Search Results

Advanced search parameters have been applied.
open access

Catalyzed Water Oxidation by Solar Irradiation of Band-Gap-Narrowed Semiconductors (Part 2. Overview).

Description: The objectives of this report are: (1) Investigate the catalysis of water oxidation by cobalt and manganese hydrous oxides immobilized on titania or silica nanoparticles, and dinuclear metal complexes with quinonoid ligands in order to develop a better understanding of the critical water oxidation chemistry, and rationally search for improved catalysts. (2) Optimize the light-harvesting and charge-separation abilities of stable semiconductors including both a focused effort to improve the best … more
Date: March 18, 2008
Creator: Fujita, E.; Khalifah, P.; Lymar, S.; Muckerman, J. T. & Rodriguez, J.
Partner: UNT Libraries Government Documents Department
open access

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% … more
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
open access

Catalyzed Water Oxidation by Solar Irradiation of Band-Gap-Narrowed Semiconductors (Part 1. Overview).

Description: The objectives of this report are: (1) Investigate the catalysis of water oxidation by cobalt and manganese hydrous oxides immobilized on titania or silica nanoparticles, and dinuclear metal complexes with quinonoid ligands in order to develop a better understanding of the critical water oxidation chemistry, and rationally search for improved catalysts. (2) Optimize the light-harvesting and charge-separation abilities of stable semiconductors including both a focused effort to improve the best … more
Date: March 18, 2008
Creator: Fujita, E.; Khalifah, P.; Lymar, S.; Muckerman, J. T. & Rodgriguez, J.
Partner: UNT Libraries Government Documents Department
open access

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 cyclin… more
Date: January 31, 2006
Creator: Park, Yong Joon & Doeff, Marca M.
Partner: UNT Libraries Government Documents Department
open access

Experiments on sorption characteristics of solid desiccant materials for solar desiccant cooling systems

Description: A test facility for measuring the sorption properties of candidate solid desiccant materials under dynamic conditions as well as equilibrium conditions, those experienced during desiccant dehumidifier operation, was constructed and tested. The theory of perturbation chromatography was initially used to measure the equilibrium properties of a desiccant/water-vapor system for the first time. Silica gel, molecular sieve, and gamma-manganese dioxide were tested. The equilibrium capacity estimated b… more
Date: November 1, 1984
Creator: Pesaran, A.A.
Partner: UNT Libraries Government Documents Department
open access

Charge and spin fluctuations in the density functional theory

Description: We introduce a conceptual framework which allow us to treat charge and spin fluctuations about the Local density Approximation (LDA) to the Density Functional Theory (DFT). We illustrate the approach by explicit study of the Disordered Local Moment (DLM) state in Fe above the Curie Temperature {Tc} and the Mott insulating state in MnO. 27 refs., 6 figs.
Date: January 1, 1990
Creator: Gyoerffy, B. L.; Barbieri, A. (Bristol Univ. (UK). H.H. Wills Physics Lab.); Staunton, J. B. (Warwick Univ., Coventry (UK). Dept. of Physics); Shelton, W. A. & Stocks, G. M. (Oak Ridge National Lab., TN (USA))
Partner: UNT Libraries Government Documents Department
open access

Energy of <100> coincidence twist boundaries in transition metal oxides

Description: The energies of coincidence twist boundaries formed by rotation about a <100> axis in stoichiometric transition metal oxides crystallizing in the NaCl structure (such as NiO, MnO, and CoO) have been calculated using the ionic-type potentials for these materials. From a relaxation calculation it is found that the energies of the most prominent coincidence twist boundaries at 36.87, 22.62, 28.07, and 16.26/sup 0/ (which correspond to inverse coincidence-site densities of ..sigma.. = 5, 13, … more
Date: January 1, 1979
Creator: Wolf, D
Partner: UNT Libraries Government Documents Department
open access

Application of rock varnish dating of quaternary surficial deposits in determining times of fault movement

Description: Rock varnish, a coating commonly found on rock surfaces in arid and semiarid regions, has a significant potential in paleoseismic studies, as a wide variety of Quaternary surfaces and surficial deposits can be dated with the rock varnish technique. If the formation of geomorphic surfaces or surficial deposits can be related to times of faulting or if faulting has broken or deformed such features, then rock varnish dating can be used to constrain maximum and minimum times of motion on the relate… more
Date: January 1, 1987
Creator: Harrington, C.D.
Partner: UNT Libraries Government Documents Department
open access

SEM (Scanning Electron Microscopy) Analysis of Rock Varnish Chemistry for Cation-Ratio Dating: An Examination of Electron Beam Penetration Depths

Description: Rock varnish is a microns-thick manganese- and iron-rich coating that forms on exposed rock surfaces in arid and semi-arid environments. Empirical correlations of the varnish cation ratio (K+Ca)/Ti with age have been used to estimate ages of geomorphic surfaces, with varnish chemistry generally acquired by either proton-induced x-ray emission (PIXE) analysis of natural varnish surfaces. Chemical analyses of rock varnish with SEM/EDX utilize a sequence of accelerating voltages to vary penetratio… more
Date: April 2, 1990
Creator: Reneau, Steven L.; Raymond, Robert Jr.; Harrington, Charles D. & Hagan, Roland C.
Partner: UNT Libraries Government Documents Department
open access

Characterization of electrochemical systems and batteries: Materials and systems

Description: Materials are a pacing problem in battery development. The battery environment, particularly in rechargeable batteries, places great demands on materials. Characterization of battery materials is difficult because of their complex nature. In many cases meaningful characterization requires iii situ methods. Fortunately, several new electrochemical and spectroscopic techniques for in situ characterization studies have recently become available, and reports of new techniques have become more frequ… more
Date: January 1, 1992
Creator: McBreen, J.
Partner: UNT Libraries Government Documents Department
open access

R-curve behavior in ferrite ceramics

Description: The unusual dependence of the fracture mode of ferrite ceramics on the stress intensity factor in the subcritical crack growth regime was used to create flaws with different concentrations of crack-interface bridges. Flaws with numerous bridges were produced by indenting under dry silicone oil, while flaws with essentially no bridges were produced by indenting under water. Plots of log failure stress as a function of log indenter load for the two types of flaws reflect the differences in bridgi… more
Date: January 1, 1990
Creator: Beauchamp, E. K. & Monroe, S. L.
Partner: UNT Libraries Government Documents Department
open access

Tank waste retrieval issues and options for their resolution

Description: The US Department of Energy has undertaken the significant challenge of remediating the high-level wastes currently being stored underground in tanks located at the Hanford Site in Washington State. A key element of the remediation process is the recovery of these defense production wastes in preparation for downstream processing and disposal. A number of technical and programmatic issues have been identified with the waste recovery process, referred to as retrieval. In response to these issues… more
Date: February 1, 1993
Creator: Miller, W. C.; Henderson, J. M.; Shen, E. J.; Stegen, L. C. & Wrzesinski, W. R.
Partner: UNT Libraries Government Documents Department
open access

The structure of new synthetic manganese oxide octahedral molecular sieves

Description: Manganese K-edge X-ray absorption spectra are used to examine the average oxidation state and local structure of new synthetic manganese oxide photocatalysts, including the materials known as octahedral molecular sieves. The structures of these materials are compared to the natural minerals cryptomelane and todorokite.
Date: July 11, 1994
Creator: Wasserman, S. R.; Carrado, K. A.; Yuchs, S. E.; Shen, Y. F.; Cao, H. & Suib, S. L.
Partner: UNT Libraries Government Documents Department
open access

Chemical interactions between interconnect and electrode materials during sintering in solid oxide fuel cells

Description: Chemical interactions and interdiffusion between the interconnect, (LaCa)CrO{sub 3} and (YCa)CrO{sub 3} and the anode, Ni{center_dot}ZrO{sub 2}, and cathode, (LaSr)MnO{sub 3} and (YCa)MnO{sub 3}, were evaluated from 1300 to 1500C. Reaction of (LaCa)CrO{sub 3} and Ni{center_dot}ZrO{sub 2} cermet resulted in the formation of NiCr{sub 2}O{sub 4} spinel, while reaction of (YCa)CrO{sub 3} and Ni{center_dot}ZrO{sub 2} resulted in the formation of both NiCr{sub 2}O{sub 4} and CaZrO{sub 3}, at all temp… more
Date: May 1, 1993
Creator: Armstrong, T. R.; Chick, L. A. & Bates, J. L.
Partner: UNT Libraries Government Documents Department
open access

Physical realisation of n greater than or equal to 4 vector models

Description: Renormalization group analysis of several n greater than or equal to 4 systems was performed. The first-order transitions in Cr, Eu, UO/sub 2/, MnO, and TbP can be explained by noting that the Hamiltonians have no stable fixed-points in 4-epsilon dimensions. The phase transitions in TbAu/sub 2/, DyC/sub 2/, Tb, Ho, Dy, TbD/sub 2/, Nd, MnS/sub 2/, and K/sub 2/IrCl/sub 6/ are described by n greater than or equal to 4 Hamiltonians with a stable fixed point; critical exponents corresponding to this… more
Date: January 1, 1976
Creator: Mukamel, D.; Krinsky, S. & Bak, P.
Partner: UNT Libraries Government Documents Department
open access

Oxygen reduction at a stabilized zirconia interface with Y{sub 1-x}Ca{sub x}MnO{sub 3} or La{sub 1-x}Sr{sub x}MnO{sub 3} cathode materials

Description: Impedance spectroscopy, combined with an unbonded interface cell, has been used to assess oxygen reduction behavior at interfaces between an yttria-stabilized zirconia electrolyte and perovskite or platinum cathode materials. Intrinsic oxygen reduction specific activities of Y{sub 1-x}Ca{sub x}MnO{sub 3} (x = 0.5, 0.6 and 0.7) and La{sub 1-x}Sr{sub x}MnO{sub 3} (x = 0.1 and 0.3) were determined as a function of temperature and oxygen partial pressure, independent of the interface morphology. Th… more
Date: May 1, 1993
Creator: Youngblood, G. E.; Pederson, L. R.; Bates, J. L. & Rupaal, A. S.
Partner: UNT Libraries Government Documents Department
open access

NANOSTRUCTURED METAL OXIDES FOR ANODES OF LI-ION RECHARGEABLE BATTERIES

Description: The aligned nanorods of Co{sub 3}O{sub 4} and nanoporous hollow spheres (NHS) of SnO{sub 2} and Mn{sub 2}O{sub 3} were investigated as the anodes for Li-ion rechargeable batteries. The Co{sub 3}O{sub 4} nanorods demonstrated 1433 mAh/g reversible capacity. The NHS of SnO{sub 2} and Mn{sub 2}O{sub 3} delivered 400 mAh/g and 250 mAh/g capacities respectively in multiple galvonastatic discharge-charge cycles. It was found that high capacity of NHS of metal oxides is sustainable attributed to their… more
Date: December 4, 2009
Creator: Au, M.
Partner: UNT Libraries Government Documents Department
open access

Long-wavelength magnetic excitations in multiferroic BiFeO3

Description: Colossal magnetoresistance manganites have been subjected to extensive research due to their unique magnetic and electrical properties. The physical origin of this phenomenon has been attributed to the double-exchange model. However, this double-exchange mechanism of carriers between Mn{sup 2+} and Mn{sup 3+} ions alone cannot account for all the observed changes such as metal-insulator transition in these materials. Other factors include the highly correlated nature of the spin, lattice, charg… more
Date: January 1, 2008
Creator: Talbayev, Diyar & Taylor, Antoinette J
Partner: UNT Libraries Government Documents Department
open access

Development of ceramic mixed potential sensors for automotive application

Description: Mixed potential sensors that utilize Gd{sub 0.2}Ce{sub 0.8}O{sub 2} electrolytes and patterned dense 1 {micro}m-thick LaMnO{sub 3} thin films were studied at 600 C and 1%O{sub 2}. The response to C{sub 3}H{sub 6} and CO of two different sensor configurations were studied continuously for 1000 hrs versus an air reference. Although two different current collection schemes and two different metal oxide electrode geometries were employed, the magnitude of the mixed potential generated by both senso… more
Date: January 1, 2001
Creator: Brasha, E. (Eric); Mukundan, R. (Rangachary); Brown, D. R. (David R.); Garzon, F. H. (Fernando H.) & Visser, J. (Jaco)
Partner: UNT Libraries Government Documents Department
open access

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 oxidatio… more
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
open access

Discovery of Unusual Minerals in Paleolithic Black Pigments from Lascaux (France) and Ekain (Spain)

Description: Analyses of archaeological materials aim to rediscover the know-how of Prehistoric people by determining the nature of the painting matter, its preparation mode, and the geographic origin of its raw materials. This study deals with identification of manganese oxides in black pigments by micro-XANES (X-ray absorption near-edge structure) based on previous TEM (transmission electron microscopy) studies. Complex mixtures of the manganese oxides studied are present in some of mankind's oldest known… more
Date: December 13, 2006
Creator: Chalmin, E.; Farges, F.; Vignaud, C.; Susini, J.; Menu, M. & Brown, G. E., Jr.
Partner: UNT Libraries Government Documents Department
open access

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 neptun… more
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
open access

Plutonium Oxidation and Subsequent Reduction by Mn (IV) Minerals

Description: Plutonium sorbed to rock tuff was preferentially associated with manganese oxides. On tuff and synthetic pyrolusite (Mn{sup IV}O{sub 2}), Pu(IV) or Pu(V) was initially oxidized, but over time Pu(IV) became the predominant oxidation state of sorbed Pu. Reduction of Pu(V/VI), even on non-oxidizing surfaces, is proposed to result from a lower Gibbs free energy of the hydrolyzed Pu(IV) surface species versus that of the Pu(V) or Pu(VI) surface species. This work suggests that despite initial oxidat… more
Date: September 13, 2005
Creator: KAPLAN, DANIEL
Partner: UNT Libraries Government Documents Department
open access

Strain induced electronic structure changes in magnetic transition metal oxides thin films

Description: We show that the angular dependence of x-ray magnetic circular dichroism (XMCD) is strongly sensitive to strain-induced electronic structure changes in magnetic transition metal oxides. We observe a pronounced dependence of the XMCD spectral shape on the experimental geometry as well as nonvanishing XMCD with distinct spectral features in transverse geometry in compressively strained MnCr{sub 2}O{sub 4} films. The angular dependent XMCD can be described as a sum over an isotropic and anisotropi… more
Date: July 8, 2010
Creator: van der Laan, G.; Chopdekar, R.V.; Suzuki, Y. & Arenholz, E.
Partner: UNT Libraries Government Documents Department
Back to Top of Screen