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Sample records for mg liter-1 caco3

  1. Antibacterial characteristics of CaCO3-MgO composites

    International Nuclear Information System (INIS)

    Yamamoto, Osamu; Ohira, Toshiaki; Alvarez, Kelly; Fukuda, Masayuki

    2010-01-01

    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 3 grain, were fabricated by the thermal decomposition of dolomite. The composite obtained by heating at 800 deg. C consisted of CaCO 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. Mg and Ca isotope fractionation during CaCO3 biomineralisation

    International Nuclear Information System (INIS)

    Chang, Veronica T.-C.; Williams, R.J.P.; Makishima, Akio; Belshawl, Nick S.; O'Nions, R. Keith

    2004-01-01

    The natural variation of Mg and Ca stable isotopes of carbonates has been determined in carbonate skeletons of perforate foraminifera and reef coral together with Mg/Ca ratios to assess the influence of biomineralisation processes. The results for coral aragonite suggest its formation, in terms of stable isotope behaviour, approximates to inorganic precipitation from a seawater reservoir. In contrast, results for foraminifera calcite suggest a marked biological control on Mg isotope ratios presumably related to its low Mg content compared with seawater. The bearing of these observations on the use of Mg and Ca isotopes as proxies in paleoceanography is considered

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

    Science.gov (United States)

    McSwiggen, P.L.

    1993-01-01

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

  4. Preparation and characterization of coating sodium trisilicate (Na2O.nSiO2) at calcium carbonate (CaCO3) for blowing agent in Mg alloy foam

    Science.gov (United States)

    Erryani, Aprilia; Lestari, Franciska Pramuji; Annur, Dhyah; Kartika, Ika

    2018-05-01

    The role of blowing agent in the manufacture of porous metal alloys is very important to produce the desired pore. The thermal stability and speed of foam formation have an effect on the resulting pore structure. In porous metal alloys, uniformity of size and pore deployment are the main determinants of the resulting alloys. The coating process of calcium carbonate (CaCO3) has been done using Sodium trisilicate solution by sol-gel method. Foaming agent was pretreated by coating SiO2 passive layer on the surface of CaCO3. This coating aims to produce a more stable blowing agent so that the foaming process can produce a more uniform pore size. The microstructure of the SiO2 passive was observed using Scanning Electron Microscope (SEM) equipped by Energy Dispersive X-Ray Spectrometer (EDS) mapping. The results showed coating CaCO3 using sodium trisilicate was successfully done creating a passive layer of SiO2 on the surface of CaCO3. By the coating process, the thermal stability of coated CaCO3 increased compared to uncoated CaCO3.

  5. New High Pressure Phase of CaCO3: Implication for the Deep Diamond Formation

    Science.gov (United States)

    Mao, Z.; Li, X.; Zhang, Z.; Lin, J. F.; Ni, H.; Prakapenka, V.

    2017-12-01

    Surface carbon can be transported to the Earth's deep interior through sinking subduction slabs. Carbonates, including CaCO3, MgCO3 and MgCa(CO3)2, are important carbon carriers for the deep carbon cycle. Experimental studies on the phase stability of carbonates with coexisting mantle minerals at relevant pressure and temperature conditions are thus important for understanding the deep carbon cycle. In particular, recent petrological studies have revealed the evidence for the transportation of CaCO3 to the depth at least of the top lower mantle by analyzing the diamond inclusions. Yet the phase stability of CaCO3 at relevant pressure and temperature conditions of the top lower mantle is still unclear. Previous single-crystal study has shown that CaCO3 transforms from the CaCO3-III structure to CaCO3-VI at 15 GPa and 300 K. The CaCO3-VI is stable at least up to 40 GPa at 300 K. At high temperatures, CaCO3 in the aragonite structure will directly transform into the post-aragonite structure at 40 GPa. However, a recent theoretical study predicted a new phase of CaCO3 with a space group of P21/c between 32 and 48 GPa which is different from previous experimental results. In this study, we have investigated the phase stability of CaCO3 at high pressure-temperature conditions using synchrotron X-ray diffraction in laser-heated diamond anvil cells. We report the discovery of a new phase of CaCO3 at relevant pressure-temperature conditions of the top lower mantle which is consistent with previous theoretical predictions. This new phase is an important carrier for the transportation of carbon to the Earth's lower mantle and crucial for growing deep diamonds in the region.

  6. Thermoluminescence of CaCO3:Dy and CaCO3:Mn

    International Nuclear Information System (INIS)

    Bapat, V.N.; Nambi, K.S.V.

    1976-01-01

    CaCO 3 samples doped with Dy and Mn were prepared in the laboratory by co-precipitation techniques. Thermoluminescence and emission spectra of these phosphors were studied and were compared with those of the naturally occuring calcite and undoped CaCO 3 samples. Dy-doping seems to give a more efficient phosphor and indicates a possibility of getting a better phosphor by a judicious choice of a rare earth doping of CaCO 3 . Interesting result have been obtained on the TL glow curve variations of these phosphors with different temperature treatments prior to irradiation. (author)

  7. Preparation of core-shell structured CaCO3 microspheres as rapid and recyclable adsorbent for anionic dyes

    Science.gov (United States)

    Zhao, Mengen; Chen, Zhenhua; Lv, Xinyan; Zhou, Kang; Zhang, Jie; Tian, Xiaohan; Ren, Xiuli; Mei, Xifan

    2017-09-01

    Core-shell structured CaCO3 microspheres (MSs) were prepared by a facile, one-pot method at room temperature. The adsorbent dosage and adsorption time of the obtained CaCO3 MSs were investigated. The results suggest that these CaCO3 MSs can rapidly and efficiently remove 99-100% of anionic dyes within the first 2 min. The obtained CaCO3 MSs have a high Brunauer-Emmett-Teller surface area (211.77 m2 g-1). In addition, the maximum adsorption capacity of the obtained CaCO3 MSs towards Congo red was 99.6 mg g-1. We also found that the core-shell structured CaCO3 MSs have a high recycling capability for removing dyes from water. Our results demonstrate that the prepared core-shell structured CaCO3 MSs can be used as an ideal, rapid, efficient and recyclable adsorbent to remove dyes from aqueous solution.

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

    Science.gov (United States)

    McSwiggen, P.L.

    1993-01-01

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

  9. Effect of CaCO3(S) nucleation modes on algae removal from alkaline water.

    Science.gov (United States)

    Choi, Jin Yong; Kinney, Kerry A; Katz, Lynn E

    2016-02-29

    The role of calcite heterogeneous nucleation was studied in a particle coagulation treatment process for removing microalgae from water. Batch experiments were conducted with Scenedesmus sp. and Chlorella sp. in the presence and absence of carbonate and in the presence and absence of Mg to delineate the role of CaCO 3(S) nucleation on microalgae removal. The results indicate that effective algae coagulation (e.g., up to 81 % algae removal efficiency) can be achieved via heterogeneous nucleation with CaCO 3(S) ; however, supersaturation ratios between 120 and 200 are required to achieve at least 50% algae removal, depending on ion concentrations. Algae removal was attributed to adsorption of Ca 2+ onto the cell surface which provides nucleation sites for CaCO 3(S) precipitation. Bridging of calcite particles between the algal cells led to rapid aggregation and formation of larger flocs. However, at higher supersaturation conditions, algae removal was diminished due to the dominance of homogeneous nucleation of CaCO 3(S) . Removal of algae in the presence of Ca 2+ and Mg 2+ required higher supersaturation values; however, the shift from heteronucleation to homonucleation with increasing supersaturation was still evident. The results suggest that water chemistry, pH, ionic strength, alkalinity and Ca 2+ concentration can be optimized for algae removal via coagulation-sedimentation.

  10. CaCO3-III and CaCO3-VI, high-pressure polymorphs of calcite: Possible host structures for carbon in the Earth's mantle

    Science.gov (United States)

    Merlini, M.; Hanfland, M.; Crichton, W. A.

    2012-06-01

    Calcite, CaCO3, undergoes several high pressure phase transitions. We report here the crystal structure determination of the CaCO3-III and CaCO3-VI high-pressure polymorphs obtained by single-crystal synchrotron X-ray diffraction. This new technical development at synchrotron beamlines currently affords the possibility of collecting single-crystal data suitable for structure determination in-situ at non-ambient conditions, even after multiphase transitions. CaCO3-III, observed in the pressure range 2.5-15 GPa, is triclinic, and it presents two closely related structural modifications, one, CaCO3-III, with 50 atoms in the unit cell [a=6.281(1) Å, b=7.507(2) Å, c=12.516(3) Å, α=93.76(2)°, β=98.95(2)°, γ=106.49(2)°, V=555.26(20) Å3 at 2.8 GPa], the second, CaCO3-IIIb, with 20 atoms [a=6.144(3) Å, b=6.3715(14) Å, c=6.3759(15) Å, α= 93.84(2)°, β=107.34(3)°, γ=107.16(3)°, V=224.33(13) Å3 at 3.1 GPa]. Different pressure-time experimental paths can stabilise one or the other polymorph. Both structures are characterised by the presence of non-coplanar CO3 groups. The densities of CaCO3-III (2.99 g/cm3 at 2.8 GPa) and CaCO3-IIIb (2.96 g/cm3 at 3.1 GPa) are lower than aragonite, in agreement with the currently accepted view of aragonite as the thermodynamically stable Ca-carbonate phase at these pressures. The presence of different cation sites, with variable volume and coordination number (7-9), suggests however that these structures have the potential to accommodate cations with different sizes without introducing major structural strain. Indeed, this structure can be adopted by natural Ca-rich carbonates, which often exhibit compositions deviating from pure calcite. Mg-calcites are found both in nature (Frezzotti et al., 2011) and in experimental syntheses at conditions corresponding to deep subduction environments (Poli et al., 2009). At these conditions, the low pressure rhombohedral calcite structure is most unlikely to be stable, and, at the same

  11. Protein encapsulation via porous CaCO3 microparticles templating.

    Science.gov (United States)

    Volodkin, Dmitry V; Larionova, Natalia I; Sukhorukov, Gleb B

    2004-01-01

    Porous microparticles of calcium carbonate with an average diameter of 4.75 microm were prepared and used for protein encapsulation in polymer-filled microcapsules by means of electrostatic layer-by-layer assembly (ELbL). Loading of macromolecules in porous CaCO3 particles is affected by their molecular weight due to diffusion-limited permeation inside the particles and also by the affinity to the carbonate surface. Adsorption of various proteins and dextran was examined as a function of pH and was found to be dependent both on the charge of the microparticles and macromolecules. The electrostatic effect was shown to govern this interaction. This paper discusses the factors which can influence the adsorption capacity of proteins. A new way of protein encapsulation in polyelectrolyte microcapsules is proposed exploiting the porous, biocompatible, and decomposable microparticles from CaCO3. It consists of protein adsorption in the pores of the microparticles followed by ELbL of oppositely charged polyelectrolytes and further core dissolution. This resulted in formation of polyelectrolyte-filled capsules with protein incorporated in interpenetrating polyelectrolyte network. The properties of CaCO3 microparticles and capsules prepared were characterized by scanning electron microscopy, microelectrophoresis, and confocal laser scanning microscopy. Lactalbumin was encapsulated by means of the proposed technique yielding a content of 0.6 pg protein per microcapsule. Horseradish peroxidase saves 37% of activity after encapsulation. However, the thermostability of the enzyme was improved by encapsulation. The results demonstrate that porous CaCO3 microparticles can be applied as microtemplates for encapsulation of proteins into polyelectrolyte capsules at neutral pH as an optimal medium for a variety of bioactive material, which can also be encapsulated by the proposed method. Microcapsules filled with encapsulated material may find applications in the field of biotechnology, biochemistry, and medicine.

  12. Adsorption and Desorption Characteristics of Cd2+ and Pb2+ by Micro and Nano-sized Biogenic CaCO3

    Science.gov (United States)

    Liu, Renlu; Guan, Yong; Chen, Liang; Lian, Bin

    2018-01-01

    The purpose of this study was to elucidate the characteristics and mechanisms of adsorption and desorption for heavy metals by micro and nano-sized biogenic CaCO3 induced by Bacillus subtilis, and the pH effect on adsorption was investigated. The results showed that the adsorption characteristics of Cd2+ and Pb2+ are well described by the Langmuir adsorption isothermal equation, and the maximum adsorption amounts for Cd2+ and Pb2+ were 94.340 and 416.667 mg/g, respectively. The maximum removal efficiencies were 97% for Cd2+, 100% for Pb2+, and the desorption rate was smaller than 3%. Further experiments revealed that the biogenic CaCO3 could maintain its high adsorption capability for heavy metals within wide pH ranges (3–8). The FTIR and XRD results showed that, after the biogenic CaCO3 adsorbed Cd2+ or Pb2+, it did not produce a new phase, which indicated that biogenic CaCO3 and heavy metal ions were governed by a physical adsorption process, and the high adsorptive capacity of biogenic CaCO3 for Cd2+ and Pb2+ were mainly attributed to its large total specific surface area. The findings could improve the state of knowledge about biogenic CaCO3 formation in the environment and its potential roles in the biogeochemical cycles of heavy metals. PMID:29434577

  13. Combination of adsorption by porous CaCO3 microparticles and encapsulation by polyelectrolyte multilayer films for sustained drug delivery.

    Science.gov (United States)

    Wang, Chaoyang; He, Chengyi; Tong, Zhen; Liu, Xinxing; Ren, Biye; Zeng, Fang

    2006-02-03

    Combination of adsorption by porous CaCO(3) microparticles and encapsulation by polyelectrolyte multilayers via the layer-by-layer (LbL) self-assembly was proposed for sustained drug release. Firstly, porous calcium carbonate microparticles with an average diameter of 5 microm were prepared for loading a model drug, ibuprofen (IBU). Adsorption of IBU into the pores was characterized by ultraviolet (UV), infrared (IR), thermogravimetric analysis (TGA), Brunauer-Emmett-Teller (BET) experiment and X-ray diffraction (XRD). The adsorbed IBU amount Gamma was 45.1mg/g for one-time adsorption and increased with increasing adsorption times. Finally, multilayer films of protamine sulfate (PRO) and sodium poly(styrene sulfonate) (PSS) were formed on the IBU-loaded CaCO(3) microparticles by the layer-by-layer self-assembly. Amorphous IBU loaded in the pores of the CaCO(3) microparticles had a rapider release in the gastric fluid and a slower release in the intestinal fluid, compared with the bare IBU crystals. Polyelectrolyte multilayers assembled on the drug-loaded particles by the LbL reduced the release rate in both fluids. In this work, polymer/inorganic hybrid core-shell microcapsules were fabricated for controlled release of poorly water-soluble drugs. The porous inorganic particles are useful to load drugs in amorphous state and the polyelectrolyte multilayer films coated on the particle assuage the initial burst release.

  14. Long-term sustainability of microbial-induced CaCO3 precipitation in aqueous media.

    Science.gov (United States)

    Gat, Daniella; Ronen, Zeev; Tsesarsky, Michael

    2017-10-01

    Microbially induced CaCO 3 precipitation (MICP) via urea hydrolysis is an emerging technique for soil amelioration, building materials rehabilitation and pollutants sequestration amongst other various environmental applications. The successful application of MICP requires the sustainability of the precipitated CaCO 3 ; to which the fate of ammonia, the main by-product of ureolysis, is potentially significante. Ammonia volatilization and biological ammonia oxidation both induce a pH decrease, which, in turn, might cause CaCO 3 dissolution. To examine the potential effect of accumulated ammonia on precipitated CaCO 3 , we conducted a long-term MICP batch experiment, using environmental enrichment cultures of ureolytic bacteria. Here we show that CaCO 3 precipitation was completed within 15-27 days, along with a rise in ammonium concentration. Following completion of ureolysis and precipitation, ammonium concentrations decreased, leading to a pH decrease. About 30 days after precipitation was completed, as much as 30% CaCO 3 dissolution, was observed. A two-step model, describing urea hydrolysis followed by the removal of ammonia from the precipitation solution, predicted CaCO 3 dissolution due to ammonia volatilization. We suggest that ureolytic MICP might result in ammonia volatilization, leading to significant CaCO 3 dissolution. These results provide basic insights into the sustainability of ureolytic MICP and should further encourage removal of the accumulated ammonia from the treated site. Copyright © 2017 Elsevier Ltd. All rights reserved.

  15. Efeitos de relações CaSO4/CaCO3 na mobilidade de nutrientes no solo e no crescimento do algodoeiro

    Directory of Open Access Journals (Sweden)

    A. A. Silva

    1998-09-01

    Full Text Available O experimento, realizado em casa de vegetação no Departamento de Ciência do Solo da Universidade Federal de Lavras, teve por objetivo estudar o efeito de diferentes relações de CaSO4/CaCO3, que simulam o uso de gesso e calcário, na movimentação de nutrientes no solo e no crescimento do algodoeiro, cultivar IAC-20. As proporções de CaSO4/CaCO3 utilizadas foram: 0/100, 25/75, 50/50, 75/25 e 100/0, com base em peso equivalente, além de um tratamento-testemunha, sem aplicação de CaSO4 e CaCO3. Observou-se acentuada movimentação de cálcio e de sulfato em profundidade, como íons acompanhantes, com o aumento da relação CaSO4/CaCO3. Para o N-NO3- e Mg2+, ao contrário do N-NH4+ e K+, observou-se um acúmulo em profundidade, com a elevação da relação CaSO4/CaCO3. Neste estudo, o gesso teve pouco ou nenhum efeito sobre a acidez e Al trocável presentes nas camadas subsuperficiais. A produção de matéria seca do algodoeiro foi reduzida com o aumento da relação CaSO4/CaCO3, porém, quando comparada à do tratamento-testemunha, a aplicação de gesso aumentou-a significativamente, atestando o potencial de uso do gesso agrícola.

  16. Why Do Organisms in the Atlantic Ocean Produce So Much CaCO3?

    Science.gov (United States)

    Toggweiler, J. R.

    2010-12-01

    Sediments in the Atlantic are richer in CaCO3 than sediments in the other oceans. Sediment trap observations show that sinking particles in the Atlantic also tend to have more CaCO3 in relation to organic carbon than sinking particles elsewhere. The reason for the extra production of CaCO3 has never been very clear. The Atlantic is unusual because it receives much more than its share of the global input of river water. River water adds alkalinity to the surface ocean while the production of CaCO3 takes it away. In this presentation a new tracer, called Alk*, is derived from the surface alkalinity distribution to highlight the impact of river inputs and the production of CaCO3. If the production of CaCO3 were evenly distributed across the ocean one would expect the Atlantic to have a higher level of Alk* becaused of its river inputs. We find instead that Alk* is lower in the middle of the Atlantic than almost any place else. This, of course, is consistent with the fact that organisms in the Atlantic produce a lot of CaCO3. Comparison with other areas with especially low values of Alk* (Red Sea and northern Arabian Sea) shows that the production of CaCO3 is highly correlated across the ocean with the surface salinity. Hence, we argue that organisms in the Atlantic produce a lot of CaCO3 simply because the Atlantic is so salty. Salty waters, by definition, have more CO3= ions, which increase the supersaturation with respect to calcite and aragonite. This finding, while extremely simple, has major implifications for the impact of ocean acidification on calcifying organisms.

  17. Surface morphology and molecular bonding of CaCO3 nanocrystallites by gas diffusion method

    Science.gov (United States)

    Sulimai, N. H.; Rani, Rozina Abdul; Khusaimi, Z.; Abdullah, S.; Salifairus, M. J.; Alrokayan, Salman; Khan, Haseeb; Rusop, M.

    2018-05-01

    Calcium carbonate with the chemical formula of (CaCO3) is the most abundant element in the world. Its usage on certain applications is largely affected by its properties. The best means to control its properties is through controlled preparation of CaCO3. This study uses diffusion method between the precursors Calcium Chloride and Ammonium Carbonate. Instead of using water, ethanol was used to prepare the salt. Reaction was done in room temperature (RT) for 6h-24h. Smallest average crystallite size measured by FESEM micrograph is 500nm produced by synthesis of CaCO3 reacted for 168 hours. From energy-dispersive X-ray spectrum also indicated the smallest particle size is by CaCO3 reacted for 168 hours. Changes was seen for element Ca at 3.7keV.

  18. PENGARUH PENAMBAHAN CaCO3 DAN WAKTU PENYIMPANAN TERHADAP KADAR VITAMIN C PADA PROSES PENGHAMBATAN PEMATANGAN BUAH TOMAT (Lycopersicum esculentum Mill

    Directory of Open Access Journals (Sweden)

    Rudi Kartika

    2016-02-01

    Full Text Available The aim of this research is to know the influence of CaCO3 addition and storage duration to vitamine C concentrate in ripe obstruction process of tomato (Lycopersicum esculentum Mill. Calcium carbonate(CaCO3 which is added 0; 0.2; 0.4; 0.6 and 0.8 percent of weight and storage duration were 0; 2; 4; 6; 8; 10 and 12 days. Vitamine C was determined by using iodometric titration method. The data obtained were then analized by ANOVA test and LSD test. The result showed that CaCO3 addition could influence vitamine C concentrate in ripe obstruction process of tomato (Lycopersicum esculentum Mill on standard 5% and 1% with  Ftest > Ftabel (5% and 1% or F(7.6667 > F(2.50 and 3.60 and storage duration could influence vitamine C concentrate in ripe obstruction process of tomato (Lycopersicum esculentum Mill on standard 5% and 1% with Ftest > Ftabel (5% and 1% or F(1204.2222 > F(2.32 and 3.07. Based on the result LSD test on significant standard 5% (0.0143 and 1% (0.0190, optimum vitamine C concentrate were 0.8589 mg/10 g on 0.2% of calcium carbonate (CaCO3 addition and 10 days of storage duration. Keywords : ANOVA, CaCO3, LSD, tomato, vitamine C, storage duration

  19. Magnetic Field Effects on CaCO3 Precipitation Process in Hard Water

    Directory of Open Access Journals (Sweden)

    Nelson Saksono

    2010-10-01

    Full Text Available Magnetic treatment is applied as physical water treatment for scale prevention especially CaCO3, from hard water in piping equipment by reducing its hardness.Na2CO3 and CaCl2 solution sample was used in to investigate the magnetic fields influence on the formation of particle of CaCO3. By changing the strength of magnetic fields, exposure time and concentration of samples solution, this study presents quantitative results of total scale deposit, total precipitated CaCO3 and morphology of the deposit. This research was run by comparing magnetically and non-magnetically treated  samples. The results showed an increase of deposits formation rate and total number of precipitated CaCO3 of magnetically treated samples. The increase of concentration solution sample will also raised the deposit under magnetic  field. Microscope images showed a greater number but smaller size of CaCO3 deposits form in magnetically treated samples, and aggregation during the processes. X-ray diffraction (XRD analysis showed that magnetically samples were dominated by calcite. But, there was a significant decrease of calcite’s peak intensities from magnetized  samples that indicated the decrease of the amount of calcite and an increase of total amorphous of deposits. This result  showed that magnetization of hard water leaded to the decreasing of ion Ca2+ due to the increasing of total CaCO3 precipitation process.

  20. Effects of Calcium Source on Biochemical Properties of Microbial CaCO3 Precipitation.

    Science.gov (United States)

    Xu, Jing; Du, Yali; Jiang, Zhengwu; She, Anming

    2015-01-01

    The biochemical properties of CaCO3 precipitation induced by Sporosarcina pasteurii, an ureolytic type microorganism, were investigated. Effects of calcium source on the precipitation process were examined, since calcium source plays a key role in microbiologically induced mineralization. Regardless of the calcium source type, three distinct stages in the precipitation process were identified by Ca(2+), NH4 (+), pH and cell density monitoring. Compared with stage 1 and 3, stage 2 was considered as the most critical part since biotic CaCO3 precipitation occurs during this stage. Kinetics studies showed that the microbial CaCO3 precipitation rate for calcium lactate was over twice of that for calcium nitrate, indicating that calcium lactate is more beneficial for the cell activity, which in turn determines urease production and CaCO3 precipitation. X-ray diffraction analysis confirmed the CaCO3 crystal as calcite, although scanning electron microscopy revealed a difference in crystal size and morphology if calcium source was different. The findings of this paper further suggest a promising application of microbiologically induced CaCO3 precipitation in remediation of surface and cracks of porous media, e.g., cement-based composites, particularly by using organic source of calcium lactate.

  1. Cation exchange and CaCO 3 dissolution during artificial recharge of effluent to a calcareous sandstone aquifer

    Science.gov (United States)

    Goren, Orly; Gavrieli, Ittai; Burg, Avihu; Lazar, Boaz

    2011-03-01

    SummaryThis research describes a field study and laboratory simulations of the geochemical evolution of groundwater following a recharge of effluent into aquifers. The study was conducted in the soil aquifer treatment (SAT) system of the Shafdan sewage reclamation plant, Israel. The SAT system recharges secondary effluent into the calcareous sandstone sediments of the Israeli Coastal Aquifer as a tertiary treatment. The reclaimed effluent is recovered ca. 500 m off the recharge basin and is used for unlimited irrigation. The laboratory simulations in which effluent was pumped through experimental columns packed with pristine Shafdan sediment showed that the chemical composition of the outflowing water was controlled mainly by cation exchange and CaCO 3 dissolution. Na +, K + and Mg 2+ were adsorbed and Ca 2+ was desorbed during the initial stage of recharge. The equilibrium distribution of the adsorbed cations was: Ca 2+ ˜ 60%, Mg 2+ ˜ 20%, and Na + and K + ˜ 10% each. The Ca 2+ in the Shafdan production wells and in the experimental columns outflow (˜5 meq L -1) was always higher than the Ca 2+ in the recharged effluent (˜3.5 meq L -1), indicating continuous CaCO 3 dissolution. This study demonstrates that besides mixing, a suite of geochemical processes should be considered when assessing groundwater quality following artificial recharge of aquifers.

  2. Synthesis and characterization of nano-sized CaCO3 in purified diet

    Science.gov (United States)

    Mulyaningsih, N. N.; Tresnasari, D. R.; Ramahwati, M. R.; Juwono, A. L.; Soejoko, D. S.; Astuti, D. A.

    2017-07-01

    The growth and development of animals depend strongly on the balanced nutrition in the diet. This research aims is to characterize the weight variations of nano-sized calcium carbonate (CaCO3) in purified diet that to be fed to animal model of rat. The nano-sized CaCO3 was prepared by milling the calcium carbonate particles for 20 hours at a rotation speed of 1000 rpm and resulting particle size in a range of 2-50 nm. Nano-sized CaCO3 added to purified diet to the four formulas that were identified as normal diet (N), deficiency calcium (DC), rich in calcium (RC), and poor calcium (PC) with containing in nano-sized CaCO3 much as 0.50 %, 0.00 %, 0.75 % and 0.25 % respectively. The nutritional content of the purified diet was proximate analyzed, it resulted as followed moisture, ash, fat, protein, crude fiber. The quantities of chemical element were analyzed by atomic absorption spectrometry (AAS), it resulted iron, magnesium, potassium and calcium. The results showed that N diet (Ca: 16,914.29 ppm) were suggested for healthy rats and RC diet (Ca: 33,696.13 ppm) for conditioned osteoporosis rats. The crystalline phases of the samples that were examined by X-ray diffraction showed that crystalline phase increased with the increasing concentration of CaCO3.

  3. Characterization of Corn Starch Films Reinforced with CaCO3 Nanoparticles

    Science.gov (United States)

    Sun, Qingjie; Xi, Tingting; Li, Ying; Xiong, Liu

    2014-01-01

    The characterization of corn starch (CS) films impregnated with CaCO3 nanoparticles was investigated. Criteria such as morphology, crystallinity, water vapor permeability (WVP), opacity, and mechanical properties were the focus of the investigation. It was found that the CaCO3 contents had significant effects on the tensile properties of the nanocomposite films. The addition of CaCO3 nanoparticles to the CS films significantly increased tensile strength from 1.40 to 2.24 MPa, elongation from 79.21 to 118.98%, and Young’s modulus from 1.82 to 2.41 MPa. The incorporation of CaCO3 nanoparticles increased the opacity of films, lowered the degree of WVP and film solubility value compared to those of the CS films. The results of scanning electron microscopy (SEM) showed that with the increase of CaCO3 nanoparticles content in starch films, the roughness of the films increased, and pores or cavities were found on the surface of the films, while small cracks were observed in the structures of the fractured surfaces. X-ray diffraction showed that the addition of nanoparticles increased the peaks in the intensity of films. PMID:25188503

  4. Enzyme-assisted growth of nacreous CaCO3/polymer hybrid nanolaminates via the formation of mineral bridges

    Science.gov (United States)

    Yeom, Bongjun; Char, Kookheon

    2016-06-01

    Laminated nanostructures in nacre have been adopted as models in the fabrication of strong, tough synthetic nanocomposites. However, the utilization of CaCO3 biominerals in these composites is limited by the complexity of the synthesis method for nanosized biominerals. In this study, we use the enzymatic reaction of urease to generate a nanoscale CaCO3 thin film to prepare CaCO3/polymer hybrid nanolaminates. Additional layers of CaCO3 thin film are consecutively grown over the base CaCO3 layer with the intercalation of organic layers. The morphology and crystallinity of the added CaCO3 layers depend strongly on the thickness of the organic layer coated on the underlying CaCO3 layer. When the organic layer is less than 20 nm thick, the amorphous CaCO3 layer is spontaneously transformed into crystalline calcite layer during the growth process. We also observe crystalline continuity between adjacent CaCO3 layers through interconnecting mineral bridges. The formation of these mineral bridges is crucial to the epitaxial growth of CaCO3 layers, similar to the formation of natural nacre.

  5. Nucleation of metastable aragonite CaCO3 in seawater.

    Science.gov (United States)

    Sun, Wenhao; Jayaraman, Saivenkataraman; Chen, Wei; Persson, Kristin A; Ceder, Gerbrand

    2015-03-17

    Predicting the conditions in which a compound adopts a metastable structure when it crystallizes out of solution is an unsolved and fundamental problem in materials synthesis, and one which, if understood and harnessed, could enable the rational design of synthesis pathways toward or away from metastable structures. Crystallization of metastable phases is particularly accessible via low-temperature solution-based routes, such as chimie douce and hydrothermal synthesis, but although the chemistry of the solution plays a crucial role in governing which polymorph forms, how it does so is poorly understood. Here, we demonstrate an ab initio technique to quantify thermodynamic parameters of surfaces and bulks in equilibrium with an aqueous environment, enabling the calculation of nucleation barriers of competing polymorphs as a function of solution chemistry, thereby predicting the solution conditions governing polymorph selection. We apply this approach to resolve the long-standing "calcite-aragonite problem"--the observation that calcium carbonate precipitates as the metastable aragonite polymorph in marine environments, rather than the stable phase calcite--which is of tremendous relevance to biomineralization, carbon sequestration, paleogeochemistry, and the vulnerability of marine life to ocean acidification. We identify a direct relationship between the calcite surface energy and solution Mg:Ca [corrected] ion concentrations, showing that the calcite nucleation barrier surpasses that of metastable aragonite in solutions with Mg:Ca ratios consistent with modern seawater, allowing aragonite to dominate the kinetics of nucleation. Our ability to quantify how solution parameters distinguish between polymorphs marks an important step toward the ab initio prediction of materials synthesis pathways in solution.

  6. A new crystal growth form of vaterite, CaCO3

    International Nuclear Information System (INIS)

    Shaikh, A.M.

    1990-01-01

    Microcrystalline vaterite, CaCO 3 , has been synthesized by decomposition of ikaite, CaCO 3 .6H 2 O, crystals at room temperature. Scanning electron micrographs show that vaterite occurs as arborescent aggregates ≅30 to 40 μm in size. This growth form has not been described before. It is of interest that the overall morphology of the vaterite is reminiscent of some dendritic calcite tufas, although on a smaller scale. This similarity opens up the possibility that the calcitic tufas such as that associated with the Quaternary Lake Lahonton, Nevada, may have been deposited as vaterite that changed to calcite, while preserving the original growth form. (orig.)

  7. CaCO3 nanoparticle synthesis by carbonation of lime solution in microemulsion systems

    NARCIS (Netherlands)

    Sugih, A.K.; Shukla, D.; Heeres, H.J.; Mehra, A.

    2007-01-01

    Various aspects of nanoparticle precipitation in gas-reverse micellar systems have been studied. The experimental system chosen for investigation deals with the precipitation of CaCO3 nanoparticles. The effect of operating variables, such as water-to-surfactant molar ratio, different continuous

  8. Comparative effects of commercial lime (CaCO 3 ) and ground ...

    African Journals Online (AJOL)

    Greenhouse study was carried out to investigate the comparative effect of commercial lime (CaCO3) and ground eggshell on the uptake of calcium and dry matter yield of maize in an ultisol of Southeastern Nigeria using maize (variety Oba supper 92) as the test crop. The soil was acidic and deficient in N, O.C., K, Ca and ...

  9. Assembly of multilayer microcapsules on CacO3 particles from biocompatible polysaccharides.

    Science.gov (United States)

    Zhao, Qinghe; Mao, Zhengwei; Gao, Changyou; Shen, Jiacong

    2006-01-01

    Multilayer microcapsules were fabricated by layer-by-layer (LbL) assembly of natural polysaccharides onto CaCO3 particles, following with core removal. The micron-sized CaCO3 particles were synthesized by reaction between Ca(NO3)2 and Na2CO3 solutions in the existence of carboxylmethyl cellulose (CMC). The incorporated amount of CMC in the CaCO3 particles was found to be 5.3 wt% by thermogravimetric analysis. Two biocompatible polysaccharides, chitosan and sodium alginate were alternately deposited onto the CaCO3(CMC) templates to obtain hollow microcapsules. Regular oscillation of surface charge as detected by zeta potential demonstrated that the assembly proceeded surely in a LbL manner. The stability of the microcapsules was effectively improved by cross-linking of chitosan with glutaraldehyde. The chemical reaction was verified by infrared spectroscopy. The microcapsules thus fabricated could be spontaneously filled with positively charged low molecular weight substances such as rhodamine 6G and showed good biocompatibility, as detected by in vitro cell culture.

  10. Impact of location of CaCO3 precipitation on the development of intact anaerobic sludge

    NARCIS (Netherlands)

    Langerak, van E.P.A.; Ramaekers, H.; Wiechers, J.; Veeken, A.H.M.; Hamelers, H.V.M.; Lettinga, G.

    2000-01-01

    The development of intact anaerobic granular sludge was studied in UASB reactors under varying conditions of CaCO3 precipitation and biomass yield. Varying precipitating quantities were obtained using different calcium concentrations in the influent and different biomass yields were obtained by

  11. Effect of ball-milling to the surface morphology of CaCO3

    Science.gov (United States)

    Sulimai, N. H.; Rani, Rozina Abdul; Khusaimi, Z.; Abdullah, S.; Salifairus, M. J.; Alrokayan, Salman; Khan, Haseeb; Rusop, M.

    2018-05-01

    Calcium Carbonate can be synthesized in many approaches. This work studied on the physical changes to Calcium Carbonate (CaCO3) by ball-milling activity in different parameters; number of ball; collision duration; revolution per minute (RPM). Zirconia balls were used in the work because it has the best durability to withstand ball-milling conditions set. Industrial grade CaCO3 particles that were run in aforementioned parameters were characterized by Field Emission Scanning Electron Microscope (FE-SEM) to study the physical changes on the size and surface of the CaCO3. They were also characterized with Fourier Transform Infra-red Spectroscopy (FTIR) were fingerprint of CaCO3 regions were identified and any changes in the band position and intensity were discussed. Number of Zirconia balls and collision duration is directly proportional to the absorbance intensity whereas it is inversely proportional for the rpm. The best number of parameters producing the highest Absorbance is 100 Zirconia balls in duration of 1 hour and 100rpm.

  12. First-principles calculation of adsorption of shale gas on CaCO3 (100) surfaces.

    Science.gov (United States)

    Luo, Qiang; Pan, Yikun; Guo, Ping; Wang, Zhouhua; Wei, Na; Sun, Pengfei; Liu, Yuxiao

    2017-06-16

    To demonstrate the adsorption strength of shale gas to calcium carbonate in shale matrix, the adsorption of shale gas on CaCO3 (100) surfaces was studied using the first-principles method, which is based on the density functional theory (DFT). The structures and electronic properties of CH4, C2H6, CO2 and N2 molecules were calculated by the generalized gradient approximation (GGA), for a coverage of 1 monolayer (ML). Under the same conditions, the density of states (DOS) of CaCO3 (100) surfaces before and after the adsorption of shale gas molecules at high-symmetry adsorption sites were compared. The results showed that the adsorption energies of CH4, C2H6, CO2 and N2 on CaCO3 (100) surfaces were between 0.2683 eV and -0.7388 eV. When a CH4 molecule was adsorbed at a hollow site and its 2 hydrogen atoms were parallel to the long diagonal (H3) on the CaCO3 (100) surface, it had the most stable adsorption, and the adsorption energy was only -0.4160 eV. The change of adsorption energy of CH4 was no more than 0.0535 eV. Compared with the DOS distribution of CH4 before adsorption, it shifted to the left overall after adsorption. At the same time, the partial density of states (PDOS) curves of CaCO3 (100) surfaces before and after adsorption basically overlapped. This work showed that the adsorption effect of shale gas on calcium carbonate is very weak, and the adsorption is physisorption at the molecular level.

  13. An alternative model for CaCO3 over-shooting during the PETM : Biological carbonate compensation

    NARCIS (Netherlands)

    Luo, Yiming; Boudreau, Bernard P.; Dickens, Gerald R.; Sluijs, Appy; Middelburg, Jack J.

    2016-01-01

    Decreased CaCO3 content of deep-sea sediments argues for rapid and massive acidification of the oceans during the Paleocene–Eocene Thermal Maximum (PETM, ∼56 Ma BP). In the course of the subsequent recovery from this acidification, sediment CaCO3 content came to exceed pre-PETM levels, known as

  14. Changes in CaCO3 Burial Trump the Biological Pump

    Science.gov (United States)

    Toggweiler, J.; Dunne, J. P.

    2008-12-01

    The dramatic increases in atmospheric CO2 at the ends of ice ages are usually attributed to a one-two punch coming from the ocean. First, a weakened biological pump vents organically cycled CO2 from the deep ocean via changes in the ventilation of the deep ocean around Antarctica. The initial CO2 increase is then augmented by an enhancement of CaCO3 burial due to a process called CaCO3 compensation (after Broecker, W. S and T.-H. Peng, Global Biogeochem. Cycles, 1, 15-29, 1987). Here, we argue that the importance of the biological pump has been exaggerated. The main effect comes from circulation-induced changes in the burial of CaCO3. As shown in a recent paper by Andreas Schmittner and co-authors (Schmittner, A., E. Brook and J. Ahn, Impact of the ocean's overturning circulation on atmospheric CO2, in Ocean Circulation: Mechanisms and Impacts, Geophys. Monogr. 173, A. Schmittner, J. Chiang, and S. Hemming, eds., pp. 209-246, AGU, 2007) changes in the ventilation of the deep ocean around Antarctica gave rise to 20-30 ppm increases in atmospheric CO2 every 5,000-7,000 years during isotope stages 3 and 4 (30,000 to 70,000 years ago). None of these venting events gave rise to a compensation response. Meanwhile, Jaccard et al. (Science, 308, 1003-1006, 2005) show that all the big CO2 increases during terminations through stage 11 were accompanied by huge increases in CaCO3 burial. This suggests that the enhanced burial of CaCO3 is obligatory rather than compensatory with respect to the dramatic CO2 increases. Broecker and Peng's compensation idea is based on an assumption that the rain of CaCO3 to the sea floor is the same everywhere. More specifically, it assumes that there is no spatial correlation between the production of CaCO3 at the surface and the burial on the sea floor. We find instead that the production and burial of CaCO3 tend to be co-located in regional "hot spots" and that burial in the hot spots balances the input of Ca++ and HCO3- ions in rivers. The hot spots can also move from place to place in response to changes in circulation. The main hot spots today are the eastern Atlantic and southern Indian; the main hot spot during the last glacial was the equatorial Pacific. Renewed deep-water formation in the Atlantic at the end of the last ice age shifted the locus of CaCO3 burial back to the Atlantic and southern Indian and led to a huge drawdown in global alkalinity, which is ongoing today and accounts for most of the deglacial rise in atmospheric CO2.

  15. Fabrication of superhydrophobic surfaces via CaCO3 mineralization mediated by poly(glutamic acid)

    Science.gov (United States)

    Cao, Heng; Yao, Jinrong; Shao, Zhengzhong

    2013-03-01

    Surfaces with micrometer and nanometer sized hierarchical structures were fabricated by an one-step in situ additive controlled CaCO3 mineralization method. After chemical modification, the surfaces with various morphologies showed superhydrophobicity in different states, which could be easily adjusted by the initial supersaturation of the mineralization solution (concentration of calcium ion and poly(glutamic acid)). Generally, the "lotus state" surface which was covered by a thick layer of tetrahedron-shaped CaCO3 particles to exhibit a contact angle (CA) of 157±1° and a very low contact angle hysteresis (CAH) (roll-off angle=1°) was produced under high supersaturation. On the other hands, the petal-like surface with flower-shaped calcite spherulites was obtained in a relative low supersaturation, which showed both high CA (156±2°) and CAH (180°) in a "Cassie impregnating wetting state".

  16. Enhancing the Durability of Calcareous Stone Monuments of Ancient Egypt Using CaCO3 Nanoparticles

    Directory of Open Access Journals (Sweden)

    Mohammad A. Aldoasri

    2017-08-01

    Full Text Available The unwanted changes in valuable historic calcareous stone monuments due to exposure to many physical and chemical effects may lead to its deterioration. The growing interest in the field of conservation of stone monuments encourages the development of consolidation and water-repellent materials. The aim of this study is to evaluate the effectiveness of CaCO3 nanoparticles as a consolidation and protection material for calcareous stone monuments, when those nanoparticles used are dispersed in acrylic copolymer; polyethylmethacrylate (EMA/methylacrylate (MA (70/30, respectively. Samples were subjected to artificial aging by relative humidity/temperature to show the optimum conditions of durability and the effectiveness of the nano-mixture in improving the physical and mechanical properties of the stone material. The synthesis process of CaCO3 nanoparticles/polymer nanocomposite has been prepared by in situ emulsion polymerization system. The prepared nanocomposites with 0.15 g CaCO3 nanoparticles showed obvious transparency features and represent nanocomposites coating technology with hydrophobic, consolidating and good protection properties. Some tests were performed in order to estimate the superficial consolidating and protective effect of the treatment. The obtained nanocomposites have been characterized by TEM, while the surface morphology before and after treatment and homogeneous distribution of used consolidation materials on stone surface were examined by SEM. Improvement of stone mechanical properties was evaluated by compressive strength tests. Change in water-interaction properties was evaluated by water absorption capillarity measurements, and colorimetric measurements were used to evaluate the optical appearance. Taken together, the results indicate that CaCO3/polymer nanocomposite is a completely compatible, efficient material for the consolidation of artistic and architectural limestone monuments capable of enhancing the durability of limestone toward artificial aging and improving the stone mechanical properties compared to the samples treated with pure acrylic copolymer without Calcium carbonate nanoparticles.

  17. Crystal growth of carbonate apatite using a CaCO3 flux.

    Science.gov (United States)

    Suetsugu, Y; Tanaka, J

    1999-09-01

    Single crystals of carbonate apatite were grown using a CaCO3 flux under an Ar gas pressure of 55 MPa. The crystals obtained were observed by scanning electron microscopy, optical microscopy and X-ray diffraction. Electron probe microanalyses and thermal analyses were performed. CO3 ions in planar triangle form replaced both OH sites and PO4 tetrahedral sites in the apatite structure: in particular, the OH sites were perfectly substituted by CO3 ions using this method.

  18. Morphology and Kinetics of Growth of CaCO3 Precipitates Formed in Saline Water at 30°C

    Science.gov (United States)

    Sui, Xin; Wang, Baohui; Wu, Haiming

    2018-02-01

    The crystallization kinetics and morphology of CaCO3 crystals precipitated from the high salinity oilfield water were studied. The crystallization kinetics measurements show that nucleation and nuclei growth obey the first order reaction kinetics. The induction period of precipitation is extended in the high salinity solutions. Morphological studies show that impurity ions remain mostly in the solution phase instead of filling the CaCO3 crystal lattice. The morphology of CaCO3 precipitates can be changed from a smooth surface (calcite) to rough spheres (vaterite), and spindle rod bundles, or spherical, ellipsoid, flowers, plates and other shapes (aragonite).

  19. Pengaruh Kombinasi Senyawa Humik dan CaCO3 terhadap Alumunium dan Fosfat Typic Paleudult Kentrong Banten

    Directory of Open Access Journals (Sweden)

    Sugeng Winarso

    2009-05-01

    Full Text Available Decomposition of organic matter releases humic compounds, that can chelate metals include Al in acidic soils. This chelation of Al is important for decreasing of Al activity and P fixation in acidic soils. This study was aimed to test the effect of humic compounds extracted from rice-straw compost and CaCO3 combination on aluminium activity and phosphate (available P on an Ultisol (Typic Paleudult collected from Kentrong Banten. A laboratory study was conducted by series consentration of CaCO3 (0, 500, 1.000, 2.000, dan 3.000 ppm in 8 grams of acidic soil. The acidic soil had previously been subjected to continuously addition of humic compounds and none. Then, these mix of soil and CaCO3 were added 40 ml contained 5.000 ppm humic compounds to obtain 1:5 soil:suspension ratio and control was made by using aquadest. They were shaked for 2 hours every day and pH was measured. At 11st days incubation Alexch (N KCl and soluble of P (PB and PC were measured. The results showed that liming or addition of CaCO3 to the acidic soils decreased Alexch (precipitated to be Al(OH3 linearly with formula y = -0.778x + 6.108; y = Alexch (Cmol kg-1, x = CaCO3 (M; R² = 0,916. Combination addition of humic compounds and CaCO3 was able to increase pH and Alexch up to not detected. The increased of P-soluble or desorption P untill 384% took place at addition of 0.0016 M CaCO3 and 5000 ppm humic compounds. More desorption of P was observed if the acidic soils has previously been subjected to continuously addition of humic compounds, such us the increased of soluble P up to 739% at addition of CaCO3 0.0008 M.

  20. Potential influence of sea cucumbers on coral reef CaCO3 budget: A case study at One Tree Reef

    Science.gov (United States)

    Schneider, Kenneth; Silverman, Jacob; Woolsey, Erika; Eriksson, Hampus; Byrne, Maria; Caldeira, Ken

    2011-12-01

    To endure, coral reefs must accumulate CaCO3 at a rate greater or equal than the sum of mechanically, biologically, and chemically mediated erosion rates. We investigated the potential role of holothurians on the CaCO3 balance of a coral reef. These deposit feeders process carbonate sand and rubble through their digestive tract and dissolve CaCO3 as part of their digestive process. In aquarium incubations with Stichopus herrmanni and Holothuria leucospilota total alkalinity increased by 97 ± 13 and 47 ± 7 μmol kg-1, respectively. This increase was due to CaCO3 dissolution, 81 ± 13 and 34 ± 6 μmol kg-1 and ammonia secretion, 16 ± 2 and 14 ± 2μmol kg-1, respectively, for these species. Surveys conducted at a long-term monitoring site of community calcification (DK13) on One Tree Reef indicated that the density of sea cucumbers was approximately 1 individual m-2. We used these data and data from surveys at Shark Alley to estimate the dissolution of CaCO3 by the sea cucumbers at both sites. At DK13 the sea cucumber population was estimated to be responsible for nearly 50% of the nighttime CaCO3 dissolution, while in Shark Alley for most of the nighttime dissolution. Thus, in a healthy reef, bioeroders dissolution of CaCO3 sediment appears to be an important component of the natural CaCO3 turnover and a substantial source of alkalinity as well. This additional alkalinity could partially buffer changes in seawater pH associated with increasing atmospheric CO2 locally, thus reducing the impact of ocean acidification on coral growth.

  1. The fate of pelagic CaCO3 production in a high CO2 ocean: a model study

    Directory of Open Access Journals (Sweden)

    C. Ethe

    2007-07-01

    Full Text Available This model study addresses the change in pelagic calcium carbonate production (CaCO3, as calcite in the model and dissolution in response to rising atmospheric CO2. The parameterization of CaCO3 production includes a dependency on the saturation state of seawater with respect to calcite. It was derived from laboratory and mesocosm studies on particulate organic and inorganic carbon production in Emiliania huxleyi as a function of pCO2. The model predicts values of CaCO3 production and dissolution in line with recent estimates. The effect of rising pCO2 on CaCO3 production and dissolution was quantified by means of model simulations forced with atmospheric CO2 increasing at a rate of 1% per year from 286 ppm to 1144 ppm over a 140 year time-period. The simulation predicts a decrease of CaCO3 production by 27%. The combined change in production and dissolution of CaCO3 yields an excess uptake of CO2 from the atmosphere by the ocean of 5.9 GtC over the period of 140 years.

  2. Effects of CaCO3 treatment on the morphology, crystallinity, rheology and hydrolysis of gelatinized maize starch dispersions.

    Science.gov (United States)

    Garcia-Diaz, S; Hernandez-Jaimes, C; Escalona-Buendia, H B; Bello-Perez, L A; Vernon-Carter, E J; Alvarez-Ramirez, J

    2016-09-15

    Using calcium salts instead of lime allows for an ecological nixtamalization of maize grains, where the negative contamination impact of the traditional lime nixtamalization is reduced. This work assessed the effects of calcium carbonate (0.0-2.0%w/w CaCO3) on the morphology, crystallinity, rheology and hydrolysis of gelatinized maize starch dispersions (GMSD). Microscopy analysis showed that CaCO3 changed the morphology of insoluble remnants (ghosts) and decreased the degree of syneresis. Analysis of particle size distribution showed a slight shift to smaller sizes as the CaCO3 was increased. Also, X-ray patterns indicated that crystallinity achieved a minimum value at CaCO3 concentration in the range of 1%w/w. GMSD with higher CaCO3 concentrations exhibited higher thixotropy area and complex viscoelastic behavior that was frequency dependent. A possible mechanism involved in the starch chain modification by CaCO3 is that starch may act as a weak acid ion exchanger capable of exchanging alcoholic group protons for cations (Ca(+2)). Copyright © 2016 Elsevier Ltd. All rights reserved.

  3. Protein-assisted synthesis of double-shelled CaCO3 microcapsules and their mineralization with heavy metal ions.

    Science.gov (United States)

    Li, Xuan Qi; Feng, Zhiwei; Xia, Yinyan; Zeng, Hua Chun

    2012-02-13

    Calcium carbonate (CaCO(3)) is one of the most abundant and important biominerals in nature. Due to its biocompatibility, biodegradability and nontoxicity, CaCO(3) has been investigated extensively in recent years for various fundamental properties and technological applications. Inspired by basic wall structures of cells, we report a protein-assisted approach to synthesize CaCO(3) into a double-shelled structural configuration. Due to varying reactivities of outer and inner shells, the CaCO(3) microcapsules exhibit different sorption capacities and various resultant structures toward different kinds of heavy metal ions, analogical to biologically controlled mineralization (BCM) processes. Surprisingly, three mineralization modes resembling those found in BCM were found with these bacterium-like "CaCO(3) cells". Our investigation of the cytotoxicity (MTT assay protocol) also indicates that the CaCO(3) microcapsules have almost no cytotoxicity against HepG2 cells, and they might be useful for future application of detoxifying heavy metal ions after further study. Copyright © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  4. Control of colloidal CaCO3 suspension by using biodegradable polymers during fabrication

    Directory of Open Access Journals (Sweden)

    Nemany Abdelhamid Nemany Hanafy

    2015-03-01

    The aim of this work was to investigate the synthesis process of CaCO3 particles in different experimental conditions: calcium carbonate was produced in presence and in absence of water and with addition of appropriate polymers. In particular, chitosan (CHI and poly acrylic acid (PAA were chosen as biodegradable polymers whereas PSS and PAH were chosen as non-biodegradable polymers. Shape and diameter of particles were investigated by using transmission and scanning electron microscopy, elemental composition was inferred by energy dispersive X-ray analyses whereas their charges were explored by using zeta potential.

  5. Comparative study on the adsorption of Co2+ on CaCO3 compounds used as adsorbents

    International Nuclear Information System (INIS)

    De Jesus V, S.

    2014-01-01

    The calcium carbonate (CaCO 3 ) was synthesized by methods of precipitation, calcination, sol-gel and trigonal/sol-gel. These materials were characterized by the techniques of X-ray diffraction, scanning electron microscopy, energy dispersive X-ray spectroscopy, infrared spectroscopy and N 2 physisorption measurements in order to identify their textural, surface and structural properties. The results show that the material synthesized by sol-gel had the highest surface area of 39.5230 m 2 /g, and a total pore volume of 0.0484 m 3 /g and a pore diameter of 4.9050 nm. The synthesized materials were used to comparatively study their adsorption capacity of Co 2+ ions present in aqueous solutions, by experiments batch or batch type at an ambient temperature (25 grades C) and to 4 hours, balance time established previously under an adsorption kinetic study. They found as maximum adsorption capacities of Co 2+ in materials of 1.8582 mg/g for the calcium carbonate obtained by precipitation, of 0.8586 mg/g for the material obtained by calcining, of 3.1895 mg/g for the material obtained by sol-gel and finally of 2.5783 mg/g for the material obtained by the trigonal/sol-gel method, therefore it follows that the material having the highest adsorption capacity of Co 2+ ions was synthesized by the sol-gel method, because it showed better surface, textural and structural properties compared to other materials studied. (Author)

  6. CaCO3 dissolution by holothurians (sea cucumber): a case study from One Tree Reef, Great Barrier Reef

    Science.gov (United States)

    Schneider, K.; Silverman, J.; Kravitz, B.; Woolsey, E.; Eriksson, H.; Schneider-Mor, A.; Barbosa, S.; Rivlin, T.; Byrne, M.; Caldeira, K.

    2012-12-01

    Holothurians (sea cucumbers) are among the largest and most important deposit feeder in coral reefs. They play a role in nutrient and CaCO3 cycling within the reef structure. As a result of their digestive process they secrete alkalinity due to CaCO3 dissolution and organic matter degradation forming CO2 and ammonium. In a survey at station DK13 on One Three Reef we found that the population density of holothurians was > 1 individual m-2. The dominant sea cucumber species Holothuria leucospilota was collected from DK13. The increase in alkalinity due to CaCO3 dissolution in aquaria incubations was measured to be 47±7 μmol kg-1 in average per individual. Combining this dissolution rate with the sea cucumbers concentrations at DK13 suggest that they may account for a dissolution rate of 34.9±17.8 mmol m-2 day-1, which is equivalent to about half of night time community dissolution measured in DK13. This indicates that in reefs where the sea cucumber population is healthy and protected from fishing they can be locally important in the CaCO3 cycle. Preliminary result suggests that the CaCO3 dissolution rates are not affected by the chemistry of the sea water they are incubated in. Measurements of the empty digestive track volume of two sea cucumbers H. atra and Stichopus herrmanni were 36 ± 4 ml and 151 ± 14 ml, respectively. Based on these measurements it is estimated that these species process 19 ± 2kg and 80 ± 7kg CaCO3 sand yr-1 per individual, respectively. The annual dissolution rates of H. atra and S. herrmanni are 6.5±1.9g and 9.6±1.4g, respectively, suggest that 0.05±0.02% and 0.1±0.02% of the CaCO3 processed through their gut annually is dissolved. During the incubations the CaCO3 dissolution was 0.07±0.01%, 0.04±0.01% and 0.21±0.05% of the fecal casts for H. atra, H. leucospilota and S. herrmanni, respectively. Our result that the primary parameter determining the CaCO3 dissolution by sea cucumber is the amount of carbonate send in their gut. This suggests that sea cucumber dissolution in the future is not expected to change due to ocean acidification, but as calcification diminishes the proportion of CaCO3 dissolved by Holothurians (in protected reefs) in the coral reefs may increase.

  7. Utilization of Encapsulated CaCO_3 in Liquid Core Capsules for Improving Lactic Acid Fermentation

    International Nuclear Information System (INIS)

    Boon-Beng, Lee; Nurul Ainina Zulkifli

    2016-01-01

    Lactic acid bacteria (LAB) have been used for food fermentation due to its fermentative ability to improve and enhance the quality of the end food products. However, the performance of LAB is affected as fermentation time elapsed because the microbial growth is inhibited by its end product, for example lactic acid. In this study, a new approach was introduced to reduce the product inhibition effect using CaCO_3 which is encapsulated in spherical liquid core capsules of diameter 3.5 mm and 3.6 mm produced through extrusion dripping method. The results showed that the pH and lactic acid concentration of LAB fermentation was well maintained by the capsules. The results of the fermentation conducted to control pH and lactic acid concentration using the capsules were better than those of the control set and comparable with that of the free CaCO_3 set. In addition, the viable cell concentration of L. casei shirota was high at the end of fermentation when the fermentation was conducted using the capsules. The results of this study suggested that the capsules have high potential to be applied for pH and lactic acid level control in LAB fermentation for various productions. (author)

  8. Hierarchical CaCO3 chromatography: a stationary phase based on biominerals.

    Science.gov (United States)

    Sato, Kosuke; Oaki, Yuya; Takahashi, Daisuke; Toshima, Kazunobu; Imai, Hiroaki

    2015-03-23

    In biomineralization, acidic macromolecules play important roles for the growth control of crystals through a specific interaction. Inspired by this interaction, we report on an application of the hierarchical structures in CaCO3 biominerals to a stationary phase of chromatography. The separation and purification of acidic small organic molecules are achieved by thin-layer chromatography and flash chromatography using the powder of biominerals as the stationary phase. The unit nanocrystals and their oriented assembly, the hierarchical structure, are suitable for the adsorption site of the target organic molecules and the flow path of the elution solvents, respectively. The separation mode is ascribed to the specific adsorption of the acidic molecules on the crystal face and the coordination of the functional groups to the calcium ions. The results imply that a new family of stationary phase of chromatography can be developed by the fine tuning of hierarchical structures in CaCO3 materials. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  9. ESR studies on CaCO3 of deep-sea sediments

    International Nuclear Information System (INIS)

    Mangini, A.; Segl, M.; Schmitz, W.

    1983-01-01

    We have measured depth profiles of the ESR signals on the calcite fraction in 3 deep-sea sediments with a well-established age stratigraphy and CaCO 3 contents around 50 percent. In the ESR spectra of the foraminifera we observe 3 lines (A, B and C, following Ikeya's notation) two of which (A and C) were analysed as depth profiles. The A signal displays a continuous increase with depth over the time periods covered by the sediment cores of 400,000 and 800,000 a B.P. This suggests that a) the lifetime of the electron traps is long compared to these time intervals and b) the traps as yet unsaturated with electrons. Despite our present ignorance of the nature of the traps, these results might indicate the possible future applicability of ESR as a tool for dating sediment cores over time periods up to 1 Ma. The more prominent C signal displays a linear increase over time periods of 100,000 to 200,000 a. Beyond this age we find an overall increase, on which is superimposed short-term noise of similar amplitude that is unrelated to the 232 Th and CaCO 3 contents. (author)

  10. Heterogeneous microchemistry between CdSO4 and CaCO3 particles under humidity and liquid water

    International Nuclear Information System (INIS)

    Falgayrac, Guillaume; Sobanska, Sophie; Brémard, Claude

    2013-01-01

    Highlights: ► Raman analysis of chemical reactions between CdSO 4 and CaCO 3 particles. ► Under humid air no changes of morphology and chemical composition were observed. ► Condensation of liquid water generates an insoluble CdCO 3 layer on CaCO 3 surface. ► Addition of water previously equilibrated with CaCO 3 generates CdCO 3 and CaSO 4 . -- Abstract: Laboratory experiments using in situ Raman imaging combined with ex situ TOF-S-SIMS demonstrate the behavior of CdSO 4 ·8/3H 2 O microparticles in contact with {101 ¯ 4} CaCO 3 (calcite) surface under three different experimental conditions representative of unpolluted atmosphere. The contact of CdSO 4 ·8/3H 2 O particles with CaCO 3 surface in humid air (RH ∼ 40–80%) does not induce any chemical reaction. In contrast, the condensation of a water drop on CdSO 4 ·8/3H 2 O/CaCO 3 interface causes the free dissolution of CdSO 4 ·8/3H 2 O particle in the drop. A CdSO 4 ·8/3H 2 O microcrystal is reformed after gentle drying with a CdSO 4 ·H 2 O coating of the CaCO 3 surface. The TOF-S-SIMS image of the CaCO 3 surface provides evidence of a thin layer corresponding probably to insoluble coating of CdCO 3 (otavite) or Cd x Ca 1−x CO 3 solid solution at the liquid–solid interface. This layer armours the CaCO 3 from further dissolution and stops the reaction. The deposition of CdSO 4 ·8/3H 2 O particle in water drop previously in contact with CaCO 3 for a long time generates CdCO 3 small rhombohedral crystals while gentle drying provokes the crystallization of bar shape crystals of CaSO 4 ·2H 2 O (gypsum). These laboratory results provide valuable chemical prediction for a possible fate of cadmium rich particles emitted in the atmosphere and thus, can contribute to realistic assessment of human exposure to Cd hazard

  11. CaCO3 supplementation alleviates the inhibition of formic acid on acetone/butanol/ethanol fermentation by Clostridium acetobutylicum.

    Science.gov (United States)

    Qi, Gaoxiang; Xiong, Lian; Lin, Xiaoqing; Huang, Chao; Li, Hailong; Chen, Xuefang; Chen, Xinde

    2017-01-01

    To investigate the inhibiting effect of formic acid on acetone/butanol/ethanol (ABE) fermentation and explain the mechanism of the alleviation in the inhibiting effect under CaCO 3 supplementation condition. From the medium containing 50 g sugars l -1 and 0.5 g formic acid l -1 , only 0.75 g ABE l -1 was produced when pH was adjusted by KOH and fermentation ended prematurely before the transformation from acidogenesis to solventogenesis. In contrast, 11.4 g ABE l -1 was produced when pH was adjusted by 4 g CaCO 3 l -1 . The beneficial effect can be ascribed to the buffering capacity of CaCO 3 . Comparative analysis results showed that the undissociated formic acid concentration and acid production coupled with ATP and NADH was affected by the pH buffering capacity of CaCO 3 . Four millimole undissociated formic acid was the threshold at which the transformation to solventogenesis occurred. The inhibiting effect of formic acid on ABE fermentation can be alleviated by CaCO 3 supplementation due to its buffering capacity.

  12. Oxygen isotope fractionation in the CaCO3-DIC-H2O system

    Science.gov (United States)

    Devriendt, Laurent S.; Watkins, James M.; McGregor, Helen V.

    2017-10-01

    The oxygen isotope ratio (δ18O) of inorganic and biogenic carbonates is widely used to reconstruct past environments. However, the oxygen isotope exchange between CaCO3 and H2O rarely reaches equilibrium and kinetic isotope effects (KIE) commonly complicate paleoclimate reconstructions. We present a comprehensive model of kinetic and equilibrium oxygen isotope fractionation between CaCO3 and water (αc/w) that accounts for fractionation between both (a) CaCO3 and the CO32- pool (α c / CO32-) , and (b) CO32- and water (α CO32- / w) , as a function of temperature, pH, salinity, calcite saturation state (Ω), the residence time of the dissolved inorganic carbon (DIC) in solution, and the activity of the enzyme carbonic anhydrase. The model results suggest that: (1) The equilibrium αc/w is only approached in solutions with low Ω (i.e. close to 1) and low ionic strength such as in the cave system of Devils Hole, Nevada. (2) The sensitivity of αc/w to the solution pH and/or the mineral growth rate depends on the level of isotopic equilibration between the CO32- pool and water. When the CO32- pool approaches isotopic equilibrium with water, small negative pH and/or growth rate effects on αc/w of about 1-2‰ occur where these parameters covary with Ω. In contrast, isotopic disequilibrium between CO32- and water leads to strong (>2‰) positive or negative pH and growth rate effects on α CO32-/ w (and αc/w) due to the isotopic imprint of oxygen atoms derived from HCO3-, CO2, H2O and/or OH-. (3) The temperature sensitivity of αc/w originates from the negative effect of temperature on α CO32-/ w and is expected to deviate from the commonly accepted value (-0.22 ± 0.02‰/°C between 0 and 30 °C; Kim and O'Neil, 1997) when the CO32- pool is not in isotopic equilibrium with water. (4) The model suggests that the δ18O of planktic and benthic foraminifers reflects a quantitative precipitation of DIC in isotopic equilibrium with a high-pH calcifying fluid, leading to a relatively constant foraminifer calcite δ18O-temperature relationship (-0.21 ± 0.01‰/°C). The lower average coral δ18O data relative to foraminifers and other calcifiers is best explained by the precipitation of internal DIC derived from hydrated CO2 in a high-pH calcifying fluid and minimal subsequent DIC-H2O isotopic equilibration. This leads to a reduced and variable coral aragonite δ18O-temperature relationship (-0.11 to -0.22‰/°C). Together, the model presented here reconciles observations of oxygen isotope fractionation over a range of CaCO3-DIC-H2O systems.

  13. Thermal, Morphological and Physic-Mechanical Properties of Natural Rubber - CaCO3 Composites Using Jatropha Oil as Softener.

    Directory of Open Access Journals (Sweden)

    Nasruddin

    2018-01-01

    Full Text Available The urgency of green technology in rubber compounding has become a critical issue recently. In this research, the effect of using renewable resources in rubber compounding has been studied. Commercial Calcium Carbonate, Silica and Jatropha Oil were used in natural rubber composite. The research was designed by varying the types of commercial filler namely CaCO3 (47-51 phr, silica (47-51 phr and Jatropha Oil (4-6 phr in natural rubber composites (SIR-20. The formulas were intentionally designed for rubber tips vulcanizates. The samples were characterized by the determination of physic-mechanical, thermal (TGA and morphological (SEM properties. From the measured results, there is no significant effect on the tensile strength, specific gravity, and hardness on the loading of commercial CaCO3 and Silica in natural rubber composites using Jatropha Oil. However, a slight difference in elongation at break and abrasion resistance could be detected. Compared to the commercial rubber tips, the rubber tips produced in this research have higher tensile strength, elongation at break and abrasion resistance. Due to the usage of commercial CaCO3 and Silica, the SEM micrographs show rough surface because of the agglomeration. The thermogram shows clearly the compositional analysis of the rubber tips vulcanizates consist of Jatropha Oil and natural rubber, CaCO3, ash and other filler residues such as Silica.

  14. Nanospheres of alginate prepared through w/o emulsification and internal gelation with nanoparticles of CaCO3

    NARCIS (Netherlands)

    Paques, J.P.; Sagis, L.M.C.; Rijn, van C.J.M.; Linden, van der E.

    2014-01-01

    Gelled nanospheres of alginate are prepared through a single step technique involving emulsification and gelation. CaCO3 nanoparticles, together with glucono delta-lactone (GDL), are dispersed in an alginate solution, which is subsequently dispersed in an oil phase and followed by gelation of the

  15. Compound Method to Disperse CaCO3 Nanoparticles to Nano-Size in Water.

    Science.gov (United States)

    Gu, Sui; Cai, Jihua; Wang, Jijun; Yuan, Ye; Chang, Dewu; Chikhotkin, Viktor F

    2015-12-01

    The invalidation of CaCO3 nanoparticles (nCaCO3) is often caused by the fact of agglomeration and inhomogeneous dispersion which limits its application into water-based drilling muds for low permeability reservoirs such as coalbed methane reservoir and shale gas/oil reservoir. Effective methods to disperse nCaCO3 to nano-size (≤ 100 nm) in water have seldom been reported. Here we developed a compound method containing mechanical stirring, ultrasonic treatment, the use of surfactant and stabilizer to disperse nCaCO3 in water. It comprises the steps adding 2% nCaCO3, 1% sodium dodecyl sulfonate (SDS), 2% cetyltrimethyl ammonium bromide (CTAB), 2% OP-10, 3% to 4% biopolymer (XC) in water successively, stirring it at a shear rate of 6000 to 8000 r/min for 15 minutes and treating it with ultrasonic at a frequency of 28 KHz for 30 to 40 minutes. The dispersed nCaCO3 was characterized with scanning electron microscope (SEM), transmission electron microscope (TEM) and particle size distribution (PSD) tests. We found that nCaCO3 could be dispersed to below 100 nm in water and the medium value of nCaCO3 was below 50 nm. This method paved the way for the utilization of nCaCO3 in drilling fluid and completion fluid for low permeability reservoirs such as coal seams and shale gas/oil formations.

  16. An unaccounted fraction of marine biogenic CaCO3 particles.

    Directory of Open Access Journals (Sweden)

    Mikal Heldal

    Full Text Available Biogenic production and sedimentation of calcium carbonate in the ocean, referred to as the carbonate pump, has profound implications for the ocean carbon cycle, and relate both to global climate, ocean acidification and the geological past. In marine pelagic environments coccolithophores, foraminifera and pteropods have been considered the main calcifying organisms. Here, we document the presence of an abundant, previously unaccounted fraction of marine calcium carbonate particles in seawater, presumably formed by bacteria or in relation to extracellular polymeric substances. The particles occur in a variety of different morphologies, in a size range from 100 µm, and in a typical concentration of 10(4-10(5 particles L(-1 (size range counted 1-100 µm. Quantitative estimates of annual averages suggests that the pure calcium particles we counted in the 1-100 µm size range account for 2-4 times more CaCO(3 than the dominating coccolithophoride Emiliania huxleyi and for 21% of the total concentration of particulate calcium. Due to their high density, we hypothesize that the particles sediment rapidly, and therefore contribute significantly to the export of carbon and alkalinity from surface waters. The biological and environmental factors affecting the formation of these particles and possible impact of this process on global atmospheric CO(2 remains to be investigated.

  17. The Effects of CaCO3 Coated Wood Free Paper Usage as Filler on Water Absorption, Mechanical and Thermal Properties of Cellulose-High Density Polyethylene Composites

    Directory of Open Access Journals (Sweden)

    Emrah PEŞMAN

    2016-11-01

    Full Text Available In this study some physical, mechanical and thermal characteristics of high density polyethylene (HDPE and CaCO3 coated/pigmented wood free paper fiber composites were investigated. The fillers used in this study were uncoated cellulose, 5.8 %, 11.5 %, 16.5 % and 23.1 % CaCO3 coated wood free paper fibers. Each filler type was mixed with HDPE at 40% by weight fiber loading. In this case, the ratio of CaCO3 in plastic composites were calculated as 0 %, 2.3 %, 4.6 %, 6.6 % and 9.2 % respectively. Increased CaCO3 ratio improved the moisture resistant, flexural and tensile strength of cellulose-HDPE composites. However, the density of the cellulose-HDPE composites increased with CaCO3 addition. Energy Dispersive Spectroscopy on Scanning Electron Microscope analysis demonstrated the uniform distribution of CaCO3 and cellulose fiber in plastic matrix. In addition, the thermal properties of fiber plastic composites were investigated. The results of Differential scanning calorimetry analysis revealed that the crystallinity of the samples decreased with increasing CaCO3 content. Consequently, this work showed that CaCO3 coated waste paper fibers could be used as reinforcing filler against water absorption in thermoplastic matrix.DOI: http://dx.doi.org/10.5755/j01.ms.22.4.14222

  18. Template Adaptability is Key in the Oriented Crystallization of CaCO3

    International Nuclear Information System (INIS)

    Popescu, D.; Smulders, M.; Pichon, B.; Chebotareva, N.; Kwak, S.; van Asselen, O.; Sijbesma, R.; DiMasi, E.; Sommerdijk, N.

    2007-01-01

    In CaCO3, biomineralization nucleation and growth of the crystals are related to the presence of carboxylate-rich proteins within a macromolecular matrix, often with organized β-sheet domains. To understand the interplay between the organic template and the mineral crystal it is important to explicitly address the issue of structural adaptation of the template during mineralization. To this end we have developed a series of self-organizing surfactants (1-4) consisting of a dodecyl chain connected via a bisureido-heptylene unit to an amino acid head group. In Langmuir monolayers the spacing of these molecules in one direction is predetermined by the hydrogen-bonding distances between the bis-urea units. In the other direction, the intermolecular distance is determined by steric interactions introduced by the side groups (-R) of the amino acid moiety. Thus, by the choice of the amino acid we can systematically alter the density of the surfactant molecules in a monolayer and their ability to respond to the presence of calcium ions. The monolayer films are characterized by surface pressure-surface area (p-A) isotherms, Brewster angle microscopy, in-situ synchrotron X-ray scattering at fixed surface area, and also infrared reflection absorption spectroscopy (IRRAS) of films transferred to solid substrates. The developing crystals are studied with scanning and transmission electron microscopy (SEM, TEM), selected area electron diffraction (SAED), and crystal modeling. The results demonstrate that although all compounds are active in the nucleation of calcium carbonate, habit modification is only observed when the size of the side group allows the molecules to rearrange and adapt their organization in response to the mineral phase.

  19. Splice variants of perlucin from Haliotis laevigata modulate the crystallisation of CaCO3.

    Directory of Open Access Journals (Sweden)

    Tanja Dodenhof

    Full Text Available Perlucin is one of the proteins of the organic matrix of nacre (mother of pearl playing an important role in biomineralisation. This nacreous layer can be predominately found in the mollusc lineages and is most intensively studied as a compound of the shell of the marine Australian abalone Haliotis laevigata. A more detailed analysis of Perlucin will elucidate some of the still unknown processes in the complex interplay of the organic/inorganic compounds involved in the formation of nacre as a very interesting composite material not only from a life science-based point of view. Within this study we discovered three unknown Perlucin splice variants of the Australian abalone H. laevigata. The amplified cDNAs vary from 562 to 815 base pairs and the resulting translation products differ predominantly in the absence or presence of a varying number of a 10 mer peptide C-terminal repeat. The splice variants could further be confirmed by matrix-assisted laser desorption ionisation time of flight mass spectrometry (MALDI-ToF MS analysis as endogenous Perlucin, purified from decalcified abalone shell. Interestingly, we observed that the different variants expressed as maltose-binding protein (MBP fusion proteins in E. coli showed strong differences in their influence on precipitating CaCO3 and that these differences might be due to a splice variant-specific formation of large protein aggregates influenced by the number of the 10 mer peptide repeats. Our results are evidence for a more complex situation with respect to Perlucin functional regulation by demonstrating that Perlucin splice variants modulate the crystallisation of calcium carbonate. The identification of differentially behaving Perlucin variants may open a completely new perspective for the field of nacre biomineralisation.

  20. Synthesis and luminescent properties of CaCO3:Eu3+@SiO2 phosphors with core-shell structure

    Science.gov (United States)

    Liu, Min; Kang, Ming; Chen, Kexu; Mou, Yongren; Sun, Rong

    2018-03-01

    Integrating the processes of preparation of CaCO3:Eu3+ and its surface-coating, core-shell structured CaCO3:Eu3+@SiO2 phosphors with red emission were synthesized by the carbonation method and surface precipitation procedure using sodium silicate as silica source. The phase structure, thermal stability, morphology and luminescent property of the as-synthesized samples were characterized by X-ray diffraction, Fourier transform infrared spectrum, thermal analysis, field-emission scanning electron microscopy, transmission electron microscope and photoluminescence spectra. The experimental results show that Eu3+ ions as the luminescence center are divided into two types: one is at the surface of the CaCO3 and the other inhabits the site of Ca2+. For CaCO3:Eu3+@SiO2 phosphors, the SiO2 layers are continuously coated on the surface of CaCO3:Eu3+ and show a typical core-shell structure. After coated with SiO2 layer, the luminous intensity and the compatibility with the rubber matrix increase greatly. Additionally, the luminous intensity increases with the increasing of Eu3+ ions concentration in CaCO3 core and concentration quenching occurs when Eu3+ ions concentration exceeds 7.0 mol%, while it is 5.0 mol% for CaCO3:Eu3+ phosphors. Therefore, preparation of CaCO3:Eu3+@SiO2 phosphors can not only simplify the experimental process through integrating the preparation of CaCO3:Eu3+ and SiO2 layer, but also effectively increase the luminous intensities of CaCO3:Eu3+ phosphors. The as-obtained phosphors may have potential applications in the fields of optical materials and functional polymer composite materials, such as plastics and rubbers.

  1. Detecting the progression of ocean acidification from the saturation state of CaCO3 in the subtropical South Pacific

    Science.gov (United States)

    Murata, Akihiko; Hayashi, Kazuhiko; Kumamoto, Yuichiro; Sasaki, Ken-ichi

    2015-04-01

    Progression of ocean acidification in the subtropical South Pacific was investigated by using high-quality data from trans-Pacific zonal section at 17°S (World Ocean Circulation Experiment section P21) collected in 1994 and 2009. During this 15 year period, the CaCO3 saturation state of seawater with respect to calcite (Ωcal) and aragonite (Ωarg) in the upper water column (Pacific Ocean.

  2. Tropical Cyclones Cause CaCO3 Undersaturation of Coral Reef Seawater in a High-CO2 World

    Science.gov (United States)

    Manzello, D.; Enochs, I.; Carlton, R.; Musielewicz, S.; Gledhill, D. K.

    2013-12-01

    Ocean acidification is the global decline in seawater pH and calcium carbonate (CaCO3) saturation state (Ω) due to the uptake of anthropogenic CO2 by the world's oceans. Acidification impairs CaCO3 shell and skeleton construction by marine organisms. Coral reefs are particularly vulnerable, as they are constructed by the CaCO3 skeletons of corals and other calcifiers. We understand relatively little about how coral reefs will respond to ocean acidification in combination with other disturbances, such as tropical cyclones. Seawater carbonate chemistry data collected from two reefs in the Florida Keys before, during, and after Tropical Storm Isaac provide the most thorough data to-date on how tropical cyclones affect the seawater CO2-system of coral reefs. Tropical Storm Isaac caused both an immediate and prolonged decline in seawater pH. Aragonite saturation state was depressed by 1.0 for a full week after the storm impact. Based on current 'business-as-usual' CO2 emissions scenarios, we show that tropical cyclones with high rainfall and runoff can cause periods of undersaturation (Ω negatively impact the structural persistence of coral reefs over this century.

  3. Novel synthesis strategy for composite hydrogel of collagen/hydroxyapatite-microsphere originating from conversion of CaCO3 templates.

    Science.gov (United States)

    Wei, Qingrong; Lu, Jian; Wang, Qiaoying; Fan, Hongsong; Zhang, Xingdong

    2015-03-20

    Inspired by coralline-derived hydroxyapatite, we designed a methodological route to synthesize carbonated-hydroxyapatite microspheres from the conversion of CaCO3 spherulite templates within a collagen matrix under mild conditions and thus constructed the composite hydrogel of collagen/hydroxyapatite-microspheres. Fourier transform infrared spectroscopy (FTIR) and x-ray diffraction (XRD) were employed to confirm the successful generation of the carbonated hydroxyapatite phase originating from CaCO3, and the ratios of calcium to phosphate were tracked over time. Variations in the weight portion of the components in the hybrid gels before and after the phase transformation of the CaCO3 templates were identified via thermogravimetric analysis (TGA). Scanning electron microscopy (SEM) shows these composite hydrogels have a unique multiscale microstructure consisting of a collagen nanofibril network and hydroxyapatite microspheres. The relationship between the hydroxyapatite nanocrystals and the collagen fibrils was revealed by transmission electron microscopy (TEM) in detail, and the selected area electron diffraction (SAED) pattern further confirmed the results of the XRD analyses which show the typical low crystallinity of the generated hydroxyapatite. This smart synthesis strategy achieved the simultaneous construction of microscale hydroxyapatite particles and collagen fibrillar hydrogel, and appears to provide a novel route to explore an advanced functional hydrogel materials with promising potentials for applications in bone tissue engineering and reconstruction medicine.

  4. Blood Cockle Shells Waste as Renewable Source for the Production of Biogenic CaCO3 and Its Characterisation

    Science.gov (United States)

    Asmi, D.; Zulfia, A.

    2017-11-01

    The prowess to reuse and recycle of blood cockle shells for raw material in bio-ceramics applications is an attractive component of integrated waste management program. In this paper an attempt is made to introduce a simple process to manufacture biogenic CaCO3 powder from blood cockle shells waste. The biogenic CaCO3 powder was produced from rinsing of blood cockle shells waste using deionised water and oxalic acid for cleaning the dirt and stain on the shells, then drying and grinding followed by heat treatment at 500 and 800 °C for 5 h. The powder obtained was characterised by XRF, DTA/TG, SEM, FTIR, and XRD analysis. The amount of 97.1 % CaO was obtained from XRF result. The thermal decomposition of CaCO3 become CaO due to mass loss was observed in the TG curve. The SEM result shows the needle-like aragonite morphology of blood cockle shells powder transformed to cubic-like calcite after heat treated at 500 °C. These results were consistent with FTIR and XRD results.

  5. Compound effect of CaCO3 and CaSO4·2H2O on the strength of steel slag: cement binding materials

    International Nuclear Information System (INIS)

    Qi, Liqian; Liu, Jiaxiang; Liu, Qian

    2016-01-01

    In this study, we replaced 30% of the cement with steel slag to prepare binding material; additionally, small amounts of CaCO 3 and CaSO 4 ·2H 2 O were added. This was done to study the compound effect of CaCO 3 and CaSO 4 ·2H 2 O on the strength of steel slag-cement binding materials. The hydration degree of the steel slag cementitious material was analyzed by XRD, TG and SEM. The results showed that the optimum proportions of CaCO 3 and CaSO 4 ·2H 2 O were 3% and 2%, respectively. Compared with the steel slag-cement binders without adding CaCO 3 and CaSO 4 ·2H 2 O, the compressive strength increased by 59.9% at 3 days and by 17.8% at 28 days. Acting as the nucleation matrix, CaCO 3 could accelerate the hydration of C 3 S. In addition, CaCO 3 was involved in the hydration reaction, generating a new hydration product, which could stably exist in a slurry. Meanwhile, CaSO 4 ·2H 2 O could increase the number of AFt. The compound effect of CaCO 3 and CaSO 4 ·2H 2 O enhanced the intensity of steel slag-cement binding materials and improved the whole hydration behavior. (author)

  6. Acoustic Monitoring of Gravity-Driven Controls on CaCO3 Precipitates in a Fracture

    Science.gov (United States)

    Xu, Z.; Sheets, J.; Zhang, L.; Kim, D.; Kneafsey, T. J.; Cole, D. R.; Jun, Y. S.; Pyrak-Nolte, L. J.

    2017-12-01

    Sealing fractures by mineral precipitation is an important process for improving caprock integrity in subsurface reservoirs. In this study, the ability to monitor precipitate distribution in fractures with buoyant fluids was examined. Fractures with uniform aperture distributions of 0.5, 1.0 and 2.0 mm were created from acrylic plates to enable direct imaging of precipitate formation over time. CaCO3 precipitation was induced in a fracture from invasion of 1M CaCl2 and 0.3M Na2CO3 solutions. During chemical invasion, a fracture plane was oriented either parallel or perpendicular to gravity. Acoustic (P) wave transmission ( 1 MHz) and optical imaging were used to monitor the sample prior to, during and after fluid injection. Complementary X-ray computed tomography was performed throughout the experiments on vertical fractures and post injection for the horizontal fractures. Precipitate particle sizes during formation were determined using SAXS and WAXS. In both horizontal and vertical fractures, the density contrast between the two solutions affected the spatial distribution of precipitation. In vertical fractures, the denser CaCl2 solution almost completely displaced the NaCO3 solution, causing strong localization of precipitates. However, in the horizontal fractures, flow stratification occurred in the 2 mm aperture fractures, with the less dense Na2CO3 flowing over the CaCl2 solution, resulting in a more even distribution of precipitates cross the fracture plane. P-wave amplitudes increased up to 8% and the arrival time decreased with precipitate accumulation in the horizontal fracture. This is consistent with a three-layered approach as the seismic impedance inside the fracture increases. The initial contact between the two was observed as a decrease in the P-wave amplitude. As precipitates accumulated, the amplitude recovered and increased, with greater increases observed along the mixing flow path. Fractures in the subsurface may seal differently depending on the orientation thus affecting the ability of a fracture to self-heal if oriented vertically. This work was supported by the Center for Nanoscale Controls on Geologic CO (NCGC), an Energy Frontier Research Center funded by the U.S. Department of Energy, Office of Science, Basic Energy Sciences under Award # DE-AC02-05CH11231

  7. Biogenic CaCO3 and Opal Depositions and Their Latitudinal Comparison During the Past 600 ka in the Central Equatorial Pacific

    Directory of Open Access Journals (Sweden)

    Boo-Keun Khim

    2015-01-01

    Full Text Available The orbital-scale variations in biogenic CaCO3 and opal abundance in two piston cores collected in the central equatorial Pacific (core PC5101 from a southern site at _ and core PC5103 from a northern site at _ were compared to assess latitudinal differences. The correlation between the oxygen isotope stratigraphy of planktonic foraminifera (Globigerinoides sacculifer of PC5103 with the LR04 stacks provides the age of PC5103 to be approximately 950 ka. The age of PC5103 was further refined by correlating the CaCO3 content with the well-dated core RC11-210. The age of PC5101 was also constrained by the same CaCO3 chronostratigraphic correlation with RC11-210, resulting in an age of approximately 650 ka. Distinct orbital-scale series of CaCO3 and opal variations appear to be parallel between the two cores during the past 600 ka, which are controlled mainly by eccentricity with an approximate periodicity of 100 ka. It is worth noting that the biogenic CaCO3 and opal deposition patterns in the two cores differ between interglacial and glacial periods. During interglacial periods the biogenic opal content is higher in the southern core than in the northern core, which corresponds with the present-day condition. In contrast the CaCO3 content is higher in the northern core, which is contradictory to the present-day northward decreasing CaCO3 deposition pattern from the Equator. The collection site of PC5101 is approximately 350 m deeper than that of PC5103, which significantly promotes CaCO3 dissolution and causes unexpectedly high CaCO3 content at the northern site in contrast to the biogenic opal content.

  8. The Research on Thermal Properties and Hydrophobility of the Native Starch/hydrolysis Starch Blends with Treated CaCO3 Powder

    Science.gov (United States)

    Liu, Chia-I.; Huang, Chi-Yuan

    2008-08-01

    In this research, hydrolysis starch was added into the starch blends to study the thermal properties. The enthalpy of blends had a significant decrease to 109J/g as content of treated CaCO3 increased to 5wt%. The modified starch was degraded slightly to produce glucose in the hydrolysis treatment. The amount of glucose in native starch and hydrolysis starch was 0.09 μmol and 0.14 μmol by the DNS measurement. Moreover, CaCO3 treated with titanium coupling agent was also added to improve miscibility and hydrophobility in the starch blends. The contact angle of the blends increased from 60° to 95° when 15wt% treated CaCO3 was added. Treated CaCO3 was confirmed to improve the hydrophobility of starch blends effectively.

  9. THE RESEARCH ON THERMAL PROPERTIES AND HYDROPHOBILITY OF THE NATIVE STARCH/HYDROLYSIS STARCH BLENDS WITH TREATED CaCO3 POWDER

    International Nuclear Information System (INIS)

    Liu, C.-I; Huang, C.-Y.

    2008-01-01

    In this research, hydrolysis starch was added into the starch blends to study the thermal properties. The enthalpy of blends had a significant decrease to 109J/g as content of treated CaCO 3 increased to 5wt%. The modified starch was degraded slightly to produce glucose in the hydrolysis treatment. The amount of glucose in native starch and hydrolysis starch was 0.09 μmol and 0.14 μmol by the DNS measurement. Moreover, CaCO 3 treated with titanium coupling agent was also added to improve miscibility and hydrophobility in the starch blends. The contact angle of the blends increased from 60 deg. to 95 deg. when 15wt% treated CaCO 3 was added. Treated CaCO 3 was confirmed to improve the hydrophobility of starch blends effectively

  10. Effect of CaCO_3 addition on ash sintering behaviour during K_2CO_3 catalysed steam gasification of a Chinese lignite

    International Nuclear Information System (INIS)

    Zhang, Jiguang; Li, Jianbo; Mao, Yandong; Bi, Jicheng; Zhu, Mingming; Zhang, Zhezi; Zhang, Li; Zhang, Dongke

    2017-01-01

    Highlights: • K_2CO_3 decreased ash sintering temperature and enhanced ash melting in gasification. • CaCO_3 addition enhanced ash melting and lowered ash sintering temperatures. • CaCO_3 reacted with SiO_2 to form fluxing phases and amorphous materials. • CaCO_3 addition inhibited the potassium aluminium silicate formation. • CaCO_3 addition preserved the catalytic activity of potassium. - Abstract: The ash sintering behaviour of a Chinese lignite (LLI) with different amounts of CaCO_3 addition during K_2CO_3-catalysed gasification was investigated. 0–10 wt% K_2CO_3 was doped into the lignite for catalytic gasification, and CaCO_3 was added into the K_2CO_3-doped samples, varying in the range of 0–20 wt% relative to the lignite, for understanding its impact on ash sintering and catalytic gasification activity. Ash samples were prepared by completely gasifying the lignite samples with steam in a fixed-bed catalytic gasification system operating at 1073 K and atmospheric pressure. Sintering temperature, mineralogy and morphology of the ash samples thus obtained were determined using a pressure-drop sintering device, XRD and SEM-EDS, respectively. The results showed that the ash sintering temperature decreased as the K_2CO_3 addition increased, indicating that K_2CO_3 as the catalyst for gasification would promote ash sintering. SEM imaging analysis showed that all the ash samples from LLI with K_2CO_3 addition were composed of agglomerated particles with smooth surfaces, indicating the ashes had incurred partial melting. The degree of melting became more apparent as the K_2CO_3 addition ratio increased. These molten phases were identified as K-bearing arcanite and kaliophilite, which contributed to the formation of liquid phases at lower temperatures, resulting in lowered ash sintering temperatures. It was also revealed that the addition of CaCO_3 decreased the sintering temperatures of ash samples, indicating that the ash sintering was further enhanced by CaCO_3 addition. The surface texture of the ash particles, with the same K_2CO_3 addition level, changed from slightly melting to seriously melting or fusion as the CaCO_3 addition ratio increased. This is because the addition of CaCO_3 suppressed the formation of refractory silicon oxide and generated more fluxing feldspars and lime as well as the amorphous phases. However, the addition of CaCO_3 inhibited the formation of water-insoluble kaliophilite and thus helped preserve the catalytic activity of K_2CO_3, promoting K_2CO_3 catalysed gasification.

  11. Novel method of generation of Ca(HCO32 and CaCO3 aerosols and first determination of hygroscopic and cloud condensation nuclei activation properties

    Directory of Open Access Journals (Sweden)

    A. Trimborn

    2010-09-01

    Full Text Available Atmospheric mineral aerosols contain CaCO3 as a reactive component. A novel method to produce CaCO3 aerosol was developed by spraying Ca(HCO32 solution, which was generated from a CaCO3 suspension and CO2. By aerosol mass spectrometry the freshly sprayed and dried aerosol was characterized to consist of pure Ca(HCO32 which under annealing in a tube furnace transformed into CaCO3. Transmission Electron Microscopy demonstrated that the particles produced were spherical. The method was able to generate aerosol of sufficient concentration and proper size for the study of physiochemical properties and investigations of heterogeneous reactions of mineral aerosol. The dried Ca(HCO32 particles were somewhat more hygroscopic than CaCO3 particles. However, during humidification a restructuring took place and ∼2/3 of the Ca(HCO32 was transformed to CaCO3. The mixed Ca(HCO32/CaCO3(s particles were insoluble with a growth factor of 1.03 at 95% (hygroscopicity parameter κ=0.011±0.007 relative humidity. This compares to a corresponding growth factor of 1.01 for CaCO3(s (κ=0.0016±0.0004. Mass spectrometric composition analysis, restructuring, and insolubility of the mixed particles suggested that solid Ca(HCO32(s was observed. This would be in contrast to the current belief that Ca(HCO32(s is thermodynamically instable. The CCN activity of Ca(HCO32(s aerosol (κ≈0.15 is remarkably higher than that of CaCO3 aerosol (κ=0.0019±0.0007 and less than that of Ca(NO32. The noticeable but limited solubility of Ca(HCO32 of ≈0.01 mol/l explains limited hygroscopic growth and good CCN activity. Experiments in the Large Jülich Aerosol Chamber indicated that Ca(HCO32(s could exist for several hours under dry atmospheric conditions. However, it was likely buried in a protective layer of CaCO3(s. We conclude that Ca(HCO32 may be formed in the atmosphere in cloud droplets of activated mineral dust by reaction of CaCO3 with CO2 and H2O. The presence of Ca(HCO32 and as a consequence an enhanced CCN activity may alter the influence of mineral aerosol on global climate.

  12. Degradation pattern of porous CaCO3 and hydroxyapatite microspheres in vitro and in vivo for potential application in bone tissue engineering.

    Science.gov (United States)

    Zhong, Qiwei; Li, Wenhua; Su, Xiuping; Li, Geng; Zhou, Ying; Kundu, Subhas C; Yao, Juming; Cai, Yurong

    2016-07-01

    Despite superior clinical handling, excellent biocompatibility, biodegradation property of calcium phosphate needs to be improved to coincide with the rate of new bone formation. In this study, spherical CaCO3 are fabricated in the presence of the silk sericin and then transformed into porous hydroxyapatite (HAP) microspheres via hydrothermal method. The degradation behavior of obtained CaCO3, HAP and their mixture is first investigated in vitro. The result demonstrates that the weight loss of HAP microspheres are almost 24.3% after immersing in pH 7.40 Tris-HCl buffer solution for 12 weeks, which is far slower than that of spherical CaCO3 (97.5%). The degradation speed of the mixtures depends on the proportion of CaCO3 and HAP. The mixture with higher content of CaCO3 possesses a quicker degradation speed. The obtained CaCO3 and HAP microspheres are injected into subcutaneous tissue of ICR mice with the assistance of sodium alginate. The result in vivo also shows an obvious difference of degradation speed between the obtained CaCO3 and HAP microspheres, implying it is feasible to modulate the degradation property of the mixture through changing the proportion of CaCO3 and HAP The good cytocompatibility of the two kinds of microspheres is proved and a mild inflammation response is observed only at early stage of implantation. The job offers a simple method to modify the degradation properties of biomaterial for potential use in bone tissue engineering. Copyright © 2016 Elsevier B.V. All rights reserved.

  13. Brief communication: ikaite (CaCO3*6H2O) discovered in Arctic sea ice

    Science.gov (United States)

    Dieckmann, G. S.; Nehrke, G.; Uhlig, C.; Göttlicher, J.; Gerland, S.; Granskog, M. A.; Thomas, D. N.

    2010-02-01

    We report for the first time on the discovery of calcium carbonate crystals as ikaite (CaCO3*6H2O) in sea ice from the Arctic (Kongsfjorden, Svalbard). This finding demonstrates that the precipitation of calcium carbonate during the freezing of sea ice is not restricted to the Antarctic, where it was observed for the first time in 2008. This finding is an important step in the quest to quantify its impact on the sea ice driven carbon cycle and should in the future enable improvement parametrization sea ice carbon models.

  14. Brief Communication: Ikaite (CaCO3·6H2O discovered in Arctic sea ice

    Directory of Open Access Journals (Sweden)

    M. A. Granskog

    2010-05-01

    Full Text Available We report for the first time on the discovery of calcium carbonate crystals as ikaite (CaCO3·6H2O in sea ice from the Arctic (Kongsfjorden, Svalbard as confirmed by morphology and indirectly by X-ray diffraction as well as XANES spectroscopy of its amorophous decomposition product. This finding demonstrates that the precipitation of calcium carbonate during the freezing of sea ice is not restricted to the Antarctic, where it was observed for the first time in 2008. This observation is an important step in the quest to quantify its impact on the sea ice driven carbon cycle.

  15. Brief Communication: Ikaite (CaCO3·6H2O) discovered in Arctic sea ice

    Science.gov (United States)

    Dieckmann, G. S.; Nehrke, G.; Uhlig, C.; Göttlicher, J.; Gerland, S.; Granskog, M. A.; Thomas, D. N.

    2010-05-01

    We report for the first time on the discovery of calcium carbonate crystals as ikaite (CaCO3·6H2O) in sea ice from the Arctic (Kongsfjorden, Svalbard) as confirmed by morphology and indirectly by X-ray diffraction as well as XANES spectroscopy of its amorophous decomposition product. This finding demonstrates that the precipitation of calcium carbonate during the freezing of sea ice is not restricted to the Antarctic, where it was observed for the first time in 2008. This observation is an important step in the quest to quantify its impact on the sea ice driven carbon cycle.

  16. Studying the formation of CaCO3 polymorphs during the carbonation of nano-lime suspension in ethanol

    International Nuclear Information System (INIS)

    Sevcik, R.; Perez-Estebanez, M.; Macova, P.

    2015-01-01

    The paper is devoted to studying nano-lime and the formation of CaCO 3 polymorphs during this process. Nano-lime means a suspension of Ca(OH) 2 in alcohol, in this case ethanol (CaLoSil(R) E25). Carbonation reaction of nano-lime suspension having a concentration of 25 g l -1 and 5 ml was studied in a climatic chamber at a constant temperature and humidity conditions (T = 20 (1) DEG C., 65 (5), RH). At regular intervals (7, 14, 21 and 28 days), the samples were analyzed by infrared spectroscopy (FTIR), X-ray powder diffraction (XRPD) and observed under a scanning electron microscope (SEM). Quantitative determination was performed by Rietvelde's smoothing from XPRD data. It was found that the samples contained three crystalline forms of CaCO 3 - calcite, aragonite and vaterite, the percentage of their time was variable. These results will be used in further research on the application of nano-lime on calcareous materials. (Authors)

  17. Biochemical process of ureolysis-based microbial CaCO3 precipitation and its application in self-healing concrete.

    Science.gov (United States)

    Xu, Jing; Wang, Xianzhi; Wang, Binbin

    2018-04-01

    Urea hydrolysis has already been considered as the most effective pathway for microbially induced CaCO 3 precipitation (MICP). The present work first studied the combination of several key factors including initial pH, temperature, and dosage of urea, which contribute to the biochemical process of MICP. Under an amiable condition of pH and temperature, the dosage of urea has a significant impact on the rate of urea degradation and CaCO 3 precipitation. A bacteria-based self-healing system was developed by loading healing agents on ceramsite carriers. The self-healing efficiency was evaluated by visual inspection on crack closure, compressive strength regain, and capillary water absorption. A preferable healing effectiveness was obtained when the bacteria and organic nutrients were co-immobilized in carriers. Image analysis showed that cracks up to 273 μm could be healed with a crack closure ratio of 86% in 28 days. The compressive strength regain increased 24% and the water absorption coefficient decreased 27% compared to the reference. The findings indicated a promising application of ureolysis-based MICP in restoring the mechanical properties and enhancing the durability of concrete.

  18. Architecture of the organic matrix in the sternal CaCO3 deposits of Porcellio scaber (Crustacea, Isopoda).

    Science.gov (United States)

    Fabritius, Helge; Walther, Paul; Ziegler, Andreas

    2005-05-01

    Before the molt terrestrial isopods resorb calcium from the posterior cuticle and store it in large deposits within the first four anterior sternites. In Porcellio scaber the deposits consist of three structurally distinct layers consisting of amorphous CaCO3 (ACC) and an organic matrix that consists of concentric and radial elements. It is thought that the organic matrix plays a role in the structural organization of deposits and in the stabilization of ACC, which is unstable in vitro. In this paper, we present a thorough analysis of the ultrastructure of the organic matrix in the CaCO3 deposits using high-resolution field-emission scanning electron microscopy. The spherules and the homogeneous layer contain an elaborate organic matrix with similar structural organization consisting of concentric reticules and radial strands. The decalcification experiments reveal an inhomogeneous solubility of ACC within the spherules probably caused by variations in the stabilizing properties of matrix components. The transition between the three layers can be explained by changes in the number of spherule nucleation sites.

  19. Gasification catalysts prepared by the reaction of CaCO3 and coal. Tansan karushiumu to sekitan no ion kokan hanno ni yori choseishita kokassei gas ka shokubai

    Energy Technology Data Exchange (ETDEWEB)

    Otsuka, Y.; Asami, K. (Tohoku University, Sendai (Japan). Institute for Chemical Reaction Science)

    1991-11-07

    Properties of the active gasification catalysts prepared by ion exchange reaction of CaCO3 and coal were studied. Several kinds of Ca-loaded coal specimens were prepared to compare their properties among them by physically mixing coal particles with CaCO3 ones in air, by kneading both materials in pure water while crashing and by impregnating CaCO3 into coal while agitating them in pure water. Although Ca-loading onto the impregnated specimen was nearly one-half that of the kneaded one, its catalysis was equal to the kneaded one. CaCO3 greatly accelerated steam gasification only by mixing it with low rank coal in water, and such a high catalytic activity was caused by ion-exchanged Ca produced by the reaction between CaCO3 and COOH radical in coal. Aragonite of seashells yielded more Ca-loading than calcite of limestone, suggesting one of the useful treatment of seashell waste. 3 refs., 4 figs., 2 tabs.

  20. Evaluation of the properties of the CaCO3CaO system for metallurgical use

    International Nuclear Information System (INIS)

    Tapia, O.; Grijalva, M.; Rodriguez, A.; Formoso, A.

    1999-01-01

    The principal goal of this work, is to make a preliminary and comparative study on the physical chemistry, structural and thermal properties of the metallurgical lime production using experimental, and in some cases industrial measurements. This is important, because the characterization of the CaCO 3 CaO system, predicts the dissolution grade of the lime on the slag solution in the steel making. The mineral is located on the border of Michoacan (Lazaro Cardenas)and the Guerrero states (La Union) Mexico. This study evidences limited properties of this lime, which is due to the thermal and physical chemistry behaviour of the obtained results of this material. However, it is necessary to make a study in the future about the kinetic behavior during decomposition. This is necessary because it is important to obtain an increase in the basic oxides concentration and a decrease in the loss of ignition, which is important for the competitive lime production. (Author) 25 refs

  1. Evaluation and characterization of β -tricalcium phosphate powder prepared by CaCO3/H3PO4 system

    International Nuclear Information System (INIS)

    Shah Rizal Kasim; Yeong Meng Yee; Hazizan Md Akil; Zainal Arifin Ahmad

    2007-01-01

    Many attempts have been focused in the past on preparing of synthetic β-tricalcium (β-TCP), which being employed as bone substitute due to its biocompatibility and resorbability. Low temperature synthesize such as sol-gel method become popular due to the high product purity and homogenous composition. Sol-gel method is less economical towards commercialization because the cost of raw materials and the yield of the product that can be achieved. This paper describes the synthesis of β-TCP via mixing of CaCO 3 and H 3 PO 4 followed by calcinations process at 750 degree C - 1050 degree C. X-ray diffraction (XRD), scanning electron microscopy (SEM), differential scanning calorimeter (DSC), fourier transformation infra-red (FTIR) were used for characterization and evaluation of the phase composition, morphology, particle size and thermal behavior of the product. β-TCP phase start to occur after calcinations at 750 degree C. (Author)

  2. On the densification and hydration of CaCO3 particles by Q-switched laser pulses in water

    Science.gov (United States)

    Lin, Peng-Wen; Wu, Chao-Hsien; Zheng, Yuyuan; Chen, Shuei-Yuan; Shen, Pouyan

    2013-09-01

    Calcite powders subjected to Q-switched laser pulses in water were characterized by X-ray/electron diffraction and optical spectroscopy to have a significant internal compressive stress (up to ca. 1.5 GPa) with accompanied transformation into defective calcite II and hydrates. The defective calcite II particles were (0 1 0), (0 0 1), (0 1¯ 1), (0 1 3) and (0 1¯ 3) faceted with 2×(0 2 0)II commensurate superstructure and tended to hydrate epitaxially as monohydrocalcite co-existing with ikaite (CaCO3·6H2O) with extensive cleavages and amorphous calcium carbonate with porous structure. The colloidal suspension containing the densified calcite polymorphs and hydrates showed two UV-visible absorptions corresponding to a minimum band gap of ca. 5 and 3 eV, respectively.

  3. Synthesis and characterization of Nitrogen-doped &CaCO3-decorated reduced graphene oxide nanocomposite for electrochemical supercapacitors

    International Nuclear Information System (INIS)

    Ghouri, Zafar Khan; Barakat, Nasser A.M.; Alam, Al-Mahmnur; Alsoufi, Mohammad S.; Bawazeer, Tahani M.; Mohamed, Ahmed F.; Kim, Hak Yong

    2015-01-01

    Alone, it is expected, and also was experimentally proved, that calcium carbonate and reduced graphene oxide do have negligible specific capacitance due to the chemical composition of both materials. However, synthesis of CaCO 3 on the form of very thin sporadic layer attaching rGO results in dramatic increase in the specific capacitance of the obtained composite due to formation of the electrochemical double layer at the interfacial area. Moreover, the specific capacitance could be further enhanced by nitrogen-doping of the rGO sheets. Typically, a novel N-rGO/CaCO 3 composite has been successfully synthesized by heat reflux strategy with graphite powder, calcium acetate and urea as raw materials.The composite was characterized by X-Ray diffraction (XRD), high resolution transmission electron microscopy (HR-TEM), field-emission scanning electron microscopy (FESEM), coupled with rapid EDAX (energy dispersive analysis of X-Ray) and X-ray photoelectron spectroscopy. The utilized physiochemical characterizations indicated that the final prepared composite can be demonstrated as N-doped rGO decorated by very thin discrete layer from calcium carbonate. Supercapacitive performance of N-rGO/CaCO 3 composite has been investigated by cyclic voltammetry (CV), galvanostatic charge-discharge and electrochemical impedance spectroscopy in 1 M KOH solution. The results reveal that the N-rGO/CaCO 3 composite delivers a large specific capacitance of as high as 214 Fg −1 and 188 Fg −1 at 5 mV s −1 and 1.0 Ag −1 , according to CV and galvanostatic charge-discharge tests, respectively; while the CaCO 3 , rGO, rGO/CaCO 3 , N-rGO based electrodes has a poor electrochemical performance at the same conditions. Moreover, the as-prepared composite exhibited excellent long cycle stability with about 88.7% specific capacitance retained after 10,000 cycles.

  4. Influence of CaCO3 and SiO2 additives on magnetic properties of M-type Sr ferrites

    Science.gov (United States)

    Huang, Ching-Chien; Jiang, Ai-Hua; Hung, Yung-Hsiung; Liou, Ching-Hsuan; Wang, Yi-Chen; Lee, Chi-Ping; Hung, Tong-Yin; Shaw, Chun-Chung; Kuo, Ming-Feng; Cheng, Chun-Hu

    2018-04-01

    An experiment was carried out to investigate the influence of CaCO3 and SiO2 additives on the magnetic and physical properties of M-type Sr ferrites by changing experimental parameters such as the additive composition and Ca/Si ratio. Specimens were prepared by conventional ceramic techniques. It was found that the magnetic properties (Br = 4.42 kG, iHc = 3.32 kOe and (BH)max = 4.863 MGOe) were considerably improved upon adding CaCO3 = 1.1% and SiO2 = 0.4 wt% together with Co3O4, and the mechanical properties thereof were acceptable for motor applications. It was revealed that CaCO3 and SiO2 additives led to an upswing in the magnetic properties via the enhancement of uniform grain growth, particle alignment, and the densification of Sr ferrite.

  5. The Density and Compressibility of BaCO3-SrCO3-CaCO3-K2CO3-Na2CO3-Li2CO3 Liquids: New Measurements and a Systematic Trend with Cation Field Strength

    Science.gov (United States)

    Hurt, S. M.; Lange, R. A.; Ai, Y.

    2015-12-01

    The volumetric properties of multi-component carbonate liquids are required to extend thermodynamic models that describe partial melting of the deep mantle (e.g. pMELTS; Ghiorso et al., 2003) to carbonate-bearing lithologies. Carbonate in the mantle is an important reservoir of carbon, which is released to the atmosphere as CO2 through volcanism, and thus contributes to the carbon cycle. Although MgCO3 is the most important carbonate component in the mantle, it is not possible to directly measure the 1-bar density and compressibility of MgCO3 liquid because, like other alkaline-earth carbonates, it decomposes at a temperature lower than its melting temperature. Despite this challenge, Liu and Lange (2003) and O'Leary et al. (2015) showed that the one bar molar volume, thermal expansion and compressibility of the CaCO3 liquid component could be obtained by measuring the density and sound speeds of stable liquids in the CaCO3-Li2CO3-Na2CO3-K2CO3 quaternary system at one bar. In this study, this same strategy is employed on SrCO3- and BaCO3-bearing alkali carbonate liquids. The density and sound speed of seven liquids in the SrCO3-Li2CO3-Na2CO3-K2CO3 quaternary and three liquids in the BaCO3-Li2CO3-Na2CO3-K2CO3 quaternary were measured from 739-1367K, with SrCO3 and BaCO3 concentrations ranging from 10-50 mol%. The density measurements were made using the double-bob Archimedean method and sound speeds were obtained with a frequency-sweep acoustic interferometer. The molar volume and sound speed measurements were used to calculate the isothermal compressibility of each liquid, and the results show the volumetric properties mix ideally with composition. The partial molar volume and compressibility of the SrCO3 and BaCO3 components are compared to those obtained for the CaCO3 component as a function of cation field strength. The results reveal a systematic trend that allows the partial molar volume and compressibility of the MgCO3 liquid component to be estimated.

  6. A laboratory study of ikaite (CaCO3·6H2O) precipitation as a function of pH, salinity, temperature and phosphate concentration

    OpenAIRE

    Hu, Yu-Bin; Wolf-Gladrow, Dieter A.; Dieckmann, Gerhard S.; Völker, Christoph; Nehrke, Gernot

    2014-01-01

    Ikaite (CaCO3·6H2O) has only recently been discovered in sea ice, in a study that also provided first direct evidence of CaCO3 precipitation in sea ice. However, little is as yet known about the impact of physico-chemical processes on ikaite precipitation in sea ice. Our study focused on how the changes in pH, salinity, temperature and phosphate (PO4) concentration affect the precipitation of ikaite. Experiments were set up at pH from 8.5 to 10.0, salinities from 0 to 105 (in both artificial ...

  7. NO2-initiated multiphase oxidation of SO2 by O2 on CaCO3 particles

    Science.gov (United States)

    Yu, Ting; Zhao, Defeng; Song, Xiaojuan; Zhu, Tong

    2018-05-01

    The reaction of SO2 with NO2 on the surface of aerosol particles has been suggested to be important in sulfate formation during severe air pollution episodes in China. However, we found that the direct oxidation of SO2 by NO2 was slow and might not be the main reason for sulfate formation in ambient air. In this study, we investigated the multiphase reaction of SO2 with an O2 / NO2 mixture on single CaCO3 particles using Micro-Raman spectroscopy. The reaction converted the CaCO3 particle to a Ca(NO3)2 droplet, with CaSO4 ⚫ 2H2O solid particles embedded in it, which constituted a significant fraction of the droplet volume at the end of the reaction. The reactive uptake coefficient of SO2 for sulfate formation was on the order of 10-5, which was higher than that for the multiphase reaction of SO2 directly with NO2 by 2-3 orders of magnitude. According to our observations and the literature, we found that in the multiphase reaction of SO2 with the O2 / NO2 mixture, O2 was the main oxidant of SO2 and was necessary for radical chain propagation. NO2 acted as the initiator of radical formation, but not as the main oxidant. The synergy of NO2 and O2 resulted in much faster sulfate formation than the sum of the reaction rates with NO2 and with O2 alone. We estimated that the multiphase oxidation of SO2 by O2 initiated by NO2 could be an important source of sulfate and a sink of SO2, based on the calculated lifetime of SO2 regarding the loss through the multiphase reaction versus the loss through the gas-phase reaction with OH radicals. Parameterization of the reactive uptake coefficient of the reaction observed in our laboratory for further model simulation is needed, as well as an integrated assessment based on field observations, laboratory study results, and model simulations to evaluate the importance of the reaction in ambient air during severe air pollution episodes, especially in China.

  8. Random poly(amino acid)s synthesized by ring opening polymerization as additives in the biomimetic mineralization of CaCO3

    NARCIS (Netherlands)

    Dmitrovic, V.; Habraken, G.J.M.; Hendrix, M.M.R.M.; Habraken, W.J.E.M.; Heise, A.; With, de G.; Sommerdijk, N.A.J.M.

    2012-01-01

    Biominerals such as bones, teeth and seashells, very often have advanced material properties and are a source of inspiration for material chemists. As in biological systems acidic proteins play an important role in regulating the formation of CaCO3 biominerals, we employ poly(amino acid)s to mimic

  9. Effect of carbonation temperature on CO_2 adsorption capacity of CaO derived from micro/nanostructured aragonite CaCO_3

    International Nuclear Information System (INIS)

    Hlaing, Nwe Ni; Sreekantan, Srimala; Hinode, Hirofumi; Kurniawan, Winarto; Thant, Aye Aye; Othman, Radzali; Mohamed, Abdul Rahman; Salime, Chris

    2016-01-01

    Recent years, CaO-based synthetic materials have been attracted attention as potential adsorbents for CO_2 capture mainly due to their high CO_2 adsorption capacity. In this study, micro/nanostructured aragonite CaCO_3 was synthesized by a simple hydrothermal method with using polyacrylamide (PAM). The structural, morphological and thermal properties of the synthesized sample were investigated by X-ray diffraction (XRD), field-emission scanning electron microscopy (FESEM) and thermogravimetry analysis (TG-DTA). The XRD and FESEM results showed that the obtained sample was aragonite CaCO_3 with aggregated nanorods and microspheres composed of nanorods. A TG-DTA apparatus with Thermoplus 2 software was used to investigate the effect of carbonation temperature on the CO_2 adsorption capacity of CaO derived from aragonite CaCO_3 sample. At 300 °C, the sample reached the CO_2 adsorption capacity of 0.098 g-CO_2/g-adsorbent, whereas the sample achieved the highest capacity of 0.682 g-CO_2/g-adsorbent at 700 °C. The results showed that the carbonation temperature significantly influenced on the CO_2 adsorption capacity of the CaO derived from aragonite CaCO_3.

  10. Evaluation of options relative to the fixation and disposal of 14C-contaminated CO2 as CaCO3

    International Nuclear Information System (INIS)

    Croff, A.G.

    1976-04-01

    A paper study was conducted to determine the best method for fixing the 14 C-contaminated CO 2 resulting from an HTGR fuel block burner as CaCO 3 , and to determine the best methods for disposing of the CaCO 3 thus produced. The fixation method selected was the direct reaction of a Ca(OH) 2 slurry with the CO 2 . The least expensive disposal options which are likely to be acceptable appear to be the shallow-land burial of either drummed CaCO 3 solid (total cost = $18.47/kg heavy metal) or drummed CaCO 3 concreted with cement (total cost = $43.33/kg heavy metal). Neither placing the CO 2 fixation process before the Kr removal process nor separating the bulk of the graphite fuel block from the fuel particles is attractive on both technical and economic grounds. However, reduction of the HTGR fuel nitrogen content appears to be a more attractive method of reducing the 14 C release rate

  11. Atomic force microscopy and X-ray photoelectron spectroscopy study of NO2 reactions on CaCO3 (1014) surfaces in humid environments.

    Science.gov (United States)

    Baltrusaitis, Jonas; Grassian, Vicki H

    2012-09-13

    In this study, alternating current (AC) mode atomic force microscopy (AFM) combined with phase imaging and X-ray photoelectron spectroscopy (XPS) were used to investigate the effect of nitrogen dioxide (NO2) adsorption on calcium carbonate (CaCO3) (101̅4) surfaces at 296 K in the presence of relative humidity (RH). At 70% RH, CaCO3 (101̅4) surfaces undergo rapid formation of a metastable amorphous calcium carbonate layer, which in turn serves as a substrate for recrystallization of a nonhydrated calcite phase, presumably vaterite. The adsorption of nitrogen dioxide changes the surface properties of CaCO3 (101̅4) and the mechanism for formation of new phases. In particular, the first calcite nucleation layer serves as a source of material for further island growth; when it is depleted, there is no change in total volume of nitrocalcite, Ca(NO3)2, particles formed whereas the total number of particles decreases. This indicates that these particles are mobile and coalesce. Phase imaging combined with force curve measurements reveals areas of inhomogeneous energy dissipation during the process of water adsorption in relative humidity experiments, as well as during nitrocalcite particle formation. Potential origins of the different energy dissipation modes within the sample are discussed. Finally, XPS analysis confirms that NO2 adsorbs on CaCO3 (101̅4) in the form of nitrate (NO3(-)) regardless of environmental conditions or the pretreatment of the calcite surface at different relative humidity.

  12. Cell-Penetrating CaCO3 Nanocrystals for Improved Transport of NVP-BEZ235 across Membrane Barrier in T-Cell Lymphoma

    Science.gov (United States)

    Civallero, Monica; Citti, Cinzia; Cosenza, Maria; Baldassarre, Francesca; Cannazza, Giuseppe; Pozzi, Samantha; Sacchi, Stefano

    2018-01-01

    Owing to their nano-sized porous structure, CaCO3 nanocrystals (CaCO3NCs) hold the promise to be utilized as desired materials for encapsulating molecules which demonstrate wide promise in drug delivery. We evaluate the possibility to encapsulate and release NVP-BEZ235, a novel and potent dual PI3K/mTOR inhibitor that is currently in phase I/II clinical trials for advanced solid tumors, from the CaCO3NCs. Its chemical nature shows some intrinsic limitations which induce to administer high doses leading to toxicity; to overcome these problems, here we proposed a strategy to enhance its intracellular penetration and its biological activity. Pristine CaCO3 NCs biocompatibility, cell interactions and internalization in in vitro experiments on T-cell lymphoma line, were studied. Confocal microscopy was used to monitor NCs-cell interactions and cellular uptake. We have further investigated the interaction nature and release mechanism of drug loaded/released within/from the NCs using an alternative approach based on liquid chromatography coupled to mass spectrometry. Our approach provides a good loading efficiency, therefore this drug delivery system was validated for biological activity in T-cell lymphoma: the anti-proliferative test and western blot results are very interesting because the proposed nano-formulation has an efficiency higher than free drug at the same nominal concentration. PMID:29370086

  13. Studium tvorby polymorfů CaCO3 během karbonatace suspenze nanovápna v ethanolu

    Czech Academy of Sciences Publication Activity Database

    Ševčík, Radek; Pérez-Estébanez, Marta; Mácová, Petra

    2015-01-01

    Roč. 11, č. 1 (2015) ISSN 1336-7242. [Zjazd chemikov /67./. 07.09.2015-11.09.2015, Starý Smokovec] R&D Projects: GA ČR(CZ) GP14-20374P; GA MŠk(CZ) LO1219 Keywords : polymorphs * CaCO3 * nanolime * carbonation Subject RIV: AL - Art, Architecture, Cultural Heritage

  14. Net Loss of CaCO3 from a subtropical calcifying community due to seawater acidification: mesocosm-scale experimental evidence

    Directory of Open Access Journals (Sweden)

    K. S. Rodgers

    2009-08-01

    Full Text Available Acidification of seawater owing to oceanic uptake of atmospheric CO2 originating from human activities such as burning of fossil fuels and land-use changes has raised serious concerns regarding its adverse effects on corals and calcifying communities. Here we demonstrate a net loss of calcium carbonate (CaCO3 material as a result of decreased calcification and increased carbonate dissolution from replicated subtropical coral reef communities (n=3 incubated in continuous-flow mesocosms subject to future seawater conditions. The calcifying community was dominated by the coral Montipora capitata. Daily average community calcification or Net Ecosystem Calcification (NEC=CaCO3 production – dissolution was positive at 3.3 mmol CaCO3 m−2 h−1 under ambient seawater pCO2 conditions as opposed to negative at −0.04 mmol CaCO3 m−2 h−1 under seawater conditions of double the ambient pCO2. These experimental results provide support for the conclusion that some net calcifying communities could become subject to net dissolution in response to anthropogenic ocean acidification within this century. Nevertheless, individual corals remained healthy, actively calcified (albeit slower than at present rates, and deposited significant amounts of CaCO3 under the prevailing experimental seawater conditions of elevated pCO2.

  15. Different nature of glacial CaCO3 constituents between MIS 2 and MIS 12 in the East Sea/Japan Sea and its paleoceanographic implication

    Science.gov (United States)

    Khim, Boo-Keun; Tada, Ryuji; Itaki, Takuya

    2014-05-01

    Two piston cores (PC-05 and PC-08) were collected on the Yamato Rise in the East Sea/Japan Sea during the KR07-12 cruise. A composite core was achieved with the successful replacement of almost half of the upper part of core PC-05 by the entirety of core PC-08 based on the co-equivalence of L* values and the dark layers, because an interval (170 cm to 410 cm) of core PC-05 was considerably disturbed due to fluidization during the core execution. Chronostratigraphy of the composite core was constructed by the direct comparison of L* values to the well-dated core MD01-2407 that was obtained in the Oki Ridge. The lower-bottom of the composite core reached back to Marine Isotope Stage (MIS) 14, based on the age estimate by LR04 stacks. Downcore opal variation of the composite core exhibited the distinct orbital-scale cyclic changes; high during the interglacial and low during the glacial periods. However, downcore CaCO3 variation showed no corresponding orbital-scale cyclic change between glacial and interglacial periods. Some intervals of both periods were high in CaCO3 content. Frequent and large fluctuations in CaCO3 content seemed to be more related to the presence of dark layers containing thin lamination (TL) within the glacial and interglacial intervals. It is worthy to note that MIS 2 and MIS 12 are characterized by distinctly high CaCO3 content, showing up to 18% and 73%, respectively, among the glacial periods. Furthermore, in terms of lithology, MIS 2 was characterized by a thick dark layer (low L* values) with TL, whereas MIS 12 preserved the distinctly light layer (high L* values) with parallel laminations. Another remarkable dissimilarity between MIS 2 and MIS 12 was the nature of their CaCO3 constituent; the CaCO3 constituent of MIS 2 consisted of mostly planktonic foraminifera, whereas that of MIS 12 was mostly dump of coccolithophorids, regardless the presence of planktonic foraminifera. The distinctness of the CaCO3 constituents between MIS 2 and MIS 12 indicates that the preservation of CaCO3 contents was different temporarily during the glacial periods in the East Sea/Japan Sea. Enhanced CaCO3 preservation in MIS 2 is attributed primarily to less dissolution during the sinking through the water column or at the seafloor, but increased CaCO3 preservation in MIS 12 is mainly due to the high primary production in the surface water. With respect to the different function of the biological pump which controls CO2 cycles, the East Sea/Japan Sea clearly experienced carbonate-ocean-like state during MIS 12, despite normally silica-ocean-like state.

  16. Decadal changes in the CaCO3 saturation state along 179°E in the Pacific Ocean

    Science.gov (United States)

    Murata, Akihiko; Saito, Shu

    2012-06-01

    To assess degrees of ocean acidification, we mainly investigated decadal changes in the saturation state of seawater with respect to aragonite (Ωarg), which is a more vulnerable mineral form of CaCO3, along the 179°E meridian (WOCE P14N) in the Pacific Ocean. We found a maximum decrease of Ωarg of -0.48 (-0.034 a-1) at 200-300 dbar (isopycnal surfaces of 24.0-25.8 kg m-3) at 20°N. Between 1993 and 2007, the saturation horizon rose by 17 dbar (1.2 dbar a-1) at latitudes 10°N-50°N. Although ΔΩarg mostly reflected changes in normalized dissolved inorganic carbon (ΔnCT), it was larger than could be explained by anthropogenic CO2 storage alone. Decomposition of ΔnCT revealed that ΔΩarg was enhanced by approximately 50% by a non-anthropogenic CO2 contribution represented by changes in apparent oxygen utilization. Our results suggest that ocean acidification can be temporarily accelerated by temporal changes in oceanic conditions.

  17. Synthesis and characterization of CaCO3 (calcite) nano particles from cockle shells (Anadara granosa Linn) by precipitation method

    Science.gov (United States)

    Widyastuti, Sri; Intan Ayu Kusuma, P.

    2017-06-01

    Calcium supplements can reduce the risk of osteoporosis, but they are not automatically absorbed in the gastrointestinal tract. Nanotechnology is presumed to have a capacity in resolving this problem. The preparation and characterization of calcium carbonate nano particle to improve the solubility was performed. Calcium carbonate nano particles were synthesized using precipitation method from cockle shells (Anadara granosa Linn). Samples of the cockle shells were dried in an oven at temperature of 50°C for 7 (seven) days and subsequently they were crushed and blended into fine powder that was sieved through 125-μm sieve. The synthesis of calcium carbonate nanocrystals was done by extracting using hydro chloride acid and various concentrations of sodium hydroxide were used to precipitate the calcium carbonate nano particles. The size of the nano particles was determined by SEM, XRD data, and Fourier transform infrared spectroscopy (FT-IR). The results of XRD indicated that the overall crystalline structure and phase purity of the typical calcite phase CaCO3 particles were approximately 300 nm in size. The method to find potential applications in industry to yield the large scale synthesis of aragonite nano particles by a low cost but abundant natural resource such as cockle shells is required.

  18. Thermal treatment to improve the hydrophobicity of ground CaCO3 particles modified with sodium stearate

    Science.gov (United States)

    Liang, Yong; Yu, Keyi; Zheng, Qinzhong; Xie, Jiuren; Wang, Ting-Jie

    2018-04-01

    The surface modification of calcium carbonate (CaCO3) particles, which is used as a filler, significantly affects the properties of the composed materials. The effects of thermal treatment on ground calcium carbonate (GCC) particles subjected to hydrophobic modification using sodium stearate (RCOONa) were studied. The contact angle of the modified GCC particles increased from 24.7° to 118.9° when the amount of RCOONa added was increased from 0% to 5% and then decreased to 97.5° when the RCOONa content was further increased to 10%. When a large amount of RCOONa was added, RCOO- reacts with Ca2+ and generates (RCOO)2Ca nuclei, which are adsorbed on the surface of the GCC particles, forming a discontinuous (RCOO)2Ca modified layer. After thermal treatment under sealed conditions, the contact angle of the GCC particles modified using 1.5% RCOONa/GCC increased from 112.8° to 139.6°. The thermal stability of the (RCOO)2Ca modified layer was increased, with the temperature increase of the mass-loss peak from 358.0 to 463.0 °C. It is confirmed that the spreading of melted (RCOO)2Ca nuclei on the surface of the GCC particles during the thermal treatment increased the continuity of the modified layer, converting the physical adsorption of the (RCOO)2Ca nuclei into chemisorption. The grafting density of RCOO- on the GCC particle surface after thermal treatment approximates to 5.00/nm2, which is close to the single-molecular-layer grafting density of RCOO-, indicating that excellent modification was achieved.

  19. Characterizing 3-D flow velocity in evolving pore networks driven by CaCO3 precipitation and dissolution

    Science.gov (United States)

    Chojnicki, K. N.; Yoon, H.; Martinez, M. J.

    2015-12-01

    Understanding reactive flow in geomaterials is important for optimizing geologic carbon storage practices, such as using pore space efficiently. Flow paths can be complex in large degrees of geologic heterogeneities across scales. In addition, local heterogeneity can evolve as reactive transport processes alter the pore-scale morphology. For example, dissolved carbon dioxide may react with minerals in fractured rocks, confined aquifers, or faults, resulting in heterogeneous cementation (and/or dissolution) and evolving flow conditions. Both path and flow complexities are important and poorly characterized, making it difficult to determine their evolution with traditional 2-D transport models. Here we characterize the development of 3-D pore-scale flow with an evolving pore configuration due to calcium carbonate (CaCO3) precipitation and dissolution. A simple pattern of a microfluidic pore network is used initially and pore structures will become more complex due to precipitation and dissolution processes. At several stages of precipitation and dissolution, we directly visualize 3-D velocity vectors using micro particle image velocimetry and a laser scanning confocal microscope. Measured 3-D velocity vectors are then compared to 3-D simulated flow fields which will be used to simulate reactive transport. Our findings will highlight the importance of the 3-D flow dynamics and its impact on estimating reactive surface area over time. Sandia National Laboratories is a multi-program laboratory managed and operated by Sandia Corporation, a wholly owned subsidiary of Lockheed Martin Corporation, for the U.S. Department of Energy's National Nuclear Security Administration under contract DE-AC04-94AL85000. This material is based upon work supported as part of the Center for Frontiers of Subsurface Energy Security, an Energy Frontier Research Center funded by the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences under Award Number DE-SC0001114.

  20. Effect of coccolith polysaccharides isolated from the coccolithophorid, Emiliania huxleyi, on calcite crystal formation in in vitro CaCO3 crystallization.

    Science.gov (United States)

    Kayano, Keisuke; Saruwatari, Kazuko; Kogure, Toshihiro; Shiraiwa, Yoshihiro

    2011-02-01

    Marine coccolithophorids (Haptophyceae) produce calcified scales "coccoliths" which are composed of CaCO(3) and coccolith polysaccharides (CP) in the coccolith vesicles. CP was previously reported to be composed of uronic acids and sulfated residues, etc. attached to the polymannose main chain. Although anionic polymers are generally known to play key roles in biomineralization process, there is no experimental data how CP contributes to calcite crystal formation in the coccolithophorids. CP used was isolated from the most abundant coccolithophorid, Emiliania huxleyi. CaCO(3) crystallization experiment was performed on agar template layered onto a plastic plate that was dipped in the CaCO(3) crystallization solution. The typical rhombohedral calcite crystals were formed in the absence of CP. CaCO(3) crystals formed on the naked plastic plate were obviously changed to stick-like shapes when CP was present in the solution. EBSD analysis proved that the crystal is calcite of which c-axis was elongated. CP in the solution stimulated the formation of tabular crystals with flat edge in the agarose gel. SEM and FIB-TEM observations showed that the calcite crystals were formed in the gel. The formation of crystals without flat edge was stimulated when CP was preliminarily added in the gel. These observations suggest that CP has two functions: namely, one is to elongate the calcite crystal along c-axis and another is to induce tabular calcite crystal formation in the agarose gel. Thus, CP may function for the formation of highly elaborate species-specific structures of coccoliths in coccolithophorids.

  1. First estimates of the contribution of CaCO3 precipitation to the release of CO2 to the atmosphere during young sea ice growth

    Science.gov (United States)

    Geilfus, N.-X.; Carnat, G.; Dieckmann, G. S.; Halden, N.; Nehrke, G.; Papakyriakou, T.; Tison, J.-L.; Delille, B.

    2013-01-01

    report measurements of pH, total alkalinity, air-ice CO2 fluxes (chamber method), and CaCO3 content of frost flowers (FF) and thin landfast sea ice. As the temperature decreases, concentration of solutes in the brine skim increases. Along this gradual concentration process, some salts reach their solubility threshold and start precipitating. The precipitation of ikaite (CaCO3.6H2O) was confirmed in the FF and throughout the ice by Raman spectroscopy and X-ray analysis. The amount of ikaite precipitated was estimated to be 25 µmol kg-1 melted FF, in the FF and is shown to decrease from 19 to 15 µmol kg-1 melted ice in the upper part and at the bottom of the ice, respectively. CO2 release due to precipitation of CaCO3 is estimated to be 50 µmol kg-1 melted samples. The dissolved inorganic carbon (DIC) normalized to a salinity of 10 exhibits significant depletion in the upper layer of the ice and in the FF. This DIC loss is estimated to be 2069 µmol kg-1 melted sample and corresponds to a CO2 release from the ice to the atmosphere ranging from 20 to 40 mmol m-2 d-1. This estimate is consistent with flux measurements of air-ice CO2 exchange. Our measurements confirm previous laboratory findings that growing young sea ice acts as a source of CO2 to the atmosphere. CaCO3 precipitation during early ice growth appears to promote the release of CO2 to the atmosphere; however, its contribution to the overall release by newly formed ice is most likely minor.

  2. Effect of Polyelectrolyte and Fatty Acid Soap on the Formation of CaCO3 in the Bulk and the Deposit on Hard Surfaces.

    Science.gov (United States)

    Wang, Hao; Alfredsson, Viveka; Tropsch, Juergen; Ettl, Roland; Nylander, Tommy

    2015-09-30

    The effects of sodium polyacrylate (NaPAA) as well as potassium oleate on the nucleation and calcium carbonate crystal growth on hard surfaces, i.e., stainless steel and silica, have been investigated at different temperatures. The relation between the surface deposition and the corresponding bulk processes has been revealed by combining dynamic light scattering (DLS), scanning electron microscopy (SEM), X-ray diffraction (XRD), and ellipsometry. The aim was to further our understanding of the crystal deposition/growth mechanism and how it can be controlled by the presence of polyelectrolytes (NaPAA) or soap (potassium oleate). The addition of polyelectrolytes (NaPAA) or soap (potassium oleate) decreases the size of CaCO3 particles in bulk solution and affects both crystal structure and morphology in the bulk as well as on hard surfaces. The amount of particles on hard surfaces decreases significantly in the presence of both potassium oleate and NaPAA. This was found to be a consequence of potassium oleate or NaPAA adsorption on the hard surface as well as on the CaCO3 crystal surfaces. Here, the polymer NaPAA exhibited a stronger inhibition effect on the formation and growth of CaCO3 particles than potassium oleate.

  3. Fine scale distributions of porosity and particulate excess 210Pb, organic carbon and CaCO3 in surface sediments of the deep equatorial Pacific

    International Nuclear Information System (INIS)

    Jahnke, R.A.; Emerson, S.R.; Cochran, J.K.; Hirschberg, D.J.

    1986-01-01

    Sediment samples were recovered from the central equatorial Pacific Ocean, sectioned at 1-mm intervals, and analyzed for porosity, organic carbon, excess 210 Pb and CaCO 3 . Steep porosity gradients were measured in the upper 1 cm of the sediment column with extremely high values observed near the sediment surface. Similarly, particulate organic carbon contents are highest at the sediment surface, decrease sharply in the upper 1 cm, and are relatively constant between 1 and 5 cm. CaCO 3 values, on the other hand, are lowest at the sediment surface and increase to a constant value below 5-10 mm depth. At the carbonate ooze sites, excess 210 Pb is present throughout the upper 5 cm of the sediments suggesting relatively rapid particle mixing rates. However, extremely high excess 210 Pb activities (> 100 dpm/g) are observed at the sediment surface with sharp gradients present in the upper 1 cm which would suggest slow rates of mixing. This apparent contradiction along with the major features of the CaCO 3 and particulate organic carbon profiles can be explained by a particle-selective feeding mechanism in which organic carbon, excess 210 Pb-enriched particles are preferentially maintained at the sediment surface via ingestion and defecation by benthic organisms. (orig.)

  4. The Effect Of Gamma Irradiation And CaCO3 On The Physical And Mechanical Properties Of Natural Rubber (NR) Compound

    International Nuclear Information System (INIS)

    Iskandar, Sudrajat; Marliyanti, Isni; Kadariyah; Kardha, Made Sumarti

    2000-01-01

    The characterization of the effect of gamma irradiation and CaCO 3 on the physical and mechanical properties of NR compound (NRC) have been started. The NRC was made by blending of NR and low density polyethylene (LDPE), carbon black, additives (stearic acid, ZnO, irganox 1076, paraffin wax and minarex B oil) in certain amount and CaCO 3 with various composition of 33,67 and 100 phr (part per hundred ratio of rubber) using hot roll mill at 120 deg C and 100 deg C of front and back roll respectively. For making film, film, the NRC was then pressed by hot and cold press machine at 135 deg C and at room temperature respectively for about 3 minutes. The film was then irradiated with gamma rays at 150, 300, and 500 kGy. Characterization was done according to the Indonesian National Standard (SNI) The experimental results showed that by increasing the irradiation dose, the aging resistance, tensile strength, elongation at break, solvent xylene resistance, tear strength and hardness of natural rubber compound increased. While by increasing the CaCO 3 content, the hardness and specific gravity of irradiated NRC. Were increased. But the tensile strength, elongation at break and tear strength of irradiated NRC decreased According to SNI no 12-1000-1989 and SII 0944-84 that the experiment results may possible to used for making shoe sole and rubber carpet

  5. Study of Raman Spectroscopy on Phase Relations of CaCO3 at High Temperature and High Pressure

    Science.gov (United States)

    Li, M.; Zheng, H.; Duan, T.

    2006-05-01

    Laser Raman Spectroscopy was used to study phase relations between calcite I, calcite II and aragonite at high pressure and high temperature. The experiment was performed in an externally heated Basselt type diamond anvil cell (DAC). Natural calcite (calcite I) was used as starting mineral. The sample and a small chip of quartz were loaded in a cavity (300 μm in diameter and 250 μm in depth) in a rhenium gasket. The Na2CO3 aqueous solution of 1mol/L was also loaded as a pressure medium to yield hydrostatic pressure. The whole assembly was pressurized first and then heated stepwise to 400°C. Pressure and temperature in the chamber were determined by the shift of Raman band at 464 cm-1 of quartz and by NiCr-NiSi thermocouple, respectively. The Raman spectra were measured by a Renishaw 1000 spetrometer with 50 mW of 514.5nm argon-ion laser as the excitation light source. The slit width was 50 μm and the corresponding resolution was ±1 cm-1. From the experiments, we observed the phase transitions between calcite I and calcite II, calcite I and aragonite, calcite II and aragonite, respectively. Our data showed a negative slope for the boundary between calcite I and calcite II, which was similar to Bridgman's result, although Hess et al. gave a positive slope. The boundary with a negative slope for calcite II and aragonite was also defined, which had never been done before. And all these data can yield a more complete phase diagram of CaCO3 than the studies of Hess et al. and Suito et al.Reference:Bridgeman P. W.(1939) Journal: American Journal of Science, Vol. 237, p. 7-18Bassett W. A. et al. (1993) Journal: Review of Scientific Instruments, Vol. 64, p. 2340-2345Suito K. et al. (2001) Journal: American Mineralogist, Vol. 86, p. 997- 1002Hess N. J. et al. (1991) In A. K. Singh, Ed., Recent Trends in High Pressure Research; Proc. X IIIth AIRAPT International Conference on High Pressure Science and Technology, p. 236-241. Oxford & IBH Publishing Co. Pvt, Ltd., New Delhi.

  6. Contrasting Impact of Future CO2 Emission Scenarios on the Extent of CaCO3 Mineral Undersaturation in the Humboldt Current System

    Science.gov (United States)

    Franco, A. C.; Gruber, N.; Frölicher, T. L.; Kropuenske Artman, L.

    2018-03-01

    The eastern boundary upwelling systems are among those regions that are most vulnerable to an ocean acidification-induced transition toward undersaturated conditions with respect to mineral CaCO3, but no assessment exists yet for the Humboldt Current System. Here we use a high-resolution (˜7.5 km) regional ocean model to investigate past and future changes in ocean pH and CaCO3 saturation state in this system. We find that within the next few decades, the nearshore waters off Peru are projected to become corrosive year round with regard to aragonite, the more soluble form of CaCO3. The volume of aragonite undersaturated water off Peru will continue to increase in the future irrespective of the amount of CO2 emitted to the atmosphere. In contrast, the development of the saturation state with regard to calcite, a less soluble form of carbonate, depends strongly on the scenario followed. By 2050, calcite undersaturation appears in the nearshore waters off Peru occasionally, but by 2090 in a high-emission scenario (RCP8.5), ˜60% of the water in the euphotic zone will become permanently calcite undersaturated. Most of this calcite undersaturation off Peru can likely be avoided if a low emission scenario (RCP2.6) consistent with the Paris Agreement is followed. The progression of ocean acidification off Chile follows a similar pattern, except that the saturation states are overall higher. But also here, calcite undersaturated waters will become common in the subsurface waters under the RCP8.5 scenario by the end of this century, while this can be avoided under the RCP2.6 scenario.

  7. Concurrent removal of elemental mercury and SO2 from flue gas using a thiol-impregnated CaCO3-based adsorbent: a full factorial design study.

    Science.gov (United States)

    Balasundaram, Karthik; Sharma, Mukesh

    2018-03-22

    Mercury (Hg) emitted from coal-based thermal power plants (CTPPs) can accumulate and bio-magnify in the food chain, thereby posing a risk to humans and wildlife. The central idea of this study was to develop an adsorbent which can concurrently remove elemental mercury (Hg 0 ) and SO 2 emitted from coal-based thermal power plants (CTPPs) in a single unit operation. Specifically, a composite adsorbent of CaCO 3 impregnated with 2-mercaptobenimidazole (2-MBI) (referred to as modified calcium carbonate (MCC)) was developed. While 2-MBI having sulfur functional group could selectively adsorb Hg 0 , CaCO 3 could remove SO 2 . Performance of the adsorbent was evaluated in terms of (i) removal (%) of Hg 0 and SO 2 , (ii) adsorption mechanism, (iii) adsorption kinetics, and (iv) leaching potential of mercury from spent adsorbent. The adsorption studies were performed using a 2 2 full factorial design of experiments with 15 ppbV of Hg 0 and 600 ppmV of SO 2 . Two factors, (i) reaction temperature (80 and 120 °C; temperature range in flue gas) and (ii) mass of 2-MBI (10 and 15 wt%), were investigated for the removal of Hg 0 and SO 2 (as %). The maximum Hg 0 and SO 2 removal was 86 and 93%, respectively. The results of XPS characterization showed that chemisorption is the predominant mechanism of Hg 0 and SO 2 adsorption on MCC. The Hg 0 adsorption on MCC followed Elovich kinetic model which is also indicative of chemisorption on heterogeneous surface. The toxicity characteristic leaching procedure (TCLP) and synthetic precipitation leaching procedure (SPLP) leached mercury from the spent adsorbent were within the acceptable levels defined in these tests. The engineering significance of this study is that the 2-MBI-modified CaCO 3 -based adsorbent has potential for concurrent removal of Hg 0 and SO 2 in a single unit operation. With only minor process modifications, the newly developed adsorbent can replace CaCO 3 in the flue-gas desulfurization (FGD) system.

  8. The study of ikaite (CaCO3·6H2O) formation and its impact on biogeochemical processes in artificial sea ice brine

    OpenAIRE

    Hu, Yubin

    2014-01-01

    Calcium carbonate precipitation in polar sea ice has been proposed as one of the driving forces for the carbon pump in sea ice covered regions. After decades of controversial discussion on whether calcium carbonate can be precipitated in sea ice, the mineral ikaite (CaCO3·6H2O) was for the first time discovered in Antarctic sea ice (Dieckmann et al., 2008) and later also found in Arctic sea ice (Dieckmann et al., 2010). However, the mechanism of ikaite precipitation in sea ice is not well kno...

  9. Characterization of ikaite (CaCO3•6H2O) crystals in first year Arctic sea ice north of Svalbard

    OpenAIRE

    Nomura, Daiki; Assmy, Philipp; Nehrke, Gernot; Granskog, Mats A.; Fischer, Michael; Dieckmann, Gerhard; Fransson, Agneta; Hu, Yubin; Schnetger, Bernhard

    2013-01-01

    We identified ikaite crystals (CaCO3·6H2O) and examined their shape and size distribution in first-year Arctic pack ice, overlying snow and slush layers during the spring melt onset north of Svalbard. Additional measurements of total alkalinity (TA) were made for melted snow and sea-ice samples. Ikaite crystals were mainly found in the bottom of the snowpack, in slush and the surface layers of the sea ice where the temperature was generally lower and salinity higher than in the ic...

  10. Influence of CaCO3, Al2O3, and TiO2 microfillers on physico-mechanical properties of Luffa cylindrica/polyester composites

    Directory of Open Access Journals (Sweden)

    Vinay Kumar Patel

    2016-06-01

    Full Text Available The development of natural fibre reinforced polymer composites has gained popularity in many applications due to their environment friendly characteristics over the synthetic fibre based polymer composites. This paper describes the fabrication and physical, mechanical, three-body abrasive wear and water absorption behaviour of Luffa fibre reinforced polyester composites with and without addition of micro-fillers of Al2O3, CaCO3 and TiO2. The ranking of the composite materials has been made by using Technique for order preference by similarity to ideal solution (TOPSIS method with output parameters of their physical, mechanical and abrasive wear and water absorption attributes. The addition of microfillers has enhanced greatly the physical and mechanical properties of Luffa-fibre based composites. The addition of microfillers has influenced the physico-mechanical properties of Luffa-fibre based polyester composites in descending order of CaCO3, Al2O3, and TiO2.

  11. Seasonal formation of ikaite (caco 3 · 6h 2o) in saline spring discharge at Expedition Fiord, Canadian High Arctic: Assessing conditional constraints for natural crystal growth

    Science.gov (United States)

    Omelon, Christopher R.; Pollard, Wayne H.; Marion, Giles M.

    2001-05-01

    - Spring discharge at Expedition Fiord (Pollard et al., 1999) on Axel Heiberg Island in the Canadian High Arctic produces a variety of travertine forms in addition to a diverse collection of mineral precipitates. This paper focuses on clusters of thermally unstable crystals believed to be the mineral ikaite (CaCO 3 · 6H 2O) growing seasonally along two spring outflows at Colour Peak. This form of calcium carbonate mineral occurs along small sections of discharge outflow as white euhedral crystals up to 0.5 cm in length. Difficulty in sampling, storage and transport of the samples for analysis has hampered attempts to confirm the presence of ikaite by X-ray diffraction. However, various field observations and the remarkable instability of these crystals at normal ambient temperatures strengthens our argument. This paper provides a description of these particular CaCO 3 · 6H 2O crystals and their environmental surroundings, and attempts to determine the validity of ikaite precipitation at this site by theoretical geochemical modeling: these results are compared with other reported observations of ikaite to both understand their occurrence and help delineate their geochemical characteristics. It is believed that the restrictive combination of spring water chemistry and long periods of low temperatures characteristic of arctic climates are necessary for ikaite growth at this site. The fact that ikaite is not forming at a second group of saline springs 11 km away allows us to more specifically outline conditions controlling its presence.

  12. Mg/Ca partitioning between aqueous solution and aragonite mineral: a molecular dynamics study

    NARCIS (Netherlands)

    Ruiz-Hernandez, S.E.; Grau-Crespo, R.; Almora-Barrios, N.; Wolthers, M.; Ruiz-Salvador, A.R.; Fernandez, N.; Leeuw, N.H. de

    2012-01-01

    We have calculated the concentrations of Mg in the bulk and surfaces of aragonite CaCO3 in equilibrium with aqueous solution, based on molecular dynamics simulations and grand-canonical statistical mechanics. Mg is incorporated in the surfaces, in particular in the (001) terraces,

  13. Effect of the temperature and the CO2 concentration on the behaviour of the citric acid as a scale inhibitor of CaCO3

    Science.gov (United States)

    Blanco, K.; Aponte, H.; Vera, E.

    2017-12-01

    For all Industrial sector is important to extend the useful life of the materials that they use in their process, the scales of CaCO3 are common in situation where fluids are handled with high concentration of ions and besides this temperatures and CO2 concentration dissolved, that scale generates large annual losses because there is a reduction in the process efficiency or corrosion damage under deposit, among other. In order to find new alternatives to this problem, the citric acid was evaluated as scale of calcium carbonate inhibition in critical condition of temperature and concentration of CO2 dissolved. Once the results are obtained it was carried out the statistical evaluation in order to generate an equation that allow to see that behaviour, giving as result, a good efficiency of inhibition to the conditions evaluated the scales of products obtained were characterized through scanning electron microscopy.

  14. The dynamic ocean biological pump: Insights from a global compilation of particulate organic carbon, CaCO3, and opal concentration profiles from the mesopelagic

    Science.gov (United States)

    Lam, Phoebe J.; Doney, Scott C.; Bishop, James K. B.

    2011-09-01

    We have compiled a global data set of 62 open ocean profiles of particulate organic carbon (POC), CaCO3, and opal concentrations collected by large volume in situ filtration in the upper 1000 m over the last 30 years. We define concentration-based metrics for the strength (POC concentration at depth) and efficiency (attenuation of POC with depth in the mesopelagic) of the biological pump. We show that the strength and efficiency of the biological pump are dynamic and are characterized by a regime of constant and high transfer efficiency at low to moderate surface POC and a bloom regime where the height of the bloom is characterized by a weak deep biological pump and low transfer efficiency. The variability in POC attenuation length scale manifests in a clear decoupling between the strength of the shallow biological pump (e.g., POC at the export depth) and the strength of the deep biological pump (POC at 500 m). We suggest that the paradigm of diatom-driven export production is driven by a too restrictive perspective on upper mesopelagic dynamics. Indeed, our full mesopelagic analysis suggests that large, blooming diatoms have low transfer efficiency and thus may not export substantially to depth; rather, our analysis suggests that ecosystems characterized by smaller cells and moderately high %CaCO3 have a high mesopelagic transfer efficiency and can have higher POC concentrations in the deep mesopelagic even with relatively low surface or near-surface POC. This has negative implications for the carbon sequestration prospects of deliberate iron fertilization.

  15. Long-term effects of intravenous 1 alpha (OH)D3 combined with CaCO3 and low-calcium dialysis on secondary hyperparathyroidism and biochemical bone markers in patients on chronic hemodialysis

    DEFF Research Database (Denmark)

    Brandi, L; Daugaard, H; Nielsen, P K

    1996-01-01

    doses of CaCO3 and to reduce the doses of an aluminium-containing oral phosphate binder. A decrease in p-Ca2+ during dialysis was induced, and special care had to focus on the compliance to CaCO3, in order not to aggravate the secondary hyperparathyroidism. (2) The combination of 'low......The effects of intravenous administration of 1 alpha-hydroxycholecalciferol [1 alpha (OH)D3] in combination with CaCO3 and 'low-calcium dialysis' (1.25 mmol/l) on plasma (p) parathyroid hormone (PTH) and biochemical bone markers (osteocalcin, alkaline phosphatase, procollagen type 1 c......-terminal extension peptide) were examined in 54 patients on chronic hemodialysis with either normal or elevated PTH. Increasing doses of 1 alpha (OH)D3 were administered intravenously under careful control of p-Ca2+ and inorganic phosphate. Blood samples were obtained 1 week before the start of treatment...

  16. Long-term effects of intravenous 1 alpha (OH)D3 combined with CaCO3 and low-calcium dialysis on secondary hyperparathyroidism and biochemical bone markers in patients on chronic hemodialysis

    DEFF Research Database (Denmark)

    Brandi, L; Daugaard, H; Nielsen, P K

    1996-01-01

    doses of CaCO3 and to reduce the doses of an aluminium-containing oral phosphate binder. A decrease in p-Ca2+ during dialysis was induced, and special care had to focus on the compliance to CaCO3, in order not to aggravate the secondary hyperparathyroidism. (2) The combination of 'low......-terminal extension peptide) were examined in 54 patients on chronic hemodialysis with either normal or elevated PTH. Increasing doses of 1 alpha (OH)D3 were administered intravenously under careful control of p-Ca2+ and inorganic phosphate. Blood samples were obtained 1 week before the start of treatment...

  17. Experiments on different materials (polyamide, stainless & galvanized steel) influencing geothermal CaCO3 scaling formation: Polymorphs & elemental incorporation

    Science.gov (United States)

    Wedenig, Michael; Dietzel, Martin; Boch, Ronny; Hippler, Dorothee

    2016-04-01

    Thermal water is increasingly used for heat and electric power production providing base-load capable renewable and virtually unlimited geothermal energy. Compared to other energy sources geothermal facilities are less harmful to the environment, i.e. chemically and visually. In order to promote the economic viability of these systems compared to other traditional and renewable energy sources, production hindering processes such as corrosion and scaling of components arising from the typically high salinity thermal waters have to be considered as important economic factors. In this context, using proper materials being in contact with the thermal water is crucial and a playground for further improvements. Aim of the study presented, are basic experiments and observations of scaling and corrosive effects from hydrothermal water interacting with different materials and surfaces (stainless steel, polyamide, galvanized steel) and in particular the nucleation and growth effects of these materials regarding the precipitation of solid carbonate phases. The incorporation of Mg, Sr and Ba cations into the carbonate scalings are investigated as environmental proxy. For this purpose, hydrothermal carbonate precipitating experiments were initialized by mixing NaHCO3 and Ca-Mg-Sr-Ba-chloride solutions at temperatures ranging from 40 to 80 °C in glass reactors hosting artificial substrates of the above mentioned materials. The experiments show a strong dependence of the precipitation behaviour of calcium carbonate polymorphs on the particular material being present. Stainless steel and polyamide seem to restrict aragonite formation, whereas galvanized steel supports aragonite nucleation. Vaterite formation is promoted by polyamide surfaces. Importantly, vaterite is more soluble (less stable) compared to the other anhydrous calcium carbonate polymorphs, i.e. vaterite can be more easily re-dissolved. Thus, the use of polyamide components might reduce the amount and durability of

  18. Climatological Distributions of pH, pCO2, Total CO2, Alkalinity, and CaCO3 Saturation in the Global Surface Ocean (NCEI accession 01645680) (NCEI Accession 0164568)

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — Climatological mean monthly distributions of pH in the total H+ scale, total CO2 concentration (TCO2), and the degree of CaCO3 saturation for the global surface...

  19. Biomimetic mineralization of CaCO3 on a phospholipid monolayer: from an amorphous calcium carbonate precursor to calcite via vaterite.

    Science.gov (United States)

    Xiao, Junwu; Wang, Zhining; Tang, Yecang; Yang, Shihe

    2010-04-06

    A phospholipid monolayer, approximately half the bilayer structure of a biological membrane, can be regarded as an ideal model for investigating biomineralization on biological membranes. In this work on the biomimetic mineralization of CaCO(3) under a phospholipid monolayer, we show the initial heterogeneous nucleation of amorphous calcium carbonate precursor (ACC) nanoparticles at the air-water interface, their subsequent transformation into the metastable vaterite phase instead of the most thermodynamically stable calcite phase, and the ultimate phase transformation to calcite. Furthermore, the spontaneity of the transformation from vaterite to calcite was found to be closely related to the surface tension; high surface pressure could inhibit the process, highlighting the determinant of surface energy. To understand better the mechanisms for ACC formation and the transformation from ACC to vaterite and to calcite, in situ Brewster angle microscopy (BAM), ex situ scanning electron microscopy, transmission electron microscopy, Raman spectroscopy, and X-ray diffraction analysis were employed. This work has clarified the crystallization process of calcium carbonate under phospholipid monolayers and therefore may further our understanding of the biomineralization processes induced by cellular membranes.

  20. In situ observation of electron beam-induced phase transformation of CaCO3 to CaO via ELNES at low electron beam energies.

    Science.gov (United States)

    Golla-Schindler, Ute; Benner, Gerd; Orchowski, Alexander; Kaiser, Ute

    2014-06-01

    It is demonstrated that energy-filtered transmission electron microscope enables following of in situ changes of the Ca-L2,3 edge which can originate from variations in both local symmetry and bond lengths. Low accelerating voltages of 20 and 40 kV slow down radiation damage effects and enable study of the start and finish of phase transformations. We observed electron beam-induced phase transformation of single crystalline calcite (CaCO3) to polycrystalline calcium oxide (CaO) which occurs in different stages. The coordination of Ca in calcite is close to an octahedral one streched along the direction. Changes during phase transformation to an octahedral coordination of Ca in CaO go along with a bond length increase by 5 pm, where oxygen is preserved as a binding partner. Electron loss near-edge structure of the Ca-L2,3 edge show four separated peaks, which all shift toward lower energies during phase transformation at the same time the energy level splitting increases. We suggest that these changes can be mainly addressed to the change of the bond length on the order of picometers. An important pre-condition for such studies is stability of the energy drift in the range of meV over at least 1 h, which is achieved with the sub-Ångström low-voltage transmission electron microscope I prototype microscope.

  1. Characterization on the precipitate sample of cetyltrimethylammonium bromide adsorbed onto nanocube CaCO3 particles from aqueous-ammonia-rich solution

    International Nuclear Information System (INIS)

    Rivera Virtudazo, Raymond V.; Fuji, Masayoshi; Takai, Chika; Shirai, Takashi

    2012-01-01

    Physicochemical analysis on the precipitate samples of the cationic cetyltrimethylammonium bromide (CTAB) adsorbed onto nanocube CaCO 3 particles (NcCP) in aqueous ammonia rich (NH 4 + ) solution was initially examined. The amount of CTAB added to the (<100 nm) NcCP ranging from 0.04 to 88.5 mM was prepared under room temperature aqueous alkaline condition and characterized by thermogravimetry/differential thermogravimetric analysis (TGA/DTA), Raman spectroscopy (RS), scanning electron microscopy, transmission electron microscopy (TEM), gas chromatograph combined with mass spectrometer analysis (GC–MS), and powder X-ray diffraction pattern. RS, GC–MS, and TGA/DTA analyses indicate that only layer of CTAB molecules were present on the surface of the NcCP. Moreover, this thin sheet layer was morphologically observed by the TEM image (particularly at 88 mM concentration of CTAB). In general, adsorption of CTAB molecules onto NcCP under aqueous alkaline medium had no effect on the cubic crystal structure and particle morphology. The present study confirms the adsorption mechanism of cationic surfactant onto NcCP colloids model and contributes to the better understanding of the possible structural arrangement of the sorbed surfactant molecules onto the NcCP-aqueous alkaline interface by simple characterization method. This investigation is expected to create new, low-cost route to produce promising nanopowders and conversion to hollow particles with multi-component porous surface shell wall.

  2. Effects of pore CaCO3 form agencies on dissolution mechanisms of amoxicillin drugs encapsulated in hydrogels full-IPN chitosan N-vinyl caprolactam

    Science.gov (United States)

    Budianto, Emil; Fauzia, Maghfira

    2018-04-01

    The administration of amoxicillin trihydrate in Helicobacter pylori infection is not effective enough because the conventional preparations used have a short retention time in the stomach. To overcome this problem, amoxicillin trihydrate was encapsulated into the floating drug delivery matrix-matrix. In this study, the full-ipn acetaldehyde crosslinked hydrogel (N-vinyl caprolactam) was synthesized with a 10% CaCO3 pore forming agent and then encapsulated on amoxicillin trihydrate and studied the mechanism of drug dissolution with its kinetic kinetics approach. The K-PNVCL Hydrogel produces optimal properties which are then loaded with amoxicillin trihydrate in situ and post loading. In this research, we have got the percentage of swelling, floating time, the efficiency of in situ and post loading 873%; 3.15 minutes; 99.8% and 99.4%. The dissolution test was performed on amoxicillin trihydrate which had been encapsulated K-PNVCL hydrogel in vitro at pH 1.2 resulting in 94.5% for in situ loading and 98.5% for post loading. Results of the kinetics of drug release for post loading and in situ loading methods tend to follow the Higuchi model kinetics. The drug release mechanism occurs by Fickian diffusion. Proof of drug release mechanism from K-PNVCL hydrogel matrix is further done by Scanning Electron Microscope (SEM) instrument.

  3. The stability and Raman spectra of ikaite, CaCO3·6H2O, at high pressure and temperature

    Science.gov (United States)

    Shahar, Anat; Bassett, William A.; Mao, Ho-kwang; Chou, I-Ming; Mao, Wendy

    2005-01-01

    Raman analyses of single crystals of ikaite, CaCO3·6H2O, synthesized in a diamond-anvil cell at ambient temperature yield spectra from 0.14 to 4.08 GPa; the most intense peaks are at 228 and 1081 cm−1 corresponding to Eg(external) and A1g (internal) modes of vibrations in CO2− 3 ions, respectively. These are in good agreement with Raman spectra previously published for ikaite in powder form at ambient temperature and pressure. Visual observations of a sample consisting initially of a mixture of calcite + water in a hydrothermal diamond-anvil cell yielded a P-T phase diagram up to 2 GPa and 120 °C; the boundary for the reaction ikaite ↔ aragonite + water has a positive slope and is curved convexly toward the aragonite + water field similar to typical melt curves. This curvature can be explained in terms of the Clapeyron equation for a boundary between a solid phase and a more compressible liquid phase or largely liquid phase assemblage.

  4. Effects of freshwater Synechococcus sp. cyanobacteria pH buffering on CaCO3 precipitation: Implications for CO2 sequestration

    International Nuclear Information System (INIS)

    Martinez, Raul E.; Weber, Sebastian; Grimm, Christian

    2016-01-01

    In the present study, a mixed-flow steady-state bio-reactor was designed to biomineralize CO 2 as a consequence of photosynthesis from active Synechococcus sp. Dissolved CO 2 , generated by constant air bubbling of inorganic and cyanobacteria stock solutions, was the only source of inorganic carbon. The release of hydroxide ion by cyanobacteria from photosynthesis maintained highly alkaline pH conditions. In the presence of Ca 2+ and carbonate species, this led to calcite supersaturation under steady state conditions. Ca 2+ remained constant throughout the experiments showing the presence of steady state conditions. Similarly, the Synechococcus sp. biomass concentration remained stable within uncertainty. A gradual pH decrease was observed for the highest Ca 2+ condition coinciding with the formation of CaCO 3 . The high degree of supersaturation, under steady-state conditions, contributed to the stabilization of calcite and maintained a constant driving force for the mineral nucleation and growth. For the highest Ca 2+ condition a fast crystal growth rate was consistent with rapid calcite precipitation as suggested further by affinity calculations. Although saturation state based kinetic precipitation models cannot accurately reflect the controls on crystal growth kinetics or reliably predict growth mechanisms, the relatively reaction orders obtained from modeling of calcite precipitation rates as function of decreasing carbonate concentration suggest that the precipitation occurred via surface-controlled rate determining reactions. These high reaction orders support in addition the hypothesis that crystal growth proceeded through complex surface controlled mechanisms. In conclusion, the steady state supersaturated conditions generated by a constant cyanobacteria biomass and metabolic activity strongly suggest that these microorganisms could be used for the development of efficient CO 2 sequestration methods in a controlled large-scale environment. - Highlights: • Alkaline pH conditions sustained by photosynthesis alone gave rise to supersaturation. • Cyanobacteria confirmed not to act as nucleation sites for calcite precipitation. • Mixed flow bio-reactor used to mimic natural conditions to quantify CO 2 sequestration.

  5. Use of diluted Ca(OH)2 suspensions and their transformation into nanostructured CaCO3 coatings: A case study in strengthening heritage materials (stucco, adobe and stone)

    Science.gov (United States)

    Lanzón, Marcos; Madrid, Juan Antonio; Martínez-Arredondo, Ana; Mónaco, Soledad

    2017-12-01

    In the conservation of heritage materials, the effectiveness of diluted nanolime suspensions in consolidating surfaces is scarcely explored. This paper aims to examine the surface modification of stucco, adobe and stone by deposition of Ca(OH)2 nanoparticles. The nanoparticles were applied in five consecutive coats and transformed into CaCO3 by atmospheric CO2 creating a compatible coating with the surface. The coatings were studied by erosion tests (pull-off tests) and examined by scanning electron microscopy (SEM) and optical microscopy. The tests confirmed the surface resistance was clearly improved due to formation of nanostructured cementing CaCO3 coatings. In addition, the coatings did not practically alter the surface colour due to the diluted nature of the suspensions. To conclude, Ca(OH)2 nanoparticles-based coatings are appropriate solutions to extend the durability of traditional heritage materials, such as stucco, adobe or stone.

  6. Thermodynamic modeling of the CaO-SiO2-CaCO3-HCaCO2O closed and open system at 25ºC

    Directory of Open Access Journals (Sweden)

    Martínez-Ramírez, S.

    2003-06-01

    Full Text Available This paper reports on a thermodynamic calculation-based study of the CaO-SiOCaCO2-CaCOCaCO3-HCaCO2O closed system at 25 °C, conducted to determine the range of carbonate ion concentrations at which each phase of the system is stable. Portlandite (CH and the CSH gel were found to be stable for carbonate ion concentrations of less than or equal to 7.62 X 10-3 mM/kg and 1.62 x 10-2 mM/kg, respectively. The CSH gel was found to remain stable in the system at pH values ranging from 10.18 to 10.48. In the CaO-SiO2-H2O open system at 25 °C, likewise studied, with PCO2 held constant at atmospheric values, only hydrated silica (SH and calcite were found to be stable.En este trabajo se estudia el sistema CaO2-CaCO3-H2O, cerrado y a 25 ºC a través de cálculos termodinámicos, y se determina el rango de concentración de ion carbonato en el que son estables cada una de las fases del sistema. Se concluye que la portlandita (CH y el gel CSH son estables para concentraciones de ion carbonato iguales o inferiores a 7,62 X 10-3 niM/kg y 1,62 x 10-2 mM/kg respectivamente. El rango de pH en el que el gel CSH es estable en el sistema es 10,18-10,48. También se estudia el sistema CaO-SiO2-H2O a 25 °C, en sistema abierto a PCO2 constante e igual a la de dicho gas en la atmósfera, encontrando que solo la sílice hidratada (SH y la calcita son estables en dicho sistema.

  7. Thermodynamic investigation of the CaO-Al2O3-CaCO3-H2O closed system at 25 C and the influence of Na2O

    International Nuclear Information System (INIS)

    Damidot, D.; Stronach, S.; Kindness, A.; Atkins, M.; Glasser, F.P.

    1994-01-01

    The solubilities of calcium hemicarboaluminate, calcium monocarboaluminate and calcium tricarboaluminate have been determined and the equilibrium phase diagram for the CaO-Al 2 O 3 -CaCO 3 -H 2 O closed system at 25 C has been calculated. Six isothermally invariant points have been located involving six stable hydrates: CH, C 3 AH 6 , AH 3 , calcium hemicarboaluminate, calcium monocarboaluminate and calcite. Calcium tricarboaluminate, the carbonate analogue of ettringite, does not appear to be stable at 25 C. This study was part of a larger study on radioactive waste solidification

  8. Experimental Study Of Precipitation Competition Of Ca(OH)2 And Mg(OH)2 On MSF Desalination Condition

    International Nuclear Information System (INIS)

    Sumijanto

    2001-01-01

    Competition study has been carried out by using sea water simulation containing of 142 on deposit ppm of bicarbonate ion, 400 ppm of calcium ion and 1272 ppm of magnesium ion. Experiment was performed by heating sample at temperature 50, 60, 70, 80, and 90 C for 30 minutes. Precipitation competition of Ca(OHh and Mg(OHh was analyzed by reduction of calcium and magnesium ion. Experiment data showed information that at the temperature bellow 800 o C CaCO 3 precipitation was more dominant, meanwhile above than 80 o C precipitation Mg(OH) 2 was more dominant. This competition occurred because at temperature more than 80 o C rate of hydroxyl ion formation and Mg(OH) 2 recipitation was greater than CaCO 3 precipitation and at temperature bellow 80 o C rate of hydrolysis carbonate ion was less than thermal decomposition bicarbonates ion

  9. A Comparative Study of the Effect of MgO and CaCO3 as Support Materials in the Synthesis of Carbon Nanotubes with Fe/Co as Catalyst

    Directory of Open Access Journals (Sweden)

    Ezekiel D. Dikio

    2014-01-01

    Full Text Available A comparative study of the effect of magnesium oxide and calcium carbonate as support material in the synthesis of carbon nanotubes using the catalyst Fe/Co is presented. The synthesized carbon nanotubes were characterized with Raman spectroscopy, scanning electron spectroscopy (SEM, high-resolution transmission electron microscopy (HRTEM, X-ray diffraction spectroscopy (XRD, and energy dispersive spectroscopy (EDS. The morphology of the carbon nanotubes synthesized with magnesium oxide as support material gives rise to carbon nanotubes with consistent and well-defined structure unlike that synthesized with calcium carbonate. The ID/IG ratio of synthesized carbon nanotubes (CNTs was 0.8544 for magnesium oxide supported compared to 0.8501 for calcium carbonate supported carbon nanotube.

  10. CaCO3-N İlişkileri 4.Değişik Reaksiyonlu Toprakların Karşılaştırılması

    OpenAIRE

    BROHI, A.Raşit; Aydeniz, A.

    1990-01-01

    Kireç - azot bitkilerini açıklayabilmek için, değişik reaksiyonlu 3örnek (Rize-asit, Siverek nötr - hafif alkali, Aligör - alkali) alınarak bunların : % 0-0.5-1-1.5-2-3-4-5-10 oranlarında CaCO3 ve 0-1-5-20:50- 100-200 500 veya 1000 ppm düzeylerinde N katmak sureti ile hazırlanan topraklarda büyütme odasında, mini-biyolojik yöntemle domates yetiştirmek ve 65 gün (alkali topraktakileri 87. gün sonra) sonra hasat etmek suretiyle yapılan araştırma sonuçları şu şekilde özetlenebilir. 1.Asit top...

  11. Relationship between 13C and 18O fractionation and changes in major element composition in a recent calcite-depositing spring - a model of chemical variations with inorganic CaCO3 precipitation

    International Nuclear Information System (INIS)

    Usdowski, E.; Hoefs, J.; Menschel, G.

    1979-01-01

    A theoretical model is derived in which isotopic fractionations can be calculated as a function of variations in dissolved carbonate species on CO 2 degassing and calcite precipitation. This model is tested by application to a calcite-depositing spring system near Westerhof, Germany. In agreement with the model, 13 C of the dissolved carbonate species changes systematically along the flow path. The difference in delta values between the upper and lower part of the stream is about 1%. The 13 C content of the precipitated calcite is different from that expected from the theoretical partitioning. The isotopic composition of the solid CaCO 3 is similar to that of the dissolved carbonate, though in theory it should be isotopically heavier by about 2.4%. The 18 O composition of dissolved carbonate and H 2 O is constant along the stream. Calculated calcite-water temperatures differ by about +5 0 C from the observed temperatures demonstrating isotopic disequilibrium between the water and precipitated solid. This is attributed to kinetic effects during CaCO 3 deposited from a highly supersaturated solution, in which precipitation is faster than equilibration with respect to isotopes. Plant populations in the water have virtually no influence on CO 2 degassing, calcite saturation and isotopic fractionation. Measurements of Psub(CO 2 ), Ssub(C) and 13 C within a diurnal cycle demonstrate that metabolic effects are below the detection limit in a system with a high supply-rate of dissolved carbonate species. The observed variations are due to differences in CO 2 degassing and calcite precipitation, caused by a continuously changing hydrodynamic conditions and carbonate nucleation rates. (Auth.)

  12. Concrete-Water-Interaction and Ikaite (CaCO3.6H2O) Precipitation in a Man-Made River Bed

    Science.gov (United States)

    Boch, R.; Dietzel, M.; Reichl, P.; Leis, A.; Pölt, P.; Baldermann, A.

    2014-12-01

    Centimetre-thick, beige-colored and soft crusts were observed shortly after construction of a man-made river bed, i.e. a small natural river was bypassed flowing through a new bed lined with concrete and blocks. Hydrochemical investigations during wintertime - when water temperatures dropped down close to freezing - showed surprisingly high pH values up to 13.0 and elevated Ca2+ concentrations up to 200 mg/l. Both, the artifical and natural (downstream) section of the river bed were affected by the anomalous hydrochemistry and formation of prominent secondary precipitates. In order to better understand the particular and rapid water-rock-interaction, a hydrochemical monitoring program was launched and several of the delicate precipitates were recovered in refrigerator boxes in their original solution. The samples were analyzed in the laboratory within a few hours after sampling and stored at 1 °C. XRD and FT-IR patterns clearly revealed the predominant occurrence of "ikaite" in the crusts next to minor amounts of other carbonates (calcite, aragonite, vaterite) and detrital minerals. Ikaite - calcium carbonate hexahydrate - is a worldwide rarely documented carbonate mineral. This mineral is metastable and needs particular and narrow conditions in order to precipitate from solutions, i.e. a very limited water-temperature range between 0 and 4 °C (with ambient-pressure and low-salinity), highly alkaline pH conditions, high supersaturation values, and in many cases carbonate precipitation inhibitors (e.g. phosphates). Outside these conditions it disintegrates into calcite and water within minutes to hours. The few places of ikaite formation include Ikka Fjord in Greenland, Arctic- and Antarctic sea-ice and some sites of water mixing at Mono Lake, California. Combining detailed field monitoring results, solid-phase analyses and regional meteorological data (rainfall, water discharge, temperature) with hydrogeochemical modeling allows constraining the mechanisms of

  13. Effect of drug loading method against the dissolution mechanism of encapsulated amoxicillin trihidrate drug in matrix of semi-IPN chitosan-poly (N-vinyl pyrrolidone) hydrogel with pore forming agent CaCO3

    Science.gov (United States)

    Nurjannah, Yanah; Budianto, Emil

    2018-04-01

    Heliobacter pylori (H.pylori) is a type of bacteria that causes inflammation in the lining of the stomach. The treatment of the bacterial infection by using conventional medicine which is amoxicillin trihidrate has a very short retention time in the stomach which is about 1-1,5 hours. Floating drug delivery system is expected to have a long retention time in the stomach so the efficiency of drug can be achieved. In this study, has been synthesized matrix of semi-IPN chitosan-Poly(N-vinil pyrrolidone) hydrogel with a pore-forming agent of CaCO3 under optimum conditions. Amoxicillin is encapsulated in a matrix hydrogel to be applied as a floating drug delivery system by in situ loading and post loading methods. The encapsulation efficiency and dissolution of in situ loading and post loading hydrogels are performed in vitro on gastric pH. In situ loading hydrogel shows higer percentage of encapsulation efficiency and dissolution compared to post loading hydrogel. The encapsulation efficiency of in situ and post loading hydrogels were 92,1% and 89,4%, respectively. The aim of drug dissolution by mathematical equation model is to know kinetics and the mecanism of dissolution. The kinetics release of in situ hydrogel tends to follow first order kinetics, while the post loading hydrogel follow the Higuchi model. The dissolution mecanism of hydrogels is erosion.

  14. Synthesis and characterization of injectable composites of poly[D,L-lactide-co-(ε-caprolactone)] reinforced with β-TCP and CaCO3 for intervertebral disk augmentation.

    Science.gov (United States)

    López, Alejandro; Persson, Cecilia; Hilborn, Jöns; Engqvist, Håkan

    2010-10-01

    Degeneration of the intervertebral disk constitutes one of the major causes of low back pain in adults aged 20-50 years old. In this study, injectable, in situ setting, degradable composites aimed for intervertebral disk replacement were prepared. β-TCP and calcium carbonate particles were mixed into acrylic-terminated oligo[D,L-lactide-co-(ε-caprolactone)], which were crosslinked at room temperature. The structure of the oligomers was confirmed by 1H-NMR spectroscopy. The composites were examined via SEM, and the mechanical properties of the crosslinked networks were determined. The porous β-TCP particles showed good mechanical anchorage to the matrix due to polymer penetration into the pores. In vitro degradation tests showed that the composites containing β-TCP slowly degraded, whereas the composites containing CaCO3 exhibited apatite formation capacity. It was concluded that the surface area, morphology, and solubility of the fillers might be used to control the degradation properties. The incorporation of fillers also increased both the elastic modulus and the maximum compression strength of the composites, properties that were similar to those of the physiological disk. These materials have potential for long-term intervertebral disk replacement and regenerative scaffolds because of their low degradation rates, bioactivity, and mechanical properties.

  15. Microstructure and corrosion study of porous Mg-Zn-Ca alloy in simulated body fluid

    Science.gov (United States)

    Annur, Dhyah; Erryani, Aprilia; Lestari, Franciska P.; Nyoman Putrayasa, I.; Gede, P. A.; Kartika, Ika

    2017-03-01

    Magnesium alloys had been considered as promising biomedical devices due to their biocompatibility and biodegradability. In this present work, microstructure and corrosion properties of Mg-Zn-Ca-CaCO3 porous magnesium alloy were examined. Porous metals were fabricated through powder metallurgy process with CaCO3 addition as a foaming agent. CaCO3 content was varied (1, 5, and 10%wt) followed by sintering process in 650 °C in Argon atmosphere for 10 and 15 h. The microstructure of the resulted alloys was analyzed by scanning electron microscopy (SEM) equipped with energy dispersive spectrometry data (EDS). Further, to examine corrosion properties, electrochemical test were conducted using G750 Gamry Instrument in accordance with ASTM standard G5-94 in simulated body fluid (Hank’s solution). As it was predicted, increasing content of foaming agent was in line with the increasing of pore formation. The electrochemical testing indicated corrosion rate would increase along with the increasing of foaming agent. The porous Mg-Zn-Ca alloy which has more porosity and connecting area will corrode much faster because it can transport the solution containing chloride ion which accelerated the chemical reaction. Highest corrosion resistance was given by Mg-Zn-Ca-1CaCO3-10 h sintering with potential corrosion of  -1.59 VSCE and corrosion rate of 1.01 mmpy. From the microstructure after electrochemical testing, it was revealed that volcano shaped structure and crack would occur after exposure to Hank’s solution

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

    Directory of Open Access Journals (Sweden)

    B. Kasenov

    2012-03-01

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

  17. Calcite Wettability in the Presence of Dissolved Mg2+ and SO42-

    DEFF Research Database (Denmark)

    Generosi, Johanna; Ceccato, Marcel; Andersson, Martin Peter

    2017-01-01

    that potential determining ions in seawater, Mg2+, Ca2+, and SO42–, are responsible for altering the wettability of calcite surfaces. In favorable conditions, e.g., elevated temperature, calcium at the calcite surface can be replaced by magnesium, making organic molecules bind more weakly and water molecules...... bind more strongly, rendering the surface more hydrophilic. We used atomic force microscopy in chemical force mapping mode to probe the adhesion forces between a hydrophobic CH3-terminated AFM tip and a freshly cleaved calcite {10.4} surface to investigate wettability change in the presence of Mg2...... with calcite even after rinsing with CaCO3-saturated deionized water, suggesting sorption on or in calcite. When the calcite-saturated solution of MgSO4 was replaced by calcite-saturated NaCl at the same ionic strength, adhesion force increased again, indicating that the effect is reversible and suggesting Mg...

  18. Experimental examination of the Mg-silicate-carbonate system at ambient temperature: Implications for alkaline chemical sedimentation and lacustrine carbonate formation

    Science.gov (United States)

    Tutolo, Benjamin M.; Tosca, Nicholas J.

    2018-03-01

    Despite their clear economic significance, Cretaceous presalt carbonates of the South Atlantic continental margins are not well-described by published facies models. This knowledge gap arises, in part, because the chemical processes that generate distinctive sedimentary products in alkaline, non-marine environments are poorly understood. Here, we use constraints inferred from reported mineralogical and geochemical features of presalt carbonate rocks to design and perform a suite of laboratory experiments to quantify the processes of alkaline chemical sedimentation. Using real-time observations of in-situ fluid chemistry, post-experiment analysis of precipitated solids, and geochemical modeling tools, we illustrate that spherulitic carbonates and Mg-silicate clays observed in presalt carbonates were likely precipitated from elevated pH (∼10-10.5) waters with high concentrations of silica and alkali cations typical of intermediate to felsic rocks, such as Na+ and K+. Charge balance constraints require that these cations were not counterbalanced to any significant degree by anions typical of seawater, such as Cl- and SO4-, which implies minimal seawater involvement in presalt deposition. Experimental data suggest that, at this alkaline pH, only modest concentrations (i.e., ∼0.5-1 mmol/kg) of Ca++ would have been required to precipitate spheroidal CaCO3. Given the rapid rates of CaCO3 nucleation and growth under such conditions, it is unlikely that Ca++ concentrations in lake waters ever exceeded these values, and sustained chemical fluxes are therefore required for extensive sediment accumulation. Moreover, our experiments indicate that the original mineralogy of presalt CaCO3 could have been calcite or aragonite, but the differing time scales of precipitation between CaCO3 and Mg-silicates would have tended to skew the Mg/Ca ratio in solution towards elevated values which favor aragonite. Mg-silicate nucleation and growth rates measured during our experiments

  19. Precipitação de CaCO3 em algas marinhas calcárias e balanço de CO2 atmosférico: os depósitos calcários marinhos podem atuar como reservas planetárias de carbono?

    OpenAIRE

    Carlos Eduardo Amancio

    2007-01-01

    As atividades humanas nos últimos dois séculos vêm provocando um aumento na concentração de dióxido de carbono (CO2) atmosférico. Um dos efeitos desse aumento é um incremento na produtividade primária de algumas espécies vegetais terrestres, que dessa maneira atuam como sequestradoras de carbono. Nos oceanos, o CO2 é armazenado principalmente na forma de carbonato de cálcio (CaCO3), e o aumento na sua concentração leva a uma acidificação da água do mar e a uma menor disponibilidade de íons ca...

  20. Peletização do lodo de esgoto e adição de CaCO3 na produção de matéria seca e absorção de Zn, Cu e Ni pelo milho em três latossolos

    Directory of Open Access Journals (Sweden)

    R. S. Berton

    1997-12-01

    Full Text Available Em experimento de casa de vegetação, realizado em Campinas (SP, no período de janeiro a maio de 1980, estudaram-se os efeitos da peletização do lodo de esgoto, nas doses 0, 1 e 5% (v/v do material seco, na produção de matéria seca e na absorção de Zn, Cu e Ni pela parte aérea do milho (Zea mays L., em latossolo roxo (LR, latossolo vermelho-escuro (LE e latossolo vermelho-amarelo (LV, que receberam ou não adição de CaCO3 suficiente para elevação do pH em água para 6,0. O experimento foi realizado em vasos com dois litros de capacidade, delineados em blocos ao acaso, com três repetições, e os tratamentos arranjados num esquema fatorial. Após 200 dias de incubação dos solos com o lodo e CaCO3, cultivaram-se quatro plantas de milho em cada vaso. A parte aérea foi quantificada 56 dias após a germinação, sendo cortada, seca, pesada e analisada para os elementos Zn, Cu e Ni. Amostras de terra de cada tratamento foram retiradas e tiveram os metais extraídos pelo DTPA. A peletização do lodo de esgoto resultou em diminuição significativa na produção de matéria seca pela parte aérea do milho, nos três solos estudados, em comparação com o lodo não peletizado. A adição de CaCO3 proporcionou aumento significativo na produção de matéria seca do milho apenas nos dois solos mais ácidos (LE e LV e diminuiu o acúmulo de Zn na parte aérea desse vegetal cultivado no LE, sem distinção quanto ao tipo de lodo aplicado, não se observando diferenças significativas na absorção de Ni, em todos os solos analisados. A incorporação do lodo peletizado , que continha 19% menos Zn e Ni que o não peletizado, resultou em menor absorção de Zn, Cu e Ni nos três solos, exceto para o Ni no LR. Para todos os solos investigados, o método do DTPA mostrou-se mais adequado em prognosticar as quantidades disponíveis de Zn e de Cu para o milho, independentemente do tipo de lodo de esgoto aplicado e da elevação ou não do pH do solo pela adição de CaCO3.

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

    Science.gov (United States)

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

    2010-05-01

    Mg/Ca (1 wt.%, 5 wt.%, 10 wt.% Ca) composites were prepared from pure magnesium and calcium powders using the powder metallurgy method, aiming to enlarge the addition of Ca content without the formation of Mg(2)Ca. The microstructures, mechanical properties and cytotoxicities of Mg/Ca composite samples were investigated. The corrosion of Mg/Ca composites in Dulbecco's modified Eagle's medium (DMEM) for various immersion intervals was studied by electrochemical impedance spectroscopy measurements and environmental scanning electron microscope, with the concentrations of released Mg and Ca ions in DMEM for various immersion time intervals being measured. It was shown that the main constitutional phases were Mg and Ca, which were uniformly distributed in the Mg matrix. The ultimate tensile strength (UTS) and elongation of experimental composites decreased with increasing Ca content, and the UTS of Mg/1Ca composite was comparable with that of as-extruded Mg-1Ca alloy. The corrosion potential increased with increasing Ca content, whereas the current density and the impedance decreased. It was found that the protective surface film formed quickly at the initial immersion stage. With increasing immersion time, the surface film became compact, and the corrosion rate of Mg/Ca composites slowed down. The surface film consisted mainly of CaCO(3), MgCO(3)x3H(2)O, HA and Mg(OH)(2) after 72 h immersion in DMEM. Mg/1Ca and Mg/5Ca composite extracts had no significant toxicity (p>0.05) to L-929 cells, whereas Mg/10Ca composite extract induced approximately 40% reduced cell viability. Copyright (c) 2009 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

  2. Effect of Mg and Si co-substitution on microstructure and strength of tricalcium phosphate ceramics.

    Science.gov (United States)

    García-Páez, Ismael H; Carrodeguas, Raúl García; De Aza, Antonio H; Baudín, Carmen; Pena, Pilar

    2014-02-01

    Magnesium and silicon co-doped tricalcium phosphate (TCP) ceramics with compositions corresponding to 0, 5 and 10wt% CaMg(SiO3)2 in the system Ca3(PO4)2-CaMg(SiO3)2 were obtained by conventional sintering of compacted mixtures of Ca3(PO4)2, MgO, SiO2 and CaCO3 powders at temperatures between 1100 and 1450°C. Microstructural analyses were performed by X-ray diffraction and field emission scanning electron microscopy with energy dispersive spectroscopy. Major phases in the obtained ceramics were β- or α+β-tricalcium phosphate containing Mg and Si in solid solution. Certain amounts of liquid were formed during sintering depending on composition and temperature. There were found significant differences in distributions of strength determined by the diametral compression of disc tests (DCDT). Failure strengths were controlled by microstructural defects associated with phase development. Mg and Si additions were found to be effective to improve densification and associated strength of TCP bioceramics due to the enhancement of sintering by the low viscosity liquids formed. The highest density and strength were obtained for the TCP ceramic containing 5wt% CaMg(SiO3)2 sintered at 1300°C. Cracking and porosity increased at higher temperatures due to grain growth and swelling. © 2013 Published by Elsevier Ltd.

  3. Corrosion study of resorbable Ca60Mg15Zn25 bulk metallic glasses in physiological fluids

    Directory of Open Access Journals (Sweden)

    Rafał Babilas

    2017-10-01

    Full Text Available The corrosion activity of amorphous plates of Ca60Mg15Zn25 alloy was investigated. The biocompatible elements were selected for the alloy composition. The electrochemical corrosion and immersion tests were carried out in a multi-electrolyte fluid and Ringer's solution. Better corrosion behavior was observed for the samples tested in a multi-electrolyte fluid despite the active dissolution of Ca and Mg in Ringer's solution. The experimental results indicated that reducing concentration of NaCl from 8.6 g/dm3 for Ringer's solution to 5.75 g/dm3 caused the decrease of the corrosion rate. The volume of the hydrogen evolved after 480 min in Ringer's solution (40.1 ml/cm2 was higher in comparison with that obtained in a multi-electrolyte fluid (24.4 ml/cm2. The values of open-circuit potential (EOCP for the Ca60Mg15Zn25 glass after 1 h incubation in Ringer's solution and a multi-electrolyte fluid were determined to be −1553 and −1536 mV vs. a saturated calomel electrode (SCE. The electrochemical measurements indicated a shift of the corrosion current density (jcorr from 1062 μA/cm2 for the sample tested in Ringer's solution to 788 μA/cm2 for the specimen immersed in a multi-electrolyte fluid. The corrosion products analysis was conducted by using the X-ray photoelectron spectroscopy (XPS. The corrosion products were identified to be CaCO3, Mg(OH2, CaO, MgO and ZnO. The mechanism of corrosion process was proposed and described based on the microscopic observations. The X-ray diffraction and Fourier transform infrared spectroscopy (FTIR also indicated that Ca(OH2, CaCO3, Zn(OH2 and Ca(Zn(OH32·2H2O mainly formed on the surface of the studied alloy. Keywords: Ca-based metallic glasses, X-ray photoelectron spectroscopy, FTIR spectroscopy, X-ray diffraction, Corrosion resistance, Hydrogen evaluation

  4. Ab initio study of single-crystalline and polycrystalline elastic properties of Mg-substituted calcite crystals.

    Science.gov (United States)

    Zhu, L-F; Friák, M; Lymperakis, L; Titrian, H; Aydin, U; Janus, A M; Fabritius, H-O; Ziegler, A; Nikolov, S; Hemzalová, P; Raabe, D; Neugebauer, J

    2013-04-01

    We employ ab initio calculations and investigate the single-crystalline elastic properties of (Ca,Mg)CO3 crystals covering the whole range of concentrations from pure calcite CaCO3 to pure magnesite MgCO3. Studying different distributions of Ca and Mg atoms within 30-atom supercells, our theoretical results show that the energetically most favorable configurations are characterized by elastic constants that nearly monotonously increase with the Mg content. Based on the first principles-derived single-crystalline elastic anisotropy, the integral elastic response of (Ca,Mg)CO3 polycrystals is determined employing a mean-field self-consistent homogenization method. As in case of single-crystalline elastic properties, the computed polycrystalline elastic parameters sensitively depend on the chemical composition and show a significant stiffening impact of Mg atoms on calcite crystals in agreement with the experimental findings. Our analysis also shows that it is not advantageous to use a higher-scale two-phase mix of stoichiometric calcite and magnesite instead of substituting Ca atoms by Mg ones on the atomic scale. Such two-phase composites are not significantly thermodynamically favorable and do not provide any strong additional stiffening effect. Copyright © 2013 Elsevier Ltd. All rights reserved.

  5. 1400 Liter 1.8K Test Facility

    International Nuclear Information System (INIS)

    Peterson, T.J.; Rabehl, R.J.; Sylvester, C.D.

    1997-08-01

    A double bath superfluid helium dewar has been constructed and operated at Fermilab's Magnet Test Facility. The 1.8 K portion of the dewar is sized to contain a superconducting magnet up to 0.5 meters in diameter and 4 meters long in a vertical orientation in 0.12 MPa pressurized superfluid. The dewar can also provide a subcooled Helium I environment for tests; the entire temperature range from 4.4 K to 1. 8 K at 0.12 MPa is available. This paper describes the system design, lambda plate, heat exchanger, and performance

  6. Hydrothermal replacement of calcite by Mg-carbonates

    Science.gov (United States)

    Jonas, Laura; Mueller, Thomas; Dohmen, Ralf

    2014-05-01

    The transport of heat and mass through the Earth's crust is coupled to mineral reactions and the exchange of isotopes and elements between different phases. Carbonate minerals are a major constituent of the Earth's crust and play an important role in different physical, chemical and even biological processes. In this experimental study, the element exchange reaction between calcite (CaCO3) and a Mg-rich fluid phase is investigated under hydrothermal conditions. Single crystals of calcite (2x2x2 mm) react with 1 ml of a 1 M MgCl2 solution at 200° C in a Teflon-lined steel autoclave for different times between one day and four weeks. The reaction leads to the formation of a porous reaction front and the pseudomorphic replacement of calcite by dolomite [CaMg(CO3)2] and magnesite (MgCO3). Scanning electron microscopy revealed that the reaction rim consists of small Mg-carbonate rhombs closely attached to each other, suggesting that the replacement reaction takes place by a dissolution-precipitation mechanism. Typically, the observed reaction front can be divided into two different domains. The outer part of the reaction rim, i.e. from the mineral surface in contact to the fluid inwards, consists of magnesite, whereas the inner part of the rim surrounding the unreacted calcite core consists of Ca-rich dolomite. The formation of a porous microstructure that varies in different parts of the reaction rim is a direct result of the large molar volume change induced by the replacement of calcite by magnesite and dolomite. The developing porosity therefore creates fluid pathways that promote the progress of the reaction front towards the unreacted core of the single crystal. Compositional profiles measured perpendicular to the mineral surface across the reactions rims using electron microprobe (EMPA) further revealed a compositional gradient within the reaction rim with regard to the structure-forming elements Mg and Ca. Here, the amount of Mg incorporated in both product

  7. Control of temperature and aqueous Mg2+/Ca2+ ratio on the (trans-)formation of ikaite

    Science.gov (United States)

    Purgstaller, B.; Dietzel, M.; Baldermann, A.; Mavromatis, V.

    2017-11-01

    The calcium carbonate hexahydrate mineral ikaite (CaCO3 ṡ 6 H2O) has been documented in aquatic environments at near-freezing temperatures. An increase of the prevailing temperature in the depositional environment, results in the transformation of natural ikaite into less soluble calcium carbonate phases occasionally leaving calcite pseudomorphs in the sediments, which are considered as an indicator for primary cold water temperatures. Detailed understanding on the physicochemical parameters controlling ikaite (trans-)formation however, such as temperature and reactive solution chemical composition, are still under debate. In order to study the formation of ikaite, we conducted precipitation experiments under controlled physicochemical conditions (pH = 8.3 ± 0.1; T = 6, 12, and 18 ± 0.1 °C) at defined aqueous molar Mg/Ca ratios. The transformation of ikaite into anhydrous calcium carbonate polymorphs was investigated in solution and at air exposure. The obtained results reveal the formation of ikaite at temperatures up to 12 °C, whereas Mg-rich amorphous calcium carbonate precipitated at 18 °C. In contact with the reactive solution ikaite transformed into aragonite at aqueous molar Mg2+/Ca2+ ratios of ≥14. In contrast, ikaite separated from the Mg-rich solution and exposed to air transformed in all cases into calcite/vaterite. The herein obtained temperature limit of ≤12 for ikaite formation is significantly higher than formerly expected and most probably caused by (i) the high saturation degree of the solution with respect to ikaite and (ii) the slow dehydration of the aqueous Ca2+ ion at low temperatures. This result questions the suitability of calcite pseudomorphs (i.e. glendonites) as a proxy for near-freezing temperatures. Moreover, our findings show that the CaCO3 polymorph formed from ikaite is strongly controlled by the physicochemical conditions, such as aqueous molar Mg2+/Ca2+ ratio of the reactive fluid and H2O availability throughout the

  8. Effect of different seawater Mg

    NARCIS (Netherlands)

    Mewes, A.; Langer, G.; de Nooijer, L.J.; Bijma, J.; Reichart, G.J.

    2014-01-01

    Magnesium, incorporated in foraminiferal calcite (Mg/CaCC), is used intensively to reconstruct past seawater temperatures but, in addition to temperature, the Mg/CaCC of foraminiferal tests also depends on the ratio of Mg and Ca in seawater (Mg/CaSW). The physiological mechanisms responsible for

  9. Quasicrystal-reinforced Mg alloys.

    Science.gov (United States)

    Kyun Kim, Young; Tae Kim, Won; Hyang Kim, Do

    2014-04-01

    The formation of the icosahedral phase (I-phase) as a secondary solidification phase in Mg-Zn-Y and Mg-Zn-Al base systems provides useful advantages in designing high performance wrought magnesium alloys. The strengthening in two-phase composites (I-phase + α -Mg) can be explained by dispersion hardening due to the presence of I-phase particles and by the strong bonding property at the I-phase/matrix interface. The presence of an additional secondary solidification phase can further enhance formability and mechanical properties. In Mg-Zn-Y alloys, the co-presence of I and Ca 2 Mg 6 Zn 3 phases by addition of Ca can significantly enhance formability, while in Mg-Zn-Al alloys, the co-presence of the I-phase and Mg 2 Sn phase leads to the enhancement of mechanical properties. Dynamic and static recrystallization are significantly accelerated by addition of Ca in Mg-Zn-Y alloy, resulting in much smaller grain size and more random texture. The high strength of Mg-Zn-Al-Sn alloys is attributed to the presence of finely distributed Mg 2 Sn and I-phase particles embedded in the α -Mg matrix.

  10. Bending strength of glass-ceramics based on 3CaO.P2O5-SiO2-MgO glass system

    International Nuclear Information System (INIS)

    Daguano, J.K.M.F.; Suzuki, P.A.; Santos, C.; Fernandes, M.H.V.; Elias, C.N.

    2009-01-01

    In this work, the Modulus of Rupture of bioactive glass-ceramic based on 3CaO.P 2 O 5 -SiO 2 -MgO system was investigated, aiming its use in bone-restorations. The mechanical property was correlated with microstructural and crystallographic features of this material. High-purity starting-powders, CaCO 3 , SiO 2 , MgO, Ca (H 2 PO 4 ).H 2 O, were used in this study. The powders were mixed in a stoichiometric ratio, using planetary ball-mill. The suspensions were dried, sieved and melted at 1600 deg C, for 4h. The casting ones were cooled quickly until annealing temperature 700 deg C, in which remained for 2h, with controlled cooling-rate until ambient temperature. Bulks of glass were heat-treated with temperatures varying between 700 deg C and 1100 deg C, for 4h, being after that, cooled at 3 deg C/min. Bioactive glass and glass-ceramic were characterized by HRXRD (high resolution X-ray diffraction), where whitlockite was main phase. The microstructure was analyzed by scanning electronic microscopy. Modulus of Rupture was determined by four-point bending testing using specimens of 1.5 x 2 x 25 mm and glasses presented strength near to 70MPa, while glass ceramics treated at 975 deg C-4h, presented bending strength of 120MPa. (author)

  11. Myasthenia Gravis (MG): Medical Management

    Science.gov (United States)

    ... take effect, prior to surgery or for myasthenic crisis. However, some people receive regular plasmapheresis or IVIg as a supplement to immunosuppressant drugs. Pregnancy In rare cases, pregnancy appears to trigger the onset of MG. ...

  12. Molecular Diffusion of Toluene through CaCO3-Filled Natural Rubber Composites

    Directory of Open Access Journals (Sweden)

    Hedayatollah Sadeghi Ghari

    2012-12-01

    Full Text Available The transport properties of liquids and gases through polymeric materialsplay a very important role in some areas of industrial applications. In thisstudy, natural rubber (NR/CaCO3 composites were prepared by melt mixingmethod. By equilibrium swelling test, the transport process of toluene in the prepared natural rubber composites was investigated. The diffusion and transport of toluene through calcium carbonate-filled natural rubber composites have been studied in the temperature range 25–45°C. The diffusion of toluene through these composites was studied with special reference to the effect of filler concentration and temperature.The transport coefficients such as diffusion, permeation and sorption coefficients were estimated from the swelling data. To find out the mechanism of diffusion in prepared composites, the results of swelling studies were applied to an empirical equation. In these composites, diffusion is approximately based on Fickian diffusion mechanism and by increases in temperature; diffusion mechanism is more close to Fickian mechanism. Increase of filler content in composite would result in decreased ultimateswelling and slower diffusion rate of solvent. The diffusion rate, diffusion coefficient and the permeability increased by temperature. The study of the diffusion of toluene through filled natural rubber indicated that the concentration of filler plays an important role in the diffusion, sorption and permeation coefficients. Also interfacial interactions in NR composites were checked by dynamic-mechanical analysis. The microstructure and dispersion of calcium carbonate particles in natural rubber matrix were studiedby field emission scanning electron microscopy (FE-SEM. In general, the results of swelling tests, dynamic-mechanical analysis and FE-SEM images show that the optimized value of filler in NR composites is equal to 10 phr calcium carbonate.

  13. Acoustic and Hydrodynamic Cavitations for Nano CaCO3 Synthesis

    Science.gov (United States)

    Sonawane, Shirish H.; Kulkarni, Ravindra D.

    Calcium carbonate is a common inorganic compound known as limestone. Calcium carbonate has many applications in industries such as medicine, agriculture, paint plastic and surface coatings etc. The vast majority of calcium carbonate used in industry is extracted by mining process. Pure calcium carbonate (e.g. for food or pharmaceutical use), is synthesized by passing carbon dioxide into a solution of calcium hydroxide slurry. In this process calcium carbonate precipitates out, and this grade of product is referred to as precipitate calcium carbonate (abbreviated as PCC).

  14. Synthesis of CaCO3 nanoparticles by carbonation of lime solutions in reverse micellar systems

    NARCIS (Netherlands)

    Heeres, H.J.; Jain, R.; Mehra, A.; Dagaonkar, M.V.

    2004-01-01

    Application of reverse micelles for the synthesis of nano-sized calcium carbonate particles in different solvents (cyclohexane, decane and heptane) has been investigated. The effect of the mole ratio of water-to-surfactant (R) and type of solvent has been studied on the size and nature of the

  15. Foaming of waste cathode ray tube panel glass via CaCO3

    DEFF Research Database (Denmark)

    König, Jakob; Petersen, Rasmus Rosenlund; Yue, Yuanzheng

    The disposal of obsolete electrical and electronic equipment has become a global environmental problem. However, with responsible collecting, dismantling and materials separation, majority of materials can be recycled. Cathode ray tube (CRT) glass represents as much as two-thirds of the weight...

  16. CaCO3-N İlişkileri 7.Sonraki Etkileri

    OpenAIRE

    BROHI, A.Raşit; Aydeniz, A.

    2014-01-01

    Kireç-azot ilişkilerinin sonraki etkilerini, açıklayabilmek iç'&v topraklarımızın genel karakterlerini yansıtan kırmızı kahverenginde, alkali re aksiyonlu kil bünyeli, yüksek CaCO« ve düşük O.M. içeren; K.D.K. yük¬sek tortul kökenli Aligör (ÜrfaJ toprağı alınarak; buna 6 düzeyde (% 0-0,5-1 -2-5-1C)'kireç ve 9 düzeyde {0-1-5-2C-50-100-200-1coo-5oco ppm N) azot katılmış; büyütme odasında minibiyolojilk yönteme 87 gün süreyle domates yetiştirilmiş, 3 ay süreyle tarla ka...

  17. CaCO3-N İlişkieri 3.Nötr Toprakta

    OpenAIRE

    Aydeniz, A.; BROHİ, A.R.

    1990-01-01

    Nötral toprakta azot-kireç ilişkilerini açıklayabilmek için kireç içermeyen, nötr hafif alkali,bazaltlık kökenli Siverek toprağı alınarak bu¬na 9 düzeyde (% 0-0.5-1-1.5-2-3-4-5-10) kireç ve8 düzeyde (0-1-5-20-50 100-200-50 ppm) azot katmak suretiyle hazırlanan topraklarda; büyütme odasında, mini - biyolojik yöntemle domates yetiştirmek ve 65 gün son¬ra- hasat etmek suretiyle yapman araştırma sonuçları şu şekilde özetle¬nebilir 1. Asit toprakta, kireç katılmayan (CaC03 0> örneklerden orta...

  18. Evaluation of the CaCO3 dissolution proxies in sediment cores from above the lysocline

    Digital Repository Service at National Institute of Oceanography (India)

    Naik, S.S.; Naidu, P.D.

    and the total CaCO sub(3) content shows that the total carbonate variations are controlled by the finer fraction composed of juvenile foraminifera, foraminifera fragments and coccolithophores. This further confirms the observed variations of CaCO sub(3) content...

  19. The nature of unusual luminescence in natural calcite, CaCO3

    Energy Technology Data Exchange (ETDEWEB)

    Gaft, M.; Nagli, L.; Panczer, G.; Waychunas, G.; Porat, N.

    2008-11-01

    The unusual luminescence of particular varieties of natural pink calcite (CaCO{sub 3}) samples was studied by laser-induced time-resolved luminescence spectroscopy at different temperatures. The luminescence is characterized by intense blue emission under short-wave UV lamp excitation with an extremely long decay time, accompanied by pink-orange luminescence under long wave UV excitation. Our investigation included optical absorption, natural thermostimulated luminescence (NTL) and Laser-Induced Breakdown Spectroscopy (LIBS) studies. Two luminescence centers were detected: a narrow violet band, with {lambda}{sub max} = 412 nm, {Delta} = 45 nm, two decay components of {tau}{sub 1} = 5 ns and {tau}{sub 2} = 7.2 ms, accompanied by very long afterglow, and an orange emission band with {lambda}{sub max} = 595 nm, {Delta} = 90 nm and {tau} = 5 ns. Both luminescence centers are thermally unstable with the blue emission disappearing after heating at 500 C, and the orange emission disappearing after heating at different temperatures starting from 230 C, although sometimes it is stable up to 500 C in different samples. Both centers have spectral-kinetic properties very unusual for mineral luminescence, which in combination with extremely low impurity concentrations, prevent their identification with specific impurity related emission. The most likely explanation of these observations may be the presence of radiation-induced luminescence centers. The long violet afterglow is evidently connected with trapped charge carrier liberation, with their subsequent migration through the valence band and ultimate recombination with a radiation-induced center responsible for the unusual violet luminescence.

  20. Thermoluminescence dating of CaCO3 nodules from buried soil of the lower Narmada Valley

    International Nuclear Information System (INIS)

    Nambi, K.S.V.; Hegde, K.T.M.

    1982-01-01

    Calcium carbonate nodules excavated at an archaeological site in Lower Narmada River Valley have been dated by the thermoluminescence technique. Tiny, sensitive TL dosimeters using natural CaF 2 as the phosphor, were employed to evaluate the natural radiation levels at the excavation site over a period of a year. The estimated TL age value is 22890 yrs B.P. with an uncertainty of about +/- 8%. The reported 14 C age of these nodules is 22452 +/- 550 years B.P

  1. Improving the desulfurization performance of CaCO3 with sodium humate

    Science.gov (United States)

    Feng, Run; Sun, Zhiguo; Zhang, Wenqing; Huang, Hao; Hu, Haihang; Zhang, Li; Xie, Hongyong

    2018-02-01

    The influence of these factors on desulphurization efficiency was studied by changing the amount of calcium carbonate, the concentration of sulfur dioxide, the liquid flow rate of absorbent and the air flow rate, the optimum working condition was determined by the research of limestone-gypsum desulphurization process commonly used in industry. By changing the amount of calcium carbonate, we conclude that the volume of water in the desulfurization efficiency does not increase with the adding amount of calcium carbonate. The optimum conditions were determined : at the condicion of the concentration of 500ppm of sulfur dioxide, 10g calcium carbonate, 150L/h liquid flow and the minimum air flow rate of 6.75m3/h, the highest desulfurization efficiency was close to 100% when sodium humate was not added, but the holding time was only about 5 minutes. After adding 3g of humic acid, the desulfurization efficiency was improved obviously, and the instantaneous efficiency of 100% lasting for about 40 minutes. It can be seen that, calcium carbonate in the addition of humic acid sodium can significantly improve the absorption of calcium carbonate performance of SO2.

  2. Effects in the solubility of CaCO3: experimental study and model description.

    OpenAIRE

    Coto, Baudilio; Martos, M. Carmen; Peña, José L.; Rodríguez, Rosalía; Pastor, Gabriel

    2012-01-01

    Combustibles fósiles Crude oil is usually co-produced with reservoir water, with increasing content in the production fluid along field life. Changes in temperature, pressure, and/or chemical composition may cause significant precipitation of inorganic salts (¿scales¿) during production. Therefore, the knowledge of the influence that different variables may have on salt solubility is critical to anticipate or identify potential flow assurance problems related to scales. The pre...

  3. Effect of organic matrices on the determination of the trace element chemistry (Mg, Sr, Mg/Ca, Sr/Ca) of aragonitic bivalve shells (Arctica islandica). Comparison of ICP-OES and LA-ICP-MS data

    International Nuclear Information System (INIS)

    Schoene, Bernd R.; Zhang, Zengjie; Jacob, Dorrit; Soldate, Analia; Gillikin, David P.; Tuetken, Thomas; Garbe-Shoenberg, Dieter; McConnaughey, Ted

    2010-01-01

    The element chemistry of biogenic carbonates can provide important data on past environments. However, the Sr/Ca and Mg/Ca ratios as well as the Mg and Sr concentrations of biological carbonates, especially aragonitic bivalves often depart from apparent thermodynamic equilibrium. When measured in situ by means of LA-ICP-MS, the Mg concentration is often substantially enriched (two- to threefold) near the organic-rich, annual growth lines. To test the hypothesis that some organic components exert a major influence on the skeletal metal content, the element chemistry of different shell components (insoluble organic matrix, IOM; dissolved CaCO 3 and soluble organics, SOM) of Arctica islandica was measured by means of ICP-OES and LA-ICP-MS. The ICP-OES data indicate that the IOM is strongly enriched in Mg (130 ppm) and depleted in Sr and Ca (10 ppm and 0.22 wt%, respectively) when compared to the whole biomineral (Mg: 68 to 99 ppm, Sr: 860 to 1,060 ppm, Ca: ∼35.72 wt%). Although the average relative abundance of the IOM barely exceeds 0.46 wt%, its chemical composition in combination with its heterogeneous distribution across the shell can significantly increase estimates of the Mg concentration if measured in situ by LA-ICP-MS. Depending on the distribution of the IOM, the Ca concentration may be significantly lower locally than the average Ca concentration of the whole shell (35.72 wt%). If this remains undetected, the Mg concentration of shell portions with higher than average IOM content is overestimated by LA-ICP-MS and, conversely, the Mg concentration is underestimated in shell portions with lower than average IOM content. Removal of the IOM prior to the chemical analysis by LA-ICP-MS or mathematical correction for the IOM-derived magnesium concentrations is therefore strongly advised. The different chemistry of the IOM may also exert a major control on the trace element to calcium ratios. Shell portions enriched in IOM will show up to 200 times higher Mg

  4. Preparation and Hydrogen Storage Properties of Mg-Rich Mg-Ni Ultrafine Particles

    Directory of Open Access Journals (Sweden)

    Jianxin Zou

    2012-01-01

    Full Text Available In the present work, Mg-rich Mg-Ni ultrafine powders were prepared through an arc plasma method. The phase components, microstructure, and hydrogen storage properties of the powders were carefully investigated. It is found that Mg2Ni and MgNi2 could be obtained directly from the vapor state reactions between Mg and Ni, depending on the local vapor content in the reaction chamber. A nanostructured MgH2 + Mg2NiH4 hydrogen storage composite could be generated after hydrogenation of the Mg-Ni ultrafine powders. After dehydrogenation, MgH2 and Mg2NiH4 decomposed into nanograined Mg and Mg2Ni, respectively. Thermogravimetry/differential scanning calorimetry (TG/DSC analyses showed that Mg2NiH4 phase may play a catalytic role in the dehydriding process of the hydrogenated Mg ultrafine particles.

  5. Alterations of Mg2+ After Hemorrhagic Shock.

    Science.gov (United States)

    Lee, Mun-Young; Yang, Dong Kwon; Kim, Shang-Jin

    2017-11-01

    Hemorrhagic shock is generally characterized by hemodynamic instability with cellular hypoxia and diminishing cellular function, resulting from an imbalance between systemic oxygen delivery and consumption and redistribution of fluid and electrolytes. Magnesium (Mg) is the fourth most abundant cation overall and second most abundant intracellular cation in the body and an essential cofactor for the energy production and cellular metabolism. Data for blood total Mg (tMg; free-ionized, protein-bound, and anion-bound forms) and free Mg 2+ levels after a traumatic injury are inconsistent and only limited information is available on hemorrhagic effects on free Mg 2+ as the physiologically active form. The aim of this study was to determine changes in blood Mg 2+ and tMg after hemorrhage in rats identifying mechanism and origin of the changes in blood Mg 2+ . Hemorrhagic shock produced significant increases in blood Mg 2+ , plasma tMg, Na + , K + , Cl - , anion gap, partial pressures of oxygen, glucose, and blood urea nitrogen but significant decreases in RBC tMg, blood Ca 2+ , HCO 3 - , pH, partial pressures of carbon dioxide, hematocrit, hemoglobin, total cholesterol, and plasma/RBC ATP. During hemorrhagic shock, K + , anion gap, and BUN showed significant positive correlations with changes in blood Mg 2+ level, while Ca 2+ , pH, and T-CHO correlated to Mg 2+ in a negative manner. In conclusion, hemorrhagic shock induced an increase in both blood-free Mg 2+ and tMg, resulted from Mg 2+ efflux from metabolic damaged cell with acidosis and ATP depletion.

  6. Modeling and stabilities of Mg/MgH2 interfaces: A first-principles investigation

    Directory of Open Access Journals (Sweden)

    Jia-Jun Tang

    2014-07-01

    Full Text Available We have theoretically investigated the modeling and the structural stabilities of various Mg/MgH2 interfaces, i.e. Mg(101¯0/MgH2(210, Mg(0001/MgH2(101 and Mg(101¯0/MgH2(101, and provided illuminating insights into Mg/MgH2 interface. Specifically, the main factors, which impact the interfacial energies, are fully considered, including surface energies of two phases, mutual lattice constants of interface model, and relative position of two phases. The surface energies of Mg and MgH2, on the one hand, are found to be greatly impacting the interfacial energies, reflected by the lowest interfacial energy of Mg(0001/MgH2(101 which is comprised of two lowest energy surfaces. On the other hand, it is demonstrated that the mutual lattice constants and the relative position of two phases lead to variations of interfacial energies, thus influencing the interface stabilities dramatically. Moreover, the Mg-H bonding at interface is found to be the determinant of Mg/MgH2 interface stability. Lastly, interfacial and strain effects on defect formations are also studied, both of which are highly facilitating the defect formations. Our results provide a detailed insight into Mg/MgH2 interface structures and the corresponding stabilities.

  7. Transformation of Mg-bearing amorphous calcium carbonate to Mg-calcite - In situ monitoring

    Science.gov (United States)

    Purgstaller, Bettina; Mavromatis, Vasileios; Immenhauser, Adrian; Dietzel, Martin

    2016-02-01

    The formation of Mg-bearing calcite via an amorphous precursor is a poorly understood process that is of relevance for biogenic and abiogenic carbonate precipitation. In order to gain an improved insight on the controls of Mg incorporation in calcite formed via an Mg-rich amorphous calcium carbonate (Mg-ACC) precursor, the precipitation of Mg-ACC and its transformation to Mg-calcite was monitored by in situ Raman spectroscopy. The experiments were performed at 25.0 ± 0.03 °C and pH 8.3 ± 0.1 and revealed two distinct pathways of Mg-calcite formation: (i) At initial aqueous Mg/Ca molar ratios ⩽ 1:6, Mg-calcite formation occurs via direct precipitation from solution. (ii) Conversely, at higher initial Mg/Ca molar ratios, Mg-calcite forms via an intermediate Mg-rich ACC phase. In the latter case, the final product is a calcite with up to 20 mol% Mg. This Mg content is significant higher than that of the Mg-rich ACC precursor phase. Thus, a strong net uptake of Mg ions from the solution into the crystalline precipitate throughout and also subsequent to ACC transformation is postulated. Moreover, the temporal evolution of the geochemical composition of the reactive solution and the Mg-ACC has no significant effect on the obtained ;solubility product; of Mg-ACC. The enrichment of Mg in calcite throughout and subsequent to Mg-ACC transformation is likely affected by the high aqueous Mg/Ca ratio and carbonate alkalinity concentrations in the reactive solution. The experimental results have a bearing on the formation mechanism of Mg-rich calcites in marine early diagenetic environments, where high carbonate alkalinity concentrations are the rule rather than the exception, and on the insufficiently investigated inorganic component of biomineralisation pathways in many calcite secreting organisms.

  8. Re-examining the 26Mg(α ,α')26Mg reaction: Probing astrophysically important states in 26Mg

    Science.gov (United States)

    Adsley, P.; Brümmer, J. W.; Li, K. C. W.; Marín-Lámbarri, D. J.; Kheswa, N. Y.; Donaldson, L. M.; Neveling, R.; Papka, P.; Pellegri, L.; Pesudo, V.; Pool, L. C.; Smit, F. D.; van Zyl, J. J.

    2017-11-01

    Background: The 22Ne(α ,n )25Mg reaction is one of the neutron sources for the s process in massive stars. The properties of levels in 26Mg above the α -particle threshold control the strengths of the 22Ne(α ,n )25Mg and 22Ne(α ,γ )26Mg reactions. The strengths of these reactions as functions of temperature are one of the major uncertainties in the s process. Purpose: Information on the existence, spin, and parity of levels in 26Mg can assist in constraining the strengths of the 22Ne(α ,γ )26Mg and 22Ne(α ,n )25Mg reactions, and therefore in constraining s -process abundances. Methods: Inelastically scattered α particles from a 26Mg target were momentum-analyzed in the K600 magnetic spectrometer at iThemba LABS, South Africa. The differential cross sections of states were deduced from the focal-plane trajectory of the scattered α particles. Based on the differential cross sections, spin and parity assignments to states are made. Results: A newly assigned 0+ state was observed in addition to a number of other states, some of which can be associated with states observed in other experiments. Some of the deduced Jπ values of the states observed in the present study show discrepancies with those assigned in a similar experiment performed at RCNP Osaka. The reassignments and additions of the various states can strongly affect the reaction rate at low temperatures. Conclusion: The number, location, and assignment of levels in 26Mg that may contribute to the 22Ne+α reactions are not clear. Future experimental investigations of 26Mg must have an extremely good energy resolution to separate the contributions from different levels. Coincidence experiments of 26Mg provide a possible route for future investigations.

  9. Antibacterial biodegradable Mg-Ag alloys

    Directory of Open Access Journals (Sweden)

    D Tie

    2013-06-01

    Full Text Available The use of magnesium alloys as degradable metals for biomedical applications is a topic of ongoing research and the demand for multifunctional materials is increasing. Hence, binary Mg-Ag alloys were designed as implant materials to combine the favourable properties of magnesium with the well-known antibacterial property of silver. In this study, three Mg-Ag alloys, Mg2Ag, Mg4Ag and Mg6Ag that contain 1.87 %, 3.82 % and 6.00 % silver by weight, respectively, were cast and processed with solution (T4 and aging (T6 heat treatment.The metallurgical analysis and phase identification showed that all alloys contained Mg4Ag as the dominant β phase. After heat treatment, the mechanical properties of all Mg-Ag alloys were significantly improved and the corrosion rate was also significantly reduced, due to presence of silver. Mg(OH2 and MgO present the main magnesium corrosion products, while AgCl was found as the corresponding primary silver corrosion product. Immersion tests, under cell culture conditions, demonstrated that the silver content did not significantly shift the pH and magnesium ion release. In vitro tests, with both primary osteoblasts and cell lines (MG63, RAW 264.7, revealed that Mg-Ag alloys show negligible cytotoxicity and sound cytocompatibility. Antibacterial assays, performed in a dynamic bioreactor system, proved that the alloys reduce the viability of two common pathogenic bacteria, Staphylococcus aureus (DSMZ 20231 and Staphylococcus epidermidis (DSMZ 3269, and the results showed that the killing rate of the alloys against tested bacteria exceeded 90%. In summary, biodegradable Mg-Ag alloys are cytocompatible materials with adjustable mechanical and corrosion properties and show promising antibacterial activity, which indicates their potential as antibacterial biodegradable implant materials.

  10. Intra-individual comparison of different contrast media concentrations (300 mg, 370 mg and 400 mg iodine) in MDCT

    Energy Technology Data Exchange (ETDEWEB)

    Behrendt, Florian F.; Keil, Sebastian; Plumhans, Cedric; Guenther, Rolf W. [RWTH Aachen University, Department of Diagnostic Radiology, University Hospital, Aachen (Germany); Pietsch, Hubertus; Jost, Gregor; Sieber, Martin A.; Seidensticker, Peter [Bayer Schering Pharma AG, Berlin (Germany); Mahnken, Andreas H. [RWTH Aachen University, Department of Diagnostic Radiology, University Hospital, Aachen (Germany); RWTH Aachen University, Applied Medical Engineering, Helmholtz-Institute for Biomedical Engineering, Aachen (Germany)

    2010-07-15

    To compare intra-individual contrast enhancement in multi-detector-row computed tomography (MDCT) using contrast media (CM) containing 300, 370 and 400 mg iodine per ml (mgI/ml). Six pigs underwent repeated chest MDCT using three different CM (iopromide 300, iopromide 370, iomeprol 400). An identical iodine delivery (IDR) rate of 1.5 gI/s and a constant total iodine dose of 300 mg/kg body weight were used. Dynamic CT were acquired at the level of the pulmonary artery, and the ascending and descending aorta. After the time enhancement curves were computed, the pulmonary and aortic peak enhancement, time to peak and plateau time above 300 HU were calculated. Intra-individual peak contrast enhancement was significantly higher for the 300 mgI/ml contrast medium compared with the 370 and 400 mgI/ml media: pulmonary trunk 595 HU vs 516 HU (p = 0.0093) vs 472HU (p = 0.0005), and aorta 505 HU vs 454 HU (p = 0.0008) vs 439 HU (p = 0.0001), respectively. Comparison of time to peaks showed no significant difference. Plateau times were significantly longer for the 300 mgI/ml than for the 370 and 400 mgI/ml CM at all anatomical sites. Given normalised IDR and total iodine burden, the use of CM with a standard concentration with 300 mg iodine/ml provides improved contrast enhancement compared with highly concentrated CM in the chest. (orig.)

  11. Hydrothermal replacement of biogenic and abiogenic aragonite by Mg-carbonates - Relation between textural control on effective element fluxes and resulting carbonate phase

    Science.gov (United States)

    Jonas, Laura; Müller, Thomas; Dohmen, Ralf; Immenhauser, Adrian; Putlitz, Benita

    2017-01-01

    Dolomitization, i.e., the secondary replacement of calcite or aragonite (CaCO3) by dolomite (CaMg[CO3]2), is one of the most volumetrically important carbonate diagenetic processes. It occurs under near surface and shallow burial conditions and can significantly modify rock properties through changes in porosity and permeability. Dolomitization fronts are directly coupled to fluid pathways, which may be related to the initial porosity/permeability of the precursor limestone, an existing fault network or secondary porosity/permeability created through the replacement reaction. In this study, the textural control on the replacement of biogenic and abiogenic aragonite by Mg-carbonates, that are typical precursor phases in the dolomitization process, was experimentally studied under hydrothermal conditions. Aragonite samples with different textural and microstructural properties exhibiting a compact (inorganic aragonite single crystal), an intermediate (bivalve shell of Arctica islandica) and open porous structure (skeleton of coral Porites sp.) were reacted with a solution of 0.9 M MgCl2 and 0.015 M SrCl2 at 200 °C. The replacement of aragonite by a Ca-bearing magnesite and a Mg-Ca carbonate of non-stoichiometric dolomitic composition takes place via a dissolution-precipitation process and leads to the formation of a porous reaction front that progressively replaces the aragonite precursor. The reaction leads to the development of porosity within the reaction front and distinctive microstructures such as gaps and cavities at the reaction interface. The newly formed reaction rim consists of chemically distinct phases separated by sharp boundaries. It was found that the number of phases and their chemical variation decreases with increasing initial porosity and reactive surface area. This observation is explained by variations in effective element fluxes that result in differential chemical gradients in the fluid within the pore space of the reaction rim. Observed

  12. The effect of the MgO buffer layer thickness on magnetic anisotropy in MgO/Fe/Cr/MgO buffer/MgO(001)

    Energy Technology Data Exchange (ETDEWEB)

    Kozioł-Rachwał, Anna, E-mail: a.koziolrachwal@aist.go.jp [National Institute of Advanced Industrial Science and Technology, Spintronics Research Center, Tsukuba, Ibaraki 305-8568 (Japan); AGH University of Science and Technology, Faculty of Physics and Applied Computer Science, al. Mickiewicza 30, 30-059 Kraków (Poland); Nozaki, Takayuki; Zayets, Vadym; Kubota, Hitoshi; Fukushima, Akio; Yuasa, Shinji [National Institute of Advanced Industrial Science and Technology, Spintronics Research Center, Tsukuba, Ibaraki 305-8568 (Japan); Suzuki, Yoshishige [National Institute of Advanced Industrial Science and Technology, Spintronics Research Center, Tsukuba, Ibaraki 305-8568 (Japan); Graduate School of Engineering Science, Osaka University, 1-3 Machikaneyama, Toyonaka, Osaka 560-8531 (Japan)

    2016-08-28

    The relationship between the magnetic properties and MgO buffer layer thickness d was studied in epitaxial MgO/Fe(t)/Cr/MgO(d) layers grown on MgO(001) substrate in which the Fe thickness t ranged from 0.4 nm to 1.1 nm. For 0.4 nm ≤ t ≤ 0.7 nm, a non-monotonic coercivity dependence on the MgO buffer thickness was shown by perpendicular magneto-optic Kerr effect magnetometry. For thicker Fe films, an increase in the buffer layer thickness resulted in a spin reorientation transition from perpendicular to the in-plane magnetization direction. Possible origins of these unusual behaviors were discussed in terms of the suppression of carbon contamination at the Fe surface and changes in the magnetoelastic anisotropy in the system. These results illustrate a method to control magnetic anisotropy in MgO/Fe/Cr/MgO(d) via an appropriate choice of MgO buffer layer thickness d.

  13. Ultraviolet spectra of Mg in liquid helium

    International Nuclear Information System (INIS)

    Moriwaki, Y.; Morita, N.

    1999-01-01

    Emission and absorption spectra of Mg atoms implanted in liquid helium have been observed in the ultraviolet region. We have presented a model of exciplex formation of Mg-He 10 and found that this model is more suitable for understanding the dynamics in the 3s3p 1 P→3s 21 S transition than the bubble model. (orig.)

  14. Optical absorption and thermoluminescence in Mg O, Mg O:Ni and Mg O:Li irradiated at room temperature

    International Nuclear Information System (INIS)

    Delgado, L.

    1984-01-01

    Optical absorption and thermoluminescence (TL) studies in Mg O, Mg O:Ni and Mg O:Li irradiated at room temperature are presented. In pure Mg O the thermal annihilation of Fe3+ by recombination with thermally released electrons at ∼ 90 and 175 degree centigree and the V center annealing by hole release up to 100 degree centigree cause the observed glow peaks at these temperatures. The TL excitation spectrum shows two maxima at 245 nm (electron center) and 288 nm (Fe3+). In Mg O:Ni X irradiation induces Fe 2 + →- Fe 3 + and Ni 2 + → Ni 3 + oxidations. Two TL emission bands centered at 110 degree centigree (red) and 80 o C (green) are assigned to electron release and their recombination at Fe 3 + and Ni 3 + respectively. In Mg O:Li two TL emission bands, one blue (430 nm) and the other red (730 nm) with excitation maxima at 245 nm (electron center) and 200 nm (hole center) respectively are observed. No V-center formation was detected in both Ni and Li doped samples. (Author) 42 refs

  15. Mg2BIV: Narrow Bandgap Thermoelectric Semiconductors

    Science.gov (United States)

    Kim, Il-Ho

    2018-05-01

    Thermoelectric materials can convert thermal energy directly into electric energy and vice versa. The electricity generation from waste heat via thermoelectric devices can be considered as a new energy source. For instance, automotive exhaust gas and all industrial processes generate an enormous amount of waste heat that can be converted to electricity by using thermoelectric devices. Magnesium compound Mg2BIV (BIV = Si, Ge or Sn) has a favorable combination of physical and chemical properties and can be a good base for the development of new efficient thermoelectrics. Because they possess similar properties to those of group BIV elemental semiconductors, they have been recognized as good candidates for thermoelectric applications. Mg2Si, Mg2Ge and Mg2Sn with an antifluorite structure are narrow bandgap semiconductors with indirect band gaps of 0.77 eV, 0.74 eV, and 0.35 eV, respectively. Mg2BIV has been recognized as a promising material for thermoelectric energy conversion at temperatures ranging from 500 K to 800 K. Compared to other thermoelectric materials operating in the similar temperature range, such as PbTe and filled skutterudites, the important aspects of Mg2BIV are non-toxic and earth-abundant elements. Based on classical thermoelectric theory, the material factor β ( m* / m e)3/2μκ L -1 can be utilized as the criterion for thermoelectric material selection, where m* is the density-of-states effective mass, me is the mass of an electron, μ is the carrier mobility, and κL is the lattice thermal conductivity. The β for magnesium silicides is 14, which is very high compared to 0.8 for iron silicides, 1.4 for manganese silicides, and 2.6 for silicon-germanium alloys. In this paper, basic phenomena of thermoelectricity and transport parameters for thermoelectric materials were briefly introduced, and thermoelectric properties of Mg2BIV synthesized by using a solid-state reaction were reviewed. In addition, various Mg2BIV compounds were discussed

  16. Superconductivity in MgB{sub 2}

    Energy Technology Data Exchange (ETDEWEB)

    Muranaka, Takahiro; Akimitsu, Jun [Aoyama Gakuin Univ., Kanagawa (Japan). Dept. of Physics and Mathematics

    2011-07-01

    We review superconductivity in MgB{sub 2} in terms of crystal and electronic structure, electron-phonon coupling, two-gap superconductivity and application. Finally, we introduce the development of new superconducting materials in related compounds. (orig.)

  17. Additive Manufacturing of Magnesium (Mg) Alloys

    Data.gov (United States)

    National Aeronautics and Space Administration — The proposed work is to investigate additive manufacturing techniques for Mg alloys.  It will leverage off research being conducted at University of Florida and...

  18. Chondrogenic differentiation of ATDC5-cells under the influence of Mg and Mg alloy degradation.

    Science.gov (United States)

    Martinez Sanchez, Adela H; Feyerabend, Frank; Laipple, Daniel; Willumeit-Römer, Regine; Weinberg, Annelie; Luthringer, Bérengère J C

    2017-03-01

    Biodegradable magnesium (Mg)-based materials are a potential alternative to permanent implants for application in children. Nevertheless effects of those materials on growth plate cartilage and chondrogenesis have not been previously evaluated. In vitro differentiation of ATDC5 cells was evaluated under the influence of pure Mg (PMg), Mg with 10wt% of gadolinium (Mg-10Gd) and Mg with 2wt% of silver (Mg-2Ag) degradation products (extracts) and direct cell culture on the materials. Gene expression showed an inhibitory effect on ATDC5 mineralization with the three extracts and a chondrogenic potential of Mg-10Gd. Cells cultured in Mg-10Gd and Mg-2Ag extracts showed the same proliferation and morphology than cells cultured in growth conditions. Mg-10Gd induced an increase in production of ECM and a bigger cell size, similar to the effects found with differentiation conditions. An increased metabolic activity was observed in cells cultured under the influence of Mg-10Gd extracts, indicated by an acidic pH during most of the culture period. After 7days of culture on the materials, ATDC5 growth, distribution and ECM synthesis were higher on Mg-10Gd samples, followed by Mg-2Ag and PMg, which was influenced by the homogeneity and composition of the degradation layer. This study confirmed the tolerance of ATDC5 cells to Mg-based materials and a chondrogenic effect of Mg-10Gd. Further studies in vitro and in vivo are necessary to evaluate cell reactions to those materials, as well as the effects on bone growth and the biocompatibility of the alloying system in the body. Copyright © 2016 Elsevier B.V. All rights reserved.

  19. Mg/Ca of Continental Ostracode Shells

    Science.gov (United States)

    Ito, E.; Forester, R. M.; Marco-Barba, J.; Mezquita, F.

    2007-12-01

    Marine ionic chemistry is thought to remain constant. This, together with the belief that marine calcifiers partition Mg/Ca in a systematic manner as functions of temperature (and Mg/Ca) of water forms the basis of the Mg/Ca thermometer. In continental settings both of these assumptions are usually not true. Continental waters contain a wide variety of solutes in absolute and relative ion concentrations. Hence, waters with identical Mg/Ca may have very different concentrations of Mg and Ca and very different anions. Here we use two examples to focus on the effects of ion chemistry on Mg/Ca partitioning in continental ostracode shells and we ignore the complexities of solute evolution, which can change Mg/Ca over timescales of minutes to millennia. Palacios-Fest and Dettman (2001) conducted a monthly study of ,Cypridopsis vidua at El Yeso Lake in Sonora, Mexico. They established a relation between temperature and average shell Mg/Ca using regression analyses on averaged data. When their Mg/Ca-temperature relation is applied to monthly ,C. vidua data from Page Pond near Cleveland, Ohio, water temperatures of -8 to -1°C are obtained. The observed Mg/Ca ranges for El Yeso Lake (0.31 to 0.46) and Page Pond (0.33 to 0.46) are similar, as are their specific conductivities (700 to 850μS for El Yeso Lake; 400 to 600μS for Page Pond). However, [Ca] is 140-260 mg/L for El Yeso, but only 70-90 mg/L for Page Pond. Page Pond data, in fact, shows a good temperature shell Mg/Ca relation for .C. vidua, but the relation is different from that at El Yeso. Hence, shell Mg/Ca is a multi-valued, family of curves function of temperature and Mg/Ca of water that depends on the [Mg] and [Ca] values in water and perhaps other factors. Our second example comes from sites near Valencia, Spain and involves shell data for ,Cyprideis torosa, an estuarine ostracode that is tolerant of a wide range of salinity and can live in continental waters as long as the carbonate alkalinity to Ca ratio is

  20. Prussian Blue Mg-Li Hybrid Batteries.

    Science.gov (United States)

    Sun, Xiaoqi; Duffort, Victor; Nazar, Linda F

    2016-08-01

    The major advantage of Mg batteries relies on their promise of employing an Mg metal negative electrode, which offers much higher energy density compared to graphitic carbon. However, the strong coulombic interaction of Mg 2+ ions with anions leads to their sluggish diffusion in the solid state, which along with a high desolvation energy, hinders the development of positive electrode materials. To circumvent this limitation, Mg metal negative electrodes can be used in hybrid systems by coupling an Li + insertion cathode through a dual salt electrolyte. Two "high voltage" Prussian blue analogues (average 2.3 V vs Mg/Mg 2+ ; 3.0 V vs Li/Li + ) are investigated as cathode materials and the influence of structural water is shown. Their electrochemical profiles, presenting two voltage plateaus, are explained based on the two unique Fe bonding environments. Structural water has a beneficial impact on the cell voltage. Capacities of 125 mAh g -1 are obtained at a current density of 10 mA g -1 (≈C/10), while stable performance up to 300 cycles is demonstrated at 200 mA g -1 (≈2C). The hybrid cell design is a step toward building a safe and high density energy storage system.

  1. Formation and Corrosion Resistance of Mg-Al Hydrotalcite Film on Mg-Gd-Zn Alloy

    Science.gov (United States)

    Ba, Z. X.; Dong, Q. S.; Kong, S. X.; Zhang, X. B.; Xue, Y. J.; Chen, Y. J.

    2017-06-01

    An environment-friendly technique for depositing a Mg-Al hydrotalcite (HT) (Mg6Al2(OH)16-CO3ṡ4H2O) conversion film was developed to protect the Mg-Gd-Zn alloy from corrosion. The morphology and chemical compositions of the film were analyzed by scanning electronic microscope (SEM) equipped with energy dispersive X-ray spectroscopy (EDS), X-ray diffraction (XRD) and Raman spectroscopy (RS), respectively. The electrochemical test and hydrogen evolution test were employed to evaluate the biocorrosion behavior of Mg-Gd-Zn alloy coated with the Mg-Al HT film in the simulated body fluid (SBF). It was found that the formation of Mg-Al HT film was a transition from amorphous precursor to a crystalline HT structure. The HT film can effectively improve the corrosion resistance of magnesium alloy. It indicates that the process provides a promising approach to modify Mg-Gd-Zn alloy.

  2. Microstructural evolution in Mg-rich Mg-Zn-Y alloys

    International Nuclear Information System (INIS)

    Biswas, T.; Ranganathan, S.; Nair, S.; Bajargan, G.

    2005-01-01

    Mg-rich Mg-Zn-Y alloys with nominal compositions Mg 97 Zn 1 Y 2 , Mg 97 Zn 2 Y 1 , Mg 92 Zn 6.5 Y 1.5 and Mg 97-x Zn 1 Y 2 Zr x have been chosen for the present study. These alloys are prepared by using sand casting mold. The sand cast alloys are remelted and subjected to copper mold casting and melt spinning techniques. The effect of cooling rate on microstructures was studied. It is observed that the size of the precipitates decreases with an increase of cooling rate. The formation of nano precipitates results in higher strength of the alloy as compared to the conventional alloys. The microstructures of melt spun ribbons are compared with RS/PM (rapidly solidified power metallurgy) Mg 97 Zn 1 Y 2 alloy, obtained from a different source. (author)

  3. Melting relations in the MgO-MgSiO3 system up to 70 GPa

    Science.gov (United States)

    Ohnishi, Satoka; Kuwayama, Yasuhiro; Inoue, Toru

    2017-06-01

    Melting experiments in a binary system MgO-MgSiO3 were performed up to 70 GPa using a CO2 laser heated diamond anvil cell. The quenched samples were polished and analyzed by a dualbeam focused ion beam (FIB) and a field emission scanning electron microscope (FE-SEM), respectively. The liquidus phase and the eutectic composition were determined on the basis of textual and chemical analyses of sample cross sections. Our experimental results show that the eutectic composition is the Si/Mg molar ratio of 0.76 at 35 GPa and it decreases with increasing pressure. Above 45 GPa, it becomes relatively constant at about 0.64-0.65 Si/Mg molar ratio. Using our experimental data collected at a wide pressure range up to 70 GPa together with previous experimental data, we have constructed a thermodynamic model of the eutectic composition of the MgO-MgSiO3 system. The eutectic composition extrapolated to the pressure and temperature conditions at the base of the mantle is about 0.64 Si/Mg molar ratio. The modeled eutectic composition is quite consistent with a previous prediction from ab initio calculations (de Koker et al. in Earth Planet Sci Lett 361:58-63, 2013), suggesting that the simple assumption of a non-ideal regular solution model can well describe the melting relation of the MgO-MgSiO3 system at high pressure. Our results show that the liquidus phase changes from MgO-periclase to MgSiO3-bridgmanite at 35 GPa for the simplified pyrolite composition ( 0.7 Si/Mg molar ratio), while MgSiO3-bridgmanite is the liquidus phase at the entire lower mantle conditions for the chondritic composition ( 0.84 Si/Mg molar ratio).

  4. Chondrogenic differentiation of ATDC5-cells under the influence of Mg and Mg alloy degradation

    Energy Technology Data Exchange (ETDEWEB)

    Martinez Sanchez, Adela H., E-mail: adela.martinez@hzg.de [Helmholtz-Zentrum Geesthacht, Institute of Material Research, Department for Structural Research on Macromolecules, Geesthacht (Germany); Feyerabend, Frank; Laipple, Daniel; Willumeit-Römer, Regine [Helmholtz-Zentrum Geesthacht, Institute of Material Research, Department for Structural Research on Macromolecules, Geesthacht (Germany); Weinberg, Annelie [Department of Orthopedics and Orthopedic Surgery, Medical University of Graz (Austria); Luthringer, Bérengère J.C. [Helmholtz-Zentrum Geesthacht, Institute of Material Research, Department for Structural Research on Macromolecules, Geesthacht (Germany)

    2017-03-01

    Biodegradable magnesium (Mg)-based materials are a potential alternative to permanent implants for application in children. Nevertheless effects of those materials on growth plate cartilage and chondrogenesis have not been previously evaluated. In vitro differentiation of ATDC5 cells was evaluated under the influence of pure Mg (PMg), Mg with 10 wt% of gadolinium (Mg-10Gd) and Mg with 2 wt% of silver (Mg-2Ag) degradation products (extracts) and direct cell culture on the materials. Gene expression showed an inhibitory effect on ATDC5 mineralization with the three extracts and a chondrogenic potential of Mg-10Gd. Cells cultured in Mg-10Gd and Mg-2Ag extracts showed the same proliferation and morphology than cells cultured in growth conditions. Mg-10Gd induced an increase in production of ECM and a bigger cell size, similar to the effects found with differentiation conditions. An increased metabolic activity was observed in cells cultured under the influence of Mg-10Gd extracts, indicated by an acidic pH during most of the culture period. After 7 days of culture on the materials, ATDC5 growth, distribution and ECM synthesis were higher on Mg-10Gd samples, followed by Mg-2Ag and PMg, which was influenced by the homogeneity and composition of the degradation layer. This study confirmed the tolerance of ATDC5 cells to Mg-based materials and a chondrogenic effect of Mg-10Gd. Further studies in vitro and in vivo are necessary to evaluate cell reactions to those materials, as well as the effects on bone growth and the biocompatibility of the alloying system in the body. - Highlights: • Degradation of PMg, and Mg-2Ag do not influence ATDC5 cells growth and chondrogenic redifferentiation. • Mg-10Gd enhances fast chondrogenic redifferentiation and expression of hyperthrophic markers on ATDC5 cells. • Further evaluation of the effects of PMg, Mg-10Gd and Mg-2Ag in vivo are necessary to confirm its potential for application in growing bones.

  5. Chondrogenic differentiation of ATDC5-cells under the influence of Mg and Mg alloy degradation

    International Nuclear Information System (INIS)

    Martinez Sanchez, Adela H.; Feyerabend, Frank; Laipple, Daniel; Willumeit-Römer, Regine; Weinberg, Annelie; Luthringer, Bérengère J.C.

    2017-01-01

    Biodegradable magnesium (Mg)-based materials are a potential alternative to permanent implants for application in children. Nevertheless effects of those materials on growth plate cartilage and chondrogenesis have not been previously evaluated. In vitro differentiation of ATDC5 cells was evaluated under the influence of pure Mg (PMg), Mg with 10 wt% of gadolinium (Mg-10Gd) and Mg with 2 wt% of silver (Mg-2Ag) degradation products (extracts) and direct cell culture on the materials. Gene expression showed an inhibitory effect on ATDC5 mineralization with the three extracts and a chondrogenic potential of Mg-10Gd. Cells cultured in Mg-10Gd and Mg-2Ag extracts showed the same proliferation and morphology than cells cultured in growth conditions. Mg-10Gd induced an increase in production of ECM and a bigger cell size, similar to the effects found with differentiation conditions. An increased metabolic activity was observed in cells cultured under the influence of Mg-10Gd extracts, indicated by an acidic pH during most of the culture period. After 7 days of culture on the materials, ATDC5 growth, distribution and ECM synthesis were higher on Mg-10Gd samples, followed by Mg-2Ag and PMg, which was influenced by the homogeneity and composition of the degradation layer. This study confirmed the tolerance of ATDC5 cells to Mg-based materials and a chondrogenic effect of Mg-10Gd. Further studies in vitro and in vivo are necessary to evaluate cell reactions to those materials, as well as the effects on bone growth and the biocompatibility of the alloying system in the body. - Highlights: • Degradation of PMg, and Mg-2Ag do not influence ATDC5 cells growth and chondrogenic redifferentiation. • Mg-10Gd enhances fast chondrogenic redifferentiation and expression of hyperthrophic markers on ATDC5 cells. • Further evaluation of the effects of PMg, Mg-10Gd and Mg-2Ag in vivo are necessary to confirm its potential for application in growing bones.

  6. Effects of limestone, N, K and Mg fertilizers on Mg absorption by oats and barley

    Energy Technology Data Exchange (ETDEWEB)

    Alston, A M

    1966-01-01

    Oats grown in a pot experiment on two sandy loams were sampled at four stages of growth. Neither KCl nor MgSO/sub 4/. 7H/sub 2/O had any effect on yield but % Mg and total Mg uptake were consistently decreased by applying K and increased by applying Mg. Ca(NO/sub 3/)/sub 2/ increased % Mg more than did (NH/sub 4/)/sub 2/SO/sub 4/, but yield and total Mg uptake were higher where (NH/sub 4/)/sub 2/SO/sub 4/ was applied. The effects of fertilizers were similar on both soils. The effects of applying (NH/sub 4/)/sub 2/SO/sub 4/ and NaNO/sub 2/ to the soil on % Mg in barley were compared in a field experiment on an acid loam to which several rates of limestone had been applied. Treatments had no effect on the % Mg in grain or straw at maturity. At four earlier stages of growth (NH/sub 4/)/sub 2/SO)/sub 4/ increased % Mg in the plants more than did NaNO/sub 2/. Limestone slightly increased % Mg. Nitrification of NH/sub 4/ in the soil was rapid.

  7. Mg Incorporation Efficiency in Pulsed MOCVD of N-Polar GaN:Mg

    Science.gov (United States)

    Marini, Jonathan; Mahaboob, Isra; Hogan, Kasey; Novak, Steve; Bell, L. D.; Shahedipour-Sandvik, F.

    2017-10-01

    We report on the effect of growth polarity and pulsed or δ -doped growth mode on impurity incorporation in metalorganic chemical vapor deposition-grown GaN. In Ga-polar orientation, up to 12× enhancement in Mg concentration for given Mg flow rate is observed, resulting in enhanced p-type conductivity for these samples. In contrast, this enhancement effect is greatly diminished for N-polar samples, falling off with increasing Mg flow and showing maximum enhancement of 2.7× at 30 nmol/min Mg flow. At higher Mg flow rates, Mg incorporation at normal levels did not correspond to p-type conductivity, which may be due to Mg incorporation at nonacceptor sites. Concentrations of C, O, and Si were also investigated, revealing dependence on Mg flow in N-polar pulsed samples. Carbon incorporation was found to decrease with increasing Mg flow, and oxygen incorporation was found to remain high across varied Mg flow. These effects combine to result in N-polar samples that are not p-type when using the pulsed growth mode.

  8. Structural characteristics and corrosion behavior of biodegradable Mg-Zn, Mg-Zn-Gd alloys.

    Science.gov (United States)

    Kubásek, J; Vojtěch, D

    2013-07-01

    In this research, binary Mg-Zn (up to 3 wt% Zn) and ternary Mg-Zn-Gd (up to 3 wt% Gd, 3 wt% Zn) alloys were prepared by induction melting in an argon atmosphere. The structures of these alloys were characterized using light and scanning electron microscopy, energy dispersive spectrometry, X-ray diffraction and X-ray fluorescence. In addition, Brinell hardness measurements were taken to supplement these studies. Corrosion behavior was evaluated by immersion tests and potentiodynamic measurements in a physiological solution (9 g/l NaCl). Depending on the composition, structures of the as-cast alloys contained α-Mg dendrites, MgZn, Mg5Gd and Mg3Gd2Zn3 phases. Compared to pure Mg, zinc improved the corrosion resistance of binary Mg-Zn. Gadolinium also improved the corrosion resistance in the case of Mg-1Zn-3Gd alloy. The highest corrosion rate was observed for Mg-3Zn-3Gd alloy. Our results improve the understanding of the relationships between the structure and corrosion behavior of our studied alloy systems.

  9. Thermoelectric power of PrMg3

    Science.gov (United States)

    Isikawa, Yosikazu; Somiya, Kazuya; Koyanagi, Huruto; Mizushima, Toshio; Kuwai, Tomohiko; Tayama, Takashi

    2010-01-01

    PrMg3 is supposed to be one of the strongly correlated electron systems originated from the hybridization between the Pr 4f and conduction electrons, because the gigantic electronic specific heat coefficient C/T was observed at low temperatures. However, a typical behaviour of - ln T dependence was not observed in the temperature dependence of the electrical resistivity. The thermoelectric power S is a powerful tool to investigate the density of states at the Fermi energy. We measured carefully the thermoelectric power of PrMg3 in the temperature range between 2 and 300 K. S is extremely small, ranged within ±1 μV/K over the whole temperature. The value of S/T at low temperature limit was also significantly smaller than expected from the specific heat results. We therefore conclude that the density of state at the Fermi level is not enhanced in PrMg3.

  10. Thermoelectric power of PrMg3

    International Nuclear Information System (INIS)

    Isikawa, Yosikazu; Somiya, Kazuya; Koyanagi, Huruto; Mizushima, Toshio; Kuwai, Tomohiko; Tayama, Takashi

    2010-01-01

    PrMg 3 is supposed to be one of the strongly correlated electron systems originated from the hybridization between the Pr 4f and conduction electrons, because the gigantic electronic specific heat coefficient C/T was observed at low temperatures. However, a typical behaviour of - ln T dependence was not observed in the temperature dependence of the electrical resistivity. The thermoelectric power S is a powerful tool to investigate the density of states at the Fermi energy. We measured carefully the thermoelectric power of PrMg 3 in the temperature range between 2 and 300 K. S is extremely small, ranged within ±1 μV/K over the whole temperature. The value of S/T at low temperature limit was also significantly smaller than expected from the specific heat results. We therefore conclude that the density of state at the Fermi level is not enhanced in PrMg 3 .

  11. Excited states in 22Mg via the 12C(12C,2n)22Mg reaction

    International Nuclear Information System (INIS)

    Jewett, Cybele; Baktash, Cyrus; Bardayan, Daniel W.; Blackmon, Jeff C.; Chipps, K.; Galindo-Uribarri, Alfredo; Greife, U.; Gross, Carl J.; Jones, K. L.; Liang, Junjien; Livesay, Jake; Kozub, R. L.; Nesaraja, Caroline D; Radford, David C.; Sarazin, F.; Smith, Michael Scott; Thomas, J. S.; Yu, Chang-Hong

    2007-01-01

    The 12C(12C, 2n)22Mg reaction was measured with the CLARION array and the RMS separator at the Holifield Facility of Oak Ridge National Laboratory. This experiment was performed to gather more information on the excited states in 22Mg, which might be of relevance to recent radioactive ion beam measurements of the astrophysically important 21Na(p,γ)22Mg reaction. The results are compared to direct measurements, transfer experiments and a competing experiment performed with Gammasphere

  12. Mifepristone 5 mg versus 10 mg for emergency contraception: double-blind randomized clinical trial

    Directory of Open Access Journals (Sweden)

    Carbonell JL

    2015-01-01

    Full Text Available Josep Lluis Carbonell,1 Ramon Garcia,2 Adriana Gonzalez,2 Andres Breto,2 Carlos Sanchez2 1Mediterranea Medica Clinic, Valencia, Spain; 2Eusebio Hernandez Gynecology and Obstetrics Teaching Hospital, Havana, Cuba Purpose: To estimate the efficacy and safety of 5 mg and 10 mg mifepristone for emergency contraception up to 144 hours after unprotected coitus. Methods: This double-blind randomized clinical trial was carried out at Eusebio Hernandez Hospital (Havana, Cuba. A total of 2,418 women who requested emergency contraception after unprotected coitus received either 5 mg or 10 mg mifepristone. The variables for assessing efficacy were the pregnancies that occurred and the fraction of pregnancies that were prevented. Other variables assessed were the side effects of mifepristone, vaginal bleeding, and changes in the date of the following menstruation. Results: There were 15/1,206 (1.2% and 9/1,212 (0.7% pregnancies in the 5 mg and 10 mg group, respectively (P=0.107. There were 88% and 93% prevented pregnancies in the 5 mg and 10 mg group, respectively. The side effect profiles were similar in both groups. Delayed menstruation ≥7 days was experienced by 4.9% and 11.0% of subjects in the 5 mg and 10 mg group, respectively (P=0.001. There was a significant high failure rate for women weighing >75 kg in the 5 mg group. Conclusion: It would be advisable to use the 10 mg dose of mifepristone for emergency contraception as there was a trend suggesting that the failure rate of the larger dose was lower. Keywords: mifepristone, emergency contraception

  13. Superconducting properties of MgB2 particle impregnated with Mg-based alloys

    International Nuclear Information System (INIS)

    Shimizu, Yusuke; Matsuda, Kenji; Mizutani, Manabu; Nishimura, Katsuhiko; Kawabata, Tokimasa; Ikeno, Susumu; Hishinuma, Yoshimitsu; Aoyama, Shigeki

    2011-01-01

    The three-dimensional penetration method combined with semi-solid casting (SS-3DPC) was utilized to prepare magnesium diboride (MgB 2 ) powder composite materials with various host materials of Mg, Mg-3%Al, Mg-3%Al-1%Zn, Mg-9%Al, and Mg-9%Al-1%Zn. X-ray diffraction measurements indicated predominant peak patterns of MgB 2 and a host alloy, implying that the host material tightly bonded MgB 2 grains without melting the MgB 2 powder. This was confirmed by SEM images. Measured electrical resistivity and magnetization versus temperature showed clear signals of superconducting transition temperature of 27-38 K for all the samples cut out from the billets. Magnetic hysteresis loop observed at 5 K enabled us to estimate a critical current density (J c ) based on the extended Bean model. Additions of aluminum and zinc elements to magnesium host-matrix were found to enhance J c and increase residual resistivity (ρ 0 ) suggesting that aluminum and zinc have an effect on pinning magnetic flux flow for J c enhancement, and scattering conduction electrons for increase of ρ 0 . (author)

  14. Electronic structure of MgB2

    Indian Academy of Sciences (India)

    Abstract. Results of ab initio electronic structure calculations on the compound MgB2 using the. FPLAPW method employing GGA for the exchange-correlation energy are presented. Total energy minimization enables us to estimate the equilibrium volume, c/a ratio and the bulk modulus, all of which are in excellent ...

  15. Electronic structure of MgB 2

    Indian Academy of Sciences (India)

    Results of ab initio electronic structure calculations on the compound MgB2 using the FPLAPW method employing GGA for the exchange-correlation energy are presented. Total energy minimization enables us to estimate the equilibrium volume, / ratio and the bulk modulus, all of which are in excellent agreement with ...

  16. doped LiMgPO4 phosphor

    Indian Academy of Sciences (India)

    attention because of their remarkable luminescence proper- ties and .... Figure 1. (a) X-ray diffraction patterns of LiMgPO4:Tb3+ phosphor and (b) standard data. ICDD file. .... ground signal which affects the signal to noise ratio [17]. MDD was ...

  17. Preliminary study of the characteristics of a high Mg containing Al-Mg-Si alloy

    International Nuclear Information System (INIS)

    Yan, F; McKay, B J; Fan, Z; Chen, M F

    2012-01-01

    An Al-20Mg-4Si high Mg containing alloy has been produced and its characteristics investigated. The as-cast alloy revealed primary Mg 2 Si particles evenly distributed throughout an α-Al matrix with a β-Al 3 Mg 2 fully divorced eutectic phase observed in interdendritic regions. The Mg 2 Si particles displayed octahedral, truncated octahedral, and hopper morphologies. Additions of Sb, Ti and Zr had a refining influence reducing the size of the Mg 2 Si from 52 ± 4 μm to 25 ± 0.1 μm, 35 ± 1 μm and 34 ± 1 μm respectively. HPDC tensile test samples could be produced with a 0.6 wt.% Mn addition which prevented die soldering. Solution heating for 1 hr was found to dissolve the majority of the Al 3 Mg 2 eutectic phase with no evidence of any effect on the primary Mg 2 Si. Preliminary results indicate that the heat treatment has a beneficial effect on the elongation and the UTS.

  18. Investigation of the 24Mg(d, p)25Mg reaction

    NARCIS (Netherlands)

    Meurders, F.; Korte, G. de

    1975-01-01

    Abstract Proton angular distributions from the 24Mg(d, p)25Mg reaction at Ed = 12.0 MeV have been measured with a split-pole magnetic spectrograph for Ex < 6 MeV at an average resolution (FWHM) of 7 keV. New ln values have been determined for three levels. A DWBA analysis yielded spectroscopic

  19. Investigation of the 26Mg(d, p)27Mg reaction

    NARCIS (Netherlands)

    Meurders, F.; Steld, A. van der

    1974-01-01

    The angular distributions of 31 protons groups from the 26Mg(d, p)27Mg reaction have been measured at Ed = 12.0 MeV with a split-pole magnetic spectrograph. Excitation energies have been determined for 29 bound states. Three new levels have been found. A DWBA analysis yields ln values for 19 levels;

  20. Respiratory outcomes following 100 mg/kg v. 200 mg/kg of poractant ...

    African Journals Online (AJOL)

    In keeping with current evidence, the initial dose of poractant alpha was increased from 100 mg/kg to 200 mg/kg. e outcomes of newborns requiring treatment with surfactant before and aer this change were reviewed. Methods. Electronic clinical records were reviewed of infants admitted to ACH who received surfactant ...

  1. Mg/Ca ratio in fertilization and agricultural soils, Mg percent of liming ...

    African Journals Online (AJOL)

    Strong increase of NPK (nitrogen, phosphorus and potassium) in mineral fertilization (fm) included relative delay in Mg supplementation and dilution in plant available silicon (Si) via recycled nutrients (rcl). (Silicon is not included in essential fertilizers in Finland.) Methods: We have assessed old data on Ca and Mg in ...

  2. Decay of a Jπ=36+ Resonance in the 24Mg+24Mg Reaction

    International Nuclear Information System (INIS)

    Salsac, M.-D.; Haas, F.; Courtin, S.

    2005-01-01

    For the 24 Mg+ 24 Mg reaction, striking narrow and correlated resonance structures have been observed previously in the excitation functions of the elastic and low-lying channels. In our study we have decided to focus on the resonance at E C M =45.7 MeV, which is known to have J π =36 + . Despite the very high excitation energy(∼60 MeV) in the 48 Cr composite system, this resonance has a narrow total width of 170 keV. To determine precisely which states in the inelastic 24 Mg channels carry away the resonance flux, an experiment, on the 24 Mg + 24 Mg reaction at energies On and OFF resonance, has been performed at the Legnaro Tandem accelerator using the Prisma fragment spectrometer associated with the CLARA γ array

  3. Magnesium sulphate’s influence on calcium carbonate minerals

    DEFF Research Database (Denmark)

    Nielsen, Mia Rohde

    The purpose of this PhD thesis was to explore the influence of magnesium sulphate (MgSO4 (aq)) on calcium carbonate (CaCO3) minerals and what role the MgSO40 ion pair had. CaCO3 minerals are abundant and widespread on Earth, particularly in marine environments, and have been so throughout Earth...

  4. Mg II Line Variation of 32 Cygni

    Directory of Open Access Journals (Sweden)

    Young Woon Kang

    1992-12-01

    Full Text Available The Mg II lines have been extracted from the IUE archival spectra of 32 Cygni to investigate the effect of the atmospheric eclipse. The UV light curve has been reduced from the continuum flux at the center wavelength of 2807.5 Å in the IUE spectra. The equivalent width of the Mg II k absoption line has been measured for each spectra. The results of the light variation and flux tracing of the absorption line at the vicinity of the primary eclipse confirmed the atmospheric eclipse. The atmospheric effect lasted until the phase 0.06 in the absorptin line tracing, while it lasted until the phase 0.02 in the UV light curve, respectively.

  5. High temperature mechanical forming of Mg alloys

    International Nuclear Information System (INIS)

    Mwembela, A.; McQueen, H.J.; Myshlyaev, M.

    2002-01-01

    Mg alloys are hot worked in the range 180-450 o C and 0.0-10 s -1 ; the present project data are compared with a wide selection of published results. The flow stresses and their dependence on temperature and strain rate are fairly similar to simple Al alloys: however, the hot ductility is much lower (≤3 in torsion). Twinning plays a significant role in Mg alloys almost independently of temperature; the twins initiate at low strains in grains poorly oriented for basal slip and in consequence become well disposed for such slip. As T rises, there is increasing formation of subgrains that spread toward the grain centers from grain and twin boundaries: this is indicative of stress concentrations inducing non-basal sup which helps provide the geometrically necessary dislocations. Above about 240 o C, dynamic (DRX) nucleates at grain and twin boundaries, preferentially at intersections; this again is evidence of non-basal slip that provides the highly misoriented cells. The boundaries in which further strain concentrates producing further DRX. The microstructure remains very heterogeneous compared to the uniform dynamically recovered substructure in Al alloys, thus giving rise to the reduced ductility. These results are employed to interpret the mechanical and microstructural behavior of Mg alloys in extrusion, rolling and forging. (author)

  6. Mg,Ca-ATPase activity under irradiation

    International Nuclear Information System (INIS)

    Ladutin, V.V.; Orlova, V.V.; Lob, P.A.; Gerasiminko, I.V.; Mack, E.I.

    2003-01-01

    Full text: The influence of different doses irradiation at the Mg,Ca-ATPase activity at the rat brain has been investigated. The analyses were made at the apparatus of LKB and Carl-Ceis-Jena firm with help of reagents of Sigma and Boehringer firm. Rats decapitated after 1, 3, 6, 24 and 48 h after action of irradiation. Dose 0.206 C/kg. Erythrocytes. 1 and 3h after irradiation influence- decrease of Mg,Ca-ATPase activity to 86-87% relatively control level, 24 and 48 h - increase of activity to the control level. Dose 0.312 C/kg. Large hemispheres. 1h - decrease of ATPase activity to 90% relatively control, 3h - increase to control level, 24h - fall to 86%, after 48h small increase to 93% relatively control. Dose 9.287 C/kg. Large hemispheres. 1h - sharp fall of Mg, Ca-ATPase activity to 67 % relatively control, increase of activity to 96% after 3h and sharp fall of activity to 64% 6h after action of irradiation. Dose 9.287 C/kg. Cerebellum. 1h - sharp decrease of ATPase activity to 80%. After 3h -sharp increase to 160% relatively control level and sharp fall of ATPase activity to 47% relatively control after 6h. The mechanism of radiation pathology of active ion transport has been discussed

  7. Interstitial Fe in MgO

    CERN Document Server

    Mølholt, T E; Gunnlaugsson, H P; Svane, A; Masenda, H; Naidoo, D; Bharuth-Ram, K; Fanciulli, M; Gislason, H P; Johnston, K; Langouche, G; Ólafsson, S; Sielemann, R; Weyer, G

    2014-01-01

    Isolated Fe-57 atoms were studied in MgO single-crystals by emission Mossbauer spectroscopy following implantation of Mn-57 decaying to Fe-57. Four Mossbauer spectral components were found corresponding to different Fe lattice positions and/or charge states. Two components represent Fe atoms substituting Mg as Fe2+ and Fe3+, respectively; a third component is due to Fe in a strongly implantation-induced disturbed region. The fourth component, which is the focus of this paper, can be assigned to Fe at an interstitial site. Comparison of its measured isomer shift with ab initio calculations suggests that the interstitial Fe is located on, or close to, the face of the rock-salt MgO structure. To harmonize such an assignment with the measured near-zero quadrupole interaction a local motion process (cage motion) of the Fe has to be stipulated. The relation of such a local motion as a starting point for long range diffusion is discussed.

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

    Energy Technology Data Exchange (ETDEWEB)

    Mueller, M.

    2007-07-11

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

  9. Comparison of hydrogen storage properties of pure Mg and milled ...

    Indian Academy of Sciences (India)

    Administrator

    increase the hydriding and dehydriding rates, pure Mg was ground under hydrogen atmosphere (reactive .... Hydrogen storage properties of pure Mg and milled pure Mg. 833. Figure 3. ... elongated and flat shapes via collisions with the steel.

  10. The initial stages of template-controlled CaCO3 formation revealed by Cryo-TEM

    NARCIS (Netherlands)

    Pouget, E.M.; Bomans, P.H.H.; Goos, J.A.C.M.; Frederik, P.M.; With, de G.; Sommerdijk, N.A.J.M.

    2009-01-01

    Biogenic calcium carbonate forms the inorganic component of seashells, otoliths, and many marineskeletons, and its formation is directed by an ordered template of macromolecules. Classicalnucleation theory considers crystal formation to occur from a critical nucleus formed by theassembly of ions

  11. Application of lime (CaCO3) to promote forest recovery from severe acidification increases potential for earthworm invasion

    Science.gov (United States)

    Homan, Caitlin; Beirer, Colin M; McCay, Timothy S; Lawrence, Gregory B.

    2016-01-01

    The application of lime (calcium carbonate) may be a cost-effective strategy to promote forest ecosystem recovery from acid impairment, under contemporary low levels of acidic deposition. However, liming acidified soils may create more suitable habitat for invasive earthworms that cause significant damage to forest floor communities and may disrupt ecosystem processes. We investigated the potential effects of liming in acidified soils where earthworms are rare in conjunction with a whole-ecosystem liming experiment in the chronically acidified forests of the western Adirondacks (USA). Using a microcosm experiment that replicated the whole-ecosystem treatment, we evaluated effects of soil liming on Lumbricus terrestris survivorship and biomass growth. We found that a moderate lime application (raising pH from 3.1 to 3.7) dramatically increased survival and biomass of L. terrestris, likely via increases in soil pH and associated reductions in inorganic aluminum, a known toxin. Very few L. terrestris individuals survived in unlimed soils, whereas earthworms in limed soils survived, grew, and rapidly consumed leaf litter. We supplemented this experiment with field surveys of extant earthworm communities along a gradient of soil pH in Adirondack hardwood forests, ranging from severely acidified (pH 5). In the field, no earthworms were observed where soil pH 4.4 and human dispersal vectors, including proximity to roads and public fishing access, were most prevalent. Overall our results suggest that moderate lime additions can be sufficient to increase earthworm invasion risk where dispersal vectors are present.

  12. Physical and nanomechanical properties of the synthetic anhydrous crystalline CaCO3 polymorphs: vaterite, aragonite and calcite

    Czech Academy of Sciences Publication Activity Database

    Ševčík, Radek; Šašek, Petr; Viani, Alberto

    2018-01-01

    Roč. 53, č. 6 (2018), s. 4022-4033 ISSN 0022-2461 R&D Projects: GA MŠk(CZ) LO1219; GA ČR(CZ) GA17-05030S Keywords : X-ray-diffraction * thermal expansion * mechanical characterization * relative-humidity * carbonates * mortars Subject RIV: CA - Inorganic Chemistry OBOR OECD: Inorganic and nuclear chemistry Impact factor: 2.599, year: 2016 https://www.springerprofessional.de/en/physical-and-nanomechanical-properties-of-the-synthetic-anhydrou/15290962

  13. TEM preparation methods and influence of radiation damage on the beam sensitive CaCO3 shell of Emiliania huxleyi.

    Science.gov (United States)

    Hoffmann, Ramona; Wochnik, Angela S; Betzler, Sophia B; Matich, Sonja; Griesshaber, Erika; Schmahl, Wolfgang W; Scheu, Christina

    2014-07-01

    The ultrastructure of biologically formed calcium carbonate crystals like the shell of Emiliania huxleyi depends on the environmental conditions such as pH value, temperature and salinity. Therefore, they can be used as indicator for climate changes. However, for this a detailed understanding of their crystal structure and chemical composition is required. High resolution methods like transmission electron microscopy can provide those information on the nanoscale, given that sufficiently thin samples can be prepared. In our study, we developed sample preparation techniques for cross-section and plan-view investigations and studied the sample stability under electron bombardment. In addition to the biological material (Emiliania huxleyi) we also prepared mineralogical samples (Iceland spar) for comparison. High resolution transmission electron microscopy imaging, electron diffraction and electron energy-loss spectroscopy studies revealed that all prepared samples are relatively stable under electron bombardment at an acceleration voltage of 300 kV when using a parallel illumination. Above an accumulated dose of ∼10(5) e/nm2 the material--independent whether its origin is biological or geological--transformed to poly-crystalline calcium oxide. Copyright © 2014 Elsevier Ltd. All rights reserved.

  14. Predicting Calcite (CaCO3) Requirements of Sphagnum Peat Moss from pH Titration Curves

    Science.gov (United States)

    Liming materials are required to neutralize acidity in peat moss to make it a suitable substrate for growing container crops. A series of time-consuming incubations of peat:lime mixtures are typically used to determine the liming rate to achieve a desired pH. Our objective was to evaluate the util...

  15. A strategy of precipitated calcium carbonate (CaCO3) fillers for enhancing the mechanical properties of polypropylene polymers

    International Nuclear Information System (INIS)

    Thenepalli, Thriveni; Ahn, Ji Whan; Ahn, Young Jun; Han, Choon; Ramakrishna, Chilakala

    2015-01-01

    A wide variety of fillers are currently used in more than twenty types of polymer resins, although four of them alone (polypropylene, polyamides, thermoplastic polyesters, and polyvinyl chloride) account for 90% of the market of mineral fillers in plastics. Polypropylene (PP) and PVC dominate the market for calcium carbonate. PP is a versatile reinforcement material that can meet engineering and structural specifications and is widely used for automotive components, home appliances, and industrial applications. Talc, mica, clay, kaolin, wollastonite, calcium carbonates, feldspar, aluminum hydroxide, glass fibers, and natural fibers are commonly used in fillers. Among these, calcium carbonate (both natural and synthetic) is the mos abundant and affords the possibility of improved surface finishing, control over the manufacture of products, and increased electric resistance and impact resistance. Meeting the global challenge to reduce the weight of vehicles by using plastics is a significant issue. The current the global plastic and automobile industry cannot survive without fillers, additives, and reinforcements. Polypropylene is a major component of the modern plastic industry, and currently is used in dashboards, wheel covers, and some engine parts in automobiles. This article reports that the use of calcium carbonate fillers with polypropylene is the best choice to enhance the mechanical properties of plastic parts used in automobiles

  16. Predominance of heavily calcified coccolithophores at low CaCO3 saturation during winter in the Bay of Biscay

    OpenAIRE

    Smith, Helen E. K.; Tyrrell, Toby; Charalampopoulou, Anastasia; Dumousseaud, Cynthia; Legge, Oliver J.; Birchenough, Sarah; Pettit, Laura R.; Garley, Rebecca; Hartman, Sue E.; Hartman, Mark C.; Sagoo, Navjit; Daniels, Chris J.; Achterberg, Eric P.; Hydes, David J.

    2012-01-01

    Coccolithophores are an important component of the Earth system, and, as calcifiers, their possible susceptibility to ocean acidification is of major concern. Laboratory studies at enhanced pCO2 levels have produced divergent results without overall consensus. However, it has been predicted from these studies that, although calcification may not be depressed in all species, acidification will produce “a transition in dominance from more to less heavily calcified coccolithophores” [Ridgwell A,...

  17. Desiccator Volume: A Vital Yet Ignored Parameter in CaCO3 Crystallization by the Ammonium Carbonate Diffusion Method

    Directory of Open Access Journals (Sweden)

    Joe Harris

    2017-07-01

    Full Text Available Employing the widely used ammonium carbonate diffusion method, we demonstrate that altering an extrinsic parameter—desiccator size—which is rarely detailed in publications, can alter the route of crystallization. Hexagonally packed assemblies of spherical magnesium-calcium carbonate particles or spherulitic aragonitic particles can be selectively prepared from the same initial reaction solution by simply changing the internal volume of the desiccator, thereby changing the rate of carbonate addition and consequently precursor formation. This demonstrates that it is not merely the quantity of an additive which can control particle morphogenesis and phase selectivity, but control of other often ignored parameters are vital to ensure adequate reproducibility.

  18. A quasi-time-resolved CryoTEM study of the nucleation of CaCO3 under Langmuir monolayers

    NARCIS (Netherlands)

    Pichon, B.P.R.; Bomans, P.H.H.; Frederik, P.M.; Sommerdijk, N.A.J.M.

    2008-01-01

    Calcium carbonate biomineralization uses complex assemblies of macromolecules that control the nucleation, growth, and positioning of the mineral with great detail. To investigate the mechanisms involved in these processes, for many years Langmuir monolayers have been used as model systems. Here, we

  19. Pengaruh serbuk serat batang pisang sebagai filler terhadap sifat mekanis dari komposit PVC– CaCO3

    Directory of Open Access Journals (Sweden)

    Supraptiningsih

    2012-12-01

    Full Text Available ABSTRACT The aim of research was to study the effect to the mechanical properties of banana fiber as a filler of PVC-calcium carbonate composite. Banana stem powder was made from banana stem which was grounded and soaked in 15 % NaOH for 24 hours to remove the lignin, dried and screened to 200 mesh, PVC-calcium carbonate composite was made using a Two Roll Mill at o temperature of 50 C, for 10 minutes and 50 rpm. The composition of PVC and additiveswere not varied, while the variations made on banana fiber, ie 0, 10; 20, 30, and 40 phr (per hundred resin. The observation showed the mechanical properties of PVC- calcium carbonate 2 composite has value of weight per unit area between 4.55 to 5.90 kg/m , bulk densities from 1.503 3 2 to 1.999 g/cm , tensile strength from 67.56 to 79.03 kg/cm , hardness 55.00 to 66.66 shore D, 2 water absorption from 0.960 to 3.322 %, flexibility test from 118.99 to 165.09 kg/cm , flash point 0.032 0.075 inc / sec, water density was good (not drop happened and the ability of sawed and nailed was good (no defected/cracked. When the test results of PVC-calcium carbonate composite with banana fiber compared with SNI 15-0233-1989 Mutu dan Cara Uji Lembaran Serat Semen, indicates that

  20. Assessing of the effect of hydrodynamics in the growth of scale (CaCO3) in rotating cylinder electrode

    Science.gov (United States)

    García, M.; Espinosa Cardenal, E. J.; Vera, E.

    2017-12-01

    Fouling is a common problem related to different industries in which the solubility of dissolved minerals in water changes leading to the formation of deposits on the surface of the equipment, for instance, in oil production the scale can be formed on the wellbore, on the well tubing or superficial facilities. Over the last years, several studies have been carried out in order to determine the effect of operational conditions in the scale growth but there are no conclusive results. This paper presents the results of calcium carbonate deposition on the surface of stainless steel AISI 316 at 71°C, and the influence of rotating velocity on the quantity and morphology of the generated scale. The tests were carried out by using a rotating cylinder electrode and X-Ray Diffraction (DRX), and Scanning Electron Microscopy (SEM) of the scale obtained was analysed. The results show that the amount of scale formed changes regarding the velocity of the fluid, as well as the morphology of the deposited crystals.

  1. Discharge behaviour of Mg-Al-Pb and Mg-Al-Pb-In alloys as anodes for Mg-air battery

    International Nuclear Information System (INIS)

    Wang, Naiguang; Wang, Richu; Peng, Chaoqun; Peng, Bing; Feng, Yan; Hu, Chengwang

    2014-01-01

    Highlights: • We investigate the effect of indium on the discharge behaviour of Mg-Al-Pb alloy. • We evaluate the performance of Mg-air batteries with Mg-Al-Pb and Mg-Al-Pb-In anodes. • We analyze the activation mechanism of Mg-Al-Pb-In alloy in the discharge process. - Abstract: The discharge behaviour of Mg-Al-Pb and Mg-Al-Pb-In alloys in 3.5 wt.% NaCl solution is investigated by electrochemical techniques, and compared with that of pure magnesium. The results show that Mg-Al-Pb-In alloy provides a more negative potential and exhibits a higher utilization efficiency in contrast with Mg-Al-Pb alloy and pure magnesium during the half-cell test at a large current density, and gives desirable discharge performance when used as anode for Mg- air battery. The peak power density of the Mg-air battery with Mg-Al-Pb-In anode is 94.5 mW cm −2 , which is comparable with those of Mg-H 2 O 2 semi-fuel batteries. Moreover, the activation mechanism of Mg-Al-Pb-In alloy during the discharge process is also analyzed

  2. Proton resonance elastic scattering of $^{30}$Mg for single particle structure of $^{31}$Mg

    CERN Multimedia

    The single particle structure of $^{31}$Mg, which is located in the so-called “island of inversion”, will be studied through measuring Isobaric Analog Resonances (IARs) of bound states of $^{31}$Mg. They are located in the high excitation energy of $^{31}$Al. We are going to determine the spectroscopic factors and angular momenta of the parent states by measuring the excitation function of the proton resonance elastic scattering around 0 degrees in the laboratory frame with around 3 MeV/nucleon $^{30}$Mg beam. The present study will reveal the shell evolution around $^{32}$Mg. In addition, the spectroscopic factor of the (7/2)$^{−}$ state which was not yet determined experimentally, may allow one to study the shape coexistence in this nucleus.

  3. Applications of thermodynamic calculations to Mg alloy design: Mg-Sn based alloy development

    International Nuclear Information System (INIS)

    Jung, In-Ho; Park, Woo-Jin; Ahn, Sang Ho; Kang, Dae Hoon; Kim, Nack J.

    2007-01-01

    Recently an Mg-Sn based alloy system has been investigated actively in order to develop new magnesium alloys which have a stable structure and good mechanical properties at high temperatures. Thermodynamic modeling of the Mg-Al-Mn-Sb-Si-Sn-Zn system was performed based on available thermodynamic, phase equilibria and phase diagram data. Using the optimized database, the phase relationships of the Mg-Sn-Al-Zn alloys with additions of Si and Sb were calculated and compared with their experimental microstructures. It is shown that the calculated results are in good agreement with experimental microstructures, which proves the applicability of thermodynamic calculations for new Mg alloy design. All calculations were performed using FactSage thermochemical software. (orig.)

  4. Green emission from ZnO–MgO nanocomposite due to Mg diffusion at the interface

    International Nuclear Information System (INIS)

    Sowri Babu, K.; Ramachandra Reddy, A.; Venugopal Reddy, K.

    2015-01-01

    The origin and electronic transitions responsible for green emission observed from ZnO–MgO nanocomposite are investigated. The photoluminescence (PL) spectrum of ZnO–MgO nanocomposite annealed at 600 °C showed only a sharp and intense UV emission peak centered at 396 nm. As the annealing temperature increased from 600 °C to 1000 °C, the green emission positioned at 503 nm is emerged and its intensity enhanced gradually and reached maximum value at 900 °C and then decreased at 1000 °C. It is observed that both UV and green emission intensities are enhanced with variation of atomic ratio (Zn/Mg=1.52, 0.50, 0.30, 0.21, 0.15). Our experiments confirmed that the enhancement of green emission intensity is due to the formation of oxygen vacancies (V o ) due to Mg doping at the interface of ZnO and MgO. This experimental observation is in good agreement with the recent theoretical predictions which states that Mg doping in ZnO lowers the formation energies of oxygen vacancies (V o ) and zinc interstitials (Zn i ) significantly. PL excitation and emission spectra analysis reveals that excited state for both UV and green emissions is same and lies 0.24 eV below the conduction band of ZnO. Hence, the green emission is attributed to the transition of an electron form the shallow donor (defect level of Zn i ) to the deep acceptor (defect level of V o ). - Highlights: • It is found that the UV emission intensity from ZnO–MgO nanocomposite enhanced with increase of Mg concentration. • The intensity of the green emission is enhanced gradually as the temperature increased from 600 °C to 900 °C and then decreased at 1000 °C. • The effect of Mg concentration, MgO, strain at the interface on green emission is investigated. • These experiments confirmed that green emission is due to the oxygen vacancies created in ZnO due to the Mg doping at the interface and it is in good agreement with the theoretical predictions. • The decrease of green emission intensity is

  5. Corrosion analysis of AlMg2 and AlMgSi using electrochemical method

    International Nuclear Information System (INIS)

    Dian A; Maman Kartaman; Rosika K; Yanlinastuti

    2014-01-01

    Corrosion test of cladding materials and structures of research reactor fuel, AlMgSi and AlMg2 have been performed in demineralized water of pH 2 and 6.7 using an electrochemical method. Corrosion phenomenon is affected by several factor such as composition and condition of solution. The purpose of this activity is to investigate the corrosion phenomena through the determination of the parameters of corrosion and polarization curve. The materials used are AlMg2 and AlMgSi alloy in circular dish shape with an area of 1 Cm"2. Preparation of the test sample is performed through several stages polishing, cleaning and drying procedures followed ASTM G3. The electrochemical method is done by measuring the open circuit potential (OCP), polarization resistance and potentiodynamic in demineralized water of pH 2 and pH 6.7 at temperature of 25°C. The results of the OCP is the corrosion potential (Ecorr) of AlMg2 and AlMgSi each of -906.1 mV and -619.8 mV at pH 2 and -868.6 and -756.7 mV at pH 6.7 mV. The results of measurements by polarization resistance technique showed that the corrosion rate of AlMg2 and AlMgSi in safe category (<2 mpy) at pH 6.7 and at pH 2 corrosion rate increased significantly, but still in the lightweight category (<20 mpy). Potentiodynamic curves showed that the passivation at pH 6.7 is very low while the passivation at pH 2 occurs within a relatively short range potential and followed events corroded. (author)

  6. A study on preparation and hydriding of β-Mg2Al3 and γ-Mg17Al12

    International Nuclear Information System (INIS)

    Hadi Suwarno

    2009-01-01

    The mechanism of the synthetic formation of β-Mg 2 Al 3 and γ-Mg 17 Al 12 has been studied. Mechanical alloying of Mg and Al powders with the atomic ratio of Mg:Al = 2:3 in toluene solution yields β-Mg 2 Al 3 compound after milling for 30 h. The γ-Mg 17 Al 12 can be formed by heating the β-Mg 2 Al 3 at 430°C under high vacuum. The measured hydrogen capacities of β-Mg 2 Al 3 and γ-Mg 17 Al 12 as hydride at 300°C are 3.2 and 4.9 wt%, respectively. Microstructure of the Mg-Al specimen shows that on hydriding at 300°C the polygonal shape of the γ-Mg 17 Al 12 changes into irregular shapes which are composed of γ-MgH 2 and Al. (author)

  7. Hydrogen absorption kinetics and structural properties of Mg85Ni10Ca5 and Mg90Ni10

    International Nuclear Information System (INIS)

    Aoki, Masakazu; Saito, Katsushi; Towata, Shin-ichi

    2005-01-01

    Mg 85 Ni 10 Ca 5 and Mg 90 Ni 10 were prepared by melting mixtures of the elements in mild steel crucibles and pouring them into copper molds. Hydrogen absorption kinetics and structural properties of the alloys were characterized by the volumetric method using a Sievert's apparatus, X-ray diffraction (XRD), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The crystallite size of Mg in Mg 85 Ni 10 Ca 5 , which is evaluated by XRD peak broadening, is about 50% smaller than that in Mg 90 Ni 10 . In addition, the nanometer-scale structure composed of Mg, Mg 2 Ni, Mg 2 Ca was observed in Mg 85 Ni 10 Ca 5 . Mg 85 Ni 10 Ca 5 shows better hydrogen absorption kinetics than Mg 90 Ni 10 in the temperature range of room temperature to 573 K. The better absorption kinetics of Mg 85 Ni 10 Ca 5 is mainly attributed to the nanometer-scale structure

  8. Reconstructive structural phase transitions in dense Mg

    International Nuclear Information System (INIS)

    Yao Yansun; Klug, Dennis D

    2012-01-01

    The question raised recently about whether the high-pressure phase transitions of Mg follow a hexagonal close-packed (hcp) → body centered cubic (bcc) or hcp → double hexagonal close-packed (dhcp) → bcc sequence at room temperature is examined by the use of first principles density functional methods. Enthalpy calculations show that the bcc structure replaces the hcp structure to become the most stable structure near 48 GPa, whereas the dhcp structure is never the most stable structure in the pressure range of interest. The characterized phase-transition mechanisms indicate that the hcp → dhcp transition is also associated with a higher enthalpy barrier. At room temperature, the structural sequence hcp → bcc is therefore more energetically favorable for Mg. The same conclusion is also reached from the simulations of the phase transitions using metadynamics methods. At room temperature, the metadynamics simulations predict the onset of a hcp → bcc transition at 40 GPa and the transition becomes more prominent upon further compression. At high temperatures, the metadynamics simulations reveal a structural fluctuation among the hcp, dhcp, and bcc structures at 15 GPa. With increasing pressure, the structural evolution at high temperatures becomes more unambiguous and eventually settles to a bcc structure once sufficient pressure is applied. (paper)

  9. Phase formation in Mg-Sn-Si and Mg-Sn-Si-Ca alloys

    Energy Technology Data Exchange (ETDEWEB)

    Kozlov, A.; Groebner, J. [Institute of Metallurgy, Clausthal University of Technology, Robert-Koch-Str. 42, D-38678 Clausthal-Zellerfeld (Germany); Schmid-Fetzer, R., E-mail: schmid-fetzer@tu-clausthal.de [Institute of Metallurgy, Clausthal University of Technology, Robert-Koch-Str. 42, D-38678 Clausthal-Zellerfeld (Germany)

    2011-02-17

    Research highlights: > The solidification paths of ternary and quaternary alloys are analyzed in detail, using the tool of thermodynamic calculations. > The precipitation sequence of phases and their amounts compare well with the microstructure of alloys. > The most efficient comparison to the experimental thermal analysis data is done by calculation of the enthalpy variation with temperature. > The viability of a procedure for the selection of multicomponent key samples is demonstrated for the development of the Mg-Ca-Si-Sn phase diagram. - Abstract: Experimental work is done and combined with the Calphad method to generate a consistent thermodynamic description of the Mg-Ca-Si-Sn quaternary system, validated for Mg-rich alloys. The viability of a procedure for the selection of multicomponent key samples is demonstrated for this multicomponent system. Dedicated thermal analysis with DTA/DSC on sealed samples is performed and the microstructure of slowly solidified alloys is analyzed using SEM/EDX. The thermodynamic description and phase diagram of the ternary Mg-Si-Sn system, developed in detail also in this work, deviates significantly from a previous literature proposal. The phase formation in ternary and quaternary alloys is analyzed using the tool of thermodynamic equilibrium and Scheil calculations for the solidification paths and compared with present experimental data. The significant ternary/quaternary solid solubilities of pertinent intermetallic phases are quantitatively introduced in the quaternary Mg-Ca-Si-Sn phase diagram and validated by experimental data.

  10. Half-life determination for 27Mg

    Science.gov (United States)

    Zahn, G. S.; Genezini, F. A.

    2015-07-01

    In this work, the half-life of the short-lived magnesium radionuclide 27Mg was measured by following the activity of samples after they were irradiated in the IEA-R1 reactor. An exponential decay function was then fitted to the results using the counts from a 60Co source as livetime chronometer; the individual half-life values obtained for each irradiation were compiled using both the usual unweighted and σ-2-weighted averages, as well as the robust averages obtained using the Normalized Residuals and the Rajeval techniques. The final halflive values obtained aren't compatible with the ENSDF compilation values, but have a similar uncertainty; analysis of the experimental literature values, all from the 50’s-60’s, show that further measurements should be undertaken in order to achieve a more robust consensus value for this half-life.

  11. Experimental lifetimes for Mg-like chlorine

    International Nuclear Information System (INIS)

    Engstroem, L.; Bengtsson, P.; Jupen, C.; Livingston, A.E.; Martinson, I.

    1995-01-01

    The results of beam-foil measurements of lifetimes for low-lying singlet levels in Mg-like chlorine, Cl VI, are presented. The decay curves were analyzed by means of the arbitrarily normalized decay curve method, combined with the recently developed CANYL code, which facilitates studies of decay chains. Cascade corrected data are presented for the levels 3s3p 1 P, 3p 2 1 S, 3p 2 1 D, and 3s3d 1 D, whereas less rigorous lifetime values, based on curve fits, were obtained for the 3p3d 1 D, 3p3d 1 F, and 3s4f 1 F levels. The data are in excellent agreement with recent theoretical values, and previous discrepancies between experiment and theory for short-lived states have been removed

  12. MgO by injection CVD

    International Nuclear Information System (INIS)

    Abrutis, A.; Kubilius, V.; Teiserkis, A.; Bigelyte, V.; Vengalis, B.; Jukna, A.; Butkute, R.

    1997-01-01

    Epitaxial YBa 2 Cu 3 O 7 layers with 45 in-plane orientation have been grown by injection CVD on MgO substrates polished off-axis to within 1.4-1.9 of the [100] direction. This new single-source CVD process is based on computer-controlled injection of precise microdoses of a metal-organic precursor solution into a CVD reactor. A wide range of solution compositions was tested to investigate compositional effects on phase purity, surface morphology, texturing and superconducting properties of the prepared films. The highest quality films with pure 45 texture had a smooth surface, zero resistance T c (R=0) of 88-89 K, and critical current density J c (77 K) above 10 6 A/cm 2 . (orig.) and critical current density J c (77 K) above 10 6 A/cm 2 . (orig.)

  13. The three shapes of 32Mg

    International Nuclear Information System (INIS)

    Poves, A.; Nowacki, F.; Caurier, E.

    2014-01-01

    The N=20 and N=28 'islands of inversion' are described by large scale shell model calculations which mix configurations with different Nℎω or equivalently with different number of particles promoted from the sd-shell to the p f-shell. We pay particular attention to the properties of the states at fix Nℎω which turn out to be the real protagonists of the physics at N=20. In particular we study the appearance of spherical, deformed and superdeformed structures in 32 Mg at fixed 0p-0h, 2p-2h and 4p-4h configurations. Finally we show that the islands of deformation at N=20 and N=28 merge in a single one for Magnesium isotopes. (authors)

  14. Mg amorphous alloys for biodegradable implants

    International Nuclear Information System (INIS)

    Danez, G.P.; Koga, G.Y.; Tonucci, S.; Bolfarini, C.; Kiminami, C.S.; Botta Filho, W.J.

    2010-01-01

    The use of implants made from amorphous alloys magnesium-based with additions of zinc and calcium are promising. Properties such as biocompatibility, low density, high mechanical strength, low modulus (as compared to alloys such as stainless steel and titanium), corrosion resistance and wear resistance make it attractive for use in implants. Moreover, the by-products of corrosion and wear are not toxic and may contribute to fixation. Aiming to understand the tendency of this amorphous ternary (Mg-Zn-Ca) and expand the information about this system, this work involved the use of the topological criterion of instability (λ) and the criterion of electronegativity (Δe) to the choice of compositions. The alloys were processed into wedge-shaped and analyzed structurally and in X-ray diffraction and scanning electron microscopy. (author)

  15. Estabilidad de tabletas de Rifampicina 300 mg

    Directory of Open Access Journals (Sweden)

    Lisette Martínez Miranda

    2001-04-01

    Full Text Available Se realizó el estudio de estabilidad de las tabletas de rifampicina 300 mg. Se utilizó para la cuantificación del principio activo un método analítico desarrollado y validado por cromatografía líquida de alta resolución en fase reversa y detección ultravioleta. El estudio de estabilidad de las tabletas se efectuó mediante los métodos de vida útil y acelerado en condiciones isotérmicas; no se obtuvo una variación notable de la concentración en el tiempo de estudio y se demostró así la estabilidad química y térmica del principio activo, por lo que se proponen 2 años como fecha de vencimiento. La humedad relativa de 75, 84 y 92 % tuvo influencia en la estabilidad de la formulación en el período analizado.The stability study of rifampicin 300 mg was conducted. An analytical method developed and validated by high pressure liquid chromatography in reverse phase and ultraviolet detection was used for the quantification of the actives principle. The stability study of the tablets was conducted by the method of useful life and the accelerated method under isothermic conditions. There was no significant variation of the concentration during the time of study and, thus, the chemical and thermal stability of the active principle was proved. A period of 2 years was proposed as expiration date. A relative humidity of 75, 84 and 92% influenced on the stability of the formulation in the analyzed period.

  16. Hydriding and dehydriding rates of Mg, Mg-10TaF5, and Mg-10NbF5 prepared via reactive mechanical grinding

    Science.gov (United States)

    Song, Myoung Youp; Kwak, Young Jun; Lee, Seong Ho; Park, Hye Ryoung

    2015-01-01

    In this work, TaF5 and NbF5 were chosen as additives to enhance the hydriding and dehydriding rates of Mg. Mg, Mg-10TaF5, and Mg-10NbF5 samples were prepared by reactive mechanical grinding. The hydriding and dehydriding properties of the samples were then examined. Mg-10TaF5 had the largest amount of hydrogen absorbed for 30 min and the highest initial dehydriding rate after incubation period, followed in order by Mg-10NbF5, and Mg. At 593 K under 12 bar H2 at the first cycle, Mg-10TaF5 absorbed 3.63 wt% H for 5 min and 4.53 wt% H for 30 min. At 593 K under 1.0 bar H2 at the first cycle, Mg-10TaF5 desorbed 0 wt% H for 2.5 min, 0.59 wt% H for 5 min, 3.42 wt% H for 30 min, and 4.24 wt% H for 60 min. The reactive mechanical grinding of Mg with TaF5 or NbF5 is believed to have facilitated the nucleation and to have decreased the diffusion distances of hydrogen atoms. These two effects are believed to have increased the hydriding and dehydriding rates of Mg. The MgF2 and Ta2H formed in Mg-10TaF5, and the MgF2, NbH2, and NbF3 formed in Mg-10NbF5 are considered to have enhanced both of these effects.

  17. Mechanochemical Synthesis of Nanostructured MgXNi1-XO Compound by Mg-NiO Mixture

    Directory of Open Access Journals (Sweden)

    Nader Setoudeh

    2017-06-01

    Full Text Available Synthesis of magnesium nickel oxide phase such as MgxNi1-xO solid solutions has been studied in this research article using mechnochmical reaction between magnesium and nickel oxide. Mixtures of magnesium powder and nickel oxide (Mg+NiO with stoichiometric compositions were milled for different times in a planetary ball mill. Reduction reaction of nickel oxide by magnesium via a mechanically induced self-sustaining reaction (MSR was confirmed in the XRD measurements of the as-milled samples. Formation of nanostructured magnesium nickel oxide phases (such as Mg0.4Ni0.6O or MgNiO2 was observed after isothermal heating of the 30 minutes milled samples at 1000°C where nickel phase seems to disappear in XRD patterns. The traces of phases such as Mg0.4Ni0.6O or MgNiO2 were also observed in the as-milled mixtures. Therefore, the XRD results of the as-milled samples suggested that the formation of magnesium nickel oxide phases could be possible even after prolonged milling. The XRD and SEM results of both as-milled and isothermally heated samples indicated that the crystallite size and particle size of the final products reached to nanoscale after milling. Morphological and compositional evolution of the samples after heat treatment was monitored through SEM imaging and elemental analyses. The results confirmed that the composition of final product is close to Mg0.4Ni0.6O compound.

  18. Seasonal variations in C:N:Si:Ca:P:Mg:S:K:Fe relationships of seston from Norwegian coastal water: Impact of extreme offshore forcing during winter-spring 2010.

    Science.gov (United States)

    Erga, Svein Rune; Haugen, Stig Bjarte; Bratbak, Gunnar; Egge, Jorun Karin; Heldal, Mikal; Mork, Kjell Arne; Norland, Svein

    2017-11-20

    The aim of this study was to reveal the relative content of C, N, Ca, Si, P, Mg, K, S and Fe in seston particles in Norwegian coastal water (NCW), and how it relates to biological and hydrographic processes during seasonal cycles from October 2009-March 2012. The following over all stoichiometric relationship for the time series was obtained: C 66 N 11 Si 3.4 Ca 2.3 P 1 Mg 0.73 S 0.37 K 0.35 Fe 0.30 , which is novel for marine waters. A record-breaking (187-year record) negative North Atlantic Oscillation (NAO) index caused extreme physical forcing on the Norwegian Coastal Current Water (NCCW) during the winter 2009-2010, and the inflow and upwelling of saline Atlantic water (AW) in the fjord was thus extraordinary during late spring-early summer in 2010. The element concentrations in fjord seston particles responded strongly to this convection, revealed by maximum values of all elements, except Fe, exceeding average values with 10.8 × for Ca, 9.3 for K, 5.3 for S, 5.1 for Mg, 4.6 for Si, 4.0 for P, 3.8 for C, and 3.3 for N and Fe. This indicates that the signature of the Atlantic inflow was roughly two times stronger for Ca and K than for the others, probably connected with peaks in coccolithophorids and diatoms. There is, however, 1.5 × more of Si than Ca contained in the seston, which could be due to a stronger dominance of diatoms than coccolithophorids, confirming their environmental fitness. In total our data do not indicate any severe nutrient limitation with respect to N, P and Fe, but accumulation of iron by Fe-sequestering bacteria might at times reduce the availability of the dissolved Fe-fraction. There is a high correlation between most of the measured elements, except for Ca, which together with Fe only weakly correlated with the other elements. It is to be expected that environmental alterations in NCW related to climate change will influence the seston elemental composition, but the full effect of this will be strongly dependent on the future

  19. Porous composite materials ZrO2(MgO)-MgO for osteoimplantology

    International Nuclear Information System (INIS)

    Buyakov, Ales; Litvinova, Larisa; Shupletsova, Valeria; Kulbakin, Denis; Kulkov, Sergey

    2016-01-01

    The pore structure and phase composition of ceramic composite material ZrO 2 (Mg)-MgO at different sintering temperatures were studied. The main mechanical characteristics of the material were determined and it was shown that they are close to the characteristics of natural bone tissues. It was shown that material structure has a positive effect on the pre-osteoblast cells proliferation. In-vitro studies of pre-osteoblast cells, cultivation on material surface showed a good cell adhesion, proliferation and differentiation of MMSC by osteogenic type.

  20. Sorption of selenium on Mg-Al and Mg-Al-Eu layered double hydroxides

    International Nuclear Information System (INIS)

    Curtius, H.; Paparigas, Z.; Kaiser, G.

    2008-01-01

    Salt domes represent deep geological formations which are under consideration as final repositories for irradiated research reactor fuel elements. For long-term safety aspects the mobilisation of the radionuclides due to a water ingress is intensively investigated. At the Institute of Energy Research (IEF-6), leaching experiments were performed in a hot cell facility with UAl x -Al and U 3 Si 2 -Al dispersed research reactor fuel elements in repository-relevant MgCl 2 -rich salt brines under anaerobic conditions. The fuel plates corroded completely within one year and a Mg-Al-layered double hydroxide (LDH) with chloride as interlayer anion was identified as one crystalline phase component of the corrosion products (secondary phases). This Mg-Al-LDH was synthesized, characterized, and the ability to retard europium by an incorporation process was investigated. Europium, as a representative for lanthanides, was identified to be one of the radionuclides which were found in the corrosion products. We could show that europium was incorporated in the lattice structure. LDHs have high anion exchange capacities that enhance their potential to remove anionic contaminants from aqueous systems. In this work the sorption behaviour of selenium in the chemical form as selenite (SeO 3 2- ) on Mg-Al-LDH and on Mg-Al-Eu-LDH was investigated. Especially the influence of the larger europium-III ion was of interest. It represents in the Mg-Al-Eu-LDH about 10% of the molar aluminium amount. The sorption has been experimentally studied in a wide range of pH, ionic strength, radionuclide and sorbent concentration. Both LDHs with chloride as interlayer anion were synthesized by a coprecipitation method under controlled conditions, and their main physico-chemical properties were analyzed prior to the sorption experiments. The sorption kinetics of selenite on the LDHs in water and in MgCl 2 -rich brine were rapid using a LDH concentration of 10 g/L. Equilibrium, indicated by stable p

  1. Porous composite materials ZrO{sub 2}(MgO)-MgO for osteoimplantology

    Energy Technology Data Exchange (ETDEWEB)

    Buyakov, Ales, E-mail: alesbuyakov@gmail.com [Institute of Strength Physics and Materials Science SB RAS, Tomsk, 634055 (Russian Federation); National Research Tomsk State University, Tomsk, 634050 (Russian Federation); Litvinova, Larisa, E-mail: larisalitvinova@yandex.ru; Shupletsova, Valeria, E-mail: vshupletsova@mail.ru [Immanuel Kant Baltic Federal University, Kaliningrad (Russian Federation); Kulbakin, Denis, E-mail: kulbakin2012@gmail.com [Tomsk Cancer Research Institute, Tomsk, 634050 (Russian Federation); Kulkov, Sergey, E-mail: kulkov@ispms.ru [Institute of Strength Physics and Materials Science SB RAS, Tomsk, 634055 (Russian Federation); National Research Tomsk State University, Tomsk, 634050 (Russian Federation); National Research Tomsk Polytechnic University, Tomsk, 634050 (Russian Federation)

    2016-08-02

    The pore structure and phase composition of ceramic composite material ZrO{sub 2}(Mg)-MgO at different sintering temperatures were studied. The main mechanical characteristics of the material were determined and it was shown that they are close to the characteristics of natural bone tissues. It was shown that material structure has a positive effect on the pre-osteoblast cells proliferation. In-vitro studies of pre-osteoblast cells, cultivation on material surface showed a good cell adhesion, proliferation and differentiation of MMSC by osteogenic type.

  2. Role of dopants in LiF:Mg,Cu, LiF:Mg,P and LiF:Mg,Cu,P detectors

    International Nuclear Information System (INIS)

    Mohammadi, Kh.; Moussavi Zarandi, A.; Afarideh, H.; Shahmaleki, S.

    2013-01-01

    In this study, electronic structure of LiF crystal doped with Mg,Cu,P impurities was studied with WIEN2k code on the basis of FPLAPW+lo method. Results show that in Mg-doped LiF composition, an electronic trap was created with impurity concentration of 1.56% and 3.125%. In this condition, the electronic trap with increasing the percentage of the impurities up to 4.687% is annihilated. It was found, that by doping of Mg and Cu or P simultaneously, a hole-trap is created in valence band. It was realized that in LiF:Mg,Cu, LiF:Mg,P and LiF:Mg,Cu,P, Cu impurity and Li atom, have a key role in creation of levels which lead to create electronic and hole traps. Mg impurity and F atom, only have a role in creation of electronic traps. In addition, P impurity has a main role in creation of the electronic and hole traps in LiF:Mg,Cu,P. The activation energy of electronic and hole trap in LiF:Mg,Cu, LiF:Mg,P and LiF:Mg,Cu,P crystalline lattice were obtained as 0.3 and 5.5 eV, 0.92 and 3.4 eV and 0.75 and 3.1 eV, respectively. - Graphical abstract: Figure (a) and (b) shows changes in electronic structure and band gap energy of LiF crystal due to presence of Mg and Cu, Mg and P ions respectively. - Highlights: • Electronic structure of LiF, LiF:Mg,Cu, LiF:Mg,P and LiF:Mg,Cu,P materials were studied with WIEN2K code. • In LiF:Mg,Cu and LiF:Mg,Cu,P, Li atom and Cu impurity have a key role in creation of levels. • F atom and Mg impurity only have a role in creation of electronic traps. • In LiF:Mg,Cu,P, P impurity has a main role in creation of electronic and hole traps

  3. Ab initio study of MgH2 formation

    International Nuclear Information System (INIS)

    Novakovic, Nikola; Matovic, Ljiljana; Novakovic, Jasmina Grbovic; Manasijevic, Miodrag; Ivanovic, Nenad

    2009-01-01

    Even if there is considerable literature dealing with structure and properties of MgH 2 compound there are still some uncertain details about nature of bonding governing its formation and decomposition. In order to better understand the processes essential for absorption and desorption of MgH 2 , ab initio DFT based calculations of rutile MgH 2 compound, elemental hcp-Mg, and three different hypothetical hcp-Mg-derived hydrides are performed. Our findings show that all structures are unstable, and that MgH (Wurtzite) is a closest possible candidate for intermediate phase between the hcp-Mg and MgH 2 at 1:1 stoichiometry. An alternative hydration pathway is suggested, including promotion of hcp-Mg to bcc-Mg and consecutive transformation to rutile MgH 2 by means of hydrogen incorporation into Mg matrix. Rutile MgH 2 calculations with various hydrogen vacancies concentration are performed. Calculation shows that at high hydrogen concentration close to 1:2, stable substoichiometric hydride is possible. Calculation also shows that high vacancy (low hydrogen) concentration favors bcc-Mg 2 H over rutile Mg 2 H structure.

  4. The Influence of MgH2 on the Assessment of Electrochemical Data to Predict the Degradation Rate of Mg and Mg Alloys

    Directory of Open Access Journals (Sweden)

    Wolf-Dieter Mueller

    2014-06-01

    Full Text Available Mg and Mg alloys are becoming more and more of interest for several applications. In the case of biomaterial applications, a special interest exists due to the fact that a predictable degradation should be given. Various investigations were made to characterize and predict the corrosion behavior in vitro and in vivo. Mostly, the simple oxidation of Mg to Mg2+ ions connected with adequate hydrogen development is assumed, and the negative difference effect (NDE is attributed to various mechanisms and electrochemical results. The aim of this paper is to compare the different views on the corrosion pathway of Mg or Mg alloys and to present a neglected pathway based on thermodynamic data as a guideline for possible reactions combined with experimental observations of a delay of visible hydrogen evolution during cyclic voltammetry. Various reaction pathways are considered and discussed to explain these results, like the stability of the Mg+ intermediate state, the stability of MgH2 and the role of hydrogen overpotential. Finally, the impact of MgH2 formation is shown as an appropriate base for the prediction of the degradation behavior and calculation of the corrosion rate of Mg and Mg alloys.

  5. The role of MgO content in ex situ MgB2 wires

    DEFF Research Database (Denmark)

    Kovac, P.; Hugek, I.; Meligek, T.

    2004-01-01

    An experimental study of the effect of MgO content in the MgB2 powder used for ex situ made composite wires was carried out. Two single-core MgB2/Fe/Cu wires were made using commercial MgB2 powders from Alfa Aesar containing different fraction of MgO. Critical temperature and critical currents of...

  6. Positron annihilation study of formation of Mg vacancy in MgO

    International Nuclear Information System (INIS)

    Mizuno, M.; Araki, H.; Shirai, Y.; Inoue, Y.; Sugita, K.; Mizoguchi, T.; Tanaka, I.; Adachi, H.

    2004-01-01

    We have investigated the formation of Mg vacancy induced by ultra-dilute trivalent impurities in MgO by a combination of positron annihilation measurement and theoretical calculations of positron lifetimes. The undoped MgO yields the shortest positron lifetime of 130 ps that is shorter than that of 166 ps previously reported using a single crystal sample. The positron lifetime of the doped samples increases with the increase of the Al or Ga dopant concentration and is saturated at around 170 ps. This result indicates that the previously reported value of 166 ps is ascribed to not the bulk but the vacancy state induced by impurities. The experimental bulk lifetime of 130 ps, which is obtained by employing trapping model, is well reproduced by the theoretical calculation using the semiconductor model. The calculated defect lifetime is about 20 ps longer than the experimental value. This may be due to the lattice relaxation around Mg vacancy associated with the trapping of positrons. (orig.)

  7. Positron annihilation study of formation of Mg vacancy in MgO

    Energy Technology Data Exchange (ETDEWEB)

    Mizuno, M.; Araki, H.; Shirai, Y. [Science and Technology Center for Atoms, Molecules and Ions Control, Osaka Univ., Osaka (Japan); Inoue, Y.; Sugita, K. [Dept. of Materials Science and Engineering, Osaka Univ., Osaka (Japan); Mizoguchi, T.; Tanaka, I.; Adachi, H. [Dept. of Materials Science and Engineering, Kyoto Univ., Kyoto (Japan)

    2004-07-01

    We have investigated the formation of Mg vacancy induced by ultra-dilute trivalent impurities in MgO by a combination of positron annihilation measurement and theoretical calculations of positron lifetimes. The undoped MgO yields the shortest positron lifetime of 130 ps that is shorter than that of 166 ps previously reported using a single crystal sample. The positron lifetime of the doped samples increases with the increase of the Al or Ga dopant concentration and is saturated at around 170 ps. This result indicates that the previously reported value of 166 ps is ascribed to not the bulk but the vacancy state induced by impurities. The experimental bulk lifetime of 130 ps, which is obtained by employing trapping model, is well reproduced by the theoretical calculation using the semiconductor model. The calculated defect lifetime is about 20 ps longer than the experimental value. This may be due to the lattice relaxation around Mg vacancy associated with the trapping of positrons. (orig.)

  8. Surface treatments for controlling corrosion rate of biodegradable Mg and Mg-based alloy implants

    International Nuclear Information System (INIS)

    Uddin, M S; Hall, Colin; Murphy, Peter

    2015-01-01

    Due to their excellent biodegradability characteristics, Mg and Mg-based alloys have become an emerging material in biomedical implants, notably for repair of bone as well as coronary arterial stents. However, the main problem with Mg-based alloys is their rapid corrosion in aggressive environments such as human bodily fluids. Previously, many approaches such as control of alloying materials, composition and surface treatments, have been attempted to regulate the corrosion rate. This article presents a comprehensive review of recent research focusing on surface treatment techniques utilised to control the corrosion rate and surface integrity of Mg-based alloys in both in vitro and in vivo environments. Surface treatments generally involve the controlled deposition of thin film coatings using various coating processes, and mechanical surfacing such as machining, deep rolling or low plasticity burnishing. The aim is to either make a protective thin layer of a material or to change the micro-structure and mechanical properties at the surface and sub-surface levels, which will prevent rapid corrosion and thus delay the degradation of the alloys. We have organised the review of past works on coatings by categorising the coatings into two classes—conversion and deposition coatings—while works on mechanical treatments are reviewed based on the tool-based processes which affect the sub-surface microstructure and mechanical properties of the material. Various types of coatings and their processing techniques under two classes of coating and mechanical treatment approaches have been analysed and discussed to investigate their impact on the corrosion performance, biomechanical integrity, biocompatibility and cell viability. Potential challenges and future directions in designing and developing the improved biodegradable Mg/Mg-based alloy implants were addressed and discussed. The literature reveals that no solutions are yet complete and hence new and innovative approaches

  9. Efficacy of 5MG and 10MG rosuvastatin in type-2 diabetes mellitus with hypercholesteroalemia

    International Nuclear Information System (INIS)

    Ullah, F.; Rahim, F.; Rahman, S.U.; Ashfaq, M.; Afridi, A.K.

    2015-01-01

    Background: Coronary Heart Disease (CHD) is the most important complication and the leading cause of death in patients with type 2 diabetes mellitus (T2DM). Hypercholesterolemia is an important modifiable risk factor for CHD. Statins are the first line drugs for the treatment of hypercholesterolemia in DM. Comparative studies between different statins are available but different doses of the same statin have not been compared in our population. The objective of this study is to compare mean reduction in serum LDL-C level after using 5mg and 10mg of rosuvastatin among T2DM patients with hypercholesterolemia. This study will help finding lowest effective dose of rosuvastatin to achieve internationally set low density lipoprotein cholesterol (LDL-C) goals. Method: A total of 82 patients with T2DM having fasting LDL-C levels equal or more than 100mg/dl were randomly allocated into two groups with 41 patients in each group. Baseline fasting serum LCL-C levels were obtained in all patients. Group A received 5mg while group B received 10mg of rosuvastatin daily at night. After 6 weeks, fasting LDL-C levels were obtained and analysed to compare the mean±SD reduction of LDL-C levels in both groups. Results: Baseline mean±SD LDL-C levels in group A and group B were 134.12±30.02 and 143.49±32.01 respectively (p 0.176). Follow up mean ± SD LDL-C levels were 81.59±28.47 and 83.24±36.06 respectively (p 0.818). Mean ± SD reduction in LDL-C levels from baseline levels in group A and group B were 52.51±19.49 and 60.20±24.09 (p 0.116). Conclusion: Rosuvastatin 5mg is as effective as 10mg in reducing the LDL-C levels in type 2 diabetic patients with hypercholesterolemia. (author)

  10. Surface treatments for controlling corrosion rate of biodegradable Mg and Mg-based alloy implants

    Science.gov (United States)

    Uddin, M S; Hall, Colin; Murphy, Peter

    2015-01-01

    Due to their excellent biodegradability characteristics, Mg and Mg-based alloys have become an emerging material in biomedical implants, notably for repair of bone as well as coronary arterial stents. However, the main problem with Mg-based alloys is their rapid corrosion in aggressive environments such as human bodily fluids. Previously, many approaches such as control of alloying materials, composition and surface treatments, have been attempted to regulate the corrosion rate. This article presents a comprehensive review of recent research focusing on surface treatment techniques utilised to control the corrosion rate and surface integrity of Mg-based alloys in both in vitro and in vivo environments. Surface treatments generally involve the controlled deposition of thin film coatings using various coating processes, and mechanical surfacing such as machining, deep rolling or low plasticity burnishing. The aim is to either make a protective thin layer of a material or to change the micro-structure and mechanical properties at the surface and sub-surface levels, which will prevent rapid corrosion and thus delay the degradation of the alloys. We have organised the review of past works on coatings by categorising the coatings into two classes—conversion and deposition coatings—while works on mechanical treatments are reviewed based on the tool-based processes which affect the sub-surface microstructure and mechanical properties of the material. Various types of coatings and their processing techniques under two classes of coating and mechanical treatment approaches have been analysed and discussed to investigate their impact on the corrosion performance, biomechanical integrity, biocompatibility and cell viability. Potential challenges and future directions in designing and developing the improved biodegradable Mg/Mg-based alloy implants were addressed and discussed. The literature reveals that no solutions are yet complete and hence new and innovative approaches

  11. Comparison of initial loading doses of 5 mg and 10 mg for warfarin therapy

    Directory of Open Access Journals (Sweden)

    Sidnei Lastória

    2014-03-01

    Full Text Available CONTEXT: The question of what is the best loading dosage of warfarin when starting anticoagulant treatment has been under discussion for ten years. We were unable to find any comparative studies of these characteristics conducted here in Brazil. OBJECTIVE: To compare the safety and efficacy of two initial warfarin dosage regimens for anticoagulant treatment. METHODS: One-hundred and ten consecutive patients of both sexes, with indications for anticoagulation because of venous or arterial thromboembolism, were analyzed prospectively. During the first 3 days of treatment, these patients were given adequate heparin to keep aPTT (activated partial thromboplastin time between 1.5 and 2.5, plus 5 mg of warfarin. From the fourth day onwards, their warfarin doses were adjusted using International Normalized Ratios (INR; target range: 2 to 3. This prospective cohort was compared with a historical series of 110 patients had been given 10 mg of warfarin on the first 2 days and 5 mg on the third day with adjustments based on INR thereafter. Outcomes analyzed were as follows: recurrence of thromboembolism, bleeding events and time taken to enter the therapeutic range. RESULTS: Efficacy, safety and length of hospital stay were similar in both samples. The sample that were given 10 mg entered the therapeutic range earlier (means: 4.5 days vs. 5.8 days, were on lower doses at discharge and had better therapeutic indicators at the first return appointment. CONCLUSIONS: The 10 mg dosage regimen took less time to attain the therapeutic range and was associated with lower warfarin doses at discharge and better INR at first out-patients follow-up visit.

  12. Enzymatic, urease-mediated mineralization of gellan gum hydrogel with calcium carbonate, magnesium-enriched calcium carbonate and magnesium carbonate for bone regeneration applications

    DEFF Research Database (Denmark)

    Douglas, Timothy E L; Łapa, Agata; Samal, Sangram Keshari

    2017-01-01

    enzymatically with CaCO3 , Mg-enriched CaCO3 and magnesium carbonate to generate composite biomaterials for bone regeneration. Hydrogels loaded with the enzyme urease were mineralized by incubation in mineralization media containing urea and different ratios of calcium and magnesium ions. Increasing...

  13. Seasonality and variability of coccolithophore fluxes in response to diverse oceanographic regimes in the Bay of Bengal: Sediment trap results

    Digital Repository Service at National Institute of Oceanography (India)

    Mergulhao, L.P.; Guptha, M.V.S.; Unger, D.; Murty, V.S.N.

    carbonate and diatom opal fluxes continued to increase. Tanaka and Kawahata (2001) reported that the calculated coccolith- CaCO3 fluxes ranged between 6.8 and 49.6 mg m-2day-1 and contributed 23.3% of total CaCO3 flux in the west Caroline Basin...

  14. Performance of Mg-14Li-1Al-0.1Ce as anode for Mg-air battery

    Energy Technology Data Exchange (ETDEWEB)

    Ma, Yibin; Li, Deyu [School of Chemical Engineering and Technology, Harbin Institute of Technology, West Street No. 92, Harbin 150001 (China); Li, Ning [School of Chemical Engineering and Technology, Harbin Institute of Technology, West Street No. 92, Harbin 150001 (China); Key Laboratory of Superlight Materials and Surface Technology, Ministry of Education, Harbin Engineering University, Harbin 150001 (China); Zhang, Milin; Huang, Xiaomei [Key Laboratory of Superlight Materials and Surface Technology, Ministry of Education, Harbin Engineering University, Harbin 150001 (China)

    2011-02-15

    In this research, a new Mg-air battery based on Mg-14Li-1Al-0.1Ce was prepared and the battery performance was investigated by constant current discharge test. The corrosion behavior of Mg, AZ31 and Mg-Li-Al-Ce were studied by self-corrosion rate measurement and potentiodynamic polarization measurement. The characteristics of Mg-Li-Al-Ce after discharge were investigated by electrochemical impedance spectroscopy (EIS), scanning electron microscopy (SEM) and X-ray diffraction (XRD). The results show that Mg-Li-Al-Ce is more active than Mg and AZ31. The self-corrosion rate is found to be in the order: Mg-Li-Al-Ce < Mg < AZ31. It has been observed that the Mg-air battery based on Mg-Li-Al-Ce offers higher operating voltage, anodic efficiency and capacity than those with Mg and AZ31. SEM and EIS results show that the discharge product of Mg-Li-Al-Ce is loosely adhered to the alloy surface, and thus Mg-Li-Al-Ce could keep high discharge activity during discharge. (author)

  15. Photodissociation spectroscopy of the Mg+-acetic acid complex

    Science.gov (United States)

    Abate, Yohannes; Kleiber, P. D.

    2006-11-01

    We have studied the structure and photodissociation of Mg+-acetic acid clusters. Ab initio calculations suggest four relatively strongly bound ground state isomers for the [MgC2H4O2]+ complex. These isomers include the cis and trans forms of the Mg+-acetic acid association complex with Mg+ bonded to the carbonyl O atom of acetic acid, the Mg+-acetic acid association complex with Mg+ bonded to the hydroxyl O atom of acetic acid, or to a Mg+-ethenediol association complex. Photodissociation through the Mg+-based 3p←3s absorption bands in the near UV leads to direct (nonreactive) and reactive dissociation products: Mg+, MgOH+, Mg(H2O )+, CH3CO+, and MgCH3+. At low energies the dominant reactive quenching pathway is through dehydration to Mg(H2O)+, but additional reaction channels involving C-H and C-C bond activation are also open at higher energies.

  16. Mg-Ca Alloys Produced by Reduction of CaO: Understanding of ECO-Mg Alloy Production

    Science.gov (United States)

    Jung, In-Ho; Lee, Jin Kyu; Kim, Shae K.

    2017-04-01

    There have been long debates about the environment conscious (ECO) Mg technology which utilizes CaO to produce Ca-containing Mg alloys. Two key process technologies of the ECO-Mg process are the chemical reduction of CaO by liquid Mg and the maintenance of melt cleanliness during the alloying of Ca. Thermodynamic calculations using FactSage software were performed to explain these two key issues. In addition, an experimental study was performed to compare the melt cleanliness of the Ca-containing Mg alloys produced by the conventional route with metallic Ca and the ECO-Mg route with CaO.

  17. LOW Mg/Si PLANETARY HOST STARS AND THEIR Mg-DEPLETED TERRESTRIAL PLANETS

    Energy Technology Data Exchange (ETDEWEB)

    Carter-Bond, Jade C.; O' Brien, David P. [Planetary Science Institute, 1700 E. Fort Lowell, Tucson, AZ 85719 (United States); Delgado Mena, Elisa; Israelian, Garik; Gonzalez Hernandez, Jonay I. [Instituto de Astrofisica de Canarias, 38200 La Laguna, Tenerife (Spain); Santos, Nuno C., E-mail: j.bond@unsw.edu.au [Centro de Astrofisica, Universidade do Porto, Rua das Estrelas, 4150-762 Porto (Portugal)

    2012-03-15

    Simulations have shown that a diverse range of extrasolar terrestrial planet bulk compositions are likely to exist based on the observed variations in host star elemental abundances. Based on recent studies, it is expected that a significant proportion of host stars may have Mg/Si ratios below 1. Here we examine this previously neglected group of systems. Planets simulated as forming within these systems are found to be Mg-depleted (compared to Earth), consisting of silicate species such as pyroxene and various feldspars. Planetary carbon abundances also vary in accordance with the host star C/O ratio. The predicted abundances are in keeping with observations of polluted white dwarfs, lending validity to this approach. Further studies are required to determine the full planetary impacts of the bulk compositions predicted here.

  18. Thermodynamic properties of Mg2Si and Mg2Ge investigated by first principles method

    International Nuclear Information System (INIS)

    Wang, Hanfu; Jin, Hao; Chu, Weiguo; Guo, Yanjun

    2010-01-01

    The lattice dynamics and thermodynamic properties of Mg 2 Si and Mg 2 Ge are studied based on the first principles calculations. We obtain the phonon dispersion curves and phonon density of states spectra using the density functional perturbation theory with local density approximations. By employing the quasi-harmonic approximation, we calculate the temperature dependent Helmholtz free energy, bulk modulus, thermal expansion coefficient, specific heat, Debye temperature and overall Grueneisen coefficient. The results are in good agreement with available experimental data and previous theoretical studies. The thermal conductivities of both compounds are then estimated with the Slack's equation. By carefully choosing input parameters, especially the acoustic Debye temperature, we find that the calculated thermal conductivities agree fairly well with the experimental values above 80 K for both compounds. This demonstrates that the lattice thermal conductivity of simple cubic semiconductors may be estimated with satisfactory accuracy by combining the Slack's equation with the necessary thermodynamics parameters derived completely from the first principles calculations.

  19. Relativistic quasiparticle band structures of Mg2Si, Mg2Ge, and Mg2Sn: Consistent parameterization and prediction of Seebeck coefficients

    Science.gov (United States)

    Shi, Guangsha; Kioupakis, Emmanouil

    2018-02-01

    We apply density functional and many-body perturbation theory calculations to consistently determine and parameterize the relativistic quasiparticle band structures of Mg2Si, Mg2Ge, and Mg2Sn, and predict the Seebeck coefficient as a function of doping and temperature. The quasiparticle band gaps, including spin-orbit coupling effects, are determined to be 0.728 eV, 0.555 eV, and 0.142 eV for Mg2Si, Mg2Ge, and Mg2Sn, respectively. The inclusion of the semicore electrons of Mg, Ge, and Sn in the valence is found to be important for the accurate determination of the band gaps of Mg2Ge and Mg2Sn. We also developed a Luttinger-Kohn Hamiltonian and determined a set of band parameters to model the near-edge relativistic quasiparticle band structure consistently for all three compounds that can be applied for thermoelectric device simulations. Our calculated values for the Seebeck coefficient of all three compounds are in good agreement with the available experimental data for a broad range of temperatures and carrier concentrations. Our results indicate that quasiparticle corrections are necessary for the accurate determination of Seebeck coefficients at high temperatures at which bipolar transport becomes important.

  20. Decomposition of supersaturated solid solutions Mg-Ho and Mg-Gd

    International Nuclear Information System (INIS)

    Sukhanov, V.D.; Dobromyslov, A.V.; Rokhlin, L.L.; Dobatkina, T.V.

    2002-01-01

    Methods of electron microscopy and X-ray diffraction analysis are applied to study ageing magnesium base alloys with holmium and gadolinium. It is shown that the precipitation of supersaturated Mg base solid solutions goes through several subsequent stages and is accompanied by a considerable precipitation hardening effect at the stage of metastable phase precipitation. The influence of aging time and temperature on precipitation kinetics is established [ru

  1. Simulation of precipitation and strengthening in MG-RE alloys

    OpenAIRE

    Liu, Hong

    2017-01-01

    Magnesium - rare earth (Mg-RE) alloys have received considerable attention in the past decades for wider applications in the aerospace industry due to their relatively high strength and excellent creep resistance. Most rare-earth containing magnesium alloys, such as Mg-Y, Mg-Gd, and Mg-Y-Nd, are precipitation hardenable. A technical barrier to the wider applications of such alloys is the lack of a sufficiently large age hardening response. To further improve this response, an improved underst...

  2. Combinatorial search for hydrogen storage alloys: Mg-Ni and Mg-Ni-Ti

    Energy Technology Data Exchange (ETDEWEB)

    Oelmez, Rabia; Cakmak, Guelhan; Oeztuerk, Tayfur [Dept. of Metallurgical and Materials Engineering, Middle East Technical University, 06531 Ankara (Turkey)

    2010-11-15

    A combinatorial study was carried out for hydrogen storage alloys involving processes similar to those normally used in their fabrication. The study utilized a single sample of combined elemental (or compound) powders which were milled and consolidated into a bulk form and subsequently deformed to heavy strains. The mixture was then subjected to a post annealing treatment, which brings about solid state reactions between the powders, yielding equilibrium phases in the respective alloy system. A sample, comprising the equilibrium phases, was then pulverized and screened for hydrogen storage compositions. X-ray diffraction was used as a screening tool, the sample having been examined both in the as processed and the hydrogenated state. The method was successfully applied to Mg-Ni and Mg-Ni-Ti yielding the well known Mg{sub 2}Ni as the storage composition. It is concluded that a partitioning of the alloy system into regions of similar solidus temperature would be required to encompass the full spectrum of equilibrium phases. (author)

  3. Mg-lattice associations in red coralline algae

    Science.gov (United States)

    Kamenos, N. A.; Cusack, M.; Huthwelker, T.; Lagarde, P.; Scheibling, R. E.

    2009-04-01

    Recent investigations have shown red coralline algae to record ambient temperature in their calcite skeletons. Temperature recorded by variation in Mg concentrations within algal growth bands has sub-annual resolution and high accuracy. The conversion of Mg concentration to temperature is based on the assumption of Ca replacement by Mg within the algal calcite skeleton at higher temperatures. While Mg-temperature relationships in coralline algae have been calibrated for some species, the location of Mg within the calcite lattice remains unknown. Critically, if Mg is not a lattice component but associated with organic components this could lead to erroneous temperature records. Before coralline algae are used in large scale climate reconstructions it is therefore important to determine the location of Mg. Synchrotron Mg-X-ray absorbance near edge structure (XANES) indicates that Mg is associated with the calcite lattice in Lithothamnion glaciale (contemporary free-living, contemporary encrusting and sub-fossil free-living) and Phymatolithon calcareum (contemporary free-living) coralline algae. Mg is deposited within the calcite lattice in all seasons ( L. glaciale & P. calcareum) and thallus areas ( P. calcareum). These results suggest L. glaciale and P. calcareum are robust Mg-palaeotemperature proxies. We suggest that similar confirmation be obtained for Mg associations in other species of red coralline algae aiding our understanding of their role in climate reconstruction at large spatial scales.

  4. Carbonate mineral solubility at low temperatures in the Na-K-Mg-Ca-H-Cl-SO 4-OH-HCO 3-CO 3-CO 2-H 2O system

    Science.gov (United States)

    Marion, Giles M.

    2001-06-01

    Carbonate minerals have played an important role in the geochemical evolution of Earth, and may have also played an important role in the geochemical evolution of Mars and Europa. Several models have been published in recent years that describe chloride and sulfate mineral solubilities in concentrated brines using the Pitzer equations. Few of these models are parameterized for subzero temperatures, and those that are do not include carbonate chemistry. The objectives of this work are to estimate Pitzer-equation bicarbonate-carbonate parameters and carbonate mineral solubility products and to incorporate them into the FREZCHEM model to predict carbonate mineral solubilities in the Na-K-Mg-Ca-H-Cl-SO 4-OH-HCO 3-CO 3-CO 2-H 2O system at low temperatures (≤25°C) with a special focus on subzero temperatures. Most of the Pitzer-equation parameters and equilibrium constants are taken from the literature and extrapolated into the subzero temperature range. Solubility products for 14 sodium, potassium, magnesium, and calcium bicarbonate and carbonate minerals are included in the model. Most of the experimental data are at temperatures ≥ -8°C; only for the NaHCO 3-NaCl-H 2O and Na 2CO 3-NaCl-H 2O systems are there bicarbonate and carbonate data to temperatures as low as -21.6°C. In general, the fit of the model to the experimental data is good. For example, calculated eutectic temperatures and compositions for NaHCO 3, Na 2CO 3, and their mixtures with NaCl and Na 2SO 4 salts are in good agreement with experimental data to temperatures as low as -21.6°C. Application of the model to eight saline, alkaline carbonate waters give predicted pHs ranging from 9.2 to 10.2, in comparison with measured pHs that range from 8.7 to 10.2. The model suggests that the CaCO 3 mineral that precipitates during seawater freezing is probably calcite and not ikaite. The model demonstrates that a proposed salt assemblage for the icy surface of Europa consisting of highly hydrated MgSO 4

  5. The dependence of Raman scattering on Mg concentration in Mg-doped GaN grown by MBE

    International Nuclear Information System (INIS)

    Flynn, Chris; Lee, William

    2014-01-01

    Magnesium-doped GaN (GaN:Mg) films having Mg concentrations in the range 5 × 10 18 –5 × 10 20 cm −3 were fabricated by molecular beam epitaxy. Raman spectroscopy was employed to study the effects of Mg incorporation on the positions of the E 2 and A 1 (LO) lines identifiable in the Raman spectra. For Mg concentrations in excess of 2 × 10 19 cm −3 , increases in the Mg concentration shift both lines to higher wave numbers. The shifts of the Raman lines reveal a trend towards compressive stress induced by incorporation of Mg into the GaN films. The observed correlation between the Mg concentration and the Raman line positions establish Raman spectroscopy as a useful tool for optimizing growth of Mg-doped GaN. (papers)

  6. Structural and electronic properties of Mg and Mg-Nb co-doped TiO2 (101) anatase surface

    International Nuclear Information System (INIS)

    Sasani, Alireza; Baktash, Ardeshir; Mirabbaszadeh, Kavoos; Khoshnevisan, Bahram

    2016-01-01

    Highlights: • Formation energy of Mg and Mg-Nb co-doped TiO_2 anatase surface (101) is studied. • Effect of Mg defect to the TiO_2 anatase (101) surface and bond length distribution of the surface is studied and it is shown that Mg defects tend to stay far from each other. • Effect of Mg and Nb to the bond length distribution of the surface studied and it is shown that these defects tend to stay close to each other. • Effects of Mg and Mg-Nb defects on DSSCs using TiO_2 anatase hosting these defects are studied. - Abstract: In this paper, by using density functional theory, Mg and Nb-Mg co-doping of TiO_2 anatase (101) surfaces are studied. By studying the formation energy of the defects and the bond length distribution of the surface, it is shown that Mg defects tend to stay as far as possible to induce least possible lattice distortion while Nb and Mg defects stay close to each other to cause less stress to the surface. By investigating band structure of the surface and changes stemmed from the defects, potential effects of Mg and Mg-Nb co-doping of TiO_2 surface on dye-sensitized solar cells are investigated. In this study, it is shown that the Nb-Mg co-doping could increase J_S_C of the surface while slightly decreasing V_O_C compared to Mg doped surface, which might result in an increase in efficiency of the DSSCs compared to Nb or Mg doped surfaces.

  7. Structural and electronic properties of Mg and Mg-Nb co-doped TiO2 (101) anatase surface

    Energy Technology Data Exchange (ETDEWEB)

    Sasani, Alireza [Department of Science, Karaj Islamic Azad University, Karaj, Alborz, P.O. Box 31485-313 (Iran, Islamic Republic of); Baktash, Ardeshir [Institute of Nano Science and Nano Technology, University of Kashan, Kashan, P.O. Box 87317-51167 (Iran, Islamic Republic of); Mirabbaszadeh, Kavoos, E-mail: mirabbas@aut.ac.ir [Department of Energy Engineering and Physics, Amirkabir University of Technology, Tehran, P. O. Box 15875-4413 (Iran, Islamic Republic of); Khoshnevisan, Bahram [Institute of Nano Science and Nano Technology, University of Kashan, Kashan, P.O. Box 87317-51167 (Iran, Islamic Republic of)

    2016-10-30

    Highlights: • Formation energy of Mg and Mg-Nb co-doped TiO{sub 2} anatase surface (101) is studied. • Effect of Mg defect to the TiO{sub 2} anatase (101) surface and bond length distribution of the surface is studied and it is shown that Mg defects tend to stay far from each other. • Effect of Mg and Nb to the bond length distribution of the surface studied and it is shown that these defects tend to stay close to each other. • Effects of Mg and Mg-Nb defects on DSSCs using TiO{sub 2} anatase hosting these defects are studied. - Abstract: In this paper, by using density functional theory, Mg and Nb-Mg co-doping of TiO{sub 2} anatase (101) surfaces are studied. By studying the formation energy of the defects and the bond length distribution of the surface, it is shown that Mg defects tend to stay as far as possible to induce least possible lattice distortion while Nb and Mg defects stay close to each other to cause less stress to the surface. By investigating band structure of the surface and changes stemmed from the defects, potential effects of Mg and Mg-Nb co-doping of TiO{sub 2} surface on dye-sensitized solar cells are investigated. In this study, it is shown that the Nb-Mg co-doping could increase J{sub SC} of the surface while slightly decreasing V{sub OC} compared to Mg doped surface, which might result in an increase in efficiency of the DSSCs compared to Nb or Mg doped surfaces.

  8. Constraints on the ^22Ne(α,n)^25Mg reaction rate from ^natMg+n Total and ^25Mg(n,γ ) Cross Sections

    Science.gov (United States)

    Koehler, Paul

    2002-10-01

    The ^22Ne(α,n)^25Mg reaction is the neutron source during the s process in massive and intermediate mass stars as well as a secondary neutron source during the s process in low mass stars. Therefore, an accurate determination of this rate is important for a better understanding of the origin of nuclides heavier than iron as well as for improving s-process models. Also, because the s process produces seed nuclides for a later p process in massive stars, an accurate value for this rate is important for a better understanding of the p process. Because the lowest observed resonance in direct ^22Ne(α,n)^25Mg measurements is considerably above the most important energy range for s-process temperatures, the uncertainty in this rate is dominated by the poorly known properties of states in ^26Mg between this resonance and threshold. Neutron measurements can observe these states with much better sensitivity and determine their parameters much more accurately than direct ^22Ne(α,n)^25Mg measurements. I have analyzed previously reported Mg+n total and ^25Mg(n,γ ) cross sections to obtain a much improved set of resonance parameters for states in ^26Mg in this region, and an improved estimate of the uncertainty in the ^22Ne(α,n)^25Mg reaction rate. This work was supported by the U.S. DOE under contract No. DE-AC05-00OR22725 with UT-Battell, LLC.

  9. Coherent interface structures and intergrain Josephson coupling in dense MgO/Mg{sub 2}Si/MgB{sub 2} nanocomposites

    Energy Technology Data Exchange (ETDEWEB)

    Ueno, Katsuya; Takahashi, Kazuyuki; Uchino, Takashi, E-mail: uchino@kobe-u.ac.jp [Department of Chemistry, Graduate School of Science, Kobe University, Nada, Kobe 657-8501 (Japan); Nagashima, Yukihito [Nippon Sheet Glass Co., Ltd., Konoike, Itami 664-8520 (Japan); Seto, Yusuke [Department of Planetology, Graduate School of Science, Kobe University, Nada, Kobe 657-8501 (Japan); Matsumoto, Megumi; Sakurai, Takahiro [Center for Support to Research and Education Activities, Kobe University, Nada, Kobe 657-8501 (Japan); Ohta, Hitoshi [Molecular Photoscience Research Center, Kobe University, Nada, Kobe 657-8501 (Japan)

    2016-07-07

    Many efforts are under way to control the structure of heterointerfaces in nanostructured composite materials for designing functionality and engineering application. However, the fabrication of high-quality heterointerfaces is challenging because the crystal/crystal interface is usually the most defective part of the nanocomposite materials. In this work, we show that fully dense insulator (MgO)/semiconductor(Mg{sub 2}Si)/superconductor(MgB{sub 2}) nanocomposites with atomically smooth and continuous interfaces, including epitaxial-like MgO/Mg{sub 2}Si interfaces, are obtained by solid phase reaction between metallic magnesium and a borosilicate glass. The resulting nanocomposites exhibit a semiconductor-superconducting transition at 36 K owing to the MgB{sub 2} nanograins surrounded by the MgO/Mg{sub 2}Si matrix. This transition is followed by the intergrain phase-lock transition at ∼24 K due to the construction of Josephson-coupled network, eventually leading to a near-zero resistance state at 17 K. The method not only provides a simple process to fabricate dense nanocomposites with high-quality interfaces, but also enables to investigate the electric and magnetic properties of embedded superconducting nanograins with good intergrain coupling.

  10. Photoluminescence of Mg_2Si films fabricated by magnetron sputtering

    International Nuclear Information System (INIS)

    Liao, Yang-Fang; Xie, Quan; Xiao, Qing-Quan; Chen, Qian; Fan, Meng-Hui; Xie, Jing; Huang, Jin; Zhang, Jin-Min; Ma, Rui; Wang, Shan-Lan; Wu, Hong-Xian; Fang, Di

    2017-01-01

    Highlights: • High quality Mg_2Si films were grown on Si (111) and glass substrates with magnetron sputtering, respectively. • The first observation of Photoluminescence (PL) of Mg_2Si films was reported. • The Mg_2Si PL emission wavelengths are almost independence on temperature in the range of 77–300 K. • The strongest PL emissions may be attributed to interstitial Mg donor level to valence band transitions. • The activation energy of Mg_2Si is determined from the quenching of major luminescence peaks. - Abstract: To understand the photoluminescence mechanisms and optimize the design of Mg_2Si-based light-emitting devices, Mg_2Si films were fabricated on silicon (111) and glass substrates by magnetron sputtering technique, and the influences of different substrates on the photoelectric properties of Mg_2Si films were investigated systematically. The crystal structure, cross-sectional morphology, composition ratios and temperature-dependent photoluminescence (PL) of the Mg_2Si films were examined using X-ray diffraction (XRD), Scanning electron microscope (SEM), energy dispersive X-ray spectroscopy (EDS) and PL measurement system, respectively. XRD results indicate that the Mg_2Si film on Si (111) displays polycrystalline structure, whereas Mg_2Si film on glass substrate is of like-monocrystalline structure.SEM results show that Mg_2Si film on glass substrate is very compact with a typical dense columnar structure, and the film on Si substrate represents slight delamination phenomenon. EDS results suggest that the stoichiometry of Mg and Si is approximately 2:1. Photoluminescence (PL) of Mg_2Si films was observed for the first time. The PL emission wavelengths of Mg_2Si are almost independence on temperature in the range of 77–300 K. The PL intensity decreases gradually with increasing temperature. The PL intensity of Mg_2Si films on glass substrate is much larger than that of Mg_2Si film on Si (111) substrate. The activation energy of 18 meV is

  11. Study of some Mg-based ferrites as humidity sensors

    International Nuclear Information System (INIS)

    Rezlescu, N; Rezlescu, E; Doroftei, C; Popa, P D

    2005-01-01

    The micostructure and humidity sensitivity of MgFe 2 O 4 + CaO, Mg 0.5 Cu 0.5 Fe 1.8 Ga 0.2 O 4 , Mg 0.5 Zn 0.5 Fe 2 O 4 + KCl and MgMn 0.2 Fe 1.8 O 4 ferrites were investigated. We have found that the humidity sensitivity largely depends on composition, crystallite size, surface area and porosity. The best results concerning humidity sensitivity were obtained for MgMn 0.2 Fe 1.8 O 4 ferrite

  12. Intrinsic Conductivity in Magnesium-Oxygen Battery Discharge Products: MgO and MgO2

    DEFF Research Database (Denmark)

    Smith, Jeffrey G.; Naruse, Junichi; Hiramatsu, Hidehiko

    2017-01-01

    Nonaqueous magnesium–oxygen (or “Mg-air”) batteries are attractive next generation energy storage devices due to their high theoretical energy densities, projected low cost, and potential for rechargeability. Prior experiments identified magnesium oxide, MgO, and magnesium peroxide, MgO2...

  13. A Computational Investigation of Precipitates in Mg-RE Alloys With Applications To Mg-X Systems

    Science.gov (United States)

    Issa, Ahmed

    Increasing fuel efficiency in transportation vehicles is a major policy goal for both government and auto and aerospace manufacturers. Lightweight structural materials, such as magnesium alloys, hold great promise in enabling such fuel efficiency gains. Understanding the controlling factors in Mg alloy strengthening is crucial for the rational design of structurally strong and inexpensive Mg alloys. In this work, we seek to understand the energetic underpinnings giving rise to a class of remarkably strong Mg alloys: Mg-RE systems. We use first-principles methods to efficiently explore seventeen Mg-RE systems, drawing out broad patterns and distilling our knowledge into simple design rules for Mg alloys. We begin by investigating the controlling factors for the Mg-strengthening prismatic plate precipitates in Mg-RE systems, discovering the critical role of strain in such systems. We then proceed to investigate the surprising role of interfacial energies in determining the course of the Mg-RE precipitation reactions. Using strain and interfacial energies, we construct a phase-field model which accurately depicts the precipitate morphology as a function of time and size in a Mg-Nd system. Finally, we combine our gained insights to implement a computational alloy design scheme on a large portion of the periodic table where we seek Mg-strengthening solutes. Our work advances the understanding of strengthening in Mg alloys and lays the groundwork for full scale computational alloy design.

  14. Enhanced post-annealing stability of perpendicular Ta/CoFeB/Mg/MgO multilayers by inhibiting Ta diffusion

    Energy Technology Data Exchange (ETDEWEB)

    Li, Xu-Jing; Jiang, Shao-Long; Zhang, Jing-Yan; Liu, Qian-Qian; Liu, Yi-Wei; Zhao, Jian-Cheng [Department of Materials Physics and Chemistry, University of Science and Technology Beijing, Beijing 100083 (China); Wu, Zheng-Long [Analytical and Testing Center, Beijing Normal University, Beijing 100875 (China); Feng, Chun, E-mail: fengchun@ustb.edu.cn [Department of Materials Physics and Chemistry, University of Science and Technology Beijing, Beijing 100083 (China); Li, Ming-Hua [Department of Materials Physics and Chemistry, University of Science and Technology Beijing, Beijing 100083 (China); Yu, Guang-Hua, E-mail: ghyu@mater.ustb.edu.cn [Department of Materials Physics and Chemistry, University of Science and Technology Beijing, Beijing 100083 (China)

    2016-03-01

    Graphical abstract: To reveal the underlying mechanism of Mg influence on the enhanced post-annealing stability of perpendicular Ta/CoFeB/Mg/MgO multilayers, the X-ray photoelectron spectroscopy analysis have been performed. It is found that a certain amount of Mg interlayer at the CoFeB/MgO interface could prevent the Ta oxidation to some extent due to the oxygen deficit MgO{sub x} (x < 1), and consequently lower the diffusion motivation of Ta from the bottom layer to the CoFeB/MgO interfaces to some extent during the annealing process. The prevention of Ta diffusion realizes the effective hybridization of Fe and O at the CoFeB/MgO interface and maintains interfacial magnetic anisotropy (K{sub CoFeB/MgO}). As a result, the perpendicular magnetic anisotropy at high annealing temperatures was maintained. - Highlights: • High annealing stability of perpendicular Ta/CoFeB/Mg/MgO multilayers was realized. • X-ray photoelectron spectroscopy analysis has been performed to explore the reasons. • The prevention of Ta diffusion was realized by introducing Mg at the CoFeB/MgO interface. - Abstracts: To reveal the underlying mechanism of Mg influence on the enhanced post-annealing stability of perpendicular Ta/CoFeB/Mg/MgO multilayers, the X-ray photoelectron spectroscopy analysis has been performed. It is found that a certain amount of Mg interlayer at the CoFeB/MgO interface could prevent the Ta oxidation, and consequently lower the diffusion motivation of Ta from the bottom layer to the CoFeB/MgO interfaces to some extent in the annealing process. The prevention of Ta diffusion realizes the effective hybridization of Fe and O at the CoFeB/MgO interface and maintains interfacial magnetic anisotropy (KCoFeB/MgO). As a result, the perpendicular magnetic anisotropy at high annealing temperatures is maintained.

  15. Single crystal structures of the new vanadates CuMgVO{sub 4} and AgMgVO{sub 4}

    Energy Technology Data Exchange (ETDEWEB)

    Ben Yahia, Hamdi, E-mail: Hyahia@qf.org.qa [Research Institute of Electrochemical Energy, National Institute of Advanced Industrial Science and Technology (AIST), 1-8-31 Midorigaoka, Ikeda, Osaka 563-8577 (Japan); Qatar Environment and Energy Research Institute, Hamad Bin Khalifa University, Qatar Foundation, PO Box 5825, Doha (Qatar); Shikano, Masahiro, E-mail: shikano.masahiro@aist.go.jp [Research Institute of Electrochemical Energy, National Institute of Advanced Industrial Science and Technology (AIST), 1-8-31 Midorigaoka, Ikeda, Osaka 563-8577 (Japan); Essehli, Rachid; Belharouak, Ilias [Qatar Environment and Energy Research Institute, Hamad Bin Khalifa University, Qatar Foundation, PO Box 5825, Doha (Qatar)

    2016-08-01

    The new compounds CuMgVO{sub 4} and AgMgVO{sub 4} have been synthesized by a solid state reaction route. Their crystal structures were determined from single-crystal X-ray diffraction data. CuMgVO{sub 4} crystallizes with Na{sub 2}CrO{sub 4}-type structure with space group Cmcm, a = 5.6932 (10), b = 8.7055 (15), c = 6.2789 (10) Å, V = 311.20 (9) Å{sup 3}, and Z = 4, whereas AgMgVO{sub 4} crystallizes in the maricite-type structure with space group Pnma, a = 9.4286 (14), b = 6.7465 (10), c = 5.3360 (8) Å, V = 339.42 (9) Å{sup 3}, and Z = 4. Both structures of CuMgVO{sub 4}, and AgMgVO{sub 4} contain MgO{sub 4} chains made up of edge-sharing MgO{sub 6} octahedra. In CuMgVO{sub 4} the MgO{sub 4} chains are interconnected through CuVO{sub 4} double chains made up of VO{sub 4} and CuO{sub 4} tetrahedra sharing corners and edges, however in AgMgVO{sub 4} the chains are interlinked by the VO{sub 4} and AgO{sub 4} tetrahedra sharing only corners. - Highlights: • We have been able to grow CuMgVO{sub 4} and AgMgVO{sub 4} single crystals. • We solved their crystal structures using single crystal data. • We compared the crystal structures of CuMgVO{sub 4} and AgMgVO{sub 4}.

  16. Enhanced post-annealing stability of perpendicular Ta/CoFeB/Mg/MgO multilayers by inhibiting Ta diffusion

    International Nuclear Information System (INIS)

    Li, Xu-Jing; Jiang, Shao-Long; Zhang, Jing-Yan; Liu, Qian-Qian; Liu, Yi-Wei; Zhao, Jian-Cheng; Wu, Zheng-Long; Feng, Chun; Li, Ming-Hua; Yu, Guang-Hua

    2016-01-01

    Graphical abstract: To reveal the underlying mechanism of Mg influence on the enhanced post-annealing stability of perpendicular Ta/CoFeB/Mg/MgO multilayers, the X-ray photoelectron spectroscopy analysis have been performed. It is found that a certain amount of Mg interlayer at the CoFeB/MgO interface could prevent the Ta oxidation to some extent due to the oxygen deficit MgO_x (x < 1), and consequently lower the diffusion motivation of Ta from the bottom layer to the CoFeB/MgO interfaces to some extent during the annealing process. The prevention of Ta diffusion realizes the effective hybridization of Fe and O at the CoFeB/MgO interface and maintains interfacial magnetic anisotropy (K_C_o_F_e_B_/_M_g_O). As a result, the perpendicular magnetic anisotropy at high annealing temperatures was maintained. - Highlights: • High annealing stability of perpendicular Ta/CoFeB/Mg/MgO multilayers was realized. • X-ray photoelectron spectroscopy analysis has been performed to explore the reasons. • The prevention of Ta diffusion was realized by introducing Mg at the CoFeB/MgO interface. - Abstracts: To reveal the underlying mechanism of Mg influence on the enhanced post-annealing stability of perpendicular Ta/CoFeB/Mg/MgO multilayers, the X-ray photoelectron spectroscopy analysis has been performed. It is found that a certain amount of Mg interlayer at the CoFeB/MgO interface could prevent the Ta oxidation, and consequently lower the diffusion motivation of Ta from the bottom layer to the CoFeB/MgO interfaces to some extent in the annealing process. The prevention of Ta diffusion realizes the effective hybridization of Fe and O at the CoFeB/MgO interface and maintains interfacial magnetic anisotropy (KCoFeB/MgO). As a result, the perpendicular magnetic anisotropy at high annealing temperatures is maintained

  17. Structural and optical properties of ZnMgO nanostructures formed by Mg in-diffused ZnO nanowires

    International Nuclear Information System (INIS)

    Pan, C.-J.; Hsu, H.-C.; Cheng, H.-M.; Wu, C.-Y.; Hsieh, W.-F.

    2007-01-01

    ZnMgO nanostructures with wurtzite phase were prepared by thermal diffusion of Mg into the ZnO nanowires. As ZnO light-emitting devices have been operated by using ZnMgO layers as energy barrier layers to confine the carriers, it is essential to realize the characterization of ZnMgO particularly. In this work, the Mg content in Zn 1 -x Mg x O alloy determined by X-ray diffraction (XRD) and photoluminescence (PL) shows a good coincidence. The variation of lattice constant and the blueshift of near-band-edge emission indicate that Zn 2+ ions are successfully substituted by Mg 2+ ions in the ZnO lattice. In Raman-scattering studies, the change of E 2 (high) phonon line shape in ZnO:Mg nanostructures reveals the microscopic substitutional disorder. In addition to the host phonons of ZnO, two additional bands around 383 and 510 cm -1 are presumably attributed to the Mg-related vibrational modes. - Graphical abstract: We reported the synthesis of the ZnMgO nanostructures prepared by a simple vapor transport method. Magnesium-related anomalous modes are observed by Raman spectra for the first time in ZnMgO system

  18. From $^{27}$Mg to ${33}$Mg transition to the "Island of inversion"

    CERN Document Server

    Yordanov, Deyan

    Since introduced in nuclear physics, the concept of shell structure and magic numbers has governed our understanding of nuclear matter in atomic nuclei close to stability. Nuclear species with a magic number of protons and/or neutrons are known to be more stable and close to spherical in shape. Experimental studies of 30Ne, 31Na and 32Mg, systems with a closed neutron sd shell (N=20), provide evidence for a ground-state deformation in these nuclei. The observed phenomenon is understood as an inversion of the normal spherical ground-state configuration, expected according to the traditional shell model, with deformed states governed by particle-hole excitations over the N=20 shell gap. The properties of nuclei in this Island of inversion are of particular importance for the theoretical modeling of the region. The present doctoral dissertation reports on the first determination of the nuclear ground-state spins and magnetic moments of 31,33Mg, obtained by means of laser spectroscopy in combination with nuclear...

  19. Mg concentration profile and its control in the low temperature grown Mg-doped GaN epilayer

    Science.gov (United States)

    Liu, S. T.; Yang, J.; Zhao, D. G.; Jiang, D. S.; Liang, F.; Chen, P.; Zhu, J. J.; Liu, Z. S.; Liu, W.; Xing, Y.; Zhang, L. Q.; Wang, W. J.; Li, M.; Zhang, Y. T.; Du, G. T.

    2018-01-01

    In this work, the Cp2Mg flux and growth pressure influence to Mg doping concentration and depth profiles is studied. From the SIMS measurement we found that a transition layer exists at the bottom region of the layer in which the Mg doping concentration changes gradually. The thickness of transition layer decreases with the increases of Mg doping concentration. Through analysis, we found that this is caused by Ga memory effect which the Ga atoms stay residual in MOCVD system will react with Mg source, leading a transition layer formation and improve the growth rate. And the Ga memory effect can be well suppressed by increasing Mg doping concentration and growth pressure and thus get a steep Mg doping at the bottom region of p type layer.

  20. Industrial production of MgH2 and its application

    International Nuclear Information System (INIS)

    Uesugi, H.; Sugiyama, T.; Nii, H.; Ito, T.; Nakatsugawa, I.

    2011-01-01

    Research highlights: → Tablet and powder Mg were hydrogenated in a 50 kg batch furnace based on thermal equilibrium method. → Compression of Mg tablet improved the hydrogenation yield. → Hydrolysis of MgH 2 using citric acid generated hydrogen under 373 K. → A MgH 2 -hydrogen reactor utilizing hydraulic head pressure was developed. → - Abstract: A process for the industrial production of magnesium hydride (MgH 2 ) based on a thermal equilibrium method and its application to portable hydrogen sources is proposed. Mg powders and tablets compressed with mechanically ground Mg ribbons were successfully hydrogenated in a 50-kg-batch furnace. The resultant MgH 2 showed a hydrogen yield of around 96% with good reproducibility. The compression ratio of Mg tablets was found to be an important factor in the hydrogenation yield. A hydrolysis technique using citric acid as an additive was employed to generate hydrogen under 373 K. Increasing the concentration of citric acid and the temperature accelerated the hydrolysis reactivity. A hydrogen reactor utilizing hydraulic head pressure was developed. It generated hydrogen continuously for 1 h at a flow rate of 100 ml min -1 with hydrolysis of 5 g of tablet-form MgH 2 . The conversion yield was around 70%, regardless of the flow rate.

  1. Corrosion behavior of Mg/graphene composite in aqueous electrolyte

    International Nuclear Information System (INIS)

    Selvam, M.; Saminathan, K.; Siva, P.; Saha, P.; Rajendran, V.

    2016-01-01

    In the present work, the electrochemical corrosion behavior of magnesium (Mg) and thin layer graphene coated Mg (Mg/graphene) are studied in different salt electrolyte such as NaCl, KCl and Na_2SO_4. The phase structure, crystallinity, and surface morphology of the samples are investigated using X-ray diffraction (XRD) analysis, scanning electron microscopy coupled with energy dispersive X-ray analysis (SEM/EDAX), and Raman spectroscopy techniques. The electrochemical corrosion behavior of the Mg and graphene coated Mg are also investigated using Electrochemical Impedance Spectroscopy (EIS) analysis. The tafel plot reveals that the corrosion of Mg drastically drops when coated with thin layer graphene (Mg/graphene) compared to Mg in KCl electrolyte. Moreover, the EIS confirms that Mg/graphene sample shows improve corrosion resistance and lower corrosion rate in KCl solution compare to all other electrolytes studied in the present system. - Highlights: • The corrosion behavior of magnesium alloy (AZ91) was investigated in three different electrolyte solution. • To study the anti-corrosion behavior of graphene coated with magnesium alloy. • To improve the corrosion resistance for magnesium alloy. • Nyquist plots confirms that MgG shows better corrosion resistance and lower corrosion rate in KCl solution.

  2. Corrosion behavior of Mg/graphene composite in aqueous electrolyte

    Energy Technology Data Exchange (ETDEWEB)

    Selvam, M. [Centre for Nano Science and Technology, KS Rangasamy College of Technology, Tiruchengode, 637215, Tamil Nadu (India); Saminathan, K., E-mail: ksaminath@gmail.com [Centre for Nano Science and Technology, KS Rangasamy College of Technology, Tiruchengode, 637215, Tamil Nadu (India); Siva, P. [Centre for Nano Science and Technology, KS Rangasamy College of Technology, Tiruchengode, 637215, Tamil Nadu (India); Saha, P. [Department of Ceramic Engineering, National Institute of Technology, Rourkela, India-769008 (India); Rajendran, V. [Centre for Nano Science and Technology, KS Rangasamy College of Technology, Tiruchengode, 637215, Tamil Nadu (India)

    2016-04-01

    In the present work, the electrochemical corrosion behavior of magnesium (Mg) and thin layer graphene coated Mg (Mg/graphene) are studied in different salt electrolyte such as NaCl, KCl and Na{sub 2}SO{sub 4}. The phase structure, crystallinity, and surface morphology of the samples are investigated using X-ray diffraction (XRD) analysis, scanning electron microscopy coupled with energy dispersive X-ray analysis (SEM/EDAX), and Raman spectroscopy techniques. The electrochemical corrosion behavior of the Mg and graphene coated Mg are also investigated using Electrochemical Impedance Spectroscopy (EIS) analysis. The tafel plot reveals that the corrosion of Mg drastically drops when coated with thin layer graphene (Mg/graphene) compared to Mg in KCl electrolyte. Moreover, the EIS confirms that Mg/graphene sample shows improve corrosion resistance and lower corrosion rate in KCl solution compare to all other electrolytes studied in the present system. - Highlights: • The corrosion behavior of magnesium alloy (AZ91) was investigated in three different electrolyte solution. • To study the anti-corrosion behavior of graphene coated with magnesium alloy. • To improve the corrosion resistance for magnesium alloy. • Nyquist plots confirms that MgG shows better corrosion resistance and lower corrosion rate in KCl solution.

  3. Low-energy radioactive ion beam production of 22Mg

    International Nuclear Information System (INIS)

    Duy, N.N.; Kubono, S.; Yamaguchi, H.; Kahl, D.; Wakabayashi, Y.; Teranishi, T.; Iwasa, N.; Kwon, Y.K.; Khiem, L.H.; Kim, Y.H.; Song, J.S.; Hu, J.; Ayyad, Y.

    2013-01-01

    The 22 Mg nucleus plays an important role in nuclear astrophysics, specially in the 22 Mg(α,p) 25 Al and proton capture 22 Mg(p,γ) 23 Al reactions. It is believed that 22 Mg is a waiting point in the αp-process of nucleosynthesis in novae. We proposed a direct measurement of the 22 Mg+α resonance reaction in inverse kinematics using a radioactive ion (RI) beam. A 22 Mg beam of 3.73 MeV/u was produced at CRIB (Center for Nuclear Study (CNS) low-energy RI Beam) facility of the University of Tokyo located at RIKEN (Japan) in 2011. In this paper we present the results about the production of the 22 Mg beam used for the direct measurement of the scattering reaction 22 Mg(α,α) 22 Mg, and the stellar reaction 22 Mg(α,p) 25 Al in the energy region concerning an astrophysical temperature of T 9 =1–3 GK

  4. The structural, electrical and optical properties of Mg-doped ZnO with different interstitial Mg concentration

    Energy Technology Data Exchange (ETDEWEB)

    Hu, Yonghong, E-mail: hchyh@njust.edu.cn [School of Nuclear Technology and Chemistry & Biology, Hubei University of Science and Technology, Xianning 437100 (China); Institute of Optoelectronics & Nanomaterials, College of Materials Science and Engineering, Nanjing University of Science and Technology, Nanjing 210094 (China); Zeng, Haibo [Institute of Optoelectronics & Nanomaterials, College of Materials Science and Engineering, Nanjing University of Science and Technology, Nanjing 210094 (China); Du, Jifu [School of Nuclear Technology and Chemistry & Biology, Hubei University of Science and Technology, Xianning 437100 (China); Hu, Ziyu [Beijing Computational Science Research Center, Beijing 100084 (China); Zhang, Shengli [Institute of Optoelectronics & Nanomaterials, College of Materials Science and Engineering, Nanjing University of Science and Technology, Nanjing 210094 (China)

    2016-10-01

    Through first principle calculations, we studied the structural, electronic and optical properties of ZnO doped by interstitial Mg. With the increase of Mg content (x), the derivations of lattice parameters from the wurtzite ZnO become more and more significant. The Mg-doped ZnO with x below 15.79% is found to be n-type semiconductor. The minimum of energy band gap and light transmittance in high energy region (7.5–25 eV) decrease while the conductivity and refractive index increase with increasing x. Further increasing x up to 20%, the Mg-doped ZnO is found to be direct-band-gap semiconductor with great structural derivation from wurtzite phase. The light transmittance increases while the refractive index decreases with the increase of x due to the change of geometry and electronic structure. So, it’s concluded that the electronic and optical properties of ZnO doped by interstitial Mg may be greatly influenced by Mg content. - Graphical abstract: The minimum of energy gap decreases while the corresponding relative number of electrons into the conduction bands increases when the interstitial Mg content x in Mg-doped ZnO increases (0 ≤ x ≤ 15.79%). - Highlights: • The energy band gap decreases with the increase of interstitial Mg content from 5.88% to 15.79%. • The conductivity increases with the increase of interstitial Mg content from 5.88% to 15.79%. • The Mg{sub x}Zn{sub 1-x}O (interstitial Mg content x= 20%) is found to be a direct-band-gap semiconductor. • The light transmittance decreases with the increase of interstitial Mg content from 5.88% to 15.79%. • The refractive index increases with the increase of interstitial Mg content from 5.88% to 15.79%.

  5. Adsorption of arginine, glycine and aspartic acid on Mg and Mg-based alloy surfaces: A first-principles study

    Science.gov (United States)

    Fang, Zhe; Wang, Jianfeng; Yang, Xiaofan; Sun, Qiang; Jia, Yu; Liu, Hairong; Xi, Tingfei; Guan, Shaokang

    2017-07-01

    Studying the adsorption behaviors of biomolecules on the surface of Mg and Mg-based alloy has a fundamental and important role for related applications in biotechnology. In the present work, we systematically investigate and compare the adsorption properties of three typical amino acids, i.e., Arg (arginine), Gly (glycine) and Asp (aspartic acid), which form RGD tripeptide, on the Mg (0 0 0 1) surface with various doping (Zn, Y, and Nd), and aim to realize proper binding between biomolecules and Mg and Mg-based biomedical materials. Our results show that flat adsorption configurations of the functional groups binding to the surfaces are favored in energy for all the three selected amino acids. In specific, for the amino acids adsorped on clean Mg (0 0 0 1) surface, the adsorption energy (Eads) of Arg is found to be -1.67 eV for the most stable configuration, with amino and guanidyl groups binding with the surface. However, Gly (Asp) is found to binding with the surface through amino and carboxyl groups, with a -1.16 eV (-1.15 eV) binding energy. On the 2% Zn doped Mg (0 0 0 1) alloy surface (Mg-Zn (2%)), the Eads are significantly increased to be -1.91 eV, -1.32 eV and -1.35 eV for Arg, Gly and Asp, respectively. While the Mg-Y (1%) and Mg-Nd (1%) slightly weaken the adsorption of three amino acids. Moreover, we have performed detail discussions of the binding properties between amino acids and surfaces by projected density of states (PDOS) combined with charge transfer analyses. Our studies provide a comprehensive understanding on the interactions between amino acids and Mg and Mg-based alloy surfaces, with respect to facilitate the applications of Mg and Mg-based biomedical alloys in biosensing, drug delivery, biomolecule coating and other fields in biotechnology.

  6. Corrosion properties of the Mg alloy coated with polypyrrole films

    International Nuclear Information System (INIS)

    Grubač, Zoran; Rončević, Ivana Škugor; Metikoš-Huković, Mirjana

    2016-01-01

    Highlights: • Electropolymerization of pyrrole on Mg-alloy surface in presence of salicylate. • Salicylate dual role in PPy deposition: passivation and electron transfer mediation. • Redox potential of salicylate corresponds to potential of PPy nucleation. • EIS and polarization corrosion studies of PPy coated Mg-alloy in Hanks’ solution. • Polypyrrole significantly slowdown Mg alloy corrosion in Hanks’ solution. - Abstract: In the present study the reactive surface of Mg alloy was coated with the nontoxic biocompatible polypyrrole (PPy) film synthesized by electrochemical oxidation from an aqueous salicylate solution. Salicylate ions prevent Mg dissolution and act as an electron transfer mediator during the PPy film nucleation, formation and growth on the alloy surface. Kinetics of the pyrrole polymerization as well as corrosion resistance of the PPy coated Mg alloy in the Hanks’ solution were investigated using dc electrochemical methods and electrochemical impedance spectroscopy (EIS). Characterization of the surface film was performed by optical and Fourier transform infrared spectroscopy (FTIR).

  7. Thermoelectric properties and microstructure of Mg3Sb2

    International Nuclear Information System (INIS)

    Condron, Cathie L.; Kauzlarich, Susan M.; Gascoin, Franck; Snyder, G. Jeffrey

    2006-01-01

    Mg 3 Sb 2 has been prepared by direct reaction of the elements. Powder X-ray diffraction, thermal gravimetric, differential scanning calorimetery, and microprobe data were obtained on hot pressed samples. Single phase samples of Mg 3 Sb 2 were prepared and found to contain oxygen at the grain boundaries and to lose Mg and oxidize at temperatures above 900 K. Thermoelectric properties were characterized by Seebeck, electrical resistivity, and thermal conductivity measurements from 300 to 1023 K, and the maximum zT was found to be 0.21 at ∼875 K. - Graphical abstract: Dimensionless figure of merit for Mg 3 Sb 2 hot pressed and sintered at 873 K. The inset illustrates the crystal structure of Mg 3 Sb 2 along the [100] direction (white=Mg, black=Sb)

  8. A high resolution atlas of Mg II profiles

    Science.gov (United States)

    Ewald, R.; Nichols-Bohlin, Joy Y.; Kondo, Yoji

    1990-01-01

    An atlas of high dispersion Mg II profiles for standard stars of spectral types B0 through G9 is presented. The atlas contains plots of the Mg II profiles for approximately 65 stars and associated equivalent width measurements for both absorption and emission components, and the subordinate lines. The atlas is used to investigate systematic behavior of the Mg II profiles and correlation of the behavior with spectral classification.

  9. MgO nanoparticles as antibacterial agent: preparation and activity

    Energy Technology Data Exchange (ETDEWEB)

    Tang, Zhen-Xing, E-mail: tangzhenxing@126.com [Department of Food Science, Anqing, Vocational and Technical College, Anqing, Anhui (China); Lv, Bin-Feng [Date Palm Research Center, King Faisal University, (Saudi Arabia)

    2014-07-15

    Bacterial pollution is a great risk for human health. Nanotechnology offers a way to develop new inorganic antibacterial agents. Nano-inorganic metal oxide has a potential to reduce bacterial contamination. MgO is an important inorganic oxide and has been widely used in many fields. Many studies have shown that MgO nanoparticles have good antibacterial activity. Therefore, in this paper, the main synthesis methods, antibacterial activity and antibacterial mechanisms of MgO nanoparticles are reviewed. (author)

  10. MgO nanoparticles as antibacterial agent: preparation and activity

    International Nuclear Information System (INIS)

    Tang, Zhen-Xing; Lv, Bin-Feng

    2014-01-01

    Bacterial pollution is a great risk for human health. Nanotechnology offers a way to develop new inorganic antibacterial agents. Nano-inorganic metal oxide has a potential to reduce bacterial contamination. MgO is an important inorganic oxide and has been widely used in many fields. Many studies have shown that MgO nanoparticles have good antibacterial activity. Therefore, in this paper, the main synthesis methods, antibacterial activity and antibacterial mechanisms of MgO nanoparticles are reviewed. (author)

  11. Effect of amorphous Mg50Ni50 on hydriding and dehydriding behavior of Mg2Ni alloy

    International Nuclear Information System (INIS)

    Guzman, D.; Ordonez, S.; Fernandez, J.F.; Sanchez, C.; Serafini, D.; Rojas, P.A.; Aguilar, C.; Tapia, P.

    2011-01-01

    Composite Mg 2 Ni (25 wt.%) amorphous Mg 50 Ni 50 was prepared by mechanical milling starting with nanocrystalline Mg 2 Ni and amorphous Mg 50 Ni 50 powders, by using a SPEX 8000 D mill. The morphological and microstructural characterization of the powders was performed via scanning electron microscopy and X-ray diffraction. The hydriding characterization of the composite was performed via a solid gas reaction method in a Sievert's-type apparatus at 363 K under an initial hydrogen pressure of 2 MPa. The dehydriding behavior was studied by differential thermogravimetry. On the basis of the results, it is possible to conclude that amorphous Mg 50 Ni 50 improved the hydriding and dehydriding kinetics of Mg 2 Ni alloy upon cycling. A tentative rationalization of experimental observations is proposed. - Research Highlights: → First study of the hydriding behavior of composite Mg 2 Ni (25 wt.%) amorphous Mg 50 Ni 50 . → Microstructural characterization of composite material using XRD and SEM was obtained. → An improved effect of Mg 50 Ni 50 on the Mg 2 Ni hydriding behavior was verified. → The apparent activation energy for the hydrogen desorption of composite was obtained.

  12. Lattice stability and formation energies of intrinsic defects in Mg2Si and Mg2Ge via first principles simulations

    International Nuclear Information System (INIS)

    Jund, Philippe; Viennois, Romain; Tédenac, Jean-Claude; Colinet, Catherine; Hug, Gilles; Fèvre, Mathieu

    2013-01-01

    We report an ab initio study of the semiconducting Mg 2 X (with X = Si, Ge) compounds and in particular we analyze the formation energies of the different point defects with the aim of understanding the intrinsic doping mechanisms. We find that the formation energy of Mg 2 Ge is 50% larger than that of Mg 2 Si, in agreement with the experimental tendency. From a study of the stability and the electronic properties of the most stable defects, taking into account the growth conditions, we show that the main cause of the n doping in these materials comes from interstitial magnesium defects. Conversely, since other defects acting like acceptors such as Mg vacancies or multivacancies are more stable in Mg 2 Ge than in Mg 2 Si, this explains why Mg 2 Ge can be of n or p type, in contrast to Mg 2 Si. The finding that the most stable defects are different in Mg 2 Si and Mg 2 Ge and depend on the growth conditions is important and must be taken into account in the search for the optimal doping to improve the thermoelectric properties of these materials.

  13. Hydrodechlorination of Tetrachloromethane over Palladium Catalysts Supported on Mixed MgF2-MgO Carriers

    Directory of Open Access Journals (Sweden)

    Magdalena Bonarowska

    2016-11-01

    Full Text Available Pd/MgO, Pd/MgF2 and Pd/MgO-MgF2 catalysts were investigated in the reaction of CCl4 hydrodechlorination. All the catalysts deactivated in time on stream, but the degree of deactivation varied from catalyst to catalyst. The MgF2-supported palladium with relatively large metal particles appeared the best catalyst, characterized by good activity and selectivity to C2-C5 hydrocarbons. Investigation of post-reaction catalyst samples allowed to find several details associated with the working state of hydrodechlorination catalysts. The role of support acidity was quite complex. On the one hand, a definite, although not very high Lewis acidity of MgF2 is beneficial for shaping high activity of palladium catalysts. The MgO-MgF2 support characterized by stronger Lewis acidity than MgF2 contributes to very good catalytic activity for a relatively long reaction period (~5 h but subsequent neutralization of stronger acid centers (by coking eliminates them from the catalyst. On the other hand, the role of acidity evolution, which takes place when basic supports (like MgO are chlorided during HdCl reactions, is difficult to assess because different events associated with distribution of chlorided support species, leading to partial or even full blocking of the surface of palladium, which plays the role of active component in HdCl reactions.

  14. Enhanced voltage-controlled magnetic anisotropy in magnetic tunnel junctions with an MgO/PZT/MgO tunnel barrier

    Science.gov (United States)

    Chien, Diana; Li, Xiang; Wong, Kin; Zurbuchen, Mark A.; Robbennolt, Shauna; Yu, Guoqiang; Tolbert, Sarah; Kioussis, Nicholas; Khalili Amiri, Pedram; Wang, Kang L.; Chang, Jane P.

    2016-03-01

    Compared with current-controlled magnetization switching in a perpendicular magnetic tunnel junction (MTJ), electric field- or voltage-induced magnetization switching reduces the writing energy of the memory cell, which also results in increased memory density. In this work, an ultra-thin PZT film with high dielectric constant was integrated into the tunneling oxide layer to enhance the voltage-controlled magnetic anisotropy (VCMA) effect. The growth of MTJ stacks with an MgO/PZT/MgO tunnel barrier was performed using a combination of sputtering and atomic layer deposition techniques. The fabricated MTJs with the MgO/PZT/MgO barrier demonstrate a VCMA coefficient, which is ˜40% higher (19.8 ± 1.3 fJ/V m) than the control sample MTJs with an MgO barrier (14.3 ± 2.7 fJ/V m). The MTJs with the MgO/PZT/MgO barrier also possess a sizeable tunneling magnetoresistance (TMR) of more than 50% at room temperature, comparable to the control MTJs with an MgO barrier. The TMR and enhanced VCMA effect demonstrated simultaneously in this work make the MgO/PZT/MgO barrier-based MTJs potential candidates for future voltage-controlled, ultralow-power, and high-density magnetic random access memory devices.

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

    Directory of Open Access Journals (Sweden)

    Jianjun Song

    2013-01-01

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

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

    International Nuclear Information System (INIS)

    Liu, X.L.; Zhou, W.R.; Wu, Y.H.; Cheng, Y.; Zheng, Y.F.

    2013-01-01

    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

  17. Mg and Mg alloys: how comparable are in vitro and in vivo corrosion rates? A review.

    Science.gov (United States)

    Martinez Sanchez, Adela Helvia; Luthringer, Bérengère J C; Feyerabend, Frank; Willumeit, Regine

    2015-02-01

    Due to their biodegradability, magnesium and magnesium-based alloys could represent the third generation of biomaterials. However, their mechanical properties and time of degradation have to match the needs of applications. Several approaches, such as choice of alloying elements or tailored microstructure, are employed to tailor corrosion behaviour. Due to the high electrochemical activity of Mg, numerous environmental factors (e.g. temperature and surrounding ion composition) influence its corrosion behaviour, making it unpredictable. Nevertheless, the need of reliable in vitro model(s) to predict in vivo implant degradation is increasing. In an attempt to find a correlation between in vitro and vivo corrosion rates, this review presents a systematic literature survey, as well as an attempt to correlate the different results. Copyright © 2014 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

  18. Defect structure of ultrafine MgB2 nanoparticles

    International Nuclear Information System (INIS)

    Bateni, Ali; Somer, Mehmet; Repp, Sergej; Erdem, Emre; Thomann, Ralf; Acar, Selçuk

    2014-01-01

    Defect structure of MgB 2 bulk and ultrafine particles, synthesized by solid state reaction route, have been investigated mainly by the aid of X-band electron paramagnetic resonance spectrometer. Two different amorphous Boron (B) precursors were used for the synthesis of MgB 2 , namely, boron 95 (purity 95%–97%, <1.5 μm) and nanoboron (purity >98.5%, <250 nm), which revealed bulk and nanosized MgB 2 , respectively. Scanning and transmission electron microscopy analysis demonstrate uniform and ultrafine morphology for nanosized MgB 2 in comparison with bulk MgB 2 . Powder X-ray diffraction data show that the concentration of the by-product MgO is significantly reduced when nanoboron is employed as precursor. It is observed that a significant average particle size reduction for MgB 2 can be achieved only by using B particles of micron or nano size. The origin and the role of defect centers were also investigated and the results proved that at nanoscale MgB 2 material contains Mg vacancies. Such vacancies influence the connectivity and the conductivity properties which are crucial for the superconductivity applications

  19. Mechanism of magnetoresistance ratio enhancement in MgO/NiFe/MgO heterostructure by rapid thermal annealing

    Science.gov (United States)

    Zhao, Chong-Jun; Liu, Yang; Zhang, Jing-Yan; Sun, Li; Ding, Lei; Zhang, Peng; Wang, Bao-Yi; Cao, Xing-Zhong; Yu, Guang-Hua

    2012-08-01

    To reveal thermal effects on the film quality/microstructure evolution and the resulted magnetoresistance (MR) ratio in MgO/NiFe/MgO heterostructures, positron annihilation spectroscopy studies have been performed. It is found that the ionic interstitials in the MgO layers recombine with the nearby vacancies at lower annealing temperatures (200-300 °C) and lead to a slow increase in sample MR. Meanwhile, vacancy defects agglomeration/removal and ordering acceleration in MgO will occur at higher annealing temperatures (450-550 °C) and the improved MgO and MgO/NiFe interfaces microstructure are responsible for the observed significant MR enhancement.

  20. The in vitro biocompatibility and macrophage phagocytosis of Mg17Al12 phase in Mg-Al-Zn alloys.

    Science.gov (United States)

    Liu, Chen; He, Peng; Wan, Peng; Li, Mei; Wang, Kehong; Tan, Lili; Zhang, Yu; Yang, Ke

    2015-07-01

    Mg alloys are gaining interest for applications as biodegradable medical implant, including Mg-Al-Zn series alloys with good combination of mechanical properties and reasonable corrosion resistance. However, whether the existence of second phase particles in the alloys exerts influence on the biocompatibility is still not clear. A deeper understanding of how the particles regulate specific biological responses is becoming a crucial requirement for their subsequent biomedical application. In this work, the in vitro biocompatibility of Mg17Al12 as a common second phase in biodegradable Mg-Al-Zn alloys was investigated via hemolysis, cytotoxicity, cell proliferation, and cell adhesion tests. Moreover, osteogenic differentiation was evaluated by the extracellular matrix mineralization assay. The Mg17Al12 particles were also prepared to simulate the real situation of second phase in the in vivo environment in order to estimate the cellular response in macrophages to the Mg17Al12 particles. The experimental results indicated that no hemolysis was found and an excellent cytocompatibility was also proved for the Mg17Al12 second phase when co-cultured with L929 cells, MC3T3-E1 cells and BMSCs. Macrophage phagocytosis co-culture test revealed that Mg17Al12 particles exerted no harmful effect on RAW264.7 macrophages and could be phagocytized by the RAW264.7 cells. Furthermore, the possible inflammatory reaction and metabolic way for Mg17Al12 phase were also discussed in detail. © 2014 Wiley Periodicals, Inc.

  1. Bioequivalence of a single 400-mg dose of imatinib 100-mg oral tablets and a 400-mg tablet in healthy adult Korean volunteers.

    Science.gov (United States)

    Lee, Hae Won; Seong, Sook Jin; Park, Sung Min; Lee, Joomi; Gwon, Mi-Ri; Kim, Hyun-Ju; Lim, Sung Mook; Lim, Mi-Sun; Kim, Woomi; Yang, Dong Heon; Yoon, Young-Ran

    2015-06-01

    Imatinib mesylate (IM) is a selective tyrosine kinase inhibitor for the treatment of chronic myeloid leukemia and gastrointestinal stromal tumors. A new once-daily 400-mg film-coated tablet of imatinib has been developed by a pharmaceutical company in Korea. The present study was designed to assess and compare the PK parameters, bioavailability, and bioequivalence of the new imatinib 400-mg formulation (test) versus the conventional 100-mg formulation (reference) administered as a single 400-mg dose in healthy adult male volunteers. This randomized, open-label, single-dose, two-way crossover study was conducted in healthy Korean male volunteers. Eligible subjects were randomly assigned in a 1 : 1 ratio to receive 400 mg of the test (one 400-mg tablet) or reference (four 100-mg tablets) formulation, followed by a 2-week washout period and administration of the alternate formulation. Serial blood samples were collected at 0 (predose), 0.5, 1, 1.5, 2, 2.5, 3, 4, 6, 8, 10, 12, 24, 48, and 72 hours after administration. Plasma imatinib concentrations were determined using liquid chromatography coupled with tandem mass spectrometry. The formulations were to be considered bioequivalent if the 90% confidence intervals (CIs) of the adjusted geometric mean ratios for Cmax, AUC(0-t), and AUC(0-∞)ž were within the predetermined range of 0.80 - 1.25. In total, 35 subjects completed the study. No serious adverse event was reported during the study. The 90% CIs of the adjusted geometric mean ratios of the test formulation to the reference formulation for C(max), AUC(0-t) and AUC(0-∞)ž of imatinib were all within the bioequivalence criteria range of 0.8 - 1.25. The test formulation of imatinib met the Korean regulatory requirements for bioequivalence. Both imatinib formulations were well-tolerated in all subjects.

  2. Detection of Mg spinel lithologies on central peak of crater ...

    Indian Academy of Sciences (India)

    identified Fe bearing Mg-spinel-rich rock types are defined by their strong 2-μm ... The Modified Gaussian Modeling (MGM) analysis ... study the deep crustal and/or upper mantle composition and may lead to a fresh ... Lunar surface; Mg-spinel; central peak; Theophilus; remote sensing. .... The explanation of these spec-.

  3. Projectile deformation effects in the breakup of 37Mg

    Directory of Open Access Journals (Sweden)

    Shubhchintak

    2016-01-01

    Full Text Available We study the breakup of 37Mg on Pb at 244MeV/u with the recently developed extended theory of Coulomb breakup within the postform finite range distorted wave Born approximation that includes deformation of the projectile. Comparing our calculated cross section with the available Coulomb breakup data we determine the possible ground state configuration of 37Mg.

  4. Phosphorus Doped Zn 1- x Mg x O Nanowire Arrays

    KAUST Repository

    Lin, S. S.; Hong, J. I.; Song, J. H.; Zhu, Y.; He, H. P.; Xu, Z.; Wei, Y. G.; Ding, Y.; Snyder, R. L.; Wang, Z. L.

    2009-01-01

    We demonstrate the growth of phosphorus doped Zn 1-xMg xO nanowire (NW) using pulsed laser deposition. For the first time, p-type Zn 0.92Mg 0.08O:P NWs are likely obtained In reference to atomic force microscopy based piezoelectric output

  5. Structural and transport properties of Sn-Mg alloys

    International Nuclear Information System (INIS)

    Meydaneri, F.; Saatci, E.; Oezdemir, M.; Ari, M.; Durmus, S.

    2010-01-01

    The structural and temperature dependence transport of Sn-Mg alloys have been investigated for five different samples (Pure Sn, Sn-1.0 wt % Mg , Sn-2.0 wt % Mg , Sn-6.0 wt.% Mg and Pure Mg). Scanning Electron Microscopy (SEM), x-ray diffraction (XRD) and Energy Dispersive x-ray Analysis (EDX) measurements were carried out in order to clarify the structural properties of the samples. It has been found that, the samples have tetragonal crystal symmetry except the pure Mg which has hexagonal crystal symmetry. The cell parameters decrease slightly with addition of Mg element. The SEM micrographs of the samples show that, the samples have smooth surfaces with clear grain boundary. There is no crack, porosity or defects on the surfaces. The electrical resistivity of the samples increases almost linearly with the increasing temperature, which were measured by four-point probe technique. The thermal conductivity values are in between 0.60-1.00 W/Km, which are decrease slightly with temperature and increase with composition of Mg. The thermal conductivity values of the alloys are in between the values of the pure samples. Thermal conductivity results of the alloys have been compared with available other studies and a good agreement has been seen between the results. In addition, the temperature coefficients of electrical resistivity and thermal conductivity have been determined, which are independent with the compositions of alloying elements

  6. Stabilization of Reactive MgO Surfaces by Ni Doping

    Science.gov (United States)

    Mazheika, Aliaksei; Levchenko, Sergey V.

    Ni-MgO solid solutions are promising materials for catalytic reduction of CO2 and dry reforming of CH4. To explain the catalytic activity, an ab initio study of Ni-substitutional defects in MgO (NiMg) has been performed. At first, the validation of the theory level was done. We compared results of CCSD(T) embedded-cluster calculations of NiMg formation energies and adsorption energies of CO, CO2 and H2 on them to the HSE(α) hybrid DFT functional with the fraction of the exact exchange α varied between 0 and 1. HSE(0.3) was found to be the best compromise in this study. Our periodic HSE(0.3) calculations show that NiMg defects are most stable at corner sites, followed by steps, and are least stable at (001) terraces. Thus, Ni-doping stabilizes stepped MgO surfaces. The dissociative adsorption of H2 on the terrace is found to be endothermic (+ 1 . 1 eV), whereas on (110) surface with NiMg it is highly exothermic (- 1 . 6 eV). Adsorbed CO2 is also significantly stabilized (- 0 . 6 vs. - 2 . 2 eV). These findings explain recent microcalorimetry measurements of H2 and CO2 adsorption at doped Ni-MgO samples. partially supported by UniCat (Deutsche Forschungsgemeinschaft).

  7. Sorption of malachite green (MG) by cassava stem biochar (CSB ...

    African Journals Online (AJOL)

    Cassava stem biochar (CSB) was produced by pyrolyzing CS at 500°C for 2 hours at nitrogen environment. Proximate and ultimate analyses were conducted on CS and CSB. Batch sorption experiment on synthetic MG wastewater was optimized for the sorbent dosage, MG solution pH and contact time. Sorption data was ...

  8. Strength and residual stress of Mg-PSZ after grinding

    NARCIS (Netherlands)

    van den Berg, P.H.J.; With, de G.

    1993-01-01

    The influence of grinding with two grinding wheels, differing mainly in diamond-grain size, on the properties of MgO-partially stabilized ZrO2 ceramics (Mg-PSZ) was examd. The residual stress, the amt. of monoclinic zirconia, and the strength of the material were detd. From these measurements, depth

  9. Search for C+ C clustering in Mg ground state

    Indian Academy of Sciences (India)

    2017-01-04

    Jan 4, 2017 ... Finite-range knockout theory predictions were much larger for (12C,212C) reaction, indicating a very small 12C−12C clustering in 24Mg. (g.s.) . Our present results contradict most of the proposed heavy cluster (12C+12C) structure models for the ground state of 24Mg. Keywords. Direct nuclear reactions ...

  10. WIPP Magnesium Oxide (MgO) - Planned Change Request

    Science.gov (United States)

    On April 10, 2006, the DOE submitted a planned change request pertaining to the amount of MgO emplaced in the WIPP repository. MgO is an engineered barrier that DOE included as part of the original WIPP Certification Decision.

  11. Nanostructured Layered Cathode for Rechargeable Mg-Ion Batteries.

    Science.gov (United States)

    Tepavcevic, Sanja; Liu, Yuzi; Zhou, Dehua; Lai, Barry; Maser, Jorg; Zuo, Xiaobing; Chan, Henry; Král, Petr; Johnson, Christopher S; Stamenkovic, Vojislav; Markovic, Nenad M; Rajh, Tijana

    2015-08-25

    Nanostructured bilayered V2O5 was electrochemically deposited within a carbon nanofoam conductive support. As-prepared electrochemically synthesized bilayered V2O5 incorporates structural water and hydroxyl groups, which effectively stabilizes the interlayers and provides coordinative preference to the Mg(2+) cation in reversible cycling. This open-framework electrode shows reversible intercalation/deintercalation of Mg(2+) ions in common electrolytes such as acetonitrile. Using a scanning transmission electron microscope we demonstrate that Mg(2+) ions can be effectively intercalated into the interlayer spacing of nanostructured V2O5, enabling electrochemical magnesiation against a Mg anode with a specific capacity of 240 mAh/g. We employ HRTEM and X-ray fluorescence (XRF) imaging to understand the role of environment in the intercalation processes. A rebuilt full cell was tested by employing a high-energy ball-milled Sn alloy anode in acetonitrile with Mg(ClO4)2 salt. XRF microscopy reveals effective insertion of Mg ions throughout the V2O5 structure during discharge and removal of Mg ions during electrode charging, in agreement with the electrode capacity. We show using XANES and XRF microscopy that reversible Mg intercalation is limited by the anode capacity.

  12. Mechanical alloying and sitering of TI - 10WT.% MG powders

    CSIR Research Space (South Africa)

    Machio, Christopher N

    2009-06-01

    Full Text Available A Ti-10wt.%Mg powder alloy has been produced by mechanical alloying. Elemental powders of Ti and Mg were ball milled in a Zoz-Simoloyer CM01 for 16 and 20 hours under argon. Mechanical alloying was followed by XRD, SEM and particle size analysis...

  13. Selective antibacterial effects of mixed ZnMgO nanoparticles

    International Nuclear Information System (INIS)

    Vidic, Jasmina; Stankic, Slavica; Haque, Francia; Ciric, Danica; Le Goffic, Ronan; Vidy, Aurore; Jupille, Jacques; Delmas, Bernard

    2013-01-01

    Antibiotic resistance has impelled the research for new agents that can inhibit bacterial growth without showing cytotoxic effects on humans and other species. We describe the synthesis and physicochemical characterization of nanostructured ZnMgO whose antibacterial activity was compared to its pure nano-ZnO and nano-MgO counterparts. Among the three oxides, ZnO nanocrystals—with the length of tetrapod legs about 100 nm and the diameter about 10 nm—were found to be the most effective antibacterial agents since both Gram-positive (B. subtilis) and Gram-negative (E. coli) bacteria were completely eradicated at concentration of 1 mg/mL. MgO nanocubes (the mean cube size ∼50 nm) only partially inhibited bacterial growth, whereas ZnMgO nanoparticles (sizes corresponding to pure particles) revealed high specific antibacterial activity to Gram-positive bacteria at this concentration. Transmission electron microscopy analysis showed that B. subtilis cells were damaged after contact with nano-ZnMgO, causing cell contents to leak out. Our preliminary toxicological study pointed out that nano-ZnO is toxic when applied to human HeLa cells, while nano-MgO and the mixed oxide did not induce any cell damage. Overall, our results suggested that nanostructured ZnMgO, may reconcile efficient antibacterial efficiency while being a safe new therapeutic for bacterial infections.

  14. Revisiting Mg–Mg2Ni System from Electronic Perspective

    Directory of Open Access Journals (Sweden)

    Zhao Qian

    2017-11-01

    Full Text Available Both Mg and Mg2Ni are promising electrode materials in conversion-type secondary batteries. Earlier studies have shown their single-phase prospects in electro-devices, while in this work, we have quantitatively reported the electronic properties of their dual-phase materials, that is, Mg–Mg2Ni alloys, and analyzed the underlying reasons behind the property changes of materials. The hypoeutectic Mg–Mg2Ni alloys are found to be evidently more conductive than the hypereutectic Mg–Mg2Ni system. The density functional theory (DFT calculations give the intrinsic origin of electronic structures of both Mg2Ni and Mg. The morphology of quasi-nanoscale eutectics is another factor that can affect the electronic properties of the investigated alloy system; that is, the electrical property change of the investigated alloys system is due to a combination of the intrinsic property difference between the two constituting phases and the change of eutectic microstructures that affect electron scattering. In addition, regarding the Mg–Mg2Ni alloy design for device applications, the electronic property and mechanical aspect should be well balanced.

  15. Multiband model for tunneling in MgB2 junctions

    NARCIS (Netherlands)

    Brinkman, Alexander; Golubov, Alexandre Avraamovitch; Rogalla, Horst; Dolgov, O.V.; Kortus, J.; Kong, Y.; Jepsen, O.; Andersen, O.K.

    2002-01-01

    A theoretical model for quasiparticle and Josephson tunneling in multiband superconductors is developed and applied to MgB2-based junctions. The gap functions in different bands in MgB2 are obtained from an extended Eliashberg formalism, using the results of band structure calculations. The

  16. Selective antibacterial effects of mixed ZnMgO nanoparticles

    Science.gov (United States)

    Vidic, Jasmina; Stankic, Slavica; Haque, Francia; Ciric, Danica; Le Goffic, Ronan; Vidy, Aurore; Jupille, Jacques; Delmas, Bernard

    2013-05-01

    Antibiotic resistance has impelled the research for new agents that can inhibit bacterial growth without showing cytotoxic effects on humans and other species. We describe the synthesis and physicochemical characterization of nanostructured ZnMgO whose antibacterial activity was compared to its pure nano-ZnO and nano-MgO counterparts. Among the three oxides, ZnO nanocrystals—with the length of tetrapod legs about 100 nm and the diameter about 10 nm—were found to be the most effective antibacterial agents since both Gram-positive ( B. subtilis) and Gram-negative ( E. coli) bacteria were completely eradicated at concentration of 1 mg/mL. MgO nanocubes (the mean cube size 50 nm) only partially inhibited bacterial growth, whereas ZnMgO nanoparticles (sizes corresponding to pure particles) revealed high specific antibacterial activity to Gram-positive bacteria at this concentration. Transmission electron microscopy analysis showed that B. subtilis cells were damaged after contact with nano-ZnMgO, causing cell contents to leak out. Our preliminary toxicological study pointed out that nano-ZnO is toxic when applied to human HeLa cells, while nano-MgO and the mixed oxide did not induce any cell damage. Overall, our results suggested that nanostructured ZnMgO, may reconcile efficient antibacterial efficiency while being a safe new therapeutic for bacterial infections.

  17. Selective antibacterial effects of mixed ZnMgO nanoparticles

    Energy Technology Data Exchange (ETDEWEB)

    Vidic, Jasmina, E-mail: jasmina.vidic@jouy.inra.fr [VIM, Institut de la Recherche Agronomique (France); Stankic, Slavica, E-mail: slavica.stankic@insp.jussieu.fr; Haque, Francia [CNRS, Institut des Nanosciences de Paris, UMR 7588 (France); Ciric, Danica; Le Goffic, Ronan; Vidy, Aurore [VIM, Institut de la Recherche Agronomique (France); Jupille, Jacques [CNRS, Institut des Nanosciences de Paris, UMR 7588 (France); Delmas, Bernard [VIM, Institut de la Recherche Agronomique (France)

    2013-05-15

    Antibiotic resistance has impelled the research for new agents that can inhibit bacterial growth without showing cytotoxic effects on humans and other species. We describe the synthesis and physicochemical characterization of nanostructured ZnMgO whose antibacterial activity was compared to its pure nano-ZnO and nano-MgO counterparts. Among the three oxides, ZnO nanocrystals-with the length of tetrapod legs about 100 nm and the diameter about 10 nm-were found to be the most effective antibacterial agents since both Gram-positive (B. subtilis) and Gram-negative (E. coli) bacteria were completely eradicated at concentration of 1 mg/mL. MgO nanocubes (the mean cube size {approx}50 nm) only partially inhibited bacterial growth, whereas ZnMgO nanoparticles (sizes corresponding to pure particles) revealed high specific antibacterial activity to Gram-positive bacteria at this concentration. Transmission electron microscopy analysis showed that B. subtilis cells were damaged after contact with nano-ZnMgO, causing cell contents to leak out. Our preliminary toxicological study pointed out that nano-ZnO is toxic when applied to human HeLa cells, while nano-MgO and the mixed oxide did not induce any cell damage. Overall, our results suggested that nanostructured ZnMgO, may reconcile efficient antibacterial efficiency while being a safe new therapeutic for bacterial infections.

  18. Catalysis and Downsizing in Mg-Based Hydrogen Storage Materials

    Directory of Open Access Journals (Sweden)

    Jianding Li

    2018-02-01

    Full Text Available Magnesium (Mg-based materials are promising candidates for hydrogen storage due to the low cost, high hydrogen storage capacity and abundant resources of magnesium for the realization of a hydrogen society. However, the sluggish kinetics and strong stability of the metal-hydrogen bonding of Mg-based materials hinder their application, especially for onboard storage. Many researchers are devoted to overcoming these challenges by numerous methods. Here, this review summarizes some advances in the development of Mg-based hydrogen storage materials related to downsizing and catalysis. In particular, the focus is on how downsizing and catalysts affect the hydrogen storage capacity, kinetics and thermodynamics of Mg-based hydrogen storage materials. Finally, the future development and applications of Mg-based hydrogen storage materials is discussed.

  19. Theoretical Limiting Potentials in Mg/O2 Batteries

    DEFF Research Database (Denmark)

    Smith, Jeffrey G.; Naruse, Junichi; Hiramatsu, Hidehiko

    2016-01-01

    A rechargeable battery based on a multivalent Mg/O2 couple is an attractive chemistry due to its high theoretical energy density and potential for low cost. Nevertheless, metal-air batteries based on alkaline earth anodes have received limited attention and generally exhibit modest performance....... In addition, many fundamental aspects of this system remain poorly understood, such as the reaction mechanisms associated with discharge and charging. The present study aims to close this knowledge gap and thereby accelerate the development of Mg/O2 batteries by employing first-principles calculations...... by the presence of large thermodynamic overvoltages. In contrast, MgO2-based cells are predicted to be much more efficient: superoxide-terminated facets on MgO2 crystallites enable low overvoltages and round-trip efficiencies approaching 90%. These data suggest that the performance of Mg/O2 batteries can...

  20. Microstructure and properties of Mg-Al binary alloys

    Directory of Open Access Journals (Sweden)

    ZHENG Wei-chao

    2006-11-01

    Full Text Available The effects of different amounts of added Al, ranging from 1 % to 9 %, on the microstructure and properties of Mg-Al binary alloys were investigated. The results showed that when the amount of added Al is less than 5%, the grain size of the Mg-Al binary alloys decreases dramatically from 3 097 μm to 151 μm with increasing addition of Al. Further addition of Al up to 9% makes the grain size decrease slowly to 111 μm. The α-Mg dendrite arms are also refined. Increasing the amount of added Al decreases the hot cracking susceptibility of the Mg-Al binary alloys remarkably, and enhances the micro-hardness of the α-Mg matrix.

  1. Characterization of Mg-containing hydroxyapatites synthesized by combustion method

    Science.gov (United States)

    Kaygili, Omer; Keser, Serhat; Bulut, Niyazi; Ates, Tankut

    2018-05-01

    In the present paper, Mg-substituted hydroxyapatites with the morphology, composed of the stacked plate- and rod-like structures, were prepared at the temperature of 600 °C by combustion method using glycerine as a fuel. A significant decrease in the crystallite size values calculated for both Scherrer and Williamson-Hall methods is found. The crystallinity, lattice parameter of a, stress and anisotropic energy density values decreased by adding of Mg, whereas the lattice strain increased. The amount of HAp phase decreases with increasing amount of Mg and the β-tricalcium phosphate content increases. Mg incorporation the apatitic structure was detected. Depending on the increase in Mg content, Ca-deficiency was observed.

  2. Resetting of Mg isotopes between calcite and dolomite during burial metamorphism: Outlook of Mg isotopes as geothermometer and seawater proxy

    Science.gov (United States)

    Hu, Zhongya; Hu, Wenxuan; Wang, Xiaomin; Lu, Yizhou; Wang, Lichao; Liao, Zhiwei; Li, Weiqiang

    2017-07-01

    Magnesium isotopes are an emerging tool to study the geological processes recorded in carbonates. Calcite, due to its ubiquitous occurrence and the large Mg isotope fractionation associated with the mineral, has attracted great interests in applications of Mg isotope geochemistry. However, the fidelity of Mg isotopes in geological records of carbonate minerals (e.g., calcite and dolomite) against burial metamorphism remains poorly constrained. Here we report our investigation on the Mg isotope systematics of a dolomitized Middle Triassic Geshan carbonate section in eastern China. Magnesium isotope analysis was complemented by analyses of Sr-C-O isotopic compositions, major and trace element concentrations, and petrographic and mineralogical features. Multiple lines of evidence consistently indicated that post-depositional diagenesis of carbonate minerals occurred to the carbonate rocks. Magnesium isotope compositions of the carbonate rocks closely follow a mixing trend between a high δ26Mg dolomite end member and a low δ26Mg calcite end member, irrespective of sample positions in the section and calcite/dolomite ratio in the samples. By fitting the measured Mg isotope data using a two-end member mixing model, an inter-mineral Δ26Mgdolomite-calcite fractionation of 0.72‰ was obtained. Based on the experimentally derived Mg isotope fractionation factors for dolomite and calcite, a temperature of 150-190 °C was calculated to correspond to the 0.72‰ Δ26Mgdolomite-calcite fractionation. Such temperature range matches with the burial-thermal history of the local strata, making a successful case of Mg isotope geothermometry. Our results indicate that both calcite and dolomite had been re-equilibrated during burial metamorphism, and based on isotope mass balance of Mg, the system was buffered by dolomite in the section. Therefore, burial metamorphism may reset Mg isotope signature of calcite, and Mg isotope compositions in calcite should be dealt with caution in

  3. Effect of Mg on the Microstructure and Corrosion Resistance of the Continuously Hot-Dip Galvanizing Zn-Mg Coating

    Directory of Open Access Journals (Sweden)

    Anping Dong

    2017-08-01

    Full Text Available The microstructure of continuously hot-dip galvanizing Zn-Mg coating was investigated in order to obtain the mechanism of the effects of Mg on the corrosion resistance. In this paper, the vertical section of the Zn-0.20 wt % Al-Mg ternary phase diagram near the Al-low corner was calculated. The results indicates that the phase composition of the Zn-0.20 wt % Al-Mg ternary phase diagram near the Al-low corner is the same as Zn-Mg binary phase diagram, suggesting Al in the Zn-Mg (ZM coatings mainly concentrates on the interfacial layer between the coating and steel substrate. The microstructure of continuously hot-dip galvanizing ZM coatings with 0.20 wt % Al containing 1.0–3.0 wt % Mg was investigated using tunneling electron microscopy (TEM. The morphology of Zn in the coating changes from bulk to strip and finally to mesh-like, and the MgZn2 changes from rod-like to mesh-like with the Mg content increasing. Al in the ZM coatings mainly segregates at the Fe2Al5 inhibition layer and the Mg added to the Zn bath makes this inhibition layer thinner and uneven. Compared to GI coating, the time of the first red rust appears increases by more than two-fold and expansion rate of red rust reduces by more than four-fold in terms of salt spray experiment. The ZM coating containing 2.0 wt % Mg has the best corrosion resistance. The enhanced corrosion resistance of ZM coatings mainly depends on different corrosion products.

  4. Effect of Mg content on microstructure and corrosion behavior of hot dipped Zn–Al–Mg coatings

    Energy Technology Data Exchange (ETDEWEB)

    Yao, Caizhen; Lv, Haibing [Research Centre of Laser Fusion, CAEP, P.O.Box 919-988-5, Mianyang, Sichuan 621900 (China); Zhu, Tianping [Department of Chemical and Materials Engineering, The University of Auckland, PB 92019, Auckland 1142 (New Zealand); Zheng, Wanguo [Research Centre of Laser Fusion, CAEP, P.O.Box 919-988-5, Mianyang, Sichuan 621900 (China); Yuan, Xiaodong, E-mail: xdyuan@caep.cn [Research Centre of Laser Fusion, CAEP, P.O.Box 919-988-5, Mianyang, Sichuan 621900 (China); Gao, Wei, E-mail: w.gao@auckland.ac.nz [Department of Chemical and Materials Engineering, The University of Auckland, PB 92019, Auckland 1142 (New Zealand)

    2016-06-15

    In this article, Zn–Al–Mg coatings were prepared by hot dipping method. The surface morphology, cross–section microstructure, microhardness, composition, corrosion behaviour of ZAM coatings were investigated by using X–ray diffraction (XRD), Optical microscope, Environmental scanning electron microscopy equipped with EDS (FESEM–EDS), Microhardness tester and Electrochemical analysis respectively. Corrosion test was also performed in a standard salt fog spray chamber. Microstructure studies indicates that Zn grain size was refined and eutectic areas at Zn grain boundary areas increased with increasing Mg content. ZA5M1.5 and ZA5M2 coatings have two distinct layers. Mg tends to exist in the outer layer while Al is in the inner layer. The inner layer is composed of Al{sub 5}Fe{sub 2}Zn{sub 0.4} intermetallic, which may to contribute to the microhardness. The outer layer is Zn grains surrounded by Zn–Mg etutectics, which may improve the corrosion resistance. The microhardness is more than 700 HV{sub 50g} for Al-rich layer and around 151 HV{sub 25g} for Mg-rich layer. The improved corrosion resistance of Zn–5%Al-1.5%Mg coating comes from the corrosion product of flocculent type simonkolleite, which prolongs the micro-path and impedes the movement of O{sub 2} and H{sub 2}O, ultimately retards the overall corrosion process. - Highlights: • Two-layer structured Zn–Al–Mg coatings were prepared by hot dipping method. • Mg exists in the outer layer while Al exists in the inner layer of Zn–Al–Mg coating. • Zn–Al–Mg coating has better protective ability than Zn and Zn–Al coatings. • The Mg-modified simonkolleite is the reason of the enhanced corrosion resistance.

  5. Mg doping of GaN by molecular beam epitaxy

    International Nuclear Information System (INIS)

    Lieten, R R; Buchowicz, G; Dubon, O; Motsnyi, V; Zhang, L; Cheng, K; Leys, M; Degroote, S; Borghs, G

    2011-01-01

    We present a systematic study on the influence of growth conditions on the incorporation and activation of Mg in GaN layers grown by plasma-assisted molecular beam epitaxy. We show that high quality p-type GaN layers can be obtained on GaN-on-silicon templates. The Mg incorporation and the electrical properties have been investigated as a function of growth temperature, Ga : N flux ratio and Mg : Ga flux ratio. It was found that the incorporation of Mg and the electrical properties are highly sensitive to the Ga : N flux ratio. The highest hole mobility and lowest resistivity were achieved for slightly Ga-rich conditions. In addition to an optimal Ga : N ratio, an optimum Mg : Ga flux ratio was also observed at around 1%. We observed a clear Mg flux window for p-type doping of GaN : 0.31% 17 cm -3 and a mobility of 15 cm 2 V -1 s -1 . Temperature-dependent Hall effect measurements indicate an acceptor depth in these samples of 100 meV for a hole concentration of 5.5 x 10 17 cm -3 . The corresponding Mg concentration is 5 x 10 19 cm -3 , indicating approximately 1% activation at room temperature. In addition to continuous growth of Mg-doped GaN layers we also investigated different modulated growth procedures. We show that a modulated growth procedure has only limited influence on Mg doping at a growth temperature of 800 deg. or higher. This result is thus in contrast to previously reported GaN : Mg doping at much lower growth temperatures of 500 deg. C.

  6. Pharmacokinetic characterization of three novel 4-mg nicotine lozenges
.

    Science.gov (United States)

    Sukhija, Manpreet; Srivastava, Reena; Kaushik, Aditya

    2018-03-01

    Nicotine replacement therapy (NRT) increases the probability of smoking cessation. This study was conducted to determine if three prototype 4-mg nicotine lozenges produced locally in India were bioequivalent to a globally marketed reference product, Nicorette® 4-mg nicotine lozenge. Healthy adult smokers (N = 39) were treated with three prototype 4-mg nicotine lozenges in comparison with a reference 4-mg lozenge in this single-center, randomized, open-label, single-dose, 4-way crossover study. Pharmacokinetic sampling was obtained to test for bioequivalence using maximal plasma concentration (Cmax) and extent of absorption (AUC0-t). Secondarily, AUC;0-∞, time to maximal plasma concentration (tmax), half-life (T1/2), elimination rate constant (Kel), and safety of the prototype lozenges versus the reference lozenge were compared. Each prototype 4-mg nicotine lozenge was found to be bioequivalent to the reference 4-mg nicotine lozenge based on the ratio of geometric means and 90% confidence intervals for Cmax, AUC0-t, and AUC;0-∞. Although tmax; was significantly longer for prototype III, all four lozenges achieved maximum plasma nicotine concentrations at a median of 1.5 hours. The safety profiles of the three prototype 4-mg lozenges did not differ from that of the 4-mg reference product. Each prototype 4-mg nicotine lozenge was bioequivalent to the reference 4-mg nicotine lozenge and was well tolerated. Furthermore, as these bioequivalent prototypes differed in in-vitro dissolution profiles, these data suggest that performance from the in -vitro method deployed is not a firm predictor of pharmacokinetic behavior.
.

  7. In vitro degradation and electrochemical corrosion evaluations of microarc oxidized pure Mg, Mg-Ca and Mg-Ca-Zn alloys for biomedical applications.

    Science.gov (United States)

    Pan, Yaokun; He, Siyu; Wang, Diangang; Huang, Danlan; Zheng, Tingting; Wang, Siqi; Dong, Pan; Chen, Chuanzhong

    2015-02-01

    Calcium phosphate (CaP) ceramic coatings were fabricated on pure magnesium (Mg) and self-designed Mg-0.6Ca, Mg-0.55Ca-1.74Zn alloys by microarc oxidation (MAO). The coating formation, growth and biomineralization mechanisms were discussed. The coating degradability and bioactivity were evaluated by immersion tests in trishydroxymethyl-aminomethane hydrochloric acid (Tris-HCl) buffer and simulated body fluid (SBF) solutions, respectively. The coatings and corrosion products were characterized by scanning electron microscope (SEM), X-ray diffractometer (XRD), X-ray photoelectron spectrometer (XPS) and fourier transform infrared spectrometer (FT-IR). The electrochemical workstation was used to investigate the electrochemical corrosion behaviors of substrates and coatings. Results showed that Mg-0.55Ca-1.74Zn alloy exhibits the highest mechanical strength and electrochemical corrosion resistance among the three alloys. The MAO-coated Mg-0.55Ca-1.74Zn alloy has the potential to be served as a biodegradable implant. Copyright © 2014 Elsevier B.V. All rights reserved.

  8. Improved hydrogen sorption kinetics in wet ball milled Mg hydrides

    Energy Technology Data Exchange (ETDEWEB)

    Meng, Li

    2011-05-04

    In this work, wet ball milling method is used in order to improve hydrogen sorption behaviour due to its improved microstructure of solid hydrogen materials. Compared to traditional ball milling method, wet ball milling has benefits on improvement of MgH{sub 2} microstructure and further influences on its hydrogen sorption behavior. With the help of solvent tetrahydrofuran (THF), wet ball milled MgH{sub 2} powder has much smaller particle size and its specific surface area is 7 times as large as that of dry ball milled MgH{sub 2} powder. Although after ball milling the grain size is decreased a lot compared to as-received MgH{sub 2} powder, the grain size of wet ball milled MgH{sub 2} powder is larger than that of dry ball milled MgH{sub 2} powder due to the lubricant effect of solvent THF during wet ball milling. The improved particle size and specific surface area of wet ball milled MgH{sub 2} powder is found to be determining its hydrogen sorption kinetics especially at relatively low temperatures. And it also shows good cycling sorption behavior, which decides on its industrial applicability. With three different catalysts MgH{sub 2} powder shows improved hydrogen sorption behavior as well as the cyclic sorption behavior. Among them, the Nb{sub 2}O{sub 5} catalyst is found to be the most effective one in this work. Compared to the wet ball milled MgH{sub 2} powder, the particle size and specific surface area of the MgH{sub 2} powder with catalysts are similar to the previous ones, while the grain size of the MgH{sub 2} with catalysts is much finer. In this case, two reasons for hydrogen sorption improvement are suggested: one is the reduction of the grain size. The other may be as pointed out in some literatures that formation of new oxidation could enhance the hydrogen sorption kinetics, which is also the reason why its hydrogen capacity is decreased compared to without catalysts. After further ball milling, the specific surface area of wet ball milled Mg

  9. Synthesis, crystal growth and structure of Mg containing β-rhombohedral boron: MgB17.4

    International Nuclear Information System (INIS)

    Adasch, Volker; Hess, Kai-Uwe; Ludwig, Thilo; Vojteer, Natascha; Hillebrecht, Harald

    2006-01-01

    For the first time, single crystals of Mg containing β-rhombohedral boron MgB 17.4 were synthesised from the elements in a Mg/Cu melt at 1600deg. C. The crystal structure determined by the refinement of single crystal data (space group R-3m, a=10.991(2)A, c=24.161(4)A, 890 reflections, 123 variables, R 1 (F)=0.049, wR 2 (I)=0.122) improves and modifies the former structure model derived from earlier investigations on powder samples. Mg is located on four different positions with partial occupation. While the occupation of the sites D (53.3%), E (91%) and F (7.2%) is already known from other boron-rich borides related to β-rhombohedral boron, the occupation of the fourth position (18h, 6.7%) is observed for the first time. Two boron positions show partial occupation. The summation reveals the composition MgB 17.4 and Mg 5.85 B 101.9 , respectively, confirmed by WDX measurements. The single crystals of MgB 17.4 show the highest Mg content ever found. Preliminary measurements indicate no superconductivity

  10. Influence of a transition metal atom on the geometry and electronic structure of Mg and Mg-H clusters

    International Nuclear Information System (INIS)

    Siretskiy, M.Yu.; Shelyapina, M.G.; Fruchart, D.; Miraglia, S.; Skryabina, N.E.

    2009-01-01

    We report on the study of (MgH 2 ) n + M complexes (M = Ti or Ni) carried out within the framework of the cluster density functional theory (DFT) method. The influence of such transition metal atoms on the cluster geometry and electronic structure is discussed considering the stability of MgH 2 hydride.

  11. Ab-initio calculations of semiconductor MgGeP{sub 2} and MgGeAs{sub 2}

    Energy Technology Data Exchange (ETDEWEB)

    Kocak, B.; Ciftci, Y.O., E-mail: yasemin@gazi.edu.tr

    2016-05-15

    Highlights: • MgGeP{sub 2} and MgGeAs{sub 2} are semiconductor compounds. • MgGeP{sub 2} and MgGeAs{sub 2} are energetically, mechanically and dynamically stable. • The electronic charge density contour plot shows that the nature of bonding is a mixture of ionic-covalent. - Abstract: In this study, we focus on structural, electronic, elastic, lattice dynamic and optic properties of MgGeP{sub 2} and MgGeAs{sub 2} using ab-initio density-functional theory (DFT) within Armiento-Mattson 2005 (AM05) scheme of the generalized gradient approximation (GGA) for the exchange-correlation potential. Our computed structural results are in reasonable agreement with the literature. The band gap of these compounds is predicted to be direct. Our elastic results prove that these compounds are mechanically stable. The obtained phonon spectra of MgGeP{sub 2} and MgGeAs{sub 2} do not exhibit any significant imaginary branches using GGA-AM05 for the exchange-correlation approximation. Further analysis of the optical response of the dielectric functions, optical reflectivity, refractive index, extinction coefficient and electron energy loss delves into for the energy range of 0–22.5 eV. It motivated that there exists an optical polarization anisotropy of these compounds for optoelectronic device applications.

  12. Thermal behaviour of Cu-Mg-Mn and Ni-Mg-Mn layered double hydroxides and characterization of formed oxides

    Czech Academy of Sciences Publication Activity Database

    Kovanda, F.; Grygar, Tomáš; Dorničák, V.; Rojka, T.; Bezdička, Petr; Jirátová, Květa

    2005-01-01

    Roč. 28, 1-4 (2005), s. 121-136 ISSN 0169-1317 Institutional research plan: CEZ:AV0Z40320502 Keywords : Cu-Mg-Mn basic carbonates * Ni-Mg-Mn hydrotalcite Subject RIV: CA - Inorganic Chemistry Impact factor: 1.324, year: 2005

  13. Ipilimumab 10 mg/kg versus ipilimumab 3 mg/kg in patients with unresectable or metastatic melanoma

    DEFF Research Database (Denmark)

    Ascierto, Paolo A; Del Vecchio, Michele; Robert, Caroline

    2017-01-01

    of ipilimumab 10 mg/kg versus 3 mg/kg. METHODS: This randomised, double-blind, multicentre, phase 3 trial was done in 87 centres in 21 countries worldwide. Patients with untreated or previously treated unresectable stage III or IV melanoma, without previous treatment with BRAF inhibitors or immune checkpoint...

  14. Phase diagrams of aluminium alloys of Al-Cu-Mg, Al-Mg-Si-Cu, and Al-Mg-Li system

    International Nuclear Information System (INIS)

    Ber, L.B.; Kaputkin, E.Ya.

    2001-01-01

    Isothermal diagrams of phase transformations (DPT) and temperature-time charts (TTC) of variation of electric conductivity and of mechanical features at tension were plotted following thermal treatment according to the pattern of direct hardening and ageing and according to the pattern of normal aging for D16 commercial alloy, Al-Cu-Mg model alloy of the same system, AD37 commercial alloys of Al-Mg-Si-Cu and 1424 one of Al-Li-Mg system. Phase transformations were studied by means of fluorescence electron microscopy, micro-X-ray spectral analysis, X-ray phase analysis of single crystals and polycrystals and differential scanning calorimetry. For every alloy comparison of TTC and DPT enables to clarity the mechanism of phase composition effect on features and to optimize conditions of hardening cooling and ageing [ru

  15. In vivo and in vitro degradation comparison of pure Mg, Mg-10Gd and Mg-2Ag: a short term study

    Directory of Open Access Journals (Sweden)

    I Marco

    2017-02-01

    Full Text Available The purpose of this study was to compare short term in vitro and in vivo biodegradation studies with low purity Mg (> 99.94 %, Mg-10Gd and Mg-2Ag designed for biodegradable implant applications. Three in vitro testing conditions were applied, using (i phosphate buffered saline (PBS, (ii Hank’s balanced salt solution (HBSS and (iii Dulbecco’s modified eagle medium (DMEM in 5 % CO2 under sterile conditions. Gas evolution and mass loss (ML were assessed, as well as the degradation layer, by elemental mapping and scanning electron microscopy (SEM. In vivo, implantations were performed on male Sprague-Dawley rats evaluating both, gas cavity volume and implant volume reduction by micro-computed tomography (µCT, 7 d after implantation. Samples were produced by casting, solution heat treatment and extrusion in disc and pin shape for the in vitro and in vivo experiments, respectively. Results showed that when the processing of the Mg sample varied, differences were found not only in the alloy impurity content and the grain size, but also in the corrosion behaviour. An increase of Fe and Ni or a large grain size seemed to play a major role in the degradation process, while the influence of alloying elements, such as Gd and Ag, played a secondary role. Results also indicated that cell culture conditions induced degradation rates and degradation layer elemental composition comparable to in vivo conditions. These in vitro and in vivo degradation layers consisted of Mg hydroxide, Mg-Ca carbonate and Ca phosphate.

  16. Effect of solution concentration on sealing treatment of Mg-Al hydrotalcite film on AZ91D Mg alloy

    Directory of Open Access Journals (Sweden)

    Qiangsheng Dong

    2017-09-01

    Full Text Available Cerium-based sealing treatment was developed for Mg-Al hydrotalcite film on AZ91D Mg alloy, and the influence of cerium salt solution was investigated to modify the surface integrity and corrosion resistance. Scanning electron microscope (SEM and X-ray diffraction (XRD measurements were carried out to analyze the surface morphology and phase composition. The corrosion resistance of Mg-Al hydrotalcite film after sealing treatment was evaluated by the polarization curve and electrochemical impedance spectroscopy (EIS tests. The results showed that lower concentration of Ce-containing solution was beneficial to seal the micro-cracks on Mg-Al hydrotalcite film, and improve the surface integrity and corrosion resistance; higher concentration of Ce-containing solution could seal fewer micro-cracks, and the corrosion resistance was decreased owing to the disintegration of Mg-Al hydrotalcite film.

  17. Phase-field simulations of dendrite morphologies and selected evolution of primary {alpha}-Mg phases during the solidification of Mg-rich Mg-Al-based alloys

    Energy Technology Data Exchange (ETDEWEB)

    Wang, Mingyue [Key Laboratory for Advanced Materials Processing Technology, Ministry of Education, Department of Mechanical Engineering, Tsinghua University, Beijing 100084 (China); Jing, Tao; Liu, Baicheng [Key Laboratory for Advanced Materials Processing Technology, Ministry of Education, Department of Mechanical Engineering, Tsinghua University, Beijing 100084 (China)

    2009-10-15

    A formulation of solid-liquid interfacial thermodynamic and kinetic anisotropic characteristics for hexagonal close-packed metals is proposed. The two- and three-dimensional dendritic growth of primary Mg in undercooled Mg-Al alloy melts is modeled using the phase-field method, based on a combination of crystallographic lattice symmetry and experimental observations. The morphologies of three-dimensional dendrites are obtained and the calculated results show intricately hierarchical branched structures. The excess free energy of the solution system is based on the Redlich-Kister model.

  18. Phase-field simulations of dendrite morphologies and selected evolution of primary α-Mg phases during the solidification of Mg-rich Mg-Al-based alloys

    International Nuclear Information System (INIS)

    Wang, Mingyue; Jing, Tao; Liu, Baicheng

    2009-01-01

    A formulation of solid-liquid interfacial thermodynamic and kinetic anisotropic characteristics for hexagonal close-packed metals is proposed. The two- and three-dimensional dendritic growth of primary Mg in undercooled Mg-Al alloy melts is modeled using the phase-field method, based on a combination of crystallographic lattice symmetry and experimental observations. The morphologies of three-dimensional dendrites are obtained and the calculated results show intricately hierarchical branched structures. The excess free energy of the solution system is based on the Redlich-Kister model.

  19. Atorvastatin 10 mg plus ezetimibe 10mg compared with atorvastatin 20 mg: impact on the lipid profile in Japanese patients with abnormal glucose tolerance and coronary artery disease.

    Science.gov (United States)

    Uemura, Yusuke; Watarai, Masato; Ishii, Hideki; Koyasu, Masayoshi; Takemoto, Kenji; Yoshikawa, Daiji; Shibata, Rei; Matsubara, Tatsuaki; Murohara, Toyoaki

    2012-01-01

    Oxidized low-density lipoprotein (LDL) cholesterol is a sensitive lipid marker for predicting atherosclerosis. Ezetimibe and statins are reported to decrease both LDL cholesterol and oxidized LDL cholesterol. This prospective randomized open-label crossover study compared combination therapy with atorvastatin plus ezetimibe versus high-dose atorvastatin monotherapy. Changes in serum lipids, including malondialdehyde-modified LDL (MDA-LDL) as a representative form of oxidized LDL cholesterol, and glucose metabolism were assessed. The subjects were 39 Japanese patients with coronary artery disease and type 2 diabetes or impaired glucose tolerance who were taking 10 mg/day of atorvastatin (30 men and 9 women with a mean age of 67.8 years). They were randomized to a group that first received add-on ezetimibe (10 mg/day) or a group that first received atorvastatin monotherapy at a higher dose of 20 mg/day. Both treatments were given for 12 weeks each in a crossover fashion. Add-on ezetimibe significantly decreased MDA-LDL (109.0 ± 31.9 mg/dl to 87.7 ± 29.4 mg/dl, p=0.0009), while up-titration of atorvastatin did not. The decrease with add-on ezetimibe was significantly greater than with up-titration of atorvastatin (p=0.0006). Total cholesterol and LDL cholesterol were significantly decreased by both treatments, but the percent reduction with add-on ezetimibe was significantly greater (pHigh-density lipoprotein cholesterol was significantly increased by both treatments and there was no significant difference between them. The apolipoprotein B/apolipoprotein A-I ratio and remnant-like particle cholesterol were only significantly decreased by add-on ezetimibe. Both treatments caused similar elevation of hemoglobin A(1c). In Japanese patients with type 2 diabetes or impaired glucose tolerance and coronary artery disease, adding ezetimibe (10 mg/day) to atorvastatin (10 mg/day) significantly improved the lipid profile compared with atorvastatin monotherapy at 20 mg

  20. Synthesis and crystal structure of MgB12

    International Nuclear Information System (INIS)

    Adasch, Volker; Hess, Kai-Uwe; Ludwig, Thilo; Vojteer, Natascha; Hillebrecht, Harald

    2006-01-01

    Single crystals of MgB 12 were synthesized from the elements in a Mg/Cu melt at 1600deg. C. MgB 12 crystallizes orthorhombic in space group Pnma with a=16.632(3)A, b=17.803(4)A and c=10.396(2)A. The crystal structure (Z=30, 5796 reflections, 510 variables, R 1 (F)=0.049, wR 2 (I)=0.134) consists of a three dimensional net of B 12 icosahedra and B 21 units in a ratio 2:1. The B 21 units are observed for the first time in a solid compound. Mg is on positions with partial occupation. The summation reveals the composition MgB 12.35 or Mg 0.97 B 12 , respectively. This is in good agreement with the value of MgB 11.25 as expected by electronic reasons to stabilize the boron polyhedra B 12 2- and B 21 4-

  1. Comparison of 1 mg and 2 mg overnight dexamethasone suppression tests for the screening of Cushing's syndrome in obese patients.

    Science.gov (United States)

    Sahin, Mustafa; Kebapcilar, Levent; Taslipinar, Abdullah; Azal, Omer; Ozgurtas, Taner; Corakci, Ahmet; Akgul, Emin Ozgur; Taslipinar, Mine Yavuz; Yazici, Mahmut; Kutlu, Mustafa

    2009-01-01

    Obesity is currently a major public health problem and one of the potential underlying causes of obesity in a minority of patients is Cushing's syndrome (CS). Traditionally, the gold standard screening test for CS is 1 mg dexamethasone overnight suppression test. However, it is known that obese subjects have high false positive results with this test. We have therefore compared the 1 mg and 2 mg overnight dexamethasone suppression tests in obese subjects. Patients whose serum cortisol after ODST was >50 nM underwent and a low-dose dexamethasone suppression test (LDDST); 24-hour urine cortisol was collected for basal urinary free cortisol (UFC). For positive results after overnight 1-mg dexamethasone suppression test we also performed the overnight 2-mg dexamethasone suppression test. We prospectively evaluated 100 patients (22 men and 78 women, ranging in age from 17 to 73 years with a body mass index (BMI) >30 kg/m2 who had been referred to our hospital-affiliated endocrine clinic because of simple obesity. Suppression of serum cortisol to suppression. Thyroid function tests, lipid profiles, homocysteine, antithyroglobulin, anti-thyroid peroxidase antibody levels, vitamin B12, folate levels, insulin resistance [by homeostasis model assessment (HOMA)] and 1.0 mg postdexamethasone (postdex) suppression cortisol levels were measured. We found an 8% false-positive rate in 1 mg overnight test and 2% in 2 mg overnight test (p=0.001). There was no correlation between the cortisol levels after ODST and other parameters. Our results indicate that the 2 mg overnight dexamethasone suppression test (ODST) is more convenient and accurate than 1-mg ODST as a screening test for excluding CS in subjects with simple obesity.

  2. Mg{sub 2}Sn heterostructures on Si(111) substrate

    Energy Technology Data Exchange (ETDEWEB)

    Dózsa, L., E-mail: dozsa@mfa.kfki.hu [Institute of Technical Physics and Materials Science, Centre for Energy Research, Hungarian Academy of Sciences, 1525 Budapest Pf, 49 (Hungary); Galkin, N.G. [Institute of Automation and Control Processes of FEB RAS, 5 Radio St., Vladivostok 690041 (Russian Federation); Far Eastern Federal University, 8 Sukhanova St., Vladivostok 690950 (Russian Federation); Pécz, B.; Osváth, Z.; Zolnai, Zs. [Institute of Technical Physics and Materials Science, Centre for Energy Research, Hungarian Academy of Sciences, 1525 Budapest Pf, 49 (Hungary); Németh, A. [Wigner Research Centre for Physics, Institute for Particle and Nuclear Physics, 1525 Budapest, P.O.B. 49 (Hungary); Galkin, K.N.; Chernev, I.M. [Institute of Automation and Control Processes of FEB RAS, 5 Radio St., Vladivostok 690041 (Russian Federation); Dotsenko, S.A. [Institute of Automation and Control Processes of FEB RAS, 5 Radio St., Vladivostok 690041 (Russian Federation); Far Eastern Federal University, 8 Sukhanova St., Vladivostok 690950 (Russian Federation)

    2017-05-31

    Highlights: • Investigations show that the nanostructures have significant changes during the applied regular experimental investigations. • It is especially true for transmittance electron microscopy, where the investigated layers have to be thinned near to the nanostructure size. • The time order of the applied experimental investigation has a dominant effect on the experimetal results. - Abstract: Thin un-doped and Al doped polycrystalline Mg-stannide films consisting mainly of Mg{sub 2}Sn semiconductor phase have been grown by deposition of Sn-Mg multilayers on Si(111) p-type wafers at room temperature and annealing at 150 °C. Rutherford backscattering measurement spectroscopy (RBS) were used to determine the amount of Mg and Sn in the structures. Raman spectroscopy has shown the layers contain Mg{sub 2}Sn phase. Cross sectional transmission electron microscopy (XTEM) measurements have identified Mg{sub 2}Sn nanocrystallites in hexagonal and cubic phases without epitaxial orientation with respect to the Si(111) substrate. Significant oxygen concentration was found in the layer both by RBS and TEM. The electrical measurements have shown laterally homogeneous conductivity in the grown layer. The undoped Mg{sub 2}Sn layers show increasing resistivity with increasing temperature indicating the scattering process dominates the resistance of the layers, i.e. large concentration of point defects was generated in the layer during the growth process. The Al doped layer shows increase of the resistance at low temperature caused by freeze out of free carriers in the Al doped Mg{sub 2}Sn layer. The measurements indicate the necessity of protective layer grown over the Mg{sub 2}Sn layers, and a short time delay between sample preparation and cross sectionalTEM analysis, since the unprotected layer is degraded by the interaction with the ambient.

  3. Pulse laser irradiation into superconducting MgB2 detector

    International Nuclear Information System (INIS)

    Fujiwara, Daisuke; Miki, Shigehito; Satoh, Kazuo; Yotsuya, Tsutomu; Shimakage, Hisashi; Wang, Zhen; Okayasu, Satoru; Katagiri, Masaki; Machida, Masahiko; Kato, Masaru; Ishida, Takekazu

    2005-01-01

    We performed 20-ps pulse laser irradiation experiments on a MgB 2 neutron detector to know a thermal-relaxation process for designing a MgB 2 neutron detector. The membrane-type structured MgB 2 device was fabricated to minimize the heat capacity of sensing part of a detector as well as to enhance its sensitivity. We successfully observed a thermal-relaxation signal resulting from pulse laser irradiation by developing a detection circuit. The response time was faster than 1 μs, meaning that the detector would be capable of counting neutrons at a rate of more than 10 6 events per second

  4. Interaction of hydrogen with an Mg-Al alloy

    International Nuclear Information System (INIS)

    Andreasen, A.; Sorensen, M.B.; Burkarl, R.; Moller, B.; Molenbroek, A.M.; Pedersen, A.S.; Andreasen, J.W.; Nielsen, M.M.; Jensen, T.R.

    2005-01-01

    The interaction of hydrogen with an Mg-Al alloy pre-exposed to air have been studied with in situ time resolved X-ray powder diffraction. Phase fractions as a function of time are derived from series of consecutive diffraction patterns allowing kinetic analysis. The apparent activation energy for dehydrogenation of the Mg-Al alloy is found to be 160 kJ/mol. This is not significantly higher than for pure and fully activated Mg. It is suggested that the addition of Al improves the resistance towards oxygen contamination

  5. The role of Mg in the crystallization of monohydrocalcite

    Science.gov (United States)

    Rodriguez-Blanco, Juan Diego; Shaw, Samuel; Bots, Pieter; Roncal-Herrero, Teresa; Benning, Liane G.

    2014-02-01

    Monohydrocalcite is a member of the carbonate family which forms in Mg-rich environments at a wide range of Mg/Ca ratios Mg2+aq/Ca2+aq≥0.17stock solutions. However, its crystallite and particle size are inversely proportional to these parameters. At high supersaturations (SIMHC = 3.89) nanometer-sized single crystals of monohydrocalcite form, while at low values (SIMHC = 2.43) the process leads to low-angle branching spherulites. Many carbonates produced during biomineralization form at similar conditions to most synthetic monohydrocalcites, and thus we hypothesize that some calcite or aragonite deposits found in the geologic record that have formed at high Mg/Ca ratios could be secondary in origin and may have originally formed via a metastable monohydrocalcite intermediate. High-Mg monohydrocalcite (χMgCO3 > 0.06) consists of individual nanometer-sized crystals (500 °C (Fig. 9b). Such high-Mg monohydrocalcites are uncommon in nature, but can be synthesized in the laboratory at high initial supersaturation levels (SI > 3.25). Low-Mg monohydrocalcite (χMgCO3 bonded to Mg, so it fully dehydrates at low temperatures (150-200 °C). They have the same composition as natural monohydrocalcites reported in the literature, and can be synthesized in the laboratory at lower supersaturation levels (SI relationships. Firstly, our on-line experiment shows an increase in nanocrystal sizes during the secondary crystallization of monohydrocalcite, which is coupled with a significant decrease in χMgCO3 (from ˜0.26 to ˜0.065). This corresponds to the transition from high- to low-Mg monohydrocalcite, suggesting that the former would be metastable and rapidly transforming to the latter, possibly triggered by the removal of Mg from aqueous solution. Secondly, Davis et al. (2000) determined that the solubility of Mg-calcite (Ca1-xMgxCO3; x = 0-0.20) varies by approximately half an order of magnitude depending on the Mg content of the solid (Ksp = 10-8.0-10-8.5). A similar

  6. Catalytic activity of Co-Mg-Al, Cu-Mg-Al and Cu-Co-Mg-Al mixed oxides derived from hydrotalcites in SCR of NO with ammonia

    Energy Technology Data Exchange (ETDEWEB)

    Chmielarz, Lucjan; Kustrowski, Piotr; Rafalska-Lasocha, Alicja [Faculty of Chemistry, Jagiellonian University, Ingardena 3, 30-060 Krakow (Poland); Majda, Dorota; Dziembaj, Roman [Regional Laboratory for Physicochemical Analyses and Structural Research, Ingardena 3, 30-060 Krakow (Poland)

    2002-01-10

    M-Mg-Al hydrotalcites (where M=Cu{sup 2+}, Co{sup 2+} and Cu{sup 2+}+Co{sup 2+}) with M ranging from 5 to 20% (as atomic ratio) were prepared by co-precipitation method. Obtained samples were characterised by XRD and TGA techniques. The influence of transition metal content on thermal decomposition of hydrotalcites was observed. Calcination of the hydrotalcites at 600C resulted in the formation of mixed oxides with surface areas in the range 71-154m{sup 2}/g. Calcined hydrotalcites were tested as catalysts in the selective reduction of NO with ammonia (NO-SCR). The catalytic activity depends on the kind of transition metal, as well as its content. For the NO-SCR the following reactivity order was found: Cu-Mg-Al>Cu-Co-Mg-Al>Co-Mg-Al. Temperature-programmed methods (TPD, TPSR, stop flow-TPD), as well as FT-IR spectroscopy have been applied to determine interaction of NO and NH{sub 3} molecules with the catalyst surface.

  7. Synthesis of Mg(OH)2, MgO, and Mg nanoparticles using laser ablation of magnesium in water and solvents

    Energy Technology Data Exchange (ETDEWEB)

    Tran, P.X.; Howard, B.H.; Martello, D.V.; Soong, Y.; Chyu, M.K.

    2008-01-01

    laser ablation of magnesium in deionized water (OW), solutions of OW and sodium dodecyl sulfate (50S) with different concentrations, acetone and 2-propanol has been conducted, The results showed that ablation in acetone and 2-propanol yielded MgO and Mg nanocrystallites as isolated particles and agglomerated chains probably intermixed with organic residues resulting from the alterationj decomposition of the solvents under the high-energy conditions. Brucite-like Mg(OH)2 particles were mainly produced by laser ablation of Mg in either OW or OW~SOS solutions. Ablation in OW yielded particles of fiber-like shapes having a diameter of about 5-lOnm and length as long as 150nm. Materials produced in DW-SOS solutions were composed of various size and shape particles, Some had rough surfaces with irregular shapes. Small particles were about 20-30nm and larger particles were about 120 nm. Particles with rod-like, triangular, and plate-like shapes were also observed.

  8. Synthesis of Mg(OH)2, MgO, and Mg nanoparticles using laser ablation of magnesium in water and solvents

    Energy Technology Data Exchange (ETDEWEB)

    Phuoc, Tran X. [National Energy Technology Lab. (NETL), Pittsburgh, PA, (United States); Howard, Bret. H. [National Energy Technology Lab. (NETL), Pittsburgh, PA, (United States); Martello, Donald V. [National Energy Technology Lab. (NETL), Pittsburgh, PA, (United States); Soong, Yee [National Energy Technology Lab. (NETL), Pittsburgh, PA, (United States); Chyu, Minking K. [Univ. of Pittsburgh, PA (United States)

    2008-11-01

    Laser ablation of magnesium in deionized water (DW), solutions of DW and sodium dodecyl sulfate (SDS) with different concentrations, acetone and 2-propanol has been conducted. The results showed that ablation in acetone and 2-propanol yielded MgO and Mg nanocrystallites as isolated particles and agglomerated chains probably intermixed with organic residues resulting from the alteration/decomposition of the solvents under the high-energy conditions. Brucite-like Mg(OH)2 particles were mainly produced by laser ablation of Mg in either DW or DW-SDS solutions. Ablation in DW yielded particles of fiber-like shapes having a diameter of about 5-10nm and length-as long as 150 nm. Materials produced in DW-SDS solutions were composed of various size and shape particles. Some had rough surfaces with irregular shapes. Small particles were about 20-30 nm and larger particles were about 120 nm. Particles with rodlike, triangular, and plate-like shapes were also observed.

  9. Synthesis of Mg(OH) 2, MgO, and Mg nanoparticles using laser ablation of magnesium in water and solvents

    Science.gov (United States)

    Phuoc, Tran X.; Howard, Bret. H.; Martello, Donald V.; Soong, Yee; Chyu, Minking K.

    2008-11-01

    Laser ablation of magnesium in deionized water (DW), solutions of DW and sodium dodecyl sulfate (SDS) with different concentrations, acetone and 2-propanol has been conducted. The results showed that ablation in acetone and 2-propanol yielded MgO and Mg nanocrystallites as isolated particles and agglomerated chains probably intermixed with organic residues resulting from the alteration/decomposition of the solvents under the high-energy conditions. Brucite-like Mg(OH) 2 particles were mainly produced by laser ablation of Mg in either DW or DW-SDS solutions. Ablation in DW yielded particles of fiber-like shapes having a diameter of about 5-10 nm and length as long as 150 nm. Materials produced in DW-SDS solutions were composed of various size and shape particles. Some had rough surfaces with irregular shapes. Small particles were about 20-30 nm and larger particles were about 120 nm. Particles with rod-like, triangular, and plate-like shapes were also observed.

  10. Defect kinetics in spinels: Long-time simulations of MgAl2O4, MgGa2O4, and MgIn2O4

    International Nuclear Information System (INIS)

    Uberuaga, B. P.; Voter, A. F.; Sickafus, K. E.; Bacorisen, D.; Smith, Roger; Ball, J. A.; Grimes, R. W.

    2007-01-01

    Building upon work in which we examined defect production and stability in spinels, we now turn to defect kinetics. Using temperature accelerated dynamics (TAD), we characterize the kinetics of defects in three spinel oxides: magnesium aluminate MgAl 2 O 4 , magnesium gallate MgGa 2 O 4 , and magnesium indate MgIn 2 O 4 . These materials have varying tendencies to disorder on the cation sublattices. In order to understand chemical composition effects, we first examine defect kinetics in perfectly ordered, or normal, spinels, focusing on point defects on each sublattice. We then examine the role that cation disorder has on defect mobility. Using TAD, we find that disorder creates local environments which strongly trap point defects, effectively reducing their mobility. We explore the consequences of this trapping via kinetic Monte Carlo (KMC) simulations on the oxygen vacancy (V O ) in MgGa 2 O 4 , finding that V O mobility is directly related to the degree of inversion in the system

  11. FRACTIONAL RECRYSTALLIZATION KINETICS IN DIRECTLY COLD ROLLED Al-Mg, Al-Mg-Sc AND Al-Mg-Sc-Zr ALLOY

    Directory of Open Access Journals (Sweden)

    M. S. Kaiser

    2014-12-01

    Full Text Available The evaluation of texture as a function of recrystallization has been characterized for directly cold rolled Al-6Mg, Al-6Mg-0.4Sc and Al-6Mg-0.4Sc-0.2Zr alloys. Samples were annealed isothermally at 400 °C for 1 to 240 minutes to allow recrystallization. Recrystallization kinetics of the alloys is analyzed from the micro-hardness variation. Isothermally annealed samples of aluminum alloys were also studied using JMAK type analysis to see if there exists any correlation between the methods. Recrystallization fraction behavior between two methods the scandium added alloys show the higher variation due to precipitation hardening and higher recrystallization behavior. The scandium and zirconium as a combined shows the more variation due to formation of Al3(Sc, Zr precipitate. From the microstructure it is also observed that the base Al-Mg alloy attained almost fully re-crystallized state after annealing at 400 °C for 60 minutes

  12. Nicotine chewing gum (2 mg, 4 mg) and cigarette smoking: comparative effects upon vigilance and heart rate.

    Science.gov (United States)

    Parrott, A C; Winder, G

    1989-01-01

    Sixteen male smokers, abstinent the morning before testing, were assessed under four conditions: placebo chewing gum, 2 mg nicotine chewing gum, 4 mg nicotine gum, and cigarette smoking. Placebo gum was administered in the cigarette condition, while sham smoking occurred in the gum conditions. Pre-drug administration and post-drug difference scores were calculated for each assessment measure: rapid visual information processing (RVIP), memory for new information, and heart rate. Nicotine raised heart rate in a significant monotonic dose-related manner (P less than 0.001): placebo +0.2; 2 mg gum +5.1; 4 mg gum +9.8; cigarette +17.5 bpm. Rapid visual information processing target detections were also significantly related to dose (P less than 0.01), with this increased vigilance significant under 4 mg nicotine gum and cigarette smoking. Memory task performance was not significantly affected. Self-reported feelings of alertness/energy were higher while smoking than under placebo or 4 mg gum. Complaints about the taste of the 4 mg nicotine gum were frequent.

  13. Corrosion and Discharge Behaviors of Mg-Al-Zn and Mg-Al-Zn-In Alloys as Anode Materials

    Directory of Open Access Journals (Sweden)

    Jiarun Li

    2016-03-01

    Full Text Available The Mg-6%Al-3%Zn and Mg-6%Al-3%Zn-(1%, 1.5%, 2%In alloys were prepared by melting and casting. Their microstructures were investigated via metallographic and energy-dispersive X-ray spectroscopy (EDS analysis. Moreover, hydrogen evolution and electrochemical tests were carried out in 3.5 wt% NaCl solution aiming at identifying their corrosion mechanisms and discharge behaviors. The results suggested that indium exerts an improvement on both the corrosion rate and the discharge activity of Mg-Al-Zn alloy via the effects of grain refining, β-Mg17Al12 precipitation, dissolving-reprecipitation, and self-peeling. The Mg-6%Al-3%Zn-1.5%In alloy with the highest corrosion rate at free corrosion potential did not perform desirable discharge activity indicating that the barrier effect caused by the β-Mg17Al12 phase would have been enhanced under the conditions of anodic polarization. The Mg-6%Al-3%Zn-1.0%In alloy with a relative low corrosion rate and a high discharge activity is a promising anode material for both cathodic protection and chemical power source applications.

  14. MgB{sub 2} superconductors for applications

    Energy Technology Data Exchange (ETDEWEB)

    Glowacki, B A; Majoros, M; Eisterer, M; Toenies, S; Weber, H W; Fukutomi, M; Komori, K; Togano, K

    2003-05-01

    The paper presents up to date results on MgB{sub 2} filamentary conductors and coated conductors from the point of view of their possible applications. Basic physical parameters of MgB{sub 2} compound relevant to conductor design are introduced. The correlation between the slope of the irreversibility line, critical temperature and critical current density is discussed with respect to the conductor performance and applicability. The possible origin of the observed anomalous decrease of ac susceptibility at 50 K in copper clad in situ powder-in-tube MgB{sub 2} wires is presented. Some numerical results on critical currents, thermal stability and ac losses of the MgB{sub 2} multifilamentary and coated conductors with magnetic cladding of their filaments are given.

  15. Development of Al-Mg-Li alloys for fusion reactor

    International Nuclear Information System (INIS)

    Shoji, Yoshifusa; Yoshida, Hideo; Uno, Teruo; Baba, Yoshio; Kamada, Koji.

    1985-01-01

    Aluminum-magnesium-lithium alloys featuring low residual induced radioactivity and high electrical resistivity have been developed for fusion reactor structural materials. The addition of lithium in aluminum and Al-Mg alloys markedly increases electrical resistivity and tensile strength of them. However the elongation of Al-Mg-Li alloys containing more than 2 mass% lithium are less than 10 %. The Al-4--5 mass%Mg-1 mass%Li alloys are optimum for fusion reactor materials, and exhibit high resistivity (86 nΩm: 20 %IACS), medium strength (300 MPa) and good formability (22 % elongation). The variation of electrical resistivity of Al-Li and Al-Mg-Li alloys in solid solution can be approximated by the Matthiessen's rule. (author)

  16. $^{31}$Mg $\\beta$-NMR applied in chemistry and biochemistry

    CERN Multimedia

    Magnesium ions, Mg$^{2+}$, are essential in biological systems, taking part in practically all phosphate chemistry, in photosynthesis as an integral component of chlorophyll, and they are regulated via transport through selective membrane proteins. Nonetheless, the function of magnesium ions in biochemistry is difficult to characterize, as it is practically invisible to current experimental techniques. With this proposal we aim to advance the use of $^{31}$Mg $\\beta$-NMR to liquid samples, building on the experience from the successful Letter of Intent INTC-I-088 “$\\beta$-NMR as a novel technique for biological applications”. Initially a series of experiments will be conducted aiming to characterize the coordination chemistry of Mg$^{2+}$ in ionic liquids (ILs), demonstrating that it is possible within the lifetime of the radioisotope to achieve binding of Mg$^{2+}$ to a molecule dissolved in the IL. ILs are chosen as they display a very low vapor pressure, and are thus straightforwardly compatible with t...

  17. Soluble salts addition modifies MgO hydration

    International Nuclear Information System (INIS)

    Santos, A.M.; Pandolfelli, V.C.; Salomao, R.

    2012-01-01

    Magnesium oxide (MgO) show great technological interest on refractories due to its high refractoriness, basic slag corrosion resistance and competitive cost. However, the hydration reaction of MgO produces magnesium hydroxide. This reaction generates a significant volumetric expansion that can lead to material breakdown inhibiting its use in refractory castables. This reaction can be affected by several factors such as magnesia source, purity, calcination temperature, pH, CaO/SiO 2 ratio and agitation speed. In the present work, soluble salts (CaCl 2 and MgCl 2 ) were used in MgO aqueous suspensions (caustic and sinter). The results were evaluated by means of techniques of degree of hydration (termogravimetric), Scanning electron microscopy, apparent volumetric expansion and x-ray Diffraction which showed that the degree of hydration was noticeably less to sinter aqueous and the expansive effects were less with the addition of CaCl 2 . (author)

  18. MgO monolayer epitaxy on Ni (100)

    Science.gov (United States)

    Sarpi, B.; Putero, M.; Hemeryck, A.; Vizzini, S.

    2017-11-01

    The growth of two-dimensional oxide films with accurate control of their structural and electronic properties is considered challenging for engineering nanotechnological applications. We address here the particular case of MgO ultrathin films grown on Ni (100), a system for which neither crystallization nor extended surface ordering has been established previously in the monolayer range. Using Scanning Tunneling Microscopy and Auger Electron Spectroscopy, we report on experiments showing MgO monolayer (ML) epitaxy on a ferromagnetic nickel surface, down to the limit of atomic thickness. Alternate steps of Mg ML deposition, O2 gas exposure, and ultrahigh vacuum thermal treatment enable the production of a textured film of ordered MgO nano-domains. This study could open interesting prospects for controlled epitaxy of ultrathin oxide films with a high magneto-resistance ratio on ferromagnetic substrates, enabling improvement in high-efficiency spintronics and magnetic tunnel junction devices.

  19. The investigation of radiation induced defects in MgO

    International Nuclear Information System (INIS)

    Puetz, M.

    1990-05-01

    In this paper Frenkel defects were induced in MgO by 3 MeV electrons at low temperature. These defects were investigated by measurements of the optical absorption, by investigating the lattice parameters and Huang diffuse scattering. (WL)

  20. Facile fabrication of hydrophobic surfaces on mechanically alloyed-Mg/HA/TiO{sub 2}/MgO bionanocomposites

    Energy Technology Data Exchange (ETDEWEB)

    Khalajabadi, Shahrouz Zamani [Medical Devices and Technology Group (MEDITEG), Faculty of Biosciences and Medical Engineering, Universiti Teknologi Malaysia, 81310 Johor Bahru, Johor (Malaysia); Abdul Kadir, Mohammed Rafiq, E-mail: rafiq@biomedical.utm.my [Medical Devices and Technology Group (MEDITEG), Faculty of Biosciences and Medical Engineering, Universiti Teknologi Malaysia, 81310 Johor Bahru, Johor (Malaysia); Izman, Sudin; Mohd Yusop, Mohd Zamri [Department of Materials, Manufacturing and Industrial Engineering, Faculty of Mechanical Engineering, Universiti Teknologi Malaysia, 81310 Johor Bahru, Johor (Malaysia)

    2015-01-01

    Highlights: • Mg/HA/TiO{sub 2}-based nanocomposite was produced using mechanical alloying. • The hydrophobic surface coverage was fabricated on the mechanical alloyed samples by annealing. • The morphological characteristics, phase evolution and wettability of nanocomposites and the hydrophobic surface coverage were investigated. • The activation energies and reaction kinetic of the powder mixture of nanocomposites were calculated. - Abstract: The effect of mechanical alloying and post-annealing on the phase evolution, microstructure, wettability and thermal stability of Mg–HA–TiO{sub 2}–MgO composites was investigated in this study. Phase evolution and microstructure analysis were performed using X-ray diffraction, field-emission scanning electron microscopy, transmission electron microscopy and atomic force microscopy, as well as the wettability determined by contact angle measurements with SBF. The 16-h mechanical alloying resulted in the formation of MgTiO{sub 3}, CaTiO{sub 3}, Mg{sub 3}(PO{sub 4}){sub 2} and Mg(OH){sub 2} phases and a decrease in wettability of the nanocomposites. A hydrophobic film with hierarchical structures comprising nanoflakes of MgTiO{sub 3}, nano-cuboids of CaTiO{sub 3}, microspheres of Mg{sub 3}(PO{sub 4}){sub 2} and Mg(OH){sub 2} was successfully constructed on the surface of the Mg-based nanocomposites substrates as a result of the post-annealing process. After 1-h annealing at 630 °C, the synthesized hydrophobic surface on the nanocomposite substrates decreased the wettability, as the 8-h-mechanically alloyed samples exhibited a contact angle close to 93°. The formation activation energies and reaction kinetics of the powder mixture were investigated using differential thermal analysis and thermal gravimetric analysis. The released heat, weight loss percentage and reaction kinetics increased, while the formation activation energies of the exothermic reactions decreased following an increase in the milling time.

  1. Pseudopotential approach to superconductivity in MgB2

    International Nuclear Information System (INIS)

    Sharma, K.S.; Bhargava, Nidhi; Jain, Ritu; Goyal, Varsha; Sharma, Ritu; Sharma, Smita

    2010-01-01

    Superconductivity in MgB 2 has been re-examined in BCS-Eliashberg framework by employing Mc-Millan's T c -equation and form factors of MgB 2 computed from the form factors of component metals (Model-I). The empty core model pseudopotential due to Ashcroft and random phase approximation form of dielectric screening due to Gellmann and Brueckner are used in the present work. An excellent agreement between the present values and other theoretically computed values of T c and with the relevant experimental data for MgB 2 confirms the validity of the present approach. The explicit dependence of λ and T c on the isotopic masses of Mg and B, as revealed from the present work, confirms the role of lattice vibrations in the superconducting behaviour of MgB 2 and the high value of T c in it may be attributed to the phonon mediated e-e interaction coupled with higher values of phonon frequencies due to light mass of B atoms. It has also been observed that the pseudo-atom model (Model-II) with appropriate choice of the potential parameter r c successfully explains high value of T c and isotope effect in MgB 2 , confirming the prominent role played by electron-phonon interaction in the high-T c superconductivity observed in MgB 2 . The isotope effect exponent α-values obtained from the two models are in complete agreement with each other and the present value α = 0.46 is also much closer to the BCS value of 0.5. Interaction strength N 0 V values obtained from the two models are also in perfect agreement with each other and the present value N 0 V = 0.48 suggests that MgB 2 is a strong coupling superconductor. (author)

  2. The Abundance of Mg in the Interstellar Medium

    Science.gov (United States)

    Fitzpatrick, Edward L.

    1997-06-01

    An empirical determination of the f-values of the far-UV Mg II λλ1239, 1240 lines is reported. The strong near-UV Mg II λλ2796, 2803 lines are generally highly saturated along most interstellar sight lines outside the local interstellar medium (ISM) and usually yield extremely uncertain estimates of Mg+ column densities in interstellar gas. Since Mg+ is the dominant form of Mg in the neutral ISM, and since Mg is expected to be a significant constituent of interstellar dust grains, the far-UV lines are critical for assessing the role of this important element in the ISM. This study consists of complete component analyses of the absorption along the lines of sight toward HD 93521 in the Galactic halo and ξ Persei and ζ Ophiuchi in the Galactic disk, including all four UV Mg+ lines and numerous other transitions. The three analyses yield consistent determinations of the λλ1239, 1240 f-values, with weighted means of (6.4 +/- 0.4) × 10-4 and (3.2 +/- 0.2) × 10-4, respectively. These results are a factor of ~2.4 larger than a commonly used theoretical estimate, and a factor of ~2 smaller than a recently suggested empirical revision. The effects of this result on gas- and dust-phase abundance measurements of Mg are discussed. Based on observations with the NASA/ESA Hubble Space Telescope, obtained at the Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy, under NASA contract NAS5-2655. This Letter is dedicated to the memory of Professor Lyman Spitzer Jr. He was a great guy.

  3. Mg and Sr in Arctic echinoderm calcite: Nature or nurture?

    Science.gov (United States)

    Iglikowska, A.; Borszcz, T.; Drewnik, A.; Grabowska, M.; Humphreys-Williams, E.; Kędra, M.; Krzemińska, M.; Piwoni-Piórewicz, A.; Kukliński, P.

    2018-04-01

    The Mg/Ca and Sr/Ca ratios in echinoderm skeletal calcite are used as a proxy for Phanerozoic seawater changes, since the skeletal concentrations are, to some extent, controlled by environmental factors. However, it remains unclear how the influence of environmental factors is modified by vital effects, especially in polar waters. Therefore, the goal of this study was to compare the ratios of Mg/Ca and Sr/Ca among the skeletal parts of 10 common Arctic echinoderm species belonging to three classes Echinoidea, Asteroidea and Ophiuroidea that contribute substantially to the carbon cycle in the Arctic benthic system. Significant differences were recorded in echinoid skeletal element concentrations among specific skeletal parts. The lowest Mg/Ca and Sr/Ca ratios were detected in the spines (mean Mg/Ca 37.5 ± 8.8 SD; Sr/Ca 1.8 ± 0.1). The components of the Aristotle's lantern (epiphyses, pyramids and rotulas) were characterised by the highest Mg levels (Mg/Ca 79.9 ± 6.0; 75.2 ± 9.1; 60.1 ± 3.8, respectively). It is likely that mouth parts experience greater mechanical pressure compared to other body parts, and the higher content of Mg in the Aristotle's lantern contributes to its robustness. We did not find any distinctive trends in the distribution of skeletal elements in the asteroid and ophiuroid skeletal parts. The heterogeneous concentrations of Mg and Sr in different skeleton parts of the echinoids suggest possible physiological regulation of the chemical composition rather than the composition only being influenced by the environment. We cannot recommend echinoderm skeletons as reliable indicators in palaeoenvironmental reconstructions due to the possible biological control of skeletal chemistry, which may interfere with the effect of environmental variables.

  4. A metastable Mg11Sm phase obtained by rapid solidification

    International Nuclear Information System (INIS)

    Budurov, S.

    1993-01-01

    Molten Mg-Sm alloys with a Sm concentration of 4.93, 6.86, and 8.35 at.% were rapidly soldified with the aid of a shock wave gun device. Investigations of the obtained splats were performed with the aid of DSC, X-ray analysis, and metallography. Rapid soldification of the eutectic MgSm 8.35 alloy forms a new Im3m-type phase. (orig.)

  5. Strength of FePd/MgO and FePt/MgO interfaces from first principles

    Science.gov (United States)

    Černý, M.

    2018-04-01

    Cleavage characteristics such as the cleavage energy and the cleavage stress of FePd/MgO and FePt/MgO interfaces are computed from first principles. Considering several possible cleavage planes, the weakest link in these systems is found as the plane with the lowest cleavage stress. This weakest plane is identified in both systems with the interface plane, where the cohesion is reduced by 30% compared to the MgO bulk. Two distinct models of tensile test are employed to verify the results and convergence of computed values with respect to size of the simulation cell is discussed.

  6. A double-blind study comparing ibuprofen 1800 mg or 2400 mg daily and placebo in sports injuries.

    Science.gov (United States)

    Hutson, M A

    1986-01-01

    In a double-blind, placebo-controlled study of forty-six patients with acute ligamentous damage of the knee, ibuprofen in dosages 1800 mg and 2400 mg produced significant improvements in joint mobility, weight bearing ability and match fitness. Joint effusion, pain on stress and pain severity was significantly improved by all three treatments. Only two patients reported side-effects (one while taking placebo and one taking ibuprofen 2400 mg). The study confirmed the efficacy and excellent tolerance to ibuprofen in patients with sports injuries to the knee.

  7. Hydrogen incorporation in high hole density GaN:Mg

    Science.gov (United States)

    Zvanut, M. E.; Uprety, Y.; Dashdorj, J.; Moseley, M.; Doolittle, W. Alan

    2011-03-01

    We investigate hydrogen passivation in heavily doped p-type GaN using electron paramagnetic resonance (EPR) spectroscopy. Samples include both conventionally grown GaN (1019 cm-3 Mg, 1017 cm-3 holes) and films grown by metal modulation epitaxy (MME), which yielded higher Mg (1- 4 x 1020 cm-3) and hole (1- 40 x 1018 cm-3) densities than found in conventionally grown GaN. The Mg acceptor signal is monitored throughout 30 minute annealing steps in N2 :H2 (92%:7%)) and subsequently pure N2 . N2 :H2 heat treatments of the lower hole density films begin to reduce the Mg EPR intensity at 750 o C, but quench the signal in high hole density films at 600 o C. Revival of the signal by subsequent N2 annealing occurs at 800 o C for the low hole density material and 600 o C in MME GaN. The present work highlights chemical differences between heavily Mg doped and lower doped films; however, it is unclear whether the difference is due to changes in hydrogen-Mg complex formation or hydrogen diffusion. The work at UAB is supported by the NSF.

  8. In vitro degradation of pure Mg in response to glucose

    Science.gov (United States)

    Zeng, Rong-Chang; Li, Xiao-Ting; Li, Shuo-Qi; Zhang, Fen; Han, En-Hou

    2015-08-01

    Magnesium and its alloys are promising biodegradable biomaterials but are still challenging to be used in person with high levels of blood glucose or diabetes. To date, the influence of glucose on magnesium degradation has not yet been elucidated, this issue requires more attention. Herein, we present pure Mg exhibiting different corrosion responses to saline and Hank’s solutions with different glucose contents, and the degradation mechanism of pure Mg in the saline solution with glucose in comparison with mannitol as a control. On one hand, the corrosion rate of pure Mg increases with the glucose concentration in saline solutions. Glucose rapidly transforms into gluconic acid, which attacks the oxides of the metal and decreases the pH of the solution; it also promotes the absorption of chloride ions on the Mg surface and consequently accelerates corrosion. On the other hand, better corrosion resistance is obtained with increasing glucose content in Hank’s solution due to the fact that glucose coordinates Ca2+ ions in Hank’s solution and thus improves the formation of Ca-P compounds on the pure Mg surface. This finding will open up new avenues for research on the biodegradation of bio-Mg materials in general, which could yield many new and interesting results.

  9. Behavior of lambda 2800 Mg II in stellar spectra

    International Nuclear Information System (INIS)

    Gurzadyan, G.A.

    1975-01-01

    The results of measurements of the equivalent widths of the resonance doublet of ionized magnesium lambda 2800 Mg II in the spectra of 51 relatively faint stars, up to 10/sup m/, of the spectral classes B1-K5 are presented. The observed material has been obtained by means of the space observatory ''Orion-2''. Some regularities in the behavior of lambda 2800 Mg II in stellar spectra have been revealed: wide and deep depression of the continuous spectra at 2800 A in F-G type stars; the presence of the doublet lambda 2800 Mg II in the form of weak emission in the spectra of cold stars (K2-K5); the presence both of the multiplet lambda 3080 Ti II and the doublet lambda 2800 Mg II simultaneously either in emission--in the late-type stars--or in absorption in earlier types; the existence of combined profiles of lambda 2800 Mg II, i.e., a wide absorption line with a weak emission in the center, in stars of the transitional class (G5-K0), etc. A well-defined empirical relationship between the equivalent width of lambda 2800 Mg II and the spectral class of the star has been established (Fig. 8). (U.S.)

  10. 40 CFR 797.1600 - Fish early life stage toxicity test.

    Science.gov (United States)

    2010-07-01

    ... expressed as calcium carbonate (mg CaCO3/liter). (10) “Loading” the ratio of biomass (grams of fish, wet..., empty shells, opaque embryos, and embryos with fungus or partial shells attached shall be removed and...

  11. Loss of Endothelial Barrier in Marfan Mice (mgR/mgR Results in Severe Inflammation after Adenoviral Gene Therapy.

    Directory of Open Access Journals (Sweden)

    Philipp Christian Seppelt

    Full Text Available Marfan syndrome is an autosomal dominant inherited disorder of connective tissue. The vascular complications of Marfan syndrome have the biggest impact on life expectancy. The aorta of Marfan patients reveals degradation of elastin layers caused by increased proteolytic activity of matrix metalloproteinases (MMPs. In this study we performed adenoviral gene transfer of human tissue inhibitor of matrix metalloproteinases-1 (hTIMP-1 in aortic grafts of fibrillin-1 deficient Marfan mice (mgR/mgR in order to reduce elastolysis.We performed heterotopic infrarenal transplantation of the thoracic aorta in female mice (n = 7 per group. Before implantation, mgR/mgR and wild-type aortas (WT, C57BL/6 were transduced ex vivo with an adenoviral vector coding for human TIMP-1 (Ad.hTIMP-1 or β-galactosidase (Ad.β-Gal. As control mgR/mgR and wild-type aortas received no gene therapy. Thirty days after surgery, overexpression of the transgene was assessed by immunohistochemistry (IHC and collagen in situ zymography. Histologic staining was performed to investigate inflammation, the neointimal index (NI, and elastin breaks. Endothelial barrier function of native not virus-exposed aortas was evaluated by perfusion of fluorescent albumin and examinations of virus-exposed tissue were performed by transmission electron microscopy (TEM.IHC and ISZ revealed sufficient expression of the transgene. Severe cellular inflammation and intima hyperplasia were seen only in adenovirus treated mgR/mgR aortas (Ad.β-Gal, Ad.hTIMP-1 NI: 0.23; 0.43, but not in native and Ad.hTIMP-1 treated WT (NI: 0.01; 0.00. Compared to native mgR/mgR and Ad.hTIMP-1 treated WT aorta, the NI is highly significant greater in Ad.hTIMP-1 transduced mgR/mgR aorta (p = 0.001; p = 0.001. As expected, untreated Marfan grafts showed significant more elastolysis compared to WT (p = 0.001. However, elastolysis in Marfan aortas was not reduced by adenoviral overexpression of hTIMP-1 (compared to untreated

  12. MgB2 and Mg1-xAlxB2 single crystals: high pressure growth and physical properties

    International Nuclear Information System (INIS)

    Karpinski, J.; Kazakov, S.M.; Jun, J.; Zhigadlo, N.D.; Angst, M.; Puzniak, R.; Wisniewski, A.

    2004-01-01

    Single crystals of MgB 2 have been grown with a high pressure cubic anvil technique. They grow via the peritectic decomposition of the MgNB 9 ternary nitride. The crystals are of a size up to 2 x 1 x 0.1 mm 3 with a weight up to 230 μg. Typically they have transition temperatures between 38 and 38.6 K with a width of 0.3-0.5 K. Investigations of the P-T phase diagram prove that the MgB 2 phase is stable at least up to 2190 deg. C at high hydrostatic pressure in the presence of Mg vapor under high pressure. Substitution of aluminum for magnesium in single crystals leads to stepwise decrease of T c . This indicates a possible appearance of superstructures or phases with different T c 's. The upper critical field decreases with Al doping

  13. First-principles study of the (0001)-MgB2 surface finished in Mg and B

    International Nuclear Information System (INIS)

    Segura, Sully; Martínez, Jairo Arbey Rodríguez; Moreno-Armenta, María Guadalupe

    2014-01-01

    We present a study based on Density Functional Theory (DFT) of the volume and two surfaces (0001) of MgB 2 , one of them terminated in Mg and the other one terminated in B. Each one of the surface was relaxed and their electronic properties were determined. From calculation of the enthalpy of formation we found that the Mg-terminated surface is energetically favored. The bands seem to present a formation similar to the Dirac's cone as that are presented in graphene, but in MgB 2 is above of the Fermi level. In the three cases, volume and the two surfaces, the behaviour is boron-metallic, because there are strong presence of B orbital's in the neighborhood of the Ferm level

  14. Density functional theory (DFT) study on the hydrolysis behavior of degradable Mg/Mg alloys for biomedical applications

    Science.gov (United States)

    Nezafati, Marjan

    Magnesium-based (Mg and/or Mg alloys) materials possess many advantageous physicochemical/biological characteristics such as good biocompatibility and similarity of the mechanical properties to the human bone tissue, which renders this material a promising candidate for the biomedical and implant applications. One of the most attractive features of Mg-based materials is the degradability in the physiological environment. With the burst of research on the biodegradable materials for the healthcare device applications, Mg and its alloys attracted a strong attention in the bioengineering field in recent years. However, the major limitation of applying Mg-based materials to biomedical applications is the fast degradation/corrosion rate with regards to the healing process time-span. In the present thesis, an atomistic model employing the density-functional theory (DFT) has been developed to study the hydrolysis process by understanding the influences of commonly used alloying elements (zinc (Zn), calcium (Ca), aluminum (Al), and yttrium (Y)) and the crystallographic orientation of the dissolution surfaces (basal (0001), prism (1010), and pyramidal (1011) planes) on the corrosion behavior. These parameters are known to strongly impact the initial hydrolysis phenomena of Mg-based materials. To develop the atomistic computational model, we have implemented the Dmol3 software package in conjunction with PBE (Perdew, Burke and Ernzerhof) correlation energy functional in the GGA (generalized gradient approximation) scheme. Throughout the thesis, we performed three sets of calculations, i) surface energy, ii) dissolution potential, and iii) water adsorption computations, to examine the hydrolysis mechanism and the subsequent corrosion/degradation of Mg/Mg alloys. The total energy changes of various Mg-based systems in different conditions for these surface energies, dissolution behavior, and tendency of the system for adsorbing the water molecule were quantified. The results

  15. Phototransfered thermoluminescence for dose reassessment in LiF:mg,ti , LiF: mg,Cu,p TL detectors

    International Nuclear Information System (INIS)

    Rodriguez Otazo, M.; Baly, L.

    2001-01-01

    Phototransfered Thermoluminescence (PTTL) from LiF:Mg,Ti (TLD-100) and LiF: Mg,Cu,P (GR-200) was studied at different conditions using different sources of UV light for dose reassessment purposes. The TL dosimeters were irradiated with 137Cs in the range 2 mGy to 100 mGy. The convenience of using PTTL for dose reassessment was analyzed

  16. Corrosion inhibition of powder metallurgy Mg by fluoride treatments.

    Science.gov (United States)

    Pereda, M D; Alonso, C; Burgos-Asperilla, L; del Valle, J A; Ruano, O A; Perez, P; Fernández Lorenzo de Mele, M A

    2010-05-01

    Pure Mg has been proposed as a potential degradable biomaterial to avoid both the disadvantages of non-degradable internal fixation implants and the use of alloying elements that may be toxic. However, it shows excessively high corrosion rate and insufficient yield strength. The effects of reinforcing Mg by a powder metallurgy (PM) route and the application of biocompatible corrosion inhibitors (immersion in 0.1 and 1M KF solution treatments, 0.1M FST and 1M FST, respectively) were analyzed in order to improve Mg mechanical and corrosion resistance, respectively. Open circuit potential measurements, polarization techniques (PT), scanning electrochemical microscopy (SECM) and electrochemical impedance spectroscopy (EIS) were performed to evaluate its corrosion behavior. SECM showed that the local current of attacked areas decreased during the F(-) treatments. The corrosion inhibitory action of 0.1M FST and 1M FST in phosphate buffered solution was assessed by PT and EIS. Under the experimental conditions assayed, 0.1M FST revealed better performance. X-ray photoelectron spectroscopy, energy dispersive X-ray and X-ray diffraction analyses of Mg(PM) with 0.1M FST showed the presence of KMgF(3) crystals on the surface while a MgF(2) film was detected for 1M FST. After fluoride inhibition treatments, promising results were observed for Mg(PM) as degradable metallic biomaterial due to its higher yield strength and lower initial corrosion rate than untreated Mg, as well as a progressive loss of the protective characteristics of the F(-)-containing film which ensures the gradual degradation process. Copyright (c) 2009 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

  17. Corrosion behaviour of Mg-Cu and Mg-Mo composites in 3.5% NaCl

    International Nuclear Information System (INIS)

    Budruk Abhijeet, S.; Balasubramaniam, R.; Gupta, M.

    2008-01-01

    The corrosion behaviour of pure magnesium, Mg-Cu (0.3, 0.6, and 1 vol.%) and Mg-Mo (0.1, 0.3, and 0.6 vol.%) composites has been studied in 3.5% NaCl solution by weight loss and polarisation methods. Corrosion rates determined by weight loss method were considerably higher than that determined by polarisation method. The corrosion rate increased with increasing volume fraction of reinforcement in Mg-Cu and Mg-Mo composites. At the same volume fraction of reinforcement, molybdenum reinforced composite corroded faster than copper reinforced composite. The galvanic current density between Mg-Cu and Mg-Mo couples has been experimentally measured using zero resistance ammeter technique. The experimentally observed galvanic current densities were in close agreement with those obtained using mixed potential theory analysis. SEM observation of corroded samples confirmed microgalvanic activity at the matrix/reinforcement interfaces. The poor corrosion resistance of composites has been attributed to microgalvanic effects between the matrix and reinforcements and inferior quality of surface films

  18. Experimental investigation and thermodynamic calculation of the Fe-Mg-Mn and Fe-Mg-Ni systems

    Energy Technology Data Exchange (ETDEWEB)

    Wang, Peisheng; Zhao, Jingrui; Xu, Honghui; Liu, Shuhong; Ouyang, Hongwu [Central South Univ., Hunan (China). State Key Lab. of Powder Metallurgy; Du, Yong [Central South Univ., Hunan (China). State Key Lab. of Powder Metallurgy; Harbin Institute of Technology (China). State Key Lab. of Advanced Welding Production Technology; Gang, Tie; Fen, Jicai [Harbin Institute of Technology (China). State Key Lab. of Advanced Welding Production Technology; Zhang, Lijun [Central South Univ., Hunan (China). State Key Lab. of Powder Metallurgy; Bochum Univ. (Germany). ICAMS Inst.; He, Cuiyun [Guangxi Univ. (China). College of Physical Science and Technology

    2011-01-15

    Based on the thermodynamic calculations extrapolated from the corresponding binary sub-systems, four decisive alloys in the Fe-Mg-Mn system and three in the Fe-Mg-Ni system were selected and prepared using a powder metallurgy method to measure the isothermal sections at 500 C in both systems. The prepared samples were annealed at 500 C, and then subjected to X-ray diffraction, optical microscopy, scanning electron microscopy with energy-dispersive X-ray spectrometry as well as electron probe microanalysis. Taking into account the presently obtained experimental data and the experimental data available in the literature, thermodynamic modeling was performed for the above systems. It was found that a direct extrapolation from the corresponding three binary systems can well reproduce all the experimental data in the Fe-Mg-Mn system, while two thermodynamic parameters are needed in the Fe-Mg-Ni system to fit all the experimental data. The liquidus projections and reaction schemes for the Fe-Mg-Mn and Fe-Mg-Ni systems are also presented. (orig.)

  19. Comparison of effects of ATP-MgCl2 and adenosine-MgCl2 on renal function following ischemia

    International Nuclear Information System (INIS)

    Sumpio, B.E.; Hull, M.J.; Baue, A.E.; Chaudry, I.H.

    1987-01-01

    ATO-MgCl 2 administration had been shown to accelerate the recovery of renal function following warm ischemia. However, since the major breakdown product of ATP is adenosine, the relative contribution of ATP vs. adenosine in improving renal function following ischemia remains to be determined. To study this, kidneys were subjected to 45 min of normothermic ischemia and then perfused at 100 mmHg with oxygenated Krebs-HCO 3 buffer containing albumin, [ 3 H]inulin, substrates, and either 0.3 mM ATP-MgCl 2 or adenosine-MgCl 2 for 110 min. Perfusate and timed urine samples were collected and analyzed for radioactivity and [Na + ]. The functional parameters indicated that although adenosine-MgCl 2 treatment provided a transient improvement, it failed to provided a sustained improvement in renal function or attain control valued compared with ATP-MgCl 2 treatment. Thus, the salutary effects of ATP-MgCl 2 following warm ischemia in the kidney are not mediated by adenosine

  20. Influences of the quantity of Mg2Sn phase on the corrosion behavior of Mg-7Sn magnesium alloy

    International Nuclear Information System (INIS)

    Liu Xianbin; Shan Dayong; Song Yingwei; Chen Rongshi; Han Enhou

    2011-01-01

    The influence of the quantity of the Mg 2 Sn phase on the corrosion behavior of different solution temperature treated Mg-7Sn magnesium alloy has been investigated by electrochemical measurements, scanning electron microscope (SEM) observation, X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS) analysis. With the increase of solution temperature, the quantity of Mg 2 Sn phase decreased and the tin concentration of matrix increased. The dissolved tin in Mg matrix took part in the film formation and the constituent of film was magnesium oxide and stannic oxide. The corrosion mode and corrosion rate were associated with the quantity of Mg 2 Sn phases and tin concentration of the matrix. If most of tin was present as Mg 2 Sn, the corrosion mode was pitting corrosion and it accelerated the corrosion rate. If most of tin was dissolved in matrix, the corrosion mode was filiform corrosion and it decreased the corrosion rate. The experiment evidences demonstrated that the corrosion resistance can be improved by increasing the tin concentration of matrix and the lowest corrosion rate was observed for sample solution treated at 540 o C.

  1. Formation of Al3Ti/Mg composite by powder metallurgy of Mg-Al-Ti system.

    Science.gov (United States)

    Yang, Zi R; Qi Wang, Shu; Cui, Xiang H; Zhao, Yu T; Gao, Ming J; Wei, Min X

    2008-07-01

    An in situ titanium trialuminide (Al 3 Ti)-particle-reinforced magnesium matrix composite has been successfully fabricated by the powder metallurgy of a Mg-Al-Ti system. The reaction processes and formation mechanism for synthesizing the composite were studied by differential scanning calorimetry (DSC), x-ray diffractometry (XRD), scanning electron microscopy (SEM) and energy-dispersive x-ray spectroscopy (EDS). Al 3 Ti particles are found to be synthesized in situ in the Mg alloy matrix. During the reaction sintering of the Mg-Al-Ti system, Al 3 Ti particles are formed through the reaction of liquid Al with as-dissolved Ti around the Ti particles. The formed intermetallic particles accumulate at the original sites of the Ti particles. As sintering time increases, the accumulated intermetallic particles disperse and reach a relatively homogeneous distribution in the matrix. It is found that the reaction process of the Mg-Al-Ti system is almost the same as that of the Al-Ti system. Mg also acts as a catalytic agent and a diluent in the reactions and shifts the reactions of Al and Ti to lower temperatures. An additional amount of Al is required for eliminating residual Ti and solid-solution strengthening of the Mg matrix.

  2. Catalytic effect of Ni, Mg2Ni and Mg2NiH4 upon hydrogen desorption from MgH2

    Czech Academy of Sciences Publication Activity Database

    Čermák, Jiří; David, Bohumil

    2011-01-01

    Roč. 36, č. 21 (2011), s. 13614-13620 ISSN 0360-3199 R&D Projects: GA ČR GA106/09/0814; GA ČR(CZ) GAP108/11/0148 Institutional research plan: CEZ:AV0Z20410507 Keywords : MgH2 * Hydrogen storage * Hydrogen desorption * Catalysis Subject RIV: JG - Metallurgy Impact factor: 4.054, year: 2011

  3. Photoneutron strengths in 26Mg at energies of astrophysical interest

    Science.gov (United States)

    deBoer, R. J.; Best, A.; Görres, J.; Smith, K.; Tan, W.; Wiescher, M.; Raut, R.; Rusev, G.; Tonchev, A. P.; Tornow, W.

    2014-05-01

    Background: The 22Ne(α,n)25Mg reaction is an important source of neutrons for s-process nucleosynthesis. The neutron production from the reaction is quite sensitive to the low-energy cross section, which is dominated by narrow resonances. The high level density of the 26Mg compound nucleus above the α separation energy prevents simple extrapolations from higher energy and the high Coulomb barrier makes the direct measurements extremely difficult. For this reason, indirect methods must be employed to study the level properties of 26Mg. Purpose: The current measurement utilizes the reaction 26Mg(γ,n)25Mg to probe the level structure of the 26Mg compound nucleus from the neutron-separation energy at 11.093 MeV up to Ex≈ 12 MeV. Methods: The High-Intensity γ-ray Source of the Triangle Universities Nuclear Laboratory was used to bombard a ˜16 g sample of enriched 26Mg oxide and the resulting decay neutrons were detected with an array of nine liquid scintillator detectors. Neutron time-of-flight peaks with corresponding energies as low as ˜50 keV were detected. An efficiency measurement of the detectors was made at the University of Notre Dame's nuclear science laboratory to energies as low as 45 keV. Results: Five resonances were observed at Eγ = 11.150, 11.289, 11.329, 11.506, and 11.749 MeV and their strengths have been extracted. Conclusion:. The resulting strengths at Eγ = 11.289, 11.329, 11.506, and 11.749 MeV are in good agreement with previous measurements. The strength of the resonance at Eγ = 11.150 MeV is somewhat lower than previously measured but is in reasonable agreement when systematic uncertainties are considered. The results are also consistent with those of 25Mg(n,γ)26Mg studies where a comparison shows that many of the resonances observed here are the result of multiple unresolved narrow resonances.

  4. Ab initio calculations of half-metallic ferromagnetism in Cr-doped MgSe and MgTe semiconductors

    Energy Technology Data Exchange (ETDEWEB)

    Noor, N.A. [Department of Physics, University of the Punjab, Quaid-e-Azam Campus, 54590 Lahore (Pakistan); Alay-e-Abbas, S.M. [Department of Physics, University of Sargodha, Sargodha 40100 (Pakistan); Department of Physics, GC University Faisalabad, Allama Iqbal Road, Faisalabad 38000 (Pakistan); Sohaib, M.U. [Lahore Development Authority, 54590 Lahore (Pakistan); Ghulam Abbas, S.M. [Department of Chemistry, University of Agriculture, Faisalabad 38040 (Pakistan); Shaukat, A., E-mail: schaukat@gmail.com [Department of Physics, University of Sargodha, Sargodha 40100 (Pakistan)

    2015-01-15

    The full-potential linear-augmented-plane-waves plus local-orbitals (FP-LAPW+lo) method has been employed for investigation of half-metallic ferromagnetism in Cr-doped ordered zinc-blende MgSe and MgTe semiconductors. Calculations of exchange and correlation (XC) effects have been carried out using generalized gradient approximation (GGA) and orbital independent modified Becke–Johnson potential coupled with local (spin) density approximation (mBJLDA). The thermodynamic stability of the compounds and their preferred magnetic orders have been analyzed in terms of the heat of formation and minimum total energy difference in ferromagnetic (FM) and anti-ferromagnetic (AFM) ordering, respectively. Calculated electronic properties reveal that the Cr-doping induces ferromagnetism in MgSe and MgTe which gives rise to a half-metallic (HM) gap at Fermi level (E{sub F}). Further, the electronic band structure is discussed in terms of s (p)–d exchange constants that are consistent with typical magneto-optical experiment and the behavior of charge spin densities is presented for understanding the bonding nature. Our results demonstrate that the higher effective potential for the spin-down case is responsible for p–d exchange splitting. Total magnetic moment (mainly due to Cr-d states) of these compounds is 4µ{sub B}. Importantly, the electronic properties and HM gap obtained using mBJLDA show remarkable improvement as compared to the results obtained using standard GGA functional. - Highlights: • Spin effect theoretical study on Cr-doped MgSe and MgTe is performed. • Half-metallic ferromagnetism in Cr{sub x}Mg{sub 1−x}Se and Cr{sub x}Mg{sub 1−x}Te is established. • Results of WC-GGA and mBJLDA are compared for performance. • HM gaps for Cr{sub x}Mg{sub 1−x}Se and Cr{sub x}Mg{sub 1−x}Te show nonlinear variation with x. • Important values of exchange splitting/constants and moments are reported.

  5. Dry cryomagnetic system with MgB2 coil

    Science.gov (United States)

    Abin, D. A.; Mineev, N. A.; Osipov, M. A.; Pokrovskii, S. V.; Rudnev, I. A.

    2017-12-01

    MgB2 may be the future superconducting wire material for industrial magnets due to it’s higher operation temperature and potentially lower cost than low temperature superconductors (LTS) have. We designed a compact cryomagnetic system with the use of MgB2. The possibility of creating a magnet with a central field of 5 T from a commercial MgB2 wire by the “react and wound” method was investigated. The magnetic system is cooled by a cryocooler through a copper bus. The magnet has a warm bore diameter of 4 cm. The design of a magnet consisting of three concentric solenoids is proposed: an internal one of high-temperature superconductor (HTS), an average of MgB2, and an external of NbTi. The operating current of the system is 100 A. Two pairs of current leads are used. A separate pair of current leads for power supplying NbTi coil allows testing of MgB2 and HTS coils in an external field. The load curves for each of the magnets are calculated.

  6. Multifunctional MgO Layer in Perovskite Solar Cells.

    Science.gov (United States)

    Guo, Xudong; Dong, Haopeng; Li, Wenzhe; Li, Nan; Wang, Liduo

    2015-06-08

    A multifunctional magnesium oxide (MgO) layer was successfully introduced into perovskite solar cells (PSCs) to enhance their performance. MgO was coated onto the surface of mesoporous TiO(2) by the decomposition of magnesium acetate and, therefore, could block contact between the perovskite and TiO(2). X-ray photoelectron spectroscopy and infrared spectroscopy showed that the amount of H(2)O/hydroxyl absorbed on the TiO(2) decreased after MgO modification. The UV/Vis absorption spectra of the perovskite with MgO modification revealed an enhanced photoelectric performance compared with that of unmodified perovskite after UV illumination. In addition to the photocurrent, the photovoltage and fill factor also showed an enhancement after modification, which resulted in an increase in the overall efficiency of the cell from 9.6 to 13.9 %. Electrochemical impedance spectroscopy (EIS) confirmed that MgO acts as an insulating layer to reduce charge recombination. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  7. Formation of MgZnO alloy under thermodynamic conditions

    Energy Technology Data Exchange (ETDEWEB)

    Markevich, I.V.; Stara, T.R., E-mail: stara_t@ukr.net; Kuchuk, A.V.; Polishchuk, Yu.O.; Kladko, V.P.

    2014-11-15

    Mg{sub x}Zn{sub 1−x}O ceramics with x=0.10, 0.15, 0.20, 0.25 and 0.30 were sintered at T{sub s}=700–1250 °C. Photoluminescence (PL) and PL excitation (PLE) spectra as well as X-ray diffraction patterns were measured at 293 K. Bandgap width was evaluated from the position of PLE peak. Non-monotonous dependence of PLE peak position on T{sub s} was observed for all used x. This effect was concluded to be caused by the formation of cubic phase side by side with hexagonal one and the enhancement of this process with increasing T{sub s}, which resulted in the decrease of Mg content in the hexagonal phase at T{sub s}>1000 °C. Temperature range of 1000–1050 °C was found to be the optimum one for the formation of hexagonal MgZnO alloy at used x. It was shown that x=0.20 was the solubility limit of MgO in hexagonal Mg{sub x}Zn{sub 1−x}O ceramics.

  8. Use of porous MgO in pyrochemical applications

    International Nuclear Information System (INIS)

    Maiya, P.S.; Sweeney, S.M.; Carroll, L.A.; Dusek, J.T.

    1994-11-01

    Pyrochemical methods for the extraction of transuranic elements from light water reactor spent fuel require a reduction step in which the oxide fuel is reduced to metals by Li in molten LiCl. The Li 2 O formed is electrolytically reduced to metal in a cell that uses a carbon (or inert) anode and a Li cathode to recycle the salt and minimize the waste. Use of a carbon anode causes carbon dust that interferes with the process. Moreover, current efficiency is reduced as a result of oxidation of Li to Li 2 O by CO 2 . A porous MgO shroud around the anode was found to obviate these problems. Porous MgO crucibles and rectangular bar specimens were fabricated from MgO powders (electrically fused MgO, reagent grade MgO were mixed in appropriate combinations with a binder and lubricant). Particle size, force applied to the powders during cold pressing, and sintering temperature were varied to achieve a total porosity of >45% (mostly open porosity) and to control pore size and pore distribution. Mercury intrusion porosimetry was used to determine the pore size and pore size distribution. Flexural strength is observed to be proportional to the square root of pore size, which is consistent with fracture mechanics

  9. Magnesium balances and 28Mg studies in man

    International Nuclear Information System (INIS)

    Spencer, H.; Schwartz, R.; Osis, D.

    1988-01-01

    The intestinal absorption of magnesium was determined under strictly controlled dietary conditions in patients with normal renal function and also in patients with chronic renal failure. The average net absorption of magnesium of patients with normal renal function, expressed as percent of the magnesium intake, was 48.5%, while that of patients with chronic renal failure was significantly lower, 17%. Increasing the calcium intake from a low calcium intake of 200 mg/day to different higher intake levels up to 2000 mg/day did not change the magnesium balance nor the net absorption of magnesium of both types of patients. The lack of effect of the higher calcium intake on the absorption of magnesium was confirmed in 28 Mg studies in which an oral dose of 28 Mg, as the chloride, was given. The excretion of the absorbed magnesium into the intestine, the endogenous fecal magnesium, was low. Also, increasing the phosphorus intake up to 2000 mg/day in subjects with normal renal function did not affect the magnesium balance, regardless of the calcium intake

  10. Mg-MOF-74/MgF₂ Composite Coating for Improving the Properties of Magnesium Alloy Implants: Hydrophilicity and Corrosion Resistance.

    Science.gov (United States)

    Liu, Wei; Yan, Zhijie; Ma, Xiaolu; Geng, Tie; Wu, Haihong; Li, Zhongyue

    2018-03-07

    Surface modification on Mg alloys is highly promising for their application in the field of bone repair. In this study, a new metal-organic framework/MgF₂ (Mg-MOF-74/MgF₂) composite coating was prepared on the surface of AZ31B Mg alloy via pre-treatment of hydrofluoric acid and in situ hydrothermal synthesis methods. The surface topography of the composite coating is compact and homogeneous, and Mg-MOF-74 has good crystallinity. The corrosion resistance of this composite coating was investigated through Tafel polarization test and immersion test in simulated body fluid at 37 °C. It was found that Mg-MOF-74/MgF₂ composite coating significantly slowed down the corrosion rate of Mg alloy. Additionally, Mg-MOF-74/MgF₂ composite coating expresses super-hydrophilicity with the water contact angle of nearly 0°. In conclusion, on the basis of MgF₂ anticorrosive coating, the introduction of Mg-MOF-74 further improves the biological property of Mg alloys. At last, we propose that the hydrophilicity of the composite coating is mainly owing to the large number of hydroxyl groups, the high specific surface area of Mg-MOF-74, and the rough coating produced by Mg-MOF-74 particles. Hence, Mg-MOF-74 has a great advantage in enhancing the hydrophilicity of Mg alloy surface.

  11. Comparative study of 250 mg/day terbinafine and 100 mg/day itraconazole for the treatment of cutaneous sporotrichosis.

    Science.gov (United States)

    Francesconi, Glaucia; Francesconi do Valle, Antonio Carlos; Passos, Sonia Lambert; de Lima Barros, Mônica Bastos; de Almeida Paes, Rodrigo; Curi, André Luiz Land; Liporage, José; Porto, Cássio Ferreira; Galhardo, Maria Clara Gutierrez

    2011-05-01

    Itraconazole is currently used for the treatment of cutaneous sporotrichosis. Terbinafine at a daily dose of 250 mg has been successfully applied to the treatment of cutaneous sporotrichosis. To compare the efficacy of 250 mg/day terbinafine and 100 mg/day itraconazole for the treatment of cutaneous sporotrichosis. A bidirectional cohort study was conducted on 55 patients receiving 250 mg/day terbinafine and 249 patients receiving 100 mg/day itraconazole. The latter patients were matched for age and clinical form to the terbinafine group at a ratio of 5:1. Sporothrix schenckii was isolated by culture from all patients (age range: 18-70 years), who were submitted to the standard care protocol consisting of clinical and laboratory evaluation and periodic visits. Cure was observed in 51 (92.7%) patients of the terbinafine group and 229 (92%) of the itraconazole group within a similar mean period of time (11.5 and 11.8 weeks, respectively). An increase in the terbinafine dose to 500 mg was necessary in two patients due to the lack of a response, and one patient presented recurrence. In the itraconazole group, two patients required a dose increase and three presented recurrence. Adverse events were equally frequent among patients receiving terbinafine (n = 4, 7.3%) and itraconazole (n = 19, 7.6%) and were generally mild without the need for drug discontinuation, except for two patients of the itraconazole group. Terbinafine administered at a daily dose of 250 mg is an effective and well-tolerated option for the treatment of cutaneous sporotrichosis.

  12. Stability of rapidly quenched and hydrogenated Mg-Ni-Y and Mg-Cu-Y alloys in extreme alkaline medium

    International Nuclear Information System (INIS)

    Gebert, A.; Khorkounov, B.; Wolff, U.; Mickel, Ch.; Uhlemann, M.; Schultz, L.

    2006-01-01

    Amorphous-nanocrystalline Mg 50 Ni 30 Y 20 and Mg 63 Ni 30 Y 7 and amorphous Mg 65 Cu 25 Y 10 alloys were produced by melt-spinning and characterized regarding their microstructure and thermal behaviour using XRD, TEM and DSC. Their electrochemical behaviour in the as-quenched state and after hydrogen charging at -25 mA/cm 2 for up to 20 h was studied in electrolytes with pH 5-7 and 13, but mainly in a battery electrolyte: 6 M KOH with pH 14.8 by means of anodic and cathodic polarization measurements. In the as-quenched state, the highest alloys stability was observed at pH 13. At pH 14.8, gradual oxidation and dissolution of copper or nickel governs the anodic behaviour before a passive state is attained. The dissolution of nickel is much more inhibited than that of copper due to its lower tendency to form soluble oxidized ions and to a stabilizing effect of higher fractions of yttrium in the alloy on the passivation. By galvanostatic charging, the Mg 65 Cu 25 Y 10 alloy shows the highest hydrogen absorption capacity followed by Mg 50 Ni 30 Y 20 and Mg 63 Ni 30 Y 7 . During the charging process, the alloys exhibit a change in the surface state chemistry, i.e. an enrichment of nickel- or copper-rich species, causing preferential oxidation and dissolution during subsequent exposure under free corrosion and anodic conditions. Mg-Ni-Y alloys demonstrate a higher stability during this treatment in extreme alkaline medium. The reasons for this and consequences regarding the use as electrode materials are discussed in detail

  13. Optical absorption and thermoluminescence in Mg O, Mg O:Ni and Mg O:Li irradiated at room temperature; Absorcion optica y termoluminiscencia en MgO, MgO:Ni y MgO:Li irradiados a temperatura ambiente

    Energy Technology Data Exchange (ETDEWEB)

    Delgado, L

    1984-07-01

    Optical absorption and thermoluminescence (TL) studies in Mg O, Mg O:Ni and Mg O:Li irradiated at room temperature are presented. In pure Mg O the thermal annihilation of Fe3+ by recombination with thermally released electrons at {approx} 90 and 175 degree centigree and the V center annealing by hole release up to 100 degree centigree cause the observed glow peaks at these temperatures. The TL excitation spectrum shows two maxima at 245 nm (electron center) and 288 nm (Fe3+). In Mg O:Ni X irradiation induces Fe{sup 2}+ {yields}- Fe{sup 3}+ and Ni{sup 2}+ {yields} Ni{sup 3}+ oxidations. Two TL emission bands centered at 110 degree centigree (red) and 80 o{sup C} (green) are assigned to electron release and their recombination at Fe{sup 3}+ and Ni{sup 3}+ respectively. In Mg O:Li two TL emission bands, one blue (430 nm) and the other red (730 nm) with excitation maxima at 245 nm (electron center) and 200 nm (hole center) respectively are observed. No V-center formation was detected in both Ni and Li doped samples. (Author) 42 refs.

  14. Thermophysical properties of some liquid binary Mg-based alloys

    Directory of Open Access Journals (Sweden)

    Plevachuk Y.

    2017-01-01

    Full Text Available In this study, some structure-sensitive thermophysical properties, namely, electrical conductivity, thermal conductivity and thermoelectric power of liquid binary alloys Al33.3Mg66.7, Mg47.6Zn52.4 and Mg33.3Zn66.7 (all in wt.%, as the most promising cast alloys to fabricate components for cars, aircraft and other complex engineering products, were investigated. The electrical conductivity and thermoelectric power were measured in a wide temperature range by the four-point contact method. The thermal conductivity was measured by the steady-state concentric cylinder method. The obtained results are compared with literature experimental and calculated data.

  15. Improved Mg-based alloys for hydrogen storage

    Energy Technology Data Exchange (ETDEWEB)

    Sapru, K.; Ming, L.; Stetson, N.T.; Evans, J. [Energy Conversion Devices, Inc., Troy, MI (United States)

    1998-08-01

    The overall objective of this on-going work is to develop low temperature alloys capable of reversibly storing at least 3 wt.% hydrogen, allowing greater than for 2 wt.% at the system level which is required by most applications. Surface modification of Mg can be used to improve its H-sorption kinetics. The authors show here that the same Mg-transition metal-based multi-component alloy when prepared by melt-spinning results in a more homogeneous materials with a higher plateau pressure as compared to preparing the material by mechanical grinding. They have also shown that mechanically alloyed Mg{sub 50}Al{sub 45}Zn{sub 5} results in a sample having a higher plateau pressure.

  16. Beta decay of 31,32Na and 31Mg

    International Nuclear Information System (INIS)

    Klotz, G.; Baumann, P.; Bounajma, M.; Huck, A.; Knipper, A.; Walter, G.; Poves, A.; Retamosa, J.

    1993-01-01

    31,32 Na and 31 Mg beta decays were studied at the CERN on-line mass separator ISOLDE by gamma, gamma-gamma and neutron-gamma measurements. In the 31 Na decay, the assignment of previously reported γ transitions and the observation of a new level at 3760 keV lead to a revised decay scheme. In the 31 Mg → 31 Al decay, a new decay scheme involves ten β branches and three states are reported for the first time. New spectroscopic results have been obtained in the 32 Na β - decay. A previously non-interpreted 1436 keV γ ray is now assigned in the 32 Mg scheme. (author) 33 refs., 16 figs., 12 tabs

  17. Beta-delayed proton emission from {sup 20}Mg

    Energy Technology Data Exchange (ETDEWEB)

    Lund, M.V.; Fynbo, H.O.U.; Howard, A.M.; Kirsebom, O.S.; Munch, M.; Riisager, K. [Aarhus University, Department of Physics and Astronomy, Aarhus C (Denmark); Andreyev, A.; Wadsworth, R. [University of York, Department of Physics, York (United Kingdom); Borge, M.J.G. [CSIC, Instituto de Estructura de la Materia, Madrid (Spain); CERN, ISOLDE, PH Department, Geneva 23 (Switzerland); Cederkaell, J. [Lund University, Department of Nuclear Physics, Lund (Sweden); Witte, H. de; Huyse, M.; Duppen, P. van [Instituut voor Kern- en Stralingsfysica, KU-Leuven, Leuven (Belgium); Fraile, L.M.; Vedia, V. [Universidad Complutense de Madrid, CEI Moncloa, Facultad de Ciencias Fisicas, Madrid (Spain); Greenlees, P.T.; Konki, J.; Rahkila, P. [University of Helsinki, Helsinki Institute of Physics, Helsinki (Finland); University of Jyvaeskylae, Department of Physics, Jyvaeskylae (Finland); Harkness-Brennan, L.J.; Judson, D.S.; Page, R.D. [University of Liverpool, Department of Physics, Oliver Lodge Laboratory, Liverpool (United Kingdom); Jonson, B.; Lindberg, S.; Nilsson, T. [Chalmers University of Technology, Department of Physics, Goeteborg (Sweden); Kurcewicz, J.; Madurga, M.; Rapisarda, E. [CERN, ISOLDE, PH Department, Geneva (Switzerland); Lazarus, I.; Pucknell, V. [STFC Daresbury, Daresbury, Warrington (United Kingdom); Lica, R. [CERN, ISOLDE, PH Department, Geneva (Switzerland); ' ' Horia Hulubei' ' National Institute of Physics and Nuclear Engineering, Magurele (Romania); Marginean, N.; Marginean, R.; Mihai, C.; Negret, A.; Pascu, S.; Rotaru, F.; Stanoiu, M.; Turturica, A. [' ' Horia Hulubei' ' National Institute of Physics and Nuclear Engineering, Magurele (Romania); Marroquin, I.; Nacher, E.; Perea, A.; Tengblad, O. [CSIC, Instituto de Estructura de la Materia, Madrid (Spain); Sotty, C. [Instituut voor Kern- en Stralingsfysica, KU-Leuven, Leuven (Belgium); ' ' Horia Hulubei' ' National Institute of Physics and Nuclear Engineering, Magurele (Romania); Warr, N. [Universitaet Koeln, Institut fuer Kernphysik, Koeln (Germany); Collaboration: IDS Collaboration

    2016-10-15

    Beta-delayed proton emission from {sup 20} Mg has been measured at ISOLDE, CERN, with the ISOLDE Decay Station (IDS) setup including both charged-particle and gamma-ray detection capabilities. A total of 27 delayed proton branches were measured including seven so far unobserved. An updated decay scheme, including three new resonances above the proton separation energy in {sup 20}Na and more precise resonance energies, is presented. Beta-decay feeding to two resonances above the Isobaric Analogue State (IAS) in {sup 20}Na is observed. This may allow studies of the 4032.9(2.4) keV resonance in {sup 19}Ne through the beta decay of {sup 20}Mg, which is important for the astrophysically relevant reaction {sup 15}O(α, γ){sup 19}Ne. Beta-delayed protons were used to obtain a more precise value for the half-life of {sup 20}Mg, 91.4(1.0) ms. (orig.)

  18. Electromagnetic densification of MgB2/Cu wires

    International Nuclear Information System (INIS)

    Woźniak, M; Glowacki, B A

    2014-01-01

    Electromagnetic compaction of in situ MgB 2 /Cu wire has been achieved using a custom-built 200 J device. The monofilament core packing density was increased by 8% and up to 31% for unreacted and reacted wires respectively. The higher density of the MgB 2 core resulted in a critical current density increase of up to 75% in comparison to that for cold-drawn-only wire. Applying this treatment to a wire with Cu powder additions to the core and with an optimized heat treatment resulted in one of the highest ever reported values of J c for MgB 2 /Cu wires of 6.83 × 10 3  A cm −2 at 4.2 K and 6 T. (paper)

  19. Strong, Ductile, and Thermally Stable bcc-Mg Nanolaminates.

    Science.gov (United States)

    Pathak, Siddhartha; Velisavljevic, Nenad; Baldwin, J Kevin; Jain, Manish; Zheng, Shijian; Mara, Nathan A; Beyerlein, Irene J

    2017-08-15

    Magnesium has attracted attention worldwide because it is the lightest structural metal. However, a high strength-to-weight ratio remains its only attribute, since an intrinsic lack of strength, ductility and low melting temperature severely restricts practical applications of Mg. Through interface strains, the crystal structure of Mg can be transformed and stabilized from a simple hexagonal (hexagonal close packed hcp) to body center cubic (bcc) crystal structure at ambient pressures. We demonstrate that when introduced into a nanocomposite bcc Mg is far more ductile, 50% stronger, and retains its strength after extended exposure to 200 C, which is 0.5 times its homologous temperature. These findings reveal an alternative solution to obtaining lightweight metals critically needed for future energy efficiency and fuel savings.

  20. MgB2 superconducting wires basics and applications

    CERN Document Server

    2016-01-01

    The compendium gives a complete overview of the properties of MgB2 (Magnesium Diboride), a superconducting compound with a transition temperature of Tc = 39K, from the fundamental properties to the fabrication of multifilamentary wires and to the presentation of various applications. Written by eminent researchers in the field, this indispensable volume not only discusses superconducting properties of MgB2 compounds, but also describes known preparation methods of thin films and of bulk samples obtained under high pressure methods. A unique selling point of the book is the detailed coverage of various applications based on MgB2, starting with MRI magnets and high current cables, cooled by Helium (He) vapor. High current cables cooled by liquid hydrogen are also highlighted as an interesting alternative due to the shrinking He reserves on earth. Other pertinent subjects comprise permanent magnets, ultrafine wires for space applications and wind generator projects.

  1. Thermodynamic evaluation of the Cu-Mg-Zr system

    International Nuclear Information System (INIS)

    Haemaelaeinen, M.; Zeng, K.

    1999-01-01

    The thermodynamic evaluation of the Cu-Mg-Zr system is presented in this paper. A literature survey was carried out first based on the most recent literature, which was scanned from the THERMET literature database. The evaluation of the thermodynamic parameters was carried out using Thermo-Calc (version H) software. The evaluation of the Cu-Mg-Zr system was carried out using the most recent experimental data from the literature and a set of DTA measurements. DTA measurements were done using alumina (Al 2 O 3 ) crucibles under helium atmosphere with the niobium (Nb) reference crucible. The evaluated Cu-Mg-Zr phase diagram fitted well with experimental data with the liquidus data in a limited range of composition. There were two miscibility gaps observe in the system. New τ phase was detected using the X-ray and microscopic analysis and the data was used in this evaluation. (orig.)

  2. The electric dipole moment of magnesium deuteride, MgD.

    Science.gov (United States)

    Steimle, Timothy C; Zhang, Ruohan; Wang, Hailing

    2014-06-14

    The (0,0) A(2)Π-X (2)Σ(+) band of a cold molecular beam sample of magnesium monodeuteride, MgD, has been recorded field-free and in the presence of a static electric field of up to 11 kV/cm. The lines associated with the lowest rotational levels are detected for the first time. The field-free spectrum was analyzed to produce an improved set of fine structure parameters for the A(2)Π (v = 0) state. The observed electric field induced splittings and shifts were analyzed to produce permanent electric dipole moments, μ(el) of 2.567(10)D and 1.31(8)D for A(2)Π (v = 0) and X(2)Σ(+)(v = 0) states, respectively. The recommended value for μ(el)(X(2)Σ(+) (v = 0)) for MgH, based upon the measured value for MgD, is 1.32(8)D.

  3. Sequential magnetic switching in Fe/MgO(001) superlattices

    Science.gov (United States)

    Magnus, F.; Warnatz, T.; Palsson, G. K.; Devishvili, A.; Ukleev, V.; Palisaitis, J.; Persson, P. O. Å.; Hjörvarsson, B.

    2018-05-01

    Polarized neutron reflectometry is used to determine the sequence of magnetic switching in interlayer exchange coupled Fe/MgO(001) superlattices in an applied magnetic field. For 19.6 Å thick MgO layers we obtain a 90∘ periodic magnetic alignment between adjacent Fe layers at remanence. In an increasing applied field the top layer switches first followed by its second-nearest neighbor. For 16.4 Å MgO layers, a 180∘ periodic alignment is obtained at remanence and with increasing applied field the layer switching starts from the two outermost layers and proceeds inwards. This sequential tuneable switching opens up the possibility of designing three-dimensional magnetic structures with a predefined discrete switching sequence.

  4. Growth and scintillation properties of BaMgF4

    International Nuclear Information System (INIS)

    Yanagida, Takayuki; Kawaguchi, Noriaki; Fujimoto, Yutaka; Sugiyama, Makoto; Furuya, Yuki; Kamada, Kei; Yokota, Yuui; Yoshikawa, Akira; Chani, Valery

    2010-01-01

    By using the micro-pulling down (μ-PD) method, the barium magnesium fluoride (BaMgF 4 ) single crystalline scintillator was produced. The crystal was cut and mirror polished to the physical dimensions of 1x2x10 mm 3 for examination of scintillation properties. BaMgF 4 demonstrated ∼70% transmittance in wavelength range above 170 nm, and strong emission peaking around 205 nm was observed under X-ray excitation. The absolute light yield of BaMgF 4 was 1300±100 ph/MeV, and the decay time profile showed two components as 0.57±0.01 (70%) and 2.2±0.31 (30%) ns at room temperature.

  5. High production rate of IBAD-MgO buffered substrate

    Energy Technology Data Exchange (ETDEWEB)

    Yoshizumi, M., E-mail: myoshizumi@istec.or.j [Superconductivity Research Laboratory, ISTEC, Shinonome 1-10-13, Koto-ku, Tokyo 135-0062 (Japan); Miyata, S.; Ibi, A.; Fukushima, H.; Yamada, Y.; Izumi, T.; Shiohara, Y. [Superconductivity Research Laboratory, ISTEC, Shinonome 1-10-13, Koto-ku, Tokyo 135-0062 (Japan)

    2009-10-15

    The conventional IBAD (Ion Beam Assisted Deposition) process using fluorite materials yields low production rates, resulting in high production cost, which reduces the motivation for practical application in spite of its high quality. The IBAD process using rock salt materials, e.g. MgO, is well known as a strong candidate of practical application due to its potential of high production rate and high in-plane grain alignment. In this work, the IBAD-MgO process was investigated for a newly developed architecture of PLD (Pulsed Laser Deposition)-CeO{sub 2}/sputter-LMO (LaMnO{sub 3})/IBAD-MgO/sputter-GZO (Gd{sub 2}Zr{sub 2}O{sub 7})/Hastelloy{sup TM} to make long buffered metal tapes with high properties and a high production rate. The 50 m-long IBAD-MgO substrates with about 4 deg. of DELTAphiCeO{sub 2} in an XRD phi scan could be fabricated repeatedly. A GdBCO (GdBa{sub 2}Cu{sub 3}O{sub x}) layer deposited on the buffered substrate showed the minimum I{sub c} value of 325 A/cm-w in a 41 m-long tape. Almost of the tape showed 500-600 A/cm-w of I{sub c} value. The deposition time for the IBAD-MgO layer was 60 s which was about 2 orders of magnitude shorter than the conventional IBAD process. The production rate of 24 m/h was realized at the IBAD-MgO process to fabricate the GdBCO coated conductor with high J{sub c} and I{sub c} properties.

  6. Divorced Eutectic Solidification of Mg-Al Alloys

    Science.gov (United States)

    Monas, Alexander; Shchyglo, Oleg; Kim, Se-Jong; Yim, Chang Dong; Höche, Daniel; Steinbach, Ingo

    2015-08-01

    We present simulations of the nucleation and equiaxed dendritic growth of the primary hexagonal close-packed -Mg phase followed by the nucleation of the -phase in interdendritic regions. A zoomed-in region of a melt channel under eutectic conditions is investigated and compared with experiments. The presented simulations allow prediction of the final properties of an alloy based on process parameters. The obtained results give insight into the solidification processes governing the microstructure formation of Mg-Al alloys, allowing their targeted design for different applications.

  7. Comparison of characteristics of LiF:Mg,Ti e LiF:Mg,Cu,P thermoluminescent dosemeters; Comparacao das caracteristicas dos dosimetros termoluminescentes LiF:Mg,Ti e LiF:Mg,Cu,P

    Energy Technology Data Exchange (ETDEWEB)

    Pereira, M.S.; Filipov, D., E-mail: dfilipov@utfpr.edu.br [Universidade Tecnologica Federal do Parana (UTFPR/DAFIS), Curitiba, PR (Brazil). Departamento Academicao de Fisica; Schelin, H.R. [Instituto de Pesquisa Pele Pequeno Principe (IPPPP), Curitiba, PR (Brazil)

    2014-07-01

    The aim of the current study was to compare the thermoluminescent dosimeters LiF:Mg,Ti (TLD-100) and LiF:Mg,Cu,P (MCP) data, which were acquired by the Federal Technological University - Parana. Tests were realized, for this purpose, such as: sensitivity (only one MCP TLD did not present results within the limit range), linearity (whose MCP result was better than the TLD-100 one), energy dependence (TLD-100 presented lower variation than MCP TLD) and reproducibility (whose TLD-100 results were better than the MCP ones). The results from both dosimeters show that these TLDs attend radiodiagnostic dosimetry criteria, however MCP had more satisfactory results. (author)

  8. Exploring the island of inversion with the d({sup 30}Mg,p){sup 31}Mg reaction

    Energy Technology Data Exchange (ETDEWEB)

    Bildstein, Vinzenz

    2010-12-07

    In this thesis the results of a d({sup 30}Mg,p){sup 31}Mg experiment at REX-ISOLDE are presented. {sup 31}Mg is located directly on the border of the so-called ''Island of Inversion'', a region of the nuclear chart around {sup 32}Mg where deformed intruder states of the fp shell form the ground states of the nuclei instead of the normal spherical states of the sd shell. A recent experiment has shown the ground state of {sup 31}Mg to be a 1/2{sup +} state and indicates more than 90% intruder configuration. The question whether the low-lying excited states of {sup 31}Mg are deformed intruder states as well or rather spherical states from the sd shell, indicating shape coexistence, is still open. The d({sup 30}Mg,p) {sup 31}Mg reaction is thus a good tool to gain more insight into the nature of the Island of Inversion. In the framework of this thesis the angular distribution of protons was measured for the second excited state at 221 keV in coincidence with de-excitation {gamma}-rays. The angular distribution was compared to DWBA calculations for different transferred orbital momenta, identifying the state for the first time as an l=1 state. The experiment was performed with the new charged particle detector setup T-REX. The setup is optimized for transfer reactions with radioactive beams in inverse kinematics. T-REX was developed, built, installed, and used for this first one neutron transfer experiment in the context of this thesis. The T-REX setup consists of {delta}E-E{sub Rest} telescopes made out of position sensitive silicon detectors that cover almost 4{pi} of the solid angle and can be combined with the MINIBALL {gamma}-ray detector array. It has a large solid angle for the detection and identification of the light recoils from transfer reactions. T-REX allows in combination with the MINIBALL Germanium detector array the tagging of the excited states by their characteristic {gamma}-rays. The combination of T-REX and MINIBALL achieves an

  9. Microstructure and fatigue properties of Mg-to-steel dissimilar resistance spot welds

    International Nuclear Information System (INIS)

    Liu, L.; Xiao, L.; Chen, D.L.; Feng, J.C.; Kim, S.; Zhou, Y.

    2013-01-01

    Highlights: ► Mg/steel dissimilar spot weld had the same fatigue strength as Mg/Mg similar weld. ► Crack propagation path of Mg/Mg and Mg/steel welds was the same. ► Penetration of Zn into the Mg base metal led to crack initiation of Mg/steel weld. ► HAZ weakening and stress concentration led to crack initiation of Mg/Mg weld. -- Abstract: The structural application of lightweight magnesium alloys in the automotive industry inevitably involves dissimilar welding with steels and the related durability issues. This study was aimed at evaluating the microstructural change and fatigue resistance of Mg/steel resistance spot welds, in comparison with Mg/Mg welds. The microstructure of Mg/Mg spot welds can be divided into: base metal, heat affected zone and fusion zone (nugget). However, the microstructure of Mg/steel dissimilar spot welds had three different regions along the joined interface: weld brazing, solid-state joining and soldering. The horizontal and vertical Mg hardness profiles of Mg/steel and Mg/Mg welds were similar. Both Mg/steel and Mg/Mg welds were observed to have an equivalent fatigue resistance due to similar crack propagation characteristics and failure mode. Both Mg/steel and Mg/Mg welds failed through thickness in the magnesium sheet under stress-controlled cyclic loading, but fatigue crack initiation of the two types of welds was different. The crack initiation of Mg/Mg welds was occurred due to a combined effect of stress concentration, grain growth in the heat affected zone (HAZ), and the presence of Al-rich phases at HAZ grain boundaries, while the penetration of small amounts of Zn coating into the Mg base metal stemming from the liquid metal induced embrittlement led to crack initiation in the Mg/steel welds.

  10. A study of stability of MgH{sub 2} in Mg-8at%Al alloy powder

    Energy Technology Data Exchange (ETDEWEB)

    Tanniru, Mahesh; Ebrahimi, Fereshteh [Materials Science and Engineering Department, University of Florida, Gainesville, FL 32611 (United States); Slattery, Darlene K. [Florida Solar Energy Center (FSEC), Cocoa, FL (United States)

    2010-04-15

    To investigate the effect of Al addition on the stability of magnesium hydride, the hydrogenation characteristics of a Mg-8at%Al alloy powder synthesized using the electrodeposition technique were evaluated. The characterization of the hydrogenation behavior within the 180 C-280 C temperature range and the subsequent microstructural analysis elucidated that the amount of Al present in the hydride decreased with increasing temperature. This observation suggests that Al has very low solubility in magnesium hydride but Al can be accommodated in MgH{sub 2} by processing under non-equilibrium conditions. Pressure-composition isotherms were developed at different temperatures for the Mg-Al powder as well as pure Mg powder. The results indicate that the enthalpy of formation was slightly lower for the Mg-8at%Al powder while the enthalpy of dissociation did not change. The absence of noticeable influence of Al addition on the stability of magnesium hydride is attributed to its lack of solubility. (author)

  11. Effect of amorphous lamella on the crack propagation behavior of crystalline Mg/amorphous Mg-Al nanocomposites

    Science.gov (United States)

    Hai-Yang, Song; Yu-Long, Li

    2016-02-01

    The effects of amorphous lamella on the crack propagation behavior in crystalline/amorphous (C/A) Mg/Mg-Al nanocomposites under tensile loading are investigated using the molecular dynamics simulation method. The sample with an initial crack of orientation [0001] is considered here. For the nano-monocrystal Mg, the crack growth exhibits brittle cleavage. However, for the C/A Mg/Mg-Al nanocomposites, the ‘double hump’ behavior can be observed in all the stress-strain curves regardless of the amorphous lamella thickness. The results indicate that the amorphous lamella plays a critical role in the crack deformation, and it can effectively resist the crack propagation. The above mentioned crack deformation behaviors are also disclosed and analyzed in the present work. The results here provide a strategy for designing the high-performance hexagonal-close-packed metal and alloy materials. Project supported by the National Natural Science Foundation of China (Grant Nos. 11372256 and 11572259), the 111 Project (Grant No. B07050), the Program for New Century Excellent Talents in University of Ministry of Education of China (Grant No. NCET-12-1046), and the Program for New Scientific and Technological Star of Shaanxi Province, China (Grant No. 2012KJXX-39).

  12. Antacid activity of Laportea aestuans (L.) Chew

    DEFF Research Database (Denmark)

    Christensen, Charlotte Bremer; Soelberg, Jens; Jäger, Anna K

    2015-01-01

    to mimic the movements of the stomach. A titration was carried out with an artificial gastric acid to the end point of pH 3. The acid secretion rate was approximately 3mL and pH was monitored with a pH meter. Concentrations of 666 and 1332mg dried plant material were tested, both with and without addition...... of calcium carbonate (CaCO3). RESULTS: Both CaCO3 and L. aestuans had a significant better ability than water to neutralise an artificial stomach acid. 666mg plant material together with CaCO3 compared to CaCO3 alone showed approximately the same neutralisation time. When mixing 1332mg plant material with Ca...

  13. Brand versus generic dispensing trend for ciprofloxacin 500 mg, levofloxacin 500 mg, and moxifloxacin 400 mg (oral dosage forms) among pharmacies of Karachi, Pakistan.

    Science.gov (United States)

    Zehra, Fatima; Naqvi, Atta Abbas; Tasneem, Sumbul; Ahmad, Rizwan; Ahmad, Niyaz; Shamsi, Adnan Zia; Asghar, Naqiya Ali; Khan, Ghufran Ullah

    2017-01-01

    Pakistan spends 0.7% of its gross domestic product on health. The public sector health-care system provides services to 22% of population thus paving the way for a dominant private sector. Patients in Pakistan mostly pay their medical expenses directly, and 64% of the health expenditures are borne by the household. Expenditure on medicine constitutes 43% of the total household expenditure. A quantitative cross-sectional study was conducted in Karachi, Pakistan, for a month. It was aimed at gathering response from different pharmacies to understand the brand versus generic dispensing trend of ciprofloxacin 500 mg, levofloxacin 500 mg, and moxifloxacin 400 mg oral dosage forms. The study employed convenience sampling and used a survey checklist. The data gathered was entered in SPSS version 22. The mean price per tablet for ciprofloxacin brand and generic was reported at Pakistani Rupees (PKR) 48.44 and PKR 26.85, respectively. The trend for dispensing ciprofloxacin highlighted a split in the market between brand (51%) and generic (49%). For levofloxacin brand and generic, the price per tablet was reported at PKR 36.50 and PKR 36.15 respectively, and despite same price, the market was dominated by generic levofloxacin (92%). Due to a price difference between brand and generic moxifloxacin, i.e., PKR 129.44 and PKR 71.91, respectively, the market was mostly occupied by the generic form (75%). Pricing mechanism must be revisited, and the authorities should take stern actions against any illegitimate price hike. The surging burden of drug expenditure on poorer sections of the society must be addressed by the government on an urgent basis.

  14. Comparison of the Effect of 800 mg Ibuprofen and 30 mg Predenisolone on Relief of Post Endodontic Pain

    Directory of Open Access Journals (Sweden)

    S.M. Jalalzadeh

    2009-04-01

    Full Text Available Introduction & Objective: One of the important problems in dentistry is post endodontic pains .The purpose of this study was comparison of the effect of prophylactic oral ibuprofen 800mg and oral predenisolone 30mg on prevention of post endodontic pain.Materials & Methods: The present study is a double-blind, randomized and controlled trial. It was conducted on 60 patient (16men and 44 women between the ages of 18-63 who needed endodontic treatment. Inclusive criteria for selecting of patients were: need for root canal therapy in one of the posterior teeth, having no systemic problem, no evidence of abscess; not taking analgesic or similar drug for at least 6 hours before treatment. Patients were divided into three experimental groups randomly taking one of the drugs before the treatment {ibuprofen 800 mg, prednisolone30mg and placebo (oral dextrose}. Patients completed VAS at 6,12 and 24 hours post root canal therapy and analyzed using the spss15 by chi-square, ANOVA test and Tukey test.Results: During 24 hours after treatment post endodontic pain is 95%- 100% in the placebo group. The prevalence of no-pain was not significant 6, 12 and 24 hours after treatment between the ibuprofen and predenisolone groups. The mean scale of pain in ibuprofen and predenisolone groups was significantly lower than placebo group 6, 12 and 24 hours after treatment. Differences between the drug groups are significant only on 6 and 12 hours after treatment.Conclusion: Post endodontic pains are present 24 hours after treatment. 6 and 12 hours after treatment 30 mg predenisolone are significantly better for pain relief than 800 mg ibuprofen. But after 24 hours it is not significant.

  15. Permanent magnet with MgB{sub 2} bulk superconductor

    Energy Technology Data Exchange (ETDEWEB)

    Yamamoto, Akiyasu, E-mail: yamamoto@appchem.t.u-tokyo.ac.jp [The University of Tokyo, 7-3-1 Hongo, Bunkyo, Tokyo 113-8656 (Japan); JST-PRESTO, 4-1-8 Honcho, Kawaguchi, Saitama 332-0012 (Japan); Ishihara, Atsushi; Tomita, Masaru [Railway Technical Research Institute, 2-8-38 Hikari, Kokubunji, Tokyo 185-8540 (Japan); Kishio, Kohji [The University of Tokyo, 7-3-1 Hongo, Bunkyo, Tokyo 113-8656 (Japan)

    2014-07-21

    Superconductors with persistent zero-resistance currents serve as permanent magnets for high-field applications requiring a strong and stable magnetic field, such as magnetic resonance imaging. The recent global helium shortage has quickened research into high-temperature superconductors (HTSs)—materials that can be used without conventional liquid-helium cooling to 4.2 K. Herein, we demonstrate that 40-K-class metallic HTS magnesium diboride (MgB{sub 2}) makes an excellent permanent bulk magnet, maintaining 3 T at 20 K for 1 week with an extremely high stability (<0.1 ppm/h). The magnetic field trapped in this magnet is uniformly distributed, as for single-crystalline neodymium-iron-boron. Magnetic hysteresis loop of the MgB{sub 2} permanent bulk magnet was determined. Because MgB{sub 2} is a simple-binary-line compound that does not contain rare-earth metals, polycrystalline bulk material can be industrially fabricated at low cost and with high yield to serve as strong magnets that are compatible with conventional compact cryocoolers, making MgB{sub 2} bulks promising for the next generation of Tesla-class permanent-magnet applications.

  16. Characterization of the microstructure in Mg based alloy

    KAUST Repository

    Kutbee, Arwa T

    2013-01-01

    hardening is essential for age hardenable Mg-based alloys. In this work, microstructural investigation of the Mg–1.4Sn–1.3Zn–0.1Mn (at.%) precipitation system was performed using TEM. The chemical composition of the precipitates was analyzed using EDS. APT

  17. Microwave absorption studies of MgB2 superconductor

    Indian Academy of Sciences (India)

    band (9–. 10 GHz) spectrometer. Both polycrystalline pellet and single-grain MgB2, having nearly the same Tc (∼ 39 K) and same size (3×2×1 mm3), were used in the present investigations. Low field modulated microwave absorption signals ...

  18. Electronic structure and superconductivity of MgB 2

    Indian Academy of Sciences (India)

    Results of ab initio electronic structure calculations on the compound, MgB2, using the FPLAPW method employing GGA for the exchange–correlation energy are presented. Total energy minimization enables us to estimate the equilibrium volume, / ratio and the bulk modulus, all of which are in excellent agreement with ...

  19. Individual Low-Energy Toroidal Dipole State in Mg 24

    Science.gov (United States)

    Nesterenko, V. O.; Repko, A.; Kvasil, J.; Reinhard, P.-G.

    2018-05-01

    The low-energy dipole excitations in Mg 24 are investigated within the Skyrme quasiparticle random phase approximation for axial nuclei. The calculations with the force SLy6 reveal a remarkable feature: the lowest IπK =1-1 excitation (E =7.92 MeV ) in Mg 24 is a vortical toroidal state (TS) representing a specific vortex-antivortex realization of the well-known spherical Hill's vortex in a strongly deformed axial confinement. This is a striking example of an individual TS which can be much more easily discriminated in experiment than the toroidal dipole resonance embracing many states. The TS acquires the lowest energy due to the huge prolate axial deformation in Mg 24 . The result persists for different Skyrme parametrizations (SLy6, SVbas, SkM*). We analyze spectroscopic properties of the TS and its relation with the cluster structure of Mg 24 . Similar TSs could exist in other highly prolate light nuclei. They could serve as promising tests for various reactions to probe a vortical (toroidal) nuclear flow.

  20. The M/G/1 queue with permanent customers

    NARCIS (Netherlands)

    Boxma, O.J.; Cohen, J.W.

    1991-01-01

    The authors examine an M/G/1 FCFS (first come, first served) queue with two types of customers: ordinary customers, who arrive according to a Poisson process, and permanent customers, who immediately return to the end of the queue after having received a service. The influence of the permanent

  1. Laser cladding of Zr on Mg for improved corrosion properties

    International Nuclear Information System (INIS)

    Subramanian, R.; Sircar, S.; Mazumder, J.

    1989-01-01

    This paper reports the results of laser cladding of Mg-2wt%Zr, and Mg-5wt%Zr powder mixture onto magnesium. The microstructure of the laser clad was studied. From the microstructural study, the epitaxial regrowth of the clad region on the underlying substrate was observed. Martensite plates of different size were observed in transmission electron microscope for MG-2wt%Zr and Mg-5wt%Zr laser clad. The corrosion properties of the laser clad were evaluated in sea water (3.5% NaCl). The position of the laser claddings in the galvanic series of metals in sea water, the anodic polarization characteristics of the laser claddings and the protective nature and the stability of the passivating film formed have been determined. The formation of pits on the surface of the laser clad subjected to corrosion is reported. The corrosion properties of the laser claddings are compared with that of the commercially used magnesium alloy AZ91B

  2. Comparison of the effects of esomeprazole 40 mg, rabeprazole 20 mg, lansoprazole 30 mg, and pantoprazole 40 mg on intragastrıc pH in extensive metabolizer patients with gastroesophageal reflux disease.

    Science.gov (United States)

    Çelebi, Altay; Aydın, Dinçer; Kocaman, Orhan; Konduk, Buğra Tolga; Şentürk, Ömer; Hülagü, Sadetin

    2016-09-01

    Studies on the therapeutic efficacy of proton pump inhibitors (PPIs) in patients with gastroesophageal reflux disease (GERD) have been recently published. In most of these studies, comparison of only two PPIs have been made. There are few studies on the comparison of four or more PPIs. We aimed to compare the acid inhibitory effects of esomeprazole 40 mg, rabeprazole 20 mg, lansoprazole 30 mg, and pantoprazole 40 mg on days 1 and 5 of treatment in patients with GERD, who were extensive metabolizers in regard to the CYP2C19 genotype. Helicobacter pylori-negative with typical symptoms of GERD patients were randomly divided into four treatment groups. Efficacy analysis on days 1 and 5 were performed on the four groups which comprised 10 (esomeprazole), 11 (rabeprazole), 10 (lansoprazole), and 10 (pantoprazole) patients. On day 1 of PPI treatment, the mean percentage of time with intragastric Ph>4 were 54%, 58%, 60%, and 35% for the groups, respectively, and on day 5, these values were 67%, 60%, 68%, and 59%, respectively. Esomeprazole, rabeprazole, and lansoprazole were found to be superior to pantoprazole on the first day of treatment. Pantoprazole is a less potent proton pump inhibitor than the other PPIs tested on the first day of treatment. When the time needed to raise the intragatric pH to over 4 was evaluated, esomeprazole was found to have the most rapid action, followed by lansoprazole and rabeprazole.

  3. Structure and electron-ion correlation in liquid Mg

    Energy Technology Data Exchange (ETDEWEB)

    Tahara, Shuta [Graduate School of Sciences, Kyushu University, 4-2-1 Ropponmatsu Chuo-ku, Fukuoka 810-8560 (Japan); Fujii, Hiroyuki [Graduate School of Sciences, Kyushu University, 4-2-1 Ropponmatsu Chuo-ku, Fukuoka 810-8560 (Japan); Japan Synchrotron Radiation Research Institute, 1-1-1 Kouto Sayo-cho, Sayo-gun, Hyogo 679-5198 (Japan); Yokota, Yukinobu [Graduate School of Sciences, Kyushu University, 4-2-1 Ropponmatsu Chuo-ku, Fukuoka 810-8560 (Japan); Kawakita, Yukinobu [Department of Physics, Faculty of Sciences, Kyushu University, 4-2-1 Ropponmatsu Chuo-ku, Fukuoka 810-8560 (Japan); Kohara, Shinji [Japan Synchrotron Radiation Research Institute, 1-1-1 Kouto Sayo-cho, Sayo-gun, Hyogo 679-5198 (Japan); Takeda, Shin' ichi [Department of Physics, Faculty of Sciences, Kyushu University, 4-2-1 Ropponmatsu Chuo-ku, Fukuoka 810-8560 (Japan)]. E-mail: takeda@rc.kyushu-u.ac.jp

    2006-11-15

    For liquid Mg at 700 deg. C, structure factors were obtained from both neutron and X-ray diffraction measurements. The bond angle and coordination number distributions were derived from the reverse Monte Carlo analysis. By a combination of both structure factors, charge density function and electron-ion partial structure factor were deduced.

  4. DISTRIBUTION OF MAJOR ELEMENTS (NA, K, CA, MG) IN THE ...

    African Journals Online (AJOL)

    Levels of sodium, potassium, calcium and magnesium were determined in plant organs (bud, flowers, fruit, seed, leaves, stems, roots, cobs, styles, shaft, grains and efflorescences) of three Fadama farms located in Ifaki-Ekiti, Ado-Ekiti and Ikere-Ekiti of Ekiti State, Nigeria. The highest levels of Mg, K, Na and Ca were ...

  5. EXAFS investigations of Cu-Mg-O compound

    CERN Document Server

    Sidorenko, A F; Babanov, Y A; Naumov, S V; Samokhvalov, A A

    2001-01-01

    The interest to systems containing copper oxide is connected with the problem of high-temperature superconductivity because of the closeness of its basic physical properties and properties of superconductor mother Cu-compounds. In this work, EXAFS study of the Cu sub 0 sub . sub 2 Mg sub 0 sub . sub 8 O compound is presented. A new iterative algorithm of the solution of ill-posed problem on determining three partial pair correlation functions from one EXAFS-data set near the Cu K-edge is described. The results of X-ray scattering study of a given sample show a presence of a single phase with the MgO structure and a lattice parameter of 4.219 A instead of 4.208 A for pure MgO. From the EXAFS investigations, we find the local distortion of the lattice. We revealed that the short range order differs both from a hypothetical alloy with the MgO structure and from copper oxide.

  6. Preparation and characterization of MgB2 superconductor

    Indian Academy of Sciences (India)

    2Tata Institute of Fundamental Research, Homi Bhabha Road, Mumbai 400 005, India. Abstract. The MgB2 superconductor, synthesized using solid-state and liquid-phase sintering methods, have been characterized for various properties. The upper critical field, irreversibility line and critical current density have been ...

  7. Oncolytic Maraba Virus MG1 as a Treatment for Sarcoma.

    Science.gov (United States)

    Le Boeuf, Fabrice; Selman, Mohammed; Son, Hwan Hee; Bergeron, Anabel; Chen, Andrew; Tsang, Jovian; Butterwick, Derek; Arulanandam, Rozanne; Forbes, Nicole E; Tzelepis, Fanny; Bell, John C; Werier, Joel; Abdelbary, Hesham; Diallo, Jean-Simon

    2017-09-15

    The poor prognosis of patients with advanced bone and soft-tissue sarcoma has not changed in the past several decades, highlighting the necessity for new therapeutic approaches. Immunotherapies, including oncolytic viral (OV) therapy, have shown great promise in a number of clinical trials for a variety of tumor types. However, the effective application of OV in treating sarcoma still remains to be demonstrated. Although few pre-clinical studies using distinct OVs have been performed and demonstrated therapeutic benefit in sarcoma models, a side-by-side comparison of clinically relevant OV platforms has not been performed. Four clinically relevant OV platforms (Reovirus, Vaccinia virus, Herpes-simplex virus and Rhabdovirus) were screened for their ability to infect and kill human and canine sarcoma cell lines in vitro, and human sarcoma specimens ex vivo. In vivo treatment efficacy was tested in a murine model. The rhabdovirus MG1 demonstrated the highest potency in vitro. Ex vivo, MG1 productively infected more than 80% of human sarcoma tissues tested, and treatment in vivo led to a significant increase in long-lasting cures in sarcoma-bearing mice. Importantly, MG1 treatment induced the generation of memory immune response that provided protection against a subsequent tumor challenge. This study opens the door for the use of MG1-based oncolytic immunotherapy strategies as treatment for sarcoma or as a component of a combined therapy. © 2017 UICC.

  8. Thermically stimulated exoelectronic emissions and thermoluminescence of MgO

    International Nuclear Information System (INIS)

    Chubaci, J.F.D.

    1987-01-01

    In this work, studies were performed on the following topics: i) thermically stimulated exoelectronic emission (TSEE) in pure MgO single crystals ion implanted, submitted to thermal treatment with fast on slow cooling and water adsorption; ii) ultraviolet light effect on TSEE; iii) thermoluminescent emission; iv) crystallization of FeCoB amorphous alloys. (A.C.A.S.) [pt

  9. Mechanism of Mg2+-Accompanied Product Release in Sugar Nucleotidyltransferases.

    Science.gov (United States)

    Vithani, Neha; Ankush Jagtap, Pravin Kumar; Verma, Sunil Kumar; Tripathi, Ravi; Awasthi, Shalini; Nair, Nisanth N; Prakash, Balaji

    2018-03-06

    The nucleotidyl transfer reaction, catalyzed by sugar nucleotidyltransferases (SNTs), is assisted by two active site Mg 2+ ions. While studying this reaction using X-ray crystallography, we captured snapshots of the pyrophosphate (product) as it exits along a pocket. Surprisingly, one of the active site Mg 2+ ions remains coordinated to the exiting pyrophosphate. This hints at the participation of Mg 2+ in the process of product release, besides its role in catalyzing nucleotidyl transfer. These observations are further supported by enhanced sampling molecular dynamics simulations. Free energy computations suggest that the product release is likely to be rate limiting in SNTs, and the origin of the high free energy barrier for product release could be traced back to the "slow" conformational change of an Arg residue at the exit end of the pocket. These results establish a dual role for Mg 2+ , and propose a general mechanism of product release during the nucleotidyl transfer by SNTs. Copyright © 2018 Elsevier Ltd. All rights reserved.

  10. Suppression of Mg propagation into subsequent layers grown by MOCVD

    Science.gov (United States)

    Agarwal, Anchal; Tahhan, Maher; Mates, Tom; Keller, Stacia; Mishra, Umesh

    2017-01-01

    Low temperature (LT) flow modulation epitaxy (FME) or "pulsed" growth was successfully used to prevent magnesium from Metalorganic Chemical Vapor Deposition (MOCVD) grown p-GaN:Mg layers riding into subsequently deposited n-type layers. Mg concentration in the subsequent layers was lowered from ˜1 × 1018 cm-3 for a medium temperature growth at 950 °C to ˜1 × 1016 cm-3 for a low temperature growth at 700 °C via FME. The slope of the Mg concentration drop in the 700 °C FME sample was 20 nm/dec—the lowest ever demonstrated by MOCVD. For growth on Mg implanted GaN layers, the drop for a medium temperature regrowth at 950 °C was ˜10 nm/dec compared to >120 nm/dec for a high temperature regrowth at 1150 °C. This drop-rate obtained at 950 °C or lower was maintained even when the growth temperature in the following layers was raised to 1150 °C. A controlled silicon doping series using LT FME was also demonstrated with the lowest and highest achieved doping levels being 5 × 1016 cm-3 and 6 × 1019 cm-3, respectively.

  11. Nonparametric inference from the M/G/1 workload

    DEFF Research Database (Denmark)

    Hansen, Martin Bøgsted; Pitts, Susan M.

    2006-01-01

    Consider an M/G/1 queue with unknown service-time distribution and unknown traffic intensity ρ. Given systematically sampled observations of the workload, we construct estimators of ρ and of the service-time distribution function, and we study asymptotoic properties of these estimators....

  12. Nonparametric inference from the M/G/1 workload

    DEFF Research Database (Denmark)

    Hansen, Martin Bøgsted; Pitts, Susan M.

    Consider an M/G/1 queue with unknown service-time distribution and unknown traffic intensity $\\rho$. Given systematically sampled observations of the workload, we construct estimators of $\\rho$ and of the service-time distribution function, and we study asymptotic properties of these estimators....

  13. Lithium ion implantation effects in MgO (100)

    NARCIS (Netherlands)

    van Huis, MA; Fedorov, AV; van Veen, A; Labohm, F; Schut, H; Mijnarends, PE; Kooi, BJ; De Hosson, JTM; Triftshauser, W; Kogel, G; Sperr, P

    2001-01-01

    Single crystals of MgO (100) were implanted with 10(16) (6)Li ions cm(-2) at an energy of 30 keV. After ion implantation the samples were annealed isochronally in air at temperatures up to 1200K. After implantation and after each annealing step, the defect evolution was monitored with optical

  14. The effects of Mg incorporation and annealing temperature on the ...

    Indian Academy of Sciences (India)

    Home; Journals; Pramana – Journal of Physics; Volume 88; Issue 2. The effects of Mg incorporation and annealing temperature on the physicochemical properties and antibacterial activity against {\\it Listeria monocytogenes} of ZnO nanoparticles. NIMA SHADAN ALI ABDOLAHZADEH ZIABARI RAFIEH MERAAT KAMYAR ...

  15. Dosimetric properties of LIF:Mg,CuP+PTFE

    International Nuclear Information System (INIS)

    Gonzalez Martinez, P.R.; Azorin Nieto, J.; Ramirez Luna, A.

    1998-01-01

    The work presents the preparation method, as well as the characterization of the dosemeters of LiF;Mg,Cu+PTFE developed in the National Institute of Nuclear Investigations (ININ) Mexico, Among the carried out tests can mention, sensibility, detection threshold, equivalent of bottom, uniformity, reproducibility, dissipation, answer in function of the dose and kinetic parameters

  16. Atomistic simulations of Mg-Cu metallic glasses: Mechanical properties

    DEFF Research Database (Denmark)

    Bailey, Nicholas; Schiøtz, Jakob; Jacobsen, Karsten Wedel

    2004-01-01

    The atomistic mechanisms of plastic deformation in amorphous metals are far from being understood. We have derived potential parameters for molecular dynamics simulations of Mg-Cu amorphous alloys using the Effective Medium Theory. We have simulated the formation of alloys by cooling from the melt...

  17. Multiwavelength observations of the Type IIb supernova 2009mg

    DEFF Research Database (Denmark)

    Oates, S. R.; Bayless, A. J.; Stritzinger, M. D.

    2012-01-01

    -time temporal index of SN 2009mg, determined from 40 d post-explosion, is consistent with the decay rate of SN 1993J, but inconsistent with the decay of 56Co. This suggests leakage of γ-rays out of the ejecta and a stellar mass on the small side of the mass distribution. Our XRT non-detection provides an upper...

  18. Measurements of Narrow Mg II Associated Absorption Doublets with ...

    Indian Academy of Sciences (India)

    2016-01-27

    Jan 27, 2016 ... The measurement of the variations of absorption lines over time is a good method to study the physical conditions of absorbers. In this paper, we measure the variations of the line strength of 36 narrow Mg II2796, 2803 associated absorption doublets, which are imprinted on 31 quasar spectra with two ...

  19. Microwave absorption studies of MgB 2 superconductor

    Indian Academy of Sciences (India)

    Microwave absorption studies have been carried out on MgB2 superconductor using a standard X-band EPR spectrometer. The modulated low-field microwave absorption signals recorded for polycrystalline (grain size ∼ 10m) samples suggested the absence of weak-link character. The field dependent direct microwave ...

  20. Understanding Active Metal Reaction Kinetics with Cu–Mg ...

    Indian Academy of Sciences (India)

    magnesium metal (Mg(s)) in the cathode and chlorine (Cl2(g)) in the anode ... der acidic (pH ≤ 4) and basic (pH≥ 9) conditions, the oxide layer is broken and its .... and high ionic strength of the environment (such as sea water. ([Cl−] = from ...

  1. Soldering of Mg Joints Using Zn-Al Solders

    Science.gov (United States)

    Gancarz, Tomasz; Berent, Katarzyna; Skuza, Wojciech; Janik, Katarzyna

    2018-04-01

    Magnesium has applications in the automotive and aerospace industries that can significantly contribute to greater fuel economy and environmental conservation. The Mg alloys used in the automotive industry could reduce mass by up to 70 pct, providing energy savings. However, alongside the advantages there are limitations and technological barriers to use Mg alloys. One of the advantages concerns phenomena occurring at the interface when joining materials investigated in this study, in regard to the effect of temperature and soldering time for pure Mg joints. Eutectic Zn-Al and Zn-Al alloys with 0.05 (wt pct) Li and 0.2 (wt pct) Na were used in the soldering process. The process was performed for 3, 5, and 8 minutes of contact, at temperatures of 425 °C, 450 °C, 475 °C, and 500 °C. Selected, solidified solder-substrate couples were cross-sectioned, and their interfacial microstructures were investigated by scanning electron microscopy. The experiment was designed to demonstrate the effect of time, temperature, and the addition of Li and Na on the kinetics of the dissolving Mg substrate. The addition of Li and Na to eutectic Zn-Al caused to improve mechanical properties. Higher temperatures led to reduced joint strength, which is caused by increased interfacial reaction.

  2. Lines of MgI Detected in Solar Prominences

    Czech Academy of Sciences Publication Activity Database

    Heinzel, Petr; Kupryakov, Yu. A.; Schwartz, P.

    2016-01-01

    Roč. 40, č. 1 (2016), s. 87-91 ISSN 1845-8319. [Hvar Astrophysical Colloquium /14./. Hvar, 26.09.2016-30.09.2016] Institutional support: RVO:67985815 Keywords : prominences * limb-flare * MgI emession Subject RIV: BN - Astronomy, Celestial Mechanics, Astrophysics

  3. Insulator layer formation in MgB2 SIS junctions

    International Nuclear Information System (INIS)

    Shimakage, H.; Tsujimoto, K.; Wang, Z.; Tonouchi, M.

    2005-01-01

    The dependence of current-voltage characteristics on thin film deposition conditions was investigated using MgB 2 /AlN/NbN SIS junctions. By increasing the substrate temperature in AlN insulator deposition, the current density decreased and the normal resistance increased. The results indicated that an additional insulator layer between the MgB 2 and AlN formed, either before or during the AlN deposition. The thickness of the additional insulator layer was increased with an increase in the AlN deposition temperature. From the dependence of current density on the thickness of AlN in low temperature depositions, the thickness of the additional insulator layer was estimated to be 1-1.5 nm when the AlN insulator was deposited from 0.14 to 0.7 nm. Moreover, with the current density of MgB 2 /AlN/MgB 2 SIS junctions, further insulator layer formation was confirmed

  4. Enhanced Optical Performance of BaMgAl

    NARCIS (Netherlands)

    Yin, L.J.; Dong, Juntao; Wang, Yinping; Zhang, Bi; Zhou, Zheng Yang; Jian, Xian; Wu, Mengqiang; Xu, Xin; van Ommen, J.R.; Hintzen, H.T.J.M.

    2016-01-01

    Many strategies have been adopted to improve thermal degradation of phosphors. Because of the stability and high transmittance of graphene, here we report a novel method of carbon coating on BaMgAl10O17:Eu2+ (BAM) phosphor particles through chemical vapor

  5. Controlled release of ibuprofen using Mg Al LDH nano carrier

    Science.gov (United States)

    Dasgupta, Sudip

    2017-08-01

    In the present study, NSAID (non-steroidal anti-inflammatory drugs) such as ibuprofen in anionic form has been intercalated in-situ into the interlayer space of Mg Al LDH nanoparticle during co-precipitation of hydroxides. LDH nanohybrids are characterized by XRD, FTIR and UV spectroscopy. Mg1-xAlx(NO3)x(OH)2.nH2O nanoparticles were synthesized using co-precipitation method from an aqueous solution of Mg(NO3)2.6H2O and Al(NO3)3.9H2O. Ibuprofen was intercalated in inter layer space of Mg-Al LDH during coprecipitation of drug LDH conjugate in nitrogen atmosphere. The nanopowders synthesised were in the size range between 25 to 90 nm with an average particle size of 55 nm. XRD analysis proved that there is an increase in d003 spacing from 7.89 Å for pristine LDH to 14.71 Å for ibuprofen intercalated LDH due to the intercalation of bigger ibuprofen molecule in the interlayer space of LDH. FTIR analysis showed hydroxyl and carbonyl stretching of ibuprofen in LDH-IBU sample confirming the intercalation of ibuprofen in the interlayer structure of LDH. The drug release study in phosphate buffer solution at pH 7.4 using UV-Vis spectroscopy demonstrated that 50 % drug molecules were released in 15 hours and more than 85 % release was achieved after 36 hours.

  6. Using CaO- and MgO-rich industrial waste streams for carbon sequestration

    International Nuclear Information System (INIS)

    Stolaroff, Joshuah K.; Lowry, Gregory V.; Keith, David W.

    2005-01-01

    To prevent rapid climate change, it will be necessary to reduce net anthropogenic CO 2 emissions drastically. This likely will require imposition of a tax or tradable permit scheme that creates a subsidy for negative emissions. Here, we examine possible niche markets in the cement and steel industries where it is possible to generate a limited supply of negative emissions (carbon storage or sequestration) cost-effectively. Ca(OH) 2 and CaO from steel slag or concrete waste can be dissolved in water and reacted with CO 2 in ambient air to capture and store carbon safely and permanently in the form of stable carbonate minerals (CaCO 3 ). The kinetics of Ca dissolution for various particle size fractions of ground steel slag and concrete were measured in batch experiments. The majority of available Ca was found to dissolve on a time scale of hours, which was taken to be sufficiently fast for use in an industrial process. An overview of the management options for steel slag and concrete waste is presented, which indicates how their use for carbon sequestration might be integrated into existing industrial processes. Use of the materials in a carbon sequestration scheme does not preclude subsequent use and is likely to add value by removing the undesirable qualities of water absorption and expansion from the products. Finally, an example scheme is presented which could be built and operated with current technology to sequester CO 2 with steel slag or concrete waste. Numerical models and simple calculations are used to establish the feasibility and estimate the operating parameters of the scheme. The operating cost is estimated to be US$8/t-CO 2 sequestered. The scheme would be important as an early application of technology for capturing CO 2 directly from ambient air

  7. A randomized comparison of daunorubicin 90 mg/m2 vs 60 mg/m2 in AML induction

    DEFF Research Database (Denmark)

    Burnett, A. K.; Russell, N. H.; Hills, R. K.

    2015-01-01

    Modifying induction therapy in acute myeloid leukemia (AML) may improve the remission rate and reduce the risk of relapse, thereby improving survival. Escalation of the daunorubicin dose to 90 mg/m(2) has shown benefit for some patient subgroups when compared with a dose of 45 mg/m(2), and has been...... = .15). In an exploratory subgroup analysis, there was no subgroup that showed significant benefit, although there was a significant interaction by FLT3 ITD mutation. This trial is registered at http://www.isrctn.com as #ISRCTN55675535....

  8. Band structure of semiconductor compounds of Mg sub 2 Si and Mg sub 2 Ge with strained crystal lattice

    CERN Document Server

    Krivosheeva, A V; Shaposhnikov, V L; Krivosheev, A E; Borisenko, V E

    2002-01-01

    The effect of isotopic and unaxial deformation of the crystal lattice on the electronic band structure of indirect band gap semiconductors Mg sub 2 Si and Mg sub 2 Ge has been simulated by means of the linear augmented plane wave method. The reduction of the lattice constant down to 95 % results in a linear increase of the direct transition in magnesium silicide by 48%. The stresses arising under unaxial deformation shift the bands as well as result in splitting of degenerated states. The dependence of the interband transitions on the lattice deformation is nonlinear in this case

  9. Luna 24 ferrobasalt as a low-Mg primary melt

    International Nuclear Information System (INIS)

    Norman, M.; Ryder, G.

    1980-01-01

    Luna 24 very-low titanium (VLT) ferrobasalts, metabasalts, brown glasses and impact melts form a tight compositional cluster with no gradation to other groupings postulated for the Luna 24 core components. This suggests that the Luna 24 VLT ferrobasalt was extruded as a liquid of its own composition and was not derived by fractional crystallization from a more magnesian parent in a surface flow. Furthermore, the characteristics of the core lithologies are not easily visualized as components of such a differential flow, e.g. brown glasses. Gravitative settling models purporting to demonstrate the validity of the flow differentiation model are merely permissive. Subsurface fractionation requires that plagioclase, not olivine, be the liquidus phase. The high-Mg component in the Luna 24 core can be constrained, though not identified, chemically, and it has neither the major element, trace element, isotopic, nor mineralogical characteristics required of a possible parent to the Luna 24 VLT ferrobasalt. Thus models of fractionation lack a physical expression of the less differentiated compositions, contrary to the belief that the high-Mg component in the core is the parent material. The Luna 24 VLT ferrobasalt is probably a primary low-Mg melt from a plagioclase-bearing source region, and may have undergone little or no fractionation prior to eruption. Such a model is compatible with, and suggested by, chemical and experimental data. Caution against posulating that all Mg-poor melts are fractionated products, based on terrestrial models, is advised. The terrestrial oceanic situation of 'primary melts' with similar Mg/Fe is probably not valid for the Moon. (Auth.)

  10. On heavy carbon doping of MgB2

    International Nuclear Information System (INIS)

    Kasinathan, Deepa; Lee, K.-W.; Pickett, W.E.

    2005-01-01

    Heavy carbon doping of MgB 2 is studied by first principles electronic structure studies of two types, an ordered supercell (Mg(B 1-x C x ) 2 , x 0.0833) and also the coherent potential approximation method that incorporates effects of B-C disorder. For the ordered model, the twofold degenerate σ-bands that are the basis of the high temperature superconductivity are split by 60 meV (i.e. 7 meV/% C) and the σ Fermi cylinders contain 0.070 holes/cell, compared to 0.11 for MgB 2 . A virtual crystal treatment tends to overestimate the rate at which σ holes are filled by substitutional carbon. The coherent potential approximation (CPA) calculations give the same rate of band filling as the supercell method. The occupied local density of states of C is almost identical to that of B in the upper 2 eV of the valence bands, but in the range -8 eV to -2 eV, C has a considerably larger density of states. The calculations indicate that the σ Fermi surface cylinders pinch off at the zone center only above the maximum C concentration x ∼ 0.10. These results indicate that Mg(B 1-x C x ) 2 as well as Mg 1-x Al x B 2 is a good system in which to study the evolution of the unusual electron-phonon coupling character and strength as the crucial σ hole states are filled

  11. Frovatriptan 2.5 mg plus dexketoprofen (25 mg or 37.5 mg) in menstrually related migraine. Subanalysis from a double-blind, randomized trial.

    Science.gov (United States)

    Allais, G; Bussone, G; Tullo, V; Cortelli, P; Valguarnera, F; Barbanti, P; Sette, G; D'Onofrio, F; Curone, M; Benedetto, C

    2015-01-01

    The purpose of this article is to investigate the efficacy and safety of frovatriptan plus dexketoprofen 25 or 37.5 mg (FroDex25 or FroDex37.5, respectively) compared to that of frovatriptan 2.5 mg (Frova) in menstrually related migraine (MRM). The aim of this article is to analyze a subgroup of 76 women who treated an MRM attack in this multicenter, randomized, double-blind, parallel-group study. The primary end-point was the proportion of patients who were pain free (PF) at two hours. Secondary end-points included pain-relief (PR) at two hours and 48 hours sustained pain free (SPF). PF rates at two hours were 29% under Frova, 48% under FroDex25 and 64% under FroDex37.5 (p dexketoprofen produced higher PF rates at two hours compared to Frova while maintaining efficacy at 48 hours. Tolerability profiles were comparable. © International Headache Society 2014 Reprints and permissions: sagepub.co.uk/journalsPermissions.nav.

  12. The role of Mg interface layer in MgO magnetic tunnel junctions with CoFe and CoFeB electrodes

    Directory of Open Access Journals (Sweden)

    Hyunsoo Yang

    2012-03-01

    Full Text Available The tunneling spin polarization (TSP is directly measured from reactively sputter deposited crystalline MgO tunnel barriers with various CoFe(B compositions using superconducting tunneling spectroscopy. We find that the Mg interface layer thickness dependence of TSP values for CoFeB/Mg/MgO junctions is substantially different from those for CoFe/Mg/MgO especially in the pre-annealed samples due to the formation of boron oxide at the CoFeB/MgO interface. Annealing depletes boron at the interface thus requiring a finite Mg interface layer to prevent CoFeOx formation at the CoFeB/MgO interface so that the TSP values can be optimized by controlling Mg thickness.

  13. Uncovering the Local Magnesium Environment in the Metal–Organic Framework Mg 2 (dobpdc) Using 25 Mg NMR Spectroscopy

    Energy Technology Data Exchange (ETDEWEB)

    Xu, Jun; Blaakmeer, E. S. Merijn [Institute; Lipton, Andrew S. [Environmental; McDonald, Thomas M.; Liu, Yifei Michelle; Smit, Berend [Laboratory; Long, Jeffrey R. [Materials; Kentgens, Arno P. M. [Institute; Reimer, Jeffrey A. [Materials

    2017-09-06

    The incorporation of N,N'-dimethylethylenediamine into an expanded MOF-74 framework has yielded a material (mmen-Mg2(dobpdc)) exhibiting “step-shaped” CO2 adsorption isotherms. The coordination of mmen at the Mg open metal center is essential for the unique cooperative adsorption mechanism elucidated for this material. Despite its importance for carbon capture, there is as yet no experimental structure determination available for the underlying metal– organic framework Mg2(dobpdc). Our 25Mg solid-state NMR data unravel the local Mg environments in several Mg2(dobpdc) samples, unambiguously confirming the formation of fivecoordinate Mg centers in the activated material and six-coordinate Mg centers in the solvent- or diamine-loaded samples, such as mmen-Mg2(dobpdc). A fraction of the Mg centers are locally disordered due to the framework deformation accompanied by the guest distributions and dynamics.

  14. Research on MgLi and a specifically German consequence. MgLi-Forschung und ihre spezifisch deutsche Konsequenz

    Energy Technology Data Exchange (ETDEWEB)

    Hehmann, F [Office National d' Etudes et de Recherches Aerospatiales (ONERA), 92 - Chatillon (France)

    1994-05-01

    When light weight structural applications are of prime concern, magnesium cannot be ignored. When magnesium is of prime concern, of course, the research cannot be ignored, either. Since there is not much to be ignored (or not), however, it is the research on MgLi that takes the lead in the German press. ''Rock-solid as Kruppstahl'' was it meant to be, though MgLi-alloys soften quite appreciable already at ambient temperature. A hydrogen treatment of the MgLi melt was the phenomenon that was naturally astounded. In the meantime, however, it became very tranquilly around the contest for the selection of the species from the ''MgLi-Born''. Has the hot air already escaped Warm wind is not bad in each case. Daily discipline, however, has scaled ever since with the natural beauty of the more concrete results by working. What follows is an article that looks upon this particular German variant at the ''histoire parallele'' in the field of metallic innovations as well as upon the sound base of such deliberately outbalanced renaissances. (orig.)

  15. Catalytically Enhanced Hydrogen Sorption in Mg-MgH2 by Coupling Vanadium-Based Catalyst and Carbon Nanotubes

    Directory of Open Access Journals (Sweden)

    Atikah Kadri

    2015-06-01

    Full Text Available Mg (MgH2-based composites, using carbon nanotubes (CNTs and pre-synthesized vanadium-based complex (VCat as the catalysts, were prepared by high-energy ball milling technique. The synergistic effect of coupling CNTs and VCat in MgH2 was observed for an ultra-fast absorption rate of 6.50 wt. % of hydrogen per minute and 6.50 wt. % of hydrogen release in 10 min at 200 °C and 300 °C, respectively. The temperature programmed desorption (TPD results reveal that coupling VCat and CNTs reduces both peak and onset temperatures by more than 60 °C and 114 °C, respectively. In addition, the presence of both VCat and CNTs reduces the enthalpy and entropy of desorption of about 7 kJ/mol H2 and 11 J/mol H2·K, respectively, as compared to those of the commercial MgH2, which ascribe to the decrease of desorption temperature. From the study of the effect of CNTs milling time, it is shown that partially destroyed CNTs (shorter milling time are better to enhance the hydrogen sorption performance.

  16. Theoretical and experimental study of the intrinsic physical properties of the Mg-MgH{sub 2} system

    Energy Technology Data Exchange (ETDEWEB)

    Puszkiel, Julian A.; Gervasoni, Juana L. [Centro Atomico Bariloche (CAB) - Instituto Balseiro (IB) - Comision Nacional de Energia Atomica (CNEA), Av. Bustillo km 9.5, R8402 AGP S.C. de Bariloche (Argentina)

    2010-06-15

    Due to the fundamental problems of energy source limitations and environmental pollution, hydrogen has become an attractive clean energy source for the future. Despite the fact that the incentive to switch to a hydrogen economy has increased, there are many problems which must be solved. One of the main unsolved issues is hydrogen storage. Among the potential materials to store hydrogen in a safe way, Mg has drawn interest owing to its high hydrogen capacity (7.6 wt%), light weight and low cost. In order to improve the hydrogen capacity of potential storage materials such as Mg, it is important to understand the site preferences of hydrogen atoms in the metal. Such behavior depends mainly on the screening charge density ({delta}n(r)) of the system proton-metallic host, from which all the physical macroscopic properties (viz. V{sub H}, {delta}H{sub S}, B, etc.) and IDOS are determined. In the present work we study the interaction between a proton and Mg as host metal via ab initio calculations, using the Jellium model, based on the density-functional theory (DFT). The macroscopic properties are determined and compared with experimental results and values found in the bibliography. Furthermore, in order to obtain information about the electronic distribution of hydrogen and the nature of the Mg-H bonding, the IDOS is described. (author)

  17. Discovery of the shape coexisting 0+ state in 32Mg

    International Nuclear Information System (INIS)

    Wimmer, Kathrin

    2010-01-01

    The evolution of shell structure in exotic nuclei as a function of proton (Z) and neutron (N) number is currently at the center of many theoretical and experimental investigations. It has been realized that the interaction of the last valence protons and neutrons, in particular the monopole component of the residual interaction between those nucleons, can lead to significant shifts in the single-particle energies, leading to the collapse of classic shell closures and the appearance of new shell gaps. The ''Island of Inversion'' around 32 Mg, which is one of the most studied phenomena in the nuclear chart, is a well known example for such changes in nuclear structure. In this region of neutron-rich nuclei around the magic number N=20 strongly deformed ground states in Ne, Na, and Mg isotopes have been observed. Due to the reduction of the N=20 shell gap quadrupole correlations can enable low-lying deformed 2p-2h intruder states from the fp-shell to compete with spherical normal neutron 0p-0h states of the sd-shell. In this situation the promotion of a neutron pair across the N=20 gap can result in deformed intruder ground states. Consequentially the two competing configurations can lead to the coexistence of spherical and deformed 0 + states in the neutron rich nuclei 30,32 Mg. In this work the shape coexistence in 32 Mg was studied by a two neutron transfer reaction at the REX-ISOLDE facility (CERN). The two neutron transfer reaction with a 30 Mg beam involved for the first time the use of a radioactive tritium target in combination with a radioactive heavy ion beam. Light charged particles emitted from the target were detected and identified by the T-REX particle detector while γ-rays were detected by the MINIBALL Germanium detector array. The shape of the angular distribution of the protons allows to unambiguously determine the angular momentum transfer ΔL of the reaction and thus to identify the 0 + states. The analysis of excitation energies and angular

  18. Recovery of SO2 and MgO from By-Products of MgO Wet Flue Gas Desulfurization.

    Science.gov (United States)

    Yan, Liyun; Lu, Xiaofeng; Wang, Quanhai; Guo, Qiang

    2014-11-01

    An industrial demonstration unit using natural gas as a heat source was built to calcine the by-products of MgO wet flue gas desulfurization from power plants; influencing factors on the SO 2 content in calciner gas were comprehensively analyzed; and an advantageous recycling condition of MgO and SO 2 from by-products was summarized. Results showed that the SO 2 content in the calciner gas was increased by more than 10 times under a lower excess air coefficient, a higher feed rate, a lower crystal water in by-products, and a higher feed port position. For the tests conducted under the excess air coefficient above and below one, the effect of the furnace temperature on the SO 2 content in the calciner gas was reversed. Results of activity analysis indicate that particles of MgO generated under the calcination temperature of 900-1,000°C had a high activity. In contrast, due to the slight sintering, MgO generated under the calcination temperature of 1,100°C had a low activity. To recycle SO 2 as well as MgO, a temperature range of 900-927°C for TE103 is proposed. These studies will prompt the desulfurization market diversification, reduce the sulfur's dependence on imports for making sulfuric acid, be meaningful to balance the usage of the natural resource in China, and be regarded as a reference for the development of this technology for other similar developing countries.

  19. The impact of Mg contents on Sr partitioning in benthic foraminifers

    NARCIS (Netherlands)

    Mewes, Antje; Langer, Gerald; Reichart, Gert Jan; de Nooijer, L.J.; Nehrke, Gernot; Bijma, Jelle

    2015-01-01

    Foraminiferal calcite Mg/Ca (Mg/CaCC) is used in paleoceanographic studies to reconstruct temperature. Furthermore, the Mg/CaCC is influenced by different seawater Mg/Ca (Mg/CaSW). Foraminiferal calcite Sr/Ca (Sr/CaCC) can potentially be used to reconstruct Sr/Ca ratios of seawater (Sr/CaSW). As

  20. Stability of a formulation of zidovudine 300 mg tablets

    International Nuclear Information System (INIS)

    Ibannez Calvo, Sergio; Garcia Penna, Caridad Margarita; Leon Rodriguez, Rafael

    2010-01-01

    Authors developed a validation of analytical method by high-performance liquid applicable to stability study of Zidovudine (300 mg tablets). The validated analytical method was linear, specific and exact. Above mentioned study was developed determing its expiry date. This study was conducted by fixed life and of accelerated stability methods by high-performance liquid chromatography, validated in Drugs Research and Development Center (Havana, Cuba). Fixed life study was conducted during 24 months at room temperature whereas the accelerated stability study was conducted exposing the product to light influence and humidity during three months and to temperature during 6 months. Zidovudine formula (300 mg tablets) fulfilled the quality specifications described in Pharmacopeia. After 24 months results of stability study by fixed life showed that product maintained the parameters determining its quality during that period and in accelerated studies there was not a significant degradation of product. Two years was established as expiry date in above mentioned conditions

  1. Stannate conversion coatings on Mg-8Li alloy

    International Nuclear Information System (INIS)

    Yang Lihui; Zhang Milin; Li Junqing; Yu Xiang; Niu Zhongyi

    2009-01-01

    The stannate conversion coatings (SnCC) on Mg-8Li alloy were investigated by simple immersion method. The surface morphology and composition were studied by scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS) and X-ray diffraction spectroscopy (XRD) techniques. The corrosion resistance was assessed by means of potentiodynamic polarization measurements and electrochemical impedance spectra (EIS). The effects of time of a stannate bath on the quality of stannate conversion coatings were investigated by SEM and EIS. It was found that the coating particles were mainly composed of hemispherical particles MgSnO 3 .3H 2 O. A comparison of results revealed the coating treated for 60 min exhibited the most uniform, dense and corrosion-resistant

  2. Active Protection of an MgB2 Test Coil

    Science.gov (United States)

    Park, Dong Keun; Hahn, Seungyong; Bascuñán, Juan; Iwasa, Yukikazu

    2011-01-01

    This paper presents results of a study, experimental and computational, of a detect-and-activate-the-heater protection technique applied to a magnesium diboride (MgB2) test coil operated in semi-persistent mode. The test coil with a winding ID of 25 cm and wound with ~500-m long reacted MgB2 wire was operated at 4.2 K immersed in a bath of liquid helium. In this active technique, upon the initiation of a “hot spot” of a length ~10 cm, induced by a “quench heater,” a “protection heater” (PH) of ~600-cm long planted within the test coil is activated. The normal zone created by the PH is large enough to absorb the test coil’s entire initial stored energy and still keeps the peak temperature within the winding below ~260 K. PMID:22081754

  3. HRTEM investigation of orthorhombic phase in Mg-PSZ

    International Nuclear Information System (INIS)

    Liu, Z.W.; Spargo, A.E.C.; Hannink, R.H.J.

    1997-01-01

    Tetragonal, orthorhombic and monoclinic phases are only slight distortions of the cubic structure. Due to minor differences in unit cell parameters it is difficult to distinguish these phases only by high resolution images. However, using high resolution transmission electron microscopy (HRTEM) observation in combination with image simulation and digital Fourier transformation of HRTEM images, it was found that one tetragonal precipitate can be transformed to several orthorhombic domains with different orientations in MgO-partially-stabilized zirconia (Mg-PSZ). The lattice correspondence between two adjacent orthorhombic domains is such that their b axes are parallel, while their a axes are perpendicular to each other. Also it was found that cubic ZrO 2 could be transformed to orthorhombic ZrO 2 . 8 refs., 1 tab., 4 figs

  4. Rocksalt MgS solar blind ultra-violet detectors

    Directory of Open Access Journals (Sweden)

    Ying-Hoi Lai

    2012-03-01

    Full Text Available Studies using in-situ Auger electron spectroscopy and reflection high energy electron diffraction, and ex-situ high resolution X-ray diffraction and electron backscatter diffraction reveal that a MgS thin film grown directly on a GaAs (100 substrate by molecular beam epitaxy adopts its most stable phase, the rocksalt structure, with a lattice constant of 5.20 Å. A Au/MgS/n+-GaAs (100 Schottky-barrier photodiode was fabricated and its room temperature photoresponse was measured to have a sharp fall-off edge at 235 nm with rejection of more than three orders at 400 nm and higher than five orders at 500 nm, promising for various solar-blind UV detection applications.

  5. Mg2FeH6 Synthesis Efficiency Map

    Directory of Open Access Journals (Sweden)

    Katarzyna Witek

    2018-02-01

    Full Text Available The influences of the processing parameters on the Mg2FeH6 synthesis yield were studied. Mixtures of magnesium hydride (MgH2 and iron (Fe were mechanically milled in a planetary ball mill under argon for 0.5-, 1-, 2- and 3-h periods and subsequently sintered at temperatures from 300–500 ∘ C under hydrogen. The reaction yield, phase content and hydrogen storage properties of the received materials were investigated. The morphologies of the powders after synthesis were studied by SEM. The synthesis effectiveness map was presented. The obtained results prove that synthesis parameters, such as the milling time and synthesis temperature, greatly influence the reaction yield and material properties and show that extended mechanical milling may not be beneficial to the reaction efficiency.

  6. Luminescence characteristics of Mg2SiO4:Nd

    International Nuclear Information System (INIS)

    Indira, P.; Subrahmanyam, R.V.; Murthy, K.V.R.

    2011-01-01

    Thermoluminescence (TL) properties of Magnesium Ortho silicate (2:1) Mg 2 SiO 4 doped with various concentrations of rare earth (Nd) have been studied. The phosphor material were prepared using standard solid state reaction technique and heated specimens at 1100 ± 20 deg C for two hours. 4% Ammonium chloride was used as flux. The received material was grinded in an agate mortar and pestle. The TL exhibited by the Mg 2 SiO 4 with varying concentration of Nd is interesting in nature. It is interesting to note but as the concentration of Nd increases the peak around 125 deg C TL peak intensity increases. But the hump around 200 deg C resolved as TL peak at 253 deg C with high intensity. (author)

  7. AMOC studies of positronium in fine MgO powder

    International Nuclear Information System (INIS)

    Waeyenberge, B. van; Dauwe, C.

    2001-01-01

    A first set of AMOC spectra on fine powdered MgO were measured at the Stuttgart relativistic positron beam facility. A special AMOC spectrometer was set up in order to determine the long lifetimes of ortho-positronium in the powder cavities. The spectra were taken on pellets of pressed powder in air and in an oxygen atmosphere to ensure ortho- to para-positronium conversion. An analysis of the data is made in the light of previous lifetime measurements on MgO. Here the lifetime spectrum was fitted with an age dependent lifetime describing the slow thermalisation of epithermal ortho-positronium between the powder grains. Based on the lifetime spectrum of the integrated AMOC spectra the data could not discriminate between a 5-component model and a model including slow positronium thermalisation. On the other hand, analysis of the age dependent line shape parameter shows better variances for a thermalisation model. (orig.)

  8. AMOC studies of positronium in fine MgO powder

    Energy Technology Data Exchange (ETDEWEB)

    Waeyenberge, B. van; Dauwe, C. [Ghent Univ. (Belgium). Dept. of Subatomic and Radiation Physics; Stoll, H. [Max-Planck-Institut fuer Metallforschung, Stuttgart (Germany)

    2001-07-01

    A first set of AMOC spectra on fine powdered MgO were measured at the Stuttgart relativistic positron beam facility. A special AMOC spectrometer was set up in order to determine the long lifetimes of ortho-positronium in the powder cavities. The spectra were taken on pellets of pressed powder in air and in an oxygen atmosphere to ensure ortho- to para-positronium conversion. An analysis of the data is made in the light of previous lifetime measurements on MgO. Here the lifetime spectrum was fitted with an age dependent lifetime describing the slow thermalisation of epithermal ortho-positronium between the powder grains. Based on the lifetime spectrum of the integrated AMOC spectra the data could not discriminate between a 5-component model and a model including slow positronium thermalisation. On the other hand, analysis of the age dependent line shape parameter shows better variances for a thermalisation model. (orig.)

  9. Superconductivity near ferromagnetism in MgCNi3

    International Nuclear Information System (INIS)

    Rosner, H.; Weht, R.; Johannes, M.; Pickett, W.E.; Tosatti, E.

    2001-06-01

    Superconductivity and ferromagnetism have been believed to be incompatible over any extended temperature range until certain specific examples - RuSr 2 GdCu 2 O 8 and UGe 2 - have arisen in the past 2-3 years. The discovery of superconductivity above 8 K in MgCNi 3 , which is primarily the ferromagnetic element Ni and is strongly exchange-enhanced, provides a probable new and different example. This compound is shown here to be near ferromagnetism, requiring only hole-doping by 12% substitution of Mg by Na or Li. This system will provide the means to probe coupling, and possible coexistence, of these two forms of collective behavior without the requirement of pressure. (author)

  10. Observation of pseudogap in MgB2

    Science.gov (United States)

    Patil, S.; Medicherla, V. R. R.; Ali, Khadiza; Singh, R. S.; Manfrinetti, P.; Wrubl, F.; Dhar, S. K.; Maiti, Kalobaran

    2017-11-01

    We investigate the electronic structure of a specially prepared highly dense conventional high temperature superconductor, MgB2, employing high resolution photoemission spectroscopy. The spectral evolution close to the Fermi energy is commensurate to BCS descriptions as expected. However, the spectra in the wider energy range reveal the emergence of a pseudogap much above the superconducting transition temperature indicating an apparent departure from the BCS scenario. The energy scale of the pseudogap is comparable to the energy of the E2g phonon mode responsible for superconductivity in MgB2 and the pseudogap can be attributed to the effect of electron-phonon coupling on the electronic structure. These results reveal a scenario of the emergence of the superconducting gap within an electron-phonon coupling induced pseudogap and have significant implications in the study of high temperature superconductors.

  11. An accurate potentiometric titration of 5-25 mg uranium

    International Nuclear Information System (INIS)

    Slanina, J.; Bakker, F.; Lingerak, W.A.

    1976-01-01

    A potentiometric titration of 5 to 25 mg uranium is described. Sulphamic and phosphoric acid are added to the sample (volume 1 ml), U VI is reduced to U IV by Fe 2+ and the excess of Fe 2+ is oxidized by a mixture of nitric acid, sulphamic acid and ammonium molybdate; vanadyl sulphate is added to ensure a sharp end-point of the titration. The resultant U IV is titrated automatically with 0.02500N potassiumdichromate using a platinum indicator electrode. The automatic titration is performed both with a commercial titrator (Mettler) and with an R.C.N. titrator which waits after each addition until the equilibrium is reached. Using the Mettler titrator an accuracy of 0.05% relative was reached. The R.C.N. setpoint titrator gave results with an accuracy of 0.04% relative at the 20-mg U level. Each titration takes 5 to 7 min. (author)

  12. Study of the 50 mg Propylthiouracil tablets stability

    International Nuclear Information System (INIS)

    Valdes Bendoyro, Maria Olga; Garcia Penna, Caridad Margarita; Lugones Fernandez, Juan

    2010-01-01

    Authors developed a stability study of 50 mg Propylthiouracil tablets and determination of its expiry date. This study was conducted by fixed life methods and of accelerated stability by high-performance liquid chromatography, validated in Drugs Research and Development Center. Fixed life study was conducted during 24 months at room temperature; whereas the accelerated stability study was conducted exposing the product to light influence, humidity and temperature; during 3 months a analysis was performed for the two first ones and over 6 months in the case of temperature study. Propylthiouracil formula (50 mg tablets) fulfilled the quality specifications described in Pharmacopeia. Results of stability study by fixed life after 24 months showed that thr product maintain the parameter determining its quality during this period, and in the accelerated studies there was not a significant degradation of product. Two years was the expity date established in above mentioned conditions

  13. Investigation of pinning in MgB2 superconductors

    International Nuclear Information System (INIS)

    Mohammad, S.; Reissner, M.; Steiner, W.; Bauer, E.; Giovannini, M.

    2006-01-01

    Full text: The pinning behaviour of bulk MgB 2 superconductors is peculiar in many respects. Pinning seems to be stronger than in classical high T C materials and there seems to be no weak link problem in these compounds, giving hope to produce bulk samples and wires with current densities appropriate for technical applications. But, although many studies concerning the pinning behaviour in this compound appeared in recent years, the results are still contradictory. In the present work we present results of an investigation of the pinning behaviour by magnetic relaxation measurements of three MgB 2 samples: a pure one, a sample with 8 at% Al substitution and a sample with 10 wt% of SiC admixture. A comparison of different analyses methods is given. (author)

  14. Secondary precipitation in an Al-Mg-Si-Cu alloy

    International Nuclear Information System (INIS)

    Buha, J.; Lumley, R.N.; Crosky, A.G.; Hono, K.

    2007-01-01

    Interruption of a conventional T6 heat treatment at 177 deg. C for the Al-Mg-Si-Cu alloy 6061 after a short period of time (20 min), by inserting a dwell period at a lower temperature (e.g. 65 deg. C), promotes secondary precipitation of Guinier-Preston (GP) zones. As a consequence, a much greater number of precursors to the β'' precipitates are produced so that a finer and denser dispersion of this phase is formed when T6 ageing is resumed. This change in microstructure causes significant and simultaneous improvements in tensile properties and fracture toughness. Secondary precipitation of GP zones occurs through a gradual evolution of a large number of Mg-Si(-Cu)-vacancy co-clusters formed during the initial ageing at 177 deg. C. The precise mechanism of secondary precipitation has been revealed by three-dimensional atom probe microscopy supplemented by transmission electron microscopy and differential scanning calorimetry

  15. Microstructure and hydrogen sorption kinetics of Mg nanopowders with catalyst

    International Nuclear Information System (INIS)

    Revesz, A.; Fatay, D.; Spassov, T.

    2007-01-01

    MgH 2 powders were ball-milled with and without catalysts (Nb 2 O 5 ) under hydrogen in a high-energy mill for 10 h. Morphological, structural and microstructural characterization of the nanocomposites, including particle and crystallite size distribution were carried out before and after hydrogen absorption. In order to study the above-mentioned microstructural parameters imaging and X-ray scattering techniques (high-resolution X-ray diffractometry) have been employed. The effect of the particle and grain size on the hydriding/dehydriding kinetics of ball-milled MgH 2 + catalyst powders was analyzed. The grain and particle size reduction enhances substantially the hydriding/dehydriding

  16. Luminescence of color centers in MgF2 crystals

    International Nuclear Information System (INIS)

    Vakhidov, Sh.A.; Nuritdinov, I.; Musaeva, M.A.

    1999-01-01

    The photoluminescence characteristics of the proper radiation color centers of the MgF 2 crystals are studied. The samples were irradiated by the 60 Co source γ-rays up to the dose 10 7 Gy. The bands with the maxima in the area of 420, 460, 550 and 620 nm were identified, which are excited correspondingly in the bands with the maxima of 370, 320, 410 and 480 nm

  17. Study of the $\\beta$-decay of $^{20}$Mg

    CERN Multimedia

    Cederkall, J A; Riisager, K; Garcia borge, M J; Madurga flores, M; Jonson, B N G; Fynbo, H O U; Koldste, G T; Giles, T J; Nilsson, T; Perea martinez, A

    We propose to perform a detailed study of the $\\beta$-decay of the dripline nucleus $^{20}$Mg. This will provide important information on resonances in $^{20}$Na relevant for the astrophysical rp-process as well as improved information for detailed comparison with state-of-the-art Shell-Model calculations and for comparison with the mirror $\\beta$-decay of $^{20}$O.

  18. Tetragonal to orthorhombic transformation in Mg-PSZ

    International Nuclear Information System (INIS)

    Liu, Z.W.; Spargo, A.E.C.; Hannink, R.H.J.; Drennan, J.

    1997-01-01

    The phase transformation from tetragonal to orthorhombic in MgO-partially-stabilized zirconia has been investigated by using high resolution transmission electron microscopy (HRTEM). Evidences are given to show that orthorhombic ZrO 2 frequently observed in transmission electron microscopy (TEM) thin foil studies was induced by dimpling and polishing during the specimen preparation. It was also found that the orthorhombic to monoclinic transformation was less sensitive to stress that the tetragonal to monoclinic transformation. 20 refs., 1 tab., 8 figs

  19. Thermodynamic modeling of the Mg-Al-Ca system

    Energy Technology Data Exchange (ETDEWEB)

    Janz, A.; Groebner, J. [Clausthal University of Technology, Institute of Metallurgy, Robert-Koch-Str. 42, D-38678 Clausthal-Zellerfeld (Germany); Cao, H.; Zhu, J.; Chang, Y.A. [Department of Materials Science and Engineering, University of Wisconsin, 1509 University Ave., Madison, WI 53706 (United States); Schmid-Fetzer, R. [Clausthal University of Technology, Institute of Metallurgy, Robert-Koch-Str. 42, D-38678 Clausthal-Zellerfeld (Germany)], E-mail: schmid-fetzer@tu-clausthal.de

    2009-02-15

    A thermodynamic model has been developed that provides a quantitative description for a wide area of the Mg-Al-Ca system. All available experimental data plus new key experiments using differential scanning calorimetry/differential thermal analysis have been considered to create a dataset which reproduces the primary crystallizing phases, the extensive ternary solubilities of binary phases and the ternary C36 Laves phase. This enables validated thermodynamic calculations in various areas of this ternary system.

  20. Substrate and Mg doping effects in GaAs nanowires

    Directory of Open Access Journals (Sweden)

    Perumal Kannappan

    2017-10-01

    Full Text Available Mg doping of GaAs nanowires has been established as a viable alternative to Be doping in order to achieve p-type electrical conductivity. Although reports on the optical properties are available, few reports exist about the physical properties of intermediate-to-high Mg doping in GaAs nanowires grown by molecular beam epitaxy (MBE on GaAs(111B and Si(111 substrates. In this work, we address this topic and present further understanding on the fundamental aspects. As the Mg doping was increased, structural and optical investigations revealed: i a lower influence of the polytypic nature of the GaAs nanowires on their electronic structure; ii a considerable reduction of the density of vertical nanowires, which is almost null for growth on Si(111; iii the occurrence of a higher WZ phase fraction, in particular for growth on Si(111; iv an increase of the activation energy to release the less bound carrier in the radiative state from nanowires grown on GaAs(111B; and v a higher influence of defects on the activation of nonradiative de-excitation channels in the case of nanowires only grown on Si(111. Back-gate field effect transistors were fabricated with individual nanowires and the p-type electrical conductivity was measured with free hole concentration ranging from 2.7 × 1016 cm−3 to 1.4 × 1017 cm−3. The estimated electrical mobility was in the range ≈0.3–39 cm2/Vs and the dominant scattering mechanism is ascribed to the WZ/ZB interfaces. Electrical and optical measurements showed a lower influence of the polytypic structure of the nanowires on their electronic structure. The involvement of Mg in one of the radiative transitions observed for growth on the Si(111 substrate is suggested.

  1. Obtention of Al-Mg alloys of porous morphology

    International Nuclear Information System (INIS)

    Barragan V, J.; Zamora R, L.; Sandoval J, A.R.; Iturbe G, J.L.

    2006-01-01

    With the objective of using it as fuel cell, a Mg 25 AI alloy of porous morphology was obtained. The material it was hydrogenates at 200 C by different time. It was analyzed by Scanning Electron Microscopy SEM and X-ray diffraction, XRD. Those XRD diffractographs present peaks run toward the origin, that which indicates a volume increase of the unitary cell by effect of the hydrogen absorption. (Author)

  2. Flexible MgO Barrier Magnetic Tunnel Junctions.

    Science.gov (United States)

    Loong, Li Ming; Lee, Wonho; Qiu, Xuepeng; Yang, Ping; Kawai, Hiroyo; Saeys, Mark; Ahn, Jong-Hyun; Yang, Hyunsoo

    2016-07-01

    Flexible MgO barrier magnetic tunnel junction (MTJ) devices are fabricated using a transfer printing process. The flexible MTJ devices yield significantly enhanced tunneling magnetoresistance of ≈300% and improved abruptness of switching, as residual strain in the MTJ structure is released during the transfer process. This approach could be useful for flexible electronic systems that require high-performance memory components. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  3. Enhanced magnetization at the Cr/MgO(001) interface

    Energy Technology Data Exchange (ETDEWEB)

    Leroy, M.-A. [Laboratoire Léon Brillouin, IRAMIS, CEA Saclay, 91191 Gif sur Yvette (France); Institut Jean Lamour, Université de Lorraine, 54500 Vandoeuvre les Nancy (France); Bataille, A. M., E-mail: alexandre.bataille@cea.fr; Ott, F. [Laboratoire Léon Brillouin, IRAMIS, CEA Saclay, 91191 Gif sur Yvette (France); Wang, Q.; Fitzsimmons, M. R. [Los Alamos National Laboratory, Los Alamos, New Mexico 87545 (United States); Bertran, F.; Le Fèvre, P.; Taleb-Ibrahimi, A.; Vlad, A.; Coati, A. [Synchrotron SOLEIL, L' Orme des merisiers, 91192 Gif sur Yvette (France); Garreau, Y. [Synchrotron SOLEIL, L' Orme des merisiers, 91192 Gif sur Yvette (France); Matériaux et phénomènes quantiques (MPQ), Université Paris Diderot - Paris 7, Sorbonne-Paris-Cité, CNRS, UMR 7162, 10, rue A. Domon et L. Duquet 75205 Paris Cedex 13 (France); Hauet, T.; Andrieu, S. [Institut Jean Lamour, Université de Lorraine, 54500 Vandoeuvre les Nancy (France); Gatel, C. [CEMES-CNRS, 29 rue Jeanne Marvig, 31055 Toulouse Cedex (France)

    2015-12-21

    We report on the magnetization at the Cr/MgO interface, which we studied through two complementary techniques: angle-resolved photoemission spectroscopy and polarized neutron reflectivity. We experimentally observe an enhanced interface magnetization at the interface, yet with values much smaller than the ones reported so far by theoretical and experimental studies on Cr(001) surfaces. Our findings cast some doubts on the interpretations on previous works and could be useful in antiferromagnetic spin torque studies.

  4. Magnetic domains in martensite of Ni-Mg-Ga alloy

    International Nuclear Information System (INIS)

    Kokorin, V.V.; Babij, O.M.; Dubinko, S.V.; Prokopov, A.R.

    2006-01-01

    The structural changes attendant on intermartensitic transformation in a Ni-Mg-Ga shape memory alloy are considered using magneto-optical visualization with the help of ferrite-garnet monocrystalline films. It is established that on the intermartensitic transformation the complete reorganization of martensite macrostructure fails. Martensite crystals resulted from the basic transformation change somewhat their sizes on intermartensitic transition. The existence of large-scale labyrinth magnetic domain structure is revealed [ru

  5. Nucleation of CaCO3 polymorphs from a colloidal alcoholic solution of Ca(OH)2 nanocrystals exposed to low humidity conditions

    OpenAIRE

    Gómez Villalba, Luz Stella; López-Arce, Paula; Fort González, Rafael

    2011-01-01

    A study of the stability of calcium carbonate polymorphs formed as a result of the carbonation process from an alcoholic colloidal solution of nanocrystals of Ca(OH)2 in low relative humidity (RH) conditions (33% and 54% RH) is presented in this research. The crystalline behavior, the time dependence of nucleation and the phases’ transformations as a result of exposure to low humidity conditions are evaluated. The carbonation process is slow, starting with the nucleation of amorphous calcium ...

  6. Chemistry of Organophosphonate Scale Growth lnhibitors: 3. Physicochemical Aspects of 2-Phosphonobutane-1,2,4-Tricarboxylate (PBTC) And Its Effect on CaCO3 Crystal Growth

    OpenAIRE

    Demadis, Konstantinos D.; Lykoudis, Panos

    2005-01-01

    Industrial water systems often suffer from undesirable inorganic deposits, such as calcium carbonate, calcium phosphates, calcium sulfate, magnesium silicate, and others. Synthetic water additives, such as phosphonates and phosphonocarboxylates, are the most important and widely utilized scale inhibitors in a plethora of industrial applications including cooling water, geothermal drilling, desalination, etc. The design of efficient and cost-effective inhibitors, as well as the study ...

  7. Diagenetic and Paleoceanographic variations in sedimentary Mn, Ba, and CaCO3, with emphasis on the eastern Mediterranean sapropel S1

    NARCIS (Netherlands)

    Reitz, Anja

    2005-01-01

    The original geochemical signal in marine Corg-rich or formerly Corg-rich sediments is usually highly overprinted by a sequence of diagenetic processes depending on the amount of metabolizable organic carbon and the environmental conditions determining the redox potential. In general, biogenic

  8. Return of the coral reef hypothesis: basin to shelf partitioning of CaCO3 and its effect on atmospheric CO2.

    Science.gov (United States)

    Opdyke, B N; Walker, J C

    1992-08-01

    Differences in the rate of coral reef carbonate deposition from the Pleistocene to the Holocene may account for the Quaternary variation of atmospheric CO2. Volumes of carbonate associated with Holocene reefs require an average deposition rate of 2.0 x 10(13) mol/yr for the past 5 ka. In light of combined riverine, midocean ridge, and ground-water fluxes of calcium to the oceans of 2.3 x 10(13) mol/yr, the current flux of calcium carbonate to pelagic sediments must be far below the Pleistocene average of 1.2 x 10(13) mol/yr. We suggest that sea-level change shifts the locus of carbonate deposition from the deep sea to the shelves as the normal glacial-interglacial pattern of deposition for Quaternary global carbonates. To assess the impact of these changes on atmospheric CO2, a simple numerical simulation of the global carbon cycle was developed. Atmospheric CO2 as well as calcite saturation depth and sediment responses to these carbonate deposition changes are examined. Atmospheric CO2 changes close to those observed in the Vostok ice core, approximately 80 ppm CO2, for the Quaternary are observed as well as the approximate depth changes in percent carbonate of sediments measured in the Pacific Ocean over the same time interval.

  9. Preparation and characterization of ZnO microfiltration membrane and its support using kaolin (DD3 and CaCO3

    Directory of Open Access Journals (Sweden)

    B. Boudaira

    Full Text Available Abstract The objective of the present paper was to prepare a ceramic support with membrane. Tubular ceramic supports prepared from kaolin (DD3 and calcium carbonate with 6 and 10 mm inner and outer diameters, respectively, were extruded and sintered at 1200 °C. It has been found that sintered supports had interesting characteristics: average pore size of about 5µm, porosity of about 50%, and monomodal pore size distribution. This support was used to be substrate for a membrane layer of microfiltration. This membrane layer was elaborated from zinc oxide, using slip casting technique. The specimens were subsequently sintered at 1000 °C. The microstructure and porosity as well as the permeability have also been studied. It has been found that the average pore size was about 1.2µm, the layer thickness was ~33µm, and the water permeability measured was about 880 L.h-1.m-2.bar-1.

  10. Seasonal variation of CaCO3 saturation state in bottom water of a biological hotspot in the Chukchi Sea, Arctic Ocean

    Directory of Open Access Journals (Sweden)

    M. Yamamoto-Kawai

    2016-11-01

    Full Text Available Distribution of calcium carbonate saturation state (Ω was observed in the Chukchi Sea in autumn 2012 and early summer 2013. Ω in bottom water ranged from 0.3 to 2.0 for aragonite and from 0.5 to 3.2 for calcite in 2012. In 2013, Ω in bottom water was 1.1–2.8 for aragonite and 1.7–4.4 for calcite. Aragonite and calcite undersaturation was found in high productivity regions in autumn 2012 but not in early summer 2013. Comparison with other parameters has indicated that biological processes – respiration and photosynthesis – are major factors controlling the regional and temporal variability of Ω. From these ship-based observations, we have obtained empirical equations to reconstruct Ω from temperature, salinity and apparent oxygen utilization. Using 2-year-round mooring data and these equations, we have reconstructed seasonal variation of Ω in bottom water in Hope Valley, a biological hotspot in the southern Chukchi Sea. Estimated Ω was high in spring and early summer, decreased in later summer, and remained relatively low in winter. Calculations indicated a possibility that bottom water could have been undersaturated for aragonite on an intermittent basis even in the pre-industrial period, and that anthropogenic CO2 has extended the period of aragonite undersaturation to more than 2-fold longer by now.

  11. LDEO Carbonate Data - CaCO3 Percentages for 328 Sediments Cores, Principally from The Atlantic Ocean Spanning 100,000 to 200,000 Years bp

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — LDEO Carbonate data were compiled under the direction of A. Esmay and W.F. Ruddiman at the Lamont-Doherty Earth Observatory of Columbia University. Data include...

  12. Study of sintering on Mg-Zn-Ca alloy system

    Science.gov (United States)

    Annur, Dhyah; Lestari, Franciska P.; Erryani, Aprilia; Kartika, Ika

    2018-05-01

    Magnesium and its alloy have gained a lot of interest to be used in biomedical application due to its biodegradable and biocompatible properties. In this study, sintering process in powder metallurgy was chosen to fabricatenonporous Mg-6Zn-1Ca (in wt%) alloy and porous Mg-6Zn-1Ca-10 Carbamide alloy. For creating porous alloy, carbamide (CO(NH2)2 was added to alloy system as the space holder to create porous structure material. Effect of the space holder addition and sintering temperature on porosity, phase formation, mechanical properties, and corrosion properties was observed. Sintering process was done in a tube furnace under Argon atmosphere in for 5 hours. The heat treatment was done in two steps; heated up at 250 °C for 4 hours to decompose spacer particle, followed by heated up at 580 °C or 630 °C for 5 hours. The porous structure of the resulted alloys was examined using Scanning Electron Microscope (SEM), while the phase formation was characterized by X-ray diffraction (XRD) analysis. Mechanical properties were examined using compression testing. From this study, increasing sintering temperature up to 630 °C reduced the mechanical properties of Mg-Zn-Ca alloy.

  13. Structural and mechanical properties of ZnMgO nanoparticles

    Energy Technology Data Exchange (ETDEWEB)

    Tosun, M. [Istanbul Technical University, Faculty of Mechanical Engineering, 34437, Gumussuyu, Istanbul (Turkey); Ataoglu, S. [Istanbul Technical University, Faculty of Civil Engineering, 34469, Maslak, Istanbul (Turkey); Istanbul Technical University, Earthquake Engineering and Disaster Management Institute, 34469, Maslak, Istanbul (Turkey); Arda, L., E-mail: lutfi.arda@bahcesehir.edu.tr [Bahcesehir University, Faculty of Arts and Sciences, Department of Mathematics and Computer Sciences, Ciragan Cad, Osmanpasa Mektebi Sok, 34349, Besiktas, Istanbul (Turkey); Ozturk, O.; Asikuzun, E. [Kastamonu University, Faculty of Arts and Sciences, Department of Physics, 37100, Kastamonu (Turkey); Akcan, D. [Bahcesehir University, Faculty of Arts and Sciences, Department of Mathematics and Computer Sciences, Ciragan Cad, Osmanpasa Mektebi Sok, 34349, Besiktas, Istanbul (Turkey); Cakiroglu, O. [Hasan Ali Yucel Education Faculty, Istanbul University, 34452, Beyazit, Istanbul (Turkey)

    2014-01-10

    This study reports the effect of annealing temperature on the structure and mechanical properties of Zn{sub 0.95}Mg{sub 0.05}O bulk samples by using digital Vickers microhardness tester, X-ray diffraction analysis, scanning electron microscopy and electron dispersive X-ray measurements. The samples were prepared using Zn and Mg based alkoxed by the sol–gel technique and annealed at various temperatures (500, 600, 700 and 800 °C). Vickers microhardness, elastic modulus, yield strength and fracture toughness values of Zn{sub 0.95}Mg{sub 0.05}O bulk samples were separately calculated and compared with each other. The experimental results of hardness measurements were analyzed using Meyer's law, Proportional Specimen Resistance (PSR) and Elastic/Plastic Deformation (EPD) models and Hays–Kendall (HK) approach. Finally, it was seen that HK approach is the most successful model for the microhardness analysis of these materials.

  14. Resonant proton scattering of $^{22}$Mg and $^{21}$Na

    CERN Multimedia

    Di julio, D D; Jansson, K; Rudolph, D; Fynbo, H O U; Nilsson, T; Perea martinez, A

    In our letter-of-intent, INTC-I-051, we discussed the physics case for scattering and transfer reactions involving light nuclei in the break-out region of the rp-process. The Committee found the physics case compelling and supported the letter-of-intent under the premise that beams of proper quality were developed and that an adequate detector set-up was presented. As these two requirements have been met recently we now propose to study resonant proton scattering of $^{22}$Mg to identify the states at 1.733 MeV and 2.575 MeV in $^{23}$Al that have been reported from the $^{24}$Mg($^{7}$Li,$^{8}$He)$\\,^{23}\\!$Al reaction but that remained unobserved in the only resonant proton scattering experiment performed with $^{22}$Mg so far. In particular we should be able to investigate the character of the proton emission of the 2.575 MeV state which may also have a significant inelastic branch. We also propose to perform resonant proton scattering on $^{21}$Na above $\\alpha$-particle threshold with $^{18}$Ne to study ...

  15. Adsorption of Na, Mg, and Al atoms on BN nanotubes

    Energy Technology Data Exchange (ETDEWEB)

    Beheshtian, Javad [Department of Chemistry, Shahid Rajaee Teacher Training University, P.O. Box: 16875-163, Tehran (Iran, Islamic Republic of); Peyghan, Ali Ahmadi, E-mail: ahmadi.iau@gmail.com [Young Researchers Club, Islamic Azad University, Islamshahr Branch, Tehran (Iran, Islamic Republic of); Bagheri, Zargham [Physics group, Science department, Islamic Azad University, Islamshahr Branch, P.O. Box: 33135-369, Islamshahr, Tehran (Iran, Islamic Republic of)

    2012-12-30

    Adsorption of three metals (Na, Mg, and Al) on the surface of BN nanotubes (BNNT) has been investigated by using density functional theory. Adsorption energies for Na and Al atoms have been calculated to be about - 0.22 to - 0.61 eV, respectively. Upon the metal adsorption, energy gap between highest occupied and lowest unoccupied orbitals of the tube is dramatically decreased, resulting in enhanced electrical conductivity. However, in the case of Mg atom, the low adsorption energy cannot change electronic property of the tube. The semi-conductive BNNT transform to n-type semiconductor after adsorption of Na atom. The metal adsorption modifies work function of the BNNT and consequently the field-emission current densities of metal-BNNT may be significantly enhanced. - Highlights: Black-Right-Pointing-Pointer Adsorption of Na, Mg, and Al atoms on the BN nanotubes (BNNT) was studied. Black-Right-Pointing-Pointer Adsorption energies for Na and Al atoms are about - 0.22 to - 0.61 eV, respectively. Black-Right-Pointing-Pointer Energy gap of the tube dramatically decreases upon the metals adsorption. Black-Right-Pointing-Pointer Semiconductor BNNT transform to n-type ones upon adsorption of Na and Al atoms. Black-Right-Pointing-Pointer The field-emission current densities of metal-BNNT may be significantly enhanced.

  16. Neural network potential for Al-Mg-Si alloys

    Science.gov (United States)

    Kobayashi, Ryo; Giofré, Daniele; Junge, Till; Ceriotti, Michele; Curtin, William A.

    2017-10-01

    The 6000 series Al alloys, which include a few percent of Mg and Si, are important in automotive and aviation industries because of their low weight, as compared to steels, and the fact their strength can be greatly improved through engineered precipitation. To enable atomistic-level simulations of both the processing and performance of this important alloy system, a neural network (NN) potential for the ternary Al-Mg-Si has been created. Training of the NN uses an extensive database of properties computed using first-principles density functional theory, including complex precipitate phases in this alloy. The NN potential accurately reproduces most of the pure Al properties relevant to the mechanical behavior as well as heat of solution, solute-solute, and solute-vacancy interaction energies, and formation energies of small solute clusters and precipitates that are required for modeling the early stage of precipitation and mechanical strengthening. This success not only enables future detailed studies of Al-Mg-Si but also highlights the ability of NN methods to generate useful potentials in complex alloy systems.

  17. Reaction rate of 24Mg(p,γ)25Al

    International Nuclear Information System (INIS)

    Powell, D.C.; Iliadis, C.; Champagne, A.E.; Grossmann, C.A.; Hale, S.E.; Hansper, V.Y.; McLean, L.K.

    1999-01-01

    The proton-capture reaction on 24 Mg has been investigated in the bombarding energy range of E p =0.2-1.7 MeV. Resonance properties (strengths, branching ratios and lifetimes) of low-energy resonances have been measured. From the experimental results, accurate proton partial widths, γ-ray partial widths and total widths (Γ p , Γ γ , and Γ) have been deduced. The present experimental information establishes the 24 Mg+p reaction rates over the temperature range T=0.02-2.0 GK with statistical uncertainties of 5% to 21%. Our recommended reaction rates deviate from previous estimates by 18% to 45%. Based on our results, we can rule out the recent suggestion that the total width of the E R =223 keV resonance has a significant influence on the reaction rates. We also discuss several effects that might give rise to systematic uncertainties in the reaction rates. The astrophysical implications for hydrogen burning of 24 Mg at low stellar temperatures are presented

  18. Characterization of the microstructure in Mg based alloy

    KAUST Repository

    Kutbee, Arwa T

    2013-06-01

    The cast products Mg–Sn based alloys are promising candidates for automobile industries, since they provide a cheap yet thermally stable alternative to existing alloys. One drawback of the Mg–Sn based alloys is their insufficient hardness. The hardenability can be improved by engineering the microstructure through additions of Zn to the base alloy and selective aging conditions. Therefore, detailed knowledge about the microstructural characteristics and the role of Zn to promote precipitation hardening is essential for age hardenable Mg-based alloys. In this work, microstructural investigation of the Mg–1.4Sn–1.3Zn–0.1Mn (at.%) precipitation system was performed using TEM. The chemical composition of the precipitates was analyzed using EDS. APT was employed to obtain precise chemical information on the distribution of Zn in the microstructure. It was found from microstructural studies that different precipitates with varying sizes and phases were present; lath-shaped precipitates of the Mg2Sn phase have an incoherent interface with the matrix, unlike the lath-shaped MgZn2 precipitates. Furthermore, nano-sized precipitates dispersed in the microstructure with short-lath morphology can either be enriched with Sn or Zn. On the other hand, APT analysis revealed the strong repulsion between Sn and Zn atoms in a portion of the analysis volume. However, larger reconstruction volume required to identify the role of Zn is still limited to the optimization of specimen preparation.

  19. Phosphorus Doped Zn 1- x Mg x O Nanowire Arrays

    KAUST Repository

    Lin, S. S.

    2009-11-11

    We demonstrate the growth of phosphorus doped Zn 1-xMg xO nanowire (NW) using pulsed laser deposition. For the first time, p-type Zn 0.92Mg 0.08O:P NWs are likely obtained In reference to atomic force microscopy based piezoelectric output measurements, X-ray photoelectron spectroscopy, and the transport property between the NWs and a n-type ZnO film. A shallow acceptor level of ∼140 meV Is identified by temperaturedependent photoluminescence. A piezoelectric output of 60 mV on average has been received using the doped NWs. Besides a control on NW aspect ratio and density, band gap engineering has also been achieved by alloying with Mg to a content of x = 0.23. The alloyed NWs with controllable conductivity type have potential application In high-efficiency all-ZnO NWs based LED, high-output ZnO nanogenerator, and other optical or electrical devices. © 2009 American Chemical Society.

  20. The electric dipole moment of magnesium deuteride, MgD

    Energy Technology Data Exchange (ETDEWEB)

    Steimle, Timothy C., E-mail: TSteimle@asu.edu; Zhang, Ruohan [Department of Chemistry and Biochemistry, Arizona State University, Tempe, Arizona 85287-1604 (United States); Wang, Hailing [State Key Laboratory of Precision Spectroscopy, East China Normal University, Shanghai, 200062 (China)

    2014-06-14

    The (0,0) A{sup 2}Π–X {sup 2}Σ{sup +} band of a cold molecular beam sample of magnesium monodeuteride, MgD, has been recorded field-free and in the presence of a static electric field of up to 11 kV/cm. The lines associated with the lowest rotational levels are detected for the first time. The field-free spectrum was analyzed to produce an improved set of fine structure parameters for the A{sup 2}Π (v = 0) state. The observed electric field induced splittings and shifts were analyzed to produce permanent electric dipole moments, μ{sup -vector}{sub el} of 2.567(10)D and 1.31(8)D for A{sup 2}Π (v = 0) and X{sup 2}Σ{sup +}(v = 0) states, respectively. The recommended value for μ{sup -vector}{sub el}(X{sup 2}Σ{sup +} (v = 0)) for MgH, based upon the measured value for MgD, is 1.32(8)D.