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Effect of Structure on the Storage Characteristics of ManganeseOxide Electrode Materials

Description: Eleven types of manganese-containing electrode materialswere subjected to long-term storage at 55oC in 1M LiPF6 ethylenecarbonate/dimethyl carbonate (EC/DMC) solutions. The amount of manganesedissolution observed depended upon the sample surface area, the averageMn oxidation state, the structure, and substitution levels of themanganese oxide. In some cases, structural changes such as solvateformation were exacerbated by the high temperature storage, andcontributed to capacity fading upon cycling even in the absence ofsignificant Mn dissolution. The most stable materials appear to beTi-substituted tunnel structures and mixed metal layered oxides with Mnin the +4 oxidation state.
Date: January 31, 2006
Creator: Park, Yong Joon & Doeff, Marca M.
Partner: UNT Libraries Government Documents Department

Transuranic interfacial reaction studies on manganese oxidemineral surfaces

Description: Several DOE sites have been contaminated by transuranicradionuclide (TRU) discharges including neptunium and plutonium. Theirinteraction with the surrounding geological media can affect thetransport and remediation of these radionuclides in the environment.Manganese based minerals, present as minor phases in the vadose zone, canpreferentially sequester TRU over other minerals present in largerquantities. The objective of this project is to understand theinteractions between plutonium and neptunium and manganese oxyhydroxideminerals to predict potential hazards they represent to the environment,as well as to provide important scientific information for the design ofeffective remediation strategies for contaminated DOE sites.
Date: May 15, 2002
Creator: Shaughnessy, Dawn A.; Nitsche, Heino; Serne, R. Jeffrey; Shuh,David K.; Waychunas, Glenn A.; Booth, Corwin H. et al.
Partner: UNT Libraries Government Documents Department

Thermodynamic properties of solid solutions at high temperatures

Description: The research carried out under this cortract was concerned with the determination of thermodynamic properties of inorganic matenials at high temperatures. Experimental methods were developed which permit accurate and reliable determination of activity-composition relations in solid solutions, and stabilities of end-member compounds. The data provide insight irto the general laws governing the behavior of materials in high-temperature envirorments. The phases selected for the experimental studies include onthosilicates, metasilicates, oxides of periclase structure, spinels, and titarates. It has been shown that directions of conjugation lines between coexisting solid-solution phases provide a powerful tool for determnining relative stabilities of endmember compounds and activity-composition relations of solid solutions. In general, oxide phases (including silicates and titanates) forming complete solid-solution series at high temperatures show less deviations from ideality in their activity- composition relations than do alloy systems. Deviations from ideality are particularly small for many solid solutions of relatively simple structures (e.g. oxides of peniclase structure), whereas those of greater structural complexities (e.g. spinels) show larger deviations from ideality. (auth)
Date: January 1, 1973
Creator: Muan, A.
Partner: UNT Libraries Government Documents Department

Investigation of Manganese Dioxide as an Improved Solid Desiccant

Description: This report describes the preparation of a series of manganese oxides and an analysis of their sorptive, structural, and surface characteristics as low-energetic desiccants for passive dehumidification and active desiccant cooling systems. A cusped Type III isotherm for the adsorption of water is reported for the first time. The data are interpreted as evidence of a first-order phase change from a two-dimensional gas to a liquid film in the first reversibly adsorbed layer. It appears that the water adsorption characteristics of MnO2 compared to standard desiccants which exhibit Type II isotherms are due at least in part to differences in the physical topography and electronic properties of the desiccant substrates: MnO2 is a p-type semiconductor with essentially-flat, monoenergetic surface structures, while standard desiccants like silica gel are electronic insulators with irregular, heteroenergetic surfaces.
Date: March 1983
Creator: Fraioli, Anthony V.
Partner: UNT Libraries Government Documents Department

Effect of Titanium Substitution on the Compatiblity of Electrodeswith Pyrrolidinium-Based Ionic Liquid Electrolytes

Description: The quest for the development of rechargeable lithium-metal batteries has attracted vigorous worldwide research efforts because this system offers the highest theoretical specific energy [1]. For this to be achieved, the repetitive deposition and stripping of lithium must be close to fully reversible. Thus, alternative electrolytes have been investigated, such as the room-temperature ionic liquid (RTILs). Lithium can be cycled with a high degree of reversibility with efficiencies exceeding 99% using systems based on N-methyl N-alkyl pyrrolidinium (P{sub 1X}{sup +}) combined with the TFSI anion [2]. More recent efforts have been directed towards systems based on P{sub 1X}{sup +} cations with the FSI anion and appear to be even more promising [3,4]. In this work, we discuss to what extent RTILs based on P{sub 1X}{sup +} cations with TFSI or FSI anions can be used as electrolytes for rechargeable Li batteries. In particular, their physical and chemical properties are thoroughly discussed so as to explain the difference observed in their electrochemical behavior. Although these two systems seem to be stable against lithium, their compatibilities with cathode materials require full assessment as well. Thus, various manganese oxide cathodes are investigated in this study. Strategies to minimize cathode dissolution are also debated, such as the substitution of part of the manganese for titanium.
Date: May 16, 2007
Creator: Saint, Juliette A.; Shin, Joon-Ho; Best, Adam; Hollenkamp,Anthony; Kerr, John & Doeff, Marca M.
Partner: UNT Libraries Government Documents Department

Growth and Dissolution of Iron and Manganese Oxide Films

Description: Growth and dissolution of Fe and Mn oxide films are key regulators of the fate and transport of heavy metals in the environment, especially during changing seasonal conditions of pH and dissolved oxygen. The Fe and Mn are present at much higher concentrations than the heavy metals, and, when Fe and Mn precipitate as oxide films, heavy metals surface adsorb or co-precipitate and are thus essentially immobilized. Conversely, when the Fe and Mn oxide films dissolve, the heavy metals are released to aqueous solution and are thus mobilized for transport. Therefore, understanding the dynamics and properties of Fe and Mn oxide films and thus on the uptake and release of heavy metals is critically important to any attempt to develop mechanistic, quantitative models of the fate, transport, and bioavailablity of heavy metals. A primary capability developed in our earlier work was the ability to grow manganese oxide (MnO{sub x}) films on rhodochrosite (MnCO{sub 3}) substrate in presence of dissolved oxygen under mild alkaline conditions. The morphology of the films was characterized using contact-mode atomic force microscopy. The initial growth began by heteroepitaxial nucleation. The resulting films had maximum heights of 1.5 to 2 nm as a result of thermodynamic constraints. Over the three past years, we have investigated the effects of MnO{sub x} growth on the interactions of MnCO{sub 3} with charged ions and microorganisms, as regulated by the surface electrical properties of the mineral. In 2006, we demonstrated that MnO{sub x} growth could induce interfacial repulsion and surface adhesion on the otherwise neutral MnCO{sub 3} substrate under environmental conditions. Using force-volume microscopy (FVM), we measured the interfacial and adhesive forces on a MnO{sub x}/MnCO{sub 3} surface with a negatively charged silicon nitride tip in a 10-mM NaNO3 solution at pH 7.4. The interfacial force and surface adhesion of MnOx ...
Date: December 22, 2008
Creator: Martin, Scot T.
Partner: UNT Libraries Government Documents Department

Plutonium(VI) sorption to manganese dioxide.

Description: Redox-active metal oxides may strongly affect the environmental behavior and mobility of actinides . Manganese oxides are relatively common redox-active soil components, which have a high surface area and which some studies show sorb plutonium selectively over other mineral phases .' For plutonium, oxidation states that could exist in the environment include +111 to +VI, with Pu(IV) being predominant in the insoluble phase. Plutonium(V), and to a lesser extent Pu(VI), are the stable Pu oxidation states in solution under environmental conditions .Z We are using synthetic 6-Mn02 because it is most similar to the common natural manganese oxide mineral birnessite . Previously, we have shown that Pu(V) is oxidized to Pu(VI) in solution by 8-Mn02, then very effectively sorbed to the mineral . We are now studying Pu(VI) sorption to synthetic 8-Mn02 in detail to determine its sorption mechanisms and sorption capacity .
Date: January 1, 2003
Creator: Reilly, S. D. (Sean D.); Myers, W. K. (William K.); Stout, S. A. (Stephen A.); Smith, D. M. (Donna M.); Ginder-Vogel, M. A. (Matthew A.) & Neu, M. P. (Mary P.)
Partner: UNT Libraries Government Documents Department

Thin-film rechargeable lithium batteries with amorphous Li{sub x}Mn{sub 2}O{sub 4} cathodes

Description: Cathode films of amorphous Li{sub x}Mn{sub 2}O{sub 4} have been grown by rf magnetron sputtering on unheated substrates. A low process gas pressure and a positive substrate bias were found to give the most conductive cathodes. The batteries were completed with subsequent deposition of a lithium phosphorous oxynitride electrolyte and Li anode. These cells were cycled at 25-100 C between 4.5 and 1.5 V which corresponds to {approximately}0 to 2 Li per Mn{sub 2}O{sub 4}. The amorphous cathodes have a highs pecific capacity and a low capacity loss per cycle.
Date: January 1, 1996
Creator: Dudney, N.J.; Bates, J.B.; Lubben, D. & Hart, F.X
Partner: UNT Libraries Government Documents Department

High-temperature magnetic anomalies in Sr-doped La manganite structures

Description: The temperature dependence of the magnetization M, susceptibility {chi}, and magnetoresistance MR for 3 perovskite-variant manganite structures were studied: monoclinic (x=0.075) and orthorhombic (x=0. 125) La{sub 1-x}Sr{sub x}MnO{sub 3}, and tetragonal layered La{sub 2- 2x}Sr{sub 1+2x}Mn{sub 2}O{sub 7} (x=0.4) with x also indicating the nominal fraction of Mn{sup 4+}. In each case, evidence is found for unusual magnetic states at temperatures T above their primary magnetic transitions. In the first case, the high-T {chi} deviates from Curie-Weiss expectations, in the second case the MR extends to high T, and in the last, M and {chi} exhibit short-range anomalies at high T. This suggests that a key feature of these systems is the existence of multiple magnetic energy scales, independent of structure, dimensionality, or doping levels.
Date: November 1996
Creator: Potter, C. D.; Swiatek, M.; Mitchell, J. F.; Hinks, D. G.; Jorgensen, J. D.; Bader, S. D. et al.
Partner: UNT Libraries Government Documents Department

Synthesis, tailored microstructures and `colossal` magnetoresistance in oxide thin films

Description: We have grown La{sub 1-x}Sr{sub x}MnO{sub 3} films, using both pulsed laser deposition and a polymeric sol-gel route. These two growth techniques result in different microstructures, but in both cases the texture (epitaxy or polycrystallinity) can be controlled by choice of substrates and growth conditions. The crystallography and microstructure of these films were studied using XRD and high- resolution TEM. The magnetic/magnetotransport properties of these films are discussed in context of their growth and microstructural parameters.
Date: September 1, 1996
Creator: Krishnan, K.M.; Modak, A.R.; Ju, H. & Bandaru, P.
Partner: UNT Libraries Government Documents Department

Structural and electrochemical studies of alpha manganese dioxide ({alpha}-MnO{sub 2})

Description: The structural and electrochemical properties of alpha-MnO[sub 2], prepared by acid digestion of Mn[sub 2]O[sub 3], and its lithiated derivatives xLi[sub 2] O . MnO[sub 2] (where x is greater than or equal to zero and less than or equal to 0.25) have been investigated as insertion compounds in the search for new and viable cathode materials for rechargeable 3-V batteries. The alpha-MnO[sub 2] product fabricated by this technique contains water within the large (2x2) channels of the structure; the water can be removed from the alpha-MnO[sub 2] framework without degradation of the structure, and then at least partially replaced by Li[sub 2]O. The lithia-doped alpha-MnO[sub 2] electrodes, described generically as xLi[sub 2]O . Mno[sub 2], stabilize the structure and provide higher capacities on cycling than the parent material. The structures of these alpha- MnO[sub 2]-type electrode materials are described. and electrochemical data are presented for both liquid electrolyte and polymer electrolyte Li/alpha-MnO[sub 2] and Li/xLi[sub 2]O . MnO[sub 2] cells.
Date: August 1, 1996
Creator: Johnson, C.S.; Dees, D.W.; Mansuetto, M.F.; Thackeray, M.M.; Vissers, D.R.; Argyriou, D. et al.
Partner: UNT Libraries Government Documents Department

Two-dimensional intrinsic and extrinsic ferromagnetic behavior of layered La{sub 1.2}Sr{sub 1.8}Mn{sub 2}O{sub 7} single crystals

Description: The low-field magnetization M and susceptibility {chi} are reported for the two-layered Ruddleson-Popper phase SrO(La{sub 1{minus}x}Sr{sub x}MnO{sub 3}){sub 2} for x = 0.4 (denoted La{sub 1.2}Sr{sup 1.8}Mn{sub 2}O{sub 7}) with an in-plane magnetic easy axis. As T approaches the Curie temperature (T{sub C} = 116 K) on cooling, where the metal-insulator transition occurs in zero-field, {chi} diverges as H{sup {minus}1/{delta}{prime}}, with {delta}{prime} = 21 {+-} 5. Also, near an extrinsic Curie transition attributed to {approximately} 0.1% volume fraction of intergrowths at T* = 2.47T{sub C}, M scales as (1 {minus} T/T*){sup {beta}}, with {beta} = 0.25 {+-} 0.02. These results can be understood within the context of 2D XY models, and provide a new perspective of the layered manganites.
Date: June 6, 1997
Creator: Potter, C. D.; Swiatek, M.; Bader, S. D.; Argyriou, D.N.; Mitchell, J. F.; Miller, D. J. et al.
Partner: UNT Libraries Government Documents Department

Hysteresis in Thin-Film Rechargeable Lithium Batteries

Description: Discharge - charge cycling of thin-film rechargeable lithium batteries with an amorphous or nanocrystalline LiXMn2.Y04 cathode reveals evidence for a true hysteresis in the lithium insertion reaction. This is compared with an apparent hysteresis attributed to a kinetically hindered phase transition near 3 V for batteries with either a crystalline or a nanocrystalline LiJ@Yo4 cathode.
Date: April 25, 1999
Creator: Bates, J.B.; Dudney, N.J.; Evans, C.D. & Hart, F.X.
Partner: UNT Libraries Government Documents Department

Short range spin correlations in the CMR material La{sub 1.41}Sr{sub 1.6}Mn{sub 2}O{sub 7}

Description: The (La{sub 1{minus}x}Sr{sub x}){sub 2}Mn{sub 3}O{sub 7} compounds are layered materials that exhibit higher magneto-resistance than the corresponding 3D manganite perovskites. Quasi-elastic neutron scattering on a polycrystalline sample of La{sub 1.4}Sr{sub 1.6}Mn{sub 2}O{sub 7} shows that the spin fluctuation spectrum of these layered CMR materials is qualitatively similar to those found in the perovskite manganites (La,Ca)MnO{sub 3}; their concentration, lifetime, and coherence length increase as T decreases to {Tc}. Unlike the perovskites the authors found a lower spin-diffusion constant above {Tc} of {approximately} 5 meV {angstrom}{sup 2}.
Date: December 1, 1997
Creator: Kelley, T.M.; Argyriou, D.N.; Robinson, R.A.; Nakotte, H.; Mitchell, J.F.; Osborn, R. et al.
Partner: UNT Libraries Government Documents Department

Spectroscopic study of the proton dynamics in manganese dioxide electrode materials

Description: Proton or lithium diffusion is a critical electrode process that occurs in manganese dioxide electrode materials during cycling of either aqueous (alkaline) or non-aqueous (lithium) batteries. The structural and electrochemical properties of a number of hydrated alpha-phase manganese dioxide compounds ({alpha}-MnO{sub 2}{lg_bullet}nH{sub 2}O; n{approx}0.2-0.33), the heat-treated products (n{approx}0-0.1), as well as their more stable lithia-doped derivatives, {alpha}-[xLi{sub 2}O]{lg_bullet}MnO{sub 2} (0 {le} x {le} 0.25), have been investigated. Inelastic neutron scattering was used as a means to differentiate and interrogate the key proton or water interactions in these MnO{sub 2} structures. The neutron spectra reveal excitations associated with the hydrogen vibrations centered at 4, 13, 16, 26, 36, 65, 90, 110, 140, 200, 420, and 490 meV in the alpha-phase and 14, 24, 65, 84, 100, 202, and 425 meV in the lithia-doped derivatives. Band assignments were carried out by comparing these frequencies with those reported for structurally similar hydrated {gamma}-MnO{sub 2} compounds and comparison with infrared data.
Date: October 1, 1997
Creator: Johnson, C.S.; Thackeray, M.M.; Nipko, J.C. & Loong, C.K.
Partner: UNT Libraries Government Documents Department

Autogenous electrolyte, non-pyrolytically produced solid capacitor structure

Description: This report discusses the design of a solid electrolytic capacitor having a solid electrolyte comprised of manganese dioxide dispersed in an aromatic polyamide capable of to forming polyimide linkages. This solid electrolyte being disposed between a first electrode made of valve metal covered by an anodic oxide film and a second electrode opposite the first electrode. The electrolyte autogenously produces water, oxygen, and hydroxyl groups which act as healing substances and is not itself produced pyrolytically. Reduction of the manganese dioxide and the water molecules released by formation of imide linkages result in substantially improved self-healing of anodic dielectric layer defects.
Date: April 1, 1998
Creator: Sharp, D.J.; Armstrong, P.S. & Paintz, J.K.G.
Partner: UNT Libraries Government Documents Department

Time dependent effects and transport evidence for phase separation in La{sub 0.5}Ca{sub 0.5}MnO{sub 3}

Description: The ground state of La{sub 1{minus}x}Ca{sub x}MnO{sub 3} changes from a ferromagnetic metallic to an antiferromagnetic charge-ordered state as a function of Ca concentration at x {approximately} 0.50. The authors present evidence from transport measurements on a sample with x = 0.50 that the two phases can coexist, in agreement with other observations of phase separation in these materials. They also observe that, by applying and then removing a magnetic field to the mainly charge-ordered state at some temperatures, they can ``magnetically anneal'' the charge order, resulting in a higher zero-field resistivity. They also observe logarithmic time dependence in both resistivity and magnetization after a field sweep at low temperatures.
Date: February 17, 2000
Creator: Roy, M.; Mitchell, J. F. & Schiffer, P.
Partner: UNT Libraries Government Documents Department