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Manganese Oxide (manganese + oxide)
Selected AbstractsSynthesis of Polyaniline Nanotubes with a Reactive Template of Manganese Oxide,ADVANCED MATERIALS, Issue 3 2007J. Pan Polyaniline nanotubes are synthesized from manganese oxide templates (see figure and cover). Manganese oxide is used as the physical template and the chemical oxidative initiator for the aniline polymerization. The template can be removed after the reaction, as manganese oxide is reduced into soluble Mn2+ ions. Many morphologies of polyaniline structures, such as nanotubes, spherical tube brushes, and double-shell nanotubes, can be fabricated using this method. [source] Binary Phase Diagram of the Manganese Oxide,Iron Oxide SystemJOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 10 2009Jarrod V. Crum The phase equilibrium of the MnOx,FeOy binary system was measured within a temperature range of 750°,1590°C in air to examine inconsistencies found in literature, i.e., discrepancies related to the boundary between the spinel and hausmannite+spinel phase fields. Several studies are available in the literature that describe this boundary however the results and methods by which they were studied vary namely in terms of the atmosphere (air versus reducing) used and heat treatment/analysis methods. In addition, samples in the discrepancy region of the diagram revert to the hausmannite phase spontaneously upon cooling due to a displacive transformation. In order to accurately measure the phase boundaries, the following measurement methods were used: isothermal heat treatments followed by rapid quenching (in air or water), dilatometry, differential thermal analysis with thermogravimetric analysis, as well as room temperature and hot-stage X-ray diffraction (XRD). Phase assemblage(s) in each specimen were determined by XRD. Data were compared with literature and a new, self consistent phase diagram was developed. The results are reported along with background information and a comparison with previously reported data. This study will support development of a model for thermodynamic equilibria in complex, multioxide silicate melts. [source] Cathode Properties of Nanocrystalline Manganese Oxide Synthesized Through Soft Solution Processing.CHEMINFORM, Issue 2 2006Takashi Watanabe Abstract For Abstract see ChemInform Abstract in Full Text. [source] Infiltration pattern in a regolith,fractured bedrock profile: field observation of a dye stain patternHYDROLOGICAL PROCESSES, Issue 2 2006Jae Gon Kim Abstract We examined the infiltration pattern of water in a regolith,bedrock profile consisting of two overburdens (OB1 and OB2), a buried rice paddy soil (PS), two texturally distinctive weathered materials (WM1 and WM2) and a fractured sedimentary rock (BR), using a Brilliant Blue FCF dye tracer. A black-coloured coating in conducting fractures in WM1, WM2 and BR was analysed by X-ray diffraction and scanning electron microscopy. The dye tracer penetrated to greater than 2 m depth in the profile. The macropore flow and saturated interflow were the major infiltration patterns in the profile. Macropore flow and saturated interflow were observed along fractures in WM1, WM2 and BR and at the dipping interfaces of PS,WM1, PS,WM2 and PS,BR respectively. Heterogeneous matrix flow occurred in upper overburden (OB1) and PS. Compared with OB1, the coarser textured OB2 acted as a physical barrier for vertical flow of water. The PS with low bulk density and many fine roots was another major conducting route of water in the profile. Manganese oxide and iron oxide were positively identified in the black coating material and had low crystallinity and high surface area, indicating their high reactivity with conducting contaminants. Copyright © 2006 John Wiley & Sons, Ltd. [source] Synthesis of Polyaniline Nanotubes with a Reactive Template of Manganese Oxide,ADVANCED MATERIALS, Issue 3 2007J. Pan Polyaniline nanotubes are synthesized from manganese oxide templates (see figure and cover). Manganese oxide is used as the physical template and the chemical oxidative initiator for the aniline polymerization. The template can be removed after the reaction, as manganese oxide is reduced into soluble Mn2+ ions. Many morphologies of polyaniline structures, such as nanotubes, spherical tube brushes, and double-shell nanotubes, can be fabricated using this method. [source] A multicopper oxidase is essential for manganese oxidation and laccase-like activity in Pedomicrobium sp.ENVIRONMENTAL MICROBIOLOGY, Issue 4 2007ACM 306 Summary Pedomicrobium sp. ACM 3067 is a budding-hyphal bacterium belonging to the ,- Proteobacteria which is able to oxidize soluble Mn2+ to insoluble manganese oxide. A cosmid, from a whole-genome library, containing the putative genes responsible for manganese oxidation was identified and a primer-walking approach yielded 4350 bp of novel sequence. Analysis of this sequence showed the presence of a predicted three-gene operon, moxCBA. The moxA gene product showed homology to multicopper oxidases (MCOs) and contained the characteristic four copper-binding motifs (A, B, C and D) common to MCOs. An insertion mutation of moxA showed that this gene was essential for both manganese oxidation and laccase-like activity. The moxB gene product showed homology to a family of outer membrane proteins which are essential for Type I secretion in Gram-negative bacteria. moxBA has not been observed in other manganese-oxidizing bacteria but homologues were identified in the genomes of several bacteria including Sinorhizobium meliloti 1021 and Agrobacterium tumefaciens C58. These results suggest that moxBA and its homologues constitute a family of genes encoding an MCO and a predicted component of the Type I secretion system. [source] Cadmium uptake by earthworms as related to the availability in the soil and the intestineENVIRONMENTAL TOXICOLOGY & CHEMISTRY, Issue 8 2001Leonard A. Oste Abstract The free metal concentration in the soil solution is often considered a key parameter for metal uptake by and toxicity to soft-bodied soil organisms. The equilibrium partitioning theory, which assumes a relationship between the contaminant concentration in pore water and the contaminant concentration in the body tissue, can be used to describe uptake by earthworms. This theory has proved useful for organic chemicals, but its applicability is less clear for metals. In this study, the Cd concentration in soil pore water (pw) was varied by increasing the soil pH by the addition of lime (Ca(OH)2) and by adding manganese oxide (MnO2), which has a high metal binding capacity. Both lime (0.135% w/w) and MnO2 (1% w/w) decreased [Cd2+]pw by a factor of 25, while CdWorm was reduced only by a factor of 1.3 in lime-treated soils and 2.5 in MnO2 -treated soils. Cadmium uptake was weakly related to the free metal concentration (R2adj = 0.66). Adding pH as an explanatory variable increased R2adj to 0.89, indicating that Cd uptake from pore water is pH dependent, which might be attributed to competition of protons and Cd at the surface of the earthworm body. However, previous earthworm experiments in reconstituted groundwater showed a conspicuously smaller pH dependency of Cd uptake. The differences in metal uptake between earthworms in lime- and MnO2 -treated soils are therefore more likely to reflect the predominance of pH-independent intestinal uptake of Cd. Equilibrating the soil with a solution of 0.01 M CaCl2 and 0.1 M triethanolamine (buffered at pH 7.2), simulating the conditions prevailing in the worm intestine, yielded free Cd concentrations that were closely (R2adj = 0.83) and linearly related to the Cd concentration in the earthworm tissue. [source] Novel Multifunctional Properties Induced by Interface Effects in Perovskite Oxide HeterostructuresADVANCED MATERIALS, Issue 45 2009Kui-juan Jin Abstract Multilayer structures have emerged as a leading research topic and researchers expect that multilayers may lead to interesting artificial materials with novel properties. In this Research News we show that the introduction of interfaces into perovskite oxides can induce a series of novel properties including an unusual positive magnetoresistance, great enhancement of lateral photovoltage in La0.9Sr0.1MnO3/SrNb0.01Ti0.99O3, and an electrical modulation of the magnetoresistance in multi-p-n heterostructures of SrTiO3,,/La0.9Sr0.1MnO3/SrTiO3,,/La0.9Sr0.1MnO3/Si. This novel positive magnetoresistance is attributed to the creation of a space charge region at the interface where the spin of the carriers is anti-parallel to that of the carriers in the region far from the interface of manganese oxide in the heterostructures. [source] Synthesis of Polyaniline Nanotubes with a Reactive Template of Manganese Oxide,ADVANCED MATERIALS, Issue 3 2007J. Pan Polyaniline nanotubes are synthesized from manganese oxide templates (see figure and cover). Manganese oxide is used as the physical template and the chemical oxidative initiator for the aniline polymerization. The template can be removed after the reaction, as manganese oxide is reduced into soluble Mn2+ ions. Many morphologies of polyaniline structures, such as nanotubes, spherical tube brushes, and double-shell nanotubes, can be fabricated using this method. [source] MR tracking of transplanted cells with "positive contrast" using manganese oxide nanoparticlesMAGNETIC RESONANCE IN MEDICINE, Issue 1 2008Assaf A. Gilad Abstract Rat glioma cells were labeled using electroporation with either manganese oxide (MnO) or superparamagnetic iron oxide (SPIO) nanoparticles. The viability and proliferation of SPIO-labeled cells (1.9 mg Fe/ml) or cells electroporated with a low dose of MnO (100 ,g Mn/ml) was not significantly different from unlabeled cells; a higher MnO dose (785 ,g Mn/ml) was found to be toxic. The cellular ion content was 0.1,0.3 pg Mn/cell and 4.4 pg Fe/cell, respectively, with cellular relaxivities of 2.5,4.8 s,1 (R1) and 45,84 s,1 (R2) for MnO-labeled cells. Labeled cells (SPIO and low-dose MnO) were each transplanted in contralateral brain hemispheres of rats and imaged in vivo at 9.4T. While SPIO-labeled cells produced a strong "negative contrast" due to the increase in R2, MnO-labeled cells produced "positive contrast" with an increased R1. Simultaneous imaging of both transplants with opposite contrast offers a method for MR "double labeling" of different cell populations. Magn Reson Med 60:1,7, 2008. © 2008 Wiley-Liss, Inc. [source] X-ray powder diffraction and electron diffraction studies of the thortveitite-related L phase, (Zn,Mn)2V2O7ACTA CRYSTALLOGRAPHICA SECTION B, Issue 2 2009Kevin M. Knowles The phase designated ,-Zn3(VO4)2 reported as a minor second phase in zinc oxide-based varistor materials doped with vanadium oxide and manganese oxide is shown to be the L phase, (Zn1,,,xMnx)2V2O7 (0.188 < x < 0.538), in the pseudo-binary Mn2V2O7,Zn2V2O7 system. Analysis of X-ray powder diffraction patterns and electron diffraction patterns of this phase shows that the previously published a, c and , values for this thortveitite-related phase are incorrect. Instead, Rietveld refinement of the X-ray powder pattern of the L phase shows that it has a monoclinic C lattice with Z = 6, with a = 10.3791,(1), b = 8.5557,(1), c = 9.3539,(1),Å and , = 98.467,(1)°. Although prior convergent-beam electron diffraction work of `,-Zn3(VO4)2' confirmed the C Bravais lattice, the space group was found to be Cm rather than C2/m, the difference perhaps arising from the inability of the X-rays to detect small displacements of oxygen. Attempts to refine the structure in Cm did not produce improved R factors. The relationship between the crystal structure of the L phase and the high-temperature C2/m,,-Zn2V2O7 thortveitite-type solid solution is discussed. [source] Influence of gamma radiation on the electrical properties of MnO and MnO/TeO2 thin filmsANNALEN DER PHYSIK, Issue 1-2 2004K. Arshak Abstract The pure and mixed oxide materials, such as manganese oxide (MnO) and tellurium dioxide (TeO2), in the form of thermally deposited thin films were studied in terms of their susceptibility to gamma radiation exposure. Radiation-induced changes in their electrical properties indicated the level of radiation damage. These thin film devices showed increase in values of current by the increase in the radiation dose. The dose response was found to be composition- and thickness-dependant. [source] Pyrolysis of a Three-Dimensional MnII/MnIII Network To Give a Multifunctional Porous Manganese Oxide MaterialCHEMISTRY - A EUROPEAN JOURNAL, Issue 4 2010Sanjit Nayak Dr. Pores for thought! Thermolysis of a 3D coordination network of MnII/MnIII produces a novel spongelike morphology of manganese oxide by a degassing mechanism (see picture). This porous material shows high capacitance when used as an anode in a Li-ion battery and efficient catalytic activity for cyclohexene oxidation. [source] Characterization and Activity of Cu-MnOx/,-Al2O3 Catalyst for Hydrogenation of Carbon DioxideCHINESE JOURNAL OF CHEMISTRY, Issue 5 2001Gong-Xin Qi Abstract The effect of manganese on the dispersion, reduction behavior and active states of surface of supported copper oxide catalysts have been investigated by XRD, temperature-programmed reduction and XPS. The activity of methanol synthesis from CO2/H2 was also investigated. The catalytic activity over CuO-MnOx/,-Al2O3 catalyst for CO2 hydrogenation is higher than that of CuO/,-Al2O3. The adding of manganese is beneficial in enhancing the dispersion of the supported copper oxide and make the TPR peak of the CuO-MnKx/,-Al2O3 catalyst different from the individual supported copper and manganese oxide catalysts, which indicates that there exists strong interaction between the copper and manganese oxide. For the CuO/,-Al2O3 catalyst there are two reducible copper oxide species; , and , peaks are attributed to the reduction of highly dispersed copper oxide species and bulk CuO species, respectively. For the CuO-MnOx/,-Al2O3 catalyst, four reduction peaks are observed, , peak is attributed to the dispersed copper oxide species; , peak is ascribed to the bulk CuO; , peak is attributed to the reduction of high dispersed CuO interacting with manganese; , peak may be the reduction of the manganese oxide interacting with copper oxide. XPS results show that Cu+ mostly existed on the working surface of the Cu-Mn/,-Al2O3 catalysts. The activity was promoted by Cu with positive charge which was formed by means of long path exchange function between CuOMn. These results indicate that there is synergistic interaction between the copper and manganese oxide, which is responsible for the high activity of CO2 hydrogenation. [source] Raman identification of natural red to yellow pigments: ochre and iron-containing oresJOURNAL OF RAMAN SPECTROSCOPY, Issue 5 2008Françoise Froment Abstract Red and yellow natural (roasted) pigments have been used for millennia. This paper reports on the Raman characterization of about 50 pigments of the Ôkhra ,Mathériauthèque' collection from different origins: violet, red, orange, apricot, yellow ochre, Umbrian and Siena earths from France (Puisaye, Ardennes, Vaucluse), Italy (Siena, Sardinia, Venice, etc.), Germany, Sweden, Cyprus and India (Madras). Comparison is made with ,Bengara' Japanese pigments. Goethite is the chromophore of yellow pigments, and haematite (sometimes with magnetite) that of red ochre and earths. Umbrian pigment (,Terre d'Ombre') contains additional manganese oxides. Color shades are related to the content of secondary phases: iron oxides (haematite, goethite, magnetite), quartz, gypsum and anhydrite, calcite, dolomite, alums (jarosites), and to the Fe/M substitution in the haematite structure. The set of secondary phases can be used to confirm a provenance signature (Supplementary Material available). Copyright © 2008 John Wiley & Sons, Ltd. [source] Behaviour of cadmium and nickel in a soil amended with sewage sludgeLAND DEGRADATION AND DEVELOPMENT, Issue 1 2001I. Sastre Abstract Various urban and industrial sewage sludges were applied to a soil at two doses (50 and 100,t ha,1 y,1) during eight years in a field experiment. The soil was analysed at two depths (0,30 and 30,60,cm) for extractable cadmium and nickel. In general these trace metal increased with dosage. However, cadmium formed complexes with organic matter and nickel bound to iron and manganese oxides. Hence, the available fractions of these metals constituted a small proportion of the total content. The results obtained show a low risk of contamination due to the available fractions of these metals at sludges dosages of up to 100,t ha,1. Copyright © 2001 John Wiley & Sons, Ltd. [source] Praseodymium deficiency effects on the physical properties of Pr1.2,x,xSr1.8Mn2O7 bilayer manganese oxidesPHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue 9 2006M. Triki Abstract The praseodymium deficiency effects on the structural, magnetic and electrical properties of the lacunar bilayers manganese oxides Pr1.2,x,xSr1.8Mn2O7 (0 , x , 0.15) were studied. Rietveld refinements of the X-ray diffraction patterns show that all our samples are single phase and crystallize in the tetragonal structure with I4/mmm space group. All our samples exhibit a paramagnetic-ferromagnetic transition on cooling. The praseodymium deficiency leads to a decrease of the Curie temperature. Resistivity measurements as a function of temperature show that only the parent sample Pr1.2Sr1.8Mn2O7 exhibits a semiconducting-metallic transition with decreasing temperature. (© 2006 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Epithermal Gold-Silver Mineralization of the Asachinskoe Deposit in South Kamchatka, RussiaRESOURCE GEOLOGY, Issue 4 2007Ryohei Takahashi Abstract The Asachinskoe epithermal Au-Ag deposit is a representative low-sulfidation type of deposit in Kamchatka, Russia. In the Asachinskoe deposit there are approximately 40 mineralized veins mainly hosted by dacite,andesite stock intrusions of Miocene,Pliocene age. The veins are emplaced in tensional cracks with a north orientation. Wall-rock alteration at the bonanza level (170,200 m a.s.l.) consists of the mineral assemblage of quartz, pyrite, albite, illite and trace amounts of smectite. Mineralized veins are well banded with quartz, adularia and minor illite. Mineralization stages in the main zone are divided into stages I,IV. Stage I is relatively barren quartz,adularia association formed at 4.7 ± 0.2 Ma (K-Ar age). Stage II consists of abundant illite, Cu-bearing cryptomelane and other manganese oxides and hydroxides, electrum, argentite, quartz, adularia and minor rhodochrosite and calcite. Stage III, the main stage of gold mineralization (4.5,4.4 ± 0.1,3.1 ± 0.1 Ma, K-Ar age), consists of a large amount of electrum, naumannite and Se-bearing polybasite with quartz,adularia association. Stage IV is characterized by hydrothermal breccia, where electrum, tetrahedrite and secondary covellite occur with quartz, adularia and illite. The concentration of Au+Ag in ores has a positive correlation with the content of K2O + Al2O3, which is controlled by the presence of adularia and minor illite, and both Hg and Au also have positive correlations with the light rare-earth elements. Fluid inclusion studies indicate a salinity of 1.0,2.6 wt% NaCl equivalent for the whole deposit, and ore-forming temperatures are estimated as approximately 160,190°C in stage III of the present 218 m a.s.l. and 170,180°C in stage IV of 200 m a.s.l. The depth of ore formation is estimated to be 90,400 m from the paleo-water table for stage IV of 200 m a.s.l., if a hydrostatic condition is assumed. An increase of salinity (>CNaCl, 0.2 wt%) and decrease of temperature (>T , 30°C) within a 115-m vertical interval for the ascending hydrothermal solution is calculated, which is interpreted as due to steam loss during fluid boiling. Ranges of selenium and sulfur fugacities are estimated to be logfSe2 = ,17 to ,14.5 and logfS2 = ,15 to ,12 for the ore-forming solution that was responsible for Au-Ag-Se precipitation in stage III of 200 m a.s.l. Separation of Se from S-Se complex in the solution and its partition into selenides could be due to a relatively oxidizing condition. The precipitation of Au-Ag-Se was caused by boiling in stage III, and the precipitation of Au-Ag-Cu was caused by sudden decompression and boiling in stage IV. [source] | ||||||||||||||||||||||