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Christian M Julien, Alain Mauger
Manganese dioxides, inorganic materials which have been used in industry for more than a century, now find great renewal of interest for storage and conversion of energy applications. In this review article, we report the properties of MnO₂ nanomaterials with different morphologies. Techniques used for the synthesis, structural, physical properties, and electrochemical performances of periodic and aperiodic frameworks are discussed. The effect of the morphology of nanosized MnO₂ particles on their fundamental features is evidenced...
November 17, 2017: Nanomaterials
Rajesh V Chopdekar, Vivek K Malik, Alexander Kane, Apurva Mehta, Elke Arenholz, Yayoi Takamura
The extent of interfacial charge transfer and the resulting impact on magnetic interactions were investigated as a function of sublayer thickness in La<sub>0.7</sub>Sr<sub>0.3</sub>MnO<sub>3</sub>/La<sub>0.7</sub>Sr<sub>0.3</sub>CoO<sub>3</sub> ferromagnetic superlattices. Element-specific soft x-ray magnetic spectroscopy reveals that the electronic structure is altered within 5-6 unit cells of the chemical interface, and can lead to a synthetic ferromagnet with strong magnetic coupling between the sublayers...
November 16, 2017: Journal of Physics. Condensed Matter: An Institute of Physics Journal
Guangrui Gao, Ying Li, Chaozhong Li, Dan Hu, Zhengxian Li, Zhengping Xi
Ceramic coatings with high emissivity were fabricated on TC4 alloys by micro-arc oxidation technique (MAO) in mixed silicate and phosphate electrolytes with varying KMnO₄ addition. The microstructure, phase and chemical composition were characterized by scanning electron microscope (SEM), X-ray diffraction (XRD), and X-ray photoelectron spectroscopy (XPS), and the infrared emissivity of the MAO coatings was measured in a waveband of 5-20 μm. The results show that the thickness of the coatings increased with the addition of KMnO₄, but the roughness of the coatings first decreased and then increased slightly due to the inhibitory effect of KMnO₄ on Na₂SiO₃ deposition...
November 13, 2017: Materials
Wei Chen, Jue Lu, Shao-Yong Jiang, Kuidong Zhao, Deng-Fei Duan
Carbon isotopes have been widely used in tracing a wide variety of geological and environmental processes. The carbon isotope composition of bulk rocks and minerals was conventionally analyzed by isotope ratio mass spectrometry (IRMS), and more recently secondary ionization mass spectrometry (SIMS) has been widely used to determine carbon isotope composition of carbon-bearing solid materials with good spatial resolution. Here we present a new method that couples a RESOlution S155 193 nm laser ablation system with a Nu Plasma II MC-ICP-MS, with the aim of measuring carbon isotopes in situ in carbonate minerals (i...
November 9, 2017: Analytical Chemistry
Natalia Levin, Julián Perdoménico, Eckhard Bill, Thomas Weyhermüller, Leonardo D Slep
Photodelivery of NO requires stable compounds which can be made reactive by irradiation with (visible) light. Traditional {MNO}(6) complexes require a substantial ligand design to shift their absorption spectra to the appropriate region of the electromagnetic spectrum. [Fe((CH2Py2)2Me[9]aneN3)(NO)](BF4)2 is a new {FeNO}(7) octahedral coordination compound, which is thermally and air-stable in solution. Illumination with a 450 nm light source induces significant photodetachment of the coordinated NO (ϕNO = 0...
November 9, 2017: Dalton Transactions: An International Journal of Inorganic Chemistry
Jingjing Li, Chen Wu, Pingfu Hou, Min Zhang, Kai Xu
Magnetic resonance imaging (MRI) contrast agents have become a necessary part for clinical practice to improve the sensitivity for the diagnosis of small lesions and injuries. Among them, manganese oxide nanoparticle (MnO NPs)-based MRI contrast agent attracts more and more attention because of their better performance in the detection of brain disease and positive enhancement in T1-weighted image. However, the relatively low r1 relaxivity and complex synthetic route hampered their wider applications. In this work, we proposed a one-pot approach to prepare hydrophilic MnO NPs via a polyol-like method with poly (ethylene glycol) (PEG) as both a solvent and surfactant...
October 27, 2017: Biosensors & Bioelectronics
Haojie Fei, Nabanita Saha, Natalia Kazantseva, Robert Moucka, Qilin Cheng, Petr Saha
The flexible supercapacitors (SCs) of the conventional sandwich-type structure have poor flexibility due to the large thickness of the final entire device. Herein, we have fabricated a highly flexible asymmetric SC using manganese dioxide (MnO₂) and reduced graphene oxide (RGO) nanosheet-piled hydrogel films and a novel bacterial cellulose (BC)-filled polyacrylic acid sodium salt-Na₂SO₄ (BC/PAAS-Na₂SO₄) neutral gel electrolyte. Apart from being environmentally friendly, this BC/PAAS-Na₂SO₄ gel electrolyte has high viscosity and a sticky property, which enables it to combine two electrodes together...
October 30, 2017: Materials
Ragab Mahani, Fatma Atia, Mohammed M Al Neklawy, Amin Fahem
X-ray fluorescence (XRF) study has been shown that the water hyacinth plant is an effective tool for the removals of heavy metals (As, Ba, Cr, Cu, Ni, Pb, Rb, Sr, Zn and Zr) and metal oxides (SiO2, K2O, CaO, Al2O3, Fe2O3, MgO, Na2O, MnO, P2O5, SO3 and TiO2) from agriculture (media 1) and agriculture wastewaters drainage polluted with municipal wastewater (media 2). As a general description, the heavy metals and metal oxides were found at higher levels in the plant collected from media 1 than those in the plant collected from media 2...
October 10, 2017: Spectrochimica Acta. Part A, Molecular and Biomolecular Spectroscopy
Alexander Ottmann, Maik Scholz, Marcel Haft, Elisa Thauer, Philip Schneider, Markus Gellesch, Christian Nowka, Sabine Wurmehl, Silke Hampel, Rüdiger Klingeler
The ferrimagnetic and high-capacity electrode material Mn3O4 is encapsulated inside multi-walled carbon nanotubes (CNT). We show that the rigid hollow cavities of the CNT enforce size-controlled nanoparticles which are electrochemically active inside the CNT. The ferrimagnetic Mn3O4 filling is switched by electrochemical conversion reaction to antiferromagnetic MnO. The conversion reaction is further exploited for electrochemical energy storage. Our studies confirm that the theoretical reversible capacity of the Mn3O4 filling is fully accessible...
October 19, 2017: Scientific Reports
Fangjie Li, Huigai Li, Shaobo Zheng, Jinglin You, Ke Han, Qijie Zhai
This study explores the effect of introducing additional alloy elements not only in a different order but also at different stages of the Ruhrstahl-Heraeus (RH) process of low-carbon silicon steel production. A more economical method, described as "pre-alloying", has been introduced. The evolution of MnO-FeO inclusions produced by pre-alloying was investigated. Results show that spherical 3FeO·MnO inclusions form first, then shelled FeO·zMnO (z = 0.7-4) inclusions nucleate on the surface of pre-existing 3FeO·MnO...
October 19, 2017: Materials
Wenxin Huang, Jun Li, Yunhe Xu
The nucleation and growth mechanisms of porous MnO₂ coating deposited on graphite in MnSO₄ solution were investigated in detail by cyclic voltammetry, chronoamperometry and scanning electron microscopy. The electrochemical properties of honeycomb-like MnO₂ were evaluated by cycle voltammetry and galvanostatic charge-discharge. Results indicated that MnO₂ was synthesized by the following steps: Mn(2+)→ Mn(3+)+ e⁻, Mn(3+)+2H2O → MnOOH + 3H⁺, and MnOOH → MnO₂ + H⁺+ e⁻. The deposition of MnO₂ was divided into four stages...
October 19, 2017: Materials
Ségolène Vandevelde, Jacques Élie Brochier, Christophe Petit, Ludovic Slimak
Soot marks, witnesses of past human activities, can sometimes be noticed in concretions (speleothem, travertine, carbonated crust, etc.) formed in cavities. We demonstrate here that these deposits, generally ignored in archaeological studies, turned out to be a perfectly suitable material for micro-chronological study of hominin activities in a site. At the Grotte Mandrin (Mediterranean France), thousands of clastic fragments from the rock walls were found in every archaeological level of the shelter. Calcareous crusts containing soot deposits are recorded on some of their surfaces...
November 2017: Journal of Human Evolution
Yanzhen He, Ping Xu, Bin Zhang, Yunchen Du, Bo Song, Xijiang Han, Huisheng Peng
Sodium ion batteries (SIBs) have attracted increasing attentions as promising alternatives to lithium ion batteries (LIBs). Herein, we design and synthesize ultrasmall MnO nanoparticles (∼4 nm) supported on nitrogen-doped carbon nanotubes (NDCT@MnO) as promising anode materials of SIBs. It is revealed that the carbonization temperature can greatly influence the structural features and thus the Na-storage behavior of the NDCT@MnO nanocomposites. The synergetic interaction between MnO and NDCT in the NDCT@MnO nanocomposites provides high rate capability and long-term cycling life due to high surface area, electrical conductivity, enhanced diffusion rate of Na(+) ions, and prevented agglomeration and high stability of MnO nanoparticles...
November 8, 2017: ACS Applied Materials & Interfaces
Edith Perret, Kaushik Sen, Jarji Khmaladze, Ben Mallett, Meghdad Yazdi-Rizi, Premysl Marsik, Saikat Das, Ivan Marozau, Miguel Uribe-Laverde, Roberto de Andrés Prada, J Strempfer, Max Doebeli, Neven Biskup, Maria Varela, Yves-Laurent Mathis, Christian Bernhard
We studied the structural, magnetic and electronic properties of SrFeO<sub>3-δ</sub> (SFO) thin films and SrFeO<sub>3-δ</sub> /La<sub>2/3</sub>Ca<sub>1/3</sub>MnO<sub>3</sub> (LCMO) superlattices that have been grown with pulsed laser deposition (PLD) on La<sub>0.3</sub>Sr<sub>0.7</sub>Al<sub>0.65</sub>Ta<sub>0.35</sub>O<sub>3</sub> (LSAT) substrates. X-ray reflectometry and scanning transmission electron microscopy (STEM) confirm the high structural quality of the films and flat and atomically sharp interfaces of the superlattices...
October 16, 2017: Journal of Physics. Condensed Matter: An Institute of Physics Journal
Niloufar Eskandarpour, Hassan Sereshti
The nanofibrous polycaprolactam (polyamide 6 (PA6)) incorporated with manganese oxide (MnO) nanoparticles was fabricated by electrospinning and used as a new fiber coating for headspace-solid phase microextraction (HS-SPME) of the selected phthalate esters (PEs) in water samples prior to GC-μECD. The adsorbent was fully characterized using scanning electron microscopy (SEM), Fourier transform-infrared (FT-IR) spectroscopy and thermogravimetric analysis (TGA). The main parameters that affect the HS-SPME efficiency such as extraction temperature, ionic strength, extraction and desorption times were investigated...
October 5, 2017: Chemosphere
Ruilin Zheng, Qi Zhang, Kehan Yu, Chunxiao Liu, Jianyong Ding, Peng Lv, Wei Wei
A kind of Sn(2+)/Mn(2+) co-doped fluorphosphate (FP) glasses that served as single-component continuous tunable broadband emitting multi-chromatic phosphors are developed for the first time. Importantly, these FP glasses have high thermal conductivity (3.25-3.70  W/m·K) and good chemical stability in water (80°C). By combining with commercially available UV-LEDs directly, the emission colors can be tuned from blue/cold-white to warm-white/red through the energy transfer from Sn(2+) to Mn(2+), and the broadband spectra covering the whole visible region from 380 nm to 760 nm...
October 15, 2017: Optics Letters
Seung-Yong Lee, Lijun Wu, Altug S Poyraz, Jianping Huang, Amy C Marschilok, Kenneth J Takeuchi, Esther S Takeuchi, Miyoung Kim, Yimei Zhu
Manganese oxide (α-MnO2 ) has been considered a promising energy material, including as a lithium-based battery electrode candidate, due to its environmental friendliness. Thanks to its unique 1D [2 × 2] tunnel structure, α-MnO2 can be applied to a cathode by insertion reaction and to an anode by conversion reaction in corresponding voltage ranges, in a lithium-based battery. Numerous reports have attributed its remarkable performance to its unique tunnel structure; however, the precise electrochemical reaction mechanism remains unknown...
October 6, 2017: Advanced Materials
N Palma-Aramburu, I Santamaría-Holek
In this work we propose a theoretical model that accounts for the main features of the loading-unloading process of a symmetric redox MnO_{2}-based supercapacitor dominated by fast electrochemical reactions at the electrodes. The model is formulated on the basis of nonequilibrium thermodynamics from which we are able to deduce generalized expressions for the electrochemical affinity, the load-voltage and the current-voltage equations that constitute generalizations of the current-overpotential and Butler-Volmer equations, and that are used to describe experimental voltagram data with good agreement...
August 2017: Physical Review. E
Di Yi, Charles L Flint, Purnima P Balakrishnan, Krishnamurthy Mahalingam, Brittany Urwin, Arturas Vailionis, Alpha T N'Diaye, Padraic Shafer, Elke Arenholz, Yongseong Choi, Kevin H Stone, Jiun-Haw Chu, Brandon M Howe, Jian Liu, Ian R Fisher, Yuri Suzuki
Perpendicular magnetic anisotropy (PMA) plays a critical role in the development of spintronics, thereby demanding new strategies to control PMA. Here we demonstrate a conceptually new type of interface induced PMA that is controlled by oxygen octahedral rotation. In superlattices comprised of La_{1-x}Sr_{x}MnO_{3} and SrIrO_{3}, we find that all superlattices (0≤x≤1) exhibit ferromagnetism despite the fact that La_{1-x}Sr_{x}MnO_{3} is antiferromagnetic for x>0.5. PMA as high as 4×10^{6}  erg/cm^{3} is observed by increasing x and attributed to a decrease of oxygen octahedral rotation at interfaces...
August 18, 2017: Physical Review Letters
Shinya Suzuki, Masaru Miyayama
Co-Mn oxide nanosheets with the chemical composition H0.23Co0.23Mn0.77O₂ (C23M77NS) and MnO₂ nanosheets (M100NS) were prepared by exfoliation of layer-structured oxides via chemical processing in an aqueous medium. The optical properties of C23M77NS and M100NS were compared using UV-Vis spectroscopy, and the valence states of Mn and Co and local structures around them were examined using X-ray absorption spectroscopy. M100NS with an average Mn valence of 3.6 exhibits large structural distortion, whereas C23M77NS with an average Mn valence of 4...
September 25, 2017: Nanomaterials
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