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1

Oxidative basis of manganese neurotoxicity.  

PubMed

Exposure to excessive levels of manganese, an essential trace element, can evoke severe psychiatric and extrapyramidal motor dysfunction closely resembling Parkinson's disease. The clinical manifestations of manganese toxicity arise from focal injury to the basal ganglia. This region, characterized by intense consumption of oxygen and significant dopamine content, can incur mitochondrial dysfunction, depletion of levels of peroxidase and catalase, and catecholamine biochemical imbalances following manganese exposure. The site specificity of the pathology and the nature of the cellular damage caused by manganese have been attributed to its capacity to produce cytotoxic levels of free radicals. However, support for such a pro-oxidant role for manganese has been largely limited to inferences drawn from histopathological observations. More recently, research efforts into the molecular details of manganese toxicity have provided evidence of an etiological relationship between oxidative stress and manganese-related neurodegeneration. This review focuses on studies that evaluate the redox chemistry of manganese during the neurodegenerative process and its molecular consequences. PMID:15105260

HaMai, Diem; Bondy, Stephen C

2004-03-01

2

Manganese oxide cathodes for rechargeable batteries  

Microsoft Academic Search

Manganese oxides are considered as promising cathodes for rechargeable batteries due to their low cost and low toxicity as well as the abundant natural resources. In this dissertation, manganese oxides have been investigated as cathodes for both rechargeable lithium and alkaline batteries. Nanostructured lithium manganese oxides designed for rechargeable lithium cells have been synthesized by reducing lithium permanganate with methanol

Dongmin Im

2002-01-01

3

The reduction and oxidation behaviour of manganese oxides  

Microsoft Academic Search

The reduction of manganese oxides with methane was studied to investigate the suitability of manganese as an oxygen storage compound. Manganese oxides are reduced by CH4 to a lower-valent manganese oxide, producing CO2 and water. Once the manganese oxide is reduced, it can be regenerated, i.e. reoxidised. By integrating this exothermic oxidation cycle with endothermic methane reforming, a new setup

E. R. Stobbe; B. A. de Boer; J. W. Geus

1999-01-01

4

Microalgal-facilitated bacterial oxidation of manganese  

Microsoft Academic Search

In the presence of unicellular microalgae, bacterial manganese oxidation was increased by up to ten times the rate produced by bacterial oxidation alone. Azide-poisoned controls demonstrated that the manganese-oxidizing bacteria were active in the algal-bacterial oxidation of manganese. Scanning electron microscopy showed that oxide formation occurred in a number of structurally different deposits on the surface of the alga. Studies

R M Stuetz; A C Greene; J C Madgwick

1996-01-01

5

A comparative evaluation of cobalt chromium oxide, cobalt manganese oxide, cobalt manganese oxide, and copper manganese oxide as catalysts for the water-gas shift reaction  

Microsoft Academic Search

Cobalt chromium oxide, cobalt manganese oxide, and copper manganese oxide have been compared as catalysts for the water-gas shift reaction. Cobalt chromium oxide and cobalt manganese oxide catalysts can give both high activity and long lifetimes for this reaction. Cobalt chromium oxide catalysts display higher activity compared to the other catalyst systems and this is shown that both the cobalt

G. J. Hutchings; R. G. Copperthwaite; F. M. Gottschalk; R. Hunter; J. Mellor; S. W. Orchard; T. Sangiorgio

1992-01-01

6

40 CFR 721.10011 - Barium calcium manganese strontium oxide.  

Code of Federal Regulations, 2013 CFR

...2013-07-01 2013-07-01 false Barium calcium manganese strontium oxide. 721.10011...Chemical Substances § 721.10011 Barium calcium manganese strontium oxide. (a...chemical substance identified as barium calcium manganese strontium oxide (PMN...

2013-07-01

7

40 CFR 721.10201 - Cobalt lithium manganese nickel oxide.  

Code of Federal Regulations, 2013 CFR

...2013-07-01 2013-07-01 false Cobalt lithium manganese nickel oxide. 721...Chemical Substances § 721.10201 Cobalt lithium manganese nickel oxide. ...The chemical substance identified as cobalt lithium manganese nickel...

2013-07-01

8

40 CFR 721.10011 - Barium calcium manganese strontium oxide.  

Code of Federal Regulations, 2010 CFR

...2010-07-01 2010-07-01 false Barium calcium manganese strontium oxide. ...Chemical Substances § 721.10011 Barium calcium manganese strontium oxide. ...The chemical substance identified as barium calcium manganese strontium...

2010-07-01

9

40 CFR 721.10011 - Barium calcium manganese strontium oxide.  

Code of Federal Regulations, 2010 CFR

...2009-07-01 2009-07-01 false Barium calcium manganese strontium oxide. ...Chemical Substances § 721.10011 Barium calcium manganese strontium oxide. ...The chemical substance identified as barium calcium manganese strontium...

2009-07-01

10

Manganese potentiates nitric oxide production by microglia.  

PubMed

Manganese toxicity has been associated with clinical symptoms of neurotoxicity which are similar to the symptoms observed in Parkinson's disease. Earlier reports indicated that reactive microglia was present in the substantia nigra of patients with Parkinson's disease. Using N9 microglial cells, the current study was designed to determine whether high levels of manganese were associated with microglial activation. Results indicated that manganese significantly increased the bacterial lipopolysaccharide-induced nitric oxide production. This potent activity of manganese was not shared by other transition metals tested, including iron, cobalt, nickel, copper and zinc. Immunohistochemical staining and Western blot analysis indicated that manganese increased the cellular production of inducible nitric oxide synthase. Northern blot analysis indicated that manganese likely increased iNOS gene transcription since this agent increased the mRNA level of the inducible nitric oxide synthase. In contrast to other transition metals tested, manganese did not appear to be cytotoxic to microglial cells. These results suggested that manganese could induce sustained production of neurotoxic nitric oxide by activated microglial cells, which might cause detrimental consequences to surrounding neurons. PMID:10320780

Chang, J Y; Liu, L Z

1999-05-01

11

The Structural Stability of Manganese Oxide Electrodes for Lithium Batteries  

Microsoft Academic Search

Manganese oxides are of interest as insertion electrodes for rechargeable 3 V and 4 V lithium batteries. During discharge, lithium ions are inserted into the manganese oxide host structure with a concomitant reduction of the manganese ions; the reverse process occurs on charge. The cycle life of these batteries is critically dependent on the ability of the manganese oxide structure

Michael M. Thackeray

1997-01-01

12

Rechargeable manganese oxide batteries. (Genopladelige manganoxid batterier).  

National Technical Information Service (NTIS)

Former work on lithium and sodium batteries proved the feasibility of making solid state cells with high energy density and reversibility. The utility of manganese oxides as cathode material in rechargeable alkali metal solid state intercalation batteries...

B. Zachau-Christensen K. West S. Skaarup

1992-01-01

13

Battles with Iron: Manganese in Oxidative Stress Protection*  

PubMed Central

The redox-active metal manganese plays a key role in cellular adaptation to oxidative stress. As a cofactor for manganese superoxide dismutase or through formation of non-proteinaceous manganese antioxidants, this metal can combat oxidative damage without deleterious side effects of Fenton chemistry. In either case, the antioxidant properties of manganese are vulnerable to iron. Cellular pools of iron can outcompete manganese for binding to manganese superoxide dismutase, and through Fenton chemistry, iron may counteract the benefits of non-proteinaceous manganese antioxidants. In this minireview, we highlight ways in which cells maximize the efficacy of manganese as an antioxidant in the midst of pro-oxidant iron.

Aguirre, J. Dafhne; Culotta, Valeria C.

2012-01-01

14

Manganese.  

PubMed

Manganese is a very hard, brittle metal, which is used to increase the strength of steel alloys. Absorption from the gastrointestinal tract occurs in the divalent and tetravalent forms. Permanganates, which are strong oxidizing agents, have a +7 valence. The principal organomanganese compound is the anti-knock additive, methylcyclopentadienyl manganese tricarbonyl. Manganese is a ubiquitous constituent of the environment comprising about 0.1% of the earth's crust. For the general population, food is the most important source of manganese with daily intake ranging from 2-9 mg Mn. Combustion of gasoline containing methylcyclopentadienyl manganese tricarbonyl releases submicron particles of Mn3O4 that are potentially respirable. Biomagnification of manganese in the food chain probably does not occur. The lungs and gastrointestinal tract absorb some manganese, but the relative amounts absorbed from each site are not known. Homeostatic mechanisms limit the absorption of manganese from the gastrointestinal tract. Elimination of manganese occurs primarily by excretion into the bile. Animal studies indicate that manganese is an essential co-factor for enzymes, such as hexokinase, superoxide dismutase, and xanthine oxidase. However, no case of manganese deficiency in humans has been identified. Manganism is a central nervous system disease first described in the 1800s following exposure to high concentrations of manganese oxides. Manganese madness was the term used to describe the initial psychiatric syndrome (compulsive behavior, emotional lability, hallucinations). More commonly, these workers developed a Parkinson's-like syndrome. Currently, the risks of exposure to low concentrations of manganese in the industrial and in the environmental settings (e.g., methylcyclopentadienyl manganese tricarbonyl in gasoline) are being evaluated with regards to the development of subclinical neuropsychological changes. The American Conference of Governmental and Industrial Hygienists recently lowered the TLV-TWA for manganese compounds and inorganic manganese compounds to 0.2 mg Mn/m3. PMID:10382563

Barceloux, D G

1999-01-01

15

Anodically deposited manganese oxide and manganesetungsten oxide electrodes for oxygen evolution from seawater  

Microsoft Academic Search

The oxygen evolution efficiency in seawater electrolysis has been examined for manganese oxide and manganesetungsten oxide electrodes anodically deposited on iridium oxide-coated titanium substrates as a function of pH of the deposition electrolytes and tungsten content in the oxides. The oxygen evolution efficiency in 0.5M NaCl solution at 30C on the MnO2 electrodes increases with a decrease in pH of

K. Izumiya; E. Akiyama; H. Habazaki; N. Kumagai; A. Kawashima; K. Hashimoto

1998-01-01

16

Lithium manganese oxides for rechargeable lithium batteries  

Microsoft Academic Search

Lithium manganese spinel compounds HT-LiMn2O4 (HT means high temperature) synthesized at > 700 C have high capacity in the 4 V range (LixMn2O4, x ? 1), However, lithium manganese oxides LT-LiMn2O4 (LT means low temperature) synthesized at temperatures lower than 400 C, resemble to the spinel structure and tend to have a reduced capacity in the 4 V range. We

Yoshiaki Nitta; Kazuhiro Okamura; Masatoshi Nagayama; Akira Ohta

1997-01-01

17

Electrochemical lithium intercalation in disordered manganese oxides  

Microsoft Academic Search

Four highly disordered manganese oxides were prepared by reduction of sodium permanganate by chloride, iodide, hydrogen peroxide or oxalate in aqueous medium containing a large excess of Li+ ions, yielding hydrated oxides with Mn valence in the range 3.803.92. Thermogravimetric studies showed that the iodide-reduced oxide can be dehydrated to 92% at 240C, while the other three ones retain water

A Ibarra Palos; M Anne; P Strobel

2001-01-01

18

Structural stability of lithium manganese oxides  

Microsoft Academic Search

We have studied stability of lithium-manganese oxides using density functional theory in the local density and generalized gradient approximation (GGA). In particular, the effect of spin-polarization and magnetic ordering on the relative stability of various structures is investigated. At all lithium compositions the effect of spin polarization is large, although it does not affect different structures to the same extent.

S. K. Mishra; G. Ceder

1999-01-01

19

Oxidative coupling of methane over natural manganese oxide  

Microsoft Academic Search

Oxydehydrogenative coupling of methane to higher hydrocarbons has been achieved with high selectivity towards C2 products over natural mineral manganese oxides. Oxide treatments under hydrocarbon atmosphere show that the reduction of manganese ions Mn(IV), Mn(III) to Mn(II) is mainly responsible for the catalyst deactivation. The tests using CH4 + CD4 equimolecular mixtures and the analysis of the (HD)C2 products by

L. M. Ioffe; T. Lopez; Y. G. Borodko; R. Gomez

1995-01-01

20

Manganese oxide reduction as a form of anaerobic respiration  

Microsoft Academic Search

Some instances of bacterial manganese oxide reduction observed in nature and under laboratory conditions are a form of respiration. Anaerobiosis is not a necessary condition for its occurrence, although anaerobic reduction of manganese oxide which is inhibited by air has been reported. It is the kind of manganese reducing microorganism involved which determines whether anaerobic conditions are required. In at

Henry L. Ehrlich

1987-01-01

21

Manganese oxide cathodes for rechargeable batteries  

NASA Astrophysics Data System (ADS)

Manganese oxides are considered as promising cathodes for rechargeable batteries due to their low cost and low toxicity as well as the abundant natural resources. In this dissertation, manganese oxides have been investigated as cathodes for both rechargeable lithium and alkaline batteries. Nanostructured lithium manganese oxides designed for rechargeable lithium cells have been synthesized by reducing lithium permanganate with methanol or hydrogen in various solvents followed by firing at moderate temperatures. The samples have been characterized by wet-chemical analyses, thermal methods, spectroscopic methods, and electron microscopy. It has been found that chemical residues in the oxides such as carboxylates and hydroxyl groups, which could be controlled by varying the reaction medium, reducing agents, and additives, make a significant influence on the electrochemical properties. The Li/Mn ratio in the material has also been found to be a critical factor in determining the rechargeability of the cathodes. The optimized samples exhibit a high capacity of close to 300 mAh/g with good cyclability and charge efficiency. The high capacity with a lower discharge voltage may make these nanostructured oxides particularly attractive for lithium polymer batteries. The research on the manganese oxide cathodes for alkaline batteries is focused on an analysis of the reaction products generated during the charge/discharge processes or by some designed chemical reactions mimicking the electrochemical processes. The factors influencing the formation of Mn3O4 in the two-electron redox process of delta-MnO2 have been studied with linear sweep voltammetry combined with X-ray diffraction. The presence of bismuth, the discharge rate, and the microstructure of the electrodes are found to affect the formation of Mn3O4, which is known to be electrochemically inactive. A faster voltage sweep and a more intimate mixing of the manganese oxide and carbon in the cathode are found to suppress the formation of Mn3O4. Bismuth has also been found to be beneficial in the one-electron process of gamma-MnO 2 when incorporated into the cathode. The results of a series of chemical reactions reveal that bismuth is blocking some reaction paths leading to the unwanted birnessite or Mn3O4. Barium is also found to play a similar role, but it is less effective than bismuth for the same amount of additive. Optimization of the additives has the potential to make the rechargeable alkaline cells based on manganese oxides to successfully compete with other rechargeable systems due to their low cost, environmental friendliness, and excellent safety features.

Im, Dongmin

22

Sol-gel synthesis of manganese oxides  

NASA Astrophysics Data System (ADS)

Transparent and stable manganese dioxide gels are obtained upon reduction of permanganate aqueous solutions AMnO4 [A = Li, Na, K, NH4, N(CH3)4] by fumaric acid. All xerogels are amorphous when dried at room temperature. Their thermal behavior however depends on the nature of the counter cation A+. Ammonium permanganates lead to the formation of ?- or ?-Mn2O3 while AMnO2 mixed oxides are obtained at high temperature when A = Li, Na, K. Other crystalline phases such as LiMn2O4 or Na0.7MnO2 are also formed at lower temperature around 500C. Oxidation of these mixed oxides into sulfuric acid lead to the formation of ?- or ?-MnO2 while A+ and Mn2+ ions are released into the solution. Such manganese dioxides could be good candidates for making reversible cathodes in nonaqueous lithium batteries.

Bach, S.; Henry, M.; Baffier, N.; Livage, J.

1990-10-01

23

Electrochemical lithium intercalation in nanosized manganese oxides  

NASA Astrophysics Data System (ADS)

X-ray amorphous manganese oxides were prepared by reduction of sodium permanganate by lithium iodide in aqueous medium (MnOx-I) and by decomposition of manganese carbonate at moderate temperature (MnOx-C). TEM showed that these materials are not amorphous, but nanostructured, with a prominent spinel substructure in MnOx-C. These materials intercalate lithium with capacities up to 200 mAh/g at first cycle (potential window 1.8 4.3 V) and 175 mAh/g at 100th cycle. Best performances for MnOx-C are obtained with cobalt doping. Potential electrochemical spectroscopy shows that the initial discharge induces a 2-phase transformation in MnOx-C phases, but not in MnOx-I ones. EXAFS and XANES confirm the participation of manganese in the redox process, with variations in local structure much smaller than in known long-range crystallized manganese oxides. X-ray absorption spectroscopy also shows that cobalt in MnOx-C is divalent and does not participate in the electrochemical reaction.

Strobel, P.; Darie, C.; Thiry, F.; Ibarra-Palos, A.; Bacia, M.; Proux, O.; Soupart, J. B.

2006-05-01

24

A microbial fuel cell using manganese oxide oxygen reduction catalysts  

Microsoft Academic Search

Microbial fuel cells (MFCs) are a potential method for enhanced water and waste treatment, which offer the additional benefit\\u000a of energy generation. Manganese oxide was prepared by a simple chemical oxidation using potassium permanganate. Carbon-supported\\u000a manganese oxide nanoparticles were successfully characterised as cathode materials for MFCs. The manganese oxide particles\\u000a when used in a two-chamber MFC, using inoculum from an

I. Roche; K. Katuri; K. Scott

2010-01-01

25

Lithium-manganese oxide rechargeable battery  

Microsoft Academic Search

A new type of rechargeable battery in which lithium ions shuttle between a lithium-manganese oxide electrode and a carbon electrode was unveiled recently by chemists from Bell Communications Research (Bellcore), Red Bank, N.J. The new battery--still experimental--is safer, longer lasting, and potentially cheaper to manufacture than other lithium-ion batteries. In addition, it provides three times the energy of nickel-cadmium cells,

Dagani

1993-01-01

26

Lithium Manganese Oxide Prepared by Flux Methods  

Microsoft Academic Search

Plate-like crystals of spinel-type lithium manganese oxide with sizes in the micrometer range were obtained in a flux system\\u000a of LiCl-Mn(NO3)2. The crystals were grown by a dissolution-recrystallization mechanism. Polyhedral crystals with sizes in the millimeter range\\u000a were grown in a flux system of LiCl-Mn(NO3)2 by an evaporation-recrystallization mechanism.

W. Tang; Q. Feng; X. Yang; R. Chitrakar; K. Ooi

27

EXAFS studies of lithium manganese oxides  

Microsoft Academic Search

Lithium manganese oxides are the subject of intense interest due to their potential application as the positive electrode in rechargeable lithium batteries. Strategies to improve the performance include variation of the chemical structure, via doping with other cations, and changing the crystal structure. In this paper the local structure in spinel LiMn2O4, both pure and doped with Co, Ni, Ga

A. V. Chadwick; S. L. P. Savin; R. J. Packer; A. N. Blacklocks; R. A. Davis; M. S. Islam

2005-01-01

28

EXAFS studies of lithium manganese oxides  

NASA Astrophysics Data System (ADS)

Lithium manganese oxides are the subject of intense interest due to their potential application as the positive electrode in rechargeable lithium batteries. Strategies to improve the performance include variation of the chemical structure, via doping with other cations, and changing the crystal structure. In this paper the local structure in spinel LiMn2O4, both pure and doped with Co, Ni, Ga and In, and layered LiMnO2 have been investigated by EXAFS spectroscopy.

Chadwick, A. V.; Savin, S. L. P.; Packer, R. J.; Blacklocks, A. N.; Davis, R. A.; Islam, M. S.

2005-01-01

29

A comparative evaluation of cobalt chromium oxide, cobalt manganese oxide, cobalt manganese oxide, and copper manganese oxide as catalysts for the water-gas shift reaction  

SciTech Connect

Cobalt chromium oxide, cobalt manganese oxide, and copper manganese oxide have been compared as catalysts for the water-gas shift reaction. Cobalt chromium oxide and cobalt manganese oxide catalysts can give both high activity and long lifetimes for this reaction. Cobalt chromium oxide catalysts display higher activity compared to the other catalyst systems and this is shown that both the cobalt chromium oxide and the cobalt manganese oxide catalysts are not sensitive to the presence of up to 240 ppm feedstock sulphur impurities (H{sub 2}S and COS) and high catalyst activity can be maintained either in the presence or in the absence of feedstock sulphur. The copper manganese oxide catalysts are demonstrated to be particularly sensitive to feedstock sulphur, being significantly poisoned at levels as low as 1 ppm H{sub 2}S. An investigation of the mechanism of the water-gas shift mechanism over the three catalyst systems is also described using both kinetic and model reagent studies. Based on these studies, a mechanism is proposed for the cobalt- and copper-containing catalyst systems involving the formation of a surface formate intermediate.

Hutchings, G.J. (Univ. of Liverpool (United Kingdom)); Copperthwaite, R.G.; Gottschalk, F.M.; Hunter, R.; Mellor, J.; Orchard, S.W.; Sangiorgio, T. (Univ. of the Witwatersrand, Johannesburg (South Africa))

1992-10-01

30

Preparation of the electrochemically formed spinel-lithium manganese oxides  

Microsoft Academic Search

Electrochemically formed spinel-lithium manganese oxides were synthesized from manganese hydroxides prepared by a cathodic electrochemical precipitation from various concentrations of manganese nitrate solutions. Two types of manganese hydroxides were formed from diluted and concentrated Mn(NO3)2 aqueous solutions. Uniform and equi-sized disk shaped Mn(OH)2 crystals of 0.25?m in diameter were obtained on a Pt substrate after the electrochemical precipitation from lower

Katsumi Katakura; Kohei Wada; Yoshiyuki Kajiki; Akiko Yamamoto; Zempachi Ogumi

2009-01-01

31

Orbital anisotropy in paramagnetic manganese oxide nanostripes  

NASA Astrophysics Data System (ADS)

We have detected a clear magnetic anisotropy in the temperature and field dependent Mn L2,3 magnetic circular dichroism (MCD) spectra of 28 wide paramagnetic manganese oxide nanostripes, which we relate to the presence of a largely unquenched orbital moment revealed by MCD sum rule analysis. Polarization, angle, and temperature dependent linear dichroism spectra indicate that the observed anisotropy is related to a depletion of 3d states with ml=2 orbital quantum number in the ground state of the paramagnetic system. Strongly anisotropic electrostatic coupling provides an internal source of spatial symmetry breaking which might generally yield paramagnetic anisotropy phenomena in 3d oxide nanostructures.

Altieri, S.; Allegretti, F.; Steurer, W.; Surnev, S.; Finazzi, M.; Sessi, V.; Brookes, N. B.; Valeri, S.; Netzer, F. P.

2013-06-01

32

40 CFR 721.4587 - Lithium manganese oxide (LiMn204) (generic name).  

Code of Federal Regulations, 2010 CFR

... 2010-07-01 false Lithium manganese oxide (LiMn204) (generic name...Substances § 721.4587 Lithium manganese oxide (LiMn204) (generic name...identified generically as lithium manganese oxide (LiMn204)...

2010-07-01

33

40 CFR 721.4587 - Lithium manganese oxide (LiMn204) (generic name).  

Code of Federal Regulations, 2010 CFR

... 2009-07-01 false Lithium manganese oxide (LiMn204) (generic name...Substances § 721.4587 Lithium manganese oxide (LiMn204) (generic name...identified generically as lithium manganese oxide (LiMn204)...

2009-07-01

34

Thermochemistry of iron manganese oxide spinels  

SciTech Connect

Oxide melt solution calorimetry has been performed on iron manganese oxide spinels prepared at high temperature. The enthalpy of formation of (Mn{sub x}Fe{sub 1-x}){sub 3}O{sub 4} at 298K from the oxides, tetragonal Mn{sub 3}O{sub 4} (hausmannite) and cubic Fe{sub 3}O{sub 4} (magnetite), is negative from x=0 to x=0.67 and becomes slightly positive for 0.670.6) spinels of intermediate compositions. The enthalpies of formation are discussed in terms of three factors: oxidation-reduction relative to the end-members, cation distribution, and tetragonality. A combination of measured enthalpies and Gibbs free energies of formation in the literature provides entropies of mixing. {delta}S{sub mix}, consistent with a cation distribution in which all trivalent manganese is octahedral and all other ions are randomly distributed for x>0.5, but the entropy of mixing appears to be smaller than these predicted values for x<0.4.

Guillemet-Fritsch, Sophie [Centre InterUniversitaire de Recherche et d'Ingenierie des Materiaux (CIRIMAT/LCMIE), Universite Paul Sabatier, Ba-hat timent 2R1, 118, route de Narbonne, 31062 Toulouse, Cedex 04 (France); Navrotsky, Alexandra [Thermochemistry Facility and NEAT ORU, University of California at Davis, One Shields Avenue, Davis, CA 95616-877 (United States)]. E-mail: anavrotsky@ucdavis.edu; Tailhades, Philippe [Centre InterUniversitaire de Recherche et d'Ingenierie des Materiaux (CIRIMAT/LCMIE), Universite Paul Sabatier, Ba-hat timent 2R1, 118, route de Narbonne, 31062 Toulouse, Cedex 04 (France); Coradin, Herve [Centre InterUniversitaire de Recherche et d'Ingenierie des Materiaux (CIRIMAT/LCMIE), Universite Paul Sabatier, Ba-hat timent 2R1, 118, route de Narbonne, 31062 Toulouse, Cedex 04 (France); Wang Miaojun [Thermochemistry Facility and NEAT ORU, University of California at Davis, One Shields Avenue, Davis, CA 95616-877 (United States)

2005-01-15

35

Lithium-manganese oxide rechargeable battery  

SciTech Connect

A new type of rechargeable battery in which lithium ions shuttle between a lithium-manganese oxide electrode and a carbon electrode was unveiled recently by chemists from Bell Communications Research (Bellcore), Red Bank, N.J. The new battery--still experimental--is safer, longer lasting, and potentially cheaper to manufacture than other lithium-ion batteries. In addition, it provides three times the energy of nickel-cadmium cells, the most popular type of rechargeable battery. Bellcore scientists believe the new battery could replace nickel-cadmium and small lead-acid batteries in many applications.

Dagani, R.

1993-01-04

36

Structural stability in partially substituted lithium manganese spinel oxide cathode  

Microsoft Academic Search

LiMn2O4 is one of the most promising cathode materials for lithium secondary battery because of natural abundance of manganese in\\u000a the crust and its low toxicity to environment. Lithium ion can almost reversibly intercalate into or deintercalate from lithium\\u000a manganese spinel oxide LiMn2O4. A part of substitution of manganese with other transition metals brings the improvement of cycle life. We

Masataka Wakihara; Hiromasa Ikuta; Yoshiharu Uchimoto

2002-01-01

37

Oxidative removal of aqueous steroid estrogens by manganese oxides  

Microsoft Academic Search

This study investigated the oxidative removal of steroid estrogens from water by synthetic manganese oxide (MnO2) and the factors influencing the reactions. Using 110?5M MnO2 at pH 4, estrone (E1), 17?-estradiol (E2), estriol (E3) and 17?-ethinylestradiol (EE2), all at 410?6M, were rapidly removed within 220min, indicating the effectiveness of MnO2 as an oxidizing agent towards estrogens. E2 removal increased with

Lei Xu; Chao Xu; Meirong Zhao; Yuping Qiu; G. Daniel Sheng

2008-01-01

38

MANGANESE OXIDE REDUCTION IN LABORATORY MICROCOSMS  

Microsoft Academic Search

Manganese biogeochemistry holds special interest for the characterization of passive treatment systems designed to treat acidic mine waters while meeting enforceable effluent discharge limits set for manganese. In the present study, an initial anoxic enrichment culture was developed for use as an inoculum in experimental systems. Standard anoxic microcosms capable of reducing manganese from ~n~' to ~n'' were established from

Richard A. Royer; Richard F. Unz

2006-01-01

39

Structural stability of lithium manganese oxides  

NASA Astrophysics Data System (ADS)

We have studied stability of lithium-manganese oxides using density functional theory in the local density and generalized gradient approximation (GGA). In particular, the effect of spin-polarization and magnetic ordering on the relative stability of various structures is investigated. At all lithium compositions the effect of spin polarization is large, although it does not affect different structures to the same extent. At composition LiMnO2, globally stable Jahn-Teller distortions could only be obtained in the spin-polarized GGA approximation, and antiferromagnetic spin ordering was critical to reproduce the orthorhombic LiMnO2 structure as ground state. We also investigate the effect of magnetism on the Li intercalation potential, an important property for rechargeable Li batteries.

Mishra, S. K.; Ceder, G.

1999-03-01

40

Comparison of manganese oxide nanoparticles and manganese sulfate with regard to oxidative stress, uptake and apoptosis in alveolar epithelial cells  

Microsoft Academic Search

Due to their physicochemical characteristics, metal oxide nanoparticles (NPs) interact differently with cells compared to larger particles or soluble metals. Oxidative stress and cellular metal uptake were quantified in rat type II alveolar epithelial cells in culture exposed to three different NPs: manganese(II,III) oxide nanoparticles (Mn3O4-NPs), the soluble manganese sulfate (Mn-salt) at corresponding equivalent doses, titanium dioxide (TiO2-NPs) and cerium

Ramon Frick; Bjrn Mller-Edenborn; Andreas Schlicker; Barbara Rothen-Rutishauser; David O. Raemy; Detlef Gnther; Bodo Hattendorf; Wendelin Stark; Beatrice Beck-Schimmer

2011-01-01

41

Three manganese oxide-rich marine sediments harbor similar communities of acetate-oxidizing manganese-reducing bacteria  

PubMed Central

Dissimilatory manganese reduction dominates anaerobic carbon oxidation in marine sediments with high manganese oxide concentrations, but the microorganisms responsible for this process are largely unknown. In this study, the acetate-utilizing manganese-reducing microbiota in geographically well-separated, manganese oxide-rich sediments from Gullmar Fjord (Sweden), Skagerrak (Norway) and Ulleung Basin (Korea) were analyzed by 16S rRNA-stable isotope probing (SIP). Manganese reduction was the prevailing terminal electron-accepting process in anoxic incubations of surface sediments, and even the addition of acetate stimulated neither iron nor sulfate reduction. The three geographically distinct sediments harbored surprisingly similar communities of acetate-utilizing manganese-reducing bacteria: 16S rRNA of members of the genera Colwellia and Arcobacter and of novel genera within the Oceanospirillaceae and Alteromonadales were detected in heavy RNA-SIP fractions from these three sediments. Most probable number (MPN) analysis yielded up to 106 acetate-utilizing manganese-reducing cells cm?3 in Gullmar Fjord sediment. A 16S rRNA gene clone library that was established from the highest MPN dilutions was dominated by sequences of Colwellia and Arcobacter species and members of the Oceanospirillaceae, supporting the obtained RNA-SIP results. In conclusion, these findings strongly suggest that (i) acetate-dependent manganese reduction in manganese oxide-rich sediments is catalyzed by members of taxa (Arcobacter, Colwellia and Oceanospirillaceae) previously not known to possess this physiological function, (ii) similar acetate-utilizing manganese reducers thrive in geographically distinct regions and (iii) the identified manganese reducers differ greatly from the extensively explored iron reducers in marine sediments.

Vandieken, Verona; Pester, Michael; Finke, Niko; Hyun, Jung-Ho; Friedrich, Michael W; Loy, Alexander; Thamdrup, Bo

2012-01-01

42

Three manganese oxide-rich marine sediments harbor similar communities of acetate-oxidizing manganese-reducing bacteria.  

PubMed

Dissimilatory manganese reduction dominates anaerobic carbon oxidation in marine sediments with high manganese oxide concentrations, but the microorganisms responsible for this process are largely unknown. In this study, the acetate-utilizing manganese-reducing microbiota in geographically well-separated, manganese oxide-rich sediments from Gullmar Fjord (Sweden), Skagerrak (Norway) and Ulleung Basin (Korea) were analyzed by 16S rRNA-stable isotope probing (SIP). Manganese reduction was the prevailing terminal electron-accepting process in anoxic incubations of surface sediments, and even the addition of acetate stimulated neither iron nor sulfate reduction. The three geographically distinct sediments harbored surprisingly similar communities of acetate-utilizing manganese-reducing bacteria: 16S rRNA of members of the genera Colwellia and Arcobacter and of novel genera within the Oceanospirillaceae and Alteromonadales were detected in heavy RNA-SIP fractions from these three sediments. Most probable number (MPN) analysis yielded up to 10(6) acetate-utilizing manganese-reducing cells cm(-3) in Gullmar Fjord sediment. A 16S rRNA gene clone library that was established from the highest MPN dilutions was dominated by sequences of Colwellia and Arcobacter species and members of the Oceanospirillaceae, supporting the obtained RNA-SIP results. In conclusion, these findings strongly suggest that (i) acetate-dependent manganese reduction in manganese oxide-rich sediments is catalyzed by members of taxa (Arcobacter, Colwellia and Oceanospirillaceae) previously not known to possess this physiological function, (ii) similar acetate-utilizing manganese reducers thrive in geographically distinct regions and (iii) the identified manganese reducers differ greatly from the extensively explored iron reducers in marine sediments. PMID:22572639

Vandieken, Verona; Pester, Michael; Finke, Niko; Hyun, Jung-Ho; Friedrich, Michael W; Loy, Alexander; Thamdrup, Bo

2012-05-10

43

Solution-based synthesis of manganese oxide cathodes for lithium batteries  

Microsoft Academic Search

With an objective to overcome the cyclability problems of manganese oxides, solution-based procedures are pursued to synthesize metastable manganese oxides. Reduction of permanganate with lithium iodide in an acetonitrile medium followed by heating at 250 C in vacuum gives an amorphous lithium sodium manganese oxyiodide that is intimately mixed with crystalline NaIO. On the other hand, oxidation of manganese acetate

A. Manthiram; J. Kim; S. Choi

2000-01-01

44

The thermal stability of lithium-manganese-oxide spinel phases  

Microsoft Academic Search

The thermal stability of stoichiometric spinel phases in the system Li1+?Mn2-?O4 (0 ? ? ? 0.33) has been investigated by high-temperature powder X-ray diffraction, differential thermal analysis, and thermogravimetric analysis. At elevated temperatures, the lithium-manganese-oxide spinels undergo phase changes by loss of oxygen and lithia (Li2O). The data highlight the importance of temperature control when synthesising lithium-manganese-oxide spinel compounds.

M. M. Thackeray; M. F. Mansuetto; D. W. Dees; D. R. Vissers

1996-01-01

45

A study of layered lithium manganese oxide cathode materials  

Microsoft Academic Search

Substituted layered sodium manganese oxide bronzes with the P2 structure were prepared by glycine-nitrate combustion synthesis. The Na in the as-prepared materials could be completely ion-exchanged for Li under mild conditions. All lithium manganese oxide compounds obtained after ion-exchange have O2 stacking of the layers. Cyclic voltammetry and stepped potential experiments on lithium cells containing these materials show that the

Tom A Eriksson; Marca M Doeff

2003-01-01

46

Laser microstructuring and annealing processes for lithium manganese oxide cathodes  

Microsoft Academic Search

It is expected that cathodes for lithium-ion batteries (LIB) composed out of nano-composite materials lead to an increase in power density of the LIB due to large electrochemically active surface areas but cathodes made of lithium manganese oxides (LiMnO) suffer from structural instabilities due to their sensitivity to the average manganese oxidation state. Therefore, thin films in the LiMnO system

J. Prll; R. Kohler; M. Torge; S. Ulrich; C. Ziebert; M. Bruns; H. J. Seifert; W. Pfleging

2011-01-01

47

Spinel lithium manganese oxide synthesized under a pressurized oxygen atmosphere  

Microsoft Academic Search

Spinel lithium manganese oxide was synthesized via co-precipitation. The prepared lithium manganese oxide powder was further heated at 700C for 15h under pressurized (3bar) oxygen atmosphere. The resultant exhibited a highly crystalline cubic spinel phase with space group Fd3m, as confirmed by X-ray diffraction. The spinel compound exhibited a slightly smaller lattice constant than a conventional spinel compound, even though

Ki-Soo Lee; Seung-Taek Myung; Hun-Gi Jung; Jung Kyoo Lee; Yang-Kook Sun

2010-01-01

48

Manganese oxide reduction in laboratory microcosms  

Microsoft Academic Search

Manganese biogeochemistry holds special interest for the characterization of passive treatment systems designed to treat acidic\\u000a mine waters while meeting enforceable effluent discharge limits set for manganese. In the present study, an initial anoxic\\u000a enrichment culture was developed for use as an inoculum in experimental systems. Standard anoxic microcosms capable of reducing\\u000a manganese from Mn4+ to Mn2+ were established from

Richard A. Royer; Richard F. Unz

1999-01-01

49

The molecular biogeochemistry of manganese(II) oxidation.  

PubMed

Micro-organisms capable of oxidizing the redox-active transition metal manganese play an important role in the biogeochemical cycle of manganese. In the present mini-review, we focus specifically on Mn(II)-oxidizing bacteria. The mechanisms by which bacteria oxidize Mn(II) include a two-electron oxidation reaction catalysed by a novel multicopper oxidase that produces Mn(IV) oxides as the primary product. Bacteria also produce organic ligands, such as siderophores, that bind to and stabilize Mn(III). The realization that this stabilized Mn(III) is present in many environments and can affect the redox cycles of other elements such as sulfur has made it clear that manganese and the bacteria that oxidize it profoundly affect the Earth's biogeochemistry. PMID:23176462

Geszvain, Kati; Butterfield, Cristina; Davis, Richard E; Madison, Andrew S; Lee, Sung-Woo; Parker, Dorothy L; Soldatova, Alexandra; Spiro, Thomas G; Luther, George W; Tebo, Bradley M

2012-12-01

50

Oxidations of bifunctional substrates with soluble manganese(IV) phosphate  

Microsoft Academic Search

Water-soluble manganese(IV) phosphate which is capable of auto-catalytic oxidation of compounds containing two functional groups, was prepared in 3 M phosphoric acid. The reaction was studied with an ethylene glycol-glycollic aldehyde-glycollic acid-glyoxylic a acid sequence of compounds, and a reaction mechanism is proposed. The autocatalytic effect is due to manganese(III), which is in itself much less reactive to these substrates.

Mikls Jky

1995-01-01

51

Oxidation kinetics of manganese (II) in seawater at nanomolar concentrations  

Microsoft Academic Search

Manganese oxidation rates were determined at low (? 20 nM) concentrations in seawater by measuring dissolved manganese (Mn(II)) using flow injection analysis with chemiluminescence detection. Mn(II) was measured in samples that had been filtered (0.2 ?m) and kept in the dark under controlled temperature and pH conditions for time periods up to 6 months. Eight 9 L carboys with mean

Peter J. von Langen; Kenneth S. Johnson; Kenneth H. Coale; Virginia A. Elrod

1997-01-01

52

Electrochemical supercapacitor material based on manganese oxide: preparation and characterization  

Microsoft Academic Search

A novel class of electrochemical supercapacitor electrode material has been electrochemically synthesized from a manganese halide complex in water-containing acetonitrile electrolyte at room temperature. This material has been physically and chemically characterized by scanning electron microscopy, X-ray photoelectron microscopy (XPS), FT-Raman microscopy and cyclic voltammetry. XPS and FT-Raman characterization suggest that this material is composed of manganese oxide with a

Junhua Jiang; Anthony Kucernak

2002-01-01

53

Manganese oxidation state mediates toxicity in PC12 cells  

Microsoft Academic Search

The role of the manganese (Mn) oxidation state on cellular Mn uptake and toxicity is not well understood. Therefore, undifferentiated PC12 cells were exposed to 0200 ?M Mn(II)chloride or Mn(III)pyrophosphate for 24 h, after which cellular manganese levels were measured along with measures of cell viability, function, and cytotoxicity (trypan blue exclusion, medium lactate dehydrogenase (LDH), 8-isoprostanes, cellular ATP, dopamine,

S. H.. Reaney; D. R. Smith

2005-01-01

54

The Molecular Geomicrobiology of Bacterial Manganese(II) Oxidation  

Microsoft Academic Search

\\u000a Manganese is the second most abundant transition metal found in the Earths crust. It has a significant biological role as\\u000a it is a cofactor of enzymes such as superoxide dismutase and is the key metal in the reaction center of photosystem II. In\\u000a the environment, manganese is mostly found in three different oxidation states: II, III, and IV. Mn(II), primarily

Bradley M. Tebo; Kati Geszvain; Sung-Woo Lee

55

Solution synthesis and characterization of lithium manganese oxide cathode materials  

Microsoft Academic Search

A nonaqueous coprecipitation process has been developed to prepare controlled stoichiometry lithium manganese oxalate precipitates. The process involved mixing a methanolic Li-Mn nitrate solution with a methanolic solution containing tetramethylammonium oxalate as the precipitating agent. The resulting oxalates were readily converted to a variety of phase pure lithium manganese oxides at moderate temperatures (600°C), where the phase formed was determined

J. A. Voigt; T. J. Boyle; D. H. Doughty

1995-01-01

56

Lithium Isotope Selectivity of Sorbents Prepared from Lithium Manganese Oxides  

Microsoft Academic Search

Sorbents are prepared by extracting lithium ions from lithium manganese oxides with the lithium\\/manganese mole ratio (Li\\/Mn ratio) varying between 0.42 and 0.84, and their lithium isotope selectivities are investigated. All the sorbents are Li-specific and the values of the Li-to-Li isotopic separation factor (S) are between 1.0040 and 1.0092 at 25C. The S value is slightly dependent on the

HIROTSUGU TAKEUCHI; TAKAO OI; MORIKAZU HOSOE

1999-01-01

57

Mineralogical Characterization of Manganese Oxides in Mine Water Treatment Systems  

NASA Astrophysics Data System (ADS)

The removal of manganese(II) from mine water is a significant problem for both operating and abandoned mines across the United States. In many situations, manganese removal represents the most costly aspect of mine water treatment. Active treatment of Mn-containing mine water requires adjustment of pH to 9-10, and results in the abiotic precipitation of manganese oxides (MnOx). After manganese removal, this high pH water must be neutralized before release. Alternatively, passive limestone beds can be used for neutralization of low-pH mine water and subsequent manganese removal. Although limestone beds are effective for Mn removal, the processes involved are not clear (e.g., relative importance of biological Mn(II) oxidation versus surface mediated oxidation) and the characteristics of the manganese "crusts" formed are not well studied. In this field-based study, we have collected natural manganese oxides from two different limestone beds designed to treat mine water from abandoned coal strip mines in Pennsylvania. Samples were collected at different locations in the beds and at different seasons to capture possible variations in mineralogical characteristics. Water samples were also collected to measure the corresponding solution chemistry and revealed that manganese removal was strongly temperature dependent. Solid samples have been examined by scanning and transmission electron microscopy, and by X-ray diffraction. Micro-diffraction XRD has been used to tentatively identify disordered buserite as a predominant mineral in many of these crust samples. Additional characterizations will include particle size distribution and surface charge. Synchroton-based X-ray techniques such as scanning transmission X-ray microscopy (STXM) and X-ray spectroscopy (XAS) may also be pursued.

Tan, H.; Heaney, P.; Post, J.; Burgos, W.

2006-05-01

58

Amorphous manganese oxide remains amorphous upon lithium intercalation and cycling  

Microsoft Academic Search

Lithium intercalation in amorphous manganese oxide, synthesized by a room temperature aqueous oxidation route, is analyzed. As reported before, the material yields a very high intercalation capacity and also shows promising rate capability as cathode for rechargeable lithium batteries. The present study investigates the structure of the material using X-ray powder diffraction conducted on composite cathode pellets at different stages

Xu Jun John; Ye Hui; Jain Gaurav; Yang Jingsi

2004-01-01

59

New Vanadium and Manganese Oxides for Lithium Batteries  

Microsoft Academic Search

Transition metal oxides, that can intercalate lithium ions in a reversible manner and with an energy in the range of 3 to 4 volts, are a critical link in the advancement of high energy density lithium batteries. Vanadium, manganese and iron oxides form the appropriate polyhedral structures that might intercalate small ions. Such structures have been formed at low temperatures

M. Stanley Whittingham; Peter Y. Zavalij; Thomas Chirayil; Rongji Chen

1997-01-01

60

Energetic basis of catalytic activity of layered nanophase calcium manganese oxides for water oxidation.  

PubMed

Previous measurements show that calcium manganese oxide nanoparticles are better water oxidation catalysts than binary manganese oxides (Mn3O4, Mn2O3, and MnO2). The probable reasons for such enhancement involve a combination of factors: The calcium manganese oxide materials have a layered structure with considerable thermodynamic stability and a high surface area, their low surface energy suggests relatively loose binding of H2O on the internal and external surfaces, and they possess mixed-valent manganese with internal oxidation enthalpy independent of the Mn(3+)/Mn(4+) ratio and much smaller in magnitude than the Mn2O3-MnO2 couple. These factors enhance catalytic ability by providing easy access for solutes and water to active sites and facile electron transfer between manganese in different oxidation states. PMID:23667149

Birkner, Nancy; Nayeri, Sara; Pashaei, Babak; Najafpour, Mohammad Mahdi; Casey, William H; Navrotsky, Alexandra

2013-05-10

61

Acetone Oxidation using Ozone on Manganese Oxide Catalysts  

SciTech Connect

Supported manganese oxide catalysts were prepared by the impregnation of alumina foam blocks washcoated with alumina and silica. The manganese content based on the weight of the washcoats was 10 wt % calculated as MnO{sub 2}. Fourier transform profiles of the Mn K-edge EXAFS spectra for these samples gave three distinctive peaks at 0.15, 0.25, and 0.32 nm and were close to the profiles of Mn{sub 3}O{sub 4} and {beta}-MnO{sub 2}. The number of surface active sites was determined through oxygen chemisorption measurements at a reduction temperature (T{sub red} = 443 K) obtained from temperature-programmed reduction (TPR) experiments. Acetone catalytic oxidation was studied from room temperature to 573 K, and was found to be highly accelerated by the use of ozone on both catalysts with substantial reductions in the reaction temperature. The only carbon-containing product detected was CO{sub 2}. The alumina-supported catalyst was found to be more active than the silica-supported catalyst in acetone and ozone conversion, with higher turnover frequencies (TOFs) for both reactions. The pressure drop through the foam was low and increased little (0.003 kPa/10 000 h{sup -1}) with space velocity. In situ steady-state Raman spectroscopy measurements during the acetone catalytic oxidation reaction showed the presence of an adsorbed acetone species with a C-H bond at 2930 cm{sup -1} and a peroxide species derived from ozone with an O-O bond at 890 cm{sup -1}.

Xi,Y.; Reed, C.; Lee, Y.; Oyama, S.

2005-01-01

62

The sorption of silver by poorly crystallized manganese oxides  

USGS Publications Warehouse

The sorption of silver by poorly crystallized manganese oxides was studied using synthesized samples of three members of the manganous manganite (birnessite) group, of different chemical composition and crystallinity, and a poorly organized ??-MnO2. All four oxides sorbed significant quantities of silver. The manganous manganites showed the greatest sorption (up to 0.5 moles silver/mole MnOx at pH 7) while the ??-MnO2 showed the least (0.3 moles silver/ mole MnOx at pH 7). Sorption of silver was adequately described by the Langmuir equation over a considerable concentration range. The relationship failed at low pH values and high equilibrium silver concentrations. The sorption capacity showed a direct relationship with pH. However, the rate of increase of sorption capacity decreased at the higher pH values. Silver sorption maxima. were not directly related to surface area but appeared to vary with the amount of occluded sodium and potassium present in the manganese oxide. The important processes involved in the uptake of silver by the four poorly crystallized manganese oxides ara considered to be surface exchange for manganese, potassium and sodium as well as exchange for structural manganese, potassium and sodium. ?? 1973.

Anderson, B. J.; Jenne, E. A.; Chao, T. T.

1973-01-01

63

Biochemical changes in pulmonary cells following manganese oxide inhalation.  

PubMed

Inhalation of manganese oxide (Mn dose, 879.0 micrograms/m3) for 2 h reduced the total number of alveolar macrophages obtained by endotracheal lavage in pulmonary cell populations, slightly reduced cellular viability, and reduced both phagocytic capability and total protein in sonicated pulmonary cells. Increases in intracellular adenosine triphosphate and acid phosphatase specific activity were also exhibited by the pulmonary cells, but sonicated cells obtained from the exposed mice showed no change in lactic acid dehydrogenase specific activity. A slight increase in extracellular protein in the fluid phase of the lavage suspension was observed after manganese oxide exposure. PMID:7392103

Adkins, B; Luginbuhl, G H; Gardner, D E

1980-03-01

64

The thermal stability of lithium-manganese-oxide spinel phases  

SciTech Connect

The thermal stability of stoichiometric spinel phases in the system Li{sub 1+{delta}}Mn{sub 2{minus}{delta}}O{sub 4} (0 {le} {delta} {le} 0.33) has been investigated by high-temperature powder X-ray diffraction, differential thermal analysis, and thermogravimetric analysis. At elevated temperatures, the lithium-manganese-oxide spinels undergo phase changes by loss of oxygen and lithia (Li{sub 2}O). The data highlight the importance of temperature control when synthesizing lithium-manganese-oxide spinel compounds.

Thackeray, M.M.; Mansuetto, M.F.; Dees, D.W.; Vissers, D.R. [Argonne National Lab., IL (United States)

1996-02-01

65

Electrochemical properties of iodine-containing lithium manganese oxide spinel  

Microsoft Academic Search

Iodine-containing, cation-deficient, lithium manganese oxides (ICCD-LMO) are prepared by reaction of MnO2 with LiI. The MnO2 is completely transformed into spinel-structured compounds with a nominal composition of Li1??Mn2?2?O4Ix. A sample prepared at 800C, viz. Li0.99Mn1.98O4I0.02, exhibits an initial discharge capacity of 113mAhg?1 with good cycleability and rate capability in the 4-V region. Iodine-containing, lithium-rich lithium manganese oxides (ICLR-LMO) are also

Chi-Hwan Han; Young-Sik Hong; Hyun-Sil Hong; Keon Kim

2002-01-01

66

40 CFR 721.10529 - Cobalt iron manganese oxide, carboxylic acid-modified (generic).  

Code of Federal Regulations, 2013 CFR

...2013-07-01 2013-07-01 false Cobalt iron manganese oxide, carboxylic acid-modified...Chemical Substances § 721.10529 Cobalt iron manganese oxide, carboxylic acid-modified...chemical substance identified generically as cobalt iron manganese oxide, carboxylic...

2013-07-01

67

40 CFR 721.10010 - Barium manganese oxide (BaMnO3).  

Code of Federal Regulations, 2010 CFR

...2009-07-01 2009-07-01 false Barium manganese oxide (BaMnO3). 721.10010...Chemical Substances § 721.10010 Barium manganese oxide (BaMnO3 ). (a...The chemical substance identified as barium manganese oxide (BaMnO3 )...

2009-07-01

68

40 CFR 721.10010 - Barium manganese oxide (BaMnO3).  

Code of Federal Regulations, 2010 CFR

...2010-07-01 2010-07-01 false Barium manganese oxide (BaMnO3). 721.10010...Chemical Substances § 721.10010 Barium manganese oxide (BaMnO3). (a...The chemical substance identified as barium manganese oxide (BaMnO3 )...

2010-07-01

69

40 CFR 721.10010 - Barium manganese oxide (BaMnO3).  

Code of Federal Regulations, 2013 CFR

...2013-07-01 2013-07-01 false Barium manganese oxide (BaMnO3). 721.10010...Chemical Substances § 721.10010 Barium manganese oxide (BaMnO3 ). (a...The chemical substance identified as barium manganese oxide (BaMnO3 )...

2013-07-01

70

40 CFR 721.10009 - Manganese yttrium oxide (MnYO3).  

Code of Federal Regulations, 2013 CFR

...2013-07-01 2013-07-01 false Manganese yttrium oxide (MnYO3). 721.10009...Chemical Substances § 721.10009 Manganese yttrium oxide (MnYO3 ). (a...The chemical substance identified as manganese yttrium oxide (MnYO3 ) (PMN...

2013-07-01

71

40 CFR 721.10013 - Manganese yttrium oxide (Mn2YO5).  

Code of Federal Regulations, 2013 CFR

...2013-07-01 2013-07-01 false Manganese yttrium oxide (Mn2YO5). 721.10013...Chemical Substances § 721.10013 Manganese yttrium oxide (Mn2 YO5 ). ...The chemical substance identified as manganese yttrium oxide (Mn2 YO5 )...

2013-07-01

72

40 CFR 721.10008 - Manganese strontium oxide (MnSrO3).  

Code of Federal Regulations, 2013 CFR

...2013-07-01 2013-07-01 false Manganese strontium oxide (MnSrO3). 721...Chemical Substances § 721.10008 Manganese strontium oxide (MnSrO3 ). ...The chemical substance identified as manganese strontium oxide (MnSrO3 )...

2013-07-01

73

Interaction of dietary calcium, manganese, and manganese source (Mn oxide or Mn methionine complex) on chick performance and manganese utilization  

Microsoft Academic Search

Two trials were conducted to determine the utilization of manganese (Mn) as influenced by the level and source of Mn and the\\u000a level of dietary calcium (Ca) in broiler chickens. Trial One was a 2 2 3 factorial arrangement of two Mn sources (Mn methionine\\u000a or manganous oxide), two levels of dietary Ca (1.8 or 1.0), and three

Sheila E. Scheideler

1991-01-01

74

The Structural Stability of Manganese Oxide Electrodes for Lithium Batteries  

NASA Astrophysics Data System (ADS)

Manganese oxides are of interest as insertion electrodes for rechargeable 3 V and 4 V lithium batteries. During discharge, lithium ions are inserted into the manganese oxide host structure with a concomitant reduction of the manganese ions; the reverse process occurs on charge. The cycle life of these batteries is critically dependent on the ability of the manganese oxide structure to maintain its structural integrity during discharge and charge. Although manganese dioxide exists in several polymorphic forms, most of these undergo severe crystallographic distortions or transformations on lithiation, for example, rutile-Li_xMnO_2, ramsdellite-Li_xMnO2 and spinel-Li_1+xMn_2O_4. The distortions arise largely because of the onset of a Jahn-Teller effect when the concentration of Mn^3+ (d^4) ions reaches a critical value. This paper discusses the progress that has been made to stabilize various MnO2 structures to enhance their stability to lithium insertion/extraction reactions.

Thackeray, Michael M.

1997-03-01

75

Manganese oxidation state and its implications for toxicity.  

PubMed

Manganese (Mn) is ubiquitous in mammalian systems and is essential for proper development and function, though it can also be toxic at elevated exposures. While essential biologic functions of Mn depend on its oxidation state [e.g., Mn(II), Mn(III)], little is known about how the oxidation state of elevated Mn exposures affect cellular uptake, and function/toxicity. Here we report the dynamics of EPR measurable Mn(II) in fresh human plasma and cultured PC12 cell lysates as a function of exposure to either manganese(II) chloride or manganese(III) pyrophosphate, and the effects of exposure to Mn(II) versus Mn(III) on total cellular aconitase activity and cellular Mn uptake. The results indicate that Mn(II) or Mn(III) added in vitro to fresh human plasma or cell lysates yielded similar amounts of EPR measurable Mn(II). In contrast, Mn added as Mn(III) was significantly more effective in inhibiting total cellular aconitase activity, and intact PC12 cells accumulated significantly more Mn when exposures occurred as Mn(III). Collectively, these data reflect the dynamic nature of Mn speciation in simple biological systems, and the importance of Mn oxidation/speciation state in mediating potential cellular toxicity. This study supports concern over increased environmental exposures to Mn in different oxidation states [Mn(II), Mn(III), and Mn(IV)] that may arise from combustion products of the gasoline antiknock additive methycyclopentadienyl manganese tricarbonyl (MMT). PMID:12230404

Reaney, Stephen H; Kwik-Uribe, Catherine L; Smith, Donald R

2002-09-01

76

Synthesis of single crystalline layered lithium manganese oxide nanorods  

Microsoft Academic Search

Single-crystalline layered lithium manganese oxide nanorods were prepared via a low-temperature molten salt synthesis method. The material was investigated by a variety of techniques, including X-ray powder diffraction (XRD), transmission electron microscopy (TEM), and X-ray photoelectron spectrum (XPS).

Xiong Wang; Jimei Song; Lisheng Gao; Huagui Zheng; Mingrong Ji; Zude Zhang

2004-01-01

77

Nanostructured manganese oxides as lithium battery cathode materials  

Microsoft Academic Search

We have designed and synthesized a novel nanocrystalline manganese oxide with a nanofibrous morphology by employing an electrodeposition process in the presence of a non-ionic surfactant. This unique nanoporous\\/nanocrystalline material effectively accommodates the structural transformation during lithium insertion and avoids deleterious morphological changes as observed in battery materials composed of large particles. Consequently, the material exhibits outstanding cycling stability in

Ping Liu; Se-Hee Lee; Yanfa Yan; C. Edwin Tracy; John A. Turner

2006-01-01

78

The role of manganese in photosynthetic water oxidation  

Microsoft Academic Search

Summary The process of photosynthetic water oxidation to dioxygen under proton release takes place via a sequence of four univalent redox steps in a manganese-containing unit. In this mini-review the current state of knowledge is briefly described with special emphasis on the following topics: (a) the nature of the catalytic site, (b) the structure of the redox chemistry of the

G. Renger; T. Wydrzynski

1991-01-01

79

Sol-gel synthesis of manganese oxides  

Microsoft Academic Search

Transparent and stable manganese dioxide gels are obtained upon reduction of permanganate aqueous solutions AMnO4 [A = Li, Na, K, NH4, N(CH3)4] by fumaric acid. All xerogels are amorphous when dried at room temperature. Their thermal behavior however depends on the nature of the counter cation A+. Ammonium permanganates lead to the formation of alpha- or gamma-Mn2O3 while AMnO2 mixed

S. Bach; M. Henry; N. Baffier; J. Livage

1990-01-01

80

Chlorobenzene oxidation using ozone over iron oxide and manganese oxide catalysts  

Microsoft Academic Search

A low-temperature catalytic oxidation of chlorobenzene (CB) has been performed at temperatures of 60210C using ozone (O3) over iron oxide and manganese oxide, respectively. In the absence of ozone, CB conversion achieved with these two catalysts at 200C was below 10%. However, addition of 1200ppm ozone results in a remarkable increase in CB conversion and the conversion reaches 91.7% at

Hou Chuan Wang; Hsu Shang Liang; Moo Been Chang

2011-01-01

81

Manganese (II) oxidation by microperoxidase-11 in hydrophilic organic media  

Microsoft Academic Search

Microperoxidase-11 (MP-11) derived from horse heart cytochrome c was utilized as a peroxidative catalyst. MnII-oxidation activity of MP-11 was demonstrated for the first time. Although the activity of MP-11 was low compared to manganese peroxidase (MnP) from Phanerochaete chrysosporium in aqueous system, it can be utilized in water-miscible organic solvents if at least 5% water exists. MnII-oxidation by MP-11 was

Masafumi Oyadomari; Mari Kabuto; Hiroyuki Wariishi; Hiroo Tanaka

2003-01-01

82

Nano-sized manganese oxides as biomimetic catalysts for water oxidation in artificial photosynthesis: a review  

PubMed Central

There has been a tremendous surge in research on the synthesis of various metal compounds aimed at simulating the water-oxidizing complex (WOC) of photosystem II (PSII). This is crucial because the water oxidation half reaction is overwhelmingly rate-limiting and needs high over-voltage (approx. 1 V), which results in low conversion efficiencies when working at current densities required for hydrogen production via water splitting. Particular attention has been given to the manganese compounds not only because manganese has been used by nature to oxidize water but also because manganese is cheap and environmentally friendly. The manganesecalcium cluster in PSII has a dimension of about approximately 0.5 nm. Thus, nano-sized manganese compounds might be good structural and functional models for the cluster. As in the nanometre-size of the synthetic models, most of the active sites are at the surface, these compounds could be more efficient catalysts than micrometre (or bigger) particles. In this paper, we focus on nano-sized manganese oxides as functional and structural models of the WOC of PSII for hydrogen production via water splitting and review nano-sized manganese oxides used in water oxidation by some research groups.

Najafpour, Mohammad Mahdi; Rahimi, Fahimeh; Aro, Eva-Mari; Lee, Choon-Hwan; Allakhverdiev, Suleyman I.

2012-01-01

83

Distributions of manganese, iron, and manganese-oxidizing bacteria in Lake Superior sediments of different organic carbon content  

Microsoft Academic Search

Profiles of oxygen, soluble and particulate manganese and iron, organic carbon and nitrogen were examined in Lake Superior sediment cores, along with the distribution and abundance of heterotrophic and manganese oxidizing bacteria. Analyses were performed using cores collected with the submersible Johnson Sea Link II. Three cores, exhibiting a range of organic carbon content, were collected from the deepest basin

Laurie L. Richardson; Kenneth H. Nealson

1989-01-01

84

Thin film passivation of laser generated 3D micro patterns in lithium manganese oxide cathodes  

NASA Astrophysics Data System (ADS)

The increasing need for long-life lithium-ion batteries requires the further development of electrode materials. Especially on the cathode side new materials or material composites are needed to increase the cycle lifetime. On the one hand, spinel-type lithium manganese oxide is a promising candidate to be used as cathode material due to its non-toxicity, low cost and good thermal stability. On the other hand, the spinel structure suffers from change in the oxidation state of manganese during cycling which is also accompanied by loss of active material into the liquid electrolyte. The general trend is to enhance the active surface area of the cathode in order to increase lithium-ion mobility through the electrode/electrolyte interface, while an enhanced surface area will also promote chemical degradation. In this work, laser microstructuring of lithium manganese oxide thin films was applied in a first step to increase the active surface area. This was done by using 248 nm excimer laser radiation and chromium/quartz mask imaging techniques. In a second step, high power diode laser-annealing operating at a wavelength of 940 nm was used for forming a cubic spinel-like battery phase. This was verified by means of Raman spectroscopy and cyclic voltammetric measurements. In a last step, the laser patterned thin films were coated with indium tin oxide (ITO) layers with a thickness of 10 nm to 50 nm. The influence of the 3D surface topography as well as the ITO thickness on the electrochemical performance was studied by cyclic voltammetry. Post-mortem studies were carried out by using scanning electron microscopy and focused ion beam analysis.

Prll, J.; Kohler, R.; Bruns, M.; Oberst, V.; Weidler, P. G.; Heiler, S.; Kbel, C.; Scherer, T.; Prang, R.; Seifert, H. J.; Pfleging, W.

2013-03-01

85

Manganese oxidation state mediates toxicity in PC12 cells.  

PubMed

The role of the manganese (Mn) oxidation state on cellular Mn uptake and toxicity is not well understood. Therefore, undifferentiated PC12 cells were exposed to 0-200 microM Mn(II)-chloride or Mn(III)-pyrophosphate for 24 h, after which cellular manganese levels were measured along with measures of cell viability, function, and cytotoxicity (trypan blue exclusion, medium lactate dehydrogenase (LDH), 8-isoprostanes, cellular ATP, dopamine, serotonin, H-ferritin, transferrin receptor (TfR), Mn-superoxide dismutase (MnSOD), and copper-zinc superoxide dismutase (CuZnSOD) protein levels). Exposures to Mn(III) >10 microM produced 2- to 5-fold higher cellular manganese levels than equimolar exposures to Mn(II). Cell viability and ATP levels both decreased at the highest Mn(II) and Mn(III) exposures (150-200 microM), while Mn(III) exposures produced increases in LDH activity at lower exposures (> or =50 microM) than did Mn(II) (200 microM only). Mn(II) reduced cellular dopamine levels more than Mn(III), especially at the highest exposures (50% reduced at 200 microM Mn(II)). In contrast, Mn(III) produced a >70% reduction in cellular serotonin at all exposures compared to Mn(II). Different cellular responses to Mn(II) exposures compared to Mn(III) were also observed for H-ferritin, TfR, and MnSOD protein levels. Notably, these differential effects of Mn(II) versus Mn(III) exposures on cellular toxicity could not simply be accounted for by the different cellular levels of manganese. These results suggest that the oxidation state of manganese exposures plays an important role in mediating manganese cytotoxicity. PMID:15922012

Reaney, S H; Smith, D R

2004-12-08

86

Determination of the oxidation states of manganese in brain, liver, and heart mitochondria.  

PubMed

Excess brain manganese can produce toxicity with symptoms that resemble those of Parkinsonism and causes that remain elusive. Manganese accumulates in mitochondria, a major source of superoxide, which can oxidize Mn2+ to the powerful oxidizing agent Mn3+. Oxidation of important cell components by Mn3+ has been suggested as a cause of the toxic effects of manganese. Determining the oxidation states of intramitochondrial manganese could help to identify the dominant mechanism of manganese toxicity. Using X-ray absorbance near edge structure (XANES) spectroscopy, we have characterized the oxidation state of manganese in mitochondria isolated from brain, liver, and heart over concentrations ranging from physiological to pathological. Results showed that (i) spectra from different model manganese complexes of the same oxidation state were similar to each other and different from those of other oxidation states and that the position of the absorption edge increases with oxidation state; (ii) spectra from intramitochondrial manganese in isolated brain, heart and liver mitochondria were virtually identical; and (iii) under these conditions intramitochondrial manganese exists primarily as a combination of Mn2+ complexes. No evidence for Mn3+ was detected in samples containing more than endogenous manganese levels, even after incubation under conditions promoting reactive oxygen species (ROS) production. While the presence of Mn3+ complexes cannot be proven in the spectrum of endogenous mitochondrial manganese, the shape of this spectrum could suggest the presence of Mn3+ near the limit of detection, probably as MnSOD. PMID:14690515

Gunter, Thomas E; Miller, Lisa M; Gavin, Claire E; Eliseev, Roman; Salter, Jason; Buntinas, Linas; Alexandrov, Andrei; Hammond, Sean; Gunter, Karlene K

2004-01-01

87

Distributions of manganese, iron, and manganese-oxidizing bacteria in Lake Superior sediments of different organic carbon content  

SciTech Connect

Profiles of oxygen, soluble and particulate manganese and iron, organic carbon and nitrogen were examined in Lake Superior sediment cores, along with the distribution and abundance of heterotrophic and manganese oxidizing bacteria. Analyses were performed using cores collected with the submersible Johnson Sea Link II. Three cores, exhibiting a range of organic carbon content, were collected from the deepest basin in Lake Superior and the north and south ends of the Caribou trough, and brought to the surface for immediate analysis. Minielectrode profiles of oxygen concentration of the three cores were carried out using a commercially available minielectrode apparatus. Oxygen depletion to less than 1% occurred within 4 cm of the surface for two of the cores, but not until approximately 15 cm for the core from the south basin of the Caribou trough. The three cores exhibited very different profiles of soluble, as well as leachable, manganese and iron, suggesting different degrees of remobilization of these metals in the sediments. Vertical profiles of viable bacterial and Mn oxidizing bacteria, determined by plating and counting, showed that aerobic heterotrophic bacteria were present at the highest concentrations near the surface and decreased steadily with depth, while Mn oxidizing bacteria were concentrated primarily at and above the oxic/anoxic interface. Soluble manganese in the pore waters, along with abundant organic carbon, appeared to enhance the presence of manganese oxidizing bacteria, even below the oxic/anoxic interface. Profiles of solid-phase leachable manganese suggested a microbial role in manganese reprecipitation in these sediments.

Richardson, L.L.; Nealson, K.H.

1989-01-01

88

Manganese oxide nanowires, films, and membranes and methods of making  

DOEpatents

Nanowires, films, and membranes comprising ordered porous manganese oxide-based octahedral molecular sieves, and methods of making, are disclosed. A single crystal ultra-long nanowire includes an ordered porous manganese oxide-based octahedral molecular sieve, and has an average length greater than about 10 micrometers and an average diameter of about 5 nanometers to about 100 nanometers. A film comprises a microporous network comprising a plurality of single crystal nanowires in the form of a layer, wherein a plurality of layers is stacked on a surface of a substrate, wherein the nanowires of each layer are substantially axially aligned. A free standing membrane comprises a microporous network comprising a plurality of single crystal nanowires in the form of a layer, wherein a plurality of layers is aggregately stacked, and wherein the nanowires of each layer are substantially axially aligned.

Suib, Steven Lawrence (Storrs, CT); Yuan, Jikang (Storrs, CT)

2008-10-21

89

Preliminary LIBS analysis of Yucca Mountain manganese oxide minerals  

SciTech Connect

The licensing and performance of a potential repository at Yucca Mountain will require the characterization of radionuclide sorptive capacity of the host rock, which in turn calls for hundreds of analyses based on extensive sampling or in situ measurements. A rapid method specifically for characterizing the manganese oxide minerals occurring heterogeneously throughout the Yucca Mountain block as fracture surface coatings is needed. Our unique solution is a laser-induced breakdown spectroscopy (LIBS) surface-analysis technique that is usable in the field to produce high-resolution atomic emission spectra. In tests with manganese oxide minerals and fracture surface coatings from a few Yucca Mountain core samples, we used four spectral bands to show that qualitative measurement of all constituent elements except K and Na (in the presence of Mn) is possible with LIBS. Detailed calibration of final hardware will make the system quantitative.

Blacic, J.; Pettit, D.; Cremers, D.

1996-01-01

90

Environmental oxidation rate of manganese(II): bacterial catalysis  

Microsoft Academic Search

A simple mass balance for dissolved manganese(II) in waters containing low levels of oxygen in Saanich Inlet indicates that the residence time for Mn(II) removal to the solid phase is on the order of a few days. The average oxidation state of Mn in particulate material sampled from the region of Mn removal was 2.3-2.7, and electron micrographs revealed structures

Steven Emerson; Susan Kalhorn; Lucinda Jacobs; Bradley M. Tebo; Kenneth H. Nealson; Reinhardt A. Rosson

1982-01-01

91

A redox-assisted supramolecular assembly of manganese oxide nanotube  

Microsoft Academic Search

In this paper, we report the hydrothermal synthesis of manganese oxide nanotube from an aqueous medium of pH 7, using KMnO4 and MnCl2 as inorganic precursors, polyoxyethylene (10) nonyl phenyl ether (TX-10) a surfactant and acetaldehyde an additive. The characterization of X-ray diffraction (XRD), transmission electron microscopy (TEM), selected area electron diffraction (SAED) and N2 adsorption at 77K (BET) reveals

Li Tao; Cheng-Gao Sun; Mei-Lian Fan; Cai-Juan Huang; Hai-Long Wu; Zi-Sheng Chao; He-Sheng Zhai

2006-01-01

92

Hydrothermal synthesis of nanostructured spinel lithium manganese oxide  

Microsoft Academic Search

Nanostructured spherical spinel lithium manganese oxide (LiMnO) with about 200nm in diameter was synthesized for the first time by mild hydrothermal method. The formation of the nanostructured spheres was through self-assembly of the nanoparticles and nanobelts. The influence of the reaction temperature and the time of formation of the nanostructures have been systematically studied. The thermal stability of the nanostructures

Zhanqiang Liu; Wen-Lou Wang; Xianming Liu; Minchang Wu; Dan Li; Zhen Zeng

2004-01-01

93

Electrochemical characterization of commercial lithium manganese oxide powders  

Microsoft Academic Search

Five commercial lithium manganese oxide powders have been studied. The XRD spectra showed all samples to exhibit the spinel structure. The composition and morphology were analyzed by JaegerVetter titration and scanning electron microscopy. The lithium intercalation\\/de-intercalation characteristics and the cycleability have been studied using state-of-the-art cells. The morphology of the particles and crystallites, as well as the defect structure of

H. Huang; C. H. Chen; R. C. Perego; E. M. Kelder; L. Chen; J. Schoonman; W. J. Weydanz; D. W. Nielsen

2000-01-01

94

Prismatic cell lithium-ion battery using lithium manganese oxide  

Microsoft Academic Search

Lithium-ion (Li-ion) batteries have demonstrated the ability to fulfill the energy storage needs of many new technologies. The most significant drawbacks of currently available technologies, such as LiCoO 2 based Li-ion cells, is their high cost and significant environmental hazards. Li-ion cells which use a lithium manganese oxide (LiMn2O4) spinel) based cathode material should be much less costly and safer

G. M. Ehrlich; R. M. Hellen; T. B. Reddy

1997-01-01

95

Synthesis of lithium-manganese oxide spinel in hydrothermal conditions  

Microsoft Academic Search

Lithium-manganese oxide spinel LiMn2O4 was synthesized in hydrothermal conditions (400C, 20 MPa) in the course of thermovaporous treatment mixtures of MnO2 and LiOH\\/or Li2CO3. The conditions of synthesis of the spinel as monophase product were determined. The obtained product has been characterized by means of various physical and chemical methods. The spinel has been used for manufacturing cathodes of rechargeable

G. Panasyuk; I. Voroshilov; G. Boudova; L. Azarova; V. Privalov; V. Minin; A. Skundin; L. Kanevsky; T. Kulova; M. Danchevskaya; Yu. Ivaki

2001-01-01

96

Study of zone-center phonons in lithium manganese oxide  

Microsoft Academic Search

The zone-center phonons of spinel structure lithium manganese oxide have been investigated by applying de Launey angular force constant model. The calculation is extended to lithium extracted phases Li0.5Mn2O4 and Li0.015Mn2O4 also. The lattice phonons thus obtained are compared with available experimental results. The lithiation effects on phonon modes are also discussed.

M. M. Sinha; H. C. Gupta

2002-01-01

97

Lithium insertion in manganese oxides: A model lithium ion system  

Microsoft Academic Search

A model lithium ion system, based on the manganese oxide, LixMn2O4, has been used to study the reversibility of the lithium insertion processes in both the approximate 3 V and 4 V versus LiLi+ voltages ranges. We have used the half-cell voltage responses for the Li1 ? xMn2O4 and Li1 + xMn2O4 electrodes to predict the voltage profile for the

Jerry Barker; Ren Koksbang; M. Yazid Sadi

1995-01-01

98

Cathodic behavior of alkali manganese oxides from permanganate  

Microsoft Academic Search

Extensive research is currently underway to find promising candidates for cathode materials in lithium secondary batteries, and a manganese oxide that behaved like the layered LiCoCO would be a prime candidate for this application because of its high free-energy of reaction with lithium and relatively low cost. The reaction of potassium, sodium, and lithium permanganate in water at 170 C

Rongji Chen; M. S. Whittingham

1997-01-01

99

Giant magnetoresistance of manganese oxides with a layered perovskite structure  

Microsoft Academic Search

MANGANESE oxides with the cubic perovskite structure (typified by LaMnO3) have stimulated considerable interest because of their magnetoresistive properties1-9 they exhibit extremely large changes in electrical resistance in response to applied magnetic fields, a property that is of technological relevance for the development of magnetic memory and switching devices. But for such applications to be viable, great improvements will be

Y. Moritomo; A. Asamitsu; H. Kuwahara; Y. Tokura

1996-01-01

100

Electrodeposited the gold\\/manganese oxides as nano supercapacitor  

Microsoft Academic Search

In this study, the nano-supercapacitors were electrodeposited the gold\\/manganese oxides thin film with potassium permanganate and gold chloride solution on ITO substrate. It was deposited for 200 s by potentiostatic method (0.7 V v.s. open circuit). The morphology and the microstructure of the films were examined by SEM (scan electron microscopy). The thickness of the thin films was about 30~100

Yi Hu; Jiun-Shing Liu

2010-01-01

101

Influence of oxalic acid on the dissolution kinetics of manganese oxide  

NASA Astrophysics Data System (ADS)

The kinetics and electrochemical processes of the dissolution of manganese oxides with various oxidation states in sulfuric acid solutions containing oxalate ion additives is studied under variable conditions (concentration, pH, temperature). The parameters favoring a higher degree of the dissolution of manganese oxides in acidic media are determined. The optimal conditions are found for the dissolution of manganese oxides in acidic media in the presence of oxalate ions. The mechanism proposed for the dissolution of manganese oxides in sulfuric acid solutions containing oxalic acid is based on the results of kinetic and electrochemical studies. The steps of the dissolution mechanism are discussed.

Godunov, E. B.; Artamonova, I. V.; Gorichev, I. G.; Lainer, Yu. A.

2012-11-01

102

Catalytic oxidation of benzene with ozone over alumina-supported manganese oxides  

Microsoft Academic Search

Catalytic oxidation of benzene with ozone over alumina-supported manganese oxides was carried out at room temperature (295 K) to investigate the behavior of benzene oxidation and COx formation. The ratio of the decomposition rate for ozone to that for benzene was found to be 6, independent of ozone concentration, reaction times, and the amount of Mn loading. A linear correlation

Hisahiro Einaga; Shigeru Futamura

2004-01-01

103

A redox-assisted supramolecular assembly of manganese oxide nanotube  

SciTech Connect

In this paper, we report the hydrothermal synthesis of manganese oxide nanotube from an aqueous medium of pH 7, using KMnO{sub 4} and MnCl{sub 2} as inorganic precursors, polyoxyethylene (10) nonyl phenyl ether (TX-10) a surfactant and acetaldehyde an additive. The characterization of X-ray diffraction (XRD), transmission electron microscopy (TEM), selected area electron diffraction (SAED) and N{sub 2} adsorption at 77 K (BET) reveals that the synthesized manganese oxide nanotube has a mesopore size of ca. 3.65 nm and a wall thickness of ca. 12 nm, with the wall being composed of microporous crystals of monoclinic manganite. The X-ray photoelectron spectroscopy (XPS) result demonstrates a decrease of the binding energy of the Mn{sup 3+} in the manganese oxide nanotube, which may be related to both the nanotubular morphology and the crystalline pore wall. A mechanism of a redox-assisted supramolecular assembly, regulated by acetaldehyde, is postulated.

Tao Li [College of Chemistry and Chemical Engineering, Hunan University, Key Laboratory of Chemometrics and Chemical Biological Sensing Technologies, Ministry of Education, Changsha 410082 (China); Sun Chenggao [College of Chemistry and Chemical Engineering, Hunan University and Key Laboratory of Chemometrics and Chemical Biological Sensing Technologies, Ministry of Education, Changsha 410082 (China); Fan Meilian [College of Chemistry and Chemical Engineering, Hunan University, Key Laboratory of Chemometrics and Chemical Biological Sensing Technologies, Ministry of Education, Changsha 410082 (China); Huang Caijuan [College of Chemistry and Chemical Engineering, Hunan University, Key Laboratory of Chemometrics and Chemical Biological Sensing Technologies, Ministry of Education, Changsha 410082 (China); Wu Hailong [College of Chemistry and Chemical Engineering, Hunan University, Key Laboratory of Chemometrics and Chemical Biological Sensing Technologies, Ministry of Education, Changsha 410082 (China); Chao Zisheng [College of Chemistry and Chemical Engineering, Hunan University, Key Laboratory of Chemometrics and Chemical Biological Sensing Technologies, Ministry of Education, Changsha 410082 (China)]. E-mail: zschao@yahoo.com; Zhai Hesheng [College of Chemistry and Chemical Engineering, Xiamen University, Xiamen 361005 (China)]. E-mail: hszhai@xmu.edu.cn

2006-11-09

104

Diode laser heat treatment of lithium manganese oxide films  

NASA Astrophysics Data System (ADS)

The crystallization of lithium manganese oxide thin films prepared by radio frequency magnetron sputtering on stainless steel substrates under 10 Pa argon pressure is demonstrated by a laser annealing technique. Laser annealing processes were developed as a function of annealing time and temperature with the objective to form an electrochemically active lithium manganese oxide cathode. It is demonstrated, that laser annealing with 940 nm diode laser radiation and an annealing time of 2000 s at 600 C delivers appropriate parameters for formation of a crystalline spinel-like phase. Characteristic features of this phase could be detected via Raman spectroscopy, showing the characteristic main Raman band at 627 cm-1. Within cyclic voltammetric measurements, the two characteristic redox pairs for spinel lithium manganese oxide in the 4 V region could be detected, indicating that the film was well-crystallized and de-/intercalation processes were reversible. Raman post-analysis of a cycled cathode showed that the spinel-like structure was preserved within the cycling process but mechanical degradation effects such as film cracking were observed via scanning electron microscopy. Typical features for the formation of an additional surface reaction layer could be detected using X-ray photoelectron spectroscopy.

Prll, J.; Kohler, R.; Mangang, A.; Ulrich, S.; Bruns, M.; Seifert, H. J.; Pfleging, W.

2012-04-01

105

Improved cycling performance of bismuth-modified amorphous manganese oxides as cathodes for rechargeable lithium batteries  

Microsoft Academic Search

Bismuth-modified amorphous manganese oxides were synthesized via a room temperature aqueous route. They were galvanostatically tested as intercalation cathodes for rechargeable lithium batteries at 1mAcm?2 between 1.5 and 4.3V. In sharp contrast to severe capacity fading of unmodified amorphous manganese oxide synthesized by the same route, a stable cycling performance of the bismuth-modified amorphous manganese oxide was observed. After an

Jingsi Yang; Terrill B Atwater; Jun John Xu

2005-01-01

106

Strontium and Actinides Removal from Savannah River Site Actual Waste Samples by Freshly Precipitated Manganese Oxide  

SciTech Connect

The authors investigated the performance of freshly precipitated manganese oxide and monosodium titanate (MST) for the removal of strontium (Sr) and actinides from actual high-level waste. Manganese oxide precipitation occurs upon addition of a reductant such as formate (HCO2-) or peroxide (H2O2) to a waste solution containing permanganate (MnO4-). Tests described in this document address the capability of manganese oxide treatment to remove Rs, Pu, and Np from actual high-level waste containing elevated concentrations of Pu. Additionally, tests investigate MST (using two unique batches) performance with the same waste for direct comparison to the manganese oxide performance.

Barnes, M.J.

2003-10-30

107

Manganese oxidation by spores and spore coats of a marine Bacillus species  

SciTech Connect

Bacillus sp. strain SG-1 is a marine bacterial species isolated from a near-shore manganese sediment sample. Its mature dormant spores promote the oxidation of Mn/sup 2 +/ to MnO/sub 2/. By quantifying the amounts of immobilized and oxidized manganese, it was established that bound manganese was almost instantaneously oxidized. When the final oxidation of manganese by the spores was partly inhibited by NaN/sub 3/ or anaerobiosis, an equivalent decrease in manganese immobilization was observed. After formation of a certain amount of MnO/sub 2/ by the spores, the oxidation rate decreased. A maximal encrustment was observed after which no further oxidation occurred. The oxidizing activity could be recovered by reduction of the MnO/sub 2/ with hydroxylamine. Once the spores were encrusted, they could bind significant amounts of manganese, even when no oxidation occurred. Purified spore coat preparations oxidized manganese at the same rate as intact spores. During the oxidation of manganese in spore coat preparations, molecular oxygen was consumed and protons were liberated. The data indicate that a spore coat component promoted the oxidation of Mn/sup 2 +/ in a biologically catalyzed process, after adsorption of the ion to incipiently formed MnO/sub 2/. Eventually, when large amounts of MnO/sub 2/ were allowed to accumulate the active sites were masked and further oxidation was prevented.

de Vrind, J.P.M.; de Vrind-de Jong, E.W.; de Voogt, J.W.H.; Westbroek, P.; Boogerd, F.C.; Rosson, R.A.

1986-11-01

108

Constraints on superoxide mediated formation of manganese oxides  

PubMed Central

Manganese (Mn) oxides are among the most reactive sorbents and oxidants within the environment, where they play a central role in the cycling of nutrients, metals, and carbon. Recent discoveries have identified superoxide (O2?) both of biogenic and abiogenic origin as an effective oxidant of Mn(II) leading to the formation of Mn oxides. Here we examined the conditions under which abiotically produced superoxide led to oxidative precipitation of Mn and the solid-phases produced. Oxidized Mn, as both aqueous Mn(III) and Mn(III/IV) oxides, was only observed in the presence of active catalase, indicating that hydrogen peroxide (H2O2), a product of the reaction of O2? with Mn(II), inhibits the oxidation process presumably through the reduction of Mn(III). Citrate and pyrophosphate increased the yield of oxidized Mn but decreased the amount of Mn oxide produced via formation of Mn(III)-ligand complexes. While complexing ligands played a role in stabilizing Mn(III), they did not eliminate the inhibition of net Mn(III) formation by H2O2. The Mn oxides precipitated were highly disordered colloidal hexagonal birnessite, similar to those produced by biotically generated superoxide. Yet, in contrast to the large particulate Mn oxides formed by biogenic superoxide, abiotic Mn oxides did not ripen to larger, more crystalline phases. This suggests that the deposition of crystalline Mn oxides within the environment requires a biological, or at least organic, influence. This work provides the first direct evidence that, under conditions relevant to natural waters, oxidation of Mn(II) by superoxide can occur and lead to formation of Mn oxides. For organisms that oxidize Mn(II) by producing superoxide, these findings may also point to other microbially mediated processes, in particular enzymatic hydrogen peroxide degradation and/or production of organic ligand metabolites, that allow for Mn oxide formation.

Learman, Deric R.; Voelker, Bettina M.; Madden, Andrew S.; Hansel, Colleen M.

2013-01-01

109

Improvement of lithium-containing manganese dioxide (composite dimensional manganese oxide: CDMO) as positive material for lithium secondary batteries  

Microsoft Academic Search

The paper describes the development of an improved lithium-containing manganese dioxide (composite dimensional manganese oxide, CDMO) as a positive material for lithium secondary batteries with high discharge voltage and capacity. It was found that CDMO charged to a high potential (i.e., 3.6 V compared with normal charge 3.3. V) exhibited a higher discharge voltage and a greater capacity. The optimum

T. Nohma; Y. Yamamoto; I. Nakane; N. Furukawa

1992-01-01

110

Rechargeable 3 V Li cells using hydrated lamellar manganese oxide  

SciTech Connect

The synthesis and the electrochemical features of hydrated lamellar manganese oxides are reported. The authors use the reduction of aqueous permanganate solution by fumaric acid and the oxidation of manganese hydroxide by an aqueous permanganate solution to obtain sol-gel birnessite and classical X-exchanged birnessites (X = Li, Al, Na), respectively. The high oxidation state of Mn associated with the 2D character of the hot lattice allows high specific capacities (150 to 200 Ah/kg) available in the potential range of 4 to 2 V. Interlayer water provides the structural stability of the host lattice required for long cycling. Rechargeable two-electrode Li cells using starved or flooded electrolytes were built with the cathodic materials. The batteries exhibit a satisfactory behavior with a specific capacity of 160 Ah/kg recovered after 30 cycles at the C/20 discharge-charge rate for the sol-gel birnessite. This paper demonstrates an interest in cathodic materials based on oxides containing structural water for use in secondary Li batteries.

Bach, S.; Pereira-Ramos, J.P. [CNRS, Thiais (France). Electrochimie, Catalyse et Synthese Organique; Baffier, N. [CNRS, Paris (France). Chimie Appliquee de l`Etat Solide

1996-11-01

111

Self-assembly of manganese oxide nanoparticles and hollow spheres. Catalytic activity in carbon monoxide oxidation.  

PubMed

Reactions between MnSO(4) and KMnO(4) in the presence of carboxylic acids provide a facile, one-pot route to nanostructured manganese oxides with high surface areas. Acetic and propionic acid induce formation of hierarchical nanosphere morphologies whereas butyric acid promotes assembly of hollow spheres. The materials are active catalysts for CO oxidation. PMID:21655565

Ching, Stanton; Kriz, David A; Luthy, Kurt M; Njagi, Eric C; Suib, Steven L

2011-06-07

112

Photoassisted catalytic oxidation of alcohols and halogenated hydrocarbons with amorphous manganese oxides  

Microsoft Academic Search

This manuscript discusses the synthesis of Amorphous Manganese Oxide (AMO) materials that are used for efficient photoassisted catalytic oxidation of alcohols and halogenated hydrocarbons. Characterization studies suggest that oxygen is lost from AMO very readily under illumination, creating oxygen vacancies that may be important in photooxidation reactions. Alcohols are converted to ketones such as acetone from isopropanol with 100% selectivity

Jie Chen; Jung Chou Lin; Vandana Purohit; Michael B. Cutlip; Steven L. Suib

1997-01-01

113

Platinum nanoparticlesmanganese oxide nanorods as novel binary catalysts for formic acid oxidation  

Microsoft Academic Search

The current study proposes a novel binary catalyst system (composed of metal\\/metal oxide nanoparticles) as a promising electrocatalyst in formic acid oxidation. The electro-catalytic oxidation of formic acid is carried out with binary catalysts of Pt nanoparticles (nano-Pt) and manganese oxide nanorods (nano-MnOx) electrodeposited onto glassy carbon (GC) electrodes. Cyclic voltammetric (CV) measurements showed that unmodified GC and nano-MnOx\\/GC electrodes

Mohamed S. El-Deab

114

The partition of vanadium and molybdenum between manganese oxides and sea water  

NASA Astrophysics Data System (ADS)

The partition of V and Mo between manganese oxides and sea water was investigated in the sea water supply system for aquaria at the Marine Science Museum, Tokai University, where both todorokite and birnessite are precipitated from aerated well sea water. The distribution coefficient of V was an order of magnitude higher than that of Mo. Assuming that the distribution coefficients can be applied to marine environments and that manganese oxides are precipitated from sea water, the calculated contents of these oxyanionic elements in manganese oxides were comparable to those in marine manganese nodules.

Takematsu, N.; Sato, Y.; Okabe, S.; Nakayama, E.

1985-11-01

115

The X-ray photoelectron spectroscopy of surface composition of aged mixed copper manganese oxide catalysts  

Microsoft Academic Search

A series of copper manganese oxide catalysts of approximate composition Cu1+xMn2?xO4 (x = 0.54 0.04), which was aged at various times and at different pH values, has been studied by X-ray photoelectron spectroscopy (XPS). In all cases, copper (II) and manganese (IV) are the only oxidation states. The copper\\/manganese concentration ratio exceeds the bulk value (0.5) at short ageing

Ali Akbar Mirzaei; Hamid Reza Shaterian; Massoud Kaykhaii

2005-01-01

116

Capacity fading of the acid-treated lithium manganese oxides in high-temperature storage  

Microsoft Academic Search

We have studied capacity fadings of acid-treated lithium manganese oxides in high-temperature storage. The amounts of dissolved lithium and manganese ions and consumed acids were determined in the reaction of lithium manganese oxides with acids. Discharge capacities of the acid-treated samples were measured and the small capacity fadings were observed. X-ray diffraction patterns of the acid-treated samples were almost the

Motoharu Saitoh; Shinichiro Yoshida; Hisayuki Yamane; Mitsuru Sano; Miho Fujita; Koichi Kifune; Yoshiki Kubota

2003-01-01

117

Manganese(III) Oxidation of Alanine in Aqueous Ethanoic Acid Medium: A Kinetic and Mechanistic Study  

Microsoft Academic Search

A stock solution of manganese(III) acetate in aqueous acetic acid has been prepared using a standard electrochemical method. The nature of the oxidizing species present in manganese(III) solutions has been characterized by spectrophotometric and redox potential measurements. Kinetics of oxidation of DL-alanine (Ala) by manganese(III) in aqueous acetic acid solution at 313 K have been investigated. The experimental rate law

C. S. Chidan Kumar; S. Chandraju; Netkal M. Made Gowda

2011-01-01

118

Manganese oxide composite electrodes for lithium batteries  

DOEpatents

An activated electrode for a non-aqueous electrochemical cell is disclosed with a precursor of a lithium metal oxide with the formula xLi.sub.2MnO.sub.3.(1-x)LiMn.sub.2-yM.sub.yO.sub.4 for 0

Thackeray, Michael M. (Naperville, IL); Johnson, Christopher S. (Naperville, IL); Li, Naichao (Croton on Hudson, NY)

2007-12-04

119

Manganese oxide composite electrodes for lithium batteries  

DOEpatents

An activated electrode for a non-aqueous electrochemical cell is disclosed with a precursor thereof a lithium metal oxide with the formula xLi.sub.2MnO.sub.3.(1-x)LiMn.sub.2-yM.sub.yO.sub.4 for 0.5

Johnson, Christopher S. (Naperville, IL); Kang, Sun-Ho (Naperville, IL); Thackeray, Michael M. (Naperville, IL)

2009-12-22

120

Lithiated manganese oxide cathodes for rechargeable lithium batteries  

Microsoft Academic Search

Lithiated manganese oxides LixMnyO2 prepared at the low temperature of 400-450C exhibited significantly different electrochemical properties than the spinel phase, LiMn2O4, formed at 650-850C. The former was nonstoichiometric and yielded a capacity of ~0.7 LiMn2 unit at ~2.8 V in polymer electrolyte-based Li cells. Its excellent rechargeability was demonstrated by more than 100 charge\\/discharge cycles. Spinel Li2Mn4 was formed by

K. M. Abraham; D. M. Pasquariello; T. H. Hguyen; Z. Jiang; D. Peramunage

1996-01-01

121

Chemical lithium extraction from manganese oxides for lithium rechargeable batteries  

Microsoft Academic Search

Chemical lithium extraction has been carried out on the following manganese oxides: the spinel-type compounds LiMn2O4 and Li(4\\/3)Mn(5\\/3)O4, and the rocksalt-related compound Li2MnO3. Lithium can be partially removed chemically from these compounds without destroying the host framework. Some compounds obtained by this method have been tested as cathodic materials in rechargeable lithium cells. Electrochemical results and X-ray diffraction patterns of

F. Lubin; A. Lecerf; M. Broussely; J. Labat

1991-01-01

122

Nanostructured lithium nickel manganese oxides for lithium-ion batteries  

Microsoft Academic Search

Nanostructured lithium nickel manganese oxides were investigated as advanced positive electrode materials for lithium-ion batteries designated to power plug-in hybrid electric vehicles and all-electric vehicles. The investigation included material characterization and electrochemical testing. In cell tests, the Li{sub 1.375}Ni{sub 0.25}Mn{sub 0.75}O{sub 2.4375} composition achieved high capacity (210 mAh g) at an elevated rate (230 mA g), which makes this material

Haixia Deng; Ilias Belharouak; Russel E. Cook; Huiming Wu; Yang-Kook Sun; Khalil Amine

2010-01-01

123

Giant magnetoresistance of manganese oxides with a layered perovskite structure  

NASA Astrophysics Data System (ADS)

MANGANESE oxides with the cubic perovskite structure (typified by LaMnO3) have stimulated considerable interest because of their magnetoresistive properties1-9 they exhibit extremely large changes in electrical resistance in response to applied magnetic fields, a property that is of technological relevance for the development of magnetic memory and switching devices. But for such applications to be viable, great improvements will be needed in both the sensitivity and temperature dependence of the magnetoresistive response. One approach under consideration for optimizing these properties is chemical substitution10. Here we demonstrate an alternative strategy, in which we synthesize layered variants of the cubic perovskite parent compounds that have a controlled number of MnO2 sheets per unit cell. This strategy is structurally analogous to that employed for the systematic exploration of the high-transition-temperature copper oxide superconductors11. We find that the magneto-resistive properties of these materials depend sensitively on the dimensionality of the manganese oxide lattice. Although the properties of our materials are still far from optimal, further exploration of this series of layered perovskites may prove fruitful.

Moritomo, Y.; Asamitsu, A.; Kuwahara, H.; Tokura, Y.

1996-03-01

124

Nanorods of manganese oxides: Synthesis, characterization and catalytic application  

SciTech Connect

Single-crystalline nanorods of {beta}-MnO{sub 2}, {alpha}-Mn{sub 2}O{sub 3} and Mn{sub 3}O{sub 4} were successfully synthesized via the heat-treatment of {gamma}-MnOOH nanorods, which were prepared through a hydrothermal method in advance. The calcination process of {gamma}-MnOOH nanorods was studied with the help of Thermogravimetric analysis and X-ray powder diffraction. When the calcinations were conducted in air from 250 to 1050 deg. C, the precursor {gamma}-MnOOH was first changed to {beta}-MnO{sub 2}, then to {alpha}-Mn{sub 2}O{sub 3} and finally to Mn{sub 3}O{sub 4}. When calcined in N{sub 2} atmosphere, {gamma}-MnOOH was directly converted into Mn{sub 3}O{sub 4} at as low as 500 deg. C. Transmission electron microscopy (TEM) and high-resolution TEM were also used to characterize the products. The obtained manganese oxides maintain the one-dimensional morphology similar to the precursor {gamma}-MnOOH nanorods. Further experiments show that the as-prepared manganese oxide nanorods have catalytic effect on the oxidation and decomposition of the methylene blue (MB) dye with H{sub 2}0009O.

Yang Zeheng [School of Chemical Engineering, Hefei University of Technology, Hefei, Anhui 230009 (China); Zhang Yuancheng [School of Chemical Engineering, Hefei University of Technology, Hefei, Anhui 230009 (China); Zhang Weixin [School of Chemical Engineering, Hefei University of Technology, Hefei, Anhui 230009 (China)]. E-mail: wxzhang@hfut.edu.cn; Wang Xue [School of Chemical Engineering, Hefei University of Technology, Hefei, Anhui 230009 (China); Qian Yitai [School of Chemical Engineering, Hefei University of Technology, Hefei, Anhui 230009 (China); Wen Xiaogang [Department of Chemistry and Institute of Nano Science and Technology, Hong Kong University of Science and Technology, Clear Water Bay, Kowloon, Hong Kong (China); Yang Shihe [Department of Chemistry and Institute of Nano Science and Technology, Hong Kong University of Science and Technology, Clear Water Bay, Kowloon, Hong Kong (China)]. E-mail: chsyang@ust.hk

2006-03-15

125

New Vanadium and Manganese Oxides for Lithium Batteries  

NASA Astrophysics Data System (ADS)

Transition metal oxides, that can intercalate lithium ions in a reversible manner and with an energy in the range of 3 to 4 volts, are a critical link in the advancement of high energy density lithium batteries. Vanadium, manganese and iron oxides form the appropriate polyhedral structures that might intercalate small ions. Such structures have been formed at low temperatures under conditions of kinetic rather than thermodynamic control. In the case of vanadium six new compounds have been formed using the tetramethylammonium ion, TMA, as the structure directing agent. One of these is a new form of vanadium dioxide, a perfect form of the vanadium pentoxide structure, which is electrochemically active and can intercalate a wide range of molecular and ionic species. Others contain the TMA cation and have layered lattices. A new magnetically active form of nickel manganate has also been synthesized, as have several layered alkali metal manganese oxides with the titanium disulfide type lattice. Their structural characterization and property determination will be described. Supported by NSF-DMR.

Whittingham, M. Stanley; Zavalij, Peter Y.; Chirayil, Thomas; Chen, Rongji

1997-03-01

126

Manganese sulfide formation via concomitant microbial manganese oxide and thiosulfate reduction.  

PubMed

The dissimilatory metal-reducing bacterium, Shewanella oneidensis MR-1 produced ?-MnS (rambergite) nanoparticles during the concurrent reduction of MnO? and thiosulfate coupled to H? oxidation. To investigate effect of direct microbial reduction of MnO? on MnS formation, two MR-1 mutants defective in outer membrane c-type cytochromes (?mtrC/?omcA and ?mtrC/?omcA/?mtrF) were also used and it was determined that direct reduction of MnO? was dominant relative to chemical reduction by biogenic sulfide generated from thiosulfate reduction. Although bicarbonate was excluded from the medium, incubations of strain MR-1 with lactate as the electron donor produced MnCO? (rhodochrosite) as well as MnS in nearly equivalent amounts as estimated by micro X-ray diffraction (micro-XRD) analysis. It was concluded that carbonate released from lactate metabolism promoted MnCO? formation and that Mn(II) mineralogy was strongly affected by carbonate ions even in the presence of abundant sulfide and weakly alkaline conditions expected to favour the precipitation of MnS. Formation of MnS, as determined by a combination of micro-XRD, transmission electron microscopy, energy dispersive X-ray spectroscopy, and selected area electron diffraction analyses was consistent with equilibrium speciation modelling predictions. Biogenic manganese sulfide may be a manganese sink in the Mn biogeochemical cycle in select environments such as deep anoxic marine basins within the Baltic Sea. PMID:21951417

Lee, Ji-Hoon; Kennedy, David W; Dohnalkova, Alice; Moore, Dean A; Nachimuthu, Ponnusamy; Reed, Samantha B; Fredrickson, James K

2011-09-27

127

Synchrotron-Based Studies of Manganese Oxide Biomineralization  

NASA Astrophysics Data System (ADS)

Natural Mn oxide colloids and grain coatings are ubiquitous in the environment and profoundly impact the quality of soils and soil solutions via their ability to degrade and sequester contaminants. These oxides are generated via oxidation of Mn(II) by freshwater and marine bacteria and have extremely high sorptive capacities for heavy metals. Mn oxides readily oxidize a variety of recalcitrant organic and inorganic compounds. The mechanism(s) and products of bacterial Mn(II) oxidtion are therefore believed to have deep and wide-ranging roles in the environmental cycling of trace metals, organics, and carbon. We have utilized X-ray absorption spectroscopy (XAS) and synchrotron-based in-situ transmission XRD (SR-XRD) to probe the structure of fully hydrated biogenic manganese oxides produced by spores of the marine bacterium, Bacillus spp., strain SG-1. Biogenic oxides were produced in the absence and then presence of co-metal solutes Co(II), which have high affinities for Mn oxides, but present contrasting redox proerties and coordination chemistries, thus providing greater probe capability. The primary biogenic product is a poorly crystalline solid similar to delta MnO2 in which Mn has an oxidation state close to 4+. The structure of the oxide is analogous to acid birnessite, but with fewer layer vacancies and greater local order around Mn(IV). Co(II) is oxidizied to Co(III) and incorporated at Mn(IV) sites in the octahedral layer. The presence of Co(III) alters the stability and structure of the host Mn oxides. This observation, combined with the very high sorptive capacity of the Mn oxides, imply that bacteria can exert tremendous influence over Co cycling in impacted waters via Mn oxide biomineralization.

Webb, S. M.; Bargar, J. R.; Tebo, B. M.

2002-12-01

128

Nanostructured amorphous manganese oxide cryogel as a high-rate lithium intercalation host  

Microsoft Academic Search

Amorphous manganese oxides have received increasing attention in recent years as high-capacity intercalation cathodes for rechargeable lithium batteries. Nanostructured electrodes have been shown to exhibit enhanced rate capabilities. In this paper, a nanostructured amorphous manganese oxide cryogel is reported that combines the advantages of the amorphous structure and the nano-architecture, leading to high lithium intercalation capacity and high rate capability.

Jun John Xu; Jingsi Yang

2003-01-01

129

Population Structure of Manganese-Oxidizing Bacteria in Stratified Soils and Properties of Manganese Oxide Aggregates under Manganese-Complex Medium Enrichment.  

PubMed

Manganese-oxidizing bacteria in the aquatic environment have been comprehensively investigated. However, little information is available about the distribution and biogeochemical significance of these bacteria in terrestrial soil environments. In this study, stratified soils were initially examined to investigate the community structure and diversity of manganese-oxidizing bacteria. Total 344 culturable bacterial isolates from all substrata exhibited Mn(II)-oxidizing activities at the range of 1 M to 240 M of the equivalent MnO2. The high Mn(II)-oxidizing isolates (>50 mM MnO2) were identified as the species of phyla Actinobacteria, Firmicutes and Proteobacteria. Seven novel Mn(II)-oxidizing bacterial genera (species), namely, Escherichia, Agromyces, Cellulomonas, Cupriavidus, Microbacterium, Ralstonia, and Variovorax, were revealed via comparative phylogenetic analysis. Moreover, an increase in the diversity of soil bacterial community was observed after the combined enrichment of Mn(II) and carbon-rich complex. The phylogenetic classification of the enriched bacteria represented by predominant denaturing gradient gel electrophoresis bands, was apparently similar to culturable Mn(II)-oxidizing bacteria. The experiments were further undertaken to investigate the properties of the Mn oxide aggregates formed by the bacterial isolates with high Mn(II)-oxidizing activity. Results showed that these bacteria were closely encrusted with their Mn oxides and formed regular microspherical aggregates under prolonged Mn(II) and carbon-rich medium enrichment for three weeks. The biotic oxidation of Mn(II) to Mn(III/IV) by these isolates was confirmed by kinetic examinations. X-ray diffraction assays showed the characteristic peaks of several Mn oxides and rhodochrosite from these aggregates. Leucoberbelin blue tests also verified the Mn(II)-oxidizing activity of these aggregates. These results demonstrated that Mn oxides were formed at certain amounts under the enrichment conditions, along with the formation of rhodochrosite in such aggregates. Therefore, this study provides insights into the structure and diversity of soil-borne bacterial communities in Mn(II)-oxidizing habitats and supports the contribution of soil-borne Mn(II)-oxidizing bacteria to Mn oxide mineralization in soils. PMID:24069232

Yang, Weihong; Zhang, Zhen; Zhang, Zhongming; Chen, Hong; Liu, Jin; Ali, Muhammad; Liu, Fan; Li, Lin

2013-09-12

130

Population Structure of Manganese-Oxidizing Bacteria in Stratified Soils and Properties of Manganese Oxide Aggregates under Manganese-Complex Medium Enrichment  

PubMed Central

Manganese-oxidizing bacteria in the aquatic environment have been comprehensively investigated. However, little information is available about the distribution and biogeochemical significance of these bacteria in terrestrial soil environments. In this study, stratified soils were initially examined to investigate the community structure and diversity of manganese-oxidizing bacteria. Total 344 culturable bacterial isolates from all substrata exhibited Mn(II)-oxidizing activities at the range of 1 M to 240 M of the equivalent MnO2. The high Mn(II)-oxidizing isolates (>50 mM MnO2) were identified as the species of phyla Actinobacteria, Firmicutes and Proteobacteria. Seven novel Mn(II)-oxidizing bacterial genera (species), namely, Escherichia, Agromyces, Cellulomonas, Cupriavidus, Microbacterium, Ralstonia, and Variovorax, were revealed via comparative phylogenetic analysis. Moreover, an increase in the diversity of soil bacterial community was observed after the combined enrichment of Mn(II) and carbon-rich complex. The phylogenetic classification of the enriched bacteria represented by predominant denaturing gradient gel electrophoresis bands, was apparently similar to culturable Mn(II)-oxidizing bacteria. The experiments were further undertaken to investigate the properties of the Mn oxide aggregates formed by the bacterial isolates with high Mn(II)-oxidizing activity. Results showed that these bacteria were closely encrusted with their Mn oxides and formed regular microspherical aggregates under prolonged Mn(II) and carbon-rich medium enrichment for three weeks. The biotic oxidation of Mn(II) to Mn(III/IV) by these isolates was confirmed by kinetic examinations. X-ray diffraction assays showed the characteristic peaks of several Mn oxides and rhodochrosite from these aggregates. Leucoberbelin blue tests also verified the Mn(II)-oxidizing activity of these aggregates. These results demonstrated that Mn oxides were formed at certain amounts under the enrichment conditions, along with the formation of rhodochrosite in such aggregates. Therefore, this study provides insights into the structure and diversity of soil-borne bacterial communities in Mn(II)-oxidizing habitats and supports the contribution of soil-borne Mn(II)-oxidizing bacteria to Mn oxide mineralization in soils.

Zhang, Zhongming; Chen, Hong; Liu, Jin; Ali, Muhammad; Liu, Fan; Li, Lin

2013-01-01

131

Oxidation of propylene on cobalt-manganese spinels with lithium, titanium, and copper oxides added  

Microsoft Academic Search

1.Adding oxides of lithium, titanium, and copper to samples of straight and reverse cobalt-manganese spinels does not change the direction of deep propylene oxidation nor does it change the form of the kinetic law.2.With spinels containing additives as well as with pure samples, the oxidation rate is observed to vary in the same way as the oxygen chemisorption rate.3.Adding lithium

V. R. Linde; L. Ya. Margolis

1962-01-01

132

Oxidation kinetics of manganese (II) in seawater at nanomolar concentrations  

NASA Astrophysics Data System (ADS)

Manganese oxidation rates were determined at low ( 20 nM) concentrations in seawater by measuring dissolved manganese (Mn(II)) using flow injection analysis with chemiluminescence detection. Mn(II) was measured in samples that had been filtered (0.2 ?m) and kept in the dark under controlled temperature and pH conditions for time periods up to 6 months. Eight 9 L carboys with mean pH values ranging from 8 to 8.7 were held at 25C, another carboy (pH = 9.32) was kept at 5C. Oxidation followed the Morgan (1967) homogeneous rate equation ( d[Mn(II)]/ dt = k1 [O 2][OH -] 2[Mn(II)]). The mean rate constant k1 = 1.7 0.7 10 12 M -3 d -1 (95% CI), determined using hydroxide ion activities determined with pH measurements on the NBS scale, was in agreement with work by Morgan (1967; k1 = 4 10 12 M -3 d -1) and Davies and Morgan (1989; k1 = 1.1 10 12 M -3 d -1) in dilute solutions. The rate constant at 5C was 1.3 0.3 10 12 M -3 d -1. If free hydroxide concentrations (based on the free proton pH scale) are used, then the rate constant at 25C was k 1? = 0.34 0.14 10 12 M -3d -1. Autocatalytic increases in Mn(II) oxidation rates, as predicted by a heterogeneous reaction mechanism (Morgan, 1967) ( d[Mn(II)]/ dt= k2'[Mn(II)][MnO 2]) were not observed, indicating that the homogeneous reaction dominates Mn(II) oxidation at low nM concentrations in seawater. Bacteria were enumerated by 4',6-diamidino-2-phenylindole (DAPI) staining during the experiments. No significant correlation between bacterial concentrations and Mn(II) oxidation rates was found.

von Langen, Peter J.; Johnson, Kenneth S.; Coale, Kenneth H.; Elrod, Virginia A.

1997-12-01

133

Influence of synthesis conditions on the electrochemical properties of nanostructured amorphous manganese oxide cryogels  

Microsoft Academic Search

Amorphous manganese oxides have received increasing attention in recent years as intercalation cathodes for rechargeable lithium batteries. The solgel method is a versatile method for achieving nanostructured amorphous oxides. In this paper, two different solgel routes are investigated, where nanostructured amorphous manganese oxide cryogels are obtained via freeze drying Mn(IV) oxide hydrogels formed in situ. In one route the hydrogels

Jingsi Yang; Jun John Xu

2003-01-01

134

Chromite oxidation by manganese oxides in subseafloor basalts and the presence of putative fossilized microorganisms  

PubMed Central

Chromite is a mineral with low solubility and is thus resistant to dissolution. The exception is when manganese oxides are available, since they are the only known naturally occurring oxidants for chromite. In the presence of Mn(IV) oxides, Cr(III) will oxidise to Cr(VI), which is more soluble than Cr(III), and thus easier to be removed. Here we report of chromite phenocrysts that are replaced by rhodochrosite (Mn(II) carbonate) in subseafloor basalts from the Koko Seamount, Pacific Ocean, that were drilled and collected during the Ocean Drilling Program (ODP) Leg 197. The mineral succession chromite-rhodochrosite-saponite in the phenocrysts is interpreted as the result of chromite oxidation by manganese oxides. Putative fossilized microorganisms are abundant in the rhodochrosite and we suggest that the oxidation of chromite has been mediated by microbial activity. It has previously been shown in soils and in laboratory experiments that chromium oxidation is indirectly mediated by microbial formation of manganese oxides. Here we suggest a similar process in subseafloor basalts.

2011-01-01

135

Porous manganese oxide octahedral molecular sieves and octahedral layered materials.  

PubMed

This Account first gives a historical overview of the development of octahedral molecular sieve (OMS) and octahedral layer (OL) materials based on porous mixed-valent manganese oxides. Unique properties of such systems include excellent semiconductivity and porosity. Materials that are conducting and porous are rare and can offer novel properties not normally available with most molecular sieve materials. The good semiconductivity of OMS and OL systems not only permits potential applications of the conductivity of these materials but also allows characterization of these systems where charging effects are often a problem. Porous manganese oxide natural materials are found as manganese nodules, and these materials when dredged from the ocean floors have been used as excellent adsorbents of metals such as from electroplating wastes and have been shown to be excellent catalysts. Rational for synthesis of novel OMS and OL materials is related to the superb conductivity, microporosity, and catalytic activity of these natural materials. The natural systems are often found as mixtures, are poorly crystalline, and have incredibly diverse compositions due to exposure to various aqueous environments in nature. Such exposure allows ion exchange to occur. Preparation of pure crystalline OL and OMS systems is one of the very significant goals of this work. The status of this research area is one of moderate development. Opportunities exist for preparation of a multitude of novel materials. Some applications of these materials have recently been achieved primarily in the area of catalysis and membranes, and others such as sensors and adsorptive systems are likely. Characterization studies are becoming more sophisticated as new materials and proper preparation of materials for such characterization studies are being done. The research area involved in this work is solid state chemistry. The fields of materials synthesis, characterization, and applications of materials are all important in developments of this field. Researchers in chemistry, chemical engineering, materials science, physics, and biological sciences are actively pursuing research in this area. The most significant results found in this work are related to the novel structural and physical properties of porous manganese oxide materials. Variable pore size materials have been synthesized using structure directors and with a variety of synthetic methodologies. Transformations of tunnel materials with temperature and in specific atmosphere have recently been studied with in situ synchrotron methods. Conductivities of these materials appear to be related to the structural properties of these systems with more open structures being less conductive. Catalytic properties of these OMS and OL materials have been shown to be related to the redox cycling of various oxidations states of manganese such as Mn2+, Mn3+, and Mn4+. Chemists interested in synthesis of new materials, the chemistry of solids, enhancing the rates of catalytic reactions, and finding new applications of materials would be interested in these novel materials. Fundamental properties of electron transfer are critical to this research. Concepts of nonstoichiometry, defects, oxygen vacancies, and intermediates are fundamental to many of the syntheses, characterization, and applications such as fuel cells, catalysis, adsorption, sensors, batteries, and related applications. PMID:18232663

Suib, Steven L

2008-01-31

136

Oxidation of As(III) by Hydrous Manganese Oxide: Effect of Carbonate  

Microsoft Academic Search

The mobility of arsenic in aquatic environment is largely governed by its speciation and adsorption on the surfaces of minerals. Hydrous manganese oxide (HMO) plays an important role in redox transformation of arsenic in aquatic environment and is available for remedy of groundwater with high arsenic concentration. Carbonate is often present as major anion in groundwater and its influence on

Zhixi Zhao; Shanlin Zhao; Yongfeng Jia

2011-01-01

137

Nickel and Lead Sequestration in Manganese Oxide-coated Montmorillonite  

SciTech Connect

Amorphous hydrous manganese oxide (HMO) is an important mineral in soils and sediments influencing the mobility and bioavailability of metal contaminants. In this study, nickel and lead sorption to discrete HMO and HMO-coated montmorillonite was investigated mechanistically. The effect of pH and concentration revealed that when normalized to the mass of oxide present, the HMO-coated montmorillonite behaved similarly to the discrete Mn oxide, where both ions sorbed onto HMO-coated montmorillonite as inner-sphere complexes. Ni coordinated to the vacancy sites in the Mn oxide structure, while Pb formed bidentate corner-sharing complexes. These coordination environments were observed not only as a function of loading, pH, and ionic strength, but also in long-term studies where sorption increased by as much as 100% (from 6 x 10{sup -4} to 1.2 x 10{sup -3} mol Ni/g HMO-coated montmorillonite). In this slower sorption process, intraparticle diffusion, the internal surface sites along microporous walls appear to be no different than external ones. Best fit diffusivities ranged from 10{sup -12} to 10{sup -13} cm{sup 2}/s for Ni and 10{sup -17} to 10{sup -20} cm{sup 2}/s for Pb. The significant difference in the diffusivities for the two ions is consistent with site activation theory, where theoretical surface diffusivities were predicted and given their error were in agreement with experimental results. Mn oxides sequester heavy metals in the environment.

Boonfueng,T.; Axe, L.; Xu, Y.; Tyson, T.

2006-01-01

138

Speciation, oxidation state, and reactivity of particulate manganese in marine sediments  

Microsoft Academic Search

Particulate manganese oxides take a significant part in benthic biogeochemical processes of modern marine sediments. Thermodynamics calculations tell us that the reactivity of the different Mn oxides is variable. We describe here a method adapted for marine sediments, which allowed us to extract Mn oxides and determine the mean oxidation state of particulate Mn. Mn oxides are known to be

Pierre Anschutz; Karine Dedieu; Franck Desmazes; Gwnalle Chaillou

2005-01-01

139

INVESTIGATIONS OF HUMIDITY PROPERTIES OF ON INDIUM OXIDE THIN FILMS COATED QUARTZ CRYSTAL MICROBALANCES  

Microsoft Academic Search

Indium oxide thin films prepared by the chemical solution-based process had been investigated for humidity sensing application. The physical properties of thin films have been first characterized by various techniques such as scanning electron microscopy (SEM) to obtain morphological information of the layers. Humidity sensors were featured by combination of quartz crystals as transducers and indium oxide thin films as

Leping Chen; Jian Zhang; X H Zhai; J Y Lu

2012-01-01

140

Redox behavior of the nickel oxide electrode system: quartz crystal microbalance studies  

Microsoft Academic Search

The electrochemical reactions occurring in the nickel oxide electrode system have been studied with the quartz crystal microbalance. Following cathodic deposition from nickel sulfate solutions, ?-nickel hydroxide films were cycled in 1.0M alkali metal hydroxide solutions. The oxidation process produced frequency decreases in these solutions, indicating a corresponding increase in mass in the electrode layer. Upon subsequent reduction, a return

Graham T. Cheek; William E. O'Grady

1997-01-01

141

Comparative evaluation of oxidative stress status and manganese availability in plants growing on manganese mine.  

PubMed

This study pioneered an approach that determined the effects of excess manganese (Mn) on three species; Datura stramonium, Alhagi camelthorn and Chenopodium ambrosioides. We investigated their levels of Mn, antioxidative enzymes and oxidative damage biomarkers in plants (zone 1) in and outside (zone 2) the Mn mine. The results showed that total and available Mn were at toxic levels for plants growing on zone 1. The Mn levels in each plant species were higher in leaves, stems and roots. Mn was only accumulated significantly in leaf vacuoles of A. camelthorn. Antioxidative enzyme activities of C. ambrosioides and/or D. stramonium in zone 1 were higher in leaves, stems and then in their roots. Malondialdehyde (MDA) and dityrosine levels were insignificantly higher in tissues of the studied plants in zone 1 with respect to zone 2. The roots of studied plants showed significantly higher levels of these biomarkers in comparison with their leaves in zone 1. Accordingly, antioxidative enzymatic response to Mn-stress in D. stramonium and C. ambrosioides and possibly accumulation of Mn in leaf vacuoles of A. camelthorn, protected them from oxidative damages and involved in their tolerance in Mn mine. PMID:18068229

Boojar, Massod Mashhadi Akbar; Goodarzi, Faranak

2007-12-18

142

Green Oxidations. Manganese(II) Sulfate Aided Oxidations of Organic Compounds by Potassium Permanganate  

Microsoft Academic Search

Summary.The oxidation of arenes and sulfides by potassium permanganate was accomplished in good yields under solvent free and heterogeneous\\u000a conditions when manganese(II) sulfate is used as a solid support. After extraction of the organic products, the inorganic\\u000a products can be reoxidized to permanganate. This result is important because it provides an approach to oxidation reactions\\u000a that is, in theory, infinitely

Ahmad Shaabani; Abbas Rahmati; Masoumeh Sharifi; Jafar Mogimi Rad; Behnaz Aghaaliakbari; Elham Farhangi; Donald G. Lee

2007-01-01

143

Nanostructured manganese oxide particles from coordination complex decomposition and their catalytic properties for ethanol oxidation.  

PubMed

Novel manganese oxide particles with complex morphologies and different nanostructures (i.e., spherical/lamellar) were synthesized by initial preparation of a coordination complex of manganese with 1,4,7,10-tetraazacyclododecane (cyclen), followed by characterization of the nanostructured oxide as a catalytic material for ethanol oxidation. The samples present a bulk gamma-MnO2 structure although X-ray photoelectron spectroscopy analysis reveals that their surfaces have different chemical compositions. Some of these nanostructured particles show high catalytic activities for ethanol oxidation enabling a decrease of the reaction temperature by more than 80 degrees C as compared with traditional MnO2 particles. The high catalytic activity of the particles depends on their morphology and a relationship between morphology and specific area was established. It is proposed that these novel nanostructured manganese oxide particles may be highly active in the catalytic oxidation of other volatile organic compounds (VOCs) opening up their further development for environmental applications. PMID:23421183

Palza, Humberto; Maturana, Andrs; Gracia, Francisco; Neira, Andrnico; Fuenzalida, Victor M; Avila, Jonathan; Sanchez-Ballester, Noelia M; Elsegood, Mark R J; Teat, Simon J; Ariga, Katsuhiko; Hill, Jonathan P

2012-10-01

144

Deuterium and lithium-6 MAS NMR studies of manganese oxide electrode materials  

Microsoft Academic Search

Electrolytic manganese dioxide (EMD) is used world wide as the cathode materials in both lithium and alkaline primary (non-rechargeable) batteries. We have developed deuterium and lithium MAS NMR techniques to study EMD and related manganese oxides and hydroxides, where diffraction techniques are of limited value due to a highly defective nature of the structures. Deuterons in EMD, manganite, groutite, and

Younkee Paik

2003-01-01

145

Chemical lithium extraction from manganese oxides for lithium rechargeable batteries  

NASA Astrophysics Data System (ADS)

Chemical lithium extraction has been carried out on the following manganese oxides: the spinel-type compounds LiMn2O4 and Li(4/3)Mn(5/3)O4, and the rocksalt-related compound Li2MnO3. Lithium can be partially removed chemically from these compounds without destroying the host framework. Some compounds obtained by this method have been tested as cathodic materials in rechargeable lithium cells. Electrochemical results and X-ray diffraction patterns of cycled cathodes are presented. Electrochemical insertion/extraction of Li(+) ions occurs with tetragonal/cubic distortion in the spinel framework, whereas Li(+) ions can move in compounds having the rocksalt structure, without significant modification of the X-ray patterns.

Lubin, F.; Lecerf, A.; Broussely, M.; Labat, J.

1991-03-01

146

Improvement of lithium-containing manganese dioxide (composite dimensional manganese oxide: CDMO) as positive material for lithium secondary batteries  

NASA Astrophysics Data System (ADS)

The paper describes the development of an improved lithium-containing manganese dioxide (composite dimensional manganese oxide, CDMO) as a positive material for lithium secondary batteries with high discharge voltage and capacity. It was found that CDMO charged to a high potential (i.e., 3.6 V compared with normal charge 3.3. V) exhibited a higher discharge voltage and a greater capacity. The optimum conditions for preparing improved CDMO include heat treatment (at about 250 C) of LiOH and electrolytic manganese dioxide at a Li/Li + Mn atomic ratio of 0.3. The improved CDMO exhibits a discharge capacity of over 200 A h/g, and excellent rechargeability.

Nohma, T.; Yamamoto, Y.; Nakane, I.; Furukawa, N.

1992-06-01

147

Manganese catalyst of oxidation of water attached to a bilayer lipid membrane  

SciTech Connect

The authors examine the oxygen-releasing behavior of photosynthetic lipid membranes in plants during the photooxidation of water under the influence of a manganese oxide catalyst and in the presence of a ruthenium dipyridyl oxidizer. The mechanism of catalysis consists of the oxidation of manganese ions and the subsequent oxidation of water by high-valence manganese oxides. The kinetics involved in the attachment of the reactants to the lipid vesicle are investigated using the oxygen 18 isotope. The isotopic composition of the water and the liberated oxygen indicated that oxygen is generated from water on the manganese catalyst in the presence of vesicles. The import of the results for solar energy conversion is cited.

Knerel'man, E.I.; Luneva, N.P.; Shafirovich, V.Ya.; Shilov, A.E.

1987-05-01

148

Synthesis and characterization of cobaltmanganese oxides  

NASA Astrophysics Data System (ADS)

Cobalt doped/un-doped manganese oxides materials were synthesized at various doping rates by soft chemical reactions, oxidation-reduction method, which allows generating a metal-mixed oxide. The synthesized materials were characterized using several techniques including chemical analysis, X-rays diffraction (XRD), scanning electron microscopy (SEM), thermogravimetric analysis (TGA), and vibrating sample magnetometer (VSM). The chemical analysis confirmed the presence of cobalt in the samples. XRD patterns reveal mainly a spinel-like structure and SEM micrographs exhibited morphology with fine aggregate of particles. TGA profiles showed weight loss due to loss of water in a first step, followed by a loss of oxygen from the lattice associated with partial reduction of Mn4+ to Mn3+. VSM was used to measure the magnetization as a function of the applied magnetic field at temperatures T=50 and 300 K. Different magnetic behaviors were observed when cobalt percentage changed in the samples. These behaviors are considered to be related to the size of the particles and composition of the materials. Higher coercive field and lesser magnetization were observed for the sample with higher cobalt content.

Valencia, J.; Arias, N. P.; Giraldo, O.; Rosales-Rivera, A.

2012-08-01

149

Oxidation of phenolic acids by soil iron and manganese oxides  

Microsoft Academic Search

Phenolic acids are intermediary metabolites of many aromatic chemicals and may be involved in humus formation, allelopathy, and nutrient availability. Depending on their structures, six phenolic acids were shown to react at different rates with oxidized forms of Fe and Mn in a Palouse soil (fine-silty, mixed, mesic Pachic Ultic Haploxeroll). Increasing methoxy substitution on the aromatic ring of phenolic

R. G. Lehmann; H. H. Cheng; J. B. Harsh

2008-01-01

150

Hydrogen peroxide decomposition on manganese oxide (pyrolusite): Kinetics, intermediates, and mechanism  

Microsoft Academic Search

The objective of this study is the kinetic interpretation of hydrogen peroxide decomposition on manganese oxide (pyrolusite) and the explanation of the reaction mechanism including the hydroperoxide\\/superoxide anion. The decomposition of hydrogen peroxide on manganese oxide at pH 7 was represented by a pseudo first-order model. The maximum value of the observed first-order rates constants (kobs) was 0.741min?1 at 11.8

Si-Hyun Do; Bill Batchelor; Hong-Kyun Lee; Sung-Ho Kong

2009-01-01

151

Chemical Mechanical Polishing for Oxygen Free Copper with Manganese Oxide Abrasives  

Microsoft Academic Search

The purpose of this study is to make clear the polishing characteristics of the manganese oxide slurry for wire material of Cu. To examine the polishing characteristics of the manganese oxide slurry, a series of polishing experiments for oxygen free copper have been carried out by using MnO2, Mn2O3 and Al2O3 as abrasive grains and polishing properties have been discussed.

Ryunosuke Sato; Yoshio Ichida; Yoshitaka Morimoto; Kenji Shimizu

2008-01-01

152

Strontium and Actinides Removal from Savannah River Site Actual Waste Samples by Freshly Precipitated Manganese Oxide  

Microsoft Academic Search

The authors investigated the performance of freshly precipitated manganese oxide and monosodium titanate (MST) for the removal of strontium (Sr) and actinides from actual high-level waste. Manganese oxide precipitation occurs upon addition of a reductant such as formate (HCO2-) or peroxide (H2O2) to a waste solution containing permanganate (MnO4-). An addition of non-radioactive strontium typically precedes the MnO4- and reductant

2002-01-01

153

Investigations of lithium manganese oxide materials for lithium-ion batteries  

Microsoft Academic Search

As candidates for cathode materials in lithium-ion batteries, lithium manganese oxides are attractive and competitive. In this work, the feasibility of using a novel manganese oxide with a large-tunnel structure (i.e. todorokite, tunnel size: 3 3) as cathode material in lithiumion batteries has been explored. It is found that the initial capacity of todorokite material with Mg2+ in the

Y. Yang; D. Shu; H. Yu; X. Xia; Z. G. Lin

1997-01-01

154

Electrochromic properties of manganese oxide thin films prepared by chemical vapor deposition  

SciTech Connect

Electrochromic manganese oxide thin films were prepared by chemical vapor deposition. The source material was manganese (III) acetylacetonate. Transparent Mn{sub 3}O{sub 4} thin films were obtained at a substrate temperature above 250 C. Oxidation and reduction of the films in a 0.3 M LiClO{sub 4} propylene carbonate solution resulted in desirable changes in optical absorption. Coulometry indicated that the coloration efficiency was 6.03 cm{sup 2}/C.

Maruyama, Toshiro; Osaki, Yoshinori [Kyoto Univ. (Japan). Dept. of Chemical Engineering

1995-09-01

155

Lithium manganese oxideconductive carbon nanocomposite cathodes for rechargeable lithium batteries  

Microsoft Academic Search

A nanostructured lithium manganese oxide (LixMnOz) synthesized by reducing lithium permanganate with methanol in presence of lithium hydroxide has been mixed with conductive carbon in two different ways: ball milling and mixing in a mortar and pestle. The manganese oxideconductive carbon composite cathodes thus obtained are characterized by electrochemical dischargecharge, density, and BrunauerEmmettTeller (BET) surface area measurements as well as

D. Im; A. Manthiram

2003-01-01

156

Rapid discharge performance of composite electrode of hydrated sodium manganese oxide and acetylene black  

Microsoft Academic Search

Hydrated sodium manganese oxide was synthesized by reducing permanganate ion using ethanol by a solgel method. By including acetylene black in the synthetic reaction, we obtained composite materials in which sodium manganese oxide hydrate particles were small and mixed well with the acetylene black. We evaluated those composites as a lithium battery cathode and found that they showed 170mAhg?1 under

Mitsuhiro Hibino; Hirokazu Kawaoka; Haoshen Zhou; Itaru Honma

2004-01-01

157

Catalytic graphitization of PAN-based carbon fibers by spontaneously deposited manganese oxides  

Microsoft Academic Search

A simple method for the spontaneous deposition of manganese oxides on the surface of polyacrylonitrile (PAN)-based carbon\\u000a fibers by a direct redox reaction between carbon fibers and permanganate ions is described. Catalytic graphitization of the\\u000a PAN-based carbon fibers coated with manganese oxides was investigated by X-ray diffraction, Raman spectroscopy, and scanning\\u000a electron microscopy. The results indicate that the graphitization of

Shoujun Yi; Chao Wu; Zhen Fan; Yafei Kuang; Jinhua Chen

2009-01-01

158

Removal of Arsenate from Aqueous Solution by Manganese and Iron (hydr)oxides Coated Resin  

Microsoft Academic Search

A composite adsorbent MIR, manganese and iron (hydr)oxides coated resin, was prepared by coating manganese and iron (hydr)oxides onto the weak basic anion exchange resin D301. The effects of solution pH, contact time, ionic strength, and coexisting ions on arsenate removal with MIR were investigated in batch experiments. The results showed that As(V) can be effectively removed in a wide

Hongmei Ma; Zhiliang Zhu; Lijing Dong; Yanling Qiu; Jianfu Zhao

2010-01-01

159

Carbon-supported manganese oxide nanocatalysts for rechargeable lithiumair batteries  

Microsoft Academic Search

Manganese oxide based catalysts were synthesised in the form of nano-particles using a redox reaction of MnSO4 and KMnO4, housed into the pores of a carbon matrix and followed by a thermal treatment. Particle sizes of the manganese oxide nanocatalysts were around 50nm, based on the tunnelling electron microscope measurement. They were uniformly distributed in the carbon matrix, which contributed

H. Cheng; K. Scott

2010-01-01

160

Electron-energy-loss core-edge structures in manganese oxides  

Microsoft Academic Search

Oxygen K and manganese L2,3 edges electron-energy-loss spectra have been measured for a series of manganese oxides with different nominal oxidation states for the cation (MnO, Mn3O4, Mn2O3, MnO2, and BaMnO4). Spectra have been processed for quantitative elemental analysis and for the evaluation of manganese L2,3 white-line intensity ratios and normalized total intensities. Prepeaks on the oxygen K edge are

Hiroki Kurata; Christian Colliex

1993-01-01

161

Manganese oxide octahedral molecular sieves: Preparation, characterization, and applications  

SciTech Connect

A thermally stable 3 x 3 octahedral molecular sieve corresponding to natural todorokite (OMS-1) has been synthesized by autoclaving layer-structure manganese oxides, which are prepared by reactions of MnO[sub 4][minus] and Mn[sup 2+] under markedly alkaline conditions. The nature and thermal stability of products depend strongly on preparation parameters, such as the MnO[sub 4][minus]/Mn[sup 2+] ratio, pH, aging, and autoclave conditions. The purest and the most thermally stable todorokite is obtained at a ratio of 0.30 to 0.40. Autoclave treatments at about 150[degrees] to 180[degrees]C for more than 2 days yield OMS-1, which is as thermally stable (500[degrees]C) as natural todorokite minerals. Adsorption data give a tunnel size of 6.9 angstroms and an increase of cyclohexane or carbon tetrachloride uptake with dehydration temperature up to 500[degrees]C. At 600[degrees]C, the tunnel structure collapses. Both Lewis and Bronsted acid sites have been observed in OMS-1. Particular applications of these materials include adsorption, electrochemical sensors, and oxidation catalysis.

Shen, Y.F.; Zerger, R.P.; DeGuzman, R.N.; Suib, S.L.; McCurdy, L.; Potter, D.I. (Univ. of Connecticut, Storrs (United States)); O'Young, C.L. (Texaco, Inc., Beacon, NY (United States))

1993-04-23

162

Graphene oxide thin film coated quartz crystal microbalance for humidity detection  

Microsoft Academic Search

In this paper, we demonstrated that chemically derived graphene oxide (GO) thin film as a humidity sensitive coating deposited on quartz crystal microbalances (QCMs) for humidity detection. By exposing GO thin film coated QCMs to various relative humidity (RH) environments at room temperature, the humidity sensing characteristics of the QCMs such as sensitivity and linearity, response and recovery, humidity hysteresis

Yao Yao; Xiangdong Chen; Huihui Guo; Zuquan Wu

2011-01-01

163

Prophylactic use of polyvinylpyridine-N-oxide (PVNO) in baboons exposed to quartz dust  

SciTech Connect

Twelve baboons were exposed to a quartz dust cloud. Four of these were also given polyvinylpyridine-N-oxide (PVNO) by aerosol and four received PVNO by aerosol and injection. A prophylactic effect was demonstrated during the course of treatment, but when treatment stopped the silicosis progressed to the same degree of severity as in the untreated animals.

Goldstein, B.; Rendall, R.E.G.

1987-04-01

164

Relationship between external and internal parameters of exposure to manganese in workers from a manganese oxide and salt producing plant  

Microsoft Academic Search

In a plant producing manganese (Mn) oxides and salts, 11 different workplaces were identified. The current exposure to airborne Mn (total dust, personal sampling, n = 80) varied from 0.07 to 8.61 mg\\/m3. The geometric mean and median values amounted approximately to 1 mg\\/m3 and the 95th percentile was 3.30 mg\\/m3. The concentration of Mn in blood (Mn-B) in a

H. Roels; R. Lauwerys; P. Genet; M. J. Sarhan; M. de Fays; I. Hanotiau; J. P. Buchet

1987-01-01

165

A 2-(2-hydroxyphenyl)-1H-benzimidazole-manganese oxide hybrid as a promising structural model for the tyrosine 161/histidine 190-manganese cluster in photosystem II.  

PubMed

In this communication, we report the synthesis, characterization, and electrochemistry of a 2-(2-hydroxyphenyl)-1H-benzimidazole-manganese oxide hybrid. Our results suggest that this compound is a promising model for the manganese cluster together with tyrosine-161 and histidine-190 in photosystem II of plants, algae and cyanobacteria. PMID:23178300

Najafpour, Mohammad Mahdi; Amouzadeh Tabrizi, Mahmoud; Haghighi, Behzad; Govindjee

2013-01-28

166

Manganese augments nitric oxide synthesis in murine astrocytes: a new pathogenetic mechanism in manganism?  

PubMed

Since manganese (Mn2+) is known to be sequestered in glial cells, we investigated possible neurotoxic mechanisms involving astrocytes in vitro. Low concentrations of Mn2+ were toxic only in astrocyte-neuronal cocultures but not in pure astrocyte or neuronal cultures. As a possible mediator of manganese-derived neurotoxicity, we measured the production of nitric oxide in astrocytes. Manganese, but not other transition metals, dose dependently increased iNOS mRNA and protein levels and the release of nitric oxide in activated astrocytes. This effect was specific for astrocytes, since we observed no stimulation in microglial cells. The observations suggest that besides the known inhibition of mitochondrial function the neurotoxic effect of manganese in low concentrations might be mediated by the increased production of nitric oxide in astrocytes. PMID:9454637

Spranger, M; Schwab, S; Desiderato, S; Bonmann, E; Krieger, D; Fandrey, J

1998-01-01

167

Development and utility of manganese oxides as cathodes in lithiuim batteries.  

SciTech Connect

Manganese oxides have a long history of serving as a cathode in charge storage applications. Electrolytic manganese dioxide (EMD) is widely used in alkaline batteries and MnO{sub 2} originally was part of the Leclanch{acute e} wet cell patented in 1866. Leclanch{acute e} wet cells used a naturally occurring MnO{sub 2} ore with Zn metal as anode and ammonium chloride electrolyte. While there are a vast number of topics to discuss on manganese oxides, in this short paper, two topics researched at Argonne over the last 12 years are highlighted. First, the addition of lithia (Li{sub 2}O) as a stabilizing component in 3 V alpha-MnO{sub 2} is examined. Second, an overview of the evolution of layered-layered composite-structured electrodes derived from the lithium-manganese oxide (Li{sub 2}MnO{sub 3}) layered rock-salt phase is presented.

Johnson, C. S.; Chemical Engineering

2007-01-01

168

Manganese induces oxidative impairment in cultured rat astrocytes.  

PubMed

Excessive free radical formation has been implicated as a causative factor in neurotoxic damage associated with exposures to a variety of metals, including manganese (Mn). It is well established that Mn accumulates in astrocytes, affecting their ability to indirectly induce and/or exacerbate neuronal dysfunction. The present study examined the effects of Mn treatment on the following endpoints in primary astrocyte cultures: (1) oxidative injury, (2) alterations in high-energy phosphate (adenosine 5'-triphosphate, ATP) levels, (3) mitochondrial inner membrane potential, and (4) glutamine uptake and the expression of glutamine transporters. We quantified astrocyte cerebral oxidative damage by measuring F(2)-isoprostanes (F(2)-IsoPs) using stable isotope dilution methods followed by gas chromatography-mass spectrometry with selective ion monitoring. Our data showed a significant (p < 0.01) elevation in F(2)-IsoPs levels at 2 h following exposure to Mn (100 microM, 500 microM, or 1 mM). Consistent with this observation, Mn induced a concentration-dependent reduction in ATP and the inner mitochondrial membrane potential (DeltaPsi(m)), measured by the high pressure liquid chromatography method and the potentiometric dye, tetramethyl rhodamine ethyl ester, respectively. Moreover, 30 min of pretreatment with Mn (100 microM, 500 microM, or 1 mM) inhibited the net uptake of glutamine (GLN) ((3)H-glutamine) measured at 1 and 5 min. Expression of the messenger RNA coding the GLN transporters, SNAT3/SN1 and SNAT1, was inhibited after 100 and 500 microM Mn treatment for 24 h. Our results demonstrate that induction of oxidative stress, associated mitochondrial dysfunction, and alterations in GLN/glutamate cycling in astrocytes represent key mechanisms by which Mn exerts its neurotoxicity. PMID:17468184

Milatovic, Dejan; Yin, Zhaobao; Gupta, Ramesh C; Sidoryk, Marta; Albrecht, Jan; Aschner, Judy L; Aschner, Michael

2007-04-27

169

Effects of FeS on Chromium Oxidation Mediated by Manganese Oxidizers  

SciTech Connect

Reductive immobilization of Cr(VI) has been widely explored as a cost-effective approach for Cr-contaminated site remediation. The long-term stability of the immobilized Cr(III), however, is a concern. Cr(III) is known to be oxidized by Mn oxides chemically and Mn-oxides could be produced through microbially mediated Mn(II) oxidation. This study examined the effect of FeS on Cr(III) oxidation mediated by Pseudomonas putida. The results showed that commercial granular FeS did not affect Cr(III) oxidation in the culture of P. putida with Mn(II), but freshly precipitated FeS slurry inhibited Cr(III) oxidation. A 10 mg/l of FeS did not inhibit the microbial growth, but delayed the production of Mn oxides, thus postponing potential Cr(III) oxidation. In the presence of excessive FeS slurry, both Cr(VI) and Mn oxides were reduced rapidly. The reduced Cr(III) could not be re-oxidized as long as freshly formed FeS was present, even in the presence of the manganese oxidizers.

Wu, Youxian; Deng, Baolin

2004-03-31

170

Chronic manganese oxide ingestion in rats: hematological effects.  

PubMed

Hematological values were studied in Long Evans rats after chronic exposure to manganese oxide (Mn3O4). Data were obtained at selected ages from the P0 through the F2 generation. Effects of exposure to Mn3O4 during Fe deficiency were determined by placing half of the animals on a low-Fe diet (20 mg/kg) while the other half were maintained on a normal-Fe diet (240 mg/kg). Animals treated with Mn3O4 and maintained on a normal-Fe diet showed little variation from controls through 100 d of age. However, animals (24-100 d of age) maintained on a low-Fe diet and receiving Mn treatment during the prenatal and postnatal periods developed microcytic anemia. Irrespective of the dietary Fe level, serum creatinine levels decreased in the groups receiving 400 and 1100 ppm Mn while serum Ca and P levels increased in the group receiving 1100 ppm Mn at 100 d of age. Serum values for lactate dehydrogenase, alkaline phosphatase (100 d of age), and serum glutamic-oxaloacetic transaminase (224 d of age) were elevated for all animals on low-Fe diets. Globulin, albumin (100 d of age), and glucose (224 d of age) levels were depressed in all low-Fe groups. PMID:7381971

Carter, S D; Hein, J F; Rehnberg, G L; Laskey, J W

1980-01-01

171

Morphology of graphite-supported iron-manganese catalyst particles: Formation of hollow spheres during oxidation  

SciTech Connect

Transmission electron microscopy (TEM) and Moessbauer spectroscopy (MES) were used to study the morphology of graphite-supported iron-manganese particles. Following oxidation at 500 K MES showed the iron in the particles to be fully oxidized. TEM showed all the particles to be torroidal in appearance. However, tilting resulting in no change in the apparent dimensions of the particles, yet the apparent distances between particles were sharply reduced. These results suggest the particles are actually spherical. On the basis of these experiments, and similar experiments with reduced particles, a model was developed: Following reduction the particles are spherical and consist of a metallic iron core surrounded by a shell of manganese oxide. During oxidation, iron ions diffuse through the manganese oxide shell to the particle surface. Eventually, this results in the formation of nearly spherical particles with hollow centers, inner shells of iron-manganese spinel, and outer shells of iron oxide. Upon an additional reduction the hollow center remains, but the shells phase segregate into regions of iron metal and manganese oxide.

Chen, A.A.; Vannice, M.A.; Phillips, J. (Pennsylvania State Univ., University Park (USA))

1989-04-01

172

Electron energy-loss safe-dose limits for manganese valence measurements in environmentally relevant manganese oxides.  

PubMed

Manganese (Mn) oxides are among the strongest mineral oxidants in the environment and impose significant influence on mobility and bioavailability of redox-active substances, such as arsenic, chromium, and pharmaceutical products, through oxidation processes. Oxidizing potentials of Mn oxides are determined by Mn valence states (2+, 3+, 4+). In this study, the effects of beam damage during electron energy-loss spectroscopy (EELS) in the transmission electron microscope have been investigated to determine the "safe dose" of electrons. Time series analyses determined the safe dose fluence (electrons/nm(2)) for todorokite (10(6) e/nm(2)), acid birnessite (10(5)), triclinic birnessite (10(4)), randomly stacked birnessite (10(3)), and ?-MnO(2) (<10(3)) at 200 kV. The results show that meaningful estimates of the mean Mn valence can be acquired by EELS if proper care is taken. PMID:22148625

Livi, Kenneth J T; Lafferty, Brandon; Zhu, Mengqiang; Zhang, Shouliang; Gaillot, Anne-Claire; Sparks, Donald L

2011-12-22

173

Experimental evaluation of the effects of quench rate and quartz surface area on homogeneous mercury oxidation  

SciTech Connect

This paper presents a mercury oxidation data set suitable for validation of fundamental kinetic models of mercury chemistry and for mechanism development. Experimental facilities include a mercury reactor fitted with a 300-W, quartz-glass burner and a quartz reaction chamber. While operated with a temperature profile representative of a typical boiler, a residence time of 6 s was achieved. Participating reacting species (chlorine, mercury) were introduced through the burner to produce a radical pool representative of real combustion systems. Speciated mercury measurements were performed using a Tekran 2537A Analyzer coupled with a conditioning system. Homogeneous mercury reactions involving chlorine have been investigated under two different temperature profiles producing quench rates of -210 K/s and -440 K/s. The larger quench rate produced 52% greater total oxidation than the lower quench at chlorine concentrations of 200 ppm. The effect of reactor surface area on oxidation was also investigated. The quartz surfaces interacted with mercury only in the presence of chlorine and their overall effect was to weakly inhibit oxidation. The extent of oxidation was predicted using a detailed kinetic model. The model predicted the effects of quench rate and chlorine concentration shown in experimentation. 12 refs., 5 figs., 3 tabs.

Andrew Fry; Brydger Cauch; Geoffrey D. Silcox; JoAnn S. Lighty; Constance L. Senior [University of Utah, Salt Lake City, UT (United States). Department of Chemical Engineering

2007-07-01

174

Water oxidation catalysed by manganese compounds: from complexes to 'biomimetic rocks'.  

PubMed

One of the most fundamental processes of the natural photosynthetic reaction sequence is the light-driven oxidation of water to molecular oxygen. In vivo, this reaction takes place in the large protein ensemble Photosystem II, where a ?-oxido-Mn(4)Ca- cluster, the oxygen-evolving-complex (OEC), has been identified as the catalytic site for the four-electron/four-proton redox reaction of water oxidation. This Perspective presents recent progress for three strategies which have been followed to prepare functional synthetic analogues of the OEC: (1) the synthesis of dinuclear manganese complexes designed to act as water-oxidation catalysts in homogeneous solution, (2) heterogeneous catalysts in the form of clay hybrids of such Mn(2)-complexes and (3) the preparation of manganese oxide particles of different compositions and morphologies. We discuss the key observations from the studies of such synthetic manganese systems in order to shed light upon the catalytic mechanism of natural water oxidation. Additionally, it is shown how research in this field has recently been motivated more and more by the prospect of finding efficient, robust and affordable catalysts for light-driven water oxidation, a key reaction of artificial photosynthesis. As manganese is an abundant and non-toxic element, manganese compounds are very promising candidates for the extraction of reduction equivalents from water. These electrons could consecutively be fed into the synthesis of "solar fuels" such as hydrogen or methanol. PMID:22068958

Wiechen, Mathias; Berends, Hans-Martin; Kurz, Philipp

2011-11-08

175

Emulsion-derived lithium manganese oxide powder for positive electrodes in lithium-ion batteries  

Microsoft Academic Search

Lithium manganese oxide (LiMn2O4) used as a positive-electrode material in lithium-ion batteries is prepared by a new water-in-oil emulsion process. An aqueous solution containing lithium and manganese cations is emulsified in kerosene by adding sorbitan monooleate as the surfactant. When the precursor solution is agitated by a magnetic mixer, impure products are obtained. LiMn2O4 is formed along with residual Mn2O3

Chung-Hsin Lu; Shang-Wei Lin

2001-01-01

176

The stabilization of layered manganese oxides for use in rechargeable lithium batteries  

Microsoft Academic Search

The layered structure LiTiS and LiCoO are excellent reversible cathodes for lithium batteries. However, layered lithium manganese oxides are metastable relative to the spinel form on cycling in lithium batteries. They may be stabilized in the layer form by insertion of larger ions such as potassium in the interlayer region, which minimizes the diffusion of the manganese ions from the

M. S. Whittingham; P. Zavalij; F. Zhang; P. Sharma; G. Moore

2000-01-01

177

Development and utility of manganese oxides as cathodes in lithium batteries  

Microsoft Academic Search

Manganese oxides have a long history of serving as a cathode in charge storage applications. Electrolytic manganese dioxide (EMD) is widely used in alkaline batteries and MnO2 originally was part of the Leclanch wet cell patented in 1866. Leclanch wet cells used a naturally occurring MnO2 ore with Zn metal as anode and ammonium chloride electrolyte. While there are a

Christopher S. Johnson

2007-01-01

178

Depth profile analysis of a cycled lithium ion manganese oxide battery electrode via the valence state of manganese, with soft X-ray emission spectroscopy  

Microsoft Academic Search

A 50-?m thick lithium manganese oxide (parent material LiMn2O4) battery electrode (positive electrode; cathode) was charged, slightly discharged and then sliced with a scotch tape test-type method. A selected number of slices was then subject to synchrotron soft X-ray emission spectroscopy near the Mn L?,? emission lines in order to determine changes in the oxidation state of the manganese as

Artur Braun; Hongxin Wang; Tobias Funk; Soenke Seifert; Elton J. Cairns

2010-01-01

179

Solution synthesis and characterization of lithium manganese oxide cathode materials.  

National Technical Information Service (NTIS)

A nonaqueous coprecipitation process has been developed to prepare controlled stoichiometry lithium manganese oxalate precipitates. The process involved mixing a methanolic Li-Mn nitrate solution with a methanolic solution containing tetramethylammonium o...

J. A. Voigt T. J. Boyle D. H. Doughty

1995-01-01

180

Wet oxidation of phenol catalyzed by unpromoted and platinum-promoted manganese/cerium oxide  

SciTech Connect

Manganese/cerium composite oxide (MnO{sub 2}/CeO{sub 2}) proved to be a potent solid catalyst for the catalytic wet oxidation (CWO) of aqueous phenol under mild treatment conditions (80--130 C, 0.5 MPa O{sub 2} pressure). Despite the fact this catalyst exhibited an important activity in eliminating completely phenol and total organic carbon (TOC), its poor selectivity to CO{sub 2} was demonstrated as a result of deposition on the catalyst surface of carbonaceous deposits with high carbon content. Promotion of MnO{sub 2}/CeO{sub 2} with platinum improved the CO{sub 2} yield of phenol oxidation. Evidence for the reduction of the carbonaceous deposit over Pt-MnO{sub 2}/CeO{sub 2} was confirmed via elemental analysis and temperature-programmed oxidation (TPO). Surface analysis by X-ray photoelectron spectroscopy (XPS) indicated that the deposits built up more on cerium than on manganese and that platinum increased the aromaticity of the deposit.

Hamoudi, S.; Larachi, F. [Laval Univ., Quebec (Canada). Dept. of Chemical Engineering; Cerrella, G.; Cassanello, M. [Univ. de Buenos Aires (Argentina)

1998-09-01

181

Acute exposure of laboratory mice to manganese oxide.  

PubMed

An acute inhalation exposure of laboratory mice to respirable Mn3O4 aerosols is described. The generation system consisted of a Wright dust generator which produced 1.40 micrometer aerosols. A non-linear loss of deposited manganese from mouse lungs over the inital 24-hour post-exposure period was observed. Systemic distribution of the manganese was observed in various tissues following exposure. PMID:7415970

Adkins, B; Luginbuhl, G H; Gardner, D E

1980-07-01

182

Catalytic role of Manganese oxides in prebiotic Nucleobases synthesis from Formamide  

NASA Astrophysics Data System (ADS)

The evolution of living cell from chemicals is more complicated reaction which could be studied in multistep. A study of prebiotic synthesis of naturally occurring purine and pyrimidine derivatives from formamide under catalytic condition with different oxides of manganese reveals a significant role. Manganese oxides are highly efficient in the conversion of formamide into different nucleobases. Neat formamide is converted to the purine, 9-(hydroxyacetyl) purine, cytosine, 4(3H)-pyrimidinone, thymine and adenine in good yield. Metal oxides have provided their surfaces and catalyzed the reactions from simple molecules to more complex bio-organic molecules. Our results show that probably prebiotic reactions might have occured on the sea floor where the existence of manganese oxide is second to iron transition metal minerals.

Bhushan, Brij

2012-07-01

183

Porous manganese oxide synthesized through organic-electrolyte templates and their catalytic applications  

SciTech Connect

We report a facile approach to the preparation of porous manganese oxide materials by the organic-electrolyte templates based on strategy. The final products are thoroughly characterized by X-ray diffraction (XRD), thermogravimetric analysis (TGA), field-emission scanning electron microscopy (SEM), transmission electron microscopy (TEM), Fourier transform infrared spectroscopy (FT-IR), X-ray photoelectron spectroscopy (XPS), inductively coupled plasma-optical emission spectroscopy (ICP-OES), and Brunauer-Emmett-Teller (BET) techniques. The results reveal that porosity (pore size and distribution, surface area) of these manganese oxides has strong relationship with the templates used, which implies a simple way to obtain a series of porous materials. By comparing the catalytic effects of these manganese oxides in oxidation of indene and benzyl alcohol, we find that the pore size and distribution are also crucial to the catalytic properties of these porous materials.

Zhang Wei [CAS Key Laboratory of Soft Matter Chemistry, Department of Polymer Science and Engineering, University of Science and Technology of China, Hefei 230026 (China); Li Jiangying [Department of Chemistry, University of Science and Technology of China, Hefei 230026 (China); Du Xuemin [CAS Key Laboratory of Soft Matter Chemistry, Department of Polymer Science and Engineering, University of Science and Technology of China, Hefei 230026 (China); Zhang Zhicheng, E-mail: zczhang@ustc.edu.cn [CAS Key Laboratory of Soft Matter Chemistry, Department of Polymer Science and Engineering, University of Science and Technology of China, Hefei 230026 (China)

2009-11-15

184

Studies of jet fuel thermal stability and oxidation using a quartz crystal microbalance and pressure measurements  

SciTech Connect

The thermal stability of aircraft jet fuels was measured in real time with a quartz crystal microbalance (QCM) at 140 C. Qualitative data on the oxidation of these fuels was also obtained by monitoring the system pressure during thermal stressing. The system was operated at relatively low oxygen availability (1 atm air) which more closely approximates the oxygen availability of flowing fuel tests and real fuel systems than previous work. The high sensitivity and good reproducibility of the QCM permitted deposition measurements under unaccelerated conditions (i.e., relatively low temperature and oxygen availability). Correlation of oxidation and deposition behavior provided insight into the deposition and oxidation processes.

Zabarnick, S. (Univ. of Dayton Research Inst., OH (United States). Aerospace Mechanics Div.)

1994-05-01

185

Oxidative dehydrogenation of 1-butene over manganese oxide octahedral molecular sieves  

SciTech Connect

Steady state kinetic studies of the oxidative dehydrogenation of 1-butene to 1,3-butadiene have been carried out on manganese oxide octahedral molecular sieve (OMS) and octahedral layered (OL) materials. Process parameters such as temperature, feed composition of 1-butene and oxygen, and feed flow rates were varied to study their effect on the activity and selectivity toward the oxidative dehydrogenation process. In addition to process parameters, modifications in the catalyst such as the ion-exchange of tunnel cations and framework substitution of manganese cations were also implemented in order to observe their effects on catalytic activity and the selectivity of 1,3-butadiene production. The ion-exchanged OMS and OL materials showed rapid deactivation with time when subjected to reaction mixtures of 1% 1-butene/0.7% oxygen/Ar and 1% 1-butene/1.1% oxygen/Ar at reaction temperatures greater than 400 C. Their selectivity toward 1,3-butadiene were typically from 15--20% (yield of 4--6%). The other products were cis and trans 2-butene and carbon dioxide and water (40--60% selectivity). Much of the oxidation was therefore nonselective. XRD data have shown that there is a phase change of the original precursor to a mixture of Mn{sub 3}O{sub 4}/MnO or plain MnO, in some cases after exposing the catalyst to reaction conditions for about 1--2 h. Framework substitution of some of the manganese with copper (OMS and OL), however, has led to higher yields and selectivities toward 1,3-butadiene. [Cu] OL-1 showed a yield of 11.8% and a maximum selectivity of 26% toward 1,3-butadiene. [Cu] OMS-1 shows a dramatically high selectivity of 36% and a yield of 11% toward 1,3-butadiene. The effect of framework substitution seems to also impede the phase change to Mn{sub 3}O{sub 4} (Hausmannite). The TPR spectra also show an increase in the lattice oxygen peak by about 40 C, in comparison with ion-exchanged OMS. This is sufficient indication that framework substitution of manganese by copper, partially, has enhanced the stability of the catalyst and improved its capacity for selective oxidation.

Krishnan, V.V.; Suib, S.L. [Univ. of Connecticut, Storrs, CT (United States)

1999-06-10

186

Solution-based synthesis of manganese oxide cathodes for lithium batteries  

SciTech Connect

With an objective to overcome the cyclability problems of manganese oxides, solution-based procedures are pursued to synthesize metastable manganese oxides. Reduction of permanganate with lithium iodide in an acetonitrile medium followed by heating at 250 C in vacuum gives an amorphous lithium sodium manganese oxyiodide that is intimately mixed with crystalline NaIO{sub 3}. On the other hand, oxidation of manganese acetate with lithium or hydrogen peroxide in presence of lithium hydroxide followed by firing at T < 500 C gives the metastable spinel oxides, Li{sub 4}Mn{sub 5}O{sub 12} and Li{sub 2}Mn{sub 4}O{sub 9{minus}{delta}}. The amorphous manganese oxide exhibits excellent cyclability with a capacity >275 mAh/g at 4.3-1.5 V. The presence of NaIO{sub 3} and a unique microstructure are found to play a critical role in the electrochemical properties. Although Li{sub 4}Mn{sub 5}O{sub 12} could be achieved without much oxygen vacancies, Li{sub 2}Mn{sub 4}O{sub 9{minus}{delta}} has significant amount of oxygen vacancies with {delta} > 0.35. Both Li{sub 4}Mn{sub 5}O{sub 12} and Li{sub 2}Mn{sub 4}O{sub 9{minus}{delta}} exhibit capacities around 150 mAh/g with good cyclability in the 3 V region.

Manthiram, A.; Kim, J.; Choi, S.

2000-07-01

187

Nanostructured lithium nickel manganese oxides for lithium-ion batteries.  

SciTech Connect

Nanostructured lithium nickel manganese oxides were investigated as advanced positive electrode materials for lithium-ion batteries designated to power plug-in hybrid electric vehicles and all-electric vehicles. The investigation included material characterization and electrochemical testing. In cell tests, the Li{sub 1.375}Ni{sub 0.25}Mn{sub 0.75}O{sub 2.4375} composition achieved high capacity (210 mAh g{sup -1}) at an elevated rate (230 mA g{sup -1}), which makes this material a promising candidate for high energy density Li-ion batteries, as does its being cobalt-free and uncoated. The material has spherical morphology with nanoprimary particles embedded in micrometer-sized secondary particles, possesses a multiphase character (spinel and layered), and exhibits a high packing density (over 2 g cm{sup -3}) that is essential for the design of high energy density positive electrodes. When combined with the Li{sub 4}Ti{sub 5}O{sub 12} stable anode, the cell showed a capacity of 225 mAh g{sup -1} at the C/3 rate (73 mA g{sup -1}) with no capacity fading for 200 cycles. Other chemical compositions, Li{sub (1+x)}Ni{sub 0.25}Mn{sub 0.75}O{sub (2.25+x/2)} (0.32 {le} x {le} 0.65), were also studied, and the relationships among their structural, morphological, and electrochemical properties are reported.

Deng, H.; Belharouak, I.; Cook, R. E.; Wu, H.; Sun, Y.-K.; Amine, K.; Hanyang Univ.

2010-02-25

188

New Reagent, Manganese Dioxide Supported on Kieselguhr, for Effective Oxidation of Benzoins  

Microsoft Academic Search

A new reagent, manganese dioxide supported on kieselguhr, for effective oxidation of benzoins into corresponding benzils under heterogeneous and reflux conditions is described. The present oxidations are completed within 10h with yields of 8695%. The main advantages of the present procedure are that the preparation of supported reagent is more convenient and the reaction times are relatively short.

Li-Hong Huang; Qiang Wang; Yi-Chun Ma; Ji-Dong Lou; Changhe Zhang

2011-01-01

189

EFFECTS OF SOLAR RADIATION ON MANGANESE OXIDE REACTIONS WITH SELECTED ORGANIC COMPOUNDS  

EPA Science Inventory

The effects of sunlight on aqueous redox reactions between manganese oxides (MnOx) and selected organic substances are reported. o sunlight-induced rate enhancement was observed for the MnOx oxidation of substituted phenols, anisole, o-dichlorobenzene, or p-chloroaniline. n the o...

190

Directed vapor deposition of lithium manganese oxide films  

NASA Astrophysics Data System (ADS)

Electron beam evaporation and sputtering techniques are used to fabricate multilayered thin film structures. However, these techniques suffer several drawbacks resulting from (i) the complex chemistries of the lithiated oxide layers used for the cathode and electrolyte, (ii) the need for precise microstructure control in systems with many metastable phases, and (iii) the low deposition rate and poor material utilization efficiency, which slows the application of this energy storage approach. This dissertation has investigated the use of a novel electron-beam directed vapor deposition (EB-DVD) method for the synthesis of thin film batteries. The dissertation focuses upon the cathode layer of a representative Li-ion thin film battery system and investigates in detail the deposition of lithium manganese oxide films. Many phases with offering various electrochemical performance exist in the Li-Mn-O system and the thesis also investigates the use of processing conditions to control the structure and composition of these cathode layers. In the EB-DVD approach, a high voltage electron beam is used to evaporate a source material in the throat of a nozzle that forms a coaxial transonic gas jet around the vapor. The gas jet entrains and transports the vapor to a substrate where the deposition occurs. Directed simulation of Monte Carlo (DSMC) methods indicated that the vapor plume could be matched to a substrate diameter, and the deposition rate (and vapor utilization efficiency) therefore controlled by adjusting the pressure ratio up and downstream of the nozzle opening in the deposition chamber, and by varying the gas jet density and speed. The highest deposition rates were obtained with a high pressure ratio and the gas jet density. These observations are found to be consistent with the experimental results. Deposition rates up to 16 nm/s could be achieved using the most effective gas entrainment conditions identified by DSMC calculation. This was about a factor of ten times higher than the deposition rate reported for the growth of this material by sputtering (1.5 nm/s) and other vapor deposition techniques. As-deposited lithium manganese oxide films grown on substrates at ambient temperature using high pressure ratios were found to have a disordered structure intermediate between that of the spinel (Fd3m) and rock-salt (Fm3m) phases. Post-annealing of the films in air led to a gradual structural ordering to the Fd3m, spinel structure (the thermodynamically stable phase in air) as the temperature increased to 700C. The fully transformed films had a pure cubic spinel structure with a slightly manganese deficient composition, Li1+xMn2-yO4 where 0.08 texture. The change in film porosity and texture could be explained by the degree of homogeneous vapor phase clustering that was controllable by the gas jet pressure ratio. When deposition was conducted at elevated temperatures up to 700C, films with various atomic structures could be fabricated. Films grown below 500C contained mixtures of the orthorhombic LiMnO2 and the metastable rock-salt structures. Annealing these films in air resulted in a transformation to a single phase spinel structure. Films grown above 600C had a single phase orthorhombic LiMnO2 structure. Post-annealing of these films in air led to mixtures of t

Jin, Sang-Wan

191

The durability of manganesemolybdenum oxide anodes for oxygen evolution in seawater electrolysis  

Microsoft Academic Search

MnO2-type manganesemolybdenum oxides have been anodically deposited under various conditions on IrO2-coated titanium substrates, and the durability of the oxide anodes for oxygen evolution in seawater electrolysis has been examined. When sufficiently thick oxides are deposited, all the oxide anodes containing 8 mol% or more molybdenum in cationic percentage show an initial oxygen evolution efficiency of almost 100% at a

K Fujimura; T Matsui; H Habazaki; A Kawashima; N Kumagai; K Hashimoto

2000-01-01

192

Effect of respiration and manganese on oxidative stress resistance of Lactobacillus plantarum WCFS1.  

PubMed

Lactobacillus plantarum is a facultatively anaerobic bacterium that can perform respiration under aerobic conditions in the presence of haem, with vitamin K2 acting as a source of menaquinone. We investigated growth performance and oxidative stress resistance of Lb. plantarum WCFS1 cultures grown in de Man, Rogosa and Sharpe (MRS) medium without and with added manganese under fermentative, aerobic, aerobic with haem, and respiratory conditions. Previous studies showed that Lb. plantarum WCFS1 lacks a superoxide dismutase and requires high levels of manganese for optimum fermentative and aerobic growth. In this study, respiratory growth with added manganese resulted in significantly higher cell densities compared to the other growth conditions, while without manganese added, similar but lower cell densities were reached. Notably, cells derived from the respiratory cultures showed the highest hydrogen peroxide resistance in all conditions tested, although similar activity levels of haem-dependent catalase were detected in cells grown under aerobic conditions with haem. These results indicate that oxidative stress resistance of Lb. plantarum is affected by respiratory growth, growth phase, haem and manganese. As levels of haem and manganese can differ considerably in the raw materials used in fermentation processes, including those of milk, meat and vegetables, the insight gained here may provide tools to increase the performance and robustness of starter bacteria. PMID:22016573

Watanabe, Masayuki; van der Veen, Stijn; Nakajima, Hadjime; Abee, Tjakko

2011-10-20

193

Strontium and Actinides Removal from Savannah River Site Actual Waste Samples by Freshly Precipitated Manganese Oxide  

SciTech Connect

The authors investigated the performance of freshly precipitated manganese oxide and monosodium titanate (MST) for the removal of strontium (Sr) and actinides from actual high-level waste. Manganese oxide precipitation occurs upon addition of a reductant such as formate (HCO2-) or peroxide (H2O2) to a waste solution containing permanganate (MnO4-). An addition of non-radioactive strontium typically precedes the MnO4- and reductant addition, which serves primarily to isotopically dilute the strontium-90 (90Sr) present in the waste. Tests utilized a Tank 37H/44F composite waste solution. Personnel significantly increased the concentration of actinides in the waste by the addition of acidic americium/curium solution (F-Canyon Tank 17.1 solution), which contained a significant quantity of plutonium (Pu), and neptunium-237 (237Np) stock solution. Initial tests examined three manganese oxide treatment options.

Barnes, M.J.

2002-10-18

194

Ambient temperature carbon monoxide oxidation using copper manganese oxide catalysts: Effect of residual Na + acting as catalyst poison  

Microsoft Academic Search

The effect of ageing of copper manganese oxide catalysts prepared by co-precipitation is described and discussed. In particular, the ageing leads to a significant decrease in the concentration of surface sodium and this correlates with the catalytic activity for the oxidation of carbon monoxide at the extended ageing time.

Ali A Mirzaei; Hamid R Shaterian; Richard W Joyner; Michael Stockenhuber; Stuart H Taylor; Graham J Hutchings

2003-01-01

195

Synthesis and Characterization of a Layered Manganese Oxide: Materials Chemistry for the Inorganic or Instrumental Methods Lab  

ERIC Educational Resources Information Center

|A three-week laboratory project involving synthesis and characterization of a layered manganese oxide provides an excellent vehicle for teaching important concepts of inorganic chemistry and instrumental methods related to non-molecular systems. Na-birnessite is an easily prepared manganese oxide with a 7 A interlayer spacing and Na[superscript

Ching, Stanton; Neupane, Ram P.; Gray, Timothy P.

2006-01-01

196

Adsorption behavior of Li + onto nano-lithium ion sieve from hybrid magnesium\\/lithium manganese oxide  

Microsoft Academic Search

Magnesium (II) doped spinel lithium manganese oxide (LMS) was synthesized by soft chemical method and nanosized ion sieve manganese oxide (HMS) was prepared by extracting lithium and magnesium from LMS. The characteristics of HMS were studied by X-ray diffraction, scanning electron microscopy, transmission electron microscopy, surface areas and determination of pH at the point of zero charge. Experiments were performed

Liyan Tian; Wei Ma; Mei Han

2010-01-01

197

Low-temperature hydrothermal synthesis of spinel-type lithium manganese oxide nanocrystallites  

Microsoft Academic Search

A mild hydrothermal method has been developed to synthesize spinel-type lithium manganese oxide nanocrystallites directly from commercial LiOH, Mn(NO3)2 and H2O2 at 90110 C for 8 h. The as-prepared products were characterized by X-ray diffraction (XRD), inductively coupled plasmaatomic emission spectroscopy and chemical analysis. The analysis results indicated that spinel-type lithium manganese oxides with the compositions of Li1+xMn2?xO4?? (0.09?x?0.28, ?<0.05)

Yong Cai Zhang; Hao Wang; Hai Yan Xu; Bo Wang; Hui Yan; Anwar Ahniyaz; Masahiro Yoshimura

2003-01-01

198

Manganese oxide helices, rings, strands, and films, and methods for their preparation  

DOEpatents

Methods for the preparation of mixed-valence manganese oxide compositions with quaternary ammonium ions are described. The compositions self-assemble into helices, rings, and strands without any imposed concentration gradient. These helices, rings, and strands, as well as films having the same composition, undergo rapid ion exchange to replace the quaternary ammonium ions with various metal ions. And the metal-ion-containing manganese oxide compositions so formed can be heat treated to form semi-conducting materials with high surface areas.

Suib, Steven L. (Storrs, CT); Giraldo, Oscar (Storrs, CT); Marquez, Manuel (Wheeling, IL); Brock, Stephanie (Detroit, MI)

2003-01-07

199

Preparation and characterization of A-site doped Perovskite-type manganese oxides  

NASA Astrophysics Data System (ADS)

Perovskite type manganese oxide is a kind of in solid state chemistry and the field of condensed matter physics are used extensively in the study of materials. Application of sol-gel method on perovskite type manganese oxide doping, preparation out series of samples La0.6BaxSr(0.4-x)MnO3, including powder and flake. After annealing treatment, the X ray diffraction tests of different annealing temperature on the influence of the structure of the samples was studied.

Huang, Yingqun; Li, Xiong; Che, Xinglai; Ju, Hailang

2013-08-01

200

Processes of nickel and cobalt uptake by a manganese oxide forming sediment in Pinal Creek, Globe mining district, Arizona  

USGS Publications Warehouse

A series of column experiments was conducted using manganese oxide coated sediments collected from the hyporheic zone in Pinal Creek (AZ), a metal-contaminated stream, to study the uptake and retention of Mn, Ni, and Co. Experimental variables included the absence (abiotic) and presence (biotic) of active Mn-oxidizing bacteria, the absence and presence of dissolved Mn, and sediment manganese oxide content. Uptake of Mn under biotic conditions was between 8 and 39% higher than under abiotic conditions. Continuous uptake of Mn due to biotic oxidation was evident from extraction of column sediments. Manganese uptake is hypothesized to initially occur as adsorption, which led to subsequent surface and/or microbial oxidation. Complete breakthrough of Ni within 100 pore volumes indicated no process of continuous uptake and was modeled as an equilibrium adsorption process. Nickel uptake in the presence of dissolved Mn was 67-100% reversible. Sediment extractions suggest that Ni uptake occurred through weak and strong adsorption. Continuous uptake of cobalt increased with sediment manganese oxide content, and Co uptake was up to 75% greater under biotic than abiotic conditions. Cobalt uptake was controlled by both existing and newly formed manganese oxides. Only a small amount of Co uptake was reversible (10-25%). XANES spectral analysis indicated that most Co(II) was oxidized to Co(III) and probably incorporated structurally into manganese oxides. Although manganese oxides were the primary phase controlling uptake and retention of Mn, Ni, and Co, the mechanisms varied among the metals.

Kay, J. T.; Conklin, M. H.; Fuller, C. C.; O'Day, P. A.

2001-01-01

201

Manganese removal from the Qiantang River source water by pre-oxidation: A case study  

Microsoft Academic Search

We evaluated several different pre-oxidation treatments, namely the introduction of either potassium permanganate (KMnO4), chlorine (Cl2), or both to remove manganese (Mn) from the Qiantang River source water. Our results showed that Mn removal percentages were\\u000a 12.7%, 71.0%, 17.4% and 58.7% when none of the oxidants, KMnO4 only, Cl2 only, or both oxidants were added, respectively. Furthermore, a field study

Jian-wen Zhu; Zhen Zhang; Xiao-min Li; Xin-hua Xu; Da-hui Wang

2009-01-01

202

The scavenging of silver by manganese and iron oxides in stream sediments collected from two drainage areas of Colorado  

USGS Publications Warehouse

Stream sediments of two well-weathered and aerated drainage areas of Colorado containing anomalous amounts of silver were allowed to react by shaking with nitric acid of different concentrations (1-10M). Silver, manganese, and iron simultaneously dissolved were determined by atomic absorption. The relationship between silver dissolution and the dissolution of manganese and/or iron was evaluated by linear and multiple regression analyses. The highly significant correlation coefficient (r = 0.913) between silver and manganese dissolution suggests that manganese oxides are the major control on the scavenging of silver in these stream sediments, whereas iron oxides only play a secondary role in this regard. ?? 1974.

Chao, T. T.; Anderson, B. J.

1974-01-01

203

Surfactant manganese complexes as models for the oxidation of water  

SciTech Connect

Surfactant manganese complexes have been studied spectroscopically and electrochemically as models for the catalysts involved in the photooxidation of water to produce oxygen. Evidence has been obtained for the participation of the suggested redox cycle Mn/sup II/ to Mn/sup III/ to Mn/sup IV/ and back to Mn/sup II/ with the evolution of oxygen.

Wohlgemuth, R.; Otvos, J.W.; Calvin, M.

1984-02-01

204

Reactivity of biogenic manganese oxide for metal sequestration and photochemistry: Computational solid state physics study  

SciTech Connect

Many microbes, including both bacteria and fungi, produce manganese (Mn) oxides by oxidizing soluble Mn(II) to form insoluble Mn(IV) oxide minerals, a kinetically much faster process than abiotic oxidation. These biogenic Mn oxides drive the Mn cycle, coupling it with diverse biogeochemical cycles and determining the bioavailability of environmental contaminants, mainly through strong adsorption and redox reactions. This mini review introduces recent findings based on quantum mechanical density functional theory that reveal the detailed mechanisms of toxic metal adsorption at Mn oxide surfaces and the remarkable role of Mn vacancies in the photochemistry of these minerals.

Kwon, K.D.; Sposito, G.

2010-02-01

205

Synthesis Of Different Phases Of Nano Manganese Oxides And Their Dielectric Behaviour In Chitosan Composites  

NASA Astrophysics Data System (ADS)

Nanoscale oxides of transition metals, particularly manganese, are desirable for many applications in designing electric, magnetic and heterogeneous catalytic materials. Manganese oxides exist in different phases, viz. MnO, MnO2, Mn2O3, Mn2O7 and Mn3O4. Using different synthetic routes it is possible to synthesize different phases of manganese oxides. Moreover, composites of these oxides with polymer have the potential to address the needs of emerging dielectric technologies. In the present work, using manganese chloride and hydrazine hydrate, Mn3O4 and Mn2O3 nanoparticles were successfully synthesized by conventional and hydrothermal method respectively. The variation in the formation of the different phases has been discussed. The nanoparticles were well characterized by X-ray Diffraction and using the Debye Scherrer formula, the average size of Mn3O4 and Mn2O3 nanoparticles were calculated to be 35 nm and 25 nm respectively. Using solution casting method, nanocomposites of chitosan/Mn3O4 were prepared and their electrochemical properties were studied using electrochemical impedance spectroscopy. It was observed that with increase in the content of nano oxides, the conductivity of the films increased. Also, the variation in the permittivity of these samples with respect to frequency was studied. The results suggest that the composites have a fair chance to be used in energy storage devices.

Harshita, B. A.; Bhat, D. Krishna; Bhatt, Aarti S.

2011-10-01

206

Reduction and dissolution of manganese(III) and manganese(IV) oxides by organics. Part 2. Survey of the reactivity of organics  

SciTech Connect

Reduction and dissolution of manganese(III,IV) oxide suspensions by 27 aromatic and nonaromatic compounds resembling natural organics were examined in order to understand the solubilization reaction in nature. At pH 7.2 10/sup -3/ M formate, fumarate, glycerol, lactate, malonate, phthalate, propanol, propionaldehyde, propionate, and sorbitol did not dissolve appreciable amounts of oxide after 3 h of reaction. The following organics did dissolve manganese oxides under these conditions and are listed in order of decreasing reactivity: 3-methoxycatechol approx. catechol approx. 3,4-dihydroxybenzoic acidapprox. ascorbate > 4-nitro-catechol > thiosalicylate > hydroquinone > 2,5-dihydroxybenzoic acid > syringic acid > o-methoxyphenol > vanillic acidapprox. orcinol approx. 3,5-dihydroxybenzoic acid > resorcinol > oxalite approx. pyruvate approx. salicylate. Relative reactivities of organic substrates are discussed in terms of surface complex formation prior to electron transfer. Dissolution of manganese oxides by marine fulvic acid was enhanced by illumination, verifying that the reaction is photocatalyzed.

Stone, A.T.; Morgan, J.J.

1984-01-01

207

Growth and Dissolution of Iron and Manganese Oxide Films  

SciTech Connect

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 were approximately 40 pN and 600 pN, respectively, whereas those of MnCO{sub 3} were essentially zero. The force differences between MnO{sub x} and MnCO{sub 3} suggest that oxide film growth can focus adsorbates to certain parts of the surface and thereby templating a heterogeneous layout of them. We suspected that the force differences were in part due to the differences in surface electrical properties. In 2007, we investigated two important electrical properties of MnO{sub x} and MnCO{sub 3} surfaces, namely surface potential and ion mobility. Surface potential is a composite quantity that can be linked to the local lattice structure of the reconstructed surface and the adsorption of water layers. The mobile surface ions formed by dissolution can also contribute to surface potential. Using Kelvin probe force microscopy (KPFM) and scanning polarization force microscopy (SPFM), we found that MnOx possessed excess surface potentials of over +200 mV in humid nitrogen and the excess surface potential decreased with increasing relative humidity (i.e., increasing adsorbed water layers on the mineral surface). The dependence of the excess surface potential was attributed to the change of the contributions from mobile ions. These results supported our earlier hypothesis that MnO{sub x} and MnCO{sub 3} had different surface electrical properties. In the third year, we systematically characterized that the change of the electrical double layer (EDL) structure of MnCO{sub 3} surface due to MnO{sub x} growth in aqueous solution and its dependence on pH. The structure of the electrical double layer determines the electrostatic interactions between the mineral surface and charged adsorbates. As described by the Derjaguin-Landau-Verwey-Overbeek (DLVO) theory, the electrostatic force, together with van der Waals interaction, regulates surface adsorption and bacterial attachment. Once adsorbates establish contact with the surface, they must resist hydraulic shear forces through surface adhesion. The adhesion of mineral surfaces is also affected by their electrostatic interactions with adsorbates. To probe the EDL structure, we ap

Scot T. Martin

2008-12-22

208

Enhanced dissolution of manganese oxide in ice compared to aqueous phase under illuminated and dark conditions.  

PubMed

Manganese is one of the common elements in the Earth's crust and an essential micronutrient for all living things. The reductive dissolution of particulate manganese oxide is a dominant process to enhance mobility and bioavailability of manganese for the use of living organisms. In this work, we investigated the reductive dissolution of manganese oxides trapped in ice (at -20 C) under dark and light irradiation (visible: ? > 400 nm and UV: ? > 300 nm) in comparison with their counterparts in aqueous solution (at 25 C). The reductive dissolution of synthetic MnO?, which took place slowly in aqueous solution, was significantly accelerated in ice phase both in the presence and absence of light: about 5 times more dissolution in ice phase than in liquid water after 6 h UV irradiation in the presence of formic acid. The enhanced dissolution in ice was observed under both UV and visible irradiation although the rate was much slower in the latter condition. The reductive dissolution rate of Mn(II)(aq) (under both irradiation and dark conditions) gradually increased with decreasing pH below 6 in both aqueous and ice phases, and the dissolution rates were consistently faster in ice under all tested conditions. The enhanced generation of Mn(II)(aq) in ice can be mainly explained in terms of freeze concentration of electron donors, protons, and MnO? in liquid-like ice grain boundaries. The outdoor solar experiment conducted in Arctic region (Ny-lesund, Svalbard, 7855'N) also showed that the photoreductive dissolution of manganese oxide is enhanced in ice. The present results imply that the dissolution of natural minerals like manganese oxides can be enhanced in icy environments such as polar region, upper atmosphere, and frozen soil. PMID:23153016

Kim, Kitae; Yoon, Ho-Il; Choi, Wonyong

2012-12-04

209

Using nitrogen isotope fractionation to assess the oxidation of substituted anilines by manganese oxide.  

PubMed

We explored the N isotope fractionation associated with the oxidation of substituted primary aromatic amines, which are often the position of initial attack in transformation processes of environmental contaminants. Apparent (15)N-kinetic isotope effects, AKIE(N), were determined for the oxidation of various substituted anilines in suspensions of manganese oxide (MnO(2)) and compared to reference experiments in homogeneous solutions and at electrode surfaces, as well as to density functional theory calculations of intrinsic KIE(N)for electron and hydrogen atom transfer reactions. Owing to the partial aromatic imine formation after one-electron oxidation and corresponding increase in C-N bond strength, AKIE(N)-values were inverse, substituent-dependent, and confined to the range between 0.992 and 0.999 in agreement with theory. However, AKIE(N)-values became normal once the fraction of cationic species prevailed owing to (15)N-equilibrium isotope effects, EIE(N), of 1.02 associated with N atom deprotonation. The observable AKIE(N)-values are substantially modulated by the acid/base pre-equilibria of the substituted anilines and isotope fractionation may even vanish under conditions where normal EIE(N) and inverse AKIE(N) cancel each other out. The pH-dependent trends of the AKIE(N)-values provide a new line of evidence for the identification of contaminant degradation processes via oxidation of primary aromatic amino groups. PMID:21627095

Skarpeli-Liati, Marita; Jiskra, Martin; Turgeon, Aurora; Garr, Ashley N; Arnold, William A; Cramer, Christopher J; Schwarzenbach, Ren P; Hofstetter, Thomas B

2011-05-31

210

The Structure and Properties of Plasma Sprayed Iron Oxide Doped Manganese Cobalt Oxide Spinel Coatings for SOFC Metallic Interconnectors  

Microsoft Academic Search

Manganese cobalt oxide spinel doped with Fe2O3 was studied as a protective coating on ferritic stainless steel interconnects. Chromium alloying causes problems at high\\u000a operation temperatures in such oxidizing conditions where chromium compounds evaporate and poison the cathode active area,\\u000a causing the degradation of the solid oxide fuel cell. In order to prevent chromium evaporation, these interconnectors need\\u000a a protective

Jouni Puranen; Juha Lagerbom; Leo Hyvrinen; Mikko Kylmlahti; Olli Himanen; Mikko Pihlatie; Jari Kiviaho; Petri Vuoristo

2011-01-01

211

Enhanced electro-oxidation of formic acid at manganese oxide single crystalline nanorod-modified Pt electrodes  

Microsoft Academic Search

The electrocatalytic activity of Pt towards the oxidation of formic acid is significantly enhanced upon the electrodeposition of manganese oxide nanorods (in the (111) single crystalline phase, ?-MnOOH). The modified Pt electrodes are shown to support the direct oxidation of formic acid to CO2 (i.e., dehydrogenation pathway), while suppressing the dehydration pathway (producing the poisoning intermediate CO). This behaviour is

Mohamed S. El-Deab; Ludwig A. Kibler; Dieter M. Kolb

2009-01-01

212

Hybrid ternary rice paper-manganese oxide-carbon nanotube nanocomposites for flexible supercapacitors.  

PubMed

Modern portable electronic devices create a strong demand for flexible energy storage devices. Paper based nanocomposites are attractive as sustainable materials for such applications. Here, we directly explored the hydroxyl chemistry of cellulose fibers to synthesize hybrid ternary nanocomposites, comprised of rice paper, single-walled carbon nanotubes (SWCNTs) and manganese oxide nanoparticles. The functional groups on cellulose fibers can react with adsorbed permanganate ions, resulting in uniform deposition of manganese oxide nanoparticles. SWCNTs coated on top of manganese oxide nanoparticles form a highly conductive network connecting individual manganese oxide particles. By using the hybrid ternary composites as electrodes, the assembled two-electrode supercapacitors demonstrated high capacitance (260.2 F g(-1)), energy (9.0 W h kg(-1)), power (59.7 kW kg(-1)), and cycle stability (12% drop after 3000 cycles). In addition, the nanocomposites show good strength and excellent mechanical flexibility, and their capacitance shows negligible changes after bending more than 100 times. These findings suggest that opportunities exist to further explore the rich chemistry of cellulose fibers for innovative energy applications. PMID:24077360

Jiang, Wenchao; Zhang, Kaixi; Wei, Li; Yu, Dingshan; Wei, Jun; Chen, Yuan

2013-09-27

213

SERUM CHEMISTRIES OF COTURNIX JAPONICA GIVEN DIETARY MANGANESE OXIDE (MN3O4)  

EPA Science Inventory

Plasma creatinine and inorganic phosphorus were increased in manganese oxide (Mn3O4)-treated adult male Coturnix quail, but BUN, BUN/creatinine ratio, uric acid, and total calcium were decreased. 2. Serum enzymes (alkaline phosphatase glutamic oxaloacetic transaminase, glutamic p...

214

Electrodeposited amorphous manganese oxide nanowire arrays for high energy and power density electrodes  

Microsoft Academic Search

Arrays of manganese oxide nanowires were electrodeposited into anodized alumina membranes. These nanowire arrays were investigated in terms of their structural and electrochemical properties as cathodes for high energy and high power density Li ion batteries. The nanowire arrays were assembled with a Li counter electrode and non-aqueous electrolyte to form secondary batteries. These cells were capable of multiple charge\\/discharge

W. C. West; N. V. Myung; J. F. Whitacre; B. V. Ratnakumar

2004-01-01

215

Effects of manganese oxide on monkeys as revealed by a combined neurochemical, histological and neurophysiological evaluation  

Microsoft Academic Search

Four monkeys were exposed to a total of 8 g each of manganese as oxide by repetitive subcutaneous injections during 5 months, after which they were left for 1 week to 6 months before they were sacrificed. All animals developed hyperactive behaviour after about 2 months. About 5 months after the start of the exposure the animals became hypoactive with

Hhkan Eriksson I; Katarina Mgiste; Lars-Olof Plantin; Frode Fonnum; Karl-Gran Hedstrm; Elvar Theodorsson-Norheim; Krister Kristensson; Erik Stlberg; Edith Heilbronn I

1987-01-01

216

Synthesis of Lithium-Manganese-Oxide Spinels: A Study by Thermal Analysis  

Microsoft Academic Search

The synthesis of lithium-manganese-oxide spinels by reaction of Li2CO3 and MnCO3 in air and under nitrogen to Tmax = 600C has been investigated by thermogravimetric analysis and differential scanning calorimetry. When the reaction is conducted in air, the stoichiometric spinel LiMn2O4 is produced via a series of intermediate \\

M. M. Thackeray; M. H. Rossouw

1994-01-01

217

Electronic structures of lithium manganese oxides for rechargeable lithium battery electrodes  

Microsoft Academic Search

The modification of electronic structures of manganese oxides due to lithium intercalation has been investigated by the DV-X? molecular orbital method. In this study the process of lithium intercalation is assumed to be divided into two steps: the lithium occupancy (chemical effect) and the lattice expansion (structural effect). By the lithium occupancy the energy gap lying between the O-2p and

Yi Liu; T Fujiwara; H Yukawa; M Morinaga

1999-01-01

218

Electrochemical impedance spectroscopy studies of lithium diffusion in doped manganese oxide.  

National Technical Information Service (NTIS)

Cathode performance is critical to lithium ion rechargeable battery performance; effects of doping lithium manganese oxide cathode materials on cathode performance are being investigated. In this paper, Li diffusion in Al-doped LiMn(sub 2)O(sub 4) was stu...

B. J. Johnson D. H. Doughty J. A. Voigt T. J. Boyle

1996-01-01

219

Lithium Potassium Manganese Mixed Metal Oxide Material for Rechargeable Electrochemical Cells.  

National Technical Information Service (NTIS)

A family of potassium-doped manganese oxide materials were synthesized with the stoichiometric formula Li0.9-xKxMn2O4, where X = 0.0 to 0.25, and evaluated for their viability as a cathode material for a rechargeable lithium battery. A performance maximum...

A. J. Salkind T. B. Atwater

2010-01-01

220

Photocatalytic oxidation of stilbene by self-assembled stacks of manganese porphyrins.  

PubMed

Self-assembled stacks of trimeric manganese porphyrins exhibit high activity in the photocatalytic epoxidation of stilbene using O2 as the oxidant. The supramolecular structure of the catalyst leads to increased stability of the system and enhances the stereoselectivity of the reaction. PMID:24116375

de Torres, Miriam; van Hameren, Richard; Nolte, Roeland J M; Rowan, Alan E; Elemans, Johannes A A W

2013-10-24

221

Sulfur resistance and high activity of hydrated manganese sulfate in the catalytic oxidation of methanethiol  

Microsoft Academic Search

Hydration of manganese sulfate at a low reaction temperature (150C) induces high heterogeneous catalytic activity and stability in the oxidation of methanethiol. The temperature of the reaction controls the reversible change of structure, i.e., hydration\\/dehydration processes as well as the associated changes of activity and selectivity.

Caroline Cellier; Eric M. Gaigneaux; Paul Grange

2004-01-01

222

Allylic oxidation of cyclohexene catalyzed by manganese porphyrins: DFT studies  

Microsoft Academic Search

The present paper summarizes density functional theory studies on hydroxylation of cyclohexene catalyzed by manganese oxo porphyrin. The reaction is preceded by the physisorption of the substrate over the catalyst molecule at the distance of 2.18. Next, a hydrogen atom form the CH bond is abstracted by the catalyst oxo group and the cyclohexene radical is readily bound to the

D. Rutkowska-Zbik; M. Witko; E. M. Serwicka

2011-01-01

223

Environmental Factors Affecting Oxidation of Manganese in Pinal Creek, Arizona  

Microsoft Academic Search

The objectives of the laboratory work reported here were to quantify the net rates of removal of manganese (Mn(II)) by streambed sediments collected from a metals contaminated, perennial stream system (Pinal Creek near Globe AZ) and to determine the key variable(s) responsible for the limited removal of Mn(II) observed at this field site. Pinal Creek is characterized by significant spatial

Justin C. Marble; Timothy L. Corley; Martha H. Conklin; Christopher C. Fuller

224

Lithium Nickel Manganese Oxides for Advanced Lithium-ion Batteries  

Microsoft Academic Search

for advanced lithium-ion batteries. These samples can be prepared by adjusting the molar ratio of lithium, nickel, and manganese. A common feature among a series of lithium insertion materials is that well-defined crystals are superior to ill-defined crystals in terms of rechargeable capacity, rate-capability, and cycleability. Therefore, we usually apply the high-temperature synthesis of these lithium insertion materials.

Tsutomu Ohzuku; Kingo Ariyoshi

225

Growth of a manganese oxidizing Pseudomonas sp. in continuous culture  

Microsoft Academic Search

Strain S-36, a marine Pseudomonas sp., was grown under manganese limitation in continuous culture. At dilution rates below a maximal growth rate of 0.066 h-1, the rate at which the organism fixed CO2 into macromolecules was equal to the cell carbon production rate. In addition, the total amount of cell carbon or CO2 fixed at steady-state was in proportion to

P. E. Kepkay; K. H. Nealson

1987-01-01

226

Amperometric Biosensors Based on Carbon Paste Electrodes Modified with Nanostructured Mixed-valence Manganese Oxides and Glucose Oxidase  

SciTech Connect

Nanostructured multivalent manganese oxides octahedral molecular sieve (OMS), including cryptomelane-type manganese oxides and todorokite-type manganese oxides, were synthesized and evaluated for chemical sensing and biosensing at low operating potential. Both cryptomelane-type manganese oxides and todorokite-type manganese oxides are nanofibrous crystals with sub-nanometer open tunnels that provide a unique property for sensing applications. The electrochemical and electrocatalytic performance of OMS for the oxidation of H2O2 have been compared. Both cryptomelane-type manganese oxides and todorokite-type manganese oxides can be used to fabricate sensitive H2O2 sensors. Amperometric glucose biosensors are constructed by bulk modification of carbon paste electrodes (CPEs) with glucose oxidase as a biocomponent and nanostructured OMS as a mediator. A Nafion thin film was applied as an immobilization/encapsulation and protective layer. The biosensors were evaluated as an amperometric glucose detector at phosphate buffer solution with a pH 7.4 at an operating potential of 0.3 V (vs. Ag/AgCl). The biosensor is characterized by a well-reproducible amperometric response, linear signal-to-glucose concentration range up to 3.5 mM and 1.75 mM, and detection limits (S/N = 3) of 0.1 mM and 0.05 mM for todorokite-type manganese oxide and cryptomelane-type manganese oxide modified electrodes, respectively. The biosensors based on OMS exhibit considerable good reproducibility and stability, and the construction and renewal are simple and inexpensive.

Cui, Xiaoli; Liu, Guodong; Lin, Yuehe

2005-06-01

227

Cobalt(II) Oxidation by the Marine Manganese(II)-Oxidizing Bacillus sp. Strain SG-1  

PubMed Central

The geochemical cycling of cobalt (Co) has often been considered to be controlled by the scavenging and oxidation of Co(II) on the surface of manganese [Mn(III,IV)] oxides or manganates. Because Mn(II) oxidation in the environment is often catalyzed by bacteria, we have investigated the ability of Mn(II)-oxidizing bacteria to bind and oxidize Co(II) in the absence of Mn(II) to determine whether some Mn(II)-oxidizing bacteria also oxidize Co(II) independently of Mn oxidation. We used the marine Bacillus sp. strain SG-1, which produces mature spores that oxidize Mn(II), apparently due to a protein in their spore coats (R.A. Rosson and K. H. Nealson, J. Bacteriol. 151:1027-1034, 1982; J. P. M. de Vrind et al., Appl. Environ. Microbiol. 52:1096-1100, 1986). A method to measure Co(II) oxidation using radioactive 57Co as a tracer and treatments with nonradioactive (cold) Co(II) and ascorbate to discriminate bound Co from oxidized Co was developed. SG-1 spores were found to oxidize Co(II) over a wide range of pH, temperature, and Co(II) concentration. Leucoberbelin blue, a reagent that reacts with Mn(III,IV) oxides forming a blue color, was found to also react with Co(III) oxides and was used to verify the presence of oxidized Co in the absence of added Mn(II). Co(II) oxidation occurred optimally around pH 8 and between 55 and 65C. SG-1 spores oxidized Co(II) at all Co(II) concentrations tested from the trace levels found in seawater to 100 mM. Co(II) oxidation was found to follow Michaelis-Menten kinetics. An Eadie-Hofstee plot of the data suggests that SG-1 spores have two oxidation systems, a high-affinity-low-rate system (Km, 3.3 10-8 M; Vmax, 1.7 10-15 M spore-1 h-1) and a low-affinity-high-rate system (Km, 5.2 10-6 M; Vmax, 8.9 10-15 M spore-1 h-1). SG-1 spores did not oxidize Co(II) in the absence of oxygen, also indicating that oxidation was not due to abiological Co(II) oxidation on the surface of preformed Mn(III,IV) oxides. These results suggest that some microorganisms may directly oxidize Co(II) and such biological activities may exert some control on the behavior of Co in nature. SG-1 spores may also have useful applications in metal removal, recovery, and immobilization processes. Images

Lee, Yoon; Tebo, Bradley M.

1994-01-01

228

A novel method for preparing lithium manganese oxide nanorods from nanorod precursor  

Microsoft Academic Search

Lithium manganese oxide nanorods were prepared from manganese dioxide nanorods precursor. The structure and morphology were\\u000a confirmed by X-ray diffraction (XRD) and transmission electron microscope (TEM). The data of the Rietveld refinement indicate\\u000a that the nanorods preferentially grow along the [111] direction. After chargedischarge test at 1.0mAcm?2 in 3.04.4V, the nanorods LiMn2O4 showed the 134.5mAhg?1 initial discharge capacity and only

Haowen Liu; Long Tan

2010-01-01

229

Lattice vibrations of materials for lithium rechargeable batteries III. Lithium manganese oxides  

Microsoft Academic Search

Structural features of several lithiated manganese oxides are studied using Raman scattering (RS) spectroscopy. This local probe is capable to analyse directly the near-neighbour environment of oxygen coordination around manganese and lithium cations. The samples include: orthorhombic and monoclinic LiMnO2, spinel LiMn2O4, monoclinic Li2MnO3, lithiated-spinel Li2Mn2O4, Li-birnessite, LT- and HT-Li0.52MnO2.1, spinel Li4Mn5O12, and Li0.33MnO2. Thus, as a first approach, we

C. M. Julien; M. Massot

2003-01-01

230

Structural and electrochemical effects of cobalt doping on lithium manganese oxide spinel  

Microsoft Academic Search

Pure LiMn2O4 and lithium manganese oxide spinels with partial replacement of manganese by cobalt up to 20 mole%, LiCoxMn2?xO4, were prepared. The effect of extended cycling on the crystal structure was investigated. A capacity decrease with increasing\\u000a cobalt content was observed in the potential range about 4100 mV vs. Li\\/Li+. Cycling behavior is significantly improved, compared to LiMn2O4. LiCoxMn2?xO4 is

A. Butz; M. Wohlfahrt-Mehrens; R. Oesten; R. A. Huggins

1996-01-01

231

Oxidative stress is induced in the rat brain following repeated inhalation exposure to manganese sulfate  

Microsoft Academic Search

Eight-week-old rats inhaled manganese (Mn) in the form of MnSO4 at 0, 0.03, 0.3, or 3.0 mg Mn\\/m3 for 6 h\\/d for 7 d\\/wk (14 consecutive exposures). Brain manganese concentrations in these animals were reported by Dorman\\u000a et al. in 2001, noting the following rank order: olfactory bulb>striatum>cerebellum. We assessed biochemical end points indicative\\u000a of oxidative stress in these three

Allison W. Dobson; Sarah Weber; David C. Dorman; Lawrence K. Lash; Keith M. Erikson; Michael Aschner

2003-01-01

232

Decarboxylative coupling of heptanoic acid. Manganese, cerium and zirconium oxides as catalysts  

Microsoft Academic Search

A series of catalysts containing 20wt.% of Mn, Ce and Zr oxides deposited on Al2O3, SiO2 and TiO2 has been studied in ketonisation of heptanoic acid. The most pronounced effect of alumina support on catalysts activity has been noted. Manganese oxide catalysts have shown the highest activity. The dependence of the concentration of MnO2 active phase on catalyst activity has

M Gli?ski; J Kije?ski

2000-01-01

233

Early Indications for Manganese Oxidation State Changes During Photosynthetic Oxygen Production: A Personal Account  

Microsoft Academic Search

One of the major questions yet to be answered in photosynthesis research today is what is the chemical mechanism for the oxidation\\u000a of water into molecular oxygen. It is well established that an inorganic cluster of four manganese ions and at least one calcium\\u000a ion form the catalytic core. As the oxidation potential generated by the Photosystem II reaction center

Thomas J. Wydrzynski

2004-01-01

234

Enhanced electrochemical characteristics of lithium manganese oxide thin film cathodes for lithium-ion rechargeable microbatteries  

Microsoft Academic Search

Spinel LiMn2O4 (average oxidation state of Mn = 3.5) thin film has been introduced for a promising cathode of thin film lithium-ion microbatteries because of its advantages over other cathodes. Thus, many research groups have been investigating the thin film lithium manganese oxide cathode using several different techniques but only a few of them achieved acceptable electrochemical properties required for

Won-Seok Kim

2004-01-01

235

Designing High Capacity, Stable Lithium-Manganese Oxide Insertion Electrodes with First Principles Computations  

Microsoft Academic Search

The viability of rechargeable lithium batteries in many applications hinges on finding electrode materials with high capacity, excellent chemical and phase stability, and low cost. LiCoO_2, the intercalation oxide currently used is too expensive and unsafe for large-scale batteries. Manganese oxides are a possible low cost alternative, but spinel LiMn_2O _4, the common form of the material, has too low

John Reed; Anton van der Ven; Gerbrand Ceder

2001-01-01

236

Recalculation, evaluation, and prediction of surface complexation constants for metal adsorption on iron and manganese oxides  

Microsoft Academic Search

The triple-layer model of the oxide\\/water interface can be used to calculate the partitioning of metals among solid and aqueous phases. The defensible use of the triple-layer model in groundwater\\/sediment systems requires an adequate and consistent set of intrinsic adsorption constants. In the present study, published values of p{sup *}K{sup int} for cation adsorption on iron and manganese oxides have

Robert W. Smith; E. A. Jenne

1991-01-01

237

Manganese-Cobalt Mixed Spinel Oxides as Surface Modifiers for Stainless Steel Interconnects of Solid Oxide Fuel Cells  

Microsoft Academic Search

Ferritic stainless steels are promising candidates for interconnect applications in low- and mid-temperature solid oxide fuel cells (SOFCs). A couple of issues however remain for the particular application, including the chromium poisoning due to chromia evaporation, and long-term surface and electrical stability of the scale grown on these steels. Application of a manganese colbaltite spinel protection layer on the steels

Gordon Xia; Z Gary Yang; Jeffry W. Stevenson

2006-01-01

238

Kinetics of microbial manganese oxidation and trace metal binding in sediments: Results from an in situ dialysis technique  

Microsoft Academic Search

Sediments associated with freshwater fcrromanganese concretions in Lake Charlotte, Nova Sco- tia, contained microscopic precipitates of manganese and iron. These precipitates were dispersed throughout the sediment and were as rich in nickel, cobalt, and copper as deep sea concretions. In addition, the development of the precipitates appeared to be associated with the microbial oxidation of manganese. Results from the deployment

Paul E. Kepkay

1985-01-01

239

Water-oxidation catalysis by manganese in a geochemical-like cycle  

NASA Astrophysics Data System (ADS)

Water oxidation in all oxygenic photosynthetic organisms is catalysed by the Mn4CaO4 cluster of Photosystem II. This cluster has inspired the development of synthetic manganese catalysts for solar energy production. A photoelectrochemical device, made by impregnating a synthetic tetranuclear-manganese cluster into a Nafion matrix, has been shown to achieve efficient water oxidation catalysis. We report here in situ X-ray absorption spectroscopy and transmission electron microscopy studies that demonstrate that this cluster dissociates into Mn(II) compounds in the Nafion, which are then reoxidized to form dispersed nanoparticles of a disordered Mn(III/IV)-oxide phase. Cycling between the photoreduced product and this mineral-like solid is responsible for the observed photochemical water-oxidation catalysis. The original manganese cluster serves only as a precursor to the catalytically active material. The behaviour of Mn in Nafion therefore parallels its broader biogeochemistry, which is also dominated by cycles of oxidation into solid Mn(III/IV) oxides followed by photoreduction to Mn2+.

Hocking, Rosalie K.; Brimblecombe, Robin; Chang, Lan-Yun; Singh, Archana; Cheah, Mun Hon; Glover, Chris; Casey, William H.; Spiccia, Leone

2011-06-01

240

Topotactic oxidative and reductive control of the structures and properties of layered manganese oxychalcogenides.  

PubMed

Topotactic modification, by both oxidation and reduction, of the composition, structures, and magnetic properties of the layered oxychalcogenides Sr4Mn3O7.5Cu2Ch2 (Ch=S, Se) is described. These Mn3+ compounds are composed of alternating perovskite-type strontium manganese oxide slabs separated by anti-fluorite-type copper chalcogenide layers and are intrinsically oxide deficient in the central layer of the perovskite slabs. The systems are unusual examples of perovskite-related compounds that may topotactically be both oxidized by fluorination and reduced by deintercalation of oxygen from the oxide-deficient part of the structure. The compounds exhibit antiferromagnetic ordering of the manganese magnetic moments in the outer layers of the perovskite slabs, while the other moments, in the central layers, exhibit spin-glass-like behavior. Fluorination has the effect of increasing the antiferromagnetic ordering temperature and the size of the ordered moment, whereas reduction destroys magnetic long-range order by introducing chemical disorder which leads to both further disorder and frustration of the magnetic interactions in the manganese oxide slab. PMID:17705487

Hyett, Geoffrey; Barrier, Nicolas; Clarke, Simon J; Hadermann, Joke

2007-08-18

241

In situ quartz crystal microbalance studies of nickel hydrous oxide films in alkaline electrolytes  

SciTech Connect

The microgravimetric characteristics of electrodeposited nickel and composite Ni/Co hydrous oxide films on Au electrodes in KOH electrolytes were examined in situ with a combination of quartz crystal microbalance (QCM) and voltammetric techniques. In the case of freshly prepared {alpha}-Ni(OH){sub 2} hydrous oxide films, denoted as {alpha}-Ni(OH){sub 2}(hyd), the mass increased during oxidation and then decreased upon subsequent reduction. As the redox cycling was continued, however, this behavior gradually reversed, i.e., the mass decreased upon oxidation and then increased following further reduction. This unique effect could be correlated with a shift in the position of the oxidation peak maximum (E{sub p}{sup ox}) in the voltammogram toward more positive potentials, which has been ascribed to the transformation of {alpha}-Ni(OH){sub 2}(hyd) into {beta}-Ni(OH){sub 2}(hyd). Based on these findings, it can be concluded that the mechanism of ionic charge transport in these two types of lattices is markedly different. In contrast, composite Ni/Co (9:1) hydrous oxide films displayed qualitatively the same behavior as pure freshly prepared Ni(OH){sub 2}(hyd) in the same alkaline media regardless of the extent of cycling. This observation provides evidence that the incorporation of cobalt into Ni(OH){sub 2}(hyd) modifies the structural properties of the lattice during the oxidation/reduction process.

Mo, Y.; Hwang, E.; Scherson, D.A. [Case Western Reserve Univ., Cleveland, OH (United States). Dept. of Chemistry

1996-01-01

242

The effect of zirconium oxide and quartz pigments on the heat and corrosion resistance properties of the silicone based coatings  

Microsoft Academic Search

Silicone resin based protective coatings are generally used for high temperature applications. In this work, anti-corrosive and heat resistant properties of titanium dioxide, mica, zirconium oxide and quartz combination pigments with silicone resin as carrier vehicle in primer and top coat for mild steel surface have been evaluated. Promising results were obtained, showing that the ceramic pigments (zirconium oxide and

L. Mathivanan; A. K. Arof

2000-01-01

243

Effect of Structure on the Storage Characteristics of ManganeseOxide Electrode Materials  

SciTech Connect

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.

Park, Yong Joon; Doeff, Marca M.

2006-01-31

244

Electrocatalysis by nanoparticles: Oxidation of formic acid at manganese oxide nanorods-modified Pt planar and nanohole-arrays  

Microsoft Academic Search

The electro-oxidation of formic acid (an essential reaction in direct formic acid fuel cells) is a challenging process because of the deactivation of anodes by the adsorption of the poisoning intermediate carbon monoxide (CO). Pt electrodes in two geometries (planar and nanohole-array) were modified by the electrodeposition of manganese oxide nanorods (nano-MnOx). The modified Pt electrodes were then tested for

Mohamed S. El-Deab

2010-01-01

245

A rapid evaluation of vanadium oxide and manganese oxide as battery materials with a micro-electrochemistry technique  

Microsoft Academic Search

The electrochemical behavior of vanadium oxide V2O5 and bismuth doped manganese oxide BiMnO2 as battery materials was studied with a cavity microelectrode (CME). This technique, which allows working on a very few amount of material, appears to be suitable when high scan rates are used. Thus, it is possible to perform many hundreds cycles in a short time. The performances

V. Vivier; S. Belair; C. Cachet-Vivier; J.-Y. Nedelec; L. T. Yu

2001-01-01

246

H2 uptake and synthesis of the Li-dispersed manganese oxide nanotubes.  

PubMed

Well aligned Li-dispersed manganese oxide nanotubes were prepared using LiNO3, Mn(NO3)2 x xH2O and an anodic aluminum oxide template by solvent-free method for potential applications in H2 storage. The obtained nanotubes were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), and transmission electron microscopy (TEM). The analyses revealed the Mn2O3 nanotubes to have a cubic structure with a uniform length, 40-50 nm in wall thickness and 250 +/- 10 nm in the outer diameter. The level of H2 adsorption was determined using the gravimetric method. The Li-dispersed manganese oxide nanotubes showed a 0.26 wt% for the amount of hydrogen adsorption at 77 K under 4.5 MPa. PMID:18047112

Lee, Jin Bae; Lee, Soon Chang; Kim, Hae Jin

2007-11-01

247

Synthesis of porous CrO{sub x} pillared octahedral layered manganese oxide materials  

SciTech Connect

Chromium oxide pillared manganese oxide materials were prepared by intercalating layered manganese oxide with chromium hydroxyl acetate clusters under reflux condition. The as-synthesized materials were heated at 200 C in flowing nitrogen for 1 h to result in chromium oxide pillared manganese oxides. X-ray diffraction, UV-vis, FTIR, BET surface area and pore size distribution, temperature programmed desorption, elemental analysis, and X-ray absorption spectrometry were used to study the intercalating process and the structures of the pillared materials. Porous materials with a high specific surface area and a narrow pore size distribution (18 {angstrom}) were obtained. The removal of bound water and dehydroxylated water was responsible for the production of high surface area in the pillared material. The decomposition of acetate groups bidentate-linked to Cr starting at 200 C in N{sub 2} resulted in a concomitant decrease in porosity. Although the ordering of the layers was largely destroyed and the materials remained amorphous under XRD study, TEM morphology studies suggest that the material was still layered EXAFS studies indicate the formation of Cr-O-Mn bonds in the resultant materials via corner-shared linkages of CrO{sub 6} and MnO{sub 6} octahedra.

Ma, Y.; Suib, S.L.; Ressler, T.; Wong, J.; Lovallo, M.; Tsapatsis, M.

1999-12-01

248

The oxidative dechlorination reaction of 2,4,6-trichlorophenol in dilute aqueous suspensions of manganese oxides  

SciTech Connect

Oxidation of 2,4,6-trichlorophenol (TCP) by layered manganese oxides (Na and Co-buserite) in dilute acidified aqueous suspension gives 2,6-dichloro-p-benzoquinone as a major product. This compound is likely to further polymerize and become incorporated into humus like materials. The oxidation rate was higher at lower pH and higher on Na-buserite compared to Co-buserite. TCP reacted at a faster rate than unsubstituted phenol at pH3 and 5.5, which is explained by (a) the lower half-wave potential of TCP compared to phenol; (b) a stronger bond dipole associated with the electronegative halogen, favoring an addition step in nucleophilic substitution; and (c) easier depronation of TCP at the manganese oxide-water interface due to its lower pK[sub a]. IR spectroscopy shows that TCP adsorbs in deprotonated form on the surface of manganese oxide, and it cannot be washed from the surface by water. Nucleophilic attack by addition-elimination is suggested as a mechanism of TCP dechlorination and oxidation.

Ukrainczyk, L.; McBride, M.B. (Cornell Univ., Ithaca, NY (United States). Dept. of Soil, Crop and Atmospheric Sciences)

1993-11-01

249

Improved manganese-oxidizing activity of DypB, a peroxidase from a lignolytic bacterium.  

PubMed

DypB, a dye-decolorizing peroxidase from the lignolytic soil bacterium Rhodococcus jostii RHA1, catalyzes the peroxide-dependent oxidation of divalent manganese (Mn(2+)), albeit less efficiently than fungal manganese peroxidases. Substitution of Asn246, a distal heme residue, with alanine increased the enzyme's apparent k(cat) and k(cat)/K(m) values for Mn(2+) by 80- and 15-fold, respectively. A 2.2 resolution X-ray crystal structure of the N246A variant revealed the Mn(2+) to be bound within a pocket of acidic residues at the heme edge, reminiscent of the binding site in fungal manganese peroxidase and very different from that of another bacterial Mn(2+)-oxidizing peroxidase. The first coordination sphere was entirely composed of solvent, consistent with the variant's high K(m) for Mn(2+) (17 2 mM). N246A catalyzed the manganese-dependent transformation of hard wood kraft lignin and its solvent-extracted fractions. Two of the major degradation products were identified as 2,6-dimethoxybenzoquinone and 4-hydroxy-3,5-dimethoxybenzaldehyde, respectively. These results highlight the potential of bacterial enzymes as biocatalysts to transform lignin. PMID:23305326

Singh, Rahul; Grigg, Jason C; Qin, Wei; Kadla, John F; Murphy, Michael E P; Eltis, Lindsay D

2013-01-18

250

Kinetics of microbial manganese oxidation and trace metal binding in sediments: results from an in situ dialysis technique  

SciTech Connect

Sediments associated with freshwater ferromanganese concretions in Lake Charlotte, Nova Scotia, contained microscopic precipitates of manganese and iron. These precipitates were dispersed throughout the sediment and were as rich in nickel, cobalt, and copper as deep sea concretions. In addition, the development of the precipitates appeared to be associated with the microbial oxidation of manganese. Results from the deployment of poisoned and unpoisoned dialysis probes or peepers demonstrated that microbial manganese oxidation and nickel binding were closely associated, causing a fivefold enhancement of abiotic processes such as adsorption. The microbial enhancement of copper binding was far less pronounced, due to organic-metal interactions in competition with manganese oxidation. Organic-metal interactions and oxidation may both have been in effect during iron binding, but the relative importance of the two processes could not be determined from the kinetic data.

Not Available

1985-07-01

251

Lattice vibrations of manganese oxides. Part I. Periodic structures.  

PubMed

Raman scattering (RS) and Fourier transform-infrared (FT-IR) spectroscopy have been applied to the structural characterisation of manganese dioxides (MDOs). A variety of synthetic battery-grade MDOs are investigated for comparison to the natural phases. The RS and FT-IR spectra are analysed on the basis of the local environment in the MDO structures considering the vibrations of the MnO6 octahedral building the lattices. The vibrational modes of the MnO6 units expand over 400-650 cm(-l) with additional bands in the low-wavelength region. Structural trends are deduced from the comparison of the vibrational spectra of the MDO phases investigated: birnessite, bixbyite, coronadite, groutite, hausmannite, hollandite, manganosite, pyrolusite, ramsdellite, romanechite, spinel, and todorokite. PMID:14747095

Julien, C M; Massot, M; Poinsignon, C

2004-02-01

252

Combination of a non-thermal plasma and a catalyst for toluene removal from air: Manganese based oxide catalysts  

Microsoft Academic Search

A series of manganese based catalysts have been tested in a combined plasma-catalyst reactor in the reaction of toluene removal from air. In the standard conditions (toluene=240ppm, energy density=172J\\/L, 1g of catalyst, 315mL\\/min), the best catalyst (manganese oxide supported on active carbon) is able to transform 55% of the toluene into carbon oxides. According to the study of the reaction

Sophie Delagrange; Ludovic Pinard; Jean-Michel Tatibout

2006-01-01

253

Reactive sorbent based on manganese oxide nanotubes and nanosheets for the decontamination of 2-chloro-ethyl ethyl sulphide  

Microsoft Academic Search

Novel mesoporous reactive sorbent based on nanosheets and nanotubes of manganese oxide was prepared by the flocculation precipitation of manganese oxide nanosheet solutions. Obtained porous aggregates were characterized by X-ray diffraction, transmission electron microscopy, scanning electron microscopy coupled with energy dispersive analysis of X-rays, N2-BET and thermogravimetry techniques. The data revealed the formation of aggregates composed of nanotubes and nanosheets

G. K. Prasad; T. H. Mahato; P. Pandey; Beer Singh; M. V. S. Suryanarayana; Amit Saxena; K. Shekhar

2007-01-01

254

Electrochemical performance of LBO-coated spinel lithium manganese oxide as cathode material for Li-ion battery  

Microsoft Academic Search

Surface treatment of the lithium manganese oxide cathode material coated by lithium borate glass (Li2O2B2O3) with improved electrochemical cyclability and structural stability was conducted in this study. The lithium manganese oxide powder doped with various weight percentages of LBO glass was calcined to form a fine powder with single spinel phase, exhibiting different particle size, size distribution and morphology. The

Hung-Wei Chan; Jenq-Gong Duh; Shyang-Roeng Sheen

2004-01-01

255

Manganese(III,IV) and manganese(III) oxide clusters trapped by copper(II) complexes.  

PubMed

Reactions of quinquedentate Schiff base ligands with Mn and Cu ions afforded icosa- and hexadecanuclear mixed-metal clusters in which dinuclear CuII complexes trapped oxo-bridged [MnIII8MnIV4O12] and [MnIII6O6] cores, respectively. Maximum entropy method analysis for synchrotron X-ray diffraction data was used to determine the oxidation states of the Mn ions. PMID:17432848

Yamashita, Satoshi; Shiga, Takuya; Kurashina, Masashi; Nihei, Masayuki; Nojiri, Hiroyuki; Sawa, Hiroshi; Kakiuchi, Toru; Oshio, Hiroki

2007-04-14

256

[Adsorption of heavy metal ions on two types of manganese oxides analyzed by AAS and AFS].  

PubMed

Two types of manganese oxides, the octahedral layer structure (OL) and the octahedral molecular tunnel structure (OMS), were controllably synthesized via a facilely hydrothermal route and used to remove heavy metal ions (Pb2+, Cu2+, Ni2+ , Hg2+) in solutions. The heavy metal ion concentrations before and after adsorption were determined by atomic absorption spectroscopy (AAS) and atomic fluorescence spectroscopy (AFS) to evaluate the material adsorption performance. The competitive adsorption of the four ions (Pb2+, Cu2+, Ni2+, Hg2+) on manganese oxides was also investigated. The results showed that OMS exhibited better adsorption ability than OL and had excellent adsorption selectivity to Pb2+, with 98% adsorption efficiency in two minutes. Therefore, this can be proposed as a simple, green and efficient method for treatment of polluted water. PMID:23285900

Xu, Liu; Zhang, Li-Chun; Hou, Xian-Deng; Xu, Kai-Lai

2012-10-01

257

Low-temperature, manganese oxide-based, thermochemical water splitting cycle  

PubMed Central

Thermochemical cycles that split water into stoichiometric amounts of hydrogen and oxygen below 1,000?C, and do not involve toxic or corrosive intermediates, are highly desirable because they can convert heat into chemical energy in the form of hydrogen. We report a manganese-based thermochemical cycle with a highest operating temperature of 850?C that is completely recyclable and does not involve toxic or corrosive components. The thermochemical cycle utilizes redox reactions of Mn(II)/Mn(III) oxides. The shuttling of Na+ into and out of the manganese oxides in the hydrogen and oxygen evolution steps, respectively, provides the key thermodynamic driving forces and allows for the cycle to be closed at temperatures below 1,000?C. The production of hydrogen and oxygen is fully reproducible for at least five cycles.

Xu, Bingjun; Bhawe, Yashodhan; Davis, Mark E.

2012-01-01

258

Interactions between manganese oxides and multiple-ringed aromatic compounds  

SciTech Connect

Objective is to determine whether Mn reductive dissolution can oxidize multiple-ringed aromatics, such as PAHs, in an oxic environment Research indicated that certain PAHs (eg, dihydrodiols and diones that form free-radical intermediates) are susceptible to oxidation and polymerization. Over 14 days, 83, 76, 54, 70, and 20% of the Mn was reduced by 2,3-, 1,3-, and 1,4-naphthalenediol, quinizarin, and 1,4-naphthoquinone, respectively. 100, 100, and 65% of the first three PAHs were oxidized, respectively. Aromatics with diol functional groups were more easily oxidized than those with only dione groups. Relatively insoluble compounds like quinizarin can be oxidized; insoluble ''humic-like'' material precipitated, indicating a polymerization-humification process. Results suggest that electron transfer/organic release from the oxide surface is the rate-limiting step.

Whelan, G. (Pacific Northwest Lab., Richland, WA (United States)); Sims, R.C. (Utah State Univ., Logan, UT (United States). Dept. of Civil and Environmental Engineering)

1992-08-01

259

Interactions between manganese oxides and multiple-ringed aromatic compounds  

SciTech Connect

Objective is to determine whether Mn reductive dissolution can oxidize multiple-ringed aromatics, such as PAHs, in an oxic environment? Research indicated that certain PAHs (eg, dihydrodiols and diones that form free-radical intermediates) are susceptible to oxidation and polymerization. Over 14 days, 83, 76, 54, 70, and 20% of the Mn was reduced by 2,3-, 1,3-, and 1,4-naphthalenediol, quinizarin, and 1,4-naphthoquinone, respectively. 100, 100, and 65% of the first three PAHs were oxidized, respectively. Aromatics with diol functional groups were more easily oxidized than those with only dione groups. Relatively insoluble compounds like quinizarin can be oxidized; insoluble ``humic-like`` material precipitated, indicating a polymerization-humification process. Results suggest that electron transfer/organic release from the oxide surface is the rate-limiting step.

Whelan, G. [Pacific Northwest Lab., Richland, WA (United States); Sims, R.C. [Utah State Univ., Logan, UT (United States). Dept. of Civil and Environmental Engineering

1992-08-01

260

Effects of Manganese (Mn) on the Developing Rat Brain: Oxidative-Stress Related Endpoints  

Microsoft Academic Search

We evaluated biochemical endpoints related to oxidative stress in brains of neonatal rats exposed to manganese (Mn). Oral Mn chloride (MnCl2) (0, 25, or 50mg Mn chloride kg?1 body weight per day) was given daily to neonatal rats throughout lactation (i.e. from postnatal day (PND) 1 to 21). As previously reported by [J. Appl. Toxicol. 20 (2000) 179], this treatment

Sarah Weber; David C. Dorman; Lawrence H. Lash; Keith Erikson; Kent E. Vrana; Michael Aschner

2002-01-01

261

Ceria associated manganese oxide nanoparticles: Synthesis, characterization and arsenic(V) sorption behavior  

Microsoft Academic Search

Four samples of ceria incorporated manganese oxide (NCMO) were prepared by co-precipitation-calcinations and solgel methods, and characterized by X-ray diffraction, scanning electron microscopy, transmission electron microscopy, atomic force microscopy, BET surface area etc. The synthetic samples were nanoparticle agglomerates with irregular surface morphology (Ce:Mn=1:1). The NCMO-1b sample, prepared by the calcination of metal hydroxide at 573K for 3.0h, was a

Kaushik Gupta; Sayan Bhattacharya; Dhrubajyoti Chattopadhyay; Aniruddha Mukhopadhyay; Harishankar Biswas; Jagannath Dutta; Nihar Ranjan Ray; Uday Chand Ghosh

2011-01-01

262

Preparation of lithium manganese oxide fine particles by spray pyrolysis and their electrochemical properties  

Microsoft Academic Search

Highly crystalline nano-sized lithium manganese oxide particles were fabricated by spray pyrolysis. The resultant particles had well-developed facet planes in a transmission electron microscopy (TEM) image and electron diffraction pattern from a single particle also showed clear diffraction spots, indicating that the prepared particles were highly crystalline. The mean crystallite size estimated from X-ray diffraction peaks was ca. 18nm, which

Y. Iriyama; Y. Tachibana; R. Sasasoka; N. Kuwata; T. Abe; M. Inaba; A. Tasaka; K. Kikuchi; J. Kawamura; Z. Ogumi

2007-01-01

263

Effect of oxygen non-stoichiometry on the electrochemical performance of lithium manganese oxide spinels  

Microsoft Academic Search

The effect of oxygen non-stoichiometry on the electrochemical performance of lithium manganese oxide spinels is investigated. Spinels with different oxygen contents are obtained from citrate gel synthesis followed by calcination in air in the temperature range 200850C. Spinels that were formed at low temperatures are found suitable for 3V applications, whereas those formed at high temperatures perform better at 4V.

A. R Naghash; Jim Y Lee

2001-01-01

264

X-ray diffraction and impedance spectroscopy studies of lithium manganese oxide spinel  

Microsoft Academic Search

Phase transition in lithium manganese oxide spinel synthesized by solgel technique and in samples prepared from commercially available powders of LiMn2O4 (Alfa-Aesar and SigmaAldrich) was investigated. In addition to the standard impedance measurements and the X-ray diffraction in BraggBrentano geometry, simultaneous measurements of impedance spectrum and X-ray pattern in non-focusing geometry were performed in the temperature range between ?25 and

M. Kope?; D. Lisovytskiy; M. Marzantowicz; J. R. Dygas; F. Krok; Z. Kaszkur; J. Pielaszek

2006-01-01

265

Electrochemical properties of lithium manganese oxides with different surface areas for lithium ion batteries  

Microsoft Academic Search

Two lithium manganese oxides, Li1.03Mn1.96O4, with different surface areas of 3.55 and 0.68m2\\/g were prepared and their electrochemical properties were studied as positive electrodes for lithium ion batteries. Cycle performance tests gave capacity losses of 9 and 18% at 25C, and 28 and 33% at 55C for the samples with larger and smaller surface areas, respectively. The recovery of capacity

Koh Takahashi; Motoharu Saitoh; Norimitsu Asakura; Takashi Hibino; Mitsuru Sano; Miho Fujita; Koich Kifune

2004-01-01

266

Lattice dynamics and vibrational spectra of lithium manganese oxides: A computer simulation and spectroscopic study  

Microsoft Academic Search

The lattice vibrational modes of spinel-structured lithium manganese oxides have been calculated using atomistic modeling methods. The simulations allow the Raman and infrared spectra of lithiated, fully delithiated, and partially delithiated phases to be assigned for the first time. Calculations for the spinels LiMnO, λ-MnO, and Li{sub 0.5}MnO are compared with experimental Raman data measured for thin films of the

Brett Ammundsen; Gary R. Burns; M. Saiful Islam; Hirofumi Kanoh; J. Roziere

1999-01-01

267

Battery performance of nanostructured lithium manganese oxide synthesized by ultrasonic spray pyrolysis at elevated temperature  

Microsoft Academic Search

Nanostructured lithium manganese oxide with spherical particles was synthesized via ultrasonic spray pyrolysis technique.\\u000a The material shows a pronounced stability upon prolonged cycling at room temperature at high chargedischarge rates up to\\u000a 10C. The electrochemical performance of the cell at elevated temperature was remarkably improved by addition of AlPO4 to the electrolyte. The AC impedance spectroscopy study showed the interface

Zhumabay Bakenov; Masataka Wakihara; Izumi Taniguchi

2008-01-01

268

Lattice vibrations of materials for lithium rechargeable batteries I. Lithium manganese oxide spinel  

Microsoft Academic Search

Raman scattering (RS) and Fourier transform infrared (FTIR) spectroscopy have been applied to the study of local structure of lithium manganese oxides. We report the analysis of the vibrational spectra of spinel LiMn2O4 structure using both the classical group factor analysis (Oh7) and a local environment model. The RS and FTIR spectra are analysed on the basis of LiO4 tetrahedra

C. M. Julien; M. Massot

2003-01-01

269

Lithium-manganese-oxide thin-film cathodes prepared by plasma-enhanced chemical vapor deposition  

Microsoft Academic Search

Lithium-manganese-oxide thin-film electrodes have been fabricated using the plasma-enhanced chemical vapor deposition technique. Process parameters such as flow rates of the reactants, deposition temperature, and RF power have been systematically varied to optimize the charge and discharge properties. The thin films are amorphous as found by X-ray diffraction spectrometry and can be cycled reversibly in the range from 4.5 to

Ping Liu; J. G. Zhang; J. A. Turner; C. E. Tracy; D. K. Benson

1999-01-01

270

Performance of lithium-manganese oxide spinel electrodes in a lithium polymer electrolyte cell  

Microsoft Academic Search

The cycling performance of a lithium-manganese oxide spinel (prepared from MnO2 and Li2CO3) has been investigated as a function of preparation temperature in a lithium polymer electrolyte cell. Excellent reversibility and high rate performance have been observed from a spinel phase prepared at 450 C and of general formula Li(x)Mn(2-z)O(4) x = 0.0-1.13, z = 0.0-0.33. This phase has a

W. J. Macklin; R. J. Neat; R. J. Powell

1991-01-01

271

Electrochemical impedance spectroscopy studies of lithium diffusion in doped manganese oxide  

Microsoft Academic Search

Cathode performance is critical to lithium ion rechargeable battery performance; effects of doping lithium manganese oxide cathode materials on cathode performance are being investigated. In this paper, Li diffusion in Al-doped LiMnO was studied and found to be controlled by the quantity of Al dopant. Electrochemical cycling was conducted at 0.5mA\\/cm; electrochemical impedance spectra were taken at open circuit potential,

B. J. Johnson; D. H. Doughty; J. A. Voigt; T. J. Boyle

1996-01-01

272

The influence of ceria surface additions on manganese oxidation at high temperatures  

SciTech Connect

The kinetics, scale composition, and growth mechanism of ceria-coated and blank specimens of manganese oxidation in air were examined. The scale growth obeys the parabolic rate law at 700{degrees}C for all specimens. Lower parabolic rate constants for coated specimens are attributed to the presence of a CeO{sub 2} external scale. It constitutes a limiting factor of the oxygen activity at the gas-oxide interface. This lower-oxygen activity leads to a less-metal-deficient state of the scale. Due to this, the inner-MnO scale becomes more adherent to the substrate. Preheating at 700{degrees}C, in hydrogen (P{sub 02}=10{sup {minus}24} atm), was performed in order to be placed in the MnO stability domain and try to introduce cerium in the manganese-oxide scale. This pretreatment promotes macroscopic bonding in the layer formed during subsequent oxidation in air. It ensures a better scale adherence. FA new diffusional-transport mechanism in manganosite is proposed in accordance with all experimental observations of the literature and with the cerium-manganese-oxygen system studied in the present work. This model considers the high Mn{sup 3+} stability in octahedral sites of the MnO oxygen ion body. Low-oxygen partial pressure conditions permit the formation of an adherent inner-MnO scale on coated specimens. A CeO{sub 2} scale formed above the MnO scale; MnO is present as a minor component in this scale and it is located mainly at the internal interface. The difficulties in forming the cerium-orthomanganite are attributed to the very high stability of MnO related to this wide range of nonstoichiometry and to the low manganese diffusivity through the cerium-containing scale.

Buscail, H.; Larpin, J.P. [Laboratoire de Recherches sur la Reactivite des Solides, Dijon (France)

1995-04-01

273

The influence of ceria surface additions on manganese oxidation at high temperatures  

Microsoft Academic Search

The kinetics, scale composition, and growth mechanism of ceria-coated and blank specimens of manganese oxidation in air were examined. The scale growth obeys the parabolic rate law at 700C for all specimens. Lower parabolic rate constants for coated specimens are attributed to the presence of a CeO2 external scale. It constitutes a limiting factor of the oxygen activity at the

H. Buscail; J. P. Larpin

1995-01-01

274

An in situ XRD investigation of singly and doubly promoted manganese oxide methane coupling catalysts  

Microsoft Academic Search

In situ X-ray diffraction (XRD) and concurrent measurements of catalytic performance have been used to characterize the solid phases present during various stages in the history of working methane coupling catalytic systems. Three such systems were studied: unpromoted, K-promoted, and KCl-promoted manganese oxide. In each case the effect of pulses of CHCl on the activity, selectivity, and catalyst structure was

G. D. Moggridge; T. Rayment; R. M. Lambert

1992-01-01

275

Hole dispersions in the G- and C-type orbital ordering backgrounds: Doped manganese oxides  

Microsoft Academic Search

In the framework of the linear spin-wave theory and orbital-charge separation, we calculate quasiparticle (QP) dispersions for two different antiferromagnetic orbital structures in the fully saturated spin phase of manganese oxides. Although with the same orbital wave excitations, the QP bands of C- and G-type orbital structures exhibit completely different shapes. The pseudogap observed in the density of states and

Xiao-Juan Fan; Shun-Qing Shen; Z. D. Wang; X.-G. Li; Qiang-Hua Wang

2000-01-01

276

Manganese oxide nanoparticle-assisted laser desorption\\/ionization mass spectrometry for medical applications  

Microsoft Academic Search

We prepared and characterized manganese oxide magnetic nanoparticles (d =5.6 nm) and developed nanoparticle-assited laser desorption\\/ionization (nano-PALDI) mass spectrometry. The nanoparticles had MnO2 and Mn2O3 cores conjugated with hydroxyl and amino groups, and showed paramagnetism at room temperature. The nanoparticles worked as an ionization assisting reagent in mass spectroscopy. The mass spectra showed no background in the low m\\/z. The

Shu Taira; Kenji Kitajima; Hikaru Katayanagi; Eiichiro Ichiishi; Yuko Ichiyanagi

2009-01-01

277

Weathering of the Rio Blanco Quartz Diorite, Luquillo Mountains, Puerto Rico: Coupling Oxidation, Dissolution, And Fracturing  

SciTech Connect

In the mountainous Rio Icacos watershed in northeastern Puerto Rico, quartz diorite bedrock weathers spheroidally, producing a 0.2-2 m thick zone of partially weathered rock layers ({approx}2.5 cm thickness each) called rindlets, which form concentric layers around corestones. Spheroidal fracturing has been modeled to occur when a weathering reaction with a positive {Delta}V of reaction builds up elastic strain energy. The rates of spheroidal fracturing and saprolite formation are therefore controlled by the rate of the weathering reaction. Chemical, petrographic, and spectroscopic evidence demonstrates that biotite oxidation is the most likely fracture-inducing reaction. This reaction occurs with an expansion in d (0 0 1) from 10.0 to 10.5 {angstrom}, forming 'altered biotite'. Progressive biotite oxidation across the rindlet zone was inferred from thin sections and gradients in K and Fe(II). Using the gradient in Fe(II) and constraints based on cosmogenic age dates, we calculated a biotite oxidation reaction rate of 8.2 x 10{sup -14} mol biotite m{sup -2} s{sup -1}. Biotite oxidation was documented within the bedrock corestone by synchrotron X-ray microprobe fluorescence imaging and XANES. X-ray microprobe images of Fe(II) and Fe(III) at 2 {micro}m resolution revealed that oxidized zones within individual biotite crystals are the first evidence of alteration of the otherwise unaltered corestone. Fluids entering along fractures lead to the dissolution of plagioclase within the rindlet zone. Within 7 cm surrounding the rindlet-saprolite interface, hornblende dissolves to completion at a rate of 6.3 x 10{sup -13} mol hornblende m{sup -2} s{sup -1}: the fastest reported rate of hornblende weathering in the field. This rate is consistent with laboratory-derived hornblende dissolution rates. By revealing the coupling of these mineral weathering reactions to fracturing and porosity formation we are able to describe the process by which the quartz diorite bedrock disaggregates and forms saprolite. In the corestone, biotite oxidation induces spheroidal fracturing, facilitating the influx of fluids that react with other minerals, dissolving plagioclase and chlorite, creating additional porosity, and eventually dissolving hornblende and precipitating secondary minerals. The thickness of the resultant saprolite is maintained at steady state by a positive feedback between the denudation rate and the weathering advance rate driven by the concentration of pore water O{sub 2} at the bedrock-saprolite interface.

Buss, H.L.; Sak, P.B.; Webb, S.M.; Brantley, S.L.

2009-05-12

278

Upgrading of Low-Grade Manganese Ore by Selective Reduction of Iron Oxide and Magnetic Separation  

NASA Astrophysics Data System (ADS)

The utilization of low-grade manganese ores has become necessary due to the intensive mining of high-grade ores for a long time. In this study, calcined ferruginous low-grade manganese ore was selectively reduced by CO, which converted hematite to magnetite, while manganese oxide was reduced to MnO. The iron-rich component was then separated by magnetic separation. The effects of the various reduction parameters such as particle size, reduction time, temperature, and CO content on the efficiency of magnetic separation were studied by single-factor experiments and by a comprehensive full factorial experiment. Under the best experimental conditions tested, the manganese content in the ore increased from around 36 wt pct to more than 44 wt pct, and almost 50 wt pct of iron was removed at a Mn loss of around 5 pct. The results of the full factorial experiments allowed the identification of the significant effects and yielded regression equations for pct Fe removed, Mn/Fe, and pct Mn loss that characterize the efficiency of the upgrading process.

Gao, Yubo; Olivas-Martinez, M.; Sohn, H. Y.; Kim, Hang Goo; Kim, Chan Wook

2012-12-01

279

Effect of iron manganese oxide solid solutions on selectivity for lower hydrocarbons from carbon monoxide hydrogenation  

SciTech Connect

There exists considerable current interest in the study of catalysts that demonstrate high selectivities for C/sub 2/-C/sub 4/ hydrocarbons from carbon monoxide hydrogenation. In this respect iron manganese matrix catalysts have been well studied by a number of authors since Koelbel initially disclosed that these catalysts could give high yields of C/sub 2/-C/sub 4/ hydrocarbons with a corresponding very low methane selectivity. The mechanism by which the manganese component causes these product distributions is at present poorly understood. Recently Jensen and Massoth have proposed that small iron particles are supported on and electronically promoted by MnO. Although these oxide solid solutions have been identified there have been no reported studies that have investigated the effect of these catalyst components on catalyst selectivity. Oxide solid solutions are known to be important as catalysts of a number of reactions involving carbon monoxide. In this note the authors present their initial findings for the effect of iron manganese oxide solid solutions on catalyst selectivity in carbon monoxide hydrogenation. 24 references.

Hutchings, G.J.; Boeyens, J.C.A.

1986-08-01

280

Growth and Dissolution of Iron and Manganese Oxide Films  

Microsoft Academic Search

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

Scot T. Martin

2008-01-01

281

Biological water-oxidizing complex: a nano-sized manganese-calcium oxide in a protein environment.  

PubMed

The resolution of Photosystem II (PS II) crystals has been improved using isolated PS II from the thermophilic cyanobacterium Thermosynechococcus vulcanus. The new 1.9 resolution data have provided detailed information on the structure of the water-oxidizing complex (Umena et al. Nature 473: 55-61, 2011). The atomic level structure of the manganese-calcium cluster is important for understanding the mechanism of water oxidation and to design an efficient catalyst for water oxidation in artificial photosynthetic systems. Here, we have briefly reviewed our knowledge of the structure and function of the cluster. PMID:22941557

Najafpour, Mohammad Mahdi; Moghaddam, Atefeh Nemati; Yang, Young Nam; Aro, Eva-Mari; Carpentier, Robert; Eaton-Rye, Julian J; Lee, Choon-Hwan; Allakhverdiev, Suleyman I

2012-09-02

282

State of atoms and interatomic interactions in complex perovskite-like oxides: I. State of manganese atoms in LaSrMnAl-O solid solutions  

Microsoft Academic Search

Study of the temperature and concentration dependences of the magnetic properties of solid solutions of layered oxides containing manganese and aluminum atoms in similar crystallographic positions revealed a change in the ground state of part of the manganese atoms. Such an effect was previously observed for iron, cobalt, and nickel atoms in similar solid solutions. In the case of manganese,

N. P. Bobrysheva; N. V. Chezhina

1994-01-01

283

Amorphous Manganese-Calcium Oxides as a Possible Evolutionary Origin for the CaMn4 Cluster in Photosystem II  

NASA Astrophysics Data System (ADS)

In this paper a few calcium-manganese oxides and calcium-manganese minerals are studied as catalysts for water oxidation. The natural mineral marokite is also studied as a catalyst for water oxidation for the first time. Marokite is made up of edge-sharing Mn3+ in a distorted octahedral environment and eight-coordinate Ca2+ centered polyhedral layers. The structure is similar to recent models of the oxygen evolving complex in photosystem II. Thus, the oxygen evolving complex in photosystem II does not have an unusual structure and could be synthesized hydrothermally. Also in this paper, oxygen evolution is studied with marokite (CaMn2O4), pyrolusite (MnO2) and compared with hollandite (Ba0.2Ca0.15K0.3Mn6.9Al0.2Si0.3O16), hausmannite (Mn3O4), Mn2O3.H2O, CaMn3O6.H2O, CaMn4O8.H2O, CaMn2O4.H2O and synthetic marokite (CaMn2O4). I propose that the origin of the oxygen evolving complex in photosystem II resulted from absorption of calcium and manganese ions that were precipitated together in the archean oceans by protocyanobacteria because of changing pH from ~5 to ~8-10. As reported in this paper, amorphous calcium-manganese oxides with different ratios of manganese and calcium are effective catalysts for water oxidation. The bond types and lengths of the calcium and manganese ions in the calcium-manganese oxides are directly comparable to those in the OEC. This primitive structure of these amorphous calcium-manganese compounds could be changed and modified by environmental groups (amino acids) to form the oxygen evolving complex in photosystem II.

Najafpour, Mohammad Mahdi

2011-06-01

284

Manganese (Mn) Oxidation Increases Intracellular Mn in Pseudomonas putida GB-1  

PubMed Central

Bacterial manganese (Mn) oxidation plays an important role in the global biogeochemical cycling of Mn and other compounds, and the diversity and prevalence of Mn oxidizers have been well established. Despite many hypotheses of why these bacteria may oxidize Mn, the physiological reasons remain elusive. Intracellular Mn levels were determined for Pseudomonas putida GB-1 grown in the presence or absence of Mn by inductively coupled plasma mass spectrometry (ICP-MS). Mn oxidizing wild type P. putida GB-1 had higher intracellular Mn than non Mn oxidizing mutants grown under the same conditions. P. putida GB-1 had a 5 fold increase in intracellular Mn compared to the non Mn oxidizing mutant P. putida GB-1-007 and a 59 fold increase in intracellular Mn compared to P. putida GB-1 ?2665 ?2447. The intracellular Mn is primarily associated with the less than 3 kDa fraction, suggesting it is not bound to protein. Protein oxidation levels in Mn oxidizing and non oxidizing cultures were relatively similar, yet Mn oxidation did increase survival of P. putida GB-1 when oxidatively stressed. This study is the first to link Mn oxidation to Mn homeostasis and oxidative stress protection.

Banh, Andy; Chavez, Valarie; Doi, Julia; Nguyen, Allison; Hernandez, Sophia; Ha, Vu; Jimenez, Peter; Espinoza, Fernanda; Johnson, Hope A.

2013-01-01

285

Manganese (Mn) Oxidation Increases Intracellular Mn in Pseudomonas putida GB-1.  

PubMed

Bacterial manganese (Mn) oxidation plays an important role in the global biogeochemical cycling of Mn and other compounds, and the diversity and prevalence of Mn oxidizers have been well established. Despite many hypotheses of why these bacteria may oxidize Mn, the physiological reasons remain elusive. Intracellular Mn levels were determined for Pseudomonas putida GB-1 grown in the presence or absence of Mn by inductively coupled plasma mass spectrometry (ICP-MS). Mn oxidizing wild type P. putida GB-1 had higher intracellular Mn than non Mn oxidizing mutants grown under the same conditions. P. putida GB-1 had a 5 fold increase in intracellular Mn compared to the non Mn oxidizing mutant P. putida GB-1-007 and a 59 fold increase in intracellular Mn compared to P. putida GB-1 ?2665 ?2447. The intracellular Mn is primarily associated with the less than 3 kDa fraction, suggesting it is not bound to protein. Protein oxidation levels in Mn oxidizing and non oxidizing cultures were relatively similar, yet Mn oxidation did increase survival of P. putida GB-1 when oxidatively stressed. This study is the first to link Mn oxidation to Mn homeostasis and oxidative stress protection. PMID:24147089

Banh, Andy; Chavez, Valarie; Doi, Julia; Nguyen, Allison; Hernandez, Sophia; Ha, Vu; Jimenez, Peter; Espinoza, Fernanda; Johnson, Hope A

2013-10-17

286

The Role of High Molecular Weight Polyethylene Oxide in Reducing Quartz Gangue Entrainment in Chalcopyrite Flotation by Xanthate Collectors  

NASA Astrophysics Data System (ADS)

Fine particles pose two challenging problems to all mineral processors around the world today. The problems are the inefficient collection of hydrophobic particles (low recovery), and mechanical/hydraulic entrainment of hydrophilic gangue particles (low concentrate grade). Extensive research has been conducted to improve the flotation recovery of fine hydrophobic particles. However, much less effort was made to lower the mechanical/hydraulic entrainment of fine gangue mineral particles. In this study, polyethylene oxide (PEO) was used to flocculate and depress fine quartz particles. Batch flotation results indicated that the addition of low dosages of PEO improved value mineral recovery and concentrate grade in the flotation of artificial mixtures of chalcopyrite/quartz and a commercial Au-Cu sulfide ore sample. It was found that PEO adsorbed on both minerals mainly through hydrogen bonding and caused non-selective flocculation of quartz and chalcopyrite, forming large hetero-aggregates. However, the addition of potassium amyl xanthate (KAX), a specific sulfide mineral collector, adsorbed on chalcopyrite through chemical interaction, replaced PEO and caused the chalcopyrite particles to break away from the hetero-aggregates, forming separate homo-aggregates of quartz and chalcopyrite. The flotation of the chalcopyrite and the depression of the quartz were thus both improved due to the larger sizes of the homo-aggregates compared to the discrete particles. It was also observed that a completely solubilized PEO solution could not flocculate quartz, while a partially solubilized PEO solution was most effective. This was attributed to the better bridging functions of the undissolved PEO aggregates when it was partially solubilized. When the PEO was fully solubilized, the individual PEO molecules were probably too flexible and tended to flatten on the adsorbed solid surface and thus could not function as an effective bridging flocculant. Furthermore, it was found that PEO could function as a collector for quartz due to its affinity to air-water interface and quartz, and it could increase quartz entrainment when used at high dosages. Selective flocculation and depression of the quartz gangue during chalcopyrite flotation could only be achieved at low PEO dosages. The implication of these observations on how to utilize the polyethylene oxide in industrial flotation was discussed.

Gong, Jihua

287

Characterization of structure and electrochemical properties of lithium manganese oxides for lithium secondary batteries hydrothermally synthesized from ?-K x MnO 2  

Microsoft Academic Search

Lithium manganese oxides have attracted much attention as cathode materials for lithium secondary batteries in view of their high capacity and low toxicity. In this study, layered manganese oxide (?-KxMnO2) has been synthesized by thermal decomposition of KMnO4, and four lithium manganese oxide phases have been synthesized for the first time by mild hydrothermal reactions of this material with different

Yanluo Lu; Min Wei; Zhiqiang Wang; D. G. Evans; Xue Duan

2004-01-01

288

Coprecipitation mechanisms and products in manganese oxidation in the presence of cadmium  

Microsoft Academic Search

Manganese oxidation products were precipitated in an aerated open-aqueous system where a continuous influx of mixed Mn{sup 2+} and Cd{sup 2+} solution was supplied and pH was maintained with an automated pH-stat adding dilute NaOH. X-ray diffraction and electron diffraction identified the solids produced as mixtures of CdMn{sup 4+}O, Mn{sup 2+}Mn{sup 4+}O, MnO (ramsdellite), and CdCO. Mean oxidation numbers of

J. D. Hem; C. J. Lind

1991-01-01

289

Structural and magnetic properties of the iron substituted lithiummanganese spinel oxides  

Microsoft Academic Search

Most studies on the lithiummanganese oxide as a cathode material have concentrated on the stabilization of the cubic spinel structure, mainly by doping other transition metal ions into LiMn2O4 lattice. Partial substitution of Fe3+ ions for Mn3+ restrains the JahnTeller effect, owing to the reduction of Mn3+\\/Mn4+ ratio. In LiFe0.1Mn1.9O4 spinel oxide the phase transitions from cubic to orthorhombic and\\/or

Emilia Wolska; Michael Tovar; Bartlomiej Andrzejewski; Waldemar Nowicki; Jolanta Darul; Pawel Piszora; Michael Knapp

2006-01-01

290

c-Type cytochromes and manganese oxidation in Pseudomonas putida MnB1  

SciTech Connect

Pseudomonas putida MnB1 is an isolate from an Mn oxide-encrusted pipeline that can oxidize Mn(II) to Mn oxides. The authors used transposon mutagenesis to construct mutants of strain MnB1 that are unable to oxidize manganese, and they characterized some of these mutants. The mutants were divided into three groups: mutants defective in the biogenesis of c-type cytochromes, mutants defective in genes that encode key enzymes of the tricarboxylic acid cycle, and mutants defective in the biosynthesis of tryptophan. The mutants in the first two groups were cytochrome c oxidase negative and did not contain c-type cytochromes. Mn(II) oxidation capability could be recovered in a c-type cytochrome biogenesis-defective mutant by complementation of the mutation.

Caspi, R.; Tebo, B.M.; Haygood, M.G. [Univ. of California, San Diego, La Jolla, CA (United States). Scripps Institution of Oceanography

1998-10-01

291

Oxidation of manganese and iron by Leptothrix discophora: Use of N,N,N prime ,N prime -tetramethyl-p-phenylenediamine as an indicator of metal oxidation  

Microsoft Academic Search

A new method for the quantification and characterization of manganese-oxidizing activity by spent culture medium of Leptothrix discophora SS-1 was developed. It is based on the formation of the dye Wurster blue from N,N,N,N-tetramethyl-p-phenylenediamine by oxidized manganese generated in the spent medium. The kinetic parameters thus obtained agreed well with data obtained with other methods. It was also possible to

E. W. de Vrind-de Jong; P. L. A. M. Corstjens; E. S. Kempers; P. Westbroek; J. P. M. de Vrind

1990-01-01

292

Characterization of layered lithium nickel manganese oxides synthesized by a novel oxidative coprecipitation method and their electrochemical performance as lithium insertion electrode materials  

Microsoft Academic Search

Lithium nickel manganese oxides, LiNi{sub 1-y}Mn{sub y}O{sub 2+δ}, (0 y 0.5) were prepared via a new solution technique. The corresponding mixed nickel manganese hydroxide precursors were synthesized in an oxidative coprecipitation method. Subsequent calcination in the presence of LiOH leads to crystalline products with a partially disordered layered-type α-NaFeO structure. X-ray photoelectron spectroscopic analysis has indicated a strong

Michael E. Spahr; P. Novak; B. Schnyder; O. Haas; R. Nesper

1998-01-01

293

Nanophase Manganese Oxides: Chemisorbed Water and Small Particle Size Promote Large Thermodynamically Driven Shifts in Oxidation-Reduction Equilibria  

NASA Astrophysics Data System (ADS)

Manganese oxides are important in terrestrial and Martian settings, and changes in oxidation state (Mn 2+, 3+, 4+) produce different phases. This study focuses on changes in redox energetics at the nanoscale in the Mn-O system with water present. Nanophase hausmannite (Mn3O4), bixbyite (Mn2O3), and pyrolusite (MnO2) were synthesized using minor modifications of previously published methods, stored at room temperature, and then analyzed by powder-XRD, BET surface area measurement, and TGA for total water content. High-temperature oxide-melt drop solution calorimetry was performed on a series of characterized samples with known surface area and water content. The differential heat of water adsorption as a function of coverage was also measured. The surface enthalpies of manganese oxide phases, hausmannite (Mn3O4), bixbyite (Mn2O3), and pyrolusite (MnO2), were determined using the data from high-temperature oxide melt calorimetry and water adsorption calorimetry. Surface energy for the hydrous Mn3O4 tetragonal spinel phase is 0.960.08 J/m2, for Mn2O3 cubic phase is 1.290.10 J/m2, and for MnO2 cubic rutile phase is 1.640.10 J/m2. Surface energy for the anhydrous Mn3O4 is 1.310.08 J/m2, for Mn2O3 is 1.570.10 J/m2, and for MnO2 is 1.990.10 J/m2. Supporting preliminary findings, the spinel phase (hausmannite) has a lower surface energy than bixbyite, while the latter has a smaller surface energy than pyrolusite. We also observed phase changes, some of them rapidly reversible, associated with water adsorption/desorption for the nanophase manganese oxide assemblages. There are geochemical consequences. (1) At the nanoscale, both the pyrolusite/bixbyite and bixbyite/hausmannite equilibria are shifted to higher oxygen fugacity because the reduced phase has the lower surface energy. (2) The ready inter-conversion of phases with different oxidation states under aqueous conditions implies that, after a manganese oxide nanophase forms, it can easily transform to other phases with different oxidation states and water contents and perhaps record changes in environmental conditions after, as well as during, its initial formation.

Birkner, N.; Navrotsky, A.

2011-12-01

294

Facile synthesis of manganese oxide loaded hollow silica particles and their application for methylene blue degradation.  

PubMed

A facile poly acrylic acid (PAA) soft templating method was developed to fabricate manganese oxide loaded hollow silica particles (MHSPs). The synthesis involves PAA-Mn aggregation to form spherical particles and silica coating layer formation on the outer surface of the particles. Subsequent calcination in air at 500 C removes the polymer inside the particles, and hollow silica spheres with trapped metal oxide particles are thus formed. The PAA traps the Mn ions and forms aggregates which template the silica shell formation in this process. The Mn content and the structure of the MHSPs can be tuned by changing doses of the Mn salt initially added. Moreover, decomposition of PAA during calcination endows high surface areas of the MHSPs. Catalytic oxidation of methylene blue (MB) with H2O2 was tested on the MHSPs. The results show that the MHSPs with hollow structure and high surface areas enhance the catalytic activity compare to the corresponding manganese oxide solid particles (MSPs). This strategy can also be used to synthesize other metal oxides (such as MgO and NiO) loaded hollow silica particles. PMID:23777863

Meng, Qingnan; Xiang, Siyuan; Cheng, Wei; Chen, Qiaonan; Xue, Pengfei; Zhang, Kai; Sun, Hongchen; Yang, Bai

2013-05-31

295

Formation of iodinated organic compounds by oxidation of iodide-containing waters with manganese dioxide.  

PubMed

This study shows that iodinated organic compounds can be produced when iodide-containing waters are in contact with manganese oxide birnessite (delta-MnO2) in the pH range of 5-7. In the absence of natural organic matter (NOM), iodide is oxidized to iodate that is also adsorbed onto delta-MnO2. In the presence of iodide and NOM, adsordable organic iodine compounds (AOI) are formed at pH < 7 because of the oxidation of iodide to iodine by delta-MnO2 and the reactions of iodine with NOM. In addition, iodoacetic acid and iodoform have been identified as specific iodinated byproducts. Formation of iodoform is not observed for high NOM/delta-MnO2 ratios due to inhibition of the catalytic effect of delta-MnO2 by NOM poisoning. Experiments with model compounds such as resorcinol and 3,5-heptanedione confirmed that the delta-MnO2/l(-) system is very effective for the formation of iodinated organic compounds. These results suggest that birnessite acts as a catalyst through the oxidation of iodide to iodine and the polarization of the iodine molecule, which then reacts with NOM moieties. Furthermore, our results indicate that during water treatment in the presence of manganese oxide, iodinated organic compounds may be formed, which may lead to taste and odor or toxicological problems. PMID:19806734

Gallard, Herv; Allard, Sbastien; Nicolau, Rudy; von Gunten, Urs; Crou, Jean Philippe

2009-09-15

296

Transformation from layered to tunnel structures: Synthesis, characterization, and applications of manganese oxide octahedral molecular sieves  

NASA Astrophysics Data System (ADS)

Manganese oxide based octahedral molecular sieves (OMS) have been found to have a wide variety of applications as catalysts, absorbents, and battery materials due to their unique structures and physical and chemical properties. OMS materials are made up of manganese oxide octahedral building blocks sharing comers and edges to form tunnel structures. Manganese species in the framework of OMS materials are mixed valent with various ion-exchangeable cations residing in the tunnels playing important roles in charge balancing and special chemical activities. With different synthetic parameters such as the template used, temperature, pressure, and the pH of the synthetic media, layered birnessite materials were hydrothermally transformed into distinct tunnel structures with different tunnel sizes, including Mg-3x3 (OMS-1), NH4-2x2 (NH4-OMS-2), Na-2x4 (OMS-5), and other manganese oxides. Characterization of the OMS materials with a wide variety of instruments has revealed that most of them are nano-fibrous hollow crystals ith large surface areas, high ion-exchange capabilities, and relatively high thermal stabilities. The Na-2x4 tunnel structure sodium MnOx has been synthesized for the first time and studied in detail, including synthetic strategies, structural analyses, and other physical and chemical property analyses. As catalysts, the synthetic OMS materials show high catalytic activities and shape-selective properties. For example, the results of the competitive oxidation of cycloalkanes with tertiary butyl hydrogen peroxide (TBHP) over different tunnel sized ONIS materials have proven that the OMS materials with larger tunnels are more favorable for the oxidation of the biggest molecule, cyclooctane, than the smallest one, cyclohexane. Besides the tunnel size effects, tunnel cations in the OMS materials also have influences on their catalytic activities. The study of carbon monoxide cleanup for fuel cell applications demonstrates that Ag-OMS-2 (a hollandite structured OMS catalyst with Ag cations residing in the tunnels) is the best oxidative catalyst among many other catalysts. The amount of Ag loading and the average oxidation state of Mn in a Ag-OMS-2 catalyst are the major influences on their catalytic performance. A suitable working temperature range for complete removal of CO from hydrogen-rich reformates using a Ag-OMS-2 catalyst may be adjusted by changing the Ag loading.

Xia, Guan-Guang

297

Directed vapor deposition of lithium manganese oxide films  

Microsoft Academic Search

Electron beam evaporation and sputtering techniques are used to fabricate multilayered thin film structures. However, these techniques suffer several drawbacks resulting from (i) the complex chemistries of the lithiated oxide layers used for the cathode and electrolyte, (ii) the need for precise microstructure control in systems with many metastable phases, and (iii) the low deposition rate and poor material utilization

Sang-Wan Jin

2008-01-01

298

Lewis-acid-promoted stoichiometric and catalytic oxidations by manganese complexes having cross-bridged cyclam ligand: a comprehensive study.  

PubMed

Redox-inactive metal ions have been recognized to be able to participate in redox metal-ion-mediated biological and chemical oxidative events; however, their roles are still elusive. This work presents how the redox-inactive metal ions affect the oxidative reactivity of a well-investigated manganese(II) with its corresponding manganese(IV) complexes having cross-bridged cyclam ligand. In dry acetone, the presence of these metal ions can greatly accelerate stoichiometric oxidations of triphenylphosphine and sulfides by the manganese(IV) complexes through electron transfer or catalytic sulfoxidations by the corresponding manganese(II) complexes with PhIO. Significantly, the rate enhancements are highly Lewis-acid strength dependent on added metal ions. These metal ions like Al(3+) can also promote the thermodynamic driving force of the Mn(IV)-OH moiety to facilitate its hydrogen abstraction from ethylbenzene having a BDE(CH) value of 85 kcal/mol, while it is experimentally limited to 80 kcal/mol for Mn(IV)-OH alone. Adding Al(3+) may also improve the manganese(II)-catalyzed olefin epoxidation with PhIO. However, compared with those in electron transfer, improvements in hydrogen abstraction and electron transfer are minor. The existence of the interaction between Lewis acid and the manganese(IV) species was evidenced by the blue shift of the characteristic absorbance of the manganese(IV) species from 554 to 537 nm and by converting its EPR signal at g = 2.01 into a hyperfine 6-line signal upon adding Al(3+) (I = 5/2). Cyclic voltammograms of the manganese(IV) complexes reveal that adding Lewis acid would substantially shift its potential to the positive direction, thus enhancing its oxidizing capability. PMID:23600453

Dong, Lei; Wang, Yujuan; Lv, Yanzong; Chen, Zhuqi; Mei, Fuming; Xiong, Hui; Yin, Guochuan

2013-04-19

299

The Surface Structure of the Proton-Exchanged Lithium Manganese Oxide Spinels and Their Lithium-Ion Sieve Properties  

Microsoft Academic Search

The spinel structure and the valence states of the Mn ions both at the surface and the bulk were characterized for the Li+extracted and inserted manganese oxide spinels. The Li+extraction from the orthorhombic LiMn2O4spinel results in the formation of the cubic spinel, the crystal structure of which is the same as?-MnO2. The LiMn2O4spinel prepared from an electrolytically prepared manganese dioxide

K. Sato; D. M. Poojary; A. Clearfield; M. Kohno; Y. Inoue

1997-01-01

300

The hydrothermal synthesis of sodium manganese oxide and a lithium vanadium oxide  

Microsoft Academic Search

We report here the direct synthesis of the hexagonal form of sodium manganese dioxide using the mild hydrothermal decomposition of sodium permanganate in water at 170 C. Sodium manganate, Na0.35MnO2 0.7H2O, has an R3?m rhombohedral structure like Lix(H2O)TiS2 with a 7 repeat distance indicative of a monolayer of water between the manganese dioxide layers. The water may be

Rongji Chen; Tom Chirayil; Peter Zavalij; M. Stanley Whittingham

1996-01-01

301

Bioaccumulation of manganese and its toxicity in feral pigeons (Columba livia) exposed to manganese oxide dust (Mn3O4).  

PubMed

Manganese tetroxide (Mn3O4) is a product from the combustion of methylcyclopentadienyl manganese tricarbonyl. Exposure to high levels of manganese can lead to serious health effects especially to the central nervous and respiratory systems. Very few studies on the effects of long-term low level exposure to Mn3O4 have been reported. The present study was therefore conducted to examine the bioaccumulation and toxicity of manganese in various organs of feral pigeons (Columba livia) when exposed to low levels of Mn3O4 via inhalation and hence to find any possible relationship between these two parameters. A total of 22 pigeons was exposed to 239 micrograms/m3 of manganese for 7 h/day, 5 days/week for 5, 9, and 13 consecutive weeks. Manganese concentrations in various tissues, e.g., brain (mesencephalon), lung, liver, intestine, pancreas, kidney, muscle, bone, and whole blood, were measured by neutron activation analysis. Various biochemical parameters in blood, e.g., hematocrit, total proteins, glucose, uric acid, alanine aminotransferase, total iron, blood urea nitrogen and triglycerides, were also measured. Manganese concentrations in brain, lung, and bone were significantly higher in Mn3O4-exposed pigeons (0.59, 0.58, and 3.02 micrograms wet tissue, respectively) than in the control group (0.46, 0.19, 1.74 micrograms/g wet tissue, respectively). However, except for total proteins such exposure did not produce any changes in various biochemical parameters which were within the normal values. Thus these results have shown that, despite significant bioaccumulation of manganese in some tissues, no significant toxic effects could be seen. PMID:9841807

Sierra, P; Chakrabarti, S; Tounkara, R; Loranger, S; Kennedy, G; Zayed, J

1998-11-01

302

Green decomposition of organic dyes using octahedral molecular sieve manganese oxide catalysts.  

PubMed

The catalytic degradation of organic dye (methylene blue, MB) has been studied using green oxidation methods (tertiary-butyl hydrogen peroxide, TBHP, as the oxidant with several doped mixed-valent and regular manganese oxide catalysts in water) at room and higher temperatures. These catalysts belong to a class of porous manganese oxides known as octahedral molecular sieves (OMS). The most active catalysts were those of Mo(6+)- and V(5+)-doped OMS. Rates of reaction were found to be first-order with respect to the dye. TBHP has been found to enhance the MB decomposition, whereas H(2)O(2) does not. Reactions were studied at pH 3-11. The optimum pH for these reactions was pH 3. Dye-decomposing activity was proportional to the amount of catalyst used, and a significant increase in catalytic activity was observed with increasing temperature. X-ray diffraction (XRD), energy dispersive spectroscopy (EDX), and thermogravimetric analysis (TGA) studies showed that no changes in the catalyst structure occurred after the dye-degradation reaction. The products as analyzed by electrospray ionization mass spectrometry (ESI-MS) showed that MB was successively decomposed through different intermediate species. PMID:19178167

Sriskandakumar, Thamayanthy; Opembe, Naftali; Chen, Chun-Hu; Morey, Aimee; King'ondu, Cecil; Suib, Steven L

2009-01-29

303

Characterization of layered lithium nickel manganese oxides synthesized by a novel oxidative coprecipitation method and their electrochemical performance as lithium insertion electrode materials  

SciTech Connect

Lithium nickel manganese oxides, LiNi{sub 1{minus}y}Mn{sub y}O{sub 2+{delta}}, (0 {le} y {le} 0.5) were prepared via a new solution technique. The corresponding mixed nickel manganese hydroxide precursors were synthesized in an oxidative coprecipitation method. Subsequent calcination in the presence of LiOH leads to crystalline products with a partially disordered layered-type {alpha}-NaFeO{sub 2} structure. X-ray photoelectron spectroscopic analysis has indicated a strong enrichment of lithium at the surface. The electrochemical performance of these materials as positive electrodes in lithium-ion batteries was evaluated as a function of the calcination temperature and manganese content. A calcination temperature of 700 C leads to the best cycling stability. At this temperature, a sufficiently high degree of crystallinity was achieved, having a strong influence on the cycling stability of these 4 V materials. The specific charge and cycling stability obtained for the solution-prepared pure lithium nickel oxide, LiNiO{sub 2}, was low, but was significantly enhanced by replacing some nickel with manganese. With increasing manganese content, the specific charge increased to about 170 mAh/g for materials with a Ni:Mn ratio of about 1:1. Ex situ magnetic susceptibility measurements proved that during lithium deinsertion, the trivalent manganese is preferentially oxidized, and seems to be the more reactive redox center in these oxides.

Spahr, M.E. [Paul Scherrer Inst., Villigen (Switzerland). Electrochemistry Section]|[Swiss Federal Inst. of Tech., Zurich (Switzerland). Lab. of Inorganic Chemistry; Novak, P.; Schnyder, B.; Haas, O. [Paul Scherrer Inst., Villigen (Switzerland). Electrochemistry Section; Nesper, R. [Swiss Federal Inst. of Tech., Zurich (Switzerland). Lab. of Inorganic Chemistry

1998-04-01

304

Metal Inhibition of Growth and Manganese Oxidation in Pseudomonas putida GB-1  

NASA Astrophysics Data System (ADS)

Biogenic manganese oxides (MnO2) are ubiquitous nanoparticulate minerals that contribute to the adsorption of nutrient and toxicant metals, the oxidative degradation of various organic compounds, and the respiration of metal-reducing bacteria in aquatic and terrestrial environments. The formation of these minerals is catalyzed by a diverse and widely-distributed group of bacteria and fungi, often through the enzymatic oxidation of aqueous Mn(II) to Mn(IV). In metal-impacted ecosystems, toxicant metals may alter the viability and metabolic activity of Mn-oxidizing organisms, thereby limiting the conditions under which biogenic MnO2 can form and diminishing their potential as adsorbent materials. Pseudomonas putida GB-1 (P. putida GB-1) is a model Mn-oxidizing laboratory culture representative of freshwater and soil biofilm-forming bacteria. Manganese oxidation in P. putida GB-1 occurs via two single-electron-transfer reactions, involving a multicopper oxidase enzyme found on the bacterial outer membrane surface. Near the onset of the stationary phase of growth, dark brown MnO2 particles are deposited in a matrix of bacterial cells and extracellular polymeric substances, thus forming heterogeneous biomineral assemblages. In this study, we assessed the influence of various transition metals on microbial growth and manganese oxidation capacity in a P. putida GB-1 culture propagated in a nutrient-rich growth medium. The concentration-response behavior of actively growing P. putida GB-1 cells was investigated for Fe, Co, Ni, Cu and Zn at pH ? 6 in the presence and absence of 1 mM Mn. Toxicity parameters such as EC0, EC50 and Hillslope, and EC100 were obtained from the sigmoidal concentration-response curves. The extent of MnO2 formation in the presence of the various metal cations was documented 24, 50, 74 and 104 h after the metal-amended medium was inoculated. Toxicity values were compared to twelve physicochemical properties of the metals tested. Significant correlations were found between EC50 values and reduction potential, electronegativity and the covalent index. Thus, metal toxicity in P. putida GB-1 appears to be modulated by the metals propensity to participate in covalent interactions and generate oxidative stress. This study provides a quantitative measure of metal tolerance in P. putida GB-1, as well as operational limits for Mn oxidation in this model system, both of which have important implications for the reactivity of P. putida-MnO2 assemblages formed in metal-impacted ecosystems.

Pena, J.; Sposito, G.

2009-12-01

305

Potassium manganesevanadium oxide cathodes prepared by hydrothermal synthesis  

Microsoft Academic Search

Hydrothermal reactions between potassium permanganate and vanadyl sulfate have been used to synthesize new forms of vanadium oxides. Depending on the reactant ratios and pH values of the reaction mixtures, two different layered materials have been identified. The first one formed at a pH value of 1.6 has an interlayer distance of 10.90 and a composition of K0.16Mn0.04V2O4.940.14H2O, while the

Ping Liu; Ji-Guang Zhang; John A. Turner

2001-01-01

306

Geology, alteration, age, and origin of iron oxide-apatite deposits in Upper Eocene quartz monzonite, Zanjan district, NW Iran  

NASA Astrophysics Data System (ADS)

Iron oxide-apatite deposits are present in Upper Eocene pyroxene-quartz monzonitic rocks of the Zanjan district, northwestern Iran. Mineralization occurred in five stages: (1) deposition of disseminated magnetite and apatite in the host rock; (2) mineralization of massive and banded magnetite ores in veins and stockwork associated with minor brecciation and calcic alteration of host rocks; (3) deposition of sulfide ores together with potassic alteration; (4) formation of quartz and carbonate veins and sericite, chlorite, epidote, silica, carbonate, and tourmaline alteration; and (5) supergene alteration and weathering. U-Pb dating of monazite inclusions in the apatite indicates an age of 39.99 0.24 Ma, which is nearly coeval with the time of emplacement of the host quartz monzonite, supporting the genetic connection. Fluid inclusions in the apatite have homogenization temperatures of about 300 C and oxygen isotopic compositions of the magnetite support precipitation from magmatic fluids. Late-stage quartz resulted from the introduction of a cooler, less saline, and isotopically depleted fluid. The iron oxide-apatite deposits in the Tarom area of the Zanjan district are typical of a magmatic-hydrothermal origin and are similar to the Kiruna-type deposits with respect to mineral assemblages, fabric and structure of the iron ores, occurrence of the ore bodies, and wall rock alteration.

Nabatian, Ghasem; Ghaderi, Majid; Corfu, Fernando; Neubauer, Franz; Bernroider, Manfred; Prokofiev, Vsevolod; Honarmand, Maryam

2013-09-01

307

Preparation of manganese oxide with high density by decomposition of MnCO 3 and its application to synthesis of LiMn 2O 4  

Microsoft Academic Search

Manganese oxide with high tap density was prepared by decomposition of spherical manganese carbonate, and then LiMn2O4 cathode materials were synthesized by solid-state reaction between the manganese oxide and lithium carbonate. Structure and properties of the samples were determined by X-ray diffraction, BrunauerEmmerTeller surface area analysis, scanning electron microscope and electrochemical measurements. With increase of the decomposition temperature from 350C

Hua-jun Guo; Xin-hai Li; Zhi-xing Wang; Wen-jie Peng; Xuan Cao; Hui-feng Li

2009-01-01

308

The Structure and Properties of Plasma Sprayed Iron Oxide Doped Manganese Cobalt Oxide Spinel Coatings for SOFC Metallic Interconnectors  

NASA Astrophysics Data System (ADS)

Manganese cobalt oxide spinel doped with Fe2O3 was studied as a protective coating on ferritic stainless steel interconnects. Chromium alloying causes problems at high operation temperatures in such oxidizing conditions where chromium compounds evaporate and poison the cathode active area, causing the degradation of the solid oxide fuel cell. In order to prevent chromium evaporation, these interconnectors need a protective coating to block the chromium evaporation and to maintain an adequate electrical conductivity. Thermal spraying is regarded as a promising way to produce dense and protective layers. In the present work, the ceramic Mn-Co-Fe oxide spinel coatings were produced by using the atmospheric plasma spray process. Coatings with low thickness and low amount of porosity were produced by optimizing deposition conditions. The original spinel structure decomposed because of the fast transformation of solid-liquid-solid states but was partially restored by using post-annealing treatment.

Puranen, Jouni; Lagerbom, Juha; Hyvrinen, Leo; Kylmlahti, Mikko; Himanen, Olli; Pihlatie, Mikko; Kiviaho, Jari; Vuoristo, Petri

2011-01-01

309

The Structure and Properties of Plasma Sprayed Iron Oxide Doped Manganese Cobalt Oxide Spinel Coatings for SOFC Metallic Interconnectors  

NASA Astrophysics Data System (ADS)

Manganese cobalt oxide spinel doped with Fe2O3 was studied as a protective coating on ferritic stainless steel interconnects. Chromium alloying causes problems at high operation temperatures in such oxidizing conditions where chromium compounds evaporate and poison the cathode active area, causing the degradation of the solid oxide fuel cell. In order to prevent chromium evaporation, these interconnectors need a protective coating to block the chromium evaporation and to maintain an adequate electrical conductivity. Thermal spraying is regarded as a promising way to produce dense and protective layers. In the present work, the ceramic Mn-Co-Fe oxide spinel coatings were produced by using the atmospheric plasma spray process. Coatings with low thickness and low amount of porosity were produced by optimizing deposition conditions. The original spinel structure decomposed because of the fast transformation of solid-liquid-solid states but was partially restored by using post-annealing treatment.

Puranen, Jouni; Lagerbom, Juha; Hyvrinen, Leo; Kylmlahti, Mikko; Himanen, Olli; Pihlatie, Mikko; Kiviaho, Jari; Vuoristo, Petri

2010-11-01

310

Promotion of the hydrogen peroxide decomposition activity of manganese oxide catalysts  

Microsoft Academic Search

Pure (MnOx), mixed (AyMn1?yOx) and composite ((A,B)yMn1?yOx) manganese oxide based catalysts were prepared, where A is either NiII, CuII, BiIII or CeIV, A and B are various combinations of them, and y=0.4. Subsequently, they were characterized for the crystalline bulk structure by X-ray powder diffractometry, the electron availability by magnetic susceptibility measurements, the surface area by BET-analysis of nitrogen adsorption

Muhammad A Hasan; Mohamed I Zaki; Lata Pasupulety; Kamlesh Kumari

1999-01-01

311

Synthesis and structural characterization of defect spinels in the lithium-manganese-oxide system  

Microsoft Academic Search

Lithium-manganese-oxides prepared at moderate temperatures are under investigation as insertion electrodes for rechargeable lithium batteries. The structure of two defect-spinel compounds synthesized by the reaction of MnCO[sub 3] and Li[sub 2]CO[sub 3] at 400 C are reported. The cation distribution in the structures were determined by neutron-diffraction to be Li[sub .85][open square][sub .15][sub 8a][Mn[sub 1.74]Li[sub .26

M. M. Thackeray; A. de Kock; W. I. F. David

1993-01-01

312

Synthesis and structural characterization of defect spinels in the lithium-manganese-oxide system  

SciTech Connect

Lithium-manganese-oxides prepared at moderate temperatures are under investigation as insertion electrodes for rechargeable lithium batteries. The structure of two defect-spinel compounds synthesized by the reaction of MnCO[sub 3] and Li[sub 2]CO[sub 3] at 400 C are reported. The cation distribution in the structures were determined by neutron-diffraction to be Li[sub .85][open square][sub .15][sub 8a][Mn[sub 1.74]Li[sub .26

Thackeray, M.M.; Kock, A. de (CSIR, Pretoria (South Africa). Div. of Materials Science and Technology); David, W.I.F. (Rutherford Appleton Lab., Oxfordshire (United Kingdom))

1993-10-01

313

Nano-sized lithium manganese oxide dispersed on carbon nanotubes for energy storage applications  

Microsoft Academic Search

Nano-sized lithium manganese oxide (LMO) dispersed on carbon nanotubes (CNT) has been synthesized successfully via a microwave-assisted hydrothermal reaction at 200C for 30min using MnO2-coated CNT and an aqueous LiOH solution. The initial specific capacity is 99.4mAh\\/g at a 1.6 C-rate, and is maintained at 99.1mAh\\/g even at a 16 C-rate. The initial specific capacity is also maintained up to

Sang-Bok Ma; Kyung-Wan Nam; Won-Sub Yoon; Seong-Min Bak; Xiao-Qing Yang; Byung-Won Cho; Kwang-Bum Kim

2009-01-01

314

Development of composites based on lithium manganese nickel oxide and electroactive polymers  

Microsoft Academic Search

A new composite cathode-active material based on lithium manganese nickel oxide (LiMn2?xNixO4), poly(2,5-dimercapto-1,3,4-thiadiazole) (PDMcT) and polyaniline (PAni) was synthesized. The formation of the uniform and well-connected polymer film on the surface of LiMn2?xNixO4 particles was confirmed by Fourier-transform infrared spectra (FT-IR) and scanning electronic micrographs (SEM). The amounts of each constituent cannot be separately determined by thermogravimetric analysis (TGA). By

Sheila C. Canobre; Livia Montanhez; Carla Polo Fonseca; Silmara Neves

2009-01-01

315

A sodium layered manganese oxides as 3 V cathode materials for secondary lithium batteries  

Microsoft Academic Search

The synthesis of a new anhydrous sodium manganese oxide ?-Na0.66MnO2.13 obtained via a solgel process in organic medium is reported. The partial and limited removal of sodium ions from the layered host lattice (hexagonal symmetry; a=2.84, c=11.09) allows to get a high and stable specific capacity of 180mAhg?1 at C\\/20 in the cycling limits 4.3\\/2V with a mean working voltage

S. Bach; J. P. Pereira-Ramos; P. Willmann

2006-01-01

316

Processing-structure-property-performance investigations of lithium manganese-based oxides for lithium rechargeable batteries  

Microsoft Academic Search

A study of the processing - structure - property - performance interrelationship was performed on several lithium manganese oxides that are candidates for use in lithium rechargeable batteries. The materials studied were LiMn 2O4, Mn-substituted LiMn2O4 (LiMn 2-yMeyO4), and Li1.5Na0.5 MnO2.85I0.12. Processing evaluations pertained to the substitution of Mn by other cations (Me = Li, Co, or Ni). Atomic and

Craig Richard Horne

2000-01-01

317

Oxidative stress involvement in manganese-induced alpha-synuclein oligomerization in organotypic brain slice cultures.  

PubMed

Overexposure to manganese (Mn) has been known to induce neuronal damage. However, little is known of the role that reactive oxygen species (ROS) play in protein aggregation resulting from Mn exposure. The current study investigated whether oxidative stress is involved in manganese-induced alpha-synuclein oligomerization in organotypic brain slices. After application of Mn (0-400?M) for 24h, there was a dose-dependent increase in average percentage of propidium iodide positive (PI(+)) nuclei in slices and levels of lactate dehydrogenase (LDH) in the culture medium. Moreover, the treatment with Mn resulted in a dose-dependent increase in neurocyte apoptosis, ROS level, and decrease in superoxide dismutase (SOD) activity. Mn also caused oxidative damage in cell lipid and protein. At the same time, the exposure of Mn leaded to significantly increase in the expression of alpha-synuclein mRNA and protein. Alpha-synuclein oligomerization occurred in Mn-treated slices, especially on membrane-bound form. It indicated that alpha-synuclein oligomers were more likely to combination cell membranes and resulting in membrane damage. Mn-induced neurocyte damage and alpha-synuclein oligomerization were also partially alleviated by the pretreatment with GSH and aggravated by H2O2 pretreatment. The findings revealed Mn might exert its neurotoxic effects by oxidative stress-mediated alpha-synuclein oligomerization in organotypic brain slices. PMID:23353026

Xu, Bin; Wu, Sheng-Wen; Lu, Chun-Wei; Deng, Yu; Liu, Wei; Wei, Yan-Gang; Yang, Tian-Yao; Xu, Zhao-Fa

2013-01-23

318

Photocatalytic Water Oxidation Using Manganese Compounds Immobilized in Nafion Polymer Membranes  

PubMed Central

Robust water oxidation catalysts using earth abundant metals are required as part of an overall scheme to convert sunlight into fuels. Here, we report the immobilization of [Mn4IVO5(terpy)4(H2O)2](ClO4)6 (terpy = 2,2?;6?,2?-terpyridine), [Mn4O6(tacn)4](ClO4)4 (tacn = 1,4,7-triazacyclononane), and manganese dioxide nanoparticles in Nafion on fluorine-doped tin oxide conducting glass electrodes. The electrodes are illuminated with white light in the presence of an applied potential and the resulting photocurrent is assigned to the oxidation of solvent water. Photodecomposition of the tetrameric complexes results in a material that is more active for light-driven electrooxidation of water. The reactivity, wavelength dependence, and stability of the compounds in Nafion under illumination are discussed.

Young, Karin J.; Gao, Yunlong; Brudvig, Gary W.

2011-01-01

319

Origin of the high voltage (>4.5 V) capacity of spinel lithium manganese oxides  

Microsoft Academic Search

With an objective to develop a better understanding of the origin of high voltage (>4.5 V) capacities, the electrochemical behaviors of a number of spinel lithium manganese oxides with and without other transition metal ions have been studied and compared. The oxides investigated are LiMn2?yMyO4 (M=Co, Ni, and Cu), LiMn2?y?zMyLizO4, LiMn2?yLiyO4, Li2Mn4O9??, and Li4Mn5O12. The LiMn2?yLiyO4 (0.05?y?0.12) oxides are found

Youngjoon Shin; Arumugam Manthiram

2003-01-01

320

Oxidative cleavage of a phenolic diarylpropane lignin model dimer by manganese peroxidase from Phanerochaete chrysosporium  

SciTech Connect

In the presence of Mn{sup II} and H{sub 2}O{sub 2}, homogeneous manganese peroxidase oxidized 1-(3,5-dimethoxy-4-hydroxy phenyl)-2- (4-methoxyphenyl)- 1,3-dihydroxypropane (I) to yield 1-(3,5- dimethoxy-4- hydroxyphenyl)-2- (4-methoxyphenyl)-1-oxo-3- hydroxy propane (II), 2,6-dimethoxy- 1,4-benzoquinone (III), 2,6-dimethoxy- 1,4-dihydroxy benzene (IV), 1-(4-methoxyphenyl)- 1-oxo-2-hydroxyethane (V), 1-(4-methoxyphenyl)- 1,2-dihydroxyethane (VI), syringaldehyde (VIII), and 2-(4-methoxyphenyl)- 3-hydroxypropanal (IX). Chemically prepared manganese(III) malonate catalyzed the same reactions. Oxidation of I in H{sub 2}{sup 18}O under argon resulted in >80% incorporation of {sup 18}O into the phenylglycol VI, the hydroquinone IV, and the quinone III. Oxidation of I in H{sub 2}{sup 18}O under aerobic conditions resulted in 40% incorporation of {sup 18}O into VI but no {sup 18}O incorporation into V. Finally, oxidation of I under {sup 18}O{sub 2} resulted in 89% and 28% incorporation of {sup 18}O into V and VI, respectively. These results are explained by mechanisms involving the one-electron oxidation of the substrate I by enzyme-generated Mn{sup III} to produce a phenoxy radical intermediate I{prime}. Subsequent C{sub {alpha}}-C{sub {beta}} bond cleavage of the radical intermediate yields syringaldehyde (VIII) and a C{sub 6}-C{sub 2} benzylic radical. Syringaldehyde is oxidized by Mn{sup III} in several steps to a cyclohexadiene cation intermediate I{double prime}, which is attacked by water to yield the benzoquinone III. The C{sub 6}-C{sub 2} radical is scavenged by O{sub 2} to form a peroxy radical that decomposes to V and VI. In these reactions, Mn{sup III} generated by manganese peroxidase catalyzes both formation of the substrate phenoxy radical and oxidation of carbon-centered radical intermediates, to yield reactive cations.

Wariishi, Hiroyuki; Valli, K.; Gold, M.H. (Oregon Graduate Center, Beaverton (USA))

1989-07-11

321

Lithium manganese oxide as an effective buffer layer between organic and metal layers in organic light-emitting devices  

NASA Astrophysics Data System (ADS)

Tris(8-hydroxyquinolinato)aluminum (Alq3)-based organic light-emitting devices using a thermally deposited lithium manganese oxide layer between aluminum (Al) cathode and Alq3 have been fabricated. The highest luminance efficiency obtained with a 1-nm-thick LiMnxOy layer is very similar to that of the device with 1-nm-thick LiF. However, the device with an 18 nm LiMnxOy layer obtained a longer operational stability although the luminance efficiency is lower. The improvements are attributed to lithium extractions of the lithium manganese oxide layer and the interfacial properties between Alq3 and Al are discussed.

Liu, Tswen-Hsin

2006-09-01

322

Deuterium and lithium-6 MAS NMR studies of manganese oxide electrode materials  

NASA Astrophysics Data System (ADS)

Electrolytic manganese dioxide (EMD) is used world wide as the cathode materials in both lithium and alkaline primary (non-rechargeable) batteries. We have developed deuterium and lithium MAS NMR techniques to study EMD and related manganese oxides and hydroxides, where diffraction techniques are of limited value due to a highly defective nature of the structures. Deuterons in EMD, manganite, groutite, and deuterium-intercalated pyrolusite and ramsdellite were detected by NMR, for the first time, and their locations and motions in the structures were analyzed by applying variable temperature NMR techniques. Discharge mechanisms of EMD in alkaline (aqueous) electrolytes were studied, in conjunction with step potential electrochemical spectroscopic (SPECS) method, and five distinctive discharge processes were proposed. EMD is usually heat-treated at about 300--400C to remove water to be used in lithium batteries. Details of the effects of heat-treatment, such as structural and compositional changes as a function of heat-treatment temperature, were studied by a combination of MAS NMR, XRD, and thermogravimetric analysis. Lithium local environments in heat-treated EMD (HEMD) that were discharged in lithium cells, were described in terms of related environments found in model compounds pyrolusite and ramsdellite where specific Li + sites were detected by MAS NMR and the hyperfine shift scale method of Grey et al. Acid-leaching of Li2MnO3 represents an approach for synthesizing new or modified manganese oxide electrode materials for lithium rechargeable batteries. Progressive removal of lithium from specific crystallographic sites, followed by a gradual change of the crystal structure, was monitored by a combination of NMR and XRD techniques.

Paik, Younkee

323

Anomalous pseudocapacitive behavior of a nanostructured, mixed-valent manganese oxide film for electrical energy storage.  

PubMed

While pseudocapacitors represent a promising option for electrical energy storage, the performance of the existing ones must be dramatically enhanced to meet today's ever-increasing demands for many emerging applications. Here we report a nanostructured, mixed-valent manganese oxide film that exhibits anomalously high specific capacitance (?2530 F/g of manganese oxide, measured at 0.61 A/g in a two-electrode configuration with loading of active materials ?0.16 mg/cm(2)) while maintaining excellent power density and cycling life. The dramatic performance enhancement is attributed to its unique mixed-valence state with porous nanoarchitecture, which may facilitate rapid mass transport and enhance surface double-layer capacitance, while promoting facile redox reactions associated with charge storage by both Mn and O sites, as suggested by in situ X-ray absorption spectroscopy (XAS) and density functional theory calculations. The new charge storage mechanisms (in addition to redox reactions of cations) may offer critical insights to rational design of a new-generation energy storage devices. PMID:22681539

Song, Min-Kyu; Cheng, Shuang; Chen, Haiyan; Qin, Wentao; Nam, Kyung-Wan; Xu, Shucheng; Yang, Xiao-Qing; Bongiorno, Angelo; Lee, Jangsoo; Bai, Jianming; Tyson, Trevor A; Cho, Jaephil; Liu, Meilin

2012-06-13

324

Lithium-manganese-oxide thin-film cathodes prepared by plasma-enhanced chemical vapor deposition  

SciTech Connect

Lithium-manganese-oxide thin-film electrodes have been fabricated using the plasma-enhanced chemical vapor deposition technique. Process parameters such as flow rates of the reactants, deposition temperature, and RF power have been systematically varied to optimize the charge and discharge properties. The thin films are amorphous as found by X-ray diffraction spectrometry and can be cycled reversibly in the range from 4.5 to 3 V or 4.5 to 2.5 V with maximum capacities of 30 and 39 {mu}Ah/cm{sup 2}, respectively. The capacity fade of the films is ca. 0.04% per cycle over more than 700 cycles when tested in liquid electrolytes. Films which are optimized for cycling between 4.5 and 3 V demonstrate a near-perfect balance between the charge and discharge capacities during the initial cycle and also show very small capacity fade in the subsequent cycles. Results indicate that these lithium manganese oxide thin films are good candidates for use as cathodes in thin-film lithium-ion batteries.

Liu, P.; Zhang, J.G.; Turner, J.A.; Tracy, C.E.; Benson, D.K. [National Renewable Energy Lab., Golden, CO (United States)

1999-06-01

325

Decolorization of methylene blue in layered manganese oxide suspension with H2O2.  

PubMed

Layered birnessite-type manganese oxides (Na-OL-1) were prepared via a redox reaction involving MnO(4)(-) and Mn(2+) under markedly alkaline conditions. According to the XRD analysis, the resulting material exhibited a well-crystallized octahedral layer (OL) structure with several different phases, including ?-MnOOH, ?-MnOOH and ?-Mn(3)O(4). The catalyst was highly effective for the decolorization and degradation of methylene blue (MB) in the presence of H(2)O(2) at neutral pH. The tested MB was completely decolorized in Na-OL-1 suspension by the fraction dosing of H(2)O(2) (556.5mM at the beginning and then 183.8mM at 40 min). Based on the studies of electron spin resonance and the effect of radical scavengers, the (1)O(2) and O(2)(-) were the main reactive oxygen species (ROS) in the reaction. It was found that both oxygen and ROS were generated from the decomposition of H(2)O(2) in Na-OL-1 suspension, wherein the decomposition pathways were proposed. The generation of H(2)O(2) in Na-OL-1 suspension at air atmosphere indicated that the existence of multivalent manganese oxides greatly enhanced the interfacial electron transfer, leading to the high activity of Na-OL-1. PMID:21524842

Zhang, Lili; Nie, Yulun; Hu, Chun; Hu, Xuexiang

2011-04-07

326

Adsorption of copper, cadmium, lead and zinc onto a synthetic manganese oxide.  

PubMed

Due to its simple and inexpensive synthesis, a new amorphous hydrous manganese oxide (AMO) has been studied as a possible chemical stabilizing agent for soils contaminated with metals. Preliminary experiments evaluating the stability of AMO in pure water have reported only minor dissolution (5.70% and 0.24% depending on the w/v ratio). Sorption kinetics have shown fast metal adsorption, especially for Pb. The sorption capacities of AMO for Cu, Cd, Pb, and Zn have been described and compared with synthetic birnessite for pH 4 and 5.5. Both oxides show similar sorption capacities at pH 4 despite the fact that birnessite characteristics (pH of zero point charge, specific surface area and cation exchange capacity) are more favorable for metal sorption. Moreover, the pH adsorption-edges show that the AMO is more pH-dependent than birnessite. PMID:23566588

Della Puppa, Loc; Komrek, Michael; Bordas, Franois; Bollinger, Jean-Claude; Joussein, Emmanuel

2013-02-27

327

Nano-sized Lithium Manganese Oxide Dispersed on Carbon Nanotubes for Energy Storage Applications  

SciTech Connect

Nano-sized lithium manganese oxide (LMO) dispersed on carbon nanotubes (CNT) has been synthesized successfully via a microwave-assisted hydrothermal reaction at 200 C for 30 min using MnO{sub 2}-coated CNT and an aqueous LiOH solution. The initial specific capacity is 99.4 mAh/g at a 1.6 C-rate, and is maintained at 99.1 mAh/g even at a 16 C-rate. The initial specific capacity is also maintained up to the 50th cycle to give 97% capacity retention. The LMO/CNT nanocomposite shows excellent power performance and good structural reversibility as an electrode material in energy storage systems, such as lithium-ion batteries and electrochemical capacitors. This synthetic strategy opens a new avenue for the effective and facile synthesis of lithium transition metal oxide/CNT nanocomposite.

Bak, S.B.

2009-08-01

328

Electrochemical impedance spectroscopy studies of lithium diffusion in doped manganese oxide  

SciTech Connect

Cathode performance is critical to lithium ion rechargeable battery performance; effects of doping lithium manganese oxide cathode materials on cathode performance are being investigated. In this paper, Li diffusion in Al-doped LiMn{sub 2}O{sub 4} was studied and found to be controlled by the quantity of Al dopant. Electrochemical cycling was conducted at 0.5mA/cm{sub 2}; electrochemical impedance spectra were taken at open circuit potential, with impedance being measured at 65 kHz-0.01 Hz. As the Al dopant level was increased, the Li diffusion rate decreased; this was attributed to the decreased lattice parameter of the doped oxide.

Johnson, B.J.; Doughty, D.H.; Voigt, J.A.; Boyle, T.J.

1996-06-01

329

In Situ X-ray Absorption Study of a Layered Manganese-chromium Oxide-based Cathode Material  

SciTech Connect

We have investigated the electronic and atomic structure of a manganese-chromium-based layered oxide material Li[Li{sub 0.2}Cr{sub 0.4}Mn{sub 0.4}]O{sub 2} during electrochemical cycling using in situ X-ray absorption spectroscopy. Our results indicate that charge compensation in the cathode material is achieved by the oxidation/reduction of octahedral Cr(III) ions to tetrahedral Cr(VI) ions during delithiation/lithiation. Manganese ions are present predominantly in the Mn(IV) oxidation state and do not appear to actively participate in the charge compensation process. To accommodate the large changes in coordination symmetry of the Cr(III) and Cr(VI) ions, the chromium ions have to move between the regular octahedral sites in the R{bar 3}m-like lattice to interstitial tetrahedral sites during the charge/discharge process. The highly reversible (at least after the first charge) three-electron oxidation/reductions and the easy mobility of the chromium between octahedral and tetrahedral sites are very unusual and interesting. Equally interesting is the fact that chromium is the active metal undergoing oxidation/reduction rather than manganese. Our results also suggest that in the local scale manganese and chromium ions are not evenly distributed in the as-prepared material, but are present in separate domains of Mn and Cr-rich regions.

Balasubramanian, M.; McBreen, J; Davidson, I; Whitfield, P; Kargina, I

2010-01-01

330

Tissue Manganese Concentrations in Young Male Rhesus Monkeys following Subchronic Manganese Sulfate Inhalation  

Microsoft Academic Search

High-dose human exposure to manganese results in manganese accumulation in the basal ganglia and dopaminergic neuropa- thology. Occupational manganese neurotoxicity is most frequently linked with manganese oxide inhalation; however, exposure to other forms of manganese may lead to higher body burdens. The objective of this study was to determine tissue manganese con- centrations in rhesus monkeys following subchronic (6 h\\/day,

David C. Dorman; Melanie F. Struve; Marianne W. Marshall; Carl U. Parkinson; R. Arden James; Brian A. Wong

2006-01-01

331

Effects of manganese oxide on monkeys as revealed by a combined neurochemical, histological and neurophysiological evaluation.  

PubMed

Four monkeys were exposed to a total of 8 g each of manganese as oxide by repetitive subcutaneous injections during 5 months, after which they were left for 1 week to 6 months before they were sacrificed. All animals developed hyperactive behaviour after about 2 months. About 5 months after the start of the exposure the animals became hypoactive with an unsteady gait, and subsequently an action tremor appeared in some of the animals. The animals lost power in both upper and lower limbs and the movements of the hands and feet were very clumsy. The serum content of manganese rose 10-40 times during the exposure time and the content in brain was generally increased more than 10 times, with the highest content found in globus pallidus and putamen. The observed neurochemical effects were also largest in globus pallidus and putamen. In these regions there was a considerable depletion of dopamine and 3,4-dihydroxyphenylacetic acid, while the homovanillic acid content remained almost unchanged. A severe neuronal cell loss was observed in globus pallidus but not in other regions. This is in accordance with results from the most recent neuropathological study of a human suffering from chronic manganese poisoning [Yamada et al. (1986) Acta Neuropathol 70: 273-278] where globus pallidus was devoid of neuronal cells while the content of pigmented cells in substantia nigra was normal. Our data suggest a reduction in number of dopaminergic nerve terminals, as the activity of the dopamine synthesizing enzyme DOPA-decarboxylase was also lowered.(ABSTRACT TRUNCATED AT 250 WORDS) PMID:3439874

Eriksson, H; Mgiste, K; Plantin, L O; Fonnum, F; Hedstrm, K G; Theodorsson-Norheim, E; Kristensson, K; Stlberg, E; Heilbronn, E

1987-01-01

332

Results from eleven years of neurological health surveillance at a manganese oxide and salt producing plant.  

PubMed

In 1983, Roels et al. (1987a, b) collected blood and urine samples and conducted neurological testing of workers at a manganese oxide and salt producing plant in Belgium, and at a nearby chemical plant. Workers from the manganese plant performed significantly worse than workers from the chemical plant on tests of short-term memory capacity, eye-hand coordination, hand steadiness, and visual reaction time. Between 1985 and 1996, workers at the manganese plant were tested routinely using the same battery of neurological tests and biological sampling that were employed by Roels et al. Blood and urine Mn levels remained comparable throughout the eleven years of testing to those measured in 1983 by Roels et al. On a gross basis, neurological test results during this period were comparable or superior to results obtained by Roels et al., despite the fact that workers were older and had been exposed longer. Large year-to-year differences were observed in some neurological test outcomes that could not be explained by age or Mn exposure. Older age was significantly associated with poorer performance on tests of short-term memory and eye-hand coordination. After controlling for age and year of testing, reduced hand steadiness was significantly associated with blood Mn and (Marginally) urine Mn, and both reaction time and one measure of hand steadiness were significantly associated with years of Mn exposure. No significant associations were found between any measure of Mn exposure and results from either short-term memory or eye-hand coordination tests. Investigations regarding whether neurological scores of individual workers studied by Roels et al. continued to worsen with continued occupational Mn exposure were hampered by lack of a suitable comparison group. However, there was no evidence that neurological effects seen earlier in these workers by Roels et al. were progressing towards clinical detectable signs. PMID:10385890

Crump, K S; Rousseau, P

333

Thiol-mediated oxidation of nonphenolic lignin model compounds by manganese peroxidase of Phanerochaete chrysosporium  

SciTech Connect

In the presence of Mn{sup II}, H{sub 2}O{sub 2}, and glutathione (GSH), manganese peroxidase oxidized veratryl alcohol (1) to veratraldehyde (4). Anisyl alcohol (2) and benzyl alcohol (3) were also oxidized by this system to their corresponding aldehydes, anisaldehyde (5) and benzaldehyde (6). In the presence of GSH, chemically prepared Mn{sup III} or {gamma}-irradiation also catalyzed the oxidation of 1, 2, and 3 to 4, 5, and 6, respectively. GSH and dithiothreitol rapidly reduced Mn{sup III} to Mn{sup II} in the absence of aromatic substrates and the dithiothreitol was oxidized to its disulfide (4,5-dihydroxyl-1,2-dithiane). These results indicate that the thiol is oxidized by enzyme-generated Mn{sup III} to a thiyl radical. The latter abstracts a hydrogen from the substrate , forming a benzylic radical which reacts with another thiyl radical to yield an intermediate which decomposes to the benzaldehyde product. 51 refs., 5 figs., 2 tabs.

Wariishi, Hiroyuki; Valli, K.; Renganathan, V.; Gold, M.H. (Oregon Graduate Center, Beaverton (United States))

1989-08-25

334

Molecular-Level Processes Governing the Interaction of Contaminants with Iron and Manganese Oxides - Final Report  

SciTech Connect

Many of the inorganic and organic contaminants present in sediments at DOE sites can be altered or destroyed by reduction and oxidation (redox) reactions occurring at mineral surfaces. A fundamental understanding of such redox processes provided by molecular-level studies on structurally and compositionally well-defined mineral surfaces will lead to: (i) improved models of contaminant fate and transport in geochemical systems, and (ii) optimized manipulation of these processes for remediation purposes. To contribute to this understanding, we will study, both experimentally and theoretically, redox processes involving three important contaminants - chromate ion, carbon tetrachloride, and trichloroethene TCE, on the following iron and manganese oxides - hematite, magnetite, maghemite, and pyrolusite. These oxides and their hydroxylated analogs commonly occur as coatings on minerals or as interfaces in the subsurface environment. Single-crystal surfaces of these oxides will be synthesized in carefully controlled fashion by molecular beam epitaxy. These surfaces, as well as high surface are powdered samples of these oxides, will be used in spectroscopic and kinetic experiments in both aqueous and gas phases. Our goal is to identify products and to determine the kinetics and mechanisms of surface-catalyzed redox reaction of Cr(VI) and CR(III), and the reductive dechlorination of carbon tetrachloride and TCE. The combination of theory and experiment will provide the base information needed to scale from the molecular level to the microscopic grain level minerals.

Brown Jr., G. E.; Chambers, S. A.

1999-10-31

335

Genome Sequence of Deep-Sea Manganese-Oxidizing Bacterium Marinobacter manganoxydans MnI7-9  

PubMed Central

Here we report the draft genome of Marinobacter manganoxydans MnI7-9, isolated from a deep-sea hydrothermal vent in the Indian Ocean and capable of oxidizing manganese even when there is a very high concentration of Mn2+. The strain also displayed high resistance and adsorption ability toward many metal(loid)s.

Wang, Haifang; Li, Hang; Shao, Zongze; Liao, Shuijiao; Johnstone, Laurel; Rensing, Christopher

2012-01-01

336

ADSORPTION OF LEAD FROM A CONTAMINATED SOIL TREATED WITH PHOSPHORUS AND MANGANESE OXIDES BY APRAGUE-DAWLEY RATS  

EPA Science Inventory

In addition to the formation of insoluble lead (Pb) compounds as a mean of reducing Pb bioavalability, adsorption is another potentially important process controlling the bioavailability of Pb in soils. Less attention has been given to manganese (Mn) oxides, even though they are ...

337

Synthesis and structures of lithium manganese oxide spinel, LiMn 2O 4? ? (0? ??0.27)  

Microsoft Academic Search

Lithium manganese oxides spinels were synthesized under various synthesis conditions and their structures were determined by TOF neutron powder diffraction measurements. Oxygen vacancies exist for the samples synthesized above 800C, and the amount of vacancies was found to be sensitive to the synthesis conditions. The nearly stoichiometric spinels were synthesized at 750C in O2 followed by heating at 470C. The

Ryoji Kanno; Masao Yonemura; Tomoko Kohigashi; Yoji Kawamoto; Mitsuharu Tabuchi; Takashi Kamiyama

2001-01-01

338

In Situ XAS and XRD Studies of Substituted Spinel Lithium Manganese Oxides in the 4-5 V Region  

Microsoft Academic Search

Partial substitution of Mn in lithium manganese oxide spinel materials by Cu and Ni greatly affects the electrochemistry and the phase behavior of the cathode. Substitution with either metal or with a combination of both shortens the 4.2 V plateau and results in higher voltage plateaus. In situ x-ray absorption (XAS) studies indicate that the higher voltage plateaus are related

J. McBreen; S. Mukerjee; X. Q. Yang; X. Sun; Y. Ein-Eli

1998-01-01

339

Manganese: A transition metal protects nigrostriatal neurons from oxidative stress in the iron-induced animal model of Parkinsonism  

Microsoft Academic Search

It has been suggested that transition metals such as iron and manganese produce oxidative injury to the dopaminergic nigrostriatal system, which may play a critical role in the pathogenesis of Parkinson's disease. Intranigral infusion of ferrous citrate (0 to 8.4 nmol, i.n.) acutely increased lipid peroxidation in the substantia nigra and dopamine turnover in the caudate nucleus. Subsequently, it caused

I. Szirki; K. P. Mohanakumar; P. Rauhala; H. G. Kim; K. J. Yeh; C. C. Chiueh

1998-01-01

340

Manganese-Catalyzed Selective Oxidation of Aliphatic C?H groups and Secondary Alcohols to Ketones with Hydrogen Peroxide.  

PubMed

An efficient and simple method for selective oxidation of secondary alcohols and oxidation of alkanes to ketones is reported. An in?situ prepared catalyst is employed based on manganese(II) salts, pyridine-2-carboxylic acid, and butanedione, which provides good-to-excellent conversions and yields with high turnover numbers (up to 10?000) with H2 O2 as oxidant at ambient temperatures. In substrates bearing multiple alcohol groups, secondary alcohols are converted to ketones selectively and, in general, benzyl C?H oxidation proceeds in preference to aliphatic C?H oxidation. PMID:24009102

Dong, Jia Jia; Unjaroen, Duenpen; Mecozzi, Francesco; Harvey, Emma C; Saisaha, Pattama; Pijper, Dirk; de Boer, Johannes W; Alsters, Paul; Feringa, Ben L; Browne, Wesley R

2013-09-05

341

Low Temperature Synthesis of Lithium Manganese Oxide Using LiCl-Li2CO3 and Manganese Acetate Eutectic Mixture  

Microsoft Academic Search

Fine crystalline LiMn2O4 powders have been prepared by Molten-Salt Synthesis (MSS) at 500C, using an eutectic mixture of lithium chloride, lithium carbonate and manganese acetate salts. Thermo Gravimetric and Differential Thermal Analysis (TGA\\/DTA) measurements are performed to investigate the thermal decomposition behavior of the precursor salts. The single-phase cubic structure of LiMn2O4 is confirmed by X-ray powder diffraction analysis. The

M. Helan; L. John Berchmans

2011-01-01

342

Preparation of poly(aniline-co-o-anisidine)-intercalated mesostructured manganese oxide composites by exchange reaction  

SciTech Connect

Layered mesostructured manganese oxide (mesostructured MnO{sub 2}) was synthesized using manganese chloride and lithium hydroxide as the raw materials and cetyltrimethylammonium bromide (CTAB) as the structure-directing agent. Poly(aniline-co-o-anisidine)-intercalated mesostructured MnO{sub 2} composites (P(An-co-oAs)/MnO{sub 2}) were synthesized in an organic solvent through the exchange reaction between the CTAB in MnO{sub 2} gallery and the P(An-co-oAs). The interlayer spacing (I{sub c} values) of mesostructured MnO{sub 2} enlarged from 2.52 to 4.41 nm as the added amount of P(An-co-oAs) increased from 0 to 0.5 g per 0.5 g of mesostructured MnO{sub 2}. The regularity of the layered structure of the composites was firstly decreased due to intercalation of low amounts of P(An-co-oAs). However, with increasing the intercalated amount of P(An-co-oAs) the layered structure of the composites becomes more regular. The electrical conductivity of the composites is 10{sup 2} to 10{sup 3} times higher than that of the mesostructured MnO{sub 2}.

Wang Gengchao [Key Laboratory for Ultrafine Materials of Ministry of Education, School of Materials Science and Engineering, East China University of Science and Technology, Shanghai 200237 (China)], E-mail: gengchaow@ecust.edu.cn; Yang Zhenyu; Li Xingwei; Li Chunzhong [Key Laboratory for Ultrafine Materials of Ministry of Education, School of Materials Science and Engineering, East China University of Science and Technology, Shanghai 200237 (China); Yuan Weikang [UNILAB, State Key Laboratory of Chemical Reaction Engineering, East China University of Science and Technology, Shanghai 200237 (China)

2008-08-04

343

Electrochemical and magnetic properties of lithium manganese oxide spinels prepared by oxidation at low temperature of hydrothermally obtained LiMnO 2  

Microsoft Academic Search

Cubic and tetragonally distorted lithium manganese oxide spinels (LiMnO2 + x) were obtained by progressive oxidation of LiMnO2 between 300 and 400 C. Orthorhombic LiMnO2 was prepared by hydrothermal treatment of either ?-MnOOH or Mn(COOCH3)3 2H2O with LiOH H2O in large excess. The reversible specific capacity for LiMnO2 + x was found to be sensitive to average manganese

Mitsuharu Tabuchi; Kazuaki Ado; Christian Masquelier; Ichiro Matsubara; Hikari Sakaebe; Hiroyuki Kageyama; Hironori Kobayashi; Ryoji Kanno; Osamu Nakamura

1996-01-01

344

Preparation of an electrochemically-formed spinel lithium manganese oxide and its chargedischarge behaviors  

Microsoft Academic Search

Manganese hydroxides were prepared by a cathodic electrochemical precipitation from a manganese nitrate solution. The grass blade-like precipitate, which is ascribed to manganese hydroxide was 2080?m long and 15?m wide and was spread out on a Pt substrate after the electrochemical precipitation. When the electrochemically precipitated manganese hydroxides were kept in an alkali metal hydroxide aqueous solution, such as NaOH,

Katsumi Katakura; Shin-ichi Nishimura; Zempachi Ogumi

2005-01-01

345

THEORETICAL TECHNIQUE FOR DETERMINING THE CUMULATIVE IMPACT OF IRON AND MANGANESE OXIDATION IN STREAMS RECEIVING COAL-MINE DISCHARGE.  

USGS Publications Warehouse

Two U. S. Geological Survey computer programs are modified and linked to predict the cumulative impact of iron and manganese oxidation in coal-mine discharge on the dissolved-chemical quality of a receiving stream. The coupled programs calculate the changes in dissolved-iron, dissolved-manganese, and dissolved-oxygen concentrations, and the pH of surface water downstream from the discharge. The cumulative impact of representative discharges from several coal mines on stream quality in a small watershed in southwestern Indiana was simulated to determine the effectiveness and sensitivity of the coupled programs.

Bobay, Keith, E.; Banaszak, Konrad, J.

1985-01-01

346

Degradation of ciprofloxacin by cryptomelane-type manganese(III/IV) oxides.  

PubMed

The objective of this study is to investigate and understand the oxidizing properties of a manganese oxide, specifically synthetic cryptomelane (KMn(8)O(16)) and its derivatives, in aqueous solution. Ciprofloxacin (CIP), a commonly used fluoroquinolone antibiotic, was used as the probe. Synthetic cryptomelane, known as octahedral molecular sieves (OMS-2), was synthesized, and its derivatives were prepared by adding transition metal oxides, V(2)O(5) or MoO(3), as dopants during synthesis. The solids were characterized by x-ray powder diffraction (XRD), SEM-energy-dispersive spectrometry (SEM-EDX), x-ray photoelectron spectroscopy (XPS), Fourier transform infrared spectra (FTIR), Raman spectra, and N(2)-Brunauer-Emmett-Teller method. Degradation of CIP by different doped OMS-2 was carried out. Process conditions were optimized using response surface methodology (RSM). XRD patterns indicated the crystal phase of regular and doped OMS-2 as the cryptomelane type. Presence of the dopants in doped cryptomelane was confirmed by SEM-EDX and XPS. FTIR and Raman results suggested that the dopants were substituted into the framework in place of manganese. SEM images, XRD analysis, and surface area analysis of doped OMS-2 indicated decreased particle size, decreased crystallinity, and increased surface area compared to regular OMS-2. Higher oxidizing reactivity of doped OMS-2 was also observed with increased CIP removal rates from aqueous solution. The enhancement of reactivity may be due to the increase of surface areas. Nine percent Mo/OMS-2, the most effective oxidant of all synthesized derivatives, was selected for optimization study. Favorable treatment conditions were obtained using RSM at pH 3 with molar ratio [9 % Mo/OMS-2]/[CIP] ? 50. Under such conditions, more than 90 % CIP can be removed in 30 min. The degradation kinetics was modeled by a modified first order rate with introduction of a retardation factor-? (R (2) > 0.98). Analysis of degradation products indicated that oxidation takes place mainly on the piperazine ring of CIP. PMID:22723249

Xiao, Xiao; Sun, Sheng-Peng; McBride, Murray B; Lemley, Ann T

2012-06-22

347

SPECTROFLUORIMETRIC DETERMINATION OF MANGANESE AT THE NANOGRAM LEVEL BY CATALYTIC OXIDATION OF 2HYDROXY1NAPHTHALDEHYDE SALICYLOYLHYDRAZONE BY HYDROGEN PEROXIDE  

Microsoft Academic Search

A new fluorescent reagent, 2-hydroxy-1-naphthaldehyde salicyloylhydrazone (HNSH), was synthesized and its ionization constants were established spectrophotometrically. The fluorescent reaction of this reagent with hydrogen peroxide, catalysed by Mn(II), was studied. Based on this oxidation reaction, a spectrofluorimetric method was developed for the determination of manganese in a water-ethanol (5.5+4.5, v\\/v) medium at pH 10.90. Under these conditions, the oxidation reaction

Bo Tang; Fang Han

2001-01-01

348

Reaction of Formic Acid over Amorphous Manganese Oxide Catalytic Systems: An In Situ Study  

SciTech Connect

The interaction of formic acid with amorphous manganese oxide (AMO) is investigated using in situ photoelectron and infrared spectroscopy techniques. Soft X-ray photoelectron spectroscopy (sXPS) and in situ FTIR illustrate two possible modes of formate bound species at the AMO surface. Two peaks in the IR region from 1340-1390 cm{sup -1} are indicative of formate species bound to the surface in a bidentate configuration. However, a 224 cm{sup -1} band gap between v{sub s}OCO and v{sub as}OCO suggests formate is bound in a bridging configuration. Temperature-programmed desorption studies confirm the formate bound species desorbs as carbon dioxide from the surface at multiple binding sites. At temperatures above 700 K, the presence of K{sup +} {hor_ellipsis} OC complex suggests the bound species interacts at vacant sites related to framework oxygen and cation mobility.

J Durand; S Senanayake; S Suib; D Mullins

2011-12-31

349

A 4 V lithium manganese oxide cathode for rocking-chair lithium-ion cells  

SciTech Connect

Composite cathodes for lithium-ion rocking-chair cells have been fabricated based on LiMn[sub 2]O[sub 4] which was synthesized by a new solution route that may be carried out in air. These cathodes have been cycled in three-electrode cells at discharge and charging current densities of 1 and 0.5 mA cm[sup [minus]2], respectively (corresponding to a discharge rate of C/2), between limits of 4.4 and 3.3 V. The specific discharge capacity obtained initially is 110 mAhg[sup [minus]1] of active material decreasing by only 25 mAhg[sup [minus]1] to yield a capacity of 85 mAhg[sup [minus]1] at 300 cycles. This performed is very promising in the context of developing rechargeable lithium-ion batteries using lithium manganese oxide-based positive electrodes.

Huang, Haitao; Bruce, P.G. (Univ. of St. Andrews, Fife (United Kingdom). School of Chemistry)

1994-09-01

350

Partially substituted lithium manganese oxides as 3V cathode materials for secondary lithium batteries  

Microsoft Academic Search

Low temperature synthesis and electrochemical properties of partially substituted lithium manganese oxides are reported. We\\u000a demonstrate various metallic cations (Cu2+, Ni2+, Fe3+, Co3+) can be incorporated in the 3V layered cathodic material Li0.45MnO2.1. New compounds Li0.45Mn0.88Fe0.12O2.1, Li0.45Mn0.84Ni0.16O2.05, Li0.45Mn0.79Cu0.21O2.3, Li0.45Mn0.85Co0.15O2.3 are prepared. These 3V cathode materials are characterized by the same shape of discharge-charge profiles but different\\u000a values of the specific

S. Franger; S. Bach; J. P. Pereira-Ramos; N. Baffier

2006-01-01

351

Lithiummanganesenickel-oxide electrodes with integrated layeredspinel structures for lithium batteries  

Microsoft Academic Search

A series of lithiummanganesenickel-oxide compositions that can be represented in three-component notation, xLi[Mn1.5Ni0.5]O4(1?x){Li2MnO3Li(Mn0.5Ni0.5)O2}, in which a spinel component, Li[Mn1.5Ni0.5]O4, and two layered components, Li2MnO3 and Li(Mn0.5Ni0.5)O2, are structurally integrated in a highly complex manner, have been evaluated as electrodes in lithium cells for x=1, 0.75, 0.50, 0.25 and 0. In this series of compounds, which is defined by the Li[Mn1.5Ni0.5]O4{Li2MnO3Li(Mn0.5Ni0.5)O2}

S.-H. Park; S.-H. Kang; C. S. Johnson; K. Amine; M. M. Thackeray

2007-01-01

352

Manganese oxide nanoparticle-assisted laser desorption/ionization mass spectrometry for medical applications  

NASA Astrophysics Data System (ADS)

We prepared and characterized manganese oxide magnetic nanoparticles (d =5.6 nm) and developed nanoparticle-assited laser desorption/ionization (nano-PALDI) mass spectrometry. The nanoparticles had MnO2 and Mn2O3 cores conjugated with hydroxyl and amino groups, and showed paramagnetism at room temperature. The nanoparticles worked as an ionization assisting reagent in mass spectroscopy. The mass spectra showed no background in the low m/z. The nanoparticles could ionize samples of peptide, drug and proteins (approx. 5000 Da) without using matrix, i.e., 2,5-dihydroxybenzoic acid (DHB), 4-hydroxy-?-cinnamic acid (CHCA) and liquid matrix, as conventional ionization assisting reagents. Post source decay spectra by nano-PALDI mass spectrometry will yield information of the chemical structure of analytes.

Taira, Shu; Kitajima, Kenji; Katayanagi, Hikaru; Ichiishi, Eiichiro; Ichiyanagi, Yuko

2009-06-01

353

Recovery of manganese oxides from spent alkaline and zinc-carbon batteries. An application as catalysts for VOCs elimination.  

PubMed

Manganese, in the form of oxide, was recovered from spent alkaline and zinc-carbon batteries employing a biohydrometallurgy process, using a pilot plant consisting in: an air-lift bioreactor (containing an acid-reducing medium produced by an Acidithiobacillus thiooxidans bacteria immobilized on elemental sulfur); a leaching reactor (were battery powder is mixed with the acid-reducing medium) and a recovery reactor. Two different manganese oxides were recovered from the leachate liquor: one of them by electrolysis (EMO) and the other by a chemical precipitation with KMnO4 solution (CMO). The non-leached solid residue was also studied (RMO). The solids were compared with a MnOx synthesized in our laboratory. The characterization by XRD, FTIR and XPS reveal the presence of Mn2O3 in the EMO and the CMO samples, together with some Mn(4+) cations. In the solid not extracted by acidic leaching (RMO) the main phase detected was Mn3O4. The catalytic performance of the oxides was studied in the complete oxidation of ethanol and heptane. Complete conversion of ethanol occurs at 200C, while heptane requires more than 400C. The CMO has the highest oxide selectivity to CO2. The results show that manganese oxides obtained using spent alkaline and zinc-carbon batteries as raw materials, have an interesting performance as catalysts for elimination of VOCs. PMID:23562448

Gallegos, Mara V; Falco, Lorena R; Peluso, Miguel A; Sambeth, Jorge E; Thomas, Horacio J

2013-04-04

354

Theory of chemical bonds in metalloenzymes - Manganese oxides clusters in the oxygen evolution center -  

NASA Astrophysics Data System (ADS)

In early 1980 we have initiated broken-symmetry (BS) MO theoretical calculations of transition-metal oxo species M = O (M = Ti,V,Cr,Mn,Fe,Ni,Cu) to elucidate the nature of d?-p? and d?-p? bonds. It has been concluded that high-valent M = O species such as [Mn(IV) = O]2+ and [Fe(IV) = O]2+ exhibit electrophilic property in a sharp contrast with nucleophilic character of low-valent M = O bonds: [M(II)O2-]0, and closed-shell d?-p? bonds of high-valent M = O species often suffer the triplet-instability, giving rise to open-shell (BS) configurations with significant metal-diradical (MDR) character: M-O: note that these bonds are therefore regarded as typical examples of strongly correlated electron systems. Because of the MDR character, 1,4-metal diradical mechanism was indeed preferable to four-centered mechanism in the case of addition reaction of naked Mn(IV) = O to ethylene. Recently the manganese-oxo species have been receiving renewed interest in relation to catalytic cycle of oxygen evolution from water molecules in the photosynthesis II (PSII) system. Accumulated experimental results indicate that this process is catalyzed with four manganese oxide clusters coordinated with calcium ion (CaMn4O4). Past decade we have performed BS MO theoretical investigations of manganese oxide clusters related to CaMn4O4. These calculations have elucidated that high-valent Mn(X) = O (X = IV,V) bonds exhibit intermediate MDR character (y=40-60%) in the case of total low-spin (LS) configuration but the MDR character decreases with coordination of Ca2+ and water molecules. While the MDR character of the Mn-oxo bonds becomes very high at the high-spin (HS) configuration. Our computational results enabled us to propose two possible mechanisms on the theoretical ground: (A) electrophilic (EP) mechanism and (B) radical coupling (RC) mechanism. The theoretical results indicate that the EP mechanism is preferable for the low-spin (LS) state in polar media like in the protein environments (native OEC), whereas the RC mechanism is feasible at the state without such environmental stabilization: local singlet and local triplet diradical mechanisms are proposed for the OO coupling process. Possibilities of EP and RC mechanisms are examined in comparison with a lot of experimental results accumulated and theoretical results with several groups.

Yamaguchi, K.; Shoji, M.; Saito, T.; Isobe, H.; Yamada, S.; Nishihara, S.; Kawakami, T.; Kitagawa, Y.; Yamanaka, S.; Okumura, M.

2012-12-01

355

Treatment of dye wastewater with permanganate oxidation and in situ formed manganese dioxides adsorption: Cation blue as model pollutant  

Microsoft Academic Search

This study investigated the process of potassium permanganate (KMnO4) oxidation and in situ formed hydrous manganese dioxides (?MnO2) (i.e., KMnO4 oxidation and ?MnO2 adsorption) for the treatment of dye wastewater. The effectiveness of decolorization, removing dissolved organic carbon (DOC), and increasing biodegradable oxygen demand (BOD) were compared among these processes of KMnO4 oxidation, ?MnO2 adsorption, and KMnO4 oxidation and ?MnO2

Ruiping Liu; Huijuan Liu; Xu Zhao; Jiuhui Qu; Ran Zhang

2010-01-01

356

Electrochemical quartz crystal microbalance investigation of surface fouling due to phenol oxidation  

Microsoft Academic Search

An electrochemical quartz crystal microbalance is employed for investigating the formation of inhibitory polyphenol layers on the surface of gold electrodes. The frequencytime profiles are indicative of the formation of a thin insulating polymeric layer, that meets the rigid film requirement, and are in good agreement with the voltammetric response. Once access to the monomer is blocked, no further frequency

Joseph Wang; Mian Jiang; Fang Lu

1998-01-01

357

Quartz crystal microbalance coated with solgel-derived indiumtin oxide thin films as gas sensor for NO detection  

Microsoft Academic Search

This paper presents the possibilities and properties of indiumtin oxide (ITO)-covered quartz crystal microbalances (QCM) as a NOx toxic gas sensors. The starting solgel solution was prepared by mixing indium chloride dissolved in acetylacetone and tin chloride dissolved in ethanol (020% by weight). The ITO thin films were deposited on the gold electrodes of quartz crystals by spin-coating and annealing

J Zhang; J Hu; Z. Q Zhu; H Gong; S. J OShea

2004-01-01

358

Effects of oxidative stress on apoptosis in manganese-induced testicular toxicity in cocks.  

PubMed

Manganese (Mn) is a trace element known to be essential for maintaining the proper function and regulation of many biochemical and cellular reactions. However, little is known about the reproductive toxicity of Mn in birds. To investigate the toxicity of Mn on male reproduction in birds, 50-day-old cocks were fed either a commercial diet or a Mn-supplemented diet containing 600, 900, and 1800mg/kg MnCl2. After being treated with Mn for 30, 60, and 90d, the following were determined: Mn content; histological and ultrastructural changes in the testes, apoptosis; the malondialdehyde (MDA) level; the activities of superoxide dismutase (SOD); the inhibition ability of hydroxyl radicals (OH); the levels of nitric oxide (NO), nitric oxide synthase (NOS), and protein carbonyl in the testes; the DNA-protein crosslinks (DPC); and the activity of the ATP enzyme. Exposure to Mn significantly lowered the activity of SOD and glutathione peroxidase (GPx) and the inhibition ability of OH. Mn exposure also increased the levels of MDA, NO, NOS, DPC, and protein carbonyl; the number of apoptotic cells; and the Mn content and caused obvious histopathological changes in the testes. These findings suggested that Mn exposure resulted in the oxidative damage of cock testicular tissue by altering radical formation, ATP enzyme systems, apoptosis, and DNA damage, which are possible underlying reproductive toxicity mechanisms induced by Mn exposure. PMID:23907021

Liu, Xiao-Fei; Zhang, Li-Ming; Guan, Hua-Nan; Zhang, Zi-Wei; Xu, Shi-Wen

2013-07-29

359

Manganese-induced effects on cerebral trace element and nitric oxide of Hyline cocks.  

PubMed

Exposure to Manganese (Mn) is a common phenomenon due to its environmental pervasiveness. To investigate the Mn-induced toxicity on cerebral trace element levels and crucial nitric oxide parameters on brain of birds, 50-day-old male Hyline cocks were fed either a commercial diet or a Mn-supplemented diet containing 600, 900, 1,800 mg kg(-1). After being treated with Mn for 30, 60, and 90 days, the following were determined: the changes in contents of copper (Cu), iron (Fe), zinc (Zn), calcium (Ca), selenium (Se) in brain; inducible nitric oxide synthase-nitric oxide (iNOS-NO) system activity in brain; and histopathology and ultrastructure changes of cerebral cortex. The results showed that Mn was accumulated in brain and the content of Cu and Fe increased. However, the levels of Zn and Se decreased and the Ca content presented no obvious regularity. Exposure to Mn significantly elevated the content of NO and the expression of iNOS mRNA. Activity of total NO synthase (T NOS) and iNOS appeared with an increased tendency. These findings suggested that Mn exposure resulted in the imbalance of cerebral trace elements and influenced iNOS in the molecular level, which are possible underlying nervous system injury mechanisms induced by Mn exposure. PMID:23813426

Liu, Xiaofei; Zuo, Nan; Guan, Huanan; Han, Chunran; Xu, Shi Wen

2013-06-29

360

Metals, oxidative stress and neurodegeneration: a focus on iron, manganese and mercury.  

PubMed

Essential metals are crucial for the maintenance of cell homeostasis. Among the 23 elements that have known physiological functions in humans, 12 are metals, including iron (Fe) and manganese (Mn). Nevertheless, excessive exposure to these metals may lead to pathological conditions, including neurodegeneration. Similarly, exposure to metals that do not have known biological functions, such as mercury (Hg), also present great health concerns. This review focuses on the neurodegenerative mechanisms and effects of Fe, Mn and Hg. Oxidative stress (OS), particularly in mitochondria, is a common feature of Fe, Mn and Hg toxicity. However, the primary molecular targets triggering OS are distinct. Free cationic iron is a potent pro-oxidant and can initiate a set of reactions that form extremely reactive products, such as OH. Mn can oxidize dopamine (DA), generating reactive species and also affect mitochondrial function, leading to accumulation of metabolites and culminating with OS. Cationic Hg forms have strong affinity for nucleophiles, such as -SH and -SeH. Therefore, they target critical thiol- and selenol-molecules with antioxidant properties. Finally, we address the main sources of exposure to these metals, their transport mechanisms into the brain, and therapeutic modalities to mitigate their neurotoxic effects. PMID:23266600

Farina, Marcelo; Avila, Daiana Silva; da Rocha, Joo Batista Teixeira; Aschner, Michael

2012-12-21

361

Mitochondria protection of baicalein against oxidative damage via induction of manganese superoxide dismutase.  

PubMed

This study investigated the cytoprotective effect of baicalein (5,6,7-trihydroxyflavone) against oxidative stress-induced mitochondrial dysfunction. Electron spin resonance (ESR) spectrometry revealed that baicalein showed significant scavenging effects on superoxide radicals and hydroxyl radicals. When H(2)O(2) treatment induces an increase in mitochondrial reactive oxygen species (ROS), baicalein treatment decreased high level of ROS. Baicalein significantly reduced alteration of Bcl-2 family proteins, the release of cytochrome c from mitochondria into the cytosol via inhibition of mitogen-activated protein kinase kinase-4 (MKK4/SEK1) and c-Jun NH(2)-terminal kinase (JNK) cascades induced by H(2)O(2) treatment. Manganese superoxide dismutase (MnSOD) is an important antioxidant enzyme in mitochondria against oxidative stress. Baicalein restored both MnSOD protein expression and activity, which were abolished by H(2)O(2) treatment. The transcription factor NF-E2-related factor 2 (Nrf2) is a critical regulator of MnSOD, achieved by binding to the antioxidant response element (ARE). Baicalein restored nuclear Nrf2 protein expression and its ARE binding activity, which were abolished by H(2)O(2) treatment. These studies demonstrate that baicalein attenuates mitochondrial oxidative stress by activating Nrf2-mediated MnSOD induction. PMID:21787690

Lee, In Kyung; Kang, Kyoung Ah; Zhang, Rui; Kim, Bum Joon; Kang, Sam Sik; Hyun, Jin Won

2010-11-09

362

Lithium niji denchiyo seikyoku zairyo no ko energy. Vanadium oyobi mangan sankabutsu no shoki tokusei. (Evaluation of cathode materials for high energy lithium secondary batteries. Electrochemical behavior of vanadium oxides and a manganese oxide).  

National Technical Information Service (NTIS)

Batteries of higher energy density are desired to realize a load conditioner of longer life and more compact geometry. Experimental researches were carried out by using test batteries using vanadium oxides and a manganese oxide which are expected to theor...

N. Terada K. Takei T. Ikeya T. Iwahori

1990-01-01

363

Chemical syntheses of manganese and tantalum oxide octahedral molecular sieves and their structural characterization by powder x-ray diffraction  

NASA Astrophysics Data System (ADS)

This research consists of soft chemical synthesis and structural investigations of manganese and tantalum oxide octahedral molecular sieves. These include the use of sol-gel, hydrothermal and reflux methods for syntheses and the employment of various techniques for characterization, especially the Rietveld analysis of powder X-ray diffraction data for structural refinements. The manganese oxide cryptomelane (K-OMS-2) with a tunnel structure and birnessite layered materials (OL-1) were prepared by the sol gel method. The synthesis consists of reacting MnO4- solutions with fumaric acid or glucose to form a gel, and heating the xerogels at a temperature effective to produce the final manganese oxide materials. These sol-gel methods give many advantages, such as high thermal stabilities of products, over other preparation routes. The synthetic parameters have been optimized to prepare pure K-OMS-2 and OL-1. The crystal structure of K-OMS-2 has been refined by the Rietveld method from in-house powder X-ray diffraction data. The potassium tantalate defect pyrochlores were prepared by hydrothermal methods at a temperature of 200C. The materials were crystallized from tantalum pentoxide in a potassium hydroxide solution, with a uniform crystal size of about 1 mum. They were ion-exchanged with H+ at low temperatures in a nitric acid solution. A BET surface area of 15 m 2/g was obtained. The structure of this defect pyrochlore and its acid exchanged form were determined by Rietveld refinement from powder X-ray diffraction data. The reflux method was also employed to search for new manganese oxide microporous materials. A ramsdellite material with a 1 x 2 tunnel structure and high surface area of 70 m2/g was prepared. Catalytic oxidations of hexane and cyclohexane with tert-butyl hydroperoxide have shown good activities with this catalyst. This investigation suggests that shape selectivity plays a role in the high catalytic activities of the oxidations of these saturated hydrocarbons.

Duan, Niangao

364

Manganese scavenging and oxidation at hydrothermal vents and in vent plumes  

NASA Astrophysics Data System (ADS)

Hydrothermal vents provide a major source of dissolved Mn(II) to the oceans, where concentrations range from 5 mM within the 350C hot smokers to just above ambient seawater concentration in far field vent plumes. The Mn(II)-rich environments within warm vents and vent plumes provide a suitable habitat for Mn(II) oxidizing bacteria. In order to compare rates of scavenging and oxidation of Mn(II) proximally within vent fields (<30 m from venting water and temperatures <16C) and distally within vent plumes, and to determine the relative contribution of microbes, incubation experiments using 54 Mn as a radiotracer were conducted in situ and on collected water samples from three hydrothermal vent locations: the Guaymas basin (GB), the Galapagos spreading center (GA), and the Endeavor Ridge of the Juan de Fuca spreading center (JDF). Both the adsorbed and oxidized fractions of the total 54 Mn scavenged were determined and found to often be significant (as high as 65 and 74%, respectively). Manganese scavenging rates were generally higher in in situ incubations than in incubations conducted on board ship. Inhibition of 54 Mn scavenging by sodium azide provided evidence for microbially mediated Mn(II) uptake and oxidation in waters both proximal (GA and GB) and distal to the vents (GA and JDF), even at distances as great as 17 km from the ridge axis at JDF. The highest manganese scavenging rates were observed within the vent fields (up to 2.5 nM/day). The residence times of dissolved Mn(II) were shorter in the GB and GA vent fields (26 and 28 days) than in the JDF vent field (1.4 years). This difference may be due to different mechanisms of Mn(II) precipitation in operation. At the GA vent field Mn(II) precipitation was often strongly inhibited by sodium azide and therefore apparently due to microbial activity. In contrast, Mn(II) scavenging within the JDF vent field was not significantly affected by sodium azide. Because 54 Mn scavenging in the JDF vent field was dependent on the presence of oxygen and a much larger fraction of the total 54 Mn scavenged was adsorbed than oxidized, manganese scavenging appears to occur primarily by an abiological mechanism, perhaps coprecipitation with iron oxyhydroxides. In comparison to the vent fields, Mn(II) scavenging rates were lower within the vent plumes (<0.6 nM/ day for GA and <0.2 nM/day for JDF), whereas residence times were not significantly different (as low as 34 days for GA and 1.0 years for JDF). The short residence times (90 and 118 days) and high microbial activity measured in bottom waters beneath the vent plumes at GA and JDF probably resulted from enhanced scavenging by manganate-coated bacteria that settled out from the vent plume and accumulated near the bottom. Therefore, bacteria not only enhance the scavenging of Mn within vent waters, but also facilitate Mn deposition to the sediments.

Mandernack, Kevin W.; Tebo, Bradley M.

1993-08-01

365

The structure and catalytic activity of anatase and rutile titania supported manganese oxide catalysts for selective catalytic reduction of NO by NH3.  

PubMed

The structure and catalytic properties of anatase and rutile supported manganese oxide catalysts prepared by impregnation method have been studied by using X-ray diffraction (XRD), laser Raman spectroscopy (LRS), X-ray photoelectron spectroscopy (XPS), H(2) temperature-programmed reduction (H(2)-TPR) and BET surface area measurements combined with activity testing of selective catalytic reduction (SCR) of NO by NH(3). It has been shown that the manganese oxide loadings on the two TiO(2) supports exert great influences on the SCR activity. For the rutile supported manganese oxide catalysts, increasing manganese oxide loading leads to the increase of reducibility of dispersed manganese oxide species and the rate constant k, which reaches a maximum around 9.6 10(-6) mol g(Mn)(-1) s(-1) at 0.5 mmol Mn per 100 m(2) TiO(2). When the manganese oxide loading is beyond this value, the existence of amorphous MnO(x) multiple layers will certainly reduce the ratio of manganese oxide species exposed on the surface and the reducibility of dispersed manganese oxide species, resulting in the rapid decrease of rate constant k. The LRS and XPS results have revealed that for the anatase supported manganese oxide catalysts manganese oxide species exist in Mn(+4) as a major species with Mn(+3) species and partially undecomposed Mn-nitrate as the minor species. Under the SCR reaction conditions, Mn(+3) species on anatase are oxidized to Mn(+4) species, inserting in the surface of anatase and promoting the anatase-to-rutile transformation in the surface layers of the anatase support. Since these Mn(4+) cations are actually dispersed on the support with a rutile shell-anatase core structure and its concentration is very near to that of MnO(x)/TiO(2) (R) catalyst, the relation between the rate constant k and the MnO(x) loading on the anatase support is similar to that on the rutile support, and that the rate constant k values for anatase and rutile supported manganese oxide catalysts are very close at the same MnO(x) loading. PMID:21258687

Zhuang, Ke; Qiu, Jing; Tang, Fushun; Xu, Bolian; Fan, Yining

2011-01-24

366

Curcumin protects against cytotoxic and inflammatory effects of quartz particles but causes oxidative DNA damage in a rat lung epithelial cell line  

SciTech Connect

Chronic inhalation of high concentrations of respirable quartz particles has been implicated in various lung diseases including lung fibrosis and cancer. Generation of reactive oxygen species (ROS) and oxidative stress is considered a major mechanism of quartz toxicity. Curcumin, a yellow pigment from Curcuma longa, has been considered as nutraceutical because of its strong anti-inflammatory, antitumour and antioxidant properties. The aim of our present study was to investigate whether curcumin can protect lung epithelial cells from the cytotoxic, genotoxic and inflammatory effects associated with quartz (DQ12) exposure. Electron paramagnetic resonance (EPR) measurements using the spin-trap DMPO demonstrated that curcumin reduces hydrogen peroxide-dependent hydroxyl-radical formation by quartz. Curcumin was also found to reduce quartz-induced cytotoxicity and cyclooxygenase 2 (COX-2) mRNA expression in RLE-6TN rat lung epithelial cells (RLE). Curcumin also inhibited the release of macrophage inflammatory protein-2 (MIP-2) from RLE cells as observed upon treatment with interleukin-1 beta (IL-1{beta}) and tumour necrosis factor-alpha (TNF{alpha}). However, curcumin failed to protect the RLE cells from oxidative DNA damage induced by quartz, as shown by formamidopyrimidine glycosylase (FPG)-modified comet assay and by immunocytochemistry for 8-hydroxydeoxyguanosine. In contrast, curcumin was found to be a strong inducer of oxidative DNA damage itself at non-cytotoxic and anti-inflammatory concentrations. In line with this, curcumin also enhanced the mRNA expression of the oxidative stress response gene heme oxygenase-1 (ho-1). Curcumin also caused oxidative DNA damage in NR8383 rat alveolar macrophages and A549 human lung epithelial cells. Taken together, these observations indicate that one should be cautious in considering the potential use of curcumin in the prevention or treatment of lung diseases associated with quartz exposure.

Li Hui; Berlo, Damien van; Shi Tingming [Institut fuer umweltmedizinische Forschung (IUF) at the Heinrich-Heine-University Duesseldorf gGmbH, Auf'm Hennekamp 50, 40225 Duesseldorf (Germany); Speit, Guenter [Institute of Human Genetics, University of Ulm (Germany); Knaapen, Ad M. [Department of Health Risk Analysis and Toxicology, Nutrition and Toxicology Research Institute Maastricht (NUTRIM), University of Maastricht (Netherlands); Borm, Paul J.A. [Institut fuer umweltmedizinische Forschung (IUF) at the Heinrich-Heine-University Duesseldorf gGmbH, Auf'm Hennekamp 50, 40225 Duesseldorf (Germany); Centre for Expertise in Life Sciences, Zuyd University, Heerlen (Netherlands); Albrecht, Catrin [Institut fuer umweltmedizinische Forschung (IUF) at the Heinrich-Heine-University Duesseldorf gGmbH, Auf'm Hennekamp 50, 40225 Duesseldorf (Germany); Schins, Roel P.F. [Institut fuer umweltmedizinische Forschung (IUF) at the Heinrich-Heine-University Duesseldorf gGmbH, Auf'm Hennekamp 50, 40225 Duesseldorf (Germany)], E-mail: roel.schins@uni-duesseldorf.de

2008-02-15

367

Oxidative stress and mitochondrial-mediated apoptosis in dopaminergic cells exposed to methylcyclopentadienyl manganese tricarbonyl.  

PubMed

Methylcyclopentadienyl manganese tricarbonyl (MMT), an organic manganese-containing gasoline additive, was investigated to determine whether MMT potentially causes dopaminergic neurotoxic effects. MMT is acutely cytotoxic and dopamine-producing cells (PC-12) seemed to be more susceptible to cytotoxic effects than nondopaminergic cells (striatal gamma-aminobutyric acidergic and cerebellar granule cells). MMT also potently depleted dopamine apparently by cytoplasmic vesicular release to the cytosol, a neurochemical change resembling other dopaminergic neurotoxicants. Generation of reactive oxygen species (ROS), an early effect in toxicant-induced apoptosis, occurred within 15 min of MMT exposure. MMT caused a loss of mitochondrial transmembrane potential (DeltaPsim), a likely source of ROS generation. The ROS signal further activated caspase-3, an important effector caspase, which could be inhibited by antioxidants (Trolox or N-acetyl cysteine). Predepletion of dopamine by using alpha-methyl-p-tyrosine (tyrosine hydroxylase inhibitor) treatment partially prevented caspase-3 activation, denoting a significant dopamine and/or dopamine by-product contribution to initiation of apoptosis. Genomic DNA fragmentation, a terminal hallmark of apoptosis, was induced concentration dependently by MMT but completely prevented by pretreatment with Trolox, deprenyl (monoamine oxidase-B inhibitor), and alpha-methyl-p-tyrosine. A final set of critical experiments was performed to verify the pharmacological studies using a stable Bcl-2-overexpressing PC-12 cell line. Bcl-2-overexpressing cells were significantly refractory to MMT-induced ROS generation, caspase-3 activation, and loss of DeltaPsim and were completely resistant to MMT-induced DNA fragmentation. Taken together, the results presented herein demonstrate that oxidative stress plays an important role in mitochondrial-mediated apoptotic cell death in cultured dopamine-producing cells after exposure to MMT. PMID:12065696

Kitazawa, Masashi; Wagner, Jarrad R; Kirby, Michael L; Anantharam, Vellareddy; Kanthasamy, Anumantha G

2002-07-01

368

The oxidation of acid azo dye AY 36 by a manganese oxide containing mine waste.  

PubMed

The oxidative breakdown of acid azo dye acid yellow 36 (AY 36) by a Mn oxide containing mine tailings is demonstrated. The oxidation reaction is pH dependent with the rate of decolorization increasing with decreasing pH. The oxidation reaction mechanism is initiated at the amino moiety and proceeds via successive, one electron transfers from the dye to the Mn oxide minerals. The reaction pathway involves the formation of a number of colorless intermediate products, some of which hydrolyze in a Mn oxide-independent step. Decolorization of the dye is rapid and is observed before the cleavage of the azo-bond, which is a slower process. The terminal oxidation products were observed to be p-benzoquinone and 3-hydroxybenzenesulfonate. The reaction order of the initial decolorization was determined to be pseudo fractional order with respect to pH and pseudo first order with respect to dye concentration and Mn tailings' surface area. PMID:23333488

Clarke, Catherine E; Kielar, Filip; Johnson, Karen L

2012-12-20

369

Weathering of the Rio Blanco quartz diorite, Luquillo Mountains, Puerto Rico: Coupling oxidation, dissolution, and fracturing  

Microsoft Academic Search

In the mountainous Rio Icacos watershed in northeastern Puerto Rico, quartz diorite bedrock weathers spheroidally, producing a 0.22m thick zone of partially weathered rock layers (?2.5cm thickness each) called rindlets, which form concentric layers around corestones. Spheroidal fracturing has been modeled to occur when a weathering reaction with a positive ?V of reaction builds up elastic strain energy. The rates

Heather L. Buss; Peter B. Sak; Samuel M. Webb; Susan L. Brantley

2008-01-01

370

The Relationship Between the Diagenetic Cycles of Reducible Iron and Manganese Oxides and Dissolved Organic Carbon (DOC)  

NASA Astrophysics Data System (ADS)

Field evidence suggests that the fate of sedimentary DOC is intimately linked to the diagenetic cycles of iron and manganese in marine sediments. Co-variations of their concentrations in sediment pore water [1], as well as the release of DOC upon the reductive dissolution of authigenic iron and manganese oxides [1] suggest that sorption (i.e., co-precipitation and/or adsorption) onto these oxides may play an important role on the diagenetic behavior of DOC. Whereas the diagenetic cycling of iron and manganese between oxic and suboxic sediments is well documented, DOC pore water gradients have most often been interpreted uniquely as indicative of a flux of DOC out of the sediments to the overlying bottom waters [2-5]. This interpretation stems from our inability to resolve a subsurface DOC sink from the vertical distribution of sedimentary particulate organic carbon (POC). This DOC sink, if it exists, would considerably alter our views of the mechanisms that regulate DOC fluxes across the sediment-water interface as well as their quantification. Sorption onto authigenic metal oxides may also lead to a molecular and isotopic fractionation of DOC. Furthermore, if DOC sorption to metal oxides is a reversible process, it may buffer pore water DOC concentrations and release to the overlying waters. Oxic surface sediments recovered from the St. Lawrence Estuary and the Saguenay Fjord were incubated under anaerobic conditions and extracted with a mild reducing agent to determine the amount and composition (molecular and isotopic) of the DOC associated with the authigenic iron and manganese oxides. Preliminary results from the study will be presented. References: [1] Deflandre et al. (2002) Geochim. Cosmochim. Acta, 66; 14, 2547-2558. [2] Alperin et. al., (1999) Geochim. Cosmochim. Acta, 63; 3-4, 427-448. [3] Burdige et al., (1999) Geochim. Cosmochim. Acta, 63; 10, 507-1515. [4] Holcombe et al., (2001) Limnol. Oceanogr., 46; 2, 298-308. [5] Papadimitriou et. al. (2002) Mar. Chem., 79, 37-47.

Barazzuol, L. N.; Mucci, A.; Glinas, Y.

2004-05-01

371

A designed single-step method for synthesis and structural study of organic-inorganic hybrid materials: well-ordered layered manganese oxide nanocomposites.  

PubMed

A fast and single-step method was successfully developed toward synthesizing well-ordered organic-inorganic hybrid layered manganese oxide (LMO) nanocomposites and Keggin/organic ions intercalated into layered manganese oxide at room temperature in 1 day. The ordering of layered structures is highly dependent on pH and drying conditions. The Keggin/organic intercalated LMO shows improved thermal stability of the layered structure over that of hybrid LMO. PMID:18847264

Chen, Chun-Hu; Crisostomo, Vincent Mark B; Li, Wei-Na; Xu, Linping; Suib, Steven L

2008-10-11

372

Effects of synthetic parameters on structure and electrochemical performance of spinel lithium manganese oxide by citric acid-assisted solgel method  

Microsoft Academic Search

The spinel lithium manganese oxide cathode materials were prepared by citric acid-assisted solgel method at 6231073K in air. The effects of pH value, raw material, synthesis temperature and time on structure and electrochemical performance of spinel lithium manganese oxide are investigated by X-ray diffraction (XRD), scanning electronic microscope (SEM) and cyclic voltammetry (CV). XRD data results strongly suggest that the

Tingfeng Yi; Changsong Dai; Kun Gao; Xinguo Hu

2006-01-01

373

Oxidative precipitation of arsenic(III) with manganese(II) and iron(II) in dilute acidic solution by ozone  

Microsoft Academic Search

Oxidative precipitation using ozone has been examined for removal of arsenic with manganese from dilute acidic sulfate solution under the following conditions: the initial concentrations of arsenic(III) and arsenic(V)=1100 mg\\/L, the initial mole ratio of Mn\\/As=10100, pH=0.45.0 and temperature=1580 C. The oxidationreduction potential (ORP) of the system was continuously measured to monitor the process of oxidation reactions. The O3O2 gas

T Nishimura; Y Umetsu

2001-01-01

374

Manganese Triazacyclononane Oxidation Catalysts Grafted under Reaction Conditions on Solid Co-Catalytic Supports  

SciTech Connect

Manganese complexes of 1,4,7-trimethyl-1,4,7-triazacyclononane (tmtacn) are highly active and selective alkene oxidation catalysts with aqueous H{sub 2}O{sub 2}. Here, carboxylic acid-functionalized SiO{sub 2} simultaneously immobilizes and activates these complexes under oxidation reaction conditions. H{sub 2}O{sub 2} and the functionalized support are both necessary to transform the inactive [(tmtacn)Mn{sup IV}({mu}-O)3Mn{sup IV}(tmtacn)]{sup 2+} into the active, dicarboxylate-bridged [(tmtacn)Mn{sup III}({mu}-O)({mu}-RCOO){sub 2}Mn{sup III}(tmtacn)]{sup 2+}. This transformation is assigned on the basis of comparison of diffuse reflectance UV-visible spectra to known soluble models, assignment of oxidation state by Mn K-edge X-ray absorption near-edge spectroscopy, the dependence of rates on the acid/Mn ratios, and comparison of the surface structures derived from density functional theory with extended X-ray absorption fine structure. Productivity in cis-cyclooctene oxidation to epoxide and cis-diol with 2-10 equiv of solid cocatalytic supports is superior to that obtained with analogous soluble valeric acid cocatalysts, which require 1000-fold excess to reach similar levels at comparable times. Cyclooctene oxidation rates are near first order in H{sub 2}O{sub 2} and near zero order in all other species, including H{sub 2}O. These observations are consistent with a mechanism of substrate oxidation following rate-limiting H{sub 2}O{sub 2} activation on the hydrated, supported complex. This general mechanism and the observed alkene oxidation activation energy of 38 {+-} 6 kJ/mol are comparable to H{sub 2}O{sub 2} activation by related soluble catalysts. Undesired decomposition of H{sub 2}O{sub 2} is not a limiting factor for these solid catalysts, and as such, productivity remains high up to 25 C and initial H{sub 2}O{sub 2} concentration of 0.5 M, increasing reactor throughput. These results show that immobilized carboxylic acids can be utilized and understood like traditional carboxylic acids to activate non-heme oxidation catalysts while enabling higher throughput and providing the separation and handling benefits of a solid catalyst.

Schoenfeldt, Nicholas J.; Ni, Zhenjuan; Korinda, Andrew W.; Meyer, Randall J.; Notestein, Justin M. (NWU); (UIC)

2012-01-23

375

Removal of phosphorus by a composite metal oxide adsorbent derived from manganese ore tailings.  

PubMed

The selective adsorption of phosphate (P) from wastewater is a promising method for controlling eutrophication in water bodies. In this study, an adsorbent of composite metal oxides (CMOMO) was synthesized from manganese ore tailings by the process of digestion-oxidation-coprecipitation. CMOMO was characterized using several methods, and its adsorption behaviors for phosphate were investigated. Based on the results from SEM and BET analysis, CMOMO exhibited a rough surface and a large surface area (307.21 m(2)/g). According to the results of EDAX, XRD and XPS, its main constituents were determined to be amorphous FeOOH, MnO(2) and AlOOH. The kinetic data were best fit using the Elovich model due to its complicate composites. The maximal adsorption capacity of P would increase with elevated temperatures. Additionally, it was found that the P removal efficiency decreased with an increase of pH (4-10) or a decrease of ion strength (1-0.01 M). The coexisting anions had little effects on phosphate removal, implying the specific adsorption of P by CMOMO. Furthermore, the desorption and reuse results indicated that this adsorbent could be regenerated using alkali solutions. PMID:22464586

Liu, Ting; Wu, Kun; Zeng, Lihua

2012-03-09

376

Studies of oxygen species in synthetic Todorokite-like manganese oxide octahedral molecular sieves  

SciTech Connect

Manganese oxide octahedral molecular sieves of 3 x 3 tunnel structure (OMS-1) doped with various cations possess high thermal stability and were studied by means of temperature-programmed desorption and reduction by H[sub 2] and CO. Different oxygen species can be discerned according to their peak positions in the temperature-programmed desorption and reduction and assigned to chemisorbed dioxygen, oxygen atoms bound to Mn[sup 2+], and those bound to Mn[sup 4+] ions in the framework. Differences in peak positions and availabilities of these species during TPD and TPR can be explained by creation of nascent Mn[sup 2+] ions during TPR. The effects of doping cations on the reactivity and availability of these oxygen species are demonstrated to be more pronounced in TPR in H[sub 2] or CO than in TPD. In some instances, the trends of changes in reactivity and availability of the oxygen species due to doping of Cu[sup 2+], Ni[sup 2+], Zn[sup 2+], and Mg[sup 2+] correlated with the changes in the heat of formation of oxides of these cations. Temperature-programmed reactions with methane show some reactivity of these doped OMS-1 materials. Pulse reactions with CO show higher reactivity of Cu-doped OM-1 than with butane. However, the recovery of Cu-doped OMS-1 by reoxidation with oxygen pulses seems rather incomplete at the same temperature. 27 refs., 9 figs.

Yin, Yuan-Gen; Xu, Wen-Qing; Shen, Yan-Fei; Suib, S.L. (Univ. of Connecticut, Storrs, CT (United States)); O'Young, C.L. (Texaco Research Center, New York, NY (United States))

1994-10-01

377

Manganese oxide/titania materials for removal of NOx and elemental mercury from flue gas  

SciTech Connect

A novel catalyst for low temperature selective catalytic reduction (SCR) using CO as reductant, MnOx supported on titania, has been shown to be effective for both elemental mercury capture and low temperature SCR. In low temperature (200{sup o}C) SCR trials using an industrially relevant space velocity (50 000 h{sup -1}) and oxygen concentration (2 vol %), nearly quantitative reduction of NOx was obtained using CO as the reductant. Fresh catalyst used as an adsorbent for elemental mercury from an inert atmosphere showed remarkable mercury capture capacity, as high as 17.4 mg/g at 200{sup o}C. The catalyst effectively captured elemental mercury after use in NOx reduction. Mercury capture efficiency was not affected by the presence of water vapor. Mercury capacity was reduced in the presence of SO{sub 2}. Manganese loading and bed temperature, which influence surface oxide composition, were found to be important factors for mercury capture. X-ray photoelectron spectroscopy (XPS) results reveal that the mercury is present in its oxidized form (HgO) in spent catalyst, indicating the participation of lattice oxygen of the catalyst in the reaction. These results suggest that a single-step process integrating low temperature SCR and mercury capture from flue gas might be feasible. 42 refs., 10 figs., 2 tabs.

Lei Ji; Pavani M. Sreekanth; Panagiotis G. Smirniotis; Stephen W. Thiel; Neville G. Pinto [University of Cincinnati, Cincinnati, OH (United States). Department of Chemical & Materials Engineering

2008-07-15

378

Growth of different phases of yttrium manganese oxide thin films by pulsed laser deposition  

SciTech Connect

Various phases of yttrium manganese oxide (YMO) thin films have been synthesized on different substrates from a single target of h-YMnO{sub 3}. It is observed that the phase stability and crystallinity of YMO thin films depend on the substrate used and oxygen partial pressure (OPP). (110) oriented and polycrystalline growth of h-YMnO{sub 3} are observed on the Al{sub 2}O{sub 3} (0001) and NGO (110) substrates respectively, when grown in OPP {approx_equal} 10{sup -6} Torr. While for similar OPP value, growth of mixed phases (h-YMnO{sub 3} and o-YMn{sub 2}O{sub 5}) is observed on Si (001) substrate. Oriented growth of O-YMn{sub 2}O{sub 5} phase film on Si (001) substrate is observed first time, when deposited at OPP value of 225 and 350 mTorr. +3 and mixed oxidation states (+3 and +4) of Mn were confirmed by x-ray photoelectron spectroscopy in pure YMnO{sub 3} phase and YMn{sub 2}O{sub 5} phase respectively.

Kumar, Manish; Choudhary, R. J.; Phase, D. M. [UGC-DAE Consortium for Scientific Research, Khandwa Road, Indore, 452001 (India)

2012-06-05

379

Designing High Capacity, Stable Lithium-Manganese Oxide Insertion Electrodes with First Principles Computations  

NASA Astrophysics Data System (ADS)

The viability of rechargeable lithium batteries in many applications hinges on finding electrode materials with high capacity, excellent chemical and phase stability, and low cost. LiCoO_2, the intercalation oxide currently used is too expensive and unsafe for large-scale batteries. Manganese oxides are a possible low cost alternative, but spinel LiMn_2O _4, the common form of the material, has too low a capacity and some stability problems. Recently, layered LiMnO _2, isostructural to LiCoO _2, has been synthesized. After a few battery cycles this material irreversibly transforms to a spinel structure, with loss of battery capacity. In this work we use Density Functional Theory to investigate why LiMnO2 transforms so rapidly to spinel but LiCoO 2 does not, even though both are known to be thermodynamically unstable towards this transformation. We find that the difference between the two compound is due to remarkably rapid diffusion of Mn ^3+. Diffusion of Mn^3+ occurs by disproportionation into Mn ^2+ an Mn ^4+ which gives the system a remarkable flexibility in its hybridization with the oxygen ions, even at the saddle point for diffusion. This knowledge has now been used to suggest compositional modifications of LiMnO 2 which slow down or even prevent the transformation to a spinel.

Reed, John; van der Ven, Anton; Ceder, Gerbrand

2001-03-01

380

Lithium extraction from orthorhombic lithium manganese oxide and the phase transformation to spinel  

SciTech Connect

Development of rechargeable lithium batteries is limited by a concern regarding their safety. Current efforts are focused on rocking-chair'' cells which avoid the use of metallic lithium electrodes and are therefore potentially far safer than conventional lithium cells. Carbon is the anode material of choice for rocking-chair'' cells as it gives good reversibility, high capacity and low average voltage versus lithium, resulting in high energy density cells. Carbon anodes must be coupled with lithium-rich or discharged cathodes. When the cell is first charged, lithium is transferred from the lithium-rich cathode to the carbon anode. However, not all the lithium can be recovered from the anode on the subsequent discharge; surplus cathode capacity is therefore required in the initial cathode to counteract this loss. Lithium transition-metal oxides are being developed as cathode materials for rocking-chair'' batteries. Lithium manganese oxides, which are cheap and non-toxic, are favored over the lithium-cobalt-oxide, LiCoO[sub 2], and lithium-nickel-oxide, LiNiO[sub 2].Here, orthorhombic LiMnO[sub 2] products, synthesized by the reaction of [gamma]-MnO[sub 2] and LiOH in argon at 600--620 C using carbon as a reducing agent, have been evaluated as electrode materials in lithium cells. Products that contained a minor proportion of a lithiated spinel phase showed greater electrochemical activity than pure LiMnO[sub 2]. On delithiation, LiMnO[sub 2] transforms irreversibly to a spinel-type structure. A mechanism for the orthorhombic Li[sub x]MnO[sub 2]-spinel phase transformation is proposed.

Gummow, R.J.; Liles, D.C.; Thackeray, M.M. (CSIR, Pretoria (South Africa). Div. of Materials Science and Technology)

1993-12-01

381

Synthesis of manganese oxide electrodes with interconnected nanowire structure as an anode material for rechargeable lithium ion batteries.  

PubMed

Manganese oxide electrodes composed of interconnected nanowires are electrochemically synthesized in manganous acetate solution at room temperature without any template and catalyst. Annealing temperature affects the electrode morphology, crystallization, and electrochemical performance. Scanning electron microscope (SEM) results show that nanowires are uniformly distributed and sizes are about 12-18 nm in diameter; the diameter decreases to about 8-12 nm after annealing at 300 degrees C. X-ray diffraction (XRD) and transmission electron microscope (TEM) images indicate that nanowires have poor crystalline characteristics. The higher the annealing temperature, the higher the crystalline degree is in manganese oxide. The synthesized anode material shows a much larger capacity than the traditional graphite materials for lithium storage. After annealing at 300 degrees C, the electrode's reversible capacity reaches 800 mAhg(-1), and the specific capacity retention remains nearly constant after 100 cycles. PMID:16375294

Wu, Mao-Sung; Chiang, Pin-Chi Julia; Lee, Jyh-Tsung; Lin, Jung-Cheng

2005-12-15

382

Effect of Li ion in transition metal sites on electrochemical behavior of layered lithium manganese oxides solid solutions  

Microsoft Academic Search

Two solid solutions of Li[Li1\\/5Ni1\\/10Co1\\/5Mn1\\/2]O2 and Li[Ni1\\/4Co1\\/2Mn1\\/4]O2 compositions were synthesized using a solgel method. The solid solutions with layered manganese oxides were both formed with typical hexagonal structure with maintaining the manganese oxidation state of 4+. The electrochemical characterization of the synthesized materials showed a monotonous discharge curve shape without structural transformation to spinel during chargedischarge processes. The Li[Li1\\/5Ni1\\/10Co1\\/5Mn1\\/2]O2 and

K. S Park; M. H Cho; S. J Jin; K. S Nahm; Y. S Hong

2004-01-01

383

Improvement in the production of extracellular lignin peroxidases by Phanerochaete chrysosporium: effect of solid manganese(IV)oxide  

Microsoft Academic Search

Addition of solid manganese(IV)oxide to cultures of Phanerochaete chrysosporium at the beginning of ligninolytic activity was shown to improve production, enzymatic activity, and stability of the ligninases produced. Darkening of mycelia incubated with shaking and N-limitation coincides with the onset of ligninolytic activity and is due to the deposition of amorphous MnO2. By the addition of MnO2, probably mimicking the

Hartmut W. Kern

1989-01-01

384

Development of a manganese dioxide solid-phase reactor for oxidation of toxins associated with paralytic shellfish poisoning  

Microsoft Academic Search

Using manganese dioxide as a solid-phase oxidant, a post-column HPLC reactor for paralytic shellfish poison toxins was constructed and evaluated. Operating parameters such as reaction temperature and pH, flow-rate, reactor column size, and MnO2 particle size were studied. Based on a 3:1 signal-to-noise ratio, the limits of detection for the non-hydroxylated toxins were in the sub-nanogram range, while the hydroxylated

James F. Lawrence; Barbara Wong

1996-01-01

385

Changes in the local structure and Li + ion dynamics in lithium manganese oxides prepared by mechanical milling  

Microsoft Academic Search

XRD, 7Li MAS NMR, and electrical resistivity measurements were carried out to probe the local structure and the Li+ ionic diffusion in lithium manganese oxide Li2MnO3 prepared by mechanical milling and solid state reaction. XRD profiles and NMR spectra remarkably changed as milling time increased, and it is suggested that a disordered frame structure consisting of MnO polyhedral blocks was

Koichi Nakamura; Hiroshi Hirano; Yoshitaka Michihiro; Toshihiro Moriga

2010-01-01

386

Low Temperature Synthesis of Nano-Sized Lithium Manganese Oxide Powder by the Sol-Gel Process Using PVA  

Microsoft Academic Search

Lithium manganese oxide (LiMn2O4) powder with spinel structure has been synthesized by a sol-gel method using an aqueous solution of metal nitrates containing polyvinyl alcohol (PVA). The role of PVA and the calcination conditions for the formation of LiMn2O4 have been studied. Homogeneity and reactivity of the precursor powder are enhanced with an increase in the amount of PVA in

Chung-Hsin Lu; Susanta Kumar Saha

2001-01-01

387

Capacity loss of lithium manganese oxide spinel in LiPF\\/ethylene carbonate-dimethyl carbonate electrolytes  

Microsoft Academic Search

The stability of lithium manganese oxide spinel in LiPF\\/EC:DMC (ethylene carbonate-dimethyl carbonate) based electrolytes has been investigated at different states of charge and at temperatures between 21 and 55 C. Reversible capacity loss due to reinsertion of lithium takes place at all states of charge and temperature. This reaction can proceed to the extent of inserting more than one Li

Haitao Huang; C. A. Vincent; P. G. Bruce

1999-01-01

388

Lithium manganese oxide as an effective buffer layer between organic and metal layers in organic light-emitting devices  

Microsoft Academic Search

Tris(8-hydroxyquinolinato)aluminum (Alq3)-based organic light-emitting devices using a thermally deposited lithium manganese oxide layer between aluminum (Al) cathode and Alq3 have been fabricated. The highest luminance efficiency obtained with a 1-nm-thick LiMnxOy layer is very similar to that of the device with 1-nm-thick LiF. However, the device with an 18 nm LiMnxOy layer obtained a longer operational stability although the luminance

Tswen-Hsin Liu

2006-01-01

389

Manganese associated nanoparticles agglomerate of iron(III) oxide: Synthesis, characterization and arsenic(III) sorption behavior with mechanism  

Microsoft Academic Search

Three samples of manganese associated hydrous iron(III) oxide (MNHFO), prepared by incinerating metal hydroxide precipitate at T (5)=90, 300 and 600C, showed increase of crystalline nature in XRD patterns with decreasing As(III) removal percentages. TEM images showed the increase of crystallinity from sample-1 (MNHFO-1) to sapmple-3 (MNHFO-3). Dimensions (nm) of particles estimated were 5.0, 7.0 and 97.5. Optimization of pH

Kaushik Gupta; Arjun Maity; Uday Chand Ghosh

2010-01-01

390

Intercalation of methylene blue into layered manganese oxide and application of the resulting material in a reagentless hydrogen peroxide biosensor  

Microsoft Academic Search

Methylene blue (MB) has been intercalated into layered manganese oxide (birnessite) by a delamination\\/reassembly process and the resulting MB-intercalated birnessite (MB-Bir) material characterized by X-ray powder diffraction (XRD), Fourier transform infrared (FTIR) spectroscopy, and electrochemical measurements. A novel reagentless hydrogen peroxide biosensor was fabricated by using the MB-Bir as an electron mediator. Cyclic voltammetry and amperometric measurements demonstrated that methylene

Xiushuang Yang; Xu Chen; Wensheng Yang; David G. Evans

2008-01-01

391

OXIDATION OF URONIC ACIDS BY MANGANESE(III) SULFATE IN ACID SOLUTION: A KINETIC AND MECHANISTIC STUDY  

Microsoft Academic Search

The kinetics and mechanism of oxidation of D-glucuronic acid and D-galacturonic acid by manganese(III) sulfate, in aqueous sulfuric acid solution at 30C, was followed spectrophotometrically at ?max=500 nm. A first-order dependence of the rate each on [Mn(III)] and [uronic acid] was observed. The rate is independent of the concentration of hydrogen ions and the reaction product, Mn(II). Effects of varying

K. S. Rangappa; N. Anitha; M. Ayesha Nikath; K. M. L. Rai; N. M. Made Gowda

2001-01-01

392

Electrical resistivity measurements on manganese oxides with layer and tunnel structures: Birnessites, todorokites, and cryptomelanes  

SciTech Connect

Direct-current measurements were used to determine the electrical resistivities of several manganese oxide materials having either layered or tunnel structures. Birnessite (Na-OL-1, OL=octahedral layer) consists of layers of edge- and corner-sharing Mn{sub 6} octahedral units with Na{sup +} in the interlayer regions. Todorokite and cryptomelane (Mg-OMS-1 and K-OMS-2, respectively, OMS = octahedral molecular sieve) are similarly built from MnO{sub 6} units, but in these systems the octahedral join to form 6.9 and 4.6 {Angstrom} tunnels occupied by Mg{sup 2+} and K{sup +}, respectively. Resistivities were also measured for OL-1, OMS-1, and OMS-2 materials in which (a) cation exchange was carried out at layer and tunnel sites or (b) isomorphous subsititution for Mn was performed by doping small amounts of foreign cations into the manganese oxide framework. Four probe measurements on pressed pellets reveal that OL-1 and OMS-1 materials have resistivities on the order of 10{sup 5}-10{sup 6} {Omega}cm at 298 K. OMS-2 materials have resistivities on the order of 10{sup 5}-10{sup 6} {Omega} cm at 298 K. Variable-temperature measurements establish a general pattern of increasing resistivity with decreasing temperature. However, between 153 and 293 K, OL-1 and OMS-1 materials do not obey a simple exponential variation of resistivity and temperature. By contrast, OMS-2 samples follow the Arrhenius relationship over a comparable temperature range. Activation energies for the conductivity OMS-2 materials were calculated to be in the range 0.5-0.6 eV. Solid-state voltammetry was used to determine the electrical resistance of OMS-1 and OMS-2 samples at higher temperatures from 298 to 673 K. A general exponential decrease in resistance with increasing temperature was observed for both classes of materials. Ac resistivity measurements show similar trends to dc resistivity data. 36 refs., 8 figs., 3 tabs.

De Guzman, R.N.; Awaluddin, A.; Shen, Y.F. [and others

1995-07-01

393

Protective effects of manganese(II) chloride on hyaluronan degradation by oxidative system ascorbate plus cupric chloride  

PubMed Central

The degradation of several high-molar-mass hyaluronan samples was investigated in the presence of ascorbic acid itself and further by an oxidative system composed of ascorbic acid plus transition metal ions, i.e. Fe(II) or Cu(II) ions. The latter oxidative system imitates conditions in a joint synovial fluid during early phase of acute joint inflammation and can be used as a model for monitoring oxidative degradation of hyaluronan under pathophysiological conditions. The system Cu(II) plus ascorbate (the Weissberger oxidative system) resulted in a more significant decrease of hyaluronan molar mass compared to the oxidative system Fe(II) plus ascorbate. Addition of manganese(II) chloride was found to decrease the rate of the oxidative damage of hyaluronan initiated by ascorbate itself and by the Weissberger system.

Valachova, Katarina; Kogan, Grigorij; Gemeiner, Peter; Soltes, Ladislav

2010-01-01

394

Protective effects of manganese(II) chloride on hyaluronan degradation by oxidative system ascorbate plus cupric chloride.  

PubMed

The degradation of several high-molar-mass hyaluronan samples was investigated in the presence of ascorbic acid itself and further by an oxidative system composed of ascorbic acid plus transition metal ions, i.e. Fe(II) or Cu(II) ions. The latter oxidative system imitates conditions in a joint synovial fluid during early phase of acute joint inflammation and can be used as a model for monitoring oxidative degradation of hyaluronan under pathophysiological conditions. The system Cu(II) plus ascorbate (the Weissberger oxidative system) resulted in a more significant decrease of hyaluronan molar mass compared to the oxidative system Fe(II) plus ascorbate. Addition of manganese(II) chloride was found to decrease the rate of the oxidative damage of hyaluronan initiated by ascorbate itself and by the Weissberger system. PMID:21217868

Valachov, Katarna; Kogan, Grigorij; Gemeiner, Peter; Solts, Ladislav

2010-03-29

395

Chemical oxidation of phenolic acids by soil iron and manganese oxides  

SciTech Connect

The oxidation of six phenolic acids by soil Fe and Mn oxides was demonstrated by changes in phenolic acid extractability from soil with time, by production of Fe(II) and soluble Mn from the oxidation reaction, by quantitative recoveries of added phenolic acids from soil pretreated with dithionite-citrate to remove Fe and Mn oxides, and by the reactivity of phenolic acids in the presence of pure Mn and Fe oxides. The reactivities of phenolic acids were associated with the structures of the chemicals. Increasing methoxy substitution on the aromatic ring increased reactivity, and cinnamic acid derivatives were more reactive than benzoic acid derivatives. Oxidation products of /sup 14/C labeled ferulic acid were sorbed to MnO/sub 2/ within minutes and were unextractable by organic solvents unless the mineral was pretreated with 6 M HCl or 0.5 M NaOH. The oxidation rate of ferulic acid by MnO/sub 2/ approached zero after four days even with a surplus of reactants.

Lehmann, R.G.

1986-01-01

396

Retention of nickel from aqueous solutions using iron oxide and manganese oxide coated sand: kinetic and thermodynamic studies.  

PubMed

In this study, the removal of nickel ions from aqueous solutions using iron oxide and manganese oxide coated sand (ICS and MCS) under different experimental conditions was investigated. The effect of metal concentration, contact time, solution pH and temperature on the amount of Ni(II) sorbed was studied and discussed. Langmuir and Freundlich isotherm constants and correlation coefficients for the present systems at different temperatures were calculated and compared. The equilibrium process was well described by the Langmuir isotherm model: the maximum sorption capacities (at 29 K) were 2.73 mg Ni/g and 3.33 mg Ni/g of sorbent for ICS and MCS, respectively. Isotherms were also used to evaluate the thermodynamic parameters (deltaG degrees, deltaH degrees, deltaS degrees) of adsorption. The sorption kinetics were tested for the pseudo-first-order, pseudo-second-order and intra-particle diffusion models. Good correlation coefficients were obtained for the pseudo-second-order kinetic model, showing that the nickel uptake process followed the pseudo-second-order rate expression. PMID:21275258

Boujelben, N; Bouzid, J; Elouear, Z; Feki, M

2010-12-14

397

New redox deposition-precipitation method for preparation of supported manganese oxide catalysts  

Microsoft Academic Search

A new preparation method has been developed to produce homogeneous coatings of manganese compounds on alumina-coated monoliths by redox deposition-precipitation using acetone as solvent. The deposition is produced by reduction of manganese permanganate with ethanol. The Lewis acid sites on the alumina catalyze this reaction. Thus, the precipitation is produced preferentially on the surface of the monolith and not in

Izaskun Barrio; Iigo Legrburu; Mario Montes; Mara Isabel Domnguez; Miguel Angel Centeno; Jos Antonio Odriozola

2005-01-01

398

Structural and optical properties of polycrystalline thin films of rare earth oxides grown on fused quartz by low pressure MOCVD  

NASA Astrophysics Data System (ADS)

We report the structural and optical properties of oriented polycrystalline thin films of rare earth oxides (REO), namely Er2O3, Gd2O3, Eu2O3, and Yb2O3 grown on fused quartz by low-pressure metalorganic chemical vapour deposition (MOCVD) in the temperature range of 450 800 C, using adducted ?-diketonate complexes of rare earth metals as precursors. The films were characterized by X-ray diffraction (XRD) and UV visible spectrophotometry. While the films grown at low temperatures (500 C) are poorly crystalline, those grown on or above 525 C display a significant (1 1 1) texture. Growth of textured cubic REO in (1 1 1) direction on amorphous substrate is interpreted in terms of minimization of surface energy at the film substrate interface. The degree of misfit between the interatomic distances in the disordered fused quartz substrate and those in the crystalline REO is invoked to explain the presence (absence) of low-intensity reflections other than (1 1 1). The incorporation of carbon (from the precursor) into the films affects the optical properties of REO, as examined by UV visible spectroscopy.

Singh, M. P.; Shivashankar, S. A.

2005-03-01

399

Quartz Crystal Microbalance Analysis: Partial Cation Release During Oxidation of Conducting Polymers.  

National Technical Information Service (NTIS)

In the process of charging (or oxidizing) conducting polymers, e.g., polypyrrole, polythiophene, polyaniline, it has been common to assume that exclusively anions can compensate the excess charge of the radical cation sites of polypyrrole in the oxidized ...

K. Naoi W. H. Smyrl

1990-01-01

400

The Influence of Manganese Oxide on the Sintering Behavior of Yttria Tetragonal Zirconia  

SciTech Connect

The sintering behavior of yttria-stabilized zirconia, with the influence of small additions of MnO{sub 2}(up to 1 wt %) sintered over the temperature range from 1250 deg. C to 1500 deg. C was investigated. It was found that the mechanical properties of Y-TZP were dependent on the dopant amount and sintering temperature. The results revealed that relative densities above 97.5% of theoretical (i.e. >5.95 Mgm{sup -3}) could be obtained in Y-TZPs sintered at low temperatures, 1250 deg. C and 1300 deg. C, with the additions of {<=}0.3 wt% MnO{sub 2}. In comparison to the undoped samples, the additions of up to 1 wt%MnO{sub 2} and for sintering up to 1350 deg. C was found to be beneficial in enhancing the Vickers hardness of the ceramic. The fracture toughness of Y-TZP however, was found to increase only in the 1 wt% MnO{sub 2}-doped samples when sintered above 1400 deg. C. The relation between the measured mechanical properties is discussed with the emphasis on the role of the manganese oxide.

Meenaloshini, S.; Amiriyan, M.; Sankar, U.; Tolouei, R.; Ramesh, S. [Ceramics Technology Laboratory, University Tenaga Nasional, 43009 Kajang Selangor (Malaysia)

2011-01-17

401

Layered manganese oxide intergrowth electrodes for rechargeable lithium batteries: Part 1-substitution with Co or Ni  

SciTech Connect

Lithium manganese oxides substituted with nickel or cobalt were characterized electrochemically in lithium cell configurations. The compounds studied were either single-phase layered structures with either primarily O2 or O3 stacking arrangements, or O2/O3 intergrowths, prepared from P2, P3 and P2/P3 sodium-containing precursors, respectively. The stacking arrangements are extremely sensitive to the Na/T. M. (T. M. = transition metal) ratios and the level of substitution. Phase diagrams showing the stability regions of the various arrangements for the Na-Ni-Mn-O system are presented. A possible correlation between vacancies and electrochemical performance is suggested. For high levels of substitution with Ni, fewer defects are possible for materials containing more O3 component and higher discharge capacities can be achieved, but spinel conversion upon cycling also occurs more rapidly as the O3 content increases. Intergrowths show intermediate behavior and represent a potential route towards designing stable, high capacity electrodes.

Dolle, Mickael; Patoux, Sebastien; Doeff, Marca M.

2004-09-08

402

Magnetic studies of manganese oxide octahedral molecular sieves: A new class of spin glasses  

SciTech Connect

Ac and dc magnetic susceptibility measurements of octahedral molecular sieves (OMS) of mixed-valent manganese oxide composition such as (Mg[sup 2+][sub 0.98[minus]1.35]Mn[sup 2+][sub 1.89[minus]1.94]Mn[sup 4+][sub 4.38[minus]4.54])O[sub 12]4.47-4.55H[sub 2]O for synthetic todorokite and KMn[sub 8]O[sub 16] for synthetic cryptomelane are reported here. Data for temperature and frequency dependence of the real components of the ac susceptibility suggest that synthetic cryptomelane (K-OMS-2) materials are spin glasses having a typical T[sub f]([omega]) dependence. The imaginary components of the ac susceptibility at various frequencies also show behavior that is typical of spin glass systems. Zero-field-cooled and field-cooled dc magnetization data as a function of temperature exhibit irreversibility, again consistent with the spin glass assignment for synthetic cryptomelane. Synthetic todorokite having a 3 [times] 3 MnO[sub 6] octahedral tunnel structure does not appear to be a true spin glass. 31 refs., 9 figs.

Suib, S.L. (Univ. of Connecticut, Storrs, CT (United States)); Iton, L.E. (Argonne National Lab., IL (United States))

1994-04-01

403

Effects of manganese on inositol polyphosphate receptors and nitric oxide synthase activity in rat brain.  

PubMed

The neurotoxic effects of excessive exposure to manganese (Mn) include degeneration of dopaminergic neurons, impairment of energy metabolism, and perturbations in phosphoinositide (PI) hydrolysis leading to altered calcium (Ca2+) homeostasis. This study is designed to assess the in vitro and in vivo effects of Mn on Ca2+/calmodulin-dependent neuronal nitric oxide synthase (nNOS) activity and on the regulation of inositol 1,4,5-trisphosphate (InsP3) and inositol 1,3,4,5-tetrakisphosphate (InsP4) receptors involved in intracellular and extracellular mobilization of Ca2+. In vivo Mn exposure significantly increased 3H-InsP3 and 3H-InsP4 binding in the cerebellum and the cerebral cortex in a dose-dependent manner. However, in vitro Mn decreased 3H-InsP3 binding and increased 3H-InsP4 binding. In vitro and in vivo exposure of Mn inhibited nNOS activity in the cerebellum and the cerebral cortex. Immunohistochemical studies also showed a notable decrease in nNOS immunoreactivity in the granule cell layer of the cerebellum, whereas no significant changes were observed in the cerebral cortex. These data suggest that Mn neurotoxicity may be due to altered calcium homeostasis by its modulation of inositol polyphosphate receptors. Further, the inhibition of nNOS by Mn is of considerable importance because NO regulates a number of neurotransmitter functions. PMID:11766125

Chetty, C S; Reddy, G R; Suresh, A; Desaiah, D; Ali, S F; Slikker, W J

404

Relationship of crystal structure to interionic interactions in the lithium-manganese spinel oxides  

PubMed

Lithium manganese oxides in the form of cubic spinel phases (space group Fd3m) are formed in a LixMn3-xO4 system for rather limited values of x. Structural investigations by X-ray powder diffraction, applied to the Li-Mn-O compounds, indicate the formation of a second crystalline phase, Li2MnO3 (space group C2/m), with the increasing lithium content. Total Li+ content per unit cell and the cation distribution over a spinel lattice in LixMn3-xO4 have been studied by measurements of integrated intensities of X-ray reflections, and by structure refinement using Rietveld profile analysis. In an attempt to understand the factors affecting cation distribution in the spinel lattice, we applied the computer modelling techniques and investigated the Li+, Mn3+ and Mn4+ ion distribution by calculating the lattice energy, combined with energy minimisation procedures, using the General Utility Lattice Program (GULP), a program designed for simulation of ionic and semi-ionic solids, based on interatomic potential models. PMID:10890371

Piszora; Catlow; Woodley; Wolska

2000-07-01

405

Investigation of nanostructured iron and manganese oxides as novel intercalation hosts for lithium  

NASA Astrophysics Data System (ADS)

Rechargeable lithium battery systems are being pushed to the limits of their performance in modern portable devices, with increasing demands for higher energy and higher power. The intercalation cathode or positive electrode in these batteries is one of the primary bottlenecks in terms of performance. In this thesis, investigation of nanostructured iron and manganese oxide compounds that show immense promise as cathode materials for rechargeable lithium batteries has been conducted. The electrochemical performance of these nanostructured compounds is dramatically superior to their microcrystalline counterparts, with higher specific discharge capacities, improved capacity retention upon charge-discharge cycling and enhanced rate performance. Tied to these promising electrochemical properties are unconventional structural and mechanistic characteristics that have been examined carefully. Higher solid-solubility of lithium in the nanostructured hosts, reduced tendency to undergo phase transformations typically observed in microcrystalline hosts, perfectly reversible lithium intercalation-deintercalation in nanostructured compounds possessing hydroxyl species, are some characteristics illustrated here. The properties exhibited by these materials are dependent upon such structural aspects as lack of long-range order, nano-sized morphology, disordered surface structure and non-stoichiometry. A detailed characterization of these compounds is conducted by studying the local atomic and electronic structures via x-ray absorption spectroscopy (XAS), in conjunction with studying the crystal structure via x-ray diffraction (XRD). The synthesis, electrochemistry, and structural phenomena that possess general relevance to fundamental nanoscale materials science, are highlighted in this work.

Jain, Gaurav

406

Complexation and redox interactions between aqueous plutonium and manganese oxide interfaces  

SciTech Connect

The sorption of Pu(VI) and Pu(V) onto manganite (MnOOH) and Hausmannite (Mn3O4) was studied at pH 5. Manganite sorbed 21-24% from a 1x10-4 M plutonium solution and the hausmannite removed between 43-66% of the plutonium. The increased sorption by hausmannite results from its larger surface area (about twice that of manganite) plus a larger number of active surface sites. X-ray absorption near-edge structure (XANES) spectra taken at the Pu LIII edge were compared to standard spectra of plutonium in single oxidation states. Based on these spectra, it appears that both manganite and hausmannite reduce the higher valent plutonium species to Pu(IV). Between 53-59% of the plutonium was present as Pu(IV) in the manganite samples while 55-61% of the plutonium complexed to the hausmannite had also been reduced to Pu(IV). The exact mechanism behind this redox interaction between the plutonium and the manganese needs to be identified.

Shaughnessy, Dawn A.; Nitsche, Heino; Booth, Corwin H.; Shuh, David K.; Waychunas, Glenn A.; Wilson, Richard E.; Cantrell, Kirk J.; Serne, R. Jeffrey

2001-11-01

407

Arsenic desorption from ferric and manganese binary oxide by competitive anions: significance of pH.  

PubMed

Ferric and manganese binary oxide (FMBO) has been used to remediate an arsenic (As)-polluted river in China, but insufficient data was available to (1) evaluate its effects on the environment and (2) propose a feasible strategy of addressing the arsenic-bearing FMBO. The desorption behavior of arsenic in the presence of four competitive anions (i.e., phosphate, silicate, sulfate, and bicarbonate) at different concentrations was investigated with pH ranging from 3 to 11. The presence of these anions promoted the desorption of arsenic from arsenic-bearing FMBO and followed the sequence of phosphate > silicate > sulfate approximately equal to bicarbonate across a wide pH range. Desorption of arsenate (As[V]) was more significant than that of arsenite (As[III]). Sequence dissolution of arsenic-bearing FMBO particles by NH4-oxalate/oxalic acid and hydrochloric acid were performed. The laboratory results indicated that As(III) was primarily occluded in the crystalline parts of the FMBO. The desorption behavior of arsenic could be described by kinetic models using the Elovich and power function equations under different pH conditions and was related to the adsorption of phosphate and silicate. pH played an important role in the desorption of arsenic, because of its effects on the species distribution of anions, surface charge of the arsenic-bearing FMBO, and subsequent electrostatic forces between anions and FMBO. PMID:22866393

Xu, Wei; Wang, Hongjie; Wu, Kun; Liu, Ruiping; Gong, Wenxin; Qu, Jiuhui

2012-06-01

408

LETTER TO THE EDITOR: Single-crystal growth and properties of the double-layered manganese oxides  

Microsoft Academic Search

The giant-magnetoresistance cubic perovskite oxides of the type 0953-8984\\/9\\/34\\/003\\/img1 can be tailored by layering with additional 0953-8984\\/9\\/34\\/003\\/img2 sheets. The layered manganese oxides, 0953-8984\\/9\\/34\\/003\\/img3, produce variants that adopt the 0953-8984\\/9\\/34\\/003\\/img4 structure for n = 1 and n = 2 similar to that of the high-0953-8984\\/9\\/34\\/003\\/img5 cuprates, and exhibit interesting properties. Single crystals of the two-layer (n = 2) perovskites of the

G. Balakrishnan; M. R. Lees; D. McK Paul

1997-01-01

409

A study on the reaction characteristics of vanadium-impregnated natural manganese oxide in ammonia selective catalytic reduction.  

PubMed

This study investigated the effect of adding vanadium (V) to natural manganese oxide (NMO) in ammonia (NH3) selective catalytic reduction (SCR). The addition of V to NMO decreased the catalytic activity at low temperatures by blocking the active site. However, the enhancement of catalytic activity was achieved by controlling NH3 oxidation at high temperatures. From the NH3 temperature programmed desorption and oxygen on/off test, it was confirmed that the amount of Lewis acid site and active lattice oxygen of the catalyst affects the catalytic performance at low temperature. PMID:21608495

Kim, Sung Su; Lee, Sang Moon; Park, Kwang Hee; Kwon, Dong Wook; Hong, Sung Chang

2011-05-01

410

Synthesis of manganese oxide nanocrystal by ultrasonic bath: effect of external magnetic field.  

PubMed

A novel technique was used for the synthesis of manganese oxide nanocrystal by applying an external magnetic field (EMF) on the precursor solution before sonication with ultrasonic bath. The results were compared in the presence and absence of EMF. Manganese acetate solution as precursor was circulated by a pump at constant speed (7 rpm, equal to flow rate of 51.5 mL/min) in an EMF with intensity of 0.38 T in two exposure times (t(MF), 2h and 24h). Then, the magnetized solution was irradiated indirectly by ultrasonic bath in basic and neutral media. One experiment was designed for the effect of oxygen atmosphere in the case of magnetic treated solution in neutral medium. The as prepared samples were characterized with X-ray diffraction (XRD), Fourier transform infrared (FTIR) spectroscopy, transmission electron microscopy (HRTEM, TEM), energy-dispersive spectrum (EDS), and superconducting quantum interference device (SQUID) analysis. In neutral medium, the sonication of magnetized solution (t(MF), 24h) led mainly to a mixture of Mn(3)O(4) (hausmannite) and ?-MnOOH (manganite) and sonication of unmagnetized solution led to a pure Mn(3)O(4). In point of particle size, the larger and smaller size of nanoparticles was obtained with and without magnetic treatment, respectively. In addition, the EMF was retarded the nucleation process, accelerated the growth of the crystal, and increased the amount of rod-like structure especially in oxygen atmosphere. In basic medium, a difference was observed on the composition of the products between magnetic treated and untreated solution. For these samples, the magnetic measurements as a function of temperature were exhibited a reduction in ferrimagnetic temperature to T(c)=39K, and 40K with and without magnetic treatment, respectively. The ferrimagnetic temperature was reported for the bulk at T(c)=43K. A superparamagnetic behavior was observed at room temperature without any saturation magnetization and hysteresis in the measured field strength. The effect of EMF on the sample prepared in the basic medium was negligible but, in the case of neutral medium, the EMF affected the slope of the magnetization curves. The magnetization at room temperature was higher for the samples obtained in neutral medium without magnetic treatment. In addition, a horizontal shift loop was observed in neutral medium at low temperature. PMID:22221536

Bastami, Tahereh Rohani; Entezari, Mohammad H

2011-12-13

411

Oxidative degradation of azo dyes by manganese peroxidase under optimized conditions.  

PubMed

The application of enzyme-based systems in waste treatment is unusual, given that many drawbacks are derived from their use, including low efficiency, high costs and easy deactivation of the enzyme. The goal of this study is the development of a degradation system based on the use of the ligninolytic enzyme manganese peroxidase (MnP) for the degradation of azo dyes. The experimental work also includes the optimization of the process, with the objective of determining the influence of specific physicochemical factors, such as organic acids, H(2)O(2) addition, Mn(2+) concentration, pH, temperature, enzyme activity and dye concentration. A nearly total decolorization was possible at very low reaction times (10 min) and at high dye concentration (up to 1500 mg L(-)(1)). A specific oxidation capacity as high as 10 mg dye degraded per unit of MnP consumed was attained for a decolorization higher than 90%. Among all, the main factor affecting process efficiency was the strategy of H(2)O(2) addition. The continuous addition at a controlled flow permitted the progressive participation of H(2)O(2) in the catalytic cycle through a suitable regeneration of the oxidized form of the enzyme, which enhanced both the extent and the rate of decolorization. It was also found that, in this particular case, the presence of a chelating organic acid (e.g., malonic) was not required for an effective operation. Probably, Mn(3+) was chelated by the dye itself. The simplicity and high efficiency of the process open an interesting possibility of using of MnP for solving other environmental problems. PMID:12675567

Mielgo, I; Lpez, C; Moreira, M T; Feijoo, G; Lema, J M

412

Effects of inorganic cation templates on octahedral molecular sieves of manganese oxide  

SciTech Connect

Five hydrated inorganic divalent cations, Mg[sup 2+], Co[sup 2+], Ni[sup 2+], Cu[sup 2+], and Zn[sup 2+], have successfully been used as templates for the synthesis of manganese oxide octahedral molecular sieves (OMS-1) having the todorokite structure. The OMS-1 samples have been well characterized by X-ray diffraction, differential scanning calorimetry, thermogravimetric analysis, scanning electron microscopy/energy dispersive X-ray studies, inductively coupled plasma analysis, electron paramagnetic resonance, Fourier transform infrared spectroscopy, thiosulfate titration, and cyclohexane sorption. Catalytic CO oxidation and 2-propanol decomposition were carried out. Results show that these OMS-1 samples with a tunnel size of about 6.9 angstroms are crystalline and chemically pure. They have the following formulas: Mg[sub 3.17]Mn[sub 5.05]O[sub 12] [center dot] 4.52H[sub 2]O, Co[sub 1.84]Mn[sub 5.59]O[sub 12] [center dot] 3.45H[sub 2]O, Ni[sub 1.64]Mn[sub 5.75]O[sub 12] [center dot] 4.19H[sub 2]O, Cu[sub 3.50]Mn[sub 4.45]O[sub 12] [center dot] 5.33H[sub 2]O, and Zn[sub 3.55]Mn[sub 4.47]O[sub 12] [center dot] 2.59H[sub 2]O. Their thermal stability largely depends on the nature of the cations. 47 refs., 16 figs., 3 tabs.

Shen, Y.F.; Suib, S.L. (Univ. of Connecticut, Storrs, CT (United States)); O'Young, C.L. (Texaco, Inc., Beacon, NY (United States))

1994-11-30

413

Cobalt immobilization by manganese oxidizing bacteria from the Indian ridge system.  

PubMed

Co immobilization by two manganese oxidizing isolates from Carlsberg Ridge waters (CR35 and CR48) was compared with that of Mn at same molar concentrations. At a lower concentration of 10 ?M, CR35 and CR48 immobilized 22 and 23 fM Co cell(-1) respectively, which was 1.4 to 2 times higher than that of Mn oxidation, while at 10 mM the immobilization was 15-69 times lower than that of Mn. Scanning electron microscope and energy dispersive X-ray analyses of intact bacterial cells grown in 1 mM Co revealed Co peaks showing extracellular binding of the metal. However, it was evident from transmission electron microscope analyses that most of the sequestered Co was bound intracellularly along the cell membrane in both the isolates. Change in morphology was one of the strategies bacteria adopted to counter metal stress. The cells grew larger and thus maintained a lower than normal surface area-volume ratio on exposure to Co to reduce the number of binding sites. An unbalanced growth with increasing Co additions was observed in the isolates. Cells attained a length of 10-18 ?m at 10 mM Co which was 11-15 times the original cell length. Extensive cell rupture indicated that Co was harmful at this concentration. It is apparent that biological and optimal requirement of Mn is more than Co. Thus, these differences in the immobilization of the two metals could be driven by the differences in the requirement, cell physiology and the affinities of the isolates for the concentrations of the metals tested. PMID:21046399

Antony, Runa; Sujith, P P; Fernandes, Sheryl Oliveira; Verma, Pankaj; Khedekar, V D; Bharathi, P A Loka

2010-10-30

414

Manganese-induced neurotoxicity: the role of astroglial-derived nitric oxide in striatal interneuron degeneration.  

PubMed

Chronic exposure to excessive manganese (Mn) is the cause of a neurodegenerative movement disorder, termed manganism, resulting from degeneration of neurons within the basal ganglia. Pathogenic mechanisms underlying this disorder are not fully understood but involve inflammatory activation of glial cells within the basal ganglia. It was postulated in the present studies that reactive astrocytes are involved in neuronal injury from exposure to Mn through increased release of nitric oxide. C57Bl/6 mice subchronically exposed to Mn by intragastric gavage had increased levels of Mn in the striatum and displayed diminutions in both locomotor activity and striatal DA content. Mn exposure resulted in neuronal injury in the striatum and globus pallidus, particularly in regions proximal to the microvasculature, indicated by histochemical staining with fluorojade and cresyl fast violet. Neuropathological assessment revealed marked perivascular edema, with hypertrophic endothelial cells and diffusion of serum albumin into the perivascular space. Immunofluorescence studies employing terminal deoxynucleotidyl transferase-mediated deoxyuridine triphosphate (DUTP)-biotin nick-end labeling revealed the presence of apoptotic neurons expressing neuronal nitric oxide synthase (NOS), choline acetyltransferase, and enkephalin in both the striatum and globus pallidus. In contrast, soma and terminals of dopaminergic neurons were morphologically unaltered in either the substantia nigra or striatum, as indicated by immunohistochemical staining for tyrosine hydroxylase. Regions with evident neuronal injury also displayed increased numbers of reactive astrocytes that coexpressed inducible NOS2 and localized with areas of increased neuronal staining for 3-nitrotyrosine protein adducts, a marker of NO formation. These data suggest a role for astrocyte-derived NO in injury to striatal-pallidal interneurons from Mn intoxication. PMID:16551646

Liu, Xuhong; Sullivan, Kelly A; Madl, James E; Legare, Marie; Tjalkens, Ronald B

2006-03-21

415

Detection of different oxidation states of individual manganese porphyrins during their reaction with oxygen at a solid/liquid interface  

NASA Astrophysics Data System (ADS)

Manganese porphyrins have been extensively investigated as model systems for the natural enzyme cytochrome P450 and as synthetic oxidation catalysts. Here, we report single-molecule studies of the multistep reaction of manganese porphyrins with molecular oxygen at a solid/liquid interface, using a scanning tunnelling microscope (STM) under environmental control. The high lateral resolution of the STM, in combination with its sensitivity to subtle differences in the electronic properties of molecules, allowed the detection of at least four distinct reaction species. Real-space and real-time imaging of reaction dynamics enabled the observation of active sites, immobile on the experimental timescale. Conversions between the different species could be tuned by the composition of the atmosphere (argon, air or oxygen) and the surface bias voltage. By means of extensive comparison of the results to those obtained by analogous solution-based chemistry, we assigned the observed species to the starting compound, reaction intermediates and products.

den Boer, Duncan; Li, Min; Habets, Thomas; Iavicoli, Patrizia; Rowan, Alan E.; Nolte, Roeland J. M.; Speller, Sylvia; Amabilino, David B.; de Feyter, Steven; Elemans, Johannes A. A. W.

2013-07-01

416

Mimicking the reduced, oxidized and azide inhibited form of manganese superoxide dismutase by mononuclear Mn compounds utilizing tridentate ligands  

Microsoft Academic Search

The manganese complexes [MnII(Hbmimpm)2(NO3)](NO3)Et2O (1), [MnIII(bmimpm)2(OAc)]2CH2Cl2(2), and [MnIII(bmiapm)2(OAc)]MeOHH2OCH2Cl2(3) containing the new ligands Bis(1-methylimidazol-2-yl)-(4-methoxyphen-1-yl)methanol (Hbmimpm) and Bis[(1-methylimidazol-2-yl)](2-aminophenyl)methanol (Hbmiapm) were synthesized. They are good structural models for the reduced (1) and oxidized (2, 3) form of manganese superoxide dismutase. All complexes were characterized by spectroscopic methods and X-ray structure analysis. Compounds 1 and 2 crystallize in the monoclinic space group P21\\/c whereas

D Pursche; M. U Triller; C Slinn; N Reddig; A Rompel; B Krebs

2004-01-01

417

Detection of different oxidation states of individual manganese porphyrins during their reaction with oxygen at a solid/liquid interface.  

PubMed

Manganese porphyrins have been extensively investigated as model systems for the natural enzyme cytochrome P450 and as synthetic oxidation catalysts. Here, we report single-molecule studies of the multistep reaction of manganese porphyrins with molecular oxygen at a solid/liquid interface, using a scanning tunnelling microscope (STM) under environmental control. The high lateral resolution of the STM, in combination with its sensitivity to subtle differences in the electronic properties of molecules, allowed the detection of at least four distinct reaction species. Real-space and real-time imaging of reaction dynamics enabled the observation of active sites, immobile on the experimental timescale. Conversions between the different species could be tuned by the composition of the atmosphere (argon, air or oxygen) and the surface bias voltage. By means of extensive comparison of the results to those obtained by analogous solution-based chemistry, we assigned the observed species to the starting compound, reaction intermediates and products. PMID:23787754

den Boer, Duncan; Li, Min; Habets, Thomas; Iavicoli, Patrizia; Rowan, Alan E; Nolte, Roeland J M; Speller, Sylvia; Amabilino, David B; De Feyter, Steven; Elemans, Johannes A A W

2013-06-02

418

New divalent manganese complex with pyridine carboxylate N-oxide ligand: Synthesis, structure and magnetic properties  

SciTech Connect

Two new manganese complexes, [Mn{sub 3}(L{sup 1}){sub 4}(NO{sub 3}){sub 2}]{sub n} (1, HL{sup 1}=nicotinate N-oxide acid) and [MnL{sup 2}Cl]{sub n} (2, HL{sup 2}=isonicotinate N-oxide acid)], have been hydrothermally synthesized and characterized by elemental analysis, IR and single-crystal X-ray diffraction. In 1, the L{sup 1} ligands take two different coordinated modes bridging four and three Mn{sup II} ions. The nitrate anions take chelating coordination modes, leading one type of the Mn{sup II} ions as a 4-connected node. The whole net can be viewed as a 3, 4, 6-connected 4-nodal net with Schlaefli notation {l_brace}4{sup 3{r_brace}}2{l_brace}4{sup 4}; 6{sup 2{r_brace}}4{l_brace}4{sup 6}; 6{sup 6}; 8{sup 3{r_brace}}. Complex 2 has a honeycomb layer mixed bridged by chlorine, N-oxide and carboxylate. The adjacent layers are linked by the phenyl ring of L{sup 2} ligand, giving a 3D framework with a {l_brace}3{sup 4}; 5{sup 4{r_brace}} {l_brace}3{sup 2};4;5{sup 6};6{sup 6{r_brace}} 4, 6-connect net. Magnetic studies indicate that 1 is an antiferromagnet with low-dimensional characteristic, in which a -J{sub 1}J{sub 1}J{sub 2}- coupled alternating chain is predigested. Fitting the data of 1 gives the best parameters J{sub 1}=-2.77, J{sub 2}=-0.67 cm{sup -1}. The magnetic properties of complex 2 represent the character of the 2D honeycomb layer with the J{sub 1}=-2.05 and J{sub 2}=0.55 cm{sup -1}, which results in a whole antiferromagnetic state. - Graphical abstract: The synthesis, crystal structure and magnetic properties of two new MnII complexes with pyridyl-carboxylate N-oxide ligands are reported.

Liu Fuchen, E-mail: fuchenliutj@yahoo.co [School of Chemistry and Chemical Engineering, Tianjin University of Technology, Tianjin 300384 (China); Xue Min; Wang Haichao [School of Chemistry and Chemical Engineering, Tianjin University of Technology, Tianjin 300384 (China); Ouyang Jie, E-mail: ouyang@tjut.edu.c [School of Chemistry and Chemical Engineering, Tianjin University of Technology, Tianjin 300384 (China)

2010-09-15

419

Low-potential Amperometric Determination of Hydrogen Peroxide with a Carbon Paste Electrode Modified with Nanostructured Cryptomelane-type Manganese Oxides  

SciTech Connect

Nanostructured cryptomelane-type manganese oxides were synthesized, characterized, and evaluated for chemical sensing. Cryptomelane-type manganese oxides are nanofibrous crystals with sub-nanometer open tunnels that provide a unique property for sensing applications. Carbon paste electrodes (CPEs), modified with the nanostructured cryptomelane-type manganese oxides, were investigated for amperometric detection of hydrogen peroxide. With an operating potential of +0.3 V versus Ag/AgCl, H{sub 2}O{sub 2} produces catalytic oxidation currents at the modified CPE, which can be exploited for quantitative determinations. The amperometric signals are linearly proportional to H{sub 2}O{sub 2} concentration in the range 1.0 x 10{sup -4}-6.9 x 10{sup -4} M with a correlation coefficient of 0.995 (n = 7). At a signal-to-noise ratio of 3, a detection limit of 2 {micro}M can be observed for the carbon paste electrode modified with 5.5 wt% cryptomelane-type manganese oxides. In addition, the sensor has a good stability and reproducibility. The construction and renewal are simple and inexpensive. A possible response mechanism was proposed and discussed. The significant electrocatalytic activity of the modified CPE may result from the nanostructure of cryptomelane-type manganese oxides.

Lin, Yuehe; Cui, Xiaoli; Li, Liyu

2005-02-01

420

Manganese-Cobalt Mixed Spinel Oxides as Surface Modifiers for Stainless Steel Interconnects of Solid Oxide Fuel Cells  

SciTech Connect

Ferritic stainless steels are promising candidates for interconnect applications in low- and mid-temperature solid oxide fuel cells (SOFCs). A couple of issues however remain for the particular application, including the chromium poisoning due to chromia evaporation, and long-term surface and electrical stability of the scale grown on these steels. Application of a manganese colbaltite spinel protection layer on the steels appears to be an effective approach to solve the issues. For an optimized performance, Mn{sub 1+x}Co{sub 2-x}O{sub 4} (-1 {le} x {le} 2) spinels were investigated against properties relative for protection coating applications on ferritic SOFC interconnects. Overall it appears that the spinels with x around 0.5 demonstrate a good CTE match to ceramic cell components, a relative high electrical conductivity, and a good thermal stability up to 1,250 C. This was confirmed by a long-term test on the Mn{sub 1.5}Co{sub 1.5}O{sub 4} protection layer that was thermally grown on Crofer22 APU, indicating the spinel protection layer not only significantly decreased the contact resistance between a LSF cathode and the stainless steel interconnects, but also inhibited the sub-scale growth on the stainless steels.

Xia, Gordon; Yang, Z Gary; Stevenson, Jeffry W.

2006-11-06

421

Kinetics of the catalytic oxidation of phenol over manganese oxide in supercritical water  

SciTech Connect

A kinetic analysis was made for the phenol disappearance rate in catalytic oxidation of phenol over MnO{sub 2} in supercritical water at a fixed temperature of 425 C and pressures between 22.7 and 27.2 MPa. The nonsupported MnO{sub 2} catalyst possessed a strong activity for promoting phenol oxidation, though the overall reaction rate was appreciably influenced by internal mass-transfer resistance. From the kinetic analysis on the reaction rate of the phenol disappearance, the global rate expression of the surface reaction was obtained, where the reaction orders with respect to phenol, oxygen, and water were almost unity, 0.7, and {minus}2.0, respectively. A Langmuir-type mechanism, in which phenol and oxygen adsorbed on the catalytic sites and water adsorbed on the same site to inhibit the phenol and oxygen adsorption, was proposed to explain the reaction orders for phenol, oxygen, and water.

Oshima, Yoshito; Tomita, Kengo; Koda, Seiichiro

1999-11-01

422

Nanocrystalline lithiummanganese oxide spinels for Li-ion batteries Sol-gel synthesis and characterization of their structure and selected physical properties  

Microsoft Academic Search

Nanocrystalline lithiummanganese oxide spinels were synthesized by a modified sol-gel method. Simple salts of lithium, manganese and iron were used as starting reagents and citric acid as a complexing agent. The gelled materials turned into nanopowders after the calcination was carried out in air in the 450700C temperature range. The combined DSC-TGA measurements have shown important stages of the syntheses.

M. Michalska; L. Lipi?ska; M. Mirkowska; M. Aksienionek; R. Diduszko; M. Wasiucionek

2011-01-01

423

PROGRESS REPORT. TRANSURANIC INTERFACIAL REACTION STUDIES ON MANGANESE OXIDE HYDROXIDE MINERAL SURFACES  

EPA Science Inventory

Several DOE sites have been contaminated by transuranic radionuclide (TRU) discharges including neptunium and plutonium. Their interaction with the surrounding geological media can affect the transport and remediation of these radionuclides in the environment. Manganese based min...

424

Long-term exposure to "low levels" of manganese oxides and neurofunctional changes in ferroalloy workers.  

PubMed

Occupational exposure to manganese can cause early neurobehavioral effects in low- or a-symptomatic workers. A battery of neuropsychological tests was administered to a group of 61 ferroalloy male workers and 87 controls. The average (geometric mean) manganese concentrations in total dust at the plant have changed from 1981 to 1997 respectively from 1597.03 micrograms/m3 to 239 micrograms/m3 at the furnace area; from 151.53 to 255.76 micrograms/m3 at the casting area; from 167 to 54.7 micrograms/m3 at the maintenance (welding operations), yielding a current overall value of 54.25 micrograms/m3. A cumulative exposure index was calculated for each alloy worker and the average value (geometric mean) resulted to be 1204.87 micrograms/m3 x years, which divided by the average length of exposure (15.17 years), showed the concentration of 70.83 micrograms/m3 of manganese in total dust. Blood and urinary manganese geometric means resulted significantly higher in the exposed workers (9.18 micrograms/l and 1.53 micrograms/g creatinine, respectively) than in controls (5.74 micrograms/l and 0.40 microgram/g creatinine, respectively). A positive correlation was observed between the airborne manganese concentrations in total dust and blood manganese (n = 55; R = 0.36; R2 = 0.13; p = 0.0068), whereas no association resulted between cumulative exposure index and both blood manganese and urinary manganese. Higher prevalence of symptoms reporting was observed in the alloy workers concerning irritability, loss of equilibrium and rigidity. Tremor parameters including the central frequency and its dispersion, resulted to be statistically different in the exposed workers compared to the controls. Motor functions exploring the coordination of rapid and alternating movements and memory functions resulted to be impaired in the manganese workers. Dose-effect relationships were observed between the cumulative exposure index and some of the test results, whereas no relationship was found with the airborne manganese concentrations and the biological indicators of exposure. These findings are consistent with the existing knowledge of a cumulative mechanism of action of manganese, which must be carefully considered when setting safe exposure levels. In order to be protective for the entire working life, the average annual exposure level should be lower than 100 micrograms/m3. PMID:10385891

Lucchini, R; Apostoli, P; Perrone, C; Placidi, D; Albini, E; Migliorati, P; Mergler, D; Sassine, M P; Palmi, S; Alessio, L

425

Effect of the high pressure on the structure and intercalation properties of lithium-nickel-manganese oxides  

SciTech Connect

Lithium-nickel-manganese oxides (Li{sub 1+} {sub x} (Ni{sub 1/2}Mn{sub 1/2}){sub 1-} {sub x} O{sub 2}, x=0 and 0.2), having different cationic distributions and an oxidation state of Ni varying from 2+ to 3+, were formed under a high-pressure (3 GPa). The structure and cationic distribution in these oxides were examined by powder X-ray diffraction, infrared (IR) and electron paramagnetic resonance (EPR) in X-band (9.23 GHz) and at higher frequencies (95 and 285 GHz). Under a high pressure, a solid-state reaction between NiMnO{sub 3} and Li{sub 2}O yields LiNi{sub 0.5}Mn{sub 0.5}O{sub 2} with a disordered rock-salt type structure. The paramagnetic ions stabilized in this oxide are mainly Ni{sup 2+} and Mn{sup 4+} together with Mn{sup 3+} (about 10%). The replacement of Li{sub 2}O by Li{sub 2}O{sub 2} permits increasing the oxidation state of Ni ions in lithium-nickel-manganese oxides. The higher oxidation state of Ni ions favours the stabilization of the layered modification, where the Ni-to-Mn ratio is preserved: Li(Li{sub 0.2}Ni{sub 0.4}Mn{sub 0.4})O{sub 2}. The paramagnetic ions stabilized in the layered oxide are mainly Ni{sup 3+} and Mn{sup 4+} ions. The disordered and ordered phases display different intercalation properties in respect of lithium. The changes in local Ni,Mn-environment during the electrochemical reaction are discussed on the basis of EPR and IR spectroscopy. - Graphical abstract: Lithium-nickel-manganese oxides (Li{sub 1+} {sub x} (Ni{sub 1/2}Mn{sub 1/2}){sub 1-} {sub x} O{sub 2}, x=0 and 0.2), having different cationic distributions and an oxidation states of Ni varying from 2+ to 3+, were formed under a high-pressure (3 GPa)

Yoncheva, M. [Institute of General and Inorganic Chemistry, Bulgarian Academy of Sciences, 1113 Sofia (Bulgaria); Stoyanova, R. [Institute of General and Inorganic Chemistry, Bulgarian Academy of Sciences, 1113 Sofia (Bulgaria); Zhecheva, E. [Institute of General and Inorganic Chemistry, Bulgarian Academy of Sciences, 1113 Sofia (Bulgaria)], E-mail: zhecheva@svr.igic.bas.bg; Alcantara, R. [Laboratorio de Quimica Inorganica, Facultad de Ciencias, Universidad de Cordoba, 14071 Cordoba (Spain); Ortiz, G. [Laboratorio de Quimica Inorganica, Facultad de Ciencias, Universidad de Cordoba, 14071 Cordoba (Spain); Tirado, J.L. [Laboratorio de Quimica Inorganica, Facultad de Ciencias, Universidad de Cordoba, 14071 Cordoba (Spain)

2007-06-15

426

Electrodeposited Manganese Oxides on Three-Dimensional Carbon Nanotube Substrate: Supercapacitive Behaviour in Aqueous and Organic Electrolytes  

SciTech Connect

Thin amorphous manganese oxide layers with a thickness of 3-5nm are electrodeposited on a carbon nanotube (CNT) film substrate that has a three-dimensional nanoporous structure (denoted asMnO2/CNT electrode). For the purpose of comparison, manganese oxide films are also electrodeposited on a flat Pt-coated Si wafer substrate (denoted as MnO2 film electrode). The pseudocapacitive properties of the MnO2 film and MnO2/CNT electrodes are examined in both aqueous electrolyte (1.0M KCl) and nonaqueousorganic electrolyte (1.0M LiClO4 in propylene carbonate). While both types of electrode showpseudocapacitive behaviour in the aqueous electrolyte, only the MnO2/CNT electrode does so in the organic electrolyte, due to its high oxide/electrolyte interfacial area and improved electron conduction through the CNT substrate. Compared with the MnO2 film electrode, the MnO2/CNT electrode shows a much higher specific capacitance and better high-rate capability, regardless of the electrolyte used.Use of the organic electrolyte results in a ?6 times higher specific energy compared with that obtained with the aqueous electrolyte, while maintaining a similar specific power. The construction of a threedimensional nanoporous network structure consisting of a thin oxide layer on a CNT film substrate at the nm scale and the use of an organic electrolyte are promising approaches to improving the specific energyof supercapacitors.

Nam,K.W.; Yang,X.

2009-03-01

427

Capacity fading mechanisms and origin of the capacity above 4.5 V of spinel lithium manganese oxides  

NASA Astrophysics Data System (ADS)

Lithium ion batteries have become attractive for portable devices due to their high operating voltage, high energy density, low self-discharge, and long cycle life. Lithium ion cells currently use the layered LiCoO 2 cathode, but cobalt is expensive and relatively toxic. In this regard, spinel LiMn2O4 has become appealing since manganese is inexpensive and environmentally benign. However, LiMn2O 4 exhibits severe capacity fade. This dissertation explores the electrochemical performances of spinel oxides derived from LiMn2O4 in a wide voltage range of 3.5 to 5.2 V to understand the capacity fading mechanisms and the origin of the high voltage capacity above 4.5 V. From a systematic investigation of a series of singly substituted LiMn 2-yMyO4 and doubly substituted LiMn 2-y-zMyLizO4 (M = Li, Al, or transition metal) oxides, the doubly substituted LiMn2-y-z NiyLizO4 oxides are found to show superior cyclability, low irreversible capacity (IRC), high rate capability, low electrode resistance, and excellent storage performance compared to LiMn2O 4 despite a similar manganese dissolution. For example, LiMn1.85 Ni0.075Li0.075O4 retains more than 99 and 97% of its initial capacity after 50 cycles at, respectively, 25 and 60C. Its excellent electrochemical performances are found to be due to the small lattice parameter difference between the two cubic phases formed in the two-phase region during cycling and the consequent low microstrain. This concept of minimizing the lattice parameter difference and microstrain could successfully enable the use of spinel lithium manganese oxides for electric vehicle applications. In contrast to the literature suggestions that other transition metal ions or excess oxygen are essential to impart the high voltage (>4.5 V) capacity, spinel lithium manganese oxides free from other transition metal ions are found to show capacity above 4.5 V even with a significant amount of oxygen deficiency if there are extractable Li+ ions in the 8a tetrahedral sites after the oxidation state of manganese reaches 4+. In the presence of other transition metals, the reversibility of the high voltage capacity depends on the element replacing Mn3+, and it decreases in the order LiMn2-yNiyO4 > LiMn2-yCoyO4 ? LiMn 2-y-zCoyLizO4 > LiMn 2-y-zNiyLizO4. Based on the results, the capacity above 4.5 V in manganese-based spinel oxides could be understood to arise from a participation of the O2-:2p band or a hybridized band involving M3+/4+:3d (or M 2+/3+:3d) and O2-:2p.

Shin, Youngjoon

2003-06-01

428

Studies of stability and reactivity of synthetic cryptomelane-like manganese oxide octahedral molecular sieves  

SciTech Connect

Cryptomelane is known to be a manganese oxide octahedral molecular sieve having a well-defined 2 x 2 tunnel structure (OMS-2) with K{sup +} situated in tunnel positions. The mobility and reactivity of oxygen in such tunnel structures with different tunnel cations were studied by means of temperature-programmed desorption (TPD) and reduction with H{sub 2} and CO{sub 2}. Oxygen released during TPD from OMS-2 materials is significantly greater in amount than that from OMS-1 (3x3 tunnel structure), although the relative populations of oxygen from different desorption temperature regimes are much the same as that of OMS-1. Oxygen species corresponding to low-temperature, medium-temperature, and high-temperature TPD peaks can be assigned to weakly bound chemisorbed dioxygen, oxygen atoms bound to lower valent Mn ions, and those bound to Mn{sup 4+} ions in the framework, just as is the case for OMS-1. Among the different tunnel cations, Cu{sup 2+} exhibits a distinct feature of having more available oxygen species that are reactive at low temperature. The availability of oxygen in Cu{sup 2+} exhibits a distinct feature of having more available oxygen species that are reactive at low temperature. The availability of oxygen in Cu{sup 2+}-doped OMS-2 was also studied by frontal reduction at 563 K with CO/He. The amount of oxygen depleted during frontal reduction is close to that during TPR by CO/He. The depleted Cu{sup 2+} hollandite can be reoxidized to about 85% recovery of oxygen by oxygen pulse reactions. X-ray diffraction patterns show that 2 x 2 tunnel structure remains intact after heating in an oxygen-free gas stream up to 778 K, but collapses after reduction in CO at 563 K. These studies emphasize the importance of pretreatment of OMS materials prior to use in catalysis or adsorption.

Yin, Yuan-Gen; Xu, Wen-Qing; DeGuzman, R. [Univ. of Connecticut, Storrs, CT (United States)] [and others

1994-09-14

429

Oxidative coupling of methane over oxide-supported sodium-manganese catalysts  

SciTech Connect

The oxidative coupling of methane over Mn/Na{sub 2}WO{sub 4}/SiO{sub 2}, Mn/Na{sub 2}WO{sub 4}/MgO, and NaMnO{sub 4}/MgO catalysts was studied using both a cofeed flow system and a pulse reactor. At 800{degrees}C and 1 atm, and using a CH{sub 4}/O{sub 2} ratio of ca. 8/1, a methane conversion of 20% was achieved at a C{sub 2+} selectivity of {ge}80%, with no diluent in the reagents. The similar catalytic behaviors of the three catalysts suggest that a common active site, consisting of an Na-O-Mn species, may be involved. Results from a pulse reaction sequence (an O{sub 2} pulse followed by a series of pure CH{sub 4} pulses) indicate that the active species are not stable under reaction conditions unless gas phase O{sub 2} is present, and that bulk lattice oxygen does not participate in the methane coupling reaction when carried out in the cofeed mode. There is a linear relationship between the specific activity for CH{sub 4} conversion and the concentration of surface Mn, which is believed to be responsible for the activation of O{sub 2}. The resulting form of oxygen then abstracts a hydrogen atom from CH{sub 4}. Sodium is essential for preventing the complete oxidation of CH{sub 4}, perhaps by isolating the Mn ions. The tungstate ions appear to impart stability to the catalysts. 39 refs., 11 figs., 5 tabs.

Wang, Dingjun; Rosynek, M.P.; Lunsford, J.H. [Texas A & M Univ., College Station, TX (United States)

1995-09-01

430

Biological and Chemical Interactions with U(VI) During Anaerobic Enrichment in the Presence of Iron Oxide Coated Quartz  

SciTech Connect

Microcosm experiments were performed to understand chemical and biological interactions with hexavalent uranium (U(VI)) in the presence of iron oxide bearing minerals and trichloroethylene (TCE) as a co-contaminant. Interactions of U(VI) and hydrous iron oxide moieties on the mineral oxide surfaces were studied during enrichments for dissimilatory iron reducing (DIRB) and sulfate reducing bacteria (SRB). Microbes enriched from groundwater taken from the Test Area North (TAN) site at the Idaho National Engineering and Environmental Laboratory (INEEL) were able to reduce the U(VI) in the adsorption medium as well as the iron on quartz surfaces. Early in the experiment disappearance of U(VI) from solution was a function of chemical interactions since no microbial activity was evident. Abiotic removal of U(VI) was enhanced in the presence of carbonate. As the experiment proceeded, further removal of U(VI) from solution was associated with the fermentation of lactate to propionate and acetate. During later phases of the experiment when lactate was depleted from the growth medium in the microcosm containing the DIRB enrichments, U(VI) concentrations in the solution phase increased until additional lactate was added. When lactate fermentation proceeded, U(VI) concentrations in the liquid phase again returned to near zero. Similar results were shown for the SRB enrichment but less uranium was released back into solution, while in the enrichment with carbonate uranium was not released back into solution. Chemical and biological interactions appear to be important on the mobilization/immobilization of U(VI) in an iron oxide system when TCE is present as a co-contaminant. Interestingly, TCE present in the microcosm experiments was not dechlorinated which was probably an effect of redox conditions that were unsuitable for reductive dechlorination by the microbial culture tested.

Brady D. Lee; Michelle R. Walton; Jodette L. Megio

2005-11-01

431

In situ examination of tin oxide atomic layer deposition using quartz crystal microbalance and Fourier transform infrared techniques  

NASA Astrophysics Data System (ADS)

The atomic layer deposition (ALD) of tin oxide thin films has been examined using in situ quartz crystal microbalance (QCM) and Fourier transform infrared (FTIR) techniques. The SnOx films were deposited using sequential exposures of SnCl4 and H2O2 at temperatures from 150 to 430 C. The linear growth of the tin oxide ALD films was observed by both the mass gain during QCM measurements and the background infrared absorbance increase during FTIR investigations. The FTIR spectra revealed the loss and gain of the O-H stretching vibrations of the hydroxyl group for the SnCl4 and H2O2 exposures, respectively. The background infrared absorbance also oscillated after each SnCl4 and H2O2 exposure. The background absorbance increased after SnCl4 exposure and decreased after H2O2 exposure. QCM measurements were consistent with a tin oxide ALD growth rate of ~60 ng cm-2 per cycle. This mass change corresponds to a growth rate of ~0.7 A?/cycle at 325 C assuming a SnO2 density of 6.9 g cm-3. Additional ex situ surface analysis using x-ray photoelectron spectroscopy (XPS) and Auger electron spectroscopy (AES) revealed that the SnOx films grown at 325 C were defined by x<2. Atomic force microscope (AFM) results also showed that the SnOx ALD films deposited on Si(100) wafers have a very rough surface. Understanding and controlling the growth of tin oxide ALD films should be useful to enhance the sensitivity of SnOx gas sensors.

Du, X.; Du, Y.; George, S. M.

2005-07-01

432

Enhanced electrochemical characteristics of lithium manganese oxide thin film cathodes for lithium-ion rechargeable microbatteries  

NASA Astrophysics Data System (ADS)

Spinel LiMn2O4 (average oxidation state of Mn = 3.5) thin film has been introduced for a promising cathode of thin film lithium-ion microbatteries because of its advantages over other cathodes. Thus, many research groups have been investigating the thin film lithium manganese oxide cathode using several different techniques but only a few of them achieved acceptable electrochemical properties required for a thin film cathode for 4 V region. However, for 3 V application the wide applications of LiMn2O 4 film as a cathode in rechargeable microbatteries have been restricted by electrochemically unfavorable facts such as capacity fade on cycling and poor rate capability at high rates. In this study, we examined the mechanisms responsible for capacity fade on cycling and rate capability of LiMn 2O4 thin film cathodes with the help of pulsed laser deposition (PLD) technique. In an attempt to address these issues, a three-part experimental procedure has been designed to look at the effect of structure and compositions of the thin film cathodes on their electrochemical characteristics. First, the effect of growth temperature of the thin film cathodes has been investigated. Next, LiMn2O4 thin film cathodes doped with aluminum, which replaces Mn3+ in the spinet structure, have been synthesized and characterized as a function of the amount of aluminum substituted. Finally, ultraviolet radiation was added to a PLD system for in situ ultraviolet-assisted PLD (UVPLD) growth of cathode films. Through the addition of ultraviolet radiation, highly reactive oxygen species are generated which alter the oxygenation conditions and dynamically alter the films properties such as crystallinity and composition. A variety of characterization techniques indicate that LiMn2O 4 thin film cathodes grown at 400500C exhibit the optimized electrochemical characteristics in terms of capacity, capacity retention, and rate capability. Al-doped LiMn2O4 thin films show a more stable structure, leading to higher capacity retention with some sacrifice of discharge capacity and rate capability. Oxygen-rich spinel (LiMn2O4+delta, delta > 0) thin film cathodes produced by UVPLD result in very high capacity and better rechargeability but lower rate capability.

Kim, Won-Seok

433

Processing-structure-property-performance investigations of lithium manganese-based oxides for lithium rechargeable batteries  

NASA Astrophysics Data System (ADS)

A study of the processing - structure - property - performance interrelationship was performed on several lithium manganese oxides that are candidates for use in lithium rechargeable batteries. The materials studied were LiMn 2O4, Mn-substituted LiMn2O4 (LiMn 2-yMeyO4), and Li1.5Na0.5 MnO2.85I0.12. Processing evaluations pertained to the substitution of Mn by other cations (Me = Li, Co, or Ni). Atomic and electronic structure was investigated using X-ray diffraction, FTIR, 7Li NMR, and a variety of X-ray spectroscopy techniques. The properties investigated included the voltage profile during charge and discharge in a Li metal cell along with the structural changes taking place upon lithium extraction or insertion. Performance evaluation consisted of cycling several of these materials within a Li metal cell. Among the significant findings of this study are that a dynamic Jahn-Teller distortion takes place in LiMn2O4 and that the Li + inserted derivative (Li2Mn2O4) possess a significantly greater degree of covalency with respect Mn oxides with similar atomic structure. These results are used to construct a structural reaction mechanism for the Li+ extraction and insertion reactions in LiMn2O4 and the phase transformation that accompanies Li+ insertion. In contrast, evidence for increased covalency upon lithium insertion was not apparent in Li1.5Na0.5MnO 2.85I0.12, an amorphous material. Furthermore, it was found that the distortion of the [MnO6] octahedra occurring upon Li + insertion is reversible. This is consistent with the high degree of cycling stability in this material and attributable to the amorphous nature. It was also found that the degree of covalency increases when substituting Mn with either Li, Co, or Ni. The amount of increased covalency depends on the degree of substitution and the substituent used. It was found that substitution lowers the discharge voltage along with affecting the degree of distortion and volume change that takes place during the cubic to tetragonal phase transformation concomitant with Li+ insertion. Assimilating these results with the increased cyclability of Mn substituted spinels reveals that lowering the discharge voltage and/or the volume change associated with the phase transformation will result in a spinel with improved performance. The understanding gained in this dissertation leads to guidelines for engineering improved lithium rechargeable battery electrode materials.

Horne, Craig Richard

434

Effects of vanadium- and iron-doping on crystal morphology and electrochemical properties of 1D nanostructured manganese oxides  

Microsoft Academic Search

One-dimensional (1D) nanostructures of vanadium- and iron-doped manganese oxides, Mn1?xMxO2 (M=V and Fe), are synthesized via one-pot hydrothermal reactions. The results of X-ray diffraction studies and electron microscopic analyses demonstrate that all the present 1D nanostructured materials possess ?-MnO2-type structure. While the vanadium dopants produce 1D nanorods with a smaller aspect ratio of ?35, iron dopants produce 1D nanowires with

Ha Na Yoo; Dae Hoon Park; Seong-Ju Hwang

2008-01-01

435

Influence of synthesis temperature on the crystal structure and electrode property of sulfur-doped manganese oxide nanowires.  

PubMed

Sulfur-doped manganese oxide 1D nanostructures with controllable crystal structures and crystallite dimensions have been synthesized via one-pot non-hydrothermal solution route. Powder X-ray diffraction analysis clearly demonstrated that the crystal structures of the sulfur-doped manganates can be tailored by the change of reaction temperature; layered delta-MnO2-structured material was obtained at 60 degrees C while the reaction at 90 degrees C produced tunnel alpha-MnO2 structured material. According to field emission-scanning electron microscopy, both sulfur-doped manganates possess 1D nanostructure-type morphology with the diameter of approximately 20 nm and the length of approximately 1 microm for delta-MnO2-type material, and the diameter of approximately 100 nm and the length of approximately 800 nm for alpha-MnO2-type material, respectively. From X-ray photoelectron and X-ray absorption spectroscopic analyses, sulfur ions exist as highly oxidized sulfate cluster on surface or grain boundary of the manganate crystallite whereas manganese ions are stabilized in octahedral geometry with the mixed oxidation state of Mn+3/Mn+4. Of special importance is that both sulfur-doped manganate nanowires show promising electrode performances for lithium secondary batteries. PMID:19198483

Park, Dae Hoon; Kim, Tae Woo; Oh, Eun-Jin; Hwang, Seong-Ju

2008-10-01

436

Multi-functional porous mix-valent manganese oxide nano-materials and ruthenium/titanium dioxide for magnetic, electronic, and catalytic applications  

NASA Astrophysics Data System (ADS)

This thesis contains two parts: (1) development of porous mixed-valent manganese oxide octahedral molecular sieve (OMS) nano-materials with controlled tunnel structures and muilt-functionalities and (2) application of H 2 adsorption for metal particle size evaluation on TiO2 supported Ru Fischer-Tropsch catalysts. Manganese oxide OMS with different nano-scale tunnel sizes may result in various microporosities for different selective catalysis and separation applications. A hydrothermal method was developed to synthesize manganese oxide nano-materials with controlled nano-scale tunnel sizes by hydrothermal treatments of layered structure manganese oxides under different pH conditions. Manganese oxides with increasing tunnel sizes of 2.3 A x 2.3 A (1x1 tunnel structure), 4.6 A x 6.9 A (2x3 tunnel structure), and 4.6 A x 9.2 A (2x4 tunnel structure) were synthesized with increasing pH value from 1.0, 7.0, to 13.0, respectively. Phase transformation mechanism of layered precursors to tunnel structures was obtained by characterization of the materials during synthesis using in situ synchrotron X-ray diffraction. The obtained phase transformation mechanism was used for synthesis of better materials such as new lxl/1x2 tunnel structures and controlled BET surface areas. Most manganese oxide OMS materials show paramagnetism at temperatures from 100 to 350 K. A new method was established to measure the average oxidation state (AOS) of mix-valent manganese in OMS materials by describing their paramagnetic behavior using the Curie-Weiss law. Measurement results show a maximum 7% deviation error compared to the reference titration method for 10 different samples. Magnetism of OMS was further explored by doping Fe into KOMS-2 (a 2x2 tunnel structure manganese oxide) to create high temperature ferromagnetism. The possession of both semiconducting and high temperature ferromagnetism in the Fe-doped KOMS-2 created a highly promising new group of functional materials for spintronics applications. In the second part, effects of temperatures, H2 pressures and adsorption equilibration times on H2 adsorption on Ru/TiO 2 were investigated. By assuming that exposed Ru atoms equally contribute to the three low index planes with the highest atomic density [(001), (100), and (110) planes], the average Ru particle size calculated from monolayer H2 chemisorption (4.6 nm) showed good agreement with the TEM measurement results (4.1 nm).

Shen, Xiongfei

437

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