Sample records for zn fe mg

  1. EFFECT OF Mg AND TEMPERATURE ON Fe-Al ALLOY LAYER IN Fe/(Zn-6%Al-x%Mg) SOLID-LIQUID DIFFUSION COUPLES

    NASA Astrophysics Data System (ADS)

    Liang, Liu; Liu, Ya-Ling; Liu, Ya; Peng, Hao-Ping; Wang, Jian-Hua; Su, Xu-Ping

    Fe/(Zn-6%Al-x%Mg) solid-liquid diffusion couples were kept at various temperatures for different periods of time to investigate the formation and growth of the Fe-Al alloy layer. Scanning electron microscopy (SEM), energy dispersive spectrometry (EDS) and X-ray diffraction (XRD) were used to study the constituents and morphology of the Fe-Al alloy layer. It was found that the Fe2Al5Znx phase layer forms close to the iron sheet and the FeAl3Znx phase layer forms near the side of the melted Zn-6%Al-3%Mg in diffusion couples. When the Fe/(Zn-6%Al-3%Mg) diffusion couple is kept at 510∘C for more than 15min, a continuous Fe-Al alloy layer is formed on the interface of the diffusion couple. Among all Fe/(Zn-6%Al-x%Mg) solid-liquid diffusion couples, the Fe-Al alloy layer on the interface of the Fe/(Zn-6% Al-3% Mg) diffusion couple is the thinnest. The Fe-Al alloy layer forms only when the diffusion temperature is above 475∘. These results show that the Fe-Al alloy layer in Fe/(Zn-6%Al-x%Mg) solid-liquid diffusion couples is composed of Fe2Al5Znx and FeAl3Znx phase layers. Increasing the diffusing temperature and time period would promote the formation and growth of the Fe-Al alloy layer. When the Mg content in the Fe/(Zn-6%Al-x%Mg) diffusion couples is 3%, the growth of the Fe-Al alloy layer is inhibited. These results may explain why there is no obvious Fe-Al alloy layer formed on the interface of steel with a Zn-6%Al-3%Mg coating.

  2. Novel ZnO/MgO/Fe2O3 composite optomagnetic nanoparticles.

    PubMed

    Kamińska, I; Sikora, B; Fronc, K; Dziawa, P; Sobczak, K; Minikayev, R; Paszkowicz, W; Elbaum, D

    2013-05-15

    A facile sol-gel synthesis of novel ZnO/MgO/Fe2O3 nanoparticles (NPs) is reported and their performance is compared to that of ZnO/MgO. Powder x-ray diffraction (XRD) patterns reveal the crystal structure of the prepared samples. The average particle size of the sample was found to be 4.8 nm. The optical properties were determined by UV-vis absorption and fluorescence measurements. The NPs are stable in biologically relevant solutions (phosphate buffered saline (PBS), 20 mM, pH = 7.0) contrary to ZnO/MgO NPs which degrade in the presence of inorganic phosphate. Superparamagnetic properties were determined with a superconducting quantum interference device (SQUID). Biocompatible and stable in PBS ZnO/MgO/Fe2O3 core/shell composite nanocrystals show luminescent and magnetic properties confined to a single NP at room temperature (19-24 ° C), which may render the material to be potentially useful for biomedical applications.

  3. Surface and local electronic structure modification of MgO film using Zn and Fe ion implantation

    NASA Astrophysics Data System (ADS)

    Singh, Jitendra Pal; Lim, Weon Cheol; Lee, Jihye; Song, Jonghan; Lee, Ik-Jae; Chae, Keun Hwa

    2018-02-01

    Present work is motivated to investigate the surface and local electronic structure modifications of MgO films implanted with Zn and Fe ions. MgO film was deposited using radio frequency sputtering method. Atomic force microscopy measurements exhibit morphological changes associated with implantation. Implantation of Fe and Zn ions leads to the reduction of co-ordination geometry of Mg2+ ions in host lattice. The effect is dominant at bulk of film rather than surface as the large concentration of implanted ions resides inside bulk. Moreover, the evidences of interaction among implanted ions and oxygen are not being observed using near edge fine structure measurements.

  4. Effect of MgO on Liquidus Temperatures in the ZnO-"FeO"-Al2O3-CaO-SiO2-MgO System in Equilibrium with Metallic Iron

    NASA Astrophysics Data System (ADS)

    Zhao, Baojun; Hayes, Peter C.; Jak, Evgueni

    2011-06-01

    The phase equilibria in the ZnO-"FeO"-Al2O3-CaO-SiO2-MgO system have been determined experimentally in equilibrium with metallic iron. Synthetic slags were equilibrated at a high temperature, quenched, and then the compositions of the phases in equilibrium were measured using electron probe X-ray microanalysis. Pseudoternary sections of the form ZnO-"FeO"-(Al2O3 + CaO + SiO2) for CaO/SiO2 = 0.71, (CaO + SiO2)/Al2O3 = 5 and fixed MgO concentrations of 2, 4, and 6 wt pct have been constructed. Wustite (Fe2+,Mg,Zn)O and spinel (Fe2+,Mg,Zn)O·(Al,Fe3+)2O3 are the major primary phases in the temperature and composition ranges investigated. The liquidus temperatures are increased by 140 K in the wustite primary phase field and by 70 K in the spinel primary phase field with the addition of 6 wt pct MgO in the slag. The partitioning of MgO and ZnO between the solid and liquid phases has been discussed.

  5. Thermal stability and magnetic properties of MgFe2O4@ZnO nanoparticles

    NASA Astrophysics Data System (ADS)

    Mallesh, S.; Prabu, D.; Srinivas, V.

    2017-05-01

    Magnesium ferrite, MgFe2O4, (MgFO) nanoparticles (NPs) have been synthesized through sol-gel process. Subsequently, as prepared particles were coated with Zinc-oxide (ZnO) layer(s) through ultrasonication process. Thermal stability, structure and magnetic properties of as-prepared (AP) and annealed samples in the temperature range of 350 °C-1200 °C have been investigated. Structural data suggests that AP MgFO NPs and samples annealed below 500 °C in air exhibit stable ferrite phase. However, α-Fe2O3 and a small fraction of MgO secondary phases appear along with ferrite phase on annealing in the temperatures range 500 °C- 1000 °C. This results in significant changes in magnetic moment for AP NPs 0.77 μB increases to 0.92 μB for 1200 °C air annealed sample. The magnetic properties decreased at intermediate temperatures due to the presence of secondary phases. On the other hand, pure ferrite phase could be stabilized with an optimum amount of ZnO coated MgFO NPs for samples annealed in the temperature range 500 °C-1000 °C with improvement in magnetic behavior compared to that of MgFO samples.

  6. Analysis of Relations Between the Level of Mg, Zn, Ca, Cu, and Fe and Depressiveness in Postmenopausal Women.

    PubMed

    Szkup, Małgorzata; Jurczak, Anna; Brodowska, Aleksandra; Brodowska, Agnieszka; Noceń, Iwona; Chlubek, Dariusz; Laszczyńska, Maria; Karakiewicz, Beata; Grochans, Elżbieta

    2017-03-01

    Numerous observations suggest a possible connection between the levels of Mg, Zn, Fe, and Zn and the incidence of depressive symptoms. Depression is two to three times more common in women than in men. The menopausal period is extremely conducive to depressive disorders. The aim of this study was to assess the severity of depressive symptoms in postmenopausal women depending on the levels of Mg, Zn, Ca, Cu, and Fe. The study included 198 healthy postmenopausal women at the average age of 56.26 ± 5.55 years. In the first part of the study, standardized research tools were used, namely the Primary Care Evaluation of Mental Disorders (PRIME-MD) and the Beck Depression Inventory (BDI). The second part involved biochemical analysis of Mg, Zn, Ca, Cu, and Fe levels in blood serum. The lowest Cu levels were observed in women without depressive symptoms (1.07 ± 0.22 mg/l) and the highest in those with severe depressive symptoms (1.19 ± 0.17 mg/l), (p ≤ 0.05). The lowest Mg levels were observed in women with depressive symptoms (14.28 ± 2.13 mg/l), and the highest in women without depressive symptoms (16.30 ± 3.51 mg/l), (p ≤ 0.05). The average serum Mg levels (15.75 ± 3.23 mg/l) decreased compared to the reference values (18.77-24 mg/l). What is striking is a potential relation between the levels of Mg and Cu and depressiveness. Our results indicate to a higher vulnerability to depression in a group of women with lower levels of Mg and higher levels of Cu.

  7. Photocatalytic study and superparamagnetic nature of Zn-doped MgFe2O4 colloidal size nanocrystals prepared by solvothermal reflux method.

    PubMed

    Manohar, A; Krishnamoorthi, C

    2017-08-01

    Biocompatible Mg 1-x Zn x Fe 2 O 4 (x=0.2, 0.4, 0.5, 0.6 & 0.8) nanoparticles were synthesized by solvothermal reflux method. All compounds were crystallized in cubic spinel structure with slightly enhance of lattice parameter with biocompatible substituent Zn 2+ concentration. All compounds were shown spherical geometry with average particle diameter is around 12nm (colloidal size). The spinel structure formation was confirmed by X-ray diffraction,electron diffraction, infrared, Raman shift measurements. Infrared analysis shows oleic acid coating on the surface of nanoparticles and TGA analysis shows that oleic acid desorbs from nanoparticle by decomposition at around 400°C. UV-Vis-NIR spectra show all the compounds show energy band gap in the semiconductor range (≈ 1.9eV). All compounds show superparamagnetic characteristics at room temperature with enhanced saturated mass magnetization (M s ) with Zn 2+ concentration up to x=0.5 and then reduces with further enhance of x up to 0.8. The M s changes were ascribed to occupation of Zn 2+ at tetrahedral sites and proportional enhance of Fe 3+ at octahedral sites. The enhanced Fe 3+ concentration at octahedral sublattice leads to formation Fe 3+ -O 2- -Fe 3+ networks which favor antiferromagnetic interactions due to superexchange phenomenon. Photocatalytic activity of all compounds were studied through methylene blue (MB) degradation analysis. All compounds show ≈ 96% degradation of MB upon 70min irradiation of light on photoreactor vessel. In addition, photocatalytic activity (degradation efficiency) enhances with Zn 2+ concentration in MgFe 2 O 4 . The Zn 2+ substitution enhances both M s and photocatalytic activity biocompatible of MgFe 2 O 4 nanoparticles. Copyright © 2017. Published by Elsevier B.V.

  8. Mg-Al and Zn-Fe layered double hydroxides used for organic species storage and controlled release.

    PubMed

    Seftel, E M; Cool, P; Lutic, D

    2013-12-01

    Layered double hydroxides (LDH) containing (Mg and Al) or (Zn and Fe) were prepared by coprecipitation at constant pH, using NaOH and urea as precipitation agents. The most pure LDH phase in the Zn/Fe system was obtained with urea and in Mg/Al system when using NaOH. The incorporation of phenyl-alanine (Phe) anions in the interlayer of the LDH was performed by direct coprecipitation, ionic exchange and structure reconstruction of the mixed oxide obtained by the calcination of the coprecipitated product at 400°C. The reconstruction method and the direct coprecipitation in a medium containing Phe in the initial mixture were less successful in terms of high yields of organic-mineral composite than the ionic exchange method. A spectacular change in sample morphology and yield in exchanged solid was noticed for the Zn3Fe sample obtained by ionic exchange for 6h with Phe solution. A delivery test in PBS of pH=7.4 showed the release of the Phe in several steps up to 25 h indicating different host-guest interactions between the Phe and the LDH matrix. This behavior makes the preparation useful to obtain late delivery drugs, by the incorporation of the anion inside the LDH layer. © 2013.

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

    NASA Astrophysics Data System (ADS)

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

    2018-05-01

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

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

    PubMed

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

    2016-06-01

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

  11. Bioaccessibility of Ca, Cu, Fe, Mg, Zn, and crude protein in beef, pork and chicken after thermal processing.

    PubMed

    Menezes, Eveline A; Oliveira, Aline F; França, Celia J; Souza, Gilberto B; Nogueira, Ana Rita A

    2018-02-01

    The bioaccessibility of Ca, Cu, Fe, Mg, Zn, and crude protein was evaluated after submitting beef, pork, and chicken to five different thermal treatments. The bioaccessibility of crude protein and metals were simulated by using in vitro enzymatic digestion with a gastric fluid solution and dialysability approach. Inductively coupled plasma optical spectrometry was used to quantify the dialyzable fraction and the total mineral content after microwave-assisted digestion. Graphite furnace atomic absorption spectrometry quantified Cu in chicken dialyzable fraction. The increase of temperature and heat exposure period decreased the protein bioaccessibility. Considering the total and dialyzable fraction, beef is an important source of Cu, Fe, Mg, and Zn to the human diet. The results of Fourier-transform infrared spectroscopy indicated physical changes in the treated samples related to protein denaturation, which was probably responsible for the decreased bioaccessibility of minerals and protein, mainly at higher temperatures. Copyright © 2017 Elsevier Ltd. All rights reserved.

  12. Synthesis and characterization of Cu0.3Zn0.5Mg0.2Fe2O4 nanoparticles as a magnetic drug delivery system

    NASA Astrophysics Data System (ADS)

    Ansari, Mohammad; Bigham, Ashkan; Hassanzadeh-Tabrizi, S. A.; Abbastabar Ahangar, H.

    2017-10-01

    Mixed spinel ferrite nanoparticles are being applied in biomedical applications due to their biocompatibility, antibacterial activity, particular magnetic and electronic properties with chemical and thermal stabilities. The Cu0.3Zn0.5Mg0.2Fe2O4 nanoparticles are synthesized through the thermal treatment method. Polyvinyl alcohol (PVA) is used as the capping agent to stabilize the particles and prevent their agglomeration. The synthesized nanoparticles are characterized through X-ray diffractometer (XRD), Fourier transform infrared spectroscopy (FTIR), N2 adsorption-desorption, field emission scanning electron microscopy (FESEM), and transmission electron microscope (TEM). The magnetic characterization is made on a vibrating sample magnetometer (VSM), which displayed super-paramagnetic behavior of the synthesized sample. Potential application of the Cu0.3Zn0.5Mg0.2Fe2O4 nanoparticles as a drug delivery agent is assessed in vitro by estimating their release properties. The obtained results indicate that the amount of ibuprofen (IBU) adsorbed into the nanocarrier of Cu0.3Zn0.5Mg0.2Fe2O4 is 104 mg/g and the drug release is sustained up to 72 h.

  13. Spinel, YbFe2O4, and Yb2Fe3O7 types of structure for compounds in the In2O3 and Sc2O3-A2O3-BO systems (A: Fe, Ga, or Al; B: Mg, Mn, Fe, Ni, Cu, or Zn) at temperatures over 1000C

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

    Kimizuka, N.; Mohri, T.

    In the Sc2O3-Ga2O3-CuO, Sc2O3-Ga2O3-ZnO, and Sc2O3-Al2O3-CuO systems, ScGaCuO4, ScGaZnO4, and ScAlCuO4 with the YbFe2O4-type structure and Sc2Ga2CuO7 with the Yb2Fe3O7-type structure were obtained. In the In2O3-A2O3-BO systems (A: Fe, Ga, or Al; B: Mg, Mn, Fe, Ni, or Zn), InGaFeO4, InGaNiO4, and InFeT MgO4 with the spinel structure, InGaZnO4, InGaMgO4, and InAl-CuO4 with the YbFe2O4-type structure, and In2Ga2MnO7 and In2Ga2ZnO7 with the Yb2Fe3O7-type structure were obtained. InGaMnO4 and InFe2O4 had both the YbFe2O4-type and spinel-type structures. The revised classification for the crystal structures of AB2O4 compounds is presented, based upon the coordination numbers of constituent A and B cations. 5more » references, 2 tables.« less

  14. Surfactant-free synthesis of octahedral ZnO/ZnFe2O4 heterostructure with ultrahigh and selective adsorption capacity of malachite green

    NASA Astrophysics Data System (ADS)

    Liu, Jue; Zeng, Min; Yu, Ronghai

    2016-05-01

    A new octahedral ZnO/ZnFe2O4 heterostructure has been fabricated through a facile surfactant-free solvothermal method followed by thermal treatment. It exhibits a record-high adsorption capacity (up to 4983.0 mg·g-1) of malachite green (MG), which is a potentially harmful dye in prevalence and should be removed from wastewater and other aqueous solutions before discharging into the environment. The octahedral ZnO/ZnFe2O4 heterostructure also demonstrates strong selective adsorption towards MG from two kinds of mixed solutions: MG/methyl orange (MO) and MG/rhodamine B (RhB) mixtures, indicating its promise in water treatment.

  15. Surfactant-free synthesis of octahedral ZnO/ZnFe2O4 heterostructure with ultrahigh and selective adsorption capacity of malachite green

    PubMed Central

    Liu, Jue; Zeng, Min; Yu, Ronghai

    2016-01-01

    A new octahedral ZnO/ZnFe2O4 heterostructure has been fabricated through a facile surfactant-free solvothermal method followed by thermal treatment. It exhibits a record-high adsorption capacity (up to 4983.0 mg·g−1) of malachite green (MG), which is a potentially harmful dye in prevalence and should be removed from wastewater and other aqueous solutions before discharging into the environment. The octahedral ZnO/ZnFe2O4 heterostructure also demonstrates strong selective adsorption towards MG from two kinds of mixed solutions: MG/methyl orange (MO) and MG/rhodamine B (RhB) mixtures, indicating its promise in water treatment. PMID:27142194

  16. Investigations on structural, vibrational and dielectric properties of nanosized Cu doped Mg-Zn ferrites

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

    Yadav, Anand; Department of Physics, MEDICAPS Institute of Science and Technology, Pithampur 453331; Rajpoot, Rambabu

    2016-05-23

    Transition metal Cu{sup 2+} doped Mg-Zn ferrite [Mg{sub 0.5}Zn{sub 0.5-x}Cu{sub x}Fe{sub 2}O{sub 4} (0.0 ≤ x ≤ 0.5)] were prepared by sol gel auto combustion (SGAC) method to probe the structural, vibrational and electrical properties. X-ray diffraction (XRD) pattern reveals a single-phase cubic spinel structure without the presence of any secondary phase corresponding to other structure. The average particle size of the parent Mg{sub 0.5}Zn{sub 0.5}Fe{sub 2}O{sub 4} is found to be ~29.8 nm and is found to increase with Cu{sup 2+} doping. Progressive reduction in lattice parameter of Mg{sub 0.5}Zn{sub 0.5}Fe{sub 2}O{sub 4} has been observed due to difference inmore » ionic radii of cations with improved Cu doping. Spinel cubic structure is further confirmed by Raman spectroscopy. Small shift in Raman modes towards higher wave number has been observed in doped Mg-Zn ferrites. The permittivity and dielectric loss decreases at lower doping and increases at higher order doping of Cu{sup 2+}.« less

  17. Microstructural characteristics and aging response of Zn-containing Al-Mg-Si-Cu alloy

    NASA Astrophysics Data System (ADS)

    Cai, Yuan-hua; Wang, Cong; Zhang, Ji-shan

    2013-07-01

    Al-Mg-Si-Cu alloys with and without Zn addition were fabricated by conventional ingot metallurgy method. The microstructures and properties were investigated using optical microscopy (OM), field emission scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM), tensile test, hardness test, and electrical conductivity measurement. It is found that the as-cast Al-Mg-Si-Cu-Zn alloy is composed of coarse dendritic grains, long needle-like β/δ-AlFeSi white intermetallics, and Chinese script-like α-AlFeSi compounds. During high temperature homogenization treatment, only harmful needle-like β-AlFeSi phase undergoes fragmentation and spheroidizing at its tips, and the destructive needle-like δ-phase does not show any morphological and size changes. Phase transitions from β-AlFeSi to α-AlFeSi and from δ-AlFeSi to β-AlFeSi are also not found. Zn addition improves the aging hardening response during the former aging stage and postpones the peak-aged hardness to a long aging time. In T4 condition, Zn addition does not obviously increase the yield strength and decrease the elongation, but it markedly improves paint-bake hardening response during paint-bake cycle. The addition of 0.5wt% Zn can lead to an increment of 99 MPa in yield strength compared with the value of 69 MPa for the alloy without Zn after paint-bake cycle.

  18. Mg1-xZnxFe2O4 nanoparticles: Interplay between cation distribution and magnetic properties

    NASA Astrophysics Data System (ADS)

    Raghuvanshi, S.; Mazaleyrat, F.; Kane, S. N.

    2018-04-01

    Correlation between cationic distribution, magnetic properties of Mg1-xZnxFe2O4 (0.0 ≤ x ≤ 1.0) ferrite is demonstrated, hardly shown in literature. X-ray diffraction (XRD) confirms the formation of cubic spinel nano ferrites with grain diameter between 40.8 to 55.4 nm. Energy dispersive spectroscopy (EDS) confirms close agreement of Mg/Fe, Zn/Fe molar ratio, presence of all elements (Mg, Zn, Fe, O), formation of estimated ferrite composition. Zn addition (for Mg) shows: i) linear increase of lattice parameter aexp, accounted for replacement of an ion with higher ionic radius (Zn > Mg); ii) presence of higher population of Fe3+ ions on B site, and unusual occurrence of Zn, Mg on A and B site leads to non-equilibrium cation distribution where we observe inverse to mixed structure, and is in contrast to reported literature where inverse to normal transition is reported; iii) effect on A-A, A-B, B-B exchange interactions, affecting coercivity Hc, Ms. A new empirical relation is also obtained showing linear relation between saturation magnetization Ms - inversion parameter δ, oxygen parameter u4 ¯ 3 m. Non-zero Y-K angle (αYK) values implies Y-K type magnetic ordering in the studied samples.

  19. Synthesis and characterization of Zn-Mg ferrite

    NASA Astrophysics Data System (ADS)

    Singh, Shailndra; Barbar, S. K.; Ram, Sahi

    2018-05-01

    The Zn-Mg ferrite sample of general formula Zn0.5Mg0.5Fe2O4 have been prepared by standard solid state reaction technique using high purity oxides. X-ray diffraction analysis shows the formation of a zinc-magnesium ferrite cubic phase at room temperature with space group Fd3m. FTIR spectra show two significant absorption bands first at 665.15 cm-1 corresponding to tetrahedral (A) and second band at 434 cm-1 corresponding to octahedral (B) sites of the spinel. Morphology of the sample determined by the SEM measurement and EDS analysis has confirmed the composition of atoms in the sample.

  20. Structural, optical and magnetic studies of CuFe2O4, MgFe2O4 and ZnFe2O4 nanoparticles prepared by hydrothermal/solvothermal method

    NASA Astrophysics Data System (ADS)

    Kurian, Jessyamma; Mathew, M. Jacob

    2018-04-01

    In this paper we report the structural, optical and magnetic studies of three spinel ferrites namely CuFe2O4, MgFe2O4 and ZnFe2O4 prepared in an autoclave under the same physical conditions but with two different liquid medium and different surfactant. We use water as the medium and trisodium citrate as the surfactant for one method (Hydrothermal method) and ethylene glycol as the medium and poly ethylene glycol as the surfactant for the second method (solvothermal method). The phase identification and structural characterization are done using XRD and morphological studies are carried out by TEM. Cubical and porous spherical morphologies are obtained for hydrothermal and solvothermal process respectively without any impurity phase. The optical studies are carried out using FTIR and UV-Vis reflectance spectra. In order to elucidate the nonlinear optical behaviour of the prepared nanomaterial, open aperture z-scan technique is used. From the fitted z-scan curves nonlinear absorption coefficient and the saturation intensity are determined. The magnetic characterization of the samples is performed at room temperature using vibrating sample magnetometer measurements. The M-H curves obtained are fitted using theoretical equation and the different components of magnetization are determined. Nanoparticles with high saturation magnetization are obtained for MgFe2O4 and ZnFe2O4 prepared under solvothermal reaction. The magnetic hyperfine parameters and the cation distribution of the prepared materials are determined using room temperature Mössbauer spectroscopy. The fitted spectra reveal the difference in the magnetic hyperfine parameters owing to the change in size and morphology.

  1. Quaternary BeMgZnO by plasma-enhanced molecular beam epitaxy for BeMgZnO/ZnO heterostructure devices

    NASA Astrophysics Data System (ADS)

    Ullah, M. B.; Toporkov, M.; Avrutin, V.; Özgür, Ü.; Smith, D. J.; Morkoç, H.

    2017-02-01

    We investigated the crystal structure, growth kinetics and electrical properties of BeMgZnO/ZnO heterostructures grown by Molecular Beam Epitaxy (MBE). Transmission Electron Microscopy (TEM) studies revealed that incorporation of Mg into the BeZnO solid solution eliminates the high angle grain boundaries that are the major structural defects in ternary BeZnO. The significant improvement of x-ray diffraction intensity from quaternary BeMgZnO alloy compared to ternary BeZnO was attributed to the reduction of lattice strain, which is present in the latter due to the large difference of covalent radii between Be and Zn (1.22 Å for Zn, 0.96 Å for Be). Incorporation of Mg, which has a larger covalent radius of 1.41Å, reduced the strain in BeMgZnO thin films and also enhanced Be incorporation on lattice sites in the wurtzite lattice. The Zn/(Be + Mg) ratio necessary to obtain single-crystal O-polar BeMgZnO on (0001) GaN/sapphire templates was found to increase with increasing substrate temperature:3.9, 6.2, and 8.3 at substrate temperatures of 450°C, 475°C, and 500°C, respectively. Based on analysis of photoluminescence spectra from Be0.03MgyZn0.97-yO and evolution of reflection high-energy electron diffraction patterns observed in situ during the MBE growth, it has been deduced that more negative formation enthalpy of MgO compared to ZnO and the increased surface mobility of Mg adatoms at elevated substrate temperatures give rise to the nucleation of a MgO-rich wurtzite phase at relatively low Zn/(Be + Mg) ratios. We have demonstrated both theoretically and experimentally that the incorporation of Be into the barrier in Zn-polar BeMgZnO/ZnO and O-polar ZnO/BeMgZnO polarization doped heterostructures allows the alignment of piezoelectric polarization vector with that of spontaneous polarization due to the change of strain sign, thus increasing the amount of net polarization. This made it possible to achieve Zn-polar BeMgZnO/ZnO heterostructures grown on Ga

  2. Two-dimensional electron gases in MgZnO/ZnO and ZnO/MgZnO/ZnO heterostructures grown by dual ion beam sputtering

    NASA Astrophysics Data System (ADS)

    Singh, Rohit; Arif Khan, Md; Sharma, Pankaj; Than Htay, Myo; Kranti, Abhinav; Mukherjee, Shaibal

    2018-04-01

    This work reports on the formation of high-density (~1013-1014 cm-2) two-dimensional electron gas (2DEG) in ZnO-based heterostructures, grown by a dual ion beam sputtering system. We probe 2DEG in bilayer MgZnO/ZnO and capped ZnO/MgZnO/ZnO heterostructures utilizing MgZnO barrier layers with varying thickness and Mg content. The effect of the ZnO cap layer thickness on the ZnO/MgZnO/ZnO heterostructure is also studied. Hall measurements demonstrate that the addition of a 5 nm ZnO cap layer results in an enhancement of the 2DEG density by about 1.5 times compared to 1.11 × 1014 cm-2 for the uncapped bilayer heterostructure with the same 30 nm barrier thickness and 30 at.% Mg composition in the barrier layer. From the low-temperature Hall measurement, the sheet carrier concentration and mobility are both found to be independent of the temperature. The capacitance-voltage measurement suggests a carrier density of ~1020 cm-3, confined in 2DEG at the MgZnO/ZnO heterointerface. The results presented are significant for the optimization of 2DEG for the eventual realization of cost-effective and large-area MgZnO/ZnO-based high-electron-mobility transistors.

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

    PubMed Central

    Dong, Anping; Li, Baoping; Lu, Yanling; Zhu, Guoliang; Xing, Hui; Shu, Da; Sun, Baode; Wang, Jun

    2017-01-01

    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. PMID:28829393

  4. Comparison of the solar photocatalytic activity of ZnO-Fe2O3 and ZnO-Fe(0) on 2,4-D degradation in a CPC reactor.

    PubMed

    Maya-Treviño, M L; Villanueva-Rodríguez, M; Guzmán-Mar, J L; Hinojosa-Reyes, L; Hernández-Ramírez, A

    2015-03-01

    In this work a comparative study of the catalytic activity of ZnO-Fe2O3 and ZnO-Fe(0) 0.5 wt% materials was carried out in the degradation of 2,4-dichlorophenoxyacetic acid (2,4-D) as a commercial formulation Hierbamina®, using a compound parabolic collector (CPC) reactor. The catalysts were synthesized by the sol-gel method and characterized by X-ray diffraction, UV-Vis diffuse reflectance spectroscopy, Fourier transform infrared spectroscopy (FTIR) and scanning electron microscopy. The textural properties of solids were determined from N2 adsorption isotherms using the Brunauer-Emmett-Teller (BET) method. The incorporation of Fe(0) onto ZnO was demonstrated by X-ray photoelectron spectroscopy analysis. The photocatalytic tests were performed at pH 7, using 10 mg L(-1) of herbicide and 0.5 g L(-1) of catalyst loading. The decay in herbicide concentration was followed by reversed-phase chromatography. A complete degradation of 2,4-D was achieved using ZnO-Fe(0) while 47% of herbicide removal was attained with ZnO-Fe2O3 mixed oxide for an accumulated energy QUV ≈ 2 kJ L(-1). The removal percentage of total organic carbon (TOC) during the solar photocatalytic process was superior using ZnO-Fe(0), achieving 45% compared to the 15% obtained with the mixed oxide catalyst.

  5. Nonstoichiometric Zn Ferrite and ZnFe2O4/Fe2O3 Composite Spheres: Preparation, Magnetic Properties, and Chromium Removal

    NASA Astrophysics Data System (ADS)

    Hang, Chun-Liang; Yang, Li-Xia; Sun, Chang-Mei; Liang, Ying

    2018-03-01

    Monodisperse and porous nonstoichiometric Zn ferrite can be prepared by a solvothermal method. Such non-Zn ferrite was used to be the precursor for synthesis of ZnFe2O4/Fe2O3 composite via calcination at 600°C for 3 h in air. X-ray powder diffractometer (XRD) and Energy Dispersive Spectrometer (EDS) proved the nonstoichiometry of Zn ferrite synthesized by solvothermal method and the formation of ZnFe2O4/Fe2O3 composite via calcination. TEM image showed that non-Zn ferrite spheres with wormlike nanopore structure were made of primary nanocrystals. BET surface area of non-Zn ferrite was much higher than that of ZnFe2O4/Fe2O3 composite. Saturation magnetization of non-Zn ferrites was significantly higher than that of ZnFe2O4/Fe2O3 composites. Calcination of non-Zn ferrite resulted in the formation of large amount of non-magnetic Fe2O3,which caused a low magnetization of composite. Because of higher BET surface area and higher saturation magnetization, non-Zn ferrite presented better Cr6+ adsorption property than ZnFe2O4/Fe2O3 composites.

  6. High-strain-rate superplasticity of the Al-Zn-Mg-Cu alloys with Fe and Ni additions

    NASA Astrophysics Data System (ADS)

    Kotov, A. D.; Mikhaylovskaya, A. V.; Borisov, A. A.; Yakovtseva, O. A.; Portnoy, V. K.

    2017-09-01

    During high-strain-rate superplastic deformation, superplasticity indices, and the microstructure of two Al-Zn-Mg-Cu-Zr alloys with additions of nickel and iron, which contain equal volume fractions of eutectic particles of Al3Ni or Al9FeNi, have been compared. It has been shown that the alloys exhibit superplasticity with 300-800% elongations at the strain rates of 1 × 10-2-1 × 10-1 s-1. The differences in the kinetics of alloy recrystallization in the course of heating and deformation at different temperatures and rates of the superplastic deformation, which are related to the various parameters of the particles of the eutectic phases, have been found. At strain rates higher than 4 × 10-2, in the alloy with Fe and Ni, a partially nonrecrystallized structure is retained up to material failure and, in the alloy with Ni, a completely recrystallized structure is formed at rates of up to 1 × 10-1 s-1.

  7. Novel multifunctional NiFe2O4/ZnO hybrids for dye removal by adsorption, photocatalysis and magnetic separation

    NASA Astrophysics Data System (ADS)

    Zhu, Hua-Yue; Jiang, Ru; Fu, Yong-Qian; Li, Rong-Rong; Yao, Jun; Jiang, Sheng-Tao

    2016-04-01

    Novel multifunctional NiFe2O4/ZnO hybrids were prepared by a hydrothermal method and their physicochemical properties were characterized by XRD, SEM, TEM, TGA, VSM, BET and UV-vis DRS. The adsorption and photocatalytic performance of NiFe2O4/ZnO hybrids were systematically investigated using congo red as a model contaminant. With the introduction of NiFe2O4, NiFe2O4/ZnO hybrids can absorb the whole light from 300 nm to 700 nm. The adsorption capacity (221.73 mg g-1) of NiFe2O4/ZnO hybrids is higher than those of NiFe2O4, ZnO and mechanically mixed NiFe2O4/ZnO hybrids. The removal of congo red solution (20 mg L-1) by NiFe2O4/ZnO hybrids was about 94.55% under simulated solar light irradiation for 10 min. rad OH and h+ play important roles in the decolorization of congo red solution by NiFe2O4/ZnO hybrids under simulated solar light irradiation. The decolorization efficiency of congo red solution is 97.23% for the fifth time by NiFe2O4/ZnO hybrids under simulate solar light irradiation, indicating the high photostability and durability. NO3- and Cl- anions which are ubiquitous components in dye-containing wastewater have negligible influence on the effectiveness of NiFe2O4/ZnO hybrids. Moreover, the magnetic NiFe2O4/ZnO hybrids can be easily separated from the reacted solution by an external magnet.

  8. Structural and functional responses of periphyton and macroinvertebrate communities to ferric Fe, Cu, and Zn in stream mesocosms.

    PubMed

    Cadmus, Pete; Guasch, Helena; Herdrich, Adam T; Bonet, Berta; Urrea, Gemma; Clements, William H

    2018-05-01

    Two mesocosm experiments were conducted to examine effects of ferric iron (Fe) and mixtures of ferric Fe with aqueous metals (Cu, Zn) on stream benthic communities. Naturally colonized benthic communities were exposed to a gradient of ferric Fe (0, 0.4, 1.0, 2.5, 6.2, and 15.6 mg/L) that bracketed the current US Environmental Protection Agency water quality criterion value (1.0 mg/L). After 10 d of exposure to ferric Fe, total macroinvertebrate abundance, number of taxa, and abundance of all major macroinvertebrate groups (Ephemeroptera, Plecoptera, Trichoptera, and Diptera) were significantly reduced. Heptageniid mayflies and chironomids were especially sensitive to Fe oxide deposition and were significantly reduced at 0.4 and 1.0 mg/L total Fe, respectively. In a second mesocosm experiment, periphyton and macroinvertebrate communities were exposed to ferric Fe (0.60 mg/L) with or without aqueous Cu and Zn at 2 treatment levels: low (0.01 mg/L Cu + 0.1 mg/L Zn) and high (0.05 mg/L Cu + 0.5 mg/L Zn). In contrast to previous research, we observed no evidence of a protective effect of Fe on toxicity of metals. Growth rates and protein content of periphyton were significantly reduced by both ferric Fe and aqueous metals, whereas abundance of heptageniid mayflies (Cinygmula) and whole community metabolism were significantly reduced by ferric Fe alone. We hypothesize that Fe oxides inhibited algal growth and enhanced metal accumulation, leading to a reduction in the quantity and quality of food resources for grazers. Mesocosm experiments conducted using natural benthic communities provide a unique opportunity to quantify the relative importance of indirect physical effects and to develop a better understanding of the relationship between basal food resources and consumers in natural stream ecosystems. Environ Toxicol Chem 2018;37:1320-1329. © 2017 SETAC. © 2017 SETAC.

  9. Synthesis, structural and magnetic properties of Mg0.6Zn0.4CrxFe2-xO4 (0.0 ≤ x ≤ 2.0) nano ferrite

    NASA Astrophysics Data System (ADS)

    Verma, R.; Kane, S. N.; Raghuvanshi, S.; Satalkar, M.; Modak, S. S.; Mazaleyrat, F.

    2018-05-01

    Present study reports, effect on structural, magnetic properties of Cr doped Mg-Zn nano-ferrite: Mg0.6Zn0.4CrxFe2-xO4 (0.0≤ x≤2.0), synthesized by sol-gel auto combustion method. X-ray diffraction (XRD), vibrating sample magnetometer (VSM), scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS) techniques were utilized to monitor the effect of Cr substitution on structural, magnetic properties, and correlation between them. XRD confirms the formation of single phase spinel nano ferrite with particle size ranging between 3.9 - 40.5 nm, whereas EDS confirms the formation of the estimated ferrite composition. Distribution of Mg, Zn, Cr, Fe cations on tetrahedral (A), octahedral (B) site show mixed spinel structure. Increase of Cr content leads to increase of specific surface area (4.35 - 28.28 m2/g), decrease of experimental saturation magnetization at 300 K (varies between 0.57 - 40.95 Am2/kg), and theoretical magnetization at 0 K (range between 13.37 - 56.77 Am2/kg). Observed changes in coercivity values reflect soft magnetic nature of the studied ferrites.

  10. Bioavailability of Fe and Zn in selected legumes, cereals, meat and milk products consumed in Fiji.

    PubMed

    Singh, Poonam; Prasad, Surendra; Aalbersberg, William

    2016-09-15

    The present study reports contents and the bioavailability of Fe and Zn from 25 selected raw and cooked food samples. The results showed highest variation of Fe content in raw food samples ranging from 2.19 ± 0.04 to 0.93 ± 0.03 mg/100g in legumes. The raw black eye bean, cheese and fish showed high Zn content up to 8.85 ± 0.01, 12.93 ± 0.26 and 172.03 ± 5.09 mg/100g, respectively. Pulses and cereals showed high level of ionizable Fe. Zn bioavailability was quite low in cereals as compared to pulses; 4.02% in yellow split to 17.40% in Bengal gram. Zn bioavailability of 17.40% is in cheese. Fe bioavailability is high in cooked rice 160.60%, white bread 428.30% and milk powder 241.67% showing that Fe bioavailability increased after cooking whereas the lowest in fish 0.84%. The multivariate and cluster analysis categorized studied foods into two main groups. Copyright © 2016 Elsevier Ltd. All rights reserved.

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

    NASA Astrophysics Data System (ADS)

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

    2016-02-01

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

  12. Mg Content Dependence of EML-PVD Zn-Mg Coating Adhesion on Steel Strip

    NASA Astrophysics Data System (ADS)

    Jung, Woo Sung; Lee, Chang Wook; Kim, Tae Yeob; De Cooman, Bruno C.

    2016-09-01

    The effect of coating thickness and Mg concentration on the adhesion strength of electromagnetic levitation physical vapor deposited Zn-Mg alloy coatings on steel strip was investigated. The phase fraction of Zn, Mg2Zn11, and MgZn2 was determined for a coating Mg concentration in the 0 to 15 wt pct range. Coatings with a Mg content less than 5 pct consisted of an Zn and Mg2Zn11 phase mixture. The coatings showed good adhesion strength and ductile fracture behavior. Coatings with a higher Mg concentration, which consisted of a Mg2Zn11 and MgZn2 phase mixture, had a poor adhesion strength and a brittle fracture behavior. The adhesion strength of PVD Zn-Mg alloy coatings was found to be related to the pure Zn phase fraction. The effect of coating thickness on adhesion strength was found to be negligible. The microstructure of the interface between steel and Zn-Mg alloy coatings was investigated in detail by electron microscopy, electron diffraction, and atom probe tomography.

  13. Electron confinement at diffuse ZnMgO/ZnO interfaces

    NASA Astrophysics Data System (ADS)

    Coke, Maddison L.; Kennedy, Oscar W.; Sagar, James T.; Warburton, Paul A.

    2017-01-01

    Abrupt interfaces between ZnMgO and ZnO are strained due to lattice mismatch. This strain is relaxed if there is a gradual incorporation of Mg during growth, resulting in a diffuse interface. This strain relaxation is however accompanied by reduced confinement and enhanced Mg-ion scattering of the confined electrons at the interface. Here we experimentally study the electronic transport properties of the diffuse heteroepitaxial interface between single-crystal ZnO and ZnMgO films grown by molecular-beam epitaxy. The spatial extent of the interface region is controlled during growth by varying the zinc flux. We show that, as the spatial extent of the graded interface is reduced, the enhancement of electron mobility due to electron confinement more than compensates for any suppression of mobility due to increased strain. Furthermore, we determine the extent to which scattering of impurities in the ZnO substrate limits the electron mobility in diffuse ZnMgO-ZnO interfaces.

  14. Biocompatibility Assessment of Novel Bioresorbable Alloys Mg-Zn-Se and Mg-Zn-Cu for Endovascular Applications: In- Vitro Studies.

    PubMed

    Persaud-Sharma, Dharam; Budiansky, Noah; McGoron, Anthony J

    2013-01-01

    Previous studies have shown that using biodegradable magnesium alloys such as Mg-Zn and Mg-Zn-Al possess the appropriate mechanical properties and biocompatibility to serve in a multitude of biological applications ranging from endovascular to orthopedic and fixation devices. The objective of this study was to evaluate the biocompatibility of novel as-cast magnesium alloys Mg-1Zn-1Cu wt.% and Mg-1Zn-1Se wt.% as potential implantable biomedical materials, and compare their biologically effective properties to a binary Mg-Zn alloy. The cytotoxicity of these experimental alloys was evaluated using a tetrazolium based- MTS (3-(4,5-dimethylthiazol-2-yl)-5-(3-carboxymethoxyphenyl)-2-(4-sulfophenyl)-2H-tetrazolium) assay and a lactate dehydrogenase membrane integrity assay (LDH). The MTS assay was performed on extract solutions obtained from a 30-day period of alloy immersion and agitation in simulated body fluid to evaluate the major degradation products eluted from the alloy materials. Human foreskin fibroblast cell growth on the experimental magnesium alloys was evaluated for a 72 hour period, and cell death was quantified by measuring lactate dehydrogenase concentrations. Both Mg-Zn-Se and Mg-Zn-Cu alloys exhibit low cytotoxicity levels which are suitable for biomaterial applications. The Mg-Zn-Cu alloy was found to completely degrade within 72 hours, resulting in lower human foreskin fibroblast cell viability. The Mg-Zn-Se alloy was shown to be less cytotoxic than both the Mg-Zn-Cu and Mg-Zn alloys.

  15. Biocompatibility Assessment of Novel Bioresorbable Alloys Mg-Zn-Se and Mg-Zn-Cu for Endovascular Applications: In- Vitro Studies

    PubMed Central

    Budiansky, Noah; McGoron, Anthony J.

    2013-01-01

    Previous studies have shown that using biodegradable magnesium alloys such as Mg-Zn and Mg-Zn-Al possess the appropriate mechanical properties and biocompatibility to serve in a multitude of biological applications ranging from endovascular to orthopedic and fixation devices. The objective of this study was to evaluate the biocompatibility of novel as-cast magnesium alloys Mg-1Zn-1Cu wt.% and Mg-1Zn-1Se wt.% as potential implantable biomedical materials, and compare their biologically effective properties to a binary Mg-Zn alloy. The cytotoxicity of these experimental alloys was evaluated using a tetrazolium based- MTS (3-(4,5-dimethylthiazol-2-yl)-5-(3-carboxymethoxyphenyl)-2-(4-sulfophenyl)-2H-tetrazolium) assay and a lactate dehydrogenase membrane integrity assay (LDH). The MTS assay was performed on extract solutions obtained from a 30-day period of alloy immersion and agitation in simulated body fluid to evaluate the major degradation products eluted from the alloy materials. Human foreskin fibroblast cell growth on the experimental magnesium alloys was evaluated for a 72 hour period, and cell death was quantified by measuring lactate dehydrogenase concentrations. Both Mg-Zn-Se and Mg-Zn-Cu alloys exhibit low cytotoxicity levels which are suitable for biomaterial applications. The Mg-Zn-Cu alloy was found to completely degrade within 72 hours, resulting in lower human foreskin fibroblast cell viability. The Mg-Zn-Se alloy was shown to be less cytotoxic than both the Mg-Zn-Cu and Mg-Zn alloys. PMID:24058329

  16. Synthesis and characterization of mesoporous and hollow-mesoporous MxFe3-xO4 (M=Mg, Mn, Fe, Co, Ni, Cu, Zn) microspheres for microwave-triggered controllable drug delivery

    NASA Astrophysics Data System (ADS)

    Chen, Ping; Cui, Bin; Bu, Yumei; Yang, Zhenfeng; Wang, Yaoyu

    2017-12-01

    Spinel ferrites can be used in magnetic targeting and microwave heating and can therefore be used for targeted and controllable drug delivery. We used the cetyltrimethylammonium bromide-assisted solvothermal method to synthesize a series of spinel ferrites (MxFe3-xO4, M=Mg, Mn, Fe, Co, Ni, Cu, Zn) with a mesoporous or hollow-mesoporous structure suitable for direct drug loading and the particle diameters ranging from 200 to 350 nm. We investigated the effects of M2+ cation on the morphology and properties of these products by analyzing their transmission electron microscopy images, mesoporous properties, magnetic properties, and microwave responses. We chose hollow-mesoporous MxFe3-xO4 (M=Fe, Co, Zn) nanoparticles, which had better overall properties, for the drug VP16 (etoposide) loading and microwave-controlled release. The CoxFe3-xO4 and Fe3O4 particles trapped 61.5 and 64.8%, respectively, of the VP16, which were higher than that (60.4%) of ZnxFe3-xO4. Controllable drug release by these simple magnetic nanocarriers can be achieved by microwave irradiation, and VP16-loaded CoxFe3-xO4 released the most VP16 molecules (more than 50% after 1 h and 69.1% after 6 h) under microwave irradiation. Our results confirm the favorable drug loading and microwave-controlled delivery by these ferrites, and lay a theoretical foundation to promote clinical application of the targeted controllable drug delivery system. [Figure not available: see fulltext.

  17. Mössbauer spectroscopy of ZnxMg1-x Fe2O4 (0 ≤ x ≤ 0.74) nanostructures crystallized from borate glasses

    NASA Astrophysics Data System (ADS)

    El Shabrawy, S.; Miglierini, M.; Schaaf, P.; Tzankov, D.; Georgieva, M.; Harizanova, R.; Rüssel, C.

    2018-03-01

    Glasses in the system 51.7 B2O3/9.3 K2O/1 P2O5/10.4 Fe2O3/(27.6 - y) MgO/y ZnO (with y = 0, 1, 2.5, 5, 7.5, 10, 13.8, and 20) were prepared by the conventional melt quenching method. The glass samples were thermally treated at 560 °C for 3 h in ambient conditions. Using 57Fe Mössbauer spectroscopy, the effect of the substitution of MgO by ZnO in the glass network and the effect on the precipitated crystallized phase was studied. The results showed that the ratio of Zn2+:Mg2+ in the precipitated crystals increases with the ZnO concentration in the glass. The isomer shift values indicated that iron occurs as Fe3+, which is distributed at the tetrahedral (A) and the octahedral [B] sites. Introducing ZnO leads to a relative increase of the Fe3+ concentration at the B sites at the expense of that occupying the A sites. This indicates the precipitation of ZnxMg1-x Fe2O4 nanoparticles, where Zn2+ ions favorably occupy the A sites. The average hyperfine field of the samples showed a strong dependence on the Zn concentration. At the highest Zn concentration of 13.8 and 20 mol%, the samples are paramagnetic, while for the smaller ones, the samples are superparamagnetic.

  18. Investigation of structural, morphological and electromagnetic properties of Mg0.25Mn0.25Zn0.5-xSrxFe2O4 ferrites

    NASA Astrophysics Data System (ADS)

    Rahaman, Md. D.; Nusrat, Tania; Maleque, Rumana; Hossain, A. K. M. Akther

    2018-04-01

    Polycrystalline Mg0.25Mn0.25Zn0.5-xSrxFe2O4 (0 ≤ x ≤ 0.20) ferrites were synthesized using the solid state reaction sintering at 1373 K and 1473 K for 4 h. The XRD patterns revealed the formation of single phase cubic spinel with Sr2FeO4 and SrFe12O19 as impurity phases. The decrement in the lattice parameter for Sr2+ substituted samples is attributed to the difference in ionic radii of cations. The crystallite size decreases with increase in Sr2+ content. Low frequency dielectric dispersion is attributed due to the Maxwell-Wagner interfacial polarization. The appearance of the peak in dielectric loss spectrum for x = 0.15 and 0.20 at 1373 K and x = 0.20 at 1473 K suggests the presence of relaxing dipoles. The loss peak shifts towards lower frequency side with Sr2+ content at 1373 K which is due to the strengthening of dipole-dipole interactions. The complex impedance spectra clearly revealed that the both grain and grain boundary effects on the electrical properties. A complex electric modulus spectrum indicates that a non-Debye type of conductivity relaxation exists. The saturation magnetization and remanence gradually decreases with Sr2+ substitution which may be due to the existence of non-magnetic phase in the space between the magnetic particles and the substitution of Zn2+ cation in Mg0.25Mn0.25Zn0.5Fe2O4 ferrite lattice by Sr2+ content. The permeability decreases significantly while the cut-off frequency increases with the Sr2+ content at 1373 K and decreases at 1473 K, obeying the Snoek's law. The decrease in permeability with Sr2+ content is attributed due to the decrease in magnetization because non-magnetic ions weaken the inter-site exchange interaction.

  19. Structural, dielectric and ferroelectric studies of BZT doped Mg0.2Cu0.3Zn0.5Fe2O4 magnetoelectric composites

    NASA Astrophysics Data System (ADS)

    Khader, S. Abdul; Parveez, Asiya; Giridharan, N. V.; Sankarappa, T.

    2018-05-01

    The composites of ferrite-ferroelectric system (x) Mg0.2Cu0.3Zn0.5Fe2O4+ (1-x) Ba0.8Zr0.2TiO3 (x=15%, 30%, 45%) were synthesized by sintering mixtures of ferroelectric Ba0.8Zr0.2TiO3 (BZT) and ferrite component Mg0.2Cu0.3Zn0.5Fe2O4 (MCZF). The presences of two phases in magneto-electric composites were probed by X-ray diffraction (XRD) studies. The peaks observed in the XRD spectrum indicated spinel cubic structure for MCZF ferrite and tetragonal perovskite structure for BZT and, both spinel and pervoskite structures for synthesized composites. Surface morphology of the samples has been investigated using Field Emission Scanning Electron Microscope (FESEM). Frequency dependent dielectric properties of synthesized composites were measured from 100 Hz to 1 MHz at RT using HIOKI LCR HI-TESTER. The dielectric dispersion is observed at lower frequencies for the synthesized ME composites. The ferroelectric properties of synthesized composites were analyzed using a Precision ferroelectric tester. It is observed that the composites exhibited ferroelectric hysteresis with wide loops indicating lossy nature of composites.

  20. Development of biodegradable Zn-1X binary alloys with nutrient alloying elements Mg, Ca and Sr.

    PubMed

    Li, H F; Xie, X H; Zheng, Y F; Cong, Y; Zhou, F Y; Qiu, K J; Wang, X; Chen, S H; Huang, L; Tian, L; Qin, L

    2015-05-29

    Biodegradable metals have attracted considerable attentions in recent years. Besides the early launched biodegradable Mg and Fe metals, Zn, an essential element with osteogenic potential of human body, is regarded and studied as a new kind of potential biodegradable metal quite recently. Unfortunately, pure Zn is soft, brittle and has low mechanical strength in the practice, which needs further improvement in order to meet the clinical requirements. On the other hand, the widely used industrial Zn-based alloys usually contain biotoxic elements (for instance, ZA series contain toxic Al elements up to 40 wt.%), which subsequently bring up biosafety concerns. In the present work, novel Zn-1X binary alloys, with the addition of nutrition elements Mg, Ca and Sr were designed (cast, rolled and extruded Zn-1Mg, Zn-1Ca and Zn-1Sr). Their microstructure and mechanical property, degradation and in vitro and in vivo biocompatibility were studied systematically. The results demonstrated that the Zn-1X (Mg, Ca and Sr) alloys have profoundly modified the mechanical properties and biocompatibility of pure Zn. Zn-1X (Mg, Ca and Sr) alloys showed great potential for use in a new generation of biodegradable implants, opening up a new avenue in the area of biodegradable metals.

  1. Development of biodegradable Zn-1X binary alloys with nutrient alloying elements Mg, Ca and Sr

    PubMed Central

    Li, H. F.; Xie, X. H.; Zheng, Y. F.; Cong, Y.; Zhou, F. Y.; Qiu, K. J.; Wang, X.; Chen, S. H.; Huang, L.; Tian, L.; Qin, L.

    2015-01-01

    Biodegradable metals have attracted considerable attentions in recent years. Besides the early launched biodegradable Mg and Fe metals, Zn, an essential element with osteogenic potential of human body, is regarded and studied as a new kind of potential biodegradable metal quite recently. Unfortunately, pure Zn is soft, brittle and has low mechanical strength in the practice, which needs further improvement in order to meet the clinical requirements. On the other hand, the widely used industrial Zn-based alloys usually contain biotoxic elements (for instance, ZA series contain toxic Al elements up to 40 wt.%), which subsequently bring up biosafety concerns. In the present work, novel Zn-1X binary alloys, with the addition of nutrition elements Mg, Ca and Sr were designed (cast, rolled and extruded Zn-1Mg, Zn-1Ca and Zn-1Sr). Their microstructure and mechanical property, degradation and in vitro and in vivo biocompatibility were studied systematically. The results demonstrated that the Zn-1X (Mg, Ca and Sr) alloys have profoundly modified the mechanical properties and biocompatibility of pure Zn. Zn-1X (Mg, Ca and Sr) alloys showed great potential for use in a new generation of biodegradable implants, opening up a new avenue in the area of biodegradable metals. PMID:26023878

  2. Magnetic characteristics of M2FeV3O11 (M = Mg, Zn, Pb, Co, Ni) compounds

    NASA Astrophysics Data System (ADS)

    Groń, T.; Blonska-Tabero, A.; Filipek, E.; Stokłosa, Z.; Duda, H.; Sawicki, B.

    2018-02-01

    The unusual physical characteristics of the multicomponent oxide systems renewed the interest as the potential cathode materials in high-energy cells. Since the earlier magnetic characteristics were not entirely conclusive, we report the results of dc magnetic measurements including higher harmonics of ac magnetic susceptibility of the M2FeV3O11 (M = Mg, Zn, Pb, Co, Ni) compounds. Ferrimagnetic long-range and antiferromagnetic short-range interactions for all compounds under study at low temperatures as well as superparamagnetic-like behavior with the blocking temperature of 29 K and the freezing parameter of 0.013 were observed. These effects are discussed within the framework of superexchange and double exchange magnetic interactions as well as the mixed valence band of iron ions.

  3. Superparamagnetic behavior of heat treated Mg{sub 0.5}Zn{sub 0.5}Fe{sub 2}O{sub 4} ferrite nanoparticles studied by Mössbauer spectroscopy

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

    Srinivas, Ch., E-mail: srinivas.chintoju75@gmail.com; Prasad, S. A. V.; Singh, S. B.

    2016-05-23

    Nanoparticles of Mg{sub 0.5}Zn{sub 0.5}Fe{sub 2}O{sub 4} ferrite have been synthesized by co-precipitation method. XRD and Mössbauer spectroscopic results of Mg{sub 0.5}Zn{sub 0.5}Fe{sub 2}O{sub 4} annealed at 200 °C, 500 °C and 800 °C are reported. It was observed that the crystallite size increases and the lattice parameter decreases with increase in annealing temperature. The observed decrease in lattice strain supports the increase in crystallite size. The Mössbauer spectra of the samples annealed at 200 °C and 500 °C exhibits superparamagnetic doublets whereas the Mössbauer spectrum of the sample annealed at 800 °C exhibits paramagnetic doublet along with weak sextetmore » of hyperfine interaction. The values of isomer shift resemble the presence of high spin iron ions. The studied ferrite nanoparticles are suitable for biomedical applications. The results are incorporated employing core-shell model and cation redistribution.« less

  4. Magnetic, Electric and Optical Properties of Mg-Substituted Ni-Cu-Zn Ferrites

    NASA Astrophysics Data System (ADS)

    Kabbur, S. M.; Ghodake, U. R.; Kambale, Rahul C.; Sartale, S. D.; Chikhale, L. P.; Suryavanshi, S. S.

    2017-10-01

    The Ni0.25- x Mg x Cu0.30Zn0.45Fe2O4 ( x = 0.00 mol, 0.05 mol, 0.10 mol, 0.15 mol, 0.20 mol and 0.25 mol) magnetic oxide system was prepared by a sol-gel auto-combustion method using glycine as a fuel. X-ray diffraction study reveals the formation of pure spinel lattice symmetry along with the presence of a small fraction of unreacted Fe2O3 phase as a secondary phase due to incomplete combustion reaction between fuel and oxidizer. The lattice constant ( a) was found to decrease with the increase of Mg2+ content; the average crystallite size ( D) is observed in the range of 26.78-33.14 nm. At room temperature, all the samples show typical magnetic hysteresis loops with the decrease of magnetic moment ( n B) of Ni-Cu-Zn ferrites with the increase of Mg2+ content. The intrinsic vibrational absorption bands for the tetrahedral and octahedral sites of the spinel structure were confirmed by infrared (IR) spectroscopy. The optical parameters such as refractive index ( η), velocity of IR waves ( v) and jump rates ( J 1, J 2, J) were studied and found to be dependent on the variation of the lattice constant. The Curie temperature ( T c) of Ni-Cu-Zn mixed ferrite was found to decrease with Mg2+ addition. The composition x = 0.15 mol.% with a low dielectric loss tangent of 2% seems to have potential for multilayer chip inductor applications at a wide range of frequencies.

  5. Exciting transition metal doped dilute magnetic thin films: MgO:Er and ZnO:Er

    NASA Astrophysics Data System (ADS)

    Ćakıcı, T.; Sarıtaş, S.; Muǧlu, G. Merhan; Yıldırım, M.

    2017-02-01

    Erbium doped MgO and doped ZnO thin films have reasonably important properties applications in spintronic devices. These films were synthesized on glass substrates by Chemical Spray Pyrolysis (CSP) method. In the literature there has been almost no report on preparation of MgO:Er dilute magnetic thin films by means of CSP. Because doped thin films show different magnetic behaviors, depending upon the type of magnetic material ions, concentration of them, synthesis route and experimental conditions, synthesized MgO:Er and ZnO:Er films were compared to thin film properties. Optical analyses of the synthesized thin films were examined spectral absorption and transmittance measurements by UV-Vis double beam spectrophotometer technique. Structural analysis of the thin films was examined by using XRD, Raman Analysis, FE-SEM, EDX and AFM techniques. Also, magnetic properties of the MgO:Er and ZnO:Er films were investigated by vibrating sample magnetometer (VSM) which show that diamagnetic behavior of the MgO:Er thin film and ferromagnetic (FM) behavior of the ZnO:Er film were is formed.

  6. Effects of Long-Term Exposure to Zinc Oxide Nanoparticles on Development, Zinc Metabolism and Biodistribution of Minerals (Zn, Fe, Cu, Mn) in Mice

    PubMed Central

    Wang, Chao; Lu, Jianjun; Zhou, Le; Li, Jun; Xu, Jiaman; Li, Weijian; Zhang, Lili; Zhong, Xiang; Wang, Tian

    2016-01-01

    Zinc oxide nanoparticles (nano-ZnOs) are widely used and possess great potentials in agriculture and biomedicine. It is inevitable for human exposure to these nanoparticles. However, no study had been conducted to investigate the long term effects of nano-ZnOs. This study aimed at investigating effects of nano-ZnOs on development, zinc metabolism and biodistribution of minerals (Zn, Fe, Cu, and Mn) in mice from week 3 to 35. After the characteristics of nano-ZnOs were determined, they were added into the basal diet at 0, 50, 500 and 5000 mg/kg. Results indicated that added 50 and 500 mg/kg nano-ZnOs showed minimal toxicity. However, 5000 mg/kg nano-ZnOs significantly decreased body weight (from week 4 to 16) and increased the relative weights of the pancreas, brain and lung. Added 5000 mg/kg nano-ZnOs significantly increased the serum glutamic-pyruvic transaminase activity and zinc content, and significantly enhanced mRNA expression of zinc metabolism-related genes, including metallothionein 1(32.66 folds), metallothionein 2 (31.42 folds), ZIP8 (2.21folds), ZIP14 (2.45 folds), ZnT1 (4.76 folds), ZnT2 (6.19 folds) and ZnT4 (1.82 folds). The biodistribution determination showed that there was a significant accumulation of zinc in the liver, pancreas, kidney, and bones (tibia and fibula) after receiving 5000 mg/kg nano-ZnO diet, while no significant effects on Cu, Fe, and Mn levels, except for liver Fe content and pancreas Mn level. Our results demonstrated that long term exposure to 50 and 500 mg/kg nano-ZnO diets showed minimal toxicity. However, high dose of nano-ZnOs (5000 mg/kg) caused toxicity on development, and altered the zinc metabolism and biodistribution in mice. PMID:27732669

  7. Effects of Long-Term Exposure to Zinc Oxide Nanoparticles on Development, Zinc Metabolism and Biodistribution of Minerals (Zn, Fe, Cu, Mn) in Mice.

    PubMed

    Wang, Chao; Lu, Jianjun; Zhou, Le; Li, Jun; Xu, Jiaman; Li, Weijian; Zhang, Lili; Zhong, Xiang; Wang, Tian

    2016-01-01

    Zinc oxide nanoparticles (nano-ZnOs) are widely used and possess great potentials in agriculture and biomedicine. It is inevitable for human exposure to these nanoparticles. However, no study had been conducted to investigate the long term effects of nano-ZnOs. This study aimed at investigating effects of nano-ZnOs on development, zinc metabolism and biodistribution of minerals (Zn, Fe, Cu, and Mn) in mice from week 3 to 35. After the characteristics of nano-ZnOs were determined, they were added into the basal diet at 0, 50, 500 and 5000 mg/kg. Results indicated that added 50 and 500 mg/kg nano-ZnOs showed minimal toxicity. However, 5000 mg/kg nano-ZnOs significantly decreased body weight (from week 4 to 16) and increased the relative weights of the pancreas, brain and lung. Added 5000 mg/kg nano-ZnOs significantly increased the serum glutamic-pyruvic transaminase activity and zinc content, and significantly enhanced mRNA expression of zinc metabolism-related genes, including metallothionein 1(32.66 folds), metallothionein 2 (31.42 folds), ZIP8 (2.21folds), ZIP14 (2.45 folds), ZnT1 (4.76 folds), ZnT2 (6.19 folds) and ZnT4 (1.82 folds). The biodistribution determination showed that there was a significant accumulation of zinc in the liver, pancreas, kidney, and bones (tibia and fibula) after receiving 5000 mg/kg nano-ZnO diet, while no significant effects on Cu, Fe, and Mn levels, except for liver Fe content and pancreas Mn level. Our results demonstrated that long term exposure to 50 and 500 mg/kg nano-ZnO diets showed minimal toxicity. However, high dose of nano-ZnOs (5000 mg/kg) caused toxicity on development, and altered the zinc metabolism and biodistribution in mice.

  8. Effect of Mg interlayer on perpendicular magnetic anisotropy of CoFeB films in MgO/Mg/CoFeB/Ta structure

    NASA Astrophysics Data System (ADS)

    Ma, Q. L.; Iihama, S.; Kubota, T.; Zhang, X. M.; Mizukami, S.; Ando, Y.; Miyazaki, T.

    2012-09-01

    The effects of Mg metallic interlayer on the magnetic properties of thin CoFeB films in MgO/Mg (tMg)/CoFeB (1.2 nm)/Ta structures were studied in this letter. Our experimental result shows that the CoFeB film exhibits perpendicular magnetic anisotropy (PMA) when the CoFeB and MgO layers are separated by a metallic Mg layer with a maximum thickness of 0.8 nm. The origin of PMA was discussed by considering the preferential transmission of the Δ1 symmetry preserved by the Mg interlayer in crystallized MgO/Mg/CoFeB/Ta. In addition, the thin Mg interlayer also contributes to enhancing the thermal stability and reducing the effective damping constant and coercivity of the CoFeB film.

  9. Effects of annealing heat treatment on the corrosion resistance of Zn/Mg/Zn multilayer coatings

    NASA Astrophysics Data System (ADS)

    Bae, KiTae; La, JoungHyun; Lee, InGyu; Lee, SangYul; Nam, KyungHoon

    2017-05-01

    Zn coatings alloyed with magnesium offer superior corrosion resistance compared to pure Zn or other Zn-based alloy coatings. In this study, Zn/Mg/Zn multilayer coatings with various Mg layer thicknesses were synthesized using an unbalanced magnetron sputtering process and were annealed to form Zn-Mg intermetallic phases. The effects of the annealing heat treatment on the corrosion resistance of the Zn/Mg/Zn multilayer coatings were evaluated using electrochemical measurements. The extensive diffusion of magnesium species into the upper and lower zinc layer from the magnesium layer in the middle of the coating was observed after the heat treatment. This phenomenon caused (a) the porous microstructure to transition into a dense structure and (b) the formation of a MgZn2 intermetallic phase. The results of the electrochemical measurements demonstrated that the heat treated Zn/Mg/Zn multilayer coatings possessed higher levels of corrosion resistance than the non-heat treated coatings. A Zn/Mg/Zn multilayer coating with MgZn2 and (Zn) phases showed the best corrosion resistance among the heat treated coatings, which could be attributed to the reduced galvanic corrosion effects due to a small potential gradient between the MgZn2 and zinc.

  10. Zn-Fe-CNTs catalytic in situ generation of H2O2 for Fenton-like degradation of sulfamethoxazole.

    PubMed

    Liu, Yong; Fan, Qin; Wang, Jianlong

    2018-01-15

    A novel Fenton-like catalyst (Zn-Fe-CNTs) capable of converting O 2 to H 2 O 2 and further to OH was prepared through infiltration fusion method followed by chemical replacement in argon atmosphere. The catalyst was characterized by SEM, EDS, TEM, XRD and XPS. The reaction between Zn-Fe-CNTs and O 2 in aqueous solution could generate H 2 O 2 in situ, which was further transferred to OH. The Fenton-like degradation of sulfamethoxazole (SMX) using Zn-Fe-CNTs as catalyst was evaluated. The results indicated that Zn-Fe-CNTs had a coral porous structure with a BET area of 51.67m 2 /g, exhibiting excellent adsorption capacity for SMX, which enhanced its degradation. The particles of Zn 0 and Fe 0 /Fe 2 O 3 were observed on the surface of Zn-Fe-CNTs. The mixture of Zn 0 and CNTs could reduce O 2 into H 2 O 2 by micro-electrolysis and Fe 0 /Fe 2 O 3 could catalyze in-situ generation of H 2 O 2 to produce OH through Fenton-like process. When initial pH=1.5, T=25°C, O 2 flow rate=400mL/min, Zn-Fe-CNTs=0.6g/L, SMX=25mg/L and reaction time=10min, the removal efficiency of SMX and TOC was 100% and 51.3%, respectively. The intermediates were detected and the possible pathway of SMX degradation and the mechanism of Zn-Fe-CNTs/O 2 process were tentatively proposed. Copyright © 2017 Elsevier B.V. All rights reserved.

  11. Investigation of high density two-dimensional electron gas in Zn-polar BeMgZnO/ZnO heterostructures

    NASA Astrophysics Data System (ADS)

    Ding, K.; Ullah, M. B.; Avrutin, V.; Özgür, Ü.; Morkoç, H.

    2017-10-01

    Zn-polar BeMgZnO/ZnO heterostructures grown by molecular beam epitaxy on high resistivity GaN templates producing high-density two-dimensional electron gas (2DEG) are investigated. This is motivated by the need to reach plasmon-longitudinal optical (LO) phonon resonance for attaining minimum LO phonon lifetime. Achievement of high 2DEG concentration in MgZnO/ZnO heterostructures requires growth of the MgZnO barrier at relatively low temperatures, which compromises the ternary quality that in turn hinders potential field effect transistor performance. When this ternary is alloyed further with BeO, the sign of strain in the BeMgZnO barrier on ZnO switches from compressive to tensile, making the piezoelectric and spontaneous polarizations to be additive in the BeMgZnO/ZnO heterostructures much like the Ga-polar AlGaN/GaN heterostructures. As a result, a 2DEG concentration of 1.2 × 1013 cm-2 is achieved in the Be0.03Mg0.41Zn0.56O/ZnO heterostructure. For comparison, a 2DEG concentration of 7.7 × 1012 cm-2 requires 2% Be and 26% Mg in the barrier, whereas the same in the MgZnO/ZnO system would require incorporation of more than 40% Mg into the barrier, which necessitates very low growth temperatures. Our results are consistent with the demands on achieving short LO phonon lifetimes through plasmon-LO phonon resonance for high carrier velocity.

  12. Dopant concentration dependent growth of Fe:ZnO nanostructures

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

    Sahai, Anshuman; Goswami, Navendu, E-mail: navendugoswami@gmail.com

    2016-05-23

    Systematic investigations of structural properties of 1-10% Fe doped ZnO nanostructure (Fe:ZnO NS) prepared via chemical precipitation method have been reported. Structural properties were probed thoroughly employing scanning electron microscope (SEM) and transmission electron microscope (TEM), energy dispersive X-ray (EDAX) analysis and X-ray diffraction (XRD). Morphological transformation of nanostructures (NS) with Fe incorporation is evident in SEM/TEM images. Nanoparticles (NP) obtained with 1% Fe, evolve to nanorods (NR) for 3% Fe; NR transform to nanocones (NC) (for 5% and 7% Fe) and finally NC transform to nanoflakes (NF) at 10% Fe. Morover, primary phase of Zn{sub 1-x}Fe{sub x}O along withmore » secondary phases of ZnFe{sub 2}O{sub 4} and Fe{sub 2}O{sub 3} were also revealed through XRD measurements. Based on collective XRD, SEM, TEM, and EDAX interpretations, a model for morphological evolution of NS was proposed and the pivotal role of Fe dopant was deciphered.« less

  13. Transport characteristics of a ZnMgO/ZnO hetero junction and the effect of temperature and Mg content

    NASA Astrophysics Data System (ADS)

    Uslu, Salih; Yarar, Zeki

    2017-02-01

    The Ensemble Monte Carlo method is used to calculate the transport characteristics of two dimensional electron gas (2DEG) at a ZnMgO/ZnO hetero structure. The spontaneous and piezoelectric polarizations are considered and there is no intentional doping in either material. Numerical Schrödinger and Poisson equations are solved self consistently to obtain the scattering rates of various scattering mechanisms. The density of carriers, each energy sub bands, potential profile and corresponding wave functions are obtained from the self consistent calculations. The self consistent sub band wave functions of acoustic and optic phonon scattering and interface roughness scattering are used in Monte Carlo method to obtain transport characteristics at ZnMgO/ZnO junction. Two dimensional electron gas confined to ZnMgO/ZnO hetero structure is studied and the effect of temperature and Mg content are investigated.

  14. Fenton-like oxidation of 4-chlorophenol using H2O2 in situ generated by Zn-Fe-CNTs composite.

    PubMed

    Liu, Yong; Fan, Qing; Liu, Yanlan; Wang, Jianlong

    2018-05-15

    In this paper, a zinc-iron-carbon nanotubes (Zn-Fe-CNTs) composite was prepared, characterized and used to develop a Fenton-like system of Zn-Fe-CNTs/O 2 for the degradation of 4-chlorophenol (4-CP), in which H 2 O 2 was generated in situ from zinc-carbon galvanic cells and oxygen in aqueous solution was activated by iron attached on the surface of CNTs to produce ·OH radicals for the oxidation of 4-CP. The experimental results showed that the particles of Zn and Fe in Zn-Fe-CNTs composite were adhered to the surface of CNTs, which accelerated the electron transfer process. The BET area of Zn-Fe-CNTs composite was 32.9 m 2 /g. The contents of Zn and Fe (% w) in the composite were 44.7% and 4.2%, respectively. The removal efficiency of 4-CP and TOC in Zn-Fe-CNTs/O 2 system was 90.8% and 52.9%, respectively, with the initial pH of 2.0, O 2 flow rate of 800 mL/min, Zn-Fe-CNTs dosage of 1.0 g/L, 4-CP concentration of 50 mg/L and reaction time of 20 min. Based on the analysis of the degradation intermediate products with LC-MS and IC, a possible degradation pathway of 4-CP in Zn-Fe-CNTs/O 2 system was proposed. Copyright © 2018 Elsevier Ltd. All rights reserved.

  15. Interstitial Fe in MgO

    NASA Astrophysics Data System (ADS)

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

    2014-01-01

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

  16. Behaviour of Fe4O5-Mg2Fe2O5 solid solutions and their relation to coexisting Mg-Fe silicates and oxide phases

    NASA Astrophysics Data System (ADS)

    Uenver-Thiele, Laura; Woodland, Alan B.; Miyajima, Nobuyoshi; Ballaran, Tiziana Boffa; Frost, Daniel J.

    2018-03-01

    Experiments at high pressures and temperatures were carried out (1) to investigate the crystal-chemical behaviour of Fe4O5-Mg2Fe2O5 solid solutions and (2) to explore the phase relations involving (Mg,Fe)2Fe2O5 (denoted as O5-phase) and Mg-Fe silicates. Multi-anvil experiments were performed at 11-20 GPa and 1100-1600 °C using different starting compositions including two that were Si-bearing. In Si-free experiments the O5-phase coexists with Fe2O3, hp-(Mg,Fe)Fe2O4, (Mg,Fe)3Fe4O9 or an unquenchable phase of different stoichiometry. Si-bearing experiments yielded phase assemblages consisting of the O5-phase together with olivine, wadsleyite or ringwoodite, majoritic garnet or Fe3+-bearing phase B. However, (Mg,Fe)2Fe2O5 does not incorporate Si. Electron microprobe analyses revealed that phase B incorporates significant amounts of Fe2+ and Fe3+ (at least 1.0 cations Fe per formula unit). Fe-L2,3-edge energy-loss near-edge structure spectra confirm the presence of ferric iron [Fe3+/Fetot = 0.41(4)] and indicate substitution according to the following charge-balanced exchange: [4]Si4+ + [6]Mg2+ = 2Fe3+. The ability to accommodate Fe2+ and Fe3+ makes this potential "water-storing" mineral interesting since such substitutions should enlarge its stability field. The thermodynamic properties of Mg2Fe2O5 have been refined, yielding H°1bar,298 = - 1981.5 kJ mol- 1. Solid solution is complete across the Fe4O5-Mg2Fe2O5 binary. Molar volume decreases essentially linearly with increasing Mg content, consistent with ideal mixing behaviour. The partitioning of Mg and Fe2+ with silicates indicates that (Mg,Fe)2Fe2O5 has a strong preference for Fe2+. Modelling of partitioning with olivine is consistent with the O5-phase exhibiting ideal mixing behaviour. Mg-Fe2+ partitioning between (Mg,Fe)2Fe2O5 and ringwoodite or wadsleyite is influenced by the presence of Fe3+ and OH incorporation in the silicate phases.

  17. Enriching rice with Zn and Fe while minimizing Cd risk

    PubMed Central

    Slamet-Loedin, Inez H.; Johnson-Beebout, Sarah E.; Impa, Somayanda; Tsakirpaloglou, Nikolaos

    2015-01-01

    Enriching iron (Fe) and zinc (Zn) content in rice grains, while minimizing cadmium (Cd) levels, is important for human health and nutrition. Natural genetic variation in rice grain Zn enables Zn-biofortification through conventional breeding, but limited natural Fe variation has led to a need for genetic modification approaches, including over-expressing genes responsible for Fe storage, chelators, and transporters. Generally, Cd uptake and allocation is associated with divalent metal cations (including Fe and Zn) transporters, but the details of this process are still unknown in rice. In addition to genetic variation, metal uptake is sometimes limited by its bioavailability in the soil. The availability of Fe, Zn, and Cd for plant uptake varies widely depending on soil redox potential. The typical practice of flooding rice increases Fe while decreasing Zn and Cd availability. On the other hand, moderate soil drying improves Zn uptake but also increases Cd and decreases Fe uptake. Use of Zn- or Fe-containing fertilizers complements breeding efforts by providing sufficient metals for plant uptake. In addition, the timing of nitrogen fertilization has also been shown to affect metal accumulation in grains. The purpose of this mini-review is to identify knowledge gaps and prioritize strategies for improving the nutritional value and safety of rice. PMID:25814994

  18. The phase relations in the In 2O 3Fe 2ZnO 4ZnO system at 1350°C

    NASA Astrophysics Data System (ADS)

    Nakamura, Masaki; Kimizuka, Noboru; Mohri, Takahiko

    1990-05-01

    The phase relations in the In 2O 3Fe 2ZnO 4ZnO system at 1350°C are determined by means of a classical quenching method. There are a series of homologous solid solutions, In 1.28Fe 0.72O 3(ZnO)InFeO 3(ZnO), In 1.69Fe 0.31O 3(ZnO) 2InFeO 3(ZnO) 2In 0.85Fe 1.15O 3(ZnO) 2, In 2O 3(ZnO) 3InFeO 3(ZnO) 3In 0.78Fe 1.22O 3(ZnO) 3, In 2O 3(ZnO) 4InFeO 3(ZnO) 4In 0.62Fe 1.38O 3(ZnO) 4, In 2O 3(ZnO) 5InFeO 3(ZnO) 5In 0.67Fe 1.33O 3(ZnO) 5, In 2O 3(ZnO) 6InFeO 3(ZnO) 6In 0.60Fe 1.40O 3(ZnO) 6, In 2O 3(ZnO) 7InFeO 3(ZnO) 7In 0.51Fe 1.49O 3(ZnO) 7, In 2O 3(ZnO) 8InFeO 3(ZnO) 8In 1- xFe 1+ xO 3(ZnO) 8 (0.44 ≦ x ≦ 0.64), In 2O 3(ZnO) 9InFeO 3(ZnO) 9In 0.20Fe 1.80O 3(ZnO) 9, In 2O 3(ZnO) 10InFeO 3(ZnO) 10In 1- xFe 1+ xO 3(ZnO) 10 (0.74 ≦ x ≦ 0.89), In 2O 3(ZnO) 11InFeO 3(ZnO) 11In 1- xFe 1+ xO 3(ZnO) 11 (0.60 ≦ x < 1.00), and In 2O 3(ZnO) 13InFeO 3(ZnO) 13Fe 2O 3(ZnO) 13 having the layered structures with space group R overline3m (m = odd) or {P6 3}/{mmc} (m = even) for m in the InFeO 3(ZnO) m. We conclude that there are a series of homologous phases, (Fe 2O 3)(ZnO) m (m ≧ 12) , in the binary ZnOFe 2O 3 system. The lattice constants for these solid solutions are presented as a hexagonal crystal system. It is also concluded that the crystal structures for each solid solution consist of three kinds of layers which are stacked perpendicular to the c-axis in the hexagonal crystal system. In 1+ xFe 1- xO 3(ZnO) m (0 ≦ x ≦ 1) is composed of the InO 1.5, (In xFe 1- xZn)O 2.5, and ZnO layers, and In 1- xFe 1+ xO 3(ZnO) m (0 ≦ x ≦ 1) is composed of (In 1- xFe x)O 1.5, (FeZn)O 2.5, and ZnO layers, respectively. The solid solution range between Fe 2ZnO 4 and In xFe 2- xZnO 4 ( x = 0.40 ± 0.02) with a spinel structure is observed.

  19. Preparation and photo-catalytic activities of FeOOH/ZnO/MMT composite

    NASA Astrophysics Data System (ADS)

    Zhou, Yao; Liu, Fusheng; Yu, Shitao

    2015-11-01

    Montmorillonite (MMT) was used as the carrier for synthesis of FeOOH and FeOOH/ZnO nano-material. FeOOH and FeOOH/ZnO were synthesized by the aqueous solutions of Fe(NO3)3-HNO3 and Zn(NO3)2-NaOH/Fe(NO3)3-HNO3 with the carrier of montmorillonite respectively. Transmission electron-microscopy (TEM) and X-ray diffraction (XRD) were used to study the morphology form and structure of the nano-materials. TEM was also used to demonstrate that FeOOH/ZnO can be formed with the appropriate interface. According to UV-vis absorption spectra, FeOOH/ZnO has a better response to visible light than FeOOH and ZnO, which indicates there is some coupling effect between FeOOH and ZnO. Pentachlorophenol (PCP) was used as a representative organic pollutant to evaluate the photo-catalytic efficiency of the FeOOH/ZnO and FeOOH catalysts in visible light (λ > 400 nm). The photo-catalytic efficiency of FeOOH/ZnO/MMT is better than FeOOH/MMT. According to FTIR, changes of pH and TOC, the degradation mechanism was also discussed. PCP was degraded to aromatic ketone and chloro-hydrocarbon compounds and then to H2O, CO2 and HCl.

  20. Solvothermal synthesis, characterization and optical properties of ZnO, ZnO-MgO and ZnO-NiO, mixed oxide nanoparticles

    NASA Astrophysics Data System (ADS)

    Aslani, Alireza; Arefi, Mohammad Reza; Babapoor, Aziz; Amiri, Asghar; Beyki-Shuraki, Khalil

    2011-03-01

    ZnO-MgO and ZnO-NiO mixed oxides nanoparticles were produced from a solution containing Zinc acetate, Mg and Ni nitrate by Solvothermal method. The calcination process of the ZnO-MgO and ZnO-NiO composites nanoparticles brought forth polycrystalline two-phase ZnO-MgO and ZnO-NiO nanoparticles of 40-80 nm in diameters. ZnO, MgO and NiO were crystallized into würtzite and rock salt structures, respectively. The optical properties of ZnO-MgO and ZnO-NiO nanoparticles were obtained by solid state UV and solid state florescent. The XRD, SEM and Raman spectroscopies of these nanoparticles were analyzed.

  1. ZnO and MgZnO Nanocrystalline Flexible Films: Optical and Material Properties

    DOE PAGES

    Huso, Jesse; Morrison, John L.; Che, Hui; ...

    2011-01-01

    An emore » merging material for flexible UV applications is Mg x Zn 1 − x O which is capable of tunable bandgap and luminescence in the UV range of ~3.4 eV–7.4 eV depending on the composition x . Studies on the optical and material characteristics of ZnO and Mg 0.3 Zn 0.7 O nanocrystalline flexible films are presented. The analysis indicates that the ZnO and Mg 0.3 Zn 0.7 O have bandgaps of 3.34 eV and 4.02 eV, respectively. The photoluminescence (PL) of the ZnO film was found to exhibit a structural defect-related emission at ~3.316 eV inherent to the nanocrystalline morphology. The PL of the Mg 0.3 Zn 0.7 O film exhibits two broad peaks at 3.38 eV and at 3.95 eV that are discussed in terms of the solubility limit of the ZnO-MgO alloy system. Additionally, external deformation of the film did not have a significant impact on its properties as indicated by the Raman LO-mode behavior, making these films attractive for UV flexible applications.« less

  2. In vitro degradation of ZnO flowered coated Zn-Mg alloys in simulated physiological conditions.

    PubMed

    Alves, Marta M; Prosek, Tomas; Santos, Catarina F; Montemor, Maria F

    2017-01-01

    Flowered coatings composed by ZnO crystals were successfully electrodeposited on Zn-Mg alloys. The distinct coatings morphologies were found to be dependent upon the solid interfaces distribution, with the smaller number of bigger flowers (ø 46μm) obtained on Zn-Mg alloy containing 1wt.% Mg (Zn-1Mg) contrasting with the higher number of smaller flowers (ø 38μm) achieved on Zn-Mg alloy with 2wt.% Mg (Zn-2Mg). To assess the in vitro behaviour of these novel resorbable materials, a detailed evaluation of the degradation behaviour, in simulated physiological conditions, was performed by electrochemical impedance spectroscopy (EIS). The opposite behaviours observed in the corrosion resistances resulted in the build-up of distinct corrosion layers. The products forming these layers, preferentially detected at the flowers, were identified and their spatial distribution disclosed by EDS and Raman spectroscopy techniques. The presence of smithsonite, simonkolleite, hydrozincite, skorpionite and hydroxyapatite were assigned to both corrosion layers. However the distinct spatial distributions depicted may impact the biocompatibility of these resorbable materials, with the bone analogue compounds (hydroxyapatite and skorpionite) depicted in-between the ZnO crystals and on the top corrosion layer of Zn-1Mg flowers clearly contrasting with the hindered layer formed at the interface of the substrate with the flowers on Zn-2Mg. Copyright © 2016 Elsevier B.V. All rights reserved.

  3. Light-controlled resistive switching characteristics in ZnO/BiFeO3/ZnO thin film

    NASA Astrophysics Data System (ADS)

    Liang, Dandan; Li, Xiaoping; Wang, Junshuai; Wu, Liangchen; Chen, Peng

    2018-07-01

    ZnO/BiFeO3/ZnO multilayer was fabricated on silicon (Si) substrate by radio-frequency magnetron sputtering system. The resistive switching characteristics in ZnO/BiFeO3/ZnO devices are observed, and the resistive switching behavior can be modulated by white light.

  4. Effect of a CoFeB layer on the anisotropic magnetoresistance of Ta/CoFeB/MgO/NiFe/MgO/CoFeB/Ta films

    NASA Astrophysics Data System (ADS)

    Li, Minghua; Shi, Hui; Dong, Yuegang; Ding, Lei; Han, Gang; Zhang, Yao; Liu, Ye; Yu, Guanghua

    2017-10-01

    The anisotropic magnetoresistance (AMR) and magnetic properties of NiFe films can be remarkably enhanced via CoFeB layer. In the case of an ultrathin NiFe film having a Ta/CoFeB/MgO/NiFe/MgO/CoFeB/Ta structure, the CoFeB/MgO layers suppressed the formation of magnetic dead layers and the interdiffusions and interface reactions between the NiFe and Ta layers. The AMR reached a maximum value of 3.56% at 450 °C. More importantly, a single NiFe (1 1 1) peak can be formed resulting in higher AMR values for films having CoFeB layer. This enhanced AMR also originated from the significant specular reflection of electrons owing to the crystalline MgO layer, together with the sharp interfaces with the NiFe layer. These factors together resulted in higher AMR and improved magnetic properties.

  5. High Zn Content Single-phase RS-MgZnO Suitable for Solar-blind Frequency Applications

    NASA Astrophysics Data System (ADS)

    Liang, H. L.; Mei, Z. X.; Liu, Z. L.; Guo, Y.; Azarov, A. Yu.; Kuznetsov, A. Yu.; Hallen, A.; Du, X. L.

    2010-11-01

    Single-phase rock-salt MgZnO films with high Zn content were successfully fabricated on the templates of MgO (111)/α-sapphire (0001) by radio-frequency plasma assisted molecular beam epitaxy. The influence of growth temperature on epitaxy of MgZnO alloy films was investigated by the combined studies of crystal structures, compositions, and optical properties. It is found that the incorporation of Zn atoms into the rock-salt MgZnO films is greatly enhanced at low temperature, confirmed by in-situ reflection high-energy electron diffraction observations and ex-situ X-ray diffraction characterization. Zn fraction in the single-phase rock-salt Mg0.53Zn0.47O film was determined by Rutherford backscattering spectrometry. Optical properties of the films were investigated by transmittance spectroscopy and reflectance spectroscopy, both of which demonstrate the solar-blind band gap and its dependence on Zn content.

  6. Comprehensive structural and chemical (CO2, Fe/Fe Mg, H2O) investigations of Mg-Fe cordierite with micro Raman spectroscopy

    NASA Astrophysics Data System (ADS)

    Haefeker, U.; Kaindl, R.; Tropper, P.

    2012-04-01

    The Mg-Fe silicate cordierite with the idealized formula (Fe, Mg)2Al4Si5O18 occurs as a hexagonal and an orthorhombic polymorph with disordered/ordered Al-Si distribution on the tetrahedral sites. Most of the natural cordierites are fully ordered. Six-membered rings of (Si,Al)O4 are piled in the direction of the crystallographic c-axis and form channels, laterally and vertically linked by additional (Al, Si) tetrahedrons. Mg and Fe in varying fractions occupy the octahedrally coordinated M-sites. CO2 and H2O (and other volatiles) can be incorporated into the structural channels, thus cordierite can be used for paleofluid reconstruction. The vibration energies of incorporated volatiles, their interaction with the lattice and variations of certain lattice-vibration energies caused by the Mg-Fe exchange can be determined with Raman spectroscopy, allowing chemical quantifications and structural investigations. A method for the semi-quantitative determination of CO2-contents of natural cordierites by Kaindl et al. (2006) was optimized and enhanced by Haefeker et al. (2007). CO2 contents can be measured in single crystals and thin sections with an error of ± 0.05 - 0.09 wt.-%. Based on the Mg-Fe exchange with garnet, cordierite can be used as a geothermobarometer. Recent investigations of synthetic Mg-Fe cordierites with XFe = 0 - 1 have shown a linear downshift of six selected lattice peaks between 100 and 1250 cm-1 with the Mg-Fe contents. Correlation diagrams allow an estimation of the Mg-Fe contents in synthetic and natural samples. The experimental data are in good agreement with the results of quantum-mechanical calculations of the Raman spectra of Mg- and Fe cordierite (Kaindl et al., 2011) allowing the assignment of the peaks to specific vibrations of tetrahedral and octahedral sites. Natural Mg-Fe cordierites are mainly orthorhombic with a fully ordered Al/Si distribution on the tetrahedral sites. However, the disordered hexagonal polymorph is observed in many

  7. Chelation of Cu(II), Zn(II), and Fe(II) by tannin constituents of selected edible nuts.

    PubMed

    Karamać, Magdalena

    2009-12-22

    The tannin fractions isolated from hazelnuts, walnuts and almonds were characterised by colorimetric assays and by an SE-HPLC technique. The complexation of Cu(II) and Zn(II) was determined by the reaction with tetramethylmurexide, whereas for Fe(II), ferrozine was employed. The walnut tannins exhibited a significantly weaker reaction with the vanillin/HCl reagent than hazelnut and almond tannins, but the protein precipitation capacity of the walnut fraction was high. The SE-HPLC chromatogram of the tannin fraction from hazelnuts revealed the presence of oligomers with higher molecular weights compared to that of almonds. Copper ions were most effectively chelated by the constituents of the tannin fractions of hazelnuts, walnuts and almonds. At a 0.2 mg/assay addition level, the walnut tannins complexed almost 100% Cu(II). The Fe(II) complexation capacities of the tannin fractions of walnuts and hazelnuts were weaker in comparison to that of the almond tannin fraction, which at a 2.5 mg/assay addition level, bound Fe(II) by approximately 90%. The capacity to chelate Zn(II) was quite varied for the different nut tannin fractions: almond tannins bound as much as 84% Zn(II), whereas the value for walnut tannins was only 8.7%; and for hazelnut tannins, no Zn(II) chelation took place at the levels tested.

  8. Chelation of Cu(II), Zn(II), and Fe(II) by Tannin Constituents of Selected Edible Nuts

    PubMed Central

    Karamać, Magdalena

    2009-01-01

    The tannin fractions isolated from hazelnuts, walnuts and almonds were characterised by colorimetric assays and by an SE-HPLC technique. The complexation of Cu(II) and Zn(II) was determined by the reaction with tetramethylmurexide, whereas for Fe(II), ferrozine was employed. The walnut tannins exhibited a significantly weaker reaction with the vanillin/HCl reagent than hazelnut and almond tannins, but the protein precipitation capacity of the walnut fraction was high. The SE-HPLC chromatogram of the tannin fraction from hazelnuts revealed the presence of oligomers with higher molecular weights compared to that of almonds. Copper ions were most effectively chelated by the constituents of the tannin fractions of hazelnuts, walnuts and almonds. At a 0.2 mg/assay addition level, the walnut tannins complexed almost 100% Cu(II). The Fe(II) complexation capacities of the tannin fractions of walnuts and hazelnuts were weaker in comparison to that of the almond tannin fraction, which at a 2.5 mg/assay addition level, bound Fe(II) by ~90%. The capacity to chelate Zn(II) was quite varied for the different nut tannin fractions: almond tannins bound as much as 84% Zn(II), whereas the value for walnut tannins was only 8.7%; and for hazelnut tannins, no Zn(II) chelation took place at the levels tested. PMID:20054482

  9. Magnetically separable core–shell ZnFe{sub 2}O{sub 4}@ZnO nanoparticles for visible light photodegradation of methyl orange

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

    Kulkarni, Suresh D., E-mail: suresh.dk@manipal.edu; Kumbar, Sagar; Menon, Samvit G.

    Highlights: • Phase pure, magnetic ZnFe{sub 2}O{sub 4}@ZnO nanoparticles synthesized with excellent yield. • ZnFe{sub 2}O{sub 4}@ZnO displayed higher UV photocatalytic efficiency than ZnO nanoparticles. • First report on visible light photodegradation of methyl orange by ZnFe{sub 2}O{sub 4}@ZnO. • Excellent reusability of ZnFe{sub 2}O{sub 4}@ZnO nanoparticles observed for azo dye removal. - Abstract: Visible light photodegradation of aqueous methyl orange using magnetically separable core–shell ZnFe{sub 2}O{sub 4}@ZnO nanoparticles is reported. A combination of low temperature (190 °C) microwave synthesis and hydrothermal method were used to prepare phase pure material with excellent yield (95%). The magnetic separability, surface area ofmore » 41 m{sup 2}/g and visible light absorption make ZnFe{sub 2}O{sub 4}@ZnO nanoparticles a good solar photocatalyst. ZnFe{sub 2}O{sub 4}@ZnO displayed greater UV photocatalytic efficiency than ZnO owing to the generation of large number of electron-hole pairs. Visible light photodegradation of MO using ZnFe{sub 2}O{sub 4}@ZnO nanoparticles is reported for the first time. Higher first order rate constants under both UV and visible light for core-shell nanoparticles suggested their superiority over its individual oxides. The ZnFe{sub 2}O{sub 4}@ZnO showed excellent reusability with high photocatalytic efficiencies suggesting its suitability for solar photocatalytic applications.« less

  10. Selective antibacterial effects of mixed ZnMgO nanoparticles

    NASA Astrophysics Data System (ADS)

    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.

  11. Growth of ZnMgTe/ZnTe waveguide structures on ZnTe (0 0 1) substrates by molecular beam epitaxy

    NASA Astrophysics Data System (ADS)

    Kumagai, Y.; Imada, S.; Baba, T.; Kobayashi, M.

    2011-05-01

    ZnMgTe/ZnTe/ZnMgTe layered structures were grown on (0 0 1) ZnTe substrates by molecular beam epitaxy. This structure was designed to apply to waveguides in various optoelectronic devices to reduce light loss. Since the lattice mismatch between ZnTe and ZnMgTe was not negligible, the critical layer thickness (CLT) was theoretically derived. Structures with varying Mg composition and layer thickness of ZnMgTe cladding layer were grown and examined for crystal quality with respect to theoretical data. The crystal quality was investigated by means of cross sectional transmission electron microscopy (TEM) and reciprocal space mapping (RSM). Optical confinements were observed by irradiating a laser beam from one end of the sample and monitoring the transmitted light from the other end.

  12. Polymeric phase change nanocomposite (PMMA/Fe:ZnO) for electronic packaging application

    NASA Astrophysics Data System (ADS)

    Maji, Pranabi; Choudhary, Ram Bilash; Majhi, Malati

    2018-01-01

    This paper reported the effect of Fe-doped ZnO (Fe:ZnO) nanoparticles on the structural, morphological, thermal, optical and dielectric properties of PMMA matrix. Fe-doped ZnO nanoparticle was synthesized by co-precipitation method, after its surface modification incorporated into the PMMA matrix by free radical polymerization method. The phase analysis and crystal structure were investigated by XRD and FTIR technique. These studies confirmed the chemical structure of the PMMA/Fe:ZnO nanocomposite. FESEM image showed the pyramidal shape and high porosity of PMMA/Fe:ZnO nanocomposite. Thermal analysis of the sample was carried out by thermo-gravimetric analyzer. PMMA/Fe:ZnO nanocomposite was found to have better thermal stability compared to pure one. Broadband dielectric spectroscopic technique was used to investigate the transition of electrical properties of Fe-doped ZnO nanoparticle reinforced PMMA matrix in temperature range 313-373 K. The results elucidated a phase transition from glassy to rubbery state at 344 K.

  13. Mechanical Properties and Tensile Failure Analysis of Novel Bio-absorbable Mg-Zn-Cu and Mg-Zn-Se Alloys for Endovascular Applications

    PubMed Central

    Persaud-Sharma, Dharam; Budiansky, Noah; McGoron, Anthony J.

    2013-01-01

    In this paper, the mechanical properties and tensile failure mechanism of two novel bio-absorbable as-cast Mg-Zn-Se and Mg-Zn-Cu alloys for endovascular medical applications are characterized. Alloys were manufactured using an ARC melting process and tested as-cast with compositions of Mg-Zn-Se and Mg-Zn-Cu, being 98/1/1 wt.% respectively. Nanoindentation testing conducted at room temperature was used to characterize the elastic modulus (E) and surface hardness (H) for both the bare alloys and the air formed oxide layer. As compared to currently available shape memory alloys and degradable as-cast alloys, these experimental alloys possess superior as-cast mechanical properties that can increase their biocompatibility, degradation kinetics, and the potential for medical device creation. PMID:23543822

  14. Nanofibrillated Cellulose-Assisted Synthesis of Fiber-Like ZnO-ZnFe2O4 Composites with Enhanced Visible-Light-Driven Photocatalytic Activity

    NASA Astrophysics Data System (ADS)

    Cai, Aijun; Guo, Aiying; Du, Liqiang; Chang, Yongfang; Wang, Xiuping

    2018-05-01

    In this article, fiber-like ZnO-ZnFe2O4 composites are obtained by using nanofibrillated cellulose as a biotemplate. The as-prepared composites exhibit strong absorbance in the visible-light region. The ZnO-ZnFe2O4 composites exhibit a similar bandgap (1.88 eV) compared with the ZnFe2O4 (1.85 eV). The ZnO-ZnFe2O4 composites can be easily collected by an external magnet, which contributes to improving the utilization efficiency of the photocatalysts. The photocatalytic activity of the ZnO-ZnFe2O4 catalysts was evaluated by photodegrading rhodamine B (RhB) under visible-light irradiation. Compared with ZnO and ZnFe2O4, the ZnO-ZnFe2O4 catalysts show higher photocatalytic activity due to the efficient electron-hole separation.

  15. Enhanced Al and Zn removal from coal-mine drainage during rapid oxidation and precipitation of Fe oxides at near-neutral pH

    USGS Publications Warehouse

    Burrows, Jill E.; Cravotta, Charles A.; Peters, Stephen C.

    2017-01-01

    Net-alkaline, anoxic coal-mine drainage containing ∼20 mg/L FeII and ∼0.05 mg/L Al and Zn was subjected to parallel batch experiments: control, aeration (Aer 1 12.6 mL/s; Aer 2 16.8 mL/s; Aer 3 25.0 mL/s), and hydrogen peroxide (H2O2) to test the hypothesis that aeration increases pH, FeII oxidation, hydrous FeIII oxide (HFO) formation, and trace-metal removal through adsorption and coprecipitation with HFO. During 5.5-hr field experiments, pH increased from 6.4 to 6.7, 7.1, 7.6, and 8.1 for the control, Aer 1, Aer 2, and Aer 3, respectively, but decreased to 6.3 for the H2O2 treatment. Aeration accelerated removal of dissolved CO2, Fe, Al, and Zn. In Aer 3, dissolved Al was completely removed within 1 h, but increased to ∼20% of the initial concentration after 2.5 h when pH exceeded 7.5. H2O2 promoted rapid removal of all dissolved Fe and Al, and 13% of dissolved Zn.Kinetic modeling with PHREEQC simulated effects of aeration on pH, CO2, Fe, Zn, and Al. Aeration enhanced Zn adsorption by increasing pH and HFO formation while decreasing aqueous CO2 available to form ZnCO30 and Zn(CO3)22− at high pH. Al concentrations were inconsistent with solubility control by Al minerals or Al-containing HFO, but could be simulated by adsorption on HFO at pH < 7.5 and desorption at higher pH where Al(OH)4− was predominant. Thus, aeration or chemical oxidation with pH adjustment to ∼7.5 could be effective for treating high-Fe and moderate-Zn concentrations, whereas chemical oxidation without pH adjustment may be effective for treating high-Fe and moderate-Al concentrations.

  16. Comparison of structural and magnetic properties of Zn{sub x}Mg{sub 1.5-x}Mn{sub 0.5}FeO{sub 4} and MgAl{sub x}Cr{sub x}Fe{sub 2-2x}O{sub 4} spinel oxides

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

    Thummer, K. P., E-mail: kpthummer@yahoo.co.in; Tanna, A. R., E-mail: ashish.tanna@rku.ac.in; Joshi, H. H.

    2016-05-23

    The spinel oxides Zn{sub x}Mg{sub 1.5-x}Mn{sub 0.5}FeO{sub 4} (x = 0.0 to 0.6) and MgAl{sub x}Cr{sub x}Fe{sub 2-2x}O{sub 4} (x = 0.0 to 0.6) abbreviated as ZMMFO and MACFO respectively, were synthesized by standard ceramic processing. The compositional purity of all the specimens was checked by EDAX technique. The X-ray diffractometry was employed to determine the lattice constants and distribution of cations in the interstitial voids. The initial decrease of cell edge parameter (a) for ZMMFO up to x = 0.2 and thereafter expected rise in the ‘a’ and the initial slower rate of reduction in the lattice constant formore » MACFO are explained as basic of cation occupancy. The magnetic ordering in both systems is explained by invoking statistical canting models. The compositional variation of magneton number (n{sub B}) for ZMMFO could be very well explained by Localized canting of spin (LCS) model while Random canting of spin (RCS) model was used for MACFO system.« less

  17. Codoping characteristics of Zn with Mg in GaN

    NASA Astrophysics Data System (ADS)

    Kim, K. S.; Han, M. S.; Yang, G. M.; Youn, C. J.; Lee, H. J.; Cho, H. K.; Lee, J. Y.

    2000-08-01

    The doping characteristics of Mg-Zn codoped GaN films grown by metalorganic chemical vapor deposition are investigated. By means of the concept of Mg-Zn codoping technique, we have grown p-GaN showing a low electrical resistivity (0.72 Ω cm) and a high hole concentration (8.5×1017cm-3) without structural degradation of the film. It is thought that the codoping of Zn atoms with Mg raises the Mg activation ratio by reducing the hydrogen solubility in p-GaN. In addition, the measured specific contact resistance of Mg-Zn codoped GaN film is 5.0×10-4 Ω cm2, which is one order of magnitude lower than that of Mg doped only GaN film (1.9×10-3 Ω cm2).

  18. Electrical modulus and dielectric behavior of Cr3+ substituted Mg-Zn nanoferrites

    NASA Astrophysics Data System (ADS)

    Mansour, S. F.; Abdo, M. A.

    2017-04-01

    The dielectric parameters and ac electrical conductivity of Mg0.8Zn0.2CrxFe2-xO4; (0≤x≤0.025) nanoferrites synthesized citrate-nitrate auto-combustion method were studied using the complex impedance technique in the frequency and temperature ranges 4 Hz-5 MHz and 303-873 K respectively. Hopping of charge carriers plus interfacial polarization could interpret the behaviors of dielectric constant (ε‧), dielectric loss tangent (tanδ) and ac electrical conductivity (σac) with frequency, temperatures and composition. The up-normal behavior observed in tanδ trend with temperatures confirms the presence of relaxation loss (dipoles losses). Correlated barrier hopping (CBH) of electron is the conduction mechanism of the investigated nanoferrites. Cole-Cole plots at different temperatures emphasize the main role of grain and grain boundaries in the properties of the investigated nanoferrites. Cr3+ substitution can control the dielectric parameters and ac electrical conductivity of Mg-Zn nanoferrites making it candidates for versatile applications.

  19. Synthesis, characterization and hemolysis studies of Zn(1-x)CaxFe2O4 ferrites synthesized by sol-gel for hyperthermia treatment applications

    NASA Astrophysics Data System (ADS)

    Jasso-Terán, Rosario Argentina; Cortés-Hernández, Dora Alicia; Sánchez-Fuentes, Héctor Javier; Reyes-Rodríguez, Pamela Yajaira; de-León-Prado, Laura Elena; Escobedo-Bocardo, José Concepción; Almanza-Robles, José Manuel

    2017-04-01

    The synthesis of Zn(1-x)CaxFe2O4 nanoparticles, x=0, 0.25, 0.50, 0.75 and 1.0, was performed by sol-gel method followed by a heat treatment at 400 °C for 30 min. These ferrites showed nanometric sizes and nearly superparamagnetic behavior. The Zn0.50Ca0.50Fe2O4 and CaFe2O4 ferrites presented a size within the range of 12-14 nm and appropriate heating ability for hyperthermia applications. Hemolysis testing demonstrated that Zn0.50Ca0.50Fe2O4 ferrite was not cytotoxic when using 10 mg of ferrite/mL of solution. According to the results obtained, Zn0.50Ca0.50Fe2O4 is a potential material for cancer treatment by magnetic hyperthermia therapy.

  20. Effect of metal cation ratio on chemical properties of ZnFe2O4/AC composite and adsorption of organic contaminant

    NASA Astrophysics Data System (ADS)

    Meilia, Demara; Misbah Khunur, Mochamad; Setianingsih, Tutik

    2018-01-01

    Porous woody char is biochar prepared through pyrolisis. The biochar can be used as adsorbent. In this research, ZnFe2O4/AC composite was synthesized through imregnation of the woody biochar with ZnFe2O4 to study effect of mol ratio of Fe(III) and Zn(II) toward their physicochemistry and adsorption of drug wastewater. Paracetamol was used as adsorbate model. This research was conducted in several steps, including activation of the woody biochar using KOH activator at temperatur 500 °C for 15 min to produce the activated carbon, fungsionalization of the carbon using H2SO4 oxidator (6M) at temperature of 80 °C for 3 h, impregnation of the oxidized activated carbon with Zn-Fe-LDH (Layered Double Hydroxide) at various mol ratio of Fe(III) and Zn(III), including 1:2, 1:3 and 1:4 using NaOH solution (5M) for coprecipitation, and calcination of Zn-Fe-LDH/AC at 950 °C for 5 min to produce ZnFe2O4/AC. FTIR diffraction characterization indicated existence of M-O (M = Zn(II), Fe(III)) and OH functional groups. FTIR spectra showed increasing of bands connected to -OH by increasing of the ratio till the ratio was achieved at 1:4, then decreased again. The ratio mol showed effect on the adsorption of paracetamol. Profile of adsorption value was fit with changing of functional groups. The highest adsorption was achieved at the ratio of 1:4. After calcination it gave the adsorption value of 17,66 mg/g.

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

    PubMed

    Kojta, Anna K; Falandysz, Jerzy

    2016-06-01

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

  2. Room temperature ferromagnetism in Mg-doped ZnO nanoparticles

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

    Singh, Jaspal, E-mail: jaspal0314@gmail.com; Vashihth, A.; Gill, Pritampal Singh

    Zn{sub 1-x}Mg{sub x}O (x = 0, 0,10) nanoparticles were successfully synthesized using sol-gel method. X-ray diffraction (XRD) confirms that the synthesized nanoparticles possess wurtzite phase having hexagonal structure. Morphological analysis was carried out using transmission electron microscopy (TEM) which depicts the spherical morphology of ZnO nanoparticles. Energy dispersive spectroscopy (EDS) showed the presence of Mg in ZnO nanoparticles. Electron spin resonance (ESR) signal was found to be decreasing with increasing of Mg-doping concentration. The room temperature ferromagnetism was observed in undoped and Mg-doped ZnO nanoparticles. The increase of Mg-doping concentration resulted in decrease of saturation magnetization value which could bemore » attributed to decrease of oxygen vacancies present in host nanoparticles.« less

  3. Different copolymer films on ZnFeCo particles: Synthesis and anticorrosion properties

    NASA Astrophysics Data System (ADS)

    Ozyilmaz, A. Tuncay; Avsar, Busra; Ozyilmaz, Gul; Karahan, İ. Hakkı; Camurcu, Taskin; Colak, Fatma

    2014-11-01

    Zinc-iron-cobalt (ZnFeCo) particles were electrochemically deposited on carbon steel (CS) electrode applying current of 3 mA with chronopotentiometry technique. ZnFeCo particles had homogenous, smooth with prismatic structure. It was shown that the ZnFeCo particles exhibited important barrier effect on CS substrate. Poly(aniline-co-o-anisidine), poly(aniline-co-pyrrole), poly(aniline-co-N-methylpyrrole) and poly(o-anisidine-co-pyrrole) copolymer films were obtained on CS/ZnFeCo electrode. Evaluation of anticorrosion performance of copolymer coatings in 3.5% NaCl solution was investigated by using AC impedance spectroscopy (EIS) technique, anodic polarization and the Eocp-time curves. Copolymer films exhibited significant physical barrier behavior on ZnFeCo plated carbon steel, in longer exposure time.

  4. Third generation biosensing matrix based on Fe-implanted ZnO thin film

    NASA Astrophysics Data System (ADS)

    Saha, Shibu; Gupta, Vinay; Sreenivas, K.; Tan, H. H.; Jagadish, C.

    2010-09-01

    Third generation biosensor based on Fe-implanted ZnO (Fe-ZnO) thin film has been demonstrated. Implantation of Fe in rf-sputtered ZnO thin film introduces redox center along with shallow donor level and thereby enhance its electron transfer property. Glucose oxidase (GOx), chosen as model enzyme, has been immobilized on the surface of the matrix. Cyclic voltammetry and photometric assay show that the prepared bioelectrode, GOx/Fe-ZnO/ITO/Glass is sensitive to the glucose concentration with enhanced response of 0.326 μA mM-1 cm-2 and low Km of 2.76 mM. The results show promising application of Fe-implanted ZnO thin film as an attractive matrix for third generation biosensing.

  5. Structural, dielectric and ferroelectric studies of (x) Mg0.25Cu0.25Zn0.5Fe2O4 + (1-x) BaTiO3 magnetoelectric nano-composites

    NASA Astrophysics Data System (ADS)

    Khader, S. Abdul; Muneeswaran, M.; Giridharan, N. V.; Sankarappa, T.

    2016-05-01

    The Particulate nano-composites of ferrite and ferroelectric phases having the general formula (x) Mg0.25Cu0.25Zn0.5Fe2O4 + (1-x) BaTiO3 (x=15%, 30% and 45%) were synthesized by sintering mixtures of highly ferroelectric BaTiO3 (BT) and highly magneto-strictive magnetic component Mg0.25Cu0.25Zn0.5Fe2O4(MCZF). The presence of constituent phases of ferrite, ferroelectric and their composites were probed and confirmed by X-ray diffraction (XRD) studies. Surface morphology of the samples has been investigated using Field Emission Scanning Electron Microscope (FESEM). The variation of dielectric constant and dissipation factor as a function of frequency from 100 Hz to 1 MHz at room temperature were carried out using a Hioki LCR Hi-Tester. The dielectric constant and dielectric loss were found to decrease rapidly in the low frequency region and became almost constant in the high frequency region. The electrical conductivity deduced from the measured dielectric data has been thoroughly analyzed and found that the conduction mechanism in these composites is in conformity with small polaron hopping model. The ferroelectric properties of synthesized magneto-electric nano-composites were measured using P-E loop tracer.

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

    NASA Astrophysics Data System (ADS)

    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.

  7. Study of ZnO and Mg doped ZnO nanoparticles by sol-gel process

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

    Ansari, Mohd Meenhaz, E-mail: meenhazphysics@gmail.com; Arshad, Mohd; Tripathi, Pushpendra

    Nano-crystalline undoped and Mg doped ZnO (Mg-ZnO) nanoparticles with compositional formula Mg{sub x}Zn{sub 1-x}O (x=0,1,3,5,7,10 and 12 %) were synthesized using sol-gel process. The XRD diffraction peaks match with the pattern of the standard hexagonal structure of ZnO that reveals the formation of hexagonal wurtzite structure in all samples. SEM images demonstrates clearly the formation of spherical ZnO nanoparticles, and change of the morphology of the nanoparticles with the concentration of the magnesium, which is in close agreement with that estimated by Scherer formula based on the XRD pattern. To investigate the doping effect on optical properties, the UV–VIS absorptionmore » spectra was obtained and the band gap of the samples calculated.« less

  8. Improving the selective cancer killing ability of ZnO nanoparticles using Fe doping.

    PubMed

    Thurber, Aaron; Wingett, Denise G; Rasmussen, John W; Layne, Janet; Johnson, Lydia; Tenne, Dmitri A; Zhang, Jianhui; Hanna, Charles B; Punnoose, Alex

    2012-06-01

    This work reports a new method to improve our recent demonstration of zinc oxide (ZnO) nanoparticles (NPs) selectively killing certain human cancer cells, achieved by incorporating Fe ions into the NPs. Thoroughly characterized cationic ZnO NPs (∼6 nm) doped with Fe ions (Zn(1-x )Fe (x) O, x = 0-0.15) were used in this work, applied at a concentration of 24 μg/ml. Cytotoxicity studies using flow cytometry on Jurkat leukemic cancer cells show cell viability drops from about 43% for undoped ZnO NPs to 15% for ZnO NPs doped with 7.5% Fe. However, the trend reverses and cell viability increases with higher Fe concentrations. The non-immortalized human T cells are markedly more resistant to Fe-doped ZnO NPs than cancerous T cells, confirming that Fe-doped samples still maintain selective toxicity to cancer cells. Pure iron oxide samples displayed no appreciable toxicity. Reactive oxygen species generated with NP introduction to cells increased with increasing Fe up to 7.5% and decreased for >7.5% doping.

  9. Mg-doped ZnO nanoparticles for efficient sunlight-driven photocatalysis.

    PubMed

    Etacheri, Vinodkumar; Roshan, Roshith; Kumar, Vishwanathan

    2012-05-01

    Magnesium-doped ZnO (ZMO) nanoparticles were synthesized through an oxalate coprecipitation method. Crystallization of ZMO upon thermal decomposition of the oxalate precursors was investigated using differential scanning calorimetry (DSC) and X-ray diffraction (XRD) techniques. XRD studies point toward a significant c-axis compression and reduced crystallite sizes for ZMO samples in contrast to undoped ZnO, which was further confirmed by HRSEM studies. X-ray photoelectron spectroscopy (XPS), UV/vis spectroscopy and photoluminescence (PL) spectroscopy were employed to establish the electronic and optical properties of these nanoparticles. (XPS) studies confirmed the substitution of Zn(2+) by Mg(2+), crystallization of MgO secondary phase, and increased Zn-O bond strengths in Mg-doped ZnO samples. Textural properties of these ZMO samples obtained at various calcination temperatures were superior in comparison to the undoped ZnO. In addition to this, ZMO samples exhibited a blue-shift in the near band edge photoluminescence (PL) emission, decrease of PL intensities and superior sunlight-induced photocatalytic decomposition of methylene blue in contrast to undoped ZnO. The most active photocatalyst 0.1-MgZnO obtained after calcination at 600 °C showed a 2-fold increase in photocatalytic activity compared to the undoped ZnO. Band gap widening, superior textural properties and efficient electron-hole separation were identified as the factors responsible for the enhanced sunlight-driven photocatalytic activities of Mg-doped ZnO nanoparticles.

  10. Structure and magnetic properties of Fe-doped ZnO prepared by the sol-gel method.

    PubMed

    Liu, Huilian; Yang, Jinghai; Zhang, Yongjun; Yang, Lili; Wei, Maobin; Ding, Xue

    2009-04-08

    Zn(0.97)Fe(0.03)O nanoparticles were synthesized by the sol-gel method. X-ray diffraction (XRD) and transmission electron microscope (TEM) analysis revealed that the samples had pure ZnO wurtzite structure and Fe ions were well incorporated into the ZnO crystal lattice. X-ray photoelectron spectroscopy (XPS) showed that both Fe(2+) and Fe(3+) existed in Zn(0.97)Fe(0.03)O. The result of x-ray absorption near-edge structure (XANES) further testified that Fe ions took the place of Zn sites in our samples. Magnetic measurements indicated that Zn(0.97)Fe(0.03)O was ferromagnetic at room temperature.

  11. Photoluminescence of ZnTe/ZnMgTe multiple quantum well structures grown on ZnTe substrates by molecular beam epitaxy

    NASA Astrophysics Data System (ADS)

    Tanaka, Tooru; Ohshita, Hiroshi; Saito, Katsuhiko; Guo, Qixin

    2018-02-01

    Photoluminescence (PL) properties of ZnTe/ZnMgTe quantum well (QW) structures grown by molecular beam epitaxy (MBE) were investigated systematically with respect to well widths and Mg contents. Observed PL peak energies were consistent well with the calculated emission energies of the QWs considering a lattice distortion in the ZnTe well. From the temperature dependence of PL intensity, it was found that a suppression of a carrier escape from QW is crucial to obtain a PL at higher temperature in the ZnTe/ZnMgTe QW. Based on the results, multiple quantum well structures were designed and fabricated, which exhibited a green PL at room temperature.

  12. Instrument-Free and Autonomous Generation of H2O2 from Mg-ZnO/Au Hybrids for Disinfection and Organic Pollutant Degradations

    NASA Astrophysics Data System (ADS)

    Park, Seon Yeong; Jung, Yeon Wook; Hwang, Si Hyun; Jang, Gun Hyuk; Seo, Hyunseon; Kim, Yu-Chan; Ok, Myoung-Ryul

    2018-03-01

    We proposed a new hybrid system that autonomously generates H2O2 without any instrument or external energy source, such as light. Electrons formed during spontaneous degradation process of Mg were conveyed to ZnO/Au oxygen-reduction-reaction nanocatalysts, and these transferred electrons converted O2 molecules in aqueous solution into H2O2. Autonomously released H2O2 from Mg-ZnO/Au hybrids effectively killed 97% of Escherichia coli cells within 1 h. Moreover, Mg-ZnO/Au nanohybrids could gradually degrade methylene blue over time with Fe2+. We believe our approach utilizing degradable metals and catalytic metal oxides in mesoporous-film form can be a promising method in the field of environment remediation.

  13. Instrument-Free and Autonomous Generation of H2O2 from Mg-ZnO/Au Hybrids for Disinfection and Organic Pollutant Degradations

    NASA Astrophysics Data System (ADS)

    Park, Seon Yeong; Jung, Yeon Wook; Hwang, Si Hyun; Jang, Gun Hyuk; Seo, Hyunseon; Kim, Yu-Chan; Ok, Myoung-Ryul

    2018-05-01

    We proposed a new hybrid system that autonomously generates H2O2 without any instrument or external energy source, such as light. Electrons formed during spontaneous degradation process of Mg were conveyed to ZnO/Au oxygen-reduction-reaction nanocatalysts, and these transferred electrons converted O2 molecules in aqueous solution into H2O2. Autonomously released H2O2 from Mg-ZnO/Au hybrids effectively killed 97% of Escherichia coli cells within 1 h. Moreover, Mg-ZnO/Au nanohybrids could gradually degrade methylene blue over time with Fe2+. We believe our approach utilizing degradable metals and catalytic metal oxides in mesoporous-film form can be a promising method in the field of environment remediation.

  14. [Catalytic stability in wet air oxidation of carboxylic acids over ZnFe0.25Al1.75 O4 catalyst].

    PubMed

    Xu, Ai-hua; Yang, Min; Du, Hong-zhang; Peng, Fu-yong; Sun, Cheng-lin

    2007-07-01

    Oxalic, formic and acetic acid are main intermediate products in catalytic wet air oxidation process (CWAO). The catalytic activity and stability in CWAO of the three short-chain organic acids over ZnFe0.25Al1.75O4 catalyst were studied. Oxalic acid is the only oxidizable intermediate and the largest amount of Fe leaching is 9.5 mg L(-1) at 160 degrees C during CWAO process. Formic and acetic acid have little influence on Fe leaching. Due to the strong reducible ability of oxalic acid, the amount of Fe leaching is larger in nitrogen atmosphere than that in oxygen atmosphere. Salicylic acid can be also degraded by ZnFe0.25Al1.75O4 catalyst with a high catalytic activity and stability.

  15. Room temperature electroluminescence from n-ZnO:Ga/ i-ZnO/ p-GaN:Mg heterojunction device grown by PLD

    NASA Astrophysics Data System (ADS)

    Zhang, Lichun; Li, Qingshan; Wang, Feifei; Qu, Chong; Zhao, Fengzhou

    2014-05-01

    The n-ZnO:Ga/ p-GaN:Mg and n-ZnO:Ga/ i-ZnO/ p-GaN:Mg heterojunction light emitting diodes (LEDs) were fabricated by the pulsed laser deposition (PLD) technique. The blue electroluminescence (EL) of the n-ZnO:Ga/ p-GaN:Mg heterojunction LEDs is emitted mainly from the p-GaN layer instead of the n-ZnO:Ga layer, for the reason that the electron injection from n-ZnO:Ga prevailed over the hole injection from p-GaN:Mg due to the higher carrier concentration and carrier mobility in n-ZnO:Ga. On the other hand, the n-ZnO:Ga/ i-ZnO/ p-GaN:Mg heterojunction LEDs exhibited dominant ultraviolet-blue emission. The reason for this difference is attributed to the inserted undoped i-ZnO layer between n-ZnO:Ga and p-GaN:Mg, in which the holes from p-GaN:Mg and the electrons from n-ZnO:Ga are recombined.

  16. Deformation-Induced Dynamic Precipitation and Resulting Microstructure in a Mg-Zn-Ca Alloy

    NASA Astrophysics Data System (ADS)

    Du, Yuzhou; Zheng, Mingyi; Jiang, Bailing; Zhou, Kesong

    2018-05-01

    The microstructure of an Mg-Zn-Ca extrusion was investigated by transmission electron microscopy, and the interaction between dynamic precipitation and dynamic recrystallization was analyzed. The results showed that dynamic precipitation significantly affected the microstructure of the as-extruded Mg-Zn-Ca alloy. The pinning effects of precipitates on dislocations effectively prohibited dynamic recrystallization processes, while the grain boundary precipitate Ca2Mg6Zn3, inhibited the growth of dynamically recrystallized grains. Consequently, a bimodal microstructure with fine dynamically recrystallized (DRXed) grains and elongated deformed regions was obtained for the Mg-Zn-Ca extrusion. High-resolution transmission electron microscopy indicated that the intragranular precipitate MgZn2 had a crystal orientation relationship with α-Mg in the form of (0002)Mg//(10-13)MgZn2 and [1-100]Mg//[1-210]MgZn2, which was beneficial for strength improvement.

  17. Cryogenic and elevated temperature strengths of an Al-Zn-Mg-Cu alloy modified with Sc and Zr

    NASA Astrophysics Data System (ADS)

    Senkova, S. V.; Senkov, O. N.; Miracle, D. B.

    2006-12-01

    The effect of minor additions of Sc and Zr on tensile properties of two developmental Al-Zn-Mg-Cu alloys was studied in the temperature range -196°C to 300°C. Due to the presence of Sc and Zr in a fine dispersoid form, both low-temperature and elevated temperature strengths of these alloys are much higher than those of similar 7000 series alloys that do not contain these elements. After short holding times (up to 10 hours) at 205°C, the strength of these alloys is higher than those of high-temperature Al alloys 2219-T6 and 2618-T6; however, the latter alloys show better strength after longer holding times. It is suggested that additional alloying of the Sc-containing Al-Zn-Mg-Cu alloys with other dispersoid-forming elements, such as Ni, Fe, Mn, and Si, with a respective decrease in the amounts of Zn and Mg may further improve the elevated temperature strength and decrease the loss of strength with extended elevated temperature exposure.

  18. Surface effects on exciton diffusion in non polar ZnO/ZnMgO heterostructures

    NASA Astrophysics Data System (ADS)

    Sakr, G.; Sartel, C.; Sallet, V.; Lusson, A.; Patriarche, G.; Galtier, P.; Barjon, J.

    2017-12-01

    The diffusion of excitons injected in ZnO/Zn0.92Mg0.08O quantum well heterostructures grown by metal-organic-vapor-phase-epitaxy on non-polar ZnO substrates is investigated at room temperature. Cathodoluminescence linescans in a field-emission-gun scanning-electron-microscope are performed across cleaved cross-sections. A 55 nm diffusion length is assessed for excitons in bulk ZnMgO. When prepared as small angle bevels using focused ion beam (FIB), the effective diffusion length of excitons is shown to decrease down to 8 nm in the thinner part of the slab. This effect is attributed to non-radiative surface recombinations, with a 7  ×  104 cm s-1 recombination velocity estimated at the FIB-machined ZnMgO surface. The strong reduction of the diffusion extent in such thin lamellae usually used for transmission electron microscopy could be use improve the spatial resolution of cathodoluminescence images, often limited by diffusion processes.

  19. Boric acid flux synthesis, structure and magnetic property of MB₁₂O₁₄(OH)₁₀ (M=Mn, Fe, Zn)

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

    Yang, Dingfeng; Cong, Rihong; Gao, Wenliang, E-mail: gaowl@cqu.edu.cn

    2013-05-01

    Three new borates MB₁₂O₁₄(OH)₁₀ (M=Mn, Fe, Zn) have been synthesized by boric acid flux methods, which are isotypic to NiB₁₂O₁₄(OH)₁₀. Single-crystal XRD was performed to determine the crystal structures in detail. They all crystallize in the monoclinic space group P2₁/c. The size of MO{sub 6} (M=Mg, Mn, Fe, Co, Ni, Zn) octahedron shows a good agreement with the Shannon effective ionic radii of M²⁺. Magnetic measurements indicate MnB₁₂O₁₄(OH)₁₀ is antiferromagnetic without a long-range ordering down to 2 K. The values of its magnetic superexchange constants were evaluated by DFT calculations, which explain the observed magnetic behavior. The UV–vis diffuse reflectancemore » spectrum of ZnB₁₂O₁₄(OH)₁₀ suggests a band gap ~4.6 eV. DFT calculations indicate it has a direct band gap 4.9 eV. The optical band gap is contributed by charge transfers from the occupied O 2p to the unoccupied Zn 4s states. - Graphical abstract: Experimental and theoretical studies indicate MnB₁₂O₁₄(OH)₁₀ is antiferromagnetic without a long-range ordering. DFT calculations show ZnB₁₂O₁₄(OH)₁₀ has a direct band gap of 4.9 eV. Highlights: • MB₁₂O₁₄(OH)₁₀ (M=Mn, Fe, Zn) are synthesized by two-step boric acid flux method. • Single-crystal XRD was performed to determine the crystal structures in detail. • Size of MO₆ (M=Mg, Mn, Fe, Co, Ni, Zn) agrees with the effective ionic radii. • MnB₁₂O₁₄(OH)₁₀ is antiferromagnetic without a long-range ordering down to 2 K. • DFT calculations indicate ZnB₁₂O₁₄(OH)₁₀ has a direct band gap 4.9 eV.« less

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

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

    Annur, Dhyah; Franciska, P.L.; Erryani, Aprilia

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

  1. Melting relations in the system FeCO3-MgCO3 and thermodynamic modelling of Fe-Mg carbonate melts

    NASA Astrophysics Data System (ADS)

    Kang, Nathan; Schmidt, Max W.; Poli, Stefano; Connolly, James A. D.; Franzolin, Ettore

    2016-09-01

    To constrain the thermodynamics and melting relations of the siderite-magnesite (FeCO3-MgCO3) system, 27 piston cylinder experiments were conducted at 3.5 GPa and 1170-1575 °C. Fe-rich compositions were also investigated with 13 multi-anvil experiments at 10, 13.6 and 20 GPa, 1500-1890 °C. At 3.5 GPa, the solid solution siderite-magnesite coexists with melt over a compositional range of X Mg (=Mg/(Mg + Fetot)) = 0.38-1.0, while at ≥10 GPa solid solution appears to be complete. At 3.5 GPa, the system is pseudo-binary because of the limited stability of siderite or liquid FeCO3, Fe-rich carbonates decomposing at subsolidus conditions to magnetite-magnesioferrite solid solution, graphite and CO2. Similar reactions also occur with liquid FeCO3 resulting in melt species with ferric iron components, but the decomposition of the liquid decreases in importance with pressure. At 3.5 GPa, the metastable melting temperature of pure siderite is located at 1264 °C, whereas pure magnesite melts at 1629 °C. The melting loop is non-ideal on the Fe side where the dissociation reaction resulting in Fe3+ in the melt depresses melting temperatures and causes a minimum. Over the pressure range of 3.5-20 GPa, this minimum is 20-35 °C lower than the (metastable) siderite melting temperature. By merging all present and previous experimental data, standard state (298.15 K, 1 bar) thermodynamic properties of the magnesite melt (MgCO3L) end member are calculated and the properties of (Fe,Mg)CO3 melt fit by a regular solution model with an interaction parameter of -7600 J/mol. The solution model reproduces the asymmetric melting loop and predicts the thermal minimum at 1240 °C near the siderite side at X Mg = 0.2 (3.5 GPa). The solution model is applicable to pressures reaching to the bottom of the upper mantle and allows calculation of phase relations in the FeO-MgO-O2-C system.

  2. Synthesis and characterization of Mn-ZnFe2O4 and Mn-ZnFe2O4/rGO nanocomposites from waste batteries for photocatalytic, electrochemical and thermal studies

    NASA Astrophysics Data System (ADS)

    Mylarappa, M.; Venkata Lakshmi, V.; Vishnu Mahesh, K. R.; Nagaswarupa, H. P.; Raghavendra, N.

    2017-11-01

    In the present paper, Mn-ZnFe2O4 and Mn-ZnFe2O4/rGO composites recovered from waste batteries using acid dissolution and ferrite processing were studied. The recovered Mn-ZnFe2O4 nanocomposites were decorated onto rGO using the facile hydrothermal method. The recovered material was characterized using x-ray powder diffraction to study the particle size and crystallinity. The morphology of the composites was analyzed using scanning electron microscopy, and elements present in the materials were studied using energy dispersive x-ray analysis. The functional groups attached were observed using a Fourier transform infrared spectrometer. Furthermore, the recovered composites were evaluated in thermal studies using thermal gravimetric analysis, differential scanning calorimetry and dynamic thermal analysis. The material was used as a photocatalyst for the removal of acid orange 88 dye, and as an electrocatalyst. The decreased band gap energy for the Mn-ZnFe2O4/rGO composite was displayed in better photocatalytic activity for a given reaction. The electrochemical properties of Mn-ZnFe2O4 and Mn-ZnFe2O4/rGO have been investigated using cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) with a paste-type electrode. The CV indicated the reversibility of the electrode reaction, and the EIS revealed that a decrease in the charge transfer resistance increases the double layer capacitance of the rGO/Mn-ZnFe2O4 electrode.

  3. Effect of NaFeEDTA-fortified soy sauce on zinc absorption in children.

    PubMed

    Li, Min; Wu, Jinghuan; Ren, Tongxiang; Wang, Rui; Li, Weidong; Piao, Jianhua; Wang, Jun; Yang, Xiaoguang

    2015-03-01

    NaFeEDTA has been applied in many foods as an iron fortificant and is used to prevent iron deficiency in Fe-depleted populations. In China, soy sauce is fortified with NaFeEDTA to control iron deficiency. However, it is unclear whether Fe-fortified soy sauce affects zinc absorption. To investigate whether NaFeEDTA-fortified soy sauce affects zinc absorption in children, sixty children were enrolled in this study and randomly assigned to three groups (10 male children and 10 female children in each group). All children received daily 3 mg of (67)Zn and 1.2 mg of dysprosium orally, while the children in the three groups were supplemented with NaFeEDTA-fortified soy sauce (6 mg Fe, NaFeEDTA group), FeSO₄-fortified soy sauce (6 mg Fe, FeSO₄ group), and no iron-fortified soy sauce (control group), respectively. Fecal samples were collected during the experimental period and analyzed for the Zn content, (67)Zn isotope ratio and dysprosium content. The Fe intake from NaFeEDTA-fortified and FeSO₄-fortified groups was significantly higher than that in the control group (P < 0.0001). The daily total Zn intake was not significantly different among the three groups. There were no significant differences in fractional Zn absorption (FZA) (P = 0.3895), dysprosium recovery (P = 0.7498) and Zn absorption (P = 0.5940) among the three groups. Therefore, NaFeEDTA-fortified soy sauce does not affect Zn bioavailability in children.

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

    PubMed

    Dong, Anping; Li, Baoping; Lu, Yanling; Zhu, Guoliang; Xing, Hui; Shu, Da; Sun, Baode; Wang, Jun

    2017-08-22

    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.

  5. Synthesis, characterization, and magnetic properties of ZnO-ZnFe2O4 nanoparticles with high photocatalytic activity

    NASA Astrophysics Data System (ADS)

    Falak, P.; Hassanzadeh-Tabrizi, S. A.; Saffar-Teluri, A.

    2017-11-01

    In the present research, a magnetic ZnO-ZnFe2O4 binary nanocomposite was synthesized by a one-step microemulsion method. The characteristics of the synthesized powders were characterized using various analytical instruments including X-ray diffraction, scanning electron microscope, transmission electron microscope, thermogravimetric and differential thermal analysis, vibrating sample magnetometer, and ultraviolet-visible spectroscopy. The results of transmission electron microscope proved that the synthesized nanoparticles have irregular morphologies and the average particle size is about 20 nm. The photocatalytic investigation of ZnO-ZnFe2O4 nanoparticles was carried out using methylene blue solution under UV light. The synthesized nanoparticles showed enhanced photocatalytic performance in comparison with the ZnO nanoparticles more than 40%. The magnetization saturation value of ZnO-ZnFe2O4 nanoparticles was about 5.8 emu/g, which was high enough to be magnetically removed by applying a magnetic field. The results showed that the magnetization and coercivity of the samples reduced by increasing calcination temperature.

  6. Structural, dielectric and magnetic studies of (x) Mg0.2Cu0.3Zn0.5Fe2O4 + (1-x) Ba0.8Zr0.2TiO3 magnetoelectric composites

    NASA Astrophysics Data System (ADS)

    Khader, S. Abdul; Giridharan, N. V.; Chaudhuri, Arka; Sankarappa, T.

    2016-05-01

    The Magneto-electric composites (x) Mg0.2Cu0.3Zn0.5Fe2O4 + (1-x) Ba0.8Zr0.2TiO3 (x=15%,30%,45%) were synthesized by sintering mixtures of highly ferroelectric Ba0.8Zr0.2TiO3 (BZT) and highly magneto-strictive component Mg0.2Cu0.3Zn0.5Fe2O4 (MCZF). The presences of two phases in magneto-electric composites were probed by X-ray diffraction (XRD) studies. The peaks observed in the XRD spectrum indicated spinel cubic structure for MCZF ferrite and tetragonal perovskite structure for BZT and, both spinel and pervoskite structures for synthesized composites. Surface morphology of the samples has been investigated using Field Emission Scanning Electron Microscope (FESEM). Frequency dependent dielectric properties of synthesized composites were measured from 100 Hz to 1 MHz at RT using HIOKI LCR HI-TESTER. The dielectric dispersion is observed at lower frequencies for the synthesized ME composites. The magnetic properties of synthesized composites were analyzed using a Vibrating Sample Magnetometer (VSM). It is observed that the values of saturation magnetization increases along with the ferrite content.

  7. Effect of Zn Concentration on the Microstructure and Mechanical Properties of Al-Mg-Si-Zn Alloys Processed by Gravity Die Casting

    NASA Astrophysics Data System (ADS)

    Li, Longfei; Ji, Shouxun; Zhu, Qiang; Wang, Yun; Dong, Xixi; Yang, Wenchao; Midson, Stephen; Kang, Yonglin

    2018-06-01

    The microstructure and mechanical properties of Al-8.1Mg-2.6Si-(0.08 to 4.62)Zn alloys (in wt pct) have been investigated by the permanent mold casting process. X-ray diffraction analysis shows that the τ-Mg32(Al, Zn)49 phase forms when the Zn content is 1.01 wt pct. With higher Zn contents of 2.37 and 3.59 wt pct, the η-MgZn2 and τ-Mg32(Al, Zn)49 phases precipitate in the microstructure, and the η-MgZn2 phase forms when the Zn content is 4.62 wt pct. Metallurgical analysis shows that the η-MgZn2 and τ-Mg32(Al, Zn)49 phases strengthen the Al-8.1Mg-2.6Si-(0.08 to 4.62)Zn alloys. After solutionizing at 510 °C for 180 minutes and aging at 180 °C for 90 minutes, the η'-MgZn2 phase precipitates in the α-Al matrix, which significantly enhances the mechanical properties. Addition of 3.59 wt pct Zn to the Al-8.1Mg-2.6Si alloy with heat treatment increases the yield strength from 96 to 280 MPa, increases the ultimate tensile strength from 267 to 310 MPa, and decreases the elongation from 9.97 to 1.74 pct.

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

    NASA Astrophysics Data System (ADS)

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

    2017-12-01

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

  9. Assessment of retrogression and re-aging treatment on microstructural and mechanical properties of Al-Zn-Mg-Cu P/M alloy

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

    Naeem, Haider T.; College of Engineering, Al-Muthanna University, South Baghdad; Mohammad, Kahtan S.

    2015-05-15

    In order to understand the importance of the retrogression and re-aging as a heat treatment for improving microstructural and mechanical properties of the Al-Zn-Mg-Cu powder metallurgy alloys, Al-Zn-Mg-Cu-Fe-Cr alloys were fabricated from the elemental powders. Green compacts are compressed under compaction pressure about 370 MPa. The sintering process carried out for the samples of aluminum alloys at temperature was 650°C under argon atmosphere for two hours. The sintered compacts were subjected into homogenizing condition at 470°C for 1.5 hours and then aged at 120°C for 24 hours (T6 temper) after that it carried out the retrogressed at 180°C for 30more » min., and then re-aged at 120°C for 24 hours (RRA). Observations microstructures were examined using optical, scanning electron microscopy coupled with energy dispersive spectroscopy and X-ray diffraction. Density and porosity content was conducted for the samples of alloys. The result showing that the highest Vickers hardness exhibited for an Al-Zn-Mg-Cu alloy after underwent the retrogression and reaging treatment. Increasing in hardness was because of the precipitation hardening through precipitate the (Mg Zn) and (Mg{sub 2}Zn{sub 11}) phases during matrix of aluminum-alloy.« less

  10. Polarization Induced Doping in p-ZnMgO

    DTIC Science & Technology

    2013-09-06

    Zn +Mg  ratio.   3. Good...conditions  were   investigated   to   obtain  a  high  quality  film:  the  sequence  of   Zn  and  O  sources  for...and   Zn /O   ratio.   Resultant   epitaxial   ZnO   films   demonstrated   a   root-­‐mean-­‐square   surface  

  11. Biodegradable CaMgZn bulk metallic glass for potential skeletal application.

    PubMed

    Wang, Y B; Xie, X H; Li, H F; Wang, X L; Zhao, M Z; Zhang, E W; Bai, Y J; Zheng, Y F; Qin, L

    2011-08-01

    A low density and high strength alloy, Ca65Mg15Zn20 bulk metallic glass (CaMgZn BMG), was evaluated by both in vitro tests on ion release and cytotoxicity and in vivo implantation, aimed at exploring the feasibility of this new biodegradable metallic material for potential skeletal applications. MTT assay results showed that the experimental CaMgZn BMG extracts had no detectable cytotoxic effects on L929, VSMC and ECV304 cells over a wide range of concentrations (0-50%), whereas for MG63 cells concentrations in the range ~5-20% promoted cell viability. Meanwhile, alkaline phosphatase (ALP) activity results showed that CaMgZn BMG extracts increased alkaline phosphatase (ALP) production by MG63 cells. However, Annexin V-fluorescein isothiocyanate and propidium iodide staining indicated that higher concentrations (50%) might induce cell apoptosis. The fluorescence observation of F-actin and nuclei in MG63 cells showed that cells incubated with lower concentrations (0-50%) displayed no significant change in morphology compared with a negative control. Tumor necrosis factor-α expression by Raw264.7 cells in the presence of CaMgZn BMG extract was significantly lower than that of the positive and negative controls. Animal tests proved that there was no obvious inflammation reaction at the implantation site and CaMgZn BMG implants did not result in animal death. The cortical thickness around the CaMgZn BMG implant increased gradually from 1 to 4 weeks, as measured by in vivo micro-computer tomography. Copyright © 2011 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

  12. A novel biphenolic ligand for selective Mg2+ and Zn2+ ions sensing followed by colorimetric, spectroscopic and cell imaging methods.

    PubMed

    Maheswari, Palanisamy Uma; Renuga, Duraisamy; Henry, Linda Jeeva Kumari; Ruckmani, Kandasamy

    2018-04-30

    The (E)-2-((2-hydrohy-5-methylphenylimino) methyl) phenol ligand was synthesized. The receptor was characterized by IR, 1 H and 13 C NMR and CHN analysis. The ligand exhibits colorimetric and fluorometric sensing of Zn 2+ and Mg 2+ ions in semi-aqueous medium (DMSO-H2O). The receptor was tested with series of transition metal ions (Cr 2+ , Fe 2+ , Ni 2+ , Co 2+ , Cu 2+ , Zn 2+ ) and heavy metal ions (Sn 2+ , Pd 2+ , Ce 2+ , Hg 2+ , Cd 2+ ) and the essential human body elements like Ca 2+ , Mg 2+ , Na + and K + ions. The naked eye colorimetric sensing was absorbed only for Zn 2+ and Mg 2+ . Both ions (ZnCl 2 and MgCl 2 in H 2 O), when added to the colorless solutions of the receptor of about 1 equivalence in incremental additions turn the solution into bright turmeric yellow. All other ions remain inactive, in colorimetric sensing. Further the Zn 2+ and Mg 2+ ions were probed by absorption and emission spectroscopy through incremental addition of respective metal ions. The in-situ deprotonation of the ligand on both Mg 2+ and Zn 2+ ions binding was confirmed by 1 H NMR titration studies. The imino nitrogen of the receptor is not coordinated to the metal ions. The Job's plot studies reveal the 1:2 binding ratio of metal ions to the receptor. The high fold fluorescence output on metal ions binding was positively used to sense the Zn 2+ and Mg 2+ ions, separately and together in HeLa cancer cells through cell imaging. Copyright © 2018 Elsevier B.V. All rights reserved.

  13. Effect of temperature on the electrical properties of Zn0.95M0.05O (M = Zn, Fe, Ni)

    NASA Astrophysics Data System (ADS)

    Sedky, A.; Mohamed, S. B.

    2014-01-01

    We report here the structural and electrical properties of Zn0.95M0.05O ceramic varistors, M = Zn, Ni and Fe. The samples were tested for phase purity and structural morphology by using X-Ray diffraction XRD and scanning electron microscope SEM techniques. The current-voltage characteristics J-E were obtained by dc electrical measurements in the temperature range of 300-500 K. Addition of doping did not influence the hexagonal wurtzite structure of ZnO ceramics. Furthermore, the lattice parameters ratio c/a for hexagonal distortion and the length of the bond parallel to the c axis, u were nearly unaffected. The average grain size was decreased from 1.57 μm for ZnO to 1.19 μm for Ni sample and to 1.22 μm for Fe sample. The breakdown field EB was decreased as the temperature increased, in the following order: Fe > Zn > Ni. The nonlinear region was clearly observed for all samples as the temperature increased up to 400 K and completely disappeared with further increase of temperature up to 500 K. The values of nonlinear coefficient, a were between 1.16 and 42 for all samples, in the following order: Fe > Zn > Ni. Moreover, the electrical conductivity s was gradually increased as the temperature increased up to 500 K, in the following order: Ni > Zn > Fe. On the other hand, the activation energies were 0.194 eV, 0.136 and 0.223 eV for all samples, in the following order: Fe, Zn and Ni. These results have been discussed in terms of valence states, magnetic moment and thermo-ionic emission, which were produced by the doping, and controlling the potential barrier of ZnO.

  14. Understanding the role of iron in the magnetism of Fe doped ZnO nanoparticles.

    PubMed

    Beltrán, J J; Barrero, C A; Punnoose, A

    2015-06-21

    The actual role of transition metals like iron in the room temperature ferromagnetism (RTFM) of Fe doped ZnO nanoparticles is still an unsolved problem. While some studies concluded that the Fe ions participate in the magnetic interaction, others in contrast do not believe Fe to play a direct role in the magnetic exchange interaction. To contribute to the understanding of this issue, we have carefully investigated the structural, optical, vibrational and magnetic properties of sol-gel synthesized Zn1-xFexO (0 < x < 0.10) nanoparticles. No Fe(2+) was detected in any sample. We found that high spin Fe(3+) ions are substitutionally incorporated at the Zn(2+) in the tetrahedral-core sites and in pseudo-octahedral surface sites in ZnO. Superficial OH(-) was observed in all samples. For x ≤ 0.03, an increment in Fe doping concentration decreased a and c lattice parameters, average Zn-O bond length, average crystallite size and band gap; while it increased the degree of distortion and quadrupole splitting. Undoped ZnO nanoparticles exhibited very weak RTFM with a saturation magnetization (Ms) of ∼0.47 memu g(-1) and this value increased to ∼2.1 memu g(-1) for Zn0.99Fe0.01O. Very interestingly, the Ms for Zn0.99Fe0.01O and Zn0.97Fe0.03O increased by a factor of about ∼2.3 by increasing annealing for 1 h to 3 h. For x ≥ 0.05, ferrimagnetic disordered spinel ZnFe2O4 was formed and this phase was found to become more ordered with increasing annealing time. Fe does not contribute directly to the RTFM, but its presence promoted the formation of additional single charged oxygen vacancies, zinc vacancies, and more oxygen-ended polar terminations at the nanoparticle surface. These defects, which are mainly superficial, altered the electronic structure and are considered as the main sources of the observed ferromagnetism.

  15. Effect of γ-rays irradiation on the structural, magnetic, and electrical properties of Mg-Cu-Zn and Ni-Cu-Zn ferrites

    NASA Astrophysics Data System (ADS)

    Assar, S. T.; Abosheiasha, H. F.; El Sayed, A. R.

    2017-01-01

    Nanoparticles of Ni0.35Cu0.15Zn0.5Fe2O4 and Mg0.35Cu0.15Zn0.5Fe2O4, have been synthesized by citrate precursor method. Then some of the prepared samples have been irradiated by γ-rays of 60Co radioactive source at room temperature with doses of 1 Mrad and 2 Mrad, at a dose rate of 0.1 Mrad/h to study the effect of γ-rays irradiation on some structural, magnetic and electrical properties of the samples. The X-ray diffraction analysis (XRD), transmission electron microscopy, Fourier transform infrared spectroscopy and vibrating sample magnetometer measurements have been used to investigate the samples. The XRD results show that the irradiation has caused a decrease in the crystallite size and the measured density and an increase in the porosity, specific surface area, and microstrain in the case of Ni-Cu-Zn ferrite whereas in the case of Mg-Cu-Zn ferrite the reverse trend has been noticed. The lattice constant of the investigated samples has been increased with the increase of irradiation due to the conversion of Fe3+ (0.67 Å) to Fe2+ (0.76 Å). The magnetization results show an increase in saturation and remnant magnetizations for the two prepared ferrites after γ-rays irradiation. The main reason of this behavior is most probably due to the redistribution of the cations between A and B sites. The cation distribution has been proposed such that the values of theoretical and experimental magnetic moment are identical and increase as the magnetization increases. Moreover, a theoretical estimation of the lattice constant has been calculated on the basis of the proposed cation distribution for each sample and compared with the corresponding experimental values obtained by XRD analysis; where they have been found in a good agreement with each other. This can be considered as another confirmation of the validity of the cation distribution. Moreover, the cation distribution is thought to play an important role in increasing the values of dc conductivity of all samples

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

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

    Kozioł-Rachwał, Anna, E-mail: a.koziolrachwal@aist.go.jp; AGH University of Science and Technology, Faculty of Physics and Applied Computer Science, al. Mickiewicza 30, 30-059 Kraków; Nozaki, Takayuki

    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 inmore » 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.« less

  17. Fabrication of biodegradable Zn-Al-Mg alloy: Mechanical properties, corrosion behavior, cytotoxicity and antibacterial activities.

    PubMed

    Bakhsheshi-Rad, H R; Hamzah, E; Low, H T; Kasiri-Asgarani, M; Farahany, S; Akbari, E; Cho, M H

    2017-04-01

    In this work, binary Zn-0.5Al and ternary Zn-0.5Al-xMg alloys with various Mg contents were investigated as biodegradable materials for implant applications. Compared with Zn-0.5Al (single phase), Zn-0.5Al-xMg alloys consisted of the α-Zn and Mg 2 (Zn, Al) 11 with a fine lamellar structure. The results also revealed that ternary Zn-Al-Mg alloys presented higher micro-hardness value, tensile strength and corrosion resistance compared to the binary Zn-Al alloy. In addition, the tensile strength and corrosion resistance increased with increasing the Mg content in ternary alloys. The immersion tests also indicated that the corrosion rates in the following order Zn-0.5Al-0.5Mg-0.5Al-0.3Mg-0.5Al-0.1Mg-0.5Al. The cytotoxicity tests exhibited that the Zn-0.5Al-0.5Mg alloy presents higher viability of MC3T3-E1 cell compared to the Zn-0.5Al alloy, which suggested good biocompatibility. The antibacterial activity result of both Zn-0.5Al and Zn-0.5Al-Mg alloys against Escherichia coli presented some antibacterial activity, while the Zn-0.5Al-0.5Mg significantly prohibited the growth of Escherichia coli. Thus, Zn-0.5Al-0.5Mg alloy with appropriate mechanical properties, low corrosion rate, good biocompatibility and antibacterial activities was believed to be a good candidate as a biodegradable implant material. Copyright © 2016 Elsevier B.V. All rights reserved.

  18. Magnetic properties of Mn0.1Mg0.2TM0.7Fe2O4 (TM = Zn, Co, or Ni) prepared by hydrothermal processes: The effects of crystal size and chemical composition

    NASA Astrophysics Data System (ADS)

    Nhlapo, T. A.; Msomi, J. Z.; Moyo, T.

    2018-02-01

    Nano-crystalline Zn-, Co-, and Ni-substituted Mn-Mg ferrites were prepared by hydrothermal process and annealed at 1100 °C. Annealing conditions are critical on the crystalline phase. TEM and XRD data reveal particle sizes between 8 nm and 15 nm for the as-prepared fine powders, which increase to about 73 nm after sintering at 1100 °C. Mӧssbauer spectra show well resolved magnetic splitting in bulk samples. The as-prepared fine powders show weak hyperfine splitting and broad central doublets associated with fine particles. Magnetization data reveal a high coercive field at about 300 K of about 945 Oe in the Co-based nanosized oxide, which reduces to about 360 Oe after thermal annealing at 1100 °C. The magnetization curves of Zn- and Ni-based samples show much lower coercive fields indicative of superparamagnetic nanoparticles. The crystallite size and chemical composition have significant effects on the properties of Mn0.1Mg0.2(Zn,Co,Ni)0.7Fe2O4 investigated.

  19. Structural and electrical properties of ZnO/Zn0.85Mg0.15O thin film prepared by pulsed laser deposition

    NASA Astrophysics Data System (ADS)

    Yang, Jing-Jing; Wang, Gang; Du, Wen-Han; Xiong, Chao

    2017-07-01

    The electrical transport properties are the key factors to determine the performance of ZnO-based quantum effect device. ZnMgO is a typical material to regulate the band of ZnO. In order to investigate the electrical properties of the interface of ZnO/Zn0.85Mg0.15O films, three kinds of ZnO/Zn0.85Mg0.15O films have been fabricated with different thickness. After comparing the structural and electrical properties of the samples, we found that the independent Zn0.85Mg0.15O hexagonal wurtzite structure (002) peak can be detected in XRD spectra. Hall-effect test data confirmed that the two-dimensional electron gas (2DEG) became lower because of the decrease of thickness of Zn0.85Mg0.15O films, increase of impurity scattering and lattice structure distortion caused by the increase of Mg content.

  20. Section 2: Phase transformation studies in mechanically alloyed Fe-Nz and Fe-Zn-Si intermetallics

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

    Jordan, A.; Uwakweh, O.N.C.; Maziasz, P.J.

    1997-04-01

    The initial stage of this study, which was completed in FY 1995, entailed an extensive analysis characterizing the structural evolution of the Fe-Zn intermetallic system. The primary interest in these Fe-Zn phases stems from the fact that they form an excellent coating for the corrosion protection of steel (i.e., automobile body panels). The Fe-Zn coating generally forms up to four intermetallic phases depending on the particular industrial application used, (i.e., galvanization, galvannealing, etc.). Since the different coating applications are non-equilibrium in nature, it becomes necessary to employ a non-equilibrium method for producing homogeneous alloys in the solid-state to reflect themore » structural changes occurring in a true coating. This was accomplished through the use of a high energy/non-equilibrium technique known as ball-milling which allowed the authors to monitor the evolution process of the alloys as they transformed from a metastable to stable equilibrium state. In FY 1996, this study was expanded to evaluate the presence of Si in the Fe-Zn system and its influence in the overall coating. The addition of silicon in steel gives rise to an increased coating. However, the mechanisms leading to the coating anomaly are still not fully understood. For this reason, mechanical alloying through ball-milling of pure elemental powders was used to study the structural changes occurring in the sandelin region (i.e., 0.12 wt % Si). Through the identification of invariant reactions (i.e., eutectic, etc.) the authors were able to explore the sandelin phenomenon and also determine the various fields or boundaries associated with the Fe-Zn-Si ternary system.« less

  1. Effect of MgO spacer and annealing on interface and magnetic properties of ion beam sputtered NiFe/Mg/MgO/CoFe layer structures

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

    Bhusan Singh, Braj; Chaudhary, Sujeet

    2012-09-15

    The effect of variation in the thickness of ion assisted ion beam sputtered MgO spacer layer deposited at oxygen ion assisted energy of 50 eV on the extent of magnetic coupling of NiFe and CoFe layers in Si/NiFe(10 nm)/Mg(1 nm)/MgO(2,4,6 nm)/CoFe(10 nm) sandwich structure is investigated. At MgO spacer layer thickness of 4 nm, the separate reversal of magnetizations of the two ferromagnetic layers is observed in the hystresis loop recorded along easy direction. This results in a 3.5 Oe wide plateau like region during magnetization reversal, which became 4.5 Oe at 6 nm thin MgO. At 2 nm thinmore » MgO, the absence of plateau during magnetization reversal region revealed ferromagnetic coupling between the two ferromagnetic layers, which is understood to arise due to the growth of very thin and low density (1.22 gm/cc) MgO spacer layer, indicating the presence of pinholes as revealed by x-ray reflectometry. After vaccum annealing (200 Degree-Sign C/1 h), the plateau region for 4 and 6 nm thin MgO case decreased to 1.5 Oe and 2.0 Oe, respectively, due to enhanced interface roughness/mixing. In addition, an enhancement of the in-plane magnetic anisotropy is also observed.« less

  2. Zincobotryogen, ZnFe3+(SO4)2(OH)ṡ7H2O: validation as a mineral species and new data

    NASA Astrophysics Data System (ADS)

    Yang, Zhuming; Giester, Gerald; Mao, Qian; Ma, Yuguang; Zhang, Di; Li, He

    2017-06-01

    Zincobotryogen occurs in the oxidation zone of the Xitieshan lead-zinc deposit, Qinghai, China. The mineral is associated with jarosite, copiapite, zincocopiapite, and quartz. The mineral forms prismatic crystals, 0.05 to 2 mm in size. It is optically positive (2Vcalc = 54.1°), with Z ‖ b and X ∧ c = 10°. The elongation is negative. The refractive indices are n α = 1.542(5), n β = 1.551(5), n γ = 1.587(5). The pleochroism scheme is X = colorless, Y = light yellow, Z = yellow. Microprobe analysis gave (in wt%): SO3 = 38.04, Al2O3 = 0.04, Fe2O3 = 18.46, ZnO = 13.75, MgO = 1.52, MnO = 1.23, H2O = 31.06 (by calculation), Total = 104.10. The simplified formula is (Zn,Mg)Fe3+(SO4)2(OH)ṡ7H2O. The mineral is monoclinic, P121/ n1, a = 10.504(2), b = 17.801(4), c = 7.1263(14) Å, and β = 100.08(3)°, V = 1311.9(5) Å3, Z = 4. The strongest lines in the powder X-ray diffraction pattern d(I)( hkl) are: 8.92 (100)(110), 6.32 (77)(-101), 5.56 (23)(021), 4.08 (22)(-221),3.21 (31)(231), 3.03 (34)(032), 2.77 (22)(042). The crystal structure was refined using 2816 unique reflections to R1( F) = 0.0355 and wR2( F 2) = 0.0651. The refined formula is (Zn0.84Mg0.16)Fe3+(SO4)2(OH)ṡ7H2O. The atomic arrangement is characterized by chains with composition [Fe3+(SO4)2(OH)(H2O)]2- and 7 Å repeat distance running parallel to the c-axis. The chain links to a [ MO(H2O)5] octahedron ( M = Zn, Mg) and an unshared H2O molecule, and forms a larger chain building module with composition [ M 2+Fe3+(SO4)2(OH)(H2O)6(H2O)]. The inter-chain module linkage involves only hydrogen bonding.

  3. Synthesis, characterization and antibacterial property of ZnO:Mg nanoparticles

    NASA Astrophysics Data System (ADS)

    Kompany, A.; Madahi, P.; Shahtahmasbi, N.; Mashreghi, M.

    2012-09-01

    Sol-gel method was successfully used for the synthesis of ZnO nanoparticles (NPs) doped with different concentrations of Mg and the structural, optical and antibacterial properties of the nanoparticles were studied. The synthesized ZnO:Mg powders were characterized using x-ray diffraction (XRD), transmission electron microscopy (TEM), Fourier transformation Infrared (FTIR) and UV-Vis spectroscopy. It was revealed that the samples have hexagonal Wurtzite structure, and the phase segregation takes place for 15% Mg content. TEM images show that the average size of the particles is about 50 nm. Also, the antibacterial activities of the nanoparticles were tested against Escherichia coli (Gram negative) cultures. ZnO:Mg nanofluid showed good antibacterial activity which increases with the increase of NPs concentration, and decreases slightly with the amount of Mg.

  4. Hot LO-phonon limited electron transport in ZnO/MgZnO channels

    NASA Astrophysics Data System (ADS)

    Šermukšnis, E.; Liberis, J.; Matulionis, A.; Avrutin, V.; Toporkov, M.; Özgür, Ü.; Morkoç, H.

    2018-05-01

    High-field electron transport in two-dimensional channels at ZnO/MgZnO heterointerfaces has been investigated experimentally. Pulsed current-voltage (I-V) and microwave noise measurements used voltage pulse widths down to 30 ns and electric fields up to 100 kV/cm. The samples investigated featured electron densities in the range of 4.2-6.5 × 1012 cm-2, and room temperature mobilities of 142-185 cm2/V s. The pulsed nature of the applied field ensured negligible, if any, change in the electron density, thereby allowing velocity extraction from current with confidence. The highest extracted electron drift velocity of ˜0.5 × 107 cm/s is somewhat smaller than that estimated for bulk ZnO; this difference is explained in the framework of longitudinal optical phonon accumulation (hot-phonon effect). The microwave noise data allowed us to rule out the effect of excess acoustic phonon temperature caused by Joule heating. Real-space transfer of hot electrons into the wider bandgap MgZnO layer was observed to be a limiting factor in samples with a high Mg content (48%), due to phase segregation and the associated local lowering of the potential barrier.

  5. On the synthesis, structural, optical and magnetic properties of nano-size Zn-MgO

    NASA Astrophysics Data System (ADS)

    Varshney, Dinesh; Dwivedi, Sonam

    2015-09-01

    Chemical co-precipitation method is employed to synthesize ZnO, MgO and Zn0.5Mg0.5O nanoparticles. X-ray diffraction (XRD) pattern infers that the sample of ZnO is in single-phase wurtzite structure (hexagonal phase, P63mc), MgO crystallizes in cubic Fd3m space group and Zn0.5Mg0.5O represents mixed nature of ZnO and MgO lattices. MgO nanocrystals band around 1078 cm-1 is ascribed to the TO-LO surface phonon modes in MgO lattice. In case of Zn0.5Mg0.5O lattice illustrating two bands at 436 and 1087 cm-1. FTIR spectra clearly show the broad band within 450-600 cm-1 is associated with the special vibration of magnesium oxide. FT-IR spectrum of Zn0.5Mg0.5O represents the combined bands of both ZnO-MgO oxides. Further the optical study obtained value of MgO (4.08 eV) is much lower than the corresponding bulk value (7.08 eV). All samples show diamagnetic nature at room temperature.

  6. Quaternary M{sub 0.25}Cu{sub 0.25}Mg{sub 0.5}Fe{sub 2}O{sub 4} (M = Ni, Zn, Co, Mn) ferrite oxides: Synthesis, characterization and magnetic properties

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

    Ciocarlan, Radu George; Laboratory of Adsorption and Catalysis, Department of Chemistry, University of Antwerpen; Pui, Aurel, E-mail: aurel@uaic.ro

    2016-09-15

    Highlights: • Superparamagnetic quaternary nanoferrite (M{sub 0.25}Cu{sub 0.25}Mg{sub 0.5}Fe{sub 2}O{sub 4,} where M = Mn, Zn, Co, Ni) were obtained. • C, O, H and metals were observed by XPS analysis. • Phases purity were confirmed by XRD diffraction and crystallite size (3–10 nm) were determind. - Abstract: We report the synthesis of M{sub 0.25}Cu{sub 0.25}Mg{sub 0.5}Fe{sub 2}O{sub 4} (where M = Mn, Zn, Co, Ni) nanoparticles using the coprecipitation method in the presence of carboxymethyl cellulose (CMC) as the in-situ surfactant. The crystalline structure and surface morphology were examined by means of X-ray diffraction (XRD) and scanning electron microscopymore » (SEM) and it was established that the average diameter of the magnetic nanoparticles (MNPs) is in the range of 3–10 nm. X-ray photoelectron spectroscopy (XPS) and Fourier transform infrared spectroscopy (FTIR) show that the MNPs are activated by the hydrophilic groups of the surfactant, which coat them and enhance their stability. The vibrating sample magnetometry measurements show the superparamagnetic behavior of the nanoparticles. Due to their small crystallite size, which implies large surface area, and their functionalization with organic groups, the obtained nanoparticles could have medical and catalytic applications.« less

  7. Electron Raman scattering in a strained ZnO/MgZnO double quantum well

    NASA Astrophysics Data System (ADS)

    Mojab-abpardeh, M.; Karimi, M. J.

    2018-02-01

    In this work, the electron Raman scattering in a strained ZnO / MgZnO double quantum wells is studied. The energy eigenvalues and the wave functions are obtained using the transfer matrix method. The effects of Mg composition, well width and barrier width on the internal electric field in well and barrier layers are investigated. Then, the influences of these parameters on the differential cross-section of electron Raman scattering are studied. Results indicate that the position, magnitude and the number of the peaks depend on the Mg composition, well width and barrier width.

  8. Vertical Geochemical Variations and Speciation Studies of As, Fe, Mn, Zn, and Cu in the Sediments of the Central Gangetic Basin: Sequential Extraction and Statistical Approach

    PubMed Central

    Ramanathan, AL.

    2018-01-01

    A geochemical and speciation study of As, Fe, Mn, Zn, and Cu was performed using sequential extraction and statistical approaches in the core sediments taken at two locations—Rigni Chhapra and Chaube Chhapra—of the central Gangetic basin (India). A gradual increase in the grain size (varying from clay to coarse sands) was observed in both the core profiles up to 30.5 m depth. The concentrations of analyzed elements ranged as follows: 6.9–14.2 mg/kg for As, 13,849–31,088 mg/kg for Fe, 267–711 mg/kg for Mn, 45–164 mg/kg for Cu for Rigni Chhapra while for Chaube Chhapra the range was 7.5–13.2 mg/kg for As, 10,936–37,052 mg/kg for Fe, 267–1052 mg/kg for Mn, 60–198 mg/kg for Zn and 60–108 mg/kg for Cu. Significant amounts (53–95%) of all the fractionated elemental concentrations were bound within the crystal structure of the minerals as a residual fraction. The reducible fraction was the second most dominant fraction for As (7% and 8%), Fe (3%), Mn (20% and 26%), and Cu (7% and 6%) respectively for both the cores. It may be released when aquifers subjected to changing redox conditions. The acid soluble fraction was of most interest because it could quickly mobilize into the water system which formed the third most dominating among all three fractions. Four color code of sediments showed an association with total As concentration and did not show a relation with any fraction of all elements analyzed. The core sediment was observed enriched with As and other elements (Cu, Fe, Mn, and Zn). However, it fell under uncontaminated to moderately contaminate which might exhibit a low risk in prevailing natural conditions. X-ray diffraction analyses indicated the availability of siderite and magnetite minerals in the core sediments in a section of dark grey with micaceous medium sand with organic matter (black). PMID:29360767

  9. Tri-functional Fe2O3-encased Ag-doped ZnO nanoframework: magnetically retrievable antimicrobial photocatalyst

    NASA Astrophysics Data System (ADS)

    Karunakaran, Chockalingam; Vinayagamoorthy, Pazhamalai

    2016-11-01

    Fe2O3-encased ZnO nanoframework was obtained by hydrothermal method and was doped with Ag through photoreduction process. Energy dispersive x-ray spectroscopy, transmission electron microscopy (TEM), high resolution TEM, selected area electron diffractometry, x-ray diffractometry and Raman spectroscopy were employed for the structural characterization of the synthesized material. While the charge transfer resistance of the prepared nanomaterial is larger than those of Fe2O3 and ZnO the coercivity of the nanocomposite is less than that of hydrothermally obtained Fe2O3 nanostructures. Although Fe2O3/Ag-ZnO exhibits weak visible light absorption its band gap energy does not differ from that of ZnO. The photoluminescence of the fabricated nanoframework is similar to that of ZnO. The radiative recombination of charge carriers is slightly slower in Fe2O3/Ag-ZnO than in ZnO. The synthesized Fe2O3-encased Ag-doped ZnO, under UV A light, exhibits sustainable photocatalytic activity to degrade dye and is magnetically recoverable. Also, the Fe2O3/Ag-ZnO nanocomposite disinfects bacteria effectively in absence of direct illumination.

  10. Experimental study of the Ca-Mg-Zn system using diffusion couples and key alloys

    NASA Astrophysics Data System (ADS)

    Zhang, Yi-Nan; Kevorkov, Dmytro; Bridier, Florent; Medraj, Mamoun

    2011-03-01

    Nine diffusion couples and 32 key samples were prepared to map the phase diagram of the Ca-Mg-Zn system. Phase relations and solubility limits were determined for binary and ternary compounds using scanning electron microscopy, electron probe microanalysis and x-ray diffraction (XRD). The crystal structure of the ternary compounds was studied by XRD and electron backscatter diffraction. Four ternary intermetallic (IM) compounds were identified in this system: Ca3MgxZn15-x (4.6<=x<=12 at 335 °C, IM1), Ca14.5Mg15.8Zn69.7 (IM2), Ca2Mg5Zn13 (IM3) and Ca1.5Mg55.3Zn43.2 (IM4). Three binary compounds were found to have extended solid solubility into ternary systems: CaZn11, CaZn13 and Mg2Ca form substitutional solid solutions where Mg substitutes for Zn atoms in the first two compounds, and Zn substitutes for both Ca and Mg atoms in Mg2Ca. The isothermal section of the Ca-Mg-Zn phase diagram at 335 °C was constructed on the basis of the obtained experimental results. The morphologies of the diffusion couples in the Ca-Mg-Zn phase diagram at 335 °C were studied. Depending on the terminal compositions of the diffusion couples, the two-phase regions in the diffusion zone have either a tooth-like morphology or contain a matrix phase with isolated and/or dendritic precipitates.

  11. Effect of Mg doping in ZnO buffer layer on ZnO thin film devices for electronic applications

    NASA Astrophysics Data System (ADS)

    Giri, Pushpa; Chakrabarti, P.

    2016-05-01

    Zinc Oxide (ZnO) thin films have been grown on p-silicon (Si) substrate using magnesium doped ZnO (Mg: ZnO) buffer layer by radio-frequency (RF) sputtering method. In this paper, we have optimized the concentration of Mg (0-5 atomic percent (at. %)) ZnO buffer layer to examine its effect on ZnO thin film based devices for electronic and optoelectronic applications. The crystalline nature, morphology and topography of the surface of the thin film have been characterized. The optical as well as electrical properties of the active ZnO film can be tailored by varying the concentration of Mg in the buffer layer. The crystallite size in the active ZnO thin film was found to increase with the Mg concentration in the buffer layer in the range of 0-3 at. % and subsequently decrease with increasing Mg atom concentration in the ZnO. The same was verified by the surface morphology and topography studies carried out with scanning electron microscope (SEM) and atomic electron microscopy (AFM) respectively. The reflectance in the visible region was measured to be less than 80% and found to decrease with increase in Mg concentration from 0 to 3 at. % in the buffer region. The optical bandgap was initially found to increase from 3.02 eV to 3.74 eV by increasing the Mg content from 0 to 3 at. % but subsequently decreases and drops down to 3.43 eV for a concentration of 5 at. %. The study of an Au:Pd/ZnO Schottky diode reveals that for optimum doping of the buffer layer the device exhibits superior rectifying behavior. The barrier height, ideality factor, rectification ratio, reverse saturation current and series resistance of the Schottky diode were extracted from the measured current voltage (I-V) characteristics.

  12. Effect of ZnO nanoparticles to mechanical properties of thixoformed Mg-Al-Zn alloy

    NASA Astrophysics Data System (ADS)

    Kusharjanto; Soepriyanto, Syoni; Ardian Korda, Akhmad; Adi Dwiwanto, Supono

    2018-03-01

    Magnesium alloys are lightweight metallic materials with low mechanical properties. Therefore, in order to meet the requirements in various industrial sector applications such as automotive, aerospace and electronic frame, improvement strength and ductility is required. The purpose of this research is to investigate the effect of adding ZnO nanoparticles to changes in microstructure, hardness, mechanical properties regarding with yield and ultimate strength. In this research, the molten Mg-Al-Zn alloy is added ZnO nanoparticles with a various range of 0, 1; 3 and 5 wt% and then cooling in the room temperature. Futhermore, Mg-Al-Zn-ZnO is heated at a temperature of 530 °C (in the semi-solid temperature range 470 °C–595 °C or 53% solid fraction) and then thixoforming process is performed. The characterization results of the thixoforming product show that, the microstructure is globular in shape with maximum hardness value of 107.14 VHN, the yield strength of 214.87 MPa, and the ultimate tensile strength of 311.25 MPa in 5 wt% ZnO nanoparticles.

  13. Structural and Magnetic Properties of Transition-Metal-Doped Zn 1-x Fe x O.

    PubMed

    Abdel-Baset, T A; Fang, Yue-Wen; Anis, B; Duan, Chun-Gang; Abdel-Hafiez, Mahmoud

    2016-12-01

    The ability to produce high-quality single-phase diluted magnetic semiconductors (DMS) is the driving factor to study DMS for spintronics applications. Fe-doped ZnO was synthesized by using a low-temperature co-precipitation technique producing Zn 1-x Fe x O nanoparticles (x= 0, 0.02, 0.04, 0.06, 0.08, and 0.1). Structural, Raman, density functional calculations, and magnetic studies have been carried out in studying the electronic structure and magnetic properties of Fe-doped ZnO. The results show that Fe atoms are substituted by Zn ions successfully. Due to the small ionic radius of Fe ions compared to that of a Zn ions, the crystal size decreases with an increasing dopant concentration. First-principle calculations indicate that the charge state of iron is Fe (2+) and Fe (3+) with a zinc vacancy or an interstitial oxygen anion, respectively. The calculations predict that the exchange interaction between transition metal ions can switch from the antiferromagnetic coupling into its quasi-degenerate ferromagnetic coupling by external perturbations. This is further supported and explains the observed ferromagnetic bahaviour at magnetic measurements. Magnetic measurements reveal that decreasing particle size increases the ferromagnetism volume fraction. Furthermore, introducing Fe into ZnO induces a strong magnetic moment without any distortion in the geometrical symmetry; it also reveals the ferromagnetic coupling.

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

    NASA Astrophysics Data System (ADS)

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

    2014-04-01

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

  15. The effect of Fe2NiO4 and Fe4NiO4Zn magnetic nanoparticles on anaerobic digestion activity.

    PubMed

    Chen, Jian Lin; Steele, Terry W J; Stuckey, David C

    2018-06-11

    Two types of magnetic nanoparticles (MNPs), i.e. Ni ferrite nanoparticles (Fe 2 NiO 4 ) and Ni Zn ferrite nanoparticles (Fe 4 NiO 4 Zn) containing the trace metals Ni and Fe, were added to the anaerobic digestion of synthetic municipal wastewater at concentrations between 1 and 100 mg Ni L -1 in order to compare their effects on biogas (methane) production and sludge activity. Using the production of methane over time as a measure, the assays revealed that anaerobic digestion was stimulated by the addition of 100 mg Ni L -1 in Fe 2 NiO 4 NPs, while it was inhibited by the addition of 1-100 mg Ni L -1 in Fe 4 NiO 4 Zn NPs. Especially at 100 mg Ni L -1 , Fe 4 NiO 4 Zn NPs resulted in a total inhibition of anaerobic digestion. The metabolic activity of the anaerobic sludge was tested using the resazurin reduction assay, and the assay clearly revealed the negative effect of Fe 4 NiO 4 Zn NPs and the positive effect of Fe 2 NiO 4 NPs. Re-feeding fresh synthetic medium reactivated the NPs added to the anaerobic sludge, except for the experiment with 100 mg Ni L -1 addition of Fe 4 NiO 4 Zn NPs. The findings in this present study indicate a possible new strategy for NPs design to enhance anaerobic digestion. Crown Copyright © 2018. Published by Elsevier B.V. All rights reserved.

  16. Pressure induced increase of the exciton phonon interaction in ZnO/(ZnMg)O quantum wells

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

    Jarosz, D.; Suchocki, A.; Kozanecki, A.

    2016-03-15

    It is a well-established experimental fact that exciton-phonon coupling is very efficient in ZnO. The intensities of the phonon-replicas in ZnO/(ZnMg)O quantum structures strongly depend on the internal electric field. We performed high-pressure measurements on the single ZnO/(ZnMg)O quantum well. We observed a strong increase of the intensity of the phonon-replicas relative to the zero phonon line. In our opinion this effect is related to pressure induced increase of the strain in quantum structure. As a consequence, an increase of the piezoelectric component of the electric field is observed which leads to an increase of the intensity of the phonon-replicas.

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

    PubMed

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

    2012-07-11

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

  18. Structural and optical characterization of ZnO/Mg(x)Zn(1-x)O multiple quantum wells based random laser diodes.

    PubMed

    Jiang, Qike; Zheng, He; Wang, Jianbo; Long, Hao; Fang, Guojia

    2012-12-01

    Two kinds of laser diodes (LDs) comprised of ZnO/Mg(x)Zn(1-x)O (ZnO/MZO) multiple quantum wells (MQWs) grown on GaN (MQWs/GaN) and Si (MQWs/Si) substrates, respectively, have been constructed. The LD with MQWs/GaN exhibits ultraviolet random lasing under electrical excitation, while that with MQWs/Si does not. In the MQWs/Si, ZnO/MZO MQWs consist of nanoscaled crystallites, and the MZO layers undergo a phase separation of cubic MgO and hexagonal ZnO. Moreover, the Mg atom predominantly locates in the MZO layers along with a significant aggregation at the ZnO/MZO interfaces; in sharp contrast, the ZnO/MZO MQWs in the MQWs/GaN show a well-crystallized structure with epitaxial relationships among GaN, MZO, and ZnO. Notably, Mg is observed to diffuse into the ZnO well layers. The structure-optical property relationship of these two LDs is further discussed.

  19. Antibacterial activity of trimetal (CuZnFe) oxide nanoparticles.

    PubMed

    Alzahrani, Khalid E; Niazy, Abdurahman A; Alswieleh, Abdullah M; Wahab, Rizwan; El-Toni, Ahmed M; Alghamdi, Hamdan S

    2018-01-01

    The increasing resistance of pathogenic bacteria to antibiotics is a challenging worldwide health problem that has led to the search for new and more efficient antibacterial agents. Nanotechnology has proven to be an effective tool for the fight against bacteria. In this paper, we present the synthesis and traits of trimetal (CuZnFe) oxide nanoparticles (NPs) using X-ray diffraction, high-resolution transmission electron microscopy, and energy dispersive x-ray spectroscopy. We evaluated the antibacterial activity of these NPs against gram-negative Escherichia coli and gram-positive Enterococcus faecalis and then compared it to that of their pure single-metal oxide components CuO and ZnO. Our study showed that the antibacterial activity of the trimetal oxide NPs was greater against E . coli than against E . faecalis . Overall, the antimicrobial effect of trimetal NPs is between those of pure ZnO and CuO nanoparticles, which may mean that their cytotoxicity is also between that of pure ZnO and CuO NPs, making them potential antibiotics. However, the cytotoxicity of trimetal NPs to mammalian cells needs to be verified. The combination of three metal oxide NPs (ZnO, CuO, and Fe 2 O 3 ) in one multimetal (CuZnFe) oxide NPs will enhance the therapeutic strategy against a wide range of microbial infections. Bacteria are unlikely to develop resistance against this new NP because bacteria must go through a series of mutations to become resistant to the trimetal oxide NP. Therefore, this NP can combat existing and emerging bacterial infections.

  20. Disinfection of Multidrug Resistant Escherichia coli by Solar-Photocatalysis using Fe-doped ZnO Nanoparticles.

    PubMed

    Das, Sourav; Sinha, Sayantan; Das, Bhaskar; Jayabalan, R; Suar, Mrutyunjay; Mishra, Amrita; Tamhankar, Ashok J; Stålsby Lundborg, Cecilia; Tripathy, Suraj K

    2017-03-07

    Spread of antibiotic resistant bacteria through water, is a threat to global public health. Here, we report Fe-doped ZnO nanoparticles (Fe/ZnO NPs) based solar-photocatalytic disinfection (PCD) of multidrug resistant Escherichia coli (MDR E. coli). Fe/ZnO NPs were synthesized by chemical precipitation technique, and when used as photocatalyst for disinfection, proved to be more effective (time for complete disinfection = 90 min) than ZnO (150 min) and TiO 2 (180 min). Lipid peroxidation and potassium (K + ) ion leakage studies indicated compromisation of bacterial cell membrane and electron microscopy and live-dead staining confirmed the detrimental effects on membrane integrity. Investigations indicated that H 2 O 2 was the key species involved in solar-PCD of MDR E. coli by Fe/ZnO NPs. X-ray diffraction and atomic absorption spectroscopy studies showed that the Fe/ZnO NPs system remained stable during the photocatalytic process. The Fe/ZnO NPs based solar-PCD process proved successful in the disinfection of MDR E. coli in real water samples collected from river, pond and municipal tap. The Fe/ZnO NPs catalyst made from low cost materials and with high efficacy under solar light may have potential for real world applications, to help reduce the spread of resistant bacteria.

  1. Structural and magnetic properties of spark plasma sintered Co-Mg-Zn substituted Ba-Sr hexagonal ferrite magnets

    NASA Astrophysics Data System (ADS)

    Harikrishnan, V.; Vizhi, R. Ezhil; Rajan Babu, D.; Saravanan, P.

    2018-02-01

    The effect of conventional and spark plasma sintering processes on the structural and magnetic properties of Ba0.5Sr0.5Fe12-2xCox(MgZn)x/2O19 (x = 0.2, 0.4 and 0.6) was investigated in this study. XRD patterns of both conventionally sintered (CS) and spark plasma sintered (SPS) samples with x = 0.2 and 0.4 showed the crystallization of Ba0.5Sr0.5Fe12O19-phase with space group of P63/mmc. However, in the case of SPS sample with x = 0.4, a secondary peak of α-Fe2O3 was observed. SEM analysis on the SPS samples revealed dense morphology with low porosity; while the CS samples showed the presence of aggregated particles with spherical shapes. Maximum values of saturation magnetization, MS (58 emu/g) and coercivity, HC (3.5 kOe) were obtained for the CS samples with x = 0.4; while their SPS counterparts revealed increased MS (65 emu/g) and HC (3.9 kOe) values. The observed magnetization reversal behaviour for both sintering conditions were not smooth in the case of x = 0.2, which indicated the existence of two-phase behavior. The temperature dependent magnetization studies for x = 0.2 and 0.4 were performed in order to analyze the variation in Curie temperature against Co-Mg-Zn substitution and the obtained results are discussed on the basis of crystallization of hexaferrite-phase.

  2. Fixed distance photoinduced electron transfer between Fe and Zn porphyrins encapsulated within the Zn HKUST-1 metal organic framework.

    PubMed

    Larsen, Randy W; Wojtas, Lukasz

    2015-02-21

    An attractive strategy for the development of photocatalytic metal organic framework (MOF) materials is to co-encapsulate a photoactive electron donor with a catalytic electron acceptor within the MOF. Here we report the co-encapsulation of both Zn(ii) tetrakis(tetra 4-sulphonatophenyl)porphyrin (Zn4SP) and Fe(iii) tetrakis(tetra 4-sulphonatophenyl)porphyrin (Fe4SP) into an HKUST-1 (Zn) MOF and demonstrate photoinduced electron transfer (ET) between the co-encapsulated guest. Photo-excitation of the Zn4SP results in fixed-distance inter-molecular ET between the encapsulated (3)Zn4SP and the Fe(iii)4SP as evident by the reduction in the encapsulated (3)Zn4SP lifetime from 890 μs (kobs = 1.1 × 10(3) s(-1)) to 83 μs (kobs = 1.2 × 10(4) s(-1)) in the presence of Fe4SP giving a kET ∼ 1.1 × 10(4) s(-1). The data are consistent with ET taking place between encapsulated porphyrins that are two cages apart in distance with a reorganizational energy of ∼1.65 eV, β = 1.25 and ΔG° = -0.97 eV (within a semi-classical Marcus theory framework).

  3. Hydrogen kinetics studies of MgH2-FeTi composites

    NASA Astrophysics Data System (ADS)

    Meena, Priyanka; Jangir, Mukesh; Singh, Ramvir; Sharma, V. K.; Jain, I. P.

    2018-05-01

    MgH2 + x wt% FeTi (x=10, 25, 50) nano composites were ball milled to get nano structured material and characterized for structural, morphological and thermal properties. XRD of the milled samples revealed the formation of MgH2, FeTi, Fe2Ti and H0.06FeTi phases. Morphological studies by SEM were undertaken to investigate the effect of hydrogenation of nanostructure alloy. EDX confirmed elemental composition of the as-prepared alloy. TGA studies showed higher desorption temperature for milled MgH2 compared to x wt% FeTi added MgH2. Activation energy for hydrogen desorption was found to be -177.90, -215.69, -162.46 and -87.93 kJ/mol for milled MgH2 and Mg2+x wt% FeTi (10, 25, 50), showing 89.97 kJ/ mol reduction in activation energy for 50 wt% alloy additives resulting in improved hydrogen storage capacity. DSC investigations were carried out to investigate the effect of alloy on hydrogen absorption behavior of MgH2.

  4. The magnetic, electrical transport and thermal transport properties of Fe-based antipervoskite compounds ZnCxFe3

    NASA Astrophysics Data System (ADS)

    Lin, S.; Wang, B. S.; Lin, J. C.; Huang, Y. N.; Hu, X. B.; Lu, W. J.; Zhao, B. C.; Tong, P.; Song, W. H.; Sun, Y. P.

    2011-10-01

    The effects of carbon concentration on the crystal structure, magnetic, and electrical/thermal transport properties of ZnCxFe3 (1.0 ≤ x ≤ 1.5) have been investigated systematically. Both the Curie temperature and the saturated magnetization decrease firstly and then reach saturation with increasing x. The investigations of heat capacity and resistivity indicate that ZnC1.2Fe3 displays a strongly correlated Fermi liquid behavior considering its Kadowaki-Woods ratio (˜0.64 a0). Around the ferromagnetic-paramagnetic phase transition (˜358 K), a reversible room-temperature magnetocaloric effect is observed. The relative cooling power (RCP) is ˜164 J/kg (˜385 J/kg) with the magnetic field change ΔH = 20 kOe (45 kOe). Considering the considerable large RCP, inexpensive and innoxious raw materials, ZnC1.2Fe3 is suggested to be a promising candidate for room-temperature magnetic refrigeration. Furthermore, the studies of thermal transport properties indicate that ZnC1.2Fe3 can also be a potential thermoelectric material with the dimensionless figure of merit (ZT = α2T/ρk) reaching its maximum of 0.0112 around 170 K.

  5. Synthesis and Characterization of Photocatalytic TiO 2 -ZnFe 2 O 4 Nanoparticles

    DOE PAGES

    Srinivasan, Sesha S.; Wade, Jeremy; Stefanakos, Elias K.

    2006-01-01

    A new coprecipimore » tation/hydrolysis synthesis route is used to create a TiO 2 -ZnFe 2 O 4 nanocomposite that is directed towards extending the photoresponse of TiO 2 from UV to visible wavelengths ( > 400   nm ). The effect of TiO 2 's accelerated anatase-rutile phase transformation due to the presence of the coupled ZnFe 2 O 4 narrow-bandgap semiconductor is evaluated. The transformation's dependence on pH, calcinations temperature, particle size, and ZnFe 2 O 4 concentration has been analyzed using XRD, SEM, and UV-visible spectrometry. The requirements for retaining the highly photoactive anatase phase present in a ZnFe 2 O 4 nanocomposite are outlined. The visible-light-activated photocatalytic activity of the TiO 2 -ZnFe 2 O 4 nanocomposites has been compared to an Aldrich TiO 2 reference catalyst, using a solar-simulated photoreactor for the degradation of phenol.« less

  6. Synthesis and characterization of ZnS@Fe3O4 fluorescent-magnetic bifunctional nanospheres

    NASA Astrophysics Data System (ADS)

    Koc, Kenan; Karakus, Baris; Rajar, Kausar; Alveroglu, Esra

    2017-10-01

    Herein, we synthesized and characterized fluorescent and super paramagnetic ZnS@Fe3O4 nanospheres. First, (3-mercaptopropyl) trimethoxysilane (MPS) capped ZnS quantum dots (QDs) and SiO2 coated Fe3O4 nanoparticles were synthesized separately by using solution growth and co-precipitation techniques. After synthesis and characterization of these two nanoparticles, they were conglutinated together in a nano sized sphere. The QDs were attached to the surface of the Fe3O4 nanoparticles by Sisbnd Osbnd Si bonds and so Sisbnd Osbnd Si bonds created a SiO2 network around the nanoparticles during the formation of the ZnS@Fe3O4 nanospheres. The synthesized MPS capped ZnS fluorescent QDs, SiO2 coated magnetite super paramagnetic nanoparticles and ZnS@Fe3O4 fluorescent-magnetic bifunctional nanospheres were characterized by using UV-Vis Absorption Spectroscopy, Fluorescence Spectroscopy, X-ray analysis, Vibrating Sample Magnetometer analysis, Attenuated Total Reflection-Fourier Transform Infrared Spectroscopy, Scanning Electron Microscope and Energy-dispersive X-ray spectroscopy. ZnS@Fe3O4 bifunctional nanospheres were shown to retain the magnetic properties of magnetite, while exhibiting the luminescent optical properties of ZnS nanoparticles. The combination of fluorescent and magnetic behaviors of nano composites make them useful for potential applications in the field of bio-medical and environmental.

  7. Zn0-CNTs-Fe3O4 catalytic in situ generation of H2O2 for heterogeneous Fenton degradation of 4-chlorophenol.

    PubMed

    Yang, Zhao; Gong, Xiao-Bo; Peng, Lin; Yang, Dan; Liu, Yong

    2018-06-04

    A novel Zn 0 -CNTs-Fe 3 O 4 composite was synthesized by the chemical co-precipitation combined with high sintering process at nitrogen atmosphere. The as-prepared composite was characterized by SEM, EDS, XRD, XPS, VSM and N 2 adsorption/desorption experiments. A novel heterogeneous Fenton-like system, composed of Zn 0 -CNTs-Fe 3 O 4 composite and dissolved oxygen (O 2 ) in solution, which can in situ generate H 2 O 2 and OH, was used for the degradation of 4-chlorophenol (4-CP). The influences of various operational parameters, including the initial pH, dosage of Zn 0 -CNTs-Fe 3 O 4 and initial concentration of 4-CP on the removal of 4-CP were investigated. The removal efficiencies of 4-CP and total organic carbon (TOC) were 99% and 57%, respectively, at the initial pH of 1.5, Zn 0 -CNTs-Fe 3 O 4 dosage of 2 g/L, 4-CP initial concentration of 50 mg/L and oxygen flow rate of 400 mL/min. Based on the results of the radical scavenger effect study, the hydroxyl radical was considered as the main reactive oxidants in Zn 0 -CNTs-Fe 3 O 4 /O 2 system and a possible degradation pathway of 4-CP was proposed. Copyright © 2018. Published by Elsevier Ltd.

  8. Magnetic properties of M0.3Fe2.7O4 (M = Fe, Zn and Mn) ferrites nanoparticles

    NASA Astrophysics Data System (ADS)

    Modaresi, Nahid; Afzalzadeh, Reza; Aslibeiki, Bagher; Kameli, Parviz

    2018-06-01

    In the present article a comparative study on the structural and magnetic properties of nano-sized M0.3Fe0.7Fe2O4 (M = Fe, Zn and Mn) ferrites have been reported. The X-ray diffraction (XRD) patterns show that the crystallite size depends on the cation distribution. The Rietveld refinement of XRD patterns using MAUD software determines the distribution of cations and unit cell dimensions. The magnetic measurements show that the maximum and minimum value of saturation magnetization is obtained for Zn and Mn doped samples, respectively. The peak temperature of AC magnetic susceptibility of Zn and Fe doped samples below 300 K shows the superparamagnetic behavior in these samples at room temperature. the AC susceptibility results confirm the presence of strong interactions between the nanoparticles which leads to a superspin glass state in the samples at low temperatures.

  9. Soldering of Mg Joints Using Zn-Al Solders

    NASA Astrophysics Data System (ADS)

    Gancarz, Tomasz; Berent, Katarzyna; Skuza, Wojciech; Janik, Katarzyna

    2018-07-01

    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.

  10. Soldering of Mg Joints Using Zn-Al Solders

    NASA Astrophysics Data System (ADS)

    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.

  11. Oxygen vacancy induced by La and Fe into ZnO nanoparticles to modify ferromagnetic ordering

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

    Verma, Kuldeep Chand, E-mail: kuldeep0309@yahoo.co.in; Kotnala, R.K., E-mail: rkkotnala@gmail.com

    We reported long-range ferromagnetic interactions in La doped Zn{sub 0.95}Fe{sub 0.05}O nanoparticles that mediated through lattice defects or vacancies. Zn{sub 0.92}Fe{sub 0.05}La{sub 0.03}O (ZFLaO53) nanoparticles were synthesized by a sol–gel process. X-ray fluorescence spectrum of ZFLaO53 detects the weight percentage of Zn, Fe, La and O. X-ray diffraction shows the hexagonal Wurtzite ZnO phase. The Rietveld refinement has been used to calculate the lattice parameters and the position of Zn, Fe, La and O atoms in the Wurtzite unit cell. The average size of ZFLaO53 nanoparticles is 99 nm. The agglomeration type product due to OH ions with La resultsmore » into ZnO nanoparticles than nanorods that found in pure ZnO and Zn{sub 0.95}Fe{sub 0.05}O sample. The effect of doping concentration to induce Wurtzite ZnO structure and lattice defects has been analyzed by Raman active vibrational modes. Photoluminescence spectra show an abnormal emission in both UV and visible region, and a blue shift at near band edge is formed with doping. The room temperature magnetic measurement result into weak ferromagnetism but pure ZnO is diamagnetic. However, the temperature dependent magnetic measurement using zero-field and field cooling at dc magnetizing field 500 Oe induces long-range ferromagnetic ordering. It results into antiferromagnetic Neel temperature of ZFLaO53 at around 42 K. The magnetic hysteresis is also measured at 200, 100, 50 and 10 K measurement that indicate enhancement in ferromagnetism at low temperature. Overall, the La doping into Zn{sub 0.95}Fe{sub 0.05}O results into enhanced antiferromagnetic interaction as well as lattice defects/vacancies. The role of the oxygen vacancy as the dominant defects in doped ZnO must form Bound magnetic polarons has been described. - Graphical abstract: The long-range ferromagnetic order in Zn{sub 0.92}Fe{sub 0.05}La{sub 0.03}O nanoparticles at low temperature measurements involves oxygen vacancy as the medium of magnetic

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

    NASA Astrophysics Data System (ADS)

    Holmström, E.; Stixrude, L.

    2016-05-01

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

  13. Effects of phase transformation on the microstructures and magnetostriction of Fe-Ga and Fe-Ga-Zn ferromagnetic shape memory alloys

    NASA Astrophysics Data System (ADS)

    Lin, Yin-Chih; Lin, Chien-Feng

    2015-05-01

    The phase transformation and magnetostriction of bulk Fe73Ga27 and Fe73Ga18Zn9 (at. %) ferromagnetic shape memory alloys (FSMs) were investigated by transmission electron microscopy (TEM), x-ray diffraction (XRD), and a magnetostrictive-meter setup. For the Fe73Ga27 FSM alloy solution treated at 1100 °C for 4 h and quenched in ice brine, the antiphase boundary segments of the D03 domain were observed in the A2 (disordered) matrix, and the Fe73Ga27 FSM alloy had an optimal magnetostriction (λ‖s = 71 × 10-6 and λ⊥s = -31 × 10-6). In Fe73Ga27 FSM alloy as-quenched, aged at 700 °C for 24 h, and furnace cooled, D03 nanoclusters underwent phase transformation to an intermediate tetragonal phase (i.e., L10-like martensite) via Bain distortion, and finally L12 (Fe3Ga) structures precipitated, as observed by TEM and XRD. The L10-like martensite and L12 phases in the aged Fe73Ga27 FSM alloy drastically decreased the magnetostriction from positive to negative (λ‖s = -20 × 10-6 and λ⊥s = -8 × 10-6). However, in Fe73Ga18Zn9 FSM alloy as-quenched and aged, the phase transformation of D03 to an intermediate tetragonal martensite phase and precipitation of L12 structures were not found. The results indicate that the aged Fe73Ga18Zn9 FSM alloy maintained stable magnetostriction (λ‖s = 36 × 10-6 and λ⊥s = -31 × 10-6). Adding Zn can improve the ferromagnetic shape memory effect of aged Fe73Ga18Zn9 alloy, which may be useful in application of the alloy in high temperature environments.

  14. Shape anisotropy and hybridization enhanced magnetization in nanowires of Fe/MgO/Fe encapsulated in carbon nanotubes

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

    Aryee, Dennis; Seifu, Dereje

    Arrays of tunneling magnetoresistance (TMR) nanowires were synthesized for the first time by filling Fe/MgO/Fe inside vertically grown and substrate supported carbon nanotubes. The magnetic properties of nanowires and planar nanoscale thin films of Fe/MgO/Fe showed several similarities, such as two-fold magnetic symmetry and ratio of orbital moment to spin moment. Nanowires of Fe/MgO/Fe showed higher saturation magnetization by a factor of 2.7 compared to planar thin films of Fe/MgO/Fe at 1.5 kOe. The enhanced magnetic properties likely resulted from shape anisotropy of the nanowires and as well as the hybridization that occur between the π- electronic states of carbonmore » and 3d-bands of the Fe-surface.« less

  15. Structural and optical properties of ZnO nanorods on Mg0.2Zn0.8O seed layers grown by hydrothermal method.

    PubMed

    Kim, Min Su; Kim, Do Yeob; Kim, Sung-O; Leem, Jae-Young

    2013-05-01

    ZnO nanorods were grown on the Mg0.2Zn0.8O seed layers with different thickness by hydrothermal method. Scanning electron microscopy (SEM), X-ray diffraction (XRD), and photoluminescence (PL) were carried out to investigate the effects of the Mg0.2Zn0.8O seed layer thickness on the structural and the optical properties of the ZnO nanorods. The residual stress in the Mg0.2Zn0.8O seed layers was depended on the thickness while the texture coefficient of the Mg0.2Zn0.8O seed layers was not affected significantly. The smaller full width at half maximum (FWHM) of the ZnO (002) diffraction and near-band-edge emission (NBE) peak and the larger average grain size were observed from the ZnO nanorods grown on the Mg0.2Zn0.8O seed layers with 5 layers (thickness of 350 nm), which indicate the enhancement the structural and the optical properties of the ZnO nanorods.

  16. Effect of annealing temperature and copper mole ratio on the morphology, structure and magnetic properties of Mg0.5-xCuxZn0.5Fe2O4 nanoparticles prepared by the modified Pechini method

    NASA Astrophysics Data System (ADS)

    Loghman-Estarki, M. R.; Torkian, S.; Rastabi, R. Amini; Ghasemi, A.

    2017-11-01

    In this study, magnesium copper zinc ferrite (MCZ) nanoparticles were synthesized by the modified Pechini method. In this approach, the magnesium nitrate, copper nitrate, zinc nitrate, iron nitrate, citric acid and diethylene glycol (instead of ethylene glycol in conventional Pechini method) were used as a source of Mg2+, Cu2+, Zn2+, complex and stabilizer and solvent agent, respectively. The effect of annealing temperature and copper mole ratio on the morphology, structural and magnetic properties of Mg0.5xCuxZn0.5Fe2O4 (x = 0-0.5) nanoparticles were investigated. Various characterization methods, including X-ray diffraction (XRD), field emission scanning electron microscope (FeSEM), energy-dispersive spectroscopy (EDS), X-ray mapping, Fourier transforms infrared spectroscopy (FTIR), adsorption-desorption isotherm and vibrating sample magnetometer (VSM) were used to study the phase, microstructure, particle size, elemental distribution, functional group determination, porosity and magnetic properties of nanoparticles, respectively. The results showed that cubic spinel phase with various morphologies such as semi-spherical, sheet-like shapes was obtained by the modified Pechini method. Furthermore, the nanoparticles with the x value of 0.2, annealed at 700 °C have the highest saturation magnetization (Ms = 56.5 emu/g) among the other synthesized MCZ ferrite nanoparticles.

  17. Molecular controls on Cu and Zn isotopic fractionation in Fe-Mn crusts

    NASA Astrophysics Data System (ADS)

    Little, S. H.; Sherman, D. M.; Vance, D.; Hein, J. R.

    2014-06-01

    The isotopic systems of the transition metals are increasingly being developed as oceanic tracers, due to their tendency to be fractionated by biological and/or redox-related processes. However, for many of these promising isotope systems the molecular level controls on their isotopic fractionations are only just beginning to be explored. Here we investigate the relative roles of abiotic and biotic fractionation processes in controlling modern seawater Cu and Zn isotopic compositions. Scavenging to Fe-Mn oxides represents the principal output for Cu and Zn to sediments deposited under normal marine (oxic) conditions. Using Fe-Mn crusts as an analogue for these dispersed phases, we investigate the phase association and crystal chemistry of Cu and Zn in such sediments. We present the results of an EXAFS study that demonstrate unequivocally that Cu and Zn are predominantly associated with the birnessite (δ-MnO2) phase in Fe-Mn crusts, as previously predicted from sequential leaching experiments (e.g., Koschinsky and Hein, 2003). The crystal chemistry of Cu and Zn in the crusts implies a reduction in coordination number in the sorbed phase relative to the free metal ion in seawater. Thus, theory would predict equilibrium fractionations that enrich the heavy isotope in the sorbed phase (e.g., Schauble, 2004). In natural samples, Fe-Mn crusts and nodules are indeed isotopically heavy in Zn isotopes (at ∼1‰) compared to deep seawater (at ∼0.5‰), consistent with the predicted direction of equilibrium isotopic fractionation based on our observations of the coordination environment of sorbed Zn. Further, ∼50% of inorganic Zn‧ is chloro-complexed (the other ∼50% is present as the free Zn2+ ion), and complexation by Cl- is also predicted to favour equilibrium partitioning of light Zn isotopes into the dissolved phase. The heavy Zn isotopic composition of Fe-Mn crusts and nodules relative to seawater can therefore be explained by an inorganic fractionation during

  18. Transverse excitations in liquid Fe, Cu and Zn

    NASA Astrophysics Data System (ADS)

    Hosokawa, S.; Inui, M.; Kajihara, Y.; Tsutsui, S.; Baron, A. Q. R.

    2015-05-01

    Transverse acoustic (TA) excitation modes were observed in inelastic x-ray scattering spectra of liquid Fe, Cu and Zn. From the analysis of current correlation functions, we concluded that TA excitation modes can experimentally be detected through the quasi-TA branches in the longitudinal current correlation spectra in these liquid metals. The microscopic elastic constants are estimated and a characteristic difference from macroscopic polycrystalline value was found in Poisson's ratio of liquid Fe, which shows an extremely softer value of ∼0.38 compared with the macroscopic value of ∼0.275. The lifetime of the TA modes were determined to be ∼0.45 ps for liquid Fe and Cu and ∼0.55 ps for liquid Zn, reflecting different interatomic correlations between liquid transition metals and non-transition metals. The propagation length of the TA modes are ∼0.85 nm in all of liquid metals, corresponding to the size of icosahedral or similar size of cages formed instantaneously in these liquid metals.

  19. Asymmetric angular dependence of spin-transfer torques in CoFe/Mg-B-O/CoFe magnetic tunnel junctions

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

    Tang, Ling, E-mail: lingtang@zjut.edu.cn; Xu, Zhi-Jun, E-mail: xzj@zjut.edu.cn; Zuo, Xian-Jun

    Using a first-principles noncollinear wave-function-matching method, we studied the spin-transfer torques (STTs) in CoFe/Mg-B-O/CoFe(001) magnetic tunnel junctions (MTJs), where three different types of B-doped MgO in the spacer are considered, including B atoms replacing Mg atoms (Mg{sub 3}BO{sub 4}), B atoms replacing O atoms (Mg{sub 4}BO{sub 3}), and B atoms occupying interstitial positions (Mg{sub 4}BO{sub 4}) in MgO. A strong asymmetric angular dependence of STT can be obtained both in ballistic CoFe/Mg{sub 3}BO{sub 4} and CoFe/Mg{sub 4}BO{sub 4} based MTJs, whereas a nearly symmetric STT curve is observed in the junctions based on CoFe/Mg{sub 4}BO{sub 3}. Furthermore, the asymmetry ofmore » the angular dependence of STT can be suppressed significantly by the disorder of B distribution. Such skewness of STTs in the CoFe/Mg-B-O/CoFe MTJs could be attributed to the interfacial resonance states induced by the B diffusion into MgO spacer.« less

  20. Multifunctional Fe3O4/ZnO nanocomposites with magnetic and optical properties.

    PubMed

    Zou, Peng; Hong, Xia; Chu, Xueying; Li, Yajun; Liu, Yichun

    2010-03-01

    Multifunctional Fe3O4/ZnO nanocomposites were successfully synthesized through two-step solution-based methods. Fe3O4 nanoparticles were used as seeds for the deposit and growth of ZnO nanocrystals. Transmission electron microscopy (TEM) images, X-ray diffraction (XRD) patterns, and inductively coupled plasma-atomic emission spectroscopy (ICP-AES) were employed to observe the morphology, size, structure, and crystalline phase of the nanocomposites and confirm their chemical composition. The results of magnetization curves, resonant Raman scattering, and photoluminescence spectra revealed that the nanocomposites simultaneously possessed the super-paramagnetism of Fe3O4 and the multiphonon resonant Raman scattering and photoluminescence (PL) properties of ZnO. Compared with that of pure Fe3O4, the saturation magnetization of the Fe3O4 component within the nanocomposites was enhanced. The Raman spectroscopic fingerprint of ZnO component was preserved, and the fluorescent background was efficiently reduced. The interfacial effect was found to play an important role in modulating or improving the properties of the nanocomposites.

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

    PubMed

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

    2013-12-01

    A fast and straightforward method of the analysis of coffee infusions was developed for measurements of total concentrations of Ca, Cu, Fe, Mg, Mn and Zn by flame atomic absorption spectrometry. Its validity was proved by the analysis of spiked samples; recoveries of added metals were found to be within 98-104% while the precision was better than 4%. The method devised was used for the analysis of re-distilled water infusions of six popular ground coffees available in the Polish market. Using the mud coffee preparation it was established that percentages of metals leached in these conditions varied a lot among analysed coffees, especially for Ca (14-42%), Mg (6-25%) and Zn (1-24%). For remaining metals, the highest extractabilities were assessed for Mn (30-52%) while the lowest for Fe (4-16%) and Cu (2-12%). In addition, it was found that the water type and the coffee brewing preparation method influence the concentration of studied metals in coffee infusions the most. Copyright © 2013 Elsevier Ltd. All rights reserved.

  2. Catalytic conversion of syngas to mixed alcohols over Zn-Mn promoted Cu-Fe based catalyst

    DOE PAGES

    Lu, Yongwu; Yu, Fei; Hu, Jin; ...

    2012-04-12

    Zn-Mn promoted Cu-Fe based catalyst was synthesized by the co-precipitation method. Mixed alcohols synthesis from syngas was studied in a half-inch tubular reactor system after the catalyst was reduced. Zn-Mn promoted Cu-Fe based catalyst was characterized by SEM-EDS, TEM, XRD, and XPS. The liquid phase products (alcohol phase and hydrocarbon phase) were analyzed by GC-MS and the gas phase products were analyzed by GC. The results showed that Zn-Mn promoted Cu-Fe based catalyst had high catalytic activity and high alcohol selectivity. The maximal CO conversion rate was 72%, and the yield of alcohol and hydrocarbons were also very high. Cumore » (111) was the active site for mixed alcohols synthesis, Fe 2C (101) was the active site for olefin and paraffin synthesis. The reaction mechanism of mixed alcohols synthesis from syngas over Zn-Mn promoted Cu-Fe based catalyst was proposed. Here, Zn-Mn promoted Cu-Fe based catalyst can be regarded as a potential candidate for catalytic conversion of biomass-derived syngas to mixed alcohols.« less

  3. Room-Temperature Quantum Cascade Laser: ZnO/Zn1- x Mg x O Versus GaN/Al x Ga1- x N

    NASA Astrophysics Data System (ADS)

    Chou, Hung Chi; Mazady, Anas; Zeller, John; Manzur, Tariq; Anwar, Mehdi

    2013-05-01

    A ZnO/Zn1- x Mg x O-based quantum cascade laser (QCL) is proposed as a candidate for generation of THz radiation at room temperature. The structural and material properties, field dependence of the THz lasing frequency, and generated power are reported for a resonant phonon ZnO/Zn0.95Mg0.05O QCL emitting at 5.27 THz. The theoretical results are compared with those from GaN/Al x Ga1- x N QCLs of similar geometry. Higher calculated optical output powers [ {P}_{{ZnMgO}} = 2.89 mW (nonpolar) at 5.27 THz and 2.75 mW (polar) at 4.93 THz] are obtained with the ZnO/Zn0.95Mg0.05O structure as compared with GaN/Al0.05Ga0.95N QCLs [ {P}_{{AlGaN}} = 2.37 mW (nonpolar) at 4.67 THz and 2.29 mW (polar) at 4.52 THz]. Furthermore, a higher wall-plug efficiency (WPE) is obtained for ZnO/ZnMgO QCLs [24.61% (nonpolar) and 23.12% (polar)] when compared with GaN/AlGaN structures [14.11% (nonpolar) and 13.87% (polar)]. These results show that ZnO/ZnMgO material is optimally suited for THz QCLs.

  4. Study on the Electrochemical Reaction Mechanism of ZnFe2O4 by In Situ Transmission Electron Microscopy

    PubMed Central

    Su, Qingmei; Wang, Shixin; Yao, Libing; Li, Haojie; Du, Gaohui; Ye, Huiqun; Fang, Yunzhang

    2016-01-01

    A family of mixed transition–metal oxides (MTMOs) has great potential for applications as anodes for lithium ion batteries (LIBs). However, the reaction mechanism of MTMOs anodes during lithiation/delithiation is remain unclear. Here, the lithiation/delithiation processes of ZnFe2O4 nanoparticles are observed dynamically using in situ transmission electron microscopy (TEM). Our results suggest that during the first lithiation process the ZnFe2O4 nanoparticles undergo a conversion process and generate a composite structure of 1–3 nm Fe and Zn nanograins within Li2O matrix. During the delithiation process, volume contraction and the conversion of Zn and Fe take place with the disappearance of Li2O, followed by the complete conversion to Fe2O3 and ZnO not the original phase ZnFe2O4. The following cycles are dominated by the full reversible phase conversion between Zn, Fe and ZnO, Fe2O3. The Fe valence evolution during cycles evidenced by electron energy–loss spectroscopy (EELS) techniques also exhibit the reversible conversion between Fe and Fe2O3 after the first lithiation, agreeing well with the in situ TEM results. Such in situ TEM observations provide valuable phenomenological insights into electrochemical reaction of MTMOs, which may help to optimize the composition of anode materials for further improved electrochemical performance. PMID:27306189

  5. Rapid and High-Efficiency Laser-Alloying Formation of ZnMgO Nanocrystals

    PubMed Central

    Liu, Peisheng; Wang, Hao; Chen, Jun; Li, Xiaoming; Zeng, Haibo

    2016-01-01

    Applications of ZnMgO nanocrystals (NCs), especially in photoelectric detectors, have significant limitations because of the unresolved phase separation in the synthesis process. Here, we propose a rapid and highly efficient ZnMgO NC alloying method based on pulsed laser ablation in liquid. The limit value of homogeneous magnesium (Mg) is pushed from 37% to 62%, and the optical band gap is increased to 3.7 eV with high doping efficiency (>100%). Further investigations on the lattice geometry of ZnMgO NCs indicate that all ZnMgO NCs are hexagonal wurtzite structures, and the (002) and (100) peaks shift to higher diffraction angles with the increase in Mg doping content. The calculated results of the lattice constants a and c slightly decrease based on Bragg’s law and lattice geometry equations. Furthermore, the relationship between annealing temperature and the limit value of homogeneous Mg is examined, and the results reveal that the latter decreases with the former because of the phase separation of MgO. A probable mechanism of zinc magnesium alloy is introduced to expound on the details of the laser-alloying process. PMID:27324296

  6. Improvement of in vitro corrosion and cytocompatibility of biodegradable Fe surface modified by Zn ion implantation

    NASA Astrophysics Data System (ADS)

    Wang, Henan; Zheng, Yang; Li, Yan; Jiang, Chengbao

    2017-05-01

    Pure Fe was surface-modified by Zn ion implantation to improve the biodegradable behavior and cytocompatibility. Surface topography, chemical composition, corrosion resistance and cytocompatibility were investigated. Atomic force microscopy, auger electron spectroscopy and X-ray photoelectron spectroscopy results showed that Zn was implanted into the surface of pure Fe in the depth of 40-60 nm and Fe2O3/ZnO oxides were formed on the outmost surface. Electrochemical measurements and immersion tests revealed an improved degradable behavior for the Zn-implanted Fe samples. An approximately 12% reduction in the corrosion potential (Ecorr) and a 10-fold increase in the corrosion current density (icorr) were obtained after Zn ion implantation with a moderate incident ion dose, which was attributed to the enhanced pitting corrosion. The surface free energy of pure Fe was decreased by Zn ion implantation. The results of direct cell culture indicated that the short-term (4 h) cytocompatibility of MC3T3-E1 cells was promoted by the implanted Zn on the surface.

  7. Investigation on microstructure characterization and property of rapidly solidified Mg-Zn-Ca-Ce-La alloys

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

    Zhou Tao, E-mail: tzhou1118@163.com; Chen Zhenhua, E-mail: chenzhenhua45@hotmail.com; Yang Mingbo, E-mail: yangmingbo@cqit.edu.cn

    2012-01-15

    Rapidly solidified (RS) Mg-Zn-Ca-Ce-La (wt.%) alloys have been produced via atomizing the alloy melt and subsequent splat-quenching on the water-cooled copper twin-rollers in the form of flakes. Microstructure characterization, phase compositions and thermal stability of the alloys have been systematically investigated. The results showed that with addition of RE (Ce and La) to the Mg-6Zn-5Ca alloy, the stable intermetallic compounds i.e. the Mg{sub x}Zn{sub y}RE{sub z} phase with a few Ca (about 3 at.%), shortened as the T Prime phase, were formed at the expense of the binary Mg-Zn and Ca{sub 2}Mg{sub 6}Zn{sub 3} phases, which was possibly beneficial tomore » the enhanced thermal stability of the alloy. In the Mg-6Zn-5Ca-3Ce-0.5La alloy, the composition of the T Prime phase in the grain interior was different from that at the grain boundaries, in which the segregation of the La elements was found, and the atomic percentage ratio of Zn to Ce in the T Prime phase within the grains was close to 2. Moreover, the stable Mg{sub 2}Ca phases were detected around the T Prime phases at the grain boundaries in the alloy. - Research Highlights: Black-Right-Pointing-Pointer The phase constitution of RS Mg-6Zn-5Ca alloy can be improved by RE additions. Black-Right-Pointing-Pointer In the Mg-Zn-Ca-Ce-La alloys, the Mg{sub x}Zn{sub y}RE{sub z} phase with a few Ca (T Prime phase) is formed. Black-Right-Pointing-Pointer The formation of the T Prime phase leads to the loss of the Mg-Zn and Ca{sub 2}Mg{sub 6}Zn{sub 3} phases. Black-Right-Pointing-Pointer The composition of the T Prime phase differs from the grain interior to the grain boundary.« less

  8. Fabrication of stable, wide-bandgap thin films of Mg, Zn and O

    DOEpatents

    Katiyar, Ram S.; Bhattacharya, Pijush; Das, Rasmi R.

    2006-07-25

    A stable, wide-bandgap (approximately 6 eV) ZnO/MgO multilayer thin film is fabricated using pulsed-laser deposition on c-plane Al2O3 substrates. Layers of ZnO alternate with layers of MgO. The thickness of MgO is a constant of approximately 1 nm; the thicknesses of ZnO layers vary from approximately 0.75 to 2.5 nm. Abrupt structural transitions from hexagonal to cubic phase follow a decrease in the thickness of ZnO sublayers within this range. The band gap of the thin films is also influenced by the crystalline structure of multilayer stacks. Thin films with hexagonal and cubic structure have band-gap values of 3.5 and 6 eV, respectively. In the hexagonal phase, Mg content of the films is approximately 40%; in the cubic phase Mg content is approximately 60%. The thin films are stable and their structural and optical properties are unaffected by annealing at 750.degree. C.

  9. Compositional tuning of atomic layer deposited MgZnO for thin film transistors

    NASA Astrophysics Data System (ADS)

    Wrench, J. S.; Brunell, I. F.; Chalker, P. R.; Jin, J. D.; Shaw, A.; Mitrovic, I. Z.; Hall, S.

    2014-11-01

    Thin film transistors (TFTs) have been fabricated using magnesium zinc oxide (MgZnO) layers deposited by atomic layer deposition at 200 °C. The composition of the MgZnO is systematically modified by varying the ratio of MgO and ZnO deposition cycles. A blue-shift of the near band-edge photoluminescence after post-deposition annealing at 300 °C indicates significant activation of the Mg dopant. A 7:1 ratio of ZnO:MgO deposition cycles was used to fabricate a device with a TFT channel width of 2000 μm and a channel length of 60 μm. This transistor yielded an effective saturation mobility of 4 cm2/V s and a threshold voltage of 7.1 V, respectively. The on/off ratio was 1.6 × 10 6 and the maximum interface state density at the ZnO/SiO2 interface is ˜ 6.5 × 10 12 cm-2.

  10. Electrical properties of Mg doped ZnO nanostructure annealed at different temperature

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

    Mohamed, R., E-mail: ruziana12@gmail.com; Mamat, M. H., E-mail: hafiz-030@yahoo.com; Rusop, M., E-mail: nanouitm@gmail.com

    In this work, ZincOxide (ZnO) nanostructures doped with Mg were successfully grown on the glass substrate. Magnesium (Mg) metal element was added in the ZnO host which acts as a doping agent. Different temperature in range of 250°C to 500°C was used in order to investigate the effect of annealing temperature of ZnO thin films. Field Emission Scanning Electron Microscopy (FESEM) was used to investigate the physical characteristic of ZnO thin films. FESEM results have revealed that ZnO nanorods were grown vertically aligned. The structural properties were determined by using X-Ray Diffraction (XRD) analysis. XRD results showed Mg doped ZnOmore » thin have highest crystalinnity at 500°C annealing temperature. The electrical properties were investigating by using Current-Voltage (I-V) measurement. I-V measurement showed the electrical properties were varied at different annealing temperature. The annealing temperature at 500°C has the highest electrical conductance properties.« less

  11. Effects of complexing agents on electrochemical deposition of FeS x O y in ZnO/FeS x O y heterostructures

    NASA Astrophysics Data System (ADS)

    Supee, A.; Ichimura, M.

    2017-12-01

    Heterostructures which consist of ZnO and FeS x O y were deposited via electrochemical deposition (ECD) for application to solar cells. Galvanostatic ECD was used in FeS x O y deposition with a solution containing 100 mM Na2S2O3 and 30 mM FeSO4. To alter the film properties, L(+)-tartaric acid (C4H6O6) and lactic acid [CH3CH(OH)COOH] were introduced as the complexing agents into the FeS x O y deposition solution. Larger film thickness and smaller oxygen content were obtained for the films deposited with the complexing agents. ZnO was deposited on FeS x O y by two-step pulse ECD from a solution containing Zn(NO3)2. For the ZnO/FeS x O y heterostructures fabricated with/without complexing agents, rectifying properties were confirmed in the current density-voltage ( J- V) characteristics. However, photovoltaic properties were not improved with addition of both complexing agents.

  12. Understanding corrosion behavior of Mg-Zn-Ca alloys from subcutaneous mouse model: effect of Zn element concentration and plasma electrolytic oxidation.

    PubMed

    Jang, Yongseok; Tan, Zongqing; Jurey, Chris; Xu, Zhigang; Dong, Zhongyun; Collins, Boyce; Yun, Yeoheung; Sankar, Jagannathan

    2015-03-01

    Mg-Zn-Ca alloys are considered as suitable biodegradable metallic implants because of their biocompatibility and proper physical properties. In this study, we investigated the effect of Zn concentration of Mg-xZn-0.3Ca (x=1, 3 and 5wt.%) alloys and surface modification by plasma electrolytic oxidation (PEO) on corrosion behavior in in vivo environment in terms of microstructure, corrosion rate, types of corrosion, and corrosion product formation. Microstructure analysis of alloys and morphological characterization of corrosion products were conducted using x-ray computed tomography (micro-CT) and scanning electron microscopy (SEM). Elemental composition and crystal structure of corrosion products were determined using x-ray diffraction (XRD) and electron dispersive x-ray spectroscopy (EDX). The results show that 1) as-cast Mg-xZn-0.3Ca alloys are composed of Mg matrix and a secondary phase of Ca2Mg6Zn3 formed along grain boundaries, 2) the corrosion rate of Mg-xZn-0.3Ca alloys increases with increasing concentration of Zn in the alloy, 3) corrosion rates of alloys treated by PEO sample are decreased in in vivo environment, and 4) the corrosion products of these alloys after in vivo tests are identified as brucite (Mg(OH)2), hydroxyapatite (Ca10(PO4)6(OH)2), and magnesite (MgCO3·3H2O). Copyright © 2014 Elsevier B.V. All rights reserved.

  13. Thermodynamic analysis and experimental study on the oxidation of the Zn-Al-Mg coating baths

    NASA Astrophysics Data System (ADS)

    Su, Xuping; Zhou, Jie; Wang, Jianhua; Wu, Changjun; Liu, Ya; Tu, Hao; Peng, Haoping

    2017-02-01

    Surface oxidation of molten Zn-6Al baths containing 0.0, 3.0 and 6.0 wt. % Mg were analyzed using X-ray photoelectron spectroscopy. γ-Al2O3 is formed on the surface of the Zn-6Al bath, while MgAl2O4 and MgO occur at 460 °C in the Zn-6Al-3Mg and Zn-6Al-6Mg baths, respectively. Thermodynamic analysis on the oxidation of the Zn-Al-Mg baths was performed. Calculated phase diagrams at 460 °C and 560 °C show good agreements with the experimental results. MgO or MgAl2O4 exists in almost the entire composition range of the calculated oxidation diagrams. According to the calculation, oxidation products depend on the composition and temperature of the baths. The primary and secondary oxidation products of the Zn-Al-Mg baths can be reasonably explained by oxidation phase diagrams. Utilizing these results, the favorable practical bath melts and operating conditions can be designed.

  14. Primary fragmentation pathways of gas phase [M(uracil-H)(uracil)]+ complexes (M=Zn, Cu, Ni, Co, Fe, Mn, Cd, Pd , Mg, Ca, Sr, Ba, and Pb): loss of uracil versus HNCO.

    PubMed

    Ali, Osama Y; Randell, Nicholas M; Fridgen, Travis D

    2012-04-23

    Complexes formed between metal dications, the conjugate base of uracil, and uracil are investigated by sustained off-resonance irradiation collision-induced dissociation (SORI-CID) in a Fourier transform ion cyclotron resonance (FTICR) mass spectrometer. Positive-ion electrospray spectra show that [M(Ura-H)(Ura)](+) (M=Zn, Cu, Ni, Co, Fe, Mn, Cd, Pd, Mg, Ca, Sr, Ba, or Pb) is the most abundant ion even at low concentrations of uracil. SORI-CID experiments show that the main primary decomposition pathway for all [M(Ura-H)(Ura)](+) , except where M=Ca, Sr, Ba, or Pb, is the loss of HNCO. Under the same SORI-CID conditions, when M is Ca, Sr, Ba, or Pb, [M(Ura-H)(Ura)](+) are shown to lose a molecule of uracil. Similar results were observed under infrared multiple-photon dissociation excitation conditions, except that [Ca(Ura-H)(Ura)](+) was found to lose HNCO as the primary fragmentation product. The binding energies between neutral uracil and [M(Ura-H)](+) (M=Zn, Cu, Ni, Fe, Cd, Pd ,Mg, Ca, Sr Ba, or Pb) are calculated by means of electronic-structure calculations. The differences in the uracil binding energies between complexes which lose uracil and those which lose HNCO are consistent with the experimentally observed differences in fragmentation pathways. A size dependence in the binding energies suggests that the interaction between uracil and [M(Ura-H)](+) is ion-dipole complexation and the experimental evidence presented supports this. Copyright © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  15. Fe/Mg smectite formation under acidic conditions on early Mars

    NASA Astrophysics Data System (ADS)

    Peretyazhko, T. S.; Sutter, B.; Morris, R. V.; Agresti, D. G.; Le, L.; Ming, D. W.

    2016-01-01

    Phyllosilicates of the smectite group detected in Noachian and early Hesperian terrains on Mars have been hypothesized to form under neutral to alkaline conditions. These pH conditions would also be favorable for formation of widespread carbonate deposits which have not been detected on Mars. We propose that smectite deposits on Mars formed under moderately acidic conditions inhibiting carbonate formation. We report here the first synthesis of Fe/Mg smectite in an acidic hydrothermal system [200 °C, pHRT ∼ 4 (pH measured at room temperature) buffered with acetic acid] from Mars-analogue, glass-rich, basalt simulant with and without aqueous Mg or Fe(II) addition under N2-purged anoxic and ambient oxic redox conditions. Synthesized Fe/Mg smectite was examined by X-ray-diffraction, Mössbauer spectroscopy, visible and near-infrared reflectance spectroscopy, scanning electron microscopy and electron microprobe to characterize mineralogy, morphology and chemical composition. Alteration of the glass phase of basalt simulant resulted in formation of the Fe/Mg smectite mineral saponite with some mineralogical and chemical properties similar to the properties reported for Fe/Mg smectite on Mars. Our experiments are evidence that neutral to alkaline conditions on early Mars are not necessary for Fe/Mg smectite formation as previously inferred. Phyllosilicate minerals could instead have formed under mildly acidic pH conditions. Volcanic SO2 emanation and sulfuric acid formation is proposed as the major source of acidity for the alteration of basaltic materials and subsequent formation of Fe/Mg smectite.

  16. Biological activity evaluation of magnesium fluoride coated Mg-Zn-Zr alloy in vivo.

    PubMed

    Jiang, Hongfeng; Wang, Jingbo; Chen, Minfang; Liu, Debao

    2017-06-01

    To explore the biodegradable characteristics and biological properties, which could promote new bone formation, of MgF 2 coated magnesium alloy (Mg-3wt%Zn-0.5wt%Zr) in rabbits. Magnesium alloy with MgF 2 coating was made and the MgF 2 /Mg-Zn-Zr was implanted in the femoral condyle of rabbits. Twelve healthy adult Japanese white rabbits in weight of 2.8-3.2kg were averagely divided into A(Mg-Zn-Zr) group and B(MgF 2 /MgZn-Zr) group. Indexes such as microstructural evolution, SEM scan, X-ray, Micro-CT and mechanical properties were observed and detected at 1th day, 2th, 4th, 8th, 12th, 24th week after implantation. Low-density regions occurred around the cancellous bone, and the regions gradually expanded during the 12weeks after implantation. The implant was gradually absorbed from 12 to 24weeks. The density of surrounding cancellous bone increased compared with the 12th week data. The degradation rate of B group was lower than that of A group (P<0.01), while the density of the surrounding cancellous bone increased more evenly. In B group, SEM images after 12weeks showed the rich bone tissues on the alloy surface that were attached by active fibers. Micro-CT also presented alloy residue potholes on the surfaces of alloy combinated with bone tissues. Additionally, the trabecular bone had relatively integrated structures with surrounding cavities. MgF 2 can effectively decrease the degradation rate of Mg-Zn-Zr in vivo. Mg-Zn-Zr coated with MgF 2 can effectively inhibit the corrosion, and delay the release of magnesium ions. The biological properties of the coating itself presented good biocompatibility and bioactivity. Copyright © 2017 Elsevier B.V. All rights reserved.

  17. Chemoselectivity-induced multiple interfaces in MWCNT/Fe3O4@ZnO heterotrimers for whole X-band microwave absorption.

    PubMed

    Wang, Zhijiang; Wu, Lina; Zhou, Jigang; Jiang, Zhaohua; Shen, Baozhong

    2014-11-07

    A chemoselective route to induce Fe3O4@ZnO core-shell nanoparticles decorating carbon nanotubes to form MWCNT/Fe3O4@ZnO heterotrimers has been developed. Charges are redistributed in the heterotrimers through C-O-Zn, C-O-Fe and Fe-O-Zn bondings, giving rise to multiple electronic phases. The generated significant interfacial polarization and synergetic interaction between dielectric and magnetic absorbers result in the MWCNT/Fe3O4@ZnO heterotrimers with high-performance microwave absorption in an entire X band.

  18. Fe-tannic acid complex dye as photo sensitizer for different morphological ZnO based DSSCs

    NASA Astrophysics Data System (ADS)

    Çakar, Soner; Özacar, Mahmut

    2016-06-01

    In this paper we have synthesized different morphological ZnO nanostructures via microwave hydrothermal methods at low temperature within a short time. We described different morphologies of ZnO at different Zn(NO3)2/KOH mole ratio. The ZnO nanostructures were characterized via X-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM) and UV-vis spectrophotometry. All ZnO structures have hexagonal wurtzite type structures. The FESEM images showed various morphologies of ZnO such as plate, rod and nanoparticles. Dye sensitized solar cells have been assembled by these different morphological structures photo electrode and tannic acid or Fe-tannic acid complex dye as sensitizer. We have achieved at maximum efficiencies of photovoltaic cells prepared with ZnO plate in all dye systems. The conversion efficiencies of dye sensitized solar cells are 0.37% and 1.00% with tannic acid and Fe-tannic acid complex dye, respectively.

  19. Ab initio understanding of magnetic properties in Zn2+ substitution of Fe3O4 ultra-thin film with dilute Zn substitution

    NASA Astrophysics Data System (ADS)

    Huang, Zhaocong; Chen, Qian; Jiang, Sheng; Dong, Shuai; Zhai, Ya

    2018-05-01

    The mechanism of the magnetic properties on the Zn2+ substituted Fe3O4 film have been investigated based on first principle calculations. It is found that the surface effect plays an important role in the occupation of Zn ion, and in turn changes the magnetic moment. It may also destroy the half metallic behavior of Fe3O4 film even if the Zn2+ concentration only is one Zn2+ per unit cell (4%), which is different from that in bulk material.

  20. Transport and spin transfer torques in Fe/MgO/Fe tunnel barriers.

    NASA Astrophysics Data System (ADS)

    Heiliger, Christian

    2008-03-01

    The prediction of very high tunneling magnetoresistance (TMR) ratios in crystalline Fe/MgO/Fe [1,2] tunnel junctions has been verified by a number of experiments [3,4]. The high TMR can be understood in terms of the electronic structure of the system. In MgO the δ1 states at the Brillouin zone center decay the most slowly and dominate the tunnelling current. For coherent interfaces, which are achievable due to the small lattice mismatch between Fe and MgO, these δ1 states at the Brillouin zone center are half-metallic in the Fe layers. The dominance of the δ1 states and their half-metallicity cause the high tunnelling magnetoresistance measured in Fe/MgO/Fe tunnel junctions [5]. For the spin transfer torque, we calculate the linear response for small currents and voltages. Our calculations show that the half metallicity of the Fe δ1 states leads to a strong localization of the spin transfer torque to the interface. As a result, the linear current dependence of the torque in the plane of the two magnetizations is independent of the free layer thickness for more than three monolayers of Fe. For perfect samples we also find a linear current dependence of the out-of-plane component. However, this linear piece oscillates rapidly with thickness and averages to zero in the presence of structural imperfections like thickness fluctuation, in agreement with experiment [6]. In this talk I discuss the bias dependence of the TMR and spin transfer torque effects mentioned above and the influence on them of the following factors: the interface structure Fe/MgO, the barrier thickness, and the structure of the leads [7]. This work has been supported in part by the NIST-CNST/UMD-NanoCenter Cooperative Agreement. [1] W. Butler, X.-G. Zhang, T. Schulthess, J. MacLaren, Phys. Rev. B 63 (2001) 054416. [2] J. Mathon, A. Umerski, Phys. Rev. B 63 (2001) 220403. [3] S. Yuasa, T. Nagahama, A. Fukushima, Y. Suzuki, K. Ando, Nature Materials 3 (2004) 868. [4] S.S.P. Parkin, C. Kaiser, A

  1. Different magnetic origins of (Mn, Fe)-codoped ZnO powders and thin films

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

    Fan, Jiuping; Jiang, Fengxian; Quan, Zhiyong

    2012-11-15

    Graphical abstract: The effects of the sample forms, fabricated methods, and process conditions on the structural and magnetic properties of (Mn, Fe)-codoped ZnO powders and films were systematically studied. The origins of ferromagnetism in the vacuum-annealed powder and PLD-deposited film are different. The former originates from the impurities of magnetic clusters, whereas the latter comes from the almost homogenous phase. Highlights: ► The magnetic natures of Zn{sub 0.98}Mn{sub 0.01}Fe{sub 0.01}O powders and thin films come from different origins. ► The ferromagnetism of the powder is mainly from the contribution of magnetic clusters. ► Whereas the ferromagnetic behavior of the filmmore » comes from the almost homogenous phase. -- Abstract: The structural and magnetic properties of (Mn, Fe)-codoped ZnO powders as well as thin films were investigated. The X-ray diffraction and magnetic measurements indicated that the higher sintering temperature facilitates more Mn and Fe incorporation into ZnO. Magnetic measurements indicated that the powder sintered in air at 800 °C showed paramagnetic, but it exhibited obvious room temperature ferromagnetism after vacuum annealing at 600 °C. The results revealed that magnetic clusters were the major contributors to the observed ferromagnetism in vacuum-annealed Zn{sub 0.98}Mn{sub 0.01}Fe{sub 0.01}O powder. Interestingly, the room temperature ferromagnetism was also observed in the Zn{sub 0.98}Mn{sub 0.01}Fe{sub 0.01}O film deposited via pulsed laser deposition from the air-sintered paramagnetic target, but the secondary phases in the film were not detected from X-ray diffraction, transmission electron microscopy, and zero-field cooling and field cooling. Apparently, the magnetic natures of powders and films come from different origins.« less

  2. Extremely High Phosphate Sorption Capacity in Cu-Pb-Zn Mine Tailings.

    PubMed

    Huang, Longbin; Li, Xiaofang; Nguyen, Tuan A H

    2015-01-01

    Elevated inorganic phosphate (Pi) concentrations in pore water of amended tailings under direct revegetation may cause toxicity in some native woody species but not native forbs or herb species, all of which are key constituents in target native plant communities for phytostabilizing base metal mine tailings. As a result, Pi sorption capacity has been quantified by a conventional batch procedure in three types of base metal mine tailings sampled from two copper (Cu)-lead (Pb)-zinc (Zn) mines, as the basis for Pi-fertiliser addition. It was found that the Pi-sorption capacity in the tailings and local soil was extremely high, far higher than highly weathered agricultural soils in literature, but similar to those of volcanic ash soils. The Langmuir P-sorption maximum was up to 7.72, 4.12, 4.02 and 3.62 mg P g-1 tailings, in the fresh tailings of mixed Cu-Pb-Zn streams (MIMTD7), the weathered tailings of mixed Cu-Pb-Zn streams (MIMTD5), EHM-TD (fresh Cu-stream, high magnetite content) and local soil (weathered shale and schist), respectively. Physicochemical factors highly correlated with the high Pi-sorption in the tailings were fine particle distribution, oxalate and dithionite-citrate-bicarbonate extractable Fe (FeO and Fed), oxalate-extractable Al and Mn, and the levels of soluble Cd and Zn, and total S and Fe. Large amounts of amorphous Fe oxides and oxyhydroxides may have been formed from the oxidation of pyritic materials and redox cycles of Fe-minerals (such as pyrite (FeS2), ankerite (Ca(Fe Mg)(CO3)2 and siderite (FeCO3), as indicated by the extractable FeO values. The likely formation of sparingly soluble Zn-phosphate in the Pb-Zn tailings containing high levels of Zn (from sphalerite ((Zn,Fe)S, ZnS, (Zn,Cd)S)) may substantially lower soluble Zn levels in the tailings through high rates of Pi-fertiliser addition. As a result, the possibility of P-toxicity in native plant species caused by the addition of soluble phosphate fertilizers would be minimal.

  3. Fe{sub 3}O{sub 4}/CuO/ZnO/Nano graphene platelets (Fe{sub 3}O{sub 4}/CuO/ZnO/NGP) composites prepared by sol-gel method with enhanced sonocatalytic activity for the removal of dye

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

    Hendry, Tju; Taufik, Ardiansyah; Saleh, Rosari, E-mail: rosari.saleh@gmail.com, E-mail: rosari.saleh@ui.ac.id

    2016-04-19

    In this study, an attempt has been made to synthesize nanographene platelets coupled with Fe3O4/CuO/ZnO (Fe3O4/CuO/ZnO/NGP) with various ZnO loadings using a two step methods, sol-gel followed by hydrothermal method. Characterization was carried out by X-ray diffraction, energy-dispersive X-ray spectroscopy and vibrating sample magnetometer. The sonocatalytic performance was evaluated by degradation of methylene blue under ultrasonic irradiation.The Fe3O4/CuO/ZnO/NGP showed superior sonocatalytic activity than the Fe3O4/CuO/ZnO materials. They also showed high stability and can be easily separated from the reaction system for recycling process.

  4. Intersubband spectroscopy of ZnO/ZnMgO quantum wells grown on m-plane ZnO substrates for quantum cascade device applications (Conference Presentation)

    NASA Astrophysics Data System (ADS)

    Quach, Patrick; Jollivet, Arnaud; Isac, Nathalie; Bousseksou, Adel; Ariel, Frédéric; Tchernycheva, Maria; Julien, François H.; Montes Bajo, Miguel; Tamayo-Arriola, Julen; Hierro, Adrián.; Le Biavan, Nolwenn; Hugues, Maxime; Chauveau, Jean-Michel

    2017-03-01

    Quantum cascade (QC) lasers opens new prospects for powerful sources operating at THz frequencies. Up to now the best THz QC lasers are based on intersubband emission in GaAs/AlGaAs quantum well (QW) heterostructures. The maximum operating temperature is 200 K, which is too low for wide-spread applications. This is due to the rather low LO-phonon energy (36 meV) of GaAs-based materials. Indeed, thermal activation allows non-radiative path through electron-phonon interaction which destroys the population inversion. Wide band gap materials such as ZnO have been predicted to provide much higher operating temperatures because of the high value of their LO-phonon energy. However, despite some observations of intersubband absorption in c-plane ZnO/ZnMgO quantum wells, little is known on the fundamental parameters such as the conduction band offset in such heterostructures. In addition the internal field inherent to c-plane grown heterostuctures is an handicap for the design of QC lasers and detectors. In this talk, we will review a systematic investigation of ZnO/ZnMgO QW heterostructures with various Mg content and QW thicknesses grown by plasma molecular beam epitaxy on low-defect m-plane ZnO substrates. We will show that most samples exhibit TM-polarized intersubband absorption at room temperature linked either to bound-to-quasi bound inter-miniband absorption or to bound-to bound intersubband absorption depending on the Mg content of the barrier material. This systematic study allows for the first time to estimate the conduction band offset of ZnO/ZnMgO heterostructures, opening prospects for the design of QC devices operating at THz frequencies. This was supported by the European Union's Horizon 2020 research and innovation programme under grant agreement #665107.

  5. Effect of Fe doping concentration on photocatalytic activity of ZnO nanosheets under natural sunlight

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

    Khokhra, Richa; Kumar, Rajesh, E-mail: rajesh.kumar@juit.ac.in

    2015-05-15

    A facile room temperature, aqueous solution-based chemical method has been adopted for large-scale synthesis of Fe doped ZnO nanosheets. The XRD and SEM results reveal the as-synthesized products well crystalline and accumulated by large amount of interweave nanosheets, respectively. Energy dispersive spectroscopy data confirmed Fe doping of the ZnO nanosheets with a varying Fe concentration. The photoluminescence spectrum reveals a continuous suppression of defect related emissions intensity by increasing the concentration of the Fe ion. A photocatalytic activity using these samples under sunlight irradiation in the mineralization of methylene blue dye was investigated. The photocatalytic activity of Fe doped ZnOmore » nanosheets depends upon the presence of surface oxygen vacancies.« less

  6. Enhanced solar-blind responsivity of photodetectors based on cubic MgZnO films via gallium doping.

    PubMed

    Xie, Xiuhua; Zhang, Zhenzhong; Li, Binghui; Wang, Shuangpeng; Jiang, Mingming; Shan, Chongxin; Zhao, Dongxu; Chen, Hongyu; Shen, Dezhen

    2014-01-13

    We report on gallium (Ga) doped cubic MgZnO films, which have been grown by metal organic chemical vapor deposition. It was demonstrated that Ga doping improves the n-type conduction of the cubic MgZnO films. A two-orders of magnitude enhancement in lateral n-type conduction have been achieved for the cubic MgZnO films. The responsivity of the cubic MgZnO-based photodetector has been also enhanced. Depletion region electric field intensity enhanced model was adopted to explain the improvement of quantum efficiency in Ga doped MgZnO-based detectors.

  7. Effect of Si, Mg, and Mg Zn doping on structural properties of a GaN layer grown by metalorganic chemical vapor deposition

    NASA Astrophysics Data System (ADS)

    Cho, H. K.; Lee, J. Y.; Kim, K. S.; Yang, G. M.

    2001-12-01

    We have studied the structural properties of undoped, Si-doped, Mg-doped, and Mg-Zn codoped GaN using high-resolution X-ray diffraction (HRXRD) and transmission electron microscopy. When compared with undoped GaN, the dislocation density at the surface of the GaN layer decreases with Si doping and increases with Mg doping. In addition, we observed a reduction of dislocation density by codoping with Zn atoms in the Mg-doped GaN layer. The full width at half maximum of HRXRD shows that Si doping and Mg-Zn codoping improve the structural quality of the GaN layer as compared with undoped and Mg-doped GaN, respectively.

  8. Metalliclike behavior of the exchange coupling in (001) Fe/MgO/Fe junctions

    NASA Astrophysics Data System (ADS)

    Bellouard, C.; Duluard, A.; Snoeck, E.; Lu, Y.; Negulescu, B.; Lacour, D.; Senet, C.; Robert, S.; Maloufi, N.; Andrieu, S.; Hehn, M.; Tiusan, C.

    2017-10-01

    Exchange magnetic coupling between Fe electrodes through a thin MgO interlayer in epitaxial junctions has been investigated as a function of temperature, MgO thickness, and interface quality. Depending on the MgO thickness, which has been varied from 1.5 to 4 monolayers, two opposite temperature dependences are clearly disentangled. For a thin MgO spacer, the main component decreases with temperature following a metalliclike behavior. On the contrary, for the thickest MgO layers, the main component increases with temperature, following an Arrhenius law. Moreover, the insertion of a monoatomic roughness at the bottom MgO interface, induced by the addition of a fraction of a Fe monolayer, exacerbates the metallic features as an oscillatory behavior from antiferromagnetic to ferromagnetic is observed. These results allow questioning the simple tunneling mechanism usually invoked for MgO coupling, and suggest a crossover behavior of the thin MgO spacer from metallic to insulating with a progressive opening of the gap.

  9. Highly selective removal of Zn(II) ion from hot-dip galvanizing pickling waste with amino-functionalized Fe3O4@SiO2 magnetic nano-adsorbent.

    PubMed

    Bao, Shuangyou; Tang, Lihong; Li, Kai; Ning, Ping; Peng, Jinhui; Guo, Huibin; Zhu, Tingting; Liu, Ye

    2016-01-15

    Amino-functionalized Fe3O4@SiO2 magnetic nano-adsorbent was used as a novel sorbent to highly selective removal of Zn(II) ion from hot-dip galvanizing pickling waste in the presence of Fe(II). These hot-dip galvanizing pickling waste mainly contain ZnCl2 and FeCl2 in aqueous HCl media. The properties of this magnetic adsorbent were examined by transmission electron microscopy (TEM), powder X-ray diffraction (XRD), infrared spectrometer (FT-IR) and BET surface area measurements. Various factors influencing the adsorption of Zn(II) ion such as initial concentration of metal ions, the amount of adsorbent, pH value of the solutions, the concentration of coexisting iron ion were investigated by batch experiments. The results indicated that the adsorption equilibrium data obeyed the Freundlich model with maximum adsorption capacities for Zn(II) to 169.5mg/g. The maximum adsorption occurred at pH 5±0.1 and Fe(II) interferences had no obvious influence. This work provides a potential and unique technique for zinc ion removal from hot-dip galvanizing pickling waste. Copyright © 2015 Elsevier Inc. All rights reserved.

  10. Interface engineering of high-Mg-content MgZnO/BeO/Si for p-n heterojunction solar-blind ultraviolet photodetectors

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

    Liang, H. L.; Mei, Z. X.; Zhang, Q. H.

    2011-05-30

    High-quality wurtzite MgZnO film was deposited on Si(111) substrate via a delicate interface engineering using BeO, by which solar-blind ultraviolet photodetectors were fabricated on the n-MgZnO(0001)/p-Si(111) heterojunction. A thin Be layer was deposited on clean Si surface with subsequent in situ oxidation processes, which provides an excellent template for high-Mg-content MgZnO growth. The interface controlling significantly improves the device performance, as the photodetector demonstrates a sharp cutoff wavelength at 280 nm, consistent with the optical band gap of the epilayer. Our experimental results promise potential applications of this technique in integration of solar-blind ultraviolet optoelectronic device with Si microelectronic technologies.

  11. Structure and Stoichiometry of MgxZny in Hot-Dipped Zn-Mg-Al Coating Layer on Interstitial-Free Steel

    NASA Astrophysics Data System (ADS)

    Kim, Jaenam; Lee, Chongsoo; Jin, Youngsool

    2018-03-01

    Correlations of stoichiometry and phase structure of MgxZny in hot-dipped Zn-Mg-Al coating layer which were modified by additive element have been established on the bases of diffraction and phase transformation principles. X-ray diffraction (XRD) results showed that MgxZny in the Zn-Mg-Al coating layers consist of Mg2Zn11 and MgZn2. The additive elements had a significant effect on the phase fraction of Mg2Zn11 while the Mg/Al ratio had a negligible effect. Transmission electron microscope (TEM) assisted selected area electron diffraction (SAED) results of small areas MgxZny were indexed dominantly as MgZn2 which have different Mg/Zn stoichiometry between 0.10 and 0.18. It is assumed that the MgxZny have deviated stoichiometry of the phase structure with additive element. The deviated Mg2Zn11 phase structure was interpreted as base-centered orthorhombic by applying two theoretical validity: a structure factor rule explained why the base-centered orthorhombic Mg2Zn11 has less reciprocal lattice reflections in the SAED compared to hexagonal MgZn2, and a phase transformation model elucidated its reasonable lattice point sharing of the corresponding unit cell during hexagonal MgZn2 (a, b = 0.5252 nm, c = 0.8577 nm) transform to intermediate tetragonal and final base-centered orthorhombic Mg2Zn11 (a = 0.8575 nm, b = 0.8874 nm, c = 0.8771 nm) in the equilibrium state.

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

    NASA Astrophysics Data System (ADS)

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

    2017-05-01

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

  13. Impact of strain on electronic defects in (Mg,Zn)O thin films

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

    Schmidt, Florian, E-mail: fschmidt@physik.uni-leipzig.de; Müller, Stefan; Wenckstern, Holger von

    2014-09-14

    We have investigated the impact of strain on the incorporation and the properties of extended and point defects in (Mg,Zn)O thin films by means of photoluminescence, X-ray diffraction, deep-level transient spectroscopy (DLTS), and deep-level optical spectroscopy. The recombination line Y₂, previously detected in ZnO thin films grown on an Al-doped ZnO buffer layer and attributed to tensile strain, was exclusively found in (Mg,Zn)O samples being under tensile strain and is absent in relaxed or compressively strained thin films. Furthermore a structural defect E3´ can be detected via DLTS measurements and is only incorporated in tensile strained samples. Finally it ismore » shown that the omnipresent deep-level E3 in ZnO can only be optically recharged in relaxed ZnO samples.« less

  14. Uniform Fe3O4 coating on flower-like ZnO nanostructures by atomic layer deposition for electromagnetic wave absorption.

    PubMed

    Wan, Gengping; Wang, Guizhen; Huang, Xianqin; Zhao, Haonan; Li, Xinyue; Wang, Kan; Yu, Lei; Peng, Xiange; Qin, Yong

    2015-11-21

    An elegant atomic layer deposition (ALD) method has been employed for controllable preparation of a uniform Fe3O4-coated ZnO (ZnO@Fe3O4) core-shell flower-like nanostructure. The Fe3O4 coating thickness of the ZnO@Fe3O4 nanostructure can be tuned by varying the cycle number of ALD Fe2O3. When serving as additives for microwave absorption, the ZnO@Fe3O4-paraffin composites exhibit a higher absorption capacity than the ZnO-paraffin composites. For ZnO@500-Fe3O4, the effective absorption bandwidth below -10 dB can reach 5.2 GHz and the RL values below -20 dB also cover a wide frequency range of 11.6-14.2 GHz when the coating thickness is 2.3 mm, suggesting its potential application in the treatment of the electromagnetic pollution problem. On the basis of experimental observations, a mechanism has been proposed to understand the enhanced microwave absorption properties of the ZnO@Fe3O4 composites.

  15. Study of interlayer coupling between FePt and FeCoB thin films through MgO spacer layer

    NASA Astrophysics Data System (ADS)

    Singh, Sadhana; Kumar, Dileep; Gupta, Mukul; Reddy, V. Raghvendra

    2017-05-01

    Interlayer exchange coupling between hard-FePt and soft-FeCoB magnetic layers has been studied with increasing thickness of insulator MgO spacer layer in FePt/MgO/FeCoB sandwiched structure. A series of the samples were prepared in identical condition using ion beam sputtering method and characterized for their magnetic and structural properties using magneto-optical Kerr effect (MOKE) and X-ray reflectivity measurements. The nature of coupling between FePt and FeCoB was found to be ferromagnetic which decreases exponentially with increasing thickness of MgO layer. At very low thickness of MgO layer, both layers were found strongly coupled thus exhibiting coherent magnetization reversal. At higher thickness, both layers were found decoupled and magnetization reversal occurred at different switching fields. Strong coupling at very low thickness is attributed to pin holes in MgO layer which lead to direct coupling whereas on increasing thickness, coupling may arise due to magneto-static interactions.

  16. Adsorption of multi-heavy metals Zn and Cu onto surficial sediments: modeling and adsorption capacity analysis.

    PubMed

    Li, Shanshan; Zhang, Chen; Wang, Meng; Li, Yu

    2014-01-01

    Improved multiple regression adsorption models (IMRAMs) was developed to estimate the adsorption capacity of the components [Fe oxides (Fe), Mn oxides (Mn), organic materials (OMs), residuals] in surficial sediments for multi-heavy metal Zn and Cu. IMRAM is an improved version over MRAM, which introduces a computer program in the model developing process. As MRAM, Zn(Cu) IMRAM, and Cu(Zn) IMRAM again confirmed that there is significant interaction effects that control the adsorption of compounded Zn and Cu, which was neglected by additional adsorption model. The verification experiment shows that the relative deviation of the IMRAMs is less than 13%. It is revealed by the IMRAMs that Mn, which has the greatest adsorption capability for compounded Zn and Cu (54.889 and 161.180 mg/l, respectively), follows by interference adsorption capacity of Fe/Mn (-1.072 and -24.591 mg/l respectively). Zn and Cu influence each other through different mechanisms. When Zn is the adsorbate, compounded Cu mainly affects the adsorption capacities of Fe/Mn and Fe/Mn/OMs; while when Cu is the adsorbate, compounded Zn mainly exerts its effect on Mn, Fe/Mn, and Mn/OMs. It also shows that the compounded Zn or Cu weakened the interference adsorption of Fe/Mn, and meanwhile, strengthened the interference adsorption of Mn/OMs.

  17. Influence of severe plastic deformation on intermetallic particles in Mg-12 wt.%Zn alloy investigated using transmission electron microscopy

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

    Němec, M., E-mail: nemecm@fzu.cz

    The in-depth microstructural characterization of intermetallic particles in an Mg-12 wt.%Zn binary alloy subjected to a severe plastic deformation is presented. The alloy was processed by four passes via equal channel angular pressing with an applied back pressure at a gradually decreasing temperature and analyzed using transmission electron microscopy techniques to observe the influence of processing on intermetallic particles. The results are compared with the initial state of the material prior to severe plastic deformation. The microstructural evolution of the α-Mg matrix and the Mg{sub 21}Zn{sub 25}, Mg{sub 51}Zn{sub 20} and MgZn{sub 2} was analyzed using bright field imaging, selectedmore » area electron diffraction, high-resolution transmission electron microscopy and high-angle annular dark field imaging in scanning mode. The plastic deformation process influenced the α-Mg matrix and each type of intermetallic particle. The α-Mg matrix consisted of two types of areas. The first type of area had a highly deformed structure, and the second type of area had a partially recrystallized structure with an average grain size of approximately 250 nm. The Mg{sub 21}Zn{sub 25} microparticles exhibited distinct forms in the α-Mg matrix that were characterized as a single-crystalline form, a nano-crystalline form and a broken up form. No evidence of Mg{sub 51}Zn{sub 20} nanoparticles within the α-Mg matrix was found in the microstructure, which indicates their dissolution or phase transformation during the deformation process. MgZn{sub 2} nanoparticles exhibited different behavior in both types of α-Mg matrix. Two orientation relationships toward the highly deformed α-Mg matrix were observed; however, there was no relationship toward the partially recrystallized α-Mg matrix. Additionally, the growth of the MgZn{sub 2} nanoparticles was different in the two types of α-Mg matrix. The Mg{sub 51}Zn{sub 20} nanoparticles inside Mg{sub 21}Zn{sub 25} microparticles

  18. Preparation and characterization of porous Mg-Zn-Ca alloy by space holder technique

    NASA Astrophysics Data System (ADS)

    Annur, D.; Lestari, Franciska P.; Erryani, A.; Sijabat, Fernando A.; G. P. Astawa, I. N.; Kartika, I.

    2018-04-01

    Magnesium had been recently researched as a future biodegradable implant material. In the recent study, porous Mg-Zn-Ca alloys were developed using space holder technique in powder metallurgy process. Carbamide (10-20%wt) was added into Mg-6Zn-1Ca (in wt%) alloy system as a space holder to create porous structure material. Sintering process was done in a tube furnace under Argon atmosphere in 610 °C for 5 hours. Porous structure of the resulted alloy was examined using Scanning Electron Microscope (SEM), while the phase formation was characterized by X-ray diffraction analysis (XRD). Further, mechanical properties of porous Mg-Zn-Ca alloy was examined through compression testing. Microstructure characterization showed higher content of Carbamide in the alloy would give different type of pores. However, compression test showed that mechanical properties of Mg-Zn-Ca alloy would decrease significantly when higher content of carbamide was added.

  19. In vitro degradation behavior and biocompatibility of Mg-Nd-Zn-Zr alloy by hydrofluoric acid treatment.

    PubMed

    Mao, Lin; Yuan, Guangyin; Niu, Jialin; Zong, Yang; Ding, Wenjiang

    2013-01-01

    In this paper, Mg-Nd-Zn-Zr alloy (denoted as JDBM) coated with hydrofluoric acid (HF) chemical conversion film (MgF2) was researched as a potential biodegradable cardiovascular stent material. The microstructures, in vitro degradation and biocompatibility were investigated. The field emission scanning electron microscopy (FE-SEM) and X-ray photoelectron spectroscopy (XPS) showed that a compact MgF2 film was formed on the surface of JDBM. The corrosion rate decreased in artificial plasma from 0.337 to 0.253 mm·y(-1) and the electrochemical measurement demonstrated that the corrosion resistance of JDBM alloy could be obviously improved due to the protective MgF2 film on the surface of the substrate. Meanwhile, the hemolysis ratio of JDBM decreased from 52.0% to 10.1% and the cytotoxicity met the requirement of cellular application after HF treatment. In addition, JDBM and MgF2 film showed good anti-platelet adhesion, which is a very favorable property for implant material in contact with blood directly. Copyright © 2012 Elsevier B.V. All rights reserved.

  20. Controlled electroluminescence of n-ZnMgO/p-GaN light-emitting diodes

    NASA Astrophysics Data System (ADS)

    Goh, E. S. M.; Yang, H. Y.; Han, Z. J.; Chen, T. P.; Ostrikov, K.

    2012-12-01

    Effective control of room-temperature electroluminescence of n-ZnMgO/p-GaN light-emitting diodes (LEDs) over both emission intensity and wavelength is demonstrated. With varied Mg concentration, the intensity of LEDs in the near-ultraviolet region is increased due to the effective radiative recombination in the ZnMgO layer. Furthermore, the emission wavelength is shifted to the green/yellow spectral region by employing an indium-tin-oxide thin film as the dopant source, where thermally activated indium diffusion creates extra deep defect levels for carrier recombination. These results clearly demonstrate the effectiveness of controlled metal incorporation in achieving high energy efficiency and spectral tunability of the n-ZnMgO/p-GaN LED devices.

  1. Characterization and application of the hetero-junction ZnFe2O4/TiO2 for Cr(VI) reduction under visible light

    NASA Astrophysics Data System (ADS)

    Rekhila, G.; Trari, M.; Bessekhouad, Y.

    2017-06-01

    The spinel ZnFe2O4 prepared by nitrate route is used as dispersed photons collector capable to sensitize TiO2 under visible light and to reduce Cr(VI) into trivalent state. The transport properties, optical and photo-electrochemical characterizations are correlated, to build the energetic diagram of the hetero-system ZnFe2O4/TiO2/CrO4 - solution. A gap of 1.97 eV is obtained for the spinel from the diffuse reflectance. The conduction band of ZnFe2O4 (-1.47 V SCE) favors the electrons injection into TiO2, permitting a physical separation of the charge carriers. The oxidation of oxalic acid by photoholes prevents the corrosion of the spinel. The best configuration ZnFe2O4 (75 %)/TiO2 (25 %) is used to catalyze the downhill reaction (2HCrO4 - + 3C2H4O4 + 1.5O2 + 8H+ → 2Cr3+ + 6CO2 + 11 H2O, Δ G° = -557 kcal mol-1). 60 % of Cr(VI) are reduced after 3 h of visible light illumination and the photoactivity follows a first-order kinetic with a half-life of 70 min. The water reduction competes with the HCrO4 - reduction which is the reason in the regression of the photoactivity; a hydrogen evolution rate of 24 µmol mg-1 h-1 is obtained.

  2. Influence of Zn Interlayer on Interfacial Microstructure and Mechanical Properties of TIG Lap-Welded Mg/Al Joints

    NASA Astrophysics Data System (ADS)

    Gao, Qiong; Wang, Kehong

    2016-03-01

    This study explored 6061 Al alloy and AZ31B Mg alloy joined by TIG lap welding with Zn foils of varying thicknesses, with the additional Zn element being imported into the fusion zone to alloy the weld seam. The microstructures and chemical composition in the fusion zone near the Mg substrate were examined by SEM and EDS, and tensile shear strength tests were conducted to investigate the mechanical properties of the Al/Mg joints, as well as the fracture surfaces, and phase compositions. The results revealed that the introduction of an appropriate amount of Zn transition layer improves the microstructure of Mg/Al joints and effectively reduces the formation of Mg-Al intermetallic compounds (IMCs). The most common IMCs in the fusion zone near the Mg substrate were Mg-Zn and Mg-Al-Zn IMCs. The type and distribution of IMCs generated in the weld zone differed according to Zn additions; Zn interlayer thickness of 0.4 mm improved the sample's mechanical properties considerably compared to thicknesses of less than 0.4 mm; however, any further increase in Zn interlayer thickness of above 0.4 mm caused mechanical properties to deteriorate.

  3. UV-luminescent MgZnO semiconductor alloys: nanostructure and optical properties

    DOE PAGES

    Thapa, Dinesh; Huso, Jesse; Miklos, Kevin; ...

    2016-10-24

    MgZnO is emerging as a vital semiconductor-alloy system with desirable optical properties that can span a large range of the UV spectrum. Due to its benign chemical character, MgZnO is considered to be an environmentally friendly material. This paper presents studies on annealing as a useful and straightforward approach for the enhancement of the optical and crystal quality of Mg 0.17Zn 0.83O nanocrystalline films grown via DC sputtering. The alloys were studied via several imaging and optical techniques. It was found that high-temperature annealing, ~900 °C, in Argon atmosphere, significantly improves the solubility of the alloy. This temperature range ismore » consistent with the thermal diffusion temperature of Mg needed for the creation of a soluble alloy. Moreover, the annealing process was found to minimize the undesirable visible luminescence, attributed to Mg and Zn interstitials, while significantly enhancing the bandgap sharpness and the efficiency of the UV-luminescence at ~3.5 eV. The analysis indicated that these optical attributes were achieved due to the combined effects of good solubility, an improved morphology, and a reduction of native defects. The annealing was also proven to be beneficial for the reduction of the compressive stress in the alloy: a relaxation ~1.8 GPa was calculated via Raman scattering. The inherent stress was inferred to originate mainly from the granular morphology of the alloys.« less

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

    PubMed

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

    2011-10-07

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

  5. Surface and cut-edge corrosion behavior of Zn-Mg-Al alloy-coated steel sheets as a function of the alloy coating microstructure

    NASA Astrophysics Data System (ADS)

    Oh, Min-Suk; Kim, Sang-Heon; Kim, Jong-Sang; Lee, Jae-Won; Shon, Je-Ha; Jin, Young-Sool

    2016-01-01

    The effects of Mg and Al content on the microstructure and corrosion resistance of hot-dip Zn-Mg-Al alloycoated steel sheets were investigated. Pure Zn and Zn-based alloy coatings containing Mg (0-5 wt%) and Al (0.2-55 wt%) were produced by a hot-dip galvanizing method. Mg and Al addition induced formation of intermetallic microstructures, like primary Zn, Zn/MgZn2 binary eutectic, dendric Zn/Al eutectoid, and Zn/Al/MgZn2/ternary eutectic structures in the coating layer. MgZn2-related structures (Zn/MgZn2, Zn/Al/MgZn2, MgZn2) played an important role in increasing the corrosion resistance of Zn-Mg-Al alloy-coated steel sheets. Zn-3%Mg-2.5%Al coating layer containing a large volume of lamellar-shaped Zn/MgZn2 binary eutectic structures showed the best cut-edge corrosion resistance. The analysis indicated that Mg dissolved from MgZn2 in the early stage of corrosion and migrated to the cathodic region of steel-exposed cut-edge area to form dense and ordered protective corrosion products, leading to prolonged cathodic protection of Zn-Mg-Al alloy-coated steel sheets.

  6. Structural and optical properties of Mg doped ZnS quantum dots and biological applications

    NASA Astrophysics Data System (ADS)

    Ashokkumar, M.; Boopathyraja, A.

    2018-01-01

    Zn1-xMgxS (x = 0, 0.2 and 0.4) quantum dots (QDs) were prepared by co-precipitation method. The Mg dopant did not modify the cubic blende structure of ZnS QDs. The Mg related secondary phase was not detected even for 40% of Mg doping. The size mismatch between host Zn ion and dopant Mg ion created distortion around the dopant. The creation of distortion centres produced small changes in the lattice parameters and diffraction peak position. All the QDs showed small sulfur deficiency and the deficiency level were increased by Mg doping. Band gap of the QD was decreased due to the dominated quantum confinement effect over compositional effect at initial doping of Mg. But at higher doping the band gap was increased due to compositional effect, since there was no change in average crystallite size. The prepared QDs had three emission bands in the UV and Visible regions corresponding to near band edge emission and defect related emissions. The electron transport reaction chain which forms free radicals was broken by sulfur vacancy trap sites. Therefore, the ZnS QDs had better antioxidant activity and the antioxidant behaviour was enhanced by Mg doping. The enhanced UV absorption and emission of 20% of Mg doped ZnS QDs let to maximize the zone of inhibition against E. Coli bacterial strain.

  7. FE and MG Isotopic Analyses of Isotopically Unusual Presolar Silicate Grains

    NASA Technical Reports Server (NTRS)

    Nguyen, A. N.; Messenger, S.; Ito, M.; Rahman, Z.

    2011-01-01

    Interstellar and circumstellar silicate grains are thought to be Mg-rich and Fe-poor, based on astronomical observations and equilibrium condensation models of silicate dust formation in stellar outflows. On the other hand, presolar silicates isolated from meteorites have surprisingly high Fe contents and few Mg-rich grains are observed. The high Fe contents in meteoritic presolar silicates may indicate they formed by a non-equilibrium condensation process. Alternatively, the Fe in the stardust grains could have been acquired during parent body alteration. The origin of Fe in presolar silicates may be deduced from its isotopic composition. Thus far, Fe isotopic measurements of presolar silicates are limited to the Fe-54/Fe-56 ratios of 14 grains. Only two slight anomalies (albeit solar within error) were observed. However, these measurements suffered from contamination of Fe from the adjacent meteorite matrix, which diluted any isotopic anomalies. We have isolated four presolar silicates having unusual O isotopic compositions by focused ion beam (FIB) milling and obtained their undiluted Mg and Fe isotopic compositions. These compositions help to identify the grains stellar sources and to determine the source of Fe in the grains.

  8. Tuning the Kondo effect in Yb(Fe 1-xCo x) 2Zn 20

    DOE PAGES

    Kong, Tai; Taufour, Valentin; Bud'ko, Sergey L.; ...

    2017-04-03

    We study the evolution of the Kondo effect in heavy fermion compounds, Yb(Fe 1-xCo x) 2Zn 20 (0 ≲ x ≲ 1), by means of temperature-dependent electric resistivity and speci c heat. The ground state of YbFe 2Zn 20 can be well described by a Kondo model with degeneracy N = 8 and a T K ~30 K. In the presence of a very similar total CEF splitting with YbFe 2Zn 20, the ground state of YbCo 2Zn 20 is close to a Kondo state with degeneracy N = 2 and a much lower TK ~ 2 K. Upon Comore » substitution, the coherence temperature of YbFe 2Zn 20 is suppressed, accompanied by an emerging Schottky-like feature in speci c heat associated with the thermal depopulation of CEF levels upon cooling. For 0.4 ≲ x ≲ 0.9, the ground state remains roughly the same which can be qualitatively understood by Kondo effect in the presence of CEF splitting. There is no clear indication of Kondo coherence observable in resistivity within this substitution range down to 500 mK. The coherence re-appears at around x≳ 0.9 and the coherence temperature increases with higher Co concentration levels.« less

  9. Extremely High Phosphate Sorption Capacity in Cu-Pb-Zn Mine Tailings

    PubMed Central

    Huang, Longbin; Li, Xiaofang; Nguyen, Tuan A. H.

    2015-01-01

    Elevated inorganic phosphate (Pi) concentrations in pore water of amended tailings under direct revegetation may cause toxicity in some native woody species but not native forbs or herb species, all of which are key constituents in target native plant communities for phytostabilizing base metal mine tailings. As a result, Pi sorption capacity has been quantified by a conventional batch procedure in three types of base metal mine tailings sampled from two copper (Cu)-lead (Pb)-zinc (Zn) mines, as the basis for Pi-fertiliser addition. It was found that the Pi-sorption capacity in the tailings and local soil was extremely high, far higher than highly weathered agricultural soils in literature, but similar to those of volcanic ash soils. The Langmuir P-sorption maximum was up to 7.72, 4.12, 4.02 and 3.62 mg P g-1 tailings, in the fresh tailings of mixed Cu-Pb-Zn streams (MIMTD7), the weathered tailings of mixed Cu-Pb-Zn streams (MIMTD5), EHM-TD (fresh Cu-stream, high magnetite content) and local soil (weathered shale and schist), respectively. Physicochemical factors highly correlated with the high Pi-sorption in the tailings were fine particle distribution, oxalate and dithionite-citrate-bicarbonate extractable Fe (FeO and Fed), oxalate-extractable Al and Mn, and the levels of soluble Cd and Zn, and total S and Fe. Large amounts of amorphous Fe oxides and oxyhydroxides may have been formed from the oxidation of pyritic materials and redox cycles of Fe-minerals (such as pyrite (FeS2), ankerite (Ca(Fe Mg)(CO3)2 and siderite (FeCO3), as indicated by the extractable FeO values. The likely formation of sparingly soluble Zn-phosphate in the Pb-Zn tailings containing high levels of Zn (from sphalerite ((Zn,Fe)S, ZnS, (Zn,Cd)S)) may substantially lower soluble Zn levels in the tailings through high rates of Pi-fertiliser addition. As a result, the possibility of P-toxicity in native plant species caused by the addition of soluble phosphate fertilizers would be minimal. PMID

  10. High-performance solar-blind ultraviolet photodetector based on mixed-phase ZnMgO thin film

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

    Fan, M. M.; State Key Laboratory of Luminescence and Applications, Changchun Institute of Optics, Fine Mechanics and Physics, Chinese Academy of Sciences, No. 3888 Dongnanhu Road, 130033 Changchun; Liu, K. W., E-mail: liukw@ciomp.ac.cn, E-mail: shendz@ciomp.ac.cn

    High Mg content mixed-phase Zn{sub 0.38}Mg{sub 0.62}O was deposited on a-face sapphire by plasma-assisted molecular beam epitaxy, based on which a metal-semiconductor-metal solar-blind ultraviolet (UV) photodetector was fabricated. The dark current is only 0.25 pA at 5 V, which is much lower than that of the reported mixed-phase ZnMgO photodetectors. More interestingly, different from the other mixed-phase ZnMgO photodetectors containing two photoresponse bands, this device shows only one response peak and its −3 dB cut-off wavelength is around 275 nm. At 10 V, the peak responsivity is as high as 1.664 A/W at 260 nm, corresponding to an internal gain of ∼8. The internal gain is mainlymore » ascribed to the interface states at the grain boundaries acting as trapping centers of photogenerated holes. In view of the advantages of mixed-phase ZnMgO photodetectors over single-phase ZnMgO photodetectors, including easy fabrication, high responsivity, and low dark current, our findings are anticipated to pave a new way for the development of ZnMgO solar-blind UV photodetectors.« less

  11. Melting behavior of (Mg,Fe)O solid solutions at high pressure

    NASA Astrophysics Data System (ADS)

    Zhang, Li; Fei, Yingwei

    2008-07-01

    High pressure melting of (Mg,Fe)O ferropericlase, the second most abundant mineral in the Earth's lower mantle, is of fundamental importance for understanding the chemical differentiation, geodynamics and thermal evolution of the Earth's interior. We report the first systematic experimental study of melting behavior in the MgO-FeO system up to 3600 K and 7 GPa, indicating the ideal solution between solid and liquid (Mg,Fe)O in the MgO-rich portion. The zero pressure melting slope of MgO is ~221 K/GPa derived from our resistance heating measurements, which is several times higher than the value from the previous measurements in a CO2-laser heated diamond anvil cell, but consistent with the theoretically predicted melting curves. Our results combined with the previous first-principles simulations suggest that the melting temperature of MgO-rich (Mg,Fe)O is significantly higher than the geotherm through the lower mantle and this would place an upper bound on the solidus of the lower mantle.

  12. Effects of phase transformation on the microstructures and magnetostriction of Fe-Ga and Fe-Ga-Zn ferromagnetic shape memory alloys

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

    Lin, Yin-Chih, E-mail: lin3312@cc.kuas.edu.tw; Lin, Chien-Feng

    2015-05-07

    The phase transformation and magnetostriction of bulk Fe{sub 73}Ga{sub 27} and Fe{sub 73}Ga{sub 18}Zn{sub 9} (at. %) ferromagnetic shape memory alloys (FSMs) were investigated by transmission electron microscopy (TEM), x-ray diffraction (XRD), and a magnetostrictive-meter setup. For the Fe{sub 73}Ga{sub 27} FSM alloy solution treated at 1100 °C for 4 h and quenched in ice brine, the antiphase boundary segments of the D0{sub 3} domain were observed in the A2 (disordered) matrix, and the Fe{sub 73}Ga{sub 27} FSM alloy had an optimal magnetostriction (λ{sub ‖}{sup s }= 71 × 10{sup −6} and λ{sub ⊥}{sup s }= −31 × 10{sup −6}). In Fe{sub 73}Ga{sub 27} FSM alloy as-quenched, aged at 700 °C formore » 24 h, and furnace cooled, D0{sub 3} nanoclusters underwent phase transformation to an intermediate tetragonal phase (i.e., L1{sub 0}-like martensite) via Bain distortion, and finally L1{sub 2} (Fe{sub 3}Ga) structures precipitated, as observed by TEM and XRD. The L1{sub 0}-like martensite and L1{sub 2} phases in the aged Fe{sub 73}Ga{sub 27} FSM alloy drastically decreased the magnetostriction from positive to negative (λ{sub ‖}{sup s }= −20 × 10{sup −6} and λ{sub ⊥}{sup s }= −8 × 10{sup −6}). However, in Fe{sub 73}Ga{sub 18}Zn{sub 9} FSM alloy as-quenched and aged, the phase transformation of D0{sub 3} to an intermediate tetragonal martensite phase and precipitation of L1{sub 2} structures were not found. The results indicate that the aged Fe{sub 73}Ga{sub 18}Zn{sub 9} FSM alloy maintained stable magnetostriction (λ{sub ‖}{sup s }= 36 × 10{sup −6} and λ{sub ⊥}{sup s }= −31 × 10{sup −6}). Adding Zn can improve the ferromagnetic shape memory effect of aged Fe{sub 73}Ga{sub 18}Zn{sub 9} alloy, which may be useful in application of the alloy in high temperature environments.« less

  13. Effects of Fe-Enrichment on the Equation of State and Stability of (Mg,Fe)SiO3 Perovskite and Post-Perovskite

    NASA Astrophysics Data System (ADS)

    Dorfman, S. M.; Holl, C. M.; Meng, Y.; Prakapenka, V.; Duffy, T. S.

    2010-12-01

    Fe-enrichment in the deep lower mantle has been proposed as an explanation for seismic anomalies such as large low shear velocity provinces (LLSVPs) and ultralow velocity zones (ULVZs). In order to resolve the effect of Fe on the stability and equation of state of the lower mantle’s dominant constituent, (Mg,Fe)SiO3 perovskite, we have studied Fe-rich natural orthopyroxenes, (Mg0.61Fe0.37Ca0.02)SiO3 and (Mg0.25Fe0.70Ca0.05)SiO3 (compositions determined by microprobe analysis), at lower mantle P-T conditions. Pyroxene starting materials were mixed with Au (pressure calibrant and laser absorber) and loaded with NaCl or Ne (pressure medium and thermal insulator) in a symmetric diamond anvil cell. X-ray diffraction experiments at pressures up to 122 GPa with in-situ laser heating were performed at the GSECARS (13-ID-D) and HPCAT (16-ID-B) sectors of the Advanced Photon Source. Heating samples to 2000 K produced single-phase orthorhombic GdFeO3-type perovskite at 63 GPa for the Mg# 61 composition and at 72 GPa for the Mg# 25 composition. At lower pressures (56 GPa for Mg# 61, 67 GPa for Mg# 25), heating both compositions resulted in a mixture of perovskite, SiO2 and (Mg,Fe)O. These measurements provide new constraints on the dependence of (Mg,Fe)SiO3 perovskite stability on pressure and composition. Upon further compression to 93 GPa and higher pressures with laser heating, Mg# 25 perovskite transformed to a two-phase mixture of perovskite and post-perovskite. This is consistent with previous findings that Fe substitution destabilizes (Mg,Fe)SiO3 perovskite relative to (Mg,Fe)SiO3 post-perovskite (Mao et al. 2004, Caracas and Cohen 2005). The bulk modulus at 80 GPa (K80) is ~550 GPa for both Fe-rich perovskites, comparable to values measured for MgSiO3 perovskite (Lundin et al. 2008). However, the volume of Fe-rich perovskites increases linearly with Fe-content. The (Mg0.25Fe0.70Ca0.05)SiO3 perovskite is 3% greater at 80 GPa than V80 for the Mg end

  14. Study of sintering on Mg-Zn-Ca alloy system

    NASA Astrophysics Data System (ADS)

    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.

  15. Dielectric relaxation behavior and impedance studies of Cu2+ ion doped Mg - Zn spinel nanoferrites

    NASA Astrophysics Data System (ADS)

    Choudhary, Pankaj; Varshney, Dinesh

    2018-03-01

    Cu2+ substituted Mg - Zn nanoferrites is synthesized by low temperature fired sol gel auto combustion method. The spinel nature of nanoferrites was confirmed by lab x-ray technique. Williamson - Hall (W-H) analysis estimate the average crystallite size (22.25-29.19 ± 3 nm) and micro strain induced Mg0.5Zn0.5-xCuxFe2O4 (0.0 ≤ x ≤ 0.5). Raman scattering measurements confirm presence of four active phonon modes. Red shift is observed with enhanced Cu concentration. Dielectric parameters exhibit a non - monotonous dispersion with Cu concentration and interpreted with the support of hopping mechanism and Maxwell-Wagner type of interfacial polarization. The ac conductivity of nanoferrites increases with raising the frequency. Complex electrical modulus reveals a non - Debye type of dielectric relaxation present in nanoferrites. Reactive impedance (Z″) detected an anomalous behavior and is related with resonance effect. Complex impedance demonstrates one semicircle corresponding to the intergrain (grain boundary) resistance and also explains conducting nature of nanoferrites. For x = 0.2, a large semicircle is observed revealing the ohmic nature (minimum potential drop at electrode surface). Dielectric properties were improved for nanoferrites with x = 0.2 and is due to high dielectric constant, conductivity and minimum loss value (∼0.009) at 1 MHz.

  16. Synthesis of ZnFe2O4/SiO2 composites derived from a diatomite template.

    PubMed

    Liu, Zhaoting; Fan, Tongxiang; Zhou, Han; Zhang, Di; Gong, Xiaolu; Guo, Qixin; Ogawa, Hiroshi

    2007-03-01

    A novel porous ZnFe2O4/SiO2 composite product has been generated with a template-directed assembly method from porous diatomite under different synthesis conditions, such as precursor concentrations (metallic nitrates), calcination temperature and diatomite type. The phase composition and morphology of all the materials were examined by x-ray diffraction (XRD), field emission scanning electron microscopy (FESEM) and transmission electron microscopy (TEM). The results indicated that an inherited hierarchical porous structure from the diatomite template can be obtained, and the synthesis conditions were found to have clear effects on the formation of the ZnFe2O4/SiO2 composite. The ideal composite of ZnFe2O4/SiO2 can be obtained through optimization of diatomite template type, precursor solution and calcination temperature. Furthermore, the adsorption abilities of two types of diatomites were analyzed in detail using FTIR spectra and nitrogen adsorption measurements etc, which proved that A-diatomite (Shengzhou-diatomite) is better than B-diatomite (Changbai-diatomite) on the aspect of adsorbing Zn and Fe ions, and of forming the ZnFe2O4.

  17. Electronic structures of filled tetrahedral semiconductors LiMgN and LiZnN: conduction band distortion

    NASA Astrophysics Data System (ADS)

    Yu, L. H.; Yao, K. L.; Liu, Z. L.

    2004-12-01

    The band structures of the filled tetrahedral semiconductors LiMgN and LiZnN, viewed as the zinc-blende (MgN) - and (ZnN) - lattices partially filled with He-like Li + ion interstitials, were studied using the full-potential linearized augmented plane wave method (FP-LAPW) within density functional theory. The conduction band distortions of LiMgN and LiZnN, compared to their “parent” zinc-blende analog AlN and GaN, are discussed. It was found that the insertion of Li + ions at the interstitial sites near the cation or anion pushes the conduction band minimum of the X point in the Brillouin zone upward, relative to that of the Γ point, for both (MgN) - and (ZnN) - lattices (the valence band maximum is at Γ for AlN, GaN, LiMgN, and LiZnN), which provides a method to convert a zinc-blende indirect gap semiconductor into a direct gap material, but the conduction band distortion of the β phase (Li + near the cation) is quite stronger than that of the α phase (Li + near the anion). The total energy calculations show the α phase to be more stable than the β phase for both LiMgN and LiZnN. The Li-N and Mg-N bonds exhibit a strong ionic character, whereas the Zn-N bond has a strong covalent character in LiMgN and LiZnN.

  18. Enhanced Photocatalytic Activity of Two-Pot-Synthesized BiFeO3-ZnFe2O4 Heterojunction Nanocomposite

    NASA Astrophysics Data System (ADS)

    Ghasemi, A.; Hasheminiasari, M.; Masoudpanah, S. M.; Safizade, B.

    2018-04-01

    BiFeO3-ZnFe2O4 heterojunction nanocomposites have been produced by a chemical synthesis method using one- and two-pot approaches. X-ray diffraction patterns of as-calcined samples indicated formation of pure zinc ferrite (ZnFe2O4) and bismuth ferrite (BiFeO3) phases, each retaining its crystal structure. Diffuse reflectance spectrometry was applied to calculate the optical bandgap of the photocatalysts, revealing values in the range from 2.03 eV to 2.17 eV, respectively. The maximum photodegradation of methylene blue of about 97% was achieved using two-pot-synthesized photocatalyst after 120 min of visible-light irradiation due to the higher probability of charge separation of photogenerated electron-hole pairs in the heterojunction structure. Photoluminescence spectra showed lower emission intensity of two-pot-synthesized photocatalyst, due to its lower recombination rate originating from greater charge separation.

  19. Abnormal variation of band gap in Zn doped Bi{sub 0.9}La{sub 0.1}FeO{sub 3} nanoparticles: Role of Fe-O-Fe bond angle and Fe-O bond anisotropy

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

    Xu, Xunling; Liu, Weifang, E-mail: wfliu@tju.edu.cn, E-mail: shouyu.wang@yahoo.com; Wu, Ping

    2015-07-27

    Bi{sub 0.9}La{sub 0.1}FeO{sub 3} (BLFO) and Bi{sub 0.9}La{sub 0.1}Fe{sub 0.99}Zn{sub 0.01}O{sub 3} (BLFZO) nanoparticles were prepared via a sol-gel method. The oxygen vacancies and holes increase with Zn doping analyzed through X-ray photoelectron spectroscopy, which could contribute to the increase of leakage current density. However, with the increase of the defects (oxygen vacancies and holes), the band gap of BLFZO also is increased. To explain the abnormal phenomenon, the bandwidth of occupied and unoccupied bands was analyzed based on the structural symmetry driven by the Fe-O-Fe bond angle and Fe-O bond anisotropy.

  20. The accumulation of elements in plants growing spontaneously on small heaps left by the historical Zn-Pb ore mining.

    PubMed

    Stefanowicz, Anna M; Stanek, Małgorzata; Woch, Marcin W; Kapusta, Paweł

    2016-04-01

    The study evaluated the levels of nine metals, namely Ca, Cd, Fe, K, Mg, Mn, Pb, Tl, and Zn, in soils and tissues of ten plant species growing spontaneously on heaps left by historical mining for Zn-Pb ores. The concentrations of Cd, Pb, Tl, and Zn in heap soils were much higher than in control soils. Plants growing on heaps accumulated excessive amounts of these elements in tissues, on average 1.3-52 mg Cd kg(-1), 9.4-254 mg Pb kg(-1), 0.06-23 mg Tl kg(-1) and 134-1479 mg Zn kg(-1) in comparison to 0.5-1.1 mg Cd kg(-1), 2.1-11 mg Pb kg(-1), 0.02-0.06 mg Tl kg(-1), and 23-124 mg Zn kg(-1) in control plants. The highest concentrations of Cd, Pb, and Zn were found in the roots of Euphorbia cyparissias, Fragaria vesca, and Potentilla arenaria, and Tl in Plantago lanceolata. Many species growing on heaps were enriched in K and Mg, and depleted in Ca, Fe, and Mn. The concentrations of all elements in plant tissues were dependent on species, organ (root vs. shoot), and species-organ interactions. Average concentrations of Ca, K, and Mg were generally higher in shoots than in roots or similar in the two organs, whereas Cd, Fe, Pb, Tl, and Zn were accumulated predominantly in the roots. Our results imply that heaps left by historical mining for Zn-Pb ores may pose a potential threat to the environment and human health.

  1. Viscosity Measurements of SiO2-"FeO"-MgO System in Equilibrium with Metallic Fe

    NASA Astrophysics Data System (ADS)

    Chen, Mao; Raghunath, Sreekanth; Zhao, Baojun

    2014-01-01

    The present study delivers the measurements of viscosities in the SiO2-"FeO"-MgO system in equilibrium with metallic Fe. The rotational spindle technique was used for the measurements at the temperature range of 1523 K to 1773 K (1250 °C to 1500 °C). Molybdenum crucibles and spindles were employed in all measurements. The viscosity measurements were carried out at 31 to 47 mol pct SiO2 and up to 18.8 mol pct MgO. Analysis of the quenched sample by Electron probe X-ray microanalysis after the viscosity measurement enables the composition and microstructure of the slag to be directly linked with the viscosity. The replacement of "FeO" by MgO was found to increase viscosity and activation energy of the SiO2-"FeO"-MgO slags. The modified Quasi-chemical Viscosity Model was further optimized in this system based on the current viscosity measurements.

  2. Modeling (Mg,Fe)O creep at Lowermost Mantle conditions

    NASA Astrophysics Data System (ADS)

    Reali, R.; Jackson, J. M.; Van Orman, J. A.; Carrez, P.; Cordier, P.

    2017-12-01

    The viscosity of the lower mantle results from the rheological behavior of its two main constituent minerals, aluminous (Mg,Fe)SiO3 bridgmanite and (Mg,Fe)O ferropericlase. Understanding the rheology of lower mantle aggregates is of primary importance in geophysics and it is a challenging task, due to the extreme time-varying conditions to which such aggregates are subjected.Here we focus on the creep behavior of (Mg,Fe)O at the bottom of the lower mantle, where the presence of thermo-chemical anomalies such as ultralow-velocity zones (ULVZ) can significantly alter the composition and therefore the properties of this region. Two different iron concentrations of (Mg1-xFex)O are considered: one mirroring the average composition of ferropericlase throughout most of the lower mantle (x = 0.20) and another representing a candidate component of ULVZs near the base of the mantle (x = 0.84) [1]. The investigated pressure-temperature conditions span from 120 GPa and 2800 K, corresponding to the geotherm at this depth, to core-mantle conditions of 135 GPa and 3800 K.In this study, dislocation creep of (Mg,Fe)O is investigated by Dislocation Dynamics (DD) simulations, a modeling tool which considers the collective motion and interactions of dislocations. To model their behavior, a 2.5 Dimensional Dislocation Dynamics approach (2.5D-DD) is employed. Within this method, both glide and climb mechanisms can be taken into account, and the interplay of these features results in a steady-state condition. This allows the retrieval of the creep strain rates at different temperatures, pressures, applied stresses and iron concentrations across the (Mg,Fe)O solid solution, providing information on the viscosity for these materials. This numerical approach has been validated at ambient conditions, where it was benchmarked with respect to experimental data on MgO [2]. [1] J.K. Wicks, J.M. Jackson, W. Sturhahn and D. Zhang, GRL, 44, 2017.[2] R. Reali, F. Boioli, K. Gouriet, P. Carrez, B

  3. Implementation of ZnO/ZnMgO strained-layer superlattice for ZnO heteroepitaxial growth on sapphire

    NASA Astrophysics Data System (ADS)

    Petukhov, Vladimir; Bakin, Andrey; Tsiaoussis, Ioannis; Rothman, Johan; Ivanov, Sergey; Stoemenos, John; Waag, Andreas

    2011-05-01

    The main challenge in fabrication of ZnO-based devices is the absence of reliable p-type material. This is mostly caused by insufficient crystalline quality of the material and not well-enough-developed native point defect control of ZnO. At present high-quality ZnO wafers are still expensive and ZnO heteroepitaxial layers on sapphire are the most reasonable alternative to homoepitaxial layers. But it is still necessary to improve the crystalline quality of the heteroepitaxial layers. One of the approaches to reduce defect density in heteroepitaxial layers is to introduce a strained-layer superlattice (SL) that could stop dislocation propagation from the substrate-layer interface. In the present paper we have employed fifteen periods of a highly strained SL structure. The structure was grown on a conventional double buffer layer comprising of high-temperature MgO/low-temperature ZnO on sapphire. The influence of the SLs on the properties of the heteroepitaxial ZnO layers is investigated. Electrical measurements of the structure with SL revealed very high values of the carrier mobility up to 210 cm2/Vs at room temperature. Structural characterization of the obtained samples showed that the dislocation density in the following ZnO layer was not reduced. The high mobility signal appears to come from the SL structure or the SL/ZnO interface.

  4. Auger electron diffraction study of the growth of Fe(001) films on ZnSe(001)

    NASA Astrophysics Data System (ADS)

    Jonker, B. T.; Prinz, G. A.

    1991-03-01

    The growth of Fe films on ZnSe(001) epilayers and bulk GaAs(001) substrates has been studied to determine the mode of film growth, the formation of the interface, and the structure of the overlayer at the 1-10 monolayer level. Auger electron diffraction (AED), x-ray photoelectron spectroscopy (XPS), and reflection high-energy electron diffraction data are obtained for incremental deposition of the Fe(001) overlayer. The coverage dependence of the AED forward scattering peaks reveals a predominantly layer-by-layer mode of film growth at 175 °C on ZnSe, while a more three-dimensional growth mode occurs on the oxide-desorbed GaAs(001) substrate. XPS studies of the semiconductor 3d levels indicate that the Fe/ZnSe interface is less reactive than the Fe/GaAs interface.

  5. Mechanochemical destruction of DDTs with Fe-Zn bimetal in a high-energy planetary ball mill.

    PubMed

    Sui, Hong; Rong, Yuzhou; Song, Jing; Zhang, Dongge; Li, Haibo; Wu, Peng; Shen, Yangyang; Huang, Yujuan

    2018-01-15

    Mechanochemical destruction has been proposed as a promising, non-combustion technology for the disposal of toxic, halogenated, organic pollutants. In the study presented, additives including Fe, Zn, Fe-Zn bimetal, CaO and Fe 2 O 3 were tested for their effectiveness to remove DDTs by MC. The results showed that Fe-Zn bimetal was the most efficient additive, with 98% of DDTs removed after 4h. The Fe-Zn mass ratio was optimized to avoid possible spontaneous combustion of the ground sample during subsample collection. Inorganic water-soluble chloride in the ground sample increased by 91% after 4h of grinding, which indicated dechlorination during destruction of DDTs. In addition, relationships were established between the rate constant and the rotation speed or the charge ratio. Discrete Element Method (DEM) modeling was used to simulate the motion of the grinding ball and calculate both total impact energy and normal impact energy. The latter expressed a stronger, linear correlation with the rate constant. Therefore, normal impact energy is proposed to be the main driving force in the MC destruction of DDTs. Copyright © 2017 Elsevier B.V. All rights reserved.

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

    PubMed Central

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

    2016-01-01

    In clinical practice, tumor recurrence and metastasis after orthopedic prosthesis implantation is an intensely troublesome matter. Therefore, to develop implant materials with antitumor property is extremely necessary and meaningful. Magnesium (Mg) alloys possess superb biocompatibility, mechanical property and biodegradability in orthopedic applications. However, whether they possess antitumor property had seldom been reported. In recent years, it showed that zinc (Zn) not only promote the osteogenic activity but also exhibit good antitumor property. In our present study, Zn was selected as an alloying element for the Mg-1Ca-0.5Sr alloy to develop a multifunctional material with antitumor property. We investigated the influence of the Mg-1Ca-0.5Sr-xZn (x = 0, 2, 4, 6 wt%) alloys extracts on the proliferation rate, cell apoptosis, migration and invasion of the U2OS cell line. Our results show that Zn containing Mg alloys extracts inhibit the cell proliferation by alteration the cell cycle and inducing cell apoptosis via the activation of the mitochondria pathway. The cell migration and invasion property were also suppressed by the activation of MAPK (mitogen-activated protein kinase) pathway. Our work suggests that the Mg-1Ca-0.5Sr-6Zn alloy is expected to be a promising orthopedic implant in osteosarcoma limb-salvage surgery for avoiding tumor recurrence and metastasis. PMID:26907515

  7. Microstructural Development in a Laser-Remelted Al-Zn-Si-Mg Coating.

    PubMed

    Godec, M; Podgornik, B; Nolan, D

    2017-11-23

    In the last five decades, there has been intense development in the field of Zn-Al galvanic coating modification. Recently, Mg was added to improve corrosion properties. Further improvements to the coating are possible with additional laser surface treatment. In this article, we focus on remelting the Al-Zn-Mg-Si layer, using a diode laser with a wide-beam format, concentrating on the microstructure development during extreme cooling rates. Laser remelting of the Al-Zn-Mg-Si coating and rapid self-quenching produces a finer grain size, and a microstructure that is substantially refined and homogenized with respect to the phase distribution. Using EBSD results, we are able to understand microstructure modification. The laser modified coating has some porosity and intergranular cracking which are difficult to avoid, however this does not seem to be detrimental to mechanical properties, such as ductility on bending. The newly developed technology has a high potential for improved corrosion performance due to highly refined microstructure.

  8. Synthesis of magnetic Bi2O2CO3/ZnFe2O4 composite with improved photocatalytic activity and easy recyclability

    NASA Astrophysics Data System (ADS)

    Liu, Yumin; Ren, Hao; Lv, Hua; Guang, Jing; Cao, Yafei

    2018-03-01

    Magnetic Bi2O2CO3/ZnFe2O4 heterojunction photocatalysts with varying content of ZnFe2O4 were constructed by modifying Bi2O2CO3 nanosheets with mesoporous ZnFe2O4 nanoparticles. The photoactivity of the products was investigated by decomposing RhodamineB (RhB) and it was found that the photoactivity of Bi2O2CO3/ZnFe2O4 composite was closely related to the loading amount of ZnFe2O4. Under simulant sunlight irradiation, the optimum photoactivity of Bi2O2CO3/ZnFe2O4 composite was almost 2.3 and 2.1 times higher than that by bare ZnFe2O4 and Bi2O2CO3, respectively. The improved photoactivity resulted from the synergistic effect of Bi2O2CO3 and ZnFe2O4, which not only extended the photoabsorption region but also significantly facilitated the interfacial charge transfer. Besides the high photocatalytic performance, Bi2O2CO3/ZnFe2O4 composite also exhibited excellent stable and recycling properties, which enabled it have great potential in a long-term practical use.

  9. Optical and superparamagnetic behavior of ZnFe2O4 nanoparticles

    NASA Astrophysics Data System (ADS)

    Lal, Ganesh; Punia, Khushboo; Dolia, S. N.; Kumar, Sudhish

    2018-05-01

    Nanoparticles of zinc ferrite have been synthesized using a low temperature citrate sol-gel route and characterized by powder X-ray diffraction (XRD), Raman & UV-Vis-NIR spectroscopic and SQUID magnetometry measurements. Analysis of XRD pattern and Raman spectrum confirmed that the synthesized ZnFe2O4 sample crystallizes in single phase fcc spinel ferrite structure and the average particle size of nanoparticles is estimated to 24nm. Optical absorption study shows that maximum photo absorption take place in the visible band and peaking in UV band at 206nm and the band gap energy is estimated to Eg = 2.1eV. Zero Field Cooled (ZFC) and Field Cooled (FC) modes of magnetization down to 5K and in fields up to 20kOe shows that ZnFe2O4 nanoparticles exhibits superparamagnetism with high magneto-crystalline anisotropy and high magnetization. Small difference of 9K between the separation temperature TS=˜30K and blocking temperature TB= 21K are suggestive of the formation of ferromagnetic clusters and a narrow particle size distribution of the nanoparticles in superparamagnetic ZnFe2O4 nanoparticles.

  10. Effect of thermal annealing on the structure and magnetism of Fe-doped ZnO nanocrystals synthesized by solid state reaction

    NASA Astrophysics Data System (ADS)

    Wang, Dong; Chen, Z. Q.; Wang, D. D.; Gong, J.; Cao, C. Y.; Tang, Z.; Huang, L. R.

    2010-11-01

    High purity Fe 2O 3/ZnO nanocomposites were annealed in air at different temperatures between 100 and 1200 °C to get Fe-doped ZnO nanocrystals. The structure and grain size of the Fe 2O 3/ZnO nanocomposites were investigated by X-ray diffraction 2θ scans. Annealing induces an increase of the grain size from 25 to 195 nm and appearance of franklinite phase of ZnFe 2O 4. Positron annihilation measurements reveal large number of vacancy defects in the interface region of the Fe 2O 3/ZnO nanocomposites, and they are gradually recovered with increasing annealing temperature. After annealing at temperatures higher than 1000 °C, the number of vacancies decreases to the lower detection limit of positrons. Room temperature ferromagnetism can be observed in Fe-doped ZnO nanocrystals using physical properties measurement system. The ferromagnetism remains after annealing up to 1000 °C, suggesting that it is not related with the interfacial defects.

  11. Composition dependence of spin transition in (Mg,Fe)SiO 3 bridgmanite

    DOE PAGES

    Dorfman, Susannah M.; Badro, James; Rueff, Jean -Pascal; ...

    2015-10-01

    Spin transitions in (Mg,Fe)SiO 3 bridgmanite have important implications for the chemistry and dynamics of Earth’s lower mantle, but have been complex to characterize in experiments. We examine the spin state of Fe in highly Fe-enriched bridgmanite synthesized from enstatites with measured compositions (Mg 0.61Fe 0.38Ca 0.01)SiO 3 and (Mg 0.25Fe 0.74Ca 0.01)SiO 3. Bridgmanite was synthesized at 78-88 GPa and 1800-2400 K and X-ray emission spectra were measured on decompression to 1 bar (both compositions) and compression to 126 GPa ((Mg 0.61Fe 0.38Ca 0.01)SiO 3 only) without additional laser heating. Observed spectra confirm that Fe in these bridgmanites ismore » dominantly high spin in the lower mantle. However, the total spin moment begins to decrease at ~50 GPa in the 74% FeSiO 3 composition. Lastly, these results support density functional theory predictions of a lower spin transition pressure in highly Fe-enriched bridgmanite and potentially explain the high solubility of FeSiO 3 in bridgmanite at pressures corresponding to Earth’s deep lower mantle.« less

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

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

    Peng, Chao; State Key Laboratory of Silicate Materials for Architectures, Wuhan University of Technology, Wuhan 430070; Dai, Jing

    2015-05-15

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

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

    NASA Astrophysics Data System (ADS)

    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.

  14. Preparation of Zn(BH4)2 and diborane and hydrogen release properties of Zn(BH4)2+xMgH2 (x=1, 5, 10, and 15)

    NASA Astrophysics Data System (ADS)

    Kwak, Young Jun; Kwon, Sung Nam; Song, Myoung Youp

    2015-09-01

    Zn(BH4)2 was prepared by milling ZnCl2 and NaBH4 in a planetary ball mill under Ar atmosphere, and Zn(BH4)2+xMgH2 (x=1, 5, 10, and 15) samples were prepared. Diborane (B2H6) and hydrogen release characteristics of the Zn(BH4)2 and Zn(BH4)2+xMgH2 samples were studied. The samples synthesized by milling ZnCl2 and NaBH4 contained Zn(BH4)2 and NaCl, together with small amounts of ZnCl2 and NaBH4. We designated these samples as Zn(BH4)2(+NaCl). The weight loss up to 400 °C of the Zn(BH4)2(+NaCl) sample synthesized by milling 4 h was 11.2 wt%. FT-IR analysis showed that Zn(BH4)2 was formed in the Zn(BH4)2(+NaCl) samples. MgH2 was also milled in a planetary ball mill, and mixed with the Zn(BH4)2(+NaCl) synthesized by milling for 4 h in a mortar and pestle. The weight loss up to 400 °C of Zn(BH4)2(+NaCl)+MgH2 was 8.2 wt%, corresponding to the weight % of diborane and hydrogen released from the Zn(BH4)2(+NaCl)+MgH2 sample, with respect to the sample weight. DTA results of Zn(BH4)2(+NaCl)+xMgH2 showed that the decomposition peak of Zn(BH4)2 was at about 61 °C, and that of MgH2 was at about 370-389 °C.

  15. Adsorption of heavy metals from aqueous solutions by Mg-Al-Zn mingled oxides adsorbent.

    PubMed

    El-Sayed, Mona; Eshaq, Gh; ElMetwally, A E

    2016-10-01

    In our study, Mg-Al-Zn mingled oxides were prepared by the co-precipitation method. The structure, composition, morphology and thermal stability of the synthesized Mg-Al-Zn mingled oxides were analyzed by powder X-ray diffraction, Fourier transform infrared spectrometry, N 2 physisorption, scanning electron microscopy, differential scanning calorimetry and thermogravimetry. Batch experiments were performed to study the adsorption behavior of cobalt(II) and nickel(II) as a function of pH, contact time, initial metal ion concentration, and adsorbent dose. The maximum adsorption capacity of Mg-Al-Zn mingled oxides for cobalt and nickel metal ions was 116.7 mg g -1 , and 70.4 mg g -1 , respectively. The experimental data were analyzed using pseudo-first- and pseudo-second-order kinetic models in linear and nonlinear regression analysis. The kinetic studies showed that the adsorption process could be described by the pseudo-second-order kinetic model. Experimental equilibrium data were well represented by Langmuir and Freundlich isotherm models. Also, the maximum monolayer capacity, q max , obtained was 113.8 mg g -1 , and 79.4 mg g -1 for Co(II), and Ni(II), respectively. Our results showed that Mg-Al-Zn mingled oxides can be used as an efficient adsorbent material for removal of heavy metals from industrial wastewater samples.

  16. Synthesis of Fe-based core@ZnO shell nanopowders by laser pyrolysis for biomedical applications

    NASA Astrophysics Data System (ADS)

    Gavrila-Florescu, Lavinia; Dumitrache, Florian; Balas, Mihaela; Fleaca, Claudiu Teodor; Scarisoreanu, Monica; Morjan, Iuliana P.; Dutu, Elena; Ilie, Alina; Banici, Ana-Maria; Locovei, Claudiu; Prodan, Gabriel

    2017-12-01

    Nano-sized Fe-based (metallic, carbidic and/or oxidic) core@ZnO shell particles have been successfully synthesized in one step by the laser-induced pyrolysis method in an oxygen-deficient environment. The specific precursors were separately introduced through a three concentric nozzles injector: Fe(CO)5 vapors carried by C2H4 sensitizer (central flow), Zn(C2H5)2 vapors carried and diluted with Ar (middle annular coflow) and Ar containing low amount of O2 (external flow). Keeping constant the ethylene-carried Fe(CO)5 and O2 flows, while diminishing the Zn(C2H5)2 flow, we observed an increase of the Fe/Zn ratio in the resulted nanopowders. Also, using the same metal precursor flows, a nonlinear correlation between O2 external flow and nanocomposite atomic oxygen content is evidenced, indicating a possible interference of supplementary oxidation after air exposure. However, the lowest oxygen content along with metallic zinc was found in the sample synthesized in the most oxygen-deficient environment. Transmission electron microscopy (TEM), high-resolution electron microscopy (HRTEM), selected area electron diffraction (SAED), X-ray diffraction (XRD), energy-dispersive X-ray analysis (EDS), X-ray photoelectron spectroscopy (XPS) and magnetic analyses were performed for a comprehensive characterization. The aqueous Fe-based@ZnO nanoparticles (NPs) suspensions were prepared using L-Dopa ( l-3,4-dihydroxy-phenylalanine) as stabilizing agent in physiologic media. Also, a biocompatibility in vitro study was performed for PBS (phosphate buffered saline)-dispersed L-Dopa-stabilized Fe-based@ZnO nanoparticles with the best core-shell structural features on both human normal lung fibroblasts and tumoral colorectal cells. Our results proved the ability of these newly synthesized nanostructures to target cancer cells in order to induce cytotoxicity and to exhibit biocompatibility on normal cells for maintaining the proper function of healthy tissue.

  17. Facile synthesis of p-type Zn-doped α-Fe2O3 films for solar water splitting

    NASA Astrophysics Data System (ADS)

    Kuo, Chun-Lin; Hsu, Yu-Kuei; Lin, Yan-Gu

    2014-10-01

    A facile and simple fabrication of Zn-doped α-Fe2O3 thin films as a photocathode for solar hydrogen generation was proposed in this report. Transparent Zn-doped α-Fe2O3 films were prepared by a deposition-annealing (DA) process using nontoxic iron(III) chloride as the Fe precursor and zinc chloride as a acceptor dopant, followed by annealing at 550 °C in air. In terms of the structural examination of as-grown samples, X-ray diffraction analysis demonstrated an increase in the lattice parameters of Zn incorporated in Fe2O3 by substituting Fe in the host lattice. No second phase was determined, indicating no phase separation in the ternary materials. Energy dispersive spectroscopy results demonstrated that Zn, Fe, and O elements existed in the deposits. Furthermore, impedance measurements show that the Zn-dopant serves as an hole acceptor and increases the acceptor concentration by increasing concentration of zinc precursor. Significantly, the photoelectrochemical measurements exhibited remarkable cathodic current, corresponding to the reduction reaction of hydrogen. Finally, the optimum photocurrent can be achieved by controlled variation of the Fe and Zni precursor concentration, annealing conditions, and the number of DA cycles. According to our investigation, the understandings of morphology effect on PEC activity give the blueprint for materials design in the application of solar hydrogen.

  18. Multifunctions of dual Zn/Mg ion co-implanted titanium on osteogenesis, angiogenesis and bacteria inhibition for dental implants.

    PubMed

    Yu, Yiqiang; Jin, Guodong; Xue, Yang; Wang, Donghui; Liu, Xuanyong; Sun, Jiao

    2017-02-01

    In order to improve the osseointegration and long-term survival of dental implants, it is urgent to develop a multifunctional titanium surface which would simultaneously have osteogeneic, angiogeneic and antibacterial properties. In this study, a potential dental implant material-dual Zn/Mg ion co-implanted titanium (Zn/Mg-PIII) was developed via plasma immersion ion implantation (PIII). The Zn/Mg-PIII surfaces were found to promote initial adhesion and spreading of rat bone marrow mesenchymal stem cells (rBMSCs) via the upregulation of the gene expression of integrin α1 and integrin β1. More importantly, it was revealed that Zn/Mg-PIII could increase Zn 2+ and Mg 2+ concentrations in rBMSCs by promoting the influx of Zn 2+ and Mg 2+ and inhibiting the outflow of Zn 2+ , and then could enhance the transcription of Runx2 and the expression of ALP and OCN. Meanwhile, Mg 2+ ions from Zn/Mg-PIII increased Mg 2+ influx by upregulating the expression of MagT1 transporter in human umbilical vein endothelial cells (HUVECs), and then stimulated the transcription of VEGF and KDR via activation of hypoxia inducing factor (HIF)-1α, thus inducing angiogenesis. In addition to this, it was discovered that zinc in Zn/Mg-PIII had certain inhibitory effects on oral anaerobic bacteria (Pg, Fn and Sm). Finally, the Zn/Mg-PIII implants were implanted in rabbit femurs for 4 and 12weeks with Zn-PIII, Mg-PIII and pure titanium as controls. Micro-CT evaluation, sequential fluorescent labeling, histological analysis and push-out test consistently demonstrated that Zn/Mg-PIII implants exhibit superior capacities for enhancing bone formation, angiogenesis and osseointegration, while consequently increasing the bonding strength at bone-implant interfaces. All these results suggest that due to the multiple functions co-produced by zinc and magnesium, rapid osseointegration and sustained biomechanical stability are enhanced by the novel Zn/Mg-PIII implants, which have the potential

  19. Electrically driven deep ultraviolet MgZnO lasers at room temperature

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

    Suja, Mohammad; Bashar, Sunayna Binte; Debnath, Bishwajit

    Semiconductor lasers in the deep ultraviolet (UV) range have numerous potential applications ranging from water purification and medical diagnosis to high-density data storage and flexible displays. Nevertheless, very little success was achieved in the realization of electrically driven deep UV semiconductor lasers to date. Here, we report the fabrication and characterization of deep UV MgZnO semiconductor lasers. These lasers are operated with continuous current mode at room temperature and the shortest wavelength reaches 284 nm. The wide bandgap MgZnO thin films with various Mg mole fractions were grown on c-sapphire substrate using radio-frequency plasma assisted molecular beam epitaxy. Metal-semiconductor-metal (MSM)more » random laser devices were fabricated using lithography and metallization processes. Besides the demonstration of scalable emission wavelength, very low threshold current densities of 29-33 A/cm 2 are achieved. Furthermore, numerical modeling reveals that impact ionization process is responsible for the generation of hole carriers in the MgZnO MSM devices. The interaction of electrons and holes leads to radiative excitonic recombination and subsequent coherent random lasing.« less

  20. Electrically driven deep ultraviolet MgZnO lasers at room temperature

    DOE PAGES

    Suja, Mohammad; Bashar, Sunayna Binte; Debnath, Bishwajit; ...

    2017-06-01

    Semiconductor lasers in the deep ultraviolet (UV) range have numerous potential applications ranging from water purification and medical diagnosis to high-density data storage and flexible displays. Nevertheless, very little success was achieved in the realization of electrically driven deep UV semiconductor lasers to date. Here, we report the fabrication and characterization of deep UV MgZnO semiconductor lasers. These lasers are operated with continuous current mode at room temperature and the shortest wavelength reaches 284 nm. The wide bandgap MgZnO thin films with various Mg mole fractions were grown on c-sapphire substrate using radio-frequency plasma assisted molecular beam epitaxy. Metal-semiconductor-metal (MSM)more » random laser devices were fabricated using lithography and metallization processes. Besides the demonstration of scalable emission wavelength, very low threshold current densities of 29-33 A/cm 2 are achieved. Furthermore, numerical modeling reveals that impact ionization process is responsible for the generation of hole carriers in the MgZnO MSM devices. The interaction of electrons and holes leads to radiative excitonic recombination and subsequent coherent random lasing.« less

  1. Lattice parameters and electronic structure of BeMgZnO quaternary solid solutions: Experiment and theory

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

    Toporkov, M.; Avrutin, V.; Morkoç, H.

    2016-03-07

    Be{sub x}Mg{sub y}Zn{sub 1−x−y}O semiconductor solid solutions are attractive for UV optoelectronics and electronic devices owing to their wide bandgap and capability of lattice-matching to ZnO. In this work, a combined experimental and theoretical study of lattice parameters, bandgaps, and underlying electronic properties, such as changes in band edge wavefunctions in Be{sub x}Mg{sub y}Zn{sub 1−x−y}O thin films, is carried out. Theoretical ab initio calculations predicting structural and electronic properties for the whole compositional range of materials are compared with experimental measurements from samples grown by plasma assisted molecular beam epitaxy on (0001) sapphire substrates. The measured a and c latticemore » parameters for the quaternary alloys Be{sub x}Mg{sub y}Zn{sub 1−x} with x = 0−0.19 and y = 0–0.52 are within 1%–2% of those calculated using generalized gradient approximation to the density functional theory. Additionally, composition independent ternary BeZnO and MgZnO bowing parameters were determined for a and c lattice parameters and the bandgap. The electronic properties were calculated using exchange tuned Heyd-Scuseria-Ernzerhof hybrid functional. The measured optical bandgaps of the quaternary alloys are in good agreement with those predicted by the theory. Strong localization of band edge wavefunctions near oxygen atoms for BeMgZnO alloy in comparison to the bulk ZnO is consistent with large Be-related bandgap bowing of BeZnO and BeMgZnO (6.94 eV). The results in aggregate show that precise control over lattice parameters by tuning the quaternary composition would allow strain control in Be{sub x}Mg{sub y}Zn{sub 1−x−y}O/ZnO heterostructures with possibility to achieve both compressive and tensile strain, where the latter supports formation of two-dimensional electron gas at the interface.« less

  2. Investigation on structural and electrical properties of Fe doped ZnO nanoparticles synthesized by solution combustion method

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

    Ram, Mast, E-mail: mastram1999@yahoo.com; Bala, Kanchan; Sharma, Hakikat

    In the present study, nanoparticles of Fe doped zinc oxide (ZnO) [Zn{sub 1-x}Fe{sub x}O where x=0.0, 0.01, 0.02, 0.03 and 0.05] were prepared by cost effective solution combustion method. The powder X-ray diffractometry confirms the formation of single phase wurtzite structure. Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) were used to investigate the micrsostructure of Fe-doped ZnO nanoparticles. The DC electrical conductivity was found to increase with temperature and measurement was carried out in the temperature range of 300-473K. DC electrical conductivity increases with temperature and decreases with Fe doping concentration.

  3. Ultraviolet photodetector based on Mg{sub x}Zn{sub 1-x}O films using plasma-enhanced atomic layer deposition

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

    Lin, Yu-Chang; Lee, Hsin-Ying, E-mail: hylee@ee.ncku.edu.tw; Lee, Ching-Ting

    2016-01-15

    A plasma-enhanced atomic layer deposition (PE-ALD) system was used to deposit magnesium zinc oxide (Mg{sub x}Zn{sub 1−x}O) films with various Mg content (x). The Mg{sub x}Zn{sub 1-x}O films were applied to metal–semiconductor–metal ultraviolet (UV) photodetectors (MSM-UPDs) as an active layer. The Mg content in the Mg{sub x}Zn{sub 1-x}O films was modulated by adjusting the ZnO–MgO cycle ratios to 15:1, 12:1, and 9:1. Correspondingly, the Mg content in the Mg{sub x}Zn{sub 1-x}O films characterized using an energy dispersive spectrometer was 0.10, 0.13, and 0.16, respectively. The optical bandgap of the Mg{sub x}Zn{sub 1-x}O films increased from 3.56 to 3.66 eV withmore » an increase in Mg content from 0.10 to 0.16. The peak position of photoresponsivity for the Mg{sub x}Zn{sub 1-x}O MSM-UPDs was also shifted from 350 to 340 nm. The UV-visible rejection ratios of the Mg{sub x}Zn{sub 1-x}O MSM-UPDs were higher than 3 orders of magnitude. In addition, excellent detectivity and noise equivalent power for the Mg{sub x}Zn{sub 1-x}O MSM-UPDs were observed at a bias voltage of 5 V. The high performance of the Mg{sub x}Zn{sub 1-x}O MSM-UPDs was achieved by PE-ALD at a low temperature.« less

  4. Effect of Inner Electrode on Reliability of (Zn,Mg)TiO3-Based Multilayer Ceramic Capacitor

    NASA Astrophysics Data System (ADS)

    Lee, Wen‑His; Su, Chi‑Yi; Lee, Ying Chieh; Yang, Jackey; Yang, Tong; PinLin, Shih

    2006-07-01

    In this study, different proportions of silver-palladium alloy acting as the inner electrode were adopted to a (Zn,Mg)TiO3-based multilayer ceramic capacitor (MLCC) sintered at 925 °C for 2 h to evaluate the effect of the inner electrode on reliability. The main results show that the lifetime is inversely proportional to Ag content in the Pd/Ag inner electrode. Ag+1 diffusion into the (Zn,Mg)TiO3-based MLCC during cofiring at 925 °C for 2 h and Ag+1 migration at 140 °C against 200 V are both responsible for the short lifetime of the (Zn,Mg)TiO3-based MLCC, particularly the latter factor. A (Zn,Mg)TiO3-based MLCC with high Ag content in the inner electrode Ag/Pd=99/01 exhibits the shortest lifetime (13 h), and the effect of Ag+1 migration is markedly enhanced when the activation energy of the (Zn,Mg)TiO3 dielectric is greatly lowered due to the excessive formation of oxygen vacancies and the semiconducting Zn2TiO4 phase when Ag+ substitutes for Zn+2 during co-firing.

  5. Magnetically addressable fluorescent Fe3O4/ZnO nanocomposites: Structural, optical and magnetization studies

    NASA Astrophysics Data System (ADS)

    Roychowdhury, A.; Pati, S. P.; Mishra, A. K.; Kumar, S.; Das, D.

    2013-06-01

    Fe3O4/ZnO nanocomposites (NCs) are prepared by a wet chemical route. X-ray diffraction, transmission electron microscopy and Fourier transform infrared spectroscopy studies confirm the coexistence of Fe3O4 and ZnO phases in the NCs. The UV-vis absorption spectra show a red shift of the absorption peak with increase in Fe3O4 content indicating a modification of the band structure of ZnO in the NCs. Photoluminescence emission spectra of the NCs display strong excitonic emission in the UV region along with weak emission bands in the visible range caused by electronic transitions involving defect-related energy levels in the band gap of ZnO. Positron annihilation lifetimes indicate that cation vacancies in the ZnO structure are the strong traps for positrons and the overall defect concentration in the NCs decreases with increase in Fe3O4 content. Dc magnetization measurements reveal an anomalous temperature dependence of the coercivity of the NCs that is argued to be due to the anomalous variation of magnetocrystalline anisotropy at lower temperature. The irreversibility observed in the temperature dependent ZFC-FC magnetization points to the presence of a spin-glass phase in the NCs.

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

    NASA Astrophysics Data System (ADS)

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

    2017-02-01

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

  7. Nondestructive atomic compositional analysis of BeMgZnO quaternary alloys using ion beam analytical techniques

    NASA Astrophysics Data System (ADS)

    Zolnai, Z.; Toporkov, M.; Volk, J.; Demchenko, D. O.; Okur, S.; Szabó, Z.; Özgür, Ü.; Morkoç, H.; Avrutin, V.; Kótai, E.

    2015-02-01

    The atomic composition with less than 1-2 atom% uncertainty was measured in ternary BeZnO and quaternary BeMgZnO alloys using a combination of nondestructive Rutherford backscattering spectrometry with 1 MeV He+ analyzing ion beam and non-Rutherford elastic backscattering experiments with 2.53 MeV energy protons. An enhancement factor of 60 in the cross-section of Be for protons has been achieved to monitor Be atomic concentrations. Usually the quantitative analysis of BeZnO and BeMgZnO systems is challenging due to difficulties with appropriate experimental tools for the detection of the light Be element with satisfactory accuracy. As it is shown, our applied ion beam technique, supported with the detailed simulation of ion stopping, backscattering, and detection processes allows of quantitative depth profiling and compositional analysis of wurtzite BeZnO/ZnO/sapphire and BeMgZnO/ZnO/sapphire layer structures with low uncertainty for both Be and Mg. In addition, the excitonic bandgaps of the layers were deduced from optical transmittance measurements. To augment the measured compositions and bandgaps of BeO and MgO co-alloyed ZnO layers, hybrid density functional bandgap calculations were performed with varying the Be and Mg contents. The theoretical vs. experimental bandgaps show linear correlation in the entire bandgap range studied from 3.26 eV to 4.62 eV. The analytical method employed should help facilitate bandgap engineering for potential applications, such as solar blind UV photodetectors and heterostructures for UV emitters and intersubband devices.

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

    PubMed Central

    Odkhuu, Dorj

    2016-01-01

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

  9. Exciton localization and large Stokes shift in quaternary BeMgZnO grown by molecular beam epitaxy

    NASA Astrophysics Data System (ADS)

    Toporkov, Mykyta; Ullah, Md. Barkat; Hafiz, Shopan; Nakagawara, Tanner; Avrutin, Vitaliy; Morkoç, Hadis; Özgür, Ümit

    2016-02-01

    Owing to wide range bandgap tunability to more than 5 eV, the quaternary (Be,Mg)ZnO solid solutions are attractive for a variety of UV optoelectronic applications, inclusive of solar blind photodetectors, and intersubband transition devices. The mutual compensation effects of Be and Mg on the formation energy and strain allows a wide range of compositions and bandgaps beyond those achievable by MgZnO and BeZnO ternaries. Localization effects are well pronounced in such wide-bandgap semiconductor alloys due to large differences in metal covalent radii and the lattice constants of the binaries, resulting in strain-driven compositional variations within the film and consequently large potential fluctuations, in addition to that possibly caused by defects. However, carrier localization may suppress recombination through nonradiative channels, and thus, facilitate high-efficiency optoelectronic devices. To investigate potential fluctuations and localization in BexMgyZn(1-x-y)O films grown by plasma-assisted molecular beam epitaxy, optical absorption and steady-state and time-resolved photoluminescence (PL) measurements were performed. O-polar BexMgyZn(1-x-y)O samples grown on GaN templates with compositions up to x = 0.04 and y = 0.18 were used for timeresolved studies, and O-polar BexMgyZn(1-x-y)O samples grown on sapphire with compositions up to x = 0.19 and y = 0.52 were used for absorption measurements. From spectrally resolved PL transients, BeMgZnO samples with higher Mg/Be content ratio were found to exhibit smaller localization depth, Δ0=98 meV for Be0.04Mg0.17Zn0.79O and Δ0=173 meV for Be0.10Mg0.25Zn0.65O, compared to samples with smaller Mg/Be ratio, Δ0=268 meV for Be0.11Mg0.15Zn0.74O. Similar correlation is observed in temporal redshift of the PL peak position of 8 meV, 42 meV and 55 meV for Be0.04Mg0.17Zn0.79O, Be0.10Mg0.25Zn0.65O and Be0.11Mg0.15Zn0.74O, respectively, that originates from potential fluctuations and removal of band filling effect in the

  10. Heat capacities and entropies at 298.15 K of MgTiO3 (geikielite), ZnO (zincite), and ZnCO3 (smithsonite)

    USGS Publications Warehouse

    Robie, R.A.; Haselton, H.T.; Hemingway, B.S.

    1989-01-01

    Heat capacities of synthetic MgTiO3 (geikielite), ZnO (zincite), and natural crystals of smithsonite (ZnCO3) were measured between 9 and 366 K using an automatic adiabatically shielded calorimeter. At 298.15 K the standard molar entropies Smo of MgTiO3, ZnO, and ZnCO3 are (74.64 ?? 0.15), (43.16 ?? 0.09), and (81.19 ?? 0.16) J??K-1??mol-1, respectively. Debye temperatures for MgTiO3 and ZnO calculated from our Cp, mo values below 20 K are (900 ?? 20) K and (440 ?? 25) K respectively. Heat capacities for MgTiO3 and ZnO were combined with enthalpy increments from the literature to derive heat-capacity equations for these phases from 260 to about 1800 K. The heat capacities of MgTiO3 between 260 and 1720 K were fitted with an average deviation of 0.3 per cent by the equation: C??p,m/(J??K-1??mol-1) = 222.5-0.05274(T/K)-6.092x105(T/K)-1-1874.6(T/K) -1/2+1.878x10-5(T/K)2 and for ZnO the equation: C??p,m/(J??K-1??mol-1) = 53.999+7.851x10-4(T/K)-5.868x105(T/K)-2 -127.50(T/K)-:1/2+1.9376x10-6(T/K)2 fits the heat capacities in the temperature interval of 250 to 1800 K with an average deviation of 0.7 per cent. ?? 1989.

  11. Monodisperse Zn-doped Fe3O4 formation and photo-Fenton activity for degradation of rhodamine B in water

    NASA Astrophysics Data System (ADS)

    Cen, Huoshi; Nan, Zhaodong

    2018-10-01

    Zn-doped Fe3O4 can be used as a catalyst in the photo-Fenton process to degrade dye molecules dissolved in water, in which cluster-shaped Zn-doped Fe3O4 (CSZnFe) was synthesized. To enhance the catalytic activity, monodisperse Zn-doped Fe3O4 (MZnFe) was facilely synthesized by a modified solvothermal method through replacement of sodium acetate by urea as a base. The particle size of MZnFe was about 9-16 nm. MZnFe exhibits a larger surface area and higher photo-Fenton catalytic activity for degradation of rhodamine B in water than CSZnFe. Additionally, MZnFe exhibits high saturation magnetization (about 80 emu/g), which is very convenient for separation of MZnFe from solution by a magnet. The growth processes for MZnFe were proposed on the basis of results from in situ calorimetry and other techniques, which indicated different formation mechanisms for MZnFe and CSZnFe.

  12. Effect of surfactant amount on the morphology and magnetic properties of monodisperse ZnFe{sub 2}O{sub 4} nanoparticles

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

    Zhao, Haitao, E-mail: zht95711lunwen@163.com; Liu, Ruiping; Zhang, Qiang

    2016-03-15

    Graphical abstract: Polyol process to monodisperse ZnFe{sub 2}O{sub 4} nanoparticles. - Highlights: • An one-step, facile and inexpensive synthetic route to monodisperse ZnFe{sub 2}O{sub 4} nanoparticles is described. • The sodium citrate stabilized ZnFe{sub 2}O{sub 4} nanoparticles with a diameter in the 5–8 nm size range can be easily dispersed in water. • The synthesis is very robust in terms of variations of experimental parameters. • ZnFe{sub 2}O{sub 4} nanoparticles present ferrimagnetic behavior at room temperature with a small hysteresis. - Abstract: The spinel ZnFe{sub 2}O{sub 4} ferrites with sodium citrate as a surfactant were fabricated by polyol process. Themore » effect of surfactant amount on the structure, morphology and magnetic properties of ZnFe{sub 2}O{sub 4} ferrites were investigated by X-ray diffraction(XRD), transmission electron microscope (TEM), thermogravimetric and differential scanning calorimetry (TG–DSC) and vibrating sample magnetometry (VSM), respectively. The results indicate that the structure of ZnFe{sub 2}O{sub 4} ferrites is a pure cubic spinel structure with a particle size of 5–8 nm. The dispersion of the synthesized ZnFe{sub 2}O{sub 4} is enhanced when the mole ratio of Fe(acac){sub 3} to sodium citrate decreases. The synthesized particles present ferrimagnetic behavior with a small hysteresis at room temperature. The increase of surfactant amount conversely leads to the decrease in the saturation magnetization value (Ms) especially when the mole ratio of Fe(acac){sub 3} to sodium citrate decreases to 8:3. Its Ms value is drastically reduced to 18.97 emu/g.« less

  13. Effect of the interfacial O and Mg vacancies on electronic structure and transport properties of the FeRh/MgO/FeRh (0 0 1) magnetic tunnel junction: DFT calculations

    NASA Astrophysics Data System (ADS)

    Sakhraoui, T.; Said, M.

    2017-12-01

    The electronic, magnetic and transport properties of oxygen or magnesium vacancies at the FeRh/MgO/FeRh (0 0 1) magnetic tunnel junction are studied within first principles. Configurations with one O or Mg vacancy per C(2 × 2) surface unit cell, which is located in the MgO interfacial layers, are investigated. We observed that the O and Mg vacancies defect have a very little influence on the magnetic state of the spacer. Very interestingly, the Fe atoms exhibit an enhanced magnetic moment in the case of Mg-vacancy, this latter was found to decrease in the case of O-vacancy. The variations in the spin polarization and magnetic moment values for Fe and Rh atoms at the interface were found to be larger in presence of Mg vacancy. An analysis of the charge densities of our systems was also performed; large variations in the Mg-vacancy system were observed. This affects more the t2g states of the interfacial Fe atom. Moreover, we present an ab initio calculated transmission and I-V characteristics for FeRh/MgO/FeRh (0 0 1) magnetic tunnel junction and we compare results to those of O and Mg-vacancy at the interface using the TRANSIESTA code, which combines the DFT electronic structure calculations with the non-equilibrium Green function formalism (NEGF) for transport properties. The results show that the zero-bias minority spin transmission is much larger than the majority spin transmission for all structures. In all systems and for all magnetic configurations, minority spin currents are higher than majority spin ones, this means that transport properties are, mainly, determined by minority spin channel.

  14. Facile synthesis of magnetic ZnFe2O4-reduced graphene oxide hybrid and its photo-Fenton-like behavior under visible iradiation.

    PubMed

    Yao, Yunjin; Qin, Jiacheng; Cai, Yunmu; Wei, Fengyu; Lu, Fang; Wang, Shaobin

    2014-06-01

    A magnetic ZnFe2O4-reduced graphene oxide (rGO) hybrid was successfully developed as a heterogeneous catalyst for photo-Fenton-like decolorization of various dyes using peroxymonosulfate (PMS) as an oxidant under visible light irradiation. Through an in situ chemical deposition and reduction, ZnFe2O4 nanoparticles (NPs) with an average size of 23.7 nm were anchored uniformly on rGO sheets to form a ZnFe2O4-rGO hybrid. The catalytic activities in oxidative decomposition of organic dyes were evaluated. The reaction kinetics, effect of ion species and strength, catalytic stability, degradation mechanism, as well as the roles of ZnFe2O4 and graphene were also studied. ZnFe2O4-rGO showed to be a promising photocatalyst with magnetism for the oxidative degradation of aqueous organic pollutants and simple separation. The combination of ZnFe2O4 NPs with graphene sheets leads to a much higher catalytic activity than pure ZnFe2O4. Graphene acted as not only a support and stabilizer for ZnFe2O4 to prevent them from aggregation, largely improving the charge separation in the hybrid material, but also a catalyst for activating PMS to produce sulfate radicals at the same time. The ZnFe2O4-rGO hybrid exhibited stable performance without losing activity after five successive runs.

  15. Sustainable synthesis of metals-doped ZnO nanoparticles from zinc-bearing dust for photodegradation of phenol.

    PubMed

    Wu, Zhao-Jin; Huang, Wei; Cui, Ke-Ke; Gao, Zhi-Fang; Wang, Ping

    2014-08-15

    A novel strategy of waste-cleaning-waste is proposed in the present work. A metals-doped ZnO (M-ZnO, M = Fe, Mg, Ca and Al) nanomaterial has been prepared from a metallurgical zinc-containing solid waste "fabric filter dust" by combining sulfolysis and co-precipitation processes, and is found to be a favorable photocatalyst for photodegradation of organic substances in wastewater under visible light irradiation. All the zinc and dopants (Fe, Mg, Ca and Al) for preparing M-ZnO are recovered from the fabric filter dust, without any addition of chemical as elemental source. The dust-derived M-ZnO samples deliver single phase indexed as the hexagonal ZnO crystal, with controllable dopants species. The photocatalytic activity of the dust-derived M-ZnO samples is characterized by photodegradation of phenol aqueous solution under visible light irradiation, giving more prominent photocatalytic behaviors than undoped ZnO. Such enhancements may be attributed to incorporation of the dust-derived metal elements (Fe, Mg, Ca and Al) into ZnO structure, which lead to the modification of band gap and refinement of grain size. The results show a feasibility to utilize the industrial waste as a resource of photodegradating organic substances in wastewater treatments. Copyright © 2014 Elsevier B.V. All rights reserved.

  16. On local structural changes in lizardite-1 T: {Si4+/Al3+}, {Si4+/Fe3+}, [Mg2+/Al3+], [Mg2+/Fe3+] substitutions

    NASA Astrophysics Data System (ADS)

    Scholtzová, Eva; Smrčok, Ľubomír

    2005-09-01

    Geometrical changes induced by cation substitutions {Si4+/Al3+}[Mg2+/Al3+], {2Si4+/2Al3+} [2Mg2+/2Al3+], {Si4+/Fe3+} [Mg2+/Al3+] or [Mg2+/Fe3+], where {} and [] indicate tetrahedral and octahedral sheet in lizardite 1 T, are studied by ab-initio quantum chemistry calculations. The majority of the models are based on the chemical compositions reported for various lizardite polytypes with the amount of Al in the tetrahedral sheets reported to vary from 3.5% to 8% in the 1 T and 2 H 1, up to 30% in the 2 H 2 polytype. Si4+ by Fe3+ substitution in the tetrahedral sheet with an Al3+ (Fe3+) in the role of a charge compensating cation in the octahedral sheet is also examined. The cation substitutions result in the geometrical changes in the tetrahedral sheets, while the octahedral sheets remain almost untouched. Substituted tetrahedra are tilted and their basal oxygens pushed down from the plane of basal oxygens. Ditrigonal deformation of tetrahedral sheets depends on the substituting cation and the degree of substitution.

  17. Isotopic composition of Mg and Fe in garnet peridotites from the Kaapvaal and Siberian cratons

    NASA Astrophysics Data System (ADS)

    An, Yajun; Huang, Jin-Xiang; Griffin, W. L.; Liu, Chuanzhou; Huang, Fang

    2017-03-01

    We present Mg and Fe isotopic data for whole rocks and separated minerals (olivine, clinopyroxene, orthopyroxene, garnet, and phlogopite) of garnet peridotites that equilibrated at depths of 134-186 km beneath the Kaapvaal and Siberian cratons. There is no clear difference in δ26Mg and δ56Fe of garnet peridotites from these two cratons. δ26Mg of whole rocks varies from -0.243‰ to -0.204‰ with an average of -0.225 ± 0.037‰ (2σ, n = 19), and δ56Fe from -0.038‰ to 0.060‰ with an average of -0.003 ± 0.068‰ (2σ, n = 19). Both values are indistinguishable from the fertile upper mantle, indicating that there is no significant Mg-Fe isotopic difference between the shallow and deep upper mantle. The garnet peridotites from ancient cratons show δ26Mg similar to komatiites and basalts, further suggesting that there is no obvious Mg isotopic fractionation during different degrees of partial melting of deep mantle peridotites and komatiite formation. The precision of the Mg and Fe isotope data (⩽±0.05‰ for δ26Mg and δ56Fe, 2σ) allows us to distinguish inter-mineral isotopic fractionations. Olivines are in equilibrium with opx in terms of Mg and Fe isotopes. Garnets have the lowest δ26Mg and δ56Fe among the coexisting mantle minerals, suggesting the dominant control of crystal structure on the Mg-Fe isotopic compositions of garnets. Elemental compositions and mineralogy suggest that clinopyroxene and garnet were produced by later metasomatic processes as they are not in chemical equilibrium with olivine or orthopyroxene. This is consistent with the isotopic disequilibrium of Mg and Fe isotopes between orthopyroxene/olivine and garnet/clinopyroxene. Combined with one sample showing slightly heavy δ26Mg and much lighter δ56Fe, these disequilibrium features in the garnet peridotites reveal kinetic isotopic fractionation due to Fe-Mg inter-diffusion during reaction between peridotites and percolating melts in the Kaapvaal craton.

  18. Ultrasonic Vibration and Rheocasting for Refinement of Mg-Zn-Y Alloy Reinforced with LPSO Structure

    NASA Astrophysics Data System (ADS)

    Lü, Shulin; Yang, Xiong; Hao, Liangyan; Wu, Shusen; Fang, Xiaogang; Wang, Jing

    2018-05-01

    In this work, ultrasonic vibration (UV) and rheo-squeeze casting was first applied on the Mg alloy reinforced with long period stacking ordered (LPSO) structure. The semisolid slurry of Mg-Zn-Y alloy was prepared by UV and processed by rheo-squeeze casting in succession. The effects of UV, Zr addition and squeeze pressure on microstructure of semisolid Mg-Zn-Y alloy were studied. The results revealed that the synergic effect of UV and Zr addition generated a finer microstructure than either one alone when preparing the slurries. Rheo-squeeze casting could significantly refine the LPSO structure and α-Mg matrix in Mg96.9Zn1Y2Zr0.1 alloy without changing the phase compositions or the type of LPSO structure. When the squeeze pressure increased from 0 to 400 MPa, the block LPSO structure was completely eliminated and the average thickness of LPSO structure decreased from 9.8 to 4.3 μm. Under 400 MPa squeeze pressure, the tensile strength and elongation of the rheocast Mg96.9Zn1Y2Zr0.1 alloy reached the maximum values, which were 234 MPa and 17.6%, respectively, due to its fine α-Mg matrix (α1-Mg and α2-Mg grains) and LPSO structure.

  19. Facile synthesis of ZnFe2O4 photocatalysts for decolourization of organic dyes under solar irradiation

    PubMed Central

    Behera, Arjun; Kandi, Debasmita; Majhi, Sanjit Manohar

    2018-01-01

    ZnFe2O4 was fabricated by a simple solution-combustion method. The structural, optical and electronic properties are investigated by XRD, TEM, FESEM, UV–vis DRS, PL, FTIR and photocurrent measurements. The photocatalytic activity of the prepared material is studied with regard to the degradation of rhodamine B (Rh B) and Congo red under solar irradiation. The kinetic study showed that the material exhibits zeroth and first order reaction kinetics for the degradation of Rh B and Congo red, respectively. The photocatalytic behaviour of ZnFe2O4 was systematically studied as a function of the activation temperature. ZnFe2O4 prepared at 500 °C showed the highest activity in degrading Rh B and Congo red. The highest activity of ZnFe2O4-500 °C correlates well with the lowest PL intensity, highest photocurrent and lowest particle size. PMID:29515956

  20. Fe induced optical limiting properties of Zn1-xFexS nanospheres

    NASA Astrophysics Data System (ADS)

    Vineeshkumar, T. V.; Raj, D. Rithesh; Prasanth, S.; Unnikrishnan, N. V.; Mahadevan Pillai, V. P.; Sudarasanakumar, C.

    2018-02-01

    Zn1-xFexS (x = 0.00, 0.01, 0.03, 0.05) nanospheres were synthesized by polyethylene glycol assisted hydrothermal method. XRD studies revealed that samples of all concentrations exhibited cubic structure with crystallite grain size 7-9 nm. TEM and SEM show the formation of nanospheres by dense aggregation of smaller particles. Increasing Zn/Fe ratio tune the band gap from 3.4 to 3.2 eV and also quenches the green luminescence. FTIR spectra reveal the presence of capping agent, intensity variation and shifting of LO and TO phonon modes confirm the presence of Fe ions. Nonlinear optical properties were measured using open and closed aperture z-scan techniques, employing frequency doubled 532 nm pumping sources which indicated reverse saturable absorption (RSA) process. The nonlinear optical coefficients are obtained by two photon absorption (2PA). Composition dependent nonlinear optical coefficients ;β;, nonlinear refractive index, third order susceptibility and optical limiting threshold were estimated. The sample shows good nonlinear absorption and enhancement of optical limiting behavior with increasing Fe volume fraction. Contribution of RSA on optical nonlinearity of Zn1-xFexS nanospheres are also investigated using three different input energies. Zn1-xFexS with comparatively small limiting threshold value is a promising candidate for optical power limiting applications.

  1. Sequential magnetic switching in Fe/MgO(001) superlattices

    NASA Astrophysics Data System (ADS)

    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.

  2. Micronutrients (B, Co, Cu, Fe, Mn, Mo, and Zn) content in made tea (Camellia sinensis L.) and tea infusion with health prospect: A critical review.

    PubMed

    Karak, Tanmoy; Kutu, Funso Raphael; Nath, Jyoti Rani; Sonar, Indira; Paul, Ranjit Kumar; Boruah, Romesh Kumar; Sanyal, Sandip; Sabhapondit, Santanu; Dutta, Amrit Kumar

    2017-09-22

    Tea (Camellia sinensis L.) is a perennial acidophilic crop, and known to be a nonalcoholic stimulating beverage that is most widely consumed after water. The aim of this review paper is to provide a detailed documentation of selected micronutrient contents, viz. boron (B), cobalt (Co), copper (Cu), iron (Fe), manganese (Mn), molybdenum (Mo), and zinc (Zn) in made tea and tea infusion. Available data from the literature were used to calculate human health aspect associated with the consumption of tea infusion. A wide range of micronutrients reported in both made tea and tea infusion could be the major sources of micronutrients for human. The content of B, Co, Cu, Fe, Mn, Mo, and Zn in made tea are ranged from 3.04 to 58.44 μg g -1 , below detectable limit (BDL) to 122.4 μg g -1 , BDL to 602 μg g -1 , 0.275 to 13,040 μg g -1 , 0.004 to 15,866 μg g -1 , 0.04 to 570.80 μg g -1 and 0.01 to 1120 μg g -1 , respectively. Only 3.2 μg L -1 to 7.25 mg L -1 , 0.01 μg L -1 to 7 mg L -1 , 3.80 μg L -1 to 6.13 mg L -1 , 135.59 μg L -1 -11.05 mg L -1 , 0.05 μg L -1 to 1980.34 mg L -1 , 0.012 to 3.78 μg L -1 , and 1.12 μg L -1 to 2.32 μg L -1 of B, Co, Cu, Fe, Mn, Mo, and Zn, respectively, are found in tea infusion which are lower than the prescribed limit of micronutrients in drinking water by World Health Organization. Furthermore, micronutrient contents in tea infusion depend on infusion procedure as well as on the instrument used for analysis. The proportion of micronutrients found in different tea types are 1.0-88.9% for B, 10-60% for Co, 2.0-97.8% for Cu, 67.8-89.9% for Fe, 71.0-87.4% for Mn, 13.3-34% for Mo, and 34.9-83% for Zn. From the results, it can also be concluded that consumption of three cups of tea infusion per day does not have any adverse effect on human health with respect to the referred micronutrients rather got beneficial effects to human.

  3. Triple-mixture of Zn, Mn, and Fe increases bioaccumulation and causes oxidative stress in freshwater neotropical fish.

    PubMed

    de Oliveira, Luciana Fernandes; Santos, Caroline; Risso, Wagner Ezequiel; Dos Reis Martinez, Claudia Bueno

    2018-06-01

    Metal bioaccumulation and oxidative stress biomarkers were determined in Prochilodus lineatus to understand the effects of short-term exposure to a triple-mixture of Zn, Mn, and Fe. Three independent tests were carried out, in which fish were exposed to 3 concentrations of Zn (0.18, 1.0, and 5.0 mg L -1 ), Mn (0.1, 0.5, and 5.0 mg L -1 ), and in the mix test to Fe (5.0 mg L -1 ) and a mixture of Zn (1.0 mg L -1 ) + Mn (0.5 mg L -1 ), with and without Fe. After exposure for 96 h, tissues were removed for metal bioaccumulation analysis and oxidative stress biomarkers were determined in liver, along with DNA damage in blood cells. Our results revealed that Zn and Mn were bioaccumulated in fish tissues after exposure to 5.0 mg L -1 , whereas Fe only bioaccumulated in muscle and gills after mixture exposure. Results indicated that 1 metal interfered with the other's bioaccumulation. In P. lineatus, 5 mg L -1 of both Mn and Fe were toxic, because damage was observed (lipid peroxidation [LPO] in liver and DNA damage in blood cells), whereas Zn induced liver responses (metallothionein [MT] and reduced glutathione [GSH] increases) to prevent damage. In terms of bioaccumulation and alterations of oxidative stress biomarkers, we showed that Zn, Mn, and Fe triple-mixture enhances individual metal toxicity in Neotropical fish P. lineatus. Environ Toxicol Chem 2018;37:1749-1756. © 2018 SETAC. © 2018 SETAC.

  4. Synthesis and Characterization of Mg-doped ZnO Nanorods for Biomedical Applications

    NASA Astrophysics Data System (ADS)

    Gemar, H.; Das, N. C.; Wanekaya, A.; Delong, R.; Ghosh, K.

    2013-03-01

    Nanomaterials research has become a major attraction in the field of advanced materials research in the area of Physics, Chemistry, and Materials Science. Bio-compatible and chemically stable metal nanoparticles have biomedical applications that includes drug delivery, cell and DNA separation, gene cloning, magnetic resonance imaging (MRI). This research is aimed at the fabrication and characterization of Mg-doped ZnO nanorods. Hydrothermal synthesis of undoped ZnO and Mg-doped ZnO nanorods is carried out using aqueous solutions of Zn(NO3)2 .6H2O, MgSO4, and using NH4OH as hydrolytic catalyst. Nanomaterials of different sizes and shapes were synthesized by varying the process parameters such as molarity (0.15M, 0.3M, 0.5M) and pH (8-11) of the precursors, growth temperature (130°C), and annealing time during the hydrothermal Process. Structural, morphological, and optical properties are studied using various techniques such as XRD, SEM, UV-vis and PL spectroscopy. Detailed structural, and optical properties will be discussed in this presentation. This work is partially supported by National Cancer Institute (1 R15 CA139390-01).

  5. NH3 molecule adsorption on spinel-type ZnFe2O4 surface: A DFT and experimental comparison study

    NASA Astrophysics Data System (ADS)

    Zou, Cong-yang; Ji, Wenchao; Shen, Zhemin; Tang, Qingli; Fan, Maohong

    2018-06-01

    Ammonia (NH3) is a caustic environment pollutant which contributes to haze formation and water pollution. Zinc ferrite (ZnFe2O4) exhibits good catalytic activity in NH3 removal. The density functional theory (DFT) was applied to explore the interaction mechanism of NH3 molecule adsorption on spinel-type ZnFe2O4 (1 1 0) surface with GGA-PW91 method in atomic and electronic level. The results indicated that NH3 molecule preferred to adsorb on surface Zn atom with the formation of H3Nsbnd Zn coordinate bond over ZnFe2O4 (1 1 0) surface. The H3Nsbnd Zn state was exothermic process with adsorption energy of -203.125 kJ/mol. About 0.157e were transferred from NH3 molecule to the surface which resulted in strong interaction. Higher activation degree occurred in H3Nsbnd Zn configuration with two Nsbnd H bonds elongated and NH3 structure became more flat on the surface. The PDOS change of NH3 molecule was consistent with the result of adsorption energy. It was concluded that s orbital of NH3 (N) and s, p orbitals of Zn atom overlapped at -0.619 Ha. The p orbital of NH3 (N) has interaction with d orbital of Zn atom suggesting the hybridization between them. Based on NH3 removal experimental and XPS spectra results, NH3sbnd ZnFe2O4 interaction was mainly depended on the coordination between Zn atom and NH3 molecule. The DFT calculations have deepened our understanding on NH3sbnd ZnFe2O4 interaction system.

  6. Fe, Ca and Mg contents in selected fast food products in Poland.

    PubMed

    Grajeta, H; Prescha, A; Biernat, J

    2002-02-01

    The Fe and Mg contents in selected fast food products available in restaurants and fast food outlets in Poland were determined by AAS, and the Ca content by AES. The mean Fe contents in the studied fast food products were from 0.7 to 2.3 mg/100 g, or from 0.6 to 2.3 per single serving. The highest means for this element were found in a serving of hamburger (2.3 mg), fishburger (2.0 mg) and chicken sandwich (2.0 mg). The mean Ca contents in the studied products were from 11.6 to 192.2 mg/100 g, or 10 to 192.2 mg per serving. The highest means for this element were found in a serving of pizza (192.2 mg) and cheeseburger (134.8 mg). The mean Mg contents in the studied products were from 6.8 to 34.1 mg/100 g1 or 5.9 to 37.3 mg per serving. The highest means for this element were found in a serving of french fries (37.3 mg), chicken sandwich (34.7 mg) and fishburger (30.4 mg). Based on the Fe, Ca and Mg contents found in these products, the percentage of the Recommended Dietary Allowance (RDA) of these elements was calculated for one serving of each product. These calculations were done for various groups of people in Poland. The highest percentage of the recommended Fe intake could be covered by one serving of hamburger (15-23% RDA), fishburger (14-20% RDA), or chicken sandwich (13-20% RDA). The highest percentage of the recommended Ca intake could be covered by one serving of pizza (17-24% RDA) or cheeseburger (12-17% RDA); and for Mg one serving of french fries (11-19% RDA), chicken sandwich (10-17% RDA), or fishburger (9-15% RDA). From the conducted studies it may be concluded that some fast food products can serve as a source of Fe, Ca and Mg in the diet of people of various ages.

  7. Structural and Optical Studies of ZnCdSe/ZnSe/ZnMgSSe Separate Confinement Heterostructures with Different Buffer Layers

    NASA Astrophysics Data System (ADS)

    Tu, Ru-Chin; Su, Yan-Kuin; Huang, Ying-Sheng; Chen, Giin-Sang; Chou, Shu-Tsun

    1998-09-01

    Detailed structural and optical studies of ZnCdSe/ZnSe/ZnMgSSe separate confinementheterostructures (SCH) grown on ZnSe, ZnSe/ZnSSe strained-layer superlattices (SLS),and GaAs buffer layers at the II VI/GaAs interface have been carried out by employingtransmission electron microscopy, variable temperature photoluminescence (PL), andcontactless electroreflectance (CER) measurements. A significant improvement onthe defect reduction and the optical quality has been observed by using either theZnSe/ZnSSe SLS or GaAs as the buffer layers when compared to that of the sample usingonly ZnSe as the buffer layer. However, the sample grown with the SLS buffer layersreveals a room temperature PL intensity higher than that of the sample grown witha GaAs buffer layer, which may still suffer from the great ionic differences betweenthe II V and III V atoms. Using 15 K CER spectra, we have also studied variousexcitonic transitions originating from strained Zn0.80Cd0.20Se/ZnSe single quantumwell in SCH with different buffer layers. An analysis of the CER spectra has ledto the identification of various excitonic transitions, mnH (L), between the mthconduction band state and the nth heavy (light)-hole band state. An excellentagreement between experiments and theoretical calculations based on the envelopefunction approximation model has been achieved.

  8. The structural, magnetic and optical properties of TMn@(ZnO)42 (TM = Fe, Co and Ni) hetero-nanostructure.

    PubMed

    Hu, Yaowen; Ji, Chuting; Wang, Xiaoxu; Huo, Jinrong; Liu, Qing; Song, Yipu

    2017-11-28

    The magnetic transition-metal (TM) @ oxide nanoparticles have been of great interest due to their wide range of applications, from medical sensors in magnetic resonance imaging to photo-catalysis. Although several studies on small clusters of TM@oxide have been reported, the understanding of the physical electronic properties of TM n @(ZnO) 42 is far from sufficient. In this work, the electronic, magnetic and optical properties of TM n @(ZnO) 42 (TM = Fe, Co and Ni) hetero-nanostructure are investigated using the density functional theory (DFT). It has been found that the core-shell nanostructure Fe 13 @(ZnO) 42 , Co 15 @(ZnO) 42 and Ni 15 @(ZnO) 42 are the most stable structures. Moreover, it is also predicted that the variation of the magnetic moment and magnetism of Fe, Co and Ni in TM n @ZnO 42 hetero-nanostructure mainly stems from effective hybridization between core TM-3d orbitals and shell O-2p orbitals, and a magnetic moment inversion for Fe 15 @(ZnO) 42 is investigated. Finally, optical properties studied by calculations show a red shift phenomenon in the absorption spectrum compared with the case of (ZnO) 48 .

  9. Effect of substrate on texture and mechanical properties of Mg-Cu-Zn thin films

    NASA Astrophysics Data System (ADS)

    Eshaghi, F.; Zolanvari, A.

    2018-04-01

    In this work, thin films of Mg-Cu-Zn with 60 nm thicknesses have been deposited on the Si(100), Al, stainless steel, and Cu substrates using DC magnetron sputtering. FESEM images displayed uniformity of Mg-Cu-Zn particles on the different substrates. AFM micrograph revealed the roughness of thin film changes due to the different kinds of the substrates. XRD measurements showed the existence of strong Mg (002) reflections and weak Mg (101) peaks. Residual stress and adhesion force have been measured as the mechanical properties of the Mg-Cu-Zn thin films. The residual stresses of thin films which have been investigated by X-ray diffraction method revealed that the thin films sputtered on the Si and Cu substrates endure minimum and maximum stresses, respectively, during the deposition process. However, the force spectroscopy analysis indicated that the films grew on the Si and Cu experienced maximum and minimum adhesion force. The texture analysis has been done using XRD instrument to make pole figures of Mg (002) and Mg (101) reflections. ODFs have been calculated to evaluate the distribution of the orientations within the thin films. It was found that the texture and stress have an inverse relation, while the texture and the adhesion force of the Mg-Cu-Zn thin films have direct relation. A thin film that sustains the lowest residual stresses and highest adhesive force had the strongest {001} basal fiber texture.

  10. Disturbance of tunneling coherence by oxygen vacancy in epitaxial Fe/MgO/Fe magnetic tunnel junctions.

    PubMed

    Miao, G X; Park, Y J; Moodera, J S; Seibt, M; Eilers, G; Münzenberg, M

    2008-06-20

    Oxygen vacancies in the MgO barriers of epitaxial Fe/MgO/Fe magnetic tunnel junctions are observed to introduce symmetry-breaking scatterings and hence open up channels for noncoherent tunneling processes that follow the normal WKB approximation. The evanescent waves inside the MgO barrier thus experience two-step tunneling, the coherent followed by the noncoherent process, and lead to lower tunnel magnetoresistance, higher junction resistance, as well as increased bias and temperature dependence. The characteristic length of the symmetry scattering process is determined to be about 1.6 nm.

  11. 230% room-temperature magnetoresistance in CoFeB /MgO/CoFeB magnetic tunnel junctions

    NASA Astrophysics Data System (ADS)

    Djayaprawira, David D.; Tsunekawa, Koji; Nagai, Motonobu; Maehara, Hiroki; Yamagata, Shinji; Watanabe, Naoki; Yuasa, Shinji; Suzuki, Yoshishige; Ando, Koji

    2005-02-01

    Magnetoresistance (MR) ratio up to 230% at room temperature (294% at 20 K) has been observed in spin-valve-type magnetic tunnel junctions (MTJs) using MgO tunnel barrier layer fabricated on thermally oxidized Si substrates. We found that such a high MR ratio can be obtained when the MgO barrier layer was sandwiched with amorphous CoFeB ferromagnetic electrodes. Microstructure analysis revealed that the MgO layer with (001) fiber texture was realized when the MgO layer was grown on amorphous CoFeB rather than on polycrystalline CoFe. Since there have been no theoretical studies on the MTJs with a crystalline tunnel barrier and amorphous electrodes, the detailed mechanism of the huge tunneling MR effect observed in this study is not clear at the present stage. Nevertheless, the present work is of paramount importance in realizing high-density magnetoresistive random access memory and read head for ultra high-density hard-disk drives into practical use.

  12. Uniformly Dispersed ZnFe2O4 Nanoparticles on Nitrogen-Modified Graphene for High-Performance Supercapacitor as Electrode.

    PubMed

    Li, Lei; Bi, Huiting; Gai, Shili; He, Fei; Gao, Peng; Dai, Yunlu; Zhang, Xitian; Yang, Dan; Zhang, Milin; Yang, Piaoping

    2017-02-21

    A facile strategy has been adopted for the preparation of ZnFe 2 O 4 /NRG composite by anchoring ultrasmall ZnFe 2 O 4 nanoparticles on nitrogen-doped reduced graphene (denoted as NRG) for high-performance supercapacitor electrode. Remarkably, the growth of ZnFe 2 O 4 nanocrystals, the reduction of graphitic oxide and the doping of nitrogen to graphene have been simultaneously achieved in one process. It is found that the NRG employed as substrate can not only control the formation of nano-sized ZnFe 2 O 4 , but also guarantee the high dispersion without any agglomeration. Benefiting from this novel combination and construction, the hybrid material has large surface area which can provide high exposure of active sites for easy access of electrolyte and fast electron transport. When served as supercapacitor electrode, the ZnFe 2 O 4 /NRG composite exhibits a favorable specific capacitance of 244 F/g at 0.5 A/g within the potential range from -1 to 0 V, desirable rate stability (retain 131.5 F/g at 10 A/g) and an admirable cycling durability of 83.8% at a scan rate of 100 mV/s after 5000 cycles. When employed as symmetric supercapacitor, the device demonstrates favorable performance. These satisfactory properties of the ZnFe 2 O 4 /NRG composite can make it be of great promise in the supercapacitor application.

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

    NASA Astrophysics Data System (ADS)

    Al-Ebraheem, A.; Mersov, A.; Gurusamy, K.; Farquharson, M. J.

    2010-07-01

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

  14. Effect of Co and Pr doping on the properties of solar-reflective ZnFe2O4 dark pigment

    NASA Astrophysics Data System (ADS)

    Suwan, M.; Sangwong, N.; Supothina, S.

    2017-03-01

    High NIR-reflective Co-doped ZnFe2O4 black pigments were synthesized by a simple solid-state reaction of ZnO and Fe2O3 in the presence of 3 to 30 wt.% Co3O4 at 1000 and 1100 °C. A series of black pigments with low L* values in a range of 25.5-26.5 and NIR reflectance of 39.5-48.7% were obtained at 1000 °C while the pigments with comparable L* values and slightly lower NIR reflectance were obtained at 1100 °C. A change of the pigment property could be attributed to substitution of Co2+ for Zn2+ as revealed by XRD analysis as well as reflectance spectra. Calcination of ZnO and Fe2O3 in the presence of 3 to 30 wt.% Pr6O11 at 1100 °C resulted in dark brown composite pigments consisting of ZnFe2O4, PrFe2O3 and unreacted Fe2O3 with L* value around 40 ±1 and NIR reflectance in a range of 48-50%.

  15. Nanoheterostructures with CdTe/ZnMgSeTe Quantum Dots for Single-Photon Emitters Grown by Molecular Beam Epitaxy

    NASA Astrophysics Data System (ADS)

    Sorokin, S. V.; Sedova, I. V.; Belyaev, K. G.; Rakhlin, M. V.; Yagovkina, M. A.; Toropov, A. A.; Ivanov, S. V.

    2018-03-01

    Data on the molecular beam epitaxy (MBE) technology, design, and luminescent properties of heterostructures with CdTe/Zn(Mg)(Se)Te quantum dots on InAs(001) substrates are presented. X-ray diffraction has been used to study short-period ZnTe/MgTe/MgSe superlattices used as wide-bandgap barriers in structures with CdTe/ZnTe quantum dots for the effective confinement of holes. It is shown that the design of these superlattices must take into account the replacement of Te atoms by selenium on MgSe/ZnTe and MgTe/MgSe heterointerfaces. Heterostructures with CdTe/Zn(Mg)(Se)Te quantum dots exhibit photoluminescence at temperatures up to 300 K. The spectra of microphotoluminescence at T = 10 K display a set of emission lines from separate CdTe/ZnTe quantum dots, the surface density of which is estimated at 1010 cm-2.

  16. Influence of Fe doping on the structural, optical and acetone sensing properties of sprayed ZnO thin films

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

    Prajapati, C.S.; Kushwaha, Ajay; Sahay, P.P., E-mail: dr_ppsahay@rediffmail.com

    2013-07-15

    Graphical abstract: All the films are found to be polycrystalline ZnO possessing hexagonal wurtzite structure. The intensities of all the peaks are diminished strongly in the Fe-doped films, indicating their lower crystallinity as compared to the undoped ZnO film. The average crystallite size decreases from 35.21 nm (undoped sample) to 15.43 nm (1 at% Fe-doped sample). - Highlights: • Fe-doped ZnO films show smaller crystallinity with crystallite size: 15–26 nm. • Optical band gap in ZnO films decreases on Fe doping. • Fe-doped films exhibit the normal dispersion for the wavelength range 450–600 nm. • PL spectra of the Fe-dopedmore » films show quenching of the broad green-orange emission. • Acetone response of the Fe-doped films increases considerably at 300 °C. - Abstract: The ZnO thin films (undoped and Fe-doped) deposited by chemical spray pyrolysis technique have been analyzed by X-ray powder diffraction (XRD), atomic force microscopy (AFM) and scanning electron microscopy (SEM). Results show that all the films possess hexagonal wurtzite structure of zinc oxide having crystallite sizes in the range 15–36 nm. On 1 at% Fe doping, the surface roughness of the film increases which favors the adsorption of atmospheric oxygen on the film surface and thereby increase in the gas response. Optical studies reveal that the band gap decreases due to creation of some defect energy states below the conduction band edge, arising out of the lattice disorder in the doped films. The refractive index of the films decreases on Fe doping and follows the Cauchy relation of normal dispersion. Among all the films examined, the 1 at% Fe-doped film exhibits the maximum response (∼72%) at 300 °C for 100 ppm concentration of acetone in air.« less

  17. The Formation of Fe/Mg Smectite Under Mildly Acidic Conditions on Early Mars

    NASA Technical Reports Server (NTRS)

    Sutter, B.; Golden, D. C.; Ming, Douglas W.; Niles, P. B.

    2011-01-01

    The detection of Fe/Mg smectites and carbonate in Noachian and early Hesperian terrain of Mars suggests that neutral to mildly alkaline conditions prevailed during the early history of Mars. If early Mars surface geochemical conditions were neutral to moderately alkaline with a denser CO2 atmosphere than today, then large carbonates deposits should be more widely detected in Noachian terrain. Why have so few carbonate deposits been detected compared to Fe/Mg smectites? Fe/Mg smectites on early Mars formed under mildly acidic conditions, which would preclude the extensive formation of carbonate deposits. The goal of the proposed work is to evaluate the formation of Fe/Mg smectites under mildly acidic conditions.

  18. UV Light-Driven Photodegradation of Methylene Blue by Using Mn0.5Zn0.5Fe2O4/SiO2 Nanocomposites

    NASA Astrophysics Data System (ADS)

    Indrayana, I. P. T.; Julian, T.; Suharyadi, E.

    2018-04-01

    The photodegradation activity of nanocomposites for 20 ppm methylene blue solution has been investigated in this work. Nanocomposites Mn0.5Zn0.5Fe2O4/SiO2 have been synthesized using coprecipitation method. The X-ray diffraction (XRD) pattern confirmed the formation of three phases in sample Mn0.5Zn0.5Fe2O4/SiO2 i.e., Mn0.5Zn0.5Fe2O4, Zn(OH)2, and SiO2. The appearance of SiO2 phase showed that the encapsulation process has been carried out. The calculated particles size of Mn0.5Zn0.5Fe2O4/SiO2 is greater than Mn0.5Zn0.5Fe2O4. Bonding analysis via vibrational spectra for Mn0.5Zn0.5Fe2O4/SiO2 confirmed the formation of bonds Me-O-Si stretching (2854.65 cm-1) and Si-O-Si asymmetric stretching (1026.13 cm-1). The optical gap energy of Mn0.5Zn0.5Fe2O4/SiO2 was smaller (2.70 eV) than Mn0.5Zn0.5Fe2O4 (3.04 eV) due to smaller lattice dislocation and microstrain that affect their electronic structure. The Mn0.5Zn0.5Fe2O4/SiO2 showed high photodegradation ability due to smaller optical gap energy and the appearance of SiO2 ligand that can easily attract dye molecules. The Mn0.5Zn0.5Fe2O4/SiO2 also showed high degradation activity even without UV light radiation. The result showed that photodegradation reaction doesn’t follow pseudo-first order kinetics.

  19. Structure, mechanical characteristics and in vitro degradation, cytotoxicity, genotoxicity and mutagenicity of novel biodegradable Zn-Mg alloys.

    PubMed

    Kubásek, J; Vojtěch, D; Jablonská, E; Pospíšilová, I; Lipov, J; Ruml, T

    2016-01-01

    Zn-(0-1.6)Mg (in wt.%) alloys were prepared by hot extrusion at 300 °C. The structure, mechanical properties and in vitro biocompatibility of the alloys were investigated. The hot-extruded magnesium-based WE43 alloy was used as a control. Mechanical properties were evaluated by hardness, compressive and tensile testing. The cytotoxicity, genotoxicity (comet assay) and mutagenicity (Ames test) of the alloy extracts and ZnCl2 solutions were evaluated with the use of murine fibroblasts L929 and human osteosarcoma cell line U-2 OS. The microstructure of the Zn alloys consisted of recrystallized Zn grains of 12 μm in size and fine Mg2Zn11 particles arranged parallel to the hot extrusion direction. Mechanical tests revealed that the hardness and strength increased with increasing Mg concentration. The Zn-0.8 Mg alloys showed the best combination of tensile mechanical properties (tensile yield strength of 203 MPa, ultimate tensile strength of 301 MPa and elongation of 15%). At higher Mg concentrations the plasticity of Zn-Mg alloys was deteriorated. Cytotoxicity tests with alloy extracts and ZnCl2 solutions proved the maximum safe Zn(2+) concentrations of 120 μM and 80 μM for the U-2 OS and L929 cell lines, respectively. Ames test with extracts of alloys indicated that the extracts were not mutagenic. The comet assay demonstrated that 1-day extracts of alloys were not genotoxic for U-2 OS and L929 cell lines after 1-day incubation. Copyright © 2015 Elsevier B.V. All rights reserved.

  20. A Passively Q-Switched, CW-Pumped Fe:ZnSe Laser

    DTIC Science & Technology

    2014-03-01

    passively Q-switched microchip lasers using semiconductor saturable absorbers,” J. Opt. Soc. Amer. B, Opt. Phys., vol. 16, no. 3, pp. 376–388, Mar. 1999...204 IEEE JOURNAL OF QUANTUM ELECTRONICS, VOL. 50, NO. 3, MARCH 2014 A Passively Q-Switched, CW-Pumped Fe:ZnSe Laser Jonathan W. Evans, Patrick A...Berry, and Kenneth L. Schepler Abstract— We report the demonstration of high-average-power passively Q-switched laser oscillation from Fe2+ ions in zinc

  1. Influence of valence electron concentration on Laves phases: Structures and phase stability of pseudo-binary MgZn 2-xPd x

    DOE PAGES

    Thimmaiah, Srinivasa; Miller, Gordon J.

    2015-06-03

    A series of pseudo-binary compounds MgZn 2-xPd x (0.15 ≤ x ≤ 1.0) were synthesized and structurally characterized to understand the role of valence electron concentration (vec) on the prototype Laves phase MgZn 2 with Pd-substitution. Three distinctive phase regions were observed with respect to Pd content, all exhibiting fundamental Laves phase structures: 0.1 ≤ x ≤ 0.3 (MgNi 2-type, hP24; MgZn 1.80Pd 0.20(2)), 0.4 ≤ x ≤ 0.6 (MgCu 2-type, cF24; MgZn 1.59Pd 0.41(2)), and 0.62 ≤ x ≤ 0.8 (MgZn 2-type, hP12: MgZn 1.37Pd 0.63(2)). Refinements from single-crystal X-ray diffraction indicated nearly statistical distributions of Pd and Znmore » atoms among the majority atom sites in these structures. Interestingly, the MgZn 2-type structure re-emerges in MgZn 2–xPd x at x ≈ 0.7 with the refined composition MgZn 1.37(2)Pd 0.63 and a c/a ratio of 1.59 compared to 1.64 for binary MgZn 2. Electronic structure calculations on a model “MgZn 1.25Pd 0.75” yielded a density of states (DOS) curve showing enhancement of a pseudogap at the Fermi level as a result of electronic stabilization due to the Pd addition. Moreover, integrated crystal orbital Hamilton population values show significant increases of orbital interactions for (Zn,Pd)–(Zn,Pd) atom pairs within the majority atom substructure, i.e., within the Kagomé nets as well as between a Kagomé net and an apical site, from binary MgZn 2 to the ternary “MgZn 1.25Pd 0.75”. Multi-centered bonding is evident from electron localization function plots for “MgZn 1.25Pd 0.75”, an outcome which is in accordance with analysis of other Laves phases.« less

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

    PubMed

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

    2016-02-16

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

  3. Mid-infrared Fe2+:ZnSe semiconductor saturable absorber mirror for passively Q-switched Er3+-doped ZBLAN fiber laser

    NASA Astrophysics Data System (ADS)

    Ning, Shougui; Feng, Guoying; Dai, Shenyu; Zhang, Hong; Zhang, Wei; Deng, Lijuan; Zhou, Shouhuan

    2018-02-01

    A mid-infrared (mid-IR) semiconductor saturable absorber mirror (SESAM) based on Fe2+:ZnSe for passively Q-switched Er3+-doped ZBLAN fiber laser has been demonstrated. Fe2+:ZnSe SESAM was fabricated by electron beam evaporation method. Fe2+ was innovatively doped into the reflective Bragg stack, in which ZnSe layer served as both doped matrix and high refractive layer during the fabricating process. By using the Fe2+:ZnSe SESAM, stable passively Q-switched pulses with the minimum pulse width of 0.43 μs under a repetition rate of 160.82 kHz were obtained. The recorded maximum average output power of 873 mW with a peak power of 12.59 W and pulse energy of 5.43 μJ were achieved. The results demonstrated a new method for fabricating Fe2+:ZnSe SESAM, which can be used in compact mid-IR Q-switched fiber laser.

  4. Intersubband transitions and many body effects in ZnMgO/ZnO quantum wells

    NASA Astrophysics Data System (ADS)

    Hierro, Adrian; Montes Bajo, Miguel; Tamayo-Arriola, Julen; Hugues, Maxime; Ulloa, J. M.; Le Biavan, N.; Peretti, Romain; Julien, François; Faist, Jerome; Chauveau, Jean-Michel

    2018-02-01

    In this work we show the potential of the ZnO/ZnMgO material system for intersubband (ISB)-based devices. This family of alloys presents a unique set of properties that makes it highly attractive for THz emission as well as strong coupling regimes: it has a very large longitudinal optical phonon energy of 72 meV, it can be doped up to 1021 cm-3, it is very ionic with a large difference between the static and high frequency dielectric constants, and it can be grown homoepitaxially on native substrates with low defect densities. The films analyzed here are grown by molecular beam epitaxy (MBE) on a non-polar orientation, the m-plane, with varying QW thicknesses and 30% Mg concentrations in the barrier, and are examined with polarization-dependent IR absorption spectroscopy. The QW band structure and the intersubband transitions energies are modeled considering many body effects, which are key to predict correctly the measured values.

  5. Apollo 15 Mg- and Fe-norites - A redefinition of the Mg-suite differentiation trend

    NASA Technical Reports Server (NTRS)

    Lindstrom, M. M.; Marvin, U. B.; Mittlefehldt, D. W.

    1989-01-01

    The Apollo 15 highland rocks from the Apennine Front include clasts of mafic plutonic rocks from deep in the lunar crust that were brought to the surface by the Imbrium and Serenitatis impacts. The Apollo 15 norites exhibit wide variations in mineral and bulk compositions and include Fe-norites that plot between the three major pristine rock fields on a diagram of Mg' in mafic minerals vs An in paglioclase. Based on assemblages and compositions of minerals, and on ratios of elemental abundances, it is concluded that these Apollo 15 Fe-norites are differentiated members of the Mg-norite suite. The Apollo 15 and 17 norites and troctolites form a closely related suite of rocks, whose variations in mineral compositions represent the main differentiation trend of the Mg-suite. This trend in mineral compositions has a steeper slope than the previous Mg-suite field. The parent magmas for these Mg-suite rocks formed by partial melting deep in the lunar mantle. Differentiation by fractional crystallization may also have included assimilation of crustal components as the magmas rose from the mantle and crystallized plutons in the lower crust.

  6. Fabrication of magnetic Fe@ZnO0.6S0.4 nanocomposite for visible-light-driven photocatalytic inactivation of Escherichia coli

    NASA Astrophysics Data System (ADS)

    Peng, Ziling; Wu, Dan; Wang, Wei; Tan, Fatang; Ng, Tsz Wai; Chen, Jianguo; Qiao, Xueliang; Wong, Po Keung

    2017-02-01

    Bacterial inactivation by magnetic photocatalysts has now received growing interests due to the easy separation for recycle and reuse of photocatalysts. In this study, magnetic Fe@ZnO0.6S0.4 photocatalyst was prepared by a facile two-step precipitation method. Multiple techniques such as X-ray diffraction (XRD), transmission electron microscope (TEM), scanning electron microscope (SEM), X-ray photoelectron spectroscopy (XPS), UV-vis diffused reflectance spectra (UV-vis DRS) and vibrating sample magnetometer (VSM) were employed to characterize the structure, morphology and physicochemical properties of the photocatalyst. The as-obtained Fe@ZnO0.6S0.4 possessing magnetic property was easily collected from the reaction system by a magnet. Under white light-emitting-diode (LED) lamp irradiation, Fe@ZnO0.6S0.4 nanocomposite could completely inactivate 7-log of Escherichia coli K-12 within 5 h. More importantly, almost no decrease of photocatalytic efficiency in bacterial inactivation was observed even after five consecutive cycles, demonstrating Fe@ZnO0.6S0.4 exhibited good stability for reuse. The low released rate of Fe2+/Fe3+ and Zn2+ from Fe@ZnO0.6S0.4 composite further indicated the photocatalyst showed low cytotoxicity to bacterium and high stability under LED lamp irradiation. Facile preparation, high photocatalytic efficiency, good stability and reusability, and magnetic recovery property endow Fe@ZnO0.6S0.4 nanocomposite to be a promising photocatalytic material for bacterial inactivation.

  7. Antioxidant response and carboxylate metabolism in Brassica rapa exposed to different external Zn, Ca, and Mg supply.

    PubMed

    Blasco, Begoña; Graham, Neil S; Broadley, Martin R

    2015-03-15

    Zinc (Zn), calcium (Ca), and magnesium (Mg) malnutrition are common deficiencies in many developed and developing countries, resulting in a widespread health problem. Biofortification of food crops is an agricultural strategy that can be used to increase the levels of these elements in the edible portions of crops. Deficiency or toxicity of these cations in soils reduces plant growth, crop yield, and the quality of plant foodstuff. The aim of this study was to investigate the effect of external Zn, Ca, and Mg supply on accumulation and distribution of this elements as well as antioxidant response and organic acid composition of Brassica rapa ssp. trilocularis line R-o-18. Plants were grown at low Zn (0.05 μM Zn) and high Zn (500 μM Zn), low Ca (0.4 mM) and high Ca (40 mM), and low Mg (0.2 mM), and high Mg (20 mM) to simulate deficiency and toxicity conditions. Larger shoot biomass reductions were observed under high Zn, Ca and Mg treatments, and superoxide dismutase (SOD), ascorbate peroxidase (APX), H2O2, malondialdehyde (MDA), and total ascorbate (AA) showed a marked increase in these treatments. Therefore, Brassica plants might be more sensitive to excess of these elements in the nutrient solution. The translocation factor (TF) and distribution coefficient (DC) values of Zn, Ca, and Mg indicated higher translocation and accumulation in deficient conditions. High biosynthesis and citrate content in Brassica plants may be associated mainly with a high-nutrient solution extraction ability of these plants. These results provide background data, which will be used to characterize TILLING mutants to study the effects of mutations in genes involved in regulating Zn, Ca, and Mg distribution and accumulation in plants. Copyright © 2014 Elsevier GmbH. All rights reserved.

  8. Improvement of the magnetic moment of NiZn ferrites induced by substitution of Nd3+ ions for Fe3+ ions

    NASA Astrophysics Data System (ADS)

    Wu, Xuehang; Chen, Wen; Wu, Wenwei; Wu, Juan; Wang, Qing

    2018-05-01

    Four types of Ni-Zn based ferrites materials having the general formula Ni0.5Zn0.5NdxFe2-xO4 (0.0 ≤ x ≤ 0.12) have been successfully synthesized by calcining oxalates in air and the influence of Nd content on the structure and magnetic properties of Ni0.5Zn0.5NdxFe2-xO4 is studied. X-ray diffraction examination confirms that a high-crystallized Ni0.5Zn0.5NdxFe2-xO4 with cubic spinel structure is obtained when the precursor is calcined at 1000 °C in air for 2 h. The substitutions of Nd3+ ions for partial Fe3+ ions do not change the spinel crystalline structure of MFe2O4. The incorporation of Nd3+ ions in place of Fe3+ ions in Ni-Zn ferrites increases the average crystallite size. Specific saturation magnetization decreases with increase in Nd content. This is because Nd3+ ions with smaller magnetic moment preferentially fill the octahedral sites. In addition, antiferromagnetic FeNdO3 increases with increase in Nd content. In this study, Ni0.5Zn0.5Nd0.08Fe1.92O4, calcined at 1000 °C, exhibits the highest magnetic moment (4.2954 μB) and the lowest coercivity (28.82 Oe).

  9. Microstructure, Mechanical Properties and Corrosion Behavior of Porous Mg-6 wt.% Zn Scaffolds for Bone Tissue Engineering

    NASA Astrophysics Data System (ADS)

    Yan, Yang; Kang, Yijun; Li, Ding; Yu, Kun; Xiao, Tao; Wang, Qiyuan; Deng, Youwen; Fang, Hongjie; Jiang, Dayue; Zhang, Yu

    2018-03-01

    Porous Mg-based scaffolds have been extensively researched as biodegradable implants due to their attractive biological and excellent mechanical properties. In this study, porous Mg-6 wt.% Zn scaffolds were prepared by powder metallurgy using ammonium bicarbonate particles as space-holder particles. The effects of space-holder particle content on the microstructure, mechanical properties and corrosion resistance of the Mg-6 wt.% Zn scaffolds were studied. The mean porosity and pore size of the open-cellular scaffolds were within the range 6.7-52.2% and 32.3-384.2 µm, respectively. Slight oxidation was observed at the grain boundaries and on the pore walls. The Mg-6 wt.% Zn scaffolds were shown to possess mechanical properties comparable with those of natural bone and had variable in vitro degradation rates. Increased content of space-holder particles negatively affected the mechanical behavior and corrosion resistance of the Mg-6 wt.% Zn scaffolds, especially when higher than 20%. These results suggest that porous Mg-6 wt.% Zn scaffolds are promising materials for application in bone tissue engineering.

  10. Combinatorial sputtering of Ga-doped (Zn,Mg)O for contact applications in solar cells

    DOE PAGES

    Rajbhandari, Pravakar P.; Bikowski, Andre; Perkins, John D.; ...

    2016-09-20

    In this study, the development of tunable contact materials based on environmentally friendly chemical elements using scalable deposition approaches is necessary for existing and emerging solar energy conversion technologies. In this paper, the properties of ZnO alloyed with magnesium (Mg), and doped with gallium (Ga) are studied using combinatorial thin film experiments. As a result of these studies, the optical band gap of the sputtered Zn 1-xMg xO thin films was determined to vary from 3.3 to 3.6 eV for a compositional spread of Mg content in the 0.04 < x < 0.17 range. Depending on whether or not Gamore » dopants were added, the electron concentrations were on the order of 10 17 cm -3 or 10 20 cm -3, respectively. Based on these results and on the Kelvin Probe work function measurements, a band diagram was derived using basic semiconductor physics equations. The quantitative determination of how the energy levels of Ga-doped (Zn, Mg)O thin films change as a function of Mg composition presented here, will facilitate their use as optimized contact layers for both Cu 2ZnSnS 4 (CZTS), Cu(In, Ga)Se 2 (CIGS) and other solar cell absorbers.« less

  11. Chemical and electronic studies of CoFeB / MgO / CoFeB magnetic tunnel junctions

    NASA Astrophysics Data System (ADS)

    Read, J.; Cha, J.; Huang, P.; Egelhoff, W.; Muller, D.; Buhrman, R.

    2008-03-01

    MgO based magnetic tunnel junctions (MTJs), particularly the CoFeB/MgO/CoFeB system, exhibit large tunneling magnetoresistance (TMR) which makes them viable for MRAM [1] and sensor applications. Careful engineering of the MgO tunnel barriers, CoFeB electrodes, and their interfaces is essential for optimizing device performance [2,3], which motivates investigation of the chemical and electronic properties of high quality MTJs. We correlate scanning tunneling (STS), x-ray photoelectron (XPS) [4], and electron energy loss (EELS) [5] spectroscopies with current-in-plane tunneling (CIPT) measurements to gain insight on the electronic structure and chemistry of MgO MTJ structures. The measurements reveal that quite high TMR (>200%) can be obtained when there is substantial boron in the tunnel barrier, showing that proper doping of the MgO layer plays a significant role in the performance of such MTJs. We will discuss the impact of materials properties upon transport measurements and provide suggestions for greater control over MTJ device characteristics. [1] Parkin, Nat. Mater. 3, 862 (2004). [2] Nagamine, APL 89, 162507 (2006). [3] Lee, APL 90, 212507 (2007). [4] Read, APL 90, 132503 (2007). [5] Cha, APL 91, 062516 (2007).

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

    NASA Astrophysics Data System (ADS)

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

    1985-11-01

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

  13. Calculation of phase diagrams for the FeCl2, PbCl2, and ZnCl2 binary systems by using molecular dynamics simulation

    NASA Astrophysics Data System (ADS)

    Seo, Won-Gap; Matsuura, Hiroyuki; Tsukihashi, Fumitaka

    2006-04-01

    Recently, molecular dynamics (MD) simulation has been widely employed as a very useful method for the calculation of various physicochemical properties in the molten slags and fluxes. In this study, MD simulation has been applied to calculate the structural, transport, and thermodynamic properties for the FeCl2, PbCl2, and ZnCl2 systems using the Born—Mayer—Huggins type pairwise potential with partial ionic charges. The interatomic potential parameters were determined by fitting the physicochemical properties of iron chloride, lead chloride, and zinc chloride systems with experimentally measured results. The calculated structural, transport, and thermodynamic properties of pure FeCl2, PbCl2, and ZnCl2 showed the same tendency with observed results. Especially, the calculated structural properties of molten ZnCl2 and FeCl2 show the possibility of formation of polymeric network structures based on the ionic complexes of ZnCl{4/2-}, ZnCl{3/-}, FeCl{4/2-}, and FeCl{3/-}, and these calculations have successfully reproduced the measured results. The enthalpy, entropy, and Gibbs energy of mixing for the PbCl2-ZnCl2, FeCl2-PbCl2, and FeCl2-ZnCl2 systems were calculated based on the thermodynamic and structural parameters of each binary system obtained from MD simulation. The phase diagrams of the PbCl2-ZnCl2, FeCl2-PbCl2, and FeCl2-ZnCl2 systems estimated by using the calculated Gibbs energy of mixing reproduced the experimentally measured ones reasonably well.

  14. Development of Room Temperature Excitonic Lasing From ZnO and MgZnO Thin Film Based Metal-Semiconductor-Metal Devices

    NASA Astrophysics Data System (ADS)

    Suja, Mohammad Zahir Uddin

    Room temperature excitonic lasing is demonstrated and developed by utilizing metal-semiconductor-metal devices based on ZnO and MgZnO materials. At first, Cu-doped p-type ZnO films are grown on c-sapphire substrates by plasma-assisted molecular beam epitaxy. Photoluminescence (PL) experiments reveal a shallow acceptor state at 0.15 eV above the valence band edge. Hall effect results indicate that a growth condition window is found for the formation of p-type ZnO thin films and the best conductivity is achieved with a high hole concentration of 1.54x1018 cm-3, a low resistivity of 0.6 O cm and a moderate mobility of 6.65 cm2 V -1 s-1 at room temperature. Metal oxide semiconductor (MOS) capacitor devices have been fabricated on the Cu-doped ZnO films and the characteristics of capacitance-voltage measurements demonstrate that the Cu-doped ZnO thin films under proper growth conditions are p-type. Seebeck measurements on these Cu-doped ZnO samples lead to positive Seebeck coefficients and further confirm the p-type conductivity. Other measurements such as XRD, XPS, Raman and absorption are also performed to elucidate the structural and optical characteristics of the Cu-doped p-type ZnO films. The p-type conductivity is explained to originate from Cu substitution of Zn with a valency of +1 state. However, all p-type samples are converted to n-type over time, which is mostly due to the carrier compensation from extrinsic defects of ZnO. To overcome the stability issue of p-type ZnO film, alternate devices other than p-n junction has been developed. Electrically driven plasmon-exciton coupled random lasing is demonstrated by incorporating Ag nanoparticles on Cu-doped ZnO metal-semiconductor-metal (MSM) devices. Both photoluminescence and electroluminescence studies show that emission efficiencies have been enhanced significantly due to coupling between ZnO excitons and Ag surface plasmons. With the incorporation of Ag nanoparticles on ZnO MSM structures, internal quantum

  15. Band-gap bowing and p-type doping of (Zn, Mg, Be)O wide-gap semiconductor alloys: a first-principles study

    NASA Astrophysics Data System (ADS)

    Shi, H.-L.; Duan, Y.

    2008-12-01

    Using a first-principles band-structure method and a special quasirandom structure (SQS) approach, we systematically calculate the band gap bowing parameters and p-type doping properties of (Zn, Mg, Be)O related random ternary and quaternary alloys. We show that the bowing parameters for ZnBeO and MgBeO alloys are large and dependent on composition. This is due to the size difference and chemical mismatch between Be and Zn(Mg) atoms. We also demonstrate that adding a small amount of Be into MgO reduces the band gap indicating that the bowing parameter is larger than the band-gap difference. We select an ideal N atom with lower p atomic energy level as dopant to perform p-type doping of ZnBeO and ZnMgBeO alloys. For N doped in ZnBeO alloy, we show that the acceptor transition energies become shallower as the number of the nearest neighbor Be atoms increases. This is thought to be because of the reduction of p- d repulsion. The NO acceptor transition energies are deep in the ZnMgBeO quaternary alloy lattice-matched to GaN substrate due to the lower valence band maximum. These decrease slightly as there are more nearest neighbor Mg atoms surrounding the N dopant. The important natural valence band alignment between ZnO, MgO, BeO, ZnBeO, and ZnMgBeO quaternary alloy is also investigated.

  16. Fabrication of a novel NiFe2O4/Zn-Al layered double hydroxide intercalated with EDTA composite and its adsorption behavior for Cr(VI) from aqueous solution

    NASA Astrophysics Data System (ADS)

    Deng, Lin; Shi, Zhou; Wang, Li; Zhou, Shiqing

    2017-05-01

    A novel magnetic NiFe2O4/Zn-Al layered double hydroxide intercalated with EDTA composite (NiFe2O4/ZnAl-EDTA LDH) was prepared through modified coprecipitation method and employed for adsorptive removal of Cr(VI) from aqueous solution. The adsorbents were characterized using Brunauer-Emmett-Teller (BET), scanning electron microscopy (SEM), transmission electron microscope (TEM), X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), vibrating sample magnetometer (VSM), and X-ray photoelectron spectroscopy (XPS). Factors affecting the Cr(VI) adsorption, such as initial solution pH, adsorbent dosage, contact time, initial Cr(VI) concentration, temperature and coexisting ions, were studied systematically. Experiments results show that the magnetic NiFe2O4/ZnAl-EDTA LDH exhibits high adsorption efficiency within a wide pH range of 3.0-7.0 (R>80% at Cr(VI) concentration 50 mg L-1, contact time 360 min, and adsorbent dosage 2 g/L) and quick separation property. The adsorption process is fitted well with the Langmuir isotherm and pseudo-second-order kinetic model. The maximum theoretical adsorption capacity is found to be 77.22 mg g-1 at pH 6.0 and 318 K. The positive ΔH value (2.907 kJ mol-1) and negative ΔG value (-4.722 kJ mol-1) at 298-318 K reveals that the adsorption process is feasible, spontaneous and endothermic. Coexisting anions (PO43-, SO42-, CO32-, HCO3-, Cl-, and NO3-) have no significant effect on Cr(VI) removal. The mechanism study indicates that the adsorption of Cr(VI) onto NiFe2O4/ZnAl-EDTA LDH mainly involves electrostatic attraction and ion exchange interaction. It is interesting to note that a proportion of Cr(VI) adsorbed on the adsorbent surface are reduced to Cr(III) during the adsorption process. Results from this study demonstrate the potential utility of the magnetic NiFe2O4/ZnAl-EDTA LDH that could be developed into a viable technology for efficient removal of Cr(VI) from aqueous solution.

  17. Negative tunneling magnetoresistance of Fe/MgO/NiO/Fe magnetic tunnel junction: Role of spin mixing and interface state

    NASA Astrophysics Data System (ADS)

    Zhang, Y.; Yan, X. H.; Guo, Y. D.; Xiao, Y.

    2017-08-01

    Motivated by a recent tunneling magnetoresistance (TMR) measurement in which the negative TMR is observed in MgO/NiO-based magnetic tunnel junctions (MTJs), we have performed systematic calculations of transmission, current, and TMR of Fe/MgO/NiO/Fe MTJ with different thicknesses of NiO and MgO layers based on noncollinear density functional theory and non-equilibrium Green's function theory. The calculations show that, as the thickness of NiO and MgO layers is small, the negative TMR can be obtained which is attributed to the spin mixing effect and interface state. However, in the thick MTJ, the spin-flipping scattering becomes weaker, and thus, the MTJs recover positive TMR. Based on our theoretical results, we believe that the interface state at Fe/NiO interface and the spin mixing effect induced by noncollinear interfacial magnetization will play important role in determining transmission and current of Fe/MgO/NiO/Fe MTJ. The results reported here will be important in understanding the electron tunneling in MTJ with the barrier made by transition metal oxide.

  18. Effect of Fe incorporation on the optical behavior of ZnO thin films prepared by sol-gel derived spin coating techniques

    NASA Astrophysics Data System (ADS)

    Rakkesh, R. Ajay; Malathi, R.; Balakumar, S.

    2013-02-01

    In this work, Fe doped Zinc Oxide (ZnO) thin films were fabricated on the glass substrate by sol-gel derived spin coating technique. X-ray Diffraction studies revealed that the obtained pure and Fe doped ZnO thin films were in the wurtzite and spinel phase respectively. The three well defined Raman lines at 432, 543 and 1091 cm-1 also confirmed the lattice structure of the ZnO thin film has wurtzite symmetry. While doping Fe atoms in the ZnO, there was a significant change in the phase from wurtzite to spinel structure; owing to Fe (III) ions being incorporated into the lattice through substitution of Zn (II) ions. Room temperature PL spectra showed that the role of defect mediated red emissions at 612 nm was due to radial recombination of a photogenerated hole with an electron that belongs to the Fe atoms, which were discussed in detail.

  19. Layered double hydroxides as adsorbents and carriers of the herbicide (4-chloro-2-methylphenoxy)acetic acid (MCPA): systems Mg-Al, Mg-Fe and Mg-Al-Fe.

    PubMed

    Bruna, F; Celis, R; Pavlovic, I; Barriga, C; Cornejo, J; Ulibarri, M A

    2009-09-15

    Hydrotalcite-like compounds [Mg(3)Al(OH)(8)]Cl x 4H(2)O; [Mg(3)Fe(OH)(8)]Cl x 4H(2)O; [Mg(3)Al(0.5)Fe(0.5)(OH)(8)]Cl x 4H(2)O (LDHs) and calcined product of [Mg(3)Al(OH)(8)]Cl x 4H(2)O, Mg(3)AlO(4.5) (HT500), were studied as potential adsorbents of the herbicide MCPA [(4-chloro-2-methylphenoxy)acetic acid] as a function of pH, contact time and pesticide concentration, and also as support for the slow release of this pesticide, with the aim to reduce the hazardous effects that it can pose to the environment. The information obtained in the adsorption study was used for the preparation of LDH-MCPA complexes. The results showed high and rapid adsorption of MCPA on the adsorbents as well as that MCPA formulations based on LDHs and HT500 as pesticide supports displayed controlled release properties and reduced herbicide leaching in soil columns compared to a standard commercial MCPA formulation. Thereby, we conclude that the LDHs employed in this study can be used not only as adsorbents to remove MCPA from aqueous solutions, but also as supports for the slow release of this highly mobile herbicide, thus controlling its immediate availability and leaching.

  20. The Formation of Fe/Mg Smectite Under Mildly Acidic Conditions on Early Mars

    NASA Technical Reports Server (NTRS)

    Sutter, Brad; Golden, D. C.; Ming, Douglas W.; Niles, P. B.

    2011-01-01

    The detection of Fe/Mg smectites and carbonate in Noachian and early Hesperian terrain of Mars has been used to suggest that neutral to mildly alkaline conditions prevailed during the early history of Mars. However, if early Mars was neutral to moderately alkaline with a denser CO2 atmosphere than today, then large carbonates deposits should be more widely detected in Noachian terrain. The critical question is: Why have so few carbonate deposits been detected compared to Fe/Mg smectites? We suggest that Fe/Mg smectites on early Mars formed under mildly acidic conditions, which would inhibit the extensive formation of carbonate deposits. The goal of this work is to evaluate the formation of Fe/Mg smectites under mildly acidic conditions. The stability of smectites under mildly acidic conditions is attributed to elevated Fe/Mg activities that inhibit smectite dissolution. Beidelite and saponite have been shown to form from hydrothermal alteration of basaltic glass at pH 3.5-4.0 in seawater solutions. Nontronite is also known to be stable in mildly acidic systems associated with mafic and ultramafic rock. Nontronite was shown to form in acid sulfate soils in the Bangkok Plain, Thailand due to oxidation of Fe-sulfides that transformed saponite to nontronite. Smectite is known to transform to kaolinite in naturally acid soils due to selective leaching of Mg. However, if Mg removal is limited, then based on equilibrium relationships, the dissolution of smectite should be minimized. If Fe and Mg solution activities are sufficiently high, such as might be found in a low water/rock ratio system that is poorly drained, smectite could form and remain stable under mildly acidic conditions on Mars. The sources of mild acidity on early Mars includes elevated atmospheric CO2 levels, Fe-hydrolysis reactions, and the presence of volcanic SO2 aerosols. Equilibrium calculations dictate that water equilibrated with an early Mars CO2 atmosphere at 1 to 4 bar yields a pH of 3.6 to 3

  1. Fe2 PO5 -Encapsulated Reverse Energetic ZnO/Fe2 O3 Heterojunction Nanowire for Enhanced Photoelectrochemical Oxidation of Water.

    PubMed

    Qin, Dong-Dong; He, Cai-Hua; Li, Yang; Trammel, Antonio C; Gu, Jing; Chen, Jing; Yan, Yong; Shan, Duo-Liang; Wang, Qiu-Hong; Quan, Jing-Jing; Tao, Chun-Lan; Lu, Xiao-Quan

    2017-07-10

    Zinc oxide is regarded as a promising candidate for application in photoelectrochemical water oxidation due to its higher electron mobility. However, its instability under alkaline conditions limits its application in a practical setting. Herein, we demonstrate an easily achieved wet-chemical route to chemically stabilize ZnO nanowires (NWs) by protecting them with a thin layer Fe 2 O 3 shell. This shell, in which the thickness can be tuned by varying reaction times, forms an intact interface with ZnO NWs, thus protecting ZnO from corrosion in a basic solution. The reverse energetic heterojunction nanowires are subsequently activated by introducing an amorphous iron phosphate, which substantially suppressed surface recombination as a passivation layer and improved photoelectrochemical performance as a potential catalyst. Compared with pure ZnO NWs (0.4 mA cm -2 ), a maximal photocurrent of 1.0 mA cm -2 is achieved with ZnO/Fe 2 O 3 core-shell NWs and 2.3 mA cm -2 was achieved for the PH 3 -treated NWs at 1.23 V versus RHE. The PH 3 low-temperature treatment creates a dual function, passivation and catalyst layer (Fe 2 PO 5 ), examined by X-ray photoelectron spectroscopy, TEM, photoelectrochemical characterization, and impedance measurements. Such a nano-composition design offers great promise to improve the overall performance of the photoanode material. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  2. Effects of Sm addition on electromagnetic interference shielding property of Mg-Zn-Zr alloys

    NASA Astrophysics Data System (ADS)

    Yang, Chubin; Pan, Fusheng; Chen, Xianhua; Luo, Ning

    2017-06-01

    The electromagnetic interference (EMI) shielding of Sm-containing magnesium alloys in the 30-1500 MHz testing frequency range was investigated by coaxial cable method. The results demonstrated that Mg-3Zn alloys displayed the best electromagnetic shielding property. When 0.5 wt% of Zr was added for crystal grain refinement, the shielding effectiveness (SE) was apparently reduced. The addition of the rare earth element Sm in ZK magnesium alloys can improve the electromagnetic interference shielding of magnesium alloys. The main reason for the differences in electromagnetic interference shielding of magnesium alloys was the change in conductivity. The addition of Zr in Mg-Zn alloys can refine the grains and consequently improve the grain boundary area significantly. Therefore, the number of irregularly arranged atoms at the grain boundaries increased, decreasing the conductivity of magnesium alloys and leading to a decrease in the electromagnetic interference shielding. Following the Sm addition, the Mg-Zn-Sm phase was precipitated at the grain boundaries and in cores. The precipitation of Sm-containing rare earth phases could consume the solid-soluted Zn atoms within the Mg, resulting in an increase in electrical conductivity and electromagnetic interference shielding improvement.

  3. Deep-Ultraviolet Luminescence of Rocksalt-Structured Mg x Zn1-x O (x > 0.5) Films on MgO Substrates

    NASA Astrophysics Data System (ADS)

    Kaneko, Kentaro; Tsumura, Keiichi; Ishii, Kyohei; Onuma, Takayoshi; Honda, Tohru; Fujita, Shizuo

    2018-04-01

    Rocksalt-structured Mg x Zn1-x O films with Mg composition x of 0.47, 0.57, and 0.64 were grown on (100)-oriented MgO substrates using mist chemical vapor deposition. Cathodoluminescence measurements showed deep ultraviolet (DUV) emission peaking at 4.88 eV (254 nm), 5.15 eV (241 nm), and 5.21 eV (238 nm), respectively, at 12 K. The peak energies were lower than the band gap energies by ca. 1 eV, suggesting that the deep ultraviolet (DUV) emission may be recognized as near band edge luminescence but is associated with impurities, defects, or band fluctuations. The use of carbon-free precursors in the growth is suggested to eliminate carbon impurities and to improve the optical properties of Mg x Zn1-x O.

  4. Synthesis, characterization, and antibacterial activities of ZnLaFe2O4/NiTiO3 nanocomposite

    NASA Astrophysics Data System (ADS)

    Sobhani-Nasab, Ali; Zahraei, Zohreh; Akbari, Maryam; Maddahfar, Mahnaz; Hosseinpour-Mashkani, S. Mostafa

    2017-07-01

    In this research, for the first time, ZnLaFe2O4/NiTiO3 nanocomposites have been synthesized through a polyol assistant sol-gel method. To investigate the effect of different surfactants on the morphology and particle size of ZnLaFe2O4 nanostructure, cetrimonium bromide, sodium dodecyl sulfate, polyvinylpyrrolidone, polyvinyl alcohol, and oleic acid were used as surfactant agents. Based on the SEM results, it was found that morphology and particle size of the products could be affected by these surfactants. Furthermore, study on antibacterial effect of ZnLaFe2O4/NiTiO3 nanocomposites by colony forming unit (CFU) reduction assay showed that ZnLaFe2O4/NiTiO3 nanocomposites have antibacterial activity against Gram-negative Escherchia coli (ATCC 10536) and Gram-positive Staphylococcus aureus (ATCC 29737). Antibacterial results demonstrate that nanocomposite significantly reduced the growth rate of E. coli bacteria and S. aureus after 120 min. The structure and morphology of the resulting particles were characterized by XRD, FT-IR, EDX, and SEM analysis.

  5. Structure and electromagnetic properties of FeSiAl particles coated by MgO

    NASA Astrophysics Data System (ADS)

    Zhang, Yu; Zhou, Ting-dong

    2017-03-01

    FeSiAl particles with a layer of MgO surface coating have excellent soft magnetic and electromagnetic properties. In order to obtain the FeSiAl/MgO composites, Mg(OH)2 sol prepared by sol-gel process was well-mixed with FeSiAl flake particles, and then treated by calcination at 823 K in vacuum. The microstructural, morphological and electromagnetic parameters of FeSiAl/MgO particles were tested. Accordingly, the electromagnetic wave reflection loss in the frequency range of 0.5-18 GHz was calculated. The results show that the surface coating increases coercivity Hc and decreases complex permittivity, leading to a good impedance matching. When the coating amount was 7.5%, reflection loss of the composite particles can reach to -33 dB.

  6. Fe2O3/ZnO/ZnFe2O4 composites for the efficient photocatalytic degradation of organic dyes under visible light

    NASA Astrophysics Data System (ADS)

    Li, Xiaojuan; Jin, Bo; Huang, Jingwen; Zhang, Qingchun; Peng, Rufang; Chu, Shijin

    2018-06-01

    In this study, novel ternary Fe2O3/ZnO/ZnFe2O4 (ZFO) composites were successfully prepared through a simple hydrothermal reaction with subsequent thermal treatment. The as-prepared products were characterized by X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), Brunauer-Emmett-Teller (BET) analysis, Barrett-Joyner-Halenda (BJH) measurement, and UV-vis diffuse reflectance spectroscopy (UV-vis DRS). The photocatalytic degradation of rhodamine B (Rh B) under visible light irradiation indicated that the ZFO composites calcined at 500 °C has the best photocatalytic activity (the photocatalytic degradation efficiency can reach up to 95.7% within 60 min) and can maintain a stable photocatalytic degradation efficiency for at least three cycles. In addition, the photocatalytic activity of ZFO composites toward dye decomposition follows the order cationic Rh B > anionic methyl orange. Finally, using different scavengers, superoxide and hydroxyl radicals were identified as the primary active species during the degradation reaction of Rh B.

  7. Preparation, characterization and photocatalytic activity of visible-light-driven plasmonic Ag/AgBr/ZnFe{sub 2}O{sub 4} nanocomposites

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

    Li, Xiaojuan, E-mail: lixiaojuan@fzu.edu.cn; Tang, Duanlian; Tang, Fan

    2014-08-15

    Highlights: • A plasmonic Ag/AgBr/ZnFe{sub 2}O{sub 4} photocatalyst has been successfully synthesized. • Ag/AgBr/ZnFe{sub 2}O{sub 4} nanocomposites exhibit high visible light photocatalytic activity. • Ag/AgBr/ZnFe{sub 2}O{sub 4} photocatalyst is stable and magnetically separable. - Abstract: A visible-light-driven plasmonic Ag/AgBr/ZnFe{sub 2}O{sub 4} nanocomposite has been successfully synthesized via a deposition–precipitation and photoreduction through a novel one-pot process. X-ray diffraction spectroscopy, X-ray photoelectron spectroscopy, scanning electron microscopy, transmission electron microscopy and UV–vis diffuse reflectance spectroscopy were employed to investigate the crystal structure, chemical composition, morphology, and optical properties of the as-prepared nanocomposites. The photocatalytic activities of the nanocomposites were evaluated by photodegradationmore » of Rhodamine B (RhB) and phenol under visible light. The results demonstrated that the obtained Ag/AgBr/ZnFe{sub 2}O{sub 4} nanocomposites exhibited higher photocatalytic activity as compared to pure ZnFe{sub 2}O{sub 4}. In addition, the sample photoreduced for 20 min and calcined at 500 °C achieved the highest photocatalytic activity. Furthermore, the Ag/AgBr/ZnFe{sub 2}O{sub 4} nanocomposite has high stability under visible light irradiation and could be conveniently separated by using an external magnetic field.« less

  8. Performance of Zn-Fe-Mn/MCM-48 sorbents for high temperature H2S removal and analysis of regeneration process

    NASA Astrophysics Data System (ADS)

    Huang, Z. B.; Liu, B. S.; Wang, F.; Amin, R.

    2015-10-01

    MCM-48 was synthesized using a rapid and facile process at room temperature. A series of 50%Zn-Fe-Mn/MCM-48 sorbents were prepared and their performance of hot coal gas desulfurization was investigated. High breakthrough sulfur capacity (13.2 g-S/100 g sorbent) and utilization (66.1%) of 50%1Zn2Fe2Mn/MCM-48 sorbent at 550 °C was achieved. The characterization results of XRD, BET, TPR and FT-IR revealed that MCM-48 had excellent thermal stability at less than 700 °C, ZnMn2O4 and (Mn, Zn)Fe2O4 were mainly active particles in fresh sorbents which were highly dispersed on support. The MCM-48 mesoporous structure remained intact after eight successive desulfurization/regeneration cycles. The regeneration process of 50%1Zn2Fe2Mn/MCM-48 sorbent was analyzed, it indicated that the breakthrough sulfur capacity decline of sorbent was due to the migration of Zn onto the sorbent surface and Zn accumulated on the surface and vaporized to the exterior from the surface. In the TPO test, the oxidation of Zn was different for 50%Zn/MCM-48 at 700 °C. It revealed that the temperature of regeneration for ZnO sorbent should be higher than 700 °C.

  9. Enhanced antibacterial properties, biocompatibility, and corrosion resistance of degradable Mg-Nd-Zn-Zr alloy.

    PubMed

    Qin, Hui; Zhao, Yaochao; An, Zhiquan; Cheng, Mengqi; Wang, Qi; Cheng, Tao; Wang, Qiaojie; Wang, Jiaxing; Jiang, Yao; Zhang, Xianlong; Yuan, Guangyin

    2015-06-01

    Magnesium (Mg), a potential biodegradable material, has recently received increasing attention due to its unique antibacterial property. However, rapid corrosion in the physiological environment and potential toxicity limit clinical applications. In order to improve the corrosion resistance meanwhile not compromise the antibacterial activity, a novel Mg alloy, Mg-Nd-Zn-Zr (Hereafter, denoted as JDBM), is fabricated by alloying with neodymium (Nd), zinc (Zn), zirconium (Zr). pH value, Mg ion concentration, corrosion rate and electrochemical test show that the corrosion resistance of JDBM is enhanced. A systematic investigation of the in vitro and in vivo antibacterial capability of JDBM is performed. The results of microbiological counting, CLSM, SEM in vitro, and microbiological cultures, histopathology in vivo consistently show JDBM enhanced the antibacterial activity. In addition, the significantly improved cytocompatibility is observed from JDBM. The results suggest that JDBM effectively enhances the corrosion resistance, biocompatibility and antimicrobial properties of Mg by alloying with the proper amount of Zn, Zr and Nd. Copyright © 2015 Elsevier Ltd. All rights reserved.

  10. Effect of NiO spin orientation on the magnetic anisotropy of the Fe film in epitaxially grown Fe/NiO/Ag(001) and Fe/NiO/MgO(001)

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

    Kim, W.; Jin, E.; Wu, J.

    Single crystalline Fe/NiO bilayers were epitaxially grown on Ag(001) and on MgO(001), and investigated by Low Energy Electron Diffraction (LEED), Magneto-Optic Kerr Effect (MOKE), and X-ray Magnetic Linear Dichroism (XMLD). We find that while the Fe film has an in-plane magnetization in both Fe/NiO/Ag(001) and Fe/NiO/MgO(001) systems, the NiO spin orientation changes from in-plane direction in Fe/NiO/Ag(001) to out-of-plane direction in Fe/NiO/MgO(001). These two different NiO spin orientations generate remarkable different effects that the NiO induced magnetic anisotropy in the Fe film is much greater in Fe/NiO/Ag(001) than in Fe/NiO/MgO(001). XMLD measurement shows that the much greater magnetic anisotropy inmore » Fe/NiO/Ag(001) is due to a 90{sup o}-coupling between the in-plane NiO spins and the in-plane Fe spins.« less

  11. Effect of CaO on Hot Workability and Microstructure of Mg-9.5Zn-2Y Alloy

    NASA Astrophysics Data System (ADS)

    Kwak, Tae-yang; Kim, Daeguen; Yang, Jaehack; Yoon, Young-ok; Kim, Shae K.; Lim, Hyunkyu; Kim, Woo Jin

    Mg-Zn-Y system alloys have been a great interest because Mg-Zn-Y alloys with I-phase exhibited high ductility at room and elevated temperatures. According to our preliminary experiments, the addition of CaO improved strength, but the process window became narrow. Therefore, the aim of current work was to find optimum extrusion conditions for CaO added Mg-Zn-Y alloys by processing maps. The 0.3 wt.% of CaO added Mg-9.5Zn-2Y (Mg95.6Zn3.8Y0.6) alloy was prepared by casting into steel mold and homogenizing. Hot compression test were performed in the Gleeble machine at temperature range of 250-400 °C with various strain rates. The alloys were extruded with a reduction ratio of 20:1. To analyze the microstructure and texture, optical micrograph, scanning electron microscope and electron backscattered diffraction were used. Moreover, we investigated the effects of metallic Ca addition in this alloy to compare with the addition of CaO.

  12. Influence of Cu Addition on the Structure, Mechanical and Corrosion Properties of Cast Mg-2%Zn Alloy

    NASA Astrophysics Data System (ADS)

    Lotfpour, M.; Emamy, M.; Dehghanian, C.; Tavighi, K.

    2017-05-01

    Effects of different concentrations of Cu on the structure, mechanical and corrosion properties of Mg-2%Zn alloy were studied by the use of x-ray diffraction, optical microscopy, scanning electron microscopy, energy dispersive spectroscopy, standard tensile testing, polarization and electrochemical impedance spectroscopy (EIS) measurements. The average grain size of the alloy decreased from above 1000 μm to about 200 μm with 5 wt.% Cu addition in as-cast condition. Microstructural studies revealed that Mg-2Zn- xCu alloys matrix typically consists of primary α-Mg and MgZnCu and Mg(Zn,Cu)2 intermetallics which are mainly found at the grain boundaries. The results obtained from mechanical testing ascertained that Cu addition increased the hardness values significantly. Although the addition of 0.5 wt.% Cu improved the ultimate tensile strength and elongation values, more Cu addition (i.e., 5 wt.%) weakened the tensile properties of the alloy by introducing semi-continuous network of brittle intermetallic phases. Based on polarization test results, it can be concluded that Cu eliminates a protective film on Mg-2%Zn alloy surface. Among Mg-2%Zn- x%Cu alloys, the one containing 0.1 wt.% Cu exhibited the best anti-corrosion property. However, further Cu addition increased the volume fraction of intermetallics culminating in corrosion rate enhancement due to the galvanic couple effect. EIS and microstructural analysis also confirmed the polarization results.

  13. Homoepitaxial nonpolar (10-10) ZnO/ZnMgO monolithic microcavities: Towards reduced photonic disorder

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

    Zuniga-Perez, J., E-mail: jzp@crhea.cnrs.fr; Kappei, L.; Deparis, C.

    2016-06-20

    Nonpolar ZnO/ZnMgO-based optical microcavities have been grown on (10-10) m-plane ZnO substrates by plasma-assisted molecular beam epitaxy. Reflectivity measurements indicate an exponential increase of the cavity quality factor with the number of layers in the distributed Bragg reflectors. Most importantly, microreflectivity spectra recorded with a spot size in the order of 2 μm show a negligible photonic disorder (well below 1 meV), leading to local quality factors equivalent to those obtained by macroreflectivity. The anisotropic character of the nonpolar heterostructures manifests itself both in the surface features, elongated parallel to the in-plane c direction, and in the optical spectra, with twomore » cavity modes being observed at different energies for orthogonal polarizations.« less

  14. Critical Slowing Down in Zn-Mg-Ho Quasicrystal

    NASA Astrophysics Data System (ADS)

    Sugiyama, Jun; Nozaki, Hiroshi; Ansaldo, Eduardo J.; Morris, Gerald D.; Brewer, Jess H.; Sato, Taku J.

    By means of longitudinal field muon-spin spectroscopy, we have found a clear critical slowing down caused by spin fluctuation of Ho moments in the icosahedral quasicrystal (QC), i-ZnMgHo, with freezing temperature (Tf =1.95 K), for which the susceptibility showed an anomaly at5K. The difference is attributed to crystalline elec-tric field (CEF) effects. The muons experience a broad, fluctuating, field distribution, of width Δ ∼6.3Taround Tf . The effect of the CEF is also apparent in zero field and weak applied transverse field measurements, with an onset around 60 K. For the Cd-based QCs (CdMgHo and CdMgGd), which exhibited two freezing temperatures in the susceptibility, the change in fluctuation rate, i.e. freezing, occurs at the lower Tf .

  15. Magneto-optical properties of α-Fe2O3@ZnO nanocomposites prepared by the high energy ball-milling technique

    NASA Astrophysics Data System (ADS)

    Chaudhury, Chandana Roy; Roychowdhury, Anirban; Das, Anusree; Das, Dipankar

    2016-05-01

    Magnetic-fluorescent nanocomposites (NCs) with 10 wt% of α-Fe2O3 in ZnO have been prepared by the high energy ball-milling. The crystallite sizes of α-Fe2O3 and ZnO in the NCs are found to vary from 65 nm to 20 nm and 47 nm to 15 nm respectively as milling time is increased from 2 to 30 h. XRD analysis confirms presence of α-Fe2O3 and ZnO in pure form in all the NCs. UV-vis study of the NCs shows a continuous blue-shift of the absorption peak and a steady increase of band gap of ZnO with increasing milling duration that are assigned to decreasing particle size of ZnO in the NCs. Photoluminescence (PL) spectra of the NCs reveal three weak emission bands in the visible region at 421, 445 and 485 nm along with the strong near band edge emission at 391 nm. These weak emission bands are attributed to different defect - related energy levels e.g. Zn-vacancy, Zn interstitial and oxygen vacancy. Dc and ac magnetization measurements show presence of weakly interacting superparamagnetic (SPM) α-Fe2O3 particles in the NCs. 57Fe-Mössbauer study confirms presence of SPM hematite in the sample milled for 30 h. Positron annihilation lifetime measurements indicate presence of cation vacancies in ZnO nanostructures confirming results of PL studies.

  16. In vitro corrosion behavior and in vivo biodegradation of biomedical β-Ca3(PO4)2/Mg-Zn composites.

    PubMed

    Yu, Kun; Chen, Liangjian; Zhao, Jun; Li, Shaojun; Dai, Yilong; Huang, Qiao; Yu, Zhiming

    2012-07-01

    In this study 5, 10 and 15% β-Ca(3)(PO(4))(2)/Mg-Zn composites were prepared through powder metallurgy methods, and their corrosion behavior and mechanical properties were studied in simulated body fluid (SBF) at 37°C. The 10% β-Ca(3)(PO(4))(2)/Mg-Zn composite was selected for cytocompatibility assessment and in vivo biodegradation testing. The results identified the α-Mg, MgZn and β-Ca(3)(PO(4))(2) phases in these sintered composites. The density and elastic modulus of the β-Ca(3)(PO(4))(2)/Mg-6% Zn composite match those of natural bone, and the strength is approximately double that of natural bone. The 10% β-Ca(3)(PO(4))(2)/Mg-6% Zn composites exhibit good corrosion resistance, as determined by a 30 day immersion test and electrochemical measurements in SBF at 37°C. The 10% β-Ca(3)(PO(4))(2)/Mg-6% Zn composite is safe for cellular applications, with a cytotoxicity grade of ∼0-1 against L929 cells in in vitro testing. The β-Ca(3)(PO(4))(2)/Mg-6% Zn composite also exhibits good biocompatibility with the tissue and the important visceral organs the heart, kidney and liver of experimental rabbits. The composite has a suitable degradation rate and improves the concrescence of a pre-broken bone. The corrosion products, such as Mg(OH)(2) and Ca(5)(PO(4))(6)(OH)(2), can improve the biocompatibility of the β-Ca(3)(PO(4))(2)/Mg-Zn composite. Copyright © 2012 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

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

    DTIC Science & Technology

    2013-08-20

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

  18. Formation of the ZnFe2O4 phase in an electric arc furnace off-gas treatment system.

    PubMed

    Suetens, T; Guo, M; Van Acker, K; Blanpain, B

    2015-04-28

    To better understand the phenomena of ZnFe2O4 spinel formation in electric arc furnace dust, the dust was characterized with particle size analysis, X-ray fluorescence (XRF), electron backscatter diffraction (EBSD), and electron probe micro-analysis (EPMA). Different ZnFe2O4 formation reaction extents were observed for iron oxide particles with different particle sizes. ZnO particles were present as both individual particles and aggregated on the surface of larger particles. Also, the slag particles found in the off-gas were shown not to react with the zinc vapor. After confirming the presence of a ZnFe2O4 formation reaction, the thermodynamic feasibility of in-process separation - a new electric arc furnace dust treatment technology - was reevaluated. The large air intake and the presence of iron oxide particles in the off-gas were included into the thermodynamic calculations. The formation of the stable ZnFe2O4 spinel phase was shown to be thermodynamically favorable in current electric arc furnace off-gas ducts conditions even before reaching the post combustion chamber. Copyright © 2015 Elsevier B.V. All rights reserved.

  19. Adaptation to chronic MG132 reduces oxidative toxicity by a CuZnSOD-dependent mechanism

    PubMed Central

    Leak, Rehana K.; Zigmond, Michael J.; Liou, Anthony K. F.

    2010-01-01

    To study whether and how cells adapt to chronic cellular stress, we exposed PC12 cells to the proteasome inhibitor MG132 (0.1 μM) for 2 weeks and longer. This treatment reduced chymotrypsin-like proteasome activity by 47% and was associated with protection against both 6-hydroxydopamine (6-OHDA, 100 μM) and higher dose MG132 (40 μM). Protection developed slowly over the course of the first 2 weeks of exposure and was chronic thereafter. There was no change in total glutathione levels after MG132. Buthionine sulfoximine (100 μM) reduced glutathione levels by 60%, but exacerbated 6-OHDA toxicity to the same extent in both MG132-treated and control cells and failed to reduce MG132-induced protection. Chronic MG132 resulted in elevated antioxidant proteins CuZn superoxide dismutase (SOD, +55%), MnSOD (+21%), and catalase (+15%), as well as chaperone heat shock protein 70 (+42%). Examination of SOD enzyme activity revealed higher levels of CuZnSOD (+40%), with no change in MnSOD. We further assessed the mechanism of protection by reducing CuZnSOD levels with two independent siRNA sequences, both of which successfully attenuated protection against 6-OHDA. Previous reports suggested that artificial overexpression of CuZnSOD in dopaminergic cells is protective. Our data complement such observations, revealing that dopaminergic cells are also able to use endogenous CuZnSOD in self-defensive adaptations to chronic stress, and that they can even do so in the face of extensive glutathione loss. PMID:18466318

  20. The hot deformation behavior and microstructure evolution of HA/Mg-3Zn-0.8Zr composites for biomedical application.

    PubMed

    Liu, Debao; Liu, Yichi; Zhao, Yue; Huang, Y; Chen, Minfang

    2017-08-01

    The hot deformation behavior of nano-sized hydroxylapatite (HA) reinforced Mg-3Zn-0.8Zr composites were performed by means of Gleeble-1500D thermal simulation machine in a temperature range of 523-673K and a strain rate range of 0.001-1s -1 , and the microstructure evolution during hot compression deformation were also investigated. The results show that the flow stress increases increasing strain rates at a constant temperature, and decreases with increasing deforming temperatures at a constant strain rate. Under the same processing conditions, the flow stresses of the 1HA/Mg-3Zn-0.8Zr specimens are higher than those of the Mg-3Zn-0.8Zr alloy specimens, and the difference is getting closer with increasing deformation temperature. The hot deformation behaviors of Mg-3Zn-0.8Zr and 1HA/Mg-3Zn-0.8Zr can be described by constitutive equation of hyperbolic sine function with the hot deformation activation energy being 124.6kJ/mol and 125.3kJ/mol, respectively. Comparing with Mg-3Zn-0.8Zr alloy, the instability region in the process map of 1HA/Mg-3Zn-0.8Zr expanded to a bigger extent at the same conditions. The optimum process conditions of 1HA/Mg-3Zn-0.8Zr composite is concluded as between the temperature window of 573-623K with a strain rate range of 0.001-0.1s -1 . A higher volume fraction and smaller grain size of dynamic recrystallization (DRX) grains was observed in 1HA/Mg-3Zn-0.8Zr specimens after the hot compression deformation compared with Mg-3Zn-0.8Zr alloy, which was ascribed to the presence of the HA particles that play an important role in particle-stimulated nucleation (PSN) mechanism and can effectively hinder the migration of interfaces. Copyright © 2017 Elsevier B.V. All rights reserved.

  1. XAS study of chromium in Li 2MSiO 4 (M=Mg, Zn)

    NASA Astrophysics Data System (ADS)

    Jousseaume, C.; Ribot, F.; Kahn-Harari, A.; Vivien, D.; Villain, F.

    2003-01-01

    X-ray absorption spectroscopy (XAS) investigations at the Cr K-edge on Cr:Li 2MSiO 4 (M=Mg, Zn) have been performed to understand the exceptionally long fluorescence lifetime of Cr IV. Previous work has shown the simultaneous presence of three oxidation states Cr IV, Cr V and Cr VI. X-ray absorption near edge structure measurements confirm that Cr in Li 2MSiO 4 (M=Mg, Zn) single crystals is in tetrahedral coordination. They also reveal that Cr VI is the dominant species in Li 2MgSiO 4, and that Li 2ZnSiO 4 contains more Cr V than Li 2MgSiO 4. The extended X-ray absorption fine structure spectra of Cr:Li 2MgSiO 4 single crystals recorded at the Cr K-edge, are fitted with two types of Cr environments: the first one corresponds to oxygen atoms at a mean distance of 1.68 Å and the second to oxygen atoms at a mean distance of 2.07 Å. This second environment is attributed to Cr III in the minor parasitic phase LiCr IIIO 2. The first environment corresponds to Cr that substitutes silicon in the Li 2MgSiO 4 lattice in the silicon site if the cations sizes are considered.

  2. Hot-pressed production and laser properties of ZnSe:Fe2+

    NASA Astrophysics Data System (ADS)

    Avetisov, R. I.; Balabanov, S. S.; Firsov, K. N.; Gavrishchuk, E. M.; Gladilin, A. A.; Ikonnikov, V. B.; Kalinushkin, V. P.; Kazantsev, S. Yu.; Kononov, I. G.; Zykova, M. P.; Mozhevitina, E. N.; Khomyakov, A. V.; Savin, D. V.; Timofeeva, N. A.; Uvarov, O. V.; Avetissov, I. Ch.

    2018-06-01

    A new approach for fabrication of laser elements in form of plates based on ZnSe:Fe2+ with undoped faces, combining the advantages of hot pressing and diffusion techniques has been proposed. CVD-ZnSe was used as a host material. 1 μm Fe film was deposited by electron-beam technique on one side of the polished CVD-ZnSe plate (20 mm in diameter and 2 mm in thickness). The elements were stacked in contact by iron surfaces, placed in a hot press-mold die, heated under vacuum to 1000 °C, exposed during 60 min with the application of 25 MPa uniaxial pressure. The iron film was dissolved in ZnSe matrix and elements welded together. The samples were subjected to hot isostatic pressing (HIP) during 29 h at 100 MPa argon pressure and 1300 °C. The influence of sintering and HIP processing conditions on local morphology and properties of the interface of welded elements was studied by SEM, TEM and optical microscopy. For all composite elements the lasing was obtained at a pumping by HF-laser at RT with high efficiency around 40%. The proposed technique removes restrictions on the size of laser elements and appears to be very promising for the management of the distribution profile of the doping component.

  3. Preparation of low cost n-ZnO/MgO/p-Si heterojunction photodetector by laser ablation in liquid and spray pyrolysis

    NASA Astrophysics Data System (ADS)

    Ismail, Raid A.; Khashan, Khawla S.; Jawad, Muslim F.; Mousa, Ali M.; Mahdi, Farah

    2018-05-01

    In this study, low cost ZnO/Si and ZnO/MgO/Si heterojunction (HJ) photodetectors were fabricated using laser ablation and spray Pyrolysis techniques. MgO nanofibers were synthesized by laser ablation of Mg target in distilled water. Also; the ZnO films were prepared by spray pyrolysis technique. The optical and structural properties of nanostructured MgO were investigated using XRD, SEM and FT-IR. The XRD results showed that the MgO was polycrystalline with cubic structure. SEM investigation confirmed the formation of MgO nanofibers and sub-microparticles. The optical energy gaps of MgO and ZnO were calculated and found to be 5.7 eV and 3.3 eV, respectively. For the electrical properties; responsivity, quantum efficiency, specific detectivity, and speed of response of the photodetector were measured and found to enhance after the insertion of nanostructured MgO film. The Photoresponse results at 3 V reverse bias showed that the maximum responsivity of ZnO/Si and ZnO/MgO/Si photodetectors were 185 and 331 mAW‑1 at 500 nm, respectively. The specific detectivity of ZnO/MgO/Si Photodetector was higher than that of ZnO/Si.

  4. Broad range tuning of structural and optical properties of Zn x Mg1-x O nanostructures grown by vapor transport method

    NASA Astrophysics Data System (ADS)

    Vanjaria, Jignesh V.; Azhar, Ebraheem Ali; Yu, Hongbin

    2016-11-01

    One-dimensional (1D) Zn x Mg1-x O nanomaterials have drawn global attention due to their remarkable chemical and physical properties, and their diverse current and future technological applications. In this work, 1D ZnMgO nanostructures with different magnesium concentrations and different morphologies were grown directly on zinc oxide-coated silicon substrates by thermal evaporation of zinc oxide, magnesium boride and graphite powders. Highly well-defined Mg-rich ZnMgO nanorods with a rock salt structure and Zn-rich ZnMgO nanostructures with a wurtzite structure have been deposited individually by careful optimization of the source mixture and process parameters. Structural and optical properties of the deposited products were studied by scanning electron microscopy, energy dispersive x-ray spectroscopy, x-ray diffraction, and Raman spectroscopy. Cathodoluminescence measurements demonstrate strong dominant peaks at 3.3 eV in Mg poor ZnMgO nanostructures and 4.8 eV in Mg rich nanostructures implying that the ZnMgO nanostructures can be used for the fabrication of deep UV optoelectronic devices. A mechanism for the formation and achieved diverse morphology of the ZnMgO nanostructures was proposed based on the characterization results.

  5. Magnetically recyclable Ni0.5Zn0.5Fe2O4/Zn0.95Ni0.05O nano-photocatalyst: structural, optical, magnetic and photocatalytic properties.

    PubMed

    Qasim, Mohd; Asghar, Khushnuma; Singh, Braj Raj; Prathapani, Sateesh; Khan, Wasi; Naqvi, A H; Das, Dibakar

    2015-02-25

    A novel visible light active and magnetically separable nanophotocatalyst, Ni0.5Zn0.5Fe2O4/Zn0.95Ni0.05O (denoted as NZF@Z), with varying amount of Ni0.5Zn0.5Fe2O4, has been synthesized by egg albumen assisted sol gel technique. The structural, optical, magnetic, and photocatalytic properties have been studied by powder X-ray diffraction (XRD), transmission electron microscopy (TEM), field emission scanning electron microscopy (FESEM), fourier transform infrared spectroscopy (FTIR), UV-visible (UV-Vis) spectroscopy, and vibrating sample magnetometry (VSM) techniques. Powder XRD, TEM, FTIR and energy dispersive spectroscopic (EDS) analyses confirm coexistence of Ni0.5Zn0.5Fe2O4 and Zn0.95Ni0.05O phases in the catalyst. Crystallite sizes of Ni0.5Zn0.5Fe2O4 and Zn0.95Ni0.05O in pure phases and nanocomposites, estimated from Debye-Scherrer equation, are found to be around 15-25 nm. The estimated particle sizes from TEM and FESEM data are ∼(22±6) nm. The calculated energy band gaps, obtained by Tauc relation from UV-Vis absorption spectra, of Zn0.95Ni0.05O, 15%NZF@Z, 40%NZF@Z and 60%NZF@Z are 2.95, 2.72, 2.64, and 2.54 eV respectively. Magnetic measurements (field (H) dependent magnetization (M)) show all samples to be super-paramagnetic in nature and saturation magnetizations (Ms) decrease with decreasing ferrite content in the nanocomposites. These novel nanocomposites show excellent photocatalytic activities on Rhodamin Dye. Copyright © 2014 Elsevier B.V. All rights reserved.

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

    PubMed

    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.

  7. Microstructure and bio-corrosion behaviour of Mg-5Zn-0.5Ca -xSr alloys as potential biodegradable implant materials

    NASA Astrophysics Data System (ADS)

    Yan, Li; Zhou, Jiaxing; Sun, Zhenzhou; Yang, Meng; Ma, Liqun

    2018-04-01

    Magnesium alloys are widely studied as biomedical implants owing to their biodegradability. In this work, novel Mg-5Zn-0.5Ca-xSr (x = 0, 0.14, 0.36, 0.50, 0.70 wt%) alloys were prepared as biomedical materials. The influence of strontium (Sr) addition on the microstructure, corrosion properties and corrosion morphology of the as-cast Mg-5Zn-0.5Ca-xSr alloys is investigated by a variety of techniques such as scanning electron microscopy, x-ray diffraction, and electrochemical measurements. The Sr-free alloy is composed of three phases, namely, α-Mg, CaMg2 and Ca2Mg6Zn3, while the alloys with the Sr addition consist of α-Mg, CaMg2 and Ca2Mg6Zn3 and Mg17Sr2. Corrosion experiments in Hank’s solution show that the addition of a small amount of Sr can improve the corrosion resistance of the Mg-5Zn-0.5Ca alloy. The corrosion products include Mg(OH)2, Zn(OH)2, Ca(OH)2, and HA (Ca5(PO4)3(OH)). Mg-5Zn-0.5Ca-0.36Sr alloy has the minimum weight loss rate (0.68 mm/a), minimal hydrogen evolution (0.08 ml/cm2/d) and minimum corrosion current density (7.4 μA/cm2), indicating that this alloy shows the best corrosion resistance.

  8. The in vitro biological properties of Mg-Zn-Sr alloy and superiority for preparation of biodegradable intestinal anastomosis rings

    PubMed Central

    Liu, Ling; Li, Nianfeng; Lei, Ting; Li, Kaimo; Zhang, Yangde

    2014-01-01

    Background Magnesium (Mg) alloy is a metal-based biodegradable material that has received increasing attention in the field of clinical surgery, but it is currently seldom used in intestinal anastomosis. This study was conducted to comprehensively assess a ternary magnesium (Mg)-zinc (Zn)-strontium (Sr) alloy’s biological superiorities as a preparation material for intestinal anastomosis ring. Material/Methods Mouse L-929 fibroblasts were cultured with Mg-Zn-Sr alloy extract and compared with both positive (0.64% phenol) and negative (original broth culture) controls. The cell morphology of different groups was examined using microscopy, and a cytotoxicity assessment was performed. Fresh anticoagulated human blood was mixed with Mg-Zn-Sr alloy extract and compared with both positive (distilled water) and negative (normal saline) controls. The absorbance of each sample at 570 nm was used to calculate the Mg-Zn-Sr alloy hemolysis ratio in order to test the Mg alloy’s blood compatibility. Bacterial cultures of Escherichia coli, Pseudomonas aeruginosa, and Staphylococcus aureus were added to Mg-Zn-Sr alloy block samples and compared with positive (Ceftazidime), negative (316LSS stainless steel), and blank controls. The broth cultures were sampled to compare their bacterial colony counts so as to evaluate the antibacterial properties of the Mg-Zn-Sr alloy. The Mg-Zn-Sr alloy was surface-coated with a layer of poly(lactic-co-glycolic acid) carrying everolimus. The surface morphology and degradability of the coating were examined so as to demonstrate feasibility of coating, which can release the drug evenly. Results The experiments proved that Mg-Zn-Sr alloy has good biocompatible, antibacterial, and drug-loaded coating performances, which are lacking in existing intestinal anastomosis devices/materials. Conclusions The Mg-Zn-Sr alloy increases biocompatibility, and yields a safer and better therapeutic effect; therefore, it is a novel biomaterial that is feasible for

  9. Examination of the magnetic hyperthermia and other magnetic properties of CoFe2O4@MgFe2O4 nanoparticles using external field Mössbauer spectroscopy

    NASA Astrophysics Data System (ADS)

    Park, Jeongho; Choi, Hyunkyung; Kim, Sam Jin; Kim, Chul Sung

    2018-05-01

    CoFe2O4@MgFe2O4 core/shell nanoparticles were synthesized by high temperature thermal decomposition with seed-mediated growth. The crystal structure and magnetic properties of the nanoparticles were investigated using X-ray diffractometry (XRD), vibrating sample magnetometry (VSM), and Mössbauer spectrometry. The magnetic hyperthermia properties were investigated using a MagneTherm device. Analysis of the XRD patterns showed that CoFe2O4@MgFe2O4 had a cubic spinel crystal structure with space group Fd-3m and a lattice constant (a0) of 8.3686 Å. The size and morphology of the CoFe2O4@MgFe2O4 nanoparticles were confirmed by HR-TEM. The VSM measurements showed that the saturation magnetization (MS) of CoFe2O4@MgFe2O4 was 77.9 emu/g. The self-heating temperature of CoFe2O4@MgFe2O4 was 37.8 °C at 112 kHz and 250 Oe. The CoFe2O4@MgFe2O4 core/shell nanoparticles showed the largest saturation magnetization value, while their magnetic hyperthermia properties were between those of the CoFe2O4 and MgFe2O4 nanoparticles. In order to investigate the hyperfine interactions of CoFe2O4, MgFe2O4, and CoFe2O4@MgFe2O4, we performed Mössbauer spectrometry at various temperatures. In addition, Mössbauer spectrometry of CoFe2O4@MgFe2O4 was performed at 4.2 K with applied fields of 0-4.5 T, and the results were analyzed with sextets for the tetrahedral A-site and sextets for the octahedral B-site.

  10. Ab initio simulation of elastic and mechanical properties of Zn- and Mg-doped hydroxyapatite (HAP).

    PubMed

    Aryal, Sitaram; Matsunaga, Katsuyuki; Ching, Wai-Yim

    2015-07-01

    Hydroxyapatite (HAP) is an important bioceramic which constitutes the mineral components of bones and hard tissues in mammals. It is bioactive and used as bioceramic coatings for metallic implants and bone fillers. HAP readily absorbs a large amount of impurities. Knowledge on the elastic and mechanical properties of impurity-doped HAP is a subject of great importance to its potential for biomedical applications. Zn and Mg are the most common divalent cations HAP absorbs. Using density function theory based ab initio methods, we have carried out a large number of ab initio calculations to obtain the bulk elastic and mechanical properties of HAP with Zn or Mg doped in different concentration at the Ca1 and Ca2 sites using large 352-atom supercells. Detailed information on their dependece on the concetraion of the substitued impurity is obtained. Our results show that Mg enhances overall elastic and bulk mechanical properties whereas Zn tends to degrade except at low concentrations. At a higher concentration, the mechanical properties of Zn and Mg doped HAP also depend significantly on impurity distribution between the Ca1 and Ca2 sites. There is a strong evidence that Zn prefers Ca2 site for substituion whereas Mg has no such preference. These results imply that proper control of dopant concentration and their site preference must carefully considered in using doped HAP for specific biomedical applications. Copyright © 2015 Elsevier Ltd. All rights reserved.

  11. Effect of annealing on microstructure evolution in CoFeB/MgO/CoFeB heterostructures by positron annihilation

    NASA Astrophysics Data System (ADS)

    Zhao, Chong-Jun; Lu, Xiang-An; Zhao, Zhi-Duo; Li, Ming-Hua; Zhang, Peng; Wang, Bao-Yi; Cao, Xing-Zhong; Zhang, Jing-Yan; Yu, Guang-Hua

    2013-09-01

    As one of the most powerful tools for investigation of defects of materials, positron annihilation spectroscopy was employed to explore the thermal effects on the film microstructure evolution in CoFeB/MgO/CoFeB heterostructures. It is found that high annealing temperature can drive vacancy defects agglomeration and ordering acceleration in the MgO barrier. Meanwhile, another important type of defects, vacancy clusters, which are formed via the agglomeration of vacancy defects in the MgO barrier after annealing, still exists inside the MgO barrier. All these behaviors in the MgO barrier could potentially impact the overall performance in MgO based magnetic tunnel junctions.

  12. Defect-Tolerant Diffusion Channels for Mg 2+ Ions in Ribbon-Type Borates: Structural Insights into Potential Battery Cathodes MgVBO 4 and Mg x Fe 2–xB 2O 5

    DOE PAGES

    Bo, Shou-Hang; Grey, Clare P.; Khalifah, Peter G.

    2015-06-10

    The reversible room temperature intercalation of Mg 2+ ions is difficult to achieve, but may offer substantial advantages in the design of next-generation batteries if this electrochemical process can be successfully realized. Two types of quadruple ribbon-type transition metal borates (Mg xFe 2-xB 2O 5 and MgVBO 4) with high theoretical capacities (186 mAh/g and 360 mAh/g) have been synthesized and structurally characterized through the combined Rietveld refinement of synchrotron and time-of-flight neutron diffraction data. Neither MgVBO 4 nor Mg xFe 2-xB 2O 5 can be chemically oxidized at room temperature, though Mg can be dynamically removed from themore » latter phase at elevated temperatures (approximately 200 - 500 °C). Findings show that Mg diffusion in the Mg xFe 2-xB 2O 5 structure is more facile for the inner two octahedral sites than for the two outer octahedral sites in the ribbons, a result supported by both the refined site occupancies after Mg removal and by bond valence sum difference map calculations of diffusion paths in the pristine material. Mg diffusion in this pyroborate Mg xFe 2-xB 2O 5 framework is also found to be tolerant to the presence of Mg/Fe disorder since Mg ions can diffuse through interstitial channels which bypass Fe-containing sites.« less

  13. Mechano-luminescence studies of nano ZnMgAl10O17:Eu phosphor under UV irradiation

    NASA Astrophysics Data System (ADS)

    Verma, Akshkumar; Verma, Ashish; Panda, Maheswar

    2018-05-01

    ZnMgAl10O17:Eu nano phosphors were prepared successfully, using the combustion route by employing urea as a fuel. The structural, and Morphological, properties were measured using x-ray diffraction (XRD) Scanning electron microscopy (SEM) transition electron microscopy. The BET surface area of sample were found to be of ˜13.92 m2/g. The ML (Mechano-luminescence) were measured to the home made instrument. The phosphor showed more strong and high ML intensity to the without UV irradiated material. Therefore ZnMgAl10O17:Eu2+ phosphor may use as a damage sensor and dosimetry material. The ML emission spectra of the Zn0.99MgAl10O17:Eu0.01 phosphor showed the characteristic Eu2+ emission peaks ˜453nm (blue) originating from the transitions 4f65d1→4f7, Therefore ZnMgAl10O17:Eu2+ phosphor may use as a blue phosphor material.

  14. Perpendicular magnetic anisotropy in Ta|Co{sub 40}Fe{sub 40}B{sub 20}|MgAl{sub 2}O{sub 4} structures and perpendicular CoFeB|MgAl{sub 2}O{sub 4}|CoFeB magnetic tunnel junction

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

    Tao, B. S.; Li, D. L.; Yuan, Z. H.

    2014-09-08

    Magnetic properties of Co{sub 40}Fe{sub 40}B{sub 20} (CoFeB) thin films sandwiched between Ta and MgAl{sub 2}O{sub 4} layers have been systematically studied. For as-grown state, Ta/CoFeB/MgAl{sub 2}O{sub 4} structures exhibit good perpendicular magnetic anisotropy (PMA) with interface anisotropy K{sub i} = 1.22 erg/cm{sup 2}, which further increases to 1.30 erg/cm{sup 2} after annealing, while MgAl{sub 2}O{sub 4}/CoFeB/Ta multilayer shows in-plane magnetic anisotropy and must be annealed in order to achieve PMA. For bottom CoFeB layer, the thickness window for PMA is from 0.6 to 1.0 nm, while that for top CoFeB layer is between 0.8 and 1.4 nm. Perpendicular magnetic tunnel junctions (p-MTJs) with a coremore » structure of CoFeB/MgAl{sub 2}O{sub 4}/CoFeB have also been fabricated and tunneling magnetoresistance ratio of about 36% at room temperature and 63% at low temperature have been obtained. The intrinsic excitations in the p-MTJs have been identified by inelastic electron-tunneling spectroscopy.« less

  15. Molecular layers of ZnPc and FePc on Au(111) surface: Charge transfer and chemical interaction

    NASA Astrophysics Data System (ADS)

    Ahmadi, Sareh; Shariati, M. Nina; Yu, Shun; Göthelid, Mats

    2012-08-01

    We have studied zinc phthalocyanine (ZnPc) and iron phthalocyanine (FePc) thick films and monolayers on Au(111) using photoelectron spectroscopy and x-ray absorption spectroscopy. Both molecules are adsorbed flat on the surface at monolayer. ZnPc keeps this orientation in all investigated coverages, whereas FePc molecules stand up in the thick film. The stronger inter-molecular interaction of FePc molecules leads to change of orientation, as well as higher conductivity in FePc layer in comparison with ZnPc, which is reflected in thickness-dependent differences in core-level shifts. Work function changes indicate that both molecules donate charge to Au; through the π-system. However, the Fe3d derived lowest unoccupied molecular orbital receives charge from the substrate when forming an interface state at the Fermi level. Thus, the central atom plays an important role in mediating the charge, but the charge transfer as a whole is a balance between the two different charge transfer channels; π-system and the central atom.

  16. Inversion domain boundaries in ZnO with additions of Fe2O3 studied by high-resolution ADF imaging.

    PubMed

    Wolf, Frank; Freitag, Bert H; Mader, Werner

    2007-01-01

    Columns of metal atoms in the polytypoid compound Fe2O3(ZnO)15 could be resolved by high angle annular dark field imaging in a transmission electron microscopy (TEM)/STEM electron microscope--a result which could not be realized by high-resolution bright field imaging due to inherent strain from inversion domains and inversion domain boundaries (IDBs) in the crystals. The basal plane IDB was imaged in [11 00] yielding the spacing of the two adjacent ZnO domains, while imaging in [21 1 0] yields the position of single metal ions. The images allow the construction of the entire domain structure including the stacking sequence and positions of the oxygen ions. The IDB consists of a single layer of octahedrally co-ordinated Fe3+ ions, and the inverted ZnO domains are related by point symmetry at the iron position. The FeO6 octahedrons are compressed along the ZnO c-axis resulting in a FeO bond length of 0.208 nm which is in the range of FeO distances in iron containing oxides. The model of the basal plane boundary resembles that of the IDB in polytypoid ZnO-In2O3 compounds.

  17. Dynamic defect annealing in wurtzite MgZnO implanted with Ar ions

    NASA Astrophysics Data System (ADS)

    Azarov, A. Yu.; Wendler, E.; Du, X. L.; Kuznetsov, A. Yu.; Svensson, B. G.

    2015-09-01

    Successful implementation of ion beams for modification of ternary ZnO-based oxides requires understanding and control of radiation-induced defects. Here, we study structural disorder in wurtzite ZnO and MgxZn1-xO (x ⩽ 0.3) samples implanted at room and 15 K temperatures with Ar ions in a wide fluence range (5 × 1012-3 × 1016 cm-2). The samples were characterized by Rutherford backscattering/channeling spectrometry performed in-situ without changing the sample temperature. The results show that all the samples exhibit high radiation resistance and cannot be rendered amorphous even for high ion fluences. Increasing the Mg content leads to some damage enhancement near the surface region; however, irrespective of the Mg content, the fluence dependence of bulk damage in the samples displays the so-called IV-stage evolution with a reverse temperature effect for high ion fluences.

  18. Effect of 120 MeV 28Si9+ ion irradiation on structural and magnetic properties of NiFe2O4 and Ni0.5Zn0.5Fe2O4

    NASA Astrophysics Data System (ADS)

    Sharma, R.; Raghuvanshi, S.; Satalkar, M.; Kane, S. N.; Tatarchuk, T. R.; Mazaleyrat, F.

    2018-05-01

    NiFe2O4, Ni0.5Zn0.5Fe2O4 samples were synthesized using sol-gel auto combustion method, and irradiated by using 120 MeV 28Si9+ ion with ion fluence of 1×1012 ions/cm2. Characterization of pristine, irradiated samples were done using X-Ray Diffraction (XRD), Field Emission Scanning Microscopy (FE-SEM), Energy Dispersive X-ray Analysis (EDAX) and Vibrating Sample Magnetometer (VSM). XRD validates the single phase nature of pristine, irradiated Ni- Zn nano ferrite except for Ni ferrite (pristine, irradiated) where secondary phases of α-Fe2O3 and Ni is observed. FE- SEM images of pristine Ni, Ni-Zn ferrite show inhomogeneous nano-range particle size distribution. Presence of diamagnetic ion (Zn2+) in NiFe2O4 increases oxygen positional parameter (u 4¯3m ), experimental, theoretical saturation magnetization (Msexp., Msth.), while decreases the grain size (Ds) and coercivity (Hc). With irradiation Msexp., Msth. increases but not much change are observed in Hc. New antistructure modeling for the pristine, irradiated Ni and Ni-Zn ferrite samples was used for describing the surface active centers.

  19. Surface compositions of atomic layer deposited Zn{sub 1−x}Mg{sub x}O thin films studied using Auger electron spectroscopy

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

    Xie, Ting; Romero, Danilo; Gomez, Romel D., E-mail: rdgomez@umd.edu

    2015-09-15

    In this paper, the authors present Auger electron spectroscopy (AES) studies of Zn{sub 1−x}Mg{sub x}O (ZMO) films grown via interrupted atomic-layer deposition (ALD) techniques. The ZMO films were fabricated by alternating ALD deposition of ZnO and MgO layers up to 1000 cycles. Zn{sub 1−x}Mg{sub x}O films with progressively decreasing Mg/Zn ratios (Mg/Zn = 1/1, 1/2, 1/3, 1/4, 1/5, 1/6, 1/9, and 2/8, 3/12, 4/16, and 5/20) were fabricated for this study. The AES results exhibit an abrupt drop of Mg composition on the ZMO surface when the Mg/Zn < 1/3. Additionally, the surface composition ratios of O to Mg, O to Zn, and Mgmore » to Zn were estimated with known Auger sensitivity factors. The results indicate that Mg ions diffuse into the bulk, forming Zn{sub 1−x}Mg{sub x}O alloys.« less

  20. [Effects of annealing temperature on the structure and optical properties of ZnMgO films prepared by atom layer deposition].

    PubMed

    Sun, Dong-Xiao; Li, Jin-Hua; Fang, Xuan; Chen, Xin-Ying; Fang, Fang; Chu, Xue-Ying; Wei, Zhi-Peng; Wang, Xiao-Hua

    2014-07-01

    In the present paper, we report the research on the effects of annealing temperature on the crystal quality and optical properties of ZnMgO films deposited by atom layer deposition(ALD). ZnMgO films were prepared on quartz substrates by ALD and then some of the samples were treated in air ambient at different annealing temperature. The effects of annealing temperature on the crystal quality and optical properties of ZnMgO films were characterized by X-ray diffraction (XRD), photoluminescence (PL) and ultraviolet-visible (UV-Vis) absorption spectra. The XRD results showed that the crystal quality of ZnMgO films was significantly improved when the annealing temperature was 600 degrees C, meanwhile the intensity of(100) diffraction peak was the strongest. Combination of PL and UV-Vis absorption measurements showed that it can strongly promote the Mg content increasing in ZnMgO films and increase the band gap of films. So the results illustrate that suitable annealing temperature can effectively improve the crystal quality and optical properties of ZnMgO films.

  1. Structural and magnetic properties of Ni-Zn and Ni-Zn-Co ferrites

    NASA Astrophysics Data System (ADS)

    Knyazev, A. V.; Zakharchuk, I.; Lähderanta, E.; Baidakov, K. V.; Knyazeva, S. S.; Ladenkov, I. V.

    2017-08-01

    Ni-Zn and Ni-Zn-Co ferrite powders with nominal compositions Ni0.5Zn0.5Fe2O4 and Ni0.5Zn0.3Co0.2Fe2O4 were prepared by the solid-state reaction synthesis with periodic regrinding during the calcination at 1073 K. The structure of Ni0.5Zn0.5Fe2O4 and Ni0.5Zn0.3Co0.2Fe2O4 was refined assuming space group F d-3m. Scanning electron microscopy revealed the average sizes of the crystalline ferrite particles are 130-630 nm for Ni0.5Zn0.5Fe2O4 and 140-350 nm for Ni0.5Zn0.3Co0.2Fe2O4. The room temperature saturation magnetizations are 59.7 emu/g for Ni0.5Zn0.5Fe2O4 and 57.1 emu/g for Ni0.5Zn0.3Co0.2Fe2O4. The coercivity of the samples is found to be much larger than that of bulk ferrites and increases with Co introduction. The Curie temperature tends to increase upon Zn substitution by Co, as well. The temperature dependences of magnetization measured using zero-field cooled and field cooled protocols exhibit large spin frustration and spin-glass-like behavior.

  2. Spin-orbit torque in Cr/CoFeAl/MgO and Ru/CoFeAl/MgO epitaxial magnetic heterostructures

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

    Wen, Zhenchao; Kim, Junyeon; Sukegawa, Hiroaki

    2016-05-15

    We study the spin-orbit torque (SOT) effective fields in Cr/CoFeAl/MgO and Ru/CoFeAl/MgO magnetic heterostructures using the adiabatic harmonic Hall measurement. High-quality perpendicular-magnetic-anisotropy CoFeAl layers were grown on Cr and Ru layers. The magnitudes of the SOT effective fields were found to significantly depend on the underlayer material (Cr or Ru) as well as their thicknesses. The damping-like longitudinal effective field (ΔH{sub L}) increases with increasing underlayer thickness for all heterostructures. In contrast, the field-like transverse effective field (ΔH{sub T}) increases with increasing Ru thickness while it is almost constant or slightly decreases with increasing Cr thickness. The sign of ΔH{submore » L} observed in the Cr-underlayer devices is opposite from that in the Ru-underlayer devices while ΔH{sub T} shows the same sign with a small magnitude. The opposite directions of ΔH{sub L} indicate that the signs of spin Hall angle in Cr and Ru are opposite, which are in good agreement with theoretical predictions. These results show sizable contribution from SOT even for elements with small spin orbit coupling such as 3d Cr and 4d Ru.« less

  3. Study on the mechanism of perpendicular magnetic anisotropy in Ta/CoFeB/MgO system

    NASA Astrophysics Data System (ADS)

    Lou, Yongle; Zhang, Yuming; Guo, Hui; Xu, Daqing; Yimen, Zhang

    2017-06-01

    The mechanism of perpendicular magnetic anisotropy (PMA) in a MgO-based magnetic tunnel junction (MTJ) has been studied in this article. By comparing the magnetic properties and elementary composition analysis for different CoFeB-based structures, such as Ta/CoFeB/MgO, Ta/CoFeB/Ta and Ru/CoFeB/MgO structures, it is found that a certain amount of Fe-oxide existing at the interface of CoFeB/MgO is helpful to enhance the PMA and the PMA is originated from the interface of CoFeB/MgO. In addition, Ta film plays an important role to enhance the PMA in Ta/CoFeB/MgO structure. Project supported by the National Defense Advance Research Foundation (No. 9140A08XXXXXX0DZ106), the Basic Research Program of Ministry of Education, China (No. JY10000925005), the Scientific Research Program Funded by Shaanxi Provincial Education Department (No.11JK0912), the Scientific Research Foundation of Xi’an University of Science and Technology (No. 2010011), the Doctoral Research Startup Fund of Xi’an University of Science and Technology (No. 2010QDJ029).

  4. The effect of growth sequence on magnetization damping in Ta/CoFeB/MgO structures

    NASA Astrophysics Data System (ADS)

    Liu, Bo; Huang, Dawei; Gao, Ming; Tu, Hongqing; Wang, Kejie; Ruan, Xuezhong; Du, Jun; Cai, Jian-Wang; He, Liang; Wu, Jing; Wang, Xinran; Xu, Yongbing

    2018-03-01

    Magnetization damping is a key parameter to control the critical current and the switching speed in magnetic random access memory, and here we report the effect of the growth sequence on the magnetic dynamics properties of perpendicularly magnetized Ta/CoFeB/MgO structures. Ultrathin CoFeB films have been grown between Ta and MgO but with different stack sequences, i.e. substrate/Ta/CoFeB/MgO/Ta and substrate/Ta/MgO/CoFeB/Ta. The magnetization dynamics induced by femtosecond laser was investigated by using all-optical pump-probe measurements. We found that the Gilbert damping constant was modulated by reversing stack structures, which offers the potential to tune the damping parameter by the growth sequence. The Gilbert damping constant was enhanced from 0.017 for substrate/Ta/CoFeB/MgO/Ta to 0.027 for substrate/Ta/MgO/CoFeB/Ta. We believe that this enhancement originates from the increase of intermixing at the CoFeB/Ta when the Ta atom layer was grown after the CoFeB layer.

  5. Preparation of Superparamagnetic Zn0.5Mn0.5Fe2O4 Particle by Coprecipitation-Sonochemical Method for Radar Absorbing Material

    NASA Astrophysics Data System (ADS)

    Taufiq, A.; Bahtiar, S.; Sunaryono; Hidayat, N.; Hidayat, A.; Mufti, N.; Diantoro, M.; Fuad, A.; Munasir; Rahmawati, R.; Adi, W. A.; Pratapa, S.; Darminto

    2017-05-01

    One of many applications of spinel ferrite nanoparticles is related to their performance as radar absorbing materials. In this work, we report developing synthesis method through combined coprecipitation-sonochemical routes in preparing Zn0.5Mn0.5Fe2O4 nanoparticle from iron sand in Indonesia as a vital raw material. The structure, size, morphology, and elements of the Zn0.5Mn0.5Fe2O4 nanoparticle were investigated via X-Ray diffractometry and Transmission/Scanning Electron Microscopy (TEM/SEM) combining Energy Dispersive Spectroscopy (EDS). The magnetic properties of the Zn0.5Mn0.5Fe2O4 nanoparticle were characterized by using Vibrating Sample Magnetometer (VSM). Furthermore, the reflection loss character of the Zn0.5Mn0.5Fe2O4 nanoparticle was determined via Vector Network Analyzer (VNA). From the qualitative and quantitative analysis of the XRD data, it can be identified that the Zn0.5Mn0.5Fe2O4 particle formed a spinel cubic structure in a single phase with the lattice parameter of approximately 8.401 Å. It is known from the TEM image that the Zn0.5Mn0.5Fe2O4 particle had a size of about 9.7 nm and tended to agglomerate. Furthermore, the data analysis of the M(H) curve presented that the Zn0.5Mn0.5Fe2O4 nanoparticle has a superparamagnetic behavior with the saturation magnetization of approximately 43 emu/g. Finally, the data analysis of the reflection loss as a function of frequency showed that the Zn0.5Mn0.5Fe2O4 nanoparticle performs as a radar absorbing material with the absorption performance of approximately -11.0 dB at the frequency of 10.8 GHz

  6. The impact of processing parameters on the properties of Zn-bonded Nd-Fe-B magnets

    NASA Astrophysics Data System (ADS)

    Kelhar, Luka; Zavašnik, Janez; McGuiness, Paul; Kobe, Spomenka

    2016-12-01

    We report on the effect of loading factor and pressure on the density and the magnetic properties of Zn-bonded Nd-Fe-B magnets produced by pulsed-electric-current sintering (PECS). The idea behind this study is to fabricate bonded magnets with a metallic binder in order for the bonded magnet to operate at temperatures higher than 180 °C: the current upper-limit for polymer-bonded magnets. These composites are made of hard-magnetic powder in the form of melt-spun ribbons bonded with the low-melting-point metal Zn. The binder additions were varied from 10 to 30 wt%, and pressures of 50 and 500 MPa were applied. The high-pressure mode with 20 wt% Zn resulted in a 24% increase of Jr, compared to the low-pressure mode. The magnetic measurements revealed a maximum remanence of 0.64 T for 10 wt% Zn, while the coercivity is largely unaffected by the processing conditions. The density of the composites was up to 7.0 g/cm3, corresponding to 94% of the theoretical density. Compared to commercial polymer-bonded magnets, the Zn-bonded counterparts exhibit a slightly lower Jr, but the coercivity is retained. We show that there is a minor diffusion of Zn into the Nd-Fe-B, forming a 1 μm thin transition layer, but it does not harm the magnetic properties. These metal-bonded Nd-Fe-B magnets are ideal for use in high-temperature automotive applications like under-the-hood sensors and other magnet-based devices that are close to the engine.

  7. Protein profile of Lupinus texensis phloem sap exudates: searching for Fe- and Zn-containing proteins.

    PubMed

    Lattanzio, Giuseppe; Andaluz, Sofía; Matros, Andrea; Calvete, Juan José; Kehr, Julia; Abadía, Anunciación; Abadía, Javier; López-Millán, Ana-Flor

    2013-08-01

    The aim of this study was to obtain a comprehensive overview of the phloem sap protein profile of Lupinus texensis, with a special focus on proteins binding Fe and Zn. L. texensis was chosen as model plant given the simplicity to obtain exudates from sieve elements. Protein profiling by 2DE revealed 249 spots, and 54 of them were unambiguously identified by MALDI-MS and ESI-MS/MS. The largest number of identified protein species belongs to protein modification/turnover and general metabolism (19-21%), followed by redox homeostasis (9%) and defense and cell structural components (7%). This protein profile is similar to that reported in other plant species, suggesting that the phloem sap proteome is quite conserved. Staining of 2DE gels for Fe-containing proteins and affinity chromatography experiments revealed the presence of two low molecular weight Fe-binding proteins in phloem sap: a metallothionein-like protein type 2B identified in the Fe-affinity chromatography, and a second protein identified with both Fe staining methods. This protein species had a molecular weight of 13.5 kDa, a pI of 5.6 and 51% homology to a phloem-specific protein from Medicago truncatula. Zinc affinity chromatography revealed four Zn-binding proteins in phloem sap, one belonging to the dehydrin family and three Zn finger proteins. © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  8. Ca:Mg:Zn:CO3 and Ca:Mg:CO3-tri- and bi-elemental carbonate microparticles for novel injectable self-gelling hydrogel-microparticle composites for tissue regeneration.

    PubMed

    Douglas, Timothy E L; Sobczyk, Katarzyna; Łapa, Agata; Włodarczyk, Katarzyna; Brackman, Gilles; Vidiasheva, Irina; Reczyńska, Katarzyna; Pietryga, Krzysztof; Schaubroeck, David; Bliznuk, Vitaliy; Voort, Pascal Van Der; Declercq, Heidi A; Bulcke, Jan Van den; Samal, Sangram Keshari; Khalenkow, Dmitry; Parakhonskiy, Bogdan V; Van Acker, Joris; Coenye, Tom; Lewandowska-Szumieł, Małgorzata; Pamuła, Elżbieta; Skirtach, Andre G

    2017-03-24

    Injectable composites for tissue regeneration can be developed by dispersion of inorganic microparticles and cells in a hydrogel phase. In this study, multifunctional carbonate microparticles containing different amounts of calcium, magnesium and zinc were mixed with solutions of gellan gum (GG), an anionic polysaccharide, to form injectable hydrogel-microparticle composites, containing Zn, Ca and Mg. Zn and Ca were incorporated into microparticle preparations to a greater extent than Mg. Microparticle groups were heterogeneous and contained microparticles of differing shape and elemental composition. Zn-rich microparticles were 'star shaped' and appeared to consist of small crystallites, while Zn-poor, Ca- and Mg-rich microparticles were irregular in shape and appeared to contain lager crystallites. Zn-free microparticle groups exhibited the best cytocompatibility and, unexpectedly, Zn-free composites showed the highest antibacterial activity towards methicilin-resistant Staphylococcus aureus. Composites containing Zn-free microparticles were cytocompatible and therefore appear most suitable for applications as an injectable biomaterial. This study proves the principle of creating bi- and tri-elemental microparticles to induce the gelation of GG to create injectable hydrogel-microparticle composites.

  9. Heterostructured ZnFe2O4/Fe2TiO5/TiO2 Composite Nanotube Arrays with an Improved Photocatalysis Degradation Efficiency Under Simulated Sunlight Irradiation

    NASA Astrophysics Data System (ADS)

    Xiong, Kun; Wang, Kunzhou; Chen, Lin; Wang, Xinqing; Fan, Qingbo; Courtois, Jérémie; Liu, Yuliang; Tuo, Xianguo; Yan, Minhao

    2018-03-01

    To improve the visible light absorption and photocatalytic activity of titanium dioxide nanotube arrays (TONTAs), ZnFe2O4 (ZFO) nanocrystals were perfused into pristine TONTA pipelines using a novel bias voltage-assisted perfusion method. ZFO nanocrystals were well anchored on the inner walls of the pristine TONTAs when the ZFO suspensions (0.025 mg mL-1) were kept under a 60 V bias voltage for 1 h. After annealing at 750 °C for 2 h, the heterostructured ZFO/Fe2TiO5 (FTO)/TiO2 composite nanotube arrays were successfully obtained. Furthermore, Fe3+ was reduced to Fe2+ when solid solution reactions occurred at the interface of ZFO and the pristine TONTAs. Introducing ZFO significantly enhanced the visible light absorption of the ZFO/FTO/TONTAs relative to that of the annealed TONTAs. The coexistence of type I and staggered type II band alignment in the ZFO/FTO/TONTAs facilitated the separation of photogenerated electrons and holes, thereby improving the efficiency of the ZFO/FTO/TONTAs for photocatalytic degradation of methylene blue when irradiated with simulated sunlight. [Figure not available: see fulltext.

  10. A study of the properties and microstructure of Ni 81Fe 19 ultrathin films with MgO

    NASA Astrophysics Data System (ADS)

    Li, Minghua; Han, Gan; Ding, Lei; Wang, Xiaocui; Liu, Yang; Feng, Chun; Wang, Haicheng; Yu, Guanghua

    2012-01-01

    The anisotropic magnetoresistance (AMR) of a Ta (5 nm)/MgO (3 nm)/Ni81Fe19 (10 nm)/MgO (2 nm)/Ta (3 nm) film with MgO-Nano Oxide Layer (NOL) increases dramatically from 1.05% to 3.24% compared with a Ta (5 nm)/Ni81Fe19 (10 nm)/Ta (3 nm) film without the MgO-NOL layer after annealing at 380 °C for 2 h. Although the MgO destroys the NiFe (1 1 1) texture, it enhances the specular electron scattering of the conduction electrons at the NOL interface and suppresses the interface reactions and diffusion at the Ta/NiFe and NiFe/Ta interfaces. The NiFe (1 1 1) texture was formed after the annealing, resulting in a higher AMR ratio. X-ray photoelectron spectroscope results show that Mg and Mg2+ were present in the MgOx films.

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

    NASA Astrophysics Data System (ADS)

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

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

  12. Study on the Mg-Li-Zn ternary alloy system with improved mechanical properties, good degradation performance and different responses to cells.

    PubMed

    Liu, Yang; Wu, Yuanhao; Bian, Dong; Gao, Shuang; Leeflang, Sander; Guo, Hui; Zheng, Yufeng; Zhou, Jie

    2017-10-15

    Novel Mg-(3.5, 6.5wt%)Li-(0.5, 2, 4wt%)Zn ternary alloys were developed as new kinds of biodegradable metallic materials with potential for stent application. Their mechanical properties, degradation behavior, cytocompatibility and hemocompatibility were studied. These potential biomaterials showed higher ultimate tensile strength than previously reported binary Mg-Li alloys and ternary Mg-Li-X (X=Al, Y, Ce, Sc, Mn and Ag) alloys. Among the alloys studied, the Mg-3.5Li-2Zn and Mg-6.5Li-2Zn alloys exhibited comparable corrosion resistance in Hank's solution to pure magnesium and better corrosion resistance in a cell culture medium than pure magnesium. Corrosion products observed on the corroded surface were composed of Mg(OH) 2 , MgCO 3 and Ca-free Mg/P inorganics and Ca/P inorganics. In vitro cytotoxicity assay revealed different behaviors of Human Umbilical Vein Endothelial Cells (HUVECs) and Human Aorta Vascular Smooth Muscle Cells (VSMCs) to material extracts. HUVECs showed increasing nitric oxide (NO) release and tolerable toxicity, whereas VSMCs exhibited limited decreasing viability with time. Platelet adhesion, hemolysis and coagulation tests of these Mg-Li-Zn alloys showed different degrees of activation behavior, in which the hemolysis of the Mg-3.5Li-2Zn alloy was lower than 5%. These results indicated the potential of the Mg-Li-Zn alloys as good candidate materials for cardiovascular stent applications. Mg-Li alloys are promising as absorbable metallic biomaterials, which however have not received significant attention since the low strength, controversial corrosion performance and the doubts in Li toxicity. The Mg-Li-Zn alloy in the present study revealed much improved mechanical properties higher than most reported binary Mg-Li and ternary Mg-Li-X alloys, with superior corrosion resistance in cell culture media. Surprisingly, the addition of Li and Zn showed increased nitric oxide release. The present study indicates good potential of Mg-Li-Zn alloy as

  13. ZIF-8 derived hexagonal-like α-Fe2O3/ZnO/Au nanoplates with tunable surface heterostructures for superior ethanol gas-sensing performance

    NASA Astrophysics Data System (ADS)

    Chen, Ying; Li, Hui; Ma, Qian; Che, Quande; Wang, Junpeng; Wang, Gang; Yang, Ping

    2018-05-01

    A series of hexagonal-like α-Fe2O3/ZnO/Au nanoplate heterostructures with tunable morphologies and superior ethanol gas-sensing performance were successfully synthesized via the facile multi-step reaction processes. Hexagonal-like α-Fe2O3 nanoplates with uniform size around 150 nm are employed as new sensor substrates for loading the well-distributed ZnO and Au nanoparticles with adjustable size distribution on the different surfaces. Brunauer-EmmeQ-Teller (BET) surface areas of α-Fe2O3 and α-Fe2O3/ZnO samples are evaluated to be 37.94 and 61.27 m2/g, respectively, while α-Fe2O3/ZnO/Au composites present the highest value of 79.08 m2/g. These α-Fe2O3-based functional materials can exhibit outstanding sensing properties to ethanol. When the ethanol concentration is 100 ppm, the response value of α-Fe2O3/ZnO/Au composites can reach up to 170, which is 14.6 and 80.3 times higher than that of α-Fe2O3/ZnO and pure α-Fe2O3, respectively. The recycling stability and long-time effectiveness can be availably maintained within 30 days, as well as the response and recovery times are shortened to 4 and 5 s, respectively. Significantly, the response value of α-Fe2O3/ZnO/Au composite is still up to 63 at an operating temperature of 280 °C even though the ethanol concentration decreases to 10 ppm. The enhanced gas sensing mechanism would be focused on the synergistic effects of phase compositions, surface heterogeneous structures, large specific surface area, and the selective depositions of Au nanoparticles in α-Fe2O3/ZnO/Au sensors. The synergistic effect of different surface heterostructures referring to α-Fe2O3/Au and α-Fe2O3/ZnO/Au and their novel electron transport processes on the surfaces are first investigated and discussed in details. It is expected that hexagonal-like α-Fe2O3/ZnO/Au nanoplate heterostructures with excellent sensing performance can be the promising highly-sensitive materials in the actual application for monitoring and detecting ethanol.

  14. Effect of Hydroxyapatite on the Mechanical Properties and Corrosion Behavior of Mg-Zn-Y Alloy

    PubMed Central

    Chiu, Chun; Lu, Chih-Te; Chen, Shih-Hsun; Ou, Keng-Liang

    2017-01-01

    Mg-Zn-Y alloys with a long period stacking ordered (LPSO) phase are potential candidates for biodegradable implants; however, an unfavorable degradation rate has limited their applications. Hydroxyapatite (HA) has been shown to enhance the corrosion resistance of Mg alloys. In this study, Mg97Zn1Y2-0.5 wt% HA composite was synthesized and solution treated at 500 °C for 10 h. The corrosion behavior of the composite was studied by electrochemical and immersion tests, while the mechanical properties were investigated by a tensile test. Addition of HA particles improves the corrosion resistance of Mg97Zn1Y2 alloy without sacrificing tensile strength. The improved corrosion resistance is due to the formation of a compact Ca-P surface layer and a decrease of the volume fraction of the LPSO phase, both resulting from the addition of HA. After solution-treatment, the corrosion resistance of the composite decreases. This is due to the formation of a more extended LPSO phase, which weakens its role as a corrosion barrier in protecting the Mg matrix. PMID:28773216

  15. The effects of Mg incorporation and annealing temperature on the physicochemical properties and antibacterial activity against Listeria monocytogenes of ZnO nanoparticles

    NASA Astrophysics Data System (ADS)

    Shadan, Nima; Ziabari, Ali Abdolahzadeh; Meraat, Rafieh; Jalali, Kamyar Mazloum

    2017-02-01

    In this paper, Mg-doped ZnO nanoparticles were synthesized by the facile sol-gel method. The crystalline structure, characteristic absorption bands and morphology of the obtained Mg-doped ZnO nanoparticles were studied by XRD, FTIR and TEM. The thermal degradation behaviour of the samples was investigated by differential scanning calorimetry (DSC) and thermogravimetry (TG). The effect of Mg concentrations and annealing temperatures on the antibacterial properties of the obtained nanoparticles was investigated in detail. The results indicated that doping Mg ions into ZnO lattice could enhance its antibacterial activity. Antibacterial assay demonstrated that Mg-doped ZnO with 7% Mg content annealed at 400 ∘C had the strongest antibacterial activity against Listeria monocytogenes (98.7%). This study indicated that the inhibition rate of ZnO nanoparticles increased with the formation of granular structure and the decrease of ZnO size due to the doping of Mg ions into the ZnO lattice.

  16. Electrochemical corrosion behavior, microstructure and magnetic properties of sintered Nd-Fe-B permanent magnet doped by CuZn5 powders

    NASA Astrophysics Data System (ADS)

    Liu, W. Q.; Wang, Z.; Sun, C.; Yue, M.; Liu, Y. Q.; Zhang, D. T.; Zhang, J. X.

    2014-05-01

    Nd-Fe-B permanent magnets with a small amount of CuZn5 powders doping were prepared by conventional sintered method. The effects of CuZn5 contents on magnetic properties and microstructure, electrochemical corrosion resistance of sintered Nd-Fe-B magnets were systematically studied. The results show that the magnetic properties of magnets do not have a significant variation by CuZn5 powders doping; the coercivity of magnets rises gradually, while the remanence of the magnets decreases a little with increasing of the CuZn5 amount. The CuZn5 doped magnets have more positive corrosion potential, Ecorr, and much lower corrosion current density, icorr, than the magnets without CuZn5 doping, indicating CuZn5 doping could improve the corrosion resistance. Both Zn and Cu enrich mainly into the Nd-rich phase, fully improve the wettability between the Nd-rich phase and the Nd2Fe14B phase, and repair the defects of the main phase, so the coercivity of magnets doped with CuZn5 powders rises. Such microstructure modification effectively restrains the aggressive inter-granular corrosion. As a result, the CuZn5 doped magnet possesses excellent corrosion resistance in NaCl electrolyte.

  17. Mg- and Zn-modified calcium phosphates prepared by biomimetic precipitation and subsequent treatment at high temperature.

    PubMed

    Rabadjieva, D; Tepavitcharova, S; Gergulova, R; Sezanova, K; Titorenkova, R; Petrov, O; Dyulgerova, E

    2011-10-01

    Powders of magnesium-modified as well as zinc-modified calcium phosphates (Me-β-TCP and HA) with a (Ca(2+)+Mg(2+)+Zn(2+)+Na(+)+K(+))/P ratio of 1.3-1.4 and various Me(2+)/(Me(2+)+Ca(2+)) ratios (from 0.005 to 0.16) were prepared in biomimetic electrolyte systems at pH 8, mother liquid maturation and further syntering at 600-1000°C. Some differences in zinc and magnesium modifications have been prognosed on the basis of thermodynamic modeling of the studied systems and explained by the Mg(2+) and Zn(2+) ion chemical behaviour. The temperature as well as the degree of Zn(2+) and Mg(2+) ions substitutions were found to stabilize the β-TCP structure and this effect was more prononced for zinc. Thus, zinc-modified β-TCP powders consisting of idiomorphic crystals were obtained through sintering of Zn(2+) ion substituted calcium phosphates precursors at 800-1000°C. The Mg(2+) ion substitution leads to obtaining magnesium-modified β-TCP with spherical grains.

  18. In vitro bioaccessibility of β-carotene, Ca, Mg and Zn in landrace carrots (Daucus carota, L.).

    PubMed

    Zaccari, Fernanda; Cabrera, María Cristina; Ramos, Ana; Saadoun, Ali

    2015-01-01

    Four landrace carrots ("Becaria", "CRS", "González" and "Rodríguez") and two marketable cultivars (Kuroda and Brasilia), raw and steamed, were characterised by the total content of β-carotene Ca, Mg and Zn, in vitro bioaccessibility and by colour and were evaluated to determine the effect of particle size in nutrient bioaccessibility. Steaming increased the content of β-carotene extracted from "CRS" and Brasilia (29% and 75%) and decreased the content of β-carotene extracted from "CRS" by 23% in "Rodríguez." In addition, steaming caused a loss of Ca (21%) but did not change the amount of Mg and Zn. The bioaccessibility of β-carotene in raw and pulped carrots was very low (<0.5%). Furthermore, steaming and a smaller particle size increased the bioaccessibility of β-carotene by 3-16 times. Additionally, cooking increased the in vitro bioaccessibility of Ca and Zn but had no effect on Mg. Moreover, homogenisation increased the bioaccessibility by 20% in Ca, 17% in Mg, and 10% in Zn compared to pulping. Copyright © 2014 Elsevier Ltd. All rights reserved.

  19. Graphene-palladium nanowires based electrochemical sensor using ZnFe2O4-graphene quantum dots as an effective peroxidase mimic.

    PubMed

    Liu, Weiyan; Yang, Hongmei; Ma, Chao; Ding, Ya-nan; Ge, Shenguang; Yu, Jinghua; Yan, Mei

    2014-12-10

    We proposed an electrochemical DNA sensor by using peroxidase-like magnetic ZnFe2O4-graphene quantum dots (ZnFe2O4/GQDs) nanohybrid as a mimic enzymatic label. Aminated graphene and Pd nanowires were successively modified on glassy carbon electrode, which improved the electronic transfer rate as well as increased the amount of immobilized capture ssDNA (S1). The nanohybrid ZnFe2O4/GQDs was prepared by assembling the GQDs on the surface of ZnFe2O4 through a photo-Fenton reaction, which was not only used as a mimic enzyme but also as a carrier to label complementary ssDNA (S3). By synergistically integrating highly catalytically activity of nano-sized GQDs and ZnFe2O4, the nanohybrid possessed highly-efficient peroxidase-like catalytic activity which could produce a large current toward the reduction of H2O2 for signal amplification. Thionine was used as an excellent electron mediator. Compared with traditional enzyme labels, the mimic enzyme ZnFe2O4/GQDs exhibited many advantages such as environment friendly and better stability. Under the optimal conditions, the approach provided a wide linear range from 10(-16) to 5×10(-9) M and low detection limit of 6.2×10(-17) M. The remarkable high catalytic capability could allow the nanohybrid to replace conventional peroxidase-based assay systems. The new, robust and convenient assay systems can be widely utilized for the identification of other target molecules. Copyright © 2014 Elsevier B.V. All rights reserved.

  20. Activation of an intense near band edge emission from ZnTe/ZnMgTe core/shell nanowires grown on silicon.

    PubMed

    Wojnar, P; Szymura, M; Zaleszczyk, W; Kłopotowski, L; Janik, E; Wiater, M; Baczewski, L T; Kret, S; Karczewski, G; Kossut, J; Wojtowicz, T

    2013-09-13

    The absence of luminescence in the near band edge energy region of Te-anion based semiconductor nanowires grown by gold catalyst assisted molecular beam epitaxy has strongly limited their applications in the field of photonics. In this paper, an enhancement of the near band edge emission intensity from ZnTe/ZnMgTe core/shell nanowires grown on Si substrates is reported. A special role of the use of Si substrates instead of GaAs substrates is emphasized, which results in an increase of the near band edge emission intensity by at least one order of magnitude accompanied by a simultaneous reduction of the defect related luminescence. A possible explanation of this effect relies on the presence of Ga-related deep level defects in structures grown on GaAs substrates, which are absent when Si substrates are used. Monochromatic mapping of the cathodoluminescence clearly confirms that the observed emission originates, indeed, from the ZnTe/ZnMgTe core/shell nanowires, whereas individual objects are studied by means of microphotoluminescence.

  1. Magnetic and dielectric properties in the UHF frequency band of half-dense Ni-Zn-Co ferrites ceramics with Fe-excess and Fe-deficiency

    NASA Astrophysics Data System (ADS)

    Mattei, Jean-Luc; Souriou, David; Chevalier, Alexis

    2018-02-01

    This work investigates electromagnetic properties of half-dense ceramics with compositions Ni0.5Zn0.3Co0.2FeyO4-δ where y = 1.98 (Iron deficient, noted ID) or y = 2.3 (Iron in excess, noted IE). IE and ID materials are obtained by chemical coprecipitation route. The obtained nano-sized powders are pressed and annealed at two temperatures (800 °C, 900 °C), so has to obtain half-massive ceramics. Ferrous and ferric ions coexist in the crystalline structures, but the former in a less extend for ID ferrite. The concomitant influences of Fe2+ and Fe3+ on the dielectric and magnetic losses (ε″/ε‧ and μ″/μ‧, respectively) are considered at frequency up to 6 GHz. The permeability dispersion changes from relaxation-like to resonance-like with the decrease in ferrous ions. In reason of the relaxing-like behavior of Fe2+, and because of a relatively high amount in Fe2+, IE sample shows lower total losses (magnetic and dielectric) than ID sample. These conclusions applied for TA = 900 °C. At frequencies above 700 MHz, the total loss values (IE and ID samples) are prohibitive for antenna downsizing whatever is the firing temperature value (800 °C and 900 °C). Whereas at frequencies below 700 MHz Ni0.5Zn0.3Co0.2Fe2.3O4+δ may leads to better antenna performances than Ni0.5Zn0.3Co0.2Fe1.98O4-δ.

  2. Synthesis and gas sensing properties of α-Fe(2)O(3)@ZnO core-shell nanospindles.

    PubMed

    Zhang, Jun; Liu, Xianghong; Wang, Liwei; Yang, Taili; Guo, Xianzhi; Wu, Shihua; Wang, Shurong; Zhang, Shoumin

    2011-05-06

    α-Fe(2)O(3)@ZnO core-shell nanospindles were synthesized via a two-step hydrothermal approach, and characterized by means of SEM/TEM/XRD/XPS. The ZnO shell coated on the nanospindles has a thickness of 10-15 nm. Considering that both α-Fe(2)O(3) and ZnO are good sensing materials, we have investigated the gas sensing performances of the core-shell nanocomposite using ethanol as the main probe gas. It is interesting to find that the gas sensor properties of the core-shell nanospindles are significantly enhanced compared with pristine α-Fe(2)O(3). The enhanced sensor properties are attributed to the unique core-shell nanostructure. The detailed sensing mechanism is discussed with respect to the energy band structure and the electron depletion theory. The core-shell nanostructure reported in this work provides a new path to fabricate highly sensitive materials for gas sensing applications.

  3. Formation of Fe/mg Smectite Under Acidic Conditions from Synthetic Adirondack Basaltic Glass: an Analog to Fe/mg Smectite Formation on Mars

    NASA Technical Reports Server (NTRS)

    Sutter, B.; Peretyazhko, T.; Morris, R. V.; Ming, D. W.

    2014-01-01

    Smectite has been detected as layered material hundreds of meters thick, in intracrater depositional fans, in plains sediments, and deposits at depth on Mars. If early Mars hosted a dense CO2 atmosphere, then extensive carbonate should have formed in the neutral/alkaline conditions expected for smectite formation. However, large carbonate deposits on Mars have not been discovered. Instead of neutral to moderately alkaline conditions, early Mars may have experienced mildly acidic conditions that allowed for Fe/Mg smectite formation but prevented widespread carbonate formation. The objective of this work is to demonstrate that Fe(II)/Mg saponite and nontronite can form in mildly acidic solutions (e.g., pH 4). Synthetic basaltic glass (< 53 microns) of Adirondack rock class composition was exposed to pH 4 (acetic acid buffer) and N2 purged (anoxic) solutions amended with 0 and 10 mM Mg or Fe(II). Basaltic glass in these solutions was heated to 200 C in batch reactors for 1, 7, and 14 days. X-ray diffraction analysis of reacted materials detected the presence of phyllosilicates as indicated by a approx. 15.03-15.23Angstroms (001) peak. Smectite was confirmed as the phyllosilicate after treatments with glycerol and KCl and heating to 550 C. Trioctahedral saponite was confirmed by the presence of a 4.58 to 4.63 Angstroms (02l) and 1.54Angstroms (060) peaks. Saponite concentration was highest, as indicated by XRD peak intensity, in the 10 mM Mg treatment followed by the 0 mM and then 10 mM Fe(II) treatments. This order of sapontite concentration suggests that Fe(II) additions may have a role in slowing the kinetics of saponite formation relative to the other treatments. Nontronite synthesis was attempted by exposing Adirondack basaltic glass to pH 4 oxic solutions (without N2 purge) at 200 C for 14 days. X-ray diffraction analysis indicated that mixtures of trioctahedral (saponite) and dioctahedral (nontronite) may have formed in these experiments based on the 02l and 060

  4. Formation of Fe/Mg Smectite under acidic conditions from synthetic Adirondack Basaltic Glass: An Analog to Fe/Mg Smectite Formation on Mars.

    NASA Astrophysics Data System (ADS)

    Sutter, B.; Peretyazhko, T.; Morris, R. V.; Ming, D. W.

    2014-12-01

    Smectite has been detected as layered material hundreds of meters thick, in intracrater depositional fans, in plains sediments, and deposits at depth on Mars. If early Mars hosted a dense CO2 atmosphere, then extensive carbonate should have formed in the neutral/alkaline conditions expected for smectite formation. However, large carbonate deposits on Mars have not been discovered. Instead of neutral to moderately alkaline conditions, early Mars may have experienced mildly acidic conditions that allowed for Fe/Mg smectite formation but prevented widespread carbonate formation. The objective of this work is to demonstrate that Fe(II)/Mg-saponite and nontronite can form in mildly acidic solutions (e.g., pH 4). Synthetic basaltic glass (< 53 μm) of Adirondack rock class composition was exposed to pH 4 (acetic acid buffer) and N2 purged (anoxic) solutions amended with 0 and 10 mM Mg or Fe(II). Basaltic glass in these solutions was heated to 200ºC in batch reactors for 1, 7, and 14 days. X-ray diffraction analysis of reacted materials detected the presence of phyllosilicates as indicated by a ~15.03-15.23Ǻ (001) peak. Smectite was confirmed as the phyllosilicate after treatments with glycerol and KCl and heating to 550°C. Trioctahedral saponite was confirmed by the presence of a 4.58 to 4.63 Ǻ (02l) and 1.54Ǻ (060) peaks. Saponite concentration was highest, as indicated by XRD peak intensity, in the 10 mM Mg treatment followed by the 0 mM and then 10 mM Fe(II) treatments. This order of sapontite concentration suggests that Fe(II) additions may have a role in slowing the kinetics of saponite formation relative to the other treatments. Nontronite synthesis was attempted by exposing Adirondack basaltic glass to pH 4 oxic solutions (without N2 purge) at 200ºC for 14 days. X-ray diffraction analysis indicated that mixtures of trioctahedral (saponite) and dioctahedral (nontronite) may have formed in these experiments based on the 02l and 060 peaks. Mössbauer analysis

  5. Photocatalytic degradation of organic dyes by Er3+: YAlO3/Co- and Fe-doped ZnO coated composites under solar irradiation

    NASA Astrophysics Data System (ADS)

    Chen, Yang; Lu, Chunxiao; Tang, Liang; Song, Yahui; Wei, Shengnan; Rong, Yang; Zhang, Zhaohong; Wang, Jun

    2016-12-01

    In this work, the Er3+: YAlO3/Co- and Fe-doped ZnO coated composites were prepared by the sol-gel method. Then, they were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and energy dispersive X-ray spectroscopy (EDX). Photo-degradation of azo fuchsine (AF) as a model dye under solar light irradiation was studied to evaluate the photocatalytic activity of the Er3+: YAlO3/Co- and Fe-doped ZnO coated composites. It was found that the photocatalytic activity of Co- and Fe-doped ZnO composites can be obviously enhanced by upconversion luminescence agent (Er3+: YAlO3). Besides, the photocatalytic activity of Er3+: YAlO3/Fe-doped ZnO is better than that of Er3+: YAlO3/Co-doped ZnO. The influence of experiment conditions, such as the concentration of Er3+: YAlO3, heat-treatment temperature and time on the photocatalytic activity of the Er3+: YAlO3/Co- and Fe-doped ZnO coated composites was studied. In addition, the effects of solar light irradiation time, dye initial concentration, Er3+: YAlO3/Co- and Fe-doped ZnO amount on the photocatalytic degradation of azo fuchsine in aqueous solution were investigated in detail. Simultaneously, some other organic dyes, such as Methyl Orange (MO), Rhodamine B (RM-B), Acid Red B (AR-B), Congo Red (CR), and Methyl Blue (MB) were also studied. The possible excitation principle of Er3+: YAlO3/Co- and Fe-doped ZnO coated composites under solar light irradiation and the photocatalytic degradation mechanism of organic dyes were discussed.

  6. Sulfidation behavior of ZnFe2O4 roasted with pyrite: Sulfur inducing and sulfur-oxygen interface exchange mechanism

    NASA Astrophysics Data System (ADS)

    Min, Xiaobo; Zhou, Bosheng; Ke, Yong; Chai, Liyuan; Xue, Ke; Zhang, Chun; Zhao, Zongwen; Shen, Chen

    2016-05-01

    The sulfidation roasting behavior was analyzed in detail to reveal the reaction mechanism. Information about the sulfidation reaction, including phase transformation, ionic migration behavior and morphological change, were obtained by XRD, 57Fe Mossbauer spectroscopy, XPS and SEM analysis. The results showed that the sulfidation of zinc ferrite is a process of sulfur inducing and sulfur-oxygen interface exchange. This process can be divided into six stages: decomposition of FeS2, formation of the oxygen-deficient environment, migration of O2- induced by S2(g), formation of ZnFe2O4-δ, migration of Fe2+ accompanied by the precipitation of ZnO, and the sulfur-oxygen interface exchange reaction. The sulfidation products were zinc blende, wurtzite, magnetite and a fraction of zinc-bearing magnetite. These findings can provide theoretical support for controlling the process during which the recovery of Zn and Fe is achieved through the combined flotation-magnetic separation process.

  7. In vivo evaluation of Mg-6Zn and titanium alloys on collagen metabolism in the healing of intestinal anastomosis

    NASA Astrophysics Data System (ADS)

    Wang, Xiao-Hu; Ni, Jian-Shu; Cao, Nai-Long; Yu, Song; Chen, Yi-Gang; Zhang, Shao-Xiang; Gu, Bao-Jun; Yan, Jun

    2017-03-01

    There is a great clinical need for biodegradable materials, which were used as pins of circular staplers, for gastrointestinal reconstruction in medicine. In this work we compared the effects of the Mg-6Zn and the titanium alloys on collagen metabolism in the healing of the intestinal tract in vivo. The study included Sprague-Dawley rats and their effect was compared on rat’s intestinal tract, using serum magnesium, radiology, and immunohistochemistry in vivo. Radiographic and scanning electron microscope evaluation confirmed the degradation by Mg-6Zn alloy during the implantation period. Biochemical measurements including serum magnesium, creatinine, blood urea nitrogen and glutamic-pyruvic-transaminase proved that degradation of Mg-6Zn alloy showed no impact on serum magnesium and the function of other important organs. Superior to titanium alloy, Mg-6Zn alloy enhanced the expression of collagen I/III and relatively suppressed the expression of MMP-1/-13 in the healing tissues, leading to more mature collagen formation at the site of anastomosis. In conclusion, Mg-6Zn alloy performed better than titanium alloy on collagen metabolism and promoted the healing of intestinal anastomosis. Hence, Mg-6Zn may be a promising candidate for use of stapler pins for intestinal reconstruction in the clinically.

  8. Mössbauer spectroscopy of MgxCu0.5-xZn0.5Fe2O4 (x = 0.0, 0.2 and 0.5) ferrites system irradiated by γ-rays

    NASA Astrophysics Data System (ADS)

    Ahmed, M. A.; Hassan, H. E.; Eltabey, M. M.; Latka, K.; Tatarchuk, T. R.

    2018-02-01

    The effect of the Mg-content on the cation distribution of cubic MgxCu0.5-xZn0.5Fe2O4(x = 0.0, 0.2, 0.3, 0.5) prepared by conventional ceramic method was investigated using Mössbauer spectroscopy at room temperature. We aimed to estimate the enhanced changes in the inversion parameter of MgxCu0.5-xZn0.5Fe2O4 system due to γ-ray irradiation as a function of the Mg-content in the range 0.5 ≥ x ≥ 0.0. The samples were irradiated by 1173 keV + 1332.5 keV γ-rays emitted from 60Co radioactive source. The total absorbed dose was 1.9 MGy with dose rate 5 kGy/h. The observed superposition of more than one sextet that belong to either octahedral [B] or tetrahedral (A) sites in the Mössbauer spectra before and after γ-irradiation was interpreted by the effect of spin canting. Moreover, there is an evidence on the presence of the Fe2+ charge state at A-sites in the irradiated samples. The quadrupole splittings showed that the orientation of the magnetic hyperfine field with respect to the principle axes of the electric field gradient was random. The magnetic hyperfine field values indicated also that the A sites had more A-O-B super exchange interactions than the B sites. New antistructure modeling for the pristine and irradiated MgxCu0.5-xZn0.5Fe2O4 samples at different γ-doses was used for describing of the lattice defects and surface centers.

  9. Popcorn balls-like ZnFe2O4-ZrO2 microsphere for photocatalytic degradation of 2,4-dinitrophenol

    NASA Astrophysics Data System (ADS)

    Chen, Xi; Liu, Yutang; Xia, Xinnian; Wang, Longlu

    2017-06-01

    In this paper, novel popcorn balls-like ZnFe2O4-ZrO2 composite microspheres were successfully fabricated by a simple hydrothermal method. The morphology, structure and optical property of the microspheres were characterized. The microspheres were used as the photocatalysts to degrade 2,4-dinitrophenol, and exhibited superior photocatalytic performance. Under simulated solar visible light irradiation, the degradation rate of ZnFe2O4-ZrO2 photocatalyst (mass ratio of ZnFe2O4/ZrO2 = 2:1) was almost 7.4 and 2.4 times higher than those of pure ZnFe2O4 and ZrO2. The enhancement could attribute to stronger light absorption, lower carrier recombination and multi-porous structure of the microspheres. Moreover, the popcorn balls-like photocatalysts can be easily separated, because of the magnetism of the samples. After five times runs, the photocatalyst still showed 90% of its photocatalytic degradation efficiency. This work demonstrated a good prospect for removing organic pollutants in water.

  10. Shape and Site Dependent in Vivo Degradation of Mg-Zn Pins in Rabbit Femoral Condyle

    PubMed Central

    Han, Pei; Tan, Moyan; Zhang, Shaoxiang; Ji, Weiping; Li, Jianan; Zhang, Xiaonong; Zhao, Changli; Zheng, Yufeng; Chai, Yimin

    2014-01-01

    A type of specially designed pin model of Mg-Zn alloy was implanted into the full thickness of lesions of New Zealand rabbits’ femoral condyles. The recovery progress, outer surface healing and in vivo degradation were characterized by various methods including radiographs, Micro-CT scan with surface rendering, SEM (scanning electron microscope) with EDX (Energy Dispersive X-ray analysis) and so on. The in vivo results suggested that a few but not sufficient bridges for holding force were formed between the bone and the implant if there was a preexisting gap between them. The rapid degradation of the implantation in the condyle would result in the appearance of cavities. Morphological evaluation of the specially designed pins indicated that the cusp was the most vulnerable part during degradation. Furthermore, different implantation sites with distinct components and biological functions can lead to different degradation rates of Mg-Zn alloy. The rate of Mg-Zn alloy decreases in the following order: implantation into soft tissue, less trabecular bone, more trabecular bone, and cortical bone. Because of the complexities of in vivo degradation, it is necessary for the design of biomedical Mg-Zn devices to take into consideration the implantation sites used in clinics. PMID:24566138

  11. Shape and site dependent in vivo degradation of Mg-Zn pins in rabbit femoral condyle.

    PubMed

    Han, Pei; Tan, Moyan; Zhang, Shaoxiang; Ji, Weiping; Li, Jianan; Zhang, Xiaonong; Zhao, Changli; Zheng, Yufeng; Chai, Yimin

    2014-02-20

    A type of specially designed pin model of Mg-Zn alloy was implanted into the full thickness of lesions of New Zealand rabbits' femoral condyles. The recovery progress, outer surface healing and in vivo degradation were characterized by various methods including radiographs, Micro-CT scan with surface rendering, SEM (scanning electron microscope) with EDX (Energy Dispersive X-ray analysis) and so on. The in vivo results suggested that a few but not sufficient bridges for holding force were formed between the bone and the implant if there was a preexisting gap between them. The rapid degradation of the implantation in the condyle would result in the appearance of cavities. Morphological evaluation of the specially designed pins indicated that the cusp was the most vulnerable part during degradation. Furthermore, different implantation sites with distinct components and biological functions can lead to different degradation rates of Mg-Zn alloy. The rate of Mg-Zn alloy decreases in the following order: implantation into soft tissue, less trabecular bone, more trabecular bone, and cortical bone. Because of the complexities of in vivo degradation, it is necessary for the design of biomedical Mg-Zn devices to take into consideration the implantation sites used in clinics.

  12. Low temperature magnetization and anomalous high temperature dielectric behaviour of (1-x) YMnO3/xZnFe2O4 composites

    NASA Astrophysics Data System (ADS)

    Kumar, Virendra; Gaur, Anurag

    2018-04-01

    We synthesized YMnO3 and ZnFe2O4 composites, (1-x)YMnO3/x(ZnFe2O4) with x = 0, 0.05, 0.10, and 0.15 by high temperature sintering. X-ray diffraction (XRD) patterns indicate the successful formation of composites. Weak ferromagnetism is manifested below Néel temperature (TN) for pristine YMnO3, according to (M-H) study performed at 10 K. For (1-x)YMnO3/xZnFe2O4 (x = 0.05, 0.10, 0.15) a thin coercivity is observed in all compositions, due to short range magnetic ordering at low temperature after the insertion of ZnFe2O4. For pristine YMnO3 explicit divarication between FC-ZFC curves is observed, with crimps observed in both FC and ZFC curves at 75 K, which is the TN of YMnO3. For 1-x(YMnO3)/x ZnFe2O4 composites (x = 0.05, 0.10, 0.15) crimps are perceived only in ZFC curves at slightly varying values of 39.8, 42.32 and 45.63 K respectively. Anomalous peaks are observed in high temperature dielectric curves above 400 K for 1-x(YMnO3)/xZnFe2O4 (x = 0, 0.05, 0.10, 0.15) composites due to Maxwell-Wagner relaxation effect.

  13. Enhancement of Fe diffusion in ZnSe/S laser crystals under hot isostatic pressing

    NASA Astrophysics Data System (ADS)

    Gafarov, Ozarfar; Martinez, Alan; Fedorov, Vladimir; Mirov, Sergey

    2017-02-01

    Many organic molecules have strong and narrow absorption features in the middle Infrared (mid-IR) spectral range. The ability to directly probe absorption features of molecules enables numerous mid-IR applications in non-invasive medical diagnosis, industrial processing and process control, environmental monitoring, etc. Thus, there is a strong demand for lasers operating in mid-IR spectral range. Transition metal (TM) doped II-VI semiconductors such as Fe/Cr:ZnSe/S are the material of choice for fabrication of mid-IR gain media due to favorable combination of properties: a four level energy structure, absence of excited state absorption , broad mid-IR vibronic absorption and emission bands. Despite the significant progress in post-growth thermal diffusion technology of TM:II-VI fabrication there are still some difficulties associated with diffusion of certain TM's in these materials. In this work we address the issue of poor diffusion of Fe in ZnSe/S polycrystals. It is well known that with the temperature increase the diffusion rate of impurity also increases. However, simple application of high temperatures during the diffusion process is problematic for ZnSe/S crystals due to their strong sublimation. The sublimation processes can be suppressed by application of high pressures. Hot isostatic pressing was utilized as the means for simultaneous application of high temperatures (1300°C) and high pressures (1000atm, 3000atm). It was determined that diffusion coefficient of Fe was improved 13 and 14 fold in ZnSe and ZnS, respectively, as compared to the standard diffusion at 950°C. The difference in diffusion coefficients can be due to strong increase in the grain size of polycrystals.

  14. Efficacy of heat generation in CTAB coated Mn doped ZnFe2O4 nanoparticles for magnetic hyperthermia

    NASA Astrophysics Data System (ADS)

    Raland, R. D.; Borah, J. P.

    2017-01-01

    Manganese doped Zinc ferrite (Mn-ZnFe2O4, where Mn  =  0%, 3%, 5% and 7%) nanoparticles were synthesized by a simple co-precipitation method. CTAB (cetyltrimethylammonium bromide) was used as a surfactant to inhibitgrowth and agglomeration. In this work, we have discussed on the influence of CTAB and Mn doping in tailoring the structural and magnetic properties of Mn-ZnFe2O4 nanoparticles for the effective application of magnetic hyperthermia. X-ray diffraction (XRD) pattern confirmed the formation of cubic spinel structure of Mn-ZnFe2O4 nanoparticles. Lattice parameter and x-ray densities were obtained from the Rietveld refinement of the XRD pattern. The presence of CTAB as a stabilizing layer adsorbed on the surface of the nanoparticles were confirmed by transmission electron microscope (TEM) and Raman vibrational spectrum. The saturation magnetization showsan increasing trend with Mn addition owing to cationic re-distribution and an increase super-exchange interaction between the two sub-lattices. Superparamagnetic behaviorof Mn-ZnFe2O4 nanoparticles were confirmed by temperature-dependent zero-field-cooling (ZFC) and field-cooling (FC) magnetization curves. The efficiency of induction heating measured by its specific absorption rate (SAR) and intrinsic loss power (ILP) value varies as a function of saturation magnetization. It has been hypothesized that the maximum generation of heat arises from Neel relaxation mechanism. The optimum generation of heat of Mn-ZnFe2O4 nanoparticle is determined by the higher frequency (f  =  337 kHz) range and maximum concentration of Mn doping.

  15. Improving the corrosion resistance of Mg-4.0Zn-0.2Ca alloy by micro-arc oxidation.

    PubMed

    Xia, Y H; Zhang, B P; Lu, C X; Geng, L

    2013-12-01

    In this paper, corrosion resistance of the Mg-4.0Zn-0.2Ca alloy was modified by micro-arc oxidation (MAO) process. The microstructure and phase constituents of MAO layer were characterized by SEM, XRD and X-ray photoelectron spectroscopy (XPS). The corrosion resistance of MAO treated Mg-4.0Zn-0.2Ca alloy in the simulated body fluid were characterized by potentiodynamic polarization and electrochemical impedance spectroscopy (EIS) techniques. The microstructure results indicated that a kind of ceramic film was composed by MgO and MgF2 was formed on the surface of Mg-4.0Zn-0.2Ca alloy after MAO treatment. The electrochemical test reveals that the corrosion resistance of MAO treated samples increase 1 order of magnitude. The mechanical intensity test showed that the MAO treated samples has suitable mechanical properties. © 2013.

  16. Mobility and fractionation of Fe, Pb and Zn in river sediments from a silver and base-metals mining area: Taxco, México.

    PubMed

    Espinosa, E; Armienta, M A

    2007-08-01

    The impact of mining wastes on both the concentration and environmental mobility of Zn, Pb and Fe was studied in a shallow river. The studied tributary of the Taxco river is located south of the historical Ag, Zn, Cu and Pb mining area of Taxco, about 150 km south of México City. Methodology included total concentration determinations and sequential extraction analyses of the operational defined fractions of sediments. Results indicated that Fe, Pb and Zn concentrations are up to 5, 100 and 390 times respectively, greater than regional background concentrations. Higher contents of Pb and Zn were observed in the rainy season versus the dry season, whereas Fe was lower in the rainy season. Zinc and lead increased downflow in the dry season, and did not show any trend during the rainy season. Speciation showed that Zn was mainly linked to the carbonatic fraction (25-39%), to the hydrous Fe/Mn oxides fraction (15-25%) and to the organic matter and sulfide fraction (14-48%); lead was mainly associated to the hydrous Fe/Mn oxides (49-59%) and residual (22-39%) fractions; finally, iron was contained mainly in the residual (65-78%) and the hydrous Fe/Mn oxides fraction (15%). Mobility decreased according to the relation: Zn > Pb > Fe. Sediments were classified as strongly polluted in zinc, strongly to very strongly polluted in Pb, and moderately to strongly polluted in iron. However, a low proportion of metals in the exchangeable fractions, indicates low bioavailability. Limestone presence played a very important role on Zn and Pb fractionation and environmental mobility. Results show the importance of including geological background in river pollution studies.

  17. Growth Evolution and Characterization of PLD Zn(Mg)O Nanowire Arrays

    NASA Astrophysics Data System (ADS)

    Rahm, Andreas; Nobis, Thomas; Lorenz, Michael; Zimmermann, Gregor; Boukos, Nikos; Travlos, Anastasios; Grundmann, Marius

    ZnO and Zn0.98Mg0.02O nanowires have been grown by high-pressure pulsed laser deposition on sapphire substrates covered with gold colloidal particles as nucleation sites. We present a detailed study of the nanowire size and length distribution and of the growth evolution. We find that the aspect ratio varies linearly with deposition time. The linearity coefficient is independent of the catalytic gold particle size and lateral nanowire density. The superior structural quality of the whiskers is proven by X-ray diffraction and transmission electron microscopy. The defect-free ZnO nanowires exhibit a FWHM(2θ-ω) of the ZnO(0002) reflection of 22 arcsec. We show (0-11) step habit planes on the side faces of the nanowires that are a few atomic steps in height. The microscopic homogeneity of the optical properties is confirmed by temperature-dependent cathodoluminescence.

  18. In-situ synthesized ZnFe2O4 firmly anchored to the surface of MWCNTs as a long-life anode material with high lithium storage performance

    NASA Astrophysics Data System (ADS)

    Yang, Tianbo; Zhang, Wanxi; Li, Linlin; Jin, Bo; Jin, Enmei; Jeong, Sangmoon; Jiang, Qing

    2017-12-01

    Because of two different metal cations in the crystal structures, binary transition metal oxides possess a lot of unique properties. ZnFe2O4 emerges from these transition metal oxides on account of its high theoretical capacity (1072 mAh g-1). One-dimensional multi-walled carbon nanotubes (MWCNTs) would be a desirable conductive additive for ZnFe2O4, thereby improving the electrochemical performance of ZnFe2O4. In this work, we prepare ZnFe2O4/MWCNTs by solvothermal method with further heat-treatment. ZnFe2O4 nanoparticles are firmly anchored to the surface of MWCNTs. ZnFe2O4/MWCNTs nanocomposite displays high specific capacity (1278 mAh g-1 at a current density of 200 mA g-1 after 200 cycles, and 565 mAh g-1 at a current density of 1500 mA g-1 after 500 cycles), and good rate performance (367 mAh g-1 even at a current density of 6000 mAh g-1 after 80 cycles). The superior electrochemical performance may promote ZnFe2O4 to be a promising alternative anode in lithium-ion batteries.

  19. Zn(II) stimulation of Fe(II)-activated repression in the iron-dependent repressor from Mycobacterium tuberculosis.

    PubMed

    Stapleton, Brian; Walker, Lawrence R; Logan, Timothy M

    2013-03-19

    Thermodynamic measurements of Fe(II) binding and activation of repressor function in the iron-dependent repressor from Mycobacterium tuberculosis (IdeR) are reported. IdeR, a member of the diphtheria toxin repressor family of proteins, regulates iron homeostasis and contributes to the virulence response in M. tuberculosis. Although iron is the physiological ligand, this is the first detailed analysis of iron binding and activation in this protein. The results showed that IdeR binds 2 equiv of Fe(II) with dissociation constants that differ by a factor of 25. The high- and low-affinity iron binding sites were assigned to physical binding sites I and II, respectively, using metal binding site mutants. IdeR was also found to contain a high-affinity Zn(II) binding site that was assigned to physical metal binding site II through the use of binding site mutants and metal competition assays. Fe(II) binding was modestly weaker in the presence of Zn(II), but the coupled metal binding-DNA binding affinity was significantly stronger, requiring 30-fold less Fe(II) to activate DNA binding compared to Fe(II) alone. Together, these results suggest that IdeR is a mixed-metal repressor, where Zn(II) acts as a structural metal and Fe(II) acts to trigger the physiologically relevant promoter binding. This new model for IdeR activation provides a better understanding of IdeR and the biology of iron homeostasis in M. tuberculosis.

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

    PubMed

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

    2008-12-15

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

  1. Alizarin red S dye removal from contaminated water on calcined [Mg/Al, Zn/Al and MgZn/Al]-LDH

    NASA Astrophysics Data System (ADS)

    Aissat, Miloud; Hamouda, Sara; Benhadria, Naceur; Chellali, Rachid; Bettahar, Noureddine

    2018-05-01

    The waste water rejected by the textile industries is loaded with organic dyes, responsible for the high color present in the effluents. Some dyes and / or their degradation products could be carcinogenic and may have mutagenic properties. The rapid growth of the global economy has caused many environmental problems with a huge pollution problem. The abuse use of chemicals product is an environmental toxicological problem. The consequences can be serious for water resources. In this perspective, our study comes to participate with new means of depollution using new materials with interesting properties in the treatment of pollution. Among these materials, LDHs whose synthesis is easy and inexpensive can be a tool in the treatment of water Polluted [1]. Our contribution consists in using HDL as a means of sorption of dyes which are considered as polluting agents of waters especially for the industry textile. This study considers the removal of the Alizarine Red S (AR) from water on calcined MgAl,ZnAL and MgZnAL-layered double hydroxides. The different LDH was prepared by copreprecipation method. The materials was obtained for molar ratios R =2 for the different LDH. The carbonated layered Calcination of these solids leads to the formation of mixed oxides which have the property of being able to be regenerated by adsorbing new anionic entities. Adsorbents and adsorption products were characterized by physicochemical techniques. The structural characterization of the material was carried out by X-ray diffraction, infrared spectroscopy (FTIR). Dosages of the polluted solutions were monitored by UV-Visible spectrometry.

  2. Structural and spectral properties of MgZnO2:Sm3+ phosphor

    NASA Astrophysics Data System (ADS)

    Rajput, Preasha; Sharma, Pallavi; Biswas, Pankaj; Kamni

    2018-05-01

    The samarium doped MgZnO2 phosphor was synthesized by the low-cost combustion method. The powder X-ray diffraction (XRD) analysis confirmed the crystallinity and phase purity of the phosphor. The lattice parameters were determined by indexing the diffraction peaks. The photoluminescence (PL) study revealed that the phosphor exhibited a broad excitation band in the UV region ranging between 200 to 350 nm. The 601 nm emission was ascribed to 4G5/2 to 6H7/2 transitions of the Sm3+ ion. The optical bandgap of MgZnO2:Sm3+ was obtained to be 3.56 eV. The phosphor can be projected as a useful material in X- and gamma-ray scintillators.

  3. Two-Dimensional Fluorescence Difference Spectroscopy of ZnO and Mg Composites in the Detection of Physiological Protein and RNA Interactions

    PubMed Central

    Hoffman, Amanda; Wu, Xiaotong; Wang, Jianjie; Brodeur, Amanda; Thomas, Rintu; Thakkar, Ravindra; Hadi, Halena; Glaspell, Garry P.; Duszynski, Molly; Wanekaya, Adam; DeLong, Robert K.

    2017-01-01

    Two-dimensional fluorescence difference spectroscopy (2-D FDS) was used to determine the unique spectral signatures of zinc oxide (ZnO), magnesium oxide (MgO), and 5% magnesium zinc oxide nanocomposite (5% Mg/ZnO) and was then used to demonstrate the change in spectral signature that occurs when physiologically important proteins, such as angiotensin-converting enzyme (ACE) and ribonuclease A (RNase A), interact with ZnO nanoparticles (NPs). When RNase A is bound to 5% Mg/ZnO, the intensity is quenched, while the intensity is magnified and a significant shift is seen when torula yeast RNA (TYRNA) is bound to RNase A and 5% Mg/ZnO. The intensity of 5% Mg/ZnO is quenched also when thrombin and thrombin aptamer are bound to the nanocomposite. These data indicate that RNA–protein interaction can occur unimpeded on the surface of NPs, which was confirmed by gel electrophoresis, and importantly that the change in fluorescence excitation, emission, and intensity shown by 2-D FDS may indicate specificity of biomolecular interactions. PMID:29244716

  4. Structural Properties of Alternate Monatomic Layered [Fe/Co]n Epitaxial Films on MgO Substrate

    NASA Astrophysics Data System (ADS)

    Chu, In Chang; Saki, Yoshinobu; Kawasaki, Shohei; Doi, Masaaki; Sahashi, Masashi

    2008-06-01

    Body-centered-cubic (bcc) Fe50Co50 material is reported to show a high bulk spin scattering coefficient on current perpendicular to plane-giant magneto-resistance (CPP-GMR) system. But the origin of that phenomenon does not make sure yet. We prepared artificially alternate monatomic layered (AML) [Fe/Co] 41 MLs epitaxial films (Ts: 75, 250 °C) by monatomic deposition method and investigated the topology of AML [Fe/Co]n epitaxial films on MgO substrate with different orientation (001), (011) by the scanning tunnel microscopy (STM) and reflection high energy electron diffraction (RHEED), which we could confirm Frank-van der Merwe (FM) growth mode for AML [Fe/Co]n on MgO(001) and Volmer-Weber (VW) growth mode for that on Mg(011). The roughness of surface, Ra (0.20 nm) of AML [Fe/Co] 41 MLs epitaxial film grown at 75 °C on MgO(001) is smaller than that (0.46 nm) of AML [Fe/Co] grown at 250 °C on MgO(001), which has the large terraces of over 50 nm (Ra: 0.17 nm), even though there are some valleys between large terraces. Moreover we confirmed the structural properties of trilayered epitaxial films with AML [Fe/Co]n (Ra: 0.18 nm) and Fe50Co50 alloy epitaxial film on Au electrode by RHEED before confirming the characteristics of CPP-GMR devices.

  5. Novel solid-state synthesis of α-Fe and Fe3O4 nanoparticles embedded in a MgO matrix

    NASA Astrophysics Data System (ADS)

    Schneeweiss, O.; Zboril, R.; Pizurova, N.; Mashlan, M.; Petrovsky, E.; Tucek, J.

    2006-01-01

    Thermally induced reduction of amorphous Fe2O3 nanopowder (2-3 nm) with nanocrystalline Mg (~20 nm) under a hydrogen atmosphere is presented as a novel route to obtain α-Fe and Fe3O4 magnetic nanoparticles dispersed in a MgO matrix. The phase composition, structural and magnetic properties, size and morphology of the nanoparticles were monitored by x-ray diffraction, 57Fe Mössbauer spectroscopy at temperatures of 24-300 K, transmission electron microscopy and magnetic measurements. Spherical magnetite nanoparticles prepared at a reaction temperature of 300 °C revealed a well-defined structure, with a ratio of tetrahedral to octahedral Fe sites of 1/2 being common for the bulk material. A narrow particle size distribution (20-30 nm) and high saturation magnetization (95 ± 5 A m2 kg-1) predispose the magnetite nanoparticles to various applications, including magnetic separation processes. The Verwey transition of Fe3O4 nanocrystals was found to be decreased to about 80 K. The deeper reduction of amorphous ferric oxide at 600 °C allows α-Fe (40-50 nm) nanoparticles to be synthesized with a coercive force of about 30 mT. They have a saturation magnetization 2.2 times higher than that of synthesized magnetite nanoparticles, which corresponds well with the ratio usually found for the pure bulk phases. The magnetic properties of α-Fe nanocrystals combined with the high chemical and thermal stability of the MgO matrix makes the prepared nanocomposite useful for various magnetic applications.

  6. BaFe2As2/Fe Bilayers with [001]-tilt Grain Boundary on MgO and SrTiO3 Bicrystal Substrates

    NASA Astrophysics Data System (ADS)

    Iida, K.; Haindl, S.; Kurth, F.; Hänisch, J.; Schulz, L.; Holzapfel, B.

    Co-doped BaFe2As2 (Ba-122) can be realized on both MgO and SrTiO3 bicrystal substrates with [001]-tilt grain boundary by employing Fe buffer layers. However, an additional spinel (i.e. MgAl2O4) buffer between Fe and SrTiO3 is necessary since an epitaxial, smooth surface of Fe layer can not be grown on bare SrTiO3. Both types of bicrystal films show good crystalline quality.

  7. Sol-Gel Derived Hydroxyapatite Coating on Mg-3Zn Alloy for Orthopedic Application

    NASA Astrophysics Data System (ADS)

    Singh, Sanjay; Manoj Kumar, R.; Kuntal, Kishor Kumar; Gupta, Pallavi; Das, Snehashish; Jayaganthan, R.; Roy, Partha; Lahiri, Debrupa

    2015-04-01

    In recent years, magnesium and its alloys have gained a lot of interest as orthopedic implant constituents because their biodegradability and mechanical properties are closer to that of human bone. However, one major concern with Mg in orthopedics is its high corrosion rate that results in the reduction of mechanical integrity before healing the bone tissue. The current study evaluates the sol-gel-derived hydroxyapatite (HA) coating on a selected Mg alloy (Mg-3Zn) for decreasing the corrosion rate and increasing the bioactivity of the Mg surface. The mechanical integrity of the coating is established as a function of the surface roughness of the substrate and the sintering temperature of the coating. Coating on a substrate roughness of 15-20 nm and sintering at 400°C shows the mechanical properties in similar range of bone, thus making it suitable to avoid the stress-shielding effect. The hydroxyapatite coating on the Mg alloy surface also increases corrosion resistance very significantly by 40 times. Bone cells are also found proliferating better in the HA-coated surface. All these benefits together establish the candidature of sol-gel HA-coated Mg-3Zn alloy in orthopedic application.

  8. A novel method for vanadium slag comprehensive utilization to synthesize Zn-Mn ferrite and Fe-V-Cr alloy.

    PubMed

    Liu, Shi-Yuan; Li, Shu-Jin; Wu, Shun; Wang, Li-Jun; Chou, Kuo-Chih

    2018-07-15

    Vanadium slag is a by-product from steelmaking process of vanadium-titanium magnetite, which mainly contains FeO, MnO, V 2 O 3 , and Cr 2 O 3 , The elements Fe and Mn are major components of Mn-Zn ferrite. The elements V and Cr are major components of V-Cr alloy. In view of the potential application in these study, a Mn 0.8 Zn 0.2 Fe 2 O 4 of high saturation magnetization (Ms = 68.6 emu/g) and low coercivity (Hc = 3.3 Oe) was successfully synthesized from the leaching solutions of vanadium slag by adding appropriate chemical reagents, ZnCl 2 and MnCl 2 ·4H 2 O, via roasting at 1300 °C for 1 h. The minor components (CaO and SiO 2 ) in the leaching solution of vanadium slag segregated to the grain boundaries resulting in increasing the resistivity of ferrite. The value of DC resistivity of Mn 0.8 Zn 0.2 Fe 2 O 4 at 25 °C reached 1230.7Ω m. The residue containing Fe, V and Cr was chlorinated by AlCl 3 and the Fe 3+ , V 3+ , and Cr 3+ ions were released into the NaCl-KCl eutectic. The current-time curve for the electrolysis of molten salt was investigated. Alloy (Fe, V, and Cr) of granular shape was obtained. The residue can be used to produce the mulite. This process provided a new approach to utilize slag from steelmaking. Copyright © 2018 Elsevier B.V. All rights reserved.

  9. Cu, Fe, and Zn Isotope Variations Within a High-Temperature Mid-Ocean Ridge Sulfide Structure

    NASA Astrophysics Data System (ADS)

    Ewing, S. M.; Nelson, B. K.; Kelley, D. S.; Nielsen, D. C.

    2006-12-01

    Hydrothermal processes at mid-ocean ridges play an important role in controlling the transition metal budget of seawater and the crust through which it circulates. Preliminary work has shown stable metal isotope variations accompany these processes. We report Cu, Zn, and Fe isotope analyses of transects through a high temperature sulfide structure ("Fin") collected during the 1998 Edifice Rex Sulfide Recovery Project. We analyzed two horizontal transects through the sulfide edifice, from inner conduit to outer surface. Transects A and F are 9 and 6 cm in length, respectively. Each displays radially zoned mineralogy progressing from a chalcopyrite (ccp) zone through zones of zinc sulfide, pyrite-anhydrite (pyr-anh) matrix, zinc sulfide-anhydrite (zns-anh) matrix, to an outer well-cemented silica (Si) zone. Additional ccp and pyr-anh zones appear in transect A resulting from a smaller breakout conduit. In transect A, Cu displays the most isotopic variation, with little variation in Fe and Zn isotopes. From the inner ccp zone outward, the Cu isotope profile shows a 0.4‰ (±0.05‰ 2σ) increase in the first pyr-anh zone over the coarse-grained ccp zone. The δ65Cu drops by 0.6‰ in the secondary ccp zone and recovers to values of the innermost wall in the following zone where it is constant until the outermost portion of the Si rich zone, which shows a 1.3‰ increase over inner zone values. The Zn isotope profile has a total variation of 0.27‰ (±0.05‰ 2σ), with a 0.2‰ increase in the first pyr- anh zone followed by a .27‰ decrease in the adjacent zone, and recovering to its heaviest values in the second pyr-anh zone. The Zn profile lacks any significant increase of the δ^{64}Zn in the outermost zones. The Fe isotope profile shows very little variation across the chimney wall, but does have a sharp 0.7‰ (±0.1‰ 2σ) increase in the δ56Fe in the well-cemented Si rich zone. In transect F, the Cu isotope profile again shows the most variation, but

  10. In-situ grown MgO-ZnO ceramic coating with high thermal emittance on Mg alloy by plasma electrolytic oxidation

    NASA Astrophysics Data System (ADS)

    Li, Hang; Lu, Songtao; Qin, Wei; Wu, Xiaohong

    2017-07-01

    Intense solar radiation and internal heat generation determine the equilibrium temperature of an in-orbit spacecraft. Thermal control coatings with low solar absorptance and high thermal emittance effectively maintain the thermal equilibrium within safe operating limits for exposed, miniaturized and highly integrated components. A novel ceramic coating with high thermal emittance and good adhesion was directly prepared on the Mg substrate using an economical process of controlled plasma electrolytic oxidation (PEO) in the electrolyte containing ZnSO4. XRD and XPS results showed that this coating was mainly composed of the MgO phase as well as an unusual ZnO crystalline phase. The adhesive strength between the coating and substrate determined by a pull-off test revealed an excellent adhesion. Thermal and optical properties test revealed that the coating exhibited a high infrared emittance of 0.88 (2-16 μm) and low solar absorptance of 0.35 (200-2500 nm). The result indicated that the formation of ZnO during the PEO process played an important role in the improvement of the coating emittance. The process developed provides a simple surface method for improving the thermal emittance of Mg alloy, which presents a promising application prospect in the thermal management of the spacecraft.

  11. Photoluminescence spectroscopy and positron annihilation spectroscopy probe of alloying and annealing effects in nonpolar m-plane ZnMgO thin films

    NASA Astrophysics Data System (ADS)

    Yang, A. L.; Song, H. P.; Liang, D. C.; Wei, H. Y.; Liu, X. L.; Jin, P.; Qin, X. B.; Yang, S. Y.; Zhu, Q. S.; Wang, Z. G.

    2010-04-01

    Temperature-dependent photoluminescence characteristics of non-polar m-plane ZnO and ZnMgO alloy films grown by metal organic chemical vapor deposition have been studied. The enhancement in emission intensity caused by localized excitons in m-plane ZnMgO alloy films was directly observed and it can be further improved after annealing in nitrogen. The concentration of Zn vacancies in the films was increased by alloying with Mg, which was detected by positron annihilation spectroscopy. This result is very important to directly explain why undoped Zn1-xMgxO thin films can show p-type conduction by controlling Mg content, as discussed by Li et al. [Appl. Phys. Lett. 91, 232115 (2007)].

  12. Fe, Zn, and Cd stable isotopes from the eastern tropical South Pacific from GEOTRACES cruise GP16 - Methods and data

    NASA Astrophysics Data System (ADS)

    Helgoe, J. M.; Townsend, E.; John, S.

    2014-12-01

    A new method has been developed for the rapid analysis of metal concentrations and stable isotope ratios using a prepFAST automated sample processing robot. Although concentrations and isotopes are processed separately, similar methods are used for both. Initially all seawater is acidified to pH 2. Then Nobias resin with EDTA/IDA functional groups is added to either 10mL of sample for concentrations or ~1L samples for isotopes. Fe binds to the resin at low pH, and the pH is subsequently raised to allow Zn and Cd to bind. For concentration analyses, all subsequent chemistry is automated on the prepFAST including removal of seawater, rinsing of resin, and elution of resin into acid. For isotope samples these extraction techniques are performed manually, but the subsequent purification of Fe, Zn, and Cd by anion exchange chromatography is automated using the prepFAST. With these new methods, samples from the US GEOTRACES cruise GP16, in the eastern tropical South Pacific, are being analyzed. High concentrations of dissolved Fe are observed near the continental shelf and near submarine hydrothermal vents. Interestingly, isotope data show that dissolved Fe near the continental shelf generally has a δ56Fe close to 0 ‰. This δ56 Fe signature is suggestive of a non-reductive dissolution source for Fe, as Fe(II) released by reductive dissolution is typically closer to -2 ‰. Preliminary data show nutrient-type profiles for Zn and Cd, with Zn matching Si and Cd having a similar distribution to P. An increase in dissolved Zn near hydrothermal vents suggests a possible hydrothermal zinc source to the deep ocean. Continuing analysis of isotope data will reveal more about the source and biogeochemical cycling of these three chemically and biologically important trace metals throughout the eastern tropical Pacific Ocean.

  13. Avalanche solar blind photodetectors based on single crystalline Mg0.47Zn0.53O thin film on Ga:ZnO substrate

    NASA Astrophysics Data System (ADS)

    Chen, Hao; Zhang, Jingtao; Chen, Zuxin; Liu, Huiqiang; Ma, Xinzhou; Li, Qiuguo; Chu, Guang; Chu, Sheng

    2018-05-01

    Single crystalline wurtzite Mg0.47Zn0.53O films were grown on Ga:ZnO substrates by pulse laser deposition. The band gap of the films was measured to be 4.43 eV. Vertical devices were fabricated for solar blind photodetection, realizing a high responsivity of 2 A W‑1 at 278 nm and  ‑5 V bias as well as a rejection ratio (R 278 nm/R 350 nm) of over 6  ×  103. A cut-off wavelength of 286 nm and a response time of 77 ms were also achieved. Besides, the devices showed stable response without degeneration under repeating illumination. The high performance of this photodetector was analyzed and attributed to the avalanche effect from high quality Mg0.47Zn0.53O/Ga:ZnO heterojunction at reverse bias. The avalanche gain was calculated to be 14.5 at  ‑10 V.

  14. Effects of MgO modified β-TCP nanoparticles on the microstructure and properties of β-TCP/Mg-Zn-Zr composites.

    PubMed

    Zheng, H R; Li, Z; You, C; Liu, D B; Chen, M F

    2017-03-01

    The mechanical properties and corrosion resistance of magnesium alloy composites were improved by the addition of MgO surface modified tricalcium phosphate ceramic nanoparticles (m-β-TCP). Mg-3Zn-0.8Zr composites with unmodified (MZZT) and modified (MZZMT) nanoparticles were produced by high shear mixing technology. Effects of MgO m-β-TCP nanoparticles on the microstructure, mechanical properties, electrochemical corrosion properties and cytocompatibility of Mg-Zn-Zr/β-TCP composites were investigated. After hot extrusion deformation and dynamic recrystallization, the grain size of MZZMT was the half size of MZZT and the distribution of m-β-TCP particles in the matrix was more uniform than β-TCP particles. The yield tensile strength (YTS), ultimate tensile strength (UTS), and corrosion potential (Ecorr) of MZZMT were higher than MZZT; the corrosion current density (I corr ) of MZZMT was lower than MZZT. Cell proliferation of co-cultured MZZMT and MZZT composite samples were roughly the same and the cell number at each time point is higher for MZZMT than for MZZT samples.

  15. Green synthesis of novel zinc iron oxide (ZnFe2O4) nanocomposite via Moringa Oleifera natural extract for electrochemical applications

    NASA Astrophysics Data System (ADS)

    Matinise, N.; Kaviyarasu, K.; Mongwaketsi, N.; Khamlich, S.; Kotsedi, L.; Mayedwa, N.; Maaza, M.

    2018-07-01

    The main motivation of the research study involves development of reliable, accurate, inexpensive and environmental friendly method for the synthesis of zinc ferrite (ZnFe2O4) nanocomposites. It was thought of interest to synthesized zinc ferrite via green synthetic method using Moringa Oleifera extract. For the first time, we used green synthetic route via Moringa Oleifera extract acted as both chelating and reducing agents to synthesis spinel ZnFe2O4 nanocomposites. The physical and electrochemical properties were characterized using different techniques such as High Resolve Transmission Electron Microscope (HRTEM) Energy Dispersive X-ray Spectroscopy (EDS) X-ray diffraction (XRD) Fourier transform-infrared (FT-IR) Cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). The XRD pattern thus clearly illustrated that the ZnFe2O4 nanocmposites synthesized by the green method were good crystalline in nature. The time constant and exchange current of ZnFe2O4 nanocomposites from EIS analysis were calculated and found to be 5.2001 × 10-4 s/rad and 6.59432 × 10-4 A, respectively. Based on the electrochemical results, GCE/ZnFe2O4 electrode exhibited a good voltametric response, high electro-activity, and excellent electrochemical performance making it a highly suitable/promising electrode for electrochemical applications.

  16. Dual nature of 3 d electrons in YbT 2 Zn 20 (T = Co; Fe) evidenced by electron spin resonance

    DOE PAGES

    Ivanshin, V. A.; Litvinova, T. O.; Gimranova, K.; ...

    2015-03-18

    The electron spin resonance experiments were carried out in the single crystals YbFe 2Zn 20. The observed spin dynamics is compared with that in YbCo 2Zn 20 and Yb 2Co 12P 7 as well as with the data of inelastic neutron scattering and electronic band structure calculations. Our results provide direct evidence that 3d electrons are itinerant in YbFe 2Zn 20 and localized in YbCo 2Zn 20. Possible connection between spin paramagnetism of dense heavy fermion systems, quantum criticality effects, and ESR spectra is discussed.

  17. Neutron monochromators of BeO, MgO and ZnO single crystals

    NASA Astrophysics Data System (ADS)

    Adib, M.; Habib, N.; Bashter, I. I.; Morcos, H. N.; El-Mesiry, M. S.; Mansy, M. S.

    2014-05-01

    The monochromatic features of BeO, MgO and ZnO single crystals are discussed in terms of orientation, mosaic spread, and thickness within the wavelength band from 0.05 up to 0.5 nm. A computer program MONO, written in “FORTRAN”, has been developed to carry out the required calculations. Calculation shows that a 5 mm thick MgO single crystal cut along its (2 0 0) plane having mosaic spread of 0.5° FWHM has the optimum parameters when it is used as a neutron monochromator. Moreover, at wavelengths shorter than 0.24 nm the reflected monochromatic neutrons are almost free from the higher order ones. The same features are seen with BeO (0 0 2) with less reflectivity than that of the former. Also, ZnO cut along its (0 0 2) plane is preferred over the others only at wavelengths longer than 0.20 nm. When the selected monochromatic wavelength is longer than 0.24 nm, the neutron intensities of higher orders from a thermal reactor flux are higher than those of the first-order one. For a cold reactor flux, the first order of BeO and MgO single crystals is free from the higher orders up to 0.4 nm, and ZnO at wavelengths up to 0.5 nm.

  18. Enhanced photocatalytic performances and magnetic recovery capacity of visible-light-driven Z-scheme ZnFe2O4/AgBr/Ag photocatalyst

    NASA Astrophysics Data System (ADS)

    He, Jie; Cheng, Yahui; Wang, Tianzhao; Feng, Deqiang; Zheng, Lingcheng; Shao, Dawei; Wang, Weichao; Wang, Weihua; Lu, Feng; Dong, Hong; Zheng, Rongkun; Liu, Hui

    2018-05-01

    High efficiency, high stability and easy recovery are three key factors for practical photocatalysts. Z-scheme heterostructure is one of the most promising photocatalytic systems to meet all above requirements. However, efficient Z-scheme photocatalysts which could absorb visible light are still few and difficult to implement at present. In this work, the composite photocatalysts ZnFe2O4/AgBr/Ag were prepared through a two-step method. A ∼92% photodegradation rate on methyl orange was observed within 30 min under visible light, which is much better than that of individual ZnFe2O4 or AgBr/Ag. The stability was also greatly improved compared with AgBr/Ag. The increased performance is resulted from the suitable band alignment of ZnFe2O4 and AgBr, and it is defined as Z-scheme mechanism which was demonstrated by detecting active species and electrochemical impedance spectroscopy. Besides, ZnFe2O4/AgBr/Ag is ferromagnetic and can be recycled by magnet. These results show that ZnFe2O4/AgBr/Ag is a potential magnetically recyclable photocatalyst which can be driven by visible light.

  19. Processes and time scales of magmatic evolution as revealed by Fe-Mg chemical and isotopic zoning in natural olivines

    NASA Astrophysics Data System (ADS)

    Oeser, Martin; Dohmen, Ralf; Horn, Ingo; Schuth, Stephan; Weyer, Stefan

    2015-04-01

    In this study, we applied high-precision in situ Fe and Mg isotope analyses by femtosecond laser ablation (fs-LA) MC-ICP-MS on chemically zoned olivine xeno- and phenocrysts from intra-plate volcanic regions in order to investigate the magnitude of Fe and Mg isotope fractionation and its suitability to gain information on magma evolution. Our results show that chemical zoning (i.e., Mg#) in magmatic olivines is commonly associated with significant zoning in δ56Fe and δ26Mg (up to 1.7‰ and 0.7‰, respectively). We explored different cases of kinetic fractionation of Fe and Mg isotopes by modeling diffusion in the melt or olivine and simultaneous growth or dissolution. Combining the information of chemical and isotopic zoning in olivine allows to distinguish between various processes that may occur during magma evolution, namely diffusive Fe-Mg exchange between olivine and melt, rapid crystal growth, and Fe-Mg inter-diffusion simultaneous to crystal dissolution or growth. Chemical diffusion in olivine appears to be the dominant process that drives isotope fractionation in magmatic olivine. Simplified modeling of Fe and Mg diffusion is suitable to reproduce both the chemical and the isotopic zoning in most of the investigated olivines and, additionally, provides time information about magmatic processes. For the Massif Central (France), modeling of diffusive re-equilibration of mantle olivines in basanites revealed a short time span (<2 years) between the entrainment of a mantle xenolith in an intra-plate basaltic magma and the eruption of the magma. Furthermore, we determined high cooling rates (on the order of a few tens to hundreds of °C per year) for basanite samples from a single large outcrop in the Massif Central, which probably reflects the cooling of a massive lava flow after eruption. Results from the modeling of Fe and Mg isotope fractionation in olivine point to a systematic difference between βFe and βMg (i.e., βFe/βMg ≈ 2), implying that the

  20. Study of 57Fe Mössbauer effect in RFe 2Zn 20 ( R = Lu, Yb, Gd)

    DOE PAGES

    Bud’ko, Sergey L.; Kong, Tai; Ma, Xiaoming; ...

    2015-08-04

    In this document we report measurements of 57Fe Mössbauer spectra for RFe 2Zn 20 ( R = Lu, Yb, Gd) from ~ 4.5 K to room temperature. The obtained isomer shift values are very similar for all three compounds, their temperature dependence was analyzed within the Debye model and resulted in an estimate of the Debye temperatures of 450-500 K. The values of quadrupole splitting at room temperature change with the cubic lattice constant a in a linear fashion. For GdFe 2Zn 20, ferromagnetic order is seen as an appearance of a sextet in the spectra. The 57Fe site hyperfinemore » field for T → 0 was evaluated to be ~ 2.4 T.« less

  1. Ion beam synthesis of Fe nanoparticles in MgO and yttria-stabilized zirconia

    NASA Astrophysics Data System (ADS)

    Potzger, K.; Reuther, H.; Zhou, Shengqiang; Mücklich, A.; Grötzschel, R.; Eichhorn, F.; Liedke, M. O.; Fassbender, J.; Lichte, H.; Lenk, A.

    2006-04-01

    To form embedded Fe nanoparticles, MgO(001) and YSZ(001) single crystals have been implanted at elevated temperatures with Fe ions at energies of 100 keV and 110 keV, respectively. The ion fluence was fixed at 6×1016 cm-2. As a result, γ- and α-phase Fe nanoparticles were synthesized inside MgO and YSZ, respectively. A synthesis efficiency of 100% has been achieved for implantation at 1273 K into YSZ. The ferromagnetic behavior of the α-Fe nanoparticles is reflected by a magnetic hyperfine field of 330 kOe and a hysteretic magnetization reversal. Electron holography showed a fringing magnetic field around some, but not all of the particles.

  2. Estimated daily intake of Fe, Cu, Ca and Zn through common cereals in Tehran, Iran.

    PubMed

    Kashian, S; Fathivand, A A

    2015-06-01

    This paper presents the findings of study undertaken to estimate the dietary intake of iron (Fe), copper (Cu), calcium (Ca) and zinc (Zn) through common cereals in Tehran, Iran. 100 samples of rice, wheat and barley were collected from various brands between August and October 2013. The samples were analyzed performing instrumental neutron activation analysis (INAA). The dietary intake for adults was estimated by a total cereal study. Calculations were carried out on the basis of the reported adults' average food consumption rate data. The total daily intake estimated in mgd(-1) for Tehran population were 3.6 (Fe), 10.2 (Zn), 0.3 (Cu) and 234.5 (Ca). Wheat showed the highest contribution to Zn, Cu and Ca intakes. Furthermore, intakes were compared with recommended dietary allowance (RDA). Zn total intake (10.2mgd(-1)) was comparable with RDA values for males (11mgd(-1)) and was higher than recommended value for females (8mgd(-1)). The intakes of other studied elements were below the respective RDAs. Copyright © 2014 Elsevier Ltd. All rights reserved.

  3. Regulating the local pH level of titanium via Mg-Fe layered double hydroxides films for enhanced osteogenesis.

    PubMed

    Li, Qianwen; Wang, Donghui; Qiu, Jiajun; Peng, Feng; Liu, Xuanyong

    2018-05-01

    Hard tissue implant materials which can cause a suitable alkaline microenvironment are thought to be beneficial for stimulating osteoblast differentiation while suppressing osteoclast generation. To make the local pH around the interface between materials and cells controllable, we prepared a series of Mg-Fe layered double hydroxide (LDH) films on acid-etched pure titanium surfaces via hydrothermal treatment. By adjusting the Mg/Fe proportion ratio, the interlayer spacing of Mg-Fe LDHs was regulated, making their OH- exchange abilities adjustable, and this ultimately resulted in a microenvironment with a controllable pH value. In vitro experiments demonstrated that the Mg-Fe LDH film-modified titanium surface possessed good biocompatibility and osteogenic activity, especially the Mg-Fe LDH film with Mg/Fe proportion ratio of 4, which could form a suitable alkaline microenvironment for the growth and osteogenetic differentiation of stem cells. These results demonstrate the potential application of the prepared Mg-Fe LDH films in enhancing the osteogenesis of implant materials while providing a new way into the design of controllable alkaline environment.

  4. Fabrication of wide-band-gap Mg{sub x}Zn{sub 1-x}O quasi-ternary alloys by molecular-beam epitaxy

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

    Tanaka, Hiroshi; Fujita, Shigeo; Fujita, Shizuo

    2005-05-09

    A series of wurtzite MgZnO quasi-ternary alloys, which consist of wurtzite MgO/ZnO superlattices, were grown by molecular-beam epitaxy on sapphire substrates. By changing the thicknesses of ZnO layers and/or of MgO layers of the superlattice, the band-gap energy was artificially tuned from 3.30 to 4.65 eV. The highest band gap, consequently realized by the quasi-ternary alloy, was larger than that of the single MgZnO layer, we have ever reported, keeping the wurtzite structure. The band gap of quasi-ternary alloys was well analyzed by the Kronig-Penny model supposing the effective masses of wurtzite MgO as 0.30m{sub 0} and (1-2)m{sub 0} formore » electrons and holes, respectively.« less

  5. CoFe2O4-TiO2 and CoFe2O4-ZnO thin film nanostructures elaborated from colloidal chemistry and atomic layer deposition.

    PubMed

    Clavel, Guylhaine; Marichy, Catherine; Willinger, Marc-Georg; Ravaine, Serge; Zitoun, David; Pinna, Nicola

    2010-12-07

    CoFe(2)O(4)-TiO(2) and CoFe(2)O(4)-ZnO nanoparticles/film composites were prepared from directed assembly of colloidal CoFe(2)O(4) in a Langmuir-Blodgett monolayer and atomic layer deposition (ALD) of an oxide (TiO(2) or ZnO). The combination of these two methods permits the use of well-defined nanoparticles from colloidal chemistry, their assembly on a large scale, and the control over the interface between a ferrimagnetic material (CoFe(2)O(4)) and a semiconductor (TiO(2) or ZnO). Using this approach, architectures can be assembled with a precise control from the Angstrom scale (ALD) to the micrometer scale (Langmuir-Blodgett film). The resulting heterostructures present well-calibrated thicknesses. Electron microscopy and magnetic measurement studies give evidence that the size of the nanoparticles and their intrinsic magnetic properties are not altered by the various steps involved in the synthesis process. Therefore, the approach is suitable to obtain a layered composite with a quasi-monodisperse layer of ferrimagnetic nanoparticles embedded in an ultrathin film of semiconducting material.

  6. Pt–Mg, Pt–Ca, and Pt–Zn lantern complexes and metal-only donor–acceptor interactions [Pt-Mg Pt-Ca and Pt-Zn compounds with metal-only donor-acceptor interactions

    DOE PAGES

    Baddour, Frederick G.; Hyre, Ariel S.; Guillet, Jesse L.; ...

    2016-12-12

    Here, Pt-based heterobimetallic lantern complexes of the form [PtM(SOCR) 4(L)] have been shown previously to form intermolecular metallophilic interactions and engage in antiferromagnetic coupling between lanterns having M atoms with open shell configurations. In order to understand better the influence of the carboxylate bridge and terminal ligand on the electronic structure, as well as the metal–metal interactions within each lantern unit, a series of diamagnetic lantern complexes, [PtMg(SAc) 4(OH 2)] (1), [PtMg(tba) 4(OH 2)] (2), [PtCa(tba) 4(OH 2)] (3), [PtZn(tba) 4(OH 2)] (4), and a mononuclear control (Ph 4P) 2[Pt(SAc) 4] (5) have been synthesized. Crystallographic data show close Pt–Mmore » contacts enforced by the lantern structure in each dinuclear case. 195Pt-NMR spectroscopy of 1–4, (Ph 4P) 2[Pt(SAc) 4] (5), and several previously reported lanterns revealed a strong chemical shift dependence on the identity of the second metal (M), mild influence by the thiocarboxylate ligand (SOCR; R = CH 3 (thioacetate, SAc), C 6H 5 (thiobenzoate, tba)), and modest influence from the terminal ligand (L). Fluorescence spectroscopy has provided evidence for a Pt···Zn metallophilic interaction in [PtZn(SAc) 4(OH 2)], and computational studies demonstrate significant dative character. In all of 1–4, the short Pt–M distances suggest that metal-only Lewis donor (Pt)–Lewis acceptor (M) interactions could be present. DFT and NBO calculations, however, show that only the Zn examples have appreciable covalent character, whereas the Mg and Ca complexes are much more ionic.« less

  7. Pt–Mg, Pt–Ca, and Pt–Zn lantern complexes and metal-only donor–acceptor interactions [Pt-Mg Pt-Ca and Pt-Zn compounds with metal-only donor-acceptor interactions

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

    Baddour, Frederick G.; Hyre, Ariel S.; Guillet, Jesse L.

    Here, Pt-based heterobimetallic lantern complexes of the form [PtM(SOCR) 4(L)] have been shown previously to form intermolecular metallophilic interactions and engage in antiferromagnetic coupling between lanterns having M atoms with open shell configurations. In order to understand better the influence of the carboxylate bridge and terminal ligand on the electronic structure, as well as the metal–metal interactions within each lantern unit, a series of diamagnetic lantern complexes, [PtMg(SAc) 4(OH 2)] (1), [PtMg(tba) 4(OH 2)] (2), [PtCa(tba) 4(OH 2)] (3), [PtZn(tba) 4(OH 2)] (4), and a mononuclear control (Ph 4P) 2[Pt(SAc) 4] (5) have been synthesized. Crystallographic data show close Pt–Mmore » contacts enforced by the lantern structure in each dinuclear case. 195Pt-NMR spectroscopy of 1–4, (Ph 4P) 2[Pt(SAc) 4] (5), and several previously reported lanterns revealed a strong chemical shift dependence on the identity of the second metal (M), mild influence by the thiocarboxylate ligand (SOCR; R = CH 3 (thioacetate, SAc), C 6H 5 (thiobenzoate, tba)), and modest influence from the terminal ligand (L). Fluorescence spectroscopy has provided evidence for a Pt···Zn metallophilic interaction in [PtZn(SAc) 4(OH 2)], and computational studies demonstrate significant dative character. In all of 1–4, the short Pt–M distances suggest that metal-only Lewis donor (Pt)–Lewis acceptor (M) interactions could be present. DFT and NBO calculations, however, show that only the Zn examples have appreciable covalent character, whereas the Mg and Ca complexes are much more ionic.« less

  8. Elucidation of structural, vibrational and dielectric properties of transition metal (Co2+) doped spinel Mg-Zn chromites

    NASA Astrophysics Data System (ADS)

    Choudhary, Pankaj; Varshney, Dinesh

    2018-05-01

    Co2+ doped Mg-Zn spinel chromite compositions Mg0.5Zn0.5-xCoxCr2O4 (0.0 ≤ x ≤ 0.5) have been synthesized by the high-temperature solid state method. Synchrotron and X-ray diffraction (XRD) studies show single-phase crystalline nature. The structural analysis is validated by Rietveld refinement confirms the cubic structure with space group Fd3m. Crystallite size is estimated from Synchrotron XRD which was found to be 30-34 nm. Energy dispersive analysis confirms stoichiometric Mg0.5Zn0.5-xCoxCr2O4 composition. Average crystallite size distribution is estimated from imaging software (Image - J) of SEM is in the range of 100-250 nm. Raman spectroscopy reveals four active phonon modes, and a pronounced red shift is due to enhanced Co2+ concentration. Increased Co2+ concentration in Mg-Zn chromites shows a prominent narrowing of band gap from 3.46 to 2.97 eV. The dielectric response is attributed to the interfacial polarization, and the electrical modulus study supports non-Debye type of dielectric relaxation. Ohmic junctions (minimum potential drop) at electrode interface are active at lower levels of doping (x < 0.2) give rise to a low-frequency semicircle as evidenced from the complex impedance analysis. The low dielectric loss and high ac conductivity of Co2+ doped Mg-Zn spinel chromites are suitable for power transformer applications at high frequencies.

  9. Enhanced photocatalytic activity and characterization of magnetic Ag/BiOI/ZnFe2O4 composites for Hg0 removal under fluorescent light irradiation

    NASA Astrophysics Data System (ADS)

    Li, Chengwei; Zhang, Anchao; Zhang, Lixiang; Song, Jun; Su, Sheng; Sun, Zhijun; Xiang, Jun

    2018-03-01

    A series of magnetic Ag/BiOI/ZnFe2O4 hybrids synthesized via hydrothermal process, subsequent deposition-precipitation and photoreduction method were employed to remove elemental mercury (Hg0) under fluorescent light irradiation. The effects of Ag content, fluorescent light irradiation, reaction temperature, pH value, flue gas composition, anions and photocatalyst dosage on Hg0 removal were investigated in detail. The as-synthesized photocatalysts were characterized using N2 adsorption-desorption, XRD, SEM, TEM, HRTEM, XPS, VSM, DRS, ESR, PL and photocurrent response. The results showed that the ternary Ag/BiOI/ZnFe2O4 hybrids possessed enhanced visible-light-responsive photocatalytic performances for Hg0 removal. Ag/BiOI/ZnFe2O4 photocatalyst could be easily recovered from the reaction solution by an extra magnet and was stable in the process of Hg0 removal. Lower content of Ag was highly dispersed on the surface of BiOI/ZnFe2O4, while higher content of Ag would result in some aggregations and/or the blockages of micropore. In comparison to BiOI/ZnFe2O4, Ag deposited BiOI/ZnFe2O4 material showed lower recombination rate of electron-hole pairs. The superior Hg0 oxidation removal could correspond to good match of BiOI and ZnFe2O4, excellent fluidity and surface plasmon resonance effect of Ag0 nanoparticles, which led to higher separation efficiency of photogenerated electrons and holes, thereby enhancing the hybrids' photocatalytic activity.

  10. Effects of Sn Addition on the Microstructures and Mechanical Properties of Mg-6Zn-3Cu- xSn Magnesium Alloys

    NASA Astrophysics Data System (ADS)

    Zhang, Tao; Shen, Jun; Sang, Jia-Xin; Li, Yang; He, Pei-Pei

    2015-08-01

    In this paper, Mg-6Zn-3Cu- xSn (ZC63- xSn) magnesium alloys with different Sn contents (0, 1, 2, 4 wt pct) were fabricated and subjected to different heat treatments. The microstructures and mechanical properties of the obtained ZC63- xSn samples were investigated by optical microscopy, X-ray diffraction, scanning electron microscopy, Vickers hardness testing, and tensile testing. It was found that the As-cast Mg-6Zn-3Cu (ZC63) magnesium alloy mainly contained α-Mg grains and Mg(Zn,Cu) particles. Sn dissolved in α-Mg grains when Sn content was below 2 wt pct while Mg2Sn phase forms in the case of Sn content was above 4 wt pct. Addition of Sn refined both α-Mg grains and Mg(Zn,Cu) particles, and increased the volume fraction of Mg(Zn,Cu) particles. Compared with the Sn-free alloy, the microhardness of Sn-containing alloys increased greatly and that of As-extrude ZC63-4Sn sample achieved the highest value. The strength of ZC63 magnesium alloy was significantly enhanced because of Sn addition, which was attributed to grain refinement strengthening, solid solution strengthening, and precipitation strengthening. Furthermore, the ultimate yield stress, yield strength, and elongation of ZC63- xSn magnesium alloys were increased owing to the deceasing grain size induced by extrusion process.

  11. Unraveling the mechanism of ultraviolet-induced optical gating in Zn1-x Mg x O nanocrystal solid solution field effect transistors

    NASA Astrophysics Data System (ADS)

    Kim, Youngjun; Cho, Seongeun; Park, Byoungnam

    2018-03-01

    We report ultraviolet (UV)-induced optical gating in a Zn1-x Mg x O nanocrystal solid solution (NCSS) field effect transistor (FET) through a systematic study in which UV-induced charge transport properties are probed as a function of Mg composition. Change in the electrical properties of Zn1-x Mg x O NCSS associated with electronic traps is investigated by field effect-modulated current-voltage characteristic curves in the dark and under illumination. Under UV illumination, significant threshold voltage shift to a more negative value in an n-channel Zn1-x Mg x O NCSS FET is observed. Importantly, as the Mg composition increases, the effect of UV illumination on the threshold voltage shift is alleviated. We found that threshold voltage shift as a function of Mg composition in the dark and under illumination is due to difference in the deep trap density in the Zn1-x Mg x O NCSS. This is supported by Mg composition dependent photoluminescence intensity in the visible range and reduced FET mobility with Mg addition. The presence of the deep traps and the corresponding trap energy levels in the Zn1-x Mg x O NCSS are ensured by photoelectron spectroscopy in air.

  12. Photocatalytic decomposition of Congo red under visible light irradiation using MgZnCr-TiO2 layered double hydroxide.

    PubMed

    Ma, Chi; Wang, Fenghua; Zhang, Chang; Yu, Zhigang; Wei, Jingjing; Yang, Zhongzhu; Li, Yongqiu; Li, Zihao; Zhu, Mengying; Shen, Liuqing; Zeng, Guangming

    2017-02-01

    The new nanophotocatalyst MgZnCr-TiO 2 was prepared by co-precipitation under different molar ratio of metals (Zn:Cr) and the loaded amount of TiO 2 . And it was characterized by X-ray diffraction, Raman spectroscopy, X-ray photoelectron spectroscopy et al. Langmuir model fitted well the adsorption isotherm with the value of R 2 0.9765, the maximum adsorption capacity was 526.32 mg g -1 , the adsorption followed pseudo second order kinetic by MgZnCr-TiO 2 (1:1:2-0.05). The photocatalytic oxidation of Congo red was used to determine the photocatalytic performance of MgZnCr-TiO 2 (1:1:2-0.05) under visible light irradiation, and the removal rate reached 98% after reaction for 40 min. The degradation mechanism of Congo red also was proposed, and the MgZnCr-TiO 2 (1:1:2-0.05) was stable after five cycles. Compared to the adsorption, Congo red was removed fundamentally by photocatalysis and it is expected to be an effective way to eliminate Congo red. Copyright © 2016 Elsevier Ltd. All rights reserved.

  13. A novel reduced symmetry oxide (Mg3B2O6) for magnetic tunnel junctions based on FeCo or Fe leads

    NASA Astrophysics Data System (ADS)

    Stewart, Derek

    2010-03-01

    Magnetic tunnel junctions with high TMR values, such as FeMgOFe, capitalize on spin filtering in the oxide due to the band symmetry of incident electrons. However, these structures rely on magnetic leads and oxide regions of the same cubic symmetry class. This raises the question of whether reducing the oxide symmetry can enhance spin filtering. A new magnetic tunnel junction (FeCoMg3B2O6FeCo) is presented that uses a reduced symmetry oxide region (orthorhombic) to filter spins between two cubic magnetic leads. Symmetry analysis of coupling between states in the cubic leads and the orthorhombic oxide indicates that majority carrier tunneling through the oxide should be favored over minority carriers. Complex band structure analysis of Mg3B2O6 shows that the relevant evanescent states in the band gap are due to boron p states and that there is sufficient difference in the decay rates of the imaginary bands for spin filtering to occur. Electronic transport calculations through a FeMg3B2O6Fe magnetic tunnel junction are also performed to address the possible influence of interface states. Some recent experimental studies of FeCoBMgOFeCoB junctions, with B diffusion into the MgO region, indicate that this new type of junction may have already been fabricated. The prospect of developing a general class of magnetic tunnel junctions based on reduced symmetry oxides is also examined.

  14. Electromigration of Mn, Fe, Cu and Zn with citric acid in contaminated clay.

    PubMed

    Pazos, M; Gouveia, S; Sanroman, M A; Cameselle, C

    2008-07-01

    Metal reactivity, speciation and solubility have an important influence in its transportation through a porous matrix by electrokinetics and, therefore, they dramatically affect the removal efficiency. This work deals with the effect of solubility and transport competition among several metals (Mn, Fe, Cu and Zn) during their transport through polluted clay. The unenhancement electrokinetic treatment results in a limited removal of the tested metals because they were retained into the kaolinite sample by the penetration of the alkaline front. Metals showed a removal degree in accordance with the solubility of the corresponding hydroxide and its formation pH. In 7 days of treatment, the removal results were: 75.6% of Mn; 68.5% of Zn, 40.6% of Cu and 14.8% of Fe. In order to avoid the negative effects of the basic front generated at the cathode, two different techniques were proposed and tested: the addition of citric acid as complexing agent to the polluted kaolinite sample and the use of citric acid to control de pH on the cathode chamber. Both techniques are based on the capability of citric acid to act as a complexing and neutralizing agent. Almost complete removal of Mn, Cu and Zn was achieved when citric acid was used (as neutralizing or complexing agent). But Fe only reached 33% of removal because it formed a negatively charged complex with citrate that retarded its transportation to the cathode.

  15. Growth kinetics of O-polar BexMgyZn1-x-yO alloy: Role of Zn to Be and Mg flux ratio as a guide to growth at high temperature

    NASA Astrophysics Data System (ADS)

    Ullah, M. B.; Avrutin, V.; Nakagawara, T.; Hafiz, S.; Altuntaş, I.; Özgür, Ü.; Morkoç, H.

    2017-05-01

    We studied the effect of the substrate temperature, in the range from 450 °C to 500 °C, on the required Zn to (Be + Mg) flux ratio for plasma-assisted molecular beam epitaxy growth of O-polar BexMgyZn1-x-yO on (0001)-GaN/sapphire templates. Achievement of single-crystalline BexMgyZn1-x-yO with improved optical and structural qualities required relatively high substrate temperatures, which necessitated the Zn to (Be + Mg) flux ratio to be increased from 3.9 at 450 °C to 8.3 at 500 °C. This resulted in a reduction of Mg incorporation from 25% to 15% for a fixed Be content of ˜3%. With increasing Zn to (Be + Mg) ratio, 15 K photoluminescence energy for the dominant emission remained unchanged at around 3.75 eV and 3.55 eV for the samples grown at 475 °C and 500 °C, respectively. These findings readily suggest a kinetic limitation of Mg and Be incorporation into wurtzite BexMgyZn1-x-yO lattice, resulting in the formation of second phase due mainly to the enhanced surface mobility of Mg adatoms and, therefore, an increase in the probability of the formation of Mg-rich clusters. An increase in the in-plane lattice parameter, deduced from the Reflection High Energy Electron Diffraction, at the onset of the phase segregation suggests the formation of the wurtzite phase MgO rich alloy(s).

  16. Three-State Quantum Dot Gate FETs Using ZnS-ZnMgS Lattice-Matched Gate Insulator on Silicon

    NASA Astrophysics Data System (ADS)

    Karmakar, Supriya; Suarez, Ernesto; Jain, Faquir C.

    2011-08-01

    This paper presents the three-state behavior of quantum dot gate field-effect transistors (FETs). GeO x -cladded Ge quantum dots (QDs) are site-specifically self-assembled over lattice-matched ZnS-ZnMgS high- κ gate insulator layers grown by metalorganic chemical vapor deposition (MOCVD) on silicon substrates. A model of three-state behavior manifested in the transfer characteristics due to the quantum dot gate is also presented. The model is based on the transfer of carriers from the inversion channel to two layers of cladded GeO x -Ge quantum dots.

  17. Mg-doped Li2FeSiO4/C as high-performance cathode material for lithium-ion battery

    NASA Astrophysics Data System (ADS)

    Qu, Long; Luo, Dong; Fang, Shaohua; Liu, Yi; Yang, Li; Hirano, Shin-ichi; Yang, Chun-Chen

    2016-03-01

    Mg-doped Li2FeSiO4/C is synthesized by using Fe2O3 nanoparticle as iron source. Through Rietveld refinement of X-ray diffraction data, it is confirmed that Mg-doped Li2FeSiO4 owns monoclinic P21/n structure and Mg occupies in Fe site in the lattice. Through energy dispersive X-ray measurement, it is detected that Mg element is distributed homogenously in the resulting product. The results of transmission electron microscopy measurement reveal that the effect of Mg-doping on Li2FeSiO4 crystallite size is not obvious. As a cathode material for lithium-ion battery, this Mg-doped Li2FeSiO4/C delivers high discharge capacity of 190 mAh g-1 (the capacity was with respect to the mass of Li2FeSiO4) at 0.1C and its capacity retention of 100 charge-discharge cycles reaches 96% at 0.1C. By the analysis of electrochemical impedance spectroscopy, it is concluded that Mg-doping can help to decrease the charge-transfer resistance and increase the Li+ diffusion capability.

  18. Photoelectrochemical enhancement of ZnO/BiVO4/ZnFe2O4/rare earth oxide hetero-nanostructures

    NASA Astrophysics Data System (ADS)

    She, Xuefeng; Zhang, Zhuo; Baek, Minki; Yong, Kijung

    2018-01-01

    Over the decades, researchers have made great efforts to turn the world into a cleaner place through efficient recycling of industrial waste and developing of green energy. Here we demonstrate a prototype heterostructure photoelectrochemical (PEC) cell fabricated using recycled industrial waste. ZnFe2O4 (ZFO) nanorod (NR) clusters were synthesized on the BiVO4@ZnO hetero-nanostructures using recycled rare earth oxide (REO) slags as Fe source. The NR-based PEC cell exhibited a significantly enhanced photon to hydrogen conversion efficiency over the entire UV and visible spectrum. Further study demonstrates that the photo-carrier separation and migration processes can be facilitated by the cascade band alignment of the heterostructure and the clustered nanostructure network. In addition, the life-time of the photo-carriers can be enhanced by the REO passivation layer, leading to a further increased PEC performance. Our results present a novel approach for high efficiency PEC cells, and offer great promises to the efficient recycling of industrial waste for clean renewable energy applications.

  19. Hydrogen storage properties of Mg xFe (x: 2, 3 and 15) compounds produced by reactive ball milling

    NASA Astrophysics Data System (ADS)

    Puszkiel, J. A.; Arneodo Larochette, P.; Gennari, F. C.

    This work deals with the assessment of the thermo-kinetic properties of Mg-Fe based materials for hydrogen storage. Samples are prepared from Mg xFe (x: 2, 3 and 15) elemental powder mixtures via low energy ball milling under hydrogen atmosphere at room temperature. The highest yield is obtained with Mg 15Fe after 150 h of milling (90 wt% of MgH 2). The thermodynamic characterization carried out between 523 and 673 K shows that the obtained Mg-Fe-H hydride systems have similar thermodynamic parameters, i.e. enthalpy and entropy. However, in equilibrium conditions, Mg 15Fe has higher hydrogen capacity and small hysteresis. In dynamic conditions, Mg 15Fe also shows better hydrogen capacity (4.85 wt% at 623 K absorbed in less than 10 min and after 100 absorption/desorption cycles), reasonably good absorption/desorption times and cycling stability in comparison to the other studied compositions. From hydrogen uptake rate measurements performed at 573 and 623 K, the rate-limiting step of the hydrogen uptake reaction is determined by fitting particle kinetic models. According to our results, the hydrogen uptake is diffusion controlled, and this mechanism does not change with the Mg-Fe proportion and temperature.

  20. Mg-Fe Isotope Systems of Mantle Xenoliths: Constrains on the Evolution of Siberian Craton

    NASA Astrophysics Data System (ADS)

    An, Y.; Kiseeva, E. S.; Sobolev, N. V.; Zhang, Z.

    2017-12-01

    Mantle xenoliths bring to the surface a variety of lithologies (dunites, lherzolites, harzburgites, wehrlites, eclogites, pyroxenites, and websterites) and represent snapshots of the geochemical processes that occur deep within the Earth. Recent improvements in the precision of the MC-ICP-MS measurements have allowed us to expand the amount of data on Mg and Fe isotopes for mantle-derived samples. For instance, to constrain the isotopic composition of the Earth based on the study of spinel and garnet peridotites (An et al., 2017; Teng et al., 2010), to trace the origin and to investigate the isotopic fractionation mechanism during metamorphic process using cratonic or orogenic eclogites (Li et al., 2011; Wang et al., 2012) and to reveal the metasomatism-induced mantle heterogeneity by pyroxenites (Hu et al., 2016). Numerous multi-stage modification events and mantle layering are detected in the subcontinental lithospheric mantle under the Siberian craton (Ashchepkov et al., 2008a; Sobolev et al., 1975, etc). Combined analyses of Mg and Fe isotopic systems could provide new constraints on the formation and evolution of the ancient cratonic mantle. In order to better constrain the magnitude and mechanism of inter-mineral Mg and Fe isotopic fractionations at high temperatures, systematic studies of mantle xenoliths are needed. For example, theoretical calculations and natural samples measurements have shown that large equilibrium Mg isotope fractionations controlled by the difference in coordination number of Mg among minerals could exist (Huang et al., 2013; Li et al., 2011). Thus, the Mg isotope geothermometer could help us trace the evolution history of ancient cratons. In this study we present Mg and Fe isotopic data for whole rocks and separated minerals (clinopyroxene (cpx) and garnet (grt)) from different types of mantle xenoliths (garnet pyroxenites, eclogites, grospydites and garnet peridotites) from a number of kimberlite pipes in Siberian craton (Udachnaya

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

    PubMed

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

    2016-11-01

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

  2. Investigation of site preference of Zn doped Ba{sub 3}Co{sub 2−x}Zn{sub x}Fe{sub 24}O{sub 41} by Mössbauer spectroscopy

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

    Lim, Jung Tae; Kim, Chul Sung, E-mail: cskim@kookmin.ac.kr

    2014-05-07

    The polycrystalline Ba{sub 3}Co{sub 2−x}Zn{sub x}Fe{sub 24}O{sub 41} (x = 0.0, 0.5, 1.0) samples were prepared by using solid-state-reaction method. The crystal structures and magnetic properties of samples were investigated with x-ray diffractometer, vibrating sample magnetometer, and Mössbauer spectroscopy. The crystal structure of Ba{sub 3}Co{sub 2−x}Zn{sub x}Fe{sub 24}O{sub 41} (x = 0.0, 0.5, 1.0) samples was determined to be a hexagonal structure with P6{sub 3}/mmc space group at 295 K, and the saturation magnetization (M{sub s}) of Ba{sub 3}Co{sub 2−x}Zn{sub x}Fe{sub 24}O{sub 41} (x = 0.0, 0.5, 1.0) samples were found to be M{sub s} = 50.9, 53.1, 55.0 emu/g, respectively. From the temperature dependence of magnetizationmore » curves under 100 Oe between 4.2 and 740 K, we were able to observe the spin transition, and both spin transition temperature (T{sub s}) and Curie temperature (T{sub C}) decrease with increasing Zn concentration. Mössbauer spectra of all samples were obtained and analyzed at various temperatures ranging from 4.2 to 295 K. With ten-sextets for Fe sites corresponding to the Z-type hexagonal crystallographic sites, all spectra below T{sub C} were fitted by least-square method. In addition, from the site occupation numbers of Fe, calculated from the relative areas fitted to the Mössbauer spectra, we find that Zn ions preferentially occupy the tetrahedral sublattices of down sites.« less

  3. Synthesis, characterization and adsorptive performance of MgFe2O4 nanospheres for SO2 removal.

    PubMed

    Zhao, Ling; Li, Xinyong; Zhao, Qidong; Qu, Zhenping; Yuan, Deling; Liu, Shaomin; Hu, Xijun; Chen, Guohua

    2010-12-15

    A type of uniform Mg ferrite nanospheres with excellent SO(2) adsorption capacity could be selectively synthesized via a facile solvothermal method. The size of the MgFe(2)O(4) nanospheres was controlled to be 300-400 nm in diameter. The structural, textural, and surface properties of the adsorbent have been fully characterized by a variety of techniques (Brunauer-Emmett-Teller, BET; X-ray diffraction analysis, XRD; scanning electron microscopy, SEM; and energy-dispersive X-ray spectroscopy, EDS). The valence states and the surface chemical compositions of MgFe(2)O(4) nanospheres were further identified by X-ray photoelectron spectroscopy (XPS). The behaviors of SO(2) oxidative adsorption on MgFe(2)O(4) nanospheres were studied using Fourier transform infrared spectroscopy (FTIR). Both the sulfite and sulfate species could be formed on the surface of MgFe(2)O(4). The adsorption equilibrium isotherm of SO(2) was analyzed using a volumetric method at 298 K and 473 K. The results indicate that MgFe(2)O(4) nanospheres possess a good potential as the solid-state SO(2) adsorbent for applications in hot fuel gas desulfurization. Copyright © 2010 Elsevier B.V. All rights reserved.

  4. The Adsorption of Dextranase onto Mg/Fe-Layered Double Hydroxide: Insight into the Immobilization

    PubMed Central

    Ding, Yi; Liu, Le; Fang, Yaowei; Zhang, Xu; Lyu, Mingsheng; Wang, Shujun

    2018-01-01

    We report the adsorption of dextranase on a Mg/Fe-layered double hydroxide (Mg/Fe-LDH). We focused the effects of different buffers, pH, and amino acids. The Mg/Fe-LDH was synthesized, and adsorption experiments were performed to investigate the effects. The maximum adsorption occurred in pH 7.0 4-(2-hydroxyethyl)-1-piperazineethanesulfonic acid (HEPES) buffer, and the maximum dextranase adsorption uptake was 1.38 mg/g (416.67 U/mg); histidine and phenylalanine could affect the adsorption. A histidine tag could be added to the protein to increase the adsorption significantly. The performance features and mechanism were investigated with X-ray diffraction patterns (XRD) and Fourier transform infrared spectra (FTIR). The protein could affect the crystal structure of LDH, and the enzyme was adsorbed on the LDH surface. The main interactions between the protein and LDH were electrostatic and hydrophobic. Histidine and phenylalanine could significantly affect the adsorption. The hexagonal morphology of LDH was not affected after adsorption. PMID:29562655

  5. X-ray diffraction study of the caged magnetic compound DyFe 2 Zn 20 at low temperatures

    NASA Astrophysics Data System (ADS)

    Ohashi, M.; Ohashi, K.; Sawabu, M.; Miyagawa, M.; Maeta, K.; Isikawa, Y.

    2018-05-01

    We have carried out high-angle X-ray powder diffraction measurements of the caged magnetic compound DyFe2Zn20 at low temperature between 14 and 300 K. Even though a strong magnetic anisotropy exists in the magnetization and magnetic susceptibility due to strong exchange interaction between Fe and Dy, almost all X-ray powder diffraction peaks correspond to Bragg reflections of the cubic structural models not only at room temperature paramagnetic state but also at low temperature magnetic ordering state. The Debye temperature is obtained to be 227 K from the results of the volumetric thermal expansion coefficient, which is approximately coincident with that of CeRu2Zn20 (245 K) and that of pure Zn metal (235 K).

  6. Synergetic effect of Zn substitution on the electron and phonon transport in Mg2Si0.5Sn0.5-based thermoelectric materials.

    PubMed

    Gao, Hongli; Zhu, Tiejun; Zhao, Xinbing; Deng, Yuan

    2014-10-07

    Mg2Si1-xSnx alloys are a prospective material for thermoelectric generators at moderate temperatures. The thermoelectric properties of Mg2Si0.5Sn0.5-based thermoelectric materials with only Zn substitution or Zn/Sb co-doping were investigated. Isoelectronic Zn substitution did not affect the carrier concentration, but improved the carrier mobility. Zn atoms incorporated into a Sb-doped Mg2Si0.5Sn0.5 matrix simultaneously boosted the power factor and suppressed the lattice thermal conductivity, leading to an enhancement of the thermoelectric figure of merit ZT of the resulting bulk materials. The interplay between the electron and phonon transport of Mg2Si0.5Sn0.49Sb0.01 substituted with Zn at Mg sites results in an enhancement of the ZT by 25% at ∼730 K, from ZT≈ 0.8 in Mg2Si0.5Sn0.49Sb0.01 to ZT≈ 1.0 in Mg1.98Zn0.02Si0.5Sn0.49Sb0.01. Solid solutions in the Mg2Si-Mg2Sn system appear to be more promising for thermoelectric applications.

  7. Differential Depletion of Mg and Fe in Planetary Nebulae: Implications for the Composition of AGB-Star Dust

    NASA Astrophysics Data System (ADS)

    Dinerstein, Harriet L.; Prasla, F.; Speck, A. K.

    2012-01-01

    We have investigated the gas-phase abundances of Mg and Fe, both refractory elements that are potentially major constituents of silicates and other minerals, for 25 planetary nebulae. The Mg abundances are derived from Mg II 4481 A, a recombination line of Mg++; we obtain Fe/H from [Fe III] 4658 A, after correcting for ionization structure. We find strikingly different behavior for the two elements. Fe is deficient by factors of 20-200 relative to solar, presumably due to incorporation into dust that condensed while the star was on the Asymptotic Giant Branch (AGB). On the other hand, Mg/H is virtually solar, implying that Mg is at most minimally depleted. This result is surprising since some of the nebulae display mid-infrared emission features often attributed to forsterite, the pure-Mg form of crystalline olivine. If this identification is correct, there must be only a small mass of Mg-rich crystalline silicate dust, coexisting with a larger amount of Fe-rich amorphous silicates or another Fe-bearing material. Another possibility is that the observed features might actually arise from Fe-rich crystalline silicates such as fayalite, which provide a good fit to the spectra of some AGB stars (Pitman et al. 2010, MNRAS, 406, 460; Guha Nigoya et al. 2011, ApJ, 733, 93). Finally, our Mg abundances are based on an optical recombination line (ORL), and such lines from C, N, O, Ne tend to be anomalously strong in nebulae. Although empirically Mg does not correlate with the ORL abundance discrepancy (Barlow et al. 2003, ASPC, 209, 273; Wang & Liu 2007, MNRAS, 381, 669), solving the origin of the ORL effect would increase our confidence in our Mg/H values. This work was supported by NSF grants AST-0708245 to HLD and CAREER AST-0642991 to AKS, and Big XII Faculty Fellowships to both.

  8. Metastable electronic populations and relaxation of Fe(I), Fe(II), and Fe(III) in MgO observed by Mössbauer emission spectroscopy

    NASA Astrophysics Data System (ADS)

    Tuczek, F.; Spiering, H.; Gütlich, P.

    1990-06-01

    Magnetic-field Mössbauer emission spectra of 57Co in MgO single crystals covering a broad velocity range and measured up to high signal-to-noise ratios are presented. In accordance with a previous study, three charge states of 57Fe are found after 57Co(EC)57Fe (EC stands for electron capture). The evaluation of the Fe(III) fraction indicates nonthermalized populations of the 6A1 ground-state Zeeman levels. The field, temperature, and angular dependences of these populations are evaluated and display qualitative differences to the findings in 57Co/LiNbO3. The implications of the cubic symmetry on the spin-selective ground-state population are considered. In addition, a completely analogous phenomenon is evidenced for the first time within an Fe(II) electronic manifold, namely, the Γ5g ground state of Fe(II) in MgO, after the nuclear decay. In contrast to the Fe(III) case, these populations are not static within the Mössbauer time window. It turns out that the attainment of thermal equilibrium can be conveniently observed by changing the field value, evidencing a direct relaxation process at 4.2 K within Γ5g. The relaxation rates are compatible with static strain data; an initial alignment is observed. Finally, there is strong evidence that the Fe(I) fraction is also populated out of thermal equilibrium. In addition to these ground-state spectra, two features are present that may be attributed to metastable excited states of Fe(II) and Fe(III). It is described in detail how these various contributions can be disentangled.

  9. Disproportionation of (Mg,Fe)SiO 3 perovskite in Earth's deep lower mantle

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

    Zhang, L.; Meng, Y.; Yang, W.

    2014-05-22

    The mineralogical constitution of the Earth's mantle dictates the geophysical and geochemical properties of this region. Previous models of a perovskite-dominant lower mantle have been built on the assumption that the entire lower mantle down to the top of the D" layer contains ferromagnesian silicate [(Mg,Fe)SiO 3] with nominally 10 mole percent Fe. On the basis of experiments in laser-heated diamond anvil cells, at pressures of 95 to 101 gigapascals and temperatures of 2200 to 2400 kelvin, we found that such perovskite is unstable; it loses its Fe and disproportionates to a nearly Fe-free MgSiO 3 perovskite phase and anmore » Fe-rich phase with a hexagonal structure. This observation has implications for enigmatic seismic features beyond ~2000 kilometers depth and suggests that the lower mantle may contain previously unidentified major phases.« less

  10. Disproportionation of (Mg,Fe)SiO3 perovskite in Earth's deep lower mantle

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

    Zhang, L.; Meng, Y.; Yang, W.

    2014-05-22

    The mineralogical constitution of the Earth’s mantle dictates the geophysical and geochemical properties of this region. Previous models of a perovskite-dominant lower mantle have been built on the assumption that the entire lower mantle down to the top of the D'' layer contains ferromagnesian silicate [(Mg,Fe)SiO3] with nominally 10 mole percent Fe. On the basis of experiments in laser-heated diamond anvil cells, at pressures of 95 to 101 gigapascals and temperatures of 2200 to 2400 kelvin, we found that such perovskite is unstable; it loses its Fe and disproportionates to a nearly Fe-free MgSiO3 perovskite phase and an Fe-rich phasemore » with a hexagonal structure. This observation has implications for enigmatic seismic features beyond ~2000 kilometers depth and suggests that the lower mantle may contain previously unidentified major phases.« less

  11. The Raman spectrum of Ca-Mg-Fe carbonates; Applications in geobiology

    NASA Astrophysics Data System (ADS)

    van Zuilen, M. A.; Rividi, N.; Ménez, B.; Philippot, P.

    2012-04-01

    Carbonates form a very important mineral group in geobiological studies. They are a common mineral matrix for putative carbonaceous microfossils in Archean greenstone belts, form an important chemical deposit in seafloor hydrothermal systems, and are a common product in biomineralization processes. In many geobiological studies there is a specific need for simple characterization of carbonate composition while avoiding complex sample preparation or sample destruction. Raman spectroscopy is a highly versatile non-destructive technique enabling in-situ characterization of minerals and carbonaceous materials. It can be combined with confocal microscopy enabling high-resolution Raman mapping of entire rock thin sections, or can be integrated in submersibles and potentially Mars-rovers for direct field-based mineral identification. It is thus important that well-established spectral databases exist which enable unambiguous identification of a wide variety of carbonate minerals. The most common carbonates in the Ca-Mg-Fe system include the CaCO3 polymorphs calcite, aragonite, and vaterite, as well as the solid solutions CaMg(CO3)2-CaFe(CO3)2 (dolomite-ankerite) and MgCO3-FeCO3 (magnesite-siderite). Although various carbonate end-members have been studied exhaustively by Raman spectroscopy, a simple protocol for rapid distinction of various carbonate solid solutions is still lacking. Here we present a detailed study of Raman shifts in various carbonate standards of known composition in the Ca-Mg-Fe system. Carbonates with rhombohedral symmetry display a Raman spectrum with six characteristic vibrational modes - four of these represent vibrations within the (CO3)2- unit and two represent external vibrations of the crystal lattice. We show that Raman band shifts of internal mode 2ν2 (range 1725-1765 cm-1), and external modes T (range 170-215 cm-1) and L (range 285-330 cm-1) for siderite-magnesite and ankerite-dolomite solid solutions display distinct and well defined

  12. Spin injection into silicon in three-terminal vertical and four-terminal lateral devices with Fe/Mg/MgO/Si tunnel junctions having an ultrathin Mg insertion layer

    NASA Astrophysics Data System (ADS)

    Sato, Shoichi; Nakane, Ryosho; Hada, Takato; Tanaka, Masaaki

    2017-12-01

    We demonstrate that the spin injection/extraction efficiency is enhanced by an ultrathin Mg insertion layer (⩽2 nm) in Fe /Mg /MgO /n+-Si tunnel junctions. In diode-type vertical three-terminal devices fabricated on a Si substrate, we observe the narrower three-terminal Hanle (N-3TH) signals indicating true spin injection into Si and estimate the spin polarization in Si to be 16% when the thickness of the Mg insertion layer is 1 nm, whereas no N-3TH signal is observed without the Mg insertion. This means that the spin injection/extraction efficiency is enhanced by suppressing the formation of a magnetically dead layer at the Fe/MgO interface. We also observe clear spin transport signals, such as nonlocal Hanle signals and spin-valve signals, in a lateral four-terminal device with the same Fe /Mg /MgO /n+-Si tunnel junctions fabricated on a Si-on-insulator substrate. It is found that both the intensity and linewidth of the spin signals are affected by the geometrical effects (device geometry and size). We have derived analytical functions taking into account the device structures, including channel thickness and electrode size, and estimated important parameters: spin lifetime and spin polarization. Our analytical functions explain the experimental results very well. Our study shows the importance of suppressing a magnetically dead layer and provides a unified understanding of spin injection/detection signals in different device geometries.

  13. Determination of some heavy metals (Fe, Cu, Zn and Pb) in blood by total reflection X-ray fluorescence

    NASA Astrophysics Data System (ADS)

    Bounakhla, M.; Doukkali, A.; Lalaoui, K.; Aguenaou, H.; Mokhtar, N.; Attrassi, B.

    2003-05-01

    The main purpose of this study is the interaction between nutrition (micronutrients heavy metals: Fe, Zn, Cu) and toxic heavy metals such as Pb in blood of children living in Gharb region of Morocco. This region receives all pollution carried by the Sebou river coming mainly from industrial activities. A rapid and simple analytical procedure was used for the determination of Fe, Cu and Zn trace amounts in blood by total-reflection X-ray fluorescence technique. This method is an energy dispersive XRF technique in a special geometry of primary beam, sample and detector. The sample is deposited on a plane polished surface of a suitable reflector material. It is presented as a few drops (25 μl) from a solution of blood digested in a mixture of HNO3 and H2O2 using a microwaves accelerated reaction system. The accuracy of measurements has been investigated by using certified materials. The concentration of Cu was found to be normal in all samples (\\cong1 ppm) which ruled out any interaction between this element and the others. On the other hand, amounts of Fe and Zn are very variables, suggesting an interaction between Fe and Zn. However, amounts of Pb in blood are inferior to 50 ppb, suggesting that no interaction exist with this metal and micronutrients.

  14. Investigation of iron spin crossover pressure in Fe-bearing MgO using hybrid functional

    NASA Astrophysics Data System (ADS)

    Cheng, Ya; Wang, Xianlong; Zhang, Jie; Yang, Kaishuai; Zhang, Chuanguo; Zeng, Zhi; Lin, Haiqin

    2018-04-01

    Pressure-induced spin crossover behaviors of Fe-bearing MgO were widely investigated by using an LDA  +  U functional for describing the strongly correlated Fe–O bonding. Moreover, the simulated spin crossover pressures depend on the applied U values, which are sensitive to environments and parameters. In this work, the spin crossover pressures of (Mg1‑x ,Fe x )O are investigated by using the hybrid functional with a uniform parameter. Our results indicate that the spin crossover pressures increase with increasing iron concentration. For example, the spin crossover pressure of (Mg0.03125,Fe0.96875)O and FeO was 56 GPa and 127 GPa, respectively. The calculated crossover pressures agreed well with the experimental observations. Therefore, the hybrid functional should be an effective method for describing the pressure-induced spin crossover behaviors in transition metal oxides.

  15. Enhanced magnetic fluid hyperthermia by micellar magnetic nanoclusters composed of Mn(x)Zn(1-x)Fe(2)O(4) nanoparticles for induced tumor cell apoptosis.

    PubMed

    Qu, Yang; Li, Jianbo; Ren, Jie; Leng, Junzhao; Lin, Chao; Shi, Donglu

    2014-10-08

    Monodispersed MnxZn1-xFe2O4 magnetic nanoparticles of 8 nm are synthesized and encapsulated in amphiphilic block copolymer for development of the hydrophilic magnetic nanoclusters (MNCs). These MNCs exhibit superparamagnetic characteristics, high specific absorption rate (SAR), large saturation magnetization (Ms), excellent stability, and good biocompatibility. MnFe2O4 and Mn0.6Zn0.4Fe2O4 are selected as optimum compositions for the MNCs (MnFe2O4/MNC and Mn0.6Zn0.4Fe2O4/MNC) and employed for magnetic fluid hyperthermia (MFH) in vitro. To ensure biosafety of MFH, the parameters of alternating magnetic field (AMF) and exposure time are optimized with low frequency, f, and strength of applied magnetic field, Happlied. Under optimized conditions, MFH of MnFe2O4/MNC and Mn0.6Zn0.4Fe2O4/MNC result in cancer cell death rate up to 90% within 15 min. The pathway of cancer cell death is identified as apoptosis, which occurs in mild hyperthermia near 43 °C. Both MnFe2O4/MNC and Mn0.6Zn0.4Fe2O4/MNC show similar efficiencies on drug-sensitive and drug-resistant cancer cells. On the basis of these findings, those MnxZn1-xFe2O4 nanoclusters can serve as a promising candidate for effective targeting, diagnosis, and therapy of cancers. The multimodal cancer treatment is also possible as amphiphilic block copolymer can encapsulate, in a similar fashion, different nanoparticles, hydrophobic drugs, and other functional molecules.

  16. Renierite, Cu10ZnGe2Fe4S16-Cu11GeAsFe4S16: a coupled solid solution series.

    USGS Publications Warehouse

    Bernstein, L.R.

    1986-01-01

    The composition of renierite is found to be Cu10(Zn1-xCux)Ge2-xAsxFe4S16 (0 = or < x = or < 1), with continuous solid solution between the zincian and arsenian end-members, Cu10ZnGe2Fe4S16 and Cu11GeAsFe4S16, through the coupled substitution Zn(II) + Ge(IV) = Cu(I) + As(V). This is the first reported example of extensive coupled solid solution in a sulphide mineral. Arsenian renierite, not previously characterized, is similar to zincian renierite in polished section, with a slightly redder colour and lower anisotropy. It is reddish orange with relief very similar to that of bornite, though it is harder (VHN25 = 286) and does not tarnish in air. It is slightly bireflective, with colours varying from orange-yellow to reddish orange in nearly crossed polarizers. The strongest powder XRD lines are: 3.042(100), 1.861(29), 1.869(16), 1.594(11) and 1.017(10) A; D(calc.) 4.50 g/cm3. Specimens have been found at the Ruby Creek copper deposit, Alaska, where zincian renierite also occurs, and at the Inexco no. 1 mine, Jamestown, Colorado.-J.A.Z.

  17. Preparation of a nanosized as(2)o(3)/mn(0.5)zn(0.5)fe(2)o(4) complex and its anti-tumor effect on hepatocellular carcinoma cells.

    PubMed

    Zhang, Jia; Zhang, Dongsheng

    2009-01-01

    Manganese-zinc-ferrite nanoparticles (Mn(0.5)Zn(0.5)Fe(2)O(4), MZF-NPs) prepared by an improved co-precipitation method and were characterized by transmission electron microscopy (TEM), X-ray diffraction (XRD) and energy dispersive spectrometry (EDS). Then thermodynamic testing of various doses of MZF-NPs was performed in vitro. The cytotoxicity of the Mn(0.5)Zn(0.5)Fe(2)O(4) nanoparticles in vitro was tested by the MTT assay. A nanosized As(2)O(3)/Mn(0.5)Zn(0.5)Fe(2)O(4) complex was made by an impregnation process. The complex's shape, component, envelop rate and release rate of As(2)O(3) were measured by SEM, EDS and atom fluorescence spectrometry, respectively. The therapeutic effect of nanosized As(2)O(3)/Mn(0.5)Zn(0.5)Fe(2)O(4) complex combined with magnetic fluid hyperthermia (MFH) on human hepatocelluar cells were evaluated in vitro by an MTT assay and flow cytometry. The results indicated that Mn(0.5)Zn(0.5)Fe(2)O(4) and nanosized As(2)O(3)/Mn(0.5)Zn(0.5)Fe(2)O(4) complex were both prepared successfully. The Mn(0.5)Zn(0.5)Fe(2)O(4) nanoparticles had powerful absorption capabilities in a high-frequency alternating electromagnetic field, and had strong magnetic responsiveness. Moreover, Mn(0.5)Zn(0.5)Fe(2)O(4) didn't show cytotoxicity in vitro. The therapeutic result reveals that the nanosized As(2)O(3)/Mn(0.5)Zn(0.5)Fe(2)O(4) complex can significantly inhibit the growth of hepatoma carcinoma cells.

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

    PubMed

    Kusleika, Saulius

    2002-01-01

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

  19. Crystallization of MgFe2O4 from a glass in the system K2O/B2O3/MgO/P2O5/Fe2O3

    NASA Astrophysics Data System (ADS)

    El Shabrawy, Samha; Bocker, Christian; Rüssel, Christian

    2016-10-01

    Spherical magnetic Mg-Fe-O nanoparticles were successfully prepared by the crystallization of glass in the system K2O/B2O3/MgO/P2O5/Fe2O3. The magnetic glass ceramics were prepared by melting the raw materials using the conventional melt quenching technique followed by a thermal treatment at temperatures in the range 560-700 °C for a time ranging from 2 to 8 h. The studies of the X-ray diffraction, electron microscopy and FTIR spectra confirmed the precipitation of finely dispersed spherical (Mg, Fe) based spinel nanoparticles with a minor quantity of hematite (α-Fe2O3) in the glass matrix. The average size of the magnetic nano crystals increases slightly with temperature and time from 9 to 15 nm as determined by the line broadening from the XRD patterns. XRD studies show that annealing the glass samples for long periods of time at temperature ≥604 °C results in an increase of the precipitated hematite concentration, dissolution of the spinel phase and the formation of magnesium di-borate phase (Mg2B2O5). For electron microscopy, the particles were extracted by two methods; (i) replica extraction technique and (ii) dissolution of the glass matrix by diluted acetic acid. An agglomeration of the nano crystals to larger particles (25-35 nm) was observed.

  20. Comparison of serum Concentration of Se, Pb, Mg, Cu, Zn, between MS patients and healthy controls

    PubMed Central

    Alizadeh, Anahita; Mehrpour, Omid; Nikkhah, Karim; Bayat, Golnaz; Espandani, Mahsa; Golzari, Alireza; Jarahi, Lida; Foroughipour, Mohsen

    2016-01-01

    Introduction Multiple Sclerosis (MS) is defined as one of the inflammatory autoimmune disorders and is common. Its exact etiology is unclear. There are some evidences on the role of environmental factors in susceptible genetics. The aim of this study is to evaluate the possible role of Selenium, Zinc, Copper, Lead and Magnesium metals in Multiple Sclerosis patients. Methods In the present analytical cross-sectional study, 56 individuals including 26 patients and 30 healthy controls were enrolled in the evaluation. The serum level of Se, Zn, Cu, Pb were quantified in graphite furnace conditions and flame conditions by utilizing an atomic absorption Perkin Elmer spectrophotometer 3030. The serum levels of Mg were measured by auto analyzer 1500 BT. The mean level of minerals (Zn, Pb, Cu, Mg, Se) in serum samples were compared in both cases and controls. The mean level of minerals (Zn, Pb, Cu, Mg, Se) in serum samples were compared in both cases and controls by using independent-samples t-test for normal distribution and Mann-Whitney U test as a non-parametric test. All statistical analyses were carried out using SPSS 11.0. Results As well as the Zn, Cu, and Se, there was no significant difference between MS patients and healthy individuals in Pb concentrations (p-value = 0.11, 0.14, 0.32, 0.20 respectively) but the level of Mg was significantly different (p= 0.001). Conclusion All serum concentrations of Zn, Pb, Se, Cu in both groups were in normal ranges and there was no difference in MS patients compared with the healthy group who were matched in genetics. Blood level of Mg was significantly lower in MS patients. But it should be noted that even with the low level of serum magnesium in MS patients, this value is still in the normal range. PMID:27757186

  1. Mechanism of γ-irradiation induced phase transformations in nanocrystalline Mn{sub 0.5}Zn{sub 0.5}Fe{sub 2}O{sub 4} ceramics

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

    Jagadeesha Angadi, V.; Anupama, A.V.; Choudhary, Harish K.

    The structural, infrared absorption and magnetic property transformations in nanocrystalline Mn{sub 0.5}Zn{sub 0.5}Fe{sub 2}O{sub 4} samples irradiated with different doses (0, 15, 25 and 50 kGy) of γ-irradiation were investigated in this work and a mechanism of phase transformation/decomposition is provided based on the metastable nature of the Mn-atoms in the spinel lattice. The nano-powder sample was prepared by solution combustion route and the pellets of the sample were exposed to γ-radiation. Up to a dose of 25 kGy of γ-radiation, the sample retained the single phase cubic spinel (Fd-3m) structure, but the disorder in the sample increased. On irradiatingmore » the sample with 50 kGy γ-radiation, the spinel phase decomposed into new stable phases such as α-Fe{sub 2}O{sub 3} and ZnFe{sub 2}O{sub 4} phases along with amorphous MnO phase, leading to a change in the surface morphology of the sample. Along with the structural transformations the magnetic properties deteriorated due to breakage of the ferrimagnetic order with higher doses of γ-irradiation. Our results are important for the understanding of the stability, durability and performance of the Mn-Zn ferrite based devices used in space applications. - Graphical abstract: The nanocrystalline Mn{sub 0.5}Zn{sub 0.5}Fe{sub 2}O{sub 4} ceramic sample transforms to crystalline α-Fe{sub 2}O{sub 3} and ZnFe{sub 2}O{sub 4} phases (and amorphous MnO phase) at a γ-irradiation dose of 50 kGy, as MnO goes out of the spinel lattice. The high energy γ-irradiation causes structural damage to the nanomaterials leading to change in morphology of the sample as seen in the SEM images. - Highlights: • Mn atoms are more unstable in the Mn-Zn ferrite spinel lattice than Zn-atoms. • Displacement of Mn atoms by γ-radiation from the lattice renders phase transformation. • In Mn{sub 0.5}Zn{sub 0.5}Fe{sub 2}O{sub 4}, Mn-ferrite cell transforms to crystalline α-Fe{sub 2}O{sub 3} and amorphous MnO. • The stable ZnFe

  2. [Structure and luminescence properties of MgGa2O4 : Cr3+ with Zn substituted for Mg].

    PubMed

    Zhang, Wan-Xin; Wang, Yin-Hai; Li, Hai-Ling; Wang, Xian-Sheng; Zhao, Hui

    2013-01-01

    A series of red long afterglow phosphors with composition Zn(x) Mg(1-2) Ga2 O4 : Cr3+ (x = 0, 0.2, 0.6, 0.8, 1.0) were synthesized by a high temperature solid-state reaction method. The X-ray diffraction studies show that the phase of the phosphors is face-centered cubic structure. Photoluminescence spectra show that the red emission of Cr3+ originated from the transition of 2E-4A2. Due to the large overlap between absorption band of Cr3+ and emission band of the host. Cr3+ could obtain the excitation energy from the host via the effective energy transfer. The afterglow decay characteristics show that the phosphor samples with different Zn contents have different afterglow time and the afterglow time also changes with the value of x. The measurement of thermoluminescence reveals that the trap depth of the phosphor samples with different Zn contents is different. The samples with deeper traps have longer afterglow time.

  3. Structure and properties of hopeites (Mg xZn 1- x) 3(PO 4) 2 · 4H 2O

    NASA Astrophysics Data System (ADS)

    Haussühl, S.; Middendorf, B.; Dörffel, M.

    1991-07-01

    Mg-hopeites (Mg xZn 1- x) 3(PO 4) 2 · 4H 2O were prepared by crystallization from hot aqueous solutions (70°C). The structure of (Mg 0.206Zn 0.794) 3(PO 4) 2 · 4H 2O has been determined from 1612 unique reflections (MoKα, R = 0.033): Pnma, a1 = 10.594(2), a2 = 18.333(2), a3 = 5.029(2)Å, Z = 4, Dcalc = 2.943g cm -3. The structure resembles that of pure hopeite. However, the magnesium atoms occupy only the sixcoordinated site. The thermal behavior of hopeites is strongly influenced by the substitution of Zn by Mg. The dehydration range is shifted to higher temperatures with increasing Mg content. A strongly anisotropic thermal expansion was measured by X-ray diffraction in a temperature range of -40° to 50°C. Experiments to substitute Zn by Ca, Sr, and Ba in the hopeite failed. A hitherto unknown monoclinic phase with the composition BaZn 2(PO 4) 2 · H 2O and a1 = 4.707(2), a2 = 7.840(2), a3 = 8.061(3)Å, and α 2 = 88.99(4)° was found.

  4. Capturing Guest Dynamics in Metal-Organic Framework CPO-27-M (M = Mg, Zn) by (2)H Solid-State NMR Spectroscopy.

    PubMed

    Xu, Jun; Sinelnikov, Regina; Huang, Yining

    2016-06-07

    Metal-organic frameworks (MOFs) are promising porous materials for gas separation and storage as well as sensing. In particular, a series of isostructural MOFs with coordinately unsaturated metal centers, namely, CPO-27-M or M-MOF-74 (M = Mg, Zn, Mn, Fe, Ni, Co, Cu), have shown exceptional adsorption capacity and selectivity compared to those of classical MOFs that contain only fully coordinated metal sites. Although it is widely accepted that the interaction between guest molecules and exposed metal centers is responsible for good selectivity and large maximum uptake, the investigation of such guest-metal interaction is very challenging because adsorbed molecules are usually disordered in the pores and undergo rapid thermal motions. (2)H solid-state NMR (SSNMR) spectroscopy is one of the most extensively used techniques for capturing guest dynamics in porous materials. In this work, variable-temperature (2)H wide-line SSNMR experiments were performed on CPO-27-M (M = Mg, Zn) loaded with four prototypical guest molecules: D2O, CD3CN, acetone-d6, and C6D6. The results indicate that different guest molecules possess distinct dynamic behaviors inside the channel of CPO-27-M. For a given guest molecule, its dynamic behavior also depends on the nature of the metal centers. The binding strength of guest molecules is discussed on the basis of the (2)H SSNMR data.

  5. Effect of interfacial structures on spin dependent tunneling in epitaxial L1 0-FePt/MgO/FePt perpendicular magnetic tunnel junctions

    DOE PAGES

    Yang, G.; Li, D. L.; Wang, S. G.; ...

    2015-02-24

    In this study, epitaxial FePt(001)/MgO/FePt magnetic tunnel junctions with L1 0-FePt electrodes showing perpendicular magnetic anisotropy were fabricated by molecular beam epitaxial growth. Tunnel magnetoresistance ratios of 21% and 53% were obtained at 300 K and 10 K, respectively. Our previous work, based on transmission electron microscopy, confirmed a semi-coherent interfacial structure with atomic steps (Kohn et al., APL 102, 062403 (2013)). Here, we show by x-ray photoemission spectroscopy and first-principles calculation that the bottom FePt/MgO interface is either Pt-terminated for regular growth or when an Fe layer is inserted at the interface, it is chemically bonded to O. Finally,more » both these structures have a dominant role in spin dependent tunneling across the MgO barrier resulting in a decrease of the tunneling magnetoresistance ratio compared with previous predictions.« less

  6. (Cd,Zn,Mg)Te-based microcavity on MgTe sacrificial buffer: Growth, lift-off, and transmission studies of polaritons

    NASA Astrophysics Data System (ADS)

    Seredyński, B.; Król, M.; Starzyk, P.; Mirek, R.; Ściesiek, M.; Sobczak, K.; Borysiuk, J.; Stephan, D.; Rousset, J.-G.; Szczytko, J.; Pietka, B.; Pacuski, W.

    2018-04-01

    Opaque substrates precluded, so far, transmission studies of II-VI semiconductor microcavities. This work presents the design and molecular beam epitaxy growth of semimagnetic (Cd,Zn,Mn)Te quantum wells embedded into a (Cd,Zn,Mg)Te-based microcavity, which can be easily separated from the GaAs substrate. Our lift-off process relies on the use of a MgTe sacrificial layer which stratifies in contact with water. This allowed us to achieve a II-VI microcavity prepared for transmission measurements. We evidence the strong light-matter coupling regime using photoluminescence, reflectivity, and transmission measurements at the same spot on the sample. By comparing a series of reflectance spectra before and after lift-off, we prove that the microcavity quality remains high. Thanks to Mn content in quantum wells we show the giant Zeeman splitting of semimagnetic exciton-polaritons in our transmitting structure.

  7. Mixed Metal Oxides of the Type CoxZn1-xFe2O4 as Photocatalysts for Malachite Green Degradation Under UV Light Irradiation.

    PubMed

    Tzvetkov, Martin; Milanova, Maria; Cherkezova-Zheleva, Zara; Spassova, Ivanka; Valcheva, Evgenia; Zaharieva, Joana; Ivan, Mitov

    2017-06-01

    A combination of thermal and mechanical (high energy ball milling) treatment was applied in an attempt to obtain polycrystalline mixed metal binary and ternary oxides of the type CoxZn1-xFe2O4 (x = 0; 0.25; 0.5; 0.75; 1). The synthetic procedure used successfully produced single-phased, homogeneous ZnFe2O4, CoFe2O4, and Co0.75Zn0.25Fe2O4, as well as mixed oxides, whose composition depended both on the duration of the high energy ball milling and the ratio Zn(II)/Co(II). The formation of spinel-like structures was proved by XRD, Mössbauer spectroscopy and Raman spectroscopy. For the characterization of the samples low-temperature N2 adsorption, UV/Vis spectroscopy and transmission electron microscopy were applied. The energy band gap of the samples was calculated, suggesting they are promising photocatalysts. The decomposition of the Malachite Green in model water solutions under UV-light irradiation was successfully achieved in the presence of the samples as photocatalysts. The highest rate constant was obtained for the sample synthesized at longer milling time in combination with higher Zn(II)/Co(II) ratio. The photocatalytic activity of the ternary mixed oxides was compared with the pure hematite, α-Fe2O3, and the binary ZnFe2O4 and CoFe2O4 ferrites with spinel structure that were treated in the same way. A synergetic effect of α-Fe2O3 and the spinel-like structure on the photocatalytic properties of ternary mixed metal oxides was detected.

  8. Optical, electrical and ferromagnetic studies of ZnO:Fe diluted magnetic semiconductor nanoparticles for spintronic applications.

    PubMed

    Elilarassi, R; Chandrasekaran, G

    2017-11-05

    In the present investigation, diluted magnetic semiconductor (Zn 1-x Fe x O) nanoparticles with different doping concentrations (x=0, 0.02, 0.04, 0.06, and 0.08) were successfully synthesized by sol-gel auto-combustion method. The crystal structure, morphology, optical, electrical and magnetic properties of the prepared samples were characterized by X-ray diffraction (XRD), scanning electron microscope (SEM), energy dispersive analysis using x-rays (EDAX), ultraviolet-visible spectrophotometer, fluorescence spectroscope (FS), vibrating sample magnetometer (VSM) and broad band dielectric spectrometer (BDS). XRD results reveal that all the samples possess hexagonal wurtzite crystal structure with good crystalline quality. The absence of impurity phases divulge that Fe ions are well incorporated into the ZnO crystal lattice. The substitutional incorporation of Fe 3+ at Zn sites is reflected in optical absorption spectra of the samples. Flouorescence spectra of the samples show a strong near-band edge related UV emission as well as defect related visible emissions. The semiconducting behavior of the samples has been confirmed through electrical conductivity measurements. Magnetic measurements indicated that all the samples possess ferromagnetism at room temperature. Copyright © 2017 Elsevier B.V. All rights reserved.

  9. Impact of interface manipulation of oxide on electrical transport properties and low-frequency noise in MgO/NiFe/MgO heterojunctions

    NASA Astrophysics Data System (ADS)

    Li, Jian-wei; Zhao, Chong-jun; Feng, Chun; Zhou, Zhongfu; Yu, Guang-hua

    2015-08-01

    Low-frequency noise and magnetoresistance in sputtered-deposited Ta(5 nm)/MgO (3 nm)/NiFe(10 nm)/MgO(3 nm)/Ta(3 nm) films have been measured as a function of different annealing times at 400°C. These measurements did not change synchronously with annealing time. A significant increase in magnetoresistance is observed for short annealing times (of the order of minutes) and is correlated with a relatively small reduction in 1/f noise. In contrast, a significant reduction in 1/f noise is observed for long annealing times (of the order of hours) accompanied by a small change in magnetoresistance. After annealing for 2 hours, the 1/f noise decreases by three orders of magnitude. Transmission electron microscopy and slow positron annihilation results implicate the cause being micro-structural changes in the MgO layers and interfaces following different annealing times. The internal vacancies in the MgO layers gather into vacancy clusters to reduce the defect density after short annealing times, whereas the MgO/NiFe and the NiFe/MgO interfaces improve significantly after long annealing times with the amorphous MgO layers gradually crystallizing following the release of interfacial stress.

  10. Impact of interface manipulation of oxide on electrical transport properties and low-frequency noise in MgO/NiFe/MgO heterojunctions

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

    Li, Jian-wei; School of Materials Science and Engineering, University of Science and Technology Beijing, Beijing 100083; Zhao, Chong-jun

    2015-08-15

    Low-frequency noise and magnetoresistance in sputtered-deposited Ta(5 nm)/MgO (3 nm)/NiFe(10 nm)/MgO(3 nm)/Ta(3 nm) films have been measured as a function of different annealing times at 400°C. These measurements did not change synchronously with annealing time. A significant increase in magnetoresistance is observed for short annealing times (of the order of minutes) and is correlated with a relatively small reduction in 1/f noise. In contrast, a significant reduction in 1/f noise is observed for long annealing times (of the order of hours) accompanied by a small change in magnetoresistance. After annealing for 2 hours, the 1/f noise decreases by three ordersmore » of magnitude. Transmission electron microscopy and slow positron annihilation results implicate the cause being micro-structural changes in the MgO layers and interfaces following different annealing times. The internal vacancies in the MgO layers gather into vacancy clusters to reduce the defect density after short annealing times, whereas the MgO/NiFe and the NiFe/MgO interfaces improve significantly after long annealing times with the amorphous MgO layers gradually crystallizing following the release of interfacial stress.« less

  11. Microstructure Evolution in Mg-Zn-Zr-Gd Biodegradable Alloy: The Decisive Bridge Between Extrusion Temperature and Performance

    PubMed Central

    Yao, Huai; Wen, Jiu-Ba; Xiong, Yi; Lu, Yan; Huttula, Marko

    2018-01-01

    Being a biocompatible metal with similar mechanical properties as bones, magnesium bears both biodegradability suitable for bone substitution and chemical reactivity detrimental in bio-ambiences. To benefit its biomaterial applications, we developed Mg-2.0Zn-0.5Zr-3.0Gd (wt%) alloy through hot extrusion and tailored its biodegradability by just varying the extrusion temperatures during alloy preparations. The as-cast alloy is composed of the α-Mg matrix, a network of the fish-bone shaped and ellipsoidal (Mg, Zn)3Gd phase, and a lamellar long period stacking ordered phase. Surface content of dynamically recrystallized (DRXed) and large deformed grains increases within 330–350°C of the extrusion temperature, and decreases within 350–370°C. Sample second phase contains the (Mg, Zn)3Gd nano-rods parallel to the extrusion direction, and Mg2Zn11 nanoprecipitation when temperature tuned above 350°C. Refining microstructures leads to different anticorrosive ability of the alloys as given by immersion and electrochemical corrosion tests in the simulated body fluids. The sample extruded at 350°C owns the best anticorrosive ability thanks to structural impacts where large DRXed portions and uniform nanosized grains reduce chemical potentials among composites, and passivate the extruded surfaces. Besides materials applications, the in vitro mechanism revealed here is hoped to inspire similar researches in biometal developments. PMID:29616216

  12. Microstructure evolution in Mg-Zn-Zr-Gd biodegradable alloy: the decisive bridge between extrusion temperature and performance

    NASA Astrophysics Data System (ADS)

    Yao, Huai; Wen, Jiu-Ba; Xiong, Yi; Lu, Yan; Huttula, Marko

    2018-03-01

    Being a biocompatible metal with similar mechanical properties as bones, magnesium bears both biodegradability suitable for bone substitution and chemical reactivity detrimental in bio-ambiences. To benefit its biomaterial applications, we developed Mg-2.0Zn-0.5Zr-3.0Gd (wt%) alloy through hot extrusion and tailored its biodegradability by just varying the extrusion temperatures during alloy preparations. The as-cast alloy is composed of the α-Mg matrix, a network of the fish-bone shaped and ellipsoidal (Mg, Zn)3Gd phase, and a lamellar long period stacking ordered phase. Surface content of dynamically recrystallized (DRXed) and large deformed grains increases within 330-350 C of the extrusion temperature, and decreases within 350-370 C. Sample second phase contains the (Mg, Zn)3Gd nano-rods parallel to the extrusion direction, and Mg2Zn11 nanoprecipitation when temperature tuned above 350 C. Refining microstructures leads to different anticorrosive ability of the alloys as given by immersion and electrochemical corrosion tests in the simulated body fluids. The sample extruded at 350 C owns the best anticorrosive ability thanks to structural impacts where large DRXed portions and uniform nanosized grains reduce chemical potentials among composites, and passivate the extruded surfaces. Besides materials applications, the in vitro mechanism revealed here is hoped to inspire similar researches in biometal developments.

  13. High-Pressure Study of Perovskites and Postperovskites in the (Mg,Fe)GeO 3 System

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

    Stan, Camelia V.; Dutta, Rajkrishna; Cava, Robert J.

    2017-06-22

    The effect of incorporation of Fe 2+ on the perovskite (Pbnm) and postperovskite (Cmcm) structures was investigated in the (Mg,Fe)GeO 3 system at high pressures and temperatures using laser-heated diamond anvil cell and synchrotron X-ray diffraction. Samples with compositions of Mg# ≥ 48 were shown to transform to the perovskite (~30 GPa and ~1500 K) and postperovskite (>55 GPa, ~1600–1800 K) structures. Compositions with Mg# ≥ 78 formed single-phase perovskite and postperovskite, whereas those with Mg# < 78 showed evidence for partial decomposition. The incorporation of Fe into the perovskite structure causes a decrease in octahedral distortion as well asmore » a modest decrease in bulk modulus (K 0) and a modest increase in zero-pressure volume (V 0). It also leads to a decrease in the perovskite-to-postperovskite phase transition pressure by ~9.5 GPa over compositions from Mg#78 to Mg#100.« less

  14. Magnesium effects on CdSe self-assembled quantum dot formation on Zn xCd yMg 1-x-ySe layers

    NASA Astrophysics Data System (ADS)

    Noemi Perez-Paz, M.; Lu, Hong; Shen, Aidong; Jean Mary, F.; Akins, Daniel; Tamargo, Maria C.

    2006-09-01

    Optical and morphological studies are used to investigate the effects of chemical composition and, in particular, the magnesium content of the Zn xCd yMg 1-x-ySe barrier layers on the size, density and uniformity of CdSe self-assembled quantum dots (QDs). A reduction of the uncapped QD size, as well as a blue shift of the capped QD photoluminescence peak position by increasing Mg concentration in the Zn xCd yMg 1-x-ySe barrier has been demonstrated by changing the Mg cell temperature during growth. In addition, a more uniform and more densely packed QD layer has been observed with an increase of the MgSe fraction in the Zn xCd yMg 1-x-ySe barrier layer using three-dimensional topographic atomic force microscopy images of the surface of uncapped QDs. Results point to Mg as a chemical factor that induces QD formation, either by increasing the density of atomic steps or/and by changing the energy of the Zn xCd yMg 1-x-ySe surface.

  15. Three-dimensional hole transport in nickel oxide by alloying with MgO or ZnO

    NASA Astrophysics Data System (ADS)

    Alidoust, Nima; Carter, Emily A.

    2015-11-01

    It has been shown previously that the movement of a hole in nickel oxide is confined to two dimensions, along a single ferromagnetic plane. Such confinement may hamper hole transport when NiO is used as a p-type transparent conductor in various solar energy conversion technologies. Here, we use the small polaron model, along with unrestricted Hartree-Fock and complete active space self-consistent field calculations to show that forming substitutional MxNi1-xO alloys with M = Mg or Zn reduces the barrier for movement of a hole away from the ferromagnetic plane to which it is confined. Such reduction occurs for hole transfer alongside one or two M ions that have been substituted for Ni ions. Furthermore, the Mg and Zn ions do not trap holes on O sites in their vicinity, and NiO's transparency is preserved upon forming the alloys. Thus, forming MxNi1-xO alloys with M = Mg or Zn may enhance NiO's potential as a p-type transparent conducting oxide, by disrupting the two-dimensional confinement of holes in pure NiO.

  16. Enhancement of Strength and Ductility of Mg96Zn2Y2 Rolled Sheet by Controlling Structure and Plastic Deformation

    NASA Astrophysics Data System (ADS)

    Noda, Masafumi; Kawamura, Yoshihito; Sakurai, Hiroshi; Funami, Kunio

    Mg-Zn-Y alloys are well known to possess greatly enhanced strength during plastic deformation because of the presence of kink bands in the LPSO phase and refinement of the grains of the alpha Mg phase. On the other hand, Mg-rare earth (RE) and Mg-Zn-RE alloys with a long period stacking order (LPSO) phase show a high tensile yield strength when subjected to an extrusion process but it is not known whether the LPSO and alpha Mg phases develop during plastic deformation. We examined the effect of the finely dispersed LPSO phase and the alpha Mg phase on the development of high strength in sheets of Mg96Zn2Y2 subjected to a few passes of rolling. The mechanical properties and thermal stability of the alloy were also investigated. The tensile yield strength of rolled sheets of Mg96Zn2Y2 was 360 MPa and its elongation was 5% when the material was subjected to thermomechanically controlled processing at 673 K with a four-pass rolling schedule. However, the tensile yield strength decreased and the elongation increased at annealing temperature of 623 K or above, because of the presence of grain growth in the alpha Mg phase and the restoration of kink bands in the LPSO phase.

  17. Paragenesis and chemistry of multistage tourmaline formation in the sullivan Pb-Zn-Ag deposit, British Columbia

    USGS Publications Warehouse

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

    1998-01-01

    Detailed petrographic study, scanning electron microscope imaging, and electron microprobe analyses of tourmalines from the Sullivan Pb-Zn-Ag massive sulfide deposit (British Columbia, Canada) document multiple paragenetic stages and large compositional variations. The tourmalines mainly belong to two common solid-solution series: dravite-schorl and dravite-uvite. Ca- and Fe-rich feruvite and alkali-deficient tourmalines are present locally. Products of tourmaline-forming stages include (from oldest to youngest): (1) rare Fe-rich dravite-schorl within black tourmalinite clasts in footwall fragmental rocks; (2) widespread Mg-rich, very fine grained, felted dravite in the footwall (the main type of tourmaline in the footwall tourmalinite pipe); (3) recrystallized, Fe-rich dravite-schorl (locally Ca-Fe feruvite) in the tourmalinite pipe, which preferentially occurs near postore gabbroic intrusions; (4) Mg-rich dravite or uvite associated with chlorite-pyrrhotite and chlorite-albite-pyrite-altered rocks in the shallow footwall and hanging wall; (5) discrete Mg-rich tourmaline grains associated with chlorite and discordant Mg-rich tourmaline rims which occur on disseminated Fe-rich schorl in the bedded Pb-Zn-Ag ores. The timing of rare Fe-rich schorl in the bedded ores is uncertain, but it most likely occurred during or between stages 2 and 3. The different paragenetic stages and their respective tourmaline compositions are interpreted in terms of a multistage evolution involving contributions from: (1) variable mixtures of synsedimentary, Fe-rich hydrothermal fluids and entrained seawater; (2) postore, Fe-rich, gabbro-related hydrothermal fluids; and (3) postore metamorphic reactions. Early synsedimentary, Fe-rich hydrothermal fluids which contained little or no entrained seawater formed Fe-rich black tourmalinite clasts locally in the footwall. The major type of tourmaline in the footwall tourmalinite pipe is Mg rich, recording seawater entrainment under high water

  18. Unique dielectric features of a ceramic-semiconductor nanocomposite MgNb2O6 + 0.25Zn0.5Cd0.5S

    NASA Astrophysics Data System (ADS)

    Pukazhselvan, D.; Selvaraj, Nivas Babu; Bdikin, Igor; Saravanan, R. Sakthi Sudar; Jakka, Suresh Kumar; Soares, M. J.; Fagg, Duncan Paul

    2017-12-01

    The present communication deals with the optical/dielectric characteristics of MgNb2O6 + 0.25Zn0.5Cd0.5S nanocomposite (10-30 nm) mixture. Zn0.5Cd0.5S (size ∼10 nm) was synthesized by microwave assisted solvo-thermal method. Monophase magnesium niobate (MN) nanoparticles (10-20 nm) were synthesized in a single step by mechanochemical treatment of MgO + Nb2O5 under dry N2 atmosphere. The nanocomposite, MgNb2O6 + 0.25Zn0.5Cd0.5S, was prepared by mechanical admixing of MgNb2O6 and Zn0.5Cd0.5S taken in 4:1 molar ratio. The photoluminescence study shows violet, yellow and orange-red emissions by the MgNb2O6 + 0.25Zn0.5Cd0.5S composite. The observed dielectric constant value (ε) for MgNb2O6 + 0.25Zn0.5Cd0.5S is only 4.7, which is ∼5 times smaller than the ε value of MgNb2O6 while a dielectric loss for the composite being closer to zero ensures promising commercial applications.

  19. Examining Two Sets of Introgression Lines in Rice (Oryza sativa L.) Reveals Favorable Alleles that Improve Grain Zn and Fe Concentrations

    PubMed Central

    Hu, Xia; Cheng, Li-Rui; Xu, Jian-Long; Shi, Yu-Min; Li, Zhi-Kang

    2015-01-01

    In the modern world, the grain mineral concentration (GMC) in rice (Oryza sativa L.) not only includes important micronutrient elements such as iron (Fe) and zinc (Zn), but it also includes toxic heavy metal elements, especially cadmium (Cd) and lead (Pb). To date, the genetic mechanisms underlying the regulation of GMC, especially the genetic background and G × E effects of GMC, remain largely unknown. In this study, we adopted two sets of backcross introgression lines (BILs) derived from IR75862 (a Zn-dense rice variety) as the donor parent and two elite indica varieties, Ce258 and Zhongguangxiang1, as recurrent parents to detect QTL affecting GMC traits including Fe, Zn, Cd and Pb concentrations in two environments. We detected a total of 22 loci responsible for GMC traits, which are distributed on all 12 rice chromosomes except 5, 9 and 10. Six genetic overlap (GO) regions affecting multiple elements were found, in which most donor alleles had synergistic effects on GMC. Some toxic heavy metal-independent loci (such as qFe1, qFe2 and qZn12) and some regions that have opposite genetic effects on micronutrient (Fe and Zn) and heavy metal element (Pb) concentrations (such as GO-IV) may be useful for marker-assisted biofortification breeding in rice. We discuss three important points affecting biofortification breeding efforts in rice, including correlations between different GMC traits, the genetic background effect and the G × E effect. PMID:26161553

  20. Rapid degradation of azo dye Direct Black BN by magnetic MgFe2O4-SiC under microwave radiation

    NASA Astrophysics Data System (ADS)

    Gao, Jia; Yang, Shaogui; Li, Na; Meng, Lingjun; Wang, Fei; He, Huan; Sun, Cheng

    2016-08-01

    A novel microwave (MW) catalyst, MgFe2O4 loaded on SiC (MgFe2O4-SiC), was successfully synthesized by sol-gel method, and pure MgFe2O4 was used as reference. The MgFe2O4 and MgFe2O4-SiC catalysts were characterized by X-ray diffraction (XRD), Scanning electron microscopy (SEM), Transmission electron microscopy (TEM), N2 adsorption analyzer (BET specific surface area), X-ray photoelectron spectroscopy (XPS). The electromagnetic parameters of the prepared catalysts were measured by vector network analyzer. The reflection loss (RL) based on the electromagnetic parameters calculated in Matlab showed MgFe2O4-SiC attained the maximum absorbing value of 13.32 dB at 2.57 GHz, which reached extremely high RL value at low frequency range, revealing the excellent MW absorption property of MgFe2O4-SiC. MW-induced degradation of Direct Black BN (DB BN) over as-synthesized MgFe2O4-SiC indicated that degradation efficiency of DB BN (20 mg L-1) in 5 min reached 96.5%, the corresponding TOC removal was 65%, and the toxicity of DB BN after degradation by MgFe2O4-SiC obviously decreased. The good stability and applicability of MgFe2O4-SiC on the degradation process were also discovered. Moreover, the ionic chromatogram during degradation of DB BN demonstrated that the C-S, C-N and azo bonds in the DB BN molecule were destroyed gradually. MW-induced rad OH and holes could be responsible for the efficient removal involved in the system. These findings make MgFe2O4-SiC become an excellent MW absorbent as well as an effective MW catalyst with rapid degradation of DB BN. Therefore, it may be promising for MgFe2O4-SiC under MW radiation to deal with various dyestuffs and other toxic organic pollutants.

  1. Study on the Microstructure, Mechanical Properties and Corrosion Behavior of Mg-Zn-Ca Alloy Wire for Biomaterial Application

    NASA Astrophysics Data System (ADS)

    Zheng, Maobo; Xu, Guangquan; Liu, Debao; Zhao, Yue; Ning, Baoqun; Chen, Minfang

    2018-03-01

    Due to their excellent biocompatibility and biodegradability, magnesium alloy wires have attracted much attention for biomaterial applications including orthopedic K-wires and sutures in wound closure. In this study, Mg-3Zn-0.2Ca alloy wires were prepared by cold drawing combined with proper intermediate annealing process. Microstructures, texture, mechanical properties and corrosion behavior of Mg-3Zn-0.2Ca alloy wire in a simulated body fluid were investigated. The results showed that the secondary phase and average grain size of the Mg-3Zn-0.2Ca alloy were refined in comparison with the as-extruded alloy and a strong (0002)<10-10>//DD basal fiber texture system was formed after multi-pass cold drawing. After the annealing, most of the basal planes were tilted to the drawing direction (DD) by about 35°, presenting the characteristics of random texture, and the texture intensity decreased. The as-annealed wire shows good mechanical properties with the ultimate tensile strength (UTS), yield strength (YS) and elongation of 253 ± 8.5 MPa, 212 ± 11.3 MPa and 9.2 ± 0.9%, respectively. Electrochemical and hydrogen evolution measurements showed that the corrosion resistance of the Mg-3Zn-0.2Ca alloy wire was improved after the annealing. The immersion test indicated that the Mg-3Zn-0.2Ca wire exhibited uniform corrosion behavior during the initial period of immersion, but then exhibited local corrosion behavior.

  2. Investigation on the formation process of single-crystalline GaO x barrier in Fe/GaO x /MgO/Fe magnetic tunnel junctions

    NASA Astrophysics Data System (ADS)

    Krishna, N. S.; Doko, N.; Matsuo, N.; Saito, H.; Yuasa, S.

    2017-11-01

    We have grown Fe(0 0 1)/GaO x (0 0 1)/MgO(0 0 1)/Fe(0 0 1) magnetic tunnel junctions (MTJs) with or without in situ annealing after the deposition of GaO x layer and performed structural characterizations by focusing on the formation process of the single-crystalline GaO x . It was found that, even without the in situ annealing, the as-grown GaO x grown on the MgO was mostly single-crystalline except near the surface region (amorphous). The crystallization temperature of the amorphous region was reduced from 500 °C down to 250 °C by depositing the Fe upper electrode (poly-crystalline). It was clarified that the crystallization of the amorphous region near the Fe/GaO x interface caused the realignments of the crystal grains in the poly-crystalline Fe upper electrode, and, as a result, the fully epitaxial Fe/GaO x /MgO/Fe structure is eventually formed. All the MTJs showed high tunneling magnetoresistance ratios (about 100%) at room temperature, which was almost independent of the formation temperature of the single-crystalline GaO x .

  3. Influence of Aluminum on the Formation Behavior of Zn-Al-Fe Intermetallic Particles in a Zinc Bath

    NASA Astrophysics Data System (ADS)

    Park, Joo Hyun; Park, Geun-Ho; Paik, Doo-Jin; Huh, Yoon; Hong, Moon-Hi

    2012-01-01

    The shape, size, and composition of dross particles as a function of aluminum content at a fixed temperature were investigated for aluminum added to the premelted Zn-Fe melt simulating the hot-dip galvanizing bath by a sampling methodology. In the early stage, less than 30 minutes after Al addition, local supersaturation and depletion of the aluminum concentration occurred simultaneously in the bath, resulting in the nucleation and growth of both Fe2Al5Zn x and FeZn13. However, the aluminum was homogenized continuously as the reaction proceeded, and fine and stable FeZn10Al x formed after 30 minutes. An Al-depleted zone (ADZ) mechanism was newly proposed for the "η→η+ζ→δ" phase transformations. The ζ phase bottom dross partly survived for a relatively long period, i.e., 2 hours in this work, whereas the η phase disappeared after 30 minutes. In the early stage of dross formation, both Al-free large particles as well as high-Al tiny particles were formed. The dross particle size decreased slightly with increased reaction time before reaching a plateau. The opposite tendency was observed when the Al content was 0.130 mass pct; with a relatively high Al content, the nucleation of tiny η phase dross was significantly enhanced because of the high degree of supersaturation. This unstable η phase dissolved continuously and underwent simple transformation to the stable δ phase. The relationship between nucleation potential and supersaturation ratio of species is discussed based on the thermodynamics of classical nucleation theory.

  4. Interfacial Characterization of Dissimilar Joints Between Al/Mg/Al-Trilayered Clad Sheet to High-Strength Low-Alloy Steel

    NASA Astrophysics Data System (ADS)

    Macwan, A.; Jiang, X. Q.; Chen, D. L.

    2015-07-01

    Magnesium (Mg) alloys are increasingly used in the automotive and aerospace sectors to reduce vehicle weight. Al/Mg/Al tri-layered clad sheets are deemed as a promising alternative to improve the corrosion resistance and formability of Mg alloys. The structural application of Al/Mg/Al tri-layered clad sheets inevitably involves welding and joining in the multi-material vehicle body manufacturing. This study aimed to characterize the bonding interface microstructure of the Al/Mg/Al-clad sheet to high-strength low-alloy steel with and without Zn coating using ultrasonic spot welding at different levels of welding energy. It was observed that the presence of Zn coating improved the bonding at the interface due to the formation of Al-Zn eutectic structure via enhanced diffusion. At a higher level of welding energy, characteristic flow patterns of Zn into Al-clad layer were observed with an extensive penetration mainly along some high angle grain boundaries. The dissimilar joints without Zn coating made at a high welding energy of 800 J failed partially from the Al/Fe weld interface and partially from the Al/Mg clad interface, while the joints with Zn coating failed from the Al/Mg clad interface due to the presence of brittle Al12Mg17 phase.

  5. Pure ultraviolet emission from ZnO quantum dots-based/GaN heterojunction diodes by MgO interlayer

    NASA Astrophysics Data System (ADS)

    Chen, Cheng; Liang, Renli; Chen, Jingwen; Zhang, Jun; Wang, Shuai; Zhao, Chong; Zhang, Wei; Dai, Jiangnan; Chen, Changqing

    2017-07-01

    We demonstrate the fabrication and characterization of ZnO/GaN-based heterojunction light-emitting diodes (LEDs) by using air-stable and solution-processable ZnO quantum dots (QDs) with a thin MgO interlayer acting as an electron blocking layer (EBL). The ZnO QDs/MgO/ p-GaN heterojunction can only display electroluminescence (EL) characteristic in reverse bias regime. Under sufficient reverse bias, a fairly pure ultraviolet EL emission located at 370 nm deriving from near band edge of ZnO with a full width at half maximum (FWHM) of 8.3 nm had been obtained, while the deep-level emission had been almost totally suppressed. The EL origination and corresponding carrier transport mechanisms were investigated qualitatively in terms of photoluminescence (PL) results and energy band diagram.[Figure not available: see fulltext.

  6. The Influence of CuFe2O4 Nanoparticles on Superconductivity of MgB2

    NASA Astrophysics Data System (ADS)

    Novosel, Nikolina; Pajić, Damir; Skoko, Željko; Mustapić, Mislav; Babić, Emil; Zadro, Krešo; Horvat, Joseph

    The influence of CuFe2O4 nanoparticle doping on superconducting properties of Fe-sheated MgB2 wires has been studied. The wires containing 0, 3 and 7.5 wt.% of monodisperse superparamagnetic nanoparticles (˜7 nm) were sintered at 650°C or 750°C for 1 hour in the pure argon atmosphere. X-ray diffraction patterns of doped samples showed very small maxima corresponding to iron boride and an increase in the fraction of MgO phase indicating some interaction of nanoparticles with Mg and B. Both magnetic and transport measurements (performed in the temperature range 2-42 K and magnetic field up to 16 T) showed strong deterioration of the superconducting properties upon doping with CuFe2O4. The transition temperatures, Tc, of doped samples decreased for about 1.4 K per wt.% of CuFe2O4. Also, the irreversibility fields Birr(T) decreased progressively with increasing doping. Accordingly, also the suppression of Jc with magnetic field became stronger. The observed strong deterioration of superconducting properties of MgB2 wires is at variance with reported enhancement of critical currents at higher temperatures (determined from magnetization) in bulk MgB2 samples doped with Fe3O4 nanoparticles. The probable reason for this discrepancy is briefly discussed

  7. Effect of Mg doping in the gas-sensing performance of RF-sputtered ZnO thin films

    NASA Astrophysics Data System (ADS)

    Vinoth, E.; Gowrishankar, S.; Gopalakrishnan, N.

    2018-06-01

    Thin films of Mg-free and Mg-doped (3, 10 and 20 mol%) ZnO thin films have been deposited on Si (100) substrates by RF magnetron sputtering for gas-sensing application. Preferential orientation along (002) plane with hexagonal wurtzite structure has been observed in X-ray diffraction analysis. The conductivity, resistivity, and mobility of the deposited films have been measured by Hall effect measurement. The bandgap of the films has been calculated from the UV-Vis-NIR spectroscopy. It has been found that the bandgap was increased from 3.35 to 3.91 eV with Mg content in ZnO due to the radiative recombination of excitons. The change in morphology of the grown films has been investigated by scanning electron microscope. Gas-sensing measurements have been conducted for fabricated films. The sensor response, selectivity, and stability measurement were done for the fabricated films. Though better response was found towards ethanol, methanol, and ammonia for MZ2 (Mg at 10 mol%) film and maximum gas response was observed towards ammonia. The selectivity measurement reveals maximum sensitivity about 42% for ammonia. The low response time of 123 s and recovery time of 152 s towards ammonia were observed for MZ2 (Mg at 10 mol%). Stability of the Mg-doped ZnO thin film confirmed by the continuous sensing measurements for 4 months.

  8. Mössbauer study and magnetic properties of MgFe2O4 crystallized from the glass system B2O3/K2O/P2O5/MgO/Fe2O3

    NASA Astrophysics Data System (ADS)

    Shabrawy, S. El; Bocker, C.; Miglierini, M.; Schaaf, P.; Tzankov, D.; Georgieva, M.; Harizanova, R.; Rüssel, C.

    2017-01-01

    An iron containing magnesium borate glass with the mol% composition 51.7 B2O3/9.3 K2O /1 P2O5/27.6MgO/10.4Fe2O3was prepared by the conventional melts quenching method followed by a thermal treatment process at temperatures in the range from 530 to 604 °C.The thermally treated samples were characterized by X-ray diffraction, scanning and transmission electron microscopy. It was shown that superparamagnetic MgFe2O4 nanoparticles were formed during thermal treatment. The size of the spinel type crystals was in the range from 6 to 15 nm. Mössbauer spectra of the powdered glass ceramic samples and the extracted nanoparticles after dissolving the glass matrix in diluted acid were recorded at room temperature. The deconvolution of the spectra revealed the crystallization of two spinel phases MgFe2O4 (as a dominant phase) and superparamagnetic maghemite, γ-Fe2O3 (as a secondary phase). Room temperature magnetic measurements showed that, increasing the crystallization temperature changed the superparamagnetic behavior of the samples to ferrimagnetic behavior. The Curie temperatures of the samples were measured and showed a higher value than that of the pure bulk MgFe2O4.

  9. Structural classification of RAO3( MO) n compounds ( R =Sc, In, Y, or lanthanides; A =Fe(III), Ga, Cr, or Al; M =divalent cation; n = 1-11)

    NASA Astrophysics Data System (ADS)

    Kimizuka, Noboru; Mohri, Takahiko

    1989-01-01

    A series of new compounds RAO3( MO) n ( n = 1-11) having spinel, YbFe 2O 4, or InFeO 3(ZnO) n types of structures were newly synthesized ( R =Sc, In, Y, Lu, Yb, Tm, or Er; A =Fe(III), Ga, Cr, or Al; M =Mg, Mn, Fe(II), Co, Ni, Zn, or Cd) at elevated temperatures. The conditions of synthesis and the lattice constants for these compounds are reported. The stacking sequences of the InO 1.5, (FeZn)O 2.5, and ZnO layers for InFeO 3(ZnO) 10 and the TmO 1.5, (AlZn)O 2.5, and ZnO layers for TmAlO 3(ZnO) 11 are presented, respectively. The crystal structures of the( RAO3) m( MO) n phases ( R =Sc, In, Y, or lanthanide elements; A =Fe(III), Ga, Cr, or Al; M =divalent cation elements; m and n =integer) are classified into four crystal structure types (K 2NiF 4, CaFe 2O 4, YbFe 2O 4, and spinel), based upon the constituent cations R, A, and M

  10. Synthesis of hierarchical Mg-doped Fe3O4 micro/nano materials for the decomposition of hexachlorobenzene.

    PubMed

    Su, Guijin; Liu, Yexuan; Huang, Linyan; Lu, Huijie; Liu, Sha; Li, Liewu; Zheng, Minghui

    2014-03-01

    An ethylene-glycol (EG) mediated self-assembly process was firstly developed to synthesize micrometer-sized nanostructured Mg-doped Fe3O4 composite oxides to decompose hexachlorobenzene (HCB) at 300°C. The synthesized samples were characterized by scanning electron microscopy, transmission electron microscopy, X-ray diffraction, energy dispersive X-ray spectroscopy and inductively coupled plasma optical emission spectrometer. The morphology and composition of the composite oxide precursor were regulated by the molar ratio of the magnesium acetate and ferric nitrate as the reactants. Calcination of the precursor particles, prepared with different molar ratio of the metal salts, under a reducing nitrogen atmosphere, generated three kinds of Mg doped Fe3O4 composite oxide micro/nano materials. Their reactivity toward HCB decomposition was likely influenced by the material morphology and content of Mg dopants. Ball-like MgFe2O4-Fe3O4 composite oxide micro/nano material showed superior HCB dechlorination efficiencies when compared with pure Fe3O4 micro/nano material, prepared under similar experimental conditions, thus highlighting the benefits of doping Mg into Fe3O4 matrices. Copyright © 2013 Elsevier Ltd. All rights reserved.

  11. Probing the Li Insertion Mechanism of ZnFe 2O 4 in Li-Ion Batteries: A Combined X-Ray Diffraction, Extended X-Ray Absorption Fine Structure, and Density Functional Theory Study [Probing the Li insertion mechanism of ZnFe 2O 4 in Li ion batteries: A combined XRD, EXAFS, and DFT study

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

    Zhang, Yiman; Pelliccione, Christopher J.; Brady, Alexander B.

    Here, we report an extensive study on fundamental properties that determine the functional electrochemistry of ZnFe 2O 4 spinel (theoretical capacity of 1000 mAh/g). For the first time, the reduction mechanism is followed through a combination of in situ X-ray diffraction data, synchrotron based powder diffraction, and ex-situ extended X-ray absorption fine structure allowing complete visualization of reduction products irrespective of their crystallinity. The first 0.5 electron equivalents (ee) do not significantly change the starting crystal structure. Subsequent lithiation results in migration of Zn 2+ ions from 8a tetrahedral sites into vacant 16c sites. Density functional theory shows that Limore » + ions insert into 16c site initially and then 8a site with further lithiation. Fe metal is formed over the next eight ee of reduction with no evidence of concurrent Zn 2+ reduction to Zn metal. Despite the expected formation of LiZn alloy from the electron count, we find no evidence for this phase under the tested conditions. Additionally, upon oxidation to 3 V, we observe an FeO phase with no evidence of Fe 2O 3. Electrochemistry data show higher electron equivalent transfer than can be accounted for solely based on ZnFe 2O 4 reduction indicating excess capacity ascribed to carbon reduction or surface electrolyte interphase formation.« less

  12. Probing the Li Insertion Mechanism of ZnFe 2O 4 in Li-Ion Batteries: A Combined X-Ray Diffraction, Extended X-Ray Absorption Fine Structure, and Density Functional Theory Study [Probing the Li insertion mechanism of ZnFe 2O 4 in Li ion batteries: A combined XRD, EXAFS, and DFT study

    DOE PAGES

    Zhang, Yiman; Pelliccione, Christopher J.; Brady, Alexander B.; ...

    2017-04-24

    Here, we report an extensive study on fundamental properties that determine the functional electrochemistry of ZnFe 2O 4 spinel (theoretical capacity of 1000 mAh/g). For the first time, the reduction mechanism is followed through a combination of in situ X-ray diffraction data, synchrotron based powder diffraction, and ex-situ extended X-ray absorption fine structure allowing complete visualization of reduction products irrespective of their crystallinity. The first 0.5 electron equivalents (ee) do not significantly change the starting crystal structure. Subsequent lithiation results in migration of Zn 2+ ions from 8a tetrahedral sites into vacant 16c sites. Density functional theory shows that Limore » + ions insert into 16c site initially and then 8a site with further lithiation. Fe metal is formed over the next eight ee of reduction with no evidence of concurrent Zn 2+ reduction to Zn metal. Despite the expected formation of LiZn alloy from the electron count, we find no evidence for this phase under the tested conditions. Additionally, upon oxidation to 3 V, we observe an FeO phase with no evidence of Fe 2O 3. Electrochemistry data show higher electron equivalent transfer than can be accounted for solely based on ZnFe 2O 4 reduction indicating excess capacity ascribed to carbon reduction or surface electrolyte interphase formation.« less

  13. Composite multifunctional nanostructures based on ZnO tetrapods and superparamagnetic Fe3O4 nanoparticles.

    PubMed

    Villani, M; Rimoldi, T; Calestani, D; Lazzarini, L; Chiesi, V; Casoli, F; Albertini, F; Zappettini, A

    2013-04-05

    A nanocomposite material is obtained by coupling superparamagnetic magnetite nanoparticles (Fe3O4 NP) and vapor phase grown zinc oxide nanostructures with 'tetrapod' morphology (ZnO TP). The aim is the creation of a multifunctional material which retains the attractive features of ZnO (e.g. surface reactivity, strong UV emission, piezoelectricity) together with added magnetism. Structural, morphological, optical, magnetic and functional characterization are performed. In particular, the high saturation magnetization of Fe3O4 NP (above 50 A m(2) kg(-1)), the strong UV luminescence and the enhanced photocatalytic activity of coupled nanostructures are discussed. Thus the nanocomposite turns out to be suitable for applications in energy harvesting and conversion, gas- and bio-sensing, bio-medicine and filter-free photocatalysis.

  14. Crystal Structure and Magnetic Properties of New Cubic Quaternary Compounds RT2Sn2Zn18 (R = La, Ce, Pr, and Nd, and T = Co and Fe)

    NASA Astrophysics Data System (ADS)

    Isikawa, Yosikazu; Mizushima, Toshio; Ejiri, Jun-ichi; Kitayama, Shiori; Kumagai, Keigou; Kuwai, Tomohiko; Bordet, Pierre; Lejay, Pascal

    2015-07-01

    The new cubic quaternary intermetallic compounds RT2Sn2Zn18 (R = La, Ce, Pr, and Nd, and T = Co and Fe) were synthesized by the mixture-metal flux method using Zn and Sn. The crystal structure was investigated by powder X-ray diffraction and with a four-circle X-ray diffractometer using single crystals. The space group of the compounds is Fdbar{3}m (No. 227). The rare-earth atom is at the cubic site which is the center of a cage composed of Zn and Sn atoms. The crystal structure is the same as the CeCr2Al20-type crystal structure except the atoms at the 16c site, i.e., the Zn atoms at the 16c site are completely replaced by Sn atoms, indicating that the compounds are crystallographically new ordered quaternary compounds. The lattice parameter a and the physical properties of the magnetic susceptibility χ, the magnetization M, and the specific heat C of these cubic caged compounds were investigated. LaCo2Sn2Zn18 and LaFe2Sn2Zn18 are enhanced Pauli paramagnets that originate from the Co and Fe itinerant 3d electrons. CeCo2Sn2Zn18 and CeFe2Sn2Zn18 are also enhanced Pauli paramagnets that originate from both the 3d electrons and Ce 4f electrons. PrCo2Sn2Zn18 and PrFe2Sn2Zn18 are nonmagnetic materials with huge values of C divided by temperature, which indicates that the ground state of Pr ions is a non-Kramers' doublet. NdCo2Sn2Zn18 and NdFe2Sn2Zn18 are magnetic materials with the Néel temperatures of 1.0 and 3.8 K, respectively. All eight compounds have large magnetic moments of Co/Fe in the paramagnetic temperature region, and thus their magnetic moments are inferred to be magnetically frustrating owing to the pyrochlore lattice in the low-temperature region.

  15. Structural, optical and NO2 gas sensing properties of ZnMgO thin films prepared by the sol gel method

    NASA Astrophysics Data System (ADS)

    Chebil, W.; Boukadhaba, M. A.; Madhi, I.; Fouzri, A.; Lusson, A.; Vilar, C.; Sallet, V.

    2017-01-01

    In this present work, ZnO and ZnMgO thin films prepared by a sol-gel process were deposited on glass substrates via spin coating technique. The structural, morphological and optical properties of the obtained films were investigated. X-ray diffraction study revealed that all layers exhibit a hexagonal wurtzite structure without any secondary phase segregation. The atomic force microscopy (AFM) depicts that the grains size of ours samples decreases as magnesium content increases. The absorption spectra obtained on ZnMgO thin films show a band gap tuning from 3.19 to 3.36 eV, which is also consistent with blue shifting of near-band edge PL emission, measured at low temperature. The incorporated amount of magnesium was calculated and confirmed by EDX. The gas sensing performances were tested in air containing NO2 for different operating temperatures. The experimental result exhibited that ZnMgO sensors shows a faster response and recovery time than the ZnO thin films. The resistivity and the sensor response as function of Mg content were also investigated.

  16. The role of reduced graphene oxide on the electrochemical activity of MFe2O4 (M = Fe, Co, Ni and Zn) nanohybrids

    NASA Astrophysics Data System (ADS)

    Suresh, Shravan; Prakash, Anand; Bahadur, D.

    2018-02-01

    In this work, a comparative study of electrochemical performance of reduced graphene oxide-ferrites (RGO-MFe2O4, M = Fe, Co, Ni, and Zn) nanohybrids synthesized by hydrothermal method was done. The structural morphology and investigation of other physical properties of nanohybrids confirm the cubic spinel phase of the MFe2O4, reduction of graphene oxide and the distribution of ferrite nanoparticles (NPs) on RGO nanosheets. The role of RGO on the electrochemical behavior of nanohybrids was understood by quantifying the charge storage capacitance and charging-discharging behavior in a 0.1 M Na2SO4 electrolyte. The specific capacitance values of pristine Fe3O4, CoFe2O4, NiFe2O4, and ZnFe2O4 are 128, 117, 15.2 and 9.1 F g-1 respectively whereas specific capacitance of RGO-Fe3O4, RGO-CoFe2O4, RGO-NiFe2O4 and RGO-ZnFe2O4 are 233, 200, 25 and 66.8 F g-1 respectively. Our investigation suggests that apart from specific surface area of nanohybrids other factors such as structural morphology determine interaction between nanohybrids and electrolyte ions which play critical role in elevating the performance of electrodes.

  17. Mechanism of single metal exchange in the reactions of [M4(SPh)10]2- (M = Zn or Fe) with CoX2 (X = Cl or NO3) or FeCl2.

    PubMed

    Autissier, Valerie; Henderson, Richard A

    2008-07-21

    The kinetics of the reactions between [Zn4(SPh)10](2-) and an excess of MX2 (M = Co, X = NO3 or Cl; M = Fe, X = Cl), in which a Zn(II) is replaced by M(II), have been studied in MeCN at 25.0 degrees C. (1)H NMR spectroscopy shows that the ultimate product of the reactions is an equilibrium mixture of clusters of composition [Zn(n)M(4-n)(SPh)10](2-), and this is reflected in the multiphasic absorbance-time curves observed over protracted times (several minutes) using stopped-flow spectrophotometry to study the reactions. The kinetics of only the first phase have been determined, corresponding to the equilibrium formation of [Zn3M(SPh)10](2-). The effects of varying the concentrations of cluster, MX2, and ZnCl2 on the kinetics have been investigated. The rate law is consistent with the equilibrium nature of the metal exchange process and indicates a mechanism for the formation of [Zn3M(SPh)10](2-) involving two coupled equilibria. In the initial step binding of MX2 to a bridging thiolate in [Zn4(SPh)10](2-) results in breaking of a Zn-bridging thiolate bond. In the second step replacement of the cluster Zn involves transfer of the bridging thiolates from the Zn to M, with breaking of a Zn-bridged thiolate bond being rate-limiting. The kinetics for the reaction of ZnCl2 with [Zn3M(SPh)10](2-) (M = Fe or Co)} depends on the identity of M. This behavior indicates attack of ZnCl2 at a M-mu-SPh-Zn bridged thiolate. Similar studies on the analogous reactions between [Fe4(SPh)10](2-) and an excess of CoX2 (X = NO3 or Cl) in MeCN exhibit simpler kinetics but these are also consistent with the same mechanism.

  18. Improved Stress Corrosion Cracking Resistance and Strength of a Two-Step Aged Al-Zn-Mg-Cu Alloy Using Taguchi Method

    NASA Astrophysics Data System (ADS)

    Lin, Lianghua; Liu, Zhiyi; Ying, Puyou; Liu, Meng

    2015-12-01

    Multi-step heat treatment effectively enhances the stress corrosion cracking (SCC) resistance but usually degrades the mechanical properties of Al-Zn-Mg-Cu alloys. With the aim to enhance SCC resistance as well as strength of Al-Zn-Mg-Cu alloys, we have optimized the process parameters during two-step aging of Al-6.1Zn-2.8Mg-1.9Cu alloy by Taguchi's L9 orthogonal array. In this work, analysis of variance (ANOVA) was performed to find out the significant heat treatment parameters. The slow strain rate testing combined with scanning electron microscope and transmission electron microscope was employed to study the SCC behaviors of Al-Zn-Mg-Cu alloy. Results showed that the contour map produced by ANOVA offered a reliable reference for selection of optimum heat treatment parameters. By using this method, a desired combination of mechanical performances and SCC resistance was obtained.

  19. Multistage hydrothermal silicification and Fe-Tl-As-Sb-Ge-REE enrichment in the Red Dog Zn-Pb-Ag district, northern Alaska: Geochemistry, origin, and exploration applications

    USGS Publications Warehouse

    Slack, J.F.; Kelley, K.D.; Anderson, V.M.; Clark, J.L.; Ayuso, R.A.

    2004-01-01

    Geochemical analyses of major, trace, and rare earth elements (REE) in more than 200 samples of variably silicified and altered wall rocks, massive and banded sulfide, silica rock, and sulfide-rich and unmineralized barite were obtained from the Main, Aqqaluk, and Anarraaq deposits in the Red Dog Zn-Pb-Ag district of northern Alaska. Detailed lithogeochemical profiles for two drill cores at Aqqaluk display an antithetic relationship between SiO2/Al2O3 and TiO2/Zr which, together with textural information, suggest preferential silicification of carbonate-bearing sediments. Data for both drill cores also show generally high Tl, Sb, As, and Ge and uniformly positive Eu anomalies (Eu/Eu* > 1.0). Similar high Tl, Sb, As, Ge, and Eu/Eu* values are present in the footwall and shallow hanging wall of Zn-Pb-Ag sulfide intervals at Anarraaq but are not as widely dispersed. Net chemical changes for altered wall rocks in the district, on the basis of average Al-normalized data relative to unaltered black shales of the host Kuna Formation, include large enrichments (>50%) of Fe, Ba, Eu, V, S, Co, Zn, Pb, Tl, As, Sb, and Ge at both Red Dog and Anarraaq, Si at Red Dog, and Sr, U, and Se at Anarraaq. Large depletions (>50%) are evident for Ca at both Red Dog and Anarraaq, for Mg, P, and Y at Red Dog, and for Na at Anarraaq. At both Red Dog and Anarraaq, wall-rock alteration removed calcite and minor dolomite during hydrothermal decarbonation reactions and introduced Si, Eu, and Ge during silicification. Sulfidation reactions deposited Fe, S, Co, Zn, Pb, Tl, As, and Sb; barite mineralization introduced Ba, S, and Sr. Light REE and U were mobilized locally. This alteration and mineralization occurred during Mississippi an hydrothermal events that predated the Middle Jurassic-Cretaceous Brookian orogeny. Early hydrothermal silicification at Red Dog took place prior to or during massive sulfide mineralization, on the basis of the dominantly planar nature of Zn-Pb veins, which suggests

  20. Experimentally determined isotope effect during Mg-Fe interdiffusion in olivine

    NASA Astrophysics Data System (ADS)

    Sio, C. K. I.; Roskosz, M.; Dauphas, N.; Bennett, N.; Mock, T. D.; Shahar, A.

    2017-12-01

    Isotopic fractionation provides the most direct means to investigate the nature of chemical zoning in minerals, which can be produced by either diffusive transport or crystal growth. Misinterpreting the nature of chemical zoning can result in erroneous conclusions regarding magmatic cooling rates and diffusion timescales. Isotopes are useful in this regard because the light isotopes diffuse faster than their heavier counterparts. As a result, isotopic fractionations should be associated with chemical zoning profiles if they are diffusion-driven. In contrast, little isotopic fractionation is associated with crystal growth during slow cooling at magmatic temperatures. The isotope effect for diffusion is described by β and is related to the mass (m) and diffusivity (D) of isotopes i and j of an element via: Di/Dj = (mj/mi)β. To model isotopic profiles, knowledge of β is required. Several estimates of β for Mg and Fe diffusion in olivine have been reported using natural samples but these estimates are uncertain because they depend on the choice of modeling parameters (Sio et al., 2013; Oeser et al., 2015; Collinet et al., 2017). We have experimentally determined β for FeFe) in olivine as a function of crystallographic orientation, composition, and temperature. Thirty experiments have been conducted by juxtaposing crystallographically oriented olivine crystals to make Fo83.4-Fo88.8 and Fo88.8-Fo100 diffusion couples. These diffusion couples were annealed in a 1 atm gas mixing furnace at 1200 °C, 1300 °C or 1400 °C at QFM - 1.5 for up to 15 days. Chemical profiles were characterized using an electron microprobe and isotopic analyses were done using laser ablation MC-ICPMS. We found a crystallographic dependence of βFe for the Fo88.8-Fo100 couple where βFe [100] ≈ βFe [010] > βFe [001]. For the Fo83.4-Fo88.8 couple, βFe is 0.16 ± 0.09 (2σ) for all 3 major crystallographic axes. A temperature dependence of βFe could not be resolved. These

  1. Incorporation of Mg and Ca into nanostructured Fe2O3 improves Fe solubility in dilute acid and sensory characteristics in foods.

    PubMed

    Hilty, Florentine M; Knijnenburg, Jesper T N; Teleki, Alexandra; Krumeich, Frank; Hurrell, Richard F; Pratsinis, Sotiris E; Zimmermann, Michael B

    2011-01-01

    Iron deficiency is one of the most common micronutrient deficiencies worldwide. Food fortification can be an effective and sustainable strategy to reduce Fe deficiency but selection of iron fortificants remains a challenge. Water-soluble compounds, for example, FeSO(4), usually demonstrate high bioavailability but they often cause unacceptable sensory changes in foods. On the other hand, poorly acid-soluble Fe compounds, for example FePO(4), may cause fewer adverse sensory changes in foods but are usually not well bioavailable since they need to be dissolved in the stomach prior to absorption. The solubility and the bioavailability of poorly acid-soluble Fe compounds can be improved by decreasing their primary particle size and thereby increasing their specific surface area. Here, Fe oxide-based nanostructured compounds with added Mg or Ca were produced by scalable flame aerosol technology. The compounds were characterized by nitrogen adsorption, X-ray diffraction, transmission electron microscopy, and Fe solubility in dilute acid. Sensory properties of the Fe-based compounds were tested in 2 highly reactive, polyphenol-rich food matrices: chocolate milk and fruit yoghurt. The Fe solubility of nanostructured Fe(2)O(3) doped with Mg or Ca was higher than that of pure Fe(2)O(3). Since good solubility in dilute acid was obtained despite the inhomogeneity of the powders, inexpensive precursors, for example Fe- and Ca-nitrates, can be used for their manufacture. Adding Mg or Ca lightened powder color, while sensory changes when added to foods were less pronounced than for FeSO(4). The combination of high Fe solubility and low reactivity in foods makes these flame-made nanostructured compounds promising for food fortification. Practical Application: The nanostructured iron-containing compounds presented here may prove useful for iron fortification of certain foods; they are highly soluble in dilute acid and likely to be well absorbed in the gut but cause less severe

  2. Magnetic and photocatalytic studies on Zn1-xMgxFe2O4 nanocolloids synthesized by solvothermal reflux method.

    PubMed

    Manohar, A; Krishnamoorthi, C

    2017-12-01

    Biocompatible magnetic semiconductor Zn 1-x Mg x Fe 2 O 4 (x=0, 0.1, 0.3, 0.5 & 0.7) nanoparticles of around 10nm diameter were synthesized by solvothermal reflux method. The method produces well separated and narrow size distributed nanoparticles. Crystal structure, morphology, particles surface properties, surfactant quantity, colloidal stability, magnetic properties and photocatalytic properties of the synthesized nanoparticles were studied. Different characterizations confirmed that all compounds were single crystals and superparamagnetic at room temperature. Saturation mass magnetization (M s =57.5emu/g) enhances with substituent Mg 2+ concentration due to promotion of mixed spinel (normal and inverse) structure. Photocatalytic activity of all synthesized magnetic semiconductor nanoparticles were studied through methylene blue degradation. The degradation of 98% methylene blue was observed on 60 min irradiation of light. It is observed that photocatalytic activity slightly enhances with substituent Mg 2+ concentration. The synthesized biocompatible magnetic semiconductor nanoparticles can be utilized as photocatalysts and could also be recycled and separated by applying an external magnetic field. Copyright © 2017 Elsevier B.V. All rights reserved.

  3. In situ investigations of phase transformations in Fe-sheathed MgB2 wires

    NASA Astrophysics Data System (ADS)

    Grivel, J.-C.; Pinholt, R.; Andersen, N. H.; Kovác, P.; Husek, I.; Homeyer, J.

    2006-01-01

    The phase evolution inside Fe-sheathed wires containing precursor powders consisting of a mixture of Mg and B has been studied in situ by means of x-ray diffraction with hard synchrotron radiation (90 keV). Mg was found to disappear progressively during the heating stage. At 500 °C, the intensity of the Mg diffraction lines is reduced by about 20%. This effect is partly attributable to MgO formation. The MgB2 phase was detected from 575 °C. Fe2B was forming at the interface between the sheath and the ceramic core at sintering temperatures of 780 and 700 °C, but not at 650 °C. The formation rate of this phase is strongly dependent on the heat treatment temperature. Its presence can be readily detected as soon as the average interface reaction thickness exceeds 150-200 nm.

  4. Zincoberaunite, ZnFe3+ 5(PO4)4(OH)5ṡ6H2O, a new mineral from the Hagendorf South pegmatite, Germany

    NASA Astrophysics Data System (ADS)

    Chukanov, Nikita V.; Pekov, Igor V.; Grey, Ian E.; Price, Jason R.; Britvin, Sergey N.; Krzhizhanovskaya, Maria G.; Kampf, Anthony R.; Dünkel, Bernhard; Keck, Erich; Belakovskiy, Dmitry I.; MacRae, Colin M.

    2017-06-01

    The new mineral zincoberaunite, ideally ZnFe3+ 5(PO4)4(OH)5·6H2O, the Zn analogue of beraunite, is found in the Hagendorf South granitic pegmatite, Hagendorf, Bavaria, Germany, in two associations: (1) with potassium feldspar, quartz, jungite, phosphophyllite and mitridatite (the holotype) and (2) with flurlite, plimerite, Zn-bearing beraunite, schoonerite, parascholzite/scholzite, robertsite and altered phosphophyllite (the cotype). Zincoberaunite occurs as radial or randomly oriented aggregates of flexible fibers up to 1.5 mm long and up to 3 μm thick. D calc is 2.92 g/cm3 for the holotype and 2.94 g/cm3 for the cotype. Zincoberaunite is optically biaxial (-), α = 1.745(5), β = 1.760(5), γ = 1.770(5), 2 V meas = 80(5)°. Chemical composition of the holotype (electron probe microanalyser; H2O by gas chromatography of ignition products) is: MgO 0.28 wt%, CaO 0.47 wt%, ZnO 7.36 wt%, Al2O3 0.88 wt%, Fe2O3 42.42 wt%, P2O5 31.63 wt%, H2O 16.2 wt%, total 101.1 wt%. The empirical formula calculated on the basis of 27 oxygen atoms per formula unit is (Zn0.83Ca0.08Mg0.06)∑0.97(Fe3+ 4.88Al0.16)∑5.04(PO4)4.09(OH)4.78 · 5.86H2O. Zincoberaunite is monoclinic, space group C2 /c; refined unit cell parameters (for the holotype at room temperature and the cotype at 100 K, respectively) are: a 20.837(2) and 20.836(4), b 5.1624(4) and 5.148(1), c 19.250(1) and 19.228(4) Å, β 93.252(5) and 93.21(3)°, V 2067.3(3) and 2059.2(7) Å3, Z = 4. The crystal structure of the holotype specimen has been refined by the Rietveld method ( R p = 0.30 %; R B = 0.18 %) whereas the structure of the cotype has been solved from the single crystal data and refined to R 1 = 0.056 based on 1900 unique reflections with I > 2σ( I). The strongest reflections of the powder X-ray diffraction pattern of the holotype specimen [( d, Å) ( I, %) ( hkl)] are: 10.37 (100) (200), 9.58 (32) (002), 7.24 (26) (20-2), 4.817 (22) (111), 4.409 (13) (112), 3.483 (14) (11-4, 600), 3.431 (14) (404), 3.194 (15

  5. Removal of dibutyl phthalate from aqueous environments using a nanophotocatalytic Fe, Ag-ZnO/VIS-LED system: modeling and optimization.

    PubMed

    Akbari-Adergani, B; Saghi, M H; Eslami, A; Mohseni-Bandpei, A; Rabbani, M

    2018-06-01

    An (Fe, Ag) co-doped ZnO nanostructure was synthesized by a simple chemical co-precipitation method and used for the degradation of dibutyl phthalate (DBP) in aqueous solution under visible light-emitting diode (LED) irradiation. (Fe, Ag) co-doped ZnO nanorods were characterized by powder X-ray diffraction, Fourier transform infrared spectroscopy, UV-VIS diffuse reflectance spectroscopy, elemental mapping, Field emission scanning electron microscopy, transmission electron microscope and Brunauer-Emmett-Teller surface area analysis. A Central Composite Design was used to optimize the reaction parameters for the removal of DBP by the (Fe, Ag) co-doped ZnO nanorods. The four main reaction parameters optimized in this study were the following: pH, time of radiation, concentration of the nanorods and initial DBP concentration. The interaction between the four parameters was studied and modeled using the Design Expert 10 software. A maximum reduction of 95% of DBP was achieved at a pH of 3, a photocatalyst concentration of 150 mg L -1 and a DBP initial DBP concentration of 15 mg L -1 . The results showed that the (Fe, Ag) co-doped ZnO nanorods under low power LED irradiation can be used as an effective photocatalyst for the removal of DBP from aqueous solutions.

  6. Enhanced magnetic properties in Mn0.6Zn0.4-xNixFe2O4 (x=0-0.4) nanoparticles

    NASA Astrophysics Data System (ADS)

    Mallesh, S.; Mandal, P.; Srinivas, V.

    2018-04-01

    Ni substituted MnZn ferrite fine particles were synthesized through sol-gel method. The structure, stability and magnetic properties have been investigated. Thermal stability of as-prepared (AP) particles is improved compared to that of Mn0.6Zn0.4Fe2O4 (MZF) ferrite particles. The as-prepared and samples annealed at 1200 °C exhibit pure spinel ferrite phase, while samples at intermediate temperatures (600 - 1000 °C) exhibit secondary phase of α-Fe2O3 along with ferrite phase. The Mn0.6Zn0.1Ni0.3Fe2O4 (Ni-MZF) sample shows significantly lower volume fraction of secondary phase compared to that of MZF. The observed magnetization of Ni-MZF is twice of that MZF samples. Present results suggest that a small amount (x=0.3) of Ni in place of nonmagnetic Zn in MZF significantly decreases the secondary phase fraction and improves the magnetic properties.

  7. Effect of interfacial structures on spin dependent tunneling in epitaxial L1{sub 0}-FePt/MgO/FePt perpendicular magnetic tunnel junctions

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

    Yang, G.; Li, D. L.; Wang, S. G., E-mail: Sgwang@iphy.ac.cn

    2015-02-28

    Epitaxial FePt(001)/MgO/FePt magnetic tunnel junctions with L1{sub 0}-FePt electrodes showing perpendicular magnetic anisotropy were fabricated by molecular beam epitaxial growth. Tunnel magnetoresistance ratios of 21% and 53% were obtained at 300 K and 10 K, respectively. Our previous work, based on transmission electron microscopy, confirmed a semi-coherent interfacial structure with atomic steps (Kohn et al., APL 102, 062403 (2013)). Here, we show by x-ray photoemission spectroscopy and first-principles calculation that the bottom FePt/MgO interface is either Pt-terminated for regular growth or when an Fe layer is inserted at the interface, it is chemically bonded to O. Both these structures have a dominantmore » role in spin dependent tunneling across the MgO barrier resulting in a decrease of the tunneling magnetoresistance ratio compared with previous predictions.« less

  8. The influence of an MgO nanolayer on the planar Hall effect in NiFe films

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

    Li, Minghua, E-mail: mhli@ustb.edu.cn; Department of Electrical Engineering, University of California, Los Angeles, California 90095; Zhao, Zhiduo

    2015-03-28

    The Planar Hall Effect (PHE) in NiFe films was studied using MgO as the buffer and capping layer to reduce the shunt effect. The thermal annealing was found to be effective in increasing the sensitivity. The sensitivity of the magnetic field reached as high as 865 V/AT in a MgO (3 nm)/NiFe (5 nm)/MgO(3 nm)/Ta(3 nm) structure after annealing at 500 °C for 2 h, which is close to the sensitivity of semiconductor Hall Effect (HE) sensors. X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD) and high-resolution transmission electron microscopy (HRTEM) were used to study the sample. The results show that the top crystallization of MgO and NiFemore » (111) texture were improved by proper annealing. The smooth and clear bottom MgO/NiFe and top NiFe/MgO interface is evident from our data. In addition, the shunt current of Ta was decreased. These combined factors facilitate the improvement of the sensitivity of the magnetic field.« less

  9. Investigation of Cu-, Zn- and Fe-containing human brain proteins using isotopic-enriched tracers by LA-ICP-MS and MALDI-FT-ICR-MS

    NASA Astrophysics Data System (ADS)

    Becker, J. Susanne; Zoriy, Miroslav; Pickhardt, Carola; Przybylski, Michael; Becker, J. Sabine

    2005-04-01

    Identification of metal-containing proteins and determination of Cu, Fe, Zn concentration in very small protein volumes is of increasing importance in protein research. Proteins containing metal ions were analyzed directly and simultaneously in separated protein spots in two-dimensional gels (2D gels) by laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) as an element mass spectrometric technique. In order to study the formation of proteins containing Cu, Zn and Fe in a human brain sample, isotopic-enriched tracers (54Fe, 65Cu and 67Zn) were doped to two-dimensional gels of separated Alzheimer-diseased brain proteins after two-dimensional (2D) gel electrophoresis. The protein spots were screened systematically by LA-ICP-MS with respect to these metal ion intensities. 54Fe/56Fe, 65Cu/63Cu and 67Zn/64Zn isotope ratios in metal-containing proteins were measured directly by LA-ICP-MS. The isotope ratio measurements obtained by LA-ICP-MS indicate certain protein spots with a natural isotope composition of Cu, Zn and/or Fe. These proteins already contained the metal investigated in the original proteins and are stable enough to survive the reducing conditions during gel electrophoresis. On the other hand, proteins with a changed isotope ratio of metals in comparison to the isotope ratio in nature demonstrate the accumulation of tracers within the protein complexes during the tracer experiments in 2D gels. The identification of singular protein spots from Alzheimer-diseased brain separated by 2D gel electrophoresis was attempted by biopolymer mass spectrometry using MALDI-FTICR-MS after excision from the 2D gel and tryptic digestion.

  10. Cytocompatibility and early inflammatory response of human endothelial cells in direct culture with Mg-Zn-Sr alloys

    PubMed Central

    Cipriano, Aaron F.; Sallee, Amy; Tayoba, Myla; Cortez Alcaraz, Mayra C.; Lin, Alan; Guan, Ren-Guo; Zhao, Zhan-Yong; Liu, Huinan

    2018-01-01

    Crystalline Mg-Zinc (Zn)-Strontium (Sr) ternary alloys consist of elements naturally present in the human body and provide attractive mechanical and biodegradable properties for a variety of biomedical applications. The first objective of this study was to investigate the degradation and cytocompatibility of four Mg-4Zn-xSr alloys (x = 0.15, 0.5, 1.0, 1.5 wt%; designated as ZSr41A, B, C, and D respectively) in the direct culture with human umbilical vein endothelial cells (HUVEC) in vitro. The second objective was to investigate, for the first time, the early-stage inflammatory response in cultured HUVECs as indicated by the induction of vascular cellular adhesion molecule-1 (VCAM-1). The results showed that the 24-h in vitro degradation of the ZSr41 alloys containing a β-phase with a Zn/Sr at% ratio ~1.5 was significantly faster than the ZSr41 alloys with Zn/Sr at% ~1. Additionally, the adhesion density of HUVECs in the direct culture but not in direct contact with the ZSr41 alloys for up to 24 h was not adversely affected by the degradation of the alloys. Importantly, neither culture media supplemented with up to 27.6 mM Mg2+ ions nor media intentionally adjusted up to alkaline pH 9 induced any detectable adverse effects on HUVEC responses. In contrast, the significantly higher, yet non-cytotoxic, Zn2+ ion concentration from the degradation of ZSr41D alloy was likely the cause for the initially higher VCAM-1 expression on cultured HUVECs. Lastly, analysis of the HUVEC-ZSr41 interface showed near-complete absence of cell adhesion directly on the sample surface, most likely caused by either a high local alkalinity, change in surface topography, and/or surface composition. The direct culture method used in this study was proposed as a valuable tool for studying the design aspects of Zn-containing Mg-based biomaterials in vitro, in order to engineer solutions to address current shortcomings of Mg alloys for vascular device applications. PMID:27746360

  11. Growth, structure, and magnetic properties of γ-Fe2O3 epitaxial films on MgO

    NASA Astrophysics Data System (ADS)

    Gao, Y.; Kim, Y. J.; Thevuthasan, S.; Chambers, S. A.; Lubitz, P.

    1997-04-01

    Single-crystal epitaxial thin films of γ-Fe2O3(001) have been grown on MgO(001) using oxygen-plasma-assisted molecular beam epitaxy. The structure and magnetic properties of these films have been characterized by a variety of techniques, including reflection high-energy electron diffraction (RHEED), low-energy electron diffraction (LEED), x-ray photoelectron spectroscopy and x-ray photoelectron/Auger electron diffraction (XPD/AED), vibrating sample magnetometry, and ferromagnetic resonance. Real-time RHEED reveals that the film growth occurs in a layer-by-layer fashion. The γ-Fe2O3(001) film surface exhibits a (1×1) LEED pattern. The growth of γ-Fe2Ooverflow="scroll">3 films at 450 °C is accompanied by significant Mg outdiffusion. AED of Mg KLL Auger emission reveals that Mg substitutionally incorporates in the γ-Fe2O3 lattice, occupying the octahedral sites. Magnetic moments are ˜2300 G and ˜4500 G for γ-Fe2O3 films grown at 250 °C and 450 °C, respectively. The high magnetic moment for the films grown at 450 °C could be attributed to the high degree of structural order of the films and Mg substitution at octahedral sites.

  12. The influence of HF treatment on corrosion resistance and in vitro biocompatibility of Mg-Zn-Zr alloy

    NASA Astrophysics Data System (ADS)

    Ye, Xin-Yu; Chen, Min-Fang; You, Chen; Liu, De-Bao

    2010-06-01

    The samples made of a Mg-2.5wt.%Zn-0.5wt.%Zr alloy were immersed in the 20% hydrofluoric acid (HF) solution at room temperature for different time, with the aim of improving the properties of magnesium (Mg) alloy in applications as biomaterials. The corrosion resistance and in vitro biocompatibility of untreated and fluoride-coated samples were investigated. The results show that the optimum process is to immerse Mg alloys in the 20% HF solution for 6 h. After the immersion, a dense magnesium fluoride (MgF2) coating of 0.5 μm was synthesized on the surface of Mg-Zn-Zr alloy. Polarization tests recorded a reduction in the corrosion current density from 2.10 to 0.05 μA/cm2 due to the MgF2 protective coating. Immersion tests in the simulated body fluid (SBF) also reveal a much milder corrosion on the fluoride-coated samples, and its corrosion rate was calculated to be 0.05 mm/yr. Hemolysis test suggests that the conversion coated Mg alloy has no obvious hemolysis reaction. The hemolysis ratio (HR) of the samples decreases from 11.34% to 1.86% with the HF treatment, which meets the requirements of biomaterials (HR < 5%). The coculture of 3T3 fibroblasts with Mg alloy results in the adhesion and proliferation of cells on the surface of fluoride-coated samples. All the results show that the MgF2 conversion coating would markedly improve the corrosion resistance and in vitro biocompatibility of Mg-Zn-Zr alloy.

  13. Magnetic anisotropy modulation of epitaxial Fe3O4 films on MgO substrates

    NASA Astrophysics Data System (ADS)

    Chichvarina, O.; Herng, T. S.; Xiao, W.; Hong, X.; Ding, J.

    2015-05-01

    Fe3O4 has been widely studied because of its great potential in spintronics and other applications. As a magnetic electrode, it is highly desired if magnetic anisotropy can be controlled. Here, we report the results from our systematic study on the magnetic properties of magnetite (Fe3O4) thin films epitaxially grown on various MgO substrates. Strikingly, we observed a prominent perpendicular magnetic anisotropy in Fe3O4 film deposited on MgO (111) substrate. When measured in out-of-plane direction, the film (40 nm thick) exhibits a well-defined square hysteresis loop with coercivity (Hc) above 1 kOe, while much lower coercivity was obtained in the in-plane orientation. In sharp contrast, the films deposited onto MgO (100) and MgO (110) substrates show in-plane magnetic anisotropy. These films exhibit a typical soft magnet characteristic—Hc lies within the range of 200-400 Oe. All the films showed a clear Verwey transition near 120 K—a characteristic of Fe3O4 material. In addition, a series of magnetoresistance (MR) measurements is performed and the MR results are in good agreement with the magnetic observations. The role of the substrate orientation and film thickness dependency is also investigated.

  14. Room-temperature H2S Gas Sensor Based on Au-doped ZnFe2O4 Yolk-shell Microspheres.

    PubMed

    Yan, Yin; Nizamidin, Patima; Turdi, Gulmira; Kari, Nuerguli; Yimit, Abliz

    2017-01-01

    Room-temperature type H 2 S sensing devices that use Au-doped ZnFe 2 O 4 yolk-shell microspheres as the active material have been fabricated using a solvothermal method as well as subsequent annealing and a chemical etching process. The samples are characterized using X-ray diffraction (XRD), energy-dispersive X-ray spectroscopy (EDS), field-emission scanning electron microscopy (FESEM), and X-ray photoelectron spectroscopy (XPS). The results demonstrate that the doping of Au does not change the spinel structure of the products, which were yolk-shell microspheres, while the particle size varied with the Au doping concentration. Also, the as-fabricated sensor device exhibited excellent selectivity toward H 2 S gas at the room temperature; the gas-sensing property of 2 wt% Au-doped ZnFe 2 O 4 microspheres was the best. The Au-doped ZnFe 2 O 4 yolk-shell microspheres can be promising as a sensing material for H 2 S gas detecting at room temperature.

  15. Localized-Surface-Plasmon Enhanced the 357 nm Forward Emission from ZnMgO Films Capped by Pt Nanoparticles

    PubMed Central

    2009-01-01

    The Pt nanoparticles (NPs), which posses the wider tunable localized-surface-plasmon (LSP) energy varying from deep ultraviolet to visible region depending on their morphology, were prepared by annealing Pt thin films with different initial mass-thicknesses. A sixfold enhancement of the 357 nm forward emission of ZnMgO was observed after capping with Pt NPs, which is due to the resonance coupling between the LSP of Pt NPs and the band-gap emission of ZnMgO. The other factors affecting the ultraviolet emission of ZnMgO, such as emission from Pt itself and light multi-scattering at the interface, were also discussed. These results indicate that Pt NPs can be used to enhance the ultraviolet emission through the LSP coupling for various wide band-gap semiconductors. PMID:20596433

  16. Quasicrystal-reinforced Mg alloys.

    PubMed

    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.

  17. Effect of Mg(2+), Ca(2+), Sr(2+) and Ba(2+) metal ions on the antifungal activity of ZnO nanoparticles tested against Candida albicans.

    PubMed

    Haja Hameed, Abdulrahman Syedahamed; Karthikeyan, Chandrasekaran; Senthil Kumar, Venugopal; Kumaresan, Subramanian; Sasikumar, Seemaisamy

    2015-01-01

    The antifungal ability of pure and alkaline metal ion (Mg(2+), Ca(2+), Sr(2+) and Ba(2+)) doped ZnO nanoparticles (NPs) prepared by the co-precipitation method was tested against the pathogenic yeast, Candida albicans (C. albicans), and the results showed that the Mg-doped ZnO NPs possessed greater effect than the other alkaline metal ion doped ZnO NPs. The impact of the concentration of Mg doped ZnO sample on the growth of C. albicans was also studied. The Minimal Fungicidal Concentration (MFC) of the Mg doped ZnO NPs was found to be 2000 μg/ml for which the growth of C. albicans was completely inhibited. The ZnO:Mg sample (1.5mg/ml) with various concentrations of histidine reduced the fungicidal effect of the nanoparticles against C. albicans, which was deliberately explained by the role of ROS. The ZnO:Mg sample added with 5mM of histidine scavenged the ample amount of generated ROS effectively. The binding of the NPs with fungi was observed by their FESEM images and their electrostatic attraction is confirmed by the zeta potential measurement. Copyright © 2015. Published by Elsevier B.V.

  18. Ferroelectric enhancement in heterostructured ZnO /BiFeO3-PbTiO3 film

    NASA Astrophysics Data System (ADS)

    Yu, Shengwen; Chen, Rui; Zhang, Guanjun; Cheng, Jinrong; Meng, Zhongyan

    2006-11-01

    The authors have prepared heterostructured ZnO /BiFeO3-PbTiO3 (BFO-PT) composite film and BFO-PT film on Pt /Ti/SiO2/Si substrates by pulsed-laser deposition. The structure and morphologies of the films were characterized by x-ray diffraction (XRD) and scanning electron microscope. XRD results show that both films are perovskite structured last with different orientations. The leakage current density in the ZnO /BFO-PT film was found to be nearly two orders of magnitude lower. This could be due to the introduced ZnO layer behaving as a Schottky barrier between the BFO-PT film and top electrodes. The dramatic ferroelectric enhancement in ZnO /BFO-PT film is mostly ascribed to the improved insulation.

  19. Gas response properties of citrate gel synthesized nanocrystalline MgFe{sub 2}O{sub 4}: Effect of sintering temperature

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

    Patil, J.Y.; Mulla, I.S.; Suryavanshi, S.S., E-mail: sssuryavanshi@rediffmail.com

    2013-02-15

    Graphical abstract: Display Omitted Highlights: ► Synthesis of nanocrystalline MgFe{sub 2}O{sub 4} by economical citrate gel combustion method. ► Structural, morphological, and gas response properties of MgFe{sub 2}O{sub 4}. ► Enhancement in selectivity of MgFe{sub 2}O{sub 4} towards LPG with sintering temperature. ► Use of MgFe{sub 2}O{sub 4} to detect different gases at different operating temperatures. -- Abstract: Spinel type MgFe{sub 2}O{sub 4} material was synthesized by citrate gel combustion method. The effect of sintering temperature on structural, morphological, and gas response properties was studied. The powder X-ray diffraction pattern and transmission electron microscope study confirms nanocrystalline spinel structure ofmore » the synthesized powder. The material was tested for response properties to various reducing gases like liquid petroleum gas (LPG), acetone, ethanol, and ammonia. The results demonstrated n-type semiconducting behavior of MgFe{sub 2}O{sub 4} material. It was revealed that MgFe{sub 2}O{sub 4} sintered at 973 K was most sensitive to LPG at 648 K and to acetone at 498 K. However MgFe{sub 2}O{sub 4} sintered at 1173 K exhibited higher response and selectivity to LPG with marginal increase in the operating temperature. Furthermore, the sensor exhibited a fast response and a good recovery. It was observed that the particles size, porosity, and surface activity of the sensor material is affected by the sintering temperature.« less

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

    PubMed

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

    2016-01-29

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