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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

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

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

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

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

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

KINETICS OF Mn-BASED SORBENTS FOR HOT COAL GAS DESULFURIZATION

Description: Mixed manganese oxide sorbents have been investigated for high-temperature removal of hydrogen sulfide (the primary sulfur bearing compound) from hot coal gases. The sorbents were screened by thermodynamic equilibrium considerations for sulfidation. Preliminary experimental work using thermogravimetric analysis (TGA) indicated titania to be a superior substrate than alumina. Four formulations showing superior reactivity in a TGA were then tested in an ambient pressure fixed-bed reactor to determine steady state H 2 S concentrations, breakthrough times and effectiveness of the sorbent when subjected to cyclic sulfidation and regeneration testing. Eight tests were conducted with each test consisting of five cycles of sulfidation and regeneration. Sulfidation occurred at 600 o C using a simulated coal gas at an empty-bed space velocity of approximately 12,000 per hour. Manganese-based sorbents with molar ratios > 1:1 Mn:Substrate were effective in reducing the H 2 S concentration in simulated coal gases to less than 100 ppmv over five cycles. Actual breakthrough time for formulation C6-2-1100 was as high as 73% of breakthrough time based on wt% Mn in sorbent at 600 o C. Regeneration tests determined that loaded pellets can be essentially completely regenerated in an air/steam mixture at 750 o C with minimal sulfate formation. The leading formulation (designated C6-2) from the fixed-bed tests was then further tested under varying sorbent induration temperature, sulfidation temperature and superficial gas velocity. Four tests were conducted with each test consisting of four cycles of sulfidation and regeneration. Results showed that the induration temperature of the sorbent and the reaction temperature greatly affected the H 2 S removal capacity of the sorbent while the superficial gas velocity between 1090 and 1635 cm/min had minimal affect on the sorbent's breakthrough capacity. Testing showed that the sorbent's strength was a strong function of the sorbent induration temperature. Sorbent also showed 30 ...
Date: September 15, 1997
Creator: BERNS, J.J.; SADECKI, K.A. & HEPWORTH, M.T.
Partner: UNT Libraries Government Documents Department

Structural and magnetic states in layered manganites: An expanding view of the phase diagram

Description: Colossal magnetoresistive (CMR) manganites display a spectacular range of structural, magnetic, and electronic phases as a function of hole concentration, temperature, magnetic field, etc. A1though the bulk of research has concentrated on the 3-D perovskite manganites, the ability to study anisotropic magnetic and electronic interactions made available in reduced dimensions has accelerated interest in the layered Ruddlesden-Popper (R-P) phases of the manganite class. The quest for understanding the coupling among lattice, spin, and electronic degrees of freedom (and dimensionality) is driven by the availability of high quality materials. In this talk, the authors will present recent results on synthesis and magnetic properties of layered manganites from the La{sub 2{minus}2x}Sr{sub 1+2x}Mn{sub 2}O{sub 7} series in the Mn{sup 4+}-rich regime x >0.5. This region of the composition diagram is populated by antiferromagnetic structures that evolve from the A-type layered order to G-type ''rocksalt'' order as x increases. Between these two regimes is a wide region (0.7 < x < 0.9) where an incommensurate magnetic structure is observed. The IC structure joins spin canting and phase separation as a mode for mixed-valent manganites to accommodate FM/AF competition. Transport in these materials is dominated by highly insulating behavior, although a region close to x = 0.5 exhibits metal-nonmetal transitions and an extreme sensitivity to oxygen content. They suggest two possible explanations for this transport behavior at doping just above x = O.5: localization by oxygen defects or charge ordering of Mn{sup 3+}/Mn{sup 4+}sites.
Date: January 5, 2000
Creator: Mitchell, J. F.; Millburn, J. E.; Ling, C.; Argyriou, D. N. & Bordallo, H. N.
Partner: UNT Libraries Government Documents Department

Structure--properties relationships for manganese perovskites

Description: By combining the results of dc magnetization, ac susceptibility, magnetoresistivity, magnetostriction, and x-ray and neutron powder diffraction data for stoichiometric La{sub 1{minus}x}Sr{sub x}MnO{sub 3} the authors have constructed a phase diagram that describes the magnetic, transport, and structural properties and the relationships among them as a function of composition and temperature. Correlations among physical and structural properties have been observed that are consistent with a competition between ferromagnetism and JT distortion. A metallic state occurs below the Curie temperature when both coherent and incoherent JT distortions are suppressed.
Date: October 14, 1999
Creator: Dabrowski, B.; Xiong, X.; Chmaissem, O.; Bukowski, Z. & Jorgensen, J. D.
Partner: UNT Libraries Government Documents Department

Spinel electrodes for rechargeable lithium batteries.

Description: This paper gives a historical account of the development of spinel electrodes for rechargeable lithium batteries. Research in the late 1970's and early 1980's on high-temperature . Li/Fe{sub 3}O{sub 4} cells led to the evaluation of lithium spinels Li[B{sub 2}]X{sub 4} at room temperature (B = metal cation). This work highlighted the importance of the [B{sub 2}]X{sub 4}spinel framework as a host electrode structure and the ability to tailor the cell voltage by selection of different B cations. Examples of lithium-ion cells that operate with spinel anode/spinel cathode couples are provided. Particular attention is paid to spinels within the solid solution system Li{sub 1+x}Mn{sub 2-x}O{sub 4} (0 {le} x {le} 0.33).
Date: November 10, 1999
Creator: Thackeray, M. M.
Partner: UNT Libraries Government Documents Department