Sample records for mg mn ca

  1. Ca, Mg, Zn, Fe, Cu and Mn content of ass’s milk

    Elisabetta Salimei


    Full Text Available The aim of this study was to determine Ca, Mg, Zn, Fe, Cu and Mn content of ass’s milk. Twenty four individual milk samples were collected from 4 lactating asses. During the experi- mental period milk samples were collected every 3 weeks interval, using a milking machine; asses were housed with the foals that were separated from the jennets 3 hours before milking. Milk was analysed for Ca, Mg, Zn, Fe, Cu and Mn content by atomic absorption spectrometry. The concentration mean (±SD of Ca Mg, Zn, Fe, and Cu were respectively 334.61±39.80, 58.46±8.43, 1.99±0.51, 1.15±0.52, 0.16±0.06 mg/kg. Mn was found only at trace level. Iron content of ass’s milk was the most variable ranging from 0.43 to 1.88 mg/kg. Correlation coefficients were positive and significant between Ca and Mg (r=0.63, Zn and Mg (r=0.45, Zn and Fe (r=0.49 and Zn and Cu (r=0.50. In this study, except for Fe, mean concentration of Ca, Mg, Zn, and Cu in ass’s milk was similar to those reported in literature for human milk.

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

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


    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.

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

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


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

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

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


    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. Mechanical and corrosion properties of biodegradable Mg-1.5Mn-1Ca-xSr alloys

    Sun, X.; Sun, S. Y.; Ning, Y. H.; Ning, Y. T.


    The mechanical properties and corrosion mechanism of both as-cast and solution-naturally age (T4) treated Mg-1.5Mn-1Ca-xSr alloys were investigated. The results showed that Sr is helpful to decrease grain size and increase the strength. The corrosion process of alloys was mainly determined by the quantity and distribution of second phases. Mg17Sr2, α-Mn and Ca-Sr phases acted as cathodes accelerated the corrosion of Mg2Ca anodic phase and α-Mg matrix. However, continuous distributed Mg17Sr2 was beneficial to resist the happening of localized corrosion because of its barrier effect. T4 treatment could significantly improve the mechanical properties and corrosion resistance of Mg alloys because of the dissolution of Mg2Ca phase and the dispersive distribution of Mg17Sr2 and α-Mn phases.

  6. Purification and characteristics of Ca2+,Mg2+- and Ca2+,Mn2+-dependent and acid DNases from spermatozoa of the sea urchin Strongylocentrotus intermedius.

    Shastina, V V; Menzorova, N I; Sibirtsev, Yu T; Rasskazov, V A


    Ca2+,Mg2+- and Ca2+,Mn2+-dependent and acid DNases were isolated from spermatozoa of the sea urchin Strongylocentrotus intermedius. The enzymes have been purified by successive chromatography on DEAE-cellulose, phenyl-Sepharose, Source 15Q, and by gel filtration, and the principal physicochemical and enzymatic properties of the purified enzymes were determined. Ca2+,Mg2+-dependent DNase (Ca,Mg-DNase) is a nuclear protein with molecular mass of 63 kD as the native form and its activity optimum is at pH 7.5. The enzyme activity in the presence of bivalent metal ions decreases in the series (Ca2+ + Mg2+) > Mn2+ = (Ca2+ + Mn2+) > (Mg2+ + EGTA) > Ca2+. Ca,Mg-DNase retains its maximal activity in sea water and is not inhibited by G-actin and N-ethylmaleimide, whereas Zn(2+) inhibits the enzyme. The endogenous Ca,Mg-DNase is responsible for the internucleosomal cleavage of chromosomal DNA of spermatozoa. Ca2+,Mn2+-dependent DNase (Ca,Mn-DNase) has molecular mass of 25 kD as the native form and the activity optimum at pH 8.5. The enzyme activity in the presence of bivalent metal ions decreases in the series (Ca2+ + Mn2+) > (Ca2+ + Mg2+) > Mn2+ > (Mg2+ + EGTA). In seawater the enzyme is inactive. Zinc ions inhibit Ca,Mn-DNase. Acid DNase of spermatozoa (A-DNase) is not a nuclear protein, it has molecular mass of 37 kD as a native form and the activity optimum at pH 5.5, it is not activated by bivalent metal ions, and it is inhibited by N-ethylmaleimide and iodoacetic acid. Mechanisms of the endonuclease cleavage of double-stranded DNA have been established for the three enzymes. The possible involvement of DNases from sea urchin spermatozoa in programmed cell death is discussed.

  7. Microwave Dielectric Properties of A2P2O7 (A = Ca, Sr, Ba; Mg, Zn, Mn)

    Bian, Jian-jiang; Kim, Dong-Wan; Hong, Kug Sun


    Microwave dielectric properties of A2P2O7 (A = Ca, Sr, Ba, Mn, Mg, Ba) ceramic materials were investigated by a network analyzer at the frequency of 10 GHz. It was found that A2P2O7 ceramics could be sintered at relatively lower temperature below 1150°C, although the thortveitite type series, Mn2P2O7, α-Mg2P2O7 and α-Zn2P2O7 with smaller ionic radii of A cations were hard to sinter to full density. The dielectric constant of A2P2O7 is lower than 10. The Q× f value increased according to the sequence of δ-Ba2P2O7, α-Sr2P2O7 and β-Ca2P2O7 in dichromatic type series, and the sequence of Mn2P2O7, α-Mg2P2O7 and α-Zn2P2O7 in thortveitite type series, respectively. The temperature coefficient of resonant frequency τf for all samples exhibits negative value. Larger τf for α-Zn2P2O7, α-Mg2P2O7 and δ-Ba2P2O7 is mainly due to their reversible phase transformations. The microwave dielectric properties were discussed from the point view of bond valence.

  8. Improving in-vitro biocorrosion resistance of Mg-Zn-Mn-Ca alloy in Hank’s solution through addition of cerium

    张凡; 马爱斌; 宋丹; 江静华; 卢富敏; 张留艳; 杨东辉; 陈建清


    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.

  9. Hydrothermal synthesis and corrosion behavior of the protective coating on Mg-2Zn-Mn-Ca-Ce alloy

    Dan Song


    Full Text Available Protective coatings were synthesized on the Mg-2Zn-Mn-Ca-Ce Mg alloy through the hydrothermal method with de-ionized water as the reagent. The coatings were composed of Mg hydroxide, generally uniform and compact. Hydrogen evolution tests and electrochemical tests in the Hanks’ solution demonstrated that the Mg(OH2 coatings effectively decreased the bio-degradation rate of the Mg alloy substrate. Microstructure observation showed that the coating formation on the secondary phases was more difficult than that on the α-Mg matrix, which led to micro cracks and pores on the secondary phases after drying. Over synthesizing time, the coating layer on secondary phases gradually becomes more compact and uniform. Meanwhile, owing to the thicker and more compact coatings, the corrosion resistance and protective efficiency were significantly improved with longer synthesizing time as well.

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

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


    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.

  11. On the crystal chemistry of olivine-type germanate compounds, Ca1 + xM1 - xGeO4 (M2+ = Ca, Mg, Co, Mn).

    Redhammer, Günther J; Roth, Georg; Amthauer, Georg; Lottermoser, Werner


    Germanate compounds, CaMGeO(4) with M(2+) = Ca, Mg, Co and Mn, were synthesized as single crystals by slow cooling from the melt or by flux growth techniques. All the compositions investigated exhibit Pnma symmetry at 298 K and adopt the olivine structure. The M2 site is exclusively occupied by Ca(2+), while on M1 both Ca(2+) and M(2+) cations are found. The amount of Ca(2+) on M1 increases with the size of the M1 cation, with the smallest amount in the Mg compound (0.1 atoms per formula unit) and the largest in the Mn compound (0.20 atoms per formula unit), while in Ca(2)GeO(4), also with olivine structure, both sites are completely filled with Ca(2+). When compared with those of Ca silicate olivine, the lattice parameters a and c are distinctly larger in the analogous germanate compounds, while b has essentially the same values, regardless of the tetrahedral cation, meaning that b is independent of the tetrahedral cation. Structural variations on the octahedrally coordinated M1 site are largely determined by the size of the M1 cation, the average M1-O bond lengths being identical in Ca silicate and Ca germanate olivine. Increasing the size of the M1 cation induces an increasing polyhedral distortion, expressed by the parameters bond-length distortion, octahedral angle variance and octahedral quadratic elongation. However, the Ca germanate olivine compounds generally have more regular octahedra than the analogous silicates. The octahedrally coordinated M2 site does not exhibit large variations in structural parameters as a consequence of the constant chemical composition; the same is valid for the tetrahedral site.

  12. Mg/Ca and Mn/Ca ratios in benthic foraminifera: the potential to reconstruct past variations in temperature and hypoxia in shelf regions

    J. Groeneveld


    Full Text Available Shelf and coastal regions are exceptionally important for many countries as they provide the main habitat for many economically important fish and shellfish species. With ongoing climate change and human-induced eutrophication the shelf regions are especially affected, resulting in increased temperatures and stratification as well as oxygen depletion of the bottom waters. In order to be able to predict the magnitude of these changes in the future, it is necessary to study how they varied in the past. Commonly used foraminiferal climate and environmental proxies, e.g., stable isotopes and trace metal/Ca ratios, that are applied in open-ocean settings are not necessarily applicable in shelf regions, either as faunas are significantly different or as conditions can change much faster compared to the open ocean. In this study we explore the use of Mg/Ca as paleothermometer and Mn/Ca as a potential proxy for changing dissolved oxygen conditions in bottom water on the benthic foraminifera Bulimina marginata and Globobulimina turgida. Living specimens were collected from the Skagerrak and the Gullmar Fjord (SW Sweden; the latter is hypoxic for several months a year. As the specimens were alive when collected, we assume it unlikely that any diagenetic coatings have already significantly affected the trace metal/Ca ratios. The Mg/Ca ratios are similar to previously published values but display much larger variation than would be expected from the annual temperature change of less than 2 °C. An additional impact of the difference in the calcite saturation state between the Skagerrak and the Gullmar Fjord could explain the results. Mn/Ca ratios from G. turgida can potentially be related to variations in dissolved oxygen of the habitat where the foraminifera calcify. Samples from the Skagerrak display increased Mn/Ca in specimens that lived deeper in the sediment than those that lived near the surface. G. turgida samples from the low-oxygen Gullmar Fjord

  13. Luminescence Properties of Eu2+ and Mn2+ Co-Doped Ca8Mg(SiO4)4Cl2

    方英; 庄卫东; 孙益民; 滕晓明; 何华强; 黄小卫


    The green phosphor for white LED, Ca8Mg(SiO4)4Cl2∶Eu2+, Mn2+, was synthesized by high temperature solid state reaction under reducing atmosphere. During the process of the phosphor prepared, the excess CaCl2 can improve the intensity of emission. The experimental results indicate that there is an effective energy transfer from Eu2+ to Mn2+in Ca8Mg(SiO4)4Cl2 host. This kind of energy transfer may be due to resonance transfer, and this energy transfer is limited.

  14. 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

    H. Kennedy


    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 P. 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 shell Mg content influencing Sr and Mn heterogeneity, the influence of shell organic content and/or conditions at the shell crystal-solution interface. Invariant Mg/Ca ratios observed in the mid and innermost regions of the P. maximus shell suggests a potential application as a palaeotemperature proxy.

  15. Extraction Equilibrium of Mn2+, Ca2+, and Mg2+ from Chloride Solutions by Di(2-ethylhexyl)phosphoric Acid Dissolved in Kerosene

    Zhang, Chuanfu; Cao, Wenxin; Zhan, Jing; Ding, Fenghua; Hwang, Jiann-Yang


    The presence of calcium and magnesium affects the purity of the final product MnCl2 in hydrometallurgical treatment processes. The solvent extraction method can be used to separate Ca2+ and Mg2+ from Mn2+ solutions containing impurity ions such as Ca2+ and Mg2+. This article aims to investigate the single-stage extraction equilibrium of Ca2+, Mg2+, and Mn2+ in chloride medium using di(2-ethylhexyl)phosphoric acid in kerosene (O:A = 1:1). The results show that the pH0.5 values are 1.11, 1.56, and 2.18 for Ca2+, Mn2+, and Mg2+, respectively. The mechanism of extraction and stoichiometries of metal-containing extracted species were illustrated based on a slope analysis. The composition of the extracted species in the organic phase is proposed to be MnR2·R2H2, CaR2·R2H2, and MgR2·(R2H2)2, respectively.

  16. Monolayer alkali and transition-metal monoxides: MgO, CaO, MnO, and NiO

    Shayeganfar, F.; Vasu, K. S.; Nair, R. R.; Peeters, F. M.; Neek-Amal, M.


    Two-dimensional crystals with strong interactions between layers has attracted increasing attention in recent years in a variety of fields. In particular, the growth of a single layer of oxide materials (e.g., MgO, CaO, NiO, and MnO) over metallic substrates were found to display different physical properties than their bulk. In this study, we report on the physical properties of a single layer of metallic oxide materials and compare their properties with their bulk and other two-dimensional (2D) crystals. We found that the planar structure of metallic monoxides are unstable whereas the buckled structures are thermodynamically stable. Also, the 2D-MnO and NiO exhibit different magnetic (ferromagnetic) and optical properties than their bulk, whereas band-gap energy and linear stiffness are found to be decreasing from NiO to MgO. Our findings provide insight into oxide thin-film technology applications.

  17. 胶州湾双壳类壳体中的Ca,Mg,Mn,Sr元素组成及影响因素%Components of Ca, Mg, Mn and Sr in Bivalve Shells from Jiaozhou Bay and Their Influence Factors

    张爱滨; 刘升发; 范德江; 颜文涛


    探讨影响双壳类元素组成的可能因素,从胶州湾沿岸不同取样点采集黄海近海常见的菲律宾蛤仔(Ruditapes philippinarum)、褶牡蛎(Oystrea denselamellosa)和紫贻贝(Mytilus galloprovincialis),分别测量了3种壳体的矿物物相类型和壳体中的Ca,Mg,Mn,Sr元素组成.研究表明:3种壳体分别属于文石质、方解石质和混合质壳;Ca,Mn元素含量在菲律宾蛤仔、褶牡蛎和紫贻贝壳体中没有差别,而Mg元素含量在菲律宾蛤仔壳体中含量较低,在褶牡蛎壳体和紫贻贝壳体中含量较高,Sr元素恰好与Mg元素相反.双壳类壳体中元素组成主要受壳体矿物物相类型的制约,而与水体环境要素之间的关系弱.

  18. Thermodynamic Assessment of MnO and FeO Activities in FeO–MnO–MgO–P2O5–SiO2(–CaO) Molten Slag

    Kim, Sun-Joong; Takekawa, Jun; Shibata, Hiroyuki; Kitamura, Shin-ya; Yamaguchi, Katsunori; Kang, Youn-Bae


    The activity coefficients of MnO and FeO in an FeO–MnO–MgO–P2O5–SiO2(–CaO) slag system were measured on the basis of the equilibrium between Ag and molten slag at 1673 K under a controlled atmosphere...

  19. 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

    P. S. Freitas


    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.

  20. 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

    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...

  1. Concentrations of As, Ca, Cd, Co, Cr, Cu, Fe, Hg, K, Mg, Mn, Mo, Na, Ni, Pb, and Zn in uruguayan rice determined by atomic absorption spectrometry

    Mario E. Rivero Huguet


    Full Text Available The United Nations General Assembly declared the year 2004 the International Year of Rice and the concept "Rice is life". The largest nutritional problems occurring globally are protein-energy malnutrition, and Ca, Fe, I, Zn, and vitamin A deficiency. In this report, 49 rice samples (Oryza sativa L. were digested by dry ashing in order to determine As, Cd, Cr, and Pb by ETA-AAS; while Ca, Co, Cu, Fe, K, Mg, Mo, Mn, Na, Ni, and Zn were determined by FAAS; and Hg by CV-AAS using microwave-assisted decomposition. The following concentration ranges were obtained for Ca (9.1-15 mg/100 g, Cd (2.30-4.12 µg/kg, Co (41-60 µg/kg, Cu (1.33-180 mg/kg, Fe (4.41-7.15 mg/kg, K (167-217 mg/100 g, Mg (45-121 mg/100 g, Mo (0.52-0.97 mg/kg, Mn (5.45-25.4 mg/kg, Na (0.95-2.50 mg/100g, Ni (0.53-0.72 mg/kg, and Zn (5.86-12.6 mg/kg. Mean recoveries of elements from fortified rice were: 87±12% for As, 95.3±8.9% for Ca, 106.2±7.7% for Cd, 103.3±6.5% for Co, 89.4±8.1% for Cr, 99.3±4.6% for Cu, 103±10% for Fe, 96.3±9.3% for Hg, 95.4±12% for K, 98.3±8.0% for Mg, 93.4±7.8% for Mo, 95.3±9.9% for Mn, 89±12% for Na, 90.3±9.7% for Ni, 91.2±5.5% for Pb and 92.0±9.4% for Zn. The concentrations of the minerals and microelements studied fall within the typical range of rice grown around the world. Potassium was the most abundant mineral, followed by Mg and Ca; among microelements, the concentrations of Cu, Fe, Mo, Mn, Na, and Zn in rice were outstanding. It was also found that the milling process highly affects the K, Mg, Mn, Na, and Zn concentrations, while it has little influence on Ca, Co, Cu, and Fe. On the other hand, there is a loss of Ca, Fe, and Mn during the parboiling process. Recent studies have shown the potential to exploit the genetic variation of rice seeds with regard to the concentration of some minerals (Ca, Fe, Zn, etc. without affecting yield or adding new traits. All rice samples tested showed lower levels of As, Cd, Hg, and Pb in comparison

  2. Effect of Synthesizing Temperature on Microstructure and Electrochemical Property of the Hydrothermal Conversion Coating on Mg-2Zn-0.5Mn-Ca-Ce Alloy

    Guanghui Guo


    Full Text Available Mg(OH2 conversion coatings were formed on an Mg-2Zn-0.5Mn-Ca-Ce alloy via hydrothermal method at three different synthesizing temperatures (160, 170 and 180 °C. The effect of synthesizing temperature on microstructure and electrochemical property of the coatings were systematically studied. With increasing synthesizing temperature, the coating became thicker due to the faster reaction and deposition of Mg(OH2 on the α-Mg phase and secondary phases of the substrate Mg alloy. Internal micro-cracks were also generated in the higher-temperature synthesized coatings due to the increased shrinking stress, but the cross-cutting micro-cracks were suppressed. Benefiting from the improved barrier effect against penetration of corrosive medium, the higher-temperature synthesized thicker coating presented significantly enhanced electrochemical property and anti-corrosion efficiency in Hanks’ solution.

  3. Examination of Perovskite Structure CaMnO3-δ with MgO Addition as Oxygen Carrier for Chemical Looping with Oxygen Uncoupling Using Methane and Syngas

    Dazheng Jing


    Full Text Available Perovskite structure oxygen carriers with the general formula CaMnxMg1-xO3-δ were spray-dried and examined in a batch fluidized bed reactor. The CLOU behavior, reactivity towards methane, and syngas were investigated at temperature 900°C to 1050°C. All particles showed CLOU behavior at these temperatures. For experiments with methane, a bed mass corresponding to 57 kg/MW was used in the reactor, and the average CH4 to CO2 conversion was above 97% for most materials. Full syngas conversion was achieved for all materials utilizing a bed mass corresponding to 178 kg/MW. SEM/EDX and XRD confirmed the presence of MgO in the fresh and used samples, indicating that the Mg cation is not incorporated into the perovskite structure and the active compound is likely pure CaMnO3-δ. The very high reactivity with fuel gases, comparable to that of baseline oxygen carriers of NiO, makes these perovskite particles highly interesting for commercial CLC application. Contrary to NiO, oxygen carriers based on CaMnO3-δ have no thermodynamic limitations for methane oxidation to CO2 and H2O, not to mention that the materials are environmentally friendly and can utilize much cheaper raw materials for production. The physical properties, crystalline phases, and morphology information were also determined in this work.

  4. Magnetic bioactive glass ceramic in the system CaO-P2O5-SiO2-MgO-CaF2-MnO2-Fe2O3 for hyperthermia treatment of bone tumor.

    Li, Guangda; Feng, Shuying; Zhou, Dali


    Magnetic bioactive glass ceramic (MG) in the system CaO-SiO(2)-P(2)O(5)-MgO-CaF(2)-MnO(2)-Fe(2)O(3) for hyperthermia treatment of bone tumor was synthesized. The phase composition was investigated by XRD. The magnetic property was measured by VSM. The in vitro bioactivity was investigated by simulated body fluid (SBF) soaking experiment. Cell growth on the surface of the material was evaluated by co-culturing osteoblast-like ROS17/2.8 cells with materials for 7 days. The results showed that MG contained CaSiO(3) and Ca(5)(PO(4))(3)F as the main phases, and MnFe(2)O(4) and Fe(3)O(4) as the magnetic phases. Under a magnetic field of 10,000 Oe, the saturation magnetization and coercive force of MG were 6.4 emu/g and 198 Oe, respectively. After soaking in SBF for 14 days, hydroxyapatite containing CO(3)(2-) was observed on the surface of MG. The experiment of co-culturing cells with material showed that cells could successfully attach and well proliferate on MG.

  5. Improving tensile properties of dilute Mg-0.27Al-0.13Ca-0.21Mn (at.%) alloy by low temperature high speed extrusion

    Nakata, T., E-mail: [Nagaoka University of Technology, 1603-1, Kamitomioka, Nagaoka 940-2188 (Japan); Mezaki, T.; Xu, C.; Oh-ishi, K. [Nagaoka University of Technology, 1603-1, Kamitomioka, Nagaoka 940-2188 (Japan); Shimizu, K.; Hanaki, S. [Sankyo Tateyama, Inc., Sankyo Material-Company, 8-3, Nagonoe, Imizu, Toyama 934-8515 (Japan); Kamado, S. [Nagaoka University of Technology, 1603-1, Kamitomioka, Nagaoka 940-2188 (Japan)


    As-cast Mg-0.27Al-0.13Ca-0.21Mn (at.%) alloy was extruded at temperatures from 350 °C to 500 °C. We examined the microstructural changes during extrusion at different temperatures to clarify dynamic recrystallization mechanisms during extrusion, and also investigated the effect of extrusion temperature on microstructures and mechanical properties of the alloy. High extrusion exit speed of 60 m/min was successfully achieved at wide range of temperatures from 350 °C to 500 °C even when as-cast dilute Mg-0.27Al-0.13Ca-0.21Mn (at.%) alloy was used as a billet for the extrusion. The extrusion at low temperature refines grain size and weakens basal texture due to continuous dynamic recrystallization (CDRX) together with double twinning. As a result, the alloy sample extruded at 350 °C exhibits higher tensile proof stress of 206 MPa and higher tensile ductility of 29% than T5-treated 6063 aluminum alloy and commercial AZ31 magnesium alloy even in an as-extruded condition. Furthermore, Hall–Petch coefficient for compressive proof stress is 1.8 times larger than that for tensile one, resulting in improvement of yield stress anisotropy (compressive proof stress/tensile yield stress ratio). - Highlights: • Dilute Mg–Al–Ca–Mn alloy can be extruded at high die-exit speed of 60 m/min. • The extrusion at low temperature refines recrystallized grain size and weakens basal texture. • Grain refining improves mechanical properties of dilute Mg–Al–Ca–Mn alloys.

  6. Determinação direta de Ca, Mg, Mn e Zn em amostras de leite de búfala da Ilha de Marajó por espectrometria de absorção atômica com chama (FAAS Direct determination of Ca, Mg, Mn and Zn in buffalo milk of the Marajó Island by FAAS

    João B. Pereira Junior


    Full Text Available This work proposes an analytical procedure for direct determination of calcium, magnesium, manganese and zinc in buffalo milk by flame atomic absorption spectrometry (FAAS. Samples were diluted with a solution containing 10% (v/v of water-soluble tertiary amines (CFA-C at pH 8. For comparison, buffalo milk samples were digested with HNO3 and H2O2. According to a paired t-test, the results obtained in the determination of Ca, Mg, Mn and Zn in digested samples and in 10% (v/v CFA-C medium were in agreement at a 95% confidence level. The developed procedure is simple, rapid, decrease the possibility of contamination and can be applied for the routine determination of Ca, Mg, Mn and Zn in buffalo milk samples without any difficulty caused by matrix constituents, such as fat content, and particle size distribution in the milk emulsion.

  7. Effects of different cooling rates during two casting processes on the microstructures and mechanical properties of extruded Mg-Al-Ca-Mn alloy

    Xu, S.W., E-mail: [Department of Mechanical Engineering, Nagaoka University of Technology, Nagaoka 940-2188 (Japan); Oh-ishi, K.; Kamado, S.; Takahashi, H.; Homma, T. [Department of Mechanical Engineering, Nagaoka University of Technology, Nagaoka 940-2188 (Japan)


    Highlights: Black-Right-Pointing-Pointer Ordered monolayer GP zone was formed by increasing cooling rate. Black-Right-Pointing-Pointer Finer extruded microstructure was obtained by increasing cooling rate. Black-Right-Pointing-Pointer Higher number density precipitates was obtained by increasing cooling rate. Black-Right-Pointing-Pointer Tensile 0.2% proof stress was increased by 105 MPa by increasing cooling rate. Black-Right-Pointing-Pointer Extruded DC-cast alloy shows higher tensile 0.2% proof stress of 409 MPa. - Abstract: In this study, Mg-3.6Al-3.4Ca-0.3Mn (wt.%) (which is denoted AXM4303) alloy ingots were prepared by two casting processes with different cooling rates: permanent mold (PM) casting, which has a lower cooling rate of 10-20 Degree-Sign C/s and direct chill (DC) casting, which has a higher cooling rate of 100-110 Degree-Sign C/s. Then, these two types of AXM4303 alloy ingots were hot extruded at 400 Degree-Sign C under the same conditions. The microstructures of the as-cast and extruded alloy samples were systematically investigated by field-emission scanning electron microscope (FE-SEM), transmission electron microscope (TEM) and electron backscattered diffraction (EBSD) systems. The effects of the different cooling rates during the casting process on the microstructures and mechanical properties of the extruded AXM4303 alloy samples were evaluated. The results show that the strength of the extruded Mg-Al-Ca-Mn alloy can be substantially increased by microstructural control during the casting process. Because the cooling rate of the DC casting process is much faster than the cooling rate of PM casting, the DC-cast AXM4303 has the following properties: (i) the lamellar eutectic structure and dendrite cell size are significantly refined, (ii) the ordered monolayer GP zones enriched with Al and Ca nucleate with no growth, and (iii) most of the Mn remains in solution in the matrix. Thus, after hot extrusion, the DC-cast AXM4303 has finer

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

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


    Owing to their potential as single-source precursors for compositionally complex materials, there is growing interest in the rational design of multimetallic compounds containing fluorinated ligands. In this work, we show that chemical and structural principles for a materials-by-design approach to bimetallic trifluoroacetates can be established through a systematic investigation of the crystal-chemistry of their monometallic counterparts. A(CF3COO)2·nH2O (A = Mg, Ca, Sr, Ba, Mn) monometallic trifluoroacetates were employed to demonstrate the feasibility of this approach. The crystal-chemistry of monometallic trifluoroacetates was mapped using variable-temperature single-crystal X-ray diffraction, powder X-ray diffraction, and thermal analysis. The evolution with temperature of the previously unknown crystal structure of Mg(CF3COO)2·4H2O was found to be identical to that of Mn(CF3COO)2·4H2O. More important, the flexibility of Mnx(CF3COO)2x·4H2O (x = 1, 3) to adopt two structures, one isostructural to Mg(CF3COO)2·4H2O, the other isostructural to Ca3(CF3COO)6·4H2O, enabled the synthesis of Mg-Mn and Ca-Mn bimetallic trifluoroacetates. Mg0.45Mn0.55(CF3COO)2·4H2O was found to be isostructural to Mg(CF3COO)2·4H2O and exhibited isolated metal-oxygen octahedra with Mg(2+) and Mn(2+) nearly equally distributed over the metal sites (Mg/Mn: 45/55). Ca1.72Mn1.28(CF3COO)6·4H2O was isostructural to Ca3(CF3COO)6·4H2O and displayed trimers of metal-oxygen corner-sharing octahedra; Ca(2+) and Mn(2+) were unequally distributed over the central (Ca/Mn: 96/4) and terminal (Ca/Mn: 38/62) octahedral sites.

  9. Formation Mechanism of CaO-SiO2-Al2O3-(MgO) Inclusions in Si-Mn-Killed Steel with Limited Aluminum Content During the Low Basicity Slag Refining

    Wang, Kunpeng; Jiang, Min; Wang, Xinhua; Wang, Ying; Zhao, Haoqian; Cao, Zhanmin


    Pilot trails were carried out to study the formation mechanism of CaO-SiO2-Al2O3-(MgO) inclusions in tire cord steel. 48 samples were taken from 8 heats of liquid steel during secondary refining, which were subsequently examined by an automatic scanning electron microscope with energy dispersive spectrometer (SEM-EDS). Characteristics of thousands of oxide inclusions at different refining stages were obtained, including their compositions, sizes, morphologies, etc. Based on the obtained information of inclusions, details during formation of CaO-SiO2-Al2O3-(MgO) inclusions were revealed and a new mechanism was proposed, including their origin, formation, and evolution during the refining process. It was found that CaO-SiO2-Al2O3-(MgO) inclusions were initially originated from the CaO-SiO2-MnO-(MgO) inclusions, which were formed during BOF tapping by the coalescence between MnO-SiO2 deoxidation products and the emulsified slag particles because of violent flow of steel. This can be well confirmed by the evaluation of the formation thermodynamics of CaO-SiO2-MnO-(MgO) inclusions, which was proved very difficult to be produced by intrinsic reactions inside liquid steel. Because of chemical reactions between CaO-SiO2-MnO-(MgO) inclusions and molten steel, they were mainly changed into CaO-SiO2-MnO-Al2O3-(MgO) and partially into CaO-SiO2-Al2O3-(MgO), which may be detrimental to the cold drawing ability of coils. Based on this finding, improvements were made in industrial production during BOF tapping and secondary refining. The results indicated that such (CaO-SiO2)-based inclusions existed in conventional process were effectively decreased after the improvements.

  10. Research of Luminescence Properties on MO-RE2 O3 -B2 O3:Eu, Mn(M=Mg, Ca, Sr; RE=Y, La, Gd)

    Liang Zhongyi; He Dawei; Shi Yanning


    A series of phosphor of MO-RE2 O3-B2 O3: Eu, Mn ( M = Mg, Ca, Sr; RE = Y, La, Gd) were prepared and studied.Excitation spectra exhibited high absorption in UV region (370 ~ 400 nm).There existed two valence states for europium ions Eu2+ and Eu 3+, the broad emission band peaking at 515 nm correspond to the 5d-4f emission transition of Eu2+ , the sharp emission peaking at 590 and 610 nm correspond to the 5D0→7FJ(J = 1,2,3,4) emission transition of Eu 3 + By the introduction of Mg and Y into MO-RE2O3-B2O3: Eu, blue-green emission was restrained ultimately and red emission peaking at 610 nm was enhanced strongly, intensity and colorimetric purity of red light were both enhanced.Furthermore, Mg1-xSrxO-Y2O3-B2O3: Eu was also researched, the introduction of Sr into MgO-Y2O3-B2O3:Eu gives rise to a shift to longer wavelengths of the position of the excitation peak, and the emission spectra varies with the increasing of x simultaneously.

  11. Ionic transport and structural investigations on MSn(OH){sub 6} (M = Ba, Ca, Mg, Co, Zn, Fe, Mn) hydroxide perovskites synthesized by wet sonochemical methods

    Jena, Hrudananda [Materials Chemistry Division, Indira Gandhi Centre for Atomic Research, Kalpakkam 603102 (India)]. E-mail:; Kutty, K.V. Govindan [Materials Chemistry Division, Indira Gandhi Centre for Atomic Research, Kalpakkam 603102 (India); Kutty, T.R.N. [Materials Research Centre, Indian Institute of Science, Bangalore 560012 (India)


    Hydroxide perovskites of MSn(OH){sub 6} (M = Ba, Ca, Mg, Co, Zn, Fe or Mn) were synthesized by co-precipitation and sonochemical reaction routes. Some of the compounds were also prepared by the hydrothermal method. These were characterized by XRD, TGA/DTA, TEM and IR studies. The hydroxide perovskites are stable up to {approx}523 K and all the compounds stabilize in cubic crystal system (SG = Pn3m) at 298-523 K except BaSn(OH){sub 6}. The as-prepared powders of the above compositions show cubic square net in the reciprocal lattice of their electron diffraction patterns. Among these perovskites; MgSn(OH){sub 6} and CoSn(OH){sub 6} exhibit proton conduction at 298-500 K. Above {approx}523 K, solid solutions of SnO{sub 2} and the corresponding MO components were observed. On heat-treatment at 850-950 K, M{sub 2-x}(V{sub M}){sub x}SnO{sub 4} (M-deficient spinel, x {<=} 1) along with SnO{sub 2} are observed. On further sintering to 1773 K for a duration of 6-7 h, M{sub 2-x}(V{sub M}){sub x}SnO{sub 4} phase is stabilized. The electrical properties of these compounds were measured by four-probe dc method. Co{sub 2-x}(V{sub Co}){sub x}SnO{sub 4} + SnO{sub 2} mixed phase showed oxide ion conductivity at 500-1273 K. The activation energy of oxide ion conduction is 0.93 eV. CaSn(OH){sub 6}does not show any type of electrical conduction at 298-850 K. The loss of proton conduction above 523 K may be ascribed to dehydroxylation and subsequent decomposition to SnO{sub 2} + M{sub 2-x}SnO{sub 4} (defect spinel, M = Mg, Zn, Co) or MSnO{sub 3} (M = Ba, Ca000.

  12. Efeitos da suplementação de fitase sobre a disponibilidade aparente de Mg, Ca, Zn, Cu, Mn e Fe em alimentos vegetais para a tilápia-do-nilo Effects of phytase supplementation on apparent availability of Mg, Ca, Zn, Cu, Mn, and Fe of plant feedstuffs for nile tilapia

    Giovani Sampaio Gonçalves


    Full Text Available Cem juvenis de tilápia-do-nilo (Oreochromis niloticus; PV = 100.0 ± 5.0 g foram distribuídos em 10 tanques-rede com o objetivo de avaliar o efeito da suplementação da enzima fitase (0, 1.000 e 2.000 UFA/kg sobre a disponibilidade de minerais em alguns alimentos energéticos (milho, milho extrusado, farelo de trigo, farelo de arroz e farelo de sorgo e protéicos (farelo de soja extrusado, farelo de soja, farelo de girassol, farelo de algodão e glúten de milho utilizados na alimentação de tilápia-do-nilo (Oreochromis niloticus. Para determinação dos coeficientes de disponibilidade aparente (CDA do cálcio (Ca, magnésio (Mg, zinco (Zn, cobre (Cu, ferro (Fe e manganês (Mn, foram confeccionadas 31 rações, marcadas com 0,10% de óxido de crômio III uma referência (ração purificada e 30 contendo os dez alimentos e os diferentes níveis de suplementação da enzima fitase. O CDA dos nutrientes foi calculado com base no teor de crômio da ração e das fezes. A fitase aumenta, nos vegetais, a disponibilidade do Mg, Cu, Zn e Mn, os quais apresentam tendência diferenciada, em razão do seu valor biológico e do nível de suplementação de enzima.One hundred Nile tilapia juveniles (Oreochromis niloticus; BW= 100.0 ± 5.0 g were assigned to 10 experimental cages to evaluate the effects of phytase supplementation (0, 1,000, and 2,000 FTU/kg on calcium (Ca, magnesium (Mg, zinc (Zn, copper (Cu, iron (Fe and manganese (Mn availability of ten feedstuffs: five energetic (corn, extruded corn, wheat meal, rice meal and low-tannin sorghum and five protein (extruded soybean, soybean meal, sunflower meal, cottonseed meal and corn gluten meal. As reference, an albumin and gelatin-based diet [with 0.10 % chromic oxide (III as external marker] was fed to the juveniles. Thirty-one diets (one reference and 30 based on all feedstuffs and increasing levels of phytase were formulated to determine the coefficients of apparent availability of minerals (Mg

  13. Thermodynamic Behavior of Manganese and Phosphorus between Liquid Iron and CaO-MgO-SiO2-Al2O3-FetO-MnO-P2O5 Slags


    The thermodynamic behavior of manganese and phosphorus betwe en liquid iron and CaO-MgO-SiO2-Al2O3-FetO-MnO-P2O5 ladle slag system was addressed by investigating the thermodynamic equilibria between li quid iron containing Mn and P and the ladle slag at 1873K. The Mn dist ribution ratio LMn increases with increasing FetO content and decreasi ng the basicity ((%CaO + %MgO)/ +%Al2O3+%P2O5)) in slag, while the P d istribution ratio LP seems to be increased as FetO content and the bas icity increases. The values of LMn and LP decrease by the addition of Al2O3 into slag. The expression of the dependence of LMn and LP on the basicity and content in slag was obtained.

  14. Direct transformation of calcium sulfite to {alpha}-calcium sulfate hemihydrate in a concentrated Ca-Mg-Mn chloride solution under atmospheric pressure

    Baohong Guan; Hailu Fu; Jie Yu; Guangming Jiang; Bao Kong; Zhongbiao Wu [Zhejiang University, Hangzhou (China). Department of Environmental Engineering


    Massive quantities of sulfite-rich flue gas desulfurization (FGD) scrubber sludge have been generated by coal burning power plants. Utilization of the sulfite-rich sludge for preparing {alpha}-calcium sulfate hemihydrate ({alpha}-HH), an important kind of cementitious material, is of particular interest to electric utilities and environmental preservation. In the experiment, calcium sulfite hemihydrate was directly transformed to {alpha}-HH without the occurrence of calcium sulfate dihydrate (DH). The transformation was performed in a concentrated CaCl{sub 2} solution containing Mg{sup 2+} and Mn{sup 2+} at 95{sup o}C, atmospheric pressure and low pH. The oxidation of calcium sulfite and the subsequent crystallization of {alpha}-HH constitute the whole conversion, during which the oxidation turns out to be the rate controlling step. Solid solution comprised of calcium sulfite hemihydrate and calcium sulfate was found to coexist with {alpha}-HH in the suspension. Calcium sulfate increases and calcium sulfite decreases spontaneously until the solid solution disappears. Thus, it is a potential alternative to utilize sulfite-rich FGD scrubber sludge for the direct preparation of {alpha}-HH. 36 refs., 10 figs., 1 tab.

  15. Analysis of (Ba,Ca,Sr){sub 3}MgSi{sub 2}O{sub 8}:Eu{sup 2+}, Mn{sup 2+} phosphors for application in solid state lighting

    Han, J.K. [University of California, San Diego, Materials Science and Engineering Program, La Jolla, CA 92093 (United States); Piqutte, A.; Hannah, M.E. [OSRAM SYLVANIA Central Research, 71 Cherry Hill Drive Beverly, MA 01915 (United States); Hirata, G.A. [Centro de Nanociencias y Nanotecnolgía, Universidad Nacional Autónoma de México, Km. 107 Carretera Tijuana-Ensenada Apdo, Ensenada MX CP 22860 (Mexico); Talbot, J.B. [University of California, San Diego, Materials Science and Engineering Program, La Jolla, CA 92093 (United States); University of California, San Diego, Department of Nanoengineering, La Jolla, CA 92093 (United States); Mishra, K.C. [OSRAM SYLVANIA Central Research, 71 Cherry Hill Drive Beverly, MA 01915 (United States); McKittrick, J., E-mail: [University of California, San Diego, Materials Science and Engineering Program, La Jolla, CA 92093 (United States); University of California, San Diego, Department of Mechanical and Aerospace Engineering, La Jolla, CA 92093 (United States)


    The luminescence properties of Eu{sup 2+} and Mn{sup 2+} co-activated (Ba,Ca,Sr){sub 3}MgSi{sub 2}O{sub 8} phosphors prepared by combustion synthesis were studied. Eu{sup 2+}-activated (Ba,Ca,Sr){sub 3}MgSi{sub 2}O{sub 8} has a broad blue emission band centered at 450–485 nm and Eu{sup 2+}–Mn{sup 2+}-activated (Ba,Ca,Sr){sub 3}MgSi{sub 2}O{sub 8} exhibits a red emission around 620–703 nm, depending on the relative concentrations of Ba, Ca and Sr. The particle size of Eu{sup 2+} and Mn{sup 2+} co-activated (Ba,Ca){sub 3}MgSi{sub 2}O{sub 8} ranges from 300 nm to 1 μm depending on the metal ion and are agglomerated due to post-synthesis, high temperature annealing. The green emission of Ba{sub 3}MgSi{sub 2}O{sub 8} originates from secondary phases (Ba{sub 2}SiO{sub 4} and BaMgSiO{sub 4}) confirmed by emission spectra and X-ray diffraction patterns. The secondary phases of Ba{sub 3}MgSi{sub 2}O{sub 8} are removed by the addition of Sr. The quantum efficiencies range from 45% to 70% under 400 nm excitation and the lifetime of red emission of Ba{sub 3}MgSi{sub 2}O{sub 8} decreases significantly with increasing temperature, which is 54% at 400 K of that at 80 K compared to that of blue emission (90% at 400 K of that at 80 K). -- highlights: • (Ba,Ca,Sr){sub 3}MgSi{sub 2}O{sub 8}:Eu{sup 2+}, Mn{sup 2+} phosphors were prepared by a combustion synthesis method. • The emission spectra consist of broad blue-emission band and red-emission band. • The quantum efficiencies range between 45% and 70%, depending on the relative concentrations of Ba, Ca and Sr. • The secondary phases were eliminated by additions of Sr. • Lifetime of the red-emission decreases with increasing temperature, suggesting that these phosphors are not useful for solid state lighting applications.

  16. 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.

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


    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.

  17. Heat capacities and thermodynamic functions of new nanosized ferro-chromo-manganites LaM0.5 IIFeCrMnO6.5 (MII-Mg, Ca, Sr, Ba)

    Kasenov, B. K.; Kasenova, Sh. B.; Sagintaeva, Zh. I.; Turtubaeva, M. O.; Kakenov, K. S.; Esenbaeva, G. A.


    The heat capacities of nanosized ferro-chromo-manganites LaM0.5 IIFeCrMnO6.5 (MII-Mg, Ca, Sr, Ba) are measured via dynamic calorimetry in the temperature range of 298.15-673 K using an IT-S-400 instrument. It is established that the C°p f( T) function of LaM0.5 IIFeCrMnO6.5 (MII-Mg, Ca, Sr, Ba) has λ-type effects, due probably to phase transitions of the second order. Considering the temperatures of the phase transitions, equations of the heat capacity of ferro-chromo-manganites LaM0.5 IIFeCrMnO6.5 (MII-Mg, Ca, Sr, Ba) as a function of temperature are derived on the basis of experimental data. Thermodynamic functions H°( T)- H°(298.15), S°( T), and V xx( T) are calculated in the temperature range of 298.15-675 K.

  18. Phase diagram prediction of systems Mn(NO3)2-M(NO3)n-H2O(M=Ca,Mg and Li) with modified BET-model

    曾德文; 樊栓狮; 陈四海


    BET-model parameters for the binary system Mn(NO3 )2-H2 O were obtained by fitting experimental water activities at 298.15 K. The values obtained in this work were compared to those fitted previously for the systems Ca(NO3)2-H2O and Zn(NO3)2-H2O, showing reasonable agreement. With the model parameters fitted at 298 K,the vapor pressure of the saturated solution for the phases Mn(NO3 )2 · 6 H2 O and Mn(NO3 )2 · 4 H2 O were predicted and shows quite good agreement with the experimental values. The phase diagram of the Mn(NO2 )2-H2O system reproduced by the BET model shows smaller deviation from the experimental data than that by the extended UNIQUAC model. The ternary phase diagrams of the systems Me(NO3)n-Mn(NO3)2-H2O (Me= Mg, Ca and Li) are predicted with the binary model parameter and compared with available experimental data. The predicted eutectic compositions were given as possible heat storage materials.

  19. Tululite, Ca14(Fe3+,Al)(Al,Zn,Fe3+,Si,P,Mn,Mg)15O36: a new Ca zincate-aluminate from combustion metamorphic marbles, central Jordan

    Khoury, Hani N.; Sokol, Ella V.; Kokh, Svetlana N.; Seryotkin, Yurii V.; Nigmatulina, Elena N.; Goryainov, Sergei V.; Belogub, Elena V.; Clark, Ian D.


    Tululite (Ca14(Fe3+,Al)(Al,Zn,Fe3+,Si,P,Mn,Mg)15O36 (the hypothetical end-member formula Ca14{Fe3+O6}[SiO4][Zn5Al9]O26) (IMA2014-065) is a new natural Ca zincate-aluminate, identified in medium-temperature (800-850 °C) combustion metamorphic (CM) spurrite-fluorellestadite marbles from central Jordan. The type locality (Tulul Al Hammam area) is situated in the northern part of the Siwaqa complex, the largest area of the "Mottled Zone" Formation in the Dead Sea region. The marbles originated from bitumen-rich chalky marine sediments of the Maastrichtian-Paleogene Muwaqqar Chalk Marl Formation, which have low clay content (and, consequently, low Al) and high Zn, Cd, and U enrichments. The bulk CM rocks derived from the low-Al protolith have unusually high (Zn + Cd)/Al ratios ( 0.2) and, as a result, a mineralogy with negligibly small percentages of Ca aluminates having low Ca:Al molar ratios (minerals of mayenite supergroup, Ca:Al = 6:7) common to most of calcareous CM rocks in the Mottled Zone. Instead, the mineral assemblage of the Zn-rich marbles contains tululite, with high Ca:Al = 2.55 molar ratios and Zn substituting for a large portion of Al (Zn:Al = 1.1). Tululite occurs in thin clusters as irregular grains with indented outlines (20-100 μm in size), having typical open-work textures associated with rock-forming calcite, fluorellestadite, spurrite, and accessory Zn-rich periclase, lime-monteponite solid solutions, calcium uranates, and zincite. Marbles also bear brownmillerite, dorrite, fluormayenite, high-fluorine Ca aluminate, and lakargiite. Secondary phases are brucite, gel-like calcium silicate hydrates and calcium silicate aluminate hydrates, including Zn- and U-bearing and Cd-rich compounds, Si-bearing hydrated compounds after calcium uranates, and basic Cd chlorides. The empirical formula of the holotype tululite (a mean of 32 analyses) is (Ca13.29Cd0.75)Σ14.04(Al5.46Zn5.20Fe3+ 2.23Si0.95Mn3+ 1.01Mg0.78P0.41)Σ16.04O36. Tululite is cubic, space

  20. Substitution of Mn for Mg in MgB_2*

    Fitzpatrick, Michael D.; Johnston, David C.; Miller, Lance L.; Hill, Julienne M.


    The study of solid solutions in which the Mg in MgB2 is partially replaced by magnetic 3d or 4f atoms can potentially reveal important information on the superconducting state of MgB_2. As an end-member of the hypothetical Mg_1-xMn_xB2 system, MnB2 is isostructural with MgB2 and is an antiferromagnet below TN = 760 K which becomes canted at 157 K. A previous study by Moritomo et al.[1] examined the structure and properties of multi-phase samples with 0.01J. Phys. Soc. Japan b70, 1889 (2001).; “Effects of transition metal doping in MgB2 superconductor", Y. Moritomo at al. arXiv:cond-mat/0104568.

  1. Synthesis of Ba0.905Ca0.845Mg0.25SiO4:xEu2+, yMn2+ White-Light Phosphors with the Single-Stage Method and Their Luminescent Properties%用一步法合成Ba0.905Ca0.845Mg0.25Si04:xEu2+,yMn2+白光荧光粉及其发光性能

    陈永杰; 李郎楷; 肖林久; 郑志辉; 谢颖


    采用高温同相法合成一系列碱土硅酸盐Ba0.905Ca0.845Mg0.25SiO4:xEu2+,yMn2+(x、y为摩尔比)荧光粉.探讨烧结温度、时间、助熔剂BaCl2和Eu22+及Mn2+掺量对荧光粉发光性能的影响.通过热重一差热分析确定荧光粉的合成温度,用X射线衍射、扫描电子显微镜和荧光光谱表征荧光粉的结构、形貌和发光性能.1 000~1 100℃合成的Ba0.905Ca0.845Mg0 25SiO4:Eu2+荧光粉具有Ba1.31Ca0.69SiO4和BaCa2Mg(SiO4)2晶相、在300~410nm有强吸收,可与紫光InGaN基发光二极管芯片(340~420nm)匹配,在紫光激发下,发射覆盖蓝光到红光连续光谱的白光,可很好地应用于白光发光二极管.%A series of Ba0.905Ca0.845Mg0.25SiO4:xEu2+,yMn2+ phosphors were synthesized by the high-temperature solid-state reaction method. Influence of firing temperature and time, fluxing agent BaCl2 and dosages of Eu2+ & Mn2+ on luminescence properties were investigated. A better preparation temperature was determined by the thermogravimetric-differential thermal analysis, and morphology, topography and luminescence properties of the phosphors were checked by the X-ray diffraction, scanning electron microscopy and fluorescence spectra, respectively. The Ba0.905Ca0.845Mg0.25SiOn:Eu2+ phosphors synthesized under 1 000-1 100 ℃ have both Ba1.31Ca0.69SiO4 and BaCa2Mg(SiO4)2 phases. Ba0.905Ca0.845Mg0.25SiO4:xEu2+, yMn2+ phosphors have a strong absorption for ultraviolet (UV) light between 300 nm and 410 nm, and are comparable to UV InGaN-based light-emitting diodes (LED) chips (340420 nm). These phosphors can emit white light with a continuous spectrum under UV light excitation, covering from blue light to red-light, and can be better applied in white LEDs.

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

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


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

  3. 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

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


    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

  4. Ca3Mn2O7.

    Guiblin, Nicolas; Grebille, Dominique; Leligny, Henri; Martin, Christine


    The tricalcium dimanganese heptaoxide (Ca3Mn2O7) member of the Ruddlesden-Popper series Ca(n+1)Mn(n)O(3n+1), i.e. with n = 2, was previously reported with an I-centred tetragonal lattice [a(t) = 3.68 and c(t) = 19.57 A] by Fawcett, Sunstrom, Greenblatt, Croft & Ramanujachary [Chem. Mater. (1998), 10, 3643-3651]. It is now found to be orthorhombic, with an A-centred lattice [a = 5.2347 (6), b = 5.2421 (2) and c = 19.4177 (19) A]. The structure has been refined in space group A2(1)am using X-ray single-crystal diffraction data and assuming the existence of twin domains related by the (1-10) plane. A comparison with the basic perovskite structure CaMnO3 (n = infinity) is proposed.

  5. Magnetization and ESR studies of La{sub 0.67}(Ca{sub 1−x}Mg{sub x}){sub 0.33}MnO{sub 3} systems

    Sendil Kumar, A., E-mail: [School of Physics, University of Hyderabad, Hyderabad, Telangana, 500 046 (India); Ravinder Reddy, K [School of Engineering Sciences & Technology, University of Hyderabad, Hyderabad, Telangana, 500 046 (India); Bhatnagar, Anil K. [School of Physics, University of Hyderabad, Hyderabad, Telangana, 500 046 (India); School of Engineering Sciences & Technology, University of Hyderabad, Hyderabad, Telangana, 500 046 (India)


    Highlights: • Mg substitution reduces the ferromagnetic strength. • Inhomogeneous broadening is due to phase separation. • Griffiths phase existence is probed. - Abstract: Magnetization studies and line shape analysis on Electron Spin Resonance (ESR) spectra of La{sub 0.67}(Ca{sub 1−x}Mg{sub x}){sub 0.33}MnO{sub 3} are carried out. In paramagnetic phase well above T{sub c}, the ESR spectra are single Lorentzian but below and near T{sup ∗}{sub ΔHPP}, (T{sup ∗}{sub ΔHPP} is temperature at which line width is minimum) inhomogeneous broadening with asymmetry in the signal is observed due to phase separation. The resonance field below T{sup ∗}{sub ΔHPP} decreases with decreasing temperature. Above T{sub c} the intensity of the ESR spectra obeys the thermally activated model (Arrhenius behavior). Substitution of Mg weakens the ferromagnetic interaction and evolution of change in lineshape near T{sub c} is an evidence of Griffiths phase (coexistence of paramagnetic and ferromagnetic) in Mg doped LCMO system.

  6. Synthesis and characterization of Mn intercalated Mg-Al hydrotalcite.

    Yang, Chengxue; Liao, Libing; Lv, Guocheng; Wu, Limei; Mei, Lefu; Li, Zhaohui


    Mn intercalated hydrotalcite was prepared using a reconstruction method. And Mn intercalation was confirmed by XRD, FTIR, and thermal analyses. The different valences of Mn were present as determined by XPS. Calcination slightly promoted the isomorphic replacement of Mn(2+) and Mn(3+) for Mg(2+) and Al(3+), especially the replacement of Mn(2+) for Mg(2+) and Al(3+), and to some extent, reduced Mn intercalation. Ultrasonic treatment significantly increased Mn intercalation in permanganate form (Mn(7+)), and promoted the replacement of Mn(2+) for Mg(2+) and Al(3+). XRF analysis showed that ultrasonic treatment decreased the unbalanced layer charge of Mn intercalated hydrotalcite, while prolonged calcination increased it. These results may provide guidance on the preparation and application of Mn intercalated hydrotalcite. Extended calcination time and ultrasonic vibration increased the interlayer spacing of hydrotalcite, as a result of reduction in layer charge. As the layer charge was not completely balanced after Mn intercalation, a certain amount of CO3(2-) was re-adsorbed into the interlayer space. Mn-hydrotalcites with different layer charges, different contents of Mn with varying valences are expected to have different performances in the process of adsorption, degradation, and catalysis.

  7. Diffusion of Ca and Mg in Calcite

    Cygan, R.T.; Fisler, D.K.


    The self-diffusion of Ca and the tracer diffusion of Mg in calcite have been experimentally measured using isotopic tracers of {sup 25}Mg and {sup 44}Ca. Natural single crystals of calcite were coated with a thermally-sputtered oxide thin film and then annealed in a CO{sub 2} gas at one atmosphere total pressure and temperatures from 550 to 800 C. Diffusion coefficient values were derived from the depth profiles obtained by ion microprobe analysis. The resultant activation energies for Mg tracer diffusion and Ca self-diffusion are respectively: E{sub a}(Mg) = 284 {+-} 74 kJ/mol and E{sub a}(Ca) = 271 {+-} 80 kJ/mol. For the temperature ranges in these experiments, the diffusion of Mg is faster than Ca. The results are generally consistent in magnitude with divalent cation diffusion rates obtained in previous studies and provide a means of interpreting the thermal histories of carbonate minerals, the mechanism of dolomitization, and other diffusion-controlled processes. The results indicate that cation diffusion in calcite is relatively slow and cations are the rate-limiting diffusing species for the deformation of calcite and carbonate rocks. Application of the calcite-dolomite geothermometer to metamorphic assemblages will be constrained by cation diffusion and cooling rates. The direct measurement of Mg tracer diffusion in calcite indicates that dolomitization is unlikely to be accomplished by Mg diffusion in the solid state but by a recrystallization process.

  8. Coupling of electric charge and magnetic field via electronic phase separation in (La,Pr,Ca)MnO3/Pb(Mg1/3Nb2/3)O3-PbTiO3 multiferroic heterostructures

    Zheng, Ming; Wang, Wei


    The electric-field-tunable non-volatile resistivity and ferromagnetism switching in the (La0.5Pr0.5)0.67Ca0.33MnO3 films grown on (111)-oriented 0.7Pb(Mg1/3Nb2/3)O3-0.3PbTiO3 ferroelectric single-crystal substrates have been investigated. By combining the 180° ferroelectric domain switching and in situ X-ray diffraction and resistivity measurements, we identify that this voltage control of order parameters stems from the domain switching-induced accumulation/depletion of charge carriers at the interface rather than induced lattice strain effect. In particular, the polarization-induced charge effect (i.e., ferroelectric field effect) is strongly dependent on the magnetic field. This, together with the charge-modulated magnetoresistance and magnetization, reveals the strong correlation between the electric charge and the magnetic field. Further, we found that this coupling is essentially driven by the electronic phase separation, the relative strength of which could be determined by recording charge-tunability of resistivity [ (Δρ/ρ)c h arg e ] under various magnetic fields. These findings present a potential strategy for elucidating essential physics of perovskite manganites and delivering prototype electronic devices for non-volatile information storage.

  9. Electrochemical formation of Mg-Li-Ca alloys by codeposition of Mg, Li and Ca from LiCl-KCl-MgCl2-CaCl2 melts.

    Yan, Yong De; Zhang, Mi Lin; Xue, Yun; Han, Wei; Cao, Dian Xue; Jing, Xiao Yan; He, Li Yi; Yuan, Yi


    This work presents electrochemical formation of Mg-Li-Ca alloys via codeposition of Mg, Li and Ca on a molybdenum electrode in KCl-LiCl-MgCl(2)-CaCl(2) melts at 943 K. Cyclic voltammograms (CVs) showed that the underpotential deposition (UPD) of calcium on pre-deposited magnesium leads to the formation of a liquid Mg-Ca alloy, and the succeeding underpotential deposition of lithium on pre-deposited Mg-Ca alloy leads to the formation of a liquid Mg-Li-Ca solution. Chronopotentiometric measurements indicated that the codepositon of Mg, Li and Ca occurs at current densities more negative than -0.31 A cm(-2) in LiCl-KCl-MgCl(2) (5 wt%) melts containing 1 wt% CaCl(2). Chronoamperograms demonstrated that the onset potential for the codeposition of Mg, Li and Ca is -2.200 V, and the codeposition of Mg, Li and Ca is formed when the applied potentials are more negative than -2.200 V. X-Ray diffraction (XRD) indicated that Mg-Li-Ca alloys with different phases were formed via galvanostatic electrolysis. The microstructures of typical alpha and beta phases of Mg-Li-Ca alloys were characterized by optical microscope (OM) and scanning electron microscopy (SEM). The analysis of energy dispersive spectrometry (EDS) showed that the element Ca mainly distributes along grain boundary in Mg-Li-Ca alloys. The results of inductively coupled plasma analysis determined that the chemical compositions of Mg-Li-Ca alloys correspond with the phase structures of XRD patterns, and the lithium and calcium contents of Mg-Li-Ca alloys depend on the concentrations of MgCl(2) and CaCl(2).


    mine, have a nearly ideal "picrotephroite" composition which is halfway between ... The iron and manganese ores, which are in proximity with each other but well .... From the chemical analysis of the studied Mn-Mg olivines, the numbers of.

  11. Effects of Different Phosphorus Rates on Variations of Mn, Al, Mg and Ca Concentrations in Soil Solution and Wheat Growth in Acid Red Soil%不同磷水平对红壤溶液中锰、铝、镁和钙浓度变化以及小麦生长的影响

    邵继锋; 陈荣府; 董晓英; 沈仁芳


    为了探明不同磷水平对红壤中土壤溶液主要金属离子变化的影响以及小麦对磷的响应,确定红壤中小麦适宜的施磷水平,采用原位提取土壤溶液和比较生物量的方法,监测了短期内红壤溶液中主要金属离子浓度变化及小麦生物量的变化.结果表明:碳酸钙的加入可以显著升高酸性红壤的pH,土壤溶液中铝、锰和镁浓度显著低于未加碳酸钙处理;800 mg/kg磷处理后铝、锰、镁和钙的浓度要比未加磷处理分别至少降低47%、44%、37%和33%.随着施磷量的增加,小麦在200 mg/kg磷处理时积累的生物量最大,随后磷增加,小麦生物量反而降低.而加碳酸钙处理小麦地下部生物量随着施磷量增加则降低.结果表明碳酸钙不仅可以有效升高土壤pH,降低土壤溶液铝浓度,还降低土壤溶液中锰的浓度.磷的加入同样可以降低锰和铝的浓度,缓解铝和锰毒害.红壤中生长小麦的适宜施磷量为200 mg/kg.%To investigate the effects of different phosphorus rates on the variations of Mn, Al, Mg and Ca concentrations in soil solutions and wheat responses to phosphorus in acid red soil, a pot experiment with a non-destructive soil-solution sampler preinstalled were conducted with increasing phosphorus fertilizer levels from 0 to 800 mg/kg. The results showed that pH was increased while the concentrations of Mn, Al, Mg and Ca in soil solutions were significance lower amended with CaCO3 than without CaCO3. Compared to 0 mg/kg phosphorus treatment the concentrations of Al, Mn, Mg and Ca at least decreased 47%, 44%, 37% and 33% after 800 mg/kg phosphorus treatment no matter amended with CaCO3 or not. Wheat biomass was accumulated highest in 200 mg/kg phosphorus treatment then decreased as phosphorus rates increased. However, the root biomass trended to decline as phosphorus rate increased while the soil was amended with CaCO3. Those results indicated that CaCO3 could increase pH and decrease Mn

  12. Benthic foraminiferal Mn / Ca ratios reflect microhabitat preferences

    Koho, Karoliina A.; de Nooijer, Lennart J.; Fontanier, Christophe; Toyofuku, Takashi; Oguri, Kazumasa; Kitazato, Hiroshi; Reichart, Gert-Jan


    The Mn / Ca of calcium carbonate tests of living (rose-Bengal-stained) benthic foraminifera (Elphidium batialis, Uvigerina spp., Bolivina spissa, Nonionellina labradorica and Chilostomellina fimbriata) were determined in relation to pore water manganese (Mn) concentrations for the first time along a bottom water oxygen gradient across the continental slope along the NE Japan margin (western Pacific). The local bottom water oxygen (BWO) gradient differs from previous field study sites focusing on foraminiferal Mn / Ca and redox chemistry, therefore allowing further resolution of previously observed trends. The Mn / Ca ratios were analysed using laser ablation inductively coupled plasma-mass spectrometer (ICP-MS), allowing single-chamber determination of Mn / Ca. The incorporation of Mn into the carbonate tests reflects environmental conditions and is not influenced by ontogeny. The inter-species variability in Mn / Ca reflected foraminiferal in-sediment habitat preferences and associated pore water chemistry but also showed large interspecific differences in Mn partitioning. At each station, Mn / Ca ratios were always lower in the shallow infaunal E. batialis, occupying relatively oxygenated sediments, compared to intermediate infaunal species, Uvigerina spp. and B. spissa, which were typically found at greater depth, under more reducing conditions. The highest Mn / Ca was always recorded by the deep infaunal species N. labradorica and C. fimbriata. Our results suggest that although partitioning differs, Mn / Ca ratios in the intermediate infaunal taxa are promising tools for palaeoceanographic reconstructions as their microhabitat exposes them to higher variability in pore water Mn, thereby making them relatively sensitive recorders of redox conditions and/or bottom water oxygenation.

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

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


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

  14. Microstructure, mechanical and bio-corrosion properties of Mn-doped Mg–Zn–Ca bulk metallic glass composites

    Wang, Jingfeng, E-mail: [National Engineering Research Center for Magnesium Alloys, College of Materials Science and Engineering, Chongqing University, Chongqing 400044 (China); Huang, Song; Li, Yang; Wei, Yiyun [National Engineering Research Center for Magnesium Alloys, College of Materials Science and Engineering, Chongqing University, Chongqing 400044 (China); Xi, Xingfeng; Cai, Kaiyong [College of Bioengineering, Chongqing University, Chongqing 400044 (China)


    The effects of Mn substitution for Mg on the microstructure, mechanical properties, and corrosion behavior of Mg{sub 69−x}Zn{sub 27}Ca{sub 4}Mn{sub x} (x = 0, 0.5 and 1 at.%) alloys were investigated using X-ray diffraction, compressive tests, electrochemical treatments, and immersion tests, respectively. Microstructural observations showed that the Mg{sub 69}Zn{sub 27}Ca{sub 4} alloy was mainly amorphous. The addition of Mn decreases the glass-forming ability, which results in a decreased strength from 545 MPa to 364 MPa. However, this strength is still suitable for implant application. Polarization and immersion tests in the simulated body fluid at 37 °C revealed that the Mn-doped Mg–Zn–Ca alloys have significantly higher corrosion resistance than traditional ZK60 and pure Mg alloys. Cytotoxicity test showed that cell viabilities of osteoblasts cultured with Mn-doped Mg–Zn–Ca alloys extracts were higher than that of pure Mg. Mg{sub 68.5}Zn{sub 27}Ca{sub 4}Mn{sub 0.5} exhibits the highest bio-corrosion resistance, biocompatibility and has desirable mechanical properties, which could suggest to be used as biomedical materials in the future. - Highlights: • Novel Mn-doped Mg–Zn–Ca bulk metallic glass composites were made by copper mold cast. • The strength of the Mn-doped Mg–Zn–Ca is suitable for implant application. • The Mn-doped Mg–Zn–Ca alloys have significantly high bio-corrosion resistance. • The Mn-doped Mg–Zn–Ca alloys show better cell viabilities than that of pure Mg.

  15. Engineering multiferroism in CaMnO3.

    Bhattacharjee, Satadeep; Bousquet, Eric; Ghosez, Philippe


    Structural instabilities of CaMnO3 are investigated from first principles. We point out that, on top of a strong antiferrodistortive instability responsible for its orthorhombic ground state, the cubic perovskite structure of CaMnO3 also exhibits a weak ferroelectric instability. Although ferroelectricity is suppressed by antiferrodistortive motions, we show that it can be favored using strain or chemical engineering in order to make CaMnO3 multiferroic. We finally highlight that the ferroelectric instability of CaMnO3 is Mn-dominated. This illustrates that, contrary to common belief, ferroelectricity and magnetism are not necessarily exclusive but can be driven by the same cation.

  16. New procedure of quantitative mapping of Ti and Al released from dental implant and Mg, Ca, Fe, Zn, Cu, Mn as physiological elements in oral mucosa by LA-ICP-MS.

    Sajnóg, Adam; Hanć, Anetta; Koczorowski, Ryszard; Barałkiewicz, Danuta


    A new procedure for determination of elements derived from titanium implants and physiological elements in soft tissues by laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) is presented. The analytical procedure was developed which involved preparation of in-house matrix matched solid standards with analyte addition based on certified reference material (CRM) MODAS-4 Cormorant Tissue. Addition of gelatin, serving as a binding agent, essentially improved physical properties of standards. Performance of the analytical method was assayed and validated by calculating parameters like precision, detection limits, trueness and recovery of analyte addition using additional CRM - ERM-BB184 Bovine Muscle. Analyte addition was additionally confirmed by microwave digestion of solid standards and analysis by solution nebulization ICP-MS. The detection limits are in range 1.8μgg(-1) to 450μgg(-1) for Mn and Ca respectively. The precision values range from 7.3% to 42% for Al and Zn respectively. The estimated recoveries of analyte addition line within scope of 83%-153% for Mn and Cu respectively. Oral mucosa samples taken from patients treated with titanium dental implants were examined using developed analytical method. Standards and tissue samples were cryocut into 30µm thin sections. LA-ICP-MS allowed to obtain two-dimensional maps of distribution of elements in tested samples which revealed high content of Ti and Al derived from implants. Photographs from optical microscope displayed numerous particles with µm size in oral mucosa samples which suggests that they are residues from implantation procedure. Copyright © 2017 Elsevier B.V. All rights reserved.

  17. High-pressure compressibility and vibrational properties of (Ca,Mn)CO 3

    Liu, Jin; Caracas, Razvan; Fan, Dawei; Bobocioiu, Ema; Zhang, Dongzhou; Mao, Wendy L.


    Knowledge of potential carbon carriers such as carbonates is critical for our understanding of the deep-carbon cycle and related geological processes within the planet. Here we investigated the high-pressure behavior of (Ca,Mn)CO3 up to 75 GPa by synchrotron single-crystal X-ray diffraction, laser Raman spectroscopy, and theoretical calculations. MnCO3-rich carbonate underwent a structural phase transition from the CaCO3-I structure into the CaCO3-VI structure at 45–48 GPa, while CaCO3-rich carbonate transformed into CaCO3-III and CaCO3-VI at approximately 2 and 15 GPa, respectively. The equation of state and vibrational properties of MnCO3-rich and CaCO3-rich carbonates changed dramatically across the phase transition. The CaCO3-VI-structured CaCO3-rich and MnCO3-rich carbonates were stable at room temperature up to at least 53 and 75 GPa, respectively. The addition of smaller cations (e.g., Mn2+, Mg2+, and Fe2+) can enlarge the stability field of the CaCO3-I phase as well as increase the pressure of the structural transition into the CaCO3-VI phase.

  18. Effects of Ca additions on some Mg-alloy hydrides

    Lupu, D.; Biris, A.; Indrea, E.; Bucur, R.V.


    The hydrogenation of the alloy of composition CaMg/sub 1/ /sub 8/Ni/sub 0/ /sub 5/ containing CaMg/sub 2/ and MgNi/sub 2/ shows fast activation kinetics. The Mg/sub 2/Ni phase is observed in the dehydrided samples. The three plateaus on the hydrogen desorption isotherms correspond to the most stable magnesium hydrides observed up to now in Mg-alloy ( H = 20 to 24 kcal/mol H/sub 2/). The effects of Ca additions on the hydrogen storage capacity and desorption rates of some Mg-rich alloys have been studied. 16 references, 3 figures, 1 table.

  19. 53Mn-53Cr chronology of Ca-Fe silicates in CV3 chondrites

    MacPherson, Glenn J.; Nagashima, Kazuhide; Krot, Alexander N.; Doyle, Patricia M.; Ivanova, Marina A.


    High precision secondary ion mass-spectrometry (SIMS) analyses of kirschsteinite (CaFeSiO4) in the reduced CV3 chondrites Vigarano and Efremovka yield well resolved 53Cr excesses that correlate with 55Mn/52Cr, demonstrating in situ decay of the extinct short-lived radionuclide 53Mn. To ensure proper correction for relative sensitivities between 55Mn+ and 52Cr+ ions, we synthesized kirschsteinite doped with Mn and Cr to measure the relative sensitivity factor. The inferred initial ratio (53Mn/55Mn)0 in chondritic kirschsteinite is (3.71 ± 0.50) × 10-6. When anchored to 53Mn-53Cr relative and U-corrected 207Pb-206Pb absolute ages of the D'Orbigny angrite, this ratio corresponds to kirschsteinite formation 3.2-0.7+08 Ma after CV Ca-, Al-rich inclusions. The kirschsteinite data are consistent within error with the data for aqueously-formed fayalite from the Asuka 881317 CV3 chondrite as reported by Doyle et al. (2015), supporting the idea that Ca-Fe silicates in CV3 chondrites are cogenetic with fayalite (and magnetite) and formed during metasomatic alteration on the CV3 parent body. Concentrically-zoned crystals of kirschsteinite and hedenbergite indicate that they initially formed as near end-member compositions that became more Mg-rich with time, possibly as a result of an increase in temperature.

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

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


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

  1. 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.

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


    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.

  2. The van der Waals potentials of MgCa, MgSr, MgBa, CaSr, CaBa, and SrBa

    Wei, L. M.; Li, P.; Tang, K. T.


    Based on the facts that the potential energy curves of the homo-nuclear group 2 dimers (group IIA metal), except Be2, are conformal, and they can be described by the Tang-Toennies potential model, a set of simple combining rules are proposed for the parameters of the reduced potentials of the hetero-nuclear dimers. Together with the well-established combining rules of the range parameters of the exponential repulsion and the known dispersion coefficients, these rules enable us to determine the ground state potential energy curves of MgCa, MgSr, MgBa, CaSr, CaBa, and SrBa from those of Mg2, Ca2, Sr2, and Ba2. The determined potentials are comparable to some ab initio calculations and in excellent agreement with the experiment.

  3. The suitability of the simplified method of the analysis of coffee infusions on the content of Ca, Cu, Fe, Mg, Mn and Zn and the study of the effect of preparation conditions on the leachability of elements into the coffee brew.

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


    A fast and straightforward method of the analysis of coffee infusions was developed for measurements of total concentrations of Ca, Cu, Fe, Mg, Mn and Zn by flame atomic absorption spectrometry. Its validity was proved by the analysis of spiked samples; recoveries of added metals were found to be within 98-104% while the precision was better than 4%. The method devised was used for the analysis of re-distilled water infusions of six popular ground coffees available in the Polish market. Using the mud coffee preparation it was established that percentages of metals leached in these conditions varied a lot among analysed coffees, especially for Ca (14-42%), Mg (6-25%) and Zn (1-24%). For remaining metals, the highest extractabilities were assessed for Mn (30-52%) while the lowest for Fe (4-16%) and Cu (2-12%). In addition, it was found that the water type and the coffee brewing preparation method influence the concentration of studied metals in coffee infusions the most.

  4. Microstructure, In Vitro Corrosion Behavior and Cytotoxicity of Biodegradable Mg-Ca-Zn and Mg-Ca-Zn-Bi Alloys

    Bakhsheshi-Rad, H. R.; Hamzah, E.; Tok, H. Y.; Kasiri-Asgarani, M.; Jabbarzare, S.; Medraj, M.


    The effects of bismuth (Bi) addition on the microstructure and corrosion behavior of the Mg-Ca-Zn-Bi alloys were evaluated using electron microscopy, electrochemical test and electrochemical impedance spectroscopy. Microstructural observations showed that Mg-1.2Ca-1Zn- xBi ( x = 0.5, 1.5, 3 wt.%) are composed of Mg2Ca, Ca2Mg6Zn3 and Mg3Bi2 phases while a new phase Mg2Bi2Ca appeared after the addition of 5 and 12 wt.% Bi to the Mg-1.2Ca-1Zn alloy. Furthermore, the additions of 0.5 wt.% Bi to the Mg-1.2Ca-1Zn alloy slightly improved the corrosion behavior of the alloy, while further increase in Bi amount from 1.5 to 12 wt.% has a deleterious effect on the corrosion behavior of the ternary Mg-1.2Ca-1Zn alloy which is driven by galvanic coupling effect. Cytotoxicity tests indicate that the Mg-1.2Ca-1Zn presents higher cell viability compared to Mg-1.2Ca-1Zn-0.5Bi alloy. In addition, the cell viability of both alloys increased with increasing incubation time while diluting the extracts to 50% and 10% improved the cell viabilities. The present results suggest that the Mg-1.2Ca-1Zn-0.5Bi can be interesting candidate for the development of degradable biomaterials and it is worthwhile for further investigation in an in vivo environment.

  5. Structural Diversities in Heterometallic Mn-Ca Cluster Chemistry from the Use of Salicylhydroxamic Acid: {Mn(III)4Ca2}, {Mn(II/III)6Ca2}, {Mn(III/IV)8Ca}, and {Mn(III)8Ca2} Complexes with Relevance to Both High- and Low-Valent States of the Oxygen-Evolving Complex.

    Alaimo, Alysha A; Koumousi, Evangelia S; Cunha-Silva, Luís; McCormick, Laura J; Teat, Simon J; Psycharis, Vassilis; Raptopoulou, Catherine P; Mukherjee, Shreya; Li, Chaoran; Gupta, Sayak Das; Escuer, Albert; Christou, George; Stamatatos, Theocharis C


    One-pot reactions between the [Mn3O(O2CPh)6(py)x](+/0) triangular precursors and either CaBr2·xH2O or CaCl2·6H2O, in the presence of salicylhydroxamic acid (shaH2), have afforded the heterometallic complexes [Mn(III)4Ca2(O2CPh)4(shi)4(H2O)3(Me2CO)] (1) and (pyH)[Mn(II)2Mn(III)4Ca2Cl2(O2CPh)7(shi)4(py)4] (2), respectively, in good yields. Further reactions but using a more flexible synthetic scheme comprising the Mn(NO3)2·4H2O/Ca(NO3)2·4H2O and Mn(O2CPh)2·2H2O/Ca(ClO4)2·4H2O "metal blends" and shaH2, in the presence of external base NEt3, led to the new complexes (NHEt3)2[Mn(III)4Mn(IV)4Ca(OEt)2(shi)10(EtOH)2] (3) and (NHEt3)4[Mn(III)8Ca2(CO3)4(shi)8] (4), respectively. In all reported compounds, the anion of the tetradentate (N,O,O,O)-chelating/bridging ligand salicylhydroxime (shi(3-)), resulting from the in situ metal-ion-assisted amide-iminol tautomerism of shaH2, was found to bridge both Mn and Ca atoms. Complexes 1-4 exhibit a variety of different structures, metal stoichiometries, and Mn oxidation-state descriptions; 1 possesses an overall octahedral metal arrangement, 2 can be described as a Mn4Ca2 octahedron bound to an additional Mn2 unit, 3 consists of a Mn8 "ring" surrounding a Ca(II) atom, and 4 adopts a rectangular cuboidal motif of eight Mn atoms accommodating two Ca(II) atoms. Solid-state direct-current magnetic susceptibility studies revealed the presence of predominant antiferromagnetic exchange interactions between the Mn centers, leading to S = 0 spin ground-state values for all complexes. From a bioinorganic chemistry perspective, the reported compounds may demonstrate some relevance to both high-valent scheme (3) and lower-oxidation-level species (1, 2, and 4) of the catalytic cycle of the oxygen-evolving complex.

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

    Liang, S. H.; Tao, L. L.; Liu, D. P., E-mail:; Han, X. F., E-mail: [State Key Laboratory of Magnetism, Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing 100190 (China); Lu, Y. [Institut Jean Lamour, UMR 7198, CNRS-Nancy Université, BP 239, 54506 Vandoeuvre (France)


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

  7. The preferred orientation of Mn3 spins in magnetic multiferroic CaMn7O12

    Dai, Jian-Qing; Zhang, Hu; Song, Yu-Min


    The remarkable ferroelectricity in CaMn7O12 originates from the helicoidal spin spiral, in which the Mn3 (3b Wyckoff position) spin direction remains controversial. In this paper, the total energy, phase transition path, and spontaneous polarization of CaMn7O12 are investigated by using first-principle methods. We show that, in order to account for the giant electric polarization and the correct phase transition sequence, the relative orientation between the spins of Mn3 and Mn2 (9d Wyckoff position) sites with the same coordinate along the hexagonal c-axis can not be antiparallel, i.e. their relative orientation angle should be ϕ≈0.84π instead of ϕ=π. The most likely reason for the observation of ϕ=π can be attributed to the withdrawal of spin-orbital coupling between the Mn2 and Mn3 spins, which is caused by doping Cu2+ in the samples for neutron powder diffraction measurements.

  8. Fate of half-metallicity near interfaces: The case of NiMnSb/MgO and NiMnSi/MgO

    Zhang, Ruijing


    The electronic and magnetic properties of the interfaces between the half-metallic Heusler alloys NiMnSb, NiMnSi, and MgO have been investigated using first-principles density-functional calculations with projector augmented wave potentials generated in the generalized gradient approximation. In the case of the NiMnSb/MgO (100) interface, the half-metallicity is lost, whereas the MnSb/MgO contact in the NiMnSb/MgO (100) interface maintains a substantial degree of spin polarization at the Fermi level (∼60%). Remarkably, the NiMnSi/MgO (111) interface shows 100% spin polarization at the Fermi level, despite considerable distortions at the interface, as well as rather short Si/O bonds after full structural optimization. This behavior markedly distinguishes NiMnSi/MgO (111) from the corresponding NiMnSb/CdS and NiMnSb/InP interfaces. © 2014 American Chemical Society.

  9. Fate of half-metallicity near interfaces: the case of NiMnSb/MgO and NiMnSi/MgO.

    Zhang, Rui-Jing; Eckern, Ulrich; Schwingenschlögl, Udo


    The electronic and magnetic properties of the interfaces between the half-metallic Heusler alloys NiMnSb, NiMnSi, and MgO have been investigated using first-principles density-functional calculations with projector augmented wave potentials generated in the generalized gradient approximation. In the case of the NiMnSb/MgO (100) interface, the half-metallicity is lost, whereas the MnSb/MgO contact in the NiMnSb/MgO (100) interface maintains a substantial degree of spin polarization at the Fermi level (∼60%). Remarkably, the NiMnSi/MgO (111) interface shows 100% spin polarization at the Fermi level, despite considerable distortions at the interface, as well as rather short Si/O bonds after full structural optimization. This behavior markedly distinguishes NiMnSi/MgO (111) from the corresponding NiMnSb/CdS and NiMnSb/InP interfaces.

  10. CaMn2Al10 : Itinerant Mn magnetism on the verge of magnetic order

    Steinke, L.; Simonson, J. W.; Yin, W.-G.; Smith, G. J.; Kistner-Morris, J. J.; Zellman, S.; Puri, A.; Aronson, M. C.


    We report the discovery of CaMn2Al10 , a metal with strong magnetic anisotropy and moderate electronic correlations. Magnetization measurements find a Curie-Weiss moment of 0.83 μB/Mn , significantly reduced from the Hund's rule value, and the magnetic entropy obtained from specific heat measurements is correspondingly small, only ≈9 % of R ln 2 . These results imply that the Mn magnetism is highly itinerant, a conclusion supported by density functional theory calculations that find strong Mn-Al hybridization. Consistent with the layered nature of the crystal structure, the magnetic susceptibility χ is anisotropic below 20 K, with a maximum ratio of χ[010 ]/χ[001 ]≈3.5 . A strong power-law divergence χ (T ) ˜T-1.2 below 20 K implies incipient ferromagnetic order with a low Curie temperature TC<2 K . Our experiments indicate that CaMn2Al10 is a rare example of a system where the weak and itinerant Mn-based magnetism is poised on the verge of order.

  11. Interfacial ferromagnetism and exchange bias in CaRuO3/CaMnO3 superlattices.

    He, C; Grutter, A J; Gu, M; Browning, N D; Takamura, Y; Kirby, B J; Borchers, J A; Kim, J W; Fitzsimmons, M R; Zhai, X; Mehta, V V; Wong, F J; Suzuki, Y


    We have found ferromagnetism in epitaxially grown superlattices of CaRuO(3)/CaMnO(3) that arises in one unit cell at the interface. Scanning transmission electron microscopy and electron energy loss spectroscopy indicate that the difference in magnitude of the Mn valence states between the center of the CaMnO(3) layer and the interface region is consistent with double exchange interaction among the Mn ions at the interface. Polarized neutron reflectivity and the CaMnO(3) thickness dependence of the exchange bias field together indicate that the interfacial ferromagnetism is only limited to one unit cell of CaMnO(3) at each interface. The interfacial moment alternates between the 1 μ(B)/interface Mn ion for even CaMnO(3) layers and the 0.5 μ(B)/interface Mn ion for odd CaMnO(3) layers. This modulation, combined with the exchange bias, suggests the presence of a modulating interlayer coupling between neighboring ferromagnetic interfaces via the antiferromagnetic CaMnO(3) layers.

  12. NF3 Decomposition over Mn/MgO and Cr/MgO Without Water%NF3在Mn/MgO和Cr/MgO上的分解反应

    殷春晓; 毕翠玉; 张烽林; 徐秀峰


    Mn (NO3)2和Cr(NO3)3溶液浸渍MgO制备了Mn/MgO和Cr/MgO系列脱氟剂;考察了无水条件下,NF3在Mn/MgO和Cr/MgO上的分解反应,并对反应前后的脱氟剂进行了XRD、N2吸附-脱附和EDX表征,分析了影响脱氟活性的原因.实验结果表明,Mn/MgO的脱氟活性显著高于MgO,但Cr/MgO的脱氟活性比MgO低;在反应气体积组成2%NF3/98%He、流量50 mL/min、脱氟剂用量2 g、400℃的条件下,NF3在10%(Mn原子与MgO的质量比)Mn/MgO上的全转化时间达460 min.依据表征结果和热力学计算数据,认为NF3与Mn/MgO反应生成的表层MnF3可与MgO进行氟/氧交换,促进了MgO的氟化反应,提高了Mn/MgO的脱氟活性;而NF3与Cr/MgO反应生成的表层CrF3不能与MgO进行氟/氧交换反应,且低比表面积、低孔体积的CrF3致密层附着在MgO表面,限制了NF3扩散至MgO孔中进行分解反应,降低了Cr/MgO的脱氟活性.

  13. Microstructures and Mechanical Study of Mg Alloy Foam Based on Mg-Zn-Ca-CaCO3 System

    Erryani, A.; Pramuji, F.; Annur, D.; Amal, M. I.; Kartika, I.


    Magnesium alloy, a material that has potential to use some applications such as aerospace components, computer parts, and mobile phones. Magnesium alloy can also be a popular candidate as an orthopedic implant material for biodegradability, non-toxicity, and mechanical and physical properties that are excellent. Magnesium, one of the main macro elements required for the proper functioning of the human organism, is used to test the materials for biodegradable implants. The main objective of this study was to find out the microstructure, and mechanical characteristics of the Mg-Ca-Zn-CaCO3 alloy as porous implant materials are biodegradable. The presence of CaCO3 on the alloy functions as a foaming agent expected to produce gas bubbles during manufacturing process taken place that will form pores in the alloy. Mg-Ca-Zn-CaCO3 alloy was made by powder metallurgy method with three variations of composition (96Mg-Ca-3Zn-CaCO3, 91Mg-Ca-3Zn-5CaCO3, and 86Mg-Ca-3Zn-10CaCO3 wt%). Milling process was by using a shaker mill for 2 hours to produce a powder size distribution which was more homogeneous. The mixed powder was uniaxially pressed at a pressure of 100 MPa for 2 minutes and 200 MPa for 3 minutes into green compacts with dimensions of 10 mm in diameter and 10 mm in length. The sintering process was carried out at 650°C with a variation of holding time of 10 and 15 hours, and then the specimens were cooled down at room temperature. Microstructural analysis was performed by using X-Ray diffraction technique and Scanning electron microscopy equipped with an energy disperse spectrometry (EDS). The mechanical characteristics were analyzed by using Universal Testing Machine. The density and porosity of specimen were further measured by using Archimedes method. The results show that the optimum microstructure and mechanical characteristics are the holding time of 10 hours. The value of compression was 208.398 N/mm2, the density was 1.63 g/cc and a porosity was 18% on the

  14. Study on the Prepareration of Thermoelectric CaMnO3%CaMnO3热电陶瓷合成条件研究

    刘军伟; 刘巧丽; 路大勇; 钟滔


    利用固相反应法制备了CaMnO3热电陶瓷,探究了原料、合成温度、烧结时间对CaMnO3陶瓷结构的影响。结果表明:在纯度相同的情况下,不同厂家MnO2的结构存在较大差异,直接影响了生成物的相结构;最终以上海帝阳MnO2为原料,在1300℃/36 h烧结条件下合成出高质量的钙钛矿型 CaMnO3陶瓷。%CaMnO3 thermoelectric ceramics was prepared by solid state reaction method,the influences of reagent、temperature and sintering time on the structure of CaMnO3 were studied. The results show that MnO2 bought from different manufacturer with same purity are significantly different,which affect the composition of resultant. High purity of perovskite CaMnO3 was finally synthesized under the condition of 1 300℃/36h using MnO2 of Diyang Co.

  15. Superior solid solubility of MnSiO3 in CaSiO3 perovskite

    Li, Lin; Nagai, Takaya; Seto, Yusuke; Fujino, Kiyoshi; Kawano, Jun; Itoh, Shoich


    The silicate perovskite phase relation between CaSiO3 and MnSiO3 was investigated at 35-52 GPa and at 1,800 K using laser-heated diamond anvil cells combined with angle-dispersive synchrotron X-ray diffraction and energy-dispersive X-ray spectroscopic chemical analyses with scanning or transmission electron microscopy. We found that MnSiO3 can be incorporated into CaSiO3 perovskite up to 55, and 20 mol % of CaSiO3 is soluble in MnSiO3 perovskite. The range of 55-80 mol % of MnSiO3 in the CaSiO3-MnSiO3 perovskite system could be immiscible. We also observed that the two perovskite structured phases of the Mn-bearing CaSiO3 and the Ca-bearing MnSiO3 coexisted at these conditions. The Mn-bearing CaSiO3 perovskite has non-cubic symmetry and the Ca-bearing MnSiO3 perovskite has an orthorhombic structure with space group Pbnm. All the perovskite structured phases in the CaSiO3-MnSiO3 system convert to the amorphous phase during pressure release. MnSiO3 is the first chemical component confirmed to show such a superior solid solubility in CaSiO3 perovskite.

  16. MgO-CaO耐火材料性能研究进展%Research progress of MgO-CaO refractory

    王宏联; 崔庆阳; 薛群虎


    介绍了MgO-CaO耐火材料的特性.总结了提高MgO-CaO耐火材料的抗水化性、烧结性、抗渣性、抗剥落性等的技术措施.提出了 MgO-CaO耐火材料的发展方向,即:开发高CaO含量的MgO-CaO耐火材料;进一步开发不烧MgO-CaO耐火材料;开发水泥回转窑再MgO-CaO耐火材料.

  17. The effect of Mn and Zr additions on Fe impurities and the corrosion performance of Mg

    Gandel, Darren Samuel


    Manganese (Mn) and zirconium (Zr) are two common alloying additions in magnesium (Mg) alloys. Both of these elements, while having low solubilities in Mg, each serve a specific purpose when added to Mg. Mn is often added to improve the extrudability and formability of Mg alloys and in aluminium (Al) containing Mg alloys to produce the Al8(Mn,Fe)5 phase which is able to remove iron (Fe) impurities to dramatically improve the corrosion resistance. Zr is incorporated in Mg mainly due to its uniq...

  18. Phosphate Capacities of CaF2-MgO and CaF2-CaO-MgO Slags

    Akbari, F.; Pickles, C. A.


    Previously published sulphide capacity data and thermodynamic arguments have been employed to calculate the phosphate capacities and the phosphorus partition ratios between a molten carbon saturated iron alloy and binary CaF2-MgO slags and also ternary CaF2 -CaO-MgO slags at 1450 °C. For the CaF2-MgO binary system, a linear relationship was found between the phosphate and the sulphide capacities as follows: log ? = 1.2 log Cs + 25.2. For the ternary CaF2-CaO-MgO system at 1450 °C, the logarithm of the calculated phosphate capacities ranged from 19.47 to 20.15. With the addition of CaO, the phosphate capacities initially increased, reached a maximum and then decreased slightly. The addition of MgO to the CaF2-CaO system resulted in a decrease in the phosphate capacity. The calculated phosphorus partition ratios increased slightly with increasing mole fraction of CaO in the ternary system.

  19. Electronic structure of perovskite LaMnO{sub 3} and CaMnO{sub 3}

    Chen, B.; Zhao, Y. [University of NSW, Sydney (Australia). School of Materials Science and Engineering; Zheng, X. [University of Sydney, NSW (Australia). School of Chemistry


    Perovskite structured lanthanum manganite (LaMnO{sub 3}) can be made to exhibit both strong ferromagnetism and metallic conductivity by partial substitution of La ions (3+ valence) with 2+ valence ions such as Ca. The electronic structures of LaMnO{sub 3} and CaMnO{sub 3} were calculated using Hartree Fock-linear combination of atomic orbitals (LCAO) and Local Density-Molecular Dynamics programs. The band structure show that both are isolators. The valence energy bands are highly degenerated at {Gamma} point in reciprocal space for LaMnO{sub 3}. The conduction bands are partly degenerated in both structures. The dispersion of valence band of LaMnO{sub 3} is about 1.7 eV and the dispersion of conduction band is about 2.0 eV from {Gamma} point to M point. The top two valence bonds of CaMnO{sub 3} are quite flat. The conduction band disperse down significantly, this behaviour could give some reasons why Ca doped LaMnO{sub 3} is metallic conductor. The energy gap was obtained but overestimated as expected. The total density of states was found and compared with experimental results. The electronic images show that the interactions between Mn, Ca and three O are stronger than that between La and O. The bonding of Mn-O is pd{sigma} bond

  20. Epithelial Ca2+ and Mg2+ channels in kidney disease.

    Thebault, S.C.; Hoenderop, J.G.J.; Bindels, R.J.M.


    Many physiological functions rely on the precise maintenance of body calcium (Ca2+) and magnesium (Mg2+) balance, which is tightly regulated by the concerted actions of intestinal absorption, renal reabsorption, and exchange with bone. The kidney plays an important role in the homeostasis of divalen



    the elements with all values falling within 1-10 showing that the degree of accumulation was intensive. ... ionized water added and filtered into 50 mL standard flask. ... Distribution of Na, K, Ca, Mg in Fadama crops in Ekiti State, Nigeria. Bull.

  2. Physiology of epithelial Ca2+ and Mg2+ transport

    Graaf, S.F.J. van de; Bindels, R.J.M.; Hoenderop, J.G.J.


    Ca2+ and Mg2+ are essential ions in a wide variety of cellular processes and form a major constituent of bone. It is, therefore, essential that the balance of these ions is strictly maintained. In the last decade, major breakthrough discoveries have vastly expanded our knowledge of the mechanisms un

  3. Stability and hydrogen adsorption properties of Mg/TiMn2 interface by first principles calculation

    Dai, J. H.; Jiang, X. W.; Song, Y.


    First principles calculations were carried out to study the stability and hydrogen adsorption properties of Mg/TiMn2 interface. The surface stability and hydrogen adsorption of TiMn2 were explored. The Mn terminated (001) is the most stable surface among the considered surfaces of TiMn2 and TiMn2 surface shows better hydrogen adsorption ability than the pure Mg surface. Two models coupling the Mg(0001) surface and the TiMn2(001) surface with different terminations were constructed to explore the Mg/TiMn2 interface. The Mg(0001)/Mn terminated TiMn2(001) with interface is much more stable than that of Ti terminated system. These two interfaces both show good hydrogen adsorption ability, in which the Mn terminated interface shows - 1.62 eV of hydrogen adsorption energy. The electronic structures of the considered systems are evaluated. The negative adsorption energies of hydrogen on the surface and interface systems are further explained by the analysis of the density of states.

  4. Strong magnetic pair breaking in Mn-substituted MgB2 single crystals

    Rogacki, K.; Batlogg, B.; Karpinski, J.; Zhigadlo, N.D.; Schuck, G.; Kazakov, S.M.; Wägli, P.; Puzniak, R.; Wisniewski, A.; Carbone, F.; Brinkman, Alexander; van der Marel, D.


    Magnetic ions (Mn) were substituted in MgB2 single crystals resulting in a strong pair-breaking effect. The superconducting transition temperature, Tc, in Mg1−xMnxB2 has been found to be rapidly suppressed at an initial rate of 10 K∕%Mn, leading to a complete suppression of superconductivity at

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

    Youwen Yang


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

  6. In-situ thermal analysis and macroscopical characterization of Mg-xCa and Mg-0.5Ca-xZn alloy systems

    Farahany, Saeed [Department of Materials Engineering, Faculty of Mechanical Engineering, Universiti Teknologi Malaysia, 81310 Johor Bahru, Johor (Malaysia); Bakhsheshi-Rad, Hamid Reza, E-mail: [Department of Materials Engineering, Faculty of Mechanical Engineering, Universiti Teknologi Malaysia, 81310 Johor Bahru, Johor (Malaysia); Idris, Mohd Hasbullah [Department of Materials Engineering, Faculty of Mechanical Engineering, Universiti Teknologi Malaysia, 81310 Johor Bahru, Johor (Malaysia); Abdul Kadir, Mohammed Rafiq [Medical Implants Technology Group, Universiti Teknologi Malaysia, 81310 Johor Bahru, Johor (Malaysia); Department of Biomechanics and Biomedical Materials, Faculty of Biomedical Engineering and Health Sciences, Universiti Teknologi Malaysia, 81310 Johor Bahru, Johor (Malaysia); Lotfabadi, Amir Fereidouni [Department of Manufacturing and Industrial Engineering, Faculty of Mechanical Engineering, Universiti Teknologi Malaysia, 81310 Johor Bahru, Johor (Malaysia); Ourdjini, Ali [Department of Materials Engineering, Faculty of Mechanical Engineering, Universiti Teknologi Malaysia, 81310 Johor Bahru, Johor (Malaysia)


    Highlights: Black-Right-Pointing-Pointer The effect of Ca and Zn addition on Mg-Ca and Mg-Ca-Zn were investigated. Black-Right-Pointing-Pointer Ca and Zn addition decreased solid fraction at coherency point. Black-Right-Pointing-Pointer T{sub N}-T{sub DCP} increased by adding Ca and Zn in Mg-Ca and Mg-Ca-Zn, respectively. Black-Right-Pointing-Pointer Three reactions were detected when Zn/Ca atomic ratio less than 1.25 in Mg-Ca-Zn. Black-Right-Pointing-Pointer A new peak Mg{sub 51}Zn{sub 20} was identified in Mg-0.5Ca-9Zn in addition of other peaks. - Abstract: This research described the identification phases by thermal analysis and microscopy inspection of Mg-xCa and Mg-0.5%Ca-xZn alloys that were solidified at slow cooling rate. Analysis of cooling curve after Ca addition shows the evolution of the Mg{sub 2}Ca intermetallic phase at around 520 Degree-Sign C in addition to {alpha}-Mg phase. First derivative curves of alloys after the addition of Zn to Mg-0.5Ca alloy reveals three peaks related to {alpha}-Mg, Mg{sub 2}Ca and Ca{sub 2}Mg{sub 6}Zn{sub 3} for alloys that have Zn/Ca atomic ratio less than 1.23. The peak of Mg{sub 2}Ca reaction on the first derivative curves disappeared for alloys containing Zn/Ca ratio more than 1.23. A new peak was also observed at 330 Degree-Sign C for Mg-0.5Ca-9Zn which was identified as Mg{sub 51}Zn{sub 20}. Solid fraction at coherency point decreased with increasing Ca and Zn elements. However, coherency time and difference between the nucleation and coherency temperatures (T{sub N}-T{sub DCP}) increased by adding Ca and Zn in Mg-Ca and Mg-Ca-Zn systems.

  7. Effect of Mn on microstructure and corrosion properties of extruded Mg-1%Zn alloy

    Zhang, Z. M.; Ma, Y.; Xi, Z. Z.; Xu, C. J.; Lv, Z. L.


    The microstructure of the extruded Mg-1Zn alloy doped with different content of manganese was analyzed by optical microscopy, scanning electron microscopy with energy dispersive X-ray spectroscopy and X-ray diffractometry. The mass-loss immersion method and electrochemical test were used to evaluate the corrosion properties. The results show that the microstructure of the extruded Mg-1%Zn-x%Mn (mass fraction, x=0.4, 0.8, 1.2) alloys consists of α-Mg and α-Mn, the grain size of α-Mg decreases with increasing Mn content. Electrochemical corrosion behavior of the alloys is similar. Mn has considerable effect on the corrosion rate, the corrosion process is exacerbated by the galvanic corrosion occurred at interface between α-Mg and α-Mn. The corrosion rate increases as the Mn content increases. Mg-1%Zn-0.4% Mn alloy exhibits the best corrosion resistance between the Mg-1%Zn-x%Mn alloys

  8. Electric-Field-Tunable Ferroelastic Control of Nonvolatile Resistivity and Ferromagnetic Switching in Multiferroic La0.67Ca0.33MnO3/[PbMg1/3Nb2/3O3] 0.7[PbTiO3]0.3 Heterostructures

    Zheng, Ming; Zheng, Ren-Kui


    The electric-field-modulated nonvolatile resistivity and magnetization switching in elastically coupled La0.67Ca0.33MnO3 films grown on (111)-oriented 0.7 Pb (Mg1 /3Nb2 /3)O3-0.3 PbTiO3 substrates is achieved through the ferroelastic effect. By taking advantage of the 180° ferroelectric and non-180° ferroelastic domain switching, we identify that such changes in order parameters stem from domain-switching-induced strain rather than accumulation or depletion of charge carriers at the interface. Specifically, the strong correlation between the ferroelastic strain and the magnetic field is manifested not only by the strain-tunable magnetoresistance effect but also by the magnetically manipulated strain effect, which is essentially driven by the electronic phase separation. These findings present a potential strategy for elucidating the essential physics of the ferroelastic-strain effect and delivering prototype devices for energy-efficient and nonvolatile information storage.

  9. Structural Changes in the Mn4Ca Cluster and the Mechanism of Photosynthetic Water Splitting

    Pushkar, Y.; Yano, J.; Sauer, K.; Boussac, A.; Yachandra, V.K.


    Photosynthetic water oxidation, where water is oxidized to dioxygen, is a fundamental chemical reaction that sustains the biosphere. This reaction is catalyzed by a Mn4Ca complex in the photosystem II (PS II) oxygen-evolving complex (OEC): a multiproteinassembly embedded in the thylakoid membranes of green plants, cyanobacteria, and algae. The mechanism of photosynthetic water oxidation by the Mn4Ca cluster in photosystem II is the subject of much debate, although lacking structural characterization of the catalytic intermediates. Biosynthetically exchanged Ca/Sr-PS II preparations and x-ray spectroscopy, including extended x-ray absorption fine structure (EXAFS), allowed us to monitor Mn-Mn and Ca(Sr)-Mn distances in the four intermediate S states, S0 through S3, of the catalytic cycle that couples the one-electron photochemistry occurring at the PS II reaction center with the four-electron water-oxidation chemistry taking place at the Mn4Ca(Sr) cluster. We have detected significant changes in the structure of the complex, especially in the Mn-Mn and Ca(Sr)-Mn distances, on the S2-to-S3 and S3-to-S0 transitions. These results implicate the involvement of at least one common bridging oxygen atom between the Mn-Mn and Mn-Ca(Sr) atoms in the O-O bond formation. Because PS II cannot advance beyond the S2 state in preparations that lack Ca(Sr), these results show that Ca(Sr) is one of the critical components in the mechanism of the enzyme. The results also show that Ca is not just a spectator atom involved in providing a structural framework, but is actively involved in the mechanism of water oxidation and represents a rare example of a catalytically active Ca cofactor.

  10. Orientation-modulated exchange coupling in La0.67Ca0.33MnO3/CaMnO3 bilayer films

    Wang, F.; Bai, Y.; Liu, W.; Zhang, H. R.; Li, S. K.; Dai, Z. M.; Ma, S.; Zhao, X. G.; Wang, S. C.; Wang, Z. J.; Zhang, Z. D.


    Epitaxial La0.67Ca0.33MnO3/CaMnO3 (LCMO/CMO) bilayers and the reference single layers were deposited by pulsed laser deposition on (001)- and (110)-oriented SrTiO3 (STO) substrates, allowing us to perform a detailed study of the dependence of exchange coupling on crystal orientations. It is found that the exchange bias (coercive) field of the (110)-oriented LCMO/CMO bilayer are decreased (increased) compared to that of (001)-oriented bilayer, due to the enhanced (weakened) Mn3+-Mn4+ ferromagnetic double-exchange interaction of LCMO layer. It is clear that the spin flop coupling that leads to the enhanced coercivity and the spin glass state that results in the exchange bias effect can coexist and are determined by the competition between Mn3+-Mn4+ ferromagnetic double-exchange and Mn4+-Mn4+ antiferromagnetic super-exchange interactions at the interface. We propose that strong Mn3+-Mn4+ ferromagnetic double-exchange interaction facilitates the existence of spin flop coupling, not the formation of spin glass state at the LCMO/CMO interface.

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

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


    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

  12. The preferred orientation of Mn3 spins in magnetic multiferroic CaMn{sub 7}O{sub 12}

    Dai, Jian-Qing, E-mail:; Zhang, Hu; Song, Yu-Min


    The remarkable ferroelectricity in CaMn{sub 7}O{sub 12} originates from the helicoidal spin spiral, in which the Mn3 (3b Wyckoff position) spin direction remains controversial. In this paper, the total energy, phase transition path, and spontaneous polarization of CaMn{sub 7}O{sub 12} are investigated by using first-principle methods. We show that, in order to account for the giant electric polarization and the correct phase transition sequence, the relative orientation between the spins of Mn3 and Mn2 (9d Wyckoff position) sites with the same coordinate along the hexagonal c-axis can not be antiparallel, i.e. their relative orientation angle should be ϕ≈0.84π instead of ϕ=π. The most likely reason for the observation of ϕ=π can be attributed to the withdrawal of spin–orbital coupling between the Mn2 and Mn3 spins, which is caused by doping Cu{sup 2+} in the samples for neutron powder diffraction measurements. - Highlights: • In CaMn{sub 7}O{sub 12}, the preferred orientation angle of the Mn3 spins remains controversial. • The relative orientation angle between Mn3 and Mn2 spins should be 0.84π instead of π. • For ϕ=π, phase transition path and polarization are inconsistent with experiments. • The reason for observation of ϕ=π is due to Cu{sup 2+}-doping in the experimental samples.

  13. Manganese and Mn/Ca ratios in soil and vegetation in forests across the northeastern US: Insights on spatial Mn enrichment.

    Richardson, J B


    Manganese (Mn) cycling in the Critical Zone is important because of its role as an essential nutrient and potential toxicity to plants and organisms. Quantifying Mn enrichment in terrestrial environments has been limited since Mn is monoisotopic. However, elemental ratios of Mn/Ca ratios may be used to determine spatial Mn enrichment and in aboveground and belowground pools. The objectives of this study were to quantify the spatial variation in Mn concentrations and Mn/Ca ratios in foliage, bolewood, forest floor, and mineral soil horizons across the northeastern United States and compare Mn/Ca ratios to estimate enrichment. Forest floor and mineral soil samples were collected from 26 study sites across the northeastern United States and analyzed by strong acid digestion. Foliage and bolewood was collected from 12 of the 26 sites and analyzed for total Mn and Ca. Our results show forest floor and mineral soil horizon Mn concentrations and Mn/Ca ratios were higher at Pennsylvania and New York sites than New Hampshire and Vermont sites. Using a modified isotope equation, enrichment factors (EF) for Mn/Ca ratios were calculated to be ~3.6 in the forest floor, upper and lower mineral soil horizons at sites in New York and Pennsylvania compared to reference sites in New Hampshire and Vermont. Foliar and bolewood Mn concentrations also decreased from Pennsylvania towards New Hampshire. Moreover, foliar and bolewood Mn concentrations were strongly correlated to forest floor, upper, and lower mineral soil Mn concentrations. It was hypothesized that internal cycling (uptake, throughfall, and litterfall) of Mn controls retention of enriched Mn in forests. Geologic influences from a lithologic gradient and soil pH gradient could also influence Mn enrichment in addition to Mn pollution. Ratios of Mn/Ca and other elemental ratios hold promise as geochemical tracers but require further development. Copyright © 2016 Elsevier B.V. All rights reserved.

  14. The effect of Ca2+ ions and ionic strength on Mn(II) oxidation by spores of the marine Bacillus sp. SG-1

    Toyoda, Kazuhiro; Tebo, Bradley M.


    Manganese(IV) oxides, believed to form primarily through microbial activities, are extremely important mineral phases in marine environments where they scavenge a variety of trace elements and thereby control their distributions. The presence of various ions common in seawater are known to influence Mn oxide mineralogy yet little is known about the effect of these ions on the kinetics of bacterial Mn(II) oxidation and Mn oxide formation. We examined factors affecting bacterial Mn(II) oxidation by spores of the marine Bacillus sp. strain SG-1 in natural and artificial seawater of varying ionic conditions. Ca2+ concentration dramatically affected Mn(II) oxidation, while Mg2+, Sr2+, K+, Na+ and NO3- ions had no effect. The rate of Mn(II) oxidation at 10 mM Ca2+ (seawater composition) was four or five times that without Ca2+. The relationship between Ca2+ content and oxidation rate demonstrates that the equilibrium constant is small (on the order of 0.1) and the binding coefficient is 0.5. The pH optimum for Mn(II) oxidation changed depending on the amount of Ca2+ present, suggesting that Ca2+ exerts a direct effect on the enzyme perhaps as a stabilizing bridge between polypeptide components. We also examined the effect of varying concentrations of NaCl or KNO3 (0-2000 mM) on the kinetics of Mn(II) oxidation in solutions containing 10 mM Ca2+. Mn(II) oxidation was unaffected by changes in ionic strength (I) below 0.2, but it was inhibited by increasing salt concentrations above this value. Our results suggest that the critical coagulation concentration is around 200 mM of salt (I = ca. 0.2), and that the ionic strength of seawater (I > 0.2) accelerates the precipitation of Mn oxides around the spores. Under these conditions, the aggregation of Mn oxides reduces the supply of dissolved O2 and/or Mn2+ and inhibits the Mn(II) → Mn(III) step controlling the enzymatic oxidation of Mn(II). Our results suggest that the hardness and ionic strength of the aquatic environment

  15. Development of MgO-CaO crucible for vacuum smelting%真空冶炼用MgO-CaO坩埚的研制

    刘彦海; 段百泉; 胡希东



  16. Atomic Structure of Ca40+xMg25Cu35-x Metallic Glasses (Preprint)


    13 Approved for public release; distribution unlimited fivefold bonds, with local atom arrangements very similar to the competing Mg2Cu ( Laves phase ...Ca50Mg25Cu25 alloys forms three equally probable crystal phases , CaMg2 Cu2Mg and CaCu [5,6]. CaMg2 is a hexagonal Laves phase (space group P63/mmc...containing 12 Mg and 4 Ca atoms in the first shell. Cu2Mg is a cubic Laves phase (space group is Fd-3m, space group number 227) with the lattice

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

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


    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.

  18. Effect of nonmagnetic substituents Mg and Zn on the phase competition in the multiferroic antiferromagnet MnWO4

    Meddar, Lynda; Josse, Michael; Deniard, Philippe; La, Carole; André, Gilles; Damay, Françoise; Petricek, Vaclav; Jobic, Stéphane; Whangbo, Myung-Hwan; Maglione, Mario; Payen, Christophe


    The effects of substituting nonmagnetic Mg2+ and Zn2+ ions for the Mn2+ (S = 5/2) ions on the structural, magnetic and dielectric properties of the multiferroic frustrated antiferromagnet MnWO4 were investigated. Polycrystalline samples of Mn1-xMgxWO4 and Mn1-xZnxWO4 (0

  19. Infrared study of the phonon modes in PrMnO{sub 3} and CaMnO{sub 3}

    Sopracase, Rodolphe; Gruener, Gisele; Olive, Enrick [Universite Francois Rabelais, Laboratoire d' Electrodynamyque des Materiaux Avances, UMR CNRS - CEA 6157, Parc de Grandmont, 37200 Tours (France); Soret, Jean-Claude, E-mail: soret@phys.univ-tours.f [Universite Francois Rabelais, Laboratoire d' Electrodynamyque des Materiaux Avances, UMR CNRS - CEA 6157, Parc de Grandmont, 37200 Tours (France)


    The infrared (IR) reflectivity spectra of orthorhombic manganese perovskites PrMnO{sub 3} and CaMnO{sub 3} are studied in the frequency range of optical phonon modes at temperatures varying from 300 to 4 K. The IR phonon spectra of these two materials are analyzed by a fitting procedure based on a Lorentz model, and assigned to definite vibrational modes of Pnma structures by comparison with the results of lattice dynamical calculations. The calculations have been performed in the framework of a shell model using short range Born-Mayer-Buckingham and long range Coulomb potentials, whose parameters have been optimized in order that the calculated Raman and IR active phonon frequencies, and lattice parameters match with their experimental values. We find a close correspondence between the values of the IR phonon frequencies of PrMnO{sub 3} and CaMnO{sub 3}, which shows that the substitution of the Pr{sup 3+} ions with Ca{sup 2+} results in a reduction of the frequency of medium- and high-energy IR phonons, and an increase of the frequency of those of low-energy. Nevertheless, the experimentally obtained IR phonon amplitudes of the two materials appear to be unrelated. A comparative study of the vibrational patterns of these modes reveals that most of them correspond to complex atomic vibrations significantly different from PrMnO{sub 3} to CaMnO{sub 3} which cannot be assigned only to a given type of vibration (external, bending, or stretching modes). In particular, these results confirm that the structure of CaMnO{sub 3} is quite far from the ideal (cubic) perovskite structure.

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

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


    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.

  1. Role of charge transfer configurations in LaMnO3, CaMnO3, and CaFeO3.

    Sadoc, Aymeric; Broer, Ria; de Graaf, Coen


    A simple scheme is proposed to analyze the N-electron wave function obtained in embedded cluster calculations in valence bond terms such as ligand-to-metal charge transfer and non-charge-transfer determinants. The analysis is based on a unitary transformation of pairs of natural orbitals to optimal atomiclike orbitals. The procedure is applied to compare the degree of ionicity in NiO and MnO and to explain the existence or absence of Jahn-Teller distortions in LaMnO3, CaMnO3, and CaFeO3. The authors find that the ground state of LaMnO3 is dominated by non-charge-transfer configurations, whereas the charge transfer configurations dominate the ground state wave function in the other two perovskites.

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

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


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

    B. Kasenov


    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.

  4. Thermodynamic properties of multiferroic Mg doped YbMnO{sub 3}

    Sattibabu, Bhumireddi, E-mail: [School of Engineering Sciences and Technology, University of Hyderabad, Hyderabad 500046 (India); Bhatnagar, A.K., E-mail: [School of Engineering Sciences and Technology, University of Hyderabad, Hyderabad 500046 (India); School of Physics, University of Hyderabad, Hyderabad 500046 (India); Samatham, S. Shanmukharao; Singh, D. [Low Temperature Laboratory, UGC-DAE Consortium for Scientific Research, University Campus, Khandwa Road, Indore 452001, M.P. (India); Rayaprol, S. [UGC-DAE Consortium for Scientific Research, Mumbai Centre, BARC Campus, Mumbai 400085 (India); Das, D. [School of Engineering Sciences and Technology, University of Hyderabad, Hyderabad 500046 (India); Siruguri, V. [UGC-DAE Consortium for Scientific Research, Mumbai Centre, BARC Campus, Mumbai 400085 (India); Ganesan, V. [Low Temperature Laboratory, UGC-DAE Consortium for Scientific Research, University Campus, Khandwa Road, Indore 452001, M.P. (India)


    Highlights: • Specific heat data shows that T{sub N} increases for Mg doped YbMnO{sub 3} from 83 K to 86 K. • Yb{sub 1−x}Mg{sub x}MnO{sub 3} (x = 0.0 and 0.05) shows multiple magnetic transitions. • RCP are found to be 26.1 J/mol and 27.2 J/mol for YbMnO{sub 3} and Yb{sub 0.95}Mg{sub 0.05}MnO{sub 3}. - Abstract: Calorimetric studies of polycrystalline samples Yb{sub 1−x}Mg{sub x}MnO{sub 3} with x = 0.0 and 0.05 are reported. It is revealed that the Mg doping raises the antiferromagnetic ordering temperature, T{sub N,} from 83 K for x = 0.0 to 86 K for x = 0.05. A ferromagnetic ordering is also observed around 3 K. The broad feature in the specific heat data just above ferromagnetic ordering, is attributed to the Schottky anomaly. The estimated effective molecular fields from the Schottky analysis are H{sub mf} = 3.0 and 3.5 T for YbMnO{sub 3} and Yb{sub 0.95}Mg{sub 0.05}MnO{sub 3}, respectively. High temperature shift of Schottky anomaly with Mg doping indicates increase in effective molecular field of Mn at the Yb 4b site. The data supports that the idea that although molecular field is mainly responsible for the Schottky anomaly in Yb{sub 1−x}Mg{sub x}MnO{sub 3} and Mn{sup 3+} spin ordering also affects it. Magnetic part of the specific heat is obtained by subtracting the lattice contribution estimated using two Debye temperatures. The magnetic entropy change (ΔS{sub mag}) for pure and doped samples are 2.0 J mol{sup −1} K{sup −1} and 2.1 J mol{sup −1} K{sup −1} respectively, while the relative cooling power (RCP) calculate 26.1 J/mol, 27.2 J/mol for a field change of 10 T.

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

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


    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.


    A method of producing solid solution MgO-NiO and MgO-MnO single-crystals is presented. The com presive yield strength of MgO is shown to in crease...nearly four-fold when small amounts of either NiO or MnO is in solid solution in MgO. The cleavage and slip behavior of these alloy crystals are found to be identical to that of MgO. (Author)

  7. 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⁺.

    Michalopoulos, Charalampos; Tzamtzis, Nikolaos; Liodakis, Stylianos


    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.

  8. Magnetic and magnetotransport properties of the orthorhombic perovskites (Lu,Ca)MnO3

    Imamura, N.; Karppinen, M.; Motohashi, T.; Yamauchi, H.


    Here we extend the research of the (R,Ca)MnO3 perovskites to the smallest- R end member (Lu,Ca)MnO3 . Magnetic and magnetotransport properties of the (Lu1-xCax)MnO3 system are systematically investigated in regard to carrier doping. It is found that hole doping into the antiferromagnetic x=0.0 phase, LuMnO3 , causes a spin-glass-like magnetic competition in the wide doping range of 0.1≤x≤0.6 , whereas electron doping into the antiferromagnetic x=1.0 phase, CaMnO3 , induces a large magnetoresistance effect for 0.8≤x≤0.95 .

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

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


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

  10. Modelling the chemistry of Mn-doped MgO for bulk and (100) surfaces.

    Logsdail, Andrew J; Downing, Christopher A; Keal, Thomas W; Sherwood, Paul; Sokol, Alexey A; Catlow, C Richard A


    We have investigated the energetic properties of Mn-doped MgO bulk and (100) surfaces using a QM/MM embedding computational method, calculating the formation energy for doped systems, as well as for surface defects, and the subsequent effect on chemical reactivity. Low-concentration Mn doping is endothermic for isovalent species in the bulk but exothermic for higher oxidation states under p-type conditions, and compensated by electrons going to the Fermi level rather than cation vacancies. The highest occupied dopant Mn 3d states are positioned in the MgO band gap, about 4.2 eV below the vacuum level. Surface Mn-doping is more favourable than subsurface doping, and marginally exothermic on a (100) surface at high O2 pressures. For both types of isovalent Mn-doped (100) surfaces, the formation energy for catalytically important oxygen defects is less than for pristine MgO, with F(0) and F(2+)-centres favoured in n- and p-type conditions, respectively. In addition, F(+)-centres are stabilised by favourable exchange coupling between the Mn 3d states and the vacancy-localised electrons, as verified through calculation of the vertical ionisation potential. The adsorption of CO2 on to the pristine and defective (100) surface is used as a probe of chemical reactivity, with isovalent subsurface Mn dopants mildly affecting reactivity, whereas isovalent surface-positioned Mn strongly alters the chemical interactions between the substrate and adsorbate. The differing chemical reactivity, when compared to pristine MgO, justifies further detailed investigations for more varied oxidation states and dopant species.

  11. Evolution of Mg-5Al-0.4Mn microstructure after rare earth elements addition

    A. Żydek


    Full Text Available Mg-5Al-0.4Mn-xRE (x = 0, 1, 2, 3 wt.% magnesium alloys were prepared successfully by casting method. The microstructure wasinvestigated by light microscopy. The influence of rare earth (RE elements on the area fraction of eutectic was analysed. The obtainedresults revealed that the as-cast Mg-5Al-0.4Mn alloy consist of α - Mg matrix and eutectic α + γ (where γ is Mg17Al12. However, whilerare earth elements were added to the Mg-Al type alloy, Al11RE3 precipitates were formed. The amount of the Al11RE3 precipitatesincreased with increasing addition of RE, but the amount of γ - Mg17Al12 decreased.

  12. Coral Cd/Ca and Mn/Ca records of ENSO variability in the Gulf of California

    J. D. Carriquiry


    Full Text Available We analyzed the trace element ratios Cd/Ca and Mn/Ca in three coral colonies (Porites panamensis (1967–1989, Pavona clivosa (1967–1989 and Pavona gigantea (1979–1989 from Cabo Pulmo reef, Southern Gulf of California, Mexico, to assess the oceanographic changes caused by El Niño – Southern Oscillation (ENSO events in the Eastern Tropical North Pacific (ETNP. Interannual variations in the coral Cd/Ca and Mn/Ca ratios showed clear evidence that incorporation of Cd and Mn in the coral skeleton was influenced by ENSO conditions, but the response for each metal was controlled by different processes. The Mn/Ca ratios were significantly higher during ENSO years (p<0.05 relative to non-ENSO years for the three species of coral. In contrast, the Cd/Ca was systematically lower during ENSO years, but the difference was significant (p<0.05 only in Pavona gigantea. A decrease in the incorporation of Cd and a marked increase in Mn indicated strongly reduced vertical mixing in the Gulf of California during the mature phase of El Niño. The oceanic warming during El Niño events produces a relaxation of upwelling and a stabilization of the thermocline, which may act as a physical barrier limiting the transport of Cd from deeper waters into the surface layer. In turn, this oceanic condition can increase the residence time of particulate-Mn in surface waters, allowing an increase in the photo-reduction of particulate-Mn and the release of available Mn into the dissolved phase. These results support the use of Mn/Ca and Cd/Ca ratios in biogenic carbonates as tracers of increases in ocean stratification and trade wind weakening and/or collapse in the ETNP during ENSO episodes.

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

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


    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.

  14. CaMnO_3和LaMnO_3的电子结构研究%Study on Electronic Structures of CaMnO_3 and LaMnO_3

    朱林; 李林; 李忠虎; 魏国柱


    Density function theory(DFT) method is difficult to treat strongly correlated system,while DFT+U produces U-dependent results.The electronic structures of two typical antiferromagnetic insulators CaMnO3 and LaMnO3 in perovskite manganese oxides were investigated by using the hybrid functional HSE,which combined the DFT exchange-correlation potential and the nonlocal Hartree-Fock exact exchange potential.The relationship among the energy gap nature,the valence states of Mn,the magnetic structure was discussed.The results showed that CaMnO3 is classified as charge-transfer insulator according to ZSA(Zaanen-Sawatzky-Allen) scheme.The energy gap of LaMnO3 shows anisotropic character,in which the Mott-Hubbard character is dominant along c axis and in spin-majority channel within ab plane,while the charge-transfer character is exhibited in spin-minority channel.%密度泛函理论(DFT)方法通常难以处理强关联体系,而DFT+U方法的计算结果强烈地依赖于U的取值.利用一种混合了部分DFT交换关联势和非局域Hartree-Fock精确交换势的杂化泛函HSE方法,研究了钙钛矿锰氧化物的两个典型反铁磁绝缘体CaMnO3和LaMnO3的电子结构,分析了二者的能隙特征与Mn离子价态和磁有序态的关联.根据ZSA方案CaMnO3可划分为电荷转移型绝缘体.LaMnO3的能隙表现出各向异性特征,其中沿c轴方向及ab面内的自旋多数通道中能隙的Mott-Hubbard特征更为显著,而自旋少数通道显示出完全的电荷转移型特征.

  15. Effect of sterilization process on surface characteristics and biocompatibility of pure Mg and MgCa alloys

    Liu, X.L.; Zhou, W.R.; Wu, Y.H.; Cheng, Y. [Center for Biomedical Materials and Tissue Engineering, Academy for Advanced Interdisciplinary Studies, Peking University, Beijing 100871 (China); Zheng, Y.F., E-mail: [Center for Biomedical Materials and Tissue Engineering, Academy for Advanced Interdisciplinary Studies, Peking University, Beijing 100871 (China); State Key Laboratory for Turbulence and Complex System, College of Engineering, Peking University, Beijing 100871 (China); Department of Materials Science and Engineering, College of Engineering, Peking University, Beijing 100871 (China)


    The aim of this work was to investigate the effect of various sterilization methods on surface characteristics and biocompatibility of MgCa alloy, with pure Mg as a comparison, including steam autoclave sterilization (SA), ethylene oxide steam sterilization (EO), glutaraldehyde sterilization (GD), dry heat sterilization (DH) and Co60 γ ray radiation sterilization (R) technologies. The surface characterizations were performed by environmental scanning electron microscopy, energy-dispersive X-ray spectroscopy, X-ray photoelectron spectroscopy, grazing incidence X-ray diffraction, water contact angle and surface free energy measurement, whereas the cytotoxicity and hemocompatibility were evaluated by cellular adhesive experiment, platelet adhesion and hemolysis test. The results showed that the five sterilization processes caused more changes on the surface of MgCa alloy than that on the surface of pure Mg. The GD sterilization caused the most obvious changes on the surface of the pure Mg, and the SA sterilization made the largest alteration on the MgCa alloy surface. The GD and DH sterilization processes could cause increases on surface free energy for both pure Mg and MgCa alloys, while the other three sterilization processes reduced the surface free energy. The DH and GD sterilization processes caused the least alteration on the cell adhesion on pure Mg surface, whereas the EO sterilization performed the greatest impact on the cell adhesion on the Mg–Ca alloy surface. The hemolysis percentage of pure Mg and MgCa alloys were reduced by SA sterilization, meanwhile the other four sterilization processes increased their hemolysis percentages significantly, especially for the EO sterilization. - Highlights: • The effect of sterilization on surface chemistry and biocompatibility was studied. • Sterilization caused more surface changes on MgCa alloy than pure Mg. • Co60 γ ray radiation is the most appropriate sterilization process.

  16. Measurements of low photon doses using LiF:Mg,Cu,P and CaF{sub 2}:Cu dosimeters

    Prokert, K. [Dresden Univ. of Technology (Germany). Inst. of Radiation Protection Physics; Mann, G. [Dresden Univ. of Technology (Germany). Inst. of Radiation Protection Physics


    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.)

  17. Quantitative structural refinement of Mn K edge XANES in LaMnO{sub 3} and CaMnO{sub 3} perovskites

    Monesi, C. [Dipartimento di Fisica, Universita di ' Roma Tre' , Via Della Vasca Navale, 84, I-00146 Rome (Italy); Meneghini, C. [Dipartimento di Fisica, Universita di ' Roma Tre' , Via Della Vasca Navale, 84, I-00146 Rome (Italy) and INFM-GILDA, c/o ESRF, Grenoble (France)]. E-mail:; Bardelli, F. [Dipartimento di Fisica, Universita di ' Roma Tre' , Via Della Vasca Navale, 84, I-00146 Rome (Italy); INFM-GILDA, c/o ESRF, Grenoble (France); Benfatto, M. [INFN Laboratori Nazionali di Frascati, Via E. Fermi 40, I-00044 Frascati (Italy); Mobilio, S. [Dipartimento di Fisica, Universita di ' Roma Tre' , Via Della Vasca Navale, 84, I-00146 Rome (Italy); INFM-GILDA, c/o ESRF, Grenoble (France); INFN Laboratori Nazionali di Frascati, Via E. Fermi 40, I-00044 Frascati (Italy); Manju, U. [Solid State and Structural Chemistry Unit, Indian Institute of Science, Bangalore 560 012 (India); Sarma, D.D. [Solid State and Structural Chemistry Unit, Indian Institute of Science, Bangalore 560 012 (India)


    The special magnetotransport properties of hole doped manganese perovskites originate from a complex interplay among structural, magnetic and electronic degree of freedom. In this picture the local atomic structure around Mn ions plays a special role and this is the reason why short range order techniques like X-ray absorption spectroscopy (XAS) have been deeply exploited for studying these compounds. The analysis of near edge region features (XANES) of XAS spectra can provide very fine details of the local structure around Mn, complementary to the EXAFS, so contributing to the full understanding of the peculiar physical properties of these materials. Nevertheless the XANES analysis is complicated by the large amount of structural and electronic details involved making difficult the quantitative interpretation. This work exploits the recently developed MXAN code to achieve a full structural refinement of the Mn K edge XANES of LaMnO{sub 3} and CaMnO{sub 3} compounds; they are the end compounds of the doped manganite series La {sub x}Ca{sub 1-x}MnO{sub 3}, in which the Mn ions are present only in one charge state as Mn{sup 3+} and Mn{sup 4+} respectively. The good agreement between the results derived from the analysis of near edge and extended region of the XAS spectra demonstrates that a quantitative picture of the local structure can be obtained from structural refinement of Mn K edge XANES data in these crystalline compounds. The XANES analysis offers, in addition, the possibility to directly achieve information on the topology of local atomic structure around the absorber not directly achievable from EXAFS.

  18. Collective modes in Ca70Mg30 glass

    B Y Thakore; P N Gajjar; A R Jani


    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.

  19. Dependence of improper ferroelectricity on the preferred orientation of Mn3 spins in CaMn7O12

    Dai, Jian-Qing


    The improper ferroelectricity of CaMn7O12 is studied by examining the influence of the orientation angle of Mn3 spins on the basis of first-principles density functional theory. We analyze the helicoidal magnetic order induced forces, ionic displacements, and polarization contributions from both atomic and mode- decomposition viewpoints. Our work unambiguously reveals the critical role of the orientation angle of Mn3 spins in determining the improper ferroelectricity of CaMn7O12. The ferroelectric polarization can be reversed by changing the orientation angle of Mn3 spins without switching spin chirality of the helicoidal magnetic order. We demonstrate that the particular helicoidal magnetic order induces remarkable mismatch of the Born effective charges with the lattice symmetry, which leads to the dominant contribution to ferroelectric polarization from purely Raman-type ionic displacements. However, this significant polarization contribution from the purely Raman-type distortion cannot survive in the absence of IR-active ionic displacements.

  20. Examining the Evidence for the Influence of Carbonate Saturation State on Benthic Foraminiferal Mg/Ca

    Martin, P. A.; Lea, D. W.; McCorkle, D. C.


    Benthic foraminiferal Mg/Ca paleothermometry is based on an empirical relationship between the Mg/Ca of benthic foraminifera recovered from core tops and in situ bottom water temperatures (Rosenthal, 1997; Martin et al, in press; Lear et al, in review). While there is a tight correlation between shell Mg/Ca and temperature over a broad range of temperatures (-1 to 20 degrees C), Mg/Ca variation over the small range of deep water temperatures reveals departures from the calibration curve at low temperatures. Lower Mg/Ca values are generally associated with the deepest sites from the Atlantic and Pacific, contributing to an apparently steeper Mg/Ca-T response for abyssal benthics. The steeper response of abyssal benthics may reflect an influence of decreasing carbonate saturation with depth. Saturation related effects have already been documented for Mg in planktonic foraminifera and for other metals (Cd, Ba, and Zn) in benthic foraminifera shells (see Marchitto and ref. therein). Although it is difficult to definitively separate the effects of various environmental parameters (including temperature, depth, and relative saturation states), which often change in unison, we can use the core top Mg/Ca data to estimate the potential influence of saturation state. An alternative calibration of the benthic Mg/Ca - T relationship can be derived from core top benthic foraminifera based only on sites bathed in waters above carbonate saturation that yields a slightly smaller change in Mg/Ca per degree C (~9.5% vs. 11%) but better explains benthic Mg/Ca from the coldest sites (-1degrees C). Using this alternative Mg/Ca -T relation and a subset of data from the Ceara Rise and Ontong Java Plateau, we can estimate a maximum Mg/Ca offset attributable to saturation state. By comparing core top and downcore data, we can also address possible differences in the primary Mg-T response and carbonate saturation related effects between different genera (Cibicidoides and Uvigerina).

  1. Synthesis, structure, magnetic, electrical and electrochemical properties of Al, Cu and Mg doped MnO{sub 2}

    Hashem, Ahmed M., E-mail: [National Research Centre, Inorganic Chemistry Department, Behoes St., Dokki, Cairo (Egypt); Institute for Complex Materials, IFW Dresden, Helmholtzstr. 20, D-01069 Dresden (Germany); Abuzeid, Hanaa M. [National Research Centre, Inorganic Chemistry Department, Behoes St., Dokki, Cairo (Egypt); Narayanan, N. [Institute for Complex Materials, IFW Dresden, Helmholtzstr. 20, D-01069 Dresden (Germany); Ehrenberg, Helmut [Institute for Complex Materials, IFW Dresden, Helmholtzstr. 20, D-01069 Dresden (Germany); Materials Science, Technische Universitaet Darmstadt, Petersenstr. 23, D-64287 Darmstadt (Germany); Julien, C.M. [Universite Pierre et Marie Curie, Physicochimie des Electrolytes, Colloides et Sciences Analytiques (PECSA), 4 place Jussieu, 75005 Paris (France)


    Highlights: {yields} Al, Mg and Cu doped MnO{sub 2} as cathode in Li-ion batteries. {yields} Pure phase MnO{sub 2} for virgin and doped MnO{sub 2} were obtained. {yields} Doping elements improve the electrical conductivity of MnO{sub 2}. {yields} Electrochemical behaviour of MnO{sub 2} improved after doping by Al, Mg and Cu. - Abstract: Pure and doped manganese dioxides were prepared by wet-chemical method using fumaric acid and potassium permanganate as raw materials. X-ray diffraction patterns show that pure and Al, Cu and Mg doped manganese dioxides (d-MnO{sub 2}) crystallized in the cryptomelane-MnO{sub 2} structure. Thermal analysis show that, with the assistance of potassium ions inside the 2 x 2 tunnel, the presence of Al, Cu and Mg doping elements increases the thermal stability of d-MnO{sub 2}. The electrical conductivity of d-MnO{sub 2} increases in comparison with pure MnO{sub 2}, while Al-doped MnO{sub 2} exhibits the lower resistivity. As shown in the magnetic measurements, the value of the experimental effective magnetic moment of Mn ions decreases with introduction of dopants, which is attributed to the presence of a mixed valency of high-spin state Mn{sup 4+}/Mn{sup 3+}. Doped MnO{sub 2} materials show good capacity retention in comparison with virgin MnO{sub 2}. Al-doped MnO{sub 2} shows the best electrochemical results in terms of capacity retention and recharge efficiency.

  2. Far-infrared and dc-Magnetotransport of CaMnO3 CaRuO3 Superlattices

    Yordanov, P. [Max-Planck-Institut fur Feskorperforschung, Stuttgart, Germany; Boris, A. V. [Max-Planck-Institut fur Feskorperforschung, Stuttgart, Germany; Freeland, J. W. [Argonne National Laboratory (ANL); Kavich, J. J. [University of Illinois, Chicago; Chakhalian, J. [University of Arkansas; Lee, Ho Nyung [ORNL; Keimer, Bernhard [Max-Planck-Institut fur Feskorperforschung, Stuttgart, Germany


    We report temperature- and magnetic-field-dependent measurements of the dc resistivity and the far-infrared reflectivity (FIR) (photon energies {h_bar}{omega} = 50-700 cm{sup -1}) of superlattices comprising ten consecutive unit cells of the antiferromagnetic insulator CaMnO{sub 3}, and four to ten unit cells of the correlated paramagnetic metal CaRuO{sub 3}. Below the Neel temperature of CaMnO{sub 3}, the dc resistivity exhibits a logarithmic divergence upon cooling, which is associated with a large negative, isotropic magnetoresistance. The {omega} {yields} 0 extrapolation of the resistivity extracted from the FIR reflectivity, on the other hand, shows a much weaker temperature and field dependence. We attribute this behavior to scattering of itinerant charge carriers in CaRuO{sub 3} from sparse, spatially isolated magnetic defects at the CaMnO{sub 3}-CaRuO{sub 3} interfaces. This field-tunable 'transport bottleneck' effect may prove useful for functional metal-oxide devices.

  3. Electronic Structure and Oxidation State Changes in the Mn (4) Ca Cluster of Photosystem II

    Yano, J.; Pushkar, Y.; Messinger, J.; Bergmann, U.; Glatzel, P.; Yachandra, V.K.; /SLAC


    Oxygen-evolving complex (Mn{sub 4}Ca cluster) of Photosystem II cycles through five intermediate states (S{sub i}-states, i = 0-4) before a molecule of dioxygen is released. During the S-state transitions, electrons are extracted from the OEC, either from Mn or alternatively from a Mn ligand. The oxidation state of Mn is widely accepted as Mn{sub 4}(III{sub 2},IV{sub 2}) and Mn{sub 4}(III,IV{sub 3}) for S{sub 1} and S{sub 2} states, while it is still controversial for the S{sub 0} and S{sub 3} states. We used resonant inelastic X-ray scattering (RIXS) to study the electronic structure of Mn{sub 4}Ca complex in the OEC. The RIXS data yield two-dimensional plots that provide a significant advantage by obtaining both K-edge pre-edge and L-edge-like spectra (metal spin state) simultaneously. We have collected data from PSII samples in the each of the S-states and compared them with data from various inorganic Mn complexes. The spectral changes in the Mn 1s2p{sub 3/2} RIXS spectra between the S-states were compared to those of the oxides of Mn and coordination complexes. The results indicate strong covalency for the electronic configuration in the OEC, and we conclude that the electron is transferred from a strongly delocalized orbital, compared to those in Mn oxides or coordination complexes. The magnitude for the S{sub 0} to S{sub 1}, and S{sub 1} to S{sub 2} transitions is twice as large as that during the S{sub 2} to S{sub 3} transition, indicating that the electron for this transition is extracted from a highly delocalized orbital with little change in charge density at the Mn atoms.

  4. Thermoluminescence characteristics of MgSO sub 4 :Dy,Mn phosphor

    Luo Da Ling; Deng Zou Ping; Li Guo Zhen


    The MgSO sub 4 :Dy,Mn thermoluminescence (TL) phosphors have been prepared by co-doping with various concentrations of activators the Dy and Mn. The dose-responses to gamma-rays are studied by deconvolution of the TL glow curves. It is found that the TL sensitivity of the MgSO sub 4 :Dy,Mn phosphor is comparable to that of the phosphor LiF:Mg,Ti. Besides, there is only one main dosimetric peak at 383 deg. C in its TL glow curve. The trap parameters of the dosimetric peak were obtained as activation energy E approx 1.972 eV, the frequency-factor s approx 4.294x10 sup 1 sup 4 s sup - sup 1 and the kinetic order b approx 2 by fitting the glow curves with general-order kinetics. The area of this dosimetric peak is approx 90% of the integral area of the whole glow curve for a gamma dose range of 0.1 Gy-20 kGy. The dose response of MgSO sub 4 :Dy,Mn to gamma-rays in this dose range is supralinear. There are no radiation damage effects observed in TL glow curves above 1 kGy as that occurred in LiF dosimeters.

  5. Optical Properties and Photocatalytic Activity of Marokite-Type CaMn2O4

    WU Xue-Wei; ZHANG Hai-Xin; LIU Xiao-Jun; ZHANG Xing-Gan


    The optical properties and electronic structure of marokite-type CaMn2O4 are investigated by using UV-vis spectroscopy and the local-spin-density approximation plus the Hubbard-U (LSDA +U ) method.Four absorption bands are observed at 638nm (1.94eV),512nm (2.42eV),377nm (3.29eV) and 248nm (5.00eV),which are ascribed to the charge transfer transitions O2p↑→Mn3d eg↑,O2p↓→Mn3d eg↑,Mn3d eg↑→Mn3d t2g↓ and O2p↑→Mn3d t2g↓,respectively.We further use CaMn2O4 as a photocatalyst to decompose an azo-dye acid orange 7 (AO7) under irradiation of visible light and find that the decomposition ratio of AO7 reaches 15.9% under the irradiation of visible light for two hours.Photocatalysis with oxide semiconductors has attracted increasing attention due to its high efficiency and potential for wide applications in environmental pollution decomposition.[1-3]%The optical properties and electronic structure of marokite-type CaMn2 O4 are investigated by using UV-vis spectroscopy and the local-spin-density approximation plus the Hubbard-U (LSDA+U) method. Four absorption bands are observed at 638nm (1.94eV), 512nm (2.42eV), 377nm (3.29eV) and 248nm (5.00eV), which are ascribed to the charge transfer transitions O2p↑→Mn3d e9↑, 02p↓→Mn3d e9↑, Mn3d e9↑→Mn3d t2g↓ and O2p↑→Mn'id t2g↓, respectively. We further use CaMn2O4 as a photocatalyst to decompose an azo-dye acid orange 7 (AO7) under irradiation of visible light and find that the decomposition ratio of A07 reaches 15.9% under the irradiation of visible light for two hours.

  6. Mn(Ⅱ)在LiCI-KCI-MgCl2-MnCl2 熔盐体系中的电化学行为%Electrochemical Behavior of Mn( Ⅱ ) in the Melt LiCkl-KCl-MgCl2-MnCl2

    陈丽军; 张密林; 韩伟; 颜永得; 曹鹏


    采用循环伏安和计时电位等电化学技术研究了Mn(Ⅱ)在LiCl-KCl-MgCl2-MnCl2熔盐体系中的电还原过程和Mg-Li-Mn合金的共沉积条件.结果显示,在LiCl-KCl-MgCl2-MnCl2熔盐体系中,Mn(Ⅱ),Mg(Ⅱ)和Li(Ⅰ)的还原电位分别为-1.14,-1.78和-2.19 V.Mn先析出,在钼电极表面沉积;Mg在Mn上欠电位沉积生成Mg-Mn合金;而Li在Mg-Mn合金上欠电位沉积形成Mg-Li-Mn合金.实验结果表明,Mn(Ⅱ)在熔盐中的还原电极过程受扩散控制.Mn(Ⅱ)在熔盐中的扩散系数约为10-5 cm2/s.运用XRD技术对恒电流电解制备的Mg-Li-Mn合金进行了分析,结果表明,Mg-Li-Mn合金中含有β-Li,α-Mg和Mn 3个相.%The reduction of Mn( Ⅱ ) on a molybdenum electrode in the melt LiCl-KCl-MgCl2-MnCl2 at 898 K and the conditions of the co-deposition of Mg-Li-Mn alloys were investigated. Cyclic voltammetry and chrono-potentiometry show that the reductions of Mn( Ⅱ), Mg( Ⅱ ) and Ii( Ⅰ ) start at -1. 14, -1. 78 and -2. 19 V, respectively. And the underpotential deposition of magnesium on pre-deposited manganese leads to the formation of a liquid Mg-Mn solution, then a liquid Mg-Li-Mn solution forms for the succeeding underpotential deposition of lithium on pre-deposited Mg-Mn. The diffusion coefficient of Mn( Ⅱ ) in the melts was also calculated with different methods, which was about 10-5 cmVs. The analysis of X-ray diffraction indicate that there are three phases (β-Li, α-Mg and Mn) in the Mg-Li-Mn alloy.

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

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


    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.

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

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


    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.

  9. Calcium EXAFS establishes the Mn-Ca cluster in the oxygen-evolving complex of Photosystem II

    Cinco, Roehl M.; McFarlane Holman, Karen L.; Robblee, John H.; Yano, Junko; Pizarro, Shelly A.; Bellacchio, Emanuele; Sauer, Kenneth; Yachandra, Vittal K.


    The proximity of Ca to the Mn cluster of the photosynthetic water-oxidation complex is demonstrated by X-ray absorption spectroscopy. We have collected EXAFS data at the Ca K-edge using active PS II membrane samples that contain approximately 2 Ca per 4 Mn. These samples are much less perturbed than previously investigated Sr-substituted samples, which were prepared subsequent to Ca depletion. The new Ca EXAFS clearly shows backscattering from Mn at 3.4 angstroms, a distance that agrees with that surmised from previously recorded Mn EXAFS. This result is also consistent with earlier related experiments at the Sr K-edge, using samples that contained functional Sr, that show Mn is {approx}; 3.5 angstroms distant from Sr. The totality of the evidence clearly advances the notion that the catalytic center of oxygen evolution is a Mn-Ca heteronuclear cluster.

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


    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.

  11. Sol gel synthesis and characterization studies of Cupromanganite CaCu3Mn4O12

    Nurulhuda, A.; Warikh, A. R. M.; Hafizzal, Y.


    A single-phase CaCu3Mn4O12 electroceramic had been prepared via sol gel method and fairly well densified at relative low temperature under atmospheric condition where the crystallization of CaCu3Mn4O12 occurred due to amorphous polymeric mixture. The precursor was prepared by mixing the solutions with 0.6 M citric acid (C6H8O7) as a chelating reagent with the mol ratio 1:2. The precursor gel formed was calcined and sintered at range 400 °C to 800°C by varying dwell time. Material formations under the reported conditions have been confirmed by X-ray diffraction (XRD). The results show that the formation of CaCu3Mn4O12 started at 500 ° C and was formed completely at 700 ° C for 18 hours. The microstructure of all CaCu3Mn4O12 was analysed using field emission scanning electron microscopy (FESEM). A smaller particle size with higher grain boundary was obtained at sintering 700°C to 800°C. FESEM results show the significant influence of calcinations and sintering parameter on the microstructure behaviour of CaCu2Mn4O12.

  12. High-Resolution Structure of the Photosynthetic Mn4Ca Catalyst from X-ray Spectroscopy

    Yachandra, Vittal; Yano, Junko; Kern, Jan; Pushkar, Yulia; Sauer, Kenneth; Glatzel, Pieter; Bergmann, Uwe; Messinger, Johannes; Zouni, Athina; Yachandra, Vittal K.


    The application of high-resolution X-ray spectroscopy methods to study the photosynthetic water oxidizing complex, which contains a unique hetero-nuclear catalytic Mn4Ca cluster, are described. Issues of X-ray damage especially at the metal sites in the Mn4Ca cluster are discussed. The structure of the Mn4Ca catalyst at high-resolution which has so far eluded attempts of determination by X-ray diffraction, EXAFS and other spectroscopic techniques has been addressed using polarized EXAFS techniques applied to oriented PS II membrane preparations and PS II single crystals. A review of how the resolution of traditional EXAFS techniques can be improved, using methods such as range-extended EXAFS is presented, and the changes that occur in the structure of the cluster as it advances through the catalytic cycle are described. X-ray absorption and emission techniques (XANES and K? emission) have been used earlier to determine the oxidation states of the Mn4Ca cluster, and in this report we review the use of X-ray resonant Raman spectroscopy to understand the electronic structure of the Mn4Ca cluster as it cycles through the intermediate S-states.

  13. Photoluminescence Properties of Red-Emitting Mn2+-Activated CaAlSiN3 Phosphor for White-LEDs

    Zhang, Z.; Delsing, A.C.A.; Notten, P.H.L.; Zhao, J.; Dorenbos, P.; Hintzen, H.T.


    Mn2+-doped CaAlSiN3 phosphors have been prepared by a solid-state reaction method at high temperature and the solubility of Mn2+ in the host lattice as well as their photoluminescence properties were investigated. In CaAlSiN3, not only Ca2+ sites, but also Al3+ sites can be substituted by Mn2+ ions.

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

    Ruiyu Jiang; Honghong Shan; Chunyi Li; Chaohe Yang


    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.

  15. Magnetic manifestations of thermoluminescence excitation in CaF{sub 2}:Mn (TLD-400)

    Danilkin, Mikhail [University of Tartu, Faculty of Physics and Chemistry, Taehe 4-101, Tartu 51010 (Estonia)], E-mail:; Kirillov, Aleksei [University of Tartu, Faculty of Physics and Chemistry, Taehe 4-101, Tartu 51010 (Estonia); Klimonsky, Sergei; Kuznetsov, Vyacheslav [Mendeleyev University of Chemical Technology of Russia, Miusskaya Sqr. 9, Moscow (Russian Federation); Lust, Aime; Maendar, Hugo [University of Tartu, Faculty of Physics and Chemistry, Taehe 4-101, Tartu 51010 (Estonia); Nikiforov, Vladimir [Moscow State University, Department of Low-Temperature Physics and Superconductivity, 119899, Moscow (Russian Federation); Ratas, Arno [University of Tartu, Faculty of Physics and Chemistry, Taehe 4-101, Tartu 51010 (Estonia); Ruchkin, Aleksandr [Moscow State University, Department of Low-Temperature Physics and Superconductivity, 119899, Moscow (Russian Federation); Seeman, Viktor [University of Tartu, Faculty of Physics and Chemistry, Taehe 4-101, Tartu 51010 (Estonia)


    Magnetic susceptibility as a function of temperature (4-250K) and EPR spectra at room temperature were studied for thermoluminescence detectors (TLD) CaF{sub 2}:Mn with either stored dose information or cleaned dose by annealing. No essential variations of Mn{sup 2+} number in detectors were found due to dose storage; however, the exchange interactions between manganese ions are observed as deviations from Curie-Weiss law. These deviations are removed when samples are irradiated with high doses (250-500Gy) and appear again after dose annealing. The effect is regarded as indirect evidence of trapped exciton formation in the close vicinity of Mn{sup 2+} impurity, with the exchange interaction being destroyed by fluorine displacement from regular lattice position. The unusually high stability of trapped impurity excitons is explained by partial relaxation of lattice distortion caused by substitution of Ca{sup 2+} with a smaller Mn{sup 2+}.

  16. The Evolution and Effect of Mn Element in Mg-Zn-Mn Alloy%Mn元素在Mg-Zn-Mn合金中演变形式和作用的研究

    张丁非; 石国梁; 赵霞兵; 齐福刚


    The form and effect of Mn in Mg-6wt%Zn-lwt%Mn(ZM61) alloy were investigated by transmission electron microscopy(TEM). The results show that most Mn soluted in matrix in as-cast microstructure; a small a-mount of fine Mn dispersoids were formed during homogenization treatment; the majority of Mn precipitated as regular shape Mn dispersiods after solution treatment, the main shape of these Mn particles are regular polygon, spherical and rod-like; the form of Mn existence in as-aged samples is similar with those solution treated samples. High resolution transmission microscopy observation and fast fourier transform analysis revealed that there are cohenrent interface re-lationship between α-Mn and α-Mg, it is (1010)α-Mg//(301)α-Mn, [12l6]α-Mg//[12 3]α-Mn. According to the classical two-dimensional lattice mismatch model "Bramifit" it can be calculated that the lattice misfit between crMn and MgZn2 is only 2.14%, when their orientation relationship is (200)α-Mn//(1010)MgZnz . [012]rMn//Cl213]MgZh2. Therefore, α-Mn particles can act as heterogeneous nucleas for MgZn2 phase during aging, but the MgZn2 particles are always coar-ser than those that don't't nucleate on orMn particles.%利用透射电子显微镜(TEM)研究了Mg-6%(质量分数,下同)Zn-1% Mn(ZM61)镁合金中Mn在不同状态下的存在形式和作用.结果表明,铸态组织中大多数Mn固溶于基体中;均匀化处理以后,组织中析出少量细小的α-Mn颗粒;挤压和固溶时大部分Mn以形状规则的α-Mn颗粒的形式析出,主要有3种形态,即规则多边形(以六边形为主)、球状和棒状.通过高分辨透射电子显微分析发现,α-Mn颗粒与α-Mg基体之间存在共格界面关系((1010)α-Mg//(301)α-Mn,[1216]α-Mg//[123]α-Mn).研究还发现α-Mn颗粒可以作为时效过程中MgZn2相的异质形核核心,但依附α-Mn颗粒形核的MgZn2相都较粗大.根据二维晶格错配度“Bramifit模型”计算得出,当α-Mn颗粒与MgZn2

  17. Effects of AlMnCa and AlMnFe Alloys on Deoxidization of Low Carbon and Low Silicon Aluminum Killed Steels

    ZHAN Dong-ping; ZHANG Hui-shu; JIANG Zhou-hua


    To confirm the effects of AlMnCa and AIMnFe alloys on the deoxidization and modification of Al2O3 inclu-sions, experiments of 4-heat low carbon and low silicon aluminum killed steels deoxidized by AlMnCa and AlMnFe alloys were done in a MoSi2 furnace at 1 873 K. It is found that the 1# A1MnCa alloy has the best ability of deoxidi-zation and modification of Al2 O3 inclusions than 2# A1MnCa and A1MnFe alloys. Steel A deoxidized by 1# AlMnCa alloy has the lowest total oxygen content in the terminal steel, which is 37 × 10-6. Most of the inclusions in the steel deoxidized by 1# AIMnCa alloy are spherical CaO-containing compound inclusions, and 89. 1% of them are smaller than 10 μm. The diameter of the inclusion bigger than 50 μm is not found in the final steels deoxidized by AlMnCa alloys. Whereas, for the steels deoxidized by AlMnFe alloys, most inclusions in the terminal steel are Al2O3 or Al2O3-MnO inclusions, and a few of them are spherical, and only 76. 8% of them are smaller than 10 μm. Some in-clusions bigger than 50 μm are found in the steel D deoxidized by AlMnFe alloy.

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

    Jin-Kyu LEE; Shae K. KIM


    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.

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

    J. B. Ries


    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




    In situ high pressure energy dispersive X-ray diffraction measurements on layered perovskite-like manganate Ca3Mn2O7 under pressures up to 35 GPa have been Performed by using diamond anvil cell with synchrotron radiation.The results show that the structure of layered perovskite-like manganate Ca3Mn2O7 is unstable under pressure due to the easy compression of NaCl-type blocks.The structure of Ca3Mn2O7 underwent two phase transitions under pressures in the range of 0-35GPa.One was at about 1.3GPa with the crystal structure changing from tetragonalt go orthorhombic.The other was at about 9.5GPa with the crystal structure changing form orthorhombic back to another tetragonal.

  1. Thermoelectric properties of Ca1-xYxMnO3 and Ca0.9Y0.1-yFeyMnO3 perovskite compounds

    Thuy, Nguyen Thi; Minh, Dang Le; Van Nong, Ngo


    Polycrystalline Ca1-xYxMnO3 (x = 0.0; 0.1; 0.3; 0.5; 0.7) and Ca0.9Y0.1-yFeyMnO3 (y = 0.00; 0.01; 0.03; 0.05) compounds were prepared by solid-state reaction. X-ray diffraction (XRD) analysis revealed all XRD peaks of all the samples as identical to the orthorhombic structure. The thermoelectric...... properties of these compounds were investigated from 300 K to 1200 K. It was found that the studied samples are n-type thermoelectric material with thepower factor (PF) of the undoped (x = 0.0) sample was 1.8 × 10-4 Wm1 K2 at about 1150 K and the PF of x = 0.1 sample was 1.0 × 10-4 Wm1 K2 in the temperature...

  2. Structural and magnetic investigation of Ca2MnReO6 doped with Ce

    J. B. Depianti


    Full Text Available We have studied the properties of Ce doping in Ca-site of Ca2MnReO6 double perovskite up to 10%. These compounds have presented a monoclinic cell with P2(1/n space group. A small increase of lattice parameters in doped sample were observed through Rietveld refinement of X-ray diffraction pattern. The spectra at the Mn K-edge and Re L3-edge showed a mixed valence for Mn and Re in both samples. We do not observed any variation on Mn K-edge valence in XANES measurements under pressure. However a change was observed for Re L3-edge as a function of applied pressure. The Ce-doped sample showed a magnetic geometric frustration and a small decrease of the temperature frustration as compared with Ca2MnReO6 sample. The decrease of temperature frustration can be related to the MnO6 and ReO6 octahedral distortion.

  3. Reversal transient laser-induced voltages in La2/3Ca1/3MnO3 films

    Zhao Kun; He Meng; Lü Hui-Bin


    This paper reports that the transient laser-induced voltages have been observed in La2/3Ca1/3MnO3 thin films on MgO (001) in the absence of an applied current.A peak voltage of~0.15V Was detected in response to 0.015 J pulse of 308 nm laser.It is demonstrated that the signal polarity is reversed when the films are irradiated through the substrate rather than at the air/film interface.Off-diagonal thermoelectricity may support the inversion of the signal when the irradiation direction is reversed.

  4. Structural and magnetic properties of layered perovskite manganite LaCaBiMn2O7

    Oubla M.


    Full Text Available The layered perovskite oxide, LaCaBiMn2O7, has been prepared by the conventional aqueous solution precipitation method. The powder X-ray diffraction studies suggest that the phase crystallizes with tetragonal unit cell in the space group I4/mmm. The magnetic properties suggest that the ferromagnetic interactions are dominant and manganese ion in the phase is present in mixed valence states Mn3+and Mn4+. The thermomagnetization curve is found to obey the Bloch law. Spin wave stiffness constant D and the approximate value for JMnMnexchange interaction were estimated from the experimental results.

  5. Electric Field Control of the Ferromagnetic CaRuO3 /CaMnO3 Interface

    Grutter, Alexander; Kirby, Brian; Gray, Matthew; Flint, Charles; Suzuki, Yuri; Borchers, Julie


    Electric field control of magnetism has been recognized as one of the most important goals in nanoscale magnetics research. The most popular routes towards achieving magnetoelectric (ME) coupling have focused on heterostructures incorporating multiferroics or ferroelectrics. Such studies often rely on voltage induced distortion to induce strain in the magnetic film and alter the magnetic properties. However, successful attempts to induce ME coupling without multiferroicity or magnetoelasticity remain relatively rare. The ferromagnetic interface between the antiferromagnetic insulator CaMnO3 and the paramagnetic metal CaRuO3 is a promising candidate for direct magnetization control. This interfacial ferroagnetism is stabilized through the competition between interfacial double exchange and antiferromagnetic superexchange between adjacent Mn4+ so that the system is expected to be very sensitive to small changes in interfacial carrier density. Using polarized neutron reflectometry, we have probed the electric field dependence of the interfacial magnetization of CaRuO3/CaMnO3 bilayers deposited on SrTiO3. We find that electric fields of +/-8 kV/m are sufficient to switch the interfaces from largely ferromagnetic to completely antiferromagnetic.

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

    Langelier, Brian, E-mail: [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)


    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.

  7. Mg fractionation in crustose coralline algae: Geochemical, biological, and sedimentological implications of secular variation in the Mg/Ca ratio of seawater

    Ries, Justin B.


    The Mg/Ca ratio of seawater has varied significantly throughout the Phanerozoic Eon, primarily as a function of the rate of ocean crust production. Specimens of the crustose coralline alga Neogoniolithon sp. were grown in artificial seawaters encompassing the range of Mg/Ca ratios shown to have existed throughout the Phanerozoic. Significantly, the coralline algae's skeletal Mg/Ca ratio varied in lockstep with the Mg/Ca ratio of the artificial seawater. Specimens grown in seawater treatments formulated with identical Mg/Ca ratios but differing absolute concentrations of Mg and Ca exhibited no significant differences in skeletal Mg/Ca ratios, thereby emphasizing the importance of the ambient Mg/Ca ratio, and not the absolute concentration of Mg, in determining the Mg/Ca ratio of coralline algal calcite. Specimens grown in seawater of the lowest molar Mg/Ca ratio ( mMg/Ca = 1.0) actually changed their skeletal mineralogy from high-Mg (skeletal mMg/Ca > 0.04) to low-Mg calcite (skeletal mMg/Ca algae, which exhibit morphologies and modes of calcification comparable to Neogoniolithon sp., would have produced low-Mg calcite from the middle Cambrian to middle Mississippian and during the middle to Late Cretaceous, when oceanic mMg/Ca approached unity. By influencing the original Mg content of carbonate facies in which these algae have been ubiquitous, this condition has significant implications for the geochemistry and diagenesis of algal limestones throughout most of the Phanerozoic. The crustose coralline algae's precipitation of high-Mg calcite from seawater that favors the abiotic precipitation of aragonite indicates that these algae dictate the precipitation of the calcitic polymorph of CaCO 3. However, the algae's nearly abiotic pattern of Mg fractionation in their skeletal calcite suggests that their biomineralogical control is limited to polymorph specification and is generally ineffectual in the regulation of skeletal Mg incorporation. Therefore, the Mg/Ca ratio

  8. Chamber formation leads to Mg/Ca banding in the planktonic foraminifer

    Jonkers, L.; Buse, B.; Brummer, G.-J. A.; Hall, I.R.


    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

  9. Electronic and crystal structures of thermoelectric CaMgSi intermetallic compound

    Miyazaki, Hidetoshi, E-mail: [Department of Frontier Materials, Nagoya Institute of Technology, Nagoya 466-8555 (Japan); Inukai, Manabu [Department of Frontier Materials, Nagoya Institute of Technology, Nagoya 466-8555 (Japan); Soda, Kazuo [Department of Quantum Engineering, Graduate School of Engineering, Nagoya University, Nagoya 464-8603 (Japan); Miyazaki, Nobufumi; Adachi, Nozomu; Todaka, Yoshikazu [Department of Mechanical Engineering, Toyohashi University of Technology, Toyohashi 441-8580 (Japan); Nishino, Yoichi [Department of Frontier Materials, Nagoya Institute of Technology, Nagoya 466-8555 (Japan)


    Highlights: • We report the electronic and crystal structures of the TiNiSi-type CaMgSi compound. • CaMgSi has a semiconductor-like electronic structure with a small band gap. • CaMgSi is a Mott-type insulator owing to strongly correlated electrons effect. - Abstract: We investigated the electronic and crystal structures of a new thermoelectric material, CaMgSi compound, by using synchrotron radiation photoemission spectroscopy (SR-PES), synchrotron radiation X-ray powder diffraction (SR-XRD) measurements, and electronic band structure calculation to understand the way leading to improvement in the thermoelectric properties of this material. Electronic band structure calculation of the CaMgSi compound using the crystal structure determined from SR-XRD measurement showed a semi-metallic electronic structure with a pseudo-gap at the Fermi level. In contrast to the predicted semi-metallic electronic structure, the SR-PES results showed a small semiconductor-like gap at the Fermi level. This result revealed that the CaMgSi compound is a Mott-type insulator owing to strongly correlated electrons effect in the Ca 3d and Mg 3p states being well hybridized with those in the Si 3p states. The observed electronic structure of the CaMgSi compound suggests that an optimal carrier doping exists to best control the n- and p-type thermoelectric properties and enhance the power factors.

  10. Microstructures and mechanical properties of high strength Mg-Zn-Mn alloy


    The microstructures and mechanical properties of a new Mg-6%Zn-1%Mn (mass fraction) wrought magnesium alloy were studied, which could be extruded smoothly at 310~330 ℃ with a complete dynamic recrystallization. After solution treatment one and two-step aging techniques were used. All as-aged mierostructures contained two types of dispersed phases: ,β phases and pure α-Mn particles. The two-step aging had a better strengthening effect than the traditional one-step aging, and the strength value achieved by the two-step aging could reach that of the ZK60 wrought magnesium alloy. The outstanding precipitation strengthening effect of the alloy should be attribute to the GP zones, diffusive solute-rich zones and some metastable phases formed during the first step aging that provide more effective nuclei for Mg-Zn strengthening phases during the second step aging.

  11. Corrosion resistance of Mg-Mn-Ce magnesium alloy modified by polymer plating


    Polymeric nano-film on the surface of Mg-Mn-Ce magnesium alloy was fabricated by polymer plating of 6-dihexylamino-1,3,5-triazine-2,4-dithiol monosodium(DHN)to improve its corrosion resistance.The electrochemical reaction process was analyzed by cyclic voltammetry and two obvious peaks of oxidation reaction were observed.The static contact angle of distilled water on polymer-plated surface can be up to 106.3°while on the blank surface it is 45.8°.Potentiodynamic polarization results show that the polymeric film Can increase the corrosion potential from-1.594 V VS SCE for blank to-0.382 V VS SCE.The results of electrochemical impedance spectroscopy indicate that the charge transfer resistances of blank and polymer-plated fabricating hydrophobic film on Mg-Mn-Ce alloy surface and improving its anti-corrosion property.

  12. Electron leakage and double-exchange ferromagnetism at the interface between a metal and an antiferromagnetic insulator: CaRuO3/CaMnO3.

    Nanda, B R K; Satpathy, S; Springborg, M S


    Density-functional electronic structure studies of a prototype interface between a paramagnetic metal and an antiferromagnetic (AFM) insulator (CaRuO(3)/CaMnO(3)) reveal the exponential leakage of the metallic electrons into the insulator side. The leaked electrons in turn control the magnetism at the interface via the ferromagnetic (FM) Anderson-Hasegawa double exchange, which competes with the AFM superexchange of the bulk CaMnO3. The competition produces a FM interfacial CaMnO3 layer (possibly canted); but beyond this layer, the electron penetration is insufficient to alter the bulk magnetism.

  13. Cationic disorder and Mn{sup 3+}/Mn{sup 4+} charge ordering in the B′ and B″ sites of Ca{sub 3}Mn{sub 2}NbO{sub 9} perovskite: a comparison with Ca{sub 3}Mn{sub 2}WO{sub 9}

    López, C.A., E-mail: [INTEQUI-Área de Química General e Inorgánica “Dr. G. F. Puelles”, Facultad de Química, Bioquímica y Farmacia, Universidad Nacional de San Luis, Chacabuco y Pedernera, 5700 San Luis (Argentina); Centro Atómico Bariloche, Comisión Nacional de Energía Atómica and Instituto Balseiro, Universidad Nacional de Cuyo, 8400S.C. de Bariloche, Río Negro (Argentina); Saleta, M.E. [Centro Atómico Bariloche, Comisión Nacional de Energía Atómica and Instituto Balseiro, Universidad Nacional de Cuyo, 8400S.C. de Bariloche, Río Negro (Argentina); Pedregosa, J.C. [INTEQUI-Área de Química General e Inorgánica “Dr. G. F. Puelles”, Facultad de Química, Bioquímica y Farmacia, Universidad Nacional de San Luis, Chacabuco y Pedernera, 5700 San Luis (Argentina); Sánchez, R.D. [Centro Atómico Bariloche, Comisión Nacional de Energía Atómica and Instituto Balseiro, Universidad Nacional de Cuyo, 8400S.C. de Bariloche, Río Negro (Argentina); Alonso, J.A. [Instituto de Ciencia de Materiales de Madrid, CSIC, Cantoblanco, E-28049 Madrid (Spain); and others


    We describe the preparation, crystal structure determination, magnetic and transport properties of two novel Mn-containing perovskites, with a different electronic configuration for Mn atoms located in B site. Ca{sub 3}Mn{sup 3+}{sub 2}WO{sub 9} and Ca{sub 3}Mn{sup 3+/4+}{sub 2}NbO{sub 9} were synthesized by standard ceramic procedures; the crystallographic structure was studied from X-ray powder diffraction (XRPD) and neutron powder diffraction (NPD). Both phases exhibit a monoclinic symmetry (S.G.: P2{sub 1}/n); Ca{sub 3}Mn{sub 2}WO{sub 9} presents a long-range ordering over the B sites, whereas Ca{sub 3}Mn{sub 2}NbO{sub 9} is strongly disordered. By “in-situ” NPD, the temperature evolution of the structure study presents an interesting evolution in the octahedral size (〈Mn–O〉) for Ca{sub 3}Mn{sub 2}NbO{sub 9}, driven by a charge ordering effect between Mn{sup 3+} and Mn{sup 4+} atoms, related to the anomaly observed in the transport measurements at T≈160 K. Both materials present a magnetic order below T{sub C}=30 K and 40 K for W and Nb materials, respectively. The magneto-transport measurements display non-negligible magnetoresistance properties in the paramagnetic regime. - Graphical abstract: Comparison between the octahedron size and the magnetic behaviour for Ca{sub 3}Mn{sub 2}NbO{sub 9} in the temperature region where the charge and magnetic order occur. Display Omitted - Highlights: • Two novel Mn-containing double perovskites were obtained by solid-state reactions. • Both double perovskites are monoclinic (P2{sub 1}/n) determined by XRPD and NPD. • Ca{sub 3}Mn{sub 2}WO{sub 9} contains Mn{sup 3+} while Ca{sub 3}Mn{sub 2}NbO{sub 9} includes mixed-valence cations Mn{sup 3+}/Mn{sup 4+}. • Ca{sub 3}Mn{sub 2}NbO{sub 9} presents a charge-ordering effect between Mn{sup 3+} and Mn{sup 4+} evidenced by NPD. • The magnetic and transport studies evidenced the charge ordering in Ca{sub 3}Mn{sub 2}NbO{sub 9}.

  14. Nonstoichiometric perovskite CaMnO(3-δ) for oxygen electrocatalysis with high activity.

    Du, Jing; Zhang, Tianran; Cheng, Fangyi; Chu, Wangsheng; Wu, Ziyu; Chen, Jun


    Perovskite oxides offer efficient and cheap electrocatalysts for both oxygen reduction reactions and oxygen evolution reactions (ORR/OER) in diverse oxygen-based electrochemical technologies. In this study, we report a facile strategy to enhance the electrocatalytic activity of CaMnO3 by introducing oxygen defects. The nonstoichiometric CaMnO(3-δ) (0 < δ ≤ 0.5) was prepared through thermal reduction of pristine perovskite microspheres and nanoparticles, which were synthesized from thermal-decomposition of carbonate precursors and the Pechini route, respectively. The as-prepared samples were analyzed by chemical titration, structural refinement, thermogravimetric analysis, and energy spectrometry. In 0.1 M KOH aqueous solution, the nonstoichiometric CaMnO(3-δ) with δ near 0.25 and an average Mn valence close to 3.5 exhibited the highest ORR activity (36.7 A g(-1) at 0.70 V vs RHE, with onset potential of 0.96 V), which is comparable to that of benchmark Pt/C. Density functional theory (DFT) studies and electrical conductivity measurement revealed that the enhanced ORR kinetics is due to facilitated oxygen activation and improved electrical properties. Besides high activity, the nonstoichiometric perovskite oxides showed respectable catalytic stability. Furthermore, the moderate oxygen-defective CaMnO(3-δ) (δ ≈ 0.25) favored the OER because of the improved electrical conductivity. This study makes nonstoichiometric CaMnO(3-δ) a promising active, inexpensive bifunctional catalytic material for reversible ORR and OER.

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

    Ries, J. B.


    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"; 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/Ca2=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 seawater Mg/Ca, a probable consequence of them inducing a less controlled mode of calcification simply through the removal of CO2 via photosynthesis. This body of work also has implications for thermal

  16. Experimental 25Mg and 13C NMR and Computational Modeling Studies of Amorphous Mg-Ca Carbonates

    Singer, J. W.; Yazaydin, A. O.; Kirkpatrick, R. J.; Saharay, M.; Bowers, G. M.


    Nuclear magnetic resonance (NMR) spectroscopy of synthetic Mg-Ca amorphous carbonates (AMC-ACC) provides direct, element specific structural information about these complicated phases. The 13C, 25Mg, and 43Ca resonances are typically broad and span the chemical shift ranges of all the crystalline polymorphs in the Ca-Mg-CO3-H2O system. In a fashion similar to our previous analysis of 43Ca NMR results for ACC,1 here we integrate new experimental 13C and 25Mg spectra obtained at 20T for samples with Mg/(Ca+Mg) ratios from x=0 to x=1 with quantum chemical calculations of the NMR parameters of the crystalline phases using CASTEP calculations, simulations of the spectra using the SIMPSON software, and classical molecular dynamics calculations. XRD and 13C NMR results are in general agreement with the one-phase/two-phase model of ACC-AMC derived from thermochemical work by others.2 13C-NMR spectra of amorphous materials having intermediate compositions can not be completely fit by mechanical mixing of ACC and AMC end members—requiring a degree of Ca/Mg solid solution. Amorphous samples in two-phase region crystallize to assemblages of dolomite-like (x~0.5) and hydromagnesite-like (x~1) defective structures, but we also observe aragonite co-nucleation in the presence of excess water, indicative of a more complex evolution. While 43Ca NMR of X-ray amorphous materials shows featureless, symmetric, Gaussian line shapes, the large quadrupole moment of 25Mg gives rise to superposition of several quadrupolar line shapes representing different local structural environments. Singularities of static Mg spectra are best explained by local environments similar to nequehonite, hydromagnesite, and landsfordite. The spectra can not exclude minor contributions from anhydrous phases dolomite, huntite, and magnesite. Additional sites having very large quadrupolar coupling and/or site asymmetry are not explained by any known reference phases. CITATIONS (1) Singer, J. W.; Yazaydin, A. O

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

    WANG Jiandong; GE Changchun; SHEN Weiping


    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.

  18. Metabolismo del Mg, Cu, Zn, Cr, Mn, y Ni en la diabetes melitus


    En los últimos años, a los elementos traza y al mg se las ha implicado en la patologenesis de las complicaciones crónicas de la diabetes mellitus (dm). Las alteraciones del estado mineral asociadas a la dm podrían estar influidas, entre otros factores, por el grado de control metabólico y la asociación, o no, de otras patologías metabólicas como la hipertensión arterial (hta), la dislipemia y la obesidad. A pesar de que el mg, cu, zn, cr, mn y ni son cationes de localización principalmente in...

  19. Progress of Ca-Site Doping in Rare Earth for CaMnO3 Oxide%稀土元素Ca位掺杂CaMnO3材料的热电性能研究进展

    王艳; 张俊吉; 祝启涛; 许志忠



  20. Structural study of nanosized yttrium-doped CaMnO3 perovskites

    J Zagorac; A Zarubica; A Radosavljevic-Mihajlovic; D Zagorac; B Matovic


    Nanostructured compounds with general formula Ca1-YMnO3 (0 ≤ ≤ 1) were synthesized by modified glycine nitrate procedure. In the next step, we have investigated crystal structure and microstructure of the synthesized samples using X-ray methods and Rietveld analysis. Focus of this research was the structural stability of the yttrium-doped CaMnO3 perovskite phases, which crystallize in orthorhombic space group Pnma. We observed that the unit cell volumes of the investigated compounds increase proportionally with yttrium amount. Furthermore, we investigated the influence of yttrium amount on Mn–O bond angles and distances, tilting of MnO6 octahedra and deformation due to the presence of Jahn–Teller distortion around Mn3+ cation. In order to estimate effective coordination of and sites, bond valence calculations (BVC) were performed for and site cations. Finally, the photoelectron spectroscopy (XPS) method was applied in order to follow yttrium concentration in the perovskite phases.

  1. Interfacial Ferromagnetism in LaNiO3/CaMnO3 Superlattices

    Grutter, Alexander J.; Yang, Hao; Kirby, B. J.; Fitzsimmons, M. R.; Aguiar, Jeffery A.; Browning, Nigel D.; Jenkins, C. A.; Arenholz, Elke; Mehta, V. V.; Alaan, U. S.; Suzuki, Y.


    We observe interfacial ferromagnetism in superlattices of the paramagnetic metal LaNiO3 and the antiferromagnetic insulator CaMnO3. LaNiO3 exhibits a thickness dependent metal-insulator transition and we find the emergence of ferromagnetism to be coincident with the conducting state of LaNiO3. That is, only superlattices in which the LaNiO3 layers are metallic exhibit ferromagnetism. Using several magnetic probes, we have determined that the ferromagnetism arises in a single unit cell of CaMnO3 at the interface. Together these results suggest that ferromagnetism can be attributed to a double exchange interaction among Mn ions mediated by the adjacent itinerant metal.

  2. Interfacial ferromagnetism in LaNiO3/CaMnO3 superlattices.

    Grutter, A J; Yang, H; Kirby, B J; Fitzsimmons, M R; Aguiar, J A; Browning, N D; Jenkins, C A; Arenholz, E; Mehta, V V; Alaan, U S; Suzuki, Y


    We observe interfacial ferromagnetism in superlattices of the paramagnetic metal LaNiO3 and the antiferromagnetic insulator CaMnO3. LaNiO3 exhibits a thickness dependent metal-insulator transition and we find the emergence of ferromagnetism to be coincident with the conducting state of LaNiO3. That is, only superlattices in which the LaNiO3 layers are metallic exhibit ferromagnetism. Using several magnetic probes, we have determined that the ferromagnetism arises in a single unit cell of CaMnO3 at the interface. Together these results suggest that ferromagnetism can be attributed to a double exchange interaction among Mn ions mediated by the adjacent itinerant metal.

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

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


    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.

  4. Robertsite, Ca2MnIII3O2(PO43·3H2O

    Marcelo B. Andrade


    Full Text Available Robertsite, ideally Ca2Mn3O2(PO43·3H2O [calcium manganese(III tris(orthophosphate trihydrate], can be associated with the arseniosiderite structural group characterized by the general formula Ca2A3O2(TO43·nH2O, with A = Fe, Mn; T = As, P; and n = 2 or 3. In this study, single-crystal X-ray diffraction data were used to determine the robertsite structure from a twinned crystal from the type locality, the Tip Top mine, Custer County, South Dakota, USA, and to refine anisotropic displacement parameters for all atoms. The general structural feature of robertsite resembles that of the other two members of the arseniosiderite group, the structures of which have previously been reported. It is characterized by sheets of [MnO6] octahedra in the form of nine-membered pseudo-trigonal rings. Located at the center of each nine-membered ring is a PO4 tetrahedron, and the other eight PO4 tetrahedra sandwich the Mn–oxide sheets. The six different Ca2+ ions are seven-coordinated in form of distorted pentagonal bipyramids, [CaO5(H2O2], if Ca—O distances less than 2.85 Å are considered. Along with hydrogen bonding involving the water molecules, they hold the manganese–phosphate sheets together. All nine [MnO6] octahedra are distorted by the Jahn–Teller effect.

  5. Structural and magnetic modulations in CaCu(x)Mn(7 - x)O(12).

    Sławiński, W; Przeniosło, R; Sosnowska, I; Bieringer, M


    Low temperature atomic position modulations and magnetic moment modulations are reported for CaCu(x)Mn(7 - x)O(12) (x = 0.0, 0.1 and 0.23) using neutron powder diffraction. Both modulations are described with propagation vectors (0, 0, q) parallel to the c-axis in the hexagonal setting. The present neutron diffraction studies confirm the quantitative model describing the atomic position modulations in CaCu(x)Mn(7 - x)O(12) (x = 0.0 and 0.1) as derived from synchrotron based powder x-ray diffraction studies (Sławiński et al 2009 Acta Crystallogr. B 65 535). Neutron diffraction studies confirm the relation between the atomic position modulation length L(p) and the magnetic modulation length L(m) = 2L(p) between 50 K and the Néel temperature T(N). CaCu(x)Mn(7 - x)O(12) (x = 0.1 and 0.23) shows a magnetic phase transition near 50 K associated with considerable changes of the magnetic modulation length and the magnetic coherence length, similar to that observed in the parent CaMn(7)O(12).

  6. The magnetic Curie temperature and exchange coupling between cations in tetragonal spinel oxide Mn{sub 2.5}M{sub 0.5}O{sub 4} (M = Co, Ni, Mn, Cr, and Mg) films

    Kuo, K.; Cheng, C. W.; Chern, G. [Physics Department and SPIN Research Center, National Chung Cheng University, Chia-Yi, Taiwan, 621 (China)


    Mn{sub 3}O{sub 4} is a Jahn-Taller tetragonal ferrite that has a relatively low Curie temperature (T{sub c}) of {approx}43 K due to weak coupling between the canting spins. In this study, we fabricated a series of 100-nm-thick Mn{sub 2.5}M{sub 0.5}O{sub 4} (M = Co, Ni, Mn, Cr, and Mg) films via oxygen-plasma-assisted molecular beam epitaxy and measured the structural and magnetic properties of these films. These films show single phase quality, and the c-axis lattice parameter of pure Mn{sub 3}O{sub 4} is 0.944 nm, with a c/a ratio {approx}1.16, consistent with the bulk values. The replacement of Mn by M (M = Co, Ni, Cr, and Mg) changes the lattice parameters, and the c/a ratio varies between 1.16 and 1.06 depending upon the cation distribution of the films. The magnetic Curie temperatures of these films also vary in the range of 25-66 K in that Ni and Co enhance the T{sub c} whereas Mg reduces the T{sub c} (Cr shows no effect on the T{sub c}). These changes to the T{sub c} are related to both the element electronic state and the cation distributions in these compounds. As a non-collinear spin configuration can induce electrical polarization, the present study provides a systematic way to enhance the magnetic transition temperature in tetragonal spinel ferrites.

  7. Desulfurization technology by using Mg+CaO powder injection in hot metal ladle%铁水包喷吹Mg+CaO粉剂脱硫技术

    刘勇; 龙川江; 战东平; 张慧书; 姜周华


    分析了宝山钢铁股份有限公司采用TDS(Torpedo Car Desulphurization)、PTC(Hot Metal Pretreatment center)和铁水包单枪、双枪喷Mg+CaO脱硫模式的生产情况.结果表明,采用铁水包喷吹Mg+CaO脱硫在喷吹时间、脱硫效果、粉剂消耗、生产组织及经济效益等方面明显优于混铁车喷吹脱硫.

  8. Biodegradable Orthopedic Magnesium-Calcium (MgCa Alloys, Processing, and Corrosion Performance

    Yuebin Guo


    Full Text Available Magnesium-Calcium (Mg-Ca alloy has received considerable attention as an emerging biodegradable implant material in orthopedic fixation applications. The biodegradable Mg-Ca alloys avoid stress shielding and secondary surgery inherent with permanent metallic implant materials. They also provide sufficient mechanical strength in load carrying applications as opposed to biopolymers. However, the key issue facing a biodegradable Mg-Ca implant is the fast corrosion in the human body environment. The ability to adjust degradation rate of Mg-Ca alloys is critical for the successful development of biodegradable orthopedic implants. This paper focuses on the functions and requirements of bone implants and critical issues of current implant biomaterials. Microstructures and mechanical properties of Mg-Ca alloys, and the unique properties of novel magnesium-calcium implant materials have been reviewed. Various manufacturing techniques to process Mg-Ca based alloys have been analyzed regarding their impacts on implant performance. Corrosion performance of Mg-Ca alloys processed by different manufacturing techniques was compared. In addition, the societal and economical impacts of developing biodegradable orthopedic implants have been emphasized.

  9. Interfacial contributions to perpendicular magnetic anisotropy in Pd/Co2MnSi/MgO trilayer films

    Fu, Huarui; You, Caiyin; Li, Yunlong; Wang, Ke; Tian, Na


    Heusler alloy Co2MnSi is widely selected as the ferromagnetic layer to achieve a giant tunneling magnetic resistance (TMR). It is also one of the most promising materials for potential spintronic applications of magnetic random access memory (MRAM) due to the high spin polarization, in which the configuration of perpendicular magnetic anisotropy (PMA) possesses great advantages over the in-plane ones. Therefore, it is highly desirable to investigate the PMA effects of the Co2MnSi layer with a suitable stack structure. In this work, a strong PMA (1.61  ×  106 erg cm-3) is demonstrated in the system of Pd/Co2MnSi/MgO trilayer films. The contributions of the interfaces beside the ferromagnetic Co2MnSi layer were quantitatively clarified. The interfacial anisotropy K s,MgO of 0.79 erg cm-2 at the Co2MnSi/MgO interface is larger than the K s,Pd value of 0.26 erg cm-2 at the Pd/Co2MnSi interface. Due to the dual interfacial effects, the strong PMA can be sustained at the high annealing temperature with a thick Co2MnSi layer of about 4.9 nm, which is favorable to the potential spintronic application. The Mn-O bonding was also found to be enriched at the Co2MnSi/MgO interface for the annealed Pd/Co2MnSi (3.4 nm)/MgO film with the large PMA, showing an experimental evidence for the theoretical results of the Mn-O bonding contribution to PMA.

  10. Quantifying the Potential Influence of Carbonate Saturation State on Benthic Foraminiferal Mg/Ca

    Martin, P. A.; Lea, D. W.; McCorkle, D. C.


    Benthic foraminiferal Mg/Ca paleothermometry is based on an empirical relationship between the Mg/Ca of benthic foraminifera recovered from core tops and in situ bottom water temperatures (Rosenthal, 1997; Martin et al, in press; Lear et al, in review). While there is a tight correlation between shell Mg/Ca and temperature over a broad range of temperatures (-1 to 20 degrees C), Mg/Ca variation over the small range of deep water temperatures reveals departures from the calibration curve at low temperatures. Lower Mg/Ca values are generally associated with the deepest sites from the Atlantic and Pacific, contributing to an apparently steeper Mg/Ca-T response for abyssal benthics. The steeper response of abyssal benthics may reflect an influence of decreasing carbonate saturation with depth. Dissolution or other saturation related effects have already been documented for Mg in planktonic foraminifera and for other metals (Cd, Ba, and Zn) in benthic foraminifera shells (see Marchitto and ref. therein). Although it is difficult to definitively separate the effects of various environmental parameters (including temperature, depth, and relative saturation states), which often change in unison, we can use to the core top Mg/Ca data to estimate the potential influence of saturation state. An alternative calibration of the benthic Mg/Ca - T relationship can be derived based on core top benthic foraminifera only from sites bathed in waters above carbonate saturation, which yields a slightly smaller change in Mg/Ca per degree C (~9.5% vs. 11%) but better explains benthic Mg/Ca from the coldest sites (-1oC). Using this alternative Mg/Ca -T relation and a subset of the data from the Ceara Rise and Ontong Java Plateau, we can estimate a maximum Mg/Ca offset attributable to saturation state. The uncertainty this implies for downcore reconstructions varies widely (exceeding 1.5oC), depending on the hydrographic setting and which proxy is used to estimate saturation state.

  11. Evaluation of Ca3(Co,M2O6 (M=Co, Fe, Mn, Ni as new cathode materials for solid-oxide fuel cells

    Fushao Li


    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=CoMn, and the over-potential increased in the order of M=Fe≈M=CoMnCa3(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.

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


    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.

  13. High-Resolution Mn EXAFS of the Oxygen-Evolving Complex inPhotosystem II: Structural Implications for the Mn4Ca Cluster

    Yano, Junko; Pushkar, Yulia; Glatzel, Pieter; Lewis, Azul; Sauer,Kenneth; Messinger, Johannes; Bergmann, Uwe; Yachandra, Vittal


    The biological generation of oxygen by the oxygen-evolving complex in photosystem II (PS II) is one of natures most important reactions. The recent X-ray crystal structures, while limited by resolutions of 3.2 to 3.5 A, have located the electron density associated with the Mn4Ca complex within the multi-protein PS II complex. Detailed structures critically depend on input from spectroscopic techniques such as EXAFS and EPR/ENDOR, as the XRD resolution does not allow for accurate determination of the position of Mn/Ca or the bridging and terminal ligand atoms. The number and distances of Mn-Mn/Ca/ligand interactions determined from EXAFS provide important constraints for the structure of the Mn cluster. Here we present data from a high-resolution EXAFS method using a novel multi-crystal monochromator that show three short Mn-Mn distances between 2.7 and 2.8 A and hence the presence of three di-mu-oxobridged units in the Mn4Ca cluster. This result imposes clear limitations on the proposed structures based on spectroscopic and diffraction data and provides input for refining such structures.




    Full Text Available In this work, powders of three different compositions, each having 34 SiO2-14.5 P2O5-1 CaF2-0.5 MgF (% wt and ratio of CaO/MgO varying from 11.5:1 to 1:11.5 were thoroughly mixed and melted under oxy-acetylene flame in a fire clay crucible that made the glass formation cheaper in time and cost. The melt of each composition was quenched in water to form three different glasses. Every glass was sintered at 950°C to form three glass ceramics named G1, G2 and G3 respectively. To study the dissolution behavior, each sample was immersed in a simulated body fluid (SBF for 2, 5, 10, 20 and 25 days at room temperature. Thin film XRD analysis revealed that the samples with larger CaO/MgO ratio exhibited better bioactivity. pH of SBF increased efficiently in case of G1 whereas in case of G2 and G3, this increase was slower due to greater amount of MgO. The concentrations of Ca, P, Mg and Si ions were measured by Atomic Absorption Spectroscopy. EDS analysis showed the increase in P and Ca ions and presence of C in G1 after 5 days immersion and after 10 days, in case of G2 indicating the higher formation rate of hydroxycarbonate Apatite layer in G1 as compared to G2 due to greater CaO/MgO ratio whereas in G3 Mg-hydroxycarbonate apatite (Ca(Mg5(CO3(PO43(OH (heneuite layer was recognized after 20 days showing the least bioactivity due to very large amount of Mg and the least CaO/MgO ratio.

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

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


    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.

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

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


    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.

  17. In vitro corrosion of Mg-Ca alloy — The influence of glucose content

    Cui, Lan-Yue; Li, Xiao-Ting; Zeng, Rong-Chang; Li, Shuo-Qi; Han, En-Hou; Song, Liang


    Influence of glucose on corrosion of biomedical Mg-1.35Ca alloy was made using hydrogen evolution, pH and electrochemical polarization in isotonic saline solution. The corrosion morphologies, compositions and structures were probed by virtue of SEM, EDS, FTIR, XRD and XPS. Results indicate that the glucose accelerated the corrosion of the alloy. The elemental Ca has no visible effect on the corrosion mechanism of glucose for the Mg-1.35Ca alloy in comparison with pure Mg. In addition, the presence of CO2 has beneficial effect against corrosion due to the formation of a layer of carbonatecontaining products.

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

    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:, E-mail:, E-mail:, E-mail:, E-mail:, E-mail:, E-mail: [Lifetech Scientific (Shenzhen) Co. Ltd, Hi-Tech Park, Shenzhen 518000 (China)


    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.

  19. Mg-Mn-Y-Nd挤压变形镁合金的组织和腐蚀性能%Microstructures and Corrosion Properties of Extruded Mg-Mn-Y-Nd Alloys

    房大庆; 金亚旭; 刘杰兴; 柴跃生


    Basing on a rare earth alloying method,two kinds of Mg-Mn-RE alloys were fabricated by adding Y and Nd element into the extruded Mg-Mn alloy.The alloys were prepared by a conventional casting method.The determination of the phases in the investigated alloys was carried out by energy-dispersive spectroscopy and X-ray diffractometer.The corrosion properties of the Mg-Mn-RE alloys were studied by electrochemical impedance spectra.The results show that Nd element is beneficial for the grain refinement of the alloys.The average grain size of the Mg-1Mn-2Y-1Nd alloys is 410~360 μm.The obvious recrystallization in the Mg-2Y-1Mn-2Nd alloy leads to the large average grain size as well as a number of coarse Mg12Nd phase particles and fine Mg24Y5 phase particles.The Nd elements make Mg-Mn alloy suffer corrosion easily.%以Mg-Mn合金为基体材料,通过Y、Nd稀土元素合金化的方法,制备了新型Mg-Mn-RE挤压变形镁合金.采用扫描电镜、透射电镜、X射线衍射仪等实验设备,系统地研究了Mg-Mn-RE挤压镁合金的相组成、微观组织、常规性能;采用交流阻抗谱研究了Mg-Mn-RE挤压镁合金的腐蚀机理.铸态Mg-1Mn-2Y-1Nd合金的显微组织主要由平均晶粒尺寸为410~360 μm的α-Mg晶粒组成.随着Nd含量的增加,铸态Mg-1Mn-2Y-2Nd合金的显微组织明显细化并且包含了Mg12Nd相和Mg24Y5相.在热挤压过程中,与Mg-1Mn-2Y-1Nd合金相比,Mg-2Y-1Mn-2Nd合金中发生了明显的再结晶,再结晶晶粒尺寸变大,同时形成粗大的Mg12Nd相和细小的Mg24Y5相.电化学交流阻抗谱结果表明,Nd的加入使Mg-Mn系合金的抗腐蚀性能降低.

  20. Punta Pitt Stable Isotope and Ion Data (delta 18O, delta 13C, Cd/Ca, Mn/Ca) for 1936 to 1982.5

    National Oceanic and Atmospheric Administration, Department of Commerce — File contains data presented by Shen et al. (1992a). Table includes d18O, d13C, Cd/Ca, Mn/Ca, and Ba/Ca data from a 2m coral head and, for comparison, SST records...

  1. The Dissolution Kinetics of MgO into CaO-MgO-Fe2O3 Slag

    Wei, Ruirui; Lv, Xuewei; Yue, Zhiwen; Xiang, Shenglin


    Calcium ferrite is the main binding phase for high-basicity sinter. The production and structure of calcium ferrite greatly influence the quality of the sinter. With the change in gangue composition, MgO becomes an important factor in the generation of calcium ferrite. In this study, the rotating cylinder method was used to study the dissolution kinetics of MgO into CaO-MgO-Fe2O3 melt. The experimental variables included the temperature, the initial composition of the melt, the Fe2O3/CaO mass ratio, the rotation time, and the rotation speed. The results indicate that the dissolution rate increases with increasing dissolution time, temperature, and rotation speed but decreases with increasing MgO content and Fe2O3/CaO mass ratio in the initial slag. The dissolution rate was observed to increase and then decrease with the addition of SiO2 in the initial slag. The activation energy and diffusion coefficient for MgO dissolution were found to range from 117.31 to 234.24 kJ mol-1 and from 1.03 × 10-6 to 1.18 × 10-5 cm2 s-1, respectively. The concentration difference between the solid and liquid phases is the main driving force for dissolution, but the viscosity and magnesium ion diffusivity of the melt also affect the process.

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

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


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

  3. 少量缺铁对Mg-Mn-Zn铁氧体性能的影响%Effects of Small Amount of Iron Deficiency on the Properties of Mg-Mn-Zn Ferrites

    范积伟; 赵慧君


    基于化学式为Mg0.65Zn0.35Mn0.1Fe1.9-xO4-8的Mg-Mn-Zn铁氧体材料,采用具有高化学均匀性的柠檬酸有机凝胶法制备技术来研究少量缺铁(Iron deficient,x=0,0.05,0.1)对Mg-Mn-Zn铁氧体烧结密度、微观结构和磁性能的影响.实验表明:与符合化学计量比的Mg-Mn-Zn铁氧体相比,少量缺铁的Mg-Mn-Zn铁氧体具有更高的相对烧结密度和起始磁导率,然而具有较高的磁损耗;相对高的烧结密度和较大的晶粒尺寸导致了高的起始磁导率,较大的晶粒尺寸以及观察到的在少量缺铁样品晶界上析出的富镁锌方铁体(Wustite)相可能是造成少量缺铁Mg-Mn-Zn铁氧体具有较高磁损耗的原因.

  4. Surface stability of spinel MgNi{sub 0.5}Mn{sub 1.5}O{sub 4} and MgMn{sub 2}O{sub 4} as cathode materials for magnesium ion batteries

    Jin, Wei; Yin, Guangqiang [School of Physical Electronics, University of Electronic Science and Technology of China, Chengdu, 610054 (China); Wang, Zhiguo, E-mail: [School of Physical Electronics, University of Electronic Science and Technology of China, Chengdu, 610054 (China); Fu, Y.Q., E-mail: [Department of Physics and Electrical Engineering, Faculty of Engineering and Environment, University of Northumbria, Newcastle upon Tyne, NE1 8ST (United Kingdom)


    Highlights: • Surface of spinel MgMn{sub 2}O{sub 4} and MgNi{sub 0.5}Mn{sub 1.5}O{sub 4} cathodes were investigated. • The surface energies show less dependence on the Ni-doping. • Atomic reconstruction occurred due to atomic relaxation at the surface. - Abstract: Rechargeable ion batteries based on the intercalation of multivalent ions are attractive due to their high energy density and structural stability. Surface of cathode materials plays an important role for the electrochemical performance of the rechargeable ion batteries. In this work we calculated surface energies of (001), (110) and (111) facets with different terminations in spinel MgMn{sub 2}O{sub 4} and MgNi{sub 0.5}Mn{sub 1.5}O{sub 4} cathodes. Results showed clearly that atomic reconstruction occurred due to surface relaxation. The surface energies for the (001), (110) and (111) surfaces of the MgNi{sub 0.5}Mn{sub 1.5}O{sub 4} were 0.08, 0.13 and 0.11 J/m{sup 2}, respectively, whereas those of the Ni-doped MgMn{sub 2}O{sub 4} showed less dependence on the surface structures.

  5. Stable isotopes, Sr/Ca, and Mg/Ca in biogenic carbonates from Petaluma Marsh, northern California, USA

    Ingram, B.L.; De Deckker, P.; Chivas, A.R.; Conrad, M.E.; Byrne, A.R.


    Stable isotope ({sup 18}O/{sup 16}O and {sup 13}C/{sup 12}C) and minor-element compositions (Sr/Ca and Mg/Ca ratios) of ostracodes and gastropods separated from marsh sediments from San Francisco Bay, Northern California, were used to reconstruct paleoenvironmental changes in Petaluma Marsh over the past 700 yr. The value of {delta}{sup 18}O in the marsh carbonates reflects changes in freshwater inflow, evaporation, and temperature. Mg/Ca and Sr/Ca in ostracode calcite reflect changes in both freshwater inflow and temperature, although primarily reflect temperature changes in the salinity range of about 10-35 {per_thousand}. Ostracode {delta}{sup 18}O values show a gradual increase by 5 {per_thousand} between 500 yr BR and the present, probably reflecting rising sea level and increased evaporation in the marsh. Superimposed on this trend are higher frequency Mg/Ca and {delta}{sup 18}O variations (3-4 {per_thousand}), probably reflecting changes in freshwater inflow and evaporation. A period of low Mg/Ca occurred between about 100-300 cal yr BP, suggesting wetter and cooler conditions during the Little Ice Age. Higher Mg/Ca ratios occurred 600-700 cal yr BP, indicating drier and warmer conditions during the end of the Medieval Warm Period. Both ostracode and gastropod {delta}{sup 13}C values decrease up-core, reflecting decomposition of marsh vegetation, which changes from C{sub 4} ({delta}{sup 13}C {approx} -12{per_thousand}) to CAM ({delta}{sup 13}C = -26 {per_thousand})-type vegetation over time.

  6. Coral Cd/Ca and Mn/Ca records of El Niño variability in the Gulf of California

    J. D. Carriquiry


    Full Text Available We analyzed the trace element ratios Cd/Ca and Mn/Ca in three coral colonies (Pavona gigantea, Pavona clivosa and Porites panamensis from Cabo Pulmo reef, Southern Gulf of California, Mexico, to assess the oceanographic changes caused by El Niño – Southern Oscillation (ENSO events in the Eastern Tropical North Pacific (ETNP. The interannual variations in the coral Cd/Ca and Mn/Ca ratios show clear evidence that incorporation of Cd and Mn in the coral skeleton are influenced by ENSO conditions, but the response for each metal is controlled by different process. The Mn/Ca ratios were significantly higher during ENSO years (p<0.05 relative to non-ENSO years for the three species of coral. In contrast, the Cd/Ca was systematically lower during ENSO years, but it was significant (p<0.05 only in P. gigantea. The decrease in the incorporation of Cd, and the marked increase in Mn during the mature phase of El Niño indicate strongly reduced vertical mixing in the Gulf of California. The oceanic warming during El Niño events produces a relaxation of upwelling and a stabilization of the thermocline which acts as a physical barrier limiting the transport of Cd from deeper waters into the surface layer. In turn, this oceanic condition can increase the residence time of particulate-Mn in surface waters, which in turn increases the photo-reduction of particulate-Mn and the release of the available Mn into the dissolved phase. These results provide validation for using Mn/Ca and Cd/Ca in biogenic carbonates as tracers of changes in ocean stratification and trade wind weakening and/or collapse in the ETNP during ENSO episodes.

  7. FeMnMg氧化物Fenton催化降解有机废水%Research of FeMnMg Oxide Nano Particles Fenton-Degraded Methylene Blue

    贾若琨; 李佳


    采用高温煅烧硝化法制备FeMnMg氧化物纳米晶,并采用扫描电镜( SEM)对FeMnMg氧化物进行表征。结果表明,高温煅烧硝化法制备的FeMnMg氧化物粒径为纳米范围,具有均匀的粒子尺寸和晶体尺寸。采用不同配比的FeMnMg氧化物纳米晶催化剂对亚甲基蓝模拟的有机废水进行Fenton催化降解实验,对实验结果进行分析讨论。 FeMnMg的摩尔比为2∶3∶1的氧化物对亚甲基蓝的降解效果最好。当pH值为7左右,反应温度为25℃时,降解速率最快。 FeMnMg 氧化物催化剂的投加量为0.012 g,保证了亚甲基蓝较好的降解率。在反应体系中采用选取30% H2O20.5 mL(即2 mmol/L),能达到较好的氧化降解效果。%FeMnMg oxide nanocrystals were prepared by a high temperature calcination method,and they were characterized by scanning electron microscope ( SEM ) . The results showed that FeMnMg oxide nanocrystals prepared with temperature calcination method were nano particle size range, and the FeMnMg oxide nanocrystals had uniform particle size and crystallite size. The strong H2 O2-activating ability of FeMnMg oxide nanocrystals showed promising applications in the oxidative degradation of organic pollutants methylene blue. Using the best catalyst of degradation effect of methylene blue in the experiments,carried on the optimal Fenton catalytic conditions on the exploring experiment. We studied the dosing quantity of catalyst FeMnMg oxide nanocrystals,the addition content of H2 O2 ,pH value and reaction temperature effect influence on catalytic deg-radation of methylene blue solution.

  8. Effect of sertraline on [Ca2+](i) and viability of human MG63 osteosarcoma cells.

    Lin, Ko-Long; Chi, Chao-Chuan; Lu, Ti; Tseng, Li-Ling; Wang, Jue-Long; Lu, Yi-Chau; Jan, Chung-Ren


    The antidepressant, sertraline, has been shown to have diverse in vitro effects. This study examined whether sertraline altered [Ca(2+)](i) in MG63 human osteosarcoma cells by using fura-2 as a Ca(2+)-sensitive fluorescent dye. At 50-200 µM, sertraline induced a [Ca(2+)](i) rise in a concentration-dependent manner. Ca(2+) response was decreased by removing extracellular Ca(2+), suggesting that Ca(2+) entry and release contributed to the [Ca(2+)](i) signal. Sertraline-induced Ca(2+) entry was inhibited by nifedipine, La(3+), Gd(3+), and SK&F96365. When extracellular Ca(2+) was removed, pretreatment with the endoplasmic reticulum (ER) Ca(2+) pump inhibitor, thapsigargin, or 2,5-di-tert-butylhydroquinone (BHQ) abolished the sertraline-evoked [Ca(2+)](i) rise. Incubation with sertraline also abolished the thapsigargin or BHQ-induced [Ca(2+)](i) rise. Inhibition of phospholipase C (PLC) with U73122 abolished the sertraline-induced [Ca(2+)](i) rise. At 20-30 µM, overnight treatment with sertraline killed cells in a concentration-dependent manner. The cytotoxic effect of sertraline was not reversed by chelating cytosolic Ca(2+) with 1,2-bis(2-aminophenoxy)ethane-N,N,N',N'-tetraacetic acid (BAPTA). Annexin V/propidium iodide staining data demonstrate that sertraline (30 µM) evoked apoptosis. Sertraline (20 and 30 µM) also increased levels of reactive oxygen species. Together, in human osteosarcoma cells, sertraline evoked a [Ca(2+)](i) rise by inducing PLC-dependent Ca(2+) release from the ER and Ca(2+) entry by L-type Ca(2+) channels and store-operated Ca(2+) channels. Sertraline induced cell death that may involve apoptosis by mitochondrial pathways.

  9. The precipitation process in Mg-Ca-(Zn) alloys investigated by positron annihilation spectroscopy

    Ortega, Yanicet [Departamento de Fisica, Universidad Carlos III de Madrid, 28911 Leganes (Spain); Departamento de Fisica de Materiales, Facultad de Ciencias Fisicas, Universidad Complutense de Madrid, 28040 Madrid (Spain)], E-mail:; Monge, Miguel Angel; Pareja, Ramiro [Departamento de Fisica, Universidad Carlos III de Madrid, 28911 Leganes (Spain)


    Coincidence doppler broadening (CDB) spectroscopy has been applied to study the precipitation process induced by aging in Mg-1.0 wt.% Ca and Mg-1.0 wt.% Ca-1.0 wt.% Zn alloys. In addition positron lifetime experiments and microhardness measurements have been performed. A peak centered at {approx}11.5 x 10{sup -3}m{sub 0}c is found in the CDB ratio spectra of the alloys aged at 473 K. It is attributed to annihilations with the core electrons of Ca. The results indicate the formation of a particle dispersion that hardens the alloys. This dispersion is correlated with the appearance of the peak attributed to Ca atoms. Zn atoms in the Mg matrix inhibit the formation of quenched-in vacancies bound to Ca atoms in the aged ternary alloy producing the dispersion refinement.

  10. Corrosion Mechanism of Ladle Furnace Refining Slag to Fired MgO-CaO Bricks

    ZHU Boquan; FANG Binxiang; ZHANG Wenjie; LI Xiangcheng; WAN Hongbo


    Corrosion effect of ladle furnace(LF)refining slag on fired MgO-CaO bricks with about 34% CaO was studied by static crucible method,and corrosion mechanism was analyzed by techniques of scan electron micrograph,energy dispersive spectrometer,and X-ray dif-fraction.The results show that: MgO-CaO bricks exhibit excellent corrosion resistance but poor penetration in reaction zone results in volume expansion forming MgO-CaO bricks increases liquid phases which accelerates corrosion of the bricks; a protective layer of 2CaO·SiO2 formed on reaction interface prevents penetration of C2F to the bricks.

  11. The ternary system K2SO4MgSO4CaSO4

    Rowe, J.J.; Morey, G.W.; Silber, C.C.


    Melting and subsolidus relations in the system K2SO4MgSO4CaSO4 were studied using heating-cooling curves, differential thermal analysis, optics, X-ray diffraction at room and high temperatures and by quenching techniques. Previous investigators were unable to study the binary MgSO4CaSO4 system and the adjacent area in the ternary system because of the decomposition of MgSO4 and CaSO4 at high temperatures. This problem was partly overcome by a novel sealed-tube quenching method, by hydrothermal synthesis, and by long-time heating in the solidus. As a result of this study, we found: (1) a new compound, CaSO4??3MgSO4 (m.p. 1201??C) with a field extending into the ternary system; (2) a high temperature form of MgSO4 with a sluggishly reversible inversion. An X-ray diffraction pattern for this polymorphic form is given; (3) the inversion of ??-CaSO4 (anhydrite) to ??-CaSO4 at 1195??C, in agreement with grahmann; (1) (4) the melting point of MgSO4 is 1136??C and that of CaSO4 is 1462??C (using sealed tube methods to prevent decomposition of the sulphates); (5) calcium langbeinite (K2SO4??2CaSO4) is the only compound in the K2SO4CaSO4 binary system. This resolved discrepancies in the results of previous investigators; (6) a continuous solid solution series between congruently melting K2SOP4??2MgSO4 (langbeinite) and incongruently melting K2SO4??2CaSO4 (calcium langbeinite); (7) the liquidus in the ternary system consists of primary phase fields of K2SO4, MgSO4, CaSO4, langbeinite-calcium langbeinite solid solution, and CaSO4??3MgSO4. The CaSO4 field extends over a large portion of the system. Previously reported fields for the compounds (K2SO4??MgSO4??nCaSO4), K2SO4??3CaSO4 and K2SO4??CaSO4 were not found; (8) a minimum in the ternary system at: 740??C, 25% MgSO4, 6% CaSO4, 69% K2SO4; and ternary eutectics at 882??C, 49% MgSO4, 19% CaSO4, 32% K2SO4; and 880??, 67??5% MgSO4, 5% CaSO4, 27??5% K2SO4. ?? 1967.

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

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


    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.

  13. Isotopic Fractionation of Mg2+(aq), Ca2+(aq), and Fe2+(aq) with Carbonate Minerals

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


    Density functional electronic structure calculations are used to compute the equilibrium constant (the isotope fractionation factor) 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 103ln(K) at 25 °C, of -5.3, -1.1, and +1.1 for 26Mg/24Mg exchange between calcite (CaCO3), magnesite (MgCO3), and dolomite (Ca0.5Mg0.5CO3), respectively, and Mg2+(aq), with positive values indicating enrichment in the mineral phase. For 44Ca/40Ca exchange between calcite and Ca2+(aq), the calculations predict values of +1.5 for Ca2+(aq) in six-fold coordination and +4.1 for Ca2+(aq) in seven-fold coordination. We find that the reduced partition function ratios can be reliably computed from systems as small as M(CO3)610- and M2+(H2O)6 embedded in a set of fixed atoms representing the 2nd 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 2 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 Fe3+-hematite and Fe2+-siderite fractionations arise from an insufficiently accurate reduced partition function ratio for the Fe3+(aq) and Fe2+(aq) species.

  14. Microstructural evolution during friction stir welding of AlSi1MgMn alloy

    M. Janjić


    Full Text Available This paper provides the research of the infl uence of geometric and kinematic parameters on the microstructure and mechanical properties of welded joint of aluminum alloy AlSi1MgMn (6082-T6 obtained through the Friction Stir Welding (FSW process. The experiment parameters were welding speed, rotation speed, angle of pin slope, pin diameter and shoulder diameter. On the obtained welded workpieces the dynamic testing on the impact toughness, and determination of microstructural zones were carried out.

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

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


    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.

  16. Structure and magnetic investigations of Ca1-xYxMnO3 (x=0, 0.1, 0.2, 0.3 and Mn4+/Mn3+ relation analysis

    Zagorac J.


    Full Text Available Structure and magnetic features of nanostructured materials with general formula Ca1-xYxMnO3 (x = 0; 0.1; 0.2; 0.3 were investigated. Goldschmidt tolerance factor, Gt and global instability index, GII were calculated for Ca1-xYxMnO3 (x = 0, 0.25, 0.5, 0.75, 1 using the software SPuDS (Structure Prediction Diagnostic Software. According to these two parameters possibility of forming perovskite structure type for Ca1-xYxMnO3 solid solution was analyzed. Substitution of Y3+ for Ca2+ provokes reduction of equivalent amount Mn4+ into Mn3+, the presence of which is a reason for many interesting magnetic, transport and structural features of doped CaMnO3. Crystal structure refinement was carried out using Rietveld analysis. Ca1-xYxMnO3 (x = 0; 0.1; 0.2; 0.3 has an orthorombic, Pnma space group that, according to Glazer´s classification belongs to a-b+a- tilt system. Influence of Y amount on Mn-O bond angles and distances, tilting of MnO6 octahedra around all three axes and octahedra deformation were analyzed. Bond valence calculations (BVC were performed to determine Mn valence state. Using EPR (electron paramagnetic resonance magnetic measurements were performed and magnetic properties of solid solutions, orthorombicity degree of unit cell, as well as Mn4+/Mn3+ cations ratio in position B were analyzed. Microstructure size-strain analysis was performed and these results are in nanometric range which is confirmed by TEM images.

  17. Electrodeposition of Ca-P coatings on biodegradable Mg alloy: in vitro biomineralization behavior.

    Song, Yang; Zhang, Shaoxiang; Li, Jianan; Zhao, Changli; Zhang, Xiaonong


    Preparing stabilized apatite on biodegradable Mg alloy may improve biocompatibility and promote osteointegration. In the present work, three kinds of Ca-P coatings, brushite (DCPD, CaHPO(4).2H(2)O), hydroxyapatite (HA, Ca(10)(PO(4))(6)(OH)(2)) and fluoridated hydroxyapatite (FHA, Ca(5)(PO(4))(3)(OH)(1-)(x)F(x)) are fabricated by electrodeposition on a biodegradable Mg-Zn alloy. The crystalline structures, morphologies and compositions of these Ca-P coatings have been characterized by X-ray diffrection, scanning electron microscopy and energy-dispersive spectoscopy. The effects of these coatings on the degradation behavior and mineralization activity of the Mg-Zn alloy have also been investigated. The experimental results showed that these coatings decreased the degradation rate of Mg-Zn alloy, while the precipitates on the uncoated and DCPD-coated Mg-Zn alloy in modified simulated biological fluid had low Ca/P molar ratios, which delayed bone-like apatite formation. Both the HA and FHA coating could promote the nucleation of osteoconductive minerals (bone-like apatite or beta-TCP) for 1month. However, the HA coating transformed from DCPD through alkali heat treatment was fragile and less stable, and therefore its long-term corrosion resistance was not satisfactory. Instead, the FHA was more stable and had better corrosion resistance, and thus it should be better suited as a coating of Mg implants for orthopedic applications.

  18. Red emission of additional Pr³⁺ and adjusting effect of additional Mg²⁺ in Ca₃Sc₂Si₃O₁₂:Ce³⁺, Mn²⁺ phosphor.

    Qiao, Jun; Zhang, Jiahua; Zhang, Xia; Hao, Zhendong; Liu, Yongfu; Pan, Guohui


    In this Letter, we report the addition of Pr3+ and Mg2+ in CSS:Ce3+, Mn2+ phosphor for improving the performances of white light-emitting diodes (LEDs). The additional trivalent Pr3+ will occupy the Ca2+ site in this host like the situation of Ce3+, its concentration can be enhanced by the addition of Mg2+ in Sc3+ site due to the substitution of Mg2+ for Sc3+ can compensate the charge mismatch between Pr3+ and Ca2+. Based on the efficient Ce3+→Pr3+ and Mn2+→Pr3+ energy transfers (ETs) and the compensation effect of Mg2+, the additional Pr3+ in our present phosphors exhibits an intense red-emission around 610 nm, which is significant for enhancing the color rendering property. In addition, we also find that the additional Mg2+ in Sc3+ site can markedly adjust the photoluminescence (PL) spectrum shape of our phosphor by controlling the distribution of Mn2+ at Ca2+ and Sc3+ sites. A new tunable full-color emission is obtained via the ETs (Ce3+→Mn2+, Ce3+→Pr3+ and Mn2+→Pr3+) and the adjusting effect of Mg2+ in our present phosphors. Finally, a white LED with higher color rendering index of 90, lower correlated color temperature of 4980 K, and chromaticity coordinates of (0.34, 0.31) was obtained by combining the single CSS:0.08Ce3+, 0.01Pr3+, 0.3Mn2+, 0.2Mg2+ phosphor with a blue-emitting InGaN LED chip.

  19. Determination of P, K, Ca, Mg, Mn, Fe, Cu, Na, Zn and Al in compound fertilizers by X-ray fluorescence spectrometry with fused glass disc sample preparation%熔融制样-X射线荧光光谱法快速测定复合肥中的磷、钾、钙、镁、锰、铁、铜、钠、锌和铝

    任春生; 廖海平; 鲍惠君; 朱迪琦; 何阳


    为实现复合肥样品中多元素的同时分析,采用熔融片法制样,有效地消除了试样的粒度效应,用X射线荧光光谱法测定复合肥样品中磷、钾、钙、镁、锰、铁、铜、钠、锌和铝10个元素,对仪器工作条件进行了试验并选定最佳条件,使各元素测定所要求的灵敏度和准确度得到满足,以8个合成的样品作为校准样品,采用固定理论α影响系数进行回归及基体效应校正,方法精密度(RSD,n=8)≤1.36%,分析结果与化学法进行对照基本一致.%A method for the determination of including P, K, Ca, Mg, Mn, Fe, Cu, Na, Zn and Al in compound fertilizers by X-ray fluorescence spectrometry with fused glass disc sample preparation was reported in this paper.The granularity effect in the analysis was eliminated by the fusion method of sam pie-dissolution.The working conditions of the instrument were also studied and optimized to meet with the requirements of sensitivity and accuracy of determination.Eight composed samples were used as the calibration standards.The matrix effect was corrected with fixed theoretical alpha coefficient method.The precision of the method was RSD≤1.36% (n =8).The results were in agreement with those by chemical methods.

  20. The effect of sulfate on CaCO_{3} mineralogy and the incorporation of Mg^{2+}

    Goetschl, Katja Elisabeth; Mavromatis, Vasileios; Dietzel, Martin


    Sulfate is the second most concentrated anion in seawater, and it forms strong complexes with Ca2+ and Mg2+ in aqueous solutions. However, up to now not much is known about the effect of dissolved SO42- on the formation of calcium carbonate minerals. For example, it has earlier been documented that the primary CaCO3 polymorph in marine sediments was oscillating between calcite and aragonite throughout the Phanerozoic, reflecting changes in seawater chemistry, among them SO42- concentration. Most of the previous experimental work, however, has focused mainly on the Mg/Ca ratio in seawater as the major driver for a preferential formation of calcite or aragonite. It has thus been shown that Mg substitution affects the thermodynamic stability of calcite, causing precipitation of aragonite instead of calcite at an aqueous Mg/Ca ratio higher than ˜1.3 [1]. To shed light on the mechanisms controlling the calcium carbonate mineral formation in the presence of sulfate, we performed steady-state precipitation experiments with calcite seed material at 25 ˚ C. Furthermore in this study we examine the Mg partitioning and isotope fractionation during its incorporation in calcite. For this, throughout the experimental runs, the aqueous Mg concentration was kept constant at different growth rates and different concentrations of dissolved SO42- have been used. Our data show that the presence of sulfate induces the formation of aragonite on calcite seeds at elevated growth rates, whereas we see no formation of aragonite in the experiments performed in the absence of sulfate, but at the same Mg/Ca ratio. On a further step the effect of sulfate on Mg partitioning and stable isotope fractionation of Mg in calcite will be examined. These results will improve the general understanding of the controls of solution chemistry on the formation of CaCO3 minerals and in specific the effect of sulfate on the incorporation of Mg into the crystal lattice. [1] Morse et al., 1997, Geology

  1. Porous perovskite CaMnO3 as an electrocatalyst for rechargeable Li-O2 batteries.

    Han, Xiaopeng; Hu, Yuxiang; Yang, Jingang; Cheng, Fangyi; Chen, Jun


    We report a facile synthesis method of preparing interconnected porous CaMnO3 nanostructures and their utilization as new cathode catalysts in rechargeable lithium-oxygen (Li-O2) batteries. The CaMnO3-based electrode enables much enhanced cyclability with a 620 mV smaller discharge-recharge voltage gap than that of the carbon-only cathode at a current rate of 50 mA gcarbon(-1). The improved performance is attributed to the high electrocatalytic activity of CaMnO3 with a porous nanostructure.

  2. Structure and magnetic properties of La{sub 2/3}Sr{sub 1/3}MnO{sub 3}/CaMnO{sub 3} multilayers

    Granada, Mara [Centro Atomico Bariloche and Instituto Balseiro, CNEA-UNC, Av. Bustillo 9500, 8400 San Carlos de Bariloche (Argentina)]. E-mail:; Sirena, Martin [Centro Atomico Bariloche and Instituto Balseiro, CNEA-UNC, Av. Bustillo 9500, 8400 San Carlos de Bariloche (Argentina); Steren, Laura B. [Centro Atomico Bariloche and Instituto Balseiro, CNEA-UNC, Av. Bustillo 9500, 8400 San Carlos de Bariloche (Argentina); Leyva, Gabriela [Depto. de Fisica, Centro Atomico Constituyentes, CNEA, Av. Gral. Paz y Constituyentes, 1650 San Martin (Argentina)


    Structural and magnetic properties of manganite-based multilayers, La{sub 2/3}Sr{sub 1/3}MnO{sub 3}/CaMnO{sub 3}, composed of ferromagnetic metals and antiferromagnetic insulator barriers are investigated in this work. Compounds of similar lattice parameters were used to build the samples, so we expect an excellent stacking of the different layers along the structure. To get a first insight of this system, the crystalline structure of a series of samples, grown on (1 0 0) SrTiO{sub 3} and (1 0 0) MgO single-crystalline substrates, has been studied. X-ray diffraction patterns show that the structure is strongly textured in the (1 0 0) direction when grown on SrTiO{sub 3}, regardless the composition of the bottom layer. A different result is found on the same system grown on MgO: when the buffer layer is CaMnO{sub 3}, the structure grows in the (1 1 0) orientation while it grows in the (1 0 0) direction when the bottom layer is La{sub 2/3}Sr{sub 1/3}MnO{sub 3}. Magnetic coupling of the ferromagnetic layers across the antiferromagnetic spacer has been studied with magnetization measurements.

  3. Where Water is Oxidized to Dioxygen: Structure of thePhotosynthetic Mn4Ca Cluster

    Yano, Junko; Kern, Jan; Sauer, Kenneth; Latimer, Matthew J.; Pushkar, Yulia; Biesiadka, Jacek; Loll, Bernhard; Saenger, Wolfram; Messinger, Johannes; Zouni, Athina; Yachandra, Vittal K.


    Oxidation of water to dioxygen is catalyzed withinphotosystem II (PSII) by a Mn4Ca cluster, the structure of which remainselusive. Polarized extended X-ray absorption fine structure (EXAFS)measurements on PSII single crystals constrain the Mn4Ca cluster geometryto a set of three similar high-resolution structures. Combining polarizedEXAFS and X-ray diffraction data, the cluster was placed within PSIItaking into account the overall trend of the electron density of themetal site and the putative ligands. The structure of the cluster fromthe present study is unlike either the 3.0 or 3.5 Angstrom resolutionX-ray structures, and other previously proposed models.

  4. Microstructure and Mechanical Properties of Mg-Al-Ca-Nd Alloys Fabricated by Gravity Casting


    The aims of this study are to investigate the effects of Nd addition in the Mg-Al-Ca alloys on microstructure and mechanical properties. Microstructure of as-cast Mg-5Al-3Ca alloy containing Nd consists of α-Mg matrix,eutectic phase and Al-Nd rich intermetallic compound. As Nd addition was increased, α-Mg matrix morphology was changed from dendritic to equiaxed grains and average value of grain size was decreased. Nd addition to Mg-5Al-3Ca based alloys resulted in the formation of Al-Nd rich intermetallic compounds at grain boundary and α-Mg matrix grains. And these Al-Nd rich intermetallic compounds were dispersed homogeneously. In these alloys, two kinds of eutectic phases were observed, i.e. coarse irregular-shape structure at grain boundary and fine needle-shape structure in the α-Mg matrix grain. It is found that the ultimate strength showed the maximum value of 271 MPa at Mg-5Al-3Ca-2Nd alloy and elongation was decreased as the addition of Nd was increased.

  5. Afterglow kinetics and storage mechanism in CaF{sub 2}:Mn (TLD-400)

    Danilkin, M. [Faculty of Physics and Chemistry, University of Tartu, Taehe 4, 51010 Tartu (Estonia)], E-mail:; Lust, A.; Ratas, A.; Seeman, V.; Kerikmaee, M. [Faculty of Physics and Chemistry, University of Tartu, Taehe 4, 51010 Tartu (Estonia)


    Thermoluminescence (TL) of CaF{sub 2}:Mn and the isothermal afterglow curves were studied after a pre-annealing of irradiated samples. Afterglow kinetics can be easily approximated with two exponents. A simple kinetic model is suggested. The TL main peak activation energy (1.597 eV) is very close to the dissociation energy of F{sub 2} molecule (1.606 eV) and exceeds the thermal decay activation energies of all the other intrinsic defects previously known in CaF{sub 2}. A mechanism of energy storage and release is discussed.

  6. Effect of doping Ca on polaron hopping in LaSr2Mn2O7

    S N Bhatia; Osama A Yassin


    From the transport studies in the bilayer manganites LaSr2-CaMn2O7, we have found the variable-range hopping model proposed by Viret et al to be inadequate to describe the transport of charge in these materials. The polarons appear to hop to their nearest neighbors with an activation energy, which in part is dependent on the magnetic interactions in the lattice.

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

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


    The kidney plays an important role in maintaining the systemic Ca2+ and Mg2+ balance. Thus the renal reabsorptive capacity of these cations can be amended to adapt to disturbances in plasma Ca2+ and Mg2+ concentrations. The reabsorption of Ca2+ and Mg2+ is driven by transport of other electrolytes......, sometimes through selective channels and often supported by hormonal stimuli. It is, therefore, not surprising that monogenic disorders affecting such renal processes may impose a shift in, or even completely blunt, the reabsorptive capacity of these divalent cations within the kidney. Accordingly, in Dent......'s disease, a disorder with defective proximal tubular transport, hypercalciuria is frequently observed. Dysfunctional thick ascending limb transport in Bartter's syndrome, familial hypomagnesaemia with hypercalciuria and nephrocalcinosis, and diseases associated with Ca2+-sensing receptor defects, markedly...

  8. Evolutions of Microclusters of Biodegradable Mg3Ca7 Potential Medical Implant Alloy

    ZHOU Li-li; ZHOU Yan-hong; PENG You-lin; TIAN Ze-an; LIU Rang-su


    The molecular dynamics simulation calculation on the microclusters evo-lution properties of liquid Mg 3Ca7 during the rapid solidifications has been performed. Re-sults indicated that the icosahedron microcluster played key role in the glass transition which happened at about 600 K;it suggests that the formation and evolution mechanism of icosahedral order is important for the corrosion resistance of medical implant material of Mg-and Mg-Ca based alloys. It is also found that the icosahedron structure is unstable in the liquid and supercooled liquid until the glass transition occurs.

  9. Effects of praseodymium doping on thermoelectric transport properties of CaMnO3 compound system

    张飞鹏; 牛保成; 张坤书; 张忻; 路清梅; 张久兴


    The rare earth Pr doped Ca1-xPrxMnO3 (x=0, 0.06, 0.08, 0.1, 0.12, and 0.14) compound bulk samples were prepared to study the effect of Pr doping on thermoelectric transport properties of CaMnO3 compound system. The doped samples exhibited sin-gle phase composition within the experimental doping range, with condensed bulk microstructure and small porosities. The electrical resistivity was remarkably reduced for doped samples, on account of the enhanced carrier concentration;the absolute value of See-beck coefficient was deteriorated mainly due to enhanced electron carrier concentration. The electrical performances of the doped samples reflected by resistivity and Seebeck coefficient fluctuations were optimistically tuned, with an optimized power factor value of 0.342 mW/(m·K2) at 873 K for x=0.08 sample, which was very much higher comparing with that of the un-doped sample. The lattice thermal conduction was really confined, leading to distinctly repressed total thermal conductivity. The thermoelectric per-formance was noticeably improved by Pr doping and the dimensionless figure of merit ZT for the Ca0.92Pr0.08MnO3 compound was favorably optimized with the maximum value 0.16 at 873 K.

  10. Intrinsic scintillators: TlMgCl3 and TlCaI3

    Hawrami, R.; Ariesanti, E.; Wei, H.; Finkelstein, J.; Glodo, J.; Shah, K. S.


    Two intrinsic scintillators TlMgCl3 and TlCaI3 with excellent energy resolution and fast scintillation decay are presented. Crack-free transparent crystals were successfully grown by the Bridgman method. The scintillation light yields of TlMgCl3 and TlCaI3 are approximately 30,600 ph/MeV and 42,200 ph/MeV, respectively. Their energy resolutions at 662 keV are 3.7% for TlMgCl3 and 6.2% for TlCaI3. The scintillation decay times of TlMgCl3 are 46 ns, 166 ns, and 449 ns. The scintillation decay times of TlCaI3 are 62 ns, 200 ns, and 1.44 μs. Under X-ray irradiation, the emission of TlMgCl3 is between 300 nm and 540 nm with the peak at 409 nm. TlCaI3 has a broad emission band between 300 nm and 750 nm. Due to their excellent scintillation properties, these two scintillators can be developed for gamma-ray detection. Additionally, TlMgCl3 is non-hygroscopic.

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

    Xi Chen


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

  12. Synthesis and tunable luminescence of RbCaGd(PO4)2:Ce3+, Mn2+ phosphors

    Chen, Xue; Lv, Fengzhu; Li, Penggang; Zhang, Yihe


    RbCaGd(PO4)2 doped with Ce3+, Mn2+ was synthesized by the sol-gel method. The crystal structure and crystallographic location of Ce3+ in RbCaGd(PO4)2 were identified by Rietveld refinement. Powder X-ray diffraction (XRD) revealed that the structure of RbCaGd(PO4)2:Ce3+ compounds is hexagonal structure which is similar to that of hexagonal LnPO4 with the lattice constant of a = b = 7.005(57) Å, c = 6.352(05) Å, and V (cell volume) = 269.980 Å3. The photoluminescence behavior and emission mechanism were studied systematically by doping activators in the RbCaGd(PO4)2 host. The Mn2+ incorporated RbCaGd(PO4)2:Ce3+, Mn2+ compounds exhibited blue emission from the parity- and spin-allowed f-d transition of Ce3+ and orange-to-red emission from the forbidden 4T1 → 6A1 transition of Mn2+. The emission chromaticity coordinates of RbCaGd(PO4)2:0.10Ce3+, xMn2+ (x = 0.16, 0.25) are close to the white region due to an energy transfer process and the energy transfer mechanism from Ce3+ to Mn2+ in the RbCaGd(PO4)2 host was dominated by dipole-dipole interactions.

  13. The effects of diagenesis and dolomitization on Ca and Mg isotopes in marine platform carbonates: Implications for the geochemical cycles of Ca and Mg

    Fantle, Matthew S.; Higgins, John


    The Ca, Mg, O, and C isotopic and trace elemental compositions of marine limestones and dolostones from ODP Site 1196A, which range in depth (∼58 to 627 mbsf) and in depositional age (∼5 and 23 Ma), are presented. The objectives of the study are to explore the potential for non-traditional isotope systems to fingerprint diagenesis, to quantify the extent to which geochemical proxies are altered during diagenesis, and to investigate the importance of diagenesis within the global Ca and Mg geochemical cycles. The data suggest that Ca, which has a relatively high solid to fluid mass ratio, can be isotopically altered during diagenesis. In addition, the alteration of Ca correlates with the alteration of Mg in such a way that both can serve as useful tools for deciphering diagenesis in ancient rocks. Bulk carbonate δ44Ca values vary between 0.60 and 1.31‰ (SRM-915a scale); the average limestone δ44Ca is 0.97 ± 0.24‰ (1SD), identical within error to the average dolostone (1.03 ± 0.15 1SD ‰). Magnesium isotopic compositions (δ26Mg, DSM-3 scale) range between -2.59‰ and -3.91‰, and limestones (-3.60 ± 0.25‰) and dolostones (-2.68 ± 0.07‰) are isotopically distinct. Carbon isotopic compositions (δ13C, PDB scale) vary between 0.86‰ and 2.47‰, with average limestone (1.96 ± 0.31‰) marginally offset relative to average dolostone (1.68 ± 0.57‰). The oxygen isotopic compositions (δ18O, PDB scale) of limestones (-1.22 ± 0.94‰) are substantially lower than the dolostones measured (2.72 ± 1.07‰). The isotopic data from 1196A suggest distinct and coherent trends in isotopic and elemental compositions that are interpreted in terms of diagenetic trajectories. Numerical modeling supports the contention that such trends can be interpreted as diagenetic, and suggests that the appropriate distribution coefficient (KMg) associated with limestone diagenesis is ∼1 to 5 × 10-3, distinctly lower than those values (>0.015) reported in laboratory

  14. Electronic transport in ferroelectric-ferromagnetic composites La5/8(Ba,Ca)3/8MnO3:LuMnO3

    Mandal, P.; Choudhury, P.; Ghosh, B.


    An almost complete immiscibility between metallic ferromagnet La5/8Ba3/8MnO3 or La5/8Ca3/8MnO3 and insulating ferroelectric LuMnO3 has been established from structural, magnetic, and transport studies. Both (x) La5/8Ba3/8MnO3:(1-x)LuMnO3 and (x) La5/8Ca3/8MnO3:(1-x)LuMnO3 show a metal-insulator transition below a critical volume fraction xvc of the metallic component. Over the entire range of x>xvc , electronic conduction follows a classical percolation model. The conductivity scaling exponent t is the same as that of the universal value (=2) for the three-dimensional (3D) system; xvc is also close to the theoretical prediction for the 3D continuum model. For xLuMnO3 . The temperature dependence of both resistivity and thermopower for 0≤x

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

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


    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

  16. n型CaMnO3基氧化物热电材料研究进展%Progress in n-type CaMnO3-based Oxide Thermoelectric Materials

    张飞鹏; 郭志超; 刘剑; 王新练; 张坤书


      n型CaMnO3基氧化物是一种具有优异高温热电性能的n型热电材料体系,从CaMnO3基热电氧化物晶体结构、物性、电子结构、电热传输理论以及Ca位掺杂、Mn位掺杂、Ca和Mn位复合掺杂优化其电热输运性能的角度,综述了 n 型 CaMnO3基热电氧化物的最新研究进展,给出了存在的问题和今后研究的方向。%The n-type CaMnO3 oxide based compound is one of the most promising thermoelectric materials due to its high temperature thermoelectric properties. The paper summarizes the CaMnO3 oxide based thermoelectric materials, mainly in terms of the crystal structure, physical properties, electronic structure, thermoelectric transport theory and Ca site doping, Mn site doping, as well as double doping effects on thermoelectric transport properties. And the research issues and orientations in the near future are pointed out.

  17. Comparative in vitro Study on Pure Metals (Fe, Mn, Mg, Zn and W)as Biodegradable Metals

    J.Cheng; B.Liu; Y.H.Wu; Y.F.Zheng


    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:Mg > Fe > 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.

  18. Perpendicular magnetic anisotropy of Mn{sub 4}N films on MgO(001) and SrTiO{sub 3}(001) substrates

    Yasutomi, Yoko; Ito, Keita; Sanai, Tatsunori; Toko, Kaoru; Suemasu, Takashi, E-mail: [Institute of Applied Physics, Graduate School of Pure and Applied Sciences, University of Tsukuba, 1-1-1 Tennodai, Tsukuba, Ibaraki 305-8573 (Japan)


    We grew Mn{sub 4}N epitaxial thin films capped with Au layers on MgO(001) and SrTiO{sub 3}(001) substrates by molecular beam epitaxy. Perpendicular magnetic anisotropy (PMA) was confirmed in all the samples at room temperature from the magnetization versus magnetic field curves using superconducting quantum interference device magnetometer. From the ω-2θ x-ray diffraction (XRD) and ϕ-2θ{sub χ} XRD patterns, the ratios of perpendicular lattice constant c to in-plane lattice constant a, c/a, were found to be about 0.99 for all the samples. These results imply that PMA is attributed to the in-plane tensile strain in the Mn{sub 4}N films.

  19. Synthesis, structure, and magnetic properties of novel B-site ordered double perovskites, SrLaMReO6 (M = Mg, Mn, Co and Ni).

    Thompson, Corey M; Chi, Lisheng; Hayes, John R; Hallas, Alannah M; Wilson, Murray N; Munsie, Timothy J S; Swainson, Ian P; Grosvenor, Andrew P; Luke, Graeme M; Greedan, John E


    Four new double perovskites, SrLaMReO(6) (M = Mg, Mn, Co, Ni) in which Re(5+) (5d(2)) is present, were prepared via conventional solid state reactions and characterized by X-ray and neutron powder diffraction, XANES, SQUID magnetometry, and muon spin relaxation (μSR). Synchrotron X-ray and neutron diffraction experiments confirmed that all compounds crystallize in the monoclinic P2(1)/n structure type, which consists of alternately corner-shared octahedra of MO(6) and ReO(6). Rietveld refinement results indicated anti-site mixing of less than 7% on the M/Re sites. Bond valence sum calculations (BVS) suggest all M and Re ions are 2+ and 5+, respectively, and for the Mn-containing phase this is also supported by XANES measurements. All of the materials are paramagnetic at room-temperature and their Curie-Weiss temperatures are positive (except for Mg) indicating net ferromagnetic interactions. No evidence for long-range magnetic order is evident in the dc magnetic susceptibility and μSR measurements for SrLaMgReO(6) to 2 K. The Mn-phase shows long-range order at T(C) = 190 K and neutron diffraction revealed a ferromagnetic structure with a refined net moment of ∼3.7μ(B). Both Co- and Ni-containing phases exhibit spin glass behavior at T(G) = 23 and 30 K, respectively, which is supported by neutron diffraction and a.c. susceptibility data. The structure and physical properties of these four new rhenium based ordered double perovskites are compared to the closely related "pillared perovskites", La(5)Re(3)MO(16), the isoelectronic Os(6+) (5d(2)) double perovskite Sr(2)CoOsO(6), and the Re(6+) (5d(1)) double perovskites, Sr(2)MReO(6), (M = Mg, Ca, Mn, Co, Ni).

  20. Culture-based Calibration of the Benthic Foraminiferal Mg/Ca Paleothermometer: Initial Results

    Lincoln, S. A.; Filipsson, H. L.; Bernhard, J. M.; McCorkle, D. C.; Shimizu, N.; Birdwhistell, S. P.


    The magnesium calcium (Mg/Ca) paleothermometer has become a widely used tool for estimating deep water temperatures. To date, calibrations of the proxy have relied on core-top samples; in such studies, water chemistry and biological factors including food supply often co-vary with temperature, making it difficult to isolate the true Mg/Ca / temperature relationship. A multi-temperature culture experiment was conducted at the Woods Hole Oceanographic Institution from December 2006 through May 2007 in order to study the relationship between Mg/Ca and temperature under controlled conditions. Several species of benthic foraminifera were collected from four locations (the Skagerrak and Gullmar Fjord, Sweden; the Bahamas; and the Charleston Bump, United States; 70 to 800 m water depth), and were grown in microcosms under known, constant physical and chemical conditions at 3.5, 7.0, 14.0, and 21 C. Bulimina species ( B. aculeata and B. marginata) were the most successful, reproducing at 7.0 and 14.0 C and adding chambers at all temperatures. These newly added chambers are the focus of our first Mg/Ca analyses. Because cultured benthic foraminifera are typically lightly calcified, sensitive microanalytical techniques with high spatial resolution are required to measure trace element concentrations in single chambers of cultured specimens. We have explored the use of both secondary ion mass spectrometry and laser ablation inductively coupled mass spectrometry for this application, and present preliminary Mg/Ca data from Bulimina species across the experimental temperature range.

  1. Influences of Dopants on Microstructure and Magnetic Properties of(Mg0.476Mn0.448Zn0.007)(Fe1.997Ti0.002)O4 Ferrites

    LU Hongzhi


    Influences of addition of CaO,CoO and V2O5 on the microstructure and magnetic properties of(Mg(0.476)Mn(0.448)Zn(0.007))(Fe(1.997)Ti(0.002))O4 ferrites were investigated.The powders of(Mg(0.476)Mn(0.448)Zn(0.007))(Fe(1.997)Ti(0.002))O4 composition were prepared by using a conventional ceramic powder processing technique.The experimental results showed that the average grain size of the sintered ferrites codoped with 0.03wt% CaO,0.04wt% CoO and 0.06wt% V2O5 was about 15 μm;the saturation magnetization of ferrites was 68.78 emu/g.The addition of V2O5 in the ferrites can not only increase value of the saturation magnetization,but also decrease the average grain size of(Mg(0.476)Mn(0.448)Zn(0.007))(Fe(1.997)Ti(0.002))O4 ferrites.Simultaneous incorporation of CoO,CaO and V2O5 dopants into(Mg0.476Mn0.448Zn0.007)(Fe(1.997)Ti(0.002))O4 ferrites can not only improve the saturation magnetization of the materials,but also inhibit abnormal grain growth.

  2. Mechanical, thermal, and physical properties of Mg-Ca compounds in the framework of the modified embedded-atom method.

    Groh, Sébastien


    Interatomic potentials for pure Ca and the Mg-Ca binary have been developed in the framework of the second nearest-neighbors modified embedded-atom method (MEAM). The validity and the transferability of the Ca MEAM potential was performed by calculating physical, mechanical, and thermal properties. These properties were compared to experimental data and numerical data obtained from existing Ca potentials, and a good agreement was found. In addition, the dissociation of the edge dislocation into two Shockley partials aligns with the linear elasticity solution. Furthermore, the velocity of an edge dislocation under static and dynamics loading conditions predicted in Ca using the MEAM formalism reproduces the expected behavior of an edge dislocation in fcc crystal structures. The Ca MEAM potential was then coupled to an existing Mg MEAM potential to describe the properties of the Mg-Ca alloys. Heat of formation, structural energy difference, and elastic constants were calculated for several ordered Mg-Ca compounds containing different concentrations of Ca. As expected from first-principle calculations based on DFT, Mg2Ca with the Laves phase C14 was found to be the most stable structure with the lowest heat of formation compared to compounds with other Ca concentrations (Mg3Ca, MgCa, and MgCa3). Moreover, the mechanical stability was recovered for the different tested compounds and is in agreement with first-principle data.

  3. Thermoelectric properties of Ca0.8Dy0.2MnO3 synthesized by solution combustion process

    Park Kyeongsoon


    Full Text Available Abstract High-quality Ca0.8Dy0.2MnO3 nano-powders were synthesized by the solution combustion process. The size of the synthesized Ca0.8Dy0.2MnO3 powders was approximately 23 nm. The green pellets were sintered at 1150-1300°C at a step size of 50°C. Sintered Ca0.8Dy0.2MnO3 bodies crystallized in the perovskite structure with an orthorhombic symmetry. The sintering temperature did not affect the Seebeck coefficient, but significantly affected the electrical conductivity. The electrical conductivity of Ca0.8Dy0.2MnO3 increased with increasing temperature, indicating a semiconducting behavior. The absolute value of the Seebeck coefficient gradually increased with an increase in temperature. The highest power factor (3.7 × 10-5 Wm-1 K-2 at 800°C was obtained for Ca0.8Dy0.2MnO3 sintered at 1,250°C. In this study, we investigated the microstructure and thermoelectric properties of Ca0.8Dy0.2MnO3, depending on sintering temperature.

  4. Low temperature specific heat (zero field and with field) of Fe and Mn-doped MgB{sub 2}

    Rao, Ashok [Department of Physics, Manipal Institute of Technology, Manipal 576104 (India)], E-mail:; Gahtori, Bhasker; Agarwal, S.K. [Superconductivity and Cryogenics Division, National Physical Laboratory, Dr. K.S. Krishnan Road, New Delhi 110012 (India); Chakraborty, Tirthankar; Sarkar, Chandan Kumar [Department of Electronics and Telecommunication Engineering, Jadavpur University, Kolkata 700032 (India); Das, Anirban [Department of Physics, Sikkim Manipal Institute of Technology, Majitar, Rangpo, Sikkim 737132 (India)


    Polycrystalline samples of MgB{sub 2} superconductor (Mn-doped as well as pristine) were investigated by measurements of the electrical resistivity, magneto-resistance in the temperature range of 4-300 K. All the samples show metallic behaviour. It is observed that the upper critical field slightly decreases with Mn concentration. Specific heat measurements were performed with field as well as without field. For comparison, we also prepared one Fe-doped and specific heat measurements were also carried out on this sample. It is observed that the jump in specific heat decreases with increase in Mn content.

  5. A comparison of benthic foraminiferal Mn / Ca and sedimentary Mn / Al as proxies of relative bottom-water oxygenation in the low-latitude NE Atlantic upwelling system

    McKay, C. L.; Groeneveld, J.; Filipsson, H. L.; Gallego-Torres, D.; Whitehouse, M. J.; Toyofuku, T.; Romero, O. E.


    Trace element incorporation into foraminiferal shells (tests) is governed by physical and chemical conditions of the surrounding marine environment, and therefore foraminiferal geochemistry provides a means of palaeo-oceanographic reconstructions. With the availability of high-spatial-resolution instrumentation with high precision, foraminiferal geochemistry has become a major research topic over recent years. However, reconstructions of past bottom-water oxygenation using foraminiferal tests remain in their infancy. In this study we explore the potential of using Mn / Ca determined by secondary ion mass spectrometry (SIMS) as well as by flow-through inductively coupled plasma optical emission spectroscopy (FT-ICP-OES) in the benthic foraminiferal species Eubuliminella exilis as a proxy for recording changes in bottom-water oxygen conditions in the low-latitude NE Atlantic upwelling system. Furthermore, we compare the SIMS and FT-ICP-OES results with published Mn sediment bulk measurements from the same sediment core. This is the first time that benthic foraminiferal Mn / Ca is directly compared with Mn bulk measurements, which largely agree on the former oxygen conditions. Samples were selected to include different productivity regimes related to Marine Isotope Stage 3 (35-28 ka), the Last Glacial Maximum (28-19 ka), Heinrich Event 1 (18-15.5 ka), Bølling Allerød (15.5-13.5 ka) and the Younger Dryas (13.5-11.5 ka). Foraminiferal Mn / Ca determined by SIMS and FT-ICP-OES is comparable. Mn / Ca was higher during periods with high primary productivity, such as during the Younger Dryas, which indicates low-oxygen conditions. This is further supported by the benthic foraminiferal faunal composition. Our results highlight the proxy potential of Mn / Ca in benthic foraminifera from upwelling systems for reconstructing past variations in oxygen conditions of the sea floor environment as well as the need to use it in combination with other proxy records such as faunal

  6. Charge transport and magnetization profile at the interface between the correlated metal CaRuO3 and the antiferromagnetic insulator CaMnO3

    Freeland, J. W. [Argonne National Laboratory (ANL); Chakhalian, J. [University of Arkansas; Boris, A. V. [Max-Planck-Institut fur Feskorperforschung, Stuttgart, Germany; Tonnerre, J.-M. [CNRS, France; Kavich, J. J. [University of Illinois, Chicago; Yordanov, P. [Max-Planck-Institut fur Feskorperforschung, Stuttgart, Germany; Grenier, S. [CNRS, Grenoble, France; Lee, Ho Nyung [ORNL; Keimer, Bernhard [Max-Planck-Institut fur Feskorperforschung, Stuttgart, Germany


    A combination of spectroscopic probes was used to develop a detailed experimental description of the transport and magnetic properties of superlattices composed of the paramagnetic metal CaRuO3 and the antiferromagnetic insulator CaMnO3. The charge carrier density and Ru valence state in the superlattices are not significantly different from those of bulk CaRuO3. The small charge transfer across the interface implied by these observations confirms predictions derived from density functional calculations. However, a ferromagnetic polarization due to canted Mn spins penetrates 3-4 unit cells into CaMnO3, far exceeding the corresponding predictions. The discrepancy may indicate the formation of magnetic polarons at the interface.

  7. Effects of Mg2+ on Ca2+ handling by the sarcoplasmic reticulum in skinned skeletal and cardiac muscle fibres.

    Kabbara, A A; Stephenson, D G


    The influence of myoplasmic Mg2+ (0.05-10 mM) on Ca2+ accumulation (net Ca2+ flux) and Ca2+ uptake (pump-driven Ca2+ influx) by the intact sarcoplasmic reticulum (SR) was studied in skinned fibres from the toad iliofibularis muscle (twitch portion), rat extensor digitorum longus (EDL) muscle (fast twitch), rat soleus muscle (slow twitch) and rat cardiac trabeculae. Ca2+ accumulation was optimal between 1 and 3 mM Mg2+ in toad fibres and reached a plateau between 1 and 10 mM Mg2+ in the rat EDL fibres and between 3 and 10 mM Mg2+ in the rat cardiac fibres. In soleus fibres, optimal Ca2+ accumulation occurred at 10 mM Mg2+. The same trend was obtained with all preparations at 0.3 and 1 microM Ca2+. Experiments with 2,5-di-(tert-butyl)-1,4-benzohydroquinone, a specific inhibitor of the Ca2+ pump, revealed a marked Ca2+ efflux from the SR of toad iliofibularis fibres in the presence of 0.2 microM Ca2+ and 1 mM Mg2+. Further experiments indicated that the SR Ca2+ leak could be blocked by 10 microM ruthenium red without affecting the SR Ca2+ pump and this allowed separation between SR Ca2+ uptake and SR Ca2+ accumulation. At 0.3 microM Ca2+, Ca2+ uptake was optimal with 1 mM Mg2+ in the toad iliofibularis and rat EDL fibres and between 1 and 10 mM Mg2+ in the rat soleus and trabeculae preparations. At higher [Ca2+] (1 microM), Ca2+ uptake was optimal with 1 mM Mg2+ in the iliofibularis fibres and between 1 and 3 mM Mg2+ in the EDL fibres.(ABSTRACT TRUNCATED AT 250 WORDS)

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

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


    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...... 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......6 channels are located in the renal distal convolution, the main site of active transcellular Ca(2+) and Mg(2+) transport. The channels are regulated by a multitude of factors and hormones that contribute importantly to keeping the systemic concentrations of Ca(2+) and Mg(2+) within normal limits...

  9. Lithio­marsturite, LiCa2Mn2Si5O14(OH)

    Yang, Hexiong; Downs, Robert T.; Yang, Yongbo W.


    Lithio­marsturite, ideally LiCa2Mn2Si5O14(OH), is a member of the pectolite–pyroxene series of pyroxenoids (hydro­pyroxenoids) and belongs to the rhodonite group. A previous structure determination of this mineral based on triclinic symmetry in space group P by Peacor et al. [Am. Mineral. (1990), 75, 409–414] converged with R = 0.18 without reporting any information on atomic coordinates and displacement param­eters. The current study redetermines its structure from a natural specimen from the type locality (Foote mine, North Carolina) based on single-crystal X-ray diffraction data. The crystal structure of lithio­marsturite is characterized by ribbons of edge-sharing CaO6 and two types of MnO6 octa­hedra as well as chains of corner-sharing SiO4 tetra­hedra, both extending along [110]. The octa­hedral ribbons are inter­connected by the rather irregular CaO8 and LiO6 polyhedra through sharing corners and edges, forming layers parallel to (1), which are linked together by the silicate chains. Whereas the coordination environments of the Mn and Li cations can be compared to those of the corresponding cations in nambulite, the bonding situations of the Ca cations are more similar to those in babingtonite. In contrast to the hydrogen-bonding scheme in babingtonite, which has one O atom as the hydrogen-bond donor and a second O atom as the hydrogen-bond acceptor, our study shows that the situation is reversed in lithio­marsturite for the same two O atoms, as a consequence of the differences in the bonding environments around O atoms in the two minerals. PMID:22199471

  10. Lithio-marsturite, LiCa(2)Mn(2)Si(5)O(14)(OH).

    Yang, Hexiong; Downs, Robert T; Yang, Yongbo W


    Lithio-marsturite, ideally LiCa(2)Mn(2)Si(5)O(14)(OH), is a member of the pectolite-pyroxene series of pyroxenoids (hydro-pyroxenoids) and belongs to the rhodonite group. A previous structure determination of this mineral based on triclinic symmetry in space group P[Formula: see text] by Peacor et al. [Am. Mineral. (1990), 75, 409-414] converged with R = 0.18 without reporting any information on atomic coordinates and displacement param-eters. The current study redetermines its structure from a natural specimen from the type locality (Foote mine, North Carolina) based on single-crystal X-ray diffraction data. The crystal structure of lithio-marsturite is characterized by ribbons of edge-sharing CaO(6) and two types of MnO(6) octa-hedra as well as chains of corner-sharing SiO(4) tetra-hedra, both extending along [110]. The octa-hedral ribbons are inter-connected by the rather irregular CaO(8) and LiO(6) polyhedra through sharing corners and edges, forming layers parallel to ([Formula: see text]1[Formula: see text]), which are linked together by the silicate chains. Whereas the coordination environments of the Mn and Li cations can be compared to those of the corresponding cations in nambulite, the bonding situations of the Ca cations are more similar to those in babingtonite. In contrast to the hydrogen-bonding scheme in babingtonite, which has one O atom as the hydrogen-bond donor and a second O atom as the hydrogen-bond acceptor, our study shows that the situation is reversed in lithio-marsturite for the same two O atoms, as a consequence of the differences in the bonding environments around O atoms in the two minerals.

  11. Ferromagnetism in IV main group element (C and transition metal (Mn doped MgO: A density functional perspective

    Vinit Sharma


    Full Text Available The formation of magnetic moment due to the dopants with p-orbital (d-orbital is named d0 (d − magnetism, where the ion without (with partially filled d states is found to be responsible for the observed magnetic properties. To study the origin of magnetism at a fundamental electronic level in such materials, as a representative case, we theoretically investigate ferromagnetism in MgO doped with transition metal (Mn and non-metal (C. The generalized gradient approximation based first-principles calculations are used to investigate substitutional doping of metal (Mn and non-metal (C, both with and without the presence of neighboring oxygen vacancy sites. Furthermore, the case of co-doping of (Mn, C in MgO system is also investigated. It is observed that the oxygen vacancies do not play a role in tuning the ferromagnetism in presence of Mn dopants, but have a significant influence on total magnetism of the C doped system. In fact, we find that in MgO the d0 magnetism through C doping is curtailed by pairing of the substitutional dopant with naturally occurring O vacancies. On the other hand, in case of (Mn, C co-doped MgO the strong hybridization between the C (2p and the Mn(3d states suggests that co-doping is a promising approach to enhance the ferromagnetic coupling between the nearest-neighboring dopant and host atoms. Therefore, (Mn,C co-doped MgO is expected to be a ferromagnetic semiconductor with long ranged ferromagnetism and high Curie temperature.

  12. Mg/Ca and Sr/Ca as novel geochemical proxies for understanding sediment transport processes within coral reefs

    Gacutan, J.; Vila-Concejo, A.; Nothdurft, L. D.; Fellowes, T. E.; Cathey, H. E.; Opdyke, B. N.; Harris, D. L.; Hamylton, S.; Carvalho, R. C.; Byrne, M.; Webster, J. M.


    Sediment transport is a key driver of reef zonation and biodiversity, where an understanding of sediment dynamics gives insights into past reef processes and allows the prediction of geomorphic responses to changing environmental conditions. However, modal conditions within the back-reef seldom promote sediment transport, hence direct observation is inherently difficult. Large benthic foraminifera (LBF) have previously been employed as 'tracers' to infer sediment transport pathways on coral reefs, as their habitat is largely restricted to the algal flat and post-mortem, their calcium carbonate test is susceptible to sediment transport forces into the back-reef. Foraminiferal test abundance and post-depositional test alteration have been used as proxies for sediment transport, although the resolution of these measures becomes limited by low test abundance and the lack of variation within test alteration. Here we propose the novel use of elemental ratios as a proxy for sediment transport. Two species, Baculogypsina sphaerulata and Calcarina capricornia, were analysed using a taphonomic index within One Tree and Lady Musgrave reefs, Great Barrier Reef (Australia). Inductively coupled plasma-atomic emission spectrometry (ICP-AES) was used to determine Mg/Ca and Sr/Ca and these ratios were compared with taphonomic data. Decreases in test Mg/Ca accompany increases in Sr/Ca in specimens from algal-flat to lagoonal samples in both species, mirroring trends indicated by taphonomic values, therefore indicating a relationship with test alteration. To delineate mechanisms driving changes in elemental ratios, back-scattered electron (BSE) images, elemental mapping and in situ quantitative spot analyses by electron microprobe microanalysis (EPMA) using wavelength dispersive X-ray spectrometers (WDS) were performed on un-altered algal flat and heavily abraded tests for both species. EPMA analyses reveal heterogeneity in Mg/Ca between spines and the test wall, implying the loss of

  13. Mixed Mg-Mn ferrites for high frequency applications processed by citrate precursor technique

    Kumar, Gagan; Chand, Jagdish; Verma, Satish; Singh, M, E-mail: [Department of Physics, Himachal Pradesh University, Shimla, 171005 India (India)


    Mg{sub 0.9}Mn{sub 0.1}In{sub x}Fe{sub 2-x} O{sub 4} (x = 0.1 and 0.2) and Mg{sub 0.9}Mn{sub 0.1}Al{sub y}Fe{sub 2-y} O{sub 4} (y = 0.1, 0.5 and 0.7) ferrites, with improved initial permeability and extremely low relative loss factor (RLF), were synthesized by the citrate precursor technique. Structural studies were made by using the x-ray diffraction technique and scanning electron microscopy (SEM), which confirm the formation of single-phase spinel structure. The size of the particle was of the order of {approx}0.5 {mu}m for the samples sintered at 1200 {sup 0}C, which is smaller than that obtained for ferrite powders by the conventional ceramic method. The magnetic properties such as initial permeability and RLF with frequency, in the range 0.1-20 MHz, at different temperatures have been investigated. Initial permeability ({mu}{sub i}) attains a very high value, 17342, for the In{sup 3+} doped ferrite series and for the Al{sup 3+} doped ferrite series the maximum value is 3785. The RLF was found to have low values and is of the order of 10{sup -5}-10{sup -4} in the frequency range 0.1-20 MHz. In addition to this, an increase in the value of {mu}{sub i} was observed with the rise in the temperature for all the series of ferrites.

  14. Correlation effects in MgO and CaO Cohesive energies and lattice constants

    Doll, K; Stoll, H; Doll, Klaus; Dolg, Michael; Stoll, Hermann


    A recently proposed computational scheme based on local increments has been applied to the calculation of correlation contributions to the cohesive energy of the CaO crystal. Using ab-initio quantum chemical methods for evaluating individual increments, we obtain 80% of the difference between the experimental and Hartree-Fock cohesive energies. Lattice constants corrected for correlation effects deviate by less than 1% from experimental values, in the case of MgO and CaO.

  15. Mg/Ca and δ18O in the calcite of benthic foraminifera: does size matter?

    de Nooijer, Lennart; Bijma, Jelle; -Jan Reichart, Gert; Hathorne, Ed


    Mg/Ca and del-18O are popular proxies for past sea water temperatures, ice volume and, together, salinity. The biological control that foraminifera have over calcification results in precipitation of calcium carbonate that has an isotope and element composition that is very different from those of inorganically precipitated calcium carbonates. Indications for an effect of ontogeny (i.e. size of a specimen) on the fractionation of oxygen isotopes are contradictory, while for the incorporation of most (trace) elements, data are lacking. The causes of size-based variability in element incorporation and isotope fractionation need to be understood and quantified in order to reliably use them as paleoproxies. In this study, we present Mg/Ca and oxygen isotope data from cultured specimens of the benthic foraminifer Ammonia tepida. When asexual reproduction takes place in this species, 50-300 genetically identical juveniles (i.e. clones) are produced. These juveniles are cultured at constant temperature, carbonate chemistry, salinity, etc to determine inter- and intra-specimen variability in Mg/Ca, Ba/Ca and Sr/Ca. From the same groups of clones, del-18O was determined from specimens with different sizes. Results show that the variability differs greatly between the analysed elements (e.g. relatively constant for Sr and Ba, variable for Mg) and isotopes, underscoring the need for a biological understanding of foraminiferal calcification pathways.

  16. Structural and magnetic properties of ferrimagnetic ε-phase Mn4N and antiferromagnetic ζ-phase Mn10N thin films on MgO(001)

    Foley, Andrew; Corbett, Joseph; Richard, Andrea L.; Alam, Khan; Ingram, David C.; Smith, Arthur R.


    Single phase ε-Mn4N and ζ-Mn10N thin films are grown on MgO(001) using molecular beam epitaxy. The films are identified and characterized using reflection high-energy electron diffraction, x-ray diffraction, back scattered electron scanning electron microscopy, atomic/magnetic force microscopy and Rutherford backscattering spectrometry. These films are found to be highly smooth with root-mean-squared roughnesses 3.39 nm and below. The quality of ε-Mn4N grown is strongly dependent on substrate temperature during growth. Epitaxial growth of substantial grains composed of the antiferromagnetic η-phase Mn3N2 side by side with ferrimagnetic ε-phase grains is observed when growth temperature is below 480 °C. Ising domains isolated within areas roughly 0.5 μm across are observed in the ferrimagnetic ε-phase grains of samples consisting of a mix of η- and ε-phase grains. Magnetic domains following semi-continuous paths, which are 0.7-7.2 μm across, are observed in single phase ε-Mn4N. Measurements of the ζ-phase detail the structure and magnetism of the material as high Mn content γ-type ζ-phase with a regular surface corrugation along the [100]-direction and antiferromagnetic.

  17. Catalytic Combustion of Low Concentration Methane over Catalysts Prepared from Co/Mg-Mn Layered Double Hydroxides

    Hongfeng Liu


    Full Text Available A series of Co/Mg-Mn mixed oxides were synthesized through thermal decomposition of layered double hydroxides (LDHs precursors. The resulted catalysts were then subjected for catalytic combustion of methane. Experimental results revealed that the Co4.5Mg1.5Mn2LDO catalyst possessed the best performance with the T90=485°C. After being analyzed via XRD, BET-BJH, SEM, H2-TPR, and XPS techniques, it was observed that the addition of cobalt had significantly improved the redox ability of the catalysts whilst certain amount of magnesium was essential to guarantee the catalytic activity. The presence of Mg was helpful to enhance the oxygen mobility and, meanwhile, improved the dispersion of Co and Mn oxides, preventing the surface area loss after calcination.

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

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


    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.

  19. Study on Corrosion Mechanism Between MgO-CaO Refractories and Slag

    YU Yanwen; WANG Ning


    Magnesia-Calcia materials containing 22- 53wt% CaO have been investigated for refinery slag corrosion and penetration resistance by Scanning Electron Microscopy (SEM) and XRD. The corrosion and penetration resistance of MgO-CaO materials is enhanced with the increase of CaO content in specimens. It can be explained that, with increase of CaO content, the specimens reacted with slag form higher melting point minerals of C3S and C2S, creating a dense surface layer.which stopped others from penetrating further. Thus. the corrosion and penetration resistance was improved. No matter what kinds of slag were chosen, the depth of penetration decreased with increase of CaO content.

  20. Synthesis and Luminescence Properties of Red Phosphors:Mn2+ Doped MgSiO3 and Mg2SiO4 Prepared by Sol-Gel Method


    Sol-gel method was utilized to synthesize two different series of red silicate phosphors:MgSiO3 and Mg2SiO4 powder samples doped with Mn2+, conducted the investigation of red long-lasting phosphor: MgSiO3:Eu2+, Dy3+, Mn2+. TGA curves of the gel precursor for two series depicted that the loss of residual organic groups and NO3 groups occurs below 450 ℃. According to the XRD patterns, the major diffraction peaks of the MgSiO3 and Mg2SiO4 series are consistent with a proto-enstatite structure (JCPDS No.11-0273) and a forsterite structure (JCPDS No.85-1364) respectively. With the excitation at 415 nm, the red emission band of Mn2+ ions is peaked at 661 nm for MgSiO3:1%(atom fraction) Mn2+ or 644 nm for Mg2SiO4:1%(atom fraction) Mn2+. Compared with Mg2SiO4:Mn2+ samples, MgSiO3:Mn2+ samples exhibit higher luminescence intensity and higher quenching concentration. In addition, the two series co-doped with Eu2+, Dy3+, Mn2+ were also prepared. Photo-luminescence and afterglow properties of the two co-doped series were analyzed, which show that MgSiO3:Eu2+, Dy3+, Mn2+ is more suitable for a red long-lasting phosphor.

  1. Shear strain in Nd0.5Ca0.5MnO3 at high pressures.

    Arulraj, Anthony; Dinnebier, Robert E; Carlson, Stefan; Hanfland, Michael; van Smaalen, Sander


    High-pressure x-ray powder diffraction has been measured on the half doped rare earth manganite Nd0.5Ca0.5MnO3 up to a pressure of 15 GPa. We report the presence of a quantifiable amount of shear distortion of the MnO6 octahedra in Nd0.5Ca0.5MnO3 at high pressures. The lattice strain of Nd0.5Ca0.5MnO3 is minimal at a crossover pressure of p* approximately 7 GPa, with the same lattice strain above and below this pressure achieved by shear and Jahn-Teller-type distortions, respectively. The increase in shear strain with increasing pressure provides a mechanism for the insulating behavior of manganites at high pressures that has not been considered before.

  2. Investigation of the Mn{sub 3−δ}Ga/MgO interface for magnetic tunneling junctions

    ViolBarbosa, C. E., E-mail:; Ouardi, S.; Fecher, G. H.; Felser, C. [Max-Planck-Institut für Chemische Physik fester Stoffe, Nöthnitzer Strasse 40, 01187 Dresden (Germany); Kubota, T.; Mizukami, S.; Miyazaki, T. [WPI Advanced Institute for Materials Research, Tohoku University, 980-8577 Sendai (Japan); Kozina, X.; Ikenaga, E. [JASRI, SPring-8, Sayo-cho, Hyogo 679-5198 (Japan)


    The Mn{sub 3}Ga Heusler compound and related alloys are the most promising materials for the realization of spin-transfer-torque magnetoresistive memories. Mn–Ga films exhibits perpendicular magnetic anisotropy and high spin polarization and can be used to improve the performance of MgO-based magneto tunneling junctions. The interface between Mn–Ga and MgO films were chemically characterized by hard x-ray photoelectron spectroscopy. The experiment indicated the formation of Ga-O bonds at the interface and evidenced changes in the local environment of Mn atoms in the proximity of the MgO film. We show that the deposition of few monoatomic layers of Mg on top of Mn–Ga film, before the MgO deposition, strongly suppresses the oxidation of gallium.

  3. Effects of homogenization on microstructures and properties of a new type Al-Mg-Mn-Zr-Ti-Er alloy

    He, L.Z., E-mail: [Key Lab of Electromagnetic Processing of Materials, Ministry of Education, Northeastern University, Shenyang 110004, Liaoning (China); Li, X.H. [Chalco Ruimin Corporation, Limited, Fuzhou 350015 (China); Liu, X.T.; Wang, X.J.; Zhang, H.T.; Cui, J.Z. [Key Lab of Electromagnetic Processing of Materials, Ministry of Education, Northeastern University, Shenyang 110004, Liaoning (China)


    Research highlights: These new type alloys are very potential for increased use in aerospace and automobile industries. However, most of published reports have focused on the effects of Cu, Sc, Zr, Ag, rare metals and Si additions, Portevin-LeChatelier effect, corrosion properties, friction stir welding and superplasticity in 5000-series aluminum alloy, few investigated on Er and stepped homogenization on the precipitation of dispersoids in Al-Mg-Mn alloy. The purpose of this work was to study the effects of Er and homogenization treatment on mechanical properties and microstructural evolution in new type Al-Mg-Mn-Er alloy. - Abstract: Microstructural evolutions and mechanical properties of Al-Mg-Mn-Zr-Ti-Er alloy after homogenization were investigated in detail by optical microscope (OM), scanning electronic microscope (SEM), transmission electronic microscope (TEM), energy dispersive spectrum (EDS) and tensile test. A maximum tensile strength is obtained when the alloy homogenized at 510 deg. C for 16 h. With increasing preheating temperature (200-400 deg. C), the strength of the alloy finial homogenized at 490 deg. C for 16 h increases. When the preheating temperature is {>=}300 deg. C, the strengths of the two-step homogenized alloys are higher than those of the single homogenized alloys. The preheating stage plays an important role in the microstructures and properties of the final homogenized alloy. Many fine (Mn,Fe)Al{sub 6} precipitates when the preheating temperature is 400 deg. C. ErAl{sub 3} phase cannot be observed during preheating stage. Plenty of fine (Mn,Fe)Al{sub 6} and ErAl{sub 3} precipitate in finial homogenized alloy when the preheating temperature is {>=}300 deg. C. The Al-Mg-Mn-Zr-Ti-Er alloy is effectively strengthened by substructure and dispersoids of (Mn,Fe)Al{sub 6} and ErAl{sub 3}.

  4. Manipulation of Mg(2+)-Ca(2+) Switch on the Development of Bone Mimetic Hydroxyapatite.

    Andrés, Nancy C; D'Elía, Noelia L; Ruso, Juan M; Campelo, Adrián E; Massheimer, Virginia L; Messina, Paula V


    Ionic substitution can affect essential physicochemical properties leading to a specific biological behavior upon implantation. Therefore, it has been proposed as a tool to increase the biological efficiency of calcium phosphate based materials. In the following study, we have evaluated the contribution of an important cation in nature, Mg(2+), into the structure of previously studied biocompatible and biodegradable hydroxyapatite (HA) nanorods and its subsequent effect on its chemical, morphology, and bone mimetic articulation. Mg(2+)-substituted HA samples were synthesized by an aqueous wet-chemical precipitation method, followed by an hydrothermal treatment involving a Mg(2+) precursor that partially replace Ca(2+) ions into HA crystal lattice; Mg(2+) concentrations were modulated to obtain a nominal composition similar to that exists in calcified tissues. Hydrothermally synthesized Mg(2+)-substituted HA nanoparticles were characterized by X-ray powder diffraction, FT-NIR and EDX spectroscopies, field emission scanning and high resolution transmission electron microscopies (FE-SEM, H-TEM). Molecular modeling combining ab initio methods and power diffraction data were also performed. Results showed that Mg(2+)-substitution promoted the formation of calcium deficient HA (cdHA) where Mg(2+) replacement is energetically favored at Ca(1) position in a limited and specific amount directing the additional Mg(2+) toward the surface of the crystal. The control of Mg(2+) incorporation into HA nanorods gave rise to a tailored crystallinity degree, cell parameters, morphology, surface hydration, solubility, and degradation properties in a dose-replacement dependent manner. The obtained materials show qualities that conjugated together to drive an optimal in vitro cellular viability, spreading, and proliferation confirming their biocompatibility. In addition, an improved adhesion of osteoblast was evidenced after Mg(2+)-Ca(2+) substitution.

  5. Removal of K+, Na+, Ca2+, and Mg2+ from saline-alkaline water using the microalga Scenedesmus obliquus

    Yao, Zongli; Ying, Chengqi; Lu, Jianxue; Lai, Qifang; Zhou, Kai; Wang, Hui; Chen, Ling


    The capability of Scenedesmus obliquus to remove cations (K+, Na+, Ca2+, Mg2+) from saline-alkaline water was investigated at different salinities (0, 5, 10, 15, 20, 25) and carbonate alkalinities (0, 5, 10, 15, 20, 25, 30, 35 mmol/L). K+, Na+, Ca2+, and Mg2+ in saline-alkaline water were efficiently removed by S. obliquus. The maximum removal of the cations (29.37 mg for K+, 185.85 mg for Na+, 23.07 mg for Ca2+, 66.14 mg for Mg2+) occurred at salinity 25. The maximum removal of K+ (2.28 mg), Na+ (6.62 mg), Ca2+ (1.01 mg), and Mg2+ (0.62 mg) occurred at carbonate alkalinities of 25 mmol/L for K+, 35 mmol/L for Na+, 20 mmol/L for Ca2+, and 25 mmol/L for Mg2+, respectively. Under a salinity stress, the concentration of Na+ in S. obliquus increased significantly, while that of K+ decreased significantly. The concentrations of Ca2+ and Mg2+ decreased as well. The ratios of K+/Na+, Ca2+/Na+, and Mg2+/Na+ were significantly lower in all salinity treatments than those of the control. Under alkaline stress, the concentrations of Na+ and K+ in S. obliquus decreased significantly and the ratios of K+/Na+, Ca2+/Na+, and Mg2+/Na+ were significantly higher in all treatments than in the control. Moreover, the concentrations of Ca2+ and Mg2+ in S. obliquus at alkalinities of 5-10 mmol/L were significantly higher than those of the other treatments. The removal of Na+ by S. obliquus mainly occurs through biosorption, and Mg2+ and Ca2+ were removed through both biosorption and bioaccumulation.

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

    Minjung Kang


    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.

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

    Liu Lin [School of Forestry, Northeast Forestry University, Harbin 150040 (China); Gao Dawen, E-mail: [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)


    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.

  8. Exploring Mg-Zn-Ca-Based Bulk Metallic Glasses for Biomedical Applications Based on Thermodynamic Approach

    Ramya, M.; Sarwat, Syed Ghazi; Udhayabanu, V.; Raj, Baldev; Ravi, K. R.


    Magnesium (Mg)-based metallic glasses are considered as possible candidates in orthopedic implant applications. This paper aims to theoretically predict the glass-forming ability (GFA) in Mg-Zn-Ca alloy using a newly proposed thermodynamic model ( P HHS), and the consistency of this model is verified through experimental analysis. P HHS is based on thermodynamic parameters such as enthalpy of chemical mixing, elastic enthalpy, and configurational entropy, thus incorporating the pivotal effects, i.e., electron transfer effects, effect of atomic size mismatch, and effect of randomness, which aid to high GFA. In essence, P HHS can be visualized as the energy barrier that exists between the transformations of random atomic structure of glass to ordered crystalline structure. When the P HHS value is more negative, the energy barrier will be high, supporting easy glass formation. Various Mg-Zn-Ca metallic glass compositions displayed almost an expected and supporting trend, where the critical diameter of the metallic glass rod increased with a more negative P HHS value. Among the predicted Mg-Zn-Ca systems, the Mg60Zn35Ca5 composition shows deviation from the expected trend. This discrepancy has been clearly elucidated using a eutectic phase diagram. In addition to the consistency of the P HHS parameter to verifying the GFA of various compositions, the unique ability of this model is to predict unexplored Mg-Zn-Ca glass-forming compositions using contour development. Thus, proving P HHS parameter to be used as an efficient tool in predicting new glass-forming compositions.

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

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


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

  10. Dramatic changes in the magnetic coupling mechanism for La-doped CaMnO3.

    Granado, E; Moreno, N O; Martinho, H; García, A; Sanjurjo, J A; Torriani, I; Rettori, C; Neumeier, J J; Oseroff, S B


    The exchange interactions in polycrystalline samples of Ca1-xLaxMnO3 (0.00< or =x< or =0.05) are studied by means of Raman scattering and electron paramagnetic resonance. Dramatic reductions in the spin-phonon interactions and magnetic correlations are observed for La doping levels as small as approximately 2%-3%. These results show that the charge carriers play an important role in the overall exchange coupling in the electron-doped manganites, even at very low doping levels.

  11. Efficient sensitization of Eu2+/Mn2+ emissions by Ce3+ doping in NaMgPO4 host under UV excitation

    Zheng, Zhang; Wanjun, Tang


    A series of Ce3+/Eu2+/Mn2+-tridoped NaMgPO4 phosphors were synthesized using the combustion-assisted synthesis method. The luminescence properties and energy transfer from Ce3+/Eu2+ to Mn2+ in NaMgPO4 host have been studied. Co-doping Ce3+/Mn2+ is proved to be an ineffective approach to enhance the red emission of Mn2+, while effective energy transfer from Eu2+ to Mn2+ occurs in NaMgPO4:Eu2+,Mn2+ due to good spectrum overlap between the emission band of NaMgPO4:Eu2+ and the excitation band of NaMgPO4:Eu2+,Mn2+. NaMgPO4:Eu2+,Mn2+ phosphor shows a blue emission centered at 442 and a red emission peaking at 635 nm, which could be ascribed to the allowed 5 d-4 f transition of Eu2+ ions and the 4T1(4G)-6A1(6S) transition of Mn2+ ions, respectively. Co-doping Ce3+ ions can greatly enhance both the emission intensities of Eu2+ and Mn2+ ions, which is attributed to an efficient Ce3+ → Eu2+ → Mn2+ energy transfer and an increase in the number of luminescent centers (Eu2+) on Ce doping.

  12. Electronic and magnetic properties of Cr-Mn-Ni-Al compound with LiMgPdSb-type structure

    Wang, L. Y.; Wang, X. T.; Guo, R. K.; Lin, T. T.; Liu, G. D.


    We investigate the electronic and magnetic properties of Cr-Mn-Ni-Al compound with a LiMgPdSn-type structure in three different atomic arrangement configurations (AAC) by using the first-principles calculations. It was found that Cr-Mn-Ni-Al compound with type I AAC exhibits a spin-gapless semiconductive characteristic. The type II AAC is the most stable one and exhibits an especial band structure where the Fermi level slightly crosses the top of the valence bands in spin-up channel and the bottom of conductive bands in spin-down channel, which leads to the electronic transport with the spin-resolved carrier type. The Cr-Mn-Ni-Al compound shows an ordinary metallic behavior in type III AAC. The three nonequivalent atomic arrangement configurations of Cr-Mn-Ni-Al are all in ferromagnetic ground state under their equilibrium lattice parameters.

  13. Mg/Ca temperature calibration for the benthic foraminifer Cibicidoides pachyderma

    Marchitto, T. M.; Bryan, S. P.; Curry, W. B.; McCorkle, D. C.


    The recent development of foraminiferal Mg/Ca as a paleotemperature proxy has enabled the extraction of global ice volume and local salinity from the more traditional paleotemperature proxy δ18O. The benthic foraminiferal genus Cibicidoides is widely used in paleoceanographic reconstructions because of its epifaunal habitat and cosmopolitan distribution, and it has received early attention in Mg/Ca work. However, existing temperature calibrations for Cibicidoides rely heavily on C. pachyderma core top data from one location, Little Bahamas Bank, where authigenic processes and/or reworking may result in elevated warm water Mg/Ca values. Here we present new C. pachyderma Mg/Ca data from a series of 29 high-quality multicore tops collected in the Florida Straits, spanning a temperature range of 5.8-18.6°C. In contrast to previous calibrations, we find no evidence for a strongly exponential response to temperature. The data are best explained by a linear relationship, with a sensitivity of 0.12 mmol mol-1 per °C.

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

    Bairagi C Mallick; Sa-Ouk Kang; Suman Jha


    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.

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

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


    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

  16. Mg/Ca and ?18O in the brackish shallow-water benthic foraminifer Ammonia 'beccarii'

    Toyofuku, T.; Suzuki, M.; Suga, H.; Sakai, S.; Suzuki, A.; Ishikawa, T.; Nooijer, L.J. de; Schiebel, R.; Kawahata, H.; Kitazato, H.


    Specimens of the benthic foraminifer Ammonia beccarii were cultured in the laboratory in order to determine the relation between temperature and Mg/Ca and oxygen isotope values in their tests. Asexual reproduction in this species provides a large number of juveniles that were allowed to grow into

  17. A DFT study of hydrogen adsorption on Be, Mg and Ca frameworks in erionite zeolite

    Fellah, Mehmet Ferdi


    The molecular hydrogen adsorption was investigated on additional frameworks with earth alkaline metal atoms (Be, Mg and Ca) in 24T ERI zeolite cluster model by means of Density Functional Theory study. HOMO and LUMO energy values, chemical potential, chemical hardness, electronegativity, adsorption energy and adsorption enthalpy values have been calculated in this study. Mg-ERI and Ca-ERI clusters have much lower chemical potentials with much lower adsorption energy values when compared to the value of Be-ERI cluster. Additionally, they are softer than Be-ERI cluster with respect to their lower chemical hardness values. Hydrogen adsorption enthalpy values were computed as -3.6 and -3.9 kJ/mol on Mg-ERI and Ca-ERI clusters, respectively. These adsorption enthalpy values are significantly larger than the enthalpy value of liquefaction for hydrogen molecule. This consequently specifies that Mg-ERI and Ca-ERI zeolite structures which have higher chemical reactivity appear to be a promising candidate cryoadsorbent for hydrogen storage.

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

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


    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

  19. Mg/Ca and ?18O in the brackish shallow-water benthic foraminifer Ammonia 'beccarii'

    Toyofuku, T.; Suzuki, M.; Suga, H.; Sakai, S.; Suzuki, A.; Ishikawa, T.; Nooijer, L.J. de; Schiebel, R.; Kawahata, H.; Kitazato, H.


    Specimens of the benthic foraminifer Ammonia beccarii were cultured in the laboratory in order to determine the relation between temperature and Mg/Ca and oxygen isotope values in their tests. Asexual reproduction in this species provides a large number of juveniles that were allowed to grow into ma

  20. Epithelial Ca2+ and Mg2+ channels in health and disease.

    Hoenderop, J.G.J.; Bindels, R.J.M.


    A near constancy of the extracellular Ca(2+) and Mg(2+) concentration is required for numerous physiologic functions at the organ, tissue, and cellular levels. This suggests that minor changes in the extracellular concentration of these divalents must be detected to allow the appropriate correction

  1. Automated cleaning of foraminifera shells before Mg/Ca analysis using a pipette robot

    Johnstone, Heather J. H.; Steinke, Stephan; Kuhnert, Henning; Bickert, Torsten; Pälike, Heiko; Mohtadi, Mahyar


    The molar ratio of magnesium to calcium (Mg/Ca) in foraminiferal calcite is a widely used proxy for reconstructing past seawater temperatures. Thorough cleaning of tests is required before analysis to remove contaminant phases such as clay and organic matter. We have adapted a commercial pipette robot to automate an established cleaning procedure, the "Mg-cleaning" protocol of Barker et al. (2003). Efficiency of the automated nine-step method was assessed through monitoring Al/Ca of trial samples (GeoB4420-2 core catcher). Planktonic foraminifera Globigerinoides ruber, Globigerinoides sacculifer, and Neogloboquadrina dutertrei from this sample gave Mg/Ca consistent with the habitat range of the three species, and 40-60% sample recovery after cleaning. Comparison between manually cleaned and robot-cleaned samples of G. ruber (white) from a sediment core (GeoB16602) showed good correspondence between the two methods for Mg/Ca (r = 0.93, p robot-cleaned samples was 0.05 mmol/mol, showing that the samples are cleaned effectively by the robot. The robot offers increased sample throughput as batch sizes of up to 88 samples/blanks can be processed in ˜7 h with little intervention.

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

    HUANG Qing-Ming


    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.

  3. N型CaMnO3热电材料的制备及性能研究%Preparation and Properties of N-type CaMnO3 Thermoelectric Materials



    该文通过实验研究了采用自燃法并在不同的温度下煅烧试样合成 Ca1-xSmxMnO3(x=0~0.06)粉末的工艺,以及在Ca位上掺杂不同含量的 Sm元素对材料性能的影响。自燃法结合球磨工艺可以制得平均粒径在2μm左右的Ca1-xSmxMnO3(x=0~0.06)超细粉末。X射线衍射(XRD)分析表明自燃法可以合成物相单一的 Ca1-xSmx MnO3(x=0~0.06)粉末材料。在CaMnO3热电材料的Ca位上掺杂 Sm 元素降低了材料的 Seebeck 系数,但同时也降低了材料的电阻率,而电导率增加幅度高于 Seebeck系数的降低幅度,故而总体上Ca1-xSmxMnO3(x=0~0.06)热电陶瓷材料的功率因子也增大了,从而有望使材料达到较高的热电优值,具有一定的商业应用价值。%In this paper,thermoelectric oxide Ca1-xSmxMnO3 (x=0~0.06)powder was synthesized by auto-igni-tion and the reaction temperature of the CaMnO3 synthesis process were investigated.We also studied the thermoelec-tric performance depending on different content of Sm element into Ca site.The Ca1-xSmxMnO3 (x=0~0.06)ultra fine powder with mean particle size of about 2μm has been successfully synthesized by auto-ignition combining with the ball mill process.X-ray diffraction showed that Ca1-xSmxMnO3 has formed by auto-ignition without distinguished im-purity.The Ca-site of CaMnO3 doped with Sm reduced the Seebeck coefficient and at the same time,the electrical con-ductivity was significantly improved and the power factor of Ca1-xSmxMnO3 TE materials was increased.Therefore, the TE merit of Ca1-xSmxMnO3 may come to a high level and have some commercial applications.

  4. Atomic Structure of Ca40+xMg25Cu35-x Metallic Glasses (Postprint)


    arrangements very similar to the competing Mg2Cu ( Laves phase ) and YCu2 crystals. Simi- lar comparison of coordination polyhedra in the amorphous structure of...hexagonal Laves phase (space group P63/mmc, space group number 194) with lattice parameters a¼ 5.170 Å and c¼ 8.50 Å. This crystal structure contains three...centered (0,0,12,4) Friauf polyhedron containing 12 Mg and 4 Ca atoms in the first shell. Cu2Mg is a cubic Laves phase (space group is Fd-3 m, space group

  5. Valence state of Mn in Ca-doped LaMnO3 studied by high-resolution Mn K ß emission spectroscopy

    Tyson, T.A.; Qian, Q.; Kao, C.-C.; Rueff, J.-P.; Groot, F.M.F. de; Croft, M.; Cheong, S.-W.; Greenblatt, M.; Subramanian, M.A.


    Mn K ß x-ray emission spectra provide a direct method to probe the effective spin state and charge density on the Mn atom and is used in an experimental study of a class of Mn oxides. Specifically, the Mn K ß line positions and detailed spectral shapes depend on the oxidation and the spin state of

  6. Valence state of Mn in Ca-doped LaMnO3 studied by high-resolution Mn K ß emission spectroscopy

    Tyson, T.A.; Qian, Q.; Kao, C.-C.; Rueff, J.-P.; Groot, F.M.F. de; Croft, M.; Cheong, S.-W.; Greenblatt, M.; Subramanian, M.A.


    Mn K ß x-ray emission spectra provide a direct method to probe the effective spin state and charge density on the Mn atom and is used in an experimental study of a class of Mn oxides. Specifically, the Mn K ß line positions and detailed spectral shapes depend on the oxidation and the spin state of t

  7. Na4Ca3(AlO2)10:Eu2+,Mn2+荧光粉的发光特性%Photoluminescence Characteristics of Na4 Ca3(AlO2)10:Eu2+ ,Mn2+

    王雪; 田莲花


    A novel phosphor Na4Ca3(AlO2) 10:Eu2+ was prepared by solid state reaction method in a thermal-carbon reducing atmosphere. The photoluminescence(PL) properties were investigated in this paper. The excitation spectrum of Na4Ca3(AlO2) 10:Eu2+ showed two absorption bands centered at 262 nm and 320 nm respectively. The photoluminescence spectrum of Na4Ca3(AlO2) 10:Eu2+ exhibited a single emission peak centered at 441 nm, which could be attributed to 5d-4f transition of Eu + . The excitation spectrum of Na4Ca3(AlO2) 10:Eu2+ showed absorption peak at about 440 nm monitoring at 542 nm, which shows spectral overlap between emission spectrum of Na4Ca3(AlO2) 10:Eu2+. Co-doped Mn2+ with Eu2+, the photoluminescence spectra of Na4Ca3(AlO2) 10:Eu2+ were observed two peaks centered at 441 nm and 542 nm corresponding to the 5d-4f transition of Eu2+ and the d-d transition of Mn2+ , respectively. With increasing the concentration of Mn2+ ,the emission intensity of 5d-4f transition of Eu2+ at 441 nm was significantly decreased,whereas the d-d transition of Mn2+ at 542 nm was found to increase. The decay lifetime for Eu2+ was found to decrease with increasing Mn2+ dopant content, which was strong evidence for the energy transfer from Eu2+ to Mn2+ . We were also interested in investigating the energy transfer efficiency ηT of Eu2+→Mn2+ . With increasing Mn2+ dopant content, the energy transfer efficiency ηT was found to increase gradually. According to the Dexter's energy transfer formula of multipolar interaction, it was demonstrated that the energy transfer from Eu2+ to Mn2+ was due to the electric quadripole-quadripole interaction of the resonance transfer. According to the CIE chromaticity coordinates of Na4Ca3(AlO2) 10:Eu2+ , it was clearly observed that the CIE chro-maticity coordinates with the increase of Mn content shifted from blue region to white region.

  8. Effects of disorder in the Heusler alloy Co{sub 2}MnSi and properties of the Co{sub 2}MnSi(100)/MgO interface; Effekte von Unordnung in der Heusler-Legierung Co{sub 2}MnSi und Eigenschaften der Co{sub 2}MnSi (100)/MgO-Grenzflaeche

    Huelsen, Bjoern


    Mn{sub 3}Si at room temperature. In the third part of this work structural, magnetic and electronic properties of the Co{sub 2}MnSi(100)/MgO interface are investigated. The stability of different terminations (CoCo, MnSi, MnMn and SiSi) at different registries with respect to MgO (O-top, Mg-top, bridge and hollow site) are estimated with the method of ab initio thermodynamics. In thermodynamic equilibrium the CoCo/O and the MnSi/O heterojunctions are stable. They show interface states at the Fermi energy in the spin down channel and therefore have reduced spin polarization. The metastable MnMn terminated interface has a band gap. (orig.)

  9. Unique antitumor property of the Mg-Ca-Sr alloys with addition of Zn.

    Wu, Yuanhao; He, Guanping; Zhang, Yu; Liu, Yang; Li, Mei; Wang, Xiaolan; Li, Nan; Li, Kang; Zheng, Guan; Zheng, Yufeng; Yin, Qingshui


    In clinical practice, tumor recurrence and metastasis after orthopedic prosthesis implantation is an intensely troublesome matter. Therefore, to develop implant materials with antitumor property is extremely necessary and meaningful. Magnesium (Mg) alloys possess superb biocompatibility, mechanical property and biodegradability in orthopedic applications. However, whether they possess antitumor property had seldom been reported. In recent years, it showed that zinc (Zn) not only promote the osteogenic activity but also exhibit good antitumor property. In our present study, Zn was selected as an alloying element for the Mg-1Ca-0.5Sr alloy to develop a multifunctional material with antitumor property. We investigated the influence of the Mg-1Ca-0.5Sr-xZn (x = 0, 2, 4, 6 wt%) alloys extracts on the proliferation rate, cell apoptosis, migration and invasion of the U2OS cell line. Our results show that Zn containing Mg alloys extracts inhibit the cell proliferation by alteration the cell cycle and inducing cell apoptosis via the activation of the mitochondria pathway. The cell migration and invasion property were also suppressed by the activation of MAPK (mitogen-activated protein kinase) pathway. Our work suggests that the Mg-1Ca-0.5Sr-6Zn alloy is expected to be a promising orthopedic implant in osteosarcoma limb-salvage surgery for avoiding tumor recurrence and metastasis.

  10. High temperature EPR study of the M3Fe4V6O24 (M = Cu, Zn, Mg and Mn

    Guskos Niko


    Full Text Available Electron paramagnetic resonance (EPR spectra of M3Fe4V6O24 (M = Cu, Zn, Mg and Mn compounds in high temperature range (293 K to 493 K have been investigated. The role of magnetic (Cu, Mn and non-magnetic (Zn, Mg ions in M3Fe4V6O24 structure in formation of magnetic resonance spectra was studied. Temperature dependence of EPR parameters: resonance field, linewidth and integrated intensity were examined. Similarities and differences in temperature behavior of these parameters has been discussed in terms of different relaxation mechanisms and magnetic interactions in the spin systems. An important role of additional magnetic ions (M = Mn or Cu in the M3Fe4V6O24 structure has been identified and its consequences considered.

  11. Coupled magnetic and elastic properties in LaPr(CaSr)MnO manganites

    Eslava, G. G.; Parisi, F.; Bernardo, P. L.; Quintero, M.; Leyva, G.; Cohen, L. F.; Ghivelder, L.


    We investigate a series of manganese oxides, the La0.225Pr0.4(Ca1-xSrx)0.375MnO3 system. The x = 0 sample is a prototype compound for the study of phase separation in manganites, where ferromagnetic and charge ordered antiferromagnetic phases coexist. Replacing Ca2+ by Sr2+ gradually turns the system into a homogeneous ferromagnet. Our results show that the material structure plays a major role in the observed magnetic properties. On cooling, at temperatures below ∼ 100 K, a strong contraction of the lattice is followed by an increase in the magnetization. This is observed both through thermal expansion and magnetostriction measurements, providing distinct evidence of magneto-elastic coupling in these phase separated compounds.

  12. Effects of Ba doping on physical properties of La-Ca-Mn-O thin films

    Hong, N H; Sakai, J; Iwasaki, H


    Transport and magnetic properties of La-Ba-Ca-Mn-O thin films fabricated by the pulsed laser deposition technique had been investigated systematically to see the effects of substitution of the small atom Ca by Ba which is much bigger. The induced insulator-to-metal (IM) transition was obtained not only in compositions near 0.5 and 0.18 which are boundaries between metallic and insulating phases but also in the heavily doped region. In the region of x > 0.5, the Ba doping causes an anomalous response of the system to the magnetic field and a positive magnetoresistance was observed. Besides, our results concerning the vicinity of 0.5 imply the existence of phase separation. As for x < 0.5, the doping enhances remarkably the paramagnetism-ferromagnetism transition and the IM transition temperatures.

  13. Chemical zoning and diffusion of Ca, Al, Mn, and Cr in olivine of springwater pallasite

    Zhou, Y.; Steele, Ian M.


    The pallasites, consisting mainly of Fe-Ni metal and olivine, are thought to represent the interior of a planetary body which slowly cooled from high temperature. Although the olivines are nearly homogeneous, ion microprobe studies revealed variations of Ca, Ti, Co, Cr, and Ni near grain edges. These variations were thought to represent diffusion in response to falling temperature of the parent body. Pallasite cooling rates have been estimated based on kamacite taenite textures but results differ by x100. In principle elemental profiles in olivine can allow estimates of cooling rate if diffusion coefficients are known; in addition, given a cooling rate, diffusion coefficients could be derived. Data are presented which show that apparent diffusion profiles can be measured for Al, Ca, Cr, and Mn which qualitatively agree with expected diffusion rates and have the potential of providing independent estimates of pallasite cooling rates.

  14. Interplay of Ca(2+) and Mg (2+) in sodium-calcium exchanger and in other Ca(2+)-binding proteins: magnesium, watchdog that blocks each turn if able.

    Levitsky, Dmitri O; Takahashi, Masayuki


    Sodium-calcium exchange across plasma membrane is regulated by intracellular calcium ions. The sodium-calcium exchanger (NCX1) is activated by successive saturation of numerous Ca(2+)-binding sites located in the intracellular loop of the protein. The progressive saturation of the binding domain CBD12 by Ca(2+) results in a series of conformational changes of CBD12 as well as of entire NCX1 molecule. Like other soluble and membrane Ca(2+)-binding proteins, NCX1 can also be regulated by Mg(2+) that antagonises Ca(2+) at the level of divalent cation-binding sites. This chapter summarises data on Mg(2+) impacts in the cells. Regulatory action of Mg(2+) on intracellular Ca(2+)-dependent processes can be achieved due to changes of its cytoplasmic level, which take place in the range of [Mg(2+)](i) from 0.5 to 3 mM. Under normal conditions, these changes are ensured by activation of plasmalemmal Mg(2+) transport systems and by variations in ATP level in cytoplasm. In heart and in brain, some pathological conditions, such as hypoxia, ischemia and ischemia followed by reperfusion, are associated with an important increase in intracellular Ca(2+). The tissue damage due to Ca(2+) overload may be prevented by Mg(2+). The protective actions of Mg(2+) can be achieved due to its ability to compete with Ca(2+) for the binding sites in a number of proteins responsible for the rise in intracellular free Ca(2+), including NCX1, in case when the reverse mode of Na(+)/Ca(2+) exchange becomes predominant. Saturation of CBD12 by Mg(2+) results in important changes of NCX1 conformation. Modulating actions of Mg(2+) on the conformation of NCX1 were detected at a narrow range of Mg(2+) concentration, from 0.5 to 1 mM. These data support an idea that variations of intracellular Mg(2+) could modify transmembrane Ca(2+) movements ensured by NCX1.

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

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


    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. Interplay of Dirac electrons and magnetism in CaMnBi2 and SrMnBi2

    Zhang, Anmin; Liu, Changle; Yi, Changjiang; Zhao, Guihua; Xia, Tian-Long; Ji, Jianting; Shi, Youguo; Yu, Rong; Wang, Xiaoqun; Chen, Changfeng; Zhang, Qingming


    Dirac materials exhibit intriguing low-energy carrier dynamics that offer a fertile ground for novel physics discovery. Of particular interest is the interplay of Dirac carriers with other quantum phenomena such as magnetism. Here we report on a two-magnon Raman scattering study of AMnBi2 (A=Ca, Sr), a prototypical magnetic Dirac system comprising alternating Dirac carrier and magnetic layers. We present the first accurate determination of the exchange energies in these compounds and, by comparison with the reference compound BaMn2Bi2, we show that the Dirac carrier layers in AMnBi2 significantly enhance the exchange coupling between the magnetic layers, which in turn drives a charge-gap opening along the Dirac locus. Our findings break new grounds in unveiling the fundamental physics of magnetic Dirac materials, which offer a novel platform for probing a distinct type of spin-Fermion interaction. The results also hold great promise for applications in magnetic Dirac devices.

  17. Arsenate uptake and arsenite simultaneous sorption and oxidation by Fe-Mn binary oxides: influence of Mn/Fe ratio, pH, Ca2+, and humic acid.

    Zhang, Gaosheng; Liu, Huijuan; Qu, Jiuhui; Jefferson, William


    Arsenate retention, arsenite sorption and oxidation on the surfaces of Fe-Mn binary oxides may play an important role in the mobilization and transformation of arsenic, due to the common occurrence of these oxides in the environment. However, no sufficient information on the sorption behaviors of arsenic on Fe-Mn binary oxides is available. This study investigated the influences of Mn/Fe molar ratio, solution pH, coexisting calcium ions, and humic acids have on arsenic sorption by Fe-Mn binary oxides. To create Fe-Mn binary oxides, simultaneous oxidation and co-precipitation methods were employed. The Fe-Mn binary oxides exhibited a porous crystalline structure similar to 2-line ferrihydrite at Mn/Fe ratios 1:3 and below, whereas exhibited similar structures to δ-MnO(2) at higher ratios. The As(V) sorption maximum was observed at a Mn/Fe ratio of 1:6, but As(III) uptake maximum was at Mn/Fe ratio 1:3. However, As(III) adsorption capacity was much higher than that of As(V) at each Mn/Fe ratio. As(V) sorption was found to decrease with increasing pH, while As(III) sorption edge was different, depending on the content of MnO(2) in the binary oxides. The presence of Ca(2+) enhanced the As(V) uptake under alkaline pH, but did not significantly influence the As(III) sorption by 1:9 Fe-Mn binary oxide; whereas the presence of humic acid slightly reduced both As(V) and As(III) uptake. These results indicate that As(III) is more easily immobilized than As(V) in the environment, where Fe-Mn binary oxides are available as sorbents and they represent attractive adsorbents for both As(V) and As(III) removal from water and groundwater. Copyright © 2011 Elsevier Inc. All rights reserved.

  18. The structure and mechanical properties of Al-Mg-Mn alloys shaped in the process of thermomechanical treatment

    W. Ozgowicz


    Full Text Available Purpose: The aim of research was to investigate the effect of heat treatment and low-temperature thermomechanical treatment (LTMT on the structure and mechanical properties of Al-Mg-Mn alloys.Design/methodology/approach: The range of researches included: performance of heat treatment and low-temperature thermomechanical treatment of AlMg1.5 and AlMg3.5Mn alloys, carry out of static tensile tests, measurements of hardness, metallographic observation (TEM and fractography (SEM.Findings: Analysis of the results allows to determine the effect of precipitation hardening and low-temperature thermomechanical treatment on the structure and mechanical properties of AlMg1.5 and AlMg3.5Mn alloys and to determine the effect on the topography of the specimens fracture after decohesion in tensile tests. Moreover, SEM researches allow to identity the chemical composition of precipitates in the structure of investigated alloys.Practical implications: The obtained results may serve as a basis for optimization of the process of the material used as components of vessels.Originality/value: The mechanical properties of the investigated aluminium alloys increase with the quantity of Mg, independently of their state and the parameters of heat treatment and low-temperature thermomechanical treatment. More refinement of precipitations, which affect the mechanical properties in ageing, ensured by LTMT compared with conventional heat treatment

  19. MgO含量对CaZrO3-MgO陶瓷烧结特性及组成与结构的影响%Effects of MgO Content on Sintering Characteristics, Composition and Microstructure of CaZrO3-MgO Ceramics

    刘会; 王榕林; 顾佳妮; 姬莹莹; 卜景龙


    采用常压烧结方法制备了CaZrO3-MgO陶瓷.研究了MgO含量对CaZrO3-MgO陶瓷的显气孔率、体积密度、抗弯强度、物相组成、显微结构和断裂方式的影响.结果表明:含有lwt%~3wt% MgO的CaZrO3-MgO陶瓷由CaZrO3单相构成,气孔率低,体积密度高,抗弯强度大,断裂方式为穿晶与沿晶共存的混合断裂;含有20wt% ~40wt% MgO的CaZrO3-MgO陶瓷由MgO和CaZrO3两相构成,气孔率高,体积密度低,抗弯强度小,CaZrO3与MgO两相间的断裂方式为沿晶断裂;当MgO含量为2wt%时CaZrO3-MgO陶瓷的烧结性能最好,当MgO含量为40wt%时CaZrO3-MgO陶瓷的烧结性能最差.少量Mg2+的引入因其向CaZrO3中单向扩散而促进材料烧结,大量Mg2+的引入因其与Zr4+互扩散导致CaZrO3分解而阻碍材料烧结.

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

    Karita, Shingo; Kaneta, Takashi


    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.

  1. Y3+掺杂对CaMnO3热电性能的影响%Effect of Y3+Doping on Thermoelectric Properties of CaMnO3

    盛得雪; 贺毅; 龚鹏; 宋少伟; 刘杨琼


    CaMnO3 is an important N-type thermoelectric material. (Ca1-xYx)MnO3(x=0, 0. 03, 0. 05, 0. 07, 0. 09)thermoe-lectric samples were synthesized based on solid state reaction method, and thermoelectric properties were measured with self-made e-quipment. The results show that Y3+doping can improve the thermoelectric properties effectively. As for Ca0. 91 Y0. 09 MnO3 , during the test temperature of high side reaches 880K, the resistivity, Seebeck coefficient and maximum output power are equal to 7. 4 × 10 -4Ω· m, -112 μV/K, 68 mW, respectively.%用固相反应法制备( Ca1-x Yx ) MnO3( x分别为0、0.03、0.05、0.07、0.09 mol)热电材料,用自制设备测试样品的热电性能,研究了Y3+掺杂对CaMnO3热电性能的影响。结果表明:Y3+掺杂可以有效地改善样品的热电性能,其中( Ca0.91 Y0.09) MnO3样品的热电性能较优;当高温端温度为880 K时,测得电阻率为74 mΩ·m,Seebeck系数为-112μV/K,输出功率达到68 mW。

  2. Enhanced moments in bcc Co{sub 1−x}Mn{sub x} on MgO(001)

    Snow, R.J.; Bhatkar, H. [Department of Physics, Montana State University, Bozeman, MT 59715 (United States); N' Diaye, A.T.; Arenholz, E. [Advanced Light Source, Lawrence Berkeley Nat. Labs, Berkeley, CA 94720 (United States); Idzerda, Y.U., E-mail: [Department of Physics, Montana State University, Bozeman, MT 59715 (United States)


    A 40% enhancement of the Co magnetic moment has been found for thin films of bcc Co{sub 1−x}Mn{sub x} grown by molecular beam epitaxy on a 2 nm bcc Fe buffer layer on MgO(001). Although the bcc phase cannot be stabilized in the bulk, we confirm that it is stable as an epitaxial film in the composition range x=0–0.7. Using X-ray absorption spectroscopy and X-ray magnetic circular dichroism, we show that the Co moment is a maximum of 2.38 μ{sub B} at x=0.24, while the net Mn moment remains roughly constant until x=0.24, then drops steadily. Mn is found to align parallel with Co for all ferromagnetic concentrations, up to x=0.7, where the total moment of the film abruptly collapses to zero, most likely due to the onset of the observed structural instability. - Highlights: • Stabilization of bcc Co{sub 1−x}Mn{sub x} films in the composition range of x=0 to 0.7. • Enhancement of Co moment by 40% from pure bcc Co. • Parallel alignment of Mn moment and Co moment. • Measured the elemental moment of Co and Mn as a function of composition.

  3. Effect of hydrogen on Ca and Mg acceptors in GaN

    Lee, J.W.; Pearton, S.J. [Univ. of Florida, Gainesville, FL (United States); Zolper, J.C. [Sandia National Labs., Albuquerque, NM (United States); Stall, R.A. [EMCORE Corp., Somerset, NJ (United States)


    The influence of minority carrier injection on the reactivation of hydrogen passivated Mg in GaN at 175 C has been investigated in p-n junction diodes. The dissociation of the neutral MgH complexes is greatly enhanced in the presence of minority carrier and the reactivation process follows second order kinetics. Conventional annealing under zero-bias conditions does not produce Mg-H dissociation until temperatures {ge} 450 C. These results provide an explanation for the e-beam induced reactivation of Mg acceptors in hydrogenated GaN. Exposure to a hydrogen plasma at 250 C of p-type GaN (Ca) prepared by either Ca{sup +} or Ca{sup +} plus P{sup +} coimplantation leads to a reduction in sheet carrier density of approximately an order of magnitude (1.6 {times} 10{sup 12} cm{sup {minus}2} to 1.8 {times} 10{sup 11} cm{sup {minus}2}), and an accompanying increase in hole mobility (6 cm{sup 2}/Vs to 18 cm{sup 2}/Vs). The passivation process can be reversed by post-hydrogenation annealing at 400--500 C under a N{sub 2} ambient. This reactivation of the acceptors is characteristic of the formation of neutral (Ca-H) complexes in the GaN. The thermal stability of the passivation is similar to that of Mg-H complexes in material prepared in the same manner (implantation) with similar initial doping levels. Hydrogen passivation of acceptor dopants in GaN appears to be a ubiquitous phenomenon, as it is in other p-type semiconductors.

  4. Preparation and thermoelectric properties of M0.05Ca0.95MnO3%M0.05Ca0.95MnO3的制备及其热电性能

    许洁; 魏长平; 贾坤


    采用溶胶-凝胶法,以硝酸盐为原料,在常压空气气氛中于1 000℃烧结8 h制备出CaMnO3和M0.05Ca0.95MnO3(M=Sr2+,Sm3+)块体材料。利用X线衍射、扫描电子显微镜等研究材料的物相和微观形貌,考察Sr2+和Sm3+M+掺杂对CaMnO3的高温热电性能参数Seebeck系数、电阻率和功率因子的影响。研究结果表明:制备的样品具有单一的物相,结构致密;金属离子Sr2+和Sm3+掺杂可以有效地改善其热电性能;当Sm3+的掺杂量为0.05时可获得最佳的热电性能,600℃时功率因子为23×10-5W·m-1·K-2。%CaMnO3 and M0.05Ca0.95MnO3 (M=Sr2+, Sm3+) samples were synthesized by sol-gel method and sintered in air at 1 000 "C for 8 h with nitrates as starting materials. The phase composition and microstructure were studied by XRD and SEM. Thermoelectric properties such as the Seebeck coefficient, electrical resistivity and power factor of M0.05Ca0.95MnO3 samples were studied. The results show that theM0.05Ca0.95MnO3 samples have single phase and condensed microstructure. The samples substituted by metal ions(Sr2+, Sm3+) enhance the electrical transmission performance effectively, and the highest power factor is 23×10-5 W·m-1·K-2 at 600 ℃ for the sample of Sm0.05Ca0.95MnO3.

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

    张庆安; 赵刚; 斯庭智; 庞刚


    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.

  6. Microstructural Characteristics of La0.7Ca0.3MnO3 Films and Multilayers


    La0.7Ca0.3MnO3 (LCMO) films and La0.7Ca0.3MnO3/Gd0.7Ca0.3MnO3 (LCMO/GCMO) multilayers have been prepared by pulsed laser deposition. The microstructures of both systems were investigated by transmission electron microscopy (TEM). The main structure of the films and the multilayers was monoclinic with a unit cell of size 2ap × √-2ap × √-2ap, where ap is the lattice constant of single perovskite crystal. The LCMO films were composed of three-dimension multitwinning domains, while the LCMO/GCMO multilayers showed two-domain structure. In LCMO/GCMO multilayers, LCMO layers were coherent with GCMO layers and the interfaces between LCMO and GCMO layers were free from mismatch dislocation, which resulted in highly strained multilayerd structures.

  7. Phase transition in layered perovskite-like manganate Ca3Mn2O7 under high pressure

    朱嘉林; 陈良辰; 禹日成; 李凤英; 刘景; 靳常青


    In situ high pressure energy dispersive X-ray diffraction measurements on the layered perovskite-like manganate Ca3Mn2O7 powder under pressures were performed by using the diamond anvil cell with synchrotron radiation. The results show that the structure of layered perovskite-like manganate Ca3Mn2O7 is unstable under pressure due to the easy compression of NaCl-type blocks. The structure of Ca3Mn2O7 underwent two phase transitions under pressures in the range of 0-35 GPa. One was at about 1.3 GPa with the crystal structure changing from tetragonal to orthorhombic. The other was at about 9.5 GPa with the crystal structure changing from orthorhombic back to another tetragonal.

  8. n型CaMnO_3基氧化物热电材料研究进展

    张飞鹏; 郭志超; 刘剑; 王新练; 张坤书



  9. Effects of micro-alloying with Sc and Mn on microstructure and mechanical properties of Al-Mg based alloys

    CHEN Xian-ming; LUO Cheng-ping; PAN Qing-lin; YIN Zhi-ming


    An extensive investigation was made on the effects of micro-alloying with small amounts of Sc and Mn on the microstructure and mechanical properties of the Al-Mg based alloys. It is found that the micro-alloying can significantly enhance the tensile strength of the alloys, and eliminate the dendritic cast structure in it. Many fine,spherical and dispersive Al3Sc particles are found in the annealed Al-Mg-Mn-Sc alloys, which can strongly pin up dislocations and subgrain boundaries, thus strongly retarding the recrystallization of the alloys. The strengthening of the micro-alloyed Al-Mg alloys is attributed to the precipitation strengthening by the Al3Sc particles and to the substructure strengthening.

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

    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: [Center for Biomedical Materials and Tissue Engineering, Academy for Advanced Interdisciplinary Studies, Peking University, Beijing 100871 (China)


    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.

  11. Heavy Metals (Mg, Mn, Ni and Sn contamination in Soil Samples of Ahvaz II Industrial Estate of Iran in 2013

    Soheil l Sobhanardakani


    Full Text Available Background & Aims of the Study: Due to the rapid industrial development in Khuzestan province of Iran during recent years, this study was performed to analyze the variation of metals concentrations (Mg, Mn, Ni, and Sn in soil samples of Ahvaz II Industrial estate during the spring season of 2013. Materials & Methods: In this experimental study, 27 topsoil samples were collected from nine stations. The intensity of the soil contamination was evaluated, using a contamination factor (Cf and geo-accumulation index (I-geo. Results:  The mean soil concentrations (in mg kg-1 (dry weight were in ranged within 870-1144 (Mg, 188-300 (Mn, 93-199 (Ni and 9-15 (Sn. The data indicated that the I-geo value for all metals falls in class ‘1’. Also the Cf value for Mg and Mn falls in class ‘0’, the Cf value for Sn falls in class ‘1’ and the Cf value for Ni falls in the classes of ‘1’ and ‘2’. The result of the Pearson correlation showed that there were significant positive associations between all metals. Conclusions: According to the results which were achieved by a cluster analysis, there were significant positive associations among all metals based on Pearson correlation coefficient, especially between Ni and Sn; also both of them with Mn. Because the Ni originates from oil sources it can be resulted that Mn and Sn originate from oil sources, too. Therefore, industrial activities and exploitation of oil reservoirs are the main cause of pollution in that area. Also, it can be concluded that, with increasing the distance from the source of pollution, the accumulation of contaminants in the soil samples decreased.

  12. Structural, chemical and electronic properties of the Co2MnSi(001)/MgO interface

    Fetzer, Roman; Wüstenberg, Jan-Peter; Taira, Tomoyuki; Uemura, Tetsuya; Yamamoto, Masafumi; Aeschlimann, Martin; Cinchetti, Mirko


    The performance of advanced magnetic tunnel junctions build of ferromagnetic (FM) electrodes and MgO as insulating barrier depends decisively on the properties of the FM/insulator interface. Here, we investigate interface formation between the half-metallic compound Co2MnSi (CMS) and MgO by means of Auger electron spectroscopy, low energy electron diffraction and low energy photoemission. The studies are performed for different annealing temperatures TA and MgO layer coverages (4, 6, 10, 20 a...

  13. Concentrations of morphologically normal, motile spermatozoa: Mg, Ca and Zn in the semen of infertile men.

    Pandy, V K; Parmeshwaran, M; Soman, S D; Dacosta, J C


    Semen from infertile men (n = 23) has been compared with that of control subjects (n = 25). Whereas the concentrations of morphologically normal, motile sperms, Mg, Ca and Zn fell within the acceptable limits for all the control subjects, only two infertile men qualified by all five parameters. Of the patient group, seven were abnormal on all counts; sperm motility, Mg and Zn were low in 16, Ca in 19 and abnormal morphology was encountered in 12. Since there was no linear correlation between any two parameters, it is possible that each factor may singly or jointly influence the physiological integrity of the spermatozoa. The results are discussed from a consideration of pathological manifestations known to occur in deficiency of these trace elements à propos their role in determining the fertility index of the semen.

  14. Selective oxidation behavior of an ignition-proof Mg-Y-Ca-Ce alloy

    周娜; 章桢彦; 董杰; 靳丽; 丁文江


    A Mg-Y-Ca-Ce magnesium alloy was optimized for high ignition-proof property, which did not burn in air at 1233 K up to 30 min. Oxidation behavior of the alloy was investigated by X-ray diffraction (XRD), scanning electron microscopy (SEM), and thermodynamics calculation at 673, 773 and 873 K. XRD and SEM analysis indicated that dense and compact oxide films composed of MgO, Y2O3 and CaO formed. The oxidation behavior was characterized by the selective oxidation. Based on Pilling-Bedworth ra-tio (PBR) and energy dispersive spectrometer (EDS) analysis, Y2O3 contributed more to form the compact surface oxide film, which led to the excellent ignition-proof performance. The thermodynamics analysis and EDS results implied that the Y-rich areas were preferred paths for the selective oxidation.

  15. Phase controlled synthesis of (Mg, Ca, Ba)-ferrite magnetic nanoparticles with high uniformity

    Wang, S. F.; Li, Q.; Zu, X. T.; Xiang, X.; Liu, W.; Li, S.


    (Mg, Ca, Ba)-ferrite magnetic nanoparticles were successfully synthesized through modifying the atomic ratio of polysaccharide and chelating agent at an optimal sintering temperature. In the process, the polysaccharide plays an important role in drastically shrinking the precursor during the gel drying process. In the metal-complex structure, M2+ ion active sites were coordinated by -OH of the water molecules except for EDTA anions. The MFe2O4 magnetic nanoparticles exhibited enhanced magnetic properties when compared with nano-MFe2O4 of similar particle size synthesized by other synthesis route reported in the literature. In particular, the sintering temperature improves the crystallinity and increases the hysteresis loop squareness ratio of (Mg, Ca, Ba)-ferrite nanoparticles significantly.

  16. Property Research on MgO-CaO-ZrO2 Castable

    HU Sihai; ZHU Boquan; HONG Xueqin


    Studies were conducted on how the structure and property of magnesia castable was affected when the magnesia zirconia calcium composite was incorporated. The experimental result indicates that the component CaZrO3 is easily decomposed by reacting with silica fume to form a low melting point material CMS and CaZr4O9 in the silica fume bonded MgO castable, resulting in occurrence of microcracks, which will improve the thermal shock resistance and strength at moderate temperature. In a word, CaZrO3 improves slag infiltration resistance in spite of lowering the slag corrosion resistance, by absorbing and reacting with components in the slag like Al2O3, TiO2 and FeO.

  17. Fabrication and Characterization of Ca-Mg-P Containing Coating on Pure Magnesium

    Yanjin Lu; Lili Tan; Honglia. ng Xiang; Bingchun Zhang; Ke Yang; Yangde Li


    A biodegradable Ca-P coating mainly consisting of β-tricalcium phosphate (β-TCP) was fabricated on pure magnesium via the chemical deposition in a simulated Hank’s solution. The method significantly accelerated the coating formation on magnesium. Moreover, the morphology, phase/chemical composition, the coating formation mechanism as well as degradation behavior in phosphate buffered saline (PBS) solution were in- vestigated. Scanning electron microscopy (SEM) images showed that the coating had three layers and X-ray diffraction (XRD) patterns showed that the coating mainly contained Ca3(PO4)2 and (Ca,Mg)3(PO4)2. Elec- trochemical test showed that the corrosion current density (Icorr) of the coated Mg was decreased by about one order of magnitude as compared to that of pure magnesium. The immersion test indicated that the coating could obviously reduce the degradation rate.


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


    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.

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

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


    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.


    Danielle Inácio Alves


    Full Text Available Objetivou-se neste trabalho, estudar a distribuição espacial do Ca e Mg do pecíolo do mamoeiro por meio de krigagem indicativa. As folhas (pecíolo, recém-maduras, foram coletadas em uma lavoura comercial de mamão localizada no norte do Estado do Espírito Santo, sendo os pontos amostrados definidos em uma malha amostral georreferenciada. Após coleta e processamento do material em laboratório foi realizada a análise descritiva e geoestatística dos dados. A krigagem indicativa foi usada para estimar a probabilidade de ocorrência do Ca e do Mg na lavoura e como ponto de corte utilizaram-se os níveis considerados adequados para a cultura. Ambos nutrientes apresentaram valores abaixo do nível adequado para a cultura, podendo ser observado também nos mapas de distribuição, onde a maior parte da área apresentou valores abaixo do nível adequado. Por meio dos mapas gerados é possível a realização da fertilização com Ca e Mg de forma diferenciada na área, aplicando-se o fertilizante apenas nas áreas com baixa ocorrência do nutriente foliar.

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

    Yamamoto, Osamu, E-mail: [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)


    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.

  2. Nanoscale precipitates strengthened lanthanum-bearing Mg-3Sn-1Mn alloys through continuous rheo-rolling

    Guan, R. G.; Shen, Y. F.; Zhao, Z. Y.; Misra, R. D. K.


    We elucidate the effect of lanthanum (La) on the microstructure and mechanical properties of Mg-3Sn-1Mn-xLa (wt.%) alloy plates processed through continuous rheo-rolling for the first time. At x = 0.2 wt.%, La dissolved completely in the α-Mg matrix. As the La content was increased to 0.6 wt.%, a new plate-shaped three-phase compound composed of La5Sn3, Mg2Sn and Mg17La2 phases was formed with an average length of 380 ± 10 nm and an average width of 110 ± 5 nm. This compound had a pinning effect on the α-Mg grain boundary and on dislocations. With further increase in La-content to 1.0 wt.%, the length of the plate-shaped compound increased to an average length of 560 ± 10 nm, while the width was reduced to 90 ± 5 nm. The particle size of Mg2Sn decreased from 100 nm to 50 nm with increase in La-content from 0.2 to 1.4 wt.%. At La content of 1.0 wt.%, the tensile strength and elongation of the alloy was maximum, with 29% and 32% increase, respectively, compared to the Mg-3Sn-1Mn (wt.%) alloy, and 37% and 89% increase, in comparison to the Mg-3Sn-1Mn-0.87 Ce (wt.%) alloy. PMID:26988533

  3. Prediction of possible CaMnO3 modifications using an ab initio minimization data-mining approach.

    Zagorac, Jelena; Zagorac, Dejan; Zarubica, Aleksandra; Schön, J Christian; Djuris, Katarina; Matovic, Branko


    We have performed a crystal structure prediction study of CaMnO3 focusing on structures generated by octahedral tilting according to group-subgroup relations from the ideal perovskite type (Pm\\overline 3 m), which is the aristotype of the experimentally known CaMnO3 compound in the Pnma space group. Furthermore, additional structure candidates have been obtained using data mining. For each of the structure candidates, a local optimization on the ab initio level using density-functional theory (LDA, hybrid B3LYP) and the Hartree--Fock (HF) method was performed, and we find that several of the modifications may be experimentally accessible. In the high-pressure regime, we identify a post-perovskite phase in the CaIrO3 type, not previously observed in CaMnO3. Similarly, calculations at effective negative pressure predict a phase transition from the orthorhombic perovskite to an ilmenite-type (FeTiO3) modification of CaMnO3.

  4. Empirical assessment of coral Sr/Ca and Mg/Ca ratios as climate proxies using colonies grown at different temperatures

    Inoue, Mayuri; Suzuki, Atsushi; Nohara, Masato; Hibino, Kohei; Kawahata, Hodaka


    Coral strontium/calcium (Sr/Ca) and magnesium/calcium (Mg/Ca) ratios might be useful for reconstructing past sea surface temperature (SST) in tropical oceans where instrumental data are limited. However, the link between coral skeletal trace elements and SST is disputed, and biological factors such as skeletal growth rate may also affect trace elements in a coral. We studied the relationships between growth rate and SST and Sr/Ca and Mg/Ca ratios using corals (Porites spp.) cultured in thermostated tanks. Sr/Ca was controlled primarily by SST, while Mg/Ca mainly reflected the growth rate with negligible contribution from species on both the variations. These relationships are consistent with modeled results of cation partitioning during aragonite crystal formation.

  5. Packing interactions between transmembrane helices alter ion selectivity of the yeast Golgi Ca2+/Mn2+-ATPase PMR1.

    Mandal, Debjani; Rulli, Samuel J; Rao, Rajini


    PMR1 is the yeast secretory pathway pump responsible for high affinity transport of Mn2+ and Ca2+ into the Golgi, where these ions are sequestered and effectively removed from the cytoplasm. Phenotypic growth assays allow for convenient screening of side chains important for Ca2+ and Mn2+ transport. Earlier we demonstrated that mutant Q783A at the cytoplasmic interface of M6 could transport Ca2+, but not Mn2+. Scanning mutagenesis of side chains proximal to residue Gln-783 in membrane helices M2, M4, M5, and M6 revealed additional residues near the cytoplasmic interface, notably Leu-341 (M5), Phe-738 (M5), and Leu-785 (M6) that are sensitive to substitution. Importantly, we obtained evidence for a packing interaction between Val-335 in M4 and Gln-783 in M6 that is critical for Mn2+ transport. Thus, mutant V335G mimics the Mn2+ transport defect of Q783A and mutant V335I can effectively suppress the Mn2+-defective phenotype of Q783A. These changes in ion selectivity were confirmed by cation-dependent ATP hydrolysis using purified enzyme. Other substitutions at these sites are tolerated individually, but not in combination. Exchange of side chains at 335 and 783 also results in ion selectivity defects, suggesting that the packing interaction may be conformation-sensitive. Homology models of M4, M5, and M6 of PMR1 have been generated, based on the structures of the sarcoplasmic reticulum Ca2+-ATPase. The models are supported by data from mutagenesis and reveal that Gln-783 and Val-335 show conformation-sensitive packing at the cytoplasmic interface. We suggest that this region may constitute a gate for access of Mn2+ ions.

  6. Li/Ca, B/Ca, and Mg/Ca content in sea urchin spines cultured at different temperatures and pCO2

    Nguyen, T.; Eagle, R.; Courtney, T.; Ries, J. B.; Brillo, V.; Rollion-Bard, C.; Gabitov, R. I.; Tripati, A. K.


    Element/calcium ratios within biogenic calcium carbonate minerals have been used as tools to reconstruct seawater temperature and pH. Most recent studies have focused on examining systematics governing elemental incorporation in coral, foraminifera, and otoliths [1-3, etc.]. In this study we focus on examining Li/Ca, B/Ca, and Mg/Ca ratios in sea urchins cultured at different temperatures and pCO2. We conducted in situ secondary ion mass spectrometry (SIMS) analyses on two different species of sea urchins. A temperate species of sea urchin (Arbacia punctulata) was cultured at variable pCO2 (400, 600, 900, 2850 ppmv) and at a constant temperature (25°C) [4]. We also investigated a tropical species of sea urchins (Echinometra viridis) that was cultured at variable pCO2 (400 and 1000 ppmv) and variable temperature (20°C and 30°C). The highly porous spines were embedded in epoxy and polished with 3 μm diamond suspension. SIMS analyses were performed with an oxygen primary beam and a lateral spatial resolution of about 40 μm. The standard deviation for SIMS spot analysis of Li in the reference synthetic calcite, CAL-HTP, was 3.5 % (1σ). The standard deviation of SIMS spots analyses of coral reference material M93-TB-FC-1 was 9.5 % (1σ). The bulk B content in this reference coral was determined by LA-ICP-MS as 39.3 ppm [6]. The standard deviation for the SIMS spot analysis of Mg in the reference synthetic calcite, UCI, was 1% (1σ). For the temperate species, B/Ca ratios decrease from ~0.39 to 0.29 mmol/mol as pCO2 increase from 400 to 2850 ppmv. This suggests that B/Ca ratios in this species may be a viable proxy for paleo-seawater pH. Other elements such as Li/Ca showed an increase from .047 to .052 mmol/mol as pCO2 increased. However, Mg/Ca did not show any significant trend as pCO2 increased. The tropical species showed a general increase in Li/Ca, B/Ca, Mg/Ca with increasing temperature. When temperature was held constant, there was no significant effect of

  7. Activities of MnO in CaO-SiO2-Al2O3-MnO (FetO(<3 pct) slags saturated with liquid iron

    Ohta, Hiroki; Suito, Hideaki


    Activity coefficients of MnO and Fe,0 in CaO-SiO2-Al2O3-MnO(FetO were found to be constant in the studied concentration range of MnO and FetO. The former increased with an increase in the CaO content, while the latter increased with an increase in the SiO2 content.

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

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


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

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

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


    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.

  10. Symmetric interfacial reconstruction and magnetism in La0.7Ca0.3MnO3/YBa2Cu3O7/La0.7Ca0.3MnO3 heterostructures

    Visani, C. [Universidad Complutense, Spain; Tornos, J. [Universidad Complutense, Spain; Nemes, Norbert [Universidad Complutense, Spain; Rocci, M. [Universidad Complutense, Spain; Leon, C. [Universidad Complutense, Spain; Santamaria, J. [Universidad Complutense, Spain; te Velthuis, G. E. [Argonne National Laboratory (ANL); Liu, Y. [Argonne National Laboratory (ANL); Hoffman, A. [Argonne National Laboratory (ANL); Freeland, J. W. [Argonne National Laboratory (ANL); Garcia-Hernandez, M [Instituto de Ciencia de Materiales de Madrid (ICMM); Fitzsimmons, M. R. [Los Alamos National Laboratory (LANL); Kirby, B. J. [Los Alamos National Laboratory (LANL); Varela del Arco, Maria [ORNL; Pennycook, Stephen J [ORNL


    We have analyzed the interface structure and composition of La{sub 0.7}Ca{sub 0.3}MnO{sub 3}/YBa{sub 2}Cu{sub 3}O{sub 7}/La{sub 0.7}Ca{sub 0.3}MnO{sub 3} trilayers by combined polarized neutron reflectometry, aberration-corrected microscopy, and atomic column resolution electron-energy-loss spectroscopy and x-ray absorption with polarization analysis. We find the same stacking sequence at both top and bottom cuprate interfaces. X-ray magnetic circular dichroism experiments show that both cuprate interfaces are magnetic with a magnetic moment induced in Cu atoms as expected from symmetric Mn-O-Cu superexchange paths. These results supply a solid footing for the applicability of recent theories explaining the interplay between magnetism and superconductivity in this system in terms of the induced Cu spin polarization at both interfaces.

  11. Toughness behaviour of the aluminium alloy AlMg4. 5Mn down to 4. 2 K. Zaehigkeitsverhalten der Aluminiumlegierung AlMg4,5Mn bis 4,2 K

    Huppertz, P.H.; Haering, H.W.; Baeumler, F.; Henn, G. (Linde AG, Hoellriegelskreuth (Germany, F.R.). Werksgruppe Tieftemperatur und Verfahrenstechnik)


    For testing the toughness of metallic materials - in the case in point of AlMg4.5Mn - within the reported investigations (1) notched-bar impact tests, (2) tensile test for determining the notch tensile/yield ratio and (3) fracture-mechanical tests were brought into use. For this reason the traditional notched-bar impact test has been improved in evidential emphasis by instrumentation with supplementary fractographic testing. The advantage of instrumentation as opposed to the usual test procedure lies in the fact that notch impact load/deflection diagrams are obtained and these give information on the deformability and the type of crack-propagation. The reported summarized version of the test results shows that despite low notch impact energy values at 77 K and a deformation rate of 5.5 m/sec specimens of AlMg4.5Mn do not result in any unstable crack-propagation. Measurements of the ratio of notch tensile strength to yield which were made by us on notched and unnotched round tensile test specimens made of AlMg4.5Mn base an weld metal give a ratio of more than 1.8 at temperatures down to 4 K. (orig./RHM).

  12. High-temperature Electric Properties of Polycrystalline La-doped CaMnO3 Ceramics

    Jinle Lan; Yuanhua Lin; Ao Mei; Cewen Nan; Yong Liu; Boping Zhang; Jingfeng Li


    Polycrystalline La-doped CaMnO3 ceramics have been prepared by a solid-state sintering method. Analysis of microstructure and phase composition indicates that the addition of La can prohibit the further growth of grain, and no impurity phase appears. The results revealed that the La doping can lead to a large change of the activation energy (from 0.22 to 0.02 eV), and thus result in a marked increase in electric conductivity of 2-4 orders of magnitude. The power factor can reach about 1.5×10-4 W·m-1·K-2 in a wide temperature range, which potentially make them attractive for n-type high-temperature thermoelectric materials.

  13. Phonon spectra of La0.5Ca0.5MnO3

    Cao Xian-Sheng; Chen Chang-Le


    This paper presents a microscopic theory to explain different Raman modes of La0.5Ca0.5MnO3 based on the electronic Hamiltonian of the Kondo lattice model, which adds phonon interaction to the hybridization between the conduction electrons of the system and the l-electrons. The spectral density is calculated by the Green function technique of Zubarev at zero wave vector and in the low temperature limit. It finds that there are three Raman-active modes and the spectral densities of these modes are substantially influenced by model parameters such as the position of Mevel (εJT), the effective electron-phonon coupling strength (g) and the hybridization parameter (v). Finally, the intensity changes of those peaks are investigated.

  14. Effects of citric acid ratio on nanosized crystalline CaMnO3 powder%柠檬酸用量对制备纳米晶CaMnO3粉末的影响

    张飞鹏; 张久兴; 路清梅; 张冰心


    柠檬酸的用量将影响CaMnO3粉末性能.以金属硝酸盐为原料,去离子水和乙二醇为溶剂,在不同柠檬酸络合剂用量的情况下,采用溶胶-凝胶法制备了CaMnO3溶胶.通过煅烧干凝胶前驱物制得了钙钛矿型CaMnO3多晶粉末.利用X射线衍射仪、扫描电子显微镜、激光粒度分析仪等手段分析了所得粉末.结果表明:所得钙钛矿型CaMnO3晶粒度在20~50 nm之间,粉末为300~500 nm 多边形颗粒,粒度随柠檬酸用量增加而增大,晶粒尺寸也逐渐增大,增幅均较小.

  15. Exchange interactions of CaMnO3 in the bulk and at the surface

    Keshavarz, Samara; Rodrigues, Debora; Pereiro, Manuel; Di Marco, Igor; Autieri, Carmine; Nordstrom, Lars; Solovyev, Igor; Sanyal, Biplab; Eriksson, Olle


    In this work, we present electronic and magnetic properties of CaMnO3 (CMO) as obtained from ab initio calculations. We identify the preferable magnetic order by means of density functional theory plus Hubbard U calculations and extract the effective exchange parameters (Jij's) using the magnetic force theorem. We find that the effects of geometrical relaxation at the surface as well as the change of crystal field are very strong and are able to influence the lower energy magnetic configuration. In particular, our analysis reveals that the exchange interaction between the Mn atoms belonging to the surface and the subsurface layers is very sensitive to the structural changes. An earlier study [A. Filippetti and W.E. Pickett, Phys. Rev. Lett. 83, 4184 (1999)] suggested that this coupling is ferromagnetic and gives rise to the spin flip process on the surface of CMO. In our work we confirm their finding for an unrelaxed geometry, but once the structural relaxations are taken into account, this exchange coupling ...

  16. Influence of substrate and Ca substitution on multiferroic BiMnO3 thin films

    K S Pugazhvadivu; L Balakrishnan; K Tamilarasan


    BiMnO3 (BMO) and Ca (10 at%) substituted BiMnO3 (BCMO) thin films are grown on n-type Si (100) and Pt/Ti/SiO2/Si (100) substrates by RF magnetron sputtering. The structural, elemental, morphological, magnetic, dielectric and ferroelectric properties of the films are investigated by X-ray diffraction (XRD), energy-dispersive X-ray analysis (EDAX), atomic force microscope (AFM), vibrating sample magnetometer (VSM), dielectric and ferroelectric measurements, respectively. The XRD pattern shows that the films acquire monoclinic structure with C2 space group. The elemental composition and surface roughness of the films are also measured by EDAX and AFM analysis, respectively. The VSM results exhibit that all the films possess room temperature ferromagnetism and the BCMO film deposited on the Si substrate has better magnetic properties (rem = 1.8 × 10−3 emu cm−3) than the other films. The dielectric measurement also reveals that the BCMO film has the highest value of dielectric constant (497) with less dielectric loss (0.3). Similarly, the ferroelectric measurement implies that all the films possess room temperature ferroelectricity.

  17. MgCaCO3 Versus CaCO3 in Peritoneal Dialysis Patients – A Cross-Over Pilot Trial

    Evsanaa, Baigalmaa; Liu, Irene; Aliazardeh, Babak; Mahdavi, Sara; Bajwa, Gursarn; Gula, Jerry; Tam, Michelle; Sze, Elena; Roscoe, Janet M.; Tam, Paul Y.; Sikaneta, Tabo


    ♦ Background: Despite adverse effects such as constipation, vascular calcification, and hypercalcemia, calcium-based salts are relatively affordable and effective phosphate binders that remain in widespread use in the dialysis population. We conducted a pilot study examining whether the use of a combined magnesium/calcium-based binder was as effective as calcium carbonate at lowering serum phosphate levels in peritoneal dialysis (PD) patients. ♦ Methods: This was a cross-over, investigator-masked pilot study in which prevalent PD patients received calcium carbonate alone (200 mg calcium per tablet) or calcium magnesium carbonate (100 mg calcium, 85 mg magnesium per tablet). Primary outcome was serum phosphate level at 3 months. Analysis was as per protocol. ♦ Results: Twenty patients were recruited, 17 completed the study. Mean starting dose was 11.35 ± 7.04 pills per day of MgCaCO3 and 9.00 ± 4.97 pills per day of CaCO3. Mean phosphate levels fell from 2.13 mmol/L to 2.01 mmol/L (95% confidence interval (CI): 1.76 – 2.30, p = 0.361) in the MgCaCO3 group, and 1.81 mmol/L (95% CI: 1.56 – 2.0, p = 0.026) in the CaCO3 alone group. Six (35%) patients taking MgCaCO3 and 9 (54%) taking CaCO3 alone achieved Kidney Disease Outcomes Quality Initiative (KDOQI) serum phosphate targets at 3 months. Diarrhea developed in 9 patients taking MgCaCO3 and 3 taking CaCO3. Serum magnesium exceeded 1.4 mmol/L in 5 patients taking MgCaCO3 while serum calcium exceeded 2.65 mmol/L in 3 patients receiving CaCO3. When compared to the initial dose, the prescribed dose at 3 months was reduced by 44% (to 6.41 tablets/day) in the MgCaCO3 group and by 8% (to 8.24 pills per day) in the CaCO3 alone group. ♦ Conclusion: Compared with CaCO3 alone, the preparation and dose of MgCaCO3 used in this pilot study was no better at lowering serum phosphate levels in PD patients, and was associated with more dose-limiting side effects. PMID:24584605

  18. Electronic and Optical Properties of Ca3MN (M = Ge, Sn, Pb, P, As, Sb and Bi) Antiperovskite Compounds

    Iqbal, Samad; Murtaza, G.; Khenata, R.; Mahmood, Asif; Yar, Abdullah; Muzammil, M.; Khan, Matiullah


    The electronic and optical properties of cubic antiperovskites Ca3MN (M = Ge, Sn, Pb, P, As, Sb and Bi) were investigated by applying the full potential linearized augmented plane wave plus local orbitals (FP-LAPW + lo) scheme based on density functional theory. Different exchange correlation potentials were adopted for the calculations. The results of band structure and density of states show that, by changing the central anion of Ca3MN, the nature of the materials change from metallic (Ca3GeN, Ca3SnN, Ca3PbN) to semiconducting with small band gaps (Ca3SbN and Ca3BiN) to insulating (Ca3PN and Ca3AsN). The optical properties such as dielectric function, absorption coefficient, optical conductivity, reflectivity and refractive indices have also been calculated. The results reveal that all the studied compounds are optically active in the visible and ultraviolet energy regions, and therefore can be effectively utilized for optoelectronic devices.

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

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


    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

  20. Normal and inverse magnetocaloric effects in LaCaMnNiO

    Krishnamoorthi, C.; Barik, S. K.; Siu, Z.; Mahendiran, R.


    We have investigated magnetic and magnetocaloric properties of La 0.5Ca 0.5Mn 1- xNi xO 3 ( x=0, 0.02, 0.04, 0.06, & 0.08). It is shown that charge-ordered antiferromagnetic ground state of x=0 is destabilized and ferromagnetism is induced by just 2% Ni substitution. The ferromagnetic Curie temperature (TC) decreases from TC=220 K for x=0 to 85 K (x=0.08). Unusual field-induced metamagnetic transition is found above TC for x=0.02-0.06 and even below TC in the parent compound (x=0). Magnetic entropy change (ΔSm) was estimated from isothermal magnetization data and it is found that the parent compound (x=0) exhibits both normal (negative ΔSm) and inverse (positive ΔSm) magnetocaloric effects at TC and TN (Neel temperature), respectively. The ΔSm=+6.5 J kg K at TN is twice larger than that at TC(ΔSm=-3 JkgK) for a field change (ΔH) of 5 T. However, all the Ni doped samples in La 0.5Ca 0.5Mn 1- xNi xO 3 system show only normal magnetocaloric effect at TC. The largest MCE in the Ni doped series occurs for x=0.04 (ΔSm=-3.9 JkgK,ΔH=5 T) which also has the largest relative cooling power (RCP=235 J/kg,ΔH=5 T) in the series. We discuss our results in the scenario of phase separation induced by Ni substitution.

  1. Fabrication and microstructure of nanostructured Mg-3Ni-2MnO_2 by ball milling in hydrogen atmosphere

    FANG Wen-bin; FANG Wa; SUN Hong-fei; YU Zhen-xing


    Nanostructured Mg-3Ni-2MnO_2 was synthesized by ball milling elemental powders of Mg, Ni and MnO_2 in hydrogen atmosphere. The microstructures of the powder prepared at different milling time were analyzed by X-ray diffractometry(XRD), scanning electron microscopy(SEM) and high resolution electron microscopy(HREM). The milling time is the most key parameter impacting on the grain size and the microstructure of material. With prolonging the milling time, particle size becomes smaller and smaller. But after the ball milling time reaches about 20 h, reduction of grain size becomes slowly. When the milling time is more than 50 h, nanocrystailine fully forms. When the milling time is more than 80 h, there are more amorphous phases in materials. The average particle diameter of material is about 1 μm and the grain size is 10-30 nm.

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

    戴曦; 甘雪萍; 张传福


    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.

  3. The Dependence of Creep Behavior on Elemental Partitioning in Mg-5Al-3Ca- xSn Alloys

    TerBush, Jessica R.; Chen, Olivia H.; Jones, J. Wayne; Pollock, Tresa M.


    Cast Mg-5Al-3Ca- xSn alloys have been examined to investigate the effect of Sn additions on elemental partitioning during solidification, microstructure development, and compressive creep behavior at 453 K (180 °C). Alloys containing 0.25 to 3.0 wt pct Sn were cast with a permanent mold technique. The addition of 0.75 to 1.0 wt pct Sn had a beneficial effect on Ca partitioning to the α-Mg phase. Additions beyond 1 wt pct Sn resulted in the formation of an orthorhombic Mg-Ca-Sn phase, with decreased Ca partitioning to the α-Mg. A lower minimum creep rate was observed for the Mg-5Al-3Ca- xSn alloy with increased Ca partitioning. Consistent with this finding, analyses that consider the influence of solute and precipitation strengthening on creep in Mg-5Al-3Ca- xSn alloys suggest that Ca in the α-Mg contributes to a greater degree than Al in solution to the creep resistance at 453 K (180 °C).

  4. Hydrogenated uniform Pt clusters supported on porous CaMnO(3) as a bifunctional electrocatalyst for enhanced oxygen reduction and evolution.

    Han, Xiaopeng; Cheng, Fangyi; Zhang, Tianran; Yang, Jingang; Hu, Yuxiang; Chen, Jun


    Hydrogenated uniform Pt clusters supported on porous CaMnO3 nanocomposites are synthesized and investigated as a new electrocatalytic material for oxygen reduction and evolution reactions. Due to the synergistic effect of Pt and CaMnO3, the nanocomposites exhibit superior activity and durability to the benchmark Pt/C catalyst.

  5. Density Functional Theory Study on Electronic and Magnetic Properties of Mn-doped (MgO)n (n=2-10) Clusters

    Peng Wang; Ming-xia Yang; Sheng-li Zhang; Shi-ping Huang; Hui-ping Tian


    We study the geometries,stabilities,electronic and magnetic properties of (MgO),(n=2-10) clusters doped with a single Mn atom using the density functional theory with the generalized gradient approximation.The optimized geometries show that the impurity Mn atom prefers to replace the Mg atom which has low coordination number in all the lowest-energy MnMgn-1On (n=2-10) structures.The stability analysis clearly represents that the average binding energies of the doped clusters are larger than those of the corresponding pure (MgO),clusters.Maximum peaks of the second order energy differences are observed for MnMg_1On clusters at n=6,9,implying that these clusters exhibit higher stability than their neighboring clusters.In addition,all the Mn-doped Mg clusters exhibit high total magnetic moments with the exception of MnMgO2 which has 3.00 μB.Their magnetic behavior is attributed to the impurity Mn atom,the charge transfer modes,and the size of MnMgn-1On clusters.

  6. CaMnO3热电材料的低温烧结研究%Study on the Low-temperature Sintering of Thermoelectric Material CaMnO3

    王琴; 盛得雪; 鲁云; 宋少伟; 陈建文; 金应荣


    It is Proposed to fabricate a thermoelectric generator with P - N structure by sintering the N - type CaMnO3 together with the P - type Ca3 Co4 O9 directly. It is necessary to sinter CaMnO3 ceramic below the phase transition temperature of Ca3 Co4 O9 , 926 癈. In this paper, CaMnO3 powder wsa synthesized using the solid reaction method, then mixed with Bi2O3 and pressed into pellet. Sintering was carried out in air at 900cC for 12h. The microstructure and thermoelectric properties of prepared sample were also investigated. As a result, there was no detectable secondary phase caused by additional Bi2O3; the average electrical conductivity increased and the approximate Seebeck coefficient decreased with increasing adding of Bi2 O3; the average electrical conductivity and the approximate Seebeck coefficient increased with increasing temperature. The addition of Bi2O3 promoted the sintering process and decreased the sintering temperature, and effectively improved the thermoelectric properties of CaMnO3 sample as well.%采用固相反应法制备CaMnO3粉末,加入Bi2O3混合、压块后,在900℃烧结12h得到样品,并对样品的物相、组织和热电性能进行了测试分析.结果表明:制备出的热电材料是单相的CaMnO3,加入Bi2O3后没有形成可观测的第二相;随着Bi2O3加入量的增加,样品的平均电导率增大,温差电势减小;平均电导率随温度的增加而增加,呈半导体特性,温差电势随温度的增加而增大;加入Bi2O3促进了烧结,降低了烧结温度,改善了材料的热电性能.

  7. Green-emitting (La,M,Tb)OCl (M = Mg, Ca, and Sr) phosphors

    Kim, Sun Woog; Jyoko, Kazuya; Masui, Toshiyuki; Imanaka, Nobuhito


    Green-emitting (La1-x-yMxTby)OCl (0 ⩽ x ⩽ 0.13, 0.03 ⩽ y ⩽ 0.15, M = Mg, Ca, and Sr) single phase phosphors were synthesized using a liquid-phase method and their photoluminescence properties were characterized. The excitation spectrum consisted of a strong broad band from 220 to 290 nm, which corresponds to the 4f-5d transition of Tb3+. The oxychloride phosphors exhibit typical emission peaks assigned to the transition from 5D4 to 7FJ (J = 6, 5, 4, and 3) of Tb3+, and the luminescence emission intensity was successfully enhanced by doping divalent alkaline earth metal ions (M = Mg2+, Ca2+, and Sr2+) into La3+ sites of the host LaOCl lattice. The highest green emission intensity was obtained for (La0.88Ca0.05Tb0.07)OCl, of which the relative emission intensity was 75% of that for a commercial green-emitting (La0.52Ce0.31Tb0.17)PO4 phosphor.

  8. Combining benthic foraminiferal ecology and shell Mn/Ca to deconvolve past bottom water oxygenation and paleoproductivity

    Koho, K. A.; de Nooijer, L. J.; Reichart, G. J.


    The Mn/Ca of carbonate tests of living deep-sea foraminifera (Hoeglundina elegans, Bulimina aculeata, Uvigerina peregrina and Melonis barleeanus) were determined together with pore water manganese along a bottom water oxygen gradient across the lower boundary of the Arabian Sea oxygen minimum zone.

  9. 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

    Vanessa David Domingos


    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

  10. Effect of hot plastic deformation on microstructure and mechanical property of Mg-Mn-Ce magnesium alloy


    Hot plastic deformation was conducted using a new solid die on a Mg-Mn-Ce magnesium alloy. The results of microstructural examination through OM and TEM show that the grain size is greatly refined from 45 μm to 1.1 μm with uniform distribution due to the occurrence of dynamic recrystallization. The grain refinement and high angle grain boundary formation improve the mechanical properties through tensile testing with the strain rate of 1.0× 10-4 s-1 at room temperature and Vickers microhardness testing. The maximum values of tensile strength, elongation and Vickers microhardness are increased to 256.37 MPa,17.69% and HV57.60, which are 21.36%, 133.80% and 20.50% more than those of the as-received Mg-Mn-Ce magnesium alloy,respectively. The SEM morphologies of tensile fractured surface indicate that the density and size of ductile dimples rise with accumulative strain increasing. The mechanism of microstructural evolution and the relationship between microstructure and mechanical property of Mg-Mn-Ce magnesium alloy processed by this solid die were also analyzed.

  11. The Effect of Oxidation/Reduction Disposing on Optical Properties of Mg:Fe:Mn:LiNbO3 Crystals


    The congruent tri-doped Mg:Mn:Fe:LiNbO3 crystal has been grown by Czochralski method. Some crystal samples are reduced in Li2CO3 powder at 500 ℃ for 24 hours or oxidized for 10 hours at 1100 ℃ in Nb2O5 powder. Compared with As-grown Mg:Mn:Fe:LiNbO3, the absorption edge in UV-Vis. absorption spectrum of the oxidized sample and the reduced shifts to the violet and the red, respectively. Reduction increases the absorption of crystals in visible light region. In two-wave coupling experiments, the writing time, maximum diffraction efficiency and the erasure time of crystal samples in the same conditions are determined. The results indicate that oxidation and reduction disposing has great effect on the holographic recording properties of these crystals. The reduced crystal exhibits the fastest response time of 160 s among the crystal series. The mechanism of post-disposing effect on the holographic recording properties of Mg:Mn:Fe:LiNbO3 crystals are investigated.

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

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


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

  13. Synthesis and Study of Optical properties of MgO based TM oxide (TM=Cu, Mn and Zn) nanocomposites

    Tamizh Selvi, K.; Alamelumangai, K.; Priya, M.; Rathnakumari, M.; Kumar, P. Suresh; Sagadevan, Suresh


    A nanocomposite of MgO based transition metal (TM) oxide (TM=Zn, Mn, and Cu) was synthesized using sol-gel method. The powder x-ray diffraction confirmed the phase purity and particle size. The surface morphology and elemental composition were examined by High resolution scanning electron microscopy and energy-dispersive x-ray spectroscopy. The change in optical band gap of the synthesized nanocomposites, by increasing the Mg content was determined using UV-vis spectra and the luminescent properties were analyzed using photoluminescence spectra.

  14. Corrosion behavior of Mg-Zn-Ca amorphous alloys with Nd addition in simulated body fluids

    Qin Chunling; Xiao Tongna; Li Yongyan; Wang Zhifeng; Liu Li; Xiong Hanqing; Zhao Weimin


    The effects of Nd addition on corrosion behavior of Mg66Zn30Ca4 amorphous al oys in simulated body fluids (SBF) were studied in this paper. Electrochemical properties of the samples before and after corrosion were determined. Surface morphologies of samples after immersion in SBF at 37 ºC for different times were observed under scanning electron microscope (SEM). Results show that the corrosion resistance of Mg-based al oys in SBF is improved with the addition of Nd element. The electrochemical properties indicate that microal oying Nd element to the al oys leads to an ennoblement in the open circuit potentials of the al oys and a decrease in the anodic current density in SBF, especial y for the Mg66-xZn30Ca4Ndx al oys with Nd content of 1.0at.%-1.5at.%. It was observed that the surface morphologies of the al oys immersed in SBF change with the Nd addition. A flake-like structure paral el to the al oy substrate formed on the surface of 1.0at.% Nd-containing al oy immersed in SBF for 7 days improves the corrosion resistance of the amorphous al oys by blocking the corrosion liquid from attacking the al oys.

  15. Corrosion behavior of Mg-Zn-Ca amorphous alloys with Nd addition in simulated body fluids

    Qin Chunling


    Full Text Available The effects of Nd addition on corrosion behavior of Mg66Zn30Ca4 amorphous alloys in simulated body fluids (SBF were studied in this paper. Electrochemical properties of the samples before and after corrosion were determined. Surface morphologies of samples after immersion in SBF at 37 篊 for different times were observed under scanning electron microscope (SEM. Results show that the corrosion resistance of Mg-based alloys in SBF is improved with the addition of Nd element. The electrochemical properties indicate that microalloying Nd element to the alloys leads to an ennoblement in the open circuit potentials of the alloys and a decrease in the anodic current density in SBF, especially for the Mg66-xZn30Ca4Ndx alloys with Nd content of 1.0at.%-1.5at.%. It was observed that the surface morphologies of the alloys immersed in SBF change with the Nd addition. A flake-like structure parallel to the alloy substrate formed on the surface of 1.0at.% Nd-containing alloy immersed in SBF for 7 days improves the corrosion resistance of the amorphous alloys by blocking the corrosion liquid from attacking the alloys.

  16. Influence of Cu content on the mechanical properties and corrosion resistance of Mg-Zn-Ca bulk metallic glasses

    Zhao, Yan-feng; Zhu, Jian; Chang, Li; Song, Jing-guo; Chen, Xiao-hua; Hui, Xi-dong


    (Mg66.2Zn28.8Ca5)100- x Cu x (at%, x = 0, 1, 3, and 5) bulk metallic glasses (BMGs) of 2 mm in diameter were prepared by the conventional copper mold injection casting method. Besides, the influence of Cu content on the microstructure, thermal stability, mechanical properties, and corrosion behavior of Mg-Zn-Ca BMGs was investigated. It is found that the addition of Cu decreases the glass-forming ability of Mg-Zn-Ca BMGs. Crystalline phases are precipitated at a higher Cu content, larger than 3at%. The compressive fracture strength of Mg-Zn-Ca BMGs is enhanced by the addition of Cu. With the formation of in-situ composites, the compressive strength of the Mg-Zn-Ca alloy with 3at% Cu reaches 979 MPa, which is the highest strength among the Mg-Zn-Ca alloys. Furthermore, the addition of Cu also results in the increase of corrosion potential and the decrease of corrosion current density in Mg-Zn-Ca BMGs, thereby delaying their biodegradability.

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

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


    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

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


    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. Recrystallization behaviour of CaO-MgO-SiO{sub 2} system ceramic fibers

    Wang Xitang; Zhang Baoguo [Hubei Province Key Lab. of Ceramics and Refractories, Wuhan Univ. of Science and Technology, Wuhan (China)


    Various kinds of ceramic fibers are used in industries for thermal insulation. Traditional Al{sub 2}O{sub 3}-SiO{sub 2} refractory ceramic fibers have potential health hazard when they come into the lung of human beings. The bio-soluble ceramic fibers in CaO-MgO-SiO{sub 2} system, as a new group of synthetic glass fibers, have been developed recently for high-temperature insulation applications. The fibers were specially designed to have high solubility and hence low bio-durability in human body lung solution. Various calcium magnesium silicate bio-soluble glass fibers are produced at present to replace aluminium silicate ceramic fibers. In practical applications such as fiber lining of various kinds of high temperature furnace or kiln, devitrification of the fibers take place and consequently fiber surface become rougher. Formation and growth of crystal phases could cause the destruction and pulverization of the fibers after a long exposure at high temperature. For traditional Al{sub 2}O{sub 3}-SiO{sub 2} refractory ceramic fibers the recrystallization temperature of the fibers starts at 980 C with the formation of mullite and cristobalite phases. Comparing with Al{sub 2}O{sub 3}-SiO{sub 2} ceramic fibers, the relatively lower application temperature of CaO-MgO-SiO{sub 2} system bio-soluble fibers is considered. In this paper, the studies were focused on recrystallization behaviour of CaO-MgO-SiO{sub 2} system soluble ceramic fibers. (orig.)

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

    Georgios S.E. Antipas


    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.

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

    Gorzelak, Przemysław; Krzykawski, Tomasz; Stolarski, Jarosław


    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

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

    Milenin A.


    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.

  3. 铸造Al-Mg-Mn合金的显微组织及力学性能%Microstructure and Tensile Properties of Al-Mg-Mn Alloy

    孙景旺; 王渠东; 丁文江


    研究了Mg含量、冷却速度、固溶处理对A1-6.8Mg-0.3Mn、Al-3.8Mg-0.3Mn两种合金力学性能的影响.结果表明,随着Mg含量提高,晶界相增多.当Mg含量提高到6.8%时,晶界出现网状组织;随着Mg含量升高,合金强度提高,塑性下降;通过砂型铸造空冷、金属型铸造空冷、金属型铸造淬火来实现不同的冷却速度,发现金属型淬火试样的金相组织中,在晶界附近没有析出网絮状或颗粒状第二相,而强度和伸长率要高于其他两种工艺.两种合金经过430℃×60 h固溶处理后,合金的综合力学性能得到大幅度提高.Al-6.8Mg-0.3Mn金属型铸造空冷试样固溶后抗拉强度由280 MPa提高到335 MPa,伸长率由10.4%提高到20%.%Effects of Mg content, cooling rate and solution treatment on the tensile properties of Al-6. 8Mg-0. 3Mn, Al-3. 8Mg-0. 3Mn alloy were investigated. The results show that the amount of grain boundary phases is increased with increasing in Mg content, and with 6. 8% Mg content, network structure occurs in grain boundary. In addition, strength is improved and the plasticity of the magnesium alloy is decreased with the Mg content increases. Mg alloy samples were fabricated in sand casting with air-cooled, metal mold casting with air-cooled, metal mold casting quenched in water to achieve different cooling rates, respectively. The results reveal that absence of flocculent or granular precipitation in the grain boundary of microstructure in quenched sample can be observed, and the strength and elongation are higher than those of the samples fabricated in the other two cooling rates. After 430℃ for 60 h solution treatment, comprehensive properties of the two alloys have been substantially improved. Tensile strength and elongation of Al-6. 8Mg-0. 3Mn alloy in permanent mold casting with air cooled are improved from 280 Mpa to 335 Mpa and from 10. 4% to 20%; respectively, after solid solution treatment.

  4. Influence of Ca substitution by Mg on the Ca{sub 3}Co{sub 4}O{sub 9} performances

    Constantinescu, G.; Rasekh, S.; Torres, M. A.; Chocarro, C.; Diez, J. C.; Madre, M. A.; Sotelo, A.


    Ca{sub 3}-xMg{sub x}Co{sub 4}O{sub 9} polycrystalline thermoelectric ceramics with small amounts of Mg have been synthesized by the classical solid state method. Microstructural characterizations have shown that all the Mg has been incorporated into the Ca{sub 3}Co{sub 4}O{sub 9} structure and no Mg-based secondary phases have been identified. Apparent density measurements have shown that samples do not modify their density until 0.05 Mg content, decreasing for higher contents. Electrical resistivity decreases and Seebeck coefficient slightly raises when Mg content increases until 0.05 Mg addition. The improvement in both parameters leads to higher power factor values than the usually obtained in samples prepared by the conventional solid state routes and close to those obtained in textured materials. (Author)

  5. Defective maintenance of intracellular Ca2+ homeostasis is linked to increased muscle fatigability in the MG29 null mice


    Mitsugumin 29 (MG29) is a transmembrane protein that is normally found in the triad junction of skeletal muscle. Our previous studies have shown that targeted deletion of mg29 from the skeletal muscle resulted in abnormality of the triad junction structure, and also increased susceptibility to muscle fatigue. To elucidate the basis of these effects, we investigated the properties of Ca2+-uptake and -release in toxin-skinned Extensor Digitorium Longus (EDL) muscle fibers from control and mg29 knockout mice. Compared with the control muscle, submaximal Ca2+-uptake into the sarcoplasmic reticulum (SR) was slower and the storage of Ca2+ inside the SR was less in the mutant muscle, due to increased leakage process-of Ca2+ movement across the SR. The leakage pathway is associated with the increased sensitivity of Ca2+/caffeine -induced Ca2+ release to myoplasmic Ca2+. Therefore, the increased fatigability of mutant EDL muscles can result from a combination of a slowing of Ca2+ uptake, modification of Ca2+-induced Ca2+ release (CICR), and a reduction in total SR Ca2+ content.

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

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


    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. Where Water is Oxidized to Dioxygen: Structure of the Photosynthetic Mn4Ca Cluster from X-ray Spectroscopy

    Yano, Junko; Yano, Junko; Yachandra, Vittal K.


    Light-driven oxidation of water to dioxygen in plants, algae and cyanobacteria iscatalyzed within photosystem II (PS II) by a Mn4Ca cluster. Although the cluster has been studied by many different methods, the structure and the mechanism have remained elusive. X-ray absorption and emission spectroscopy and EXAFS studies have been particularly useful in probing the electronic and geometric structure, and the mechanism of the water oxidation reaction. Recent progress, reviewed here, includes polarized X-ray absorption spectroscopy measurements of PS II single crystals. Analysis of those results has constrained the Mn4Ca cluster geometry to a setof three similar high-resolution structures. The structure of the cluster from the present study is unlike either the 3.0 or 3.5 Angstrom-resolution X-ray structures or other previously proposed models. The differences between the models derived from X-rayspectroscopy and crystallography are predominantly because of damage to the Mn4Ca cluster by X-rays under the conditions used for structure determination by X-ray crystallography. X-ray spectroscopy studies are also used for studying the changes in the structure of the Mn4Ca catalytic center as it cycles through the five intermediate states known as the Si-states (i=0-4). The electronic structure of the Mn4Ca cluster has been studied more recently using resonant inelastic X-ray scattering spectroscopy (RIXS), in addition to the earlier X-ray absorption and emission spectroscopy methods. These studies are revealing that the assignment of formaloxidation states is overly simplistic. A more accurate description should consider the charge density on the Mn atoms that includes the covalency of the bonds and delocalization of the charge over the cluster. The geometric and electronic structure of the Mn4Ca cluster in the S-states derived from X-ray spectroscopy are leading to a detailed understanding of the mechanism of the O-O bond formation during the photosynthetic water

  8. Experimental Investigation of CaMnO3−δ Based Oxygen Carriers Used in Continuous Chemical-Looping Combustion

    Peter Hallberg


    Full Text Available Three materials of perovskite structure, CaMn1−xMxO3−δ (M = Mg or Mg and Ti, have been examined as oxygen carriers in continuous operation of chemical-looping combustion (CLC in a circulating fluidized bed system with the designed fuel power 300 W. Natural gas was used as fuel. All three materials were capable of completely converting the fuel to carbon dioxide and water at 900°C. All materials also showed the ability to release gas phase oxygen when fluidized by inert gas at elevated temperature (700–950°C; that is, they were suitable for chemical looping with oxygen uncoupling (CLOU. Both fuel conversion and oxygen release improved with temperature. All three materials also showed good mechanical integrity, as the fraction of fines collected during experiments was small. These results indicate that the materials are promising oxygen carriers for chemical-looping combustion.

  9. Synthesis and Electrochemical Characterization of M2Mn3O8 (M=Ca,Cu) Compounds and Derivatives

    Park, Yong Joon; Doeff, Marca M.


    M{sub 2}Mn{sub 3}O{sub 8} (M=Ca{sup 2+}, Cu{sup 2+}) compounds were synthesized and characterized in lithium cells. The M{sup 2+} cations, which reside in the van der Waal's gaps between adjacent sheets of Mn{sub 3}O{sub 8}{sup 4-}, may be replaced chemically (by ion-exchange) or electrochemically with Li. More than 7 Li{sup +}/Cu{sub 2}Mn{sub 3}O{sub 8} may be inserted electrochemically, with concomitant reduction of Cu{sup 2+} to Cu metal, but less Li can be inserted into Ca{sub 2}Mn{sub 3}O{sub 8}. In the case of Cu{sup 2+}, this process is partially reversible when the cell is charged above 3.5 V vs. Li, but intercalation of Cu{sup +} rather than Cu{sup 2+} and Li{sup +}/Cu{sup +} exchange occurs during the subsequent discharge. If the cell potential is kept below 3.4 V, the Li in excess of 4Li{sup +}/Cu{sub 2}Mn{sub 3}O{sub 8} can be cycled reversibly. The unusual mobility of +2 cations in a layered structure has important implications both for the design of cathodes for Li batteries and for new systems that could be based on M{sup 2+} intercalation compounds.

  10. Effect of Ce/La microalloying on microstructural evolution of Mg-Zn-Ca alloy during solution treatment

    张庆鑫; 佟立波; 程丽任; 江中浩; 孟健; 张洪杰


    The effect of Ce/La misch metal addition on the microstructural evolution of as-cast and as-soluted Mg-5.3Zn-0.5Ca (wt.%) alloys was systematically investigated. It was found that Ce/La could effectively refine the as-cast alloy and restrain grain growth during solution treatment, which was derived from the constitutional supercooling during solidification process and the formation of stable intermetallic compounds CeMg12 and Mg17La2. Furthermore, Ce/La microalloying and solution treatment resulted in an evolu-tion from the original lamellar Ca2Mg6Zn3/α-Mg to the divorced eutectic structure. The thermal stability of Mg-Zn-Ca alloy could be effectively improved by Ce/La addition, because the low-melting-point binary Mg-Zn phase was transformed to MgxZny-Ca-(Ce/La) phase with higher thermal stability and the amount of Ca2Mg6Zn3/α-Mg eutectic structure was reduced.

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

    T. Toharmat


    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.

  12. Use of NIRS technology with a remote reflectance fibre-optic probe for predicting mineral composition (Ca, K, P, Fe, Mn, Na, Zn), protein and moisture in alfalfa.

    González-Martín, I; Hernández-Hierro, J M; González-Cabrera, J M


    In the present work we study the use of near-infrared spectroscopy (NIRS) technology together with a remote reflectance fibre-optic probe for the analysis of major (Ca, K, P) and minor (Fe, Mn, Na, Zn) elements, protein and moisture in alfalfa. The method allows immediate analysis of the alfalfa without prior sample treatment or destruction through direct application of the fibre-optic probe on ground samples in the case of the mineral composition and on-ground and compacted (baled) samples in the case of protein and humidity. The regression method employed was modified partial least-squares (MPLS). The calibration results obtained using samples of alfalfa allowed the determination of Ca, K, P, Fe, Mn, Na and Zn, with a standard error of prediction (SEP(C)) and a correlation coefficient (RSQ) expressed in mg/kg of alfalfa of 1.37x10(3) and 0.878 for Ca, 1.10x10(3) and 0.899 for K, 227 and 0.909 for P, 103 and 0.948 for Fe, 5.1 and 0.843 for Mn, 86.2 and 0.979 for Na, and of 1.9 and 0.853 for Zn, respectively. The SEP(C) and RSQ values (in %) for protein and moisture in ground samples were 0.548 and 0.871 and 0.150 and 0.981, respectively; while in the compacted samples they were 0.564 and 0.826 and 0.262 and 0.935, respectively. The prediction capacity of the model and the robustness of the method were checked in the external validation in alfalfa samples of unknown composition, and the results confirmed the suitability of the method.

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

    Itoh, Yutaka; Isobe, Masahiko


    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,, 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.

  14. Glass-ceramic coated Mg-Ca alloys for biomedical implant applications.

    Rau, J V; Antoniac, I; Fosca, M; De Bonis, A; Blajan, A I; Cotrut, C; Graziani, V; Curcio, M; Cricenti, A; Niculescu, M; Ortenzi, M; Teghil, R


    Biodegradable metals and alloys are promising candidates for biomedical bone implant applications. However, due to the high rate of their biodegradation in human body environment, they should be coated with less reactive materials, such, for example, as bioactive glasses or glass-ceramics. Fort this scope, RKKP composition glass-ceramic coatings have been deposited on Mg-Ca(1.4wt%) alloy substrates by Pulsed Laser Deposition method, and their properties have been characterized by a number of techniques. The prepared coatings consist of hydroxyapatite and wollastonite phases, having composition close to that of the bulk target material used for depositions. The 100μm thick films are characterized by dense, compact and rough morphology. They are composed of a glassy matrix with various size (from micro- to nano-) granular inclusions. The average surface roughness is about 295±30nm due to the contribution of micrometric aggregates, while the roughness of the fine-texture particulates is approximately 47±4nm. The results of the electrochemical corrosion evaluation tests evidence that the RKKP coating improves the corrosion resistance of the Mg-Ca (1.4wt%) alloy in Simulated Body Fluid.

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

    Jeong-Hui Ji


    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.

  16. Dependence of electrical transport properties of CaO(CaMnO3)m (m = 1, 2, 3, ∞) thermoelectric oxides on lattice periodicity

    Baranovskiy, Andrei; Amouyal, Yaron


    The electrical transport properties of CaO(CaMnO3)m (m = 1, 2, 3, ∞) compounds are studied applying the density functional theory (DFT) in terms of band structure at the vicinity of the Fermi level (EF). It is shown that the total density of states (DOS) values at EF increase with increase in the m-values, which implies an increase in the electrical conductivity, σ, with increasing m-values, in full accordance with experimental results. Additionally, the calculated values of the relative slopes of the DOS at EF correlate with the experimentally measured Seebeck coefficients. The electrical conductivity and Seebeck coefficients were calculated in the framework of the Boltzmann transport theory applying the constant relaxation time approximation. By the analysis of experimental and calculated σ(Τ) dependences, the electronic relaxation time and mean free path values were estimated. It is shown that the electrical transport is dominated by electron scattering on the boundaries between perovskite (CaMnO3) and Ca oxide (CaO) layers inside the crystal lattice.

  17. Inhibition of the erythrocyte (Ca2+ + Mg2+)-ATPase by nonheme iron.

    Leclerc, L; Marden, M; Poyart, C


    The erythrocyte calmodulin-stimulated (Ca2+ + Mg2+)-ATPase (CaM-ATPase), an integral membrane protein, is inhibited in different types of congenital hemolytic anemias for which oxidative processes appear as a common feature. The oxidation of hemoglobin and its degradation lead to the accumulation of ferric heme (hemin) and nonheme iron in the red cell. We have shown previously that hemin inhibits the activity of the enzyme of normal erythrocyte (Leclerc et al. (1988) Biochim. Biophys. Acta, 946, 49-56) involving an oxidation of thiol groups. The present study demonstrates that nonheme iron also inhibits the CaM-ATPase activity. In contrast with hemin, the inhibition of the enzyme induced by the nonheme treatment is prevented by butylated hydroxytoluene, a protecting agent of unsaturated phospholipid peroxidations, while dithiothreitol, a reducing agent of protein disulfide bridges, does not restore the activity of the enzyme. We conclude that nonheme iron inhibits the enzyme at least in part, through the peroxidation of phospholipids of the membrane bilayer.

  18. Effect of Qingyitang on activity of intracellular Ca2+-Mg2+-ATPase in rats with acute pancreatitis

    Ying Qiu; Yong-Yu Li; Shu-Guang Li; Bo-Gen Song; Gui-Fen Zhao


    AIM: To study the change of intracellular calcium-magnesium ATPase (Ca2+-Mg2+-ATPase) activity in pancreas, liver and kidney tissues of rats with acute pancreatitis (AP), and to investigate the effects of Qingyitang (QYT) (Decoction for clearing the pancreas) and tetrandrine (Tet) and vitamin E (VitE) on the activity of Ca2+-Mg2+-ATPase.METHODS: One hundred and five Sprague-Dawley rats were randomly divided into: normal control group, AP group,treatment group with QYT (1 mi/100 g) or Tet (0.4 ml/L00 g)or VitE (100 mg/kg). AP model was prepared by a retrograde injection of sodium taurocholate into the pancreatic duct.Tissues of pancreas, liver and kidney of the animals were taken at 1 h, 5 h, 10 h respectively after AP induction, and the activity of Ca2+-Mg2+-ATPase was studied using enzymehistochemistry staining. Meanwhile, the expression of Ca2+-Mg2+-ATPase of the tissues was studied by RT-PCR.RESULTS: The results showed that the positive rate of Ca2+-Mg2+-ATPase in AP group (8.3%, 25%, 29.2%) was lower than that in normal control group (100%) in all tissues (P<0.01), the positive rate of Ca2+-Mg2+-ATPase in treatment group with QYT (58.3%, 83.3%, 83.3%), Tet (50.0%,70.8%, 75.0%) and VitE (54.2%, 75.0%, 79.2%) was higher than that in AP group (8.3%, 25.0%, 29.2%) in all tissues (P<0.01). RT-PCR results demonstrated that in treatment groups Ca2+-Mg2+-ATPase gene expression in pancreas tissue was higher than that in AP group at the observing time points, and the expression at 5 h was higher than that at L h. The expression of Ca2+-Mg2+-ATPase in liver tissue was positive, but without significant difference between different groups.CONCLUSION: The activity and expression of intracellular Ca2+-Mg2+-ATPase decreased in rats with AP, suggesting that Ca2+-Mg2+-ATPase may contribute to the occurrence and development of cellular calcium overload in AP. QYT, Tet and VitE can increase the activity and expression of Ca2+-Mg2+-ATPase and may relieve intracellular calcium

  19. Corrosion of Biocompatible Mg66+xZn30-xCa4 (x=0.2 Bulk Metallic Glasses

    Nowosielski R.


    Full Text Available The aim of this paper was to investigate the corrosion resistance of Mg66Zn30Ca4 and Mg68Zn28Ca4 metallic glasses and evaluate the ability of this amorphous alloy use for medical applications as biodegradable medical implants. Taking into account the amount of Mg, Zn, Ca elements dissolved in multielectrolyte physiological fluid (MPF from Mg66+xZn30-xCa4 (x=0.2 alloys the daily dose of evolved ions from alloys components was determined. Additional goal of the paper was determination of corrosion rate (Vcorr and amount of hydrogen evolved from amorphous magnesium alloys in simulated environment of human body fluids during 24h immersion and during electrochemical tests. Corrosion studies were done in the multielectrolyte physiological fluid (MPF at 37°C. The amount of hydrogen evolved [ml/cm2] and corrosion rate Vcorr [mm/year] of amorphous Mg66Zn30Ca4 and Mg68Zn28Ca4 alloys were compared. The work also presents characterization of Mg-based bulk metallic glasses structure in the form of 2 mm thickness plates. Samples structure was analyzed by means of X-ray diffraction. Fracture and surface morphology of magnesium alloy samples were identified using scanning electron microscopy.

  20. Non-ferromagnetic Insulating Interface Region in La0.14Pr0.56Sr0.3MnO3/SrTiO3 and La0.7Ca0.3MnO3/Gd0.7Ca0.3MnO3 Multilayers

    王昕; 刘大猛; 连贵君; 熊光成


    La0.14Pr0.56Sr0.3MnO3/SrTiO3 and La0.7Ca0.3MnO3/Gd0.7Ca0.3MnO3 multilayers have been fabricated by using pulsed laser deposition. The insulator-metal transition temperatures of the multilayers decrease with the decreasing thickness of the ferromagnetic layers. It is confirmed from the experiment and analysis that a nonferromagnetic insulating region exists near the interface, which could not be attributed to the roughness of the growth surfaces and disorder of the ferromagnetic layers.

  1. ICP-AES法测定土易溶盐中的CaO、MgO、SO42-

    阳国运; 唐裴颖


    文章对土易溶盐的传统分析方法进行了一些改进,建立了ICP-AES测定土易溶盐中CaO、MgO、SO42-的方法。方法线性范围CaO为0.1~40 mg/L;MgO为0.02~10 mg/L,SO42-为0.2~100 mg/L。方法检出限CaO为0.022 4 mg/L,MgO为0.003 8 mg/L,SO42-为0.0279 mg/L。精密度(RSD)CaO为0.99%,MgO为1.71%, SO42-为1.66%。回收率(R)为96.0%~103.2%。

  2. Red emission generation through highly efficient energy transfer from Ce(3+) to Mn(2+) in CaO for warm white LEDs.

    Feng, Leyu; Hao, Zhendong; Zhang, Xia; Zhang, Liangliang; Pan, Guohui; Luo, Yongshi; Zhang, Ligong; Zhao, Haifeng; Zhang, Jiahua


    CaO:Ce(3+),Mn(2+) phosphors with various Mn(2+) concentrations were synthesized by a solid state reaction method. Efficient energy transfer from Ce(3+) to Mn(2+) was observed and it allows the emission color of CaO:Ce(3+),Mn(2+) to be continuously tuned from yellow (contributed by Ce(3+)) to red (by Mn(2+)) with an increase in Mn(2+) concentration and upon blue light excitation. The red emission becomes dominant when the Mn(2+) concentration is ≥0.014 with an energy transfer efficiency higher than 87% which can reach as high as 94% for a Mn(2+) concentration of only 0.02. A critical distance of 10.5 Å for the Ce(3+)-Mn(2+) energy transfer was determined. A faster decrease of Ce(3+) luminescence intensity in comparison with its lifetime was observed on increasing the Mn(2+) concentration. The analysis of this feature reveals that the Ce(3+) excitation energy can be completely transferred to Mn(2+) if the Ce(3+)-Mn(2+) distance is shorter than 7.6 Å. A warm white LED was fabricated through integrating an InGaN blue LED chip and a blend of two phosphors (YAG:Ce(3+) yellow phosphor and CaO:0.007Ce(3+),0.014Mn(2+) red phosphor) into a single package, which has CIE chromaticity coordinates of (x = 0.37, y = 0.35), a correlated color temperature of 3973 K and a color rendering index of 83.1. The results indicate that CaO:Ce(3+),Mn(2+) may serve as a potential red phosphor for blue LED based warm white LEDs.

  3. Solid state synthesis, luminescent properties and energy transfer from Eu2+ to Mn2+ in red phosphor BaMg2Si2O7:Eu2+,Mn2+

    Xiao, Weiqin; Lei, Fang; Yin, Luqiao; Shi, Ying; Xie, Jianjun; Zhang, Lei


    A series of red phosphors Ba1-yMg2-xSi2O7: xMn2+,yEu2+ have been synthesized by solid-state reaction at 1200 °C for 4 h under H2 atmosphere. The crystal structure and photoluminescence properties have been measured and analyzed. Under excitation of 342 nm, Eu2+ doped Ba1-yMg2Si2O7 (y = 0.05-0.06) shows violet emission at 400 nm, which is due to the 4f-5d transition of Eu2+, while Mn2+ doped BaMg2-xSi2O7 (x = 0.02-0.40) shows weak reddish emission with a broad band centered at around 640 nm, which is caused by the 4T1(4G) -6A1(6S) transitions of Mn2+. When Eu2+ and Mn2+ were co-doped, excellent red emission is shown under the n-UV excitation. Eu2+ and Mn2+ co-doped BaMg2Si2O7 phosphor shows two intense emission bands with the peak at 400 nm and 660 nm, respectively. The broad emission band for Eu2+ overlaps with the excitation peaks of Mn2+ in the range of 400-450 nm, which shows that the emission of Mn2+ is dominantly ascribed to the persistent energy transfer from Eu2+. By changing the ratio of Eu2+/Mn2+, the emission color can be tuned from violet to red. When the doping content is fixed at 0.16 for Mn2+ and 0.32 for Eu2+, the CIE of the phosphor is (0.495,0.315). Eu2+ and Mn2+ co-doped BaMg2Si2O7 phosphors may have potential application for near-UV light-emitting diodes.

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

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


    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...

  5. A global evaluation of temperature and carbonate ion control on Mg/Ca ratios of ostracoda genus Krithe.

    Elmore, A.C.; Sosdian, S; Rosenthal, Y.; Wright, J. D.


    [1] Improving estimates of past ocean temperatures is paramount to our understanding of ocean circulation and its role in climate change. Magnesium/calcium (Mg/Ca) ratios of carapaces of the benthic ostracod genus Krithe were determined from new, globally distributed core top samples from the Norwegian Sea, Cape Hatteras shelf, Gulf of Mexico, Sulawesi Margin (Indonesia), New Zealand shelf, Ceara Rise, and the North Atlantic. A linear regression of the Krithe Mg/Ca ratios and bottom water tem...

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

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


    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...

  7. Rotational band structure in Mg>32mn>

    Crawford, H. L.; Fallon, P.; Macchiavelli, A. O.; Poves, A.; Bader, V. M.; Bazin, D.; Bowry, M.; Campbell, C. M.; Carpenter, M. P.; Clark, R. M.; Cromaz, M.; Gade, A.; Ideguchi, E.; Iwasaki, H.; Langer, C.; Lee, I. Y.; Loelius, C.; Lunderberg, E.; Morse, C.; Richard, A. L.; Rissanen, J.; Smalley, D.; Stroberg, S. R.; Weisshaar, D.; Whitmore, K.; Wiens, A.; Williams, S. J.; Wimmer, K.; Yamamato, T.


    There is significant evidence supporting the existence of deformed ground states within the neutron-rich N ≈ 20 neon, sodium, and magnesium isotopes that make up what is commonly called the “island of inversion.” However, the rotational band structures, which are a characteristic fingerprint of a rigid nonspherical shape, have yet to be observed. In this work, we report on a measurement and analysis of the yrast (lowest lying) rotational band in 32 Mg up to spin I = 6 + produced in a two-step projectile fragmentation reaction and observed using the state-of-the-art γ -ray tracking detector array, GRETINA ( γ -ray energy tracking in-beam nuclear array). Large-scale shell-model calculations using the SDPF-U-MIX effective interaction show excellent agreement with the new data. Moreover, a theoretical analysis of the spectrum of rotational states as a function of the pairing gap, together with cranked-shell-model calculations, provides intriguing evidence for a reduction in pairing correlations with increased angular momentum, also in line with the shell-model results.

  8. Synthesis, microstructure and EPR of CaMnO{sub 3} and Eu{sub x}Ca{sub 1-x}MnO{sub 3} manganite, obtained by coprecipitation

    Santiago T, M.; Hernandez C, L.; Legorreta G, F. [Universidad Autonoma del Estado de Hidalgo, AACTyM, Carretera Pachuca-Tulancingo Km 4.5, 42074 Pachuca, Hidalgo (Mexico); Montiel S, H. [UNAM, Centro de Ciencias Aplicadas y Desarrollo Tecnologico, Departamento de Tecnociencias, Ciudad Universitaria, 04510 Mexico D. F. (Mexico); Alvarez L, G. [IPN, Escuela Superior de Fisica y Matematicas, Departamento de Fisica, U. P. Adolfo Lopez Mateos, Edif. 9, Col. Lindavista, 07738 Mexico D. F. (Mexico); Flores G, M. A., E-mail: [Universidad Politecnica de Pachuca, Laboratorio de Nanotecnologia y Bioelectromagnetismo Aplicado, Carretera Pachuca-Cd. Sahagun Km 20, Ex-Hacienda de Santa Barbara, 43830 Zempoala, Hidalgo (Mexico)


    The synthesis of CaMnO{sub 3} and Eu{sub x}Ca{sub 1-x}MnO{sub 3} obtained by coprecipitation method is showed. The synthesized samples were characterized by X-ray diffraction and scanning electronic microscopy, the powders showed orthorhombic structure and pnma space group. When it was doped with Europium, their morphology tendency was spherical. Measurements were carried out on electron paramagnetic resonance (EPR) with constant frequency = 9.4 GHz (band X) and dc magnetic field (H dc) 0-0.8 T, measurements were at 300 K and 77 K. EPR spectra showed significant differences between both samples, indicating that the substitution of divalent alkaline earth cations by trivalent rare earth ions, allowing the formation of a mixed valence state of manganese, Mn{sup 3+} and Mn{sup 4+}. A 77 K, the manganite of concentration x = 0.30 had a magnetic ordering, noted by the presence of hysteresis. (Author)

  9. Thickness dependence of microstructure in LaCaMnO thin films

    Gross, G.M.; Razavi, F.S.; Praus, R.B.; Habermeier, H.-U. E-mail:


    Introducing biaxial strain in doped lanthanum manganite thin films is an excellent tool to modify the electrical and transport properties systematically by controlled changes of the microstructure on an atomic scale. We deposited La{sub 2/3}Ca{sub 1/3}MnO{sub 3} thin films onto SrTiO{sub 3} single-crystal substrates under reproducible conditions in an optimized pulsed laser deposition process. A thickness range of 40 to 500 nm was chosen for the manganite layers to investigate the variation of the average lattice parameters with thickness using X-ray diffraction. We re-investigated the samples after annealing to determine the structural aspects of the relaxation behavior of the layers. A second set of samples was prepared with an analogous in situ annealing process. AFM was applied to examine the morphology and grain size of the layers. Due to a thermally induced strain relaxation process the thicker films show a gradual approach of the out-of-plane lattice constant to the bulk ceramic value. Further relaxation could be achieved with an annealing at 900 deg. C for 1 h. Lattice parameter changes with varying thickness and annealing processes are correlated with transport and magnetic properties.

  10. Remanent resistance changes in metal- PrCaMnO-metal sandwich structures

    Scherff, Malte; Meyer, Bjoern-Uwe; Scholz, Julius; Hoffmann, Joerg; Jooss, Christian [Institute of Materials Physics, University of Goettingen (Germany)


    The non-volatile electric pulse induced resistance change (EPIR) seems to be a rather common feature of oxides sandwiched by electrodes. However, microscopic mechanisms are discussed controversially. We present electrical transport measurements of sputtered Pr{sub 0.7}Ca{sub 0.3}MnO{sub 3} films sandwiched by metallic electrodes with variation of electrode materials, device geometry and PCMO deposition parameters. Cross-plane transport measurements have been performed as function of temperature and magnetic field. Specifically, the transition from dynamic resistance changes due to non-linear transport to remanent switching is analyzed. By analyzing changes of magneto-resistance at low temperatures in different resistance states we aim for separation between interface and film contributions to switching. Comparing switching behavior in symmetric and asymmetric electrode configuration allows for identification of the active, single interface in the switching process and the origin of an observed switching polarity inversion. The influence of excitation field and power on the switching characteristics of different noble metal electrodes is discussed. Samples from macroscopic devices and in situ stimulated sandwich structures were studied in a transmission electron microscope in order to investigate the induced structural, chemical and electronic changes.

  11. n型CaMnO3热电氧化物的制备、表征及电性能%Preparation and electrical properties of n-Type CaMnO3 thermoelectric oxide

    张冰心; 路清梅; 张忻; 张飞鹏; 张久兴


    以金属硝酸盐为起始原料,采用溶胶一凝胶法制备了CaMnO3粉末,分别采用真空放电等离子烧结(SPS)和在常压烧结的方法制备了CaMnO3块体,并对其物相、微观形貌和电性能进行了分析和测试.结果 表明,制得粉末为单一物相的CaMnO3粉末;空气气氛烧结样品与真空放电等离子烧结样品相比,具有较致密结构和较好的电性能.其中500 MPa成型,烧结温度为1200℃的样品在温度700℃时功率因子高达2.056 X 10-3W·m-1·K-2.

  12. 稀土-铜共掺对CaMnO3热电性能的影响%Effects of RE-Cu Co-doping on Thermoelectric Properties of CaMnO3

    刘杨琼; 盛得雪; 贺毅; 龚鹏; 金玉山; 苏敏


    采用固相反应法制备CaMnO3热电材料,研究Ca位分别掺Pr和Ce,Mn位掺Cu对CaMnO3材料热电性能的影响.结果表明:Pr-Cu共掺和Ce-Cu共掺都没有改变材料的晶体结构,随着掺Cu量的增加,CaMnO3热电材料的Seebeck系数的绝对值、电阻率和热导率都呈现先降低后增加的变化趋势;掺Cu能够适当提高样品的功率因子和ZT值;当掺Pr量摩尔比为0.01,掺Cu量摩尔比为0.05,测试温度为973 K时ZT值达到0.088;当掺Ce量摩尔比为0.05,掺Cu量摩尔比为0.02,测试温度为973 K时ZT值达到0.08.

  13. Preparation and thermoelectric properties of CaMnO3 with Sm3+ ion doped%Sm3+掺杂CaMnO3的制备与热电性能

    贾坤; 魏长平; 许洁; 吕志军



  14. Computational Model on Surface Tension of CaO-MnO-SiO2 Slag System%CaO-MnO-SiO2渣系的表面张力计算模型

    吴铖川; 成国光


    基于熔渣结构离子与分子共存理论和Butler方程,建立了CaO-MnO-SiO2熔渣表面张力计算模型.模型利用纯组元的表面张力和摩尔体积以及熔渣中各组元表面相和体相中作用浓度(活度)可以计算出CaO-MnO-SiO2熔渣表面张力随熔渣成分、温度的变化规律.表面张力的计算结果与文献介绍的值吻合很好.计算了1773 K下CaO-MnO-SiO2渣系的等表面张力线,并进一步考察了炉渣成分对表面张力的影响.

  15. Structural and thermal characterization of CaO-MgO-SiO2-P2O5-CaF2 glasses

    Kansal, Ishu; Goel, Ashutosh; Tulyaganov, Dilshat U.; Rajagopal, Raghu R.; Ferreira, Jose M.


    The paper presents the influence of varying CaO/MgO ratio on the structure and thermal properties of CaO-MgO-SiO2-P2O5-CaF2 glasses. A series of eight glass compositions in the glass forming region of diopside (CaMgSi2O6) - fluorapatite [Ca5(PO4)3F] - wollastonite (CaSiO3) ternary system have been designed and synthesized by varying diopside/wollastonite ratio in glasses. The as prepared melt-quenched glasses have been characterized for their structure by infrared spectroscopy (FTIR) and magic angle spinning (MAS)-nuclear magnetic resonance (NMR) spectroscopy. Silicon is predominantly present as Q2 (Si) species, while phosphorus tends to coordinate in orthophosphate environment in all the investigated glasses. The change in CaO/MgO ratio had an insignificant affect on the structure of glasses. The thermal sintering and crystallization parameters for the studied glasses have been obtained from differential thermal analysis (DTA) while crystalline phase fractions in the sintered glass-ceramics have been analyzed by X-ray diffraction adjoined with Rietveld refinement. Diopside, fluorapatite, wollastonite and pseudowollastonite have crystallized as the main crystalline phases in all the glass-ceramics with their content varying with respect to variation in CaO/MgO ratio in glasses. Scanning electron microscopy (SEM) has been used to shed light on the microstructure of glass-ceramics. The possible implications of structure and sintering behaviour of glasses on their bioactivity have been discussed.

  16. In-plain electric properties of [CaMnO3/REMO3] (RE=Bi, La M=Fe, Fe0.8Mn0.2) superlattices grown by pulsed laser deposition method

    Iwata, N.; Watabe, Y.; Oikawa, T.; Takase, K.; Huijben, M.; Inaba, T.; Oshima, K.; Rijnders, A.J.H.M.; Yamamoto, H.


    The [CaMnO3 (CMO)/REMO3] (RE = Bi, La M = Fe, Fe0.8Mn0.2) superlattices show semiconducting behavior with transition temperatures (TEg) of 71, 127, and 151 K in the [CMO/BiFe0.8Mn0.2O3], [CMO/BiFeO3], and [CMO/LaFeO3] superlattices. The formation of a magnetic polaron is expected in the CMO layer of

  17. Spin-polarized investigation of ferromagnetism on magnetic semiconductors Mn{sub x}Ca{sub 1−x}S in the rock-salt phase

    Choutri, H.; Ghebouli, M.A. [LMSE Laboratory, University of Bachir Ibrahimi, 34265 Bordj-Bou-Arréridj (Algeria); Ghebouli, B. [Laboratory of Surface and Interface Studies of Solid Materials, Department of Physics, Faculty of Science, Setif University 1, Setif 19000 (Algeria); Bouarissa, N., E-mail: [Department of Physics, Faculty of Science, University of M' sila, 28000 M' sila (Algeria); Uçgun, E.; Ocak, H.Y. [Department of Physics, Faculty of Arts and Sciences, Dumlupinar University, Kutahya (Turkey)


    The structural, elastic, electronic and magnetic properties of the diluted magnetic semiconductors Mn{sub x}Ca{sub 1−x}S in the rock-salt phase have been investigated using first-principles calculations with both LDA and LDA + U functional. Features such as lattice constant, bulk modulus, elastic constants, spin-polarized band structure, total and local densities of states have been computed. We predict the values of the exchange constants and the band edge spin splitting of the valence and conduction bands. The hybridization between S-3p and Mn-3d produces small local magnetic moment on the nonmagnetic Ca and S sites. The ferromagnetism is induced due to the exchange splitting of S-3p and Mn-3d hybridized bands. The total magnetic moment per Mn of Mn{sub x}Ca{sub 1−x}S is 4.4μ{sub B} and 4.5μ{sub B} for LDA and LDA + U functional and is independent of the Mn concentration. The unfilled Mn-3d levels reduce the local magnetic moment of Mn from its free space charge value of 5μ{sub B}–4.4μ{sub B} and4.5μ{sub B} for LDA and LDA + U functional due to 3p–3d hybridization. - Highlights: • Fundamental properties of magnetic semiconductors Mn{sub x}Ca{sub 1−x}S. • Rock-salt phase of Mn{sub x}Ca{sub 1−x}S. • Magnetic properties of the diluted magnetic semiconductors Mn{sub x}Ca{sub 1−x}S. • The use of LDA + U functionals.

  18. Differential response of corals to regional mass-warming events as evident from skeletal Sr/Ca and Mg/Ca ratios

    Clarke, Harry; D'Olivo, Juan Pablo; Falter, James; Zinke, Jens; Lowe, Ryan; McCulloch, Malcolm


    During the summer of 2010/2011, a regional marine heat wave resulted in coral bleaching of variable severity along much of the western coastline of Australia. At Ningaloo Reef, a 300 km long fringing reef system and World Heritage site, highly contrasting coral bleaching was observed between two morphologically distinct nearshore reef communities located on either side of the Ningaloo Peninsula: Tantabiddi (˜20% bleaching) and Bundegi (˜90% bleaching). For this study, we collected coral cores (Porites sp.) from Tantabiddi and Bundegi reef sites to assess the response of the Sr/Ca temperature proxy and Mg/Ca ratios to the variable levels of thermal stress imposed at these two sites during the 2010/2011 warming event. We found that there was an anomalous increase in Sr/Ca and decrease in Mg/Ca ratios in the Bundegi record that was coincident with the timing of severe coral bleaching at the site, while no significant changes were observed in the Tantabiddi record. We show that the change in the relationship of Sr/Ca and Mg/Ca ratios with temperature at Bundegi during the 2010/2011 event reflects changes in related coral "vital" processes during periods of environmental stress. These changes were found to be consistent with a reduction in active transport of Ca2+ to the site of calcification leading to a reduction in calcification rates and reduced Rayleigh fractionation of incorporated trace elements.

  19. Li3Mg2NbO6:Mn4+ red phosphor for light-emitting diode: Synthesis and luminescence properties

    Cao, Renping; Shi, Zhihui; Quan, Guanjun; Luo, Zhiyang; Tang, Pengjie; Ao, Hui; Yu, Xiaoguang


    Novel double perovskite Li3Mg2NbO6:Mn4+ deep red-emitting phosphor is synthesized by solid-state reaction method in air. Emission band peaking at ∼670 nm with chromaticity coordinates (0.722, 0.278) is observed in the range of 600-780 nm due to 2E → 4A2 transition of Mn4+ ion. Excitation spectrum monitored at 670 nm contains three excitation bands peaking at ∼310, 395, and 470 nm within the range 220-600 nm, which indicate that Li3Mg2NbO6:Mn4+ phosphor can be excited by ultraviolet, near ultraviolet, and blue light-emitting diode chips. The optimal Mn4+ doping concentration is about 0.4 mol%. Fluorescence lifetime decreases from 0.485 to 0.32 ms with increasing Mn4+ ion concentration from 0.2 to 1.2 mol%. Time resolved emission spectra and lifetime data confirm that there is only a single type of Mn4+ ion luminescent center in Li3Mg2NbO6:Mn4+ phosphor. The possible luminous mechanism of Mn4+ ion is analyzed by Tanabe-Sugano energy diagram.

  20. Effect of Mn-site vacancies on the magnetic entropy change and the Curie temperature of La0.67Ca0.33Mn1-xO3 perovskite

    Chen, Wei; Nie, L.Y.; Xu, Zhao;


    Single-phase polycrystalline samples of La0.67Ca0.33Mn1-xO3 (x = 0.00, 0.02, 0.04, 0.06) have been prepared using the sol-gel method. The structure, magnetocaloric properties and the Curie temperature of the samples with different Mn vacancy concentrations have been investigated. The experimental...

  1. Temperature dependent changes of the Mn 3d and 4p bands near $T_{c}$ in Colossal Magnetoresistance systems : a XANES study of $La_{1-x}Ca_{x}MnO_{3}$

    Bridges, F; Booth, C. H.; Kwei, G. H.; Neumeier, J. J.; Sawatzky, G. A.


    Abstract: We report high-resolution X-ray Absorption Near Edge Structure (XANES)measurements at the Mn K-edge as a function of temperature, forLa$_{1-x}$Ca$_x$MnO$_3$ samples, with a focus mainly on the pre-edge region.Small peaks labeled A$_1$-A$_3$ are observed which corresponds to

  2. Oxygen nonstoichiometry and defect equilibrium in Ca1- x Pr x MnO3-δ manganites

    Leonidov, I. A.; Konstantinova, E. I.; Markov, A. A.; Merkulov, O. V.; Patrakeev, M. V.; Kozhevnikov, V. L.


    The content of oxygen in Ca1- x Pr x MnO3-δ ( x = 0.1) material with perovskite-like structure is determined at 750-950°C and oxygen partial pressures in the gas phase from 3 × 10-6 to 0.55 atm. The regions of existence of orthorhombic, tetragonal, and cubic structural modifications are determined. The equilibrium constants, enthalpies, and entropies of reactions of the formation of defects are determined, allowing us to describe the experimental δ ({p_{{O_2}}}, T) dependences accurately and calculate the concentrations of manganese ions. It is shown that a change in Ca0.9Pr0.1MnO3-δ structure has a considerable effect on the thermodynamic functions of reactions of the formation of defects.

  3. Preparation and properties of luminous materials of CaSiO3:Pb, Mn by sol-gel method

    YANG Liangzhun; FANG Min; Liu Yuejiao; LIU Chao; WANG Xiuying; YU Xibin


    The luminous materials of CaSiO3: Pb, Mn were synthesized by sol-gel method and ultrasound technology.The properties of the phosphors were characterized by luminescence spectrum, differential thermal analysis and thermal gravimetry analysis (DTA-TG), X-ray diffraction(XRD), Fourier transform infrared spectrometer (FT-IR)and transmission electron microscopy (TEM). The effects of factors such as the synthetic material compositions,ultrasound time and annealed temperature on phosphorescent brightness of sample were studied and the optimum synthetic conditions were determined. The results show that, compared with the sample made by the high temperature solid-state reaction, the luminescent intensity of the CaSiO3:Pb, Mn sample increased by about 200% and the mean diameter of particles of the sample decreased by about 300 nm.

  4. Evolution of Intermetallics, Dispersoids, and Elevated Temperature Properties at Various Fe Contents in Al-Mn-Mg 3004 Alloys

    Liu, K.; Chen, X.-G.


    Nowadays, great interests are rising on aluminum alloys for the applications at elevated temperature, driven by the automotive and aerospace industries requiring high strength, light weight, and low-cost engineering materials. As one of the most promising candidates, Al-Mn-Mg 3004 alloys have been found to possess considerably high mechanical properties and creep resistance at elevated temperature resulted from the precipitation of a large number of thermally stable dispersoids during heat treatment. In present work, the effect of Fe contents on the evolution of microstructure as well as high-temperature properties of 3004 alloys has been investigated. Results show that the dominant intermetallic changes from α-Al(MnFe)Si at 0.1 wt pct Fe to Al6(MnFe) at both 0.3 and 0.6 wt pct Fe. In the Fe range of 0.1-0.6 wt pct studied, a significant improvement on mechanical properties at elevated temperature has been observed due to the precipitation of dispersoids, and the best combination of yield strength and creep resistance at 573 K (300 °C) is obtained in the 0.3 wt pct Fe alloy with the finest size and highest volume fraction of dispersoids. The superior properties obtained at 573 K (300 °C) make 3004 alloys more promising for high-temperature applications. The relationship between the Fe content and the dispersoid precipitation as well as the materials properties has been discussed.

  5. Multi-specimen and multi-site calibration of Aleutian coralline algal Mg/Ca to sea surface temperature

    Williams, B.; Halfar, J.; DeLong, K. L.; Hetzinger, S.; Steneck, R. S.; Jacob, D. E.


    Higher latitude oceanic and climatic reconstructions are needed to distinguish natural climate variability from anthropogenic warming in regions projected to experience significant increases in temperature during this century. Clathromorphum nereostratum is a long-lived coralline alga abundant along the Aleutian archipelago that records seasonal to centennial fluctuations in seawater temperatures in its high-Mg calcite skeleton. Thus, C. nereostratum is an important proxy archive to reconstruct past seawater temperature variability in this data-poor subarctic region. Here, we measured magnesium to calcium ratios (Mg/Ca) by laser ablation-inductively coupled plasma-mass spectrometry (LA-ICP-MS) along the growth axis in six live-collected specimens from three islands in the Aleutian archipelago to assess Mg/Ca reproducibility and to calibrate algal Mg/Ca against modern gridded sea surface temperature (SST) data products. The master Mg/Ca-SST transfer function, determined by averaging the algal Mg/Ca-SST from each island (n = 6), resulted in a reconstruction error of ±0.45 °C, a 31-46% reduction in error compared to the reconstruction error for a single alga. The master algal-SST record interpolated to monthly and annual resolution significantly varied with gridded SST data products (r2 = 0.98, p coralline algal Mg/Ca-derived SST reconstructions record absolute changes in past SST variability in the Aleutian archipelago. The transfer functions developed here can be applied to Mg/Ca records generated from long-lived specimens of C. nereostratum to reconstruct northern North Pacific and Bering Sea SST variability for the past several hundred years.

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

    T. Rzychoń


    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.

  7. Conformational changes in the (Ca2+ + Mg2+)-ATPase of sarcoplasmic reticulum detected using phosphorescence polarization.

    Restall, C J; Coke, M; Murray, E K; Chapman, D


    The technique of time-averaged phosphorescence has been used to study the interaction of calcium ions and ATP with the (Ca2+ + Mg2+)-ATPase in sarcoplasmic reticulum vesicles. The presence of excess calcium ions was found to cause a 20% decrease in the phosphorescence emission anisotropy. This is interpreted as being due to a conformational change in the protein and is supported by data from time-resolved phosphorescence measurements which also show a lowering of the anisotropy. This change in the decay of the emission anisotropy is associated with only minor changes in the rotational relaxation time of the protein and is again suggestive of a conformational change in the protein. In some cases ATP was also observed to lower the time-averaged phosphorescence anisotropy possibly via an interaction with the low-affinity regulatory site of the protein.

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


    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.

  9. Effect of multiaxial forging on microstructure and mechanical properties of Mg-o.8Ca alloy

    Yurchenko, N. Yu; Stepanov, N. D.; Salishchev, G. A.; Rokhlin, L. L.; Dobatkin, S. V.


    It was shown that multiaxial forging with continuous decrease of temperature from 450°C to 250°C turns coarse structure of the Mg-0.8Ca alloy in homogenized state with grain size of several hundreeds gm into fine structure with average grain size of about 2.1 gm. Refinement of structure is accompanied by drastic increase of mechanical properties: tensile yield strength increases from 50 MPa to 193 MPa, ultimate tensile strength increases from 78 to 308 MPa and elongation to fracture increases from 3.0% to 7.2%. The microstructural evolution during multiaxial forging is studied using optical microscopy, scanning electron microscopy and EBSD analysis. The mechanisms responsible for refinement of microstructure are discussed

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

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


    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.

  11. Study of the electronic structure and half-metallicity of CaMnO3/BaTiO3 superlattice

    Wang, Kai; Jiang, Wei; Chen, Jun-Nan; Huang, Jian-Qi


    In this paper, the electronic structure, magnetic properties and half-metallicity of the CaMnO3/BaTiO3 superlattice are investigated by employing the first-principle calculation based on density functional theory within the GGA or GGA + U exchange-correlation functional. The CaMnO3/BaTiO3 superlattice is constructed by the cubic CaMnO3 and the tetragonal ferroelectric BaTiO3 growing alternately along (0 0 1) direction. The cubic CaMnO3 presents a robust half-metallicity and a metastable ferromagnetic phase. Its magnetic moment is an integral number of 3.000 μB per unit cell. However, the CaMnO3/BaTiO3 superlattice has a stable ferromagnetic phase, for which the magnetic moment is 12.000 μB per unit cell. It also retains the robust half-metallicity which mainly results from the strong hybridization between Mn and O atoms. The results show that the constructed CaMnO3/BaTiO3 superlattice exhibits superior magnetoelectric properties. It may provide a theoretical reference for the design and preparation of new multiferroic materials.

  12. Ascorbate protects against tert-butyl hydroperoxide inhibition of erythrocyte membrane Ca2+ + Mg2(+)-ATPase.

    Moore, R B; Bamberg, A D; Wilson, L C; Jenkins, L D; Mankad, V N


    The incubation of erythrocyte suspensions or isolated membranes containing a residual amount of hemoglobin (0.04% of original cellular hemoglobin) with tert-butyl hydroperoxide (tBHP, 0.5 mM) caused significant inhibition of basal and calmodulin-stimulated Ca2+ + Mg2(+)-ATPase activities and the formation of thiobarbituric acid reactive products measured as malondialdehyde. In contrast, the treatment of white ghosts (membranes not containing hemoglobin) with tBHP (0.5 mM) did not lead to appreciable enzyme inhibition within the first 20 min and did not result in malondialdehyde (MDA) formation. However, the addition of either 10 microM hemin or 100 microM ferrous chloride + 1 mM ADP to white ghosts produced hydroperoxide effects similar to those in pink ghosts (membranes with 0.04% hemoglobin). The concentrations of hemin and ferrous chloride which caused half-maximal inhibition of Ca2+ + Mg2(+)-ATPase activity at 10 min were 0.5 and 30 microM, respectively. The effects of several antioxidants (mannitol, thiourea, hydroxyurea, butylated hydroxytoluene, and ascorbate) were investigated for their protective effects against oxidative changes resulting from tBHP treatment. Over a 30-min incubation period only ascorbate significantly reduced the enzyme inhibition, MDA formation, and protein polymerization. Thiourea and hydroxyurea decreased MDA formation and protein polymerization but failed to protect against the enzyme inhibition. Butylated hydroxytoluene was similar to thiourea and hydroxyurea but with better protection at 10 min. Mannitol, under these conditions, was an ineffective antioxidant for all parameters tested.

  13. Influence of solid-solution treatment on microstructure, mechanical property and corrosion behavior of biodegradable Mg-Zn-Ca alloy

    Ly, Xuan Nam; Yang, S.; Qin, Y.


    The influence of solid-solution treatment on microstructure, mechanical property and corrosion behavior of Mg-Zn-Ca alloy was studied in the present investigation by SEM, tensile test, electrochemical and immersion test. The results show that the microstructure of Mg alloys after solid solution treatment significantly changed, a large number of the second phase (Ca2Mg6Zn3, Mg2Ca) dissolved into the α-Mg matrix reaching a supersaturated state, and the grains size was bigger than before solid solution treatment; the mechanical properties were obviously improved. In particular the tensile strength of 0.5wt.% Ca of Mg alloy reached 220MPa and the ductility reached 16.6%. Compared with the as-cast Mg alloys, the corrosion potential after solid-solution treatment slightly shifted negative, but the corrosion current density significantly decreased. After solid solution treatment, the surface corrosion was not serious and the result of weight gain was lower compared with those of the as-cast Mg alloys.

  14. Large Magnetic Entropy Effect in La2/3Ca1/3MnO3



    The magnetocaloric effect in the colossal magnetoresistance material La2/3Ca1/3MnO3 was studied.From the measurements of temperature dependence of magnetization in various magnetic fields,the large magnetic entropy change associated with the ferromagnetic-paramagnetic transition was discovered.This result suggests that perovskite manganites are suitable candidates as working substance in magnetic refrigeration technology.

  15. Materiales de Al2O3 - MgAl2O4 - CaAl12O19 - Ca2Mg2Al28O46 obtenidos mediante un proceso de sinterización reactiva entre Al2O3 y CaMg(CO32

    Pena, P.


    Full Text Available Taking into account the system Al2O3-MgO-CaO, refractory materials containing Al2O3-MgAl2O4-CaAl12O19-Ca2Mg2Al28O46 has been obtained by reaction-sintering of appropriate mixtures of Al2O3 and CaMg(CO32. The study of the mechanism of reaction was carried out by differential thermal analysis (DTA and thermogravimetry (TG, followed by dilatometric and xray diffraction (XRD studies. A static study of the reaction was performed at different temperatures. After each thermal treatment a XRD analysis of the phases present was made, as well as a microestructural study by scanning electron microscopy (SEM coupled with energy-dispersive spectroscopy (EDS. From the results obtained, and taking into account the free energy of formation of the different compounds, the mechanism of reaction was established.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(CO32. 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 difracción de rayos X y microscopía electrónica de barrido con microanálisis mediante dispersión de energías. Los resultados obtenidos revelan que la reacción entre las materias primas tiene lugar en varias etapas con formación de fases transitorias, dando lugar a una microestructura final con granos aciculares de CaAl12O19 y partículas de la fase ternaria Ca2Mg2Al28O46 formadas en aquellos puntos en los que entran en contacto las fases de MgAl2O4 y CaAl12O19.

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

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


    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.

  17. La-(Ca-Ba-Sr)-Mn-O锰氧化物高低温输运特性%Transport Property at Low and High Temperatures in La-(Ca-Ba-Sr)-Mn-O Manganite Perovskite

    陈志高; 陈水源; 黄志高; 赖恒; 都有为


    Polycrystalline samples La2/3Ca1/3MnO3 (LCMO), La2/3(Ca0.5Ba0.5)1/3MnO3 (LCBMO), La2/3Ba1/3MnO3 (LBMO),La2/3(Sr0.5Ba0.5)1/3MnO3 (LSBMO) and La2/3Sr1/3MnO3 (LSMO) have been prepared by a solid state reaction method. We have observed the temperature dependences of the electric resistivity and magnetoresistance from 77 K up to 800 K. Experimental results indicate that the presence of grain boundaries in the colossal magnetoresistance (CMR) materials prepared by the mechanical alloyed method leads to a large magnetoresistance effect at low temperature, and there exists a pronounced metal-semiconductor transition around Tc. According to the models of spin-polarized electron tunneling and percolation, the magnetoresistance as a function of temperature has been explained well. The temperature dependence of resistivity at high temperature is well fit by nonadiabatic small polaron hopping model for LCBMO and LSBMO samples, and their activation energies are obtained. Also it has been found that annealing processing affects the resistivity significantly.%用固相反应烧结法制备了多晶体材料La2/3Ca1/3MnO3(LCMO),La2/3(Ca0.5Ba0.5)1/3MnO3(LCBMO)、La2/3Ba1/3MnO3(LBMO),La2/3(Sr0.5Ba0.5)1/3MnO3(LSBMO)和La2/3Sr1/3MnO3(LSMO),测量了它们在77 K~800 K的电阻和磁电阻特性.实验发现,通过一定的工艺技术制备出的CMR材料有强烈的相界效应,在低温下有大的磁电阻,且在Tc附近存在明显的从金属态向半导体态的转变;用自旋极化电子隧道效应和靠近居里点逾渗模型较好地解释了电阻和磁电阻行为;用非绝热小极化子跃迁模型对高温的电阻特性进行拟合处理,得到了激活能;同时发现退火处理对样品的电阻率有重要的影响.

  18. Synthesis and structural characterization of the Ca2MnReO6 double perovskite Síntese e caracterização estrutural da dupla perovsquita Ca2MnReO6

    H. P. S Corrêa


    Full Text Available The Ca2Mn1Re1O6 double perovskite has been prepared in polycrystalline form by using the encapsulated quartz tube method. The partial oxygen pressure inside the quartz tube revealed this to be a crucial synthesis parameter for the production of a single structural phase sample. This parameter was controlled using the ratio between ReO2 and ReO3 content and the filling factor parameter (ratio between mass and total inner volume of the quartz tube. The morphology and chemical composition was investigated by scanning electron microscopy and energy dispersive X-ray spectroscopy. The crystal structure parameters were determined by analysis of the synchrotron high-resolution X-ray powder diffraction pattern. The analysis indicates that the sample is an ideal single-phase compound with a monoclinic crystal structure (space group P2(1/n with a = 5.44445(2 Å; b = 5.63957(3 Å; c = 7.77524(3 Å; and β = 90.18(1º. Computer simulations were performed considering two cation valence configurations, namely, (i Mn2+Re6+ or (ii Mn3+Re5+, for the Ca2Mn1Re1O6 compound. XANES analysis measurements indicated +2.3 for the average valence of Mn (a mixture of Mn2+ and Mn3+ and +5.7 for the effective valence of Re (an intermediate valence between Re4+ (ReO2 and Re6+ (ReO3. As a summary, we concluded there is a mixed valence configuration for Mn and Re in Ca2Mn1Re1O6 , taken into account the oxygen content of 6.0±0.1.A dupla perovsquita Ca2MnReO6 na forma policristalina foi preparada utilizando o método do tubo de quartzo encapsulado. A pressão parcial de oxigênio dentro do tubo de quartzo mostrou-se ser um parâmetro crucial para a produção de uma amostra estrutural monofásica. Esse parâmetro foi controlado usando a relação entre o conteúdo dos precursores ReO2 e ReO3 e o parâmetro fator de preenchimento (razão entre a massa e o volume interno total do tubo de quartzo.A morfologia e a composição química foi investigada através da microscopia eletr

  19. Correlation between coercive field and radiation attenuation in Ni and Mg ferrite doped with Mn and Co

    Silva, José Eves M., E-mail: [Chemistry Institute, UFRN, Cep. 59078-970, Natal, do Norte (Brazil); Nasar, Ricardo S., E-mail: [Chemistry Institute, UFRN, Cep. 59078-970, Natal, do Norte (Brazil); Nasar, Marinalva C., E-mail: [Chemistry Institute, UFRN, Cep. 59078-970, Natal, do Norte (Brazil); Firme, Caio L. [Chemistry Institute, UFRN, Cep. 59078-970, Natal, do Norte (Brazil); Araújo, José H., E-mail: [Department of Theoretical and Experimental Physics, UFRN, Cep. 59078-970, Natal, Grande do Norte (Brazil)


    It was investigated NiMg{sub 0.1}M{sub x}Fe{sub 2}O{sub 4} ferrite where M stands for Mn, Co or simultaneously Mn and Co dopants. The concentration of M is 0.1 and it was divided by two in the sample with addition of Mn and Co. It was used the method of citrate precursors with 1100 °C calcination. The materials were characterized by X-ray diffractometer (XRD), scanning electron microscopy (SEM), vibrating sample magnetometer (VSM) and reflectivity measures by waveguide method. The X-ray diffraction measures, with Rietveld refinement, present average crystallite sizes between 0.576 and 0.626 µm. The SEM analysis shows clustered particles smaller than 1 µm at 1100 °C, in agreement with Rietveld refinement. The compositions with Mn reach magnetization between 42.09 and 53.20 Am{sup 2}/kg, which does not generate high microwave absorption. The 0.1 Co addition reached greater coercivity (2.96×10{sup −2} T), with up to 84% reflectivity at 10.17 GHz frequency. The Co material has high magnetocrystalline anisotropy, which is associated with the increase of coercive field, H{sub c}. The higher coercivity optimizes the reflectivity results. - Highlights: • Manganese diffusion occurs in octahedral sites. • Analysis by SEM and by Rietved shows agreement. • The structure is the inverse spinel type. • Low loss leads to obtain low radiation absorption. • The Co addition gets high reflectivity and coincides with high coercivity.

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

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


    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.

  1. Polarity Switchable Photovoltages in Miscut La0.67Ca0.33MnO3 Films

    J. Wang


    Full Text Available We report the transient laser-induced anomalous photovoltaic effect in the La0.67Ca0.33MnO3 film grown on miscut LaSrAlO4 (001 substrate under 248 nm pulsed laser irradiation at ambient temperature without any applied bias. A photovoltaic pulse signal was observed when the La0.67Ca0.33MnO3 film was irradiated directly, and the signal polarity was reversed when the sample was irradiated through the LaSrAlO4 substrate, while the signal recorded between the two electrodes on the surface of LaSrAlO4 was not reversed when the sample was irradiated through La0.67Ca0.33MnO3 film rather than at the surface of LaSrAlO4. The switchable signal polarity provides a potential application of miscut manganite films as optical components. A possible mechanism is introduced to explain the experiment results.

  2. Dimensionality dependent magnetic and magnetocaloric response of La0.6Ca0.4MnO3 manganite.

    Anwar, M S; Ahmed, Faheem; Koo, Bon Heun


    We report the sol-gel synthesis and impact of reduced dimensionality on the magnetocaloric properties of La0.6Ca0.4MnO3 manganite. The synthesized powders were characterized by using X-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM) and magnetization measurements. The XRD results indicated that the La0.6Ca0.4MnO3 nanoparticles have single phase nature with orthorhombic structure. FE-SEM results suggested that the nanoparticles are agglomerated and crystallite size increases with the annealing temperature. Magnetization measurements show that the La0.6Ca0.4MnO3 nanoparticles exhibit transition temperature (T(c)) below room temperature. The transition temperature was found to increase with the increasing the crystallite size. Maximum in magnetic entropy change, (ΔS(M))(max) shows interesting behaviour and was found to vary with the particle size. At magnetic field of 1 T, the value of (ΔS(M))(max) - 0.13 J/kg K was observed at 213 K for the sample annealed at 600 degrees C. Also, the increment in the value of (ΔS(M))(max) was observed at higher annealing temperature. This study shows that the magnetic entropy of pervoskite manganite can be tuned by tuning the crystallite size of the manganites.

  3. Thermoelectric Properties of Ca1−xGdxMnO3−δ (0.00, 0.02, and 0.05 Systems

    Ankam Bhaskar


    Full Text Available Polycrystalline samples of Ca1−GdMnO3− (=0.00, 0.02, and 0.05 have been studied by X-ray diffraction (XRD, electrical resistivity (ρ, thermoelectric power (S, and thermal conductivity (κ. All the samples were single phase with an orthorhombic structure. The Seebeck coefficient of all the samples was negative, indicating that the predominant carriers are electrons over the entire temperature range. The iodometric titration measurements indicate that the electrical resistivity of Ca1−GdMnO3− correlated well with the average valence of Mn+ and oxygen deficiency. Among the doped samples, Ca0.98Gd0.02MnO3− had the highest dimensionless figure of merit 0.018 at 300 K, representing an improvement of about 125% with respect to the undoped GaMnO3− sample at the same temperature.

  4. Solvent-free oxidation of aldehydes to acids by TBHP using environmental-friendly MnO$^{−1}_{4}$-exchanged Mg-Al hydrotalcite catalyst

    Vasant R Choudhary; Deepa K Dumbre; Vijay S Narkhede


    A number of hydrotalcite (Mg-Al, Mn-Al, Co-Al, Ni-Al, Mg-Fe, Mg-Cr and Cu-Al) catalysts, with or without MnO$^{−1}_{4}$-exchange, were evaluated for their performance in the solvent-free oxidation of benzaldehyde to benzoic acid by tert-butyl hydroperoxide under reflux in the absence of any solvent. The MnO$^{−1}_{4}$-exchanged Mg-Al-hydrotalcite (Mg/Al = 10) showed high activity in the oxidation of different aromatic and aliphatic aldehydes to their corresponding acids and also showed excellent reusability in the oxidation process which is environmental-friendly.

  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

    刘一驰; 刘德宝; 赵越; 陈民芳


    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. Microstructure and mechanical properties of spray-deposited Al-Si-Fe-Cu-Mg alloy containing Mn


    Al-20Si-5Fe-3Cu-lMg alloy was synthesized by the spray atomization and deposition technique. The microstructure and mechanical properties of the spray deposited hypereutectic Al-Si alloy were studied using optical microscopy, scanning electron microscopy, X-ray diffraction, TEM (Transmission Electron Microscope) and HREM (High-resolution Electron Microscope), DSC (Differential Scanning Calorimetry), microhardness measurement, and tensile tests. The effects of Mn on the microstructural evolution of the highsilicon aluminum alloy after extrusion and heat treatment have been examined. The results show that two kinds of phases, i.e. S (Al2CuMg) and σ(Al5Cu6Mg2), precipitated from matrix and improved the tensile strength of the alloy efficiently at both the ambient and elevated temperatures (300℃). The tensile test results indicate that the spray-deposited Al-20Si-SFe-3Cu-1Mg alloy has better strength than the powder metallurgy processed Al-20Si-3Cu-1Mg alloy at elevated temperature.

  7. Synthesis and TL characteristics of MgB{sub 4}O{sub 7}:Mn,Tb phosphor

    Sahare, P.D., E-mail: [Department of Physics & Astrophysics University of Delhi, Delhi 110007 (India); Singh, Manveer [Department of Physics & Astrophysics University of Delhi, Delhi 110007 (India); Kumar, Pratik [Medical Physics Unit, IRCH, AIIMS, New Delhi 110 029 (India)


    In the present paper optimized dosimetric characteristics of low-Z magnesium tetra-borate MgB{sub 4}O{sub 7}:Mn,Tb using a thermoluminescence (TL) technique have been reported. The phosphor material was synthesized using a conventional high temperature solid-state diffusion reaction. The crystalline structure and phase purity of synthesized powder were confirmed by powder X-ray diffraction (XRD) analysis. The material in the microcrystalline form was found to be in orthorhombic form. The comparative dosimetric properties of the phosphor material have been extensively investigated for its applications in personal and medical dosimetry. It has been found that the codoped MgB{sub 4}O{sub 7}:Mn,Tb material, exposed to γ rays, shows better TL sensitivity and has an edge over the Mn and Tb doped samples as it is much more sensitive than the formers (550 and 40 times, respectively, more than the later ones). It has a simple glow curve structure (two well separated TL peaks centered at around 475 and 650 K). They are sufficiently above the room temperature (RT) to show low fading (~10% in a month after storing in dark at RT). However, the fading is much faster, if exposed to sunlight/room light/UV radiation. This has been a serious problem with many borate based phosphors. A detailed study on bleaching to UV–visible light of different wavelengths (energies) has been carried out and a new mechanism based on redox reactions is proposed. Low fading (~10% in a month) at room temperature on storing in dark, high TL sensitivity (3.5 times than that of TLD-100), tissue equivalence (Z{sub eff}≈8.23) and linear dose response up to wide range (0.1 Gy to ~5.0 kGy) of γ rays make it a suitable candidate for the radiation dosimetry and monitoring. However, it needs to be protected from sunlight/room light for fast fading. - Highlights: • Synthesized MgB{sub 4}O{sub 7}:Tb,Mn by a very simple solid state reaction. • Optimized annealing temperature and dopant concentration for

  8. Research on Properties of Low Fluorine CaF2-CaO-Al2O3-MgO-SiO2 Refining Slag%低氟CaF2-CaO-Al2O3-MgO-SiO2系精炼渣的性能

    史冠勇; 张廷安; 牛丽萍; 豆志河


    设计了精炼铜-铬合金用低氟CaF2-CaO-Al2O3-MgO-SiO2五元渣系,并研究了其粘度、密度、表面张力及熔化温度等性能.结果表明,该渣系的熔化温度在1336~1402℃之间;高温F该渣系的密度和表面张力均随温度升高而减小,且随CaF2含量和MgO含量增加逐渐降低;增加CaF2添加量可降低渣系粘度;CaF2含量较低时,MgO含量增加也可降低渣系粘度,CaF2含量较高时,渣粘度在MgO含量为6%时最小,MgO含量续增加到9%时粘度反而上升.该渣系粘度较低,表面张力较小,具有良好的精炼效果.%Low fluorine CaF2-CaO-Al2O3-MgO-SiO2 slag system was used as refining slag for preparation of Cu-Cr alloy. Its viscosity, density, surface tension and melting temperature were studied. The results indicated that the melting temperature of the slag was between 1336-1402'C. The density and surface tension of CaF2-CaO-Al2O3-MgO-SiO2 slag decreased with increasing of temperature, adding of CaF2 and MgO could decrease its density and surface tension. Its viscosity decreased with increasing of MgO and CaF2 content, and achieved the minimum value when MgO content was 6%, and increased when MgO content up to 9% with 10% and 15% CaF2 content. The slag had lower surface tension and better fluidity, so the refining efficiency with it was very good.

  9. Collisional broadening of Mg, Sr, Ca and Na resonance lines by atomic hydrogen

    Kerkeni, B.; Barklem, P. S.; Spielfiedel, A.; Feautrier, N.


    This paper compares different approaches used in the calculation of the broadening of spectral lines by H-atom collisions. Firstly, the validity of the semi-classical approach for the collision versus the quantum one is discussed. It is shown that, at the temperatures typical of stellar atmospheres (from 3000 to 10 000 K), a classical approach (with the advantage of reduced computation times) is sufficient. The dependence of the broadening constants on interatomic potentials is also studied. Two different approaches were used to derive these potentials: in the first approach, the interaction energy is determined by the usual methods of quantum chemistry. The second approach, developed by Anstee, Barklem and O'Mara (ABO potentials), is based on second-order perturbation theory. In the case of Mg H, a hybrid potential obtained from ab initio values for the short distances and from the perturbation method in the asymptotic region was also tested. The results for the Na resonance line show that even significant differences in the potentials lead to relatively small changes in the calculated widths. From the comparison of the results for the Mg, Sr and Ca resonance lines, it appears that ABO potentials give results of the order of 8 20% smaller than results from ab initio and hybrid potentials. This difference is attributed to the presence of an avoided ionic crossing in the upper singlet Sgr states that coincides roughly with the Weisskopf radius.

  10. Discharge capacity and microstructures of La Mg Pr Al Mn Co Ni alloys for nickel-metal hydride batteries

    Casini, J.C.S.; Galdino, G.S.; Ferreira, E.A.; Takiishi, H.; Faria, R.N., E-mail: jcasini@ipen.b [Instituto de Pesquisas Energeticas e Nucleares (DM/IPEN/CNEN-SP), Sao Paulo, SP (Brazil). Dept. de Metalurgia


    La{sub 0.7-x}Mg{sub x}Pr{sub 0.3}Al{sub 0.3}Mn{sub 0.4}Co{sub 0.5}Ni{sub 3.8} (x = 0.0, 0.3 and 0.7) alloys have been investigated aiming the production of negative electrodes for nickel-metal hydride batteries. The alloys employed in this work were used in the as cast state. The results showed that the substitution of magnesium by lanthanum increased the discharge capacity of the Ni-MH batteries. A battery produced with the La{sub 0.4}Mg{sub 0.3}Pr{sub 0.3}Al{sub 0.3}Mn{sub 0.4}Co{sub 0.5}Ni{sub 3.8} alloy shown a high discharge capacity (380mAh/g) also good stability compared to other alloys. The electrode materials were characterized using scanning electron microscopy (SEM) and X-ray diffraction (XRD). (author)

  11. Evaluation of pitting corrosion of Al-Mg-Mn-Sc-Zr alloy in EXCO solution by EIS

    PENG Yong-yi; YIN Zhi-min; LI San-hua


    In order to evaluate the degree and severity of Al-Mg-Mn-Sc-Zr alloy in exfoliation corrosion(EXCO) solution quickly and nondestructively, electrochemical impedance spectroscopy(EIS) technique was employed. The Al-Mg-Mn-Sc-Zr alloy suffers pitting corrosion in the EXCO solution. During pit incubation, the Nyquist diagram is composed of a depressed capacitive arc at high-mediate frequency and an inductive arc at low frequency. The inductive arc fades with immersion time, and the beginning of pitting corrosion and the appearance of two capacitive arcs have simultaneity. During pit propagation, the Nyquist diagram is composed of two overlapped capacitive arcs. As time goes on, two time constants are more clearly distinguished. The high frequency and low frequency capacitive arc are aroused by passive surface and new interface, respectively. An equivalent circuit is designed to fit EIS, and the experimental results and the fitted results have good correspondence. The degree and severity of pitting corrosion can be obtained by the features of EIS and comparing the fitted values of parameters at different times.

  12. Sr/Ca and Mg/Ca in Glycymeris glycymeris (Bivalvia) shells from the Iberian upwelling system: Ontogeny and environmental control

    Freitas, Pedro; Richardson, Christopher; Chenery, Simon; Monteiro, Carlos; Butler, Paul; Reynolds, David; Scourse, James; Gaspar, Miguel


    Bivalve shells have a great potential as high-resolution geochemical proxy archives of marine environmental conditions. In addition, sclerochronology of long-lived bivalve species (e.g. Arctica islandica) provides a timeline of absolutely dated shell material for geochemical analysis that can extend into the past beyond the lifetime of single individuals through the use of replicated crossmatched centennial to millennial chronologies. However, the interpretation of such records remains extremely challenging and complex, with multiple environmental and biological processes affecting element incorporation in the shell (e.g. crystal fabrics, organic matrix, biomineralization mechanisms and physiological processes). As a result, the effective use of bivalve shell elemental/Ca ratios as palaeoenvironmental proxies has been limited, often to species-specific applications or applications restricted to particular environmental settings. The dog-cockle, Glycymeris glycymeris, is a relatively long-lived bivalve (up to 200 years) that occurs in coarse-grained subtidal sediments of coastal shelf seas of Europe and North West Africa. Glycymeris glycymeris shells provide a valuable, albeit not fully explored, archive to reconstruct past environmental variability in an area lacking sclerochronological studies due to the rarity of long-lived bivalves and lack of coral reefs. In this study, we evaluate the potential of Sr/Ca and Mg/Ca ratios in G. glycymeris shells as geochemical proxies of upwelling conditions in the Iberian Upwelling System, the northern section of the Canary Current Eastern Boundary Upwelling System. Sr/Ca and Mg/Ca generally co-varied significantly and a clear ontogenetic, non-environmental related change in Sr/Ca and Ba/Ca variability was observed. High Sr/Ca and Mg/Ca ratios in older shells (> 10 years old) were found to be associated with the occurrence of growth lines deposited during the winter reduction in shell growth. Nevertheless, Sr/Ca and Mg/Ca

  13. Effect of Centrifugal Speed on Microstructure and Properties of Mg-6Al-1Ca-1Nd Alloy%离心转速对Mg-6Al-1Ca-1Nd合金组织和性能的影响

    冯义成; 田靖刚; 曹国剑; 王丽萍; 姜文勇; 郭二军


    The Mg-6Al-lCa-lNd alloy samples were fabricated by centrifugal casting method and by gravity casting, respectively. The microstructure and mechanical properties of Mg-6Al-lCa-lNd alloy fabricated were characterized by OM (optical microscope), SEM (scanning electron microscope), XRD(X-ray diffraction) and hardness testing. The results show that the grain size of Mg-6Al-lCa-lNd alloy exhibiting equaixed grain fabricated by centrifugal casting is finer than that fabricated by gravity casting. With increasing in centrifugal speed, the grain size is decreased. The XRD analysis shows that there exists Mg!7 Ali2,Al2Nd and AlzCa phases anda-Mg in the Mg-6Al-lCa-lNd alloy fabricated by centrifugal casting. However, absence of Al2Ca phase can be observed, and the content of Mg17Alu and AlzNd is decreased in the Mg-6Al-lCa-lNd alloy fabricated by gravity casting. With increasing in centrifugal speed, the hardness value of the alloy fabricated by centrifugal casting is increased, and with the centrifugal speed of 1 541 r/min, the hardness value reaches HV58. 5.%以MMg-6Al-1Ca-1Nd合金为研究对象,通过重力铸造和离心铸造制备出Mg-6Al-1Ca-1Nd合金试样,运用光学金相分析(OM),扫描电子显微分析(SEM)、X射线衍射分析(XRD)、硬度测试等多种分析和测试手段,系统研究了重力铸造和离心转速对Mg-6Al-1Ca-1Nd合金组织及力学性能的影响.结果表明,与重力铸造试样相比,离心铸造Mg-6Al-1Ca-1Nd镁合金的晶粒得到了显著的细化,并且离心铸造试样为等轴晶.随着离心转速增加,合金的晶粒尺寸减小.XRD分析表明,离心铸造镁合金试样的中间相为Mg27 Al12、Al2Nd和Al2Ca;而重力铸造试样中没有发现Al2 Ca相的衍射峰,Mg17Al12和Al2Nd的衍射峰比较弱.硬度随离心转速增加而持续增加,离心速度为1541 r/min时,硬度(HV)达到最大,为58.5.

  14. Electrical properties and conduction mechanisms in La{sub 2/3}Ca{sub 1/3}MnO{sub 3} thin films prepared by pulsed laser deposition on different substrates

    Navasery, M.; Halim, S.A.; Soltani, N.; Bahmanrokh, G.; Erfani H, M.; Kamalianfar, A.; Pan, K.Y.; Chang, S.C.; Chen, S.K.; Lim, K.P.; Awang Kechik, M.M. [University Putra Malaysia, Department of Physics, Faculty of Science, Serdang, Selangor (Malaysia); Dehzangi, A. [University Kebangsaan Malaysia, Institute of Microengineering and Nanoelectronics (IMEN), Bangi, Selangor (Malaysia)


    Perovskite manganite La{sub 2/3}Ca{sub 1/3}MnO{sub 3} thin films were directly grown on MgO(100), Si(100) and glass substrates by pulsed laser deposition. From the XRD patterns, the films are found to be polycrystalline, single-phase orthorhombic. The metal-insulator transition temperature is 209 K for LCMO/MgO, 266 K for LCMO/Si and 231 K for film deposited on the glass substrate. The conduction mechanism in these films is investigated in different temperature regimes. Low-temperature resistivity data below the phase transition temperature (T{sub P}) have been fitted with the relation ρ = ρ{sub 0} + ρ{sub 2}T{sup 2} + ρ{sub 4.5}T{sup 4.5}, indicating that the electron-electron scattering affects the conduction of these materials. The high-temperature resistivity data (T > T{sub P}) were explained using variable-range hopping (VRH) and small-polaron hopping (SPH) models. Debye temperature values are 548 K for LCMO/Cg, 568 K for LCMO/Si and 508 K for LCMO/MgO thin films. In all thin films, the best fitting in the range of VRH is found for 3D dimension. The density of states near the Fermi level N (E{sub F}) for LCMO/MgO is lower due to the prominent role of the grain boundary in LCMO/MgO and increase in bending of Mn-O-Mn bond angle, which decreases the double exchange coupling of Mn{sup 3+}-O{sup 2}-Mn{sup 4+} and in turn makes the LCMO/MgO sample less conducting as compared to the other films. (orig.)

  15. The influence of doping with Ca and Mg in YBa2Cu3O7-δ ceramic

    Vecchione A.


    Full Text Available We have investigated the effect of partial substitution of Ca for Y and/or Mg for Cu on structural, compositional and magnetic properties in γBa2Cu3O7-δ polycrystalline compounds. All prepared samples were found to be single phase with small fraction of Ba-secondary phases. Substitution by more than 2% of magnesium causes an increase of spurious phases. Energy Dispersive Spectroscopy (EDS revealed that the distribution of Ca in the sample is quite homogenous. DC susceptibility measurements show that superconducting transition temperature Tc is reduced much more by Ca than Mg. Hysteresis loops reveal that magnetic irreversibility is decreased by Ca and Mg content. The deduced critical current density Jc does not follow the same variation. Ca alone reduces Jc for x=0.1 and x=0.2. Together with Ca, Mg compensates the reduction of Jc and increasing its content near the solubility limit gives higher Jc than in the undoped sample.

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

    Peltekov A.B.


    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.

  17. Effect of ferroelectric polarization switching on the electronic transport properties of La0.8Ca0.2MnO3 film

    Xie, Qiyun; Zhai, Zhangyin; Wu, Xiaoshan; Gao, Ju


    La0.8Ca0.2MnO3 thin film grown on 0.67Pb(Mg1/3Nb2/3)O3-0.33PbTiO3 (PMN-PT) substrate has shown very interesting transport properties, which is modulated by the ferroelectric polarization switching in the substrate. The ferroelectric poling reduces the in-plane strain by about 0.135% with the applied piezovoltage of 500 V to PMN-PT substrate. The resistance is lowered and the metal-insulator transition temperature (Tp) is increased due to the reduced in-plane strain. Moreover, it is shown that the ferroelectric field effect competes strongly with the strain effect especially when the temperature is lowered below Tp in our film.

  18. Anti-site mixing governs the electrochemical performances of olivine-type MgMnSiO4 cathodes for rechargeable magnesium batteries.

    Mori, Takuya; Masese, Titus; Orikasa, Yuki; Huang, Zhen-Dong; Okado, Tetsuya; Kim, Jungeun; Uchimoto, Yoshiharu


    Rechargeable magnesium batteries are deemed as the next-generation secondary battery systems because of their high theoretical capacity and the terrestrial abundance of magnesium, which is used as the anode in these batteries. The cathode material is an important factor to improve the energy density of the magnesium batteries. In this study, we investigate olivine-type MgMnSiO4 cathode materials owing to their high theoretical capacity (>300 mA h g(-1)). The low-temperature synthesis of MgMnSiO4 suppresses anti-site mixing between Mg and Mn, which drastically improves the charge-discharge capacities of the magnesium battery cathode. Our results show that the suppression of the degree of anti-site mixing between Mg and Mn enhances the diffusion of Mg(2+) during magnesium (de)insertion, and therefore, it is a dominant factor that affects the electrochemical performance of olivine-type MgMnSiO4.

  19. Mg2+ ions reduce microglial and THP-1 cell neurotoxicity by inhibiting Ca2+ entry through purinergic channels.

    Lee, Moonhee; Jantaratnotai, Nattinee; McGeer, Edith; McLarnon, James G; McGeer, Patrick L


    Mg(2+) is a known antagonist of some Ca(2+) ion channels. It may therefore be able to counteract the toxic consequences of excessive Ca(2+) entry into immune-type cells. Here we examined the effects of Mg(2+) on inflammation induced by Ca(2+) influx into microglia and THP-1 cells following activation of purinergic receptors. Using tissue culture, an inflammatory response was induced by treatment with either the P2X7 purinergic receptor agonist 2',3'-[benzoyl-4-benzoyl]-ATP (BzATP) or the P2Y2,4 receptor agonist uridine 5'-triphosphate (UTP). Both microglia and THP-1 cells expressed the mRNAs for these receptors. Treatment produced a rapid rise in intracellular Ca(2+) which was significantly reduced by Mg(2+) or the calcium chelator BAPTA-AM. Purinergic receptor stimulation activated the intracellular inflammatory pathway P38 MAP kinase and NFκB. This caused release of TNFα, IL-6, nitrite ions and other materials that are neurotoxic to SH-SY5Y cells. These effects were all ameliorated by Mg(2+). They were also partly ameliorated by the P2X7R antagonists, oxATP and KN-62, the P2YR antagonist MRS2179, and the store operated Ca(2+) channel blocker, SK96365. These results indicate that elevated Mg(2+) is a broad spectrum inhibitor of Ca(2+) entry into microglia or THP-1 cells. Mg(2+) administration may be a strategy for reducing the damaging consequences Ca(2+) induced neuroinflammation in degenerative neurological disorders such as Alzheimer disease and Parkinson disease.

  20. Structure and Properties of Mg-Cu-(Y,Ca Bulk Metallic Glasses / Struktura I Własności Masywnych Szkieł Metalicznych Mg-Cu-(Y,Ca

    Babilas R.


    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.

  1. Effects of minor scandium and zirconium on microstructure and mechanical properties of Al-Mg-Mn alloys%微量Sc和Zr对Al-Mg-Mn合金组织与力学性能的影响

    陈琴; 潘清林; 王迎; 彭虹; 张志野; 尹志民


    Both AI-5.8Mg-0.4Mn and Al-5.8Mg-0.4Mn-0.25Sc-0.1Zr (mass fraction, %) alloy ingots were prepared using water chilling copper mould ingot metallurgy processing protected by active flux. The alloy ingots were finally rolled into 2 mm-thick sheets after hot rolling-intermediate annealing-cold rolling. The effects of stabilizing annealing and minor Sc, Zr on the microstructure and mechanical properties of Al-Mg-Mn alloys were studied. The results show that after adding minor Sc and Zr into Al-Mg-Mn alloy simultaneously a large number of Al3(Sc, Zr) particles dispersedly distribute in the matrix, which have function of strongly pinning sub-grain boundaries and dislocations. The anti-recrystallization ability and the mechanical properties of the Al-Mg-Mn-Sc-Zr alloy sheet are significantly improved. By annealing at 300 'C for 1 h, the Al-Mg-Mn-Sc-Zr alloy sheet can obtain the optimum application values of 0b,00.2 and S, which are 436 MPa, 327 MPa and 16.7%, respectively.%采用活性熔剂保护熔炼、水冷铜模激冷铸造制备Al-5.8Mg-0.4Mn和Al-5.8Mg-0.4Mn-0.25sc-0.1Zr(质量分数,%)两种合金铸锭.合金铸锭经热轧-中间退火-冷轧成2 mm薄板;研究稳定化退火及微量Sc和Zr对Al-Mg-Mn合金组织与性能的影响.结果表明:在Al-Mg-Mn合金中加入微量Sc和Zr后形成大量弥散的Al3(Sc,Zr)粒子,这些粒子对位错和亚晶界具有强烈的钉扎作用,能明显提高合金的抗再结晶能力和室温力学性能;Al-Mg-Mn-Sc-Zr合金板材经300℃退火1h后可获得最佳综合力学性能,其σb、σ0.2与δ分别为436 MPa、327 MPa 和16.7%.


    皮小力; 曹辉


    the sample of CaCuxMn3-x Mn4O12 (x=0.2,0.4,0.6,0.8,1.0,1.2,1.4) synthesized using wet-chemistry technique , and then sinter in higher temperature, further enrich the research of series materials. The Rietveld refinements of powder X-ray diffraction patterns show that all the samples are single phase, with cubic symmetry,the space group Im(3) and there is no change in structural symmetry at all the copper ion composition range from x=0.2 to x=1.4. The lattice parameters and volume of unit cell decrease with increasing doping level x. Although the radius of Cu2+ is larger than that of Mn3+ , Mn3+ turns into Mn4+ partially and the radii of Mn4+ smaller than that of Mn3+ , but the latter reason plays the main role , thus cause the volume of unit cell to increase. The bond angle of Mn2-O-Mn2 changes rulelessly with increasing x, which indicates the presence of Jahr-Teller effect in MnO6 octahedron. The reason of these results is the mismatch between Jahn-Teller ions Mn3+/Cu2+. The unusual features of the manganese oxides indicate that the lattice deformation directly influences the bond length and angle of MnO6 octahedron. Structural analysis is of great importance to further study the transport and magnetic properties of these manganese oxides. In addition, we studied the CMR effect of these sample and find that the MR increases with increasing x and reach the maximum at x= 1.0, then presents decreasing trend in the field of 5T. But at low-magnetic-field the resistivity changes indistinctly, these because of the spin-polarized scatter of carriers between grains and double-exchange effect.%湿化学反应法制备了CaCuxMn3-xMn4 O12(x=0.2,0.4,0.6,0.8,1.0,1.2,1.4)系列材料的前驱体,然后通过高温烧结做成样品,进一步丰富了这类样品的研究内容.X射线衍射表明掺杂Cu2+在x=0.2到x=1.4范围内这些材料都能够成单相.通过Rietveld全谱拟合的方法分析,结果表明随掺杂浓度的增大,晶体的结构对称性没有发生变

  3. Pulse electron paramagnetic resonance studies of the interaction of methanol with the S2 state of the Mn4O5Ca cluster of photosystem II.

    Oyala, Paul H; Stich, Troy A; Stull, Jamie A; Yu, Fangting; Pecoraro, Vincent L; Britt, R David


    The binding of the substrate analogue methanol to the catalytic Mn4CaO5 cluster of the water-oxidizing enzyme photosystem II is known to alter the electronic structure properties of the oxygen-evolving complex without retarding O2-evolution under steady-state illumination conditions. We report the binding mode of (13)C-labeled methanol determined using 9.4 GHz (X-band) hyperfine sublevel-correlation (HYSCORE) and 34 GHz (Q-band) electron spin-echo electron nuclear double resonance (ESE-ENDOR) spectroscopies. These results are compared to analogous experiments on a mixed-valence Mn(III)Mn(IV) complex (2-OH-3,5-Cl2-salpn)2Mn(III)Mn(IV) (salpn = N,N'-bis(3,5-dichlorosalicylidene)-1,3-diamino-2-hydroxypropane) in which methanol ligates to the Mn(III) ion ( Larson et al. (1992) J. Am. Chem. Soc. , 114 , 6263 ). In the mixed-valence Mn(III,IV) complex, the hyperfine coupling to the (13)C of the bound methanol (Aiso = 0.65 MHz, T = 1.25 MHz) is appreciably larger than that observed for (13)C methanol associated with the Mn4CaO5 cluster poised in the S2 state, where only a weak dipolar hyperfine interaction (Aiso = 0.05 MHz, T = 0.27 MHz) is observed. An evaluation of the (13)C hyperfine interaction using the X-ray structure coordinates of the Mn4CaO5 cluster indicates that methanol does not bind as a terminal ligand to any of the manganese ions in the oxygen-evolving complex. We favor methanol binding in place of a water ligand to the Ca(2+) in the Mn4CaO5 cluster or in place of one of the waters that form hydrogen bonds with the oxygen bridges of the cluster.

  4. Temperature variation of the size effect in dilute AlMg and AlCa alloys: Measurement and theory

    Gilder, H. M.; Asty, M.; Audit, Ph.


    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.

  5. Structural investigation of glasses along the MgSiO3-CaSiO3 join: Diffraction studies

    Cormier, L.; Cuello, G. J.


    The structure of glasses along the MgSiO3-CaSiO3 join has been investigated by X-ray and neutron diffraction measurements. Structure models were constructed by fitting the experimental data using the Reverse Monte Carlo method (RMC). The structural data indicate a random mixing between MgSiO3 and CaSiO3 glasses, in accordance with their melt properties. Though important disordering is observed, the structure evolves continuously along the join. The Ca environment is essentially similar for all compositions, with an average of 6 to 7-coordinated sites. The Mg environment tends to have higher coordinated sites as the MgO content decreases. There is a continuous mixing of Ca-Mg pairs with a non-random distribution emphasized by the distinct cation-cation distances. Changes were observed in the topology of the silicate network. The proportion of non-bridging oxygens decreases, the number of free-oxygens increases and the ring size distribution is shifted to high-membered rings in the Mg-rich glasses. These structural investigations indicate important differences with the crystalline pyroxene structures.

  6. Growth and investigation of the Slater-Pauling behavior by X-ray characterization of single crystal bcc FexMn1-x on MgO(001)

    Bhatkar, Harshawardhan Ramesh

    Magnetic memory storage industry is always searching for materials that can store, read, and write data ever so faster, with lower power, with accuracy and on denser packaging. The material research was spurred with discovery and successful implementation of Giant Magnetoresistance phenomena into critical components of devices. GMR devices essentially were multilayered thin films of a set of magnetically ordered metals. Fe-Mn thin films were used to create one of its moment pinning layers. Fcc Fe-Mn thin films were studied enthusiastically for their AFM properties but very little was known about the rare bcc structured single crystals. Bcc Fe-Mn was found to be ferromagnetic in parts of phase diagram of Fe-Mn. The magnetic moment of alloys usually follows a regular linear trend based upon electronic configuration of constituent elements, known as Slater-Pauling curve. While most alloys follow the trend, bcc Fe-Mn binary alloys show a dramatic collapse in the bulk magnetic moment, as concentration of Mn is varied. In this work, we successfully fabricate bcc single crystal thin film of Fe-Mn on MgO(001) substrate by Molecular Beam Epitaxy method. We confirm using Reflection High Energy Electron Diffraction that, the bcc phase of Fe-Mn thin film is achieved, albeit being a forced structure, stable up to 35% of Mn concentration. X-ray absorption spectra of individual elements were used to confirm the compositions of Fe-Mn films and x-ray magnetic circular dichroism was used to track the elemental magnetic moment as the composition was varied. We found that the magnetic moment of Fe drops faster than expected and Mn has very small identical moment in all compositions. We also successfully created a compositionally graded Fe-Mn sample in MBE and spatially mapped its Fe moment by around the critical composition. The mechanism for collapse of magnetic moment over a spread of composition of Mn is a very complex problem yet we provide our experimental findings of

  7. SYNTHESIS OF Ca_(1+x)Mn_xO_(1+3x)(x=1, 2, 3) COMPOUNDS WITH THE RUDDLESDEN-POPPER STRUCTURES AND EXTRACTION OF THEIR INTERLAYER Ca~(2+) IONS%具有Ruddlesden-Popper结构的Ca_(1+x)Mn_xO_(1+3x)(x=1,2,3)的合成及层间Ca~(2+)的抽出

    林双妹; 黄侦勇; 孙妍; 王晓蓉; 汤睿昆; 马淑兰; 杨晓晶


    采用溶胶凝胶法合成前驱体,然后在氧气气氛下加热合成了具有层状钙钛矿Ruddlesden-Popper结构的化合物Ca_(1+x)Mn_xO_(1+3x)(x=1,2,3),尝试采用酸溶液对其层间Ca~(2+)离子进行抽出.实验发现HCl处理单层Ca_2MnO_4,层状结构遭到破坏;而用(NH_4)_2S_2O_8与HCl的混合溶液处理则能维持其层状结构,且Ca~(2+)离子抽出率大于60%,其抽出机制为氧化还原和离子交换.用HCl能够抽出双层Ca_3Mn_2O_7的层间Ca~(2+),并保持较好的结构.%Ca_(1+x)Mn_xO_(1+3x)(x=1, 2, 3) compounds with a layered perovskite Ruddlesden-Popper structures were synthesized. First a precursor was prepared by a sol-gel process, this was followed by heating in an oxygen atmosphere. Extraction of Ca~(2+) ions in the interlayer was carried out by acid treatment. Mono-layered Ca_2MnO_4 after going through a HC1 solution had the layered structure demolished; whereas going through a mixed solution of (NH_4)_2S_2O_8 and HCl had the Ca~(2+) ions extracted at a rate larger than 60% whilst retaining the layered structure, through redox reaction and ion-exchange. HCl solution can extract interlayer Ca~(2+) ions from bilayered Ca_3Mn_2O_7 without disrupting the layered structure.

  8. Variation of Ca, Sr, Ba and Mg in the otolith of mudskipper in west coast of Peninsular Malaysia.

    Sarimin, A S; Ghaffar, M A; Mohamed, C A R


    A study on elemental composition in the otolith of giant mudskipper, Periophthalmodon schlosseri, was done from June to October 2003. Specimens were obtained from the mangrove areas of Kuala Selangor, Sepang and Melaka in the west coast of Peninsular Malaysia. A total of 70 sagitta otoliths were analyzed to detect variation of Sr, Ba and Mg, replacing the natural chemical composition of the otolith, which is the calcium carbonate (CaCO3). The average ratio of Sr:Ca was 0.11 x 10(-4), Ba:Ca was 5.7 x 10(-3) and Mg:Ca was 0.2 x 10(-3). Strong correlation (R > 0.8) between fish body size and otolith weight ofmudskipper (p < 0.01) also found during this study.

  9. Synthesis and electrochemical study of Mg{sub 1.5}MnO{sub 3}: A defect spinel cathode for rechargeable magnesium battery

    Saha, Partha [Department of Bioengineering, Swanson School of Engineering, University of Pittsburgh, PA 15261 (United States); US Department of Energy, National Energy Technology Laboratory, Morgantown, WV 26507 (United States); Jampani, Prashanth H., E-mail: [Department of Bioengineering, Swanson School of Engineering, University of Pittsburgh, PA 15261 (United States); Hong, DaeHo [Department of Bioengineering, Swanson School of Engineering, University of Pittsburgh, PA 15261 (United States); Gattu, Bharat [Mechanical Engineering and Materials Science, Swanson School of Engineering, University of Pittsburgh, PA 15261 (United States); Poston, James A.; Manivannan, Ayyakkannu [US Department of Energy, National Energy Technology Laboratory, Morgantown, WV 26507 (United States); Datta, Moni Kanchan [Department of Bioengineering, Swanson School of Engineering, University of Pittsburgh, PA 15261 (United States); US Department of Energy, National Energy Technology Laboratory, Morgantown, WV 26507 (United States); Kumta, Prashant N., E-mail: [Department of Bioengineering, Swanson School of Engineering, University of Pittsburgh, PA 15261 (United States); US Department of Energy, National Energy Technology Laboratory, Morgantown, WV 26507 (United States); Mechanical Engineering and Materials Science, Swanson School of Engineering, University of Pittsburgh, PA 15261 (United States); Chemical and Petroleum Engineering, Swanson School of Engineering, University of Pittsburgh, PA 15261 (United States); School of Dental Medicine, University of Pittsburgh, PA 15261 (United States); Center for Complex Engineered Multifunctional Materials, University of Pittsburgh, Pittsburgh, PA 15261 (United States)


    Graphical abstract: Mg{sub 1.5}MnO{sub 3}, a defect oxide spinel derived by the Pechini route, was tested as cathode for rechargeable magnesium battery. TEM and XRD analyses of Mg{sub 1.5}MnO{sub 3} shows the formation of ∼100 nm sized nano particles in the cubic defect spinel structure (space group: Fd3m; unit cell: 0.833294 nm). Cyclic voltammetry illustrates a reversible reaction occurring between 0.3 and 1.5 V versus magnesium. Galvanostatic cycling of the Mg{sub 1.5}MnO{sub 3} cathode exhibits a low capacity of ∼12.4 mAh/g up to 20 cycle with ∼99.9% Coulombic efficiency when cycled at a current rate of ∼C/27. XPS (X-ray photoelectron spectroscopy) surface probe of magnesiated/de-magnesiated electrodes confirm a change in the redox center of Mn-ions during intercalation/de-intercalation of Mg-ion from the Mg{sub 1.5}MnO{sub 3} electrode. The low capacity of Mg{sub 1.5}MnO{sub 3} electrode mainly stem from the kinetic limitation of Mg-ion removal from the defect oxide spinel as the electrochemical impedance spectroscopy results of electrodes after 1st and 2nd cycle show that charge transfer resistance, R{sub e}, increases post charge state whereas interfacial resistance, R{sub i}, increases after discharge state, respectively. - Highlights: • Pechini process yields 100 nm sized particles of the defect cubic spinel Mg{sub 1.5}MnO{sub 3}. • Stable capacity of ∼12.4 mAh/g obtained at C/27 rate and 99.9% Coulombic efficiency. • XPS shows change in valence state of Mn{sup 3+}/Mn{sup 4+} center with cycling. • Low capacity stems from increase in charge-transfer and interfacial resistances with cycling. - Abstract: Mg{sub 1.5}MnO{sub 3}, a defect oxide spinel (space group: Fd3m; unit cell: 0.833294 nm) of particle size ∼100 nm derived by the Pechini route was tested as a cathode for rechargeable magnesium battery. Cyclic voltammetry illustrates a reversible reaction occurring in the 0.3–2.0 V potential window versus magnesium. The spinel however

  10. Hydrogen adsorption on Be, Mg, Ca and Sr doped graphenes: The role of the dopant in the IIA main group

    Luo, Huijuan; Li, Hejun; Fu, Qiangang


    Hydrogen (H2) adsorption on the IIA elements doped double-vacancy graphenes (BeG, MgG, CaG and SrG) was studied by using dispersion-corrected density functional theory calculations. Through investigation of different numbers of hydrogen dockings from two directions, it is found that 1H2/BeG, 1H2/MgG, 8H2/CaG and 8H2/SrG are the most stable adsorption configurations for Be, Mg, Ca and Sr doped graphenes, respectively. Atomic radius, electronegativity and ionization potential of the IIA dopant contribute to the dominating adsorption mechanism under specific H2 concentration. The study would facilitate exploration of high performance graphene-related supports for hydrogen storage.

  11. Electronic and Elastic Properties of CaMg2 Alloy Phase under Various Pressures by Density Functional Theory

    Fu Jia


    Full Text Available The influencing effect of pressure on structural, elastic and electronic properties of CaMg2 Laves phase is mainly investigated. The optimized structural parameters at zero pressure are a = b = 6.250Å, c = 10.101Å, which has good agreement with the experimental and theoretical values. The elastic constants are calculated, and then the bulk modulus, shear modulus, Young’s modulus, Poisson’s ratio and anisotropy factor are determined. The results show that the applied pressure is beneficial to the elastic properties of CaMg2. The analysis of electronic density of states (DOS and Mulliken electron population reveal the bonding characteristics in CaMg2 crystal. Finally, the Debye temperatures under different pressures are obtained from the average sound velocity.

  12. Microstructural analysis and mechanical properties of biodegradable Mg-1.3Ca-5.5Zr alloy

    Istrate, B.; Munteanu, C.; Matei, MN; Oprisan, B.; Moisei, M.; Earar, K.


    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”.

  13. Magnetic and magnetocaloric properties of La0.7Ca0.3Mn1-xZnxO3

    Ho, T. A.; Lim, S. H.; Tho, P. T.; Phan, T. L.; Yu, S. C.


    The magnetic Mn3+ ions in La0.7Ca0.3MnO3 are partially replaced by nonmagnetic Zn2+ ions to form La0.7Ca0.3Mn1-xZnxO3 compounds (x=0.0, 0.06, 0.08, and 0.1), and their magnetic and magnetocaloric properties are investigated. The Curie temperature decreases drastically from 245 to 70 K as x increases from 0 to 0.1. An analysis using the Banerjee's criterion of the experimental results for magnetization as a function of temperature and magnetic field indicates that the first-to-second order magnetic phase transformation occurs at a threshold composition of x=0.06, which is further supported by the universal curves of the normalized entropy change versus reduced temperature. The maximum magnetic entropy change measured at a magnetic field span of 50 kOe, which occurs near the Curie temperature, decreases from 10.30 to 2.15 J/kg K with the increase of x from 0.0 to 0.1. However, the relative cooling power, an important parameter for practical applications, shows a maximum value of 404 J/kg at x=0.08, which is 1.5 times greater than that observed for the undoped sample.

  14. Site-sensitive energy transfer modes in Ca3Al2O6: Ce(3+)/Tb(3+)/Mn(2+) phosphors.

    Zhang, Jilin; He, Yani; Qiu, Zhongxian; Zhang, Weilu; Zhou, Wenli; Yu, Liping; Lian, Shixun


    Ce(3+)/Eu(2+), Tb(3+) and Mn(2+) co-doping in single-phase hosts is a common strategy to achieve white-light phosphors via energy transfer, which provides a high color rendering index (CRI) value and good color stability. However, not all hosts are suitable for white-light phosphors due to inefficient energy transfer. In this study, the site-sensitive energy transfer from different crystallographic sites of Ce(3+) to Tb(3+)/Mn(2+) in Ca3Al2O6 has been investigated in detail. The energy transfer from purplish-blue Ce(3+) to Tb(3+) is an electric dipole-dipole mode, and the calculated critical distance (Rc) suggests the existence of purplish-blue Ce(3+)-Tb(3+) clusters. No energy transfer is observed from purplish-blue Ce(3+) to Mn(2+). In co-doped phosphors based on greenish-blue Ce(3+), however, the radiative mode dominates the energy transfer from Ce(3+) to Tb(3+), and an electric dipole-quadrupole interaction is responsible for the energy transfer from Ce(3+) to Mn(2+). A detailed discussion on the site-sensitive energy transfer modes might provide a new aspect to discuss and understand the possibilities and mechanisms of energy transfer, according to certain crystallographic sites in a complex host with different cation sites, as well as provide a possible approach in searching for single-phase white-light-emitting phosphors.

  15. Stimulatory effects of the degradation products from Mg-Ca-Sr alloy on the osteogenesis through regulating ERK signaling pathway

    Li, Mei; He, Peng; Wu, Yuanhao; Zhang, Yu; Xia, Hong; Zheng, Yufeng; Han, Yong


    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.

  16. High-temperature segmented thermoelectric oxide module using p-type Ca3Co4O9 and n-type ZnAlO/CaMn0.95Nb0.05O3 legs

    Le, Thanh Hung; Van Nong, Ngo; Jeffrey Snyder, G.;

    temperatures up to 1200 K, where most the conventional TE materials based on alloys are often degraded over the time. In this report, oxide TE materials of p­type Ca3Co4O9, n­types ZnAlO, and CaMn0.95Nb0.05O3 were used to fabricate high temperature TE segmented modules. These oxide materials were prepared....... In these calculations, the power generation characteristics were investigated in terms of various n-­leg selections (ZnAlO, CaMn0.95Nb0.05O3, and segmented ZnAlO/CaMn0.95Nb0.05O3), while the p-leg Ca3Co4O9 was fixed. Based on the model predication, several modules were fabricated, tested, and compared again...

  17. A Novel MgO-CaO-SiO2 System for Fabricating Bone Scaffolds with Improved Overall Performance

    Hang Sun


    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.

  18. A Novel MgO-CaO-SiO2 System for Fabricating Bone Scaffolds with Improved Overall Performance

    Sun, Hang; He, Shiwei; Wu, Ping; Gao, Chengde; Feng, Pei; Xiao, Tao; Deng, Youwen; Shuai, Cijun


    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. PMID:28773411

  19. Influence of Mg2+ on Initial Stages of CaCO3 Scale Formed on Metal Surface

    CHEN Tao; Anne Neville; YUAN Ming-dong


    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.

  20. Structural and magnetic properties of CaMg2Fe16O27

    P S Sawadh; D K Kulkarni


    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.

  1. Mg, Al, Si, Ca, Ti, Fe, and Ni abundance for a sample of solar analogues

    López-Valdivia, Ricardo; Bertone, Emanuele; Chávez, Miguel


    We report on the determination of chemical abundances of 38 solar analogues, including 11 objects previously identified as super metal-rich stars. We have measured the equivalent widths for 34 lines of 7 different chemical elements (Mg, Al, Si, Ca, Ti, Fe, and Ni) in high-resolution (R ˜ 80 000) spectroscopic images, obtained at the Observatorio Astrofísico Guillermo Haro (Sonora, Mexico), with the Cananea High-resolution Spectrograph. We derived chemical abundances using ATLAS12 model atmospheres and the Fortran code MOOG. We confirmed the super metallicity status of 6 solar analogues. Within our sample, BD+60 600 is the most metal-rich star ([Fe/H]=+0.35 dex), while for HD 166991 we obtained the lowest iron abundance ([Fe/H]=-0.53 dex). We also computed the so-called [Ref] index for 25 of our solar analogues, and we found, that BD+60 600 ([Ref]=+0.42) and BD+28 3198 ([Ref]=+0.34) are good targets for exoplanet search.

  2. Influence of Flux on Structure and Luminescence of LaMgB5O10:Ce3+,Mn2+



    The influences of the flux KCl or KF on the XRD patterns,cell parameters,crystal morphology,and spectral properties of the phosphor 12.8% KCl and 5.3%,10.5% KF are added individually into the phosphor (La0.85Ce0.15)(Mg0.9Mn0.1) B5O10,some peaks of the XRD patterns are intensified and cell volumes are decreased. A small amount of Cu mono-crystal typed phase appears as more than 5% KCl is added. There are six hexagonal crystal-faces and eight triangular crystal-faces attributed to the {100} and {111} respectively. When 15% KCl is added into the phosphor,multi-faced regular crystals are formed and the crystal self-regulation appears. The emission intensity of 5d→4f(2F5/2,2F7/2) of Ce3+ and 4G→6S of Mn2+ increases up 3.41 and 2.36 times respectively.

  3. NMR and IR studies of hydroxyl groups in CaNa and MgNa forms of zeolites A

    Pruski, M.; Ernst, H.; Pfeifer, H.; Staudte, B.


    By measurement of MAS proton magnetic resonance and near-infrared spectra, the existence of bridging hydroxyl groups in MgNaA and CaNaA zeolites is excluded. The MAS proton magnetic resonance lines observed at 2.5-3 ppm for CaNaA and at 3.5 ppm for MgNaA (apart from the small contributions of "terminal" OH groups) and the corresponding bands at 4576 and 4525 cm -1 in the near-infrared spectra are attributed to hydroxyl groups attached to the exchangeable cations.

  4. Effects of rare earths doping on electrical transport properties of CaMnO3 oxide%稀土掺杂对CaMnO3氧化物电传输性能的影响

    张飞鹏; 曾宏; 路清梅; 张忻; 张久兴


    采用柠檬酸溶胶凝胶结合陶瓷烧结工艺制备了Ca位掺杂稀土的Ca0.95RE0.05 MnO3(RE=Pr,Eu,Tb)氧化物块体试样,并通过X射线衍射、扫描电子显微镜及电输运参数测试仪分析了所得试样.结果表明:所有试样呈单一物相,掺杂氧化物晶胞减小,块体试样结构致密;未掺杂的CaMnO3呈半导体传输特性,其电阻率较高,在373K时达340 mΩ·cm;Ca位掺杂稀土元素Pr,Eu,Tb之后,其电阻率大幅度降低,但各温度点电阻率随Pr,Eu,Tb略有升高;测试温度范围内所有掺杂试样载流子激活能降低,输运特性未发生改变;其中Pr掺杂试样Ca0.95 Pr0.05MnO3各温度点的电阻率最低,在373K时为最低8 mΩ·cm,远低于未掺杂氧化物.

  5. Localization and cation dependence of a Ca2+- or Mg2+-ATPase from electrocytes of Electrophorus electricus, L.

    Taffarel, M; Coelho-Sampaio, T; Teixeira-Ferreira, A; Somló, C; De Souza, W; Machado, R D; Vieyra, A


    Electrocyte membranes of Electrophorus electricus exhibit high ATPase activity, as demonstrated by cytochemical and biochemical techniques. This activity is visualized as electron-dense deposits in electron micrographs, and appears to be localized only at the innervated face of the electrocyte. ATP hydrolysis can be detected cytochemically or biochemically only in the presence of calcium or magnesium. The effects of Ca or Mg on ATPase activity can be described by Michaelis-like functions with similar apparent Km values for Ca and Mg (0.41 mM and 0.23 mM, respectively). Vmax, however, is fivefold higher in the presence of Mg. The effects of the two cations are not additive, and pH dependence of ATP hydrolysis is identical in the presence of Ca or Mg (maximal at pH 8-9). Therefore, it can be concluded that Ca and Mg activate the same enzyme, the differences in Vmax being attributable to influences in kcat.

  6. Thermodynamic properties of nonstoichiometric oxygen in manganite Ca0.9Pr0.1MnO3-δ

    Leonidov, I. A.; Konstantinova, E. I.; Patrakeev, M. V.; Kozhevnikov, V. L.


    The chemical potential of oxygen ΔμO relative to its standard state in the gas phase was calculated from the experimental dependences of the oxygen content in various polymorphic modifications of Ca0.9Pr0.1MnO3-δ on the partial pressure and temperature. The partial molar enthalpy Δ {overline H _O} and entropy Δ {overline S _O} of oxygen were obtained from the linear temperature dependences of ΔμO. Based on the ideal solution approximation, Δ {overline H _O} and Δ {overline S _O} were correlated with the enthalpies and entropies of the defect formation reactions, the concentrations of manganese cations, and the oxygen nonstoichiometry. The thermal excitation of Mn4+ cations was shown to substantially affect the thermodynamic functions of oxygen.

  7. Effect of Pr–Ca substitution on the transport and magnetic behavior of LaMnO3 perovskite

    C M Thaker; S Rayaprol; Krushna Mavani; D S Rana; M S Sahasrabudhe; S I Patil; D G Kuberkar


    The effect of simultaneous substitution of a fluctuating cation and a divalent cation in LaMnO3 perovskite modifies the properties of the material to exhibit large valence colossal magnetoresistance (CMR) effect. A good example of these properties is (La1-2PrCa)MnO3 (LPCMO) type CMR material. In this communication it is reported that, with the increase in (for = 0.1, 0.15, 0.2), the c varies between 100 and 120 K with improvisation in metal–insulator transition. Interestingly, resistance increases with from few hundred ohms to few kilo ohms with corresponding decrease in the unit cell volume. The results of the studies using X-ray diffraction (XRD), electrical resistivity, magnetoresistance and ac susceptibility measurements on LPCMO samples for understanding the structural, transport and magnetic properties are discussed in detail.

  8. Magnetotransport properties of La2/3Ca1/3MnO3/ YBa2Cu4O8/La2/3Ca1/3MnO3 sandwiches

    Zhao Kun; Feng Jia-Feng; Huang Yan-Hong; Wong Hong-Kuen


    La2/3Ca1/3MnO3 (LCMO)/YBa2Cu4O8 (YBCO)/LCMO sandwiches are prepared by the facing-target sputtering technique. The superconducting transition temperature as a function of spacer layer thickness is described by the magnetic proximity effect in the superconductor/ferromagnet structure. The metal-semiconductor transition temperature exhibits a nonmonotonic behaviour which is strongly dependent upon the YBCO layer thickness, and is also shown from the measurement of resistance and magnetoresistance. These results imply that the magnetic spin interaction between the two LCMO layers may occur through the normal-conductive YBCO layer.

  9. Anisotropic Magnetoresistance of Perovskite La2/3 Ca1/3MnO3/YBa2Cu4O8/La2/3Ca1/3MnO3 Trilayer Films

    Wu Cheng; Zhang Li; Zhao Kun


    The anisotropic magnetoresistance (MR) of La2/3Ca1/3MnO3 (LCMO)/YBa2Cu4O8 (YBCO) /LCMO sandwiches on (001) SrTiO3 were investigated. Single layer LCMO and sandwiches show in-plane anisotropy of MR. MR strongly depends on the magnetic field direction. A nearly sinusoidal dependence on the angle between the applied magnetic field and the film plane or transport current was observed. A positive MR was present with lower fields applied not only out-of-plane but also in-plane.

  10. Effect of Sc and Zr on the in-plane anisotropy of Al-Mg-Mn alloy sheets

    PENG Yongyi; YIN Zhimin; YANG Jin; DU Yuxuan


    The Al-Mg-Mn alloy sheets with and without trace Sc and Zr were investigated by means of tensile test, X-ray diffraction, optical microscope, and transmission electron microscope. The indexes of in-plane anisotropy (IIPA) of their tensile mechanical properties were calculated and their inverse pole figures were obtained by Harris method. The two alloy sheets have the same law of in-plane anisotropy and remarkable in-plane anisotropy of mechanical properties, and the IIPA of the alloy sheet with Sc and Zr is bigger than that of the alloy sheet without Sc and Zr. The relationships of the in-plane anisotropy and the anisotropy of the crystallographic texture were analyzed based on the model of monocrystal. It is the common action of the anisotropy of crystallography and microstructures that causes the in-plane anisotropy of their mechanical sotropy of the alloy sheet containing trace Sc and Zr.

  11. Synergy of the Plastic Treatment HPT and Shot Peening in Aluminium Alloy Al-Mg-Mn-Sc-Zr

    Stegliński M.


    Full Text Available An improvement in fatigue strength is one of the main factors enabling the use of high-durability Al-Mg-Mn-Sc-Zr alloys in functional components of mobile robots. As part of this study, a computer simulation was carried out using ANSYS LS-DYNA software that involved the hybridization of high pressure torsion (HPT and shot peening (SP forming processes. The numerical analysis was aimed at determining residual stresses and strains that affect the durability and stress characteristics of the analyzed Al alloy. Results of the study indicate that tensile stresses of σ = 300 MPa generated as a result of HPT are transformed into a beneficial stress of σ = 25 MPa resulting from plastic strains caused by SP surface treatment.

  12. Numerical analysis of residual stress of Al-Mg-Mn-Sc-Zr alloy subjected to surface strengthening by shot peening

    Mariusz Stegliński


    Full Text Available In this paper, we presented the results of the analysis of the stresses in the Al-Mg5%-Mn1,5%-Sc0,8%-Zr0,4% alloy after shot peening process using solver ANSYSANSYSANSYS LS-Dyna. The computational model illustrates the phenomena occurring as a result of plastic deformation caused by hitting a steel ball on the surface of the analyzed aluminium alloy. We analyzed two input variables: diameter and speed of a ball. The resulting normal stress distribution centred exposes the minimum compressive stress at a position located at a depth point of Belayev 0.125 mm with a value of σ = –345 MPa. Variable parameter shows the correlation of the boundary conditions of minimum stress increase with increasing ball’s diameter and its speed. Selected points of numerical analysis were verified with experimental results.[b]Keywords[/b]: materials science, numerical analysis, metal forming, shot peening, aluminium

  13. Determination of Cl, K, Mg, Mn, Na and V in Brazilian red wine by neutron activation analysis

    Daniele, Anna Paula; Maihara, Vera Akiko, E-mail: [Instituto de Pesquisas Energeticas e Nucleares (IPEN/CNEN-SP), Sao Paulo, SP (Brazil)


    Several studies have been carried out for determining essential elements in foodstuffs due to important nutritional role in human body functions. Such information is crucial to any intervention in the diet of a population, thus becoming representative in the public health field. Trace elements are good indicators of wine’s origin and their concentrations can be used as criteria to ensure authenticity, quality and show that the tolerance limits established by law were respected throughout the production process. Although Brazilian wine industry is among the 15 largest in the world, analytical studies on the content of organic and inorganic compounds in wine are still small compared to other major producers. This study aimed to evaluate the elemental concentration of Cl, K, Mg, Mn, Na and V in seven national red wine samples acquired in the markets of Sao Paulo city. The analytical method applied was INAA. Concentrations of the elements in wine samples showed high variation among samples. (author)

  14. The effect of welding process and shielding atmosphere on the AlMg4.5Mn weld metal properties

    Prokic Cvetkovic, Radica; Popovic, Olivera [Belgrade Univ. (Serbia). Faculty of Mechanical Engineering; Burzic, Meri; Jovicic, Radomir [Belgrade Univ. (Serbia). Innovation Center; Kastelec Macura, Sandra [Technikum Taurunum, Zemun (Serbia); Buyukyildirim, Galip [IWE, Istanbul (Turkey)


    In this paper, the AlMg4.5Mn alloy has been welded using tungsten inert gas (TIG) and metal inert gas (MIG) processes with different gas shielding atmospheres. Tensile strength, hardness, impact and fracture toughness, fatigue crack growth parameters ({Delta}K{sub th}, da/dN), as well as microstructure were determined. By comparing results for different gas mixtures, the main conclusion for TIG welding was that increased helium content has an important effect on toughness and fatigue crack growth parameters, whereas its effect on other mechanical properties is not significant. On the other hand, in the case of MIG welding, adding helium does not affect mechanical properties, except the fatigue crack growth rate. It was also established that adding nitrogen (TIG welding) and oxygen (MIG welding) reduces toughness and increases crack growth rate, so their use in shielding mixtures is not recommended. (orig.)

  15. Structure and Mechanical Properties of AlMg4.5 And AlMg4.5Mn Wires Extruded by Kobo Method

    Jaskowski M.


    Full Text Available W pracy badano wpływ liczby operacji wyciskania metodą KoBo (z identycznym sumarycznym stopniem przerobu λ = 100 na strukturę, własności mechaniczne i charakterystyki umocnieniowe drutów ze stopów AlMg4.5 i AlMg4.5Mn (AA5083. Stwierdzono, że wyciskanie jednooperacyjne prowadzi w przypadku obu stopów do formowania struktury typowej dla materia- łów zrekrystalizowanych. podczas gdy zastosowanie dwuoperacyjnego wyciskania skutkuje utworzeniem struktury włóknistej o charakterze „mieszanym”, tzn. zawierającej zarówno obszary, w których dominowały procesy intensywnego zdrowienia, jak i rekrystalizacji. W konsekwencji własności wytrzymałościowe tych ostatnich są zdecydowanie wyższe zarówno po wyciskaniu, jak i po późniejszym walcowaniu na zimno. We wszystkich przypadkach na krzywych rozciągania drutów obserwowano sko- kowe oscylacje naprężenia, charakterystyczne dla efektu Portevin - LeChatelier (P-L. W nielicznych próbach rozciągania efekt P-L poprzedzała niestateczność płynięcia plastycznego typowa dla występowania pasma LUdersa. Charakterystyki umocnienia wywołane procesem walcowania wykazywały przebieg monotonicznie rosnący.

  16. The effect of Ca-substitution in La-site on the magnetic properties of La{sub 2}CoMnO{sub 6}

    Li, Qiu-hang; Li, Na; Hu, Jian-zhong; Han, Qi; Ma, Qing-shan; Ge, Lei; Xiao, Biao; Xu, Ming-xiang, E-mail: [Department of Physics and Key Laboratory of MEMS of the Ministry of Education, Southeast University, Nanjing 210096 (China)


    Double perovskite La{sub 2-x}Ca{sub x}CoMnO{sub 6} (x = 0, 0.1, 0.2, 0.5) ceramics samples were synthesized by the standard solid-state reaction method. The crystal structures have been confirmed to be monoclinic perovskite structure with space group of P2{sub 1}/n at room temperature by the powder x-ray diffraction (Cu-Kα). The grains of the samples are relatively dense and distribute in random directions from the scanning electron microscope patterns. Holes are doped into La{sub 2}CoMnO{sub 6} with the substitution of the Ca{sup 2+} ions in La-site, and further lead to the valences of Mn ions and Co ions transforming from Mn{sup 4+} and Co{sup 2+} to Mn{sup 3+} and Co{sup 3+}, respectively. Ferromagnetic coupling of Mn{sup 4+}-O{sup 2–}-Co{sup 2+} and antiferromagnetic coupling of Mn{sup 3+}-O{sup 2–}-Co{sup 3+} are coexistent in La{sub 2-x}Ca{sub x}CoMnO{sub 6} system, which correspond to two transitions existed in field-cooling magnetization versus temperature curves. Curie temperature of La{sub 2-x}Ca{sub x}CoMnO{sub 6} system decreases with the increasing of Ca-substitution amount. The coexistence of different magnetic phases leads to the exchange bias effect.

  17. Electromagnetic properties of nanocrystalline Al$^{3+}$ substituted MgCuMn ferrites synthesized by microwave hydrothermal method



    The effect of Al$^{3+}$ substitution on electromagnetic properties has been studied for nanocrystalline Mg$_{0.8}$Cu$_{0.2}Mn$_{0.05}$Al$_x$Fe$_{1.95−x}$O$_4$ ferrites, wherein $x$ varies from 0 to 0.4 in steps of 0.1. These ferrites were synthesizedby using microwave hydrothermal method and then characterized using X-ray diffractometer (XRD), Fourier transform infrared and transmission electron microscopy. The synthesized powders were densified using microwavesintering method at 950◦C/50 min. Structural and surface morphology of sintered samples were characterized using XRD and atomic force microscopy, respectively. The complex permittivity and permeability properties were measuredover a frequency range 100 Hz–1.8 GHz. The temperature variation of magnetic properties were measured in the temperature range of 300–650 K. The electrical and magnetization studies inferred that the values of d.c. resistivity increases by 27%, whereas saturation magnetization decreases linearly from 38.6 to 23.0 emu g$^{−1}$ and Curie temperature was found to be decreased from 628 to 513 K with an increase of Al$^{3+}$ ions. The low dielectric, magnetic losses, moderate saturation magnetization and high-temperature stability properties exhibited by Al$^{3+}$ substituted MgCuMn ferrites make them find applications in microwave devices, such as circulators and isolators etc. The applicability of present samples formicrowave devices has been tested by the measurement of ferromagnetic resonance linewidth at K$_a$ band.

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

    Sronsri, Chuchai; Noisong, Pittayagorn; Danvirutai, Chanaiporn


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

  19. Structure/activity Relationship of Thapsigargin Inhibition on the Purified Golgi/secretory Pathway Ca2+/Mn2+ Transport ATPase (SPCA1a)

    Jialin, Chen; de Raeymaecker, Joren; Hovgaard, Jannik Brøndsted


    The Golgi/secretory pathway Ca2+/Mn2+ transport ATPase (SPCA1a) is implicated in breast cancer and Hailey-Hailey disease. Here, we purified recombinant human SPCA1a from Saccharomyces cerevisiae and measured Ca2+ dependent ATPase activity following reconstitution in proteoliposomes. The purified...

  20. Microstructure and Fatigue Behavior of Friction Stir-welded Noncombustive Mg-9Al-Zn-Ca Magnesium Alloy

    Zhou, L.; Li, Z. Y.; Nakata, K.; Feng, J. C.; Huang, Y. X.; Liao, J. S.


    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.

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

    Barbara Lafuente


    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.

  2. Electric, magnetic, and thermo-electric properties of Cr doped La0.8Ca0.2Mn1-xCrxMnO3 manganites

    Manjunatha, S. O.; Rao, Ashok; Babu, P. D.; Chand, Tara; Okram, G. S.


    A detailed study of the structural, magnetic, magneto-transport and thermoelectric properties of polycrystalline La0.8Ca0.2Mn1-xCrxMnO3 (0insulator transition temperature, TMI and ferromagnetic-paramagnetic (FM-PM) transition temperature, TC. With increasing Cr-content, both TMI and TC are observed to decrease. The electrical resistivity data is analyzed using different theoretical models at various regions viz., metallic, insulating and percolation region. Analysis in the metallic region (Tinsulating region (T>TMI) is well described using SPH model. However, the resistivity data in the whole temperature range is analyzed using a phenomenological model based on phase segregation of ferromagnetic metallic and paramagnetic insulating regions. Thermoelectric power, S measurements were performed to understand the conduction mechanism and to ascertain the types of charge carrier responsible for conduction. It is observed that pristine as well as Cr-doped compounds show positive value of S which demonstrates that the charge carriers are holes.

  3. Effects of Mn3O4 precipitates on the vibrational properties of epitaxial Ca-doped LaMnO3 films

    Daoudi, Kais; Alawadhi, Hussain; El Helali, Saoussen; Boudard, Michel; Othmen, Zied; Gaidi, Mounir; Oueslati, Meherzi; Tsuchiya, Tetsuo


    This work presents a systematic study by Raman spectroscopy of the vibrational properties of La0.7Ca0.3MnO3 (LCMO70/30) thin films epitaxially grown on LaAlO3 single crystalline substrates. The epitaxial LCMO70/30 thin films were prepared using a metal organic deposition process with thermal annealing at 800 °C, 900 °C and 1000 °C, with thicknesses ranging from 20–80 nm. The evolution of the Raman modes versus film thickness and annealing temperature have been investigated. The Raman spectra of the obtained films are found to be mainly dominated by three Raman lines at 225, 440 and 661 cm‑1. The first two Raman lines are assigned to the vibrational modes of the LCMO70/30 films. However, by combining magnetization, x-ray diffraction and transmission electron microscopy with Raman spectroscopy, we concluded that the 661 cm‑1 Raman line is due to the existence of a precipitate of a Mn3O4 phase in the LCMO70/30 films.

  4. A detailed study of the hysteresis in La0.67Ca0.33MnO3

    Bez, Henrique N.; Nielsen, Kaspar K.; Smith, Anders; Bahl, Christian R. H.


    We report a thorough study of the thermal hysteretic behaviour of a single phase sample of the magnetocaloric material La0.67Ca0.33MnO3. Previous reports in the literature have variously found hysteretic and non-hysteretic behaviour. We show the importance of measuring under carefully defined heating and cooling procedures. Careful analysis of the specific heat, measured at five different temperature ramp rates, and the magnetic entropy change indicates that there is no observable hysteresis, even though the behaviour of both quantities is consistent with a first-order phase transition. We discuss the reasons for this and for the differing results previously found.

  5. Substrate-induced strain effects on Pr_{0.6}Ca_{0.4}MnO_{3} films


    We report the characterization of the crystal structure, low-temperature charge and orbital ordering, transport, and magnetization of Pr_{0.6}Ca_{0.4}MnO_{3} films grown on LaAlO_{3}, NdGaO_{3}, and SrTiO_{3} substrates, which provide compressive (LaAlO_{3}) and tensile (NdGaO_{3} and SrTiO_{3}) strain. The films are observed to exhibit different crystallographic symmetries than the bulk material, and the low-temperature ordering is found to be more robust under compressive-- as opposed to te...

  6. Mg/Ca and isotopic high resolution record of deep-sea hydrothermal barnacles

    Bojar, A.-V.; Bojar, H.-P.; Tufar, W.


    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

  7. In vitro investigation of anodization and CaP deposited titanium surface using MG63 osteoblast-like cells

    Lee, J.M. [Department of Prosthodontics and Dental Research Institute, School of Dentistry, Seoul National University, 28 Yeongeon-dong, Jongno-gu, Seoul 110-749 (Korea, Republic of); Lee, J.I. [Department of Oral Pathology and Dental Research Institute, School of Dentistry, Seoul National University, Seoul (Korea, Republic of); Lim, Y.J., E-mail: [Department of Prosthodontics and Dental Research Institute, School of Dentistry, Seoul National University, 28 Yeongeon-dong, Jongno-gu, Seoul 110-749 (Korea, Republic of)


    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.

  8. Formation process of micro arc oxidation coatings obtained in a sodium phytate containing solution with and without CaCO3 on binary Mg-1.0Ca alloy

    Zhang, R. F.; Zhang, Y. Q.; Zhang, S. F.; B. Qu; Guo, S. B.; Xiang, J. H.


    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 CaCO3 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 CaCO3. 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 Mg2Ca phase. After treating for 5 s, the coating began to develop and was preferentially formed on the area nearby Mg2Ca phase, which may be resulted from the intrinsic electronegative potential of the Mg phase than that of Mg2Ca 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. CaCO3 has minor influence on the calcium content of the obtained MAO coatings.

  9. Optimization of dual effects of Mg-1Ca alloys on the behavior of chondrocytes and osteoblasts in vitro

    Yana Dou; Ayeesha Mujeeb; Yufeng Zheng; Zigang Ge


    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.

  10. Photoelectron velocity-map imaging and theoretical studies of heteronuclear metal carbonyls MNi(CO)3- (M = Mg, Ca, Al)

    Xie, Hua; Zou, Jinghan; Yuan, Qinqin; Fan, Hongjun; Tang, Zichao; Jiang, Ling


    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.

  11. In vitro bioaccessibility of β-carotene, Ca, Mg and Zn in landrace carrots (Daucus carota, L.).

    Zaccari, Fernanda; Cabrera, María Cristina; Ramos, Ana; Saadoun, Ali


    Four landrace carrots ("Becaria", "CRS", "González" and "Rodríguez") and two marketable cultivars (Kuroda and Brasilia), raw and steamed, were characterised by the total content of β-carotene Ca, Mg and Zn, in vitro bioaccessibility and by colour and were evaluated to determine the effect of particle size in nutrient bioaccessibility. Steaming increased the content of β-carotene extracted from "CRS" and Brasilia (29% and 75%) and decreased the content of β-carotene extracted from "CRS" by 23% in "Rodríguez." In addition, steaming caused a loss of Ca (21%) but did not change the amount of Mg and Zn. The bioaccessibility of β-carotene in raw and pulped carrots was very low (<0.5%). Furthermore, steaming and a smaller particle size increased the bioaccessibility of β-carotene by 3-16 times. Additionally, cooking increased the in vitro bioaccessibility of Ca and Zn but had no effect on Mg. Moreover, homogenisation increased the bioaccessibility by 20% in Ca, 17% in Mg, and 10% in Zn compared to pulping.

  12. In vitro and in vivo studies on biodegradable CaMgZnSrYb high-entropy bulk metallic glass.

    Li, H F; Xie, X H; Zhao, K; Wang, Y B; Zheng, Y F; Wang, W H; Qin, L


    In order to enhance the corrosion resistance of the Ca65Mg15Zn20 bulk metallic glass, which has too fast a degradation rate for biomedical applications, we fabricated the Ca20Mg20Zn20Sr20Yb20 high-entropy bulk metallic glass because of the unique properties of high-entropy alloys. Our results showed that the mechanical properties and corrosion behavior were enhanced. The in vitro tests showed that the Ca20Mg20Zn20Sr20Yb20 high-entropy bulk metallic glass could stimulate the proliferation and differentiation of cultured osteoblasts. The in vivo animal tests showed that the Ca20Mg20Zn20Sr20Yb20 high-entropy bulk metallic glass did not show any obvious degradation after 4 weeks of implantation, and they can promote osteogenesis and new bone formation after 2 weeks of implantation. The improved mechanical properties and corrosion behavior can be attributed to the different chemical composition as well as the formation of a unique high-entropy atomic structure with a maximum degree of disorder.

  13. Long-range interactions of excited He atoms with the alkaline earth atoms Mg, Ca, and Sr

    Zhang, J.-Y.


    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.

  14. Vipoxin specificity studied by gas chromatographic determination of enzymatic reaction products. Influence of Ca2+, Mg2+ and Sr2+

    V. Atanasov


    Full Text Available Gas chromatographic procedure with mass spectrometric detection was applied to quantitatively determine the enzymatic specificity and activity of vipoxin (a neurotoxin from the Vipera ammodytes meridionalis venom as well as the influence of Ca2+, Mg2+ and Sr2+ on these properties.

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

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


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

  16. Consequences of embedding Ti4+ 3d0 centers in Pr0.50Ca0.50MnO3 : Phase competition in Pr0.50Ca0.50Mn1-xTixO3

    García-Muñoz, J. L.; Frontera, C.; Beran, P.; Bellido, N.; Hernández-Velasco, J.; Ritter, C.


    We have studied the structural and magnetic phase coexistence/competition derived from the partial random substitution of 3d0 nonmagnetic Ti4+ ions for Mn in Pr0.50Ca0.50MnO3 , and their evolution with the doping level in Pr0.50Ca0.50Mn1-xTixO3 ( x=0 , 0.01, 0.03, and 0.05) manganites. Combining high-resolution synchrotron, neutron powder-diffraction, and muon techniques we describe with great detail the coexistence of two different structural phases below ≈240K (charge-order transition temperature, TCO ) with different cell distortion, antiferromagnetic order, and strain characteristics. The evolution of all these features with Ti substitution level is thoroughly described. Ti4+ (3d0) ions do not favor the stabilization of ferromagnetic/metallic (FM/M) islands/regions in the antiferromagnetic/insulating (AFM/I) orbital-ordered matrix. The absence of short- and long-range ferromagnetism in zero field has been confirmed by different techniques. The proportion of microdomains exhibiting pseudo-(CE)-type magnetic order (CE: charge exchange) increases with the Ti content at expenses of the CE-type regions. Differences in the stability of competing phases against magnetic field have been found by neutron-diffraction measurements under application of external fields. The phase coexistence exhibits strong anisotropic strain effects that have been thoroughly analyzed as a function of the Ti content x . We have found very remarkable changes in the strain characteristics of the AFM segregated phases on going from 1% to 5% Ti. Large anisotropic strains develop mainly in the minority phase of the material. The magnitude of strains is discussed in comparison with anisotropic strain values recently determined in the case of substitutions (such as Co) that favor FM/M domains.

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

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


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

  18. Orbital and suborbital variability in North Atlantic bottom water temperature obtained from deep-sea ostracod Mg/Ca ratios

    Cronin, T. M.; Dwyer, G.S.; Baker, P.A.; Rodriguez-Lazaro, J.; DeMartino, D.M.


    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.


    M. U. Hashmi


    Full Text Available The aim of present work is to study the relationship between crystalline phases, microstructure and mechanical properties of bioactive glass-ceramics. For this purpose, glasses of composition (50-x CaO–34SiO2–14.5P2O5–1CaF2–0.5MgF2– xMgO (wt. % (where x = 4, 25 and 46 respectively were synthesized by conventional melt-quench method. Each glass was sintered according to the endothermal and exothermal peaks of differential scanning calorimetric (DSC data to form three glass ceramics termed G1, G2 and G3 respectively. X-ray diffraction (XRD revealed crystalline phases of hydroxyapatite and wollastonite in G1 and G2, whereas in G3, a new phase ‘whitlockite’ was observed probably due to a greater concentration of MgO in this sample. Bulk density of the samples was determined by Archimedes principle. Scanning electron microscope (SEM data illustrated that the rate of densification of materials increased with the decrease of CaO/MgO ratio. Analysis of mechanical properties revealed that micro-hardness and bending strength of the samples increased with the increase in MgO content, which is in accordance with the results of XRD, SEM and bulk density.

  20. The Influence of Zn Content on the Corrosion and Wear Performance of Mg-Zn-Ca Alloy in Simulated Body Fluid

    Li, Hua; Liu, Debao; Zhao, Yue; Jin, Feng; Chen, Minfang


    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.

  1. Microscopic Ferromagnetic and Antiferromagnetic Clusters in Pr0.7Ca0.3MnO3

    Sha, Hao; Zhang, Jiandi; Ye, Feng; Fernandez-Baca, Jaime; Dai, Pengcheng; Tomioka, Y.; Tokura, Y.


    ``Colossal'' magnetorestive manganite Pr0.7Ca0.3MnO3 (PCMO30) is an ideal system to test the microscopic phase separation scenario because it has an inhomogeneous low-temperature insulating metastable state where ferromagnetic (FM), antiferromagnetic (AF), and charge/orbital (CO-OO) phases coexist. On cooling from room temperature, a CO-OO state occurs below TCO-OO ˜200 K, followed by AF ordering below TN ˜140 K. Below TC ˜110 K, the magnetic structure develops a FM component coexisting with AF ordering. We have used neutron scattering to study FM, AF and CO-OO phase transitions in a single-crystal PCMO30. The diffuse scattering of FM component demonstrates the presence of short-range ferromagnetic clusters both above and below TC, while no diffuse component in the CO-OO scattering peaks has been observed near TCO-OO. Interestingly, the short-range AF correlations associated with Mn^4+ sites but not with Mn^3+ sites are observed for both above and below TN, indicating that the local AFM clustering is directly associated with doped holes in this system. The work was supported by NSF-DMR0453804, NSF-DMR0346826, DE-FG02-05ER46202, and DOE DE-FG02-04ER46125. ORNL is managed by UT-Battelle, LLC, for the U.S. DOE under contract DE-AC05-00OR22725.

  2. Tetragonal D022 Mn3+xGe Epitaxial Films Grown on MgO(100) with a Large Perpendicular Magnetic Anisotropy

    Mizukami, Shigemi; Sakuma, Akimasa; Sugihara, Atsushi; Kubota, Takahide; Kondo, Yukio; Tsuchiura, Hiroki; Miyazaki, Terunobu


    First-principles calculation of D022 Mn3Ge shows a fully spin-polarized Δ1 band at the Fermi level, low saturation magnetization MS=180 emu/cm3, high uniaxial magnetic anisotropy Ku=23 Merg/cm3, and low Gilbert damping α=9×10-4. We also experimentally investigate D022 Mn3+xGe epitaxial films grown on MgO(100) substrates with different compositions x. The films exhibit a coercivity of about 20 kOe, MS of about 130 emu/cm3, and Ku of about 10 Merg/cm3 at x=0.55 (78 at.% Mn). These indicate that D022 Mn3Ge is a good candidate for spin-transfer-torque random access memory.

  3. 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

    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: [School of Material and Electromechanics, Jiangxi Science and Technology Normal University, Nanchang 330013 (China)


    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.

  4. Crystalline behaviour and electrical properties of manganese perovskites substituted on A or B sites: ErMnO3 modified by Ca and EuMnO3 modified by Co

    Tartaj, J.


    Full Text Available The structural and electrical features of the manganites solid solutions (Er,CaMnO3 and Eu(Co,MnO3, have been studied by X-ray diffraction and conductivity measurements. Powders were prepared by solid-state reaction between the component oxides and Calcium carbonate. Incorporation of Co2+ on the lattice in the B sites or the Ca2+ on the A sites leads to changes in the parameters and symmetry of the perovskite compound EuMnO3 and hexagonal ErMnO3 respectively. The phase transition depends on the amount of substituted Jahn-Teller Mn3+ cations. Solid solutions based on Eu(Mn,CoO3 perovskite compound change from O’-type to O-type orthorhombic perovskite symmetry when the Mn3+ cation amount decreases, because of the progressive substitution by Co. This transition occurs for an amount of Co2+ as low as ~10 at% Co2+ cation. The (Er,CaMnO3 based solid solutions showed a different behaviour. From x=0.25 there is a change in the symmetry of the solid solution from hexagonal to orthorhombic, O’-type perovskite. Steric influence seems to play a secondary role on the lattice distortion of manganites. Sintered samples of the perovskite solid solutions were measured for establishing their electrical properties. All the samples showed semiconducting behaviour.

    Las características estructurales y eléctricas de las soluciones sólidas de manganitas (Er,CaMnO3 y Eu(Co,MnO3, han sido estudiadas por difracción de rayos X y medidas de la conductividad en continua. Los polvos fueron preparados por reacción en estado sólido entre los óxidos componentes y carbonato de calcio. La incorporación de Co2+ en la red en los sitios B o de Ca2+ en los sitios A conduce a cambios en los parámetros y la simetría de EuMnO3 perovskita y ErMnO3 hexagonal, respectivamente

  5. Dissolution Behavior of Alumina-Based Inclusions in CaF2-Al2O3-CaO-MgO-SiO2 Slag Used for the Electroslag Metallurgy Process

    Yanwu Dong


    Full Text Available Removal of non-metallic inclusions to CaF2-based slag is one of the most important functions of electroslag remelting. In this work, the dissolution behavior for alumina-based inclusions in CaF2-Al2O3-CaO-MgO-SiO2 slag has been investigated. Results indicate that the diffusion or permeability capacity of slag components into alumina particles is F−, Ca2+, Si4+, Mg2+, from strongest to weakest, for CaF2-Al2O3-CaO-MgO-SiO2 slag. Alumina inclusions react with F− in liquid slag at first and then react with CaO to form xCaO-yAl2O3 system. Subsequently, MgO substitutes for CaO to form a MgO-Al2O3 system layer surrounding the other product and reactant, and then enters the liquid slag. CaF2 can improve the dissolution capacity of slag to alumina inclusions. A complex region was formed between alumina-based particles and the slag, with different areas dominated by CaF2, CaO-Al2O3, CaO-SiO2 and MgO-Al2O3. The dissolution process of alumina particles in slag is different from the formation of compound inclusions originated from the Al-O deoxidization reaction.

  6. The effect of gallic acid on cytotoxicity, Ca(2+) homeostasis and ROS production in DBTRG-05MG human glioblastoma cells and CTX TNA2 rat astrocytes.

    Hsu, Shu-Shong; Chou, Chiang-Ting; Liao, Wei-Chuan; Shieh, Pochuen; Kuo, Daih-Huang; Kuo, Chun-Chi; Jan, Chung-Ren; Liang, Wei-Zhe


    Gallic acid, a polyhydroxylphenolic compound, is widely distributed in various plants, fruits and foods. It has been shown that gallic acid passes into blood brain barrier and reaches the brain tissue of middle cerebral artery occlusion rats. However, the effect of gallic acid on Ca(2+) signaling in glia cells is unknown. This study explored whether gallic acid affected Ca(2+) homeostasis and induced Ca(2+)-associated cytotoxicity in DBTRG-05MG human glioblastoma cells and CTX TNA2 rat astrocytes. Gallic acid (20-40 μM) concentration-dependently induced cytotoxicity and intracellular Ca(2+) level ([Ca(2+)]i) increases in DBTRG-05MG cells but not in CTX TNA2 cells. In DBTRG-05MG cells, the Ca(2+) response was decreased by half by removal of extracellular Ca(2+). In Ca(2+)-containing medium, gallic acid-induced Ca(2+) entry was inhibited by store-operated Ca(2+) channel inhibitors (2-APB, econazole and SKF96365). In Ca(2+)-free medium, pretreatment with the endoplasmic reticulum Ca(2+) pump inhibitor thapsigargin abolished gallic acid-induced [Ca(2+)]i increases. Conversely, incubation with gallic acid also abolished thapsigargin-induced [Ca(2+)]i increases. Inhibition of phospholipase C with U73122 abolished gallic acid-induced [Ca(2+)]i increases. Gallic acid significantly caused cytotoxicity in DBTRG-05MG cells, which was partially prevented by prechelating cytosolic Ca(2+) with BAPTA-AM. Moreover, gallic acid activated mitochondrial apoptotic pathways that involved ROS production. Together, in DBTRG-05MG cells but not in CTX TNA2 cells, gallic acid induced [Ca(2+)]i increases by causing Ca(2+) entry via 2-APB, econazole and SKF96365-sensitive store-operated Ca(2+) entry, and phospholipase C-dependent release from the endoplasmic reticulum. This Ca(2+) signal subsequently evoked mitochondrial pathways of apoptosis that involved ROS production.

  7. Enhancement of magnetic and ferroelectric behaviour in (Ca, Co) co-doped HoMnO3 multiferroics

    Rout, P. P.; Pradhan, S. K.; Das, S. K.; Samantaray, S.; Roul, B. K.


    The effect of sintering temperature on structural, electrical and magnetic behaviours of polycrystalline samples of Ho0.9Ca0.1Mn0.9Co0.1O3 prepared by the solid state reaction route sintered at three different temperature 1250 °C, 1350 °C, 1450 °C for 10 h are investigated. XRD, SEM, magnetization, dielectric and ferroelectric measurements were carried out. Experimental results showed the nucleation of orthorhombic phase as the sintering temperature increases from 1250 °C to 1450 °C. Ferroelectric (Tc) and antiferromagnetic transition temperature (TN) increases with increase in sintering temperature. Strong bifurcation of FC and ZFC curve in sample sintered at 1450 °C showed a clear onset of ferromagnetic state around 165 °K, which is confirmed from M to H graph at 165 °K. All the sample showed ferroelectric behaviour at room temperature which are leaky in nature. Sintering temperature along with Ca and Co doping in HoMnO3 ceramics plays an important role in phase transformation along with enhancement in multiferroic properties.

  8. Preparation and improved electrical performance of the Pr-doped CaMnO3-δ thermoelectric compound

    Zhang, F. P.; Lu, Q. M.; Zhang, X.; Zhang, J. X.


    The rare earth Pr-doped Ca1-xPrxMnO3-δ (0 ⩽ x ⩽ 0.14) compound bulk samples are fabricated by citrate acid sol-gel combined with the ceramic preparation method. The effects of Pr doping on the structural and electrical transport properties of CaMnO3-δ within the high-temperature region are investigated in detail. The results show that single orthorhombic compounds can be formed in the experimental doping region. The remarkably reduced electrical resistivity is observed for the doped samples with the minimum value 3.90 mΩ cm at 373 K for the x = 0.14 sample; the absolute value of the Seebeck coefficient is decreased due to electron carrier concentration enhancement. The electrical properties of the doped samples are optimized compared with that of the parent sample,