibly, magnetic field-induced strains of about 0.12 % appear. Additionally, the alloys Ni 50 Mn 35 Sn 15 , Ni 50 Mn 37 Sn 13 , Ni 50 Mn 34 In 16 , Ni 51.5 Mn 33 In

Physical investigations on NiMn{sub 2}O{sub 4} sprayed magnetic spinel for sensitivity applications

Energy Technology Data Exchange (ETDEWEB)

Larbi, T.; Amara, A.; Ouni, B. [Unité de physique des dispositifs a semi-conducteurs, Faculté des sciences de Tunis, Tunis El Manar University, 2092 Tunis (Tunisia); Inoubli, A. [Faculté des Sciences de Bizerte Laboratoire de Physique des Matériaux Département de Physique, Zarzouna, 7021 Bizerte (Tunisia); Karyaoui, M. [Laboratoire de photovoltaïque, Centre de Recherches et des Technologies de l’Énergie, Technopole de Borj-Cédria BP 95, 2050 Hammam-Lif (Tunisia); Yumak, A. [Physics Department, Faculty of Arts and Sciences, Marmara University, Göztepe, 34722 Istanbul (Turkey); Saadallah, F. [Phothermal laboratory IPEIN, Mrezka, BP 62, 8000 Nabeul (Tunisia); Boubaker, K., E-mail: mmbb11112000@yahoo.fr [Unité de physique des dispositifs a semi-conducteurs, Faculté des sciences de Tunis, Tunis El Manar University, 2092 Tunis (Tunisia); Amlouk, M. [Unité de physique des dispositifs a semi-conducteurs, Faculté des sciences de Tunis, Tunis El Manar University, 2092 Tunis (Tunisia)

2015-08-01

NiMn{sub 2}O{sub 4} ternary nickel manganese oxide thin films spinels have been grown on glass substrates at 350 °C through spray pyrolysis technique. X-ray diffraction and Raman spectroscopy analyses show that the synthesized film has mainly cubic spinel structure with a preferred orientation along (111) plane. Some optical constants such as the refractive index (n), extinction coefficient (k), Urbach energy (E{sub U}=342 eV) and optical energy band gap (E{sub g}=1.07 eV) have been calculated from reflection-transmission spectra. The mirage effect technique has been used to estimate the thermal conductivity (K{sub c}). Its value is K{sub c}=25 W m{sup −1} K{sup −1}. The real part of the ac the conductivity behaviour has been investigated in the frequency range 100 Hz to 1 MHz. It was found that the real conductivity follows a power law (Aω{sup s}). The dc conductivity has been studied in the temperature range from 250 °C to 375 °C and supports the variable range hopping model proposed by Mott. The activation energy value estimated from the relaxation frequency is Ea~0.32 eV. Moreover, the temperature dependency of the resistance indicates that conduction was well described by a variable range hopping model, in which electron transfer takes place between Mn{sup 3+} and Mn{sup 4+} ions. - Highlights: • The nickel manganese oxide (NiMn{sub 2}O{sub 4}) has been prepared by the low-cost spray pyrolysis technique. • The optical band gap of this ternary oxide is around 1 eV and the crystallites are oriented preferentially along (111) direction. • Presenting an accurate technique “Mirage effect” for original investigation of thermal properties. • DC and AC conductivity can be both attributed to a hopping transport, while at high frequency a metallic-like behavior is observed. • A deep analysis within correlated barrier hopping (CBH) model was carried out. • Outlining a correlation between Magnetic and electrical properties.

Versatility of MnO2 for lithium battery applications

CSIR Research Space (South Africa)

Thackeray, MM

1993-03-15

Full Text Available , layered-MnO2, spinel-related Li2O.yMnO2 (y > = 2.5) and ramsdellite-MnO2 materials. An attempt has been made to clarify issues relating to the structural features of 'CDMO'-type materials that are prepared by the reaction of gamma-MnO2 with LiNO3 (or Li...

Martensitic transformation and magnetic properties of manganese-rich Ni-Mn-In and Ni-Mn-Sn Heusler alloys; Untersuchung der martensitischen Umwandlung und der magnetischen Eigenschaften Mangan-reicher Ni-Mn-In- und Ni-Mn-Sn-Heusler-Legierungen

Energy Technology Data Exchange (ETDEWEB)

Krenke, T.

2007-06-29

In the present work, the martensitic transition and the magnetic properties of Manganese rich Ni{sub 50}Mn{sub 50-x}Sn{sub x} and Ni{sub 50}Mn{sub 50-y}In{sub y} alloys with 5 at%{<=}x(y){<=}25 at% were investigated. Calorimetry, X-ray and neutron diffraction, magnetization, and strain measurements were performed on polycrystalline samples. It was shown that alloys close to the stoichiometric composition Ni{sub 50}Mn{sub 25}Sn{sub 25} and Ni{sub 50}Mn{sub 25}Sn{sub 25} do not exhibit a structural transition on lowering of the temperature, whereas alloys with x{<=}15 at% Tin and y{<=}16 at% Indium transform martensitically. The structural transition temperatures increase linearly with decreasing Tin or Indium content. The crystal structures of the low temperature martensite are modulated as well as unmodulated. Alloys with compositions close to stoichiometry are dominated by ferromagnetic interactions, whereas those close to the binary composition Ni{sub 50}Mn{sub 50} order antiferromagnetically. Ferromagnetic order and structural instability coexist in a narrow composition range between 13 at%{<=}x{<=}15 at% and 15 at%{<=}x{<=}16 at% for Ni{sub 50}Mn{sub 50-x}Sn{sub x} and Ni{sub 50}Mn{sub 50-y}In{sub y} respectively. As a consequence, interesting magnetoelastic effects are observed. The Ni{sub 50}Mn{sub 34}In{sub 16} alloy shows a magnetic field-induced structural transition, whereby application of an external magnetic field in the martensitic state stabilizes the high temperature L2{sub 1} structure. Evidence for this was given by neutron diffraction experiments in external magnetic fields. Moreover, the structural transition temperatures of this alloy show large magnetic field dependencies. By use of calorimetry, M(T), and strain measurements, changes in M{sub s} up to -11 K/Tesla are observed. Such large values have, until now, not been observed in Heusler alloys. Since during transformation the volume changes reversibly, magnetic field-induced strains of about

Leaching process for recovering valuable metals from the LiNi1/3Co1/3Mn1/3O2 cathode of lithium-ion batteries.

Science.gov (United States)

He, Li-Po; Sun, Shu-Ying; Song, Xing-Fu; Yu, Jian-Guo

2017-06-01

In view of the importance of environmental protection and resource recovery, recycling of spent lithium-ion batteries (LIBs) and electrode scraps generated during manufacturing processes is quite necessary. An environmentally sound leaching process for the recovery of Li, Ni, Co, and Mn from spent LiNi 1/3 Co 1/3 Mn 1/3 O 2 -based LIBs and cathode scraps was investigated in this study. Eh-pH diagrams were used to determine suitable leaching conditions. Operating variables affecting the leaching efficiencies for Li, Ni, Co, and Mn from LiNi 1/3 Co 1/3 Mn 1/3 O 2 , such as the H 2 SO 4 concentration, temperature, H 2 O 2 concentration, stirring speed, and pulp density, were investigated to determine the most efficient conditions for leaching. The leaching efficiencies for Li, Ni, Co, and Mn reached 99.7% under the optimized conditions of 1M H 2 SO 4 , 1vol% H 2 O 2 , 400rpm stirring speed, 40g/L pulp density, and 60min leaching time at 40°C. The leaching kinetics of LiNi 1/3 Co 1/3 Mn 1/3 O 2 were found to be significantly faster than those of LiCoO 2 . Based on the variation in the weight fraction of the metal in the residue, the "cubic rate law" was revised as follows: θ(1-f) 1/3 =(1-kt/r 0 ρ), which could characterize the leaching kinetics optimally. The activation energies were determined to be 64.98, 65.16, 66.12, and 66.04kJ/mol for Li, Ni, Co, and Mn, respectively, indicating that the leaching process was controlled by the rate of surface chemical reactions. Finally, a simple process was proposed for the recovery of valuable metals from spent LiNi 1/3 Co 1/3 Mn 1/3 O 2 -based LIBs and cathode scraps. Copyright © 2017 Elsevier Ltd. All rights reserved.

Synthesis and characterization of new fluoride-containing manganese vanadates A{sub 2}Mn{sub 2}V{sub 2}O{sub 7}F{sub 2} (A=Rb, Cs) and Mn{sub 2}VO{sub 4}F

Energy Technology Data Exchange (ETDEWEB)

Sanjeewa, Liurukara D. [Department of Chemistry and Center for Optical Materials Science and Engineering Technologies (COMSET), Clemson University, Clemson, SC 29634-0973 (United States); McGuire, Michael A. [Materials Science and Technology Division, Oak Ridge National Laboratory, Oak Ridge, TN 37831 (United States); Smith Pellizzeri, Tiffany M.; McMillen, Colin D. [Department of Chemistry and Center for Optical Materials Science and Engineering Technologies (COMSET), Clemson University, Clemson, SC 29634-0973 (United States); Ovidiu Garlea, V. [Quantum Condensed Matter Division, Oak Ridge National Laboratory, Oak Ridge, TN 37831 (United States); Willett, Daniel; Chumanov, George [Department of Chemistry and Center for Optical Materials Science and Engineering Technologies (COMSET), Clemson University, Clemson, SC 29634-0973 (United States); Kolis, Joseph W., E-mail: kjoseph@clemson.edu [Department of Chemistry and Center for Optical Materials Science and Engineering Technologies (COMSET), Clemson University, Clemson, SC 29634-0973 (United States)

2016-09-15

Large single crystals of A{sub 2}Mn{sub 2}V{sub 2}O{sub 7}F{sub 2} (A=Rb, Cs) and Mn{sub 2}VO{sub 4}F were grown using a high-temperature (~600 °C) hydrothermal technique. Single crystal X-ray diffraction and powder X-ray diffraction were utilized to characterize the structures, which both possess MnO{sub 4}F{sub 2} building blocks. The A{sub 2}Mn{sub 2}V{sub 2}O{sub 7}F{sub 2} series crystallizes as a new structure type in space group Pbcn (No. 60), Z=4 (Rb{sub 2}Mn{sub 2}V{sub 2}O{sub 7}F{sub 2}: a=7.4389(17) Å, b=11.574(3) Å, c=10.914(2) Å; Cs{sub 2}Mn{sub 2}V{sub 2}O{sub 7}F{sub 2}: a=7.5615(15) Å, b=11.745(2) Å, c=11.127(2) Å). The structure is composed of zigzag chains of edge-sharing MnO{sub 4}F{sub 2} units running along the a-axis, and interconnected through V{sub 2}O{sub 7} pyrovanadate groups. Temperature dependent magnetic susceptibility measurements on this interesting one-dimensional structural feature based on Mn{sup 2+} indicated that Cs{sub 2}Mn{sub 2}V{sub 2}O{sub 7}F{sub 2} is antiferromagnetic with a Neél temperature, T{sub N}=~3 K and a Weiss constant, θ, of −11.7(1) K. Raman and infrared spectra were also analyzed to identify the fundamental V–O vibrational modes in Cs{sub 2}Mn{sub 2}V{sub 2}O{sub 7}F{sub 2}. Mn{sub 2}(VO{sub 4})F crystalizes in the monoclinic space group of C2/c (no. 15), Z=8 with unit cell parameters of a=13.559(2) Å, b=6.8036(7) Å, c=10.1408(13) Å and β=116.16(3)°. The structure is associated with those of triplite and wagnerite. Dynamic fluorine disorder gives rise to complex alternating chains of five-and six-coordinate Mn{sup 2+}. These interpenetrating chains are additionally connected through isolated VO{sub 4} tetrahedra to form the condensed structure. - Graphical abstract: New vanadate fluorides A{sub 2}Mn{sub 2}V{sub 2}O{sub 7}F{sub 2} (A=Rb, Cs) and Mn{sub 2}(VO{sub 4})F have been synthesized hydrothermally. Upon cooling, the one-dimensional Mn(II) substructure results in antiferromagnetic

Magnetic properties of NiMn2O4−δ (nickel manganite): Multiple magnetic phase transitions and exchange bias effect

International Nuclear Information System (INIS)

Tadic, Marin; Savic, S.M.; Jaglicic, Z.; Vojisavljevic, K.; Radojkovic, A.; Prsic, S.; Nikolic, Dobrica

2014-01-01

Highlights: • We have successfully synthesized NiMn 2 O 4−δ sample by complex polymerization synthesis. • Magnetic measurements reveal complex properties and triple magnetic phase transitions. • Magnetic measurements of M(H) show hysteretic behavior below 120 K. • Hysteresis properties after cooling of the sample in magnetic field show exchange bias effect. -- Abstract: We present magnetic properties of NiMn 2 O 4−δ (nickel manganite) which was synthesized by complex polymerization synthesis method followed by successive heat treatment and final calcinations in air at 1200 °C. The sample was characterized by using X-ray powder diffractometer (XRPD), scanning electron microscopy (SEM), field-emission scanning electron microscopy (FE-SEM) and superconducting quantum interference device (SQUID) magnetometer. The XRPD and FE-SEM studies revealed NiMn 2 O 4−δ phase and good crystallinity of particles. No other impurities have been observed by XRPD. The magnetic properties of the sample have been studied by measuring the temperature and field dependence of magnetization. Magnetic measurements of M(T) reveal rather complex magnetic properties and multiple magnetic phase transitions. We show three magnetic phase transitions with transition temperatures at T M1 = 35 K (long-range antiferromagnetic transition), T M2 = 101 K (antiferromagnetic-type transition) and T M3 = 120 K (ferromagnetic-like transition). We found that the T M1 transition is strongly dependent on the strength of the applied magnetic field (T M1 decreases with increasing applied field) whereas the T M3 is field independent. Otherwise, the T M2 maximum almost disappears in higher applied magnetic fields (H = 1 kOe and 10 kOe). Magnetic measurements of M(H) show hysteretic behavior below T M3 . Moreover, hysteresis properties measured after cooling of the sample in magnetic field of 10 kOe show exchange bias effect with an exchange bias field |H EB |=196 Oe. In summary, the properties that

Single Crystal Growth of Multiferroic Double Perovskites: Yb2CoMnO6 and Lu2CoMnO6

Directory of Open Access Journals (Sweden)

Hwan Young Choi

2017-02-01

Full Text Available We report on the growth of multiferroic Yb2CoMnO6 and Lu2CoMnO6 single crystals which were synthesized by the flux method with Bi2O3. Yb2CoMnO6 and Lu2CoMnO6 crystallize in a double-perovskite structure with a monoclinic P21/n space group. Bulk magnetization measurements of both specimens revealed strong magnetic anisotropy and metamagnetic transitions. We observed a dielectric anomaly perpendicular to the c axis. The strongly coupled magnetic and dielectric states resulted in the variation of both the dielectric constant and the magnetization by applying magnetic fields, offering an efficient approach to accomplish intrinsically coupled functionality in multiferroics.

Physicochemical properties of 3,4,5-trimethoxybenzoates of Mn(II, Co(II, Ni(II and Zn(II

Directory of Open Access Journals (Sweden)

W. FERENC

2005-09-01

Full Text Available The complexes of Mn(II, Co(II, Ni(II, Cu(II and Zn(II with 3,4,5-trimethoxybenzoic acid anion of the formula: M(C10H11O52·nH2O, where n = 6 for Ni(II, n = 1 for Mn(II, Co(II, Cu(II, and n = 0 for Zn, have been synthesized and characterized by elemental analysis, IR spectroscopy, X–ray diffraction measurements, thermogravimetry and magnetic studies. They are crystalline compounds characterized by various symmetry. They decompose in various ways when heated in air to 1273 K. At first, they dehydrate in one step and form anhydrous salts. The final products of decomposition are oxides of the respective metals (Mn2O3, Co3O4, NiO, CuO, ZnO. The solubilities of the analysed complexes in water at 293 K are in the orders of 10-2 – 10-4 mol dm-3. The magnetic susceptibilities of the Mn(II, Co(II, Ni(II and Cu(II complexes were measured over the range of 76–303 K and the magnetic moments were calculated. The results show that the 3,4,5-trimethoxybenzoates of Mn(II, Co(II and Ni(II are high-spin complexes but that of Cu(II forms a dimer [Cu2(C10H11O54(H2O2]. The carboxylate groups bind as monodentate or bidentate chelating or bridging ligands.

Orbital-Specific observation of O2p and Ni3d electrons in LiNi0.5Mn0.5O2, a cathode material for lithium-ion batteries

Science.gov (United States)

Satou, Yoshinori; Komine, Shigeki; Shimizu, Sumera

2017-09-01

Cathode materials for lithium-ion batteries containing Ni2+ have attracted much interest because of their high theoretical capacity. However, the precise electronic structures of these cathode materials have not yet been clearly observed, especially the energy positions of the O2p and Ni3d orbitals and the shape of the density of states. The aim of this study was to investigate the relative energy positions and shape of the density of states of O2p and Ni3d for LiNi0.5Mn0.5O2 experimentally. We cleaved a LiNi0.5Mn0.5O2 pellet in an Ar-filled glove box and performed synchrotron ultraviolet photoelectron spectroscopy for different photon energies, which enabled us to investigate the relative cross-section intensity of O2p and Ni3d. As a result, the valence-band structure was determined. We found that O2p electrons are itinerant and exist in the vicinity of the Fermi energy more than Ni3d electrons. Ni3d electrons are more localized and spread mainly from 1.2-1.5 eV below the Fermi energy. To validate the electronic structure, we measured the synchrotron O K-edge X-ray absorption fine structure of electrochemically lithium-extracted LiNi0.5Mn0.5O2. The electronic structure demonstrated that ligand holes in the oxygen atoms form below the Fermi level during the initial stage of Li extraction and that the formation rate of the holes decreases with Li extraction.

Investigation on electronic and magnetic properties of Mn2NiAl by ab initio calculations and Monte Carlo simulations

International Nuclear Information System (INIS)

Masrour, R.; Jabar, A.; Hlil, E.K.; Hamedoun, M.; Benyoussef, A.; Hourmatallah, A.; Rezzouk, A.; Bouslykhane, K.; Benzakour, N.

2017-01-01

Self-consistent ab initio calculations, based on Density Functional Theory (DFT) approach and using Full potential Linear Augmented Plane Wave (FLAPW) method, are performed to investigate both electronic and magnetic properties of the Mn 2 NiAl. Magnetic moment considered to lie along (001) axes are computed. Obtained data from ab initio calculations are used as input for Monte Carlo simulations to compute other magnetic parameters. Also, the magnetic properties of Mn 2 NiAl are studied using the Monte Carlo simulations. The variation of magnetization and magnetic susceptibility with the reduced temperature of Mn 2 NiAl are investigated. The transition temperature of this system is deduced for different values exchange interaction and crystal field. The thermal total magnetization has been obtained, and the magnetic hysteresis cycle is established. The total magnetic moment is superior to those obtained by the other method and is mainly determined by the antiparallel aligned Mn I , Mn II and Ni spin moments. The superparamagnetic phase is found at the neighborhood of transition temperature. - Highlights: • Ab initio calculations are used to study magnetic and electronic properties of Mn 2 NiX. • The transition temperature of Mn 2 NiX is established. • The magnetic hysteresis cycle of M n2 NiX (X = Al, Ga, In, Sn) is deduced. • The magnetic coercive field of Mn 2 NiX (X = Al, Ga, In, Sn) is given.

Three NiAs-Ni 2In Type Structures in the Mn-Sn System

Science.gov (United States)

Elding-Pontén, Margareta; Stenberg, Lars; Larsson, Ann-Kristin; Lidin, Sven; Ståhl, Kenny

1997-03-01

TheB8-type structure field of the Mn-Sn system has been investigated. Two high temperature phases (HTP1 and HTP2) and one low temperature phase (Mn3Sn2) were found. They all crystallize with the NiAs structure type with part of the trigonal bipyramidal interstices filled by manganese atoms in an ordered manner. The ordering as well as the manganese content is different for the three phases, giving rise to three different orthorhombic superstructures. Mn3Sn2seems to have the lowest manganese content, since the corresponding basal unit cell is smaller than for HTP1-2. Structural models of the phases are based on selected area electron diffraction, X-ray powder diffraction, and preliminary single crystal X-ray measurements. The ideal cell parameters found are (a=7ahex,b=3ahex,c=chex), (a=5ahex,b=3ahex,c=chex), and (a=2ahex,b=3ahex,c=chex) for HTP1, HTP2, and Mn3Sn2, respectively. The crystal structure of Mn3Sn2has been refined by means of the Rietveld method from X-ray powder diffraction data. Mn3Sn2is orthorhombic,Pnma,a=7.5547(2),b=5.4994(2),c=8.5842(2) Å,Z=4. (Pbnmin the setting above.) The compound is isostructural with Ni3Sn2andγ‧-Co3Sn2(H. Fjellvåg and A. Kjekshus,Acta Chem. Scand.A40, 23-30 (1986)). FinalRp=8.97%,Rwp=11.44%, GOF=2.86, andRBragg=4.11% using 43 parameters and 5701 observations and 330 Bragg reflections.

One-pot synthesis of a Ni–Mn3O4 nanocomposite for supercapacitors

International Nuclear Information System (INIS)

Xu, Guo-rong; Shi, Jin-jin; Dong, Wen-hao; Wen, Ya; Min, Xiang-ping; Tang, An-ping

2015-01-01

Highlights: • Ni–Mn 3 O 4 nanocomposites have been synthesized simply. • Mn 3 O 4 particles were deposited on surface of Ni particles with OH functional groups. • Ni–Mn 3 O 4 composites could be quickly conditioned to birnessite-type MnO 2 . • A specific capacitance of 230 F g −1 was obtained for Ni (17.3%)–Mn 3 O 4 nanocomposite. - Abstract: Ni–Mn 3 O 4 nanocomposite has been prepared successfully by chemical oxidation in an alkaline solution of Mn 2+ on the surface of Ni nanoparticles with OH functional groups using one-pot method. The obtained Ni–Mn 3 O 4 nanocomposite was characterized using a scanning electron microscope (SEM), a transmission electron microscope (TEM), X-ray diffraction (XRD) analysis and various electrochemical techniques, such as cyclic voltammetry (CV), galvanostatic charge/discharge (GC/D) and electrochemical impedance spectroscopy (EIS). The average crystal sizes of Mn 3 O 4 were found to decrease linearly with increasing Ni content in the Ni–Mn 3 O 4 composite. The Ni–Mn 3 O 4 nanocomposite could be easily conditioned and inverted to birnessite-type MnO 2 . A specific capacitance of 230 F g −1 (based on pure Mn 3 O 4 ) was obtained for the Ni (17.3%)–Mn 3 O 4 nanocomposite at a current rate of 0.25 A g −1 , and 94% of the initial capacitance was retained after 1000 GC/D cycles at a current rate of 1 A g −1 . It is concluded that the Ni–Mn 3 O 4 nanocomposite is a promising electrode materials for supercapacitors

Novel detached system to MnCO3 nanowires: A self-sacrificing template for homomorphous Mn3O4 and α-Mn2O3 nanostructures

International Nuclear Information System (INIS)

Lei Shuijin; Peng Xiaomin; Li Xiuping; Liang Zhihong; Yang Yi; Cheng Baochang; Xiao Yanhe; Zhou Lang

2011-01-01

Research highlights: → A novel detached system along with solvothermal treatment was developed. → Radially aggregated MnCO 3 nanowires were successfully fabricated. → The detached system, solvent, surfactant and reaction time were important. → MnCO 3 nanowires could act as the self-sacrificing template for Mn 3 O 4 and α-Mn 2 O 3 . - Abstract: MnCO 3 , an important raw material, exhibits attractive properties and significant industrial applications. However, few concerns have been raised on the fabrication of its 1D nanostructures. In this paper, a novel detached system was successfully employed for the preparation of MnCO 3 nanowires by a surfactant-assisted solvothermal treatment using N,N-dimethylformamide as the solvent and cetyltrimethylammonium bromide as the surfactant. X-ray powder diffraction, scanning electron microscopy and transmission electron microscopy were employed to study the crystal structure and morphologies of the products. Experiments showed that the detached system, solvent, surfactant and reaction time were critical for the formation of the MnCO 3 nanowires. The thermal characterization was studied by differential scanning calorimetric analysis and thermogravimetric analysis measurements. The experimental results demonstrated that the as-prepared MnCO 3 nanocrystals can act as an efficient precursor for production of homomorphous Mn 3 O 4 and α-Mn 2 O 3 nanostructures by calcination at 400 deg. C under the atmosphere of argon and air, respectively. A possible growth mechanism for the MnCO 3 nanowires was also proposed.

Synthesis and characterization of Co and Mn doped NiO nanoparticles

Energy Technology Data Exchange (ETDEWEB)

Vallalperuman, Kaliyan; Parthibavarman, Mathivanan; Sathishkumar, Sekar; Durairaj, Manickam [Mahendra Engineering College, Tiruchengode (India); Thavamani, Kuppusamy [AVS Technical Campus,, Salem (India)

2014-04-15

Diluted magnetic semiconductors (DMS) are intensively studied for their potential spintronics applications, especially those with Curie temperature above the room temperature. Ni{sub 1-x}Mn{sub x}O and Ni{sub 1-x}Co{sub x}O (x=1% and 2%), nanoparticles with size around 40-50 nm, were prepared by co-precipitation method. An NiO single phase structure was confirmed by powder X-ray diffraction measurements. Also, diffraction peaks show a systematic shift towards higher angle with an increase in Mn concentration, which is associated with the lattice variation. The samples were pelleted and examined for its magnetic property using a vibrating sample magnetometer (VSM); it indicates paramagnetic-like behavior at room temperature. The increase in a.c conductivity with increasing temperature is attributed to the increase in drift mobility of the charge carriers.

Preparation of layered oxide Li(Co1/3Ni1/3Mn1/3)O2 via the sol-gel process

Institute of Scientific and Technical Information of China (English)

ZHANG Wen; LIU Hanxing; HU Chen; ZHU Xianjun; LI Yanxi

2008-01-01

To obtain homogenous layered oxide Li(Co1/3Ni1/3Ni1/3Mn1/3)O2 as a lithium insertion positive electrode material,the sol-gel process using citric acid as a chelating agent was applied.The material Li(Co1/3,Ni1/3Mn1/3)O2 was synthesized at different calcination temperatures.XRD experiment indicated that the hyered Li(Co1/3Ni1/3Mn1/3)O2material could he synthesized at a lower temperature of 800℃,and the oxidation state of Co,Ni,and Mn in the cathode confirmed by XPS were +3,+2,and +4,respectively.SEM observations showed that the synthesized material could form homogenous particle morphology with the particle size of about 200nm In spite of different calcination temperatures,the charge-discharge curves of all the samples for the initial cycle were similar,and the cathode synthesized at 900℃ showed a small irreversible capacity loss of 11.24% and a high discharge capacity of 212.2 mAh.g-1 in the voltage range of 2.9-4.6 V.

α-MnO2 nanowires transformed from precursor δ-MnO2 by refluxing under ambient pressure: The key role of pH and growth mechanism

International Nuclear Information System (INIS)

Zhang Qin; Xiao Zhidong; Feng Xionghan; Tan Wenfeng; Qiu Guohong; Liu Fan

2011-01-01

α-MnO 2 nanowires were obtained by reflux treatment of precursor δ-MnO 2 in acidic medium under ambient pressure. The great effects of pH on the transformation of δ-MnO 2 to α-MnO 2 and the concentration of coexistent cations (K + , Mn 2+ ) was investigated in systematically designed experiments by using powder X-ray diffraction and atomic absorption spectrometry analysis. The specific surface area of the products could be simply controlled by adjusting the initial pH value of the suspension. The micro-morphologies during the transition process from the precursors to final products were characterized by SEM and TEM. A dissolution-recrystallization mechanism was proposed to describe the growth process of the one-dimensional nanowire. MnO x units or MnO 6 octahedra was formed firstly from the dissolution of outmost surfaces of δ-MnO 2 , followed by a rearrangement/crystallization to form one-dimensional α-MnO 2 nanowire. In addition, the time-dependent process of dissolution would take place gradually from the external to internal of the precursor.

Coating effect of LiFePO4 and Al2O3 on Li1.2Mn0.54Ni0.13Co0.13O2 cathode surface for lithium ion batteries

CSIR Research Space (South Africa)

Seteni, Bonani

2017-06-01

Full Text Available Lithium-manganese-rich cathode material Li1.2Mn0.54Ni0.13Co0.13O2 is prepared by combustion method, and then coated with nano-sized LiFePO4 and nano-sized Al2O3 particles via a wet chemical process. The as-prepared Li1.2Mn0.54Ni0.13Co0.13O2, LiFePO4...

Effects of lithium-active manganese trioxide coating on the structural and electrochemical characteristics of LiNi{sub 0.5}Co{sub 0.2}Mn{sub 0.3}O{sub 2} as cathode materials for lithium ion battery

Energy Technology Data Exchange (ETDEWEB)

Li, Lingjun [School of Physics and Electronic Science, Changsha University of Science and Technology, Changsha 410114 (China); Department of Mechanical and Biomedical Engineering, City University of Hong Kong, 83 Tat Chee Avenue, Kowloon (Hong Kong); Yao, Qi [School of Physics and Electronic Science, Changsha University of Science and Technology, Changsha 410114 (China); Chen, Zhaoyong, E-mail: csullj@hotmail.com [School of Physics and Electronic Science, Changsha University of Science and Technology, Changsha 410114 (China); Song, Liubin [Hunan Provincial Key Laboratory of Materials Protection for Electric Power and Transportation, School of Chemistry and Biological Engineering, Changsha University of Science and Technology, Hunan, Changsha 410004 (China); Xie, Tian; Zhu, Huali; Duan, Junfei [School of Physics and Electronic Science, Changsha University of Science and Technology, Changsha 410114 (China); Zhang, Kaili, E-mail: kaizhang@cityu.edu.hk [Department of Mechanical and Biomedical Engineering, City University of Hong Kong, 83 Tat Chee Avenue, Kowloon (Hong Kong)

2015-11-25

Li{sub 2}MnO{sub 3}-coated LiNi{sub 0.5}Co{sub 0.2}Mn{sub 0.3}O{sub 2} materials are successfully synthesized by sol–gel method. The effects of various pH values and Li{sub 2}MnO{sub 3} contents on the structural and electrochemical properties of LiNi{sub 0.5}Co{sub 0.2}Mn{sub 0.3}O{sub 2} cathode materials are systematically investigated, respectively. Scanning electron microscope, transmission electron microscope and energy dispersive spectrometer confirm that the particles of LiNi{sub 0.5}Co{sub 0.2}Mn{sub 0.3}O{sub 2} are completely coated by crystalline Li{sub 2}MnO{sub 3} phase. Electrochemical tests show that suitable Li{sub 2}MnO{sub 3}-coated samples exhibit higher rate capacity and better cycling performance than those of the pristine one. This improvement can be attributed to the synergetic contribution from the neutral pH value and appropriate Li{sub 2}MnO{sub 3} amount. The neutral pH environment can protect the core material from damaging during the coating process and is conducive to relieving the rapid moisture uptaking problem of LiNi{sub 0.5}Co{sub 0.2}Mn{sub 0.3}O{sub 2}. While, suitable Li{sub 2}MnO{sub 3} coating can protect the bulk from directly contacting the electrolyte and offer a fast Li{sup +} diffusion path at the interface of bulk and electrolyte. - Graphical abstract: The 5% Li{sub 2}MnO{sub 3}-coated LiNi{sub 0.5}Co{sub 0.2}Mn{sub 0.3}O{sub 2} sample, modified at pH 6, exhibits a conformal and amorphous coating layer before calcination. After been sintered at 880 °C for 5 h, the sample shows Li{sub 2}MnO{sub 3} crystalline surface, as well as superior electrochemical performance. - Highlights: • Li{sub 2}MnO{sub 3}-coated LiNi{sub 0.5}Co{sub 0.2}Mn{sub 0.3}O{sub 2} is prepared by sol–gel method. • Neutral pH environment can protect NMC from damaging during the coating process. • Li{sub 2}MnO{sub 3} coating enhances the pristine at high cyclability and rate properties. • Suitable Li{sub 2}MnO{sub 3} modification results

The magnetic Curie temperature and exchange coupling between cations in tetragonal spinel oxide Mn{sub 2.5}M{sub 0.5}O{sub 4} (M = Co, Ni, Mn, Cr, and Mg) films

Energy Technology Data Exchange (ETDEWEB)

Kuo, K.; Cheng, C. W.; Chern, G. [Physics Department and SPIN Research Center, National Chung Cheng University, Chia-Yi, Taiwan, 621 (China)

2012-04-01

Mn{sub 3}O{sub 4} is a Jahn-Taller tetragonal ferrite that has a relatively low Curie temperature (T{sub c}) of {approx}43 K due to weak coupling between the canting spins. In this study, we fabricated a series of 100-nm-thick Mn{sub 2.5}M{sub 0.5}O{sub 4} (M = Co, Ni, Mn, Cr, and Mg) films via oxygen-plasma-assisted molecular beam epitaxy and measured the structural and magnetic properties of these films. These films show single phase quality, and the c-axis lattice parameter of pure Mn{sub 3}O{sub 4} is 0.944 nm, with a c/a ratio {approx}1.16, consistent with the bulk values. The replacement of Mn by M (M = Co, Ni, Cr, and Mg) changes the lattice parameters, and the c/a ratio varies between 1.16 and 1.06 depending upon the cation distribution of the films. The magnetic Curie temperatures of these films also vary in the range of 25-66 K in that Ni and Co enhance the T{sub c} whereas Mg reduces the T{sub c} (Cr shows no effect on the T{sub c}). These changes to the T{sub c} are related to both the element electronic state and the cation distributions in these compounds. As a non-collinear spin configuration can induce electrical polarization, the present study provides a systematic way to enhance the magnetic transition temperature in tetragonal spinel ferrites.

Structural, dielectric and gas sensing behavior of Mn substituted spinel MFe2O4 (M=Zn, Cu, Ni, and Co) ferrite nanoparticles

Science.gov (United States)

Ranjith Kumar, E.; Siva Prasada Reddy, P.; Sarala Devi, G.; Sathiyaraj, S.

2016-01-01

Spinel ferrite (MnZnFe2O4, MnCuFe2O4, MnNiFe2O4 and MnCoFe2O4) nanoparticles have been prepared by evaporation method. The annealing temperature plays an important role on changing particle size of the spinel ferrite nanoparticles was found out by X-ray diffraction and transmission electron microscopy. The role of manganese substitution in the spinel ferrite nanoparticles were also analyzed for different annealing temperature. The substitution of Mn also creates a vital change in dielectric properties have been measured in the frequency range of 100 kHz to 5 MHz. These spinel ferrites are decomposed to α-Fe2O3 after annealing above 550 °C in air. Through the characterization of the prepared powder, the effect of annealing temperature, chemical composition and preparation technique on the microstructure, particle size and dielectric properties of the Mn substituted spinel ferrite nanoparticles are discussed. Furthermore, Conductance response of Mn substituted MFe2O4 ferrite nanoparticles were measured by exposing the materials to reducing gas like liquefied petroleum gas (LPG).

Magnetic entropy change and critical exponents in double perovskite Y{sub 2}NiMnO{sub 6}

Energy Technology Data Exchange (ETDEWEB)

Sharma, G. [School of Physical Sciences, Jawaharlal Nehru University, New Delhi-110067 (India); Tripathi, T.S. [Inter-University Accelerator Centre, New Delhi-110067 (India); Saha, J. [School of Physical Sciences, Jawaharlal Nehru University, New Delhi-110067 (India); Patnaik, S., E-mail: spatnaik@mail.jnu.ac.in [School of Physical Sciences, Jawaharlal Nehru University, New Delhi-110067 (India)

2014-11-15

We report the magnetic entropy change (ΔS{sub M}) and the critical exponents in the double perovskite manganite Y{sub 2}NiMnO{sub 6} with a ferromagnetic to paramagnetic transition T{sub C}∼85K. For a magnetic field change ΔH=80kOe, a maximum magnetic entropy change ΔS{sub M}=−6.57J/kgK is recorded around T{sub C}. The critical exponents β=0.363±0.05 and γ=1.331±0.09 obtained from power law fitting to spontaneous magnetization M{sub S}(T) and the inverse initial susceptibility χ{sub 0}{sup −1}(T) satisfy well to values derived for a 3D-Heisenberg ferromagnet. The critical exponent δ=4.761±0.129 is determined from the isothermal magnetization at T{sub C}. The scaling exponents corresponding to second order phase transition are consistent with the exponents from Kouvel–Fisher analysis and satisfy Widom's scaling relation δ=1+(γ/β). Additionally, they also satisfy the single scaling equation M(H,ϵ)=ϵ{sup β}f±(H/ϵ{sup β+γ}) according to which the magnetization-field-temperature data around T{sub C} should collapse into two curves for temperatures below and above T{sub C}. - Highlights: • The magneto-caloric (MC) effect and the critical exponent analysis in Y{sub 2}NiMnO{sub 6} are studied. • Methods such as Kouvel–Fisher, Widom's and Mean-Field scaling are used. • The magnetic ground state in Y{sub 2}NiMnO{sub 6} is based on isotropic 3D Heisenberg model. • The large MC effect can be utilized towards magnetic refrigeration around 77 K. • The nearest neighbor interaction in Y{sub 2}NiMnO{sub 6} rules out ferroelectricity.

Synthesis of highly efficient Mn{sub 2}O{sub 3} catalysts for CO oxidation derived from Mn-MIL-100

Energy Technology Data Exchange (ETDEWEB)

Zhang, Xiaodong, E-mail: fatzhxd@126.com [Environment and Low-Carbon Research Center, School of Environment and Architecture, University of Shanghai for Science and Technology, Shanghai 200093 (China); Li, Hongxin; Hou, Fulin; Yang, Yang; Dong, Han; Liu, Ning [Environment and Low-Carbon Research Center, School of Environment and Architecture, University of Shanghai for Science and Technology, Shanghai 200093 (China); Wang, Yuxin [Institute of Applied Biotechnology, Taizhou Vocation & Technical College, Taizhou, Zhejiang 318000 (China); Cui, Lifeng, E-mail: lifeng.cui@gmail.com [Environment and Low-Carbon Research Center, School of Environment and Architecture, University of Shanghai for Science and Technology, Shanghai 200093 (China)

2017-07-31

Highlights: • The morphology of porous Mn{sub 2}O{sub 3} cubes was inherited from Mn-MIL-100 template. • Mn{sub 2}O{sub 3} obtained at calcined temperature of 700 °C displayed high activity. • Enhanced activity is attributed to surface active oxygen, and reduction behavior. - Abstract: In this work, metal-organic frameworks (MOFs) Mn-MIL-100 were first prepared, which were next used as templates to obtain the irregular porous Mn{sub 2}O{sub 3} cubes through calcination with air at different temperature. The catalysts were characterized by N{sub 2} adsorption-desorption, X-ray diffraction (XRD), scanning electron microscope (SEM), transmission electron microscopy (TEM), H{sub 2}-temperature program reduction (H{sub 2}-TPR) and X-ray photoelectron spectroscopic (XPS). The catalytic activity for CO oxidation over Mn{sub 2}O{sub 3} catalysts was investigated. It was found that calcination temperature had a strong effect on the structure and catalytic activity of Mn{sub 2}O{sub 3} catalyst. Mn{sub 2}O{sub 3} catalyst obtained by calcined at 700 °C (Mn{sub 2}O{sub 3}-700) showed a smaller specific surface area, but displayed a high catalytic activity and excellent stability with a complete CO conversion temperature (T{sub 98}) of 240 °C, which was attributed to the unique structure, a high quantity of surface active oxygen species, smaller particle size, oxygen vacancies and good low temperature reduction behavior. The effect of water vapor on catalytic activity was also examined. The introduction of water vapor to the feedstock induced a positive effect on CO oxidation over Mn{sub 2}O{sub 3}-700 catalyst. Furthermore, no obvious drop is observed in activity over catalysts even in the presence of water vapor during 48 h.

Solvothermal synthesis and electrochemical performance of Li2MnSiO4/C cathode materials for lithium ion batteries

International Nuclear Information System (INIS)

Wang, Yan-Chao; Zhao, Shi-Xi; Zhai, Peng-Yuan; Li, Fang; Nan, Ce-Wen

2014-01-01

Highlights: • Li 2 MnSiO 4 /C nanocomposite has been synthesized by the solvothermal method. • The particles of Li 2 MnSiO 4 /C are much smaller and more uniform. • The presence of Ni improves discharge capacity of Li 2 MnSiO 4 /C cathode material. • The initial discharge capacity of Ni-modified Li 2 MnSiO 4 /C is 274.5 mAh g −1 at 25 °C. - Abstract: Orthorhombic structure Li 2 MnSiO 4 /C with Pmn2 1 space group is synthesized by the solvothermal method. Carbon coating and Ni 2+ doping are used to improve the electronic conductivity and the cycling performance of Li 2 MnSiO 4 cathode material, respectively. The particles of Li 2 MnSiO 4 /C are much smaller and more uniform than those of Li 2 MnSiO 4 due to the carbon coating. It is shown that Ni 2+ has been reduced into metal Ni during the synthesis process. The synthesized Ni-modified Li 2 MnSiO 4 /C (denoted as (LMS@Ni)/C) cathode material exhibits better electrochemical performance in comparison with Li 2 MnSiO 4 /C, attributing to higher lithium ion diffusion coefficient as well as electronic conductivity. The initial discharge capacity of (LMS@Ni)/C is 274.5 mA h g −1 and the reversible capacity after 20 cycles is 119.8 mA h g −1 at 25 °C

NO adsorption behaviors of the MnO{sub x} catalysts in lean-burn atmospheres

Energy Technology Data Exchange (ETDEWEB)

Guo, Li [School of Chemical Engineering and Technology, Tianjin University, Tianjin 300072 (China); Tianjin Key Laboratory of Applied Catalysis Science and Technology, Tianjin 300072 (China); The Co-innovation Center of Chemistry and Chemical Engineering of Tianjin, Tianjin 300072 (China); Xian, Hui [School of Chemical Engineering and Technology, Tianjin University, Tianjin 300072 (China); Pei-Yang Distillation Engineering Limited Company, Tianjin 300072 (China); Li, Qi-Feng; Chen, Da [Tianjin Key Laboratory of Biomedical Detecting Techniques and Instruments, School of Precision Instruments and Opto-electronics Engineering, Tianjin University, Tianjin 300072 (China); Tan, Yi-Sheng [State Key Laboratory of Coal Conversion, Institute of Coal Chemistry, Chinese Academy of Science, Taiyuan 030001 (China); Zhang, Jing; Zheng, Li-Rong [Institute of High Energy Physics, Chinese Academy of Sciences, Beijing 100049 (China); Li, Xin-Gang, E-mail: xingang_li@tju.edu.cn [School of Chemical Engineering and Technology, Tianjin University, Tianjin 300072 (China); Tianjin Key Laboratory of Applied Catalysis Science and Technology, Tianjin 300072 (China); The Co-innovation Center of Chemistry and Chemical Engineering of Tianjin, Tianjin 300072 (China)

2013-09-15

Highlights: • α-Mn{sub 2}O{sub 3} is a promising NO{sub x} adsorber for lean-burn exhausts even at low temperatures. • NO{sub x} was weakly bonded on α-Mn{sub 2}O{sub 3}, but strongly bonded on β-MnO{sub 2}. • NO could efficiently adsorb/desorb within the lean/rich cyclings over α-Mn{sub 2}O{sub 3}. • The superficial oxygen species plays a key role for the NO oxidation over α-Mn{sub 2}O{sub 3}. • The NO adsorption and oxidation follow the L–H and/or E–R mechanism over α-Mn{sub 2}O{sub 3}. -- Abstract: NO{sub x} emission control of lean-burn engines is one of the great challenges in the world. Herein, the MnO{sub x} model catalysts with the different calcination temperatures were synthesized to investigate their NO adsorbability for lean-burn exhausts. The transformation from (β-)MnO{sub 2} to (α-)Mn{sub 2}O{sub 3} following the increased calcination temperatures was evidenced from the viewpoint of the local atomic level. Among these samples, the one calcined at 550 °C containing the single α-Mn{sub 2}O{sub 3} phase displayed the best NO adsorbability: NO was mainly adsorbed in the forms of NO/nitrites and NO{sub 2}/nitrates at the low and high temperatures, respectively; the NO oxidation ability displayed the volcano-shape following the increased operating temperatures, and reached the maximum, i.e. 92.4% of the NO-to-NO{sub 2} conversion, at 250 °C. Moreover, this sample presented the efficiently reversible NO adsorption/desorption performance in alternative lean-burn/fuel-rich atmospheres, due to the weakly bonded NO{sub x} on it. The superficial oxygen species plays a critical role for the NO oxidation over α-Mn{sub 2}O{sub 3}. The consumed superficial oxygen could be further compensated by the gaseous and lattice oxygen therein. Our findings show that the α-Mn{sub 2}O{sub 3} material is a promising NO{sub x} adsorber for lean-burn exhausts even at low operating temperatures.

Orbital-Specific observation of O2p and Ni3d electrons in LiNi0.5Mn0.5O2, a cathode material for lithium-ion batteries

Directory of Open Access Journals (Sweden)

Yoshinori Satou

2017-09-01

Full Text Available Cathode materials for lithium-ion batteries containing Ni2+ have attracted much interest because of their high theoretical capacity. However, the precise electronic structures of these cathode materials have not yet been clearly observed, especially the energy positions of the O2p and Ni3d orbitals and the shape of the density of states. The aim of this study was to investigate the relative energy positions and shape of the density of states of O2p and Ni3d for LiNi0.5Mn0.5O2 experimentally. We cleaved a LiNi0.5Mn0.5O2 pellet in an Ar-filled glove box and performed synchrotron ultraviolet photoelectron spectroscopy for different photon energies, which enabled us to investigate the relative cross-section intensity of O2p and Ni3d. As a result, the valence-band structure was determined. We found that O2p electrons are itinerant and exist in the vicinity of the Fermi energy more than Ni3d electrons. Ni3d electrons are more localized and spread mainly from 1.2–1.5 eV below the Fermi energy. To validate the electronic structure, we measured the synchrotron O K-edge X-ray absorption fine structure of electrochemically lithium-extracted LiNi0.5Mn0.5O2. The electronic structure demonstrated that ligand holes in the oxygen atoms form below the Fermi level during the initial stage of Li extraction and that the formation rate of the holes decreases with Li extraction.

On the sol-gel synthesis and thermal, structural, and magnetic studies of transition metal (Ni, Co, Mn) containing ZnO powders

Energy Technology Data Exchange (ETDEWEB)

Thota, Subhash; Dutta, Titas; Kumar, Jitendra [Materials Science Programme, Indian Institute of Technology Kanpur, Kanpur-208016 (India)

2006-03-01

Transition metal containing ZnO powders (Zn{sub 1-x}M{sub x}O, 0{<=}x{<=}0.30; M = Ni, Mn, Co) have been synthesized by a sol-gel process using zinc acetate dihydrate, respective acetate and oxalic acid as precursors with ethanol as a solvent. The process essentially involves gel formation, drying at 80 {sup 0}C for 24 h to provide the oxalate, and calcination at 500 {sup 0}C for 2 h to undergo an exothermic reaction and yield Zn{sub 1-x}M{sub x}O powder. Their XRD patterns correspond to a wurtzite hcp structure similar to that of pure ZnO, but with the lattice parameters varying slightly with type and extent of doping. It is shown that the dissolution of nickel and cobalt in ZnO is less than 10 at.%, whereas that of manganese lies between 10 and 15 at.%. Other phases that emerge include NiO (hexagonal, a = 2.954 A, c = 7.236 A), ZnCo{sub 2}O{sub 4} (cubic, a = 8.094 A) and ZnMnO{sub 3} (cubic, a = 8.35 A) in the Ni, Co and Mn containing ZnO systems, respectively. Observations of hysteresis loops both at 10 and 320 K and the nature of ESR spectra provide evidence for the ferromagnetic state in nickel containing ZnO powder. Besides, the deviation occurs in the magnetization versus temperature curves in zero field cooled (ZFC) and field cooled (FC) conditions (blocking temperature T{sub B} being 32 K for 5 at.% Ni). The magnetic behaviour of manganese and cobalt doped zinc oxide is, however, different, namely (i) no hysteresis loops (ii) decrease in magnetization with increase of Mn or Co content, and (iii) identical M-T curves under ZFC and FC conditions. The inverse susceptibility versus temperature curves of Zn{sub 1-x}Mn{sub x}O compounds reveal ferrimagnetism with Neel temperature T{sub N} of 4 K for x = 0.02, but antiferromagnetism for x = 0.15 and 0.25 with Curie-Weiss temperature of -43 and -30 K, respectively.

Improved Charge Transfer in a Mn2O3@Co1.2Ni1.8O4 Hybrid for Highly Stable Alkaline Direct Methanol Fuel Cells with Good Methanol Tolerance.

Science.gov (United States)

Liu, Yan; Chen, Yuanzhen; Li, Sai; Shu, Chenyong; Fang, Yuan; Song, Bo

2018-03-21

A three-dimensional Mn 2 O 3 @Co 1.2 Ni 1.8 O 4 hybrid was synthesized via facile two-step processes and employed as a cathode catalyst in direct methanol fuel cells (DMFCs) for the first time. Because of the unique architecture with ultrathin and porous nanosheets of the Co 1.2 Ni 1.8 O 4 shell, this composite exhibits better electrochemical performance than the pristine Mn 2 O 3 . Remarkably, it shows excellent methanol tolerance, even in a high concentration solution. The DMFC was assembled with Mn 2 O 3 @Co 1.2 Ni 1.8 O 4 , polymer fiber membranes, and PtRu/C as the cathode, membrane, and anode, respectively. The power densities of 57.5 and 70.5 mW cm -2 were recorded at 18 and 28 °C, respectively, especially the former is the best result reported in the literature at such a low temperature. The stability of the Mn 2 O 3 @Co 1.2 Ni 1.8 O 4 catalyzed cathode was evaluated, and the results show that this compound possesses excellent stability in a high methanol concentration. The improved electrochemical activity could be attributed to the narrow band gap of the hybrid, which accelerates the electrons jumping from the valence band to the conduction band. Therefore, Mn III could be oxidized into Mn IV more easily, simultaneously providing an electron to the absorbed oxygen.

Effect of Cu{sup 2+} and Ni{sup 2+} substitution at the Mn site in (La{sub 0.63}Ca{sub 0.37})MnO{sub 3}: A neutron powder diffraction investigation

Energy Technology Data Exchange (ETDEWEB)

Martinelli, A., E-mail: alberto.martinelli@spin.cnr.it [CNR-SPIN, C.so Perrone 24, 16152 Genova (Italy); Ferretti, M. [CNR-SPIN, C.so Perrone 24, 16152 Genova (Italy); Dipartimento di Chimica e Chimica Industriale, Università di Genova, Via Dodecaneso 31, 16146 Genova (Italy); Castellano, C. [Università degli Studi di Milano, Dipartimento di Chimica Strutturale e Stereochimica Inorganica, Via G. Venezian 21, 20133 Milano (Italy); Cimberle, M.R. [IMEM-CNR, Via Dodecaneso 33, 16146 Genova (Italy); Ritter, C. [Institute Laue—Langevin, 6 rue Jules Horowitz, 38042 Grenoble Cedex 9 (France)

2013-04-15

The crystal and magnetic structures of the (La{sub 0.63}Ca{sub 0.37})(Mn{sub 1−x}TM{sub x})O{sub 3} compounds (x=0.00, 0.03, 0.08; TM=Cu{sup 2+}, Ni{sup 2+}) were investigated between 5 K and 300 K by means of dc magnetic measurements and neutron powder diffraction analysis followed by Rietveld refinement. Both substituting cations lead to a reduction of the long range ferromagnetic ordering temperature; ferromagnetism is strongly suppressed in the 8% Cu-substituted sample, where long- and short-range FM magnetic orders coexist together with short-range A-type AFM order. This particular feature can be related to the Jahn–Teller character of Cu{sup 2+}, absent in Ni{sup 2+}, and suggests the occurrence of a quantum critical point in the (La{sub 0.63}Ca{sub 0.37})(Mn{sub 1−x}Cu{sub x})O{sub 3} system. - Graphical abstract: Rietveld refinement plot of (La{sub 0.63}Ca{sub 0.37})(Mn{sub 0.92}Cu{sub 0.08})O{sub 3} showing in the inset the coexistence of broad A-type AFM peaks with FM ones. Highlights: ► (La{sub 0.63}Ca{sub 0.37})MnO{sub 3} was substituted with Ni and Cu. ► Neutron powder diffraction and Rietveld refinement were carried out. ► A quantum critical point possibly occurs in the (La{sub 0.63}Ca{sub 0.37})(Mn{sub 1−x}Cu{sub x})O{sub 3} system.

Monodisperse MnO2@NiCo2O4 core/shell nanospheres with highly opened structures as electrode materials for good-performance supercapacitors

Science.gov (United States)

Zhou, You; Ma, Li; Gan, Mengyu; Ye, Menghan; Li, Xiurong; Zhai, Yanfang; Yan, Fabing; Cao, Feifei

2018-06-01

The monodisperse MnO2@NiCo2O4 core/shell nanospheres for good-performance supercapacitors are designed and synthesized by a two-step solution-based method and a simple post annealing process. In the composite, both MnO2 (the "core") and NiCo2O4 (the "shell") are formed by the accumulation of nanoflakes. Thus, nearly all the core/shell nanoflakes are highly opened and accessible to electrolyte, making them give full play to the Faradaic reaction. Our results demonstrate that the composite electrode exhibits desirable pseudocapacitive behaviors with higher specific capacitance (1127.27 F g-1 at a current density of 1 A g-1), better rate capability (81.0% from 1 to 16 A g-1) and superior cycling stability (actually 126.8% capacitance retention after 1000 cycles and only 3.7% loss after 10,000 cycles at 10 A g-1) in 3 M KOH aqueous solution. Moreover, it offers the excellent specific energy density of 26.6 Wh kg-1 at specific power density of 800 W kg-1. The present MnO2@NiCo2O4 core/shell nanospheres with remarkable electrochemical properties are considered as potential electrode materials for the next generation supercapacitors.

Investigation on electronic and magnetic properties of Mn{sub 2}NiAl by ab initio calculations and Monte Carlo simulations

Energy Technology Data Exchange (ETDEWEB)

Masrour, R., E-mail: rachidmasrour@hotmail.com [Laboratory of Materials, Processes, Environment and Quality, Cady Ayyed University, National School of Applied Sciences, PB 63 46000 Safi (Morocco); Jabar, A. [Laboratory of Materials, Processes, Environment and Quality, Cady Ayyed University, National School of Applied Sciences, PB 63 46000 Safi (Morocco); Hlil, E.K. [Institut Néel, CNRS, Université Grenoble Alpes, BP 166, F-38042 Grenoble cedex 9 (France); Hamedoun, M. [Institute of Nanomaterials and Nanotechnologies, MAScIR, Rabat (Morocco); Benyoussef, A. [Institute of Nanomaterials and Nanotechnologies, MAScIR, Rabat (Morocco); Hassan II Academy of Science and Technology, Rabat (Morocco); Hourmatallah, A. [Equipe de Physique du Solide, Laboratoire LIPI, Ecole Normale Supérieure, BP 5206, Bensouda, Fes (Morocco); Rezzouk, A.; Bouslykhane, K.; Benzakour, N. [Laboratoire de Physique du Solide, Université Sidi Mohammed Ben Abdellah, Faculté des sciences DharMahraz, BP 1796, Fes (Morocco)

2017-04-15

Self-consistent ab initio calculations, based on Density Functional Theory (DFT) approach and using Full potential Linear Augmented Plane Wave (FLAPW) method, are performed to investigate both electronic and magnetic properties of the Mn{sub 2}NiAl. Magnetic moment considered to lie along (001) axes are computed. Obtained data from ab initio calculations are used as input for Monte Carlo simulations to compute other magnetic parameters. Also, the magnetic properties of Mn{sub 2}NiAl are studied using the Monte Carlo simulations. The variation of magnetization and magnetic susceptibility with the reduced temperature of Mn{sub 2}NiAl are investigated. The transition temperature of this system is deduced for different values exchange interaction and crystal field. The thermal total magnetization has been obtained, and the magnetic hysteresis cycle is established. The total magnetic moment is superior to those obtained by the other method and is mainly determined by the antiparallel aligned Mn{sub I}, Mn{sub II} and Ni spin moments. The superparamagnetic phase is found at the neighborhood of transition temperature. - Highlights: • Ab initio calculations are used to study magnetic and electronic properties of Mn{sub 2}NiX. • The transition temperature of Mn{sub 2}NiX is established. • The magnetic hysteresis cycle of M{sub n2}NiX (X = Al, Ga, In, Sn) is deduced. • The magnetic coercive field of Mn{sub 2}NiX (X = Al, Ga, In, Sn) is given.

Mechanical and shape memory properties of ferromagnetic Ni2MnGa sputter-deposited films

Science.gov (United States)

Ohtsuka, M.; Matsumoto, M.; Itagaki, K.

2003-10-01

The ternary intermetallic compound Ni2MnGa is an intelligent material, which has a shape memory effect and a ferromagnetic property. Use of shape memory alloy films for an actuator of micro machines is very attractive because of its large recovery force. The data of mechanical and shape memory properties of the films are required to use for the actuator. The purpose of this study is to investigate the effects of fabrication conditions and to clarify the relationships between these properties and fabrication conditions of the Ni{2}MnGa films. The Ni{2}MnGa films were deposited with a radio-frequency magnetron sputtering apparatus using a Ni{50}Mn{25}Ga{25} or Ni{52}Mn{24}Ga{24} target. After deposition, the films were annealed at 873sim 1173 K. The asdeposited films were crystalline and had columnar grains. After the heat treatment, the grains widened and the grain boundary became indistinct with increasing heat treatment temperature. MnO and Ni{3} (Mn, Ga) precipitations were observed in the heat-treated films. The mechanical properties of the films were measured by the nanoindentation method. Hardness and elastic modulus of as-deposited films were larger than those of arcmelted bulk alloys. The hardness of the films was affected by the composition, crystal structure, microstructure and precipitation, etc. The elastic modulus of the films was also changed with the heat treatment conditions. The heat-treated films showed a thermal two-way shape memory effect.

DyNi{sub 2}Mn-magnetisation and Moessbauer spectroscopy

Energy Technology Data Exchange (ETDEWEB)

Wang Jianli; Campbell, Stewart James, E-mail: stewart.campbell@adfa.edu.au [University of New South Wales, School of Physical, Environmental and Mathematical Sciences (Australia); Kennedy, Shane Joseph [ANSTO, Bragg Institute (Australia); Dou Shixue [University of Wollongong, Institute for Superconductivity and Electronic Materials (Australia); Wu Guangheng [Chinese Academy of Science, Institute of Physics (China)

2012-03-15

The physical properties of DyNi{sub 2}Mn doped with {sup 57}Fe have been investigated by X-ray diffraction, magnetisation (10-300 K) and {sup 57}Fe Moessbauer spectroscopy measurements (5-300 K). DyNi{sub 2}Mn({sup 57}Fe) crystallizes in the MgCu{sub 2}-type cubic structure (Fd{sup }-3m space group). The ordering temperature is found to be T{sub C} = 99(2) K, much higher than those of DyNi{sub 2} ({approx}22 K) and DyMn{sub 2} ({approx}35 K). Analyses of isothermal M-H curves and the related Arrott plots confirm that the magnetic phase transition at T{sub C} is second order. The magnetic entropy change around T{sub C} is 4.0 J/kg K for a magnetic field change of 0 T to 5 T. The spectra above T{sub C} exhibit features consistent with quadrupolar effects while below T{sub C} the spectra exhibit magnetic hyperfine splitting. The Debye temperature for DyNi{sub 2}Mn has been determined as {theta}{sub D} = 200(20) K from a fit to the variable temperature isomer shift IS(T).

New perovskite-based manganite Pb2Mn2O5

International Nuclear Information System (INIS)

Hadermann, Joke; Abakumov, Artem M.; Perkisas, Tyche; D'Hondt, Hans; Tan Haiyan; Verbeeck, Johan; Filonenko, Vladimir P.; Antipov, Evgeny V.; Van Tendeloo, Gustaaf

2010-01-01

A new perovskite based compound Pb 2 Mn 2 O 5 has been synthesized using a high pressure high temperature technique. The structure model of Pb 2 Mn 2 O 5 is proposed based on electron diffraction, high angle annular dark field scanning transmission electron microscopy and high resolution transmission electron microscopy. The compound crystallizes in an orthorhombic unit cell with parameters a=5.736(1) A∼√2a p , b=3.800(1) A∼a p , c=21.562(6) A∼4√2a p (a p -the parameter of the perovskite subcell) and space group Pnma. The Pb 2 Mn 2 O 5 structure consists of quasi two-dimensional perovskite blocks separated by 1/2[110] p (101) p crystallographic shear planes. The blocks are connected to each other by chains of edge-sharing MnO 5 distorted tetragonal pyramids. The chains of MnO 5 pyramids and the MnO 6 octahedra of the perovskite blocks delimit six-sided tunnels accommodating double chains of Pb atoms. The tunnels and pyramidal chains adopt two mirror-related configurations ('left' L and 'right' R) and layers consisting of chains and tunnels of the same configuration alternate in the structure according to an -L-R-L-R-sequence. The sequence is sometimes locally violated by the appearance of -L-L- or -R-R-fragments. A scheme is proposed with a Jahn-Teller distortion of the MnO 6 octahedra with two long and two short bonds lying in the a-c plane, along two perpendicular orientations within this plane, forming a d-type pattern. - Graphical abstract: Order of the Jahn-Teller distorted MnO 6 octahedra in Pb 2 Mn 2 O 5 . Two long and two short bonds lie in the a-c plane, along two perpendicular orientations within this plane, forming a d-type pattern.

Evaluation of Ca3(Co,M2O6 (M=Co, Fe, Mn, Ni as new cathode materials for solid-oxide fuel cells

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Fushao Li

2015-10-01

Full Text Available Series compounds Ca3(Co0.9M0.12O6 (M=Co, Fe, Mn, Ni with hexagonal crystal structure were prepared by sol–gel route as the cathode materials for solid oxide fuel cells (SOFCs. Effects of the varied atomic compositions on the structure, electrical conductivity, thermal expansion and electrochemical performance were systematically evaluated. Experimental results showed that the lattice parameters of Ca3(Co0.9Fe0.12O6 and Ca3(Co0.9Mn0.12O6 were both expanded to certain degree. Electron-doping and hole-doping effects were expected in Ca3(Co0.9Mn0.12O6 and Ca3(Co0.9Ni0.12O6 respectively according to the chemical states of constituent elements and thermal-activated behavior of electrical conductivity. Thermal expansion coefficients (TEC of Ca3(Co0.9M0.12O6 were measured to be distributed around 16×10−6 K−1, and compositional elements of Fe, Mn, and Ni were especially beneficial for alleviation of the thermal expansion problem of cathode materials. By using Ca3(Co0.9M0.12O6 as the cathodes operated at 800 °C, the interfacial area-specific resistance varied in the order of M=CoNi, and the over-potential increased in the order of M=Fe≈M=CoMn. Among all of these compounds, Ca3(Co0.9Fe0.12O6 showed the best electrochemical performance and the power density as high as ca. 500 mW cm−2 at 800 °C achieved in the single cell with La0.8Sr0.2Ga0.83Mg0.17O2.815 as electrolyte and Ni–Ce0.8Sm0.2O1.9 as anode. Ca3(Co0.9M0.12O6 (M=Co, Fe, Mn, Ni can be used as the cost-effective cathode materials for SOFCs.

MnFe{sub 2}O{sub 4} as a gas sensor towards SO{sub 2} and NO{sub 2} gases

Energy Technology Data Exchange (ETDEWEB)

Rathore, Deepshikha, E-mail: deep.nano@gmail.com; Mitra, Supratim [Department of Natural Sciences, NIIT University, Neemrana, Rajasthan 301705 (India)

2016-05-06

The chemical co-precipitation method was used to synthesize MnFe{sub 2}O{sub 4} nanoparticles. Single cubic phase formation of nanoparticles was confirmed by X-ray diffraction technique. The average particle size of MnFe{sub 2}O{sub 4} nanoparticles was found to be 10.7 nm using Scherrer formula. The ultrafine powder of MnFe{sub 2}O{sub 4} nanoparticles was pressed to design pellet of 10 mm diameter and 1mm thickness. Copper electrodes have been deposited on the surface of pellet using silver paste in the form of capacitor. Fabricated gas sensing device of MnFe{sub 2}O{sub 4} nanoparticles was tested towards SO{sub 2} and NO{sub 2} gases. Cole-Cole plot of MnFe{sub 2}O{sub 4} was investigated with the help of electrochemical workstation. The performance of the sensors including sensitivity, response and recovery time was also determined. It was observed that the MnFe{sub 2}O{sub 4} nanoparticles are more sensible for NO{sub 2} gas as compared to SO{sub 2} gas.

Synthesize and electrochemical characterization of Mg-doped Li-rich layered Li[Li0.2Ni0.2Mn0.6]O2 cathode material

International Nuclear Information System (INIS)

Wang, Dan; Huang, Yan; Huo, Zhenqing; Chen, Li

2013-01-01

Highlights: • Layered Li[Li 0.2 Ni 0.2−x Mn 0.6−x Mg 2x ]O 2 (2x = 0, 0.01, 0.02, 0.05) were synthetized. • Li[Li 0.2 Ni 0.2−x Mn 0.6−x Mg 2x ]O 2 exhibit enhanced electrochemical properties. • The improved performance is attributed to enhanced structure stability. -- Abstract: Mg-doped Li[Li 0.2 Ni 0.2 Mn 0.6 ]O 2 as a Li-rich cathode material of lithium-ion batteries were prepared by co-precipitation method and ball-milling treatment using Mg(OH) 2 as a dopant. Scanning electron microscopy (SEM), ex situ X-ray powder diffraction (XRD), cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS) and galvantatic charge/discharge were used to investigate the effect of Mg doping on structure and electrochemical performance. Compared with the bare material, Mg-doped materials exhibit better cycle stabilities and superior rate capabilities. Li[Li 0.2 Ni 0.195 Mn 0.595 Mg 0.01 ]O 2 displays a high reversible capacity of 226.5 mAh g −1 after 60 cycles at 0.1 C. The excellent cycle performance can be attributed to the improvement in structure stability, which is verified by XRD tests before and after 60 cycles. EIS results show that Mg doping decreases the charge-transfer resistance and enhances the reaction kinetics, which is considered to be the major factor for higher rate performance

Neutron diffraction analysis and electrochemical performance of spinel Ni(Mn{sub 2−x}Co{sub x})O{sub 4} as anode materials for lithium ion battery

Energy Technology Data Exchange (ETDEWEB)

Zhao, Hu; Liu, Lei; Hu, Zhongbo [College of Materials Science and Opto-Electronic Technology, University of Chinese Academy of Sciences, Beijing 100049 (China); Sun, Limei, E-mail: sunlm@ciae.ac.cn [Department of Nuclear and Physics, China Institute of Atomic Energy, Beijing 102413 (China); Han, Songbai; Liu, Yuntao; Chen, Dongfeng [Department of Nuclear and Physics, China Institute of Atomic Energy, Beijing 102413 (China); Liu, Xiangfeng, E-mail: liuxf@ucas.ac.cn [College of Materials Science and Opto-Electronic Technology, University of Chinese Academy of Sciences, Beijing 100049 (China)

2016-05-15

Highlights: • The reversible capacity and cyclability of Ni(Mn{sub 2−x}Co{sub x})O{sub 4} first increases and then decreases with increasing Co content. • Neutron diffraction and Rielveld refinements are applied to analyze the site occupancies of Mn, Co, O and Ni. • Excessive Co ions in 8a and 16d sites reduce the structure stability leading to poor electrochemical performance. - Abstract: The effects of Co substitution on the structure and electrochemical performances of spinel Ni(Mn{sub 2−x}Co{sub x})O{sub 4} (x = 0, 0.5, and 1.0) have been investigated. With the increase of Co content the lattice parameters decrease owing to the smaller ion radius of Co than Mn. The reversible capacity and cyclability of Ni(Mn{sub 2−x}Co{sub x})O{sub 4} first increase and then decrease with the increase of Co content and NiMn{sub 1.5}Co{sub 0.5}O{sub 4} shows the best electrochemical performance in compared to the other two samples. Neutron diffraction and Rielveld refinement are further applied to analyze the site occupancies of the elements of Mn, Co, O and Ni. A certain amount of Co ions substitution are favorable to enhance the electrochemical performance, but excessive Co ions in 8a and 16d sites reduce the stability of host structure which leads to the poor electrochemical performance.

NiCo2O4 surface coating Li[Ni0.03Mn1.97]O4 micro-/nano- spheres as cathode material for high-performance lithium ion battery

Science.gov (United States)

Ye, Pan; Dong, Hui; Xu, Yunlong; Zhao, Chongjun; Liu, Dong

2018-01-01

Here we report a novel transitional metal oxide (NiCo2O4) coated Li[Ni0.03Mn1.97]O4 micro-/nano- spheres as high-performance Li-ion battery cathode material. A thin layer of ∼10 nm NiCo2O4 was formed by simple wet-chemistry approach adjacent to the surface of Li[Ni0.03Mn1.97]O4 micro-/nano- spheres, leading to significantly enhanced battery electrochemical performance. The optimized sample(1 wt%) not only delivers excellent discharge capacity and cycling stability improvement at both room temperature and elevated temperatures, but also effectively prevents Mn dissolution while retaining its coating structure intact according to XRF and TEM results. The CV and EIS break-down analysis indicated a much faster electrochemical reaction kinetics, more reversible electrode process and greatly reduced charge transfer and Warburg resistance, clearly illustrating the dual role of NiCo2O4 coating to boost electron transport and Li+ diffusion, and alleviation of manganese dissolving. This approach may render as an efficient technique to realize high-performance lithium ion battery cathode material.

Synthesis of Li-Mn-O mesocrystals with controlled crystal phases through topotactic transformation of MnCO3

Science.gov (United States)

Dang, Feng; Hoshino, Tatsuhiko; Oaki, Yuya; Hosono, Eiji; Zhou, Haoshen; Imai, Hiroaki

2013-02-01

Mesocrystals of Li-Mn-O compounds, such as LiMn2O4, Li2MnO3, and LiMnO2-Li2MnO3, consisting of oriented nanoscale units were selectively produced under hydrothermal conditions from biomimetically prepared MnCO3 mesocrystals. Topotactic transformation through the intermediate phase of Mn5O8 inheriting a hierarchical structure of the MnCO3 precursor was essential for the formation of the mesocrystal compounds. The crystal phases were successfully controlled by varying the conditions for the hydrothermal reactions. The Li-Mn-O mesocrystals have considerable potential as cathodes of Li-ion batteries.Mesocrystals of Li-Mn-O compounds, such as LiMn2O4, Li2MnO3, and LiMnO2-Li2MnO3, consisting of oriented nanoscale units were selectively produced under hydrothermal conditions from biomimetically prepared MnCO3 mesocrystals. Topotactic transformation through the intermediate phase of Mn5O8 inheriting a hierarchical structure of the MnCO3 precursor was essential for the formation of the mesocrystal compounds. The crystal phases were successfully controlled by varying the conditions for the hydrothermal reactions. The Li-Mn-O mesocrystals have considerable potential as cathodes of Li-ion batteries. Electronic supplementary information (ESI) available. See DOI: 10.1039/c3nr33767g

Hydrothermal synthesis of MnO2/CNT nanocomposite with a CNT core/porous MnO2 sheath hierarchy architecture for supercapacitors

Science.gov (United States)

Xia, Hui; Wang, Yu; Lin, Jianyi; Lu, Li

2012-01-01

MnO2/carbon nanotube [CNT] nanocomposites with a CNT core/porous MnO2 sheath hierarchy architecture are synthesized by a simple hydrothermal treatment. X-ray diffraction and Raman spectroscopy analyses reveal that birnessite-type MnO2 is produced through the hydrothermal synthesis. Morphological characterization reveals that three-dimensional hierarchy architecture is built with a highly porous layer consisting of interconnected MnO2 nanoflakes uniformly coated on the CNT surface. The nanocomposite with a composition of 72 wt.% (K0.2MnO2·0.33 H2O)/28 wt.% CNT has a large specific surface area of 237.8 m2/g. Electrochemical properties of the CNT, the pure MnO2, and the MnO2/CNT nanocomposite electrodes are investigated by cyclic voltammetry and electrochemical impedance spectroscopy measurements. The MnO2/CNT nanocomposite electrode exhibits much larger specific capacitance compared with both the CNT electrode and the pure MnO2 electrode and significantly improves rate capability compared to the pure MnO2 electrode. The superior supercapacitive performance of the MnO2/CNT nancomposite electrode is due to its high specific surface area and unique hierarchy architecture which facilitate fast electron and ion transport.

Coupling catalytic hydrolysis and oxidation on Mn/TiO2-Al2O3 for HCN removal

Science.gov (United States)

Wang, Langlang; Wang, Xueqian; Cheng, Jinhuan; Ning, Ping; Lin, Yilong

2018-05-01

The manganese-modified titania-alumina (Mn/TiO2-Al2O3) catalyst synthesized by sol-gol method was used to remove hydrogen cyanide (HCN) from simulated flue gas. Further, effects of the mass ratios of Ti/Al, Mn loading, calcination temperature, and relative humidity on HCN conversion efficiency and catalytic activity were systematically investigated. The results indicated that the Mn/TiO2-Al2O3 catalyst exhibited significantly enhanced HCN removal efficiency, and the maximum yield of N2 increased to 68.02% without the participation of water vapor. When water vapor was added into the flue gas, the yield of N2 decreased and the formation of NOx was also inhibited. The XRD and XPS results indicated that Mn was mainly present in the form of Mn2+, Mn3+, and Mn4+ on the surface of catalyst and chemisorbed oxygen played a major role in the HCN catalytic oxidation process. The results of DSC-TGA analysis and H2-TPR indicated that the catalyst also exhibited a good thermal and chemical stability. NH3-TPD and CO2-TPD indicated that the surface of the catalyst mainly contained acidic sites. During the reaction, part of NH3 was adsorbed by Brönsted and Lewis acid sites. NH3 adsorbed on Lewis acid sites participated in NH3-SCR, which reduced the amount of NOx produced and resulted in a high N2 yield.

The Synergy Effect of Ni-M (M = Mo, Fe, Co, Mn or Cr Bicomponent Catalysts on Partial Methanation Coupling with Water Gas Shift under Low H2/CO Conditions

Directory of Open Access Journals (Sweden)

Xinxin Dong

2017-02-01

Full Text Available Ni-M (M = Mo, Fe, Co, Mn or Cr bicomponent catalysts were prepared through the co-impregnation method for upgrading low H2/CO ratio biomass gas into urban gas through partial methanation coupling with water gas shift (WGS. The catalysts were characterized by N2 isothermal adsorption, X-ray diffraction (XRD, H2 temperature programmed reduction (H2-TPR, H2 temperature programmed desorption (H2-TPD, scanning electron microscopy (SEM and thermogravimetry (TG. The catalytic performances demonstrated that Mn and Cr were superior to the other three elements due to the increased fraction of reducible NiO particles, promoted dispersion of Ni nanoparticles and enhanced H2 chemisorption ability. The comparative study on Mn and Cr showed that Mn was more suitable due to its smaller carbon deposition rate and wider adaptability to various H2/CO and H2O/CO conditions, indicating its better synergy effect with Ni. A nearly 100 h, the lifetime test and start/stop cycle test further implied that 15Ni-3Mn was stable for industrial application.

Electrochemical performance of all-solid-state lithium secondary batteries with Li-Ni-Co-Mn oxide positive electrodes

International Nuclear Information System (INIS)

Kitaura, Hirokazu; Hayashi, Akitoshi; Tadanaga, Kiyoharu; Tatsumisago, Masahiro

2010-01-01

LiNi 1/3 Co 1/3 Mn 1/3 O 2 was applied as a promising material to the all-solid-state lithium cells using the 80Li 2 S.19P 2 S 5 .1P 2 O 5 (mol%) solid electrolyte. The cell showed the first discharge capacity of 115 mAh g -1 at the current density of 0.064 mA cm -2 and retained the reversible capacity of 110 mAh g -1 after 10 cycles. The interfacial resistance was observed in the impedance spectrum of the all-solid-state cell charged to 4.4 V (vs. Li) and the transition metal elements were detected on the solid electrolyte in the vicinity of LiNi 1/3 Co 1/3 Mn 1/3 O 2 by the TEM observations with EDX analyses. The electrochemical performance was improved by the coating of LiNi 1/3 Co 1/3 Mn 1/3 O 2 particles with Li 4 Ti 5 O 12 film. The interfacial resistance was decreased and the discharge capacity was increased from 63 to 83 mAh g -1 at 1.3 mA cm -2 by the coating. The electrochemical performance of LiNi 1/3 Co 1/3 Mn 1/3 O 2 was compared with that of LiCoO 2 , LiMn 2 O 4 and LiNiO 2 in the all-solid-state cells. The rate capability of LiNi 1/3 Co 1/3 Mn 1/3 O 2 was lower than that of LiCoO 2 . However, the reversible capacity of LiNi 1/3 Co 1/3 Mn 1/3 O 2 at 0.064 mA cm -2 was larger than that of LiCoO 2 , LiMn 2 O 4 and LiNiO 2 .

Removal of aqueous Pb(II) by adsorption on Al{sub 2}O{sub 3}-pillared layered MnO{sub 2}

Energy Technology Data Exchange (ETDEWEB)

Zhang, Haipeng; Gu, Liqin; Zhang, Ling; Zheng, Shourong; Wan, Haiqin; Sun, Jingya [State Key Laboratory of Pollution Control and Resource Reuse, Jiangsu Key Laboratory of Vehicle Emissions Control, School of the Environment, Nanjing University, Nanjing 210023 (China); Zhu, Dongqiang [School of Urban and Environmental Sciences, Peking University, Beijing 100871 (China); Xu, Zhaoyi, E-mail: zhaoyixu@nju.edu.cn [State Key Laboratory of Pollution Control and Resource Reuse, Jiangsu Key Laboratory of Vehicle Emissions Control, School of the Environment, Nanjing University, Nanjing 210023 (China)

2017-06-01

Highlights: • Al{sub 2}O{sub 3}-pillared layered MnO{sub 2} (p-MnO{sub 2}) was prepared from δ-MnO{sub 2} precursor. • p-MnO{sub 2} showed markedly higher Pb(II) adsorption capacity than pristine δ-MnO{sub 2.}. • Pillaring of Al{sub 2}O{sub 3} into the layer of δ-MnO{sub 2} enhanced the Pb(II) adsorption. - Abstract: In the present study, Al{sub 2}O{sub 3}-pillared layered MnO{sub 2} (p-MnO{sub 2}) was synthesized using δ-MnO{sub 2} as precursor and Pb(II) adsorption on p-MnO{sub 2} and δ-MnO{sub 2} was investigated. To clarify the adsorption mechanism, Al{sub 2}O{sub 3} was also prepared as an additional sorbent. The adsorbents were characterized by X-ray fluorescence analysis, powder X-ray diffraction, transmission electron microscopy, X-ray photoelectron spectroscopy and N{sub 2} adsorption-desorption. Results showed that in comparison with pristine δ-MnO{sub 2}, Al{sub 2}O{sub 3} pillaring led to increased BET surface area of 166.3 m{sup 2} g{sup −1} and enlarged basal spacing of 0.85 nm. Accordingly, p-MnO{sub 2} exhibited a higher adsorption capacity of Pb(II) than δ-MnO{sub 2}. The adsorption isotherms of Pb(II) on δ-MnO{sub 2} and Al{sub 2}O{sub 3} pillar fitted well to the Freundlich model, while the adsorption isotherm of Pb(II) on p-MnO{sub 2} could be well described using a dual-adsorption model, attributed to Pb(II) adsorption on both δ-MnO{sub 2} and Al{sub 2}O{sub 3}. Additionally, Pb(II) adsorption on δ-MnO{sub 2} and p-MnO{sub 2} followed the pseudo second-order kinetics, and a lower adsorption rate was observed on p-MnO{sub 2} than δ-MnO{sub 2}. The Pb(II) adsorption capacity of p-MnO{sub 2} increased with solution pH and co-existing cation concentration, and the presence of dissolved humic acid (10.2 mg L{sup −1}) did not markedly impact Pb(II) adsorption. p-MnO{sub 2} also displayed good adsorption capacities for aqueous Cu(II) and Cd(II). Findings in this study indicate that p-MnO{sub 2} could be used as a highly effective

Layered oxides-LiNi1/3Co1/3Mn1/3O2 as anode electrode for symmetric rechargeable lithium-ion batteries

Science.gov (United States)

Wang, Yuesheng; Feng, Zimin; Yang, Shi-Ze; Gagnon, Catherine; Gariépy, Vincent; Laul, Dharminder; Zhu, Wen; Veillette, René; Trudeau, Michel L.; Guerfi, Abdelbast; Zaghib, Karim

2018-02-01

High-performance and long-cycling rechargeable lithium-ion batteries have been in steadily increasing demand for the past decades. Nevertheless, the two dominant anodes at the moment, graphite and L4T5O12, suffer from a safety issue of lithium plating (operating voltage at ∼ 0.1 V vs. Li+/Li) and low capacity (175 mAh/g), respectively. Here, we report LiNi1/3Co1/3Mn1/3O2 as an alternative anode material which has a working voltage of ∼1.1 V and a capacity as high as 330 mAh/g at the current rate of C/15. Symmetric cells with both electrodes containing LiNi1/3Co1/3Mn1/3O2 can deliver average discharge voltage of 2.2 V. In-situ XRD, HRTEM and first principles calculations indicate that the reaction mechanism of a LiNi1/3Co1/3Mn1/3O2 anode is comprised mainly of conversion. Both the fundamental understanding and practical demonstrations suggest that LiNi1/3Co1/3Mn1/3O2 is a promising negative electrode material for lithium-ion batteries.

Nanocrystalline spinel ferrite (MFe2O4, M = Ni, Co, Mn, Mg, Zn) powders prepared by a simple aloe vera plant-extracted solution hydrothermal route

International Nuclear Information System (INIS)

Phumying, Santi; Labuayai, Sarawuth; Swatsitang, Ekaphan; Amornkitbamrung, Vittaya; Maensiri, Santi

2013-01-01

Graphical abstract: This figure shows the specific magnetization curves of the as-prepared MFe 2 O 4 (M = Ni, Co, Mn, Mg, Zn) powders obtained from room temperature VSM measurement. These curves are typical for a soft magnetic material and indicate hysteresis ferromagnetism in the field ranges of ±500 Oe, ±1000 Oe, and ±2000 Oe for the CoFe 2 O 4 , MgFe 2 O 4 and MnFe 2 O 4 respectively, whereas the samples of NiFe 2 O 4 and ZnFe 2 O 4 show a superparamagnetic behavior. Highlights: ► Nanocrystalline MFe 2 O 4 powders were synthesized by a novel hydrothermal method. ► Metal acetylacetonates and aloe vera plant-extracted solution are used. ► This biosynthetic route is very simple and provides high-yield oxide nanomaterials. ► XRD and TEM results indicate that the prepared samples have only spinel structure. ► The maximum M s of 68.9 emu/g at 10 kOe were observed for the samples of MnFe 2 O 4 . - Abstract: Nanocrystalline spinel ferrite MFe 2 O 4 (M = Ni, Co, Mn, Mg, Zn) powders were synthesized by a novel hydrothermal method using Fe(acac) 3 , M(acac) 3 (M = Ni, Co, Mn, Mg, Zn) and aloe vera plant extracted solution. The X-ray diffraction and selected-area electron diffraction results indicate that the synthesized nanocrystalline have only spinel structure without the presence of other phase impurities. The crystal structure and morphology of the spinel ferrite powders, as revealed by TEM, show that the NiFe 2 O 4 and CoFe 2 O 4 samples contain nanoparticles, whereas the MnFe 2 O 4 and MgFe 2 O 4 samples consist of many nanoplatelets and nanoparticles. Interestingly, the ZnFe 2 O 4 sample contains plate-like structure of networked nanocrystalline particles. Room temperature magnetization results show a ferromagnetic behavior of the CoFe 2 O 4 , MnFe 2 O 4 and MgFe 2 O 4 samples, whereas the samples of NiFe 2 O 4 and ZnFe 2 O 4 exhibit a superparamagnetic behavior

Structure, reactivity and electronic properties of Mn doped Ni13 clusters

International Nuclear Information System (INIS)

Banerjee, Radhashyam; Datta, Soumendu; Mookerjee, Abhijit

2013-01-01

In this work we have studied the structural and magnetic properties of Ni 13 cluster mono- and bi-doped with Mn atoms. We have noted their tendency of being reactive toward the H 2 molecule. We have found unusually enhanced stability in the mono-doped cluster (i.e. of the Ni 12 Mn) and the diminished stability of the corresponding chemisorbed cluster, Ni 12 MnH 2 . Our analysis of the stability and HOMO–LUMO gap explains this unusual behavior. Interestingly, we have also seen the quenching in the net magnetic moment upon H 2 absorption in the doped Ni 13−m Mn m alloy clusters. This has been reported earlier for smaller Ni n clusters [1

Synthesis of Li-Mn-O mesocrystals with controlled crystal phases through topotactic transformation of MnCO₃.

Science.gov (United States)

Dang, Feng; Hoshino, Tatsuhiko; Oaki, Yuya; Hosono, Eiji; Zhou, Haoshen; Imai, Hiroaki

2013-03-21

Mesocrystals of Li-Mn-O compounds, such as LiMn2O4, Li2MnO3, and LiMnO2-Li2MnO3, consisting of oriented nanoscale units were selectively produced under hydrothermal conditions from biomimetically prepared MnCO3 mesocrystals. Topotactic transformation through the intermediate phase of Mn5O8 inheriting a hierarchical structure of the MnCO3 precursor was essential for the formation of the mesocrystal compounds. The crystal phases were successfully controlled by varying the conditions for the hydrothermal reactions. The Li-Mn-O mesocrystals have considerable potential as cathodes of Li-ion batteries.

Crystalline structure and electrical properties of solid solutions YNixMn1-xO3

Directory of Open Access Journals (Sweden)

Moure, C.

1999-12-01

Full Text Available Solid solutions belonging to the Mn-rich region of the YNiXMn1-XO3 system have been studied. The powders were prepared by solid state reaction between the corresponding oxides. Sintered ceramics were obtained by firing at 1325-1350ºC. The incorporation of 20 atomic % Ni2+ to the Yttrium manganite induces the formation of a perovskite phase, with orthorhombic symmetry. Increase of the Ni amount leads to an increase of the orthorhombicity factor b/a, up to an amount of 50 atomic % Ni2+. Above this Ni amount, a biphasic system has been observed, with the presence of unreacted Y2O3. DC electrical conductivity measurements have shown semiconducting behaviour for all the solid solutions with perovskite-type structure. The room temperature conductivity increases with Ni until ~33 atomic % Ni, and then decreases. The 50/50 Ni/Mn composition has different values of conductivity and activation energy against those corresponding to samples with lower values of that ionic ratio. Small polaron hopping mechanism controls the conductivity in these ceramics. Results are discussed as a function of the Mn3+/Mn4+ ratio for each composition.Se han estudiado las soluciones sólidas correspondientes a la región rica en Mn del sistema YNiXMn1-XO3, entre 0 y 50 atomic % Ni. Los compuestos fueron preparados por reacción en estado sólido de los óxidos correspondientes. Se sinterizaron materiales cerámicos a 1325-1350ºC. Con cantidades de 20 atomic % Ni se produce la formación de una fase con estructura de perovskita, y simetría ortorrómbica. La distorsión ortorrómbica crece con el contenido de Ni. Por encima de 50 atomic % Ni, aparece Y2O3 sin reaccionar. Las soluciones sólidas muestran semiconducción con valores de σ que aumentan con el contenido de Ni hasta ~33 atomic %, para luego decrecer, hasta x=0.5. La composición 50/50 Ni/Mn muestra un comportamiento eléctrico algo diferente. Se discuten los resultados en función de la razón Mn3+/Mn4+ para cada

Microwave-assisted synthesis of high-voltage nanostructured LiMn1.5Ni0.5O4 spinel: tuning the Mn3+ content and electrochemical performance

CSIR Research Space (South Africa)

Jafta, CJ

2013-08-01

Full Text Available on the Mn3+ concentration and electrochemistry of the LiMn1.5Ni0.5O4 spinel. It is shown that microwave is capable of tuning the Mn3+ content of the spinel for enhanced electrochemical performance (high capacity, high capacity retention, excellent rate...

Zn-Doped LiNi1/3Co1/3Mn1/3O2 Composite as Cathode Material for Lithium Ion Battery: Preparation, Characterization, and Electrochemical Properties

Directory of Open Access Journals (Sweden)

Han Du

2015-01-01

Full Text Available Zn-doped LiNi1/3Co1/3Mn1/3O2 composite, Li(Ni1/3Co1/3Mn1/31–xZnxO2 (x = 0.02; 0.05; 0.08, is synthesized by the sol-gel method. The crystal structure, morphology, and electrochemical performance are investigated via X-ray diffraction (XRD, scanning electron microscope (SEM, cyclic voltammetry (CV, and constant current charge/discharge experiment. The result reveals that Zn-doping cathode material can reach the initial charge/discharge capacity of 188.8/162.9 mAh·g−1 for Li(Ni1/3Co1/3Mn1/30.98Zn0.02O2 and 179.0/154.1 mAh·g−1 for Li(Ni1/3Co1/3Mn1/30.95Zn0.05O2 with the high voltage of 4.4 V at 0.1 C. Furthermore, the capacity retention of Li(Ni1/3Co1/3Mn1/30.98Zn0.02O2 is 95.1% at 0.5 C after 50 cycles at room temperature. The improved electrochemical properties of Zn-doped LiNi1/3Co1/3Mn1/3O2 are attributed to reduced electrode polarization, enhanced capacity reversibility, and excellent cyclic performance.

Synthesis, structure and magnetic behavior of a new three-dimensional Manganese phosphite-oxalate: [C2N2H10][Mn2II(OH2)2(HPO3)2(C2O4)

International Nuclear Information System (INIS)

Ramaswamy, Padmini; Mandal, Sukhendu; Natarajan, Srinivasan

2009-01-01

A novel manganese phosphite-oxalate, [C 2 N 2 H 10 ][Mn 2 II (OH 2 ) 2 (HPO 3 ) 2 (C 2 O 4 )] has been hydothermally synthesized and its structure determined by single-crystal X-ray diffraction. The structure consists of neutral manganese phosphite layers, [Mn(HPO 3 )] ∞ , formed by MnO 6 octahedra and HPO 3 units, cross-linked by the oxalate moieties. The organic cations occupy the middle of the 8-membered one-dimensional channels. Magnetic studies indicate weak antiferromagnetic interactions between the Mn 2+ ions. - Abstract: A new antiferromagnetic three-dimensional inorganic-organic hybrid compound, [C 2 N 2 H 10 ][Mn 2 II (OH 2 ) 2 (HPO 3 ) 2 (C 2 O 4 )] has been prepared hydrothermally. The compound has neutral manganese layers pillared by oxalate units. The neutral manganese layers are shown here. Display Omitted

Effect of Ni content on microwave absorbing properties of MnAl powder

Energy Technology Data Exchange (ETDEWEB)

Wang, Zhen-zhong; Lin, Pei-hao, E-mail: gllph2002@163.com; Huang, Wei-chao; Pan, Shun-kang; Liu, Ye; Wang, Lei

2016-09-01

MnAlNi powder was prepared by the process of vacuum levitation melting and high-energy ball milling, The morphology and phase structure of the powder were analyzed by Scanning Electron Microscope(SEM), X-ray diffraction(XRD) and the effect of the Ni content on microwave absorbing properties of MnAl powder was investigated by an vector network analyzer. The addition of Ni, which improved the microwave absorbing properties of MnAl powder but not changed the composition of Al{sub 8}Mn{sub 5} alloy. The minimum reflectivity of (Al{sub 8}Mn{sub 5}){sub 0.95}Ni{sub 0.05} powder with a coating thickness (d) of 1.8 mm was about −40.8 dB and has better bandwidth effect, the absorbing mechanism of AlMnNi powders on the electromagnetic was related to the electromagnetic loss within the absorbing coatings and the effect of coating thickness on the interference loss of electromagnetic wave. - Highlights: • The grain size and cell volume of Al{sub 8}Mn{sub 5} alloy phase were decreased with the increasing of Ni. • ε″ and μ″ of powder moves toward low frequency region at the beginning then moves high. • The minimum reflectivity of (Al{sub 8}Mn{sub 5}){sub 0.95}Ni{sub 0.05} powder was −40.8 dB with 1.8 mm thickness. • The lowest reflection loss peak of (Al{sub 8}Mn{sub 5}){sub 0.95}Ni{sub 0.05} was −46.3 dB with 2.2 mm thickness.

Effects of cationic substitution on the electronic and magnetic properties of manganocuprate with a layered Eu3Ba2Mn2Cu2O12 structure

International Nuclear Information System (INIS)

Matsubara, Ichiro; Funahashi, Ryoji; Ueno, Kazuo; Ishikawa, Hiroshi; Kida, Noriaki; Ohno, Nobuhito

1998-01-01

Systematic studies on the effect of substitutions on the layered manganocuprate Eu 3 Ba 2 Mn 2 Cu 2 O 12 have been conducted. To introduce holes, the authors have made substitutions of Ca for Eu and/or Sc for Mn, (Eu 3-x Ca x )Ba 2 (Mn 2-y Sc y )Cu 2 O 12 . Single-phase compounds are obtained over a fairly wide range of x and y values for x ≤ 0.7 (y = 0), x ≤ 0.5 (y = 0.5), and x ≤ 0.1 (y = 1.0). The doped holes are received predominantly at the Mn-O site and change the charge of Mn from 3+ to 4+, and no superconductivity has been obtained for any sample. The electronic ground state of (Eu 3-x Ca x )Ba 2 (Mn 2-y Sc y )Cu 2 O 12 is discussed by comparing with that of the three-dimensional perovskite La 1-x Ca x MnO 3 and K 2 NiF 4 -type La 1-x Sr 1+x MnO 4 compounds. The substitution of Sr for Ba gives rise to a different crystal structure, the Sr 3 Ti 2 O 7 structure

The influence of Mn species on the SO2 removal of Mn-based activated carbon catalysts

International Nuclear Information System (INIS)

Qu, Yi-Fan; Guo, Jia-Xiu; Chu, Ying-Hao; Sun, Ming-Chao; Yin, Hua-Qiang

2013-01-01

Using Mn(NO 3 ) 2 as precursor, a series of Mn-based activated carbon catalysts were prepared by ultrasound-assisted excessive impregnation method and characterized by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and temperature programmed reduction (TPR). The influences of Mn species and nitric acid pretreatment on the removal role of SO 2 were investigated. MnO and Mn 3 O 4 coexist in catalysts calcined at 650 and 800 °C and exhibit best SO 2 removal ability, whereas Mn 2 O 3 formed in the catalyst calcined at 500 °C and shows poor activity. After treatment by nitric acid, the C=O of activated carbon support increases and the crystal size of MnO decreases, resulting in the enhancement of the catalytic activity. During reaction process, manganese oxides are gradually transferred into MnO 2 . And this change directly results in a decrease of activity. But the SO 2 removal rate has been maintained in the range of 30–40%, indicating that MnO 2 still has a certain SO 2 removal ability.

Interactive effects of MnO2, organic matter and pH on abiotic formation of N2O from hydroxylamine in artificial soil mixtures

Science.gov (United States)

Liu, Shurong; Berns, Anne E.; Vereecken, Harry; Wu, Di; Brüggemann, Nicolas

2017-02-01

Abiotic conversion of the reactive nitrification intermediate hydroxylamine (NH2OH) to nitrous oxide (N2O) is a possible mechanism of N2O formation during nitrification. Previous research has demonstrated that manganese dioxide (MnO2) and organic matter (OM) content of soil as well as soil pH are important control variables of N2O formation in the soil. But until now, their combined effect on abiotic N2O formation from NH2OH has not been quantified. Here, we present results from a full-factorial experiment with artificial soil mixtures at five different levels of pH, MnO2 and OM, respectively, and quantified the interactive effects of the three variables on the NH2OH-to-N2O conversion ratio (RNH2OH-to-N2O). Furthermore, the effect of OM quality on RNH2OH-to-N2O was determined by the addition of four different organic materials with different C/N ratios to the artificial soil mixtures. The experiments revealed a strong interactive effect of soil pH, MnO2 and OM on RNH2OH-to-N2O. In general, increasing MnO2 and decreasing pH increased RNH2OH-to-N2O, while increasing OM content was associated with a decrease in RNH2OH-to-N2O. Organic matter quality also affected RNH2OH-to-N2O. However, this effect was not a function of C/N ratio, but was rather related to differences in the dominating functional groups between the different organic materials.

Exchange bias of Ni nanoparticles embedded in an antiferromagnetic IrMn matrix

International Nuclear Information System (INIS)

Kuerbanjiang, Balati; Herr, Ulrich; Wiedwald, Ulf; Haering, Felix; Ziemann, Paul; Biskupek, Johannes; Kaiser, Ute

2013-01-01

The magnetic properties of Ni nanoparticles (Ni-NPs) embedded in an antiferromagnetic IrMn matrix were investigated. The Ni-NPs of 8.4 nm mean diameter were synthesized by inert gas aggregation. In a second processing step, the Ni-NPs were in situ embedded in IrMn films or SiO x films under ultrahigh vacuum (UHV) conditions. Findings showed that Ni-NPs embedded in IrMn have an exchange bias field H EB = 821 Oe at 10 K, and 50 Oe at 300 K. The extracted value of the exchange energy density is 0.06 mJ m −2 at 10 K, which is in good accordance with the results from multilayered thin film systems. The Ni-NPs embedded in SiO x did not show exchange bias. As expected for this particle size, they are superparamagnetic at T = 300 K. A direct comparison of the Ni-NPs embedded in IrMn or SiO x reveals an increase of the blocking temperature from 210 K to around 400 K. The coercivity of the Ni-NPs exchange coupled to the IrMn matrix at 10 K is 8 times larger than the value for Ni-NPs embedded in SiO x . We studied time-dependent remanent magnetization at different temperatures. The relaxation behavior is described by a magnetic viscosity model which reflects a rather flat distribution of energy barriers. Furthermore, we investigated the effects of different field cooling processes on the magnetic properties of the embedded Ni-NPs. Exchange bias values fit to model calculations which correlate the contribution of the antiferromagnetic IrMn matrix to its grain size. (paper)

Microemulsion based approach for nanospheres assembly into anisotropic nanostructures of NiMnO3 and their magnetic properties

Science.gov (United States)

Jha, Menaka; Kumar, Sandeep; Garg, Neha; Ramanujachary, Kandalam V.; Lofland, Samuel E.; Ganguli, Ashok K.

2018-02-01

The present study focuses on synthesis of anisotropic nanostructures of nickel manganese oxide (NiMnO3) obtained by thermal decomposition of nanocrystalline nickel manganese oxalate precursor, Ni0.5Mn0.5(C2O4)·2H2O which crystallized as nanorods. The synthesis of the oxalate precursor has been carried out via microemulsion-mediated process with cationic and non-ionic surfactants. The microemulsion led to reverse micelles, and the film flexibility of the micelle in presence of non-ionic surfactant (Tergitol) was reduced by increasing the chain length of the co-surfactant (1-butanol, 1-hexanol and 1-octanol) which led to the increase in reaction rate and hence increase in the aspect ratio of the nickel manganese oxalate by up to four times. However, in the presence of cationic surfactant, highly uniform nickel manganese oxalate nanorods were obtained. Further, the decomposition of the oxalate precursor was optimized to maintain the anisotropy of the rods of ternary metal oxide (NiMnO3). An electron microscopy study showed that the rods were made up of an assembly of ultrafine nanospheres. The NiMnO3 nanostructures were all ferrimagnetic with Curie temperature ranging between 437 and 467 K showing increasing saturation magnetization with increase in aspect ratio of the nanorods.

Thermodynamic investigations of the Mn-Ni-C-N quarternary alloys by solid-state galvanic cell technique

International Nuclear Information System (INIS)

Teng Lidong; Aune, Ragnhild; Seetharaman, Seshadri

2005-01-01

In view of the important applications of carbides and nitrides of transition metals in the hard materials industries, the thermodynamic activities of manganese in Mn-Ni-C-N alloys have been studied by solid-state galvanic cell technique with CaF 2 as the solid electrolyte. The phase compositions and microstructure of various alloys have been analyzed by X-ray diffraction (XRD) and scanning electron microscopy (SEM). Nitrogen was introduced into the alloy by equilibrating with N 2 gas. It was established during the experiments that the solubility of nitrogen in the alloys was affected by the carbon content. A (Mn,Ni) 4 (N,C) nitride was formed during the nitriding procedure in the alloys. The electromotive force (EMF) measurements were carried out in the temperature range 940-1127 K in order to determine the activities of Mn in the alloys. The activities of manganese were calculated and compared with those of the corresponding Mn-Ni-C ternary alloys

One-pot synthesis of a Ni–Mn{sub 3}O{sub 4} nanocomposite for supercapacitors

Energy Technology Data Exchange (ETDEWEB)

Xu, Guo-rong, E-mail: grxu@hnust.edu.cn; Shi, Jin-jin; Dong, Wen-hao; Wen, Ya; Min, Xiang-ping; Tang, An-ping

2015-05-05

Highlights: • Ni–Mn{sub 3}O{sub 4} nanocomposites have been synthesized simply. • Mn{sub 3}O{sub 4} particles were deposited on surface of Ni particles with OH functional groups. • Ni–Mn{sub 3}O{sub 4} composites could be quickly conditioned to birnessite-type MnO{sub 2}. • A specific capacitance of 230 F g{sup −1} was obtained for Ni (17.3%)–Mn{sub 3}O{sub 4} nanocomposite. - Abstract: Ni–Mn{sub 3}O{sub 4} nanocomposite has been prepared successfully by chemical oxidation in an alkaline solution of Mn{sup 2+} on the surface of Ni nanoparticles with OH functional groups using one-pot method. The obtained Ni–Mn{sub 3}O{sub 4} nanocomposite was characterized using a scanning electron microscope (SEM), a transmission electron microscope (TEM), X-ray diffraction (XRD) analysis and various electrochemical techniques, such as cyclic voltammetry (CV), galvanostatic charge/discharge (GC/D) and electrochemical impedance spectroscopy (EIS). The average crystal sizes of Mn{sub 3}O{sub 4} were found to decrease linearly with increasing Ni content in the Ni–Mn{sub 3}O{sub 4} composite. The Ni–Mn{sub 3}O{sub 4} nanocomposite could be easily conditioned and inverted to birnessite-type MnO{sub 2}. A specific capacitance of 230 F g{sup −1} (based on pure Mn{sub 3}O{sub 4}) was obtained for the Ni (17.3%)–Mn{sub 3}O{sub 4} nanocomposite at a current rate of 0.25 A g{sup −1}, and 94% of the initial capacitance was retained after 1000 GC/D cycles at a current rate of 1 A g{sup −1}. It is concluded that the Ni–Mn{sub 3}O{sub 4} nanocomposite is a promising electrode materials for supercapacitors.

Study on lithium extraction from brines based on LiMn2O4/Li1-xMn2O4 by electrochemical method

International Nuclear Information System (INIS)

Zhao, Meng-Yao; Ji, Zhi-Yong; Zhang, Yong-Guang; Guo, Zhi-Yuan; Zhao, Ying-Ying; Liu, Jie; Yuan, Jun-Sheng

2017-01-01

Highlights: •A recovery system with LiMn 2 O 4 /Li 1-x Mn 2 O 4 as electrodes was used to extract lithium. •The influence sequence of coexisting ions on lithium extraction was Mg 2+ > Na + > Ca 2+ > K + . •The values of α Li-Na , α Li-Mg and α Li-Ca were more than 300, 70 and 110, respectively. •The specific energy consumption was between 18 and 19 W h·mol −1 . -- Abstract: Lithium rechargeable batteries have been used for lithium extraction in recent years. Here, we report on a highly selective lithium recovery system that consists of a LiMn 2 O 4 positive electrode, a Li 1-x Mn 2 O 4 negative electrode and a monovalent selective anion-exchange membrane. The effect of potential, temperature and coexisting ions on lithium extraction were investigated in this paper, and the lithium recovery system was applied to extract lithium from brine and concentrated seawater. The extraction capacity of Li + reached 34.31 mg· (1 g LiMn 2 O 4 ) −1 at 1.2 V. With higher reaction rate and lower energy consumption, 25 °C (room temperature) was considered as the appropriate temperature. The system still remained high selective for Li + even in the presence of impurity ions (K + , Na + , Mg 2+ , Ca 2+ ). With simulated brine and concentrated seawater as source solutions, the concentrations of Na + , Mg 2+ and Ca 2+ were reduced more than 300, 70 and 100 times, consuming 18–19 W h per mole of lithium recovered. And the electrodes still had high separation coefficients of Li + and Me n+ (Na + , Mg 2+ , Ca 2+ ) after five cycles although a slight drop was existing.

Improved high-voltage performance of LiNi1/3Co1/3Mn1/3O2 cathode with Tris(2,2,2-trifluoroethyl) phosphite as electrolyte additive

International Nuclear Information System (INIS)

Wang, Long; Ma, Yulin; Li, Qin; Cui, Yingzhi; Wang, Panpan; Cheng, Xinqun; Zuo, Pengjian; Du, Chunyu; Gao, Yunzhi

2017-01-01

Tris(2,2,2-trifluoroethyl) phosphite (TTFEP) is investigated as an electrolyte additive to improve the electrochemical performance of LiNi 1/3 Co 1/3 Mn 1/3 O 2 cathode at high operating voltage (4.6 V). Charge/discharge measurements demonstrate that TTFEP is effective to improve the cycling stability and rate capability of LiNi 1/3 Co 1/3 Mn 1/3 O 2 cathode. The capacity retention of LiNi 1/3 Co 1/3 Mn 1/3 O 2 /Li cell with 1% TTFEP-containing electrolyte reaches up to 85.4% after 100 cycles at 0.5C (1C = 160 mA g −1 ), while that of the cell with the baseline electrolyte (1 M LiPF 6 in EC/DMC electrolyte) only remains 74.2%. Moreover, the discharge capacity of the cathode with 1% TTFEP-containing electrolyte could maintain around 112.0 mAh g −1 at 4C. Based on the characterization of electrochemical impedance spectroscopy (EIS), scanning electron microscopy (SEM), X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS), a protective interphase film formed on the cathode surface can be found due to the preferential oxidation of TTFEP, which inhibits the electrolyte decomposition and mitigates the cathode structural destruction, leading to the improved electrochemical performance of LiNi 1/3 Co 1/3 Mn 1/3 O 2 cathode at high voltage.

GITT studies on oxide cathode LiNi1/3Co1/3Mn1/3O2 synthesized ...

Indian Academy of Sciences (India)

2016-08-26

Aug 26, 2016 ... GITT studies on oxide cathode LiNi1/3Co1/3Mn1/3O2 synthesized by citric acid assisted high-energy ball milling ... The State Key Laboratory Base of Novel Functional Materials and Preparation Science; The Faculty of Materials Science and Chemical Engineering, Ningbo University, Ningbo 315211, P. R. ...

Magnetic interactions in martensitic Ni-Mn based Heusler systems

Energy Technology Data Exchange (ETDEWEB)

Aksoy, Seda

2010-04-22

In this work, magnetic, magnetocaloric and structural properties are investigated in Ni-Mn-based martensitic Heusler alloys with the aim to tailor these properties as well as to understand in detail the magnetic interactions in the various crystallographic states of these alloys. We choose Ni{sub 50}Mn{sub 34}In{sub 16} as a prototype which undergoes a martensitic transformation and exhibits field-induced strain and the inverse magnetocaloric effect. Using the structural phase diagram of martensitic Ni-Mn-based Heusler alloys, we substitute gallium and tin for indium to carry these effects systematically closer to room temperature by shifting the martensitic transformation. A magneto-calorimeter is designed and built to measure adiabatically the magnetocaloric effect in these alloys. The temperature dependence of strain under an external magnetic field is studied in Ni{sub 50}Mn{sub 50-x}Z{sub x} (Z: Ga, Sn, In and Sb) and Ni{sub 50}Mn{sub 34}In{sub 16-x}Z{sub x} (Z: Ga and Sn). An argument based on the effect of the applied magnetic field on martensite nucleation is adopted to extract information on the direction of the magnetization easy axis in the martensitic unit cell in Heusler alloys. Parallel to these studies, the structure in the presence of an external field is also studied by powder neutron diffraction. It is demonstrated that martensite nucleation is influenced by cooling the sample under a magnetic field such that the austenite phase is arrested within the martensitic state. The magnetic interactions in Ni{sub 50}Mn{sub 37}Sn{sub 13} and Ni{sub 50}Mn{sub 40}Sb{sub 10} are characterized by using neutron polarization analysis. Below the martensitic transformation temperature, M{sub s}, an antiferromagnetically correlated state is found. Ferromagnetic resonance experiments are carried out on Ni{sub 50}Mn{sub 37}Sn{sub 13} and Ni{sub 50}Mn{sub 34}In{sub 16} to gain more detailed information on the nature of the magnetic interactions. The experimental

Synthesis of Li{sub 2}Si{sub 2}O{sub 5}-coated LiNi{sub 0.6}Co{sub 0.2}Mn{sub 0.2}O{sub 2} cathode materials with enhanced high-voltage electrochemical properties for lithium-ion batteries

Energy Technology Data Exchange (ETDEWEB)

Liu, Shengjie; Wu, Hao; Huang, Ling; Xiang, Mingwu; Liu, Heng; Zhang, Yun, E-mail: y_zhang@scu.edu.cn

2016-07-25

electrode (52% retention) due to the robust protective effect of the Li{sub 2}Si{sub 2}O{sub 5} coating layer. All these results indicate that the Li{sub 2}Si{sub 2}O{sub 5}-coated LiNi{sub 0.6}Co{sub 0.2}Mn{sub 0.2}O{sub 2} will be a promising cathode material for lithium-ion batteries with fascinating electrochemical energy storage capabilities. - Graphical abstract: Silicic acid is used as a remover to react with lithium residues (LiOH and Li{sub 2}CO{sub 3}) on the surface of LiNi{sub 0.6}Co{sub 0.2}Mn{sub 0.2}O{sub 2} and subsequently generate an ion-conductive coating layer of Li{sub 2}Si{sub 2}O{sub 5} after heat treatment. The surface-coated cathode materials show a remarkably enhanced rate capability, discharge specific capacities, and cycling performance for Li-ion batteries. - Highlights: • H{sub 2}SiO{sub 3} is used as a remover to react with lithium residues on LiNi{sub 0.6}Co{sub 0.2}Mn{sub 0.2}O{sub 2} surface. • A surface coating layer of Li{sup +}-conductive Li{sub 2}Si{sub 2}O{sub 5} is formed. • Coating layer improves the velocity of Li{sup +} migration on electrode surface. • Erosion from the HF and CO{sub 2} on electrode is greatly suppressed.

Enhanced electrochemical performance of LiMn2O4 by constructing a stable Mn2+-rich interface

Science.gov (United States)

Lu, Zhongpei; Lu, Xiaojun; Ding, Jingjing; Zhou, Ting; Ge, Tao; Yang, Gang; Yin, Fan; Wu, Mingfang

2017-12-01

Spinel LiMn2O4 has drawn continuous attentions due to its low cost, good electrochemical performance, environmental friendliness and natural abundant resources. In view of its severe capacity fading, some types of manganese-based compounds with different Mn oxidation states are selected to protect bare LiMn2O4 by constructing a stable coating layer. In this work, LiMn2O4@LiMnPO4 composite, spherical LiMn2O4 (LMO) as core and Mn2+-rich phase of LiMnPO4 (LMP) as shell, is designed and synthesized. Two composites of LiMn2O4 particles coated with 3 wt% and 10 wt% LiMnPO4 have been compared studied. After 100 cycles at 0.5C rate, the two samples deliver capacity retentions of 96.63% and 93.23% of their initial capacities. Moreover, LMO coated by 3 wt% LiMnPO4 delivers 100.3 mAh g-1 after 200 cycles at 10C rate and 76.3 mAh g-1 after 1000 cycles at 20C rate, much higher than bare LiMn2O4 with 90 mAh g-1 and 45.8 mAh g-1, respectively. This core-shell structure with Mn2+-rich phase as a coating layer effectively enhance the material's cycling performance and rate capacity by reducing the contact of LiMn2O4 with electrolyte.

Cation Effects on the Layer Structure of Biogenic Mn-Oxides

Energy Technology Data Exchange (ETDEWEB)

Zhu, M.; Ginder-Vogel, M; Parikh, S; Feng, X; Sparks, D

2010-01-01

Biologically catalyzed Mn(II) oxidation produces biogenic Mn-oxides (BioMnO{sub x}) and may serve as one of the major formation pathways for layered Mn-oxides in soils and sediments. The structure of Mn octahedral layers in layered Mn-oxides controls its metal sequestration properties, photochemistry, oxidizing ability, and topotactic transformation to tunneled structures. This study investigates the impacts of cations (H{sup +}, Ni(II), Na{sup +}, and Ca{sup 2+}) during biotic Mn(II) oxidation on the structure of Mn octahedral layers of BioMnO{sub x} using solution chemistry and synchrotron X-ray techniques. Results demonstrate that Mn octahedral layer symmetry and composition are sensitive to previous cations during BioMnO{sub x} formation. Specifically, H{sup +} and Ni(II) enhance vacant site formation, whereas Na{sup +} and Ca{sup 2+} favor formation of Mn(III) and its ordered distribution in Mn octahedral layers. This study emphasizes the importance of the abiotic reaction between Mn(II) and BioMnO{sub x} and dependence of the crystal structure of BioMnO{sub x} on solution chemistry.

Synthesis and properties of Li{sub 2}MnO{sub 3}-based cathode materials for lithium-ion batteries

Energy Technology Data Exchange (ETDEWEB)

Xue, Leigang; Zhang, Shu; Li, Shuli; Lu, Yao; Toprakci, Ozan [Fiber and Polymer Science Program, Department of Textile Engineering, Chemistry and Science, North Carolina State University, Raleigh, NC 27695-8301 (United States); Xia, Xin [Fiber and Polymer Science Program, Department of Textile Engineering, Chemistry and Science, North Carolina State University, Raleigh, NC 27695-8301 (United States); College of Textile and Clothing, Xinjiang University, Xinjiang, Urumchi 830046 (China); Chen, Chen [College of Textile and Clothing, Xinjiang University, Xinjiang, Urumchi 830046 (China); Hu, Yi [Fiber and Polymer Science Program, Department of Textile Engineering, Chemistry and Science, North Carolina State University, Raleigh, NC 27695-8301 (United States); Engineering Research Center for Eco-Dyeing and Finishing of Textiles, Zhejiang Sci-Tech University, Hangzhou, Zhejiang 310018 (China); Zhang, Xiangwu, E-mail: xiangwu_zhang@ncsu.edu [Fiber and Polymer Science Program, Department of Textile Engineering, Chemistry and Science, North Carolina State University, Raleigh, NC 27695-8301 (United States)

2013-11-15

Highlights: •0.3Li{sub 2}MnO{sub 3}·0.5LiMn{sub 0.5}Ni{sub 0.5}O{sub 2}·0.2LiCoO{sub 2} was synthesized by a co-precipitation method. •The preparation method is simple and this material is inexpensive due to the high contents of Mn and Ni. •The material could be charged to a high potential to extract more lithium without structural damage. •A relatively high capacity of 178 mAh g{sup −1} is delivered between 2.0 and 4.6 V with excellent cycling performance. -- Abstract: Lithium-ion batteries have been wildly used in various portable electronic devices and the application targets are currently moving from small-sized mobile devices to large-scale electric vehicles and grid energy storage. Therefore, lithium-ion batteries with higher energy densities are in urgent need. For high-energy cathodes, Li{sub 2}MnO{sub 3}–LiMO{sub 2} layered–layered (M = Mn, Co, Ni) materials are of significant interest due to their high specific capacities over wide operating potential windows. Here, three Li{sub 2}MnO{sub 3}-based cathode materials with α-NaFeO{sub 2} structure were prepared by a facile co-precipitation method and subsequent heat treatment. Among these three materials, 0.3Li{sub 2}MnO{sub 3}·0.5LiMn{sub 0.5}Ni{sub 0.5}O{sub 2}·0.2LiCoO{sub 2} shows the best lithium storage capability. This cathode material is composed of uniform nanosized particles with diameters ranging from 100 to 200 nm, and it could be charged to a high cutoff potential to extract more lithium, resulting in a high capacity of 178 mAh g{sup −1} between 2.0 and 4.6 V with almost no capacity loss over 100 cycles.

Structural and thermal stabilities of layered Li(Ni 1/3Co 1/3Mn 1/3)O 2 materials in 18650 high power batteries

Science.gov (United States)

He, Yan-Bing; Ning, Feng; Yang, Quan-Hong; Song, Quan-Sheng; Li, Baohua; Su, Fangyuan; Du, Hongda; Tang, Zhi-Yuan; Kang, Feiyu

The structural and thermal stabilities of the layered Li(Ni 1/3Co 1/3Mn 1/3)O 2 cathode materials under high rate cycling and abusive conditions are investigated using the commercial 18650 Li(Ni 1/3Co 1/3Mn 1/3)O 2/graphite high power batteries. The Li(Ni 1/3Co 1/3Mn 1/3)O 2 materials maintain their layered structure even when the power batteries are subjected to 200 cycles with 10 C discharge rate at temperatures of 25 and 50 °C, whereas their microstructure undergoes obvious distortion, which leads to the relatively poor cycling performance of power batteries at high charge/discharge rates and working temperature. Under abusive conditions, the increase in the battery temperature during overcharge is attributed to both the reactions of electrolyte solvents with overcharged graphite anode and Li(Ni 1/3Co 1/3Mn 1/3)O 2 cathode and the Joule heat that results from the great increase in the total resistance (R cell) of batteries. The reactions of fully charged Li(Ni 1/3Co 1/3Mn 1/3)O 2 cathodes and graphite anodes with electrolyte cannot be activated during short current test in the fully charged batteries. However, these reactions occur at around 140 °C in the fully charged batteries during oven test, which is much lower than the temperature of about 240 °C required for the reactions outside batteries.

The crystal structure and electrical properties of K{sub 2}NiF{sub 4}-type (Ca{sub 2−x}Sm{sub x})MnO{sub 4}

Energy Technology Data Exchange (ETDEWEB)

Taguchi, Hideki, E-mail: htaguchi@cc.okayama-u.ac.jp [The Graduate School of Natural Science and Technology (Science), Okayama University, 3-1-1 Tsushima-Naka, Kita-Ku, Okayama 700-8530 (Japan); Kido, Hiroyasu [Osaka Municipal Technical Research Institute, 1-6-50 Morinomiya, Jyoto-Ku, Osaka 536-8553 (Japan); Kato, Masaki; Hirota, Ken [Department of Molecular Chemistry and Biochemistry, Faculty of Science and Engineering, Doshisha University, Kyo-Tanabe 610-0321 (Japan)

2015-04-15

Graphical abstract: The relationship between log ρ of K{sub 2}NiF{sub 4}-type (Ca{sub 2−x}Sm{sub x})MnO{sub 4} and 1000/T. - Highlights: • K{sub 2}NiF{sub 4}-type (Ca{sub 2−x}Sm{sub x})MnO{sub 4} was synthesized using a polymerized complex route. • The semiconductive samples had minimum values of ρ and E{sub a} at x = 0.1. • The log ρ–1/T curve of x = 0.3 consisted of two different lines at 315 K. • The 1/χ − T curve of x = 0.3 had a peak at 325 K. • These results indicated the presence of a charge-ordering transition at x = 0.3. - Abstract: K{sub 2}NiF{sub 4}-type (Ca{sub 2−x}Sm{sub x})MnO{sub 4} (0.02 ≤ x ≤ 0.3) was synthesized using a polymerized complex route. The crystal structure changed from tetragonal to orthorhombic at x = 0.3. A variation in the lattice parameters was explained by the Mn–O(2) distance, the Mn−O(2)−Mn angle, and the (Ca,Sm)–(Ca,Sm) distance. The samples were n-type semiconductors, and the minimum values of electrical resistivity (ρ) and an energy gap (E{sub g}) at x = 0.1 were accounted by electron transfer through an Mn−O(2)−Mn path and overlap between the Mnt{sub 2g} and Op{sub π} orbitals. In the sample (x = 0.3), the log ρ–1000/T curve consisted of two different lines that intersected at ca. 325 K, and a peak was observed at ca. 315 K in the magnetic susceptibility–temperature curve. These results indicated the presence of a charge-ordering (CO) transition at 315–325 K.

Multireversible redox processes in pentanuclear bis(triple-helical) manganese complexes featuring an oxo-centered triangular {Mn(II)2Mn(III)(μ3-O)}5+ or {Mn(II)Mn(III)2(μ3-O)}6+ core wrapped by two {Mn(II)2(bpp)3}-.

Science.gov (United States)

Romain, Sophie; Rich, Jordi; Sens, Cristina; Stoll, Thibaut; Benet-Buchholz, Jordi; Llobet, Antoni; Rodriguez, Montserrat; Romero, Isabel; Clérac, Rodolphe; Mathonière, Corine; Duboc, Carole; Deronzier, Alain; Collomb, Marie-Noëlle

2011-09-05

A new pentanuclear bis(triple-helical) manganese complex has been isolated and characterized by X-ray diffraction in two oxidation states: [{Mn(II)(μ-bpp)(3)}(2)Mn(II)(2)Mn(III)(μ-O)](3+) (1(3+)) and [{Mn(II)(μ-bpp)(3)}(2)Mn(II)Mn(III)(2)(μ-O)](4+) (1(4+)). The structure consists of a central {Mn(3)(μ(3)-O)} core of Mn(II)(2)Mn(III) (1(3+)) or Mn(II)Mn(III)(2) ions (1(4+)) which is connected to two apical Mn(II) ions through six bpp(-) ligands. Both cations have a triple-stranded helicate configuration, and a pair of enantiomers is present in each crystal. The redox properties of 1(3+) have been investigated in CH(3)CN. A series of five distinct and reversible one-electron waves is observed in the -1.0 and +1.50 V potential range, assigned to the Mn(II)(4)Mn(III)/Mn(II)(5), Mn(II)(3)Mn(III)(2)/Mn(II)(4)Mn(III), Mn(II)(2)Mn(III)(3)/Mn(II)(3)Mn(III)(2), Mn(II)Mn(III)(4)/Mn(II)(2)Mn(III)(3), and Mn(III)(5)/Mn(II)Mn(III)(4) redox couples. The two first oxidation processes leading to Mn(II)(3)Mn(III)(2) (1(4+)) and Mn(II)(2)Mn(III)(3) (1(5+)) are related to the oxidation of the Mn(II) ions of the central core and the two higher oxidation waves, close in potential, are thus assigned to the oxidation of the two apical Mn(II) ions. The 1(4+) and 1(5+) oxidized species and the reduced Mn(4)(II) (1(2+)) species are quantitatively generated by bulk electrolyses demonstrating the high stability of the pentanuclear structure in four oxidation states (1(2+) to 1(5+)). The spectroscopic characteristics (X-band electron paramagnetic resonance, EPR, and UV-visible) of these species are also described as well as the magnetic properties of 1(3+) and 1(4+) in solid state. The powder X- and Q-band EPR signature of 1(3+) corresponds to an S = 5/2 spin state characterized by a small zero-field splitting parameter (|D| = 0.071 cm(-1)) attributed to the two apical Mn(II) ions. At 40 K, the magnetic behavior is consistent for 1(3+) with two apical S = 5/2 {Mn(II)(bpp)(3)}(-) and one S

Investigation into the dehydration of selenate doped Na2M(SO4)2·2H2O (M = Mn, Fe, Co and Ni): Stabilisation of the high Na content alluaudite phases Na3M1.5(SO4)3-1.5x(SeO4)1.5x (M = Mn, Co and Ni) through selenate incorporation

Science.gov (United States)

Driscoll, L. L.; Kendrick, E.; Knight, K. S.; Wright, A. J.; Slater, P. R.

2018-02-01

In this paper we report an investigation into the phases formed on dehydration of Na2M(SO4)2-x(SeO4)x·2H2O (0 ≤ x ≤ 1; M = Mn, Fe, Co and Ni). For the Fe series, all attempts to dehydrate the samples doped with selenate resulted in amorphous products, and it is suspected that a side redox reaction involving the Fe and selenate may be occurring leading to phase decomposition and hence the lack of a crystalline product on dehydration. For M = Mn, Co, Ni, the structure observed was shown to depend upon the transition metal cation and level of selenate doping. An alluaudite phase, Na3M1.5(SO4)3-1.5x(SeO4)1.5x, was observed for the selenate doped compositions, with this phase forming as a single phase for x ≥ 0.5 M = Co, and x = 1.0 M = Ni. For M = Mn, the alluaudite structure is obtained across the series, albeit with small impurities for lower selenate content samples. Although the alluaudite-type phases Na2+2y(Mn/Co)2-y(SO4)3 have recently been reported [1,2], doping with selenate appears to increase the maximum sodium content within the structure. Moreover, the selenate doped Ni based samples reported here are the first examples of a Ni sulfate/selenate containing system exhibiting the alluaudite structure.

Mesoporous MFe{sub 2}O{sub 4} (M = Mn, Co, and Ni) for anode materials of lithium-ion batteries: Synthesis and electrochemical properties

Energy Technology Data Exchange (ETDEWEB)

Duan, Lianfeng, E-mail: duanlf@mail.ccut.edu.cn [State Key Laboratory of Rare Earth Resource Utilization, Changchun Institute of Applied Chemistry, Chinese Academy of Sciences, Changchun 130022 (China); Key Laboratory of Advanced Structural Materials, Ministry of Education, and Department of Materials Science and Engineering, Changchun University of Technology, Changchun 130012 (China); Wang, Yuanxin; Wang, Linan [Key Laboratory of Advanced Structural Materials, Ministry of Education, and Department of Materials Science and Engineering, Changchun University of Technology, Changchun 130012 (China); Zhang, Feifei [State Key Laboratory of Rare Earth Resource Utilization, Changchun Institute of Applied Chemistry, Chinese Academy of Sciences, Changchun 130022 (China); University of Chinese Academy of Sciences, Beijing 100049 (China); Wang, Limin [State Key Laboratory of Rare Earth Resource Utilization, Changchun Institute of Applied Chemistry, Chinese Academy of Sciences, Changchun 130022 (China)

2015-01-15

Highlights: • MFe{sub 2}O{sub 4} (M = Mn, Co, and Ni) are synthesized by a template-free hydrothermal method. • The mesoporous morphology is formed by self-assembly of crystal nucleus. • The mesporous MnFe{sub 2}O{sub 4} have the active phase and the synergy for Li-ion storage. - Abstract: The MFe{sub 2}O{sub 4} (M = Mn, Co, and Ni) mesoporous spheres with an average diameter of 250 nm were synthesized through a template-free hydrothermal method. The mesoporous MnFe{sub 2}O{sub 4} with a large surface area of 87.5 m{sup 2}/g and an average pore size of 27.52 nm were obtained. As the anode materials for Li-ion batteries, the mesoporous MnFe{sub 2}O{sub 4} exhibits excellent initial charge and discharge capacities of 1010 and 642.5 mA h/g. After 50 cycles, the discharge capacity could still remain at 379 mA h/g. The results showed that the active phase and the synergy between different metal oxides greatly improved the electrochemical performance, and the mesoporous composite could stabilize the structure of the electrodes.

Liquid flow deposited spinel (Ni,Mn){sub 3}O{sub 4} thin films for microbolometer applications

Energy Technology Data Exchange (ETDEWEB)

Le, Duc Thang, E-mail: ducthang36@skku.edu [Intelligent Electronic Component Team, Electronic Materials Convergence Division, Korea Institute of Ceramic Engineering and Technology, Seoul 153-801 (Korea, Republic of); School of Advanced Materials Science & Engineering, Sungkyunkwan University, Suwon 440-746 (Korea, Republic of); Jeon, Chang Jun; Lee, Kui Woong; Jeong, Young Hun; Yun, Ji Sun [Intelligent Electronic Component Team, Electronic Materials Convergence Division, Korea Institute of Ceramic Engineering and Technology, Seoul 153-801 (Korea, Republic of); Yoon, Dae Ho, E-mail: dhyoon@skku.edu [School of Advanced Materials Science & Engineering, Sungkyunkwan University, Suwon 440-746 (Korea, Republic of); Cho, Jeong Ho, E-mail: goedc@kicet.re.kr [Intelligent Electronic Component Team, Electronic Materials Convergence Division, Korea Institute of Ceramic Engineering and Technology, Seoul 153-801 (Korea, Republic of)

2015-03-01

Highlights: • Highly quality (Ni,Mn){sub 3}O{sub 4} thin films were grown using liquid flow deposited (LFD) technique. • It is possible to deposit multi–component manganite–oxide thin films by LFD at low temperatures. • Nickel–manganite films showed a good negative temperature coefficient (NTC) characteristic. • Liquid flow deposited (Ni,Mn){sub 3}O{sub 4} thin films are very potential for microbolometer applications. - Abstract: A liquid flow deposition (LFD) technique was initially used for the fabrication of single-component Mn{sub 3}O{sub 4} thin films onto Si wafer substrates at a range of substrate temperatures of 30–80 °C, with the introduction of an oxidizing reagent (H{sub 2}O{sub 2}). As a result, solid thin films were well formed from an aqueous solution. An X-ray diffraction (XRD) analysis showed typical characteristics of hausmannite Mn{sub 3}O{sub 4} with a spinel tetragonal phase. Field-emission scanning electron microscopy (FE-SEM) observations revealed nano-sized grains arranged uniformly on a dense and smooth surface for all of the as-deposited films. On the other hand, the LFD method was then extended to prepare two-component nickel–manganite films according to the binary chemical composition of Ni{sub x}Mn{sub 3−x}O{sub 4} with x = 0.02–0.2. The as-grown nickel–manganite films showed a surface with a good quality with a spherical bead-like architecture when x ≤ 0.10, while a conversion from spherical grains into highly porous nanowalls in the microstructure was noted in films when x ≥ 0.12. These results signify that it is possible to fabricate various multi-component manganite-oxide thin films at a low temperature. In addition, the dependences of the room-temperature electrical resistivity (ρ) and the temperature coefficient of resistance (TCR) on the Ni substitution level (x) were investigated on films annealed at 400 °C.

Magnetic properties of NiMn{sub 2}O{sub 4−δ} (nickel manganite): Multiple magnetic phase transitions and exchange bias effect

Energy Technology Data Exchange (ETDEWEB)

Tadic, Marin, E-mail: marint@vinca.rs [Condensed Matter Physics Laboratory, Vinca Institute of Nuclear Sciences, University of Belgrade, POB 522, 11001 Belgrade (Serbia); Savic, S.M. [Institute for Multidisciplinary Research, University of Belgrade, Kneza Viseslava 1, 11000 Belgrade (Serbia); Jaglicic, Z. [University of Ljubljana, Faculty of Civil Engineering and Geodesy and Institute of Mathematics, Physics and Mechanics, Jadranska 19, 1000 Ljubljana (Slovenia); Vojisavljevic, K.; Radojkovic, A.; Prsic, S. [Institute for Multidisciplinary Research, University of Belgrade, Kneza Viseslava 1, 11000 Belgrade (Serbia); Nikolic, Dobrica [Department of Physics, University of Belgrade Faculty of Mining and Geology, Belgrade (Serbia)

2014-03-05

Highlights: • We have successfully synthesized NiMn{sub 2}O{sub 4−δ} sample by complex polymerization synthesis. • Magnetic measurements reveal complex properties and triple magnetic phase transitions. • Magnetic measurements of M(H) show hysteretic behavior below 120 K. • Hysteresis properties after cooling of the sample in magnetic field show exchange bias effect. -- Abstract: We present magnetic properties of NiMn{sub 2}O{sub 4−δ} (nickel manganite) which was synthesized by complex polymerization synthesis method followed by successive heat treatment and final calcinations in air at 1200 °C. The sample was characterized by using X-ray powder diffractometer (XRPD), scanning electron microscopy (SEM), field-emission scanning electron microscopy (FE-SEM) and superconducting quantum interference device (SQUID) magnetometer. The XRPD and FE-SEM studies revealed NiMn{sub 2}O{sub 4−δ} phase and good crystallinity of particles. No other impurities have been observed by XRPD. The magnetic properties of the sample have been studied by measuring the temperature and field dependence of magnetization. Magnetic measurements of M(T) reveal rather complex magnetic properties and multiple magnetic phase transitions. We show three magnetic phase transitions with transition temperatures at T{sub M1} = 35 K (long-range antiferromagnetic transition), T{sub M2} = 101 K (antiferromagnetic-type transition) and T{sub M3} = 120 K (ferromagnetic-like transition). We found that the T{sub M1} transition is strongly dependent on the strength of the applied magnetic field (T{sub M1} decreases with increasing applied field) whereas the T{sub M3} is field independent. Otherwise, the T{sub M2} maximum almost disappears in higher applied magnetic fields (H = 1 kOe and 10 kOe). Magnetic measurements of M(H) show hysteretic behavior below T{sub M3}. Moreover, hysteresis properties measured after cooling of the sample in magnetic field of 10 kOe show exchange bias effect with an

GITT studies on oxide cathode LiNi1/3Co1/3Mn1/3O2 synthesized ...

Indian Academy of Sciences (India)

Li diffusion; LiNi1/3Co1/3Mn1/3O2; lithium ion batteries; layered structure. 1. Introduction ... The coin-type cell CR2012 consisting of a metallic- lithium foil anode ... and the polyvinylidenefluoride (PVDF) binder with a mass ratio of 4:1:1 in NMP ...

Spherical α-MnO2 Supported on N-KB as Efficient Electrocatalyst for Oxygen Reduction in Al–Air Battery

Directory of Open Access Journals (Sweden)

Kui Chen

2018-04-01

Full Text Available Traditional noble metal platinum (Pt is regarded as a bifunctional oxygen catalyst due to its highly catalytic efficiency, but its commercial availability and application is often restricted by high cost. Herein, a cheap and effective catalyst mixed with α-MnO2 and nitrogen-doped Ketjenblack (N-KB (denoted as MnO2-SM150-0.5 is examined as a potential electrocatalyst in oxygen reduction reactions (ORR and oxygen evolution reactions (OER. This α-MnO2 is prepared by redox reaction between K2S2O8 and MnSO4 in acid conditions with a facile hydrothermal process (named the SM method. As a result, MnO2-SM150-0.5 exhibits a good catalytic performance for ORR in alkaline solution, and this result is comparable to a Pt/C catalyst. Moreover, this catalyst also shows superior durability and methanol tolerance compared with a Pt/C catalyst. It also displays a discharge voltage (~1.28 V at a discharge density of 50 mA cm−2 in homemade Al–air batteries that is higher than commercial 20% Pt/C (~1.19 V. The superior electrocatalytic performance of MnO2-SM150-0.5 could be attributed to its higher Mn3+/Mn4+ ratio and the synergistic effect between MnO2 and the nitrogen-doped KB. This study provides a novel strategy for the preparation of an MnO2-based composite electrocatalyst.

Effect of chemical treatment on the electrochemical properties of Li1.2NixMn0.8-xO2 (x = 0.2 and 0.25) in lithium-ion batteries

Science.gov (United States)

Konishi, Hiroaki; Hirano, Tatsumi; Takamatsu, Daiko; Gunji, Akira; Feng, Xiaoliang; Furutsuki, Sho; Okumura, Takefumi; Terada, Shohei

2018-02-01

The effect of chemical treatment using (NH4)2SO4 on the electrochemical properties of Li1.2Ni0.2Mn0.6O2 and Li1.2Ni0.25Mn0.55O2 was investigated. The treatment was effective in improving the Coulombic efficiency and discharge capacity of a Li1.2Ni0.2Mn0.6O2 cathode, but treatment with too much (NH4)2SO4 degraded the cathode's electrochemical performance. The effect of (NH4)2SO4 treatment on the charge-discharge reaction mechanism of Li1.2Ni0.2Mn0.6O2 was investigated by evaluating reaction potential, particle configuration, and oxidation state of transition metal. The experimental results indicated that the changes in the electrochemical performance of the treated cathodes were attributed to the changes in the surface state and of the element contributing to the redox reaction. Treatment with an appropriate amount of (NH4)2SO4 also improved the electrochemical performance of the high-nickel-content lithium-rich layer-structured cathode material Li1.2Ni0.25Mn0.55O2.

3D MnO2-graphene composites with large areal capacitance for high-performance asymmetric supercapacitors

Science.gov (United States)

Zhai, Teng; Wang, Fuxin; Yu, Minghao; Xie, Shilei; Liang, Chaolun; Li, Cheng; Xiao, Fangming; Tang, Renheng; Wu, Qixiu; Lu, Xihong; Tong, Yexiang

2013-07-01

In this paper, we reported an effective and simple strategy to prepare large areal mass loading of MnO2 on porous graphene gel/Ni foam (denoted as MnO2/G-gel/NF) for supercapacitors (SCs). The MnO2/G-gel/NF (MnO2 mass: 13.6 mg cm-2) delivered a large areal capacitance of 3.18 F cm-2 (234.2 F g-1) and good rate capability. The prominent electrochemical properties of MnO2/G-gel/NF are attributed to the enhanced conductivities and improved accessible area for ions in electrolytes. Moreover, an asymmetric supercapacitor (ASC) based on MnO2/G-gel/NF (MnO2 mass: 6.1 mg cm-2) as the positive electrode and G-gel/NF as the negative electrode achieved a remarkable energy density of 0.72 mW h cm-3. Additionally, the fabricated ASC device also exhibited excellent cycling stability, with less than 1.5% decay after 10 000 cycles. The ability to effectively develop SC electrodes with high mass loading should open up new opportunities for SCs with high areal capacitance and high energy density.In this paper, we reported an effective and simple strategy to prepare large areal mass loading of MnO2 on porous graphene gel/Ni foam (denoted as MnO2/G-gel/NF) for supercapacitors (SCs). The MnO2/G-gel/NF (MnO2 mass: 13.6 mg cm-2) delivered a large areal capacitance of 3.18 F cm-2 (234.2 F g-1) and good rate capability. The prominent electrochemical properties of MnO2/G-gel/NF are attributed to the enhanced conductivities and improved accessible area for ions in electrolytes. Moreover, an asymmetric supercapacitor (ASC) based on MnO2/G-gel/NF (MnO2 mass: 6.1 mg cm-2) as the positive electrode and G-gel/NF as the negative electrode achieved a remarkable energy density of 0.72 mW h cm-3. Additionally, the fabricated ASC device also exhibited excellent cycling stability, with less than 1.5% decay after 10 000 cycles. The ability to effectively develop SC electrodes with high mass loading should open up new opportunities for SCs with high areal capacitance and high energy density. Electronic

Removal of NO2 and O3 generated from corona discharge in indoor air cleaning with MnO2 catalyst

International Nuclear Information System (INIS)

Ge, H; Yu, R; Zhu, Y M; Mi, D

2013-01-01

The production rules and removal efficiency of harmful byproducts such as NO 2 and O 3 generated from DC corona discharge in indoor air cleaning were investigated. The production behaviours of NO 2 and O 3 and the relationship between the amount of catalyst (MnO 2 ) and the removal rate of harmful byproducts were experimentally studied. Further, indoor application tests were carried out in a closed room with 90 m 3 . The results showed that the concentrations of NO 2 and O 3 produced by corona discharge linearly increased with discharge time. The NO 2 yield is larger than O 3 by almost one order of magnitude under the same discharge power. To satisfy the demand of Standard of Indoor Air Quality (GB/T18883-2002), the power consumption of unit volume should be less than 1 W m −3 and the catalyst MnO 2 consumptions in positive-negative corona discharge were 200 cm 3 W −1 and 100 cm 3 W −1 , respectively.

Improving low-temperature performance of spinel LiNi0.5Mn1.5O4 electrode and LiNi0.5Mn1.5O4/Li4Ti5O12 full-cell by coating solid-state electrolyte Li-Al-Ti-P-O

Science.gov (United States)

Bi, Kun; Zhao, Shi-Xi; Huang, Chao; Nan, Ce-Wen

2018-06-01

Octahedral cathode materials LiNi0.5Mn1.5O4 (LNMO), with primary particles size of 300-600 nm are prepared through one-step co-precipitation. Then solid-state electrolyte Li2O-Al2O3-TiO2-P2O5 (LATP) was coated on LNMO to form continuous surface-modification layer. There is no obviously difference of structure, morphology between coated LATP LiNi0.5Mn1.5O4 (LATP-LNMO) and pristine LiNi0.5Mn1.5O4 (P-LNMO). Low-temperature electrochemical performance of P-LNMO and LATP-LNMO electrodes, including charge-discharge capacity, cycle performance, middle discharge voltage and electrochemical impedance spectra (EIS), were measured systematically with three electrode. The results reveal that LATP-LNMO electrode presents superior electrochemical performance at low temperature, compared to P-LNMO electrode. At -20 °C, the capacity retention of LATP-LNMO (61%) is much higher than that of P-LNMO (39%). According to EIS, the enhancement of performance of LATP-LNMO cathode at low temperature can be attribute to LATP coating, which not only promotes lithium-ion diffusion at electrode/electrolyte interface but also decreases the charge transfer resistance. Finally, the electrochemical performances of full cell of LATP-LNMO or P-LNMO cathode vs Li4Ti5O12 anode are investigated. The energy density can be achieved to 270 Wh·Kg-1 at -20 °C if using LATP-LNMO, which is much better than that of P-LNMO.

Enthalpies of formation of layered LiNi{sub x}Mn{sub x}Co{sub 1-2x}O{sub 2} (0 ≤ x ≤ 0.5) compounds as lithium ion battery cathode materials

Energy Technology Data Exchange (ETDEWEB)

Masoumi, Maryam; Cupid, Damian M.; Reichmann, Thomas L.; Seifert, Hans J. [Karlsruhe Institute of Technology, Eggenstein-Leopoldshafen (Germany). Inst. for Applied Materials - Applied Materials Physics; Chang, Keke; Music, Denis; Schneider, Jochen M. [RWTH Aachen Univ. (Germany). Materials Chemistry

2017-11-15

Layer-structured mixed transition metal oxides with the formula LiNi{sub x}Mn{sub x}Co{sub 1-2x}O{sub 2} (0 ≤ x ≤ 0.5) are considered as important cathode materials for lithium-ion batteries. In an effort to evaluate the relative thermodynamic stabilities of individual compositions in this series, the enthalpies of formation of selected stoichiometries are determined by high temperature oxide melt drop solution calorimetry and verified by ab-initio calculations. The measured and calculated data are in good agreement with each other, and the results show that LiCoO{sub 2}-LiNi{sub 0.5}Mn{sub 0.5}O{sub 2} solid solution approaches ideal behavior. By increasing x, i.e. by equimolar substitution of Mn{sup 4+} and Ni{sup 2+} for Co{sup 3+}, the enthalpy of formation of LiNi{sub x}Mn{sub x}Co{sub 1-2x}O{sub 2} from the elements becomes more exothermic, implying increased energetic stability. This conclusion is in agreement with the literature results showing improved structural stability and cycling performance of Ni/Mn-rich LiNi{sub x}Mn{sub x}Co{sub 1-2x}O{sub 2} compounds cycled to higher cut-off voltages.

Electrical conduction mechanism of LaNi{sub x}Me{sub 1−x}O{sub 3−δ} (Me = Fe, Mn)

Energy Technology Data Exchange (ETDEWEB)

Niwa, Eiki, E-mail: e-niwa@phys.chs.nihon-u.ac.jp [Department of Physics, College of Humanities and Sciences, Nihon University, Setagaya-ku, Tokyo 156-8550 (Japan); Department of Integrated Sciences in Physics and Biology, College of Humanities and Sciences, Nihon University, Setagaya-ku, Tokyo 156-8550 (Japan); Maeda, Hiroki; Uematsu, Chie [Department of Integrated Sciences in Physics and Biology, College of Humanities and Sciences, Nihon University, Setagaya-ku, Tokyo 156-8550 (Japan); Hashimoto, Takuya [Department of Physics, College of Humanities and Sciences, Nihon University, Setagaya-ku, Tokyo 156-8550 (Japan); Department of Integrated Sciences in Physics and Biology, College of Humanities and Sciences, Nihon University, Setagaya-ku, Tokyo 156-8550 (Japan)

2015-10-15

Graphical abstract: Compositional dependence of (a) electrical conductivity and (b) E{sub a} for hopping conduction of LaNi{sub x}Me{sub 1−x}O{sub 3} (Me = Fe, Mn). - Highlights: • Electrical conduction mechanism of LaNi{sub x}Me{sub 1−x}O{sub 3} (Me = Fe, Mn) was investigated. • Hopping conduction model could be applied for conductivity of both specimens. • The difference of E{sub a} due to that of energy level of Fe and Mn was observed. • Hole concentration estimated by iodimetry increases with increasing Ni content. - Abstract: Electrical conduction mechanism of LaNi{sub x}Fe{sub 1−x}O{sub 3−δ} and LaNi{sub x}Mn{sub 1−x}O{sub 3+δ} expected as Sr-free new cathode material for solid oxide fuel cells was analyzed. Electrical conduction behaviors of both specimens could be well fitted by small polaron hopping conduction model. The electrical conductivity of LaNi{sub x}Fe{sub 1−x}O{sub 3−δ} increased with increasing Ni content, showing agreement with decrease of activation energy for hopping conduction. The decrease of electrical conductivity and increase of activation energy of LaNi{sub x}Mn{sub 1−x}O{sub 3+δ} were observed with increasing Ni content for 0.0 ≤ x ≤ 0.4. Further Ni substitution increased electrical conductivity and decreased activation energy for 0.4 ≤ x ≤ 0.6. It was revealed using iodometry that the difference of hole carrier density between LaNi{sub x}Fe{sub 1−x}O{sub 3−δ} and LaNi{sub x}Mn{sub 1−x}O{sub 3+δ} was small. It was suspected that the origin of the difference of electrical conduction behavior of LaNi{sub x}Fe{sub 1−x}O{sub 3−δ} and LaNi{sub x}Mn{sub 1-x}O{sub 3+δ} was difference of energy level of e{sub g} band composed of Fe 3d or Mn 3d orbitals and their overlapping quantity with O 2p and Ni 3d band.

Monodispersed MnO nanoparticles with epitaxial Mn{sub 3}O{sub 4} shells

Energy Technology Data Exchange (ETDEWEB)

Berkowitz, A E; Rodriguez, G F [Department of Physics, University of California, San Diego La Jolla, CA 92093 (United States); Hong, J I; Fullerton, E E [Center for Magnetic Recording Research, University of California-San Diego La Jolla, CA 92093 (United States); An, K; Hyeon, T [National Creative Research Initiative Center for Oxide Nanocrystalline Materials, Seoul National University, Seoul 151-744 (Korea, Republic of); Agarwal, N; Smith, D J [School of Materials and Department of Physics, Arizona State University, Tempe, AZ 85287 (United States)

2008-07-07

We report the microstructural and magnetic properties of monodispersed nanoparticles (NPs) of antiferromagnetic MnO (T{sub N} = 118 K), with epitaxial ferrimagnetic Mn{sub 3}O{sub 4} (T{sub C} = 43 K) shells. Above T{sub C}, an unusually large magnetization is present, produced by the uncompensated spins (UCSs) on the surface of the MnO particles. These spins impart a net anisotropy to the MnO particles that is approximately three orders of magnitude larger than the bulk value. As a result, an anomalously high blocking temperature is exhibited by the MnO particles, and finite coercivity and exchange bias are present above T{sub C}. When field cooled below T{sub C}, a strong exchange bias was established in the Mn{sub 3}O{sub 4} shells as a result of high net anisotropy of the MnO particles. A large coercivity was also observed. Models of several aspects of the behaviour of this unusual system emphasized the essential role of the UCSs on the surfaces of the MnO NPs.

A high performance flexible all solid state supercapacitor based on the MnO2 sphere coated macro/mesoporous Ni/C electrode and ionic conducting electrolyte

Science.gov (United States)

Zhi, Jian; Reiser, Oliver; Wang, Youfu; Hu, Aiguo

2016-06-01

A high contact resistance between the active materials and the current collector, a low ionic conductivity of the gel electrolyte, and an impenetrable electrode structure are the three major barriers which greatly limit the capacitance of MnO2 in solid state supercapacitors. As a potential solution to these problems, in this work we report a novel electrode for solid state supercapacitors, based on a ternary system composed of hierarchical MnO2 spheres as the active material, macroporous Ni foam as gel penetrable skeletons and an ordered mesoporous carbon (OMC) membrane as the charge-transport accelerating layer. By employing butyl-3-methylimidazolium chloride (BMIMCl) modified gels as the ionic conducting electrolyte, the utilization efficiency of MnO2 on the specific capacitance was enhanced up to 88% of the theoretical value, delivering a volumetric capacitance of 81 F cm-3, which is the highest value among MnO2 based solid state supercapacitors. Moreover, such a flexible device exhibits exceptional volumetric energy and power density (6.6 Wh L-1 and 549 W L-1, based on the whole device volume) combined with a small capacity loss of 8.5% after 6000 cycles under twisting. These encouraging findings unambiguously overcome the energy bottleneck of MnO2 in solid state supercapacitors, and open up a new application of macro/mesoporous materials in flexible devices.A high contact resistance between the active materials and the current collector, a low ionic conductivity of the gel electrolyte, and an impenetrable electrode structure are the three major barriers which greatly limit the capacitance of MnO2 in solid state supercapacitors. As a potential solution to these problems, in this work we report a novel electrode for solid state supercapacitors, based on a ternary system composed of hierarchical MnO2 spheres as the active material, macroporous Ni foam as gel penetrable skeletons and an ordered mesoporous carbon (OMC) membrane as the charge-transport accelerating

Magnetic refrigeration capabilities of magnetocaloric Ni2Mn:75Cu:25Ga

Science.gov (United States)

Mishra, S. K.; Jenkins, C. A.; Dubenko, I.; Samanta, T.; Ali, N.; Roy, S.

2013-03-01

Doping-driven competition between energetically similar ground states leads to many exciting materials phenomena such as the emergence of high-Tc superconductivity, diluted magnetic semiconductors, and colossal magnetoresistance. Doped Ni2MnGa Heusler alloy, which is a multifunctional ferromagnetic alloy with various exotic physical properties demonstrates this notion of rich phenomenology via modified ground spin states. Adopting this generic concept, here we will present a novel doped Ni2Mn.75Cu.25Ga alloy that offers unprecedented co-existence of the magnetocaloric effect and fully controlled ferromagnetism at room temperature. Application of site engineering enables us to manipulate the ground spin state that leads to the decrease in magnetic transition temperature and also increases the delocalization of the Mn magnetism. SQUID magnetometery suggests that Cu doping enhances the saturation magnetization, coercive field and clarity of magnetic hysteresis loops. By exploiting x-ray absorption techniques and measuring element specific magnetic hysteresis loops, here we will describe the microscopic origin of enhnaced magnetocaloric properties and d-d interaction driven charge transfer effects in Ni2Mn.75Cu.25Ga This work was supported by DOE Grant No. DE-FG02-06ER46291

Rietveld refinement of the crystal structures of Rb2XSi5O12 (X = Ni, Mn

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Anthony M. T. Bell

2016-02-01

Full Text Available The synthetic leucite silicate framework mineral analogues Rb2XSi5O12 {X = Ni [dirubidium nickel(II pentasilicate] and Mn [dirubidium manganese(II pentasilicate]} have been prepared by high-temperature solid-state synthesis. The results of Rietveld refinements, using X-ray powder diffraction data collected using Cu Kα X-rays, show that the title compounds crystallize in the space group Pbca and adopt the cation-ordered structure of Cs2CdSi5O12 and other leucites. The structures consist of tetrahedral SiO4 and XO4 units sharing corners to form a partially substituted silicate framework. Extraframework Rb+ cations sit in channels in the framework. All atoms occupy the 8c general position for this space group. In these refined structures, silicon and X atoms are ordered onto separate tetrahedrally coordinated sites (T-sites. However, the Ni displacement parameter and the Ni—O bond lengths suggest that for the X = Ni sample, there may actually be some T-site cation disorder.

Structure, reactivity and electronic properties of Mn doped Ni{sub 13} clusters

Energy Technology Data Exchange (ETDEWEB)

Banerjee, Radhashyam; Datta, Soumendu; Mookerjee, Abhijit, E-mail: abhijit.mookerjee61@gmail.com

2013-06-15

In this work we have studied the structural and magnetic properties of Ni{sub 13} cluster mono- and bi-doped with Mn atoms. We have noted their tendency of being reactive toward the H{sub 2} molecule. We have found unusually enhanced stability in the mono-doped cluster (i.e. of the Ni{sub 12}Mn) and the diminished stability of the corresponding chemisorbed cluster, Ni{sub 12}MnH{sub 2}. Our analysis of the stability and HOMO–LUMO gap explains this unusual behavior. Interestingly, we have also seen the quenching in the net magnetic moment upon H{sub 2} absorption in the doped Ni{sub 13−m}Mn{sub m} alloy clusters. This has been reported earlier for smaller Ni{sub n} clusters [1].

Structure of the c(2x2) Mn/Ni(001) surface alloy by quantitative photoelectron diffraction

Energy Technology Data Exchange (ETDEWEB)

Banerjee, S.; Denlinger, J.; Chen, X. [Univ. of Wisconsin, Milwaukee, WI (United States)] [and others

1997-04-01

Surface alloys are two-dimensional metallic systems that can have structures that are unique to the surface, and have no counterpart in the bulk binary phase diagram. A very unusual structure was reported for the Mn-Ni system, based on a quantitative LEED structure determination, which showed that the Mn atoms were displaced out of the surface by a substantial amount. This displacement was attributed to a large magnetic moment on the Mn atoms. The structure of the Mn-Ni surface alloy was proposed to be based on a bulk termination model. Magnetic measurements on the Mn-Ni surface alloys, however, showed conclusively that the magnetic structure of these surface alloys is completely different from the bulk alloy analogs. For example, bulk MnNi is an antiferromagnet, whereas the surface alloy is ferromagnetic. This suggests that the proposed structure based on bulk termination, may not be correct. X-ray Photoelectron Diffraction (XPD) techniques were used to investigate this structure, using both a comparison to multiple scattering calculations and photoelectron holography. In this article the authors present some of the results from the quantitative analysis of individual diffraction patterns by comparison to theory.

The influence of Mn species on the SO{sub 2} removal of Mn-based activated carbon catalysts

Energy Technology Data Exchange (ETDEWEB)

Qu, Yi-Fan [College of Architecture and Environment, Sichuan University, Chengdu 610065 (China); Guo, Jia-Xiu, E-mail: guojiaxiu@scu.edu.cn [College of Architecture and Environment, Sichuan University, Chengdu 610065 (China); National Engineering Technology Research Center for Flue Gas Desulfurization, Chengdu 610065 (China); Chu, Ying-Hao [College of Architecture and Environment, Sichuan University, Chengdu 610065 (China); National Engineering Technology Research Center for Flue Gas Desulfurization, Chengdu 610065 (China); Sun, Ming-Chao [College of Architecture and Environment, Sichuan University, Chengdu 610065 (China); Yin, Hua-Qiang, E-mail: hqyin@scu.edu.cn [College of Architecture and Environment, Sichuan University, Chengdu 610065 (China); National Engineering Technology Research Center for Flue Gas Desulfurization, Chengdu 610065 (China)

2013-10-01

Using Mn(NO{sub 3}){sub 2} as precursor, a series of Mn-based activated carbon catalysts were prepared by ultrasound-assisted excessive impregnation method and characterized by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and temperature programmed reduction (TPR). The influences of Mn species and nitric acid pretreatment on the removal role of SO{sub 2} were investigated. MnO and Mn{sub 3}O{sub 4} coexist in catalysts calcined at 650 and 800 °C and exhibit best SO{sub 2} removal ability, whereas Mn{sub 2}O{sub 3} formed in the catalyst calcined at 500 °C and shows poor activity. After treatment by nitric acid, the C=O of activated carbon support increases and the crystal size of MnO decreases, resulting in the enhancement of the catalytic activity. During reaction process, manganese oxides are gradually transferred into MnO{sub 2}. And this change directly results in a decrease of activity. But the SO{sub 2} removal rate has been maintained in the range of 30–40%, indicating that MnO{sub 2} still has a certain SO{sub 2} removal ability.

A facile synthesis of α-MnO2 used as a supercapacitor electrode material: The influence of the Mn-based precursor solutions on the electrochemical performance

Science.gov (United States)

Li, Wenyao; Xu, Jiani; Pan, Yishuang; An, Lei; Xu, Kaibing; Wang, Guangjin; Yu, Zhishui; Yu, Li; Hu, Junqing

2015-12-01

Three types of α-MnO2 nanomaterials are synthesized in different Mn-based precursor solutions by using a facile electrochemical deposition at the same depositional condition. The relationships between the precursor solutions and corresponding MnO2 nanomaterials' morphology as well as the electrochemical performance have been studied. As an electrode, electrochemical measurements show that the MnO2 deposited in MnCl2 precursor solution (MnO2-P3) exhibits an enhanced specific capacitance (318.9 F g-1 at 2 mV s-1). Moreover, this electrode demonstrates a good rate capability with 44% retention, which is higher than the MnO2-P1 deposited with Mn(CH3COOH)2 solution and the MnO2-P2 deposited with Mn(NO3)2 precursor solution. Besides, the specific capacitance of the MnO2-P3 electrode nearly has 98.2% retention after 2000 cycles, showing good long-term cycle stability. These findings show that the MnO2-P3 is a promising electrode material for supercapacitors.

Electronic Topological Transitions in CuNiMnAl and CuNiMnSn under pressure from first principles study

Science.gov (United States)

Rambabu, P.; Kanchana, V.

2018-06-01

A detailed study on quaternary ordered full Heusler alloys CuNiMnAl and CuNiMnSn at ambient and under different compressions is presented using first principles electronic structure calculations. Both the compounds are found to possess ferromagnetic nature at ambient with magnetic moment of Mn being 3.14 μB and 3.35 μB respectively in CuNiMnAl and CuNiMnSn. The total magnetic moment for both the compounds is found to decrease under compression. Fermi surface (FS) topology change is observed in both compounds under pressure at V/V0 = 0.90, further leading to Electronic Topological Transitions (ETTs) and is evidenced by the anomalies visualized in density of states and elastic constants under compression.

Enhancement of Electrochemical Performance of LiMn2O4 Spinel Cathode Material by Synergetic Substitution with Ni and S

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Monika Bakierska

2016-05-01

Full Text Available Nickel and sulfur doped lithium manganese spinels with a nominal composition of LiMn2−xNixO4–ySy (0.1 ≤ x ≤ 0.5 and y = 0.01 were synthesized by a xerogel-type sol-gel method followed by subsequent calcinations at 300 and 650 °C in air. The samples were investigated in terms of physicochemical properties using X-ray powder diffraction (XRD, transmission electron microscopy (EDS-TEM, N2 adsorption-desorption measurements (N2-BET, differential scanning calorimetry (DSC, and electrical conductivity studies (EC. Electrochemical characteristics of Li/Li+/LiMn2−xNixO4–ySy cells were examined by galvanostatic charge/discharge tests (CELL TEST, electrochemical impedance spectroscopy (EIS, and cyclic voltammetry (CV. The XRD showed that for samples calcined at 650 °C containing 0.1 and 0.2 mole of Ni single phase materials of Fd-3m group symmetry and nanoparticles size of around 50 nm were obtained. The energy dispersive X-ray spectroscopy (EDS mapping confirmed homogenous distribution of nickel and sulfur in the obtained spinel materials. Moreover, it was revealed that the adverse phase transition at around room temperature typical for the stoichiometric spinel was successfully suppressed by Ni and S substitution. Electrochemical results indicated that slight substitution of nickel (x = 0.1 and sulfur (y = 0.01 in the LiMn2O4 enhances the electrochemical performance along with the rate capability and capacity retention.

Magnetic and transport properties of Ni2MnGa-BaTiO3 metal-insulator particulate composite with percolation threshold

International Nuclear Information System (INIS)

Won, C.J.; Kambale, R.C.; Hur, N.

2011-01-01

Highlights: → The Ni 2 MnGa-BaTiO 3 type composites were first time prepared by solid state reaction. → Temperature dependent magnetic properties reveal two kinds of transitions in these composite. → The present materials show negative magnetoresistance effect. → The present studies on magnetic and electrical transport of metal/insulator (NMG/BTO) composites shows the resistivity change associated to filamentary conducting path at percolation threshold. - Abstract: Here we report the magnetic and transport properties of the metal/insulator (f NMG )Ni 2 MnGa/(1 - f NMG )BaTiO 3 composites. The X-ray diffraction study confirms the formation of both the phases in composite. The microstructure reveals that the conducting Ni 2 MnGa particles are well dispersed in an insulating BaTiO 3 matrix. Temperature dependent magnetization shows two transitions one above 300 K and other below 150 K. The temperature dependence resistivity near the percolation threshold f NMG = 0.4 had drastic changes which is higher than the f NMG = 0.5. Also the negative magnetoresistance effect was observed for the studied materials. We suggest that magnetic and transport properties at the percolation threshold can be adjusted by the strain from the surrounding insulator particle.

Influence of Temperature on the Performance of LiNi1/3Co1/3Mn1/3O2 Prepared by High-Temperature Ball-Milling Method

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Ming Tian

2018-01-01

Full Text Available Aiming at the preparation of high electrochemical performance LiNi1/3Co1/3Mn1/3O2 cathode material for lithium-ion battery, LiNi1/3Co1/3Mn1/3O2 was prepared with lithium carbonate, nickel (II oxide, cobalt (II, III oxide, and manganese dioxide as raw materials by high-temperature ball-milling method. Influence of ball-milling temperature was investigated in this work. It was shown that the fine LiNi1/3Co1/3Mn1/3O2 powder with high electrochemical performance can be produced by the high-temperature ball-milling process, and the optimal ball-milling temperature obtained in the current study was 750°C. Its initial discharge capacity was 146.0 mAhg−1 at the rate of 0.1 C, and over 50 cycles its capacity retention rate was 90.2%.

A hierarchical nanostructure consisting of amorphous MnO{sub 2}, Mn{sub 3}O{sub 4} nanocrystallites, and single-crystalline MnOOH nanowires for supercapacitors

Energy Technology Data Exchange (ETDEWEB)

Hu, Chi-Chang; Hung, Ching-Yun [Department of Chemical Engineering, National Tsing Hua University, Hsin-Chu 30013 (China); Chang, Kuo-Hsin [Department of Chemical Engineering, National Tsing Hua University, Hsin-Chu 30013 (China); Department of Chemical Engineering, National Chung Cheng University, Chia-Yi 621 (China); Yang, Yi-Lin [Department of Chemical Engineering, National Chung Cheng University, Chia-Yi 621 (China)

2011-01-15

In this communication, a porous hierarchical nanostructure consisting of amorphous MnO{sub 2} (a-MnO{sub 2}), Mn{sub 3}O{sub 4} nanocrystals, and single-crystalline MnOOH nanowires is designed for the supercapacitor application, which is prepared by a simple two-step electrochemical deposition process. Because of the gradual co-transformation of Mn{sub 3}O{sub 4} nanocrystals and a-MnO{sub 2} nanorods into an amorphous manganese oxide, the cycle stability of a-MnO{sub 2} is obviously enhanced by adding Mn{sub 3}O{sub 4}. This unique ternary oxide nanocomposite with 100-cycle CV activation exhibits excellent capacitive performances, i.e., excellent reversibility, high specific capacitances (470 F g{sup -1} in CaCl{sub 2}), high power property, and outstanding cycle stability. The highly porous microstructures of this composite before and after the 10,000-cycle CV test are examined by means of scanning electron microscopy (SEM) and transmission electron microscopy (TEM). (author)

Electrochemical Properties of the LiNi0.6Co0.2Mn0.2O2 Cathode Material Modified by Lithium Tungstate under High Voltage.

Science.gov (United States)

Fu, Jiale; Mu, Daobin; Wu, Borong; Bi, Jiaying; Cui, Hui; Yang, Hao; Wu, Hanfeng; Wu, Feng

2018-05-31

An amount (5 wt %) of lithium tungstate (Li 2 WO 4 ) as an additive significantly improves the cycle and rate performances of the LiNi 0.6 Co 0.2 Mn 0.2 O 2 electrode at the cutoff voltage of 4.6 V. The 5 wt % Li 2 WO 4 -mixed LiNi 0.6 Co 0.2 Mn 0.2 O 2 electrode delivers a reversible capacity of 199.2 mA h g -1 and keeps 73.1% capacity for 200 cycles at 1 C. It retains 67.4% capacity after 200 cycles at 2 C and delivers a discharge capacity of 167.3 mA h g -1 at 10 C, while those of the pristine electrode are only 44.7% and 87.5 mA h g -1 , respectively. It is shown that the structure of the LiNi 0.6 Co 0.2 Mn 0.2 O 2 cathode material is not affected by mixing Li 2 WO 4 . The introduced Li 2 WO 4 effectively restrains the LiPF 6 and carbonate solvent decomposition by consuming PF 5 at high cutoff voltage, forming a stable cathode/electrolyte interface film with low resistance.

Mn L2,3-edge X-ray absorption spectroscopic studies on charge-discharge mechanism of Li2MnO3