Sample records for na mg mn

  1. Oxygen redox chemistry without excess alkali-metal ions in Na2/3[Mg0.28Mn0.72]O2.

    PubMed

    Maitra, Urmimala; House, Robert A; Somerville, James W; Tapia-Ruiz, Nuria; Lozano, Juan G; Guerrini, Niccoló; Hao, Rong; Luo, Kun; Jin, Liyu; Pérez-Osorio, Miguel A; Massel, Felix; Pickup, David M; Ramos, Silvia; Lu, Xingye; McNally, Daniel E; Chadwick, Alan V; Giustino, Feliciano; Schmitt, Thorsten; Duda, Laurent C; Roberts, Matthew R; Bruce, Peter G

    2018-03-01

    The search for improved energy-storage materials has revealed Li- and Na-rich intercalation compounds as promising high-capacity cathodes. They exhibit capacities in excess of what would be expected from alkali-ion removal/reinsertion and charge compensation by transition-metal (TM) ions. The additional capacity is provided through charge compensation by oxygen redox chemistry and some oxygen loss. It has been reported previously that oxygen redox occurs in O 2p orbitals that interact with alkali ions in the TM and alkali-ion layers (that is, oxygen redox occurs in compounds containing Li + -O(2p)-Li + interactions). Na 2/3 [Mg 0.28 Mn 0.72 ]O 2 exhibits an excess capacity and here we show that this is caused by oxygen redox, even though Mg 2+ resides in the TM layers rather than alkali-metal (AM) ions, which demonstrates that excess AM ions are not required to activate oxygen redox. We also show that, unlike the alkali-rich compounds, Na 2/3 [Mg 0.28 Mn 0.72 ]O 2 does not lose oxygen. The extraction of alkali ions from the alkali and TM layers in the alkali-rich compounds results in severely underbonded oxygen, which promotes oxygen loss, whereas Mg 2+ remains in Na 2/3 [Mg 0.28 Mn 0.72 ]O 2 , which stabilizes oxygen.

  2. Oxygen redox chemistry without excess alkali-metal ions in Na2/3[Mg0.28Mn0.72]O2

    NASA Astrophysics Data System (ADS)

    Maitra, Urmimala; House, Robert A.; Somerville, James W.; Tapia-Ruiz, Nuria; Lozano, Juan G.; Guerrini, Niccoló; Hao, Rong; Luo, Kun; Jin, Liyu; Pérez-Osorio, Miguel A.; Massel, Felix; Pickup, David M.; Ramos, Silvia; Lu, Xingye; McNally, Daniel E.; Chadwick, Alan V.; Giustino, Feliciano; Schmitt, Thorsten; Duda, Laurent C.; Roberts, Matthew R.; Bruce, Peter G.

    2018-03-01

    The search for improved energy-storage materials has revealed Li- and Na-rich intercalation compounds as promising high-capacity cathodes. They exhibit capacities in excess of what would be expected from alkali-ion removal/reinsertion and charge compensation by transition-metal (TM) ions. The additional capacity is provided through charge compensation by oxygen redox chemistry and some oxygen loss. It has been reported previously that oxygen redox occurs in O 2p orbitals that interact with alkali ions in the TM and alkali-ion layers (that is, oxygen redox occurs in compounds containing Li+-O(2p)-Li+ interactions). Na2/3[Mg0.28Mn0.72]O2 exhibits an excess capacity and here we show that this is caused by oxygen redox, even though Mg2+ resides in the TM layers rather than alkali-metal (AM) ions, which demonstrates that excess AM ions are not required to activate oxygen redox. We also show that, unlike the alkali-rich compounds, Na2/3[Mg0.28Mn0.72]O2 does not lose oxygen. The extraction of alkali ions from the alkali and TM layers in the alkali-rich compounds results in severely underbonded oxygen, which promotes oxygen loss, whereas Mg2+ remains in Na2/3[Mg0.28Mn0.72]O2, which stabilizes oxygen.

  3. High waterborne Mg does not attenuate the toxic effects of Fe, Mn, and Ba on Na+ regulation of Amazonian armored catfish tamoatá (Hoplosternum litoralle).

    PubMed

    Duarte, Rafael M; Benaduce, Ana Paula; Garcia, Luciano; Gomes, Levy C; Gomes, Adriana Chippari; Val, Adalberto L; Baldisserotto, Bernardo

    2018-04-24

    Formation water (FoW) is a by-product from oil and gas production and usually has high concentrations of soluble salts and metals. Calcium (Ca) and magnesium (Mg) have been shown to reduce the toxicity of metals to aquatic animals, and previous study showed that high waterborne Ca exerts mild effect against disturbances on Na + regulation in Amazonian armored catfish tamoatá (Hoplosternum littorale) acutely exposed to high Fe, Mn, and Ba levels. Here, we hypothesized that high Mg levels might also reduce the toxic effects of these metals on Na + regulation of tamoatá. The exposure to 5% FoW promoted an increase in Na + uptake and a rapid accumulation of Na + in all tissues analyzed (kidneyMg lowered Na + efflux rates and markedly inhibited Na + uptake, and also reduced both NKA activity and newly Na + accumulation in gills of fish. High Fe levels increased Na + net losses and inhibited Na + uptake in tamoatá. The diffusive Na + losses and the newly accumulated Na + in gills were reduced in fish exposed to high Mn and Ba. High waterborne Ba also inhibited NKA in gills, while both high Mn and Ba inhibited v-type H + -ATPase in kidney of tamoatá. High Mg did not lessen the toxic effect of Fe on Na + net fluxes, and reduced even more Na + uptake and the newly Na + accumulation in gills and plasma, and did not prevent the inhibition of both NKA and v-type H + -ATPases in kidney. Furthermore, Mg did not attenuate the effect of Mn on inhibition Na + uptake, keeping the activity of v-type H + -ATPase in kidney significantly lowered. High Mg levels mildly attenuated the effects of Ba in Na + balance by increasing the new accumulation of Na + in liver, and restore the activity of both NKA and v-type H + -ATPase in gills of tamoatá. Overall, high waterborne Mg does not have a strong contribution to, or have only minor effects, in protecting

  4. Performance of Al-0.5 Mg-0.02 Ga-0.1 Sn-0.5 Mn as anode for Al-air battery in NaCl solutions

    NASA Astrophysics Data System (ADS)

    Ma, Jingling; Wen, Jiuba; Gao, Junwei; Li, Quanan

    2014-05-01

    In this research, metal-air battery based on Al, Zn, Al-0.5 Mg-0.02 Ga-0.1 Sn and Al-0.5 Mg-0.02 Ga-0.1 Sn-0.5 Mn (wt%) is prepared and the battery performance is investigated by constant current discharge test in 2 mol L-1 NaCl solutions. The characteristics of the anodes after discharge are investigated by electrochemical impedance spectroscopy (EIS), scanning electron microscopy (SEM). The corrosion behavior of the anodes is studied by self-corrosion rate measurement and potentiodynamic polarization measurement. The results show that Al-Mg-Ga-Sn-Mn is more active than Al, Zn and Al-Mg-Ga-Sn anodes. The self-corrosion rate is found to be in the order: Al < Al-Mg-Ga-Sn-Mn < Al-Mg-Ga-Sn < Zn. It has been observed that the Al-air battery based on Al-Mg-Ga-Sn-Mn offers higher operating voltage and anodic utilization than those with others. SEM and EIS results of the alloy are in good agreement with corrosion characteristics.

  5. Adsorption of phosphate from seawater on calcined MgMn-layered double hydroxides.

    PubMed

    Chitrakar, Ramesh; Tezuka, Satoko; Sonoda, Akinari; Sakane, Kohji; Ooi, Kenta; Hirotsu, Takahiro

    2005-10-01

    Adsorptive properties of MgMn-3-300 (MgMn-type layered double hydroxide with Mg/Mn mole ratio of 3, calcined at 300 degrees C) for phosphate were investigated in phosphate-enriched seawater with a concentration of 0.30 mg-P/dm3. It showed the highest phosphate uptake from the seawater among the inorganic adsorbents studied (hydrotalcite, calcined hydrotalcite, activated magnesia, hydrous aluminum oxide, manganese oxide (delta-MnO2)). The phosphate uptake by MgMn-3-300 reached 7.3 mg-P/g at an adsorbent/solution ratio of 0.05 g/2 dm3. The analyses of the uptakes of other constituents (Na+, K+, Ca(+, Cl-, and SO(2-)4) of seawater showed that the adsorbent had a markedly high selectivity for the adsorption of phosphate ions. Effects of initial phosphate concentration, temperature, pH, and salinity on phosphate uptake were investigated in detail by a batch method. The phosphate uptake increased slightly with an increase in the adsorption temperature. The adsorption isotherm followed Freundlich's equation with constants of logK(F)=1.25 and 1/n=0.65, indicating that it could effectively remove phosphate even from a solution of markedly low phosphate concentration as well as with large numbers of coexisting ions. The pH dependence showed a maximum phosphate uptake around pH 8.5. The pH dependence curve suggested that selective phosphate adsorption progresses mainly by the ion exchange of HPO(2-)4. The study on the effect of salinity suggested the presence of two kinds of adsorption sites in the adsorbent: one nonspecific site with weak interaction and one specific site with strong interaction. The effective desorption of phosphate could be achieved using a mixed solution of 5 M NaCl + 0.1 M NaOH (1 M = 1 mol/dm3), with negligible dissolution of adsorbent. The adsorbent had high chemical stability against the adsorption/desorption cycle; it kept a good phosphate uptake even after the repetition of the seventh cycle.

  6. Determination of the Mg/Mn ratio in foraminiferal coatings: An approach to correct Mg/Ca temperatures for Mn-rich contaminant phases

    NASA Astrophysics Data System (ADS)

    Hasenfratz, Adam P.; Martínez-García, Alfredo; Jaccard, Samuel L.; Vance, Derek; Wälle, Markus; Greaves, Mervyn; Haug, Gerald H.

    2017-01-01

    The occurrence of manganese-rich coatings on foraminifera can have a significant effect on their bulk Mg/Ca ratios thereby biasing seawater temperature reconstructions. The removal of this Mn phase requires a reductive cleaning step, but this has been suggested to preferentially dissolve Mg-rich biogenic carbonate, potentially introducing an analytical bias in paleotemperature estimates. In this study, the geochemical composition of foraminifera tests from Mn-rich sediments from the Antarctic Southern Ocean (ODP Site 1094) was investigated using solution-based and laser ablation ICP-MS in order to determine the amount of Mg incorporated into the coatings. The analysis of planktonic and benthic foraminifera revealed a nearly constant Mg/Mn ratio in the Mn coating of ∼0.2 mol/mol. Consequently, the coating Mg/Mn ratio can be used to correct for the Mg incorporated into the Mn phase by using the down core Mn/Ca values of samples that have not been reductively cleaned. The consistency of the coating Mg/Mn ratio obtained in this study, as well as that found in samples from the Panama Basin, suggests that spatial variation of Mg/Mn in foraminiferal Mn overgrowths may be smaller than expected from Mn nodules and Mn-Ca carbonates. However, a site-specific assessment of the Mg/Mn ratio in foraminiferal coatings is recommended to improve the accuracy of the correction.

  7. Spin dependent transport properties of Mn-Ga/MgO/Mn-Ga magnetic tunnel junctions with metal(Mg, Co, Cr) insertion layer

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Liang, S. H.; Tao, L. L.; Liu, D. P., E-mail: dpliu@iphy.ac.cn

    We report a first principles theoretical investigation of spin polarized quantum transport in Mn{sub 2}Ga/MgO/Mn{sub 2}Ga and Mn{sub 3}Ga/MgO/Mn{sub 3}Ga magnetic tunneling junctions (MTJs) with the consideration of metal(Mg, Co, Cr) insertion layer effect. By changing the concentration of Mn, our calculation shows a considerable disparity in transport properties: A tunneling magnetoresistance (TMR) ratio of 852% was obtained for Mn{sub 2}Ga-based MTJs, however, only a 5% TMR ratio for Mn{sub 3}Ga-based MTJs. In addition, the influence of insertion layer has been considered in our calculation. We found the Co insertion layer can increase the TMR of Mn{sub 2}Ga-based MTJ tomore » 904%; however, the Cr insertion layer can decrease the TMR by 668%; A negative TMR ratio can be obtained with Mg insertion layer. Our work gives a comprehensive understanding of the influence of different insertion layer in Mn-Ga based MTJs. It is proved that, due to the transmission can be modulated by the interfacial electronic structure of insertion, the magnetoresistance ratio of Mn{sub 2}Ga/MgO/Mn{sub 2}Ga MTJ can be improved by inserting Co layer.« less

  8. Experimental and theoretical insight into the cooperativity effect in composite wax powder and ternary complex of coronene with CH4 and Mn+ (Mn+ = Li+, Na+, K+, Be2+, Mg2+ or Ca2+)

    NASA Astrophysics Data System (ADS)

    Jiang, Le-tao; Bai, Pei-kang; Wang, Jian-hong; Liu, Bin; Li, Yu-xin

    2018-01-01

    The experimental infrared (IR) spectrum of composite wax powder was investigated. The frequency shifts of the C=C anti-symmetrical stretching mode were observed and the experimental cooperativity effect involving Na+...π interaction was suggested. In order to further reveal the nature of cooperativity effect, the interaction energies in Mn+...coronene...CH4 (Mn+ = Li+, Na+, K+, Be2+, Mg2+ or Ca2+) as the model systems of composite wax powder were calculated by using the B3LYP, M06-2X and MP2 methods with 6-311++G** basis set. The results show that the Mn+...π interactions were strengthened upon the formation of ternary complexes. Although the changes of absolute values of the interactions between CH4 and coronene were not obvious, the relative values were considerably significant upon the formation of ternary complexes. The cooperativity effect was perhaps the reason for the formation of notable advantage of composite wax powder upon the introduction of surfactant with cation into wax powder. Reduced density gradient and atoms-in-molecules analysis confirm the cooperativity effect in Mn+...coronene...CH4, and reveal the nature of the formation of the predominant advantage of composite wax powder.

  9. Chondritic Mn/Na ratio and limited post-nebular volatile loss of the Earth

    NASA Astrophysics Data System (ADS)

    Siebert, Julien; Sossi, Paolo A.; Blanchard, Ingrid; Mahan, Brandon; Badro, James; Moynier, Frédéric

    2018-03-01

    The depletion pattern of volatile elements on Earth and other differentiated terrestrial bodies provides a unique insight as to the nature and origin of planetary building blocks. The processes responsible for the depletion of volatile elements range from the early incomplete condensation in the solar nebula to the late de-volatilization induced by heating and impacting during planetary accretion after the dispersion of the H2-rich nebular gas. Furthermore, as many volatile elements are also siderophile (metal-loving), it is often difficult to deconvolve the effect of volatility from core formation. With the notable exception of the Earth, all the differentiated terrestrial bodies for which we have samples have non-chondritic Mn/Na ratios, taken as a signature of post-nebular volatilization. The bulk silicate Earth (BSE) is unique in that its Mn/Na ratio is chondritic, which points to a nebular origin for the depletion; unless the Mn/Na in the BSE is not that of the bulk Earth (BE), and has been affected by core formation through the partitioning of Mn in Earth's core. Here we quantify the metal-silicate partitioning behavior of Mn at deep magma ocean pressure and temperature conditions directly applicable to core formation. The experiments show that Mn becomes more siderophile with increasing pressure and temperature. Modeling the partitioning of Mn during core formation by combining our results with previous data at lower P-T conditions, we show that the core likely contains a significant fraction (20 to 35%) of Earth's Mn budget. However, we show that the derived Mn/Na value of the bulk Earth still lies on the volatile-depleted end of a trend defined by chondritic meteorites in a Mn/Na vs Mn/Mg plot, which tend to higher Mn/Na with increasing volatile depletion. This suggests that the material that formed the Earth recorded similar chemical fractionation processes for moderately volatile elements as chondrites in the solar nebula, and experienced limited post

  10. Mild hydrothermal crystal growth of new uranium(IV) fluorides, Na{sub 3.13}Mg{sub 1.43}U{sub 6}F{sub 30} and Na{sub 2.50}Mn{sub 1.75}U{sub 6}F{sub 30}: Structures, optical and magnetic properties

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Yeon, Jeongho; Smith, Mark D.; Tapp, Joshua

    Two new uranium(IV) fluorides, Na{sub 3.13}Mg{sub 1.43}U{sub 6}F{sub 30} (1) and Na{sub 2.50}Mn{sub 1.75}U{sub 6}F{sub 30} (2), were synthesized through an in situ mild hydrothermal route, and were structurally characterized by single crystal X-ray diffraction. The compounds exhibit complex crystal structures composed of corner- or edge-shared UF{sub 9} and MF{sub 6} (M=Mg, Mn) polyhedra, forming hexagonal channels in the three-dimensional framework, in which ordered or disordered divalent metal and sodium atoms reside. The large hexagonal voids contain the nearly regular M(II)F{sub 6} octahedra and sodium ions, whereas the small hexagonal cavities include M(II) and sodium ions on a mixed-occupied site.more » Magnetic susceptibility measurements yielded effective magnetic moments of 8.36 and 11.6 µ{sub B} for 1 and 2, respectively, confirming the presence and oxidation states of U(IV) and Mn(II). The large negative Weiss constants indicate the spin gap between a triplet and a singlet state in the U(IV). Magnetization data as a function of applied fields revealed that 2 exhibits paramagnetic behavior due to the nonmagnetic singlet ground state of U(IV) at low temperature. UV–vis diffuse reflectance and X-ray photoelectron spectroscopy data were also analyzed. - Graphical abstract: Two new quaternary U(IV) fluorides, Na{sub 3.13}Mg{sub 1.43}U{sub 6}F{sub 30} and Na{sub 2.50}Mn{sub 1.75}U{sub 6}F{sub 30}, were crystallized via an in situ reduction step of U(VI) to U(IV) under mild hydrothermal conditions. The compounds show complex crystal structures based on the 3-D building block of U{sub 6}F{sub 30}. Magnetic property measurements revealed that the U(IV) exhibits a nonmagnetic singlet ground state at low temperature with a spin gap. - Highlights: • Na{sub 3.13}Mg{sub 1.43}U{sub 6}F{sub 30} and Na{sub 2.50}Mn{sub 1.75}U{sub 6}F{sub 30} have been synthesized and characterized. • The U(IV) fluorides exhibit complex three-dimensional crystal structures.

  11. Mild hydrothermal crystal growth of new uranium(IV) fluorides, Na3.13Mg1.43U6F30 and Na2.50Mn1.75U6F30: Structures, optical and magnetic properties

    NASA Astrophysics Data System (ADS)

    Yeon, Jeongho; Smith, Mark D.; Tapp, Joshua; Möller, Angela; zur Loye, Hans-Conrad

    2016-04-01

    Two new uranium(IV) fluorides, Na3.13Mg1.43U6F30 (1) and Na2.50Mn1.75U6F30 (2), were synthesized through an in situ mild hydrothermal route, and were structurally characterized by single crystal X-ray diffraction. The compounds exhibit complex crystal structures composed of corner- or edge-shared UF9 and MF6 (M=Mg, Mn) polyhedra, forming hexagonal channels in the three-dimensional framework, in which ordered or disordered divalent metal and sodium atoms reside. The large hexagonal voids contain the nearly regular M(II)F6 octahedra and sodium ions, whereas the small hexagonal cavities include M(II) and sodium ions on a mixed-occupied site. Magnetic susceptibility measurements yielded effective magnetic moments of 8.36 and 11.6 μB for 1 and 2, respectively, confirming the presence and oxidation states of U(IV) and Mn(II). The large negative Weiss constants indicate the spin gap between a triplet and a singlet state in the U(IV). Magnetization data as a function of applied fields revealed that 2 exhibits paramagnetic behavior due to the nonmagnetic singlet ground state of U(IV) at low temperature. UV-vis diffuse reflectance and X-ray photoelectron spectroscopy data were also analyzed.

  12. Oxidation of MnO(100) and NaMnO2 formation: Characterization of Mn2+ and Mn3+ surfaces via XPS and water TPD

    NASA Astrophysics Data System (ADS)

    Feng, Xu; Cox, David F.

    2018-09-01

    The oxidation of clean and Na precovered MnO(100) has been investigated by X-ray photoelectron spectroscopy (XPS), low energy electron diffraction (LEED) and temperature programmed desorption (TPD) of adsorbed water. XPS results indicate that Mn3O4-like and Mn2O3-like surfaces can be formed by various oxidation treatments of clean and nearly-stoichiometric MnO(100), while a NaMnO2-like surface can be produced by the oxidation of MnO(100) pre-covered with multilayers of metallic Na. Water TPD results indicate that water adsorption/desorption is sensitive to the available oxidation states of surface Mn cations, and can be used to distinguish between surfaces exposing Mn2+and Mn3+ cations, or a combination of these oxidation states. Carbon dioxide and water TPD results from the NaMnO2-like surface indicate that pre-adsorbed water blocks the uptake of CO2, while water displaces pre-adsorbed CO2. No indication of a strong reactive interaction is observed between CO2, water and the NaMnO2-like surface under the conditions of our study.

  13. Effect of Extrusion Parameters on Texture and Microstructure Evolution of Extruded Mg-1 pctMn and Mg-1 pctMn-Sr Alloys

    NASA Astrophysics Data System (ADS)

    Borkar, Hemant; Pekguleryuz, Mihriban

    2015-01-01

    Three Mg alloys Mg-1 pctMn (M1), Mg-1 pctMn-1.3 pctSr, and Mg-1 pctMn-2.1 pctSr were subjected to two different extrusion temperatures and two different extrusion speeds in lab-scale extrusion. The extrusion temperatures of 573 K and 673 K (300 °C and 400 °C) and two ram speeds of 4 and 8 mm/s were used at constant extrusion ratio of 7. M1 exhibited strong basal texture after extrusion at 673 K (400 °C) at higher speed. At 573 K (300 °C), recrystallization in all alloys takes place completely or partially by continuous dynamic recrystallization mechanism, while particle stimulated nucleation (PSN) occurs in all M1-Sr alloys at both extrusion temperatures and speeds. At 673 K (400 °C), grain boundary bulging is the only recrystallization mechanism in alloy M1, while it occurs in combination with PSN in M1-Sr alloys. The effect of texture weakening by PSN is more significant in M1-Sr alloys extruded at 573 K (400 °C). The plant extrusion trials were carried out on Mg-1 pctMn, Mg-1 pctMn-0.3 pctSr, and Mg-1 pctMn-2.1 pctSr at 623 K (350 °C) with different speeds than in lab-scale extrusion. M1 alloy exhibited strong basal texture at both speeds, while Sr additions of 0.3 and 2.1 pct promoted similar amount of texture weakening.

  14. Mn2+ concentration manipulated red emission in BaMg2Si2O7:Eu2+,Mn2+

    NASA Astrophysics Data System (ADS)

    Ye, Song; Zhang, Jiahua; Zhang, Xia; Lu, Shaozhe; Ren, Xinguang; Wang, Xiaojun

    2007-02-01

    The luminescent properties of concentration dependence are reported in BaMg2Si2O7:Eu2+,Mn2+ red phosphor. It is observed that the broad red emission of Mn2+ consists of two bands, located at 620 and 675 nm, respectively, which are attributed to two different Mn2+ centers [Mn2+(I) and Mn2+(II)] substituting for two nonidentical Mg2+ sites [Mg2+(I) and Mg2+(II)] in the host. It is also found that the relative emission intensity of the Mn2+(II) to the Mn2+(I) increases with increasing Mn2+ concentration, leading to a red-shift of the overall emission. A detail analysis on the energy transfer from Eu2+ to the two Mn2+ centers is presented, which indicates that the number ratio of Mn2+(II) to Mn2+(I) increases with increasing Mn2+ concentration. This result is interpreted by the preferential formation of Mn2+(I) substituting for Mg2+(I) site. Based on energy transfer, the emission intensity ratios of Mn2+(I) to Eu2+ and Mn2+(II) to Eu2+, which is Mn2+ concentration dependent, are calculated using related fluorescence lifetimes. The calculated results are in good agreement with that obtained experimentally in the emission spectra.

  15. Temperature dependent luminescence and energy transfer properties of Na2SrMg(PO4)2:Eu2+, Mn2+ phosphors.

    PubMed

    Geng, Dongling; Shang, Mengmeng; Zhang, Yang; Lian, Hongzhou; Lin, Jun

    2013-11-21

    Eu(2+) singly and Eu(2+)/Mn(2+) co-doped Na2SrMg(PO4)2 (NSMP) phosphors have been prepared via a high-temperature solid-state reaction process. Upon UV excitation of 260-360 nm, the NSMP:xEu(2+) phosphors exhibit a violet band located at 399 nm and a blue band centered at 445 nm, which originate from Eu(2+) ions occupying two different crystallographic sites: Eu(2+)(I) and Eu(2+)(II), respectively. Excitation wavelengths longer than 380 nm can selectively excite Eu(2+)(II) to emit blue light. Energy transfer processes in the Eu(2+)(I)-Eu(2+)(II) and Eu(2+)-Mn(2+) pairs have been observed and investigated by luminescence spectra and decay curves. The emission color of as-prepared samples can be tuned by changing the relative concentrations of Eu(2+) and Mn(2+) ions and adjusting the excitation wavelength. Under UV excitation of 323 nm, the absolute quantum yield of NSMP:0.005Eu(2+) is 91%, which is higher than most of the other Eu(2+)-doped phosphors reported previously. The temperature dependent luminescence properties and decay curves (4.3-450 K) of NSMP:Eu(2+) and NSMP:Eu(2+), Mn(2+) phosphors have been studied in detail. Thermal quenching of Eu(2+) has been observed while the emission band of Mn(2+) shows a blue-shift and an abnormal increase of intensity with increasing temperature. The unusual thermal quenching behavior indicates that the NSMP compound can serve as a good lattice host for Mn(2+) ions which can be used as a red-emitting phosphor. Additionally, the lifetimes for Eu(2+)(I) and Eu(2+)(II) increase with increasing temperatures.

  16. The Enhancement of Mg Corrosion Resistance by Alloying Mn and Laser-Melting

    PubMed Central

    Yang, Youwen; Wu, Ping; Wang, Qiyuan; Wu, Hong; Liu, Yong; Deng, Youwen; Zhou, Yuanzhuo; Shuai, Cijun

    2016-01-01

    Mg has been considered a promising biomaterial for bone implants. However, the poor corrosion resistance has become its main undesirable property. In this study, both alloying Mn and laser-melting were applied to enhance the Mg corrosion resistance. The corrosion resistance, mechanical properties, and microstructure of rapid laser-melted Mg-xMn (x = 0–3 wt %) alloys were investigated. The alloys were composed of dendrite grains, and the grains size decreased with increasing Mn. Moreover, Mn could dissolve and induce the crystal lattice distortion of the Mg matrix during the solidification process. Mn ranging from 0–2 wt % dissolved completely due to rapid laser solidification. As Mn contents further increased up to 3 wt %, a small amount of Mn was left undissolved. The compressive strength of Mg-Mn alloys increased first (up to 2 wt %) and then decreased with increasing Mn, while the hardness increased continuously. The refinement of grains and the increase in corrosion potential both made contributions to the enhancement of Mg corrosion resistance. PMID:28773342

  17. Metallic elements (Ca, Hg, Fe, K, Mg, Mn, Na, Zn) in the fruiting bodies of Boletus badius.

    PubMed

    Kojta, Anna K; Falandysz, Jerzy

    2016-06-01

    The aim of this study was to investigate and compare the levels of eight metallic elements in the fruiting bodies of Bay Bolete (Boletus badius; current name Imleria badia) collected from ten sites in Poland to understand better the value of this popular mushroom as an organic food. Bay Bolete fruiting bodies were collected from the forest area near the towns and villages of Kętrzyn, Poniatowa, Bydgoszcz, Pelplin, Włocławek, Żuromin, Chełmno, Ełk and Wilków communities, as well as in the Augustów Primeval Forest. Elements such as Ca, Fe, K, Mg, Mn, Na and Zn were analyzed by inductively coupled plasma atomic emission spectroscopy (ICP-OES), and mercury by cold vapor atomic absorption spectrometry (CV-AAS). This made it possible to assess the nutritional value of the mushroom, as well as possible toxicological risks associated with its consumption. The results were subjected to statistical analysis (Kruskal-Wallis test, cluster analysis, principal component analysis). Copyright © 2016 Elsevier Ltd. All rights reserved.

  18. Simultaneous stabilization/solidification of Mn2+ and NH4+-N from electrolytic manganese residue using MgO and different phosphate resource.

    PubMed

    Shu, Jiancheng; Wu, Haiping; Liu, Renlong; Liu, Zuohua; Li, Bing; Chen, Mengjun; Tao, Changyuan

    2018-02-01

    This study examined simultaneous stabilization and solidification (S/S) of Mn 2+ and NH 4 + -N from electrolytic manganese residue (EMR) using MgO and different phosphate resource. The characteristics of EMR NH 4 + -N and Mn 2+ S/S behavior, S/S mechanisms, leaching test and economic analysis, were investigated. The results show that the S/S efficiency of Mn 2+ and NH 4 + -N could reach 91.58% and 99.98%, respectively, and the pH value is 8.75 when the molar ratio of Mg:P is 3:1 and the dose of PM (MgO and Na 3 PO 4 ·12H 2 O) is 8wt%. In this process, Mn 2+ could mainly be stabilized in the forms of Mn(H 2 PO 4 ) 2 ·2H 2 O, Mn 3 (PO 4 ) 2 ·3H 2 O, Mn(OH) 2 , and MnOOH, and NH 4 + -N in the form of NH 4 MgPO 4 ·6H 2 O. Economic evaluation indicates that using PM process has a lower cost than HPM and HOM process for the S/S of Mn 2+ and NH 4 + -N from EMR at the same stabilization agent dose. Leaching test values of all the measured metals are within the permitted level for the GB8978-1996 test suggested when the dose of PM, HPM and HOM is 8wt%. Copyright © 2017 Elsevier Inc. All rights reserved.

  19. Synthetic control of manganese birnessite: Impact of crystallite size on Li, Na, and Mg based electrochemistry

    DOE PAGES

    Yin, Jiefu; Takeuchi, Esther S.; Takeuchi, Kenneth J.; ...

    2016-08-12

    We demonstrated the synthesis and characterization of Mg-birnessite (Mg xMnO 2) with different crystallite sizes, prepared though low temperature precipitation and ion exchange. The influence of crystallite size on electrochemical performance of Mg-birnessite was studied for the first time, where material with smaller crystallite size was demonstrated to have enhanced capacity and rate capability in Li ion, Na ion, and Mg ion based electrolytes. Cation diffusion using GITT type testing demonstrated the ion diffusion coefficient of Mg 2+ was ~10× lower compared with Li + and Na +. This work illustrates that tuning of inorganic materials properties can lead tomore » significant enhancement of electrochemical performance in lithium, sodium as well as magnesium based batteries for materials such as Mg-birnessite and provides a deliberate approach to improve electrochemical performance.« less

  20. Effect of Mn and Fe on the Formation of Fe- and Mn-Rich Intermetallics in Al-5Mg-Mn Alloys Solidified Under Near-Rapid Cooling.

    PubMed

    Liu, Yulin; Huang, Gaoren; Sun, Yimeng; Zhang, Li; Huang, Zhenwei; Wang, Jijie; Liu, Chunzhong

    2016-01-29

    Mn was an important alloying element used in Al-Mg-Mn alloys. However, it had to be limited to a low level (<1.0 wt %) to avoid the formation of coarse intermetallics. In order to take full advantage of the benefits of Mn, research was carried out to investigate the possibility of increasing the content of Mn by studying the effect of cooling rate on the formation of Fe- and Mn-rich intermetallics at different content levels of Mn and Fe. The results indicated that in Al-5Mg-Mn alloy with low Fe content (<0.1 wt %), intermetallic Al₆(Fe,Mn) was small in size and amount. With increasing Mn content, intermetallic Al₆(Fe,Mn) increased, but in limited amount. In high-Fe-containing Al-5Mg-Mn alloys (0.5 wt % Fe), intermetallic Al₆(Fe,Mn) became the dominant phase, even in the alloy with low Mn content (0.39 wt %). Cooling rate played a critical role in the refinement of the intermetallics. Under near-rapid cooling, intermetallic Al₆(Fe,Mn) was extremely refined. Even in the high Mn and/or high-Fe-containing alloys, it still demonstrated fine Chinese script structures. However, once the alloy composition passed beyond the eutectic point, the primary intermetallic Al₆(Fe,Mn) phase displayed extremely coarse platelet-like morphology. Increasing the content of Fe caused intermetallic Al₆(Fe,Mn) to become the primary phase at a lower Mn content.

  1. Efficient rare-earth free red-emitting Ca2YSbO6:Mn4+,M(M = Li+, Na+, K+, Mg2+) phosphors for white light-emitting diodes.

    PubMed

    Zhong, Jiasong; Chen, Daqin; Chen, Xiao; Wang, Keyuan; Li, Xinyue; Zhu, Yiwen; Ji, Zhenguo

    2018-05-08

    Owing to its low-cost and satisfactory luminescent-emission performance in warm white light-emitting diodes (w-LEDs), the non-rare-earth Mn4+-activated red phosphor has become a promising competitor of commercial rare-earth doped phosphor. In this study, a series of novel red-light emitting phosphors based on Ca2YSbO6:Mn4+ have been developed successfully by a conventional solid-state reaction. The structural and luminescent properties of these phosphors are systematically investigated. The as-prepared Ca2YSbO6:Mn4+ product exhibits a broad excitation band ranging from 250 to 600 nm and an abnormal intense deep-red emission centered at 680 nm with a full width at half maximum (FWHM) of ∼46 nm. The optimal Mn4+ doping concentration is about 0.3 mol%, and the concentration quenching mechanism is determined to be a dipole-dipole interaction. Impressively, the Ca2YSbO6:0.003Mn4+ phosphor shows an outstanding quantum efficiency of 62.6% and an excellent thermal stability. In addition, the effect of Li+, Mg2+, Na+ and K+ dopants on the luminescent properties of Mn4+-doped Ca2YSbO6 phosphors is elucidated. Furthermore, by employing the as-prepared Ca2YSbO6:Mn4+ as a red component, a warm w-LED with high color rendering index (Ra = 87.5) and low correlated color temperature (CCT = 3255 K) can be acquired. It is believed that the present phosphor has a potential application as a supplement of the red component for warm w-LEDs.

  2. Fabrication of Na0.7MnO2/C composite cathode material by simple heat treatment for high-power na-ion batteries

    NASA Astrophysics Data System (ADS)

    Sohn, DongRak; Lim, Sung-Jin; Nam, Do-Hwan; Hong, Kyung-Sik; Kim, Tae-Hee; Oh, SeKwon; Eom, Ji-Yong; Cho, EunAe; Kwon, HyukSang

    2018-01-01

    A Na0.7MnO2/C composite cathode material is synthesized by simple and costeffective two-step heat treatment for an improvement in the rate capability of Na0.7MnO2. The first heat treatment is to synthesize Na0.7MnO2, and the second one is a low temperature annealing at 350 °C for 1 h in air, which is necessary to suppress an interfacial reaction between the Na0.7MnO2 and C in the synthesis process of Na0.7MnO2/C composite. Structural analyses by XRD and XPS reveal that the Na0.7MnO2/C shows the same structural properties as that of the pristine Na0.7MnO2, and hence they exhibit the same initial discharge capacity of 175 mAh g-1 at 20 mA g-1. At a current density of 400 mA g-1, the discharge capacity of Na0.7MnO2 reduces to 50 mAh g-1 (28% of the initial discharge capacity), whereas that of Na0.7MnO2/C reduces to 108 mAh g-1 (61% of the initial discharge capacity). The enhanced rate capability of the Na0.7MnO2/C is attributed to the conductive carbon layer formed on the surface of Na0.7MnO2 particles, enabling the facile transport of electrons from the current collector to the surface of the Na0.7MnO2 particles. [Figure not available: see fulltext.

  3. Triple Halide Bridges in Chiral MnII2MnIII6NaI2 Cages: Structural and Magnetic Characterization.

    PubMed

    Mayans, Júlia; Font-Bardia, Mercè; Escuer, Albert

    2018-02-05

    A family of decanuclear chiral clusters with a Mn II 2 Mn III 6 Na I 2 core have been synthesized from enantiomerically pure Schiff bases. The new systems consist of two Mn II Mn III 3 Na I units linked by rare triple chloro or bromo bridges between the divalent Mn cations. Susceptibility measurements point out the weak antiferromagnetic interaction mediated by these kinds of bridges and afford the first magnetic measurements for the (μ-Br) 3 case.

  4. The enhancement of anomalous Hall effect by inserting MgO layer in perpendicular anisotropic Pd/Co2MnSi/MgO/Pd films

    NASA Astrophysics Data System (ADS)

    Fu, H. R.; Ma, L.; Tian, N.; You, C. Y.; Wang, K.

    2018-05-01

    A systematic study of anomalous Hall effect (AHE) was performed in perpendicular magnetic anisotropic Pd/Co2MnSi(tCMS)/MgO/Pd films. The AHE was significantly intensified by inserting MgO layer, which can be ascribed to the enhancement of spin-orbit coupling and interfacial scattering contribution. Moreover, it was found that the Co and Mn ions were reduced at the interface of Co2MnSi/MgO with annealing process. The stable amount of Mn-O bonding was observed at the Co2MnSi/MgO interface after annealing, implying that the proper Mn-O bonding could be favorable for achieving large AHE.

  5. Structural transition in Mg-doped LiMn 2O 4: a comparison with other M-doped Li-Mn spinels

    NASA Astrophysics Data System (ADS)

    Capsoni, Doretta; Bini, Marcella; Chiodelli, Gaetano; Massarotti, Vincenzo; Mozzati, Maria Cristina; Azzoni, Carlo B.

    2003-01-01

    The charge distribution in the Mg-doped lithium manganese spinel Li 1.02Mg xMn 1.98- xO 4 with 0.00< x≤0.20 is discussed and compared to those pertinent to other M-doped samples (M=Ni 2+, Co 3+, Cr 3+, Al 3+ and Ga 3+). EPR spectra, low temperature X-ray diffraction and conductivity data are related to the cooperative Jahn-Teller (J-T) transition occurring at about 280 K in the undoped sample. The sensitivity of the cationic sublattice in displaying electronic and magnetic changes after substitution is remarked. The inhibition of the J-T transition is related to the ratio r=|Mn 4+|/|Mn 3+| as deduced from the charge distribution model [Li 1- xt+Mg xt2+] tetr[Li y+ xt+Mg xo2+Mn 1-3 y-2 x3+Mn 1+2 y+ x4+] octa where x= xo+ xt. For y=0.02 and x=0.02, a value r=1.177 is obtained, very close to rlim=1.18, the limit value beyond which the transition is inhibited.

  6. Crafting ferromagnetism in Mn-doped MgO surfaces with p-type defects

    PubMed Central

    Panigrahi, Puspamitra; Araujo, C Moyses; Hussen, Tanveer; Ahuja, Rajeev

    2014-01-01

    We have employed first-principles calculations based on density functional theory (DFT) to investigate the underlying physics of unusual magnetism in Mn-doped MgO surface. We have studied two distinct scenarios. In the first one, two Mn atoms are substitutionally added to the surface, occupying the Mg sites. Both are stabilized in the Mn valence state carrying a local moment of 4.3 having a high-spin configuration. The magnetic interaction between the local moments display a very short-ranged characteristic, decaying very quickly with distance, and having antiferromagnetic ordering lower in energy. The energetics analysis also indicates that the Mn ions prefer to stay close to each other with an oxygen atom bridging the local interaction. In the second scenario, we started exploring the effect of native defects on the magnetism by crafting both Mg and O vacancies, which are p- and n-type defects, respectively. It is found that the electrons and holes affect the magnetic interaction between Mn ions in a totally different manner. The n-type defect leads to very similar magnetism, with the AFM configuration being energetically preferred. However, in the presence of Mg vacancy, the situation is quite different. The Mn atoms are further oxidized, giving rise to mixed Mn(d) ionic states. As a consequence, the Mn atoms couple ferromagnetically, when placed in the close configuration, and the obtained electronic structure is coherent with the double-exchange type of magnetic interaction. To guarantee the robustness of our results, we have benchmarked our calculations with three distinct theory levels, namely DFT-GGA, DFT-GGA+U and DFT-hybrid functionals. On the surface, the Mg vacancy displays lower formation energy occurring at higher concentrations. Therefore, our model systems can be the basis to explain a number of controversial results regarding transition metal doped oxides. PMID:27877684

  7. Kinetic parameters and structural variations in Cu-Al-Mn and Cu-Al-Mn-Mg shape memory alloys

    NASA Astrophysics Data System (ADS)

    Canbay, Canan Aksu

    2017-02-01

    In this work polycrystalline Cu-Al-Mn and Cu-Al-Mn-Mg SMAs were fabricated by arc melting. The thermal analysis was made to determine the characteristic transformation temperatures of the samples and kinetic parameters. Also the effect of Mg on transformation temperatures and kinetic parameters detected. The structural analysis was made to designate the diffraction planes of martensite phase at room temperature and this was supported by optical measurement observations.

  8. Laser-induced chemiluminescence of NaMg

    NASA Astrophysics Data System (ADS)

    Benard, D. J.; Michels, H. H.

    1982-03-01

    An unstructured continuum emission around 670 nm was observed when Mg was added to an optically pumped heat pipe containing Na and K vapor, in good agreement with ab initio calculations of the NaMg potential energy curves. The corresponding excitation spectrum showed that the incident radiation was observed by NaK molecules (X → C transitions).

  9. Absorption Spectra of Fe, Mn, and Mg Water Complexes Calculated Using Density Functional Theory

    DTIC Science & Technology

    2013-08-20

    Naval Research Laboratory Washington, DC 20375-5320 NRL/MR/6390--13-9479 Absorption Spectra of Fe, Mn, and Mg Water Complexes Calculated Using ...ABSTRACT c. THIS PAGE 18. NUMBER OF PAGES 17. LIMITATION OF ABSTRACT Absorption Spectra of Fe, Mn, and Mg Water Complexes Calculated Using Density...structure associated with Fe, Mn, and Mg water complexes using time-dependent density functional theory (TD-DFT). Calculation of excited state resonance

  10. Polaronic and ionic conduction in NaMnO2: influence of native point defects

    NASA Astrophysics Data System (ADS)

    Zhu, Zhen; Peelaers, Hartwin; van de Walle, Chris G.

    Layered NaMnO2 has promising applications as a cathode material for sodium ion batteries. We will discuss strategies to improve the electrical performance of NaMnO2, including how to optimize the conditions of synthesis and how impurity doping affects the performance. Using hybrid density functional theory, we explored the structural, electronic, and defect properties of bulk NaMnO2. It is antiferromagnetic in the ground state with a band gap of 3.75 eV. Small hole and electron polarons can form in the bulk either through self-trapping or adjacent to point defects. We find that both Na and Mn vacancies are shallow acceptors with the induced holes trapped as small polarons, while O vacancies are deep defect centers. Cation antisites, especially MnNa, are found to have low formation energies. As a result, we expect that MnNa exists in as-grown NaMnO2 in moderate concentrations, rather than forming only at a later stage of the charging process, at which point it causes undesirable structural phase transitions. Both electronic conduction, via polaron hopping, and ionic conduction, through VNa migration, are significantly affected by the presence of point defects. This work was supported by DOE.

  11. Interface formation of epitaxial MgO/Co2MnSi(001) structures: Elemental segregation and oxygen migration

    NASA Astrophysics Data System (ADS)

    McFadden, Anthony; Wilson, Nathaniel; Brown-Heft, Tobias; Pennachio, Daniel; Pendharkar, Mihir; Logan, John A.; Palmstrøm, Chris J.

    2017-12-01

    The interface formation in epitaxial MgO /Co2MnSi (001) films was studied using in-situ X-ray photoelectron spectroscopy (XPS). MgO was deposited on single crystal Co2MnSi (001) layers using e-beam evaporation: a technique which is expected to oxidize the Co2MnSi layer somewhat due to the rise in oxygen partial pressure during MgO deposition while leaving the deposited MgO oxygen deficient. Not unexpectedly, we find that e-beam evaporation of MgO raises the oxygen background in the deposition chamber to a level that readily oxidizes the Co2MnSi surface, with oxygen bonding preferentially to Mn and Si over Co. Interestingly, this oxidation causes an elemental segregation, with Mn-Si effectively moving toward the surface, resulting in an MgO /Co2MnSi interface with a composition significantly differing from the original surface of the unoxidized Co2MnSi film. As MgO is deposited on the oxidized Co2MnSi , the Mn-oxides are reduced, while the Si oxide remains, and is only somewhat reduced after additional annealing in ultrahigh vacuum. Annealing after the MgO is grown on Co2MnSi causes oxygen to move away from the oxidized Co2MnSi interface toward the surface and into the MgO. This observation is consistent with an increase in the tunneling magnetoresistance ratio with post-growth annealing measured in fabricated magnetic tunnel junctions (MTJs). The findings are discussed in light of fabrication of MgO/Heusler based MTJs, where the exponential decay of tunneling probability with contact separation exemplifies the importance of the ferromagnet/tunnel barrier interface.

  12. CeLa enhanced corrosion resistance of Al-Cu-Mn-Mg-Fe alloy for lithium battery shell

    NASA Astrophysics Data System (ADS)

    Du, Jiandi; Ding, Dongyan; Zhang, Wenlong; Xu, Zhou; Gao, Yongjin; Chen, Guozhen; Chen, Weigao; You, Xiaohua; Chen, Renzong; Huang, Yuanwei; Tang, Jinsong

    2017-11-01

    Effects of CeLa addition on the localized corrosion and electrochemical corrosion behavior of Al-Cu-Mn-Mg-Fe lithium battery shell alloy were investigated by immersion testing and electrochemical testing in 0.6 M NaCl solution at different temperatures. Experimental results indicated that CeLa addition resulted in the formation of AlCuCe/La (Al8Cu4Ce and Al6Cu6La) local cathodes and corrosion activity of the main intermetallic particles decreased in the order of Al2CuMg, AlCuCe/La, Al6(Mn, Fe). Corrosion potential shifted positively due to CeLa alloying. Corrosion current density of the CeLa-containing alloy was lower than that of the CeLa-free alloy at room temperature. At room temperature, there was no obvious surface passivation for both alloys. At 80 °C CeLa addition resulted in a wide passive region at the anode polarization region. Electrochemical impedance spectroscopy (EIS) analysis also indicated that corrosion resistance of the CeLa-containing alloy was much higher than that of the CeLa-free alloy.

  13. Effect of MgO and MnO on Phosphorus Utilization in P-Bearing Steelmaking Slag

    NASA Astrophysics Data System (ADS)

    Lin, Lu; Bao, Yan-Ping; Wang, Min; Li, Xiang

    2016-04-01

    In order to recycle the phosphorus in P-bearing converter slag and make it used as slag phosphate fertilizer, the effect of MgO and MnO in P-bearing steelmaking slag on phosphorus existence form, P2O5 solubility and magnetic separation behavior were researched systematically. The results show that the phosphorus in slag is mainly in the form of n2CaO · SiO2-3CaO · P2O5 (for short nC2S-C3P) solid solution in the P-rich phase for CaO-SiO2-FetO-P2O5-X (X stands for MgO and MnO, respectively). And the increasing of MgO and MnO content has no influence on precipitation of nC2S-C3P solid solution in slag, MnO and MgO mainly enter into RO phase and base phase to form MnFe2O4 and MgFe2O4, which has little effect on the P2O5 content of P-rich phase, so which has little effect on the degree of phosphorus enrichment and phosphorus occurrence form of the P-bearing slag. And adding MgO and MnO into CaO-SiO2-P2O5-Fe2O3 slag system can break the complex net structure formed by Si-O on certain degree, and also hinder the precipitation of β-Ca3(PO4)2 crystal with low citric acid solubility during the melting-cooling process. Therefore, adding appropriate MgO and MnO content into slag can improve the slag P2O5 solubility, but the effect of different amounts of MgO and MnO on the P2O5 solubility has little difference. Meanwhile, adding MgO and MnO into slag can improve the metallization of slag and magnetism of iron-rich phase, make the magnetic substances content increase and separation of phosphorus and iron incomplete, so it is adverse to phosphorus resources recovery from P-bearing slag by magnetic separation method. In order to recycle the phosphorus in P-bearing converter slag, the MgO and MnO content in the P-bearing slag should be controlled in the steelmaking process.

  14. Synthesis and electrochemical characterizations of spinel LiMn1.94MO4 (M = Mn0.06, Mg0.06, Si0.06, (Mg0.03Si0.03)) compounds as cathode materials for lithium-ion batteries

    NASA Astrophysics Data System (ADS)

    Zhao, Hongyuan; Liu, Xingquan; Cheng, Cai; Li, Qiang; Zhang, Zheng; Wu, Yue; Chen, Bing; Xiong, Weiqiang

    2015-05-01

    The spinel LiMn1.94MO4 (M = Mn0.06, Mg0.06, Si0.06, (Mg0.03Si0.03)) compounds are successfully synthesized by citric acid-assisted sol-gel method. The crystal structures and morphologies of synthesized compounds are characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM) and transmission electron microscopy (TEM), respectively. All the compounds possess the cubic spinel structure of LiMn2O4 with space group of Fd-3m. The electrochemical properties of synthesized compounds are investigated by galvanostatic charge-discharge test, cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). The results show that the Si-doping can increase the discharge capacity of LiMn2O4 due to the more expanded and regular MnO6 octahedra. In particular, for the LiMn1.94Mg0.03Si0.03O4 compound, the addition of Si4+ ions can make up for the shortage of Mg-doping in term of the discharge capacity. As a result, the Mg2+ and Si4+ co-doping has the effect of synergistic enhancement, which can make full use of the respective advantages of Mg-doping and Si-doping. The optimal LiMn1.94Mg0.03Si0.03O4 can deliver the initial discharge capacity of 128.3 mAh g-1 with good capacity retention of 92.8% after 100 cycles at 0.5 C in the voltage range of 3.20-4.35 V. Compared with the undoped LiMn2O4, the co-doped compound also presents superior rate performance, especially the capacity recovery performance.

  15. NASICON-related Na3.4Mn0.4Fe1.6(PO4)3

    PubMed Central

    Yatskin, Michael M.; Strutynska, Nataliya Yu.; Baumer, Vyacheslav N.; Ogorodnyk, Ivan V.; Slobodyanik, Nikolay S.

    2012-01-01

    The solid solution, sodium [iron(III)/manganese(II)] tris­(orthophosphate), Na3.4Mn0.4Fe1.6(PO4)3, was obtained using a flux method. Its crystal structure is related to that of NASICON-type compounds. The [(Mn/Fe)2(PO4)3] framework is built up from an (Mn/Fe)O6 octa­hedron (site symmetry 3.), with a mixed Mn/Fe occupancy, and a PO4 tetra­hedron (site symmetry .2). The Na+ cations are distributed over two partially occupied sites in the cavities of the framework. One Na+ cation (site symmetry -3.) is surrounded by six O atoms, whereas the other Na+ cation (site symmetry .2) is surrounded by eight O atoms. PMID:22807697

  16. Lavoisierite, Mn2+ 8[Al10(Mn3+Mg)][Si11P]O44(OH)12, a new mineral from Piedmont, Italy: the link between "ardennite" and sursassite

    NASA Astrophysics Data System (ADS)

    Orlandi, Paolo; Biagioni, Cristian; Pasero, Marco; Mellini, Marcello

    2013-03-01

    The new mineral species lavoisierite, ideally Mn2+ 8[Al10(Mn3+Mg)][Si11P]O44(OH)12, has been discovered in piemontite-bearing micaschists belonging to the Piedmontese Nappe from Punta Gensane, Viù Valley, Western Alps, Italy. It occurs as yellow-orange acicular to prismatic-tabular crystals up to a few millimeters in length, with white streak and vitreous luster, elongated along [010] and flattened on {001}. Lavoisierite is associated with quartz, "mica," sursassite, piemontite, spessartine, braunite, and "tourmaline." Calculated density is 3.576 g cm-3. In plane-polarized light, it is transparent, pleochroic, with pale yellow parallel to [010] and yellow-orange normal to this direction; extinction is parallel and elongation is positive. Birefringence is moderate; the calculated average refraction index n is 1.750. Lavoisierite is orthorhombic, space group Pnmm, with a 8.6891(10), b 5.7755(3), c 36.9504(20) Å, V 1854.3(2) Å3, Z = 2. Calculated main diffraction lines of the X-ray powder diffraction pattern are [ d in Å, ( I), ( hkl); relative intensities are visually estimated]: 4.62 (m) (112), 2.931 (vs) (11 10), 2.765 (s) (11 11), 2.598 (s) (310), 2.448 (ms) (028). Chemical analyses by electron microprobe give (in wt%) P2O5 2.08, V2O5 0.37, SiO2 34.81, TiO2 0.13, Al2O3 22.92, Cr2O3 0.32, Fe2O3 0.86, Mn2O3 6.92, MnO 19.09, MgO 5.73, CaO 1.94, Na2O 0.01, H2O 5.44, sum 100.62 wt%. H2O content was calculated from structure refinement. The empirical formula, based on 56 anions, is (Mn{5.340/2+}Mg1.810Ca0.686Na0.006)Σ=7.852(Al8.921Mn{1.739/3+}Mg1.010Fe{0.214/3+}Cr0.084Ti0.032)Σ=12.000(Si11.496P0.582V0.081)Σ=12.159O43.995(OH)12.005. The crystal structure of lavoisierite was solved by direct methods and refined on the basis of 1743 observed reflections to R 1 = 4.6 %. The structure is characterized by columns of edge-sharing octahedra running along [010] and linked to each other by means of [SiO4], [Si2O7], and [Si3O10] groups. Lavoisierite, named after the French

  17. Tunable-color luminescence via energy transfer in NaCa13/18Mg5/18PO4:A (A = Eu2+/Tb3+/Mn2+, Dy3+) phosphors for solid state lighting.

    PubMed

    Li, Kai; Fan, Jian; Mi, Xiaoyun; Zhang, Yang; Lian, Hongzhou; Shang, Mengmeng; Lin, Jun

    2014-11-17

    A series of NaCa13/18Mg5/18PO4(NCMPO):A (A = Eu(2+)/Tb(3+)/Mn(2+), Dy(3+)) phosphors have been prepared by the high-temperature solid-state reaction method. The X-ray diffraction (XRD) and Rietveld refinement, X-ray photoelectron spectroscopy (XPS), photoluminescence (PL), cathodoluminescence (CL), decay lifetimes, and PL quantum yields (QYs) were utilized to characterize the phosphors. The pure crystalline phase of as-prepared samples has been demonstrated via XRD measurement and Rietveld refinements. XPS reveals that the Eu(2+)/Tb(3+)/Mn(2+) can be efficiently doped into the crystal lattice. NCMPO:Eu(2+)/Tb(3+)/Mn(2+) phosphors can be effectively excited under UV radiation, which show tunable color from purple-blue to red including white emission based on energy transfer from Eu(2+) to Tb(3+)/Mn(2+) ions. Under low-voltage electron beam bombardment, the NCMPO:A (A = Eu(2+)/Tb(3+)/Mn(2+), Dy(3+)) display their, respectively, characteristic emissions with different colors, and the CL spectrum of NCMPO:0.04Tb(3+) has the comparable intensity to the ZnO:Zn commercial product. In addition, the calculated CIE coordinate of NCMPO:0.04Tb(3+) (0.252, 0.432) is more saturated than it (0.195, 0.417). These results reveal that NCMPO:A (A = Eu(2+)/Tb(3+)/Mn(2+), Dy(3+)) may be potential candidate phosphors for WLEDs and FEDs.

  18. Large enhancement of Blocking temperature by control of interfacial structures in Pt/NiFe/IrMn/MgO/Pt multilayers

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Chen, Xi; Wang, Shouguo, E-mail: sgwang@ustb.edu.cn; Han, Gang

    2015-09-15

    The Blocking temperature (T{sub B}) of Pt/NiFe/IrMn/MgO/Pt multilayers was greatly enhanced from far below room temperature (RT) to above RT by inserting 1 nm thick Mg layer at IrMn/MgO interface. Furthermore, the exchange bias field (H{sub eb}) was increased as well by the control of interfacial structures. The evidence for a significant fraction of Mn-O bonding at IrMn/MgO interface without Mg insertion layer was provided by X-ray photoelectron spectroscopy. The bonding between Mn and O can decrease the antiferromagnetism of IrMn film, leading to lower value of T{sub B} in Pt/NiFe/IrMn/MgO/Pt multilayers. Ultrathin Mg film inserted at IrMn/MgO interface actingmore » as an oxygen sinking layer can suppress the oxidation reactions between Mn and O and reduce the formation of Mn-O bonding greatly. The oxidation suppression results in the recovery of the antiferromagnetism of IrMn film, which can enhance T{sub B} and H{sub eb}. Furthermore, the high resolution transmission electron microscopy demonstrates that the Mg insertion layer can efficiently promote a high-quality MgO (200) texture. This study will enhance the understanding of physics in antiferromagnet-based spintronic devices.« less

  19. Na Diffusion in Quasi One-Dimensional Ion Conductor NaMn2O4 Observed by μ+SR

    NASA Astrophysics Data System (ADS)

    Umegaki, Izumi; Nozaki, Hiroshi; Harada, Masashi; Månsson, Martin; Sakurai, Hiroya; Kawasaki, Ikuto; Watanabe, Isao; Sugiyama, Jun

    A quasi one-dimensional (1D) compound, NaMn2O4, in which Mn2O4 zigzag chains form a 1D channel along the b-axis and Na ions locate at the center of the channel, is thought to be a good Na ionic conductor. In order to study Na-ion diffusion, we have measured μ+SR spectra using a powder sample in the temperature range between 100 and 500 K. A diffusive behavior was clearly observed above 325 K. Assuming a thermal activate process for jump diffusion of Na-ion between two nearest neighboring sites, a self diffusion coefficient of Na ion (DNa) and its activation energy (Ea) were estimated as DNa = (3.1 ± 0.2) × 10 - 11 cm2/s at 350 K and Ea = 180(9) meV.

  20. Discharge properties of Mg-Al-Mn-Ca and Mg-Al-Mn alloys as anode materials for primary magnesium-air batteries

    NASA Astrophysics Data System (ADS)

    Yuasa, Motohiro; Huang, Xinsheng; Suzuki, Kazutaka; Mabuchi, Mamoru; Chino, Yasumasa

    2015-11-01

    The discharge behaviors of rolled Mg-6 mass%Al-0.3 mass%Mn-2 mass%Ca (AMX602) and Mg-6 mass%Al-0.3 mass%Mn (AM60) alloys used as anodes for Magnesium-air batteries were investigated. The AMX602 alloy exhibited superior discharge properties compared to the AM60 alloy, especially at low current density. The discharge products of the AMX602 alloy were dense and thin, and many cracks were observed at all current densities. In addition, the discharge products were detached at some sites. These sites often corresponded to the positions of Al2Ca particles. The comparison of the discharge and corrosion tests indicated that the dense and thin discharge products of AMX602 were easily cracked by dissolution of the Mg matrix around Al2Ca particles, and the cracks promoted the penetration of the electrolyte into the discharge products, retaining the discharge activity. In contrast, concerning the AM60 alloy, thick discharge products were formed on the surface during discharge, and cracking of the discharge products hardly occurred, degrading the discharge properties. Localized and deeply corroded pits that could result from the detachment of metal pieces from the anode during discharge were partly observed in the AM60 alloy. It is suggested that these detached metal pieces are another reason for the low discharge properties of the AM60 alloy.

  1. Structure-electrochemical evolution of a Mn-rich P2 Na 2/3Fe 0.2Mn 0.8O 2 Na-ion battery cathode

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Dose, Wesley M.; Sharma, Neeraj; Pramudita, James C.

    The structural evolution of electrode materials directly influences the performance of sodium-ion batteries. In this work, in situ synchrotron X-ray diffraction is used to investigate the evolution of the crystal structure of a Mn-rich P2-phase Na 2/3Fe 0.2Mn 0.8O 2 cathode. A single-phase reaction takes place for the majority of the discharge–charge cycle at ~C/10, with only a short, subtle hexagonal P2 to hexagonal P2 two-phase region early in the first charge. Thus, a higher fraction of Mn compared to previous studies is demonstrated to stabilize the P2 structure at high and low potentials, with neither “Z”/OP4 phases in themore » charged state nor significant quantities of the P'2 phase in the discharged state between 1.5 and 4.2 V. Notably, sodium ions inserted during discharge are located on both available crystallographic sites, albeit with a preference for the site sharing edges with the MO 6 octahedral unit. The composition Na ~0.70Fe 0.2Mn 0.8O 2 prompts a reversible single-phase sodium redistribution between the two sites. Sodium ions vacate the site sharing faces (Naf), favoring the site sharing edges (Nae) to give a Nae/Naf site occupation of 4:1 in the discharged state. This site preference could be an intermediate state prior to the formation of the P'2 phase. Furthermore, this work shows how the Mn-rich Na 2/3Fe 0.2Mn 0.8O 2 composition and its sodium-ion distribution can minimize phase transitions during battery function, especially in the discharged state.« less

  2. Structure-electrochemical evolution of a Mn-rich P2 Na 2/3Fe 0.2Mn 0.8O 2 Na-ion battery cathode

    DOE PAGES

    Dose, Wesley M.; Sharma, Neeraj; Pramudita, James C.; ...

    2017-08-04

    The structural evolution of electrode materials directly influences the performance of sodium-ion batteries. In this work, in situ synchrotron X-ray diffraction is used to investigate the evolution of the crystal structure of a Mn-rich P2-phase Na 2/3Fe 0.2Mn 0.8O 2 cathode. A single-phase reaction takes place for the majority of the discharge–charge cycle at ~C/10, with only a short, subtle hexagonal P2 to hexagonal P2 two-phase region early in the first charge. Thus, a higher fraction of Mn compared to previous studies is demonstrated to stabilize the P2 structure at high and low potentials, with neither “Z”/OP4 phases in themore » charged state nor significant quantities of the P'2 phase in the discharged state between 1.5 and 4.2 V. Notably, sodium ions inserted during discharge are located on both available crystallographic sites, albeit with a preference for the site sharing edges with the MO 6 octahedral unit. The composition Na ~0.70Fe 0.2Mn 0.8O 2 prompts a reversible single-phase sodium redistribution between the two sites. Sodium ions vacate the site sharing faces (Naf), favoring the site sharing edges (Nae) to give a Nae/Naf site occupation of 4:1 in the discharged state. This site preference could be an intermediate state prior to the formation of the P'2 phase. Furthermore, this work shows how the Mn-rich Na 2/3Fe 0.2Mn 0.8O 2 composition and its sodium-ion distribution can minimize phase transitions during battery function, especially in the discharged state.« less

  3. Binder-jetting 3D printing and alloy development of new biodegradable Fe-Mn-Ca/Mg alloys.

    PubMed

    Hong, Daeho; Chou, Da-Tren; Velikokhatnyi, Oleg I; Roy, Abhijit; Lee, Boeun; Swink, Isaac; Issaev, Ilona; Kuhn, Howard A; Kumta, Prashant N

    2016-11-01

    3D printing of various biomaterials including titanium and stainless steel has been studied for treating patients with cranio-maxillofacial bone defect. The potential long term complications with use of inert biometals have opened the opportunities for use of biodegradable metals in the clinical arena. The authors previously reported that binder-jet 3D printing technique enhanced the degradation rates of biodegradable Fe-Mn alloy by creating engineered micropores rendering the system attractive as biodegradable implantable devices. In the present study, the authors employed CALPHAD modeling to systematically study and modify the Fe-Mn alloy composition to achieve enhanced degradation rates. Accordingly, Ca and Mg addition to Fe-35wt% Mn solid solution predicted increase in degradation rates. In order to validate the CALPHAD results, Fe - (35-y)wt% Mn - ywt% X (X=Ca, Mg, and y=0, 1, 2) were synthesized by using high energy mechanical alloying (HEMA). Sintered pellets of Fe-Mn-Ca and Fe-Mn-Mg were then subjected to potentiodynamic polarization (PDP) and live/dead cell viability tests. Sintered pellets of Fe-Mn, Fe-Mn-Ca, and Fe-Mn-Mg also exhibited MC3T3 murine pre-osteoblast cells viability in the live/dead assay results. Fe-Mn and Fe-Mn-1Ca were thus accordingly selected for 3D printing and the results further confirmed enhanced degradation of Ca addition to 3D printed constructs validating the theoretical and alloy development studies. Live/dead and MTT cell viability results also confirmed good cytocompatibility of the 3D-printed Fe-Mn and Fe-Mn-1Ca constructs. Bone grafting is widely used for the treatment of cranio-maxillofacial bone injuries. 3D printing of biodegradable Fe alloy is anticipated to be advantageous over current bone grafting techniques. 3D printing offers the fabrication of precise and tailored bone grafts to fit the patient specific bone defect needs. Biodegradable Fe alloy is a good candidate for 3D printing synthetic grafts to regenerate bone

  4. Low temperature NH3-SCR of NO over an unexpected Mn-based catalyst: Promotional effect of Mg doping

    NASA Astrophysics Data System (ADS)

    Fang, De; He, Feng; Liu, Xiaoqing; Qi, Kai; Xie, Junlin; Li, Fengxiang; Yu, Chongqinq

    2018-01-01

    MnOx/TiO2 catalysts doped with Mg have been prepared with the impregnation method. Surprisingly, 7% Mg-MnOx/TiO2 catalyst containing more Mn3+ ions showed superior low-temperature SCR activity and stability. Mg doping resulted in some adverse effects on the phases, BET surface areas, reducibility, NH3 adsorption, and morphology structures. However, according to the SCR performance, these effects were thought to be rather limited in comparison with the catalytic properties of MgMn2O4 which might stem from the enhancement of NH3-SCR activity and stability. Meanwhile, based on the in situ DRIFTS tests, the NH3-SCR reaction route of MnOx/TiO2 and Mg doped MnOx/TiO2 catalysts depended on the kind of gas (NH3 or NO) pre-adsorbed on the catalyst.

  5. Floating zone growth of α-Na 0.90MnO 2 single crystals

    DOE PAGES

    Dally, Rebecca; Clement, Raphaele J.; Chisnell, Robin; ...

    2016-12-03

    Here, single crystal growth of α-Na xMnO 2 (x=0.90) is reported via the floating zone technique. The conditions required for stable growth and intergrowth-free crystals are described along with the results of trials under alternate growth atmospheres. Chemical and structural characterizations of the resulting α-Na 0.90MnO 2 crystals are performed using ICP-AES NMR, XANES, XPS, and neutron diffraction measurements. As a layered transition metal oxide with large ionic mobility and strong correlation effects, α-Na xMnO 2 is of interest to many communities, and the implications of large volume, high purity, single crystal growth are discussed.

  6. High pressure experimental studies on Na3Fe(PO4)(CO3) and Na3Mn(PO4)(CO3): Extensive pressure behaviors of carbonophosphates family

    NASA Astrophysics Data System (ADS)

    Gao, Jing; Huang, Weifeng; Wu, Xiang; Qin, Shan

    2018-04-01

    Carbon-bearing phases in the Earth's interior have profound implications for the long-term Earth carbon cycle. Here we investigate high-pressure behaviors of carbonophosphates bonshtedtite Na3Fe(PO4)(CO3) and sidorenkite Na3Mn(PO4)(CO3) in diamond anvil cells up to ∼12 GPa at room temperature. Modifications in in situ synchrotron X-ray diffraction patterns and Raman spectra confirm the structural stability of carbonophosphates within the pressure region. Fitting the third-order Birch-Murnaghan equation of state to the volume compression curve, the isothermal bulk modulus parameters are obtained to be K0 = 56(1) GPa, K0' = 3.3(1), V0 = 303.3(3) Å3 for Na3Fe(PO4)(CO3) and K0 = 54(1) GPa, K0' = 3.4(1), V0 = 313.4(2) Å3 for Na3Mn(PO4)(CO3). Crystallographic axes exhibit an elastic anisotropy with a more compressible c-axis relative to the ab-plane. An inverse linear correlation between the K0 value and the ionic radius of M2+ (M = Mg, Fe, Mn) is well determined for carbonophosphates. The pressure-dependence responsiveness of [PO4] and [CO3] in carbonophosphates show a negative relationship to the M2+ radius. We also discussed the effect of [PO4] group on the structural variations and high-pressure behaviors of carbonates. Furthermore, the geochemical properties of carbonophosphates hold implications to diamond genesis.

  7. Effect of Copper on Corrosion of Forged AlSi1MgMn Automotive Suspension Components

    NASA Astrophysics Data System (ADS)

    Koktas, Serhan; Gokcil, Emre; Akdi, Seracettin; Birol, Yucel

    2017-09-01

    Recently, modifications in the alloy composition and the manufacturing process cycle were proposed to achieve a more uniform structure with no evidence of coarse grains across the section of the AlSi1MgMn alloys. Cu was added to the AlSi1MgMn alloy to improve its age hardening capacity without a separate solution heat treatment. However, Cu addition degrades the corrosion resistance of this alloy due to the formation of Al-Cu precipitates along the grain boundaries that are cathodic with respect to the aluminum matrix and thus encourage intergranular corrosion. The present work was undertaken to identify the impact of Cu addition on the corrosion properties of AlSi1MgMn alloys with different Cu contents. A series of AlSi1MgMn alloys with 0.06-0.89 wt.% Cu were tested in order to identify an optimum level of Cu addition.

  8. Synthesis of multi-walled carbon nanotubes using CoMnMgO catalysts through catalytic chemical vapor deposition

    NASA Astrophysics Data System (ADS)

    Yang, Wen; Feng, Yan-Yan; Jiang, Cheng-Fa; Chu, Wei

    2014-12-01

    The CoMgO and CoMnMgO catalysts are prepared by a co-precipitation method and used as the catalysts for the synthesis of carbon nanotubes (CNTs) through the catalytic chemical vapor deposition (CCVD). The effects of Mn addition on the carbon yield and structure are investigated. The catalysts are characterized by temperature programmed reduction (TPR) and X-ray diffraction (XRD) techniques, and the synthesized carbon materials are characterized by transmission electron microscopy (TEM) and thermo gravimetric analysis (TG). TEM measurement indicates that the catalyst CoMgO enclosed completely in the produced graphite layer results in the deactivation of the catalyst. TG results suggest that the CoMnMgO catalyst has a higher selectivity for CNTs than CoMgO. Meanwhile, different diameters of CNTs are synthesized by CoMnMgO catalysts with various amounts of Co content, and the results show that the addition of Mn avoids forming the enclosed catalyst, prevents the formation of amorphous carbon, subsequently promotes the growth of CNTs, and the catalyst with decreased Co content is favorable for the synthesis of CNTs with a narrow diameter distribution. The CoMnMgO catalyst with 40% Co content has superior catalytic activity for the growth of carbon nanotubes.

  9. Growth mechanism and magnetic and electrochemical properties of Na{sub 0.44}MnO{sub 2} nanorods as cathode material for Na-ion batteries

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Demirel, S.; Oz, E.; Altin, E.

    Nanorods of Na{sub 0.44}MnO{sub 2} are a promising cathode material for Na-ion batteries due to their large surface area and single crystalline structure. We report the growth mechanism of Na{sub 0.44}MnO{sub 2} nanorods via solid state synthesis and their physical properties. The structure and the morphology of the Na{sub 0.44}MnO{sub 2} nanorods are investigated by X-ray diffraction (XRD), scanning and tunneling electron microscopy (SEM and TEM), and energy-dispersive X-ray (EDX) techniques. The growth mechanism of the rods is investigated and the effects of vapor pressure and partial melting of Na-rich regions are discussed. The magnetic measurements show an antiferromagnetic phasemore » transition at 25 K and the μ{sub eff} is determined as 3.41 and 3.24 μ{sub B} from the χ–T curve and theoretical calculation, respectively. The electronic configuration and spin state of Mn{sup 3+} and Mn{sup 4+} are discussed in detail. The electrochemical properties of the cell fabricated using the nanorods are investigated and the peaks in the voltammogram are attributed to the diffusion of Na ions from different sites. Na intercalation process is explained by one and two Margules and van Laar models. - Highlights: • We synthesized Na{sub 0.44}MnO{sub 2} nanorods via a simple solid state reaction technique. • Our studies show that excess Na plays a crucial role in the nanorod formation. • Magnetization measurements show that Mn{sup 3+} ions are in LS and HS states. • The electrochemical properties of the cell fabricated using the nanorods are investigated. • Na intercalation process is explained by one and two Margules and van Laar models.« less

  10. Synthesis of carbon-coated Na2MnPO4F hollow spheres as a potential cathode material for Na-ion batteries

    NASA Astrophysics Data System (ADS)

    Wu, Ling; Hu, Yong; Zhang, Xiaoping; Liu, Jiequn; Zhu, Xing; Zhong, Shengkui

    2018-01-01

    Hollow sphere structure Na2MnPO4F/C composite is synthesized through spray drying, following in-situ pyrolytic carbon coating process. XRD results indicate that the well crystallized composite can be successfully synthesized, and no other impurity phases are detected. SEM and TEM results reveal that the Na2MnPO4F/C samples show intact hollow spherical architecture, and the hollow spherical shells with an average thickness of 150 nm-250 nm are composed of nanosized primary particles. Furthermore, the amorphous carbon layer is uniformly coated on the surface of the hollow sphere, and the nanosized Na2MnPO4F particles are well embedded in the carbon networks. Consequently, the hollow sphere structure Na2MnPO4F/C shows enhanced electrochemical performance. Especially, it is the first time that the obvious potential platforms (∼3.6 V) are observed during the charge and discharge process at room temperature.

  11. TL and OSL properties of Mn2+-doped MgGa2O4 phosphor

    NASA Astrophysics Data System (ADS)

    Luchechko, A.; Zhydachevskyy, Ya; Maraba, D.; Bulur, E.; Ubizskii, S.; Kravets, O.

    2018-04-01

    The oxide MgGa2O4 spinel ceramics doped with Mn2+ ions was synthesized by a solid-state reaction at 1200 °C in air. The activator concentration was equal 0.05 mol% of MnO. Phase purity of the synthesized samples was analyzed by X-ray diffraction technique. This spinel ceramics show efficient green emission in the range from 470 to 550 nm with a maximum at about 505 nm under UV or X-ray excitations, which is due to Mn2+ ions. MgGa2O4: Mn2+ exhibits intense thermoluminescence (TL) and optically stimulated luminescence (OSL) after influence of ionizing radiation. Are complex nature of the TL glow curves is associated with a significant number of structural defects that are responsible for the formation of shallow and deep electron traps. In this work, time-resolved OSL characteristics of the samples exposed to beta particles are reported for the first time. A light from green LED was used for optical stimulation. Obtained TL and OSL results suggest MgGa2O4:Mn2+ as perspective material for further research and possible application in radiation dosimetry.

  12. Na(7)Mg(13)Nd(PO(4))(12).

    PubMed

    Jerbi, Hasna; Hidouri, Mourad; Mongi, Ben Amara

    2012-06-01

    Investigations of the quasi-ternary system Na(3)PO(4)-Mg(3)(PO(4))(2)-NdPO(4) allowed us to obtain the new phosphate hepta-sodium trideca-magnesium neodymium dodeca-kis-phosphate, Na(7)Mg(13)Nd(PO(4))(12), by applying a flux method. The crystal structure is isotypic with that of the previously reported Na(7)Mg(13)Ln(PO(4))(12) (Ln = Eu, La) compounds. It consists of a complex three-dimensional framework built up from an NdO(8) polyhedron (m symmetry), an MO(6) octa-hedron statistically occupied by M = Mg and Na, and eight MgO(x) (x = 5, 6) polyhedra (four with site symmetry m), linked either directely by sharing corners, edges and faces, or by one of the eight unique PO(4) tetra-hedra through common corners. Two of the PO(4) tetra-hedra are statisticaly disordered over a mirror plane. The whole structure can be described as resutling from an assembly of two types of structural units, viz [Mg(4)MP(4)O(22)](∞) (2) layers extending parallel to (100) and stacked along [100], and [Mg(4)NdP(4)O(36)](∞) (1) undulating chains running along the [010] direction. The six different Na(+) cations (five with site symmetry m and one with 0.5 occupancy) are situated in six distinct cavities delimited by the framework. The structure was refined from data of a racemic twin.

  13. Colossal permittivity and the polarization mechanism of (Mg, Mn) co-doped LaGaO3 ceramics

    NASA Astrophysics Data System (ADS)

    Luo, Tingting; Liu, Zhifu; Zhang, Faqiang; Li, Yongxiang

    2018-03-01

    Mg and Mn co-doped LaGa0.7-xMgxMn0.3O3 (x = 0, 0.05, 0.10, 0.15) ceramics were prepared by a solid-state reaction method. The electrical properties of the LaGa0.7-xMgxMn0.3O3 ceramics were studied in detail by dielectric spectra, impedance spectra, and I-V characteristic analysis. Colossal permittivity up to 104 could be obtained across the frequency range up to 104 Hz. The impedance analysis of the co-doped LaGaO3 ceramics indicated that the Mott's variable range hopping (VRH) polarization should be the main origin of colossal permittivity. Mg and Mn co-doping suppressed the formation of Mn3+ and enhanced the VRH polarization, resulting in increased permittivity. Partial localization of electrons by Mg reduced the long-range electron hopping and led to the decrease in dielectric loss.

  14. Development and characterization of Mn2+-doped MgO nanoparticles by solution combustion synthesis

    NASA Astrophysics Data System (ADS)

    Basha, Md. Hussain; Gopal, N. O.; Rao, J. L.; Nagabhushana, H.; Nagabhushana, B. M.; Chakradhar, R. P. S.

    2015-06-01

    Mn doped MgO Nanoparticles have been prepared by Solution Combustion Synthesis. The synthesized sample is characterized by X-ray diffraction (XRD), Scanning Electron Microscopy (SEM) and Electron Paramagnetic Resonance (EPR). The prepared MgO:Mn (1 mol%) nano crystals appear to be of simple cubic crystalline phase with lattice parameters a = 4.218(2) Å and cell volume = 74.98 (7) Å3. SEM micrograph of powders show highly porous, many agglomerates with irregular morphology, large voids, cracks and pores. EPR spectrum of the sample at room temperature exhibit an isotropic sextet hyperfine pattern, centered at g=1.99, characteristic if Mn2+ ions with S=I=5/2.The observed g value and the hyperfine value reveal the ionic bonding between Mn2+ and its surroundings.

  15. Magnetic characteristics of a new cubic defect spinel Li0.5Mg0.5MnO3

    NASA Astrophysics Data System (ADS)

    Singh, V.; Seehra, M. S.; Manivannan, A.; Kumta, P. N.

    2012-04-01

    Magnetic properties of Li0.5Mg0.5MnO3-δ nanoparticles (size ≃ 20 nm) synthesized by the Pechini method are investigated using temperature dependence of its magnetization (M) and electron magnetic resonance (EMR) spectra at 9.286 GHz. Analysis of the x-ray diffraction spectra yields its structure to be a cubic defect spinel with the formula 4(Li0.5Mg0.5MnO2.75) = 3{[Li2/3Mg1/3][Mn4/3Mg1/3□1/3]O11/3]} so that Mn occupies the octahedral B-sites only. The data of M versus T yields a blocking temperature TB ≃ 9 K above which the Curie-Weiss law variation with θ = 13 K and μ = 3.96μB characteristic of Mn4+ ions is established. For T < 9 K, temperature dependent coercivity and remanence are observed. The observed temperature dependence of the EMR parameters (linewidth ΔH, resonance field Hr, and intensity Io) for T < 30 K is interpreted in terms of TB (EMR) ≃ 30 K. Formation of ferromagnetic Mn4+ clusters, resulting from the co-presence of non-magnetic Mg2+ and vacancies on the B-sites, is inferred.

  16. Origin of the 20-electron structure of Mg3 MnH7 : Density functional calculations

    NASA Astrophysics Data System (ADS)

    Gupta, M.; Singh, D. J.; Gupta, R.

    2005-03-01

    The electronic structure and stability of the 20-electron complex hydride, Mg3MnH7 is studied using density functional calculations. The heat of formation is larger in magnitude than that of MgH2 . The deviation from the 18-electron rule is explained by the predominantly ionic character of the band structure and a large crystal-field splitting of the Mn d bands. In particular, each H provides one deep band accomodating two electrons, while the Mn t2g bands hold an additional six electrons per formula unit.

  17. Giant spin splitting in optically active ZnMnTe/ZnMgTe core/shell nanowires.

    PubMed

    Wojnar, Piotr; Janik, Elżbieta; Baczewski, Lech T; Kret, Sławomir; Dynowska, Elżbieta; Wojciechowski, Tomasz; Suffczyński, Jan; Papierska, Joanna; Kossacki, Piotr; Karczewski, Grzegorz; Kossut, Jacek; Wojtowicz, Tomasz

    2012-07-11

    An enhancement of the Zeeman splitting as a result of the incorporation of paramagnetic Mn ions in ZnMnTe/ZnMgTe core/shell nanowires is reported. The studied structures are grown by gold-catalyst assisted molecular beam epitaxy. The near band edge emission of these structures, conspicuously absent in the case of uncoated ZnMnTe nanowires, is activated by the presence of ZnMgTe coating. Giant Zeeman splitting of this emission is studied in ensembles of nanowires with various average Mn concentrations of the order of a few percent, as well as in individual nanowires. Thus, we show convincingly that a strong spin sp-d coupling is indeed present in these structures.

  18. Improved passive treatment of high Zn and Mn concentrations using caustic magnesia (MgO): particle size effects.

    PubMed

    Rötting, Tobias S; Ayora, Carlos; Carrera, Jesus

    2008-12-15

    High concentrations of divalent metals such as Zn, Mn, Cu, Pb, Ni, Cd, Co, etc. are not removed satisfactorily in conventional (calcite- or organic matter-based) passive treatment systems. Caustic magnesia ("MgO") has been used successfully as an alternative alkaline material to remove these metals almost completely from water, but columns with coarse-grained MgO lost reactivity or permeability due to the accumulation of precipitates when only a small portion of the reagent had been spent. In the present study, MgO was mixed with wood chips to overcome these problems. Two columns with different MgO grain sizes were used to treat Zn- and Mn-rich water during one year. Performance was compared by measuring depth profiles of chemical parameters and hydraulic conductivity. The column containing 25% (v/v) of MgO with median particle size of about 3 mm displayed low reactivity and poor metal retention. In contrast, the column containing only 12.5% (v/v) of MgO with median particle size of 0.15 mm depleted Zn and Mn below detection limit throughout the study and had a good hydraulic performance. 95% of the applied MgO was consumed in the zone where Zn and Mn accumulated. The fine alkaline grains can dissolve almost completely before the growing layer of precipitates passivates them, whereas clogging is prevented by the large pores of the coarse inert matrix (wood chips). A reactive transport model corroborated the hypotheses that Zn(II) was removed due to its low solubility at pH near 10 achieved by MgO dissolution, whereas Mn(II) was removed due to rapid oxidation to Mn(III) at this pH and subsequent precipitation. The model also confirmed that the small size and large specific surface area of the MgO particles are the key factor to achieve a sufficiently fast dissolution.

  19. Fabrication of Mg-X-O (X = Fe, Co, Ni, Cr, Mn, Ti, V, and Zn) barriers for magnetic tunnel junctions

    NASA Astrophysics Data System (ADS)

    Yakushiji, K.; Kitagawa, E.; Ochiai, T.; Kubota, H.; Shimomura, N.; Ito, J.; Yoda, H.; Yuasa, S.

    2018-05-01

    We fabricated magnetic tunnel junctions with a 3d-transition material(X)-doped MgO (Mg-X-O) barrier, and evaluated the effect of the doping on magnetoresistance (MR) and microstructure. Among the variations of X (X = Fe, Co, Ni, Cr, Mn, Ti, V, and Zn), X = Fe and Mn showed a high MR ratio of more than 100%, even at a low resistance-area product of 3 Ωμm2. The microstructure analysis revealed that (001) textured orientation formed for X = Fe and Mn despite substantial doping (about 10 at%). The elemental mappings indicated that Fe atoms in the Mg-Fe-O barrier were segregated at the interfaces, while Mn atoms were evenly involved in the Mg-Mn-O barrier. This suggests that MgO has high adaptability for Fe and Mn dopants in terms of high MR ratio.

  20. Thermodynamic modeling of hydrogen storage capacity in Mg-Na alloys.

    PubMed

    Abdessameud, S; Mezbahul-Islam, M; Medraj, M

    2014-01-01

    Thermodynamic modeling of the H-Mg-Na system is performed for the first time in this work in order to understand the phase relationships in this system. A new thermodynamic description of the stable NaMgH3 hydride is performed and the thermodynamic models for the H-Mg, Mg-Na, and H-Na systems are reassessed using the modified quasichemical model for the liquid phase. The thermodynamic properties of the ternary system are estimated from the models of the binary systems and the ternary compound using CALPHAD technique. The constructed database is successfully used to reproduce the pressure-composition isotherms for MgH2 + 10 wt.% NaH mixtures. Also, the pressure-temperature equilibrium diagram and reaction paths for the same composition are predicted at different temperatures and pressures. Even though it is proved that H-Mg-Na does not meet the DOE hydrogen storage requirements for onboard applications, the best working temperatures and pressures to benefit from its full catalytic role are given. Also, the present database can be used for thermodynamic assessments of higher order systems.

  1. Diode-pumped Cr-doped ZnMnSe and ZnMgSe lasers

    NASA Astrophysics Data System (ADS)

    Říha, A.; Němec, M.; Jelínková, H.; Čech, M.; Vyhlídal, D.; Doroshenko, M. E.; Komar, V. K.; Gerasimenko, A. S.

    2017-12-01

    Chromium ions Cr2+ are known to have good fluorescence properties in the mid-infrared spectral region around the wavelength of 2.5 μm. The aim of this study was the investigation of new laser crystal materials - Zn0.95Mn0.05Se, Zn0.70Mn 0.30Se, and Zn0.75Mg0.25Se doped by Cr2+ ions and comparison of their spectral and laser characteristics. The spectroscopic parameters as absorption and fluorescence spectra as well as lifetimes were measured. As optical pumping the laser diode generating radiation at the wavelength of 1.69 μm (pulse repetition rate 10 Hz, pulse width 2 ms) was used. The longitudinal-pumped resonator was hemispherical with an output coupler radius of curvature 150 mm. The laser emission spectra were investigated and the highest intensity of emitted radiation was achieved at wavelengths 2451 nm, 2469 nm, and 2470 nm from the Cr:Zn0.95Mn0.05Se, Cr:Zn0.70Mn0.30Se, and Cr:Zn0.75Mg0.25Se laser systems, respectively. The input-output characteristics of laser systems were measured; the maximum output peak power 177 mW was obtained for Cr:Zn0.95Mn0.05Se laser system with slope efficiency of 6.3 % with respect to absorbed peak power. The output peak power as well as output beam spatial structure were stable during measurements. For the selection of the lasing wavelength, the single 1.5 mm thick quartz plate was placed at the Brewster angle inside the optical resonator between the output coupler and laser active medium. This element provided the tuning in the wavelength range 2290-2578 nm, 2353-2543 nm, and 2420-2551 nm for Cr:Zn0.95Mn0.05Se, Cr:Zn0.70Mn0.30Se, and Cr:Zn0.75Mg0.25Se, respectively. The obtained spectral FWHM linewidth of the individual output radiation was 10 nm. A comparison with previously measured Cr:ZnSe laser system was added in the end

  2. The enhancement in dielectric and magnetic property in Na and Mn co substituted lanthanum ferrite

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Rai, Atma, E-mail: atma@iitp.ac.in; Thakur, Awalendra K., E-mail: akt@iitp.ac.in; Centre for Energy and Environment Indian Institute of Technology Patna 800013 India

    2016-05-06

    Nanocrystalline solid solutions of La{sub 1-x}Na{sub x}Fe{sub 1-y}Mn{sub y}O{sub 3} (x=y=0.00 and 0.25) were prepared via modified Pechini route. No evidence of secondary or impurity phase has been detected up to the detection of error limit of high power X-ray diffractometer. Dielectric property of the samples has been investigated in the frequency range 100 Hz-4MHz at temperature ranging 300–450K. The value of relative permittivity (ε{sub r}) increases drastically and shows colossal dielectric response (∼10{sup 4}) by cosubstitution of Na and Mn as compared to pure LaFeO{sub 3}. Dielectric relaxation peak in loss tangent in both samples have been found and shiftmore » towards higher frequency region as temperature increases. Magnetization-Field (M-H) loop of the calcined sample have been recorded at room temperature (300K) at field ±60kOe. Magnetic property also enhanced by co substitution of Na and Mn. The change in Fe/Mn-O-Fe/Mn angle by co-substitution of Na and Mn in LaFeO{sub 3} and indirect exchange interaction between two different magnetic sub lattices Fe and Mn might be responsible for drastic change. Saturation/maximum magnetic moment increase ∼four times in LNFM25 (5.335emu/g) as compared to pure LaFeO{sub 3} (1.302emu/g).« less

  3. MnTiO3-driven low-temperature oxidative coupling of methane over TiO2-doped Mn2O3-Na2WO4/SiO2 catalyst

    PubMed Central

    Wang, Pengwei; Zhao, Guofeng; Wang, Yu; Lu, Yong

    2017-01-01

    Oxidative coupling of methane (OCM) is a promising method for the direct conversion of methane to ethene and ethane (C2 products). Among the catalysts reported previously, Mn2O3-Na2WO4/SiO2 showed the highest conversion and selectivity, but only at 800° to 900°C, which represents a substantial challenge for commercialization. We report a TiO2-doped Mn2O3-Na2WO4/SiO2 catalyst by using Ti-MWW zeolite as TiO2 dopant as well as SiO2 support, enabling OCM with 26% conversion and 76% C2-C3 selectivity at 720°C because of MnTiO3 formation. MnTiO3 triggers the low-temperature Mn2+↔Mn3+ cycle for O2 activation while working synergistically with Na2WO4 to selectively convert methane to C2-C3. We also prepared a practical Mn2O3-TiO2-Na2WO4/SiO2 catalyst in a ball mill. This catalyst can be transformed in situ into MnTiO3-Na2WO4/SiO2, yielding 22% conversion and 62% selectivity at 650°C. Our results will stimulate attempts to understand more fully the chemistry of MnTiO3-governed low-temperature activity, which might lead to commercial exploitation of a low-temperature OCM process. PMID:28630917

  4. Self-assembled decanuclear Na(I)2Mn(II)4Mn(III)4 complexes: from discrete clusters to 1-D and 2-D structures, with the Mn(II)4Mn(III)4 unit displaying a large spin ground state and probable SMM behaviour.

    PubMed

    Langley, Stuart K; Chilton, Nicholas F; Moubaraki, Boujemaa; Murray, Keith S

    2011-12-07

    The synthesis, magnetic characterization and X-ray crystal structures are reported for five new manganese compounds, [Mn(III)(teaH(2))(sal)]·(1/2)H(2)O (1), [Na(I)(2)Mn(II)(4)Mn(III)(4)(teaH)(6)(sal)(4)(N(3))(2)(MeOH)(4)]·6MeOH (2), [Na(I)(2)Mn(II)(4)Mn(III)(4)(teaH)(6)(sal)(4)(N(3))(2)(MeOH)(2)](n)·7MeOH (3), [Na(I)(2)Mn(II)(4)Mn(III)(4)(teaH)(6)(sal)(4)(N(3))(2)(MeOH)(2)](n)·2MeOH·Et(2)O (4) and [K(I)(2)Mn(II)(4)Mn(III)(4)(teaH)(6)(sal)(4)(N(3))(2)(H(2)O)(2)](n)·5MeOH (5). Complex 1 is a mononuclear compound, formed via the reaction of Mn(NO(3))(2)·4H(2)O, triethanolamine (teaH(3)) and salicylic acid (salH(2)) in a basic methanolic solution. Compound 2 is a mixed-valent hetero-metallic cluster made up of a Mn(8)Na(2) decanuclear core and is formed via the reaction of sodium azide (NaN(3)) with 1. Compounds 3-5 are isolated as 1- or 2-D coordination polymers, each containing the decanuclear Mn(8)M(2) (M = Na(+) or K(+)) core building block as the repeating unit. Compound 3 is isolated when 1 is reacted with NaN(3) over a very short reaction time and forms a 1-D coordination polymer. Each unit displays inter-cluster bridges via the O-atoms of teaH(2-) ligands bonding to the sodium ions of an adjacent cluster. Increasing the reaction time appears to drive the formation of 4 which forms 2-D polymeric sheets and is a packing polymorph of 3. The addition of KMnO(4) and NaN(3) to 1 resulted in compound 5, which also forms a 1-D coordination polymer of the decanuclear core unit. The 1-D chains are now linked via inter-cluster potassium and salicylate bridges. Solid state DC susceptibility measurements were performed on compounds 1-5. The data for 1 are as expected for an S = 2 Mn(III) ion, with the isothermal M vs. H data being fitted by matrix diagonalization methods to give values of g and the axial (D) and rhombic (E) zero field splitting parameters of 2.02, -2.70 cm(-1) and 0.36 cm(-1) respectively. The data for 2-5, each with an identical Mn(II)(4)Mn(III)(4

  5. Luminescence properties of Sr2Mg3P4O15:Mn2+ phosphor and the improvement by co-doping Bi3+

    NASA Astrophysics Data System (ADS)

    Cao, Renping; Wang, Wudi; Zhang, Jinlong; Ye, Yujiao; Chen, Ting; Guo, Siling; Xiao, Fen; Luo, Zhiyang

    2018-05-01

    Sr2Mg3P4O15:R (R = Bi3+, Mn2+, and Bi3+/Mn2+) phosphors are synthesized by a solid-state reaction method in air. Sr2Mg3P4O15:Bi3+ phosphor with excitation 380 nm shows blue light and its emission band peaking at ∼445 nm is observed. Under excitation at 355 and 416 nm, Sr2Mg3P4O15:Mn2+ phosphor shows red emission with a single broad emission band peaking at ∼630 nm in the range of 500-800 nm owing to the 4T1(G) → 6A1 transition of the Mn2+ ion. The optimal Mn2+ ion content in Sr2Mg3P4O15:Mn2+ phosphor is ∼0.05 and the lifetime of Sr2Mg2.95P4O15:0.05Mn2+ phosphor is ∼6.17 ms. After Bi3+ ion is co-doped, emission intensity of Sr2Mg3P4O15:Mn2+ phosphor can be enhanced obviously due to energy transfer (ET) from Bi3+ to Mn2+, which is confirmed by the luminescence properties and lifetimes of Sr2Mg3-xP4O15:Bi3+, Mn2+ phosphor. Luminous mechanism and ET process of Sr2Mg3-xP4O15:Bi3+, Mn2+ phosphor are explained by the simple energy level diagram of Bi3+ and Mn2+ ions.

  6. Thermodynamic Modeling of Hydrogen Storage Capacity in Mg-Na Alloys

    PubMed Central

    Abdessameud, S.; Mezbahul-Islam, M.; Medraj, M.

    2014-01-01

    Thermodynamic modeling of the H-Mg-Na system is performed for the first time in this work in order to understand the phase relationships in this system. A new thermodynamic description of the stable NaMgH3 hydride is performed and the thermodynamic models for the H-Mg, Mg-Na, and H-Na systems are reassessed using the modified quasichemical model for the liquid phase. The thermodynamic properties of the ternary system are estimated from the models of the binary systems and the ternary compound using CALPHAD technique. The constructed database is successfully used to reproduce the pressure-composition isotherms for MgH2 + 10 wt.% NaH mixtures. Also, the pressure-temperature equilibrium diagram and reaction paths for the same composition are predicted at different temperatures and pressures. Even though it is proved that H-Mg-Na does not meet the DOE hydrogen storage requirements for onboard applications, the best working temperatures and pressures to benefit from its full catalytic role are given. Also, the present database can be used for thermodynamic assessments of higher order systems. PMID:25383361

  7. Enhanced luminescence in SrMgAl(x)O(17±δ):yMn4+ composite phosphors.

    PubMed

    Cao, Renping; Sharafudeen, Kaniyarakkal N; Qiu, Jianrong

    2014-01-03

    Red-emitting SrMgAlxO17±δ:yMn(4+) composite phosphors (x=10-100; y=0.05-4.0 mol%) are synthesized by solid-state reaction method in air. Addition of Al2O3 leads to the formation of two concomitant phases, i.e., SrMgAl10O17 and Al2O3 phases in the composite phosphor. Red emission from Mn(4+) ions in the composite phosphors is greatly enhanced due to multiple scattering and absorption of excitation light between SrMgAl10O17 and Al2O3 phases. SrMgAlxO17±δ:yMn(4+) composite phosphors would be a promising candidate as red phosphor in the application of a 397 nm near UV-based W-LED. Copyright © 2013 Elsevier B.V. All rights reserved.

  8. Elemental moment variation of bcc FexMn1-x on MgO(001)

    NASA Astrophysics Data System (ADS)

    Bhatkar, H.; Snow, R. J.; Arenholz, E.; Idzerda, Y. U.

    2017-02-01

    We report the growth, structural characterization, and electronic structure evolution of epitaxially grown bcc FexMn1-x on MgO(001). It is observed that the 20 nm thick FexMn1-x alloy films remained bcc from 0.65≤x≤1, much beyond the bulk stability range of 0.88≤x≤1. X-ray absorption spectroscopy and X-ray magnetic circular dichroism show that both the Fe and Mn L3 binding energies slightly increase with Mn incorporation and that the elemental moment of Fe in the 20 nm crystalline bcc alloy film remain nearly constant, then shows a dramatic collapse near x 0.84. The Mn MCD intensity is found to be small at all compositions that exhibit ferromagnetism

  9. Effect of Al and Mg Contents on Wettability and Reactivity of Molten Zn-Al-Mg Alloys on Steel Sheets Covered with MnO and SiO2 Layers

    NASA Astrophysics Data System (ADS)

    Huh, Joo-Youl; Hwang, Min-Je; Shim, Seung-Woo; Kim, Tae-Chul; Kim, Jong-Sang

    2018-05-01

    The reactive wetting behaviors of molten Zn-Al-Mg alloys on MnO- and amorphous (a-) SiO2-covered steel sheets were investigated by the sessile drop method, as a function of the Al and Mg contents in the alloys. The sessile drop tests were carried out at 460 °C and the variation in the contact angles (θc) of alloys containing 0.2-2.5 wt% Al and 0-3.0 wt% Mg was monitored for 20 s. For all the alloys, the MnO-covered steel substrate exhibited reactive wetting whereas the a-SiO2-covered steel exhibited nonreactive, nonwetting (θc > 90°) behavior. The MnO layer was rapidly removed by Al and Mg contained in the alloys. The wetting of the MnO-covered steel sheet significantly improved upon increasing the Mg content but decreased upon increasing the Al content, indicating that the surface tension of the alloy droplet is the main factor controlling its wettability. Although the reactions of Al and Mg in molten alloys with the a-SiO2 layer were found to be sluggish, the wettability of Zn-Al-Mg alloys on the a-SiO2 layer improved upon increasing the Al and Mg contents. These results suggest that the wetting of advanced high-strength steel sheets, the surface oxide layer of which consists of a mixture of MnO and SiO2, with Zn-Al-Mg alloys could be most effectively improved by increasing the Mg content of the alloys.

  10. Strain-Engineered Multiferroicity in Pnma NaMnF_{3} Fluoroperovskite.

    PubMed

    Garcia-Castro, A C; Romero, A H; Bousquet, E

    2016-03-18

    In this study we show from first principles calculations the possibility to induce multiferroic and magnetoelectric functional properties in the Pnma NaMnF_{3} fluoroperovskite by means of epitaxial strain engineering. Surprisingly, we found a very strong nonlinear polarization-strain coupling that drives an atypical amplification of the ferroelectric polarization for either compression or expansion of the cell. This property is associated with a noncollinear antiferromagnetic ordering, which induces a weak ferromagnetism phase and makes the strained NaMnF_{3} fluoroperovskite multiferroic. The magnetoelectric response was calculated and it was found to be composed of linear and nonlinear components with amplitudes similar to the ones of Cr_{2}O_{3}. These findings show that it is possible to move the fluoride family toward functional applications with unique responses.

  11. Development and characterization of Mn{sup 2+}-doped MgO nanoparticles by solution combustion synthesis

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Basha, Md. Hussain; Gopal, N. O., E-mail: nogopal@yahoo.com; Rao, J. L.

    2015-06-24

    Mn doped MgO Nanoparticles have been prepared by Solution Combustion Synthesis. The synthesized sample is characterized by X-ray diffraction (XRD), Scanning Electron Microscopy (SEM) and Electron Paramagnetic Resonance (EPR). The prepared MgO:Mn (1 mol%) nano crystals appear to be of simple cubic crystalline phase with lattice parameters a = 4.218(2) Å and cell volume = 74.98 (7) Å{sup 3}. SEM micrograph of powders show highly porous, many agglomerates with irregular morphology, large voids, cracks and pores. EPR spectrum of the sample at room temperature exhibit an isotropic sextet hyperfine pattern, centered at g=1.99, characteristic if Mn{sup 2+} ions with S=I=5/2.The observedmore » g value and the hyperfine value reveal the ionic bonding between Mn{sup 2+} and its surroundings.« less

  12. Half-metallicity in new Heusler alloys NaTO2 (T=Sc, Ti, V, Cr, and Mn): A first-principles study

    NASA Astrophysics Data System (ADS)

    Rajabi, Kh; Ahmadian, F.

    2018-03-01

    On the basis of the full-potential linearized augmented plane wave (FPLAPW) method within density functional theory (DFT), electronic structure and magnetic properties of Heusler alloys NaTO2 (T = Sc, Ti, V, Cr, and Mn) were investigated. The negative values of formation energy showed that these compounds can be experimentally synthesized. Results showed that in all compounds, AlCu2Mn-type structure was the most favorable one. The NaTO2 (T = Sc, Ti, V, Cr, and Mn) alloys were HM ferromagnets except NaScO2 (in both structures which were nonmagnetic semiconductors) and NaVO2 (in AlCu2Mn-type structure which was a magnetic semiconductor). The origin of half-metallicity was also verified in HM alloys. NaCrO2 and NaVO2 alloys had higher half-metallic band gaps in comparison with Heusler alloys including and excluding transition metals. The total magnetic moments of HM NaTO2 (T = Ti, V, Cr, and Mn) alloys obeyed Slater-Pauling rule (Mtot = Ztot-12). Among NaTO2 (T = Sc, Ti, V, Cr, and Mn) alloys, NaCrO2 had the highest robustness of half-metallicity with variation of lattice constant in both structures.

  13. Structural and electronic properties of M-MOF-74 (M = Mg, Co or Mn)

    NASA Astrophysics Data System (ADS)

    de Oliveira, Aline; de Lima, Guilherme Ferreira; De Abreu, Heitor Avelino

    2018-01-01

    The Metal-Organic Frameworks M-MOF-74 (M = Mg, Co or Mn) were investigated through Density Functional Theory calculations. Structural parameters and band gap energies were determined in agreement with experimental data, with errors under 2%. The methods Electron Localization Function and Quantum Theory of Atoms in Molecules were applied to the analyses of the electronic density topology of the three solids. These methodologies indicated that the bonds between the metallic cations and the oxygen atoms are predominantly ionic while the other ones are predominantly covalent. Furthermore, non-conventional hydrogen bonds were identified to Mg-MOF-74 and Co-MOF-74, which were not observed to Mn-MOF-74.

  14. Silver-Containing α-MnO 2 Nanorods: Electrochemistry in Na-Based Battery Systems

    DOE PAGES

    Huang, Jianping; Poyraz, Altug S.; Lee, Seung-Yong; ...

    2016-09-01

    Manganese oxides are considered attractive cathode materials for rechargeable batteries due to the high abundance and environmental friendliness of manganese. In particular, cryptomelane and hollandite are desirable due to their ability to host cations within their octahedral molecular sieve (OMS-2) Alpha-MnO 2 structure. In this work, we investigate silver containing Alpha-MnO 2 structured materials (Ag xMn 8O 16, x = 1.22, L-Ag-OMS-2 or 1.66, H-Ag-OMS-2) as host materials for Li ion and Na ion insertion/de-insertion. The results indicate a significant difference in the lithiation versus sodiation process the OMS-2 materials. Initial reduction of Ag 1.22Mn 8O 16 to 1.0 Vmore » delivered ~370 mAh/g. Cycling of Ag1.22Mn8O16 between voltage ranges of 3.8 - 1.7 V and 3.8 - 1.3 V in a Na battery delivered initial capacities of 113 and 247 mAh/g, respectively. In contrast, Ag1.66Mn8O16 delivered only 15 mAh/g, ~0.5 electron equivalents, to 1.7 and 1.3 volts. Study of the system by electrochemical impedance spectroscopy (EIS) showed a significant decrease in charge transfer resistance from 2029 Omega to 594 Omega after 1.5 electron equivalents per Ag 1.22Mn 8O 16 formula unit of Na ion insertion. In contrast, both Ag 1.22Mn 8O 16 and Ag 1.66Mn 8O 16 exhibited gradual impedance increases during lithiation. The formation of silver metal could be detected only in the sodiated material by X-ray diffraction (XRD). Thus, the impedance of Ag-OMS-2 decreases upon sodiation coincident with the formation of silver metal during the discharge process, consistent with the more favorable formation of silver metal during the sodiation process relative to the lithation process.« less

  15. Improving the Performance of Layered Oxide Cathode Materials with Football-Like Hierarchical Structure for Na-Ion Batteries by Incorporating Mg2+ into Vacancies in Na-Ion Layers.

    PubMed

    Li, Zheng-Yao; Wang, Huibo; Chen, Dongfeng; Sun, Kai; Yang, Wenyun; Yang, Jinbo; Liu, Xiangfeng; Han, Songbai

    2018-04-09

    The development of advanced cathode materials is still a great interest for sodium-ion batteries. The feasible commercialization of sodium-ion batteries relies on the design and exploitation of suitable electrode materials. This study offers a new insight into material design to exploit high-performance P2-type cathode materials for sodium-ion batteries. The incorporation of Mg 2+ into intrinsic Na + vacancies in Na-ion layers can lead to a high-performance P2-type cathode material for sodium-ion batteries. The materials prepared by the coprecipitation approach show a well-defined morphology of secondary football-like hierarchical structures. Neutron power diffraction and refinement results demonstrate that the incorporation of Mg 2+ into intrinsic vacancies can enlarge the space for Na-ion diffusion, which can increase the d-spacing of the (0 0 2) peak and the size of slabs but reduce the chemical bond length to result in an enhanced rate capability and cycling stability. The incorporation of Mg 2+ into available vacancies and a unique morphology make Na 0.7 Mg 0.05 Mn 0.8 Ni 0.1 Co 0.1 O 2 a promising cathode, which can be charged and discharged at an ultra-high current density of 2000 mA g -1 with an excellent specific capacity of 60 mAh g -1 . This work provides a new insight into the design of electrode materials for sodium-ion batteries. © 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  16. 24Mg(p, α) 21Na reaction study for spectroscopy of 21Na

    DOE PAGES

    Cha, S. M.; Chae, K. Y.; Kim, A.; ...

    2015-11-03

    The Mg-24(p, alpha)Na-21 reaction was measured at the Holifield Radioactive Ion Beam Facility at Oak Ridge National Laboratory in order to better constrain the spins and parities of the energy levels in Na-21 for the astrophysically important F-17(alpha, p)Ne-20 reaction rate calculation. 31-MeV proton beams from the 25-MV tandem accelerator and enriched Mg-24 solid targets were used. When recoiling He-4 particles from the Mg-24(p, alpha)Na-21 reaction we used a highly segmented silicon detector array to detect them; it measured the yields of He-4 particles over a range of angles simultaneously. A observed a new level at 6661 ± 5 keVmore » in the present work. The extracted angular distributions for the first four levels of Na-21 and the results from distorted wave Born approximation (DWBA) calculations were compared to verify and extract the angular momentum transfer.« less

  17. Interpretation of Na-K-Mg relations in geothermal waters

    USGS Publications Warehouse

    Fournier, R.O.

    1990-01-01

    When using a Na-K-???Mg triangular diagram as an aid in the interpretation of a geothermal water, the estimated temperature of last water-rock equilibration may change by as much as 50??C, depending on which of the many Na/K geothermometers one assumes is correct. A particular geothermometer may work well in one place and not in another because of differences in the mineralogy of the phases that are in contact with the reservoir fluid. The position of the full equilibrium line that is used for geothermometry and for assessing degrees of departure from equilibrium also changes as the assumed K/???Mg geothermometer equation changes. The degree of ambiguity can be evaluated by utilizing the results of all the recently published Na/K geothermometers on a single Na-K-???Mg triangular plot.

  18. Manganese Recovery by Silicothermic Reduction of MnO in BaO-MnO-MgO-CaF2 (-SiO2) Slags

    NASA Astrophysics Data System (ADS)

    Heo, Jung Ho; Park, Joo Hyun

    2018-04-01

    The effects of reducing agent, CaF2 content, and reaction temperature upon the silicothermic reduction of MnO in the BaO-MnO-MgO-CaF2 (-SiO2) slags were investigated. Mn recovery was proportional to Si activity in the molten alloy. Moreover, 90 pct yield of Mn recovery was obtained under 5 mass pct CaF2 content and 1873 K (1600 °C) reaction temperature. Increasing CaF2 content above 5 pct yielded little or no further increase in Mn recovery, because it was accompanied by increased slag viscosity owing to the precipitation of high melting point compounds such as Ba2SiO4.

  19. Difference between resistance degradation of fixed valence acceptor (Mg) and variable valence acceptor (Mn)-doped BaTiO3 ceramics

    NASA Astrophysics Data System (ADS)

    Yoon, Seok-Hyun; Randall, Clive A.; Hur, Kang-Heon

    2010-09-01

    The difference in the resistance degradation behavior was investigated between fixed valence acceptor (Mg) and the variable valence acceptor (Mn)-doped BaTiO3 ceramics with an increase of each acceptor concentration. Coarse-grained specimens with uniform grain sizes and different acceptor concentrations were prepared. In the case of Mg-doped BaTiO3, the time to degradation systematically decreased with the increase in Mg concentration. In contrast, there is a systematically increased time to degradation with the increase in Mn concentration in Mn-doped BaTiO3. The fast degradation by the increase in Mg concentration directly corresponded to an increase in the Warburg impedance and ionic transference number (tion) associated with an increase in oxygen vacancy concentration ([VO••]). On the other hand, no distinct Warburg impedance or ionic conduction contribution could be observed with the increase in Mn concentration. It is supposed that the increase in [VO••] is negligible in spite of the increase in acceptor Mn concentration, when it is compared to Mg-doped BaTiO3. The much lower [VO••] and more dominant electron/hole trapping effect due to multivalence nature of Mn are supposed to cause such a contrary degradation behavior between Mg and Mn-doped BaTiO3. Reoxidation in a slightly reducing atmosphere (N2) showed better resistance to degradation behavior than in a oxidizing air atmosphere in both Mg and Mn-doped BaTiO3, which is anticipated to be an increase in the electron/hole trapping sites. All these behaviors could be explained by the low temperature defect chemical model that shows difference in the defect structure between Mg and Mn-doped BaTiO3, and its dependence on the oxygen partial pressure (pO2) during reoxidation and cooling. Not only the [VO••], but also the density of electron/hole trap sites, are believed to be crucial in controlling resistance degradation.

  20. Crystal structure and europium luminescence of NaMgH3-xFx

    NASA Astrophysics Data System (ADS)

    Pflug, Christian; Franz, Alexandra; Kohlmann, Holger

    2018-02-01

    The solid solution series NaMgH3-xFx (x = 0, 0.5, 1, 1.5, 2, 2.5, 3) was synthesized by solid-state reactions under hydrogen gas pressure from binary ionic hydrides, fluorides and magnesium. Rietveld refinement based on X-ray powder diffraction data revealed the GdFeO3-structure type for all compounds and a trend of lattice parameters according to Vegard's law. The anion distribution in NaMgD2F and NaMgD1.5F1.5 was found to be statistical by Rietveld refinement based on neutron powder diffraction data. Photoluminescence measurements on europium(II) substituted NaMgH3-xFx revealed a strong red shift of the emission wavelength (λem = 665 nm for NaMgH2F:Eu) in comparison to violet emitting NaMgF3:Eu.

  1. The enhancement in dielectric and magnetic property in Na and Mn co substituted lanthanum ferrite

    NASA Astrophysics Data System (ADS)

    Rai, Atma; Thakur, Awalendra K.

    2016-05-01

    Nanocrystalline solid solutions of La1-xNaxFe1-yMnyO3 (x=y=0.00 and 0.25) were prepared via modified Pechini route. No evidence of secondary or impurity phase has been detected up to the detection of error limit of high power X-ray diffractometer. Dielectric property of the samples has been investigated in the frequency range 100 Hz-4MHz at temperature ranging 300-450K. The value of relative permittivity (ɛr) increases drastically and shows colossal dielectric response (˜104) by cosubstitution of Na and Mn as compared to pure LaFeO3. Dielectric relaxation peak in loss tangent in both samples have been found and shift towards higher frequency region as temperature increases. Magnetization-Field (M-H) loop of the calcined sample have been recorded at room temperature (300K) at field ±60kOe. Magnetic property also enhanced by co substitution of Na and Mn. The change in Fe/Mn-O-Fe/Mn angle by co-substitution of Na and Mn in LaFeO3 and indirect exchange interaction between two different magnetic sub lattices Fe and Mn might be responsible for drastic change. Saturation/maximum magnetic moment increase ˜four times in LNFM25 (5.335emu/g) as compared to pure LaFeO3 (1.302emu/g).

  2. Synthesis and structural characterization of transition metal doped MgO: Mg0.95Mn0.01TM0.04O (TM = Co, Ni, Cu)

    NASA Astrophysics Data System (ADS)

    Islam, Ishtihadah; Khandy, Shakeel Ahmad; Hafiz, Aurangzeb Khurram

    2018-05-01

    In the present work, preparation and characterization of transition metal doped MgO: Zn0.94Mn0.01TM0.05O (TM = Co, Ni and Cu) nano-particles have been reported. Transition metal doped samples of MgO were synthesized by Sol gel auto combustion method. Structural characterisation from XRD and SEM show the formation of single-phase primary particles, nearly of spherical shaped nano-crystallites. The crystallite size was found to be 78.2, 67.02, 78.11 and 64 nm for pure, Co, Cu and Ni doped MgMnO nano-particles, respectively. Hence, the average crystallite size increases monotonously from Co to Cu doping.

  3. The Effects of Bismuth Oxide on Microstructures and Magnetic Properties of Mn-Mg-Al Ferrites

    NASA Astrophysics Data System (ADS)

    Nekouee, Kh. A.; Rahimi, A. H.; Haghighi, M. Alineghad; Ehsani, N.

    2018-04-01

    In the present paper, the effects of bismuth oxide as an additive on microstructure and magnetic properties of Mg0.9Mn0.1Al0.4Fe1.6O4 were investigated. Mg-Mn-Al ferrite powders were prepared by the conventional solid state synthesis method. Two different amounts of bismuth oxide (2.5 wt.% and 5 wt.%) were utilized as the sintering aid and their microstructure and physical properties were compared to those of the sample without additives. X-ray diffraction (XRD) analysis indicated that crystal lattice distortion due to the microstructural constraints as the result from incorporation of bismuth oxide into the microstructure was developed by adding bismuth oxide. XRD Rietveld refinement was used to define the cation distribution and to refine the lattice parameter and oxygen parameter for the sample without bismuth oxide as (Mg0.16Mn0.02Al0.15Fe0.77)A(Mg0.74Mn0.08Al0.25Fe0.83)BO4 and 8.3308 Å and 0.2542, respectively. Microstructure studies show that a bismuth rich liquid phase forms during the sintering at 1250°C, which enhances the densification of sintered bodies up to 13% (a relative density of 93%). Magnetization of sintered samples were increased from 21.1 emu/g to 26.2 emu/g upon addition of 2.5 wt.% bismuth oxide and then decreased to 24.9 emu/g when 5 wt.% bismuth oxide was added.

  4. Rational Design of Na(Li1/3 Mn2/3 )O2 Operated by Anionic Redox Reactions for Advanced Sodium-Ion Batteries.

    PubMed

    Kim, Duho; Cho, Maenghyo; Cho, Kyeongjae

    2017-09-01

    In an effort to develop high-energy-density cathodes for sodium-ion batteries (SIBs), low-cost, high capacity Na(Li 1/3 Mn 2/3 )O 2 is discovered, which utilizes the labile O 2p-electron for charge compensation during the intercalation process, inspired by Li 2 MnO 3 redox reactions. Na(Li 1/3 Mn 2/3 )O 2 is systematically designed by first-principles calculations considering the Li/Na mixing enthalpy based on the site preference of Na in the Li sites of Li 2 MnO 3 . Using the anionic redox reaction (O 2- /O - ), this Mn-oxide is predicted to show high redox potentials (≈4.2 V vs Na/Na + ) with high charge capacity (190 mAh g -1 ). Predicted cathode performance is validated by experimental synthesis, characterization, and cyclic performance studies. Through a fundamental understanding of the redox reaction mechanism in Li 2 MnO 3 , Na(Li 1/3 Mn 2/3 )O 2 is designed as an example of a new class of promising cathode materials, Na(Li 1/3 M 2/3 )O 2 (M: transition metals featuring stabilized M 4+ ), for further advances in SIBs. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  5. Immobilization of Mn and NH4 (+)-N from electrolytic manganese residue waste.

    PubMed

    Chen, Hongliang; Liu, Renlong; Liu, Zuohua; Shu, Jiancheng; Tao, Changyuan

    2016-06-01

    The objective of this work was the immobilization of soluble manganese (Mn) and ammonium nitrogen (NH4 (+)-N) leached from electrolytic manganese residue (EMR). Immobilization of Mn was investigated via carbonation using carbon dioxide (CO2) and alkaline additives. NH4 (+)-N immobilization was evaluated via struvite precipitation using magnesium and phosphate sources. Results indicated that the immobilization efficiency of Mn using CO2 and quicklime (CaO) was higher than using CO2 and sodium hydroxide (NaOH). This higher efficiency was likely due to the slower release of OH(-) during CaO hydrolysis. The immobilization efficiency of Mn was >99.99 % at the CaO:EMR mass ratio of 0.05:1 for 20-min reaction time. The struvite precipitation of NH4 (+)-N was conducted in the carbonated EMR slurry and the immobilization efficiency was 89 % using MgCl2 · 6H2O + Na3PO4 · 12H2O at the Mg:P:N molar ratio of 1.5:1.5:1 for 90-min reaction time. A leaching test showed that the concentrations of Mn and NH4 (+)-N in the filtrate of the treated EMR were 0.2 and 9 mg/L, respectively. The combined immobilization of Mn and NH4 (+)-N was an effective pretreatment method in the harmless treatment of the EMR.

  6. Structural, magnetic and Mössbauer studies of Nd-doped Mg-Mn ferrite nanoparticles

    NASA Astrophysics Data System (ADS)

    Somnath; Sharma, Indu; Kotnala, R. K.; Singh, M.; Kumar, Arun; Dhiman, Pooja; Singh, Virender Pratap; Verma, Kartikey; Kumar, Gagan

    2017-12-01

    The present work is focused on the replacement of Fe3+ ions by rare-earth Nd3+ ions and their influence on the cations distribution, structural, magnetic and Mössbauer properties of Mg-Mn nanoferrites. Nanosized Nd-doped Mg-Mn nanoferrites, Mg0.9Mn0.1NdxFe2-xO4, where x = 0.1, 0.2 & 0.3, were successfully synthesized for the first time through solution combustion technique. X-ray diffraction studies confirmed the formation of single phase nature of the synthesized nanoferrites. Williamsons-Hall plots were used to obtain the particle size and strain while the lattice parameter was obtained from Nelson-Riley plots. The particle size was observed to decrease (19.2-13.5 nm) while lattice parameter was observed to increase (8.373-8.391 Å) with the incorporation of Nd3+ ions. Cation distribution between the tetrahedral (A-site) and octahedral (B-site) was estimated by using the X-ray diffraction method & magnetization technique. The estimated cation distribution was used to investigate the detailed structural parameters. Room temperature M-H study revealed a decrease of saturation magnetization (10.15-1.83 emu/g) and an increase in coercivity (22.86-27.19 Oe) with the increasing substitution of Nd3+ ions. Magnetic results obtained in the present study indicated that the synthesized nanoferrites can be a useful candidate for electromagnet applications.

  7. Viscosity of the liquid Al-6Mg-1Mn-0.2Sc-0.1Zr alloy

    NASA Astrophysics Data System (ADS)

    Reznik, P. L.; Chikova, O. A.; Tsepelev, V. S.

    2017-07-01

    The microstructure and the phase composition of as-cast Al-Mg-Mn-Sc-Zr alloy samples are studied by electron microscopy and electron-probe microanalysis. The processes of solidification and melting of this alloy are described. The temperature dependence of the kinematic viscosity of the Al-Mg-Mn-Sc-Zr melts is studied during heating and subsequent cooling of the samples. The measurement results are used to determine the temperature at which inherited microheterogeneities in the melts are destroyed irreversibly.

  8. Synthesis and electrochemical properties of Na-rich Prussian blue analogues containing Mn, Fe, Co, and Fe for Na-ion batteries

    NASA Astrophysics Data System (ADS)

    Bie, Xiaofei; Kubota, Kei; Hosaka, Tomooki; Chihara, Kuniko; Komaba, Shinichi

    2018-02-01

    Electrochemical performance of Prussian blue analogues (PBAs) as positive electrode materials for non-aqueous Na-ion batteries is known to be highly dependent on their synthesis conditions according to the previous researches. Na-rich PBAs, NaxM[Fe(CN)6]·nH2O where M = Mn, Fe, Co, and Ni, are prepared via precipitation method under the same condition. The structure, chemical composition, morphology, valence of the transition metals, and electrochemical property of these samples are comparatively researched. The PBA with Mn shows large reversible capacity of 126 mAh g-1 in 2.0-4.2 V at a current density of 30 mA g-1 and the highest working voltage owning to high redox potential of Mn2+/3+ in MnN6 and Fe2+/3+ in FeC6. While, the PBA with Ni exhibits the best cyclability and rate performance though only 66 mAh g-1 is delivered. The significant differences in electrochemical behaviors of the PBAs originate from the various properties depending on different transition metals.

  9. First-order ferromagnetic to helimagnetic transition in MgMn6Ge6

    NASA Astrophysics Data System (ADS)

    Mazet, T.; Ihou-Mouko, H.; Malaman, B.

    2008-02-01

    The magnetic and magnetocaloric properties of the new HfFe6Ge6-type (P6/mmm) MgMn6Ge6 compound have been studied by magnetic measurements and powder neutron diffraction experiments. MgMn6Ge6 magnetically orders at TC˜345 K in a ferromagnetic easy-plane arrangement. At TAF˜235 K, it undergoes a first-order transition to a helical structure, characterized by a temperature dependent propagation vector k =⟨0,0,qz⟩ (qz˜0.116 reciprocal lattice units at 1.4 K), without structural modification. The Mn atoms carry a magnetic moment of about 2 μB. A metamagnetic transition with a low critical field (Hcr<1 T) is observed below TAF. At low temperature, both magnetic and magnetocaloric data strongly suggest that some kinds of intermediate noncollinear ferromagnetic arrangements are stabilized above the critical field while the pure ferromagnetic state is obtained for significantly higher magnetic fields (H >5 T). The magnitude of the magnetic entropy change at TC (-ΔSM˜20.5 mJ cm-3 K-1 for ΔH =5 T) is about 25% that of Gd metal. The magnetocaloric effect at the order-order transition is of opposite sign and of lower magnitude.

  10. Weak ferromagnetism and short range polar order in NaMnF3 thin films

    NASA Astrophysics Data System (ADS)

    KC, Amit; Borisov, Pavel; Shvartsman, Vladimir V.; Lederman, David

    2017-02-01

    The orthorhombically distorted perovskite NaMnF3 has been predicted to become ferroelectric if an a = c distortion of the bulk Pnma structure is imposed. In order to test this prediction, NaMnF3 thin films were grown on SrTiO3 (001) single crystal substrates via molecular beam epitaxy. The best films were smooth and single phase with four different twin domains. In-plane magnetization measurements revealed the presence of antiferromagnetic ordering with weak ferromagnetism below the Néel temperature TN = 66 K. For the dielectric studies, NaMnF3 films were grown on a 30 nm SrRuO3 (001) layer used as a bottom electrode grown via pulsed laser deposition. The complex permittivity as a function of frequency indicated a strong Debye-like relaxation contribution characterized by a distribution of relaxation times. A power-law divergence of the characteristic relaxation time revealed an order-disorder phase transition at 8 K. The slow relaxation dynamics indicated the formation of super-dipoles (superparaelectric moments) that extend over several unit cells, similar to polar nanoregions of relaxor ferroelectrics.

  11. Nanowire Na0.35MnO2 from a hydrothermal method as a cathode material for aqueous asymmetric supercapacitors

    NASA Astrophysics Data System (ADS)

    Zhang, B. H.; Liu, Y.; Chang, Z.; Yang, Y. Q.; Wen, Z. B.; Wu, Y. P.; Holze, R.

    2014-05-01

    Nanowire Na0.35MnO2 was prepared by a simple and low energy consumption hydrothermal method; its electrochemical performance as a cathode material for aqueous asymmetric supercapacitors in Na2SO4 solution was investigated. Due to the nanowire structure its capacitance (157 F g-1) is much higher than that of the rod-like Na0.95MnO2 (92 F g-1) from solid phase reaction although its sodium content is lower. When it is assembled into an asymmetric aqueous supercapacitor using activated carbon as the counter electrode and aqueous 0.5 mol L-1 Na2SO4 electrolyte solution, the nanowire Na0.35MnO2 shows an energy density of 42.6 Wh kg-1 at a power density of 129.8 W kg-1 based on the total weight of the two electrode material, higher than those for the rod-like Na0.95MnO2, with an energy density of 27.3 Wh kg-1 at a power density of 74.8 W kg-1, and that of LiMn2O4. The new material presents excellent cycling behavior even when dissolved oxygen is not removed from the electrolyte solution. The results hold great promise for practical applications of this cathode material since sodium is much cheaper than lithium and its natural resources are rich.

  12. Energy transfer between Eu-Mn and photoluminescence properties of Ba0.75Al11O17.25-BaMgAl10O17:Eu2+,Mn2+ solid solution

    NASA Astrophysics Data System (ADS)

    Zhou, Jun; Wang, Yuhua; Liu, Bitao; Li, Feng

    2010-08-01

    In order to evaluate the energy transfer between Eu-Mn in Ba0.75Al11O17.25-BaMgAl10O17 solid solution, Ba0.75Al11O17.25-BaMgAl10O17:Eu2+,Mn2+ phosphors were prepared by flux method. The crystal structure and the morphology of the solid solution were demonstrated by x-ray dirrfactometer and scanning electron microscopy. The photoluminescence mechanisms were explained by the energy transfer of Eu2+ to Mn2+ and the Dexter theory. A redshift of green emission peak and a decrease in decay time with the increase in Mn2+ concentration were observed. These phenomena are attributed to the formation of Mn2+ paired centers after analysis by a method of Pade approximations.

  13. Mechanisms for monovalent cation-dependent depletion of intracellular Mg2+:Na(+)-independent Mg2+ pathways in guinea-pig smooth muscle.

    PubMed

    Nakayama, Shinsuke; Nomura, Hideki; Smith, Lorraine M; Clark, Joseph F; Uetani, Tadayuki; Matsubara, Tatsuaki

    2003-09-15

    It has been suggested that magnesium deficiency is correlated with many diseases. 31P NMR experiments were carried out in order to investigate the effects of Na+ substitution on Mg2+ depletion in smooth muscle under divalent cation-free conditions. In the taenia of guinea-pig caeci, the intracellular free Mg2+ concentration ([Mg2+]i) was estimated from the chemical shifts of (1) the beta-ATP peak alone and (2) beta- and gamma-ATP peaks. Both estimations indicated that [Mg2+]i decreased only very slowly in Mg(2+)-free, Ca(2+)-free solutions in which Na+ was substituted with large cations such as NMDG (N-methyl-D-glucamine) and choline. Furthermore, the measurements of tension development supported the suggestion of preservation of intracellular Mg2+ with NMDG substitution. Substituting extracellular Na+ with the small cation, Li+, also shifted the beta-ATP peak towards a lower frequency, but the frequency shift was significantly less than that seen upon Na+ substitution with K+. The estimated [Mg2+]i depletion was, however, comparable with that seen after Na+ substitution with K+ using the titration curves of metal-free and Mg(2+)-bound ATP obtained in Li(+)-based model solutions. It was concluded that Mg2+ rapidly decreases only when small cations were the major electrolyte of the extracellular medium. Na+ substitutions with NMDG, choline or Li+ had little effect on intracellular ATP concentration after 100 min treatment.

  14. Jahn-Teller distortion of Mn3+-occupied octahedra in red beryl from Utah indicated by optical spectroscopy

    NASA Astrophysics Data System (ADS)

    Fridrichová, Jana; Bačík, Peter; Ertl, Andreas; Wildner, Manfred; Dekan, Július; Miglierini, Marcel

    2018-01-01

    Red beryl from Utah is chemically homogeneous and contains only Fe < 0.163, Mn < 0.018, and Mg < 0.016 apfu. Channel sites contain only up to Cs 0.011, K 0.009, Rb 0.004, and Na 0.004 apfu. This suggests only very slight tetrahedral (Cs,K,Rb)Li□-1Be-1 substitution, octahedral Na(Fe2+,Mg)□-1Al-1 substitution can be excluded. Fe and Mn are trivalent as documented by Mössbauer spectroscopy and optical absorption spectroscopy. Red beryl optimized formula is ∼[(Cs,Rb,K)0.02□0.98]Σ1.00□1.00(Al1.79Fe3+0.16Mn3+0.02Ti4+0.02Mg0.01)Σ2.00Be3(Si6O18). Location of Mn3+ was estimated to the octahedral Al3+ site, other choices are improbable due to the bond-length requirements. No Mn3+-induced Jahn-Teller structural distortion was detected due to site symmetry restrictions and small Mn3+ content. However, optical spectroscopy shows broad band at ∼7190 cm-1 assigned to the excited level of the spin-allowed pseudo-tetragonal split E ground state of elongated six-fold Mn3+ coordination. Crystal field calculations indicate that the local Mn3+ environment complies well with crystal chemical expectations for Jahn-Teller distorted Mn3+O6 octahedra.

  15. Synthesis and structural studies of Mg doped LiNi0.5Mn0.5O2 cathode materials for lithium-ion batteries

    NASA Astrophysics Data System (ADS)

    Murali, N.; Margarette, S. J.; Madhuri Sailaja, J.; Kondala Rao, V.; Himakar, P.; Kishore Babu, B.; Veeraiah, V.

    2018-02-01

    Layered Mg doped LiNi0.5Mn0.5O2 materials have been synthesized by sol-gel method. The physical properties of these materials were examined by XRD, FESEM and FT-IR studies. From XRD patterns, the phase formation of α-NaFeO2 layered structure with R\\bar 3m space group is confirmed. The surface morphology of the synthesized materials has been examined by FESEM analysis in which the average particle size is found to be about 2 - 2.5 µm. These materials show some changes in the local ion environment, as examined by FT-IR studies.

  16. Magnetic states of Mn and Co atoms at Co2MnGe/MgO interfaces seen via soft x-ray magnetic circular dichroism

    NASA Astrophysics Data System (ADS)

    Asakura, D.; Koide, T.; Yamamoto, S.; Tsuchiya, K.; Shioya, T.; Amemiya, K.; Singh, V. R.; Kataoka, T.; Yamazaki, Y.; Sakamoto, Y.; Fujimori, A.; Taira, T.; Yamamoto, M.

    2010-11-01

    The magnetic states of Mn and Co atoms in Co-rich Co2MnGe Heusler alloy thin films facing an MgO barrier were studied by means of soft x-ray magnetic circular dichroism (XMCD). In particular, the Co2MnGe film-thickness dependence of the Mn and Co magnetic moments was investigated. With a decrease in the Co2MnGe film thickness to 1-2 monolayers (MLs), the spin magnetic moment of Mn decreased and the MnL2,3 -edge x-ray absorption spectra (XAS) showed a Mn2+ -like multiplet structure in MnO, in contrast to samples thicker than 4 ML, indicating that the Mn atoms of the 1 and 2 ML samples were oxidized. The Co spin magnetic moment increased slightly with decreasing thickness. A Co2+ -like multiplet structure in CoO was not observed in all the CoL2,3 -edge XAS and XMCD, indicating that, even in the ultrathin samples, the Co atoms were not oxidized, and were more strongly spin polarized than those in the thicker samples. Co spin magnetic moments of 1.40-1.77μB larger than the theoretical value for ideal stoichiometric Co2MnGe (˜1μB) and the Co-rich film composition imply the presence of Co antisites that would lower the spin polarization.

  17. Effect of Cr and Mn addition and heat treatment on AlSi3Mg casting alloy

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Tocci, Marialaura, E-mail: m.tocci@unibs.it

    In the present paper the effect of heat treatment on an AlSi3Mg alloy with and without Cr and Mn addition was investigated. Beside the well-known modification of the morphology of Fe-containing intermetallics, it was found that Cr and Mn allowed the formation of dispersoids in the aluminium matrix after solution heat treatment at 545 °C, as shown by scanning transmission electron microscope observations. These particles were responsible of the enhanced Vickers microhardness of the aluminium matrix in comparison with the base alloy after solution treatment and quenching, according to dispersion hardening mechanism. The presence of these particles was not affectedmore » by ageing treatment, which instead allowed the precipitation of β-Mg{sub 2}Si, as shown by the elaboration of differential scanning calorimeter curves. The formation of dispersoids and the study of their effect on mechanical properties can represent an interesting development for applications at high temperatures of casting alloys due to their thermal stability compared to other strengthening phases as β-Mg{sub 2}Si. - Highlights: •Cr and Mn successfully modified the morphology of Fe-containing intermetallics. •Cr- and Mn-dispersoids formed in the aluminium matrix during solution treatment. •Dispersion hardening was detected after solution treatment for Cr-containing alloy. •The dispersion hardening effect was maintained after ageing treatment.« less

  18. New Defective Brannerite-Type Vanadates. I. Synthesis and Study of Mn 1- x- yφ xNa yV 2-2 x-yMo 2 x+yO 6 Solid Solutions

    NASA Astrophysics Data System (ADS)

    Masłowska, Bogna; Ziółkowski, Jacek

    1994-05-01

    MnV 2O 6 of the brannerite-type structure (below 540°C) doped with MoO 3 and Na 2O forms isomorphous solid solutions MnNaφ = Mn 1- x-yφ xNa yV 2-2 x-yMo 2 x+ yO 6 (φ cation vacancy in the original Mn position), belonging to the pseudoternary MnV 2O 6-NaVMoO 6-MoO 3 system. Particular cases are MnNa = Mn 1- yNa y V 2- yMo yO 6 ( x = 0), Mnφ = Mn 1- xφ xV 2-2 xMo 2 xO 6 ( y = 0), and Naφ = Na 1- xφ xV 1- xMo 1+ xO 6 ( x + y = 1). MnV 2O 6 and NaVMoO 6 show miscibility in the entire composition range (MnNa). The opposite boundary of MnNaφ passes through the (100 x, 100 y) points (45, 0), (33, 30), and (30, 70). The phase diagram of the pseudobinary MnV 2O 6-NaVMoO 6 system (determined with DTA) shows (i) a narrow double-lens-type solidus-liquidus gap at high values of y , (ii) two peritectic meltings at lower y (yielding the high temperature β-MnNa and Mn 2V 2O 7), and (iii) little area of β-MnNa. Lattice parameters of MnNa (determined with X-ray diffraction) reveal small deviations from Vegard's law. As the ionic radii of both dopants (Na + and Mo 6+) are, respectively, larger than those of mother ions (Mn 2+ and V 5+), the unit cell increases in all directions with rising y along the MnNa series of solid solutions. However, due to the anisotropy of the structure, parameter c is strongly sensitive to Na/Mn substitution, b is ruled by Mo/V, and a is weakly influenced by Mo/V. Close analogy to the behavior of the previously studied MnV 2O 6-LiVMoO 6-MoO 6 system is discussed.

  19. Polarity dependence of Mn incorporation in (Ga,Mn)N superlattices

    NASA Astrophysics Data System (ADS)

    Tropf, L.; Kunert, G.; Jakieła, R.; Wilhelm, R. A.; Figge, S.; Grenzer, J.; Hommel, D.

    2016-03-01

    In the context of recent efforts to combine high Mn concentrations in (Ga,Mn)N with a pronounced p-type carrier density, (Ga,Mn)N/GaN:Mg-superlattices have been fabricated using plasma-assisted molecular beam epitaxy. Profiles of the dopant atomic densities in the heterostructures are obtained by secondary ion mass spectroscopy. They show an abrupt drop of two to three orders of magnitude in both Mn and Mg concentrations after the first GaN:Mg layer above a critical Mg-flux. Scanning electron microscopy before and after selective etching reveals a polarity inversion from originally Ga-face to N-face GaN in samples in which high Mg fluxes were applied. From our observations, we are able to draw an analogy between the impurity incorporation laws of Mg and Mn.

  20. Combined effects Na and SO2 in flue gas on Mn-Ce/TiO2 catalyst for low temperature selective catalytic reduction of NO by NH3 simulated by Na2SO4 doping

    NASA Astrophysics Data System (ADS)

    Zhou, Aiyi; Yu, Danqing; Yang, Liu; Sheng, Zhongyi

    2016-08-01

    A series of Mn-Ce/TiO2 catalysts were synthesized through an impregnation method and used for low temperature selective catalytic reduction (SCR) of NOx with ammonia (NH3). Na2SO4 was added into the catalyst to simulate the combined effects of alkali metal and SO2 in the flue gas. Experimental results showed that Na2SO4 had strong and fluctuant influence on the activity of Mn-Ce/TiO2, because the effect of Na2SO4 included pore occlusion and sulfation effect simultaneously. When Na2SO4 loading content increased from 0 to 1 wt.%, the SCR activities of Na2SO4-doped catalysts decreased greatly. With further increasing amount of Na2SO4, however, the catalytic activity increased gradually. XRD results showed that Na2SO4 doping could induce the crystallization of MnOx phases, which were also confirmed by TEM and SEM results. BET results showed that the surface areas decreased and a new bimodal mesoporous structure formed gradually with the increasing amount of Na2SO4. XPS results indicated that part of Ce4+ and Mn3+ were transferred to Ce3+ and Mn4+ due to the sulfation after Na2SO4 deposition on the surface of the catalysts. When the doped amounts of Na2SO4 increased, NH3-TPD results showed that the Lewis acid sites decreased and the Brønsted acid sites of Mn-Ce/TiO2 increased quickly, which could be considered as another reason for the observed changes in the catalytic activity. The decreased Mn and Ce atomic concentration, the changes of their oxidative states, and the variation in acidic properties on the surface of Na2SO4-doped catalysts could be the reasons for the fluctuant changes of the catalytic activity.

  1. Critical Surface Parameters for the Oxidative Coupling of Methane over the Mn-Na-W/SiO2 Catalyst.

    PubMed

    Hayek, Naseem S; Lucas, Nishita S; Warwar Damouny, Christine; Gazit, Oz M

    2017-11-22

    The work here presents a thorough evaluation of the effect of Mn-Na-W/SiO 2 catalyst surface parameters on its performance in the oxidative coupling of methane (OCM). To do so, we used microporous dealuminated β-zeolite (Zeo), or mesoporous SBA-15 (SBA), or macroporous fumed silica (Fum) as precursors for catalyst preparation, together with Mn nitrate, Mn acetate and Na 2 WO 4 . Characterizing the catalysts by inductively coupled plasma-optical emission spectroscopy, N 2 physisorption, X-ray diffraction, high-resolution scanning electron microscopy-energy-dispersive spectroscopy, X-ray photoelectron spectroscopy, and catalytic testing enabled us to identify critical surface parameters that govern the activity and C 2 selectivity of the Mn-Na-W/SiO 2 catalyst. Although the current paradigm views the phase transition of silica to α-cristobalite as the critical step in obtaining dispersed and stable metal sites, we show that the choice of precursors is equally or even more important with respect to tailoring the right surface properties. Specifically, the SBA-based catalyst, characterized by relatively closed surface porosity, demonstrated low activity and low C 2 selectivity. By contrast, for the same composition, the Zeo-based catalyst showed an open surface pore structure, which translated up to fourfold higher activity and enhanced selectivity. By varying the overall composition of the Zeo catalysts, we show that reducing the overall W concentration reduces the size of the Na 2 WO 4 species and increases the catalytic activity linearly as much as fivefold higher than the SBA catalyst. This linear dependence correlates well to the number of interfaces between the Na 2 WO 4 and Mn 2 O 3 species. Our results combined with prior studies lead us to single out the interface between Na 2 WO 4 and Mn 2 O 3 as the most probable active site for OCM using this catalyst. Synergistic interactions between the various precursors used and the phase transition are discussed in

  2. Three-Dimensional Fibrous Network of Na0.21 MnO2 for Aqueous Sodium-Ion Hybrid Supercapacitors.

    PubMed

    Karikalan, Natarajan; Karuppiah, Chelladurai; Chen, Shen-Ming; Velmurugan, Murugan; Gnanaprakasam, Periyasami

    2017-02-16

    Sodium-ion hybrid supercapacitors are potential energy-storage devices and have recently received enormous interest. However, the development of cathode materials and the use of nonaqueous electrolyte remain a great challenge. Hence, aqueous Na-ion hybrid supercapacitors based on a three-dimensional network of NaMnO 2 were developed. The cathode material was synthesized by the electro-oxidation of potassium manganese hexacyanoferrate nanocubes. The oxidized compound was confirmed to be Na 0.21 MnO 2 by various physical characterization methods. Manganese dioxide is a well-characterized material for aqueous asymmetric pseudocapacitors, but its usage at high operating voltages is limited due to the electrochemical stability of water. Nevertheless, high-potential and high-performance aqueous supercapacitors exhibiting a cell potential of 2.7 V were developed. Further, the practical applicability of an asymmetric supercapacitor based on NaMnO 2 (cathode) and reduced graphene oxide (anode) was demonstrated by powering a 2.1 V red LED. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  3. Na2MnSiO4 as an attractive high capacity cathode material for sodium-ion battery

    NASA Astrophysics Data System (ADS)

    Law, Markas; Ramar, Vishwanathan; Balaya, Palani

    2017-08-01

    Here we report a polyanion-based cathode material for sodium-ion batteries, Na2MnSiO4, registering impressive sodium storage performances with discharge capacity of 210 mAh g-1 at an average voltage of 3 V at 0.1 C, along with excellent long-term cycling stability (500 cycles at 1 C). Insertion/extraction of ∼1.5 mol of sodium ion per formula unit of the silicate-based compound is reported and the utilisation of Mn2+ ⇋ Mn4+ redox couple is also demonstrated by ex-situ XPS. Besides, this study involves a systematic investigation of influence of the electrolyte additive (with different content) on the sodium storage performance of Na2MnSiO4. The electrolyte additive forms an optimum protective passivation film on the electrode surface, successfully reducing manganese dissolution.

  4. Strain-Engineered Multiferroicity in P n m a NaMnF3 Fluoroperovskite

    NASA Astrophysics Data System (ADS)

    Garcia-Castro, A. C.; Romero, A. H.; Bousquet, E.

    2016-03-01

    In this study we show from first principles calculations the possibility to induce multiferroic and magnetoelectric functional properties in the P n m a NaMnF3 fluoroperovskite by means of epitaxial strain engineering. Surprisingly, we found a very strong nonlinear polarization-strain coupling that drives an atypical amplification of the ferroelectric polarization for either compression or expansion of the cell. This property is associated with a noncollinear antiferromagnetic ordering, which induces a weak ferromagnetism phase and makes the strained NaMnF3 fluoroperovskite multiferroic. The magnetoelectric response was calculated and it was found to be composed of linear and nonlinear components with amplitudes similar to the ones of Cr2O3. These findings show that it is possible to move the fluoride family toward functional applications with unique responses.

  5. Weak ferromagnetism and short range polar order in NaMnF3 thin films

    NASA Astrophysics Data System (ADS)

    Kc, Amit; Borisov, Pavel; Shvartsman, Vladimir; Lederman, David

    The orthorhombically distorted perovskite NaMnF3 has been predicted to become ferroelectric if an a = c distortion of the bulk Pnma structure is imposed. In order to test this prediction, NaMnF3 thin films were grown on SrTiO3 (100) single crystal substrates via molecular beam epitaxy. The best films were smooth and single phase with four different twin domains. In-plane magnetization measurements revealed the presence of antiferromagnetic ordering with weak ferromagnetism below the Néel temperature TN = 66 K. For the dielectric studies, NaMnF3 films were grown on a 30 nm SrRuO3 (100) layer used as a bottom electrode grown via pulsed laser deposition. The complex permittivity as a function of frequency indicated a strong Debye-like relaxation contribution characterized by a distribution of relaxation times. A power-law divergence of the characteristic relaxation time revealed an order-disorder phase transition at 8 K. The slow relaxation dynamics indicated the formation of super-dipoles (superparaelectric moments) that extend over several unit cells, similar to polar nanoregions of relaxor ferroelectrics. This work was supported by the National Science Foundation (Grant 1434897) and the WVU Shared Research Facilities at West Virginia University.

  6. Structural characterization of layered Na0.5Co0.5Mn0.5O2 material as a promising cathode for sodium-ion batteries

    NASA Astrophysics Data System (ADS)

    Manikandan, Palanisamy; Heo, Seongwoo; Kim, Hyun Woo; Jeong, Hu Young; Lee, Eungje; Kim, Youngsik

    2017-09-01

    Layered Na0.5Co0.5Mn0.5O2 material is synthesized through a facile mixed hydroxy-carbonate route using (Co0.5Mn0.5)2(OH)2CO3 precursor and well characterized as a hexagonal layered structure under P63/mmc space group. The lattice parameters and unit cell volume (a = 2.8363 Å, c = 11.3152 Å and V = 78.83 Å3) are calculated by Rietveld refinement analysis. A flaky-bundle morphology is obtained to the layered Na0.5Co0.5Mn0.5O2 material with the hexagonal flake size ∼30 nm. Advanced transmission electron microscopic images are revealed the local structure of the layered Na0.5Co0.5Mn0.5O2 material with contrasting bright dots and faint dark dots corresponding to the Co/Mn and Na atoms. Two oxidation and reduction peaks are occurred in a cyclic voltammetric analysis corresponding to Co3+/Co4+ and Mn3+/Mn4+ redox processes. These reversible processes are attributed to the intercalation/de-intercalation of Na+ ions into the host structure of layered Na0.5Co0.5Mn0.5O2 material. Accordingly, the sodium cell is delivered the initial charge-discharge capacity 53/144 mAh g-1 at 0.5 C, which cycling studies are extended to rate capability test at 1 C, 3 C and 5C. Eventually, the Na-ion full-cell is yielded cathode charge-discharge capacity 55/52 mAh g-1 at 0.212 mA and exhibited as a high voltage cathode for Na-ion batteries.

  7. Ti-substituted tunnel-type Na 0.44MnO 2 oxide as a negative electrode for aqueous sodium-ion batteries

    DOE PAGES

    Wang, Yuesheng; Liu, Jue; Lee, Byungju; ...

    2015-03-25

    The aqueous sodium-ion battery system is a safe and low-cost solution for large-scale energy storage, due to the abundance of sodium and inexpensive aqueous electrolytes. Although several positive electrode materials, e.g., Na 0.44MnO 2, were proposed, few negative electrode materials, e.g., activated carbon and NaTi 2(PO 4) 3, are available. Here we show that Ti-substituted Na 0.44MnO 2 (Na 0.44[Mn 1-xTi x]O 2) with tunnel structure can be used as a negative electrode material for aqueous sodium-ion batteries. This material exhibits superior cyclability even without the special treatment of oxygen removal from the aqueous solution. Atomic-scale characterizations based on sphericalmore » aberration-corrected electron microscopy and ab initio calculations are utilized to accurately identify the Ti substitution sites and sodium storage mechanism. Ti substitution tunes the charge ordering property and reaction pathway, significantly smoothing the discharge/charge profiles and lowering the storage voltage. Both the fundamental understanding and practical demonstrations suggest that Na 0.44[Mn 1-xTi x]O 2 is a promising negative electrode material for aqueous sodium-ion batteries.« less

  8. Multiangular Rod-Shaped Na0.44MnO2 as Cathode Materials with High Rate and Long Life for Sodium-Ion Batteries.

    PubMed

    Liu, Qiannan; Hu, Zhe; Chen, Mingzhe; Gu, Qinfen; Dou, Yuhai; Sun, Ziqi; Chou, Shulei; Dou, Shi Xue

    2017-02-01

    The tunnel-structured Na 0.44 MnO 2 is considered as a promising cathode material for sodium-ion batteries because of its unique three-dimensional crystal structure. Multiangular rod-shaped Na 0.44 MnO 2 have been first synthesized via a reverse microemulsion method and investigated as high-rate and long-life cathode materials for Na-ion batteries. The microstructure and composition of prepared Na 0.44 MnO 2 is highly related to the sintering temperature. This structure with suitable size increases the contact area between the material and the electrolyte and guarantees fast sodium-ion diffusion. The rods prepared at 850 °C maintain specific capacity of 72.8 mA h g -1 and capacity retention of 99.6% after 2000 cycles at a high current density of 1000 mA g -1 . The as-designed multiangular Na 0.44 MnO 2 provides new insight into the development of tunnel-type electrode materials and their application in rechargeable sodium-ion batteries.

  9. A mixed iron-manganese based pyrophosphate cathode, Na2Fe0.5Mn0.5P2O7, for rechargeable sodium ion batteries.

    PubMed

    Shakoor, Rana A; Park, Chan Sun; Raja, Arsalan A; Shin, Jaeho; Kahraman, Ramazan

    2016-02-07

    The development of secondary batteries based on abundant and cheap elements is vital. Among various alternatives to conventional lithium-ion batteries, sodium-ion batteries (SIBs) are promising due to the abundant resources and low cost of sodium. While there are many challenges associated with the SIB system, cathode is an important factor in determining the electrochemical performance of this battery system. Accordingly, ongoing research in the field of SIBs is inclined towards the development of safe, cost effective cathode materials having improved performance. In particular, pyrophosphate cathodes have recently demonstrated decent electrochemical performance and thermal stability. Herein, we report the synthesis, electrochemical properties, and thermal behavior of a novel Na2Fe0.5Mn0.5P2O7 cathode for SIBs. The material was synthesized through a solid state process. The structural analysis reveals that the mixed substitution of manganese and iron has resulted in a triclinic crystal structure (P1[combining macron] space group). Galvanostatic charge/discharge measurements indicate that Na2Fe0.5Mn0.5P2O7 is electrochemically active with a reversible capacity of ∼80 mA h g(-1) at a C/20 rate with an average redox potential of 3.2 V. (vs. Na/Na(+)). It is noticed that 84% of initial capacity is preserved over 90 cycles showing promising cyclability. It is also noticed that the rate capability of Na2Fe0.5Mn0.5P2O7 is better than Na2MnP2O7. Ex situ and CV analyses indicate that Na2Fe0.5Mn0.5P2O7 undergoes a single phase reaction rather than a biphasic reaction due to different Na coordination environment and different Na site occupancy when compared to other pyrophosphate materials (Na2FeP2O7 and Na2MnP2O7). Thermogravimetric analysis (25-550 °C) confirms good thermal stability of Na2Fe0.5Mn0.5P2O7 with only 2% weight loss. Owing to promising electrochemical properties and decent thermal stability, Na2Fe0.5Mn0.5P2O7, can be an attractive cathode for SIBs.

  10. New series of triple molybdates AgA{sub 3}R(MoO{sub 4}){sub 5} (A=Mg, R=Cr, Fe; A=Mn, R=Al, Cr, Fe, Sc, In) with framework structures and mobile silver ion sublattices

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Kotova, Irina Yu.; Buryat State University, Smolin St. 24a, Ulan-Ude 670000, Buryat Republic; Solodovnikov, Sergey F.

    Triple molybdates AgA{sub 3}R(MoO{sub 4}){sub 5} (A=Mg, R=Cr, Fe; A=Mn, R=Al, Cr, Fe, Sc, In) of the NaMg{sub 3}In(MoO{sub 4}){sub 5} type were synthesized and single crystals of AgMg{sub 3}R(MoO{sub 4}){sub 5} (R=Cr, Fe) were grown. In their structures, the MoO{sub 4} tetrahedra, pairs and trimers of edge-shared (Mg, R)O{sub 6} octahedra are connected by common vertices to form a 3D framework. Large framework cavities involve Ag{sup +} cations disordered on three nearby positions with CN=3+1 or 4+1. Alternating (Mg, R)O{sub 6} octahedra and MoO{sub 4} tetrahedra in the framework form quadrangular windows penetrable for Ag{sup +} at elevated temperatures.more » Above 653–673 K, the newly obtained molybdates demonstrate abrupt reduction of the activation energy to 0.4–0.6 eV. At 773 K, AgMg{sub 3}Al(MoO{sub 4}){sub 5} shows electric conductivity 2.5·10{sup −2} S/cm and E{sub a}=0.39 eV compatible with characteristics of the best ionic conductors of the NASICON type. - Graphical abstract: Triple molybdates AgA{sub 3}R(MoO{sub 4}){sub 5} (A=Mg, R=Cr, Fe; A=Mn, R=Al, Cr, Fe, Sc, In) of the NaMg{sub 3}In(MoO{sub 4}){sub 5} type were synthesized, AgMg{sub 3}R(MoO{sub 4}){sub 5} (R=Cr, Fe) were structurally characterized, ion-conductive properties of AgMg{sub 3}Al(MoO{sub 4}){sub 5} were measured. Display Omitted - Highlights: • Triple molybdates AgA{sub 3}R(MoO{sub 4}){sub 5} (A=Mg, R=Cr, Fe; A=Mn, R=Al, Cr, Fe, Sc, In) of the NaMg{sub 3}In(MoO{sub 4}){sub 5} type were synthesized. • Single crystals of AgMg{sub 3}R(MoO{sub 4}){sub 5} (R=Cr, Fe) were grown and their crystal structures were determined. • Disordering Ag{sup +} ions and penetrable framework structures of AgMg{sub 3}R(MoO{sub 4}){sub 5} (R=Cr, Fe) suggest 2D-character of silver-ion mobility. • Measured ion-conductive properties of AgMg{sub 3}Al(MoO{sub 4}){sub 5} are compatible with characteristics of the best ionic conductors of the NASICON type.« less

  11. High pressure structural investigation on alluaudites Na{sub 2}Fe{sub 3}(PO{sub 4}){sub 3}-Na{sub 2}FeMn{sub 2}(PO{sub 4}){sub 3} system

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Gao, Jing; Huang, Weifeng; Qin, Shan

    Alluaudites are promising electrochemical materials benefited from the open structure. Structural variations of alluaudites Na{sub 2}M{sub 3}(PO{sub 4}){sub 3} (M{sub 3}=Fe{sub 3}, Fe{sub 2}Mn and FeMn{sub 2}) system have been studied by synchrotron radiation X-ray diffraction combined with diamond anvil cell technique up to ~10 GPa at room temperature. No phase transition is observed. The excellent structural stability is mainly due to the flexible framework plus strong covalent P-O bond. Mn{sup 2+} instead of Fe can be described as Na{sup +}+2Fe{sup 2+}→Mn{sup 2+}+Fe{sup 3+}+□ where □ represents a lattice vacancy. The replacement of Fe with larger Mn{sup 2+} is equivalentmore » to applying negative chemical pressure to the material. And it causes a more compressible b-axis, lattice expansion, structural compressibility and intensifies the core/electron-electron interactions of Fe. External pressure effect produces anisotropic lattice shrinkage. Structural considerations related to these variations and promising application prospects are discussed. - Graphical abstract: Figure 1 The crystal structure of alluaudites Na{sub 2}M{sub 3}(PO{sub 4}){sub 3} (M{sub 3}=Fe{sub 3}, Fe{sub 2}Mn and FeMn{sub 2}) projected along the c-axis. Alluaudites adopt a flexible framework plus strong covalent P-O bond, which contribute to excellent structural stability up to ~10 GPa. Mn{sup 2+} instead of Fe can be described as Na{sup ++}2Fe{sup 2+}→Mn{sup 2+}+Fe{sup 3+}+□ where □ represents a lattice vacancy, and it is equivalent to applying negative chemical pressure to the host. The substitution causes a more compressible b-axis, lattice expansion, structural compressibility and intensifies the core/electron-electron interactions of Fe.« less

  12. The magnetic Curie temperature and exchange coupling between cations in tetragonal spinel oxide Mn2.5M0.5O4 (M = Co, Ni, Mn, Cr, and Mg) films

    NASA Astrophysics Data System (ADS)

    Kuo, K.; Cheng, C. W.; Chern, G.

    2012-04-01

    Mn3O4 is a Jahn-Taller tetragonal ferrite that has a relatively low Curie temperature (Tc) of ˜43 K due to weak coupling between the canting spins. In this study, we fabricated a series of 100-nm-thick Mn2.5M0.5O4 (M = Co, Ni, Mn, Cr, and Mg) films via oxygen-plasma-assisted molecular beam epitaxy and measured the structural and magnetic properties of these films. These films show single phase quality, and the c-axis lattice parameter of pure Mn3O4 is 0.944 nm, with a c/a ratio ˜1.16, consistent with the bulk values. The replacement of Mn by M (M = Co, Ni, Cr, and Mg) changes the lattice parameters, and the c/a ratio varies between 1.16 and 1.06 depending upon the cation distribution of the films. The magnetic Curie temperatures of these films also vary in the range of 25-66 K in that Ni and Co enhance the Tc whereas Mg reduces the Tc (Cr shows no effect on the Tc). These changes to the Tc are related to both the element electronic state and the cation distributions in these compounds. As a non-collinear spin configuration can induce electrical polarization, the present study provides a systematic way to enhance the magnetic transition temperature in tetragonal spinel ferrites.

  13. A High Pressure Post-Perovskite Phase Transition in NaMgF3--a MgSiO3 Analog Material

    NASA Astrophysics Data System (ADS)

    Martin, C.; Liu, H.; Crichton, W.; Parise, J. B.

    2005-12-01

    Since Murakami et al. (2004) identified a perovskite (pv, Pbnm) to post-perovskite (ppv, Cmcm) structural phase transition in MgSiO3, the transition has been reported to occur in many oxides at ultra-high pressures (>60 GPa). The layered ppv structure is rapidly shaping a better understanding of seismic anisotropy in the controversial D" region of the lower mantle. While the ppv unit cell may be derived from indexing of the powder pattern, the structure adopted at high pressure is experimentally ill-constrained due to compromised powder diffraction statistics typically obtained from small sample volumes at extreme conditions in the diamond anvil cell. NaMgF3, a structural analog material to MgSiO3 pv, exhibits a large compressibility and presents the possibility of reducing the pv-ppv transition pressure, allowing for improved powder statistics from a larger sample volume. In accordance with our previous theoretical and experimental evidence (Liu et al., 2005; Parise et al., 2004), we have observed a phase transition in NaMgF3 during two recent independent high pressure trials utilizing monochromatic x-ray diffraction and in-situ laser heating in the diamond anvil cell at pressures as low as 30 GPa. From our analysis thus far, we have found the unit cell of the high pressure phase cannot be indexed according to pv (Pbnm) or close permutations of ppv (Cmcm) unit cells predicted for NaMgF3 or unit cells observed for ppv MgSiO3 and MgGeO3. In addition, we have precluded a breakdown to high pressure phases of NaF and MgF3 as an explanation for the observed data. Upon pressure release, we observe diffraction peaks from the high pressure phase in the absence of pv NaMgF3, suggesting the high pressure structure is quenchable to ambient conditions. The results of the work in progress will be presented at the meeting.

  14. Anti-site-induced diverse diluted magnetism in LiMgPdSb-type CoMnTiSi alloy

    NASA Astrophysics Data System (ADS)

    Lin, T. T.; Dai, X. F.; Guo, R. K.; Cheng, Z. X.; Wang, L. Y.; Wang, X. T.; Liu, G. D.

    2017-02-01

    The effect of three kinds of anti-site disorder to electronic structure and magnetic properties of the LiMgPdSb-type CoMnTiSi alloy are investigated. It was found the Mn-Ti anti-site disorder can induce the diluted magnetism in CoMnTiSi matrix. The magnetic structure has an oscillation between the ferromagnetic and antiferromagnetic states with the different degree of Mn-Ti anti-site disorder. Two novel characteristics: the diluted antiferromagnetic half-metallicity and the diluted zero-gap half-metallity are found in the different degree range of the Mn-Ti anti-site disorder. The Co-Mn and Co-Ti anti-site disorder have little effect on the magnetic properties. The width of energy gap and the intensity of DOS at the Fermi level can be adjusted by the degree of Co-Mn or Co-Ti anti-site disorder. The independent control to the carrier concentration and magnetization can be realized by introducing the different anti-site disorder.

  15. Na0.44MnO2 nanorods as a cathode material for Na-ion batteries

    NASA Astrophysics Data System (ADS)

    Avci, Sevda; Oz, Erdinc; Demirel, Serkan; Altin, Emine; Altin, Serdar; Bayri, Ali; Yakinci, Eyyuphan

    2014-03-01

    Lithium-ion batteries have dominated the rechargeable battery market because of their high energy and power capability. On the other hand, sodium is one of the more abundant elements on Earth unlike Li. Moreover, Na has similar chemical properties to Li, indicating that Na-ion batteries can be an alternative to Li counterparts. With that respect, we have synthesized Na0.44MnO2 nanorods as cathode materials for Na-ion batteries. We have investigated the effects of structural, electrical, and magnetic properties on battery performance. We report the synthesis conditions and growth mechanism of the nanorods. The structure and the morphology of the materials were investigated by X-ray diffraction (XRD), scanning electron microscopy (SEM), energy-dispersive X-ray (EDX), and atomic force microscopy (AFM) techniques. Temperature dependent structural changes were determined via in situ X-ray diffraction and TG-DTA measurements showing structural changes above room temperature. This work is funded by The Scientific and Technological Research Council of Turkey with Grant No:112M487.

  16. Numerical Study of Microstructural Evolution During Homogenization of Al-Si-Mg-Fe-Mn Alloys

    NASA Astrophysics Data System (ADS)

    Priya, Pikee; Johnson, David R.; Krane, Matthew J. M.

    2016-09-01

    Microstructural evolution during homogenization of Al-Si-Mg-Fe-Mn alloys occurs in two stages at different length scales: while holding at the homogenization temperature (diffusion on the scale of the secondary dendrite arm spacing (SDAS) in micrometers) and during quenching to room temperature (dispersoid precipitation at the nanometer to submicron scale). Here a numerical study estimates microstructural changes during both stages. A diffusion-based model developed to simulate evolution at the SDAS length scale predicts homogenization times and microstructures matching experiments. That model is coupled with a Kampmann Wagner Neumann-based precipitate nucleation and growth model to study the effect of temperature, composition, as-cast microstructure, and cooling rates during posthomogenization quenching on microstructural evolution. A homogenization schedule of 853 K (580 °C) for 8 hours, followed by cooling at 250 K/h, is suggested to optimize microstructures for easier extrusion, consisting of minimal α-Al(FeMn)Si, no β-AlFeSi, and Mg2Si dispersoids <1 μm size.

  17. Co-intercalation of Mg(2+) and Na(+) in Na(0.69)Fe2(CN)6 as a High-Voltage Cathode for Magnesium Batteries.

    PubMed

    Kim, Dong-Min; Kim, Youngjin; Arumugam, Durairaj; Woo, Sang Won; Jo, Yong Nam; Park, Min-Sik; Kim, Young-Jun; Choi, Nam-Soon; Lee, Kyu Tae

    2016-04-06

    Thanks to the advantages of low cost and good safety, magnesium metal batteries get the limelight as substituent for lithium ion batteries. However, the energy density of state-of-the-art magnesium batteries is not high enough because of their low operating potential; thus, it is necessary to improve the energy density by developing new high-voltage cathode materials. In this study, nanosized Berlin green Fe2(CN)6 and Prussian blue Na(0.69)Fe2(CN)6 are compared as high-voltage cathode materials for magnesium batteries. Interestingly, while Mg(2+) ions cannot be intercalated in Fe2(CN)6, Na(0.69)Fe2(CN)6 shows reversible intercalation and deintercalation of Mg(2+) ions, although they have the same crystal structure except for the presence of Na(+) ions. This phenomenon is attributed to the fact that Mg(2+) ions are more stable in Na(+)-containing Na(0.69)Fe2(CN)6 than in Na(+)-free Fe2(CN)6, indicating Na(+) ions in Na(0.69)Fe2(CN)6 plays a crucial role in stabilizing Mg(2+) ions. Na(0.69)Fe2(CN)6 delivers reversible capacity of approximately 70 mA h g(-1) at 3.0 V vs Mg/Mg(2+) and shows stable cycle performance over 35 cycles. Therefore, Prussian blue analogues are promising structures for high-voltage cathode materials in Mg batteries. Furthermore, this co-intercalation effect suggests new avenues for the development of cathode materials in hybrid magnesium batteries that use both Mg(2+) and Na(+) ions as charge carriers.

  18. Removal of Mn(II) from the acid mine wastewaters using coal fired bottom ash

    NASA Astrophysics Data System (ADS)

    Mahidin, M.; Sulaiman, T. N.; Muslim, A.; Gani, A.

    2017-06-01

    Acid mine wastewater (AMW), the wastewater from mining activities which has low pH about 3-5 and contains hazardous heavy metals such as Cu, Fe, Mn, Zn, Pb, etc. Those heavy metals pollution is of prime concern from the environmental view point. Among the heavy metals, Mn occupies the third position in the AMW from one the iron ore mining company in Aceh, Indonesia. In this study, the possibility use of bottom ash from coal fired boiler of steam power plants for the removal of Mn(II) in AMW has been investigated. Experimental has been conducted as follows. Activation of bottom ash was done both by physical and chemical treatments through heating at 270 °C and washing with NaOH activator 0.5 and 1 M. Adsorption test contains two parts observation; preliminary and primary experiments. Preliminary study is addressed to select the best condition of three independent variables i.e.: pH of AMW (3 & 7), bottom ash particle size (40, 60 & 100 mesh) and initial Mn(II) concentrations (100 & 600 mg/l). AMW used was synthetics wastewater. It was found that the best value for NaOH is 1 M, pH is 7, particle size is 100 meshes and initial Mn(II) concentration is 600 mg/l from the adsorption efficiency point of view. The maximum adsorption capacity (q e) is 63.7 mg/g with the efficiency of 85%.

  19. Microstructure, Mechanical Properties, and Age-Hardening Behavior of an Al-Si-Fe-Mn-Cu-Mg Alloy Produced by Spray Deposition

    NASA Astrophysics Data System (ADS)

    Feng, Wang; Jishan, Zhang; Baiqing, Xiong; Yongan, Zhang

    2011-02-01

    It has been recognized generally that the spray-deposited process is an innovative technique of rapid solidification. In this paper, Al-20Si-5Fe-3Mn-3Cu-1Mg alloy was synthesized by the spray atomization and deposition technique. The microstructure and mechanical properties of the spray-deposited alloy were studied using x-ray diffraction, scanning electron microscopy, transmission electron microscopy (TEM), and tensile tests. It is observed that the microstructure of spray-deposited Al-20Si-5Fe-3Mn-3Cu-1Mg alloy is composed of the α-Al,Si and the particle-like Al15(FeMn)3Si2 compounds. The aging process of the alloy was investigated by microhardness measurement, differential scanning calorimetry analysis, and TEM observations. The results indicate that the two types of precipitates, S-Al2CuMg and σ-Al5Cu6Mg2 precipitate from matrix and improve the tensile strength of the alloy efficiently at both the ambient and elevated temperatures (300 °C).

  20. Effect of CeLa addition on the microstructures and mechanical properties of Al-Cu-Mn-Mg-Fe alloy

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Du, Jiandi

    Development of high strength lithium battery shell alloy is highly desired for new energy automobile industry. The microstructures and mechanical properties of Al-Cu-Mn-Mg-Fe alloy with different CeLa additions were investigated through optical microscopy (OM), X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), Rietveld refinement and tensile testing. Experimental results indicate that Al{sub 8}Cu{sub 4}Ce and Al{sub 6}Cu{sub 6}La phases formed due to CeLa addition. Addition of 0.25 wt.% CeLa could promote the formation of denser precipitation of Al{sub 20}Cu{sub 2}Mn{sub 3} and Al{sub 6}(Mn, Fe) phases, which improved the mechanical properties of the alloy at room temperature.more » However, up to 0.50 wt.% CeLa addition could promote the formation of coarse Al{sub 8}Cu{sub 4}Ce phase, Al{sub 6}Cu{sub 6}La phase and Al{sub 6}(Mn, Fe) phase, which resulted in weakened mechanical properties. - Highlights: •Al-Cu-Mn-Mg-Fe alloys with different CeLa addition were fabricated through casting and rolling. •Al{sub 8}Cu{sub 4}Ce and Al{sub 6}Cu{sub 6}La phases formed after CeLa addition. •Addition of 0.25 wt.% CeLa promoted formation of denser precipitates of Al{sub 20}Cu{sub 2}Mn{sub 3} and Al{sub 6}(Mn, Fe). •Mechanical properties of the alloy was improved after 0.25 wt.% CeLa addition.« less

  1. Asymmetric supercapacitors with high energy density based on helical hierarchical porous Na x MnO2 and MoO2.

    PubMed

    Lu, Xue-Feng; Huang, Zhi-Xiang; Tong, Ye-Xiang; Li, Gao-Ren

    2016-01-01

    Helical hierarchical porous Na x MnO 2 /CC and MoO 2 /CC, which are assembled from nanosheets and nanoparticles, respectively, are fabricated using a simple electrodeposition method. These unique helical porous structures enable electrodes to have a high capacitance and an outstanding cycling performance. Based on the helical Na x MnO 2 /CC as the positive electrodes and helical MoO 2 /CC as the negative electrodes, high performance Na x MnO 2 /CC//MoO 2 /CC asymmetric supercapacitors (ASCs) are successfully assembled, and they achieve a maximum volume C sp of 2.04 F cm -3 and a maximum energy density of 0.92 mW h cm -3 for the whole device and an excellent cycling stability with 97.22% C sp retention after 6000 cycles.

  2. Spectroscopic investigation of new water soluble Mn(II)(2) and Mg(II)(2) complexes for the substrate binding models of xylose/glucose isomerases.

    PubMed

    Patra, Ayan; Bera, Manindranath

    2014-01-30

    In methanol, the reaction of stoichiometric amounts of Mn(OAc)(2)·4H(2)O and the ligand H(3)hpnbpda [H(3)hpnbpda=N,N'-bis(2-pyridylmethyl)-2-hydroxy-1,3-propanediamine-N,N'-diacetic acid] in the presence of NaOH, afforded a new water soluble dinuclear manganese(II) complex, [Mn2(hpnbpda)(μ-OAc)] (1). Similarly, the reaction of Mg(OAc)(2)·4H(2)O and the ligand H3hpnbpda in the presence of NaOH, in methanol, yielded a new water soluble dinuclear magnesium(II) complex, [Mg2(hpnbpda)(μ-OAc)(H2O)2] (2). DFT calculations have been performed for the structural optimization of complexes 1 and 2. The DFT optimized structure of complex 1 shows that two manganese(II) centers are in a distorted square pyramidal geometry, whereas the DFT optimized structure of complex 2 reveals that two magnesium(II) centers adopt a six-coordinate distorted octahedral geometry. To understand the mode of substrate binding and the mechanistic details of the active site metals in xylose/glucose isomerases (XGI), we have investigated the binding interactions of biologically important monosaccharides d-glucose and d-xylose with complexes 1 and 2, in aqueous alkaline solution by a combined approach of FTIR, UV-vis, fluorescence, and (13)C NMR spectroscopic techniques. Fluorescence spectra show the binding-induced gradual decrease in emission of complexes 1 and 2 accompanied by a significant blue shift upon increasing the concentration of sugar substrates. The binding modes of d-glucose and d-xylose with complex 2 are indicated by their characteristic coordination induced shift (CIS) values in (13)C NMR spectra for C1 and C2 carbon atoms. Copyright © 2013 Elsevier Ltd. All rights reserved.

  3. Different Effects of Al Substitution for Mn or Fe on the Structure and Electrochemical Properties of Na0.67Mn0.5Fe0.5O2 as a Sodium Ion Battery Cathode Material.

    PubMed

    Wang, Huibo; Gao, Rui; Li, Zhengyao; Sun, Limei; Hu, Zhongbo; Liu, Xiangfeng

    2018-05-07

    P2-type layered oxides based on the elements Fe and Mn have attracted great interest as sodium ion battery (SIB) cathode materials owing to their inexpensive metal constituents and high specific capacity. However, they suffer from rapid capacity fading and complicated phase transformations. In this study, we modulate the crystal structure and optimize the electrochemical performances of Na 0.67 Mn 0.5 Fe 0.5 O 2 by Al doping for Mn or Fe, respectively, and the roles of Al in the enhancement of the rate capability and cycling performance are unraveled. (1) The substitution of Al for Mn or Fe decreases the lattice parameters a and c but enlarges d spacing and lengthens Na-O bonds, which enhances Na + diffusion and rate capability especially for Na 0.67 Mn 0.5 Fe 0.47 Al 0.03 O 2 . (2) Al doping reduces the thickness of TMO 2 and strengthens TM-O/O-O bonding. This enhances the layered structure stability and the capacity retention. (3) Al doping mitigates Mn 3+ and Jahn-Teller distortion, mitigating the irreversible phase transition. (4) Al doping also alleviates the lattice volume variation and the structure strain. This further improves the stability of the layered structure and the cycling performances particularly in the case of Al doping for Fe. The in-depth insights into the roles of Al substitution might be also useful for designing high-performance cathode materials for SIBs through appropriate lattice doping.

  4. Exchange interactions in CdMnTe/CdMgTe quantum wells under high magnetic fields

    NASA Astrophysics Data System (ADS)

    Yasuhira, T.; Uchida, K.; Matsuda, Y. H.; Miura, N.; Kuroda, S.; Takita, K.

    2002-03-01

    The sp-d exchange interaction Jsp-d and the exchange interaction between the nearest neighbor Mn ions JNN were studied by magneto-photoluminescence spectra of excitons in CdMnTe/CdMgTe quantum wells in pulsed high magnetic fields up to 45 T. The magnitude of Jsp-d estimated from the observed Zeeman splitting was found to decrease as the quantum well width was decreased. The decrease is partly due to the penetration of the electron and the hole wave functions into the non-magnetic CdMgTe barrier layers, and partly due to the k-dependence of the exchange interaction. It was found that the latter effect is much larger than theoretically predicted. The observed features are well explained by a model assuming the interface disorder within some thickness near the interface. In contrast to Jsp-d, the nearest neighbor interaction JNN estimated from the steps in the photoluminescence peak was found to be independent of the well width.

  5. Simplified sample treatment for the determination of total concentrations and chemical fractionation forms of Ca, Fe, Mg and Mn in soluble coffees.

    PubMed

    Pohl, Pawel; Stelmach, Ewelina; Szymczycha-Madeja, Anna

    2014-11-15

    A simpler, and faster than wet digestion, sample treatment was proposed prior to determination of total concentrations for selected macro- (Ca, Mg) and microelements (Fe, Mn) in soluble coffees by flame atomic absorption spectrometry. Samples were dissolved in water and acidified with HNO3. Precision was in the range 1-4% and accuracy was better than 2.5%. The method was used in analysis of 18 soluble coffees available on the Polish market. Chemical fractionation patterns for Ca, Fe, Mg and Mn in soluble coffees, as consumed, using a two-column solid-phase extraction method, determined Ca, Mg and Mn were present predominantly as cations (80-93% of total content). This suggests these elements are likely to be highly bioaccessible. Copyright © 2014 Elsevier Ltd. All rights reserved.

  6. High-Performance 2.6 V Aqueous Asymmetric Supercapacitors based on In Situ Formed Na0.5 MnO2 Nanosheet Assembled Nanowall Arrays.

    PubMed

    Jabeen, Nawishta; Hussain, Ahmad; Xia, Qiuying; Sun, Shuo; Zhu, Junwu; Xia, Hui

    2017-08-01

    The voltage limit for aqueous asymmetric supercapacitors is usually 2 V, which impedes further improvement in energy density. Here, high Na content Birnessite Na 0.5 MnO 2 nanosheet assembled nanowall arrays are in situ formed on carbon cloth via electrochemical oxidation. It is interesting to find that the electrode potential window for Na 0.5 MnO 2 nanowall arrays can be extended to 0-1.3 V (vs Ag/AgCl) with significantly increased specific capacitance up to 366 F g -1 . The extended potential window for the Na 0.5 MnO 2 electrode provides the opportunity to further increase the cell voltage of aqueous asymmetric supercapacitors beyond 2 V. To construct the asymmetric supercapacitor, carbon-coated Fe 3 O 4 nanorod arrays are synthesized as the anode and can stably work in a negative potential window of -1.3 to 0 V (vs Ag/AgCl). For the first time, a 2.6 V aqueous asymmetric supercapacitor is demonstrated by using Na 0.5 MnO 2 nanowall arrays as the cathode and carbon-coated Fe 3 O 4 nanorod arrays as the anode. In particular, the 2.6 V Na 0.5 MnO 2 //Fe 3 O 4 @C asymmetric supercapacitor exhibits a large energy density of up to 81 Wh kg -1 as well as excellent rate capability and cycle performance, outperforming previously reported MnO 2 -based supercapacitors. This work provides new opportunities for developing high-voltage aqueous asymmetric supercapacitors with further increased energy density. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  7. Polymorphism of the bivalent metal vanadates MeV 2O 6 ( Me = Mg, Ca, Mn, Co, Ni, Cu, Zn, Cd)

    NASA Astrophysics Data System (ADS)

    Mocała, Krzysztof; Ziółkowski, Jacek

    1987-08-01

    Based on the literature data, our former findings and additional DTA and high-temperature X-ray studies performed for CdV 2O 6, MgV 2O 6, and MnV 2O 6, a consistent scheme of the phase transformations of the MeV 2O 6 ( Me = Mg, Ca, Mn, Co, Ni, Cu, Zn, Cd) metavanadates is constructed at normal pressure between room temperature and melting points. Three types of structures exist for the considered compounds: brannerite type (B), pseudobrannerite type (P), and NiV 2O 6 type (N). The following phase transformations have been observed: Me = Mg, B → P at 535°C; Me = Mn, B → P at 540°C; Me = Co, N → B at 660°C; Me = Cu, B (with triclinic distortion) → B at 625°C (secondary order); and Me = Cd, B → P at 170°. CaV 2O 6P, NiV 2O 6N, and ZnV 2O 6B exist in unique form in the entire temperature range. P-form seems to be favored by Me of larger ionic radii. N-form seems to appear at a peculiar d-shell structure and small Me size. Preliminary explanation of the dependence of the structure type on Me size is offered. New X-ray data are given for CdV 2O 6B, CdV 2O 6P, MgV 2O 6B, MgV 2O 6P, and MnV 2O 6P.

  8. A novel red phosphor of seven-coordinated Mn4+ ion-doped tridecafluorodizirconate Na5Zr2F13 for warm WLEDs.

    PubMed

    Xi, Luqing; Pan, Yuexiao; Huang, Shaoming; Lian, Hongzhou; Lin, Jun

    2018-04-24

    Herein, a novel red phosphor based on seven-coordinated Mn4+ ion-doped tridecafluorodizirconate, Na5Zr2F13 (NZF), has been synthesized by stirring a mixture of K2MnF6, NaF, and H2ZrF6 at room temperature. The crystal structure and morphology of the as-obtained phosphor NZF:Mn have been determined by X-ray diffraction (XRD) and scanning electron microscopy (SEM), respectively. The composition and distribution of Mn4+ ions in NZF have been confirmed by energy-dispersive spectroscopy (EDS) and element mapping via transmission electron microscopy (TEM). The phosphor NZF:Mn exhibits a strong zero phonon line (ZPL) at 616 nm under excitation of blue light from a GaN light-emitting diode (LED) chip; this is attributed to the low symmetry of Mn4+ ions occupied in a seven-coordinated environment. The luminescence intensity of NZF:Mn has been optimized by controlling the synthesis procedure and synthetic parameters. The luminescence mechanism of the red phosphor NZF:Mn has been investigated according to the detailed experimental results. A warm white light has been produced by a WLED fabricated with the red phosphor NZF:Mn and the commercial yellow phosphor Y3Al5O12:Ce3+ (YAG:Ce) on a GaN LED chip.

  9. Mechanical Properties and Microstructure of TIG and FSW Joints of a New Al-Mg-Mn-Sc-Zr Alloy

    NASA Astrophysics Data System (ADS)

    Xu, Guofu; Qian, Jian; Xiao, Dan; Deng, Ying; Lu, Liying; Yin, Zhimin

    2016-04-01

    A new Al-5.8%Mg-0.4%Mn-0.25%Sc-0.10%Zr (wt.%) alloy was successfully welded by tungsten inert gas (TIG) and friction stir welding (FSW) techniques, respectively. The mechanical properties and microstructure of the welded joints were investigated by microhardness measurements, tensile tests, and microscopy methods. The results show that the ultimate tensile strength, yield strength, and elongation to failure are 358, 234 MPa, and 27.6% for TIG welded joint, and 376, 245 MPa and 31.9% for FSW joint, respectively, showing high strength and superior ductility. The TIG welded joint fails in the heat-affected zone and the fracture of FSW joint is located in stirred zone. Al-Mg-Mn-Sc-Zr alloy is characterized by lots of dislocation tangles and secondary coherent Al3(Sc,Zr) particles. The superior mechanical properties of the TIG and FSW joints are mainly derived from the Orowan strengthening and grain boundary strengthening caused by secondary coherent Al3(Sc,Zr) nano-particles (20-40 nm). For new Al-Mg-Mn-Sc-Zr alloy, the positive effect from secondary Al3(Sc, Zr) particles in the base metal can be better preserved in FSW joint than in TIG welded joint.

  10. Extraction of Mg(OH)2 from Mg silicate minerals with NaOH assisted with H2O: implications for CO2 capture from exhaust flue gas.

    PubMed

    Madeddu, Silvia; Priestnall, Michael; Godoy, Erik; Kumar, R Vasant; Raymahasay, Sugat; Evans, Michael; Wang, Ruofan; Manenye, Seabelo; Kinoshita, Hajime

    2015-01-01

    The utilisation of Mg(OH)2 to capture exhaust CO2 has been hindered by the limited availability of brucite, the Mg(OH)2 mineral in natural deposits. Our previous study demonstrated that Mg(OH)2 can be obtained from dunite, an ultramafic rock composed of Mg silicate minerals, in highly concentrated NaOH aqueous systems. However, the large quantity of NaOH consumed was considered an obstacle for the implementation of the technology. In the present study, Mg(OH)2 was extracted from dunite reacted in solid systems with NaOH assisted with H2O. The consumption of NaOH was reduced by 97% with respect to the NaOH aqueous systems, maintaining a comparable yield of Mg(OH)2 extraction, i.e. 64.8-66%. The capture of CO2 from a CO2-N2 gas mixture was tested at ambient conditions using a Mg(OH)2 aqueous slurry. Mg(OH)2 almost fully dissolved and reacted with dissolved CO2 by forming Mg(HCO3)2 which remained in equilibrium storing the CO2 in the aqueous solution. The CO2 balance of the process was assessed from the emissions derived from the power consumption for NaOH production and Mg(OH)2 extraction together with the CO2 captured by Mg(OH)2 derived from dunite. The process resulted as carbon neutral when dunite is reacted at 250 °C for durations of 1 and 3 hours and CO2 is captured as Mg(HCO3)2.

  11. Comparative kinetic studies of Mn2+-activated and fructose-1,6-P-modified Mg2+-activated pyruvate kinase from Concholepas concholepas.

    PubMed

    Carvajal, N; González, R; Morán, A; Oyarce, A M

    1985-01-01

    Initial velocity and product inhibition studies of Mn2+-activated and FDP-modified Mg2+-activated pyruvate kinase from Concholepas concholepas, were performed. Evidence is presented to show that the Mn2+-enzyme catalyzes an ordered sequential mechanism, with ADP being the first substrate and pyruvate the last product. The results presented are consistent with a random combination of reactants with the FDP-modified Mg2+-activated enzyme and the formation of the dead-end complexes enzyme ADP-ATP and enzyme-PEP-ATP.

  12. Luminescence of Mn4+ ions in CaTiO3 and MgTiO3 perovskites: Relationship of experimental spectroscopic data and crystal field calculations

    NASA Astrophysics Data System (ADS)

    Đorđević, Vesna; Brik, Mikhail G.; Srivastava, Alok M.; Medić, Mina; Vulić, Predrag; Glais, Estelle; Viana, Bruno; Dramićanin, Miroslav D.

    2017-12-01

    Herein, the synthesis, structural and crystal field analysis and optical spectroscopy of Mn4+ doped metal titanates ATiO3 (A = Ca, Mg) are presented. Materials of desired phase were prepared by molten salt assisted sol-gel method in the powder form. Crystallographic data of samples were obtained by refinement of X-ray diffraction measurements. From experimental excitation and emission spectra and structural data, crystal field parameters and energy levels of Mn4+ in CaTiO3 and MgTiO3 were calculated by the exchange charge model of crystal-field theory. It is found that crystalline field strength is lower (Dq = 1831 cm-1) in the rhombohedral Ilmenite MgTiO3 structure due to the relatively longer average Mn4+sbnd O2- bond distance (2.059 Å), and higher (Dq = 2017 cm-1) in orthorhombic CaTiO3 which possess shorter average Mn4+sbnd O2- bond distance (1.956 Å). Spectral positions of the Mn4+2Eg → 4A2g transition maxima is 709 nm in MgTiO3 and 717 nm in CaTiO3 respectively in good agreement with calculated values.

  13. [The quantitative changes of bioelements (Ca, Zn, Mg, Cu, Mn) in crystalline lenses under the influence of hypodynamic stress and zinc].

    PubMed

    Kusleika, Saulius

    2002-01-01

    The aim of the study was to investigate and estimate quantitative changes of bioelements (Ca, Zn, Mg, Cu, Mn) in the lenses on the influence of hypodynamic stress and zinc (Zn). Hypodynamic stress of 48 days duration was provoked for Chinchilla rabbits (n = 20) by placing them in metal hutches. Every day (48 days) 10 rabbits, which had intervention received 0.3 mg/kg body wt. doses of Zn (in form of Zn acetate). The rabbits (n = 10) of the control group, which had no intervention were kept in vivarium conditions. Concentration of bioelements in the lenses of rabbits was detected by atomic absorption spectrophotometry 503 "Perkin-Elmer" (USA). The investigation revealed that hypodynamic stress of 48 days duration caused the increase in amount of Ca, Zn, Mn in lenses as compared with that in control rabbits and in rabbits receiving Zn. The concentration of bioelements (Ca, Zn, Mg, Cu, Mn) in lenses of rabbits receiving Zn in case of hypodynamic stress did not change significantly.

  14. Non-polar p-type Zn0.94Mn0.05Na0.01O texture: Growth mechanism and codoping effect

    NASA Astrophysics Data System (ADS)

    Zhang, L. Q.; Lu, B.; Lu, Y. H.; Ye, Z. Z.; Lu, J. G.; Pan, X. H.; Huang, J. Y.

    2013-02-01

    The microstructure and crystal orientations of polycrystalline films crucially affect the properties and performance of the films. Controlling preferred orientations (PO) and related film morphology are necessary to obtain the desirable properties. In this paper, we demonstrate a rational and effective route toward the realization of non-polar p-type ZnO thin film with surface texture on quartz substrate through Mn-Na codoping. It is uncovered experimentally and theoretically that mono-doping of Mn creates opportunity to realize PO from polar (c-axis) to non-polar ((101¯0), (101¯1), and (112¯0)) changing. With Mn-Na codoping, an acute modulation of the growth behavior and electrical conductivity of the film have been revealed, leading to weak p-type non-polar Zn0.94Mn0.05Na0.01O (ZMNO) texture. The dominant mechanism for the non-polar self-texture in the current paper is deliberately elucidated as resulting from the interplane surface diffusion with the cooperative effect of impurity dopants. The ZMNO films exhibit p-type conduction with hole concentration of 9.51 × 1015-1.86 × 1017 cm-3 and enhanced room temperature (RT) ferromagnetism possessing a saturation magnetization (Ms) of 1.52 μB/Mn. The results have potential applications in development of non-polar optoelectronic devices such as lighting emitting diodes (LEDs).

  15. Tetragonal Almandine, (Fe,Mg,Ca,Na)3(Al,Si,Mg)2Si3O12, a New High-Pressure Mineral from the Shergotty Impact on Mars: an Integrated FESEM-EPMA-Synchrotron Diffraction Investigation

    NASA Astrophysics Data System (ADS)

    Ma, C.; Tschauner, O. D.

    2016-12-01

    The combination of FESEM-EDS-EBSD, EPMA, and synchrotron microdiffraction is developing into a powerful tool for identification of micron-scale minerals in rocks such as high-pressure phases in shocked meteorites. During a nanomineralogy investigation of the Shergotty meteorite using this approach, we have identified a new shock-induced high-pressure silicate, majoritic almandine with a tetragonal I41/a structure, in an impact melt pocket. The Shergotty meteorite, which fell in the Gaya district, Bihar, India in 1865, is a Martian basaltic shergottite with shock features. Tetragonal almandine in Shergotty occurs as aggregates of subhedral crystals, 0.8 - 2.5 µm in diameter, along with stishovite in the central region of a shock melt pocket, showing an empirical formula of (Fe1.16Ca0.75Mg0.61Na0.42Mn0.03K0.01)(Al1.16Si0.63Mg0.19Ti0.02)Si3O12. Its general formula is (Fe,Mg,Ca,Na)3(Al,Si,Mg)2Si3O12. EBSD indicated this phase has a garnet-related structure. Synchrotron X-ray diffraction revealed that this garnet has actually a tetragonal structure (I41/a) with unit cell dimensions: a = 11.585(9) Å, c = 11.63(4) Å, V = 1561(7) Å3, and Z = 8. Tetragonal almandine is the polymorph of cubic almandine, a new high-pressure garnet mineral, formed by shock metamorphism via the Shergotty impact event on Mars. It apparently crystallized from Fe-rich shock-induced melt under high-pressure and high-temperature conditions.

  16. MgO-templated carbon as a negative electrode material for Na-ion capacitors

    NASA Astrophysics Data System (ADS)

    Kado, Yuya; Soneda, Yasushi

    2016-12-01

    In this study, MgO-templated carbon with different pore structures was investigated as a negative electrode material for Na-ion capacitors. With increasing the Brunauer-Emmett-Teller surface area, the irreversible capacity increased, and the coulombic efficiency of the 1st cycle decreased because of the formation of solid electrolyte interface layers. MgO-templated carbon annealed at 1000 °C exhibited the highest capacity and best rate performance, suggesting that an appropriate balance between surface area and crystallinity is imperative for fast Na-ion storage, attributed to the storage mechanism: combination of non-faradaic electric double-layer capacitance and faradaic Na intercalation in the carbon layers. Finally, a Na-ion capacitor cell using MgO-templated carbon and activated carbon as the negative and positive electrodes, respectively, exhibited an energy density at high power density significantly greater than that exhibited by the cell using a commercial hard carbon negative electrode.

  17. Abnormal site occupancy and high performance in warm WLEDs of a novel red phosphor, NaHF2:Mn4+, synthesized at room temperature.

    PubMed

    Xi, Luqing; Pan, Yuexiao; Zhu, Mengmeng; Lian, Hongzhou; Lin, Jun

    2017-10-17

    A novel red phosphor, NaHF 2 :Mn 4+ (NHF:Mn), was obtained via substituting Na + located at the center of the octahedron coordinated with six F - ions with Mn 4+ in the host lattice of NHF. The phase purity and the exact composition of the obtained NHF:Mn were confirmed by X-ray powder diffraction (XRD), Rietveld refinement, energy dispersive spectroscopy (EDS), transmission electron microscopy (TEM), and infrared (IR) spectroscopy, respectively. The luminescence intensity of NHF:Mn was enhanced by optimizing the synthetic conditions. A series of warm white light-emitting diodes (WLEDs) with a color rendering index (CRI) higher than 88.0 and correlated color temperatures (CCT) between 3146 and 5172 K were obtained by encapsulating the as-prepared red phosphor NHF:Mn with the yellow one Y 3 Al 5 O 12 :Ce 3+ (YAG:Ce) on blue chips. The advantage of the synthetic strategy to obtain NHF:Mn can be extended to develop novel Mn 4+ doped red phosphors via substituting for central ions with unequal electric charge in the centers of octahedra.

  18. Structural and electrochemical properties of Fe-doped Na2Mn3-xFex(P2O7)2 cathode material for sodium ion batteries

    NASA Astrophysics Data System (ADS)

    Liu, Huatao; Zhao, Yanming; Zhang, Hui; Lian, Xin; Dong, Youzhong; Kuang, Quan

    2017-12-01

    A series of Fe-doped Na2Mn3-xFex(P2O7)2 (x = 0.0, 0.5, 1.0, 1.5 and 2.0) compounds have been successfully prepared by using sol-gel method. Rietveld refinement results indicate that single phase Na2Mn3-xFex(P2O7)2 with triclinic structure can be obtained within 0 ≤ x ≤ 2 although no Na2Fe3(P2O7)2 existing under our experimental conditions, and the cell parameters (including a, b, c and V) are decreasing with the increasing of x. Our results reveal that Na2Mn3(P2O7)2 exhibits an electrochemical activity in the voltage range of 1.5 V-4.5 V vs. Na+/Na when using as the cathode material for SIBs although it gives a limited rate capability and poor capacity retention. However, the electrochemical performance of Fe-doped Na2Mn3-xFex(P2O7)2 (0 ≤ x ≤ 2) can be improved significantly where cycle performance and rate capability can be improved significantly than that of the pristine one. Sodium ion diffusion coefficient can be increased by about two orders of magnitude with the Fe-doping content higher than x = 0.5.

  19. Effects of NaBF4 + NaF on the Tensile and Impact Properties of Al-Si-Mg-Fe Alloys

    NASA Astrophysics Data System (ADS)

    Chen, Zongning; Wang, Tongmin; Zhao, Yufei; Zheng, Yuanping; Kang, Huijun

    2015-05-01

    NaBF4 + NaF were found to play three roles, i.e., Fe-eliminator, grain refiner, and eutectic modifier, in treating A356 alloy with a high Fe content. The joint effects led to significant improvement in both tensile and impact properties of thus treated alloy. The multiple reactions between the NaBF4 + NaF and Al-Si-Mg-Fe system are suggested to form Fe2B, AlB2, and Na in the melt, as per thermodynamic analysis. The three are responsible for Fe removal, grain refinement, and eutectic modification, respectively. When NaBF4 and NaF are mixed in weight ratio of 1:1, an optimum addition rate is in the range between 1.0 and 2.0 wt pct for treating AlSi7Mg0.3Fe0.65 alloy, based on the results of tensile and impact tests. Excessive addition of the salt may deteriorate the mechanical properties of the alloy, basically owing to overmodification of Si and contamination of salt inclusions.

  20. Thermochemical generation of hydrogen and oxygen from water. [NaMnO/sub 2/ and TiO/sub 2/

    DOEpatents

    Robinson, P.R.; Bamberger, C.E.

    1980-02-08

    A thermochemical cyclic process for the production of hydrogen exploits the reaction between sodium manganate (NaMnO/sub 2/) and titanium dioxide (TiO/sub 2/) to form sodium titanate (Na/sub 2/TiO/sub 3/), manganese (II) titanate (MnTiO/sub 3/) and oxygen. The titanate mixture is treated with sodium hydroxide, in the presence of steam, to form sodium titanate, sodium manganate (III), water and hydrogen. The sodium titanate-manganate (III) mixture is treated with water to form sodium manganate (III), titanium dioxide and sodium hydroxide. Sodium manganate (III) and titanium dioxide are recycled following dissolution of sodium hydroxide in water.

  1. Metal cation exchange reactions of ore minerals in Fe-Mn crusts of the Marcus Wake Rise (Pacific Ocean) in aqueous-salt solutions

    NASA Astrophysics Data System (ADS)

    Novikov, G. V.; Bogdanova, O. Yu.; Melnikov, M. E.; Drozdova, A. N.; Lobus, N. V.; Shulga, N. A.

    2017-12-01

    It is shown that the reaction ability of metal cations of ore minerals in Fe-Mn crusts of the Marcus Wake Rise increases in the following manner: (Co2+ < Cu2+ < Ni2+) < (Mg2+ < Mn2+ < K+ ≈ Ca2+ ≈ Na+). The composition of the exchange complex of the ore minerals is constant and includes these metal cations. Ca2+ and Na+ are major contributors to the exchange capacity of the ore minerals. The capacity of the ore minerals by cations of alkali and base metals is 0.43-0.60 and 2.08-2.70 mg-equiv/g, respectively. The exchange capacity of the ore minerals by cations of base metals increases linearly with the increase in the MnO2 content of the crust and does not depend on the geographical locations of the Marcus Wake guyots.

  2. One-dimensional magnetic fluctuations in the spin-2 triangular lattice alpha-NaMnO2.

    PubMed

    Stock, C; Chapon, L C; Adamopoulos, O; Lappas, A; Giot, M; Taylor, J W; Green, M A; Brown, C M; Radaelli, P G

    2009-08-14

    The S=2 anisotropic triangular lattice alpha-NaMnO2 is studied by neutron inelastic scattering. Antiferromagnetic order occurs at T< or =45 K with opening of a spin gap. The spectral weight of the magnetic dynamics above the gap (Delta approximately equal to 7.5 meV) has been analyzed by the single-mode approximation. Excellent agreement with the experiment is achieved when a dominant exchange interaction (|J|/k(B) approximately 73 K), along the monoclinic b axis and a sizable easy-axis magnetic anisotropy (|D|/k(B) approximately 3 K) are considered. Despite earlier suggestions for two-dimensional spin interactions, the dynamics illustrate strongly coupled antiferromagnetic S=2 chains and cancellation of the interchain exchange due to the lattice topology. alpha-NaMnO2 therefore represents a model system where the geometric frustration is resolved through the lowering of the dimensionality of the spin interactions.

  3. Stress corrosion cracking of sensitized AA5083 (Al-4.5Mg-1.0Mn)

    NASA Astrophysics Data System (ADS)

    Searles, J. L.; Gouma, P. I.; Buchheit, R. G.

    2001-11-01

    The AA5083 (Al-4.4Mg-0.7Mn-0.15Cr) alloy is a nonheat-treatable aluminum alloy known for its excellent corrosion resistance. However, it can become susceptible to intergranular stress corrosion cracking (IGSCC) when exposed to temperatures ranging from 50 °C to 200 °C for sufficient lengths of time. This IGSCC is widely believed to be associated with dissolution of the electrochemically active β phase, Al3Mg2, which is precipitated on grain boundaries. Recently, alternative mechanisms have been invoked related to hydrogen effects and/or free Mg segregation or depletion in the grainboundary regions. To establish a baseline for the sensitization effect, constant-extension-rate tests (CERTs) were conducted under open-circuit conditions and under potential control in 3.5 pct NaCl on samples isothermally treated at 150 °C. To aid in interpreting the CERT results, grain-boundary precipitation and solute depletion were characterized by transmission electron microscopy (TEM). Additionally, the electrochemical behavior of the β phase was characterized by anodic polarization of the intermetallic compound synthesized in bulk form. In CERTs under open-circuit conditions, the measured ductility depended strongly on sensitization time, reaching a minimum at 189 hours, followed by a slight increase at longer times. This trend correlated well with the fractional coverage of β phase on grain boundaries, which increased up to 189 hours, where it existed with nearly continuous coverage. At longer times, this film coarsened and became discontinuous. Correspondingly, some resistance to IGSCC was recovered. In polarization experiments, bulk synthesized β phase was found to be spontaneously passive from its corrosion potential (-1.40 VSCE) up to about -0.92 VSCE, where passivity was observed to break down. Sensitized AA5083 samples polarized below the β-phase breakdown potential showed almost no evidence of IGSCC, indicating that a high β dissolution rate is a requirement for

  4. Luminescence properties and warm white LED application of a ternary-alkaline fluoride red phosphor K2NaAlF6:Mn4+ .

    PubMed

    Wang, L Y; Song, E H; Deng, T T; Zhou, Y Y; Liao, Z F; Zhao, W R; Zhou, B; Zhang, Q Y

    2017-08-14

    Herein, a Mn 4+ ion doped complex ternary-alkaline fluoride red phosphor K 2 NaAlF 6 :Mn 4+ has been synthesized through a facile two-step co-precipitation method at room temperature. The crystal structure, morphological properties and influence of the dopant concentration, temperature and humidity on luminescence properties as well as the performance of the as-synthesized phosphor used in white light emitting diodes (WLEDs) were investigated carefully. Intense absorption in the blue region (∼460 nm) and bright narrow-band red emission (∼630 nm) with high color purity were observed from this resultant powder. Temperature-dependent investigation and reliability examination in a HTHH environment (85 °C high temperature and 85% high humidity) indicate that the obtained ternary-alkaline fluoride phosphor K 2 NaAlF 6 :Mn 4+ presents more exceptional thermal quenching behavior and longevity compared to some other binary-alkaline fluorides. Moreover, using K 2 NaAlF 6 :Mn 4+ as a red light component, a warm WLED with a preferable color rendering index (R a = 85.5) and luminous efficacy (LE = 91.2 lm W -1 ) as well as a low corresponding color temperature (CCT = 3650 K) is easily achieved, further revealing the great potential of the as-prepared ternary-alkaline fluoride red phosphor K 2 NaAlF 6 :Mn 4+ for WLED applications.

  5. Structural, dielectric and magnetic studies of Mn doped Y-type barium hexaferrite (Ba2Mg2Fe12O22)

    NASA Astrophysics Data System (ADS)

    Abdullah, Md. F.; Pal, P.; Mohapatra, S. R.; Yadav, C. S.; Kaushik, S. D.; Singh, A. K.

    2018-04-01

    The polycrystalline single phase Ba2Mg2Fe12O22 (BMF) and Ba2Mg2Fe11.52Mn0.48O22 (BMFM) were prepared using conventional solid state reaction route. We report the modification in structural, dielectric and magnetic properties of BMF due to 4% Mn doping at Fe site. Phase purity of both sample are confirmed by the Reitveld refinement of XRD data. Temperature dependent dielectric study shows decrease in dielectric constant (ɛ') and dielectric loss (tan δ) due to 4% Mn doping in parent sample. The ferrimagnetic to paramagnetic transition temperature (Tc) in doped sample decreases from 277°C to 150°C. Room temperature magnetization measurement shows ferrimagnetic behavior for both the samples. We have fitted the saturation magnetization data at 300 K by using least square method which confirms the enhancement of saturation magnetization and magnetic anisotropy constant in doped sample.

  6. Enhanced persistent red luminescence in Mn2+-doped (Mg,Zn)GeO3 by electron trap and conduction band engineering

    NASA Astrophysics Data System (ADS)

    Katayama, Yumiko; Kayumi, Tomohiro; Ueda, Jumpei; Tanabe, Setsuhisa

    2018-05-01

    The effect of Zn substitution on the persistent luminescence properties of MgGeO3:Mn2+-Ln3+ (Ln = Eu and Yb) red phosphors was investigated. The intensity of the persistent luminescence of the Eu3+ co-doped phosphors increased with increasing Zn content, whereas that of the Yb3+ co-doped samples decreased. For both series of lanthanide co-doped samples, the thermoluminescence (TL) glow peak shifted to the lower temperature side with increasing Zn content. These persistent luminescence properties were well explained in terms of lowering of the bottom of the conduction band relative to the ground state of the divalent lanthanide ions. Especially, in Eu3+ co-doped system, TL peak shifted from 520 K to 318 K by 50% Zn substitution. The persistent radiance of the (Mg0.5 Zn0.5)GeO3: Mn2+-Eu3+ sample at 1 h after ceasing UV light was 46 times stronger than that of MgGeO3:Mn2+-Eu3+, and 11 times stronger than that of ZnGa2O4: Cr3+ standard deep red persistent phosphor.

  7. Perpendicular magnetic tunnel junctions with Mn-modified ultrathin MnGa layer

    NASA Astrophysics Data System (ADS)

    Suzuki, K. Z.; Miura, Y.; Ranjbar, R.; Bainsla, L.; Ono, A.; Sasaki, Y.; Mizukami, S.

    2018-02-01

    Perpendicular magnetic tunnel junctions (p-MTJs) with a MgO barrier and a 1-nm-thick MnGa electrode were investigated by inserting several monolayers (MLs) of Mn. The tunnel magnetoresistance (TMR) ratio systematically increased when increasing the Mn layer thickness with a maximum of 18 (38.4)% at 300 (5) K for a Mn layer thickness of 0.6-0.8 nm. This ratio is five times higher compared to that without the Mn layer. The perpendicular magnetic anisotropy (PMA) field and the PMA constant of the ultrathin MnGa layer also increased up to 62-90 kOe and 6.2-11.3 Merg/cm3, respectively, with an increase in the Mn interlayer thickness, even for the ultrathin regime of the MnGa layer. For p-MTJs showing a high TMR and PMA, electron microscopy indicated the presence of 3-4 MLs of Mn at the MnGa/MgO interface; thus, the Mn modification enhanced the TMR as well as improved the PMA. This may be a promising finding to develop a Mn-based free layer for spin-transfer-torque devices for high-recording-density magnetoresistive random access memory and a sub-THz oscillator/detector.

  8. Symmetric Sodium-Ion Capacitor Based on Na0.44MnO2 Nanorods for Low-Cost and High-Performance Energy Storage.

    PubMed

    Chen, Zhongxue; Yuan, Tianci; Pu, Xiangjun; Yang, Hanxi; Ai, Xinping; Xia, Yongyao; Cao, Yuliang

    2018-04-11

    Batteries and electrochemical capacitors play very important roles in the portable electronic devices and electric vehicles and have shown promising potential for large-scale energy storage applications. However, batteries or capacitors alone cannot meet the energy and power density requirements because rechargeable batteries have a poor power property, whereas supercapacitors offer limited capacity. Here, a novel symmetric sodium-ion capacitor (NIC) is developed based on low-cost Na 0.44 MnO 2 nanorods. The Na 0.44 MnO 2 with unique nanoarchitectures and iso-oriented feature offers shortened diffusion path lengths for both electronic and Na + transport and reduces the stress associated with Na + insertion and extraction. Benefiting from these merits, the symmetric device achieves a high power density of 2432.7 W kg -1 , an improved energy density of 27.9 Wh kg -1 , and a capacitance retention of 85.2% over 5000 cycles. Particularly, the symmetric NIC based on Na 0.44 MnO 2 permits repeatedly reverse-polarity characteristics, thus simplifying energy management system and greatly enhancing the safety under abuse condition. This cost-effective, high-safety, and high-performance symmetric NIC can balance the energy and power density between batteries and capacitors and serve as an electric power source for future low-maintenance large-scale energy storage systems.

  9. Raman spectroscopic study of the mineral qingheiite Na2(Mn2+,Mg,Fe2+)2(Al,Fe3+)(PO4)3, a pegmatite phosphate mineral from Santa Ana pegmatite, Argentina.

    PubMed

    Frost, Ray L; Xi, Yunfei; Scholz, Ricardo; López, Andrés; Moreira, Caio; de Lena, Jorge Carvalho

    2013-10-01

    The pegmatite mineral qingheiite Na2(Mn(2+),Mg,Fe(2+))2(Al,Fe(3+))(PO4)3 has been studied by a combination of SEM and EMP, Raman and infrared spectroscopy. The studied sample was collected from the Santa Ana pegmatite, Argentina. The mineral occurs as a primary mineral in lithium bearing pegmatite, in association with beausite and lithiophilite. The Raman spectrum is characterized by a very sharp intense Raman band at 980 cm(-1) assigned to the PO4(3-) symmetric stretching mode. Multiple Raman bands are observed in the PO4(3-) antisymmetric stretching region, providing evidence for the existence of more than one phosphate unit in the structure of qingheiite and evidence for the reduction in symmetry of the phosphate units. This concept is affirmed by the number of bands in the ν4 and ν2 bending regions. No intensity was observed in the OH stretching region in the Raman spectrum but significant intensity is found in the infrared spectrum. Infrared bands are observed at 2917, 3195, 3414 and 3498 cm(-1) are assigned to water stretching vibrations. It is suggested that some water is coordinating the metal cations in the structure of qingheiite. Copyright © 2013 Elsevier B.V. All rights reserved.

  10. A comparative study of the spectroscopic properties of Mn4+ in the garnet Y2Mg3Ge3O12 and the commercial Mg28Ge7.55O32F15.04 phosphor

    NASA Astrophysics Data System (ADS)

    Srivastava, A. M.

    2018-05-01

    The spectroscopic properties of Mn4+ (3 d3) ions in the garnet Y2Mg3Ge3O12 and in the commercial Mg28Ge7.55O32F15.04 (MFG) phosphors are compared. We find that despite the differences in host crystal composition and crystal structures, the 4A2g→ 4T1g and 2Eg→4A2g optical transitions of the Mn4+ ion occur at similar energies. We provide some insights into the nature of chemical bonding that is responsible for the observed similarity in the spectroscopic data. Additionally, discussion is given to the site preference of the Mn4+ ion in the MFG host crystal.

  11. Mn²⁺/Mg ²⁺-dependent pyruvate kinase from a D-lactic acid-producing bacterium Sporolactobacillus inulinus: characterization of a novel Mn²⁺-mediated allosterically regulated enzyme.

    PubMed

    Zheng, Lu; Xu, Tingting; Bai, Zhongzhong; He, Bingfang

    2014-02-01

    Sporolactobacillus inulinus has attracted scientific and commercial interest due to its high efficiency in D-lactic acid production. Pyruvate kinase (PYK) is one of the key regulatory points in glycolysis, and well-activated PYK can improve D-lactic acid production. A novel Mn(2+)/Mg(2+)-dependent PYK from S. inulinus was expressed in Escherichia coli and purified to homogeneity. Kinetic characterization demonstrated that the S. inulinus PYK had drastically higher activity and affinity toward substrates in the presence of Mn(2+) compared to those of the common PYK cofactor Mg(2+), and the circular dichroism spectra of the S. inulinus PYK suggested a Mn(2+)-mediated allosteric activation. The S. inulinus PYK was also allosterically regulated by ribose-5-phosphate or AMP activation and inorganic phosphate or ATP inhibition. The inhibition could be marked reduced or fully eliminated in the presence of activators. The result of fermentations by S. inulinus Y2-8 showed that the extracellular-added MnSO₄ and KH₂PO₄ significantly affected glycolysis flux and D-lactic acid production, which is consistent with the allosteric regulation of Mn(2+) and inorganic phosphate on PYK. The sophisticated regulatory role of PYK would establish the foundation of substantial disturbance or restructuring of cellular metabolism for improving the S. inulinus D-lactic acid production.

  12. Synthesis of bimetallic trifluoroacetates through a crystallochemical investigation of their monometallic counterparts: the case of (A, A')(CF3COO)2·nH2O (A, A' = Mg, Ca, Sr, Ba, Mn).

    PubMed

    Dulani Dhanapala, B; Mannino, Natalie A; Mendoza, Laura M; Tauni Dissanayake, K; Martin, Philip D; Suescun, Leopoldo; Rabuffetti, Federico A

    2017-01-31

    Owing to their potential as single-source precursors for compositionally complex materials, there is growing interest in the rational design of multimetallic compounds containing fluorinated ligands. In this work, we show that chemical and structural principles for a materials-by-design approach to bimetallic trifluoroacetates can be established through a systematic investigation of the crystal-chemistry of their monometallic counterparts. A(CF 3 COO) 2 ·nH 2 O (A = Mg, Ca, Sr, Ba, Mn) monometallic trifluoroacetates were employed to demonstrate the feasibility of this approach. The crystal-chemistry of monometallic trifluoroacetates was mapped using variable-temperature single-crystal X-ray diffraction, powder X-ray diffraction, and thermal analysis. The evolution with temperature of the previously unknown crystal structure of Mg(CF 3 COO) 2 ·4H 2 O was found to be identical to that of Mn(CF 3 COO) 2 ·4H 2 O. More important, the flexibility of Mn x (CF 3 COO) 2x ·4H 2 O (x = 1, 3) to adopt two structures, one isostructural to Mg(CF 3 COO) 2 ·4H 2 O, the other isostructural to Ca 3 (CF 3 COO) 6 ·4H 2 O, enabled the synthesis of Mg-Mn and Ca-Mn bimetallic trifluoroacetates. Mg 0.45 Mn 0.55 (CF 3 COO) 2 ·4H 2 O was found to be isostructural to Mg(CF 3 COO) 2 ·4H 2 O and exhibited isolated metal-oxygen octahedra with Mg 2+ and Mn 2+ nearly equally distributed over the metal sites (Mg/Mn: 45/55). Ca 1.72 Mn 1.28 (CF 3 COO) 6 ·4H 2 O was isostructural to Ca 3 (CF 3 COO) 6 ·4H 2 O and displayed trimers of metal-oxygen corner-sharing octahedra; Ca 2+ and Mn 2+ were unequally distributed over the central (Ca/Mn: 96/4) and terminal (Ca/Mn: 38/62) octahedral sites.

  13. A Structural Molar Volume Model for Oxide Melts Part I: Li2O-Na2O-K2O-MgO-CaO-MnO-PbO-Al2O3-SiO2 Melts—Binary Systems

    NASA Astrophysics Data System (ADS)

    Thibodeau, Eric; Gheribi, Aimen E.; Jung, In-Ho

    2016-04-01

    A structural molar volume model was developed to accurately reproduce the molar volume of molten oxides. As the non-linearity of molar volume is related to the change in structure of molten oxides, the silicate tetrahedral Q-species, calculated from the modified quasichemical model with an optimized thermodynamic database, were used as basic structural units in the present model. Experimental molar volume data for unary and binary melts in the Li2O-Na2O-K2O-MgO-CaO-MnO-PbO-Al2O3-SiO2 system were critically evaluated. The molar volumes of unary oxide components and binary Q-species, which are model parameters of the present structural model, were determined to accurately reproduce the experimental data across the entire binary composition in a wide range of temperatures. The non-linear behavior of molar volume and thermal expansivity of binary melt depending on SiO2 content are well reproduced by the present model.

  14. Optical properties of Ni2+ and radiation defects in MgF sub 2 and MnF sub 2

    NASA Astrophysics Data System (ADS)

    Feuerhelm, L. N.

    1980-03-01

    The radiation defects in pure MgF2 were made by observating the polarized absorption, luminescence, and excitation spectra in electron-irradiated MgF2. Additionally, studies of the absorption, emission, excitation, and temperature dependence of the lifetimes of transitions in nickel-doped MgF2 and MnF2 were accomplished, as well as the observation of radiation effects on these crystals. The absorption band at about 320 nm in irradiated MgF2 is identified to be due to the F2(D2b) center, and to have an emission at about 450 nm. Analysis of the temperature dependence of this band indicates a dominant phonon mode of 255 cm(-1) for the excited state. The F2(C1) center is identified with an absorption of about 360 nm and an emission of 410 nm. An absorption peak at 300 nm, for which no corresponding emission was found, is tentatively identified to be the F3-center, and to have a dominant phonon mode of 255 cm(-1). The temperature dependence of the lifetimes of transitions in nickel-doped MgF2 is analyzed by the quantum mechanical single configuration coordinate model of Struck and Fonger, and a complete configuration coordinate model is made for this crystal. Similar studies are made in MnF2:Ni.

  15. Insights into the Dual-Electrode Characteristics of Layered Na0.5Ni0.25Mn0.75O2 Materials for Sodium-Ion Batteries.

    PubMed

    Palanisamy, Manikandan; Kim, Hyun Woo; Heo, Seongwoo; Lee, Eungje; Kim, Youngsik

    2017-03-29

    Sodium-ion batteries are now close to replacing lithium-ion batteries because they provide superior alternative energy storage solutions that are in great demand, particularly for large-scale applications. To that end, the present study is focused on the properties of a new type of dual-electrode material, Na 0.5 Ni 0.25 Mn 0.75 O 2 , synthesized using a mixed hydroxy-carbonate route. Cyclic voltammetry confirms that redox couples, at high and low voltage ranges, are facilitated by the unique features and properties of this dual-electrode, through sodium ion deintercalation/intercalation into the layered Na 0.5 Ni 0.25 Mn 0.75 O 2 material. This material provides superior performance for Na-ion batteries, as evidenced by the fabricated sodium cell that yielded initial charge-discharge capacities of 125/218 mAh g -1 in the voltage range of 1.5-4.4 V at 0.5 C. At a low voltage range (1.5-2.6 V), the anode cell delivered discharge-charge capacities of 100/99 mAh g -1 with 99% capacity retention, which corresponds to highly reversible redox reaction of the Mn 4+/3+ reduction and the Mn 3+/4+ oxidation observed at 1.85 and 2.06 V, respectively. The symmetric Na-ion cell, fabricated using Na 0.5 Ni 0.25 Mn 0.75 O 2 , yielded initial charge-discharge capacities of 196/187 μAh at 107 μA. These results encourage the further development of new types of futuristic sodium-ion-battery-based energy storage systems.

  16. Improving the Elevated-Temperature Properties by Two-Step Heat Treatments in Al-Mn-Mg 3004 Alloys

    NASA Astrophysics Data System (ADS)

    Liu, K.; Ma, H.; Chen, X. Grant

    2018-05-01

    In the present work, two-step heat treatments with preheating at different temperatures (175 °C, 250 °C, and 330 °C) as the first step followed by the peak precipitation treatment (375 °C/48 h) as the second step were performed in Al-Mn-Mg 3004 alloys to study their effects on the formation of dispersoids and the evolution of the elevated-temperature strength and creep resistance. During the two-step heat treatments, the microhardness is gradually increased with increasing time to a plateau after 24 hours when first treated at 250 °C and 330 °C, while there is a minor decrease with time when first treated at 175 °C. Results show that both the yield strength (YS) and creep resistance at 300 °C reach the peak values after the two-step treatment of 250 °C/24 h + 375 °C/48 h. The formation of dispersoids is greatly related to the type and size of pre-existing Mg2Si precipitated during the preheating treatments. It was found that coarse rodlike β ' -Mg2Si strongly promotes the nucleation of dispersoids, while fine needle like β ″-Mg2Si has less influence. Under optimized two-step heat treatment and modified alloying elements, the YS at 300 °C can reach as high as 97 MPa with the minimum creep rate of 2.2 × 10-9 s-1 at 300 °C in Al-Mn-Mg 3004 alloys, enabling them as one of the most promising candidates in lightweight aluminum alloys for elevated-temperature applications.

  17. Ferromagnetic Peierls insulator state in A Mg4Mn6O15(A =K ,Rb ,Cs )

    NASA Astrophysics Data System (ADS)

    Yamaguchi, T.; Sugimoto, K.; Ohta, Y.; Tanaka, Y.; Sato, H.

    2018-04-01

    Using the density-functional-theory-based electronic structure calculations, we study the electronic state of recently discovered mixed-valent manganese oxides A Mg4Mn6O15(A =K ,Rb ,Cs ) , which are fully spin-polarized ferromagnetic insulators with a cubic crystal structure. We show that the system may be described as a three-dimensional arrangement of the one-dimensional chains of a 2 p orbital of O and a 3 d orbital of Mn running along the three axes of the cubic lattice. We thereby argue that in the ground state the chains are fully spin polarized due to the double-exchange mechanism and are distorted by the Peierls mechanism to make the system insulating.

  18. Experimental study of the astrophysically important Na 23 ( α , p ) Mg 26 and Na 23 ( α , n ) Al 26 reactions

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Avila, M. L.; Rehm, K. E.; Almaraz-Calderon, S.

    The 23Na(α,p) 26Mg and 23Na(α,n) 26Al reactions are important for our understanding of the 26Al abundance in massive stars. The aim of this work is to report on a direct and simultaneous measurement of these astrophysically important reactions using an active target system. The reactions were investigated in inverse kinematics using 4He as the active target gas in the detector. We measured the excitation functions in the energy range of about 2 to 6 MeV in the center of mass. We have found that the cross sections of the 23Na(α,p) 26Mg and the 23Na(α,n) 26Al reactions are in good agreementmore » with previous experiments and with statistical-model calculations. As a result, the astrophysical reaction rate of the 23Na(α,n) 26Al reaction has been reevaluated and it was found to be larger than the recommended rate.« less

  19. Experimental study of the astrophysically important Na 23 ( α , p ) Mg 26 and Na 23 ( α , n ) Al 26 reactions

    DOE PAGES

    Avila, M. L.; Rehm, K. E.; Almaraz-Calderon, S.; ...

    2016-12-19

    The 23Na(α,p) 26Mg and 23Na(α,n) 26Al reactions are important for our understanding of the 26Al abundance in massive stars. The aim of this work is to report on a direct and simultaneous measurement of these astrophysically important reactions using an active target system. The reactions were investigated in inverse kinematics using 4He as the active target gas in the detector. We measured the excitation functions in the energy range of about 2 to 6 MeV in the center of mass. We have found that the cross sections of the 23Na(α,p) 26Mg and the 23Na(α,n) 26Al reactions are in good agreementmore » with previous experiments and with statistical-model calculations. As a result, the astrophysical reaction rate of the 23Na(α,n) 26Al reaction has been reevaluated and it was found to be larger than the recommended rate.« less

  20. The Electrochemical Co-reduction of Mg-Al-Y Alloys in the LiCl-NaCl-MgCl2-AlF3-YCl3 Melts

    NASA Astrophysics Data System (ADS)

    Li, Mei; Liu, Yaochen; Han, Wei; Wang, Shanshan; Zhang, Milin; Yan, Yongde; Shi, Weiqun

    2015-04-01

    The electrochemical formation of Mg-Al-Y alloys was studied in the LiCl-NaCl-MgCl2 melts by the addition of AlF3 and YCl3 on a molybdenum electrode at 973 K (700 °C). In order to reduce the volatilization of salt solvent in the electrolysis process, the volatile loss of LiCl-NaCl-MgCl2 and LiCl-KCl-MgCl2 melts was first measured in the temperature range from 873 K to 1023 K (600 °C to 750 °C). Then, the electrochemical behaviors of Mg(II), Al(III), Y(III) ions and alloy formation processes were investigated by cyclic voltammetry, chronopotentiometry, and open circuit chronopotentiometry. The cyclic voltammograms indicate that the under-potential deposition of magnesium and yttrium on pre-deposited Al leads to formation of Mg-Al and Al-Y intermetallic compounds. The Mg-Al-Y alloys were prepared by galvanostatic electrolysis in the LiCl-NaCl-MgCl2-AlF3-YCl3 melts and characterized by X-ray diffraction and scanning electron microscopy with energy dispersive spectrometry. Composition of the alloys was analyzed by inductively coupled plasma-atomic emission spectrometer, and current efficiency was also determined by the alloy composition.

  1. Utilizing Co 2+/Co 3+ Redox Couple in P2-Layered Na 0.66Co 0.22Mn 0.44Ti 0.34O 2 Cathode for Sodium-Ion Batteries

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Wang, Qin-Chao; Hu, Enyuan; Pan, Yang

    Developing sodium-ion batteries for large-scale energy storage applications is facing big challenges of the lack of high-performance cathode materials. Here, a series of new cathode materials Na 0.66Co xMn 0.66–xTi 0.34O 2 for sodium-ion batteries are designed and synthesized aiming to reduce transition metal-ion ordering, charge ordering, as well as Na+ and vacancy ordering. An interesting structure change of Na 0.66Co xMn 0.66–xTi 0.34O 2 from orthorhombic to hexagonal is revealed when Co content increases from x = 0 to 0.33. In particular, Na 0.66Co 0.22Mn 0.44Ti 0.34O 2 with a P2-type layered structure delivers a reversible capacity of 120more » mAh g -1 at 0.1 C. When the current density increases to 10 C, a reversible capacity of 63.2 mAh g -1 can still be obtained, indicating a promising rate capability. The low valence Co 2+ substitution results in the formation of average Mn 3.7+ valence state in Na 0.66Co 0.22Mn 0.44Ti 0.34O 2, effectively suppressing the Mn3+-induced Jahn–Teller distortion, and in turn stabilizing the layered structure. X-ray absorption spectroscopy results suggest that the charge compensation of Na 0.66Co 0.22Mn 0.44Ti 0.34O 2 during charge/discharge is contributed by Co 2.2+/Co 3+ and Mn 3.3+/Mn 4+ redox couples. This is the first time that the highly reversible Co 2+/Co 3+ redox couple is observed in P2-layered cathodes for sodium-ion batteries. This finding may open new approaches to design advanced intercalation-type cathode materials.« less

  2. Utilizing Co 2+/Co 3+ Redox Couple in P2-Layered Na 0.66Co 0.22Mn 0.44Ti 0.34O 2 Cathode for Sodium-Ion Batteries

    DOE PAGES

    Wang, Qin-Chao; Hu, Enyuan; Pan, Yang; ...

    2017-07-06

    Developing sodium-ion batteries for large-scale energy storage applications is facing big challenges of the lack of high-performance cathode materials. Here, a series of new cathode materials Na 0.66Co xMn 0.66–xTi 0.34O 2 for sodium-ion batteries are designed and synthesized aiming to reduce transition metal-ion ordering, charge ordering, as well as Na+ and vacancy ordering. An interesting structure change of Na 0.66Co xMn 0.66–xTi 0.34O 2 from orthorhombic to hexagonal is revealed when Co content increases from x = 0 to 0.33. In particular, Na 0.66Co 0.22Mn 0.44Ti 0.34O 2 with a P2-type layered structure delivers a reversible capacity of 120more » mAh g -1 at 0.1 C. When the current density increases to 10 C, a reversible capacity of 63.2 mAh g -1 can still be obtained, indicating a promising rate capability. The low valence Co 2+ substitution results in the formation of average Mn 3.7+ valence state in Na 0.66Co 0.22Mn 0.44Ti 0.34O 2, effectively suppressing the Mn3+-induced Jahn–Teller distortion, and in turn stabilizing the layered structure. X-ray absorption spectroscopy results suggest that the charge compensation of Na 0.66Co 0.22Mn 0.44Ti 0.34O 2 during charge/discharge is contributed by Co 2.2+/Co 3+ and Mn 3.3+/Mn 4+ redox couples. This is the first time that the highly reversible Co 2+/Co 3+ redox couple is observed in P2-layered cathodes for sodium-ion batteries. This finding may open new approaches to design advanced intercalation-type cathode materials.« less

  3. Utilizing Co2+/Co3+ Redox Couple in P2-Layered Na0.66Co0.22Mn0.44Ti0.34O2 Cathode for Sodium-Ion Batteries.

    PubMed

    Wang, Qin-Chao; Hu, Enyuan; Pan, Yang; Xiao, Na; Hong, Fan; Fu, Zheng-Wen; Wu, Xiao-Jing; Bak, Seong-Min; Yang, Xiao-Qing; Zhou, Yong-Ning

    2017-11-01

    Developing sodium-ion batteries for large-scale energy storage applications is facing big challenges of the lack of high-performance cathode materials. Here, a series of new cathode materials Na 0.66 Co x Mn 0.66- x Ti 0.34 O 2 for sodium-ion batteries are designed and synthesized aiming to reduce transition metal-ion ordering, charge ordering, as well as Na + and vacancy ordering. An interesting structure change of Na 0.66 Co x Mn 0.66- x Ti 0.34 O 2 from orthorhombic to hexagonal is revealed when Co content increases from x = 0 to 0.33. In particular, Na 0.66 Co 0.22 Mn 0.44 Ti 0.34 O 2 with a P2-type layered structure delivers a reversible capacity of 120 mAh g -1 at 0.1 C. When the current density increases to 10 C, a reversible capacity of 63.2 mAh g -1 can still be obtained, indicating a promising rate capability. The low valence Co 2+ substitution results in the formation of average Mn 3.7+ valence state in Na 0.66 Co 0.22 Mn 0.44 Ti 0.34 O 2 , effectively suppressing the Mn 3+ -induced Jahn-Teller distortion, and in turn stabilizing the layered structure. X-ray absorption spectroscopy results suggest that the charge compensation of Na 0.66 Co 0.22 Mn 0.44 Ti 0.34 O 2 during charge/discharge is contributed by Co 2.2+ /Co 3+ and Mn 3.3+ /Mn 4+ redox couples. This is the first time that the highly reversible Co 2+ /Co 3+ redox couple is observed in P2-layered cathodes for sodium-ion batteries. This finding may open new approaches to design advanced intercalation-type cathode materials.

  4. P2-type Na2/3Mn1-xAlxO2 cathode material for sodium-ion batteries: Al-doped enhanced electrochemical properties and studies on the electrode kinetics

    NASA Astrophysics Data System (ADS)

    Pang, Wei-Lin; Zhang, Xiao-Hua; Guo, Jin-Zhi; Li, Jin-Yue; Yan, Xin; Hou, Bao-Hua; Guan, Hong-Yu; Wu, Xing-Long

    2017-07-01

    Recently, sodium-ion batteries (SIBs) have been considered as the promising alternative for lithium-ion batteries. Although layered P2-type transition metal oxides are an important class of cathode materials for SIBs, there are still some hurdles for the practical applications, including low specific capacity as well as poor cycling and rate properties. In this study, the electrochemical properties of layered Mn-based oxides have been effectively improved via Al doping, which cannot only promote the formation of layered P2-type structure in the preparation processes but also stabilize the lattice during the successive Na-intercalation/deintercalation due to suppression of the Jahn-Teller distortion of Mn3+. Among the as-prepared series of Na2/3Mn1-xAlxO2 (x = 0, 1/18, 1/9, and 2/9), Na2/3Mn8/9Al1/9O2 with x = 1/9 exhibits the optimal doping effect with the best electrochemical properties, in terms of the highest specific capacity of 162.3 mA h g-1 at 0.1 C, the highest rate capability, and the best cycling stability in comparison to the undoped Na2/3MnO2 and the other two materials with different Al-doped contents. Both cyclic voltammetry at varied scan rates and galvanostatic intermittent titration technique disclose the optimal electrode kinetics (the highest Na-diffusion coefficient) of the best Na2/3Mn8/9Al1/9O2.

  5. A green preparation of Mn-based product with high purity from low-grade rhodochrosite

    NASA Astrophysics Data System (ADS)

    Lian, F.; Ma, L.; Chenli, Z.; Mao, L.

    2018-01-01

    The low-grade rhodochrosite, the main resources for exploitation and applications in China, contains multiple elements such as iron, silicon, calcium and magnesium. So the conventional preparation of manganese sulphate and manganese oxide with high purity from electrolytic product is characterized by long production-cycle, high-resource input and high-pollution discharge. In our work, a sustainable preparation approach of high pure MnSO4 solution and Mn3O4 was studied by employing low-grade rhodochrosite (13.86%) as raw material. The repeated leaching of rhodochrosite with sulphuric acid was proposed in view of the same ion effect, in order to improve the solubility of Mn2+ and inhibit the dissolution of the impurities Ca2+ and Mg2+. With the aid of theoretical calculation, BaF2 was chosen to remove Ca2+ and Mg2+ completely in the process of purifying. The results showed that the impurities such as Ca2+, Mg2+, Na+ were decreased to less than 20ppm, and the Ni- and Fe- impurities were decreased to less than 1ppm, which meets the standards of high pure reagent for energy and electronic materials. The extraction ratio and the recovery ratio of manganese reached 94.3% and 92.7%, respectively. Moreover, the high pure Mn3O4 was one-step synthesized via the oxidation of MnSO4 solution with the ratios of OH-/Mn2+=2 and Mn2+/H2O2=1.03, and the recovery rate of manganese reaches 99%.

  6. (Zn, Mg)2GeO4:Mn2+ submicrorods as promising green phosphors for field emission displays: hydrothermal synthesis and luminescence properties.

    PubMed

    Shang, Mengmeng; Li, Guogang; Yang, Dongmei; Kang, Xiaojiao; Peng, Chong; Cheng, Ziyong; Lin, Jun

    2011-10-07

    (Zn(1-x-y)Mg(y))(2)GeO(4): xMn(2+) (y = 0-0.30; x = 0-0.035) phosphors with uniform submicrorod morphology were synthesized through a facile hydrothermal process. X-Ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM), photoluminescence (PL), and cathodoluminescence (CL) spectroscopy were utilized to characterize the samples. SEM and TEM images indicate that Zn(2)GeO(4):Mn(2+) samples consist of submicrorods with lengths around 1-2 μm and diameters around 200-250 nm, respectively. The possible formation mechanism for Zn(2)GeO(4) submicrorods has been presented. PL and CL spectroscopic characterizations show that pure Zn(2)GeO(4) sample shows a blue emission due to defects, while Zn(2)GeO(4):Mn(2+) phosphors exhibit a green emission corresponding to the characteristic transition of Mn(2+) ((4)T(1)→(6)A(1)) under the excitation of UV and low-voltage electron beam. Compared with Zn(2)GeO(4):Mn(2+) sample prepared by solid-state reaction, Zn(2)GeO(4):Mn(2+) phosphors obtained by hydrothermal process followed by high temperature annealing show better luminescence properties. In addition, codoping Mg(2+) ions into the lattice to substitute for Zn(2+) ions can enhance both the PL and CL intensity of Zn(2)GeO(4):Mn(2+) phosphors. Furthermore, Zn(2)GeO(4):Mn(2+) phosphors exhibit more saturated green emission than the commercial FEDs phosphor ZnO:Zn, and it is expected that these phosphors are promising for application in field-emission displays.

  7. Insights into the dual-electrode characteristics of layered Na 0.5Ni 0.25Mn 0.75O 2 materials for sodium-ion batteries

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Manikandan, Palanisamy; Kim, Hyunwoo; Heo, Seongwoo

    Sodium-ion batteries are now close to replacing lithium-ion batteries because they provide superior alternative energy storage solutions that are in great demand, particularly for large-scale applications. To that end, the present study is focused on the properties of a new type of dual-electrode material, Na 0.5Ni 0.25Mn 0.75O 2, synthesized using a mixed hydroxycarbonate route. Cyclic voltammetry confirms that redox couples, at high and low voltage ranges, are facilitated by the unique features and properties of this dual-electrode, through sodium ion deintercalation/intercalation into the layered Na 0.5Ni 0.25Mn 0.25O 2 material. This material provides superior performance for Na-ion batteries, asmore » evidenced by the fabricated sodium cell that yielded initial charge discharge capacities of 125/218 mAh g -1 in the voltage range of 1.5-4.4 V at 0.5 C. At a low voltage range (1.5-2.6 V), the anode cell delivered discharge charge capacities of 100/99 mAh g -1 with 99% capacity retention, which corresponds to highly reversible redox reaction of the Mn 4+/3+ reduction and the Mn 3+/4+ oxidation observed at 1.85 and 2.06 V, respectively. The symmetric Na-ion cell, fabricated using Na 0.5Ni 0.25Mn 0.25O 2, yielded initial charge discharge capacities of 196/187 μAh at 107 μA. Lastly, these results encourage the further development of new types of futuristic sodium-ion battery-based energy storage systems.« less

  8. Insights into the dual-electrode characteristics of layered Na 0.5Ni 0.25Mn 0.75O 2 materials for sodium-ion batteries

    DOE PAGES

    Manikandan, Palanisamy; Kim, Hyunwoo; Heo, Seongwoo; ...

    2017-03-09

    Sodium-ion batteries are now close to replacing lithium-ion batteries because they provide superior alternative energy storage solutions that are in great demand, particularly for large-scale applications. To that end, the present study is focused on the properties of a new type of dual-electrode material, Na 0.5Ni 0.25Mn 0.75O 2, synthesized using a mixed hydroxycarbonate route. Cyclic voltammetry confirms that redox couples, at high and low voltage ranges, are facilitated by the unique features and properties of this dual-electrode, through sodium ion deintercalation/intercalation into the layered Na 0.5Ni 0.25Mn 0.25O 2 material. This material provides superior performance for Na-ion batteries, asmore » evidenced by the fabricated sodium cell that yielded initial charge discharge capacities of 125/218 mAh g -1 in the voltage range of 1.5-4.4 V at 0.5 C. At a low voltage range (1.5-2.6 V), the anode cell delivered discharge charge capacities of 100/99 mAh g -1 with 99% capacity retention, which corresponds to highly reversible redox reaction of the Mn 4+/3+ reduction and the Mn 3+/4+ oxidation observed at 1.85 and 2.06 V, respectively. The symmetric Na-ion cell, fabricated using Na 0.5Ni 0.25Mn 0.25O 2, yielded initial charge discharge capacities of 196/187 μAh at 107 μA. Lastly, these results encourage the further development of new types of futuristic sodium-ion battery-based energy storage systems.« less

  9. Combustion of Na 2B 4O 7 + Mg + C to synthesis B 4C powders

    NASA Astrophysics Data System (ADS)

    Guojian, Jiang; Jiayue, Xu; Hanrui, Zhuang; Wenlan, Li

    2009-09-01

    Boron carbide powder was fabricated by combustion synthesis (CS) method directly from mixed powders of borax (Na 2B 4O 7), magnesium (Mg) and carbon. The adiabatic temperature of the combustion reaction of Na 2B 4O 7 + 6 Mg + C was calculated. The control of the reactions was achieved by selecting reactant composition, relative density of powder compact and gas pressure in CS reactor. The effects of these different influential factors on the composition and morphologies of combustion products were investigated. The results show that, it is advantageous for more Mg/Na 2B 4O 7 than stoichiometric ratio in Na 2B 4O 7 + Mg + C system and high atmosphere pressure in the CS reactor to increase the conversion degree of reactants to end product. The final product with the minimal impurities' content could be fabricated at appropriate relative density of powder compact. At last, boron carbide without impurities could be obtained after the acid enrichment and distilled water washing.

  10. Effects of Oral Administration of CrCl3 on the Contents of Ca, Mg, Mn, Fe, Cu, and Zn in the Liver, Kidney, and Heart of Chicken.

    PubMed

    Liu, Yanhan; Zhao, Xiaona; Zhang, Xiao; Zhao, Xuejun; Liu, Yongxia; Liu, Jianzhu

    2016-06-01

    This study aimed to investigate the effects of oral administration of trivalent chromium on the contents of Ca, Mg, Mn, Fe, Cu, and Zn in the heart, liver, and kidney. Different levels of 1/8, 1/4, and 1/2 LD50 (LD50 = 5000 mg/kg body mass) CrCl3 milligrams per kilogram body mass daily were added into the water to establish the chronic poisoning model. Ca, Mg, Mn, Fe, Cu, and Zn were detected with the flame atomic absorption spectrometry in the organs exposed 14, 28, and 42 days to CrCl3, respectively. Results showed that Cr was accumulated in the heart, liver, and kidney significantly (P < 0.05) with extended time and dose. The contents of Ca and Fe increased, whereas those of Mg, Mn, Cu, and Zn decreased in the heart, liver, and kidney of each treated group, which had a dose- and time-dependent relationship, but the contents of Mg and Zn in the heart took on a fluctuated change. These particular observations were different from those in the control group. In conclusion, the oral administration of CrCl3 could change the contents of Ca, Mg, Mn, Fe, Cu, and Zn in the heart, liver, and kidney, which may cause disorders in the absorption and metabolism of the metal elements of chickens.

  11. M xMn 8O 16 (M = Ag or K) as promising cathode materials for secondary Mg based batteries: The role of the cation M

    DOE PAGES

    Huang, Jianping; Takeuchi, Esther S.; Altug S. Poyraz; ...

    2016-01-01

    Here, Ag xMn 8O 16 (Ag-OMS-2) and K xMn 8O 16 (K-OMS-2) were investigated as high voltage cathode materials for Mg based batteries. Both M xMn 8O 16 materials delivered high initial capacities (>180 mA h g –1), and K xMn 8O 16 showed high cycle stability with a reversible capacity of >170 mA h g –1 after 20 cycles.

  12. Reversible hydrogen storage by NaAlH4 confined within a titanium-functionalized MOF-74(Mg) nanoreactor.

    PubMed

    Stavila, Vitalie; Bhakta, Raghunandan K; Alam, Todd M; Majzoub, Eric H; Allendorf, Mark D

    2012-11-27

    We demonstrate that NaAlH(4) confined within the nanopores of a titanium-functionalized metal-organic framework (MOF) template MOF-74(Mg) can reversibly store hydrogen with minimal loss of capacity. Hydride-infiltrated samples were synthesized by melt infiltration, achieving loadings up to 21 wt %. MOF-74(Mg) possesses one-dimensional, 12 Å channels lined with Mg atoms having open coordination sites, which can serve as sites for Ti catalyst stabilization. MOF-74(Mg) is stable under repeated hydrogen desorption and hydride regeneration cycles, allowing it to serve as a "nanoreactor". Confining NaAlH(4) within these pores alters the decomposition pathway by eliminating the stable intermediate Na(3)AlH(6) phase observed during bulk decomposition and proceeding directly to NaH, Al, and H(2), in agreement with theory. The onset of hydrogen desorption for both Ti-doped and undoped nano-NaAlH(4)@MOF-74(Mg) is ∼50 °C, nearly 100 °C lower than bulk NaAlH(4). However, the presence of titanium is not necessary for this increase in desorption kinetics but enables rehydriding to be almost fully reversible. Isothermal kinetic studies indicate that the activation energy for H(2) desorption is reduced from 79.5 kJ mol(-1) in bulk Ti-doped NaAlH(4) to 57.4 kJ mol(-1) for nanoconfined NaAlH(4). The structural properties of nano-NaAlH(4)@MOF-74(Mg) were probed using (23)Na and (27)Al solid-state MAS NMR, which indicates that the hydride is not decomposed during infiltration and that Al is present as tetrahedral AlH(4)(-) anions prior to desorption and as Al metal after desorption. Because of the highly ordered MOF structure and monodisperse pore dimensions, our results allow key template features to be identified to ensure reversible, low-temperature hydrogen storage.

  13. Constraining the astrophysical 23Mg(p, γ)24Al reaction rate using the 23Na(d,p)24Na reaction

    NASA Astrophysics Data System (ADS)

    Bennett, E. A.; Catford, W. N.; Christian, G.; Dede, S.; Hallam, S.; Lotay, G.; Ota, S.; Saastamoinen, A.; Wilkinson, R.

    2017-09-01

    The 23Mg(p, γ)24Al reaction provides an escape from the Ne-Na cycle in classical novae and is therefore important in understanding nova nucleosynthesis in the A > 20 mass range. Although several resonances may contribute to the overall rate at novae temperatures, the resonance at 475 keV is thought to be dominant. The strength of this resonance has been directly measured using a radioactive 23Mg beam impinging on a windowless H2 gas target; however, recent high-precision 24Al mass measurements have called this result into question. Here we make an indirect measurement using the 23Na(d,p)24Na reaction in inverse kinematics to study the mirror state of the 475 keV resonance in 24Na. The experiment, performed at the Texas A&M Cyclotron Institute, utilized the TIARA silicon array, four HPGe detectors, and the MDM spectrometer to measure the excited states of the 24Na nucleus. Preliminary results from the experiment will be presented along with progress from the ongoing analysis.

  14. Shape-Control of a 0D/1D NaFe0.9Mn0.1PO4 Nano-Complex by Electrospinning

    NASA Astrophysics Data System (ADS)

    Shin, Mi-Ra; Son, Jong-Tae

    2018-03-01

    NaFePO4 with a maricite structure was one of the most promising candidates for sodium ion batteries (SIBs) due to its advantages of environmental friendly and having low cost. However, it has low electrochemical conductivity and energy density, which impose limitations on its application as commercial cathode materials. In this study, other transition-metal ions such as Mn2+ were substituted into the iron (Fe2+) site in NaFePO4 to increase the surface area and the number of nanofibers in the prepared one-dimensional (1D) nano-sized material with 0D/1D dimensions to enhance the energy density. Also, the 0D/1D NaFe0.9Mn0.1PO4 cathode material has increased electrochemical conductivity because the fiber size was reduced to the nano-scale level by using the electrospinning method in order to decrease the diffusion path of Na-ions. The morphology of the 0D/1D nanofiber was evaluated by Field-emission scanning electron microscope and atomic force microscope analyses. The NaFe0.9Mn0.1PO4 nanofibers had a diameter of approximately 180 nm, while the spherical particle had a diameter 1 μm. The 0D/1D nano-sized cathode material show a discharge capacity of 27 mAhg -1 at a 0.05 C rate within the 2.0 4.5 V voltage range and a low R ct of 110 Ω.

  15. Investigation into the dehydration of selenate doped Na2M(SO4)2·2H2O (M = Mn, Fe, Co and Ni): Stabilisation of the high Na content alluaudite phases Na3M1.5(SO4)3-1.5x(SeO4)1.5x (M = Mn, Co and Ni) through selenate incorporation

    NASA Astrophysics Data System (ADS)

    Driscoll, L. L.; Kendrick, E.; Knight, K. S.; Wright, A. J.; Slater, P. R.

    2018-02-01

    In this paper we report an investigation into the phases formed on dehydration of Na2M(SO4)2-x(SeO4)x·2H2O (0 ≤ x ≤ 1; M = Mn, Fe, Co and Ni). For the Fe series, all attempts to dehydrate the samples doped with selenate resulted in amorphous products, and it is suspected that a side redox reaction involving the Fe and selenate may be occurring leading to phase decomposition and hence the lack of a crystalline product on dehydration. For M = Mn, Co, Ni, the structure observed was shown to depend upon the transition metal cation and level of selenate doping. An alluaudite phase, Na3M1.5(SO4)3-1.5x(SeO4)1.5x, was observed for the selenate doped compositions, with this phase forming as a single phase for x ≥ 0.5 M = Co, and x = 1.0 M = Ni. For M = Mn, the alluaudite structure is obtained across the series, albeit with small impurities for lower selenate content samples. Although the alluaudite-type phases Na2+2y(Mn/Co)2-y(SO4)3 have recently been reported [1,2], doping with selenate appears to increase the maximum sodium content within the structure. Moreover, the selenate doped Ni based samples reported here are the first examples of a Ni sulfate/selenate containing system exhibiting the alluaudite structure.

  16. Cross Section Measurements of the Reaction 23Na(p, γ)24Mg

    NASA Astrophysics Data System (ADS)

    Boeltzig, Axel; Deboer, Richard James; Macon, Kevin; Wiescher, Michael; Best, Andreas; Imbriani, Gianluca; Gyürky, György; Strieder, Frank

    2017-09-01

    The reaction 23Na(p, γ)24Mg can provide a link from the NeNa to the MgAl cycle in stellar burning and is therefore of interest in nuclear astrophysics. To determine the reaction rates at stellar temperatures, new cross section measurements at low proton energies have been performed recently, and further experiments are underway. The current cross section data implies that the reaction rate up to temperatures of 1 GK is determined by a few narrow resonances and direct capture. Complementary to these experimental efforts at low proton energies, cross section measurements at higher energies can help to constrain the direct capture and broad resonance contributions to the cross section and reduce the uncertainty of the extrapolation towards stellar energies. In this paper we report an experiment to measure the 23Na(p, γ)24Mg cross section with a solid target setup at the St. ANA 5U accelerator at the University of Notre Dame. The experiment and the current status of data analysis will be described. This work benefited from support by the National Science Foundation under Grant No. PHY-1430152 (JINA-CEE), the Nuclear Science Laboratory (NSL), the Istituto Nazionale di Fisica Nucleare (INFN), and the Gran Sasso Science Institute (GSSI).

  17. Effect of Synthesis Temperature and NaOH Concentration on Microstructural and Magnetic Properties of Mn0.5Zn0.5Fe2O4 Nanoparticles

    NASA Astrophysics Data System (ADS)

    Siregar, N.; Indrayana, I. P. T.; Suharyadi, E.; Kato, T.; Iwata, S.

    2017-05-01

    Mn0.5Zn0.5Fe2O4 nanoparticles have been successfully synthesized through coprecipitation method by varying NaOH concentrations from 0.5 M to 6 M and synthesis temperatures from 30 to 120 °C. The X-ray diffraction (XRD) pattern indicates samples consisting of multiphase structures such as spinel of Mn0.5Zn0.5Fe2O4, α-MnO2, ZnO, λ-MnO2, and γ-Fe2O3. The crystallite size of Mn0.5Zn0.5Fe2O4 is in the range of 14.1 to 26.7 nm. The Transmission electron microscope (TEM) image shows that sample was agglomerate. The hysteresis loops confirm that nanoparticles are soft magnetic materials with low coercivity (H c) in the range of 45.9 to 68.5 Oe. Those values increased relatively with increasing particles size. For NaOH concentration variation, the maximum magnetization of the sample increased from 10.4 emu/g to 11.6 emu/g with increasing ferrite content. Meanwhile, the maximum magnetization increased from 7.9 to 15.7 emu/g for samples with various synthesis temperature. The highest coercivity of 68.5 Oe was attained for a sample of 6 M NaOH under 90 °C. The highest magnetization of 15.7 emu/g was achieved for a sample of 1.5 M NaOH under 120 °C caused by the maximum crystallinity of sample.

  18. Dynamic study of (De)sodiation in alpha-MnO 2 nanowires

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Yuan, Yifei; Ma, Lu; He, Kun

    2016-01-01

    In this report, the electrochemical sodiation and desodiation in single crystalline alpha-MnO 2 nanowires are studied dynamically at both single particle level using in situ transmission electron microscopy (TEM) and bulk level using in situ synchrotron X-ray. The TEM results suggest that the first sodiation process starts with tunnel-based Na + intercalation, experiences the formation of Na 0.5MnO 2 as a result of tunnel degradation, and ends with the Mn 2O 3 phase. The inserted Na + can be partially extracted out of the sodiated products, and the following cycles are dominated by the reversible conversion reaction between Na 0.5MnOmore » 2 and Mn 2O 3. The Mn valence evolution inside a cycling coin using alpha-MnO 2 nanowire electrode also exhibits partially reversible characteristic, agreeing well with the in situ TEM analysis. The sodiation is compared with lithiation in the same alpha-MnO 2 nanowires. Both Na + and Li + interact with the tunneled structure via a similar tunnel -driven intercalation mechanism before Mn 4+ is reduced to Mn 3.5+. For the following deep insertion, the tunnels survive up. to LiMnO 2 (Mn3+) during lithiation, while the sodiation proceeds via a different mechanism that involves obvious phase transition and fast tunnel degradation after Mn's valence is below 3.5+. The difference in charge carrier insertion mechanisms can be ascribed to the strong interaction between the tunnel frame and inserted Na + possessing a larger ionic size than inserted Li +.« less

  19. Tunable photoluminescence properties of Ca{sub 8}NaLa(PO{sub 4}){sub 6}F{sub 2}:Eu{sup 2+},Mn{sup 2+} phosphor under UV excitation

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Zhang, Fen; Lan, Tong; Tang, Wanjun, E-mail: tangmailbox@126.com

    2015-04-15

    Highlights: • Ca{sub 8}NaLa(PO{sub 4}){sub 6}F{sub 2}:Eu{sup 2+},Mn{sup 2+} was prepared by a combustion-assisted synthesis method. • The phosphor presents blue and yellow double color emissions. • Efficient energy transfer from Eu{sup 2+} to Mn{sup 2+} in this phosphor is observed obviously. • White emitting was realized in Ca{sub 8}NaGd(PO{sub 4}){sub 6}F{sub 2}:0.10Eu{sup 2+},0.32Mn{sup 2+},0.10B phosphor. - Abstract: A series of Eu{sup 2+} and Mn{sup 2+} coactivated Ca{sub 8}NaLa(PO{sub 4}){sub 6}F{sub 2} (CNLF) phosphors have been synthesized by a combustion-assisted synthesis method. The investigation revealed that Ca{sub 8}NaLa(PO{sub 4}){sub 6}F{sub 2} crystallized in a hexagonal crystal system with the spacemore » group P6{sub 3}/m (176). The Eu{sup 2+} activated phosphors can be efficiently excited in the range of 270–400 nm and give intense blue emission peaking at 451 nm. By codoping the Eu{sup 2+} and Mn{sup 2+} ions into the CNLF host and singly varying the doping content of the Mn{sup 2+} ion, tunable colors from blue to white and eventually to yellow are obtained in CNLF:Eu{sup 2+},Mn{sup 2+} phosphors under the irradiation of 330 nm. The energy transfer from Eu{sup 2+} to Mn{sup 2+} in CNLF:Eu{sup 2+},Mn{sup 2+} has been demonstrated to be a resonant type via a dipole–dipole mechanism and the critical distance of energy transfer from Eu{sup 2+} to Mn{sup 2+} was estimated to be about 11.9 Å. The investigation indicates that the obtained samples might have potential application in white LEDs.« less

  20. Resistivity Changes Due to Precipitation Effects in Fibre Reinforced Mg-Al-Zn-Mn Alloy

    NASA Astrophysics Data System (ADS)

    Kiehn, J.; Kainer, K. U.; Vostrý, P.; Stulíková, I.

    1997-05-01

    The change of electrical properties of alumina short fibre reinforced Mg-Al-Zn-Mn alloy AZ91D during isochronal annealing up to 300 °C is discussed. The Saffil® fibres were incorporated into the magnesium alloy by direct squeeze casting. The fibre distribution is random planar parallel to the flat faces of the dc four-point resistivity specimens machined from the solution treated castings. A sharp drop of resistivity between 140 and 260 °C is explained by the formation of incoherent -phase particles. Some practical recommendations concerning the use of alumina short fibre reinforced AZ91 alloy are made on the basis of the results obtained. Es werden die Änderungen der elektrischen Eigenschaften der aluminiumoxid-kurzfaserverstärkten Mg-Al-Zn-Mn Legierung AZ91D während isochroner Wärmebehandlungen bis 300 °C diskutiert. Das direkte Preßgießverfahren diente zur Herstellung der Saffil®-Faser Magnesium Verbundwerkstoffe. Die Proben zur Widerstandsmessung nach der Vier-Punkt Methode wurden durch spanende Bearbeitung aus den lösungsgeglühten Preßgußstücken herausgearbeitet, so daß sie regellose Faserverteilung in den Ebenen parallel zu den flachen Probenseiten aufwiesen. Ein starker Abfall des elektrischen Widerstands im Temperaturbereich zwischen 140 und 260 °C wird durch die Bildung inkohärenter β-Phase erklärt. Auf Grundlage der Ergebnisse werden einige Empfehlungen zur Anwendung der kurzfaserverstärkten Legierung AZ91 gegeben.

  1. (Na,□)5[MnO2]13 nanorods: a new tunnel structure for electrode materials determined ab initio and refined through a combination of electron and synchrotron diffraction data

    PubMed Central

    Mugnaioli, Enrico; Gemmi, Mauro; Merlini, Marco; Gregorkiewitz, Michele

    2016-01-01

    (Nax□1 − x)5[MnO2]13 has been synthesized with x = 0.80 (4), corresponding to Na0.31[MnO2]. This well known material is usually cited as Na0.4[MnO2] and is believed to have a romanèchite-like framework. Here, its true structure is determined, ab initio, by single-crystal electron diffraction tomography (EDT) and refined both by EDT data applying dynamical scattering theory and by the Rietveld method based on synchrotron powder diffraction data (χ2 = 0.690, R wp = 0.051, R p = 0.037, R F2 = 0.035). The unit cell is monoclinic C2/m, a = 22.5199 (6), b = 2.83987 (6), c = 14.8815 (4) Å, β = 105.0925 (16)°, V = 918.90 (4) Å3, Z = 2. A hitherto unknown [MnO2] framework is found, which is mainly based on edge- and corner-sharing octahedra and comprises three types of tunnels: per unit cell, two are defined by S-shaped 10-rings, four by egg-shaped 8-rings, and two by slightly oval 6-rings of Mn polyhedra. Na occupies all tunnels. The so-determined structure excellently explains previous reports on the electrochemistry of (Na,□)5[MnO2]13. The trivalent Mn3+ ions concentrate at two of the seven Mn sites where larger Mn—O distances and Jahn–Teller distortion are observed. One of the Mn3+ sites is five-coordinated in a square pyramid which, on oxidation to Mn4+, may easily undergo topotactic transformation to an octahedron suggesting a possible pathway for the transition among different tunnel structures. PMID:27910840

  2. Enhanced ferromagnetic order in Sr{sub 4}Mn{sub 3}O{sub 3}(GeO{sub 4}){sub 3} featuring canted [MnO{sub 4}]{sub ∞} spin chains of mixed-valent Mn(III)/Mn(IV). Aliovalent substitution of the Sr{sub 4−x}Ln{sub x}Mn{sup III}{sub 2+x}Mn{sup IV}{sub 1−x}O{sub 3}(GeO{sub 4}){sub 3} solid-solution

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    West, J. Palmer; Sulejmanovic, Dino; Becht, Gregory

    2013-10-15

    Crystals of Sr{sub 4−x}Ln{sub x}Mn{sub 3}O{sub 3}(GeO{sub 4}){sub 3} (x=0; x∼0.15 for Ln=La, Pr, Nd, Sm. Eu, Gd, Dy; x∼0.3 for Ln=Gd) were isolated upon using high-temperature, solid-state methods in molten-salt media. These compounds are isostructural with the previously reported Na{sub 3}LnMn{sub 3}O{sub 3}(AsO{sub 4}){sub 3} (Ln=La, Sm, Gd) series that contains the same [MnO{sub 4}]{sub ∞} spin chains. The synthesis of the Sr{sub 4}Mn{sub 3}O{sub 3}(GeO{sub 4}){sub 3} (x=0) phase was carried out by a double aliovalent substitution with respect to the Sr{sup 2+} and Ge{sup 4+} ions that replace Na{sup +}/Ln{sup 3+} and As{sup 5+} in Na{sub 3}LnMn{submore » 3}O{sub 3}(AsO{sub 4}){sub 3}, respectively. The title series contains mixed-valent Mn(III)/Mn(IV) and shows a limited range of solid solution, both of which were not observed in the previously reported Na{sub 3}LnMn{sub 3}O{sub 3}(AsO{sub 4}){sub 3} series. To form the Sr{sub 4−x}Ln{sub x}Mn{sub 3}O{sub 3}(GeO{sub 4}){sub 3} solid solution, one of the Sr{sup 2+} sites, i.e., the original Ln-site in Na{sub 3}LnMn{sub 3}O{sub 3}(AsO{sub 4}){sub 3}, is partially substituted by Ln{sup 3+} in a statistical disorder of Sr{sub 1−x}/Ln{sub x}. Initial magnetic investigations of selected derivatives reveal higher ferromagnetic ordering temperatures than those reported for the Na{sub 3}LnMn{sub 3}O{sub 3}(AsO{sub 4}){sub 3} series, presumably attributed to a lesser degree of canting as a result of introducing non-Jahn–Teller Mn{sup 4+} ions. Also intriguing is the observation of multiple anomalies at low temperatures which appear to be of electronic origins. - Graphical abstract: Sr{sub 4−x}Ln{sub x}Mn(III){sub 2+x}Mn(IV){sub 1−x}O{sub 3}(GeO{sub 4}){sub 3}. Display Omitted - Highlights: • Double aliovalent substitution: Sr{sub 4}Mn{sub 3}O{sub 3}(GeO{sub 4}){sub 3} with respect to Na{sub 3}LnMn{sub 3}O{sub 3}(AsO{sub 4}){sub 3}. • Solid solution with respect to statistical disorder of Sr{sub 1

  3. Structure-dependent magnetoresistance and spin-transfer torque in antiferromagnetic Fe |MgO |FeMn |Cu tunnel junctions

    NASA Astrophysics Data System (ADS)

    Jia, Xingtao; Tang, Huimin; Wang, Shizhuo; Qin, Minghui

    2017-02-01

    We predict large magnetoresistance (MR) and spin transfer torque (STT) in antiferromagnetic Fe |MgO |FeMn |Cu tunnel junctions based on first-principles scattering theory. MR as large as ˜100 % is found in one junction. Magnetic dynamic simulations show that STT acting on the antiferromagnetic order parameter dominates the spin dynamics, and an electronic bias of order 10-1mV and current density of order 105Acm-2 can switches a junction of three-layer MgO, they are about one order smaller than that in Fe |MgO |Fe junction with the same barrier thickness, respectively. The multiple scattering in the antiferromagnetic region is considered to be responsible for the enhanced spin torque and smaller switching current density.

  4. M x Mn 8O 16 (M = Ag or K) as promising cathode materials for secondary Mg based batteries: the role of the cation M

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Huang, Jianping; Poyraz, Altug S.; Takeuchi, Kenneth J.

    2016-01-01

    2 × 2 tunneled M xMn 8O 16(M = Ag or K) materials delivered high initial capacities in Mg based electrolyte, and K xMn 8O 16 showed high cycle stability with a reversible capacity of >170 mA h g -1after 20 cycles.

  5. Synchrotron-based XAS on structure investigation of La0.99-xSrx(Na, K, Ba)0.01MnO3 nanoparticles: Evidence of magnetic properties

    NASA Astrophysics Data System (ADS)

    Daengsakul, Sujittra; Saengplot, Saowalak; Kidkhunthod, Pinit; Pimsawat, Adulphan; Maensiri, Santi

    2018-04-01

    This work presents the structural study of La0.99-xSrx(Na, K, Ba)0.01MnO3 or LSAM nanoparticles synthesized using thermal-hydro decomposition method where A denotes Na, K, Sr and Ba, respectively. The effect of ionic radii size of A dopants or rA from the substitution of A for La and Sr on the MnO6 octrahedral structure, where the average size of the cations occupying in A-site or 〈rA〉 is fixed at ∼ 1.24 Å, is focused. The LSAM nanoparticles are carefully studied using X-ray diffraction (XRD) including Rietveld refinement and X-ray Absorption Spectroscopy (XAS) including X-ray Absorption Near edge Structure (XANES) and X-ray Absorption Fine Structure (EXAFS). The Rietveld refinement shows all nano-powder samples have rhombohedral structure. By XANES technique we found that the effect of A substitutions at A-site causes a slight change of mean oxidation state of Mn between 3.54 and 3.60. Furthermore, the structural distortion of MnO6 octrahedral in samples is analysed and obtained from EXAFS. The observed trend of ferromagnetism for all LSAM samples can be clearly explained by evidences of A-site doping, structural distortion around Mn atoms and mixing Mn3+/Mn4+ valence states.

  6. Osumilite-(Mg): Validation as a mineral species and new data

    NASA Astrophysics Data System (ADS)

    Chukanov, N. V.; Pekov, I. V.; Rastsvetaeva, R. K.; Aksenov, S. M.; Belakovskiy, D. I.; Van, K. V.; Schüller, W.; Ternes, B.

    2013-12-01

    Osumilite-(Mg), the Mg-dominant analogue of osumilite, has been approved by the CNMNC IMA as a new mineral species. The holotype sample has been found at Bellerberg, Eifel volcanic area, Germany. Fluorophlogopite, sanidine, cordierite, mullite, sillimanite, topaz, pseudobrookite and hematite are associated minerals. Osumilite-(Mg) occurs as short prismatic or thick tabular hexagonal crystals reaching 0.5 × 1 mm in size in the cavities in basaltic volcanic glasses at their contact with thermally metamorphosed xenoliths of pelitic rocks. The mineral is brittle, with Mohs' hardness 6.5. Cleavage was not observed. Color is blue to brown. D meas = 2.59(1), D calc = 2.595 g/cm3. No bands corresponding to H2O and OH-groups are in the IR spectrum. Osumilite-(Mg) is uniaxial (+), ω = 1.539(2), ɛ = 1.547(2). The chemical composition (electron microprobe, average of 5 point analyses, wt %) is: 0.08 Na2O, 3.41 K2O, 0.04 CaO, 7.98 MgO, 0.28 MnO, 21.57 Al2O3, 3.59 Fe2O3, 62.33 SiO2, total 99.28. The empirical formula is: (K0.72Na0.03Ca0.01)(Mg1.97Mn0.04)[Al4.21Fe{0.45/3+}Si10.32]O30. The simplified formula is: KMg2Al3(Al2Si10)O10. The crystal structure was refined on a single crystal, R = 0.0294. Osumilite-(Mg) is hexagonal, space group P6/ mcc; a = 10.0959(1), c = 14.3282(2)Å, V = 1264.79(6) Å3, Z = 2. The strongest reflections in the X-ray powder diffraction pattern [ d, Å I %) ( hkl)] are: 7.21 (37) (002), 5.064 (85) (110), 4.137 (45) (112), 3.736 (43) (202), 3.234 (100) (211), 2.932 (42) (114), 2.767 (51) (204). A type specimen is deposited in the Fersman Mineralogical Museum, Russian Academy of Sciences, Moscow, registration number 4174/1.

  7. Band diagram and rate analysis of thin film spinel LiMn 2O 4 formed by electrochemical conversion of ALD-grown MnO

    DOE PAGES

    Young, Matthias J.; Schnabel, Hans-Dieter; Holder, Aaron M.; ...

    2016-09-22

    Nanoscale spinel lithium manganese oxide is of interest as a high-rate cathode material for advanced battery technologies among other electrochemical applications. In this work, the synthesis of ultrathin films of spinel lithium manganese oxide (LiMn 2O 4) between 20 and 200 nm in thickness by room-temperature electrochemical conversion of MnO grown by atomic layer deposition (ALD) is demonstrated. The charge storage properties of LiMn 2O 4 thin films in electrolytes containing Li +, Na +, K +, and Mg 2+ are investigated. A unified electrochemical band-diagram (UEB) analysis of LiMn 2O 4 informed by screened hybrid density functional theory calculationsmore » is also employed to expand on existing understanding of the underpinnings of charge storage and stability in LiMn 2O 4. It is shown that the incorporation of Li + or other cations into the host manganese dioxide spinel structure (λ-MnO 2) stabilizes electronic states from the conduction band which align with the known redox potentials of LiMn 2O 4. Furthermore, the cyclic voltammetry experiments demonstrate that up to 30% of the capacity of LiMn 2O 4 arises from bulk electronic charge-switching which does not require compensating cation mass transport. As a result, the hybrid ALD-electrochemical synthesis, UEB analysis, and unique charge storage mechanism described here provide a fundamental framework to guide the development of future nanoscale electrode materials for ion-incorporation charge storage.« less

  8. Impact of a long term fire retardant (Fire Trol 931) on the leaching of Na, Al, Fe, Mn, Cu and Si from a Mediterranean forest soil: a short-term, lab-scale study.

    PubMed

    Koufopoulou, Sofia; Michalopoulos, Charalampos; Tzamtzis, Nikolaos; Pappa, Athina

    2014-06-01

    Long term fire retardant (LTR) application for forest fire prevention purposes as well as wildland fires can result in chemical leaching from forest soils. Large quantities of sodium (Na), aluminium (Al), iron (Fe), manganese (Mn), copper (Cu) and silicon (Si) in leachates, mainly due to ammonium (one of the major LTR components) soil deposition, could affect the groundwater quality. The leaching of Na, Al, Fe, Mn, Cu and Si due to nitrogen based LTR application (Fire Trol 931) was studied at laboratory scale. The concentrations of Na(+), Al(3+), Fe(3+)/Fe(2+), Mn(2+), Cu(2+) and Si(4+) were measured in the resulting leachates from pots with forest soil and pine trees alone and in combination with fire. The leaching of Na, Fe and Si from treated pots was significantly greater than that from control pots. The leaching of Al, Mn and Cu was extremely low.

  9. Synthesis, characterization and vibrational spectroscopic study of Co, Mg co-doped LiMnPO4

    NASA Astrophysics Data System (ADS)

    Sronsri, Chuchai; Noisong, Pittayagorn; Danvirutai, Chanaiporn

    2016-01-01

    The isostructural olivine-like LiM(II)PO4 compounds [M(II) = Mn, Mn0.9Co0.1, Mn0.8Co0.1Mg0.1] were successfully generated through the solid state reaction from the synthesized NH4M(II)PO4• H2O precursors. The TG/DTG/DTA, AAS/AES, FTIR and XRD methods were employed to confirm both NH4M(II)PO4• H2O and LiM(II)PO4 compounds. Their morphologies were studied by SEM method. The shift of two theta angle of XRD to higher values was observed in metal doping compounds, which indicate the formation of the single phase of isodivalent doping of Co2 + and Mg2 + ions according to the change in the lattice parameters and cell volumes. Their infrared spectra are reported and discussed with respect to the normal vibrations of NH4+, PO43 -, P2O74 - and H2O molecules using factor group analysis. The correlation field splitting analysis of PO43 - in NH4M(II)PO4• H2O (orthorhombic system, Pmn21, C2v7 and Z = 2, [(3 × 5) - 6] × 2 = 18 internal modes) symbolized as Td - Cs - C2v7 suggested the number of vibrational modes to be: ΓVib = A1(6) + A2(3) + B1(6) + B2(3) and A1(6) + A2(3) + B1(3) + B2(6) for zx and yz plane respectively. While, LiM(II)PO4 crystallizes in the orthorhombic system the space group Pnma (D2h16), Z = 4 and the site symmetry of PO43 - is Cs. The correlation field splitting of type Td - Cs - D2h16 were reported in relation to [(3 × 5) - 6] × 4 = 36 internal modes for PO43 - unit in the structure.

  10. Co-Precipitation Synthesis and Optical Properties of Mn4+-Doped Hexafluoroaluminate w-LED Phosphors

    PubMed Central

    Geitenbeek, Robin G.; Meijerink, Andries

    2017-01-01

    Mn4+-activated hexafluoroaluminates are promising red-emitting phosphors for white light emitting diodes (w-LEDs). Here, we report the synthesis of Na3AlF6:Mn4+, K3AlF6:Mn4+ and K2NaAlF6:Mn4+ phosphors through a simple two-step co-precipitation method. Highly monodisperse large (~20 μm) smoothed-octahedron shaped crystallites are obtained for K2NaAlF6:Mn4+. The large size, regular shape and small size distribution are favorable for application in w-LEDs. All Mn4+-doped hexafluoroaluminates show bright red Mn4+ luminescence under blue light excitation. We compare the optical properties of Na3AlF6:Mn4+, K3AlF6:Mn4+ and K2NaAlF6:Mn4+ at room temperature and 4 K. The luminescence measurements reveal that multiple Mn4+ sites exist in M3AlF6:Mn4+ (M = Na, K), which is explained by the charge compensation that is required for Mn4+ on Al3+ sites. Thermal cycling experiments show that the site distribution changes after annealing. Finally, we investigate thermal quenching and show that the luminescence quenching temperature is high, around 460–490 K, which makes these Mn4+-doped hexafluoroaluminates interesting red phosphors for w-LEDs. The new insights reported on the synthesis and optical properties of Mn4+ in the chemically and thermally stable hexafluoroaluminates can contribute to the optimization of red-emitting Mn4+ phosphors for w-LEDs. PMID:29149083

  11. Superspace description of wagnerite-group minerals (Mg,Fe,Mn)2(PO4)(F,OH)

    PubMed Central

    Lazic, Biljana; Armbruster, Thomas; Chopin, Christian; Grew, Edward S.; Baronnet, Alain; Palatinus, Lukas

    2014-01-01

    Reinvestigation of more than 40 samples of minerals belonging to the wagnerite group (Mg, Fe, Mn)2(PO4)(F,OH) from diverse geological environments worldwide, using single-crystal X-ray diffraction analysis, showed that most crystals have incommensurate structures and, as such, are not adequately described with known polytype models (2b), (3b), (5b), (7b) and (9b). Therefore, we present here a unified superspace model for the structural description of periodically and aperiodically modulated wagnerite with the (3+1)-dimensional superspace group C2/c(0β0)s0 based on the average triplite structure with cell parameters a ≃ 12.8, b ≃ 6.4, c ≃ 9.6 Å, β ≃ 117° and the modulation vectors q = β b*. The superspace approach provides a way of simple modelling of the positional and occupational modulation of Mg/Fe and F/OH in wagnerite. This allows direct comparison of crystal properties. PMID:24675594

  12. FeOOH-loaded MnO2 nano-composite: An efficient emergency material for thallium pollution incident.

    PubMed

    Chen, Meiqing; Wu, Pingxiao; Yu, Langfeng; Liu, Shuai; Ruan, Bo; Hu, Haihui; Zhu, Nengwu; Lin, Zhang

    2017-05-01

    A FeOOH-loaded MnO 2 nano-composite was developed as an emergency material for Tl(I) pollution incident. Structural characterizations showed that FeOOH successfully loaded onto MnO 2 , the nanosheet-flower structure and high surface area (191 m 2  g -1 ) of material contributed to the excellent performance for Tl(I) removal. FeOOH-loaded MnO 2 with a Fe/Mn molar ratio of 1:2 exhibited a noticeable enhanced capacity for Tl(I) removal compared to that of pure MnO 2 . The outstanding performance for Tl(I) removal involves in extremely high efficiency (achieved equilibrium and drinking water standard within 4 min) and the large maximum adsorption capacity (450 mg g -1 ). Both the control-experiment and XPS characterization proved that the removal mechanism of Tl(I) on FeOOH-loaded MnO 2 included adsorption and oxidation: the oxidation of MnO 2 played an important role for Tl(I) removal, and the adsorption of FeOOH loaded on MnO 2 enhanced Tl(I) purification at the same time. In-depth purification of Tl(I) had reach drinking water standards (0.1 μg L -1 ) at pH above 7, and there wasn't security risk produced from the dissolution of Mn 2+ and Fe 2+ . Moreover, the as-prepared material could be utilized as a recyclable adsorbent regenerated by using NaOH-NaClO binary solution. Therefore, the synthesized FeOOH-loaded MnO 2 in this study has the potential to be applied as an emergency material for thallium pollution incident. Copyright © 2017 Elsevier Ltd. All rights reserved.

  13. Optical absorption spectra and g factor of MgO: Mn2+explored by ab initio and semi empirical methods

    NASA Astrophysics Data System (ADS)

    Andreici Eftimie, E.-L.; Avram, C. N.; Brik, M. G.; Avram, N. M.

    2018-02-01

    In this paper we present a methodology for calculations of the optical absorption spectra, ligand field parameters and g factor for the Mn2+ (3d5) ions doped in MgO host crystal. The proposed technique combines two methods: the ab initio multireference (MR) and the semi empirical ligand field (LF) in the framework of the exchange charge model (ECM) respectively. Both methods of calculations are applied to the [MnO6]10-cluster embedded in an extended point charge field of host matrix ligands based on Gellé-Lepetit procedure. The first step of such investigations was the full optimization of the cubic structure of perfect MgO crystal, followed by the structural optimization of the doped of MgO:Mn2+ system, using periodic density functional theory (DFT). The ab initio MR wave functions approaches, such as complete active space self-consistent field (CASSCF), N-electron valence second order perturbation theory (NEVPT2) and spectroscopy oriented configuration interaction (SORCI), are used for the calculations. The scalar relativistic effects have also been taken into account through the second order Douglas-Kroll-Hess (DKH2) procedure. Ab initio ligand field theory (AILFT) allows to extract all LF parameters and spin-orbit coupling constant from such calculations. In addition, the ECM of ligand field theory (LFT) has been used for modelling theoptical absorption spectra. The perturbation theory (PT) was employed for the g factor calculation in the semi empirical LFT. The results of each of the aforementioned types of calculations are discussed and the comparisons between the results obtained and the experimental results show a reasonable agreement, which justifies this new methodology based on the simultaneous use of both methods. This study establishes fundamental principles for the further modelling of larger embedded cluster models of doped metal oxides.

  14. Proton threshold states in the Na22(p,γ)Mg23 reaction and astrophysical implications

    NASA Astrophysics Data System (ADS)

    Comisel, H.; Hategan, C.; Graw, G.; Wolter, H. H.

    2007-04-01

    Proton threshold states in Mg23 are important for the astrophysically relevant proton capture reaction Na22(p,γ)Mg23. In the indirect determination of the resonance strength of the lowest states, which were not accessible by direct methods, some of the spin-parity-assignments remained experimentally uncertain. We have investigated these states with shell model, Coulomb displacement, and Thomas-Ehrman shift calculations. From the comparison of calculated and observed properties, we relate the lowest relevant resonance state at Ex=7643 keV to an excited 3/2+ state in accordance with a recent experimental determination by Jenkins From this we deduce significantly improved values for the Na22(p,γ)Mg23 reaction rate at stellar temperatures below T9=0.1 K.

  15. Molecular structure of Mg-Al, Mn-Al and Zn-Al halotrichites-type double sulfates--an infrared spectroscopic study.

    PubMed

    Palmer, Sara J; Frost, Ray L

    2011-05-01

    Near infrared (NIR), X-ray diffraction (XRD) and infrared (IR) spectroscopy have been applied to halotrichites of the formula MgAl(2)(SO(4))(4)·22H(2)O, MnAl(2)(SO(4))(4)·22H(2)O and ZnAl(2)(SO(4))(4)·22H(2)O. Comparison of the halotrichites in different spectral regions has shown that the incorporation of a divalent transition metal into the halotrichite structure causes a shift in OH stretching band positions to lower wavenumbers. Therefore, an increase of the hydrogen bond strength of the bonded water is observed for divalent cations with a larger molecular mass. XRD has confirmed the formation of halotrichite for all three samples and characteristic peaks of halotrichite have been identified for each halotrichite-type compound. It has been observed that Mg-Al and Mn-Al halotrichite are very similar in structure, while Zn-Al showed several differences particularly in the NIR spectra. This work has shown that compounds with halotrichite structures can be synthesised and characterised by infrared and NIR spectroscopy. Copyright © 2011 Elsevier B.V. All rights reserved.

  16. A kinetic study of struvite precipitation recycling technology with NaOH/Mg(OH)2 addition.

    PubMed

    Yu, Rongtai; Ren, Hongqiang; Wang, Yanru; Ding, Lili; Geng, Jingji; Xu, Ke; Zhang, Yan

    2013-09-01

    Struvite precipitation recycling technology is received wide attention in removal ammonium and phosphate out of wastewater. While past study focused on process efficiency, and less on kinetics. The kinetic study is essential for the design and optimization in the application of struvite precipitation recycling technology. The kinetics of struvite with NaOH/Mg(OH)2 addition were studied by thermogravimetry analysis with three rates (5, 10, 20 °C/min), using Friedman method and Ozawa-Flynn-Wall method, respectively. Degradation process of struvite with NaOH/Mg(OH)2 addition was three steps. The stripping of ammonia from struvite was mainly occurred at the first step. In the first step, the activation energy was about 70 kJ/mol, which has gradually declined as the reaction progress. By model fitting studies, the proper mechanism function for struvite decomposition process with NaOH/Mg(OH)2 addition was revealed. The mechanism function was f(α)=α(α)-(1-α)(n), a Prout-Tompkins nth order (Bna) model. Copyright © 2013 Elsevier Ltd. All rights reserved.

  17. ⁵³Mn-⁵³Cr and ²⁶Al-²⁶Mg ages of a feldspathic lithology in polymict ureilites

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Goodrich, Cyrena Anne; Hutcheon, Ian D.; Kita, Noriko T.

    2010-07-01

    We report 53Mn– 53Cr and 26Al– 26Mg isotopic data, obtained by in-situ SIMS analysis, for feldspathic clasts in polymict ureilites DaG 319 and DaG 165. The analyzed clasts belong to the “albitic lithology,” the most abundant population of indigenous feldspathic materials in polymict ureilites, and are highly fractionated igneous assemblages of albitic plagioclase, Fe-rich pyroxenes, phosphates, ilmenite, silica, and Fe(Mn, K, P, Ti)-enriched glass. Glass in DaG 165 clast 19 has extremely high and variable 55Mn/ 52Cr ratios (500–58,000) and shows correlated 53Cr excesses up to ~ 1500‰, clearly indicating the presence of live 53Mn at the time of formation.more » The slope of the well-correlated isochron defined by glass and pyroxenes from this clast corresponds to ( 53Mn/ 55Mn) = (2.84 ± 0.10) × 10 -6 (2σ). Data for less 55Mn/ 52Cr-enriched glasses from DaG 319 clast B1, as well as phosphates from several other clasts, are consistent with this isochron. The 53Mn/ 55Mn ratio obtained from the isochron implies that these clasts are 0.70 ± 0.18 Ma younger than the D'Orbigny angrite, corresponding to the absolute age of 4563.72 ± 0.22 Ma. Plagioclase in DaG 319 clast B1 has a fairly constant 27Al/ 24Mg ratio of ~ 900 and shows resolvable 26Mg excesses of ~ 2‰. The slope of the isochron defined by pyroxene and plagioclase in this clast is (3.0 ± 1.1) × 10 -7 (2σ), corresponding to a time difference of 5.4 (-0.3/+0.5) Ma after CAI (assuming the canonical initial 26Al/ 27Al ratio of 5 × 10 -5) and an age 0.5 (-0.3/+0.5) Ma younger than D'Orbigny. Its absolute age (relative to D'Orbigny) is 4563.9 (+ 0.4/-0.5) Ma, in agreement with the 53Mn– 53Cr age from clast 19. These data provide the first high-precision age date, ~ 5.4 Ma after CAI, for ureilites, giving a minimum estimate for the age of differentiation of their parent asteroid. Interpretation of this age for the thermal and physical history of that asteroid depends on a number of currently

  18. Enhancing Catalyzed Decomposition of Na2CO3 with Co2MnO x Nanowire-Decorated Carbon Fibers for Advanced Na-CO2 Batteries.

    PubMed

    Fang, Cong; Luo, Jianmin; Jin, Chengbin; Yuan, Huadong; Sheng, Ouwei; Huang, Hui; Gan, Yongping; Xia, Yang; Liang, Chu; Zhang, Jun; Zhang, Wenkui; Tao, Xinyong

    2018-05-23

    The metal-CO 2 batteries, especially Na-CO 2 , batteries come into sight owing to their high energy density, ability for CO 2 capture, and the abundance of sodium resource. Besides the sluggish electrochemical reactions at the gas cathodes and the instability of the electrolyte at a high voltage, the final discharge product Na 2 CO 3 is a solid and poor conductor of electricity, which may cause the high overpotential and poor cycle performance for the Na-CO 2 batteries. The promotion of decomposition of Na 2 CO 3 should be an efficient strategy to enhance the electrochemical performance. Here, we design a facile Na 2 CO 3 activation experiment to screen the efficient cathode catalyst for the Na-CO 2 batteries. It is found that the Co 2 MnO x nanowire-decorated carbon fibers (CMO@CF) can promote the Na 2 CO 3 decomposition at the lowest voltage among all these metal oxide-decorated carbon fiber structures. After assembling the Na-CO 2 batteries, the electrodes based on CMO@CF show lower overpotential and better cycling performance compared with the electrodes based on pristine carbon fibers and other metal oxide-modified carbon fibers. We believe this catalyst screening method and the freestanding structure of the CMO@CF electrode may provide an important reference for the development of advanced Na-CO 2 batteries.

  19. Aptamer biosensor for Salmonella typhimurium detection based on luminescence energy transfer from Mn2 +-doped NaYF4:Yb, Tm upconverting nanoparticles to gold nanorods

    NASA Astrophysics Data System (ADS)

    Cheng, Keyi; Zhang, Jianguo; Zhang, Liping; Wang, Lun; Chen, Hongqi

    2017-01-01

    A highly sensitive luminescent bioassay for the detection of Salmonella typhimurium was fabricated using Mn2 +-doped NaYF4:Yb,Tm upconversion nanoparticles (UCNPs) as the donor and gold nanorods (Au NRs) as the acceptor and utilizing an energy transfer (LET) system. Mn2 +-doped NaYF4:Yb,Tm UCNPs with a strong emission peak at 807 nm were obtained by changing the doped ion ratio. Carboxyl-terminated Mn2 +-doped NaYF4:Yb,Tm UCNPs were coupled with S. typhimurium aptamers, which were employed to capture and concentrate S. typhimurium. The electrostatic interactions shorten the distance between the negatively charged donor and the positively charged acceptor, which results in luminescence quenching. The added S. typhimurium leads to the restoration of luminescence due to the formation of UCNPs-aptamers-S. typhimurium, which repels the UCNPs-aptamers from the Au NRs. The LET system does not occur because of the nonexistence of the luminescence emission band of Mn2 +-doped NaYF4:Yb,Tm UCNPs, which had large spectral overlap with the absorption band of Au NRs. Under optimal conditions, the linear range of detecting S. typhimurium was 12 to 5 × 105 cfu/mL (R = 0.99). The limit of detection for S. typhimurium was as low as 11 cfu/mL in an aqueous buffer. The measurement of S. typhimurium in milk samples was satisfied in accordance with the plate-counting method, suggesting that the proposed method was of practical value in the application of food security.

  20. Seasonal Trends and Inter-Individual Heterogeneity: A multi-species record of Mg, Sr, Ba, & Mn in Planktic Foraminifera from the Modern Cariaco Basin

    NASA Astrophysics Data System (ADS)

    Davis, C. V.; Thunell, R.; Astor, Y. M.

    2017-12-01

    The trace element to calcium ratios (TE/Ca) of planktic foraminifera shells are a valuable tool for paleoceanographic reconstructions, and represent a combination of environmental, ecological and biological signals. We present here a three-year record (2010-2013) of TE/Ca (Mg, Sr, Ba, Mn) from four species of foraminifera (Orbulina universa, Globigerina ruber, Globigerinella siphonifera, and Globorotalia menardii) collected by plankton tow in the modern Cariaco basin. Each tow is paired with in situ measurements of water column properties, allowing a direct comparison between shell geochemistry and calcification environment. A combination of Laser Ablation and solution ICP-MS analyses are used to document seasonality, primarily due to the alternating influence of wind-driven coastal upwelling and riverine inputs, in shell TE/Ca. Individual shell data further allows for the quantification of trace element heterogeneity among individual shells within single tows. All TE/Ca ratios vary temporally and show inter-individual variability within single tows. The spread in TE/Ca differs between element and species, with Mg/Ca ratios being the most variable. Despite this, Mg/Ca still tracks temperature changes in G. ruber, O. universa, and G. menardii, with G. ruber most closely reproducing sea surface temperature. Some species show chamber-to-chamber differences in trace element ratios, with G. ruber Mg/Ca and Ba/Ca decreasing in younger chambers (but not other elements) and Mg/Ca, Mn/Ca and Ba/Ca decreasing in younger chambers in G. siphonifera. We find the original Mn/Ca to be variable both temporally and between species, with G. menardii in some samples having extremely high ratios (100 μmol/mol). Assessing seasonal trends and environmental drivers of TE/Ca variability and quantifying the extent of inter-individual heterogeneity in these species will inform the use of their shells as geochemical proxies.

  1. Tunable white light of a Ce3+,Tb3+,Mn2+ triply doped Na2Ca3Si2O8 phosphor for high colour-rendering white LED applications: tunable luminescence and energy transfer.

    PubMed

    Lü, Wei; Xu, Huawei; Huo, Jiansheng; Shao, Baiqi; Feng, Yang; Zhao, Shuang; You, Hongpeng

    2017-07-18

    A tunable white light emitting Na 2 Ca 3 Si 2 O 8 :Ce 3+ ,Tb 3+ ,Mn 2+ phosphor with a high color rendering index (CRI) has been prepared. Under UV excitation, Na 2 Ca 3 Si 2 O 8 :Ce 3+ phosphors present blue luminescence and exhibit a broad excitation ranging from 250 to 400 nm. When codoping Tb 3+ /Mn 2+ ions into Na 2 Ca 3 Si 2 O 8 , energy transfer from Ce 3+ to Tb 3+ and Ce 3+ to Mn 2+ ions is observed from the spectral overlap between Ce 3+ emission and Tb 3+ /Mn 2+ excitation spectra. The energy-transfer efficiencies and corresponding mechanisms are discussed in detail. The mechanism of energy transfer from Ce 3+ to Tb 3+ is demonstrated to be a dipole-quadrupole mechanism by the Inokuti-Hirayama model. The wavelength-tunable white light can be realized by coupling the emission bands centered at 440, 550 and 590 nm ascribed to the contribution from Ce 3+ , Tb 3+ and Mn 2+ , respectively. The commission on illumination value of color tunable emission can be tuned by controlling the content of Ce 3+ , Tb 3+ and Mn 2+ . Temperature-dependent luminescence spectra proved the good thermal stability of the as-prepared phosphor. White LEDs with CRI = 93.5 are finally fabricated using a 365 nm UV chip and the as-prepared Na 2 Ca 3 Si 2 O 8 :Ce 3+ ,Tb 3+ ,Mn 2+ phosphor. All the results suggest that Na 2 Ca 3 Si 2 O 8 :Ce 3+ ,Tb 3+ ,Mn 2+ can act as potential color-tunable and single-phase white emission phosphors for possible applications in UV based white LEDs.

  2. Enhancing anaerobic digestion of waste activated sludge by the combined use of NaOH and Mg(OH)2: Performance evaluation and mechanism study.

    PubMed

    Huang, Cheng; Lai, Jia; Sun, Xiuyun; Li, Jiansheng; Shen, Jinyou; Han, Weiqing; Wang, Lianjun

    2016-11-01

    In this study, the combination treatment of NaOH and Mg(OH)2 was applied to anaerobic digestion of waste activated sludge (WAS) for simultaneously enhancement of volatile fatty acids (VFAs) production, nutrients removal and sludge dewaterability. The maximum VFAs production (461mg COD/g VSS) was obtained at the NaOH/Mg(OH)2 ratio of 75:25, which was much higher than that of the blank or sole NaOH. Moreover, nutrients removal and sludge dewaterability were improved by the combined using of NaOH and Mg(OH)2. Mechanism investigations revealed that the presence of Mg(OH)2 could maintain alkaline environment, which contributed to inhibit the activity of methanogens. Also, the bridging between Mg(2+) and extracellular polymeric substances (EPS) plays an important role in the solubilization and dewatering of sludge. High-throughput sequencing analysis demonstrated that the abundance of bacteria involved in sludge hydrolysis and VFAs accumulation was greatly enriched with the mixtures of NaOH and Mg(OH)2. Copyright © 2016 Elsevier Ltd. All rights reserved.

  3. The 21 Na (p,γ) 22 Mg reaction from Ec.m. =200 to 1103 keV in novae and x-ray bursts

    NASA Astrophysics Data System (ADS)

    D'Auria, J. M.; Azuma, R. E.; Bishop, S.; Buchmann, L.; Chatterjee, M. L.; Chen, A. A.; Engel, S.; Gigliotti, D.; Greife, U.; Hunter, D.; Hussein, A.; Hutcheon, D.; Jewett, C. C.; José, J.; King, J. D.; Laird, A. M.; Lamey, M.; Lewis, R.; Liu, W.; Olin, A.; Ottewell, D.; Parker, P.; Rogers, J.; Ruiz, C.; Trinczek, M.; Wrede, C.

    2004-06-01

    The long-lived radioactive nuclide 22 Na ( t1/2 =2.6 yr) is an astronomical observable for understanding the physical processes of oxygen-neon novae. Yields of 22Na in these events are sensitive to the unknown total rate of the 21 Na (p,γ) 22 Mg reaction. Using a high intensity 21 Na beam at the TRIUMF-ISAC facility, the strengths of seven resonances in 22 Mg , of potential astrophysical importance, have been directly measured at center of mass energies from Ec.m. =200 to 1103 keV . We report the results obtained for these resonances and their respective contributions to the 21 Na (p,γ) 22 Mg rate in novae and x-ray bursts, and their impact on 22 Na production in novae.

  4. Liquid-Solid Interaction in Al-Si/Al-Mn-Cu-Mg Brazing Sheets and Its Effects on Mechanical Properties

    NASA Astrophysics Data System (ADS)

    Jin, H.; Kozdras, M. S.; Amirkhiz, B. Shalchi; Winkler, S. L.

    2018-05-01

    The liquid-solid interaction during brazing at 592 °C to 605 °C and its effects on mechanical properties were investigated in a series of Al-Si/Al-Mn-Cu-Mg brazing sheets with different Mg contents. Depending on the Mg level in core alloy and the brazing temperature, critical changes of local chemistry and microstructure related to the liquid-solid interaction occur, including solid-state diffusion, uniform clad-core interface migration, and grain boundary penetration (GBP). When the Mg in core alloy is below 1 wt pct, the interaction is limited and the formation of a dense precipitation band due to solid-state diffusion of Si from the clad to the core is dominant. As the Mg exceeds 1 wt pct, very extensive interaction occurs resulting in clad-core interface migration and GBP of Si into the core, both involving local melting and re-solidification of the core alloy. Whenever Si from the clad encounters Mg in the core due to the interaction, Mg2Si precipitates are formed leading to significant improvement of strength. However, the interface migration and GBP drastically reduce the ductility, due to the segregation of coarse secondary phase particles along the newly formed grain boundaries.

  5. Liquid-Solid Interaction in Al-Si/Al-Mn-Cu-Mg Brazing Sheets and Its Effects on Mechanical Properties

    NASA Astrophysics Data System (ADS)

    Jin, H.; Kozdras, M. S.; Amirkhiz, B. Shalchi; Winkler, S. L.

    2018-07-01

    The liquid-solid interaction during brazing at 592 °C to 605 °C and its effects on mechanical properties were investigated in a series of Al-Si/Al-Mn-Cu-Mg brazing sheets with different Mg contents. Depending on the Mg level in core alloy and the brazing temperature, critical changes of local chemistry and microstructure related to the liquid-solid interaction occur, including solid-state diffusion, uniform clad-core interface migration, and grain boundary penetration (GBP). When the Mg in core alloy is below 1 wt pct, the interaction is limited and the formation of a dense precipitation band due to solid-state diffusion of Si from the clad to the core is dominant. As the Mg exceeds 1 wt pct, very extensive interaction occurs resulting in clad-core interface migration and GBP of Si into the core, both involving local melting and re-solidification of the core alloy. Whenever Si from the clad encounters Mg in the core due to the interaction, Mg2Si precipitates are formed leading to significant improvement of strength. However, the interface migration and GBP drastically reduce the ductility, due to the segregation of coarse secondary phase particles along the newly formed grain boundaries.

  6. Comparative evaluation of some commercially available brands of pharmaceutical preparations for Na, K and Mg concentrations.

    PubMed

    Hayat, Sikander; Chughtai, Muhammad Ismail; Ansari, Tariq Mahmood; Kamal, Ghulam Mustafa

    2012-04-01

    A study was carried out to investigate the concentrations of macro-elements (Na(+), K(+) and Mg(+2)) in twelve commercially available pharmaceutical preparations used as sex stimulant, by Atomic Absorption Spectrophotometer. A wet digestion method was adopted to prepare the samples. The results indicated that sodium concentration was maximum (3702 ± 29 μg g(-1)) in LB and minimum (495 ± 06 μg g(-1)) in H-E-H. Potassium concentration was maximum (6337 ± 13 μg g(-1)) in NBA while minimum (150 ± 06 μg g(-1)) in ZGRA. Magnesium concentration was maximum in V-100 (9226 ± 11 μg g(-1)) and minimum in FGRA (1194 ± 25 μg g(-1)). The concentration of macro-elements in the imported herbal preparations was in the order of MgMg. Some of these herbal preparations contain high level of macro-elements than the recommended daily dietary allowances. The excessive use of such preparations may cause severe allergic reactions, kidney damage and pulmonary atherosclerosis.

  7. A systematic study of 25Mg NMR in paramagnetic transition metal oxides: applications to Mg-ion battery materials.

    PubMed

    Lee, Jeongjae; Seymour, Ieuan D; Pell, Andrew J; Dutton, Siân E; Grey, Clare P

    2016-12-21

    Rechargeable battery systems based on Mg-ion chemistries are generating significant interest as potential alternatives to Li-ion batteries. Despite the wealth of local structural information that could potentially be gained from Nuclear Magnetic Resonance (NMR) experiments of Mg-ion battery materials, systematic 25 Mg solid-state NMR studies have been scarce due to the low natural abundance, low gyromagnetic ratio, and significant quadrupole moment of 25 Mg (I = 5/2). This work reports a combined experimental 25 Mg NMR and first principles density functional theory (DFT) study of paramagnetic Mg transition metal oxide systems Mg 6 MnO 8 and MgCr 2 O 4 that serve as model systems for Mg-ion battery cathode materials. Magnetic parameters, hyperfine shifts and quadrupolar parameters were calculated ab initio using hybrid DFT and compared to the experimental values obtained from NMR and magnetic measurements. We show that the rotor assisted population transfer (RAPT) pulse sequence can be used to enhance the signal-to-noise ratio in paramagnetic 25 Mg spectra without distortions in the spinning sideband manifold. In addition, the value of the predicted quadrupolar coupling constant of Mg 6 MnO 8 was confirmed using the RAPT pulse sequence. We further apply the same methodology to study the NMR spectra of spinel compounds MgV 2 O 4 and MgMn 2 O 4 , candidate cathode materials for Mg-ion batteries.

  8. The electrochemical performance of aqueous rechargeable battery of Zn/Na0.44MnO2 based on hybrid electrolyte

    NASA Astrophysics Data System (ADS)

    Wu, Xianwen; Li, Yehua; Xiang, Yanhong; Liu, Zhixiong; He, Zeqiang; Wu, Xianming; Li, Youji; Xiong, Lizhi; Li, Chuanchang; Chen, Jian

    2016-12-01

    There is a broad application prospect for smart grid about aqueous rechargeable sodium-ion battery. In order to improve its electrochemical performance, a hybrid cationic aqueous-based rechargeable battery system based on the nanostructural Na0.44MnO2 and metallic zinc foil as the positive and negative electrodes respectively is built up. Nano rod-like Na0.44MnO2 is synthesized by sol-gel method followed by calcination at 850 °C for 9 h, and various characterization techniques including the X-ray diffraction (XRD) and scanning electron microscopy (SEM) are used to investigate the structure and morphology of the as-prepared material. The cyclic voltammetry, galvanostatic charge-discharge and self-discharge measurements are performed at the same time. The results show that the battery delivers a very high initial discharge capacity of 186.2 mAh g-1 at 0.2 C-rate in the range of 0.5-2.0 V, and it exhibits a discharge capacity of 113.3 mAh g-1 at high current density of 4 C-rate, indicative of excellent rate capability.

  9. The rate of sulfide oxidation by δMnO 2 in seawater

    NASA Astrophysics Data System (ADS)

    Yao, Wensheng; Millero, Frank J.

    1993-07-01

    The rate of oxidation of hydrogen sulfide by manganese dioxide in seawater was determined as a function of pH (2.0-9.0), temperature (5-45°C), and ionic strength (0-4 M). The overall rate constant, k, in seawater at pH = 8.17 was found to be first order with respect to both sulfide and manganese dioxide: - d[H 2S] T/dt = k[H 2S] τ[MnO 2] . The rate constant, k, for seawater (S = 35.8, pH = 8.17) at 25°C was found to be 436 M -1 min -1, or 0.0244 m -2 1 min -1 when [MnO 2] is expressed in surface area (m 2/L). The energies of activation were found to be 14 ± 1 KJ mol -1 and 10 ± 1 KJ mol -1, respectively, for pH = 8.2 and pH = 5.0 in seawater (S = 35). The rate increased from pH 2.0 to a maximum at a pH of about 5.0 and decreased at higher pH. This pH dependence was attributed to formation of a surface complex between >MnO - and H 2S. As the concentration of HS - increases above pH = 5 the rate of the reaction decreases. The rate of sulfide oxidation by MnO 2 is not strongly dependent on ionic strength. The rates in 0.57 M NaCl were found to be slightly higher than the rates in seawater. Measurements made in solutions of the major sea salts indicated that Ca 2+ and Mg 2+ caused the rates to decrease, apparently by absorbing on the surface of manganese dioxide. Measurements made in artificial seawater (Na +, Mg 2+, Ca 2+, Cl -, and SO 2-4) were found to be in good agreement with the measurements in actual seawater. Phosphate was found to inhibit the reaction significantly.

  10. Origin of steps in magnetization loops of martensitic Ni-Mn-Ga films on MgO(001)

    NASA Astrophysics Data System (ADS)

    Laptev, Aleksej; Lebecki, Kristof; Welker, Gesa; Luo, Yuansu; Samwer, Konrad; Fonin, Mikhail

    2016-09-01

    We study the temperature dependent magnetization properties of (010)-oriented Ni-Mn-Ga epitaxial films on MgO(001) substrates. In the martensitic phase, we observe pronounced abrupt slope changes in the magnetization loops for all studied samples. Our experimental findings are discussed in conjunction with the micromagnetic simulations, revealing that the characteristic magnetization behavior is governed solely by the magnetization switching within the specific martensitic variant pattern, and no reorientation of twin variants is involved in the process. Our study emphasizes the important role of the magnetostatic interactions in the magnetization behavior of magnetic shape memory alloy thin films.

  11. Synthesis and magnetic properties of single-crystalline Na2-xMn8O16 nanorods

    PubMed Central

    2011-01-01

    The synthesis of single-crystalline hollandite-type manganese oxides Na2-xMn8O16 nanorods by a simple molten salt method is reported for the first time. The nanorods were characterized by powder X-ray diffraction, scanning electron microscopy, transmission electron microscopy, and a superconducting quantum interference device magnetometer. The magnetic measurements indicated that the nanorods showed spin glass behavior and exchange bias effect at low temperatures. The low-temperature magnetic behaviors can be explained by the uncompensated spins on the surface of the nanorods. PMID:21711626

  12. Effect of the cation size on the framework structures of magnesium tungstate, A4Mg(WO4)3 (A = Na, K), R2Mg2(WO4)3 (R = Rb, Cs).

    PubMed

    Han, Shujuan; Wang, Ying; Jing, Qun; Wu, Hongping; Pan, Shilie; Yang, Zhihua

    2015-03-28

    A series of alkali metal magnesium tungstates, A4Mg(WO4)3 (A = Na, K), R2Mg2(WO4)3 (R = Rb, Cs), were synthesized from a high temperature solution, and their structures were determined by single-crystal X-ray diffraction. Interestingly, Na4Mg(WO4)3 crystallizes in the monoclinic space group C2/c, while K4Mg(WO4)3 having an identical stoichiometry with Na4Mg(WO4)3, exhibits a different framework structure belonging to triclinic symmetry with the space group P1[combining macron]. Isostructural Rb2Mg2(WO4)3 and Cs2Mg2(WO4)3 crystallize in the space group P213 of cubic symmetry and reveal a three dimensional framework composed of isolated WO4 tetrahedra, MgO6 octahedra and RO12 (R = Rb, Cs) polyhedra. The effect of the alkali metal cation size on the framework structures of magnesium tungstate has been discussed in detail. In addition, the infrared spectra, as well as the UV-Vis-NIR diffuse reflectance spectroscopy data, are reported. The first-principles theoretical studies are also carried out to aid the understanding of electronic structures and linear optical properties.

  13. Investigation on the Effect of Sub-Zero Treatment on Micro-Hardness and Microstructure of GTAW Welded Al-Si-Mg-Mn Alloy

    NASA Astrophysics Data System (ADS)

    Devanathan, R.; Yuvarajan, D.; Christopher Selvam, D.; Venkatamuni, T.

    2018-02-01

    In this work, the effect of sub-zero treatment on the mechanical properties of an Al-Si-Mg-Mn alloy welded by GTAW (gas tungsten arc welding) leads to significant softening in the welded region. The latter is due to melting and resolidification in the welded region, which have resulted in decomposition of the strengthening precipitates. The experiments were performed on GTAW welded plates of 6 mm thickness by varying the heat inputs, namely, of 370, 317.1, 277.5, 246.4, and 222 J/mm, and sub-zero treatment time periods. The Sub-Zero treatment was performed at-45°C using dry ice; hardness and microstructure investigations were performed in the welded region of the Al‒Si-Mg-Mn alloy that was studied in two different conditions, namely, as-welded and in that formed after post weld sub-zero treatment with artificial aging. It was found that the post weld Sub-Zero treatment followed by artificial aging had led to realization of significantly higher hardness values in the welded region due to the recurrence of the precipitation sequence.

  14. Tunnel-structured Na 0.66[Mn 0.66Ti 0.34]O 2-xF x(x <0.1) cathode for high performance sodium-ion batteries

    DOE PAGES

    Wang, Qin-Chao; Qiu, Qi-Qi; Xiao, Na; ...

    2018-03-13

    Sodium-ion batteries (SIBs) are attracting significant research attentions for large-scale energy storage applications. Cathode material is the vital part of SIBs to determine the capacity and cycle performance. Here, a series of F-doped Na 0.66[Mn 0.66Ti 0.34]O 2-xF x (x < 0.1) cathodes with tunnel structure are designed and synthesized aiming to enlarge the sodium diffusion paths. The lattice parameters of unit cell are tuned successfully by adjusting F doping amount. Na 0.66[Mn 0.66Ti 0.34]O 1.94F 0.06 with the optimized stoichiometry exhibits a reversible capacity of 97 mAh g -1 and promising cycle performance (85 mAh g -1 is maintainedmore » at 2C after 1000 cycles) with extremely low voltage polarization. More significantly, Na 0.66[Mn 0.66Ti 0.34]O 1.94F 0.06 exhibits superior low temperature performance, owing to the much enhanced thermodynamics and kinetics benefited from F doping. In conclusion, this strategy may open new opportunities to design advanced intercalation-type cathode materials for sodium ion batteries, especially for low-temperature applications.« less

  15. Tunnel-structured Na 0.66[Mn 0.66Ti 0.34]O 2-xF x(x <0.1) cathode for high performance sodium-ion batteries

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Wang, Qin-Chao; Qiu, Qi-Qi; Xiao, Na

    Sodium-ion batteries (SIBs) are attracting significant research attentions for large-scale energy storage applications. Cathode material is the vital part of SIBs to determine the capacity and cycle performance. Here, a series of F-doped Na 0.66[Mn 0.66Ti 0.34]O 2-xF x (x < 0.1) cathodes with tunnel structure are designed and synthesized aiming to enlarge the sodium diffusion paths. The lattice parameters of unit cell are tuned successfully by adjusting F doping amount. Na 0.66[Mn 0.66Ti 0.34]O 1.94F 0.06 with the optimized stoichiometry exhibits a reversible capacity of 97 mAh g -1 and promising cycle performance (85 mAh g -1 is maintainedmore » at 2C after 1000 cycles) with extremely low voltage polarization. More significantly, Na 0.66[Mn 0.66Ti 0.34]O 1.94F 0.06 exhibits superior low temperature performance, owing to the much enhanced thermodynamics and kinetics benefited from F doping. In conclusion, this strategy may open new opportunities to design advanced intercalation-type cathode materials for sodium ion batteries, especially for low-temperature applications.« less

  16. Sensitivity of the mayfly Adenophlebia auriculata (Ephemeroptera: Leptophlebiidae) to MgSO4 and Na2SO4

    NASA Astrophysics Data System (ADS)

    Vellemu, E. C.; Mensah, P. K.; Griffin, N. J.; Odume, O. N.

    2017-08-01

    Acid mine drainage (AMD) continues to deteriorate water quality in freshwater ecosystems. Sulphates, a major salt component in AMD, can exacerbate AMD effects in freshwater because salts are toxic to aquatic life in high concentrations. Sulphates are predominant in South African AMD impacted freshwater ecosystems. In this study, the sensitivity of nymphs of the mayfly Adenophlebia auriculata (Ephemeroptera: Leptophlebiidae) was investigated by exposing the organisms to magnesium sulphate (MgSO4) and sodium sulphate (Na2SO4) as models of mining salinisation in short-term (96 h) and long-term (240 h) in static system tests. Short-term and long-term lethal concentrations of each salt were estimated using regression analyses. The results indicated that A. auriculata was more sensitive to MgSO4 (LC50 = 3.81 g/L) than Na2SO4 (LC50 = 8.78 g/L) after short-term exposures. However, this species became sensitive to Na2SO4 (LC10 = 0.19 g/L) but tolerant to MgSO4 (LC10 = 0.35 g/L) after long-term exposures. These results suggest that the 0.25 g/L sulphate compliance limit for South Africa is inadequate to protect A. auriculata from Na2SO4 toxicity in the long-term, yet it overprotects this species from MgSO4 exposures in the short-term. The findings of this study are an important major step in understanding the ecological effects of AMD to aquatic life.

  17. Volatile elements in Allende inclusions. [Mn, Na and Cl relation to meteorite evolution

    NASA Technical Reports Server (NTRS)

    Grossman, L.; Ganapathy, R.

    1975-01-01

    New data are presented on the relatively volatile elements (Mn, Na, and Cl) in coarse- and fine-grained Ca/Al-rich inclusions of different textures and mineralogy in the Allende meteorite. It is shown that the coarse-grained inclusions condensed from the solar nebula at high temperature and contained vanishingly small quantities of volatile elements at that time. Later, volatiles were added to these during the metamorphism of the Allende parent body. The fine-grained inclusions were also affected by the addition of volatiles during this metamorphism but, unlike the coarse-grained ones, they incorporated large amounts of volatiles when they condensed from the solar nebula, accounting for their higher volatile element contents.

  18. [Characterization and optimization of the NaOH-EDTA extracts for solution 31P-NMR analysis of organic phosphorus in river sediments].

    PubMed

    Zhang, Wen-Qiang; Shan, Bao-Qing; Zhang, Hong; Tang, Wen-Zhong

    2014-01-01

    Optimization and mechanism of NaOH-EDTA extraction solutions were studied in phosphorus (P) pollution river sediments, which were Fe, Al-rich sediment, by solution 31P nuclear magnetic resonance spectroscopy (31P-NMR). Different proportions of NaOH and EDTA showed different extraction efficiency on total P (TP) and organic P (Po) in the sediment. The concentration of Po in NaOH + EDTA extract was higher than that in NaOH extract. The mechanism was that the TP and Po were released under the conditions of EDTA chelating with Fe and Al. The concentration of TP and Po were the highest in 1.00 mol x L(-1) NaOH +75 mmol x L(-1) EDTA extract and 0.25 mol x L(-1) NaOH + 50 mmol x L(-1) EDTA extract, which were 3.88 mg x g(-1) and 0.24 mg x g(-1), respectively. The extractions of Fe, Mn, Ca, Mg, Al were increasing as the EDTA increased under the same NaOH concentration. Extraction efficiency of Fe, Mn, Ca showed negative correlation with the pH of the extracting solution (P < 0.01). Exponential relationship was found between the extraction of Al and the pH of the extraction solution (P < 0.01) because of the AlO2- and EDTA-Al complex. The quality of spectra of NaOH-EDTA extract was better than that of NaOH extract. Six P species were detected in different extractions, including phosphonates, orthophosphate, pyrophosphate, orthophosphate monoesters, phospholipids and deoxyribonucleic acids. Therefore, 0. 25 mol x L(-1) NaOH + 50 mmol x L(-1) EDTA was the optimization extraction solution for Po analysis in Fe and Al-rich river sediment by 31P-NMR.

  19. The content of Ca, Cu, Fe, Mg and Mn and antioxidant activity of green coffee brews.

    PubMed

    Stelmach, Ewelina; Pohl, Pawel; Szymczycha-Madeja, Anna

    2015-09-01

    A simple and fast method of the analysis of green coffee infusions was developed to measure total concentrations of Ca, Cu, Fe, Mg and Mn by high resolution-continuum source flame atomic absorption spectrometry. The precision of the method was within 1-8%, while the accuracy was within -1% to 2%. The method was used to the analysis of infusions of twelve green coffees of different geographical origin. It was found that Ca and Mg were leached the easiest, i.e., on average 75% and 70%, respectively. As compared to the mug coffee preparation, the rate of the extraction of elements was increased when infusions were prepared using dripper or Turkish coffee preparation methods. Additionally, it was established that the antioxidant activity of green coffee infusions prepared using the mug coffee preparation was high, 75% on average, and positively correlated with the total content of phenolic compounds and the concentration of Ca in the brew. Copyright © 2015 Elsevier Ltd. All rights reserved.

  20. Formation of the Fe-Containing Intermetallic Compounds during Solidification of Al-5Mg-2Si-0.7Mn-1.1Fe Alloy

    NASA Astrophysics Data System (ADS)

    Que, Zhongping; Wang, Yun; Fan, Zhongyun

    2018-06-01

    Iron (Fe) is the most common and the most detrimental impurity element in Al alloys due to the formation of Fe-containing intermetallic compounds (IMCs), which are harmful to mechanical performance of the Al-alloy components. In this paper we investigate the formation of Fe-containing IMCs during solidification of an Al-5Mg-2Si-0.7Mn-1.1Fe alloy under varied solidification conditions. We found that the primary Fe-containing intermetallic compound (P-IMC) in the alloy is the BCC α-Al15(Fe,Mn)3Si2 phase and has a polyhedral morphology with {1 1 0} surface termination. The formation of the P-IMCs can be easily suppressed by increasing the melt superheat and/or cooling rate, suggesting that the nucleation of the α-Al15(Fe,Mn)3Si2 phase is difficult. In addition, we found that the IMCs with a Chinese script morphology is initiated on the {1 0 0} surfaces of the P-IMCs during the binary eutectic reaction with the α-Al phase. Both the binary and ternary eutectic IMCs are also identified as the BCC α-Al15(Fe,Mn)3Si2 phase. Furthermore, we found that the Fe content increases and the Mn content decreases in the Fe-containing intermetallic compounds with the decrease of the formation temperature, although the sum of the Fe and Mn contents in all of the IMCs is constant.

  1. Properties of complexes formed by Na(+), Mg(2+), and Fe(2+) binding with benzene molecules.

    PubMed

    Kolakkandy, Sujitha; Pratihar, Subha; Aquino, Adelia J A; Wang, Hai; Hase, William L

    2014-10-09

    A theoretical investigation was performed to study cation-π interactions in complexes of benzene (Bz) with cations, that is, M(z+)(Bz)n for M(z+) = Na(+), Mg(2+), Fe(2+) and n = 1-3, using MP2 theory with the 6-31+G* and 6-311++G** basis sets and the DFT/(B3LYP and B3LYP-D)/6-311++G** methods. Binding energies and structures of the complexes are reported. The splitting between the quintet and single states of the Fe(2+) complexes was found to depend on the number of benzene molecules in the complex and the complex's structure. All of the M(z+)(Bz) complexes prefer a half-sandwich geometry. A geometry with the cation sandwiched between the two benzene rings was found for the M(z+)(Bz)2 complexes, with the benzene rings either in an eclipsed or staggered conformation. An approximate cyclic structure, with the cation at its center, was found for three benzene molecules interacting with the cation. The cation-benzene binding energy is substantial and equal to 22, 108, and 151 kcal/mol for the Na(+)(Bz), Mg(2+)(Bz), and Fe(2+)(Bz) complexes, respectively. The strength of the interaction of the cation with an individual benzene molecule decreases as the number of benzene molecules bound to the cation increases; for example, it is 108 kcal/mol for Mg(2+)(Bz), but only 71 kcal/mol for Mg(2+)(Bz)3. There is a range of values for the M(z+)(Bz)n intermolecular vibrational frequencies; for example, they are ∼230-360 and ∼10-330 cm(-1) for the Mg(2+)(Bz) and Mg(2+)(Bz)3 complexes, respectively. Binding of the cation to benzene both red and blue shifts the benzene vibrational frequencies. This shifting is larger for the Mg(2+) and Fe(2+) complexes, as compared to those for Na(+), as a result of the former's stronger cation-benzene binding. The present study is an initial step to understand the possible importance of cation-π interactions for polycyclic aromatic hydrocarbon aggregation processes during soot formation.

  2. Formation of the structure and properties of an Mg-Al-Zn-Mn alloy during plastic deformation by rolling

    NASA Astrophysics Data System (ADS)

    Bozhko, S. A.; Betsofen, S. Ya.; Kolobov, Yu. R.; Vershinina, T. N.

    2015-03-01

    The laws of formation of an ultrafine structure in an Mg-Al-Zn-Mn alloy (MA5 alloy) under severe plastic deformation have been studied during lengthwise section rolling at a strain e = 1.59. The deformation behavior and the physical factors of anisotropy of yield strength during compression tests in various directions with respect to axis of rolling are analyzed. The role of crystallographic texture and twinning processes in the generation of strength processes and the development of plastic deformation of the alloy is analyzed.

  3. Abundances of O, Mg, S, Cr, Mn, Ti, NI and Zn from absorption lines of neutral gas in the Large Magellanic Cloud in front of R136

    NASA Astrophysics Data System (ADS)

    de Boer, K. S.; Fitzpatrick, E. L.; Savage, B. D.

    1985-11-01

    The authors have searched six high-dispersion IUE spectra of R136 for weak absorption lines of C I, O I, Mg I, Mg II, Si I, Si II, P I, Cl I, Cr II, Mn II, Fe I, Ni II, Zn II, CO and C2. The absorption detected is from neutral gas in front of the 30 Doradus H II region. For the first time abundances of Mg, Cr, Mn, Ti, Ni, and Zn are determined for an extragalactic system. The LMC abundances from the absorption lines are a factor of 2 to 3 below those of the Milky Way, in agreement with general results from emission line studies. The density and temperature of the neutral gas are estimates from the observed excitation and ionization at approximately n(H) = 300 cm-3 and T = 100K, implying a gas pressure of about 3×104cm-3K.

  4. Alkali-deficient tourmaline from the Sullivan Pb-Zn-Ag deposit, British Columbia

    USGS Publications Warehouse

    Jiang, S.-Y.; Palmer, M.R.; Slack, J.F.

    1997-01-01

    Alkali-deficient tourmalines are found in albitized rocks from the hanging-wall of the Sullivan Pb-Zn-Ag deposit (British Columbia, Canada). They approximate the Mg-equivalent of foitite with an idealized formula D???(Mg2Al)Al6Si6O18(BO 3)3(OH)4. Major chemical substitutions in the tourmalines are the alkali-defect type [Na*(x) + Mg*(Y) = ???(X) + Al(Y)] and the uvite type [Na*(X) + Al(Y) = Ca(X) + Mg*(Y)], where Na* = Na + K, Mg* = Mg + Fe + Mn. The occurrence of these alkali-deficient tourmalines reflects a unique geochemical environment that is either alkali-depleted overall or one in which the alkalis preferentially partitioned into coexisting minerals (e.g. albite). Some of the alkali-deficient tourmalines have unusually high Mn contents (up to 1.5 wt.% MnO) compared to other Sullivan tourmalines. Manganese has a strong preference for incorporation into coexisting garnet and carbonate at Sullivan, thus many tourmalines in Mn-rich rocks are poor in Mn (<0.2 wt.% MnO). It appears that the dominant controls over the occurrence of Mn-rich tourmalines at Sullivan are the local availability of Mn and the lack of other coexisting minerals that may preferentially incorporate Mn into their structures.

  5. Impact of environmental chemistry on mycogenic Mn oxide minerals

    NASA Astrophysics Data System (ADS)

    Santelli, C. M.; Farfan, G. A.; Post, A.; Post, J. E.

    2012-12-01

    Manganese (Mn) oxide minerals are ubiquitous in aquatic and terrestrial environments and their presence can have broad environmental consequences. In particular, Mn oxides scavenge nutrients and metals, degrade complex organics, and oxidize a variety of inorganic contaminants. The "reactivity" of Mn oxides, however, is highly dependent upon crystallite size, composition, and structure, which are largely determined by environmental factors such as solution chemistry. It is has been suggested that most Mn oxides in terrestrial and aquatic environments are formed by microbial activity; indeed, a diversity of Mn(II)-oxidizing bacteria and fungi have been isolated and their mineral byproducts are consistent with those observed in natural systems. Previous studies showed that Mn(II)-oxidizing Ascomycete fungi produce highly-disordered, nanocrystalline Mn oxides that are structurally similar to synthetic δ-MnO2 or natural vernadite. Unlike related studies with Mn-oxidizing bacteria, Mn oxides produced by these fungi did not "age" or transform to more crystalline mineral phases with time. We hypothesize that fungal growth conditions, in particular the low concentration of cations, are inhibiting secondary mineral formation. The overall goal of this research is to examine the structure and speciation of fungally-precipitated Mn oxides with respect to fungal species, time, and concentration of soluble Mn(II), Na, and Ca - three environmentally relevant cations that promote the transformation of δ-MnO2 to more crystalline mineral phases such as feitknechtite, birnessite, or ranciéite. For this study, we examined the Mn oxides formed by different species of Mn(II)-oxidizing fungi (Pyrenochaeta sp., Stagonospora sp., Plectosphaerella cucumerina., and Acremonium strictum). Isolates were grown for 8 or 16 days in a nutrient lean media consisting of yeast extract, trace elements and 0.2 mM MnCl2 supplemented with varying concentrations of Na, Ca, or Mn(II) compounds. The

  6. Improving the electrochemical performances of Li-rich Li1.20Ni0.13Co0.13Mn0.54O2 through a cooperative doping of Na+ and PO43- with Na3PO4

    NASA Astrophysics Data System (ADS)

    Liu, Yi; Ning, De; Zheng, Lirong; Zhang, Qinghua; Gu, Lin; Gao, Rui; Zhang, Jicheng; Franz, Alexandra; Schumacher, Gerhard; Liu, Xiangfeng

    2018-01-01

    Li-rich layered oxide cathodes suffer from poor rate capability, voltage decay and inferior cycling stability. Herein, we propose a novel synergistic strategy to improve the electrochemical performances of Li-rich Li1.20Ni0.13Co0.13Mn0.54O2 by the co-doping of Na+ and PO43-. The co-doping of Na+ for Li and PO43- for Mn is simultaneously achieved using Na3PO4 as a dopant. The co-doping of Na+ and PO43- not only enhances the high-rate performance (106.4 mAhg-1@10C) and capacity retention (93.8%@1C@100 cycles) but also mitigates the voltage decay owing to the synergistic effect of Na+ and PO43- co-doping. The synergistic mechanism is unraveled based on neutron diffraction, aberration-corrected scanning transmission electron microscope, X-ray photoelectron spectroscopy, ex-situ X-ray absorption spectra, ex-situ X-ray diffraction, electrochemical impedance spectroscopy and electrochemical measurements. The co-doping of Na+ and PO43- enlarges the interlayer spacing and suppresses Li/Ni mixing which increases Li+ diffusivity and enhances the rate capability. Meanwhile, the co-doping of Na+ and PO43- shrinks the thickness of the slabs, weakens the TM-O covalency and alleviates the volume change in the charge/discharge process which improves the layered structure stability and the cycling performances. This study presents some new insights into designing high performance cathode materials through a cooperative modulation of different crystal sites doping.

  7. Magnetic field induced mixing of light hole excitonic states in (Cd, Mn)Te/(Cd, Mg)Te core/shell nanowires

    NASA Astrophysics Data System (ADS)

    Płachta, Jakub; Grodzicka, Emma; Kaleta, Anna; Kret, Sławomir; Baczewski, Lech T.; Pietruczik, Aleksiej; Wiater, Maciej; Goryca, Mateusz; Kazimierczuk, Tomasz; Kossacki, Piotr; Karczewski, Grzegorz; Wojtowicz, Tomasz; Wojnar, Piotr

    2018-05-01

    A detailed magneto-photoluminescence study of individual (Cd, Mn)Te/(Cd, Mg)Te core/shell nanowires grown by molecular beam epitaxy is performed. First of all, an enhancement of the Zeeman splitting due to sp-d exchange interaction between band carriers and Mn-spins is evidenced in these nanostructures. Then, it is found that the value of this splitting depends strongly on the magnetic field direction with respect to the nanowire axis. The largest splitting is observed when the magnetic field is applied perpendicular and the smallest when it is applied parallel to the nanowire axis. This effect is explained in terms of magnetic field induced valence band mixing and evidences the light hole character of the excitonic emission. The values of the light and heavy hole splitting are determined for several individual nanowires based on the comparison of experimental results to theoretical calculations.

  8. Magnetic field induced mixing of light hole excitonic states in (Cd, Mn)Te/(Cd, Mg)Te core/shell nanowires.

    PubMed

    Płachta, Jakub; Grodzicka, Emma; Kaleta, Anna; Kret, Sławomir; Baczewski, Lech T; Pietruczik, Aleksiej; Wiater, Maciej; Goryca, Mateusz; Kazimierczuk, Tomasz; Kossacki, Piotr; Karczewski, Grzegorz; Wojtowicz, Tomasz; Wojnar, Piotr

    2018-05-18

    A detailed magneto-photoluminescence study of individual (Cd, Mn)Te/(Cd, Mg)Te core/shell nanowires grown by molecular beam epitaxy is performed. First of all, an enhancement of the Zeeman splitting due to sp-d exchange interaction between band carriers and Mn-spins is evidenced in these nanostructures. Then, it is found that the value of this splitting depends strongly on the magnetic field direction with respect to the nanowire axis. The largest splitting is observed when the magnetic field is applied perpendicular and the smallest when it is applied parallel to the nanowire axis. This effect is explained in terms of magnetic field induced valence band mixing and evidences the light hole character of the excitonic emission. The values of the light and heavy hole splitting are determined for several individual nanowires based on the comparison of experimental results to theoretical calculations.

  9. Fast Optimization of LiMgMnOx/La2O3 Catalysts for the Oxidative Coupling of Methane.

    PubMed

    Li, Zhinian; He, Lei; Wang, Shenliang; Yi, Wuzhong; Zou, Shihui; Xiao, Liping; Fan, Jie

    2017-01-09

    The development of efficient catalyst for oxidative coupling of methane (OCM) reaction represents a grand challenge in direct conversion of methane into other useful products. Here, we reported that a newly developed combinatorial approach can be used for ultrafast optimization of La 2 O 3 -based multicomponent metal oxide catalysts in OCM reaction. This new approach integrated inkjet printing assisted synthesis (IJP-A) with multidimensional group testing strategy (m-GT) tactfully takes the place of conventionally high-throughput synthesis-and-screen experiment. Just within a week, 2048 formulated LiMgMnO x -La 2 O 3 catalysts in a 64·8·8·8·8 = 262 144 compositional space were fabricated by IJP-A in a four-round synthesis-and-screen process, and an optimized formulation has been successfully identified through only 4·8 = 32 times of tests via m-GT screening strategy. The screening process identifies the most promising ternary composition region is Li 0-0.48 Mg 0-6.54 Mn 0-0.62 -La 100 O x with an external C 2 yield of 10.87% at 700 °C. The yield of C 2 is two times as high as the pure nano-La 2 O 3 . The good performance of the optimized catalyst formulation has been validated by the manual preparation, which further prove the effectiveness of the new combinatorial methodology in fast discovery of heterogeneous catalyst.

  10. Study of Np(V) Sorption by Ionic Exchange on Na, K, Ca and Mg-Montmorillonite

    NASA Astrophysics Data System (ADS)

    Benedicto, A.; Begg, J.; Zhao, P.; Kersting, A. B.; Zavarin, M.

    2012-12-01

    The transport behavior of actinides in soil and ground water are highly influenced by clay minerals due to their ubiquity in the environment, reactivity and colloidal properties. Neptunium(V) has been introduced in the environment as a result of nuclear weapons testing [e.g. 1, 2] and is a radionuclide of potential interest for safety assessment of high level radioactive waste disposal because its long half-life and high toxicity [3]. Surface complexation and ionic exchange have been identified as Np(V) sorption mechanisms onto montmorillonite. At pH below 5, Np(V) sorption is mainly attributed to ionic exchange. This study examines Np(V) ion exchange on Na, K, Ca and Mg forms of montmorillonite. Experiments were carried out using 237Np concentrations between 2 x 10-8 M and 5 x 10-6 M at three different ionic strengths 0.1, 0.01 and 0.001M. The pH was maintained at 4.5. Np(V) sorption to montmorillonite homoionized with monovalent cations (Na and K) demonstrated a markedly different behavior to that observed for montmorillonite homoionized with divalent cations (Ca and Mg). Np sorption to Na and K-montmorillonite was greater than Np sorption to Ca and Mg-montmorillonite. Isotherms with Na and K-montmorillonite showed a strong dependence on ionic strength: the percentage of Np adsorbed was near zero at 0.1M ionic strength, but increased to 30% at 0.001 M ionic strength. This suggests ionic exchange is the main Np adsorption mechanism under the experimental conditions investigated. Dependence on ionic strength was not observed in the Np sorption isotherms for Ca and Mg-montmorillonite indicating a low exchange capacity between Np and divalent cations. Modeling of the sorption experimental data will allow determination of the Na+↔NpO2+ and K+↔NpO2+ ionic exchange constants on montmorillonite. References: [1] A. R. Felmy; K. J. Cantrell; S. D. Conradson, Phys. Chem. Earth 2010, 35, 292-297 [2] D. K. Smith; D. L. Finnegan; S. M. Bowen, J. Environ. Radioact. 2003, 67

  11. The phase diagrams of KCaF3 and NaMgF3 by ab initio simulations

    NASA Astrophysics Data System (ADS)

    Jakymiw, Clément; Vočadlo, Lidunka; Dobson, David P.; Bailey, Edward; Thomson, Andrew R.; Brodholt, John P.; Wood, Ian G.; Lindsay-Scott, Alex

    2018-04-01

    ABF3 compounds have been found to make valuable low-pressure analogues for high-pressure silicate phases that are present in the Earth's deep interior and that may also occur in the interiors of exoplanets. The phase diagrams of two of these materials, KCaF3 and NaMgF3, have been investigated in detail by static ab initio computer simulations based on density functional theory. Six ABF3 polymorphs were considered, as follows: the orthorhombic perovskite structure (GdFeO3-type; space group Pbnm); the orthorhombic CaIrO3 structure ( Cmcm; commonly referred to as the "post-perovskite" structure); the orthorhombic Sb2S3 and La2S3 structures (both Pmcn); the hexagonal structure previously suggested in computer simulations of NaMgF3 ( P63/ mmc); the monoclinic structure found to be intermediate between the perovskite and CaIrO3 structures in CaRhO3 ( P21/ m). Volumetric and axial equations of state of all phases considered are presented. For KCaF3, as expected, the perovskite phase is shown to be the most thermodynamically stable at atmospheric pressure. With increasing pressure, the relative stability of the KCaF3 phases then follows the sequence: perovskite → La2S3 structure → Sb2S3 structure → P63/ mmc structure; the CaIrO3 structure is never the most stable form. Above about 2.6 GPa, however, none of the KCaF3 polymorphs are stable with respect to dissociation into KF and CaF2. The possibility that high-pressure KCaF3 polymorphs might exist metastably at 300 K, or might be stabilised by chemical substitution so as to occur within the standard operating range of a multi-anvil press, is briefly discussed. For NaMgF3, the transitions to the high-pressure phases occur at pressures outside the normal range of a multi-anvil press. Two different sequences of transitions had previously been suggested from computer simulations. With increasing pressure, we find that the relative stability of the NaMgF3 phases follows the sequence: perovskite → CaIrO3 structure → Sb2

  12. EPR investigation of local structure for [Mn(H 2O) 6] 2+ cluster in [M(H 2O) 6]XCl 6:Mn 2+ (M = Zn, Mg, Cd, Ca; X = Pt, Sn) systems at different temperatures

    NASA Astrophysics Data System (ADS)

    Tian, Wen-Yan; Kuang, Xiao-Yu; Li, Hui-Fang; Li, Yan-Fang; Ying-Li

    2009-01-01

    A theoretical method for studying the inter-relation between the local structure and EPR spectra is established by diagonalizing the complete energy matrices. For [M(H 2O) 6]XCl 6:Mn 2+ (M = Zn, Mg, Cd, Ca; X = Pt, Sn) systems, the calculated results demonstrate that the local structures around the octahedral Mn 2+ centers in the doped systems are very similar despite of the host crystals being different. Furthermore, it is shown that the EPR zero-field parameter D depends simultaneously on the local structure parameters R and θ while ( a - F) depends mainly on R, whether the doped systems are at liquid-nitrogen temperature or room temperature.

  13. Measurement of the 21Na(p,{gamma})22Mg Reaction with the Dragon Facility at TRIUMF-ISAC

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Chen, A.A.; Bishop, S.; D'Auria, J.M.

    2003-08-26

    The DRAGON recoil separator facility, designed to measure the rates of radiative proton and alpha capture reactions important for nuclear astrophysics, is now operational at the TRIUMF-ISAC radioactive beam facility in Vancouver, Canada. We report on first measurements of the 21Na(p,{gamma})22Mg reaction rate with radioactive beams of 21Na.

  14. Phase control of Mn-based spinel films via pulsed laser deposition

    DOE PAGES

    Feng, Zhenxing; Chen, Xiao; Fister, Timothy T.; ...

    2016-07-06

    Phase transformations in battery cathode materials during electrochemical-insertion reactions lead to capacity fading and low cycle life. One solution is to keep the same phase of cathode materials during cation insertion-extraction processes. Here, we demonstrate a novel strategy to control the phase and composition of Mn-based spinel oxides for magnesium-ion battery applications through the growth of thin films on lattice-matched substrates using pulsed laser deposition. Materials at two extreme conditions are considered: fully discharged cathode MgMn 2O 4 and fully charged cathode Mn 2O 4. The tetragonal MgMn 2O 4 (MMO) phase is obtained on MgAl 2O 4 substrates, whilemore » the cubic MMO phase is obtained on MgO substrates. Similarly, growth of the empty Mn 2O 4 spinel in the cubic phase is obtained on an MgO substrate. These results demonstrate the ability to control separately the phase of spinel thin films (e.g., tetragonal vs. cubic MMO) at nominally fixed composition, and to maintain a fixed (cubic) phase while varying its composition (MgxMn 2O 4, for x = 0, 1). As a result, this capability provides a novel route to gain insights into the operation of battery electrodes for energy storage applications.« less

  15. Phase control of Mn-based spinel films via pulsed laser deposition

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Feng, Zhenxing; Chen, Xiao; Fister, Timothy T.

    Phase transformations in battery cathode materials during electrochemical-insertion reactions lead to capacity fading and low cycle life. One solution is to keep the same phase of cathode materials during cation insertion-extraction processes. Here, we demonstrate a novel strategy to control the phase and composition of Mn-based spinel oxides for magnesium-ion battery applications through the growth of thin films on lattice-matched substrates using pulsed laser deposition. Materials at two extreme conditions are considered: fully discharged cathode MgMn 2O 4 and fully charged cathode Mn 2O 4. The tetragonal MgMn 2O 4 (MMO) phase is obtained on MgAl 2O 4 substrates, whilemore » the cubic MMO phase is obtained on MgO substrates. Similarly, growth of the empty Mn 2O 4 spinel in the cubic phase is obtained on an MgO substrate. These results demonstrate the ability to control separately the phase of spinel thin films (e.g., tetragonal vs. cubic MMO) at nominally fixed composition, and to maintain a fixed (cubic) phase while varying its composition (MgxMn 2O 4, for x = 0, 1). As a result, this capability provides a novel route to gain insights into the operation of battery electrodes for energy storage applications.« less

  16. Mg2+ ions: do they bind to nucleobase nitrogens?

    PubMed Central

    Leonarski, Filip; D'Ascenzo, Luigi; Auffinger, Pascal

    2017-01-01

    Given the many roles proposed for Mg2+ in nucleic acids, it is essential to accurately determine their binding modes. Here, we surveyed the PDB to classify Mg2+ inner-sphere binding patterns to nucleobase imine N1/N3/N7 atoms. Among those, purine N7 atoms are considered to be the best nucleobase binding sites for divalent metals. Further, Mg2+ coordination to N7 has been implied in several ribozyme catalytic mechanisms. We report that Mg2+ assigned near imine nitrogens derive mostly from poor interpretations of electron density patterns and are most often misidentified Na+, K+, NH4+ ions, water molecules or spurious density peaks. Consequently, apart from few documented exceptions, Mg2+ ions do not bind to N7 atoms. Without much of a surprise, Mn2+, Zn2+ and Cd2+, which have a higher affinity for nitrogens, may contact N7 atoms when present in crystallization buffers. In this respect, we describe for the first time a potential Zn2+ ribosomal binding site involving two purine N7 atoms. Further, we provide a set of guidelines to help in the assignment of Mg2+ in crystallographic, cryo-EM, NMR and model building practices and discuss implications of our findings related to ion substitution experiments. PMID:27923930

  17. Proton threshold states in the {sup 22}Na(p,{gamma}){sup 23}Mg reaction and astrophysical implications

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Comisel, H.; Hategan, C.; Graw, G.

    Proton threshold states in {sup 23}Mg are important for the astrophysically relevant proton capture reaction {sup 22}Na(p,{gamma}){sup 23}Mg. In the indirect determination of the resonance strength of the lowest states, which were not accessible by direct methods, some of the spin-parity-assignments remained experimentally uncertain. We have investigated these states with shell model, Coulomb displacement, and Thomas-Ehrman shift calculations. From the comparison of calculated and observed properties, we relate the lowest relevant resonance state at E{sub x}=7643 keV to an excited 3/2{sup +} state in accordance with a recent experimental determination by Jenkins et al. From this we deduce significantly improvedmore » values for the {sup 22}Na(p,{gamma}){sup 23}Mg reaction rate at stellar temperatures below T{sub 9}=0.1 K.« less

  18. Luminescence characteristics of Dy3+ activated Na 2Sr 2Mg (BO 3)2F 2: Dy 3+ phosphor

    NASA Astrophysics Data System (ADS)

    Wani, Javaid A.; Dhoble, N. S.; Dhoble, S. J.

    2012-11-01

    In this paper, we have reported a new Na 2Sr 2Mg (BO 3)2F 2:Dy 3+ thermoluminescence (TL) phosphor prepared via the wet chemical method. Prepared phosphor was characterized by X-ray powder diffraction, photoluminescence (PL), TL and scanning electronmicroscopy techniques. The scanning electronmicroscopic image of Na 2Sr 2Mg (BO 3)2F 2:Dy 3+ phosphor confirms the micron size of particles. Under the PL study, the characteristic emission spectrum of Dy 3+ corresponding to 4F 9/2→6H 15/2 (481 nm) and 4F 9/2→6H 13/2 (576 nm) transitions was observed. The TL property of the as prepared phosphor was also found to be good. TL intensity of Na 2Sr2Mg(BO 3)F 2:Dy 3+ phosphors at 0.99 kGy exposure of γ-irradiations was compared with standard CaSO 4:Dy phosphor. It was seen that TL intensity of Na 2Sr 2Mg (BO 3)2F 2: Dy 3+ phosphors is 1.1 times less compared with the standard CaSO 4:Dy TL dosimeter phosphor. The kinetic parameters are also discussed in detail. The values of activation energy E (eV) and frequency factor S (s -1) were found to be 0.57 eV and 1.25×106 s-1, respectively.

  19. Luminescence properties and energy transfer of site-sensitive Ca(6-x-y)Mg(x-z)(PO(4))(4):Eu(y)(2+),Mn(z)(2+) phosphors and their application to near-UV LED-based white LEDs.

    PubMed

    Kwon, Ki Hyuk; Im, Won Bin; Jang, Ho Seong; Yoo, Hyoung Sun; Jeon, Duk Young

    2009-12-21

    On the basis of the structural information that the host material has excellent charge stabilization, blue-emitting Ca(6-x-y)Mg(x)(PO(4))(4):Eu(y)(2+) (CMP:Eu(2+)) phosphors were synthesized and systematically optimized, and their photoluminescence (PL) properties were evaluated. Depending upon the amount of Mg added, the emission efficiency of the phosphors could be enhanced. The substitution of Eu(2+) affected their maximum wavelength (lambda(max)) and thermal stability because the substitution site of Eu(2+) could be varied. To obtain single-phase two-color-emitting phosphors, we incorporated Mn(2+) into CMP:Eu(2+) phosphors. Weak red emission resulting from the forbidden transition of Mn(2+) could be enhanced by the energy transfer from Eu(2+) to Mn(2+) that occurs because of the spectral overlap between the photoluminescence excitation (PLE) spectrum of Mn(2+) and the PL spectrum of Eu(2+). The energy transfer process was confirmed by the luminescence spectra, energy transfer efficiency, and decay curve of the phosphors. Finally, the optimized Ca(6-x-y)Mg(x-z)(PO(4))(4):Eu(y)(2+),Mn(z)(2+) (CMP:Eu(2+),Mn(2+)) phosphors were applied with green emitting Ca(2)MgSi(2)O(7):Eu(2+) (CMS:Eu(2+)) phosphors to ultraviolet (UV) light emitting diode (LED)-pumped white LEDs. The CMS:Eu(2+)-mixed CMP:Eu(2+), Mn(2+)-based white LEDs showed an excellent color rendering index (CRI) of 98 because of the broader emission band and more stable color coordinates than those of commercial Y(3)Al(5)O(12):Ce(3+) (YAG:Ce(3+))-based white LEDs under a forward bias current of 20 mA. The fabricated white LEDs showed very bright natural white light that had the color coordinate of (0.3288, 0.3401), and thus CMP:Eu(2+),Mn(2+) could be regarded as a good candidate for UV LED-based white LEDs.

  20. Tunnel magnetoresistance in ultrathin L10 MnGa/MgO perpendicular magnetic tunnel junctions

    NASA Astrophysics Data System (ADS)

    Suzuki, K. Z.; Miura, Y.; Ranjbar, R.; Sugihara, A.; Mizukami, S.

    2018-06-01

    L10 MnGa is one of the interesting magnetic alloys for spin-transfer-torque based applications because such alloys have high perpendicular magnetic anisotropy, small magnetization, and low Gilbert damping. Magnetic tunnel junctions (MTJs) with ultrathin MnGa electrodes have recently been demonstrated using the room temperature growth technique of MnGa on paramagnetic B2-ordered CoGa templates, which exhibited a small TMR ratio of  ∼3%. To obtain a higher TMR ratio, we systematically investigated the annealing dependence of the TMR ratio with MTJs with 1–5 nm thick MnGa electrodes in this study. The TMR ratios were 2%–3% without annealing, which were the same as those reported previously, and the TMR ratios reached their maximum values of 6%–8% at an annealing temperature of approximately 250 °C for the MTJs with 2–5 nm MnGa electrodes. The TMR ratio increased to approximately 25% at 10 K for those MTJs. These TMR ratios were slightly higher than those reported in MTJs with 30 nm-thick MnGa electrodes. The annealing temperature at which TMR showed the maximum value tended to decrease with decreasing MnGa thickness, and this low annealing endurance may be attributed to the atomic mixing between MnGa and barrier/buffer layers. The TMR ratio was discussed in terms of both coherent tunneling based on first principles calculations with different element terminations at the interface and incoherent tunneling.

  1. Synthesis, crystal structure and spectroscopy properties of Na 3AZr(PO 4) 3 ( A=Mg, Ni) and Li 2.6Na 0.4NiZr(PO 4) 3 phosphates

    NASA Astrophysics Data System (ADS)

    Chakir, M.; El Jazouli, A.; de Waal, D.

    2006-06-01

    Na 3AZr(PO 4) 3 ( A=Mg, Ni) phosphates were prepared at 750 °C by coprecipitation route. Their crystal structures have been refined at room temperature from X-ray powder diffraction data using Rietveld method. Li 2.6Na 0.4NiZr(PO 4) 3 was synthesized through ion exchange from the sodium analog. These materials belong to the Nasicon-type structure. Raman spectra of Na 3AZr(PO 4) 3 ( A=Mg, Ni) phosphates present broad peaks in favor of the statistical distribution in the sites around PO 4 tetrahedra. Diffuse reflectance spectra indicate the presence of octahedrally coordinated Ni 2+ ions.

  2. Crystal structure of the mineral (Na,Ca,K)2(Ca,Na)4(Mg,Fe)5(Mg,Fe,Ti)5[Si12Al4O44](F,O)4: a triclinic representative of the amphibole family

    NASA Astrophysics Data System (ADS)

    Rastsvetaeva, R. K.; Aksenov, S. M.

    2012-05-01

    A mineral belonging to the amphibole family found at the Rothenberg paleovolcano (Eifel, Germany) was studied by single-crystal X-ray diffraction. The triclinic pseudomonoclinic unit-cell parameters are a = 5.3113(1) Å, b = 18.0457(3) Å; c = 9.8684(2) Å, α = 90.016(2)°, β = 105.543(4)°, γ = 89.985(2)°. The structure was solved by direct methods in sp. gr. P1 and refined to the R factor of 2.7% based on 6432 reflections with | F| > 3σ( F) taking into account twinning. The mineral with the idealized formula (Na,Ca,K)2(Ca,Na)4(Mg,Fe)5(Mg,Fe,Ti)5[Si12Al4O44](F,O)4 has some symmetry and structural features that distinguish it from other minerals of this family.

  3. Middendorfite, K3Na2Mn5Si12(O,OH)36 · 2H2O, a new mineral species from the Khibiny pluton, Kola Peninsula

    NASA Astrophysics Data System (ADS)

    Pekov, I. V.; Chukanov, N. V.; Dubinchuk, V. T.; Zadov, A. E.

    2007-12-01

    Middendorfite, a new mineral species, has been found in a hydrothermal assemblage in Hilairite hyperperalkaline pegmatite at the Kirovsky Mine, Mount Kukisvumchorr apatite deposit, Khibiny alkaline pluton, Kola Peninsula, Russia. Microcline, sodalite, cancrisilite, aegirine, calcite, natrolite, fluorite, narsarsukite, labuntsovite-Mn, mangan-neptunite, and donnayite are associated minerals. Middendorfite occurs as rhombshaped lamellar and tabular crystals up to 0.1 × 0.2 × 0.4 mm in size, which are combined in worm-and fanlike segregations up to 1 mm in size. The color is dark to bright orange, with a yellowish streak and vitreous luster. The mineral is transparent. The cleavage (001) is perfect, micalike; the fracture is scaly; flakes are flexible but not elastic. The Mohs hardness is 3 to 3.5. Density is 2.60 g/cm3 (meas.) and 2.65 g/cm3 (calc.). Middendorfite is biaxial (-), α = 1.534, β = 1.562, and γ = 1.563; 2 V (meas.) = 10°. The mineral is pleochroic strongly from yellowish to colorless on X through brown on Y and to deep brown on Z. Optical orientation: X = c. The chemical composition (electron microprobe, H2O determined with Penfield method) is as follows (wt %): 4.55 Na2O, 10.16 K2O, 0.11 CaO, 0.18 MgO, 24.88 MnO, 0.68 FeO, 0.15 ZnO, 0.20 Al2O3, 50.87 SiO2, 0.17 TiO2, 0.23 F, 7.73 H2O; -O=F2-0.10, total is 99.81. The empirical formula calculated on the basis of (Si,Al)12(O,OH,F)36 is K3.04(Na2.07Ca0.03)Σ2.10(Mn4.95Fe0.13Mg0.06Ti0.03Zn0.03)Σ5.20(Si11.94Al0.06)Σ12O27.57(OH)8.26F0.17 · 1.92H2O. The simplified formula is K3Na2Mn5Si12(O,OH)36 · 2H2O. Middenforite is monoclinic, space group: P21/ m or P21. The unit cell dimensions are a = 12.55, b = 5.721, c = 26.86 Å; β = 114.04°, V = 1761 Å3, Z = 2. The strongest lines in the X-ray powder pattern [ d, Å, ( I)( hkl)] are: 12.28(100)(002), 4.31(81)(11overline 4 ), 3.555(62)(301, 212), 3.063(52)(008, 31overline 6 ), 2.840(90)(312, 021, 30overline 9 ), 2.634(88)(21overline 9 , 1.0.overline 1 0

  4. Magnesium-ion battery-relevant electrochemistry of MgMn 2O 4: crystallite size effects and the notable role of electrolyte water content

    DOE PAGES

    Yin, Jiefu; Brady, Alexander B.; Takeuchi, Esther S.; ...

    2017-03-06

    MgMn 2O 4 nanoparticles with crystallite sizes of 11 (MMO-1) and 31 nm (MMO-2) were synthesized and their magnesium-ion battery-relevant electrochemistry was investigated. Here, MMO-1 delivered an initial capacity of 220 mA h g –1 (678 mW h g –1). Electrolyte water content had a profound effect on cycle retention.

  5. Revival of ferromagnetic behavior in charge-ordered Pr0.75Na0.25MnO3 manganite by ruthenium doping at Mn site and its MR effect

    NASA Astrophysics Data System (ADS)

    Elyana, E.; Mohamed, Z.; Kamil, S. A.; Supardan, S. N.; Chen, S. K.; Yahya, A. K.

    2018-02-01

    Ru doping in charge-ordered Pr0.75Na0.25Mn1-xRuxO3 (x = 0-0.1) manganites was studied to investigate its effect on structure, electrical transport, magnetic properties, and magnetotransport properties. DC electrical resistivity (ρ), magnetic susceptibility, and χ' measurements showed that sample x = 0 exhibits insulating behavior within the entire temperature range and antiferromagnetic (AFM) behavior below the charge-ordering (CO) transition temperature TCO of 221 K. Ru4+ substitution (x>0.01) suppressed the CO state, which resulted in the revival of paramagnetic to ferromagnetic (FM) transition at the Curie temperature Tc, increasing from 120 K (x = 0.01) to 193 K (x = 0.1). Deviation from the Curie-Weiss law above Tc in the 1/χ' versus T plot for x = 0.01 doped samples indicated the existence of Griffiths phase with Griffith temperature at 169 K. Electrical resistivity measurements showed that Ru4+ substitution increased the metallic-to-insulating transition temperature TMI from 144 K (x = 0.01) to 192 K (x = 0.05) due to enhanced double-exchange mechanism, but TMI decreased to 176 K (x = 0.1) probably due to the existence of AFM clusters within the FM domain. The present work also discussed the possible theoretical models at the resistivity curve of Pr0.75Na0.25Mn1-xRuxO3 (x = 0-0.1) for the entire temperature range.

  6. Divalent metal ions modulated strong frustrated M(II)-Fe(III)3O (M = Fe, Mn, Mg) chains with metamagnetism only in a mixed valence iron complex.

    PubMed

    Wu, Qi-Long; Han, Song-De; Wang, Qing-Lun; Zhao, Jiong-Peng; Ma, Feng; Jiang, Xue; Liu, Fu-Chen; Bu, Xian-He

    2015-10-25

    Linking magnetically frustrated triangular FeO units by divalent metal ions (M(II) = Fe(II) for 1, Mn(II) for 2) gives isostructural 1D spin chains. Strong antiferromagnetic interactions were found in these complexes with significant frustrations but very interesting ferrimagnetic like transition and metamagnetism were found in mixed valence 1. By comparing the magnetic behaviours with isostructural complex 3 (with M(II) = Mg(II)), it is proposed that the spins of Fe(II) ions and Mn(II) ions have ferromagnetic and antiferromagnetic contributions respectively.

  7. A powder neutron diffraction study of the crystal structure of the fluoroperovskite NaMgF3 (neighborite) from 300 to 3.6 K

    NASA Astrophysics Data System (ADS)

    Mitchell, Roger H.; Alexander, Malcolm; Cranswick, Lachlan M. D.; Swainson, Ian P.

    2007-12-01

    The cell dimensions and crystal structures of the fluoroperovskite NaMgF3 (neighborite), synthesized by solid state methods, have been determined by powder neutron diffraction and Rietveld refinement over the temperature range 300 3.6 K using Pt metal as an internal standard for calibration of the neutron wavelength. These data show that Pbnm NaMgF3 does not undergo any phase transitions to structures of lower symmetry with decreasing temperature. The cell dimensions and atomic coordinates together with polyhedron volumes and distortion indices are given for Pbnm NaMgF3 at 25 K intervals from 300 to 3.6 K. Decreases in the a and c cell dimensions reach a saturation point at 50 K, whereas the b dimension becomes saturated at 150 K. The distortion of the structure of Pbnm NaMgF3 from the aristotype cubic Pmifmmodeexpandafterbarelseexpandafter\\=fi{3}m structure is described in terms of the tilting of the MgF6 octahedra according to the tilt scheme a - a - c + . With decreasing temperature the antiphase tilt ( a -) increases from 14.24° to 15.39°, whereas the in-phase tilt ( c + ) remains effectively constant at ˜10.7°. Changes in the tilt angles are insufficient to cause changes in the coordination sphere of Na that might induce a low temperature phase transition. The structure of Pbnm NaMgF3 is also described in terms of normal mode analysis and displacements of the condensed normal modes are compared with those of Pbnm KCaF3.

  8. The influence of manganese treatment on the distribution of metal elements in rats and the protection by sodium para-amino salicylic acid.

    PubMed

    Yuan, Zong-Xiang; Chen, Hai-Bin; Li, Shao-Jun; Huang, Xiao-Wei; Mo, Yu-Huan; Luo, Yi-Ni; He, Sheng-Nan; Deng, Xiang-Fa; Lu, Guo-Dong; Jiang, Yue-Ming

    2016-07-01

    Manganese (Mn) overexposure induced neurological damages, which could be potentially protected by sodium para-aminosalicylic acid (PAS-Na). In this study, we systematically detected the changes of divalent metal elements in most of the organs and analyzed the distribution of the metals in Mn-exposed rats and the protection by PAS-Na. Sprague Dawley (SD) rats received intraperitoneal injections of 15mg/kg MnCl2·4H2O (5d/week for 3 weeks), followed by subcutaneous (back) injections of PAS-Na (100 and 200mg/kg, everyday for 5 weeks). The concentrations of Mn and other metal elements [Iron (Fe), Copper (Cu), Zinc (Zn), Magnesium (Mg), Calcium (Ca)] in major organs (liver, spleen, kidney, thighbone and iliac bone, cerebral cortex, hippocampus and testes) and blood by Inductively Coupled Plasma-Atomic Emission Spectrometry (ICP-AES). The results showed that Mn overexposure significantly increased Mn in most organs, Fe and Zn in liver, Fe and Mg in blood; however decreased Fe, Cu, Zn, Mg and Ca in cortex, Cu and Zn in kidney, Cu and Mg in iliac bone, and Zn in blood. In contrast, PAS-Na treatment restored most changes particularly in cortex. In conclusion, excessive Mn exposure disturbed the balance of other metal elements but PAS-Na post-treatments could restore these alterations. Copyright © 2016 Elsevier GmbH. All rights reserved.

  9. New-concept Batteries Based on Aqueous Li+/Na+ Mixed-ion Electrolytes

    PubMed Central

    Chen, Liang; Gu, Qingwen; Zhou, Xufeng; Lee, Saixi; Xia, Yonggao; Liu, Zhaoping

    2013-01-01

    Rechargeable batteries made from low-cost and abundant materials operating in safe aqueous electrolytes are attractive for large-scale energy storage. Sodium-ion battery is considered as a potential alternative of current lithium-ion battery. As sodium-intercalation compounds suitable for aqueous batteries are limited, we adopt a novel concept of Li+/Na+ mixed-ion electrolytes to create two batteries (LiMn2O4/Na0.22MnO2 and Na0.44MnO2/TiP2O7), which relies on two electrochemical processes. One involves Li+ insertion/extraction reaction, and the other mainly relates to Na+ extraction/insertion reaction. Two batteries exhibit specific energy of 17 Wh kg−1 and 25 Wh kg−1 based on the total weight of active electrode materials, respectively. As well, aqueous LiMn2O4/Na0.22MnO2 battery is capable of separating Li+ and Na+ due to its specific mechanism unlike the traditional “rocking-chair” lithium-ion batteries. Hence, the Li+/Na+ mixed-ion batteries offer promising applications in energy storage and Li+/Na+ separation. PMID:23736113

  10. Intense red photoluminescence from Mn2+-doped (Na+; Zn2+) sulfophosphate glasses and glass ceramics as LED converters.

    PubMed

    Da, Ning; Peng, Mingying; Krolikowski, Sebastian; Wondraczek, Lothar

    2010-02-01

    We report on intense red fluorescence from Mn(2+)-doped sulfophosphate glasses and glass ceramics of the type ZnO-Na(2)O-SO(3)-P(2)O(5). As a hypothesis, controlled internal crystallization of as-melted glasses is achieved on the basis of thermally-induced bimodal separation of an SO(3)-rich phase. Crystal formation is then confined to the relict structure of phase separation. The whole synthesis procedure is performed in air at Mn(2+) species are incorporated on Zn(2+) sites with increasingly ionic character for increasing concentration. Correspondingly, in the glasses, increasing MnO content results in decreasing network polymerization. Stable glasses and continuously increasing emission intensity are observed for relatively high dopant concentration of up to 3 mol.%. Recrystallization of the glass results in strongly increasing emission intensity. Dynamic emission spectroscopy reveals only on type of emission centers in the glassy material, whereas three different centers are observed in the glass ceramic. These are attributed to octahedrally coordinated Mn(2+) in the residual glass phase and in crystalline phosphate and sulfate lattices, respectively. Relatively low crystal field strength results in almost ideal red emission, peaking around 625 nm. Excitation bands lie in the blue-to-green spectral range and exhibit strong overlap. The optimum excitation range matches the emission properties of GaN- and InGaN-based light emitting devices.

  11. Structural, magnetic and electrical properties of a new double-perovskite LaNaMnMoO6 material.

    PubMed

    Borchani, Sameh Megdiche; Koubaa, Wissem Cheikh-Rouhou; Megdiche, Makrem

    2017-11-01

    Structural, magnetic, magnetocaloric, electrical and magnetoresistance properties of an LaNaMnMoO 6 powder sample have been investigated by X-ray diffraction (XRD), magnetic and electrical measurements. Our sample has been synthesized using the ceramic method. Rietveld refinements of the XRD patterns show that our sample is single phase and it crystallizes in the orthorhombic structure with Pnma space group. Magnetization versus temperature in a magnetic applied field of 0.05 T shows that our sample exhibits a paramagnetic-ferromagnetic transition with decreasing temperature. The Curie temperature T C is found to be 320 K. Arrott plots show that all our double-perovskite oxides exhibit a second-order magnetic phase transition. From the measured magnetization data of an LaNaMnMoO 6 sample as a function of the magnetic applied field, the associated magnetic entropy change |-ΔSM| and the relative cooling power (RCP) have been determined. In the vicinity of T C , |-ΔSM| reached, in a magnetic applied field of 8 T, a maximum value of ∼4 J kg -1  K -1 . Our sample undergoes a large magnetocaloric effect at near-room temperature. Resistivity measurements reveal the presence of an insulating-metal transition at Tρ = 180 K. A magnetoresistance of 30% has been observed at room temperature for 6 T, significantly larger than that reported for the A 2 FeMoO 6 (A = Sr, Ba) double-perovskite system.

  12. Research on the optical and EPR spectral data and the local structure for the trigonal Mn4+ centers in MgTiO3 crystal

    NASA Astrophysics Data System (ADS)

    Liao, Bi-Tao; Mei, Yang; Chen, Bo-Wei; Zheng, Wen-Chen

    2017-07-01

    The optical bands and EPR (or spin-Hamiltonian) parameters (g factors g//, g⊥ and zero-field splitting D) for Mn4+ ions at the trigonal octahedral Ti4+ site of MgTiO3 crystal are uniformly computed by virtue of the complete diagonalization (of energy matrix) method based on the two-spin-orbit-parameter model, where besides the effects of spin-orbit parameter of central dn ion on the spectral data (in the classical crystal field theory), those of ligands are also contained. The computed eight optical and EPR spectral data with four suitable adjustable parameters (note: differing from those in the previous work within cubic symmetry approximation where the used Racah parameters violate the nephelauxetic effect, the present Racah parameters obey the effect and hence are suitable) are rationally coincident with the experimental values. In particular, the calculated ground state splitting 2D, the first excited splitting ΔE(2E) and g-anisotropy Δg (=g//-g⊥) (they depend strongly on the angular distortion of d3 centers) are in excellent agreement with the observed values, suggesting that the angular distortions caused by the impurity-induced local lattice relaxation obtained from the above calculation for the trigonal Mn4+ impurity center in MgTiO3: Mn4+ crystal seem to be acceptable.

  13. Tanohataite, LiMn2Si3O8(OH): a new mineral from the Tanohata mine, Iwate Prefecture, Japan

    NASA Astrophysics Data System (ADS)

    Nagase, Toshiro; Hori, Hidemichi; Kitamine, Mizuya; Nagashima, Mariko; Abduriyim, Ahmadjan; Kuribayashi, Takahiro

    Tanohataite, LiMn2Si3O8(OH), the Li analogue of serandite, has been found in a metamorphosed manganese ore deposit of the Tanohata mine, Iwate Prefecture, Japan. The mineral has the triclinic space group P1 with a = 7.612(7), b = 7.038(4), c = 6.700(4) Å, α = 90.23(6)°, β = 94.70(7)°, γ = 105.26 (8)°, V =345.0(3) Å3, and Z = 2. The seven strongest lines in the X-ray powder diffraction pattern are [d(Å), (I), (hkl)]: 6.64(35)(001), 3.67(26)(200), 3.13(89)(102), 3.11(69)(211), 2.95(100)(102), 2.81(33)(120), and 2.18(40)(103). Electron microprobe analysis and laser ablation microprobe-inductively coupled plasma-mass spectrometry gave an SiO2 content of 51.97; MnO, 37.99; MgO, 1.06; CaO, 0.41; Na2O, 1.97; Li2O, 3.34; total, 96.74 wt%, corresponding to an empirical formula of (Li0.78Na0.22)Σ1.00(Mn1.86Ca0.03Mg0.09)Σ1.98Si3.01O8(OH) on the basis of O = 9. Tanohataite is transparent and pinkish white with a vitreous and silky luster. The streak is white. The cleavage is perfect on {001} and {100}. On the Mohs' scale, the hardness is 5-51/2. The calculated density is 3.33 g/cm3. Optically, tanohataite is biaxial positive with 2Vcalc = 82(2)°, α = 1.593(3), β = 1.618(3), and γ = 1.653(3). Tanohataite occurs as an aggregation of fibrous crystals in veinlets composed mainly of quartz, aegirine, Mn-arfvedsonite, nambulite, natronambulite, and barite.

  14. Effects of aqueous extract of Hibiscus sabdariffa on renal Na(+)-K(+)-ATPase and Ca(2+)-Mg(2+)-ATPase activities in Wistar rats.

    PubMed

    Olatunji, Lawrence A; Usman, Taofeek O; Adebayo, Joseph O; Olatunji, Victoria A

    2012-09-01

    To investigate the effects of oral administration of aqueous extract of Hibiscus sabdariffa on renal Na(+)-K(+)-ATPase and Ca(2+)-Mg(2+)-ATPase activities in rats. The 25 and 50 mg/(kg·d) of aqueous extracts of H. sabdariffa were respectively given to rats in the experimental groups for 28 d, and rats in the control group received an appropriate volume of distilled water as vehicle. Na(+)-K(+)-ATPase and Ca(2+)-Mg(2+)-ATPase activities in the kidney were assayed by spectrophotometric method. Administrations of 25 and 50 mg/(kg·d) of aqueous extract of H. sabdariffa significantly decreased the Ca(2+)-Mg(2+)-ATPase activity in the kidney of rats (P<0.05). However, the renal Na(+)-K(+)-ATPase activity of the experimental rats was not affected by either dose of the extract. And the plasma Na(+), K(+) and Ca(2+) levels of the experimental rats had no significant changes. Administration of either dose of the extract did not result in any significant changes in body and kidney weights, the concentrations of plasma albumin and total protein, and alkaline phosphatase, aspartate aminotransferase and alanine aminotransferase activities. However, concentrations of creatinine and urea were significantly reduced by 50 mg/kg of the extract (P<0.05). The present study indicates that oral administration of aqueous extract of H. sabdariffa may preserve the renal function despite a decreased renal Ca(2+)-Mg(2+)-ATPase activity.

  15. Mn-Cr isotopic systematics of individual Chainpur chondrules. [Abstract only

    NASA Technical Reports Server (NTRS)

    Nyquist, L.; Lindstrom, D.; Wiesmann, H.; Martinez, R.; Bansal, B.; Mittlefehldt, D.; Shih, C.-Y.; Wentworth, S.

    1994-01-01

    Twenty-eight chondrules separated from Chainpur (LL3.4) were surveyed for abundances of Mn, Cr, Na, Fe, Sc, Hf, Ir, and Zn by Instrumental Neutron Activation Analysis (INAA). Six, weighting 0.6-1.5 mg each, were chosen for Scanning Electron Microscopy (SEM)/Energy Dispersive X-ray (EDX) and high-precision Ce-isotopic studies. LL-chondrite-normalized (Mn/Fe)(sub LL) and (Sc/Fe)(sub LL) were found to be useful in categorizing them. Five chondrules (CH-16, -17, -18, -23, and -28) were in the range 0.5 less than (Mn/Fe)(sub LL) less than 1. 4 and 0.5 less than (Sc/Fe)(sub LL) less than 1.4. The sixth (CH-25) had (Mn/Fe)(sub LL) and (Sc/Fe)(sub LL) ratios of 0.40 and 8.1, respectively, and was enriched in the refractory lithophile elements Sc and Hf and the refractory siderophile element Ir by 2.7 and 4.4x LL abundances respectively. SEM/EDX of exterior surfaces of the chondrules showed they consisted of varying proportions of low- and high-Ca pyroxenes, olivine, glass, kamacite/taenite, and Fe-sulfides. Chromium-53/chromium-52 for the six chondrules and bulk Chainpur (WR) are presented. Chromium-54/chromium-52 is close to terrestrial and does not correlate with Mn/Cr. We provisionally ignore the possibility of initial Cr isotopic heterogeneities among the chondrules. Omitting both the CH-25 and WR data, a linear regression gives initial (Mn-53/Mn-55)(sub I) = 8 +/- 4 x 10(exp -6), corresponding to chondrule formation at Delta(t)(sub LEW) = -9 +/- 4 Ma prior to igneous crystallization of the LEW 86010 angrite. If initial (Mn-53/Mn-55)(sub 0) in the solar system were as high as approximately 4.4 x 10(exp -5) when Allende CAI formed, our data suggest Chainpur chondrules formed approximately 9 Ma later, in qualitative agreement with 'late' I-Xe formation ages for most Chainpur chondrules.

  16. Photoluminescence and afterglow luminescence properties of a green-emitting Na2BeGeO4:Mn2+ phosphor

    NASA Astrophysics Data System (ADS)

    Lu, Jie; Shen, Linjiang

    2018-07-01

    Recently, developing free rare-earth (RE) doped afterglow phosphors has received great attentions in the lighting field. In this work, we prepare and report a RE-free phosphor, Na2BeGeO4:Mn2+, which can simultaneously emit the green fluorescence and afterglow luminescence upon excitation at UV light. Our results reveal that the as-prepared samples crystallize in orthorhombic type with the space group of Pmn21 (31). The green emission is a broad band centered at 525 nm, corresponds to the 4T1(4G)-6A1(6S) transition of Mn2+ ions. After exposing to a 254 nm UV lamp for 10 min, the green afterglow luminescence seen with naked eyes can last more than 5 h. Together with the structural analysis and thermoluminescence (TL) spectra, the afterglow luminescence mechanism is also discussed in this work.

  17. Ionic Strength-Controlled Mn (Hydr)oxide Nanoparticle Nucleation on Quartz: Effect of Aqueous Mn(OH)2.

    PubMed

    Jung, Haesung; Jun, Young-Shin

    2016-01-05

    The early formation of manganese (hydr)oxide nanoparticles at mineral-water interfaces is crucial in understanding how Mn oxides control the fate and transport of heavy metals and the cycling of nutrients. Using atomic force microscopy, we investigated the heterogeneous nucleation and growth of Mn (hydr)oxide under varied ionic strengths (IS; 1-100 mM NaNO3). Experimental conditions (i.e., 0.1 mM Mn(2+) (aq) concentration and pH 10.1) were chosen to be relevant to Mn remediation sites. We found that IS controls Mn(OH)2 (aq) formation, and that the controlled Mn(OH)2 (aq) formation can affect the system's saturation and subsequent Mn(OH)2 (s) and further Mn3O4 (s) nanoparticle formation. In 100 mM IS system, nucleated Mn (hydr)oxide particles had more coverage on the quartz substrate than those in 1 mM and 10 mM IS systems. This high IS also resulted in low supersaturation ratio and thus favor heterogeneous nucleation, having better structural matching between nucleating Mn (hydr)oxides and quartz. The unique information obtained in this work improves our understanding of Mn (hydr)oxide formation in natural as well as engineered aqueous environments, such as groundwater contaminated by natural leachate and acid mine drainage remediation.

  18. TH-EF-207A-02: Imaging Pancreatic Î{sup 2}-Cell Function with 51/52Mn-PET

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Graves, S; Hernandez, R; England, C

    Purpose: To image β-cells noninvasively using radio-manganese PET and to develop efficient small cyclotron production of {sup 51}Mn (t1/2=46m, β{sup +}=97%) and {sup 52}Mn (t1/2=5.6d, β{sup +}=29%). Methods: {sup 51}Mn and {sup 52}Mn were produced by 16 MeV proton irradiation (GE PETtrace) of electrodeposited {sup 54}Fe on silver and Cr metal pressed into a silver disc, respectively. {sup 51}Mn was radiochemically isolated from target material by anion exchange chromatography and {sup 52}Mn was isolated by ethanolic anion exchange trap-and-release. A final injectable product of {sup 51}Mn{sup 2+} or {sup 52}Mn{sup 2+} was obtained in 0.01M pH 6.0 NaOAc. To assessmore » pancreatic uptake, fasted ICR mice were administered and intravenous bolus or infusion of {sup 52}Mn{sup 2+}. Additionally, to demonstrate the correlation between β-cell function and {sup 52}Mn{sup 2+} pancreatic uptake, prior to tracer administration groups of ICR mice were administered glibenclamide (5mg/kg) and diazoxide (20 mg/kg) as an insulin release stimulator and blocker, respectively. To validate PET ROI quantification, ex vivo biodistribtution studies were conducted on each subject after the final imaging time-point. Results: Dynamic PET data using a left atrium ROI revealed that {sup 52}Mn{sup 2+} cleared from the blood with a 10 second half-life. Significant uptake was seen in the pancreas (approximately 20% ID/g, SUVmean= 5.5), liver, kidneys, intestine, heart, and thyroid. Pancreatic uptake was found to be highly sensitive to volatile anesthesia administration (p=0.0002), insulin release stimulation by glibenclamide (p=0.017), and by insulin release inhibition by diazoxide (p=0.046). Excellent agreement was found between in vivo PET ROI quantification and ex vivo biodistribution measurements. Conclusion: This work demonstrates the feasibility of using radiomanganese-PET for measuring functional β-cell mass in vivo. The decay characteristics and dosimetric properties of {sup 51}Mn

  19. Hybrid MnO2/carbon nanotube-VN/carbon nanotube supercapacitors

    NASA Astrophysics Data System (ADS)

    Su, Y.; Zhitomirsky, I.

    2014-12-01

    Composite materials, containing fibrous VN nanoparticles and multiwalled carbon nanotubes (MWCNT) are prepared by a chemical method for application in electrochemical supercapacitors. We demonstrate for the first time that VN-MWCNT electrodes exhibit good capacitive behavior in 0.5 M Na2SO4 electrolyte in a negative voltage window of 0.9 V. Quartz crystal microbalance studies provide an insight into the mechanism of charge storage. Composite VN-MWCNT materials show significant improvement in capacitance, compared to individual VN and MWCNT materials. Testing results indicate that VN-MWCNT electrodes exhibit high specific capacitance at high mass loadings in the range of 10-30 mg cm-2, good capacitance retention at scan rates in the range of 2-200 mV s-1 and good cycling stability. The highest specific capacitance of 160 F g-1 is achieved at a scan rate of 2 mV s-1. The new findings open a new and promising strategy in the fabrication of hybrid devices based on VN. The proof-of-principle is demonstrated by the fabrication of hybrid supercapacitor devices based on VN-MWCNT negative electrodes and MnO2 -MWCNT positive electrodes with voltage window of 1.8 V in aqueous 0.5 M Na2SO4 electrolyte. The hybrid VN-MWCNT/MnO2-MWCNT supercapacitor cells show promising capacitive and power-energy characteristics.

  20. Improved electrochemical performance of spinel LiMn(1.5)Ni(0.5)O4 through MgF2 nano-coating.

    PubMed

    Wu, Qing; Zhang, Xiaoping; Sun, Shuwei; Wan, Ning; Pan, Du; Bai, Ying; Zhu, Huiyuan; Hu, Yong-Sheng; Dai, Sheng

    2015-10-14

    A spinel LiMn1.5Ni0.5O4 (LMNO) cathode material synthesized by a sol-gel method is modified by MgF2 nano-coating via a wet coating strategy. The results of X-ray diffraction (XRD), Raman spectroscopy, field emission scanning electron microscopy (FESEM) and high resolution transmission electron microscopy (HRTEM) showed that the MgF2 nano-coating layers do not physically change the bulk structure of the pristine material. Compared with the pristine compound, the MgF2-coated LMNO electrodes display enhanced cycling stabilities. Particularly, the 5 wt% MgF2-coated LMNO demonstrates the best reversibility, with a capacity retention of 89.9% after 100 cycles, much higher than that of the pristine material, 69.3%. The dQ/dV analysis and apparent Li(+) diffusion coefficient calculation prove that the kinetic properties are enhanced after MgF2 surface modification, which partly explains the improved electrochemical performances. Electrochemical impedance spectroscopy (EIS) and Fourier transform infrared spectroscopy (FTIR) data confirm that the MgF2 coating layer helps in suppressing the fast growth of the solid electrolyte interface (SEI) film in repeated cycling, which effectively stabilizes the spinel structure. Additionally, differential scanning calorimetry (DSC) tests show that the MgF2 nano-coating layer also helps in enhancing the thermal stability of the LMNO cathode.

  1. Development of a Nanostructured α-MnO2/Carbon Paper Composite for Removal of Ni2+ / Mn2+ ions by Electrosorption.

    PubMed

    Li, Pengju; Gui, Yang; Blackwood, Daniel John

    2018-05-22

    Toxic metal ions, such as Ni2+ and Mn2+, in industrial waste streams are non-biodegradable and can cause damage to the human body. Electrochemical cleaning techniques are attractive as they offer more control and produce less sludge than chemical / biological approaches without the high pressures needed for membranes. Here nanoneedle structured α-MnO2/carbon fiber paper (CFP) composites were synthesized by a hydrothermal approach and used as electrodes for combined electro-adsorption and capacitive deionization removal of nickel and manganese ions from pseudo industrial waste streams. The specific performance of α-MnO2/CFP (16.4 mg Ni2+ per gram of active material) not only shows a great improve in comparison with its original CFP substrate (0.034 Ni2+ mg per gram), but is over six times that of activated carbon (2.5 mg Ni2+ per gram). The high performance of α-MnO2/CFP composite is attributed to its high surface area, desirable mesoporosity and pore size distribution that permits the further access of ions, and the property as a pseudocapacitor, which contributes to a more efficient electron/charge transfer in the faradic process. Unfortunately, it was also found that some Mn2+ ions are released due to partial reduction of the MnO2 when operated as a negative electrode. For the removal of Mn2+ ions an asymmetric arrangement, consisting of a MnO2/CFP positive electrode and an activated carbon negative electrode was employed. This arrangement reduced the Mn2+ concentration from 100 ppm to less than 2 ppm, a vast improvement over a systematical two activated carbon electrodes system that could only reach 42 ppm under the same conditions. It was also observed that as long as the MnO2/CFP composite was maintained as a positive electrode it was completely stable. The technique was able to reduce both Ni2+ and Mn2+ ions to well below the 10 ppm requirement for discharge into public sewers in Singapore.

  2. Raman microspectroscopic study of effects of Na(I) and Mg(II) ions on low pH induced DNA structural changes.

    PubMed

    Muntean, C M; Segers-Nolten, G M J

    2003-01-01

    In this work a confocal Raman microspectrometer is used to investigate the influence of Na(+) and Mg(2+) ions on the DNA structural changes induced by low pH. Measurements are carried out on calf thymus DNA at neutral pH (7) and pH 3 in the presence of low and high concentrations of Na(+) and Mg(2+) ions, respectively. It is found that low concentrations of Na(+) ions do not protect DNA against binding of H(+). High concentrations of monovalent ions can prevent protonation of the DNA double helix. Our Raman spectra show that low concentrations of Mg(2+) ions partly protect DNA against protonation of cytosine (line at 1262 cm(-1)) but do not protect adenine and guanine N(7) against binding of H(+) (characteristic lines at 1304 and 1488 cm(-1), respectively). High concentrations of Mg(2+) can prevent protonation of cytosine and protonation of adenine (disruption of AT pairs). By analyzing the line at 1488 cm(-1), which obtains most of its intensity from a guanine vibration, high magnesium salt protect the N(7) of guanine against protonation. A high salt concentration can prevent protonation of guanine, cytosine, and adenine in DNA. Higher salt concentrations cause less DNA protonation than lower salt concentrations. Magnesium ions are found to be more effective in protecting DNA against binding of H(+) as compared with calcium ions presented in a previous study. Divalent metal cations (Mg(2+), Ca(2+)) are more effective in protecting DNA against protonation than monovalent ions (Na(+)). Copyright 2003 Wiley Periodicals, Inc. Biopolymers (Biospectroscopy) 72: 000-000, 2003

  3. Genetic and biochemical effects induced by iron ore, Fe and Mn exposure in tadpoles of the bullfrog Lithobates catesbeianus.

    PubMed

    Veronez, Alexandra Caroline da Silva; Salla, Rômulo Victor; Baroni, Vinícius Dadalto; Barcarolli, Indianara Fernanda; Bianchini, Adalto; Dos Reis Martinez, Claudia Bueno; Chippari-Gomes, Adriana Regina

    2016-05-01

    For decades, the extraction of minerals has intensified in order to meet the demand of industry. Iron ore deposits are important sources of metals, such as iron (Fe) and manganese (Mn). The particulate ores can be dispersed during extraction, transport and storage, with potential to induce biological impacts. Amphibians are very sensitive to environmental stressors. Therefore, the present study aimed to assess the effects of iron ore, Fe and Mn exposure during the metamorphosis of Lithobates catesbeianus. Endpoints analyzed included morphological (biometrical and developmental analyses), whole body Fe and Mn concentration in, plasma ferritin concentration, erythrocyte DNA damage (measured through comet assay and micronucleus test) and liver activity of enzymes involved in oxidative status [glutathione S-transferase (GST) and catalase (CAT)]. Tadpoles were kept under control condition (no contaminant addition) or exposed to iron ore (3.79mg/L as fine particulate matter); Fe (nominal concentration: 0.51mg/L Fe as C10H12FeN2NaO8; Fe-EDTA); and Mn (nominal concentration: 5.23mg/L Mn as 4H2O.MnCl2) for 30 days. Virtually, no mortality was observed, except for one tadpole found dead in the iron ore treatment. However, tadpoles exposed to iron ore had longer tail than those kept under control conditions while tadpoles exposed to manganese chloride showed higher body length than control ones. Exposure to Fe and Mn induced a delay in tadpole metamorphosis, especially when these metals are presented not as a mixture (iron ore). Tadpoles exposed to iron ore had increased whole body Fe and Mn while those exposed to Fe and Mn accumulated each metal individually. Tadpoles exposed to any of the contaminants tested showed a significant increase in erythrocyte DNA damage and frequency of micronuclei. In addition, they showed higher liver GST activity respect with those kept under control conditions. Plasma ferritin concentration and liver CAT activity were higher only in tadpoles

  4. Insight into Ca-Substitution Effects on O3-Type NaNi1/3 Fe1/3 Mn1/3 O2 Cathode Materials for Sodium-Ion Batteries Application.

    PubMed

    Sun, Liqi; Xie, Yingying; Liao, Xiao-Zhen; Wang, Hong; Tan, Guoqiang; Chen, Zonghai; Ren, Yang; Gim, Jihyeon; Tang, Wan; He, Yu-Shi; Amine, Khalil; Ma, Zi-Feng

    2018-04-18

    O3-type NaNi 1/3 Fe 1/3 Mn 1/3 O 2 (NaNFM) is well investigated as a promising cathode material for sodium-ion batteries (SIBs), but the cycling stability of NaNFM still needs to be improved by using novel electrolytes or optimizing their structure with the substitution of different elements sites. To enlarge the alkali-layer distance inside the layer structure of NaNFM may benefit Na + diffusion. Herein, the effect of Ca-substitution is reported in Na sites on the structural and electrochemical properties of Na 1- x Ca x /2 NFM (x = 0, 0.05, 0.1). X-ray diffraction (XRD) patterns of the prepared Na 1- x Ca x /2 NFM samples show single α-NaFeO 2 type phase with slightly increased alkali-layer distance as Ca content increases. The cycling stabilities of Ca-substituted samples are remarkably improved. The Na 0.9 Ca 0.05 Ni 1/3 Fe 1/3 Mn 1/3 O 2 (Na 0.9 Ca 0.05 NFM) cathode delivers a capacity of 116.3 mAh g -1 with capacity retention of 92% after 200 cycles at 1C rate. In operando XRD indicates a reversible structural evolution through an O3-P3-P3-O3 sequence of Na 0.9 Ca 0.05 NFM cathode during cycling. Compared to NaNMF, the Na 0.9 Ca 0.05 NFM cathode shows a wider voltage range in pure P3 phase state during the charge/discharge process and exhibits better structure recoverability after cycling. The superior cycling stability of Na 0.9 Ca 0.05 NFM makes it a promising material for practical applications in sodium-ion batteries. © 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  5. Structural, magnetic and magnetocaloric properties of La{sub 0.8}Ca{sub 0.2−x}Na{sub x}MnO{sub 3} manganites (0≤x≤0.2)

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Choura Maatar, S.; M’nassri, R.; Institut NEEL, CNRS, B.P.166, 38042 Grenoble Cedex 9

    2015-05-15

    In this work, we report the effect of Na doping on the structural, magnetic and magnetocaloric properties in La{sub 0.8}Ca{sub 0.2−x}Na{sub x}MnO{sub 3} powder samples. Our polycristalline samples have been synthesized using the solid-state reaction method at high temperatures. The parent compound La{sub 0.8}Ca{sub 0.2}MnO{sub 3} crystallizes in the orthorhombic system with Pbnm space group. Na doping induces a structural transition from orthorhombic (Pbnm space group) to rhombohedral (R-3C space group) symmetry. Magnetization measurements versus temperature in a magnetic applied field of 50 mT showed that all our investigated samples display a paramagnetic-ferromagnetic transition with decreasing temperature. The Curie temperaturemore » T{sub C} increases with Na content from 240 K for x=0 to 330 K for x=0.2. A large magnetocaloric effect has been observed in all samples, the maximum entropy change, |∆S{sub M}|{sub max}, shifts to smaller values with increasing Na content, from4.56 J/kg K (x=0.05) to 2.3 J/kg K (x=0.2) under a magnetic field change ∆µ{sub 0}H of 2 T. For the same applied magnetic field of 2 T, the Relative Cooling Power (RCP) values are found to be constant around 91 J/kg. - Graphical abstract: Sodium doping induces an increase of T{sub C} from 240 K for x=0 to 330 K for x=0.2. - Highlights: • La{sub 0.8}Ca{sub 0.2−x}Na{sub x}MnO{sub 3} are synthesized using the ceramic method at high temperatures. • Na doping induces a structural transition from Pbnm to R-3C space group. • T{sub C} increases with Na content from 240 K for x=0 to 330 K for x=0.2. • RCP is constant around 91 J/kg for all compounds under 2 T.« less

  6. Influence of Na+ and Mg2+ ions on RNA structures studied with molecular dynamics simulations.

    PubMed

    Fischer, Nina M; Polêto, Marcelo D; Steuer, Jakob; van der Spoel, David

    2018-06-01

    The structure of ribonucleic acid (RNA) polymers is strongly dependent on the presence of, in particular Mg2+ cations to stabilize structural features. Only in high-resolution X-ray crystallography structures can ions be identified reliably. Here, we perform molecular dynamics simulations of 24 RNA structures with varying ion concentrations. Twelve of the structures were helical and the others complex folded. The aim of the study is to predict ion positions but also to evaluate the impact of different types of ions (Na+ or Mg2+) and the ionic strength on structural stability and variations of RNA. As a general conclusion Mg2+ is found to conserve the experimental structure better than Na+ and, where experimental ion positions are available, they can be reproduced with reasonable accuracy. If a large surplus of ions is present the added electrostatic screening makes prediction of binding-sites less reproducible. Distinct differences in ion-binding between helical and complex folded structures are found. The strength of binding (ΔG‡ for breaking RNA atom-ion interactions) is found to differ between roughly 10 and 26 kJ/mol for the different RNA atoms. Differences in stability between helical and complex folded structures and of the influence of metal ions on either are discussed.

  7. Reactivity and O2 Formation by Mn(IV)- and Mn(V)-Hydroxo Species Stabilized within a Polyfluoroxometalate Framework.

    PubMed

    Schreiber, Roy E; Cohen, Hagai; Leitus, Gregory; Wolf, Sharon G; Zhou, Ang; Que, Lawrence; Neumann, Ronny

    2015-07-15

    Manganese(IV,V)-hydroxo and oxo complexes are often implicated in both catalytic oxygenation and water oxidation reactions. Much of the research in this area is designed to structurally and/or functionally mimic enzymes. On the other hand, the tendency of such mimics to decompose under strong oxidizing conditions makes the use of molecular inorganic oxide clusters an enticing alternative for practical applications. In this context it is important to understand the reactivity of conceivable reactive intermediates in such an oxide-based chemical environment. Herein, a polyfluoroxometalate (PFOM) monosubstituted with manganese, [NaH2(Mn-L)W17F6O55](q-), has allowed the isolation of a series of compounds, Mn(II, III, IV and V), within the PFOM framework. Magnetic susceptibility measurements show that all the compounds are high spin. XPS and XANES measurements confirmed the assigned oxidation states. EXAFS measurements indicate that Mn(II)PFOM and Mn(III)PFOM have terminal aqua ligands and Mn(V)PFOM has a terminal hydroxo ligand. The data are more ambiguous for Mn(IV)PFOM where both terminal aqua and hydroxo ligands can be rationalized, but the reactivity observed more likely supports a formulation of Mn(IV)PFOM as having a terminal hydroxo ligand. Reactivity studies in water showed unexpectedly that both Mn(IV)-OH-PFOM and Mn(V)-OH-PFOM are very poor oxygen-atom donors; however, both are highly reactive in electron transfer oxidations such as the oxidation of 3-mercaptopropionic acid to the corresponding disulfide. The Mn(IV)-OH-PFOM compound reacted in water to form O2, while Mn(V)-OH-PFOM was surprisingly indefinitely stable. It was observed that addition of alkali cations (K(+), Rb(+), and Cs(+)) led to the aggregation of Mn(IV)-OH-PFOM as analyzed by electron microscopy and DOSY NMR, while addition of Li(+) and Na(+) did not lead to aggregates. Aggregation leads to a lowering of the entropic barrier of the reaction without changing the free energy barrier. The

  8. Effects of microstructure transformation on mechanical properties, corrosion behaviors of Mg-Zn-Mn-Ca alloys in simulated body fluid.

    PubMed

    Zhang, Yuan; Li, Jianxing; Li, Jingyuan

    2018-04-01

    Magnesium and its alloys have unique advantages to act as resorbable bone fixation materials, due to their moderate mechanical properties and biocompatibility, which are similar to those of human tissue. However, early resorption and insufficient mechanical strength are the main problems that hinder their application. Herein, the effects of microstructure transformation on the mechanical properties and corrosion performance of Mg-Zn-Mn-Ca were investigated with electrochemical and immersion measurements at 37 °C in a simulated body fluid (SBF). The results showed that the number density of Ca 2 Mg 6 Zn 3 /Mg 2 Ca precipitates was remarkably reduced and grain sizes were gradually increased as the temperature increased. The alloy that received the 420 °C/24 h treatment demonstrated the best mechanical properties and lowest corrosion rate (5.94 mm/a) as well as presented a compact and denser film than the others. The improvement in mechanical properties could be explained by the eutectic compounds and phases (Mg 2 Ca/Ca 2 Mg 6 Zn 3 ) gradually dissolving into a matrix, which caused severely lattice distortion and facilitated structural re-arrangement of the increased Ca solute. Moreover, the difference in potential between the precipitates and the matrix is the main essence for micro-galvanic corrosion formation as well as accelerated the dissolution activity and current exchange density at the Mg/electrolyte interface. As a result, the best Mg alloys corrosion resistance must be matched with a moderate grain size and phase volume fractions. Copyright © 2018 Elsevier Ltd. All rights reserved.

  9. Electrochemical hydrogen storage alloys and batteries fabricated from Mg containing base alloys

    DOEpatents

    Ovshinsky, Stanford R.; Fetcenko, Michael A.

    1996-01-01

    An electrochemical hydrogen storage material comprising: (Base Alloy).sub.a M.sub.b where, Base Alloy is an alloy of Mg and Ni in a ratio of from about 1:2 to about 2:1, preferably 1:1; M represents at least one modifier element chosen from the group consisting of Co, Mn, Al, Fe, Cu, Mo, W, Cr, V, Ti, Zr, Sn, Th, Si, Zn, Li, Cd, Na, Pb, La, Mm, and Ca; b is greater than 0.5, preferably 2.5, atomic percent and less than 30 atomic percent; and a+b=100 atomic percent. Preferably, the at least one modifier is chosen from the group consisting of Co, Mn, Al, Fe, and Cu and the total mass of the at least one modifier element is less than 25 atomic percent of the final composition. Most preferably, the total mass of said at least one modifier element is less than 20 atomic percent of the final composition.

  10. Exciton and intracenter radiative recombination in ZnMnTe and CdMnTe quantum wells with optically active manganese ions

    NASA Astrophysics Data System (ADS)

    Agekyan, V. F.; Akai, I.; Vasil'Ev, N. N.; Karasawa, T.; Karczewski, G.; Serov, A. Yu.; Filosofov, N. G.

    2007-06-01

    The emission spectra of Zn1-x Mn x Te/Zn0.6Mg0.4Te and Cd1-x Mn x Te/Cd0.5Mg0.5Te quantum-well structures with different manganese concentrations and quantum-well widths are studied at excitation power densities ranging from 105 to 107 W cm-2. Under strong optical pumping, intracenter luminescence of Mn2+ ions degrades as a result of the interaction of excited managanese ions with high-density excitons. This process is accompanied by a strong broadening of the emission band of quantum-well excitons due to the exciton-exciton interaction and saturation of the exciton ground state. Under pumping at a power density of 105 W cm-2, stimulated emission of quantum-well excitons arises in CdTe/Cd0.5Mg0.5Te. The luminescence kinetics of the quantum-well and barrier excitons is investigated with a high temporal resolution. The effect of the quantum-well width and the managanese concentration on the kinetics and band shape of the Mn2+ intracenter luminescence characterized by the contribution of the manganese interface ions is determined.

  11. Structural, magnetic and electrical properties of a new double-perovskite LaNaMnMoO6 material

    PubMed Central

    Borchani, Sameh Megdiche; Koubaa, Wissem Cheikh-Rouhou; Megdiche, Makrem

    2017-01-01

    Structural, magnetic, magnetocaloric, electrical and magnetoresistance properties of an LaNaMnMoO6 powder sample have been investigated by X-ray diffraction (XRD), magnetic and electrical measurements. Our sample has been synthesized using the ceramic method. Rietveld refinements of the XRD patterns show that our sample is single phase and it crystallizes in the orthorhombic structure with Pnma space group. Magnetization versus temperature in a magnetic applied field of 0.05 T shows that our sample exhibits a paramagnetic–ferromagnetic transition with decreasing temperature. The Curie temperature TC is found to be 320 K. Arrott plots show that all our double-perovskite oxides exhibit a second-order magnetic phase transition. From the measured magnetization data of an LaNaMnMoO6 sample as a function of the magnetic applied field, the associated magnetic entropy change |−ΔSM| and the relative cooling power (RCP) have been determined. In the vicinity of TC, |−ΔSM| reached, in a magnetic applied field of 8 T, a maximum value of ∼4 J kg−1 K−1. Our sample undergoes a large magnetocaloric effect at near-room temperature. Resistivity measurements reveal the presence of an insulating-metal transition at Tρ = 180 K. A magnetoresistance of 30% has been observed at room temperature for 6 T, significantly larger than that reported for the A2FeMoO6 (A = Sr, Ba) double-perovskite system. PMID:29291087

  12. Perpendicularly magnetized (001)-textured D0{sub 22} MnGa films grown on an (Mg{sub 0.2}Ti{sub 0.8})O buffer with thermally oxidized Si substrates

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Lee, Hwachol; Sukegawa, Hiroaki, E-mail: sukegawa.hiroaki@nims.go.jp; Liu, Jun

    2015-10-28

    We report the growth of (001)-textured polycrystalline D0{sub 22} MnGa films with perpendicular magnetic anisotropy (PMA) on thermally oxidized Si substrates using an (Mg{sub 0.2}Ti{sub 0.8})O (MTO) buffer layer. The ordered D0{sub 22} MnGa film grown at the optimum substrate temperature of 530 °C on the MTO buffer layer shows PMA with magnetization of 80 kA/m, PMA energy density of 0.28 MJ/m{sup 3}, and coercivity of 2.3 T. The scanning transmission electron microscope analysis confirms the formation of a highly (001)-textured structure and the elementally sharp interfaces between the MTO layer and the MnGa layer. The achieved D0{sub 22} MnGa PMA films on anmore » amorphous substrate will provide the possible pathway of integration of a Mn-based PMA film into Si-based substrates.« less

  13. The Ti-Mn system revisited: experimental investigation and thermodynamic modelling.

    PubMed

    Khan, A U; Brož, P; Premović, M; Pavlů, J; Vřeštál, J; Yan, X; Maccio, D; Saccone, A; Giester, G; Rogl, P

    2016-08-17

    As the Ti-Mn phase diagram is part of numerous ternary and higher order systems of technological importance, the present paper defines phase relations which have been experimentally established throughout this work from 800 °C to the melting range based on Differential Thermal Analyses (DTA), X-ray powder diffraction, metallography and Electron Probe Micro Analysis (EPMA) techniques on ∼50 alloys, which were prepared by arc melting or high frequency melting under high purity argon starting from freshly cleaned metal ingots. Novel compounds were identified and reaction isotherms were redefined accordingly. In the Ti-rich region a novel compound TiMn was detected, sandwiched between the known phases: TiMn1-x (∼45 at% Mn) and TiMn1+x (∼55 at% Mn). In the Mn-rich region the hitherto unknown crystal structure of TiMn∼3 was solved from X-ray single crystal diffraction data and found to be of a unique structure type Ti6(Ti1-xMnx)6Mn25 (x = 0.462; space group Pbam (#55); a = 0.79081(3) nm, b = 2.58557(9) nm, c = 0.47931(2) nm), which consists of two consecutive layers of the hexagonal MgZn2-type Laves phase (TiMn2) and a combined layer of alternate structure blocks of MgZn2 type and Zr4Al3 type. Whereas TiMn can be considered as a line compound (solubility range <∼1 at%), the homogeneity regions of the Ti-Mn compounds are significant (determined by EPMA): TiMn1-x (44.0 to 46.6 at% Mn), TiMn1+x (54.6 to 56.3 at% Mn), Ti1+xMn2-x (MgZn2-type, 59 to 69 at% Mn at 1000 °C: -0.08 < x < 0.23), TiMn∼3 (unique type; 74 to 76.5 at% Mn) and TiMn∼4 (R-phase: Ti8(TixMn1-x)6Mn39, 80 to 84 at% Ti). Supported by ab initio calculations of the ground state energy for the Laves phase, the new experimental results enabled thermodynamic modelling of the entire Ti-Mn phase diagram providing a complete and novel set of thermodynamic data thus providing a sound basis for future thermodynamic predictions of higher order Ti-Mn-X-Y systems.

  14. Cyanate groups in higher oxidation state metal cluster chemistry: Mixed-valence (II/III) Mn 16 and Mn 18 clusters

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Alexandropoulos, Dimitris I.; Moushi, Eleni E.; Papatriantafyllopoulou, Constantina

    Here, the employment of cyanato (OCN -) group in high oxidation state manganese cluster chemistry, in conjunction with carboxylate ions and the organic chelating/bridging ligand 2-(hydroxymethyl)pyridine (hmpH), is reported. The syntheses, crystal structures, and magnetochemical characterization are described for [Mn 16O 8(OR) 4(OCN) 4(O 2CMe) 12(hmp) 6(ROH) 2] (R = Me (1), Et (2)) and [Mn 18O 14(O 2CR) 18(hmp) 4(hmpH) 2(H 2O) 2] (R = Me (3), Et (4)). The 2:1:1:1 reactions of Mn(O 2CMe) 2·4H 2O, hmpH, NaOCN and NEt 3 in solvent MeOH or EtOH afford the isostructural complexes [Mn 16O 8(OR) 4(OCN) 4(O 2CMe) 12(hmp) 6(ROH)more » 2] (R = Me (1), Et (2)). The [Mn 16(μ 4-O) 4(μ 3-O) 4(μ-OMe) 4(μ 3-OR) 6(μ-OR) 6] 10+ core of representative complex 1 comprises a Mn II 4Mn III 4 double-cubane subunit attached on either side to two symmetry-related Mn IIMn III 3 defective dicubanes. A similar reaction of Mn(O 2CR) 2·4H 2O, hmpH, NaOCN and NEt 3, but in solvent MeCN, led instead to the formation of [Mn 18O 14(O 2CR) 18(hmp) 4(hmpH) 2(H 2O) 2] (R = Me (3), Et (4)). Compounds 3 and 4 are very similar to each other and can be described as a central [Mn III 4(μ-O) 6] rodlike subunit attached on either side to two symmetry-related [Mn 7O 9] subunits. Variable-temperature, solid-state dc and ac magnetic susceptibility studies revealed the presence of predominant antiferromagnetic exchange interactions in all compounds, and possible S = 2 or 1 (for 1 and 2) and S = 0 (for 3 and 4) ground state spin values. The combined results demonstrate the ability of cyanato groups to facilitate the formation of new polynuclear Mn II/III complexes with structures different than these obtained from the use of the related azides.« less

  15. Cyanate groups in higher oxidation state metal cluster chemistry: Mixed-valence (II/III) Mn 16 and Mn 18 clusters

    DOE PAGES

    Alexandropoulos, Dimitris I.; Moushi, Eleni E.; Papatriantafyllopoulou, Constantina; ...

    2015-12-02

    Here, the employment of cyanato (OCN -) group in high oxidation state manganese cluster chemistry, in conjunction with carboxylate ions and the organic chelating/bridging ligand 2-(hydroxymethyl)pyridine (hmpH), is reported. The syntheses, crystal structures, and magnetochemical characterization are described for [Mn 16O 8(OR) 4(OCN) 4(O 2CMe) 12(hmp) 6(ROH) 2] (R = Me (1), Et (2)) and [Mn 18O 14(O 2CR) 18(hmp) 4(hmpH) 2(H 2O) 2] (R = Me (3), Et (4)). The 2:1:1:1 reactions of Mn(O 2CMe) 2·4H 2O, hmpH, NaOCN and NEt 3 in solvent MeOH or EtOH afford the isostructural complexes [Mn 16O 8(OR) 4(OCN) 4(O 2CMe) 12(hmp) 6(ROH)more » 2] (R = Me (1), Et (2)). The [Mn 16(μ 4-O) 4(μ 3-O) 4(μ-OMe) 4(μ 3-OR) 6(μ-OR) 6] 10+ core of representative complex 1 comprises a Mn II 4Mn III 4 double-cubane subunit attached on either side to two symmetry-related Mn IIMn III 3 defective dicubanes. A similar reaction of Mn(O 2CR) 2·4H 2O, hmpH, NaOCN and NEt 3, but in solvent MeCN, led instead to the formation of [Mn 18O 14(O 2CR) 18(hmp) 4(hmpH) 2(H 2O) 2] (R = Me (3), Et (4)). Compounds 3 and 4 are very similar to each other and can be described as a central [Mn III 4(μ-O) 6] rodlike subunit attached on either side to two symmetry-related [Mn 7O 9] subunits. Variable-temperature, solid-state dc and ac magnetic susceptibility studies revealed the presence of predominant antiferromagnetic exchange interactions in all compounds, and possible S = 2 or 1 (for 1 and 2) and S = 0 (for 3 and 4) ground state spin values. The combined results demonstrate the ability of cyanato groups to facilitate the formation of new polynuclear Mn II/III complexes with structures different than these obtained from the use of the related azides.« less

  16. The effect of Ca2+ ions and ionic strength on Mn(II) oxidation by spores of the marine Bacillus sp. SG-1

    PubMed Central

    Tebo, Bradley M.

    2017-01-01

    Manganese(IV) oxides, believed to form primarily through microbial activities, are extremely important mineral phases in marine environments where they scavenge a variety of trace elements and thereby control their distributions. The presence of various ions common in seawater are known to influence Mn oxide mineralogy yet little is known about the effect of these ions on the kinetics of bacterial Mn(II) oxidation and Mn oxide formation. We examined factors affecting bacterial Mn(II) oxidation by spores of the marine Bacillus sp. strain SG-1 in natural and artificial seawater of varying ionic conditions. Ca2+ concentration dramatically affected Mn(II) oxidation, while Mg2+, Sr2+, K+, Na+ and NO3− ions had no effect. The rate of Mn(II) oxidation at 10mM Ca2+ (seawater composition) was four or five times that without Ca2+. The relationship between Ca2+ content and oxidation rate demonstrates that the equilibrium constant is small (on the order of 0.1) and the binding coefficient is 0.5. The pH optimum for Mn(II) oxidation changed depending on the amount of Ca2+ present, suggesting that Ca2+ exerts a direct effect on the enzyme perhaps as a stabilizing bridge between polypeptide components. We also examined the effect of varying concentrations of NaCl or KNO3 (0 mM – 2000 mM) on the kinetics of Mn(II) oxidation in solutions containing 10 mM Ca2+. Mn(II) oxidation was unaffected by changes in ionic strength (I) below 0.2, but it was inhibited by increasing salt concentrations above this value. Our results suggest that the critical coagulation concentration is around 200 mM of salt (I = ca. 0.2), and that the ionic strength of seawater (I > 0.2) accelerates the precipitation of Mn oxides around the spores. Under these conditions, the aggregation of Mn oxides reduces the supply of dissolved O2 and/or Mn2+ and inhibits the Mn(II) -> Mn(III) step controlling the enzymatic oxidation of Mn(II). Our results suggest that the hardness and ionic strength of the aquatic

  17. Improved electrochemical performance of spinel LiMn 1.5Ni 0.5O 4 through MgF 2 nano-coating

    DOE PAGES

    Wu, Qing; Zhang, Xiaoping; Sun, Shuwei; ...

    2015-07-08

    In this paper, a spinel LiMn 1.5Ni 0.5O 4 (LMNO) cathode material synthesized by a sol–gel method is modified by MgF 2 nano-coating via a wet coating strategy. The results of X-ray diffraction (XRD), Raman spectroscopy, field emission scanning electron microscopy (FESEM) and high resolution transmission electron microscopy (HRTEM) showed that the MgF 2 nano-coating layers do not physically change the bulk structure of the pristine material. Compared with the pristine compound, the MgF 2-coated LMNO electrodes display enhanced cycling stabilities. Particularly, the 5 wt% MgF 2-coated LMNO demonstrates the best reversibility, with a capacity retention of 89.9% after 100more » cycles, much higher than that of the pristine material, 69.3%. The dQ/dV analysis and apparent Li + diffusion coefficient calculation prove that the kinetic properties are enhanced after MgF 2 surface modification, which partly explains the improved electrochemical performances. Electrochemical impedance spectroscopy (EIS) and Fourier transform infrared spectroscopy (FTIR) data confirm that the MgF 2 coating layer helps in suppressing the fast growth of the solid electrolyte interface (SEI) film in repeated cycling, which effectively stabilizes the spinel structure. Finally and additionally, differential scanning calorimetry (DSC) tests show that the MgF 2 nano-coating layer also helps in enhancing the thermal stability of the LMNO cathode.« less

  18. Manganese-Chromium-Cyanide Clusters: Molecular MnCr 6(CN) 18 and Mn 3Cr 6(CN) 18 Species and a Related MnCr 3(CN) 9 Chain Compound

    NASA Astrophysics Data System (ADS)

    Heinrich, Julie L.; Sokol, Jennifer J.; Hee, Allan G.; Long, Jeffrey R.

    2001-07-01

    As part of an ongoing effort to design new single-molecule magnets, we are exploring synthetic routes to high-nuclearity metal-cyanide clusters. Here, we report the results of solution assembly reactions between [(Me3tacn)Cr(CN)3] (Me3tacn= N,N‧,N″-trimethyl-1,4,7-triazacyclononane) and selected manganese(II) salts. Reaction with the perchlorate salt in the presence of AClO4 (A=Na, K) gives A[(Me3tacn)6MnCr6(CN)18] (ClO4)3, featuring a heptanuclear cluster in which six [(Me3tacn)Cr(CN)3] units surround a central MnII ion. The Mn coordination geometry closely approaches a trigonal prism, with triangular faces twisted away from a fully eclipsed position by an angle of 12.8° and 11.3° for A=Na and K, respectively. The magnetic behavior of both compounds indicates weak antiferromagnetic coupling between neighboring MnII and CrIII centers (J=-3.0 and -3.1 cm-1, respectively) to give an S={13}/{2}; ground state. Alternatively, addition of sodium tetraphenylborate to the reaction solution yields [(Me3tacn)6(H2O)6Mn3Cr6(CN)18] (BPh4)6·12H2O, in which attachment of two MnII ions to the preceding cluster generates a new species with two trigonal bipyramids sharing a common vertex. This compound displays magnetic behavior consistent with weak antiferromagnetic coupling and an S={3}/{2} ground state. Finally, a reaction employing manganese(II) triflate is found to produce the one-dimensional solid [(Me3tacn)3MnCr3(CN)9](CF3SO3)2, exhibiting a closely related chain structure, and, again, weak antiferromagnetic coupling.

  19. Investigation of the mineralogy and the sorption mechanism of Ni, Cu, Co and Mo by turbostratic phyllomanganates of Mn-nodules from the eastern equatorial Pacific Ocean using XAS

    NASA Astrophysics Data System (ADS)

    Wegorzewski, A.; Webb, S.; Grangeon, S.; Kuhn, T.

    2016-12-01

    Mn-nodules are Mn-Fe (oxy)hydroxides bearing high amounts of economically important metals such as Ni, Cu, Co, Mo, as well as high field strength elements. According to that nodules are interesting for science and industry. Especially the sorption sites of metals (Ni, Cu, Mo) by the mineral phases are important to understand their coordination environment and further to tailor a specific metallurgical treatment in order to optimize the metal extraction procedure. Nodules used for this study were sampled from the German license area within the Clarion Clipperton Zone in the Pacific. These nodules grow on the seafloor in 4200 m depth by metal precipitation from oxic (hydrogenetic growth) and/or suboxic waters (suboxic diagenetic growth; Halbach et al., 1988). They show a complex texture characterized by irregular, concentrically banded nm- to µm-thick layered growth structures (LGS). Electronmicroprobe and X-ray diffraction analyses reveal: suboxic diagenetic LGS have high Mn/Fe ratios (9-826; Mn ≈ 40 wt. %; Fe ≈ 0.5 wt %), high Ni (0.3-2.6 wt %) and Cu (0.5-3.0 wt %) contents but low Co content (0.02±0.01 wt %). Mineralogically those LGS are turbostratic phyllomanganates (vernadite), which consist of [MnO6]-octahedral layers, separated from each other by cations (e.g., Na, Mg) and water in the interlayer, forming 7 and 10 Å phyllomanganates (Bode et al., 2007). In contrast hydrogenetic LGS show low Mn/Fe ratios (<5), low Ni+Cu content (<1 wt%) but enrichment in Co (≤0.5 wt%). Those LGS are of δ-MnO2, which is epitaxially intergrown with an amorphous FeOOH phase. In general, phyllomanganates have a high opportunity to incorporate metals due to their negative layer charge deficit cause by abundant isomorphic substitution of Mn4+ by Mn3+ and vacancies within MnO2 sheets. The negative charge deficit can be balanced by hydrated interlayer cations (e.g., Na, Mg) or due to metals adsorption at cation vacancy sites, incorporation into the MnO2 sheet and

  20. Enhancement of Mechanical Properties of Extruded Mg-9Al-1Zn-1MM-0.7CaO-0.3Mn Alloy Through Pre-aging Treatment

    NASA Astrophysics Data System (ADS)

    Jeong, Seok Hoan; Kim, Yong Joo; Kong, Kyung Ho; Cho, Tae Hee; Kim, Young Kyun; Lim, Hyun Kyu; Kim, Won Tae; Kim, Do Hyang

    2018-03-01

    The effect of pre-aging treatment before extrusion has been investigated in Mg-9.0Al-1.0Zn-1MM-0.7CaO-0.3Mn alloy. The as-cast microstructure consists of α-Mg dendrite with secondary solidification phase particles, (Mg, Al)2Ca, β-Mg17Al12 and Al11RE3 at the inter-dendritic region. After extrusion, β-Mg17Al12 precipitates are present, but higher density and more homogeneous distribution in pre-aged alloy. In addition, μm-scale banded bulk β-Mg17Al12 particles are generated during extrusion. Al11RE3 particles are broken into small particles, and are aligned along the extrusion direction. (Mg, Al)2Ca particles are only slightly elongated along the extrusion direction, providing stronger particle stimulated nucleation (PSN) effect by severe deformation during extrusion. The mechanical properties can be significantly enhanced by introducing pre-aging treatment, i.e. β-Mg17Al12 precipitates provide grain refining and strengthening effects and (Mg, Al)2Ca particles provide PSN effect.

  1. Leakage current phenomena in Mn-doped Bi(Na,K)TiO{sub 3}-based ferroelectric thin films

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Walenza-Slabe, J.; Gibbons, B. J., E-mail: brady.gibbons@oregonstate.edu

    2016-08-28

    Mn-doped 80(Bi{sub 0.5}Na{sub 0.5})TiO{sub 3}-20(Bi{sub 0.5}K{sub 0.5})TiO{sub 3} thin films were fabricated by chemical solution deposition on Pt/TiO{sub 2}/SiO{sub 2}/Si substrates. Steady state and time-dependent leakage current were investigated from room temperature to 180 °C. Undoped and low-doped films showed space-charge-limited current (SCLC) at high temperatures. The electric field marking the transition from Ohmic to trap-filling-limited current increased monotonically with Mn-doping. With 2 mol. % Mn, the current was Ohmic up to 430 kV/cm, even at 180 °C. Modeling of the SCLC showed that all films exhibited shallow trap levels and high trap concentrations. In the regime of steady state leakage, theremore » were also observations of negative differential resistivity and positive temperature coefficient of resistivity near room temperature. Both of these phenomena were confined to relatively low temperatures (below ∼60 °C). Transient currents were observed in the time-dependent leakage data, which was measured out to several hundred seconds. In the undoped films, these were found to be a consequence of oxygen vacancy migration modulating the electronic conductivity. The mobility and thermal activation energy for oxygen vacancies was extracted as μ{sub ion} ≈ 1.7 × 10{sup −12} cm{sup 2} V{sup −1} s{sup −1} and E{sub A,ion} ≈ 0.92 eV, respectively. The transient current displayed different characteristics in the 1 mol. % Mn-doped films which were not readily explained by oxygen vacancy migration.« less

  2. Influence of SaOS-2 cells on corrosion behavior of cast Mg-2.0Zn0.98Mn magnesium alloy.

    PubMed

    Witecka, Agnieszka; Yamamoto, Akiko; Święszkowski, Wojciech

    2017-02-01

    In this research, the effect of the presence of living cells (SaOS-2) on in vitro degradation of Mg-2.0Zn-0.98Mn (ZM21) magnesium alloy was examined by two methods simple immersion/cell culture tests and electrochemical measurements (electrochemical impedance spectroscopy and potentiodynamic polarization) under cell culture conditions. In immersion/cell culture tests, when SaOS-2 cells were cultured on ZM21 samples, pH of cell culture medium decreased, therefore weight loss and Mg 2+ ion release from the samples increased. Electrochemical measurements revealed the presence of living cells increased corrosion rate (I corr ) and decreased polarization resistance (R p ) after 48h of incubation. This acceleration of ZM21 corrosion can mainly be attributed to the decrease of medium pH due to cellular metabolic activities. Copyright © 2016 Elsevier B.V. All rights reserved.

  3. PVA/NaCl/MgO nanocomposites-microstructural analysis by whole pattern fitting method

    NASA Astrophysics Data System (ADS)

    Prashanth, K. S.; Mahesh, S. S.; Prakash, M. B. Nanda; Somashekar, R.; Nagabhushana, B. M.

    2018-04-01

    The nanofillers in the macromolecular matrix have displayed noteworthy changes in the structure and reactivity of the polymer nanocomposites. Novel functional materials usually consist of defects and are largely disordered. The intriguing properties of these materials are often attributed to defects. X-ray line profiles from powder diffraction reveal the quantitative information about size distribution and shape of diffracting domains which governs the contribution from small conventional X-ray diffraction (XRD) techniques to enumerate the microstructural information. In this study the MgO nanoparticles were prepared by solution combustion method and PVA/NaCl/MgO nanocomposite films were synthesized by the solvent cast method. Microstructural parameters viz crystal defects like stacking faults and twin faults, compositional inhomogeneity, crystallite size and lattice strain (g in %), were extracted using whole pattern fitting method.

  4. MnO2 Motor: A Prospective Cancer-Starving Therapy Promoter.

    PubMed

    Zhang, Yao-Hui; Qiu, Wen-Xiu; Zhang, Mingkang; Zhang, Lu; Zhang, Xian-Zheng

    2018-05-02

    Here, a tumor-targeted MnO 2 motor nanosystem (designed as MG/HA) was constructed by the assembly of glucose oxidase (GOD), manganese dioxide (MnO 2 ), and glycoprotein CD44-targeting polymer hyaluronic acid (HA) to elevate cancer-starving therapy efficacy in solid tumor. Upon the specific uptake of MG/HA by CD44 overexpressed cancer cells, GOD catalyzed the oxidation of glucose into gluconic acid and hydrogen peroxide (H 2 O 2 ) accompanying the consumption of oxygen (O 2 ). Meanwhile, MnO 2 would react with H 2 O 2 and acid to generate O 2 , which is in turn supplied to the glucose-depletion process, running like a loop. As a result, MnO 2 is displayed as a motor to promote the rate of glucose depletion that contributed to the starving therapy. In contrast to G/HA, MG/HA could not only achieve effective glucose consumption to depress cancer progression, but also alleviate hypoxia and reduce the expression of Glut1 to inhibit the metabolism for further restraining the tumor aggressiveness and metastasis. The concept of MnO 2 motor shows a promising prospect to overcome the restriction of the starving therapy.

  5. Structural characterization and magnetic properties of L10-MnAl films grown on different underlayers by molecular beam epitaxy

    NASA Astrophysics Data System (ADS)

    Takata, Fumiya; Gushi, Toshiki; Anzai, Akihito; Toko, Kaoru; Suemasu, Takashi

    2018-03-01

    We grow MnAl films on different underlayers by molecular beam epitaxy (MBE), and investigate their structural and magnetic properties. L10-ordered MnAl films were successfully grown both on an MgO(0 0 1) single-crystalline substrate and on an Mn4N(0 0 1) buffer layer formed on MgO(0 0 1) and SrTiO3(0 0 1) substrates. For the MgO substrate, post rapid thermal annealing (RTA) drastically improved the crystalline quality and the degree of L10-ordering, whereas no improvement in the crystallinity was achieved by altering the substrate temperature (TS) during MBE growth. However, high-quality L10-MnAl films were formed on the Mn4N buffer layer by simply varying TS. Structural analysis using X-ray diffraction showed MnAl on an MgO substrate had a cubic structure whereas MnAl on the Mn4N buffer had a tetragonal structure. This difference in crystal structure affected the magnetic properties of the MnAl films. The uniaxial magnetic anisotropy constant (Ku) was drastically improved by inserting an Mn4N buffer layer. We achieved a perpendicular magnetic anisotropy of Ku = 5.0 ± 0.7 Merg/cm3 for MnAl/Mn4N film on MgO and 6.0 ± 0.2 Merg/cm3 on STO. These results suggest that Mn4N has potential as an underlayer for L10-MnAl.

  6. The 18Ne(α,p)21Na breakout reaction in x-ray bursts: Experimental determination of spin-parities for α resonances in 22Mg via resonant elastic scattering of 21Na+p

    NASA Astrophysics Data System (ADS)

    He, J. J.; Zhang, L. Y.; Parikh, A.; Xu, S. W.; Yamaguchi, H.; Kahl, D.; Kubono, S.; Hu, J.; Ma, P.; Chen, S. Z.; Wakabayashi, Y.; Sun, B. H.; Wang, H. W.; Tian, W. D.; Chen, R. F.; Guo, B.; Hashimoto, T.; Togano, Y.; Hayakawa, S.; Teranishi, T.; Iwasa, N.; Yamada, T.; Komatsubara, T.

    2013-07-01

    The 18Ne(α,p)21Na reaction provides a pathway for breakout from the hot CNO cycles to the rp process in type-I x-ray bursts. To better determine this astrophysical reaction rate, the resonance parameters of the compound nucleus 22Mg have been investigated by measuring the resonant elastic scattering of 21Na+p. An 89 MeV 21Na radioactive ion beam was produced at the CNS Radioactive Ion Beam Separator and bombarded an 8.8 mg/cm2 thick polyethylene target. The recoiled protons were measured at scattering angles of θc.m.≈175∘ and 152∘ by three ΔE-E silicon telescopes. The excitation function was obtained with a thick-target method over energies Ex(22Mg) = 5.5-9.2 MeV. The resonance parameters have been determined through an R-matrix analysis. For the first time, the Jπ values for ten states above the α threshold in 22Mg have been experimentally determined in a single consistent measurement. We have made three new Jπ assignments and confirmed seven of the ten tentative assignments in the previous work. The 18Ne(α,p)21Na reaction rate has been recalculated, and the astrophysical impact of our new rate has been investigated through one-zone postprocessing x-ray burst calculations. We find that the 18Ne(α,p)21Na rate significantly affects the peak nuclear energy generation rate and the onset temperature of this breakout reaction in these phenomena.

  7. Synthesis and first use of pyridine-2,6-diylbis(pyrazine-2-ylmethanone) in metal cluster chemistry: a {Mn(III)3Na2} complex with an ideal trigonal bipyramidal geometry.

    PubMed

    Giannopoulos, Dimosthenis P; Wilson-Konderka, Cody; Gagnon, Kevin J; Teat, Simon J; Escuer, Albert; Metallinos, Costa; Stamatatos, Theocharis C

    2015-03-07

    The successful organic synthesis of a new dipyrazole/pyridine-dicarbonyl organic molecule, namely pyridine-2,6-diylbis(pyrazine-2-ylmethanone) [(pz)CO(py)CO(pz)], followed by its employment in Mn coordination chemistry has yielded the neutral cluster compound [Mn3Na2O(N3)3(L)3] (1), where L(2-) is the (pz)C(CH2COCH3)(O(-))(py)C(CH2COCH3)(O(-))(pz) dianion. The latter group was formed in situ, presumably by the nucleophilic attack of the carbanion (-)CH2COCH3 to the carbonyl carbon atoms of (pz)CO(py)CO(pz), in the presence of Mn(n+) ions under basic conditions and in solvent Me2CO. Complex 1 possesses an almost ideal trigonal bipyramidal topology, with the two Na(I) ions occupying the apical positions and the three Mn(III) ions residing in the equatorial trigonal plane. The bridging ligation about the metal ions is provided by a μ3-O(2-) ion and six μ-OR(-) groups from the L(2-) ligand, while peripheral ligation is completed by three terminal azido groups and the pyridine N and carbonyl O atoms of L(2-). Magnetic susceptibility studies revealed the presence of predominant antiferromagnetic exchange interactions between the paramagnetic Mn(III) centres; the use of an anisotropic, equilateral Mn(III)3 triangle model allowed us to fit the magnetic data and obtain the best-fit parameters: J = -10.8 cm(-1), D = -5.3 cm(-1), and g = 1.99. The combined results demonstrate the rich chemical reactivity of carbonyl groups and the ability of poly-ketone ligands to stabilize cluster compounds with unprecedented structural motifs and interesting architectures.

  8. Improving the characteristics of foundry alloys AlSiCuMg during manufacturing

    NASA Astrophysics Data System (ADS)

    Fragoso, Bruno Filipe Marques

    As piroxenas sao um vasto grupo de silicatos minerais encontrados em muitas rochas igneas e metamorficas. Na sua forma mais simples, estes silicatos sao constituidas por cadeias de SiO3 ligando grupos tetrahedricos de SiO4. A formula quimica geral das piroxenas e M2M1T2O6, onde M2 se refere a catioes geralmente em uma coordenacao octaedrica distorcida (Mg2+, Fe2+, Mn2+, Li+, Ca2+, Na+), M1 refere-se a catioes numa coordenacao octaedrica regular (Al3+, Fe3+, Ti4+, Cr3+, V3+, Ti3+, Zr4+, Sc3+, Zn2+, Mg2+, Fe2+, Mn2+), e T a catioes em coordenacao tetrahedrica (Si4+, Al3+, Fe3+). As piroxenas com estrutura monoclinica sao designadas de clinopiroxenes. A estabilidade das clinopyroxenes num espectro de composicoes quimicas amplo, em conjugacao com a possibilidade de ajustar as suas propriedades fisicas e quimicas e a durabilidade quimica, tem gerado um interesse mundial devido a suas aplicacoes em ciencia e tecnologia de materiais. Este trabalho trata do desenvolvimento de vidros e de vitro-cerâmicos baseadas de clinopiroxenas para aplicacoes funcionais. O estudo teve objectivos cientificos e tecnologicos; nomeadamente, adquirir conhecimentos fundamentais sobre a formacao de fases cristalinas e solucoes solidas em determinados sistemas vitro-cerâmicos, e avaliar a viabilidade de aplicacao dos novos materiais em diferentes areas tecnologicas, com especial enfase sobre a selagem em celulas de combustivel de oxido solido (SOFC). Com este intuito, prepararam-se varios vidros e materiais vitro-cerâmicos ao longo das juntas Enstatite (MgSiO3) - diopsidio (CaMgSi2O6) e diopsidio (CaMgSi2O6) - Ca - Tschermak (CaAlSi2O6), os quais foram caracterizados atraves de um vasto leque de tecnicas. Todos os vidros foram preparados por fusao-arrefecimento enquanto os vitro-cerâmicos foram obtidos quer por sinterizacao e cristalizacao de fritas, quer por nucleacao e cristalizacao de vidros monoliticos. Estudaram-se ainda os efeitos de varias substituicoes ionicas em composicoes de

  9. Mendigite, Mn2Mn2MnCa(Si3O9)2, a new mineral species of the bustamite group from the Eifel volcanic region, Germany

    NASA Astrophysics Data System (ADS)

    Chukanov, N. V.; Aksenov, S. M.; Rastsvetaeva, R. K.; Van, K. V.; Belakovskiy, D. I.; Pekov, I. V.; Gurzhiy, V. V.; Schüller, W.; Ternes, B.

    2015-12-01

    A new mineral, mendigite (IMA no. 2014-007), isostructural with bustamite, has been found in the In den Dellen pumice quarry near Mendig, Laacher Lake area, Eifel Mountains, Rhineland-Palatinate (Rheinland-Pfalz), Germany. Associated minerals are sanidine, nosean, rhodonite, tephroite, magnetite, and a pyrochlore-group mineral. Mendigite occurs as clusters of long-prismatic crystals (up to 0.1 × 0.2 × 2.5 mm in size) in cavities within sanidinite. The color is dark brown with a brown streak. Perfect cleavage is parallel to (001). D calc = 3.56 g/cm3. The IR spectrum shows the absence of H2O and OH groups. Mendigite is biaxial (-), α = 1.722 (calc), β = 1.782(5), γ = 1.796(5), 2 V meas = 50(10)°. The chemical composition (electron microprobe, mean of 4 point analyses, the Mn2+/Mn3+ ratio determined from structural data and charge-balance constraints) is as follows (wt %): 0.36 MgO, 10.78 CaO, 37.47 MnO, 2.91 Mn2O3, 4.42 Fe2O3, 1.08 Al2O3, 43.80 SiO2, total 100.82. The empirical formula is Mn2.00(Mn1.33Ca0.67) (Mn0.50 2+ Mn0.28 3+ Fe0.15 3+ Mg0.07)(Ca0.80 (Mn0.20 2+)(Si5.57 Fe0.27 3+ Al0.16O18). The idealized formula is Mn2Mn2MnCa(Si3O9)2. The crystal structure has been refined for a single crystal. Mendigite is triclinic, space group Pbar 1; the unit-cell parameters are a = 7.0993(4), b = 7.6370(5), c = 7.7037(4) Å, α = 79.58(1)°, β = 62.62(1)°, γ = 76.47(1)°; V = 359.29(4) Å3, Z = 1. The strongest reflections on the X-ray powder diffraction pattern [ d, Å ( I, %) ( hkl)] are: 3.72 (32) (020), 3.40 (20) (002, 021), 3.199 (25) (012), 3.000 (26), (01bar 2, 1bar 20), 2.885 (100) (221, 2bar 11, 1bar 21), 2.691 (21) (222, 2bar 10), 2.397 (21) (02bar 2, 21bar 1, 203, 031), 1.774 (37) (412, 3bar 21). The type specimen is deposited in the Fersman Mineralogical Museum, Russian Academy of Sciences, Moscow, registration number 4420/1.

  10. Magnetic properties of Mg12O12 nanocage doped with transition metal atoms (Mn, Fe, Co and Ni): DFT study

    NASA Astrophysics Data System (ADS)

    Javan, Masoud Bezi

    2015-07-01

    Binding energy of the Mg12O12 nanocage doped with transition metals (TM=Mn, Fe, Co and Ni) in endohedrally, exohedrally and substitutionally forms were studied using density functional theory with the generalized gradient approximation exchange-correlation functional along 6 different paths inside and outside of the Mg12O12 nanocage. The most stable structures were determined with full geometry optimization near the minimum of the binding energy curves of all the examined paths inside and outside of the Mg12O12 nanocage. The results reveal that for all stable structures, the Ni atom has a larger binding energy than the other TM atoms. It is also found that for all complexes additional peaks contributed by TM-3d, 4s and 4p states appear in the highest occupied molecular orbital (HOMO) and the lowest unoccupied molecular orbital (LUMO) gap of the host MgO cluster. The mid-gap states are mainly due to the hybridization between TM-3d, 4s and 4p orbitals and the cage π orbitals. The magnetic moment of the endohedrally doped TM atoms in the Mg12O12 are preserved to some extent due to the interaction between the TM and Mg12O12 nanocage, in contrast to the completely quenched magnetic moment of the Fe and Ni atoms in the Mg11(TM)O12 complexes. Furthermore, charge population analysis shows that charge transfer occurs from TM atom to the cage for endohedrally and substitutionally doping.

  11. In-Situ and Real-time Monitoring of Mechanochemical Preparation of Li2 Mg(NH2 BH3 )4 and Na2 Mg(NH2 BH3 )4 and Their Thermal Dehydrogenation.

    PubMed

    Biliškov, Nikola; Borgschulte, Andreas; Užarević, Krunoslav; Halasz, Ivan; Lukin, Stipe; Milošević, Sanja; Milanović, Igor; Novaković, Jasmina Grbović

    2017-11-16

    For the first time, in situ monitoring of uninterrupted mechanochemical synthesis of two bimetallic amidoboranes, M 2 Mg(NH 2 BH 3 ) 4 (M=Li, Na), by means of Raman spectroscopy, has been applied. This approach allowed real-time observation of key intermediate phases, and a straightforward follow-up of the reaction course. Detailed analysis of time-dependent spectra revealed a two-step mechanism through MNH 2 BH 3 ⋅NH 3 BH 3 adducts as key intermediate phases which further reacted with MgH 2 , giving M 2 Mg(NH 2 BH 3 ) 4 as final products. The intermediates partially take a competitive pathway toward the oligomeric M(BH 3 NH 2 BH 2 NH 2 BH 3 ) phases. The crystal structure of the novel bimetallic amidoborane Li 2 Mg(NH 2 BH 3 ) 4 was solved from high-resolution powder diffraction data and showed an analogous metal coordination to Na 2 Mg(NH 2 BH 3 ) 4 , but a significantly different crystal packing. Li 2 Mg(NH 2 BH 3 ) 4 thermally dehydrogenates releasing highly pure H 2 in the amount of 7 wt.%, and at a lower temperature then its sodium analogue, making it significantly more viable for practical applications. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  12. Phase equilibria in the NaF-CdO-NaPO3 system at 873 K and crystal structure and physico-chemical characterizations of the new Na2CdPO4F fluorophosphate

    NASA Astrophysics Data System (ADS)

    Aboussatar, Mohamed; Mbarek, Aïcha; Naili, Houcine; El-Ghozzi, Malika; Chadeyron, Geneviève; Avignant, Daniel; Zambon, Daniel

    2017-04-01

    Isothermal sections of the diagram representing phase relationships in the NaF-CdO-NaPO3 system have been investigated by solid state reactions and powder X-ray diffraction. This phase diagram investigation confirms the polymorphism of the NaCdPO4 side component and the structure of the ß high temperature polymorph (orthorhombic, space group Pnma and unit cell parameters a=9.3118(2), b=7.0459(1), c=5.1849(1) Å has been refined. A new fluorophosphate, Na2CdPO4F, has been discovered and its crystal structure determined and refined from powder X-ray diffraction data. It exhibits a new 3D structure with orthorhombic symmetry, space group Pnma and unit cell parameters a=5.3731(1), b=6.8530(1), c=12.2691(2) Å. The structure is closely related to those of the high temperature polymorph of the nacaphite Na2CaPO4F and the fluorosilicate Ca2NaSiO4F but differs essentially in the cationic repartition since the structure is fully ordered with one Na site (8d) and one Cd site (4c). Relationships with other Na2MIIPO4F (MII=Mg, Ca, Mn, Fe, Co, Ni) have been examined and the crystal-chemical and topographical analysis of these fluorophosphates is briefly reviewed. IR, Raman, optical and 19F, 23Na, 31P MAS NMR characterizations of Na2CdPO4F have been investigated.

  13. Sodium p-Aminosalicylic Acid Reverses Sub-Chronic Manganese-Induced Impairments of Spatial Learning and Memory Abilities in Rats, but Fails to Restore γ-Aminobutyric Acid Levels.

    PubMed

    Li, Shao-Jun; Ou, Chao-Yan; He, Sheng-Nan; Huang, Xiao-Wei; Luo, Hai-Lan; Meng, Hao-Yang; Lu, Guo-Dong; Jiang, Yue-Ming; Vieira Peres, Tanara; Luo, Yi-Ni; Deng, Xiang-Fa

    2017-04-10

    Excessive manganese (Mn) exposure is not only a health risk for occupational workers, but also for the general population. Sodium para-aminosalicylic acid (PAS-Na) has been successfully used in the treatment of manganism, but the involved molecular mechanisms have yet to be determined. The present study aimed to investigate the effects of PAS-Na on sub-chronic Mn exposure-induced impairments of spatial learning and memory, and determine the possible involvements of γ-aminobutyric acid (GABA) metabolism in vivo. Sprague-Dawley male rats received daily intraperitoneal injections MnCl₂ (as 6.55 mg/kg Mn body weight, five days per week for 12 weeks), followed by daily subcutaneous injections of 100, 200, or 300 mg/kg PAS-Na for an additional six weeks. Mn exposure significantly impaired spatial learning and memory ability, as noted in the Morris water maze test, and the following PAS-Na treatment successfully restored these adverse effects to levels indistinguishable from controls. Unexpectedly, PAS-Na failed to recover the Mn-induced decrease in the overall GABA levels, although PAS-Na treatment reversed Mn-induced alterations in the enzyme activities directly responsible for the synthesis and degradation of GABA (glutamate decarboxylase and GABA-transaminase, respectively). Moreover, Mn exposure caused an increase of GABA transporter 1 (GAT-1) and decrease of GABA A receptor (GABA A ) in transcriptional levels, which could be reverted by the highest dose of 300 mg/kg PAS-Na treatment. In conclusion, the GABA metabolism was interrupted by sub-chronic Mn exposure. However, the PAS-Na treatment mediated protection from sub-chronic Mn exposure-induced neurotoxicity, which may not be dependent on the GABA metabolism.

  14. Sodium p-Aminosalicylic Acid Reverses Sub-Chronic Manganese-Induced Impairments of Spatial Learning and Memory Abilities in Rats, but Fails to Restore γ-Aminobutyric Acid Levels

    PubMed Central

    Li, Shao-Jun; Ou, Chao-Yan; He, Sheng-Nan; Huang, Xiao-Wei; Luo, Hai-Lan; Meng, Hao-Yang; Lu, Guo-Dong; Jiang, Yue-Ming; Vieira Peres, Tanara; Luo, Yi-Ni; Deng, Xiang-Fa

    2017-01-01

    Excessive manganese (Mn) exposure is not only a health risk for occupational workers, but also for the general population. Sodium para-aminosalicylic acid (PAS-Na) has been successfully used in the treatment of manganism, but the involved molecular mechanisms have yet to be determined. The present study aimed to investigate the effects of PAS-Na on sub-chronic Mn exposure-induced impairments of spatial learning and memory, and determine the possible involvements of γ-aminobutyric acid (GABA) metabolism in vivo. Sprague-Dawley male rats received daily intraperitoneal injections MnCl2 (as 6.55 mg/kg Mn body weight, five days per week for 12 weeks), followed by daily subcutaneous injections of 100, 200, or 300 mg/kg PAS-Na for an additional six weeks. Mn exposure significantly impaired spatial learning and memory ability, as noted in the Morris water maze test, and the following PAS-Na treatment successfully restored these adverse effects to levels indistinguishable from controls. Unexpectedly, PAS-Na failed to recover the Mn-induced decrease in the overall GABA levels, although PAS-Na treatment reversed Mn-induced alterations in the enzyme activities directly responsible for the synthesis and degradation of GABA (glutamate decarboxylase and GABA-transaminase, respectively). Moreover, Mn exposure caused an increase of GABA transporter 1 (GAT-1) and decrease of GABA A receptor (GABAA) in transcriptional levels, which could be reverted by the highest dose of 300 mg/kg PAS-Na treatment. In conclusion, the GABA metabolism was interrupted by sub-chronic Mn exposure. However, the PAS-Na treatment mediated protection from sub-chronic Mn exposure-induced neurotoxicity, which may not be dependent on the GABA metabolism. PMID:28394286

  15. Na-doped La0.7Ca0.3MnO3 compounds exhibiting a large magnetocaloric effect near room temperature

    NASA Astrophysics Data System (ADS)

    Chi Linh, Dinh; Thi Ha, Nguyen; Huu Duc, Nguyen; Giang Nam, Le Huu; Bau, Le Viet; Manh An, Nguyen; Yu, Seong-Cho; Dang Thanh, Tran

    2018-03-01

    In this work, we have investigated the magnetic properties and the magnetocaloric effect of La0.7-xNaxCa0.3MnO3 compounds, which were prepared by a conventional solid-state reaction technique. The Rietveld refinement results suggested that the samples are single phase belonging to an orthorhombic structure (space group Pnma). Analyzing temperature dependence of magnetization M(T) revealed that the Curie temperature (TC) increases with increasing Na content (x). Their TC value is found to be 260-298 K for x=0.0-0.1, respectively. Base on M(T) data measured at different applied magnetic fields (H), temperature dependence of magnetic entropy change ΔSm(T) data for all the samples was calculated by using a phenomenological model. In the vicinity of TC, -ΔSm(T) curve reaches a maximum value (denoted as |ΔSmax|), which gradually increases with increasing H. Under 12 kOe, the value of |ΔSmax| is in a range of 1.47-5.19 J/kg K corresponding to the relative cooling power RCP=57.12-75.88 J/kg. Applied the universal master curve method for the magnetic entropy change, we concluded that Na-doped in La0.7-xNaxCa0.3MnO3 compounds leads to modification the nature of the magnetic phase transition from the first- to the second-order.

  16. [Properties and localization of Mg- and Ca-ATpase activities in wheat embryo cell nuclei].

    PubMed

    Vasil'eva, N A; Belkina, G G; Stepanenko, S Y; Atalykova, F I; Oparin, A I

    1978-05-01

    The isolated nuclei of wheat embryo possess the ATPase activity. The addition of Mg2+ and Ca2+ significantly increases the activities of nuclear ATPases, whereas Hg2+, Cu2+ and Mn2+ inhibit the activity. The activating effect of Mg2+ is enhanced by an addition of Na and K ions. The activity of wheat embryo nuclear Mg-ATPase is higher than its Ca-ATPase activity; both ATPases also differ in their pH optima. Separation of total nuclear protein according to the solubility of its individual protein components in wheat and strong salt solutions, using the detergents, as well as ammonium sulfate precipitation and dialysis do not result in separation of Mg-activated and Ca-activated ATPases, although their levels of activities and ratios change in the course of fractionation. The Mg- and Ca-ATPase activities of the wheat embryo nuclei were found in the nuclear fraction of albumin, in nonhistone proteins and nuclear membranes. In the albumin nuclear fraction and subfractions of non-histone proteins the higher level of activity is observed in Ca-ATPase, whereas in the nuclei and soluble fractions of residual proteins in Mg-ATPase.

  17. Effect of solution treatment on the microstructure, tensile properties, and corrosion behavior of the Mg-5Sn-2Zn-0.1Mn alloy

    NASA Astrophysics Data System (ADS)

    El Mahallawy, N.; Hammouda, R.; Shoeib, M.; Diaa, Alia A.

    2018-01-01

    Working on magnesium alloys containing relatively inexpensive alloying elements such as tin, zinc, and manganese have been a target for many studies. The binary Mg-Sn and Mg-Zn systems have a wide range of solid solubility which make them heat-treatable alloys. In the present study, the microstructure, tensile properties, and corrosion behavior of the Mg-5Sn-2Zn-0.1Mn alloy was studied in the as cast state and after heat treatment at a temperature reaching 450 °C for about 24 h. It was found that a noticeable enhancement in strength and corrosion resistance was achieved through heat treatment. The strength of the as cast alloy increased from 76.24 ± 6.21 MPa to 187.33 ± 10.3 MPa, while the corrosion rate decreased from 1.129 to 0.399 mm y-1.

  18. (Sr{sub 1-x}Na{sub x})(Cd{sub 1-x}Mn{sub x}){sub 2}As{sub 2}: A new charge and spin doping decoupled diluted magnetic semiconductors with CaAl{sub 2}Si{sub 2}-type structure

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Chen, Bijuan; Deng, Zheng; Li, Wenmin

    2016-08-28

    We report the synthesis and characterization of a new bulk diluted ferromagnetic semiconductor via Na and Mn co-doping in SrCd{sub 2}As{sub 2} with a hexagonal CaAl{sub 2}Si{sub 2}-type structure. Together with carrier doping via (Sr,Na) substitution, spin doping via (Cd,Mn) substitution results in ferromagnetic order with Curie temperature of T{sub C} up to 13 K. Negative magnetoresistance is assigned to weak localization at low temperatures, where the magnetization of samples becomes saturated. The hexagonal structure of (Sr{sub 1−x}Na{sub x})(Cd{sub 1−x}Mn{sub x}){sub 2}As{sub 2} can be acted as a promising candidate for spin manipulations owing to its relatively small coercive field ofmore » less than 24 Oe.« less

  19. Mn-Cr isotopic systematics of Chainpur chondrules and bulk ordinary chondrites

    NASA Technical Reports Server (NTRS)

    Nyquist, L.; Lindstrom, D.; Wiesmann, H.; Bansal, B.; Shih, C.-Y.; Mittlefehldt, D.; Martinez, R.; Wentworth, S.

    1994-01-01

    We report on ongoing study of the Mn-Cr systematics of individual Chainpur (LL3.4) chondrules and compare the results to those for bulk ordinary chondrites. Twenty-eight chondrules were surveyed for abundances of Mn, Cr, Na, Fe, Sc, Hf, Ir, and Zn by INAA. Twelve were chosen for SEM/EDX and high-precision Cr-isotopic studies on the basis of LL-chondrite-normalized Mn(LL), Sc(LL), (Mn/Fe)(LL), and (Sc/Fe)(LL) as well as their Mn/Cr ratios. Classification into textural types follows from SEM/EDX examination of interior surfaces.

  20. Luminescence and thermal stability tuning in (Ba,Mn)3(Gd,Y)Na(PO4)5F:Eu2+ phosphors via cation-substitution

    NASA Astrophysics Data System (ADS)

    Mei, Juan; Lv, Lemin; Gao, Junsong; Wei, Yi; Feng, Yuxin; Yan, Chunjie; Li, Guogang

    2018-04-01

    In this work, [Y3+-Gd3+] and [Mn2+-Ba2+] substitutions were designed in Ba3GdNa(PO4)5F:Eu2+ system, which were marked as BG1-xYxNPF:Eu2+ and B1-yMyGNPF:Eu2+, respectively. It is found that their luminescence properties and thermal stability could be obviously tuned. For BG1-xYxNPF:Eu2+ series, under 365 nm UV light, the emission spectra exhibited a continuous red-shift from 458 nm (x = 0) to 485 nm (x = 1) with the corresponding luminescence varying from blue light to cyan light. For B1-yMyGNPF:Eu2+ series, it was observed the coexistence of blue-green and enhanced red emission of Eu2+ and the appearance of Eu3+ emission when Mn2+ partly substituted Ba2+, resulting in a final white emission. In addition, the thermal stabilities of B1-yMyGNPF:Eu2+ were obviously improved with Mn2+ doping. The corresponding luminescence and thermal stability tuning mechanisms were investigated.

  1. Spectro-photometric determinations of Mn, Fe and Cu in aluminum master alloys

    NASA Astrophysics Data System (ADS)

    Rehan; Naveed, A.; Shan, A.; Afzal, M.; Saleem, J.; Noshad, M. A.

    2016-08-01

    Highly reliable, fast and cost effective Spectro-photometric methods have been developed for the determination of Mn, Fe & Cu in aluminum master alloys, based on the development of calibration curves being prepared via laboratory standards. The calibration curves are designed so as to induce maximum sensitivity and minimum instrumental error (Mn 1mg/100ml-2mg/100ml, Fe 0.01mg/100ml-0.2mg/100ml and Cu 2mg/100ml-10mg/ 100ml). The developed Spectro-photometric methods produce accurate results while analyzing Mn, Fe and Cu in certified reference materials. Particularly, these methods are suitable for all types of Al-Mn, Al-Fe and Al-Cu master alloys (5%, 10%, 50% etc. master alloys).Moreover, the sampling practices suggested herein include a reasonable amount of analytical sample, which truly represent the whole lot of a particular master alloy. Successive dilution technique was utilized to meet the calibration curve range. Furthermore, the workout methods were also found suitable for the analysis of said elements in ordinary aluminum alloys. However, it was observed that Cush owed a considerable interference with Fe, the later one may not be accurately measured in the presence of Cu greater than 0.01 %.

  2. Fluor-ferro-leakeite, NaNa2(FC2+2Fe3+2Li)Si8O22F2, a new alkali amphibole from the Canada Pinabete pluton, Questa, New Mexico, U.S.A.

    USGS Publications Warehouse

    Hawthorne, F.C.; Oberti, R.; Ungaretti, L.; Ottolini, L.; Grice, Joel D.; Czamanske, G.K.

    1996-01-01

    Fluor-ferro-leakeite is a new amphibole species from the Canada Pinabete pluton, Questa, New Mexico, U.S.A.; it occurs in association with quartz, alkali feldspar, acmite, ilmenite, and zircon. It forms as anhedral bluish black crystals elongated along c and up to 1 mm long. It is brittle, H = 6, Dmeas = 3.37 g/cm3, Dcalc = 3.34 g/cm3. In plane-polarized light, it is strongly pleochroic, X = very dark indigo blue, Y = gray blue, Z = yellow green; X ??? c = 10?? (in ??obtuse), Y = b, Z ??? a = 4?? (in ?? obtuse), with absorption X > Y > Z. Fluor-ferro-leakeite is biaxial positive, ?? = 1.675(2), ??= 1.683(2), ?? = 1.694(1); 2V = 87(2)??; dispersion is not visible because of the strong absorption. Fluor-ferro-leakeite is monoclinic, space group C2/m, a = 9.792(1), b = 17.938(1), c = 5.3133(4) A??, ??= 103.87(7)??, V = 906.0(1) A??3, Z = 2. The ten strongest X-ray diffraction lines in the powder pattern are [d(I,hkl)]: 2.710(100,151), 2.536(92,202), 3.404(57,131), 4.481(54,040), 8.426(45,110), 2.985(38,241), 2.585(38,061), 3.122(29,310), 2.165(26,261), and 1.586(25,403). Analysis by a combination of electron microprobe, ion microprobe, and crystal-structure refinement (Hawthorne et al. 1993) gives SiO2 51.12, Al2O3 1.13, TiO2 0.68, Fe2O3 16.73, FeO 8.87, MgO 2.02, MnO 4.51, ZnO 0.57, CaO 0.15, Na2O 9.22, K2O 1.19, Li2O 0.99, F 2.87, H2Ocalc 0.60, sum 99.44 wt%. The formula unit, calculated on the basis of 23 O atoms, is (K0.23Na0.76)(Na1.97Ca0.03)(Mg 0.46Fe2+1.4Mn2+0.59Zn0.07Fe3+1.93-Ti 0.08Al0.02Li0.61])(Si7.81Al 0.19)O22(F1.39OH0.61). A previous crystal-structure refinement (Hawthorne et al. 1993) shows Li to be completely ordered at the M3 site. Fluor-ferro-leakeite, ideally NaNa2(Fe2+2Fe3+2Li)Si8O22F2, is related to leakeite, NaNa2(Mg2Fe3+3Li)Si 8O22(OH)2, by the substitutions Fe2+ ??? Mg and F ??? OH.

  3. Cross sections for He and Ne isotopes in natural Mg, Al, and Si, He isotopes in CaF2, Ar isotopes in natural Ca, and radionuclides in natural Al, Si, Ti, Cr, and stainless steel induced by 12- to 45-MeV protons

    NASA Technical Reports Server (NTRS)

    Walton, J. R.; Heymann, D.; Yaniv, A.; Edgerley, D.; Rowe, M. W.

    1976-01-01

    Stacks of thin Mg, Al, Si, Ca, CaF2, Ti, and stainless steel foils were bombarded in twelve irradiations by a variable energy cyclotron. Cross sections are reported for He and Ne in natural Mg, Al, and Si, and for He in CaF2, and for Ar in natural Ca, as determined from mass spectrometer analysis of the inert gases. In addition, cross sections of Na-22 in natural Al and Si, of V-48 in natural Ti, and of Cr-51, Mn-52, and Co-57 in stainless steel are reported. From these were deduced Cr-51 and Mn-52 cross sections in natural Cr.

  4. Metal Binding by the D,DX35E Motif of Human Immunodeficiency Virus Type 1 Integrase: Selective Rescue of Cys Substitutions by Mn2+ In Vitro

    PubMed Central

    Gao, Kui; Wong, Steven; Bushman, Frederic

    2004-01-01

    The D,DX35E motif characteristic of retroviral integrase enzymes (INs) is expected to bind the required metal cofactors (Mg2+ or Mn2+), but direct evidence for a catalytic role has been lacking. Here we used a metal rescue strategy to investigate metal binding. We established conditions for analysis of an activity of IN, disintegration, in both Mg2+ and Mn2+, and tested IN mutants with cysteine substitutions in each acidic residue of the D,DX35E motif. Mn2+ but not Mg2+ can bind tightly to Cys, so if metal binding at the acidic residues is mechanistically important, it is expected that the Cys-substituted enzymes would be active in the presence of Mn2+ only. Of the three acidic residues, a strong metal rescue effect was obtained for D116C, a weaker rescue was seen for D64C, and no rescue was seen with E152C. Modest rescue could also be detected for D116C in normal integration in vitro. Comparison to Ser and Ala substitutions at D116 established that the rescue was selective for Cys. Further studies of the response to pH suggest that the metal cofactor may stabilize the deprotonated nucleophile active in catalysis, and studies of the response to NaCl titrations disclose an additional role for the metal cofactor in stabilizing the IN-DNA complex. PMID:15194746

  5. Perpendicular magnetic anisotropy in Mn2CoAl thin film

    NASA Astrophysics Data System (ADS)

    Sun, N. Y.; Zhang, Y. Q.; Fu, H. R.; Che, W. R.; You, C. Y.; Shan, R.

    2016-01-01

    Heusler compound Mn2CoAl (MCA) is attracting more attentions due to many novel properties, such as high resistance, semiconducting behavior and suggestion as a spin-gapless material with a low magnetic moment. In this work, Mn2CoAl epitaxial thin film was prepared on MgO(100) substrate by magnetron sputtering. The transport property of the film exhibits a semiconducting-like behavior. Moreover, our research reveals that perpendicular magnetic anisotropy (PMA) can be induced in very thin Mn2CoAl films resulting from Mn-O and Co-O bonding at Mn2CoAl/MgO interface, which coincides with a recent theoretical prediction. PMA and low saturation magnetic moment could lead to large spin-transfer torque with low current density in principle, and thus our work may bring some unanticipated Heusler compounds into spintronics topics such as the domain wall motion and the current-induced magnetization reversal.

  6. Concentration dependence of Li+/Na+ diffusion in manganese hexacyanoferrates

    NASA Astrophysics Data System (ADS)

    Takachi, Masamitsu; Fukuzumi, Yuya; Moritomo, Yutaka

    2016-06-01

    Manganese hexacyanoferrates (Mn-HCFs) with a jungle-gym-type structure are promising cathode materials for Li+/Na+ secondary batteries (LIBs/SIBs). Here, we investigated the diffusion constants D Li/D Na of Li+/Na+ against the Li+/Na+ concentration x Na/x Li and temperature (T) of A 1.32Mn[Fe(CN)6]0.833.6H2O (A = Li and Na). We evaluated the activation energy E\\text{a}\\text{Li}/E\\text{a}\\text{Na} of D Li/D Na against x Na/x Li. We found that E\\text{a}\\text{Na} steeply increases with x Na from 0.41 eV at x Na = 0.69 to 0.7 eV at 1.1. The increase in E\\text{a}\\text{Na} is ascribed to the occupancy effect of the Na+ site. The increase in E\\text{a}\\text{Li} is suppressed, probably because the number of Li+ sites is three times that of Na+ sites.

  7. High-frequency electron-spin-resonance measurements on Mn x Mg1-x O (x = 1.0×10-4) and DPPH at very low temperatures

    NASA Astrophysics Data System (ADS)

    Ishikawa, Y.; Ohya, K.; Miura, S.; Fujii, Y.; Mitsudo, S.; Mizusaki, T.; Fukuda, A.; Matsubara, A.; Kikuchi, H.; Asano, T.; Yamamori, H.; Lee, S.; Vasiliev, S.

    2018-03-01

    We have developed a millimeter-wave electron-spin-resonance (ESR) system for very low temperatures (T < 1 K) that can be employed for nuclear-magnetic-resonance measurements by using dynamic nuclear polarization. The system uses a Fabry-Pérot resonator that works in the frequency range of 125 – 130 GHz and covers the temperature range of 0.09 – 6.5 K. We have performed ESR measurements in the frequency around 128 GHz by using Mn x Mg1-x O (x = 1.0 × 10-4) and free-radical samples of 1, 1-diphenyl-2-picrylhydrazyl (DPPH), because these samples have been proposed as field and sensitivity markers. Temperature dependence of the ESR signal intensity for Mn x Mg1-x O shows anomalies originating from magnetic order are found around 3.5 – 4 K. We estimate the sensitivity of the system for ESR detections to be 6 × 1013 spins/G at 5.8 K. Because DPPH shows no observable shift in the magnetic field, we propose it as a useful standard marker for ESR measurements at very low temperatures.

  8. Siudaite, Na8(Mn2+ 2Na)Ca6Fe3+ 3Zr3NbSi25O74(OH)2Cl·5H2O: a new eudialyte-group mineral from the Khibiny alkaline massif, Kola Peninsula

    NASA Astrophysics Data System (ADS)

    Chukanov, Nikita V.; Rastsvetaeva, Ramiza K.; Kruszewski, Łukasz; Aksenov, Sergey M.; Rusakov, Vyacheslav S.; Britvin, Sergey N.; Vozchikova, Svetlana A.

    2018-03-01

    The new eudialyte-group mineral siudaite, ideally Na8(Mn2+ 2Na)Ca6Fe3+ 3Zr3NbSi25O74(OH)2Cl·5H2O, was discovered in a peralkaline pegmatite situated at the Eveslogchorr Mt., Khibiny alkaline massif, Kola Peninsula, Russia. The associated minerals are aegirine, albite, microcline, nepheline, astrophyllite, and loparite-(Ce). Siudaite forms yellow to brownish-yellow equant anhedral grains up to 1.5 cm across. Its lustre is vitreous, and the streak is white. Cleavage is none observed. The Mohs' hardness is 4½. Density measured by hydrostatic weighing is 2.96(1) g/cm3. Density calculated using the empirical formula is equal to 2.973 g/cm3. Siudaite is nonpleochroic, optically uniaxial, negative, with ω = 1.635(1) and ɛ = 1.626(1) (λ = 589 nm). The IR spectrum is given. The chemical composition of siudaite is (wt%; electron microprobe, H2O determined by HCN analysis): Na2O 8.40, K2O 0.62, CaO 9.81, La2O3 1.03, Ce2O3 1.62, Pr2O3 0.21, Nd2O3 0.29, MnO 6.45, Fe2O3 4.51. TiO2 0.54, ZrO2 11.67, HfO2 0.29, Nb2O5 2.76, SiO2 47.20, Cl 0.54, H2O 3.5, -O = Cl - 0.12, total 99.32. According to Mössbauer spectroscopy data, all iron is trivalent. The empirical formula (based on 24.5 Si atoms pfu, in accordance with structural data) is [Na7.57(H2O)1.43]Σ9(Mn1.11Na0.88Ce0.31La0.20Nd0.05Pr0.04K0.41)Σ3(H2O)1.8(Ca5.46Mn0.54)Σ6(Fe3+ 1.76Mn2+ 1.19)Σ2.95Nb0.65(Ti0.20Si0.50)Σ0.71(Zr2.95Hf0.04Ti0.01)Σ3Si24.00Cl0.47O70(OH)2Cl0.47·1.82H2O. The crystal structure was determined using single-crystal X-ray diffraction data. The new mineral is trigonal, space group R3m, with a = 14.1885(26) Å, c = 29.831(7) Å, V = 5200.8(23) Å3 and Z = 3. Siudaite is chemically related to georgbarsanovite and is its analogue with Fe3+-dominant M2 site. The strongest lines of the powder X-ray diffraction pattern [d, Å (I, %) (hkl)] are: 6.38 (60) (-114), 4.29 (55) (-225), 3.389 (47) (131), 3.191 (63) (-228). 2.963 (100) (4-15), 2.843 (99) (-444), 2.577 (49) (3-39). Siudaite is named after the Polish

  9. Electrodeposition and Characterization of Mn-Cu-Zn Alloys for Corrosion Protection Coating

    NASA Astrophysics Data System (ADS)

    Tsurtsumia, Gigla; Gogoli, David; Koiava, Nana; Kakhniashvili, Izolda; Jokhadze, Nunu; Lezhava, Tinatin; Nioradze, Nikoloz; Tatishvili, Dimitri

    2017-12-01

    Mn-Cu-Zn alloys were electrodeposited from sulphate bath, containing citrate or EDTA and their mixtures as complexing ligands. The influence of bath composition and deposition parameters on alloys composition, cathodic current efficiency and structural and electrochemical properties were studied. At a higher current density (≥ 37.5 A dm-2) a uniform surface deposit of Mn-Cu-Zn was obtained. Optimal pH of electrolyte (0.3 mol/dm3Mn2+ + 0.6 mol/dm3 (NH4)2SO4 +0.1 mol/dm3Zn2++0.005 mol/dm3 Cu2++ 0.05mol/dm3Na3Cit + 0.15mol/dm3 EDTA; t=300C; τ=20 min) for silvery, nonporous coating of Mn-Cu-Zn alloy was within 6.5-7.5; coating composition: 71-83% Mn, 6-7.8% Cu, 11.5-20% Zn, current efficiency up to 40%. XRD patterns revealed BCT (body centred tetragonal) γ-Mn solid phase solution (lattice constants a=2.68 Å c=3.59 Å). Corrosion measurements of deposited alloys were performed in aerated 3.5% NaCl solution. The corrosion current density (icorr) of the electrodeposited alloys on carbon steel was 10 times lower than corrosion rate of pure zinc and manganese coatings. Triple alloy coatings corrosion potential (Ecorr = -1140 mV vs. Ag/AgCl) preserved negative potential value longer (more than three months) compared to carbon steel substrate (Ecorr = -670 mV vs. Ag/AgCl). Tafel polarization curves taken on Mn-Cu-Zn alloy coating in aerated 3.5% NaCl solution did not show a typical passivation behaviour which can be explained by formation oflow solubility of adherent corrosion products on the alloy surface. Corrosion test of Mn-Cu-Zn electrocoating in chlorine environment shows that it is the best cathodic protective coating for a steel product.

  10. Inhibition of ATPase activity in rat synaptic plasma membranes by simultaneous exposure to metals.

    PubMed

    Carfagna, M A; Ponsler, G D; Muhoberac, B B

    1996-03-08

    Inhibition of Na+/K+-ATPase and Mg2+-ATPase activities by in vitro exposure to Cd2+, Pb2+ and Mn2+ was investigated in rat brain synaptic plasma membranes (SPMs). Cd2+ and Pb2+ produced a larger maximal inhibition of Na+/K+-ATPase than of Mg2+-ATPase activity. Metal concentrations causing 50% inhibition of Na+/K+-ATPase activity (IC50 values) were Cd2+ (0.6 microM) < Pb2+ (2.1 microM) < Mn2+ (approximately 3 mM), and the former two metals were substantially more potent in inhibiting SPM versus synaptosomal Na+/K+-ATPase. Dixon plots of SPM data indicated that equilibrium binding of metals occurs at sites causing enzyme inhibition. In addition, IC50 values for SPM K+-dependent p-nitrophenylphosphatase inhibition followed the same order and were Cd2+ (0.4 microM) < Pb2+ (1.2 microM) < Mn2+ (300 microM). Simultaneous exposure to the combinations Cd2+/Mn2+ or Pb2+/Mn2+ inhibited SPM Na+/K+-ATPase activity synergistically (i.e., greater than the sum of the metal-induced inhibitions assayed separately), while Cd2+/Pb2+ caused additive inhibition. Simultaneous exposure to Cd2+/Pb2+ antagonistically inhibited Mg2+-ATPase activity while Cd2+/Mn2+ or Pb2+/Mn2+ additively inhibited Mg2+-ATPase activity at low Mn2+ concentrations, but inhibited antagonistically at higher concentrations. The similar IC50 values for Cd2+ and Pb2+ versus Mn2+ inhibition of Na+/K+-ATPase and the pattern of inhibition/activation upon exposure to two metals simultaneously support similar modes of interaction of Cd2+ and Pb2+ with this enzyme, in agreement with their chemical reactivities.

  11. High-Capacity Mg-Organic Batteries Based on Nanostructured Rhodizonate Salts Activated by Mg-Li Dual-Salt Electrolyte.

    PubMed

    Tian, Jing; Cao, Dunping; Zhou, Xuejun; Hu, Jiulin; Huang, Minsong; Li, Chilin

    2018-04-24

    A magnesium battery is a promising candidate for large-scale transportation and stationary energy storage due to the security, low cost, abundance, and high volumetric energy density of a Mg anode. But there are still some obstacles retarding the wide application of Mg batteries, including poor kinetics of Mg-ion transport in lattices and low theoretical capacity in inorganic frameworks. A Mg-Li dual-salt electrolyte enables kinetic activation by dominant intercalation of Li-ions instead of Mg-ions in cathode lattices without the compromise of a stable Mg anode process. Here we propose a Mg-organic battery based on a renewable rhodizonate salt ( e. g., Na 2 C 6 O 6 ) activated by a Mg-Li dual-salt electrolyte. The nanostructured organic system can achieve a high reversible capacity of 350-400 mAh/g due to the existence of high-density carbonyl groups (C═O) as redox sites. Nanocrystalline Na 2 C 6 O 6 wired by reduced graphene oxide enables a high-rate performance of 200 and 175 mAh/g at 2.5 (5 C) and 5 A/g (10 C), respectively, which also benefits from a high intrinsic diffusion coefficient (10 -12 -10 -11 cm 2 /s) and pesudocapacitance contribution (>60%) of Na 2 C 6 O 6 for Li-Mg co-intercalation. The suppressed exfoliation of C 6 O 6 layers by a firmer non-Li pinning via Na-O-C or Mg-O-C and a dendrite-resistive Mg anode lead to a long-term cycling for at least 600 cycles. Such an extraordinary capacity/rate performance endows the Mg-Na 2 C 6 O 6 system with high energy and power densities up to 525 Wh/kg and 4490 W/kg (based on active cathode material), respectively, exceeding the level of high-voltage insertion cathodes with typical inorganic structures.

  12. Na4Mn9O18/Carbon Nanotube Composite as a High Electrochemical Performance Material for Aqueous Sodium-Ion Batteries.

    PubMed

    Yin, Fuxing; Liu, Zhengjun; Yang, Shuang; Shan, Zhenzhen; Zhao, Yan; Feng, Yuting; Zhang, Chengwei; Bakenov, Zhumabay

    2017-10-17

    The aqueous sodium-ion battery (ASIB) is one of the promising new energy storage systems owing to the abundant resources of sodium as well as efficiency and safety of electrolyte. Herein, we report an ASIB system with Na 4 Mn 9 O 18 /carbon nanotube (NMO/CNT) as cathode, metal Zn as anode and a novel Na + /Zn 2+ mixed ion as electrolyte. The NMO/CNT with microspherical structure is prepared by a simple spray-drying method. The prepared battery delivers a high reversible specific capacity and stable cyclability. Furthermore, the battery displays a stable reversible discharge capacity of 53.2 mAh g -1 even at a high current rate of 4 C after 150 cycles. Our results confirm that the NMO/CNT composite is a promising electrode cathode material for ASIBs.

  13. Perpendicular magnetic anisotropy in Mn{sub 2}CoAl thin film

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Sun, N. Y.; Zhang, Y. Q.; Che, W. R.

    Heusler compound Mn{sub 2}CoAl (MCA) is attracting more attentions due to many novel properties, such as high resistance, semiconducting behavior and suggestion as a spin-gapless material with a low magnetic moment. In this work, Mn{sub 2}CoAl epitaxial thin film was prepared on MgO(100) substrate by magnetron sputtering. The transport property of the film exhibits a semiconducting-like behavior. Moreover, our research reveals that perpendicular magnetic anisotropy (PMA) can be induced in very thin Mn{sub 2}CoAl films resulting from Mn-O and Co-O bonding at Mn{sub 2}CoAl/MgO interface, which coincides with a recent theoretical prediction. PMA and low saturation magnetic moment could leadmore » to large spin-transfer torque with low current density in principle, and thus our work may bring some unanticipated Heusler compounds into spintronics topics such as the domain wall motion and the current-induced magnetization reversal.« less

  14. Green thermal-assisted synthesis and characterization of novel cellulose-Mg(OH)2 nanocomposite in PEG/NaOH solvent.

    PubMed

    Ponomarev, Nikolai; Repo, Eveliina; Srivastava, Varsha; Sillanpää, Mika

    2017-11-15

    Synthesis of nanocomposites was performed using microcrystalline cellulose (MCC), MgCl 2 in PEG/NaOH solvent by a thermal-assisted method at different temperatures by varying time and the amount of MCC. Results of XRD, FTIR, and EDS mapping showed that the materials consisted of only cellulose (CL) and magnesium hydroxide (MH). According to FTIR and XRD, it was found that crystallinity of MH in cellulose nanocomposites is increased with temperature and heating time and decreased with increasing of cellulose amount. The PEG/NaOH solvent has a significant effect on cellulose and Mg(OH) 2 morphology. BET and BJH results demonstrated the effects of temperature and cellulose amount on the pore size corresponding to mesoporous materials. TG and DTG analyses showed the increased thermal stability of cellulose nanocomposites with increasing temperature. TEM and SEM analyses showed an even distribution of MH nanostructures with various morphology in the cellulose matrix. The cellulose presented as the polymer matrix in the nanocomposites. It was supposed the possible interaction between cellulose and Mg(OH) 2 . The novel synthesis method used in this study is feasible, cost-efficient and environmentally friendly. Copyright © 2017 Elsevier Ltd. All rights reserved.

  15. Secondary Al-Si-Mg High-pressure Die Casting Alloys with Enhanced Ductility

    NASA Astrophysics Data System (ADS)

    Bösch, Dominik; Pogatscher, Stefan; Hummel, Marc; Fragner, Werner; Uggowitzer, Peter J.; Göken, Mathias; Höppel, Heinz Werner

    2015-03-01

    Al-Si-Mg-based secondary cast alloys are attractive candidates for thin-walled high-pressure die castings for applications in the transport industry. The present study investigates the effect of manganese additions at high cooling rates on microstructure, mechanical properties, and on the dominating fracture mechanisms of alloy AlSi10Mg with an elevated iron concentration. Systematic variations of the Mn content from 0.20 to 0.85 wt pct at a constant Fe content of 0.55 wt pct illustrate the key changes in type, phase fraction, and shape of the Fe-containing intermetallic phases, and the corresponding influence on the alloy's ductility. For high-pressure die casting (HPDC), an optimal range of the Mn content between 0.40 and 0.60 wt pct, equivalent to a Mn/Fe ratio of approximately 1, has been identified. At these Mn and Fe contents, the high cooling rates obtained in HPDC result in the formation of fine and homogeneously distributed α-Al15(Fe,Mn)3Si2 phase, and crack initiation is transferred from AlFeSi intermetallics to eutectic silicon. The study interprets the microstructure-property relationship in the light of thermodynamic calculations which reveal a significant increase in undercooling of the α-Al15(Fe,Mn)3Si2 phase with increased Mn content. It concludes that the interdependence of the well-defined Mn/Fe ratio and the high cooling rate in HPDC can generate superior ductility in secondary AlSi10Mg cast alloys.

  16. Content and Bioaccumulation of Nine Mineral Elements in Ten Mushroom Species of the Genus Boletus

    PubMed Central

    Wang, Xue-Mei; Zhang, Ji; Li, Tao; Wang, Yuan-Zhong; Liu, Hong-Gao

    2015-01-01

    Concentrations and bioconcentration potential of nine elements (Ca, Cu, Fe, K, Mg, Mn, Na, P, and Zn) in ten species of wild edible Boletus and the corresponding underlying soils were analyzed. The analyses were performed using inductively coupled plasma atomic emission spectrophotometer. Boletus showed relative abundant contents of P, K, Fe, Mg, Ca, and Na and less of Zn, Cu, and Mn. Caps compared to stalks were enriched in P, K, Cu, Mg, and Zn, while stalks were enriched in Mn. The elements such as P and K were accumulated (BCF > 1), while Ca, Fe, Mg, Mn, and Na were excluded (BCF < 1) in the fruiting bodies. The correlation analysis indicated high correlations between Cu, Mn, Ca, and Fe in the mushrooms as compared to the corresponding soils. Significant correlations were also obtained between Cu-P (r = 0.775), Fe-P (r = 0.728), and Zn-P (r = 0.76) for caps and Cu-Mg (r = 0.721), Fe-Mg (r = 0.719), Zn-Mg (r = 0.824), and Zn-P (r = 0.818) for stalks. The results of this study imply that ability of fungi to accumulate elements from substrate could be influenced by mushroom species and underlying soil substrates. PMID:26146585

  17. Content and Bioaccumulation of Nine Mineral Elements in Ten Mushroom Species of the Genus Boletus.

    PubMed

    Wang, Xue-Mei; Zhang, Ji; Li, Tao; Wang, Yuan-Zhong; Liu, Hong-Gao

    2015-01-01

    Concentrations and bioconcentration potential of nine elements (Ca, Cu, Fe, K, Mg, Mn, Na, P, and Zn) in ten species of wild edible Boletus and the corresponding underlying soils were analyzed. The analyses were performed using inductively coupled plasma atomic emission spectrophotometer. Boletus showed relative abundant contents of P, K, Fe, Mg, Ca, and Na and less of Zn, Cu, and Mn. Caps compared to stalks were enriched in P, K, Cu, Mg, and Zn, while stalks were enriched in Mn. The elements such as P and K were accumulated (BCF > 1), while Ca, Fe, Mg, Mn, and Na were excluded (BCF < 1) in the fruiting bodies. The correlation analysis indicated high correlations between Cu, Mn, Ca, and Fe in the mushrooms as compared to the corresponding soils. Significant correlations were also obtained between Cu-P (r = 0.775), Fe-P (r = 0.728), and Zn-P (r = 0.76) for caps and Cu-Mg (r = 0.721), Fe-Mg (r = 0.719), Zn-Mg (r = 0.824), and Zn-P (r = 0.818) for stalks. The results of this study imply that ability of fungi to accumulate elements from substrate could be influenced by mushroom species and underlying soil substrates.

  18. Effects of Mg doping on the remarkably enhanced electrochemical performance of Na 3V 2(PO 4) 3 cathode materials for sodium ion batteries

    DOE PAGES

    Li, Hui; Yu, Xiqian; Bai, Ying; ...

    2015-01-01

    Na 3V 2-xMg x(PO 4) 3/C composites with different Mg 2+ doping contents (x=0, 0.01, 0.03, 0.05, 0.07 and 0.1) were prepared by a facile sol-gel method. The doping effects on the crystal structure were investigated by XRD, XPS and EXAFS. The results show that low dose doping Mg 2+ does not alter the structure of the material, and magnesium is successfully substituted for vanadium site. The Mg doped Na 3V 2-xMg x(PO 4) 3/C composites exhibit significant improvements on the electrochemistry performances in terms of the rate capability and cycle performance, especially for the Na 3V 1.95Mg 0.05(PO 4)more » 3/C. For example, when the current density increased from 1 C to 30 C, the specific capacity only decreased from 112.5 mAh g-1 to 94.2 mAh g -1 showing very good rate capability. Moreover, even cycling at a high rate of 20 C, an excellent capacity retention of 81% is maintained from the initial value of 106.4 mAh g-1 to 86.2 mAh g-1 at the 50th cycle. Enhanced rate capability and cycle performance can be attributed to the optimized particle size, structural stability and enhanced ionic and electronic conductivity induced by Mg doping.« less

  19. Vibrational spectroscopic characterization of the phosphate mineral ludlamite (Fe,Mn,Mg)₃(PO₄)₂⋅4H₂O - a mineral found in lithium bearing pegmatites.

    PubMed

    Frost, Ray L; Xi, Yunfei; Scholz, Ricardo; Belotti, Fernanda M

    2013-02-15

    The objective of this work is to analyze ludlamite (Fe,Mn,Mg)(3)(PO(4))(2)⋅4H(2)O from Boa Vista mine, Galiléia, Brazil and to assess the molecular structure of the mineral. The phosphate mineral ludlamite has been characterized by EMP-WDS, Raman and infrared spectroscopic measurements. The mineral is shown to be a ferrous phosphate with some minor substitution of Mg and Mn. Raman bands at 917 and 950 cm(-1) are assigned to the symmetric stretching mode of HOPO(3)(2-) and PO(4)(3-) units. Raman bands at 548, 564, 599 and 634 cm(-1) are assigned to the ν(4)PO(4)(3-) bending modes. Raman bands at 2605, 2730, 2896 and 3190 cm(-1) and infrared bands at 2623, 2838, 3136 and 3185 cm(-1) are attributed to water stretching vibrations. By using a Libowitzky empirical function, hydrogen bond distances are calculated from the OH stretching wavenumbers. Strong hydrogen bonds in the structure of ludlamite are observed as determined by their hydrogen bond distances. The application of infrared and Raman spectroscopy to the study of ludlamite enables the molecular structure of the pegmatite mineral ludlamite to be assessed. Copyright © 2012 Elsevier B.V. All rights reserved.

  20. Synthesis of LaMnO3 in molten chlorides: effect of preparation conditions.

    PubMed

    Vradman, Leonid; Zana, Jonatan; Kirschner, Alon; Herskowitz, Moti

    2013-07-14

    LaMnO3 perovskite was successfully synthesized in molten chlorides. In order to explore the effect of the molten salt type, NaCl-KCl and LiCl-KCl eutectic mixtures were employed as a liquid medium for the perovskite formation process. The synthesis included heating the La-nitrate, Mn-nitrate and chlorides mixture to above the melting point of the corresponding chlorides. This procedure yielded a LaMnO3 phase integrated in the fused chloride matrix. Washing with water removed the salts completely, yielding pure LaMnO3 perovskite crystals. The synthesis without molten salt at 800 °C yielded several by-products in addition to the LaMnO3 phase, while with LiCl-KCl the pure perovskite phase was obtained at temperatures as low as 600 °C. Variation of temperature in the range 600-800 °C for LiCl-KCl and 700-800 °C for NaCl-KCl had no significant effect either on the morphology or on the particle size of the product. On the other hand, the effect of the molten salt type on the morphology and size of perovskite particles was remarkable. The synthesis in NaCl-KCl resulted in sub-micron LaMnO3 particles with shapes that range from truncated hexahedrons to spheres, while in LiCl-KCl mostly cubic particles of up to 2-microns were obtained. The effect of the molten salt type on LaMnO3 perovskite formation is explained based on the nucleation and crystal growth model and difference in the melting point of eutectic mixtures.

  1. Monte Carlo and Ab-initio calculation of TM (Ti, V, Cr, Mn, Fe, Co, Ni) doped MgH2 hydride: GGA and SIC approximation

    NASA Astrophysics Data System (ADS)

    Salmani, E.; Laghrissi, A.; Laamouri, R.; Benchafia, E.; Ez-Zahraouy, H.; Benyoussef, A.

    2017-02-01

    MgH2: TM (TM: V, Cr, Mn, Fe, Co, Ni) based dilute magnetic semiconductors (DMS) are investigated using first principle calculations. Our results show that the ferromagnetic state is stable when TM introduces magnetic moments as well as intrinsic carriers in TM: Co, V, Cr, Ti; Mg0.95TM0.05H2. Some of the DMS Ferro magnets under study exhibit a half-metallic behavior, which make them suitable for spintronic applications. The double exchange is shown to be the underlying mechanism responsible for the magnetism of such materials. The exchange interactions obtained from first principle calculations and used in a classical Ising model by a Monte Carlo approach resulted in ferromagnetic states with Curie temperatures within the ambient conditions.

  2. Mosaic expression of claudins in thick ascending limbs of Henle results in spatial separation of paracellular Na+ and Mg2+ transport

    PubMed Central

    Wulfmeyer, Vera Christine; Drewell, Hoora; Mutig, Kerim; Hou, Jianghui; Breiderhoff, Tilman; Müller, Dominik; Fromm, Michael; Bleich, Markus; Günzel, Dorothee

    2017-01-01

    The thick ascending limb (TAL) of Henle’s loop drives paracellular Na+, Ca2+, and Mg2+ reabsorption via the tight junction (TJ). The TJ is composed of claudins that consist of four transmembrane segments, two extracellular segments (ECS1 and -2), and one intracellular loop. Claudins interact within the same (cis) and opposing (trans) plasma membranes. The claudins Cldn10b, -16, and -19 facilitate cation reabsorption in the TAL, and their absence leads to a severe disturbance of renal ion homeostasis. We combined electrophysiological measurements on microperfused mouse TAL segments with subsequent analysis of claudin expression by immunostaining and confocal microscopy. Claudin interaction properties were examined using heterologous expression in the TJ-free cell line HEK 293, live-cell imaging, and Förster/FRET. To reveal determinants of interaction properties, a set of TAL claudin protein chimeras was created and analyzed. Our main findings are that (i) TAL TJs show a mosaic expression pattern of either cldn10b or cldn3/cldn16/cldn19 in a complex; (ii) TJs dominated by cldn10b prefer Na+ over Mg2+, whereas TJs dominated by cldn16 favor Mg2+ over Na+; (iii) cldn10b does not interact with other TAL claudins, whereas cldn3 and cldn16 can interact with cldn19 to form joint strands; and (iv) further claudin segments in addition to ECS2 are crucial for trans interaction. We suggest the existence of at least two spatially distinct types of paracellular channels in TAL: a cldn10b-based channel for monovalent cations such as Na+ and a spatially distinct site for reabsorption of divalent cations such as Ca2+ and Mg2+. PMID:28028216

  3. Serum concentration of Na, K, Ca, Mg, P, Zn and Cu in patients with essential arterial hypertension.

    PubMed

    Uza, G; Pavel, O; Kovacs, A; Uza, D; Vlaicu, R

    1984-01-01

    Serum concentration of Na, K, Ca, Mg and inorganic phosphate as well as serum levels of Zn and Cu were determined in control subjects and in patients with essential arterial hypertension (EAH) divided according to the stage of the disease. No significant differences were found between the serum mean levels of Na, K, Ca, Mg, Zn and Cu in controls and in patients with EAH. A significant decrease of the serum Zn was noted in the third stage of EAH. A number of cases with hypomagnesemia and/or hypopotassemia probably caused by a long term uncontrolled therapy was also detected. The concentration of inorganic phosphate was significantly lower in patients with EAH associated with overweight than in hypertensive patients with normal body weight and in controls. It is considered that a sustained study of the complex interrelationship between electrolyte interaction and the functional aspects of the arterial wall could still contribute to a better understanding of pathogenic aspects of EAH and of its complications including those subsequent to modern diuretic therapy.

  4. On the entropy of glaucophane Na2Mg3Al2Si8O22(OH)2

    USGS Publications Warehouse

    Robie, R.A.; Hemingway, B.S.; Gillet, P.; Reynard, B.

    1991-01-01

    The heat capacity of glaucophane from the Sesia-Lanza region of Italy having the approximate composition (Na1.93Ca0.05Fe0.02) (Mg2.60Fe0.41) (Al1.83Fe0.15Cr0.01) (Si7.92Al0.08)O22(OH)2 was measured by adiabatic calorimetry between 4.6 and 359.4 K. After correcting the Cp0data to values for ideal glaucophane, Na2Mg3Al2Si8O22(OH)2 the third-law entropy S2980-S00was calculated to be 541.2??3.0 J??mol-1??K-1. Our value for S2980-S00is 12.0 J??mol-1??K-1 (2.2%) smaller than the value of Likhoydov et al. (1982), 553.2??3.0, is within 6.2 J??mol-1??K-1 of the value estimated by Holland (1988), and agrees remarkably well with the value calculated by Gillet et al. (1989) from spectroscopic data, 539 J??mol-1??K-1. ?? 1991 Springer-Verlag.

  5. Effect of Homogenization on Microstructure Characteristics, Corrosion and Biocompatibility of Mg-Zn-Mn-xCa Alloys

    PubMed Central

    Li, Jingyuan; Lai, Huiying; Xu, Yuzhao

    2018-01-01

    The corrosion behaviors of Mg-2Zn-0.2Mn-xCa (denoted as MZM-xCa alloys) in homogenization state have been investigated by immersion test and electrochemical techniques in a simulated physiological condition. The microstructure features were characterized using scanning electron microscopy (SEM), X-ray diffraction (XRD), transmission electron microscopy (TEM) and electron probe microanalysis (EPMA), and the corrosion mechanism was illustrated using atomic force microscope (AFM), X-ray photoelectron spectroscopy (XPS) and confocal laser scanning microscopy (CLSM). The electrochemical and immersion test verify the MZM-0.38% Ca owns the best corrosion performance with the corrosion rate of 6.27 mm/year. Furthermore, the film layer of MZM-0.38% Ca is more compact and denser than that of others. This improvement could be associated with the combined effects of the suitable content of Zn/Ca dissolving into the α-Mg matrix and the modification of Ca-containing compounds by heat-treatment. However, the morphologies were transformed from uniform corrosion to localized pitting corrosion with Ca further addition. It could be explained that the excessive Ca addition can strengthen the nucleation driving force for the second phase formation, and the large volumes fraction of micro-galvanic present interface sites accelerate the nucleation driving force for corrosion propagation. In addition, in vitro biocompatibility tests also show the MZM-0.38% Ca was safe to bone mesenchymal stem cells (BMSCs) and was promising to be utilized as implant materials. PMID:29389894

  6. Up-conversion monodispersed spheres of NaYF4:Yb3+/Er3+: green and red emission tailoring mediated by heating temperature, and greatly enhanced luminescence by Mn2+ doping.

    PubMed

    Zhu, Qi; Song, Caiyun; Li, Xiaodong; Sun, Xudong; Li, Ji-Guang

    2018-04-09

    Submicron sized, monodispersed spheres of Mn2+, Yb3+/Er3+ and Mn2+/Yb3+/Er3+ doped α-NaYF4 were easily autoclaved from mixed solutions of the component nitrates and ammonium fluoride (NH4F), in the presence of EDTA-2Na. Detailed characterizations of the resultant phosphors were obtained using XRD, Raman spectroscopy, FE-SEM, HR-TEM, STEM, PLE/PL spectroscopy, and fluorescence decay analysis. Finer structure and better crystal perfection was observed at a higher calcination temperature, and the spherical shape and excellent dispersion of the original particles was retained at temperatures up to 600 °C. Under the 980 nm infrared excitation, the Yb3+/Er3+-doped sample (calcined at 400 °C) exhibits a stronger green emission centered at ∼524 nm (2H11/2 → 4I15/2 transition of Er3+) and a weaker red emission centered at ∼657 nm (4F9/2 → 4I15/2 transition of Er3+). A 200 °C increase in the temperature from 400 °C to 600 °C resulted in the dominant red emission originating from the 4F9/2 → 4I15/2 transition of Er3+, instead of the previously dominant green one. Mn2+ doping induced a remarkable more enhanced intensity at ∼657 nm and ∼667 nm (red emission area) than that at ∼524 nm and ∼546 nm (green emission area), because of the non-radiative energy transfer between Mn2+ and Er3+. However, a poor thermal stability was induced by Mn2+ doping. The observed upconversion luminescence of the samples calcined at 400 °C and 600 °C followed the two photon process and the four photon process, respectively.

  7. Efficient removal of arsenic from water using a granular adsorbent: Fe-Mn binary oxide impregnated chitosan bead.

    PubMed

    Qi, Jianying; Zhang, Gaosheng; Li, Haining

    2015-10-01

    A novel sorbent of Fe-Mn binary oxide impregnated chitosan bead (FMCB) was fabricated through impregnating Fe-Mn binary oxide into chitosan matrix. The FMCB is sphere-like with a diameter of 1.6-1.8 mm, which is effective for both As(V) and As(III) sorption. The maximal sorption capacities are 39.1 and 54.2 mg/g, respectively, outperforming most of reported granular sorbents. The arsenic was mainly removed by adsorbing onto the Fe-Mn oxide component. The coexisting SO4(2-), HCO3(-) and SiO3(2-) have no great influence on arsenic sorption, whereas, the HPO4(2-) shows negative effects. The arsenic-loaded FMCB could be effectively regenerated using NaOH solution and repeatedly used. In column tests, about 1500 and 3200 bed volumes of simulated groundwater containing 233 μg/L As(V) and As(III) were respectively treated before breakthrough. These results demonstrate the superiority of the FMCB in removing As(V) and As(III), indicating that it is a promising candidate for arsenic removal from real drinking water. Copyright © 2015 Elsevier Ltd. All rights reserved.

  8. Bioleaching of zinc and manganese from spent Zn-Mn batteries and mechanism exploration.

    PubMed

    Xin, Baoping; Jiang, Wenfeng; Aslam, Hina; Zhang, Kai; Liu, Changhao; Wang, Renqing; Wang, Yutao

    2012-02-01

    In this work, bioleaching was used to extract valuable Zn and Mn from spent Zn-Mn batteries. The results showed that 96% of Zn extraction was achieved within 24h regardless of energy source types and bioleaching bacteria species. However, initial pH had a remarkable influence on Zn release, extraction dose sharply decreased from 2200 to 500mg/l when the initial pH value increased from 1.5 to 3.0 or higher. In contrast to Zn, all the tested factors evidently affected Mn extraction; the maximum released dose of 3020mg/l was obtained under the optimum conditions. The acidic dissolution by biogenic H(2)SO(4) by the non-contact mechanism was responsible for Zn extraction, while Mn extraction was owed to both contact/biological and non-contact mechanisms. The combined action of acidic dissolution of soluble Mn(2+) by biogenic H(2)SO(4) and reductive dissolution of insoluble Mn(4+) by Fe(2+) resulted in 60% of Mn extraction, while contact of microbial cells with the spent battery material and incubation for more than 7days was required to achieve the maximum extraction of Mn. Copyright © 2011 Elsevier Ltd. All rights reserved.

  9. Synthetic nanocomposite MgH2/5 wt. % TiMn2 powders for solid-hydrogen storage tank integrated with PEM fuel cell.

    PubMed

    El-Eskandarany, M Sherif; Shaban, Ehab; Aldakheel, Fahad; Alkandary, Abdullah; Behbehani, Montaha; Al-Saidi, M

    2017-10-16

    Storing hydrogen gas into cylinders under high pressure of 350 bar is not safe and still needs many intensive studies dedic ated for tank's manufacturing. Liquid hydrogen faces also severe practical difficulties due to its very low density, leading to larger fuel tanks three times larger than traditional gasoline tank. Moreover, converting hydrogen gas into liquid phase is not an economic process since it consumes high energy needed to cool down the gas temperature to -252.8 °C. One practical solution is storing hydrogen gas in metal lattice such as Mg powder and its nanocomposites in the form of MgH 2 . There are two major issues should be solved first. One related to MgH 2 in which its inherent poor hydrogenation/dehydrogenation kinetics and high thermal stability must be improved. Secondly, related to providing a safe tank. Here we have succeeded to prepare a new binary system of MgH 2 /5 wt. % TiMn 2 nanocomposite powder that show excellent hydrogenation/dehydrogenation behavior at relatively low temperature (250 °C) with long cycle-life-time (1400 h). Moreover, a simple hydrogen storage tank filled with our synthetic nanocomposite powders was designed and tested in electrical charging a battery of a cell phone device at 180 °C through a commercial fuel cell.

  10. The structure and mechanical properties of AlMg5Si2Mn alloy after surface alloying by the use of fiber laser

    NASA Astrophysics Data System (ADS)

    Pakieła, Wojciech; Tanski, Tomasz; Pawlyta, Mirosława; Pakieła, Katarzyna; Brytan, Zbigniew; Sroka, Marek

    2018-03-01

    Laser surface treatment is successfully applied to increase hardness as well as corrosion and wear resistance in light alloys such as aluminum or magnesium. The laser surface remelting also can be used to repair superficial cracks, voids or porosity caused by the mechanical impact, metallurgical process as well as the corrosive environment on the surface of the aluminum alloy. The purpose of this paper was to investigate the influence of a fiber laser surface treatment on the structure and properties of the EN AC AlMg5Si2Mn alloy. The goal of this investigation was to increase the hardness and improve tribological properties of the aluminum alloy surface as a result of the conducted laser surface treatment. During laser processing, the top surface of the aluminum alloy was enriched with Cr and Ni particles. The grain size of the applied particles was approximately about 60-130 m. The Cr-Ni powder has been introduced in the molten pool using vacuum feeder at a constant rate of 4.5 g/min. For surface remelting we used square laser beam at a size 3 × 3 mm and with the power of 3.0 kW. The linear laser scan rate of the beam was set at 0.5 m/min. Argon was used to protect the liquid metal alloy during surface treatment. Application of the laser treatment on aluminum alloy has enabled to obtain much harder as well as better wear resistant material compared to the untreated EN AC AlMg5Si2Mn.

  11. Soft chemical synthesis and electrochemical properties of calcium ferrite-type LixMn2O4

    NASA Astrophysics Data System (ADS)

    Mamiya, Mikito; Tokiwa, Kazuyasu; Akimoto, Junji

    2016-04-01

    Calcium ferrite (CaFe2O4)-type LixMn2O4 was prepared via high-pressure and soft chemical synthesis method. The framework structure of CaFe2O4-type NaMn2O4 was synthesized from the stoichiometric mixture of Na2CO3 and MnO2 annealed by 1273 K for 1 h under 4.5 GPa. Na/Li ion-exchange of the CaFe2O4-type NaMn2O4 was carried out by soaking molten LiNO3 at 633 K for 12 h. The electrochemical properties of the ion-exchanged CaFe2O4-type LixMn2O4 were measured. The initial discharge profile in the voltage range from 4.0 to 1.0 V showed 458 mAh g-1 of the discharge capacity with two plateaus near 3.7 V and 2.7 V (vs. Li/Li+). The discharge capacity was decreased with increasing the cycle number. After 30 cycles, the capacity was decreased to 375 mAh g-1. When the range was set between 4.8 and 3.0 V, the discharge capacity was 113 mAh g-1 in initial, and 111 mAh g-1 after 50th cycle. The reference CaFe2O4-type LiMn2O4 was prepared via one-step high-pressure synthesis and compared the electrochemical properties with the ion-exchanged sample. The initial discharge capacity of the one-step synthesized one was 108 mAh g-1 at 1.0 V (vs. Li/Li+), which was 73% lower than the value of the ion-exchanged one.

  12. Influences of Na2O and K2O Additions on Electrical Conductivity of CaO-MgO-Al2O3-SiO2 Melts

    NASA Astrophysics Data System (ADS)

    Zhang, Guo-Hua; Zheng, Wei-Wei; Chou, Kuo-Chih

    2017-04-01

    The present study investigated the influences of Na2O and K2O additions on electrical conductivity of blast furnace type CaO-MgO-Al2O3-SiO2 melts by the four-electrode method. Both the single addition of Na2O or K2O and the double additions of Na2O and K2O were studied. It was found that electrical conductivity monotonously increased as the amount of Na2O addition was gradually increased, whereas, when K2O was added, there was a continuous decrease of electrical conductivity. With melts containing both Na2O and K2O, electrical conductivity first decreased but then increased when Na2O was gradually substituted for K2O while keeping the molar fractions of other components constant. In other words, the mixed-alkali effect took place in CaO-Mg-Al2O3-SiO2-ΣR2O melts.

  13. The Mn-Fe negative correlation in olivines in ALHA 77257 ureilite

    NASA Technical Reports Server (NTRS)

    Miyamoto, M.; Furuta, T.; Fujii, N.; Mckay, D. S.; Lofgren, G. E.; Duke, M. B.

    1993-01-01

    An electron probe microanalyzer is used to measure the Mn, Fe, and oxygen zoning profiles of olivines in the ALHA 77257 ureilite. This is done to study the effects of reduction on the Mn-Fe value, as ureilite olivines exhibit thin reduced rims. Since the Mn content gradually increases toward the rim of ureilite olivines, while the Fa (= 100 x Fe/(Mg + Fe), mol percent) component decreases, the Mn-Fe content of olivine is likely related to redox conditions. The results of melting experiments suggest that the Mn-Fe positive correlation is related to temperature and that the negative correlation of Mn-Fe in olivine and low-Ca pyroxene is related to reduction.

  14. Crystal structure of the mineral (Na,Ca,K){sub 2}(Ca,Na){sub 4}(Mg,Fe){sub 5}(Mg,Fe,Ti){sub 5}[Si{sub 12}Al{sub 4}O{sub 44}](F,O){sub 4}: a triclinic representative of the amphibole family

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Rastsvetaeva, R. K., E-mail: rast@ns.crys.ras.ru; Aksenov, S. M.

    2012-05-15

    A mineral belonging to the amphibole family found at the Rothenberg paleovolcano (Eifel, Germany) was studied by single-crystal X-ray diffraction. The triclinic pseudomonoclinic unit-cell parameters are a = 5.3113(1) Angstrom-Sign , b = 18.0457(3) Angstrom-Sign ; c = 9.8684(2) Angstrom-Sign , {alpha} = 90.016(2) Degree-Sign , {beta} = 105.543(4) Degree-Sign , {gamma} = 89.985(2) Degree-Sign . The structure was solved by direct methods in sp. gr. P1 and refined to the R factor of 2.7% based on 6432 reflections with |F| > 3{sigma}(F) taking into account twinning. The mineral with the idealized formula (Na,Ca,K){sub 2}(Ca,Na){sub 4}(Mg,Fe){sub 5}(Mg,Fe,Ti){sub 5}[Si{sub 12}Al{sub 4}O{submore » 44}](F,O){sub 4} has some symmetry and structural features that distinguish it from other minerals of this family.« less

  15. Electrochemical synthesis of a surface-porous Mg70.5Al29.5 eutectic alloy in a neutral aqueous NaCl solution

    NASA Astrophysics Data System (ADS)

    Yang, Feng; Li, Yong-gang; Wei, Ying-hui; Wei, Huan; Yan, Ze-ying; Hou, Li-feng

    2018-03-01

    A surface-porous Mg-Al eutectic alloy was fabricated at room temperature via electrochemical dealloying in a neutral, aqueous 0.6 M NaCl solution by controlling the applied potential and processing duration. Selective dissolution occurred on the alloy surface. The surface-porous formation mechanism is governed by the selective dissolution of the α-Mg phase, which leaves the Mg17Al12 phase as the porous layer framework. The pore characteristics (morphology, size, and distribution) of the dealloyed samples are inherited from the α-Mg phases of the precursor Mg70.5Al29.5 (at.%) alloy. Size control in the porous layer can be achieved by regulating the synthesis parameters.

  16. Differential effect of imipramine and related compounds on Mg2+ efflux from rat erythrocytes.

    PubMed

    Ebel, H; Hollstein, M; Günther, T

    2004-12-15

    The effect of imipramine on Mg2+ efflux in NaCl medium (Na+/Mg2+ antiport), on Mg2+ efflux in choline.Cl medium (choline/Mg2+ antiport) and on Mg2+ efflux in sucrose medium (Cl- -coupled Mg2+ efflux) was investigated in rat erythrocytes. In non-Mg2+-loaded rat erythrocytes, imipramine stimulated Na+/Mg2+ antiport but inhibited choline/Mg2+ antiport and Cl- -coupled Mg2+ efflux. The same effect could be obtained by several other compounds structurally related to imipramine. These drugs contain a cyclic hydrophobic ring structure to which a four-membered secondary or tertiary amine side chain is attached. At a physiological pH, the amine side chain expresses a cationic choline-like structure. The inhibitory effect on choline/Mg2+ antiport is lost when the amine side chain is modified or abandoned, pointing to competition of the choline-like side chain with choline or another cation at the unspecific choline antiporter or at the Cl- -coupled Mg2+ efflux. Other related drugs either stimulated Na+/Mg2+ antiport and choline/Mg2+ antiport, or they were ineffective. For stimulation of Na+/Mg2+ antiport and choline/Mg2+ antiport, there is no specific common structural motif of the drugs tested. The effects of imipramine on Na+/Mg2+ antiport and choline/Mg2+ antiport are not mediated by PKCalpha but are caused by a direct reaction of imipramine with these transporters. By increasing the intracellular Mg2+ concentration, the stimulation of Na+/Mg2+ antiport at a physiological intracellular Mg2+ concentration changed to an inhibition of Na+/Mg2+ antiport. This effect can be explained by the hypothesis that Mg2+ loading induced an allosteric transition of the Mg2+/Mg2+ exchanger with low Na+/Mg2+ antiport capacity to the Na+/Mg2+ antiporter with high Na+/Mg2+ antiport capacity. Both forms of the Mg2+ exchanger may be differently affected by imipramine.

  17. A Salt-Inducible Mn-Catalase (KatB) Protects Cyanobacterium from Oxidative Stress.

    PubMed

    Chakravarty, Dhiman; Banerjee, Manisha; Bihani, Subhash C; Ballal, Anand

    2016-02-01

    Catalases, enzymes that detoxify H2O2, are widely distributed in all phyla, including cyanobacteria. Unlike the heme-containing catalases, the physiological roles of Mn-catalases remain inadequately characterized. In the cyanobacterium Anabaena, pretreatment of cells with NaCl resulted in unusually enhanced tolerance to oxidative stress. On exposure to H2O2, the NaCl-treated Anabaena showed reduced formation of reactive oxygen species, peroxides, and oxidized proteins than the control cells (i.e. not treated with NaCl) exposed to H2O2. This protective effect correlated well with the substantial increase in production of KatB, a Mn-catalase. Addition of NaCl did not safeguard the katB mutant from H2O2, suggesting that KatB was indeed responsible for detoxifying the externally added H2O2. Moreover, Anabaena deficient in KatB was susceptible to oxidative effects of salinity stress. The katB gene was strongly induced in response to osmotic stress or desiccation. Promoter-gfp analysis showed katB to be expressed only in the vegetative cells but not in heterocysts. Biochemically, KatB was an efficient, robust catalase that remained active in the presence of high concentrations of NaCl. Our findings unravel the role of Mn-catalase in acclimatization to salt/oxidative stress and demonstrate that the oxidative stress resistance of an organism can be enhanced by a simple compound such as NaCl. © 2016 American Society of Plant Biologists. All Rights Reserved.

  18. Changes in antioxidant status, protein concentration, acetylcholinesterase, (Na+,K+)-, and Mg2+ -ATPase activities in the brain of hyper- and hypothyroid adult rats.

    PubMed

    Carageorgiou, Haris; Pantos, Constantinos; Zarros, Apostolos; Mourouzis, Iordanis; Varonos, Dennis; Cokkinos, Dennis; Tsakiris, Stylianos

    2005-06-01

    It is a common knowledge that metabolic reactions increase in hyperthyroidism and decrease in hypothyroidism. The aim of this work was to investigate how the metabolic reactions could affect the total antioxidant status (TAS), protein concentration (PC) and the activities of acetylcholinesterase (AChE), (Na+,K+)-ATPase and Mg2+ -ATPase in the brain of hyper- and hypothyroid adult male rats. Hyperthyroidism was induced in rats by subcutaneous administration of thyroxine (25 microg/l00 g body weight) once daily for 14 days, while hypothyroidism was induced by oral administration of propylthiouracil (0.05%) for 21 days. TAS, PC, and enzyme activities were evaluated spectrophotometrically in the homogenated brain of each animal. TAS, PC, and Mg2+ -ATPase activity were found unaffected in hyperthyroidism, while AChE and Na+,K+ -ATPase activities were reduced by 25% (p < 0.01). In contrast, TAS, (Na+,K+)-ATPase and Mg2+-ATPase activities were found to be increased (approx. 23-30%, p < 0.001) in the hypothyroid brain, while AChE activity and PC were shown to be inhibited (approx. 23-30%, p < 0.001). These changes on brain enzyme activities may reflect the different metabolic effects of hyper- and hypothyroidism. Such changes of the enzyme activities may differentially modulate the brain intracellular Mg2+, neural excitability, as well as the uptake and release of biogenic amines.

  19. In Situ Encapsulating α-MnS into N,S-Codoped Nanotube-Like Carbon as Advanced Anode Material: α → β Phase Transition Promoted Cycling Stability and Superior Li/Na-Storage Performance in Half/Full Cells.

    PubMed

    Liu, Dai-Huo; Li, Wen-Hao; Zheng, Yan-Ping; Cui, Zheng; Yan, Xin; Liu, Dao-Sheng; Wang, Jiawei; Zhang, Yu; Lü, Hong-Yan; Bai, Feng-Yang; Guo, Jin-Zhi; Wu, Xing-Long

    2018-04-02

    Incorporation of N,S-codoped nanotube-like carbon (N,S-NTC) can endow electrode materials with superior electrochemical properties owing to the unique nanoarchitecture and improved kinetics. Herein, α-MnS nanoparticles (NPs) are in situ encapsulated into N,S-NTC, preparing an advanced anode material (α-MnS@N,S-NTC) for lithium-ion/sodium-ion batteries (LIBs/SIBs). It is for the first time revealed that electrochemical α → β phase transition of MnS NPs during the 1st cycle effectively promotes Li-storage properties, which is deduced by the studies of ex situ X-ray diffraction/high-resolution transmission electron microscopy and electrode kinetics. As a result, the optimized α-MnS@N,S-NTC electrode delivers a high Li-storage capacity (1415 mA h g -1 at 50 mA g -1 ), excellent rate capability (430 mA h g -1 at 10 A g -1 ), and long-term cycling stability (no obvious capacity decay over 5000 cycles at 1 A g -1 ) with retained morphology. In addition, the N,S-NTC-based encapsulation plays the key roles on enhancing the electrochemical properties due to its high conductivity and unique 1D nanoarchitecture with excellent protective effects to active MnS NPs. Furthermore, α-MnS@N,S-NTC also delivers high Na-storage capacity (536 mA h g -1 at 50 mA g -1 ) without the occurrence of such α → β phase transition and excellent full-cell performances as coupling with commercial LiFePO 4 and LiNi 0.6 Co 0.2 Mn 0.2 O 2 cathodes in LIBs as well as Na 3 V 2 (PO 4 ) 2 O 2 F cathode in SIBs. © 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  20. Nanostructured Mn-Fe Binary Mixed Oxide: Synthesis, Characterization and Evaluation for Arsenic Removal.

    PubMed

    Pillewan, Pradnya; Mukherjee, Shrabanti; Bansiwal, Amit; Rayalu, Sadhana

    2014-07-01

    Adsorption of arsenic on bimetallic Mn and Fe mixed oxide was carried out using both field as well as simulated water. The material was synthesized using hydrothermal method and characterized using X-ray diffraction (XRD) and scanning electron microscopy (SEM). Langmuir and Freundlich adsorption isotherms were computed using batch adsorption studies to determine the adsorption capacity of Mn-Fe binary mixed oxide for arsenic. Adsorption capacity for MFBMO obtained from Freundlich model was found to be 2.048 mg/g for simulated water and 1.084 mg/g for field water. Mn-Fe binary mixed oxide was found to be effective adsorbent for removal of arsenic from water.

  1. Effect of the addition of MgF2 and NaF on the thermal, optical and magnetic properties of fluoride glasses for sensing applications

    NASA Astrophysics Data System (ADS)

    Wang, Yujie; Wang, Shuangbao; Deng, Saifu; Liu, Jianting; Zhang, Jiahui

    2017-10-01

    Optical glass was very important for the development of optical fiber sensor. In this paper, a new type fluoride glass of ZrF4-BaF2-AlF3-NaF-MgF2(ZBANM) was synthesized for sensing application which has low loss and high magneto-optical coefficient, and it was found that the glass system had at least 60% transmittance from 3.5 μm to 7 μm and smallest verdet constant of 4.628E-5/(rad A-1) at 632.8 nm. The relationship among the compositions of sample glass with its thermal property, optical absorptivity and magnetic-optical coefficients was respectively studied with Thermal Gravimetric-Differential Thermal Analyzer, Fourier Transform infrared spectroscopy and a home-made magneto optical bench. The study indicated that transmittance of fluoride glass structure had been obviously improved after moderate content of Mg2+ and Na+ was doped. Simultaneously, with the molar ratio of alkaline-earth ions Mg increased, the Verdet constant of fluoride glass was increased. And the glass structure with composition of 48%ZrF4-24%BaF2-6%AlF3-8%NaF-14%MgF2 exhibited a small molar absorptivity and the largest Verdet constant of 2.853E-4/(rad A-1).

  2. First-principles investigation for some physical properties of some fluoroperovskites compounds ABF3 (A = K, Na; B = Mg, Zn)

    NASA Astrophysics Data System (ADS)

    Bakri, Badis; Driss, Zied; Berri, Saadi; Khenata, Rabah

    2017-12-01

    In this work, the structural, electronic and optical properties of fluoroperovskite ABF3 (A = K, Na; B = Mg, Zn) were studied using two different approaches: the full-potential linearized augmented plane wave method and the pseudo-potential plane wave scheme in the frame of generalized gradient approximation features such as the lattice constant, bulk modulus and its pressure derivative are reported. The ground state properties of these compounds such as the equilibrium lattice constant and the bulk modulus are in good agreement with the experimental results. The first principles calculations were performed to study the electronic structures of ABF3(A = K, Na; B = Mg, Zn) compounds and the results indicated that these four compounds are indirect band gap insulators. The optical properties are analysed and the source of some peaks in the spectra is discussed. Besides, the dielectric function, refractive index and extinction coefficient for radiation up to 25 eV have also been reported and discussed.

  3. Effects of hyper- and hypothyroidism on acetylcholinesterase, (Na(+), K (+))- and Mg ( 2+ )-ATPase activities of adult rat hypothalamus and cerebellum.

    PubMed

    Carageorgiou, Haris; Pantos, Constantinos; Zarros, Apostolos; Stolakis, Vasileios; Mourouzis, Iordanis; Cokkinos, Dennis; Tsakiris, Stylianos

    2007-03-01

    Thyroid hormones (THs) are recognized as key metabolic hormones, and the metabolic rate increases in hyperthyroidism, while it decreases in hypothyroidism. The aim of this work was to investigate how changes in metabolism induced by THs could affect the activities of acetylcholinesterase (AChE), (Na(+), K(+))- and Mg(2+)-ATPase in the hypothalamus and the cerebellum of adult rats. Hyperthyroidism was induced by subcutaneous administration of thyroxine (25 microg/100 g body weight) once daily for 14 days, while hypothyroidism was induced by oral administration of propylthiouracil (0.05%) for 21 days. All enzyme activities were evaluated spectrophotometrically in the homogenated brain regions of 10 three-animal pools. Neither hyper-, nor hypothyroidism had any effect on the examined hypothalamic enzyme activities. In the cerebellum, hyperthyroidism provoked a significant decrease in both the AChE (-23%, p < 0.001) and the Na(+), K(+)-ATPase activities (-26%, p < 0.001). Moreover, hypothyroidism had a similar effect on the examined enzyme activities: AChE (-17%, p < 0.001) and Na(+), K(+)-ATPase (-27%, p < 0.001). Mg(2+)-ATPase activity was found unaltered in both the hyper- and the hypothyroid brain regions. neither hyper-, nor hypothyroidism had any effect on the examined hypothalamic enzyme activities. In the cerebellum, hyperthyroidism provoked a significant decrease in both the AChE and the Na(+), K(+)-ATPase activities. The decreased (by the THs) Na(+), K(+)-ATPase activities may increase the synaptic acetylcholine release, and thus, could result in a decrease in the cerebellar AChE activity. Moreover, the above TH-induced changes may affect the monoamine neurotransmitter systems.

  4. Hierarchically structured MnO2 nanowires supported on hollow Ni dendrites for high-performance supercapacitors

    NASA Astrophysics Data System (ADS)

    Sun, Zhipeng; Firdoz, Shaik; Ying-Xuan Yap, Esther; Li, Lan; Lu, Xianmao

    2013-05-01

    We report a hierarchical Ni@MnO2 structure consisting of MnO2 nanowires supported on hollow Ni dendrites for high-performance supercapacitors. The Ni@MnO2 structure, which was prepared via a facile electrodeposition method, is highly porous and appears like a forest of pine trees grown vertically on a substrate. At a MnO2 mass loading of 0.35 mg cm-2, the Ni@MnO2 electrode demonstrated a specific capacitance of 1125 F g-1 that is close to the theoretical value. In addition, a remarkable high-rate performance (766 F g-1 at a discharge current density of 100 A g-1) was achieved. Electrochemical tests in a two-electrode configuration for the Ni@MnO2 structure with a high MnO2 loading of 3.6 mg cm-2 showed a low equivalent series resistance (ESR) of 1 Ω and a high specific power of 72 kW kg-1. This superior performance can be attributed to the highly porous and hierarchical structure of Ni@MnO2 that favors rapid diffusion of an electrolyte, highly conductive pathway for electron transport, and efficient material utilization.We report a hierarchical Ni@MnO2 structure consisting of MnO2 nanowires supported on hollow Ni dendrites for high-performance supercapacitors. The Ni@MnO2 structure, which was prepared via a facile electrodeposition method, is highly porous and appears like a forest of pine trees grown vertically on a substrate. At a MnO2 mass loading of 0.35 mg cm-2, the Ni@MnO2 electrode demonstrated a specific capacitance of 1125 F g-1 that is close to the theoretical value. In addition, a remarkable high-rate performance (766 F g-1 at a discharge current density of 100 A g-1) was achieved. Electrochemical tests in a two-electrode configuration for the Ni@MnO2 structure with a high MnO2 loading of 3.6 mg cm-2 showed a low equivalent series resistance (ESR) of 1 Ω and a high specific power of 72 kW kg-1. This superior performance can be attributed to the highly porous and hierarchical structure of Ni@MnO2 that favors rapid diffusion of an electrolyte, highly

  5. Effect of Bi(Mg1/2Ti1/2)O3 addition on the electrical properties of Si-Mn modified on SrTiO3

    NASA Astrophysics Data System (ADS)

    Roh, Yoon-ah; Masaki, Takaki; Yoon, Dae-Ho

    2015-05-01

    Single-Crystalline Strontium titanate (SrTiO3) has been widely used in many fields such as catalyst, semiconductors and dielectrics. SrTiO3 is a typical perovskite-type oxide, the physical properties of which strongly depend on its chemical composition, structure, shape, size, and crystallinity. In this work, the effects of Bi(Mg1/2Ti1/2)O3 addition on the nanostructure and the dielectric properties of Si-Mn modified SrTiO3 were investigated to develop nano-sized particles and low-temperature-fired SrTiO3-based ceramics with stable temperature characteristics. The dielectric constant of SrTiO3-Bi(Mg1/2Ti1/2)O3 was found to range from 900 to 1200 at 1 kHz for samples sintered at 1200°C. This new composition, SrTiO3-Bi(Mg1/2Ti1/2)O3, can be applied as a nano-sized dielectric materials in various fields.

  6. Dynamics of exciton magnetic polarons in CdMnSe/CdMgSe quantum wells: Effect of self-localization

    NASA Astrophysics Data System (ADS)

    Akimov, I. A.; Godde, T.; Kavokin, K. V.; Yakovlev, D. R.; Reshina, I. I.; Sedova, I. V.; Sorokin, S. V.; Ivanov, S. V.; Kusrayev, Yu. G.; Bayer, M.

    2017-04-01

    We study the exciton magnetic polaron (EMP) formation in (Cd,Mn)Se/(Cd,Mg)Se diluted-magnetic-semiconductor quantum wells by using time-resolved photoluminescence (PL). The magnetic-field and temperature dependencies of this dynamics allow us to separate the nonmagnetic and magnetic contributions to the exciton localization. We deduce the EMP energy of 14 meV, which is in agreement with time-integrated measurements based on selective excitation and the magnetic-field dependence of the PL circular polarization degree. The polaron formation time of 500 ps is significantly longer than the corresponding values reported earlier. We propose that this behavior is related to strong self-localization of the EMP, accompanied with a squeezing of the heavy-hole envelope wave function. This conclusion is also supported by the decrease of the exciton lifetime from 600 ps to 200-400 ps with increasing magnetic field and temperature.

  7. [Chemical forms and ecological effect of soil Mn in liver cancer's high incidence area in Zhu-jiang River Delta, China].

    PubMed

    Dou, Lei; Zhou, Yong-Zhang; Li, Yong; Ma, Jin; An, Yan-Fei; Du, Hai-Yan; Li, Zhan-Qiang

    2008-06-01

    The samples of surface soil, deep soil, and vegetables were collected from the liver cancer's high- and low incidence areas in Zhujiang River Delta to study the relationships between soil Mn forms and vegetables' Mn enrichment. The results showed that the soil Mn in study area was mainly derived from parent materials, and rarely come from human activities. The average soil Mn content in liver cancer's high incidence area was 577.65 mg x kg(-1), being significantly lower than that of liver cancer's low incidence area (718.04 mg x kg(-1)) and whole country (710 mg x kg(-1)). The Mn forms in high incidence area were mainly of residual Mn and Fe-Mn oxide, and less of water soluble Mn and exchangeable Mn, with the sum of the latter two's distribution coefficients being not higher than 4%. In low incidence area, the distribution pattern of soil Mn forms was similar to that in high incidence area, but the absolute contents of the Mn forms were significantly higher. Soil total Mn and soil pH had significant effects on soil Mn forms. There existed significant positive correlations between soil total Mn and the Mn forms of Fe-Mn bound, humic acid bound, carbonate bound, and residual, and negative correlations between soil pH and soil water soluble and organic bound Mn forms. Among the test five kinds of vegetables, Youmai lettuce and Chinese cabbage in liver cancer' s high incidence area had a significantly lower Mn content than in low incidence area, while the other three had less difference. The Mn enrichment in test vegetables was positively correlated with to the content of soil available Mn (sum of water soluble Mn and exchangeable Mn), but had no correlations with the contents of soil total Mn and other Mn forms.

  8. MnMoO4 nanolayers : Synthesis characterizations and electrochemical detection of QA

    NASA Astrophysics Data System (ADS)

    Muthamizh, S.; Kumar, S. Praveen; Munusamy, S.; Narayanan, V.

    2018-04-01

    MnMoO4 nanolayers were prepared by precipitation method. The MnMoO4 nanolayers were synthesized by using commercially available (CH3COO)2Mn.4H2O and Na2WO4.2H2O. The XRD pattern reveals that the synthesized MnMoO4 has monoclinic structure. In addition, lattice parameter values were also calculated using XRD data. The Raman analysis confirm the presence of Mo-O in MnMoO4 nanolayers. DRS-UV analysis shows that MnMoO4 has a band gap of 2.59 eV. FE-SEM and HR-TEM analysis along with EDAX confirms the material morphology in stacked layers like structure in nano scale. Synthesized nanolayers were utilized for the detection of biomolecule quercetin (QA).

  9. ELLERMAN BOMBS AT HIGH RESOLUTION. IV. VISIBILITY IN Na I AND Mg I

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Rutten, R. J.; Rouppe van der Voort, L. H. M.; Vissers, G. J. M., E-mail: R.J.Rutten@uu.nl

    2015-08-01

    Ellerman bombs are transient brightenings of the wings of the solar Balmer lines that mark reconnection in the photosphere. Ellerman noted in 1917 that he did not observe such brightenings in the Na i D and Mg i b lines. This non-visibility should constrain EB interpretation, but has not been addressed in published bomb modeling. We therefore test Ellerman’s observation and confirm it using high-quality imaging spectrometry with the Swedish 1-m Solar Telescope. However, we find a diffuse brightness in these lines that seems to result from prior EBs. We tentatively suggest this is a post-bomb hot-cloud phenomenon also foundmore » in recent EB spectroscopy in the ultraviolet.« less

  10. Content and distribution of macro- and micro-elements in the body of pasture-fed young horses.

    PubMed

    Grace, N D; Pearce, S G; Firth, E C; Fennessy, P F

    1999-03-01

    To determine the content and distribution of Na, K, Ca, P, Mg, S, Cu, Mn, Fe and Zn in the body of pasture-fed young horses and then use a factorial model to calculate the dietary mineral requirements for growth. Twenty-one foals were killed at about 150 days of age and the organs, soft tissues, skin and bones and a sample of muscle were dissected out and weighted. The mineral concentrations of elements in all soft tissues and bones were measured by inductively coupled emission spectrometry. The total mineral element composition associated with a tissue was determined from the weight of tissue and its mineral element concentration. Expressed as a percent of total body mineral elements, muscle contained 20% Na, 78% K, 32% Mg, 62% Cu, 36% Mn and 57% Zn, bone contained 47% Na, 99% Ca, 81% P, 62% Mg, 30% Mn and 28% Zn while the organs accounted for a smaller percentage ranging from 0.06% for Ca to 26% for Fe. In liver Cu accounted for 9.2% of total body Cu. Each kilogram of empty body weight was associated with 1.0 g Na, 2.5 g K, 17.1 g Ca, 10.1 g P, 0.4 g Mg, 1.1 mg Cu, 0.39 mg Mn, 52.5 mg Fe and 21.4 mg Zn. The mineral element content of body weight gain is a component used in the factorial model to determine dietary mineral element requirements for growth. The calculated dietary mineral requirements, expressed per kg dry matter, for a 200 kg horse gaining 1.0 kg/day were 1.0 g Na, 2.1 g K, 4.6 g Ca, 3.5 g P, 0.7 g Mg, 4.5 mg Cu and 25 mg Zn.

  11. Modulation of Mg2+ influx and cytoplasmic free Mg2+ concentration in rat ventricular myocytes.

    PubMed

    Tashiro, Michiko; Inoue, Hana; Konishi, Masato

    2018-06-16

    To examine whether TRPM7, a member of the melastatin family of transient receptor potential channels, is a physiological pathway for Mg 2+ entry in mammalian cells, we studied the effect of TRPM7 regulators on cytoplasmic free Mg 2+ concentration ([Mg 2+ ] i ) of rat ventricular myocytes. Acutely isolated single cells were AM-loaded with the fluorescent indicator furaptra, and [Mg 2+ ] i was estimated at 25 °C. After [Mg 2+ ] i was lowered by soaking the cells with a high-K + and Mg 2+ -Ca 2+ -free solution, [Mg 2+ ] i was recovered by extracellular perfusion of Ca 2+ -free Tyrode's solution that contained 1 mM Mg 2+ . The initial rate of increase in [Mg 2+ ] i was analyzed as the Mg 2+ influx rate. The Mg 2+ influx rate was increased by the TRPM7 activator, naltriben (2-50 μM), in a concentration-dependent manner with a half maximal effective concentration (EC 50 ) of 24 μM. This EC 50 value is similar to that reported for the activation of recombinant TRPM7 overexpressed in HEK293 cells. Naltriben (50 μM) caused little change in basal [Mg 2+ ] i (~ 0.9 mM) in Ca 2+ -free Tyrode's solution, but significantly raised [Mg 2+ ] i to 1.31 ± 0.03 mM in 94 min after the removal of extracellular Na + . Re-introduction of extracellular Na + lowered [Mg 2+ ] i back to the basal level even in the presence of naltriben. Application of 10 μM NS8593, an inhibitor of TRPM7, significantly lowered [Mg 2+ ] i to 0.72 ± 0.03 mM in 50-60 min independent of extracellular Na + . The results suggest that Mg 2+ entry through TRPM7 significantly contributes to physiological Mg 2+ homeostasis in mammalian heart cells.

  12. Beneficial effect of boron in layered sodium-ion cathode materials - The example of Na2/3B0.11Mn0.89O2

    NASA Astrophysics Data System (ADS)

    Vaalma, Christoph; Buchholz, Daniel; Passerini, Stefano

    2017-10-01

    Sodium-ion batteries are regarded as a complementary drop-in technology to lithium-ion batteries because they promise lower cost and a higher degree of environmental friendliness. Among other reasons, these benefits come from the use of manganese-based materials, whose stabilization via cation substitution is intensively studied to improve the electrochemical performance. Although multiple elements have been considered as substituent, surprisingly, boron has not been reported for layered sodium-ion cathode materials up to date. Our investigation of layered Na2/3B0.11Mn0.89O2 reveals an unexpectedly good electrochemical performance, with charge and discharge capacities of more than 175 mAh g-1 at 10 mA g-1 and 135 mAh g-1 at 500 mA g-1. The measured capacities are among the highest ever reported for sodium-based layered oxides in the potential range of 4.0-2.0 V vs. Na/Na+.

  13. Cu2+ Dual-Doped Layer-Tunnel Hybrid Na0.6Mn1- xCu xO2 as a Cathode of Sodium-Ion Battery with Enhanced Structure Stability, Electrochemical Property, and Air Stability.

    PubMed

    Chen, Ting-Ru; Sheng, Tian; Wu, Zhen-Guo; Li, Jun-Tao; Wang, En-Hui; Wu, Chun-Jin; Li, Hong-Tai; Guo, Xiao-Dong; Zhong, Ben-He; Huang, Ling; Sun, Shi-Gang

    2018-03-28

    Sodium-ion batteries (SIBs) have been regarded as a promising candidate for large-scale renewable energy storage system. Layered manganese oxide cathode possesses the advantages of high energy density, low cost and natural abundance while suffering from limited cycling life and poor rate capacity. To overcome these weaknesses, layer-tunnel hybrid material was developed and served as the cathode of SIB, which integrated high capacity, superior cycle ability, and rate performance. In the current work, the doping of copper was adopted to suppress the Jahn-Teller effect of Mn 3+ and to affect relevant structural parameters. Multifunctions of the Cu 2+ doping were carefully investigated. It was found that the structure component ratio is varied with the Cu 2+ doping amount. Results demonstrated that Na + /vacancy rearrangement and phase transitions were suppressed during cycling without sacrificing the reversible capacity and enhanced electrochemical performances evidenced with 96 mA h g -1 retained after 250 cycles at 4 C and 85 mA h g -1 at 8 C. Furthermore, ex situ X-ray diffraction has demonstrated high reversibility of the Na 0.6 Mn 0.9 Cu 0.1 O 2 cathode during Na + extraction/insertion processes and superior air stability that results in better storage properties. This study reveals that the Cu 2+ doping could be an effective strategy to tune the properties and related performances of Mn-based layer-tunnel hybrid cathode.

  14. An Integrated Study on the Evolution of Inclusions in EH36 Shipbuilding Steel with Mg Addition: From Casting to Welding

    NASA Astrophysics Data System (ADS)

    Zou, Xiaodong; Zhao, Dapeng; Sun, Jincheng; Wang, Cong; Matsuura, Hiroyuki

    2018-04-01

    Inclusion evolution behaviors, in terms of composition, size, and number density, and associated influence on the microstructures of the as-cast slabs, rolled plates, and simulated welded samples of plain EH36 and EH36-Mg shipbuilding steels have been systematically investigated. The results indicate that the inclusions in the as-cast plain EH36 are almost Al-Ca-S-O-(Mn) complex oxides with sizes ranging from 1.0 to 2.0 μm. After Mg addition, a large amount of individually fine MnS precipitates and Mg-containing Ti-Al-Mg-O-(Mn-S) complex inclusions are generated, which significantly refine the microstructure and are conducive to the nucleation of acicular ferrite in the rolled and welded sample. Moreover, after rolling and welding thermal simulation, the number of individual MnS decreases gradually due to its precipitation on the surface of Ti-Al-Mg-O oxides.

  15. Effects of Partial Substitutions of NaCl with KCl, CaSO4 and MgSO4 on the Quality and Sensorial Properties of Pork Patties.

    PubMed

    Davaatseren, Munkhtugs; Chun, Ji-Yeon; Cho, Hyung-Yong; Min, Sang-Gi; Choi, Mi-Jung

    2014-01-01

    This study investigated the effects of NaCl replacers (KCl, CaSO4, and MgSO4) on the quality and sensorial properties of pork patty. In the characteristics of spray-dried salt particles, KCl showed the largest particle size with low viscosity in solution. Meanwhile CaSO4 treatment resulted in the smallest particle size and the highest viscosity (p<0.05). In comparison of the qualities of pork patties manufactured by varying level of Na replacers, MgSO4 treatment exhibited low cooking loss comparing to control (p<0.05). Textural properties of KCl and MgSO4 treatments showed similar pattern, i.e., low level of the replacers caused harder and less adhesive texture than those of control (p<0.05), whereas the hardness of these products was not different with control when the replacers were added more than 1.0%. The addition of CaSO4 also manifested harder and less adhesive than control (p<0.05), but the textural properties of CaSO4 treatment was not affected by level of Ca-salt. Eventually, sensorial properties indicated that KCl and CaSO4 influenced negative effects on pork patties. In contrast, MgSO4 showed better sensorial properties in juiciness intensity, tenderness intensity as well as overall acceptability than control, reflecting that MgSO4 was an effective Na-replacer in meat product formulation.

  16. Preliminary study of the characteristics of a high Mg containing Al-Mg-Si alloy

    NASA Astrophysics Data System (ADS)

    Yan, F.; McKay, B. J.; Fan, Z.; Chen, M. F.

    2012-01-01

    An Al-20Mg-4Si high Mg containing alloy has been produced and its characteristics investigated. The as-cast alloy revealed primary Mg2Si particles evenly distributed throughout an α-Al matrix with a β-Al3Mg2 fully divorced eutectic phase observed in interdendritic regions. The Mg2Si particles displayed octahedral, truncated octahedral, and hopper morphologies. Additions of Sb, Ti and Zr had a refining influence reducing the size of the Mg2Si from 52 ± 4 μm to 25 ± 0.1 μm, 35 ± 1 μm and 34 ± 1 μm respectively. HPDC tensile test samples could be produced with a 0.6 wt.% Mn addition which prevented die soldering. Solution heating for 1 hr was found to dissolve the majority of the Al3Mg2 eutectic phase with no evidence of any effect on the primary Mg2Si. Preliminary results indicate that the heat treatment has a beneficial effect on the elongation and the UTS.

  17. Crystal structure of hexagonal MnAl(4).

    PubMed

    Pauling, L

    1987-06-01

    A structure is proposed for the hexagonal form of MnAl(4), with a(H) = 28.4 A and c(H) = 12.43 A, on the basis of a high-resolution electron micrograph and comparison with crystals of known structures. The proposed structure involves seven 104-atom complexes of 20 Friauf polyhedra, sharing some atoms with one another. It is closely related to the 23.36-A cubic structure of MnAl(4) and to the 14.19-A cubic structure of Mg(32)(Al,Zn)(49).

  18. Experimental Thermodynamics of [Na-Mg-Cl-SO4] Aqueous Solutions at GPa Pressure With Application to Icy Worlds.

    NASA Astrophysics Data System (ADS)

    Brown, J. M.; Bollengier, O.; Vance, S.

    2017-12-01

    Water competes with silicates as the main constituent of solid bodies in the outer solar system. Ganymede and Titan, the Mercury-sized satellites of Jupiter and Saturn, are made up half of water present as massive hydrospheres where pressure can reach up to 1.5 GPa. Geophysical data and planetary models unequivocally support the existence of global aqueous oceans trapped in these hydrospheres. However, the extent of these oceans and their role in the processes governing the internal structure of these moons remain unresolved. At issue is the poor to non-existent characterization, at the relevant pressures, of the properties of the aqueous fluids of significance to the outer solar system (with notably the Na-Mg-Cl-SO4 salts found in primitive chondrites), forcing current models to rely on pure water only. Our team at the University of Washington has developed an experimental apparatus to acquire the speed of sound of aqueous solutions in the 0 - 0.7 GPa and 250 - 350 K pressure and temperature ranges covering most of the conditions of existence of these extra-terrestrial oceans. Speeds of sound measured over a grid of pressures and temperatures allow calculation of the thermodynamic quantities (G, ρ, μ...) required for planetary science. Early analysis of pure water samples indicates our experimental results are on par with (at lower pressures), or better than, the IAPWS water laboratory standard, with sound speeds determined to 0.02% over our entire pressure range. For the first time at the high pressures of interest for large icy moons, we achieved the exploration of H2O-NaCl, H2O-MgSO4, H2O-Na2SO4 and H2O-MgCl2 solutions, from dilute concentrations to saturation. We are now in the process of acquiring the first data for H2O-NaCl-MgSO4 mixtures. We will briefly present our experimental setup and the underlying sound speed theory, and will then compare our results for the four endmembers, with an emphasis on their different association behavior under pressure as

  19. 3D MnO2-graphene composites with large areal capacitance for high-performance asymmetric supercapacitors

    NASA Astrophysics Data System (ADS)

    Zhai, Teng; Wang, Fuxin; Yu, Minghao; Xie, Shilei; Liang, Chaolun; Li, Cheng; Xiao, Fangming; Tang, Renheng; Wu, Qixiu; Lu, Xihong; Tong, Yexiang

    2013-07-01

    In this paper, we reported an effective and simple strategy to prepare large areal mass loading of MnO2 on porous graphene gel/Ni foam (denoted as MnO2/G-gel/NF) for supercapacitors (SCs). The MnO2/G-gel/NF (MnO2 mass: 13.6 mg cm-2) delivered a large areal capacitance of 3.18 F cm-2 (234.2 F g-1) and good rate capability. The prominent electrochemical properties of MnO2/G-gel/NF are attributed to the enhanced conductivities and improved accessible area for ions in electrolytes. Moreover, an asymmetric supercapacitor (ASC) based on MnO2/G-gel/NF (MnO2 mass: 6.1 mg cm-2) as the positive electrode and G-gel/NF as the negative electrode achieved a remarkable energy density of 0.72 mW h cm-3. Additionally, the fabricated ASC device also exhibited excellent cycling stability, with less than 1.5% decay after 10 000 cycles. The ability to effectively develop SC electrodes with high mass loading should open up new opportunities for SCs with high areal capacitance and high energy density.In this paper, we reported an effective and simple strategy to prepare large areal mass loading of MnO2 on porous graphene gel/Ni foam (denoted as MnO2/G-gel/NF) for supercapacitors (SCs). The MnO2/G-gel/NF (MnO2 mass: 13.6 mg cm-2) delivered a large areal capacitance of 3.18 F cm-2 (234.2 F g-1) and good rate capability. The prominent electrochemical properties of MnO2/G-gel/NF are attributed to the enhanced conductivities and improved accessible area for ions in electrolytes. Moreover, an asymmetric supercapacitor (ASC) based on MnO2/G-gel/NF (MnO2 mass: 6.1 mg cm-2) as the positive electrode and G-gel/NF as the negative electrode achieved a remarkable energy density of 0.72 mW h cm-3. Additionally, the fabricated ASC device also exhibited excellent cycling stability, with less than 1.5% decay after 10 000 cycles. The ability to effectively develop SC electrodes with high mass loading should open up new opportunities for SCs with high areal capacitance and high energy density. Electronic

  20. Synthesis of MnFe2O4@Mn-Co oxide core-shell nanoparticles and their excellent performance for heavy metal removal.

    PubMed

    Ma, Zichuan; Zhao, Dongyuan; Chang, Yongfang; Xing, Shengtao; Wu, Yinsu; Gao, Yuanzhe

    2013-10-21

    Magnetic nanomaterials that can be easily separated and recycled due to their magnetic properties have received considerable attention in the field of water treatment. However, these nanomaterials usually tend to aggregate and alter their properties. Herein, we report an economical and environmentally friendly method for the synthesis of magnetic nanoparticles with core-shell structure. MnFe2O4 nanoparticles have been successfully coated with amorphous Mn-Co oxide shells. The synthesized MnFe2O4@Mn-Co oxide nanoparticles have highly negatively charged surface in aqueous solution over a wide pH range, thus preventing their aggregation and enhancing their performance for heavy metal cation removal. The adsorption isotherms are well fitted to a Langmuir adsorption model, and the maximal adsorption capacities of Pb(II), Cu(II) and Cd(II) on MnFe2O4@Mn-Co oxide are 481.2, 386.2 and 345.5 mg g(-1), respectively. All the metal ions can be completely removed from the mixed metal ion solutions in a short time. Desorption studies confirm that the adsorbent can be effectively regenerated and reused.

  1. Water dissociation on Mn(1×1)/Ag(100)

    DOE PAGES

    Arble, Chris; Tong, Xiao; Giordano, Livia; ...

    2016-08-19

    In this work we utilize experimental and simulation techniques to examine the molecular level interaction of water with a MnO(1×1) thin film deposited onto Ag(100). The formation of MnO(1×1)/Ag(100) was characterized by low energy electron diffraction and scanning tunneling microscopy. Density functional theory (DFT) shows MnO(1×1) is thermodynamically more stable than MnO(2×1) by –0.4 eV per MnO. Upon exposure to 2.5 Torr water vapor at room temperature, X-ray photoemission spectroscopy results show extensive surface hydroxylation attributed to reactivity at MnO(1×1) terrace sites. DFT calculations of a water monomer on MnO(1×1)/Ag(100) show the dissociated form is energetically more favorable than molecularmore » adsorption, with a hydroxylation activation barrier 0.4 eV per H 2O. Lastly, these results are discussed and contrasted with previous studies of MgO/Ag(100) which show a stark difference in behavior for water dissociation.« less

  2. High-Pressure Phase Relations and Crystal Structures of Postspinel Phases in MgV2O4, FeV2O4, and MnCr2O4: Crystal Chemistry of AB2O4 Postspinel Compounds.

    PubMed

    Ishii, Takayuki; Sakai, Tsubasa; Kojitani, Hiroshi; Mori, Daisuke; Inaguma, Yoshiyuki; Matsushita, Yoshitaka; Yamaura, Kazunari; Akaogi, Masaki

    2018-06-04

    We have investigated high-pressure, high-temperature phase transitions of spinel (Sp)-type MgV 2 O 4 , FeV 2 O 4 , and MnCr 2 O 4 . At 1200-1800 °C, MgV 2 O 4 Sp decomposes at 4-7 GPa into a phase assemblage of MgO periclase + corundum (Cor)-type V 2 O 3 , and they react at 10-15 GPa to form a phase with a calcium titanite (CT)-type structure. FeV 2 O 4 Sp transforms to CT-type FeV 2 O 4 at 12 GPa via decomposition phases of FeO wüstite + Cor-type V 2 O 3 . MnCr 2 O 4 Sp directly transforms to the calcium ferrite (CF)-structured phase at 10 GPa and 1000-1400 °C. Rietveld refinements of CT-type MgV 2 O 4 and FeV 2 O 4 and CF-type MnCr 2 O 4 confirm that both the CT- and CF-type structures have frameworks formed by double chains of edge-shared B 3+ O 6 octahedra (B 3+ = V 3+ and Cr 3+ ) running parallel to one of orthorhombic cell axes. A relatively large A 2+ cation (A 2+ = Mg 2+ , Fe 2+ , and Mn 2+ ) occupies a tunnel-shaped space formed by corner-sharing of four double chains. Effective coordination numbers calculated from eight neighboring oxygen-A 2+ cation distances of CT-type MgV 2 O 4 and FeV 2 O 4 and CF-type MnCr 2 O 4 are 5.50, 5.16, and 7.52, respectively. This implies that the CT- and CF-type structures practically have trigonal prism (six-coordinated) and bicapped trigonal prism (eight-coordinated) sites for the A 2+ cations, respectively. A relationship between cation sizes of VIII A 2+ and VI B 3+ and crystal structures (CF- and CT-types) of A 2+ B 2 3+ O 4 is discussed using the above new data and available previous data of the postspinel phases. We found that CF-type A 2+ B 2 3+ O 4 crystallize in wide ionic radius ranges of 0.9-1.4 Å for VIII A 2+ and 0.55-1.1 Å for VI B 3+ , whereas CT-type phases crystallize in very narrow ionic radius ranges of ∼0.9 Å for VIII A 2+ and 0.6-0.65 Å for VI B 3+ . This would be attributed to the fact that the tunnel space of CT-type structure is geometrically less flexible due to the smaller coordination

  3. Role of nitric oxide of the median preoptic nucleus (MnPO) in the alterations of salivary flow, arterial pressure and heart rate induced by injection of pilocarpine into the MnPO and intraperitoneally.

    PubMed

    Saad, Wilson A; Guarda, I F M S; Camargo, L A A; Santos, T A F B; Guarda, R S; Saad, Willian A; Simões, S; Rodrigues, J Antunes

    2003-07-01

    We investigated the effect of L-NAME, a nitric oxide (NO) inhibitor and sodium nitroprusside (SNP), an NO-donating agent, on pilocarpine-induced alterations in salivary flow, mean arterial blood pressure (MAP) and heart rate (HR) in rats. Male Holtzman rats (250-300 g) were implanted with a stainless steel cannula directly into the median preoptic nucleus (MnPO). Pilocarpine (10, 20, 40, 80, 160 g) injected into the MnPO induced an increase in salivary secretion (P<0.01). Pilocarpine (1, 2, 4, 8, 16 mg/kg) ip also increased salivary secretion (P<0.01). Injection of L-NAME (40 g) into the MnPO prior to pilocarpine (10, 20, 40, 80, 160 g) injected into the MnPO or ip (1, 2, 4, 8, 16 mg/kg) increased salivary secretion (P<0.01). SNP (30 g) injected into the MnPO or ip prior to pilocarpine attenuated salivary secretion (P<0.01). Pilocarpine (40 g) injection into the MnPO increased MAP and decreased HR (P<0.01). Pilocarpine (4 mg/kg body weight) ip produced a decrease in MAP and an increase in HR (P<0.01). Injection of L-NAME (40 g) into the MnPO prior to pilocarpine potentiated the increase in MAP and reduced HR (P<0.01). SNP (30 g) injected into the MnPO prior to pilocarpine attenuated (100%) the effect of pilocarpine on MAP, with no effect on HR. Administration of L-NAME (40 g) into the MnPO potentiated the effect of pilocarpine injected ip. SNP (30 g) injected into the MnPO attenuated the effect of ip pilocarpine on MAP and HR. The present study suggests that in the rat MnPO 1) NO is important for the effects of pilocarpine on salivary flow, and 2) pilocarpine interferes with blood pressure and HR (side effects of pilocarpine), that is attenuated by NO.

  4. Enhanced torsional actuation and stress coupling in Mn-modified 0.93(Na0.5Bi0.5TiO3)-0.07BaTiO3 lead-free piezoceramic system

    PubMed Central

    Berik, Pelin; Maurya, Deepam; Kumar, Prashant; Kang, Min Gyu; Priya, Shashank

    2017-01-01

    Abstract This paper is concerned with the development of a piezoelectric d 15 shear-induced torsion actuator made of a lead-free piezoceramic material exhibiting giant piezoelectric shear stress coefficient (e 15) and piezoelectric transverse shear actuation force comparable to that of lead-based shear-mode piezoceramics. The Mn-modified 0.93(Na0.5Bi0.5TiO3)-0.07BaTiO3 (NBT-BT-Mn) composition exhibited excellent properties as a torsional transducer with piezoelectric shear stress coefficient on the order of 11.6 C m–2. The torsional transducer, consisting of two oppositely polarized NBT-BT-Mn d 15 mode piezoceramic shear patches, provided a rate of twist of 0.08 mm m–1 V–1 under quasi-static 150 V drive. The high value of piezoelectric shear d 15 coefficient in NBT-BT-Mn sample further demonstrated its potential in practical applications. These results confirm that the lead-free piezoceramics can be as effective as their lead-based counterparts. PMID:28179958

  5. Influence of Bulk Chemical Composition on Relative Sensitivity Factors for 55Mn/52Cr by SIMS: Implications for the 53Mn-53Cr Chronometer

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Matzel, J; Jacobsen, B; Hutcheon, I D

    2009-09-09

    between glasses with similar Mn/Cr ratios but variable Fe and Na content. We are developing an approach that uses multivariate analysis to evaluate the importance of different chemical components in controlling the RSF and predict the RSF of unknowns when standards of appropriate composition are not available. Our analysis suggests that Fe, Si, and Na are key compositional factors in these silicate standards. The RSF is positively correlated with Fe and Si and negatively correlated with Na. Work is currently underway to extend this analysis to a wider range of chemical compositions and to evaluate the variability of RSF on measurements obtained by NanoSIMS.« less

  6. Polydopamine and MnO2 core-shell composites for high-performance supercapacitors

    NASA Astrophysics Data System (ADS)

    Hou, Ding; Tao, Haisheng; Zhu, Xuezhen; Li, Maoguo

    2017-10-01

    Polydopamine and MnO2 core-shell composites (PDA@MnO2) for high-performance supercapacitors had been successfully synthesized by a facile and fast method. The morphology, crystalline phase and chemical composition of PDA@MnO2 composites are characterized using SEM, TEM, XRD, EDS and XPS. The performance of PDA@MnO2 composites are further investigated by cyclic voltammetry, galvanostatic charge-discharge and electrochemical impedance spectroscopy in 1 M Na2SO4 electrolyte. The PDA@MnO2 core-shell nanostructure composites exhibit a high capacitance of 193 F g-1 at the current density of 1A g-1 and retained over 81.2% of its initial capacitance after 2500 cycles of charge-discharge at 2 A g-1. The results manifest that the PDA@MnO2 composites can be potentially applied in supercapacitors.

  7. Contraction Twinning Dominated Tensile Deformation and Subsequent Fracture in Extruded Mg-1Mn (Wt Pct) at Ambient Temperature

    NASA Astrophysics Data System (ADS)

    Chakkedath, A.; Maiti, T.; Bohlen, J.; Yi, S.; Letzig, D.; Eisenlohr, P.; Boehlert, C. J.

    2018-03-01

    Due to their excellent strength-to-weight ratio, Mg alloys are attractive for applications where weight savings are critical. However, the limited cold formability of wrought Mg alloys severely restricts their widespread usage. In order to study the role that deformation twinning might play in limiting the elongation-to-failure ({ɛ} f ), in-situ tensile tests along the extrusion axis of Mg-1Mn (wt pct) were performed at 323 K, 423 K, and 523 K. The alloy exhibited a strong basal texture such that most of the grains experienced compression along their < {c}> -axis during deformation. At 323 K, fracture occurred at about 10 pct strain. Although basal, prismatic, and pyramidal < {c+a}> slip activity was observed along with extension twinning, contraction twinning significantly influenced the deformation, and such twins evolved into {10{\\bar{1}} 1}-{10{\\bar{1}} 2} double twins. Crystal plasticity simulation showed localized shear deformation within the contraction twins and double twins due to the enhanced activity of basal slip in the reoriented twin volume. Due to this, the twin-matrix interface was identified to be a potential crack initiation site. Thus, contraction twins were considered to have led to the failure of the material at a relatively low strain, suggesting that this deformation mode is detrimental to the cold formability of Mg and its alloys. With increasing temperature, there was a significant decrease in the activity of contraction twinning as well as extension twinning, along with a decrease in the tensile strength and an increase in the {ɛ} f value. A combination of basal, prismatic, and pyramidal < {c+a}> slips accounted for a large percentage of the observed deformation activity at 423 K and 523 K. The lack of contraction twinning was explained by the expected decrease in the critical resolved shear stress values for pyramidal < {c+a}> slip, and the improved {ɛ} f values at elevated temperatures were attributed to the vanishing activity of

  8. Contraction Twinning Dominated Tensile Deformation and Subsequent Fracture in Extruded Mg-1Mn (Wt Pct) at Ambient Temperature

    NASA Astrophysics Data System (ADS)

    Chakkedath, A.; Maiti, T.; Bohlen, J.; Yi, S.; Letzig, D.; Eisenlohr, P.; Boehlert, C. J.

    2018-06-01

    Due to their excellent strength-to-weight ratio, Mg alloys are attractive for applications where weight savings are critical. However, the limited cold formability of wrought Mg alloys severely restricts their widespread usage. In order to study the role that deformation twinning might play in limiting the elongation-to-failure ({ɛ} _{ {f}}), in-situ tensile tests along the extrusion axis of Mg-1Mn (wt pct) were performed at 323 K, 423 K, and 523 K. The alloy exhibited a strong basal texture such that most of the grains experienced compression along their < {c}> -axis during deformation. At 323 K, fracture occurred at about 10 pct strain. Although basal, prismatic, and pyramidal < {c+a}> slip activity was observed along with extension twinning, contraction twinning significantly influenced the deformation, and such twins evolved into {10{\\bar{1}}1}-{10{\\bar{1}}2} double twins. Crystal plasticity simulation showed localized shear deformation within the contraction twins and double twins due to the enhanced activity of basal slip in the reoriented twin volume. Due to this, the twin-matrix interface was identified to be a potential crack initiation site. Thus, contraction twins were considered to have led to the failure of the material at a relatively low strain, suggesting that this deformation mode is detrimental to the cold formability of Mg and its alloys. With increasing temperature, there was a significant decrease in the activity of contraction twinning as well as extension twinning, along with a decrease in the tensile strength and an increase in the {ɛ} _{ {f}} value. A combination of basal, prismatic, and pyramidal < {c+a}> slips accounted for a large percentage of the observed deformation activity at 423 K and 523 K. The lack of contraction twinning was explained by the expected decrease in the critical resolved shear stress values for pyramidal < {c+a}> slip, and the improved {ɛ} _{ {f}} values at elevated temperatures were attributed to the vanishing

  9. Synthesis and reaction of [[HC(CMeNAr)2]Mn]2 (Ar = 2,6-iPr2C6H3): the complex containing three-coordinate manganese(I) with a Mn-Mn bond exhibiting unusual magnetic properties and electronic structure.

    PubMed

    Chai, Jianfang; Zhu, Hongping; Stückl, A Claudia; Roesky, Herbert W; Magull, Jörg; Bencini, Alessandro; Caneschi, Andrea; Gatteschi, Dante

    2005-06-29

    This paper reports on the synthesis, X-ray structure, magnetic properties, and DFT calculations of [[HC(CMeNAr)2]Mn]2 (Ar = 2,6-iPr2C6H3) (2), the first complex with three-coordinate manganese(I). Reduction of the iodide [[HC(CMeNAr)2]Mn(mu-I)]2 (1) with Na/K in toluene afforded 2 as dark-red crystals. The molecule of 2 contains a Mn2(2+) core with a Mn-Mn bond. The magnetic investigations show a rare example of a high-spin manganese(I) complex with an antiferromagnetic interaction between the two Mn(I) centers. The DFT calculations indicate a strong s-s interaction of the two Mn(I) ions with the open shell configuration (3d54s1). This suggests that the magnetic behavior of 2 could be correctly described as the coupling between two S1 = S2 = 5/2 spin centers. The Mn-Mn bond energy is estimated at 44 kcal mol(-1) by first principle calculations with the B3LYP functional. The further oxidative reaction of 2 with KMnO4 or O2 resulted in the formation of manganese(III) oxide [[HC(CMeNAr)2]Mn(mu-O)]2 (3). Compound 3 shows an antiferromagnetic coupling between the two oxo-bridged manganese(III) centers by magnetic measurements.

  10. (K, Na, Li)(Nb, Ta)O3:Mn lead-free single crystal with high piezoelectric properties

    PubMed Central

    Huo, Xiaoqing; Zhang, Rui; Zheng, Limei; Zhang, Shujun; Wang, Rui; Wang, Junjun; Sang, Shijing; Yang, Bin; Cao, Wenwu

    2016-01-01

    Lead-free single crystal, (K, Na, Li)(Nb, Ta)O3:Mn, was successfully grown using top-seeded solution growth method. Complete matrix of dielectric, piezoelectric and elastic constants for [001]C poled single crystal was determined. The piezoelectric coefficient d33 measured by the resonance method was 545 pC/N, which is almost three times that of its ceramic counterpart. The values measured by the Berlincourt meter ( d33∗=630pC/N) and strain-field curve ( d33∗∗=870pm/V) were even higher. The differences were assumed to relate with the different extrinsic contributions of domain wall vibration and domain wall translation during the measurements by different approaches, where the intrinsic contribution (on the order of 539 pm/V) was supposed to be the same. The crystal has ultrahigh electromechanical coupling factor (k33 ~ 95%) and high ultrasound velocity, which make it promising for high frequency medical transducer applications. PMID:27594704

  11. Electrochemical synthesis of superconductive MgB 2 from molten salts

    NASA Astrophysics Data System (ADS)

    Yoshii, Kenji; Abe, Hideki

    2003-05-01

    We have found that superconductive MgB2 can be electrochemically synthesized from molten salts. The electrolysis was performed in an Ar flow at 600 °C on fused mixtures composed of MgCl2, MgB2O4, Na2B2O4 and alkali halides such as KCl, NaCl, and LiCl. Superconductivity was observed for a wide variety of electrolytes. It was also found that the magnetic and electrical transport properties are the most improved for samples prepared from MgCl2-NaCl-KCl-MgB2O4 electrolytes.

  12. TheoSSA - Model WD Spectra on Demand: The Impact of Ne, Na, Mg, and Iron-group Elements on the Balmer Lines

    NASA Astrophysics Data System (ADS)

    Reindl, N.; Rauch, T.

    2015-06-01

    The registered German Astrophysical Virtual Observatory (GAVO) service TheoSSA provides easy access to synthetic stellar spectra. This GAVO database contains already ten thousands of these, which were calculated with different chemical compositions of the elements H to Ni. In addition to the database, it is possible to calculate individual spectra for hot, compact stars based on the Tübingen NLTE Model-Atmosphere Package (TMAP) via the TMAW service. The TMAW models were, in the pilot phase, restricted to the elements H, He, C, N, and O. Now, TMAW is extended to additionally consider opacities from Ne, Na, and Mg. Soon, TMAW will also be able to include the opacities from the so-called iron-group elements (Ca - Ni). We describe the improvements and show the impact of Ne, Na, Mg, and iron-group elements on the Balmer lines.

  13. Crystal structure of hexagonal MnAl4

    PubMed Central

    Pauling, Linus

    1987-01-01

    A structure is proposed for the hexagonal form of MnAl4, with aH = 28.4 Å and cH = 12.43 Å, on the basis of a high-resolution electron micrograph and comparison with crystals of known structures. The proposed structure involves seven 104-atom complexes of 20 Friauf polyhedra, sharing some atoms with one another. It is closely related to the 23.36-Å cubic structure of MnAl4 and to the 14.19-Å cubic structure of Mg32(Al,Zn)49. Images PMID:16593837

  14. Origin of low sodium capacity in graphite and generally weak substrate binding of Na and Mg among alkali and alkaline earth metals.

    PubMed

    Liu, Yuanyue; Merinov, Boris V; Goddard, William A

    2016-04-05

    It is well known that graphite has a low capacity for Na but a high capacity for other alkali metals. The growing interest in alternative cation batteries beyond Li makes it particularly important to elucidate the origin of this behavior, which is not well understood. In examining this question, we find a quite general phenomenon: among the alkali and alkaline earth metals, Na and Mg generally have the weakest chemical binding to a given substrate, compared with the other elements in the same column of the periodic table. We demonstrate this with quantum mechanics calculations for a wide range of substrate materials (not limited to C) covering a variety of structures and chemical compositions. The phenomenon arises from the competition between trends in the ionization energy and the ion-substrate coupling, down the columns of the periodic table. Consequently, the cathodic voltage for Na and Mg is expected to be lower than those for other metals in the same column. This generality provides a basis for analyzing the binding of alkali and alkaline earth metal atoms over a broad range of systems.

  15. Room temperature ferromagnetism in Mn-doped NiO nanoparticles

    NASA Astrophysics Data System (ADS)

    Layek, Samar; Verma, H. C.

    2016-01-01

    Mn-doped NiO nanoparticles of the series Ni1-xMnxO (x=0.00, 0.02, 0.04 and 0.06) are successfully synthesized using a low temperature hydrothermal method. Samples up to 6% Mn-doping are single phase in nature as observed from powder x-ray diffraction (XRD) studies. Rietveld refinement of the XRD data shows that all the single phase samples crystallize in the NaCl like fcc structure with space group Fm-3m. Unit cell volume decreases with increasing Mn-doping. Pure NiO nanoparticles show weak ferromagnetism, may be due to nanosize nature. Introduction of Mn within NiO lattice improves the magnetic properties significantly. Room temperature ferromagnetism is found in all the doped samples whereas the magnetization is highest for 2% Mn-doping and then decreases with further doping. The ZFC and FC branches in the temperature dependent magnetization separate well above 350 K indicating transition temperature well above room temperature for 2% Mn-doped NiO Nanoparticle. The ferromagnetic Curie temperature is found to be 653 K for the same sample as measured by temperature dependent magnetization study using vibrating sample magnetometer (VSM) in high vacuum.

  16. Deformation induced dynamic recrystallization and precipitation strengthening in an Mg−Zn−Mn alloy processed by high strain rate rolling

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Jiang, Jimiao; Song, Min

    2016-11-15

    The microstructure of a high strain-rate rolled Mg−Zn−Mn alloy was investigated by transmission electron microscopy to understand the relationship between the microstructure and mechanical properties. The results indicate that: (1) a bimodal microstructure consisting of the fine dynamic recrystallized grains and the largely deformed grains was formed; (2) a large number of dynamic precipitates including plate-like MgZn{sub 2} phase, spherical MgZn{sub 2} phase and spherical Mn particles distribute uniformly in the grains; (3) the major facets of many plate-like MgZn{sub 2} precipitates deviated several to tens of degrees (3°–30°) from the matrix basal plane. It has been shown that themore » high strength of the alloy is attributed to the formation of the bimodal microstructure, dynamic precipitation, and the interaction between the dislocations and the dynamic precipitates. - Highlights: •A bimodal microstructure was formed in a high strain-rate rolled Mg−Zn−Mn alloy. •Plate-like MgZn{sub 2}, spherical MgZn{sub 2} and spherical Mn phases were observed. •The major facet of the plate-like MgZn{sub 2} deviated from the matrix basal plane.« less

  17. Accumulation of elements by edible mushroom species II. A comparison of aluminium, barium and nutritional element contents.

    PubMed

    Mleczek, Mirosław; Siwulski, Marek; Stuper-Szablewska, Kinga; Sobieralski, Krzysztof; Magdziak, Zuzanna; Goliński, Piotr

    2013-01-01

    The aim of the study was to compare accumulation efficiency of Al, Ba and nutritional elements (Ca, Fe, K, Mg, Mn, Na) exhibited by six edible mushrooms collected in particular regions of Poland during the last 20 years. The studied mushroom species were Boletus edulis, Cantharellus cibarius, Lactarius deliciosus, Leccinum aurantiacum, Suillus luteus and Xerocomus badius. The highest and the lowest concentrations of the elements in tested mushroom species were 11 - 410, 34 - 337, 16785 - 34600, 140 - 607, 12 - 75 and 16 - 143 mg kg(-1)d.m., respectively. The highest average concentrations of Al, Mg and Mn were observed in Suillus luteus fruiting bodies, while for Ba, Ca, K and Na it was in Lactarius deliciosus. BCF >1 was found for K and Mg in all tested mushroom species and additionally for the highest Ca and Na concentrations of all tested mushroom species except for C. cibarius and S. luteus, respectively. For the other tested elements (Al, Ba, Fe and Mn) BCF values < 1 were recorded.

  18. Laboratory study on the adsorption of Mn(2+) on suspended and deposited amorphous Al(OH)(3) in drinking water distribution systems.

    PubMed

    Wang, Wendong; Zhang, Xiaoni; Wang, Hongping; Wang, Xiaochang; Zhou, Lichuan; Liu, Rui; Liang, Yuting

    2012-09-01

    Manganese (II) is commonly present in drinking water. This paper mainly focuses on the adsorption of manganese on suspended and deposited amorphous Al(OH)(3) solids. The effects of water flow rate and water quality parameters, including solution pH and the concentrations of Mn(2+), humic acid, and co-existing cations on adsorption were investigated. It was found that chemical adsorption mainly took place in drinking water with pHs above 7.5; suspended Al(OH)(3) showed strong adsorption capacity for Mn(2+). When the total Mn(2+) input was 3 mg/L, 1.0 g solid could accumulate approximately 24.0 mg of Mn(2+) at 15 °C. In drinking water with pHs below 7.5, because of H(+) inhibition, active reaction sites on amorphous Al(OH)(3) surface were much less. The adsorption of Mn(2+) on Al(OH)(3) changed gradually from chemical coordination to physical adsorption. In drinking water with high concentrations of Ca(2+), Mg(2+), Fe(3+), and HA, the removal of Mn(2+) was enhanced due to the effects of co-precipitation and adsorption. In solution with 1.0 mg/L HA, the residual concentration of Mn(2+) was below 0.005 mg/L, much lower than the limit value required by the Chinese Standard for Drinking Water Quality. Unlike suspended Al(OH)(3), deposited Al(OH)(3) had a much lower adsorption capacity of 0.85 mg/g, and the variation in flow rate and major water quality parameters had little effect on it. Improved managements of water age, pipe flushing and mechanical cleaning were suggested to control residual Mn(2+). Copyright © 2012 Elsevier Ltd. All rights reserved.

  19. Texture and structure contribution to low-temperature plasticity enhancement of Mg-Al-Zn-Mn Alloy MA2-1hp after ECAP and annealing

    NASA Astrophysics Data System (ADS)

    Serebryany, V. N.; D'yakonov, G. S.; Kopylov, V. I.; Salishchev, G. A.; Dobatkin, S. V.

    2013-05-01

    Equal channel angular pressing (ECAP) in magnesium alloys due to severe plastic shear deformations provides both grain refinement and the slope of the initial basal texture at 40°-50° to the pressing direction. These changes in microstructure and texture contribute to the improvement of low-temperature plasticity of the alloys. Quantitative texture X-ray diffraction analysis and diffraction of backscattered electrons are used to study the main textural and structural factors responsible for enhanced low-temperature plasticity based on the example of magnesium alloy MA2-1hp of the Mg-Al-Zn-Mn system. The possible mechanisms of deformation that lead to this positive effect are discussed.

  20. Mn porphyrin-based SOD mimic, MnTnHex-2-PyP(5+), and non-SOD mimic, MnTBAP(3-), suppressed rat spinal cord ischemia/reperfusion injury via NF-κB pathways.

    PubMed

    Celic, T; Španjol, J; Bobinac, M; Tovmasyan, A; Vukelic, I; Reboucas, J S; Batinic-Haberle, I; Bobinac, D

    2014-12-01

    Herein we have demonstrated that both superoxide dismutase (SOD) mimic, cationic Mn(III) meso-tetrakis(N-n-hexylpyridinium-2-yl)porphyrin (MnTnHex-2-PyP(5+)), and non-SOD mimic, anionic Mn(III) meso-tetrakis(4-carboxylatophenyl)porphyrin (MnTBAP(3-)), protect against oxidative stress caused by spinal cord ischemia/reperfusion via suppression of nuclear factor kappa B (NF-κB) pro-inflammatory pathways. Earlier reports showed that Mn(III) N-alkylpyridylporphyrins were able to prevent the DNA binding of NF-κB in an aqueous system, whereas MnTBAP(3-) was not. Here, for the first time, in a complex in vivo system-animal model of spinal cord injury-a similar impact of MnTBAP(3-), at a dose identical to that of MnTnHex-2-PyP(5+), was demonstrated in NF-κB downregulation. Rats were treated subcutaneously at 1.5 mg/kg starting at 30 min before ischemia/reperfusion, and then every 12 h afterward for either 48 h or 7 days. The anti-inflammatory effects of both Mn porphyrins (MnPs) were demonstrated in the spinal cord tissue at both 48 h and 7 days. The downregulation of NF-κB, a major pro-inflammatory signaling protein regulating astrocyte activation, was detected and found to correlate well with the suppression of astrogliosis (as glial fibrillary acidic protein) by both MnPs. The markers of oxidative stress, lipid peroxidation and protein carbonyl formation, were significantly reduced by MnPs. The favorable impact of both MnPs on motor neurons (Tarlov score and inclined plane test) was assessed. No major changes in glutathione peroxidase- and SOD-like activities were demonstrated, which implies that none of the MnPs acted as SOD mimic. Increasing amount of data on the reactivity of MnTBAP(3-) with reactive nitrogen species (RNS) (.NO/HNO/ONOO(-)) suggests that RNS/MnTBAP(3-)-driven modification of NF-κB protein cysteines may be involved in its therapeutic effects. This differs from the therapeutic efficacy of MnTnHex-2-PyP(5+) which presumably occurs via reactive

  1. AFLOWLIB.ORG: a Distributed Materials Properties Repository from High-throughput Ab initio Calculations

    DTIC Science & Technology

    2011-11-15

    uncle) fcc (uncle) hcp (uncle) phase-diagram Ag Al Al Au Au Bi Bi Ca Ca Cd Cd Ce Ce Co Co Cr Cr Cu Cu Fe Fe Ga Ga Gd Gd Ge Ge Hf...Hf Hg Hg In In Ir Ir La La Li Li Mg Mg Mn Mn Mo Mo Na Na Nb Nb Ni Ni Os Os Pb Pb Pd Pd Pt Pt Rb Rb Re Re Rh Rh Ru Ru Sb Sb Sc...2 S. Curtarolo, A. N. Kolmogorov, and F. H. Cocks, High-throughput ab initio analysis of the Bi-In, Bi- Mg , Bi-Sb, In- Mg , In-Sb, and Mg -Sb systems

  2. β-delayed γ decay of 20Mg and the 19Ne(p , γ) 20 Na breakout reaction in Type I X-ray bursts

    NASA Astrophysics Data System (ADS)

    Glassman, B. E.; Pérez-Loureiro, D.; Wrede, C.; Allen, J.; Bardayan, D. W.; Bennett, M. B.; Brown, B. A.; Chipps, K. A.; Febbraro, M.; Friedman, M.; Fry, C.; Hall, M. R.; Hall, O.; Liddick, S. N.; O'Malley, P.; Ong, W. J.; Pain, S. D.; Prokop, C.; Schwartz, S. B.; Shidling, P.; Sims, H.; Thompson, P.; Zhang, H.

    2018-03-01

    Certain astrophysical environments such as thermonuclear outbursts on accreting neutron stars (Type-I X-ray bursts) are hot enough to allow for breakout from the Hot CNO hydrogen burning cycles to the rapid proton capture (rp) process. An important breakout reaction sequence is 15O(α,γ)19Ne(p,γ)20Na and the 19Ne(p,γ)20Na reaction rate is expected to be dominated by a single resonance at 457 keV above the proton threshold in 20Na. The resonance strength and, hence, reaction rate depends strongly on whether this 20Na state at an excitation energy of 2647 keV has spin and parity of 1+ or 3+. Previous 20Mg (Jπ =0+) β+ decay experiments have relied almost entirely on searches for β-delayed proton emission from this resonance in 20Na to limit the log ft value and, hence, Jπ. However there is a non-negligible γ-ray branch expected that must also be limited experimentally to determine the log ft value and constrain Jπ. We have measured the β-delayed γ decay of 20Mg to complement previous β-delayed proton decay work and provide the first complete limit based on all energetically allowed decay channels through the 2647 keV state. Our limit confirms that a 1+ assignment for this state is highly unlikely.

  3. Improvement of Superplasticity in High-Mg Aluminum Alloys by Sacrifice of Some Room Temperature Formability

    NASA Astrophysics Data System (ADS)

    Jin, H.; Amirkhiz, B. Shalchi; Lloyd, D. J.

    2018-03-01

    The mechanical properties of fully annealed Al-4.6 wt pct Mg alloys with different levels of Mn and Fe have been characterized at room and superplastic forming (SPF) temperatures. The effects of Mn and Fe on the intermetallic phase, grain structure, and cavitation were investigated and correlated to the formability at different temperatures. Although both Mn and Fe contribute to the formation of Al6(Mn,Fe) phase, which refines the grain structure by particle-stimulated nucleation and Zener pinning, their effects are different. An increasing Mn reduces the room temperature formability due to the increasing number of intermetallic particles, but significantly improves the superplasticity by fine grain size-induced grain boundary sliding. Meanwhile, the Fe makes the constituent particles very coarse, resulting in reduced formability at all temperatures due to extensive cavitation. A combination of high Mn and low Fe is therefore beneficial to SPF, while low levels of both elements are good for cold forming. Consequently, the superplasticity of high-Mg aluminum alloys can be significantly improved by modifying the chemical composition with sacrifice of some room temperature formability.

  4. In Vitro Degradation Behaviors of Manganese-Calcium Phosphate Coatings on an Mg-Ca-Zn Alloy

    PubMed Central

    Su, Yichang; Su, Yingchao; Zai, Wei

    2018-01-01

    In order to decrease the degradation rate of magnesium (Mg) alloys for the potential orthopedic applications, manganese-calcium phosphate coatings were prepared on an Mg-Ca-Zn alloy in calcium phosphating solutions with different addition of Mn2+. Influence of Mn content on degradation behaviors of phosphate coatings in the simulated body fluid was investigated to obtain the optimum coating. With the increasing Mn addition, the corrosion resistance of the manganese-calcium phosphate coatings was gradually improved. The optimum coating prepared in solution containing 0.05 mol/L Mn2+ had a uniform and compact microstructure and was composed of MnHPO4·3H2O, CaHPO4·2H2O, and Ca3(PO4)2. The electrochemical corrosion test in simulated body fluid revealed that polarization resistance of the optimum coating is 36273 Ωcm2, which is about 11 times higher than that of phosphate coating without Mn addition. The optimum coating also showed the most stable surface structure and lowest hydrogen release in the immersion test in simulated body fluid. PMID:29643970

  5. Ax(H3O)2-xMn5(HPO3)6 (A = Li, Na, K and NH4): open-framework manganese(ii) phosphites templated by mixed cationic species.

    PubMed

    Orive, Joseba; Fernández de Luis, Roberto; Fernández, Jesús Rodríguez; Lezama, Luis; Arriortua, María I

    2016-07-26

    Ax(H3O)2-xMn5(HPO3)6 (A = Li, x = 0.55 (1-Li); A = Na, x = 0.72 (2-Na); A = K, x = 0.30 (3-K); A = NH4, x = 0.59 (4-NH4)) phases were synthesized by employing mild hydrothermal conditions. 1-Li was studied by single crystal X-ray diffraction, while sodium, potassium and ammonium containing analogues were obtained as polycrystalline samples and characterized by powder X-ray diffraction. The four compounds were characterized by ICP-Q-MS, thermal analysis and XPS, IR, UV/Vis and EPR spectroscopy. Single crystal data indicate that 1-Li crystallizes in the P3[combining macron]c1 space group with lattice parameters a = 10.3764(1) Å and c = 9.4017(1) Å with Z = 2. The crystal structure of these phases is constituted by a three-dimensional [Mn(ii)5(HPO3)6](2-) anionic skeleton templated by alkali metal and ammonium cations together with protonated water molecules. Such an inorganic framework is formed by layers of edge-sharing MnO6 octahedra placed in the ab plane and joined along the c direction through phosphite pseudotetrahedra. The sheets display 12-membered ring channels parallel to the c-axis, ca. 5 Å in diameter, where the extraframework species display a strong disorder. EPR measurements point to the existence of short range ferromagnetic interactions around 12 K. Magnetic susceptibility and heat capacity measurements show that all the compounds exhibit long range antiferromagnetic order below circa 4 K, with a significant magnetocaloric effect around the Neel temperature.

  6. Tipranavir/Ritonavir (500/200 mg and 500/100 mg) Was Virologically Non-Inferior to Lopinavir/Ritonavir (400/100 mg) at Week 48 in Treatment-Naïve HIV-1-Infected Patients: A Randomized, Multinational, Multicenter Trial.

    PubMed

    Cooper, David A; Cordery, Damien V; Zajdenverg, Roberto; Ruxrungtham, Kiat; Arastéh, Keikawus; Bergmann, Frank; Neto, José L de Andrade; Scherer, Joseph; Chaves, Ricardo L; Robinson, Patrick

    2016-01-01

    Ritonavir-boosted tipranavir (TPV/r) was evaluated as initial therapy in treatment-naïve HIV-1-infected patients because of its potency, unique resistance profile, and high genetic barrier. Trial 1182.33, an open-label, randomized trial, compared two TPV/r dose combinations versus ritonavir-boosted lopinavir (LPV/r). Eligible adults, who had no prior antiretroviral therapy were randomized to twice daily (BID) 500/100 mg TPV/r, 500/200 mg TPV/r, or 400/100 mg LPV/r. Each treatment group also received Tenofovir 300 mg + Lamivudine 300 mg QD. The primary endpoint was a confirmed viral load (VL) <50 copies/mL at week 48 without prior antiretroviral regimen changes. Primary analyses examined CD4-adjusted response rates for non-inferiority, using a 15% non-inferiority margin. At week 48, VL<50 copies/mL was 68.4%, 69.9%, and 72.4% in TPV/r100, TPV/r200, and LPV/r groups, respectively, and TPV/r groups showed non-inferiority to LPV/r. Discontinuation due to adverse events was higher in TPV/r100 (10.3%) and TPV/r200 (15.3%) recipients versus LPV/r (3.2%) recipients. The frequency of grade ≥3 transaminase elevations was higher in the TPV/r200 group than the other groups, leading to closure of this group. However, upon continued treatment or following re-introduction after treatment interruption, transaminase elevations returned to grade ≤2 in >65% of patients receiving either TPV/r200 or TPV/r100. The trial was subsequently discontinued; primary objectives were achieved and continuing TPV/r100 was less tolerable than standard of care for initial highly active antiretroviral therapy. All treatment groups had similar 48-week treatment responses. TPV/r100 and TPV/r200 regimens resulted in sustained treatment responses, which were non-inferior to LPV/r at 48 weeks. When compared with the LPV/r regimen and examined in the light of more current regimens, these TPV/r regimens do not appear to be the best options for treatment-naïve patients based on their safety profiles.

  7. Simultaneous estimation of intracellular free Mg2+ and pH by use of a new pH-dependent dissociation constant of MgATP.

    PubMed

    Nakayama, Shinsuke; Nomura, Hideki; Smith, Lorraine M; Clark, Joseph F

    2002-06-01

    In the present technical note for 31P-NMR, we used a new pH-dependent dissociation constant of MgATP, and re-estimated changes in the intracellular free Mg2+ concentration and pH from the chemical shifts of beta- and gamma-ATP during Na+-removal in smooth muscle. We confirmed the role of Na+ - Mg2+ exchange.

  8. (Cd,Zn,Mg)Te-based microcavity on MgTe sacrificial buffer: Growth, lift-off, and transmission studies of polaritons

    NASA Astrophysics Data System (ADS)

    Seredyński, B.; Król, M.; Starzyk, P.; Mirek, R.; Ściesiek, M.; Sobczak, K.; Borysiuk, J.; Stephan, D.; Rousset, J.-G.; Szczytko, J.; Pietka, B.; Pacuski, W.

    2018-04-01

    Opaque substrates precluded, so far, transmission studies of II-VI semiconductor microcavities. This work presents the design and molecular beam epitaxy growth of semimagnetic (Cd,Zn,Mn)Te quantum wells embedded into a (Cd,Zn,Mg)Te-based microcavity, which can be easily separated from the GaAs substrate. Our lift-off process relies on the use of a MgTe sacrificial layer which stratifies in contact with water. This allowed us to achieve a II-VI microcavity prepared for transmission measurements. We evidence the strong light-matter coupling regime using photoluminescence, reflectivity, and transmission measurements at the same spot on the sample. By comparing a series of reflectance spectra before and after lift-off, we prove that the microcavity quality remains high. Thanks to Mn content in quantum wells we show the giant Zeeman splitting of semimagnetic exciton-polaritons in our transmitting structure.

  9. Pure MnTBAP selectively scavenges peroxynitrite over superoxide: Comparison of pure and commercial MnTBAP samples to MnTE-2-PyP in two different models of oxidative stress injuries, SOD-specific E. coli model and carrageenan-induced pleurisy

    PubMed Central

    Batinić-Haberle, Ines; Cuzzocrea, Salvatore; Rebouças, Júlio S.; Ferrer-Sueta, Gerardo; Mazzon, Emanuela; Di Paola, Rosanna; Radi, Rafael; Spasojević, Ivan; Benov, Ludmil; Salvemini, Daniela

    2009-01-01

    MnTBAP is often referred to as an SOD mimic in numerous models of oxidative stress. We have recently reported that pure MnTBAP does not dismute superoxide, but commercial/ill-purified samples are able to perform O2•− dismutation with low-to-moderate efficacy via non-innocent Mn-containing impurities. Herein, we show that neither commercial nor pure MnTBAP could substitute for SOD enzyme in the SOD-deficient E. coli model, while MnTE-2-PyP-treated SOD-deficient E. coli grew as well as wild-type strain. This SOD-specific system indicates that MnTBAP does not act as an SOD mimic in vivo. In another model, carrageenan-induced pleurisy in mice, inflammation was evidenced by increased pleural fluid exudate, and neutrophil infiltration and activation: these events were blocked by 0.3 mg/kg of MnTE-2-PyP and to a slightly lesser extent with 10 mg/kg of MnTBAP. Also, 3-nitrotyrosine formation, an indication of the peroxynitrite existence in vivo, was blocked by both compounds; again MnTE-2-PyP was 33-fold more effective. Pleurisy model data indicate that MnTBAP exert some protective actions in common with MnTE-2-PyP, which are not O2•−-related, and can be fully rationalized if one considers that the common biological role shared by MnTBAP and MnTE-2-PyP is related to their reduction of peroxynitrite and carbonate radical, the latter arising from ONOO− adduct with CO2. The log kcat (O2•−) value for MnTBAP is estimated to be about 3.16, which is ~5 and ~7 orders of magnitude smaller than the SOD activity of the potent SOD mimic MnTE-2-PyP and Cu, Zn-SOD, respectively. This very low value indicates that MnTBAP is very inefficient in dismuting superoxide to be of any biological impact, which was confirmed in the SOD-deficient E. coli model. Peroxynitrite scavenging ability of MnTBAP, however, is only ~2.5 orders of magnitude smaller than that of MnTE-2-PyP and is not significantly affected by the presence of the SOD-active impurities in commercial MnTBAP sample

  10. Thermodynamic description of Tc(iv) solubility and hydrolysis in dilute to concentrated NaCl, MgCl2 and CaCl2 solutions.

    PubMed

    Yalçıntaş, Ezgi; Gaona, Xavier; Altmaier, Marcus; Dardenne, Kathy; Polly, Robert; Geckeis, Horst

    2016-06-07

    We present the first systematic investigation of Tc(iv) solubility, hydrolysis and speciation in dilute to concentrated NaCl, MgCl2 and CaCl2 systems, and comprehensive thermodynamic and activity models for the system Tc(4+)-H(+)-Na(+)-Mg(2+)-Ca(2+)-OH(-)-Cl(-)-H2O using both SIT and Pitzer approaches. The results are advancing the fundamental scientific understanding of Tc(iv) solution chemistry and are highly relevant in the applied context of nuclear waste disposal. The solubility of Tc(iv) was investigated in carbonate-free NaCl-NaOH (0.1-5.0 M), MgCl2 (0.25-4.5 M) and CaCl2 (0.25-4.5 M) solutions within 2 ≤ pHm≤ 14.5. Undersaturation solubility experiments were performed under an Ar atmosphere at T = 22 ± 2 °C. Strongly reducing conditions (pe + pHm≤ 2) were imposed with Na2S2O4, SnCl2 and Fe powder to stabilize technetium in the +IV redox state. The predominance of Tc(iv) in the aqueous phase was confirmed by solvent extraction and XANES/EXAFS spectroscopy. Solid phase characterization was accomplished after attaining thermodynamic equilibrium using XRD, SEM-EDS, XANES/EXAFS, TG-DTA and quantitative chemical analysis, and indicated that TcO2·0.6H2O(s) exerts solubility-control in all evaluated systems. The definition of the polyatomic Tc3O5(2+) species instead of TcO(2+) is favoured under acidic conditions, consistently with slope analysis (mTcvs. pHm) of the solubility data gained in this work and spectroscopic evidence previously reported in the literature. The additional formation of Tc(iv)-OH/O-Cl aqueous species in concentrated chloride media ([Cl(-)] = 9 M) and pHm≤ 4 is suggested by solubility and EXAFS data. The pH-independent behaviour of the solubility observed under weakly acidic to weakly alkaline pHm conditions can be explained with the equilibrium reaction TcO2·0.6H2O(s) + 0.4H2O(l) ⇔ TcO(OH)2(aq). Solubility data determined in dilute NaCl systems with pHm≥ 11 follow a well-defined slope of +1, consistent with the predominance of

  11. Application of Mn/MCM-41 as an adsorbent to remove methyl blue from aqueous solution.

    PubMed

    Shao, Yimin; Wang, Xi; Kang, Yuan; Shu, Yuehong; Sun, Qiangqiang; Li, Laisheng

    2014-09-01

    In this study, the application of Mn loaded MCM-41 (Mn/MCM-41) was reported as a novel adsorbent for methyl blue (MB) from aqueous solution. The mesoporous structure of Mn/MCM-41 was confirmed by XRD technique. Surface area, pore size and wall thickness were calculated from BET equation and BJH method using nitrogen sorption technique. FT-IR studies showed that Mn were loaded on the hexagonal mesoporous structures of MCM-41. It is found that the MCM-41 structure retained after loading of Mn but its surface area and pore diameter decreased due to pore blockage. Adsorption of MB from aqueous solution was investigated by Mn/MCM-41 with changing Mn content, adsorbent dosage, initial MB concentration, contact time, pH and the temperature. Under the chosen condition (25°C, 0.02 g adsorbent dosage, 6.32 pH, 50 mg L(-1) MB, 1 wt.% Mn), a high MB adsorption capacity (45.38 mg g(-1)) was achieved by Mn/MCM-41 process at 120 min, 8.6 times higher than MCM-41. The electrostatic interaction was considered to be the main mechanism for the dye adsorption. The experimental data fitted well to Freundlich and Dubinin-Radushkevich isotherms. The adsorption of MB on Mn/MCM-41 followed pseudo-second-order kinetics. Thermodynamic parameters suggested that the adsorption process is endothermic and spontaneous. Copyright © 2014 Elsevier Inc. All rights reserved.

  12. FAST TRACK COMMUNICATION Accurate estimate of α variation and isotope shift parameters in Na and Mg+

    NASA Astrophysics Data System (ADS)

    Sahoo, B. K.

    2010-12-01

    We present accurate calculations of fine-structure constant variation coefficients and isotope shifts in Na and Mg+ using the relativistic coupled-cluster method. In our approach, we are able to discover the roles of various correlation effects explicitly to all orders in these calculations. Most of the results, especially for the excited states, are reported for the first time. It is possible to ascertain suitable anchor and probe lines for the studies of possible variation in the fine-structure constant by using the above results in the considered systems.

  13. The corrosion behavior of Fe-Mn-Al weld metals

    NASA Astrophysics Data System (ADS)

    Aidun, Daryush K.

    2001-02-01

    The corrosion resistance of a newly developed iron-base, Fe-Mn-Al austenitic, and duplex weld metal has been examined in the NACE solution consisting of 5 wt.% NaCl, 0.5 wt.% acetic acid, and the balance distilled water. The electrochemical techniques such as potentiodynamic polarization, Tafel plots, linear polarization, cyclic polarization, and open-circuit potential versus time were employed. The Fe-Mn-Al weld metals did not passivate and exhibited high corrosion rates. Fe-Cr-Ni (310 and 316) weld and base metals were also examined in the NACE solution at room temperature. The 310 and 316 base metals were more resistant to corrosion than the as-welded 310 and 316 weld metals. Postweld heat treatment (PWHT) improved the corrosion performance of the Fe-Mn-Al weld metals. The corrosion resistance of Fe-Mn-Al weld metals after PWHT was still inferior to that of the 310 and 316 weld and base metals.

  14. Comparison on the Surface Structure Properties along with Fe(II) and Mn(II) Removal Characteristics of Rice Husk Ash, Inactive Saccharomyces cerevisiae Powder, and Rice Husk

    PubMed Central

    Jiang, Zhao; Cao, Bo; Su, Guangxia; Lu, Yan; Zhao, Jiaying; Shan, Dexin; Zhang, Xiuyuan; Wang, Ziyi

    2016-01-01

    This study selected solid wastes, such as rice husk ash (RHA), inactive Saccharomyces cerevisiae powder (ISP), and rice husk (RH), as the potential adsorbents for the removal of Fe(II) and Mn(II) in aqueous solution. The structural characteristics, functional groups, and elemental compositions were determined by scanning electron microscope (SEM) and Fourier translation infrared spectrum (FT-IR) analyses, respectively. Then the influence on the Fe(II) and Mn(II) removing efficiency by the factors, such as pH, adsorbent dosage, initial Fe(II) and Mn(II) concentration, and contact time, was investigated by the static batch test. The adsorption isotherm study results show that Langmuir equation can better fit the Fe(II) and Mn(II) adsorption process by the three adsorbents. The maximum adsorption amounts for Fe(II) were 6.211 mg/g, 4.464 mg/g, and 4.049 mg/g by RHA, ISP, and RH and for Mn(II) were 3.016 mg/g, 2.229 mg/g, and 1.889 mg/g, respectively. The adsorption kinetics results show that the pseudo-second-order kinetic model can better fit the Fe(II) and Mn(II) adsorption process. D-R model and thermodynamic parameters hint that the adsorption processes of Fe(II) and Mn(II) on the three adsorbents took place physically and the processes were feasible, spontaneous, and exothermic. PMID:28042571

  15. 3D MnO2-graphene composites with large areal capacitance for high-performance asymmetric supercapacitors.

    PubMed

    Zhai, Teng; Wang, Fuxin; Yu, Minghao; Xie, Shilei; Liang, Chaolun; Li, Cheng; Xiao, Fangming; Tang, Renheng; Wu, Qixiu; Lu, Xihong; Tong, Yexiang

    2013-08-07

    In this paper, we reported an effective and simple strategy to prepare large areal mass loading of MnO2 on porous graphene gel/Ni foam (denoted as MnO2/G-gel/NF) for supercapacitors (SCs). The MnO2/G-gel/NF (MnO2 mass: 13.6 mg cm(-2)) delivered a large areal capacitance of 3.18 F cm(-2) (234.2 F g(-1)) and good rate capability. The prominent electrochemical properties of MnO2/G-gel/NF are attributed to the enhanced conductivities and improved accessible area for ions in electrolytes. Moreover, an asymmetric supercapacitor (ASC) based on MnO2/G-gel/NF (MnO2 mass: 6.1 mg cm(-2)) as the positive electrode and G-gel/NF as the negative electrode achieved a remarkable energy density of 0.72 mW h cm(-3). Additionally, the fabricated ASC device also exhibited excellent cycling stability, with less than 1.5% decay after 10,000 cycles. The ability to effectively develop SC electrodes with high mass loading should open up new opportunities for SCs with high areal capacitance and high energy density.

  16. Influence of phase composition on microstructure and properties of Mg-5Al-0.4Mn-xRE (x = 0, 3 and 5 wt.%) alloys

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Braszczyńska-Malik, K.N., E-mail: kacha@wip.pcz.pl; Grzybowska, A.

    2016-05-15

    The microstructure and mechanical properties investigations of two AME503 and AME505 experimental alloys in as-cast conditions were presented. The investigated materials were fabricated on the basis of the AM50 commercial magnesium alloy with 3 and 5 wt.% cerium rich mischmetal. In the as-cast condition, both experimental alloys were mainly composed of α-Mg, Al{sub 11}RE{sub 3} and Al{sub 10}RE{sub 2}Mn{sub 7} intermetallic phases. Additionally, due to non-equilibrium solidification conditions, a small amount of α + γ divorced eutectic and Al{sub 2}RE intermetallic phase were revealed. The obtained results also show a significant influence of rare earth elements on Brinell hardness, tensilemore » and compression properties at ambient temperature and especially on creep properties at 473 K. Improved alloy properties with a rise in rare earth elements mass fraction results from an increase in Al{sub 11}RE{sub 3} phase volume fraction and suppression of α + γ eutectic volume fraction in the alloy microstructure. Additionally, the influence of rare earth elements on the dendrite arm space value was discussed. The presented results also proved the thermal stability of the intermetallic phases during creep testing. - Highlights: • Two different Mg-5Al-0.4Mn alloys containing 3 and 5 wt.% of rare earth elements were fabricated. • Addition of rare earth elements leads to a reduction of dendrite arm spaces. • Mechanical properties depend on the phase composition of the alloys. • The increase of the rare earth elements content causes rise of the creep resistance.« less

  17. Piezoelectric properties and temperature stability of Mn-doped Pb(Mg1/3Nb2/3)-PbZrO3-PbTiO3 textured ceramics

    NASA Astrophysics Data System (ADS)

    Yan, Yongke; Cho, Kyung-Hoon; Priya, Shashank

    2012-03-01

    In this letter, we report the electromechanical properties of textured 0.4Pb(Mg1/3Nb2/3)O3-0.25PbZrO3-0.35PbTiO3 (PMN-PZT) composition which has relatively high rhombohedral to tetragonal (R-T) transition temperature (TR-T of 160 °C) and Curie temperature (TC of 234 °C) and explore the effect of Mn-doping on this composition. It was found that MnO2-doped textured PMN-PZT ceramics with 5 vol. % BaTiO3 template (T-5BT) exhibited inferior temperature stability. The coupling factor (k31) of T-5BT ceramic started to degrade from 75 °C while the random counterpart showed a very stable tendency up to 180 °C. This degradation was associated with the "interface region" formed in the vicinity of BT template. MnO2 doped PMN-PZT ceramics textured with 3 vol. % BT and subsequently poled at 140 °C (T-3BT140) exhibited very stable and high k31 (>0.53) in a wide temperature range from room temperature to 130 °C through reduction in the interface region volume. Further, the T-3BT140 ceramic exhibited excellent hard and soft combinatory piezoelectric properties of d33 = 720 pC/N, k31 = 0.53, Qm = 403, tan δ = 0.3% which are very promising for high power and magnetoelectric applications.

  18. Effect of P, Na, Mg, and Ag content on the in vitro bioactivity, wettability and mechanical strength of sol-gel glasses

    NASA Astrophysics Data System (ADS)

    Bouhazma, S.; Chajri, S.; Herradi, S.; Khaldi, M.; El Hachadi, A.; El Bali, B.; Lachkar, M.

    2018-03-01

    Bioactive glasses of the type SiO2-CaO, SiO 2 -CaO-P2O5, and SiO2-CaO-P2O5-MO (M = Na, Mg, or Ag) were obtained by the sol-gel processing method. The obtained materials was characterized by X-ray powder diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), and scanning electron microscopy coupled with energy dispersive spectroscopy (SEM/EDS). Contact angle and surface tension variation with time were determined at 25°C, respectively, by the sessile and pendant drop techniques, for distinct testing liquids: water, diiodomethane, formamide, and simulated body fluid (SBF). The in vitro studies showed that all gel-glasses compositions produced were bioactive. In the present work, three effects of elements (Mg, Na, Ag) in the glass were detected: (i) good mechanical strength with satisfactory biodegradability, (ii) formation of hydroxyapatite, which may promote good bone bonding and (iii) the good wettability.

  19. Lunar regolith dynamics based on analysis of the cosmogenic radionuclides Na-22, Al-26, and Mn-53

    NASA Technical Reports Server (NTRS)

    Fruchter, J. S.; Rancitelli, L. A.; Laul, J. C.; Perkins, R. W.

    1977-01-01

    Depth profiles of Na-22 and Al-26 in the upper portions of five lunar cores are analyzed. From the analyses, it is concluded that the natural gardening processes on the lunar surface result in mixing of the regolith to a depth of 2-3 cm over a time period which is short compared with the half-life of Al-26 (0.73 m.y.). It is also concluded that the rotary drill processes which were used to obtain the deep drill samples generally resulted in loss and/or mixing of the upper portions of the cores. In contrast, the near-surface regions of the drive tube cores appear to have a well-preserved stratigraphy. Analysis of Mn-53 in samples of six lunar rocks helps substantiate the accuracy of age date estimates by other means, and provides definite information that the total lunar surface exposure of two of these rocks has occurred during a single surface event which continued to their collection.

  20. Novel MnOOH–graphene nanocomposites: Preparation, characterization and electrochemical properties for supercapacitors

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Mei, Jun; Zhang, Long, E-mail: zhanglongzhl@163.com

    2015-01-15

    In this paper, we report a simple and controlled synthesis of novel MnOOH–graphene nanocomposites with a one-step facile hydrothermal method. It is template-free and easy to reproduce. Electrochemical properties are investigated in different media. The values of specific capacitance achieved are 112 F g{sup −1} in 1 M Na{sub 2}SO{sub 4} and 165 F g{sup −1} in 6 M KOH electrolyte, respectively. The assembly of multiple branched MnOOH and graphene flakes results in synergistic effects, forming new electron transfer channels to accelerate electron transfer and provide the pseudocapacitance to increase the overall capacitance. The novel composites have potential applications inmore » the fields of supercapacitors, lithium battery and so on. - Graphical abstract: The MnOOH–graphene nanocomposites shows better specific capacitance with the values achieved 112 F g{sup −1} in 1 M Na{sub 2}SO{sub 4} and 165 F g{sup −1} in 6 M KOH electrolyte, respectively. - Highlights: • Novel MnOOH–graphene nanocomposites were prepared by a one-step hydrothermal method. • The assembly can form new electron transfer channels to accelerate electron transfer. • The capacitive and rate performances are enhanced in both neutral and alkaline medium.« less

  1. Modified structural characteristics and enhanced electrochemical properties of oxygen-deficient Li2MnO3-δ obtained from pristine Li2MnO3

    NASA Astrophysics Data System (ADS)

    Tan, Xiao; Liu, Rui; Xie, Congxin; Shen, Qiang

    2018-01-01

    Lithium-rich manganese(IV) oxide Li2MnO3 has hardly any activity as the cathode active substance of lithium-ion batteries (LIBs) but its reversible capacity can be greatly improved by introducing oxygen deficiencies. After the solid-state heat treatment of nanocrystalline Li2MnO3 by sodium borohydride (NaBH4), the resulting Li2MnO3-δ crystallites comparatively acquire distinguishable appearances in color and shape and slight differences in surface composition and lattice structure. As a LIB cathode within the potential range of 2.5-4.7 V, at 20 mA g-1 pristine Li2MnO3 gives the specific discharge capacities of 3.3, 5.0 and 7.4 mAh·g-1 in the 1st, 10th and 100th cycles, while the derivative Li2MnO3-δ delivers the relatively high values of 64.8, 103.8 and 140.2 mAh·g-1 in the 1st, 10th and 120th cycles, respectively. Aside from the similar phenomenon of gradual electrochemical activation, substituting Li2MnO3-δ for Li2MnO3 means the great enhancements of charge-transfer ability and electrochemical performances. Especially, the cationic-anionic redox mechanisms of Li2MnO3 and Li2MnO3-δ are similar to each other, suggesting a possible solution to prepare high-performance xLi2MnO3-δ·(1-x)LiMO2 solid solutions for application purposes.

  2. Tracer Film Growth Study of the Corrosion of Magnesium Alloys AZ31B and ZE10A in 0.01% NaCl Solution

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Brady, M. P.; Fayek, M.; Leonard, D. N.

    We conducted a sequential isotopic tracer study of corrosion film growth for Mg-3Al-1Zn-0.25Mn (AZ31B) and Mg-1.2Zn-0.25Zr-<0.5Nd (ZE10A) by 4 h immersion in H 2 18O or D 2 16O, followed by a 20 h immersion in a 0.01 wt% NaCl H 2 18O or D 2 16O solution. Sputter depth profiles were obtained for 16O, 18O, H, and D using secondary ion mass spectrometry (SIMS). When compared to the previous tracer study for these alloys in salt-free water, the addition of 0.01 wt% NaCl resulted in a transition from oxygen inward-dominated film growth to a component of mixed inward/outward filmmore » growth for both alloys. The hydrogen tracer behavior remained inward growing for AZ31B, and short-circuit, inward growing for ZE10A, in both pure water and in 0.01 wt% NaCl solution, with extensive penetration of D beyond the film and into the underlying alloy also observed for ZE10A. Our analysis of the films by X-ray photoelectron spectroscopy (XPS) and cross-section scanning transmission electron microscopy (STEM) indicated intermixed Mg(OH) 2 and MgO, with the relative fraction of Mg(OH) 2 peaking near the center of the film. These findings suggest a decoupled film growth mechanism, with initial formation of oxide followed by NaCl-accelerated conversion to hydroxide, likely by both solid-state and dissolution-precipitation processes.« less

  3. Tracer Film Growth Study of the Corrosion of Magnesium Alloys AZ31B and ZE10A in 0.01% NaCl Solution

    DOE PAGES

    Brady, M. P.; Fayek, M.; Leonard, D. N.; ...

    2017-05-25

    We conducted a sequential isotopic tracer study of corrosion film growth for Mg-3Al-1Zn-0.25Mn (AZ31B) and Mg-1.2Zn-0.25Zr-<0.5Nd (ZE10A) by 4 h immersion in H 2 18O or D 2 16O, followed by a 20 h immersion in a 0.01 wt% NaCl H 2 18O or D 2 16O solution. Sputter depth profiles were obtained for 16O, 18O, H, and D using secondary ion mass spectrometry (SIMS). When compared to the previous tracer study for these alloys in salt-free water, the addition of 0.01 wt% NaCl resulted in a transition from oxygen inward-dominated film growth to a component of mixed inward/outward filmmore » growth for both alloys. The hydrogen tracer behavior remained inward growing for AZ31B, and short-circuit, inward growing for ZE10A, in both pure water and in 0.01 wt% NaCl solution, with extensive penetration of D beyond the film and into the underlying alloy also observed for ZE10A. Our analysis of the films by X-ray photoelectron spectroscopy (XPS) and cross-section scanning transmission electron microscopy (STEM) indicated intermixed Mg(OH) 2 and MgO, with the relative fraction of Mg(OH) 2 peaking near the center of the film. These findings suggest a decoupled film growth mechanism, with initial formation of oxide followed by NaCl-accelerated conversion to hydroxide, likely by both solid-state and dissolution-precipitation processes.« less

  4. MnFe2O4: Synthesis, morphology and electrochemical properties

    NASA Astrophysics Data System (ADS)

    Kulkarni, Shrikant; Thombare, Balu; Patil, Shankar

    2017-05-01

    MnFe2O4 has been synthesized by simple ammonia assisted co-precipitation method to obtain nanocrystalline powder. X-ray diffraction studies confirmed its crystallinity and phase purity. The MnFe2O4 calcined at 1000°C for 4 h has spinel crystal structure with Fd3m space group and lattice constant 8.511 Å. The electrode was prepared by dip coating method on stainless steel substrate and fired at 600°C for 2 h. Random shape grains of 0.2 to 1.5 micron with pores of 1-2 micron dimensions were observed in SEM images. The electrochemical studies of MnFe2O4 were carried out with 1 mole Na2SO4 electrolyte. The MnFe2O4 electrode shows highest specific capacitance of 27.53 F.g-1 and interfacial capacitance of 0.83 F.cm-2.

  5. Thermochemical Properties of the Lattice Oxygen in W,Mn-Containing Mixed Oxide Catalysts for the Oxidative Coupling of Methane

    NASA Astrophysics Data System (ADS)

    Lomonosov, V. I.; Gordienko, Yu. A.; Sinev, M. Yu.; Rogov, V. A.; Sadykov, V. A.

    2018-03-01

    Mixed NaWMn/SiO2 oxide, samples containing individual components (Na, W, Mn) and their double combinations (Na-W, Na-Mn, W-Mn) supported on silica were studied by temperature programmed reduction (TPR) and desorption (TPD), and heat flow calorimetry during their reoxidation with molecular oxygen in pulse mode. The NaWMn/SiO2 mixed oxide was shown to contain two different types of reactive lattice oxygen. The weakly-bonded oxygen can be reversibly released from the oxide in a flow of inert gas in the temperature range of 575‒900°C, while the strongly-bonded oxygen can be removed during the reduction of the sample with hydrogen at 700-900°C. The measured thermal effect of oxygen consumption for these two oxygen forms are 185 and 350 kJ/mol, respectively. The amount of oxygen removed at reduction ( 443 μmol/g) considerably exceeded the amount desorbed in an inert gas flow ( 56 μmol/g). The obtained results suggest that the reversible oxygen desorption is due to the redox process in which manganese ions are involved, while during the temperature programmed reduction, mainly oxygen bonded with tungsten is removed.

  6. The superoxide dismutase (SOD)-mimic manganese-deferoxamine (Mn-DFO) improves survival following hemorrhagic and endotoxic shock

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    de Garavilla, L.; Chermak, T.; Valentine, H.L.

    1990-02-26

    The novel, low-molecular weight, organo-metallic complex Mn-DFO functions in vitro as an SOD-mimic effectively dismutating the superoxide radical. Oxygen-derived free radicals appear to be involved in the pathology of both endotoxic (ENDO) and hemorrhagic (HEM) shock whereby treatment with SOD is associated with improvements in survival. Therefore, the following models were utilized to evaluate the in vivo activity of Mn-DFO. Male rats (350-450g) were anesthetized with ketamine (100mg/kg, ip) and subjected to HEM hypotension by withdrawing approximately 40% of the animals' blood volume over a 10 minute period. MABP was maintained constant at 40mmHg for 60 minutes, followed by completemore » autoreinfusion. Survival was reduced to 20% in the control group at 24 hour post-reinfusion. A single post-shock dose of Mn-DFO (10mg/kg, iv) more than doubled the survival rate for up to 24 hour post-reinfusion as compared to control. Female mice (CFmal and-1, 20-25g) were challenged with 500ug of ENDO and 0.8ug of actinomycin/animal and dosed 1 hour pre and post with Mn-DFO (30mg/kg/dose, iv). Survival improved from 60% in the control group to 100% in the Mn-DFO group at 18 hours post ENDO challenge. Using a multiple dosing regimen, Mn-DFO significantly improved survival for up to 48 hours post-ENDO. Thus, unlike other SOD-mimics, Mn-DFO appears to exhibit in vivo activity.« less

  7. Facile Synthesis of Three-Dimensional Sandwiched MnO2@GCs@MnO2 Hybrid Nanostructured Electrode for Electrochemical Capacitors.

    PubMed

    Jian, Xian; Liu, Shiyu; Gao, Yuqi; Zhang, Wanli; He, Weidong; Mahmood, Asif; M Subramaniyam, Chandrasekar; Wang, Xiaolin; Mahmood, Nasir; Dou, Shi Xue

    2017-06-07

    Designable control over the morphology and structure of active materials is highly desirable for achieving high-performance devices. Here, we develop a facile microwave-assisted synthesis to decorate MnO 2 nanocrystals on three-dimensional (3D) graphite-like capsules (GCs) to obtain sandwich nanostructures (3D MnO 2 @GCs@MnO 2 ) as electrode materials for electrochemical capacitors (ECs). A templated growth of the 3D GCs was carried out via catalytic chemical vapor deposition and MnO 2 was decorated on the exterior and interior surfaces of the GC walls through microwave irradiation to build an engineered architecture with robust structural and morphological stability. The unique sandwiched architecture has a large interfacial surface area, and allows for rapid electrolyte diffusion through its hollow/open framework and fast electronic motion via the carbon backbone. Furthermore, the tough and rigid nature of GCs provides the necessary structural stability, and the strong synergy between MnO 2 and GCs leads to high electrochemical activity in both neutral (265.1 F/g at 0.5 A/g) and alkaline (390 F/g at 0.5 A/g) electrolytes. The developed hybrid exhibits stable capacitance up to 6000 cycles in 1 M Na 2 SO 4 . The hybrid is a potential candidate for future ECs and the present study opens up an effective avenue to design hybrid materials for various applications.

  8. Heat capacities and entropies of Mg2SiOa, Mn2SiOa, and Co2SiOa between 5 and 380 K

    USGS Publications Warehouse

    Robie, Richard A.; Hemingway, Bruch S.; Takei, Humihiko

    1982-01-01

    whereas the shoulder near 12 K corresponds to the change from the collinear to a canted spin structure. Our calorimetric values for the antiferromagnetic-paramagnetictr ansition temperature (N6el Temperature) are in excellent agreement with those obtained by powder magnetic susceptibility measurements, 49t2 K and 5015 K for co2Sioa and Mn2Sioa respectively. The thermal Debye temperature, 0$, of Mg2Sioa calculated from our c$ measurements between 6.3 and 13.8 K is 768+15 K and agrees well with the elastic vaiue ofi of 758 K based on the mean sound velocity calculated from the room temperature elastic stiffness constants (ci:) of Graham and Barsch. At 298.15K (25"c) the molar heat capacitiesa re 118.6,1 28.7, and 133.4J /(mol . K) and the molar entropiesa re 94.11-r0.101, 55.910.4a nd,1 42.6-+0.J2l (mol . K) respectivelyf or Mg2SiO4M, n2SiOaa, nd Co2SiOa.

  9. Magnetic properties of Mn0.1Mg0.2TM0.7Fe2O4 (TM = Zn, Co, or Ni) prepared by hydrothermal processes: The effects of crystal size and chemical composition

    NASA Astrophysics Data System (ADS)

    Nhlapo, T. A.; Msomi, J. Z.; Moyo, T.

    2018-02-01

    Nano-crystalline Zn-, Co-, and Ni-substituted Mn-Mg ferrites were prepared by hydrothermal process and annealed at 1100 °C. Annealing conditions are critical on the crystalline phase. TEM and XRD data reveal particle sizes between 8 nm and 15 nm for the as-prepared fine powders, which increase to about 73 nm after sintering at 1100 °C. Mӧssbauer spectra show well resolved magnetic splitting in bulk samples. The as-prepared fine powders show weak hyperfine splitting and broad central doublets associated with fine particles. Magnetization data reveal a high coercive field at about 300 K of about 945 Oe in the Co-based nanosized oxide, which reduces to about 360 Oe after thermal annealing at 1100 °C. The magnetization curves of Zn- and Ni-based samples show much lower coercive fields indicative of superparamagnetic nanoparticles. The crystallite size and chemical composition have significant effects on the properties of Mn0.1Mg0.2(Zn,Co,Ni)0.7Fe2O4 investigated.

  10. Galvanostatically deposited Fe: MnO2 electrodes for supercapacitor application

    NASA Astrophysics Data System (ADS)

    Dubal, D. P.; Kim, W. B.; Lokhande, C. D.

    2012-01-01

    The present investigation describes the addition of iron (Fe) in order to improve the supercapacitive properties of MnO2 electrodes using galvanostatic mode. These amorphous worm like Fe: MnO2 electrodes are characterized by X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM), energy dispersive X-ray analysis (EDAX), Fourier transform infrared spectroscopy (FTIR) and wettability test. The supercapacitive properties of MnO2 and Fe: MnO2 electrodes are investigated using cyclic voltammetry, chronopotentiometry and impedance techniques. It is seen that the supercapacitance increases with increase in Fe doping concentration and achieved a maximum of 173 F g-1 at 2 at% Fe doping. The maximum supercapacitance obtained is 218 F g-1 for 2 at% Fe: MnO2 electrode. This hydrous binary oxide exhibited ideal capacitive behavior with high reversibility and high pulse charge-discharge property between -0.1 and +0.9 V/SCE in 1 M Na2SO4 electrolyte indicating a promising electrode material for electrochemical supercapacitors.

  11. Selective sodium intercalation into sodium nickel-manganese sulfate for dual Na-Li-ion batteries.

    PubMed

    Marinova, Delyana M; Kukeva, Rosica R; Zhecheva, Ekaterina N; Stoyanova, Radostina K

    2018-05-09

    Double sodium transition metal sulfates combine in themselves unique intercalation properties with eco-compatible compositions - a specific feature that makes them attractive electrode materials for lithium and sodium ion batteries. Herein, we examine the intercalation properties of novel double sodium nickel-manganese sulfate, Na2Ni1/2Mn1/2(SO4)2, having a large monoclinic unit cell, through electrochemical and ex situ diffraction and spectroscopic methods. The sulfate salt Na2Ni1/2Mn1/2(SO4)2 is prepared by thermal dehydration of the corresponding hydrate salt Na2Ni1/2Mn1/2(SO4)2·4H2O having a blödite structure. The intercalation reactions on Na2Ni1-xMnx(SO4)2 are studied in two model cells: half-ion cell versus Li metal anode and full-ion cell versus Li4Ti5O12 anode by using lithium (LiPF6 dissolved in EC/DMC) and sodium electrolytes (NaPF6 dissolved in EC:DEC). Based on ex situ XRD and TEM analysis, it is found that sodium intercalation into Na2Ni1/2Mn1/2(SO4)2 takes place via phase separation into the Ni-rich monoclinic phase and Mn-rich alluaudite phase. The redox reactions involving participation of manganese and titanium ions are monitored by ex situ EPR spectroscopy. It has been demonstrated that manganese ions from the sulfate salt are participating in the electrochemical reaction, while the nickel ions remain intact. As a result, a reversible capacity of about 65 mA h g-1 is reached. The selective intercalation properties determine sodium nickel-manganese sulfate as a new electrode material for hybrid lithium-sodium ion batteries that is thought to combine the advantages of individual lithium and sodium batteries.

  12. Arsenic release from Fe/Mn oxide-rich (model) soils/sediments - A comparison of single extraction procedures

    NASA Astrophysics Data System (ADS)

    Vanek, A.; Komarek, M.; Galuskova, I.

    2012-04-01

    Arsenic extractability in As-modified Fe(III) and Mn(III,IV) oxide-coated sands was tested using five widely used 2-h single extraction procedures: deionised water, 0.01 M CaCl2, 1 M NH4NO3, 0.1 M Na2HPO4 and 0.005 DTPA. In general, the highest As recoveries reaching 39-50% of total As concentration were observed for all extracting media in the birnessite (delta-MnO2) system, indicating relatively weak adsorption of As onto the Mn oxides. The Na2HPO4 extracts from the Fe oxide systems (i.e., associated with ferrihydrite and goethite) were highest in As, accounting for up to 34% of total As amount. Surprisingly, comparable recoveries of As (14-20%) yielded deionised water, CaCl2, NH4NO3, DTPA as extracting media for both ferrihydrite and goethite coatings. Deionised water and Na2HPO4 extractions are suggested for quick estimation of easily soluble, exchangeable and/or specifically adsorbed As in real soil/sediment samples.

  13. Optical properties of 3d transition-metal-doped MgAl2O4 spinels

    NASA Astrophysics Data System (ADS)

    Izumi, K.; Miyazaki, S.; Yoshida, S.; Mizokawa, T.; Hanamura, E.

    2007-08-01

    Strong emission bands in the visible region are observed in MgAl2O4 crystals doped with transition-metal ions under excitation at the band-to-band transitions. We report optical responses of Cr-, Co-, and Ni-doped MgAl2O4 and present optical models for M -doped MgAl2O4 ( M=Ti , V, Cr, Mn, Co, and Ni) to describe the charge-transfer transitions and the transitions between multiplet levels of 3d electrons, which are observed competitively or coexisting, depending on the number of 3d electrons. While the optical responses of Cr- and Ni-doped MgAl2O4 are dominated by the multiplet-multiplet transitions, those of Ti- and V-doped MgAl2O4 are governed by the charge-transfer transitions. The two kinds of transitions coexist in the Mn- and Co-doped MgAl2O4 . These behaviors are well understood based on the numerical results of unrestricted Hartree-Fock approximation.

  14. One-pot synthesis of MnO2-chitin hybrids for effective removal of methylene blue.

    PubMed

    Dassanayake, Rohan S; Rajakaruna, Erandathi; Moussa, Hanna; Abidi, Noureddine

    2016-12-01

    Manganese dioxide (MnO 2 )-chitin-hybrid material was prepared by a facile "one-pot" synthesis method. MnO 2 -chitin hybrid was used for the effective removal of methylene blue (MB) from liquid solution as model for wastewater treatment. The hybrid obtained was characterized by field emission scanning electron microscopy and energy dispersive X-ray spectroscopy, Fourier transform infrared spectroscopy, X-ray diffraction and thermogravimetric analysis. The effect of pH and temperature were studied. MnO 2 -chitin hybrid showed high performance for oxidative decolorization and removal of MB. Typically, 25mL of MB (20mg/L) can be completely decolorized in 2.5min with 8.5mg of the MnO 2 -chitin hybrid. The hybrid material exhibited excellent recyclability and durability with the degradation value of 99% for MB after ten consecutive cycles. Copyright © 2016 Elsevier B.V. All rights reserved.

  15. Strength properties and structure of a submicrocrystalline Al-Mg-Mn alloy under shock compression

    NASA Astrophysics Data System (ADS)

    Petrova, A. N.; Brodova, I. G.; Razorenov, S. V.

    2017-06-01

    The results of studying the strength of a submicrocrystalline aluminum A5083 alloy (chemical composition was 4.4Mg-0.6Mn-0.11Si-0.23Fe-0.03Cr-0.02Cu-0.06Ti wt % and Al base) under shockwave compression are presented. The submicrocrystalline structure of the alloy was produced in the process of dynamic channel-angular pressing at a strain rate of 104 s-1. The average size of crystallites in the alloy was 180-460 nm. Hugoniot elastic limit σHEL, dynamic yield stress σy, and the spall strength σSP of the submicrocrystalline alloy were determined based on the free-surface velocity profiles of samples during shock compression. It has been established that upon shock compression, the σHEL and σy of the submicrocrystalline alloy are higher than those of the coarse-grained alloy and σsp does not depend on the grain size. The maximum value of σHEL reached for the submicrocrystalline alloy is 0.66 GPa, which is greater than that in the coarse-crystalline alloy by 78%. The dynamic yield stress is σy = 0.31 GPa, which is higher than that of the coarse-crystalline alloy by 63%. The spall strength is σsp = 1.49 GPa. The evolution of the submicrocrystalline structure of the alloy during shock compression was studied. It has been established that a mixed nonequilibrium grain-subgrain structure with a fragment size of about 400 nm is retained after shock compression, and the dislocation density and the hardness of the alloy are increased.

  16. Trace elements and electrolytes in human resting mixed saliva after exercise

    PubMed Central

    Chicharro, J. L.; Serrano, V.; Urena, R.; Gutierrez, A. M.; Carvajal, A.; Fernandez-, H; Lucia, A.

    1999-01-01

    OBJECTIVES: Exercise is known to cause changes in the concentration of salivary components such as amylase, Na, and Cl. The aim of this investigation was to evaluate the effect of physical exercise on the levels of trace elements and electrolytes in whole (mixed) saliva. METHODS: Forty subjects performed a maximal exercise test on a cycle ergometer. Samples of saliva were obtained before and immediately after the exercise test. Sample concentrations of Fe, Mg, Sc, Cr, Mn, Co, Cu, Zn, Se, Sr, Ag, Sb, Cs, and Hg were determined by inductively coupled plasma mass spectrometry and concentrations of Ca and Na by atomic absorption spectrometry. RESULTS: After exercise, Mg and Na levels showed a significant increase (p < 0.05) while Mn levels fell (p < 0.05). Zn/Cu molar ratios were unaffected by exercise. CONCLUSIONS: Intense physical exercise induced changes in the concentrations of only three (Na, Mg, and Mn) of the 16 elements analysed in the saliva samples. Further research is needed to assess the clinical implications of these findings. 


 PMID:10378074

  17. Influence of the manganese and cobalt content on the electrochemical performance of P2-Na0.67MnxCo1-xO2 cathodes for sodium-ion batteries.

    PubMed

    Hemalatha, K; Jayakumar, M; Prakash, A S

    2018-01-23

    The resurgence of sodium-ion batteries in recent years is due to their potential ability to form intercalation compounds possessing a high specific capacity and energy density comparable to existing lithium systems. To comprehend the role of cobalt substitution in the structure and electrochemical performance of Na 0.67 MnO 2 , the solid solutions of P2-Na 0.67 Mn x Co 1-x O 2 (x = 0.25, 0.5, 0.75) are synthesized and characterized. The XRD-Rietveld analysis revealed that the Co-substitution in Na 0.67 MnO 2 decreases lattice parameters 'a' and 'c' resulting in the contraction of MO 6 octahedra and the enlargement of inter-layer 'd' spacing. XPS indicates that the isovalent cobalt substitution in Na 0.67 MnO 2 results in the partial/complete replacement of Jahn-Teller active trivalent manganese to form low-spin complexes of better structural stability. The Na-ion diffusion coefficient, D Na + , derived from cyclic voltammetry and impedance spectroscopy, confirmed the enhanced mass transport in Co-rich phases compared to Mn-rich phases. Furthermore, higher diffusion coefficient values are observed for Co 3+ /Co 4+ than for their Mn 3+ /Mn 4+ redox processes. In addition, Co-rich phases exhibit a high structural stability and superior capacity retention, whereas Mn-rich phases discharge higher capacities.

  18. Corrosion and Discharge Behaviors of Al-Mg-Sn-Ga-In in Different Solutions

    NASA Astrophysics Data System (ADS)

    Xiong, Hanqing; Yin, Xiang; Yan, Yang; Dai, Yilong; Fan, Sufeng; Qiao, Xueyan; Yu, Kun

    2016-08-01

    Al-0.5 wt.%Mg-0.08 wt.%Sn-0.05 wt.%Ga-0.05 wt.%In and Al-0.5 wt.%Mg-0.08 wt.%Sn-0.05 wt.%Ga alloys were prepared by melting, casting and cold rolling. Corrosion and discharge behaviors of the two experimental alloys were investigated by electrochemical measurement, self-corrosion rate measurement, air battery testing, and scanning electron microscopy. The results showed that Al-Mg-Sn-Ga-In alloy exhibited higher electrochemical activity than Al-Mg-Sn-Ga alloy in 2 M NaCl solution, while it showed lower electrochemical activity than Al-Mg-Sn-Ga alloy in 4 M NaOH solution. By comparison with the air battery based on Al-Mg-Sn-Ga alloy, the battery with Al-Mg-Sn-Ga-In alloy cannot exhibit better discharge performance in 4 M NaOH electrolyte. However, the performance of the air battery based on Al-Mg-Sn-Ga-In alloy was greatly improved due to the In-rich inclusions and the uniform corroded morphology in 2 M NaCl electrolyte. Thus, Al-Mg-Sn-Ga-In alloy was a good anode material for Al-air battery in 2 M NaCl electrolyte.

  19. Streptococcal 5′-Nucleotidase A (S5nA), a Novel Streptococcus pyogenes Virulence Factor That Facilitates Immune Evasion*

    PubMed Central

    Zheng, Lisa; Khemlani, Adrina; Lorenz, Natalie; Loh, Jacelyn M. S.; Langley, Ries J.; Proft, Thomas

    2015-01-01

    Streptococcus pyogenes is an important human pathogen that causes a wide range of diseases. Using bioinformatics analysis of the complete S. pyogenes strain SF370 genome, we have identified a novel S. pyogenes virulence factor, which we termed streptococcal 5′-nucleotidase A (S5nA). A recombinant form of S5nA hydrolyzed AMP and ADP, but not ATP, to generate the immunomodulatory molecule adenosine. Michaelis-Menten kinetics revealed a Km of 169 μm and a Vmax of 7550 nmol/mg/min for the substrate AMP. Furthermore, recombinant S5nA acted synergistically with S. pyogenes nuclease A to generate macrophage-toxic deoxyadenosine from DNA. The enzyme showed optimal activity between pH 5 and pH 6.5 and between 37 and 47 °C. Like other 5′-nucleotidases, S5nA requires divalent cations and was active in the presence of Mg2+, Ca2+, or Mn2+. However, Zn2+ inhibited the enzymatic activity. Structural modeling combined with mutational analysis revealed a highly conserved catalytic dyad as well as conserved substrate and cation-binding sites. Recombinant S5nA significantly increased the survival of the non-pathogenic bacterium Lactococcus lactis during a human whole blood killing assay in a dose-dependent manner, suggesting a role as an S. pyogenes virulence factor. In conclusion, we have identified a novel S. pyogenes enzyme with 5′-nucleotidase activity and immune evasion properties. PMID:26527680

  20. Mn 2+-Sensing Mechanisms of yybP-ykoY Orphan Riboswitches

    DOE PAGES

    Price, Ian R.; Gaballa, Ahmed; Ding, Fang; ...

    2015-03-19

    Gene regulation in cis by riboswitches is prevalent in bacteria. The yybP-ykoY riboswitch family is quite widespread, yet its ligand and function remained unknown. Here in this paper, we characterize the Lactococcus lactis yybP-ykoY orphan riboswitch as a Mn2+-dependent transcription-ON riboswitch, with a ~30–40 μM affinity for Mn 2+. We further determined its crystal structure at 2.7 Å to elucidate the metal sensing mechanism. The riboswitch resembles a hairpin, with two coaxially stacked helices tethered by a four-way junction and a tertiary docking interface. The Mn 2+-sensing region, strategically located at the highly conserved docking interface, has two metal bindingmore » sites. Whereas one site tolerates the binding of either Mg 2+ or Mn 2+, the other site strongly prefers Mn 2+ due to a direct contact from the N7 of an invariable adenosine. Lastly, mutagenesis and a Mn 2+-free E. coli yybP-ykoY structure further reveal that Mn 2+ binding is coupled with stabilization of the Mn2+-sensing region and the aptamer domain.« less

  1. Interaction of chromatin with NaCl and MgCl2. Solubility and binding studies, transition to and characterization of the higher-order structure.

    PubMed

    Ausio, J; Borochov, N; Seger, D; Eisenberg, H

    1984-08-15

    Chicken erythrocyte chromatin containing histones H1 and H5 was carefully separated into a number of well-characterized fractions. A distinction could be made between chromatin insoluble in NaCl above about 80 mM, and chromatin soluble at all NaCl concentrations. Both chromatin forms were indistinguishable electrophoretically and both underwent the transition from the low salt "10 nm" coil to the "30 nm" higher-order structure solenoid by either raising the MgCl2 concentration to about 0.3 mM or the NaCl concentration to about 75 mM. The transitions were examined in detail by elastic light-scattering procedures. It could be shown that the 10 nm form is a flexible coil. For the 30 nm solenoid, the assumption of a rigid cylindrical structure was in good agreement with 5.7 nucleosomes per helical turn. However, disagreement of calculated frictional parameters with values derived from quasielastic light-scattering and sedimentation introduced the possibility that the higher-order structure, under these conditions, is more extended, flexible, or perhaps a mixture of structures. Values for density and refractive index increments of chromatin are also given. To understand the interaction of chromatin with NaCl and with MgCl2, a number of experiments were undertaken to study solubility, precipitation, conformational transitions and binding of ions over a wide range of experimental conditions, including chromatin concentration.

  2. Slow relaxation in a one-dimensional rational assembly of antiferromagnetically coupled [Mn4] single-molecule magnets.

    PubMed

    Lecren, Lollita; Roubeau, Olivier; Coulon, Claude; Li, Yang-Guang; Le Goff, Xavier F; Wernsdorfer, Wolfgang; Miyasaka, Hitoshi; Clérac, Rodolphe

    2005-12-14

    Four discrete Mn(III)/Mn(II) tetranuclear complexes with a double-cuboidal core, [Mn(4)(hmp)(6)(CH(3)CN)(2)(H(2)O)(4)](ClO(4))(4).2CH(3)CN (1), [Mn(4)(hmp)(6)(H(2)O)(4)](ClO(4))(4).2H(2)O (2), [Mn(4)(hmp)(6)(H(2)O)(2)(NO(3))(2)](ClO(4))(2).4H(2)O (3), and [Mn(4)(hmp)(6)(Hhmp)(2)](ClO(4))(4).2CH(3)CN (4), were synthesized by reaction of Hhmp (2-hydroxymethylpyridine) with Mn(ClO(4))(2).6H(2)O in the presence of tetraethylammonium hydroxide and subsequent addition of NaNO(3) (3) or an excess of Hhmp (4). Direct current (dc) magnetic measurements show that both Mn(2+)-Mn(3+) and Mn(3+)-Mn(3+) magnetic interactions are ferromagnetic in 1-3 leading to an S(T) = 9 ground state for the Mn(4) unit. Furthermore, these complexes are single-molecule magnets (SMMs) clearly showing both thermally activated and ground-state tunneling regimes. Slight changes in the [Mn(4)] core geometry result in an S(T) = 1 ground state in 4. A one-dimensional assembly of [Mn(4)] units, catena-{[Mn(4)(hmp)(6)(N(3))(2)](ClO(4))(2)} (5), was obtained in the same synthetic conditions with the subsequent addition of NaN(3). Double chairlike N(3)(-) bridges connect identical [Mn(4)] units into a chain arrangement. This material behaves as an Ising assembly of S(T) = 9 tetramers weakly antiferromagnetically coupled. Slow relaxation of the magnetization is observed at low temperature for the first time in an antiferromagnetic chain, following an activated behavior with Delta(tau)/k(B) = 47 K and tau(0) = 7 x 10(-)(11) s. The observation of this original thermally activated relaxation process is induced by finite-size effects and in particular by the noncompensation of spins in segments of odd-number units. Generalizing the known theories on the dynamic properties of polydisperse finite segments of antiferromagnetically coupled Ising spins, the theoretical expressions of the characteristic energy gaps Delta(xi) and Delta(tau) were estimated and successfully compared to the experimental values.

  3. Concentration of Minerals in Nectar Honeys from Direct Sale and Retail in Poland.

    PubMed

    Kędzierska-Matysek, Monika; Florek, Mariusz; Wolanciuk, Anna; Barłowska, Joanna; Litwińczuk, Zygmunt

    2018-04-04

    The aim of the study was to compare the content of selected minerals in different nectar honeys (acacia, buckwheat, raspberry, linden, rapeseed, and multifloral) available on the Polish market. The degree to which the demand for eight minerals (K, Na, Mg, Ca, Zn, Fe, Mn, Cu) by adults is met by a portion of 100 g of honey was estimated as well. The material consisted of 34 artisanal honeys from direct sale and 34 samples purchased from retail stores. The artisanal honeys contained significantly more K, Mg, and Mn, but significantly less Na and Fe than the honeys purchased from the retail stores. The raspberry honey contained significantly the most K and Ca (1104.7 and 68.8 mg kg -1 ), the multifloral honey contained the most Ca and Mg (68.5 and 48.0 mg kg -1 ), and the buckwheat honey contained the most Zn and Mn (3.97 and 4.96 mg kg -1 ). The highest content of Na was shown in buckwheat and linden honeys (79.1 and 80.0 mg kg -1 ). Consumption of 100 g of honey from direct sale satisfied from 2.5 to 4.5% of the recommended intakes for K and from 10.4 to 17.3% for Mn, while the same portion of honey from retail satisfied from 1.6 to 4.8% for Fe, and from 2.3 to 6.1% for Zn and Cu. The buckwheat honey met to the greatest degree the recommended dietary intakes for Mn (16.5-27.6%), followed by raspberry honey (10.0-16.7%) and multifloral honey (6.9-11.6%).

  4. Heat capacities and entropies of rhodochrosite (MnCO3) and siderite (FeCO3) between 5 and 600 K.

    USGS Publications Warehouse

    Robie, R.A.; Haselton, H.T.; Hemingway, B.S.

    1984-01-01

    The heat capacities of rhodochrosite, (Mn0.994Fe0.005Mg0.001)CO3, and siderite, 171(Fe0.956Mn0.042Mg0.002)CO3, were measured between 5 and 550 K by combined cryogenic-adiabatic and differential scanning calorimetry. These new data were used to reanalyse the thermodynamic properties of these phases.-J.A.Z.

  5. Combined use of EPR and 23Na MAS NMR spectroscopy for assessing the properties of the mixed cobalt-nickel-manganese layers of P3-NayCo1-2xNixMnxO2.

    PubMed

    Kalapsazova, M; Ivanova, S; Kukeva, R; Simova, S; Wegner, S; Zhecheva, E; Stoyanova, R

    2017-10-11

    Knowledge on the formation of mixed transition metal layers on lithium and sodium transition metal oxides, Li/Na(Co,Ni,Mn,)O 2 , determines the ability to control their electrochemical properties as electrode materials in alkaline ion batteries. Taking this into account, herein we combine the EPR and 23 Na MAS NMR spectroscopic techniques to gain insights into the structural peculiarities of the mixed cobalt-nickel-manganese layers of Na y Co 1-2x Ni x Mn x O 2 with a three-layer stacking (P3-type) structure. Two types of compositions are examined where diamagnetic Co 3+ and paramagnetic Ni 3+ and Mn 4+ are stabilized: Na 2/3 Co 1/3 Ni 1/3 Mn 1/3 O 2 and Na 1/2 Ni 1/2 Mn 1/2 O 2 . EPR spectroscopy operating in the X- and Q-band region is applied with an aim to improve the spectra resolution and, on the other hand, to provide straightforward information on the coordination of the transition metal ions inside the layers. The analysis of EPR spectra is based on the reference for the Mn 4+ and Ni 2+ ions occurring simultaneously in oxides with two layer stacking, P2-Na 2/3 Ni 1/3 Mn 2/3 O 2 . Complementary to EPR, 23 Na MAS NMR spectroscopy at high spinning rates is undertaken to assess the local structure of the Na nucleus in the layered P3-Na y Co 1-2x Ni x Mn x O 2 oxides. All results are discussed taking into account the EPR and NMR data for the well-known lithium analogues O3-LiCo 1/3 Ni 1/3 Mn 1/3 O 2 and O3-LiNi 1/2 Mn 1/2 O 2 . Finally, the structure peculiarities of the transition metal layers extracted from the EPR and NMR methods are demonstrated by electrochemical intercalation of Li + ions into P3-Na y Co 1-2x Ni x Mn x O 2 .

  6. Investigation of structural, morphological and electromagnetic properties of Mg0.25Mn0.25Zn0.5-xSrxFe2O4 ferrites

    NASA Astrophysics Data System (ADS)

    Rahaman, Md. D.; Nusrat, Tania; Maleque, Rumana; Hossain, A. K. M. Akther

    2018-04-01

    Polycrystalline Mg0.25Mn0.25Zn0.5-xSrxFe2O4 (0 ≤ x ≤ 0.20) ferrites were synthesized using the solid state reaction sintering at 1373 K and 1473 K for 4 h. The XRD patterns revealed the formation of single phase cubic spinel with Sr2FeO4 and SrFe12O19 as impurity phases. The decrement in the lattice parameter for Sr2+ substituted samples is attributed to the difference in ionic radii of cations. The crystallite size decreases with increase in Sr2+ content. Low frequency dielectric dispersion is attributed due to the Maxwell-Wagner interfacial polarization. The appearance of the peak in dielectric loss spectrum for x = 0.15 and 0.20 at 1373 K and x = 0.20 at 1473 K suggests the presence of relaxing dipoles. The loss peak shifts towards lower frequency side with Sr2+ content at 1373 K which is due to the strengthening of dipole-dipole interactions. The complex impedance spectra clearly revealed that the both grain and grain boundary effects on the electrical properties. A complex electric modulus spectrum indicates that a non-Debye type of conductivity relaxation exists. The saturation magnetization and remanence gradually decreases with Sr2+ substitution which may be due to the existence of non-magnetic phase in the space between the magnetic particles and the substitution of Zn2+ cation in Mg0.25Mn0.25Zn0.5Fe2O4 ferrite lattice by Sr2+ content. The permeability decreases significantly while the cut-off frequency increases with the Sr2+ content at 1373 K and decreases at 1473 K, obeying the Snoek's law. The decrease in permeability with Sr2+ content is attributed due to the decrease in magnetization because non-magnetic ions weaken the inter-site exchange interaction.

  7. Oxidative removal of Mn(II) from solution catalysed by the γ-FeOOH (lepidocrocite) surface

    NASA Astrophysics Data System (ADS)

    Sung, Windsor; Morgan, James J.

    1981-12-01

    A laboratory study was undertaken to ascertain the role of surface catalysis in Mn(II) oxidative removal. γ-FeOOH, a ferric oxyhydroxide formed by O2 oxidation of ferrous iron in solution, was studied in the following ways: surface charge characteristics by acid base titration, adsorption of Mn(II) and surface oxidation of Mn(II). A rate law was formulated to account for the effects of pH and the amount of surface on the surface oxidation rate of Mn(II). The presence of milli-molar levels of γ-FeOOH was shown to reduce significantly the half-life of Mn(II) in 0.7 M NaCl from hundreds of hours to hours. The numerical values of the surface rate constants for the γ-FeOOH and that reported for colloidal MnO2 are comparable in order of magnitude.

  8. Surface studies of Li-ion and Mg battery electrodes

    NASA Astrophysics Data System (ADS)

    Esbenshade, Jennifer

    This dissertation focuses on studies of the surfaces of both Li-ion and Mg-ion battery electrodes. A fundamental understanding of processes occurring at the electrode surface is vital to the development of advanced battery systems. Additionally, modifications to the electrode surfaces are made and further characterized for improved performance. LiMn2O4 Cathodes for Li-ion Batteries: Effect of Mn in electrolyte on anode and Au coating to minimize dissolution: LiMn2O4 (LMO) is known to dissolve Mn ions with cycling. This section focuses on both the effect of the dissolution of Mn2+ into the electrolyte as well as Au coating on the LMO to improve electrochemical performance. Electrochemical quartz crystal microbalance (EQCM) was used to monitor changes in mass on the anode, SEM and AES were used to observe changes in surface morphology and chemical composition, and potentiostatic voltammetry was used to monitor charge and discharge capacity. The effect of Cu2+ addition in place of Mn2+ was also studied, as Cu is known to form an underpotential deposition (UPD) monolayer on Au electrodes. Following this, LMO particles were coated with a Au shell by a simple and scalable electroless deposition for use as Li-ion battery cathodes. The Au shell was intended to limit the capacity fade commonly seen with LMO cathodes by reducing the dissolution of Mn. Characterization by SEM, TEM, EELS, and AFM showed that the Au shell was approximately 3 nm thick. The Au shell prevented much of the Mn from dissolving in the electrolyte with 82% and 88% less dissolved Mn in the electrolyte at room temperature and 65 ºC, respectively, as compared to the uncoated LMO. Electrochemical performance studies with half cells showed that the Au shell maintained a higher discharge capacity over 400 cycles by nearly 30% with 110 mA hr g-1 for the 400th cycle as compared to a commercial LMO at 85 mA hr g-1. Similarly, the capacity fade was reduced in full cells: the coated LMO had 47% greater capacity

  9. Enhanced torsional actuation and stress coupling in Mn-modified 0.93(Na 0.5Bi 0.5TiO 3)-0.07BaTiO 3 lead-free piezoceramic system

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Berik, Pelin; Maurya, Deepam; Kumar, Prashant

    This paper is concerned with the development of a piezoelectric d 15 shear-induced torsion actuator made of a lead-free piezoceramic material exhibiting giant piezoelectric shear stress coefficient (e 15) and piezoelectric transverse shear actuation force comparable to that of leadbased shear-mode piezoceramics. The Mn-modified 0.93(Na 0.5Bi 0.5TiO 3)-0.07BaTiO 3 (NBT-BTMn) composition exhibited excellent properties as a torsional transducer with piezoelectric shear stress coefficient on the order of 11.6 C m –2. The torsional transducer, consisting of two oppositely polarized NBT-BT-Mn d 15 mode piezoceramic shear patches, provided a rate of twist of 0.08 mm m –1 V –1 under quasi-staticmore » 150 V drive. The high value of piezoelectric shear d 15 coefficient in NBT-BT-Mn sample further demonstrated its potential in practical applications. Lastly, these results confirm that the lead-free piezoceramics can be as effective as their lead-based counterparts.« less

  10. Enhanced torsional actuation and stress coupling in Mn-modified 0.93(Na 0.5Bi 0.5TiO 3)-0.07BaTiO 3 lead-free piezoceramic system

    DOE PAGES

    Berik, Pelin; Maurya, Deepam; Kumar, Prashant; ...

    2017-01-09

    This paper is concerned with the development of a piezoelectric d 15 shear-induced torsion actuator made of a lead-free piezoceramic material exhibiting giant piezoelectric shear stress coefficient (e 15) and piezoelectric transverse shear actuation force comparable to that of leadbased shear-mode piezoceramics. The Mn-modified 0.93(Na 0.5Bi 0.5TiO 3)-0.07BaTiO 3 (NBT-BTMn) composition exhibited excellent properties as a torsional transducer with piezoelectric shear stress coefficient on the order of 11.6 C m –2. The torsional transducer, consisting of two oppositely polarized NBT-BT-Mn d 15 mode piezoceramic shear patches, provided a rate of twist of 0.08 mm m –1 V –1 under quasi-staticmore » 150 V drive. The high value of piezoelectric shear d 15 coefficient in NBT-BT-Mn sample further demonstrated its potential in practical applications. Lastly, these results confirm that the lead-free piezoceramics can be as effective as their lead-based counterparts.« less

  11. The influence of laser alloying on the structure and mechanical properties of AlMg5Si2Mn surface layers

    NASA Astrophysics Data System (ADS)

    Pakieła, W.; Tański, T.; Brytan, Z.; Labisz, K.

    2016-04-01

    The goal of this paper was focused on investigation of microstructure and properties of surface layer produced during laser surface treatment of aluminium alloy by high-power fibre laser. The performed laser treatment involves remelting and feeding of Inconel 625 powder into the aluminium surface. As a base metal was used aluminium alloy AlMg5Si2Mn. The Inconel powder was injected into the melt pool and delivered by a vacuum feeder at a constant rate of 4.5 g/min. The size of Inconel alloying powder was in the range 60-130 µm. In order to remelt the aluminium alloy surface, the fibre laser of 3 kW laser beam power has been used. The linear laser scan rate of the beam was set 0.5 m/min. Based on performed investigations, it was possible to obtain the layer consisting of heat-affected zone, transition zone and remelted zone, without cracks and defects having much higher hardness value compared to the non-alloyed material.

  12. Activation of a water molecule using a mononuclear Mn complex: from Mn-aquo, to Mn-hydroxo, to Mn-oxyl via charge compensation.

    PubMed

    Lassalle-Kaiser, Benedikt; Hureau, Christelle; Pantazis, Dimitrios A; Pushkar, Yulia; Guillot, Régis; Yachandra, Vittal K; Yano, Junko; Neese, Frank; Anxolabéhère-Mallart, Elodie

    2010-07-01

    Activation of a water molecule by the electrochemical oxidation of a Mn-aquo complex accompanied by the loss of protons is reported. The sequential (2 × 1 electron/1 proton) and direct (2 electron/2 proton) proton-coupled electrochemical oxidation of a non-porphyrinic six-coordinated Mn(II)OH 2 complex into a mononuclear Mn(O) complex is described. The intermediate Mn(III)OH 2 and Mn(III)OH complexes are electrochemically prepared and analysed. Complete deprotonation of the coordinated water molecule in the Mn(O) complex is confirmed by electrochemical data while the analysis of EXAFS data reveals a gradual shortening of an Mn-O bond upon oxidation from Mn(II)OH 2 to Mn(III)OH and Mn(O). Reactivity experiments, DFT calculations and XANES pre-edge features provide strong evidence that the bonding in Mn(O) is best characterized by a Mn(III)-oxyl description. Such oxyl species could play a crucial role in natural and artificial water splitting reactions. We provide here a synthetic example for such species, obtained by electrochemical activation of a water ligand.

  13. Corrosion behavior of as-cast Mg-8Li-3Al+ xCe alloy in 3.5wt% NaCl solution

    NASA Astrophysics Data System (ADS)

    Manivannan, S.; Dinesh, P.; Mahemaa, R.; MariyaPillai, Nandhakumaran; Kumaresh Babu, S. P.; Sundarrajan, Srinivasan

    2016-10-01

    Mg-8Li-3Al+ xCe alloys ( x = 0.5wt%, 1.0wt%, and 1.5wt%) were prepared through a casting route in an electric resistance furnace under a controlled atmosphere. The cast alloys were characterized by X-ray diffraction, optical microscopy, scanning electron microscopy, and energy-dispersive X-ray spectroscopy. The corrosion behavior of the as-cast Mg-8Li-3Al+ xCe alloys were studied under salt spray tests in 3.5wt% NaCl solution at 35°C, in accordance with standard ASTM B-117, in conjunction with potentiodynamic polarization (PDP) tests. The results show that the addition of Ce to Mg-8Li-3Al (LA83) alloy results in the formation of Al2Ce intermetallic phase, refines both the α-Mg phase and the Mg17Al12 intermetallic phase, and then increases the microhardness of the alloys. The results of PDP and salt spray tests reveal that an increase in Ce content to 1.5wt% decreases the corrosion rate. The best corrosion resistance is observed for the LA83 alloy sample with 1.0wt% Ce.

  14. Enhanced photoluminescence and phosphorescence properties of green phosphor Zn2GeO4:Mn(2+)via composition modification with GeO2 and MgF2.

    PubMed

    Pan, Yuexiao; Li, Li; Lu, Jing; Pang, Ran; Wan, Li; Huang, Shaoming

    2016-06-21

    A green long-lasting phosphorescence (LLP) phosphor Zn2GeO4:Mn(2+) (ZGOM) has been synthesized by a solid-state method at 1100 °C in air. The luminescence intensity has been improved up to 9 and 6 times through mixing GeO2 and MgF2 into the composition, respectively. The phosphorescence duration of the sample has been prolonged to 5 h. The phosphor, composed of a mixture of Zn2GeO4 (ZGO), GeO2, and MgGeO3 phases, emits enhanced green luminescence with a broad excitation band between 250 nm to 400 nm. Under identical measurement conditions, the optimized phosphor ZGOM has a higher emission intensity and shows longer wavelength emission than those of the commercial green LLP phosphor SrAl2O4:Eu,Dy (SAOED) under an excitation at 336 nm. The quantum yield of the sample modified by GeO2 and MgF2 is as high as 95.0%. Understanding of the formation mechanism for enhancement of emission intensity and prolonging of phosphorescence duration of ZGOM is fundamentally important, which might be extended to other identified solid-state inorganic phosphor materials for advanced properties.

  15. Activation of a water molecule using a mononuclear Mn complex: from Mn-aquo, to Mn-hydroxo, to Mn-oxyl via charge compensation†

    PubMed Central

    Lassalle-Kaiser, Benedikt; Hureau, Christelle; Pantazis, Dimitrios A.; Pushkar, Yulia; Guillot, Régis; Yachandra, Vittal K.; Yano, Junko; Neese, Frank; Anxolabéhère-Mallart, Elodie

    2014-01-01

    Activation of a water molecule by the electrochemical oxidation of a Mn-aquo complex accompanied by the loss of protons is reported. The sequential (2 × 1 electron/1 proton) and direct (2 electron/2 proton) proton-coupled electrochemical oxidation of a non-porphyrinic six-coordinated Mn(II)OH2 complex into a mononuclear Mn(O) complex is described. The intermediate Mn(III)OH2 and Mn(III)OH complexes are electrochemically prepared and analysed. Complete deprotonation of the coordinated water molecule in the Mn(O) complex is confirmed by electrochemical data while the analysis of EXAFS data reveals a gradual shortening of an Mn–O bond upon oxidation from Mn(II)OH2 to Mn(III)OH and Mn(O). Reactivity experiments, DFT calculations and XANES pre-edge features provide strong evidence that the bonding in Mn(O) is best characterized by a Mn(III)-oxyl description. Such oxyl species could play a crucial role in natural and artificial water splitting reactions. We provide here a synthetic example for such species, obtained by electrochemical activation of a water ligand. PMID:24772190

  16. Streptococcal 5'-Nucleotidase A (S5nA), a Novel Streptococcus pyogenes Virulence Factor That Facilitates Immune Evasion.

    PubMed

    Zheng, Lisa; Khemlani, Adrina; Lorenz, Natalie; Loh, Jacelyn M S; Langley, Ries J; Proft, Thomas

    2015-12-25

    Streptococcus pyogenes is an important human pathogen that causes a wide range of diseases. Using bioinformatics analysis of the complete S. pyogenes strain SF370 genome, we have identified a novel S. pyogenes virulence factor, which we termed streptococcal 5'-nucleotidase A (S5nA). A recombinant form of S5nA hydrolyzed AMP and ADP, but not ATP, to generate the immunomodulatory molecule adenosine. Michaelis-Menten kinetics revealed a Km of 169 μm and a Vmax of 7550 nmol/mg/min for the substrate AMP. Furthermore, recombinant S5nA acted synergistically with S. pyogenes nuclease A to generate macrophage-toxic deoxyadenosine from DNA. The enzyme showed optimal activity between pH 5 and pH 6.5 and between 37 and 47 °C. Like other 5'-nucleotidases, S5nA requires divalent cations and was active in the presence of Mg(2+), Ca(2+), or Mn(2+). However, Zn(2+) inhibited the enzymatic activity. Structural modeling combined with mutational analysis revealed a highly conserved catalytic dyad as well as conserved substrate and cation-binding sites. Recombinant S5nA significantly increased the survival of the non-pathogenic bacterium Lactococcus lactis during a human whole blood killing assay in a dose-dependent manner, suggesting a role as an S. pyogenes virulence factor. In conclusion, we have identified a novel S. pyogenes enzyme with 5'-nucleotidase activity and immune evasion properties. © 2015 by The American Society for Biochemistry and Molecular Biology, Inc.

  17. Influence of 10 % Cold Rolling Reduction on Ageing Behaviour of Hot Rolled Al-Cu-Si-Mn-Mg Alloy

    NASA Astrophysics Data System (ADS)

    Ghosh, S. K.

    2014-10-01

    In the current study, the effect of 10 % cold rolling on the different ageing phenomena of Al-Cu-Si-Mn-Mg alloy was investigated. Both hot rolled and cold rolled alloys were subjected to both natural and artificial ageing processes. Hardness was measured to understand the change in the mechanical property of the alloy before and after rolling and also during ageing processes. From microscopy, it was evident that the cold rolling and subsequent ageing provided the alloy with a structure in which CuAl2 precipitates were uniformly distributed. The alloy exhibited the peak hardness value of 92 VHN after 2 days of natural ageing, whereas the cold deformed (10 %) alloy exhibited the higher peak hardness value of 139 VHN after 3 days of natural ageing. Peak hardness of the alloy reached 94 VHN, when hot rolled alloy was subjected to ageing at 250 °C for 1 h, whereas 10 % cold rolling followed by ageing (100 °C, 15 min) demonstrated accelerated and elevated hardening. The ageing behaviours thus obtained permit the alloy to provide a range of desirable combinations of strength and ductility for high strength weight saving applications.

  18. Highly atom-economic synthesis of graphene/Mn3O4 hybrid composites for electrochemical supercapacitors

    NASA Astrophysics Data System (ADS)

    Jiangying, Qu; Feng, Gao; Quan, Zhou; Zhiyu, Wang; Han, Hu; Beibei, Li; Wubo, Wan; Xuzhen, Wang; Jieshan, Qiu

    2013-03-01

    A highly atom-economic procedure for the preparation of reduced graphene oxide/Mn3O4 (rGO/Mn3O4) composites is reported. Pristine graphene oxide/manganese sulfate (GO/MnSO4) suspension produced by modified Hummers method is utilized with high efficiency, which has been in situ converted into GO/Mn3O4 hybrid composite by air oxidation, then into rGO/Mn3O4 composite by means of dielectric barrier discharge (DBD) plasma-assisted deoxygenation. The Mn3O4 content of the rGO/Mn3O4 composites can be readily tailored. It is observed that Mn3O4 nanoparticles of 15-24 nm are well-dispersed on graphene sheets with Mn3O4 loading as high as 90%. The specific capacitance of the as-prepared rGO/Mn3O4 hybrids with 90% Mn3O4 reaches 193 F g-1 when employed as the electrode material in neutral Na2SO4 electrolyte solutions (76 F g-1 for pristine graphene and 95 F g-1 for pure Mn3O4), which indicates the positive synergetic effects from both graphene and attached Mn3O4. The method developed in this study should offer a new technique for the large scale and highly atom-economic production of graphene/MnOx composites for many applications.

  19. Structure-Induced Reversible Anionic Redox Activity in Na Layered Oxide Cathode

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Rong, Xiaohui; Liu, Jue; Hu, Enyuan

    Anionic redox reaction (ARR) in lithium- and sodium-ion batteries is under hot discussion, mainly regarding how oxygen anion participates and to what extent oxygen can be reversibly oxidized and reduced. In this paper, a P3-type Na 0.6[Li 0.2Mn 0.8]O 2 with reversible capacity from pure ARR was studied. The interlayer O-O distance (peroxo-like O-O dimer, 2.506(3) Å), associated with oxidization of oxygen anions, was directly detected by using a neutron total scattering technique. Finally, different from Li 2RuO 3 or Li 2IrO 3 with strong metal-oxygen (M-O) bonding, for P3-type Na 0.6[Li 0.2Mn 0.8]O 2 with relatively weak Mn-O covalentmore » bonding, crystal structure factors might play an even more important role in stabilizing the oxidized species, as both Li and Mn ions are immobile in the structure and thus may inhibit the irreversible transformation of the oxidized species to O 2 gas.« less

  20. Structure-Induced Reversible Anionic Redox Activity in Na Layered Oxide Cathode

    DOE PAGES

    Rong, Xiaohui; Liu, Jue; Hu, Enyuan; ...

    2017-11-01

    Anionic redox reaction (ARR) in lithium- and sodium-ion batteries is under hot discussion, mainly regarding how oxygen anion participates and to what extent oxygen can be reversibly oxidized and reduced. In this paper, a P3-type Na 0.6[Li 0.2Mn 0.8]O 2 with reversible capacity from pure ARR was studied. The interlayer O-O distance (peroxo-like O-O dimer, 2.506(3) Å), associated with oxidization of oxygen anions, was directly detected by using a neutron total scattering technique. Finally, different from Li 2RuO 3 or Li 2IrO 3 with strong metal-oxygen (M-O) bonding, for P3-type Na 0.6[Li 0.2Mn 0.8]O 2 with relatively weak Mn-O covalentmore » bonding, crystal structure factors might play an even more important role in stabilizing the oxidized species, as both Li and Mn ions are immobile in the structure and thus may inhibit the irreversible transformation of the oxidized species to O 2 gas.« less

  1. Characterization of the effects of different tempers and aging temperatures on the precipitation behavior of Al-Mg (5.25at.%)-Mn alloys

    DOE PAGES

    Yi, Gaosong; Littrell, Kenneth C.; Poplawsky, Jonathan D.; ...

    2017-01-11

    We investigated the effects of different tempers (H131 and H116) and different aging temperatures (50 and 70 °C) on the precipitation behavior of Al-Mg (5.25 at.%)-Mn (Al 5083) alloys aged for a long time (41 and 30 months) using electron backscatter diffraction(EBSD), scanning transmission electron microscopy(STEM), energy-dispersive X-ray spectroscopy(EDS), atom probe tomography (APT), and small angle neutron scattering (SANS). Results for the GP zones and β'' phases were found in Al 5083 H116 aged at 50 °C for 24 months using APT. EDS and SANS revealed that a phase transformation process from GP zones to β'/β phases occurred for precipitatesmore » formed in both Al 5083 H131 and H116 aged at 70 °C. The effective diffusion coefficient of Mg in Al 5083 H131 is 1.8 times of that in Al 5083 H116 aged at 70 °C. The precipitation process in Al 5083 H116 aged at 50 °C is much slower than that in the sample aged at 70 °C. Finally, we identified the coarsening process in Al 5083 H131 and H116 aged at 70 °C for > 9 months.« less

  2. Comparison on surface properties and desulfurization of MnO2 and pyrolusite blended activated carbon by steam activation.

    PubMed

    Zhang, Guochen; Zhao, Xin; Ning, Ping; Yang, Danni; Jiang, Xia; Jiang, Wenju

    2018-04-18

    In this study, MnO 2 and pyrolusite were used as the catalysts to prepare modified activated carbon, i.e., AC-Mn and AC-P, respectively, from coals by blending method and steam activation. The BET results indicated that the AC-P had higher surface areas and micropore volumes than the AC-Mn with the same blending ratio. The relative contents of basic functional groups (i.e. C = O, π-π*) on AC-P were slightly lower than those on AC-Mn, while both contained the same main metal species, i.e. MnO. The desulfurization results showed that with 3 wt% of blending ratio, AC-Mn3 and AC-P3 had higher sulfur capacities at 220 and 205 mg/g, respectively, which were much higher than blank one (149.6 mg/g). Moreover, the AC-P had relatively higher sulfur capacity than the AC-Mn with the same contents of Mn, which might be attributed to the existence of other metals in pyrolusite. After desulfurization process, MnO were gradually transferred into MnSO 4 , and the relative contents of basic functional groups decreased evidently for both AC-Mn3 and AC-P3. The results demonstrated that pyrolusite could be one good alternative of MnO 2 to prepare modified activated carbon for desulfurization. Implication statement MnO 2 and pyrolusite were used as the additives to prepare the modified activated carbon from coals by blending method and steam activation, i.e., AC-Mn and AC-P, respectively. The AC-P had higher surface areas and micropore volumes than the AC-Mn with the same blending ratio. The AC-Mn and AC-P had higher sulfur capacities than blank one. Moreover, the AC-P had relatively higher sulfur capacity than the AC-Mn with the same contents of Mn. The results demonstrated that pyrolusite could be one good alternative of MnO 2 to prepare modified activated carbon for desulfurization.

  3. Spin reorientation transition and hard magnetic properties of MnBi intermetallic compound

    NASA Astrophysics Data System (ADS)

    Suzuki, K.; Wu, X.; Ly, V.; Shoji, T.; Kato, A.; Manabe, A.

    2012-04-01

    The effects of mechanical grinding (MG) on the crystallite size, the spin reorientation transition temperature (TSR) and the hard magnetic properties in melt-spun low temperature phase (LTP) MnBi have been investigated in order to understand the origin of magnetic hardening induced by MG. The room-temperature coercive field (μ0Hcj) is enhanced dramatically from 0.08 T before MG to 1.5 T after MG for 43.2 ks while TSR is concurrently suppressed from 110 to 38 K. The coercive force exhibits positive temperature dependence approximately 50-60 K above TSR and the lowered TSR after MG could result in magnetic hardening at room temperature. The room-temperature coercive force of LTP-MnBi is highly dependent on the crystallite size (D) and is found to be described phenomenologically by the following relationship: μ0Hcj = μ0Ha(δ/D)n, where μ0Ha is ˜ 4 T, the Bloch wall width δ is 7 nm, and the exponent n is approximately 0.7. Our results suggest that the grain refinement is the primary origin of the hardening effect induced by MG with a possible minor hardening effect due to the suppression of the spin reorientation transition temperature.

  4. Fe and Mn removal from mining drainage using goaf filling materials obtained from coal mining process.

    PubMed

    Zhang, Liping; Chen, Aolei; Qu, Hongbin; Xu, Shouqiang; Zhang, Xue; He, Xuwen

    2015-01-01

    Coal gangue, sandy soil and clay (mass ratio 45:4:1) as goaf filling materials acquired from coal mining processes were applied to remove Fe and Mn effectively from mining drainage. The results of an adsorption kinetic study showed that the Fe adsorption equation was y=21.454y+8.4712, R2=0.9924 and the Mn adsorption equation was y=7.5409x+0.905, R2=0.9957. Meanwhile, the goaf filling materials had low desorption capacity (Fe 6.765 μg/g, Mn 1.52 μg/g) and desorption ratio (Fe 8.98%, Mn 11.04%). Experiments demonstrated that Fe and Mn from mining drainage could be removed stably at a flow rate of 1.2 L/min, Fe inlet concentration of less than 40 mg/L, Mn inlet concentration of less than 2 mg/L and neutral or alkaline conditions. During a procedure of continuous experiments, the effluent quality could meet the requirement of the 'Code for Engineering Design of Sewage Regeneration-GB503352-2002'. A real-application project using goaf filling materials to treat mining drainage in Shendong coal mine showed that the average cost per ton of mining drainage was about 0.55 RMB, which could bring about considerable economic benefit for coal mining enterprises.

  5. Structure and magnetism of a Mn(III)-Mn(II)-Mn(II)-Mn(III) chain complex.

    PubMed

    Uhrecký, Róbert; Moncoľ, Ján; Koman, Marian; Titiš, Ján; Boča, Roman

    2013-07-14

    A novel tetranuclear manganese(II/III) complex with anions of pyridine-2,6-dicarboxylic acid (dipicolinic acid) has been synthesised and magneto-structurally characterised. The crystal structure of [Mn(II)2Mn(III)2(dipic)6(H2O)4]·2CH3OH·4H2O has been determined by single-crystal X-ray diffraction. The tetranuclear complex molecule [Mn(II)2Mn(III)2(dipic)6(H2O)4] is centrosymmetric and two manganese(II) and two manganese(III) atoms are bridged by four dipicolinate ligands. The complex molecules and uncoordinated water and methanol molecules are connected through hydrogen bonds and they form a 3D supramolecular hydrogen-bonding network.

  6. Assessment of the mean glandular dose using LiF:Mg,Ti, LiF:Mg,Cu,P, Li2B4O7:Mn and Li2B4O7:Cu TL detectors in mammography radiation fields

    NASA Astrophysics Data System (ADS)

    Fartaria, M. J.; Reis, C.; Pereira, J.; Pereira, M. F.; Cardoso, J. V.; Santos, L. M.; Oliveira, C.; Holovey, V.; Pascoal, A.; Alves, J. G.

    2016-09-01

    The aim of this paper is the characterization of four thermoluminescence detectors (TLD), namely, LiF:Mg,Ti, LiF:Mg,Cu,P, Li2B4O7:Mn and Li2B4O7:Cu for the measurement of the entrance surface air kerma (ESAK) and estimation of the mean glandular dose (MGD) in digital mammography examinations at hospitals and clinics. Low-energy x-ray beams in the typical energy ranges of mammography, produced with a tungsten target and additional 60 µm molybdenum filtration were implemented and characterized at the Laboratory of Metrology of Ionizing Radiation at Instituto Superior Técnico. These beams were used for the characterization of the TLDs in terms of sensitivity, linearity, reproducibility, energy dependence and fading at 40 °C. The energy dependence test was further extended using clinical beams produced by mammography units at hospitals and clinics. The method proposed by the International Atomic Energy Agency was used for the measurement of ESAK and assessment of MGD. The combined standard uncertainty for the measurement of ESAK (and MGD) was determined in accordance to the Guide to the expression of uncertainty in measurement. The x-ray beams generated in the 23-40 kVp range presented HVL values from 0.36 to 0.46 mm Al. The beam produced at 28 kVp (HVL 0.39 mm Al) was considered as reference. The radiation field defined a circle with 84 mm diameter with a maximum variation of the beam intensity of less than 1% at the top flat (plateau) within 4 cm of the central axis. The estimated total uncertainty for the measurement of air kerma was 0.42%. All the TL detectors tested showed good performance except the commercial Li2B4O7:Mn (or TLD-800) which was excluded due to its poor sensitivity in our experimental set up. Both lithium fluorides showed better linearity and reproducibility as well as lower energy dependence and fading when compared to lithium borates. The stable behaviour of LiF:Mg,Ti and LiF:Mg,Cu,P detectors is reflected in the low combined standard

  7. Shape coexistence in the N = 19 neutron-rich nucleus 31Mg explored by β-γ spectroscopy of spin-polarized 31Na

    NASA Astrophysics Data System (ADS)

    Nishibata, H.; Shimoda, T.; Odahara, A.; Morimoto, S.; Kanaya, S.; Yagi, A.; Kanaoka, H.; Pearson, M. R.; Levy, C. D. P.; Kimura, M.

    2017-04-01

    The structure of excited states in the neutron-rich nucleus 31Mg, which is in the region of the ;island of inversion; associated with the neutron magic number N = 20, is studied by β-γ spectroscopy of spin-polarized 31Na. Among the 31Mg levels below the one neutron separation energy of 2.3 MeV, the spin values of all five positive-parity levels are unambiguously determined by observing the anisotropic β decay. Two rotational bands with Kπ = 1 /2+ and 1 /2- are proposed based on the spins and energies of the levels. Comparison on a level-by-level basis is performed between the experimental results and theoretical calculations by the antisymmetrized molecular dynamics (AMD) plus generator coordinate method (GCM). It is found that various nuclear structures coexist in the low excitation energy region in 31Mg.

  8. Advanced Na[Ni0.25Fe0.5Mn0.25]O2/C-Fe3O4 sodium-ion batteries using EMS electrolyte for energy storage.

    PubMed

    Oh, Seung-Min; Myung, Seung-Taek; Yoon, Chong Seung; Lu, Jun; Hassoun, Jusef; Scrosati, Bruno; Amine, Khalil; Sun, Yang-Kook

    2014-03-12

    While much research effort has been devoted to the development of advanced lithium-ion batteries for renewal energy storage applications, the sodium-ion battery is also of considerable interest because sodium is one of the most abundant elements in the Earth's crust. In this work, we report a sodium-ion battery based on a carbon-coated Fe3O4 anode, Na[Ni0.25Fe0.5Mn0.25]O2 layered cathode, and NaClO4 in fluoroethylene carbonate and ethyl methanesulfonate electrolyte. This unique battery system combines an intercalation cathode and a conversion anode, resulting in high capacity, high rate capability, thermal stability, and much improved cycle life. This performance suggests that our sodium-ion system is potentially promising power sources for promoting the substantial use of low-cost energy storage systems in the near future.

  9. A green approach for single-pot synthesis of graphene oxide and its composite with Mn3O4

    NASA Astrophysics Data System (ADS)

    Rathour, Rishi Karan Singh; Bhattacharya, Jayanta

    2018-04-01

    Development of simple, environment friendly and effective approaches for the synthesis of graphene oxide (GO) is highly demanded because of its widespread applications. The present study focuses on synthesis of GO coupled with simultaneous conversion of waste byproduct as novel products, which was further used to synthesize Mn3O4 nanoparticle (Mn3O4NP), composite of GO with Mn3O4NP (rGO-Mn3O4NC) and high purity K2SO4 crystal. The characterization of GO, Mn3O4NP, and rGOMn3O4NC demonstrates the formation of single layer ∼2 μm lateral GO, ∼15 nm sized Mn3O4NP, and thermally stable rGO-Mn3O4NC. The experimental yields of GO, Mn3O4NP, and K2SO4 were 1.72, 2.04, and 87.0 g from 1.0, 4.0g, and 25.0mL of graphite, KMnO4, and H2SO4. The specific surface area of GO, Mn3O4NP, and rGO-Mn3O4NC were found to be 152.5, 233, and 27.6 m2/g, respectively. The adsorptive removal of lead (Pb2+) and methylene blue (MB) from aqueous solution by GO, Mn3O4NP, and rGO-Mn3O4NC shows an adsorption capacity of 42.3, 219, and 105 mg/g, for Pb2+ and 366, 7.5, and 17.5 mg/g, for MB, respectively. The cost analysis reveals that the proposed synthesis route is comparatively quite competitive.

  10. Ferromagnetic MnGaN thin films with perpendicular magnetic anisotropy for spintronics applications

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Lee, Hwachol; Sukegawa, Hiroaki, E-mail: sukegawa.hiroaki@nims.go.jp; Ohkubo, Tadakatsu

    2015-07-20

    Perpendicularly magnetized flat thin films of antiperovskite Mn{sub 67}Ga{sub 24}N{sub 9} were grown on an MgO(001) substrate by reactive sputtering using an argon/1% nitrogen gas mixture and a Mn{sub 70}Ga{sub 30} target. The films showed a saturation magnetization of 80 –100 kA/m, an effective perpendicular magnetic anisotropy (PMA) energy of 0.1–0.2 MJ/m{sup 3}, and a Curie temperature of 660–740 K. Upon increasing the N composition, the films transformed from ferromagnetic to antiferromagnetic as expected in the stoichiometric Mn{sub 3}GaN phase. Point contact Andreev reflection spectroscopy revealed that the ferromagnetic MnGaN has a current spin polarization of 57%, which is comparable to D0{sub 22}-MnGa. Thesemore » findings suggest that MnGaN is a promising PMA layer for future spintronics devices.« less

  11. Electrochemical Behavior Assessment of As-Cast Mg-Y-RE-Zr Alloy in Phosphate Buffer Solutions (X Na3PO4 + Y Na2HPO4) Using Electrochemical Impedance Spectroscopy and Mott-Schottky Techniques

    NASA Astrophysics Data System (ADS)

    Fattah-alhosseini, Arash; Asgari, Hamed

    2018-05-01

    In the present study, electrochemical behavior of as-cast Mg-Y-RE-Zr alloy (RE: rare-earth alloying elements) was investigated using electrochemical tests in phosphate buffer solutions (X Na3PO4 + Y Na2HPO4). X-ray diffraction techniques and Scanning electron microscopy equipped with energy dispersive x-ray spectroscopy were used to investigate the microstructure and phases of the experimental alloy. Different electrochemical tests such as potentiodynamic polarization (PDP), electrochemical impedance spectroscopy (EIS) and Mott-Schottky (M-S) analysis were carried out in order to study the electrochemical behavior of the experimental alloy in phosphate buffer solutions. The PDP curves and EIS measurements indicated that the passive behavior of the as-cast Mg-Y-RE-Zr alloy in phosphate buffer solutions was weakened by an increase in the pH, which is related to formation of an imperfect and less protective passive layer on the alloy surface. The presence of the insoluble zirconium particles along with high number of intermetallic phases of RE elements mainly Mg24Y5 in the magnesium matrix can deteriorate the corrosion performance of the alloy by disrupting the protective passive layer that is formed at pH values over 11. These insoluble zirconium particles embedded in the matrix can detrimentally influence the passivation. The M-S analysis revealed that the formed passive layers on Mg-Y-RE-Zr alloy behaved as an n-type semiconductor. An increase in donor concentration accompanying solutions of higher alkalinity is thought to result in the formation of a less resistive passive layer.

  12. Yb14MgBi11: structure, thermoelectric properties and the effect of the structure on low lattice thermal conductivity.

    PubMed

    Hu, Yufei; Kauzlarich, Susan M

    2017-03-21

    Zintl phases Yb 14 MnSb 11 and Yb 14 MgSb 11 , which share the same complex structure type, have been demonstrated as the best p-type thermoelectric materials for the high temperature region (800-1200 K). A new iso-structural compound, Yb 14 MgBi 11 , was synthesized in order to investigate the structure and thermoelectric properties of the Bi analogs. Yb 14 MgBi 11 crystallizes in the Ca 14 AlSb 11 structure-type with the space group I4 1 /acd [a = 16.974(2) Å, c = 22.399(4) Å, V = 6454(2) Å 3 , R 1 /wR 2 = 0.0238/0.0475]. The structure follows the previous description of this structure type and the trend observed in previous analogs. Thermoelectric properties of Yb 14 MgBi 11 are measured together with Yb 14 MnBi 11 and both compounds are metallic. Compared to Yb 14 MgSb 11 , Yb 14 MgBi 11 has a higher carrier concentration with a similar mobility and effective mass. The lattice thermal conductivity of Yb 14 MgBi 11 is extremely low, which is as low as 0.16-0.36 W(mK) -1 . The zT values of Yb 14 MgBi 11 and Yb 14 MnBi 11 reach 0.2 at 875 K.

  13. Influence of biodegradable polymer coatings on corrosion, cytocompatibility and cell functionality of Mg-2.0Zn-0.98Mn magnesium alloy.

    PubMed

    Witecka, Agnieszka; Yamamoto, Akiko; Idaszek, Joanna; Chlanda, Adrian; Święszkowski, Wojciech

    2016-08-01

    Four kinds of biodegradable polymers were employed to prepare bioresorbable coatings on Mg-2.0Zn-0.98Mn (ZM21) alloy to understand the relationship between polymer characteristics, protective effects on substrate corrosion, cytocompatibility and cell functionality. Poly-l-lactide (PLLA), poly(3-hydroxybutyrate) (PHB), poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) or poly(lactic-co-glycolic) acid (PLGA) was spin-coated on ZM21, obtaining a smooth, non-porous coating less than 0.5μm in thickness. Polymer coating characterization, a degradation study, and biocompatibility evaluations were performed. After 4 w of immersion into cell culture medium, degradation of PLGA and PLLA coatings were confirmed by ATR-FTIR observation. The coatings of PLLA, PHB and PHBV, which have lower water permeability and slower degradation than PLGA, provide better suppression of initial ZM21 degradation and faster promotion of human osteosarcoma cell growth and differentiation. Copyright © 2016 Elsevier B.V. All rights reserved.

  14. Novel Montmorillonite/TiO₂/MnAl-Mixed Oxide Composites Prepared from Inverse Microemulsions as Combustion Catalysts.

    PubMed

    Napruszewska, Bogna D; Michalik-Zym, Alicja; Rogowska, Melania; Bielańska, Elżbieta; Rojek, Wojciech; Gaweł, Adam; Wójcik-Bania, Monika; Bahranowski, Krzysztof; Serwicka, Ewa M

    2017-11-19

    A novel design of combustion catalysts is proposed, in which clay/TiO₂/MnAl-mixed oxide composites are formed by intermixing exfoliated organo-montmorillonite with oxide precursors (hydrotalcite-like in the case of Mn-Al oxide) obtained by an inverse microemulsion method. In order to assess the catalysts' thermal stability, two calcination temperatures were employed: 450 and 600 °C. The composites were characterized with XRF (X-ray fluorescence), XRD (X-ray diffraction), HR SEM (high resolution scanning electron microscopy, N₂ adsorption/desorption at -196 °C, and H₂ TPR (temperature programmed reduction). Profound differences in structural, textural and redox properties of the materials were observed, depending on the presence of the TiO₂ component, the type of neutralization agent used in the titania nanoparticles preparation (NaOH or NH₃ (aq)), and the temperature of calcination. Catalytic tests of toluene combustion revealed that the clay/TiO₂/MnAl-mixed oxide composites prepared with the use of ammonia showed excellent activity, the composites obtained from MnAl hydrotalcite nanoparticles trapped between the organoclay layers were less active, but displayed spectacular thermal stability, while the clay/TiO₂/MnAl-mixed oxide materials obtained with the aid of NaOH were least active. The observed patterns of catalytic activity bear a direct relation to the materials' composition and their structural, textural, and redox properties.

  15. Pyroxenoids of pyroxmangite-pyroxferroite series from xenoliths of Bellerberg paleovolcano (Eifel, Germany): Chemical variations and specific features of cation distribution

    NASA Astrophysics Data System (ADS)

    Shchipalkina, N. V.; Aksenov, S. M.; Chukanov, N. V.; Pekov, I. V.; Rastsvetaeva, R. K.; Schäfer, C.; Ternes, B.; Shüller, W.

    2016-11-01

    The pyroxferroite and pyroxmangite from xenoliths of aluminous gneisses in the alkaline basalts of Bellerberg paleovulcano (Eifel, Germany) have been studied by electron-probe and X-ray diffraction methods and IR spectroscopy. The parameters of the triclinic unit cells are found to be a = 6.662(1) Å, b = 7.525(1) Å, c = 15.895(2) Å, α = 91.548(3)°, β = 96.258(3)°, and γ = 94.498(3)° for pyroxferroite and a = 6.661(3) Å, b = 7.513(3) Å, c = 15.877(7) Å, α = 91.870(7)°, β = 96.369(7)°, and γ = 94.724(7)° for pyroxmangite; sp. gr. Poverline 1 . The crystallochemical formulas ( Z = 2) are, respectively, M(1-2)(Mn0.5Ca0.4Na0.1)2 M(3-6)(Fe, Mn)4 M7[Mg0.6(Fe, Mn)0.4][Si7O21] and M(1-3)(Mn, Fe)3 M(4-6)[(Fe, Mn)0.7Mg0.3]3 M7[Mg0.5(Fe, Mn)0.5][Si7O21]. For these and previously studied representatives of the pyroxmangite structural type, an analysis of the cation distribution over sites indicates wide isomorphism of Mn2+, Fe2+, and Mg in all cation M(1-7) sites and the preferred incorporation of Ca and Na into large seven-vertex M1O7 and M2O7 polyhedra and Mg into the smallest five-vertex M7O5 polyhedron.

  16. Dielectric properties of doping-free NaMn{sub 7}O{sub 12}: Origin of the observed colossal dielectric constant

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Cabassi, R.; Bolzoni, F.; Gauzzi, A.

    2006-07-15

    The semiconducting NaMn{sub 7}O{sub 12} is a doping-free compound with several coexistent properties such as orbital ordering, charge ordering, and magnetic orderings of different types. We investigated its dielectric response by means of frequency impedance measurements in the range from 20 Hz to 1 MHz. Standard measurements on metallized samples exhibit an apparent colossal dielectric constant (CDC) with an {epsilon}{sub R} value of several thousands at low frequencies, but a careful equivalent circuit analysis allows one to ascribe the observed CDC to the effect of a depletion layer on the metal-semiconductor junctions. We bypass this effect by means of amore » nonstandard technique employing mica linings: the resulting dielectric behavior exhibits the presence of the charge ordering transition at T{sub CO}=176 K and shows a net bulk dielectric constant value {epsilon}{sub R}{approx_equal}68 at room temperature.« less

  17. Recent thymic emigrants and mature naïve T cells exhibit differential DNA methylation at key cytokine loci

    PubMed Central

    Berkley, Amy M.; Hendricks, Deborah W.; Simmons, Kalynn B.; Fink, Pamela J.

    2013-01-01

    Recent thymic emigrants (RTEs) are the youngest T cells in the lymphoid periphery, and exhibit phenotypic and functional characteristics distinct from those of their more mature counterparts in the naïve peripheral T cell pool. We show here that the Il2 and Il4 promoter regions of naïve CD4+ RTEs are characterized by site-specific hypermethylation compared to those of both mature naïve (MN) T cells and the thymocyte precursors of RTEs. Thus, RTEs do not merely occupy a midpoint between the thymus and the mature T cell pool, but represent a distinct transitional T cell population. Furthermore, RTEs and MN T cells exhibit distinct CpG DNA methylation patterns both before and after activation. Compared to MN T cells, RTEs express higher levels of several enzymes that modify DNA methylation, and inhibiting methylation during culture allows RTEs to reach MN T cell levels of cytokine production. Collectively, these data suggest that the functional differences that distinguish RTEs from MN T cells are influenced by epigenetic mechanisms and provide clues to a mechanistic basis for post-thymic maturation. PMID:23686491

  18. Interstitial Fe in MgO

    NASA Astrophysics Data System (ADS)

    Mølholt, T. E.; Mantovan, R.; Gunnlaugsson, H. P.; Svane, A.; Masenda, H.; Naidoo, D.; Bharuth-Ram, K.; Fanciulli, M.; Gislason, H. P.; Johnston, K.; Langouche, G.; Ólafsson, S.; Sielemann, R.; Weyer, G.

    2014-01-01

    Isolated 57Fe atoms were studied in MgO single-crystals by emission Mössbauer spectroscopy following implantation of 57Mn decaying to 57Fe. Four Mössbauer spectral components were found corresponding to different Fe lattice positions and/or charge states. Two components represent Fe atoms substituting Mg as Fe2+ and Fe3+, respectively; a third component is due to Fe in a strongly implantation-induced disturbed region. The fourth component, which is the focus of this paper, can be assigned to Fe at an interstitial site. Comparison of its measured isomer shift with ab initio calculations suggests that the interstitial Fe is located on, or close to, the face of the rock-salt MgO structure. To harmonize such an assignment with the measured near-zero quadrupole interaction a local motion process (cage motion) of the Fe has to be stipulated. The relation of such a local motion as a starting point for long range diffusion is discussed.

  19. Multicopper Oxidase Involvement in Both Mn(II) and Mn(III) Oxidation during Bacterial Formation of MnO2

    PubMed Central

    Soldatova, Alexandra V.; Butterfield, Cristina; Oyerinde, Oyeyemi F.; Tebo, Bradley M.; Spiro, Thomas G.

    2013-01-01

    Global cycling of environmental manganese requires catalysis by bacteria and fungi for MnO2 formation, since abiotic Mn(II) oxidation is slow under ambient conditions. Genetic evidence from several bacteria implicates multicopper oxidases (MCOs) as being required for MnO2 formation. However, MCOs catalyze one-electron oxidations, whereas conversion of Mn(II) to MnO2 is a two-electron process. Trapping experiments with pyrophosphate (PP), a Mn(III) chelator, have demonstrated that Mn(III) is an intermediate in Mn(II) oxidation when mediated by exosporium from the Mn-oxidizing bacterium Bacillus SG-1. The reaction of Mn(II) depends on O2 and is inhibited by azide, consistent with MCO catalysis. We show that the subsequent conversion of Mn(III) to MnO2 also depends on O2 and is inhibited by azide. Thus, both oxidation steps appear to be MCO-mediated, likely by the same enzyme, indicated by genetic evidence to be the MnxG gene product. We propose a model of how the manganese oxidase active site may be organized to couple successive electron transfers to the formation of polynuclear Mn(IV) complexes as precursors to MnO2 formation. PMID:22892957

  20. A Possible Neuroprotective Action of a Vinylic Telluride against Mn-Induced Neurotoxicity

    PubMed Central

    Ávila, Daiana S.; Colle, Dirleise; Gubert, Priscila; Palma, Aline S.; Puntel, Gustavo; Manarin, Flávia; Noremberg, Simone; Nascimento, Paulo C.; Aschner, Michael; Rocha, João B. T.; Soares, Félix A. A.

    2010-01-01

    Manganese (Mn) is a metal required by biological systems. However, environmental or occupational exposure to high levels of Mn can produce a neurological disorder called manganism, which has similarities to Parkinson's disease. Diethyl-2-phenyl-2-tellurophenyl vinylphosphonate (DPTVP) is an organotellurium compound with a high antioxidant activity, especially in the brain. The present study was designed to investigate the effects of long-term low-dose exposure to Mn in drinking water on behavioral and biochemical parameters in rats and to determine the effectiveness of vinylic telluride in attenuating the effects of Mn. After 4 months of treatment with MnCl2 (13.7 mg/kg), rats exhibited clear signs of neurobehavioral toxicity, including a decrease in the number of rearings in the open field and altered motor performance in rotarod. The administration of DPTVP (0.150 μmol/kg, ip, 2 weeks) improved the motor performance of Mn-treated rats, indicating that the compound could be reverting Mn neurotoxicity. Ex vivo, we observed that Mn concentrations in the Mn-treated group were highest in the striatum, consistent with a statistically significant decrease in mitochondrial viability and [3H]glutamate uptake, and increased lipid peroxidation. Mn levels in the hippocampus and cortex were indistinguishable from controls, and no significant differences were noted in the ex vivo assays in these areas. Treatment with DPTVP fully reversed the biochemical parameters altered by Mn. Furthermore, DPTVP treatment was also associated with a reduction in striatal Mn levels. Our results demonstrate that DPTVP has neuroprotective activity against Mn-induced neurotoxicity, which may be attributed to its antioxidant activity and/or its effect on striatal Mn transport. PMID:20133376

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

    PubMed Central

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

    2013-01-01

    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

  2. Ca removal and Mg recovery from flue gas desulfurization (FGD) wastewater by selective precipitation.

    PubMed

    Xia, Min; Ye, Chunsong; Pi, Kewu; Liu, Defu; Gerson, Andrea R

    2017-11-01

    Selective removal of Ca and recovery of Mg by precipitation from flue gas desulfurization (FGD) wastewater has been investigated. Thermodynamic analysis of four possible additives, Na 2 CO 3 , Na 2 C 2 O 4 , NaF and Na 2 SO 4 , indicated that both carbonate and oxalate could potentially provide effective separation of Ca via precipitation from Mg in FGD wastewater. However, it was found experimentally that the carbonate system was not as effective as oxalate in this regard. The oxalate system performed considerably better, with Ca removal efficiency of 96% being obtained, with little Mg inclusion at pH 6.0 when the dosage was ×1.4 the stoichiometric requirement. On this basis, the subsequent recovery process for Mg was carried out using NaOH with two-step precipitation. The product was confirmed to be Mg(OH) 2 (using X-ray diffraction and thermo gravimetric analysis) with elemental analysis suggesting a purity of 99.3 wt.%.

  3. Quaternary M{sub 0.25}Cu{sub 0.25}Mg{sub 0.5}Fe{sub 2}O{sub 4} (M = Ni, Zn, Co, Mn) ferrite oxides: Synthesis, characterization and magnetic properties

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Ciocarlan, Radu George; Laboratory of Adsorption and Catalysis, Department of Chemistry, University of Antwerpen; Pui, Aurel, E-mail: aurel@uaic.ro

    2016-09-15

    Highlights: • Superparamagnetic quaternary nanoferrite (M{sub 0.25}Cu{sub 0.25}Mg{sub 0.5}Fe{sub 2}O{sub 4,} where M = Mn, Zn, Co, Ni) were obtained. • C, O, H and metals were observed by XPS analysis. • Phases purity were confirmed by XRD diffraction and crystallite size (3–10 nm) were determind. - Abstract: We report the synthesis of M{sub 0.25}Cu{sub 0.25}Mg{sub 0.5}Fe{sub 2}O{sub 4} (where M = Mn, Zn, Co, Ni) nanoparticles using the coprecipitation method in the presence of carboxymethyl cellulose (CMC) as the in-situ surfactant. The crystalline structure and surface morphology were examined by means of X-ray diffraction (XRD) and scanning electron microscopymore » (SEM) and it was established that the average diameter of the magnetic nanoparticles (MNPs) is in the range of 3–10 nm. X-ray photoelectron spectroscopy (XPS) and Fourier transform infrared spectroscopy (FTIR) show that the MNPs are activated by the hydrophilic groups of the surfactant, which coat them and enhance their stability. The vibrating sample magnetometry measurements show the superparamagnetic behavior of the nanoparticles. Due to their small crystallite size, which implies large surface area, and their functionalization with organic groups, the obtained nanoparticles could have medical and catalytic applications.« less

  4. Carbon dioxide sequestration using NaHSO4 and NaOH: A dissolution and carbonation optimisation study.

    PubMed

    Sanna, Aimaro; Steel, Luc; Maroto-Valer, M Mercedes

    2017-03-15

    The use of NaHSO 4 to leach out Mg fromlizardite-rich serpentinite (in form of MgSO 4 ) and the carbonation of CO 2 (captured in form of Na 2 CO 3 using NaOH) to form MgCO 3 and Na 2 SO 4 was investigated. Unlike ammonium sulphate, sodium sulphate can be separated via precipitation during the recycling step avoiding energy intensive evaporation process required in NH 4 -based processes. To determine the effectiveness of the NaHSO 4 /NaOH process when applied to lizardite, the optimisation of the dissolution and carbonation steps were performed using a UK lizardite-rich serpentine. Temperature, solid/liquid ratio, particle size, concentration and molar ratio were evaluated. An optimal dissolution efficiency of 69.6% was achieved over 3 h at 100 °C using 1.4 M sodium bisulphate and 50 g/l serpentine with particle size 75-150 μm. An optimal carbonation efficiency of 95.4% was achieved over 30 min at 90 °C and 1:1 magnesium:sodium carbonate molar ratio using non-synthesised solution. The CO 2 sequestration capacity was 223.6 g carbon dioxide/kg serpentine (66.4% in terms of Mg bonded to hydromagnesite), which is comparable with those obtained using ammonium based processes. Therefore, lizardite-rich serpentinites represent a valuable resource for the NaHSO 4 /NaOH based pH swing mineralisation process. Copyright © 2016 Elsevier Ltd. All rights reserved.

  5. In Operando XRD and TXM Study on the Metastable Structure Change of NaNi 1/3Fe 1/3Mn 1/3O 2 under Electrochemical Sodium-Ion Intercalation

    DOE PAGES

    Xie, Yingying; Wang, Hong; Xu, Guiliang; ...

    2016-09-02

    In operando XRD and TXM-XANES approaches demonstrate that structure evolution in NaNi 1/3Fe 1/3Mn 1/3O 2 during cycling follows a continuous change, and the formation of a nonequilibrium solid solution phase in the existence of two phases. Here, an O3' and P3' monoclinic phase occur, and redox couples of Ni 3+/Ni 4+ and Fe 3+/Fe 4+ are mainly responsible in the charge voltage range from 4.0 to 4.3 V.

  6. Kinetic Investigations of SiMn Slags From Different Mn Sources

    NASA Astrophysics Data System (ADS)

    Kim, Pyunghwa Peace; Tangstad, Merete

    2018-06-01

    The kinetics of MnO and SiO2 reduction were investigated for Silicomanganese (SiMn) slags using a Thermogravimetric analysis (TGA) between 1773 K and 1923 K (1500 °C and 1650 °C) under CO atmospheric pressure. The charge materials were based on Assmang ore and HC FeMn Slag. Rate models for MnO and SiO2 reduction were applied to describe the metal-producing rates, as shown by the following equations: r_{MnO} = k_{MnO} × A × ( {a_{MnO} - {a_{Mn} }/{K_{T }}} ) r_{{{SiO}2 }} = k_{SiO2} × A × ( {a_{{{SiO}2 }} - {a_{Si} }/{K_{T }}} ). The results show that the choice of raw materials in the charge considerably affected the reduction rate of MnO and SiO2. The highest reduction rate was found to be from charges using HC FeMn slag. The difference in the driving forces was insignificant among the SiMn slags, and the similar slag viscosities could not explain the different reduction rates. Instead, the difference is attributed to small amounts of sulfur and the amount of iron in the charge. In addition, the rate models were applicable to describe the reduction of MnO and SiO2 in SiMn slags.

  7. Contributions of phase and structural transformations in multicomponent Al-Mg alloys to the linear and nonlinear mechanisms of anelasticity

    NASA Astrophysics Data System (ADS)

    Golovin, I. S.; Bychkov, A. S.; Mikhailovskaya, A. V.; Dobatkin, S. V.

    2014-02-01

    The effects of the processes of severe plastic deformation (SPD), recrystallization, and precipitation of the β phase in multicomponent alloys of the Al-5Mg-Mn-Cr and Al-(4-5%)Mg-Mn-Zn-Sc systems on the mechanisms of grain-boundary relaxation and dislocation-induced microplasticity have been studied in some detail. To stabilize the ultrafine-grained structure and prevent grain growth, dispersed Al-transition-metal particles, such as Al3Zr, Al6Mn, Al7Cr, Al6(Mn,Cr), Al18Cr2Mg3 have been used. We have special interest in alloys with additions of scandium, which forms compounds of the Al3Sc type and favors the precipitation of finer particles compared to the aluminides of other transition metals. After SPD, Al-(4-5%)Mg-Mn-Zr-Sc alloys exhibit an enhanced recrystallization temperature. The general features of the dislocation and grain-boundary anelasticity that have been established for the binary Al-Mg alloys are retained; i.e., (1) the decrease in the dislocation density in the process of recrystallization of cold-worked alloys leads to the formation of a pseudo-peak in the curves of the temperature dependences of internal friction (TDIF) and to a decrease in the critical amplitude of deformation corresponding to the onset of dislocation motion in a stress field; (2) the precipitation of the β phase suppresses the grain-boundary relaxation; (3) the dissolution of the β phase, the passage of the magnesium atoms into the solid solution, and the precipitation of the β' phase upon heating hinder the motion of dislocations; (4) the coarsening of the highly dispersed particles containing Zr and Sc increases the dislocation mobility. The grain-boundary relaxation and dislocation-impurity interaction and their temperature dependences, as well as processes of the additional alloying of the binary alloys by Mn, Cr, Zr, and Sc, have been estimated quantitatively.

  8. Electrochemical performance studies of MnO{sub 2} nanoflowers recovered from spent battery

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Ali, Gomaa A.M.; Chemistry Department, Faculty of Science, Al-Azhar University, Assiut 71524; Tan, Ling Ling

    2014-12-15

    Highlights: • MnO{sub 2} is recovered from spent zinc–carbon batteries as nanoflowers structure. • Recovered MnO{sub 2} nanoflowers show high specific capacitance. • Recovered MnO{sub 2} nanoflowers show stable electrochemical cycling up to 900 cycles. • Recovered MnO{sub 2} nanoflowers show low resistance in EIS data. - Abstract: The electrochemical performance of MnO{sub 2} nanoflowers recovered from spent household zinc–carbon battery is studied by cyclic voltammetry, galvanostatic charge/discharge cycling and electrochemical impedance spectroscopy. MnO{sub 2} nanoflowers are recovered from spent zinc–carbon battery by combination of solution leaching and electrowinning techniques. In an effort to utilize recovered MnO{sub 2} nanoflowers asmore » energy storage supercapacitor, it is crucial to understand their structure and electrochemical performance. X-ray diffraction analysis confirms the recovery of MnO{sub 2} in birnessite phase, while electron microscopy analysis shows the MnO{sub 2} is recovered as 3D nanostructure with nanoflower morphology. The recovered MnO{sub 2} nanoflowers exhibit high specific capacitance (294 F g{sup −1} at 10 mV s{sup −1}; 208.5 F g{sup −1} at 0.1 A g{sup −1}) in 1 M Na{sub 2}SO{sub 4} electrolyte, with stable electrochemical cycling. Electrochemical data analysis reveal the great potential of MnO{sub 2} nanoflowers recovered from spent zinc–carbon battery in the development of high performance energy storage supercapacitor system.« less

  9. Magnetic state selected by magnetic dipole interaction in the kagome antiferromagnet NaBa2Mn3F11

    NASA Astrophysics Data System (ADS)

    Hayashida, Shohei; Ishikawa, Hajime; Okamoto, Yoshihiko; Okubo, Tsuyoshi; Hiroi, Zenji; Avdeev, Maxim; Manuel, Pascal; Hagihala, Masato; Soda, Minoru; Masuda, Takatsugu

    2018-02-01

    We haved studied the ground state of the classical kagome antiferromagnet NaBa2Mn3F11 . Strong magnetic Bragg peaks observed for d spacings shorter than 6.0 Å were indexed by the propagation vector of k0=(0 ,0 ,0 ) . Additional peaks with weak intensities in the d -spacing range above 8.0 Å were indexed by the incommensurate vector of k1=[0.3209 (2 ) ,0.3209 (2 ) ,0 ] and k2=[0.3338 (4 ) ,0.3338 (4 ) ,0 ] . Magnetic structure analysis unveils a 120∘ structure with the tail-chase geometry having k0 modulated by the incommensurate vector. A classical calculation of the Heisenberg kagome antiferromagnet with antiferromagnetic second-neighbor interaction, for which the ground state a k0120∘ degenerated structure, reveals that the magnetic dipole-dipole (MDD) interaction including up to the fourth neighbor terms selects the tail-chase structure. The observed modulation of the tail-chase structure is attributed to a small perturbation such as the long-range MDD interaction or the interlayer interaction.

  10. Nonequivalence of chemical and hydrostatic pressures: A1g and Eg frequencies and Stokes shift of Mn2+-doped perovskites

    NASA Astrophysics Data System (ADS)

    Barriuso, M. T.; Moreno, M.; Aramburu, J. A.

    2002-02-01

    The frequency of A1g and Eg modes of MnF4-6 in cubic ABF3 (A: K; B: Mg, Zn and A: Rb, Cs; B: Cd, Ca) perovskites has been derived through density functional calculations on MnF6A8B16+6 clusters which reproduce the experimental impurity-ligand distance Re. Both frequencies are found to experience a drastic decrement on passing from KMgF3:Mn2+ (ħωA=556 cm-1, ħωE=456 cm-1) to CsCdF3:Mn2+ (ħωA=317 cm-1, ħωE=239 cm-1) despite the fact that Re increases only by 5%, leading to effective Grüneisen constants (called γcA and γcE) around 3.0 along the series. This figure is 60% higher than the usual Grüneisen constant γA calculated for a given system like KMgF3:Mn2+ or KZnF3:Mn2+ when hydrostatic pressure is applied. For supporting this relevant result the value of γA for CrF3-6 in a fluoroelpasolite has been calculated as well. The obtained value γA=2.1 is close to the experimental one (γA=1.9) derived in K2NaGaF6:Cr3+ by combined optical and Raman measurements. As a salient feature, the increase of the Stokes shift when Re increases observed along the ABF3:Mn2+ series is now well explained through the bigger variations of A1g and Eg frequencies induced by the chemical pressure in comparison to those coming from an hydrostatic pressure on a given system. The difference between γcA and γA is discussed through a simple model that emphasizes the role played by the coupling of the MnF4-6 complex to the lattice. The influence of chemical and hydrostatic pressures upon the luminescence efficiency is also briefly discussed. Attention is addressed to the method of calculating impurity-associated Grüneisen constants using clusters. Recent results on Cr3+ in several cubic chloroelpasolites that support the present conclusions are briefly discussed as well.

  11. Ordovician reef-hosted Jiaodingshan Mn-Co deposit and Dawashan Mn deposit, Sichuan Province, China

    USGS Publications Warehouse

    Fan, Delian; Hein, James R.; Ye, Jie

    1999-01-01

    The Jiaodingshan Mn-Co and Dawashan Mn deposits are located in the approximately 2-m thick Daduhe unit of the Wufengian strata of Late Ordovician (Ashgill) age. Paleogeographic reconstruction places the deposits at the time of their formation in a gulf between Chengdu submarine rise and the Kangdian continent. The Jiaodingshan and Dawashan deposits occur in algal-reef facies, the former in an atoll-like structure and the latter in a pinnacle reef. Ores are mainly composed of rhodochrosite, kutnahorite, hausmannite, braunite, manganosite, and bementite. Dark red, yellowish-pink, brown, green-gray, and black ores are massive, banded, laminated, spheroidal, and cryptalgal (oncolite, stromatolite, algal filaments) boundstones. Blue, green, and red algal fossils show in situ growth positions. Samples of high-grade Jiaodingshan and Dawashan ores assay as much as 66.7% MnO. Jiaodingshan Mn carbonate ores have mean contents of Ba, Co, and Pb somewhat higher than in Dawashan ores. Cobalt is widely distributed and strongly enriched in all rock types as compared to its crustal mean content. Cobalt is correlated with Cu, Ni, and MgO in both deposits and additionally with Ba and Zn in the Dawashan deposit. The δ13C(PDB) values of Mn carbonate ores (-7.8 to -16.3‰) indicate contributions of carbon from both seawater bicarbonate and the bacterial degradation of organic matter, the latter being 33% to 68%, assuming about -24‰ for the δ13C(PDB) of the organic matter. Host limestones derived carbon predominantly from seawater bicarbonate δ1313C(PDB) of +0.2 to -7‰). NW-trending fault zones controlled development of lithofacies, whereas NE-trending fault zones provided pathways for movement of fluids. The source of Co, Ni, and Cu was mainly from weathering of mafic and ultramafic rocks on the Kangdian continent, whereas contemporaneous volcanic eruptions were of secondary importance. The reefs were likely mineralized during early diagenesis under shallow burial. The reefs

  12. A facile one-pot hydrothermal synthesis of β-MnO{sub 2} nanopincers and their catalytic degradation of methylene blue

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Cheng, Gao; Yu, Lin, E-mail: gych@gdut.edu.cn; Lin, Ting

    2014-09-15

    Branched β-MnO{sub 2} bipods with novel nanopincer morphology were prepared by a facile one-pot hydrothermal method via a redox reaction between NaClO{sub 3} and MnSO{sub 4} in sulfuric acid solution without using any surfactants or templates. The products were characterized in detail by various techniques including X-ray powder diffraction, Raman spectroscopy, X-ray photoelectron spectroscopy, surface area analyzer, field emission scanning electron microscopy and transmission electron microscopy. Results show that the obtained β-MnO{sub 2} nanopincers consist of two sharp nanorods with a diameter of 100–200 nm and a length of 1–2 μm. The concentration of H{sub 2}SO{sub 4} solution plays anmore » important role in controlling the crystal phase and morphology of the final product. A possible formation mechanism for the β-MnO{sub 2} nanopincers was proposed. Moreover, these β-MnO{sub 2} nanostructures exhibited better catalytic performance than the commercial MnO{sub 2} particles to decompose methyl blue (MB) in the presence of H{sub 2}O{sub 2}. - Graphical abstract: Branched β-MnO{sub 2} bipods with novel nanopincer morphology were prepared by a facile one-pot hydrothermal method through oxidizing MnSO{sub 4} with NaClO{sub 3} in H2SO{sub 4} condition without using any surfactants or templates. - Highlights: {sup •} Branched β-MnO{sub 2} nanopincers were prepared by a facile one-pot hydrothermal method. {sup •} Morphology and crystal phase of MnO{sub 2} were controlled by the H{sub 2}SO{sub 4} concentration. {sup •} A possible formation mechanism for the obtained β-MnO{sub 2} nanopincers was proposed. {sup •} The products showed great catalytic performance in degradation of methylene blue.« less

  13. Porous MnO2 prepared by sol-gel method for electrochemical supercapacitor

    NASA Astrophysics Data System (ADS)

    Bazzi, K.; Kumar, A.; Jayakumar, O. D.; Nazri, G. A.; Naik, V. M.; Naik, R.

    2015-03-01

    MnO2 has attracted great attention as material for electrochemical pseudocapacitor due to its high theoretical specific faradic capacitance (~ 1370 F .g-1) , environmental friendliness and wide potential window in both aqueous and nonaqueous electrolytes. However, the MnO2 has a low surface area which depresses its electrochemical performance. The amorphous α-MnO2 composite was synthesized by sol gel method in the presence of the tri-block copolymer P123. Our aim is to investigate the role of P123 on the electrochemical performance of MnO2. The samples with and without P123 were prepared and characterized by x-ray diffraction (XRD), SEM, TEM and Brunauer-Emmett-Teller (BET) method. The electrochemical performances of the amorphous MnO2 composites as the electrode materials for supercapacitors were evaluated by cyclic voltammetry and AC impedance measurements in a 1M Na2SO4 solution. The results show that the sample prepared without P123 exhibited a relatively low specific capacitance of 28F .g-1, whereas the porous MnO2 prepared with P123 exhibited 117 F .g-1at 5 mV/s. The results of crystalline MnO2 composites will also be presented. The authors acknowledge the support from the Richard J. Barber Foundation for Interdisciplinary Research.

  14. Buffer layer dependence of magnetoresistance effects in Co2Fe0.4Mn0.6Si/MgO/Co50Fe50 tunnel junctions

    NASA Astrophysics Data System (ADS)

    Sun, Mingling; Kubota, Takahide; Takahashi, Shigeki; Kawato, Yoshiaki; Sonobe, Yoshiaki; Takanashi, Koki

    2018-05-01

    Buffer layer dependence of tunnel magnetoresistance (TMR) effects was investigated in Co2Fe0.4Mn0.6Si (CFMS)/MgO/Co50Fe50 magnetic tunnel junctions (MTJs). Pd, Ru and Cr were selected for the buffer layer materials, and MTJs with three different CFMS thicknesses (30, 5, and 0.8 nm) were fabricated. A maximum TMR ratio of 136% was observed in the Ru buffer layer sample with a 30-nm-thick CFMS layer. TMR ratios drastically degraded for the CFMS thickness of 0.8 nm, and the values were 26% for Cr buffer layer and less than 1% for Pd and Ru buffer layers. From the annealing temperature dependence of the TMR ratios, amounts of interdiffusion and effects from the lattice mismatch were discussed.

  15. Energetics of cubic and hexagonal phases in Mn-doped GaN : First-principles pseudopotential calculations

    NASA Astrophysics Data System (ADS)

    Choi, Eun-Ae; Kang, Joongoo; Chang, K. J.

    2006-12-01

    We perform first-principles pseudopotential calculations to study the influence of Mn doping on the stability of two polytypes, wurtzite and zinc-blende, in GaN . In Mn δ -doped GaN and GaMnN alloys, we find similar critical concentrations of the Mn ions for stabilizing the zinc-blende phase against the wurtzite phase. Using a slab geometry of hexagonal lattices, we find that it is energetically unfavorable to form inversion domains with Mn exposure, in contrast to Mg doping. At the initial stage of epitaxial growth, a stacking fault that leads to the cubic bonds can be generated with the Mn exposure to the Ga-polar surface. However, the influence of the Mn δ -doped layer on the formation of the cubic phase is only effective for GaN layers deposited up to two monolayers. We find that the Mn ions are energetically more stable on the growth front than in the bulk, indicating that these ions act as a surfactant. Thus it is possible to grow cubic GaN if the Mn ions are periodically supplied or diffuse out from the Mn δ -doped layer to the growth front during the growth process.

  16. First principles study of structural and magnetic properties of transition metal nitrides TMN (TM = Cr, Mn)

    NASA Astrophysics Data System (ADS)

    Rajeswarapalanichamy, R.; Amudhavalli, A.; Manikandan, M.; Kavitha, M.; Iyakutti, K.

    2017-09-01

    The structural stability of chromium nitride (CrN) and manganese nitride (MnN) is investigated among four different structures, namely, NaCl (Fm3m), zinc blende (F4-3m), orthorhombic (Pnma) and tetragonal (I4/mmm). It is found that the most stable phase is the zinc blende phase for CrN and MnN. The structural phase transition from zinc blende to orthorhombic phase is predicted at high pressure. At normal pressure, CrN and MnN are found to be antiferromagnetic. As the pressure is increased, antiferromagnetic-to-nonmagnetic phase transition is observed at the pressures of 169.5 GPa in CrN and 206 GPa in MnN. The elastic constants obey the Born-Huang criteria, suggesting that they are mechanically stable. The calculated B/G values indicate that CrN and MnN are ductile in nature.

  17. Log-ratio transformed major element based multidimensional classification for altered High-Mg igneous rocks

    NASA Astrophysics Data System (ADS)

    Verma, Surendra P.; Rivera-Gómez, M. Abdelaly; Díaz-González, Lorena; Quiroz-Ruiz, Alfredo

    2016-12-01

    A new multidimensional classification scheme consistent with the chemical classification of the International Union of Geological Sciences (IUGS) is proposed for the nomenclature of High-Mg altered rocks. Our procedure is based on an extensive database of major element (SiO2, TiO2, Al2O3, Fe2O3t, MnO, MgO, CaO, Na2O, K2O, and P2O5) compositions of a total of 33,868 (920 High-Mg and 32,948 "Common") relatively fresh igneous rock samples. The database consisting of these multinormally distributed samples in terms of their isometric log-ratios was used to propose a set of 11 discriminant functions and 6 diagrams to facilitate High-Mg rock classification. The multinormality required by linear discriminant and canonical analysis was ascertained by a new computer program DOMuDaF. One multidimensional function can distinguish the High-Mg and Common igneous rocks with high percent success values of about 86.4% and 98.9%, respectively. Similarly, from 10 discriminant functions the High-Mg rocks can also be classified as one of the four rock types (komatiite, meimechite, picrite, and boninite), with high success values of about 88%-100%. Satisfactory functioning of this new classification scheme was confirmed by seven independent tests. Five further case studies involving application to highly altered rocks illustrate the usefulness of our proposal. A computer program HMgClaMSys was written to efficiently apply the proposed classification scheme, which will be available for online processing of igneous rock compositional data. Monte Carlo simulation modeling and mass-balance computations confirmed the robustness of our classification with respect to analytical errors and postemplacement compositional changes.

  18. Microstructure and Mechanical Properties of the As-Cast and As-Homogenized Mg-Zn-Sn-Mn-Ca Alloy Fabricated by Semicontinuous Casting

    PubMed Central

    Lu, Xing; Zhao, Guoqun; Zhou, Jixue; Zhang, Cunsheng; Yu, Junquan

    2018-01-01

    In this paper, a new type of low-cost Mg-3.36Zn-1.06Sn-0.33Mn-0.27Ca (wt %) alloy ingot with a diameter of 130 mm and a length of 4800 mm was fabricated by semicontinuous casting. The microstructure and mechanical properties at different areas of the ingot were investigated. The microstructure and mechanical properties of the alloy under different one-step and two-step homogenization conditions were studied. For the as-cast alloy, the average grain size and the second phase size decrease from the center to the surface of the ingot, while the area fraction of the second phase increases gradually. At one-half of the radius of the ingot, the alloy presents the optimum comprehensive mechanical properties along the axial direction, which is attributed to the combined effect of relatively small grain size, low second-phase fraction, and uniform microstructure. For the as-homogenized alloy, the optimum two-step homogenization process parameters were determined as 340 °C × 10 h + 520 °C × 16 h. After the optimum homogenization, the proper size and morphology of CaMgSn phase are conducive to improve the microstructure uniformity and the mechanical properties of the alloy. Besides, the yield strength of the alloy is reduced by 20.7% and the elongation is increased by 56.3%, which is more favorable for the subsequent hot deformation processing. PMID:29710818

  19. Microstructure and Mechanical Properties of the As-Cast and As-Homogenized Mg-Zn-Sn-Mn-Ca Alloy Fabricated by Semicontinuous Casting.

    PubMed

    Lu, Xing; Zhao, Guoqun; Zhou, Jixue; Zhang, Cunsheng; Yu, Junquan

    2018-04-29

    In this paper, a new type of low-cost Mg-3.36Zn-1.06Sn-0.33Mn-0.27Ca (wt %) alloy ingot with a diameter of 130 mm and a length of 4800 mm was fabricated by semicontinuous casting. The microstructure and mechanical properties at different areas of the ingot were investigated. The microstructure and mechanical properties of the alloy under different one-step and two-step homogenization conditions were studied. For the as-cast alloy, the average grain size and the second phase size decrease from the center to the surface of the ingot, while the area fraction of the second phase increases gradually. At one-half of the radius of the ingot, the alloy presents the optimum comprehensive mechanical properties along the axial direction, which is attributed to the combined effect of relatively small grain size, low second-phase fraction, and uniform microstructure. For the as-homogenized alloy, the optimum two-step homogenization process parameters were determined as 340 °C × 10 h + 520 °C × 16 h. After the optimum homogenization, the proper size and morphology of CaMgSn phase are conducive to improve the microstructure uniformity and the mechanical properties of the alloy. Besides, the yield strength of the alloy is reduced by 20.7% and the elongation is increased by 56.3%, which is more favorable for the subsequent hot deformation processing.

  20. Hydrothermal synthesis of novel Mn3O4 nano-octahedrons with enhanced supercapacitors performances

    NASA Astrophysics Data System (ADS)

    Jiang, Hao; Zhao, Ting; Yan, Chaoyi; Ma, Jan; Li, Chunzhong

    2010-10-01

    Uniform and single-crystalline Mn3O4 nano-octahedrons have been successfully synthesized by a simple ethylenediaminetetraacetic acid disodium salt (EDTA-2Na) assisted hydrothermal route. The octahedron structures exhibit a high geometric symmetry with smooth surfaces and the mean side length of square base of octahedrons is ~160 nm. The structure is reckoned to provide superior functional properties and the nano-size achieved in the present work is noted to further facilitate the material property enhancement. The formation process was proposed to begin with a ``dissolution-recrystallization'' which is followed by an ``Ostwald ripening'' mechanism. The Mn3O4 nano-octahedrons exhibited an enhanced specific capacitance of 322 F g-1 compared with the truncated octahedrons with specific capacitances of 244 F g-1, making them a promising electrode material for supercapacitors.Uniform and single-crystalline Mn3O4 nano-octahedrons have been successfully synthesized by a simple ethylenediaminetetraacetic acid disodium salt (EDTA-2Na) assisted hydrothermal route. The octahedron structures exhibit a high geometric symmetry with smooth surfaces and the mean side length of square base of octahedrons is ~160 nm. The structure is reckoned to provide superior functional properties and the nano-size achieved in the present work is noted to further facilitate the material property enhancement. The formation process was proposed to begin with a ``dissolution-recrystallization'' which is followed by an ``Ostwald ripening'' mechanism. The Mn3O4 nano-octahedrons exhibited an enhanced specific capacitance of 322 F g-1 compared with the truncated octahedrons with specific capacitances of 244 F g-1, making them a promising electrode material for supercapacitors. Electronic supplementary information (ESI) available: TEM images; EDTA-2Na reaction details. See DOI: 10.1039/c0nr00257g

  1. Ferrimagnetism and disorder of epitaxial Mn2-xCoxVAl Heusler compound thin films

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Meinert, Markus; Schmalhorst, Jan-Michael; Reiss, Gunter

    The quaternary full Heusler compound Mn{sub 2-x}Co{sub x}VAl with x = 1 is predicted to be a half-metallic antiferromagnet. Thin films of the quaternary compounds with x = 0-2 were prepared by dc and RF magnetron co-sputtering on heated MgO (0 0 1) substrates. The magnetic structure was examined by x-ray magnetic circular dichroism and the chemical disorder was characterized by x-ray diffraction. Ferrimagnetic coupling of V to Mn was observed for Mn{sub 2}VAl (x = 0). For x = 0.5, we also found ferrimagnetic order with V and Co antiparallel to Mn. The observed reduced magnetic moments are interpretedmore » with the help of band structure calculations in the coherent potential approximation. Mn{sub 2}VAl is very sensitive to disorder involving Mn, because nearest-neighbour Mn atoms couple antiferromagnetically. Co{sub 2}VAl has B2 order and has reduced magnetization. In the cases with x {ge} 0.9 conventional ferromagnetism was observed, closely related to the atomic disorder in these compounds.« less

  2. Phase equilibria in the NaF-CdO-NaPO{sub 3} system at 873 K and crystal structure and physico-chemical characterizations of the new Na{sub 2}CdPO{sub 4}F fluorophosphate

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Aboussatar, Mohamed; Laboratoire de Physico-Chimie de l’État Solide, Faculté des Sciences de Sfax, Université de Sfax, BP 1171, 3000 Sfax; Mbarek, Aïcha

    Isothermal sections of the diagram representing phase relationships in the NaF-CdO-NaPO{sub 3} system have been investigated by solid state reactions and powder X-ray diffraction. This phase diagram investigation confirms the polymorphism of the NaCdPO{sub 4} side component and the structure of the ß high temperature polymorph (orthorhombic, space group Pnma and unit cell parameters a=9.3118(2), b=7.0459(1), c=5.1849(1) Å has been refined. A new fluorophosphate, Na{sub 2}CdPO{sub 4}F, has been discovered and its crystal structure determined and refined from powder X-ray diffraction data. It exhibits a new 3D structure with orthorhombic symmetry, space group Pnma and unit cell parameters a=5.3731(1), b=6.8530(1),more » c=12.2691(2) Å. The structure is closely related to those of the high temperature polymorph of the nacaphite Na{sub 2}CaPO{sub 4}F and the fluorosilicate Ca{sub 2}NaSiO{sub 4}F but differs essentially in the cationic repartition since the structure is fully ordered with one Na site (8d) and one Cd site (4c). Relationships with other Na{sub 2}M{sup II}PO{sub 4}F (M{sup II}=Mg, Ca, Mn, Fe, Co, Ni) have been examined and the crystal-chemical and topographical analysis of these fluorophosphates is briefly reviewed. IR, Raman, optical and {sup 19}F, {sup 23}Na, {sup 31}P MAS NMR characterizations of Na{sub 2}CdPO{sub 4}F have been investigated. - Graphical abstract: The structure of the compound Na{sub 2}CdPO{sub 4}F, discovered during the study of the phase relationships in the NaF-CdO-NaPO{sub 3} system, has been determined and compared with other Na{sub 2}M{sup II}PO{sub 4}F fluorophosphates. - Highlights: • XRD analysis of the isothermal section of the NaF-CdO-NaPO{sub 3} system at 923 K. • Rietveld refinement of the high temperature polymorph β-NaCdPO{sub 4}. • Crystal structure of the new Na{sub 2}CdPO{sub 4}F fluorophosphate determined from powder XRD. • Crystal structure - composition relationships of Na{sub 2}M{sup II}PO{sub 4}F

  3. Graphene oxide-MnO2 nanocomposite for supercapacitor application

    NASA Astrophysics Data System (ADS)

    Muhammed Shafi, P.; Vishal, Jose K.; Chandra Bose, A.

    2016-09-01

    Increased depletion of fossil fuels along with global warming and climate change made the society to think about alternate green and sustainable energy sources and better energy storage devices. Extensive research has been performed on the development of solar cells, fuel cells, Lithium- ion battery and supercapacitors to combat the green house effect and its consequences, and to meet the increased energy crisis. Supercapacitors, also known as electrochemical capacitors are gained a great attention because of their pulse power supply, long cycle life (>100,000), simple principle and high dynamic of charge propagation. Its greater power density than lithium- ion battery and much larger energy density than conventional capacitors brought super capacitors to a promising energy storage device to meet the increased energy demands. Here we demonstrate supercapacitor electrode materials with graphene oxide (electric double layer capacitor) and α-MnO2 nanomaterial (pseudo-capacitor), as well as composite of these materials, which means that the bulk of the material undergoes a fast redox reaction to provide the capacitive response and they exhibit superior specific energies in addition to the carbon-based supercapacitors (double-layer capacitors). A simple soft chemical route is utilized to synthesize graphene oxide, α-MnO2 and graphene oxide-MnO2 composite. The phase and the structure of the synthesized materials are studied using X-ray diffractometry (XRD). The functional group and the presence of impurities are understood from Fourier transform infrared (FTIR) spectra. The capacitive properties of the graphene oxide, graphene oxide - MnO2 nanocomposite and α-MnO2 are tested with the help of cyclic voltammetry (CV) and galvanostatic charge - discharge techniques using 1 M Na2SO4 in aqueous solution as electrolyte. It was found that graphene oxide - MnO2 nanocomposite shows better electrochemical behaviour compared to individual graphene oxide and α-MnO2 nanomaterial.

  4. Kinetic and metabolic profiles of synthetic cannabinoids NNEI and MN-18.

    PubMed

    Kevin, Richard C; Lefever, Timothy W; Snyder, Rodney W; Patel, Purvi R; Gamage, Thomas F; Fennell, Timothy R; Wiley, Jenny L; McGregor, Iain S; Thomas, Brian F

    2018-01-01

    In 2014 and 2015, synthetic cannabinoid receptor agonists NNEI (N-1-naphthalenyl-1-pentyl-1H-indole-3-carboxamide) and MN-18 (N-1-naphthalenyl-1-pentyl-1H-indazole-3-carboxamide) were detected in recreationally used and abused products in multiple countries, and were implicated in episodes of poisoning and toxicity. Despite this, the pharmacokinetic profiles of NNEI and MN-18 have not been characterized. In the present study NNEI and MN-18 were incubated in rat and human liver microsomes and hepatocytes, to estimate kinetic parameters and to identify potential metabolic pathways, respectively. These parameters and pathways were then examined in vivo, via analysis of blood and urine samples from catheterized male rats following intraperitoneal (3 mg/kg) administration of NNEI and MN-18. Both NNEI and MN-18 were rapidly cleared by rat and human liver microsomes, and underwent a range of oxidative transformations during incubation with rat and human hepatocytes. Several unique metabolites were identified for the forensic identification of NNEI and MN-18 intake. Interestingly, NNEI underwent a greater number of biotransformations (20 NNEI metabolites versus 10 MN-18 metabolites), yet parent MN-18 was eliminated at a faster rate than NNEI in vivo. Additionally, in vivo elimination was more rapid than in vitro estimates. These data highlight that even closely related synthetic cannabinoids can possess markedly distinct pharmacokinetic profiles, which can vary substantially between in vitro and in vivo models. Copyright © 2017 John Wiley & Sons, Ltd.

  5. A comparative study of Ni-Mn layered double hydroxide/carbon composites with different morphologies for supercapacitors.

    PubMed

    Li, M; Liu, F; Zhang, X B; Cheng, J P

    2016-11-02

    A variety of carbon materials varying from 0D to 2D, i.e. 0D nanoparticles, 1D carbon nanotubes (CNTs) and 2D reduced graphene oxide (rGO) are selected to in situ combine with Ni-Mn layered double hydroxide (LDH) to prepare electrode materials for supercapacitors. Through a simple solution method, hierarchical Ni-Mn LDH/carbon composites can be easily fabricated. A comparative study is carried out on the sandwich-like LDH/rGO, flower-like LDH/carbon black, turbostratic-structured LDH/CNTs and ternary LDH/CNTs/rGO for their structure, morphology, porous properties and electrochemical performances. The results show that the ternary Ni-Mn LDH/CNTs/rGO composite yields the highest specific capacitance of 1268 F g -1 in 2 M KOH electrolyte and a long lifespan, exhibiting great potential for supercapacitor applications. Meanwhile, investigation on the influence of the cation species of MOH (M = Li + , Na + or K + ) and the alkali concentration of the KOH electrolyte illustrates that increasing the concentration of the KOH electrolyte can benefit the capacitive performance of the electrode and that NaOH shows great advantages as an electrolyte for the Ni-Mn LDH/CNTs/rGO electrode due to its high capacitance and small resistance.

  6. Tunable multiple emissions in manganese-concentrated sulfide through simultaneous tailoring of Mn-site coordination and Mn-Mn pair geometry

    NASA Astrophysics Data System (ADS)

    Chen, Zitao; Song, Enhai; Ye, Shi; Zhang, Qinyuan

    2017-12-01

    In contrast to generally single-band visible emission feature from Mn2+, simultaneous visible (VIS) and near-infrared (NIR) multiple emissions are demonstrated in Mn2+ concentrated sulfide (MnS) by only involving a single crystallographic site. Upon varying the Mn2+-site coordination and/or Mn-Mn pairs geometry in different structural MnS, the multiple emissions from divalent manganese can be easily tuned from 575 to 720 nm (VIS) or from 880 to 900 or 1380 nm (NIR), respectively. The excitation spectroscopy and the luminescent decay, together with crystal structural analyses, are employed to investigate the electronic transition and the excited state dynamics of these Mn2+ concentrated systems. It is found that the VIS and NIR emissions can be ascribed to the isolated Mn2+ ion and exchange coupled Mn-Mn pair center, respectively. The effect of crystal field and bridging geometry, as well as temperature on the exchange coupled Mn2+ pairs NIR emissive center, is also investigated in detail. This work not only provides keen insights into the de-excitation pathway of Mn2+-concentrated material, but also offers the possibilities of designing a novel NIR emitting source for various photonic applications.

  7. A first-principles study of the preventive effects of Al and Mg doping on the degradation in LiNi0.8Co0.1Mn0.1O2 cathode materials.

    PubMed

    Min, Kyoungmin; Seo, Seung-Woo; Song, You Young; Lee, Hyo Sug; Cho, Eunseog

    2017-01-18

    First-principles calculations have been used to investigate the effects of Al and Mg doping on the prevention of degradation phenomena in Li(Ni 0.8 Co 0.1 Mn 0.1 )O 2 cathode materials. Specifically, we have examined the effects of dopants on the suppression of oxygen evolution and cation disordering, as well as their correlation. It is found that Al doping can suppress the formation of oxygen vacancies effectively, while Mg doping prevents the cation disordering behaviors, i.e., excess Ni and Li/Ni exchange, and Ni migration. This study also demonstrates that formation of oxygen vacancies can facilitate the construction of the cation disordering, and vice versa. Delithiation can increase the probabilities of formation of all defect types, especially oxygen vacancies. When oxygen vacancies are present, Ni can migrate to the Li site during delithiation. However, Al and Mg doping can inhibit Ni migration, even in structures with preformed oxygen defects. The analysis of atomic charge variations during delithiation demonstrates that the degree of oxidation behavior in oxygen atoms is alleviated in the case of Al doping, indicating the enhanced oxygen stability in this structure. In addition, changes in the lattice parameters during delithiation are suppressed in the Mg-doped structure, which suggests that Mg doping may improve the lattice stability.

  8. Excitation functions for 7Be, 22,24Na production in Mg and Al by deuteron irradiations up to 50 MeV.

    PubMed

    Hermanne, A; Takács, S; Tárkányi, F; Adam-Rebeles, R; Ignatyuk, A

    2012-12-01

    New experimental data for production of (7)Be and (22,24)Na in deuteron irradiation of (nat)Mg and Al up to 50 MeV are presented. The induced activity, measured with HPGe spectroscopy, allows us to determine excitation functions of (nat)Mg(d,x) and (27)Al(d,x) reactions involved in the activation process with reference to (nat)Ti(d,x)(48)V monitor cross sections. A comparison with experimental literature values and results from updated theoretical codes is discussed. Thick target yields were derived from fits to our cross-sections and integrated personnel dose was calculated for different irradiation cycles and exposure scenarios around high power deuteron accelerator facilities. Copyright © 2012 Elsevier Ltd. All rights reserved.

  9. Trace elements and metals in farmed sea bass and gilthead bream from Tenerife Island, Spain.

    PubMed

    Rubio, C; Jalilli, A; Gutiérrez, A J; González-Weller, D; Hernández, F; Melón, E; Burgos, A; Revert, C; Hardisson, A

    2011-11-01

    The aim of this study was to determine the levels of metals (Ca, K, Na, Mg) and trace metals (Ni, Fe, Cu, Mn, Zn, Pb, Cd) in two fish species (gilthead bream [Sparus aurata] and sea bass [Dicentrarchus labrax]) collected from fish farms located along the coast of Tenerife Island. Ca, K, Na, Mg, Fe, Cu, Zn, and Mn were measured by flame atomic absorption spectrometry, whereas Pb, Cd, and Ni were determined using graphite furnace atomic absorption spectrometry. Mean Fe, Cu, Mn, and Zn contents were 3.09, 0.59, 0.18, and 8.11 mg/kg (wet weight) in S. aurata and 3.20, 0.76, 0.24, and 10.11 mg/kg (wet weight) in D. labrax, respectively. In D. labrax, Ca, K, Na, and Mg levels were 1,955, 2,787, 699.7, and 279.2 mg/kg (wet weight), respectively; in S. aurata, they were 934.7, 3,515, 532.8, and 262.8 mg/kg (wet weight), respectively. The Pb level in S. aurata was 7.28 ± 3.64 μg/kg (wet weight) and, in D. labrax, 4.42 ± 1.56 μg/kg (wet weight). Mean Cd concentrations were 3.33 ± 3.93 and 1.36 ± 1.53 μg/kg (wet weight) for D. labrax and S. aurata, respectively. All Pb and Cd levels measured were well below the accepted European Commission limits, 300 and 50 μg/kg for lead and cadmium, respectively.

  10. Mn(II) Oxidation by the Multicopper Oxidase Complex Mnx: A Coordinated Two-Stage Mn(II)/(III) and Mn(III)/(IV) Mechanism.

    PubMed

    Soldatova, Alexandra V; Romano, Christine A; Tao, Lizhi; Stich, Troy A; Casey, William H; Britt, R David; Tebo, Bradley M; Spiro, Thomas G

    2017-08-23

    The bacterial manganese oxidase MnxG of the Mnx protein complex is unique among multicopper oxidases (MCOs) in carrying out a two-electron metal oxidation, converting Mn(II) to MnO 2 nanoparticles. The reaction occurs in two stages: Mn(II) → Mn(III) and Mn(III) → MnO 2 . In a companion study , we show that the electron transfer from Mn(II) to the low-potential type 1 Cu of MnxG requires an activation step, likely forming a hydroxide bridge at a dinuclear Mn(II) site. Here we study the second oxidation step, using pyrophosphate (PP) as a Mn(III) trap. PP chelates Mn(III) produced by the enzyme and subsequently allows it to become a substrate for the second stage of the reaction. EPR spectroscopy confirms the presence of Mn(III) bound to the enzyme. The Mn(III) oxidation step does not involve direct electron transfer to the enzyme from Mn(III), which is shown by kinetic measurements to be excluded from the Mn(II) binding site. Instead, Mn(III) is proposed to disproportionate at an adjacent polynuclear site, thereby allowing indirect oxidation to Mn(IV) and recycling of Mn(II). PP plays a multifaceted role, slowing the reaction by complexing both Mn(II) and Mn(III) in solution, and also inhibiting catalysis, likely through binding at or near the active site. An overall mechanism for Mnx-catalyzed MnO 2 production from Mn(II) is presented.

  11. Fourier transform spectroscopy of MnH and MnD

    NASA Astrophysics Data System (ADS)

    Balfour, W. J.; Launila, O.; Klynning, L.

    Two infrared band systems, centred near 846 nm and 1060 nm in both MnH and MnD have been rotationally analysed and shown to have a common lower state. The electronic transitions lie within the quintet manifold and are here designated c 5Σ-a 5Σ and b 5Πi-a 5Σ for the 846 and 1060 nm systems, respectively. In the 846 nm system in MnH all 10 main branches have been found in the 0-0 and 1-1 bands, while in MnD the data are complete only for 0-0. Satellite branches have been identified in the 1060 nm system and all spin and Λ-type doublings have been established. The number of assigned 0-0 branches in the 1060 nm system is 35 for MnH and 37 for MnD. Molecular constants have been determined for all three states involved. Λ-doubling diagrams are presented for b 5Πi state with v = 1, 2 levels in MnH and with the v = 2 level in MnD. Local perturbations in c5Σ (v = 1) in MnH are suspected to originate from the v = 3 level of b 5Πi.

  12. Sodium deficiency effect on the transport properties of La0.8Na0.2-x□xMnO3 manganites

    NASA Astrophysics Data System (ADS)

    Elghoul, N.; Wali, M.; Kraiem, S.; Rahmouni, H.; Dhahri, E.; Khirouni, K.

    2015-12-01

    Effect of sodium deficiency on the transport properties of La0.8Na0.2-x□xMnO3 manganites is investigated using impedance spectroscopy technique. In the whole explored temperature range (77-700 K), conductivity measurements show the appearance of a metal-semiconductor transition for all investigated samples. Also, a saturation region is observed in σ (T) curves. It is found that conduction mechanism is governed by hopping process. The conductivity of the material decreases with increasing sodium deficiency. The transition temperature and the activation energy values inferred from grain boundary resistance and conductivity analysis are closed to each other. Such result confirms the contribution of grain boundary on the electrical conductivity. The variation of the Average Normalized Change (ANC) and its derivative with temperature gives important information about the available density of trapped charge states. The obtained results explain the observed saturation region in conductivity at high temperature region.

  13. A Mn(III) triplesalen-based 1D pearl necklace: exchange interactions and zero-field splittings in a C3-symmetric Mn(III)6 complex.

    PubMed

    Glaser, Thorsten; Heidemeier, Maik; Theil, Hubert; Stammler, Anja; Bögge, Hartmut; Schnack, Jürgen

    2010-01-07

    The reaction of the tert-butyl-substituted triplesalen ligand H(6)talen(t-Bu(2)) with 2.8 equivalents of Mn(OAc)(2) x 4 H(2)O in MeOH in the presence of NaBPh(4) results in the formation of the one-dimensional (1D) coordination polymer {[{(talen(t-Bu(2)))Mn(3)(MeOH)}(2)(mu(2)-OAc)(3)](mu(2)-OAc)}(n)(BPh(4))(2n) ({[Mn(III)(6)](OAc)}(n)(BPh(4))(2n)) which has been characterized by FTIR, elemental analysis, ESI-MS, single-crystal X-ray diffraction and magnetic measurements. The triplesalen ligand (talen(t-Bu(2)))(6-) provides three salen-like coordination compartments bridged in a meta-phenylene arrangement by a phloroglucinol backbone resulting in the trinuclear Mn(III) base unit {(talen(t-Bu(2)))Mn(3)}(3+). Two of these base units are bridged by three inner acetate ligands giving rise to the hexanuclear complex [{(talen(t-Bu(2)))Mn(3)(MeOH)}(2)(mu(2)-OAc)(3)](3+) ([Mn(III)(6)](3+)). These complexes are bridged by a single external acetate to form a 1D chain as pearls in a pearl necklace. Variable temperature-variable field and mu(eff)vs. T magnetic data have been analyzed in detail by full-matrix diagonalization of the appropriate spin-Hamiltonian consisting of isotropic exchange, zero-field splitting, and Zeeman interaction taking into account the relative orientation of the D-tensors. Satisfactory reproduction of the experimental data have been obtained for parameters sets J(1) = -(0.60 +/- 0.15) cm(-1), J(2) = -(1.05 +/- 0.15) cm(-1), and D(Mn) = -(3.0 +/- 0.7) cm(-1) with J(1) describing the exchange through the phloroglucinol backbone and J(2) describing the exchange through the inner acetates. The non-necessity to incorporate the bridging outer acetates correlates with the longer Mn-O bonds. The experimental data can neither be analyzed without incorporating zero-field splitting nor by the application of a single effective spin ground state.

  14. Bivalence Mn5O8 with hydroxylated interphase for high-voltage aqueous sodium-ion storage

    PubMed Central

    Shan, Xiaoqiang; Charles, Daniel S.; Lei, Yinkai; Qiao, Ruimin; Wang, Guofeng; Yang, Wanli; Feygenson, Mikhail; Su, Dong; Teng, Xiaowei

    2016-01-01

    Aqueous electrochemical energy storage devices have attracted significant attention owing to their high safety, low cost and environmental friendliness. However, their applications have been limited by a narrow potential window (∼1.23 V), beyond which the hydrogen and oxygen evolution reactions occur. Here we report the formation of layered Mn5O8 pseudocapacitor electrode material with a well-ordered hydroxylated interphase. A symmetric full cell using such electrodes demonstrates a stable potential window of 3.0 V in an aqueous electrolyte, as well as high energy and power performance, nearly 100% coulombic efficiency and 85% energy efficiency after 25,000 charge–discharge cycles. The interplay between hydroxylated interphase on the surface and the unique bivalence structure of Mn5O8 suppresses the gas evolution reactions, offers a two-electron charge transfer via Mn2+/Mn4+ redox couple, and provides facile pathway for Na-ion transport via intra-/inter-layer defects of Mn5O8. PMID:27845345

  15. Bivalence Mn5O8 with hydroxylated interphase for high-voltage aqueous sodium-ion storage

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Shan, Xiaoqiang; Charles, Daniel S.; Lei, Yinkai

    Aqueous electrochemical energy storage devices have attracted significant attention owing to their high safety, low cost, and environmental friendliness. However, their applications have been limited by a narrow potential window (~1.23 V), beyond which the hydrogen and oxygen evolution reactions occur. Here, we report the formation of layered Mn 5O 8 pseudocapacitor electrode material with a well ordered hydroxylated interphase. A symmetric full cell using such electrodes demonstrates a stable potential window of 3.0 V in an aqueous electrolyte, as well as high energy and power performance, nearly 100% coulombic efficiency and 85% energy efficiency after 25,000 charge-discharge cycles. Furthermore,more » the interplay between hydroxylated interphase on the surface and the unique bivalence structure of Mn 5O 8 suppresses the gas evolution reactions, offers a two-electron charge transfer via Mn 2+/Mn 4+ redox couple, and provides facile pathway for Na-ion transport via intra-/inter-layer defects of Mn 5O 8.« less

  16. Bivalence Mn5O8 with hydroxylated interphase for high-voltage aqueous sodium-ion storage

    DOE PAGES

    Shan, Xiaoqiang; Charles, Daniel S.; Lei, Yinkai; ...

    2016-11-15

    Aqueous electrochemical energy storage devices have attracted significant attention owing to their high safety, low cost, and environmental friendliness. However, their applications have been limited by a narrow potential window (~1.23 V), beyond which the hydrogen and oxygen evolution reactions occur. Here, we report the formation of layered Mn 5O 8 pseudocapacitor electrode material with a well ordered hydroxylated interphase. A symmetric full cell using such electrodes demonstrates a stable potential window of 3.0 V in an aqueous electrolyte, as well as high energy and power performance, nearly 100% coulombic efficiency and 85% energy efficiency after 25,000 charge-discharge cycles. Furthermore,more » the interplay between hydroxylated interphase on the surface and the unique bivalence structure of Mn 5O 8 suppresses the gas evolution reactions, offers a two-electron charge transfer via Mn 2+/Mn 4+ redox couple, and provides facile pathway for Na-ion transport via intra-/inter-layer defects of Mn 5O 8.« less

  17. Beta-delayed proton emission from 20Mg

    NASA Astrophysics Data System (ADS)

    Lund, M. V.; Andreyev, A.; Borge, M. J. G.; Cederkäll, J.; De Witte, H.; Fraile, L. M.; Fynbo, H. O. U.; Greenlees, P. T.; Harkness-Brennan, L. J.; Howard, A. M.; Huyse, M.; Jonson, B.; Judson, D. S.; Kirsebom, O. S.; Konki, J.; Kurcewicz, J.; Lazarus, I.; Lica, R.; Lindberg, S.; Madurga, M.; Marginean, N.; Marginean, R.; Marroquin, I.; Mihai, C.; Munch, M.; Nacher, E.; Negret, A.; Nilsson, T.; Page, R. D.; Pascu, S.; Perea, A.; Pucknell, V.; Rahkila, P.; Rapisarda, E.; Riisager, K.; Rotaru, F.; Sotty, C.; Stanoiu, M.; Tengblad, O.; Turturica, A.; Van Duppen, P.; Vedia, V.; Wadsworth, R.; Warr, N.

    2016-10-01

    Beta-delayed proton emission from 20 Mg has been measured at ISOLDE, CERN, with the ISOLDE Decay Station (IDS) setup including both charged-particle and gamma-ray detection capabilities. A total of 27 delayed proton branches were measured including seven so far unobserved. An updated decay scheme, including three new resonances above the proton separation energy in 20 Na and more precise resonance energies, is presented. Beta-decay feeding to two resonances above the Isobaric Analogue State (IAS) in 20 Na is observed. This may allow studies of the 4032.9(2.4)keV resonance in 19 Ne through the beta decay of 20 Mg, which is important for the astrophysically relevant reaction 15O( α, γ)19Ne . Beta-delayed protons were used to obtain a more precise value for the half-life of 20 Mg, 91.4(1.0)ms.

  18. Dual spectra band emissive Eu2+/Mn2+ co-activated alkaline earth phosphates for indoor plant growth novel phosphor converted-LEDs.

    PubMed

    Yun, Young Jun; Kim, Jin Kyu; Ju, Ji Young; Choi, Seul Ki; Park, Woon Ik; Suh, Jae Yong; Jung, Ha-Kyun; Kim, Yongseon; Choi, Sungho

    2017-05-10

    This paper reports designing a novel single composition blue/red color illuminating phosphor followed by fabricating "smart" agricultural/horticultural LED lighting. Color-tunable Eu 2+ /Mn 2+ co-activated alkaline earth phosphates, Na(Sr,Ba)PO 4 and Ca 3 Mg 3 (PO 4 ) 4 , are considered, and the stable doping sites for the corresponding activators are identified by using first-principle DFT calculations. We can realize the designated color purity with stable thermal quenching preserved luminescence behavior is induced by the Eu 2+ center positioned at different coordination states with intermixed Sr 2+ /Ba 2+ sites in Na(Sr,Ba)PO 4 hosts. Moreover, we demonstrate that the resultant LED lighting adopting the proposed novel phosphor composition stimulates the enhanced photosynthesis reaction for indoor hydroponics plants, such as oats and onions, which is superior to the narrow line emission band induced by the mixture of conventional red/green/blue LEDs. Thus, using the color-tunable single composition luminescent material may produce an innovative energy-efficient artificial lighting for indoor plant growth.

  19. Synthesis and stability of hetaerolite, ZnMn2O4, at 25°C

    USGS Publications Warehouse

    Hem, J.D.; Roberson, C.E.; Lind, C.J.

    1987-01-01

    A precipitate of nearly pure hetaerolite, ZnMn2O4, a spinel-structured analog of hausmannite, Mn3O4, was prepared by an irreversible wprecipitation of zinc with manganese at 25°C. The synthesis technique entailed constant slow addition of a dilute solution of Mn2+ and Zn2+ chlorides having a Mn/Zn ratio of 2:1 to a reaction vessel that initially contained distilled deionized water, maintained at a pH of 8.50 by addition of dilute NaOH by an automated pH stat, with continuous bubbling of CO2-free air. The solid was identified by means of X-ray diffraction and transmission electron microscopy and consisted of bipyramidal crystals generally less than 0.10 μm in diameter. Zn2+ ions are able to substitute extensively for Mn2+ ions that occupy tetrahedral sites in the hausmannite structure.Hetaerolite appears to be more stable than hausmannite with respect to spontaneous conversion to γMnOOH. The value of the standard free energy of formation of hetaerolite was estimated from the experimental data to be −289.4 ± 0.8 kcal per mole. Solids intermediate in composition between hetaerolite and hausmannite can be prepared by altering the Mn/Zn ratio in the feed solution.

  20. [Analysis of changes in minerals contents during cider fermentation process by inductively coupled plasma mass spectrometry].

    PubMed

    Ye, Meng-qi; Yue, Tian-li; Gao, Zhen-peng; Yuan, Ya-hong; Nie, Gang

    2015-01-01

    The changes in mineral elements during cider fermentation process were determined using ICP-MS. The results showed that the main minerals in the fermentation liquor included K, Na, Ca, Mg, Fe, Mn, Zn, Cu, Sr and B. The content of K was the highest in both the apple juice and the cider, being 1 853. 83 and 1 654. 38 mg . L-1 respectively. The content of minerals was in dynamic changes along with the fermentation process. As a whole, during 72-120 h and 144-216 h, most of the minerals contents underwent great fluctuation. Especially when fermented for 192 h, the content of most of the minerals reached peak value or valley value. The content of Fe and Zn achieved their peak value, while the content of K, Na, Ca, Mg, Mn and B achieved valley value. But during the following 24 h, the content of minerals underwent a sharp reversal. After fermentation, the content of K, Mg, Cu, Zn and B decreased significantly, while the content of Na, Ca, Mn, Fe and Sr did not change significantly. The correlational analysis was conducted to evaluate the correlation between the mineral elements, and the result showed that the correlation between Ca and Mn was the most significant, with the correlation index reaching 0. 924. The information of this study will supply sufficient data for the fermentation process control and quality improvement of cider.