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Remko Logemann, Alexander N Rudenko, Mikhail I Katsnelson, Andrei Kirilyuk
Magnetism of transition metal (TM) oxides is usually described in terms of the Heisenberg model, with orientation-independent interactions between the spins. However, the applicability of such a model is not fully justified for TM oxides because spin polarization of oxygen is usually ignored. In the conventional model based on the Anderson principle, oxygen effects are considered as a property of the TM ion and only TM interactions are relevant. Here, we perform a systematic comparison between two approaches for spin polarization on oxygen in typical TM oxides...
June 22, 2017: Journal of Physics. Condensed Matter: An Institute of Physics Journal
Boyang Liu, Yingfeng Shao, Xin Xiang, Fuhua Zhang, Shengchang Yan, Wenge Li
Carbon encapsulated various nanocrystals, including MnS and MnO, Cr2O3, MoO2, Fe7S8 and Fe3O4, ZrO2, are one-step in-situ prepared by a common and simple synthesis approach, respectively. The nanocrystals have an equiaxed morphology and a median size smaller than 30 nm. Tens and hundreds of these nanocrystals are entirely encapsulated by the worm-like amorphous carbon shell. The formation of core-shell structure depends on the strongly exothermic reaction of metal π-complexes with ammonium persulfate in an autoclave below 200 oC...
June 14, 2017: Nanotechnology
Jing Su, Hao Liang, Xian-Nian Gong, Xiao-Yan Lv, Yun-Fei Long, Yan-Xuan Wen
Porous MnO/C microspheres have been successfully fabricated by a fast co-precipitation method in a T-shaped microchannel reactor. The structures, compositions, and electrochemical performances of the obtained MnO/C microspheres are characterized by X-ray diffraction, field emission scanning electron microscopy (FE-SEM), transmission electron microscopy (HRTEM), Brunauer-Emmett-Teller analysis, charge-discharge testing, cyclic voltammograms, and electrochemical impedance spectra. Experimental results reveal that the as-prepared MnO/C, with a specific surface area of 96...
May 26, 2017: Nanomaterials
Yafa Zargouni, Stella Deheryan, Alex Radisic, Khaled Alouani, Philippe M Vereecken
In this work, we present the electrochemical deposition of manganese dioxide (MnO₂) thin films on carbon-coated TiN/Si micro-pillars. The carbon buffer layer, grown by plasma enhanced chemical vapor deposition (PECVD), is used as a protective coating for the underlying TiN current collector from oxidation, during the film deposition, while improving the electrical conductivity of the stack. A conformal electrolytic MnO₂ (EMD) coating is successfully achieved on high aspect ratio C/TiN/Si pillar arrays by tailoring the deposition process...
May 27, 2017: Nanomaterials
Jiefeng Xiao, Jia Li, Zhengming Xu
The large-batch application of lithium ion batteries leads to the mass production of spent batteries. So the enhancement of disposal ability of spent lithium ion batteries is becoming very urgent. This study proposes an integrated process to handle bulk spent lithium manganese (LiMn2O4) batteries to in situ recycle high value-added products without any additives. By mechanical separation, the mixed electrode materials mainly including binder, graphite and LiMn2O4 are firstly obtained from spent batteries. Then, the reaction characteristics for the oxygen-free roasting of mixed electrode materials are analyzed...
May 17, 2017: Journal of Hazardous Materials
Lina Sanchez-Botero, Adriana P Herrera, Juan P Hinestroza
We report on the synthesis of alpha manganese dioxide (α-MnO₂) nanorods using natural extracts from Vitis vinifera grape stems and Malus domestica 'Cortland' apple peels. We used a two-step method to produce highly crystalline α-MnO₂ nanorods: (1) reduction of KMnO₄ in the presence of natural extracts to initiate the nucleation process; and (2) a thermal treatment to enable further solid-state growth of the nuclei. Transmission electron microscopy (TEM) and field emission scanning electron microscopy (FESEM) images provided direct evidence of the morphology of the nanorods and these images were used to propose nucleation and growth mechanisms...
May 22, 2017: Nanomaterials
Junzhi Liu, Ji Ma, Ke Zhang, Prince Ravat, Peter Machata, Stanislav Avdoshenko, Felix Hennersdorf, Hartmut Komber, Wojciech Pisula, Jan J Weigand, Alexey A Popov, Reinhard Berger, Klaus Müllen, Xinliang Feng
Synthesis of antiaromatic polycyclic hydrocarbons (PHs) is challenging because the high energy of their highest occupied molecular orbital and low energy of their lowest unoccupied molecular orbital cause them to be reactive and unstable. In this work, two large antiaromatic acene analogues, namely, cyclopenta[pqr]indeno[2,1,7-ijk]tetraphene (CIT, 1a) and cyclopenta[pqr]indeno[7,1,2-cde]picene (CIP, 1b), as well as a curved antiaromatic molecule with 48 π-electrons, dibenzo[a,c]diindeno[7,1,2-fgh:7',1',2'-mno]phenanthro[9,10-k]tetraphene (DPT, 1c), are synthesized on the basis of the corona of indeno[1,2-b]fluorene...
June 7, 2017: Journal of the American Chemical Society
J M Michalik, D Rybicki, Z Tarnawski, M Sikora, J M De Teresa, M R Ibarra, Cz Kapusta
Temperature dependent (55)Mn NMR study of Sm0.55Sr0.45MnO3 is reported. Previous bulk magnetization measurements have shown that below T C ~ 125 K the sample is ferromagnetic metallic (FMM) and above TC it is charge ordered and insulating. In present report, we show that from zero-field NMR a single line double-exchange (DE) signal is observed at temperatures up to 139 K, which is due to a presence of FMM clusters also above T C. The intensity of the DE line follows the temperature dependence of the magnetization measured at 0...
July 5, 2017: Journal of Physics. Condensed Matter: An Institute of Physics Journal
Jennifer S Le Blond, Peter J Baxter, Dhimiter Bello, Jennifer Raftis, Yordanos B Molla, Javier Cuadros, Gail Davey
BACKGROUND: Podoconiosis, non-filarial elephantiasis, is a non-infectious disease found in tropical regions such as Ethiopia, localized in highland areas with volcanic soils cultivated by barefoot subsistence farmers. It is thought that soil particles can pass through the soles of the feet and taken up by the lymphatic system, leading to the characteristic chronic oedema of the lower legs that becomes disfiguring and disabling over time. METHODS: The close association of the disease with volcanic soils led us to investigate the characteristics of soil samples in an endemic area in Ethiopia to identify the potential causal constituents...
2017: PloS One
Girija Thesma Chandran, Gaurav Jha, Shaopeng Qiao, Mya Le Thai, Rajen Kumar Dutta, Alana F Ogata, Ji-Soo Jang, Il-Doo Kim, Reginald M Penner
The influence of hexamethylenetetraamine (HMTA) on the morphology of δ- MnO<sub>2</sub> and its properties for electrical energy storage are investigated - specifically for ultra-thick δ-MnO<sub>2<\sub> layers in the micron scale. Planar arrays of gold@δ-MnO<sub>2</sub>, core@shell nanowires, were prepared by electrodeposition with and without the HMTA and their elec- trochemical properties evaluated. HMTA alters the MnO<sub>2</sub> in three ways: First, it creates a more open morphology for the MnO<sub>2</sub> coating, characterized by "petals" with a thickness of 6 nm to 9 nm, rather than much thinner δ-MnO<sub>2</sub> sheets seen in the absence of HMTA...
April 28, 2017: Langmuir: the ACS Journal of Surfaces and Colloids
Lingling Zhang, Danhua Ge, Genlong Qu, Junwei Zheng, Xueqin Cao, Hongwei Gu
Herein, we have developed a facile and effective approach for synthesizing a novel kind of porous nitrogen-doped carbon-coated MnO nanosphere. The porous Mn2O3 nanospheres are initially obtained by the calcination treatment of a coordination self-assembled aggregation precursor (referred to as Mn(OAc)2-C-8). Then, MnO@N-doped carbon composites (MnO@NCs) are obtained by the calcination of the Mn2O3 nanospheres coated with polydopamine (Mn2O3@PDA). The MnO@NCs are evaluated as an anode for lithium ion batteries (LIBs), which exhibit high specific capacity, stable cycling performance (1096...
May 4, 2017: Nanoscale
Matthew D Sampson, Jonathan D Emery, Michael J Pellin, Alex B F Martinson
Atomic layer deposition (ALD) of several metal oxides is selectivity inhibited on alkanethiol self-assembled monolayers (SAMs) on Au, and the eventual nucleation mechanism is investigated. The inhibition ability of the SAM is significantly improved by the in situ H2-plasma pretreatment of the Au substrate prior to the gas-phase deposition of a long-chain alkanethiol, 1-dodecanethiol (DDT). This more rigorous surface preparation inhibits even aggressive oxide ALD precursors, including trimethylaluminum and water, for at least 20 cycles...
April 5, 2017: ACS Applied Materials & Interfaces
Ting Wang, Hangang Li, Shaojun Shi, Ting Liu, Gang Yang, Yimin Chao, Fan Yin
MnO as anode materials has received particular interest owing to its high specific capacity, abundant resources, and low cost. However, serious problems related to the large volume change (>170%) during the lithiation/delithiation processes still results in poor rate capability and fast capacity decay. With homogenous crystals of MnO grown in the network of carbon nanofibers (CNF), binding effect of CNF can effectively weaken the volume change of MnO during cycles. In this work, a CNF/MnO flexible electrode for lithium-ion batteries is designed and synthesized...
April 3, 2017: Small
María C Nevárez-Martínez, Marek P Kobylański, Paweł Mazierski, Jolanta Wółkiewicz, Grzegorz Trykowski, Anna Malankowska, Magda Kozak, Patricio J Espinoza-Montero, Adriana Zaleska-Medynska
Vertically oriented, self-organized TiO₂-MnO₂ nanotube arrays were successfully obtained by one-step anodic oxidation of Ti-Mn alloys in an ethylene glycol-based electrolyte. The as-prepared samples were characterized by scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDX), UV-Vis absorption, photoluminescence spectroscopy, X-ray diffraction (XRD), and micro-Raman spectroscopy. The effect of the applied potential (30-50 V), manganese content in the alloy (5-15 wt. %) and water content in the electrolyte (2-10 vol...
March 31, 2017: Molecules: a Journal of Synthetic Chemistry and Natural Product Chemistry
Wei Zhang, Jiannian Li, Jie Zhang, Jinzhi Sheng, Ting He, Meiyue Tian, Yufeng Zhao, Changjun Xie, Liqiang Mai, Shichun Mu
To overcome inferior rate capability and cycle stability of MnO-based materials as a lithium-ion battery anode associated with the pulverization and gradual aggregation during the conversion process, we constructed robust mesoporous N-doped carbon (N-C) protected MnO nanoparticles on reduced graphene oxide (rGO) (MnO@N-C/rGO) by a simple top-down incorporation strategy. Such dual carbon protection endows MnO@N-C/rGO with excellent structural stability and enhanced charge transfer kinetics. At 100 mA g(-1), it exhibits superior rate capability as high as 864...
March 31, 2017: ACS Applied Materials & Interfaces
Sajad Yazdani, Raana Kashfi-Sadabad, Alessandro Palmieri, William E Mustain, Michael Thompson Pettes
MnO is an electrically insulating material which limits its usefulness in lithium ion batteries. We demonstrate that the electrochemical performance of MnO can be greatly improved by using oxygen-functional groups created on the outer walls of multiwalled carbon nanotubes (MWCNTs) as nucleation sites for metal oxide nanoparticles. Based on the mass of the active material used in the preparation of electrodes, the composite conversion-reaction anode material Mn1-x Co x O/MWCNT with x = 0.2 exhibited the highest reversible specific capacity, 790 and 553 mAhg(-1) at current densities of 40 and 1600 mAg(-1), respectively...
April 18, 2017: Nanotechnology
Tyler E Stevens, Charles J Pearce, Caleah N Whitten, Richard P Grant, Todd C Monson
Many challenges must be overcome in order to create reliable electrochemical energy storage devices with not only high energy but also high power densities. Gaps exist in both battery and supercapacitor technologies, with neither one satisfying the need for both large power and energy densities in a single device. To begin addressing these challenges (and others), we report a process to create a self-assembled array of electrochemically active nanoparticles bound directly to a current collector using extremely short (2 nm or less) conductive tethers...
March 13, 2017: Scientific Reports
Vladislav Borisov, Sergey Ostanin, Ingrid Mertig
Magnetoelectric coupling and spin polarization at the multiferroic PbTiO3/La2/3Sr1/3MnO3 (PTO/LSMO) interface is studied from first principles in view of the recent experimental observation of the tunneling magnetoresistance sign inversion in Co/PZT/LSMO tunnel junctions (Pantel et al 2012 Nat. Mater. 11 289). Our results confirm the stabilization of the locally antiferromagnetic order in the manganite when the PTO polarization points away from the LSMO side, which changes the interface magnetization by 6.3-6...
May 4, 2017: Journal of Physics. Condensed Matter: An Institute of Physics Journal
David McNulty, Hugh Geaney, Colm O'Dwyer
We present the formation of a carbon-coated honeycomb ternary Ni-Mn-Co-O inverse opal as a conversion mode anode material for Li-ion battery applications. In order to obtain high capacity via conversion mode reactions, a single phase crystalline honeycombed IO structure of Ni-Mn-Co-O material was first formed. This Ni-Mn-Co-O IO converts via reversible redox reactions and Li2O formation to a 3D structured matrix assembly of nanoparticles of three (MnO, CoO and NiO) oxides, that facilitates efficient reactions with Li...
February 10, 2017: Scientific Reports
Lianyi Shao, Qing Zhao, Jun Chen
MnOOH nanorods, which were prepared using a hydrothermal method, have been used for the first time as anode materials for sodium ion batteries. The as-prepared MnOOH nanorods with lengths of 1.2-3.7 μm and diameters of 60-90 nm delivered high performance of reversible electrochemical Na/Na(+) storage such as an initial discharge capacity of 485.5 mA h g(-1) at 80 mA g(-1), a high initial Coulombic efficiency of 86.7% and a low average potential polarization of 0.36 V. Instrumental analyses with ex situ XRD, TEM and XPS show that the sodium storage mechanism in MnOOH can be related to the reversible formation of MnO and NaOH...
February 9, 2017: Chemical Communications: Chem Comm
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