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Manganese Dioxide (manganese + dioxide)
Selected AbstractsSynthesis and Electrical Properties of Stabilized Manganese Dioxide (,-MnO2) Thin-Film ElectrodesJOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 3 2008Do-Kyun Kwon Manganese dioxide (,-MnO2) thin films have been explored as a cathode material for reliable glass capacitors. Conducting ,-MnO2 thin films were deposited on a borosilicate glass substrate by a chemical solution deposition technique. High carbon activities originated from manganese acetate precursor, (Mn(C2H3O2)2·4H2O) and acetic acid solvent (C2H4O2), which substantially reduced MnO2 phase stability, and resulted in Mn2O3 formation at pyrolysis temperature in air. The ,-MnO2 structure was stabilized by Ba2+ insertion into a (2 × 2) oxygen tunnel frame to form a hollandite structure. With 15,20 mol% Ba addition, a conducting ,-MnO2 thin film was obtained after annealing at 600,650°C, exhibiting low electrical resistivity (,1 ,·cm), which enables application as a cathode material for capacitors. The hollandite ,-MnO2 phase was stable at 850°C, and thermally reduced to the insulating bixbyte (Mn2O3) phase after annealing at 900°C. The phase transition temperature of Ba containing ,-MnO2 was substantially higher than the reported transition temperature for pure MnO2 (,500°C). [source] ChemInform Abstract: Synthesis and Oxidative Aromatization of 5-Acetyl-2-cyanoimino-6-methyl-4-phenyl-1,2,3,4-tetrahydropyrimidine with Manganese Dioxide.CHEMINFORM, Issue 15 2010P. A. Solovyev Abstract ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a "Full Text" option. The original article is trackable via the "References" option. [source] Selective and Efficient Heterogeneous Hydration of Nitriles to Amides Using Silica Supported Manganese Dioxide.CHEMINFORM, Issue 9 2004Bhushan M. Khadilkar Abstract For Abstract see ChemInform Abstract in Full Text. [source] Synthesis and Electrical Properties of Stabilized Manganese Dioxide (,-MnO2) Thin-Film ElectrodesJOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 3 2008Do-Kyun Kwon Manganese dioxide (,-MnO2) thin films have been explored as a cathode material for reliable glass capacitors. Conducting ,-MnO2 thin films were deposited on a borosilicate glass substrate by a chemical solution deposition technique. High carbon activities originated from manganese acetate precursor, (Mn(C2H3O2)2·4H2O) and acetic acid solvent (C2H4O2), which substantially reduced MnO2 phase stability, and resulted in Mn2O3 formation at pyrolysis temperature in air. The ,-MnO2 structure was stabilized by Ba2+ insertion into a (2 × 2) oxygen tunnel frame to form a hollandite structure. With 15,20 mol% Ba addition, a conducting ,-MnO2 thin film was obtained after annealing at 600,650°C, exhibiting low electrical resistivity (,1 ,·cm), which enables application as a cathode material for capacitors. The hollandite ,-MnO2 phase was stable at 850°C, and thermally reduced to the insulating bixbyte (Mn2O3) phase after annealing at 900°C. The phase transition temperature of Ba containing ,-MnO2 was substantially higher than the reported transition temperature for pure MnO2 (,500°C). [source] Oxidative transformation of tetrachlorophenols and trichlorophenols by manganese dioxideENVIRONMENTAL TOXICOLOGY & CHEMISTRY, Issue 6 2009Ling Zhao Abstract This study examined the transformation kinetics of three tetrachlorophenols (TeCPs) and three trichlorophenols (TCPs) in the presence of MnO2 under different solution chemistry conditions. The reaction rate measured for each CP decreased as a function of solution pH, and under the same solution chemistry conditions, the measured rates may depend primarily on both the adsorbability at the MnO2 surfaces and the isomeric structures of the CPs. Isomeric effects indicated that chloro substituent on ortho or para positions exhibited faster rates of transformation than on meta positions. Gas chromatography-mass spectrometry analysis with a derivatization method showed that dimers including polychlorinated phenoxyphenols and chlorinated polyhydroxybi-phenyl were among the major products for all CPs. Monomeric products were among the major products of 2,4,6-TCP, 2,3,4-TCP, and 2,3,4,6-TeCP, whereas trimeric products also were among the major products of 2,3,4-TCP and 2,4,5-TCP. It appeared that hydroxylation of CPs and formation of dimeric or trimeric products via oxidative coupling were the major reaction mechanisms involved in the oxidation of CPs by MnO2. [source] Oxidation kinetics of pentachlorophenol by manganese dioxideENVIRONMENTAL TOXICOLOGY & CHEMISTRY, Issue 11 2006Ling Zhao Abstract This study examined the abiotic transformation kinetics of pentachlorophenol (PCP) by manganese dioxide (MnO2) at different solution chemistry and initial concentrations of PCP and MnO2. The measured PCP transformation rates were found to be on the order of 1.07 with respect to [PCP] and 0.91 and 0.87 with respect to [MnO2] and [H+], respectively. Dissolved Mn2+ and Ca2+ as background electrolytes considerably decreased the reaction rate because of their adsorption and hence blocking of active sites on MnO2 surfaces. The dechlorination number, 0.59 chloride ions per transformed PCP after a 1-h reaction, suggests that a fraction of the transformed PCP was not dechlorinated and may be coupled directly to dimeric products. Gas chromatography/ mass spectrometry and liquid chromatography/mass spectrometry/mass spectrometry techniques were used to identify two isomeric nonachlorohydroxybiphenylethers as major products and 2,3,5,6-tetrachloro-1,4-hydroquinone and tetrachlorocatechol as minor products. Product identification suggested that the reaction may include two parallel reactions to form either dimers or 2,3,5,6-tetrachloro-1,4-hydroquinone and tetrachlorocatechol via simultaneous dehydrochlorination and hydroxylation. [source] Hot water acid-resistant enamels for sheet steelMATERIALS AND CORROSION/WERKSTOFFE UND KORROSION, Issue 1 2010A. S. Kassem Abstract Several enamel frit recipes were formulated for direct-on application on sheet steel. Their suitability as hot water and acid-resistant coatings were investigated. DTA analyses were performed on raw batches to follow up physico-chemical changes occurring on firing. Then batches with different recipe compositions were fritted and mixed with mill additions. These were then tested for thermal expansion and the corresponding linear coefficients as well as glass transition temperatures and softening points were obtained. Also, the viscosity of molten frits was determined as a function of temperature. These frits were then applied on sheet steel and the following properties were investigated: resistance to hot water, acid resistance, surface gloss, and adherence to steel. It was found that recipe No. 4, containing no manganese dioxide and the highest amount of nickel oxide among all the suggested recipes, gave the best results. The optimum conditions for application on steel sheet were: firing at 850,°C for 5 min. [source] Hydrothermal Synthesis of Structure- and Shape-Controlled Manganese Oxide Octahedral Molecular Sieve NanomaterialsADVANCED FUNCTIONAL MATERIALS, Issue 9 2006W.-N. Li Abstract Highly uniform single-crystal Na-OMS-2 (OMS: octahedral molecular sieve), pyrolusite, and ,-MnO2 nanostructures with an interesting 3D urchinlike morphology have been successfully prepared using a hydrothermal method based on a mild and direct reaction between sodium dichromate and manganese sulfate. The crystal phases, shapes, and tunnel sizes of the manganese dioxide nanostructures can be tailored. Reaction temperature, concentrations of the reactants, and acidity of the solution play important roles in controlling the synthesis of these manganese dioxides. Field-emission scanning electron microscopy and transmission electron microscopy (TEM) studies show that the nanomaterials obtained are constructed of self-assembled nanorods. X-ray diffraction and TEM results indicate that the constituent manganese dioxide particles are single-crystalline materials. Energy dispersive X-ray analysis and magnetic studies imply that chromium cations may be incorporated into the framework and/or tunnels of the manganese dioxides. A mechanism for the growth of manganese dioxides with urchinlike architectures is proposed. [source] Study of structural defects in ,-MnO2 by Raman spectroscopyJOURNAL OF RAMAN SPECTROSCOPY, Issue 4 2002C. Julien The structural arrangement of ,-MnO2 is currently explained by a random intergrowth of pyrolusite layers in a ramsdellite matrix. The structures of a large variety of ,-MnO2 samples with various structural parameters Pr were studied by x-ray powder diffraction and Raman scattering spectroscopy. We show that elucidation of the quantitative determination of the structural disorder present in ,-MnO2 is accurate by Raman scattering spectroscopy. The Raman data for manganese dioxides with the ,-type structure are treated by a local environment model, which allows one to consider the relationship between the band wavenumber and the pyrolusite intergrowth that corresponds to the structural De Wolff defects. Copyright © 2002 John Wiley & Sons, Ltd. [source] | |||||||||||||