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Sample records for ca mg fe

  1. Ca, Fe, and Mg Trends Among and Within Elliptical Galaxies

    CERN Document Server

    Worthey, Guy; Serven, Jedidiah

    2012-01-01

    In a sample of elliptical galaxies that span a large range of mass, a previously unused Ca index, CaHK, shows that [Ca/Fe] and [Ca/Mg] systematically decrease with increasing elliptical galaxy mass. Metallicity mixtures, age effects, stellar chromospheric emission effects, and low-mass initial mass function (IMF) boost effects are ruled out as causes. A [Ca/Fe] range of less than 0.3 dex is sufficient to blanket all observations. Feature gradients within galaxies imply a global Ca deficit rather than a radius-dependent phenomenon. Some, but not all, Type II supernova nucleosynthetic yield calculations indicate a decreasing Ca/Fe yield ratio in more massive supernovae, lending possible support to the hypothesis that more massive elliptical galaxies have an IMF that favors more massive stars. No Type II supernova nucleosynthetic yield calculations show significant leverage in the Ca/Fe ratio as a function of progenitor metallicity. Therefore, it seems unlikely that the Ca behavior can be explained as a built-in...

  2. Isotopic fractionation of Mg 2+(aq), Ca 2+(aq), and Fe 2+(aq) with carbonate minerals

    Science.gov (United States)

    Rustad, James R.; Casey, William H.; Yin, Qing-Zhu; Bylaska, Eric J.; Felmy, Andrew R.; Bogatko, Stuart A.; Jackson, Virgil E.; Dixon, David A.

    2010-11-01

    Density-functional electronic structure calculations are used to compute the equilibrium constants for 26Mg/ 24Mg and 44Ca/ 40Ca isotope exchange between carbonate minerals and uncomplexed divalent aquo ions. The most reliable calculations at the B3LYP/6-311++G(2d,2p) level predict equilibrium constants K, reported as 10 3ln ( K) at 25 °C, of -5.3, -1.1, and +1.2 for 26Mg/ 24Mg exchange between calcite (CaCO 3), magnesite (MgCO 3), and dolomite (Ca 0.5Mg 0.5CO 3), respectively, and Mg 2+(aq), with positive values indicating enrichment of the heavy isotope in the mineral phase. For 44Ca/ 40Ca exchange between calcite and Ca 2+(aq) at 25 °C, the calculations predict values of +1.5 for Ca 2+(aq) in 6-fold coordination and +4.1 for Ca 2+(aq) in 7-fold coordination. We find that the reduced partition function ratios can be reliably computed from systems as small as M(CO)610- and M(HO)62+ embedded in a set of fixed atoms representing the second-shell (and greater) coordination environment. We find that the aqueous cluster representing the aquo ion is much more sensitive to improvements in the basis set than the calculations on the mineral systems, and that fractionation factors should be computed using the best possible basis set for the aquo complex, even if the reduced partition function ratio calculated with the same basis set is not available for the mineral system. The new calculations show that the previous discrepancies between theory and experiment for Fe 3+-hematite and Fe 2+-siderite fractionations arise from an insufficiently accurate reduced partition function ratio for the Fe 3+(aq) and Fe 2+(aq) species.

  3. Controls of Ca/Mg/Fe activity ratios in pore water chemistry models of the Callovian-Oxfordian clay formation

    Energy Technology Data Exchange (ETDEWEB)

    Lerouge, C.; Grangeon, S.; Wille, G.; Flehoc, C.; Gailhanou, H.; Gaucher, E.C.; Tournassat, C. [BRGM av. Claude Guillemin BP6009 45060 Orleans cedex 2 (France); Vinsot, A. [ANDRA Meuse/Haute-Marne Underground research Laboratory (URL), RD 960, 55290 Bure (France); Made, B.; Altmann, S. [ANDRA - Parc de la Croix Blanche, 1-7 rue Jean Monnet, 92298 Chatenay-Malabry Cedex (France)

    2013-07-01

    In the pore water chemistry model of the Callovian-Oxfordian clay formation, the divalent cations Ca, Mg, and Fe are controlled by equilibrium reactions with pure carbonates: calcite for Ca, dolomite for Mg, and siderite for Fe. Results of a petrological study and computing of the Ca/Mg and Ca/Fe activity ratios based on natural pore water chemistry provide evidence that equilibrium with pure calcite and pure dolomite is a reasonable assumption for undisturbed pore waters; on the other hand, siderite cannot be considered at equilibrium with pore waters at the formation scale. (authors)

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

    Science.gov (United States)

    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.

  5. Study of solid state interactions in the systems ZnFe2O4 - CaO, ZnFe2O4 - MgO and zinc cake with CaO and MgO

    Directory of Open Access Journals (Sweden)

    Peltekov A.B.

    2013-01-01

    Full Text Available The solid state interactions of CaO and MgO with synthetic and industrial ZnFe2O4 (in zinc cake have been studied using chemical, XRD analysis and Mössbauer spectroscopy. The exchange reactions in the systems ZnFe2O4 - CaO and ZnFe2O4 - MgO have been investigated in the range of 850-1200ºC and duration up to 180 min. It has been established that Ca2+ and Mg2+ ions exchange Zn2+ in ferrite partially and the solubility of zinc in a 7% sulfuric acid solution increases. The possibilities for utilization of the obtained results in zinc hydrometallurgy have been discussed.

  6. Structural and magnetic properties of CaMg2Fe16O27

    Indian Academy of Sciences (India)

    P S Sawadh; D K Kulkarni

    2001-02-01

    A new compound, CaMg2Fe16O27, is synthesized for the first time, in polycrystalline form, using stoichiometric mixture of oxides with standard ceramic technique and characterized by X-ray diffraction. It is found to have a hexagonal W-type structure with lattice parameters = 5.850 Å and = 33.156 Å. Electrical studies show that the compound is a semiconductor with energy of activation, = 0.56 eV. Electrical conductivity results show a transition in the conductivity vs temperature plot near the Curie temperature. The activation energy value obtained for the paramagnetic phase is found to be higher than that of the ferrimagnetic phase. The molar magnetic susceptibility was measured in the temperature range 300–850 K and the results show that the compound is ferrimagnetic at room temperature. The compound also shows hysteresis at 300 K. Paramagnetic nature of the sample above Curie temperature is also studied. The Curie molar constant calculated from the plot of 1/ vs () is found to be nearly in agreement with the expected value.

  7. Effect of Fe2O3 Addition in MgO-CaO Refractory on Desulfurization of Liquid Iron

    Institute of Scientific and Technical Information of China (English)

    WEI Yao-wu; LI Nan; CHEN Fang-yu

    2003-01-01

    The effects of Fe2O3 addition in MgO-CaO refractory on desulfurization of liquid iron were studied by SEM, EDA and chemical analysis. Fe2O3 of 1 % and 4 % were added to MgO-CaO refractory as the lining of graphite crucible in which 150 g iron powder with sulfur of 0.15 % was charged. It is found that when the sample is heated at 1 600 ℃ for 40 min, 60 min and 90 min, the addition with Fe2O3 of 1 % improves desulfurization greatly. However, the desulfurization ratio of the refractory with Fe2O3 addition of 4 % is less than that with Fe2O3 addition of 1 %. For the soaking time of 90 min, the desulfurization ratio is less than those of 40 min and 60 min. These phenomena were explained by the contrary roles of O2- and Fe2+ formed by reaction between liquid iron and Fe2O3 on desulfurization.

  8. A simplified determination of total concentrations of Ca, Fe, Mg and Mn in addition to their bioaccessible fraction in popular instant coffee brews.

    Science.gov (United States)

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

    2016-04-15

    A direct analysis of instant coffee brews with HR-CS-FAAS spectrometry to determine the total Ca, Fe, Mg and Mn content has been developed and validated. The proposed method is simple and fast; it delivers good analytical performance; its accuracy being within -3% to 3%, its precision--2-3% and detection limits--0.03, 0.04, 0.004 and 0.01 mg l(-1) for Ca, Fe, Mg and Mn, respectively. In addition, Ca, Fe, Mg and Mn bioaccessibility in instant coffee brews was measured by means of the in vitro gastrointestinal digestion with the use of simulated gastric and intestinal juice solutions. Absorption of metals in intestinal villi was simulated by means of ultrafiltration over semi-permeable membrane with a molecular weight cut-off of 5 kDa. Ca, Fe, Mg and Mn concentrations in permeates of instant coffee gastrointestinal incubates were measured with HR-CS-FAA spectrometry.

  9. Determination of Na, Mg, Al, Si, K, Cl, Ca and Fe in cigarette tobacco by fast neutron activation analysis

    International Nuclear Information System (INIS)

    FNAA has been, for many years, a technique for the non-destructive analysis of a wide variety of sample materials - liquids, solids and powders. The important advantages of fast neutron activation analysis are good analytical sensitivity without sample preparation, accuracy and total analysis in a short time. In our work, the concentrations of the elements Na, Mg, Al, Si, K, Cl, Ca and Fe, were determined in cigarette tobacco of two brands commercially available in Turkey using 14.6 MeV neutron activation analysis. (author)

  10. Thermodynamics of O, N, and S in liquid Fe equilibrated with CaO-AI2O3-MgO slags

    Science.gov (United States)

    Inoue, Ryo; Suito, Hideaki

    1994-04-01

    Nitrogen and S distribution ratios between CaO-Al2O3-MgO slags and liquid Fe were measured at 1873 K as a function of Al (or Mg, Ca) content in metal, using CaO, MgO, and A12O3 crucibles. Based on the results for the solubility product of MgO, the equilibrium constant, K Mg , for the reaction MgO = Mg + O and the first-order interaction parameter, e {O/Mg} ( e {Mg/O}), were estimated to be log K Mg = -7.8 ± 0.2 and e {O/Mg} = -190 ± 60 ( e {Mg/O} = -290 ± 90), respectively. The activities of A12O3 at the slag compositions double-saturated with CaO/MgO, MgO/ MgO A12O3, and MgO Al2O3/CaO 2A12O3 components were obtained from the S distribution ratios between slag and metal, coupled with the reported values of sulfide capacities. Nitride capacities were also estimated from the N distribution ratios and the activities of A12O3.

  11. Influence of biocompatible metal ions (Ag, Fe, Y) on the surface chemistry, corrosion behavior and cytocompatibility of Mg-1Ca alloy treated with MEVVA.

    Science.gov (United States)

    Liu, Yang; Bian, Dong; Wu, Yuanhao; Li, Nan; Qiu, Kejin; Zheng, Yufeng; Han, Yong

    2015-09-01

    Mg-1Ca samples were implanted with biocompatible alloy ions Ag, Fe and Y respectively with a dose of 2×10(17)ionscm(-2) by metal vapor vacuum arc technique (MEVVA). The surface morphologies and surface chemistry were investigated by SEM, AES and XPS. Surface changes were observed after all three kinds of elemental ion implantation. The results revealed that the modified layer was composed of two sublayers, including an outer oxidized layer with mixture of oxides and an inner implanted layer, after Ag and Fe ion implantation. Y ion implantation induced an Mg/Ca-deficient outer oxidized layer and the distribution of Y along with depth was more homogeneous. Both electrochemical test and immersion test revealed accelerated corrosion rate of Ag-implanted Mg-1Ca and Fe-implanted Mg-1Ca, whereas Y ion implantation showed a short period of protection since enhanced corrosion resistance was obtained by electrochemical test, but accelerated corrosion rate was found by long period immersion test. Indirect cytotoxicity assay indicated good cytocompatibility of Y-implanted Mg-1Ca. Moreover, the corresponding corrosion mechanisms involving implanting ions into magnesium alloys were proposed, which might provide guidance for further application of plasma ion implantation to biodegradable Mg alloys.

  12. Ternary Ca-Fe-Mg carbonates: subsolidus phase relations at 3.5 GPa and a thermodynamic solid solution model including order/disorder

    Science.gov (United States)

    Franzolin, E.; Schmidt, M. W.; Poli, S.

    2011-02-01

    Subduction carries atmospheric and crustal carbon hosted in the altered oceanic crystalline basement and in pelagic sediments back into the mantle. Reactions involving complex carbonate solid solutions(s) lead to the transfer of carbon into the mantle, where it may be stored as graphite/diamond, in fluids or melts, or in carbonates. To constrain the thermodynamics and thus reactions of the ternary Ca-Mg-Fe carbonate solid solution, piston cylinder experiments have been performed in the system CaCO3-MgCO3-FeCO3 at a pressure of 3.5 GPa and temperatures of 900-1,100°C. At 900°C, the system has two miscibility gaps: the solvus dolomite-calcite, which closes at X MgCO3 ~0.7, and the solvus dolomite-magnesite, which ranges from the Mg to the Fe side of the ternary. With increasing temperature, the two miscibility gaps become narrower until complete solid solutions between CaCO3-Ca0.5Mg0.5CO3 is reached at 1,100°C and between CaCO3-FeCO3 at 1,000°C. The solvi are characterized by strong compositional asymmetry and by an order-disorder mechanism. To deal with these features, a solid solution model based on the van Laar macroscopic formalism has been calculated for ternary carbonates. This thermodynamic solid solution model is able to reproduce the experimentally constrained phase relations in the system CaCO3-MgCO3-FeCO3 in a broad P-T range. To test our model, calculated phase equilibria were compared with experiments performed in carbonated mafic protolithes, demonstrating the reliability of our solid solution model at pressures up to 6 GPa in complex systems.

  13. Crystal structure of superparamagnetic Mg0.2Ca0.8Fe2O4 nanoparticles synthesized by sol–gel method

    International Nuclear Information System (INIS)

    Powders of magnetic iron oxide nanoparticles (Mg0.2Ca0.8Fe2O4) were prepared by a sol–gel method using ethylene glycol and nitrates of Fe, Ca and Mg as starting materials. Those powders were heat treated at different temperatures (573, 673, 773 and 873 K). In order to evaluate the effect of the heat treatment temperature on the nanoferrites properties, X-ray diffraction (XRD), vibrating sample magnetometry (VSM), transmission electron microscopy (TEM) and X-ray photoelectron spectroscopy (XPS) techniques were used. It was found that the reaction products exhibit nanometric sizes and superparamagnetic behavior. It is also demonstrated that, as the heat treatment temperature increases, the particle size and the saturation magnetization of the nanoferrites are increased. - Highlights: • Mg0.2Ca0.8Fe2O4 superparamagnetic nanoparticles were successfully synthesized. • Particle average sizes of Ca–Mg ferrites were within the range of 8–25 nm. • The nanoferrite treated at 873 K showed a stoichiometry close to Mg0.2Ca0.8Fe2O4. • The heat treatment temperature has a strong effect on the crystal structure. • These nanoparticles are potential materials for magnetic hyperthermia

  14. Separation of Phosphorus- and Iron-Enriched Phase from CaO-SiO2-FeO-MgO-P2O5 Melt with Super Gravity

    Science.gov (United States)

    Li, Chong; Gao, Jintao; Guo, Zhancheng

    2016-06-01

    Super gravity technology was used to separate the phosphorus- and iron-enriched phase from CaO-SiO2-FeO-MgO-P2O5 melt. The microstructure and X-ray diffraction showed that the P-enriched phase was intercepted by the filter screen, while the residual slag mainly composed of Fe-enriched phase that went through the filter. The recovery ratio of P2O5 in the P-enriched slag was up to 76.67 pct, and that of FeO in the Fe-enriched slag was up to 85.02 pct.

  15. Seasonal variation of major elements (Ca, Mg) and trace metals (Fe, Cu, Zn, Mn) and cultured mussel Perna viridis L. and seawater in the Dona Paula Bay, Goa

    Digital Repository Service at National Institute of Oceanography (India)

    Rivonker, C.U.; Parulekar, A.H.

    The major elements and trace metals were analysed from nussel tissue and the seawater taken from three depths (0, 5 and 9 meters) from the culture site. Range of variation in Ca, Mg, Fe, Cu, Zn and Mn were 226-399; 708-1329; 0.005-0.084; BDL-0...

  16. Melting Relations of Multicomponent Carbonate System MgCO3 - FeCO3- CaCO3- Na2CO3 at 12-23 GPa

    Science.gov (United States)

    Spivak, Anna; Solopova, Natalia; Litvin, Yuriy; Dubrovinsky, Leonid; Zakharchenko, Egor

    2014-05-01

    Considerable attention is focused on high-pressure high-temperature experimental study of melting phase relations of carbonates which were involved into a 'super-deep' diamond genesis. High-pressure stability of carbonate melts and their role in 'ultra-deep' diamonds genesis are most essential. Experimental study of melting relations of multicomponent carbonate system was carried out using multi-anvil press at the pressures 12 - 23 GPa and temperatures 800 to 1650 oC. Chemical compositions of starting carbonate system used for melting experiment were prepared by mixing: FeCO3 - 26,00; MgCO3- 26,00; CaCO3 - 25,00; Na2CO3 - 23,00 wt %. A region of partial melting for the system is experimentally determined. The partial melting field is arranged between low-temperature boundary of eutectics melting (solidus line) of the multicomponent carbonate and the boundary of complete melting (liquidus line) at higher temperature. From experimental observations, a Mg-Fe carbonate solid solution is the liquidus phase. At temperature lowering, the assemblage (Mg,Fe)CO3 + (Ca,Na2,Fe)CO3 + L (liquid) is formed. Then, the invariant eutectic assemblage (Mg,Fe)CO3 + (Ca,Na2,Fe)CO3 + Na2(Ca,Fe)(CO3)2+ L (liquid) which is determining for subsolidus assemblage (Mg,Fe)CO3 + (Ca,Na2,Fe)CO3 + Na2(Ca,Fe)(CO3)2 is formed. Next to liquidus line is one-phase field of completely miscible multicomponent carbonate melt. On the whole, the results demonstrate phase relations of solid carbonates and multicomponent carbonate liquid in the immediate vicinity to the low-temperature melting boundary. The early melting of the multicomponent carbonate system is compatible with the lower mantle geothermal conditions because the primary melting temperatures are noticeably below than the geothermal values. It is significant that multicomponent carbonate melts are stable and completely miscible under conditions as partial so complete melting. Thus, high-pressure high-temperature experimental data demonstrate

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

    Science.gov (United States)

    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). PMID:26830580

  18. Ceramsite obtained from water and wastewater sludge and its characteristics affected by Fe2O3, CaO, and MgO.

    Science.gov (United States)

    Zou, J L; Xu, G R; Li, G B

    2009-06-15

    To solve the disposal problems of residual sludges, wastewater treatment sludge (WWTS) and drinking-water treatment sludge (DWTS) were tested as components for producing ceramsite. Fe(2)O(3), CaO, and MgO were the major basic oxides in WWTS and DWTS, so their effect on characteristics of ceramsite was also investigated to optimize the process. Results show that WWTS and DWTS can be utilized for producing ceramsite with optimal contents of Fe(2)O(3), CaO, and MgO ranging 5-8%, 2.75-7%, and 1.6-4%, respectively. Ceramsite within the optimal Fe(2)O(3), CaO, and MgO contents ranges was characterized using thermal analysis, X-ray diffraction (XRD), morphological structures analyses, and compressive strength measurements. Higher strength ceramsite with more complex crystalline phases and fewer pores can be obtained at 6%needed ions for producing electrical neutrality of silicate networks. Ceramsite characteristics are not dramatically influenced by MgO because Mg(2+) cannot destroy the unity of crystalline structures. This revolutionary technology of utilization of WWTS and DWTS can produce high performance ceramsite thus reducing costs of sludge disposal, in accordance with the concept of sustainable development.

  19. Melting relations of multicomponent carbonate MgCO3-FeCO3-CaCO3-Na2CO3 system at 12-26 GPa: application to deeper mantle diamond formation

    Science.gov (United States)

    Spivak, Anna; Solopova, Natalia; Dubrovinsky, Leonid; Litvin, Yuriy

    2015-11-01

    Carbonatic components of parental melts of the deeper mantle diamonds are inferred from their primary inclusions of (Mg, Fe, Ca, Na)-carbonate minerals trapped at PT conditions of the Earth's transition zone and lower mantle. PT phase diagrams of MgCO3-FeCO3-CaCO3-Na2CO3 system and its ternary MgCO3-FeCO3-Na2CO3 boundary join were studied at pressures between 12 and 24 GPa and high temperatures. Experimental data point to eutectic solidus phase relations and indicate liquidus boundaries for completely miscible (Mg, Fe, Ca, Na)- and (Mg, Fe, Ca)-carbonate melts. PT fields for partial carbonate melts associated with (Mg, Fe)-, (Ca, Fe, Na)-, and (Na2Ca, Na2Fe)-carbonate solid solution phases are determined. Effective nucleation and mass crystallization of deeper mantle diamonds are realized in multicomponent (Mg, Fe, Ca, Na)-carbonatite-carbon melts at 18 and 26 GPa. The multicomponent carbonate systems were melted at temperatures that are lower than the geothermal ones. This gives an evidence for generation of diamond-parental carbonatite melts and formation of diamonds at the PT conditions of transition zone and lower mantle.

  20. Reproducing early Martian atmospheric carbon dioxide partial pressure by modeling the formation of Mg-Fe-Ca carbonate identified in the Comanche rock outcrops on Mars

    Science.gov (United States)

    Berk, Wolfgang; Fu, Yunjiao; Ilger, Jan-Michael

    2012-10-01

    The well defined composition of the Comanche rock's carbonate (Magnesite0.62Siderite0.25Calcite0.11Rhodochrosite0.02) and its host rock's composition, dominated by Mg-rich olivine, enable us to reproduce the atmospheric CO2partial pressure that may have triggered the formation of these carbonates. Hydrogeochemical one-dimensional transport modeling reveals that similar aqueous rock alteration conditions (including CO2partial pressure) may have led to the formation of Mg-Fe-Ca carbonate identified in the Comanche rock outcrops (Gusev Crater) and also in the ultramafic rocks exposed in the Nili Fossae region. Hydrogeochemical conditions enabling the formation of Mg-rich solid solution carbonate result from equilibrium species distributions involving (1) ultramafic rocks (ca. 32 wt% olivine; Fo0.72Fa0.28), (2) pure water, and (3) CO2partial pressures of ca. 0.5 to 2.0 bar at water-to-rock ratios of ca. 500 molH2O mol-1rock and ca. 5°C (278 K). Our modeled carbonate composition (Magnesite0.64Siderite0.28Calcite0.08) matches the measured composition of carbonates preserved in the Comanche rocks. Considerably different carbonate compositions are achieved at (1) higher temperature (85°C), (2) water-to-rock ratios considerably higher and lower than 500 mol mol-1 and (3) CO2partial pressures differing from 1.0 bar in the model set up. The Comanche rocks, hosting the carbonate, may have been subjected to long-lasting (>104 to 105 years) aqueous alteration processes triggered by atmospheric CO2partial pressures of ca. 1.0 bar at low temperature. Their outcrop may represent a fragment of the upper layers of an altered olivine-rich rock column, which is characterized by newly formed Mg-Fe-Ca solid solution carbonate, and phyllosilicate-rich alteration assemblages within deeper (unexposed) units.

  1. 低浓度甲烷催化燃烧La0.8Ca0.2FeO3/MgO蜂窝催化剂%La0.8Ca0.2FeO3/MgO honeycombs for catalytic lean burn of methane

    Institute of Scientific and Technical Information of China (English)

    史兵兵; 江志东

    2013-01-01

      开发了以MgO为第二载体的La0.8Ca0.2FeO3钙钛矿整体催化剂,用于低浓度甲烷(φ(CH4)=0.5%)的催化燃烧。首先用共沉淀法制备了不同比例Ca掺杂的钙钛矿粉体,然后在程序升温反应-质谱仪中对催化剂进行筛选,并用XRD、TPR、BET对粉末进行表征。在此基础上,选择La0.8Ca0.2FeO3并确定800℃为焙烧温度,采用浆料涂覆法将粉末La0.8Ca0.2FeO3涂覆在α-Al2O3蜂窝陶瓷基体上制成整体催化剂,在空速40000h-1下进行催化燃烧反应试验。考察了引入MgO作为第二载体的效果以及在MgO中引入少量Al2O3的影响,对MgO的焙烧温度、负载量进行了优化。结果表明,MgO对活性组分有隔离保护和高温下的分散稳定作用,而MgO与La0.8Ca0.2FeO3之间的相互作用是导致La0.8Ca0.2FeO3整体催化剂的活性比粉末催化剂高了1倍左右的主要原因。%  La0.8Ca0.2FeO3/MgO perovskite monolithic honeycomb catalysts were developed for catalytic lean burn of methane (0.5% by volume in air). Firstly, the calcium doped La1-xCaxFeO3 (x=0, 0.1, 0.2, 0.3, 0.4) powder catalysts were prepared by coprecipitation, then screened in the Temperature-Programmed Reactions-Mass Chromatograph (TPRs-MS) reactor, and characterized by XRD, TPR and BET. Based on above studies, the La0.8Ca0.2FeO3 calcined at 800℃ was picked out for preparation of the honeycomb catalysts by washcoating La0.8Ca0.2FeO3 on an α-Al2O3 ceramic honeycomb substrate and methane combustion on the honeycomb catalysts was tested under GHSV of 40 000h-1. The effects of introducing MgO as the second support and adding a small amount of Al2O3 into MgO were investigated, and MgO calcination temperature and loading amount were optimized. The results indicated that MgO performed the functions of isolating the active catalyst from the Al2O3 substrate as well as stabilizing and dispersing the active catalyst at high temperature, and the interaction of MgO with the

  2. A structure energy model for C2/c pyroxenes in the system Na-Mg-Ca-Mn-Fe-Al-Cr-Ti-Si-O

    International Nuclear Information System (INIS)

    The structure of C2/c pyroxenes in the Na-Mg-Ca-Fe-Al-Cr-Ti-Si-O system can be accurately simulated by the calculation of all interionic distances in the asymmetric unit, followed by a DLS treatment that optimizes cell parameters and atomic fractional coordinates. The precise structural simulation allows an accurate treatment of the static bulk lattice energy of the phase through two-body interaction potential calculations extended to all atoms within the asymmetric unit. The parametrization of the repulsive energy is achieved with the Huggins Mayer formulation that assumes the hardness factor of substances to be constant for all salts in the family and the repulsive factors of components to be variable from salt to salt. The linear relationship observed between repulsive factors of components and ionic radii of substituting ions on sites allows a rough estimate of lattice energy (hence of enthalpy, through the Born-Haber treatment) of unknown components. The structure-energy model developed for C2/c pyroxenes in the quadrilateral can be extended to the Na-Mg-Ca-Mn-Fe-Al-Cr-Ti-Si-O system when the molar abundances of minor components CaAl2SiO6, NaAlSi2O6, NaCrSi2O6, CaMnSi2O6, CaTiAl2O6 are limited to X ≤ 0.1 and the molar abundance of CaTiAl2O6 is restricted to X ≤ 0.05. The precision of the results rests on the precision of the enthalpy values selected at Tr, Pr reference conditions, as the uncertainty involved in the static lattice energy calculations is virtually negligible. Once new experimental data are available for the end-member components of interest, the model can be easily recast to obey the new limiting conditions

  3. Preheated shock experiments in the molten CaAl_2Si_2O_8-CaFeSi_2O_6-CaMgSi_2O_6 ternary: A test for linear mixing of liquid volumes at high pressure and temperature

    OpenAIRE

    Thomas, Claire W.; Asimow, Paul D.

    2013-01-01

    We performed 17 new shock wave experiments on preheated (1673 K) hedenbergite liquid (CaFeSi_2O_6) and two model basalt liquids (an equimolar binary mix of CaAl_2Si_2O_8 + CaFeSi_2O_6 and an equimolar ternary mix of CaAl_2Si_2O_8 + CaFeSi_2O_6 +CaMgSi_2O_6) in order to determine their equations of state (EOS). Ambient pressure density measurements on these and other Fe-bearing silicate liquids indicate that FeO has a partial molar volume that is highly dependent on composition, which leads to...

  4. Dynamics and Relationships of Ca,Mg,Fe in Litter,Soil Fauna and Soil in Pinus koraiensis-Broadleaf Mixed Forest

    Institute of Scientific and Technical Information of China (English)

    SONG Bo; YIN Xiuqin; ZHANG Yu; DONG Weihua

    2008-01-01

    The Liangshui Natural Reserve in Heilongjiang Province of China was selected as the study area.The authors collected the samples of forest litter (Tilia amurensis,Fraxinus mandshurica,Pinus koraiensis,Acer mono,Betula costata,and mixed litter),soil in humus horizon (0-5cm) and soil horizon (5-20cm),and soil macrofauna (Oligochaeta,Geophiloporpha and Juliformia) from 2001 to 2002.The role of soil macrofauna in the material cycle was analyzed through comparing the macro-element contents among various parts of the subsystems and using enrichment index (EI).The results indicate that dynamic changes of various litters are very complicated.The contents of Fe in each kind of litter increase firstly,and then decrease in the study period.The changes of macro-element contents are greater in the broad-leaf litter than in the coniferous litter,and the mixed litter is in the middle level,but the differences among them are not significant.The contents of Mg and Fe in humus are higher than those in soil,but the contents of Ca in soil are higher than that in humus.The dynamic changes of macro-element contents in soil and soil fauna are not consistent with those in litter.The diplopod presented obvious enrichment of Ca and Mg (EI>1),but it does not significantly enrich Fe.Earthworm has a stronger enrichment ability of Fe than diplopod and scolopendra,but EI<1.Soil fauna can make great influences on the material cycle of the subsystems.

  5. Ion-microprobe measurements of Mg, Ca, Ti and Fe isotopic ratios and trace element abundance in hibonite-bearing inclusions in primitive meteorites

    International Nuclear Information System (INIS)

    This thesis reports the isotopic abundances of Mg, Ca, and Ti and rare earth element (REE) abundances in 19 hibonite-bearing inclusions from primative meteorites. The isotopic ratios of Fe were measured in one of the samples, Lance HH-1. These measurements were made by means of secondary ion mass spectrometry (CAMECA IMS-3f). The novel hardware and software developments that made this work possible are described in detail. The samples were studied in thin section in order to investigate the relationship between the inclusions and their mineralogical environments. Inclusions from a number of different meteorites, specifically, Mighei, Murray, Murchison, Lance, Efremovka, Vigarano, Qingzhen, Dhajala, and Semarkona, were studied. The isotopes of Ca and Ti show large and correlated abundance anomalies in their most neutron-rich isotopes, 48Ca and 50Ti. The largest anomalies among the samples studied here are in the Murray inclusion MY-F6, with a 4.6% deficit in 48Ca and a 5.2% deficit in 50Ti, and Lance HH-1, with 3.3% and 6.0% deficits in 48Ca and 50Ti respectively. Correlated excesses of 48Ca and 50Ti, up to 2.4% and 1.4% respectively, are found in some other samples studied here. The fact that there is a correlation of isotopic anomalies in two different elements is clear evidence for a nucleosynthetic origin of these effects. Various possibilities for the origin of these isotopic anomalies are discussed and it is shown that a Cosmic Chemical Memory-like model of the incomplete mixing of dust grains from one or several supernovae is sufficient to explain the data. Magnesium isotopes show excesses of 26Mg, attributable to the in-situ decay of 26Al, in 7 of these inclusions

  6. Quantitative analysis of sodium di-uranate for Al, Ca, Fe, Mg, Mn, Na by flame-atomic absorption spectrometric method

    International Nuclear Information System (INIS)

    Nuclear Fuel Complex (NFC) receives Sodium Di-Uranate (SDU) from Uranium Corporation of India Limited (UCIL) for producing sinterable UO2 pellets for manufacturing fuel sub assemblies. Several impurities present in ore find their way into SDU during its conversion. Stringent specification have been laid down by the reactor designs for achieving the optimum performance of the fuel and several impurity element like Al, Ca, Fe, Mg, Mn, Na among others affects severely performance of UO2 fuel. Most of the impurity including the above mentioned elements are generally analysed by ICP-OES method. However, determination of Al, Ca, Fe, Mg, Mn and Na by ICP-OES requires lot of dilution as they are present at high levels in SDU. Apart from introducing dilution error, dilution process is very tedious and time consuming work and not a preferred choice in an industrial lab like control lab where large analytical load exists and time bound analysis is a requirement. To avoid these difficulties a simple and reliable Flame Atomic absorption spectrometric technique has been developed for regular analysis. Present method involves dissolution of SDU sample in Conc. HNO3 and after the complete dissolution the sample solution has been evaporated to near dryness on a hot plate. Subsequently sample solution has been brought into 4N HNO3 medium

  7. Thermodynamics Behavior of Germanium During Equilibrium Reactions between FeOx-CaO-SiO2-MgO Slag and Molten Copper

    Science.gov (United States)

    Shuva, M. A. H.; Rhamdhani, M. A.; Brooks, G. A.; Masood, S.; Reuter, M. A.

    2016-10-01

    The distribution ratio of germanium (Ge), L_{{Ge}}^{s/m} during equilibrium reactions between magnesia-saturated FeOx-CaO-SiO2 (FCS) slag and molten copper has been measured under oxygen partial pressures from 10-10 to 10-7 atm and at temperatures 1473 to 1623 K (1200 to 1350 °C). It was observed that the Ge distribution ratio increases with increasing oxygen partial pressure, and with decreasing temperature. It was also observed that the distribution ratio is strongly dependent on slag basicity. The distribution ratio was observed to increase with increasing optical basicity. At fixed CaO concentration in the slag, the distribution ratio was found to increase with increasing Fe/SiO2 ratio, tending to a plateau at L_{{Ge}}^{s/m} = 0.8. This behavior is consistent with the assessment of ionic bond fraction carried out in this study, and suggested the acidic nature of germanium oxide (GeO2) in the slag system studied. The characterisation results of the quenched slag suggested that Ge is present in the FeOx-CaO-SiO2-MgO slag predominantly as GeO2. At 1573 K (1300 °C) and p_{{{{O}}2 }} = 10-8 atm, the activity coefficient of GeO2 in the slag was calculated to be in the range of 0.24 to 1.50. The results from the current study suggested that less-basic slag, high operating temperature, and low oxygen partial pressure promote a low Ge distribution ratio. These conditions are desired for maximizing Ge recovery, for example, during pyrometallurgical processing of Ge-containing e-waste through secondary copper smelting. Overall, the thermodynamics data generated from this study can be used for process modeling purposes for improving recovery of Ge in primary and secondary copper smelting processes.

  8. Sodium, K, Ca, Mg, Fe, Cu, and Zn concentrations in molluscs from the Magellan Strait (Chile): their contribution to dietary intake.

    Science.gov (United States)

    España, M S Astorga; Rodríguez, E M Rodríguez; Romero, C Díaz

    2005-08-01

    The concentrations of the essential metals Na, K, Ca, Mg, Fe, Cu, and Zn were determined in 126 specimens of molluscs belonging to five different species: Mytilus chilensis, n=47; Nacella deaurata, n=65; Aulacomya ater, n=4; Fissurella picta, n=4; Acanthina monodon, n=6, collected from the coastline of the Magellan Strait. Significant differences were obtained among the mean metal concentrations in the mollusc species considered. The contribution to the dietary daily intake of these metals for the consumption of one serving of these molluscs was high, especially the contribution to the Fe intake for the consumption of N. deaurata. Some significant differences were observed among the mean concentrations for the studied metals according to the zone of sampling. The influence of the zone of sampling on the mean concentration of metals in N. deaurata was higher than in M. chilensis. The application of lineal discriminant analysis (LDA) made it possible to differentiate statistically between specimens according to the mollusc species. Within the each mollusc species, the LDA helped to identify specimens according to the zone of sampling and weight/length ratio. PMID:16236595

  9. Sodium, K, Ca, Mg, Fe, Cu, and Zn concentrations in molluscs from the Magellan Strait (Chile): their contribution to dietary intake.

    Science.gov (United States)

    España, M S Astorga; Rodríguez, E M Rodríguez; Romero, C Díaz

    2005-08-01

    The concentrations of the essential metals Na, K, Ca, Mg, Fe, Cu, and Zn were determined in 126 specimens of molluscs belonging to five different species: Mytilus chilensis, n=47; Nacella deaurata, n=65; Aulacomya ater, n=4; Fissurella picta, n=4; Acanthina monodon, n=6, collected from the coastline of the Magellan Strait. Significant differences were obtained among the mean metal concentrations in the mollusc species considered. The contribution to the dietary daily intake of these metals for the consumption of one serving of these molluscs was high, especially the contribution to the Fe intake for the consumption of N. deaurata. Some significant differences were observed among the mean concentrations for the studied metals according to the zone of sampling. The influence of the zone of sampling on the mean concentration of metals in N. deaurata was higher than in M. chilensis. The application of lineal discriminant analysis (LDA) made it possible to differentiate statistically between specimens according to the mollusc species. Within the each mollusc species, the LDA helped to identify specimens according to the zone of sampling and weight/length ratio.

  10. Calcioferrite with composition (Ca3.94Sr0.06Mg1.01(Fe2.93Al1.07(PO46(OH4·12H2O

    Directory of Open Access Journals (Sweden)

    Barbara Lafuente

    2014-03-01

    Full Text Available Calcioferrite, ideally Ca4MgFe3+4(PO46(OH4·12H2O (tetracalcium magnesium tetrairon(III hexakis-phosphate tetrahydroxide dodecahydrate, is a member of the calcioferrite group of hydrated calcium phosphate minerals with the general formula Ca4AB4(PO46(OH4·12H2O, where A = Mg, Fe2+, Mn2+ and B = Al, Fe3+. Calcioferrite and the other three known members of the group, montgomeryite (A = Mg, B = Al, kingsmountite (A = Fe2+, B = Al, and zodacite (A = Mn2+, B = Fe3+, usually occur as very small crystals, making their structure refinements by conventional single-crystal X-ray diffraction challenging. This study presents the first structure determination of calcioferrite with composition (Ca3.94Sr0.06Mg1.01(Fe2.93Al1.07(PO46(OH4·12H2O based on single-crystal X-ray diffraction data collected from a natural sample from the Moculta quarry in Angaston, Australia. Calcioferrite is isostructural with montgomeryite, the only member of the group with a reported structure. The calcioferrite structure is characterized by (Fe/AlO6 octahedra (site symmetries 2 and -1 sharing corners (OH to form chains running parallel to [101]. These chains are linked together by PO4 tetrahedra (site symmetries 2 and 1, forming [(Fe/Al3(PO43(OH2] layers stacking along [010], which are connected by (Ca/Sr2+ cations (site symmetry 2 and Mg2+ cations (site symmetry 2; half-occupation. Hydrogen-bonding interactions involving the water molecules (one of which is equally disordered over two positions and OH function are also present between these layers. The relatively weaker bonds between the layers account for the cleavage of the mineral parallel to (010.

  11. Crystal structure of superparamagnetic Mg{sub 0.2}Ca{sub 0.8}Fe{sub 2}O{sub 4} nanoparticles synthesized by sol–gel method

    Energy Technology Data Exchange (ETDEWEB)

    Escamilla-Pérez, A.M., E-mail: angel.mep@gmail.com [Cinvestav-Unidad Saltillo, Industria Metalúrgica No. 1062, Parque Industrial Saltillo-Ramos Arizpe, C.P. 25900, Ramos Arizpe, Coahuila (Mexico); Cortés-Hernández, D.A., E-mail: dora.cortes@cinvestav.edu.mx [Cinvestav-Unidad Saltillo, Industria Metalúrgica No. 1062, Parque Industrial Saltillo-Ramos Arizpe, C.P. 25900, Ramos Arizpe, Coahuila (Mexico); Almanza-Robles, J.M. [Cinvestav-Unidad Saltillo, Industria Metalúrgica No. 1062, Parque Industrial Saltillo-Ramos Arizpe, C.P. 25900, Ramos Arizpe, Coahuila (Mexico); Mantovani, D.; Chevallier, P. [Laboratory for Biomaterials and Bioengineering, Department of Materials Engineering and University Hospital Research Center, Laval University, Quebec City, QC (Canada)

    2015-01-15

    Powders of magnetic iron oxide nanoparticles (Mg{sub 0.2}Ca{sub 0.8}Fe{sub 2}O{sub 4}) were prepared by a sol–gel method using ethylene glycol and nitrates of Fe, Ca and Mg as starting materials. Those powders were heat treated at different temperatures (573, 673, 773 and 873 K). In order to evaluate the effect of the heat treatment temperature on the nanoferrites properties, X-ray diffraction (XRD), vibrating sample magnetometry (VSM), transmission electron microscopy (TEM) and X-ray photoelectron spectroscopy (XPS) techniques were used. It was found that the reaction products exhibit nanometric sizes and superparamagnetic behavior. It is also demonstrated that, as the heat treatment temperature increases, the particle size and the saturation magnetization of the nanoferrites are increased. - Highlights: • Mg{sub 0.2}Ca{sub 0.8}Fe{sub 2}O{sub 4} superparamagnetic nanoparticles were successfully synthesized. • Particle average sizes of Ca–Mg ferrites were within the range of 8–25 nm. • The nanoferrite treated at 873 K showed a stoichiometry close to Mg{sub 0.2}Ca{sub 0.8}Fe{sub 2}O{sub 4}. • The heat treatment temperature has a strong effect on the crystal structure. • These nanoparticles are potential materials for magnetic hyperthermia.

  12. CaO-MgO@CoFe2 O4磁性固体碱的制备及其大豆油酯交换反应催化性能%Preparation of magnetic core-shell CaO-MgO@CoFe2O4 solid base and its catalytic performance in the transesterification of soybean oil to biodiesel

    Institute of Scientific and Technical Information of China (English)

    范明明; 刘延磊; 张萍波; 蒋平平

    2016-01-01

    以草酸盐为前驱体采用两步法制备了一种以CaO-MgO作为活性组分,以CoFe2 O4作为磁核的磁性固体碱催化剂,并用于大豆油与甲醇的酯交换反应合成生物柴油。对制备的磁性固体碱催化剂进行了磁滞回线、X-射线衍射( XRD)、CO2-TPD及透射电镜( TEM)表征。考察了不同核壳物质的量比、焙烧温度、反应温度、反应时间、醇油物质的量比以及催化剂用量等因素对大豆油转化为生物柴油产率的影响。结果表明,采用核壳物质的量比为1:6、焙烧温度为700℃所制备的CaO-MgO@CoFe2 O4催化剂,当醇油物质的量比为12、催化剂用量为大豆油质量的1.0%时,在65℃下反应时间3 h,生物柴油收率高达97.1%。该催化剂具有较好的重复利用性能,重复利用四次后生物柴油的收率仍可达90%。%A magnetic core-shell CaO-MgO@CoFe2 O4 solid base was prepared with oxalates as the precursor through a two-step method, which was used as the catalyst for the transesterification of soybean oil to biodiesel with methanol. The CaO-MgO@CoFe2 O4 catalyst was characterized by magnetic hysteresis loop, X-ray diffraction ( XRD) , CO2-TPD and transmission electron microscopy ( TEM ); the effects of core-shell molar ratio, catalyst calcination temperature, reaction temperature, reaction time, methanol/oil molar ratio and catalyst amount on the yield of biodiesel were investigated. The results indicated that over the CaO-MgO@CoFe2 O4 catalyst with a core-shell molar ratio of 1:6 and calcined at 700 ℃, the biodiesel yield reaches 97 . 1% after conducting the transesterification reaction at 65℃ for 3 h, when the methanol/oil mol ratio is 12 and the amount of catalyst is 1. 0% by mass. The catalyst exhibits excellent reusability; the biodiesel yield remains above 90%after reusing for four cycles.

  13. Influência dos Íons Mg, Ca, Fe, Cu e Zn sobre a tensão superficial estática de soluções contendo surfatante Influence of Mg, Ca, Fe, Cu and Zn Ions on static surface tension of surfactant solutions

    Directory of Open Access Journals (Sweden)

    F.M.L. Silva

    2006-09-01

    Full Text Available O objetivo do estudo foi avaliar a influência da presença de cinco íons em uma calda de pulverização contendo o surfatante Aterbane. A tensão superficial foi analisada por meio da medição da massa de um conjunto de 25 gotas, com quatro repetições constituindo um tratamento. O trabalho foi dividido em duas etapas. Na primeira, os tratamentos foram combinados em esquema fatorial 9x5x2, sendo nove concentrações do surfatante Aterbane (0,01; 0,025; 0,05; 0,1; 0,2; 0,5; 1; 2; e 3%, cinco íons (Mg++, Ca++, Fe+++, Cu+++ e Zn+++ e duas concentrações desses elementos (10 e 100 ppm. Na segunda etapa, os tratamentos foram combinados em esquema fatorial 5x5x1, utilizandose os mesmos cinco elementos (Mg++, Ca++, Fe+++, Cu+++ e Zn+++, em cinco concentrações (1, 5, 20, 50 e 200 ppm, com apenas uma concentração do surfatante Aterbane (0,025%. Outros nove tratamentos permitiram avaliar as tensões superficiais das concentrações do surfatante (0,01; 0,025; 0,05; 0,1; 0,2; 0,5; 1; 2; e 3% sem a adição dos íons. Os resultados mostraram que houve interferência dos íons sobre as soluções, já que, com exceção do Fe+++ (na concentração de 10 e 100 ppm e do Cu+++ (na concentração de 100 ppm, todos os íons reduziram a tensão mínima alcançada e aumentaram a eficiência do surfatante, implicando benefícios à ação do surfatante e sobre as características de possíveis soluções de aplicação. Todos os íons avaliados promoveram reduções nas tensões superficiais de soluções do surfatante na concentração de 0,025%.The objective of this study was to evaluate the influence of 5 ions on a spray solution containing the surfactant aterbane. Surface tension was analyzed by measuring the mass of a set of 25 drops, with four repetitions constituting a treatment. The work was divided in two stages. In the first, the treatments were arranged in a 9x5x2 factorial design, nine Aterbane concentrations (0.01; 0.025; 0.05; 0.1; 0.2; 0

  14. Design and Development for Capacitive Humidity Sensor Applications of Lead-Free Ca,Mg,Fe,Ti-Oxides-Based Electro-Ceramics with Improved Sensing Properties via Physisorption

    Directory of Open Access Journals (Sweden)

    Ashis Tripathy

    2016-07-01

    Full Text Available Despite the many attractive potential uses of ceramic materials as humidity sensors, some unavoidable drawbacks, including toxicity, poor biocompatibility, long response and recovery times, low sensitivity and high hysteresis have stymied the use of these materials in advanced applications. Therefore, in present investigation, we developed a capacitive humidity sensor using lead-free Ca,Mg,Fe,Ti-Oxide (CMFTO-based electro-ceramics with perovskite structures synthesized by solid-state step-sintering. This technique helps maintain the submicron size porous morphology of the developed lead-free CMFTO electro-ceramics while providing enhanced water physisorption behaviour. In comparison with conventional capacitive humidity sensors, the presented CMFTO-based humidity sensor shows a high sensitivity of up to 3000% compared to other materials, even at lower signal frequency. The best also shows a rapid response (14.5 s and recovery (34.27 s, and very low hysteresis (3.2% in a 33%–95% relative humidity range which are much lower values than those of existing conventional sensors. Therefore, CMFTO nano-electro-ceramics appear to be very promising materials for fabricating high-performance capacitive humidity sensors.

  15. Design and Development for Capacitive Humidity Sensor Applications of Lead-Free Ca,Mg,Fe,Ti-Oxides-Based Electro-Ceramics with Improved Sensing Properties via Physisorption

    Science.gov (United States)

    Tripathy, Ashis; Pramanik, Sumit; Manna, Ayan; Bhuyan, Satyanarayan; Azrin Shah, Nabila Farhana; Radzi, Zamri; Abu Osman, Noor Azuan

    2016-01-01

    Despite the many attractive potential uses of ceramic materials as humidity sensors, some unavoidable drawbacks, including toxicity, poor biocompatibility, long response and recovery times, low sensitivity and high hysteresis have stymied the use of these materials in advanced applications. Therefore, in present investigation, we developed a capacitive humidity sensor using lead-free Ca,Mg,Fe,Ti-Oxide (CMFTO)-based electro-ceramics with perovskite structures synthesized by solid-state step-sintering. This technique helps maintain the submicron size porous morphology of the developed lead-free CMFTO electro-ceramics while providing enhanced water physisorption behaviour. In comparison with conventional capacitive humidity sensors, the presented CMFTO-based humidity sensor shows a high sensitivity of up to 3000% compared to other materials, even at lower signal frequency. The best also shows a rapid response (14.5 s) and recovery (34.27 s), and very low hysteresis (3.2%) in a 33%–95% relative humidity range which are much lower values than those of existing conventional sensors. Therefore, CMFTO nano-electro-ceramics appear to be very promising materials for fabricating high-performance capacitive humidity sensors. PMID:27455263

  16. Synthesis and Characterizations of Novel Ca-Mg-Ti-Fe-Oxides Based Ceramic Nanocrystals and Flexible Film of Polydimethylsiloxane Composite with Improved Mechanical and Dielectric Properties for Sensors

    Science.gov (United States)

    Tripathy, Ashis; Pramanik, Sumit; Manna, Ayan; Azrin Shah, Nabila Farhana; Shasmin, Hanie Nadia; Radzi, Zamri; Abu Osman, Noor Azuan

    2016-01-01

    Armalcolite, a rare ceramic mineral and normally found in the lunar earth, was synthesized by solid-state step-sintering. The in situ phase-changed novel ceramic nanocrystals of Ca-Mg-Ti-Fe based oxide (CMTFOx), their chemical reactions and bonding with polydimethylsiloxane (PDMS) were determined by X-ray diffraction, infrared spectroscopy, and microscopy. Water absorption of all the CMTFOx was high. The lower dielectric loss tangent value (0.155 at 1 MHz) was obtained for the ceramic sintered at 1050 °C (S1050) and it became lowest for the S1050/PDMS nanocomposite (0.002 at 1 MHz) film, which was made by spin coating at 3000 rpm. The excellent flexibility (static modulus ≈ 0.27 MPa and elongation > 90%), viscoelastic property (tanδ = E″/E′: 0.225) and glass transition temperature (Tg: −58.5 °C) were obtained for S1050/PDMS film. Parallel-plate capacitive and flexible resistive humidity sensors have been developed successfully. The best sensing performance of the present S1050 (3000%) and its flexible S1050/PDMS composite film (306%) based humidity sensors was found to be at 100 Hz, better than conventional materials. PMID:26927116

  17. Alternative solution model for the ternary carbonate system CaCO3 - MgCO3 - FeCO3 - I. A ternary Bragg-Williams ordering model

    Science.gov (United States)

    McSwiggen, P.L.

    1993-01-01

    The minerals of the ternary carbonate system CaCO3 - MgCO3 - FeCO3 represent a complex series of solid solutions and ordering states. An understanding of those complexities requires a solution model that can both duplicate the subsolidus phase relationships and generate correct values for the activities. Such a solution model must account for the changes in the total energy of the system resulting from a change in the ordering state of the individual constituents. Various ordering models have been applied to binary carbonate systems, but no attempts have previously been made to model the ordering in the ternary system. This study derives a new set of equations that allow for the equilibrium degree of order to be calculated for a system involving three cations mixing on two sites, as in the case of the ternary carbonates. The method is based on the Bragg-Williams approach. From the degree of order, the mole fractions of the three cations in each of the two sites can be determined. Once the site occupancies have been established, a Margules-type mixing model can be used to determine the free energy of mixing in the solid solution and therefore the activities of the various components. ?? 1993 Springer-Verlag.

  18. Design and Development for Capacitive Humidity Sensor Applications of Lead-Free Ca,Mg,Fe,Ti-Oxides-Based Electro-Ceramics with Improved Sensing Properties via Physisorption.

    Science.gov (United States)

    Tripathy, Ashis; Pramanik, Sumit; Manna, Ayan; Bhuyan, Satyanarayan; Azrin Shah, Nabila Farhana; Radzi, Zamri; Abu Osman, Noor Azuan

    2016-01-01

    Despite the many attractive potential uses of ceramic materials as humidity sensors, some unavoidable drawbacks, including toxicity, poor biocompatibility, long response and recovery times, low sensitivity and high hysteresis have stymied the use of these materials in advanced applications. Therefore, in present investigation, we developed a capacitive humidity sensor using lead-free Ca,Mg,Fe,Ti-Oxide (CMFTO)-based electro-ceramics with perovskite structures synthesized by solid-state step-sintering. This technique helps maintain the submicron size porous morphology of the developed lead-free CMFTO electro-ceramics while providing enhanced water physisorption behaviour. In comparison with conventional capacitive humidity sensors, the presented CMFTO-based humidity sensor shows a high sensitivity of up to 3000% compared to other materials, even at lower signal frequency. The best also shows a rapid response (14.5 s) and recovery (34.27 s), and very low hysteresis (3.2%) in a 33%-95% relative humidity range which are much lower values than those of existing conventional sensors. Therefore, CMFTO nano-electro-ceramics appear to be very promising materials for fabricating high-performance capacitive humidity sensors. PMID:27455263

  19. Synthesis and Characterizations of Novel Ca-Mg-Ti-Fe-Oxides Based Ceramic Nanocrystals and Flexible Film of Polydimethylsiloxane Composite with Improved Mechanical and Dielectric Properties for Sensors.

    Science.gov (United States)

    Tripathy, Ashis; Pramanik, Sumit; Manna, Ayan; Shah, Nabila Farhana Azrin; Shasmin, Hanie Nadia; Radzi, Zamri; Abu Osman, Noor Azuan

    2016-01-01

    Armalcolite, a rare ceramic mineral and normally found in the lunar earth, was synthesized by solid-state step-sintering. The in situ phase-changed novel ceramic nanocrystals of Ca-Mg-Ti-Fe based oxide (CMTFOx), their chemical reactions and bonding with polydimethylsiloxane (PDMS) were determined by X-ray diffraction, infrared spectroscopy, and microscopy. Water absorption of all the CMTFOx was high. The lower dielectric loss tangent value (0.155 at 1 MHz) was obtained for the ceramic sintered at 1050 °C (S1050) and it became lowest for the S1050/PDMS nanocomposite (0.002 at 1 MHz) film, which was made by spin coating at 3000 rpm. The excellent flexibility (static modulus ≈ 0.27 MPa and elongation > 90%), viscoelastic property (tanδ = E″/E': 0.225) and glass transition temperature (Tg: -58.5 °C) were obtained for S1050/PDMS film. Parallel-plate capacitive and flexible resistive humidity sensors have been developed successfully. The best sensing performance of the present S1050 (3000%) and its flexible S1050/PDMS composite film (306%) based humidity sensors was found to be at 100 Hz, better than conventional materials. PMID:26927116

  20. Synthesis and Characterizations of Novel Ca-Mg-Ti-Fe-Oxides Based Ceramic Nanocrystals and Flexible Film of Polydimethylsiloxane Composite with Improved Mechanical and Dielectric Properties for Sensors

    Directory of Open Access Journals (Sweden)

    Ashis Tripathy

    2016-02-01

    Full Text Available Armalcolite, a rare ceramic mineral and normally found in the lunar earth, was synthesized by solid-state step-sintering. The in situ phase-changed novel ceramic nanocrystals of Ca-Mg-Ti-Fe based oxide (CMTFOx, their chemical reactions and bonding with polydimethylsiloxane (PDMS were determined by X-ray diffraction, infrared spectroscopy, and microscopy. Water absorption of all the CMTFOx was high. The lower dielectric loss tangent value (0.155 at 1 MHz was obtained for the ceramic sintered at 1050 °C (S1050 and it became lowest for the S1050/PDMS nanocomposite (0.002 at 1 MHz film, which was made by spin coating at 3000 rpm. The excellent flexibility (static modulus ≈ 0.27 MPa and elongation > 90%, viscoelastic property (tanδ = E″/E′: 0.225 and glass transition temperature (Tg: −58.5 °C were obtained for S1050/PDMS film. Parallel-plate capacitive and flexible resistive humidity sensors have been developed successfully. The best sensing performance of the present S1050 (3000% and its flexible S1050/PDMS composite film (306% based humidity sensors was found to be at 100 Hz, better than conventional materials.

  1. Analysis of six elements (Ca, Mg, Fe, Zn, Cu, and Mn) in several wild vegetables and evaluation of their intakes based on Korea National Health and Nutrition Examination Survey 2010-2011.

    Science.gov (United States)

    Bae, Yun-Jung; Kim, Mi-Hyun; Lee, Je-Hyuk; Choi, Mi-Kyeong

    2015-03-01

    Wild vegetables, those edible among naturally grown vegetables, have been reported to contain many bioactive substances, dietary fibers, vitamins, and minerals. The purpose of this study is to examine the six elements of the wild vegetables frequently consumed by Koreans and assess the element intakes through them. Contents of six kinds of elements (Ca, Mg, Fe, Zn, Cu, and Mn) in 11 wild vegetables were analyzed by inductively coupled plasma optical emission spectroscopy. Using these analysis data, the 6-element intakes from the wild vegetables were evaluated in healthy Korean adults aged 19-64 years from the Korea National Health and Nutrition Examination Survey (2010-2011). Sedum and shepherd's purse contained over 100 mg of Ca in 100 g of their edible portion. The Mg content per 100 g of the 11 wild vegetables ranged from 12.1 mg to 43.4 mg. The wild vegetable with the highest mineral content per 100 g was sedum for Ca, spinach for Mg, shepherd's purse for Fe, spinach for Zn, bracken for Cu, and fragrant edible wild aster for Mn. The element intakes from the 11 wild vegetables compared with dietary reference intakes in the healthy Koreans were 1.0 % for Ca, 2.1 % for Mg, 5.3 % for Fe, 1.4 % for Zn, 0.3 % for Cu, and 1.8 % for Mn. Considering the low intake ratio (1.2 %) of the wild vegetable to total food intake, wild vegetables may contribute to some element intakes. Our results show the nutritional value of the wild vegetables in the aspect of mineral nutrition; however, further research is needed to evaluate the bioavailability of various elements in wild vegetables.

  2. Effects of CaO, MgO, Al2O3 and SiO2 on the carbothermic reduction of synthetic FeCr2O4

    Directory of Open Access Journals (Sweden)

    Wang Y.

    2015-01-01

    Full Text Available In order to optimize the current reduction process of chromite, a good knowledge of reduction mechanism involved is required. The basic component in chromite ore is FeCr2O4 with gangue component like MgO and Al2O3. In lack of clear and consistent explanation about the effect of addition on the reduction of FeCr2O4, investigation of synthetic FeCr2O4 with different kind and amount of additions was carried out at 1673K under isothermal mode. Kinetic mechanism was also studied by linear fitting of different kinetic equations. Combined with rate-controlling step, it could be concluded as follows. CaO could enhance the reduction because Ca2+ would replace Fe2+, thus facilitated the ion diffusion in solid phase. Al2O3 had a positive influence as well, since Al3+ could form a solid solution phase with Cr3+ and made Cr3+ reduced more easily. MgO would hinder the reduction due to formation of a more stable phase MgCr2O4. SiO2 would also hamper the Cr metallization because there was a liquid phase formed when Cr3+ was reduced to divalent, which would impede the nucleation of reduction product.

  3. Kinetics and mechanism of stepwise reduction of pure and Fe/sub 2/O/sub 3/ doped with either CaO and/or MgO fired compacts

    International Nuclear Information System (INIS)

    Fired pure Fe/sub 2/O/sub 3 doped with 0.5-5.0% of either CaO or MgO compacts were isothermally reduced at 1173-1473 K in CO atmosphere. The O/sub 2/-weight loss resulted from the reduction of iron oxide(s) was continuously recorded as a function of time. Partially and completely reduced samples were characterized. At a given temperature, compacts were reduced either directly to iron or in a stepwise manner (Fe/sub 2/O/sub 3/-Fe/sub 3/O/sub 4/-Fe) or Fe/sub 2/O/sub 3/- Fe/sub 0.943/O/sub -/Fe. Also compacts were reduced subsequently from Fe/sub 2/O/sub 3/ to Fe/sub 3/O/sub 4/ the to Fe/sub 0.943/O and finally to Fe. The apparent activation energy values were calculated at both of early and later reduction stages. Also, the different heterogeneous gas-solid reaction formulations were tested against the experimental reduction results. The structure of partially and completely reduced samples were microscopically examined and correlated with the structure to elucidate the reduction mechanism. The results obtained indicated that the presence of fluxing oxide (s) promote the reduction of pure hematite at the early stages due to the increase in their original porosity. At intermediate and later reduction stages, the presence of doping oxide(s) showed different effects depending on fluxing oxide content, reduction extent and temperature. The reduction mechanism elucidated was greatly influenced by the structure of intermediate solid phases (magnetite and/or wustite) developed prior to metallic iron. (author)

  4. The system MgCO3-FeCO3-CaCO3-Na2CO3 at 12-23 GPa: Phase relations and significance for the genesis of ultradeep diamonds

    Science.gov (United States)

    Spivak, A. V.; Solopova, N. A.; Dubrovinsky, L. S.; Litvin, Yu. A.

    2015-09-01

    Physical-chemical experimental studies at 12-23 GPa of phase relationships within four-members carbonate system MgCO3-FeCO3-CaCO3-Na2CO3 and its marginal system MgCO3-FeCO3-Na2CO3 were carried out. The systems are quite representative for a set of carbonate phases from inclusions in diamonds within transitional zone and lower mantle. PT-phase diagrams of multicomponent carbonate systems are suggested. PT parameters of boundaries of their eutectic melting (solidus), complete melting (liquids) are established. These boundaries define area of partial melting. Carbonate melts are stable, completely mixable, and effective solvents of elemental carbon thus defining the possibility of ultra-deep diamonds generation.

  5. On the Production of He, Ne, and AR Isotopes from Mg, Al, Si, Ca, Fe, and NI in an Artificially Irradiated Meteoroid

    Science.gov (United States)

    Wieler, R.; Signet, P.; Rosel, R.; Herpers, U.; Lupke, M.; Lange, H.-J.; Michel, R.

    1992-07-01

    The production of He, Ne, and Ar isotopes from their main target elements was investigated in an experiment (1) by irradiating a 50-cm-diameter gabbro sphere isotropically with 1.6 GeV protons. The model meteoroid contained, among a large number of other targets, pure element foils of Mg, Al, Si, Fe, and Ni at 10 different depths and wollastonite targets at 3 different depths in central bores. After the irradiation, radionuclide production in these targets was measured by gamma spectrometry. Stable He, Ne, and Ar isotopes were measured in statically operated mass spectrometers. Here, we report the results for stable He, Ne, and Ar isotopes and for ^22Na. The production depth profiles vary widely, ranging from profiles with near-surface production 15% higher than in the center (^22Na from Fe) to such profiles with production in the center 45% higher than near the surface (^20Ne from Mg). The isotope ratios ^3He/^4He and ^3He/^21Ne in Mg, Al, Si and ^22Ne/^21Ne in Mg all decrease significantly with increasing shielding. The production rates of He, Ne, and ^22Na from Mg, Al, and Si in the 1600-MeV simulation experiment are 1.5 to 3 times higher than in the model meteoroid of similar size but irradiated earlier with 600 MeV protons (2). This increase is attributed to the increase of the production of secondary neutrons with primary energies rising from 600 to 1600 MeV. This effect also causes the depth dependences of isotope ratios observed in the 1600-MeV simulation that was not seen in the 600-MeV experiment. Model calculations of the production of He, Ne, and Ar isotopes and of ^22Na were performed for the artificial meteorites of the 600- and 1600 MeV-exposures as well as for real meteoroids. Production rates were calculated from depth-dependent p- and n- spectra, which were derived by Monte Carlo techniques using the HERMES code system (3), and from cross sections for the relevant nuclear reactions as described earlier (4). The cross section database for p

  6. Interstitial Fe in MgO

    CERN Document Server

    Mølholt, T E; 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 Fe-57 atoms were studied in MgO single-crystals by emission Mossbauer spectroscopy following implantation of Mn-57 decaying to Fe-57. Four Mossbauer 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.

  7. Effects of Al2O3 and MgO on Softening, Melting, and Permeation Properties of CaO-FeO-SiO2 on a Coke Bed

    Science.gov (United States)

    Ueda, Shigeru; Kon, Tatsuya; Miki, Takahiro; Kim, Sun-Joong; Nogami, Hiroshi

    2016-08-01

    In ironmaking, maintaining gas permeability in blast furnace with low coke rate operation is essential to reduce carbon emissions. The high pressure loss in the cohesive zone decreases the gas permeability and affects the productivity of blast furnace. In order to increase the gas permeability in the cohesive zone, the thickness of the cohesive layer should be decreased. For this purpose, increasing softening temperature and decreasing dripping temperature of the iron ore are desired. In this study, softening, melting, and permeation of SiO2-FeO-CaO-Al2O3-MgO on a coke bed were investigated. The oxide sample in a tablet form was heated under CO/CO2 atmosphere, and the shape of the tablet was observed. The softening and melting temperatures of the SiO2-FeO-CaO system changed with the addition of Al2O3 and MgO. Oxide tablets with and without Al2O3 softened below and above the solidus temperature, respectively. The melting temperatures varied with the ratio of CO/CO2 in the gas. The permeation temperature was independent of the melting temperature, but dependent on the wettability.

  8. Magnetic Characterization of CoFeB/MgO and CoFe/MgO Interfaces

    Energy Technology Data Exchange (ETDEWEB)

    Negusse,E.; Lussier, A.; Dvorak, J.; Idzerda, Y.; Shinde, S.; Nagamine, Y.; Furukawa, S.; Tsunekawa, K.; Djayaprawira, D.

    2007-01-01

    The use of CoFeB ferromagnetic electrodes in place of CoFe has been shown to significantly increase the tunneling magnetoresistance (TMR) of MgO based magnetic tunnel junctions (MTJs). By using soft x-ray scattering techniques, we show that the behavior of the magnetic moments located at the CoFe-MgO interface are drastically different from the rest of the CoFe film, whereas the magnetic response of the CoFeB-MgO interfacial moments is coherent with the film's bulk. Our results support the view that the high TMR values observed in MgO based MTJs with CoFeB electrodes are due to the uniform magnetic response of the entire CoFeB electrode including the MgO interfacial moments.

  9. A Sulfide Capacity Prediction Model of CaO-SiO2-MgO-FeO-MnO-Al2O3 Slags during the LF Refining Process Based on the Ion and Molecule Coexistence Theory

    Science.gov (United States)

    Yang, Xue-Min; Zhang, Meng; Shi, Cheng-Bin; Chai, Guo-Ming; Zhang, Jian

    2012-04-01

    A sulfide capacity prediction model of CaO-SiO2-MgO-FeO-MnO-Al2O3 ladle furnace (LF) refining slags has been developed based on the ion and molecule coexistence theory (IMCT). The predicted sulfide capacity of the LF refining slags has better accuracy than the measured sulfide capacity of the slags at the middle and final stages during the LF refining process. Increasing slag binary basicity, optical basicity, and the Mannesmann index can lead to an increase of the predicted sulfide capacity for the LF refining slags as well as to an increase of the sulfur distribution ratio between the slags and molten steel at the middle and final stages during the LF refining process. The calculated equilibrium mole numbers, mass action concentrations of structural units or ion couples, rather than mass percentages of components, are recommended to represent the slag composition for correlating with the sulfide capacity of the slags. The developed sulfide capacity IMCT model can calculate not only the total sulfide capacity of the slags but also the respective sulfide capacity of free CaO, MgO, FeO, and MnO in the slags. The comprehensive contribution of the combined ion couples (Ca2+ + O2-) and (Mn2+ + O2-) on the desulfurization reactions accounts for 96.23 pct; meanwhile, the average contribution of the ion couple (Fe2+ + O2-) and (Mg2+ + O2-) only has a negligible contribution as 3.13 pct and 0.25 pct during the LF refining process, respectively. The oxygen activity of bulk molten steel in LF is controlled by the [Al]-[O] equilibrium, and the oxygen activity of molten steel at the slag-metal interface is controlled by the (FeO)-[O] equilibrium. The ratio of the oxygen activity of molten steel at the slag-metal interface to the oxygen activity of bulk molten steel will decrease from 37 to 5 at the initial stage, and further decrease from 28 to 4 at the middle stage, but will maintain at a reliable constant as 5 to 14 at the final stage during the LF refining process. The

  10. FeII/MgII, [Fe/Mg] Ratios and High-z Quasars

    CERN Document Server

    Korista, K; Corbin, M R; Freudling, W; Korista, Kirk; Kodituwakku, Nalaka; Corbin, Michael; Freudling, Wolfram

    2003-01-01

    It has been suggested in the literature that the (Fe/alpha) abundance ratio may be used as a chronometer, due to a delay in this ratio reaching its solar value as predicted by galactic chemical evolution models. Using grids of photoionization models along a sequence of the (Fe/Mg) abundance ratio vs.\\ metallicity with time in a giant elliptical starburst scenario, we investigate the relationship between the (Fe/Mg) abundance ratio and the FeII/MgII emission line flux ratio under the assumption that these lines originate in photoionized clouds within the broad emission line regions of quasars.

  11. A cold metal poor cloud traced by a weak MgII absorption at z~0.45. First detection of SiI, CaI and FeI in a QSO absorber

    CERN Document Server

    D'Odorico, Valentina

    2007-01-01

    We present the observations of a weak MgII absorption system detected at z~0.452 in the UVES high resolution spectrum of the QSO HE0001-2340. The weakest of the two MgII components forming the system shows associated absorptions due to SiI, CaI and FeI observed for the first time in a QSO spectrum. We investigate the nature of this absorber by comparing its properties with those of different classes of absorbers (weak MgII, Damped Ly-alpha systems and local interstellar clouds) and reproducing its ionization conditions with photoionization models. The observed absorber belongs to the class of weak MgII systems on the basis of its equivalent width, however the relative strength of commonly observed transitions deviates significantly from those of the above mentioned absorbers. A rough estimate of the probability to cross such a system with a QSO line of sight is P~0.03. The presence of rare neutral transitions suggests that the cloud is shielded by a large amount of neutral Hydrogen. A detailed comparison of t...

  12. Effect of ambient Mg/Ca ratio on Mg fractionation in calcareous marine invertebrates: A record of the oceanic Mg/Ca ratio over the Phanerozoic

    Science.gov (United States)

    Ries, Justin B.

    2004-11-01

    The Mg/Ca ratio of seawater has changed significantly over the Phanerozoic, primarily as a function of the rate of ocean-crust production. Echinoids, crabs, shrimps, and calcareous serpulid worms grown in artificial seawaters encompassing the range of Mg/Ca ratios that existed throughout the Phanerozoic exhibit a direct nonlinear relationship between skeletal and ambient Mg/Ca. Specimens grown in seawater with the lowest Mg/Ca (˜1) changed their mineralogy to low-Mg calcite (MgCO3), suggesting that these high-Mg calcareous organisms would have produced low-Mg calcite in the Cretaceous, when oceanic Mg/Ca was lowest (˜1). These results support the empirical evidence that the skeletal chemistry of calcareous organisms has varied significantly over the Phanerozoic as a function of the Mg/Ca of seawater, and that the Mg/Ca of unaltered fossils of such organisms may be a record of oceanic Mg/Ca throughout the Phanerozoic. Mg fractionation algorithms, which relate skeletal Mg/Ca, seawater Mg/Ca, and temperature, were derived from these and other experiments. They can be used to estimate paleoceanic Mg/ Ca ratios and temperatures from fossil skeletal Mg/Ca of the organisms evaluated. Pale oceanic Mg/Ca ratios, recalculated by using the echinoderm Mg fractionation algorithm from published fossil echinoid Mg/Ca, crinoid Mg/Ca, and paleotemperature data, are consistent with other estimates and models of oceanic Mg/Ca over the Phanerozoic.

  13. Phase Equilibria of ``Cu2O''-``FeO''-CaO-MgO-Al2O3 Slags at PO2 of 10-8.5 atm in Equilibrium with Metallic Copper for a Copper Slag Cleaning Production

    Science.gov (United States)

    Henao, Hector M.; Pizarro, Claudio; Font, Jonkion; Moyano, Alex; Hayes, Peter C.; Jak, Evgueni

    2010-12-01

    Limited data are available on phase equilibria of the multicomponent slag system at the oxygen partial pressures used in the copper smelting, converting, and slag-cleaning processes. Recently, experimental procedures have been developed and have been applied successfully to characterize several complex industrial slags. The experimental procedures involve high-temperature equilibration on a substrate and quenching followed by electron probe X-ray microanalysis. This technique has been used to construct the liquidus for the “Cu2O”-“FeO”-SiO2-based slags with 2 wt pct of CaO, 0.5 wt pct of MgO, and 4.0 wt pct of Al2O3 at controlled oxygen partial pressures in equilibrium with metallic copper. The selected ranges of compositions and temperatures are directly relevant to the copper slag-cleaning processes. The new experimental equilibrium results are presented in the form of ternary sections and as a liquidus temperature vs Fe/SiO2 weight ratio diagram. The experimental results are compared with the FactSage thermodynamic model calculations.

  14. Physical conditions in CaFe interstellar clouds

    OpenAIRE

    Gnacinski, P.; Krogulec, M.

    2007-01-01

    Interstellar clouds that exhibit strong Ca I and Fe I lines were called CaFe clouds. The ionisation equilibrium equations were used to model the column densities of Ca II, Ca I, K I, Na I, Fe I and Ti II in CaFe clouds. The chemical composition of CaFe clouds is that of the Solar System and no depletion of elements onto dust grains is seen. The CaFe clouds have high electron densities n=1 cm^-3 that leads to high column densities of neutral Ca and Fe.

  15. Evaporation pathways and solubility of Fe-Ca-Mg-rich salts in acid sulfate waters. A model for Martian ancient surface waters

    Science.gov (United States)

    Sobron, P.; Sansano, A.; Sanz, A.

    2011-12-01

    It has been suggested that Martian iron rich sulfate and oxyhydroxide deposits were precipitated from meltwaters[1], thought to have been acidic. Alternatively, iron(III)-rich hydrated sulfates from oxidized sulfides observed in the outcrops may occur as a result of long-term reactions[4]. Recent analysis of Martian materials support that they come from hydrothermal activity[5], which is highly consistent with the observation of enriched in iron, magnesium, silicon and calcium materials[2]. Independently of the nature of the sulfate formation paths on Mars, characterizing the interaction of saline mineral assemblages and the aqueous solutions necessary for their formation is significance in assessing Mars' hydrological and mineralogical evolution history. In this work we have characterized a layered deposit(Fig. 1) formed from the evaporation of stream water from Rio Tinto, Spain, a relevant Mars analog site[6]. The minerals detected in-situ, confirmed later via high resolution laser Raman spectroscopy in the laboratory, are, from bottom to top: (A) mixture of goethite and probably schwermannite; (B) goethite; (C) mixture of gypsum and highly hydrated ferric sulfates; (D) hexahydrite; and (E) mixture of hexahydrite and epsomite. What we observed in this deposit is the precipitation of relatively insoluble hydroxysulfates (schwermannite admixed with goethite), followed by the precipitation of other relatively insoluble ferric and gypsum, and finally the occurrence of the very soluble Mg-sulfates. We are currently investigating the correlation of this evaporite deposit with the hydrochemistry of the stream water from which it evaporated through dedicated laboratory analysis of natural mineral and aqueous samples. A solubility model including the minerals identified in this work will be reported at the conference. The study of this particular acid sulfate system (with analog mineralogy to that observed in Meridiani[3]) provides constraints on the evaporation pathways

  16. Chelating agents related to ethylenediamine bis(2-hydroxyphenyl)acetic acid (EDDHA): synthesis, characterization, and equilibrium studies of the free ligands and their Mg2+, Ca2+, Cu2+, and Fe3+ chelates.

    Science.gov (United States)

    Yunta, Felipe; García-Marco, Sonia; Lucena, Juan J; Gómez-Gallego, Mar; Alcázar, Roberto; Sierra, Miguel A

    2003-08-25

    Iron chelates such as ethylenediamine-N,N'-bis(2-hydroxyphenyl)acetic acid (EDDHA) and their analogues are the most efficient soil fertilizers to treat iron chlorosis in plants growing in calcareous soils. EDDHA, EDDH4MA (ethylenediamine-N,N'-bis(2-hydroxy-4-methylphenyl)acetic acid), and EDDCHA (ethylenediamine-N,N'-bis(2-hydroxy-5-carboxyphenyl)acetic acid) are allowed by the European directive, but also EDDHSA (ethylenediamine-N,N'-bis(2-hydroxy-5-sulfonylphenyl)acetic acid) and EDDH5MA (ethylenediamine-N,N'-bis(2-hydroxy-5-methylphenyl)acetic acid) are present in several commercial iron chelates. In this study, these chelating agents as well as p,p-EDDHA (ethylenediamine-N,N'-bis(4-hydroxyphenyl)acetic acid) and EDDMtxA (ethylenediamine-N,N'-bis(2-metoxyphenyl)acetic acid) have been obtained following a new synthetic pathway. Their chemical behavior has been studied to predict the effect of the substituents in the benzene ring on their efficacy as iron fertilizers for soils above pH 7. The purity of the chelating agents has been determined using a novel methodology through spectrophotometric titration at 480 nm with Fe(3+) as titrant to evaluate the inorganic impurities. The protonation constants were determined by both spectrophotometric and potentiometric methods, and Ca(2+) and Mg(2+) stability constants were determined from potentiometric titrations. To establish the Fe(3+) and Cu(2+) stability constants, a new spectrophotometric method has been developed, and the results were compared with those reported in the literature for EDDHA and EDDHMA and their meso- and rac-isomers. pM values have been also determined to provide a comparable basis to establish the relative chelating ability of these ligands. The purity obtained for the ligands is higher than 87% in all cases and is comparable with that obtained by (1)H NMR. No significant differences have been found among ligands when their protonation and stability constants were compared. As expected, no Fe(3

  17. The effect of CaF2 on thermodynamics of CaO-CaF2-SiO2(-MgO) slags

    Science.gov (United States)

    Choi, Chul-Hwan; Jo, Sung-Koo; Kim, Seon-Hyo; Lee, Kwang-Ro; Kim, Jeong-Tae

    2004-02-01

    To address the role of CaF2 in the CaO-CaF2-SiO2(-MgO) slag system employed for the production of low-pressure rotor steels, the thermodynamic aspects of the slag were investigated by equilibrating it with liquid iron at 1873 K in CaO or MgO crucibles. Presaturation of slag with an oxide block piece of CaO or MgO in a Pt crucible and application of a carbon paste to the outside of an oxide crucible were designed to prevent crucible failure during the slag-metal experiments. The liquidus isotherm and phase boundary of the preceding slag system were investigated using the slag-metal equilibria. Also, the effect of CaF2 on the sulfide capacity and the activity coefficient of Fe t O were of particular interest in controlling the sulfur level and cleanliness of low-pressure rotor steels.

  18. Preparation of 24Mg-Fe-Cu Target

    Institute of Scientific and Technical Information of China (English)

    FAN; Qi-wen; DU; Ying-hui; ZHANG; Rong

    2012-01-01

    <正>The three-layer-sandwich targets of 24Mg-Fe-Cu needed to be prepared in the physics experiment. The middle layers are thin ferromagnetic Fe layers of about 3.2 mg/cm2. The recoil stopper layers are thick crystallized and defect-free Cu layers of about 15 mg/cm2. The thickness of the 24Mg target layers is about 300 μg/cm2, and the uniformity should be better than 90%.

  19. Change of Electronic Structure and Magnetic Properties with MgO and Fe Thicknesses in Fe/MgO/Fe Magnetic Tunnel Junction

    Institute of Scientific and Technical Information of China (English)

    YANG Fan; BI Xiao-fang

    2006-01-01

    The effects of the thickness of MgO and Fe on the electronic structure and magnetic properties of Fe/MgO/Fe magnetic tunnel junction was studied using the first principle method. Two series of models with MgO of different thicknesses: Fe(3)MgO(t)Fe(3) (t=1,3,5,7) and with Fe of varied thicknesses: Fe(t)MgO(3)Fe(t) (t=3,4,5,6,7) were established. Calculated results show that in all the models the magnetic moment of Fe increases at the Fe/MgO interface and surface as compared with that of the inner layers. The magnetic moment of each Fe layer was found to be independent of MgO thicknesses, while the spin-polarization of Fe layer at the interface shows a slight change in function of the MgO thicknesses. The tunneling magnetoresistance (TMR) ratio estimated by the Julliere model has the same change tendency as the spin-polarization has, and the largest value is obtained at the MgO thickness of 5 atomic layers. When the Fe thickness increases, the spin-polarization of interface Fe layer follows up an increase with a decrease. The highest TMR value is achieved when the Fe thickness is of 4 atomic layers.

  20. Fabrication of ternary Ca-Mg-Zn bulk metallic glasses

    Directory of Open Access Journals (Sweden)

    R. Nowosielski

    2013-02-01

    Full Text Available Purpose: The paper describes the preparation, structure and thermal properties of ternary Ca-Mg-Zn bulk metallic glass in form of as-cast rods.Design/methodology/approach: The investigations on the ternary Ca-Mg-Zn glassy rods were conducted by using X-ray diffraction (XRD, scanning electron microscopy (SEM which energy dispersive X-ray analysis (EDS.Findings: The X-ray diffraction investigations have revealed that the studied as-cast rod was amorphous. The fractures of studied alloy could be classified as mixed fracture with indicated “river” and “smooth” fractures. Both type of the fracture surfaces consist of weakly formed “river” and “shell” patterns and “smooth” regions. The “river” patterns are characteristic for metallic glassy alloys.Practical implications: The studied Ca-based bulk metallic glasses is a relatively new group of material. Ca-based bulk metallic glasses are applied for many applications in different elements. Ca-based bulk metallic glasses have many unique properties such as low density (~2.0 g/cm3, low Youn g’s modulus ( ~20 to 30 GPa. The elastic modulus of Ca-b ased BMGs is comparable to that of hum an bone s, and Ca, Mg, and Zn are biocompatible. These features make the Ca-Mg-Zn–based alloys attractive for use in biomedical applications.Originality/value: Fabrication of amorphous alloy in the form of rod ternary Ca-Mg-Zn alloy by pressure die casting method.

  1. Fe3O4/MgO/Fe Heteroepitaxial Structures for Magnetic Tunnel Junctions

    Energy Technology Data Exchange (ETDEWEB)

    Orna, J. [University of Zaragoza, Spain; Morellon, Luis [University of Zaragoza, Spain; Algarabel, Pedro A. [University of Zaragoza, Spain; Pardo, J. A. [University of Zaragoza, Spain; Sangiao, S [Instituto de Nanociencia de Aragón, Universidad de Zaragoza, Zaragoza, 50009 Spain; Magen, C [Oak Ridge National Laboratory (ORNL); Snoeck, E. [CEMES-CNRS, Toulouse, France; De Teresa, J M [Instituto de Ciencia de Materiales de Aragón, Universidad de Zaragoza-CSIC, Zaragoza, 50009 Spain; Ibarra, M. Ricardo [University of Zaragoza, Spain

    2008-01-01

    In this work we report the growth and structural and magnetic characterization of heteroepitaxial Fe O/MgO/Fe junctions. All three layers have been deposited by pulsed laser deposition. Combining High Resolution Transmission Electron Microscopy and X-ray results, we have obtained for the heterostructure the epitaxy relation MgO(001) [100]//Fe O(001)[100]/MgO(001) [100]/Fe(001)[110]. All interfaces appear very sharp with relatively small root-mean square (rms) roughness, 0.2 nm. The magnetic coupling between Fe O and Fe electrodes is also very small, 0.03 mJ/

  2. 铁·镁·钙元素对白腐真菌生长及降解石油的影响%Effect of Fe2+ , Mg2+ and Ca2+ on Oil Degradation and the Growth of White Rot Fungi

    Institute of Scientific and Technical Information of China (English)

    谭丽泉; 黄敏; 余梅; 梁俊豪

    2012-01-01

    [目的]探讨黄孢原毛平革菌的生长及对石油的降解能力的优化条件.[方法]选用白腐真菌的典型菌种——黄孢原毛平革菌作为降解菌,研究其生长及对石油的降解性能,以不同浓度的Fe、Mg、Ca元素作为研究对象,在筛选单因素最佳水平的基础上,设计L9(33)正变表进行正变试验,对各因素的重要性及其最优水平进行分析.[结果]单因素试验表明,体系中添加Fe、Mg、Ca元素对白腐真菌的生长及其对石油的降解能力有较大的影响.正交试验结果表明,3种元素对P.C.菌降解石油的影响大小依次为Fe2+> Ca2+ >Mg2+;溶液中铁、镁、钙元素的最佳组合为0.008 g/L的Fe2、0.8g/L的Mg2+、1.5g/L的Ca2+,该条件下10d后白腐真菌对石油的降解率为70.9%.[结论]该研究为探索白腐真菌的生长及其对石油降解能力的优化提供了科学依据.%[Objective] The study aimed to discuss the growth and degradation of petroleum by white rot fungi. [Method] Taking the typical white rot fungi P. chrysosporium as the degrading fungus,its growth and degradation on the petroleum were studied. The effect of cations including Fe2+ 、Mg2+ and Ca2+ were selected as the effecting factors,on the basis of screening the best level of single factor, the orthogonal experiment with the L L9(33 )orthogonal design was conducted to analyze the importance of the factors and their optimal level. [ Result]The single test showed that Fe2+ ,Mg2+ and Ca2+ had a greater influence on the growth of white rot fungi, and biodegradation of petroleum. The results of orthogonal experiment showed that Fe2+ 、Mg2+ and Ga2 + had significant influence on the degradation of petroleum by white rot fungus, the effect was Fe2+ > Ca2+ >Mg2+ , the Degradation can reached up to 70.9% under the optimum conditions: [Fe2+ ] = 0.008 g/L,[ Mg2+ ] =0.8 g/L,[ Ca2+ ] =1.5 g/L. [Gonclusion] The study provided the scientific basis for exploring the effective method of

  3. Alternative solution model for the ternary carbonate system CaCO3 - MgCO3 - FeCO3 - II. Calibration of a combined ordering model and mixing model

    Science.gov (United States)

    McSwiggen, P.L.

    1993-01-01

    Earlier attempts at solution models for the ternary carbonate system have been unable to adequately accommodate the cation ordering which occurs in some of the carbonate phases. The carbonate solution model of this study combines a Margules type of interaction model with a Bragg-Williams type of ordering model. The ordering model determines the equilibrium state of order for a crystal, from which the cation distribution within the lattice can be obtained. The interaction model addresses the effect that mixing different cation species within a given cation layer has on the total free energy of the system. An ordering model was derived, based on the Bragg-Williams approach; it is applicable to ternary systems involving three cations substituting on two sites, and contains three ordering energy parameters (WCaMg, WCaFe, and WCaMgFe). The solution model of this study involves six Margules-type interaction parameters (W12, W21, W13, W31, W23, and W32). Values for the two sets of energy parameters were calculated from experimental data and from compositional relationships in natural assemblages. ?? 1993 Springer-Verlag.

  4. Redetermination of Post-Perovskite Structure of (Mg,Fe)SiO3

    Science.gov (United States)

    Yamanaka, T.; Mao, W. L.; Ganesh, P.; Shulenburger, L.; Cohen, R.; Meng, Y.; Prakapenka, V.; Mao, H.; Hemley, R. J.

    2008-12-01

    Since the post-perovskite (ppv) phase in MgSiO3 was discovered to be similar structure of CaIrO3 (Cmcm Z=4) under the conditions of near Earth's core-mantle boundary, many investigations have provided explanations for the presence of low seismic velocity. However, precise experimental structure analysis of ppv-(Mg1-xFex)SiO3 has never been reported because of the experimental difficulty. Fe and Mg cation distribution and ordering in ppv-(Mg,Fe)SiO3 due to cation properties including spins states are significant subject in lower mantle electronic and magnetic states. The present experiment aims the Rietveld profile fitting of ppv-(Mg0.6,Fe0.4)SiO3 by the precise powder diffraction measurements and the statistic process of the twenty observed. We found the possible structure models of ppv-(Mg,Fe)SiO3 by the Monte Carlo calculation. The most relable structure among those models in the Rietveld fitting of ppv-(Mg0.6Fe0.4)SiO3 is the structure of space group Pmma, in which Fe and Mg occupy two sites of M1 and M2: the site occupancies are (Fe0.25(3)Mg0.75(3)) in the larger M1 site and (Fe0.55(3)Mg0.45(3) ) in the larger and more distorted M2 site. Fe2+ in the M2 site is in the low-spin state, which reduces the ion radius. Consequently Fe2+ becomes smaller ion than Mg2+. These two sites are distributed alternatively zigzag mode in the direction of a. axis, About 70% of Fe atoms occupies at the M2 site. (Notice that Fe and Mg cations are randomly distributed in only one site in Cmcm.) The two-site model is consistence with the results of X-ray emission. Further more the first principles calculation also shows the two-site model is more energetically possible under high-pressure conditions. MgSiO3 may have the two-site structure of Pmma instead of Cmcm. If it is not the case, the Pmma structure is the new structure and the phase boundary in the solid solution (Mg1-xFex)SiO3 has to be determined. More data analyses based on precise powder diffraction measurements over a

  5. Structures and unimolecular chemistry of M(Pro2-H)(+) (M = Mg, Ca, Sr, Ba, Mn, Fe, Co, Ni, Cu, Zn) by IRMPD spectroscopy, SORI-CID, and theoretical studies.

    Science.gov (United States)

    Jami-Alahmadi, Yasaman; Fridgen, Travis D

    2016-01-21

    M(Pro2-H)(+) complexes were electrosprayed and isolated in an FTICR cell where their unimolecular chemistries and structures were explored using SORI-CID and IRMPD spectroscopy. These experiments were augmented by computational methods such as electronic structure, simulated annealing, and atoms in molecules (AIM) calculations. The unimolecular chemistries of the larger metal cation (Ca(2+), Sr(2+) and Ba(2+)) complexes predominantly involve loss of neutral proline whereas the complexes involving the smaller Mg(2+) and transition metal dications tend to lose small neutral molecules such as water and carbon dioxide. Interestingly, all complexes involving transition metal dications except for Cu(Pro2-H)(+) lose H2 upon collisional or IRMPD activation. IRMPD spectroscopy shows that the intact proline in the transition metal complexes and Cu(Pro2-H)(+) is predominantly canonical (charge solvated) while for the Ca(2+), Sr(2+), and Ba(2+) complexes, proline is in its zwitterionic form. The IRMPD spectra for both Mg(Pro2-H)(+) and Mn(Pro2-H)(+) are concluded to have contributions from both charge-solvated and canonical structures. PMID:26685890

  6. Effect of FeO and CaO on the Sulfide Capacity of the Ferronickel Smelting Slag

    Science.gov (United States)

    Kim, Ki Deok; Huh, Wan Wook; Min, Dong Joon

    2014-06-01

    The effect of FeO and CaO on the sulfide capacity in MgO-SiO2-FeO based slags equilibrating with Fe-Ni alloys at 1773 K and 1873 K (1500 °C and 1600 °C) was investigated. The sulfide capacity in the MgO-SiO2-FeO and MgO-SiO2-CaO-FeO slags increased with higher FeO content and higher temperatures due to an increase in the activity of O2- and a decrease in the activity coefficient of sulfide ion in slag. The sulfide capacity of the MgO-SiO2-CaO-FeO slag also increased with an increase in the CaO content due largely to the increase in the activity of O2-. Furthermore, CaO and FeO seem to be more effective than MgO in increasing the sulfide capacity in the MgO-SiO2-CaO-FeO slag system. In addition, the comparison of the experimental results with the theoretical estimate using the modified empirical optical basicity showed relatively good linear agreement.

  7. Solubility of BaS in BaO-BaF2 slag and the Influence of FeOx, SiO2, Cr2O3, BaCI2, CaO, and MgO on the sulfide capacity of this system

    Science.gov (United States)

    Rachev, Ivan P.; Tsukihashi, Fumitaka; Sano, Nobuo

    1992-03-01

    The influence of SiO2, FeOx, Cr2O3, BaCl2, CaO, and MgO on the sulfide capacity of the BaO-BaF2 system was measured at 1473 K, using a gas-slag-metal equilibration technique. It was found that the substitution of BaF2 by SiO2, FeOx, Cr2O3, and BaCl2 decreases the sulfide capacity of the BaO-BaF2 system. Similar results were obtained for the carbonate capacity. The CaO-saturated BaO-BaF2 flux, however, was found to have slightly higher sulfide and carbonate capacities than the pure BaO-BaF2 flux. The solubility of CaO increased with increasing BaF2 content and was 18 mol pet in BaF2 at 1473 K. The solubility of MgO in the BaO-BaF2 system at the same temperature is very low, and it has no effect on the sulfide and carbonate capacities. The solubility of BaS in the BaO-BaF2 system was also measured at 1473 K and had its maximum for the slag containing 40 mass pet BaO. The activity of BaO in the system was calculated from those data.

  8. Growth rate effects on Mg/Ca and Sr/Ca ratios constrained by belemnite calcite

    Science.gov (United States)

    Vinzenz Ullmann, Clemens

    2016-04-01

    Multiple temperature proxies from single species are important to achieve robust palaeotemperature estimates. Besides the commonly employed oxygen isotope thermometer, also Mg/Ca and Sr/Ca ratios perform well as proxies for calcification temperature in the shells of some species. While salinity changes affect the ratios of earth alkaline elements much less than the δ18O thermometer, metabolic effects may exert a strong control on the expression of element ratios. Such effects are hard to study because biomineralization experiments have to overcome large intraspecific variability and can hardly ever isolate the controls of a single parameter on shell geochemistry. The unique geometry of the belemnite rostrum constitutes an exception to this rule. Its shape, large size, and the visibility of growth increments as bands enable the analysis of multiple, correlatable, high resolution geochemical profiles in a single fossil. The effects of the growth rate variability amongst these profiles on Mg/Ca and Sr/Ca ratios has been tested here. Within a specimen of Passaloteuthis bisulcata (Early Toarcian, Cleveland Basin, UK), Mg/Ca and Sr/Ca data were obtained from four profiles. With respect to growth rate in the first profile, which was taken as a reference, the relative growth rates in the remaining three profiles varied by a factor of 0.9 to 2.7. Results suggest that relative growth rate is linearly correlated with Mg/Ca and Sr/Ca, with a decrease of Mg/Ca by 8 % and increase of Sr/Ca by 6 % per 100 % increase in relative growth rate. The observed trends are consistent with abiogenic precipitation experiments and suggest that crystal precipitation rate exerts a significant, predictable control on the element distribution in biogenic calcite.

  9. Ostracode Mg/Ca Paleothermometry: Applications and Complications

    Science.gov (United States)

    Cronin, T. M.; Dwyer, G. S.

    2007-12-01

    Ostracode (bivalved Crustacea) shell Mg/Ca paleothermometry has wide applicability in Cenozoic paleoclimatology over 101 to 107 year timescales because they are commonly fossilized, live in freshwater, shallow- and deep-marine habitats, and grow by molting, which minimizes Mg/Ca variability due to ontogenetic variability. Two empirically derived Mg/Ca-temperature calibrations based on core top and culturing include one for the shallow marine, estuarine genus Loxoconcha (5 to 30°C) and another for deep-sea genus Krithe (hockey stick temperature curve. The latter produced evidence for decreased deep-sea temperature during glacial intervals and the first Atlantic-wide reconstruction of deep-sea temperature during the warm mid-Pliocene. In addition to temperature, however, factors such as host-water magnesium concentrations, salinity, intra-shell, intra-population, and interspecific variabilility, seasonality, biological factors (shell secretion rate), and post-mortem dissolution can contribute to scatter in calibration datasets and uncertainty in paleotemperature estimates. We will review these processes, present a new 2000 year Chesapeake temperature record, and discuss its relation to twentieth century climate change.

  10. The Ca II triplet in red giant spectra: [Fe/H] determinations and the role of [Ca/Fe

    CERN Document Server

    Da Costa, G S

    2015-01-01

    Measurements are presented and analyzed of the strength of the Ca II triplet lines in red giants in Galactic globular and open clusters, and in a sample of red giants in the LMC disk that have significantly different [Ca/Fe] abundance ratios to the Galactic objects. The Galactic objects are used to generate a calibration between Ca II triplet line strength and [Fe/H], which is then used to estimate [Fe/H]_CaT for the LMC stars. The values are then compared with the [Fe/H]_spec determinations from high dispersion spectroscopy. After allowance for a small systematic offset the two abundance determinations are in excellent agreement. Further, as found in earlier studies, e.g., Battaglia et al. (2008), the difference is only a very weak function of the [Ca/Fe] ratio. For example, changing [Ca/Fe] from +0.3 to -0.2 causes the Ca II based abundance to underestimate [Fe/H]_spec by only ~0.15 dex, assuming a Galactic calibration. Consequently, the Ca II triplet approach to metallicity determinations can be used witho...

  11. Viscosities of FenO-MgO-SiO2 and FenO-MgO-CaO-SiO2 slags

    Institute of Scientific and Technical Information of China (English)

    戴曦; 甘雪萍; 张传福

    2003-01-01

    The viscosities of molten Fen O-MgO-SiO2 and Fen O-MgO-CaO-SiO2 semi-synthetic slags for nickel flash smelting were mearured in the temperature range of 1 200-1 450℃ by use of a rotational viscometer.The mass ratio of Fe to SiO2 was fixed at 1.2,calcium oxide and magnesium oxide contents varied in the range of 2%-8% and 9%-12%(mass fraction),respectively.The results show that silicate anions become smaller by increasing CaO content,which results in the viscosity decrease of slag.In the case of addition of MgO the viscosity behaviour is complicated When MgO content is less than 11%,the viscosity increases with the increase of MgO at all temperatures tested .However,when the MgO content is more than 11%,the viscosity decreases slightly for Fen O-MgO-CaOSiO2 system.At higher MgO contents,low-viscosity slags can be obtained by adding CaO.As for a given composition,the viscosity decreased with increasing temperature.The higher the temperature,the more MgO can be added before saturation.The effect of Fe3 O4 on the viscosity is quite significant.The viscosity of slag increases to 300 mpa tions of temperature and composition.A comparison between Fen O-MgO-SiO2 and Fen O-MgO-CaO-SiO2 systems are also given.

  12. Preparation and Characterization of Nanocomposite MgFe_2O_4/SiO_2

    Institute of Scientific and Technical Information of China (English)

    XU Li; ZOU Wenqin; HONG Jianmin

    2009-01-01

    Nanocomposites MgFe_2O_4/SiO_2 were successfully synthesized by the sol-gel method in the presence of N,N-dimethylformamide(DMF).The formation of pure MgFe_2O_4 was confirmed by powder X-ray diffraction(XRD)and electron diffraction.The structural evolution of MgFe_2O_4 nanocrystals was followed by powder X-ray diffraction and IR absorption spectroscopy.The formation of spinel structure of MgFe_2O_4 started at 800℃,and completed at 900℃.The transmission electron microscopy(TEM)measurements suggest that the particle sizes increase with the increasing annealing temperature,and the mean particle sizes of the spherical samples annealed at 800℃,900℃ and 1 050℃are ca.3 nm,8 nm and 11 nm,respectively.Magnetization measurements at room temperature and 78 K indicate superparamagnetic nature of these MgFe_2O_4 nanocrystals.

  13. Effects of an intensive hog farming operation on groundwater in east Mediterranean (II): a study on K⁺, Na⁺, Cl ⁻, PO₄³⁻-P, Ca²⁺, Mg²⁺, Fe³⁺/Fe²⁺, Mn²⁺, Cu²⁺, Zn²⁺ and Ni²⁺.

    Science.gov (United States)

    Michalopoulos, Charalampos; Tzamtzis, Nikolaos; Liodakis, Stylianos

    2014-12-01

    The application of treated animal wastewater generated in concentrated animal feeding operations on surface soil (within farm borders) leads to degradation of groundwater. Effects of an intensive hog farming operation, located at a Mediterranean limestone soil coastal area, on groundwater were investigated. Treated animal wastewater was discharged on a small plot (~10.8 ha) with a geologic fault. Samples were taken from seven groundwater monitoring wells close to the farm. A significant increase of K(+), Na(+), Cl(-), PO4 (3-)-P, Ca(2+) and Mg(2+) concentrations was found in monitoring wells which are affected by the subsurface flow of groundwater. Concentrations of Fe(3+)/Fe(2+), Mn(2+), Cu(2+), Zn(2+) and Ni(2+) in all groundwater monitoring wells were extremely low. During the winter, significant increases in concentrations of K(+) and PO4 (3-)-P were noted and attributed to high precipitation, which assisted in the leaching of K and P to groundwater.

  14. Magneto Seebeck effect in Co-Fe-B/MgO/Co-Fe-B tunnel junctions

    Energy Technology Data Exchange (ETDEWEB)

    Walter, Marvin; Walowski, Jakob; Zbarsky, Vladyslav; Muenzenberg, Markus [I. Physikalisches Institut, Universitaet Goettingen (Germany); Drewello, Volker; Ebke, Daniel; Reiss, Guenter; Thomas, Andy [Department of Physics, Bielefeld University (Germany); Peretzki, Patrick; Seibt, Michael [IV. Physikalisches Institut, Universitaet Goettingen (Germany); Czerner, Michael; Bachmann, Michael; Heiliger, Christian [I. Physikalisches Institut, Universitaet Giessen (Germany)

    2011-07-01

    Co-Fe-B/MgO/Co-Fe-B devices showing a giant TMR effect are possible candidates for the generation of spin-currents by thermal heating. We present the observation of a magneto Seebeck effect in Co-Fe-B/MgO/Co-Fe-B magnetic tunnel junctions (MTJs). The effects could be used for thermal spin-injection and thermally driven spin-transfer torque. The samples presented in this work consist of a minimal pseudo-spin-valve stack with sputtered Ta and Co-Fe-B layers and an e-beam evaporated MgO barrier. The MTJs are heated by a diode laser which achieves powers of up to 100 mW and is focused onto the sample in a standard confocal microscope setup. The heating is simulated by finite element methods and the experimental results are compared with ab initio calculations of the magneto-thermoelectric power and of the spin-Seebeck coefficient.

  15. Challenges in the study of Fe/MgO/Fe interfaces using 3D Atom Probe

    Energy Technology Data Exchange (ETDEWEB)

    Mazumder, B. [Groupe de Physique des Materiaux, UMR CNRS 6634, CORIA UMR CNRS 6614, UFR Sciences Site du Madrillet, Avenue de l' Université, B.P. 12 76801, Saint Etienne du Rouvray Cedex (France); Center for Nanophase Materials Sciences, Oak Ridge National Laboratory, Oak Ridge, TN 37831 (United States); Purohit, Viswas, E-mail: vishwas.purohit@gmail.com [Groupe de Physique des Materiaux, UMR CNRS 6634, CORIA UMR CNRS 6614, UFR Sciences Site du Madrillet, Avenue de l' Université, B.P. 12 76801, Saint Etienne du Rouvray Cedex (France); Department of Plasma Physics, Alliance College of Engineering and Design, Chikkahagade Cross, Chandapura, Anekal Main Road, Anekal, Bangalore 562106, Karnataka (India); Gruber, M.; Vella, A.; Vurpillot, F.; Deconihout, B. [Groupe de Physique des Materiaux, UMR CNRS 6634, CORIA UMR CNRS 6614, UFR Sciences Site du Madrillet, Avenue de l' Université, B.P. 12 76801, Saint Etienne du Rouvray Cedex (France)

    2015-08-31

    Detailed interface studies were conducted on two Fe/MgO/Fe systems having different thicknesses of MgO layers, using a laser assisted 3D atom probe. In conjunction with a detailed 3D reconstruction, the system exhibited an additional oxide formation at the interface between MgO and Fe of the multilayer structure. This oxide formation was found to be independent of the laser wavelength, laser fluence and the thickness of the intermediate layers. By using numerical simulations of field evaporation of two layers having two different evaporation fields, we discuss the possible oxidation mechanisms. - Highlights: • MgO layers (4, 32 nm) between Fe layers were analysed using a laser assisted atom probe. • Varying field evaporation voltages responsible for interfacial oxide layer (bottom) • Numerical simulation used to determine the phenomena taking place at the interfaces • Lasers of wavelengths 515 nm and 343 nm were used for this study.

  16. Fe, Cr, Ni, Cu, Mg, Al, Ti, and S contents in plants and soil of heaps of nickel smelting works

    Energy Technology Data Exchange (ETDEWEB)

    Banasova, V.; Hajduk, J.

    1977-01-01

    The writers established the Fe, Ce, Cr, Ni, Ca, Mg, Al, Ti and S contents in the neopedon of heaps piling up from processing of nickel ore as well as in the plants: Cardaria draba, Salsola cali, Agropyrum repens, Bromus erectus, Calamagrostis epigeios, Cynodon dactylon and Matricaria inodora, growing on such heaps. Ca, Mg and S contents were found to be higher in dicotyledons and Fe, Al, Ti, Ni and Cr contents higher in monocotyledons. The analyzed dicotyledons appeared to be concentrators of Ca and S. Highest Fe, Al, Ti, Ni and Cr contents were found in individuals of the species Agropyrum repens. The neopedon as well as the plants had extraordinarily high Cr concentrations. The species Salsola cali has been found to possess an unusually higher affinity to the dump substrate after processing of nickel ore and to be a concentrator of Mg. 16 references, 1 table.

  17. Comparing the Electrochemical Performance of LiFePO4/C Modified by Mg Doping and MgO Coating

    OpenAIRE

    Jianjun Song; Ying Zhang; Guangjie Shao

    2013-01-01

    Supervalent cation doping and metal oxide coating are the most efficacious and popular methods to optimize the property of LiFePO4 lithium battery material. Mg-doped and MgO-coated LiFePO4/C were synthesized to analyze their individual influence on the electrochemical performance of active material. The specific capacity and rate capability of LiFePO4/C are improved by both MgO coating and Mg doping, especially the Mg-doped sample—Li0.985Mg0.015FePO4/C, whose discharge capacity is up to 163 m...

  18. Testing coral paleothermometers (B/Ca, Mg/Ca, Sr/Ca, U/Ca andδ18O) under impacts of large riverine runoff

    Institute of Scientific and Technical Information of China (English)

    CHEN Tianran; YU Kefu; ZHAO Jianxin; YAN Hongqiang; SONG Yinxian; FENG Yuexing; CHEN Tegu

    2015-01-01

    Sea surface temperature (SST) proxies including B/Ca, Mg/Ca, Sr/Ca, U/Ca andδ18O were analyzed in the skeleton of aPorites coral collected from the Zhujiang River (Pearl River) Estuary (ZRE). These geochemical proxies are influenced by river runoff and this area of the northern South China Sea is strongly affected by seasonal freshwater floods. We assessed the robustness of each SST proxy through comparison with the local instrumental SST. Coral Sr/Ca shows the highest correlation with SST variations (r2=0.59), suggesting Sr/Ca is the most robust SST proxy. In contrast, coralδ18O (r2=0.46), B/Ca (r2=0.43) and U/Ca (r2=0.41) ratios were only moderately correlated with SST variations, suggesting that they are disturbed by some other factors in addition to SST. The poor correlation (r2=0.27) between SST and Mg/Ca indicates that Mg/Ca in coral skeletons is not a simple function of SST variations. This may ultimately limit the use of Mg/Ca as a coral paleothermometer.

  19. Solid state interactions in the systems CaO(CaCO3-Fe2O3 and CuFe2O4-CaO

    Directory of Open Access Journals (Sweden)

    Boyanov B.S.

    2005-01-01

    Full Text Available The solid state interactions in the systems CaO(CaCO3-Fe2O3 and CuFe2O4-CaO have been studied using X-ray diffraction analysis. The influence of the temperature on the ferrite formation process has been investigated in the range of 900-1200 oC and duration up to 360 min. It has been shown that a mixture of ferrites forms at 1000 oC and interaction of 240 min. The exchange reactions in the systems CuFe2O4-CaO and Cu0.5Zn0.5Fe2O4-CaO have been studied, too. It has been established that Ca2+ ions exchange Cu2+ and Zn2 partially and the solubility of copper and zinc in a 7 % sulfuric acid solution increases 10-15 times.

  20. Photoluminescence and Hall studies of GaN:Fe and (Ga,Fe)N:Mg layers

    Energy Technology Data Exchange (ETDEWEB)

    Wegscheider, M.; Simbrunner, C.; Navarro-Quezada, A.; Sitter, H.; Jantsch, W.; Bonanni, A. [Institut fuer Halbleiter- und Festkoerperphysik, Johannes Kepler University, Linz (Austria); Przybylinska, H.; Kiecana, M. [Institute of Physics, Polish Academy of Sciences, Warsaw (Poland); Sawicki, M. [Institute of Physics and ERATO Semiconductor Spintronics Project, Polish Academy of Sciences, Warsaw (Poland); Dietl, T. [Institute of Physics, Polish Academy of Sciences, Warsaw (Poland); Japan Science and Technology Agency, Semiconductor Spintronics Project (ERATO), Warsaw (Poland)

    2007-01-15

    Temperature dependent photoluminescence (PL) in the ultraviolet (UV) regime and Hall measurements at room temperature have been performed on Metal-Organic-Chemical-Vapour-Deposition (MOCVD) grown GaN:Fe and (Ga,Fe)N:Mg layers. PL measurements were employed in order to study the dopants' influence on the near-band edge excitonic emission and their tendency to provoke the formation and suppression of defects or incorporation of impurities. For their identification and for the understanding of the PL spectra the evaluation of the free carrier concentrations via Hall measurements were necessary. Depending on the iron concentration of the (Ga,Fe)N layers, the near-band edge emission goes through two different stages: at low Fe-concentration no excitonic emission can be seen whereas with higher doping levels, excitonic features develop. The (Ga,Fe)N films exhibit n-type behaviour. The Mg codoped samples show strong Mg and defect related luminescence bands, whose occurrence and intensity also strongly depends on whether high or low Fe concentration is present. The (Ga,Fe)N:Mg layers were semi insulating. (copyright 2007 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  1. Structural, Electronic and Elastic Properties of MgH2, CaH2 and Ca4Mg3H14 for Hydrogen Storage Materials

    Science.gov (United States)

    Djellab, Sihem; Bouhadda, Youcef; Bououdina, Mohamed; Fenineche, Noureddine; Boudouma, Youcef

    2016-08-01

    The structural, electronic and elastic properties of MgH2, CaH2 and Ca4Mg3H14 have been determined using first principles calculation based on density functional theory. The calculated lattice constants were in good agreement with the experimental values. The electronic density of states revealed that these hydrides are insulators. The calculated elastic constants of MgH2, CaH2 and Ca4Mg3H14 indicated that these hydrides are mechanically stable at zero pressure. The bulk modulus B, shear modulus G, Young's modulus E, and Poisson's ratio ν were derived, and the ductility was discussed.

  2. In vitro degradation and cytotoxicity of Mg/Ca composites produced by powder metallurgy.

    Science.gov (United States)

    Zheng, Y F; Gu, X N; Xi, Y L; Chai, D L

    2010-05-01

    Mg/Ca (1 wt.%, 5 wt.%, 10 wt.% Ca) composites were prepared from pure magnesium and calcium powders using the powder metallurgy method, aiming to enlarge the addition of Ca content without the formation of Mg(2)Ca. The microstructures, mechanical properties and cytotoxicities of Mg/Ca composite samples were investigated. The corrosion of Mg/Ca composites in Dulbecco's modified Eagle's medium (DMEM) for various immersion intervals was studied by electrochemical impedance spectroscopy measurements and environmental scanning electron microscope, with the concentrations of released Mg and Ca ions in DMEM for various immersion time intervals being measured. It was shown that the main constitutional phases were Mg and Ca, which were uniformly distributed in the Mg matrix. The ultimate tensile strength (UTS) and elongation of experimental composites decreased with increasing Ca content, and the UTS of Mg/1Ca composite was comparable with that of as-extruded Mg-1Ca alloy. The corrosion potential increased with increasing Ca content, whereas the current density and the impedance decreased. It was found that the protective surface film formed quickly at the initial immersion stage. With increasing immersion time, the surface film became compact, and the corrosion rate of Mg/Ca composites slowed down. The surface film consisted mainly of CaCO(3), MgCO(3)x3H(2)O, HA and Mg(OH)(2) after 72 h immersion in DMEM. Mg/1Ca and Mg/5Ca composite extracts had no significant toxicity (p>0.05) to L-929 cells, whereas Mg/10Ca composite extract induced approximately 40% reduced cell viability.

  3. In vitro degradation and cytotoxicity of Mg/Ca composites produced by powder metallurgy.

    Science.gov (United States)

    Zheng, Y F; Gu, X N; Xi, Y L; Chai, D L

    2010-05-01

    Mg/Ca (1 wt.%, 5 wt.%, 10 wt.% Ca) composites were prepared from pure magnesium and calcium powders using the powder metallurgy method, aiming to enlarge the addition of Ca content without the formation of Mg(2)Ca. The microstructures, mechanical properties and cytotoxicities of Mg/Ca composite samples were investigated. The corrosion of Mg/Ca composites in Dulbecco's modified Eagle's medium (DMEM) for various immersion intervals was studied by electrochemical impedance spectroscopy measurements and environmental scanning electron microscope, with the concentrations of released Mg and Ca ions in DMEM for various immersion time intervals being measured. It was shown that the main constitutional phases were Mg and Ca, which were uniformly distributed in the Mg matrix. The ultimate tensile strength (UTS) and elongation of experimental composites decreased with increasing Ca content, and the UTS of Mg/1Ca composite was comparable with that of as-extruded Mg-1Ca alloy. The corrosion potential increased with increasing Ca content, whereas the current density and the impedance decreased. It was found that the protective surface film formed quickly at the initial immersion stage. With increasing immersion time, the surface film became compact, and the corrosion rate of Mg/Ca composites slowed down. The surface film consisted mainly of CaCO(3), MgCO(3)x3H(2)O, HA and Mg(OH)(2) after 72 h immersion in DMEM. Mg/1Ca and Mg/5Ca composite extracts had no significant toxicity (p>0.05) to L-929 cells, whereas Mg/10Ca composite extract induced approximately 40% reduced cell viability. PMID:19815098

  4. Interfacial electronic transport phenomena in single crystalline Fe-MgO-Fe thin barrier junctions

    Energy Technology Data Exchange (ETDEWEB)

    Gangineni, R. B., E-mail: rameshg.phy@pondiuni.edu.in [Department of Physics, School of Physical, Chemical and Applied Sciences, Pondicherry University, R. V. Nagar, Kalapet, Pondicherry 605 014 (India); SPINTEC, UMR 8191 CEA/CNRS/UJF-Grenoble 1/Grenoble INP, INAC, 17 rue des Martyrs, F-38054 Grenoble Cedex (France); Bellouard, C., E-mail: christine.bellouard@ijl.nancy-universite.fr; Duluard, A. [Institut Jean Lamour, UMR 7198, CNRS-Université de Lorraine, BP 239, 54506 Vandoeuvre (France); Negulescu, B. [Institut Jean Lamour, UMR 7198, CNRS-Université de Lorraine, BP 239, 54506 Vandoeuvre (France); UFR de Sciences et Techniques, Matériaux, microélectronique, acoustique, nanotechnologies (GREMAN), University François Rabelais, Parc de Grandmont, 37200 Tours (France); Baraduc, C.; Gaudin, G. [SPINTEC, UMR 8191 CEA/CNRS/UJF-Grenoble 1/Grenoble INP, INAC, 17 rue des Martyrs, F-38054 Grenoble Cedex (France); Tiusan, C., E-mail: coriolan.tiusan@phys.utcluj.ro [Institut Jean Lamour, UMR 7198, CNRS-Université de Lorraine, BP 239, 54506 Vandoeuvre (France); Department of Physics and Chemistry, Center of Superconductivity, Spintronics and Surface Science, Technical University of Cluj Napoca, Str. Memorandumului No. 28, RO-400114 Cluj-Napoca (Romania)

    2014-05-05

    Spin filtering effects in nano-pillars of Fe-MgO-Fe single crystalline magnetic tunnel junctions are explored with two different sample architectures and thin MgO barriers (thickness: 3–8 monolayers). The two architectures, with different growth and annealing conditions of the bottom electrode, allow tuning the quality of the bottom Fe/MgO interface. As a result, an interfacial resonance states (IRS) is observed or not depending on this interface quality. The IRS contribution, observed by spin polarized tunnel spectroscopy, is analyzed as a function of the MgO barrier thickness. Our experimental findings agree with theoretical predictions concerning the symmetry of the low energy (0.2 eV) interfacial resonance states: a mixture of Δ{sub 1}-like and Δ{sub 5}-like symmetries.

  5. The Influences of Mg2+ , Ca2+ and Mg2+/Ca2+ Ratio in Mixed Seawater on the Emergence Rate of Penaeus japonicus Postlarva

    Institute of Scientific and Technical Information of China (English)

    臧维玲; 戴习林; 江敏; 姚庆祯; 蔡云龙; 罗春芳; 徐桂荣; 丁福江

    2003-01-01

    This paper reports the approprite ranges of Mg2+ , Ca2 + and their ratio Mg2 +/Ca2 + inmixed seawater for rearing of Penaeus japonicus larvae. The ranges for the above three indices are1150- 1450 mg/L, 360- 440 mg/L and 2.8 - 3.4, respectively. The proper sahnity range ofmixed seawater is 22.1 - 33.8 obtained by mixing estuarine water and concentrated seawater.

  6. Electronic structure of ferromagnet-insulator interfaces: Fe/MgO and Co/MgO

    Energy Technology Data Exchange (ETDEWEB)

    Mueller, M.

    2007-07-11

    In this thesis the electronic structure of Fe/MgO{sub x} and Co/MgO{sub x} ferromagnet-insulator interfaces, representing material systems which are widely used in magnetic tunnel junctions, is studied by means of spin- and angle-resolved photoemission spectroscopy. The photoemission studies focus particularly on the response of the ferromagnetic electronic system in contact with MgO of varying stoichiometries, as this reflects the mechanisms of metal-oxide bonding at real ferromagnet-insulator interfaces. The correlation between chemical bonding and electronic structure formation is analyzed by combining information from core- and valence-band photoemission spectroscopy. The spectral features are compared to band structure calculations, which are performed using the SPR-KKR method. The Fe/MgO and Co/MgO systems are prepared by molecular beam epitaxy under ultrahigh vacuum conditions on well-defined (4 x 6) GaAs(001) substrates. A structural analysis by means of low-energy electron diffraction (LEED) reveals their body-centered cubic crystalline structure, whereas the chemical characterization by Auger electron spectroscopy is used to quantify the chemical environment at the sample surfaces. The magnetic analysis, using the magneto-optical Kerr effect, reveals the uniaxial anisotropy of the ferromagnetic layers. A crucial parameter is given by the MgO degree of oxidation, which is addressed by means of core-level spectroscopy and quantified by suitable fitting procedures of the Mg 2p core level. The results of the photoemission experiments show, that the electronic structure of the Fe/MgO and Co/MgO ferromagnet/insulator interfaces and, consequently, the interfacial spin polarization are sensitively controlled by the interface chemistry. In particular, three distinct scenarios are identified: the nearly stoichiometric, the oxygen-deficient and the over-oxidized ferromagnet/MgO interface. Each case is defined by innate characteristics of the electronic structure at

  7. Effect of oxygen vacancies on interlayer exchange coupling in Fe/MgO/Fe tunnel junctions

    Energy Technology Data Exchange (ETDEWEB)

    Zhuravlev, M.Ye. [Department of Physics and Astronomy, Center for Materials Research and Analysis, University of Nebraska, Lincoln, NE 68588 (United States); Velev, J. [Department of Physics and Astronomy, Center for Materials Research and Analysis, University of Nebraska, Lincoln, NE 68588 (United States); Vedyayev, A.V. [Department of Physics, M.V. Lomonosov Moscow State University, 119899 Moscow (Russian Federation); Tsymbal, E.Y. [Department of Physics and Astronomy, Center for Materials Research and Analysis, University of Nebraska, Lincoln, NE 68588 (United States)]. E-mail: tsymbal@unl.edu

    2006-05-15

    We have investigated the interlayer exchange coupling (IEC) in Fe/MgO/Fe(0 0 1) tunnel junctions with and without oxygen vacancies in MgO, using model and density functional calculations. The model predicts that IEC changes sign from ferromagnetic to antiferromagnetic if a defect level matches the Fermi energy. Ab initio calculations show that for perfect junctions, IEC is ferromagnetic and decreases exponentially with MgO thickness. Oxygen vacancies placed in the middle of MgO make IEC antiferromagnetic for three monolayers (MLs) of MgO, but do not change the sign of IEC for five MLs. The latter fact is explained within the model, which suggests that for the impurity level lying below the Fermi energy IEC can change sign with increasing barrier thickness due to the weaker coupling of the impurity level to the ferromagnets.

  8. Effect of reaction time and (Ca+Mg)/Al molar ratios on crystallinity of Ca-Mg-Al layered double Hydroxide

    Science.gov (United States)

    Heraldy, E.; Nugrahaningtyas, K. D.; Sanjaya, F. B.; Darojat, A. A.; Handayani, D. S.; Hidayat, Y.

    2016-02-01

    Ca-Mg-Al Layered Double Hydroxides (Ca-Mg-Al-LDH) compounds were successfully synthesized from brine water and AlCl3.6H2O as the starting materials by coprecipitation method. The product result was characterized by X-ray powder diffraction (XRD) and Fourier transform infrared (FT-IR). The effects of the reaction time and the molar ratios of the raw material on the crystallinity of Ca-Mg-Al-LDH were examining. Results show that increasing reaction time (30; 60 and 90 min.) could improve the crystallinity and monodispersity of layered double hydroxide compounds particles. The well-defined Ca-Mg- Al-LDH could be prepared with (Ca+Mg)/Al molar ratios 0.5.

  9. Influence on the transport behaviors of spin-polarized electrons exerted by MgO/NiFe and NiFe/MgO heterointerfaces

    Energy Technology Data Exchange (ETDEWEB)

    Zhao, Chong-Jun [Department of Materials Physics and Chemistry, University of Science and Technology Beijing, Beijing 100083 (China); Wu, Zheng-Long [Analytical and Testing Center, Beijing Normal University, Beijing 100875 (China); Zhao, Zhi-Duo [Department of Materials Physics and Chemistry, University of Science and Technology Beijing, Beijing 100083 (China); Ding, Lei [School of Materials and Chemical Engineering, Hainan University, Haikou 570228 (China); Lu, Xiang-An; Li, Xu-Jing; Zhang, Jing-Yan [Department of Materials Physics and Chemistry, University of Science and Technology Beijing, Beijing 100083 (China); Yu, Guang-Hua, E-mail: ghyu@mater.ustb.edu.cn [Department of Materials Physics and Chemistry, University of Science and Technology Beijing, Beijing 100083 (China)

    2014-11-15

    This work reports on the influence of different MgO/NiFe and NiFe/MgO heterointerfaces on the transport behaviors of spin-polarized electrons. It is found that the NiFe films with MgO underneath exhibit better transport properties than those coated by an MgO layer. The MgO/NiFe interface can significantly enhance the specular reflection of spin-polarized electrons and favor the electronic transport. In contrast, a greater lattice mismatch between NiFe and MgO will emerge because of the epitaxial relationship at the NiFe(111)/MgO(111) interface, with the resultant formation of oxygen-deficient MgO{sub x} phase at the NiFe/MgO interface. Significantly diffusive scattering of conduction electrons from such vacancy defects can substantially degrade the electron transport properties. - Highlights: • Multilayers were grown on thermally oxidized Si wafers by magnetron sputtering. • The influence of two heterointerfaces on NiFe films properties was investigated. • The NiFe film with MgO underneath shows better properties than that with MgO coating. • The interface status plays a crucial role in determining the transport properties. • Our study advances understanding of electron transport at metal/oxide interfaces.

  10. Collective modes in Ca70Mg30 glass

    Indian Academy of Sciences (India)

    B Y Thakore; P N Gajjar; A R Jani

    2000-02-01

    The self-consistent phonon scheme given by Takeno and Goda, involving multiple scattering and phonon eigen frequencies which are expressed in terms of many-body correlation functions of atoms as well as of interatomic potential in the solids, has been used to generate the collective modes in the Ca70Mg30 glass. A model potential is proposed to describe the effective interaction in the glass. Three different forms of the local field correction functions viz. Hartree, Taylor and Ichimaru and Utsumi are used to examine relative influence of exchange and correlation effects. The phonon frequencies of the longitudinal and transverse modes are computed employing the theoretical formulation of Hubbard and Beeby. The elastic property of the glassy system is then studied using the long wavelength limits of the phonon modes. The theoretical computations reproduce much better dispersion curves (both for the longitudinal and transverse phonons) compared to earlier reports and are found to be in good agreement with the available experimental results due to neutron scattering.

  11. Phonon Dispersion in Ca70Mg30 Metallic Glass

    Institute of Scientific and Technical Information of China (English)

    Aditya M. Vora

    2006-01-01

    @@ The phonon dispersion curves (PDC) of Ca70Mg30 metallic glass has been studied at room temperature in terms of phonon eigen frequencies of longitudinal and transverse modes employing three different approaches proposed by Hubbard and Beeby (J. Phys. C: Solid State Phys. 13 (1969) 556), Takeno and Goda (Prog. Theor. Phys.45 (1971) 331; 47 (1972) 790) and Bhatia and Singh (Phys. Rev. B 31 (1985) 4751). The well recognized model potential of Gajjar et al. is employed successfully to explain electron-ion interaction in the metallic glass. The effective pair potential is used to generate the pair correlation function g(r). The local field correction function (Int. J. Mod. Phys. B 17 (2003) 6001) is used for the first time to introduce the exchange and correlation effects on the aforesaid properties. The present finjings of PDCs are found to be in agreement with the available theoretical as well as experimental data. The thermodynamic and elastic properties, i.e. longitudinal and transverse sound velocities, isothermal bulk modulus, modulus of rigidity, Poisson's ratio, Young's modulus and Debye temperature, are also investigated successfully.

  12. Distribution of P, K, Ca, Mg, Cd, Cu, Fe, Mn, Pb and Zn in wood and bark age classes of willows and poplars used for phytoextraction on soils contaminated by risk elements.

    Science.gov (United States)

    Zárubová, Pavla; Hejcman, Michal; Vondráčková, Stanislava; Mrnka, Libor; Száková, Jiřina; Tlustoš, Pavel

    2015-12-01

    Fast-growing clones of Salix and Populus have been studied for remediation of soils contaminated by risk elements (RE) using short-rotation coppice plantations. Our aim was to assess biomass yield and distributions of elements in wood and bark of highly productive willow (S1--[Salix schwerinii × Salix viminalis] × S. viminalis, S2--Salix × smithiana clone S-218) and poplar (P1--Populus maximowiczii × Populus nigra, P2--P. nigra) clones with respect to aging. The field experiment was established in April 2008 on moderately Cd-, Pb- and Zn- contaminated soil. Shoots were harvested after four seasons (February 2012) and separated into annual classes of wood and bark. All tested clones grew on contaminated soils, with highest biomass production and lowest mortality exhibited by P1 and S2. Concentrations of elements, with exception of Ca and Pb, decreased with age and were higher in bark than in wood. The Salix clones were characterised by higher removal of Cd, Mn and Zn compared to the Populus clones. Despite generally higher RE content in young shoots, partly due to lower wood/bark ratios and higher RE concentrations in bark, the overall removal of RE was higher in older wood classes due to higher biomass yield. Thus, longer rotations seem to be more effective when phytoextraction strategy is considered. Of the four selected clones, S1 exhibited the best removal of Cd and Zn and is a good candidate for phytoextraction.

  13. The synthesis and characterization of Mg-Zn-Ca alloy by powder metallurgy process

    Science.gov (United States)

    Annur, Dhyah; Franciska P., L.; Erryani, Aprilia; Amal, M. Ikhlasul; Sitorus, Lyandra S.; Kartika, Ika

    2016-04-01

    Known for its biodegradation and biocompatible properties, magnesium alloys have gained many interests to be researched as implant material. In this study, Mg-3Zn-1Ca, Mg-29Zn-1Ca, and Mg-53Zn-4.3Ca (in wt%) were synthesized by means of powder metallurgy method. The compression strength and corrosion resistance of magnesium alloy were thoroughly examined. The microstructures of the alloy were characterized using optical microscopy, Scanning Electron Microscope, and also X-ray diffraction analysis. The corrosion resistance were evaluated using electrochemical analysis. The result indicated that Mg- Zn- Ca alloy could be synthesized using powder metallurgy method. This study showed that Mg-29Zn-1Ca would make the highest mechanical strength up to 159.81 MPa. Strengthening mechanism can be explained by precipitation hardening and grain refinement mechanism. Phase analysis had shown the formation of α Mg, MgO, and intermetallic phases: Mg2Zn11 and also Ca2Mg6Zn3. However, when the composition of Zn reach 53% weight, the mechanical strength will be decreasing. In addition, all of Mg-Zn-Ca alloy studied here had better corrosion resistance (Ecorr around -1.4 VSCE) than previous study of Mg. This study indicated that Mg- 29Zn- 1Ca alloy can be further analyzed to be a biodegradable implant material.

  14. Accuracy, standardization, and interlaboratory calibration standards for foraminiferal Mg/Ca thermometry

    Science.gov (United States)

    Greaves, Mervyn; Barker, Stephen; Daunt, Caroline; Elderfield, Henry

    2005-02-01

    The use of liquid and solid standards for foraminiferal Mg/Ca and Sr/Ca determinations and interlaboratory calibration has been investigated. Preparation of single element standard solutions from primary solid standard material enables the preparation of mixed standard solutions with Mg/Ca and Sr/Ca ratios of known accuracy to better than 0.1%. We also investigated commercial reference materials to determine whether existing carbonate standards could be used as reference material for Mg/Ca determinations in foraminiferal calcite. We propose that, in the absence of a pure calcium carbonate standard certified for Mg/Ca, ECRM 752-1, a limestone CRM containing Mg/Ca within the range of typical foraminifera, is a suitable solid standard for interlaboratory calibration. Replicate Mg/Ca determinations showed that, provided silicate phases are removed by centrifugation, this material is homogenous within the precision of daily instrumental Mg/Ca determinations over a range of sample weights from 10 to 1000 mg, taken from two separate bottles of ECRM 752-1. Results gave an average value of Mg/Ca = 3.75 mmol/mol (0.015 s.d., 0.41% r.s.d.) on 118 determinations from the two bottles.

  15. Comparing the Electrochemical Performance of LiFePO4/C Modified by Mg Doping and MgO Coating

    Directory of Open Access Journals (Sweden)

    Jianjun Song

    2013-01-01

    Full Text Available Supervalent cation doping and metal oxide coating are the most efficacious and popular methods to optimize the property of LiFePO4 lithium battery material. Mg-doped and MgO-coated LiFePO4/C were synthesized to analyze their individual influence on the electrochemical performance of active material. The specific capacity and rate capability of LiFePO4/C are improved by both MgO coating and Mg doping, especially the Mg-doped sample—Li0.985Mg0.015FePO4/C, whose discharge capacity is up to 163 mAh g−1, 145.5 mAh g−1, 128.3 mAh g−1, and 103.7 mAh g−1 at 1 C, 2 C, 5 C, and 10 C, respectively. The cyclic life of electrode is obviously increased by MgO surface modification, and the discharge capacity retention rate of sample LiFePO4/C-MgO2.5 is up to 104.2% after 100 cycles. Comparing samples modified by these two methods, Mg doping is more prominent on prompting the capacity and rate capability of LiFePO4, while MgO coating is superior in terms of improving cyclic performance.

  16. Structural stability of intermetallic compounds of Mg-Al-Ca alloy

    Institute of Scientific and Technical Information of China (English)

    ZHOU Dian-wu; LIU Jin-shui; ZHANG Jian; PENG Ping

    2007-01-01

    A first-principles plane-wave pseudopotential method based on the density functional theory was used to investigate the energetic and electronic structures of intermetallic compounds of Mg-Al-Ca alloy, such as Al2Ca, Al4Ca and Mg2Ca. The negative formation heat, the cohesive energies and Gibbs energies of these compounds were estimated from the electronic structure calculations, and their structural stability was also analyzed. The results show that Al2Ca phase has the strongest alloying ability as well as the highest structural stability, next Al4Ca, finally Mg2Ca. After comparing the density of states of Al2Ca, Al4Ca and Mg2Ca phases, it is found that the highest structural stability of Al2Ca is attributed to an increase in the bonding electron numbers in lower energy range below Fermi level, which mainly originates from the contribution of valence electron numbers of Ca(s) and Ca(p) orbits, while the lowest structural stability of Mg2Ca is resulted from the least bonding electron numbers near Fermi level.

  17. High-pressure polymorphs of iron-rich (Mg, Fe)SiO3 and FeGeO3 perovskite and post-perovskite. Takamitsu Yamanaka1, Wendy L. Mao2, P. Ganesh1, Luke Shulenburger1, Ho-kwang Mao1 and Russell J. Hemley1 1Geophysical Laboratory, Carnegie Institute of Washington, Washington, D.C. 20015 2 Department of Geological and Environmental Sciences, Stanford University, Stanford, CA 94305

    Science.gov (United States)

    Yamanaka, T.; Mao, W. L.; Shulenburger, L.; Ganesh, P.; Mao, H.; Hemley, R. J.

    2010-12-01

    Discovery of a high-pressure post-perovskite phase transition of MgSiO3 opened a new paradigm for understanding the deepest region of the core-mantle boundary and the D’’ region. The structure was found to be Cmcm space group as same structure as CaIrO3. However, we discovered a new structure for the post-perovskite phase of iron rich magnesium silicate at the Earth’s core-mantle boundary. The different structure will lead to better understanding of existing anomalies in the shear wave velocities at the D’’ layer. Our discovery of a new structure also gives a much simpler picture of the spin state of the D’’ layer. We used a combination of high-pressure/high-temperature experimental techniques including X-ray diffraction and X-ray emission spectra in conjunction with first-principles calculations to study the Fe-rich phase of magnesium silicate. We find a new structure with a Pmcm space group which differs distinctly from the assumed CaIrO3 structure in which it has two distinct sites for the metal ions (iron and magnesium) as opposed to having a random distribution of the metal ions which would make the two sites crystallographically equivalent. This result is also of primary importance in the understanding of the spin state of the silicate phase. From X-ray emission studies we find that iron exists in two distinct populations, one with high spin and one with low spin rather than being in an intermediate spin state (J.F. Lin et al, 2008). Furthermore, the abundance of these populations is equivalent to the site occupancies found through the structural refinement of the X-ray diffraction data. These findings have important implications for Earth’s D” layer and core-mantle boundary,. Because the stabilities of perovskite structures are closely related to the ratio of the radii composing ABO3 compounds, the tolerance factor can be a good indicator to predict high-pressure sequence of transformation and decompression process of ABO3 compounds. In

  18. Microstructures and properties of rapidly solidified Mg-Zn-Ca alloys

    Institute of Scientific and Technical Information of China (English)

    2008-01-01

    Ternary alloys based on the Mg-Zn-Ca system were produced by twin-roll rapid solidification. The alloys were characterized by OM, SEM, HRTEM, XRD, EDS and Micro-hardness. The results show that the rapidly solidified flakes are of frnedendritic cell structures with the cell size ranging from 1 to 5 μn. The Mg-6Zn-5Ca alloy in RS and annealing (200 ℃ for 1 h) states are mainly composed of α-Mg, Mg2Ca, Ca2Mg6, Zn3 and a small quantity of Mg51Zn20, MgZn2 and Mg2Zn3. Micro-hardness increases with the increment of Ca content and age hardening occurs after aging at 200 ℃ in the flakes probably due to the precipitation strengthening of the fine precipitates Mg2Ca and Ca2Mg6, Zn3. Some phases at the grain boundary in Mg-6Zn-5Ca alloy are identified by means of HRTEM, which may be beneficial to the improvement in thermal stability of the alloy.

  19. Interlaboratory comparison study of calibration standards for foraminiferal Mg/Ca thermometry

    Science.gov (United States)

    Greaves, M.; Caillon, N.; Rebaubier, H.; Bartoli, G.; Bohaty, S.; Cacho, I.; Clarke, L.; Cooper, M.; Daunt, C.; Delaney, M.; Demenocal, P.; Dutton, A.; Eggins, S.; Elderfield, H.; Garbe-Schoenberg, D.; Goddard, E.; Green, D.; Groeneveld, J.; Hastings, D.; Hathorne, E.; Kimoto, K.; Klinkhammer, G.; Labeyrie, L.; Lea, D. W.; Marchitto, T.; MartíNez-Botí, M. A.; Mortyn, P. G.; Ni, Y.; Nuernberg, D.; Paradis, G.; Pena, L.; Quinn, T.; Rosenthal, Y.; Russell, A.; Sagawa, T.; Sosdian, S.; Stott, L.; Tachikawa, K.; Tappa, E.; Thunell, R.; Wilson, P. A.

    2008-08-01

    An interlaboratory study of Mg/Ca and Sr/Ca ratios in three commercially available carbonate reference materials (BAM RS3, CMSI 1767, and ECRM 752-1) was performed with the participation of 25 laboratories that determine foraminiferal Mg/Ca ratios worldwide. These reference materials containing Mg/Ca in the range of foraminiferal calcite (0.8 mmol/mol to 6 mmol/mol) were circulated with a dissolution protocol for analysis. Participants were asked to make replicate dissolutions of the powdered samples and to analyze them using the instruments and calibration standards routinely used in their laboratories. Statistical analysis was performed in accordance with the International Standardization Organization standard 5725, which is based on the analysis of variance (ANOVA) technique. Repeatability (RSDr%), an indicator of intralaboratory precision, for Mg/Ca determinations in solutions after centrifuging increased with decreasing Mg/Ca, ranging from 0.78% at Mg/Ca = 5.56 mmol/mol to 1.15% at Mg/Ca = 0.79 mmol/mol. Reproducibility (RSDR%), an indicator of the interlaboratory method precision, for Mg/Ca determinations in centrifuged solutions was noticeably worse than repeatability, ranging from 4.5% at Mg/Ca = 5.56 mmol/mol to 8.7% at Mg/Ca = 0.79 mmol/mol. Results of this study show that interlaboratory variability is dominated by inconsistencies among instrument calibrations and highlight the need to improve interlaboratory compatibility. Additionally, the study confirmed the suitability of these solid standards as reference materials for foraminiferal Mg/Ca (and Sr/Ca) determinations, provided that appropriate procedures are adopted to minimize and to monitor possible contamination from silicate mineral phases.

  20. Biodiesel production from soybean and Jatropha oils by magnetic CaFe2O4–Ca2Fe2O5-based catalyst

    International Nuclear Information System (INIS)

    Heterogeneous CaFe2O4–Ca2Fe2O5-based catalyst with weak magnetism was prepared by co-precipitation and calcination. It was characterized by various techniques including X-ray diffraction, X-ray photoelectron spectroscopy and temperature programmed desorption method. Its active components were identified as mainly Ca–Fe composite oxides such as CaFe2O4 for transesterification. The magnetism was further strengthened by reducing its component of Fe2O3 to Fe3O4–Fe under H2 atmosphere for better magnetic separation. Both catalysts were used for the catalytic transesterification of soybean and Jatropha oils to biodiesel. The highest biodiesel yields for soybean oil of 85.4% and 83.5% were obtained over the weak and strong magnetic catalysts, respectively under the optimized conditions (373 K, 30 min, 15/1 methanol/oil molar ratio and 4 wt% catalyst). The catalysts could be recycled three times. Biodiesel production from pretreated Jatropha oil was tested with the magnetic CaFe2O4–Ca2Fe2O5–Fe3O4–Fe catalyst, and 78.2% biodiesel yield was obtained. The magnetic CaFe2O4–Ca2Fe2O5-based catalyst shows a potential application for the green production of biodiesel. - Highlights: • Magnetic catalyst was prepared by co-precipitation, calcination and reduction. • The catalyst was composed of CaFe2O4–Ca2Fe2O5–Fe3O4–Fe. • Biodiesel yields of 83.5% and 78.2% were achieved for soybean and Jatropha oils. • The catalyst was easily separated by a magnet and used for three cycles

  1. Study of chromites YbMIICr2O5,5 (MII - Mg, Ca, Sr, Ba by X-ray diffraction

    Directory of Open Access Journals (Sweden)

    B. Kasenov

    2012-03-01

    Full Text Available Compounds of composition YbMeMnFeO5,5 (Me – Mg, Ca, Sr, Ba are synthesized from Yb2O3, , Cr2O3 and MgCO3, CaCO3, SrCO3, BaCO3 by solid phase method. X-ray powder diffraction showed that the compound YbMgCr2O5,5, YbCaCr2O5,5, YbSrCr2O5,5, YbBaCr2O5,5 crystallizes in the tetragonal crystal system.

  2. North Atlantic Globorotalia inflata coretop Mg/Ca calibrations and temperature reconstructions over Termination I

    International Nuclear Information System (INIS)

    Mg/Ca ratios from planktonic foraminifera are widely used as an independent proxy for ocean temperature. The choice of calibration is vital for reconstructing meaningful temperatures. We present preliminary results based on a new Mg/Ca-temperature calibration (Mg/Ca = 0.92e0.039T) for the thermocline-dwelling foraminifera Globorotalia inflata, derived using a suite of North Atlantic coretops. The downcore Mg/Ca record from core SU90-03 (400N, 320W) was used to compare how our new and existing calibrations performed for the Holocene and over the large scale change associated with Termination I.

  3. North Atlantic Globorotalia inflata coretop Mg/Ca calibrations and temperature reconstructions over Termination I

    Energy Technology Data Exchange (ETDEWEB)

    Farmer, Elizabeth J; Chapman, Mark R; Andrews, Julian E, E-mail: e.farmer@uea.ac.u [University of East Anglia, School of Environmental Sciences, Norwich, NR4 7TJ (United Kingdom)

    2010-03-15

    Mg/Ca ratios from planktonic foraminifera are widely used as an independent proxy for ocean temperature. The choice of calibration is vital for reconstructing meaningful temperatures. We present preliminary results based on a new Mg/Ca-temperature calibration (Mg/Ca = 0.92e{sup 0.039T}) for the thermocline-dwelling foraminifera Globorotalia inflata, derived using a suite of North Atlantic coretops. The downcore Mg/Ca record from core SU90-03 (40{sup 0}N, 32{sup 0}W) was used to compare how our new and existing calibrations performed for the Holocene and over the large scale change associated with Termination I.

  4. Structures of pure and Ca-segregated MgO (001) surfaces

    CERN Document Server

    Yanfa, Y; Pennycook, S J; Pantelides, S T

    1999-01-01

    The structures of pure and Ca-segregated MgO (001) surfaces have been studied using first-principles density functional theory. The relaxation and rumpling for the pure surface are found to be 0.48 and 1.62, respectively. Ca segregation significantly modifies the surface structure. The surface-segregated Ca atoms protrude outwards owing to the size mismatch between Ca and Mg. Consequently, their nearest neighbor oxygen atoms are pulled up. The value of the protrusion of Ca atoms is strongly dependent on the Ca coverage of the surface. (18 refs).

  5. Determination of Fe, Ca, Mg, Zn and Pb in Cinder and Activated Carbon by Flame Atomic Absorption Method%火焰原子吸收法测定煤渣和煤质活性炭中铁、钙、镁、锌、铅

    Institute of Scientific and Technical Information of China (English)

    薛慧; 董宾

    2014-01-01

    A method for measurement of metal microelements in cinders and activated carbon,such as Fe, Ca, Mg, Zn and Pb by flame atomic absorption method was established. Pretreatment procedure was studied. Cinders was treated with dry ashing and then digested,activated carbon was treated with acid extraction method. Metal microelements such as Fe,Ca and Mg in cinder were measured using standard curve method,while microelements such as Fe,Zn and Pb in activated carbon from coal were measured based on standard addition method,in order to reduce the interference of the basic. Results detected by the method were in accordance with existed references. Microelements contents were higher in cinders,especially after burning. In comparison,microelements dropped dramatically in activated carbon, due to the complex processing procedure. Recoveries of each element ranged from 88.5% to 105.5%, and the relative standard deviation was less than 2% (n=7). The detecting limits of the six elements were 0.010,0.015,0.005,0.012,0.013, 0.110 mg/L respectively, in two kinds of the specimen. It can be concluded that the flame atomic absorption method is accurate,convenient, it is suitable for the measurement of metal microelements in cinders and activated carbon.%建立了火焰原子吸收法测定煤渣和煤质活性炭中微量金属元素铁、钙、镁、锌、铅含量的方法。煤渣样品采用干灰化后消解,煤质活性炭样品采用稀酸提取进行处理。煤渣中铁、钙、镁元素用标准曲线法定量,活性炭中铁、锌、铅则采用标准加入法定量以减少基体干扰的影响。样品测定结果与文献报道相一致,煤渣尤其是燃烧处理后的煤渣中微量元素含量较高,而煤质活性炭通过复杂工艺处理后,微量元素大大减少。样品中被测元素的加标回收率在88.5%~105.5%之间,测定结果的相对标准偏差小于2%(n=7),两类样品中6种元素的检出限分别为0.010,0.015,0.005,0.012

  6. Microstructure analysis and corrosion behavior of biodegradable Mg-Ca implant alloys

    International Nuclear Information System (INIS)

    Highlights: → Evaluation of corrosion mechanism and solidification behavior of Mg-xCa. → Microstructure of Mg-xCa alloys were characterized by XRD, OM, SEM and EDS. → Thermal analysis of alloys was carried out by computer aided cooling curve analysis. → The addition of Ca content increase Mg2Ca lead to increasing corrosion rate. -- Abstract: The calcium content in binary Mg-xCa alloys affects the microstructure, corrosion and solidification behavior of the alloys. In this study, binary Mg-xCa alloys with various Ca contents from 0.5 to 10 wt.% were produced by casting process. Microstructural evolutions were characterized by optical microscopy, X-ray diffraction, scanning electron microscopy and energy dispersive X-ray spectroscopy. Solidification behavior was assessed via two thermocouple thermal analysis method. The corrosion resistance was examined in vitro by potentiodynamic polarization and immersion test in Kokubo solution at room temperature. The results revealed that the grain size and dendrite cell size decreased significantly with rising Ca content, whilst the content of Mg2Ca intermetallic phase in grain boundaries increased with increasing Ca content. Potentiodynamic polarization tests in simulated body fluid (SBF) indicated that corrosion rates of Mg-xCa alloy increased significantly with rising Ca content. Immersion tests in Kokubo solution also showed that dissolution rate of Mg-xCa alloy increased with increasing Mg2Ca content which lead to an increase in pH value. It was observed that corrosion damage in specimens with lower Ca content was more moderate and uniform than higher Ca content. Thermal analysis results showed that the fraction of primary α-Mg at dendrite coherency point (fαDCP) decreased with increasing Ca content but the liquid fraction fL increased causing the rise in eutectic Mg2Ca intermetallic phase in grain boundaries, thus increasing the corrosion rate. Our analyses showed that Mg-0.5Ca alloy is a promising alloy to be

  7. Effect of CaO composition on oxidation and burning behaviors of AM50 Mg alloy

    Institute of Scientific and Technical Information of China (English)

    Jin-Kyu LEE; Shae K. KIM

    2011-01-01

    Oxidation and burning behaviors were studied for CaO added AM50 Mg composites which were manufactured by conventional melting and casting processes without SF6 protective gas. CaO added AM50 Mg composites show the stable oxidation resistance. while AM50 Mg alloys show the poor oxidation resistance. The effects of CaO addition on the burning resistance under ambient, nitrogen and dry air atmospheres were examined for CaO added AM50 Mg composites. With increasing CaO addition, the burning temperature increases under ambient, nitrogen and dry air atmospheres. The burning temperatures of small test specimen under all conditions greatly increase even by 0.3% CaO (mass fraction) addition into AM50 Mg alloys.

  8. Review: the effects of secular variation in seawater Mg/Ca on marine biocalcification

    Directory of Open Access Journals (Sweden)

    J. B. Ries

    2009-07-01

    Full Text Available Synchronized transitions in the polymorph mineralogy of the major reef-building and sediment-producing calcareous marine organisms and abiotic CaCO3 precipitates (ooids, marine cements throughout Phanerozoic time is believed to have been caused by tectonically-induced variations in seawater molar Mg/Ca (>2="aragonite seas"; <2="calcite seas". Here, I review a series of experiments in which extant calcifying taxa were reared in experimental seawater formulated over the range of mMg/Ca ratios (1.0 to 5.2 that occurred throughout their geologic history.

    Aragonite-secreting bryopsidalean algae and scleractinian corals and calcite-secreting coccolithophores exhibited higher rates of calcification and growth in the experimental seawaters that favored their skeletal mineral. These results support the assertion that seawater Mg/Ca played an important role in determining which hypercalcifying marine organisms were the major reef-builders and sediment-producers throughout Earth history. The observation that primary production increased along with calcification in mineralogically-favorable seawater is consistent with the hypothesis that calcification promotes photosynthesis within autotrophs through the liberation of CO2.

    The Mg/Ca ratio of calcite secreted by the coccolithophores, coralline algae and reef-dwelling animals (crustacea, urchins, calcareous tube worms declined with reductions in seawater Mg/Ca. Calcifying microbial biofilms varied their mineral polymorph with seawater Mg/Ca (mMg/Ca<2=low Mg calc; mMg/Ca>2=arag+high Mg calc, suggesting a nearly abiotic mode of calcification. These results indicate that biomineralogical control can be partially overridden by ambient seawater Mg/Ca and suggests that modern high Mg calcite organisms probably secreted low Mg calcite in calcite seas of the past. Notably, Mg fractionation in autotrophic organisms was more strongly influenced by changes in

  9. Distribution of Phosphorus between CaO-CaF2 Slag and Fe-C-P Melt

    Institute of Scientific and Technical Information of China (English)

    WANG Qing-xiang; ZHOU Jian-jian; DU Xiao-jian

    2005-01-01

    The equilibrium distribution ratio of phosphorus between CaO-CaF2 molten slag and Fe-C-P melt at 1450 ℃ was measured. The phosphate capacity of slag and the activity coefficient of phosphorus oxide were calculated.

  10. Moessbauer and XRD investigations of layered double hydroxides (LDHs) with varying Mg/Fe ratios

    Energy Technology Data Exchange (ETDEWEB)

    Sipiczki, Monika [University of Szeged, Department of Inorganic and Analytical Chemistry (Hungary); Kuzmann, Erno, E-mail: kuzmann@ludens.elte.hu; Homonnay, Zoltan [Eoetvoes Lorand University, Institute of Chemistry (Hungary); Megyeri, Jozsef [Centre for Energy Research, Hungarian Academy of Sciences (Hungary); Kovacs, Krisztina [Eoetvoes Lorand University, Institute of Chemistry (Hungary); Palinko, Istvan [University of Szeged, Department of Organic Chemistry (Hungary); Sipos, Pal [University of Szeged, Department of Inorganic and Analytical Chemistry (Hungary)

    2013-04-15

    The effects of the Mg(II)/Fe(III) ratio on the structure and Fe microenvironments in MgFe LDH substances were investigated. The LDHs were prepared by the co-precipitation method with Mg(II)/Fe(III) ratios from 2:1 to 6:1. The materials were characterized by {sup 57}Fe Moessbauer spectroscopy and powder X-ray diffractometry. The {sup 57}Fe Moessbauer spectra exhibited asymmetric doublet corresponding to high-spin Fe(III) microenvironments in all LDH structure. It was found that the quadrupole splitting decreased with increasing Mg(II)/Fe(III)ratio reflecting change in the electric field gradient due to the incorporation of different amounts of iron into the Mg-containing layers.

  11. FeGa/MgO/Fe/GaAs(001) magnetic tunnel junction: Growth and magnetic properties

    Energy Technology Data Exchange (ETDEWEB)

    Gobaut, B., E-mail: benoit.gobaut@elettra.eu [Sincrotrone Trieste S.C.p.A., S.S. 14-km 163.5, Area Science Park, 34012 Trieste (Italy); Ciprian, R.; Salles, B.R.; Krizmancic, D. [Laboratorio TASC, IOM-CNR, S.S. 14-km 163.5, Basovizza, 34149 Trieste (Italy); Rossi, G. [Laboratorio TASC, IOM-CNR, S.S. 14-km 163.5, Basovizza, 34149 Trieste (Italy); Dipartimento di Fisica, Università di Milano, via Celoria 16, 20133 Milano (Italy); Panaccione, G. [Laboratorio TASC, IOM-CNR, S.S. 14-km 163.5, Basovizza, 34149 Trieste (Italy); Eddrief, M.; Marangolo, M. [Sorbonne Universites, UPMC Univ Paris 06, UMR 7588, INSP, 4 place Jussieu, 75005 Paris (France); CNRS, UMR 7588, Institut des NanoSciences de Paris, 4 place Jussieu, 75005 Paris (France); Torelli, P. [Laboratorio TASC, IOM-CNR, S.S. 14-km 163.5, Basovizza, 34149 Trieste (Italy)

    2015-06-01

    Research on spintronics and on multiferroics leads now to the possibility of combining the properties of these materials in order to develop new functional devices. Here we report the integration of a layer of magnetostrictive material into a magnetic tunnel junction. A FeGa/MgO/Fe heterostructure has been grown on a GaAs(001) substrate by molecular beam epitaxy (MBE) and studied by X-ray magnetic circular dichroism (XMCD). The comparison between magneto optical Kerr effect (MOKE) measurements and hysteresis performed in total electron yield allowed distinguishing the ferromagnetic hysteresis loop of the FeGa top layer from that of the Fe buried layer, evidencing a different switching field of the two layers. This observation indicates an absence of magnetic coupling between the two ferromagnetic layers despite the thickness of the MgO barrier of only 2.5 nm. The in-plane magnetic anisotropy has also been investigated. Overall results show the good quality of the heterostructure and the general feasibility of such a device using magnetostrictive materials in magnetic tunnel junction.

  12. Improvement of Corrosion Resistance of Binary Mg-Ca Alloys Using Duplex Aluminum-Chromium Coatings

    Science.gov (United States)

    Daroonparvar, Mohammadreza; Yajid, Muhamad Azizi Mat; Yusof, Noordin Mohd; Bakhsheshi-Rad, Hamid Reza; Adabi, Mohsen; Hamzah, Esah; Kamali, Hussein Ali

    2015-07-01

    Al-AlCr was coated on Mg-Ca and Mg-Zn-Ce-La alloys using physical vapor deposition method. The surface morphology of the specimens was characterized by x-ray diffraction, scanning electron microscopy equipped with energy-dispersive x-ray spectroscopy, and atomic force microscopy (AFM). The AFM results indicated that the average surface roughness of Al-AlCr coating on the Mg-Ca alloy is much lower than that of Al-AlCr coating on the Mg-Zn-Ce-La alloy. However, Al-AlCr coating on the Mg-Ca alloy presented a more compact structure with fewer pores, pinholes, and cracks than Al-AlCr coating on the Mg-Zn-Ce-La alloy. Electrochemical studies revealed that the novel coating (Al-AlCr) can remarkably reduce the corrosion rate of the Mg-Ca alloy in 3.5 wt.% NaCl solution. It was seen that the anodic current density of the Al-AlCr-coated Mg-Ca alloy was very small when compared to the Al-AlCr-coated Mg-Zn-Ce-La and uncoated alloys. Impedance modulus ( Z) of the Al-AlCr-coated samples was higher than that of the bare Mg alloys. Z of Al-AlCr-coated Mg-Ca alloy was higher than that of the Al-AlCr-coated Mg-Zn-Ce-La alloy at low frequency.

  13. Evolution of precipitation during non-isothermal ageing of an Mg-Ca-Zn alloy with high Ca content

    Energy Technology Data Exchange (ETDEWEB)

    Langelier, Brian, E-mail: blangeli@engmail.uwaterloo.ca [University of Waterloo, 200 University Avenue West, Waterloo, Ontario, N2L 3G1 (Canada); Wang, Xiang [McMaster University, 1280 Main Street West, Hamilton, Ontario, L8S 4L8 (Canada); Esmaeili, Shahrzad [University of Waterloo, 200 University Avenue West, Waterloo, Ontario, N2L 3G1 (Canada)

    2012-03-15

    Highlights: Black-Right-Pointing-Pointer Precipitation hardening characterized for an Mg-Ca-Zn alloy with high Ca content. Black-Right-Pointing-Pointer Evolution of precipitation during non-isothermal ageing identified by TEM and DSC. Black-Right-Pointing-Pointer DSC data de-convoluted using heat treatments developed from thermodynamic analysis. Black-Right-Pointing-Pointer De-convoluted DSC provides further insight into the complex precipitation behaviour. - Abstract: In this work, the precipitation behaviour of an Mg-Ca-Zn alloy with high content of Ca relative to Zn was studied. Differential scanning calorimetry (DSC) was combined with transmission electron microscopy (TEM) and hardness measurement to examine the precipitate evolution in this alloy. A non-isothermal age-hardening heat treatment was performed to allow for a direct comparison to DSC results. Thermodynamic analysis aided in identifying ageing heat treatments to further de-convolute the overlapping DSC data. Results suggested the precipitation events followed sequential evolution towards the formation of two types of equilibrium phases (i.e. Mg{sub 2}Ca and Mg{sub 6}Ca{sub 2}Zn{sub 3}). Early stage decomposition of the solid solution had no observable effect on hardness, but was followed by the formation of hardening GP zones. Fine basal plates, as well as large coarse basal plates of Mg{sub 2}Ca-type formed on further ageing. Contrast due to fine unidentified nanoscale precipitates was also observed in the over-aged state. These precipitates tended to disappear, while blocky Mg{sub 2}Ca equilibrium phase precipitates formed as the heat treatment progressed to the highest temperature studied (i.e. 300 Degree-Sign C). However, the equilibrium Mg{sub 6}Ca{sub 2}Zn{sub 3}phase was not observed when this final test temperature was achieved at the end of the non-isothermal heat treatment process.

  14. High-pressure X-ray diffraction and Raman spectroscopy of CaFe2O4-type β-CaCr2O4

    Science.gov (United States)

    Zhai, Shuangmeng; Yin, Yuan; Shieh, Sean R.; Shan, Shuangming; Xue, Weihong; Wang, Ching-Pao; Yang, Ke; Higo, Yuji

    2016-04-01

    In situ high-pressure synchrotron X-ray diffraction and Raman spectroscopic studies of orthorhombic CaFe2O4-type β-CaCr2O4 chromite were carried out up to 16.2 and 32.0 GPa at room temperature using multi-anvil apparatus and diamond anvil cell, respectively. No phase transition was observed in this study. Fitting a third-order Birch-Murnaghan equation of state to the P-V data yields a zero-pressure volume of V 0 = 286.8(1) Å3, an isothermal bulk modulus of K 0 = 183(5) GPa and the first pressure derivative of isothermal bulk modulus K 0' = 4.1(8). Analyses of axial compressibilities show anisotropic elasticity for β-CaCr2O4 since the a-axis is more compressible than the b- and c-axis. Based on the obtained and previous results, the compressibility of several CaFe2O4-type phases was compared. The high-pressure Raman spectra of β-CaCr2O4 were analyzed to determine the pressure dependences and mode Grüneisen parameters of Raman-active bands. The thermal Grüneisen parameter of β-CaCr2O4 is determined to be 0.93(2), which is smaller than those of CaFe2O4-type CaAl2O4 and MgAl2O4.

  15. Effect of Nano Scale Fe Doping on Superconducting Properties of MgB2

    OpenAIRE

    S. X. Dou; Soltanian, S.; Zhao, Y.; Getin, E.; Chen, Z.; Horvat, J.

    2004-01-01

    Iron is an important sheath material for fabrication of MgB2 wires. However, the effect of Fe doping on the superconducting properties of MgB2 remains controversial. In this work, we present results of nano-scale Fe particle doping in to MgB2. The Fe doping experiments were performed using both bulk and thin film form. It was found that Fe doping did not affect the lattice parameters of MgB2, as evidenced by the lack of change in the XRD peak positions for MgB2. Because of the high reactivity...

  16. Acid-base status determines the renal expression of Ca2+ and Mg2+ transport proteins.

    NARCIS (Netherlands)

    Nijenhuis, T.; Renkema, K.Y.R.; Hoenderop, J.G.J.; Bindels, R.J.M.

    2006-01-01

    Chronic metabolic acidosis results in renal Ca2+ and Mg2+ wasting, whereas chronic metabolic alkalosis is known to exert the reverse effects. It was hypothesized that these adaptations are mediated at least in part by the renal Ca2+ and Mg2+ transport proteins. The aim of this study, therefore, was

  17. Damping Capacities of Mg-4 Pct Zn-(0-0.5) Pct Ca Biomedical Alloys

    Science.gov (United States)

    Jun, Joong-Hwan; Hwang, In-Je

    2016-10-01

    This study is intended to investigate the damping capacities of cast Mg-4 pct Zn-(0-0.5) pct Ca biomedical alloys. The Mg-4 pct Zn-(0-0.5) pct Ca alloys had similar damping levels regardless of Ca content in the strain-amplitude-independent region, but showed a decreasing tendency with an increase in Ca content in the strain-amplitude-dependent region. Almost identical concentration of solutes in the α-(Mg) matrix and the increased number density of the precipitate particles are responsible for the damping behaviors in the strain-amplitude-independent and strain-amplitude-dependent regions, respectively.

  18. Chamber formation leads to Mg/Ca banding in the planktonic foraminifer Neogloboquadrina pachyderma

    Science.gov (United States)

    Jonkers, Lukas; Buse, Ben; Brummer, Geert-Jan A.; Hall, Ian R.

    2016-10-01

    Many species of planktonic foraminifera show distinct banding in the intratest distribution of Mg/Ca. This heterogeneity appears biologically controlled and thus poses a challenge to Mg/Ca paleothermometry. The cause of this banding and its relation with chamber formation are poorly constrained and most of what we know about intratest Mg/Ca variability stems from culture studies of tropical, symbiont-bearing foraminifera. Here we present data on the non-spinose, symbiont-barren Neogloboquadrina pachyderma from the subpolar North Atlantic where wintertime mixing removes vertical gradients in temperature and salinity. This allows investigation of biologically controlled Mg/Ca intratest variability under natural conditions. We find that intratest Mg/Ca varies between accounted for.

  19. Corrosion Mechanism of MgO-CaO Brick for AOD Furnace

    Institute of Scientific and Technical Information of China (English)

    WANG Jiandong; GE Changchun; SHEN Weiping

    2006-01-01

    Residual MgO-CaO brick after being used in AOD furnace was determined by OM, SEM and EDAX. Corrosion mechanism of MgO-CaO brick as furnace lining was studied. Results show that: The corrosion of MgOCaO brick is mainly attributed to the solution and infiltration of silicate liquid phase. Transverse cracks between reacted zone and original zone are parallel to the working face, which is an important factor for deteriorating the corrosion of MgO-CaO bricks.

  20. Theory of perpendicular magnetocrystalline anisotropy in Fe/MgO (001)

    Science.gov (United States)

    Odkhuu, Dorj; Yun, Won Seok; Rhim, S. H.; Hong, Soon Cheol

    2016-09-01

    The origin of large perpendicular magnetocrystalline anisotropy (PMCA) in Fe/MgO (001) is revealed by comparing Fe layers with and without the MgO. Although Fe-O p-d hybridization is weakly present, it cannot be the main origin of the large PMCA as claimed in previous study. Instead, perfect epitaxy of Fe on the MgO is more important to achieve such large PMCA. As an evidence, we show that the surface layer in a clean free-standing Fe (001) dominantly contributes to EMCA, while in the Fe/MgO, those by the surface and the interface Fe layers contribute almost equally. The presence of MgO does not change positive contribution from , wherease it reduces negative contribution from z2 |ℓX | yz > and .

  1. Foram Farming in the Mid-Continent: Culturing Low-Mg Benthic Foraminifera to Calibrate the Mg/Ca Paleothermometer

    Science.gov (United States)

    Jennings, D.; Hasiuk, F.; Thomas, E.; Varekamp, J. C.

    2014-12-01

    The initiation of Cenozoic continental ice sheets and the history of their growth/decay is difficult to reconstruct because of the mixed effects of polar ice volume and temperature on benthic foraminiferal oxygen isotope values. Coupled measurements of foraminiferal δ18O and Mg/Ca are a promising tool to unlock the history of past continental glaciation by calculating the oxygen isotopic composition of paleo-seawater. This method has been applied on Quaternary timescales with success, but uncertainty about secular changes in seawater Mg/Ca and potential changes in carbonate saturation have produced varying results with deeper time data. Currently, no experimentally-calibrated model explains how the Mg/Ca of low-Mg calcite, such as secreted by benthic foraminifera, responds to variations in seawater temperature and Mg/Ca. Our "Foram Farm" is a culture system for low-Mg calcite benthic foraminifera, composed of a colony and an experimental line. Currently, the colony hosts several species of rotaliids, miliolids, and buliminids obtained from Qatar, the Dominican Republic, Scotland, and Long Island Sound, USA. In addition, two tanks contain "live sand," a mixture of sandy material and seawater obtained from tropical reefs, and commonly used to condition hobbyist saltwater aquaria. This sand contains foraminifera and numerous other microorganisms. "Live sand" could be a source for cheap and easy to obtain test subjects. The foram farm gives access to a constant supply and variety of test subjects for the experimental line, which consists of several analytical refrigerators with varying temperatures. Each refrigerator houses petri dishes where forams are grown in water with varying Mg/Ca compositions. Elphidium excavatum, a well-researched, eurytopic taxon, will be the first to be cultured in the experimental line. After growing under experimental conditions, specimens will be analyzed using LA-ICP-MS, in order to model effects of seawater T and Mg/Ca on foram Mg/Ca

  2. Microstructural evaluation of oxide layers in CaO-added Mg alloys

    International Nuclear Information System (INIS)

    Highlights: • Oxidation layer thickness of CaO added AM60 increases with increasing amounts of CaO. • Effect of CaO is that the columnar grains on AM60 grow along the [1 0 0]MgO. • A initial oxidation layer thickness and ignition temperature is closely connected. • The columnar oxide layer formed due to Ca, which dissolved from CaO. - Abstract: A transmission electron microscopy analysis was conducted on the oxide layers of Mg–5.5Al–0.25Mn (AM60) alloys with different levels of CaO content formed in a thermogravimetric analyzer (TGA) system at 450 °C for 7 h. It was found that the oxide layer in AM60 + CaO grew as a columnar structure and, resultantly, that the oxide layers had different thicknesses with different levels of CaO content. The columnar oxide grains that were formed on the Mg + CaO alloy grew on the [1 0 0]MgO, resulting in a more compact and thicker initial oxide layer compared to the normal oxide layer. The columnar growth of the oxide layer in AM60 + CaO formed due to the Ca, which dissolved from CaO

  3. Incommensurate magnetism in FeAs strips: neutron scattering from CaFe(4)As(3).

    Science.gov (United States)

    Nambu, Yusuke; Zhao, Liang L; Morosan, Emilia; Kim, Kyoo; Kotliar, Gabriel; Zajdel, Pawel; Green, Mark A; Ratcliff, William; Rodriguez-Rivera, Jose A; Broholm, Collin

    2011-01-21

    Magnetism in the orthorhombic metal CaFe(4)As(3) was examined through neutron diffraction for powder and single crystalline samples. Incommensurate [q(m) ≈ (0.37-0.39) × b*] and predominantly longitudinally (|| b) modulated order develops through a 2nd order phase transition at TN = 89.63(6) K with a 3D Heisenberg-like critical exponent β = 0.365(6). A 1st order transition at T2 = 25.6(9)  K is associated with the development of a transverse component, locking q(m) to 0.375(2)b*, and increasing the moments from 2.1(1) to 2.2(3)  μ B for Fe2+ and from 1.3(3) to 2.4(4)  μB for Fe+. The ab initio Fermi surface is consistent with a nesting instability in cross-linked FeAs strips.

  4. Using benthic foraminiferal B/Ca to constrain the effect of dissolution on key Pliocene Mg/Ca temperature records

    Science.gov (United States)

    White, S. M.; Ravelo, A. C.

    2015-12-01

    The state of the Pliocene tropical Pacific is currently the subject of heated debate. The debate hinges on the veracity of planktic foraminiferal Mg/Ca temperatures from the west Pacific warm pool (WPWP) and the eastern equatorial Pacific (EEP) that show Pliocene WPWP temperatures similar to today but a warmer Pliocene EEP, resulting in a much reduced east-west gradient [Wara et al., 2005]. These findings form the basis of the "permanent El Niño-like state" paradigm of Pliocene climate. However, recent studies using organic biomarker proxies produce temperature records that indicate a WPWP cooling trend since the Pliocene that differs markedly from Mg/Ca-temperature records [O'Brien et al., 2014; Zhang et al., 2014]. Though much of the debate has focused on changes in seawater Mg/Ca, spatial variations in proxy agreement point to dissolution as a key factor. Dissolution, which imparts a cool bias to Mg/Ca temperatures, varies across ocean basins depending on Δ[CO32-], the difference from the carbonate ion concentration needed for calcite saturation. By necessity, dissolution corrections use the modern value of Δ[CO32-] for the entire record, so it is possible that Pliocene proxy discrepancies could stem from varying Δ[CO32-] over time. Here we present benthic foraminiferal B/Ca data (a proxy for Δ[CO32-]) from the EEP and WEP spanning the past 5 Myr, to constrain the effect of dissolution on Pliocene Mg/Ca records. To account for possible changes in seawater B/Ca, we present paired epifaunal-infaunal B/Ca data. Infaunal species are much less sensitive to Δ[CO32-] than epifaunal species, but would still record long-term changes in seawater B/Ca. The true Δ[CO32-] can thus be calculated from the epifaunal-infaunal B/Ca difference [Brown et al., 2011]. Our study is the first to apply this approach downcore; by accounting for long-term changes in seawater, it greatly expands use of the B/Ca proxy and enables a first attempt at correcting for time

  5. Timing and mechanism for intratest Mg/Ca variability in a living planktic foraminifer

    Science.gov (United States)

    Spero, Howard J.; Eggins, Stephen M.; Russell, Ann D.; Vetter, Lael; Kilburn, Matt R.; Hönisch, Bärbel

    2015-01-01

    Geochemical observations indicate that planktic foraminifer test Mg/Ca is heterogeneous in many species, thereby challenging its use as a paleotemperature proxy for paleoceanographic reconstructions. We present Mg/Ca and Ba/Ca data collected by laser ablation ICP-MS from the shells of Orbulina universa cultured in controlled laboratory experiments. Test calcite was labeled with Ba-spiked seawater for 12 h day or night calcification periods to quantify the timing of intratest Mg-banding across multiple diurnal cycles. Results demonstrate that high Mg bands are precipitated during the night whereas low Mg bands are precipitated during the day. Data obtained from specimens growing at 20 °C and 25 °C show that Mg/Ca ratios in both high and low Mg bands increase with temperature, and average test Mg/Ca ratios are in excellent agreement with previously published empirical calibrations based on bulk solution ICP-MS analyses. In general, Mg band concentrations decrease with increasing pH and/or [CO2-3] but this effect decreases as experimental temperatures increase from 20 °C to 25 °C. We suggest that mitochondrial uptake of Mg2+ from the thin calcifying fluid beneath streaming rhizopodial filaments may provide the primary locus for Mg2+ removal during test calcification, and that diurnal variations in either mitochondrial density or activity produce Mg banding. These results demonstrate that Mg banding is an inherent component of test biomineralization in O. universa and show that the Mg/Ca paleothermometer remains a fundamental tool for reconstructing past ocean temperatures from fossil foraminifers.

  6. Microstructures, mechanical properties and corrosion resistances of extruded Mg-Zn-Ca-xCe/La alloys.

    Science.gov (United States)

    Tong, L B; Zhang, Q X; Jiang, Z H; Zhang, J B; Meng, J; Cheng, L R; Zhang, H J

    2016-09-01

    Magnesium alloys are considered as good candidates for biomedical applications, the influence of Ce/La microalloying on the microstructure, mechanical property and corrosion performance of extruded Mg-5.3Zn-0.6Ca (wt%) alloy has been investigated in the current study. After Ce/La addition, the conventional Ca2Mg6Zn3 phases are gradually replaced by new Mg-Zn-Ce/La-(Ca) phases (T1'), which can effectively divide the Ca2Mg6Zn3 phase. The Ca2Mg6Zn3/T1' structure in Mg-Zn-Ca-0.5Ce/La alloy is favorably broken into small particles during the extrusion, resulting in an obvious refinement of secondary phase. The dynamic recrystallized grain size is dramatically decreased after 0.5Ce/La addition, and the tensile yield strength is improved, while further addition reverses the effect, due to the grain coarsening. However, the corrosion resistance of extruded Mg-Zn-Ca alloy deteriorates after Ce/La addition, because the diameter of secondary phase particle is remarkably decreased, which increases the amount of cathodic sites and accelerates the galvanic corrosion process. PMID:27179307

  7. Oscillator strengths for Ar VII, Ca IX and Fe XV

    Science.gov (United States)

    Tayal, S. S.

    1986-01-01

    The excitation energies and oscillator strengths are calculated for electric-dipole-allowed and intercombination transitions between 3s2 1S, 3s3p(1,3)P0, 3p2 3P, 1D, 1S and 3s3d(1,3)D states in Ar VII, Ca IX, and Fe XV ions of the magnesium sequence. These states are represented by the fairly large configuration-interaction expansions. The calculations have been carried out in both LS and intermediate coupling schemes. The relativistic corrections have been included through the Breit-Pauli Hamiltonian. The results are compared with previous theoretical calculations and with measurements.

  8. Analysis of EET on Ca increasing the melting point of Mg17Al12 phase

    Institute of Scientific and Technical Information of China (English)

    2002-01-01

    The present investigation showed that the additions of Ca to the alloy AZ91 were mainly dissolved into the Mg17Al12 phase and increased its melting point and thermal stability, which would have great effects on the high- temperature properties of AZ91 alloy. The empirical electron theory (EET) of solid and molecules was used to calculate the valence electron structures (VES) of Mg17Al12 intermetallic compound with and without Ca addition. The results showed that Ca dissolving in Mg17Al12 phase increased the strength of bonds that control the thermal stability of Mg17Al12 phase. Additions of Ca also made the distribution of the valence electrons on the dominant bond network more uniform in the whole unit cell of Mg17Al12. The theoretical conclusions well account for the experimental results.

  9. Thin film growth of CaFe2As2 by molecular beam epitaxy

    Science.gov (United States)

    Hatano, T.; Kawaguchi, T.; Fujimoto, R.; Nakamura, I.; Mori, Y.; Harada, S.; Ujihara, T.; Ikuta, H.

    2016-01-01

    Film growth of CaFe2As2 was realized by molecular beam epitaxy on six different substrates that have a wide variation in the lattice mismatch to the target compound. By carefully adjusting the Ca-to-Fe flux ratio, we obtained single-phase thin films for most of the substrates. Interestingly, an expansion of the CaFe2As2 lattice to the out-of-plane direction was observed for all films, even when an opposite strain was expected. A detailed microstructure observation of the thin film grown on MgO by transmission electron microscope revealed that it consists of cube-on-cube and 45°-rotated domains. The latter domains were compressively strained in plane, which caused a stretching along the c-axis direction. Because the domains were well connected across the boundary with no appreciable discontinuity, we think that the out-of-plane expansion in the 45°-rotated domains exerted a tensile stress on the other domains, resulting in the unexpectedly large c-axis lattice parameter, despite the apparently opposite lattice mismatch.

  10. Growth and magnetic properties of ultrathin epitaxial FeO films and Fe/FeO bilayers on MgO(001)

    Energy Technology Data Exchange (ETDEWEB)

    Kozioł-Rachwał, A., E-mail: akoziol@agh.edu.pl [Faculty of Physics and Applied Computer Science, AGH University of Science and Technology, al. Mickiewicza 30, 30-059 Kraków (Poland); National Institute of Advanced Industrial Science and Technology, Spintronics Research Center, Tsukuba, Ibaraki 305-8568 (Japan); Ślęzak, T. [Faculty of Physics and Applied Computer Science, AGH University of Science and Technology, al. Mickiewicza 30, 30-059 Kraków (Poland); Nozaki, T.; Yuasa, S. [National Institute of Advanced Industrial Science and Technology, Spintronics Research Center, Tsukuba, Ibaraki 305-8568 (Japan); Korecki, J. [Faculty of Physics and Applied Computer Science, AGH University of Science and Technology, al. Mickiewicza 30, 30-059 Kraków (Poland); Jerzy Haber Institute of Catalysis and Surface Chemistry, Polish Academy of Sciences, ul. Niezapominajek 8, 30-239 Kraków (Poland)

    2016-01-25

    Ultrathin FeO(001) films were grown via molecular beam epitaxy on MgO(001) using reactive deposition of Fe. The growth conditions were adjusted toward stabilization of the wüstite phase, the existence of which was confirmed by means of conversion electron Mössbauer spectroscopy. It was shown how the metallic Fe overlayer modified the chemical state and the magnetic properties of the FeO oxide. Finally, we observed the exchange bias for an epitaxial Fe/FeO bilayer grown on MgO(001)

  11. M\\"ossbauer and Magnetic Studies of Surfactant Mediated Ca-Mg Doped Ferrihydrite Nanoparticles

    OpenAIRE

    Layek, Samar; Mohapatra, M.; Anand, S.; Verma, H.C.

    2015-01-01

    Ultrafine (2-5 nm) particles of amorphous Ca-Mg co-doped ferrihydrite have been synthesized by surfactant mediated co-precipitation method. The evolution of the amorphous ferrihydrite by Ca-Mg co-doping is quite different from our earlier investigations on individual Ca and Mg doping studies. Amorphous phase of ferrihydrite for the present study has been confirmed by X-ray diffraction (XRD) and M\\"ossbauer spectroscopy at room temperature and low temperatures (40 K and 20 K). Hematite nanopar...

  12. Effect of Ca2+ and Mg2+ on CO2 Corrosion Behavior of Tube Steel

    Institute of Scientific and Technical Information of China (English)

    ZHAO Guo-xian; LI Jian-ping; HAO Shi-ming; L(U) Xiang-hong; LI He-lin

    2005-01-01

    Effects of Ca2+ and Mg2+ on the CO2 corrosion behaviors of tube steel were studied in simulated oil-fieldenvironment. The influence of Ca2+ and Mg2+ on the corrosion rate and morphologies of corrosion product layerwas determined by scanning electron microscope and measuring mass loss. Potentiodynamic polarization and im-pedance spectroscopy were used to investigate the change of electrochemical characteristic parameters of corrosionproduct layer and corrosion dynamic process. The results show that with Ca2+ and Mg2+ in electrolyte, the mor-phologies and microstructures of corrosion product layer changed obviously, thus affecting the corrosion process.

  13. Surface modification of an Mg-1Ca alloy to slow down its biocorrosion by chitosan.

    Science.gov (United States)

    Gu, X N; Zheng, Y F; Lan, Q X; Cheng, Y; Zhang, Z X; Xi, T F; Zhang, D Y

    2009-08-01

    The surface morphologies before and after immersion corrosion test of various chitosan-coated Mg-1Ca alloy samples were studied to investigate the effect of chitosan dip coating on the slowdown of biocorrosion. It showed that the corrosion resistance of the Mg-Ca alloy increased after coating with chitosan, and depended on both the chitosan molecular weight and layer numbers of coating. The Mg-Ca alloy coated by chitosan with a molecular weight of 2.7 x 10(5) for six layers has smooth and intact surface morphology, and exhibits the highest corrosion resistance in a simulated body fluid.

  14. Surface modification of an Mg-1Ca alloy to slow down its biocorrosion by chitosan

    Energy Technology Data Exchange (ETDEWEB)

    Gu, X N; Zheng, Y F; Lan, Q X [State Key Laboratory for Turbulence and Complex System and College of Engineering, Peking University, Beijing 100871 (China); Cheng, Y; Xi, T F [Center for Biomedical Materials and Tissue Engineering, Academy for Advanced Interdisciplinary Studies, Peking University, Beijing 100871 (China); Zhang, Z X [Biomedical Engineering Research Center, Research Institute of Peking University in Shenzhen, Shenzhen 518057 (China); Zhang, D Y, E-mail: gxn139888@pku.edu.c, E-mail: yfzheng@pku.edu.c, E-mail: 8lanqiuxiang@163.co, E-mail: chengyan@pku.edu.c, E-mail: top5460@163.co, E-mail: xitingfei@tom.co, E-mail: zhangdeyuan@lifetechmed.co [Lifetech Scientific (Shenzhen) Co. Ltd, Hi-Tech Park, Shenzhen 518000 (China)

    2009-08-15

    The surface morphologies before and after immersion corrosion test of various chitosan-coated Mg-1Ca alloy samples were studied to investigate the effect of chitosan dip coating on the slowdown of biocorrosion. It showed that the corrosion resistance of the Mg-Ca alloy increased after coating with chitosan, and depended on both the chitosan molecular weight and layer numbers of coating. The Mg-Ca alloy coated by chitosan with a molecular weight of 2.7 x 10{sup 5} for six layers has smooth and intact surface morphology, and exhibits the highest corrosion resistance in a simulated body fluid.

  15. Calcined Mg-Fe layered double hydroxide as an absorber for the removal of methyl orange

    Energy Technology Data Exchange (ETDEWEB)

    Peng, Chao [School of Civil Engineering and Mechanics, Central South University of Forestry and Technology, Changsha 410004, Hunan (China); State Key Laboratory of Silicate Materials for Architectures, Wuhan University of Technology, Wuhan 430070 (China); Dai, Jing [Key Laboratory of Advanced Technology for Special Functional Materials of Ministry of Education, Wuhan 430070 (China); Yu, Jianying, E-mail: Yujianyingwhut@163.com [State Key Laboratory of Silicate Materials for Architectures, Wuhan University of Technology, Wuhan 430070 (China); Yin, Jian [School of Civil Engineering and Mechanics, Central South University of Forestry and Technology, Changsha 410004, Hunan (China)

    2015-05-15

    In this work, methyl orange (MO) was effectively removed from aqueous solution with the calcined product of hydrothermal synthesized Mg/Fe layered double hydroxide (Mg/Fe-LDH). The structure, composition, morphology and textural properties of the Mg/Fe-LDH before and after adsorption were characterized by X-ray diffraction, Fourier transformation infrared spectroscopy, transmission electron microscopy, nitrogen adsorption apparatus and X-ray photoelectron spectroscopy. It was confirmed that MO had been absorbed by calcined Mg/Fe-LDH which had strong interactions with MO. The adsorption of MO onto the Mg/Fe-LDH was systematically investigated by batch tests. The adsorption capacity of the Mg/Fe-LDH toward MO was found to be 194.9 mg • g{sup −1}. Adsorption kinetics and isotherm studies revealed that the adsorption of MO onto Mg/Fe-LDH was a spontaneous and endothermic process. These results indicate that Mg/Fe-LDH is a promising material for the removal of MO.

  16. Ethylbenzene dehydrogenation over binary FeOx–MeOy/Mg(Al)O catalysts derived from hydrotalcites

    KAUST Repository

    Balasamy, Rabindran J.

    2010-12-20

    A series of FeOx-MeOy/Mg(Al)O catalysts were prepared from hydrotalcite-like compounds as precursors and were tested in the ethylbenzene dehydrogenation to styrene in He atmosphere at 550 °C. The hydrotalcite-like precursors of the metal compositions of Mg3Fe 0.25Me0.25Al0.5 (Me = Cu, Zn, Cr, Mn, Fe, Co and Ni) were coprecipitated from the nitrates of metal components and calcined to mixed oxides at 550 °C. After the calcination, the mixed oxides showed high surface area of 150-200 m2 gcat -1, and were mainly composed of (MgMe)(Fe3+Al)O periclase in the bulk, whereas the surface was enriched by (MgMe)(Fe3+Al)2O 4 pinel. Among the Me species tested, Co2+ was the most effective, followed by Ni2+. Co2+ addition increased the activity of original FeOx/Mg(Al)O catalyst, whereas Ni2+ increased the activity at the beginning of reaction, but deactivated the catalyst during the reaction. The other metals formed isolated MeOx species in the catalyst, resulting in a decrease in the activity compared to the original FeOx/Mg(Al)O catalyst. The active Fe species exists as metastable Fe3+ on the FeOx/Mg(Al)O catalyst. By the addition of Co2+, the reduction-oxidation between Fe3+ and Fe2+ was facilitated and, moreover, the active Fe3+ species was stabilized. It is likely that the dehydrogenation proceeds on the active Fe3+ species via its reduction-oxidation assisted by Co 2+. © 2010 Elsevier B.V.

  17. Stability relations in the system CaSiO3-CaMnSi2O6-CaFeSi2O6

    Science.gov (United States)

    Abrecht, Jürgen

    1980-10-01

    In the system CaSiO3-CaMnSi2O6-CaFeSi2O6 extensive miscibility gaps between pyroxenoids and clinopyroxenes are observed. The miscibility gap between Mn-bustamite and Mn-wollastonite has been determined experimentally by a hydrothermal technique between 400° and 1200° C at P f= 2 kbar. Further experiments have been performed at P f=9 kbar, which revealed a shifting of the miscibility gap towards more Ca-rich compositions. The bustamite phase is stabilized by high pressures and the wollastonite structure is the stable phase at high temperatures. Similar phase relations as along the join CaSiO3-CaMnSi2O6 exist along the join CaSiO3-CaFeSi2O6 but with a more extensive two-phase field of bustamite-clinopyroxene. Possible phase relations along the joins CaSiO3-CaMnSi2O6, CaSiO3-CaFeSi2O6 and CaFeSi2O6-CaMnSi2O6 are given in temperature-composition diagrams for low pressures, based on natural and experimental data.

  18. Revisited abundance diagnostics in quasars: Fe II/Mg II ratios

    CERN Document Server

    Verner, E M; Verner, D A; Johansson, S; Gull, T R

    2003-01-01

    Both the Fe II UV emission in the 2000- 3000 A region [Fe II (UV)] and resonance emission line complex of Mg II at 2800 A are prominent features in quasar spectra. The observed Fe II UV/ Mg II emission ratios have been proposed as means to measure the buildup of the Fe abundance relative to that of the alpha-elements C, N, O, Ne and Mg as a function of redshift. The current observed ratios show large scatter and no obvious dependence on redshift. Thus, it remains unresolved whether a dependence on redshift exists and whether the observed Fe II UV/ Mg II ratios represent a real nucleosynthesis diagnostic. We have used our new 830-level model atom for Fe+ in photoionization calculations, reproducing the physical conditions in the broad line regions of quasars. This modeling reveals that interpretations of high values of Fe II UV/ Mg II are sensitive not only to Fe and Mg abundance, but also to other factors such as microturbulence, density, and properties of the radiation field. We find that the Fe II UV/ Mg II...

  19. Ab-initio study of the interfacial properties in ultrathin MgO films on O-rich FeO/Fe(001) surfaces

    Energy Technology Data Exchange (ETDEWEB)

    Jeon, Junjin; Yu, Byungdeok [University of Seoul, Seoul (Korea, Republic of)

    2014-09-15

    Using ab-initio simulations based on density functional theory, we systematically studied the interfacial properties of MgO films on O-rich FeO/Fe(001) surfaces with increasing number of MgO layers from one to three monolayers (MLs). The structural and the adhesion properties of the MgO/FeO/Fe(001) system were assessed and compared with those of simple MgO/Fe(001) interfaces. Our calculated results showed that the adhesion energy for MgO/FeO/Fe(001) was smaller than that for simple MgO/Fe(001). An analysis of the electronic structures and the charge rearrangements of the MgO/FeO/Fe(001) interfaces was also performed. The work functions of the MgO/FeO/Fe(001) systems upon the deposition of MgO films exhibited smaller decreases (0.45 - 0.67 eV) than those (1.43 - 1.74 eV) of the MgO/Fe(001) systems. In addition, the obtained work functions (3.77 - 3.99 eV) for MgO/FeO/Fe(001) were much larger than those (2.12 - 2.43 eV) for MgO/Fe(001).

  20. Effect of Ca addition on the corrosion behavior of Mg-Al-Mn alloy

    Science.gov (United States)

    Yang, Jiang; Peng, Jian; Nyberg, Eric A.; Pan, Fu-sheng

    2016-04-01

    The microstructures and corrosion resistance of magnesium-5 wt% aluminum-0.3 wt% manganese alloys (Mg-Al-Mn) with different Ca additions (0.2-4 wt%) were investigated. Results showed that with increasing Ca addition, the grain of the alloys became more refined, whereas the corrosion resistant ability of the alloys initially increased and then decreased. The alloy with 2 wt% Ca addition exhibited the best corrosion resistance, attributed to the effect of the oxide film and (Mg,Al)2Ca phases which were discontinuously distributed on the grain boundaries. These phases acted as micro-victims, they preferentially corroded to protect the α-Mg matrix. The oxide film formed on the alloy surface can hinder the solution further to protect the α-Mg matrix.

  1. Crystal and local atomic structure of Co-doped MgFeBO_4 warwickites

    OpenAIRE

    Kazak, N. V.; Platunov, M. S.; Knyazev, Yu. V.; Ivanova, N. B.; Zubavichus, Y. V.; Veligzhanin, A. A.; Vasiliev, A. D.; Bezmaternykh, L. N.; Bayukov, O. A.; Arauzo, A.; Bartolomé, J.; Lamonova, K. V.; Ovchinnikov, S. G.

    2014-01-01

    Single crystalline MgFeBO_4, Mg_0.5Co_0.5FeBO_4 and CoFeBO_4 have been grown by the flux method. The samples have been characterized by X-ray spectral analysis, X-ray diffraction and X-ray absorption spectroscopy. The X-ray absorption near-edge structure (XANES) and extended X-ray absorption fine structure (EXAFS) spectra have been measured at the Fe andCoK-edges over a wide temperature range (6.5 - 300 K). The composition, the charge state and local environment of both Fe and Co atoms have b...

  2. Fabrication and Spark Plasma Sintering of Magnetic alpha-Fe/MgO Nanocomposite by Mechanical Alloying.

    Science.gov (United States)

    Lee, Chung-Hyo

    2016-02-01

    Solid-state reduction has occurred during mechanical alloying of a mixture of Fe2O3 and Mg powders at room temperature. It is found that magnetic nanocomposite in which MgO is dispersed in alpha-Fe matrix with nano-sized grains is obtained by mechanical alloying of Fe2O3 with Mg for 30 min. Consolidation of the ball-milled powders was performed in a spark plasma sintering (SPS) machine up to 800-1000 degrees C. X-ray diffraction result shows that the average grain size of alpha-Fe in a-Fe/MgO nanocomposite sintered at 800 degrees C is in the range of 110 nm. It can be also seen that the coercivity of SPS sample sintered at 800 degrees C is still high value of 88 Oe, suggesting that the grain growth of magnetic alpha-Fe phase during SPS process tends to be suppressed. PMID:27433621

  3. High-Strength Low-Alloy (HSLA) Mg-Zn-Ca Alloys with Excellent Biodegradation Performance

    Science.gov (United States)

    Hofstetter, J.; Becker, M.; Martinelli, E.; Weinberg, A. M.; Mingler, B.; Kilian, H.; Pogatscher, S.; Uggowitzer, P. J.; Löffler, J. F.

    2014-04-01

    This article deals with the development of fine-grained high-strength low-alloy (HSLA) magnesium alloys intended for use as biodegradable implant material. The alloys contain solely low amounts of Zn and Ca as alloying elements. We illustrate the development path starting from the high-Zn-containing ZX50 (MgZn5Ca0.25) alloy with conventional purity, to an ultrahigh-purity ZX50 modification, and further to the ultrahigh-purity Zn-lean alloy ZX10 (MgZn1Ca0.3). It is shown that alloys with high Zn-content are prone to biocorrosion in various environments, most probably because of the presence of the intermetallic phase Mg6Zn3Ca2. A reduction of the Zn content results in (Mg,Zn)2Ca phase formation. This phase is less noble than the Mg-matrix and therefore, in contrast to Mg6Zn3Ca2, does not act as cathodic site. A fine-grained microstructure is achieved by the controlled formation of fine and homogeneously distributed (Mg,Zn)2Ca precipitates, which influence dynamic recrystallization and grain growth during hot forming. Such design scheme is comparable to that of HSLA steels, where low amounts of alloying elements are intended to produce a very fine dispersion of particles to increase the material's strength by refining the grain size. Consequently our new, ultrapure ZX10 alloy exhibits high strength (yield strength R p = 240 MPa, ultimate tensile strength R m = 255 MPa) and simultaneously high ductility (elongation to fracture A = 27%), as well as low mechanical anisotropy. Because of the anodic nature of the (Mg,Zn)2Ca particles used in the HSLA concept, the in vivo degradation in a rat femur implantation study is very slow and homogeneous without clinically observable hydrogen evolution, making the ZX10 alloy a promising material for biodegradable implants.

  4. Ab-initio transport calculations of Fe/MgO/Fe tunnel junctions modified by Co and Cr interlayers

    Energy Technology Data Exchange (ETDEWEB)

    Bose, Peter [Martin Luther University Halle-Wittenberg (Germany); International Max Planck Research School for Science and Technology of Nanostructures (Germany); Henk, Juergen [Max Planck Institute of Microstructure Physics, Halle (Germany); Zahn, Peter [Martin Luther University Halle-Wittenberg (Germany); Mertig, Ingrid [Martin Luther University Halle-Wittenberg (Germany); Max Planck Institute of Microstructure Physics, Halle (Germany)

    2010-07-01

    For spintronic device applications, large and tuneable tunnel magnetoresistance ratios (TMR) are inevitable. However, experimental TMR ratios of epitaxial Fe/MgO/Fe junctions can be strongly reduced by imperfect Fe/MgO interfaces. A way to increase the TMR ratio is the insertion of thin metallic layers at the Fe/MgO interfaces. With respect to their magnetic and electronic properties as well as their small lattice mismatch to Fe(001), Co and Cr interlayers have been preferably studied. We report on systematic ab-initio investigations of Co and Cr interlayers focussing on the changes of the electronic structure and the transport properties. The results of spin-dependent ballistic transport calculations reveal options to specifically manipulate the TMR ratio. The observed effects are directly addressed and interpreted by means of electronic states with complex wave vectors.

  5. Epitaxial growth of Fe3Si/CaF2/Fe3Si magnetic tunnel junction structures on CaF2/Si(111) by molecular beam epitaxy

    OpenAIRE

    Kobayashi, Ken’ichi; Suemasu, Takashi; Kuwano, Noriyuki; Hara, Daisuke; Akinaga, Hiroyuki

    2007-01-01

    The Fe3Si(24 nm)/CaF2(2 nm)/Fe3Si(12 nm) magnetic tunnel junction (MTJ) structures were grown epitaxially on CaF2/Si(111) by molecular beam epitaxy (MBE). The 12-nm-thick Fe3Si underlayer was grown epitaxially on CaF2/Si(111) at approximately 400 °C; however, the surface of the Fe3Si film was very rough, and thus a lot of pinholes are considered to exist in the 2-nm-thick CaF2 barrier layer. The average roughness (Ra) of the CaF2 barrier layer was 7.8 nm. This problem was overcome by low-temp...

  6. Combinatorial pulsed laser deposition of Fe/MgO granular multilayers

    Energy Technology Data Exchange (ETDEWEB)

    Garcia-Garcia, A. [Universidad de Zaragoza-CSIC, Instituto de Ciencia de Materiales de Aragon (ICMA), Zaragoza (Spain); Universidad de Zaragoza, Departamento de Fisica de la Materia Condensada, Zaragoza (Spain); Universidade do Porto, Departamento de Fisica, IFIMUP and IN-Institute of Nanoscience and Nanotechnology, Porto (Portugal); Pardo, J.A. [Universidad de Zaragoza, Instituto de Nanociencia de Aragon (INA), Zaragoza (Spain); Universidad de Zaragoza, Departamento de Ciencia y Tecnologia de Materiales y Fluidos, Zaragoza (Spain); Navarro, E.; Strichovanec, P. [Universidad de Zaragoza, Instituto de Nanociencia de Aragon (INA), Zaragoza (Spain); Vovk, A. [Centro de Fisica da Materia Condensada Universidade de Lisboa, Lisboa (Portugal); Institute of Magnetism NAS of Ukraine, Kiev (Ukraine); Morellon, L.; Ibarra, M.R. [Universidad de Zaragoza, Departamento de Fisica de la Materia Condensada, Zaragoza (Spain); Universidad de Zaragoza, Instituto de Nanociencia de Aragon (INA), Zaragoza (Spain); Algarabel, P.A. [Universidad de Zaragoza-CSIC, Instituto de Ciencia de Materiales de Aragon (ICMA), Zaragoza (Spain); Universidad de Zaragoza, Departamento de Fisica de la Materia Condensada, Zaragoza (Spain)

    2012-06-15

    Combinatorial pulsed laser deposition (PLD) makes use of the angular spread of laser-ablated material to prepare thin films with lateral compositional gradient. In this paper we have used combinatorial PLD to grow discontinuous Fe/MgO multilayers by alternate ablation from two separate Fe and MgO targets. Films of composition [Fe(t{sub Fe})/MgO(t{sub MgO})]{sub 15} were deposited on glass substrates. The thickness of Fe and MgO were varied in the vicinity of critical values determined in previous studies to maximize the tunneling magnetoresistance (TMR) in the current-in-plane configuration. Optimized multilayers show a substantial improvement of both TMR and field sensitivity at room temperature. (orig.)

  7. Distribution equilibria of Fe, Co and Ni between MgO-saturated FeOx-MgO-SiO2 slag and Ni alloy

    International Nuclear Information System (INIS)

    As a fundamental study related to the recycle of Ni-Fe-Co alloy, the distribution equilibrium of Fe, Co and Ni between MgO saturated FeOx-MgO-SiO2 slag and nickel alloy was investigated at 1773, 1823 and 1873 K with controlled oxygen partial pressure between 10-4 to 102Pa. The distribution ratios of Fe, Co and Ni at 1773 K vary from 0.61 to 26, 0.040 to 4.2 and 0.0030 to 0.34 respectively with increasing oxygen partial pressure. The distribution ratios of Fe, Co and Ni between MgO saturated FeOx-MgO-SiO2 slag and nickel alloy suggest that most of nickel and cobalt can remain in the alloy phase with lower oxygen partial pressure, and iron can be eliminated adequately from nickel alloys with higher oxygen partial pressure. However, the solubility of nickel and cobalt oxide in the slag also increases with increasing the oxygen partial pressure. Lower oxygen partial pressure and higher temperature are favorable for decreasing the loss of nickel and cobalt into slag. An oxygen partial pressure at which the separation coefficients show minimum was observed. The MgO solubility in the FeOx-MgO-SiO2 slag decreases when the NiO content exceeds about 25% at higher oxygen partial pressure. The activity coefficients of NiO and CoO in slags were calculated and found that their values increased with increasing of the NiO and CoO contents in slag respectively. (author)

  8. Inter-species and Seasonal Variability in Mg / Ca in Larger Benthic Foraminifera: Implications for Paleo-proxy

    Science.gov (United States)

    Singh, A.; Saraswati, P. K.; Pande, K.; Sanyal, P.

    2015-12-01

    The reports of inter-species variability to intra-test heterogeneity in Mg/Ca in several species of foraminifera have raised question about its use in estimation of seawater temperatures and necessitate field and culture studies to verify it for species from different habitats. In this study, we attempt to investigate if Mg/Ca in larger benthic foraminifera (LBF) could be a potential proxy of seawater temperatures for shallow marine carbonates. The samples were collected in different seasons from coral reef at Akajima (Okinawa, Japan). The Ca and Mg of 13 species of LBF and small benthic foraminifera from the same season were determined to examine variation in Mg/Ca among the species calcified under presumably the same temperature and salinity conditions. We also analyzed Amphistegina lessoni from different seasons for Ca, Mg and δ18O to determine variation in Mg/Ca with temperature and see how the two proxies of temperatures, Mg/Ca and δ18O, correlate in the same species. The species cluster about two distinctly separated Mg/Ca values. The first group comprising species of Amphistegina, Gypsina, Ammonia and Elphidium have relatively lower Mg/Ca, varying from 30 to 45 mmol/mol. The second group, having average Mg/Ca ranging from ~110 to 170 mmol/mol, includes species of Schlumbergerella, Baculogypsinoides, Baculogypsina, Heterostegina, Operculina, Calcarina, Amphisorus, Alveolinella and Poroeponides. The result suggests large interspecies variability implying vital effect in foraminiferal Mg/Ca. There is no distinct difference in Mg/Ca values between porcelaneous and hyaline types or symbiont-bearing and symbiont-free types. In Amphistegina lessoni the variation in Mg/Ca between individuals of the same season is as large as variation across the seasons. There is no correlation between Mg/Ca and seawater temperature. Lack of correlation between Mg/Ca and δ18O further suggests that Mg/Ca in the species is not primarily controlled by temperature.

  9. Hereditary tubular transport disorders: implications for renal handling of Ca2+ and Mg2+

    DEFF Research Database (Denmark)

    Dimke, Henrik; Hoenderop, Joost G; Bindels, René J;

    2010-01-01

    change tubular transport of Ca2+ and Mg2+. In the distal convolutions, several proteins involved in Mg2+ transport have been identified [TRPM6 (transient receptor potential melastatin 6), proEGF (pro-epidermal growth factor) and FXYD2 (Na+/K+-ATPase gamma-subunit)]. In addition, conditions...

  10. Deep-sea ostracode shell chemistry (Mg:Ca ratios) and late Quaternary Arctic Ocean history

    Science.gov (United States)

    Cronin, T. M.; Dwyer, G.S.; Baker, P.A.; Rodriguez-Lazaro, J.; Briggs, W.M., Jr.

    1996-01-01

    The magnesium:calcium (Mg:Ca) and strontium:calcium (Sr:Ca) ratios were investigated in shells of the benthic ostracode genus Krithe obtained from 64 core-tops from water depths of 73 to 4411 m in the Arctic Ocean and Nordic seas to determine the potential of ostracode shell chemistry for paleoceanographic study. Shells from the abyssal plain and ridges of the Nansen, Amundsen and Makarov basins and the Norwegian and Greenland seas had a wide scatter of Mg:Ca ratios ranging from 0.007 to 0.012 that may signify post-mortem chemical alteration of the shells from Arctic deep-sea environments below about 1000 m water depth. There is a positive correlation (r2=0.59) between Mg:Ca ratios and bottom-water temperature in Krithe shells from water depths <900 m.

  11. Determination of Cu, Zn, Ca, Mg and Fe in Human Hair by ICP-AES%电感耦合等离子体原子发射光谱(ICP-AES)法测定人发中铜、锌、钙、镁、铁

    Institute of Scientific and Technical Information of China (English)

    王生进; 张琳; 刘春虎; 董龙腾; 韩夫强

    2016-01-01

    样品经硝酸-高氯酸消化溶解,高氯酸冒烟,盐酸溶解盐类后,在盐酸(5%)介质中,在选定的测定条件下,用电感耦合等离子体原子发射光谱(ICP-AES)法测定人发中微量元素铜、锌、铁、镁、钙.选择Cu 327.3、Zn 206.2、Fe 238.2、Mg 279.5、Ca 315.8 nm分别作为铜、锌、铁、镁、钙的分析线与混合标准溶液同时测定;方法加标回收率为98.6%~101%,铜、锌、铁、镁、钙的精密度(RSD,n=8)为0.37%~2%,准确度(RE)为-3.4%~1.15%,检出限分别为0.002 3、0.001 6、0.004 6、0.003 0、0.001 4 μg/mL.方法克服了分光光度法和原子吸收光谱法操作繁琐、周期长、成本高、灵敏度低等缺点.用于测定人发样品中的铜、锌、铁、镁、钙元素,测定结果与原子吸收光谱法测定值基本一致.经GB-WO7061标准物质和自制标样分析验证,测定值与标准值吻合,结果准确可靠.

  12. Multicomponent diffusion in garnets I: general theoretical considerations and experimental data for Fe-Mg systems

    Science.gov (United States)

    Borinski, Sascha André; Hoppe, Ulrich; Chakraborty, Sumit; Ganguly, Jibamitra; Bhowmik, Santanu Kumar

    2012-10-01

    We have carried out a combined theoretical and experimental study of multicomponent diffusion in garnets to address some unresolved issues and to better constrain the diffusion behavior of Fe and Mg in almandine-pyrope-rich garnets. We have (1) improved the convolution correction of concentration profiles measured using electron microprobes, (2) studied the effect of thermodynamic non-ideality on diffusion and (3) explored the use of a mathematical error minimization routine (the Nelder-Mead downhill simplex method) compared to the visual fitting of concentration profiles used in earlier studies. We conclude that incorporation of thermodynamic non-ideality alters the shapes of calculated profiles, resulting in better fits to measured shapes, but retrieved diffusion coefficients do not differ from those retrieved using ideal models by more than a factor of 1.2 for most natural garnet compositions. Diffusion coefficients retrieved using the two kinds of models differ only significantly for some unusual Mg-Mn-Ca-rich garnets. We found that when one of the diffusion coefficients becomes much faster or slower than the rest, or when the diffusion couple has a composition that is dominated by one component (>75 %), then profile shapes become insensitive to one or more tracer diffusion coefficients. Visual fitting and numerical fitting using the Nelder-Mead algorithm give identical results for idealized profile shapes, but for data with strong analytical noise or asymmetric profile shapes, visual fitting returns values closer to the known inputs. Finally, we have carried out four additional diffusion couple experiments (25-35 kbar, 1,260-1,400 °C) in a piston-cylinder apparatus using natural pyrope- and almandine-rich garnets. We have combined our results with a reanalysis of the profiles from Ganguly et al. (1998) using the tools developed in this work to obtain the following Arrhenius parameters in D = D 0 exp{-[ Q 1bar + ( P-1)Δ V +]/ RT} for D {Mg/*} and D {Fe/*}: Mg

  13. Effect of Mg/Ca ratios on microbially induced carbonate precipitation

    Science.gov (United States)

    Balci, Nurgul; Demirel, Cansu; Seref Sonmez, M.; Kurt, M. Ali

    2016-04-01

    Influence of Mg/Ca ratios on microbially induced carbonate mineralogy were investigated by series of experiments carried out under various environmental conditions (Mg/Ca ratio, temperature and salinity). Halophilic bacterial cultures used for biomineralization experiments were isolated from hypersaline Lake Acıgöl (Denizli, SW Turkey), displaying extreme water chemistry with an average pH around 8.6 (Balci eta l.,2015). Enriched bacterial culture used in the experiments consisted of Halomonas saccharevitans strain AJ275, Halomonas alimentaria strain L7B; Idiomarina sp. TBZ29, 98% Idiomarina seosensis strain CL-SP19. Biomineralization experiments were set up using above enriched culture with Mg/Ca ratios of 0.05, 1, 4 and 15 and salinity of 8% and 15% experiments at 30oC and 10oC. Additionally, long-term biomineralization experiments were set up to last for a year, for Mg/Ca=4 and Mg/Ca=15 experiments at 30oC. For each experimental condition abiotic experiments were also conducted. Solution chemistry throughout incubation was monitored for Na, K, Mg, Ca, bicarbonate, carbonate, ammonium and phosphate for a month. At the end of the experiments, precipitates were collected and morphology and mineralogy of the biominerals were investigated and results were evaluated using the software DIFFRAC.SUITE EVA. Overall the preliminary results showed chemical precipitation of calcite, halite, hydromagnesite and sylvite. Results obtained from biological experiments indicate that, low Mg/Ca ratios (0.05 and 1) favor chlorapatite precipitation, whereas higher Mg/Ca ratios favor struvite precipitation. Biomineralization of dolomite, huntite and magnesite is favorable at high Mg/Ca ratios (4 and 15), in the presence of halophilic bacteria. Moreover, results indicate that supersaturation with respect to Mg (Mg/Ca=15) combined with NaCl (15%) inhibits biomineralization and forms chemical precipitates. 15% salinity is shown to favor chemical precipitation of mineral phases more than

  14. Mg-Fe-mixed oxides derived from layered double hydroxides: A study of the surface properties

    OpenAIRE

    Marinković-Nedučin Radmila P.; Nikolić Aleksandar D.; Jović Branislav; Hadnađev-Kostić Milica S.; Vulić Tatjana J.

    2011-01-01

    The influence of surface properties on the selectivity of the synthesized catalysts was studied, considering that their selectivity towards particular hydrocarbons is crucial for their overall activity in the chosen Fischer- -Tropsch reaction. Magnesium- and iron-containing layered double hydroxides (LDH), with the general formula: [Mg1-xFex(OH)2](CO3)x/2?mH2O, x = = n(Fe)/(n(Mg)+n(Fe)), synthesized with different Mg/Fe ratio and their thermally derived mixed oxides were investigated. M...

  15. Magnetism and electronic structures of novel layered CaFeAs2 and Ca0.75(Pr/La)0.25FeAs2

    Science.gov (United States)

    Huang, Yi-Na; Yu, Xiang-Long; Liu, Da-Yong; Zou, Liang-Jian

    2015-05-01

    The magnetic and electronic properties of the parent material CaFeAs2 of new superconductors are investigated using first-principles calculations. We predict that the ground state of CaFeAs2 is a spin-density-wave (SDW)-type striped antiferromagnet driven by Fermi surface nesting. The magnetic moment around each Fe atom is about 2.1 μB. We also present electronic and magnetic structures of electron-doped phase Ca0.75(Pr/La)0.25FeAs2, the SDW order was suppressed by La/Pr substitution. The As in arsenic layers is negative monovalent and acts as blocking layers enhancing two-dimensional character by increasing the spacing distance between the FeAs layers. This favors strong antiferromagnetic fluctuations mediated pairing, implying higher Tc in Ca0.75(Pr/La)0.25FeAs2 than Ca0.75(Pr/La)0.25Fe2As2.

  16. [VUV spectral properties of CaMgSi2O6 : Eu].

    Science.gov (United States)

    Zhou, Dan; He, Da-wei; Hou, Tao

    2007-05-01

    CaMgSiOs6 : Eu samples were synthesized by a normal solid state reaction using CaCO3, MgO, SiO2 and Eu2O3 as starting materials. The properties of structure, VUV excitation and luminescence under VUV excitation were studied. CaMgSi2O6 : Eu belongs to the monoclinic space group, and the crystal structure does not change as the crystal lattice is doped with Eu ions. The emission spectra of CaMgSi2O6 : Eu3+ have revealed an intense and sharp (611 nm) red color emission from Eu3+ ((5)D0-->(7)F2) transition under 147 nm VUV excitation. The correlative data shows that the concentration quenching occurs when the Eu3+ mole concentration ranges from 0.02 to 0.10 mol. The emission spectra of CaMgSi2O6 : Eu2+ have revealed an intense and sharp (452 nm) blue color emission from Eu2+ (5d-->4f) transition under 172 nm VUV excitation. It can be seen that the intensity of the emission peak increases with increasing H3BO3 concentration. PMID:17655118

  17. Chemistry of the M (M=Fe, Ca, Ba-Se-H2O Systems at 25 °C

    Directory of Open Access Journals (Sweden)

    Fumihiko Hasegawa

    2009-09-01

    Full Text Available The chemistry of the M (M=Fe, Ca, Ba-Se-H2O systems at 25 °C is reviewed based on our previous papers. In this paper, the phase equilibria in the Fe(III-Se(IV-H2O, Ca-Se(IV,VI-H2O and Ba-Se(IV,VI-H2O systems at 25 °C are discussed. Then, the three-stage process for removal of selenium from industrial waste water [Se(IV,VI < 1,500 mg/L] containing sulfuric acid was introduced. This seems to be a promising process for selenium removal from acidic sulfate waste water containing high concentration levels of selenium to below 0.1 mg/L.

  18. 钙铁锌复合强化食醋的研究%Studies on complex Ca,Fe,Zn,supplements of vinegar

    Institute of Scientific and Technical Information of China (English)

    吴正奇; 凌秀菊; 皮志雄

    2001-01-01

    本文对钙铁锌复合强化陈醋进行了初步研究。结果表明,适宜的钙强化剂为氯化钙和醋酸钙;适宜的铁强化剂为柠檬酸铁铵和乳酸亚铁;多种锌强化剂适合陈醋的锌强化。氯化钙、柠檬酸铁铵和氯化锌对陈醋进行钙铁锌复合强化,可取得较好的效果,此时其强化量分别为1000mgCa/100ml,25mgFe/100ml和40mgZn/100ml陈醋。%The complex Ca-Fe-Zn supplements of vinegar were Studies on complexprimarily studied in this paper. The results showed that better Ca-Supplements were CaCl2 and Ca(Ac)2;suitable Fe-supplements were Fe(NH4)2H(C6H5O7)2 and FeC6H10O6;an optimum effect was obtained in complex supplemented vinegar,using cacl2 as Ca-supplement,Fe(NH4)2H(C6H5O7)2 as Fe-supplement and ZnCl2 as Zn-supplement,at the level of 1000mgca/100ml、25mgFep100ml and 40mgZn/100ml vinegar.

  19. Study on Mg/Fe Mixed Oxides Derived from Hydrotalcite as De-SOx Catalyst

    Institute of Scientific and Technical Information of China (English)

    2002-01-01

    A novel class of desulfurization agent derived from hydrotalcite has been developed and its activity for Sox uptake have been investigated. The results showed that the Mg/Fe mixed oxide having high Sox uptake ability at a broad reaction temperature (e.g. 673K ~ 973K). The Mg/Fe ratio of the mixed oxide strongly affect the desulfurization role of the material and it can be used repeatly without much loss of Sox uptake ability.

  20. Spin crossover in liquid (Mg,Fe)O at extreme conditions

    Science.gov (United States)

    Holmström, E.; Stixrude, L.

    2016-05-01

    We use first-principles free-energy calculations to predict a pressure-induced spin crossover in the liquid planetary material (Mg,Fe)O, whereby the magnetic moments of Fe ions vanish gradually over a range of hundreds of GPa. Because electronic entropy strongly favors the nonmagnetic low-spin state of Fe, the crossover has a negative effective Clapeyron slope, in stark contrast to the crystalline counterpart of this transition-metal oxide. Diffusivity of liquid (Mg,Fe)O is similar to that of MgO, displaying a weak dependence on element and spin state. Fe-O and Mg-O coordination increases from approximately 4 to 7 as pressure goes from 0 to 200 GPa. We find partitioning of Fe to induce a density inversion between the crystal and melt, implying separation of a basal magma ocean from a surficial one in the early Earth. The spin crossover induces an anomaly into the density contrast, and the oppositely signed Clapeyron slopes for the crossover in the liquid and crystalline phases imply that the solid-liquid transition induces a spin transition in (Mg,Fe)O.

  1. Ca-Mg kutnahorite and struvite production by Idiomarina strains at modern seawater salinities.

    Science.gov (United States)

    González-Muñoz, María Teresa; De Linares, Concepción; Martínez-Ruiz, Francisca; Morcillo, Fernando; Martín-Ramos, Daniel; Arias, José María

    2008-06-01

    The production of Mg-rich carbonates by Idiomarina bacteria at modern seawater salinities has been investigated. With this objective, four strains: Idiomarina abyssalis (strain ATCC BAA-312), Idiomarina baltica (strain DSM 15154), Idiomarina loihiensis (strains DSM 15497 and MAH1) were used. The strain I. loihiensis MAH1 is a new isolate, identified in the scope of this work. The four moderately halophilic strains precipitated struvite (NH4MgPO4 x 6H2O) crystals that appear encased by small Ca-Mg kutnahorite [CaMg(CO3)2] spheres and dumbbells, which are also regularly distributed in the bacterial colonies. The proportion of Ca-Mg kutnahorite produced by the bacteria assayed ranged from 50% to 20%, and I. abyssalis also produced monohydrocalcite. All precipitated minerals appeared to be related to the bacterial metabolism and, consequently, can be considered biologically induced. Amino acid metabolism resulted in a release of ammonia and CO2 that increase the pH and CO(3)(2-) concentration of the culture medium, creating an alkaline environment that favoured carbonate and struvite precipitation. This precipitation may be also related to heterogeneous nucleation on negatively charged points of biological structures. Because the nature of the organic matrix determines which ion is preferentially adsorbed and, consequently, which mineral phase is formed, the uniquely high content in odd-iso-branched fatty acids of the Idiomarina suggests that their particular membrane characteristics could induce Ca-Mg kutnahorite production. The Ca-Mg kutnahorite, a mineral with a dolomite-ordered structure, production at seawater salinities is noticeable. To date, such precipitation in laboratory cultures, has only been described in hypersaline conditions. It has also been the first time that biomineralization processes have been related to Idiomarina bacteria. PMID:18355891

  2. Gas Metal Arc Welding Using Novel CaO-Added Mg Alloy Filler Wire

    Directory of Open Access Journals (Sweden)

    Minjung Kang

    2016-07-01

    Full Text Available Novel “ECO Mg” alloys, i.e., CaO-added Mg alloys, which exhibit oxidation resistance during melting and casting processes, even without the use of beryllium or toxic protection gases such as SF6, have recently been introduced. Research on ECO Mg alloys is still continuing, and their application as welding filler metals was investigated in this study. Mechanical and metallurgical aspects of the weldments were analysed after welding, and welding behaviours such as fume generation and droplet transfer were observed during welding. The tensile strength of welds was slightly increased by adding CaO to the filler metal, which resulted from the decreased grain size in the weld metal. When welding Mg alloys, fumes have been unavoidable so far because of the low boiling temperature of Mg. Fume reduction was successfully demonstrated with a wire composed of the novel ECO Mg filler. In addition, stable droplet transfer was observed and spatter suppression could be expected by using CaO-added Mg filler wire.

  3. Comparison of Ca2+ and Mg2+ enhancing aerobic granulation in SBR

    International Nuclear Information System (INIS)

    Two sequencing batch reactors (SBRs) were operated to investigate the effect of Ca2+ and Mg2+ augmentation on aerobic granulation. Reactor R1 was augmented with Ca2+ at 40 mg/L, while Mg2+ was added to the reactor R2 with 40 mg/L. Results showed that the reactor R1 had a faster granulation process compared with R2, and the mature granules in R1 showed better physical characteristics. However, the mature granules in R2 had the higher production yield of polysaccharides and proteins, and aerobic granules in R2 experienced a faster substrate biodegradation. Microbial and genetic characteristics in mature granules were analyzed using polymerase chain reaction (PCR) and denaturing gradient gel electrophoresis (DGGE) techniques. The results revealed that Mg2+ addition led to higher microbial diversity in mature granules. In addition, an uncultured bacterium (AB447697) was major specie in R1, and β-proteobacterium was dominant in R2. It can be concluded that Ca2+ had an important effect on physical properties of aerobic granules, while Mg2+ played a key role on biological properties during the sludge granulation.

  4. Comparison of Ca{sup 2+} and Mg{sup 2+} enhancing aerobic granulation in SBR

    Energy Technology Data Exchange (ETDEWEB)

    Liu Lin [School of Forestry, Northeast Forestry University, Harbin 150040 (China); Gao Dawen, E-mail: dawengao@gmail.com [School of Forestry, Northeast Forestry University, Harbin 150040 (China); State Key Laboratory of Urban Water Resource and Environment, 73 Huanghe Rd., Harbin 150090 (China); Zhang Min [School of Forestry, Northeast Forestry University, Harbin 150040 (China); Fu Yuan [State Key Laboratory of Urban Water Resource and Environment, 73 Huanghe Rd., Harbin 150090 (China)

    2010-09-15

    Two sequencing batch reactors (SBRs) were operated to investigate the effect of Ca{sup 2+} and Mg{sup 2+} augmentation on aerobic granulation. Reactor R1 was augmented with Ca{sup 2+} at 40 mg/L, while Mg{sup 2+} was added to the reactor R2 with 40 mg/L. Results showed that the reactor R1 had a faster granulation process compared with R2, and the mature granules in R1 showed better physical characteristics. However, the mature granules in R2 had the higher production yield of polysaccharides and proteins, and aerobic granules in R2 experienced a faster substrate biodegradation. Microbial and genetic characteristics in mature granules were analyzed using polymerase chain reaction (PCR) and denaturing gradient gel electrophoresis (DGGE) techniques. The results revealed that Mg{sup 2+} addition led to higher microbial diversity in mature granules. In addition, an uncultured bacterium (AB447697) was major specie in R1, and {beta}-proteobacterium was dominant in R2. It can be concluded that Ca{sup 2+} had an important effect on physical properties of aerobic granules, while Mg{sup 2+} played a key role on biological properties during the sludge granulation.

  5. Isothermal compression behavior of (Mg,Fe)O using neon as a pressure medium

    OpenAIRE

    Zhuravlev, Kirill K.; J. M. Jackson; Wolf, A. S.; Wicks, J. K.; Yan, J.; S. M. Clark

    2010-01-01

    We present isothermal volume compression behavior of two polycrystalline (Mg,Fe)O samples with FeO = 39 and 78 mol% up to ~90 GPa at 300 K using synchrotron X-ray diffraction and neon as a pressure-transmitting medium. For the iron-rich (Mg_(0.22)Fe_(0.78))O sample, a structural transition from the B1 structure to a rhombohedral structure was observed at 41.6 GPa, with no further indication of changes in structural or compression behavior changes up to 93 GPa. In contrast, a change in the com...

  6. Morphology, magnetic and resonance properties of Fe/MgO multilayers

    Energy Technology Data Exchange (ETDEWEB)

    Garcia-Garcia, A; Algarabel, P A; Ibarra, M R [Instituto de Ciencia de Materiales de Aragon, Universidad de Zaragoza-CSIC 50009 Zaragoza (Spain); Vovk, A [Centro de Fisica da Materia Condensada Unversidade de Lisboa, Campo Grande Ed. C8, 1749-016, Lisboa (Portugal); Strichovanec, P; Pardo, J A; Magen, C [Instituto de Nanociencia de Aragon, Universidad de Zaragoza 50018 Zaragoza (Spain); Golub, V; Salyuk, O, E-mail: ayvovk@fc.ul.pt [Institute of Magnetism NAS of Ukraine, 36-b Vernnadsky blvd., 03142, Kyiv (Ukraine)

    2011-07-06

    Magnetic, resonance and transport properties of Fe(t nm)/MgO(3.0 nm) multilayers prepared by pulsed laser deposition were investigated. Comparison of the data allows conclusions on Fe layers morphology. For t<0.61 nm typical features of granular cermet films in dielectric regime are observed, i.e. high electrical resistance, isotropic magnetoresistance and strong temperature dependence of magnetization. For higher t coalescence of Fe granules occurs and metallic percolation cluster is formed at t{approx}0.81 nm. This is manifested by rapid decrease of films resistance and formation of multipeak ferromagnetic resonance spectra. For t>1.25 nm a continuous coverage of MgO by Fe takes place. However, the morphology of Fe layers is rough. This causes the appearance of magnetostatic resonance modes analogous to those observed for continuous films deposited on embossed surfaces.

  7. Temperature calibration of Mg/Ca ratios in the intermediate water benthic foraminifer Hyalinea balthica

    NARCIS (Netherlands)

    Rosenthal, Y.; Morley, A.; Barras, C.; Katz, M.E.; Jorissen, F.; Reichart, G.-J.; Oppo, D.W.; Linsley, B.K.

    2011-01-01

    Core top samples from Indonesian and northeast Atlantic depth transects were used to calibrate Mg/Ca and δ18O in tests of the calcitic benthic foraminifer Hyalinea balthica to bottom water temperature between 4°C and 13°C. This shallow infaunal species is primarily abundant in neritic to upper bathy

  8. Ca2+ and Mg2+ binding induce conformational stability of Calfumirin-1 from Dictyostelium discoideum

    Indian Academy of Sciences (India)

    Bairagi C Mallick; Sa-Ouk Kang; Suman Jha

    2014-05-01

    The apo-Calfumirin-1 (CAF-1) binds to Ca2+ with high affinity and also to Mg2+ with high positive cooperativity. The thermal unfolding curves of wtCAF-1 monitored at neutral pH by CD spectroscopy are reversible and show different thermal stabilities in the absence or presence of Ca2+ and Mg2+ ions. Metalfree wtCAF-1 shows greater thermal stability than EF-IV mutant protein. We observed that GdnHCl-induced unfolding of apo-wtCAF-1 monitored by CD and fluorescence spectroscopies increases co-operative folding with approximately same C values. Binding of Ca2+ and Mg2+ ions to CAF-1 dramatically altered the fluorescence and CD spectra, indicating metal ion-induced conformational changes both in the wild-type and mutant proteins. The hydrophobic probe, ANS is used to observe alteration in surface hydrophobicity of the protein in different ligation states. In apo-wtCAF-1, the exposed hydrophobic surfaces are able to bind ANS which is in contrast to the unfolded or the metal ions ligated conformations. Isothermal titration calorimetry (ITC) resultsshow two possible independent binding sites of comparable affinity for the metal ions. However, their binding to the EF-IV E helix-loop-F helix mutant apo-protein happens with different affinities. The present study demonstrates that Ca2+ or Mg2+ binding plays a possible role in the conformational stability of the protein.

  9. Effect of Fe on the Elastic Constants of Magnesiowustite [(Mg,Fe)O] at Ambient Conditions and High Pressure

    Science.gov (United States)

    Sinogeikin, S. V.; Reichmann, H. J.; Bass, J. D.; Mackwell, S. J.; Jacobsen, S. D.

    2001-12-01

    Magnesiowustite is a major mineral in the lower mantle of the Earth. While the effect of temperature and pressure on the elasticity of MgO is well constrained, the effect of Fe on the elastic constants and their pressure derivatives is still uncertain, especially for compositions close to the Mg end-member. Here we present the Brillouin spectroscopy measurements of the single-crystal elastic constants of magnesiowustite at ambient conditions ( ~5.8 mol.% Fe) and to high pressures up to about 10 GPa ( ~1.3 mol.% Fe). The single-crystal samples were prepared by Mg:Fe interdiffusion between periclase single crystals and magnesiowustite powders with carefully controlled oxygen fugacity. The Brillouin scattering measurements were performed in platelet symmetric geometry, which significantly increases the accuracy, and is calibrated with respect to standard periclase sample. High-pressure measurements were performed in a large optical opening Merrill-Basset type diamond anvil cell with Methanol-Ethanol-Water mixture as a pressure-transmitting medium. The new results confirm earlier single-crystal ultrasonic measurements (gigahertz interferometry) which indicated that the behavior of the elastic moduli of magnesiowustite are highly nonlinear in Mg-rich end. A pronounced decrease in acoustic velocities with increasing Fe content is especially obvious in samples with Fe contents of <10 mol. %. The pressure derivatives of the elastic moduli of the sample with XFe = 1.3 mol % are equal to those of periclase within the experimental uncertainties, although the Fe content of the sample may be too small to allow compositional trends to be clearly identified.

  10. XRD Analysis on the Fluorescence Material of Sm Doped Si-Ca-Mg System

    Institute of Scientific and Technical Information of China (English)

    HUANG Qing-Ming

    2007-01-01

    Fluorescence material of Sm doped Si-Ca-Mg system was synthesized by using the method of solid phase reaction at high temperature. The phase composition and crystal structure of this material were analyzed with XRD method for its composition and the existence form of Sm atom. We aimed to exactly determine the phase composition of this fluorescence material and the doping position and environment of rare-earth Sm atom in the system because these factors have significant effects on the properties. The analytical results show that the Sm atoms dope in Ca2O26Si6Sm8 lattice in the form of atomic site-occupation in three different space positions with different occupancy rates. Therefore, based on the XRD analytical results, the fluorescence material of Sm doped Si-Ca-Mg system with high performance can be synthesized.

  11. Structural defects analysis versus spin polarized tunneling in Co2FeAl/MgO/CoFe magnetic tunnel junctions with thick MgO barriers

    Science.gov (United States)

    Gabor, M. S.; Tiusan, C.; Petrisor, T.; Petrisor, T.; Hehn, M.; Lu, Y.; Snoeck, E.

    2013-12-01

    We report on spin polarization reduction by incoherent tunneling in single crystal Co2FeAl/MgO/Co50Fe50 magnetic tunnel junctions (MTJs). A large density of misfit dislocations in the Heusler based MTJs has been provided by a thick MgO barrier and its 3.8% lattice mismatch with the Co2FeAl electrode. Our analysis implicates a correlated structural-transport approach. The crystallographic coherence in the real space has been investigated by High Resolution Transmission Electron Microscopy phase analysis. The electronic transport experiments in variable temperature, fitted with a theoretical extended-Glazman-Matveev model, address different levels of the tunneling mechanisms from direct to multi-center hopping. We demonstrate a double impact of dislocations, as extended defects, on the tunneling polarization. Firstly, the breaking of the crystal symmetry destroys the longitudinal and lateral coherence of the propagating Bloch functions. This affects the symmetry filtering efficiency of the Δ1 states across the (001) MgO barriers and reduces the associated effective tunneling polarization. Secondly, dislocations provide localized states within the MgO gap. This determines temperature activated spin-conserving inelastic tunneling through chains of defects which are responsible for the one order of magnitude drop of the tunnel magnetoresistance from low to room temperature.

  12. Isothermal compression behavior of (Mg,Fe)O using neon as a pressure medium

    Energy Technology Data Exchange (ETDEWEB)

    Zhuravlev, Kirill K.; Jackson, J.M.; Wolf, A.S.; Wicks, J.K.; Yan, J.; Clark, S.M. (CIT); (LBNL)

    2012-04-30

    We present isothermal volume compression behavior of two polycrystalline (Mg,Fe)O samples with FeO = 39 and 78 mol% up to {approx}90 GPa at 300 K using synchrotron X-ray diffraction and neon as a pressure-transmitting medium. For the iron-rich (Mg{sub 0.22}Fe{sub 0.78})O sample, a structural transition from the B1 structure to a rhombohedral structure was observed at 41.6 GPa, with no further indication of changes in structural or compression behavior changes up to 93 GPa. In contrast, a change in the compression behavior of (Mg{sub 0.61}Fe{sub 0.39})O was observed during compression at P {ge} 71 GPa and is indicative of a spin crossover occurring in the Fe{sup 2+} component of (Mg{sub 0.61}Fe{sub 0.39})O. The low-spin state exhibited a volume collapse of {approx}3.5%, which is a larger value than what was observed for a similar composition in a laser-heated NaCl medium. Upon decompression, the volume of the high-spin state was recovered at approximately 65 GPa. We therefore bracket the spin crossover at 65 {le} P (GPa) {le} 77 at 300 K (Mg{sub 0.61}Fe{sub 0.39})O. We observed no deviation from the B1 structure in (Mg{sub 0.61}Fe{sub 0.39})O throughout the pressure range investigated.

  13. Kinetics for Formation of TbFe2 in the Ca-Tb4O7-Fe System

    Institute of Scientific and Technical Information of China (English)

    郭广思; 王广太; 隋智通

    2003-01-01

    The pure TbFe2 is a sort of intermetallic compound to produce (TbDy)Fe2. It has important practical meanings to develop a new method for producing pure TbFe2 directly from Tb4O7 with low cost and non-pollution. Based on our previous thermodynamic study on the production of TbFe2 by reduction-diffusion in Ca-Tb4O7-Fe system, kinetics has been further studied in this work. It is confirmed that the product is TbFe2 by means of XRD. The contracting core model is applied. The reactions are found to be diffusion controlled. The apparent activation energy of TbFe2 is 39 kJ*mol-1.

  14. Effect of alloying elements Al and Ca on corrosion resistance of plasma anodized Mg alloys

    Science.gov (United States)

    Anawati, Asoh, Hidetaka; Ono, Sachiko

    2016-04-01

    Plasma anodizing is a surface treatment used to form a ceramic-type oxide film on Mg alloys by the application of a high anodic voltage to create intense plasma near the metal surface. With proper selection of the process parameters, the technique can produce high quality oxide with superior adhesion, corrosion resistance, micro-hardness, wear resistance and strength. The effect of alloying element Al on plasma anodizing process of Mg alloys was studied by comparing the anodizing curves of pure Mg, AZ31, and AZ61 alloys while the effect of Ca were studied on AZ61 alloys containing 0, 1, and 2 wt% Ca. Anodizing was performed in 0.5 M Na3PO4 solution at a constant current density of 200 Am-2 at 25°C. Anodic oxide films with lava-like structure having mix composition of amorphous and crystal were formed on all of the alloys. The main crystal form of the oxide was Mg3(PO4)2 as analyzed by XRD. Alloying elements Al and Ca played role in modifying the plasma lifetime during anodization. Al tended to extend the strong plasma lifetime and therefore accelerated the film thickening. The effect of Ca on anodizing process was still unclear. The anodic film thickness and chemical composition were altered by the presence of Ca in the alloys. Electrochemical corrosion test in 0.9% NaCl solution showed that the corrosion behavior of the anodized specimens depend on the behavior of the substrate. Increasing Al and Ca content in the alloys tended to increase the corrosion resistance of the specimens. The corrosion resistance of the anodized specimens improved significantly about two orders of magnitude relative to the bare substrate.

  15. Cytotoxicity assessment of adipose-derived mesenchymal stem cells on synthesized biodegradable Mg-Zn-Ca alloys.

    Science.gov (United States)

    Fazel Anvari-Yazdi, Abbas; Tahermanesh, Kobra; Hadavi, Seyed Mohammad Mehdi; Talaei-Khozani, Tahereh; Razmkhah, Mahboobeh; Abed, Seyedeh Mehr; Mohtasebi, Maryam Sadat

    2016-12-01

    Magnesium (Mg)-based alloys have been extensively considered as biodegradable implant materials for orthopedic surgery. Mg and its alloys are metallic biomaterials that can degrade in the body and promote new bone formation. In this study, the corrosion behavior and cytotoxicity of Mg-Zn-Ca alloys are evaluated with adipose-derived mesenchymal stem cells (ASCs). Mg-2Zn and Mg-2Zn-xCa (x=1, 2 and 3wt.%) alloys were designated. Mg alloys were analyzed with scanning electron microscopy and potentiodynamic polarization. To understand the in-vitro biocompatibility and cytotoxicity of Mg-2Zn and Mg-2Zn-xCa alloys, ASCs were cultured for 24 and 72h in contact with 10%, 50% and 100% extraction of all alloys prepared in DMEM. Cell cytotoxicity and viability of ASCs were examined by MTT assay. Alloying elements including Zn and Ca improved the corrosion resistance of alloys were compared with pure Mg. The cytotoxicity results showed that all alloys had no significant adverse effects on cell viability in 24h. After 72h, cell viability and proliferation increased in the cells exposed to pure Mg and Mg-2Zn-1Ca extracts. The release of Mg, Zn and Ca ions in culture media had no toxic impacts on ASCs viability and proliferation. Mg-2Zn-1Ca alloy can be suggested as a good candidate to be used in biomedical applications.

  16. What do we know about the evolution of Mg to Ca ratios in seawater?

    Science.gov (United States)

    Broecker, Wally; Yu, Jimin

    2011-09-01

    Although most reconstructions of the evolution of the Mg to Ca ratio in seawater conclude that it has increased during the course of the Cenozoic, they disagree widely regarding the magnitude of this change. On the basis of fluid inclusion and CaCO3 mineralogy observations, the increase was at least threefold. On the basis of Mg content of foraminifera shells it was only a factor of 1.7. A recently published reconstruction based on the Mg content of calcite fillings of voids in ridge flank basalts lends support to the conclusion that the change was severalfold. But as it is very difficult to come up with a plausible geologic scenario which could account for such a large change, we lean toward the smaller estimate based on the magnesium content of foraminifera shells.

  17. Regulatory Effects of Cu, Zn, and Ca on Fe Absorption: The Intricate Play between Nutrient Transporters

    Directory of Open Access Journals (Sweden)

    Nathalie Scheers

    2013-03-01

    Full Text Available Iron is an essential nutrient for almost every living organism because it is required in a number of biological processes that serve to maintain life. In humans, recycling of senescent erythrocytes provides most of the daily requirement of iron. In addition, we need to absorb another 1–2 mg Fe from the diet each day to compensate for losses due to epithelial sloughing, perspiration, and bleeding. Iron absorption in the intestine is mainly regulated on the enterocyte level by effectors in the diet and systemic regulators accessing the enterocyte through the basal lamina. Recently, a complex meshwork of interactions between several trace metals and regulatory proteins was revealed. This review focuses on advances in our understanding of Cu, Zn, and Ca in the regulation of iron absorption. Ascorbate as an important player is also considered.

  18. Creep resistance of Mg-4 %Al-2 %RE-2 %Ca alloy

    Institute of Scientific and Technical Information of China (English)

    XUE Shan; SUN Yang-shan; ZHU Tia-bai; QIANG Li-feng; BAI Jing; ZHOU Jian

    2005-01-01

    The creep resistance of the alloy Mg-4Al-2RE-2Ca(AEC422) and the base alloy AE42 was studied. The results reveal that the precipitated phases of AEC422 consist of Al2 La and Al2Ca by contrast with the precipitated phase Al11 La3 in AE42, which is instable and decomposes to Al2 La and Al at high temperature. Creep resistance of AEC422 is significantly improved compared with that of AE42. The microstructure of AEC422 has no obvious changes after creep test at 175 ℃ and 70 MPa, as compared to that before creep test, indicating that Al2La and Al2Ca have high thermal stability. Especially Al2Ca phase largely increases the strength of the grain boundaries in AEC422, which accounts for the creep resistance improvement.

  19. PEG/CaFe2O4 nanocomposite: Structural, morphological, magnetic and thermal analyses

    Science.gov (United States)

    Khanna, Lavanya; Verma, Narendra K.

    2013-10-01

    The coating of Polyethylene Glycol (PEG) on calcium ferrite (CaFe2O4) nanoparticles has been reported in the present study. The X-ray diffraction pattern revealed the formation of orthorhombic structure of bare CaFe2O4 nanoparticles, which was also retained after the PEG coating, along with additional characteristic peaks of PEG at 19° and 23°. The rings of CaFe2O4 nanoparticles were identified by the selected area electron diffraction pattern. The characteristic bands of PEG as observed in its Fourier transform infrared spectrum were also present in PEG coated CaFe2O4 nanoparticles, hence confirming its presence. In the thermal gravimetric studies, the complete thermal decomposition of PEG occurred in a one step process, but in case of PEG coated CaFe2O4 nanoparticles, the decomposition took place at a higher temperature owing to the formation of covalent bonds of PEG with CaFe2O4 nanoparticles. The presence of PEG on CaFe2O4 nanoparticles, spherical formation of PEG coated CaFe2O4 nanoparticles and reduced agglomeration in the CaFe2O4 nanoparticles were revealed by high resolution transmission electron microscope, transmission electron microscope and scanning electron microscope studies, respectively. In vibrating sample magnetometer analysis, both bare as well as coated CaFe2O4 nanoparticles exhibited superparamagnetic behavior. However, a drop in the magnetic saturation value was observed from 36.76 emu/g for CaFe2O4 nanoparticles to 6.74 emu/g for PEG coated CaFe2O4 nanoparticles, due to the formation of magnetically dead layer of PEG. In ZFC and FC analyses, superparamagnetic behavior with blocking temperature for bare and coated nanoparticles has been observed at ∼40 K and ∼60 K, respectively. The increase in the blocking temperature is attributed to the increase in the particle size after PEG coating.

  20. Structural and hydrogen storage capacity evolution of Mg2FeH6 hydride synthesized by reactive mechanical alloying

    Institute of Scientific and Technical Information of China (English)

    LI Song-lin(李松林); R.A.Varin

    2004-01-01

    Mg-based metal hydrides are promising as hydrogen storage materials for fuel cell application. In this work, Mg2 FeH6 complex hydride phase was synthesized by controlled reactive ball milling of 2Mg-Fe (atomic ratio)powder mixture in H2. Mg2 FeH6 is confirmed to be formed via the following three stages: formation of MgH2 via the reaction of Mg with H2, incubation stage and formation of Mg2 FeH6 by reaction of fully refined MgH2 and Fe.The incubation stage is characterized by no traces of Mg or hydride crystalline phase by XRD. On the other hand,Mg is observed uniformly distributed in the milled powder by SEM-EDS. Also, almost the same amount of H2 as the first stage is detected stored in the powders of the second stage by DSC and TGA.

  1. Giant strain control of magnetoelectric effect in Ta|Fe|MgO.

    Science.gov (United States)

    Odkhuu, Dorj

    2016-01-01

    The exploration of electric field controlled magnetism has come under scrutiny for its intriguing magnetoelectric phenomenon as well as technological advances in spintronics. Herein, the tremendous effect of an epitaxial strain on voltage-controlled perpendicular magnetic anisotropy (VPMA) is demonstrated in a transition-metal|ferromagnet|MgO (TM|FM|MgO) heterostructure from first-principles electronic structure computation. By tuning the epitaxial strain in Ta|Fe|MgO as a model system of TM|FM|MgO, we find distinctly different behaviours of VPMA from V- to Λ-shape trends with a substantially large magnetoelectric coefficient, up to an order of 10(3) fJV(-1)m(-1). We further reveal that the VPMA modulation under strain is mainly governed by the inherently large spin-orbit coupling of Ta 5d-Fe 3d hybridized orbitals at the TM|FM interface, although the Fe 3d-O 2p hybridization at the FM|MgO interface is partly responsible in determining the PMA of Ta|Fe|MgO. These results suggest that the control of epitaxial strain enables the engineering of VPMA, and provides physical insights for the divergent behaviors of VPMA and magnetoelectric coefficients found in TM|FM|MgO experiments. PMID:27597448

  2. Giant strain control of magnetoelectric effect in Ta|Fe|MgO

    Science.gov (United States)

    Odkhuu, Dorj

    2016-01-01

    The exploration of electric field controlled magnetism has come under scrutiny for its intriguing magnetoelectric phenomenon as well as technological advances in spintronics. Herein, the tremendous effect of an epitaxial strain on voltage-controlled perpendicular magnetic anisotropy (VPMA) is demonstrated in a transition-metal|ferromagnet|MgO (TM|FM|MgO) heterostructure from first-principles electronic structure computation. By tuning the epitaxial strain in Ta|Fe|MgO as a model system of TM|FM|MgO, we find distinctly different behaviours of VPMA from V- to Λ-shape trends with a substantially large magnetoelectric coefficient, up to an order of 103 fJV−1m−1. We further reveal that the VPMA modulation under strain is mainly governed by the inherently large spin-orbit coupling of Ta 5d–Fe 3d hybridized orbitals at the TM|FM interface, although the Fe 3d–O 2p hybridization at the FM|MgO interface is partly responsible in determining the PMA of Ta|Fe|MgO. These results suggest that the control of epitaxial strain enables the engineering of VPMA, and provides physical insights for the divergent behaviors of VPMA and magnetoelectric coefficients found in TM|FM|MgO experiments. PMID:27597448

  3. Ca and Mg isotope constraints on the origin of Earth's deepest δ13 C excursion

    Science.gov (United States)

    Husson, Jon M.; Higgins, John A.; Maloof, Adam C.; Schoene, Blair

    2015-07-01

    Understanding the extreme carbon isotope excursions found in carbonate rocks of the Ediacaran Period (635-541 Ma), where δ13 C of marine carbonates (δ13 Ccarb) reach their minimum (- 12 ‰) for Earth history, is one of the most vexing problems in Precambrian geology. Known colloquially as the 'Shuram' excursion, the event has been interpreted by many as a product of a profoundly different Ediacaran carbon cycle. More recently, diagenetic processes have been invoked, with the very negative δ13 C values of Ediacaran carbonates explained via meteoric alteration, late-stage burial diagenesis or growth of authigenic carbonates in the sediment column, thus challenging models which rely upon a dramatically changing redox state of the Ediacaran oceans. Here we present 257 δ 44 / 40 Ca and 131 δ26 Mg measurements, along with [Mg], [Mn] and [Sr] data, from carbonates of the Ediacaran-aged Wonoka Formation (Fm.) of South Australia to bring new isotope systems to bear on understanding the 'Shuram' excursion. Data from four measured sections spanning the basin reveal stratigraphically coherent trends, with variability of ∼1.5‰ in δ26 Mg and ∼1.2‰ in δ 44 / 40 Ca. This Ca isotope variability dwarfs the 0.2-0.3 ‰ change seen coeval with the Permian-Triassic mass extinction, the largest recorded in the rock record, and is on par with putative changes in the δ 44 / 40 Ca value of seawater seen over the Phanerozoic Eon. Changes in both isotopic systems are too large to explain with changes in the isotopic composition of Ca and Mg in global seawater given modern budgets and residence times, and thus must be products of alternative processes. Relationships between δ 44 / 40 Ca and [Sr] and δ26 Mg and [Mg] are consistent with mineralogical control (e.g., aragonite vs. calcite, limestone vs. dolostone) on calcium and magnesium isotope variability. The most pristine samples in the Wonoka dataset, preserving Sr concentrations (in the 1000s of ppm range) and δ 44 / 40

  4. Optical properties of Cr3+ and Nd3+ions in GGG(Ca,Zr) and GGG(Ca,Mg,Zr)

    International Nuclear Information System (INIS)

    The discovery of Cr3+ - and Nd3+ -doped oxide garnets such as gadolinium scandium gallium garnet (GSGG) having efficiencies greater than Nd:YAG has led to their proposed use in high-average-power laser systems. The high-stimulated-emission cross section for Nd3+ in this material limits the size of the active medium, which will impose limititations on the maximum power output per laser active component. If the Nd3+ cross section in this material could be reduced, while keeping other parameters constant, the components could be scaled to larger apertures. Materials which may satisfy these requirements are gadolinium gallium garnet (GGG), whose structure is modified by calcium and zirconium GGG(Ca,Zr) or calcium, magnesium, and zirconcium GGG(Ca,Mg,Zr). These crystals were originally synthesized for use as magnetic bubble memory substrates. When doped with Nd3+, the large degree of inhomogeneous broadening evident in the emission spectrum indicates that many nonequivalent Nd3+ sites exist. These nonequivalent sites are due to the many different positions the charge-compensated ion pairs (Ca-Zr) or (Mg-Zr) may assume in the lattice. This inhomogeneous broadening lowers the stimulated emission cross section, yet leaves most other optical properties relatively unchanged compared with GGG. These materials can also be doped with Cr3+ to sensitize efficiently the Nd3+ luminescence, as is done in GSGG. Laser performance of the Cr:Nd:GGG(Ca,Zr) material exceeds that for Nd:YAG. Further improvements in performance can be expected when better optical quality in the materials is achieved

  5. Phonons and stability of infinite-layer iron oxides SrFeO2 and CaFeO2

    Science.gov (United States)

    Gupta, M. K.; Mittal, R.; Chaplot, S. L.; Tassel, Cédric; Kageyama, Hiroshi; Tomiyasu, K.; Taylor, Jon

    2016-09-01

    We present detailed ab-initio lattice dynamical analysis of the Fe-O infinite-layer compounds CaFeO2 and SrFeO2 in various magnetic configurations. These indicate strong spin-phonon coupling in SrFeO2 in contrast to that in case of CaFeO2. From our ab-initio calculations in SrFeO2 as a function of volume, we suggest that the distortion in SrFeO2 above 300 K is similar to that in CaFeO2 at ambient conditions. The distortion of the planer structure of CaFeO2 involves doubling of the planer unit cell that may be usually expected to be due to a soft phonon mode at the M-point (1/2 1/2 0). However, our ab-initio calculations show quite unusually that all the M-point (1/2 1/2 0) phonons are stable, but two stable M3+ and M2- modes anharmonically couple with an unstable Bu mode at the zone center and lead to the cell doubling and the distorted structure. Magnetic exchange interactions in both the compounds have been computed on the basis of the ideal planar structure (P4/mmm space group) and with increasing amplitude of the Bu phonon mode. These reveal that the magnetic exchange interactions reduce significantly with increasing distortion. We have extended the ab-initio phonon calculation to high pressures, which reveal that, above 20 GPa of pressure, the undistorted planer CaFeO2 becomes dynamically stable. We also report computed phonon spectra in SrFeO3 that has a cubic structure, which is useful to understand the role of the difference in geometry of oxygen atoms around the Fe atom with respect to planer SrFeO2. Finally, powder neutron inelastic scattering experiments on SrFeO2 have also been performed at temperatures from 5 K to 353 K in the antiferromagnetic phase. The 5-K data are compared to the ab-initio calculations.

  6. Chelate titrations of Ca(2+) and Mg(2+) using microfluidic paper-based analytical devices.

    Science.gov (United States)

    Karita, Shingo; Kaneta, Takashi

    2016-06-14

    We developed microfluidic paper-based analytical devices (μPADs) for the chelate titrations of Ca(2+) and Mg(2+) in natural water. The μPAD consisted of ten reaction zones and ten detection zones connected through narrow channels to a sample zone located at the center. Buffer solutions with a pH of 10 or 13 were applied to all surfaces of the channels and zones. Different amounts of ethylenediaminetetraacetic acid (EDTA) were added to the reaction zones and a consistent amount of a metal indicator (Eriochrome Black T or Calcon) was added to the detection zones. The total concentrations of Ca(2+) and Mg(2+) (total hardness) in the water were measured using a μPAD containing a buffer solution with a pH of 10, whereas only Ca(2+) was titrated using a μPAD prepared with a potassium hydroxide solution with a pH of 13. The μPADs permitted the determination of Ca(2+) and Mg(2+) in mineral water, river water, and seawater samples within only a few minutes using only the naked eye-no need of instruments.

  7. Chelate titrations of Ca(2+) and Mg(2+) using microfluidic paper-based analytical devices.

    Science.gov (United States)

    Karita, Shingo; Kaneta, Takashi

    2016-06-14

    We developed microfluidic paper-based analytical devices (μPADs) for the chelate titrations of Ca(2+) and Mg(2+) in natural water. The μPAD consisted of ten reaction zones and ten detection zones connected through narrow channels to a sample zone located at the center. Buffer solutions with a pH of 10 or 13 were applied to all surfaces of the channels and zones. Different amounts of ethylenediaminetetraacetic acid (EDTA) were added to the reaction zones and a consistent amount of a metal indicator (Eriochrome Black T or Calcon) was added to the detection zones. The total concentrations of Ca(2+) and Mg(2+) (total hardness) in the water were measured using a μPAD containing a buffer solution with a pH of 10, whereas only Ca(2+) was titrated using a μPAD prepared with a potassium hydroxide solution with a pH of 13. The μPADs permitted the determination of Ca(2+) and Mg(2+) in mineral water, river water, and seawater samples within only a few minutes using only the naked eye-no need of instruments. PMID:27181645

  8. Perpendicular magnetic anisotropy in Ta|Co40Fe40B20|MgAl2O4 structures and perpendicular CoFeB|MgAl2O4|CoFeB magnetic tunnel junction

    KAUST Repository

    Tao, B. S.

    2014-09-08

    Magnetic properties of Co40Fe40B20(CoFeB) thin films sandwiched between Ta and MgAl2O4layers have been systematically studied. For as-grown state, Ta/CoFeB/MgAl2O4structures exhibit good perpendicular magnetic anisotropy (PMA) with interface anisotropy Ki=1.22erg/cm2, which further increases to 1.30erg/cm2after annealing, while MgAl2O4/CoFeB/Ta multilayer shows in-plane magnetic anisotropy and must be annealed in order to achieve PMA. For bottom CoFeB layer, the thickness window for PMA is from 0.6 to 1.0nm, while that for top CoFeB layer is between 0.8 and 1.4nm. Perpendicular magnetic tunnel junctions (p-MTJs) with a core structure of CoFeB/MgAl2O4/CoFeB have also been fabricated and tunneling magnetoresistance ratio of about 36% at room temperature and 63% at low temperature have been obtained. The intrinsic excitations in the p-MTJs have been identified by inelastic electron-tunneling spectroscopy.

  9. Mechanically - induced disorder in CaFe2As2: a 57Fe Mössbauer study

    Science.gov (United States)

    Ma, Xiaoming; Ran, Sheng; Canfield, Paul C.; Bud'Ko, Sergey L.

    57 Fe Mössbauer spectroscopy was used to study an extremely pressure and strain sensitive compound, CaFe2As2, with different degrees of strain introduced by grinding and annealing. At the base temperature, in the antiferromagnetic/orthorhombic phase, compared to a sharp sextet Mössbauer spectrum of single crystal CaFe2As2, which is taken as an un-strained sample, an obviously broadened sextet and an extra doublet were observed for ground CaFe2As2 powders with different degrees of strain. The Mössbauer results suggest that the magnetic phase transition of CaFe2As2 can be inhomogeneously suppressed by the grinding induced strain to such an extent that the antiferromagnetic order in parts of the grains forming the powdered sample remain absent all the way down to 4.6 K. However, strain has almost no effect on the temperature dependent hyperfine magnetic field in the grains with magnetic order. The quadrupole shift in the magnetic phase approachs zero with increasing degrees of strain, indicating that the strain reduces the average lattice asymmetry at Fe atom position. Supported by US DOE under the Contract No. DE-AC02-07CH11358 and by the China Scholarship Council.

  10. Chemistry of the M (M=Fe, Ca, Ba)-Se-H2O Systems at 25 °C

    OpenAIRE

    Fumihiko Hasegawa; Tadahisa Nishimura; Ryosuke Hata

    2009-01-01

    The chemistry of the M (M=Fe, Ca, Ba)-Se-H2O systems at 25 °C is reviewed based on our previous papers. In this paper, the phase equilibria in the Fe(III)-Se(IV)-H2O, Ca-Se(IV,VI)-H2O and Ba-Se(IV,VI)-H2O systems at 25 °C are discussed. Then, the three-stage process for removal of selenium from industrial waste water [Se(IV,VI) < 1,500 mg/L] containing sulfuric acid was introduced. This seems to be a promising process for selenium removal from acidic sulfate waste water containing high con...

  11. Hydrogen Storage Properties of Ca3-x Mg2+xNi13 Alloys%Ca3-xMg2+xNi13合金的储氢性能

    Institute of Scientific and Technical Information of China (English)

    张庆安; 赵刚; 斯庭智; 庞刚

    2009-01-01

    为了弄清Mg含量对Ca3Mg2Ni13型化合物结构参数和储氢性能的影响,利用X射线衍射研究了Ca3-xMg2+x,Ni13(x=0.5,1.0和1.5)合金的相结构,并采用Sieverts型设备测量了其P-C-T曲线.研究表明,Mg在Ca3Mg2Ni13型化合物中的最大固溶度接近于Ca1.5MgNi13合金中的Mg含量.固溶的Mg含量增加导致化合物点阵常数减小,这可以有效地改善吸放氢热力学性能,其中Ca2Mg3Ni13吸、放氢的焓变分别为-28,30 kJ/mol H2.此外,Ca2Mg3Ni13在吸放氢循环过程中不发生氢致非晶化和氢致分解,因而具有良好的循环稳定性.%To understand the effects of Mg content on the structural parameters and hydrogen storage properties of Ca3Mg2Ni13-type compound, the phase structures of the Ca3-xMg2+xNi13 (x =0.5, 1.0 and 1.5 ) alloys were investigated by X-ray diffraction (XRD) and their pressure-composition isotherms (P-C-T curves) were measured with a Sieverts-type apparatus. The results indicate that the maximum solid solubility of Mg in the Ca3Mg2Ni13-type compound is close to the Mg content of Ca1.5 Mg3.5 Ni13 alloy. The increase of Mg content leads to the decrease in the lattice parameters of Ca3 Mg2Ni13-type compound, which may effectively improve the thermodynamics of hydrogen absorption-desorption. The enthalpy changes for the hydrogen absorption and desorption of Ca2Mg3Ni13 are -28 and 30 kJ/mol H2, respectively. Moreover, Ca2Mg3Ni13 shows good cycling stability because the hydrogen-induced amorphization and decomposition do not occur during hydrogen absorption-desorption cycles.

  12. The local structure of Ca-Na pyroxenes. 2-Xanes studies at the Mg and A1 K edges

    Energy Technology Data Exchange (ETDEWEB)

    Mottana, A. [Rome Univ. Roma Tre, Rome (Italy). Dipt. di Scienze Geologiche; Murata, T. [Kyoto University of Education, Kyoto (Japan). Dept. of Physics; Marcelli, A. [Istituto Nazionale di Fisica Nucleare, Frascati, RM (Italy). Laboratori Nazionali di Frascati; Wu, Z.Y. [Istituto Nazionale di Fisica Nucleare, Frascati, RM (Italy). Laboratori Nazionali di Frascati]|[Laboratoire Piere Suee, Gif-sur Yvette Cedex, (France); Cibin, G. [Istituto Nazionale di Fisica Nucleare, Frascati, RM (Italy). Laboratori Nazionali di Frascati; Paris, E. [Camerino Univ., Camerino, MC (Italy). Dipt. di Scienze della Terra; Giuli, G. [Camerino Univ., Camerino, MC (Italy). Dipt. di Scienze della Terra]|[Florence Univ., Florence (Italy). Dipt. di Scienze della Terra

    1999-07-01

    X-ray absorption spectra at the Mg and A1 K edges have been recorded on synthetic end member diopside (Di) and jadeite (Jd) and on a series of natural Fe-poor Ca-Na clinopyroxenes compositionally straddling the Jd-Di join. The spectra of C2/c members of the series (C-omphacites) are different from having P2/n symmetry (P-omphacites). Differences can be explained by theoretical spectra calculated via the multiple-scattering formalism on atomic clusters with at least 89 atoms, extending to a. 0.62 nm away from the Mg viz. A1 absorber: Xanes detects in these systems medium- rather than short-range order-disorder relationships. Near-edge features of C-omphacites reflect the single-type of octahedral arrangement of the back scattering nearest-neighbours (six O atoms) around the absorber (Mg resp. A1) at the centre of the cluster (site M1). Others arise again from medium-range order. P-omphacites show more complicated spectra than C-omphacites. Their additional features reflect the increased local disorder around the probed atom (Mg resp. A1) induced by the two alternative M1, M11 configurations of the six O atoms forming the first co-ordination spheres. Mg and A1 are confirmed to be preferentially partitioned in the M1 resp. M11 site of the P-omphacite crystal structure, however never exclusively, but in a ratio close to 85:15 (plus or minus 10%) that implies a certain degree of local disorder. Changes in the relative heights of some prominent features are more evident in the A1 than in the Mg K-edge spectra. They are diagnostic to qualitatively distinguish C-from P-omphacites.

  13. Giant strain control of magnetoelectric effect in Ta/Fe/MgO

    CERN Document Server

    Odkhuu, Dorj

    2016-01-01

    The exploration of electric field controlled magnetism has come under scrutiny for its intriguing magnetoelectric phenomenon as well as technological advances in spintronics. Herein, the tremendous effect of an epitaxial strain on voltage-controlled perpendicular magnetic anisotropy (VPMA) is demonstrated in a transition-metal/ferromagnet/MgO (TM/FM/MgO) heterostructure from first-principles electronic structure computation. By tuning the epitaxial strain in Ta/Fe/MgO as a model system of TM/FM/MgO, we find distinctly different behaviours of VPMA from V- to {\\Lambda}-shape trends with a substantially large magnetoelectric coefficient, up to an order of 1000 fJ/Vm. We further reveal that the VPMA modulation under strain is mainly governed by the inherently large spin-orbit coupling of Ta 5d-Fe 3d hybridized orbitals at the TM/FM interface, although the Fe 3d-O 2p hybridization at the FM/MgO is partly responsible in determining the PMA of Ta/Fe/MgO. These results suggest that the control of epitaxial strain ena...

  14. Determination of the percolation threshold in Fe/MgO magnetic granular multilayers

    Energy Technology Data Exchange (ETDEWEB)

    Garcia-GarcIa, A; Algarabel, P A; De Teresa, J M; Morellon, L; Ibarra, M R [Instituto de Ciencia de Materiales de Aragon, Universidad de Zaragoza-CSIC, 50009-Zaragoza (Spain); Vovk, A; Strichovanec, P; Pardo, J A; Magen, C, E-mail: vovk@imag.kiev.u [Instituto de Nanociencia de Aragon, Universidad de Zaragoza, 50018-Zaragoza (Spain)

    2010-02-10

    The evolution of the morphology, magnetic and transport properties of Fe(t nm)/MgO(3.0 nm) multilayers with respect to the nominal metallic layer thickness was investigated. A comparison with existing experimental data on discontinuous metal-insulator multilayers, ultrathin epitaxial Fe films on MgO substrates and granular cermet films is made. It is confirmed that the deposition conditions and the material composition play a crucial role in the percolation process. Nominal thicknesses of Fe layers at which an infinite metallic cluster is formed and the conditions for continuous Fe coverage were determined. Different methods of percolation threshold detection were analysed. We show that investigation of the temperature dependence of resistance in nanostructures could lead to an overestimation of the percolation threshold value, while magnetic measurements alone could lead to its underestimation.

  15. Formation of Secondary Ca-Fe-Rich Assemblages in CV Chondrites

    Science.gov (United States)

    Ganino, C.; Libourel, G.

    2016-08-01

    Chondrites have multiplied evidences for metasomatic processes during the early solar system formation. Diversity in secondary Ca-Fe silicate provides information on T-X conditions and the open/closed-system behavior.

  16. (CaFeAs)10PtzAs8 superconductors and related compounds

    International Nuclear Information System (INIS)

    The main topic of this dissertation is the identification of new compounds, structure determination, and substitution dependent investigation of properties in this new branch of the family of iron arsenide superconductors (Chapter 2). Chapter 2.1 presents the identification of the superconducting compounds and the corresponding structure elucidation identifying two dif-ferent species (CaFeAs)10Pt3As8 and (CaFeAs)10Pt4As8 in this family (abbreviated as 1038 and 1048 according to their stoichiometry). However, a closer look revealed a more challenging structure chemistry which is covered in Chapter 2.2. The following two Chapters 2.3 and 2.4 are devoted to (CaFeAs)10Pt3As8 and more detailed investigations on this parent compound of the new superconductor family. Furthermore, transition metal substitution series (CaFe1-xMxAs)10Pt3As8 were synthesized to investigate the resemblance to model systems Ba(Fe1-xMx)2Asx and LaO(Fe1-xMx)As in the scope of structural changes and superconductivity as described in Chapter 2.5. Initially amazing differences in superconducting properties com-paring 1038 and 1048 compounds are analyzed in Chapter 2.6 establishing an universal dop-ing model in the (CaFe1-xMxAs)10PtzAs8 family. Additionally substituent dependent properties upon rare earth substitution in electron doped (Ca1-yREyFeAs)10Pt3As8 are investigated in Chapter 2.7, while a detailed study of superconducting properties and magnetism in (Ca1-yLayFeAs)10Pt3As8 by the local μSR technique is presented in Chapter 2.8. In Chapter 2.9 a comparison of direct and electron doping is discussed based on codoping experiments in (Ca1-yLayFe1-xPtxAs)10Pt3As8 and (CaFe1-xPtxAs)10Pt4As8. Finally, in Chapter 2.10 electron doping in stoichiometric 1048 is studied by charge compensation experiments in (Ca1-yNayFeAs)10Pt4As8. Chapter 3 is dedicated to a new family of calcium iron arsenides featuring frameworks of interconnected iron arsenide layers. The first subchapter presents the structure

  17. Tunnel anisotropic magnetoresistance in CoFeB|MgO|Ta junctions

    Energy Technology Data Exchange (ETDEWEB)

    Hatanaka, S.; Miwa, S., E-mail: miwa@mp.es.osaka-u.ac.jp; Matsuda, K.; Nawaoka, K.; Tanaka, K.; Morishita, H.; Goto, M.; Mizuochi, N.; Shinjo, T.; Suzuki, Y. [Graduate School of Engineering Science, Osaka University, 1-3 Machikaneyama, Toyonaka, Osaka 560-8531 (Japan)

    2015-08-24

    We found that CoFeB|MgO|Ta tunnel junctions exhibit tunnel anisotropic magnetoresistance (TAMR) at room temperature. The tunnel junctions exhibit positive magnetoresistance with the application of a magnetic field normal to the film plane. The dependencies on the applied magnetic field angle and MgO thickness reveal that the magnetoresistance originates from the TAMR, caused by the spin polarization and the spin-orbit interaction at the CoFeB|MgO interface. We also found that the TAMR can be used to detect ferromagnetic resonance in the CoFeB. This detection method could be useful for the characterization of nanomagnets that are free from the spin-transfer effect and the stray field of a reference layer, unlike conventional magnetic tunnel junctions.

  18. Preparation and characterization of Mn/MgAlFe as transfer catalyst for SOx abatement

    Institute of Scientific and Technical Information of China (English)

    Ruiyu Jiang; Honghong Shan; Chunyi Li; Chaohe Yang

    2011-01-01

    A series of manganese-promoted MgAlFe mixed oxides,used as sulfur transfer catalysts,were prepared by acid-processed gelatin method and characterized by TGA-DTA,XRD,N2 adsorption-desorption and FT-IR techniques.It was found that the sulfur transfer catalysts with 0.5-3.0 wt% manganese showed its good dispersion in the precursor.The novel Mn/MgAlFe catalysts with 0.5-5.0 wt% manganese oxide showed a high oxidative adsorption rate and sulfur adsorption capacity,and 5.0 wt% Mn/MgAlFe sample was superior to the others for SO2 removal.Moreover,the presence of CO had no obvious effect on the adsorption activity of sulfur transfer catalysts for SO2 uptake.

  19. Interface study of FeMgOFe magnetic tunnel junctions using 3D Atom Probe

    CERN Document Server

    Mazumder, B; Vella, A; Vurpillot, F; Deconihout, B

    2011-01-01

    A detailed interface study was conducted on a Fe/MgO/Fe system using laser assisted 3D atom probe. It exhibits an additional oxide formation at the second interface of the multilayer structure independent of laser wavelength, laser fluence and the thickness of the tunnel barrier. We have shown with the help of simulation that this phenomena is caused by the field evaporation of two layers having two different evaporation

  20. Ethylbenzene dehydrogenation over FeOx/(Mg,Zn)(Al)O catalysts derived from hydrotalcites: Role of MgO as basic sites

    KAUST Repository

    Balasamy, Rabindran J.

    2011-05-01

    A series of Mg3-xZnxFe0.5Al0.5 mixed oxide catalysts derived from hydrotalcites were tested in the ethylbenzene dehydrogenation to styrene in He atmosphere at 550 °C. The catalysts were prepared by coprecipitation from the nitrates of metal components followed by calcination to mixed oxides at 550 °C. A part of Mg2+ in Mg 3Fe0.5Al0.5 mixed oxide was replaced with Zn2+ to test the effect of MgO as the support. The mixed oxides were composed of periclase and spinel-type compounds with a high surface area of 100-180m2gcat-1. Mössbauer and XPS measurements indicated the presence of Fe3+ on the catalysts and H2-TPR measurement suggested that the dehydrogenation reaction is catalyzed by the reduction-oxidation between Fe3+/Fe2+. The activity of Mg3-xZnxFe0.5Al0.5 mixed oxide decreased with increasing x, indicating an important role of MgO on the activity. Both CO2-TPD measurements as well as IR measurements of adsorbed CO2 clearly indicated the presence of basic sites of Mg 2+O2- on the catalysts. It seems that the combination of Mg2+O2- and Fe3+ was essential for the catalytic activity. It is concluded that the surface base sites generated on O2- bound Mg2+ near Fe3+ sites are responsible for H+-abstraction; the dehydrogenation of ethylbenzene was initiated by the H+ abstraction on Mg2+O2- basic sites, and accelerated by the reduction-oxidation of Fe3+/Fe2+ active species. © 2011 Elsevier B.V.

  1. The application of NAA and ASS techniques on determination of daily dietary intake of Ca, Fe and Zn in school-aged children in Bandung city

    International Nuclear Information System (INIS)

    Micronutrient elements contained in foods have an important role in the metabolism process in human body, so micronutrient element deficiencies can cause health problems and chronic diseases. Children are the population that generally more vulnerable in suffering of micronutrient deficiencies which have significant affects on their growth and development. Micronutrient deficiencies have long been happening in Indonesia but were not solved and the nutrition status data of children in Indonesia is still limited. Therefore, through this research the daily dietary intake of Ca, Fe and Zn micronutrient in school-aged children has been determined. Food sampling was carried out using duplicate diet method and the Fe and Zn elements were determined using Neutron Activation Analysis (NAA) while the Ca was determined using Atomic Absorption Spectrometry (AAS) method. The analysis results show the range concentration of Ca, Fe and Zn in food samples obtained were 307-1991; 10,1-95,5 and 11,9-29,4 mg/kg respectively, while the average of Ca, Fe and Zn daily intake were 228; 9.3 and 4.6 mg/day and they were only fulfill 28%, 74% and 39% of AKG (adequate value of nutrient). The Ca, Fe and Zn deficiencies were observed on school-aged children in Bandung. This result is expected to give description and information to the authority on planning and policies taking as efforts in quality improvement of the next human resources. (author)

  2. Microstructure, biocorrosion and cytotoxicity evaluations of rapid solidified Mg-3Ca alloy ribbons as a biodegradable material

    Energy Technology Data Exchange (ETDEWEB)

    Gu, X N; Zhou, W R; Zheng, Y F [State Key Laboratory for Turbulence and Complex System and Department of Advanced Materials and Nanotechnology, College of Engineering, Peking University, Beijing 100871 (China); Li, X L [Center for Biomedical Materials and Engineering, Harbin Engineering University, Harbin 150001 (China); Cheng, Y, E-mail: yfzheng@pku.edu.c [Center for Biomedical Materials and Tissue Engineering, Academy for Advanced Interdisciplinary Studies, Peking University, Beijing 100871 (China)

    2010-06-01

    Rapidly solidified (RS) Mg-3Ca alloy ribbons were prepared by the melt-spinning technique at different wheel rotating speeds (15 m s{sup -1}, 30 m s{sup -1} and 45 m s{sup -1}) with the as-cast Mg-3Ca alloy ingot as a raw material. The RS45 Mg-3Ca alloy ribbon showed a much more fine grain size feature (approximately 200-500 nm) in comparison to the coarse grain size (50-100 {mu}m) of the original as-cast Mg-3Ca alloy ingot. The corrosion electrochemical tests in simulated body fluid indicated that the corrosion rate of the as-cast Mg-3Ca alloy was strongly reduced by the RS procedure and tended to be further decreased with increasing wheel rotating speeds (1.43 mm yr{sup -1} for RS15, 0.94 mm yr{sup -1} for RS30 and 0.36 mm yr{sup -1} for RS45). The RS Mg-3Ca alloy ribbons showed more uniform corrosion morphology compared with the as-cast Mg-3Ca alloy after polarization. The cytotoxicity evaluation revealed that the three experimental as-spun Mg-3Ca alloy ribbon extracts did not induce toxicity to the L-929 cells, whereas the as-cast Mg-3Ca alloy ingot extract did. The L-929 cells showed more improved adhesion on the surfaces of the three as-spun Mg-3Ca alloy ribbons than that of the as-cast Mg-3Ca alloy ingot.

  3. Supercondcuting properties in MgB2/Fe wires prepared by PIT method

    Institute of Scientific and Technical Information of China (English)

    YAN Guo; FENG Yong; FU Baoquan; LIU Chunfang; JI Ping; ZHANG Pingxiang; ZHOU Lian

    2003-01-01

    The MgB2 formation was analyzed physically and chemically and the MgB2/Fe wires were fabricated by powder in tube (PIT) technology. The microstructureof MgB2 in wires was studied by the scanning electrical microscope (SEM), whichshows a good connection of grains and the size of MgB2 grain is 1-3μm. The results of Jc measured by the standard four probes method show that Jc value reaches 6.1×104 A/cm2 at 20 K in self field.

  4. Ca. 2.7 Ga ferropicritic magmatism: A record of Fe-rich heterogeneities during Neoarchean global mantle melting

    Science.gov (United States)

    Milidragovic, Dejan; Francis, Don

    2016-07-01

    were depleted in Ni relative to melts of pyrolitic peridotite; suggesting they were derived from garnet-free peridotite sources. Neodymium isotopic evidence indicates that the source of alkaline ferropicrites was metasomatically enriched shortly before magma generation (⩽3.0 Ga), but the subalkaline ferropicrites do not show evidence of precursor metasomatism. The metasomatic enrichment of the alkaline ferropicrite sources may have been accompanied by conversion of Fe-rich peridotite to secondary garnet-pyroxenite. Melting experiments on "pyrolitic" compositions and consideration of the dependence of the density of silicate liquids on pressure and temperature, suggest that ferropicrites cannot originate by melting of normal terrestrial mantle (Mg-number = 0.88-0.92) at high pressures and temperatures. The geochemical similarity between the subalkaline ferropicrites and the shergottite-nakhlite-chassigny (SNC) and howardite-eucrite-diogenite (HED) differentiated meteorites suggests, however, that the Fe-rich mantle may originate from the infall of Fe-rich chondritic meteorites. The occurrence of ca. 2.7 Ga Fe-rich rocks on at least six cratons that are commonly coeval with the more ubiquitous komatiites and Mg-tholeiites is consistent with the existence of heterogeneous Fe-rich "plums" throughout the Neoarchean mantle. The paucity of ferropicrites in the post-2.7 Ga geological record suggests that majority of these Fe-rich plums have been melted out during the global Neoarchean melting of the mantle.

  5. Molecular basis of epithelial Ca2+ and Mg2+ transport: insights from the TRP channel family

    DEFF Research Database (Denmark)

    Dimke, Henrik Anthony; Hoenderop, Joost G J; Bindels, René J M

    2011-01-01

    active transcellular movement of divalent cations from the lumen into the enterocyte. Furthermore, in bone, TRPV channels play important roles by influencing the osteoclastic resorption process, thereby contributing importantly to overall bone mineral content. The divalent cation-permeable TRPV5 and TRPM......Maintenance of plasma Ca(2+) and Mg(2+) levels is of vital importance for many physiological functions. This is achieved via a coordinated interplay between the intestine, bone and kidney by amending the rate of absorption, storage and excretion, respectively. Discovery of the transient receptor...... potential (TRP) family identified several new ion channels acting as gatekeepers of Ca(2+) and Mg(2+) transport in these epithelia, greatly increasing our understanding of the molecular processes that facilitate the movement of these minerals. In the intestine, TRP channels contribute to the saturable...

  6. Physical properties of Rh substituted CaFe2As2 tuned by annealing/quenching

    Science.gov (United States)

    Ran, Sheng; Bud'Ko, Sergey; Canfield, Paul

    2014-03-01

    Our previous work on CaFe2As2 single crystal grown out of FeAs flux has shown that a process of annealing and quenching can be used as an additional control parameter which can tune the ground state of CaFe2As2 systematically. We have also shown that CaFe2As2 is very pressure sensitive. Therefore, unlike the BaFe2As2 system, the effect of 4d transition metal substitution on CaFe2As2 is expected to be largely different from that of 3d transition metal substitution (e.g. cobalt or nickel substitution). In this talk we will present results of measurements on a Rh substituted CaFe2As2 system with different annealing/quenching temperatures. Phase diagrams with substitution level and annealing/quenching temperature as independent parameters are constructed and compared with that of other transition metal substitutions. Supported by the U.S. Department of Energy Basic Energy Sciences under Contract No. DE-AC02-07CH11358.

  7. Magnetic properties of soft layer/FePt-MgO exchange coupled composite Perpendicular recording media

    Institute of Scientific and Technical Information of China (English)

    Yin Jin-Hua; Takao Suzuki; Pan Li-Qing

    2008-01-01

    The magnetic properties of exchange coupled composite(ECC)media that are composed of perpendicular magnetic recording media FePt-MgO and two kinds of soft layers have been studied by using an x-ray diffractometer,a polar Kerr magneto-optical system(PMOKE)and a vibrating sample magnetometer(VSM).The results show that ECC media can reduce the coercivities of perpendicular magnetic recording media FePt-MgO.The ECC media with granular-type soft layers have weaker exchange couplings between magnetic grains and the magnetization process,for ECC media of this kind mainly follow the Stoner-Wohlfarth model.

  8. Adsorption of arsenate on Cu/Mg/Fe/La layered double hydroxide from aqueous solutions

    Energy Technology Data Exchange (ETDEWEB)

    Guo, Yanwei [State Key Laboratory of Pollution Control and Resource Reuse, Tongji University, Shanghai 200092 (China); Zhu, Zhiliang, E-mail: zzl@tongji.edu.cn [State Key Laboratory of Pollution Control and Resource Reuse, Tongji University, Shanghai 200092 (China); Qiu, Yanling [Key Laboratory of Yangtze River Water Environment, Ministry of Education, Tongji University, Shanghai 200092 (China); Zhao, Jianfu [State Key Laboratory of Pollution Control and Resource Reuse, Tongji University, Shanghai 200092 (China)

    2012-11-15

    Highlights: Black-Right-Pointing-Pointer A novel layered double hydroxide containing lanthanum (Cu/Mg/Fe/La-LDH) has been synthesized. Black-Right-Pointing-Pointer The average pore size of the materials with about 16 nm indicated that the mesoporous structures existed in the Cu/Mg/Fe/La-LDHs. Black-Right-Pointing-Pointer The adsorption capacity of As(V) increased with the increment of La{sup 3+} content in the LDH. Black-Right-Pointing-Pointer The maximum adsorption capacity of the synthesized Cu/Mg/Fe/La-LDH for arsenate was 43.5 mg/g. - Abstract: A novel layered double hydroxide containing lanthanum (Cu/Mg/Fe/La-LDH) has been synthesized and used for the removal of arsenate from aqueous solutions. The purpose of incorporation of La{sup 3+} into LDHs was tried to enhance the uptake efficiency of arsenate and broaden the application field of LDHs functional materials. Effects of various physico-chemical factors such as solution pH, adsorbent dosage, contact time and initial arsenate concentrations on the adsorption of arsenate onto Cu/Mg/Fe/La-LDH were investigated. Results showed that the removal efficiency of arsenate increased with the increment of the lanthanum content in Cu/Mg/Fe/La-LDH adsorbents, and the optimized lanthanum content was 20% of the total trivalent metals composition (Fe{sup 3+} and La{sup 3+}). The adsorption isotherms can be well described by Langmuir equation, and the adsorption kinetics of arsenate followed the pseudo-second-order kinetic model. Coexistent ions such as HPO{sub 4}{sup 2-}, CO{sub 3}{sup 2-}, SO{sub 4}{sup 2-}, Cl{sup -} and NO{sub 3}{sup -} exhibited obvious competition with arsenate for the adsorption on Cu/Mg/Fe/La-LDH. The solution pH significantly affected the removal efficiency, which was closely related to the change of arsenate species distribution under different pH conditions. The predominant adsorption mechanism can be mainly attributed to the processes including ion exchange and layer ligand exchange.

  9. Mg(2+) differentially regulates two modes of mitochondrial Ca(2+) uptake in isolated cardiac mitochondria: implications for mitochondrial Ca(2+) sequestration.

    Science.gov (United States)

    Blomeyer, Christoph A; Bazil, Jason N; Stowe, David F; Dash, Ranjan K; Camara, Amadou K S

    2016-06-01

    The manner in which mitochondria take up and store Ca(2+) remains highly debated. Recent experimental and computational evidence has suggested the presence of at least two modes of Ca(2+) uptake and a complex Ca(2+) sequestration mechanism in mitochondria. But how Mg(2+) regulates these different modes of Ca(2+) uptake as well as mitochondrial Ca(2+) sequestration is not known. In this study, we investigated two different ways by which mitochondria take up and sequester Ca(2+) by using two different protocols. Isolated guinea pig cardiac mitochondria were exposed to varying concentrations of CaCl2 in the presence or absence of MgCl2. In the first protocol, A, CaCl2 was added to the respiration buffer containing isolated mitochondria, whereas in the second protocol, B, mitochondria were added to the respiration buffer with CaCl2 already present. Protocol A resulted first in a fast transitory uptake followed by a slow gradual uptake. In contrast, protocol B only revealed a slow and gradual Ca(2+) uptake, which was approximately 40 % of the slow uptake rate observed in protocol A. These two types of Ca(2+) uptake modes were differentially modulated by extra-matrix Mg(2+). That is, Mg(2+) markedly inhibited the slow mode of Ca(2+) uptake in both protocols in a concentration-dependent manner, but not the fast mode of uptake exhibited in protocol A. Mg(2+) also inhibited Na(+)-dependent Ca(2+) extrusion. The general Ca(2+) binding properties of the mitochondrial Ca(2+) sequestration system were reaffirmed and shown to be independent of the mode of Ca(2+) uptake, i.e. through the fast or slow mode of uptake. In addition, extra-matrix Mg(2+) hindered Ca(2+) sequestration. Our results indicate that mitochondria exhibit different modes of Ca(2+) uptake depending on the nature of exposure to extra-matrix Ca(2+), which are differentially sensitive to Mg(2+). The implications of these findings in cardiomyocytes are discussed.

  10. STUDY ON THE TEXTURE OF A FRICTION STIR WELDED Mg-Al-Ca ALLOY

    Institute of Scientific and Technical Information of China (English)

    D.T. Zhang; M. Suzuki; K. Maruyama

    2006-01-01

    Macro-texture of an Mg-Al-Ca alloy prepared by friction stir welding (FSW) was investigated through pole figure measurement and X-ray diffraction (XRD) pattern analysis. It was found that at the top and bottom surfaces of friction stir zone (FSZ), (0002) basal planes of magnesium tend to be arranged parallel to the plate surface. In the cross section of FSZ, no obvious texture had evolved and (0002) basal planes showed a random distribution.

  11. Spark plasma sintering of a nanocrystalline Al-Cu-Mg-Fe-Ni-Sc alloy

    Science.gov (United States)

    Zúñiga, Alejandro; Ajdelsztajn, Leonardo; Lavernia, Enrique J.

    2006-04-01

    The microstructure and aging behavior of a nanocrystalline Al-Cu-Mg-Fe-Ni-Sc alloy was studied. The nanocrystalline powders were produced by milling at liquid nitrogen temperature and then consolidated using spark plasma sintering (SPS). The microstructure after SPS consisted of a bimodal aluminum grain structure (coarse-grained and fine-grained regions), along with Al9FeNi and Al2CuMg particles dispersed throughout. The microstructure observed in the as-consolidated sample is rationalized on the basis of high current densities that are generated during sintering. Solution treatment and aging of the SPS Al-Cu-Mg-Fe-Ni-Sc sample resulted in softening instead of hardening. This observation can be explained by the reduced amount of Cu, Mg, and Si in solid solution available to form S' Al2CuMg due to the precipitation of Al7FeCu2 and Si-rich particles, and by the fact that rodlike S' Al2CuMg particles could only precipitate out in the coarse-grained regions, greatly decreasing their influence on the hardness. This lack of precipitation in the fine-grained region is argued to represent a new physical observation and is rationalized on the basis of physical and thermodynamic effects. The nanocrystalline SPS Al-Cu-Mg-Fe-Ni-Sc sample was also extremely thermally stable, retaining a fine-grained structure even after solution treatment at 530°C for 5 h. The observed thermal stability is rationalized on the basis of solute drag and Zener pinning caused by the impurities introduced during the cryomilling process.

  12. Antibacterial characteristics of CaCO3-MgO composites

    International Nuclear Information System (INIS)

    Dentifrices, such as tooth-paste, are pastes containing insoluble abrasives that aid in the removal of plaque from the teeth and help to polish them. Composite powders contributing to oral hygiene application, i.e., nano-scale MgO crystallite dispersed in CaCO3 grain, were fabricated by the thermal decomposition of dolomite. The composite obtained by heating at 800 deg. C consisted of CaCO3 grains including 20 nm MgO fine crystallite, being the purpose powder in this study. The antibacterial activity of these powders related to gram-positive and gram-negative bacteria was evaluated in vitro. The thermal decomposition above 800 deg. C resulted in the mixture of CaO and MgO. Antibacterial activity of the composite enhanced with increasing powder concentration. Though antibacterial action toward Staphylococcus aureus was greater than towards Escherichia coli, the death rate constant was identical in both bacteria. It can be concluded that the obtained composite possesses two functions able to improve the oral hygiene: as a tooth abrasive and as an antibacterial agent.

  13. Antibacterial characteristics of CaCO{sub 3}-MgO composites

    Energy Technology Data Exchange (ETDEWEB)

    Yamamoto, Osamu, E-mail: yamamoto@cges.akita-u.ac.jp [Center for Geo-Environmental Science, Faculty of Engineering and Resource Science, Akita University, 1-1 Tegata Gakuen-machi, Akita 010-8502 (Japan); Ohira, Toshiaki; Alvarez, Kelly [Center for Geo-Environmental Science, Faculty of Engineering and Resource Science, Akita University, 1-1 Tegata Gakuen-machi, Akita 010-8502 (Japan); Fukuda, Masayuki [Division of Dentistry and Oral Surgery, Akita University Hospital, 1-1-1 Hondo, Akita 010-8543 (Japan)

    2010-10-15

    Dentifrices, such as tooth-paste, are pastes containing insoluble abrasives that aid in the removal of plaque from the teeth and help to polish them. Composite powders contributing to oral hygiene application, i.e., nano-scale MgO crystallite dispersed in CaCO{sub 3} grain, were fabricated by the thermal decomposition of dolomite. The composite obtained by heating at 800 deg. C consisted of CaCO{sub 3} grains including 20 nm MgO fine crystallite, being the purpose powder in this study. The antibacterial activity of these powders related to gram-positive and gram-negative bacteria was evaluated in vitro. The thermal decomposition above 800 deg. C resulted in the mixture of CaO and MgO. Antibacterial activity of the composite enhanced with increasing powder concentration. Though antibacterial action toward Staphylococcus aureus was greater than towards Escherichia coli, the death rate constant was identical in both bacteria. It can be concluded that the obtained composite possesses two functions able to improve the oral hygiene: as a tooth abrasive and as an antibacterial agent.

  14. Microwave plasma atomic emission spectrometric determination of Ca, K and Mg in various cheese varieties.

    Science.gov (United States)

    Ozbek, Nil; Akman, Suleyman

    2016-02-01

    Microwave plasma-atomic emission spectrometry (MP-AES) was used to determine calcium, magnesium and potassium in various Turkish cheese samples. Cheese samples were dried at 100 °C for 2 days and then digested in a mixture of nitric acid/hydrogen peroxide (3:1). Good linearities (R(2) > 0.999) were obtained up to 10 μg mL(-1) of Ca, Mg and K at 445.478 nm, 285.213 nm and 766.491 nm, respectively. The analytes in a certified reference milk powder sample were determined within the uncertainty limits. Moreover, the analytes added to the cheese samples were recovered quantitatively (>90%). All determinations were performed using aqueous standards for calibration. The LOD values for Ca, Mg and K were 0.036 μg mL(-1), 0.012 μg mL(-1) and 0.190 μg mL(-1), respectively. Concentrations of Ca, K and Mg in various types of cheese samples produced in different regions of Turkey were found between 1.03-3.70, 0.242-0.784 and 0.081-0.303 g kg(-1), respectively. PMID:26304350

  15. Preparation and characterization of regenerated MgO-CaO refractory bricks sintered under different atmospheres

    Institute of Scientific and Technical Information of China (English)

    Gui-bo Qiu; Chang-sheng Yue; Xiang Li; Min Guo; Mei Zhang

    2014-01-01

    Regenerated MgO–CaO brick samples containing 80wt%, 70wt%, and 60wt%MgO were prepared using spent MgO–CaO bricks and fused magnesia as raw materials and paraffin as a binder. The bricks were sintered at 1873 K for 2 h under an air atmosphere and under an isolating system. The microstructure, mechanical properties at room temperature, and hydration resistance of the regenerated samples were measured and compared. The results indicated that the isolating sintering generated a strongly reducing atmosphere as a result of the incomplete combustion of paraffin, and the partial oxygen pressure was approximately 6.68 × 10–7 Pa. The properties of the regenerated bricks sintered under air conditions were all higher than those of the bricks sintered under a reducing atmosphere. The deterioration of the bricks was a result of MgO reduction and a decrease in the amount of liquid phase formed during sintering under a reducing atmosphere.

  16. Sr/Ca and Mg/Ca vital effects correlated with skeletal architecture in a scleractinian deep-sea coral and the role of Rayleigh fractionation

    Science.gov (United States)

    Gagnon, Alexander C.; Adkins, Jess F.; Fernandez, Diego P.; Robinson, Laura F.

    2007-09-01

    Deep-sea corals are a new tool in paleoceanography with the potential to provide century long records of deep ocean change at sub-decadal resolution. Complicating the reconstruction of past deep-sea temperatures, Mg/Ca and Sr/Ca paleothermometers in corals are also influenced by non-environmental factors, termed vital effects. To determine the magnitude, pattern and mechanism of vital effects we measure detailed collocated Sr/Ca and Mg/Ca ratios, using a combination of micromilling and isotope-dilution ICP-MS across skeletal features in recent samples of Desmophyllum dianthus, a scleractinian coral that grows in the near constant environment of the deep-sea. Sr/Ca variability across skeletal features is less than 5% (2σ relative standard deviation) and variability of Sr/Ca within the optically dense central band, composed of small and irregular aragonite crystals, is significantly less than the surrounding skeleton. The mean Sr/Ca of the central band, 10.6 ± 0.1 mmol/mol (2σ standard error), and that of the surrounding skeleton, 10.58±0.09 mmol/mol, are statistically similar, and agree well with the inorganic aragonite Sr/Ca-temperature relationship at the temperature of coral growth. In the central band, Mg/Ca is greater than 3 mmol/mol, more than twice that of the surrounding skeleton, a general result observed in the relative Mg/Ca ratios of D. dianthus collected from separate oceanographic locations. This large vital effect corresponds to a ˜ 10 °C signal, when calibrated via surface coral Mg/Ca-temperature relationships, and has the potential to complicate paleoreconstructions. Outside the central band, Mg/Ca ratios increase with decreasing Sr/Ca. We explain the correlated behavior of Mg/Ca and Sr/Ca outside the central band by Rayleigh fractionation from a closed pool, an explanation that has been proposed elsewhere, but which is tested in this study by a simple and general relationship. We constrain the initial solution and effective partition

  17. Refinement of the crystal structure π-Al9FeMg3Si5

    International Nuclear Information System (INIS)

    The crystal structure of the quaternary so-called π-phase, which was originally solved from photographic single crystal data, has been refined from single crystal automatic four circle counter data. Single crystals were obtained from the residue of a slowly cooled melt of nominal composition (in at %) Al74.1Fe0.5Mg8.4Si17.0, which was dissolved in butanol. The composition of the π-phase crystal was Al9Fe1Mg3.5Si5.0. The π-phase crystallizes in a unique structure type (Al9FeMg3Si5-type) with the noncentrosymmetric hexagonal space group P anti 62m-D33h, No. 189. The lattice parameters obtained from a Gandolfi camera were a=0.6625(2) nm and c=0.7910(4) nm, Z=1. For 366 reflections (parallel F0 parallel ≥3σ) the residual values are R= sum (parallel ΔF parallel / sum parallel F0 parallel)=0.064, Rw=0.075. Whereas previous structure determinations claimed full atom order, the present refinement clearly indicates that the crystal structure is partially ordered with a random distribution of 0.94 Al+0.06 Mg in the 6i-sites. Furthermore, whilst lattice and atom parameter essentially correspond to the values derived earlier, the new composition as a result of the refinement (Al8.7Fe1Mg3.3Si5) is in close agreement with the experimental composition Al9FeMg3.5Si5. (orig.)

  18. Determinación de Ca, Cu, Fe y Pb por espectrofotometría de absorción atómica en aguardientes de caña

    OpenAIRE

    Magdalena Lorenzo; Arlyn Reyes; Idania Blanco; María del Carmen Vasallo

    2010-01-01

    La determinación de Ca, Cu, Fe y Pb en aguardientes¸ se realizó por espectrofotometría de absorción atómica. El volumen de inyección fue 20 uL, la calibración se llevó a cabo en intervalos de 0,5-25,0 mg.L-1 de Ca; 0,25-5,0 mg.L-1 para el Cu, Pb y el Cu, y se utilizaron las absorbancias de Ca, Cu, Fe y Pb contra la concentración de los analitos, respectivamente. Las correlaciones lineales típicas de r = 0,99 en todos los casos. El método propuesto se aplicó para la determinación directa de C...

  19. Interlayer interaction in Ca-Fe layered double hydroxides intercalated with nitrate and chloride species

    Science.gov (United States)

    Al-Jaberi, Muayad; Naille, Sébastien; Dossot, Manuel; Ruby, Christian

    2015-12-01

    Ca-Fe layered double hydroxide (LDH) intercalated with chloride and nitrate ions has been synthesized with varying CaII:FeIII molar ratios of the initial solution. Phase pure LDH is observed with CaII:FeIII molar ratio of 2:1 and a mixture of LDH and Ca(OH)2 is formed for CaII:FeIII molar ratios higher than 2:1. Vibrational spectroscopies (Raman and IR) were used successfully to understand the interaction between the cationic and anionic sheets. The Raman bands positions at lower frequencies (150-600 cm-1) are intimately correlated to the nature of the divalent and trivalent ions but also to the nature of the anions. Indeed, a shift of ˜9 cm-1 is observed for the Raman double bands situated in the 300-400 cm-1 region when comparing Raman spectra of CaFe-LDH containing either nitrate or chloride ions. Two types of nitrate environments are observed namely free (non-hydrogen bonded) nitrate and nitrate hydrogen bonded to the interlayer water or to the 'brucite-like' hydroxyl surface. Multiple types of water structure are observed and would result from different hydrogen bond structures. Water bending modes are identified at 1645 cm-1 greater than the one observed for LDH intercalated with chloride anions (1618 cm-1), indicating that the water is strongly hydrogen bonded to the nitrate anions.

  20. Co and Mn doping effect in polycrystalline (Ca,La) and (Ca,Pr)FeAs2 superconductors

    Science.gov (United States)

    Yakita, Hiroyuki; Ogino, Hiraku; Sala, Alberto; Okada, Tomoyuki; Yamamoto, Akiyasu; Kishio, Kohji; Iyo, Akira; Eisaki, Hiroshi; Shimoyama, Jun-ichi

    2015-06-01

    The superconducting properties of Mn and Co doped (Ca,RE)FeAs2 ((Ca,RE)112: RE = La, Pr) were investigated. Co doping increased Tc of (Ca,Pr)112 while Mn doping suppressed the superconductivity of (Ca,RE)112. The Co doped (Ca,La)112 exhibited a large diamagnetic screening, as well as sharper superconducting transition than Co-free (Ca,La)112. Tc zero observed in the resistivity measurements increased from 14 to 30 K by Co doping, while {{T}c}onset was not increased. The critical current density, Jc, of Co doped (Ca,La)112 was approximately 2.1 × 104 A cm-2 and 3.2 × 103 A cm-2 at 2 K and 25 K, respectively, at near zero field. These relatively high Jc values and large diamagnetic screening observed in the susceptibility measurements of the polycrystalline bulks are evidence that Co doped (Ca,RE)112 compounds possess bulk superconductivity.

  1. Mechanical alloying in Fe2O3-MO (M: Zn, Ni, Cu, Mg) systems

    DEFF Research Database (Denmark)

    Jiang, Jianzhong; Gerward, Leif; Mørup, Steen

    1999-01-01

    Mechanical alloying processes in four Fe2O3MO (M: Zn, Ni, Cu, Mg) systems by high-energy ball milling from simple oxide powder mixtures in both open and closed tungsten carbide containers have been investigated by x-ray powder diffraction and Mossbauer spectroscopy. Mechanisms for the formation o...

  2. Cap-Induced Magnetic Anisotropy in Ultra-thin Fe/MgO(001) Films

    Science.gov (United States)

    Brown-Heft, Tobias; Pendharkar, Mihir; Lee, Elizabeth; Palmstrom, Chris

    Magnetic anisotropy plays an important role in the design of spintronic devices. Perpendicular magnetic anisotropy (PMA) is preferred for magnetic tunnel junctions because the resulting energy barrier between magnetization states can be very high and this allows enhanced device scalability suitable for magnetic random access memory applications. Interface induced anisotropy is often used to control magnetic easy axes. For example, the Fe/MgO(001) system has been predicted to exhibit PMA in the ultrathin Fe limit. We have used in-situ magneto optic Kerr effect and ex-situ SQUID to study the changes in anisotropy constants between bare Fe/MgO(001) films and those capped with MgO, Pt, and Ta. In some cases in-plane anisotropy terms reverse sign after capping. We also observe transitions from superparamagnetic to ferromagnetic behavior induced by capping layers. Perpendicular anisotropy is observed for Pt/Fe/MgO(001) films after annealing to 300°C. These effects are characterized and incorporated into a magnetic simulation that accurately reproduces the behavior of the films. This work was supported in part by the Semiconductor Research Corporation programs (1) MSR-Intel, and (2) C-SPIN.

  3. Comparison of Tunneling in Fe-based Superconductors with Multi-band MgB2

    Science.gov (United States)

    Zasadzinski, John; Iavarone, Maria

    MgB2 is an s-wave, phonon coupled, multiband superconductor that exhibits novel tunneling spectra including a subtle dip feature due to quasiparticle transfer between bands. Since this feature mimics the above-gap spectral dip feature observed in Fe-based superconductors, typically attributed to a strong coupling boson, it is worthwhile to consider whether quasiparticle transfer is relevant. We first show that the dip in MgB2 appears in the π-band, DOS (Δ = 2.4 meV) and is due to quasiparticle transfer to the σ-band with Δ = 7.2 meV. Reviewing the spectral dip in Fe-based superconductors, including new data on FeSe crystals, there are inconsistencies with quasiparticle transfer as the origin. The conclusion is that the spectral dip is more likely due to a boson, the resonance spin excitation, as found in cuprate superconductors.

  4. Structural defects analysis versus spin polarized tunneling in Co2FeAl/MgO/CoFe magnetic tunnel junctions with thick MgO barriers

    International Nuclear Information System (INIS)

    We report on spin polarization reduction by incoherent tunneling in single crystal Co2FeAl/MgO/Co50Fe50 magnetic tunnel junctions (MTJs). A large density of misfit dislocations in the Heusler based MTJs has been provided by a thick MgO barrier and its 3.8% lattice mismatch with the Co2FeAl electrode. Our analysis implicates a correlated structural-transport approach. The crystallographic coherence in the real space has been investigated by High Resolution Transmission Electron Microscopy phase analysis. The electronic transport experiments in variable temperature, fitted with a theoretical extended-Glazman–Matveev model, address different levels of the tunneling mechanisms from direct to multi-center hopping. We demonstrate a double impact of dislocations, as extended defects, on the tunneling polarization. Firstly, the breaking of the crystal symmetry destroys the longitudinal and lateral coherence of the propagating Bloch functions. This affects the symmetry filtering efficiency of the Δ1 states across the (001) MgO barriers and reduces the associated effective tunneling polarization. Secondly, dislocations provide localized states within the MgO gap. This determines temperature activated spin-conserving inelastic tunneling through chains of defects which are responsible for the one order of magnitude drop of the tunnel magnetoresistance from low to room temperature. - Highlights: • The paper focuses on tunneling transport in realistic single crystal magnetic tunnel junctions involving the full Heusler alloy Co2FeAl. • Via correlated structural-transport analysis approach, the paper demonstrates the role of extended structural defects in a single crystal epitaxial barrier on the tunneling polarization efficiency. • We illustrate the effect of the crystal symmetry breaking on the spin and symmetry polarized tunneling transport. • The transport results are confronted with a theoretical model considering different orders of tunneling mechanisms, from

  5. Formation, microstructure and magnetic properties of nanocrystalline MgFe2O4

    International Nuclear Information System (INIS)

    Highlights: ► Glycine to nitrate ratio affects the microstructural and magnetic properties of MgFe2O4. ► Rapid combustion reaction between nitrates and glycine occur around 194 °C. ► The thermodynamical considerations were taken into account to study the effect of glycine to nitrate ratio on powder characteristics. ► Spinel MgFe2O4 phase even formed at fuel lean condition. - Abstract: Nanocrystalline powder of MgFe2O4 was successfully synthesized by a cost effective novel combustion route. Nitrates of the constituent elements and glycine were respectively used as an oxidizer and fuel to drive the reaction. The effect of glycine to nitrate molar ratio (G N−1) on the structure and formation of MgFe2O4 was studied in view of thermodynamic considerations like adiabatic flame temperature and gas evolved during the combustion. The as prepared powder was characterized by X-Ray Diffraction (XRD), Fourier Transform Infra Red (FTIR) spectroscopy and Scanning Electron Microscopy (SEM) for formation and microstructure analysis at various G N−1 ratios. XRD results revealed that the crystallinity of MgFe2O4 is insensitive to G N−1 variations and fuel lean combustion also lead to appropriate MgFe2O4 phase formation. Thermo Gravimetric-Differential Thermal Analysis (TG-DTA) for the precursor gel demonstrated the occurrence of rapid chemical reaction between glycine and nitrates at around 194 °C corresponding to ignition of precursors at this temperature. Transmission electron microscopy image for as prepared stoichiometric sample shows formation of nanoparticles of sizes from 28 nm to 50 nm. SEM images of MgFe2O4 nanoparticles at G N−1 ratio show remarkable change in microstructure regarding porosity and grain size. Room temperature magnetic measurements for stoichiometric sample show the magnetization (Ms) and remanence (Mr) of about 31.56 emu g−1 and 9.60 emu g−1 at ±10 kOe respectively.

  6. Análise de crescimento em Heteranthera reniformis, sob diferentes teores de Ca, Mg e S Growth analysis in Heteranthera reniformis under different contents of Ca, Mg and S

    Directory of Open Access Journals (Sweden)

    Vanessa David Domingos

    2006-01-01

    Full Text Available O objetivo deste trabalho foi estudar o crescimento, alocação de biomassa e teores de nutrientes em Heteranthera reniformis Ruiz & Pav., sob o efeito de diferentes concentrações de Ca, Mg e S. As plantas foram cultivadas em vasos plásticos preenchidos com pedra rolada, em soluções nutritivas a 80% da concentração original de Sarruge, correspondente à solução-base. O experimento foi desenvolvido em delineamento experimental inteiramente casualizado, com quatro teores (0%, 25%, 50% e 75% da solução base de 80% avaliados em Ca, Mg e S, além da testemunha (solução-base, com quatro repetições no período de 35 dias em casa de vegetação. O aumento dos teores de Ca na solução propiciou uma redução significativa na área foliar. As maiores áreas foliares ocorreram em soluções a 25% de Ca e 50% de Mg e S. A maior proporção de biomassa seca está no caule, exceto a 25% de Ca (40 mg L-1 que propiciou maior área foliar e área foliar específica. Entre os teores de Mg na solução, as maiores biomassas foram observadas a 50% de Mg (19,2 mg.L-1 e, para o S, não houve diferenças significativas, exceto a 0%. A solução com 160 mg L-1 de Ca propiciou maior concentração de Ca na folha (56,6 g kg-1. Os teores de Ca, Mg e S em solução corresponderam a um aumento proporcional na planta. Os teores de enxofre nas folhas e nos caules aumentaram com a concentração de S na solução, enquanto o teor nas raízes reduziu nas concentrações entre 12,8 e 38,4 mg.L-1.The objective was to study the growth, biomass allocation and concentration of nutrients in Heteranthera reniformis Ruiz & Pav. under the effect of different concentrations of Ca, Mg and S. The plants were cultivated in plastic pots fulfilled with rolled stone, in nutrient solutions of 80% of the original concentration of Sarruge. The experiment was carried out in a complete randomized design, with 4 contents (0, 25, 50 and 75% of the base solution evaluated in Ca, Mg and

  7. Synthesis of MgAl-LDH/CoFe2O4 and MgAl-CLDH/CoFe2O4 nanofibres for the removal of Congo Red from aqueous solution

    Indian Academy of Sciences (India)

    Zhigang Jia; Shengbiao Li; Jianhong Liu; Qi Qin; Rongsun Zhu

    2015-12-01

    MgAl-LDH/CoFe2O4 and MgAl-CLDH/CoFe2O4 nanofibres were prepared by urea-hydrolysed hydrothermal reaction and the subsequent calcinations. The morphology and structure of the products were characterized by X-ray diffraction, scanning electron microscopy and transmission electron microscope and Fourier transformed infrared. The adsorption performance of MgAl-LDH/CoFe2O4 and MgAl-CLDH/CoFe2O4 nanofibres for the removal of an anionic dye (Congo Red, CR) from aqueous solution was investigated. The results showed that MgAl-LDH/CoFe2O4 and MgAl-CLDH/CoFe2O4 nanofibres are particularly efficient in removing CR. The adsorption follows a pseudo-second-order kinetic model and best fits the Langmuir isotherm model. The maximum adsorption capacities of MgAl-LDH/CoFe2O4 and MgAl-CLDH/CoFe2O4 nanofibres for CR were found to be 213.2 and 49.8 mg g−1, respectively. The both adsorption processes were found to be spontaneous and exothermic in nature.

  8. Tuning the Mg/Ca Paleothermometer for High-Latitude Species and Insights into Intraspecific and Intrashell Variability

    Science.gov (United States)

    Davis, C. V.; Fehrenbacher, J. S.; Russell, A. D.; Spero, H. J.; Hill, T. M.

    2015-12-01

    The Mg/Ca of planktic foraminifera shells has become a widely used paleothermometer. However, culture-based calibrations have been confined primarily to low-latitude species with limited data from species growing below 12°C. Some core-top calibrations on high-latitude Neogloboquadrinids raise questions about the influence of [CO3-2] and low Mg/Ca "crusts" on shell geochemistry (e.g. 1). This study seeks to extend the low temperature range of culture-based calibrations to temperatures relevant in high-latitudes and active upwelling areas, taking into account the wide range of [CO3-2] observed in these environments. We further examine whether intrashell geochemical variability in the form of "crusting" poses a limitation to Mg/Ca paleothermometry of crust-forming species. Here we present the results of laboratory experiments with living Neogloboquadrina incompta and Neogloboquadrina pachyderma collected and cultured at UC Davis Bodega Marine Laboratory at temperatures between 6° and 12°C and a range of [CO3-2]. We use a combination of Laser Ablation Inductively Coupled Mass Spectrometry and Electron Microprobe mapping, to analyze both intraspecific and intrashell variability in Mg/Ca. We extend existing culture-based temperature calibrations to 6°C, while accounting for the effect of environmental [CO3-2]. Single-shell analyses reveal a high degree of intraspecific variability in the Mg/Ca of calcite grown under stable laboratory conditions. Intrashell analyses identify characteristic low Mg/Ca "crusts" in N. incomptagrown at constant temperature, which record chamber average Mg/Ca within the range of uncrusted conspecifics grown at the same temperature. 1. R. Kozdon et al., Reassessing Mg/Ca temperature calibrations of Neogloboquadrina pachyderma (sinistral) using paired δ44/40Ca and Mg/Ca measurements. Geochem Geophys. 10, Q03005 (2009).

  9. Interfacial electronic structure-modulated magnetic anisotropy in Ta/CoFeB/MgO/Ta multilayers

    Energy Technology Data Exchange (ETDEWEB)

    Chen, Xi; Jiang, Shao Long; Yang, Guang; Liu, Yang; Teng, Jiao; Yu, Guang Hua, E-mail: ghyu@mater.ustb.edu.cn [Department of Materials Physics and Chemistry, University of Science and Technology Beijing, Beijing 100083 (China); Wang, Kai You [SKLSM, Institute of Semiconductors, CAS, P. O. Box 912, Beijing 100083 (China); Wu, Zheng Long [Analytical and Testing Center, Beijing Normal University, Beijing 100875 (China)

    2014-09-01

    We have observed several unexpected phenomena when a trace amount of Fe atoms is deposited onto the CoFeB/MgO interface in Ta/CoFeB/MgO/Ta multilayers. With the nominal thickness of the introduced Fe atoms (t{sub Fe}) varying from 0 to 0.1 Å, the effective magnetic anisotropy energy (K{sub eff}) of annealed multilayers is remarkably enhanced from 1.28 × 10{sup 6 }erg/cm{sup 3} to 2.14 × 10{sup 6 }erg/cm{sup 3}. As t{sub Fe} further increasing, the K{sub eff} decreases and even becomes negative when t{sub Fe} > 1 Å, indicating the change from perpendicular magnetic anisotropy to in-plane magnetic anisotropy. The analysis by X-ray photoelectron spectrometer reveals that the Fe atoms at annealed CoFeB/MgO interface show different electronic structures as t{sub Fe} increasing, which combine with O atoms to form FeO{sub x} (x < 1), Fe{sub 2}O{sub 3}, and Fe{sub 3}O{sub 4}, respectively, leading to modulation of Fe 3d-O 2p orbital hybridization and thus the K{sub eff}. On the other hand, we find that the introduction of Fe atoms also helps to reduce the multilayers' magnetic damping.

  10. Taming the resistive switching in Fe/MgO/V/Fe magnetic tunnel junctions: An ab initio study

    Energy Technology Data Exchange (ETDEWEB)

    Aguiar-Hualde, J.M. [IPhT, CEA/Saclay, Orme des Merisiers, 91190 Gif-sur-Yvette Cedex (France); Alouani, M. [IPCMS, UMR 7504 CNRS-UdS, 23 rue du Loess, Strasbourg 67034 (France)

    2014-12-15

    A possible mechanism for the resistive switching observed experimentally in Fe/MgO/V/Fe junctions is presented. Ab initio total energy calculations within the local density approximation and pseudopotential theory shows that by moving the oxygen ions across the MgO/V interface one obtains a metastable state. It is argued that this state can be reached by applying an electric field across the interface. In addition, the ground state and the metastable state show different electric conductances. The latter results are discussed in terms of the changes of the density of states at the Fermi level and the charge transfer at the interface due to the oxygen ion motion. - Highlights: • Local minima are found for oxygen near the interface with at least one oxygen moved. • Relaxation of a small unit cell preserves this result and lowers energy barrier. • V on the top of Mg exhibits the minimum and a reasonable energy barrier. • Sense of switching: experimental evidence of the configuration (V on O or V on Mg). • Sense of switching can be understood in terms of charge oscillations induced by the O.

  11. Accelerated Removal of Fe-Antisite Defects while Nanosizing Hydrothermal LiFePO4 with Ca(2.).

    Science.gov (United States)

    Paolella, Andrea; Turner, Stuart; Bertoni, Giovanni; Hovington, Pierre; Flacau, Roxana; Boyer, Chad; Feng, Zimin; Colombo, Massimo; Marras, Sergio; Prato, Mirko; Manna, Liberato; Guerfi, Abdelbast; Demopoulos, George P; Armand, Michel; Zaghib, Karim

    2016-04-13

    Based on neutron powder diffraction (NPD) and high angle annular dark field scanning transmission electron microscopy (HAADF-STEM), we show that calcium ions help eliminate the Fe-antisite defects by controlling the nucleation and evolution of the LiFePO4 particles during their hydrothermal synthesis. This Ca-regulated formation of LiFePO4 particles has an overwhelming impact on the removal of their iron antisite defects during the subsequent carbon-coating step since (i) almost all the Fe-antisite defects aggregate at the surface of the LiFePO4 crystal when the crystals are small enough and (ii) the concomitant increase of the surface area, which further exposes the Fe-antisite defects. Our results not only justify a low-cost, efficient and reliable hydrothermal synthesis method for LiFePO4 but also provide a promising alternative viewpoint on the mechanism controlling the nanosizing of LiFePO4, which leads to improved electrochemical performances. PMID:26966938

  12. Interactions of Na+, K+, Mg2+, and Ca 2+ with benzene self-assembled monolayers

    DEFF Research Database (Denmark)

    Pedersen, Morten Rimmen; Matthiesen, Jesper; Bovet, Nicolas Emile;

    2014-01-01

    that are most common in the natural world, namely, Na+, K+, Mg 2+, and Ca2+. Specifically, we investigated how these ions affect the interactions between surfaces covered by self-Assembled monolayers (SAMs) terminated with benzene molecules. We used a flat oxidized silicon substrate and an atomic force...... from X-ray photoelectron spectroscopy (XPS) allowed us to conclude that K+ binds in the benzene layers, creating a positive surface charge on the benzene-covered surfaces, thus leading to lower adhesion in KCl solutions than in pure water. Evidence suggested that Ca2+ does not bind to the surfaces...... measurements. The results of our studies clearly show that even a nonpolar, hydrophobic molecule, such as benzene, has a role to play in the behavior of aqueous solutions and that it interacts differently depending on which ions are present. Even ions from the same column in the periodic table behave...

  13. Fe-Mg diffusion chronometry in orthopyroxene from the Minoan eruption of Santorini, Greece

    Science.gov (United States)

    Flaherty, Taya; Druitt, Tim; Fabbro, Gareth; Costa, Fidel; Preece, Katie; Deering, Chad

    2016-04-01

    Constraining the timescales governing magma ascent and storage prior to ignimbrite eruptions is crucial for understanding the behaviour of caldera volcanoes. Diffusion chronometry provides estimates of the pre-eruptive residence times of crystals at magmatic temperatures, and hence of the longevities of bodies of crystal-bearing magma that are finally discharged. We have used Fe-Mg diffusion chronometry in orthopyroxene (opx) crystals from the Minoan eruption of Santorini in order to calculate the pre-eruptive residence times of these crystals. The Minoan eruption occurred in the late 17th century BCE, and discharged 30-80 km3 of rhyodacitic magma containing about 10 vol.% of plagioclase, opx, cpx and Fe-Ti oxides. The orthopyroxenes have compositions of Wo2‑3En52‑70Fs28‑45 (#Mg = 0.53-0.65) with Al2O3 contents typically images reveal sector zoned morphologies with Al-rich prismatic zones and Al-poor terminations, possibly indicative of rapid growth. Representative opx crystals were extracted from pumices and mounted in epoxy grain mounts. High-resolution backscattered electron images of zoned crystals with greyscale values calibrated for Mg# were used to identify Fe-Mg gradients across zone boundaries, which were then modelled as diffusion gradients using published diffusion coefficients for Mg-Fe interdiffusion within the a-b plane of opx, a magmatic temperature (855 ± 25 ° C) and fO2 determined from touching magnetite-ilmenite pairs in the same rock. Our models assumed initial step functions in Mg and Fe concentrations, and that any non-zero width is a result of diffusion. The time required for to reach the observed width of diffusion at 855° C was taken to be a maximum residence time, and was calculated for a total of 22 zone boundaries from 13 crystals. Profiles were taken perpendicular to the crystal length, within the a-b crystallographic plane. Only zone boundaries with bounding plateaus in Mg and Fe concentrations (implicit in the diffusion model

  14. Chemical ordering and large tunnel magnetoresistance in Co2FeAl/MgAl2O4/Co2FeAl(001) junctions

    Science.gov (United States)

    Scheike, Thomas; Sukegawa, Hiroaki; Inomata, Koichiro; Ohkubo, Tadakatsu; Hono, Kazuhiro; Mitani, Seiji

    2016-05-01

    Epitaxial magnetic tunnel junctions (MTJs) with a Co2FeAl/CoFe (0.5 nm)/MgAl2O4/Co2FeAl(001) structure were fabricated by magnetron sputtering. High-temperature in situ annealing led to a high degree of B2-order in the Co2FeAl layers and cation order of the MgAl2O4 barrier. Large tunnel magnetoresistance (TMR) of up to 342% was obtained at room temperature (616% at 4 K), in contrast to the TMR ratio ( ≲ 160%) suppressed by the band-folding effect in Fe/cation-ordered MgAl2O4/Fe MTJs. The present study reveals that the high degree of B2-order and the resulting high spin polarization in the Co2FeAl electrodes enable us to bypass the band-folding problem in spinel barriers.

  15. Role of hydrogen in the electronic properties of CaFeAsH-based superconductors

    Science.gov (United States)

    Huang, Y. N.; Liu, D. Y.; Zou, L. J.; Pickett, W. E.

    2016-05-01

    The electronic and magnetic properties of the hydride superconductor CaFeAsH, which superconducts up to 47 K when electron doped with La, and the isovalent alloy system CaFeAsH1 -xFx are investigated using density functional based methods. The Q ⃗=(π ,π ,0 ) peak of the nesting function ξ (q ⃗) is found to be extremely strong and sharp, and the additional structure in ξ (q ⃗) associated with the near-circular Fermi surfaces (FSs) that may impact low energy excitations is quantified. The unusual band introduced by H, which shows strong dispersion perpendicular to the FeAs layers, is shown to be connected to a peculiar van Hove singularity just below the Fermi level. This band provides a three-dimensional electron ellipsoid Fermi surface not present in other Fe-based superconducting materials nor in CaFeAsF. Electron doping by 25% La or Co has a minor effect on this ellipsoid Fermi surface, but suppresses FS nesting strongly, consistent with the viewpoint that eliminating strong nesting and the associated magnetic order allows high Tc superconductivity to emerge. Various aspects of the isovalent alloy system CaFeAsH1 -xFx and means of electron doping are discussed in terms of influence of incipient bands.

  16. Distribution of Ca, Fe, Cu and Zn in primary colorectal cancer and secondary colorectal liver metastases

    Energy Technology Data Exchange (ETDEWEB)

    Al-Ebraheem, A. [Department of Radiography, City Community and Health Sciences, City University, London, EC1V 0HB (United Kingdom); Mersov, A. [Department of Medical Physics and Applied Radiation Sciences, McMaster University, 1280 Main St. West. Hamilton, Ontario, L8S 4L8 (Canada); Gurusamy, K. [HPB and Liver Transplant Surgery, Royal Free and University College School of Medicine, UCL and Royal Free NHS trust, London (United Kingdom); Farquharson, M.J., E-mail: farquhm@mcmaster.c [Department of Medical Physics and Applied Radiation Sciences, McMaster University, 1280 Main St. West. Hamilton, Ontario, L8S 4L8 (Canada)

    2010-07-21

    A microbeam synchrotron X-ray fluorescence ({mu}SRXRF) technique has been used to determine the localization and the relative concentrations of Zn, Cu, Fe and Ca in primary colorectal cancer and secondary colorectal liver metastases. 24 colon and 23 liver samples were examined, all of which were formalin fixed tissues arranged as microarrays of 1.0 mm diameter and 10 {mu}m thickness. The distribution of these metals was compared with light transmission images of adjacent sections that were H and E stained to reveal the location of the cancer cells. Histological details were provided for each sample which enable concentrations of all elements in different tissue types to be compared. In the case of liver, significant differences have been found for all elements when comparing tumour, normal, necrotic, fibrotic, and blood vessel tissues (Kruskal Wallis Test, P<0.0001). The concentrations of all elements have also been found to be significantly different among tumour, necrotic, fibrotic, and mucin tissues in the colon samples (Kruskal Wallis Test, P<0.0001). The concentrations of all elements have been compared between primary colorectal samples and colorectal liver metastases. Concentration of Zn, Cu, Fe and Ca are higher in all types of liver tissues compared to those in the colon tissues. Comparing liver tumour and colon tumour samples, significant differences have been found for all elements (Mann Whitney, P<0.0001). For necrotic tissues, significant increase has been found for Zn, Ca, Cu and Fe (Mann Whitney, P<0.0001 for Fe and Zn, 0.014 for Ca, and 0.001 for Cu). The liver fibrotic levels of Zn, Ca, Cu and Fe were higher than the fibrotic colon areas (independent T test, P=0.007 for Zn and Mann Whitney test P<0.0001 for Cu, Fe and Ca). For the blood vessel tissue, the analysis revealed that the difference was only significant for Fe (P=0.009) from independent T test.

  17. Measuring past changes in ENSO variance using Mg/Ca measurements on individual planktic foraminifera

    Science.gov (United States)

    Marchitto, T. M.; Grist, H. R.; van Geen, A.

    2013-12-01

    Previous work in Soledad Basin, located off Baja California Sur in the eastern subtropical Pacific, supports a La Niña-like mean-state response to enhanced radiative forcing at both orbital and millennial (solar) timescales during the Holocene. Mg/Ca measurements on the planktic foraminifer Globigerina bulloides indicate cooling when insolation is higher, consistent with an ';ocean dynamical thermostat' response that shoals the thermocline and cools the surface in the eastern tropical Pacific. Some, but not all, numerical models simulate reduced ENSO variance (less frequent and/or less intense events) when the Pacific is driven into a La Niña-like mean state by radiative forcing. Hypothetically the question of ENSO variance can be examined by measuring individual planktic foraminiferal tests from within a sample interval. Koutavas et al. (2006) used d18O on single specimens of Globigerinoides ruber from the eastern equatorial Pacific to demonstrate a 50% reduction in variance at ~6 ka compared to ~2 ka, consistent with the sense of the model predictions at the orbital scale. Here we adapt this approach to Mg/Ca and apply it to the millennial-scale question. We present Mg/Ca measured on single specimens of G. bulloides (cold season) and G. ruber (warm season) from three time slices in Soledad Basin: the 20th century, the warm interval (and solar low) at 9.3 ka, and the cold interval (and solar high) at 9.8 ka. Each interval is uniformly sampled over a ~100-yr (~10-cm or more) window to ensure that our variance estimate is not biased by decadal-scale stochastic variability. Theoretically we can distinguish between changing ENSO variability and changing seasonality: a reduction in ENSO variance would result in narrowing of both the G. bulloides and G. ruber temperature distributions without necessarily changing the distance between their two medians; while a reduction in seasonality would cause the two species' distributions to move closer together.

  18. Mg/Ca temperature calibration for the benthic foraminifers Bulimina inflata and Bulimina mexicana

    Science.gov (United States)

    Grunert, Patrick; Rosenthal, Yair; Jorissen, Frans; Holbourn, Ann

    2016-04-01

    Bulimina inflata Seguenza 1862 and Bulimina mexicana Cushman 1922 are cosmopolitan, shallow infaunal benthic foraminifers which are common in the fossil record throughout the Neogene and Quaternary. The closely related species share a similar costate shell morphology that differs in the presence or absence of an apical spine. In the present study, we evaluate the temperature dependency of Mg/Ca ratios of these species from an extensive set of core-top samples from the Atlantic and Pacific oceans. The results show no significant offset in Mg/Ca values between B. inflata, B. mexicana, and two other costate morphospecies when present in the same sample. The apparent lack of significant inter-specific/inter-morphotype differences amongst the analysed costate buliminds allows for the combined use of their data-sets for our core-top calibration. Over a bottom-water temperature range of 3-14°C, the Bulimina inflata/mexicana group shows a sensitivity of ˜0.12 mmol/mol/°C which is comparable to the epifaunal Cibicidoides pachyderma and higher than for the shallow infaunal Uvigerina spp., the most commonly used taxa in Mg/Ca-based palaeotemperature reconstruction. B. inflata and B. mexicana might thus be a valuable alternative in mesotrophic settings where many of the commonly used species are diminished or absent, and particularly useful in hypoxic settings where costate buliminds may dominate foraminiferal assemblages. This study was financially supported by the Max-Kade-Foundation and contributes to project P25831-N29 of the Austrian Science Fund (FWF).

  19. The Effect of Increasing Sn Content on High-Temperature Mechanical Deformation of an Mg-3%Cu-1%Ca Alloy

    Directory of Open Access Journals (Sweden)

    Georgios S.E. Antipas

    2013-11-01

    Full Text Available Chill casting of magnesium alloy samples with secondary alloying elements of Cu, Ca and Sn at % w.t. concentrations in the range 1–5, 0.1–5 and 0.1–3 respectively, gave rise to appreciably enhanced resistance to high-temperature creep, while maintaining good heat conductivity. The latter was considered to be driven by Cu and Mg-Cu intermetallics while it was clear that Sn mediated the high-temperature performance, mainly via networks of Mg2Sn and MgCaSn precipitates along the Mg matrix grain boundaries. It was postulated that Sn formed intermetallics by preferential substitution of Ca atoms and, thus, did not degrade the heat conductivity by retaining Cu. The % w.t. stoichiometry with the optimum combination of heat conductivity and resistance to high-temperature creep was found to be Mg-3Cu-1Ca-0.1Sn.

  20. Electronic spin and valence states of Fe in CaIrO3-type silicate post-perovskite in the Earth's lowermost mantle

    Science.gov (United States)

    Mao, Z.; Lin, J. F.; Jacobs, C.; Watson, H. C.; Xiao, Y.; Chow, P.; Alp, E. E.; Prakapenka, V. B.

    2010-11-01

    The electronic spin and valence states of Fe in post-perovskite ((Mg0.75Fe0.25)SiO3) have been investigated by synchrotron X-ray diffraction, Mössbauer and X-ray emission spectroscopy at 142 GPa and 300 K. Rietveld refinement of the X-ray diffraction patterns revealed that our sample was dominated by CaIrO3-type post-perovskite. Combined Mössbauer and X-ray emission results show that Fe in post-perovskite is predominantly Fe2+ (70%) in the intermediate-spin state with extremely high quadrupole splitting of 3.77(25) mm/s. The remaining 30% Fe can be assigned to two sites. Compared with recent studies, our results indicate that the intermediate-spin Fe2+ is stabilized in CaIrO3-type post-perovskite over a wide range of Fe content, whereas the low-spin Fe3+ is more dominant in the 2 × 1 kinked post-perovskite structure. The characterization of these structural and compositional effects on the spin and valence states of Fe in post-perovskite can help in understanding the geochemical and geophysical behavior of the core-mantle region.

  1. Effect of Ca content percentage and sintering temperature on corrosion rate in Mg-Ca composite fabricated using powder metallurgy technique

    Science.gov (United States)

    Syaza Nabilla, M. S.; Zuraidawani, C. D.; Nazree, D. M.

    2016-07-01

    Magnesium (Mg) is a good element with high potential to be used in various field of work. It has the benefit of lightweight and low density its application is limited for Mg is relatively low in term of strength. Hence, calcium (Ca) is chosen to be mixed with Mg as additional element for it is lightweight and non-toxic. In this research, Mg is prepared with different weight percentage (0, 0.5, 1, 1.5 and 2 wt. %) of Cavia powder metallurgy (PM) method. The samples were sintered at 500 and 550°Cin argon atmosphere and electrochemically using SBF solution as the electrolyte medium. The effect of Ca content on corrosion rateis investigated by focusing on the microstructure and properties of sintered sample. Increase of Ca content causes reduction in grain structure due to increase Mg2Ca phase at grain boundaries. Subsequently, reduce corrosion resistance. Hence, the amount of Ca content and sintering temperature of Mg-Ca composite is controlled to acquire optimum corrosion rate.

  2. Mg-Fe-mixed oxides derived from layered double hydroxides: A study of the surface properties

    Directory of Open Access Journals (Sweden)

    Marinković-Nedučin Radmila P.

    2011-01-01

    Full Text Available The influence of surface properties on the selectivity of the synthesized catalysts was studied, considering that their selectivity towards particular hydrocarbons is crucial for their overall activity in the chosen Fischer- -Tropsch reaction. Magnesium- and iron-containing layered double hydroxides (LDH, with the general formula: [Mg1-xFex(OH2](CO3x/2?mH2O, x = = n(Fe/(n(Mg+n(Fe, synthesized with different Mg/Fe ratio and their thermally derived mixed oxides were investigated. Magnesium was chosen because of its basic properties, whereas iron was selected due to its well-known high Fischer-Tropsch activity, redox properties and the ability to form specific active sites in the layered LDH structure required for catalytic application. The thermally less stable multiphase system (synthesized outside the optimal single LDH phase range with additional Fe-phase, having a lower content of surface acid and base active sites, a lower surface area and smaller fraction of smaller mesopores, showed higher selectivity in the Fischer-Tropsch reaction. The results of this study imply that the metastability of derived multiphase oxides structure has a greater influence on the formation of specific catalyst surface sites than other investigated surface properties.

  3. Dielectric behaviour of MgFe2O4 prepared from chemically beneficiated iron ore rejects

    Indian Academy of Sciences (India)

    K S Rane; V M S Verenkar; P Y Sawant

    2001-06-01

    Chemically beneficiated high silica/alumina iron ore rejects (27–76% Fe2O3) were used to synthesize iron oxides of purity 96–98% with SiO2/Al2O3 ratio reduced to 0.03. The major impurities on chemical beneficiations were Al, Si, and Mn in the range 2–3%. A 99.73% purity Fe2O3 was also prepared by solvent extraction method using methyl isobutyl ketone (MIBK) from the acid extracts of the ore rejects. The magnesium ferrite, MgFe2O4, prepared from these synthetic iron oxides showed high resistivity of ∼ 108 ohm cm. All ferrites showed saturation magnetization, 4s, in the narrow range of 900–1200 Gauss and the Curie temperature, c, of all these fell within a small limit of 670 ± 30 K. All ferrites had low dielectric constants ('), 12–15, and low dielectric loss, tan , which decreased with the increase in frequency indicating a normal dielectric dispersion found in ferrites. The presence of insignificant amount of polarizable Fe2+ ions can be attributed to their high resistances and low dielectric constants. Impurities inherent in the samples had no marked influence on the electrical properties of the ferrites prepared from the iron ore rejects, suggesting the possibility of formation of ferrite of constant composition, MgFe2O4, of low magnetic and dielectric losses at lower temperatures of 1000°C by ceramic technique.

  4. Hydrogen Storage Properties of Ti1.2Fe+xCa Hydrogen Storage Alloys

    Institute of Scientific and Technical Information of China (English)

    2001-01-01

    The hydrogen storage properties of Ti1.2Fe+xCa (x=1%, 3% and 5% in mass fraction) alloys was investigated. Results show that the modified alloys can be activated without any thermal treatment at room temperature due to the addition of Ca and excess Ti in the alloys. Hydrogen storage properties of these modified alloys vary with Ca amount and reaction temperature. In addition, the influence mechanism of the addition of Ca and excessive Ti on the activation behavior and hydrogen storage capacity of the alloys was discussed.

  5. Influence of the surface topography, morphology and structure on magnetic properties of ion beam sputtered iron layers, Fe/Cr/Fe- and Fe/MgO/Fe multilayers; Untersuchung der Morphologie und magnetische Eigenschaften von ionenstrahl-gesputterten Eisen-Einzelschichten, Fe/Cr/Fe- und Fe/MgO/Fe-Schichtsystemen

    Energy Technology Data Exchange (ETDEWEB)

    Steeb, Alexandra

    2007-04-05

    In this PhD Thesis, the influence of the surface topography, morphology and structure on magnetic properties of ion beam sputtered iron layers on GaAs is examined. To analyze the structure of the produced iron films, low energy electron diffraction and scanning tunneling microscopy is employed. The utilized methods to investigate the magnetic properties are Kerr- and SQUID-magnetometry and ferromagnetic resonance. It is demonstrated that on untreated as well as on presputtered and heated GaAs substrates the sputtered iron films grow epitaxially. The least surface roughness of 1 A exhibit iron films grown on untreated GaAs, while iron films on heated GaAs have the highest roughness of 30 A. The largest crystal anisotropy constant is found for the presputtered GaAs/Fe-System. For this preparation method, two monolayers of iron are determined to be magnetically dead layers. At a film thickness of 100 A, 83% of the value for saturation magnetization of bulk iron are achieved. The small observed FMR-linewidths confirm the good bulk properties of the ion beam sputtered iron. Furthermore, an antiferromagnetic interlayer exchange coupling in sputtered Fe/Cr/Fe-films was achieved. For a thickness of 12 to 17 A of the chrome interlayer, a coupling strength up to 0.2 mJ/m{sup 2} is found. To account for the small coupling strength, a strong intermixing at the interface is assumed. Finally, epitaxial Fe/MgO/Fe/FeMn multilayers are deposited on GaAs. After the structuring, it is possible to detect tunneling processes in the tunneling contacts with current-voltage measurements. The tunnel magneto resistance values of 2% are small, which can be explained by the absence of sharp, well-defined interfaces between the Fe/FeMn and the Fe/MgO interfaces. These results demonstrate, that analog to MBE the ion beam sputtering method realizes good magnetic bulk properties. However, interface sensitive phenomena are weakened because of a strong intermixing at the interfaces. (orig.)

  6. Seasonal dripwater Mg/Ca and Sr/Ca variations driven by cave ventilation: Implications for and modeling of speleothem paleoclimate records

    Science.gov (United States)

    Wong, C.I.; Banner, J.L.; Musgrove, M.

    2011-01-01

    A 4-year study in a central Texas cave quantifies multiple mechanisms that control dripwater composition and how these mechanisms vary at different drip sites. We monitored cave-air compositions, in situ calcite growth, dripwater composition and drip rate every 4-6weeks. Three groups of drip sites are delineated (Groups 1-3) based on geochemical variations in dripwater composition. Quantitative modeling of mineral-solution reactions within the host carbonate rock and cave environments is used to identify mechanisms that can account for variations in dripwater compositions. The covariation of Mg/Ca (and Sr/Ca) and Sr isotopes is key in delineating whether Mg/Ca and Sr/Ca variations are dictated by water-rock interaction (i.e., calcite or dolomite recrystallization) or prior calcite precipitation (PCP). Group 1 dripwater compositions reflects a narrow range of the extent of water-rock interaction followed by varying amounts of prior calcite precipitation (PCP). Group 2 dripwater compositions are controlled by varying amounts of water-rock interaction with little to no PCP influence. Group 3 dripwater compositions are dictated by variable extents of both water-rock interaction and PCP. Group 1 drip sites show seasonal variations in dripwater Mg/Ca and Sr/Ca, whereas the other drip sites do not. In contrast to the findings of most previous dripwater Mg/Ca-Sr/Ca studies, these seasonal variations (at Group 1 drip sites) are independent of changes in water flux (i.e., rainfall and/or drip rate), and instead significantly correlate with changes in cave-air CO2 concentrations. These results are consistent with lower cave-air CO2, related to cool season ventilation of the cave atmosphere, enhancing calcite precipitation and leading to dripwater geochemical evolution via PCP. Group 1 dripwater Mg/Ca and Sr/Ca seasonality and evidence for PCP as a mechanism that can account for that seasonality, have two implications for many other regions where seasonal ventilation of caves

  7. Diagenesis of echinoderm skeletons: Constraints on paleoseawater Mg/Ca reconstructions

    Science.gov (United States)

    Gorzelak, Przemysław; Krzykawski, Tomasz; Stolarski, Jarosław

    2016-09-01

    One of the most profound environmental changes thought to be reflected in chemical composition of numerous geological archives is Mg/Ca ratio of the seawater, which has varied dramatically throughout the Phanerozoic. Echinoderms that today typically form high magnesium calcite skeletons are increasingly being utilized as a proxy for interpreting secular changes in seawater chemistry. However, accurate characterization of the diagenetic changes of their metastable high magnesium calcite skeletons is a prerequisite for assessing their original, major-element geochemical composition. Here we expand the existing models of diagenesis of echinoderm skeleton by integration of various analytical methods that up to now rarely have been used to assess the diagenetic changes of fossil echinoderms. We validated the preservation of a suite of differently preserved echinoderm ossicles, mostly crinoids, ranging in age from the Cambrian through Recent. In 13 of 99 fossil echinoderm ossicles we found well-preserved porous microstructure (stereom), non-luminescent behaviour or blotchy dark color in cathodoluminescence, and distinct nanostructural features (layered and nanocomposite structure). Moreover, in representatives of such preserved samples, distribution of sulphates associated with organic matter is identical to those in Recent echinoderms. Only such ossicles, despite of local micrometer-scale diagenetic changes, were herein considered well-preserved, retaining their original major-element skeletal composition. By contrast, majority of samples show transformation to the stable low magnesium calcite that leads to obliteration of the primary geochemical and micro/nanostructural features and is accompanied with increase in cathodoluminescence emission intensity. Using only well-preserved fossil echinoderm samples, we found purely random variation in Mg/Ca in echinoderm skeletons through the observed time series; any periodicities in echinoderm skeletal Mg/Ca ratio which might

  8. Computer Aided Design of Wires Extrusion from Biocompatible Mg-Ca Magnesium Alloy

    Directory of Open Access Journals (Sweden)

    Milenin A.

    2014-06-01

    Full Text Available W pracy zaproponowano model matematyczny procesu wyciskania prętów o małych średnicach z biokompatybilnego stopu magnezu MgCa08 (Mg - 0.8% Ca. Na podstawie opracowanego modelu możliwy jest dobór parametrów technologicznych rozpatrywanego procesu. Model procesu wyciskania zawiera model do prognozowania utraty spójności materiału, który został opracowany w oparciu o próby spęczania oraz jednoosiowego rozciągania w zakresie temperatur 250-400°C dla różnych prędkości odkształcenia. W oparciu o metodę elementów skończonych (MES przeprowadzona została analiza numeryczna rozkładu temperatury oraz wskaźnika wykorzystania odkształcalności materiału w procesie wyciskania. Zaproponowany model zawiera dwa możliwe mechanizmy utraty spójności: a wynikający z lokalnego przekroczenia temperatury topnienia, b wynikający z wyczerpania zapasu plastyczności. W oparciu o przeprowadzoną analizę MES procesu wyciskania dla różnych temperatur oraz prędkości wyciskania opracowano diagram ELM (extrusion limit diagram dla stopu MgCa08. Na podstawie opracowanego diagramu ELM dobrano parametry procesu wyciskania prętów o średnicy 1 mm. Weryfikację modelu procesu wyciskania dla stopu MgCa08 wykonano w warunkach laboratoryjnych, gdzie przeprowadzono dwunasto żyłowy proces wyciskania prętów w temperaturze 400°C i prędkości 0.25 mm/s. Otrzymane pręty były| wolne od wad. co potwierdziło dobrą zgodność pomiędzy wynikami numerycznymi i eksperymentalnymi.

  9. TPR and TPD studies of effects of Cu and Ca promotion on Fe-Zn-based Fischer-Tropsch catalysts

    Indian Academy of Sciences (India)

    Olusola O James; Biswajit Chowdhury; Sudip Maity

    2013-05-01

    Temperature-programmed reduction (TPR) and temperature-programmed desorption (TPD) were used to study the effects of Cu and Ca promotion on Fe-Zn-based Fischer-Tropsch catalysts. The reduction temperature for Fe2O3 → Fe3O4 was unaffected by Ca addition but decreased when promoted with Cu. Fe-Zn promoted with Cu and Ca showed even much lower reduction temperature for Fe2O3→Fe3O4. Ca promotion enhances carburization and increases surface acidity and basicity of the Fe-Zn oxide precursor. While Cu inhibits carburization and decreases the surface acidity and basicity of the Fe-Zn oxide precursor. The implications of these effects on the application of catalysts for FT are discussed.

  10. Ferromagnetic resonance of epitaxial Fe nanodots grown on MgO measured using coplanar waveguides

    Energy Technology Data Exchange (ETDEWEB)

    Mizuguchi, M; Takanashi, K, E-mail: mizuguchi@imr.tohoku.ac.jp [Institute for Materials Research, Tohoku University, Sendai 980-8577 (Japan)

    2011-02-16

    Ferromagnetic resonance measurements of Fe nanodots epitaxially grown on a MgO layer were carried out using a coplanar waveguide to investigate the dynamic behaviours of spins in a magnetic dot assembly. The resonant peaks of Fe nanodots with an average diameter of 10 nm were successfully observed, and a strong magnetic anisotropy was found in the peak frequency shift depending on the magnetic field applied in the film plane. A difference was clearly seen in the peak shift behaviour between Fe nanodots and continuous Fe thin films. The Gilbert damping parameter of the Fe nanodots (nominal thickness: 3 nm) was estimated to be 0.008 12 from the width of the resonant peaks, substantially larger than that of a continuous Fe thin film with a thickness of 8 nm. This difference in damping is attributed to the distribution of the effective field in each nanodot due to size dispersion. Ferromagnetic resonance studies using coplanar waveguides thus enable clarification of the spin dynamics of magnetic dot arrays and the fundamental spin dynamics of a single nanodot.

  11. Multilayer FeRh/MgO: controllable magnetocrystalline anisotropy for an antiferromagnetic system

    Science.gov (United States)

    Zheng, Guohui; Dorj, Odkhuu; Ke, Sanhuang; Ramesh, Rammoorthy; Miao, Maosheng; Kioussis, Nickolas

    2015-03-01

    Controlling the magnetocrystalline anisotropy (MCA) of ferromagnetic (FM) thin films by tunable strain and electric field has been pursued as an effective method of achieving low-power and highly scalable memory. Comparing with FM materials, AFM are much less sensitive to external magnetic field, a substantial advantage for memory devices. Inspired by recent work on AFM memory resistors based on FeRh, we carried out a systematic first principles study of the MCA of multi-layer FeRh, either stand alone, or combined with MgO layers. FeRh is a unique material that undergoes a transition from AFM (type-II) to FM at elevated temperature of 370 K. Our calculations for thin films of FeRh from 5-15 atomic layers reveal that AFM is always the most stable configuration for Fe terminated films; while for Rh terminated films, there is a transition from FM to a configuration featured AFM at the center layers and FM at the surface layers (reconstructed). While applying the spin-orbit interactions (SOI) for the valence electrons, we found Fe-terminated films exhibit a relatively small MCA that varies and may change sign with film thickness, substrate and strain, providing a possibility of spin reorientation via the control of strain and electric field. The k-resolved MCA values reveals that the region around Gamma point adds the major contribution to the MCA.

  12. In Vitro Corrosion and Cytocompatibility of a Microarc Oxidation Coating and Poly(l-lactic acid) Composite Coating on Mg-1Li-1Ca Alloy for Orthopedic Implants.

    Science.gov (United States)

    Zeng, Rong-Chang; Cui, Lan-Yue; Jiang, Ke; Liu, Rui; Zhao, Bao-Dong; Zheng, Yu-Feng

    2016-04-20

    Manipulating the degradation rate of biomedical magnesium alloys poses a challenge. The characteristics of a microarc oxidation (MAO), prepared in phytic acid, and poly(l-lactic acid) (PLLA) composite coating, fabricated on a novel Mg-1Li-1Ca alloy, were studied through field emission scanning electron microscopy (FE-SEM), electron probe X-ray microanalysis (EPMA), energy dispersive X-ray spectroscopy (EDS) and X-ray diffraction (XRD). The corrosion behaviors of the samples were evaluated via hydrogen evolution, potentiodynamic polarization and electrochemical impedance spectroscopy in Hanks' solution. The results indicated that the MAO/PLLA composite coatings significantly enhanced the corrosion resistance of the Mg-1Li-1Ca alloy. MTT and ALP assays using MC3T3 osteoblasts indicated that the MAO/PLLA coatings greatly improved the cytocompatibility, and the morphology of the cells cultured on different samples exhibited good adhesion. Hemolysis tests showed that the composite coatings endowed the Mg-1Li-1Ca alloys with a low hemolysis ratio. The increased solution pH resulting from the corrosion of magnesium could be tailored by the degradation of PLLA. The degradation mechanism of the composite coatings was discussed. The MAO/PLLA composite coating may be appropriate for applications on degradable Mg-based orthopedic implants. PMID:27022831

  13. Status Ca, Mg dan Zn pada Kambing Peranakan Etawah Muda yang Diberi Ransum Bentuk Mash dengan Pakan Sumber Serat Berbeda

    Directory of Open Access Journals (Sweden)

    T. Toharmat

    2007-08-01

    Full Text Available Fibrous agricultural by-products are the component of most rations for ruminant raised intensively. Slow rate and low digestibility of the fibrous feed may limit mineral bioavailability. Present experiment aimed to clarify the influence of fibrous feed component in ration on the status of Ca, Mg and Zn in growing goats. Twenty of female Etawah-grade goats weighing of 13.5±2.14 kg were grouped and allocated into five treatments in a randomized block design. Rations composed of 50% fibrous feed and 50% concentrate. The fibrous feed component as treatments were: RG = napier grass, JP = rice straw, KC = cacao pod, JK = mixed rice straw and coffee husk, and CP = mixed rice straw, napier grass, coffee husk and cacao pod. Rations were offered at 3% of live weight. The result showed that fibrous feed influenced Ca, Mg, and Zn intake, Ca and Mg absorption, and Ca, Mg and Zn plasma of growing goats. Intake, absorption and plasma Ca, Mg, and Zn had positive correlation with dry mater intake. Absorption of Ca and Zn had positive correlations with crude fiber digestibility. Supplementation of Ca, Mg and Zn was necessary when the fibrous feed was included at the level of 50% in the ration of growing goats, but the supplement level varied according to the type of the fibrous feed.

  14. [Matrix Effect of Fe and Ca on EDXRF Analysis of Ce Concentration in Bayan Obo Ores].

    Science.gov (United States)

    Qi, Hai-jun; Wang, Jian-ying; Zhang, Xue-feng; Wang, Yang

    2015-12-01

    When Energy-Dispersive X-RayFluorescence (EDXRF) used for measuring cerium (Ce) content in the Bayan Obo ores, matrix effect mainly comes from iron (Fe) and calcium (Ca). Due to extensive concentration variability of the two elements, commonly employed standard sample method for matrix effect correction is invalid. To overcome the problem, testing samples were prepared based on the average contents of elements in the Bayan Obo ores, and the influence of Fe and Ca on the coefficient in a linear relationship between Ce content and XRF signal was determined by linear least squares fitting for multivariate analysis. The coefficients thus determined reflected the matrix effect on Ce emitted fluorescence from Fe emitted fluorescence and Ca absorption. When the coefficients were used in analyzing Ce content in Bayan Obo mine by EDXRF, the relative error is less than 10%. PMID:26964240

  15. Complex temperature evolution of the electronic structure of CaFe2As2

    Science.gov (United States)

    Adhikary, Ganesh; Biswas, Deepnarayan; Sahadev, Nishaina; Bindu, R.; Kumar, Neeraj; Dhar, S. K.; Thamizhavel, A.; Maiti, Kalobaran

    2014-03-01

    Employing high resolution photoemission spectroscopy, we investigate the temperature evolution of the electronic structure of CaFe2As2, which is a parent compound of high temperature superconductors—CaFe2As2 exhibits superconductivity under pressure as well as doping of charge carriers. Photoemission results of CaFe2As2 in this study reveal a gradual shift of an energy band, α away from the chemical potential with decreasing temperature in addition to the spin density wave (SDW) transition induced Fermi surface reconstruction across SDW transition temperature. The corresponding hole pocket eventually disappears at lower temperatures, while the hole Fermi surface of the β band possessing finite p orbital character survives till the lowest temperature studied. These results, thus, reveal signature of complex charge redistribution among various energy bands as a function of temperature.

  16. DOLOČANJE MAGNEZIJA V NODULATORJIH FEROSILIKO MAGNEZIJ FeSiMg 25-5-1 Z ICP-OES

    OpenAIRE

    Hamzić Gregorčič, Staša

    2013-01-01

    Osnovna dejavnost podjetja TDR Ferolegure d.o.o. je proizvodnja in prodaja legur, med katere spadajo nodulatorji, cepiva in polnjene žice. V nalogi bomo izpostavili nodulatorje z besedo ferosiliko magnezij, FeSiMg. Nodulatorji so po sestavi visokokakovostne kompleksne zlitine, katerih osnovna naloga je vnos magnezija v sivo litino. FeSiMg delajo iz osnovne zlitine FeSi, ki mu dodajajo določen delež magnezija, ki je glavni element v zlitinah. Zlitine FeSiMg vsebujejo 5 do 35 % magnezija. Poleg...

  17. Mg/Ca thermometry in planktic foraminifera: Improving paleotemperature estimations for G. bulloides and N. pachyderma left

    Science.gov (United States)

    Vázquez Riveiros, Natalia; Govin, Aline; Waelbroeck, Claire; Mackensen, Andreas; Michel, Elisabeth; Moreira, Santiago; Bouinot, Thomas; Caillon, Nicolas; Orgun, Ayche; Brandon, Margaux

    2016-04-01

    Planktic foraminiferal Mg/Ca ratios have become a fundamental seawater temperature proxy in past climate reconstructions, due to the temperature dependence of Mg uptake into foraminiferal calcite. However, empirical calibrations for single species from methodologically consistent data are still lacking. Here we present species-specific calibrations of Mg/Ca versus calcification temperature for two commonly used species of planktic foraminifera: Globigerina bulloides and Neogloboquadrina pachyderma left, based on a series of Southern Ocean and North Atlantic core tops. Combining these new data with previously published data, we derive an integrated G. bulloides Mg/Ca-temperature calibration for mid and high latitudes of both hemispheres between 2 and 18°C, where Mg/Ca = 1.006 ± 0.032 * e0.065 ± 0.003*Tiso (R2 = 0.82). G. bulloides is found to calcify deeper in the Southern Ocean (˜ 200 m) than in the North Atlantic (top 50 m). We also propose a Mg/Ca temperature calibration to describe the temperature response in N. pachyderma left that calcified away from the influence of sea ice in the Southern Ocean, valid between ˜ -1 and 9°C, of the form Mg/Ca = 0.580 ± 0.016 * e0.084 ± 0.006*Tiso (R2 = 0.70). These calibrations account for uncertainties on Mg/Ca measurements and calcification temperature that were carefully estimated and propagated using Monte Carlo iterations. The 1σ propagated error in Mg/Ca-derived temperatures is 1.1°C for G. bulloides and 0.9°C for N. pachyderma left for the presented data sets. Geographical extension of genotypes must be assessed when choosing to develop regional or global calibrations.

  18. A first principles study on newly proposed (Ca/Sr/Ba)Fe2Bi2 compounds with their parent compounds

    Science.gov (United States)

    Sundareswari, M.; Jayalakshmi, D. S.; Viswanathan, E.

    2016-02-01

    The structural, electronic, bonding and magnetic properties of newly proposed iron-based compounds viz., CaFe2Bi2, SrFe2Bi2, BaFe2Bi2 with their Fermi surface topology are reported here for the first time by means of first principles calculation. All these properties of newly proposed compounds are compared and analysed along with their respective parent compounds namely (Ca,Sr,Ba)Fe2As2.

  19. Intrinsic Proton NMR Studies of Mg(OH)2 and Ca(OH)2

    Science.gov (United States)

    Itoh, Yutaka; Isobe, Masahiko

    2016-09-01

    We studied the short proton free induction decay signals and the broad 1H NMR spectra of Mg(OH)2 and Ca(OH)2 powders at 77-355 K and 42 MHz using pulsed NMR techniques. Using a Gaussian-type back extrapolation procedure for the obscured data of the proton free induction decay signals, we obtained more precise values of the second moments of the Fourier-transformed broad NMR spectra than those in a previous report [Y. Itoh and M. Isobe, http://doi.org/10.7566/JPSJ.84.113601, J. Phys. Soc. Jpn. 84, 113601 (2015)] and compared with the theoretical second moments. The decrease in the second moment could not account for the large decrease in the magnitude of the intrinsic proton spin-lattice relaxation rate 1/T1 from Mg(OH)2 to Ca(OH)2. The analysis of 1/T1 ∝ exp(-Eg/kBT) with Eg ˜ 0.01 eV points to a local hopping mechanism, and that of 1/T1 ∝ Tn with n ˜ 0.5 points to an anharmonic rattling mechanism.

  20. Influence of Heat Treatment on Biocorrosion and Hemocompatibility of Biodegradable Mg-35Zn-3Ca Alloy

    Directory of Open Access Journals (Sweden)

    Jeong-Hui Ji

    2015-01-01

    Full Text Available Mg-35Zn-3Ca (wt.% alloy containing nontoxic and biocompatible Zn and Ca as alloying elements was prepared and subjected to heat treatment and artificial aging for different duration of time to reduce its rate of degradation. Solution heat treatment was performed at 310°C while artificial aging was performed at 170°C for 0, 2.5, 5.0, 7.5, and 10.0 h and they were designated as AT0, AT1, AT2, AT3, and AT4, respectively. The finest and most homogenous reticulum was observed on the surface of the AT2 group. The result of immersion test in Hank’s balanced salt solution (HBSS showed that the corrosion rate of the AT2 group was 2.32 mg/(cm2 day, which was significantly lower as compared to other groups P<0.05. The hemolysis value was ≤5% in all groups, indicating no toxicity during short-term blood reaction.

  1. Hyperpolarizabilities of alkaline-earth metal ions Be+, Mg+, and Ca+

    Science.gov (United States)

    Yin, Dong; Zhang, Yong-Hui; Li, Cheng-Bin; Gao, Ke-Lin; Shi, Ting-Yun

    2016-09-01

    The knowledge of the hyperpolarizabilities of atoms and ions is helpful for the analysis of the high order effects of the frequency shifts in precision spectroscopy experiments. Liu et al. [Phys. Rev. Lett. 114, 223001 (2015)] proposed to establish all-optical trapped ion clocks using laser at the magic wavelength for clock transition. To evaluate the high-order frequency shifts in this new scheme of optical clocks, hyperpolarizabilities are needed, but absent. Using the finite field method based on the B-spline basis set and model potentials, we calculated the electric-field-dependent energy shifts of the ground and low-lying excited states in Be+, Mg+, and Ca+ in the field strength range of 0.0-6×10-5 a.u.. The scalar and tensor polarizabilities ( α 0, α 2) and hyperpolarizabilities ( γ 0, γ 2, γ 4) were deduced. The results of the hyperpolarizabilities for Be+ showed good agreement with the values in literature, implying that the present method can be applied for the effective estimation of the atomic hyperpolarizabilities, which are rarely reported but needed in experiments. The feasibility of optical trapping of Ca+ is discussed, and the contributions of hyperpolarizabilities to the transition frequency shift for Ca+ in the optical dipole trap are estimated using quasi-electrostatic approximation.

  2. Effect of MgO/Fe Interface Oxidation State on Electric-Field Modulation of Interfacial Magnetic Anisotropy

    Science.gov (United States)

    Guan, X. W.; Cheng, X. M.; Wang, S.; Huang, T.; Xue, K. H.; Miao, X. S.

    2016-06-01

    The impact of the MgO/Fe interface oxidation state on the electric-field-modified magnetic anisotropy in MgO/Fe has been revealed by density functional calculations. It is shown that the influence of the interface oxidation is strong enough to dominate the effect of the electric field on the magnetic anisotropy of MgO/Fe-based films. The magnetoelectric coefficients are calculated to be positive for the ideal and overoxidized MgO/Fe interface, but an abnormal negative value emerges in the underoxidized case. By analyzing the interface states based on density of states and band structures, we demonstrate that the considerably different electronic structures of the three oxidized MgO/Fe interfaces lead to the strong discrepancy in the electric-field modulation of the interfacial magnetic anisotropy. These results are of considerable interest in the area of electric-field-controlled magnetic anisotropy and switching.

  3. Metallurgical phases and their magnetism at the interface of nanoscale MgB2/Fe layered structures.

    Science.gov (United States)

    Sahoo, B; Keune, W; Kuncser, V; Becker, H-W; Röhlsberger, R

    2011-11-30

    We report on the characterization of metallurgical phases and their magnetism at the interfaces of nanoscale MgB(2)/Fe layered structures. MgB(2)/(57)Fe multilayers with varying layer thicknesses were prepared by vacuum deposition and investigated, before and after annealing by electrical resistance measurements, x-ray diffraction and (57)Fe conversion-electron Mössbauer spectroscopy (CEMS) down to 5 K. Interfacial Fe-B phases, such as Fe(2)B, were identified by CEMS. A superparamagnetic-to-ferromagnetic transition is observed with increasing (57)Fe film thickness. Ultrahigh vacuum annealing at 500 °C of the multilayers leads to strong diffusion of Fe atoms into the boundary regions of the MgB(2) layers. MgB(2) in the as-grown multilayers is non-superconducting. Structural disorder and the effect of Fe interdiffusion contribute to the suppression of superconductivity in the MgB(2) films of all the as-grown multilayers and the thinner annealed multilayers. However, an annealed MgB(2)/(57)Fe/MgB(2) trilayer with thicker (500 Å) MgB(2) layers is observed to be superconducting with an onset temperature of 25 K. At 5 K, the annealed trilayer can be conceived as being strongly chemically modulated, consisting of two partially Fe-doped superconducting MgB(2) layers separated by an interdiffused weakly magnetic Fe-B interlayer, which is characterized by a low hyperfine magnetic field B(hf) of ∼11 T. This chemically modulated layer structure of the trilayer after annealing was verified by Rutherford backscattering.

  4. The Effects of Temperature and Salinity on Mg Incorporation in Planktonic Foraminifera Globigerinoides ruber (white): Results from a Global Sediment Trap Mg/Ca Database

    Science.gov (United States)

    Gray, W. R.; Weldeab, S.; Lea, D. W.

    2015-12-01

    Mg/Ca in Globigerinoides ruber is arguably the most important proxy for sea surface temperature (SST) in tropical and sub tropical regions, and as such guides our understanding of past climatic change in these regions. However, the sensitivity of Mg/Ca to salinity is debated; while analysis of foraminifera grown in cultures generally indicates a sensitivity of 3 - 6% per salinity unit, core-top studies have suggested a much higher sensitivity of between 15 - 27% per salinity unit, bringing the utility of Mg/Ca as a SST proxy into dispute. Sediment traps circumvent the issues of dissolution and post-depositional calcite precipitation that hamper core-top calibration studies, whilst allowing the analysis of foraminifera that have calcified under natural conditions within a well constrained period of time. We collated previously published sediment trap/plankton tow G. ruber (white) Mg/Ca data, and generated new Mg/Ca data from a sediment trap located in the highly-saline tropical North Atlantic, close to West Africa. Calcification temperature and salinity were calculated for the time interval represented by each trap/tow sample using World Ocean Atlas 2013 data. The resulting dataset comprises >240 Mg/Ca measurements (in the size fraction 150 - 350 µm), that span a temperature range of 18 - 28 °C and 33.6 - 36.7 PSU. Multiple regression of the dataset reveals a temperature sensitivity of 7 ± 0.4% per °C (p changes when variations in salinity are accounted for.

  5. The Effects of Temperature and Salinity on Mg Incorporation in Planktonic Foraminifera Globigerinoides ruber (white): Results from a Global Sediment Trap Mg/Ca Database

    Science.gov (United States)

    Gray, W. R.; Weldeab, S.; Lea, D. W.

    2015-12-01

    Mg/Ca in Globigerinoides ruber is arguably the most important proxy for sea surface temperature (SST) in tropical and sub tropical regions, and as such guides our understanding of past climatic change in these regions. However, the sensitivity of Mg/Ca to salinity is debated; while analysis of foraminifera grown in cultures generally indicates a sensitivity of 3 - 6% per salinity unit, core-top studies have suggested a much higher sensitivity of between 15 - 27% per salinity unit, bringing the utility of Mg/Ca as a SST proxy into dispute. Sediment traps circumvent the issues of dissolution and post-depositional calcite precipitation that hamper core-top calibration studies, whilst allowing the analysis of foraminifera that have calcified under natural conditions within a well constrained period of time. We collated previously published sediment trap/plankton tow G. ruber (white) Mg/Ca data, and generated new Mg/Ca data from a sediment trap located in the highly-saline tropical North Atlantic, close to West Africa. Calcification temperature and salinity were calculated for the time interval represented by each trap/tow sample using World Ocean Atlas 2013 data. The resulting dataset comprises >240 Mg/Ca measurements (in the size fraction 150 - 350 µm), that span a temperature range of 18 - 28 °C and 33.6 - 36.7 PSU. Multiple regression of the dataset reveals a temperature sensitivity of 7 ± 0.4% per °C (p < 2.2*10-16) and a salinity sensitivity of 4 ± 1% per salinity unit (p = 2*10-5). Application of this calibration has significant implications for both the magnitude and timing of glacial-interglacial temperature changes when variations in salinity are accounted for.

  6. Role of Hydrogen in the Electronic Properties of CaFeAsH-based Superconductors

    OpenAIRE

    Y. N. Huang; Liu, D.Y.; Zou, L. J.; PICKETT, W.E.

    2016-01-01

    The electronic and magnetic properties of the new hydride superconductor CaFeAsH, which superconducts up to 47 K when electron-doped with La, and the isovalent alloy system CaFeAsH$_{1-x}$F$_x$ are investigated using density functional based methods. The $\\vec Q = (\\pi,\\pi,0)$ peak of the nesting function $\\xi(\\vec q)$ is found to be extremely strong and sharp, and additional structure in $\\xi(\\vec q)$ associated with the near-circular Fermi surfaces (FSs) that may impact low energy excitatio...

  7. HPIC separation and quantification of Ca and Fe in uranium metal and alloy compounds

    International Nuclear Information System (INIS)

    The paper describes the separation and quantification of Ca and Fe from uranium metal and uranium based alloy fuels employing ion chromatography (IC). Ca separation from other metal ions of alkali and alkaline groups was carried out on a cation exchange column and the same was detected and quantified by means of conductivity detector. In case of Fe, it was separated from other transition elements using chelation ion chromatography where detection and quantification was carried out photometrically after the addition of PAR as post column reagent. For both the analyses a preliminary column chromatography separation for eliminating the bulk matrix uranium was performed. (author)

  8. FeII/MgII Emission Line Ratio in High Redshift Quasars

    DEFF Research Database (Denmark)

    Dietrich, M.; Hamann, F.; Appenzeller, I.;

    2003-01-01

    We present results of the analysis of near infrared spectroscopic observations of 6 high-redshift quasars (z > 4), emphasizing the measurement of the ultraviolet FeII/MgII emission line strength in order to estimate the beginning of intense star formation in the early universe. To investigate the...... evolution of the FeII/MgII ratio over a wider range in cosmic time, we measured this ratio for composite quasar spectra which cover a redshift range of 0 4 quasars must have started already at an epoch corresponding to z_f = 6 to 9, when the age of the universe was ~0.5 Gyr (H_o = 72 km/s/Mpc, Omega_M = 0...

  9. Very fast formation of superconducting MgB2/Fe wires with high Jc

    OpenAIRE

    Wang, X L.; Soltanian, S.; Horvat, J.; Qin, M. J.; Liu, H. K.; Dou, S.X.

    2001-01-01

    In this paper we have investigated the effects of sintering time and temperature on the formation and critical current densities of Fe-clad MgB2 wires. MgB2 wires were fabricated using the powder-in-tube process and sintered for different periods of time at predetermined temperatures. All the samples were examined using XRD, SEM and magnetisation measurements. In contrast to the common practice of sintering for several hours, the present results show that there is no need for prolonged heat t...

  10. Sorption of chromium (VI) by Mg/Fe hydrotalcite type compunds

    Energy Technology Data Exchange (ETDEWEB)

    García-Sosa, I., E-mail: irma.garcia@inin.gob.mx; Cabral-Prieto, A., E-mail: agustin.cabral@inin.gob.mx [Instituto Nacional de Investigaciones Nucleares, Departamento de Química (Mexico); Nava, N., E-mail: tnava@imp.mx; Navarrete, J. [Instituto Mexicano del Petróleo (Mexico); Olguín, M. T., E-mail: teresa.olguin@inin.gob.mx [Instituto Nacional de Investigaciones Nucleares, Departamento de Química (Mexico); Escobar, Luis, E-mail: luis.escobar@inin.gob.mx [Instituto Nacional de Investigaciones Nucleares, Departamento de Física (Mexico); López-Castañares, R., E-mail: rlc@anuies.mx; Olea-Cardoso, O., E-mail: olc@anuies.mx [Universidad Autónoma del Edo. de México, Facultad de Química (Mexico)

    2015-06-15

    The synthesis by co-precipitation and characterization by X-ray diffraction, Raman and Mössbauer spectroscopies of Mg-Fe-hydrotalcite compounds, and their sorption capacities for Cr(VI) in aqueous media were carried out. The average sorption capacity of Cr(VI) for the non-thermal treated samples was of 6.2 mg/g. The ferrihydrite was omnipresent in all prepared hydrotalcite samples. A brief discussion is made on the role of both the hydrotalcite and ferrihydrite for removing such amount of Cr(VI)

  11. Fabrication of MgFe2O4/MoS2 Heterostructure Nanowires for Photoelectrochemical Catalysis.

    Science.gov (United States)

    Fan, Weiqiang; Li, Meng; Bai, Hongye; Xu, Dongbo; Chen, Chao; Li, Chunfa; Ge, Yilin; Shi, Weidong

    2016-02-16

    A novel one-dimensional MgFe2O4/MoS2 heterostructure has been successfully designed and fabricated. The bare MgFe2O4 was obtained as uniform nanowires through electrospinning, and MoS2 thin film appeared on the surface of MgFe2O4 after further chemical vapor deposition. The structure of the MgFe2O4/MoS2 heterostructure was systematic investigated by X-ray diffraction (XRD), high-resolution transmission electron microscopy (HRTEM), X-ray photoelectron spectrometry (XPS), and Raman spectra. According to electrochemical impedance spectroscopy (EIS) results, the MgFe2O4/MoS2 heterostructure showed a lower charge-transfer resistance compared with bare MgFe2O4, which indicated that the MoS2 played an important role in the enhancement of electron/hole mobility. MgFe2O4/MoS2 heterostructure can efficiently degrade tetracycline (TC), since the superoxide free-radical can be produced by sample under illumination due to the active species trapping and electron spin resonance (ESR) measurement, and the optimal photoelectrochemical degradation rate of TC can be achieved up to 92% (radiation intensity: 47 mW/cm(2), 2 h). Taking account of its unique semiconductor band gap structure, MgFe2O4/MoS2 can also be used as an photoelectrochemical anode for hydrogen production by water splitting, and the hydrogen production rate of MgFe2O4/MoS2 was 5.8 mmol/h·m(2) (radiation intensity: 47 mW/cm(2)), which is about 1.7 times that of MgFe2O4. PMID:26797320

  12. Fabrication of MgFe2O4/MoS2 Heterostructure Nanowires for Photoelectrochemical Catalysis.

    Science.gov (United States)

    Fan, Weiqiang; Li, Meng; Bai, Hongye; Xu, Dongbo; Chen, Chao; Li, Chunfa; Ge, Yilin; Shi, Weidong

    2016-02-16

    A novel one-dimensional MgFe2O4/MoS2 heterostructure has been successfully designed and fabricated. The bare MgFe2O4 was obtained as uniform nanowires through electrospinning, and MoS2 thin film appeared on the surface of MgFe2O4 after further chemical vapor deposition. The structure of the MgFe2O4/MoS2 heterostructure was systematic investigated by X-ray diffraction (XRD), high-resolution transmission electron microscopy (HRTEM), X-ray photoelectron spectrometry (XPS), and Raman spectra. According to electrochemical impedance spectroscopy (EIS) results, the MgFe2O4/MoS2 heterostructure showed a lower charge-transfer resistance compared with bare MgFe2O4, which indicated that the MoS2 played an important role in the enhancement of electron/hole mobility. MgFe2O4/MoS2 heterostructure can efficiently degrade tetracycline (TC), since the superoxide free-radical can be produced by sample under illumination due to the active species trapping and electron spin resonance (ESR) measurement, and the optimal photoelectrochemical degradation rate of TC can be achieved up to 92% (radiation intensity: 47 mW/cm(2), 2 h). Taking account of its unique semiconductor band gap structure, MgFe2O4/MoS2 can also be used as an photoelectrochemical anode for hydrogen production by water splitting, and the hydrogen production rate of MgFe2O4/MoS2 was 5.8 mmol/h·m(2) (radiation intensity: 47 mW/cm(2)), which is about 1.7 times that of MgFe2O4.

  13. Magnetic behavior of Mg-Al-Zn-Fe mixed oxides from precursors layered double hydroxide

    Energy Technology Data Exchange (ETDEWEB)

    Oliva, M.I., E-mail: marcosivanoliva@gmail.com [Facultad de Matematica, Astronomia y Fisica, Universidad Nacional de Cordoba, M. Allende y H. de la Torre Ciudad Universitaria, 5000 Cordoba (Argentina); IFFAM AF (CONICET - FaMAF UNC), M. Allende y H. de la Torre Ciudad Universitaria, 5000 Cordoba (Argentina); Heredia, A. [CITeQ - Facultad R. Cordoba, Universidad Tecnologica Nacional Maestro Lopez esq. Cruz Roja Argentina, CP 5016 Cordoba (Argentina); Zandalazini, C.I. [Centro Laser de Ciencias Moleculares. INFIQC-FCQ-Grupo de Ciencia de Materiales-FaMAF-Universidad Nacional de Cordoba, Ciudad Universitaria, CP5000 Cordoba, Argentina CONICET (Argentina); Crivello, M. [CITeQ - Facultad R. Cordoba, Universidad Tecnologica Nacional Maestro Lopez esq. Cruz Roja Argentina, CP 5016 Cordoba (Argentina); Corchero, E. [Facultad de Matematica, Astronomia y Fisica, Universidad Nacional de Cordoba, M. Allende y H. de la Torre Ciudad Universitaria, 5000 Cordoba (Argentina)

    2012-08-15

    Mixed oxides of Mg-Al-Zn-Fe were obtained by calcination of layered double hydroxides (LDH) prepared by coprecipitation reaction with hydrothermal treatment. The structural characterization of precursors and oxides was carried out by X rays diffraction, showing increases of ZnO phase with the increase of the zinc content. Magnetic behavior was studied by vibrating sample magnetometer (VSM) and by a superconducting quantum interference device (SQUID) showing both paramagnetic and super paramagnetic behavior depending on both particles size and composition.

  14. Magnetic anisotropy and reversal in epitaxial Fe/MgO(001) films revisited

    OpenAIRE

    Zhan, Qing-feng; Vandezande, Stijn; Temst, Kristiaan; Van Haesendonck, Chris

    2008-01-01

    We investigate the magnetization reversal in Fe/MgO(001) films with fourfold in-plane magnetic anisotropy and an additional uniaxial anisotropy whose orientation and strength are tuned using different growth geometries and post growth treatments. The previously adopted mechanism of 180^{o} domain wall nucleation clearly fails to explain the observed 180^{o} magnetization reversal. A new reversal mechanism with two successive domain wall nucleations consistently predicts the switching fields f...

  15. Strain control magnetocrystalline anisotropy of Ta/FeCo/MgO heterostructures

    Energy Technology Data Exchange (ETDEWEB)

    Ong, P. V.; Kioussis, Nicholas, E-mail: nick.kioussis@csun.edu [Department of Physics and Astronomy, California State University Northridge, Northridge, California 91330 (United States); Amiri, P. Khalili; Wang, K. L. [Department of Electrical Engineering, University of California, Los Angeles, California 90095 (United States); Carman, Gregory P. [Department of Mechanical and Aerospace Engineering, University of California, Los Angeles, California 90095 (United States)

    2015-05-07

    Using ab initio electronic structure calculations, we have investigated the effect of epitaxial strain on magnetocrystalline anisotropy (MCA) of Ta/FeCo/MgO heterostructure. At small expansive strains on the FeCo layer, the system exhibits perpendicular MCA (PMA). Strain not only has a profound effect on the value of MCA but also induces a switching of magnetic easy axis. Analysis of the energy- and k-resolved distribution of orbital characters of the minority-spin band reveals that a significant contribution to PMA at zero strain arises from the spin-orbit coupling between occupied d{sub x{sup 2}−y{sup 2}} and unoccupied d{sub xy} states, derived from Fe at the FeCo/MgO interface. The strain effect is attributed to strain-induced shifts of spin-orbit coupled d-states. Our work demonstrates that strain engineering can open a viable pathway towards tailoring magnetic properties for spintronic applications.

  16. Correlation between intrinsic dipole moment and pyroelectric coefficient of Fe-Mg tourmaline

    Institute of Scientific and Technical Information of China (English)

    Chang-chun Zhao; Li-bing Liao; Jie Xing

    2014-01-01

    Single-crystal X-ray diffraction structural data of four Fe-Mg tourmalines with different Fe contents from Xinjiang, Sichuan, and Yunnan Provinces, China, were collected at room temperature and-100ºC. The intrinsic dipole moments of polyhedra and the total intrinsic dipole moment of the unit cell were calculated. By comparing the intrinsic electric dipole moments of the X, Y, Z, T, and B site polyhedra, it is found that the T site polyhedron makes the greatest contribution to the total intrinsic dipole moment. The pyroelectric coefficients of four Fe-Mg tourmalines were experimentally determined, and the influence of intrinsic dipole moments on their pyroelectric properties was inves-tigated. The experimental results show that, compared with the case at room temperature, the intrinsic dipole moments change with the total Fe content at-100ºC in a completely different way. With the decrease of temperature, the total intrinsic dipole moments of tourmaline de-crease. Over the same temperature interval, the pyroelectric coefficients increase with the increase in intrinsic dipole moment.

  17. Effects of Ca2+ and Mg2+ on the Enzymatic Properties of Cardiac Muscle Myosin%Ca2+、Mg2+对心肌肌球蛋白ATP酶活性的影响

    Institute of Scientific and Technical Information of China (English)

    朱彬; 万朝敏; 刘荣韬; 孙爱民; 黄勋; 王正荣

    2002-01-01

    目的研究Ca2+、Mg2+对心肌肌球蛋白ATP酶活性的影响.方法采用一种简便、快速的方法从心肌组织中提取肌球蛋白,根据酶反应ATP分解释放的无机磷含量检测Ca2+、Mg2+激活肌球蛋白ATP酶的Km值及最大反应速度Vmax,以及不同浓度的Ca2+、Mg2+、pH值对肌球蛋白ATP酶活性的影响.结果 Ca2+、Mg2+-肌球蛋白ATP酶Km值为5.27±2.10 mmol、7.04±2.06 mmol,Vmax分别为:1.10±0.13 μmol·mg-1·min-1、0.617±0.09 μmol·mg-1·min-1;Ca2+较Mg2+具有较大的酶激活能力(P<0.01),但Mg2+的浓度影响着肌球蛋白ATP酶对Ca2+的敏感性,当Mg2+浓度大于6 mmol/L时,酶对Ca2+的存在无反应;不同的pH值,对Mg2+激活的酶反应影响较小.结论 Ca2+、Mg2+对肌球蛋白ATP酶的作用机理不同,Mg2+是维系肌球蛋白具有酶活性构象所必需,而Ca2+在肌肉收缩过程中可能主要充当的是信号传导功能及调控功能.

  18. Valorisation of Ca and Mg by-products from mining and seawater desalination brines for water treatment applications

    OpenAIRE

    Casas Garriga, Sandra; Aladjem, Carlos; Larrotcha, Enric; Gibert Agulló, Oriol; Valderrama Angel, César Alberto; Cortina Pallás, José Luís

    2014-01-01

    BACKGROUNDBrines from the drainage of potash mine tailings and from seawater reverse osmosis (SWRO) desalination were previously evaluated as sources of NaCl for the chlor-alkali industry. Valorisation of NaCl as raw material is required to meet the membrane electrolysis specifications of NaCl saturation and control of interferences (Ca, Mg and sulphate). Brines concentration in NaCl was previously achieved for SWRO brines using electrodialysis (ED). In this work, valorisation of Ca and Mg by...

  19. Ionic-liquid gating of perpendicularly magnetised CoFeB/MgO thin films

    Science.gov (United States)

    Liu, Y. T.; Agnus, G.; Ono, S.; Ranno, L.; Bernand-Mantel, A.; Soucaille, R.; Adam, J.-P.; Langer, J.; Ocker, B.; Ravelosona, D.; Herrera Diez, L.

    2016-07-01

    We present the modulation of anisotropy field, coercivity, and domain wall (DW) velocity in CoFeB/MgO thin films with perpendicular anisotropy by applying voltages across an ionic liquid gate. Domain wall velocities in the creep regime can be modulated by a factor of 4.2, and the anisotropy field of the device can be modulated by 40 mT when going from +0.8 V to -0.8 V. The applied E-fields are seen to significantly influence DWs' pinning, depinning, and nucleation processes. In addition, we report on the evolution of the magnetic properties of the liquid/solid device as a function of time going from the pristine CoFeB/MgO film through device fabrication and operation up to one month. These results show that the solid/liquid device structure based on CoFeB/MgO thin films can be an efficient way to control magnetic properties with voltages below 1 V.

  20. Complex structures of different CaFe2As2 samples

    Science.gov (United States)

    Saparov, Bayrammurad; Cantoni, Claudia; Pan, Minghu; Hogan, Thomas C.; , William Ratcliff, II; Wilson, Stephen D.; Fritsch, Katharina; Gaulin, Bruce D.; Sefat, Athena S.

    2014-02-01

    The interplay between magnetism and crystal structures in three CaFe2As2 samples is studied. For the nonmagnetic quenched crystals, different crystalline domains with varying lattice parameters are found, and three phases (orthorhombic, tetragonal, and collapsed tetragonal) coexist between TS = 95 K and 45 K. Annealing of the quenched crystals at 350°C leads to a strain relief through a large (~1.3%) expansion of the c-parameter and a small (~0.2%) contraction of the a-parameter, and to local ~0.2 Å displacements at the atomic-level. This annealing procedure results in the most homogeneous crystals for which the antiferromagnetic and orthorhombic phase transitions occur at TN/TS = 168(1) K. In the 700°C-annealed crystal, an intermediate strain regime takes place, with tetragonal and orthorhombic structural phases coexisting between 80 to 120 K. The origin of such strong shifts in the transition temperatures are tied to structural parameters. Importantly, with annealing, an increase in the Fe-As length leads to more localized Fe electrons and higher local magnetic moments on Fe ions. Synergistic contribution of other structural parameters, including a decrease in the Fe-Fe distance, and a dramatic increase of the c-parameter, which enhances the Fermi surface nesting in CaFe2As2, are also discussed.

  1. Large influence of capping layers on tunnel magnetoresistance in CoFe/MgO/CoFe magnetic tunnel junctions

    CERN Document Server

    Zhou, Jiaqi; Wang, Yin; Peng, Shouzhong; Qiao, Junfeng; Su, Li; Zeng, Lang; Lei, Na; Zhang, Youguang; Bournel, Arnaud

    2016-01-01

    We report the first-principles theoretical investigations of the tunnel magnetoresistance(TMR) effect in the symmetric capping layer/CoFe(001)/MgO(001)/CoFe(001)/capping layer magnetic tunnel junctions(MTJs) with Ta, Hf and Ir used as capping layer materials. Spin-resolved conductance and TMR ratios are shown and it is found that the TMR ratio is sensitive to the capping layer material. The spin polarization of s state in Co atom at the CoFe/capping layer interface is presented to explain the influence on TMR ratio caused by different capping layers, and we can obtain a high spin polarization value and a giant TMR ratio when Ir is used, demonstrating that Ir is an ideal capping layer material. We also study the spin-polarized transport properties in the Brillouin zone. In the parallel condition, a central broad peak is found in the majority-spin channel due to the {\\Delta}1 state, while sharp transmission probability peaks at some k||-points appear in the minority-spin channel. The sharp peak phenomenon is at...

  2. Materiales de Al2O3 - MgAl2O4 - CaAl12O19 - Ca2Mg2Al28O46 obtenidos mediante un proceso de sinterización reactiva entre Al2O3 y CaMg(CO3)2

    OpenAIRE

    Aza Moya, Antonio H. de; Peña, P.; Moset, M.

    2002-01-01

    [ES] Utilizado la información suministrada por el diagrama de equilibrio de fases Al2O3-MgO-CaO se ha diseñado y obtenido un material de Al2O3-MgAl2O4-CaAl12O19-Ca2Mg2Al28O46 mediante sinterización reactiva de una mezcla de Al2O3 y CaMg(CO3)2. Las reacciones que tienen lugar en la mezcla durante el proceso se han estudiado usando técnicas de análisis térmico diferencial, termogravimetrico y dilatometría. Muestras reaccionadas a temperaturas seleccionadas se han estudiado por difracci...

  3. Leachable Li and Mg Evidence for Hydrological Changes in the Mono Basin, CA, USA

    Science.gov (United States)

    Sahajpal, R.; Hemming, N.; Zimmerman, S. R.; Hemming, S. R.

    2007-12-01

    Hydrology in closed basin lakes, such as Mono Lake of the US western Great Basin, is sensitive to regional climate changes. Lake level history of the Mono Basin has been put into a precise age framework using the paleomagnetic intensity of the Wilson Creek Formation sediments to North Atlantic records, and accordingly Greenland's GISP2 oxygen isotope record (Zimmerman et al., 2006, EPSL, v. 252, pp. 94- 106). This allows correlation of the lake level indicators and Greenland climate at high resolution. The physical evidence for lake level, based on the association of strata in near shore terraces, can be confidently correlated to proxies of lake chemistry preserved in the strata. We have tested the application of leachable Li, following the procedure developed by Bischoff et al. (1997, Quaternary Research, v. 48, pp. 313-325) for Owens Lake. At Owens Lake there is a positive correlation between salinity based on diatoms with leachable Li concentrations. In contrast, at Mono Lake the leachable Li concentration follows the bulk carbonate concentration, generally correlating low lake levels (high salinity) with low leachable Li concentrations. Our preferred explanation for both the carbonate and leachable Li concentrations is based on the fact that the Mono Basin rarely overflows, and therefore precipitation of minerals during evaporation leads to chemical divides (Garrels and Mackenzie., 1967, in "Equilibrium Concepts in Natural Water Systems", W. Stumm, Ed., pp. 222-242). As Li behaves conservatively compared to elements like Ca2+ and Mg2+, it might be expected that the leachable Li would be higher when lake level is lower. However, the host for the Li appears to be Mg-smectite. Therefore, the concentration of leachable Li in the sediment is controlled by the concentration of Mg-smectite, as well as the Li/Mg of the water from which the Mg- smectite precipitated and the Kd of the Li into the Mg-smectite. We are studying the Li and Mg systematics of these samples in

  4. Sensing Seasonality in the Arabian Sea: a coupled δ18O-Mg/Ca approach

    Directory of Open Access Journals (Sweden)

    W. Feldmeijer

    2014-09-01

    Full Text Available Millennial scale climate variability punctuates the record of Northern Hemisphere glacials in the form of Dansgaard–Oeschger cycles. The coldest episodes within these cycles have a marked impact on the location of the Inter-tropical Convergence Zone and thereby the intensity and extent of the Asian monsoon system. Arabian Sea oceanography is closely linked to the monsoon cycle and responds rapidly to changes therein. Seasonally varying upwelling intensity, adhesive mixing and the resulting variability on sea surface temperature and salinity, however, make it challenging to precisely reconstruct the behaviour of the Indian monsoon system through the Dansgaard–Oeschger cycles. To reconstruct impact of millennial-scale changes in the monsoon on the Arabian Sea, paired single-specimen Mg/Ca and stable oxygen isotope analyses were performed on three species of planktonic foraminifera from the northern as well as the western Arabian Sea. Mismatches between Mg/Ca- and δ18O-derived temperatures reflect changes in salinity caused by regional variability in the hydrological cycle. Comparison of Mg/Ca-derived temperatures from Globigerinoides ruber, Globigerina bulloides and Neogloboquadrina dutertrei over Heinrich Event 4 and Interstadial 8 allows for reconstructing the seasonal range in temperatures (minima and maxima and vertical stratification of the water column during these intervals. Results show that Arabian Sea surface water temperatures were lower during the North Atlantic Heinrich Event 4, and that temperatures in the northern and western Arabian Sea differed relatively much. This implies that the north east monsoon (i.e. boreal winter was enhanced during this interval. In contrast, the summer upwelling related species G. bulloides reveals lower temperatures during Interstadial 8 in the western Arabian Sea, showing an enhanced summer monsoon during the warmers stages of millennial-scale climate variability. Together, these results show that

  5. 三元复合钙基材料CaO-Ca3Al2O6-MgO的合成及其CO2吸附性能%Preparation of ternary composite Ca-based material CaO-Ca3Al2O6-MgO for high-temperature CO2 capture

    Institute of Scientific and Technical Information of China (English)

    张明明; 彭云湘; 汪瑾; 李平; 于建国

    2014-01-01

    采用Al2O3和MgO同时掺杂改性的方法制备了CaO-Ca3Al2O6-MgO复合钙基高温吸附CO2材料.复合钙基材料孔隙发达,活性物相为CaO,惰性骨架物相为Ca3Al2O6和MgO.Ca3Al2O6/MgO质量比偏小的材料,表面微粒粒径较小.在10%(体积分数,下同)CO2和90% N2的混合气气氛下,采用热重分析仪测量了复合钙基材料吸附CO2容量、碳化反应速率以及循环碳化(670℃)/煅烧(900℃)过程的稳定性.结果发现,复合钙基材料CaO-Ca3Al2O6-MgO具有较好的吸附CO2性能,提高Ca3Al2O6/MgO质量比,合成材料的循环稳定性较好;降低Ca3Al2O6/MgO质量比,合成材料的碳化反应速率加快,CaO转化率提高.最后,通过对不同循环次数下复合钙材料的比表面积、孔径分布、微观形貌、表面元素分布,晶相、晶粒大小进行研究分析,对合成材料的失活以及掺杂物质对烧结的抑制机理进行了讨论.

  6. Voltage-controlled magnetic anisotropy in Fe|MgO tunnel junctions studied by x-ray absorption spectroscopy

    Energy Technology Data Exchange (ETDEWEB)

    Miwa, Shinji, E-mail: miwa@mp.es.osaka-u.ac.jp; Matsuda, Kensho; Tanaka, Kazuhito; Goto, Minori; Suzuki, Yoshishige [Graduate School of Engineering Science, Osaka University, Toyonaka, Osaka 560-8531 (Japan); Kotani, Yoshinori; Nakamura, Tetsuya [Japan Synchrotron Radiation Research Institute/SPring-8, Sayo, Hyogo 679-5198 (Japan)

    2015-10-19

    In this study, voltage-controlled magnetic anisotropy (VCMA) in Fe|MgO tunnel junctions was investigated via the magneto-optical Kerr effect, soft x-ray absorption spectroscopy, and magnetic circular dichroism spectroscopy. The Fe|MgO tunnel junctions showed enhanced perpendicular magnetic anisotropy under external negative voltage, which induced charge depletion at the Fe|MgO interface. Despite the application of voltages of opposite polarity, no trace of chemical reaction such as a redox reaction attributed to O{sup 2−} migration was detected in the x-ray absorption spectra of the Fe. The VCMA reported in the Fe|MgO-based magnetic tunnel junctions must therefore originate from phenomena associated with the purely electric effect, that is, surface electron doping and/or redistribution induced by an external electric field.

  7. Liquidus of the HfO2-MgO and HfO2-CaO systems

    International Nuclear Information System (INIS)

    Studied is the liquidus of the HfO2-MgO and HfO2-CaO systems by the method of the thermal analysis using solar heating. The liquidus of the HfO2-MgO system is stated to be of eutectic type. The liquidus of the HfO2-CaO system is characterized by the presence of two eutectic points. The maximum on the liquidus at the temperature of 2440+-25 deg C meets the formation of the CaHfO3 compounds

  8. Ca-Fe and Alkali-Halide Alteration of an Allende Type B CAI: Aqueous Alteration in Nebular or Asteroidal Settings

    Science.gov (United States)

    Ross, D. K.; Simon, J. I.; Simon, S. B.; Grossman, L.

    2012-01-01

    Ca-Fe and alkali-halide alteration of CAIs is often attributed to aqueous alteration by fluids circulating on asteroidal parent bodies after the various chondritic components have been assembled, although debate continues about the roles of asteroidal vs. nebular modification processes [1-7]. Here we report de-tailed observations of alteration products in a large Type B2 CAI, TS4 from Allende, one of the oxidized subgroup of CV3s, and propose a speculative model for aqueous alteration of CAIs in a nebular setting. Ca-Fe alteration in this CAI consists predominantly of end-member hedenbergite, end-member andradite, and compositionally variable, magnesian high-Ca pyroxene. These phases are strongly concentrated in an unusual "nodule" enclosed within the interior of the CAI (Fig. 1). The Ca, Fe-rich nodule superficially resembles a clast that pre-dated and was engulfed by the CAI, but closer inspection shows that relic spinel grains are enclosed in the nodule, and corroded CAI primary phases interfinger with the Fe-rich phases at the nodule s margins. This CAI also contains abundant sodalite and nepheline (alkali-halide) alteration that occurs around the rims of the CAI, but also penetrates more deeply into the CAI. The two types of alteration (Ca-Fe and alkali-halide) are adjacent, and very fine-grained Fe-rich phases are associated with sodalite-rich regions. Both types of alteration appear to be replacive; if that is true, it would require substantial introduction of Fe, and transport of elements (Ti, Al and Mg) out of the nodule, and introduction of Na and Cl into alkali-halide rich zones. Parts of the CAI have been extensively metasomatized.

  9. Novel Approach for the Remediation of Radioactive Cesium Contaminated Soil with nano-Fe/Ca/CaO Dispersion Mixture in Dry Condition

    Directory of Open Access Journals (Sweden)

    Mallampati S. R.

    2013-04-01

    Full Text Available Present study, first time we developed a nano-Fe/Ca/CaO dispersion mixture based remediation and volume reduction method of real radioactive cesium contaminated soils. After soil samples treated with 10wt% of nano-Fe/Ca/CaO dispersion mixtures, emitting radiation intensity was reduced from 4.00 μSv/h to 0.95 μSv/h in non-magnetic fraction soils. While, after treatment, about 30wt% magnetic and 70wt% nonmagnetic fraction soils were separated, and it’s condensed radioactive cesium concentration was about 80% and 20%, respectively. By this way, cesium contaminated soil volume can be reduced. These preliminary results appear to be very promising and the simple mixing with the addition of nano-Fe/Ca/CaO may be considered potentially applicable for the remediation and separation of radioactive Cs contaminated soil in dry conditions.

  10. Gradiente radial de [Mg/Fe] em duas galáxias elípticas

    Science.gov (United States)

    Milone, A.; Capelato, H.

    2003-08-01

    Basicamente, são propostos dois cenários de evolução quí mio-dinâmico para os sistemas esferoidais: (i) o hierárquico através da fusão e/ou acresção de sub-sistemas com ou sem surtos de formação estelar, e (ii) o colapso monolí tico dissipativo com formação estelar interrompida por um vento galáctico. Ambos, dentro de certos limites, conseguem explicar os gradientes internos de metalicidade estelar presentes nas galáxias elí pticas bem como a relação observada entre a metalicidade central e a massa (Mg20 vs. log sv0). No entanto, nenhum prevê uma variação interna para a razão de abundâncias Mg/Fe que indiretamente define a escala temporal da formação estelar. Empregamos a espectroscopia óptica de fenda longa com a finalidade de recuperar as histórias de formação estelar, de enriquecimento quí mico e da dinâmica dentro de determinadas regiões das galáxias. Os espectros de média resolução (FWHM = 7,1 Å) e escala angular de 1,092 arcsec/pixel foram coletados com o telescópio 1,60m do OPD/LNA. Comparamos nossas medidas de linhas de absorção com resultados espectrofotométricos de modelos de populações estelares simples - mais especificamente os í ndices do Sistema Lick como Mg2, Mg b, e Hb - a fim de se investigar as variações internas de [Fe/H], [Mg/Fe] e idade. Para duas galáxias elí pticas, NGC 1052 e NGC 7796, pertencentes a ambientes de baixa densidade, encontramos uma variação radial da razão Mg/Fe decrescente do centro para fora em regiões de 0,6 e 1 raio efetivo respectivamente. Discutimos alguns cenários de enriquecimento quí mico para estas duas galáxias.

  11. The c/a Ratio in Quenched Fe-C and Fe-N steels - a Heuristic Story

    Energy Technology Data Exchange (ETDEWEB)

    Sherby, O; Wadsworth, J; Lesuer, D; Syn, C

    2006-01-31

    The body-centered tetragonal (BCT) structure in quenched Fe-C steels is usually illustrated to show a linear change in the c and a axes with an increase in carbon content from 0 to 1.4%C. The work of Campbell and Fink, however, shows that this continuous linear relationship is not correct. Rather, it was shown that the body-centered-cubic (BCC) structure is the stable structure from 0 to 0.6 wt%C with the c/a ratio equal to unity. An abrupt change in the c/a ratio to 1.02 occurs at 0.6 wt%C. The BCT structure forms, and the c/a ratio increases with further increase in carbon content. An identical observation is noted in quenched Fe-N steels. This discontinuity is explained by a change in the transformation process. It is proposed that a two-step transformation process occurs in the low carbon region, with the FCC first transforming to HCP and then from HCP to BCC. In the high carbon region, the FCC structure transforms to the BCT structure. The results are explained with the Engel-Brewer theory of valence and crystal structure of the elements. An understanding of the strength of quenched iron-carbon steels plays a key role in the proposed explanation of the c/a anomaly based on interstitial solutes and precipitates.

  12. Depressing effect of phenoxyl acetic acids on flotation of minerals containing Ca2+/Mg2+ gangues

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    Phenoxyl acetic acids were applied to determine their depressing effect on minerals containing Ca2+/Mg2+ gangues. Calcite,mixture of calcite and fluorite, and nickel ore were used in the flotation. And the depression mechanism was studied by the determination of contact angle, zeta potential, adsorptive capacity of collector, and IR analysis as well. It is found that 0.1 mmol/L of phenoxyl acetic acid derived from pyrogallol or gallic acid exhibits strong depressing ability on calcite in almost zero yields at pH value of 9.8, and calcite can be depressed in the flotation of calcite/fluorite mixture for approximate 87% yield of fluorite. The flotation result of practical nickel ore containing serpentine indicates that these two depressants may also show better depression performance to serpentine than traditional depressants such as sodium fluosilicate and carboxylmethyl cellulose. Analysis for the depression mechanism reveals that there exists strong chemical interaction between the depressants and minerals.

  13. Quantitative procedure for evaluation of microstructure of cast Mg-Al-Ca-Sr magnesium alloy

    Directory of Open Access Journals (Sweden)

    T. Rzychoń

    2010-01-01

    Full Text Available In this paper the microstructural characterization of ingot MRI-230D magnesium alloy and quantitative procedure for evaluation of microstructure are presented. The optical and scanning electron microscopy were used to study the morphology of microstructural compounds in this alloy. The X-ray diffraction was used to determination of phase composition. The as-cast microstructure of MRI-230D magnesium alloy containing aluminum, calcium and strontium consists of the dendritic α-Mg and such intermetallic compounds as: Al2Ca, Al4Sr and AlxMny. In the purpose quantitative description of microstructure semi-automatic procedures using Met-Ilo image analysis were developed. Prepared semi-automatic procedures allow a fast determination of phase content in MRI-230D alloy using light microscopy and will be useful in the quality control of MRI-230D ingots.

  14. A Study of Ca-Mg Silicate Crystalline Glazes--An Analysis on Forms of Crystals

    Institute of Scientific and Technical Information of China (English)

    LIU Pei-de; YU Ping-li; WU Ji-huai

    2004-01-01

    In the study on Ca-Mg silicate crystalline glazes, we found some disequilibrated crystallization phenomena,such as non-crystallographic small angle forking and spheroidal growth, parasitism and wedging-form of crystals, dendritic growth, secondary nucleation, etc. Those phenomena possibly resulted from two factors:(1) partial temperature gradient, which is caused by heat asymmetry in the electrical resistance furnace,when crystals crystalize from silicate melt ; (2) constitutional supercooling near the surface of crystals. The disparity of disequilibrated crystallization phenomena in different main crystalline phases causes various morphological features of the crystal aggregates. At the same time, disequilibrated crystallization causes great stress retained in the crystals, which results in cracks in glazes when the temperature drops. According to the results, the authors analyzed those phenomena and displayed correlative figures and data.

  15. Infrared spectroscopy of rare-earth-doped CaFe2As2

    Science.gov (United States)

    Xing, Zhen; Huffman, T. J.; Xu, Peng; Qazilbash, M. M.; Saha, S. R.; Drye, Tyler; Paglione, J.

    2014-03-01

    Recently, rare-earth doping in CaFe2As2 has been used to tune its electronic, magnetic, and structural properties. The substitution of rare-earth ions at the alkaline-earth sites leads to the suppression of the spin-density wave (SDW) phase transition in CaFe2As2. For example, Pr substitution results in a paramagnetic metal in the tetragonal phase that is susceptible to a low temperature structural transition to a collapsed tetragonal phase. However, La-doped CaFe2As2 remains in the uncollapsed tetragonal structure down to the lowest measured temperatures. Both the uncollapsed and collapsed tetragonal structures exhibit superconductivity with maximum Tc reaching 47 K, the highest observed in inter-metallics albeit with a small superconducting volume fraction. In this work, we perform ab-plane infrared spectroscopy of rare-earth-doped CaFe2As2 at different cryogenic temperatures. Our aim is to ascertain the contributions of electron doping and chemical pressure to the charge and lattice dynamics of this iron-arsenide system.

  16. FeMo cofactor synthesis by a nifH mutant with altered MgATP reactivity.

    Science.gov (United States)

    Gavini, N; Burgess, B K

    1992-10-15

    We have characterized a Nif- mutant of Azotobacter vinelandii, designated UW91 (Shah, V. K., Davis, L. C., Gordon, J. K., Orme-Johnson, W. H., and Brill, W. J. (1973) Biochim. Biophys. Acta 292, 246-255). The specific Fe protein mutation giving rise to the Nif- phenotype was shown by DNA sequencing and site-directed mutagenesis to be the substitution of a conserved alanine at position 157 by a serine. The UW91 Fe protein was purified and shown to have a normal [4Fe-4S] cluster and normal MgATP binding activity. The substitution of alanine 157 by serine, however, prevents the MgATP-induced conformational change that occurs for the wild-type Fe protein, prevents MgATP hydrolysis, and prevents productive electron transfer to the MoFe protein. The UW91 Fe protein does bind to the MoFe protein to give a normal cross-linking pattern; however, it does not compete very successfully with wild-type Fe protein in an activity assay. The UW91 MoFe protein was also purified and characterized and shown to be indistinguishable from the wild-type protein. Thus, the substitution of Fe protein residue alanine 157 by serine does not change the Fe protein's ability to function in FeMo cofactor biosynthesis or insertion. This demonstrates that these events do not require the MgATP-induced conformational change, MgATP hydrolysis, or productive electron transfer to the MoFe protein. PMID:1400428

  17. OH− absorption and nonvolatile holographic storage properties in Mg:Ru:Fe:LiNbO3 crystal as a function of Mg concentration

    International Nuclear Information System (INIS)

    Mg:Ru:Fe:LiNbO3 crystals with various concentrations of MgO (in mole) and fixed content of RuO2 and Fe2O3 (in mass) are grown with the Czochralski method from the congruent melt. Their infrared transmission spectra are measured and discussed to investigate the defect structure. With the increase of Mg2+ concentration the blue nonvolatile holographic storage capability is enhanced. The nonvolatile holographic storage properties of dual-wavelength recording of Mg(7 mol%):Ru:Fe:LiNbO3 nonvolatile diffraction efficiency, response time, and nonvolatile sensitivity reach 59.8%, 70 s, and 1.04 cm/J, respectively. Comparing Mg(7 mol%):Ru:Fe:LiNbO3 with Ru:Fe:LiNbO3 crystal, the response time is shortened apparently. The nonvolatile diffraction efficiency and sensitivity are raised largely. The mechanism in blue photorefractive nonvolatile holographic storage is discussed. (electromagnetism, optics, acoustics, heat transfer, classical mechanics, and fluid dynamics)

  18. A study on alkaline heat treated Mg-Ca alloy for the control of the biocorrosion rate.

    Science.gov (United States)

    Gu, X N; Zheng, W; Cheng, Y; Zheng, Y F

    2009-09-01

    To reduce the biocorrosion rate by surface modification, Mg-Ca alloy (1.4wt.% Ca content) was soaked in three alkaline solutions (Na(2)HPO(4), Na(2)CO(3) and NaHCO(3)) for 24h, respectively, and subsequently heat treated at 773K for 12h. Scanning electron microscopy and energy-dispersive spectroscopy results revealed that magnesium oxide layers with the thickness of about 13, 9 and 26microm were formed on the surfaces of Mg-Ca alloy after the above different alkaline heat treatments. Atomic force microscopy showed that the surfaces of Mg-Ca alloy samples became rough after three alkaline heat treatments. The in vitro corrosion tests in simulated body fluid indicated that the corrosion rates of Mg-Ca alloy were effectively decreased after alkaline heat treatments, with the following sequence: NaHCO(3) heatedMg-Ca alloy samples induced toxicity to L-929 cells during 7days culture.

  19. Determinación de Ca, Cu, Fe y Pb por espectrofotometría de absorción atómica en aguardientes de caña

    Directory of Open Access Journals (Sweden)

    Magdalena Lorenzo

    2010-01-01

    Full Text Available La determinación de Ca, Cu, Fe y Pb en aguardientes¸ se realizó por espectrofotometría de absorción atómica. El volumen de inyección fue 20 uL, la calibración se llevó a cabo en intervalos de 0,5-25,0 mg.L-1 de Ca; 0,25-5,0 mg.L-1 para el Cu, Pb y el Cu, y se utilizaron las absorbancias de Ca, Cu, Fe y Pb contra la concentración de los analitos, respectivamente. Las correlaciones lineales típicas de r = 0,99 en todos los casos. El método propuesto se aplicó para la determinación directa de Ca, Cu, Fe y Pb en muestras de aguardientes comerciales por triplicado y los resultados se obtuvieron por este método para un 95% de nivel de confianza.

  20. Perpendicular magnetic anisotropy of full-Heusler films in Pt/Co2FeAl/MgO trilayers

    OpenAIRE

    Li, Xiaoqi; Yin, Shaoqian; Liu, Yupeng; Zhang, Delin; Xu, Xiaoguang; Miao, Jun; Jiang, Yong

    2011-01-01

    We report on perpendicular magnetic anisotropy (PMA) in a Pt/Co2FeAl/MgO sandwiched structure with a thick Co2FeAl layer of 2-2.5 nm. The PMA is thermally stable that the anisotropy energy density Ku is 1.3{\\times}106 erg/cm3 for the structure with 2 nm Co2FeAl after annealing at 350 oC. The thicknesses of Co2FeAl and MgO layers greatly affect the PMA. Our results provide an effective way to realize relative thick perpendicularly magnetized Heusler alloy films.

  1. Crystallization of Fe78Si9B13 Bulk Crystaline/Amorphous (c/a) Composite

    Institute of Scientific and Technical Information of China (English)

    JIN Shifeng; WANG Weimin; NIU Yuchao; ZHANG Jiteng; LI Guihua; BIAN Xiufang

    2008-01-01

    A metallic crystalline/amorphous (c/a) bulk composite was prepared by the slow cooling method after remelting the amorphous Fe78Si9B13 ribbon. By X-ray diffraction (XRD),differential scanning calorimetry (DSC) and scanning electron microscope (SEM), the composite consists of the primary dendrite a-Fe (without Si) as well as the amorphous matrix. After being anneal at 800 K, the uniform spheroid particles are formed in the c/a composite, which does not form in the amorphous ribbon under the various annealing process. Energy dispersive analysis of X-rays (EDAX), SEM and XRD were applied to give more detailed information. The formation and evolution of the particle may stimulate the possible application of the Fe-matrix amorphous alloy.

  2. Blood compatibility of zinc-calcium phosphate conversion coating on Mg-1.33Li-0.6Ca alloy

    Science.gov (United States)

    Zou, Yu-Hong; Zeng, Rong-Chang; Wang, Qing-Zhao; Liu, Li-Jun; Xu, Qian-Qian; Wang, Chuang; Liu, Zhi-Wei

    2016-06-01

    Magnesium alloys as a new class of biomaterials possess biodegradability and biocompatibility in comparison with currently used metal implants. However, their rapid corrosion rates are necessary to be manipulated by appropriate coatings. In this paper, a new attempt was used to develop a zinc-calcium phosphate (Zn-Ca-P) conversion coating on Mg-1.33Li-0.6Ca alloys to increase the biocompatibility and improve the corrosion resistance. In vitro blood biocompatibility of the alloy with and without the Zn-Ca-P coating was investigated to determine its suitability as a degradable medical biomaterial. Blood biocompatibility was assessed from the hemolysis test, the dynamic cruor time test, blood cell count and SEM observation of the platelet adhesion to membrane surface. The results showed that the Zn-Ca-P coating on Mg-1.33Li-0.6Ca alloys had good blood compatibility, which is in accordance with the requirements for medical biomaterials.

  3. Blood compatibility of zinc-calcium phosphate conversion coating on Mg-1.33Li-0.6Ca alloy

    Science.gov (United States)

    Zou, Yu-Hong; Zeng, Rong-Chang; Wang, Qing-Zhao; Liu, Li-Jun; Xu, Qian-Qian; Wang, Chuang; Liu, Zhi-Wei

    2016-09-01

    Magnesium alloys as a new class of biomaterials possess biodegradability and biocompatibility in comparison with currently used metal implants. However, their rapid corrosion rates are necessary to be manipulated by appropriate coatings. In this paper, a new attempt was used to develop a zinc-calcium phosphate (Zn-Ca-P) conversion coating on Mg-1.33Li-0.6Ca alloys to increase the biocompatibility and improve the corrosion resistance. In vitro blood biocompatibility of the alloy with and without the Zn-Ca-P coating was investigated to determine its suitability as a degradable medical biomaterial. Blood biocompatibility was assessed from the hemolysis test, the dynamic cruor time test, blood cell count and SEM observation of the platelet adhesion to membrane surface. The results showed that the Zn-Ca-P coating on Mg-1.33Li-0.6Ca alloys had good blood compatibility, which is in accordance with the requirements for medical biomaterials.

  4. Optical Properties of Blue-Light-Emitting (Ca,Sr)Mg2Si3O9:Eu2+ Phosphor

    Science.gov (United States)

    Lee, Hyun Ju; Choi, Sung Hwan; Kim, Kyung Pil; Shin, Hyun Ho; Yoo, Jae Soo

    2010-10-01

    For light-emitting diode (LED) excitation at 400 nm, the optical properties of a Eu2+-activated CaO-SrO-MgO-SiO2 material system were investigated. All the materials were synthesized by solid state reaction. In particular, (Ca,Sr)Mg2Si3O9:Eu2+, which has the same crystal structure as CaMgSi2O6, was found to be promising as a blue-light-emitting phosphor for near UV LED application. The luminance intensity was optimized by controlling the Eu2+ concentration and the composition of the host lattice. The ratio of calcium ions to strontium ions was a convenient parameter for adjusting the maximum excitation peak to 400 nm, which is favorable for near UV LED excitation. The highest luminance intensity of Ca1-x-ySryMg2Si3O9:Eux2+ under 405 nm excitation was achieved at the Eu2+ concentration of x=0.01 and a Sr2+ concentration of y=0.3. The luminance intensity of (Ca,Sr)Mg2Si3O9:Eu2+ was found to be superior to that of a commercial blue-light-emitting BaMgAl10O17:Eu2+ phosphor, which is used for near-UV LED excitation.

  5. Corrosion degradation behavior of Mg-Ca alloy with high Ca content in SBF%高Ca含量Mg-Ca合金在模拟体液中的腐蚀降解行为

    Institute of Scientific and Technical Information of China (English)

    刘一驰; 刘德宝; 赵越; 陈民芳

    2015-01-01

    研究高Ca含量Mg−Ca合金作为骨修复材料在模拟体液中的腐蚀降解行为。采用扫描电子显微镜(SEM)和X射线衍射(XRD)对Mg−30%Ca(质量分数)合金的显微组织及相成分进行表征。将Mg−30%Ca合金在模拟体液中浸泡90 d后,观察和测试最终产物的微观形貌、成分以及细胞毒性。结果表明:Mg−30%Ca合金的主要相成分为α-MgMg2Ca相,在浸泡过程中,Mg2Ca相作为阳极,而α-Mg相作为阴极;Mg−30%Ca合金在模拟体液中浸泡的最终腐蚀产物由少量的的黑色沉淀颗粒和白色悬浮颗粒组成,白色悬浮颗粒为Mg(OH)2,而黑色沉淀颗粒具有核壳结构;细胞毒性实验证明黑色沉淀颗粒无细胞毒性。%The corrosion degradation behavior of a Mg−Ca alloy with high Ca content aiming for a potential bone repair material in the simulated body fluid (SBF) was investigated. The microstructure and phase constitution of the pristine Mg−30%Ca (mass fraction) alloy were characterized with scanning electron microscopy (SEM) and X-ray diffraction (XRD). The Mg−30%Ca alloy samples were immersed in the SBF for 90 d, and the morphology, composition and cytotoxicity of the final corrosion product were examined. It is found that Mg−30%Ca alloy is composed of α-Mg and Mg2Ca phases. During the corrosion process in the SBF, the Mg2Ca phase acts as an anode and theα-Mg phase acts as a cathode. The final corrosion product of the Mg−30%Ca alloy in SBF includes a small amount of black precipitates and white suspended particles. The white suspended particles are Mg(OH)2 and the black particles are believed to have a core−shell structure. The cytotoxicity experiments indicate that these black precipitates do not induce toxicity to cells.

  6. Enhanced removal performance by the core-shell zeolites/MgFe-layered double hydroxides (LDHs) for municipal wastewater treatment.

    Science.gov (United States)

    Guo, Lu; Zhang, Xiangling; Chen, Qiaozhen; Ruan, Congying; Leng, Yujie

    2016-04-01

    The application of powdered layer double hydroxides (LDHs) in constructed rapid infiltration system (CRIS) appears to be an appreciable problem still unsolved due to the small particle size and the low density. Therefore, the core-shell zeolites/MgFe-LDHs composites were prepared via using co-precipitation method in present study. To investigate the practical applicability, a detailed organics, ammonia, and total phosphorus removal study were carried out in columns to treat the municipal wastewater. The scanning electron microscope (SEM) and energy dispersive spectrometer (EDS) results confirmed the successful synthesis of core-shell zeolites/MgFe-LDHs through coating on the surface of zeolites. Accordingly, the zeolites/MgFe-LDHs largely reduced the COD by 81.14 %, NH4 (+)-N by 81.50%, and TP by 83.29%. Phosphate adsorption study revealed that the equilibrium adsorption data were better fitted by Langmuir isothermal model, with the maximum adsorption capacity of 79.3651 mg/kg for zeolites/MgFe-LDHs and 38.4615 mg/kg for the natural zeolites. In addition, economic analysis indicated that the reagent cost of synthesis of zeolites/MgFe-LDHs was economical. Herein, the zeolites/MgFe-LDHs solved the natural zeolites problem for poor P removal and the application of powdered LDHs in the solid/liquid separation process, suggesting that it was applicable as potential substrates for the removal of organics, ammonia, and total phosphorus in CRIS. PMID:26662562

  7. Woody waste air gasification in fluidized bed with Ca- and Mg-modified bed materials and additives

    International Nuclear Information System (INIS)

    This study focuses on the promotion of biomass gasification for hydrogen production in a fluidized bed reactor with the bed additives zeolite, CaO, and Ca- and Mg-based silica sands. The results show that zeolite has higher capacity for enhancing hydrogen promotion abilities than CaO with the amount was 200 g in tests. Regarding the Ca- and Mg-based silica sands, Ca/SiO2 decreases the CO2 selectivity and Mg/SiO2 enhances the H2 selectivity owing to CO2 adsorption via the formation of CaO and the promotion of the water gas shift reaction, respectively. The optimal concentration of Mg-based bed materials corresponds to a Mg concentration of 0.5 wt.%. The additives play important roles in increasing the reaction rate, enhancing the biomass gasification, and promoting carbon transformation. -- Graphical abstract: The aim of this study is not only in estimation of the influence of the alkaline metals concentrations, but also in preparation of the modified fluidization mediums. A basic stoichiometric analysis of alkaline concentration for hydrogen production during biomass gasification in fluidized bed is also in consideration. Highlights: ► Various bed-additives concentrations on syngas performance are discussed. ► All additives significantly increase rate of hydrogen production in gasification. ► Zeolite has higher capacity for enhancing hydrogen production rate than CaO. ► Ca-based additives promoted the heating value and cold gas efficiency. ► The optimal concentration of Mg-based additive was 0.5 wt.% for hydrogen production

  8. Mg/Ca, Sr/Ca, and stable isotopes in modern and Holocene Protothaca staminea shells from a northern California coastal upwelling region

    Science.gov (United States)

    Takesue, R.K.; VanGeen, A.

    2004-01-01

    This study explores the potential of intertidal Protothaca staminea shells as high-resolution geochemical archives of environmental change in a coastal upwelling region. Mg/Ca and Sr/Ca ratios were analyzed by excimer laser ablation-inductively coupled plasma mass spectrometry (LA-ICP-MS) at sub-weekly temporal resolution in shells growing ???1 mm per month. Growth patterns of a modern P. staminea shell from Humboldt Bay, California, collected in December 1999 made it possible to infer a lifespan from 1993 to 1998. Growth hiatuses in the shell may have excluded records of extreme events. Mg/Ca ratios appeared to be partly controlled by water temperature; the correlation coefficient between temperature and Mg/Ca was r = 0.71 in one of four growth increments. Significant year-to-year differences in the sensitivity of Mg/Ca to temperature in P. staminea could not be explained, however. Sr/Ca ratios appeared to be more closely related to shell growth rate. Oxygen isotopes, measured at 2-week temporal resolution in the same shell, did not show a clear relation to local temperature in summer, possibly because temperatures were higher and less variable at the King Salmon mudflat, where the shell was collected, than in the main channel of Humboldt Bay, where water properties were monitored. Negative shell ??13C values (upwelling events. The Mg contents of P. staminea midden shells dated to ???3 ka and ???9 ka were significantly lower than in the modern shell. This may have resulted from degradation of a Mg-rich shell organic matrix and precluded quantitative interpretation of the older high-resolution records. Elevated ??13C values in the ???3 ka shell suggested that the individual grew in highly productive or stratified environment, such as a shallow coastal embayment or lagoon. Copyright ?? 2004 Elsevier Ltd.

  9. Thermodynamic studies of CaLaFe11O19(s)

    International Nuclear Information System (INIS)

    Thermodynamic studies on CaLaFe11O19(s) were carried out using Knudsen effusion mass spectrometry and calorimetry, viz. differential scanning calorimetry and high temperature oxide melt solution calorimetry. Standard molar Gibbs free energy of formation (ΔfG0m), enthalpy of formation and heat capacity (C0p,m) of the compound were calculated as a function of temperature for the first time. C0p,m(CaLaFe11O19) was determined and used for second law analysis, from which enthalpy and entropy of formation of the compound were calculated and the respective values are: ΔfH0m(298.15 K)/kJ mol−1=−6057(±8) and S0m(298.15 K)/J K−1 mol−1=427(±5). ΔfH0m(298.15 K)/kJ mol−1: −6055(±6) was also calculated using oxide melt solution calorimetry, which is in close agreement with the second law value. A heat capacity anomaly was also observed at T=684 K. A table of thermodynamic data from 298.15 K to 1000 K for CaLaFe11O19(s) was also constructed to represent an optimized set of data. - graphical abstract: Variation of standard molar heat capacities of CaLaFe11O19(s) and MFe12O19(s) (M=Sr, Ba and Pb) as a function of temperature. Highlights: ► Thermodynamic studies on CaLaFe11O19(s) were performed using KEQMS and solution calorimetry. ► It was synthesized using gel combustion route and characterized by XRD technique. ► The compound is magnetic in nature and shows a heat capacity anomaly at 684 K. ► Thermodynamic table was constructed from 298 K to 1000 K

  10. Influence of chemical and magnetic interface properties of Co-Fe-B/ MgO / Co-Fe-B tunnel junctions on the annealing temperature dependenceof the magnetoresistance

    Energy Technology Data Exchange (ETDEWEB)

    Schmalhorst, J.; Thomas, A.; Kou, X.; Reiss, G.; Kou, X.; Arenholz, E.

    2007-05-01

    The knowledge of chemical and magnetic conditions at the Co{sub 40}Fe{sub 40}B{sub 20}/MgO interface is important to interpret the strong annealing temperature dependence of tunnel magnetoresistance of Co-Fe-B/MgO/Co-Fe-B magnetic tunnel junctions, which increases with annealing temperature from 20% after annealing at 200 C up to a maximum value of 112% after annealing at 350 C. While the well defined nearest neighbor ordering indicating crystallinity of the MgO barrier does not change by the annealing, a small amount of interfacial Fe-O at the lower Co-Fe-B/MgO interface is found in the as grown samples, which is completely reduced after annealing at 275 C. This is accompanied by a simultaneous increase of the Fe magnetic moment and the tunnel magnetoresistance. However, the TMR of the MgO based junctions increases further for higher annealing temperature which can not be caused by Fe-O reduction. The occurrence of an x-ray absorption near-edge structure above the Fe and Co L-edges after annealing at 350 C indicates the recrystallization of the Co-Fe-B electrode. This is prerequisite for coherent tunneling and has been suggested to be responsible for the further increase of the TMR above 275 C. Simultaneously, the B concentration in the Co-Fe-B decreases with increasing annealing temperature, at least some of the B diffuses towards or into the MgO barrier and forms a B{sub 2}O{sub 3} oxide.

  11. A density functional study of the high-pressure chemistry of MSiN2(M = Be, Mg, Ca): prediction of high-pressure phases and examination of pressure-induced decomposition

    Science.gov (United States)

    Rebecca Römer, S.; Kroll, Peter; Schnick, Wolfgang

    2009-07-01

    Normal pressure modifications and tentative high-pressure phases of the nitridosilicates MSiN2 with M = Be, Mg, or Ca have been thoroughly studied by density functional methods. At ambient pressure, BeSiN2 and MgSiN2 exhibit an ordered wurtzite variant derived from idealized filled β-cristobalite by a C1-type distortion. At ambient pressure, the structure of CaSiN2 can also be derived from idealized filled β-cristobalite by a different type of distortion (D1-type). Energy-volume calculations for all three compounds reveal transition into an NaCl superstructure under pressure, affording sixfold coordination for Si. At 76 GPa BeSiN2 forms an LiFeO2-type structure, corresponding to the stable ambient-pressure modification of LiFeO2, while MgSiN2 and CaSiN2 adopt an LiFeO2-type structure, corresponding to a metastable modification (24 and 60 GPa, respectively). For both BeSiN2 and CaSiN2 intermediate phases appear (for BeSiN2 a chalcopyrite-type structure and for CaSiN2 a CaGeN2-type structure). These two tetragonal intermediate structures are closely related, differing mainly in their c/a ratio. As a consequence, chalcopyrite-type structures exhibit tetrahedral coordination for both cations (M and Si), whereas in CaGeN2-type structures one cation is tetrahedrally (Si) and one bisdisphenoidally (M) coordinated. Both structure types, chalcopyrite and CaGeN2, can also be derived from idealized filled β-cristobalite through a B1-type distortion. The group-subgroup relation of the BeSiN2/MgSiN2, the CaSiN2, the chalcopyrite, the CaGeN2 and the idealized filled β-cristobalite structure is discussed and the displacive phase transformation pathways are illustrated. The zero-pressure bulk moduli were calculated for all phases and have been found to be comparable to compounds such as α- Si3N4, CaIrO3 and Al4C3. Furthermore, the thermodynamic stability of BeSiN2, MgSiN2 and CaSiN2 against phase agglomerates of the binary nitrides M3N2 and Si3N4 under pressure are examined.

  12. Al-Ca and Al-Fe metal-metal composite strength, conductivity, and microstructure relationships

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Hyong June [Iowa State Univ., Ames, IA (United States)

    2011-01-01

    Deformation processed metal-metal composites (DMMC’s) are composites formed by mechanical working (i.e., rolling, swaging, or wire drawing) of two-phase, ductile metal mixtures. Since both the matrix and reinforcing phase are ductile metals, the composites can be heavily deformed to reduce the thickness and spacing of the two phases. Recent studies have shown that heavily drawn DMMCs can achieve anomalously high strength and outstanding combinations of strength and conductivity. In this study, Al-Fe wire composite with 0.07, 0.1, and 0.2 volume fractions of Fe filaments and Al-Ca wire composite with 0.03, 0.06, and 0.09 volume fractions of Ca filaments were produced in situ, and their mechanical properties were measured as a function of deformation true strain. The Al-Fe composites displayed limited deformation of the Fe phase even at high true strains, resulting in little strengthening effect in those composites. Al-9vol%Ca wire was deformed to a deformation true strain of 13.76. The resulting Ca second-phase filaments were deformed to thicknesses on the order of one micrometer. The ultimate tensile strength increased exponentially with increasing deformation true strain, reaching a value of 197 MPa at a true strain of 13.76. This value is 2.5 times higher than the value predicted by the rule of mixtures. A quantitative relationship between UTS and deformation true strain was determined. X-ray diffraction data on transformation of Al + Ca microstructures to Al + various Al-Ca intermetallic compounds were obtained at the Advanced Photon Source at Argonne National Laboratory. Electrical conductivity was measured over a range of true strains and post-deformation heat treatment schedules.

  13. Ethylbenzene dehydrogenation over Mg3Fe0.5−xCoxAl0.5 catalysts derived from hydrotalcites: Comparison with Mg3Fe0.5−yNiyAl0.5 catalysts

    KAUST Repository

    Atanda, Luqman A.

    2011-04-01

    A series of Mg3Fe0.5-xCoxAl0.5 (x = 0-0.5) catalysts were prepared from hydrotalcite precursors and their activities in the dehydrogenation of ethylbenzene were compared with those of a series of Mg3Fe0.5-yNiyAl0.5 (y = 0-0.5) catalysts also derived from hydrotalcite. The hydrotalcites prepared by co-precipitation were calcined at 550 °C to the mixed oxides with a high surface area of 150-240m2gcat-1; they were composed of Mg(Fe,Me,Al)O periclase and Mg(Me)(Fe,Al)2O4 spinel (Me = Co or Ni). Bimetallic Fe3+-Co2+ system showed a synergy, i.e., an increase in the activity, whereas Fe3+-Ni2+ bimetallic system showed no synergy. The high styrene yield was obtained on Mg 3Fe0.1Co0.4Al0.5; however, a large substitution of Fe3+ with Co2+ caused a decrease in styrene selectivity along with coking on the catalysts, due to an isolation of CoOx on the catalyst surface. The highest yield as well as the highest selectivity for styrene production was obtained at x = 0.25 at time on stream of 30 min. The coprecipitation at pH = 10.0 and the composition of Mg3Fe0.25Co0.25Al0.5 were the best for preparing the active catalyst. This is partly due to the formation of a good hydrotalcite structure. On this catalyst, the active Fe3+ species was reduced at a low temperature by the Fe3+-Co2+ bimetal formation, leading to a high activity. Simultaneously, the amount of reducible Fe3+ was the smallest, resulting in a high stability of the active Fe3+ species. It is likely that the dehydrogenation was catalyzed by the reduction-oxidation between Fe3+ and Fe2+ and that Co2+ assisted the reduction-oxidation by forming Fe 3+-Co2+ (1/1) bimetallic active species. © 2011 Elsevier B.V. All rights reserved.

  14. Shock Compression and Phase Transitions of Magnesiowüstite (Mg,Fe)O up to Earth's Lowermost Mantle Conditions

    Institute of Scientific and Technical Information of China (English)

    ZHANG Li; GONG Zi-Zheng

    2006-01-01

    @@ We report new shock-compression data for polycrystalline (Mg, Fe)O up to 130 Gpa shock pressures corresponding to Earth's lowermost mantle conditions. Our data together with the existing shock-wave data of (Mg,Fe)O and its end-members MgO and FeO reveal that the Hugoniot curves of (Mg, Fe)O does not change with varying FeO content for their B1 phase (NaCl-structure) in the pressure-relative-volume plane. The evidence of the volume change within 3% at around 120 Gpa along the Hugoniot of (Mg0.6, Fe0.4)O is consistent with a structural transition from B1 phase (NaCl cubic) to B8 phase (NiAs-type hexagonal). Such a structural transition of (Mg, Fe)O, if indeed occurs, may in part contribute to the scattering of seismic waves and change in velocity gradient found in the lowermost mantle.

  15. Thickness dependence of the magnetic properties of ripple-patterned Fe/MgO(001) films

    Science.gov (United States)

    Büttner, Felix; Zhang, Kun; Seyffarth, Susanne; Liese, Tobias; Krebs, Hans-Ulrich; Vaz, C. A. F.; Hofsäss, Hans

    2011-08-01

    Grazing incidence Xe+ ion sputtering was used to create a nanoscale ripple pattern on a thin Fe film, epitaxially grown on MgO(001). The Fe film has a thickness gradient of 0-20 nm and a ripple height of about 3 nm, giving rise to a transition from a continuous film to separated nanorods with decreasing film thickness. This allowed the investigation of the competition between the uniaxial and biaxial anisotropy of the irradiated sample as a function of thickness. From magneto-optical Kerr effect measurements, we determine accurately the cubic magnetocrystalline anisotropy and the uniaxial anisotropy that originates from the ripple pattern using a coherent rotation model. Our results show that the uniaxial anisotropy strength increases, whereas the contribution of the biaxial crystal anisotropy decreases, when going from the continuous film to the nanorod structures.

  16. Thermal equation of state and stability of (Mg0.06Fe0.94)O

    Science.gov (United States)

    Wicks, June K.; Jackson, Jennifer M.; Sturhahn, Wolfgang; Zhuravlev, Kirill K.; Tkachev, Sergey N.; Prakapenka, Vitali B.

    2015-12-01

    We present the pressure-volume-temperature (P-V-T) equation of state of polycrystalline (Mg0.06Fe0.94)O (Mw94) determined from laser-heated X-ray diffraction experiments up to 122 GPa and 2100 K, conditions approaching those of the deep mantle. We conducted two sets of experiments, one with an in situ Fe metal oxygen fugacity buffer and one without such a buffer. The internal pressure markers used in these experiments were B 2 -NaCl and hcp-Fe in the buffered experiment and B 2 -NaCl in the unbuffered experiment. In the sampled P-T range of the high temperature part of this study, only the B 1 structure of Mw94 was observed, indicating that the addition of Mg to FeO stabilizes the B 1 phase with respect to the B 8 phase at these conditions. Both datasets were fit to a Birch-Murnaghan and Mie-Grüneisen-Debye thermal equation of state using a new open-source fitting routine, also presented here. Analysis of these data sets using the same internal pressure marker shows that the P-V-T data of Mw94 obtained in the unbuffered experiment are well explained by the equation of state parameters determined from the buffered data set. We have also compared the thermal equation of state of Mw94 to that of wüstite and conclude that Mw94 has measurably distinct thermoelastic properties compared with those of wüstite. We use the results obtained in the buffered experiment to determine the density and bulk sound velocity of Mw94 at the base of the mantle and compare these values to geophysical observations of ultralow-velocity zones.

  17. Ca2O3Fe2.6S2: an antiferromagnetic Mott insulator at proximity to bad metal

    International Nuclear Information System (INIS)

    We report here the first layered iron oxychalcogenide Ca2O3Fe2.6S2 that contains both planar [Ca2FeO2]2+ and [Fe2OS2]2− layers with the shortest Fe–Fe bond length. This compound is a narrow band gap (∼0.073 eV) Mott insulator. The observed antiferromagnetic (AFM) transition at 77 K is due to the ordered Fe vacancies, which can be suppressed by partial substitution of Se for S. We show that the vacancy-free phase Ca2O3Fe3S2 may become a metal with moderate electron correlation comparable to the parent compound LaOFeAs of corresponding superconductors. Our results imply that iron oxychalcogenide can be converted from an AFM Mott insulator into a bad metal like iron pnictides through Fe–Fe bond length shrinking. (paper)

  18. Hydrogen release from dialkylamine-boranes promoted by Mg and Ca complexes: a DFT analysis of the reaction mechanism.

    Science.gov (United States)

    Butera, Valeria; Russo, Nino; Sicilia, Emilia

    2014-05-12

    Mg and Ca β-diketiminato silylamides [HC{(Me)CN(2,6-iPr2C6H3)}2M(THF)n{N(SiMe3)2}] (M = Mg, n = 0; M = Ca, n = 1) were studied as precatalysts for the dehydrogenation/dehydrocoupling of secondary amine-boranes R2HNBH3 . By reaction with equimolar quantities of amine-boranes, the corresponding amidoborane derivatives are formed, which further react to yield dehydrogenation products such as the cyclic dimer [BH2-NMe2]2. DFT was used here to explore the mechanistic alternatives proposed on the basis of the experimental findings for both Mg and Ca amidoboranes. The influence of the steric demand of amine-boranes on the course of the reaction was examined by performing calculations on the dehydrogenation of dimethylamine-borane (DMAB), pyrrolidine-borane (PB), and diisopropylamine-borane. In spite of the analogies in the catalytic activity of Mg- and Ca-based complexes in the dehydrocoupling of amine-boranes, our theoretical analysis confirmed the experimentally observed lower reactivity of Ca complexes. Differences in catalytic activity of Mg- and Ca-based complexes were examined and rationalized. As a consequence of the increase in ionic radius on going from Mg(2+) to Ca(2+), the dehydrogenation mechanism changes and formation of a key metal hydride intermediate becomes inaccessible. Dimerization is likely to occur off-metal in solution for DMAB and PB, whereas steric hindrance of iPr2NHBH3 hampers formation of the cyclic dimer. The reported results are of particular interest because, although amine-borane dehydrogenation is now well established, mechanistic insight is still lacking for many systems. PMID:24700384

  19. Impact of interface manipulation of oxide on electrical transport properties and low-frequency noise in MgO/NiFe/MgO heterojunctions

    International Nuclear Information System (INIS)

    Low-frequency noise and magnetoresistance in sputtered-deposited Ta(5 nm)/MgO (3 nm)/NiFe(10 nm)/MgO(3 nm)/Ta(3 nm) films have been measured as a function of different annealing times at 400°C. These measurements did not change synchronously with annealing time. A significant increase in magnetoresistance is observed for short annealing times (of the order of minutes) and is correlated with a relatively small reduction in 1/f noise. In contrast, a significant reduction in 1/f noise is observed for long annealing times (of the order of hours) accompanied by a small change in magnetoresistance. After annealing for 2 hours, the 1/f noise decreases by three orders of magnitude. Transmission electron microscopy and slow positron annihilation results implicate the cause being micro-structural changes in the MgO layers and interfaces following different annealing times. The internal vacancies in the MgO layers gather into vacancy clusters to reduce the defect density after short annealing times, whereas the MgO/NiFe and the NiFe/MgO interfaces improve significantly after long annealing times with the amorphous MgO layers gradually crystallizing following the release of interfacial stress

  20. Impact of interface manipulation of oxide on electrical transport properties and low-frequency noise in MgO/NiFe/MgO heterojunctions

    Energy Technology Data Exchange (ETDEWEB)

    Li, Jian-wei [School of Materials Science and Engineering, Shanghai University, Shanghai 200072 (China); School of Materials Science and Engineering, University of Science and Technology Beijing, Beijing 100083 (China); Zhao, Chong-jun; Feng, Chun; Yu, Guang-hua [School of Materials Science and Engineering, University of Science and Technology Beijing, Beijing 100083 (China); Zhou, Zhongfu [School of Materials Science and Engineering, Shanghai University, Shanghai 200072 (China)

    2015-08-15

    Low-frequency noise and magnetoresistance in sputtered-deposited Ta(5 nm)/MgO (3 nm)/NiFe(10 nm)/MgO(3 nm)/Ta(3 nm) films have been measured as a function of different annealing times at 400°C. These measurements did not change synchronously with annealing time. A significant increase in magnetoresistance is observed for short annealing times (of the order of minutes) and is correlated with a relatively small reduction in 1/f noise. In contrast, a significant reduction in 1/f noise is observed for long annealing times (of the order of hours) accompanied by a small change in magnetoresistance. After annealing for 2 hours, the 1/f noise decreases by three orders of magnitude. Transmission electron microscopy and slow positron annihilation results implicate the cause being micro-structural changes in the MgO layers and interfaces following different annealing times. The internal vacancies in the MgO layers gather into vacancy clusters to reduce the defect density after short annealing times, whereas the MgO/NiFe and the NiFe/MgO interfaces improve significantly after long annealing times with the amorphous MgO layers gradually crystallizing following the release of interfacial stress.

  1. Perpendicular magnetic anisotropy in Ta/Co2FeAl/MgO multilayers

    Science.gov (United States)

    Gabor, M. S.; Petrisor, T.; Tiusan, C.; Petrisor, T.

    2013-08-01

    In this paper, we demonstrate the stabilization of perpendicular magnetic anisotropy (PMA) in Ta/Co2FeAl/MgO multilayers sputtered on thermally oxidized Si(100) substrates. The magnetic analysis points out that these films show significant interfacial anisotropy even in the as-deposited state, KS=0.67 erg/cm2, enough to provide PMA for the as-deposited films with thicknesses below 1.5 nm. Moreover, the interfacial anisotropy is enhanced by thermal annealing up to 300 °C. The presence of a magnetic dead layer, whose thickness increases with annealing temperature, was also identified.

  2. Thermostability of Al-Cu-Mg-Fe-Ni Alloy with Trace Scandium and Zirconium

    Institute of Scientific and Technical Information of China (English)

    Yu Kun; Li Songrui; Li Wenxian

    2000-01-01

    Three Al-Cu-Mg-Fe-Ni-Sc-Zr ingot metallurgy alloys with different compositions had been prepared. The hardness variations of cold-rolled alloy plates during annealing process had been measured. The tensile properties at both ambient and elevated temperatures were also measured. The microstructures of alloys were observed by using optical microscope and TEM. It was found that the dispersed Al3(Sc, Zr) particles could pin dislocations, stabilize substructures and impede the movement of boundaries. The ambient and elevated temperature properties of alloy with Al3(Sc, Zr) particles were improved. And the tensile strength of alloy did not improve obviously with rich iron and nicker addition.

  3. Spin Diode Based on Fe/MgO Double Tunnel Junction

    OpenAIRE

    Iovan, A.; Andersson, S; Naidyuk, Yu. G.; Vedyaev, A.; Dieny, B.; Korenivski, V.

    2007-01-01

    We demonstrate a spin diode consisting of a semiconductor free nano-scale Fe/MgO-based double tunnel junction. The device exhibits a near perfect spin-valve effect combined with a strong diode effect. The mechanism consistent with our data is resonant tunneling through discrete states in the middle ferromagnetic layer sandwiched by tunnel barriers of different spin-dependent transparency. The observed magneto-resistance is record high, ~4000%, essentially making the structure an on/off spin-s...

  4. Spin diode based on Fe/MgO double tunnel junction.

    Science.gov (United States)

    Iovan, A; Andersson, S; Naidyuk, Yu G; Vedyaev, A; Dieny, B; Korenivski, V

    2008-03-01

    We demonstrate a spin diode consisting of a semiconductor-free nanoscale Fe/MgO-based double tunnel junction. The device exhibits a near perfect spin-valve effect combined with a strong diode effect. The mechanism consistent with our data is resonant tunneling through discrete states in the middle ferromagnetic layer sandwiched by tunnel barriers of different spin-dependent transparency. The observed magnetoresistance is a record high>1000%, essentially making the structure an on/off spin switch. This, combined with the strong diode effect, approximately 100, demonstrates a new device principle, promising for memory and reprogrammable logic applications. PMID:18284216

  5. Structure and Properties of Mg-Cu-(Y,Ca Bulk Metallic Glasses / Struktura I Własności Masywnych Szkieł Metalicznych Mg-Cu-(Y,Ca

    Directory of Open Access Journals (Sweden)

    Babilas R.

    2015-12-01

    Full Text Available The work presents preparation methods, structure characterization and mechanical properties analysis of Mg-based bulk metallic glasses in as-cast state and after crystallization process. The studies were performed on Mg60Cu30Y10 and Mg37Cu36Ca27 glassy alloys in the form of plates and rods. The X-ray diffraction investigations revealed that the tested samples with different thicknesses and shapes were amorphous. The characteristics of the fractured surfaces showed mixed fractures with the “river” and “mirror” patterns, which are characteristic for the glassy materials and some “smooth” areas. The samples of Mg37Cu36Ca27 alloy presented a two-stage crystallization process, but addition of Y caused a single stage crystallization behavior. Qualitative phase analysis from the X-ray data of examined alloys annealed at 473 K enabled the identification of Mg, Mg2Cu, Cu2Mg and CaCu crystalline phases. The changes of compressive strength as a function of annealing temperature for studied rods were stated. The best mechanical properties including microhardness and compressive strength were obtained for the alloy with the addition of Y in as-cast state.

  6. Aplicação de métodos quimiométricos na otimização da extração de Ca, Mg, K, Fe, Zn, Cu e Mn em folhas de braquiária

    OpenAIRE

    Diego M. Souza; Beata E. Madari; Marcelo M. Sena

    2012-01-01

    This work applied a 2² factorial design to the optimization of the extraction of seven elements (calcium, magnesium, potassium, iron, zinc, copper and manganese) in brachiaria leaves, determined by flame atomic absorption spectrometry. The factors sample mass and digestion type were evaluated at two levels: 200/500 mg, and dry/wet, respectively. Principal component analysis allowed simultaneous discrimination of all the significant effects in one biplot. Wet digestion and mass of 200 mg were ...

  7. Evaluation of Ca3(Co,M2O6 (M=Co, Fe, Mn, Ni as new cathode materials for solid-oxide fuel cells

    Directory of Open Access Journals (Sweden)

    Fushao Li

    2015-10-01

    Full Text Available Series compounds Ca3(Co0.9M0.12O6 (M=Co, Fe, Mn, Ni with hexagonal crystal structure were prepared by sol–gel route as the cathode materials for solid oxide fuel cells (SOFCs. Effects of the varied atomic compositions on the structure, electrical conductivity, thermal expansion and electrochemical performance were systematically evaluated. Experimental results showed that the lattice parameters of Ca3(Co0.9Fe0.12O6 and Ca3(Co0.9Mn0.12O6 were both expanded to certain degree. Electron-doping and hole-doping effects were expected in Ca3(Co0.9Mn0.12O6 and Ca3(Co0.9Ni0.12O6 respectively according to the chemical states of constituent elements and thermal-activated behavior of electrical conductivity. Thermal expansion coefficients (TEC of Ca3(Co0.9M0.12O6 were measured to be distributed around 16×10−6 K−1, and compositional elements of Fe, Mn, and Ni were especially beneficial for alleviation of the thermal expansion problem of cathode materials. By using Ca3(Co0.9M0.12O6 as the cathodes operated at 800 °C, the interfacial area-specific resistance varied in the order of M=CoFeCa3(Co0.9Fe0.12O6 showed the best electrochemical performance and the power density as high as ca. 500 mW cm−2 at 800 °C achieved in the single cell with La0.8Sr0.2Ga0.83Mg0.17O2.815 as electrolyte and Ni–Ce0.8Sm0.2O1.9 as anode. Ca3(Co0.9M0.12O6 (M=Co, Fe, Mn, Ni can be used as the cost-effective cathode materials for SOFCs.

  8. CaMg(CO3)2为发泡剂制备泡沫铝的工艺探讨%Study on Preparation Process of Aluminum Foam by CaMg(CO3)2 Foaming Agent

    Institute of Scientific and Technical Information of China (English)

    陶勇

    2014-01-01

    CaMg(CO3)2为发泡剂,Ca粉为增粘剂,ZLD 102铝硅合金为基体制备泡沫铝,探讨其工艺可行性.结果表明,以CaMg(CO3)2为发泡剂制备泡沫铝是可行的,其最佳发泡温度为710℃,搅拌时间为2 min,保温时间为4~8min.所制备泡沫铝的孔隙率可达86.42%,密度为0.36 g/cm3.%The preparation process of aluminum foam was studied using CaMg (CO3)2 as foaming agent,Ca powder as tackifier and ZLD 102 aluminium-silicon alloy as matrix.The results show that the aluminum foam can be prepared by CaMg(CO3)2 as foaming agent.The optimal foaming temperature is 710 ℃,and the optimal stirring and holding times are 2 min and 4~8 min,respectively.The porosity of the foam aluminum is 86.42%,and the density is 0.36 g/cm3

  9. Epitaxial growth of ultrathin MgO layers on Fe3O4(0 0 1) films

    Science.gov (United States)

    Nordmann, T.; Kuschel, O.; Wollschläger, J.

    2016-09-01

    The initial growth stages of MgO on Fe3O4 films are studied by means of X-ray photoelectron spectroscopy and low energy electron diffraction to clarify stoichiometric and structural properties of these layered structures. This bilayer structure is important to fabricate high quality magnetic tunnel junctions based on Fe3O4 electrodes and MgO tunneling barriers. For this purpose, the deposition temperature of MgO has been varied between 100 °C and 250 °C. Initially, MgO grows layer-by-layer on Fe3O4/MgO(0 0 1) forming a wetting layer. Depending on the growth temperature, after growth of a 2-3 nm thick laminar wetting layer, the MgO films finally start to roughen during growth. Thus the growth of MgO on Fe3O4/MgO(0 0 1) is described by a Stranski-Krastanov growth mode. Diffraction experiments show that the magnetite (√{ 2} ×√{ 2})R45° superstructure is removed already during the initial stages of MgO deposition. Furthermore, these experiments show that MgO films are rougher for growth at low deposition temperatures.

  10. Temperature variation of the size effect in dilute AlMg and AlCa alloys: Measurement and theory

    Science.gov (United States)

    Gilder, H. M.; Asty, M.; Audit, Ph.

    1980-12-01

    Optical-interferometric-differential-length and x-ray lattice-parameter measurements performed at low temperatures in dilute AlMg and AlCa alloys indicate that the temperature variation of the size effect corresponds to a relatively large difference between the intrinsic coefficient of thermal expansion βi of the solute atom structure and that, β, of the solvent. This result is another example of the surprising expansive properties of point defects previously described by Gilder and co-workers (high-temperature vacancy diffusion) and more recently by Ganne (low-temperature dilatometry on irradiated specimens). Specifically, in the temperature range 0.2AlCa. The calculated values of Δβ(Mg)Ci, Ci being the solute concentration, and βi(Mg) fall between the measured values in the two AlMg alloys studied. The calculation of Δβ(Ca)Ci and βi(Ca) is not possible due to a lack of elastic-constants data for pure, metallic calcium. Inasmuch as, in the case of Mg, solute-solute interactions are apparent in the measured values of the size effect, ΔβCi and βi, even at Ci(Mg)~0.2 at.%, extreme care must be exercised when comparing experimental data for dilute alloys with calculations of infinitely dilute alloy properties.

  11. Synthesis and Characterization of Nanosized MgFe2O4 Powders by Hydrothermal Method%MgFe2O4纳米粉体的水热合成及其表征

    Institute of Scientific and Technical Information of China (English)

    黄玉洁; 王军; 陈乾旺

    2005-01-01

    MgFe2O4 nanoparticles were hydrothermally synthesized at 150 ℃ using iron nitrate [Fe(NO3)3·9H2O],the reaction conditions. The influences of several factors such as presence or absence of Na+, molar ratio of Fe3+ /Mg2+, concentration of mental ions, temperature and reaction time on resultant products were investigated in the hydrothermal process. The sample was characterized by X-ray diffraction (XRD) and transmission electron microscopy (TEM), and its magnetic properties were measured using vibrating sample magnetometer (VSM).

  12. Phonons of Fe-based superconductor Ca10Pt4As8(Fe1−xPtxAs)10

    International Nuclear Information System (INIS)

    We report the results of inelastic neutron scattering measurements on particular phonons of a superconducting (SC) Ca10Pt4As8(Fe1−xPtxAs)10 with the onset transition temperature T c ∼ 33 K to investigate mainly what roles orbital fluctuation plays in Cooper pairing, where we observed a slight softening of the in-plane transverse acoustic mode corresponding to the elastic constant C 66. This softening starts at temperature T well above the SC T c, as T decreases. An anomalously strong change of the scattering intensity of in-plane optical modes was observed at the M point of the pseudo tetragonal reciprocal space in the range of 35  <  ω  <  40 meV with decreasing T from far above T c. Because this ω region mainly corresponds to the motion of Fe and As atoms in the FeAs planes, the finding presents information on the coupling between the orbital fluctuation of Fe 3d electrons and the lattice system, useful for studying the possible roles of orbital fluctuation in the pairing mechanism and/or the appearance of the so-called nematic phase. (paper)

  13. Determination of Gibbs Free Energy of Formation from Elements for Ca4Fe9O17 by Solid-state Galvanic Cell

    Science.gov (United States)

    Li, Hui-Yu; Guo, Xing-Min

    2015-02-01

    Aiming to fill the thermodynamic blank in CaO-FeO-Fe2O3 system, the determination of the Gibbs free energy of formation from elements for ternary Ca4Fe9O17 was carried out using a solid-state galvanic cell with air and calcium zirconate material, respectively, as the reference electrode and electrolyte. The ternary system Ca2Fe2O5-CaFe2O4-Ca4Fe9O17 was selected as the measuring electrode and its equilibrium was confirmed. The essential thermodynamic data of Ca2Fe2O5 and CaFe2O4 were cited from the reassessed data from a previous investigation. The reversible electromotive forces of the cell were determined from 1273 K to 1473 K (1000 °C to 1200 °C). The Gibbs free energy of formation from elements for Ca4Fe9O17 was derived and given by: The increment of enthalpy and entropy of formation from elements for Ca4Fe9O17 at 298 K (25 °C) are calculated to be and . The Ellingham diagram was developed in temperature range 1273 K to 1473 K (1000 °C to 1200 °C). The oxygen potential of Ca4Fe9O17 was found to be slightly higher than CaFe2O4 and much higher than Ca2Fe2O5.

  14. Experimental Study Of Precipitation Competition Of Ca(OH)2 And Mg(OH)2 On MSF Desalination Condition

    International Nuclear Information System (INIS)

    Competition study has been carried out by using sea water simulation containing of 142 on deposit ppm of bicarbonate ion, 400 ppm of calcium ion and 1272 ppm of magnesium ion. Experiment was performed by heating sample at temperature 50, 60, 70, 80, and 90 C for 30 minutes. Precipitation competition of Ca(OHh and Mg(OHh was analyzed by reduction of calcium and magnesium ion. Experiment data showed information that at the temperature bellow 800oC CaCO3 precipitation was more dominant, meanwhile above than 80oC precipitation Mg(OH)2 was more dominant. This competition occurred because at temperature more than 80oC rate of hydroxyl ion formation and Mg(OH)2 recipitation was greater than CaCO3 precipitation and at temperature bellow 80oC rate of hydrolysis carbonate ion was less than thermal decomposition bicarbonates ion

  15. Microstructural analysis and mechanical properties of biodegradable Mg-1.3Ca-5.5Zr alloy

    Science.gov (United States)

    Istrate, B.; Munteanu, C.; Matei, MN; Oprisan, B.; Moisei, M.; Earar, K.

    2016-08-01

    Magnesium based alloys begin to be known as biodegradable materials used in medical field. Zirconium and Calcium as alloying elements, improve mechanical strength, creep resistance and refine microstructure. Also, Ca is the most spread mineral in the human body, which contributes to the osteosynthesis phenomenon. The aim of this paper is developing two original Mg-Zr-Ca biodegradable alloys, characterizing from the point of view of the microstructure, X-ray diffraction, Young modulus and scratch test. Results show evenly distributed clusters of zirconium and Mg2Ca arranged at Mg grains boundary. Also, values of Young modulus are between 25-27 GPa similar to bones Young modulus, thus avoiding the formation of “stress shield effect”.

  16. A culture-based calibration of benthic foraminiferal paleotemperature proxies: δ18O and Mg/Ca results

    Directory of Open Access Journals (Sweden)

    D. C. McCorkle

    2010-01-01

    Full Text Available Benthic foraminifera were cultured for five months at four temperatures (4, 7, 14 and 21 °C to establish the temperature dependence of foraminiferal δ18O and Mg/Ca. Two Bulimina species (B. aculeata and B. marginata were most successful, adding chambers at all four temperatures and reproducing at 7 and 14 °C. Foraminiferal δ18O values displayed ontogenetic variations, with lower values in younger individuals. The δ18O values of adult specimens decreased with increasing temperature in all but the 4 °C treatment, exhibiting a relationship consistent with previous δ18O paleotemperature calibration studies. Foraminiferal Mg/Ca values, determined by laser ablation inductively coupled plasma mass spectrometry, were broadly consistent with previous Mg/Ca calibration studies, but extremely high values in the 4 °C treatment and higher than expected values at two of the other three temperatures make it challenging to interpret these results.

  17. Stripes and antiphase boundaries in CaFe2O4

    Science.gov (United States)

    Stock, Chris; Rodriguez, Efrain; Green, Mark; Lee, Nara; Cheong, S.-W.

    2015-03-01

    We report on the magnetic structure and spin dynamics in CaFe2O4 based upon an orthorhombic structure. The magnetic structure consists of two competing magnetic phases based upon stripes of S =5/2 Fe3+ ions. The magnetic dynamics illustrate that the coupling is primarily two dimensional. On application of a magnetic field, antiphase magnetic boundaries can be introduced into the lattice and frozen in at low temperatures. We investigate the structure and dynamics of these domains using polarized and unpolarized neutron scattering and discuss how the triangular geometry allow these localized defects to be energetically favorable. Carnegie Trust for the Universities of Scotland, Royal Society, and EPSRC.

  18. Mössbauer and XRD study of intercalated CaFe-layered double hydroxides

    Science.gov (United States)

    Sipiczki, Mónika; Kuzmann, Ernő; Pálinkó, István; Homonnay, Zoltán; Sipos, Pál; Kukovecz, Ákos; Kónya, Zoltán

    2014-04-01

    N-containing fully saturated (L-prolinate) or aromatic (indole-2-carboxylate) heterocyclic anions were immobilised in CaFe-layered double hydroxide with the dehydration-rehydration method from aqueous ethanol or acetone. The structure of the resulting organic-inorganic hybrids was characterised mainly with powder X-ray diffraction and 57Fe Mössbauer spectroscopy, and as supplementary analysis scanning electron microscopy, energy dispersive X-ray spectroscopy with elemental mapping and molecular modelling were also applied. It was found that the solvent mixture used for the synthesis caused enormous difference in the interlayer spacings of the obtained inorganic-organic hybrids.

  19. The antiferromagnetic insulator Ca3FeRhO6: characterization and electronic structure calculations

    OpenAIRE

    Eyert, V.; Schwingenschloegl, U.; Fresard, R.; Maignan, A.; Martin, C.; Nguyen, N.; Hackenberger, C.; Kopp, T.

    2006-01-01

    We investigate the antiferromagnetic insulating nature of Ca3FeRhO6 both experimentally and theoretically. Susceptibility measurements reveal a Neel temperature T_N = 20 K, and a magnetic moment of 5.3 muB/f. u., while Moessbauer spectroscopy strongly suggests that the Fe ions, located in trigonal prismatic sites, are in a 3+ high spin state. Transport measurements display a simple Arrhenius law, with an activation energy of 0.2 eV. The experimental results are interpreted with LSDA band stru...

  20. Understanding MgSiO3 Post-Perovskite via NaMgF3 and CaIrO3 Analog Materials

    Science.gov (United States)

    Martin, C.; Parise, J. B.

    2006-12-01

    Knowledge of the structure and properties of MgSiO3 post-perovskite (ppv) is paramount in the study of Earth`s D" layer and core-mantle boundary. However, the extreme pressures and temperatures required to stabilize this phase make in-situ characterization difficult. Rietveld refinement of structure models obtained from x-ray and neutron diffraction data of analog materials including NaMgF3 and CaIrO3, the structure model of MgSiO3 ppv, reveal structural changes accompanying the perovskite (pv)/ppv phase transition. Refined models of NaMgF3 pv just before ppv phase transition indicate some inter-octahedral F-F distances rival the average intra-octahedral distance, which may cause instability in the pv structure and drive the transformation to the ppv phase. The dataset suggests it may be possible to predict the pressure of a ppv phase transition in other pv- (or A2X3-) type materials by extrapolating the cation polyhedra volume ratio with pressure. Diffraction data from CaIrO3 indicate significant disparity between axial compression and thermal expansion schemes (Ka > Kc &αa CaIrO3 at high temperature detail structure changes expected of MgSiO3 ppv considering the thermal gradient above Earth`s core-mantle boundary. In sum, this work assists an increasingly comprehensive understanding of the structure and properties expected of MgSiO3 ppv above the core-mantle boundary.

  1. A CoFeB/MgO/CoFeB perpendicular magnetic tunnel junction coupled to an in-plane exchange-biased magnetic layer

    Energy Technology Data Exchange (ETDEWEB)

    Zhu, M., E-mail: mzhu@sunycnse.com; Chong, H.; Vu, Q. B.; Vo, T.; Brooks, R.; Stamper, H.; Bennett, S.; Piccirillo, J. [Colleges of Nanoscale Science and Engineering, SUNY Polytechnic Institute, Albany, New York 12203 (United States)

    2015-05-25

    We report a stack structure which utilizes an in-plane exchange-biased magnetic layer to influence the coercivity of the bottom CoFeB layer in a CoFeB/MgO/CoFeB perpendicular magnetic tunnel junction. By employing a thickness wedge deposition technique, we were able to study various aspects of this stack using vibrating sample magnetometer including: (1) the coupling between two CoFeB layers as a function of MgO thickness; and (2) the coupling between the bottom CoFeB and the in-plane magnetic layer as a function of Ta spacer thickness. Furthermore, modification of the bottom CoFeB coercivity allows one to measure tunneling magnetoresistance and resistance-area product (RA) of CoFeB/MgO/CoFeB in this pseudo-spin-valve format using current-in-plane-tunneling technique, without resorting to (Co/Pt){sub n} or (Co/Pd){sub n} multilayer pinning.

  2. A CoFeB/MgO/CoFeB perpendicular magnetic tunnel junction coupled to an in-plane exchange-biased magnetic layer

    Science.gov (United States)

    Zhu, M.; Chong, H.; Vu, Q. B.; Vo, T.; Brooks, R.; Stamper, H.; Bennett, S.; Piccirillo, J.

    2015-05-01

    We report a stack structure which utilizes an in-plane exchange-biased magnetic layer to influence the coercivity of the bottom CoFeB layer in a CoFeB/MgO/CoFeB perpendicular magnetic tunnel junction. By employing a thickness wedge deposition technique, we were able to study various aspects of this stack using vibrating sample magnetometer including: (1) the coupling between two CoFeB layers as a function of MgO thickness; and (2) the coupling between the bottom CoFeB and the in-plane magnetic layer as a function of Ta spacer thickness. Furthermore, modification of the bottom CoFeB coercivity allows one to measure tunneling magnetoresistance and resistance-area product (RA) of CoFeB/MgO/CoFeB in this pseudo-spin-valve format using current-in-plane-tunneling technique, without resorting to (Co/Pt)n or (Co/Pd)n multilayer pinning.

  3. Effects of boron composition on tunneling magnetoresistance ratio and microstructure of CoFeB/MgO/CoFeB pseudo-spin-valve magnetic tunnel junctions

    Energy Technology Data Exchange (ETDEWEB)

    Kodzuka, M. [Graduate School of Pure and Applied Sciences, University of Tsukuba, Tsukuba 305-0047 (Japan); Ohkubo, T. [National Institute for Materials Science, Tsukuba 305-0047 (Japan); Hono, K. [Graduate School of Pure and Applied Sciences, University of Tsukuba, Tsukuba 305-0047 (Japan); National Institute for Materials Science, Tsukuba 305-0047 (Japan); Ikeda, S.; Ohno, H. [Center for Spintronics Integrated Systems, Tohoku University, Sendai 980-8577 (Japan); Laboratory for Nanoelectronics and Spintronics, Research Institute of Electrical Communication, Tohoku University, Sendai 980-8577 (Japan); Gan, H. D. [Center for Spintronics Integrated Systems, Tohoku University, Sendai 980-8577 (Japan)

    2012-02-15

    The effect of B concentration on the tunneling magnetoresistance (TMR) of (Co{sub 25}Fe{sub 75}){sub 100-x}B{sub x}/MgO/(Co{sub 25}Fe{sub 75}){sub 100-x}B{sub x} (x = 22 and 33) pseudo-spin-valve (P-SV) magnetic tunnel junctions (MTJs) was investigated. The TMR ratios for optimally annealed MTJs with x = 22 and 33 were 340% and 170%, respectively, at room temperature. High resolution transmission electron microscopy (HRTEM) observation showed a weaker (001) texture in the MgO barrier in the MTJ with x = 33. The bottom electrode was not fully crystallized even with a considerable amount of B in the (Co{sub 25}Fe{sub 75}){sub 67}B{sub 33}, while good epitaxy was observed between (001) textured MgO and (Co{sub 25}Fe{sub 75}){sub 78}B{sub 22} electrodes.

  4. The role of various boron precursor on superconducting properties of MgB2/Fe

    Science.gov (United States)

    Safran, S.; Kılıçarslan, E.; Kılıç, A.; Gencer, A.

    2014-09-01

    The superconducting properties of Fe sheathed MgB2 wire has been studied as a function of precursor B powder particle size. The in situ processed MgB2 samples were prepared by means of conventional solid state reaction method with magnesium powder (99.8%, 325 mesh) and three different types of amorphous boron powders (purity; 98.8%, >95% and 91.9%) from two sources, Pavezyum (Turkish supplier) and Sigma Aldrich. The particle sizes of Turkish boron precursor powder were selected between 300 and 800 nm. The structural and magnetic properties of the prepared samples were investigated by means of the X-ray powder diffraction (XRD) and ac susceptibility measurements. The XRD patterns showed that the diffraction peaks for our samples belong to the main phase of the MgB2 diffraction patterns. The highest critical temperature, Tc = 38.4 K was measured for the MgB2 sample which was fabricated by using the 98.8% B. The critical current density of this sample was extracted from the magnetization measurements and Jc = 5.4 × 105 A cm-2 at 5 K and B = 2 T. We found that the sample made by using the 98.8% boron showed almost 2 times higher Jc than that of obtained from 91.9% B powder.

  5. Effect of inorganic and organic ligands on the sorption/desorption of arsenate on/from Al-Mg and Fe-Mg layered double hydroxides

    Science.gov (United States)

    Caporale, A. G.; Pigna, M.; Dynes, J. J.; Cozzolino, V.; Zhu, J.; Violante, A.

    2012-04-01

    In recent decades, a class of anionic clays known as layered double hydroxides (LDHs) has attracted substantial attention due to the potential use in many applications, such as photochemistry, electrochemistry, polymerization, magnetization and biomedical science. There has also been considerable interest in using LDHs as adsorbents to remove environmental contaminants due to their large surface area, high anion exchange capacity and good thermal stability. We studied the sorption of arsenate on Al-Mg and Fe-Mg layered double hydroxides (easily reproducible at low-cost) as affected by pH and varying concentrations of inorganic (nitrate, nitrite, phosphate, selenite and sulphate) and organic (oxalate and tartrate) ligands, ii) the effect of residence time on the arsenate desorption by these ligands, and iii) the kinetics of arsenate desorption by phosphate. The Fe-Mg-LDH sorbed nearly twice the amount of arsenate compared to the Al-Mg-LDH, due, in part, to its greater surface area and lower degree of crystallinity. Moreover, the Fe-Mg-LDH sorbed more arsenate than phosphate, in contrast to the Al-Mg-LDH, which adsorbed more phosphate than arsenate, probably because of the greater affinity of arsenate than phosphate for Fe sites and, vice versa, the greater affinity of phosphate than arsenate for Al sites. Arsenate sorption onto samples decreased by increasing pH, due, maybe, to the high affinity of hydroxyl ions for LDHs and/or to the value of zero point charge of two sorbents. The rate of decline in the amount of arsenate sorbed was, however, relatively constant, decreasing the fastest for the Fe-Mg-LDH compared to the Al-Mg-LDH. The capacity of ligands to inhibit the fixation of arsenate followed the sequence: nitrate tartrate tartrate anions have a stronger affinity for Fe than Al and for the presence in Fe-Mg-LDH of short-range-ordered materials on which arsenate forms very strong inner-sphere complexes not easily desorbable by competing ligands. The longer the

  6. Stimulatory effects of the degradation products from Mg-Ca-Sr alloy on the osteogenesis through regulating ERK signaling pathway

    Science.gov (United States)

    Li, Mei; He, Peng; Wu, Yuanhao; Zhang, Yu; Xia, Hong; Zheng, Yufeng; Han, Yong

    2016-09-01

    The influence of Mg-1Ca-xwt.% Sr (x = 0.2, 0.5, 1.0, 2.0) alloys on the osteogenic differentiation and mineralization of pre-osteoblast MC3T3-E1 were studied through typical differentiation markers, such as intracellular alkaline phosphatase (ALP) activity, extracellular collagen secretion and calcium nodule formation. It was shown that Mg-1Ca alloys with different content of Sr promoted cell viability and enhanced the differentiation and mineralization levels of osteoblasts, and Mg-1Ca-2.0Sr alloy had the most remarkable and significant effect among all. To further investigate the underlying mechanisms, RT-PCR and Western Blotting assays were taken to analyze the mRNA expression level of osteogenesis-related genes and intracellular signaling pathways involved in osteogenesis, respectively. RT-PCR results showed that Mg-1Ca-2.0Sr alloy significantly up-regulated the expressions of the transcription factors of Runt-related transcription factor 2 (RUNX2) and Osterix (OSX), Integrin subunits, as well as alkaline phosphatase (ALP), Bone sialoprotein (BSP), Collagen I (COL I), Osteocalcin (OCN) and Osteopontin (OPN). Western Blotting results suggested that Mg-1Ca-2.0Sr alloy rapidly induced extracellular signal-regulated kinase (ERK) activation but showed no obvious effects on c-Jun N terminal kinase (JNK) and p38 kinase of MAPK. Taken together, our results demonstrated that Mg-1Ca-2.0Sr alloy had excellent biocompatibility and osteogenesis via the ERK pathway and is expected to be promising as orthopedic implants and bone repair materials.

  7. [Seasonal release characteristics of Ca, Mg and Mn of foliar litter of six tree species in subtropical evergreen broadleaved forest].

    Science.gov (United States)

    Ma, Zhi-liang; Gao, Shun; Yang, Wan-qin; Wu, Fu-zhong

    2015-10-01

    Seasonal release dynamics of Ca, Mg and Mn during decomposition of foliar litter of Pinus massoniana, Cryptomeria fortunei, Cunninghamia lanceolata, Cinnamomum camphora, Toona ciliate, and Quercus acutissima were investigated in subtropical evergreen broad-leaved forest employing the method of litterbag. After one-year decomposition, the release rates of Ca, Mg and Mn in foliar litter of the studied tree species ranged from -13.8% to 92.3%, from 4.0% to 64.8%, and from 41.6% to 81.1%, respectively. Ca dynamics in foliar litter of P. massoniana, C. camphora exhibited the pattern of accumulating early and releasing later, while that of the other four tree species showed direct release. Similarly, the dynamics of Mg released from foliar litter of C. camphora showed the pattern of accumulating early and then releasing, while that of the other five tree species exhibited continuous release. Meanwhile, the dynamics of Mn released from foliar litter of C. fortunei and T. ciliate exhibited early accumulation, and subsequent release, while that of the other four tree species showed continuous release. The releases of Ca, Mg and Mn in foliar litter were greatly influenced by seasonal rainfall, and varied with tree species. Furthermore, the rates and amounts of Ca, Mg and Mn released from foliar litter were higher in rainy season than in dry season. In conclusion, the initial nutrient concentrations and precipitation were two key factors influencing the release dynamics of Ca, Mg and Mn during decomposition of foliar litter in the subtropical evergreen broad-leaved forest. PMID:26995897

  8. Stimulatory effects of the degradation products from Mg-Ca-Sr alloy on the osteogenesis through regulating ERK signaling pathway

    Science.gov (United States)

    Li, Mei; He, Peng; Wu, Yuanhao; Zhang, Yu; Xia, Hong; Zheng, Yufeng; Han, Yong

    2016-01-01

    The influence of Mg-1Ca-xwt.% Sr (x = 0.2, 0.5, 1.0, 2.0) alloys on the osteogenic differentiation and mineralization of pre-osteoblast MC3T3-E1 were studied through typical differentiation markers, such as intracellular alkaline phosphatase (ALP) activity, extracellular collagen secretion and calcium nodule formation. It was shown that Mg-1Ca alloys with different content of Sr promoted cell viability and enhanced the differentiation and mineralization levels of osteoblasts, and Mg-1Ca-2.0Sr alloy had the most remarkable and significant effect among all. To further investigate the underlying mechanisms, RT-PCR and Western Blotting assays were taken to analyze the mRNA expression level of osteogenesis-related genes and intracellular signaling pathways involved in osteogenesis, respectively. RT-PCR results showed that Mg-1Ca-2.0Sr alloy significantly up-regulated the expressions of the transcription factors of Runt-related transcription factor 2 (RUNX2) and Osterix (OSX), Integrin subunits, as well as alkaline phosphatase (ALP), Bone sialoprotein (BSP), Collagen I (COL I), Osteocalcin (OCN) and Osteopontin (OPN). Western Blotting results suggested that Mg-1Ca-2.0Sr alloy rapidly induced extracellular signal-regulated kinase (ERK) activation but showed no obvious effects on c-Jun N terminal kinase (JNK) and p38 kinase of MAPK. Taken together, our results demonstrated that Mg-1Ca-2.0Sr alloy had excellent biocompatibility and osteogenesis via the ERK pathway and is expected to be promising as orthopedic implants and bone repair materials. PMID:27580744

  9. Spin-glass behavior in single crystals of hetero-metallic magnetic warwickites MgFeBO4, Mg0.5Co0.5FeBO4, and CoFeBO4

    Science.gov (United States)

    Arauzo, A.; Kazak, N. V.; Ivanova, N. B.; Platunov, M. S.; Knyazev, Yu. V.; Bayukov, O. A.; Bezmaternykh, L. N.; Lyubutin, I. S.; Frolov, K. V.; Ovchinnikov, S. G.; Bartolomé, J.

    2015-10-01

    Magnetic properties of heterometallic warwickites MgFeBO4, Mg0.5Co0.5FeBO4, and CoFeBO4 are presented, highlighting the effect of Co substitution on the magnetic properties of these compounds. The analysis of magnetization and heat capacity data has shown that these compounds exhibit a spin-glass transition below TSG=10, 20 and 22 K, respectively. Using zero field ac susceptibility as entanglement witness we find that the low dimensional magnetic behavior above TSG show quantum entanglement behavior χ(Τ)∝T-α(Τ) up to TE≈130 K. The α parameters have been deduced as a function of temperature and Co content, indicating the existence of random singlet phase in this temperature region. Above TE the paramagnetism is interpreted in terms of non-entangled spins giving rise to Curie-Weiss paramagnetism. The different intra- and inter-ribbon exchange interaction pathways have been calculated within a simple indirect coupling model. It is determined that the triangular motifs in the warwickite structure, together with the competing interactions, induce frustration. The spin-glass character is explained in terms of the substitutional disorder of the Mg, Fe and Co atoms at the two available crystallographic sites, and the frustration induced by the competing interactions. The Co substitution induces uniaxial anisotropy, increases the absolute magnetization and increases the spin-glass freezing temperature. The entanglement behavior is supported in the intermediate phase irrespective of the introduction of anisotropy by the Co substitution.

  10. The kinetics of Fe and Ca for the development of radiation-induced apoptosis by micro-PIXE imaging

    International Nuclear Information System (INIS)

    To study the interactions between the induction of radiation-induced apoptosis and trace elements kinetics, human leukemia cells were irradiated in vitro by 60Co γ rays, after which the cells were evaluated for the detection of apoptosis and trace element (Fe and Ca) imaging by micro-PIXE camera was carried out. In the early phase of apoptosis, high accumulation of Fe was observed in the cytosol. In the mid to end phase, the Fe accumulation was diminished; instead, Ca accumulated in the nucleus. The releasing of cytochrome-C agreed with the Fe accumulation. The caspase-3 and -8 activity agreed with the nuclear Ca accumulation in nucleus. There appear to be two steps for the development of apoptosis: (1) the signaling from cytosol to nucleus by cytochrome-C represented by Fe and (2) the degeneration of the nucleus by caspase represented by the nuclear Ca accumulation

  11. Influence of Mg2+ on Initial Stages of CaCO3 Scale Formed on Metal Surface

    Institute of Scientific and Technical Information of China (English)

    CHEN Tao; Anne Neville; YUAN Ming-dong

    2004-01-01

    Magnesium ions, which exist in formation water and injection water under downhole conditions in the oil and gas production industry, are a key determinant in the CaCO3 scale formation. Many studies have focused their attention on the effect of magnesium on the kinetics, the morphology and the content of Mg in the CaCOs scale. Little attention has been paid to the effect of Mg2+ on the initial stages of CaCO3 formation on a metal surface. In this study, an electrochemical technique was used to study the influence of Mg2+ on the initial stages of CaCO3 scale formed on a metal surface. With this electrochemical technique, the reduction of the dissolved oxygen in an analysis solution is considered on the surface of a rotating disk electrode (RDE) under potentiostatic control. The rate of oxygen reduction on the surface of the RDE enables the extent of surface coverage of scale to be assessed. With this electrochemical technique, a new insight into the effect of Mg2+ on CaCO3 scale formed on a metal surface is given.

  12. Measurements of low photon doses using LiF:Mg,Cu,P and CaF{sub 2}:Cu dosimeters

    Energy Technology Data Exchange (ETDEWEB)

    Prokert, K. [Dresden Univ. of Technology (Germany). Inst. of Radiation Protection Physics; Mann, G. [Dresden Univ. of Technology (Germany). Inst. of Radiation Protection Physics

    1997-03-01

    The new thermoluminophors LiF:Mg, Cu, P and CaF{sub 2}:Cu in form of pellets exhibit a significantly higher TL-response than the well-known dosimeters of the types TLD-100 (LiF:Mg, Ti), TLD-400 (CaF{sub 2}:Mn), TLD-900 (CaSO{sub 4}:Dy), etc. Furthermore, the thermoluminophor LiF:Mg, Cu, P shows besides its high sensitivity a good tissue equivalence and therefore, only a small variation of the dose response with the photon energy. The lower limits of detection of these new materials are about 5 {mu}Gy and 0.2 {mu}Gy resp. Therefore, short term measurements of absorbed dose can be realised in radiation fields at very low dose rates (environmental radiation, scattering radiation at medical equipment`s etc.) with an accuracy of {+-}10%. In the field of environmental monitoring the period of exposure can be limited to about 10 days. Using CaF{sub 2}:Cu detectors an exposure of 24 hours is sufficient for dose measurements with lower accuracy. The reusability of CaF{sub 2}:Cu pellets is guaranteed without loss of sensitivity independently of the application of different reading and annealing procedures. In the case of LiF:Mg, Cu, P detectors special procedures are needed in order to keep constant TL-properties. The results of dose measurements at low dose levels in different radiation fields demonstrate the advantages of these detector types. (orig.)

  13. A Novel MgO-CaO-SiO2 System for Fabricating Bone Scaffolds with Improved Overall Performance

    Directory of Open Access Journals (Sweden)

    Hang Sun

    2016-04-01

    Full Text Available Although forsterite (Mg2SiO4 possesses good biocompatibility and suitable mechanical properties, the insufficient bioactivity and degradability hinders its further application. In this study, a novel MgO-CaO-SiO2 system was developed by adding wollastonite (CaSiO3 into Mg2SiO4 to fabricate bone scaffolds via selective laser sintering (SLS. The apatite-forming ability and degradability of the scaffolds were enhanced because the degradation of CaSiO3 could form silanol groups, which could offer nucleation sites for apatite. Meanwhile, the mechanical properties of the scaffolds grew with increasing CaSiO3 to 20 wt %. It was explained that the liquid phase of CaSiO3 promoted the densification during sintering due to its low melting point. With the further increase in CaSiO3, the mechanical properties decreased due to the formation of the continuous filling phase. Furthermore, the scaffolds possessed a well-interconnected porous structure and exhibited an ability to support cell adhesion and proliferation.

  14. Evolution of Fe Bearing Intermetallics During DC Casting and Homogenization of an Al-Mg-Si Al Alloy

    Science.gov (United States)

    Kumar, S.; Grant, P. S.; O'Reilly, K. A. Q.

    2016-06-01

    The evolution of iron (Fe) bearing intermetallics (Fe-IMCs) during direct chill casting and homogenization of a grain-refined 6063 aluminum-magnesium-silicon (Al-Mg-Si) alloy has been studied. The as-cast and homogenized microstructure contained Fe-IMCs at the grain boundaries and within Al grains. The primary α-Al grain size, α-Al dendritic arm spacing, IMC particle size, and IMC three-dimensional (3D) inter-connectivity increased from the edge to the center of the as-cast billet; both α c-AlFeSi and β-AlFeSi Fe-IMCs were identified, and overall α c-AlFeSi was predominant. For the first time in industrial billets, the different Fe-rich IMCs have been characterized into types based on their 3D chemistry and morphology. Additionally, the role of β-AlFeSi in nucleating Mg2Si particles has been identified. After homogenization, α c-AlFeSi predominated across the entire billet cross section, with marked changes in the 3D morphology and strong reductions in inter-connectivity, both supporting a recovery in alloy ductility.

  15. A density functional study of the high-pressure chemistry of MSiN2(M = Be,Mg, Ca)

    OpenAIRE

    Römer, Rebecca; Kroll, Peter; Schnick, Wolfgang

    2009-01-01

    Normal pressure modifications and tentative high-pressure phases of the nitridosilicates MSiN2 with M = Be, Mg, or Ca have been thoroughly studied by density functional methods. At ambient pressure, BeSiN2 and MgSiN2 exhibit an ordered wurtzite variant derived from idealized filled β-cristobalite by a C1-type distortion. At ambient pressure, the structure of CaSiN2 can also be derived from idealized filled β-cristobalite by a different type of distortion (D1-type). Energy–volume calculations...

  16. Spectroscopic and laser characteristics of Ca, Mg, Zr substituted gadolinium gallium garnet crystals doped with chromium and neodymium

    International Nuclear Information System (INIS)

    Light Raman spectra, spectroscopic and generation charateristics of (Ca, Mg, Zr):(Cr, Nd) crystals of gadolinium-gallium garnet-base (GGG) solid solutions are studied to investigate possibilities of these crystals application as materials for laser active elements. The results presented allow one to expect generation parameters in GGG (Ca, Mg, Zr):(Cr, Nd) crystals, which would be no worse than GSGG-Cr-Nd crystal parameters and a lower temperature of their synthesis (∼ 1700 deg C) may give certain advantages when producing these crystals as compared to more high-temperature IAG and GSGG ones

  17. Effect of Additive ZrO2 on Sintering Properties of MgO-CaO Bricks

    Institute of Scientific and Technical Information of China (English)

    WANG Jiandong; GE Changchun; SHEN Weiping

    2007-01-01

    The effect of electric fused ZrO2, m-ZrO2 and zirconite on the sintering properties of MgO-CaO bricks was studied and the effect of the ZrO2 content and temperature on BD (bulk density), AP(apparent porosity)and CCS (Cold Crushing strength) of MgO-CaO bricks was investigated. The microstructure of burned specimens was analyzed by SEM. The result shows that the sintering property is best while 5% m-ZrO2 was added at 1 600 ℃.

  18. CaFeAs2: A staggered intercalation of quantum spin Hall and high-temperature superconductivity

    Science.gov (United States)

    Wu, Xianxin; Qin, Shengshan; Liang, Yi; Le, Congcong; Fan, Heng; Hu, Jiangping

    2015-02-01

    We predict that CaFeAs2, a newly discovered iron-based high-temperature (Tc) superconductor, is a staggered intercalation compound that integrates topological quantum spin Hall (QSH) and superconductivity (SC). CaFeAs2 has a structure with staggered CaAs and FeAs layers. While the FeAs layers are known to be responsible for high Tc superconductivity, we show that with spin orbital coupling each CaAs layer is a Z2 topologically nontrivial two-dimensional QSH insulator and the bulk is a three-dimensional weak topological insulator. In the superconducting state, the edge states in the CaAs layer are natural one-dimensional topological superconductors. The staggered intercalation of QSH and SC provides us a unique opportunity to realize and explore physics, such as Majorana modes and Majorana fermion chains.

  19. Hydrogen sorption properties of Mg-20wt.%Fe 23 Y8 composite prepared by reactive mechanical alloying

    Institute of Scientific and Technical Information of China (English)

    LI Zhinian; LIU Xiaopeng; HUANG Zuo; JIANG Lijun; WANG Shumao

    2006-01-01

    Mg-20wt.% Fe23Y8 composite was successfully prepared by reactive mechanical alloying (RMA). X-ray diffraction (XRD) measurement shows that the main phases of composite are MgH2 and Mg2FeH6. The composite exhibits excellent hydrogen abs/desorption properties and can absorb 4.36wt.% and 5.72wt.% hydrogen at 473 and 573 K in 10 min under 3.0 Mpa hydrogen pressure, respectively. The composite can desorb 5.27wt.% hydrogen at 573 K in 30 min under 0.02 Mpa hydrogen pressure. Compared with the pure MgH2, the hydrogen desorption temperature of Mg-20wt.% Fe23Y8 composite is decreased about 40 ℃. It is supposed that both the catalyst effect of Fe-Y distributed in Mg substrate and the crystal defects play the main role in improving hydrogen sorption properties of Mg-20wt.% Fe23Y8 composite.

  20. Reaction rim growth in the systems MgO-SiO2 and CaO-MgO-SiO2: Diffusion pathways and the effect of water

    OpenAIRE

    Joachim, Bastian

    2011-01-01

    Metamorphe Koronen sind ein typisches Merkmal metamorpher Gesteine. Das Saumwachstum wird von zahlreichen Parametern wie Druck, Temperatur, der Zeit, der chemischen Zusammensetzung und der Anwesenheit von Fluiden beeinflusst. Anhand von Laborexperimenten lassen sich Transportmechanismen, Reaktionsraten und Komponentenmobilitäten in Reaktionssäumen als Funktion dieser Parameter bestimmen. Das Ziel dieser Arbeit ist es, Komponentenmobilitäten im ternären System CaO-MgO-SiO2 zu bestimmen und anh...

  1. Effects of MgO Contents in Slag on Inclusions in H13 Steel Deoxidized with Mg-Al-Fe Alloy%渣系中 MgO 含量对镁铝铁合金脱氧 H13钢中夹杂物的影响

    Institute of Scientific and Technical Information of China (English)

    吴政; 李晶; 史成斌; 杜刚

    2015-01-01

    采用 CaO-MgO-Al2 O 3-SiO 2-CaF2渣系的精炼渣,研究了渣系中 MgO 含量对镁铝铁合金脱氧 H13钢中夹杂物密度、尺寸和成分的影响.结果表明:采用质量分数5%MgO 精炼渣精炼后,钢中的夹杂物最少,密度为55.62个.mm-2,夹杂物尺寸均小于8μm;当 MgO 的质量分数低于或高于5%时,夹杂物数量都较多,都含有尺寸为8~10μm 的大型夹杂物;当精炼渣中 MgO 的质量分数为0时,钢中夹杂物主要为 MgO.Al2 O 3和 Al2 O 3-SiO 2,当精炼渣中 MgO 的质量分数为5%,8%和12%时,钢中的夹杂物分别主要为 MgO.Al2 O 3和 Al2 O 3-SiO 2、MgO.Al2 O 3和 Al2 O 3-SiO 2-CaO、MgO.Al2 O 3和 Al2 O 3-SiO 2-CaO-MgO;通过热力学数据计算得到的与钢中镁、铝相对应的氧化物稳定区图与试验得到的 A 类夹杂物的成分一致.%The effects of MgO contents in slag system CaO-SiO 2-Al2 O 3-MgO-CaF2 on the number,size and composition of inclusions in H13 steel deoxidized with Mg-Al-Fe alloy were studied.Results show that when the content of MgO in the slag was 5wt%,the minimum number of inclusions was 55.62 per square millimeter,and the size of all inclusions was less than 8 μm.When the content of MgO in the slag was less than or more than 5wt%, there was more number of inclusions in the steel,and the size of some inclusions was 8-10 μm.When the content of MgO in the slag was 5wt%,8wt%,12wt%,respectively,the inclusions were MgO.Al2 O 3 and Al2 O 3-SiO 2 , MgO.Al2 O 3 and Al2 O 3-SiO 2-CaO,MgO.Al2 O 3 and Al2 O 3-SiO 2-CaO-MgO,respectively.A stability diagram of inclusions corresponding to magnesium and alumina contents in the steel was calculated employing available thermodynamic data,and the A-type inclusion composition experimentally obtained well agreed with the diagram.

  2. Ion microprobe assessment of the heterogeneity of Mg/Ca, Sr/Ca and Mn/Ca ratios in Pecten maximus and Mytilus edulis (bivalvia shell calcite precipitated at constant temperature

    Directory of Open Access Journals (Sweden)

    P. S. Freitas

    2009-07-01

    Full Text Available Small-scale heterogeneity of biogenic carbonate elemental composition can be a significant source of error in the accurate use of element/Ca ratios as geochemical proxies. In this study ion microprobe (SIMS profiles showed significant small-scale variability of Mg/Ca, Sr/Ca and Mn/Ca ratios in new shell calcite of the marine bivalves Pecten maximus and Mytilus edulis that was precipitated during a constant-temperature culturing experiment. Elevated Mg/Ca, Sr/Ca and Mn/Ca ratios were found to be associated with the deposition of elaborate shell features, i.e. a shell surface stria in P. maximus and surface shell disturbance marks in both species, the latter a common occurrence in bivalve shells. In both species the observed small-scale elemental heterogeneity most likely was not controlled by variable transport of ions to the extra-pallial fluid, but by factors such as the influence of shell organic content and/or crystal size and orientation, the latter reflecting conditions at the shell crystal-solution interface. In the mid and innermost regions of the P. maximus shell the lack of significant small-scale variation of Mg/Ca ratios, which is consistent with growth at constant temperature, suggest a potential application as a palaeotemperature proxy. Cross-growth band element/Ca ratio profiles in the interior of bivalve shells may provide more promising palaeo-environmental tools than sampling from the outer region of bivalve shells.

  3. CaFe2As2 Under In-Plane Uniaxial Pressure

    Science.gov (United States)

    Frampton, Miles; Zieve, Rena; Dioguardi, Adam

    2014-03-01

    Many unconventional superconductors have a planar crystal structure, with a resulting two-dimensional character that favors superconductivity. They tend to have anisotropic behavior and can be very sensitive to uniaxial pressure. Since these materials often grow preferentially as platelets perpendicular to the crystalline c axis, applying in-plane pressure is challenging. We present a new setup for studying thin samples under uniaxial pressure and our results on CaFe2As2. CaFe2As2 undergoes a magnetic transition simultaneously with a tetragonal-to-orthorhombic structural transition. In-plane uniaxial pressure detwins the orthorhombic phase and accentuates the difference between the axes. We find a significant change in Ts as well as anisotropy of the in-plane resistivity that increases with pressure.

  4. Fermi-Surface Reconstruction and Complex Phase Equilibria in CaFe2As2

    Science.gov (United States)

    Gofryk, K.; Saparov, B.; Durakiewicz, T.; Chikina, A.; Danzenbächer, S.; Vyalikh, D. V.; Graf, M. J.; Sefat, A. S.

    2014-05-01

    Fermi-surface topology governs the relationship between magnetism and superconductivity in iron-based materials. Using low-temperature transport, angle-resolved photoemission, and x-ray diffraction, we show unambiguous evidence of large Fermi-surface reconstruction in CaFe2As2 at magnetic spin-density-wave and nonmagnetic collapsed-tetragonal (cT) transitions. For the cT transition, the change in the Fermi-surface topology has a different character with no contribution from the hole part of the Fermi surface. In addition, the results suggest that the pressure effect in CaFe2As2 is mainly leading to a rigid-band-like change of the valence electronic structure. We discuss these results and their implications for magnetism and superconductivity in this material.

  5. Crystallographic and magnetostriction properties of Fe and FeB-alloy thin films formed on MgO(100 single-crystal substrates

    Directory of Open Access Journals (Sweden)

    Ohtake M.

    2013-01-01

    Full Text Available Fe(100bcc single-crystal film, Fe-B amorphous film, and Fe-B film consisting of a mixture of epitaxial bcc(100 crystal and amorphous are prepared on MgO(100 single-crystal substrates. The influence of crystallographic property on the magnetostriction behavior under rotating magnetic fields is investigated. The output waveform of magnetostriction is sinusoidal for the amorphous film, whereas that of single-crystal film shows a triangle shape. 90° magnetic domain walls are observed for the single-crystal Fe film and the film shows a four-fold symmetry in in-plane magnetic anisotropy. The observation of triangle waveforms is related to the domain wall motion in magnetically unsaturated Fe(100bcc film under rotating magnetic fields. A distortion from triangle wave is observed for the Fe-B film consisting of a mixture of bcc-crystal and amorphous. The magnetostriction behavior is influenced by the magnetization structure.

  6. Widths of KL$_{2,3}$ atomic level for Ca, Fe, Zn

    CERN Document Server

    Kozioł, Karol

    2014-01-01

    Widths of $KL_{2,3}$ atomic levels for Ca, Fe, Zn has been calculated in a fully-relativistic way using the extensive multiconfiguration Dirac-Fock and modified Dirac-Hartree-Slater calculations. The study of de-excitation of the $K^{-1}L_{2,3}^{-1}$ hole state has been presented. Additionally, the approximation to $KL_{2,3}$ level widths has been examined.

  7. Investigation of Fe and Ca in non-stimulated human saliva using NAA

    Science.gov (United States)

    de Medeiros, J. A. G.; Zamboni, C. B.; Kovacs, L.; Lewgoy, H. R.

    2015-07-01

    In this study we investigated non-stimulated human whole saliva of healthy subjects and patients with periodontal disease using Neutron Activation Analysis technique (NAA). The measurements were performed in the IEA-R1 nuclear reactor at IPEN-CNEN/SP. We found considerable metabolic changes mainly in Fe and Ca concentration in whole saliva of periodontal patients. These data are useful for identifying or preventing this oral disease in the Brazilian population.

  8. Ca-Mg inter-diffusion in synthetic polycrystalline dolomite-calcite aggregate at elevated temperatures and pressure

    Science.gov (United States)

    Huang, Wuu-Liang; Liu, Teh-Ching; Shen, Pouyan; Hsu, Allen

    2009-03-01

    This study measures the reaction rate of dolomite and aragonite (calcite) into Mg-calcite at 800, 850, and 900°C and 1.6 GPa. The dry synthetic dolomite-aragonite aggregate transformed very rapidly into dolomite-calcite polycrystalline aggregate while Mg-calcites formed at a relatively slow rate, becoming progressively richer in Mg with run time. We modeled the reaction progress semi-empirically by the first-order rate law. The temperature dependence of the overall transport rate of MgCO3 into calcite can be described by the kinetic parameters ( E = 231.7 kJ/mol and A o = 22.69 h-1). Extrapolation using the Arrhenius equation to the conditions during exhumation of UHPM rocks indicates that the reaction of dolomite with aragonite into Mg-saturated calcite can be completed as the P-T path enters the Mg-calcite stability field in a geologically short time period (340°C and >10 My). SEM-EDS analysis of individual calcite grains shows compositional gradients of Mg in the calcite grains. The Mg-Ca inter-diffusion coefficient at 850°C is around 1.68 × 10-14 m2/sec if diffusion is the major control of the reaction. The calculated closure temperatures for Ca-Mg inter-diffusion as a function of cooling rate and grain size reveal that Ca/Mg resetting in calcite in a dry polycrystalline carbonate aggregate (with grain size around 1 mm) may not occur at temperatures below 480°C at a geological cooling rate around 10°C/My, unless other processes, such as short-circuit interdiffusion along grain boundaries and dislocations, are involved.

  9. Evaluation of foraminiferal trace element cleaning protocols on the Mg/Ca of marine ostracod genus Krithe

    OpenAIRE

    Gray, W.; Holmes, J.; Shevenell, A.

    2014-01-01

    The Mg/Ca of calcite from the marine ostracod genus Krithe may be an important tool for reconstructing past changes in oceanic bottom water temperature (150–4000 m water depth). Rigorous cleaning procedures, routinely used to remove clays, organic matter and Fe–Mn oxyhydroxide coatings in trace element studies of foraminifera, are not regularly applied to marine ostracods despite the potential for Mg contamination. Here we apply standard oxidative and reductive foraminiferal cleaning procedur...

  10. X-ray absorption and x-ray magnetic dichroism study on Ca3CoRhO6 and Ca3FeRhO6

    Science.gov (United States)

    Burnus, T.; Hu, Z.; Wu, Hua; Cezar, J. C.; Niitaka, S.; Takagi, H.; Chang, C. F.; Brookes, N. B.; Lin, H.-J.; Jang, L. Y.; Tanaka, A.; Liang, K. S.; Chen, C. T.; Tjeng, L. H.

    2008-05-01

    By using x-ray absorption spectroscopy at the RhL2,3 , CoL2,3 , and FeL2,3 edges, we find a valence state of Co2+/Rh4+ in Ca3CoRhO6 and of Fe3+/Rh3+ in Ca3FeRhO6 . X-ray magnetic circular dichroism spectroscopy at the CoL2,3 edge of Ca3CoRhO6 reveals a giant orbital moment of about 1.7μB , which can be attributed to the occupation of the minority-spin d0d2 orbital state of the high-spin Co2+ (3d7) ions in trigonal prismatic coordination. This active role of the spin-orbit coupling explains the strong magnetocrystalline anisotropy and Ising-type magnetism of Ca3CoRhO6 .

  11. Assessment of Post-eutectic Reactions in Multicomponent Al-Si Foundry Alloys Containing Cu, Mg, and Fe

    Science.gov (United States)

    Javidani, Mousa; Larouche, Daniel; Grant Chen, X.

    2015-07-01

    Post-eutectic reactions occurring in Al-Si hypoeutectic alloys containing different proportions of Cu, Mg, and Fe were thoroughly investigated in the current study. As-cast microstructures were initially studied by optical and electron microscopy to investigate the microconstituents of each alloy. Differential scanning calorimetry (DSC) was then used to examine the phase transformations occurring during the heating and cooling processes. Thermodynamic calculations were carried out to assess the phase formation under equilibrium and in nonequilibrium conditions. The Q-Al5Cu2Mg8Si6 phase was predicted to precipitate from the liquid phase, either at the same temperature or earlier than the θ-Al2Cu phase depending on the Cu content of the alloy. The AlCuFe-intermetallic, which was hardly observed in the as-cast microstructure, significantly increased after the solution heat treatment in the alloys containing high Cu and Fe contents following a solid-state transformation of the β-Al5FeSi phase. After the solution heat treatment, the AlCuFe-intermetallics were mostly identified with the stoichiometry of the Al7Cu2Fe phase. Thermodynamic calculations and microstructure analysis helped in determining the DSC peak corresponding to the melting temperature of the N-Al7Cu2Fe phase. The effect of Cu content on the formation temperature of π-Al8Mg3FeSi6 is also discussed.

  12. Perpendicular Magnetic Anisotropy of Full-Heusler Films in Pt/Co2FeAl/MgO Trilayers

    Science.gov (United States)

    Li, Xiaoqi; Yin, Shaoqian; Liu, Yupeng; Zhang, Delin; Xu, Xiaoguang; Miao, Jun; Jiang, Yong

    2011-04-01

    We report on perpendicular magnetic anisotropy (PMA) in a Pt/Co2FeAl/MgO sandwiched structure with a thick Co2FeAl layer of 2-2.5 nm. The PMA is thermally stable and the anisotropy energy density Ku is 1.3×106 erg/cm3 for the structure with 2 nm Co2FeAl after annealing at 350 °C. The annealing temperature and Co2FeAl thickness greatly affect the PMA. Our results provide an effective way to realize relatively thick perpendicularly magnetized Heusler alloy films.

  13. Adjustment of the ratio of Ca/P in the ceramic coating on Mg alloy by plasma electrolytic oxidation

    International Nuclear Information System (INIS)

    The ceramic coatings containing Ca and P were prepared on AZ91D Mg alloy by plasma electrolytic oxidation technique in NaOH system and Na2SiO3 system, respectively. The phase composition, morphology and the element distribution of the coatings was studied by X-ray diffraction, scanning electron microscopy and energy dispersive spectroscopy. The corrosion resistance of the coatings was examined by polarizing curve methods in a 0.9% NaCl solution. In NaOH system, there were a large number of micro-holes distributing evenly on the surface of the coating, and the coating was mainly composed of Mg, Al, P and Ca. In Na2SiO3 system, the micro-holes in the coatings were reduced greatly in number and the distribution of the micro-holes was uneven, and the coating was mainly composed of Mg, Al, Si, P and Ca. The ratio of Ca/P in the coating can be controlled by the adjustment of the technique parameters to a certain extent. The adjustment of the concentration of Ca2+ in the electrolyte was an effective method to change the ratio of Ca/P in the coating in both systems; the reaction time and the working voltage for the adjustment of the ratio of Ca/P in the coating was more suitable for the NaSi2O3 system than the NaOH system. The polarizing curve tests showed the coatings improved the corrosion resistance of the AZ91D Mg alloy in 0.9% NaCl solution by nearly two orders of magnitude.

  14. Adsorption study of anionic reactive dye from aqueous solution to Mg-Fe-CO{sub 3} layered double hydroxide (LDH)

    Energy Technology Data Exchange (ETDEWEB)

    Ahmed, I.M., E-mail: ismawy@yahoo.ca [Hot Labs Centre, Atomic Energy Authority, P. Code 13759, Cairo (Egypt); Gasser, M.S. [Hot Labs Centre, Atomic Energy Authority, P. Code 13759, Cairo (Egypt)

    2012-10-15

    Graphical abstract: Second order kinetic model for adsorption of congo red onto Mg-Fe-LDH. Highlights: Black-Right-Pointing-Pointer Mg-Fe-CO{sub 3}-LDH was utilized as an adsorbent. Black-Right-Pointing-Pointer It was used for the removal of congo red (CR), an anionic dye from aqueous solution. Black-Right-Pointing-Pointer The adsorption of (CR) is endothermic. Black-Right-Pointing-Pointer The adsorption equilibrium was well described by the Langmuir isotherm model. Black-Right-Pointing-Pointer Adsorption kinetics of (CR) was found to conform to pseudo-second order model. - Abstract: Mg-Fe-Cl Layered double hydroxides (LDHs) have been prepared using a method involving separate nucleation and aging steps with Mg/Fe = 3. The interlayer anions readily replaced by carbonate are characterized by X-ray diffraction (XRD) and FTIR. The effects of different parameters, such as pH, contact time, concentration of dye and temperature on the capacity and adsorption mechanism of Mg-Fe-CO{sub 3}-LDH in removing an anionic dye (congo red, CR) from aqueous solution were separately investigated. The results show that Mg-Fe-CO{sub 3}-LDH is particularly efficient in removing CR and the dye removal increases with decreasing pH. The adsorption of CR on Mg-Fe-CO{sub 3}-LDH reached equilibrium after 15 min where 100 mg/L CR was removed. The equilibrium isotherm indicates that the adsorption of CR onto Mg-Fe-CO{sub 3}-LDH fits to Langmuir and Freundlich equation as well. The adsorption data obtained from the Langmuir model gave good values of the determination coefficient and the saturated adsorption capacity of Mg-Fe-CO{sub 3}-LDH for CR was found to be 104.6 mg/g. The regeneration study indicates that the prepared LDH could be used for several cycles. The thermodynamic parameters have been calculated, and the adsorption process was found to be spontaneous, endothermic in nature and follows a pseudo-second-order kinetic model.

  15. Effect of NiO spin orientation on the magnetic anisotropy of the Fe film in epitaxially grown Fe/NiO/Ag(001) and Fe/NiO/MgO(001)

    Energy Technology Data Exchange (ETDEWEB)

    Kim, W.; Jin, E.; Wu, J.; Park, J.; Arenholz, E.; Scholl, A.; Hwang, C.; Qiu, Z.

    2010-02-10

    Single crystalline Fe/NiO bilayers were epitaxially grown on Ag(001) and on MgO(001), and investigated by Low Energy Electron Diffraction (LEED), Magneto-Optic Kerr Effect (MOKE), and X-ray Magnetic Linear Dichroism (XMLD). We find that while the Fe film has an in-plane magnetization in both Fe/NiO/Ag(001) and Fe/NiO/MgO(001) systems, the NiO spin orientation changes from in-plane direction in Fe/NiO/Ag(001) to out-of-plane direction in Fe/NiO/MgO(001). These two different NiO spin orientations generate remarkable different effects that the NiO induced magnetic anisotropy in the Fe film is much greater in Fe/NiO/Ag(001) than in Fe/NiO/MgO(001). XMLD measurement shows that the much greater magnetic anisotropy in Fe/NiO/Ag(001) is due to a 90{sup o}-coupling between the in-plane NiO spins and the in-plane Fe spins.

  16. Microstructure and Fatigue Behavior of Friction Stir-welded Noncombustive Mg-9Al-Zn-Ca Magnesium Alloy

    Science.gov (United States)

    Zhou, L.; Li, Z. Y.; Nakata, K.; Feng, J. C.; Huang, Y. X.; Liao, J. S.

    2016-06-01

    Microstructure and fatigue behavior of friction stir-welded noncombustive Mg-9Al-Zn-Ca magnesium alloy were investigated. The as-received hot-extruded material consisted of equiaxed α-Mg grains with β-Mg17Al12 and Al2Ca compounds distributed along the grain boundaries. Friction stir welding produced much refined α-Mg grains accompanied by the dissolution of the eutectic β-Mg17Al12 phase, while Al2Ca phase was dispersed homogenously into the Mg matrix. Friction stir welding produced slightly increased hardness and tensile strength in the defect-free welds compared with the base material due to microstructural refinement and uniform distribution of intermetallic compounds. The load-controlled uniaxial tensile high-cycle fatigue tests indicated that fatigue strength of 90 MPa was obtained for the friction stir-welded joint with fatigue crack initiated basically near the specimen's surface and at the retreating side of the joint. Crack propagation was characterized by cleavage and fatigue striations.

  17. Electronic structure of (Ca0.85La0.15)FeAs2

    Science.gov (United States)

    Liu, Z.-H.; Kim, T. K.; Sala, A.; Ogino, H.; Shimoyama, J.; Büchner, B.; Borisenko, S. V.

    2015-02-01

    We report a comprehensive study of orbital character and tridimensional nature of the electronic structure of (Ca0.85La0.15)FeAs2 from recently discovered "112" family of Iron-based superconductors (IBS), with angle-resolved photoemission spectroscopy. We observed that the band structure is similar to that of "122" family, namely, there are three hole-like bands at the Brillouin zone (BZ) center and two electron-like bands at the BZ corner. The bands near the Fermi level (EF) are mainly derived from the Fe t2g orbitals. On the basis of our present and earlier studies, we classify IBS into the three types according to their crystal structures. We show that although the bands near EF mainly originate from Fe 3d electrons, they are significantly modified by the interaction between the superconducting slabs and the intermediate atoms.

  18. The Content of Mg, K and Ca Ions in Vine Leaf under Foliar Application of Magnesium on Calcareous Soils

    Directory of Open Access Journals (Sweden)

    David Gluhić

    2009-06-01

    Full Text Available Chlorosis frequently occurs in vine production on calcareous soils, which is usually attributed to high calcium concentrations in soil. If symptoms appear on older leaves, it is taken that chlorosis is caused by a deficit of Mg2+ ions. A method of preventing chlorosis is foliar application of magnesium; however, uncontrolled application can lead to imbalance with potassium and calcium ions. The research objective was to find out whether foliar application of magnesium could solve the problem of chlorosis, and whether magnesium affects ion interactions with potassium and calcium. The fertilizing trial was set up in vineyards, on anthropogenized rigosols, with different contents of available lime in soil (< 20, 25 and 30 % CaO. Fertilizer was applied three times during the growing period, in a total amount of 2500 g Mg/ha. According to the results, foliar application of magnesium can solve the problem of chlorosis only on soils with a lower lime content (< 20 % CaO. Magnesium concentrations in dry leaf ranged from 0.25 % (beginning of growing period to 0.64 % (post harvest, which is in agreement with literature data. On soils with a high lime content, negative correlation was determined between Mg and K ions in the leaf (r = -0.78. Although correlation between Mg and Ca in plant was positive (r = +0.61 to +0.90 during whole grape vine vegetative period, determined high ratios between Ca and Mg, especially during summer (12.4, indicated that Ca was dominant ion in plant disturbing K and Mg physiological roles.

  19. The Ca, Cl, Mg, Na, and P mass fractions in benign and malignant giant cell tumors of bone investigated by neutron activation analysis

    International Nuclear Information System (INIS)

    The Ca, Cl, Mg, Na, and P content and Ca/P, Ca/Mg, Ca/Na, Cl/Ca, and Cl/Na ratios in samples of intact bone, benign and malignant giant cell tumor (GCT) of bone were investigated by neutron activation analysis with high resolution spectrometry of short-lived radionuclides. It was found that in GCT tissue the mass fractions of Cl and Na are higher and the mass fraction of Ca and P are lower than in normal bone tissues. Moreover, it was shown that higher Cl/Na mass fraction ratios as well as lower Ca/Cl, Ca/Mg, and Ca/Na mass fraction ratios are typical of the GCT tissue compared to intact bone. Finally, we propose to use the estimation of such parameters as the Cl mass fraction and the Ca/Cl mass fraction ratio as an additional test for differential diagnosis between benign and malignant GCT. (author)

  20. The influence of an MgO nanolayer on the planar Hall effect in NiFe films

    Energy Technology Data Exchange (ETDEWEB)

    Li, Minghua, E-mail: mhli@ustb.edu.cn [Department of Material Physics and Chemistry, University of Science and Technology Beijing, Beijing 100083 (China); Department of Electrical Engineering, University of California, Los Angeles, California 90095 (United States); Zhao, Zhiduo; Ma, Lin; Lu, Xiangan; Teng, Jiao; Yu, Guanghua [Department of Material Physics and Chemistry, University of Science and Technology Beijing, Beijing 100083 (China); Yu, Guoqiang; Amiri, Pedram Khalili; Wang, Kang L. [Department of Electrical Engineering, University of California, Los Angeles, California 90095 (United States); Zhou, Wenping [Department of Electrical Engineering, University of California, Los Angeles, California 90095 (United States); Department of Physics, Inner Mongolia University, Hohhot 010021 (China)

    2015-03-28

    The Planar Hall Effect (PHE) in NiFe films was studied using MgO as the buffer and capping layer to reduce the shunt effect. The thermal annealing was found to be effective in increasing the sensitivity. The sensitivity of the magnetic field reached as high as 865 V/AT in a MgO (3 nm)/NiFe (5 nm)/MgO(3 nm)/Ta(3 nm) structure after annealing at 500 °C for 2 h, which is close to the sensitivity of semiconductor Hall Effect (HE) sensors. X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD) and high-resolution transmission electron microscopy (HRTEM) were used to study the sample. The results show that the top crystallization of MgO and NiFe (111) texture were improved by proper annealing. The smooth and clear bottom MgO/NiFe and top NiFe/MgO interface is evident from our data. In addition, the shunt current of Ta was decreased. These combined factors facilitate the improvement of the sensitivity of the magnetic field.

  1. Synthesis, characterization and adsorptive performance of MgFe2O4 nanospheres for SO2 removal

    International Nuclear Information System (INIS)

    A type of uniform Mg ferrite nanospheres with excellent SO2 adsorption capacity could be selectively synthesized via a facile solvothermal method. The size of the MgFe2O4 nanospheres was controlled to be 300-400 nm in diameter. The structural, textural, and surface properties of the adsorbent have been fully characterized by a variety of techniques (Brunauer-Emmett-Teller, BET; X-ray diffraction analysis, XRD; scanning electron microscopy, SEM; and energy-dispersive X-ray spectroscopy, EDS). The valence states and the surface chemical compositions of MgFe2O4 nanospheres were further identified by X-ray photoelectron spectroscopy (XPS). The behaviors of SO2 oxidative adsorption on MgFe2O4 nanospheres were studied using Fourier transform infrared spectroscopy (FTIR). Both the sulfite and sulfate species could be formed on the surface of MgFe2O4. The adsorption equilibrium isotherm of SO2 was analyzed using a volumetric method at 298 K and 473 K. The results indicate that MgFe2O4 nanospheres possess a good potential as the solid-state SO2 adsorbent for applications in hot fuel gas desulfurization.

  2. Structure of Na2O·MO·SiO2·CaF2 (M=Mg, Ca) oxyfluoride glasses

    International Nuclear Information System (INIS)

    (9-x)CaO·xMgO·15Na2O·60SiO2·16CaF2(x=0, 2, 4, 6, and 9) oxyfluoride glasses were prepared. Utilizing the Raman scattering technique together with 29Si and 19F MAS NMR, the effect of alkaline metal oxides on the Q species of glass was characterized. Raman results show that as magnesia is added at the expense of calcium oxide, the disproportional reaction Q3→Q4+Q2 (Qn is a SiO4 tetrahedron with n bridging oxygens) prompted due to the high ionic field strength of magnesia, magnesium oxide entered into the silicate network as tetrahedral MgO4, and removed other modifying ions for charge compensation. This reaction was confirmed by 29Si MAS NMR. 19F MAS NMR results show that fluorine exists in the form of mixed calcium sodium fluoride species in all glasses and no Si-F bonds were formed. As CaO is gradually replaced by MgO (x=6, 9), a proportion of the magnesium ions combines with fluorine to form the MgF+ species. Meanwhile, some part of Na+ ions complex F- in the form of F-Na(6).

  3. Modification of β-Al5FeSi Compound in Recycled Al-Si-Fe Cast Alloy by Using Sr, Mg and Cr Additions

    Institute of Scientific and Technical Information of China (English)

    2008-01-01

    The effects of Sr, Mg, Cr, Sr/Mg and Sr/Cr combined additions on the Fe-containing intermetallic phase in a recycled Al-Si-Fe cast alloy are investigated. The experimental results show that the additions of Cr and Sr/Cr successfully modified the platelet and flake-like β-AlsFeSi phases (β-compound) into the fibrous α-Al8Fe2Si (α-compound). The additions of Sr and Sr/Mg were less effective to modify the β-compound into the α-compound, while the eutectic Si was fully modified into the fibrous morphology. A small secondary dendrite arm spacing (DAS) was found in the Sr-added, Cr-added and Sr/Cr-added alloys, especially in a steel mold. The Sr, Sr/Cr and Sr/Mg combined additions modify the eutectic Si simultaneously. A sludge phase was found in the addition of Cr-added, Sr/Cr-added and Mg-added alloys, especially in the graphite mold casting. The volume fraction of β-compounds was decreased by the addition of various modifying elements.The Cr and Sr/Cr combined additions are very effective to modify the β-compound for the recycled Al-Si-Fe based alloys.

  4. Raman scattering, magnetization and magnetotransport study of SrFeO3-δ, Sr3Fe2O7-δ and CaFeO3

    International Nuclear Information System (INIS)

    In this thesis we have determined the Raman spectra as well as the magnetization, resistance and magnetoresistance of the compounds SrFeO3-δ, Sr3Fe2O7-δ and CaFeO3 as a function of temperature. We describe the preparation of nearly stoichiometric SrFeO3-δ crystals with δ3.00 in order to assign the phonon modes observed in infra-red experiments. We have measured the Raman spectra of the tetragonal phase in the temperature range 13 K to 300 K and of the orthorhombic phase in the temperature range 6 K to 475 K. We have measured the temperature dependence of the magnetization for the magnetic field along high-symmetry axes of the crystal structure. We have also performed neutron diffraction measurements. The resistivity and the magnetoresistance were measured in the range 10 K to 300 K. Finally we have measured the Raman spectra of the same sample in the temperature range 15 K to 440 K. In order to assign the observed modes, we have performed lattice dynamics calculations based on the published crystal structure of Sr3Fe2O7. (orig.)

  5. Phosphate-intercalated Ca-Fe-layered double hydroxides: Crystal structure, bonding character, and release kinetics of phosphate

    Science.gov (United States)

    Woo, Myong A.; Woo Kim, Tae; Paek, Mi-Jeong; Ha, Hyung-Wook; Choy, Jin-Ho; Hwang, Seong-Ju

    2011-01-01

    The nitrate-form of Ca-Fe-layered double hydroxide (Ca-Fe-LDH) was synthesized via co-precipitation method, and its phosphate-intercalates were prepared by ion-exchange reaction. According to X-ray diffraction analysis, the Ca-Fe-LDH-NO 3- compound and its H 2PO 4--intercalate showed hexagonal layered structures, whereas the ion-exchange reaction with HPO 42- caused a frustration of the layer ordering of LDH. Fe K-edge X-ray absorption spectroscopy clearly demonstrated that the Ca-Fe-LDH lattice with trivalent iron ions was well-maintained after the ion-exchange with HPO 42- and H 2PO 4-. Under acidic conditions, phosphate ions were slowly released from the Ca-Fe-LDH lattice and the simultaneous release of hydroxide caused the neutralization of acidic media. Fitting analysis based on kinetic models indicated a heterogeneous diffusion process of phosphates and a distinct dependence of release rate on the charge of phosphates. This study strongly suggested that Ca-Fe-LDH is applicable as bifunctional vector for slow release of phosphate fertilizer and for the neutralization of acid soil.

  6. Phonons of Fe-based superconductor Ca10Pt4As8(Fe1-x Pt x As)10

    Science.gov (United States)

    Ikeuchi, K.; Kobayashi, Y.; Suzuki, K.; Itoh, M.; Kajimoto, R.; Bourges, P.; Christianson, A. D.; Nakamura, H.; Machida, M.; Sato, M.

    2015-11-01

    We report the results of inelastic neutron scattering measurements on particular phonons of a superconducting (SC) Ca10Pt4As8(Fe1-x Pt x As)10 with the onset transition temperature T c ~ 33 K to investigate mainly what roles orbital fluctuation plays in Cooper pairing, where we observed a slight softening of the in-plane transverse acoustic mode corresponding to the elastic constant C 66. This softening starts at temperature T well above the SC T c, as T decreases. An anomalously strong change of the scattering intensity of in-plane optical modes was observed at the M point of the pseudo tetragonal reciprocal space in the range of 35  FeAs planes, the finding presents information on the coupling between the orbital fluctuation of Fe 3d electrons and the lattice system, useful for studying the possible roles of orbital fluctuation in the pairing mechanism and/or the appearance of the so-called nematic phase.

  7. Comparative in vitro Study on Pure Metals (Fe, Mn, Mg, Zn and W)as Biodegradable Metals

    Institute of Scientific and Technical Information of China (English)

    J.Cheng; B.Liu; Y.H.Wu; Y.F.Zheng

    2013-01-01

    Five pure metals including Fe,Mn,Mg,Zn and W have been investigated on their corrosion behavior and in vitro biocompatibility by electrochemical measurement,static immersion test,contact angle measurement,cytotoxicity and hemocompatibility tests.It is found that the sequence of corrosion rate of five metals in Hank's solution from high to low is:MgFe > Zn > Mn > W.Fe,Mg and W show no cytotoxicity to L929 and ECV304 cells,Mn induces significant cytotoxicity to both L929 and ECV304 cells,and Zn has almost no inhibition effect on the metabolic activities of ECV304 while largely reduces the cell viability of L929 cells.The hemolysis percentage of five pure metals is lower than 5% except for Mg and platelets adhered on Zn has been activated and pseudopodia-like structures can be observed while platelets on the other four metals keep normal.

  8. Mg/Ca and isotopic high resolution record of deep-sea hydrothermal barnacles

    Science.gov (United States)

    Bojar, A.-V.; Bojar, H.-P.; Tufar, W.

    2012-04-01

    Barnacles are crustaceans adapted to a sessile existence and cemented to a substrate by a protein complex. Most of the known species inhabit shallow marine environment, less than 2% of the species are found at depths between 100 and 2500 m. The shell of barnacles has a great adaptive significance, the shell of some barnacle species have been already investigated for microstructure. In this study we investigated the shell microstructure as well as the Mg/Ca and stable isotope distribution of barnacles found at a depth of around 2500m at a black smoker from the Manus Spreading centre, north-east of Papua New Guinea. The shell consists of three substructures: an outer layer with pores and aragonite crystals, a massive interior mass and an inner layer with pores. The shell shows grown lines and the outer layer exhibits longitudinal striation from base to apex. The pores have a medium size of 0.8 microns. The size of the calcitic microcrystals are in the range of 0.2 to 0.5 microns, beside, larger aragonite crystals, with size of c. 10 microns are present. The massive interior mass has a compact structure, no pores or channels could be observed. Oxygen stable isotope data of barnacle shell were performed from the centre to the border of the calcitic shells, along profiles. Within one shell, the isotope values show variations of max. 0.6 ‰. The calculated temperatures from the stable isotope data consistently indicate that the barnacles populate sites with low temperature values, up to a few °C. The calculated temperatures from the isotope data are also in agreement with the reported habitat from the North Fiji and Lau Basins, where temperatures of max. 6°C were measured at sites populated by barnacles. Both calculated and measured temperatures of a few degrees indicate that at the sites where barnacles live, hydrothermal fluid input is present, as ambient temperature is around 1.5°C. Electron-microbeam analyses were done along the interior layer of the shell. The

  9. In vitro investigation of anodization and CaP deposited titanium surface using MG63 osteoblast-like cells

    International Nuclear Information System (INIS)

    The aim of the present study was to investigate surface characteristics in four different titanium surfaces (AN: anodized at 270 V; AN-CaP: anodic oxidation and CaP deposited; SLA: sandblasted and acid etched; MA: machined) and to evaluate biological behaviors such as cell adhesion, cell proliferation, cytoskeletal organization, and osteogenic protein expression of MG63 osteoblast-like cells at the early stage. Surface analysis was performed using scanning electron microscopy, thin-film X-ray diffractometry, and a confocal laser scanning microscope. In order to evaluate cellular responses, MG63 osteoblast-like cells were used. The cell viability was evaluated by MTT assay. Immunofluorescent analyses of actin, type I collagen, osteonectin and osteocalcin were performed. The anodized and CaP deposited specimen showed homogeneously distributed CaP particles around micropores and exhibited anatase type oxides, titanium, and HA crystalline structures. This experiment suggests that CaP particles on the anodic oxidation surface affect cellular attachment and spreading. When designing an in vitro biological study for CaP coated titanium, it must be taken into account that preincubation in medium prior to cell seeding and the cell culture medium may affect the CaP coatings. All these observations illustrate the importance of the experimental conditions and the physicochemical parameters of the CaP coating. It is considered that further evaluations such as long-term in vitro cellular assays and in vivo experiments should be necessary to figure out the effect of CaP deposition to biological responses.

  10. Investigation on luminescence of red-emitting Mg3Ca3(PO4)4:Ce3+,Mn2+ phosphors

    Institute of Scientific and Technical Information of China (English)

    张佳; 张凤; 韩丽丽

    2015-01-01

    To realize red emission, the Ce3+-Mn2+ activated Mg3Ca3(PO4)4 phosphors were synthesized by solid-state reaction. The phase and luminescence properties of the as-prepared samples were characterized by using XRD and photoluminescence spectra. XRD result showed that single-phase samples were obtained successfully. The diffuse reflection spectrum of Mg3Ca3(PO4)4 revealed that two main absorptions existed, and the optical band gap was calculated to be about 5.31 eV. For Ce3+ doped Mg3Ca3(PO4)4, a broad emission band from 300 to 500 nm was observed under 254 nm excitation, which was due to the d-f transition of Ce3+; by monitoring 352 nm, the excitation spectrum covered the region from 240 to 340 nm. The Ce3+-Mn2+ co-doped Mg3Ca3(PO4)4 showed an efficient energy transfer from Ce3+ to Mn2+ upon 254 nm excitation, and the red emission was obtained by adjusting the relative concentrations of Ce3+ and Mn2+.

  11. Long-range interactions of excited He atoms with the alkaline earth atoms Mg, Ca, and Sr

    KAUST Repository

    Zhang, J.-Y.

    2013-04-05

    Dispersion coefficients for the long-range interactions of the first four excited states of He, i.e., He(2 1, 3 S) and He(2 1, 3 P), with the low-lying states of the alkaline earth atoms Mg, Ca, and Sr are calculated by summing over the reduced matrix elements of multipole transition operators.

  12. A comparison of Mg/Ca ratios in Globigerinoides ruber (white): sensu stricto versus a mixture of genotypes

    Digital Repository Service at National Institute of Oceanography (India)

    Naik, S.S.

    Version: J. Geol. Soc. India, vol.87(3); 2016; 323-326 A comparison of Mg/Ca ratios in Globigerinoides ruber (white): sensu stricto versus a mixture of genotypes SUSHANT S. NAIK* CSIR-National Institute of Oceanography, Dona Paula, Goa, 403004...

  13. Optimization of dual effects of Mg-1Ca alloys on the behavior of chondrocytes and osteoblasts in vitro

    Institute of Scientific and Technical Information of China (English)

    Yana Dou; Ayeesha Mujeeb; Yufeng Zheng; Zigang Ge

    2014-01-01

    Mg ions can enhance the proliferation and redifferentiation of chondrocytes and the osteogenic differentiation of osteoblasts at specific concentrations, respectively. However, degradation of Mg alloys at varying degradation rates could lead to complex changes in the surrounding tissue environment, such as changes in the dynamic concentration of Mg ions and subsequent pH value. Considering the above mentioned factors, the comprehensive effects of Mg alloys on chondrocytes and osteoblasts behaviors have not yet been optimized. In this study, we evaluated the effects of Mg–1Ca microspheres on cell behavior with an aim to optimize conditions favorable for both cell types. Cells were cultured with Mg–1Ca microspheres prepared using the following concentrations:250μg/ml, 500μg/ml and 1000μg/ml. At specific time points, cytotoxicity, expression of specific genes and extracellular matrix deposition by cells (Alizarin Red Staining of osteoblasts and Alcian blue staining for chondrocytes) were evaluated. The experimental results revealed that Mg–1Ca microspheres prepared at a concentration of 250μg/ml were optimum for both cell types, where chondrocytes were found to be in hypertrophy state while osteoblasts in close proximity to the microspheres showed osteogenetic differentiation. Interestingly, a slight change in osteoblasts behavior was observed nearer to and at a relative distance away from Mg–1Ca microspheres, an important observation for administering the application of microspheres as potential scaffolds.

  14. Photoelectron velocity-map imaging and theoretical studies of heteronuclear metal carbonyls MNi(CO)3- (M = Mg, Ca, Al)

    Science.gov (United States)

    Xie, Hua; Zou, Jinghan; Yuan, Qinqin; Fan, Hongjun; Tang, Zichao; Jiang, Ling

    2016-03-01

    The heteronuclear metal carbonyl anions MNi(CO)3- (M = Mg, Ca, Al) have been investigated using photoelectron velocity-map imaging spectroscopy. Electron affinities of neutral MNi(CO)3 (M = Mg, Ca, Al) are measured from the photoelectron spectra to be 1.064 ± 0.063, 1.050 ± 0.064, and 1.541 ± 0.040 eV, respectively. The C-O stretching mode in these three clusters is observed and the vibrational frequency is determined to be 2049, 2000, and 2041 cm-1 for MgNi(CO)3, CaNi(CO)3, and AlNi(CO)3, respectively. Density functional theory calculations are carried out to elucidate the geometric and electronic structures and to aid the experimental assignments. It has been found that three terminal carbonyls are preferentially bonded to the nickel atom in these heterobinuclear nickel carbonyls MNi(CO)3-1/0, resulting in the formation of the Ni(CO)3 motif. Ni remains the 18-electron configuration for MgNi(CO)3 and CaNi(CO)3 neutrals, but not for AlNi(CO)3. This is different from the homobinuclear nickel carbonyl Ni-Ni(CO)3 with the involvement of three bridging ligands. Present findings would be helpful for understanding CO adsorption on alloy surfaces.

  15. A first look at past sea surface temperatures in the equatorial Indian Ocean from Mg/Ca in foraminifera

    Digital Repository Service at National Institute of Oceanography (India)

    Saraswat, R.; Nigam, R.; Weldeab, S.; Mackensen, A.; Naidu, P.D.

    ] and artificial neural network (ANN) analyses of planktonic foraminifera [Naidu and Malmgren, 2005]. Mg/Ca ratios of foraminifera is another rather well established proxy for SST [Nu¨rnberg et al., 1996; Elderfield and Ganssen, 2000]. However, this technique has...

  16. Are CaIrO3 and MgGeO3 isomechanical to MgSiO3-post-perovskite ?

    Science.gov (United States)

    Metsue, A.; Carrez, P.; Mainprice, D.; Cordier, P.

    2007-12-01

    The recent discovery of MgSiO3 post-perovskite (pPv) and prediction of its elastic properties using atomistic modelling has major implications for the interpretation of seismic anisotropy of the D" layer. Because they don't take into account lattice preferred orientations induced by convective flow, the elastic properties are not sufficient to interpret seismic anisotropy and it is necessary to investigate the plasticity of this mineral. However, it is well known that pressure and temperature near the core-mantle boundary make experimental studies extremely difficult. To circumvent this difficulty, experimental studies are often carried out on analogous phases (stable at lower pressures) which are supposed to exhibit the same mechanical properties as the high-pressure phase. In this work, we calculate the dislocation properties of MgGeO3 pPv at 120GPa and CaIrO3 pPv at ambient pressure using the Peierls-Nabarro (PN) model. The so-called PN model is a fundamental concept of the dislocation theory which describes the resistance of the lattice to dislocation motion, a very important factor for the plasticity of silicates. The PN model also provides an analytical description of the dislocation core and of its potential spreading in the glide plane. Known for several decades, the PN model has triggered a renewed interest when Christian and Vitek (1970) showed that realistic models of dislocations could be built by incorporating generalized stacking faults (GSF) into the PN model. Here, we use the ab initio total-energy package VASP to calculate GSF, which are incorporated in the PN model. In that way, we obtain a model of the dislocation core profile and the value of the stress required to move a dislocation (the so-called Peierls stress) for ten slip systems of each compound. These results are compared to those recently published on MgSiO3 post- perovskite to assess the potential relevance of the analogue approach in studying the rheology of the D" layer. We show that

  17. Magnetism and electronic structures of novel layered CaFeAs{sub 2} and Ca{sub 0.75}(Pr/La){sub 0.25}FeAs{sub 2}

    Energy Technology Data Exchange (ETDEWEB)

    Huang, Yi-Na; Zou, Liang-Jian, E-mail: zou@theory.issp.ac.cn [Key Laboratory of Materials Physics, Institute of Solid State Physics, Chinese Academy of Sciences, P. O. Box 1129, Hefei 230031 (China); University of Science and Technology of China, Hefei, Anhui 230026 (China); Yu, Xiang-Long; Liu, Da-Yong [Key Laboratory of Materials Physics, Institute of Solid State Physics, Chinese Academy of Sciences, P. O. Box 1129, Hefei 230031 (China)

    2015-05-07

    The magnetic and electronic properties of the parent material CaFeAs{sub 2} of new superconductors are investigated using first-principles calculations. We predict that the ground state of CaFeAs{sub 2} is a spin-density-wave (SDW)-type striped antiferromagnet driven by Fermi surface nesting. The magnetic moment around each Fe atom is about 2.1 μ{sub B}. We also present electronic and magnetic structures of electron-doped phase Ca{sub 0.75}(Pr/La){sub 0.25}FeAs{sub 2}, the SDW order was suppressed by La/Pr substitution. The As in arsenic layers is negative monovalent and acts as blocking layers enhancing two-dimensional character by increasing the spacing distance between the FeAs layers. This favors strong antiferromagnetic fluctuations mediated pairing, implying higher T{sub c} in Ca{sub 0.75}(Pr/La){sub 0.25}FeAs{sub 2} than Ca{sub 0.75}(Pr/La){sub 0.25}Fe{sub 2}As{sub 2}.

  18. Divergent effects of the malignant hyperthermia-susceptible Arg(615)-->Cys mutation on the Ca(2+) and Mg(2+) dependence of the RyR1.

    OpenAIRE

    Balog, E M; Fruen, B R; Shomer, N H; Louis, C F

    2001-01-01

    The sarcoplasmic reticulum (SR) Ca(2+) release channel (RyR1) from malignant hyperthermia-susceptible (MHS) porcine skeletal muscle has a decreased sensitivity to inhibition by Mg(2+). This diminished Mg(2+) inhibition has been attributed to a lower Mg(2+) affinity of the inhibition (I) site. To determine whether alterations in the Ca(2+) and Mg(2+) affinity of the activation (A) site contribute to the altered Mg(2+) inhibition, we estimated the Ca(2+) and Mg(2+) affinities of the A- and I-si...

  19. Effects of Be, Sr, Fe and Mg interactions on the microstructure and mechanical properties of aluminum based aeronautical alloys

    Science.gov (United States)

    Ibrahim, Mohamed Fawzy

    The present work was carried out on a series of heat-treatable aluminum-based aeronautical alloys containing various amounts of magnesium (Mg), iron (Fe), strontium (Sr) and beryllium (Be). Tensile test bars (dendrite arm spacing ~ 24mum) were solutionized for either 5 or 12 hours at 540°C, followed by quenching in warm water (60°C). Subsequently, these quenched samples were aged at 160°C for times up to 12 hours. Microstructural assessment was performed. All heat-treated samples were pulled to fracture at room temperature using a servo-hydraulic tensile testing machine. The results show that Be causes partial modification of the eutectic silicon (Si) particles similar to that reported for Mg addition. Addition of 0.8 wt.% Mg reduced the eutectic temperature by ~10°C. During solidification of alloys containing high levels of Fe and Mg, without Sr, a peak corresponding to the formation of a Be-Fe phase (Al8Fe2BeSi) was detected at 611°C. The Be-Fe phase precipitates in a script-like morphology. A new quinary eutectic-like reaction was observed to take place near the end of solidification of high Mg, high Fe, Be-containing alloys. This new reaction is composed mainly of fine particles of Si, Mg2Si, pi-Al 8Mg3FeSi6 and (Be-Fe) phases. The volume fraction of this reaction decreased with the addition of Sr. The addition of Be has a noticeable effect on decreasing the beta-phase length, or volume fraction, this effect may be limited by adding Sr. Beryllium addition also results in the precipitation of the beta-phase in a nodular form, which reduces the harmful effects of these intermetallics on the alloy mechanical properties. Increasing both Mg and Fe levels led to an increase in the amount of the pi-phase; increasing the iron content led to an increase in the volume fraction of the partially soluble beta- and pi-phases, while Mg2Si particles were completely dissolved. The beta-phase platelets were observed to undergo changes in their morphology due to the

  20. Growth, structure and magnetic properties of FePt nanostructures on NaCl(001) and MgO(001)

    Energy Technology Data Exchange (ETDEWEB)

    Liscio, F; Maret, M; Doisneau-Cottignies, B [Science et Ingenierie des Materiaux et Procedes (SIMaP), INP-Grenoble/CNRS/UJF, BP 75, 38402 Saint-Martin d' Heres (France); Makarov, D; Albrecht, M [Institute of Physics, Chemnitz University of Technology, D-09107 Chemnitz (Germany); Roussel, H, E-mail: mireille.maret@simap.grenoble-inp.fr [Consortium des Moyens Technologiques Communs, INP-Grenoble, BP 75, 38402 Saint-Martin d' Heres (France)

    2010-02-10

    A comparison of the structural and magnetic properties of FePt nanostructures grown at different temperatures on NaCl(001) and MgO(001) substrates is presented. A strong influence of the deposition temperature on the epitaxial growth as well as on the size distribution of FePt nanostructures grown on NaCl substrates is observed. In spite of a large lattice mismatch between FePt and NaCl, a 'cube-over-cube' growth of nanostructures with a narrow size distribution was achieved at 520 K. Moreover, the growth of FePt nanostructures on NaCl(001) is not preceded by the formation of a wetting layer as observed on MgO(001). The higher degree of L1{sub 0} chemical ordering in FePt nanostructures grown on MgO(001) accompanied by the absence of L1{sub 0} variants with an in-plane tetragonal c-axis indicates that the tensile epitaxial stress induced by the MgO substrate is a key factor in the formation of the L1{sub 0} phase with an out-of-plane c-axis. Superparamagnetic behavior is revealed for the FePt nanostructures grown on NaCl(001) due to their small size and relatively poor chemical order.

  1. Growth, structure and magnetic properties of FePt nanostructures on NaCl(001) and MgO(001)

    Science.gov (United States)

    Liscio, F.; Makarov, D.; Maret, M.; Doisneau-Cottignies, B.; Roussel, H.; Albrecht, M.

    2010-02-01

    A comparison of the structural and magnetic properties of FePt nanostructures grown at different temperatures on NaCl(001) and MgO(001) substrates is presented. A strong influence of the deposition temperature on the epitaxial growth as well as on the size distribution of FePt nanostructures grown on NaCl substrates is observed. In spite of a large lattice mismatch between FePt and NaCl, a 'cube-over-cube' growth of nanostructures with a narrow size distribution was achieved at 520 K. Moreover, the growth of FePt nanostructures on NaCl(001) is not preceded by the formation of a wetting layer as observed on MgO(001). The higher degree of L10 chemical ordering in FePt nanostructures grown on MgO(001) accompanied by the absence of L10 variants with an in-plane tetragonal c-axis indicates that the tensile epitaxial stress induced by the MgO substrate is a key factor in the formation of the L10 phase with an out-of-plane c-axis. Superparamagnetic behavior is revealed for the FePt nanostructures grown on NaCl(001) due to their small size and relatively poor chemical order.

  2. Simultanous removal of VOCs and Nox by oxides of Mg, Cu, Al, and Fe, derivatives of hydrotalicites compounds

    International Nuclear Information System (INIS)

    A series of Mg(Cu)-AlFe mixed oxides derived from Hydrotalcites-Like compounds has been prepared. These solids were characterized by various physico-chemical methods and their catalytic performances were tested towards the catalytic oxidation of propene and the simultaneous elimination of propene and NOx. X-Ray Diffraction of the calcined samples, revealed the existence of oxide and spinel phases such as MgO, CuO,-Fe2O3 and/or Fe3O4, MgFe2O4or CuFe2O4. Moreover, the temperature programmed reduction showed that copper and iron oxide species are easily reducible. The catalytic performances of the catalysts towards propene oxidation showed a better activity for Cu2Mg2Fe2500 due to a better dispersion of copper species in this solid. On the other hand, samples with low copper and iron contents presented a better activity towards the simultaneous elimination of propene and NO. (author)

  3. Orbital and suborbital variability in North Atlantic bottom water temperature obtained from deep-sea ostracod Mg/Ca ratios

    Science.gov (United States)

    Cronin, T. M.; Dwyer, G.S.; Baker, P.A.; Rodriguez-Lazaro, J.; DeMartino, D.M.

    2000-01-01

    Magnesium/calcium (Mg/Ca) ratios were measured in the deep-sea ostracod (Crustacea) genus Krithe from Chain core 82-24-4PC from the western mid-Atlantic Ridge (3427 m) in order to estimate ocean circulation and bottom water temperature (BWT) variability over the past 200,000 years. Mg/Ca ratios have been used as a paleothermometer because the ratios are controlled primarily by ambient water temperatures at the time the organism secretes its adult carapace. Over the past two glacial-interglacial cycles, Mg/Ca values oscillated between about 7 mmol/mol and 12 mmol/mol, equivalent to a BWT range of 0 to > 3.5??C. The lowest values were obtained on specimens from glacial marine isotope stages (MISs) 2, 4 and 6; the highest values were obtained from specimens from the early part of the Holocene interglacial (MIS 1), and also from MISs 5 and 7. These trends suggest that BWTs in the North Atlantic Ocean fluctuate over orbital time scales. Suborbital variability in Mg/Ca ratios and BWT was also observed for the past 100,000 years. Ratios rose from ~8 mmol/mol to ~10 mmol/mol (implying a BWT increase of ~1 to 3??C) during 14 Mg/Ca excursions. The highest ratios were found in Krithe dated at approximately 32, 36-38, 43, 48, 73, 85 and 93 ka. Although the age model for the Chain 82-24-4PC and temporal resolution do not allow precise correlation, some of these deep-sea bottom temperature excursions appear to correspond to Heinrich events recorded in other regions of the North Atlantic and perhaps Dansgaard-Oeschger interstadial events recorded in Greenland ice cores. If confirmed, this would support the hypothesis that millennial-scale oscillations of climate in the North Atlantic are capable of affecting global climate via thermohaline circulation changes. (C) 2000 Elsevier Science B.V.

  4. Structural Properties of Alternate Monatomic Layered [Fe/Co]n Epitaxial Films on MgO Substrate

    Science.gov (United States)

    Chu, In Chang; Saki, Yoshinobu; Kawasaki, Shohei; Doi, Masaaki; Sahashi, Masashi

    2008-06-01

    Body-centered-cubic (bcc) Fe50Co50 material is reported to show a high bulk spin scattering coefficient on current perpendicular to plane-giant magneto-resistance (CPP-GMR) system. But the origin of that phenomenon does not make sure yet. We prepared artificially alternate monatomic layered (AML) [Fe/Co] 41 MLs epitaxial films (Ts: 75, 250 °C) by monatomic deposition method and investigated the topology of AML [Fe/Co]n epitaxial films on MgO substrate with different orientation (001), (011) by the scanning tunnel microscopy (STM) and reflection high energy electron diffraction (RHEED), which we could confirm Frank-van der Merwe (FM) growth mode for AML [Fe/Co]n on MgO(001) and Volmer-Weber (VW) growth mode for that on Mg(011). The roughness of surface, Ra (0.20 nm) of AML [Fe/Co] 41 MLs epitaxial film grown at 75 °C on MgO(001) is smaller than that (0.46 nm) of AML [Fe/Co] grown at 250 °C on MgO(001), which has the large terraces of over 50 nm (Ra: 0.17 nm), even though there are some valleys between large terraces. Moreover we confirmed the structural properties of trilayered epitaxial films with AML [Fe/Co]n (Ra: 0.18 nm) and Fe50Co50 alloy epitaxial film on Au electrode by RHEED before confirming the characteristics of CPP-GMR devices.

  5. Spin crossover in solid and liquid (Mg,Fe)O at extreme conditions

    Science.gov (United States)

    Stixrude, Lars; Holmstrom, Eero

    Ferropericlase, (Mg,Fe)O, is a major constituent of the Earth's lower mantle (24-136 GPa). Understanding the properties of this component is important not only in the solid state, but also in the molten state, as the planet almost certainly hosted an extensive magma ocean initially. With increasing pressure, the Fe ions in the material begin to collapse from a magnetic to a nonmagnetic spin state. This crossover affects thermodynamic, transport, and electrical properties. Using first-principles molecular dynamics simulations, thermodynamic integration, and adiabatic switching, we present a phase diagram of the spin crossover. In both solid and liquid, we find a broad pressure range of coexisting magnetic and non-magnetic ions due to the favorable enthalpy of mixing of the two. In the solid increasing temperature favors the high spin state, while in the liquid the opposite occurs, due to the higher electronic entropy of the low spin state. Because the physics of the crossover differ in solid and liquid, melting produces a large change in spin state that may affect the buoyancy of crystals freezing from the magma ocean in the earliest Earth. This research was supported by the European Research Council under Advanced Grant No. 291432 ``MoltenEarth'' (FP7/2007-2013).

  6. Growth of mixed phased films of {gamma}-Fe{sub 2}O{sub 3} and half metallic Fe{sub 3}O{sub 4} using (100) MgO/Fe under layer for spin electronic devices

    Energy Technology Data Exchange (ETDEWEB)

    Wang, M L; Nakagawa, S [Department of Physical Electronics, Tokyo Institute of Technology, 2-12-1 O-okayama, Meguro, Tokyo 152-8552 (Japan); Yu, R H, E-mail: nakagawa@pe.titech.ac.jp [Department of Materials Science and Engineering, Tsinghua University, Beijing 100084 (China)

    2011-01-01

    Half metallic magnetite films using (100) MgO/Fe under layer deposited at room temperature were prepared using facing targets sputtering method. X-ray diffractometry and TEM analyses confirmed epitaxial growth of (100) oriented Fe{sub 3}O{sub 4} layer on (100) oriented MgO under layer prepared on 5nm-thick Fe buffer layer on glass substrates. Resistivity analyses clarified that higher oxygen partial pressure caused higher oxidation of Fe ions in the films which tend to result in {gamma}-Fe{sub 2}O{sub 3}. Substrate heating is effective to improve crystallinity and magnetic properties of Fe{sub 3}O{sub 4} film. Oxygen partial pressure of 7.5%, substrate temperature of 150 deg. C and sputtering discharge current of 0.45A was suitable to prepare magnetite Fe{sub 3}O{sub 4} film with (100) preferential orientation and good magnetic properties.

  7. Formation process of micro arc oxidation coatings obtained in a sodium phytate containing solution with and without CaCO{sub 3} on binary Mg-1.0Ca alloy

    Energy Technology Data Exchange (ETDEWEB)

    Zhang, R.F. [School of Material and Electromechanics, Jiangxi Science and Technology Normal University, Nanchang 330013 (China); Zhang, Y.Q. [Zhejiang DunAn Light Alloy Technology CO,.LTD, Zhuji 311835 (China); Hunan University of Science and Technology, Xiangtan 411201 (China); Zhang, S.F.; Qu, B. [School of Material and Electromechanics, Jiangxi Science and Technology Normal University, Nanchang 330013 (China); Guo, S.B. [Hunan University of Science and Technology, Xiangtan 411201 (China); Xiang, J.H., E-mail: xiangjunhuai@163.com [School of Material and Electromechanics, Jiangxi Science and Technology Normal University, Nanchang 330013 (China)

    2015-01-15

    Highlights: • Compared to the Mg phase, the area of Mg{sub 2}Ca phase is much smaller. • The coatings are preferentially developed on the area adjacent to Mg{sub 2}Ca phase. • During MAO process, some sodium phytate molecules are hydrolyzed. • Anodic coatings are developed from uneven to uniform. - Abstract: Micro arc oxidation (MAO) is an effective method to improve the corrosion resistance of magnesium alloys. In order to reveal the influence of alloying element Ca and CaCO{sub 3} electrolyte on the formation process and chemical compositions of MAO coatings on binary Mg-1.0Ca alloy, anodic coatings after different anodizing times were prepared on binary Mg-1.0Ca alloy in a base solution containing 3 g/L sodium hydroxide and 15 g/L sodium phytate with and without addition of CaCO{sub 3}. The coating formation was studied by using scanning electron microscope (SEM), energy dispersive X-ray spectroscopy (EDS) and X-ray diffraction (XRD). The results show that Mg-1.0Ca alloy is composed of two phases, the Mg phase and Mg{sub 2}Ca phase. After treating for 5 s, the coating began to develop and was preferentially formed on the area nearby Mg{sub 2}Ca phase, which may be resulted from the intrinsic electronegative potential of the Mg phase than that of Mg{sub 2}Ca phase. Anodic coatings unevenly covered the total surface after 20 s. After 80 s, the coatings were uniformly developed on Mg-1.0Ca alloy with micro pores. During MAO process, some sodium phytate molecules are hydrolyzed into inorganic phosphate. CaCO{sub 3} has minor influence on the calcium content of the obtained MAO coatings.

  8. The Influence of Zn Content on the Corrosion and Wear Performance of Mg-Zn-Ca Alloy in Simulated Body Fluid

    Science.gov (United States)

    Li, Hua; Liu, Debao; Zhao, Yue; Jin, Feng; Chen, Minfang

    2016-09-01

    Mg-Zn-Ca alloy has been attracting increasing attention as a potential biodegradable implant material. In this paper, Mg-3Zn-0.2Ca and Mg-4Zn-0.2Ca alloys were prepared by means of vacuum melting and subsequent hot extrusion process. The influences of Zn content on the microstructure, mechanical properties, and corrosion and wear behavior of Mg-Zn-Ca alloys in simulated body fluid (SBF) were studied. The results show that with increased Zn content, the grain size and corrosion resistance were decreased, while the mechanical strength and wear resistance were increased, under both dry sliding and SBF-lubricated conditions. For the same Mg-Zn-Ca alloy, the wear loss rate under SBF lubrication was higher than dry sliding condition, indicating a strong corrosion-assisted wear effect of SBF to the Mg-Zn-Ca alloy.

  9. Effect of Ca addition on the as-cast microstructure and creep properties of Mg-5Zn-5Sn magnesium alloy

    Institute of Scientific and Technical Information of China (English)

    YANG Mingbo; CHENG Liang; SHEN Jia; PAN Fusheng

    2009-01-01

    The effect of Ca addition on the as-cast microstructure and creep properties of Mg-5Zn-5Sn magnesium alloy was investigated. The results indicate that adding 1.0 wt.% Ca to Mg-5Zn-5Sn alloy can effectively refine the as-cast microstructure of the alloy, and the CaMgSn phase with high thermal stability is formed in the alloy. In addition, adding 1.0 wt.% Ca to Mg-5Zn-5Sn alloy can also improve the creep properties of the alloy. After adding 1.0 wt.% Ca to Mg-5Zn-5Sn alloy, the second creep rate of the alloy at 150℃ and 50 MPa for 100 h decreases from 4.67×10~(-8) to 1.43×10~(-8) s~(-1). The strengthening mechanism is mainly attributed to the microstructural refinement and the formation of CaMgSn phase.

  10. The Influence of Zn Content on the Corrosion and Wear Performance of Mg-Zn-Ca Alloy in Simulated Body Fluid

    Science.gov (United States)

    Li, Hua; Liu, Debao; Zhao, Yue; Jin, Feng; Chen, Minfang

    2016-07-01

    Mg-Zn-Ca alloy has been attracting increasing attention as a potential biodegradable implant material. In this paper, Mg-3Zn-0.2Ca and Mg-4Zn-0.2Ca alloys were prepared by means of vacuum melting and subsequent hot extrusion process. The influences of Zn content on the microstructure, mechanical properties, and corrosion and wear behavior of Mg-Zn-Ca alloys in simulated body fluid (SBF) were studied. The results show that with increased Zn content, the grain size and corrosion resistance were decreased, while the mechanical strength and wear resistance were increased, under both dry sliding and SBF-lubricated conditions. For the same Mg-Zn-Ca alloy, the wear loss rate under SBF lubrication was higher than dry sliding condition, indicating a strong corrosion-assisted wear effect of SBF to the Mg-Zn-Ca alloy.

  11. Micronutrients Fe, Zn and Ca and their relationship with anthropometric indices and dental health among children

    Directory of Open Access Journals (Sweden)

    Pourhashemi S.J.

    2008-06-01

    Full Text Available Background: Proper nutrition has an important role in the physical and psychological development of children. The aim of this survey is to compare the nutrition of a community to the recommended daily amount (RDA to determine deficiencies and present recommendations for improvement.Methods: In this cross-sectional study conducted in Tehran, Iran, 788 children, all seven years of age, were selected via cluster sampling and evaluated using standard questionnaires with a 24-hr recall regarding the frequency and type of food intake. Then by measurement of weight and height, their anthropometric and DMFT (decayed/missing/filled teeth indices were determined using the Kruskal-Wallis one-way analysis of variance, and Mann-Whitney U and chi-square tests.Results: Relative to the RDA, 23.6% of children had low intake of Ca, and 3.2% and 5.2% were deficient for Fe and Zn, respectively. Anthropometric measurements showed that 15.7% were malnourished based on weight for age, 10.5% based on height for age and 16.8% based on weight for height indices. The DMFT indices for children with dietary Ca levels under 75% of the RDA were significantly higher than those with sufficient Ca intake (P<0.001. The mean DMFT indices for dental development were 0.22 for permanent teeth (four molars; SD=0.64 and 4.64 for primary teeth (SD=3.24. We found a significant correlation between DMFT indices and low Fe intake: the DMFT indices of children with iron deficiency were much higher than those with sufficient iron intake.Conclusions: Children in Tehran do not receive enough Ca Fe and Zn from their diets. This problem causes mild malnutrition and increases the risk of dental caries.

  12. Exigências de minerais para cabras durante a gestação: Na, K, Mg, S, Fe e Zn Minerals requirements of goats during the pregnancy: Na, K, Mg, S, F and Zn

    Directory of Open Access Journals (Sweden)

    Roberto Germano Costa

    2003-04-01

    Full Text Available O trabalho foi realizado com o objetivo de estimar a retenção e a exigência líquida dos minerais Na, K, Mg, S, Fe e Zn durante a gestação de cabras com um ou dois fetos. A estimativa de retenção foi baseada na diferença entre o total de cada mineral depositado no feto, útero, membranas, fluídos fetais e glândula mamária dos animais nas diferentes etapas da gestação e o total de cada mineral armazenado nas cabras vazias, utilizando-se o modelo de predição ln=A+Bx+Cx2, em que x=tempo de gestação. Os conteúdos de Na, K, Mg, S, Fe e Zn, durante as gestações de um e dois fetos foram de: 13,2 e 21,4 mg; 13,3 e 21,3 g; 2,1 e 3,7 mg; 5,5 e 9,3 mg; 575,5 e 981,0 mg; 112,6 e 164,7 mg nas gestações, resultando em exigências líquidas diárias de 0,13 e 0,11 g; 0,21 e 0,31 g; 0,06 e 0,11g; 0,17 e 0,21 g; 22,94 e 40,51 mg; 2,63 e 2,78 mg, respectivamente.This work was carried out with the purpose of evaluating the retention and the requirement of Ca e P minerals during the pregnancy of goats with one or two foetus. The estimate of retention was based in the difference between the total of each mineral stored in the foetus, uterus, membranes, fetals fluids and mammary gland of animals in the differents phases of pregnancy and the total of each mineral stored in the empty goats, using the model of prediction ln=A+Bx+Cx2, where x=time of pregnancy. The comparison of the estimative with the real values obtained show that the suggested model explained with coherence and precision the biological behavior of minerals retention during all pregnancy. The contend of Na, K, Mg, S, Fe e Zn was: 13.2 and 21.4 mg; 13.3 and 21.3 g; 2.1 and 3.7 mg; 5.5 and 9.3 mg; 575.5 and 981.0 mg; 112.6 and 164.7 mg in the pregnancy of one and two foetus, respectively, that resulted in a diary liquid requirement of 0.13 and 0.11 g; 0.21 and 0.31 g 0.06 and 0.11g; 0.17 and 0.21 g; 22.94 and 40.51 mg; 2.63 and 2.78 mg, respectively.

  13. Field‐based validation of a diagenetic effect on G. ruber Mg/Ca paleothermometry: Core top results from the Aegean Sea (eastern Mediterranean)

    OpenAIRE

    Kontakiotis, George; Mortyn, Peter Graham; Antonarakou, Assimina; Martínez Botí, M. A.; Triantaphyllou, Maria V.

    2011-01-01

    Recent work across the Mediterranean Sea has illustrated the salinity and overgrowth effects on planktonic foraminiferal Mg/Ca, which potentially confound the use of this as a temperature proxy for paleoceanographic reconstructions. To test and verify these effects, we present new Aegean Sea results which reveal Mg/Ca values that were unreasonably high to be explained by temperature or salinity variations alone, confirming that foraminiferal Mg/Ca is affected by diagenesis. We have specifical...

  14. Improving in-vitro biocorrosion resistance of Mg-Zn-Mn-Ca alloy in Hank’s solution through addition of cerium

    Institute of Scientific and Technical Information of China (English)

    张凡; 马爱斌; 宋丹; 江静华; 卢富敏; 张留艳; 杨东辉; 陈建清

    2015-01-01

    Two kinds of Mg-Zn-Mn-Ca alloys with and without cerium were designed and fabricated. In-vitro degradation tests and electrochemical evaluations were carried out to compare their biocorrosion behavior in Hank’s solution at 37 ºC. After adding cerium, the continuous network distributed Ca2Mg6Zn3 phases in Mg-2Zn-0.5Mn-1Ca alloy (Alloy I) were separated due to the emerging non-continuously distributed Mg2Ca phase and Mg12CeZn phase. This change led to corrosion acceleration of Mg ma-trix at the initial stage but also sped up the formation of compact corrosion products for Mg-2Zn-0.5Mn-1Ca-1.5Ce alloy (Alloy II), and therefore enhanced its biocorrosion resistance. Cerium containing Alloy II has the potential to be used as future biomate-rials.

  15. Review: geological and experimental evidence for secular variation in seawater Mg/Ca (calcite-aragonite seas and its effects on marine biological calcification

    Directory of Open Access Journals (Sweden)

    J. B. Ries

    2010-09-01

    Full Text Available Synchronized transitions in the polymorph mineralogy of the major reef-building and sediment-producing calcareous marine organisms and abiotic CaCO3 precipitates (ooids, marine cements throughout Phanerozoic time are believed to have been caused by tectonically induced variations in the Mg/Ca ratio of seawater (molar Mg/Ca>2="aragonite seas", <2="calcite seas". Here, I assess the geological evidence in support of secular variation in seawater Mg/Ca and its effects on marine calcifiers, and review a series of recent experiments that investigate the effects of seawater Mg/Ca (1.0–5.2 on extant representatives of calcifying taxa that have experienced variations in this ionic ratio of seawater throughout the geologic past.

    Secular variation in seawater Mg/Ca is supported by synchronized secular variations in (1 the ionic composition of fluid inclusions in primary marine halite, (2 the mineralogies of late stage marine evaporites, abiogenic carbonates, and reef- and sediment-forming marine calcifiers, (3 the Mg/Ca ratios of fossil echinoderms, molluscs, rugose corals, and abiogenic carbonates, (4 global rates of tectonism that drive the exchange of Mg2+ and Ca2+ along zones of ocean crust production, and (5 additional proxies of seawater Mg/Ca including Sr/Mg ratios of abiogenic carbonates, Sr/Ca ratios of biogenic carbonates, and Br concentrations in marine halite.

    Laboratory experiments have revealed that aragonite-secreting bryopsidalean algae and scleractinian corals and calcite-secreting coccolithophores exhibit higher rates of calcification and growth in experimental seawaters formulated with seawater Mg/Ca ratios that favor their skeletal mineral. These results support the assertion that seawater Mg/Ca played an important role in determining which hypercalcifying marine organisms were the major reef-builders and sediment-producers throughout Earth history. The observation that primary

  16. The high-pressure electronic structure of magnesiowustite (Mg, Fe)O: applications to the physics and chemistry of the lower mantle

    Science.gov (United States)

    Sherman, David M.

    1991-01-01

    The electronic structure of magnesiowustite is investigated using self-consistent field X?? scattered wave (SCF-X??-SW) molecular orbital calculations on (FeO6)10- and (FeMg12O14)2- clusters. Calculated one-electron transition energies are used to interpret the optical spectrum of (Mg, Fe)O. The results are applied to the electrical and thermal conductivity of the lower mantle. This is especially true if Fe2+ adopts the low-spin configuration. The geophysically significant properties of (Fe, Mg)O probably result from defect Fe3+. -from Author

  17. Heat capacities of synthetic hedenbergite, ferrobustamite and CaFeSi2O6 glass

    Science.gov (United States)

    Haselton, H.T., Jr.; Robie, R.A.; Hemingway, B.S.

    1987-01-01

    Heat capacities have been measured for synthetic hedenbergite (9-647 K), ferrobustamite (5-746 K) and CaFeSi2O6 glass (6-380 K) by low-temperature adiabatic and differential scanning calorimetry. The heat capacity of each of these structural forms of CaFeSiO6 exhibits anomalous behavior at low temperatures. The X-peak in the hedenbergite heat-capacity curve at 34.5 K is due to antiferromagnetic ordering of the Fe2+ ions. Ferrobustamite has a bump in its heat-capacity curve at temperatures less than 20 K, which could be due to weak cooperative magnetic ordering or to a Schottky anomaly. Surprisingly, a broad peak with a maximum at 68 K is present in the heat-capacity curve of the glass. If this maximum, which occurs at a higher temperature than in hedenbergite is caused by magnetic ordering, it could indicate that the range of distortions of the iron sites in the glass is quite small and that coupling between iron atoms is stronger in the glass than in the edge-shared octahedral chains of hedenbergite. The standard entropy change, So298.15 - So0, is 174.2 ?? 0.3, 180.5 ?? 0.3 and 185.7 ?? 0.4 J/mol??K for hedenbergite, ferrobustamite and CaFeSi2O6 glass, respectively. Ferrobustamite is partially disordered in Ca-Fe distribution at high temperatures, but the dependence of the configuratonal entropy on temperature cannot be evaluated due to a lack of information. At high temperatures (298-1600 K), the heat capacity of hedenbergite may be represented by the equation Cop(J/mol??K) = 3l0.46 + 0.01257T-2039.93T -1 2 - 1.84604?? l06T-2 and the heat capacity of ferrobustamite may be represented by Cop(J/mol??K) = 403.83-0.04444T+ 1.597?? 10-5T2-3757.3T -1 2. ?? 1987.

  18. Double-layered perpendicular magnetic recording media of granular-type FePt-MgO films

    International Nuclear Information System (INIS)

    The recording performance of double-layered granular-type FePt-MgO perpendicular magnetic recording media fabricated onto glass discs by sputtering is investigated. The (0 0 1)-textured FePt granular films are obtained by annealing FePt/MgO multilayers. Three different multilayer structures are compared in their magnetic properties and recording SNR performances. To evaluate thermal stability property of these granular-type FePt disks, the time-dependent magnetic force microscope (MFM) signal from the written bits on one of these disks is recorded in the temperature range 25-200 degree sign C. The signal decay at high observation temperature is interpreted based on the temperature dependence of magnetic anisotropy (Ku)

  19. X-ray absorption and x-ray magnetic dichroism study on Ca3CoRhO6 and Ca3FeRhO6

    OpenAIRE

    Burnus, T.; Z. Hu; Wu, Hua; Cezar, J. C.; Niitaka, S.; Takagi, H.; Chang, C. F.; Brookes, N. B.; Lin, H. -J.; Jang, L. Y.; Tanaka, A.; Liang, K. S.; Chen, C. T.; Tjeng, L. H.

    2008-01-01

    Using x-ray absorption spectroscopy at the Rh-L_2,3, Co-L_2,3, and Fe-L_2,3 edges, we find a valence state of Co^2+/Rh^4+ in Ca3CoRhO6 and of Fe^3+/Rh^3+ in Ca3FeRhO6. X-ray magnetic circular dichroism spectroscopy at the Co-L_2,3 edge of Ca3CoRhO6 reveals a giant orbital moment of about 1.7mu_B, which can be attributed to the occupation of the minority-spin d_0d_2 orbital state of the high-spin Co^2+ (3d^7) ions in trigonal prismatic coordination. This active role of the spin-orbit coupling ...

  20. Mg(2+)/Ca(2+) promotes the adhesion of marine bacteria and algae and enhances following biofilm formation in artificial seawater.

    Science.gov (United States)

    He, Xiaoyan; Wang, Jinpeng; Abdoli, Leila; Li, Hua

    2016-10-01

    Adhesion of microorganisms in the marine environment is essential for initiation and following development of biofouling. A variety of factors play roles in regulating the adhesion. Here we report the influence of Ca(2+) and Mg(2+) in artificial seawater on attachment and colonization of Bacillus sp., Chlorella and Phaeodactylum tricornutum on silicon wafer. Extra addition of the typical divalent cations in culturing solution gives rise to significantly enhanced adhesion of the microorganisms. Mg(2+) and Ca(2+) affect the adhesion of Bacillus sp. presumably by regulating aggregation and formation of extracellular polymeric substances (EPS). The ions alter quantity and types of the proteins in EPS, in turn affecting subsequent adhesion. However, it is noted that Mg(2+) promotes adhesion of Chlorella likely by regulating EPS formation and polysaccharide synthesis. Ca(2+) plays an important role in protein expression to enhance the adhesion of Chlorella. For Phaeodactylum tricornutum, Ca(2+) expedites protein synthesis for enhanced adhesion. The results shed some light on effective ways of utilizing divalent cations to mediate formation of biofilms on the marine structures for desired performances.

  1. Mg(2+)/Ca(2+) promotes the adhesion of marine bacteria and algae and enhances following biofilm formation in artificial seawater.

    Science.gov (United States)

    He, Xiaoyan; Wang, Jinpeng; Abdoli, Leila; Li, Hua

    2016-10-01

    Adhesion of microorganisms in the marine environment is essential for initiation and following development of biofouling. A variety of factors play roles in regulating the adhesion. Here we report the influence of Ca(2+) and Mg(2+) in artificial seawater on attachment and colonization of Bacillus sp., Chlorella and Phaeodactylum tricornutum on silicon wafer. Extra addition of the typical divalent cations in culturing solution gives rise to significantly enhanced adhesion of the microorganisms. Mg(2+) and Ca(2+) affect the adhesion of Bacillus sp. presumably by regulating aggregation and formation of extracellular polymeric substances (EPS). The ions alter quantity and types of the proteins in EPS, in turn affecting subsequent adhesion. However, it is noted that Mg(2+) promotes adhesion of Chlorella likely by regulating EPS formation and polysaccharide synthesis. Ca(2+) plays an important role in protein expression to enhance the adhesion of Chlorella. For Phaeodactylum tricornutum, Ca(2+) expedites protein synthesis for enhanced adhesion. The results shed some light on effective ways of utilizing divalent cations to mediate formation of biofilms on the marine structures for desired performances. PMID:27362920

  2. Analysis of Fe, Ca, Ti, Ba, Ce, Zr and La element in the Sea sediment at Muria peninsula by X RF method

    International Nuclear Information System (INIS)

    he analysis of metals (Fe, Ca, Ti, Ba, Ce, Zr and La) in the sea sediment environmental samples at Muria peninsula has been carried out with X-Ray Fluorescence (XRF) method. The aim of this analysis is to know the distribution metals which accommodate the recent environmental data in supporting the license of site and Environmental Impact Assessment (EIA) for the Nuclear Power Plants (NPP). Samples taken preparation and analysis based on the procedures of environmental analysis. The result analysis that contents of mayor elements in 7 sea sediment location of sampling were Ca, Ti and Fe with concentration are (6.74 – 11.69 ) %; (0.74 – 6.89 ) % and (0.45 -1.94 ) % successively; while minor elements were Ba, Ce, Zr and La with concentration are 451.4 – 1331.6 ) mg/kg; (201.8 – 427.3) mg/kg; (192.3 – 338.5) mg/kg dan (171.7 – 298.4) mg/kg. The statistic test result shows that sampling location there is a significant difference all of element with the level significant of 95 %. (author)

  3. Photocatalytic degradation of methylene blue on magnetically separable MgFe2O4 under visible light irradiation

    KAUST Repository

    Shahid, Muhammad

    2013-05-01

    A magnetically separable single-phase MgFe2O4 photocatalyst with a spinel crystal structure was synthesized by using the solid-state reaction method. The formation of spinel structure is confirmed by X-ray diffraction and Fourier transform infrared spectroscopy. The magnetic measurements showed that the photocatalyst material can be separated from water when an external magnetic field is added and redispersed into water solution after the external magnetic field is eliminated. It is one of the promising photocatalysts for waste water treatment. The photocatalytic activity of MgFe2O4 was investigated by using the photo-decomposition of methylene blue dye under visible light. The photoelectrochemical property of the MgFe2O4 was studied by measuring their photocurrent-potential behavior in 1 M NaOH electrolyte under AM 1.5100 mW cm-2 illumination. © 2013 Elsevier B.V. All rights reserved.

  4. Strong Dependence of Hydration State of F-Actin on the Bound Mg(2+)/Ca(2+) Ions.

    Science.gov (United States)

    Suzuki, Makoto; Imao, Asato; Mogami, George; Chishima, Ryotaro; Watanabe, Takahiro; Yamaguchi, Takaya; Morimoto, Nobuyuki; Wazawa, Tetsuichi

    2016-07-21

    Understanding of the hydration state is an important issue in the chemomechanical energetics of versatile biological functions of polymerized actin (F-actin). In this study, hydration-state differences of F-actin by the bound divalent cations are revealed through precision microwave dielectric relaxation (DR) spectroscopy. G- and F-actin in Ca- and Mg-containing buffer solutions exhibit dual hydration components comprising restrained water with DR frequency f2 (fw). The hydration state of F-actin is strongly dependent on the ionic composition. In every buffer tested, the HMW signal Dhyme (≡ (f1 - fw)δ1/(fwδw)) of F-actin is stronger than that of G-actin, where δw is DR-amplitude of bulk solvent and δ1 is that of HMW in a fixed-volume ellipsoid containing an F-actin and surrounding water in solution. Dhyme value of F-actin in Ca2.0-buffer (containing 2 mM Ca(2+)) is markedly higher than in Mg2.0-buffer (containing 2 mM Mg(2+)). Moreover, in the presence of 2 mM Mg(2+), the hydration state of F-actin is changed by adding a small fraction of Ca(2+) (∼0.1 mM) and becomes closer to that of the Ca-bound form in Ca2.0-buffer. This is consistent with the results of the partial specific volume and the Cotton effect around 290 nm in the CD spectra, indicating a change in the tertiary structure and less apparent change in the secondary structure of actin. The number of restrained water molecules per actin (N2) is estimated to be 1600-2100 for Ca2.0- and F-buffer and ∼2500 for Mg2.0-buffer at 10-15 °C. These numbers are comparable to those estimated from the available F-actin atomic structures as in the first water layer. The number of HMW molecules is roughly explained by the volume between the equipotential surface of -kT/2e and the first water layer of the actin surface by solving the Poisson-Boltzmann equation using UCSF Chimera. PMID:27332748

  5. Atomic and electronic structure of polar Fe2O3(0001)/MgO(111) interfaces

    Science.gov (United States)

    Pande, K.; Gajdardziska-Josifovska, M.; Weinert, M.

    2012-07-01

    We present a first-principles investigation of the structural, electronic, and magnetic properties of ultrathin Fe2O3(0001) films on a polar MgO(111) substrate. The results imply that the heterointerface is atomically abrupt with oxidelike stacking for film thicknesses between ˜1.5 and 8.5 Å. The Fe-Fe bilayer (nominal separation of 0.59 Å in Fe2O3) at the interface collapses into an “Fe2” monolayer. Both electronic polarization and structural relaxations effectively screen the dipole field of the polar interface system. The structural relaxations—consisting of interpenetration, separation, and merger of Fe and oxygen planes—are particularly drastic in the three- and four-bilayers-thick films, giving rise to barrierless movement of oxygen towards the surface and the formation of an “Fe2|FeO3” layer structure not seen in hematite. Comparisons to calculations of unsupported polar Fe2O3(0001) slabs demonstrate that these unusual changes in stacking sequence and electronic structure are associated with the polar nature of this oxide heterointerface.

  6. Demonstration of Mg2FeH6 as heat storage material at temperatures up to 550 °C

    Science.gov (United States)

    Urbanczyk, R.; Meggouh, M.; Moury, R.; Peinecke, K.; Peil, S.; Felderhoff, M.

    2016-04-01

    The storage of heat at high temperatures, which can be used to generate electricity after sunset in concentrating solar power plants, is one of the most challenging technologies. The use of metal hydride could be one possibility to solve the problem. During the endothermic heat storage process, the metal hydride is decomposed releasing hydrogen, which then can be stored. During the exothermic reaction of the metal with the hydrogen gas, the stored heat is then released. Previous research had shown that Mg and Fe powders can be used at temperatures up to 550 °C for heat storage and shows excellent cycle stability over hundreds of cycles without any degradation. Here, we describe the results of testing of a tube storage tank that contained 211 g of Mg and Fe powders in 2:1 ratio. Twenty-three dehydrogenations (storage) and 23 hydrogenations (heat release) in the temperature range between of 395 and 515 °C and pressure range between 1.5 and 8.6 MPa were done. During the dehydrogenation, 0.41-0.42 kWhth kg-1 of heat based on material 2 Mg/Fe can be stored in the tank. After testing, mainly Mg2FeH6 was observed and small amounts of MgH2 and Fe metal can be detected in the hydride samples. This means that the heat storage capacity of the system could be further increased if only Mg2FeH6 is produced during subsequent cycles.

  7. Tunnel magnetoresistance in thermally robust Mo/CoFeB/MgO tunnel junction with perpendicular magnetic anisotropy

    Directory of Open Access Journals (Sweden)

    B. Fang

    2015-06-01

    Full Text Available We report on tunnel magnetoresistance and electric-field effect in the Mo buffered and capped CoFeB/MgO magnetic tunnel junctions (MTJs with perpendicular magnetic anisotropy. A large tunnel magnetoresistance of 120% is achieved. Furthermore, this structure shows greatly improved thermal stability and stronger electric-field-induced modulation effect in comparison with the Ta/CoFeB/MgO-based MTJs. These results suggest that the Mo-based MTJs are more desirable for next generation spintronic devices.

  8. Mott transition in CaFe2O4 at around 50 GPa

    Science.gov (United States)

    Greenberg, Eran; Rozenberg, Gregory Kh.; Xu, Weiming; Pasternak, Moshe P.; McCammon, Catherine; Glazyrin, Konstantin; Dubrovinsky, Leonid S.

    2013-12-01

    Electrical transport and magnetic properties of CaFe2O4 have been studied at pressures up to 70 GPa using Fe57 Mössbauer spectroscopy (MS), Raman spectroscopy, and electrical resistance measurements. These studies have shown the onset of the Mott transition (MT) at a pressure of around 50 GPa, leading to the collapse of Fe3+ magnetic moments and to the insulator-metal (IM) transition. The observed onset of the MT corroborates with the recently reported isostructural transition accompanied by a 12% decrease in the Fe polyhedral volume. An analysis of the alterations of the electrical transport, magnetic, and structural properties with pressure increase and at the transition range suggests that the coinciding IM transition, magnetic moment, and volume collapse at around 50 GPa are caused by the closure of the Hubbard gap driven by the high-spin to low-spin (HS-LS) transition. At that, since MS did not reveal any evidence of a preceding LS state, it could be inferred that the HS-LS transition immediately leads to an IM transition and complete collapse of magnetism.

  9. Magnetization reversal and negative volume thermal expansion in Fe doped Ca2RuO4

    Science.gov (United States)

    Qi, T. F.; Yuan, S. J.; Ye, F.; Chi, S.; Terzic, J.; Zhang, H.; Zhao, Z.; Liu, X.; Parkin, S.; Mao, W. L.; Cao, G.

    We report structural, magnetic, transport and thermal properties of single-crystal Ca2Ru1-xFexO4 (0 pressure, magnetic field and temperature. The central findings of this work are a pronounced magnetization reversal and a negative thermal expansion that are induced by Fe doping. Our results including neutron diffraction data suggest that the magnetization reversal is primarily a result of different temperature dependences of two antiparallel, competing Ru and Fe sublattices and that the negative thermal expansion is achieved via magnetic and metal-insulator transitions. We will present and discuss our results with comparison drawn with relevant systems. This work was supported by the NSF via Grant No. DMR-1265162.

  10. Ca对碳质孕育含Fe的Mg-3%Al合金晶粒细化的“免毒化”作用%Poisoning-free effect of calcium on grain refinement of Mg-3%Al alloy containing trace Fe by carbon inoculation

    Institute of Scientific and Technical Information of China (English)

    杜军; 王海蕾; 周明川; 李文芳

    2013-01-01

    Mg-3%Al alloy was modified by combining Ca addition with carbon inoculation.The effects of Fe addition and addition sequence on the grain refinement were investigated.A higher grain refining efficiency could be obtained for the Mg-Al alloy modificd by combining Ca addition with carbon inoculation.Fe addition and addition sequence had no obvious effect on the grain refinement.Ca addition could effectively avoid grain-coarsening resulting from Fe in the carbon-inoculated Mg-Al alloy.The Al-C-O particles, actually being Al4C3,should act as potent substrates for α-Mg grains in the sample treated by combining Ca addition with carbon inoculation.However,the duplex-phase particles of Al4C3 coated on Al-Fe or Al-C-Fe should be the potent substrates for α-Mg grains if Fe existed in the Mg-Al melt.Ca addition can contribute to the formation of the particles of Al4C3 coated on Al-Fe or Al-C-Fe,regardless of the Fe addition sequence.The poisoning effect of Fe was effectively inhibited in the carbon-inoculated of Mg-Al alloy due to Ca addition,namely,Ca has a poisoning-free effect.%利用Ca和碳质孕育对Mg-3%Al合金进行复合变质处理,并研究了Fe及其Fe的添加顺序对细化效果的影响.与碳质孕育相比,Ca和碳复合孕育后的晶粒细化效果更为显著,Fe及其添加顺序对复合孕育细化效果无显著影响.Ca的添加可有效避免碳质孕育Mg-Al合金中因Fe所导致的晶粒粗化作用.在Ca和碳质复合孕育试样中可观察到大量的Al-C-O颗粒,这些颗粒实际应为Al4C3,并作为α-Mg的形核核心.然而,在熔体中添加Fe后,试样中可观察到大量在Al-Fe或Al-C-Fe表面吸附Al4C3的双相粒子,该双相粒子可作为α-Mg的形核核心并导致晶粒细化.Ca有利于该双相粒子的生存,并与工艺条件无关,从而使得Fe对晶粒细化的“毒化”作用得到有效抑制,即Ca对Fe有“免毒化”效果.

  11. Effect of Ca addition on modification of primary Mg2Si, hardness and wear behavior in Mg–Si hypereutectic alloys

    Directory of Open Access Journals (Sweden)

    M.E. Moussa

    2014-09-01

    Full Text Available The effect of Ca addition on modification of primary Mg2Si, hardness and wear behavior in Mg–5 wt.%Si hypereutectic alloy has been investigated. The results showed clearly that without Ca addition, most of primary Mg2Si appeared as coarse dendritic morphology with average size of about 215 μm. With the addition of 0.1 wt.%Ca, the average size of primary Mg2Si decreased to about 98 μm, but their morphologies did not significantly changed. As the addition level of Ca increased to 0.3 wt.%, the average size of primary Mg2Si decreased significantly to about 50 μm and their morphologies changed to polyhedral shape. However, with further increasing Ca addition to 0.6 wt.% and 1 wt.%, some needle-like and blocky CaMgSi particles formed and the average size of primary Mg2Si increased slightly, which could described as over-modification. The present work showed that the optimal modification effect could be obtained when the Ca content in the investigated alloy reached 0.3 wt.%. The modification mechanism may be referred mainly due to poisoning effect resulting from the segregation of Ca atoms at the growth front of the Mg2Si and the adsorption effect of some Ca atoms in the Mg2Si crystal growth plane. The 0.3 wt.%Ca-added alloy has the highest hardness value and the best wear resistance among all other alloys. An excessive Ca addition resulted in the formation of some needle-like and blocky CaMgSi particles, which was detrimental to hardness and wear behavior of the 0.6 wt.% and 1 wt.%Ca-added alloys. The wear mechanism of investigated alloys is a mild abrasive oxidative wear with little adhesion.

  12. Research Update: Structural and transport properties of (Ca,La)FeAs2 single crystal

    OpenAIRE

    Caglieris, F.; Sala, A.; Fujioka, M.; F. Hummel; Pallecchi, I.; Lamura, G.; Johrendt, D.; Takano, Y.; Ishida, S; A. Iyo; Eisaki, H.; Ogino, H.; H. Yakita; Shimoyama, J.; Putti, M.

    2016-01-01

    Structural and transport properties in the normal and superconducting states are investigated in a Ca0.8La0.2FeAs2 single crystal with Tc = 27 K, belonging to the newly discovered 112 family of iron based superconductors. The transport critical current density Jc for both field directions measured in a focused ion beam patterned microbridge reveals a weakly field dependent and low anisotropic behaviour with a low temperature value as high as Jc(B = 0) ∼ 105 A/cm2. This demonstrates not only b...

  13. Impact of densification on microstructure and transport properties of CaFe5O7

    Science.gov (United States)

    Delacotte, C.; Hébert, S.; Hardy, V.; Bréard, Y.; Maki, R.; Mori, T.; Pelloquin, D.

    2016-04-01

    Monophasic CaFe5O7 ceramic has been synthesized by solid state route. Its microstructural features have been studied by diffraction techniques and electron microscopy images before and after Spark Plasma Sintering (SPS) annealings. This work is completed by measurements of electrical and thermal properties. Especially, attention is focused around the structural and electronic transition at 360 K for which specific heat measurements have revealed a sharp peak. Densification by SPS techniques led to a significant improvement of electrical conductivity above 360 K.

  14. Local Inhomogeneity and Filamentary Superconductivity in Pr-Doped CaFe2As2

    Science.gov (United States)

    Gofryk, Krzysztof; Pan, Minghu; Cantoni, Claudia; Saparov, Bayrammurad; Mitchell, Jonathan E.; Sefat, Athena S.

    2014-01-01

    We use multiscale techniques to determine the extent of local inhomogeneity and superconductivity in Ca0.86Pr0.14Fe2As2 single crystal. The inhomogeneity is manifested as a spatial variation of the praseodymium concentration, local density of states, and superconducting order parameter. We show that the high-Tc superconductivity emerges from cloverlike defects associated with Pr dopants. The highest Tc is observed in both the tetragonal and collapsed tetragonal phases, and its filamentary nature is a consequence of nonuniform Pr distribution that develops localized, isolated superconducting regions within the crystals.

  15. Nanofibers of Ca2Fe2O5: A novel material for aqueous supercapacitor

    Science.gov (United States)

    Sundriyal, Sandeep Kumar; Bhagwan, Jai; Sharma, Yogesh

    2016-05-01

    Porous, aligned and high aspect ratio nanofibers of Ca2Fe2O5 (CFO) have been fabricated by varying various system and process parameter of electrospinning technique for the first time. CFO nanofibers are further characterized by XRD, FESEM and BET surface area. The diameter of as-spun nanofibers of CFO was found to be polymer concentration dependent. Heating profile is found to be responsible for alignment of CFO nanofibers. For the first time, novel CFO nanofibers were subjected to cyclic voltammetry (CV), galvanostatic charge-discharge (GCD) cycling to investigate its energy storage performance as electrode material for aqueous supercapacitor, and accordingly preliminary results are discussed.

  16. Spectrographic semi-quantitative determination of Al, Ca, Fe, Na y Si in minerals and rocks

    International Nuclear Information System (INIS)

    Here is described a method for to determine semi quantitatively Al, Ca, Fe, Na and Si in rocks and minerals. It is used the total combustion technique which uses in jointly germanium oxide (GeO2) and lithium tetraborate (Li2B4O7). The first one acts as regulator and internal standard and the second one acts as regulator and fusing. The excitation is carry out in a emission spectrograph of three meters of focal length. For certificating the obtained results, it was made a comparative study with the atomic absorption spectroscopy technique. (Author)

  17. The Interplay of Fe and Ce Magnetism in Ca0.71 Ce0.29(Fe1-xCox)As2 single crystals

    Science.gov (United States)

    Jiang, Shan; Liu, Lian; Cao, Huibo; Tian, Wei; Emmanuelidu, Eve; Shi, Aoshuang; Uemura, Yasutomo; Ni, Ni

    In this talk, we will present the synthesis and characterization of the Ca0.71 Ce0.29(Fe1-xCox)As2 single crystals. Elastic neutron scattering complemented by resistivity, susceptibility and heat capacity measurements has revealed a paramagnetic-to-antiferromagnetic phase transition of the Fe sublattice at 69K and a monoclinic-to-triclinic structural phase transition at 73 K in Ca0.71 Ce0.29FeAs2. In addition, Fe spin reorientation and Ce ordering at lower temperatures, reminiscent of the one in REFeAsO (RE=Ce, Pr, Nd) materials, exist. The Co substitution on the Fe sites completely suppresses the ordering of Fe sublattice at x=0.032. However, it only slightly affects the Ce ordering, which prevents the formation of superconductivity in Ca0.71 Ce0.29(Fe1-xCox)As2. Work at UCLA was supported by the NSF DMREF DMR-1435672. Work at Columbia and TRIUMF was supported by the NSF DMREF DMR- 1436095, PIRE project IIA 0968226 and DMR-1105961. Work at ORNL's High Flux Isotope Reactor was sponsored by DOE.

  18. Spin-glass behavior of warwickite MgFeBO{sub 4} and CoFeBO{sub 4} crystals observed by Mössbauer spectroscopy

    Energy Technology Data Exchange (ETDEWEB)

    Lyubutin, I.S.; Korotkov, N. Yu.; Frolov, K.V. [Shubnikov Institute of Crystallography, RAS, 119333 Moscow (Russian Federation); Kazak, N.V.; Platunov, M.S. [Kirensky Institute of Physics, SB of RAS, 660036 Krasnoyarsk (Russian Federation); Knyazev, Yu. V. [Siberian Federal University, 660074 Krasnoyarsk (Russian Federation); Bezmaternykh, L.N. [Kirensky Institute of Physics, SB of RAS, 660036 Krasnoyarsk (Russian Federation); Ovchinnikov, S.G. [Kirensky Institute of Physics, SB of RAS, 660036 Krasnoyarsk (Russian Federation); Siberian Federal University, 660074 Krasnoyarsk (Russian Federation); Siberian State Aerospace University, 660014 Krasnoyarsk (Russian Federation); Arauzo, A. [Servicio de Medidas Físicas, Universidad de Zaragoza, Pedro Cerbuna 12, 50009 Zaragoza (Spain); Bartolomé, J. [Instituto de Ciencia de Materiales de Aragón, CSIC-Universidad de Zaragoza and Departamento de Física de la Materia Condensada, 50009 Zaragoza (Spain)

    2015-09-05

    Highlights: • Spin-glass behavior of MgFeBO{sub 4} and CoFeBO{sub 4} observed by Mössbauer spectroscopy. • Transition temperature T{sub SG} increases strongly with Co substitution. • Dynamical scaling theory near T{sub SG} is fulfilled. • Spin-glass behavior is explained as due to short range correlations. • Inclusion of Co increases exchange interaction and magnetocrystalline anisotropy. - Abstract: Single crystals of MgFeBO{sub 4} and CoFeBO{sub 4} warwickites were obtained. The effects of charge ordering and magnetic properties were investigated by Mössbauer spectroscopy. Cation distribution over M1 and M2 nonequivalent sites and the average charge at the metal positions were established. Low temperature Mössbauer spectra reveal spin-glass behavior, with spin-freezing temperatures T{sub SG} of 15.2 and 33.2 K for Mg- and Co-warwickites, respectively, higher than that observed from the d.c. and a.c. magnetic susceptibility measurements. The difference is explained in terms of dynamical scaling theory. The specific shape of the Mössbauer spectra in the vicinity of the magnetic transition at T{sub SG} shows the difference between spin-glass and superparamagnetic behavior and demonstrates an overwhelming role of the exchange anisotropy in the properties of Mg-warwickite. In Co-warwickite the increase of magnetocrystalline anisotropy provokes an increase in magnetic viscosity.

  19. Behavior of methyl orange and orange 10 (orange G) in the presence of hydrotalcite type compounds of Mg/Al and Mg/Fe; Comportamiento de naranja de metilo y naranja 10 (orange G) en presencia de compuestos tipo hidrotalcita de mg/Al y Mg/Fe

    Energy Technology Data Exchange (ETDEWEB)

    Cruz N, G.

    2015-07-01

    This work is focused on studying the sorption capacity of methyl orange dye (Nm) and orange 10 (N-10) in the presence of hydrotalcite type compounds of Mg/Al and Mg/Fe uncalcined and calcined previously at 500 degrees Celsius. Sorption isotherms were determined and the study of the kinetics of sorption was performed. The materials were characterized before and after sorption processes of these dyes by X-ray diffraction, scanning electron microscopy, the specific surface area determination by the Brunauer-Emmett-Teller method, thermogravimetry coupled to mass and infrared spectrometry. The hydrotalcite type compounds reported in this paper were prepared in the laboratory and their acronyms are: HTMgAlG1, HTMgAlMO, HTMgFeG1 and HTMgFeG2. Note that in this work the best conditions for preparing compounds of Mg/Fe were found. From patterns of X-ray diffraction was identified the typical crystal structure of the hydrotalcite type compounds. By scanning electron microscopy the morphology could be determined in the form of flakes characteristics of these compounds. Likewise with elemental analysis of energy dispersive X-ray spectroscopy the presence of Mg, Al, Fe and C, elements of interest for this study was determined. The compounds presented a specific surface area relatively high from 80 to 120 m{sup 2}/g. Thermogravimetry results presented spectra of mass loss very characteristic associated to water losses, dehydroxylation and decarboxylation. The characteristic bands of water and carbonate were assigned by infrared spectroscopy and the bands corresponding to the dyes sulfonates were identified only for the calcined materials. The sorption capacities found of these compounds were as follows: for Nm in the compound HTMgAlG1 uncalcined was 17.82 mg/g for an initial concentration of 200 mg/L and for calcined (HTMgAlMOcal) of 99.8 mg/g with and initial concentration of 1000 mg/L. Moreover, the sorption capacity of the dye N-10 in this same material was 17.92 mg/g and 99

  20. Structural and magnetic phase transitions in triclinic Ca10(FeAs)10(Pt3As8).

    Science.gov (United States)

    Stürzer, T; Friederichs, G M; Luetkens, H; Amato, A; Klauss, H-H; Johrendt, Dirk

    2013-03-27

    We report the structural and magnetic phase transitions of triclinic Ca10(FeAs)10(Pt3As8), which is the parent compound of the 1038-type iron-arsenide superconductors. High-resolution x-ray diffraction reveals splitting of the in-plane (a,b) lattice parameters at T(s) ≈ 120 K. Platinum-doping weakens the distortion and shifts the transition temperature to 80 K in Ca10(Fe(1-x)Pt(x)As)10(Pt3As8) with x = 0.03. μSR experiments show the onset of magnetic order near T and a broad magnetic phase transition. The structural transition involves no reduction of the space group symmetry in contrast to the other parent compounds of iron-arsenide superconductors; nevertheless the local fourfold symmetry of the FeAs-layers in Ca10(FeAs)10(Pt3As8) is broken.

  1. The CaCO3-Fe interaction: Kinetic approach for carbonate subduction to the deep Earth's mantle

    Science.gov (United States)

    Martirosyan, N. S.; Yoshino, T.; Shatskiy, A.; Chanyshev, A. D.; Litasov, K. D.

    2016-10-01

    The CaCO3-Fe0 system, as a model for redox reactions between carbonates and reduced lithologies at the slab-mantle interface during subduction or at core-mantle boundary, was investigated systematically at temperatures from 650 to 1400 °C and pressures from 4 to 16 GPa using multianvil apparatus. CaCO3 reduction via reaction: 3 CaCO3 (aragonite) + 13 Fe0 (metal) = Fe7C3 (carbide) + 3 CaFe2O3 (Ca-wüstite) was observed. The thickness of the reaction-product layer (Δx) increases linearly with the square root of time in the time-series experiments (t), indicating diffusion-controlled process. The reaction rate constant (k = Δx2/2t) is log-linear relative to 1/T. Its temperature dependences was determined to be k [m2/s] = 2.1 × 10-7exp(-162[kJ/mol]/RT) at 4-6 GPa and k [m2/s] = 2.6 × 10-11exp(-65[kJ/mol]/RT) at 16 GPa. The sluggish kinetics of established CaCO3-Fe0 interaction suggests that significant amount of carbonates could survive during subduction from metal saturation boundary near 250 km depth down to the transition zone and presumably to the lower mantle if melting of carbonates is not involved.

  2. Thermal and catalytic cracking of ethylene in presence of CaO, MgO, zeolite and calcined dolomite

    Energy Technology Data Exchange (ETDEWEB)

    Taralas, G.; Sjoestroem, K.; Jaeraas, S.; Bjoernbom, E. [Royal Inst. of Tech., Stockholm (Sweden). Dept. of Chemical Technology

    1993-12-31

    The subject of the present work is to study the effect of catalysts such as calcined dolomite (CaO.MgO), CaO (quicklime), MgO and Zeolite (EKZ-4) on the cracking of ethylene in the presence and absence of steam. N-heptane, toluene, naphthalene, thiophene have been some suitable model compounds for studies of the thermal and catalytic decomposition of tar. Previous results showed that the reaction scheme of the thermal decomposition of n-heptane was consistent with the high yield of ethylene observed in thermal decomposition of n-heptane. The effect of the reactor wall and the ferric impurities in the dolomite are also subjects of the research in this study. The results may also throw some additional light on the nature of the gas-phase thermal and catalytic reactions occurring in the use of dolomite as tar cracking catalysts. 28 refs

  3. The Mechanical Properties and Corrosion Behavior of Double-Layered Nano Hydroxyapatite-Polymer Coating on Mg-Ca Alloy

    Science.gov (United States)

    Bakhsheshi-Rad, H. R.; Hamzah, E.; Abdul-Kadir, M. R.; Saud, Safaa N.; Kasiri-Asgarani, M.; Ebrahimi-Kahrizsangi, R.

    2015-10-01

    Nano-hydroxyapatite (HA)/poly(ɛ-caprolactone) (PCL) coatings with thickness of about 45-55 μm were prepared on the surface of a Mg-Ca alloy by a combination of electrochemical deposition and dip-coating methods. The results indicate that incorporation of nano-HA as an inner layer affects the porosity of the PCL-coated layer as top layer and enhances the corrosion resistance of Mg-Ca alloys. The nano-HA/PCL-coated samples showed higher R p (823.1 kΩ cm2) and lower i corr (5.85E-2 µA/cm2) compared with uncoated. Significant enhancement in the compressive strength was observed in the both nano-HA/PCL and PCL compared with uncoated samples after 10 days immersion in SBF.

  4. Vaporization behavior of lead from the FeO-CaO-SiO2-Al2O3 slag system

    Institute of Scientific and Technical Information of China (English)

    2008-01-01

    Vaporization behavior (1163-1463 K) of lead in the slag system of FeO-CaO-SiO2-Al2O3 with CaCl2 was examined.A thermodynamic estimation with the principle of Gibbs free energy minimization showed that the major vapor species from the sample of the FeO-CaO-SiO2-AI203 system+PbO+CaCl2 were metallic Pb,PbC1,PbCl2,and FeC12,at the experimental temperature range.The experimental results show that the mole ratio of vaporized CI in lead chlorides to vaporized Pb,simply expressed as CI/Pb,decreases with increasing temperature.The larger CUPb means a larger ratio of gaseous PbCl2,since metallic Pb and PbCI vapors are formed in a similar reduction atmosphere.The evaporation is initially rapid and becomes steady after holding for 10 rain.Gaseous PbCI2 is mainly formed during the heating period,and at the holding stage,it reacts with FeO to produce gaseous FeCI2.With regard to slag composition,FeO content and basicity significantly affect the evaporation of lead.High FeO content and high basicity promotes the formation of metallic Pb and PbCI,whereas,it prohibits PbCl2 evaporation.

  5. Crystallization of MgFe2O4 from a glass in the system K2O/B2O3/MgO/P2O5/Fe2O3

    Science.gov (United States)

    El Shabrawy, Samha; Bocker, Christian; Rüssel, Christian

    2016-10-01

    Spherical magnetic Mg-Fe-O nanoparticles were successfully prepared by the crystallization of glass in the system K2O/B2O3/MgO/P2O5/Fe2O3. The magnetic glass ceramics were prepared by melting the raw materials using the conventional melt quenching technique followed by a thermal treatment at temperatures in the range 560-700 °C for a time ranging from 2 to 8 h. The studies of the X-ray diffraction, electron microscopy and FTIR spectra confirmed the precipitation of finely dispersed spherical (Mg, Fe) based spinel nanoparticles with a minor quantity of hematite (α-Fe2O3) in the glass matrix. The average size of the magnetic nano crystals increases slightly with temperature and time from 9 to 15 nm as determined by the line broadening from the XRD patterns. XRD studies show that annealing the glass samples for long periods of time at temperature ≥604 °C results in an increase of the precipitated hematite concentration, dissolution of the spinel phase and the formation of magnesium di-borate phase (Mg2B2O5). For electron microscopy, the particles were extracted by two methods; (i) replica extraction technique and (ii) dissolution of the glass matrix by diluted acetic acid. An agglomeration of the nano crystals to larger particles (25-35 nm) was observed.

  6. Photoproducts of tetracycline and oxytetracycline involving self-sensitized oxidation in aqueous solutions: Effects of Ca2+ and Mg2+

    Institute of Scientific and Technical Information of China (English)

    Yong Chen; Hua Li; Zongping Wang; Tao Tao; Chun Hu

    2011-01-01

    Tetracyclines constitute one of the most important antibiotic families and represent a classic example of phototoxicity.The photoproducts of tetracyclines and their parent compounds have potentially adverse effects on natural ecosystem.In this study,the self-sensitized oxidation products of tetracycline (TC) and oxytetracycline (OTC) were determined and the effects of Ca2+ and Mg2+on self-sensitized degradation were investigated.The Ca2+ and Mg2+ in the natural water sample accounted for enhancement (pH 7.3)and inhibition (pH 9.0) of photodegradation of TC and OTC due to the formation of metal-ions complexes.The formation of Mg2+ complexes was unfavorable for the photodegradation of the tetracyclines at both pH values.In contrast,the Ca2+ complexes facilitated the attack of singlet oxygen (1O2) arising from self-sensitization at pH 7.3 and enhanced TC photodegradation.For the first time,selfsensitized oxidation products of TC and OTC were verified by quenching experiments and detected by LC/ESI-DAD-MS.The products had a nominal mass 14 Da higher than the parent drugs (designated M+14),which resulted from the 1O2 attack of the dimethylamino group on the C-4 atom of the tetracyclines.The presence of Ca2+ and Mg2+ also affected the generation of M+14 due to the formation of metal-ions complexes with TC and OTC.The findings suggest that the metal-ion complexation has significant impact on the selfsensitized oxidation processes and the photoproducts of tetracyclines.

  7. Photophysical study of a polyoxo ethylene linked naphthalene-based fluorescent chemosensor for Mg2+ and Ca2+ detection.

    Science.gov (United States)

    Xiang, Xiaoyan; Wang, Dan; Guo, Yali; Liu, Weisheng; Qin, Wenwu

    2013-07-01

    A naphthalene-based bichromophoric fluorescent sensor 2,2'-[oxy-bis(2-oxatetramethyleneoxy)]-bis[N-(2-naphthyl)-benzamide)] (1) was synthesized and characterized. Fluorescence decay for 1 in alcoholic solvents in the region of 415-460 nm revealed bi-exponential behavior. The faster component of the decay can be attributed to the formation of dimers. Above 480 nm, besides the dimer, there is also a little excimer formation and this excimer emits at longer wavelengths than the dimer. The observation of the change of the fluorescence emission spectra upon addition of water in EtOH-water mixtures is in line with the formation of water-bridged complexes preventing excimer formation. The sensor shows an increase in fluorescence intensity upon increasing Mg(2+) or Ca(2+) concentration in EtOH because the formation of the excimer can be hindered upon complexation with Mg(2+) or Ca(2+) ions. Because of the competition between hydrated metal ions and the water-bridged complex, spectral changes by complexation with Mg(2+) or Ca(2+) in EtOH-H2O (9 : 1 v/v) are quite different from those in neat ethanol. The ground-state dissociation constant K(d) estimated for the complex with Mg(2+) or Ca(2+) was found to be around 2.0 mM in EtOH-H2O (9 : 1 v/v), which makes it suitable for the measurement of the concentrations of these ions in physiologically relevant concentration ranges.

  8. Effect of Mg, Ca, and Zn on stability of LiBH{sub 4} through computational thermodynamics

    Energy Technology Data Exchange (ETDEWEB)

    Lee, Sung Hoon; Manga, Venkateswara Rao; Liu, Zi-Kui [Department of Materials Science and Engineering, The Pennsylvania State University, University Park, PA 16802 (United States)

    2010-07-15

    The effect of divalent metal-dopants, Mg, Ca, and Zn, on the stability of LiBH{sub 4} is studied by using the first-principles calculations and CALPHAD (CALculation of PHAse Diagram) modeling. The ground states of Mg{sub 1/2}BH{sub 4}, Ca{sub 1/2}BH{sub 4}, and Zn{sub 1/2}BH{sub 4} are shown to be I anti 4m2, F2dd, and I anti 4m2, respectively, through first-principles calculations. Positive enthalpy of mixing between Li and the alloying element is predicted, indicating unfavorable solubility of alloying elements in LiBH{sub 4} and thus offering possibility to decrease the stability of LiBH{sub 4}. The ionic sublattice model of (Li{sup +}, M{sup 2+}, Va){sub 1}(BH{sub 4}{sup -}){sub 1} is adopted for the metal substituted LiBH{sub 4} phase. It is observed that the addition of Mg or Zn has limited effect as the decomposition temperature is between those of LiBH{sub 4} and M{sub 1/2}BH{sub 4} for Mg and Zn substitutions. LiBH{sub 4} is destabilized with magnesium borides or LiZn{sub 4} formation but its decomposition temperature is higher than that of M{sub 1/2}BH{sub 4}. On the other hand, the addition of Ca significantly reduces the H{sub 2} releasing temperature due to the formation of highly stable CaB{sub 6}. (author)

  9. Efficient KF loaded on MgCaAl hydrotalcite-like compounds in the transesterification of Jatropha curcas oil

    Energy Technology Data Exchange (ETDEWEB)

    Guzmán-Vargas, Ariel, E-mail: aguzmanv@ipn.mx [ESIQIE-IPN, Departamento de Ingeniería Química, Laboratorio de Investigación en Materiales Porosos, Catálisis Ambiental y Química Fina, UPALM Edif.7 P.B. Zacatenco, México D.F. 07738 (Mexico); Santos-Gutiérrez, Teresa [ESIQIE-IPN, Departamento de Ingeniería Química, Laboratorio de Investigación en Materiales Porosos, Catálisis Ambiental y Química Fina, UPALM Edif.7 P.B. Zacatenco, México D.F. 07738 (Mexico); Lima, Enrique [IIM-Universidad Nacional Autónoma de México, Circuito exterior s/n, Cd. Universitaria, 04510 México DF (Mexico); Flores-Moreno, Jorge L. [UAM-Azcapotzalco, Área de Química de Materiales, Av. San Pablo 180, Col. Reynosa Tamaulipas, 02200 México DF (Mexico); Oliver-Tolentino, Miguel A.; Martínez-Ortiz, María de J. [ESIQIE-IPN, Departamento de Ingeniería Química, Laboratorio de Investigación en Materiales Porosos, Catálisis Ambiental y Química Fina, UPALM Edif.7 P.B. Zacatenco, México D.F. 07738 (Mexico)

    2015-09-15

    Highlights: • MgCaAl hydrotalcite-like compounds were synthetized. • After KF impregnation and calcination fluorinated species were detected. • Fluorinated species were stables and actives. • LDH composition and KF load effect were evaluated in biodiesel production. - Abstract: In this work a series of MgCaAl hydrotalcite-like compounds were synthetized by coprecipitation method at constant pH. In order to obtain the catalysts, the samples were modified with KF by incipient wetness impregnation at different wt%, after that, they were dried and calcined to obtain the mixed oxides. The effect of divalent cations ratio and KF load were studied in the transesterification reaction of Jatropha curcas oil to obtain biodiesel employing an inedible oil. XRD analysis showed typical diffraction patterns of LDH, by nitrogen physisorption the LDH mesoporous structure was also confirmed, {sup 27}Al NMR spectra showed bands at 10 and 88 ppm attributed to the Al coordination before and after thermal treatment. While for the impregnated samples after calcination the profiles exhibited the mixed oxide formation, in addition, another peaks appeared associated to the formation of various fluorinated species as shown by XRD, additionally, {sup 19}F NMR showed a main signal at −180 ppm indicating the presence of active tetrahedral aluminum fluoride species. The reaction evolution was monitoring calculating the oil conversion to biodiesel by integration of the signal spectra using {sup 1}H NMR spectroscopy. The results of catalytic tests in transesterification reaction showed a direct correlation between Mg/Ca ratio and KF content in the oil conversion to biodiesel, the higher conversion was achieved (90%) when Mg/Ca = 1 and KF load was 30 wt%.

  10. Tunnel magnetoresistance in textured Co2FeAl/MgO/CoFe magnetic tunnel junctions on a Si/SiO2 amorphous substrate

    Science.gov (United States)

    Wen, Zhenchao; Sukegawa, Hiroaki; Mitani, Seiji; Inomata, Koichiro

    2011-05-01

    Magnetic tunnel junctions with B2-ordered Co2FeAl full Heusler alloy as a ferromagnetic electrode were fabricated by sputtering on thermally oxidized Si/SiO2 amorphous substrates. A Co2FeAl/MgO/Co50Fe50 structure showed a highly (001)-textured structure and the tunneling magnetoresistance (TMR) ratio of 166% at room temperature and 252% at 48 K were achieved. The temperature dependence of TMR can be fitted with spin wave excitation model, and the bias voltage dependence of differential conductance demonstrated that the high TMR was mainly contributed by coherent tunneling. This work suggests the B2-Co2FeAl is one of the promising candidates for practical spintronic applications.

  11. Effect of Ca and Mg Impurity Substances on the Efficiency of Decreasing Uranium Concentration in the Waste Water

    International Nuclear Information System (INIS)

    Study of uranium waste water treatment contained Ca and Mg impurity substances using ion exchange has been experimentally investigated. This experiment was conducted by the glass column of 1.1 cm diameter containing resin Dowex 50-X8(Na). Feed of 100 ppm uranium solution at the pH of 4 with Ca and Mg impurities varied from 25, 50, 75 and 100 ppm was flown into the column of resin using masterflex pump at the constant flowrate of 2.5 ml/min. The effluents concentration of uranium flowing out of column' s resin were analyzed using spectrophotometer with arsenazo as the complexing agent. From the data of uranium concentration entering into and exiting from the column's resin could be determined the efficiency of minimization' s value of uranium concentration. From the experimental data, the efficiency of minimization' s value of uranium concentration obtained with the impurity of Ca from 99.1 % to 92 % while which the impurity of Mg from 97.8 % to 94 %. (author)

  12. Borophene as an anode material for Ca, Mg, Na or Li ion storage: A first-principle study

    Science.gov (United States)

    Mortazavi, Bohayra; Dianat, Arezoo; Rahaman, Obaidur; Cuniberti, Gianaurelio; Rabczuk, Timon

    2016-10-01

    Borophene, the boron atom analogue to graphene, being atomic thick have been just recently experimentally fabricated. In this work, we employ first-principles density functional theory calculations to investigate the interaction of Ca, Mg, Na or Li atoms with single-layer and free-standing borophene. We first identified the most stable binding sites and their corresponding binding energies as well and then we gradually increased the ions concentration. Our calculations predict strong binding energies of around 4.03 eV, 2.09 eV, 2.92 eV and 3.28 eV between the borophene substrate and Ca, Mg, Na or Li ions, respectively. We found that the binding energy generally decreases by increasing the ions content. Using the Bader charge analysis, we evaluate the charge transfer between the adatoms and the borophene sheet. Our investigation proposes the borophene as a 2D material with a remarkably high capacity of around 800 mA h/g, 1960 mA h/g, 1380 mA h/g and 1720 mA h/g for Ca, Mg, Na or Li ions storage, respectively. This study can be useful for the possible application of borophene for the rechargeable ion batteries.

  13. Spectroscopic Observation of Water-Mediated Deformation of the CARBOXYLATE-M2+ (M= Mg, Ca) Contact Ion Pair

    Science.gov (United States)

    Kelleher, Patrick J.; DePalma, Joseph W.; Johnson, Mark

    2016-06-01

    The binding of alkaline earth dications to the biologically relevant carboxylate ligand has previously been studied using vibrational sum frequency generation (VSFG) spectroscopy of the air-water interface, infrared multiple photon dissociation (IRMPD) spectroscopy of clusters, and DFT methods. These results suggest the presence of both monodentate and bidentate binding motifs of the M2+ ions to the cayboxyl head groups depending on the extent of solvation. We revisit these systems using vibrational predissociation spectroscopy to measure the gas-phase vibrational spectra of the D2-tagged microhydrated [MgOAc(H2O)n=1-5]+ and [CaOAc(H2O)n=1-6]+ clusters. The spectra show that [MgOAc(H2O)n]+ switches from bidentate to monodentate binding promptly at n = 5, while [CaOAc(H2O)n]+ retains its bidentate attachment such that the sixth water molecule initiates the second solvation shell. The difference in binding behavior between these two divalent metal ions is analyzed in the context of the local acidity of the solvent water molecules and the strength of the metal-carboxylate and metal-water interactions. This cluster study provides insight into the chemical physics underlying the unique and surprising impacts of Mg2+ and Ca2+ on the chemistry mediated by sea spray aerosols. Funding for this work was provided by the NSF's Center for Aerosol Impacts on Climate and the Environment.

  14. Studies on Thermophysical Properties of CaO and MgO by γ-Ray Attenuation

    Directory of Open Access Journals (Sweden)

    A. S. Madhusudhan Rao

    2014-01-01

    Full Text Available The study on temperature dependent γ-ray attenuation and thermophysical properties of CaO and MgO has been carried out in the temperature range 300 K–1250 K using different energies of γ-beam, namely, Am (0.0595 MeV, Cs (0.66 MeV, and Co (1.173 MeV and 1.332 MeV on γ-ray densitometer fabricated in our laboratory. The linear attenuation coefficients (μl for the pellets of CaO and MgO as a function of temperature have been determined using γ-beam of different energies. The coefficients of temperature dependence of density have been reported. The variation of density and linear thermal expansion of CaO and MgO in the temperature range of 300 K–1250 K has been studied and compared with the results available in the literature. The temperature dependence of linear attenuation coefficients, density, and thermal expansion has been represented by second degree polynomial. Volume thermal expansion coefficients have been reported.

  15. Hydroxyapatite coating on biodegradable AZ31 and Mg-Ca alloys prepared by RF-magnetron sputtering

    Energy Technology Data Exchange (ETDEWEB)

    Mukhametkaliyev, T., E-mail: mtm91@mail.ru; Surmeneva, M., E-mail: feja-mari@yandex.ru; Surmenev, R., E-mail: rsurmenev@gmail.com [National Research Tomsk Polytechnic University (Russian Federation); Mathan, B. K., E-mail: bobby.mathan@jcu.edu.au [James Cook University, Townsville (Australia)

    2015-11-17

    A thin film of hydroxyapatite (HA) was deposited on AZ31 and Mg-Ca alloys by using radio frequency (RF) magnetron sputtering. The thickness of the HA coating was determined to be 750 nm. The phase composition, microstructure, and surface morphology of the HA coatings were investigated using X-ray diffraction and scanning electron microscopy. In vitro degradation behaviour of the HA coated alloys was evaluated in simulated body fluid (SBF) and 3.5wt.% NaCl solution using electrochemical method. The coatings homogeneously covered the entire surface of the substrates. The coating structure corresponded to a nanostructured HA. The ultrathin coating significantly improved the degradation resistance of the alloy. Nanocrystalline HA coating significantly improved the corrosion resistance of the Mg-Ca and AZ31 magnesium alloys. The polarization resistance (Rp) of the coated Mg-Ca alloy was more than two-order of magnitude higher and the corrosion current density I{sub corr} reduced by ∼ 98% as compared to the base alloy.

  16. Homogeneity range and crystal structure of the Ca{sub 2}Mg{sub 5}Zn{sub 13} compound

    Energy Technology Data Exchange (ETDEWEB)

    Zhang Yinan; Kevorkov, Dmytro [Department of Mechanical Engineering, Concordia University, 1455 de Maisonneuve Blvd. W., Montreal, Quebec, H3G 1M8 (Canada); Liu Xuedong [Center for the Physics of Materials and the Department of Physics, McGill University, 3600 University Street, Montreal, Quebec, H3A 2T8 (Canada); Bridier, Florent [Department of Mechanical Engineering, Ecole de Technologie Superieure, 1100 Notre-Dame Ouest, Montreal, Quebec, H3C 1K3 (Canada); Chartrand, Patrice [Center for Research in Computational Thermochemistry Ecole Polytechnique (Universite de Montreal), Montreal, Quebec, H3C 3A7 (Canada); Medraj, Mamoun, E-mail: mmedraj@encs.concordia.ca [Department of Mechanical Engineering, Concordia University, 1455 de Maisonneuve Blvd. W., Montreal, Quebec, H3G 1M8 (Canada)

    2012-05-15

    Highlights: Black-Right-Pointing-Pointer Solubility range and crystal structure of Ca{sub 2}Mg{sub 5}Zn{sub 13} were studied. Black-Right-Pointing-Pointer The homogeneity range was determined using diffusion couples and key alloys. Black-Right-Pointing-Pointer The crystal structure was found to have a Sm{sub 3}Mg{sub 13}Zn{sub 30} prototype. Black-Right-Pointing-Pointer The atomic coordination spheres and site occupancy were discussed. - Abstract: The homogeneity range and crystal structure of the Ca{sub 2}Mg{sub 5}Zn{sub 13} ternary solid solution were determined using SEM, EPMA, EBSD, TEM and X-ray diffraction. This compound has the Ca{sub x}Mg{sub y}Zn{sub z} (8.2 {<=} x {<=} 9.1; 27.1 {<=} y {<=} 31.0; 60.8 {<=} z {<=} 64.7) composition range at 335 Degree-Sign C. The refinement of the XRD patterns was carried out by Rietveld analysis. XRD data showed that this solid solution crystallizes in a hexagonal structure having P6{sub 3}/mmc (194) space group and Sm{sub 3}Mg{sub 13}Zn{sub 30} prototype. The well indexed SAED patterns and Kikuchi diffraction pattern obtained from TEM and EBSD confirmed the crystallographic information obtained by XRD. The atomic coordination spheres and site occupancy were determined. On the basis of the atomic occupancy results and the crystallographic details, a three-sublattice model is proposed for this compound.

  17. Effects of little Ce addition on as-cast microstructure and creep properties of Mg-3Sn-2Ca magnesium alloy

    Institute of Scientific and Technical Information of China (English)

    YANG Ming-bo; MA Yan-long; PAN Fu-sheng

    2009-01-01

    The effects of little Ce addition on the as-cast microstructure and creep properties of Mg-3Sn-2Ca magnesium alloy were investigated. The results indicate that adding 0.5% (mass fraction) Ce to Mg-3Sn-2Ca alloy does not cause the formation of any new phase in the alloy. However, an interesting microstructural change in the as-cast Mg-3Sn-2Ca alloy added with 0.5%Ce is observed. After adding 0.5%Ce to Mg-3Sn-2Ca alloy, not only the volume fraction of CaMgSn phase in the alloy is decreased but also the CaMgSn phases in the alloy are refined. In addition, adding 0.5%Ce to Mg-3Sn-2Ca alloy can also improve the creep-resistant properties of the alloy. After adding 0.5%Ce to Mg-3Sn-2Ca alloy, the second creep rate of the alloy at 150 ℃ and 70 Mpa for 100 h changes from 3.28×10~(-8) to 1.81×10~(-8) s~(-1).

  18. Synthesis and photoluminescence properties of novel red-emitting Ca14Mg2(SiO4)8:Eu3+/Sm3+ phosphors

    Institute of Scientific and Technical Information of China (English)

    孙文芝; 庞然; 李海锋; 贾永雷; 张粟; 姜丽宏; 李成宇

    2015-01-01

    Novel red-emitting Eu3+, Sm3+ singly doped and co-doped Ca14Mg2(SiO4)8 phosphors were prepared by conventional solid- state reaction. Powder X-ray diffraction patterns were employed to confirm phase purity. Ca14Mg2(SiO4)8:Eu3+ phosphors exhibited intense red emission under 394 nm excitation and Ca14Mg2(SiO4)8:Sm3+ phosphors, excited at 405 nm, also showed strong red emit-ting at 602 nm. The concentration quenching mechanism of Ca14Mg2(SiO4)8:Eu3+ was dipole-dipole interaction, while that of Ca14Mg2(SiO4)8:Sm3+ was energy migration among nearest neighbor ions. The results indicated that Ca14Mg2(SiO4)8:Eu3+ and Ca14Mg2(SiO4)8:Sm3+ were promising red-emitting phosphors for WLEDs. Meanwhile, the effect of co-doping Sm3+ ions on photo-luminescence properties of Ca14Mg2(SiO4)8:Eu3+ was studied and energy transfer from Sm3+ to Eu3+ was discovered in Eu3+, Sm3+ co-doped phosphors.

  19. Inter- and intra-specimen variability masks reliable temperature control on shell Mg/Ca ratios in laboratory and field cultured Mytilus edulis and Pecten maximus (bivalvia

    Directory of Open Access Journals (Sweden)

    H. A. Kennedy

    2008-02-01

    Full Text Available The Mg/Ca ratios of biogenic calcites are commonly seen as a valuable palaeo-proxy for reconstructing past ocean temperatures. The temperature dependence of Mg/Ca ratios in bivalve calcite has been the subject of contradictory observations. The palaeoceanographic use of a geochemical proxy, like Mg/Ca ratios, is dependent on initial, rigorous calibration and validation of relationships between the proxy and the ambient environmental variable to be reconstructed. Shell Mg/Ca ratio data are reported for the calcite of two bivalve species, Mytilus edulis (common mussel and Pecten maximus (king scallop, for the first time grown in laboratory culturing experiments at controlled and constant aquarium seawater temperatures over a range from ~10 to ~20°C. Furthermore, Mg/Ca ratio data of laboratory-grown and field-grown M. edulis specimens were compared. Only a weak, albeit significant, shell Mg/Ca ratio–temperature relationship was observed in the two bivalve species: M. edulis (r2=0.37, pr2=0.50, pP. maximus (r2=0.21, p<0.001, laboratory cultured specimens only. In the two species, shell Mg/Ca ratios also were not found to be controlled by shell growth rate and salinity. Furthermore, measurement of Mg/Ca ratios in the shells of multiple specimens illustrated that a large degree of variability in the measured shell Mg/Ca ratios was significant at the species, inter- and intra-individual shell levels. The study data suggest the use of bivalve calcite Mg/Ca ratios as a reliable, precise and accurate temperature proxy still remains limited, at least in the species studied to date. Such limitations are most likely due to the presence of significant physiological effects on Mg incorporation in bivalve calcite, with such variability differing both within single shells and between shells of the same species that were precipitated under the same ambient conditions.

  20. Effect of Ca addition on modification of primary Mg2Si, hardness and wear behavior in Mg–Si hypereutectic alloys

    OpenAIRE

    M.E. Moussa; M.A. Waly; A.M. El-Sheikh

    2014-01-01

    The effect of Ca addition on modification of primary Mg2Si, hardness and wear behavior in Mg–5 wt.%Si hypereutectic alloy has been investigated. The results showed clearly that without Ca addition, most of primary Mg2Si appeared as coarse dendritic morphology with average size of about 215 μm. With the addition of 0.1 wt.%Ca, the average size of primary Mg2Si decreased to about 98 μm, but their morphologies did not significantly changed. As the addition level of Ca increased to 0.3 wt.%, the ...

  1. Equation of state of the postperovskite phase synthesized from a natural (Mg,Fe)SiO3 orthopyroxene

    OpenAIRE

    Shieh, Sean R.; Duffy, Thomas S.; Kubo, Atsushi; Shen, Guoyin; Prakapenka, Vitali B.; Sata, Nagayoshi; Hirose, Kei; Ohishi, Yasuo

    2006-01-01

    Using the laser-heated diamond anvil cell, we investigate the stability and equation of state of the postperovskite (ppv, CaIrO3-type) phase synthesized from a natural pyroxene composition with 9 mol.% FeSiO3. Our measured pressure-volume data from 12–106 GPa for the ppv phase yield a bulk modulus of 219(5) GPa and a zero-pressure volume of 164.9(6) Å3 when K′0 = 4. The bulk modulus of ppv is 575(15) GPa at a pressure of 100 GPa. The transition pressure is lowered by the presence of Fe. Our x...

  2. Transition to collapsed tetragonal phase in CaFe2As2 single crystals as seen by 57Fe Mossbauer spectroscopy

    OpenAIRE

    Bud'ko, Sergey L.; Ma, Xiaoming; Tomic, Milan; Ran, Sheng; Valenti, Roser; Canfield, Paul C.

    2015-01-01

    Temperature dependent measurements of 57Fe Mossbauer spectra on CaFe2As2 single crystals in the tetragonal and collapsed tetragonal phases are reported. Clear features in the temperature dependencies of the isomer shift, relative spectra area and quadrupole splitting are observed at the transition from the tetragonal to the collapsed tetragonal phase. From the temperature dependent isomer shift and spectral area data, an average stiffening of the phonon modes in the collapsed tetragonal phase...

  3. Structure and magnetic properties of the ZnxMg1-xFe2O4 ferrites

    Science.gov (United States)

    Gismelseed, Abbasher M.; Mohammed, K. A.; Widatallah, H. M.; Al-Rawas, A. D.; Elzain, M. E.; Yousif, A. A.

    2010-03-01

    Spinel magnesium-zinc ferrites ZnxMg1-xFe2O4 (0=0.8 and show very broad patterns for intermediate concentration of Zn2+. The variation of the magnetic properties with the Zn concentration has been explained on the basis of the cation distribution driven from the Mössbauer measurements.

  4. Synthesis of High-quality Single- and Double-walled Carbon Nanotubes on Fe/MgO Catalysts

    Directory of Open Access Journals (Sweden)

    Mehran B. Kashi

    2016-06-01

    Full Text Available In this study, Fe/MgO catalysts with three different iron contents (5, 10, and 15 wt.% were prepared by three catalyst preparation methods: impregnation, solution combustion synthesis, and co-calcination of metal ni‐ trates. The resulting catalysts were subjected to methane at 900°C in order to grow carbon nanotubes (CNTs. The powders and products were then studied by X-ray diffraction (XRD, differential thermal analysis (DTA, scanning and transmission electron microscopy (SEM and TEM, and Raman spectroscopy. Formation of MgFe2O4 upon heating the catalysts to 900°C was confirmed by XRD. After the growth step, corresponding peaks of MgFe2O4 disappeared and metallic iron peaks appeared, indicating that MgFe2O4 is the responsible phase for production of iron nanoparticles. HRTEM images showed that the product on the 5 wt.% catalysts was mostly SWNTs and DWNTs with no evidence of carbon nanofi‐ bres or multi-walled carbon nanotubes on the co-calcina‐ tion catalyst. Furthermore, ID/IG ratios obtained from Raman spectra were all below 0.1, except for one sample, showing the good quality of the products.

  5. Microstructure, mechanical characteristics and cell compatibility of β-tricalcium phosphate reinforced with biodegradable Fe-Mg metal phase.

    Science.gov (United States)

    Swain, Sanjaya K; Gotman, Irena; Unger, Ronald; Kirkpatrick, C James; Gutmanas, Elazar Y

    2016-01-01

    The use of beta-tricalcium phosphate (β-TCP) ceramic as a bioresorbable bone substitute is limited to non-load-bearing sites by the material׳s brittleness and low bending strength. In the present work, new biocompatible β-TCP-based composites with improved mechanical properties were developed via reinforcing the ceramic matrix with 30 vol% of a biodegradable iron-magnesium metallic phase. β-TCP-15Fe15Mg and β-TCP-24Fe6Mg (vol%) composites were fabricated using a combination of high energy attrition milling, cold sintering/high pressure consolidation of powders at room temperature and annealing at 400 °C. The materials synthesized had a hierarchical nanocomposite structure with a nanocrystalline β-TCP matrix toughened by a finely dispersed nanoscale metallic phase (largely Mg) alongside micron-scale metallic reinforcements (largely Fe). Both compositions exhibited high strength characteristics; in bending, they were about 3-fold stronger than β-TCP reinforced with 30 vol% PLA polymer. Immersion in Ringer׳s solution for 4 weeks resulted in formation of corrosion products on the specimens׳ surface, a few percent weight loss and about 50% decrease in bending strength. In vitro studies of β-TCP-15Fe15Mg composite with human osteoblast monocultures and human osteoblast-endothelial cell co-cultures indicated that the composition was biocompatible for the growth and survival of both cell types and cells exhibited tissue-specific markers for bone formation and angiogenesis, respectively. PMID:26409234

  6. MgFe COMPLEX OXIDES FOR SO2 OXIDATIVE ADSORPTION%不同制备方法对MgFe氧化物催化吸附SO2性能的影响

    Institute of Scientific and Technical Information of China (English)

    陈银飞; 葛忠华; 吕德伟

    2001-01-01

    Three kinds of complex oxides and mixed oxide were prepared with different methods, MgO mixed simply with Fe2O3,Fe2O3 loaded on MgO with impregnation,and MgFeOx calcined on the MgFe hydrotalcite.The desulfuration rates and the sulfur capacities of the materials were measured. It was found that MgFeOx showed the best performance and its sulfur capacity exceeded 1.4 g SO2/g material. The reason for high rate and capacity was analyzed from BET data, XRD and IR spectra. The synergistic action of Mg and Fe dispersed uniformly in complex oxide , in which Fe was the oxidizing center and Mg was the adsorbing center , speeded up the desulfuration rate and increased the sulfur capacity.%用不同的制备方式得到了3种MgFe复合氧化物和混合物,即机械混合的Fe2O3+MgO;以MgO为载体,浸渍法制备的Fe2O3/MgO;以MgFe水滑石类为前驱体,经焙烧制得MgFeOx.分别测定了3种材料对SO2氧化吸附的速率和硫容量,发现MgFeOx脱硫性能最好,硫容量达到1.4 g SO2/g吸附剂.通过BET、XRD和IR的表征,分析了材料脱硫性能好的原因.主要是高度分散状态的MgFeOx中Mg和Fe的协同作用,Fe起到了催化氧化的作用,Mg是吸附中心,氧化和吸附的耦合加快了MgFeOx对SO2的吸附速率,增加了硫容量.

  7. Effect of Nd substitution for Ca on crystal structure, optical and magnetic properties of multiferroic Bi0.9Ca0.1FeO3

    International Nuclear Information System (INIS)

    Highlights: • Crystal structure of doped samples transform to two phase coexistence. • The crystal size decreased to ∼50 nm after doping. • Ultraviolet absorption peak demonstrates apparent blue shift for doped sample. • The ratio of Fe2+ increased by merging Nd. • Ca, Nd co-doped can promote the ferromagnetism obviously. - Abstract: Pure and co-doped BiFeO3 (Ca, Nd) nanoparticles with diameter in the range of 50–250 nm were synthesized through a sol–gel method. X-ray diffraction (XRD) and Raman results show that Bi-site co-doped with Ca, Nd could result in a transition of crystal structure (from single phase rhombohedral (R3c) to two phase coexistence). An apparent blue shift can be observed in the co-doped samples along with a decrease of the direct optical band gap. Moreover, the leakage current was decreased due to the introduction of nonvolatile Ca and Nd at Bi3+ site. Analysis of MPMS-VSM magnetic hysteresis data reveals a further enhancement in magnetism in the Nd doped Bi0.9Ca0.1FeO3, which is further explained by XPS characterization

  8. Using CaO- and MgO-rich industrial waste streams for carbon sequestration

    International Nuclear Information System (INIS)

    To prevent rapid climate change, it will be necessary to reduce net anthropogenic CO2 emissions drastically. This likely will require imposition of a tax or tradable permit scheme that creates a subsidy for negative emissions. Here, we examine possible niche markets in the cement and steel industries where it is possible to generate a limited supply of negative emissions (carbon storage or sequestration) cost-effectively. Ca(OH)2 and CaO from steel slag or concrete waste can be dissolved in water and reacted with CO2 in ambient air to capture and store carbon safely and permanently in the form of stable carbonate minerals (CaCO3). The kinetics of Ca dissolution for various particle size fractions of ground steel slag and concrete were measured in batch experiments. The majority of available Ca was found to dissolve on a time scale of hours, which was taken to be sufficiently fast for use in an industrial process. An overview of the management options for steel slag and concrete waste is presented, which indicates how their use for carbon sequestration might be integrated into existing industrial processes. Use of the materials in a carbon sequestration scheme does not preclude subsequent use and is likely to add value by removing the undesirable qualities of water absorption and expansion from the products. Finally, an example scheme is presented which could be built and operated with current technology to sequester CO2 with steel slag or concrete waste. Numerical models and simple calculations are used to establish the feasibility and estimate the operating parameters of the scheme. The operating cost is estimated to be US$8/t-CO2 sequestered. The scheme would be important as an early application of technology for capturing CO2 directly from ambient air

  9. Lattice distortion and stripelike antiferromagnetic order in Ca10(Pt3As8)(Fe2As2)5

    Energy Technology Data Exchange (ETDEWEB)

    Sapkota, Aashish [Ames Laboratory; Tucker, Gregory S [Ames Laboratory; Ramazanoglu, Mehmet [Ames Laboratory; Tian, Wei [Ames Laboratory; Ni, N [University of California; Cava, R J; McQueeney, Robert J [Princeton; Goldman, Alan I [Ames Laboratory; Kreyssig, Andreas [Ames Laboratory

    2014-09-01

    Ca10(Pt3As8)(Fe2As2)5 is the parent compound for a class of Fe-based high-temperature superconductors where superconductivity with transition temperatures up to 30 K can be introduced by partial element substitution. We present a combined high-resolution high-energy x-ray diffraction and elastic neutron scattering study on a Ca10(Pt3As8)(Fe2As2)5 single crystal. This study reveals the microscopic nature of two distinct and continuous phase transitions to be very similar to other Fe-based high-temperature superconductors: an orthorhombic distortion of the high-temperature tetragonal Fe-As lattice below TS=110(2) K followed by stripelike antiferromagnetic ordering of the Fe moments below TN=96(2) K. These findings demonstrate that major features of the Fe-based high-temperature superconductors are very robust against variations in chemical constitution as well as structural imperfection of the layers separating the Fe-As layers from each other and confirms that the Fe-As layers primarily determine the physics in this class of material.

  10. Pressure-induced change of the electronic state in the tetragonal phase of CaFe2As2

    Science.gov (United States)

    Sakaguchi, Yui; Ikeda, Shugo; Kuse, Tetsuji; Kobayashi, Hisao

    2014-07-01

    We have investigated the electronic states of single-crystal CaFe2As2 under hydrostatic pressure using 57Fe Mössbauer spectroscopy and magnetization measurements. The center shift and the quadrupole splitting were refined from observed 57Fe Mössbauer spectra using the single-crystalline sample under pressure at room temperature. A discontinuous decrease in the pressure dependence of the refined center shift was observed at 0.33 GPa without any anomaly in the pressure dependence of the refined quadrupole splitting, indicating a purely electronic state change in CaFe2As2 with a tetragonal structure. Such a change is shown to be reflected in the peak-like anomalies observed in the pressure dependences of the magnetic susceptibility at 0.26 GPa above 150 K. Our results reveal that this pressure-induced electronic state change suppresses the tetragonal-to-orthorhombic structural phase transition accompanied by an antiferromagnetic ordering. We further observed superconductivity in CaFe2As2 below ˜8 K around 0.33 GPa although our sample was not in a single phase at this pressure. These findings suggest that the electronic state change observed in CaFe2As2 with the tetragonal structure is relevant to the appearance of the pressure-induced superconductivity in AFe2As2.

  11. All Ca(2+)-binding loops of light-sensitive ctenophore photoprotein berovin bind magnesium ions: The spatial structure of Mg(2+)-loaded apo-berovin.

    Science.gov (United States)

    Burakova, Ludmila P; Natashin, Pavel V; Malikova, Natalia P; Niu, Fengfeng; Pu, Mengchen; Vysotski, Eugene S; Liu, Zhi-Jie

    2016-01-01

    Light-sensitive photoprotein berovin accounts for a bright bioluminescence of ctenophore Beroe abyssicola. Berovin is functionally identical to the well-studied Ca(2+)-regulated photoproteins of jellyfish, however in contrast to those it is extremely sensitive to the visible light. Berovin contains three EF-hand Ca(2+)-binding sites and consequently belongs to a large family of the EF-hand Ca(2+)-binding proteins. Here we report the spatial structure of apo-berovin with bound Mg(2+) determined at 1.75Å. The magnesium ion is found in each functional EF-hand loop of a photoprotein and coordinated by oxygen atoms donated by the side-chain groups of aspartate, carbonyl groups of the peptide backbone, or hydroxyl group of serine with characteristic oxygen-Mg(2+) distances. As oxygen supplied by the side-chain of the twelfth residue of all Ca(2+)-binding loops participates in the magnesium ion coordination, it was suggested that Ca(2+)-binding loops of berovin belong to the mixed Ca(2+)/Mg(2+) rather than Ca(2+)-specific type. In addition, we report an effect of physiological concentration of Mg(2+) on bioluminescence of berovin (sensitivity to Ca(2+), rapid-mixed kinetics, light-sensitivity, thermostability, and apo-berovin conversion into active protein). The different impact of physiological concentration of Mg(2+) on berovin bioluminescence as compared to hydromedusan photoproteins was attributed to different affinities of the Ca(2+)-binding sites of these photoproteins to Mg(2+). PMID:26690016

  12. All Ca(2+)-binding loops of light-sensitive ctenophore photoprotein berovin bind magnesium ions: The spatial structure of Mg(2+)-loaded apo-berovin.

    Science.gov (United States)

    Burakova, Ludmila P; Natashin, Pavel V; Malikova, Natalia P; Niu, Fengfeng; Pu, Mengchen; Vysotski, Eugene S; Liu, Zhi-Jie

    2016-01-01

    Light-sensitive photoprotein berovin accounts for a bright bioluminescence of ctenophore Beroe abyssicola. Berovin is functionally identical to the well-studied Ca(2+)-regulated photoproteins of jellyfish, however in contrast to those it is extremely sensitive to the visible light. Berovin contains three EF-hand Ca(2+)-binding sites and consequently belongs to a large family of the EF-hand Ca(2+)-binding proteins. Here we report the spatial structure of apo-berovin with bound Mg(2+) determined at 1.75Å. The magnesium ion is found in each functional EF-hand loop of a photoprotein and coordinated by oxygen atoms donated by the side-chain groups of aspartate, carbonyl groups of the peptide backbone, or hydroxyl group of serine with characteristic oxygen-Mg(2+) distances. As oxygen supplied by the side-chain of the twelfth residue of all Ca(2+)-binding loops participates in the magnesium ion coordination, it was suggested that Ca(2+)-binding loops of berovin belong to the mixed Ca(2+)/Mg(2+) rather than Ca(2+)-specific type. In addition, we report an effect of physiological concentration of Mg(2+) on bioluminescence of berovin (sensitivity to Ca(2+), rapid-mixed kinetics, light-sensitivity, thermostability, and apo-berovin conversion into active protein). The different impact of physiological concentration of Mg(2+) on berovin bioluminescence as compared to hydromedusan photoproteins was attributed to different affinities of the Ca(2+)-binding sites of these photoproteins to Mg(2+).

  13. Si对Mg-7Al-2.5Ca-0.4Mn-0.25Sr合金铸态组织的影响%Effect of Si Addition on As-Cast Microstructure of Mg-7Al-2.5Ca-0.4Mn-0.25Sr Alloy

    Institute of Scientific and Technical Information of China (English)

    贺颖; 邱克强; 孙晶; 热焱; 尤俊华; 任英磊

    2012-01-01

    The effects of Si on the as-cast microstructure of Mg-7Al-2.5Ca-0.4Mn-0.25Sr alloy were investigated by using the optical microscopy, scanning electron microscope and X-ray diffraction.The results indicate that the as-cast microstructure of Mg-7Al-2.5Ca-0.4Mn-0.25Sr-xSi (x=1, 2, 3) alloys are mainly composed of α-Mg matrix, AlMn, Mg2Ca, Al2Ca and CaMgSi phases, the volume fractions of CaMgSi phase increases with increasing the Si element.The addition of Si ranging from 1% to 3% results in α-Mg dendrites developing, the eutectic (Mg2Ca+Al2Ca) decreasing and CaMgSi phase increasing, and the morphology of the CaMgSi phase gradually changes from hollow block to needle, then evolves into Chinese script, which was discussed in the paper.%通过光学显微镜、扫描电镜和X射线衍射分析等,研究了Si对铸态Mg-7Al-2.5Ca-0.4Mn-0.25Sr合金显微组织的影响.结果表明:Mg-7Al-2.5Ca-0.4Mn-0.25Sr-xSi(x=1,2,3)合金主要由α-Mg基体、AlMn相、Mg2Ca相、Al2Ca相和CaMgSi相组成.CaMgSi相含量随Si元素的增加而增加.Si含量由1%提高到3%会引起三方面变化:一是使α-Mg枝晶变得发达;二是析出的共晶组织(Mg2Ca+Al2Ca)含量有所减少;三是促进CaMgSi相的析出,且CaMgSi相的形貌逐渐由空心块状向针状、再向汉字状演化,因此合金中Si的合适加入量应控制在2%左右.对组织的演变过程进行了讨论.

  14. [Kinetics of inhibitory effect of calix[4]arene C-90 on activity of transporting plasma membrane Ca2+, Mg2+-ATPase of smooth muscle cells].

    Science.gov (United States)

    Veklich, T O; Shkrabak, O A; Mazur, Iu Iu; Rodik, R V; Kal'chenko, V I; Kosterin, S O

    2014-01-01

    In experiments on the suspension of myometrium cell plasma membrane, processed by 0.1% digitonin, the inhibitory action of calix[4]arene C-90 (5,11,17,23-tetra(threeftor)methyl(phenilsulphonilimino)-methylamino-25,26,27,28-tetrapropoxy-calix[4]arene) on the activity of Ca2+,Mg2+-ATPase was investigated. The authors also examined the influence of calix[4]arene in different concentration on affinity of enzyme (Ca2,Mg2+-ATPase) for the ATP and ions of Mg and Ca, and its influence on cooperative effect and maximum velocity of ATP hydrolysis. It is shown that calix[4]arene does not influence the affinity of Ca2+,Mg2+-ATPase for the ATP, which means that these two compounds have different binding centers. Also calix[4]arene has no influence on affinity and cooperative effect of Ca ions, if it is used in concentration lower than 50 μM. Calix[4]arene slightly increases coefficient of Ca2+,Mg2+-ATPase activation by magnesium chloride. In all three cases, where ATP, Mg and Ca ions are used to test the impact of calix[4]arene, maximum velocity of ATP hydrolysis significantly decreases. All these results clarify that calix[4]arene implements its inhibitory action through mechanism of uncompetitive inhibition of Ca2+,Mg2+-ATPase activity.

  15. Doping effects of transition metals on superconducting properties of (Ca,RE)FeAs2

    Science.gov (United States)

    Yakita, Hiroyuki; Ogino, Hiraku; Okada, Tomoyuki; Yamamoto, Akiyasu; Kishio, Kohji; Shimoyama, Jun-Ichi; Iyo, Akira; Eisaki, Hiroshi; Sala, Alberto

    2015-03-01

    At the previous March Meeting, we reported new iron based superconductors (Ca,RE)FeAs2 (Ca112) (RE = La-Nd, Sm-Gd)[ 1 , 2 ]. Superconducting transition was observed in all samples except for Ce-doped sample, and Tc of La-doped sample exceeded 30 K. In this study, we have synthesized transition metals (TM=Mn, Co, Ni) co-doped Ca112 samples. Mn co-doping suppressed superconductivity. On the contrary, enhancement of Tc with sharp superconducting transitions was observed in most of the Co or Ni co-doped samples. Tc of Co co-doped samples decreased with a decrease in ionic radii of RE3+ from 38 K for RE = La to 29 K for RE = Gd, though Eu doped sample showed exceptionally low Tc = 21 K. Jc value of La and Co co-doped sample estimated from magnetization measurement is approximately 2.0 x 104 Acm-2at 2 K suggesting bulk superconductivity.

  16. Superconductivity in Sm-doped CaFe2As2 single crystals

    Science.gov (United States)

    Dong-Yun, Chen; Bin-Bin, Ruan; Jia, Yu; Qi, Guo; Xiao-Chuan, Wang; Qing-Ge, Mu; Bo-Jin, Pan; Tong, Liu; Gen-Fu, Chen; Zhi-An, Ren

    2016-06-01

    In this article, the Sm-doping single crystals Ca1 ‑ x Sm x Fe2As2 (x = 0 ∼ 0.2) were prepared by the CaAs flux method, and followed by a rapid quenching treatment after the high temperature growth. The samples were characterized by structural, resistive, and magnetic measurements. The successful Sm-substitution was revealed by the reduction of the lattice parameter c, due to the smaller ionic radius of Sm3+ than Ca2+. Superconductivity was observed in all samples with onset T c varying from 27 K to 44 K upon Sm-doping. The coexistence of a collapsed phase transition and the superconducting transition was found for the lower Sm-doping samples. Zero resistivity and substantial superconducting volume fraction only happen in higher Sm-doping crystals with the nominal x > 0.10. The doping dependences of the c-axis length and onset T c were summarized. The high-T c observed in these quenched crystals may be attributed to simultaneous tuning of electron carriers doping and strain effect caused by lattice reduction of Sm-substitution. Project supported by the National Natural Science Foundation of China (Grant No. 11474339), the National Basic Research Program of China (Grant Nos. 2010CB923000 and 2011CBA00100), and the Strategic Priority Research Program of the Chinese Academy of Sciences (Grant No. XDB07020100).

  17. Calcination temperature influenced multiferroic properties of Ca-doped BiFeO3 nanoparticles

    Science.gov (United States)

    Dhir, Gitanjali; Uniyal, Poonam; Verma, N. K.

    2015-06-01

    The influence of Ca-doping and particle size on structural, morphological and magnetic properties of BiFeO3 nanoparticles has been studied. A sol-gel method was employed for the synthesis of nanoparticles and their particle size was tailored by varying the calcination temperature. Structural analysis revealed a rhombohedral distortion induced by Ca-substitution. The broadening of diffraction peaks with decreasing calcination temperature was indicative of reduction in crystallite size. The morphological analysis revealed the formation of agglomerated nanoparticles having average particle size ranging from 10-15 and 50-55 nm for C4 and C6, respectively. The agglomeration is attributed to high surface energy of nanoparticles. Ferromagnetism has been displayed by all the synthesized nanoparticles. Enhancement of saturation magnetization with Ca-substitution is attributed to suppression of spin cycloid structure by the reduction in size, lattice distortion and creation of oxygen vacancies by the substitution of divalent ion at trivalent site. Further, this value increases as a function of decreasing particle size. Strong particle size effects on magnetic properties of the synthesized nanoparticles are owed to increasing surface to volume ratio. All these observations are indicative of strong dependence of multiferroism on particle size.

  18. Calcination temperature influenced multiferroic properties of Ca-doped BiFeO{sub 3} nanoparticles

    Energy Technology Data Exchange (ETDEWEB)

    Dhir, Gitanjali, E-mail: gitanjali.thaprian@gmail.com; Uniyal, Poonam; Verma, N. K. [Nano Research Lab, School of Physics and Materials Science, Thapar University, Patiala-147004 (India)

    2015-06-24

    The influence of Ca-doping and particle size on structural, morphological and magnetic properties of BiFeO{sub 3} nanoparticles has been studied. A sol-gel method was employed for the synthesis of nanoparticles and their particle size was tailored by varying the calcination temperature. Structural analysis revealed a rhombohedral distortion induced by Ca-substitution. The broadening of diffraction peaks with decreasing calcination temperature was indicative of reduction in crystallite size. The morphological analysis revealed the formation of agglomerated nanoparticles having average particle size ranging from 10-15 and 50-55 nm for C4 and C6, respectively. The agglomeration is attributed to high surface energy of nanoparticles. Ferromagnetism has been displayed by all the synthesized nanoparticles. Enhancement of saturation magnetization with Ca-substitution is attributed to suppression of spin cycloid structure by the reduction in size, lattice distortion and creation of oxygen vacancies by the substitution of divalent ion at trivalent site. Further, this value increases as a function of decreasing particle size. Strong particle size effects on magnetic properties of the synthesized nanoparticles are owed to increasing surface to volume ratio. All these observations are indicative of strong dependence of multiferroism on particle size.

  19. Growth of L10-ordered crystal in FePt and FePd thin films on MgO(001) substrate

    Science.gov (United States)

    Futamoto, Masaaki; Nakamura, Masahiro; Ohtake, Mitsuru; Inaba, Nobuyuki; Shimotsu, Teruho

    2016-08-01

    Formation of L10-oredered structure from disordered A1 phase has been investigated for FePt and FePd films on MgO(001) substrates employing a two-step method consisting of low temperature deposition at 200 °C followed by high-temperature annealing at 600 °C. L10-(001) variant crystal with the c-axis perpendicular to the substrate grows preferentially in FePd films whereas L10-(100), (010) variants tend to be mixed with the L10-(001) variant in FePt films. The structure analysis by X-ray diffraction indicates that a difference in A1 lattice strain is the influential factor that determines the resulting L10-variant structure in ordered thin films. Misfit dislocations and anti-phase boundaries are observed in high-resolution transmission electron micrographs of 10 nm-thick Fe(Pt, Pd) film consisting of L10-(001) variants which are formed through atomic diffusion at 600 °C in a laterally strained FePt/PeFd epitaxial thin film. Based on the experimental results, a nucleation and growth model for explaining L10-variant formation is proposed, which suggests a possibility in tailoring the L10 variant structure in ordered magnetic thin films by controlling the alloy composition, the layer structure, and the substrate material.

  20. Study on Electronic Conductivity of CaO-SiO2-Al2O3-FeOx Slag System

    Institute of Scientific and Technical Information of China (English)

    2000-01-01

    A study on electronic conductivity of CaO-SiO2-Al2O3-FeOx slag system with Wagner polarization technique was carried out. The experimental data show that electronic conductivity is consisted of free electron conductivity and electron hole conductivity and both are related to the content of Fe3+ and Fe2+. Free electron condu ctivity is decreasing and electron hole conductivity is increasing while Fe3 + changes to Fe2+. There is a maximum electronic conductivity at some ratio of ferric ions Fe3+ to totalion content. Under the experimental conditions, the electronic conductivity is in the range of 10-4-10-2 S/cm.

  1. Perpendicular magnetization of Co2FeAl full-Heusler alloy films induced by MgO interface

    Science.gov (United States)

    Wen, Zhenchao; Sukegawa, Hiroaki; Mitani, Seiji; Inomata, Koichiro

    2011-06-01

    The perpendicular magnetization of Co2FeAl (CFA) full-Heusler alloy films was achieved in the structures of CFA/MgO and MgO/CFA with the perpendicular magnetic anisotropy energy density (KU) of 2-3×106 erg/cm3, which can be used as the perpendicular ferromagnetic electrodes of MgO-based magnetic tunnel junctions (MTJs) with high thermal stability at sub-50-nm dimension. The CFA thickness dependence of KU was investigated at different annealing temperatures, indicating that the perpendicular anisotropy of CFA is contributed by the interfacial anisotropy between CFA and MgO. This letter will open up a way for obtaining perpendicular magnetization of Co-based full-Heusler alloys, which is promising for further reduction in the critical current of current induced magnetization switching in MgO-based MTJ nanopillars with perpendicular full-Heusler alloy electrodes.

  2. High pressure phase transitions in Mg{sub 1-x}Ca{sub x}O: Theory

    Energy Technology Data Exchange (ETDEWEB)

    Srivastava, Anurag; Chauhan, Mamta [Advanced Material Research Lab, Indian Institute of Information Technology and Management, Gwalior (India); Singh, R.K. [Department of Physics, ITM University, Gurgaon (India); Padegaonker, Rishikesh [Indian Embassy School, Sana (Yemen)

    2011-08-15

    We have analysed a B1 {yields} B2 structural phase transitions in Mg{sub 1-x}Ca{sub x}O solid solutions and their ground state properties by using first principle density functional theory and charge transfer interaction potential (CTIP) approach. The effects of exchange-correlation interactions are handled by the generalized gradient approximation with Perdew-Burke-Ernzerhof type parameterization. CTIP approach includes the long range modified Coulomb with charge transfer interactions and short range part of this model includes the van der Waals as well as Hafemeister Flygare type overlap repulsive interactions. The study observes a linear variation of calculated transition pressure, bulk modulus and lattice parameter of Mg{sub 1-x}Ca{sub x}O as a function of Ca composition. The observed results for the end point members are in agreement to their experimental counterparts and the deviations have been discussed. (Copyright copyright 2011 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  3. Metal Nitrides Grown from Ca/Li Flux: Ca6Te3N2 and New Nitridoferrate(I) Ca6(LixFe1-x)Te2N3.

    Science.gov (United States)

    Dickman, Matthew J; Latturner, Susan E

    2016-08-24

    Two new tellurium-containing nitrides were grown from reactions in molten calcium and lithium. The compound Ca6Te3N2 crystallizes in space group R3̅c (a = 12.000(3)Å, c = 13.147(4)Å; Z = 6); its structure is an anti-type of rinneite (K3NaFeCl6) and 2H perovskite related oxides such as Sr3Co2O6. The compound Ca6(LixFe1-x)Te2N3 where x ≈ 0.48 forms in space group P42/m (a = 8.718(3)Å, c = 6.719(2)Å; Z = 2) with a new stuffed anti-type variant of the Tl3BiCl6 structure. Band structure calculations and easily observable red/green dichroic behavior indicate that Ca6Te3N2 is a highly anisotropic direct band gap semiconductor (Eg = 2.5 eV). Ca6(LixFe1-x)Te2N3 features isolated linear N-Fe-N units with iron in the rare Fe(1+) state. The magnetic behavior of the iron site was characterized by magnetic susceptibility measurements, which indicate a very high magnetic moment (5.16μB) likely due to a high degree of spin-orbit coupling. Inherent disorder at the Fe/Li mixed site frustrates long-range communication between magnetic centers. PMID:27479366

  4. Influence of Grain-Refiner Addition on the Morphology of Fe-Bearing Intermetallics in a Semi-Solid Processed Al-Mg-Si Alloy

    Science.gov (United States)

    Smith, Tahsina; O'Reilly, Keyna; Kumar, Sundaram; Stone, Ian

    2013-11-01

    The three-dimensional morphologies of the Fe-bearing intermetallics in a semisolid-processed Al-Mg-Si alloy were examined after extracting the intermetallics. α c-AlFeSi and β-AlFeSi are the major Fe-bearing intermetallics. Addition of Al-Ti-B grain refiner typically promotes β-AlFeSi formation. β-AlFeSi was observed with a flat, plate-like morphology with angular edges in the alloy with and without grain refiner, whereas α c-AlFeSi was observed as "flower"-like morphology in the alloy with grain refiner.

  5. A chemical index of weathering without effect of wind sorting: Fe/Mg ratios in the acid-insoluble phases of loess deposits

    Institute of Scientific and Technical Information of China (English)

    2001-01-01

    Chemical analysis of acid-insoluble fractions in loess and paleosols shows that concentrations of Fe and Mg were under control of wind sorting and post-depositional weathering-pedogenesis. The former caused Fe and Mg concentrated in the finer grain-size fractions, displaying synchronous variations, while the latter made Fe and Mg separated, leading to Fe retained in the weathered section and Mg leached out. Therefore, Fe/Mg ratios in the acid insoluble fraction of loess and paleosols can eliminate the effect of wind sorting and serve as an excellent proxy record on intensity of weathering-pedogenesis. Based on calculation,leaching percentage of Mg in the paleosol S1 from the Luochuan, Xifeng and Huanxian sections is 15%, 11% and 2%,respectively, and on average 9% for the paleosols S2-S14from the Luochuan section, with the highest value amounting to 22% in Ss-1, suggesting the strongest weathering-pedogenesis.``

  6. Low temperature dosimetry in LiF: Mg, Cu, P and CaSO{sub 4}: Dy doped crystals; Dosimetria de baja temperatura en cristales dopados LiF: Mg, Cu, P y CaSO{sub 4}: Dy

    Energy Technology Data Exchange (ETDEWEB)

    Cruz Z, E.; Ramos B, S.; Negron M, A.; Rivera, T. [Instituto de Ciencias Nucleares, UNAM, A.P. 70-543, 04510 Mexico D.F. (Mexico)

    2000-07-01

    It is presented a behavior study of LiF solid dosemeters doped with Mg, Cu and P also polycrystalline samples of CaSO{sub 4} with Dy sinterized in laboratory, both of them were subjected at low temperature. In order to analyse linear behavior to the dose of these dosemeters, it was used thermoluminescence. These materials were exposed to gamma radiation coming from a Co-60 source. The samples were irradiated at dose rates 1.08 {+-} 0.01 Gy/min at liquid nitrogen temperature (LNT) and also the response of dosemeters are compared at ambient temperature and LNT. (Author)

  7. Post-DFT methods for Earth materials: Quantum Monte Carlo simulations of (Mg,Fe)O (Invited)

    Science.gov (United States)

    Driver, K. P.; Militzer, B.; Cohen, R. E.

    2013-12-01

    (Mg,Fe)O is a major mineral phase in Earth's lower mantle that plays a key role in determining the structural and dynamical properties of deep Earth. A pressure-induced spin-pairing transition of Fe has been the subject of numerous theoretical and experimental studies due to the consequential effects on lower mantle physics. The standard density functional theory (DFT) method does not treat strongly correlated electrons properly and results can have dependence on the choice of exchange-correlation functional. DFT+U, offers significant improvement over standard DFT for treating strongly correlated electrons. Indeed, DFT+U calculations and experiments have narrowed the ambient spin-transition between 40-60 GPa in (Mg,Fe)O. However, DFT+U, is not an ideal method due to dependence on Hubbard U parameter among other approximations. In order to further clarify details of the spin transition, it is necessary to use methods that explicitly treat effects of electron exchange and correlation, such as quantum Monte Carlo (QMC). Here, we will discuss methods of going beyond standard DFT and present QMC results on the (Mg,Fe)O elastic properties and spin-transition pressure in order to benchmark DFT+U results.

  8. Influence of boron diffusion on the perpendicular magnetic anisotropy in Ta|CoFeB|MgO ultrathin films

    Energy Technology Data Exchange (ETDEWEB)

    Sinha, Jaivardhan; Gruber, Maria; Kodzuka, Masaya; Ohkubo, Tadakatsu; Mitani, Seiji; Hono, Kazuhiro; Hayashi, Masamitsu, E-mail: hayashi.masamitsu@nims.go.jp [National Institute for Materials Science, Tsukuba 305-0047 (Japan)

    2015-01-28

    We have studied structural and magnetic properties of Ta|CoFeB|MgO heterostructures using cross-section transmission electron microscopy (TEM), electron energy loss spectrum (EELS) imaging, and vibrating sample magnetometry. From the TEM studies, the CoFeB layer is found to be predominantly amorphous for as deposited films, whereas small crystallites, diameter of ∼5 nm, are observed in films annealed at 300 °C. We find that the presence of such nanocrystallites is not sufficient for the occurrence of perpendicular magnetic anisotropy. Using EELS, we find that boron diffuses into the Ta underlayer upon annealing. The Ta underlayer thickness dependence of the magnetic anisotropy indicates that ∼0.2 nm of Ta underlayer is enough to absorb the boron from the CoFeB layer and induce perpendicular magnetic anisotropy. Boron diffusion upon annealing becomes limited when the CoFeB layer thickness is larger than ∼2 nm, which coincides with the thickness at which the saturation magnetization M{sub S} and the interface magnetic anisotropy K{sub I} drop by ∼20%. These results show the direct role which boron plays in determining the perpendicular magnetic anisotropy in CoFeB|MgO heterostructures.

  9. First principle calculations for improving desorption temperature in Mg16H32 doped with Ca, Sr and Ba elements

    Indian Academy of Sciences (India)

    M Bhihi; M Lakhal; S Naji; H Labrim; A Belhaj; A Benyoussef; A Elkenz; M Loulidi; B Khalil; O Mounkachi; M Abdellaoui; E K Hlil

    2014-12-01

    Using ab initio calculations, we predict the improvement of the desorption temperature and the hydrogen storage properties of doped Mg-based hydrides such as,Mg15AMH32 (AM = Ca, Sr and Ba) as a super cell 2 × 2 × 2 of MgH2. In particular, the electronic structure has been obtained numerically using the all-electron full-potential local-orbital minimum-basis scheme FPLO9.00-34. Then, we discuss the formation energy calculations in terms of the material stabilities and the hydrogen storage thermodynamic properties improvements. Among others, we find that the stability and the temperature of desorption decrease without reducing significantly the high storage capacity of hydrogen. Moreover, it has been observed that such a doping procedure does not affect the electronic behavior as seen in MgH2, including the insulator state in contrast with the transition metal hydrides, which modify the electronic structure of pure MgH2.

  10. Different doping effect on physical properties of non-magnetic Pt and Ga in CaFe{sub 4}As{sub 3}

    Energy Technology Data Exchange (ETDEWEB)

    Wu, Dapeng

    2015-02-25

    Highlights: • CaFe{sub 3.64}Pt{sub 0.36}As{sub 3} and CaFe{sub 3.64}Ga{sub 0.36}As{sub 3} were grown using Sn flux method. • The two magnetic transition temperatures of CaFe{sub 4}As{sub 3} remain untouched upon Pt or Ga doping. • The effects of Pt and Ga doping give a different modification of physical properties and electronic structure in CaFe{sub 4}As{sub 3}. • The magnetic structure of CaFe{sub 4}As{sub 3} is insusceptible to non-magnetic dopants. - Abstract: We have successfully doped Pt and Ga into CaFe{sub 4}As{sub 3} and investigated the structure and physical properties of CaFe{sub 3.64}X{sub 0.36}As{sub 3} (X = Pt, Ga). Two magnetic transition temperatures remain unchanged upon Pt or Ga doping, as confirmed by specific heat, electrical resistivity and magnetic susceptibility. The electrical resistivity of CaFe{sub 4}As{sub 3} is reduced by approximately half with Pt dopant but increases by an order of magnitude with Ga doping, consistent with the changes in their Hall coefficients, which indicates the effects of Pt and Ga doping give us a different modification on physical properties and electronic structure in CaFe{sub 4}As{sub 3}.

  11. An improvement to the ligand optimisation method (LOM) for measuring the apparent dissociation constant and ligand purity in Ca2+ and Mg2+ buffer solutions.

    Science.gov (United States)

    McGuigan, John A S; Kay, James W; Elder, Hugh Y

    2014-01-01

    In Ca(2+)/Mg(2+) buffers the calculated ionised concentrations ([X(2+)]) can vary by up to a factor of seven. Since there are no defined standards it is impossible to check calculated [X(2+)], making measurement essential. The ligand optimisation method (LOM) is an accurate method to measure [X(2+)] in Ca(2+)/Mg(2+) buffers; independent estimation of ligand purity extends the method to pK(/) buffers, to calculate electrode and buffer characteristics as a function of Σ. Ca(2+)-electrodes have a Σ buffers. These results demonstrated that it is pK(/) that is normally distributed. Until defined standards are available, [X(2+)] in Ca(2+)/Mg(2+) buffers have to be measured. The most appropriate method is to use Ca(2+)/Mg(2) electrodes combined with the Excel programs SALE or AEC.

  12. The Perovskite to Post-Perovskite phase transition in Al-bearing (Mg,Fe)SiO3: A XANES in-situ analysis at the Fe K-edge

    Science.gov (United States)

    Andrault, D.; Munoz, M.; Bolfan-Casanova, N.; Guignot, N.; Perrillat, J.; Aquilanti, G.; Pascarelli, S.

    2008-12-01

    Phase transition from perovskite (Pv) to Post-Pv (PPv) phase in MgSiO3 has been studied by many groups since its discovery in 2004 (1,2) and the different studies find similar transition pressures. The effect of Al and Fe on the phase transition remains more controversial. The most recent studies suggest an increase of the transition pressure with increasing Fe-content (3,4), but other experimental work (5) as well as ab-initio calculations (6) show the opposite effect. The effect of Al was reported to increase slightly the pressure transition to the CaIrO3 form (4,7), but its influence on the Fe3+ content in the PPv phase has not been documented yet. By means of in situ study of the Fe K-edge fine structures (XANES), we investigated the phase relations between Pv and PPv phases for three different Al-(Mg,Fe)SiO3 compositions. For this, we synthesized various Pv and PPv mixtures using laser-heated diamond anvil cell (DAC) for pressures between 60 and 170 GPa. The sample's mineralogy, i.e. the Pv and PPv phase fractions, was determined using in-situ X-ray diffraction at the ID27 beamline of the ESRF (8,9). Then, we probed the Fe speciation, i.e. the Fe concentration in each phases, in-situ in the DAC using the µ-XANES mapping technique available at the ID24 beamline (10,11). Both pieces of information were combined to retrieve the Fe partitioning coefficient between the two high-pressure phases. Our results show that Fe partitions strongly into the PPv phase, which implies a very large binary loop of coexistence of the two phases. Thus, at the core-mantle boundary pressure (135 GPa), the Pv and PPv phase always coexist for all geophysically relevant Al-(Mg,Fe)SiO3 compositions, and the Fe-content in the PPv-phase is only a few percent. References: 1. M. Murakami, K. Hirose, K. Kawamura, N. Sata, Y. Ohishi, Science 304, 855 (2004). 2. A. R. Oganov, S. Ono, Nature 430, 445 (2004). 3. S. Tateno, K. Hirose, N. Sata, Y. Ohishi, Phys. Earth Planet. Inter. 160, 319 (2007

  13. Effect of CaO doping on mechanical properties and thermal shock resistance of 10NiO-NiFe2O4 composite ceramics

    Institute of Scientific and Technical Information of China (English)

    LAI Yan-qing; ZHANG Yong; ZHANG Gang; TIAN Zhong-liang; LI Jie

    2008-01-01

    The CaO doped 10NiO-NiFe2O4 composite ceramics were prepared by the cold isostatic pressing-sintering process, and the effects of CaO content on the phase composition, mechanical property and thermal shock resistance of 10NiO-NiFe2O4 composite ceramics were studied. The results show that the samples mainly consist of NiO and NiFe2O4 when content of CaO is less than4%(mass fraction), bending strength increases obviously by CaO doping. Bending strength of the samples doped with 2% CaO is above 185 Mpa, but that of the samples without CaO is only 60 Mpa. Fracture toughness is improved obviously by CaO doping, the undoped ceramics. CaO doping is bad to thermal shock resistance of 10NiO-NiFe2O4 composite ceramics.

  14. A reappraisal of the vital effect in cultured benthic foraminifer Bulimina marginata on Mg/Ca values: Assessing temperature uncertainty relationships

    NARCIS (Netherlands)

    Wit, J.C.; de Nooijer, L.J.; Barras, C.; Jorissen, F.J.; Reichart, G.-J.

    2012-01-01

    The reconstruction of past temperatures is often achieved through measuring the Mg/Ca value of foraminiferal test carbonate. The diversity in foraminiferal Mg/Ca–temperature calibrations suggests that there is also a biological control on this proxy. This study presents a new Mg/Ca–temperature calib

  15. Study on Ca8Mg(SiO4)4Cl2:Eu2+ Doped with Sr2+

    Institute of Scientific and Technical Information of China (English)

    2006-01-01

    Ca8Mg(SiO4)4Cl2:Eu2+ phosphor doped with Sr2+ cation for Ca2+ partially, was synthesized by solid-state reaction at high temperature under reducing atmosphere, and its luminescent properties were investigated. The experimental results indicate that the emission intensity of the phosphor increases after being doped with a few amount of Sr2+ ion. The emission peak of the phosphor blue shift to about 464 nm when the phosphor is doped with large quantity of Sr2+ ions. The excitation spectrum indicates that the phosphor can be well excited by UV and blue light from 300 to 460 nm, and the phosphor was fitted well for the excitation by UV or blue-LED.

  16. Pinning enhancement in MgB2 superconducting thin films by magnetic nanoparticles of Fe2O3

    Indian Academy of Sciences (India)

    E Taylan Koparan; A Surdu; K Kizilkaya; A Sidorenko; E Yanmaz

    2013-11-01

    MgB2 thin films were fabricated on -plane Al2O3 (1$\\bar{1}$02) substrates. First, deposition of boron was performed by rf magnetron sputtering on Al2O3 substrates and followed by a post-deposition annealing at 850 °C in magnesium vapour. In order to investigate the effect of Fe2O3 nanoparticles on the structural and magnetic properties of films, MgB2 films were coated with different concentrations of Fe2O3 nanoparticles by spin coating process. The magnetic field dependence of the critical current density c was calculated from the M–H loops and magnetic field dependence of the pinning force density, p(), was investigated for the films containing different concentrations of Fe2O3 nanoparticles. The critical current densities, c, in 3Tmagnetic field at 5 K were found to be around 2.7 × 104 A/cm2, 4.3 × 104 A/cm2, 1.3 × 105 A/cm2 and 5.2 × 104 A/cm2 for films with concentrations of 0, 25, 50 and 100% Fe2O3, respectively. It was found that the films coated with Fe2O3 nanoparticles have significantly enhanced the critical cu