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Sample records for al fe zn

  1. Preparation and characterization of MnZn/FeSiAl soft magnetic composites

    NASA Astrophysics Data System (ADS)

    Li, Jing; Peng, Xiaoling; Yang, Yanting; Ge, Hongliang

    2017-03-01

    In this paper, MnZn ferrites were used as coating agents to prepare MnZn/FeSiAl soft magnetic composites (SMCs) in order to improve the magnetic property, because of the higher permeability of magnetic MnZn ferrites than that of traditional coatings which are always nonmagnetic. The effects of molding pressure, annealing temperature, and content of insulation on the soft magnetic properties of MnZn/FeSiAl SMCs were studied. With increasing molding pressure, the effective permeability of the SMCs increased firstly and then decreased, while the core loss decreased firstly and then increased, and both have the best performance at 1.6 GPa. The permeability increased with increasing temperature, reached the maximum value at 660 °C and then decreased, while the core loss decreased with increasing temperature to 700 °C and then increased. The permeability increased with increasing MnZn content from 0.1 to 3% and then decreased, while the D-C bias property continuously increased.

  2. Effect of Al and Fe doping in ZnO on magnetic and magneto-transport properties

    NASA Astrophysics Data System (ADS)

    Kumar, Santosh; Deepika; Tripathi, Malvika; Vaibhav, Pratyush; Kumar, Aman; Kumar, Ritesh; Choudhary, R. J.; Phase, D. M.

    2016-12-01

    The structural, magnetic and magneto-transport of undoped ZnO, Zn0.97Al0.03O, Zn0.95Fe0.05O and Zn0.92Al0.03Fe0.05O thin films grown on Si(100) substrate using pulsed laser deposition were investigated. The single phase nature of the films is confirmed by X-ray diffraction and Raman spectroscopy measurements. The possibility of Fe metal cluster in Fe doped/co-doped films is ruled out by Fe 2p core level photoelectron spectra. From O 1s core level spectra it is observed that oxygen vacancy is present in all the films. The undoped ZnO film shows magnetic ordering below ∼175 K, whereas Fe doped/codoped samples show magnetic ordering even at 300 K. The Al doped sample reveals paramagnetic behavior. The magneto-transport measurements suggest that the mobile carriers undergo exchange interaction with local magnetic moments.

  3. Zirconium doped nano-dispersed oxides of Fe, Al and Zn for destruction of warfare agents

    SciTech Connect

    Stengl, Vaclav; Houskova, Vendula; Bakardjieva, Snejana; Murafa, Nataliya; Marikova, Monika; Oplustil, Frantisek; Nemec, Tomas

    2010-11-15

    Zirconium doped nano dispersive oxides of Fe, Al and Zn were prepared by a homogeneous hydrolysis of the respective sulfate salts with urea in aqueous solutions. Synthesized metal oxide hydroxides were characterized using Brunauer-Emmett-Teller (BET) surface area and Barrett-Joiner-Halenda porosity (BJH), X-ray diffraction (XRD), infrared spectroscopy (IR), scanning electron microscopy (SEM) and energy-dispersive X-ray microanalysis (EDX). These oxides were taken for an experimental evaluation of their reactivity with sulfur mustard (HD or bis(2-chloroethyl)sulfide), soman (GD or (3,3'-Dimethylbutan-2-yl)-methylphosphonofluoridate) and VX agent (S-[2-(diisopropylamino)ethyl]-O-ethyl-methylphosphonothionate). The presence of Zr{sup 4+} dopant can increase both the surface area and the surface hydroxylation of the resulting doped oxides, decreases their crystallites' sizes thereby it may contribute in enabling the substrate adsorption at the oxide surface thus it can accelerate the rate of degradation of warfare agents. Addition of Zr{sup 4+} converts the product of the reaction of ferric sulphate with urea from ferrihydrite to goethite. We found out that doped oxo-hydroxides Zr-FeO(OH) - being prepared by a homogeneous hydrolysis of ferric and zirconium oxo-sulfates mixture in aqueous solutions - exhibit a comparatively higher degradation activity towards chemical warfare agents (CWAs). Degradation of soman or VX agent on Zr-doped FeO(OH) containing ca. 8.3 wt.% of zirconium proceeded to completion within 30 min.

  4. 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.

  5. Abnormal thermal expansion properties of cubic NaZn13-type La(Fe,Al)13 compounds.

    PubMed

    Li, Wen; Huang, Rongjin; Wang, Wei; Zhao, Yuqiang; Li, Shaopeng; Huang, Chuanjun; Li, Laifeng

    2015-02-28

    The cubic NaZn13-type La(Fe,Al)13 compounds were synthesized, and their linear thermal expansion properties were investigated in the temperature range of 4.2-300 K. It was found that these compounds exhibit abnormal thermal expansion behavior, i.e., pronounced negative thermal expansion (NTE) or zero thermal expansion (ZTE) behavior, below the Curie temperature due to the magnetovolume effect (MVE). Moreover, in the La(Fe,Al)13 compounds, the modification of the coefficient of thermal expansion (CTE) as well as the abnormal thermal expansion (ATE) temperature-window is achieved through optimizing the proportion of Fe and Al. Typically, the average CTE of the LaFe13-xAlx compounds with x = 1.8 reaches as large as -10.47 × 10(-6) K(-1) between 100 and 225 K (ΔT = 125 K). Also, the ZTE temperature-window of the LaFe13-xAlx compounds with x = 2.5 and x = 2.7 could be broadened to 245 K (from 5 to 250 K). Besides, the magnetic properties of these compounds were measured and correlated with the abnormal thermal expansion behavior. The present results highlight the potential application of such La(Fe,Al)13 compounds with abnormal thermal expansion properties in cryogenic engineering.

  6. 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.

  7. Selective recovery of dissolved Fe, Al, Cu, and Zn in acid mine drainage based on modeling to predict precipitation pH.

    PubMed

    Park, Sang-Min; Yoo, Jong-Chan; Ji, Sang-Woo; Yang, Jung-Seok; Baek, Kitae

    2015-02-01

    Mining activities have caused serious environmental problems including acid mine drainage (AMD), the dispersion of mine tailings and dust, and extensive mine waste. In particular, AMD contaminates soil and water downstream of mines and generally contains mainly valuable metals such as Cu, Zn, and Ni as well as Fe and Al. In this study, we investigated the selective recovery of Fe, Al, Cu, Zn, and Ni from AMD. First, the speciation of Fe, Al, Cu, Zn, and Ni as a function of the equilibrium solution pH was simulated by Visual MINTEQ. Based on the simulation results, the predicted pHs for the selective precipitation of Fe, Al, Cu, and Zn/Ni were determined. And recovery yield of metals using simulation is over 99 %. Experiments using artificial AMD based on the simulation results confirmed the selective recovery of Fe, Al, Cu, and Zn/Ni, and the recovery yields of Fe/Al/Cu/Zn and Fe/Al/Cu/Ni mixtures using Na2CO3 were 99.6/86.8/71.9/77.0 % and 99.2/85.7/73.3/86.1 %, respectively. After then, the simulation results were applied to an actual AMD for the selective recovery of metals, and the recovery yields of Fe, Al, Cu, and Zn using NaOH were 97.2, 74.9, 66.9, and 89.7 %, respectively. Based on the results, it was concluded that selective recovery of dissolved metals from AMD is possible by adjusting the solution pH using NaOH or Na2CO3 as neutralizing agents.

  8. Implementing Lecane quadridentata acute toxicity tests to assess the toxic effects of selected metals (Al, Fe and Zn).

    PubMed

    Guzmán, Félix Torres; González, Francisco Javier Avelar; Martínez, Roberto Rico

    2010-03-01

    An environmental study revealed that three metals (Al, Fe and Zn) are common in the San Pedro River (SPR) (Aguascalientes, Mexico). Regrettably, in many samples the concentrations of these metals exceeded the maximum allowed toxicant concentrations levels as defined in by Mexican legislation. The highest concentrations of the three metals were found during the 2005 dry season, with elevated Al concentrations present along the entire river. Not surprisingly, the highest concentrations for all three metals came from locations adjacent to industrial areas. Estimates of the contribution of these metals to total toxicity revealed that these three metals are important contaminants of the river and responsible for most of the lethal toxicity found in environmental samples. To assess the importance of these reports, we conducted acute toxicity tests to determine LC50 for Al, Fe and Zn on the freshwater rotifer Lecane quadridentata. This permitted us to estimate the contribution of these metals to total toxicity during 2005-2006. Based on LC50 values, all three metals should be considered very toxic, with the zinc LC50 value (0.12 mg L(-1)) making it the most toxic metal for L. quadridentata. This approach can be applied to other sites with similar concentrations of these metals.

  9. 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.

  10. Theoretical investigations of the spin-Hamiltonian parameters and local structural distortion of Fe(3+): ZnAl2O4 crystals.

    PubMed

    Yang, Zi-Yuan

    2014-10-15

    The relations between the spin-Hamiltonian (SH) parameters and the structural parameters of the Fe(3+) ions in Fe(3+): ZnAl2O4 crystals have been established by means of the microscopic spin Hamiltonian theory and the superposition model (SPM). On the basis of this, the local structure distortion, the second-order zero-field splitting (ZFS) parameter D, the fourth-order ZFS parameter (a-F), and the Zeeman g-factors g factors: g//, g⊥, and Δg(=g//-g⊥) for Fe(3+) ions in Fe(3+): ZnAl2O4 crystals, for the first time taking into account the electronic magnetic interactions, i.e. the spin-spin (SS), the spin-other-orbit (SOO), and the orbit-orbit (OO) interactions, besides the well-known spin-orbit (SO) interaction, are theoretically investigated using complete diagonalization method (CDM). This investigation reveals that the local structure distortion effect plays an important role in explaining the spectroscopic properties of Fe(3+) ions in Fe(3+): ZnAl2O4 crystals. The theoretical second-order ZFS parameter D, the fourth-order ZFS parameter (a-F), and the Zeeman g-factors: g//, g⊥, and Δg of the ground state for Fe(3+) ion in Fe(3+): ZnAl2O4 crystals yield a good agreement with experiment findings by taking into account the lattice distortions: ΔR=0.0191nm and Δθ=0.076°. In conclusion, our research shows that there is a slight local structure distortion for Fe(3+) ions in Fe(3+): ZnAl2O4 crystals, but the site of Fe(3+) still retains D3d symmetry. On the other hand, it is found for Fe(3+) ions in Fe(3+): ZnAl2O4 crystals that the SO mechanism is the most important one, whereas the contributions to the SH parameters from other four mechanisms, including the SS, SOO, OO, and SO∼SS∼SOO∼OO mechanisms are not appreciable, especially for the ZFS parameter D.

  11. [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.

  12. 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

  13. 57Fe NMR study of the magnetoelectric hexaferrite Ba0.5Sr1.5Zn2Fe12O22 and Ba0.5Sr1.5Zn2(Fe0.92Al0.08)12O22

    NASA Astrophysics Data System (ADS)

    Kwon, Sangil; Yoon, Dong Young; Lee, Soonchil; Chai, Yi Sheng; Chun, Sae Hwan; Kim, Kee Hoon

    2013-08-01

    Magnetoelectric hexaferrite Ba0.5Sr1.5Zn2Fe12O22 (BSZFO) and Ba0.5Sr1.5Zn2(Fe0.92Al0.08)12O22 (BSZFAO) were investigated by 57Fe nuclear magnetic resonance (NMR). The spin-canting angles of all NMR peaks were measured to assign each peak to corresponding Fe3+ sites. It was revealed that the spin-canting angle of Fe3+ ions at off-centered octahedra is fixed and Al3+ ions substitute for Fe3+ ions at those sites. The temperature dependence of the NMR frequency indicates that the low-temperature excitation is spin wave in ferromagnetic phase.

  14. Accumulation of Al, Mn, Fe, Cu, Zn, Cd and Pb by the bryophyte Scapania undulata in three upland waters of different pH.

    PubMed

    Vincent, C D; Lawlor, A J; Tipping, E

    2001-01-01

    Measurements were made of the contents of Al, Mn, Fe, Cu, Zn, Cd and Pb in Scapania undulata in three streams (D2, D5, D11) in the English Lake District. The stream waters had average pH values of 5.35 (D2), 5.81 (D5) and 7.26 (D11), the main differences in other major chemical components being in Mg, Al, Ca and alkalinity. There was generally more metal accumulation in the older parts of the plants, but this was not significant in all cases. Extents of accumulation varied with stream pH and dissolved metal concentration. For Al, accumulation was greatest in streams D2 and D5. Mn accumulated most in D5 and Fe was without preference. Cu, Zn and Cd accumulated mostly in the plants in stream D11 and Pb accumulated more in D5 and D11. In terms of enrichment factors (amount of metal in the plants divided by stream water concentration) the sequence was Zn < Cd < Cu < Mn < Pb < Al < Fe. Laboratory experiments supported the findings of the field data, providing evidence that uptake increases with pH at constant total metal concentration. The results are interpreted qualitatively in terms of the chemical speciation of the metals in the stream water and competition between metal ions and protons at the plant-water interface. It is suggested that Al, Cu, Zn, Cd and Pb behave according to chemical complexation, whereas redox processes and/or colloidal interactions may be significant for Mn and Fe.

  15. Al doping effect on magnetic phase transitions of magnetoelectric hexaferrite Ba0.7Sr1.3Zn2(Fe1-xAlx)12O22

    NASA Astrophysics Data System (ADS)

    Chang, Hun; Lee, Hak Bong; Song, Young-Sang; Chung, Jae-Ho; Kim, S. A.; Oh, I. H.; Reehuis, M.; Schefer, J.

    2012-02-01

    We investigated the effect of Al doping in magnetic properties of the Y-type hexaferrite Ba0.7Sr1.3Zn2(Fe1-xAlx)12O22 (0≤x≤0.12), which exhibit field-induced magnetoelectric polarization. We find that Al doping increases the pitch of a spin helix and enhances c-axis magnetization, stabilizing longitudinal conical phases. These conical phases eventually collapse at x≥ 0.10. These results suggest that competitions between easy-axis and easy-plane anisotropy fields play a key role in generating stable magnetoelectric polarization in Y-type hexaferrites.

  16. Formation of mixed Al-Fe colloidal sorbent and dissolved-colloidal partitioning of Cu and Zn in the Cement Creek - Animas River Confluence, Silverton, Colorado

    USGS Publications Warehouse

    Schemel, L.E.; Kimball, B.A.; Runkel, R.L.; Cox, M.H.

    2007-01-01

    Transport and chemical transformations of dissolved and colloidal Al, Fe, Cu and Zn were studied by detailed sampling in the mixing zone downstream from the confluence of Cement Creek (pH 4.1) with the Animas River (pH 7.6). Complete mixing resulted in circumneutral pH in the downstream reach of the 1300 m study area. All four metals were transported through this mixing zone without significant losses to the streambed, and they exhibited transformations from dissolved to colloidal forms to varying degrees during the mixing process. Nearly all of the Al formed colloidal hydrous Al oxides (HAO) as pH increased (4.8-6.5), whereas colloidal hydrous Fe oxides (HFO) were supplied by Cement Creek as well as formed in the mixing zone primarily at higher pH (>6.5). The short travel time through the mixing zone (approx. 40 min) and pH limited the formation of HFO from dissolved Fe2+ supplied by Cement Creek. Although the proportions of HAO and HFO varied as the streams mixed, the colloidal sorbent typically was enriched in HAO relative to HFO by a factor of 1.5-2.1 (by mole) in the pH range where dissolved-to-colloidal partitioning of Cu and Zn was observed. Model simulations of sorption by HFO (alone) greatly underestimated the dissolved-to-colloidal partitioning of Zn. Previous studies have shown that HAO-HFO mixtures can sorb greater amounts of Zn than HFO alone, but the high Zn-to-sorbent ratio in this mixing zone could also account for greater partitioning. In contrast to Zn, comparisons with model simulations did not show that Cu sorption was greater than that for HFO alone, and also indicated that sorption was possibly less than what would be expected for a non-interactive mixture of these two sorbents. These field results for Cu, however, might be influenced by (organic) complexation or other factors in this natural system. Laboratory mixing experiments using natural source waters (upstream of the confluence) showed that the presence of HFO in the mixed sorbent

  17. Enhancement of photoinduced electrical properties of Al-doped ZnO/BiFeO3 layered thin films prepared by chemical solution deposition

    NASA Astrophysics Data System (ADS)

    Katayama, Takeshi; Sakamoto, Wataru; Yuitoo, Isamu; Takeuchi, Teruaki; Hayashi, Koichiro; Yogo, Toshinobu

    2015-10-01

    Polycrystalline BiFeO3 and Al-doped ZnO/BiFeO3 bilayered thin films were prepared on Pt/TiOx/SiO2/Si substrates by chemical solution deposition. Their photoinduced electrical properties under blue light irradiation were characterized. The rapid on/off response of the photocurrent to light in unpoled BiFeO3 (BFO) and Al-doped ZnO/BiFeO3 (AZO/BFO) thin films was demonstrated. The AZO/BFO layered film exhibited an approximately triple-digit larger photocurrent in comparison with a BFO single-layer film. This is attributable to the photoexcited carrier generation effect at the interface between AZO (n-type) and BFO (p-type) films. Furthermore, in the AZO/BFO layered structure, the direction of the internal bias electric field caused by the space charge distribution in the unpoled BFO film is the same as that of the built-in electric field by forming a p-n junction of AZO and BFO layers. Photovoltaic properties were also improved by fabricating such a layered film. On the other hand, when the placement of BFO to AZO was reversed, the photoelectric current decreased to approximately one-tenth of that of the BFO single-layer film. In the BFO/AZO film, the internal electric field at the p-n junction between BFO and AZO is considered to have an orientation opposite to the self-bias field formed in the BFO film.

  18. Study of cation distributions in spinel ferrites MxMn1-xFe2O4 (M=Zn, Mg, Al)

    NASA Astrophysics Data System (ADS)

    Ding, L. L.; Xue, L. C.; Li, Z. Z.; Li, S. Q.; Tang, G. D.; Qi, W. H.; Wu, L. Q.; Ge, X. S.

    2016-10-01

    Powder samples of the ferrites MxMn1-xFe2O4 (M = Zn, Mg, Al) were prepared using a chemical co-precipitation method. X-ray diffraction analysis showed that the three series of samples had a single-phase cubic spinel structure and that there was a decrease in the lattice parameters with increasing x. There were different dependences on the doping level x of the magnetic moments ( μ exp ) for the three series of samples measured at 10 K. We found a non-monotonic behavior for μ exp as a function x for the Zn doped samples with a maximum at x = 0.4, while μ exp decreased monotonically with increasing x for the Mg and Al doped samples. On the basis of the O2p itinerant electron model, the magnetic moment direction of the Mn3+ cations is expected to be antiparallel to those of the Mn2+ and Fe cations in these samples. With this assumption, the curves of μ exp versus x for the three series of samples were fitted using a quantum-mechanical potential barrier model earlier proposed by our group, and the cation distributions were obtained.

  19. Complexation of desferricoprogen with trivalent Fe, Al, Ga, In and divalent Fe, Ni, Cu, Zn metal ions: effects of the linking chain structure on the metal binding ability of hydroxamate based siderophores.

    PubMed

    Enyedy, Eva A; Pócsi, István; Farkas, Etelka

    2004-11-01

    Complexes of the natural siderophore, desferricoprogen (DFC), with several trivalent and divalent metal ions in aqueous solution were studied by pH-potentiometry, UV-Vis spectrophotometry and cyclic voltammetry. DFC was found to be an effective metal binding ligand, which, in addition to Fe(III), forms complexes of high stability with Ga(III), Al(III), In(III), Cu(II), Ni(II) and Zn(II). Fe(II), however, is oxidized by DFC under anaerobic conditions and Fe(III) complexes are formed. By comparing the results with those of desferrioxamine B (DFB), it can be concluded that the conjugated beta-double bond slightly increases the stability of the hydroxamate chelates, consequently increases the stability of mono-chelated complexes of DFC. Any steric effect by the connecting chains arises only in the bis- and tris-chelated complexes. With metal ions possessing a relatively big ionic radius (Cu(II), Ni(II), Zn(II), In(III)) DFC, containing a bit longer chains than DFB, forms slightly more stable complexes. With smaller metal ions the trend is the opposite. Also a notable difference is that stable trinuclear complex, [Cu(3)L(2)], is formed with DFC but not with DFB. Possible bio-relevance of the Fe(II)/Fe(III) results is also discussed in the paper.

  20. Effects of Al substitution and thermal annealing on magnetoelectric Ba0.5Sr1.5Zn2Fe12O22 investigated by the enhancement factor of 57Fe nuclear magnetic resonance.

    PubMed

    Kwon, Sangil; Kang, Byeongki; Kim, Changsoo; Jo, Euna; Lee, Soonchil; Chai, Yi Sheng; Chun, Sae Hwan; Kim, Kee Hoon

    2014-04-09

    The magnetoelectric properties of hexaferrite Ba0.5Sr1.5Zn2Fe12O22 are significantly improved by Al substitution and thermal annealing. Measuring the enhancement factor of 57Fe NMR, we found direct microscopic evidence that the magnetic moments of the L and S blocks are rotated by a magnetic field in such a way as to increase the net magnetic moment of a magnetic unit, even after the field is removed. Al substitution makes magnetoelectric property arise easily by suppressing the easy-plane anisotropy. The effect of thermal annealing is to stabilize the multiferroic state by reducing the number of pinning sites and the electron spin fluctuation. The transverse conic structure gradually changes to the alternating longitudinal conic structure where spins fluctuate more severely.

  1. Production and Isomeric Distribution of Xanthylium Cation Pigments and Their Precursors in Wine-like Conditions: Impact of Cu(II), Fe(II), Fe(III), Mn(II), Zn(II), and Al(III).

    PubMed

    Guo, Anque; Kontoudakis, Nikolaos; Scollary, Geoffrey R; Clark, Andrew C

    2017-03-09

    This study establishes the influence of Cu(II), Fe(II), Fe(III), Zn(II), Al(III), and Mn(II) on the oxidative production of xanthylium cations from (+)-catechin and either tartaric acid or glyoxylic acid in model wine systems. The reaction was studied at 25 °C using UHPLC and LC-HRMS for the analysis of phenolic products and their isomeric distribution. In addition to the expected products, a colorless product, tentatively assigned as a lactone, was detected for the first time. The results show the importance of Fe ions and a synergistic influence of Mn(II) in degrading tartaric acid to glyoxylic acid, whereas the other metal ions had minimal activity in this mechanistic step. Fe(II) and Fe(III) were shown to mediate the (+)-catechin-glyoxylic acid addition reaction, a role previously attributed to only Cu(II). Importantly, the study demonstrates that C-8 addition products of (+)-catechin are promoted by Cu(II), whereas C-6 addition products are promoted by Fe ions.

  2. Diverse Reactivity of ECp* (E = Al, Ga) toward Low-Coordinate Transition Metal Amides [TM(N(SiMe3)2)2] (TM = Fe, Co, Zn): Insertion, Cp* Transfer, and Orthometalation.

    PubMed

    Weßing, Jana; Göbel, Christoph; Weber, Birgit; Gemel, Christian; Fischer, Roland A

    2017-03-20

    The reactivity of the carbenoid group 13 metal ligands ECp* (E = Al, Ga) toward low valent transition metal complexes [TM(btsa)2] (TM = Fe, Co, Zn; btsa = bis(trimethylsilyl)amide) was investigated, revealing entirely different reaction patterns for E = Al and Ga. Treatment of [Co(btsa)2] with AlCp* yields [Cp*Co(μ-H)(Al(κ(2)-(CH2SiMe2)NSiMe3)(btsa))] (1) featuring an unusual heterometallic bicyclic structure that results from the insertion of AlCp* into the TM-N bond with concomitant ligand rearrangement including C-H activation at one amide ligand. For [Fe(btsa)2], complete ligand exchange gives FeCp*2, irrespective of the employed stoichiometric ratio of the reactants. In contrast, treatment of [TM(btsa)2] (TM = Fe, Co) with GaCp* forms the 1:1 and 1:2 adducts [(GaCp*)Co(btsa)2] (2) and [(GaCp*)2Fe(btsa)2] (3), respectively. The tendency of AlCp* to undergo Cp* transfer to the TM center appears to be dependent on the nature of the TM center: For [Zn(btsa)2], no Cp* transfer is observed on reaction with AlCp*; instead, the insertion product [Zn(Al(η(2)-Cp*)(btsa))2] (4) is formed. In the reaction of [Co(btsa)2] with the trivalent [Cp*AlH2], transfer of the amide ligands without further ligand rearrangement is observed, leading to [Co(μ-H)4(Al(η(2)-Cp*)(btsa))2] (5).

  3. Magnetic origin of giant magnetoelectricity in doped Y-type hexaferrite Ba(0.5)Sr(1.5)Zn(2)(Fe(1-x)Al(x))(12)O(22).

    PubMed

    Noh, Woo-Suk; Ko, Kyung-Tae; Chun, Sae Hwan; Kim, Kee Hoon; Park, Byeong-Gyu; Kim, Jae-Young; Park, Jae-Hoon

    2015-03-20

    We investigated site-specific magnetic behaviors of multiferroic Ba(0.5)Sr(1.5)Zn(2)(Fe(1-x)Al(x))(12)O(22) using Fe L(2,3)-edge x-ray magnetic circular dichroism. The Al dopants mostly replace the Fe(3+) ions at octahedral (O(h)) sites, which contribute unquenched angular momenta through off-centering displacements. This replacement greatly reduces the magnetic anisotropy energy to change the magnetic order from a helical to a heliconical type with enhanced magnetoelectric susceptibility (α(ME)). The tetrahedral (T(d)) Fe sites exhibit magnetic hysteresis distinguishable from that of the O(h) sites, especially at low magnetic fields. These results provide essential clues for the heliconical order with a giant α(ME) and multibit memory effects in the Al-doped Y-type hexaferrite.

  4. The Aqueous Ca2+ System, in Comparison with Zn2+, Fe3+, and Al3+: An Ab Initio Molecular Dynamics Study

    SciTech Connect

    Bogatko, Stuart A.; Cauet, Emilie L.; Bylaska, Eric J.; Schenter, Gregory K.; Fulton, John L.; Weare, John H.

    2013-02-21

    Results of Ab Initio Molecular Dynamics (AIMD) simulations of a Ca2+ ion in an aqueous environment (64 waters, 38ps=5ps equilibration + 33ps data collection, 300K) are reported. The 1st hydration shell contains 6-7 waters with d(OH) = 0.97Å (identical to our bulk water estimate) and average tilt angle, I = 32º. The 1st maximum in the radial distribution function occurs at GCaO(r) = 2.45Å. Our results compare well with published experimental structural data from X-Ray Absorption (XAFS) and Neutron Diffraction. We also generate simulated XAFS spectra using a 1st principles MD-XAFS procedure and show quantitative agreement with experimental XAFS data from a 0.2m Ca(ClO4)2 aqueous solution. The Ca2+ 1st shell water dipole moment of 3.1D is identical to our bulk water estimate (3.1D). The structured 2nd hydration shell, composed of ~16.5 waters, has a maximum at GCaO(r) =4.6Å. The average 2nd shell dipole moment = 2.9D, is suppressed relative to bulk water values. Detailed H-bond analysis demonstrates the waters in this shell predominately coordinate 1st shell waters with a trigonally structured H-bond network. Two exchanges between the 1st hydration shell and the bulk were observed. These were consistent with a dissociative and dissociative interchange Eigen-Wilkins ligand exchange mechanism. Many transfers between the 2nd shell and bulk are detected for Ca2+ allowing an estimation of the 2nd shell mean residence time (MRT) of 4.6ps. Comparison of the Ca2+ hydration shell structure and dynamics with those of the recently reported Zn2+, Fe3+ and Al3+ cation species show that the 1st and 2nd hydration shell parameters, d(M-OI) distance, CNII, H-bond d(OI-OII) distance and %Tetrahedral structure are correlated with cation charge density, the ratio of cation charge (Z) and size (Rion). However, important exceptions are d(M-OII) and the 2nd shell Mean Residence Time (MRT). These differences are explained in terms of the 1st shell structure parameters (d(M-OI) distance

  5. Phase Evolution and Thermal Analysis of Nanocrystalline AlCrCuFeNiZn High Entropy Alloy Produced by Mechanical Alloying

    NASA Astrophysics Data System (ADS)

    Koundinya, N. T. B. N.; Sajith Babu, C.; Sivaprasad, K.; Susila, P.; Kishore Babu, N.; Baburao, J.

    2013-10-01

    A multi-component nanocrystalline AlCrCuFeNiZn high entropy alloy with 12 nm crystallite size was successfully synthesized using high energy ball milling. The progress of solid solution formation during milling was analyzed using XRD. A major portion of the HEA is observed to be BCC in crystal structure after 30 h of milling. Thermal analysis showed that HEA powders exhibited exponential oxidation characteristics. Thermal analysis showed that low activation energy was sufficient to start recrystallization because of high energy stored in the milled powders. The crystallite size after consolidation is in nanocrystalline range due to the sluggish diffusion of atoms and nanotwinning. After consolidation, the crystallite size is around 79 nm. Samples sintered at 850 °C for 2 h exhibited high hardness values of 700 ± 15 HV1.0, major volume fraction of the phases are having FCC crystal structure along with a minor phase having BCC crystal structure. Due to positive enthalpy mixing of Cu with other elements, decomposition of BCC to new FCC phases occurs.

  6. Producing ZnFe2O4 thin films from ZnO/FeO multilayers

    NASA Astrophysics Data System (ADS)

    Salcedo Rodríguez, Karen L.; Hoffmann, Martin; Golmar, Federico; Pasquevich, Gustavo; Werner, Peter; Hergert, Wolfram; Rodríguez Torres, Claudia E.

    2017-01-01

    The present work investigates the structural and magnetic properties of ZnFe2O4 thin films obtained from ZnO/FeO multilayers deposited on MgO substrate by DC reactive sputtering. We show that this method is good to grow efficiently ordered ZnFe2O4 films. The quality of the thin films is ensured by TEM measurements, which showed a well ordered film of ZnFe2O4. The magnetic properties of these thin films present still minimal differences when compared to bulk ZnFe2O4 powders. They exhibit a ferromagnetic-like behavior at low temperatures, whereas ZnFe2O4 is expected to be antiferromagnetic. We found that the magnetic signal originated from the film surface, where cation inversion was visible from grazing incidence X-ray fluorescence measurements. The inversion of Fe ions with Zn ions caused a magnetic spin glass state, which created then the ferromagnetic-like behavior differently to bulk ZnFe2O4. These facts point to possible routes in order to improve the growing process of ZnFe2O4 via ZnO/FeO multilayers.

  7. Phase Equilibria Studies in the System ZnO-``FeO''-Al2O3-CaO-SiO2 Relevant to Imperial Smelting Furnace Slags: Part II

    NASA Astrophysics Data System (ADS)

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

    2010-04-01

    The phase equilibria and the liquidus temperatures in the system ZnO-“FeO”-Al2O3-CaO-SiO2 have been determined experimentally in equilibrium with metallic iron. Specifically, the effects of Al2O3 concentrations in Imperial Smelting Furnace slags are identified, and the results are presented in the form of pseudo-ternary sections ZnO-“FeO”-(Al2O3 + CaO + SiO2) in which CaO/SiO2 = 0.93 and (CaO + SiO2)/Al2O3 = 5.0 and 3.5, respectively. It was found that, in the presence of Al2O3, the spinel phase is formed, the spinel primary phase field expands, and the wustite and melilite primary phase fields are reduced in size with an increasing Al2O3 concentration. The implications of the findings to industrial practice are discussed.

  8. Al-Co-Fe (030)

    NASA Astrophysics Data System (ADS)

    Carow-Watamura, U.; Louzguine, D. V.; Takeuchi, A.

    This document is part of Part 1 http://dx.doi.org/10.1007/9getType="URL"/> 'Systems from Ag-Al-Ca to Au-Pd-Si' of Subvolume B 'Physical Properties of Ternary Amorphous Alloys' of Volume 37 'Phase Diagrams and Physical Properties of Nonequilibrium Alloys' of Landolt-Börnstein - Group III 'Condensed Matter'. It contains the Chapter 'Al-Co-Fe (030)' with the content:

  9. 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.

  10. Doping effect on the structural properties of Cu1-x(Ni, Zn, Al and Fe)xO samples (0

    NASA Astrophysics Data System (ADS)

    Amaral, J. B.; Araujo, R. M.; Pedra, P. P.; Meneses, C. T.; Duque, J. G. S.; dos S. Rezende, M. V.

    2016-09-01

    In this work, the effect of insertion of transition metal, TM (=Ni, Zn, Al and Fe), ions in Cu1-xTMxO samples (0Zn-doped samples show a small amount of spurious phases for concentrations above x=0.05. Based on these results, a defect disorder study for using atomistic computational simulations which is based on the lattice energy minimization technique is employed to predict the location of the dopant ions in the structure. In agreement with XRD data, our computational results indicate that the trivalent (Al and Fe ions) are more favorable to be incorporated into CuO matrix than the divalent (Ni and Zn ions).

  11. Rapidly solidified NiAl and FeAl

    NASA Technical Reports Server (NTRS)

    Gaydosh, D. J.; Crimp, M. A.

    1984-01-01

    Melt spinning was used to produce rapidly solidified ribbons of the B2 intermetallics NiAl and FeAl. Both Fe-40Al and Fe-45Al possessed some bend ductility in the as spun condition. The bend ductility of Fe-40Al, Fe-45Al, and equiatomic NiAl increased with subsequent heat treatment. Heat treatment at approximately 0.85 T (sub m) resulted in significant grain growth in equiatomic FeAl and in all the NiAl compositions. Low bend ductility in both FeAl and NiAl generally coincided with intergranular failure, while increased bend ductility was characterized by increasing amounts of transgranular cleavage fracture.

  12. Steam reforming of ethanol at moderate temperature: Multifactorial design analysis of Ni/La 2O 3-Al 2O 3, and Fe- and Mn-promoted Co/ZnO catalysts

    NASA Astrophysics Data System (ADS)

    Torres, José Antonio; Llorca, Jordi; Casanovas, Albert; Domínguez, Montserrat; Salvadó, Joan; Montané, Daniel

    Novel Co (10%) catalysts supported on ZnO and promoted with Fe and Mn (1%) were synthesized and characterized by high-resolution transmission electron microscopy (HRTEM), electron energy-loss spectroscopy (EELS), X-ray diffraction (XRD) and X-ray photoelectron spectra (XPS). Their catalytic activity for steam reforming of ethanol was compared with that of Ni catalysts supported on La 2O 3-Al 2O 3. Experiments at 400 and 500 °C, steam to carbon ratios of 2 and 4, and a wide interval of contact time were analyzed following a multifactorial experimental design. At 500 °C and a steam to carbon molar ratio of 4, complete conversion of ethanol was achieved above a contact time of 200 g min mol -1 for all catalysts. The ratio of selectivity between hydrogen and methane was around 23 mol H2/mol CH4 in the Co catalysts, while it approached the thermodynamic equilibrium (5.7 mol H2/mol CH4) in the Ni catalysts. The Co catalysts do not promote methane-forming reactions like ethanol cracking and acetaldehyde decarbonilation, nor do they facilitate the reverse methane steam reforming reaction. The catalytic behavior of cobalt is enhanced by promotion with iron or manganese through the formation of bimetallic particles, which facilitates cobalt reducibility. This suggests that Co-Mn/ZnO and Co-Fe/ZnO catalysts have a good potential for their use for ethanol reforming at moderate temperature.

  13. Enhanced mechanism investigation on violet-blue emission of ZnO films by incorporating Al and Zn to form ZnO-Al-Zn films

    NASA Astrophysics Data System (ADS)

    Chen, Haixia; Ding, Jijun; Wang, Xiaomeng; Wang, Xiaojun; Chen, Guoxiang; Ma, Li

    2016-12-01

    ZnO, ZnO-Zn, ZnO-Al0.10-Zn and ZnO-Al0.15-Zn are deposited on glass substrates by radio frequency and direct current magnetron co-sputtering. Photoluminescence (PL) measurements show that the optical performances of samples are strongly dependent on both Al and Zn incoprations. The origin of the defect-related PL emission has been investigated for a long time. Several different hypotheses have been proposed, however, they are still under investigation. Especially for the blue emissions, its origins have been debated intensely for more than thirty years because of its sparsity and instability. In this paper, both violet and blue emissions are observed in all the samples. PL emission decreases sharply as Zn is doped in ZnO to form ZnO-Zn film. However, as both Al and Zn are simultaneously doped in ZnO to form ZnO-Al0.10-Zn film, PL emission conversely increases and attains the maxima. In addition, PL emission decreases again with the increase of Al target power to form ZnO-Al0.15-Zn film. We concluded that violet-blue emission is ascribed to defect types in reverse change trend with interstitial Zn, such as Zn vacancies. This is different from previous universal hypothesis that violet-blue emission is from interstitial Zn defects.

  14. Microstructural Evolution of the 55 Wt Pct Al-Zn Coating During Press Hardening

    NASA Astrophysics Data System (ADS)

    Lee, Chang Wook; De Cooman, Bruno Charles

    2014-09-01

    Press hardening is increasingly being used to produce ultra-high strength steel parts for passenger cars. Al-Si, Zn, and Zn-alloy coatings have been used to provide corrosion protection to press hardening steel grades. The use of coatings has drawbacks such as coating delamination or liquid metal-induced embrittlement. In the present work, the microstructural evolution of Al-Zn coating during press hardening was studied. The 55 wt pct Al-Zn coating can in principle provide both Al barrier protection and Zn cathodic protection to press hardened steel. During the heat treatment associated with the press hardening, the 55 wt pct Al-Zn alloy coating is converted to an intermetallic surface layer of Fe2Al5 and a FeAl intermetallic diffusion layer. The Zn is separated from both intermetallic compounds and accumulates at grain boundaries and at the surface. This Zn separation process is beneficial in terms of providing cathodic protection to Al-Zn coated press hardening steel.

  15. SERS and DFT investigation of 1-(2-pyridylazo)-2-naphthol and its metal complexes with Al(III), Mn(II), Fe(III), Cu(II), Zn(II) and Pb(II)

    NASA Astrophysics Data System (ADS)

    Szabó, László; Herman, Krisztian; Mircescu, Nicoleta E.; Fălămaş, Alexandra; Leopold, Loredana F.; Leopold, Nicolae; Buzumurgă, Claudia; Chiş, Vasile

    The development of surface-enhanced Raman scattering (SERS) as a prospective analytical methodology for detection of metal ions was shown in recent years by several studies on metal complexes. In this work, 1-(2-pyridylazo)-2-naphthol (PAN) and its Al(III), Mn(II), Fe(III), Cu(II), Zn(II) and Pb(II) complexes were studied by FTIR, FT-Raman and surface enhanced Raman spectroscopies. Molecular geometry optimization, molecular electrostatic potential (MEP) distribution and vibrational frequencies calculations were performed using the hybrid B3LYP exchange-correlation functional for the PAN molecule and its bidentate complexes. The calculated MEP distributions indicated the atoms with highest electronegativity, the adsorption to the silver surface occurring through these atoms. Based on experimental and theoretical data we were able to identify unique and representative features, useful for the identification of each PAN-metal complex.

  16. SERS and DFT investigation of 1-(2-pyridylazo)-2-naphthol and its metal complexes with Al(III), Mn(II), Fe(III), Cu(II), Zn(II) and Pb(II).

    PubMed

    Szabó, László; Herman, Krisztian; Mircescu, Nicoleta E; Fălămaş, Alexandra; Leopold, Loredana F; Leopold, Nicolae; Buzumurgă, Claudia; Chiş, Vasile

    2012-07-01

    The development of surface-enhanced Raman scattering (SERS) as a prospective analytical methodology for detection of metal ions was shown in recent years by several studies on metal complexes. In this work, 1-(2-pyridylazo)-2-naphthol (PAN) and its Al(III), Mn(II), Fe(III), Cu(II), Zn(II) and Pb(II) complexes were studied by FTIR, FT-Raman and surface enhanced Raman spectroscopies. Molecular geometry optimization, molecular electrostatic potential (MEP) distribution and vibrational frequencies calculations were performed using the hybrid B3LYP exchange-correlation functional for the PAN molecule and its bidentate complexes. The calculated MEP distributions indicated the atoms with highest electronegativity, the adsorption to the silver surface occurring through these atoms. Based on experimental and theoretical data we were able to identify unique and representative features, useful for the identification of each PAN-metal complex.

  17. Magnetic field reversal of electric polarization and magnetoelectric phase diagram of the hexaferrite Ba1.3Sr0.7Co0.9Zn1.1Fe10.8Al1.2O22

    NASA Astrophysics Data System (ADS)

    Shen, Shipeng; Yan, Liqin; Chai, Yisheng; Cong, Junzhuang; Sun, Young

    2014-01-01

    Low magnetic field reversal of electric polarization has been demonstrated in the multiferroic Y-type hexaferrite Ba1.3Sr0.7Co0.9Zn1.1Fe10.8Al1.2O22 single crystal. The maximum magnetoelectric coefficient at 200 K reaches 1065 ps/m near zero magnetic field. By a systematic investigation of magnetic field dependence of magnetic and dielectric responses at various temperatures, we obtained the magnetoelectric phase diagram describing the detailed evolution of the spin-induced ferroelectric phases with temperature and magnetic field. Below 225 K, the transverse spin cone can be stabilized at zero magnetic field, which is responsible for the reversal behavior of electric polarization. Our study reveals how to eventually achieve magnetic field reversal of electric polarization in hexaferrites at room temperature.

  18. Magnetocaloric effect in multiferroic Y-type hexaferrite Ba0.5Sr1.5Zn2(Fe0.92Al0.08)12O22

    NASA Astrophysics Data System (ADS)

    Xu, Wenfei; Yang, Jing; Shen, Yude; Bai, Wei; Zhang, Yuanyuan; Liu, Jia; Tang, Kai; Wang, Zhi; Duan, Chun-gang; Tang, Xiaodong; Chu, Junhao

    2014-06-01

    Magnetocaloric effect is investigated in multiferroic Ba0.5Sr1.5Zn2(Fe0.92Al0.08)12O22 ceramic with Y-type hexagonal system. Three magnetic transitions, from alternating longitudinal conical to mixed conical at ˜240 K, to ferrimagnetic at ˜297 K, further to paramagnetic at ˜702 K, are unambiguously determined. Furthermore, obvious MCE is shown, and the maximum values of the magnetic entropy change and relative cooling power are evaluated to be 1.53 JKg-1K-1 and 280 JKg-1 for a field change of 7 T, respectively. In addition, inverse MCE is also observed, which might be associated with the first-order magnetic phase transition between two incommensurate longitudinal conical phases.

  19. Catalytic behaviour and copper leaching of Cu0.10Zn0.90Al1.90Fe0.10O4 spinel for catalytic wet air oxidation of phenol.

    PubMed

    Xu, Aihua; Sun, Chenglin

    2012-06-01

    A Cu0.10Zn0.90Al1.90Fe0.10O4 spinel catalyst prepared by the sol-gel method was tested for catalytic wet air oxidation (CWAO) of phenol. The catalyst showed high activity for phenol degradation. During successive test at 170 degrees C, 100% phenol conversion and 95% chemical oxygen demand (COD) removal were observed. Results from scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FT-IR) and X-ray diffraction (XRD) indicated that the catalyst structure remained unchanged during reaction. From the analysis of temperature programmed reduction (TPR), diffuse reflectance UV-Vis spectra (DR UV-Vis) and activity assay at basic solution pH, it can be suggested that the highly dispersed copper ions on the catalyst surface were almost completely dissolved into the reaction solution, whereas the tetra-coordinated copper ions were not only stable against leaching but also active towards phenol degradation.

  20. Structural, morphological and magnetic properties of Al3+ substituted Ni0.25Cu0.20Zn0.55AlxFe2-xO4 ferrites synthesized by solid state reaction route

    NASA Astrophysics Data System (ADS)

    Rahman, K. R.; Chowdhury, F.-U.-Z.; Khan, M. N. I.

    Ni-Cu-Zn ferrite materials have been extensively used in electronic materials because of their outstanding properties at high frequencies. This work investigates the impact of Al substitution on the structure, morphology and magnetic properties of Ni0.25Cu0.20Zn0.55AlxFe2-xO4 (x = 0.00, 0.05, 0.10, 0.15 and 0.20) prepared by solid state reaction method. X-ray diffractometer (XRD), field emission scanning electron microscope (FESEM), impedance analyzer and Vibrating Sample Magnetometer (VSM) were used to characterize the properties of the samples. The XRD study confirmed the cubic spinel structure with single phase for all the samples. The lattice constant, X-ray density and bulk density decrease while the porosity and grain size increase with the increase of Al content in the samples. The frequency dependence of the complex permeability sintered at 1200 °C has been measured for toroidal samples in the frequency range between 1 kHz and 120 MHz at room temperature. The decrease in initial permeability has been explained on the basis of variation in grain size. The temperature dependence of the initial permeability has been measured in the temperature range between from 30 to 250 °C. Curie temperature (Tc) has been estimated from the temperature dependence of the permeability spectra for all samples. It is found that Curie temperatures and initial permeability (μi‧) decrease on Al substitution. The saturation magnetization has been measured at room temperature and it was found to decrease with increasing of Al3+ ions.

  1. Orientation relationship of eutectoid FeAl and FeAl2

    PubMed Central

    Scherf, A.; Kauffmann, A.; Kauffmann-Weiss, S.; Scherer, T.; Li, X.; Stein, F.; Heilmaier, M.

    2016-01-01

    Fe–Al alloys in the aluminium range of 55–65 at.% exhibit a lamellar microstructure of B2-ordered FeAl and triclinic FeAl2, which is caused by a eutectoid decomposition of the high-temperature Fe5Al8 phase, the so-called ∊ phase. The orientation relationship of FeAl and FeAl2 has previously been studied by Bastin et al. [J. Cryst. Growth (1978 ▸), 43, 745] and Hirata et al. [Philos. Mag. Lett. (2008 ▸), 88, 491]. Since both results are based on different crystallographic data regarding FeAl2, the data are re-evaluated with respect to a recent re-determination of the FeAl2 phase provided by Chumak et al. [Acta Cryst. (2010 ▸), C66, i87]. It is found that both orientation relationships match subsequent to a rotation operation of 180° about a 〈112〉 crystallographic axis of FeAl or by applying the inversion symmetry of the FeAl2 crystal structure as suggested by the Chumak data set. Experimental evidence for the validity of the previously determined orientation relationships was found in as-cast fully lamellar material (random texture) as well as directionally solidified material (∼〈110〉FeAl || solidification direction) by means of orientation imaging microscopy and global texture measurements. In addition, a preferential interface between FeAl and FeAl2 was identified by means of trace analyses using cross sectioning with a focused ion beam. On the basis of these habit planes the orientation relationship between the two phases can be described by (01)FeAl || (114) and [111]FeAl || [10]. There is no evidence for twinning within FeAl lamellae or alternating orientations of FeAl lamellae. Based on the determined orientation and interface data, an atomistic model of the structure relationship of Fe5Al8, FeAl and FeAl2 in the vicinity of the eutectoid decomposition is derived. This model is analysed with respect to the strain which has to be accommodated at the interface of FeAl and FeAl2. PMID:27047304

  2. Magnetic and optical properties of MgAl2O4-(Ni0.5Zn0.5)Fe2O4 thin films prepared by pulsed laser deposition.

    PubMed

    Misu, Takeshi; Sakamoto, Naonori; Shinozaki, Kazuo; Adachi, Nobuyasu; Suzuki, Hisao; Wakiya, Naoki

    2011-06-01

    Thin films composed of MgAl2O4 and (Ni0.5Zn0.5)Fe2O4 ([MA(100-x)-NZFx] films) were grown on fused SiO2 substrates by pulsed laser deposition. X-ray diffraction measurements revealed that the films were polycrystalline, and that their lattice constant varied linearly with composition, indicating the formation of a solid solution. The film with x=60 was paramagnetic and those with x ≥ 70 were ferromagnetic. The films had a transparency above 75% in the visible range, but the transparency decreased with the x value. The optical band gaps were 2.95, 2.55, 2.30 and 1.89 eV for x=20, 40, 60, 80 and 100, respectively. The Faraday rotation angle increased with x in the visible range, and the film with x=70 exhibited a value of 2000 degrees cm(-1) at 570 nm, which is comparable to the rotation angle of Y3Fe5O12. Owing to their high transparency, which extends into the visible range, the [MA(100-x)-NZFx] films can be used in novel magneto-optical devices.

  3. Improvement in the water retention characteristics of sandy loam soil using a newly synthesized poly(acrylamide-co-acrylic acid)/AlZnFe2O4 superabsorbent hydrogel nanocomposite material.

    PubMed

    Shahid, Shaukat Ali; Qidwai, Ansar Ahmad; Anwar, Farooq; Ullah, Inam; Rashid, Umer

    2012-08-03

    The use of some novel and efficient crop nutrient-based superabsorbent hydrogel nanocomposites (SHNCs), is currently becoming increasingly important to improve the crop yield and productivity, due to their water retention properties. In the present study a poly(Acrylamide-co-acrylic acid)/AlZnFe2O4 superabsorbent hydrogel nanocomposite was synthesized and its physical properties characterized using Energy Dispersive X-ray (EDX), FE-SEM and FTIR spectroscopic techniques. The effects of different levels of SHNC were studied to evaluate the moisture retention properties of sandy loam soil (sand 59%, silt 21%, clay 19%, pH 7.4, EC 1.92 dS/m). The soil amendment with 0.1, 0.2, 0.3 and 0.4 w/w% of SHNC enhanced the moisture retention significantly at field capacity compared to the untreated soil. Besides, in a separate experiment, seed germination and seedling growth of wheat was found to be notably improved with the application of SHNC. A delay in wilting of seedlings by 5-8 days was observed for SHNC-amended soil, thereby improving wheat plant growth and establishment.

  4. Magnetic and optical properties of MgAl2O4-(Ni0.5Zn0.5)Fe2O4 thin films prepared by pulsed laser deposition

    PubMed Central

    Misu, Takeshi; Sakamoto, Naonori; Shinozaki, Kazuo; Adachi, Nobuyasu; Suzuki, Hisao; Wakiya, Naoki

    2011-01-01

    Thin films composed of MgAl2O4 and (Ni0.5Zn0.5)Fe2O4 ([MA(100-x)-NZFx] films) were grown on fused SiO2 substrates by pulsed laser deposition. X-ray diffraction measurements revealed that the films were polycrystalline, and that their lattice constant varied linearly with composition, indicating the formation of a solid solution. The film with x=60 was paramagnetic and those with x ≥ 70 were ferromagnetic. The films had a transparency above 75% in the visible range, but the transparency decreased with the x value. The optical band gaps were 2.95, 2.55, 2.30 and 1.89 eV for x=20, 40, 60, 80 and 100, respectively. The Faraday rotation angle increased with x in the visible range, and the film with x=70 exhibited a value of 2000 degrees cm-1 at 570 nm, which is comparable to the rotation angle of Y3Fe5O12. Owing to their high transparency, which extends into the visible range, the [MA(100-x)-NZFx] films can be used in novel magneto-optical devices. PMID:27877399

  5. Factors affecting Fe and Zn contents of mesozooplankton from the Costa Rica Dome

    PubMed Central

    Baines, Stephen B.; Chen, Xi; Twining, Benjamin S.; Fisher, Nicholas S.; Landry, Michael R.

    2016-01-01

    Mineral limitation of mesozooplankton production is possible in waters with low trace metal availability. As a step toward estimating mesozooplankton Fe and Zn requirements under such conditions, we measured tissue concentrations of major and trace nutrient elements within size-fractioned zooplankton samples collected in and around the Costa Rica Upwelling Dome, a region where phytoplankton growth may be co-limited by Zn and Fe. The geometric mean C, N, P contents were 27, 5.6 and 0.21 mmol gdw−1, respectively. The values for Fe and Zn were 1230 and 498 nmol gdw−1, respectively, which are low compared with previous measurements. Migrant zooplankton caused C and P contents of the 2–5 mm fraction to increase at night relative to the day while the Fe and Zn contents decreased. Fe content increased with size while Zn content decreased with size. Fe content was strongly correlated to concentrations of two lithogenic tracers, Al and Ti. We estimate minimum Fe:C ratios in large migrant and resident mixed layer zooplankton to be 15 and 60 µmol mol−1, respectively. The ratio of Zn:C ranged from 11 µmol mol−1 for the 0.2–0.5 mm size fraction to 33 µmol mol−1 for the 2–5 mm size fraction. PMID:27275034

  6. Effects of Zn additions to highly magnetoelastic FeGa alloys

    SciTech Connect

    Lograsso, Thomas A.; Jones, Nicholas J.; Wun-Fogle, Marilyn; Restorff, James B.; Schlagel, Deborah L.; Petculescu, Gabriela; Clark, Arthur E.; Hathaway, Kristl B.

    2015-05-07

    Fe{sub 1−x}M{sub x} (M = Ga, Ge, Si, Al, Mo and x ∼ 0.18) alloys offer an extraordinary combination of magnetoelasticity and mechanical properties. They are rare-earth-free, can be processed using conventional deformation techniques, have high magnetic permeability, low hysteresis, and low magnetic saturation fields, making them attractive for device applications such as actuators and energy harvesters. Starting with Fe-Ga as a reference and using a rigid-band-filling argument, Zhang et al. predicted that lowering the Fermi level by reducing the total number of electrons could enhance magnetoelasticity. To provide a direct experimental validation for Zhang's hypothesis, elemental additions with lower-than-Ga valence are needed. Of the possible candidates, only Be and Zn have sufficient solubility. Single crystals of bcc Fe-Ga-Zn have been grown with up to 4.6 at. % Zn in a Bridgman furnace under elevated pressure (15 bars) in order to overcome the high vapor pressure of Zn and obtain homogeneous crystals. Single-crystal measurements of magnetostriction and elastic constants allow for the direct comparison of the magnetoelastic coupling constants of Fe-Ga-Zn with those of other magnetoelastic alloys in its class. The partial substitution of Ga with Zn yields values for the magnetoelastic coupling factor, −b{sub 1}, comparable to those of the binary Fe-Ga alloy.

  7. Effects of Zn additions to highly magnetoelastic FeGa alloys

    NASA Astrophysics Data System (ADS)

    Lograsso, Thomas A.; Jones, Nicholas J.; Schlagel, Deborah L.; Petculescu, Gabriela; Wun-Fogle, Marilyn; Restorff, James B.; Clark, Arthur E.; Hathaway, Kristl B.

    2015-05-01

    Fe1-xMx (M = Ga, Ge, Si, Al, Mo and x ˜ 0.18) alloys offer an extraordinary combination of magnetoelasticity and mechanical properties. They are rare-earth-free, can be processed using conventional deformation techniques, have high magnetic permeability, low hysteresis, and low magnetic saturation fields, making them attractive for device applications such as actuators and energy harvesters. Starting with Fe-Ga as a reference and using a rigid-band-filling argument, Zhang et al. predicted that lowering the Fermi level by reducing the total number of electrons could enhance magnetoelasticity. To provide a direct experimental validation for Zhang's hypothesis, elemental additions with lower-than-Ga valence are needed. Of the possible candidates, only Be and Zn have sufficient solubility. Single crystals of bcc Fe-Ga-Zn have been grown with up to 4.6 at. % Zn in a Bridgman furnace under elevated pressure (15 bars) in order to overcome the high vapor pressure of Zn and obtain homogeneous crystals. Single-crystal measurements of magnetostriction and elastic constants allow for the direct comparison of the magnetoelastic coupling constants of Fe-Ga-Zn with those of other magnetoelastic alloys in its class. The partial substitution of Ga with Zn yields values for the magnetoelastic coupling factor, -b1, comparable to those of the binary Fe-Ga alloy.

  8. Stabilization Mechanism of ZnO Nanoparticles by Fe Doping

    NASA Astrophysics Data System (ADS)

    Xiao, Jianping; Kuc, Agnieszka; Frauenheim, Thomas; Heine, Thomas

    2014-03-01

    Surprisingly low solubility and toxicity of Fe-doped ZnO nanoparticles is elucidated on the basis of first-principles calculations. Various ZnO surfaces that could be present in nanoparticles are subject to substitutional Fe doping. We show that Fe stabilizes polar instable surfaces, while nonpolar surfaces, namely (101_0) and (112_0), remain intact. Polar surfaces can be stabilized indirectly through Fe2+-Fe3+ pair-assisted charge transfer, which reduces surface polarity and therefore, the solubility in polar solvents.

  9. Tetragonal magnetostriction and magnetoelastic coupling in Fe-Al, Fe-Ga, Fe-Ge, Fe-Si, Fe-Ga-Al, and Fe-Ga-Ge alloys

    NASA Astrophysics Data System (ADS)

    Restorff, J. B.; Wun-Fogle, M.; Hathaway, K. B.; Clark, A. E.; Lograsso, T. A.; Petculescu, G.

    2012-01-01

    This paper presents a comparative study on the tetragonal magnetostriction constant, λγ,2, [ = (3/2)λ100] and magnetoelastic coupling, b1, of binary Fe100-xZx (0 < x < 35, Z = Al, Ga, Ge, and Si) and ternary Fe-Ga-Al and Fe-Ga-Ge alloys. The quantities are corrected for magnetostrains due to sample geometry (the magnetostrictive form effect). Recently published elastic constant data along with magnetization measurements at both room temperature and 77 K make these corrections possible. The form effect correction lowers the magnetostriction by ˜10 ppm for high-modulus alloys and by as much as 30 ppm for low-modulus alloys. The elastic constants are also used to determine the values of the magnetoelastic coupling constant, b1. With the new magnetostriction data on the Fe-Al-Ga alloy, it is possible to show how the double peak magnetostriction feature of the binary Fe-Ga alloy flows into the single peak binary Fe-Al alloy. The corrected magnetostriction and magnetoelastic coupling data for the various alloys are also compared using the electron-per-atom ratio, e/a, as the common variable. The Hume-Rothery rules link the e/a ratio to the regions of phase stability, which appear to be intimately related to the magnetostriction versus the solute concentration curve in these alloys. Using e/a as the abscissa tends to align the peaks in the magnetostriction and magnetoelastic coupling for the Fe-Ga, Fe-Ge, Fe-Al, Fe-Ga-Al, and Fe-Ga-Ge alloys, but not for the Fe-Si alloys for which the larger atomic size difference may play a greater role in phase stabilization. Corrections for the form effect are also presented for the rhombohedral magnetostriction, λɛ,2, and the magnetoelastic coupling, b2, of Fe100-xGax (0 < x < 35) alloys.

  10. Determination of the constants of affinity of FeCl3, CuCl2, and ZnCl2 for a nitrogen-containing organosilane bonded on Al2O3-cellulose acetate hybrid material surface from ethanol solution.

    PubMed

    Lazarin, Angélica M; Landers, Richard; Kholin, Yuriy V; Gushikem, Yoshitaka

    2002-10-01

    This work describes the preparation and characterization of a cellulose acetate fiber coated with Al(2)O(3), resulting in the organic-inorganic hybrid Cel/Al(2)O(3). Furthermore, the hybrid was modified by attaching organofunctional groups by reaction with the precursor reagents (RO)(3)Si(CH(2))(3)L (L=NH(2), NH(CH(2))(2)NH(2), NH(CH(2))(2)NH(CH(2))(2)NH(2), and N(2)C(3)H(3) (imidazole)), resulting in Cel/Al(2)O(3)/Si(CH(2))(3)NH(2) (1), Cel/Al(2)O(3)/Si(CH(2))(3)NH(CH(2))(2)NH(2) (2), Cel/Al(2)O(3)/Si(CH(2))(3)NH(CH(2))(2)NH(CH(2))(2)NH(2) (3), and Cel/Al(2)O(3)/Si(CH(2))(3)N(2)C(3)H(3) (4). The amounts of attached organofunctional groups were (in mmol per gram of the material) 1=1.90, 2=1.89, 3=1.66, and 4=1.35. The isotherms of adsorption of FeCl(3), CuCl(2), and ZnCl(2) by Cel/Al(2)O(3)/Si(CH(2))(3)L from ethanol solutions were obtained at 298 K. Accurate estimates of the specific sorption capacities and the heteregeneous stability constants of the immobilized metal complexes were determined with the aid of several computational procedures. It is shown that the sorptional capacities are much less than the concentrations of the attached organofunctional groups. As all sorption isotherms are fitted properly with the Langmuir isotherm equation, the effects of the energetic heterogeneity and the lateral interactions do not affect the chemisorption equilibria. The heterogeneous stability constants of the immobilized complexes are fairly high, which provides efficient removal of the metal ions from solutions by the hybrid materials.

  11. A DFT study on the complex formation between desferrithiocin and metal ions (Mg(2+), Al(3+), Ca(2+), Mn(2+), Fe(3+), Co(2+), Ni(2+), Cu(2+), Zn(2+)).

    PubMed

    Kaviani, Sadegh; Izadyar, Mohammad; Housaindokht, Mohammad Reza

    2017-04-01

    In recent years, Metal-chelating compounds, namely siderphores have been considered very much because of their crucial role in various fields of the environmental researches. Their importance lies in the fact that they are able to be bonded to a variety of metals in addition to iron. A theoretical study on the structures of desferrithiocin siderphore coordinated to Mg(2+), Al(3+), Ca(2+), Mn(2+), Fe(3+), Co(2+), Ni(2+), Cu(2+) and Zn(2+) metal ions was carried out, using the CAM-B3LYP/6-31G(d) level of the theory in the water. In order to understand the factors which control the stability, reactivity and the strength of toxic metals excretion as well as microbial uptake of the metal-siderphore complexes, we examined the stability and binding energies of the desferrithiocin and various metal ions with different spin states. The binding affinity of desferrithiocin to Fe(3+) (log β2=23.88) showed that the desferrithiocin can scavenge the excess iron(III) from the labile sources. Also, the binding energy values were well described by addition of the dispersion-corrected D3 functional. Because of the importance of the charge transfer in the complex formation, donor-acceptor interaction energies were evaluated. Based on this analysis, an increase in the effective nuclear charge increases E(2) values. Vibrational analysis showed that the critical bonds (CO stretching and CH bending) are in the range of 1300-1800cm(-1). Finally, some probable correlations between the complexation behavior and quantum chemistry descriptors have been analyzed.

  12. Influence of hot isostatic pressing on the structure and properties of an innovative low-alloy high-strength aluminum cast alloy based on the Al-Zn-Mg-Cu-Ni-Fe system

    NASA Astrophysics Data System (ADS)

    Akopyan, T. K.; Padalko, A. G.; Belov, N. A.

    2015-11-01

    Hot isostatic pressing (HIP) is applied for treatment of castings of innovative low-ally high-strength aluminum alloy, nikalin ATs6N0.5Zh based on the Al-Zn-Mg-Cu-Ni-Fe system. The influence of HIP on the structure and properties of castings is studied by means of three regimes of barometric treatment with different temperatures of isometric holding: t 1 = 505 ± 2°C, p 1 = 100 MPa, τ1 = 3 h (HIP1); t 2 = 525 ± 2°C, p 2 = 100 MPa, τ2 = 3 h (HIP2); and t 3 = 545 ± 2°C, p 3 = 100 MPa, τ3 = 3 h (HIP3). It is established that high-temperature HIP leads to actually complete elimination of porosity and additional improvement of the morphology of second phases. Improved structure after HIP provides improvement properties, especially of plasticity. In particular, after heat treatment according of regime HIP2 + T4 (T4 is natural aging), the alloy plasticity is improved by about two times in comparison with the initial state (from ~6 to 12%). While applying regime HIP3 + T6 (T6 is artificial aging for reaching the maximum strength), the plasticity has improved by more than three times in comparison with the initial state, as after treatment according to regimes HIP1 + T6 and HIP2 + T6 (from ~1.2 to ~5.0%), which are characterized by a lower HIP temperature.

  13. Chitosan film loaded with silver nanoparticles-sorbent for solid phase extraction of Al(III), Cd(II), Cu(II), Co(II), Fe(III), Ni(II), Pb(II) and Zn(II).

    PubMed

    Djerahov, Lubomir; Vasileva, Penka; Karadjova, Irina; Kurakalva, Rama Mohan; Aradhi, Keshav Krishna

    2016-08-20

    The present study describes the ecofriendly method for the preparation of chitosan film loaded with silver nanoparticles (CS-AgNPs) and application of this film as efficient sorbent for separation and enrichment of Al(III), Cd(II), Cu(II), Co(II), Fe(III), Ni(II), Pb(II) and Zn(II). The stable CS-AgNPs colloid was prepared by dispersing the AgNPs sol in chitosan solution at appropriate ratio and further used to obtain a cast film with very good stability under storage and good mechanical strength for easy handling in aqueous medium. The incorporation of AgNPs in the structure of CS film and interaction between the polymer matrix and nanoparticles were confirmed by UV-vis and FTIR spectroscopy. The homogeneously embedded AgNPs (average diameter 29nm, TEM analysis) were clearly observed throughout the film by SEM. The CS-AgNPs nanocomposite film shows high sorption activity toward trace metals under optimized chemical conditions. The results suggest that the CS-AgNPs nanocomposite film can be feasibly used as a novel sorbent material for solid-phase extraction of metal pollutants from surface waters.

  14. Magnetic structure and effect of magnetic field on its domain structure in magnetoelectric Ba1.3Sr0.7CoZnFe11AlO22

    NASA Astrophysics Data System (ADS)

    Ueda, H.; Tanaka, Y.; Nakajima, H.; Mori, S.; Ohta, K.; Haruki, K.; Hirose, S.; Wakabayashi, Y.; Kimura, T.

    2016-10-01

    The magnetic structure and the effect of a magnetic field on its domain structure were investigated in a magnetoelectric Y-type hexaferrite, Ba1.3Sr0.7CoZnFe11AlO22, by means of mapping with a micro-focused and circularly polarized X-ray beam in the resonant X-ray diffraction. It was revealed that this hexaferrite exhibits a magnetic order characterized by two distinct antiferromagnetic components: incommensurate helical and commensurate collinear ones, which can be explained as the development of the so-called alternating longitudinal conical structure. A multi-domain state due to the handedness of the helical component, i.e., spin-chirality, is transformed into nearly a mono-domain one by using only a magnetic field. Furthermore, the sign of the spin-chirality in the mono-domain state is reversed by reversing the sign of a magnetic field. These results demonstrate that the spin-chirality in this hexaferrite can be manipulated by a magnetic field alone at room temperature.

  15. Low temperature synthesis of Mn{0.4}Zn{0.6}In{0.5}Al{0.1}Fe{1.4}O{4} nano-ferrite and characterization for high frequency applications

    NASA Astrophysics Data System (ADS)

    Mathur, P.; Thakur, A.; Singh, M.

    2008-02-01

    In the present study, nano-ferrite of composition Mn{0.4}Zn{0.6}In{0.5}Al{0.1}Fe{1.4}O{4} has been synthesized by co-precipitation method. Decomposition of residue at a temperature as low as 200 °C, gives the ferrite powder. The ferrite has been, finally, sintered at 500 °C. The structural studies have been made by using X-ray diffraction (XRD) technique and scanning electron microscopy (SEM), which confirms the formation of single spinel phase and nanostructure. The dc resistivity is studied as a function of temperature and values are found more than twice than those for the samples prepared by the other chemical methods ... It is found that the resistivity decreases with an increase in temperature. The initial permeability value is found to be higher as compared to the other chemical routes. The initial permeability value is found to increase with an increase in temperature. At a certain temperature called Curie temperature, it attains a maximum value, after which the initial permeability decreases sharply. Even at nanolevel, appreciable value of initial permeability is obtained and low magnetic losses make these ferrites especially suitable for high frequency applications. The particle size is calculated using Scherrer's equation for Lorentzian peak, which comes out between 55 nm 69 nm. Possible mechanisms contributing to these processes have been discussed.

  16. Uptake of Al, As, Cr, Cd, Cu, Fe, Mn, Ni, Pb, Sr, and Zn in native wheatgrasses, wildryes, and bluegrass on three metal-contaminated soils from Montana

    Technology Transfer Automated Retrieval System (TEKTRAN)

    One of the biggest challenges to successfully phytoremediate contaminated mineland soils is the identification of native plants that possess a broad adaptation to ecological sites and either exclude or uptake heavy metals of interest. This study evaluated forage concentrations of aluminum (Al), ars...

  17. Mechanical properties and electronic structures of Fe-Al intermetallic

    NASA Astrophysics Data System (ADS)

    Liu, YaHui; Chong, XiaoYu; Jiang, YeHua; Zhou, Rong; Feng, Jing

    2017-02-01

    Using the first-principles calculations, the elastic properties, anisotropy properties, electronic structures, Debye temperature and stability of Fe-Al (Fe3Al, FeAl, FeAl2, Fe2Al5 and FeAl3) binary compounds were calculated. The formation enthalpy and cohesive energy of these Fe-Al compounds are negative, and show they are thermodynamically stable structures. Fe2Al5 has the lowest formation enthalpy, which shows the Fe2Al5 is the most stable of Fe-Al binary compounds. These Fe-Al compounds display disparate anisotropy due to the calculated different shape of the 3D curved surface of the Young's modulus and anisotropic index. Fe3Al has the biggest bulk modulus with the value 233.2 GPa. FeAl has the biggest Yong's modulus and shear modulus with the value 296.2 GPa and 119.8 GPa, respectively. The partial density of states, total density of states and electron density distribution maps of the binary Fe-Al binary compounds are analyzed. The bonding characteristics of these Fe-Al binary compounds are mainly combination by covalent bond and metallic bonds. Meanwhile, also exist anti-bond effect. Moreover, the Debye temperatures and sound velocity of these Fe-Al compounds are explored.

  18. Control of Zn uptake in Arabidopsis halleri: a balance between Zn and Fe

    PubMed Central

    Shanmugam, Varanavasiappan; Lo, Jing-Chi; Yeh, Kuo-Chen

    2013-01-01

    Zinc (Zn) is an essential plant micronutrient but is toxic in excess. To cope with excess Zn, plant species possess a strict metal homeostasis mechanism. The Zn hyperaccumulator Arabidopsis halleri has developed various adaptive mechanisms involving uptake, chelation, translocation and sequestration of Zn. In this mini review, we broadly discuss the different Zn tolerance mechanisms and then focus on controlled Zn uptake in A. halleri. Members of the ZRT/IRT-like protein (ZIP) family of metal transporters are mainly regulated by Zn and are involved in Zn uptake. A few members of the ZIP family, such as IRT1 and IRT2, are regulated by iron (Fe) and can transport multi-metals, including Zn, Fe, Mn, Cd, and Co. This mini-review also discusses the differential expression of multiple metal ZIP transporters in A. halleri and A. thaliana, a non-hyperaccumulator, with Zn exposure as well as Fe deficiency and their role in controlled Zn uptake and tolerance. PMID:23966999

  19. Formation of layered Fe(II)-Al(III)-hydroxides during reaction of Fe(II) with aluminum oxide.

    PubMed

    Elzinga, Evert J

    2012-05-01

    The reactivity of aqueous Fe(II) with aluminum oxide in anoxic solutions was investigated with batch kinetic experiments combined with Fe K edge X-ray absorption spectroscopy measurements to characterize Fe(II) sorption products. Formation of Fe(II)-Al(III)-layered double hydroxides with an octahedral sheet structure similar to nikischerite (NaFe(II)(6) Al(3)(SO(4))(2)(OH)(18) (H(2)O)(12)) was observed within a few hours during sorption at pH 7.5 and aqueous Fe(II) concentrations of 1-3 mM. These Fe(II) phases are composed of brucite-like Fe(II)(OH)(2) sheets with partial substitution of Al(III) for Fe(II), charge balanced by anions coordinated along the basal planes. Their fast rate of formation suggests that these previously unrecognized Fe(II) phases, which are structurally and compositionally similar to green rust, may be an important sink of Fe(II) in suboxic and anoxic geochemical environments, and impact the fate of structurally compatible trace metals, such as Co(II), Ni(II), and Zn(II), as well as redox-reactive species including Cr(VI) and U(VI). Further studies are required to assess the thermodynamics, formation kinetics, and stability of these Fe(II) minerals under field conditions.

  20. Photoinduced reduction of surface states in Fe:ZnO

    SciTech Connect

    Knut, R. Palmgren, P.; Karis, O.; Lagerqvist, U.; Pohl, A.; Pal, P.; Svedlindh, P.

    2015-05-28

    We report on the electronic structure of nano-crystalline Fe:ZnO, which has recently been found to be an efficient photocatalyst. Using resonant photoemission spectroscopy, we determine the binding energy of Fe 3d states corresponding to different valencies and coordination of the Fe atoms. The photo-activity of ZnO reduces Fe from 3+ to 2+ in the surface region of the nano-crystalline material due to the formation of oxygen vacancies. Electronic states corresponding to low-spin Fe{sup 2+} are observed and attributed to crystal field modification at the surface. These states are potentially important for the photocatalytic sensitivity to visible light due to their location deep in the ZnO bandgap. X-ray absorption and x-ray photoemission spectroscopy suggest that Fe is only homogeneously distributed for concentrations up to 3%. Increased concentrations does not result in a higher concentration of Fe ions in the surface region. This is limiting the photocatalytic functionality of ZnO, where the most efficient Fe doping concentration has been shown to be 1%-4%.

  1. ZnFe2O4 antiferromagnetic structure redetermination

    NASA Astrophysics Data System (ADS)

    Kremenović, Aleksandar; Antić, Bratislav; Vulić, Predrag; Blanuša, Jovan; Tomic, Aleksandra

    2017-03-01

    Magnetic structure of ZnFe2O4 normal spinel is re-examined. Antiferromagnetic structure non-collinear model is established within Ca2 space group having four different crystallographic/magnetic sites for 32 Fe3+ spins within magnetic unit cell.

  2. An Impact of Zirconium Doping of Zn-Al Braze on the Aluminum-Stainless Steel Joints Integrity During Aging

    NASA Astrophysics Data System (ADS)

    Yang, Jinlong; Xue, Songbai; Sekulic, Dusan P.

    2016-11-01

    This work offers an analysis of the microstructure and the growth rate of an intermetallic compound within the aged AA 6061 aluminum alloy-304 stainless steel joint brazed with Zn-15Al and Zn-15Al-0.2Zr filler metals. The effect of zirconium addition on mechanical integrity of the brazed joint was studied. The experimental results confirm that the thickness of the Fe-Al intermetallic layer formed at the brazed seam/stainless steel interface increases with the increase of the aging time. Furthermore, it is established that the growth rate of the intermetallic layer for the Zn-15Al-0.2Zr brazed joint was lower than that for Zn-15Al. The results also indicate that the shear strength of both Zn-15Al and Zn-15Al-0.2Zr brazed joints decreases monotonously during aging. The value of the strength after aging lasting for 800 h for Zn-15Al and Zn-15Al-0.2Zr has decreased by 20 and 17%, respectively. The fracture of joints occurred at the interface between the brazed seam and the Fe4Al13 intermetallic layer. The morphology of the surfaces exhibits a cleavage fracture.

  3. An Impact of Zirconium Doping of Zn-Al Braze on the Aluminum-Stainless Steel Joints Integrity During Aging

    NASA Astrophysics Data System (ADS)

    Yang, Jinlong; Xue, Songbai; Sekulic, Dusan P.

    2017-01-01

    This work offers an analysis of the microstructure and the growth rate of an intermetallic compound within the aged AA 6061 aluminum alloy-304 stainless steel joint brazed with Zn-15Al and Zn-15Al-0.2Zr filler metals. The effect of zirconium addition on mechanical integrity of the brazed joint was studied. The experimental results confirm that the thickness of the Fe-Al intermetallic layer formed at the brazed seam/stainless steel interface increases with the increase of the aging time. Furthermore, it is established that the growth rate of the intermetallic layer for the Zn-15Al-0.2Zr brazed joint was lower than that for Zn-15Al. The results also indicate that the shear strength of both Zn-15Al and Zn-15Al-0.2Zr brazed joints decreases monotonously during aging. The value of the strength after aging lasting for 800 h for Zn-15Al and Zn-15Al-0.2Zr has decreased by 20 and 17%, respectively. The fracture of joints occurred at the interface between the brazed seam and the Fe4Al13 intermetallic layer. The morphology of the surfaces exhibits a cleavage fracture.

  4. Laser irradiation of ZnO:Al/Ag/ZnO:Al multilayers for electrical isolation in thin film photovoltaics

    PubMed Central

    2013-01-01

    Laser irradiation of ZnO:Al/Ag/ZnO:Al transparent contacts is investigated for segmentation purposes. The quality of the irradiated areas has been experimentally evaluated by separation resistance measurements, and the results are complemented with a thermal model used for numerical simulations of the laser process. The presence of the Ag interlayer plays two key effects on the laser scribing process by increasing the maximum temperature reached in the structure and accelerating the cool down process. These evidences can promote the use of ultra-thin ZnO:Al/Ag/ZnO:Al electrode in large-area products, such as for solar modules. PMID:24053228

  5. Magnetic properties of Al/57Fe/Cr multilayers

    NASA Astrophysics Data System (ADS)

    Jani, Snehal; Lakshmi, N.; Jain, Vishal; Reddy, V. R.; Gupta, Ajay; Venugopalan, K.

    2013-06-01

    Conversion Electron Mössbauer Spectroscopy (CEMS) and DC magnetization are used to compare magnetic properties of as-deposited multilayer (MLS) and Fe2CrAl thin film made from Al/57Fe/Cr MLS deposited by ion beam sputtering and then annealed in UHV. Interdiffusion of elements on annealing sample-1 at 500°C leads to formation of a single, disordered film of Fe2CrAl as evidenced by hyperfine field values obtained by CEMS in the film which compares well with that in bulk Fe2CrAl. CEMS also shows contributions from Fe, Fe/Cr and Fe/Al interfaces in the MLS. Saturation magnetization of as-deposited sample-1 is much less than pure Fe due to reduced Fe thickness because of interface formation and also reduction in Fe-Fe interaction due to intervening Al and Cr layers.

  6. Fabrication of Fe-Al nanoparticles by selective oxidation of Fe-Al thin films

    NASA Astrophysics Data System (ADS)

    Jang, Pyungwoo; Shin, Seungchan; Jung, Chip-Sup; Kim, Kwang-Ho; Seomoon, Kyu

    2013-04-01

    The possibility of a new technique for fabricating nanoparticles from thin films using selective oxidation in an atmosphere mixture of water vapor and hydrogen was investigated. Fe-5wt.%Al films were RF-sputtered and annealed in the atmosphere mixture at 900°C for up to 200 min, in order to oxidize aluminum selectively. Thermodynamics simulation showed that temperatures exceeding 800°C are necessary to prevent iron from being oxidized, as confirmed by the depth profile of XPS. As the annealing time increased, the morphology of the 200-nm Fe-Al films changed from the continuous to the discontinuous type; thus, particulate Fe-Al films formed after 100 min. The particulate 10- to 100-nm Fe-Al films showed super-paramagnetic behavior after the oxidation. Thus, a new technique for fabricating nanoparticles was successfully introduced using selective oxidation.

  7. Forging of FeAl intermetallic compounds

    SciTech Connect

    Flores, O.; Juarez, J.; Campillo, B.; Martinez, L.; Schneibel, J.H.

    1994-09-01

    Much activity has been concentrated on the development of intermetallic compounds with the aim of improving tensile ductility, fracture toughness and high notch sensitivity in order to develop an attractive combination of properties for high and low temperature applications. This paper reports experience in processing and forging of FeAl intermetallic of B2 type. During the experiments two different temperatures were employed, and the specimens were forged after annealing in air, 10{sup {minus}2} torr vacuum and argon. From the results it was learned that annealing FeAl in argon atmosphere prior to forging resulted in better deformation behavior than for the other two environments. For the higher forging temperature used in the experiments (700C), the as-cast microstructure becomes partially recrystallized.

  8. Zinc and iron metabolism in Euglena gracilis: metal redistribution during Zn and Fe deficiency

    SciTech Connect

    Taylor, P.; Gingrich, D.; Antholine, W.E.; Petering, D.H.

    1986-05-01

    The normal cytosolic distribution of Zn and Fe in Euglena gracilis and their changes during Zn and Fe deficiency and repletion in relationship to cell proliferation were examined. Using Sephadex G-75 chromatography, two metal pools were found-Zn and Fe bound to high molecular weight (HMW) proteins and a pool of low molecular weight (LMW) Zn and Fe of less than 2000 daltons (ZnL, FeL), containing 80-90% of the cytosolic Zn and Fe. ZnL and FeL can be separated on Sephadex G-15 and by HPLC techniques. According to ESR analysis both HMW and LMW iron is high spin Fe(III). Under conditions of Zn deficiency, cell proliferation is halted after 48 hrs. in concert with the depletion of the ZnL. Within error, HMW protein bound Zn is unaffected. ZnL appears to be a labile store of Zn to supply the cell with this essential metal. In contrast, during Fe deficiency cell proliferation is unaffected. Yet both HMW and LMW pools are depleted within 48 hrs. Both bands of Fe appear to be storage forms of the metal. Proliferative capacity of the alga is evidently more sensitive to Zn deficiency than to Fe depletion, possibly because Euglena can scavenge adventitious Fe from the medium by a siderophore-mediated mechanism.

  9. Non-linear Electrical Characteristics of ZnO Modified by Trioxides Sb2O3, Bi2O3, Fe2O3, Al2O3 and La2O3

    NASA Astrophysics Data System (ADS)

    Mekap, Anita; Das, Piyush R.; Choudhary, R. N. P.

    2016-08-01

    The non-linear behavior of polycrystalline-ZnO-based voltage-dependent resistors is considered in the present study. A high-temperature solid-state reaction route was used to synthesize polycrystalline samples of ZnO modified by small amounts of the trioxides Sb2O3, Bi2O3, Fe2O3, etc. in various proportions. X-ray diffraction and scanning electron microscopy techniques were used to study the structural and microstructural characteristics of modified ZnO. Detailed studies of non-linear phenomena of the I-V characteristics, dielectric permittivity ( ɛ r), impedance ( Z), etc. of the samples have provided many interesting results. All the samples exhibited dielectric anomaly. Non-linear variation in polarization with electric field for all the samples was observed. Moreover, significant non-linearity in the I-V characteristics was observed in the breakdown region of all the samples at room temperature. The non-linear coefficient ( α) in different cases, i.e. for I- V, ɛ r- f, ɛ r- T, and ɛ r- Z, was calculated and found to be appreciable. The frequency dependence of ac conductivity suggests that the material obeys Jonscher's universal power law.

  10. Magnetic properties of ZnFe2O4 nanoparticles

    NASA Astrophysics Data System (ADS)

    Guskos, Niko; Glenis, Spiros; Typek, Janusz; Zolnierkiewicz, Grzegorz; Berczynski, Pawel; Wardal, Kamil; Guskos, Aleksander; Sibera, Daniel; Moszyński, Dariusz; Lojkowski, Witold; Narkiewicz, Urszula

    2012-04-01

    Fine particles of ZnFe2O4 were synthesized by a wet chemical method in the (80 wt.% Fe2O3 + 20 wt.% ZnO) system. The morphological and structural properties of the mixed system were investigated by scanning electron microscopy, X-ray diffraction, inductively coupled plasma atomic emission, and X-ray photoelectron spectroscopy. The major phase was determined to be the ZnFe2O4 spinel with particle size of 11 nm. The magnetic properties of the material were investigated by ferromagnetic resonance (FMR) in the temperature range from liquid helium to room temperature. A very intense, asymmetric FMR signal from ZnFe2O4 nanoparticles was recorded, which has been analyzed in terms of two Callen-lineshape lines. Temperature dependence of the FMR parameters was obtained from fitting the experimental lines with two component lines. Analysis of the FMR spectra in terms of two separate components indicates the presence of strongly anisotropic magnetic interactions.

  11. Stability and thermal transformation studies of Zn2+- and Fe2+- loaded zeolite Y prepared from Egyptian kaolin

    NASA Astrophysics Data System (ADS)

    EL-Mekkawi, Doaa M.; Ibrahim, Fatma A.; Selim, Mohamed M.

    2015-10-01

    The stability and thermal transformation of Zn2+ and Fe2+- zeolites based kaolin were studied with respect to their loading experimental conditions. Zeolite Y prepared from Egyptian kaolin was used in our investigations. Zeolite shows different degrees of framework stability according to the type of cation and the loading experimental conditions. The obtained data indicate the predominance of adsorption and ion exchange mechanisms during Fe2+ and Zn2+ loading, respectively. The loading experimental conditions also greatly affect the solid-solid interactions of transition metal-zeolites at elevated temperatures. ZnAl2O4 and silica phases were formed upon thermal treatment of Zn-Y zeolites. The ratio of ZnAl2O4 to silica phases increases as the amount of loaded Zn2+ increases in the corresponding unheated zeolites. However, nepheline phase was obtained upon heating Fe-Y zeolites loaded at low initial Fe2+ concentrations. Upon increasing of loaded Fe2+, iron oxide beside other amorphous phases from silica, alumina and/or aluminosilicates were obtained.

  12. Nanocluster formation in Co/Fe implanted ZnO

    NASA Astrophysics Data System (ADS)

    Bharuth-Ram, K.; Masenda, H.; Doyle, T. B.; Geburt, S.; Ronning, C.

    2015-04-01

    Conversion electron Mössbauer Spectroscopy (CEMS) measurements were made on a ZnO single crystal sample implanted at room temperature (RT) with of 145 and 345 keV 59Co ions with respective fluences of 1.15×1016 ions/cm 2 and 4.17×1016 ions/cm 2, followed by implantation of 60 keV 57Fe to a fluence of 0.50×1016/cm 2 to yield a `box-shaped' implantation profile with a Co + Fe concentration of about 3.2 at. %. CEM spectra were collected after annealing the sample up to 973 K. The spectra after annealing up to 973 K are similar to spectra observed in other CEMS studies on Fe implanted ZnO, but show a dramatic change after the 973 K annealing step; it is dominated by a doublet component with fit parameters typical of Fe 3+. Magnetization curves of the sample after the 973 K anneal show hysteresis, with a small residual magnetization at RT that increases at 4 K. The saturation magnetization at 4 K was approximately 0.33 μ B/CoFe ion, in good agreement with observations for 5-8 nm sized Co nanoclusters in ZnO.

  13. Interplay between chemical state, electric properties, and ferromagnetism in Fe-doped ZnO films

    NASA Astrophysics Data System (ADS)

    Chen, G.; Peng, J. J.; Song, C.; Zeng, F.; Pan, F.

    2013-03-01

    Valence state of Fe ions plays an important role in the physical properties of Fe doped ZnO films. Here, a series of Zn1-xFexO films with different Fe concentrations (x = 0, 2.3, 5.4, 7.1, and 9.3 at. %) were prepared to investigate their structural, piezoelectric, ferroelectric, bipolar resistive switching properties, and electrical-control of ferromagnetism at room temperature. The structure characterizations indicate that the chemical state of Fe ions substituting Zn2+ site changes from Fe3+ to Fe2+ with the increase of Fe dopant concentration. We found enhanced piezoelectric and ferroelectric properties in Zn0.977Fe0.023O films with more Fe3+ due to the smaller Fe3+ ionic size in comparison with Zn2+ while the increase of Fe2+ concentration by a larger amount of Fe dopant results in the worse ferroelectric and piezoelectric performance. All Pt/Zn1-xFexO/Pt devices show bipolar resistive switching properties. Especially, devices with lower Fe dopant concentration exhibit better endurance properties due to their higher crystalline quality. The variation of oxygen vacancies during resistive switching provides an opportunity to tune ferromagnetism of Fe-doped ZnO films, giving rise to the integration of charge and spin into a simple Pt/Zn1-xFexO/Pt devices. The multifunctional properties of Fe-doped ZnO films are promising for communication systems and information storage devices.

  14. Structural and transport properties of epitaxial Fe/ZnSe/FeCo magnetic tunnel junctions

    NASA Astrophysics Data System (ADS)

    Gustavsson, F.; George, J.-M.; Etgens, V. H.; Eddrief, M.

    2001-11-01

    The use of a semiconductor barrier in heteroepitaxy with ferromagnetic metal electrodes describes a novel type of magnetic tunnel junctions. In this work, epitaxial Fe/ZnSe/FeCo magnetic tunnel junctions have been grown on ZnSe(001) buffered GaAs(001) substrates by molecular beam epitaxy. Alloying a small amount of Co with Fe in the base electrode provides a better seed epilayer for the growth of the ZnSe barrier compared to pure Fe as seen by transmission electron microscopy. Detailed characterization of the FeCo surface was performed by in situ scanning tunneling microscopy and revealed pyramid-shaped defects of up to 60 Å in height distributed on the FeCo surface. Transport measurements on microfabricated tunnel junctions yielded up to 16% magnetoresistance at 10 K and the effect is attributed to spin polarized tunneling across the semiconductor barrier in the energy range of the gap. The observed anomalous character of the magnetoresistance was attributed to conduction through the pyramidal defects in the base FeCo layer.

  15. Overview of the development of FeAl intermetallic alloys

    SciTech Connect

    Maziasz, P.J.; Liu, C.T.; Goodwin, G.M.

    1995-09-01

    B2-phase FeAl ordered intermetallic alloys based on an Fe-36 at.% Al composition are being developed to optimize a combination of properties that includes high-temperature strength, room-temperature ductility, and weldability. Microalloying with boron and proper processing are very important for FeAl properties optimization. These alloys also have the good to outstanding resistance to oxidation, sulfidation, and corrosion in molten salts or chlorides at elevated temperatures, characteristic of FeAl with 30--40 at.% Al. Ingot- and powder-metallurgy (IM and PM, respectively) processing both produce good properties, including strength above 400 MPa up to about 750 C. Technology development to produce FeAl components for industry testing is in progress. In parallel, weld-overlay cladding and powder coating technologies are also being developed to take immediate advantage of the high-temperature corrosion/oxidation and erosion/wear resistance of FeAl.

  16. Synthesis and properties of A{sub 6}B{sub 2}(OH){sub 16}Cl{sub 2}.4H{sub 2}O (A = Mg, Ni, Zn, Co, Mn and B = Al, Fe) materials for environmental applications

    SciTech Connect

    Dias, Anderson; Cunha, Lumena; Vieira, Andiara C.

    2011-09-15

    Highlights: {yields} A{sub 6}B{sub 2}(OH){sub 16}Cl{sub 2}.4H{sub 2}O (A = Mg, Ni, Zn, Co, Mn and B = Al, Fe) materials were synthesized. {yields} Chemical synthesis produced different levels of crystallinity and ordering degree. {yields} Structural investigation by Raman scattering revealed a complex band structure. {yields} A strong correlation between band structure and ionic radius was determined. -- Abstract: Double layered hydroxide materials of composition A{sub 6}B{sub 2}(OH){sub 16}Cl{sub 2}.4H{sub 2}O (A = Mg, Ni, Zn, Co, Mn and B = Al, Fe) were synthesized by chemical precipitation at 60 {sup o}C. Different levels of crystallinity and ordering degree were observed depending upon the chemical environment or the combination between divalent and trivalent cations. The results from high-resolution transmission electron microscopy revealed that nanostructured layered samples were obtained with interplanar spacing compatible with previous literature. Raman scattering was employed to investigate the complex band structure observed, particularly the lattice vibrations at lower frequencies, which is intimately correlated to the cationic radius of both divalent and trivalent ions. The results showed that strongly coordinated water and chloride ions besides highly structured hydroxide layers have a direct influence on the stability of the hydrotalcites. It was observed that transition and decomposition temperatures varied largely for different chemical compositions.

  17. Magnetic core-shell ZnFe2O4/ZnS nanocomposites for photocatalytic application under visible light.

    PubMed

    Yoo, Pil Sun; Amaranatha Reddy, D; Jia, YueFa; Bae, Sang Eun; Huh, Seong; Liu, Chunli

    2017-01-15

    Magnetic core-shell ZnFe2O4/ZnS composites were synthesized through a two-step chemical process including the hydrothermal and the co-precipitation methods. The structural characterization revealed that the composites consisted of a layer of ZnS clusters on the surface of ZnFe2O4 nanoparticles. The band gap energy of the composite was estimated to be 2.2eV through the Kubelka-Munk plot, implying the possible application as a photocatalyst under the visible light radiation. The improved photocatalytic efficiency of the ZnFe2O4/ZnS composites was confirmed through the photocatalytic degradation of Methyl Orange. The increased absorption of the visible light and the enhanced separation of the electron-hole pairs due to the relative energy band positions in ZnFe2O4 and ZnS are considered as the main advantages. Additionally, the moderate magnetization of the ZnFe2O4 core insured the easy magnetic collection of the composite materials without affecting the photocatalytic performance. Our results showed that ZnFe2O4-based nanocomposites could be used as an effective and magnetic retrievable photocatalyst.

  18. Stabilization of itinerant (band) magnetism in FeAl by Ga substitution for Al

    NASA Astrophysics Data System (ADS)

    Papaconstantopoulos, D. A.; Mazin, I. I.; Hathaway, K. B.

    2001-06-01

    Band structure calculations of FeGa1-xAlx have been performed, to further investigate the stability of ferromagnetism in FeAl. The Stoner parameter increases by about 20% at the FeGa end. This is also confirmed by our spin-polarized calculations. We conclude that Ga substitution for Al is likely to stabilize the elusive (or illusive) ferromagnetic state in FeAl.

  19. The redox state of arc mantle using Zn/Fe systematics.

    PubMed

    Lee, Cin-Ty A; Luffi, Peter; Le Roux, Véronique; Dasgupta, Rajdeep; Albaréde, Francis; Leeman, William P

    2010-12-02

    Many arc lavas are more oxidized than mid-ocean-ridge basalts and subduction introduces oxidized components into the mantle. As a consequence, the sub-arc mantle wedge is widely believed to be oxidized. The Fe oxidation state of sub-arc mantle is, however, difficult to determine directly, and debate persists as to whether this oxidation is intrinsic to the mantle source. Here we show that Zn/Fe(T) (where Fe(T) = Fe(2+) + Fe(3+)) is redox-sensitive and retains a memory of the valence state of Fe in primary arc basalts and their mantle sources. During melting of mantle peridotite, Fe(2+) and Zn behave similarly, but because Fe(3+) is more incompatible than Fe(2+), melts generated in oxidized environments have low Zn/Fe(T). Primitive arc magmas have identical Zn/Fe(T) to mid-ocean-ridge basalts, suggesting that primary mantle melts in arcs and ridges have similar Fe oxidation states. The constancy of Zn/Fe(T) during early differentiation involving olivine requires that Fe(3+)/Fe(T) remains low in the magma. Only after progressive fractionation does Fe(3+)/Fe(T) increase and stabilize magnetite as a fractionating phase. These results suggest that subduction of oxidized crustal material may not significantly alter the redox state of the mantle wedge. Thus, the higher oxidation states of arc lavas must be in part a consequence of shallow-level differentiation processes, though such processes remain poorly understood.

  20. Damage annealing in low temperature Fe/Mn implanted ZnO

    NASA Astrophysics Data System (ADS)

    Gunnlaugsson, H. P.; Bharuth-Ram, K.; Johnston, K.; Langouche, G.; Mantovan, R.; Mølholt, T. E.; Naidoo, D.; Ólafsson, O.; Weyer, G.

    2015-04-01

    57Fe Emission Mössbauer spectra obtained after low fluence (<1012 cm -2) implantation of 57Mn ( T 1/2= 1.5 min.) into ZnO single crystal held at temperatures below room temperature (RT) are presented. The spectra can be analysed in terms of four components due to Fe 2+ and Fe 3+ on Zn sites, interstitial Fe and Fe in damage regions (Fe D ). The Fe D component is found to be indistinguishable from similar component observed in emission Mössbauer spectra of higher fluence (˜1015 cm -2)57Fe/ 57Co implanted ZnO and 57Fe implanted ZnO, demonstrating that the nature of the damage regions in the two types of experiments is similar. The defect component observed in the low temperature regime was found to anneal below RT.

  1. Calorimetric Measurements of Liquid Al-Zn Alloys

    NASA Astrophysics Data System (ADS)

    Dębski, Adam; Gąsior, Władysław; Szmit, Katarzyna

    2016-10-01

    The integral molar enthalpies of mixing were determined by the drop calorimetric method for binary AL-Zn liquid solutions and compared with the Miedema model as well as the earlier experimental data. The measurements were conducted at two temperatures: 957 K and 1001 K (684 °C and 728 °C), in the entire concentration range. Based on the experimental calorimetric data of this study as well as those available in the literature and the results of the activity studies, the interaction parameters of the Redlich-Kister equation for the liquid Al-Zn phase were worked out with the use of the least square method. The partial and integral Gibbs energies, entropies and enthalpies were calculated and presented in tables and figures. Additionally, the concentration-concentration partial structure factors for the ideal and real Al-Zn solutions were calculated and graphically presented.

  2. Study of Phase Relations of ZnO-Containing Fayalite Slag Under Fe Saturation

    NASA Astrophysics Data System (ADS)

    Shi, Huayue; Chen, Liugang; Malfliet, Annelies; Jones, Peter Tom; Blanpain, Bart; Guo, Muxing

    2016-10-01

    A ZnO-containing fayalite-based slag can be formed in copper smelting from secondary raw materials and its high viscosity is a common issue that hinders slag tapping. In this work, the crystallization behavior of the industrial slag was observed in situ by confocal laser scanning microscopy. Solid precipitation was found to be the major cause of the poor slag fluidity. The phase relations in the industrial slag system ZnO-"FeO"-SiO2-Al2O3-CaO (CaO/SiO2 = 0.05, Al2O3/SiO2 = 0.15) were investigated by quenching the samples after reaching equilibrium at 1423 K (1150 °C) under iron saturation. The equilibrium composition of the phases was determined with electron probe micro-analysis. The effect of individual components, such as FeO, ZnO, and CaO on the phase equilibrium of the slag system has been quantitatively studied. The relation between the solid-phase fraction and the chemical composition of the slag has been revealed. Suggestions to modify the slag composition toward low viscosity are provided.

  3. Structural evolution in mechanically alloyed Al-Fe powders

    SciTech Connect

    Mukhopadhyay, D.K.; Suryanarayana, C.; Froes, F.H.

    1995-08-01

    The structural evolution in mechanically alloyed binary aluminum-iron powder mixtures containing 1, 4, 7.3, 10.7, and 25 at pct Fe was investigated using X-ray diffraction (XRD) and electron microscopic techniques. The constitution (number and identity of phases present), microstructure (crystal size, particle size), and transformation behavior of the powders on annealing were studied. The solid solubility of Fe in Al has been extended up to at least 4.5 at. pct, which is close to that observed using rapid solidification (RS) (4.4 at. pct), compared with the equilibrium value of 0.025 at. pct Fe at room temperature. Nanometer-sized grains were observed in as-milled crystalline powders in all compositions. Increasing the ball-to-powder weight ratio (BPR) resulted in a faster rate of decrease of crystal size. A fully amorphous phase was obtained in the Al-25 at. pct Fe composition, and a mixed amorphous phase plus solid solution of Fe in Al was developed in the Al-10.7 at. pct Fe alloy, agreeing well with the predictions made using the semiempirical Miedema model. Heat treatment of the mechanically alloyed powders containing the supersaturated solid solution or the amorphous phase resulted in the formation of the Al{sub 3}Fe intermetallic in all but the Al-25 at. pct Fe powders. In the Al-25 at. pct Fe powder, formation of nanocrystalline Al{sub 5}Fe{sub 2} was observed directly by milling. Electron microscope studies of the shock-consolidated mechanically alloyed Al-10.7 and 25 at. pct Fe powders indicated that nanometer-sized grains were retained after compaction.

  4. Preparation, structural and optical characterization of ZnO, ZnO: Al nanopowder

    SciTech Connect

    Mohan, R. Raj; Rajendran, K.; Sambath, K.

    2014-01-28

    In this paper, ZnO and ZnO:Al nanopowders have been synthesized by low cost hydrothermal method. Zinc nitrate, hexamethylenetetramine (HMT) and aluminium nitrate are used as precursors for ZnO and AZO with different molar ratios. The structural and optical characterization of doped and un-doped ZnO powders have been investigated by X-ray diffraction (XRD), Scanning electron microscopy (SEM), Energy dispersive X-ray spectroscopy (EDAX), photoluminescence (PL) and ultra violet visible (UV-Vis) absorption studies. The SEM results show that the hydrothermal synthesis can be used to obtain nanoparticles with different morphology. It is observed that the grain size of the AZO nanoparticles increased with increasing of Al concentration. The PL measurement of AZO shows that broad range of green emission around 550nm with high intensity. The green emission resulted mainly because of intrinsic defects.

  5. Preparation, structural and optical characterization of ZnO, ZnO: Al nanopowder

    NASA Astrophysics Data System (ADS)

    Mohan, R. Raj; Rajendran, K.; Sambath, K.

    2014-01-01

    In this paper, ZnO and ZnO:Al nanopowders have been synthesized by low cost hydrothermal method. Zinc nitrate, hexamethylenetetramine (HMT) and aluminium nitrate are used as precursors for ZnO and AZO with different molar ratios. The structural and optical characterization of doped and un-doped ZnO powders have been investigated by X-ray diffraction (XRD), Scanning electron microscopy (SEM), Energy dispersive X-ray spectroscopy (EDAX), photoluminescence (PL) and ultra violet visible (UV-Vis) absorption studies. The SEM results show that the hydrothermal synthesis can be used to obtain nanoparticles with different morphology. It is observed that the grain size of the AZO nanoparticles increased with increasing of Al concentration. The PL measurement of AZO shows that broad range of green emission around 550nm with high intensity. The green emission resulted mainly because of intrinsic defects.

  6. Fe, Ni and Zn speciation, in airborne particulate matter

    NASA Astrophysics Data System (ADS)

    Thiodjio Sendja, Bridinette; Aquilanti, Giuliana; Vassura, Ivano; Giorgetti, Marco

    2016-05-01

    The study of elemental speciation in atmospheric particulate matter is important for the assessment of the source of the particle as well for the evaluation of its toxicity. XANES data at Fe, Ni, and Zn K-edges are recorded on a sample of urban dust (from the Rimini area of Emilia Romagna region, Italy) deposited on a filter and on the NIST standard reference material 1648. Using linear combination fitting we give an indication of the chemical species of the three metals present in the samples.

  7. Photocatalytic degradation of methylene blue with Fe doped ZnS nanoparticles.

    PubMed

    Chauhan, Ruby; Kumar, Ashavani; Chaudhary, Ram Pal

    2013-09-01

    Fe doped ZnS nanoparticles (Zn1-xFexS; where x=0.00, 0.03, 0.05 and 0.10) were synthesized by a chemical precipitation method. The synthesized products were characterized by X-ray diffraction, scanning electron microscope, transmission electron microscope, UV-Vis and photoluminescence spectrometer. The X-ray diffraction and transmission electron microscope studies show that the size of crystallites is in the range of 2-5 nm. Photocatalytic activities of ZnS and 3, 5 and 10 mol% Fe doped ZnS were evaluated by decolorization of methylene blue in aqueous solution under ultraviolet and visible light irradiation. It was found that the Fe doped ZnS bleaches methylene blue much faster than the undoped ZnS upon its exposure to the visible light as compared to ultraviolet light. The optimal Fe/Zn ratio was observed to be 3 mol% for photocatalytic applications.

  8. Photocatalytic degradation of methylene blue with Fe doped ZnS nanoparticles

    NASA Astrophysics Data System (ADS)

    Chauhan, Ruby; Kumar, Ashavani; Chaudhary, Ram Pal

    2013-09-01

    Fe doped ZnS nanoparticles (Zn1-xFexS; where x = 0.00, 0.03, 0.05 and 0.10) were synthesized by a chemical precipitation method. The synthesized products were characterized by X-ray diffraction, scanning electron microscope, transmission electron microscope, UV-Vis and photoluminescence spectrometer. The X-ray diffraction and transmission electron microscope studies show that the size of crystallites is in the range of 2-5 nm. Photocatalytic activities of ZnS and 3, 5 and 10 mol% Fe doped ZnS were evaluated by decolorization of methylene blue in aqueous solution under ultraviolet and visible light irradiation. It was found that the Fe doped ZnS bleaches methylene blue much faster than the undoped ZnS upon its exposure to the visible light as compared to ultraviolet light. The optimal Fe/Zn ratio was observed to be 3 mol% for photocatalytic applications.

  9. Electrical and photoresponse properties of vacuum deposited Si/Al:ZnSe and Bi:ZnTe/Al:ZnSe photodiodes

    NASA Astrophysics Data System (ADS)

    Rao, Gowrish K.

    2017-04-01

    The paper reports fabrication and characterization of Bi:ZnTe/Al:ZnSe and Si/Al:ZnSe thin film photodiodes. The characteristics of the devices were studied under dark and illuminated conditions. The normalized spectral response, speed of photoresponse and variation of photocurrent with power density were studied in detail. Many vital parameters, such as diode ideality factor, barrier height, the thickness of the depletion region, trap depth, rise and decay times of photocurrent, were determined. Conduction mechanism in the photodiodes is discussed with the help of widely accepted theoretical models.

  10. 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 Mg2(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<Zn-0.5Al-0.3Mg<Zn-0.5Al-0.1Mg<Zn-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.

  11. Magnetic field reversal of electric polarization and magnetoelectric phase diagram of the hexaferrite Ba{sub 1.3}Sr{sub 0.7}Co{sub 0.9}Zn{sub 1.1}Fe{sub 10.8}Al{sub 1.2}O{sub 22}

    SciTech Connect

    Shen, Shipeng; Yan, Liqin; Chai, Yisheng; Cong, Junzhuang; Sun, Young

    2014-01-20

    Low magnetic field reversal of electric polarization has been demonstrated in the multiferroic Y-type hexaferrite Ba{sub 1.3}Sr{sub 0.7}Co{sub 0.9}Zn{sub 1.1}Fe{sub 10.8}Al{sub 1.2}O{sub 22} single crystal. The maximum magnetoelectric coefficient at 200 K reaches 1065 ps/m near zero magnetic field. By a systematic investigation of magnetic field dependence of magnetic and dielectric responses at various temperatures, we obtained the magnetoelectric phase diagram describing the detailed evolution of the spin-induced ferroelectric phases with temperature and magnetic field. Below 225 K, the transverse spin cone can be stabilized at zero magnetic field, which is responsible for the reversal behavior of electric polarization. Our study reveals how to eventually achieve magnetic field reversal of electric polarization in hexaferrites at room temperature.

  12. Precipitation of Zn2Al LDH by urease enzyme.

    PubMed

    Vial, Stephanie; Ghanbaja, Jaafar; Forano, Claude

    2006-01-21

    A biomineralization process based on the promotion of precipitating agent by the urea-urease enzymatic system is developed to prepare ZnAl layered double hydroxide materials and the effects of the enzymatic reaction parameters on the structural and textural properties of the materials are investigated on the basis of XRD and EM analysis.

  13. Thermoelectric properties of Fe and Al co-added Ge

    NASA Astrophysics Data System (ADS)

    Sasaki, Takayuki; Kurosaki, Ken; Yusufu, Aikebaier; Ohishi, Yuji; Muta, Hiroaki; Yamanaka, Shinsuke

    2017-04-01

    The polycrystalline bulk samples of Fe and Al co-added Ge were synthesized by melt-spinning followed by spark plasma sintering and the thermoelectric properties were examined. Here, Al acts as a p-type dopant, while Fe is expected to form FeGe2 as precipitates. Since the lattice mismatch between Ge and FeGe2 is small (<4%), they would coherently connect with each other, reducing the thermal conductivity without affecting the electrical transport. In this study, a reduction in thermal conductivity was achieved by dispersing the FeGe2 precipitates in the Al-doped Ge matrix, while they had little influences on both the carrier mobility and the Seebeck coefficient. As the results, the maximum ZT value of 0.13 was obtained at 773 K, which is three times higher than that of single-crystal Ge reported by the authors’ group [Y. Ohishi et al., Jpn. J. Appl. Phys. 55, 051301 (2016)].

  14. Strength anomaly in B2 FeAl single crystals

    SciTech Connect

    Yoshimi, K.; Hanada, S.; Yoo, M.H.; Matsumoto, N.

    1994-12-31

    Strength and deformation microstructure of B2 Fe-39 and 48%Al single crystals (composition given in atomic percent), which were fully annealed to remove frozen-in vacancies, have been investigated at temperatures between room temperature and 1073K. The hardness of as-homogenized Fe-48Al is higher than that of as-homogenized Fe-39Al while after additional annealing at 698K the hardness of Fe-48Al becomes lower than that of Fe-39Al. Fe-39Al single crystals slowly cooled after homogenizing at a high temperature were deformed in compression as a function of temperature and crystal orientation. A peak of yield strength appears around 0.5T{sub m} (T{sub m} = melting temperature). The orientation dependence of the critical resolved shear stress does not obey Schmid`s law even at room temperature and is quite different from that of b.c.c. metals and B2 intermetallics at low temperatures. At the peak temperature slip transition from <111>-type to <001>-type is found to occur macroscopically and microscopically, while it is observed in TEM that some of the [111] dislocations decompose into [101] and [010] on the (1096I) plane below the peak temperature. The physical sources for the positive temperature dependence of yield stress of B2 FeAl are discussed based on the obtained results.

  15. Fabric cutting application of FeAl-based alloys

    SciTech Connect

    Sikka, V.K.; Blue, C.A.; Sklad, S.P.; Deevi, S.C.; Shih, H.R.

    1998-11-01

    Four intermetallic-based alloys were evaluated for cutting blade applications. These alloys included Fe{sub 3}Al-based (FAS-II and FA-129), FeAl-based (PM-60), and Ni{sub 3}Al-based (IC-50). These alloys were of interest because of their much higher work-hardening rates than the conventionally used carbon and stainless steels. The FeAl-based PM-60 alloy was of further interest because of its hardening possibility through retention of vacancies. The vacancy retention treatment is much simpler than the heat treatments used for hardening of steel blades. Blades of four intermetallic alloys and commercially used M2 tool steel blades were evaluated under identical conditions to cut two-ply heavy paper. Comparative results under identical conditions revealed that the FeAl-based alloy PM-60 outperformed the other intermetallic alloys and was equal to or somewhat better than the commercially used M2 tool steel.

  16. Oxidation behavior of FeAl+Hf,Zr,B

    NASA Technical Reports Server (NTRS)

    Smialek, James L.; Doychak, Joseph

    1988-01-01

    The oxidation behavior of Fe-40Al-1Hf, Fe-40Al-1Hf-0.4B, and Fe-40Al-0.1Zr-0.4B (at. percent) alloys was characterized after 900, 1000, and 100 C exposures. Isothermal tests revealed parabolic kinetics after a period of transitional theta-alumina scale growth. The parabolic growth rates for the subsequent alpha-alumina scales were about five times higher than those for NiAl+0.1Zr alloys. The isothermally grown scales showed a propensity toward massive scale spallation due to both extensive rumpling from growth stresses and to an inner layer of HfO2. Cyclic oxidation for 200 1-hr cycles produced little degradation at 900 or 1000 C, but caused significant spallation at 1100 C in the form of small segments of the outer scale. The major difference in the cyclic oxidation of the three FeAl alloys was increased initial spallation for FeAl+Zr,B. Although these FeAl alloys showed many similarities to NiAl alloys, they were generally less oxidation resistant. It is believed that this resulted from nonoptimal levels of dopants and larger thermal expansion mismatch stresses.

  17. Tracing Earth's O2 Evolution Using Zn/Fe Systematics in Carbonates

    NASA Astrophysics Data System (ADS)

    Liu, X. M.; Hazen, R. M.; Kah, L. C.; Sverjensky, D. A.; Cui, H.; Kaufmann, A. J.

    2014-12-01

    Redox-sensitive major and trace elements in iron formations and black shales have been developed as proxies to reconstruct paleoenvironmental history in deep time [1, 2]. Many Proterozoic successions, however, contain abundant limestone and dolomite, and so carbonate-based redox proxies could help greatly to expand the paleoredox record in time and space. Most paleoenvironmental research on sedimentary rocks focuses on individual stratigraphic successions; here, however, we adopt a complementary strategy, analyzing a large suite of Mesozoic, Paleozoic, and Precambrian samples that enables us to make global statistical statements about elemental abundances through time. Here we explore the use of Zn/Fe ratios as proxies to trace the evolution of redox profiles in marine basins, based on analysis of major and trace element concentrations in micro-drilled carbonate rocks that are well characterized in terms of stratigraphy, environmental setting, and petrology. Consistent with previous studies, we observed a two step increase of mean Zn/Fe ratios in carbonates through Earth history: at the Paleoproterozoic Great Oxidation Event and during the later Neoproterozoic Oxidation Event. Diagenetic alteration is always an issue for carbonate rocks, and so we carefully screened these carbonates for possible late diagenetic effects and hydrothermal alteration. Individual samples may still bear a trace element signature of early diagenesis, but our statistical approach indicates that despite diagenetic issues, meaningful trends can be discerned in the data. It is unlikely that changes in depositional environment, secular evolution of the mantle, and/or directional change in continental inputs greatly influenced the observed trace element behavior. Therefore, Zn/Fe ratios in shallow marine carbonates have the potential to provide a useful tracer for the redox evolution of the oceans and the rise of atmospheric O2. References:[1] Sahoo et al. (2012) Ocean oxygenation in the wake

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

    SciTech Connect

    Kulkarni, Suresh D. Kumbar, Sagar; Menon, Samvit G.; Choudhari, K.S.; Santhosh, C.

    2016-05-15

    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 of 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.

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

    SciTech Connect

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

    2010-09-27

    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 {mu}A mM{sup -1} cm{sup -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.

  20. The electrochemical behaviors of Mg-8Li-3Al-0.5Zn and Mg-8Li-3Al-1.0Zn in sodium chloride solution

    NASA Astrophysics Data System (ADS)

    Lv, Yanzhuo; Liu, Min; Xu, Yan; Cao, Dianxue; Feng, Jing

    2013-03-01

    The electrochemical oxidation behaviors of Mg-8Li-3Al-0.5Zn and Mg-8Li-3Al-1.0Zn electrodes in 0.7 mol L-1 NaCl solution are investigated by methods of potentiodynamic polarization, potentiostatic oxidation, electrochemical impedance spectroscopy and scanning electron microscopy. The phase composition of Mg-8Li-3Al-0.5Zn and Mg-8Li-3Al-1.0Zn alloys is analyzed conducted by X-ray diffraction. The performances of Mg-8Li-3Al-0.5Zn and Mg-8Li-3Al-1.0Zn as the anode of Mg-H2O2 semi fuel cells are determined. The effect of Zn content on the corrosion resistant of these Mg-Li-based alloys is studied. It is found that the Mg-8Li-3Al-0.5Zn electrode has higher discharge activity and less corrosion resistance than that of Mg-8Li-3Al-1.0Zn electrode in 0.7 mol L-1 NaCl solution. The Mg-H2O2 semi fuel cell with Mg-8Li-3Al-0.5Zn anode presents a maximum power density of 100 mW cm-2 at room temperature, which is higher than that of Mg-8Li-3Al-1.0Zn anode (80 mW cm-2). The performance of semi fuel cell with the Mg-8Li-3Al-0.5Zn electrode is better than that with Mg-8Li-3Al-1.0Zn electrode, especially at higher current density (>30 mA cm-2).

  1. Zn-Site Determination in Protein Encapsulated ZnxFe3-xO4 Nanoparticles

    SciTech Connect

    Pool, V. L.; Klem, M. T.; Holroyd, J.; Harris, T.; Arenholz, E.; Young, M.; Douglas, T.; Idzerda, Y. U.

    2008-10-01

    The X-ray absorption spectra of the Fe and Zn L-edges for 6.7 nm Fe{sub 3}O{sub 4} nanoparticles grown inside 12 nm ferritin protein cages with 10%, 15%, 20% and 33% zinc doping, shows that the Zn is substitutional as Zn{sup 2+} within the iron oxide host structure. A Neel-Arrhenius plot of the blocking temperature in the frequency dependent ac-susceptibility measurements show that the particles are non-interacting and that the anisotropy energy barrier is reduced with Zn loading. X-ray magnetic circular dichroism (XMCD) of the Fe displays a linear decrease with Zn-doping in sharp contrast to the initial increase present in the bulk system. The most plausible explanation for the moment decrease is that Zn substitutes preferentially into the tetrahedral A-site as a Zn{sup 2+} cation, generating a mixed spinel.

  2. Semiconducting properties of Al doped ZnO thin films.

    PubMed

    Al-Ghamdi, Ahmed A; Al-Hartomy, Omar A; El Okr, M; Nawar, A M; El-Gazzar, S; El-Tantawy, Farid; Yakuphanoglu, F

    2014-10-15

    Aluminum doped ZnO (AZO) thin films were successfully deposited via spin coating technique onto glass substrates. Structural properties of the films were analyzed by X-ray diffraction, atomic force microscopy (AFM) and energy dispersive X-ray spectroscopy. X-ray diffraction results reveal that all the films are polycrystalline with a hexagonal wurtzite structure with a preferential orientation according to the direction (002) plane. The crystallite size of ZnO and AZO films was determined from Scherrer's formula and Williamson-Hall analysis. The lattice parameters of the AZO films were found to decrease with increasing Al content. Energy dispersive spectroscopy (EDX) results indicate that Zn, Al and O elements are present in the AZO thin films. The electrical conductivity, mobility carriers and carrier concentration of the films are increased with increasing Al doping concentration. The optical band gap (Eg) of the films is increased with increasing Al concentration. The AZO thin films indicate a high transparency in the visible region with an average value of 86%. These transparent AZO films may be open a new avenue for optoelectronic and photonic devices applications in near future.

  3. Synthesis and dielectric properties of Zn doped GdFeO3 ceramics

    NASA Astrophysics Data System (ADS)

    Sai Vandana, C.; Guravamma, J.; Hemalatha Rudramadevi, B.

    2016-09-01

    GdFeO3 and GdZn0.3Fe0.7O3 ceramics were prepared by standard Solid State Reaction method at 1200°C. The structural changes and crystallite sizes of the undoped and Zn doped ceramics were studied using the XRD data. Microstructural features and elemental composition of GdFeO3 and GdZn0.3Fe0.7O3 ceramics were determined from SEM and EDS analysis. Room temperature dielectric measurements such as dielectric constant (ɛ´), tangent loss (tan5) and AC conductivity (oac) were carried out in the frequency range (100Hz to 1MHz). Improved dielectric properties of GdZn0.3Fe0.7O3 over GdFeO3 ceramics with low values of dielectric loss render them as potential materials in the areas of microwave communication systems, information storage, spintronics, sensors, etc.

  4. Observations of Al, Fe and Ca(+) in Mercury's Exosphere

    NASA Technical Reports Server (NTRS)

    Bida, Thomas A.; Killen, Rosemary M.

    2011-01-01

    We report 5-(sigma) tangent column detections of Al and Fe, and strict 3-(sigma) tangent column upper limits for Ca(+) in Mercury's exosphere obtained using the HIRES spectrometer on the Keck I telescope. These are the first direct detections of Al and Fe in Mercury's exosphere. Our Ca(-) observation is consistent with that reported by The Mercury Atmospheric and Surface Composition Spectrometer (MASCS) on the MErcury Surface, Space ENvironment, GEochemistry, and Ranging (MESSENGER) spacecraft.

  5. Optically dense Fe:ZnSe crystals for energy scaled gain switched lasing

    NASA Astrophysics Data System (ADS)

    Myoung, NoSoung; Fedorov, Vladimir V.; Mirov, Sergey B.

    2010-02-01

    This work is focused on study and optimization of diffusion of Fe in ZnSe from the metal phase, comparative spectroscopic characterization of kinetic properties of Fe:ZnSe crystals with a wide range of concentrations, and energy scaling of the Fe:ZnSe gain-switched laser. Iron doping of ZnSe polycrystals was performed by thermal diffusion from the iron film made by thermal evaporation process. Special cleaning of the ZnSe surfaces and optimization of the ZnSe substrate temperature and the rate of Fe evaporation resulted in significant enhancement of the diffusion process and enabled fabrication of high optical density crystals with Fe concentration up to 2x1020 cm-3. The diffusion coefficient and diffusion length of iron in ZnSe at 1000°C were estimated as 2.1x10-9 cm2/s and 1.3 mm, respectively. We report a detailed absorption, emission, and kinetics of fluorescence of Fe:ZnSe spectroscopy performed over a broad range of Fe concentrations (5x1018 - 2x1020 cm-3) and temperatures (14-300K) under direct 2.78μm excitation.

  6. Aqueous synthesis and enhanced photocatalytic activity of ZnO/Fe2O3 heterostructures

    NASA Astrophysics Data System (ADS)

    Achouri, Faouzi; Corbel, Serge; Aboulaich, Abdelhay; Balan, Lavinia; Ghrabi, Ahmed; Ben Said, Myriam; Schneider, Raphaël

    2014-10-01

    We report a facile synthesis of ZnO/Fe2O3 heterostructures based on the hydrolysis of FeCl3 in the presence of ZnO nanoparticles. The material structure, composition, and its optical properties have been examined by means of transmission electron microscopy, scanning electron microscopy, X-ray diffraction, X-ray photoelectron spectroscopy and diffuse reflectance UV-visible spectroscopy. Results obtained show that 2.9 nm-sized Fe2O3 nanoparticles produced assemble with ZnO to form ZnO/Fe2O3 heterostructures. We have evaluated the photodegradation performances of ZnO/Fe2O3 materials using salicylic acid under UV-light. ZnO/Fe2O3 heterostructures exhibited enhanced photocatalytic capabilities than commercial ZnO due to the effective electron/hole separation at the interfaces of ZnO/Fe2O3 allowing the enhanced hydroxyl and superoxide radicals production from the heterostructure.

  7. Metastable Phases of Rapidly Solidified Al-Rich Al-Fe Alloys

    DTIC Science & Technology

    1984-01-01

    same contrast. 20 FIGURE 9. Convergent beam diffraction pattern taken from a single crystal globular "S" phase. 21 FIGURE 10. The flower -like phase. 21...FIGURE 11. Convergent beam diffraction pattern obtained from the flower -like phase. 21 iii "- "’., % i ’ % " PAGE FIGURE 12. At-i wt.% Fe. Cellular...any of the previously reported aluminum-rich phases (Al3Fe, AlxFe, AI6Fe, A19Fe2, or AlmFe) [2,3]. An additional flower - shaped phase was detected in

  8. Zn and Fe biofortification: the right chemical environment for human bioavailability.

    PubMed

    Clemens, Stephan

    2014-08-01

    A considerable fraction of global disease burden and child mortality is attributed to Fe and Zn deficiencies. Biofortification, i.e. the development of plants with more bioavailable Zn and Fe, is widely seen as the most sustainable solution, provided suitable crops can be generated. In a cereal-dominated diet availability of Fe and Zn for absorption by the human gut is generally low and influenced by a highly complex chemistry. This complexity has mostly been attributed to the inhibitory effect of Fe and Zn binding by phytate, the principal phosphorus storage compound in cereal and legume seeds. However, phytate is only part of the answer to the multifaceted bioavailability question, albeit an important one. Recent analyses addressing elemental distribution and micronutrient speciation in seeds strongly suggest the existence of different Fe and Zn pools. Exploration of natural variation in maize showed partial separation of phytate levels and Fe bioavailability. Observations made with transgenic plants engineered for biofortification lend further support to this view. From a series of studies the metal chelator nicotianamine is emerging as a key molecule. Importantly, nicotianamine levels have been found to not only increase the loading of Fe and Zn into grains. Bioavailability assays indicate a strong activity of nicotianamine also as an enhancer of intestinal Fe and Zn absorption.

  9. Structural, optical, hyperfine and magnetization studies of ZnO encapsulated α-Fe nanoparticles

    SciTech Connect

    Rathore, A.K.; Pati, S.P.; Roychowdhury, A.; Das, D.

    2014-12-15

    We report the successful preparation and characterization of magnetic-fluorescent nanoparticles (NPs) by overcoming the difficulty of handling α-Fe nanoparticles that are less stable and have high affinity to get oxidized in air even at room temperature. Nanocrystalline α-Fe particles embedded by ZnO have been synthesized by a two step chemical route. Concentration of α-Fe has been varied as 15, 30 and 50 wt% of the sample. Detailed investigations on structural, hyperfine, optical and magnetic characteristics have been carried out. X-ray diffraction, transmission electron microscopy and fourier transform infrared spectroscopy studies have been used to confirm the coexistence of Fe and ZnO phases in the nanocomposites (NCs). The presence of α-Fe is also confirmed by Mössbauer spectroscopy. However, other forms of iron are also detected in the sample. UV–vis spectrum of nanocomposites shows a red shift with respect to the pristine ZnO which is attributed to the electron transfer between Fe and ZnO that provides support to the formation of the Fe- ZnO NC. The photoluminescence (PL) spectra of Fe-ZnO nanocomposites exhibit blue shift of the UV and weaker visible emission lines compared to the pristine ZnO. Nanocomposites are found to be magnetically soft having high saturation magnetization with very low remanence. Low temperature coercivity enhancement due to freezing of uncompensated surface spins is also found in all samples.

  10. Alloy development and processing of FeAl: An overview

    SciTech Connect

    Maziasz, P.J.; Goodwin, G.M.; Alexander, D.J.; Viswanathan, S.

    1997-03-01

    In the last few years, considerable progress has been made in developing B2-phase FeAl alloys with improved weldability, room-temperature ductility, and high-temperature strength. Controlling the processing-induced microstructure is also important, particularly for minimizing trade-offs in various properties. FeAl alloys have outstanding resistance to high-temperature oxidation, sulfidation, and corrosion in various kinds of molten salts due to formation of protective Al{sub 2}O{sub 3} scales. Recent work shows that FeAl alloys are carburization-resistant as well. Alloys with 36 to 40 at. % Al have the best combination of corrosion resistance and mechanical properties. Minor alloying additions of Mo, Zr, and C, together with microalloying additions of B, produce the best combination of weldability and mechanical behavior. Cast FeAl alloys, with 200 to 400 {mu}m grain size and finely dispersed ZrC, have 2 to 5% tensile ductility in air at room-temperature, and a yield strength > 400 MPa up to about 700 to 750{degrees}C. Extruded ingot metallurgy (I/M) and powder metallurgy (P/M) materials with refined grain sizes ranging from 2 to 50 {mu}m, can have 10 to 15% ductility in air and be much stronger, and can even be quite tough, with Charpy impact energies ranging from 25 to 105 J at room-temperature. This paper highlights progress made in refining the alloy composition and exploring processing effects on FeAl for monolithic applications. It also includes recent progress on developing FeAl weld-overlay technology, and new results on welding of FeAl alloys. It summarizes some of the current industrial testing and interest for applications.

  11. In situ microcalorimetry study of ZnFe2O4 nanoparticle formation under solvothermal conditions.

    PubMed

    Liu, Jun; Nan, Zhaodong; Gao, Shengli

    2015-10-21

    Solvothermal methods have been widely used to synthesize different kinds of materials. However, only little is known about how precursor solutions react to form solid precipitates via this method. In the present study, in situ microcalorimetry is first used to investigate the formation mechanism under solvothermal conditions, where ZnFe2O4 synthesized using a solvothermal method was selected as the model sample. Some novel results are obtained, such as with the experimental temperature increase, (1) the homogeneous solution transforms to a gel containing amorphous Fe2(C2H4O2)3 and ZnC2H4O2, and NaNO3 crystals; (2) the gel dissolves; (3) α-(Fe,Zn)OOH and α-Fe2O3 are synthesized; (4) the α-(Fe,Zn)OOH transforms to α-Fe2O3; (5) Fe(2+) is formed at about 159 °C, which acts as a catalyst for the formation of Fe3O4; (6) the Fe3O4 crystals are synthesized at about 200 °C; (7) the Fe3O4 is transformed to the ZnFe2O4 with the help of NO3(-), and the reaction was kept at 200 °C for about 20 h. This study shows a facile in situ method for the investigation of reaction processes of solvothermal methods.

  12. Structural ordering tendencies in the new ferromagnetic Ni-Co-Fe-Ga-Zn Heusler alloys

    NASA Astrophysics Data System (ADS)

    Dannenberg, Antje; Siewert, Mario; Gruner, Markus E.; Wuttig, Manfred; Entel, Peter

    In search for new ferromagnetic shape memory alloys (FSMA) we have calculated structural energy differences, magnetic exchange interaction constants and mixing energies of quaternary (X1X2)YZ Heusler alloys with X1,X2,Y =Ni,Co,Fe and Z=Ga, Zn using density functional theory. The comparison of the energy profiles of (NiCo)FeZ, (FeNi)CoZ, and (FeCo)NiZ with Z=Ga and Zn as a function of the tetragonal distortion c / a reveals that the energetically preferred ordering type is (NiCo)FeGa and (NiCo)FeZn which shows that Fe prefers to occupy the same cubic sublattice as Ga or Zn what implies that Fe favors Co and Ni as nearest neighbors, respectively. The Curie temperatures of (NiCo)FeGa and (NiCo)FeZn are high of the order of 600 K. (NiCo)FeGa, which has the same valence electron concentration (e/a=7.5) as Ni2MnGa and also possesses a high martensitic transformation temperature (>500 K), is of interest for future magnetic shape memory devices.

  13. Influence of Ti and La Additions on the Formation of Intermetallic Compounds in the Al-Zn-Si Bath

    NASA Astrophysics Data System (ADS)

    Xu, Jin; Gu, Qin-Fen; Li, Qian; Lu, Hu-Sheng

    2016-12-01

    The effect of Ti and La additions on the formation of intermetallic compounds (IMCs) in the galvalume (55Al-Zn-1.6Si wt pct) bath was investigated experimentally and further studied with first-principles calculation. The studied baths contain: 1 wt pct Fe, with Ti content ranging from 0.05 to 0.15 wt pct and La content ranging from 0.05 to 0.30 wt pct. Combination of the experimental results with the thermodynamic analysis shows that the solubility of Fe in the alloy bath decreases with an increase of Ti content, which results in the formation of mass dross. Compared with the Ti-containing alloy, La promotes the formation of τ 5 phase (Fe2Al8Si). When both Ti and La are added, Fe4Al13, τ 5, τ 6 (β-Al4.5FeSi), TiAl3, and Ti2Al20La phases were observed. Since these IMCs would consume more Si in the bath, the decrease of Si content with Ti and La additions is more significant than that of the bath without these additions. Furthermore, the formation mechanism of Ti/TiAl3/Ti2La20La core-shell structure in the coating bath is proposed. This study has implications for strategic design of industry hot-dip production with exceptional mechanical properties of Al alloy coating.

  14. Photoacoustic properties of mineral marmatite (ZnS+Fe)

    NASA Astrophysics Data System (ADS)

    Nikolić, P. M.; Durić, S.; Todorović, D. M.; Blagojević, V.; Urošević, D.; Mihajlović, P.; Bojičić, A. I.; Radulović, K. T.; Vasiljević-Radović, D. G.; Elazar, J.

    1999-03-01

    Thermal diffusivity and some electron transport properties of semiconducting ore mineral marmatite (ZnS+Fe) from the Trepca mine, were determined using the photoacoustic method with a transmission detection configuration. Thermal diffusivity (for single crystal DTSC=0.2×10-5 m2/s and polycristalline small grain size DTPC=0.86×10-6 m2/s), coefficient of the carrier diffusion (DSC=0.108×10-2 m2/s and DPC=0.5×10-3 m2/s), the excess carrier life time (τSC=34 μs and τPC=5 μs) and the rear and front surface recombination velocities were calculated by fitting experimental spectra and theoretical photoacoustic amplitude and phase signals. The value of minority free carrier holes of single crystal marmatite was calculated for the first time as μp˜428 cm2/Vs.

  15. Magnetism in GdFe2Zn20

    NASA Astrophysics Data System (ADS)

    Antropov, Vladimir

    2007-03-01

    The magnetic structure formation and the origin of the exchange couplings in GdFe2Zn20 have been studied using the standard band-structure methods at T=0K and the ab-initio spin dynamics in the paramagnetic case. At low temperatures the relative importance of the different channels of the magnetic coupling have been analyzed. At high temperatures the soft spin deviation modes responsible for the observed high temperature of the magnetic phase transition [1] have been identified. Several strong magnetic short range order parameters have been found in this material. [1] S. Jia, S.L. Bud'ko, G.D. Samolyuk, P.C. Canfield. cond-mat/0606615

  16. Carbonate phobic (Zn,Mn)-Al hydrotalcite-like compounds

    NASA Astrophysics Data System (ADS)

    Sampieri, Alvaro; Fetter, Geolar; Pfeiffer, Heriberto; Bosch, Pedro

    2007-05-01

    The synthesis method of three series of nitrated (Zn,Mn)-Al hydrotalcites in the presence of microwave irradiation is presented. MnO 4- anions were partially incorporated between the layers of those compounds and a staged intercalation occurred. In the presence of CO 2, nitrated and permanganate intercalated hydrotalcites were tested in CO 32- retention. Carbonate phobic character was observed and it may be correlated to the poor basicity of hydrotalcites, thus, to the electronegativity of M 2+ cations.

  17. Fe Segregation Effects on Grain Boundary Migration in Al

    NASA Astrophysics Data System (ADS)

    Mendelev, Mikhail; Srolovitz, David; Ackland, Graeme; Han, Seungwu

    2004-03-01

    We investigate the effect of Fe impurities on grain boundary migration in Al. We fit a new interatomic potential to experimental data and our first principles results. This potential is validated by comparing simulated and experimental liquid Al-Fe alloy structure factors. This potential was used to simulate boundary migration in pure Al. The boundary velocity vs. driving force data at several temperatures were used to extract the boundary mobility and the activation energy for boundary migration. The activation energy was found to be at least an order of magnitude smaller than that obtained from experiment. This discrepancy is presumably associated with impurities in the Al samples. Therefore, we examined the effect of Fe on boundary migration in Al by determining the heat of segregation and the Fe diffusivity in Al as input to the Cahn-Lücke-Stüwe analytical impurity drag model. This analysis showed that even extremely small quantities of Fe (less than 1 ppm) in Al can reduce the grain boundary mobility by two orders of magnitude at T=723 K and even more at lower T, consistent with the extant experimental data.

  18. Zn location in the W-type hexagonal ferrite SrZnCoFe16O27.

    PubMed

    Graetsch, Heribert A

    2002-11-01

    The title compound, SrZnCoFe(16)O(27) (ZnCo-W), strontium zinc cobalt hexadecairon oxide, crystallizes in space group P6(3)/mmc, with the Sr atom at a site with -6 m 2 symmetry and Zn(2+) located at two tetrahedral sites (4e and 4f, each with 3m symmetry) of the spinel blocks. The Zn occupancy is 36% on equipoint 4e and 14% on 4f. The enrichment of diamagnetic ions on one of seven sublattices is thought to be responsible for the high temperature dependence of the saturation magnetization.

  19. Pharmocokinetical study of Al- and Zn-sulphonated phthalocyanines

    NASA Astrophysics Data System (ADS)

    Kazachkina, Natalia I.; Zharkova, Natalia N.; Fomina, Galina I.; Yakubovskaya, Raisa I.; Sokolov, Victor V.; Lukyanets, Eugeny A.

    1996-12-01

    The comparative pharmacokinetical study of Al- and Zn- sulphonated phthalocyanines (AlPcS and ZnPcS, respectively) is the aim of the present work. Mice bearing solid Ehrlich tumor were used in this study. AlPcS (sodium salt) and ZnPcS (ammonium and sodium salts were used as photosensitizers. The photosensitizers were injected i/v in various doses. The exogenous fluorescence of tissues (tumor, liver, spleen, kidneys, muscles, skin) was measured dynamically after sensitization. It was shown that all of the photosensitizers under study had similar distribution pattern in organisms of mice and were selectively accumulated in the Ehrlich tumor tissue. The exogenous fluorescence intensity of tissues and it tumor:normal muscle ratio (Cs) depended on the dosage of the preparation, on the time, which had passed after drug injection, and on the stage of tumor growth. It was also shown that the kinetics of the tissue uptake of the studied sensitizers varied to some extent. Thus, the obtained data may be interesting for deeper understanding of the interaction of the dye with malignant tissues.

  20. Methotrexate intercalated ZnAl-layered double hydroxide

    NASA Astrophysics Data System (ADS)

    Chakraborty, Manjusha; Dasgupta, Sudip; Soundrapandian, Chidambaram; Chakraborty, Jui; Ghosh, Swapankumar; Mitra, Manoj K.; Basu, Debabrata

    2011-09-01

    The anticancerous drug methotrexate (MTX) has been intercalated into an ZnAl-layered double hydroxide (LDH) using an anion exchange technique to produce LDH-MTX hybrids having particle sizes in the range of 100-300 nm. X-ray diffraction studies revealed increases in the basal spacings of ZnAl-LDH-MTX hybrid on MTX intercalation. This was corroborated by the transmission electron micrographs, which showed an increase in average interlayer spacing from 8.9 Å in pristine LDH to 21.3 Å in LDH-MTX hybrid. Thermogravimetric analyses showed an increase in the decomposition temperature for the MTX molecule in the LDH-MTX hybrid indicating enhanced thermal stability of the drug molecule in the LDH nanovehicle. The cumulative release profile of MTX from ZnAl-LDH-MTX hybrids in phosphate buffer saline (PBS) at pH 7.4 was successfully sustained for 48 h following Rigter-Peppas model release kinetics via diffusion.

  1. An Assessment of the Al- Fe- N System

    NASA Astrophysics Data System (ADS)

    Hillert, Mats; Jonsson, Stefan

    1992-11-01

    The thermodynamic properties of the Al-Fe-N system are assessed, taking various types of information into account. For solid AIN, a description very similar to that given by JANAF is found to yield reasonable predictions for the solubility of A1N in face-centered cubic (fcc) Fe and in liquid Fe. An ionic two-sublattice model is applied to the liquid phase, containing two N species, N-3 and N0 The melting point of A1N is taken as 3068 K, and a required gas pressure of 9.75 bar is predicted. A sublimation point of 2690 K at 1 bar is also predicted. A plot of the liquidus surfaces in the Fe-rich end of the Al-Fe-N system is presented.

  2. Oxidation Resistant Ti-Al-Fe Diffusion Barrier for FeCrAlY Coatings on Titanium Aluminides

    NASA Technical Reports Server (NTRS)

    Brady, Michael P. (Inventor); Smialke, James L. (Inventor); Brindley, William J. (Inventor)

    1996-01-01

    A diffusion barrier to help protect titanium aluminide alloys, including the coated alloys of the TiAl gamma + Ti3Al (alpha2) class, from oxidative attack and interstitial embrittlement at temperatures up to at least 1000 C is disclosed. The coating may comprise FeCrAlX alloys. The diffusion barrier comprises titanium, aluminum, and iron in the following approximate atomic percent: Ti-(50-55)Al-(9-20)Fe. This alloy is also suitable as an oxidative or structural coating for such substrates.

  3. Nanostructured Al-ZnO/CdSe/Cu2O ETA solar cells on Al-ZnO film/quartz glass templates

    PubMed Central

    2011-01-01

    The quartz/Al-ZnO film/nanostructured Al-ZnO/CdSe/Cu2O extremely thin absorber solar cell has been successfully realized. The Al-doped ZnO one-dimensional nanostructures on quartz templates covered by a sputtering Al-doped ZnO film was used as the n-type electrode. A 19- to 35-nm-thin layer of CdSe absorber was deposited by radio frequency magnetron sputtering, coating the ZnO nanostructures. The voids between the Al-ZnO/CdSe nanostructures were filled with p-type Cu2O, and therefore, the entire assembly formed a p-i-n junction. The cell shows the energy conversion efficiency as high as 3.16%, which is an interesting option for developing new solar cell devices. PACS: 88.40.jp; 73.40.Lq; 73.50.Pz. PMID:22136081

  4. Nanostructured Al-ZnO/CdSe/Cu2O ETA solar cells on Al-ZnO film/quartz glass templates

    NASA Astrophysics Data System (ADS)

    Wang, Xianghu; Li, Rongbin; Fan, Donghua

    2011-12-01

    The quartz/Al-ZnO film/nanostructured Al-ZnO/CdSe/Cu2O extremely thin absorber solar cell has been successfully realized. The Al-doped ZnO one-dimensional nanostructures on quartz templates covered by a sputtering Al-doped ZnO film was used as the n-type electrode. A 19- to 35-nm-thin layer of CdSe absorber was deposited by radio frequency magnetron sputtering, coating the ZnO nanostructures. The voids between the Al-ZnO/CdSe nanostructures were filled with p-type Cu2O, and therefore, the entire assembly formed a p-i-n junction. The cell shows the energy conversion efficiency as high as 3.16%, which is an interesting option for developing new solar cell devices. PACS: 88.40.jp; 73.40.Lq; 73.50.Pz.

  5. Thermoelectric Transport Properties of Fe-Enriched ZnO with High-Temperature Nanostructure Refinement.

    PubMed

    Liang, Xin

    2015-04-22

    Thermoelectric properties of Fe-doped ZnO materials are investigated and correlated with the phase and microstructural evolution. Both a ZnO solid solution phase and a ZnFe2O4 spinel phase are observed. Analysis was made of temperature measurements of Seebeck coefficients as combined with the law of mixture to estimate the Fermi level in the constituent phases, which are further correlated with the Fe solute concentration in ZnO lattices and the overall electrical conductivity. In addition, the thermoelectric figure of merit is found to increase with the actual Fe content in ZnO lattices, due to the reduced thermal conductivity by point defect scattering of phonons and enhanced electrical transport via electron doping. The maximum achievable power factor of Fe-doped ZnO material is found to be similar to that of the ZnO-In2O3 system. Another important finding of the present work is the significant nanostructure refinement in 18 month old FeO1.5-doped ZnO after high-temperature thermal treatment, leading to further reduced thermal conductivity, which is beneficial and promising for high-temperature thermoelectric performance.

  6. Geochemical studies of Fe, Mn, Co, As, Cr, Sb, Zn, Sc and V in surface sediments from Jiaozhou Bay

    NASA Astrophysics Data System (ADS)

    Wu, Run; Li, Pei-Quan; Miao, Lu-Tian; Zhang, Shu-Xin; Tian, Wei-Zhi

    1994-12-01

    The contents of nearly forty-elements in surface sediments in Jiaozhou Bay were determined using a Neutron Activation Analysis Technique (Grancini, et al., 1976; Li Peiquan et al., 1985, 1986; Li Xiuxia et al., 1986). This paper's detailed discussion on only nine elements (Fe, Mn, Co, Cr, Sc, As, Sb, Zn and V) includes their distributions, concentrations, correlationships, material sources, background, etc. Based on Zavaristski's classification method, Fe, Mn, Co, Cr and V belong to the second group; As and Sb to the eighth groups: Sc and Zn to the third and sixth groups. It was found that their notably good correlationship is mainly due to the similarity of their ionic structures and that their variation is controlled by the Fe content (except Mn). The source of sediments is mainly terristrial material, and the composition of sediment is similar to that of shale and shale+clay. The contents for a large number of elements are within the scope of the background level, but there still is pollution of Zn and Cr, at least in a few stations.

  7. Large magnetostriction in directionally solidified FeGa and FeGaAl alloys

    NASA Astrophysics Data System (ADS)

    Srisukhumbowornchai, N.; Guruswamy, S.

    2001-12-01

    The magnetostriction of Fe-x at. % Ga (x=15, 20, and 27.5) was measured, for alloys processed under different directional solidification conditions, and the effect of partial substitution of Ga with Al on the magnetostriction of the alloys was examined. Magnetostriction measurements were carried out at different prestress levels varying from 0 to 55 MPa. Ga additions in the range of 15-27.5 at. % Ga in Fe were found to improve the magnetostriction of the disordered bcc phase of Fe by as much as 1 order of magnitude. The applied fields for saturation magnetostriction and the hysteresis observed were small. Magnetostriction values as high as 271×10-6 were obtained in polycrystalline Fe-27.5 at. % Ga rods prepared using a directional growth (DG) process at a growth rate of 22.5 mm/h. This process, which is essentially a seedless vertical Bridgman technique, resulted in near [001] textured polycrystalline Fe-Ga alloys. The preferred [001] crystallographic orientation of the DG alloys was approximately 14° away from the rod direction. For Ga contents between 15 and 27.5 at. % in Fe, the Ga atoms increase the Fe-Fe spacing in the disordered bcc (A2) phase and reduce the magnetic moment of Fe. Substitution of Ga with Al has a significant effect on the magnetostriction of the Fe-Ga alloys. Small substitution of 5 at. % Al for Ga in the Fe-20 at. % Ga alloy increases the magnetostriction in Fe, and the value is slightly larger than that of the Fe-20 at. % Ga alloy. A higher substitution amount of Al tends to decrease the magnetostriction.

  8. Electrical and optical properties of Al-doped ZnO and ZnAl2O4 films prepared by atomic layer deposition

    PubMed Central

    2013-01-01

    ZnO/Al2O3 multilayers were prepared by alternating atomic layer deposition (ALD) at 150°C using diethylzinc, trimethylaluminum, and water. The growth process, crystallinity, and electrical and optical properties of the multilayers were studied with a variety of the cycle ratios of ZnO and Al2O3 sublayers. Transparent conductive Al-doped ZnO films were prepared with the minimum resistivity of 2.4 × 10−3 Ω·cm at a low Al doping concentration of 2.26%. Photoluminescence spectroscopy in conjunction with X-ray diffraction analysis revealed that the thickness of ZnO sublayers plays an important role on the priority for selective crystallization of ZnAl2O4 and ZnO phases during high-temperature annealing ZnO/Al2O3 multilayers. It was found that pure ZnAl2O4 film was synthesized by annealing the specific composite film containing alternative monocycle of ZnO and Al2O3 sublayers, which could only be deposited precisely by utilizing ALD technology. PMID:23537274

  9. Segregation-Induced Subsurface Restructuring of FeAl(100)

    NASA Astrophysics Data System (ADS)

    Kottche, M.; Graupner, H.; Hammer, L.; Heinz, K.; Zehner, D. M.

    1996-03-01

    For FeAl, the stacking sequence in the [100] direction of the bulk crystal (CsCl structure) consists of alternating, single element planes. After sputtering, the selvedge region is depleted in Al. Following annealing to 350 ^circC, Al segregates to the surface region and a c(2 x 2) structure develops.(H. Graupner, L. Hammer, K. Müller, and D. M. Zehner, Surf. Sci. 322 (1995) 103. Research is sponsored by the *University of Erlangen-Nürnberg, Germany and DAAD, and the **Division of Materials Sciences, U.S. Department of Energy, under contract DE-AC05-84OR21400 with Lockheed Martin Energy Systems, Inc.) We have used low-energy electron diffraction (LEED) and Auger electron spectroscopy to investigate the structure and composition of this surface. From a detailed LEED I-V analysis, it has been determined that the subsurface region of the (100) surface orders with annealing, to form a stable Fe_3Al slab which is capped by an Al top layer and acts as an interface to the bulk FeAl. Within the limits of error, the interfacial Fe_3Al is similar to the bulk phase with some slight geometric rippling of the layers containing both elements. Annealing to higher temperatures leads to additional Al diffusion and eliminates the restructuring, resulting in a (1 x 1) phase.

  10. In situ investigation of spinodal decomposition in hypermonotectic Al Bi and Al Bi Zn alloys

    NASA Astrophysics Data System (ADS)

    Schaffer, P. L.; Mathiesen, R. H.; Arnberg, L.; Di Sabatino, M.; Snigirev, A.

    2008-05-01

    Spinodal decomposition of hypermonotectic Al-6 wt.%Bi, Al-8 wt.%Bi and Al-6 wt.%Bi-8 wt.%Zn alloys has been investigated using synchrotron radiography. In the case of the 6 and 8 wt.%Bi binary alloys undercoolings of 70 and 110 K, respectively, were required to initiate the L→L1+L2 reaction, which appeared to occur very close to the monotectic reaction temperature. The nucleated L2 droplets were set in collective size-dependent motion by forces coupled to external fields (gravity and imposed temperature gradient) as well as forces arising due to internal fluctuations of the system. With experimental conditions similar to those realized during strip casting of the same materials, it was found that the size-dependant droplet velocity field combined with Stokes drag at the L1-L2 interfaces as well as attractive and repulsive diffusion-coupling between adjacent L2 droplets, yield complex meso- to microscale hydrodynamics. The hydrodynamics are the dominating mechanisms for L2 droplet coagulation, and are accordingly decisive for the final size distribution and geometrical dispersion of the soft Bi-rich component in the cast material. A different decomposition mode was observed in the Al-6 wt.%Bi-8 wt.%Zn ternary alloy, with the L2 droplets undergoing an immiscible-miscible-immiscible transition. In contrast to what was found for the binaries, L2 domains formed at relatively small undercoolings, and very little droplet motion was observed, as all L2 domains nucleated and remained on the crucible walls until they encroached on the monotectic front. At small distances from the monotectic front a Zn-rich solute boundary layer preceding the α-Al, caused the L2 domains to dissolve as Bi-Zn-Al regains complete miscibility upon reaching a critical Zn-concentration. In the shallow mush region behind the monotectic reaction, a high Zn solid solubility and a relatively fast diffusion of Zn in α-Al combine to cause a rapid diminishing Zn concentration in the mush liquid

  11. Room temperature ferromagnetism in undoped and Fe doped ZnO nanorods: Microwave-assisted synthesis

    SciTech Connect

    Limaye, Mukta V.; Singh, Shashi B.; Das, Raja; Poddar, Pankaj; Kulkarni, Sulabha K.

    2011-02-15

    One-dimensional (1D) undoped and Fe doped ZnO nanorods of average length {approx}1 {mu}m and diameter {approx}50 nm have been obtained using a microwave-assisted synthesis. The magnetization (M) and coercivity (H{sub c}) value obtained for undoped ZnO nanorods at room temperature is {approx}5x10{sup -3} emu/g and {approx}150 Oe, respectively. The Fe doped ZnO samples show significant changes in M -H loop with increasing doping concentration. Both undoped and Fe doped ZnO nanorods exhibit a Curie transition temperature (T{sub c}) above 390 K. Electron spin resonance and Moessbauer spectra indicate the presence of ferric ions. The origin of ferromagnetism in undoped ZnO nanorods is attributed to localized electron spin moments resulting from surface defects/vacancies, where as in Fe doped samples is explained by F center exchange mechanism. -- Graphical abstract: Room temperature ferromagnetism has been reported in undoped and Fe doped ZnO nanorods of average length {approx}1 {mu}m and diameter {approx}50 nm. Display Omitted Research Highlights: {yields} Microwave-assisted synthesis of undoped and Fe doped ZnO nanorods. {yields} Observation of room temperature ferromagnetism in undoped and Fe doped ZnO nanorods. {yields} Transition temperature (T{sub c}) obtained in undoped and doped samples is above 390 K. {yields} In undoped ZnO origin of ferromagnetism is explained in terms of defects/vacancies. {yields} Ferromagnetism in Fe doped ZnO is explained by F-center exchange mechanism.

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

    NASA Astrophysics Data System (ADS)

    Verma, Kuldeep Chand; Kotnala, R. K.

    2016-05-01

    We reported long-range ferromagnetic interactions in La doped Zn0.95Fe0.05O nanoparticles that mediated through lattice defects or vacancies. Zn0.92Fe0.05La0.03O (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 results into ZnO nanoparticles than nanorods that found in pure ZnO and Zn0.95Fe0.05O 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 Zn0.95Fe0.05O 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.

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

    NASA Astrophysics Data System (ADS)

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

    2016-02-01

    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. 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.

  15. Improved photoluminescence property of CTAB assisted polyaniline-AlZnO nanocomposite

    SciTech Connect

    Mitra, Mousumi; Banerjee, Dipali; Kargupta, Kajari; Ganguly, Saibal

    2015-06-24

    Polyaniline-Al doped ZnO ((PANI-AlZnO:: 70:30) nanocomposite was prepared via in situ chemical oxidative polymerization, while the hexagonal powder of AlZnO was synthesized via sol-gel technique, using Hexadecyltrimethylammonium bromide (CTAB) as a capping agent. The prepared nanocomposite was characterized by High resolution transmission electron microscopy (HRTEM), EDAX, X-ray diffraction (XRD) and Fourier transforms infrared (FTIR) spectra. The optical property of the nanomaterials is examined by photoluminescence (PL) spectra analysis. The XRD pattern confirms the formation of Al doped ZnO as well as PANI. The HRTEM images of the composite showed the formation of hexagonal AlZnO embedded in polyaniline matrix. EDAX spectrum shows the compositional analysis of the nanocomposite. FTIR spectra confirm the formation of nanocomposite of PANI and hexagonal AlZnO. The PL intensity of the nanocomposite is improved as compared to pure AlZnO.

  16. 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).

  17. Influence of SOP modes on Raman spectra of ZnO(Fe) nanoparticles

    NASA Astrophysics Data System (ADS)

    Hadžić, B.; Romčević, N.; Romčević, M.; Kuryliszyn-Kudelska, I.; Dobrowolski, W.; Narkiewicz, U.; Sibera, D.

    2015-04-01

    Nanocrystaline samples of ZnO(Fe) were synthesized by traditional wet chemical method followed by calcinations. Samples were characterized by X-ray diffraction to determine composition of the samples (ZnO, ZnFe2O4 and Fe2O3) and the mean crystalline size (from 8 to 51 nm). In this paper we report the experimental spectra of Raman scattering (from 200 to 1600 cm-1) with surface optical phonons (SOP) in range of 500-550 cm-1. The phonon of registered phase's exhibit effects connected to phase concentration, while the SOP phonon mode exhibit significant confinement effect.

  18. Interfacial Phenomena in Al/Al, Al/Cu, and Cu/Cu Joints Soldered Using an Al-Zn Alloy with Ag or Cu Additions

    NASA Astrophysics Data System (ADS)

    Pstruś, Janusz; Gancarz, Tomasz

    2014-05-01

    The studies of soldered joints were carried out in systems: Al/solder/Al, Al/solder/Cu, Cu/solder/Cu, where the solder was (Al-Zn)EUT, (Al-Zn)EUT with 0.5, 1.0, and 1.5 at.% of Ag and (Al-Zn)EUT with 0.5, 1.0, and 1.5 at.% of Cu addition. Brazing was performed at 500 °C for 3 min. The EDS analysis indicated that the composition of the layers starting from the Cu pad was CuZn, Cu5Zn8, and CuZn4, respectively. Wetting tests were performed at 500 °C for 3, 8, 15, and 30 min, respectively. Thickness of the layers and their kinetics of growth were measured based on the SEM micrographs. The formation of interlayers was not observed from the side of Al pads. On the contrary, dissolution of the Al substrate and migration of Al-rich particles into the bulk of the solder were observed.

  19. Preparation and photocatalytic application of Znsbnd Fe2O4@ZnO core-shell nanostructures

    NASA Astrophysics Data System (ADS)

    Rahimi, Rahmatollah; Heidari-Golafzani, Mahdi; Rabbani, Mahboubeh

    2015-09-01

    In this study, nanohallow Znsbnd Fe2O4 microspheres were synthesis by ZnCl2, FeCl3ṡ6H2O and ammonium acetate using the hydrothermal method. Then, Znsbnd Fe2O4@ZnO core-shell structured spheres were prepared by using immobilization of ZnO nanoparticles on the surface of Zn-ferrite spheres via sol-gel rout. SEM and TEM images showed morphology and core-shell structure of particles. Results of VSM illustrate that Znsbnd Fe2O4 and Znsbnd Fe2O4@ZnO particles are superparamagnetic. Photocatalytic activity studies confirm that synthesised Znsbnd Fe2O4@ZnO core-shell sphere with molar ratio of 1:1 had excellent photodegradating behavior to methylene blue (MB) as compared to other core-shell ratios, pure Znsbnd Fe2O4 and pure ZnO.

  20. Magnetic properties of spin frustrated spinel ZnFe{sub 2}O{sub 4}/ZnCr{sub 2}O{sub 4} superlattices

    SciTech Connect

    Murata, T.; Kozuka, Y. Uchida, M.; Kawasaki, M.

    2015-11-21

    Superlattice films composed of frustrated spin systems, [ZnFe{sub 2}O{sub 4}]{sub m}/[ZnCr{sub 2}O{sub 4}]{sub m}, are grown on MgAl{sub 2}O{sub 4} (111) substrates by pulsed laser deposition, and their frustrated magnetism is studied. The superlattice films show spin-glass behavior and the spin-glass transition temperature (T{sub g}) varies nonmonotonically as a function of the layer thickness m. T{sub g} increases with decreasing m due to an increase in the inhomogeneous exchange interaction between Cr{sup 3+} and Fe{sup 3+} at the interface. However, below m = 4, a decrease in T{sub g} is observed. Compared with the solid solution Zn(CrFe)O{sub 4} film and the other superlattices, the decrease in T{sub g} is considered to be a unique property of the periodically modulated short period superlattices.

  1. First principles study of magneto-optical properties of Fe-doped ZnO

    NASA Astrophysics Data System (ADS)

    Shaoqiang, Guo; Qingyu, Hou; Zhenchao, Xu; Chunwang, Zhao

    2016-12-01

    Studies on optical band gaps and absorption spectra of Fe-doped ZnO have conflicting conclusions, such as contradictory redshifted and blueshifted spectra. To solve this contradiction, we constructed models of un-doped and Fe-doped ZnO using first-principles theory and optimized the geometry of the three models. Electronic structures and absorption spectra were also calculated using the GGA+U method. Higher doping content of Fe resulted in larger volume of doped system, and higher total energy resulted in lower stability. Higher formation energy also led to more difficult doping. Meanwhile, the band gaps broadened and the absorption spectra exhibited an evident blue shift. The calculations were in good agreement with the experimental results. Given the unipolar structure of ZnO, four possible magnetic coupling configurations for Zn14Fe2O16 were calculated to investigate the magnetic properties. Results suggest that Fe doping can improve ferromagnetism in the ZnO system and that ferromagnetic stabilization was mediated by p-d exchange interaction between Fe-3d and O-2p orbitals. Therefore, the doped system is expected to obtain high stability and high Curie temperature of diluted magnetic semiconductor material, which are useful as theoretical bases for the design and preparation of the Fe-doped ZnO system's magneto-optical properties.

  2. Structural, optical and electronic properties of Fe doped ZnO thin films

    NASA Astrophysics Data System (ADS)

    Singh, Karmvir; Devi, Vanita; Dhar, Rakesh; Mohan, Devendra

    2015-09-01

    Fe doped ZnO thin films have been deposited by pulsed laser deposition technique on quartz substrate to study structural, optical and electronic structure using XRD, AFM, UV-visible and X-ray absorption spectroscopy. XRD study reveals that Fe doping has considerable effect on stress, strain, grain size and crystallinity of thin films. UV-visible study determines that band gap of pristine ZnO decreases with Fe doping, which can be directly correlated to transition tail width and grain size. Change in electronic structure with Fe doping has been examined by XAS study.

  3. Preparation of soft magnetic composites for Fe particles coated with (NiZn)Fe2O4 via microwave treatment

    NASA Astrophysics Data System (ADS)

    Peng, Yuandong; Nie, Junwu; Zhang, Wenjun; Bao, Chongxi; Ma, Jian; Cao, Yang

    2015-12-01

    Soft magnetic composites (SMCs) of Fe particles coated with fine particle Ni0.5Zn0.5Fe2O4 ferrite were prepared via microwave heat treatment, and the magnetic properties and microstructures of these composites were investigated. The results show that a well-distributed Ni0.5Zn0.5Fe2O4 coating layer was formed on the surface of the Fe particles upon microwave annealing. The SMCs sample treated by microwave heating at 800 °C for 30 min under N2 had a perfect insulation layer between the Fe particles and showed stable permeability and low core loss as well as good magnetic characteristics over a wide frequency range.

  4. Synthesis of Fe Doped ZnO Nanowire Arrays that Detect Formaldehyde Gas.

    PubMed

    Jeon, Yoo Sang; Seo, Hyo Won; Kim, Su Hyo; Kim, Young Keun

    2016-05-01

    Owing to their chemical and thermal stability and doping effects on providing electrons to the conduction band, doped ZnO nanowires have generated interest for use in electronic devices. Here we report hydrothermally grown Fe-doped ZnO nanowires and their gas-sensing properties. The synthesized nanowires have a high crystallinity and are 60 nm in diameter and 1.7 μm in length. Field-emission scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), and X-ray photoelectron spectroscopy (XPS) are employed to understand the doping effects on the microstructures and gas sensing properties. When the Fe-doped ZnO nanowire arrays were evaluated for gas sensing, responses were recorded through changes in temperature and gas concentration. Gas sensors consisting of ZnO nanowires doped with 3-5 at.% Fe showed optimum formaldehyde (HCHO) sensing performance at each working temperature.

  5. Synthesis, characterization and conductivity studies of ZnFe2O4 nanoparticles

    NASA Astrophysics Data System (ADS)

    Narsimulu, D.; Venkateswarlu, M.; Satyanarayana, N.

    2015-06-01

    Transition metal ferrites with general formula AB2O4 (A=Co, Cu, Mn, Zn, B=Fe+3) could be used as an anode materials in lithium ion battery (LIB), because, lithium ion batteries fabricated using ferrite materials show the high capacity than commonly used graphite. The ZnFe2O4 with cubic spinel structured material was prepared by acrylamide assisted citrate combustion process. Phase, structural coordination and thermal behavior of the prepared ZnFe2O4 were confirmed by powder X-ray diffraction, FTIR spectra and TG/DTA thermogram respectively. Morphology and specific surface area of the ZnFe2O4 were identified by SEM and BET surface analyzer respectively and its conductivity studies were made through impedance spectroscopy.

  6. Synthesis, characterization and conductivity studies of ZnFe{sub 2}O{sub 4} nanoparticles

    SciTech Connect

    Narsimulu, D.; Satyanarayana, N.; Venkateswarlu, M.

    2015-06-24

    Transition metal ferrites with general formula AB{sub 2}O{sub 4} (A=Co, Cu, Mn, Zn, B=Fe{sup +3}) could be used as an anode materials in lithium ion battery (LIB), because, lithium ion batteries fabricated using ferrite materials show the high capacity than commonly used graphite. The ZnFe{sub 2}O{sub 4} with cubic spinel structured material was prepared by acrylamide assisted citrate combustion process. Phase, structural coordination and thermal behavior of the prepared ZnFe{sub 2}O{sub 4} were confirmed by powder X-ray diffraction, FTIR spectra and TG/DTA thermogram respectively. Morphology and specific surface area of the ZnFe{sub 2}O{sub 4} were identified by SEM and BET surface analyzer respectively and its conductivity studies were made through impedance spectroscopy.

  7. Lubrication performance and mechanisms of Mg/Al-, Zn/Al-, and Zn/Mg/Al-layered double hydroxide nanoparticles as lubricant additives

    NASA Astrophysics Data System (ADS)

    Li, Shuo; Bhushan, Bharat

    2016-08-01

    Solid lubricant particles are commonly used as oil additives for low friction and wear. Mg/Al-, Zn/Al-, and Zn/Mg/Al-layered double hydroxides (LDH) were synthesized by coprecipitation method. The benefits of LDH nanoparticles are that they can be synthesized using chemical methods where size and shape can be controlled, and can be modified organically to allow dispersal in fluids. The LDH nanoparticles were characterized by X-ray diffraction, scanning electron microscope, thermogravimetry, and differential scanning calorimetry. A pin-on-disk friction and wear tester was used for evaluating the friction and wear properties of LDH nanoparticles as lubricant additives. LDH nanoparticles have friction-reducing and anti-wear properties compared to oil without LDHs. Mg/Al-LDH has the best lubrication, possibly due to better thermal stability in severe conditions.

  8. Kinetic study of ZnFe{sub 2}O{sub 4} formation from mechanochemically activated Zn-Fe{sub 2}O{sub 3} mixtures

    SciTech Connect

    Botta, P.M.; Aglietti, E.F.; Porto Lopez, J.M.

    2006-04-13

    The kinetics of ZnFe{sub 2}O{sub 4} formation starting from mechanochemically activated Zn-Fe{sub 2}O{sub 3} powders are studied. Mixtures of metallic Zn and hematite were activated under air atmosphere in a high energy mill and thermally treated at temperatures between 500 and 650 deg. C during several holding times. During the activation, morphological and compositional changes were observed, but ZnFe{sub 2}O{sub 4} formation was not detected. The ZnFe{sub 2}O{sub 4} content in heated samples was determined using quantitative X-ray diffraction analysis. The resulting conversion-time curves were fitted using different kinetic models of solid-state reaction, calculating the kinetic parameters of the studied reaction. The comparison with the conventional synthesis method revealed that the mechanochemical treatment provoked a change of the rate-controlling step and a significant decrease of the activation energy, which was more evident for the more activated mixtures.

  9. Half-Heusler phase related structural perturbations near stoichiometric composition FeZnSb

    SciTech Connect

    Xiong, Ding-Bang; Zhao, Yufeng

    2011-05-15

    Half-Heusler phases XYZ (Pearson symbol cF12) are chemically versatile and rich in physical properties. The half-Heusler phase in the Fe-Zn-Sb ternary system was reported in the year 2000. In this work, two new ternary phases are identified in the vicinity of the equiatomic composition FeZnSb in the same system: Fe{sub 1-x}ZnSb (tetragonal, space group P4/nmm, Pearson symbol tP6-{delta}, Z=2: a=4.1113(6) A, c=6.0127(12) A for x=0.08 (1), and a=4.1274(6) A, c=6.0068(12) A for x=0.12 (2)); and Fe{sub 7.87}Zn{sub 6.72}Sb{sub 8} (Fe{sub 0.98}Zn{sub 0.84}Sb) (3) (cubic, space group Fm-3m, Pearson symbol cF96-{delta}, Z=4, a=11.690(13) A). 1 and 2 crystallize in the PbFCl-type structure, and 3 adopts a unique 2x2x2 supercell of a normal half-Heusler structure. The structures of both the tetragonal and cubic phases can be described as assemblies of half-Heusler structure related subunits. Electrical resistivity measurement on the pure sample of 2 shows it has metallic-like behavior, and its thermal and magnetic properties are also characterized. -- Graphical Abstract: Three types of half-Heusler structure related subunit are identified in the vicinity of the equiatomic composition FeZnSb in the Fe-Zn-Sb system. Display Omitted Highlights: {yields} Two new related phases around equiatomic composition FeZnSb. {yields} Structural perturbation with the small variation of composition. {yields} Magnetic properties of the structure with defects.

  10. The evolution of authigenic Zn-Pb-Fe-bearing phases in the Grieves Siding peat, western Tasmania

    NASA Astrophysics Data System (ADS)

    Awid-Pascual, Richelle; Kamenetsky, Vadim S.; Goemann, Karsten; Allen, Neil; Noble, Taryn L.; Lottermoser, Bernd G.; Rodemann, Thomas

    2015-08-01

    A thick peat profile overlying mineralized metasediments possesses exceptionally high base metal contents (up to 28.6 wt% Zn and up to 3.8 wt% Pb) in the form of abundant detrital and authigenic minerals. This metal-rich peat was examined using X-ray diffraction, scanning electron microscopy and Raman spectroscopy to determine the characteristics, mineral associations, phase evolution and conditions of formation of Zn-Pb-Fe-bearing minerals within the peat. Mineral assemblages consisting of sulfides, silicates, sulfates, oxides, carbonates and phosphates could be classified as follows: (1) detrital minerals supplied by the surrounding rocks (i.e., Cambrian volcanics and sediments, Ordovician carbonates) and (2) authigenic phases that are precipitated in situ, including the predominant Zn-Pb-Fe-bearing phases. Detrital minerals are characterized by weathering-related morphologies (e.g., round, smooth surfaces and angular edges and dissolution pits), whereas authigenic phases are recognized by their delicate microparticle textures (e.g., bladed, framboidal and botryoidal textures). Zinc-bearing phases are represented by non-stoichiometric phases, also containing S, C, O and Al; sphalerite, baileychlore and Fe-Zn-Pb carbonate. Authigenic Pb- and Fe-bearing phases are also present in the peat such as galena, anglesite, plumbojarosite, magnetite and pyrite. A "line of descent" of authigenic sulfides has been established, suggesting that a non-stoichiometric, possibly amorphous Zn-rich phase is a precursor to the sphalerite. Stages of pyrite formation, where massive polycrystalline pyrite is produced via disseminated and framboidal pyrite, have also been hypothesized in this study. The assemblages of authigenic minerals in the peat reflect dynamic physical and chemical conditions, including biological processes, and are not necessarily in equilibrium with each other.

  11. Comparison of Fe-AlPILC and Fe-ZSM-5 catalysts used for degradation of methomyl

    NASA Astrophysics Data System (ADS)

    Lázár, Károly; Tomašević, Andjelka; Bošković, Goran; Kiss, Ernő

    2009-07-01

    Catalytic performances of Fe-AlPILC (14 wt.% Fe) and Fe-ZSM-5 (5 wt.% Fe) catalysts are compared in the wet oxidative degradation of methomyl. Fe-ZSM-5 exhibits outstanding whereas Fe-AlPILC shows only mediocre activity. Positions of iron are analysed in the two catalysts by Mössbauer spectroscopy. Iron is in highly dispersed state in Fe-AlPILC whereas in the other case a hematite/ZSM-5 composite is formed. The catalytic activity is attributed to iron located and stabilized in ionic dispersion.

  12. Electrical, magnetic, and thermal properties of the δ-FeZn10 complex intermetallic phase

    NASA Astrophysics Data System (ADS)

    Jazbec, S.; Koželj, P.; Vrtnik, S.; Jagličić, Z.; Popčević, P.; Ivkov, J.; Stanić, D.; Smontara, A.; Feuerbacher, M.; Dolinšek, J.

    2012-08-01

    We report the electrical, magnetic, and thermal properties of the δ-FeZn10 phase in the zinc-rich domain of the Fe-Zn system. The δ-FeZn10 phase possesses high structural complexity typical of complex metallic alloys: a giant unit cell comprising 556 atoms, polyhedral atomic order with icosahedrally coordinated environments, fractionally occupied lattice sites, and statistically disordered atomic clusters that introduce intrinsic disorder into the structure. Structural disorder results in suppression of the electrical and heat transport phenomena, making δ-FeZn10 a poor electrical and thermal conductor. Structural complexity results in a complex electronic structure that is reflected in the opposite signs of the thermoelectric power and the Hall coefficient. The δ-FeZn10 phase is paramagnetic down to the lowest investigated temperature of 2 K with a significant interspin coupling of antiferromagnetic type. Specific heat indicates the formation of short-range-ordered spin clusters at low temperatures, very likely a precursor of a phase transition to a collective magnetic state that would take place below 2 K. The magnetoresistance of δ-FeZn10 is sizeable, amounting to 1.5% at 2 K in a 9-T field. The electrical resistivity exhibits a maximum at about 220 K, and its temperature dependence could be explained by the theory of slow charge carriers, applicable to metallic systems with weak dispersion of the electronic bands, where the electron motion changes from ballistic to diffusive upon heating.

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

    SciTech Connect

    Khokhra, Richa; Kumar, Rajesh

    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 ZnO nanosheets depends upon the presence of surface oxygen vacancies.

  14. Effect of Cu Addition to Zn-12Al Alloy on Thermal Properties and Wettability on Cu and Al Substrates

    NASA Astrophysics Data System (ADS)

    Gancarz, Tomasz; Pstruś, Janusz; Mosińska, Sylwia; Pawlak, Sylwia

    2016-01-01

    The thermal properties, electrical resistivity, thermal linear expansion and tensile strength of a new high-temperature lead-free solder based on a eutectic Zn-Al alloy with 0.5, 1.0, or 1.5 at. pct Cu added were studied. Wettability studies on Cu substrate were performed with flux at 773 K (500 °C) for 60, 180, 240, 900, 1800, and 3600 seconds, and for 480 seconds at 733 K, 753 K, 773 K, 793 K, and 823 K (460 °C, 480 °C, 500 °C, 520 °C, and 550 °C, respectively). The experiment was designed to demonstrate the effect of the addition of Cu on the kinetics of the formation and growth of the CuZn, Cu5Zn8, CuZn4, and Al4Cu9 phases, which were identified by X-ray diffraction analysis. Wetting tests were also performed on the Al substrate, for 15 and 30 seconds at 773 K and 793 K (500 °C and 520 °C, respectively). Very low contact angles on Al pads were obtained. The electrical resistivity of Zn-Al-Cu alloys was slightly higher than that of the ZnAl eutectic alloy. The present results are discussed with respect to the available literature on Zn-Al and Zn-Al-Cu alloys.

  15. Doping concentration driven morphological evolution of Fe doped ZnO nanostructures

    SciTech Connect

    Sahai, A.; Goswami, N.; Kumar, Y.; Agarwal, V.; Olive-Méndez, S. F.

    2014-10-28

    In this paper, systematic study of structural, vibrational, and optical properties of undoped and 1-10 at.% Fe doped ZnO nanostructures, synthesized adopting chemical precipitation route, has been reported. Prepared nanostructures were characterized employing an assortment of microscopic and spectroscopic techniques, namely Scanning Electron Microscopy (SEM), Transmission Electron Microscopy (TEM), Energy Dispersive X-ray (EDX) Spectroscopy, X-ray Diffraction (XRD), Fourier Transform Infrared (FTIR), Micro-Raman Spectroscopy (μRS), and UV-visible and Photoluminescence (PL) spectroscopy. With Fe incorporation, a gradual morphological transformation of nanostructures is demonstrated vividly through SEM/TEM characterizations. Interestingly, the morphology of nanostructures evolves with 1–10 at. % Fe doping concentration in ZnO. Nanoparticles obtained with 1 at. % Fe evolve to nanorods for 3 at. % Fe; nanorods transform to nanocones (for 5 at. % and 7 at. % Fe) and finally nanocones transform to nanoflakes at 10 at. % Fe. However, at all these stages, concurrence of primary hexagonal phase of Zn{sub 1-x}Fe{sub x}O along with the secondary phases of cubic ZnFe{sub 2}O{sub 4} and rhombohedric Fe{sub 2}O{sub 3}, is revealed through XRD analysis. Based on collective XRD, SEM, TEM, and EDX interpretations, a model for morphological evolution of nanostructures was proposed and the pivotal role of Fe dopant was deciphered. Furthermore, vibrational properties analyzed through Raman and FTIR spectroscopies unravel the intricacies of formation and gradual enhancement of secondary phases with increased Fe concentration. UV-visible and PL spectroscopic analyses provided further insight of optical processes altering with Fe incorporation. The blue shift and gradual quenching of visible photoluminescence with Fe doping was found in accordance with structural and vibrational analyses and explicated accordingly.

  16. FeAl-TiC and FeAl-WC composites - melt infiltration processing, microstructure and mechanical properties

    SciTech Connect

    Subramanian, R.; Schneibel, J.H.

    1997-04-01

    TiC-based and WC-based cermets were processed with iron aluminide, an intermetallic, as a binder by pressureless melt infiltration to near full density (> 97 % theoretical density). Phase equilibria calculations in the quaternary Fe-Al-Ti-C and Fe-Al-W-C systems at 145{degrees}C were performed to determine the solubility of the carbide phases in liquid iron aluminide. This was done by using Thermocalc{trademark} and the results show that molten Fe-40 at.% Al in equilibrium with Ti{sub 0.512}C{sub 0.488} and graphite, dissolves 4.9 at% carbon and 64 atomic ppm titanium. In the Fe-Al-W-C system, liquid Fe-40 at.% Al in equilibrium with graphite dissolves about 5 at.% carbon and 1 at.% tungsten. Due to the low values for the solubility of the carbide phases in liquid iron aluminide, liquid phase sintering of mixed powders does not yield a dense, homogeneous microstructure for carbide volume fractions greater than 0.70. Melt infiltration of molten FeAl into TiC and WC preforms serves as a successful approach to process cermets with carbide contents ranging from 70 to 90 vol. %, to greater than 97% of theoretical density. Also, the microstructures of cermets prepared by melt infiltration were very homogeneous. Typical properties such as hardness, bend strength and fracture toughness are reported. SEM observations of fracture surfaces suggest the improved fracture toughness to result from the ductility of the intermetallic phase. Preliminary experiments for the evaluation of the oxidation resistance of iron aluminide bonded cermets indicate that they are more resistant than WC-Co cermets.

  17. 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.

  18. Synthesis and properties of ZnO-HMD@ZnO-Fe/Cu core-shell as advanced material for hydrogen storage.

    PubMed

    Bouazizi, N; Boudharaa, T; Bargougui, R; Vieillard, J; Ammar, S; Le Derf, F; Azzouz, A

    2017-04-01

    In this paper, a new synthetic strategy towards functionalized ZnO-HMD@ZnO-Fe/Cu core-shell using sol-gel process modified by chemical grafting of hexamethylenediamine (HMD) on the core and in-situ dispersion of Cu(0)/Fe(0) as metallic nanoparticles (M-NPs) on the shell. The as-prepared core-shell materials were fully characterized by transmission electron microscopy, X-ray powder diffractometry, diffuse reflectance and FT-IR spectrophotometery, photoluminescence, and complexes impedance spectroscopy measurements. The XRD patterns agreed with that of the ZnO typical wurtzite structure, indicating good crystallinity of ZnO-HMD@ZnO-Fe/Cu, with the presence of Fe(0) and Cu(0) phases. Hexamethylenediamine grafting and M-NPs insertion were highly activated and enhanced the core and shell interface by the physiochemical interaction. After functionalization, luminescence intensities and electrical properties of both core and core-shell nanoparticles are improved, indicating the effects of the surface groups on the charge transfer of ZnO-HMD@ZnO-Fe/Cu. The hydrogen capacity retention was depended strongly on the composition and structure of the obtained core-shell. Iron/Copper-loaded ZnO-HMD@ZnO materials exhibited the highest capacity for hydrogen storage. The excellent stability and performance of the ZnO-HMD@ZnO-Fe/Cu core-shell make it an efficient candidate for hydrogen storage.

  19. Thermoluminescence of K-Mg-Al-Zn fluorophosphate glass

    NASA Astrophysics Data System (ADS)

    Thomas, Sunil; Chithambo, M. L.

    2017-02-01

    The thermoluminescence of beta irradiated K-Mg-Al-Zn fluorophosphate glass is reported. A glow-curve corresponding to 10 Gy measured at 1 °C/s shows two peaks, a weaker-intensity one at 70 °C and a more prominent one at 235 °C, the subject of this report. The main peak was observed to fade with delay between irradiation and measurement and specifically, by 11% in 15 h. Its dose response is superlinear in the dose range 1-190 Gy although the change was linear for the initial 10 Gy. Regarding kinetic analysis, the activation energy of the higher temperature peak was evaluated as 1.31 eV and that of the lower temperature peak was found as 0.47 eV. It was also noted that the main peak is affected by thermal quenching with an activation energy for thermal quenching equal to 1.37 eV. It is proposed that the mechanism associated with the thermoluminescence in K-Mg-Al-Zn fluorophosphate glass is that electrons trapped by the metal cations are released during heating and then recombine with holes at oxygen sites.

  20. Highly selective fluorescent chemosensor for detection of Fe3+ based on Fe3O4@ZnO

    PubMed Central

    Li, Jingshuai; Wang, Qi; Guo, Zhankui; Ma, Hongmin; Zhang, Yong; Wang, Bing; Bin, Du; Wei, Qin

    2016-01-01

    The combination of fluorescent nanoparticles and specific molecular probes appears to be a promising strategy for developing fluorescent nanoprobes. In this work, L-cysteine (L-Cys) capped Fe3O4@ZnO core-shell nanoparticles were synthesized for the highly selective detection of Fe3+. The proposed nanoprobe shows excellent fluorescent property and high selectivity for Fe3+ due to the binding affinity of L-Cys with Fe3+. The binding of Fe3+ to the nanoprobe induces an apparent decrease of the fluorescence. Thus a highly selective fluorescent chemosensor for Fe3+ was proposed based on Fe3O4@ZnO nanoprobe. The magnetism of the nanoprobe enables the facile separation of bound Fe3+ from the sample solution with an external magnetic field, which effectively reduces the interference of matrix. The detection limit was 3 nmol L−1 with a rapid response time of less than 1 min. The proposed method was applied to detect Fe3+ in both serum and wastewater samples with acceptable performance. All above features indicated that the proposed fluorescent probe as sensing platform held great potential in applications of biological and analytical field. PMID:27000972

  1. Seasonal variations in the translocation of micronutrients (Fe, Zn and Cu) from soil to shoots using isotopic compositions

    NASA Astrophysics Data System (ADS)

    Pichat, S.; Fekiacova, Z.; Cadiou, J.

    2011-12-01

    We have investigated the uptake and translocation of three essential micronutrients (Fe, Zn and Cu) in four plant species using both concentrations and isotopic compositions. The goals were (1) to document the evolution of isotopic compositions in the soil and the shoots over a year, (2) to test the effect of senescence on the translocation of the micronutrients and (3) to test the effect of types of plant cover on the isotopic composition of both plants and soils. The plants were chosen to maximize the physiological (annual vs. perennial, woody vs. herbaceous) and taxonomical differences (monocotyledon vs. dicotyledon). The experiment was conducted in the field at the Oak Observatory at the Haute-Provence Observatory (O3HP), France. The area has been a fallow land for 70 years and is located far away from any anthropic pollution source. The area has been subdivided in four zones as a function of plant cover. On average, shoots are enriched in heavy Zn and Cu isotopes at fall compared to spring. The senescent leaves of oak (Quercus pubescens) and smoke bush (Cotinus coggygria) are enriched in heavy Zn isotopes and have lower Zn concentrations than the green ones. This behavior is in agreement with kinetic fractionation of Zn isotopes associated to the redistribution of Zn from senescent to green leaves by the phloem. Cu concentrations are similar in green and senescent leaves of the same species and there is no systematic behavior in terms of Cu isotopic composition. Hence, Cu does not appear to be redistributed at senescence. Previous studies have shown that strategy I plants shoots were enriched in light Fe isotopes1,2,3 compared to the soil, while there was a small enrichment in heavy isotopes (Δ56Feshoot-soil < 0.2%) for strategy II plants1 (Δ56Feshoot-soil = δ56Feshoot - δ56Fesoil; δ56Fe = [(56Fe/54Fe)sample/(56Fe/54Fe)std -1] × 103). To interpret these fractionations reduction of Fe(III) to Fe(II) before uptake was suggested to occur for strategy I

  2. Highly efficient and selective adsorption of In3+ on pristine Zn/Al layered double hydroxide (Zn/Al-LDH) from aqueous solutions

    NASA Astrophysics Data System (ADS)

    Barnabas, Mary Jenisha; Parambadath, Surendran; Mathew, Aneesh; Park, Sung Soo; Vinu, Ajayan; Ha, Chang-Sik

    2016-01-01

    A pristine Zn/Al-layered double hydroxide (Zn/Al-LDH) showed excellent adsorption ability and selectivity towards In3+ ions from aqueous solutions. The adsorption behaviour as a function of the contact time, solution pH, ionic strength, and amount of adsorbent under ambient conditions revealed a strong dependency on the pH and ionic strength over In3+ intake. The structure and properties of Zn/Al-LDH and In3+ adsorbed Zn/Al-LDH (In-Zn/Al-LDH) were examined carefully by X-ray diffraction, Fourier transform infrared spectroscopy, N2-sorption/desorption, UV-vis spectroscopy, and X-ray photoelectron spectroscopy. The adsorbent had a sufficient number of active sites that were responsible for the In3+ adsorption and quite stable even after the adsorption process. The selective adsorption of In3+ on Zn/Al-LDH was also observed even from a mixture containing competing ions, such as Mn2+, Co2+, Ni2+, Cd2+, Pb2+, and Cu2+. The adsorption experiments showed that Zn/Al-LDH is a promising material for the pre-concentration and selective removal of In3+ from large volumes of aqueous solutions.

  3. Processing and properties of FeAl-bonded composites

    SciTech Connect

    Schneibel, J.H.; Subramanian, R.; Alexander, K.B.; Becher, P.F.

    1996-12-31

    Iron aluminides are thermodynamically compatible with a wide range of ceramics such as carbides, borides, oxides, and nitrides, which makes them suitable as the matrix in composites or cermets containing fine ceramic particulates. For ceramic contents varying from 30 to 60 vol.%, composites of Fe-40 at. % Al with WC, TiC, TiB{sub 2}, and ZrB{sub 2} were fabricated by conventional liquid phase sintering of powder mixtures. For ceramic contents from 70 to 85 vol.%, pressureless melt infiltration was found to be a more suitable processing technique. In FeAl-60 vol.% WC, flexure strengths of up to 1.8 GPa were obtained, even though processing defects consisting of small oxide clusters were present. Room temperature fracture toughnesses were determined by flexure testing of chevron-notched specimens. FeAl/WC and FeAl/TiC composites containing 60 vol.% carbide particles exhibited K{sub Q} values around 20 MPa m{sup 1/2}. Slow crack growth measurements carried out in water and in dry oxygen suggest a relatively small influence of water-vapor embrittlement. It appears therefore that the mechanical properties of iron aluminides in the form of fine ligaments are quite different from their bulk properties. Measurements of the oxidation resistance, dry wear resistance, and thermal expansion of iron aluminide composites suggest many potential applications for these new materials.

  4. Development of ODS-Fe{sub 3}Al alloys

    SciTech Connect

    Wright, I.G.; Pint, B.A.; Tortorelli, P.F.; McKamey, C.G.

    1997-12-01

    The overall goal of this program is to develop an oxide dispersion-strengthened (ODS) version of Fe{sub 3}Al that has sufficient creep strength and resistance to oxidation at temperatures in the range 1000 to 1200 C to be suitable for application as heat exchanger tubing in advanced power generation cycles. The main areas being addressed are: (a) alloy processing to achieve the desired alloy grain size and shape, and (b) optimization of the oxidation behavior to provide increased service life compared to semi-commercial ODS-FeCrAl alloys intended for the same applications. The recent studies have focused on mechanically-alloyed powder from a commercial alloy vendor. These starting alloy powders were very clean in terms of oxygen content compared to ORNL-produced powders, but contained similar levels of carbon picked up during the milling process. The specific environment used in milling the powder appears to exert a considerable influence on the post-consolidation recrystallization behavior of the alloy. A milling environment which produced powder particles having a high surface carbon content resulted in a consolidated alloy which readily recrystallized, whereas powder with a low surface carbon level after milling resulted in no recrystallization even at 1380 C. A feature of these alloys was the appearance of voids or porosity after the recrystallization anneal, as had been found with ORNL-produced alloys. Adjustment of the recrystallization parameters did not reveal any range of conditions where recrystallization could be accomplished without the formation of voids. Initial creep tests of specimens of the recrystallized alloys indicated a significant increase in creep strength compared to cast or wrought Fe{sub 3}Al, but the specimens failed prematurely by a mechanism that involved brittle fracture of one of the two grains in the test cross section, followed by ductile fracture of the remaining grain. The reasons for this behavior are not yet understood. The

  5. Bipolar resistive switching and conduction mechanism of an Al/ZnO/Al-based memristor

    NASA Astrophysics Data System (ADS)

    Gul, Fatih; Efeoglu, Hasan

    2017-01-01

    In this study, a direct-current reactive sputtered Al/ZnO/Al-based memristor device was fabricated and its resistive switching (RS) characteristics investigated. The optical and structural properties were confirmed by using UV-vis spectrophotometry and x-ray diffraction, respectively. The memristive and resistive switching characteristics were determined using time dependent current-voltage (I-V-t) measurements. The typical pinched hysteresis I-V loops of a memristor were observed. In addition, the device showed forming-free, uniform and bipolar RS behavior. The low electric field region exhibited ohmic conduction, while the Schottky emission (SE) was found to be the dominant conduction mechanism in the high electric field region. A weak Poole-Frenkel (PF) emission also appeared. In conclusion, it was suggested that the SE and PF mechanisms were related to the oxygen vacancies in the ZnO.

  6. 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.

  7. Morphological evolution and strengthening behavior of α-Al(Fe,Mn)Si in Al-6Si-2Fe-xMn alloys

    NASA Astrophysics Data System (ADS)

    Gao, Tong; Hu, Kaiqi; Wang, Longshuai; Zhang, Bangran; Liu, Xiangfa

    β-Al5FeSi is preferred to form in Al-Si-Fe alloys, normally exhibiting needlelike, which is harmful for the mechanical properties. In this paper, with the addition of 1%, 1.5% and 3% Mn into an Al-6Si-2Fe alloy, β-Al5FeSi phase was found to transform to skeleton, flower-like and coarse dendritic α-Al(Fe,Mn)Si, respectively. The novel flower-like α-Al(Fe,Mn)Si crystals contain developed branches with the average diameter of ∼200 nm, performing strengthening effect on the tensile property. Detailed morphologies of α-Al(Fe,Mn)Si phase and the formation mechanism were discussed.

  8. Ferromagnetic behavior due to Al3+ doping into ZnO nanorods

    NASA Astrophysics Data System (ADS)

    Yingsamphancharoen, T.; Nakarungsee, P.; Herng, T. S.; Ding, J.; Tang, I. M.; Thongmee, S.

    2016-12-01

    Al doped ZnO nanorods (NR's) having Al concentration up to 10 mol% were grown by the hydrothermal method. XRD measurements showed that the Al substituted ZnO NR's maintained the hexagonal wurtzite structure for all levels of Al substitution. EDX measurements of the ZnO:Al NR's indicated that the Al substitution created additional Zn vacancies in the wurtzite structure which is reflected in the enhanced photoluminescence emission in the visible light spectra between 450 and 550 nm of the more heavily doped ZnO:Al NR's. SEM images of the heavier doped ZnO:Al nanorods showed nano nodules being formed on the surface of the hexagonal shaped NR's. The saturation magnetizations of the ZnO:Al NR's as measured by a SQUID magnetometer increased to 10.66×10-4 emu/g as more Al was substituted in. The hysteresis loops for the ZnO:Al NR's began to exhibit novel effects, such as horizontal shift (exchange bias field 0.0382 kOe for the 9 mol% NR) and butterfly shapes.

  9. Composition and solidification microstructure selection in the interdendritic matrix between primary Al{sub 3}Fe dendrites in hypereutectic Al-Fe alloys

    SciTech Connect

    Liang, D.; Korgul, P.; Jones, H.

    1996-07-01

    The composition and constitution of matrix microstructure between plate-like Al{sub 3}Fe dendrites in Bridgman-grown hypereutectic Al-Fe alloys has been determined as a function of alloy concentration C{sub 0} and growth velocity V in the ranges 2.5 < C{sub 0} < 28.1 wt%Fe and 0.01 < V < 5.0 mm/s. The transition at V = 0.1 mm/s from a fully eutectic matrix at C{sub 0} = 3.5 wt%Fe to one containing {alpha}Al dendrites at C{sub 0} {ge} 4.7 wt%Fe is attributed to growth temperatures of {alpha}Al dendrites that are higher than those of eutectic in a matrix of lower iron-content, which results from these conditions. The matrix eutectic changes from irregular {alpha}-Al-Al{sub 3}Fe to regular {alpha}Al-Al{sub x}Fe with increasing V, the transition velocity increasing from 0.1 to 0.2 mm/s for C{sub 0} values of 9.5 and 14 wt%Fe up to 0.35--1.0 mm/s for C{sub 0} values of 18.7--28.1 wt%Fe. This increased transition velocity, compared with that for {alpha}-Al-Al{sub 3}Fe to {alpha}Al-Al{sub 6}Fe at lower concentration, is indicative of a lower formation temperature for the {alpha}Al-Al{sub x}Fe than the {alpha}Al-Al{sub 6}Fe eutectic.

  10. Ferromagnetic behaviour of Fe-doped ZnO nanograined films.

    PubMed

    Straumal, Boris B; Protasova, Svetlana G; Mazilkin, Andrei A; Tietze, Thomas; Goering, Eberhard; Schütz, Gisela; Straumal, Petr B; Baretzky, Brigitte

    2013-01-01

    The influence of the grain boundary (GB) specific area s GB on the appearance of ferromagnetism in Fe-doped ZnO has been analysed. A review of numerous research contributions from the literature on the origin of the ferromagnetic behaviour of Fe-doped ZnO is given. An empirical correlation has been found that the value of the specific grain boundary area s GB is the main factor controlling such behaviour. The Fe-doped ZnO becomes ferromagnetic only if it contains enough GBs, i.e., if s GB is higher than a certain threshold value s th = 5 × 10(4) m(2)/m(3). It corresponds to the effective grain size of about 40 μm assuming a full, dense material and equiaxial grains. Magnetic properties of ZnO dense nanograined thin films doped with iron (0 to 40 atom %) have been investigated. The films were deposited by using the wet chemistry "liquid ceramics" method. The samples demonstrate ferromagnetic behaviour with J s up to 0.10 emu/g (0.025 μB/f.u.ZnO) and coercivity H c ≈ 0.03 T. Saturation magnetisation depends nonmonotonically on the Fe concentration. The dependence on Fe content can be explained by the changes in the structure and contiguity of a ferromagnetic "grain boundary foam" responsible for the magnetic properties of pure and doped ZnO.

  11. Ferromagnetic behaviour of Fe-doped ZnO nanograined films

    PubMed Central

    Protasova, Svetlana G; Mazilkin, Andrei A; Tietze, Thomas; Goering, Eberhard; Schütz, Gisela; Straumal, Petr B; Baretzky, Brigitte

    2013-01-01

    Summary The influence of the grain boundary (GB) specific area s GB on the appearance of ferromagnetism in Fe-doped ZnO has been analysed. A review of numerous research contributions from the literature on the origin of the ferromagnetic behaviour of Fe-doped ZnO is given. An empirical correlation has been found that the value of the specific grain boundary area s GB is the main factor controlling such behaviour. The Fe-doped ZnO becomes ferromagnetic only if it contains enough GBs, i.e., if s GB is higher than a certain threshold value s th = 5 × 104 m2/m3. It corresponds to the effective grain size of about 40 μm assuming a full, dense material and equiaxial grains. Magnetic properties of ZnO dense nanograined thin films doped with iron (0 to 40 atom %) have been investigated. The films were deposited by using the wet chemistry “liquid ceramics” method. The samples demonstrate ferromagnetic behaviour with J s up to 0.10 emu/g (0.025 μB/f.u.ZnO) and coercivity H c ≈ 0.03 T. Saturation magnetisation depends nonmonotonically on the Fe concentration. The dependence on Fe content can be explained by the changes in the structure and contiguity of a ferromagnetic “grain boundary foam” responsible for the magnetic properties of pure and doped ZnO. PMID:23844341

  12. Solid-state synthesis of the ZnO-Fe3O4 nanocomposite: Structural and magnetic properties

    NASA Astrophysics Data System (ADS)

    Bykova, L. E.; Myagkov, V. G.; Tambasov, I. A.; Bayukov, O. A.; Zhigalov, V. S.; Polyakova, K. P.; Bondarenko, G. N.; Nemtsev, I. V.; Polyakov, V. V.; Patrin, G. S.; Velikanov, D. A.

    2015-02-01

    The structural and magnetic properties of ZnO-Fe3O4 nanocomposites produced by the solid-state reaction Zn + 3Fe2O3 → ZnO + 2Fe3O4 upon annealing of Zn/α-Fe2O3 films under vacuum at a temperature of 450°C have been studied. Ferrimagnetic Fe3O4 clusters with an average grain size of 40 nm and a magnetization of ˜430 emu/cm3 at room temperature, which are surrounded by a ZnO layer with a large contact surface, have been synthesized. The magnetic characteristics of the ZnO-Fe3O4 nanocomposite in the temperature range of 10-300 K have been presented.

  13. Corrosion performance of Fe-Cr-Al and Fe aluminide alloys in complex gas environments

    SciTech Connect

    Natesan, K.; Johnson, R.N.

    1995-05-01

    Alumina-forming structural alloys can offer superior resistance to corrosion in the presence of sulfur-containing environments, which are prevalent in coal-fired fossil energy systems. Further, Fe aluminides are being developed for use as structural materials and/or cladding alloys in these systems. Extensive development has been in progress on Fe{sub 3}Al-based alloys to improve their engineering ductility. In addition, surface coatings of Fe aluminide are being developed to impart corrosion resistance to structural alloys. This paper describes results from an ongoing program that is evaluating the corrosion performance of alumina-forming structural alloys, Fe-Al and Fe aluminide bulk alloys, and Fe aluminide coatings in environments typical of coal-gasification and combustion atmospheres. Experiments were conducted at 650-1000{degrees}C in simulated oxygen/sulfur gas mixtures. Other aspects of the program are corrosion evaluation of the aluminides in the presence of HCl-containing gases. Results are used to establish threshold Al levels in the alloys for development of protective alumina scales and to determine the modes of corrosion degradation that occur in the materials when they are exposed to S/Cl-containing gaseous environments.

  14. 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

  15. 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.

  16. Comparison of metals extractability from Al/Fe-based drinking water treatment residuals.

    PubMed

    Wang, Changhui; Bai, Leilei; Pei, Yuansheng; Wendling, Laura A

    2014-12-01

    Recycling of drinking water treatment residuals (WTRs) as environment amendments has attracted substantial interest due to their productive reuse concomitant with waste minimization. In the present study, the extractability of metals within six Al/Fe-hydroxide-comprised WTRs collected throughout China was investigated using fractionation, in vitro digestion and the toxicity characteristic leaching procedure (TCLP). The results suggested that the major components and structure of the WTRs investigated were similar. The WTRs were enriched in Al, Fe, Ca, and Mg, also contained varying quantities of As, Ba, Be, Cd, Co, Cr, Cu, K, Mn, Mo, Na, Ni, Pb, Sr, V, and Zn, but Ag, Hg, Sb, and Se were not detected. Most of the metals within the WTRs were largely non-extractable using the European Community Bureau of Reference (BCR) procedure, but many metals exhibited high bioaccessibility based on in vitro digestion. However, the WTRs could be classified as non-hazardous according to the TCLP assessment method used by the US Environmental Protection Agency (USEPA). Further analysis showed the communication factor, which is calculated as the ratio of total extractable metal by BCR procedure to the total metal, for most metals in the six WTRs, was similar, whereas the factor for Ba, Mn, Sr, and Zn varied substantially. Moreover, metals in the WTRs investigated had different risk assessment code. In summary, recycling of WTRs is subject to regulation based on assessment of risk due to metals prior to practical application.

  17. Investigation of phase formation of (Zn, Mg)0.5Co0.5Fe2O4 nanoferrites

    NASA Astrophysics Data System (ADS)

    Msomi, J. Z.; Dlamini, W. B.; Moyo, T.; Ezekiel, P.

    2015-01-01

    Zn0.5Co0.5Fe2O4 and Mg0.5Co0.5Fe2O4 nanoparticles have been prepared through high energy ball milling of single phase mixtures of ZnFe2O4 and CoFe2O4 or MgFe2O4 and CoFe2O4 nanosized oxides. The Mössbauer spectra of the milled products ZnFe2O4/CoFe2O4 and MgFe2O4/CoFe2O4 reveal the presence of Zn0.5Co0.5Fe2O4 and Mg0.5Co0.5Fe2O4, respectively. In an alternative route, Zn0.5Co0.5Fe2O4 and Mg0.5Co0.5Fe2O4 compounds were prepared directly from metal chloride solutions through glycol-thermal reaction. The coercive fields of the Zn0.5Co0.5Fe2O4 and Mg0.5Co0.5Fe2O4 oxides produced by glycol-thermal reaction were found to be about 100 Oe and 161 Oe, respectively. Larger coercive fields of about 184 Oe and 255 Oe have been observed for the milled ZnFe2O4/CoFe2O4 and MgFe2O4/CoFe2O4 oxides.

  18. Investigation of Phase Equilibria and Some Properties of Alloys of Ti-Al-Fe and Ti-Al-V Systems,

    DTIC Science & Technology

    Some data on the structure and properties of Ti-Al-Fe alloys are presented. The phase equilibria in alloys in the system Ti-Al-V were studies...However, the data available in the literature on phase equilibria in the systems Ti-Al-Fe and Ti-Al-V require refinement, as they are insufficiently

  19. Photocatalytic activity of non-stoichiometric ZnFe2O4 under visible light irradiation

    NASA Astrophysics Data System (ADS)

    Šutka, A.; Pärna, R.; Kleperis, J.; Käämbre, T.; Pavlovska, I.; Korsaks, V.; Malnieks, K.; Grinberga, L.; Kisand, V.

    2014-04-01

    Nanostructured zinc ferrites with different excess iron contents (ZnFe2+zO4, where z = 0.00, 0.05, 0.10 and 0.15) have been synthesized using the sol-gel auto-combustion method. The effect of excess iron on the structural, optical and visible light photocatalytic activity of zinc ferrite samples has been investigated. X-ray diffraction (XRD), x-ray photoelectron spectroscopy (XPS), x-ray magnetic circular dichroism (XMCD), Brunauer-Emmett-Teller theory, scanning electron microscopy (SEM), diffuse reflectance spectroscopy (UV-Vis) and photoluminescence spectroscopy were used to characterize the synthesized non-stoichiometric ZnFe2O4 powders. The XRD patterns demonstrated that the samples consist of single phase spinel structure with crystallite sizes of ˜25 nm. SEM analysis indicated that the nanosized particles grow together in porous clusters with a size of several microns. The XPS and XMCD analyses revealed that the excess iron ion substitutes Zn2+ in tetrahedral sites and in octahedral sites Fe2+ can be found in addition to Fe3+, which could be created to restore the overall charge balance in the crystal lattice. Stoichiometric zinc ferrite (ZnFe2+zO4, z = 0.00) exhibited higher photocatalytic activity (40%) than the excess iron sample (ZnFe2+zO4, z = 0.15, i.e. 4%) under visible light irradiation for 3 h. This was explained by the formation of Fe2+ in the octahedral sites of excess iron ZnFe2O4; these species act as recombination centres.

  20. Development of Fe-Mn-Al-X-C alloys

    NASA Technical Reports Server (NTRS)

    Schuon, S. R.

    1982-01-01

    Development of a low cost Cr-free, iron-base alloy for aerospace applications involves both element substitution and enhancement of microstructural strengthening. When Mn is substituted for Ni and Al or Si is substituted for Cr, large changes occur in the mechanical and thermal stability of austenite in FeMnAlC alloys. The in situ strength of MC or M2C (M = Ti, V, Hf, Ta, or Mo) in FeMnAlC alloys was determined. The high temperature tensile strength depends more on the distribution of carbides than the carbide composition. Precipitation of a high volume percent-ordered phase was achieved in Fe2OMnlONi6Al6Ti (lC) alloys. As case, these alloys have a homogeneous austenitic structure. After solutioning at 1100 C for 5 hr followed by aging at 600 C for 16 hr, gamma prime or a perovskite carbide is precipitated. Overaging occurs at 900 C where eta is precipitated.

  1. Environment-Friendly Carbon Quantum Dots/ZnFe2O4 Photocatalysts: Characterization, Biocompatibility, and Mechanisms for NO Removal.

    PubMed

    Huang, Yu; Liang, Yanling; Rao, Yongfang; Zhu, Dandan; Cao, Jun-Ji; Shen, Zhenxing; Ho, Wingkei; Lee, Shun Cheng

    2017-02-10

    A highly efficient and environmentally-friendly oxidation process is always desirable for air purification. This study reported a novel carbon quantum dots (CQDs)/ZnFe2O4 composite photocatalyst for the first time through a facile hydrothermal process. The CQDs/ZnFe2O4 (15 vol %) composite demonstrates stronger transient photocurrent response, approximately 8 times higher than that of ZnFe2O4, indicating superior transfer efficiency of photogenerated electrons and separation efficiency of photogenerated electron-hole pairs. Compared with pristine ZnFe2O4 nanoparticles, CQDs/ZnFe2O4 displayed enhanced photocatalytic activities on gaseous NOx removal and high selectivity for nitrate formation under visible light (λ > 420 nm) irradiation. Electron spin resonance analysis and a series of radical-trapping experiments showed that the reactive species contributing to NO elimination were ·O2(-) and ·OH radicals. The possible mechanisms were proposed regarding how CQDs improve the photocatalytic performance of ZnFe2O4. The CQDs are believed to act as an electron reservoir and transporter as well as a powerful energy-transfer component during the photocatalysis processes over CQDs/ZnFe2O4 samples. Furthermore, the toxicity assessment authenticated good biocompatibility and low cytotoxity of CQDs/ZnFe2O4. The results of this study indicate that CQDs/ZnFe2O4 is a promising photocatalyst for air purification.

  2. Low substrate temperature deposition of transparent and conducting ZnO:Al thin films by RF magnetron sputtering

    NASA Astrophysics Data System (ADS)

    Waykar, Ravindra; Amit, Pawbake; Kulkarni, Rupali; Jadhavar, Ashok; Funde, Adinath; Waman, Vaishali; Dewan, Rupesh; Pathan, Habib; Jadkar, Sandesh

    2016-04-01

    Transparent and conducting Al-doped ZnO (ZnO:Al) films were prepared on glass substrate using the RF sputtering method at different substrate temperatures from room temperature (RT) to 200 °C. The structural, morphological, electrical and optical properties of these films were investigated using a variety of characterization techniques such as low angle XRD, Raman spectroscopy, X-ray photoelectron spectroscopy (XPS), field-emission scanning electron microscopy (FE-SEM), Hall measurement and UV-visible spectroscopy. The electrical properties showed that films deposited at RT have the lowest resistivity and it increases with an increase in the substrate temperature whereas carrier mobility and concentration decrease with an increase in substrate temperature. Low angle XRD and Raman spectroscopy analysis reavealed that films are highly crystalline with a hexagonal wurtzite structure and a preferred orientation along the c-axis. The FE-SEM analysis showed that the surface morphology of films is strongly dependent on the substrate temperature. The band gap decreases from 3.36 to 3.29 eV as the substrate temperature is increased from RT to 200 °C. The fundamental absorption edge in the UV region shifts towards a longer wavelength with an increase in substrate temperature and be attributed to the Burstein-Moss shift. The synthesized films showed an average transmission (> 85%) in the visible region, which signifies that synthesized ZnO:Al films can be suitable for display devices and solar cells as transparent electrodes.

  3. Fabrication and Electrical Characterization of the Si/ZnO/ZnO:Al Structure Deposited by RF-Magnetron Sputtering

    NASA Astrophysics Data System (ADS)

    Alaya, A.; Djessas, K.; El Mir, L.; Khirouni, K.

    2016-10-01

    The electrical transport properties of the structures of Si(p)/ZnO(i)/ZnO: Al(3%) and Si(p)/PS/ZnO(i)/ZnO: Al(3%) deposited by radio-frequency-magnetron sputtering were investigated and compared by using current-voltage and impedance spectroscopy measurements in a wide temperature range of 80-300 K. Aluminum-doped ZnO is considered to be one of the most important transparent conducting oxide materials due to its high conductivity, good transparency and low cost. From the current-voltage-temperature ( I- V- T) characteristics, it was found that both structures had a good rectifying behavior. This behavior decreases according to the porous silicon layer. The variation of the conductance with frequency indicates the semiconducting behavior and superposition of different conduction mechanisms. The insertion of the porous silicon layer results in a decrease of conductivity, which is attributed to reduced conductivity of defect-rich porous silicon.

  4. Enhanced photocatalytic performances of hierarchical ZnO/ZnAl2O4 microsphere derived from layered double hydroxide precursor spray-dried microsphere.

    PubMed

    Huo, Ruijie; Kuang, Ye; Zhao, Zhiping; Zhang, Fazhi; Xu, Sailong

    2013-10-01

    Layered double hydroxides (LDHs), also called hydrotalcites, have been widely investigated for degradation of dye molecules, in the forms of direct photocatalysts, supports or precursors to ZnO-containing photocatalysts. LDH precursor-derived ZnO/ZnAl2O4 photocatalytic nanostructures have hitherto been created, involving ZnO/ZnAl2O4 powder and templated hierarchical frameworks with laboratory-scale preparations. We herein report a scalable preparation of ZnO/ZnAl2O4 microsphere derived from ZnAl-LDH precursor spray-dried microsphere. Survey of textural properties shows that ZnO/ZnAl2O4 microspheres maintain the hierarchically spherical feature and the relatively large surface area. Photocatalytic evaluation under UV irradiation shows that the ZnO/ZnAl2O4 microspheres exhibit highly enhanced photodegradation performance to methylene blue (MB) in comparison with the commercial ZnO powder. A preferential photodegradation to methyl orange (MO) of the MO/MB mixture was also observed, which was illustrated experimentally in terms of the favorable interaction and distribution between basic MO molecules and the acidic-site ZnO/ZnAl2O4 photocatalyst. Our results may initiate large-scale production of microspheres with promising photocatalytic performances.

  5. Thermoelectric Properties of ZnO Ceramics Co-Doped with Al and Transition Metals

    NASA Astrophysics Data System (ADS)

    Yamaguchi, Hiroyuki; Chonan, Yasunori; Oda, Manabu; Komiyama, Takao; Aoyama, Takashi; Sugiyama, Shigeaki

    2011-05-01

    The effect of co-doping with transition metals (Fe, Ni, and Sm) on the thermoelectric properties of Al-doped ZnO (AZO) ceramics was studied. The electrical conductivity σ of AZO was significantly (12%) increased by Ni co-doping, while an unfavorable deterioration in σ was observed for Fe- or Sm-co-doped AZO. Hall-effect measurements indicated that the electron mobility of AZO decreased due to co-doping in all samples. Only the Ni-co-doped AZO sample showed significant enhancement in electron density, resulting in its black color. The thermal conductivity κ decreased drastically due to Ni or Sm co-doping of AZO, while only a small change was observed for Fe co-doping of AZO. The κ value at 1073 K for Ni-co-doped AZO was 77% of that for AZO. A dimensionless figure of merit ZT = 0.126 was attained at 1073 K for Ni-co-doped AZO, representing an improvement over that of conventional AZO by a factor of 1.50.

  6. Highly efficient and selective adsorption of In{sup 3+} on pristine Zn/Al layered double hydroxide (Zn/Al-LDH) from aqueous solutions

    SciTech Connect

    Barnabas, Mary Jenisha; Parambadath, Surendran; Mathew, Aneesh; Park, Sung Soo; Vinu, Ajayan; Ha, Chang-Sik

    2016-01-15

    A pristine Zn/Al-layered double hydroxide (Zn/Al-LDH) showed excellent adsorption ability and selectivity towards In{sup 3+} ions from aqueous solutions. The adsorption behaviour as a function of the contact time, solution pH, ionic strength, and amount of adsorbent under ambient conditions revealed a strong dependency on the pH and ionic strength over In{sup 3+} intake. The structure and properties of Zn/Al-LDH and In{sup 3+} adsorbed Zn/Al-LDH (In–Zn/Al-LDH) were examined carefully by X-ray diffraction, Fourier transform infrared spectroscopy, N{sub 2}-sorption/desorption, UV–vis spectroscopy, and X-ray photoelectron spectroscopy. The adsorbent had a sufficient number of active sites that were responsible for the In{sup 3+} adsorption and quite stable even after the adsorption process. The selective adsorption of In{sup 3+} on Zn/Al-LDH was also observed even from a mixture containing competing ions, such as Mn{sup 2+}, Co{sup 2+}, Ni{sup 2+}, Cd{sup 2+}, Pb{sup 2+}, and Cu{sup 2+}. The adsorption experiments showed that Zn/Al-LDH is a promising material for the pre-concentration and selective removal of In{sup 3+} from large volumes of aqueous solutions. - Highlights: • A pristine Zn/Al-layered double hydroxide showed good selectivity for In{sup 3+} ions. • The material exhibited a maximum In{sup 3+} intake of 205 mg g{sup −1} at pH 6. • The materials showed good affinity of In{sup 3+} over Cu{sup 2+} and Pb{sup 2+} from ion mixtures.

  7. Synthesis and characterization of magnetic diphase ZnFe2O4 /γ-Fe2O3 electrospun fibers

    PubMed Central

    Arias, M.; Pantojas, V.M.; Perales, O.; Otaño, W.

    2011-01-01

    Magnetic nanofibers of ZnFe2O4 / γ-Fe2O3 composite were synthesized by electrospinning from a sol-gel solution containing a molar ratio Fe/Zn of 3. The effects of the calcination temperature on the phase composition, particle size and magnetic properties have been investigated. Zinc ferrite fibers were obtained by calcinating the electrospun fibers in air from 300 °C to 800 °C and characterized by thermogravimetric analyses, Fourier transformed infrared spectroscopy, x-ray photoemission spectroscopy, x-ray diffraction, vibration sample magnetometry and magnetic force microscopy. The resulting fibers, with diameters ranging from 90 to 150 nm, were ferrimagnetic with high saturation magnetization as compared to bulk. Increasing the calcination temperature resulted in an increase in particle size and saturation magnetization. The observed increase in saturation magnetization was most likely due to the formation and growth of ZnFe2O4 /γ-Fe2O3 diphase crystals. The highest saturation magnetization (45 emu/g) was obtained for fibers calcined at 800 °C. PMID:21779141

  8. Synthesis and characterization of magnetic diphase ZnFe 2O 4/γ-Fe 2O 3 electrospun fibers

    NASA Astrophysics Data System (ADS)

    Arias, M.; Pantojas, V. M.; Perales, O.; Otaño, W.

    2011-08-01

    Magnetic nanofibers of ZnFe2O4/γ-Fe2O3 composite were synthesized by electrospinning from a sol-gel solution containing a molar ratio (Fe/Zn) of 3. The effects of the calcination temperature on phase composition, particle size and magnetic properties have been investigated. Zinc ferrite fibers were obtained by calcinating the electrospun fibers in air from 300 to 800 °C and characterized by thermogravimetric analyses, Fourier transformed infrared spectroscopy, X-ray photoemission spectroscopy, X-ray diffraction, vibration sample magnetometry and magnetic force microscopy. The resulting fibers, with diameters ranging from 90 to 150 nm, were ferrimagnetic with high saturation magnetization as compared to bulk. An increase in the calcination temperature resulted in an increase in particle size and saturation magnetization. The observed increase in saturation magnetization was most likely due to the formation and growth of ZnFe2O4/γ-Fe2O3 diphase crystals. The highest saturation magnetization (45 emu/g) was obtained for fibers calcined at 800 °C.

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

    SciTech Connect

    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 the 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.

  10. Rapid and efficient removal/recovery of molybdenum onto ZnFe2O4 nanoparticles.

    PubMed

    Tu, Yao-Jen; Chan, Ting-Shan; Tu, Hao-Wei; Wang, Shan-Li; You, Chen-Feng; Chang, Chien-Kuei

    2016-04-01

    An efficient method for removing and recovering molybdenum (Mo) from water was developed by using ZnFe2O4 nanoparticles. The Mo adsorption displayed a nonlinear isotherm that fitted well with the Langmuir isotherm, showing limited adsorption sites on the surface of ZnFe2O4. The adsorption of Mo(VI) was dependent on solution pH. With increasing pH, the build-up of negative charges of both adsorbent and adsorbate led to enhanced electric repulsion between them. The K-edge XANES spectra for the adsorbents collected after Mo adsorption revealed that Mo(VI) was the predominant oxidation state sorbed on ZnFe2O4, indicating that the reduction of Mo(VI) did not occur on ZnFe2O4. The different peak positions of k-space and R-space shown in K-edge EXAFS spectra demonstrated that the adsorbed Mo could be bound on the surface or be slipped in the vacancy position of the ZnFe2O4 crystal. Importantly, Mo could be efficiently adsorbed from photoelectric industrial wastewater and these adsorbed Mo anions were rapidly replaced by OH(-) ions, implying the potential for Mo removing and recovering in industrial wastewater.

  11. 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

  12. Distribution of Al{sub 12}Fe{sub 3}Si and (FeAl{sub 6})Si in a HIPed Al-10.71 wt. % Si casting

    SciTech Connect

    Chama, C.C.

    1996-10-01

    An investigation on microstructural development in a hot isostatically pressed (HIPed) Al-10.71 wt. % Si casting is described. The as-cast material contained 0.006 total volume fraction of Al{sub 12}Fe{sub 3}Si and (FeAl{sub 6})Si particles but HIPing at 550 C and 68.95 MPa produced a moderate increase in this fraction, to a maximum value of 0.061 when HIPed for 120 min. Dislocations appeared to be the dominant nucleation sites for the particles in both the as-cast and the HIPed materials.

  13. Fe solubility, growth mechanism, and luminescence of Fe doped ZnO nanowires and nanorods grown by evaporation-deposition

    NASA Astrophysics Data System (ADS)

    Alemán, Belén; Ortega, Yanicet; García, José Ángel; Fernández, Paloma; Piqueras, Javier

    2011-07-01

    Fe doped ZnO nanowires, nanorods, and urchin-like nanostructures have been grown using an evaporation-deposition method with compacted mixtures of ZnS and Fe2O3 powders, with different Fe contents as precursors. Treatments at 950 °C under argon flow lead to the growth of iron doped nanowires, nanorods, and other nanostructures on the surface of the compacted sample. The incorporation of iron into the nanostructures has been investigated via energy dispersive spectroscopy as well as by cathodoluminescence in a scanning electron microscope and photoluminescence in an optical microscope. The iron content in the structures is limited to the range of 0.5-0.7 at.% and does not depend on the content in the precursor. Bright and dark field imaging and twist contour analysis via transmission electron microscopy support the possibility of a dislocation driven growth of the nanowires.

  14. One-dimensional SrFe12O19/Ni(0.5)Zn(0.5)Fe2O4 composite ferrite nanofibers and enhancement magnetic property.

    PubMed

    Song, Fuzhan; Shen, Xiangqian; Liu, Mingquan; Xiang, Jun

    2011-08-01

    SrFe12O19/Ni(0.5)Zn(0.5)Fe2O4 composite ferrite nanofibers of diameters about 100 nm with mass ratio 1:1 have been prepared by the electrospinning and calcination process. The SrFe12O19/Ni(0.5)Zn(0.5)Fe2O4 composite ferrites are formed after calcined at 700 degrees C for 2 hours. The composite ferrite nanofibers are fabricated from nanosized Ni(0.5)Zn(0.5)Fe2O4 and SrFe12O19 ferrite grains with a uniform phase distribution. The ferrite grain size increases from about 11 to 36 nm for Ni(0.5)Zn(0.5)Fe12O4 and 24 to 56 nm for SrFe12O19 with the calcination temperature increasing from 700 to 1100 degrees C. With the ferrite grain size increasing, the coercivity (Hc) and remanence (Mr) for the SrFe12O19/Ni(0.5)Zn(0.5)Fe2O4 composite ferrite nanofibers initially increase, reaching a maximum value of 118.4 kA/m and 31.5 Am2/kg at the grain size about 40 nm (SrFe12O19) and 24 nm (Ni(0.5)Zn(0.5)Fe2O4) respectively, and then show a reduction tendency with a further increase of the ferrite grain size. The specific saturation magnetization (Msh) of 63.2 Am2/kg for the SrFe12O19/Ni(0.5)Zn(0.5)Fe2O4 composite ferrite nanofibers obtained at 900 degrees C for 2 hours locates between that for the single SrFe12O19 ferrite (48.5 Am2/kg) and the single Ni(0.5)Zn(0.5)Fe2O4 ferrite (69.3 Am2/kg). In particular, the Mr value 31.5 Am2/kg for the SrFe12O19/Ni(0.5)Zn(0.5)Fe2O4 composite ferrite nanofibers is much higher than that for the individual SrFe12O19 (25.9 Am2/kg) and Ni(0.5)Zn(0.5)Fe2O4 ferrite (11.2 Am2/kg). These enhanced magnetic properties for the composite ferrite nanofibers can be attributed to the exchange-coupling interaction in the composite.

  15. Aluminum-Zinc (Al-Zn) Dust Analyses for Recycling Purposes

    DTIC Science & Technology

    2011-08-01

    for x - ray fluorescence ( XRF ) analysis to determine the composition of the dust sample. Figure 1 500-lb bombs with Zn-AI coat Figure 2 50-gal drums...this PVD process. The x - ray fluorescence analyses and selected electron diffraction patter confirmed the presence of Al-Zn particles and their...DISCUSSION/CONCLUSIONS The XRF analysis revealed approximately 88.8% Zn, 10.9% Al, and minute traces of other metal elements as shown in the table. SOX

  16. Concentration dependent structural parameters of liquid Al-Fe alloys

    NASA Astrophysics Data System (ADS)

    Lalnuntluanga, C.; Mishra, Raj Kumar

    2016-10-01

    Square well potential is perturbed over Lebowtiz solution of hard sphere mixtures to determine direct correlation function,C(0) ij(r) in repulsive and attractive regions under Mean Spherical Model Approximation [1]. Obtained direct correlation functions were employed to derive partial structure factors and then total structure factor, S(k) in liquid Al-Fe alloy at different atomic percent of Al. Fourier transform of partial and total structure factors gives partial and total radial distribution functions, g(r) from which partial and total coordination numbers and the partial nearest-neighbor distances were computed.

  17. Role of Fe and sign reversal of the Hall coefficient in quasicrystalline Al-Cu-Fe

    NASA Astrophysics Data System (ADS)

    Lindqvist, P.; Berger, C.; Klein, T.; Lanco, P.; Cyrot-Lackmann, F.; Calvayrac, Y.

    1993-07-01

    Electronic transport properties were measured for the stable icosahedral phase of Al-Cu-Fe for a large number of high-structural-quality samples of different compositions. At low temperature, the Hall coefficient RH and the conductivity σ are found to best correlate with the Fe content rather than with the electron per atom parameter which is usually used; RH changes sign at a concentration of 12.5 at. % Fe, where σ is at minimum. RH has a strong temperature dependence and can change sign with temperature. These features put the focus on the Fe d states and can be interpreted by a Hume-Rothery type of behavior including the sp-d hybridization effects.

  18. Electron transport in Al-doped ZnO nanolayers obtained by atomic layer deposition

    NASA Astrophysics Data System (ADS)

    Blagoev, B. S.; Dimitrov, D. Z.; Mehandzhiev, V. B.; Kovacheva, D.; Terziyska, P.; Pavlic, J.; Lovchinov, K.; Mateev, E.; Leclercq, J.; Sveshtarov, P.

    2016-03-01

    Al-doped ZnO thin films with different Al content were prepared by atomic layer deposition (ALD). To carry out thermal ALD, diethyl zinc (DEZ) and tri-methyl aluminium (TMA) were used as Zn and Al precursors, respectively, and water vapor as oxidant. Various numbers n of DEZ and m TMA cycles was used to obtain different [ZnO] n [Al2O3] m films, where n = 100 - 95, m = 1 - 5. The X-ray diffraction analysis showed a predominantly (100) oriented polycrystalline phase for the ZnO:Al films with a low Al content (m = 1 - 3) and an amorphous structure for pure Al2O3. In ZnO:Al with a higher Al content (m = 4 - 6) the (100) reflection disappeared and the (002) peak increased. The resistivity of the films decreased with the increase in the Al content, reaching a minimum of 3.3×10-3 Ω cm at about 1.1 % Al2O3 for the [ZnO]99[Al2O3]2 sample; for higher dopant concentrations, the resistivity increased because of the increased crystal inhomogeneity due to axis reorientation.

  19. Towards a Superplastic Forming of Fe-Mn-Al Alloys

    SciTech Connect

    Guanabara, Paulo Jr.; Bueno, Levi de O.; Ferreira Batalha, Gilmar

    2011-01-17

    The aim is to study the characteristics of superplasticity, mostly on non qualified materials, such as austenitic steel of the Fe-Mn-Al alloy, which has some of the specific material parameters closely related to microstructural mechanisms. These parameters are used as indicators of material superplastic potentiality. The material was submitted to hot tensile testing, within a temperature range from 600 deg. C to 1000 deg. C and strain-rates varying from 10{sup -6} to 1 s{sup -1}. The strain rate sensitivity parameter (m) and observed maximum elongation until rupture ({epsilon}{sub r}) could be determined and also obtained from the hot tensile test. The experiments stated a possibility of superplastic behaviour in a Fe-Mn-Al alloy within a temperature range from 700 deg. C to 900 deg. C with grain size around 3 {mu}m (ASTM grain size 12) and average strain rate sensitivity of m {approx} 0.54, as well as a maximum elongation at rupture around 600%. The results are based on a more enhanced research from the authors; however, this paper has focused just on the hot tensile test, as further creep tests results are not available herein. There are rare examples of superplasticity study of an austenitic steel Fe-Mn-Al alloy, thus this work showed some possibility of exploring the potential use of such materials in this regime at temperatures {>=}700 deg. C.

  20. Yield stress anomaly in B2 FeAl

    SciTech Connect

    Yoshimi, K.; Hanada, S.; Yoo, M.H.

    1996-12-31

    The studies on yield stress anomaly of B2 FeAl single crystals are reviewed in this paper. A positive temperature dependence of yield stress, so-called yield stress anomaly, is observed in B2 FeAl in which excess vacancies are fully annealed out. Associated with the anomaly, characteristic asymmetry is found between tension and compression. While the strain-rate sensitivity is almost zero in the temperature range of the yield stress anomaly, the stress relaxation becomes significant with increasing temperature, indicating that a recovery process is thermally activated. It is ascertained by the two-surface trace analysis that slip transition from <111> direction at intermediate temperature to <100> at high temperature occurs around the peak temperature. Even at the peak temperature, in addition, operative slip vector for yielding is confirmed to be predominantly <111> by TEM. Also, it is observed that <111>-type superdislocations are frequently climb-dissociated in the temperature range of the anomaly. APB formation on {l_brace}111{r_brace} plane is energetically favorable, which is in agreement with the Flinn`s calculation for the B2 superlattice that APB energy on {l_brace}111{r_brace} plane is lower than that on {l_brace}110{r_brace} plane. Such an anisotropy of APB energy would offer specific driving force for the climb dissociation on <111> superdislocations. On the basis of the observed results, the anomalous strengthening behavior of B2 FeAl single crystals is discussed.

  1. Melting and casting of FeAl-based cast alloy

    SciTech Connect

    Sikka, V.K.; Wilkening, D.; Liebetrau, J.; Mackey, B.

    1998-11-01

    The FeAl-based intermetallic alloys are of great interest because of their low density, low raw material cost, and excellent resistance to high-temperature oxidation, sulfidation, carburization, and molten salts. The applications based on these unique properties of FeAl require methods to melt and cast these alloys into complex-shaped castings and centrifugal cast tubes. This paper addresses the melting-related issues and the effect of chemistry on the microstructure and hardness of castings. It is concluded that the use of the Exo-Melt{trademark} process for melting and the proper selection of the aluminum melt stock can result in porosity-free castings. The FeAl alloys can be melted and cast from the virgin and revert stock. A large variation in carbon content of the alloys is possible before the precipitation of graphite flakes occurs. Titanium is a very potent addition to refine the grain size of castings. A range of complex sand castings and two different sizes of centrifugal cast tubes of the alloy have already been cast.

  2. (Al, Er) co-doped ZnO nanoparticles for photodegradation of rhodamine blue

    NASA Astrophysics Data System (ADS)

    Ghomri, R.; Shaikh, M. Nasiruzzaman; Ahmed, M. I.; Bououdina, M.; Ghers, M.

    2016-10-01

    Pure and co-doped (Al, Er) ZnO nanoparticles (NPs) have been synthesized by hydrothermal method using (Zn, Er and Al) nitrates. X-ray diffraction patterns reveal the formation of single phase of ZnO würtzite-type structure. The crystallite size for pure ZnO is in the order of 26.5 nm which decreases up to the range 14.2-22.0 nm after (Al, Er) co-doping. SEM micrographs show that the specimen is composed of regular spherical particles in the nanoscale regime with homogeneous size distribution and high tendency to agglomeration. FTIR spectra exhibit absorption lines located at wavenumbers corresponding to vibration modes between the constituent atoms. Raman spectra recorded under excitation ( λ exc = 632.8 nm) reveal peaks related to modes of transverse and longitudinal optical phonons of the würtzite ZnO structure. The energy band gap E g of ZnO:(Al, Er) NPs ranges in 3.264-3.251 eV. The photocatalytic activity of pure and co-doped (Al, Er) ZnO NPs was evaluated by the photodegradation of rhodamine blue under an irradiation of wavelength 554 nm. It is found that a photodegradation rate above 90 % could be achieved for a period of time of 40 min for pure ZnO and 120 min for (Al, Er) co-doped ZnO. A photodegradation mechanism is proposed.

  3. Fe:ZnMnSe laser active material properties at room and cryogenic temperature

    NASA Astrophysics Data System (ADS)

    Jelínková, H.; Doroshenko, M. E.; Osiko, V. V.; Němec, M.; Å ulc, J.; Jelínek, M.; Vyhlídal, D.; Kubecek, V.; Čech, M.; Kovalenko, N. O.; Gerasimenko, A. S.

    2016-04-01

    Fe:Zn(1-x)Mn(x)Se solid solution spectroscopic and laser properties were investigated in the temperature range 80- 290 K. Two novel samples with different zinc - manganese (Zn-Mn) ratio described by the Mn content x (0.1 or 0.2) were used and the results were compared to the known Fe:ZnSe crystal. The samples had a broad absorption spectra with the maximum around 3 μm and therefore an Er:YAG laser (2.94 μm, 10 mJ, 120 ns) was used as a pump radiation source. The Fe:ZnMnSe fluorescence spectra are generally broad in the range 3.5 - 5.5 μm. In the case of Fe:ZnMnSe x = 0.1, the fluorescence spectrum at 290 K is ranging from 3.5 to 5.5 μm. Lowering the temperature down to 80 K lead to the spectral narrowing mainly in the mid-IR part, but the fluorescence is still up to 5 μm at 80 K. In the case of Fe:ZnMnSe x = 0.2 the fluorescence is shifted towards mid-IR up to 5.2 μm even at 80 K. The fluorescence lifetime decreases from tens of us at 80 K down to 1 us at 240 K. The laser oscillations were successfully achieved with both novel Fe:ZnMnSe crystals in the temperature range 80- 290 K. In the case of x = 0.1, the central wavelength was ~4.2 μm at 80 K and the temperature increase up to 290 K led to almost linear increase of the wavelength up to ~4.75 μm. The tendency was similar in the case of Fe:ZnMnSe x = 0.2: the output wavelength increased from ~4.3 μm up to ~4.8 μm with the temperature increase from 80 to 290 K. The laser spectral linewidth was about 300 nm. In comparison with the Fe:ZnSe crystal, the laser output wavelength shift toward mid-IR region without any spectrally tunable element in the laser cavity can be clearly observed.

  4. Organo/Zn-Al LDH Nanocomposites for Cationic Dye Removal from Aqueous Media

    NASA Astrophysics Data System (ADS)

    Starukh, G.; Rozovik, O.; Oranska, O.

    2016-04-01

    Cationic dye sorption by Zn-Al-layered double hydroxides (LDHs) modified with anionic surfactants was examined using methylene blue (MB) dye as a compound model in aqueous solutions. The modification of Zn-Al LDHs was performed by reconstruction method using dodecyl sulfate anion (DS) solutions. DS contained Zn-Al LDHs were characterized by XRD, FTIR, thermogravimetric, and SEM analysis. The reconstructed organo/Zn-Al LDHs comprise the crystalline phases (DS-intercalated LDHs, hydrotalcite), and the amorphous phase. The intercalation of DS ions into the interlayer galleries and DS adsorption on the surface of the LDHs occurred causing the MB adsorption on the external and its sorption in the internal surfaces of modified LDHs. The presence of DS greatly increased the affinity of organo/Zn-Al LDHs for MB due to hydrophobic interactions between the surfactants and the dye molecules. The optical properties of sorbed MB were studied.

  5. Preparation and Pore Structure Stability at High Temperature of Porous Fe-Al Intermetallics

    NASA Astrophysics Data System (ADS)

    Shen, P. Z.; Gao, H. Y.; Song, M.; He, Y. H.

    2013-12-01

    Porous Fe-Al intermetallics with different nominal compositions (from Fe-8 wt.% Al to Fe-50 wt.% Al) were fabricated by Fe and Al elemental powders through reaction synthesis. The effects of the Al content on the pore structure properties, and the comparison of pore structure stabilities at high-temperatures among the porous Fe-Al intermetallics and porous Ti, Ni, 316L stainless steel samples, were systematically studied. Results showed that the open porosity, maximum pore size, and permeability vary with the Al content. Porous Fe-(25-30 wt.%) Al intermetallics show good shape controllability and excellent pore structure stability at 1073 K in air, which suggests that these porous Fe-Al intermetallics could be used for filtration at high temperatures.

  6. Elastocaloric effect in CuAlZn and CuAlMn shape memory alloys under compression.

    PubMed

    Qian, Suxin; Geng, Yunlong; Wang, Yi; Pillsbury, Thomas E; Hada, Yoshiharu; Yamaguchi, Yuki; Fujimoto, Kenjiro; Hwang, Yunho; Radermacher, Reinhard; Cui, Jun; Yuki, Yoji; Toyotake, Koutaro; Takeuchi, Ichiro

    2016-08-13

    This paper reports the elastocaloric effect of two Cu-based shape memory alloys: Cu68Al16Zn16 (CuAlZn) and Cu73Al15Mn12 (CuAlMn), under compression at ambient temperature. The compression tests were conducted at two different rates to approach isothermal and adiabatic conditions. Upon unloading at a strain rate of 0.1 s(-1) (adiabatic condition) from 4% strain, the highest adiabatic temperature changes (ΔTad) of 4.0 K for CuAlZn and 3.9 K for CuAlMn were obtained. The maximum stress and hysteresis at each strain were compared. The stress at the maximum recoverable strain of 4.0% for CuAlMn was 120 MPa, which is 70% smaller than that of CuAlZn. A smaller hysteresis for the CuAlMn alloy was also obtained, about 70% less compared with the CuAlZn alloy. The latent heat, determined by differential scanning calorimetry, was 4.3 J g(-1) for the CuAlZn alloy and 5.0 J g(-1) for the CuAlMn alloy. Potential coefficients of performance (COPmat) for these two alloys were calculated based on their physical properties of measured latent heat and hysteresis, and a COPmat of approximately 13.3 for CuAlMn was obtained.This article is part of the themed issue 'Taking the temperature of phase transitions in cool materials'.

  7. Evolution of Fe Bearing Intermetallics During DC Casting and Homogenization of an Al-Mg-Si Al Alloy

    NASA Astrophysics Data System (ADS)

    Kumar, S.; Grant, P. S.; O'Reilly, K. A. Q.

    2016-06-01

    The evolution of iron (Fe) bearing intermetallics (Fe-IMCs) during direct chill casting and homogenization of a grain-refined 6063 aluminum-magnesium-silicon (Al-Mg-Si) alloy has been studied. The as-cast and homogenized microstructure contained Fe-IMCs at the grain boundaries and within Al grains. The primary α-Al grain size, α-Al dendritic arm spacing, IMC particle size, and IMC three-dimensional (3D) inter-connectivity increased from the edge to the center of the as-cast billet; both α c-AlFeSi and β-AlFeSi Fe-IMCs were identified, and overall α c-AlFeSi was predominant. For the first time in industrial billets, the different Fe-rich IMCs have been characterized into types based on their 3D chemistry and morphology. Additionally, the role of β-AlFeSi in nucleating Mg2Si particles has been identified. After homogenization, α c-AlFeSi predominated across the entire billet cross section, with marked changes in the 3D morphology and strong reductions in inter-connectivity, both supporting a recovery in alloy ductility.

  8. Structural, optical and electronic structure studies of Al doped ZnO thin films

    NASA Astrophysics Data System (ADS)

    Devi, Vanita; Kumar, Manish; Shukla, D. K.; Choudhary, R. J.; Phase, D. M.; Kumar, Ravindra; Joshi, B. C.

    2015-07-01

    Structural, optical and electronic structure of Al doped ZnO thin films grown using pulsed laser deposition on glass substrate are investigated. X-ray diffraction measurements reveal that all the films are textured along the c-axis and have wurtzite structure. Al doping in ZnO films leads to increase in grain size due to relaxation in compressive stress. Enhancement in band gap of ZnO films with the Al doping is also noticed which can be ascribed to the Brustein-Moss shift. The changes in the electronic structure caused by Al in the doped thin film samples are understood through X-ray absorption measurements.

  9. 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

  10. Synthesis and characterization of ZnFe2O4 nanoparticles and its biomedical applications

    PubMed Central

    Hossain, Md Sazzad; Choudhury, Shamima; Akhter, S.; Hyder, F.

    2015-01-01

    Biomedical applications of ZnFe2O4 nanoparticle are preferable among all kinds of ferrites due to the compatibility of Zn2+ ions for human bodies. We have followed the soft chemical route to synthesize chitosan and PEG coated ZnFe2O4 nanoparticles and also the chitosan-coated-nanoparticles encapsulated with liposome. X-ray diffraction studies by the Mo Kα target, showed the formation of single phase spinel structure. The lattice parameter turned out to be 8.48Å and grain size ~ 4.8 nm (± 0.1 nm). Similar particle size was observed by transmission electron microscope analysis. HRTEM studies showed the distinct lattice fringes thus confirming the good crystallinity of the synthesized nanoparticles. M-H curve at room temperature showed the prepared sample was superparamagnetic in nature, which is also confirmed by the doublets of Mössbauer spectroscopy. Relaxivity values (r2) of Chitosan and PEG coated ZnFe2O4 nanoparticles are 68 and 76 mM−1s−1 respectively. In order to achieve further biocompatibility the chitosan-coated-nanoparticles were encapsulated with liposome. The r2 relaxivity was found as 54mM−1s−1. MR images obtained from the in vitro experiments based on phantoms demonstrated good contrast enhancement. Induction heating of bare and coated particles was investigated to reveal the self heating temperature rising properties of ZnFe2O4 nanoparticles. PMID:26549918

  11. ZnFe2O4-TiO2 Nanoparticles within Mesoporous MCM-41

    PubMed Central

    Tang, Aidong; Deng, Yuehua; Jin, Jiao; Yang, Huaming

    2012-01-01

    A novel nanocomposite ZnFe2O4-TiO2/MCM-41 (ZTM) was synthesized by a sol-gel method and characterized through X-ray diffraction (XRD), high-resolution transmission electron microscopy (HRTEM), N2 adsorption-desorption, Raman spectroscopy, and ultraviolet visible (UV-vis) spectrophotometry. The results confirmed the incorporation of ZnFe2O4-TiO2 nanoparticles inside the pores of the mesoporous MCM-41 host without destroying its integrity. ZnFe2O4 nanoparticles can inhibit the transformation of anatase into rutile phase of TiO2. Incorporation of ZnFe2O4-TiO2 within MCM-41 avoided the agglomeration of nanoparticles and reduced the band gap energy of TiO2 to enhance its visible light photocatalytic activity. UV-vis absorption edges of ZTM nanocomposites redshifted with the increase of Zn/Ti molar ratio. The nanocomposite approach could be a potential choice for enhancing the photoactivity of TiO2, indicating an interesting application in the photodegradation and photoelectric fields. PMID:22919325

  12. Weak localization in ZnO:Ga and ZnO:Al thin films

    NASA Astrophysics Data System (ADS)

    Reukova, O. V.; Kytin, V. G.; Kulbachinskii, V. A.; Burova, L. I.; Kaul, A. R.; Ulyashin, A. G.

    2014-12-01

    The temperature dependences of the resistivity, magnetoresistance and the Hall effect of ZnO thin films doped with Ga and Al were investigated at low temperatures. According to obtained experimental data the dimensionality of the investigated films with respect to the weak localization theory changes from 2D to 3D with an increase of magnetic field and temperature. To describe the observed negative magnetoresistance under these conditions we derived a new expression for the weak localization correction to the conductivity. It was found that the obtained expression describes magnetoresistance of investigated films much better than all known expressions for negative magnetoresistence related to weak localization. The values of the electron diffusion length during the phase relaxation time of wave function were obtained by fitting of experimental magnetoresistance with derived expression. Obtained values are consistent with the applied approach.

  13. Elevated Temperature Deformation of Fe-39.8Al and Fe-15.6Mn-39.4Al

    NASA Technical Reports Server (NTRS)

    Whittenberger, J. Daniel

    2004-01-01

    The elevated temperature compressive properties of binary Fe-39.8 at % Al and Fe-15.6Mn-39.4Al have been measured between 1000 and 1300 K at strain rates between 10(exp 7) and 10(exp 3)/ s. Although the Mn addition to iron aluminide did not change the basic deformation characteristics, the Mn-modified alloy was slightly weaker. In the regime where deformation of FeAl occurs by a high stress exponent mechanism (n = 6), strength increases as the grain size decreases at least for diameters between approx. 200 and approx. 10 microns. Due to the limitation in the grain size-flow stress-temperature-strain rate database, the influence of further reductions of the grain size on strength is uncertain. Based on the appearance of subgrains in deformed iron aluminide, the comparison of grain diameters to expected subgrain sizes, and the grain size exponent and stress exponent calculated from deformation experiments, it is believed that grain size strengthening is the result of an artificial limitation on subgrain size as proposed by Sherby, Klundt and Miller.

  14. Synthesis and Characterization of Al doped ZnO (AZO) by Sol-gel Method

    NASA Astrophysics Data System (ADS)

    Munawaroh, H.; Wahyuningsih, S.; Ramelan, A. H.

    2017-02-01

    Al doped ZnO (AZO) nanoparticles have been successfully synthesized by the simple sol-gel method. The starting materials of Al doped ZnO were Zn(CH3COO)2·2H2O and Al(OH)(CH3COO)2. Preparation of AZO using polyethylene glycol as a surfactant. The solution of precursors was stirred at 60 °C for 2 hour in the conditions of Al contents are 0%, 2%, 3% and 4% (g/mL), respectivelly. In the last step reaction, gelation occurred from solution to sol gel. The sol gel then were dried at 60 °C following by annealing process for crystalization. By this simple sol gel method, the nanoparticles have been produced. The characterizations were conducted X-Ray Diffraction (XRD), Scanning Electron Microscopy (SEM), Fourrier Transform Infra-Red (FTIR) and X-Ray Fluorescence (XRF). XRD analysis reveals that all samples has crystallizes in polycrystalline nature and exhibit no other impurity phase. The variation of Al doped ZnO slighly affect the crystallinity and crystal size. Both crystallinity and crystal size decrease with increasing of Al content in AZO. Morphology of AZO shown the particle distribution more equitable with increased Al content. The synthesized AZO gaved shift peak absorption of asymetric and symetric vibrations of Zn-O-Zn around wavelengths of 680 cm-1 and 1630 cm-1 atributed of the uptake of the Al-O-Al bond instead Zn-O-Zn. XRF analysis shown that the increase ratio of Al entering into Zn influenced the Al dopant concentration.

  15. Study of difference in interfacial reaction at Fe{sub 3}O{sub 4}/ZnO and ZnO/Fe{sub 3}O{sub 4} heterostructure using synchrotron radiation

    SciTech Connect

    Wadikar, A. D. Master, Ridhi Choudhary, R. J. Phase, D. M.

    2014-04-24

    We have prepared Fe{sub 3}O{sub 4}/ZnO and ZnO/Fe{sub 3}O{sub 4} bilayer structure on p-Si substrate using pulsed laser deposition technique (PLD). X-ray diffraction study revealed (0001) oriented growth of ZnO and (111) oriented growth of Fe{sub 3}O{sub 4} in both the bilayer structure. We observed a change in the density of states near the Fermi level in valence band spectra in case of Fe{sub 3}O{sub 4}/ZnO bilayer when compared to that of ZnO/Fe{sub 3}O{sub 4}. Nonlinear current–voltage (I-V) characteristics were observed in both the samples confirmed that these bilayer structures can be used for spintronic application.

  16. Energy levels and zero field splitting parameter for Fe2+ doped in ZnS

    NASA Astrophysics Data System (ADS)

    Ivaşcu, Simona

    2013-11-01

    The aim of present paper is to report the results on the modeling of the crystal field parameters of Fe2+ doped in host matrix ZnS, simulate the energy levels scheme and calculate the zero field splitting parameter D of such system. The crystal field parameters were modeled in the frame of the superposition model of crystal field and the simulation of the energy levels scheme and calculation of the zero field splitting parameters done by diagonalization the Hamiltonian of Fe2+:ZnS system. The obtained results were disscused and compared with experimental data. Satisfactory agreement have been obtained.

  17. A Question of Balance: Facing the challenges of Cu, Fe and Zn Homeostasis

    PubMed Central

    Palmer, Christine; Guerinot, Mary Lou

    2011-01-01

    Plants have recently moved into the spotlight with the growing realization that the world needs solutions to energy and food production that are sustainable and environmentally sound. Iron (Fe), copper (Cu), and zinc (Zn) are essential for plant growth and development, yet the same properties that make these transition metals indispensable can also make them deadly in excess. Fe and Cu are most often utilized for their redox properties, while Zn is primarily utilized for is ability to act as a Lewis acid. Here we review recent advances in the field of metal homeostasis, seeking to integrate the findings on uptake, transport, and storage of these three metals. PMID:19377460

  18. Fluorescent metal-organic framework MIL-53(Al) for highly selective and sensitive detection of Fe3+ in aqueous solution.

    PubMed

    Yang, Cheng-Xiong; Ren, Hu-Bo; Yan, Xiu-Ping

    2013-08-06

    Fluorescent metal-organic frameworks (MOFs) have received great attention in sensing application. Here, we report the exploration of fluorescent MIL-53(Al) for highly selective and sensitive detection of Fe(3+) in aqueous solution. The cation exchange between Fe(3+) and the framework metal ion Al(3+) in MIL-53(Al) led to the quenching of the fluorescence of MIL-53(Al) due to the transformation of strong-fluorescent MIL-53(Al) to weak-fluorescent MIL-53(Fe), allowing highly selective and sensitive detection of Fe(3+) in aqueous solution with a linear range of 3-200 μM and a detection limit of 0.9 μM. No interferences from 0.8 M Na(+); 0.35 M K(+); 11 mM Cu(2+); 10 mM Ni(2+); 6 mM Ca(2+), Pb(2+), and Al(3+); 5.5 mM Mn(2+); 5 mM Co(2+) and Cr(3+); 4 mM Hg(2+), Cd(2+), Zn(2+), and Mg(2+); 3 mM Fe(2+); 0.8 M Cl(-); 60 mM NO2(-) and NO3(-); 10 mM HPO4(2-), H2PO4(-), SO3(2-), SO4(2-), and HCOO(-); 8 mM CO3(2-), HCO3(-), and C2O4(2-); and 5 mM CH3COO(-) were found for the detection of 150 μM Fe(3+). The possible mechanism for the quenching effect of Fe(3+) on the fluorescence of MIL-53(Al) was elucidated by inductively coupled plasma-mass spectrometry, X-ray diffraction spectrometry, and Fourier transform infrared spectrometry. The specific cation exchange behavior between Fe(3+) and the framework Al(3+) along with the excellent stability of MIL-53(Al) allows highly selective and sensitive detection of Fe(3+) in aqueous solution. The developed method was applied to the determination of Fe(3+) in human urine samples with the quantitative spike recoveries from 98.2% to 106.2%.

  19. First principles investigation of Fe and Al bearing phase H

    NASA Astrophysics Data System (ADS)

    Tsuchiya, J.; Tsuchiya, T.

    2015-12-01

    The global circulation of water in the earth is important to investigate the evolution history and dynamics of the earth, since the physical properties (e.g. atomic diffusivity, melting temperature, electrical conductivity and seismic velocities) of the constituent minerals are considerably changed by the presence of water. It has been believed that water is carried into the deep Earth's interior by hydrous minerals such as the dense hydrous magnesium silicates (DHMSs) which are also known as alphabet phases (phase A, superhydrous phase B, and phase D etc.) in the descending cold plate. It has been thought that the relay of these hydrous phases was terminated at ~1200 km depth by the dehydration of phase D which was the highest pressure phase of DHMSs. Recently, we have theoretically predicted the high pressure phase of phase D and experimentally confirmed the existence of this new DHMS in lower mantle pressure conditions above ~45 GPa. This phase has MgSiO4H2chemical composition and named as phase H. At the lower mantle pressure conditions, Al and H-bearing SiO2, δ-AlOOH, ɛ-FeOOH and phase H may be the relevant hydrous phases in the subducting slabs. Interestingly, the crystal structure of these hydrous phases are almost same and have CaCl2type structure. This suggests that these hydrous phases may potentially be able to make the wide range of solid solution. Some experimental studies already reported that Al preferentially partitioned into phase H and the stability of phase H drastically increased by incorporation of Al (Nishi et al. 2014, Ohira et al. 2014). The density of subducted MORB is reported to be denser than that of pyrolite in the lower mantle (e.g. Kawai et al. 2009). Therefore, there is a possibility that phase H containing Al and Fe in subducted MORB survive down to the bottom of lower mantle and the melting of phase H at the core mantle boundary may contribute to the cause of ultra-low velocity zones. In this study, we further extends our

  20. 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.

  1. Structure, molecular simulation, and release of aspirin from intercalated Zn-Al-layered double hydroxides.

    PubMed

    Meng, Zilin; Li, Xiaowei; Lv, Fengzhu; Zhang, Qian; Chu, Paul K; Zhang, Yihe

    2015-11-01

    Aspirin or acetylsalicylic acid (AA), a non-steroidal anti-inflammatory drug, is intercalated into Zn-Al-layered double hydroxides (ZnAl-LDHs) by co-precipitation and reconstruction methods. The composition, structure, and morphology of the intercalated products as well as their release behavior are determined experimentally and theoretically by Material Studio 5.5. Experimental results disclose the strong interaction between the LDHs sheets and AA in the intercalated ZnAl-LDHs produced by co-precipitation and slow release of AA from the intercalated ZnAl-LDHs in both phosphate buffered saline (PBS) and borate buffered saline (BBS) solutions. The percentage of AA released from the ZnAl-LDHs prepared by both methods in PBS (96.87% and 98.12%) are much more than those in BBS (68.59% and 81.22%) implying that both H4BO4(-) and H2PO4(-) can exchange with AA in the ZnAl-LDHs. After AA is released to PBS, ZnAl-LDHs break into small pieces. The experimental results are explained theoretically based on the calculation of the bonding energy between the anions and LDHs sheets as well as the AlO bond length change in the LDHs sheets.

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

    SciTech Connect

    Kim, Hyong June

    2011-01-01

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

  3. Microwave absorption behavior of ZnO whisker modified by nanosized Fe3O4 particles.

    PubMed

    Hu, Shuchun; Wu, Guofeng; Huang, Zhenhao; Chen, Xiaolang

    2010-11-01

    Tetra-needle-like ZnO whisker was magnetic modified through in situ synthesis of nanosized Fe3O4 particles on the surface of the whisker, and the microwave absorption behavior of the as-prepared product was investigated in detail. The result of the comparative microwave absorbing experiment showed that the magnetic modified ZnO whisker appeared more superior property of microwave absorption than that of the original ZnO whisker in 2-18 GHz. Further investigation indicated that the microwave absorption behavior of the product was influenced by ferrite content and Fe3O4 particles' distribution in the product. When the ferrite content of the product changed from 2 wt% to 9 wt%, the microwave absorbing ability of the product was increased; then, the microwave absorbing ability of the product decreased with the further increasing of ferrite content from 9 wt% to 16 wt%. The product with uniform distribution of Fe3O4 particles showed better microwave absorption property than that with irregular distribution of Fe3O4 particles, and this result inferred that the biphase interface between ZnO and Fe3O4 contributed to microwave absorption through interface polarization.

  4. 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.

  5. Improved Resistance Switching Stability in Fe-Doped ZnO Thin Films Through Pulsed Magnetic Field Annealing.

    PubMed

    Xu, Hongtao; Wu, Changjin; Xiahou, Zhao; Jung, Ranju; Li, Ying; Liu, Chunli

    2017-12-01

    Five percent of Fe-doped ZnO (ZnO:Fe) thin films were deposited on Pt/TiO2/SiO2/Si substrates by a spin-coating method. The films were annealed without (ZnO:Fe-0T) and with a pulsed magnetic field of 4 T (ZnO:Fe-4TP) to investigate the magnetic annealing effect on the resistance switching (RS) behavior of the Pt/ZnO:Fe/Pt structures. Compared with the ZnO:Fe-0T film, the ZnO:Fe-4TP film showed improved RS performance regarding the stability of the set voltage and the resistance of the high resistance state. Transmission electron microscopy and X-ray photoelectron spectroscopy analyses revealed that the ZnO:Fe-4TP film contains more uniform grains and a higher density of oxygen vacancies, which promote the easier formation of conducting filaments along similar paths and the stability of switching parameters. These results suggest that external magnetic fields can be used to prepare magnetic oxide thin films with improved resistance switching performance for memory device applications.

  6. Improved Resistance Switching Stability in Fe-Doped ZnO Thin Films Through Pulsed Magnetic Field Annealing

    NASA Astrophysics Data System (ADS)

    Xu, Hongtao; Wu, Changjin; Xiahou, Zhao; Jung, Ranju; Li, Ying; Liu, Chunli

    2017-03-01

    Five percent of Fe-doped ZnO (ZnO:Fe) thin films were deposited on Pt/TiO2/SiO2/Si substrates by a spin-coating method. The films were annealed without (ZnO:Fe-0T) and with a pulsed magnetic field of 4 T (ZnO:Fe-4TP) to investigate the magnetic annealing effect on the resistance switching (RS) behavior of the Pt/ZnO:Fe/Pt structures. Compared with the ZnO:Fe-0T film, the ZnO:Fe-4TP film showed improved RS performance regarding the stability of the set voltage and the resistance of the high resistance state. Transmission electron microscopy and X-ray photoelectron spectroscopy analyses revealed that the ZnO:Fe-4TP film contains more uniform grains and a higher density of oxygen vacancies, which promote the easier formation of conducting filaments along similar paths and the stability of switching parameters. These results suggest that external magnetic fields can be used to prepare magnetic oxide thin films with improved resistance switching performance for memory device applications.

  7. Atomic layer deposition of Al-doped ZnO thin films

    SciTech Connect

    Tynell, Tommi; Yamauchi, Hisao; Karppinen, Maarit; Okazaki, Ryuji; Terasaki, Ichiro

    2013-01-15

    Atomic layer deposition has been used to fabricate thin films of aluminum-doped ZnO by depositing interspersed layers of ZnO and Al{sub 2}O{sub 3} on borosilicate glass substrates. The growth characteristics of the films have been investigated through x-ray diffraction, x-ray reflection, and x-ray fluorescence measurements, and the efficacy of the Al doping has been evaluated through optical reflectivity and Seebeck coefficient measurements. The Al doping is found to affect the carrier density of ZnO up to a nominal Al dopant content of 5 at. %. At nominal Al doping levels of 10 at. % and higher, the structure of the films is found to be strongly affected by the Al{sub 2}O{sub 3} phase and no further carrier doping of ZnO is observed.

  8. Ni, Fe Co-doped ZnO nanoparticles synthesized by solution combustion method

    SciTech Connect

    Dhiman, Pooja Chand, Jagdish Verma, S. Sarveena, Singh, M.

    2014-04-24

    This paper outlines the synthesis and characterization of Ni-Fe co-doped ZnO nanoparticles by facile solution combustion method. The structural characterization by XRD confirmed the phase purity of the samples. Surface morphology studied by scanning electron microscope revealed cubic type shape of grains. EDS analysis conformed the elemental composition. Higher value of DC electrical conductivity and less band gap for co-doped ZnO from UV-Vis studies confirmed the change in defect chemistry of ZnO Matrix.

  9. Ni, Fe Co-doped ZnO nanoparticles synthesized by solution combustion method

    NASA Astrophysics Data System (ADS)

    Dhiman, Pooja; Chand, Jagdish; Verma, S.; Sarveena, Singh, M.

    2014-04-01

    This paper outlines the synthesis and characterization of Ni-Fe co-doped ZnO nanoparticles by facile solution combustion method. The structural characterization by XRD confirmed the phase purity of the samples. Surface morphology studied by scanning electron microscope revealed cubic type shape of grains. EDS analysis conformed the elemental composition. Higher value of DC electrical conductivity and less band gap for co-doped ZnO from UV-Vis studies confirmed the change in defect chemistry of ZnO Matrix.

  10. Identification of an incommensurate FeAl{sub 2} overlayer on FeAl(110) using x-ray diffraction and reflectivity

    SciTech Connect

    Baddorf, A.P.; Chandavarkar, S.S.

    1995-06-30

    FeAl, like NiAl, crystallizes in the CsCl structure. Consequently the (110) planes contain equal amounts of Fe and Al distributed as interlocking rectangles. Unlike the NiAI(110) surface, which retains the (1{times}l) in-plane symmetry of the bulk, FeAl(l10) reconstructs to form an ordered, incommensurate overlayer. The reconstructed layer introduces x-ray diffraction rods at half-order positions along the [1{bar 1}0] direction, and displaced {plus_minus}0.2905 from integer positions along the [001] direction. Peak widths reveal excellent long range order. Specular reflectivity measurements above and below the Fe K{alpha} edge can be reproduced using a model containing a single reconstructed overlayer with an Fe:Al ratio of 1:2, consistent with FeA{sub I}2.

  11. Optical characterization of Sol-Gel ZnO:Al thin films

    NASA Astrophysics Data System (ADS)

    Ivanova, T.; Harizanova, A.; Koutzarova, T.; Vertruyen, B.

    2016-03-01

    This paper presents a sol-gel technological process for preparing thin films of ZnO and ZnO:Al. The effect of annealing treatments (500, 600, 700 and 800 °C) on their properties was studied. The structural evolution with the temperature was investigated by using X-Ray diffraction (XRD). Fourier Transform Infrared (FTIR) and UV-VIS spectrophotometry were applied to characterizing the films' vibrational and optical properties. The ZnO and ZnO:Al films possessed a polycrystalline structure. The films studied are highly transparent in the visible spectral range. The optical band gap values and the haze parameter were also determined.

  12. Mixing and non-stoichiometry in Fe-Ni-Cr-Zn-O spinel compounds: density functional theory calculations.

    PubMed

    Andersson, David A; Stanek, Christopher R

    2013-10-07

    Density functional theory (DFT) calculations have been performed on A(2+)B2(3+)O4(2-) (where A(2+) = Fe, Ni or Zn, and B(3+) = Fe or Cr) spinel oxides in order to determine some of their thermodynamic properties. Mixing energies were calculated for Fe3O4-NiFe2O4, Fe3O4-ZnFe2O4, Fe3O4-FeCr2O4, NiFe2O4-ZnFe2O4, NiFe2O4-NiCr2O4, FeCr2O4-NiCr2O4, FeCr2O4-ZnCr2O4 and ZnCr2O4-ZnFe2O4 pseudo-binaries based on special quasi random (SQS) structures to account for cationic disorder. The results generally agree with available experimental data and the rule that two normal or two inverse spinel compounds easily form solid solutions, while inverse-normal spinel mixtures exhibit positive deviation from solid solution behavior (i.e. immiscibility). Even though the NiFe2O4-NiCr2O4 and Fe3O4-FeCr2O4 systems obey this rule, they exhibit additional features with implications for the corresponding phase diagrams. In addition to mixing enthalpies, non-stoichiometry was also considered by calculating the energies of the relevant defect reactions resulting in A, B and O excess (or deficiency). The DFT calculations predict close to zero or slightly exothermic reactions for both A and B excess in a number of spinel compounds.

  13. Decomposition of Al2.7Fe0.3Ti in heated Al-Al2.7Fe0.3Ti refiner fabricated by spark plasma sintering and its refining performance

    NASA Astrophysics Data System (ADS)

    Watanabe, Yoshimi; Hamada, Takayuki; Sato, Hisashi

    2017-01-01

    In our previous study, a novel Al-L12-type Al2.7Fe0.3Ti refiner was fabricated by spark plasma sintering (SPS) and its refining performance was studied. It was found that L12-type Al2.7Fe0.3Ti particles can be favorable heterogeneous nucleation sites for Al casts, since the lattice matching between Al2.7Fe0.3Ti and Al is good. It was also found that the thermal stability of heterogeneous nucleation sites affects the grain-refining performance. In this study, the decomposition phenomena of the Al2.7Fe0.3Ti phase in a refiner are studied by heating an Al-Al2.7Fe0.3Ti refiner fabricated by SPS. In addition, the refining performance of a heated Al-Al2.7Fe0.3Ti refiner is investigated.

  14. Preparation and electromagnetic properties of Polyaniline(polypyrrole)-BaFe12O19/Ni0.8Zn0.2Fe2O4 ferrite nanocomposites

    NASA Astrophysics Data System (ADS)

    Wang, Yan; Huang, Ying; Wang, Qiufen; He, Qian; Chen, Lin

    2012-10-01

    The nanocomposite of hard (BaFe12O19)/soft ferrite (Ni0.8Zn0.2 Fe2O4) was prepared by the sol-gel process, and then the polyaniline(PANI)/polypyrrole(PPY)-BaFe12O19/Ni0.8Zn0.2Fe2O4 was produced by in situ polymerization method. The structures, morphology and electromagnetic properties of the samples were characterized by various instruments. XRD, TEM, and FTIR analysis indicated that BaFe12O19/Ni0.8Zn0.2Fe2O4 ferrite were homogenously enwrapped by PANI(PPY) coating. The VSM and SDY-4 measurement show that the magnetic properties of the composites decreased with the increase in PANI(PPY) amount, However, the electrical conductivity is on the contrary. The electromagnetic properties of the composites were much better than BaFe12O19/Ni0.8Zn0.2Fe2O4 in the frequency range of 2-15 GHz, which mainly depends on the dielectric loss of PANI(PPY). A minimum reflection loss of the PANI(PPY)-BaFe12O19/Ni0.8Zn0.2Fe2O4 ferrite nanocomposite is -19.7 dB(-21.5 dB) at the frequency of 7.3 GHz (10.7 GHz).

  15. Crystallographic and magnetic properties of the hyperthermia material CoFe2O4@AlFe2O4

    NASA Astrophysics Data System (ADS)

    Choi, Hyunkyung; An, Mijeong; Eom, Wonyoung; Lim, Sae Wool; Shim, In-Bo; Kim, Chul Sung; Kim, Sam Jin

    2017-01-01

    Hard/soft CoFe2O4@AlFe2O4 core/shell nanoparticles were prepared by using a high temperature thermal decomposition method with seed-mediated growth. The structural, magnetic and thermal properties of the nanoparticles were investigated by using X-ray diffraction, vibrating sample magnetometer, MagneTherm, and Mössbauer spectroscopy. The crystal structure of nanoparticles was determined to be cubic spinel ferrite with space group Fd-3m. The CoFe2O4 nanoparticles were found to show high magnetization and coercivity while AlFe2O4 nanoparticles were found to show low magnetization and coercivity. The CoFe2O4@AlFe2O4 core/shell nanoparticles showed intermediate values of magnetization and the coercivity between those of CoFe2O4 and AlFe2O4. Also, the blocking temperature ( T B ) of the nanoparticles (NPs) was observed to be 280, 50, and 225 K for CoFe2O4, AlFe2O4 and CoFe2O4@AlFe2O4, respectively. The core/shell ferrite shows a T B near 225 K, associated with the harder CoFe2O4 NPs. Temperatures below 225 K, the zero-field-cooled curves show changes in their slopes at a temperature near 50 K, corresponding to the second blocking temperature associated with the softer AlFe2O4 NPs.

  16. Al:ZnO thin film: An efficient matrix for cholesterol detection

    NASA Astrophysics Data System (ADS)

    Batra, Neha; Tomar, Monika; Gupta, Vinay

    2012-12-01

    Al doped ZnO thin film (Al:ZnO) has been realized as a potential matrix for the development of efficient cholesterol biosensor. The correlation between the structural and electrical properties of ZnO thin film with varying Al doping concentration (1% to 5%) and their cyclic voltammetric (CV) response has been studied. 2% Al doped ZnO films were found to give the best CV response and were further utilized for immobilization of cholesterol oxidase (ChOx) to detect cholesterol. Amperometric and photometric studies reveal that the prepared bioelectrode based on 2% Al doped ZnO matrix (ChOx/Al:ZnO/Pt/glass) is highly sensitive (sensitivity = 173 μAmM-1 cm-2) to the detection of cholesterol in the wide range from 0.6-12.9 mM (25-500 mg/dl). A relatively low value of enzyme's kinetic parameter (Michaelis menten constant, 2.53 mM) indicates enhanced affinity of the immobilized ChOx toward cholesterol. The prepared bioelectrode is found to be exhibiting high shelf life (10 weeks) having negligible interference with the presence of other biomolecules in human serum indicating promising application of Al doped ZnO thin films for cholesterol biosensing.

  17. 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.

  18. First principle investigation of crystal lattice structure, thermodynamics and mechanical properties in ZnZrAl2 intermetallic compound

    NASA Astrophysics Data System (ADS)

    Wei, Zhenyi; Tou, Shushi; Wu, Bo; Bai, Kewu

    2016-12-01

    ZnZrAl2 is a kind of heterogeneous nucleation to promote the refine of grain of ZA43 alloy. ZnZrAl2 intermetallic is also considered as a candidate for superalloys. The crystal lattice structure, alloy thermodynamics and mechanical properties of ZnZrAl2 intermetallic compound were investigated by ab initio calculations based on density functional theory (DFT). In particular, the site preference of atoms in different sublattices was predicted based on alloy thermodynamics. At ground state, the most stable structure is L12 structure with sublattice model (Zn)1a(Zr0.3333Al0.6667)3c or (Zr)1a(Zn0.3333Al0.6667)3c, and the occupying preferences of Zn, Zr and Al atoms are independent with the increasing temperature. The bulk, shear, Young's modulus and the Poisson's ratio of the L12 structure ZnZrAl2 were calculated based on the site occupying configurations. The results show that ZnZrAl2 is a brittle material in nature. Electronic structures analysis revealed that Al-Zr atoms possess a covalent bonding character, while the Zn-Zr atoms have a metallic bonding character. ZnZrAl2 has stable mechanical properties at high temperature. The grain refinement effect of ZnZrAl2 precipitates in Zn-Al alloys were discussed based on crystal lattice match theory.

  19. Designing optical metamaterial with hyperbolic dispersion based on an Al:ZnO/ZnO nano-layered structure using the atomic layer deposition technique.

    PubMed

    Kelly, Priscilla; Liu, Mingzhao; Kuznetsova, Lyuba

    2016-04-10

    Nano-layered Al:ZnO/ZnO hyperbolic dispersion metamaterial with a large number of layers was fabricated using the atomic layer deposition (ALD) technique. Experimental dielectric functions for Al:ZnO/ZnO structures are obtained by an ellipsometry technique in the visible and near-infrared spectral ranges. The theoretical modeling of the Al:ZnO/ZnO dielectric permittivity is done using effective medium approximation. A method for analysis of spectroscopic ellipsometry data is demonstrated to extract the optical permittivity for this highly anisotropic nano-layered metamaterial. The results of the ellipsometry analysis show that Al:ZnO/ZnO structures with a 1:9 ALD cycle ratio exhibit hyperbolic dispersion transition change near 1.8 μm wavelength.

  20. Designing optical metamaterial with hyperbolic dispersion based on Al:ZnO/ZnO nano-layered structure using Atomic Layer Deposition technique

    DOE PAGES

    Kelly, Priscilla; Liu, Mingzhao; Kuznetsova, Lyuba

    2016-04-07

    In this study, nano-layered Al:ZnO/ZnO hyperbolic dispersion metamaterial with a large number of layers was fabricated using the atomic layer deposition (ALD) technique. Experimental dielectric functions for Al:ZnO/ZnO structures are obtained by an ellipsometry technique in the visible and near-infrared spectral ranges. The theoretical modeling of the Al:ZnO/ZnO dielectric permittivity is done using effective medium approximation. A method for analysis of spectroscopic ellipsometry data is demonstrated to extract the optical permittivity for this highly anisotropic nano-layered metamaterial. The results of the ellipsometry analysis show that Al:ZnO/ZnO structures with a 1:9 ALD cycle ratio exhibit hyperbolic dispersion transition change near 1.8more » μm wavelength.« less

  1. Designing optical metamaterial with hyperbolic dispersion based on Al:ZnO/ZnO nano-layered structure using Atomic Layer Deposition technique

    SciTech Connect

    Kelly, Priscilla; Liu, Mingzhao; Kuznetsova, Lyuba

    2016-04-07

    In this study, nano-layered Al:ZnO/ZnO hyperbolic dispersion metamaterial with a large number of layers was fabricated using the atomic layer deposition (ALD) technique. Experimental dielectric functions for Al:ZnO/ZnO structures are obtained by an ellipsometry technique in the visible and near-infrared spectral ranges. The theoretical modeling of the Al:ZnO/ZnO dielectric permittivity is done using effective medium approximation. A method for analysis of spectroscopic ellipsometry data is demonstrated to extract the optical permittivity for this highly anisotropic nano-layered metamaterial. The results of the ellipsometry analysis show that Al:ZnO/ZnO structures with a 1:9 ALD cycle ratio exhibit hyperbolic dispersion transition change near 1.8 μm wavelength.

  2. Chemical mixing at “Al on Fe” and “Fe on Al” interfaces

    SciTech Connect

    Süle, P.; Horváth, Z. E.; Kaptás, D.; Bujdosó, L.; Balogh, J.; Nakanishi, A.

    2015-10-07

    The chemical mixing at the “Al on Fe” and “Fe on Al” interfaces was studied by molecular dynamics simulations of the layer growth and by {sup 57}Fe Mössbauer spectroscopy. The concentration distribution along the layer growth direction was calculated for different crystallographic orientations, and atomically sharp “Al on Fe” interfaces were found when Al grows over (001) and (110) oriented Fe layers. The Al/Fe(111) interface is also narrow as compared to the intermixing found at the “Fe on Al” interfaces for any orientation. Conversion electron Mössbauer measurements of trilayers—Al/{sup 57}Fe/Al and Al/{sup 57}Fe/Ag grown simultaneously over Si(111) substrate by vacuum evaporation—support the results of the molecular dynamics calculations.

  3. From kesterite to stannite photovoltaics: Stability and band gaps of the Cu2(Zn,Fe)SnS4 alloy

    NASA Astrophysics Data System (ADS)

    Shibuya, Taizo; Goto, Yosuke; Kamihara, Yoichi; Matoba, Masanori; Yasuoka, Kenji; Burton, Lee A.; Walsh, Aron

    2014-01-01

    Kesterite semiconductors, particularly Cu2ZnSnS4 (CZTS), have attracted attention for thin-film solar cells. We investigate the incorporation of Fe into CZTS to form the Cu2(Zn,Fe)SnS4 solid-solution for tuning the lattice spacing and band gap. First-principles calculations confirm a phase transition from kesterite (Zn-rich) to stannite (Fe-rich) at Fe/Zn ˜ 0.4. The exothermic enthalpy of mixing is consistent with the high solubility of Fe in the lattice. There is a linear band-gap bowing for each phase, which results in a blue-shift of photo-absorption for Fe-rich alloys due to the confinement of the conduction states. We propose compositions optimal for Si tandem cells.

  4. Fabrication and microstructural characterization of Al/Zn-enriched layers on pure magnesium

    SciTech Connect

    Mola, Renata

    2013-04-15

    Al/Zn-enriched surface layers were fabricated by heating Mg specimens in contact with Al–Zn powder mixtures in a vacuum furnace at 445 °C. The layer formation process took place through partial melting at the Mg-substrate/powder-mixture interface. Heating times ranged from 20 to 80 min. The layer microstructure and composition were analyzed by optical microscopy (OM), scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS). The layers were 100–900 μm in thickness, depending on the treatment time. The examination results revealed that the layers consisted of Mg{sub 17}(Al,Zn){sub 12} and Mg{sub 5}Al{sub 2}Zn{sub 2} intermetallic phases and a solid solution of Al and Zn in Mg. Between the Al/Zn-enriched layer and the Mg substrate, there was a transition zone of a solid solution of Al and Zn in Mg with a thickness of 20–30 μm. The layers had much higher microhardness than the Mg substrate. - Highlights: ► The layers were produced by heating Mg in contact with an Al–Zn powder mixture. ► The layer formation process at 445 °C proceeded with the liquid phase contribution. ► The Al/Zn-enriched layers were thick, dense, uniform and continuous. ► The layers contained Mg–Al–Zn intermetallic phases. ► The hardness of the layers was much higher than that of the Mg substrate.

  5. Fe-doped ZnO nanoparticles: the oxidation number and local charge on iron, studied by 57Fe Mößbauer spectroscopy and DFT calculations.

    PubMed

    Xiao, Jianping; Kuc, Agnieszka; Pokhrel, Suman; Mädler, Lutz; Pöttgen, Rainer; Winter, Florian; Frauenheim, Thomas; Heine, Thomas

    2013-03-04

    Iron bru: Fe-doped ZnO may contain Fe(2+) and Fe(3+) species. Whilst Mößbauer spectroscopy can distinguish these sites in pure oxides FeO and Fe(2)O(3), it gives very similar shifts for Fe-doped phases. This result is rationalized by electron redistribution from the dopant site to the crystal matrix. Mößbauer shifts correlate with the local charge on the Fe sites and different dopant sites can be identified by the Mößbauer quadrupole splitting (see figure).

  6. Magnetism and magnetoresistance from different origins in Co/ZnO:Al granular films

    NASA Astrophysics Data System (ADS)

    Quan, Zhiyong; Liu, Xia; Song, Zhilin; Xu, Xiaohong

    2016-12-01

    Co/ZnO:Al granular films were made on glass substrates by sequential magnetron sputter deposition of ultrathin Co layer and ZnO:Al layer at room temperature. The as-deposited films consist of superparamagnetic Co particles dispersed in ZnO:Al ( 2% Al) semiconductor matrix. Distinguished magnetoresistance effect at room temperature was obtained in the as-deposited films, which obviously reduced after annealing due to the growth of Co particles. The size of important magnetic particles was analyzed by Langevin function for hysteresis loops and magnetoresistance curves at room temperature. It was found that small magnetic particle contribute to magnetoresistance behavior and large particles dominate the room temperature magnetism in Co/ZnO:Al granular films.

  7. Thermally Diffused Al:ZnO Thin Films for Broadband Transparent Conductor.

    PubMed

    Tong, Chong; Yun, Juhyung; Chen, Yen-Jen; Ji, Dengxin; Gan, Qiaoqiang; Anderson, Wayne A

    2016-02-17

    Here, we report an approach to realize highly transparent low resistance Al-doped ZnO (AZO) films for broadband transparent conductors. Thin Al films are deposited on ZnO surfaces, followed by thermal diffusion processes, introducing the Al doping into ZnO thin films. By utilizing the interdiffusion of Al, Zn, and O, the chemical state of Al on the surfaces can be converted to a fully oxidized state, resulting in a low sheet resistance of 6.2 Ω/sq and an excellent transparency (i.e., 96.5% at 550 nm and higher than 85% up to 2500 nm), which is superior compared with some previously reported values for indium tin oxide, solution processed AZO, and many transparent conducting materials using novel nanostructures. Such AZO films are also applied as transparent conducting layers for AZO/Si heterojunction solar cells, demonstrating their applications in optoelectronic devices.

  8. 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

    2017-12-01

    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 TiO2 (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 H2O2 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.

  9. Zinclipscombite, ZnFe{2/3+}(PO4)2(OH)2, a new mineral species

    NASA Astrophysics Data System (ADS)

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

    2007-12-01

    Zinclipscombite, a new mineral species, has been found together with apophyllite, quartz, barite, jarosite, plumbojarosite, turquoise, and calcite at the Silver Coin mine, Edna Mountains, Valmy, Humboldt County, Nevada, United States. The new mineral forms spheroidal, fibrous segregations; the thickness of the fibers, which extend along the c axis, reaches 20 μm, and the diameter of spherulites is up to 2.5 mm. The color is dark green to brown with a light green to beige streak and a vitreous luster. The mineral is translucent. The Mohs hardness is 5. Zinclipscombite is brittle; cleavage is not observed; fracture is uneven. The density is 3.65(4) g/cm3 measured by hydrostatic weighing and 3.727 g/cm3 calculated from X-ray powder data. The frequencies of absorption bands in the infrared spectrum of zinclipscombite are (cm-1; the frequencies of the strongest bands are underlined; sh, shoulder; w, weak band) 3535, 3330sh, 3260, 1625w, 1530w, 1068, 1047, 1022, 970sh, 768w, 684w, 609, 502, and 460. The Mössbauer spectrum of zinclipscombite contains only a doublet corresponding to Fe3+ with sixfold coordination and a quadrupole splitting of 0.562 mm/s; Fe2+ is absent. The mineral is optically uniaxial and positive, ω = 1.755(5), ɛ = 1.795(5). Zinclipscombite is pleochroic, from bright green to blue-green on X and light greenish brown on Z ( X > Z). Chemical composition (electron microprobe, average of five point analyses, wt %): CaO 0.30, ZnO 15.90, Al2O3 4.77, Fe2O3 35.14, P2O5 33.86, As2O5 4.05, H2O (determined by the Penfield method) 4.94, total 98.96. The empirical formula calculated on the basis of (PO4,AsO4)2 is (Zn0.76Ca0.02)Σ0.78(Fe{1.72/3+} Al0.36)Σ2.08[(PO4)1.86(AsO4)0.14]Σ2.00(OH)1. 80 · 0.17H2O. The simplified formula is ZnFe{2/3+} (PO4)2(OH)2. Zinclipscombite is tetragonal, space group P43212 or P41212; a = 7.242(2) Å, c = 13.125(5) Å, V = 688.4(5) Å3, Z = 4. The strongest reflections in the X-ray powder diffraction pattern ( d, ( I, %) (( hkl

  10. Magnetic properties of ball milled Fe-40Al at.% alloys

    SciTech Connect

    Amils, X.; Nogues, J.; Surinach, S.; Baro, M.D.; Munoz, J.S.

    1998-07-01

    A direct correlation between the lattice parameter and the saturation magnetization, during the disordering (ball milling) and posterior reordering (annealing) processes, has been found in Fe-40Al At.% compounds. These results indicate that the paramagnetic-ferromagnetic-paramagnetic transitions induced by ball milling and subsequent annealing could be related to the changes in volume, and not only to nearest neighbors effects as is commonly assumed. Moreover, these alloys have been found to become spin glass at low temperatures, independently of their structural state (ordered or disordered).

  11. MOKE Study of Fe/Co/Al Multilayers

    SciTech Connect

    Jani, Snehal; Lakshmi, N.; Venugopalan, K.; Rajput, Parasmani; Zajaoc, M.; Rueffer, R.; Reddy, V. R.; Gupta, Ajay

    2011-07-15

    The multilayer system (MLS)-[{sup 57}Fe{sub 25}A/Co{sub 11}A/Al{sub 17}A]x20 has been deposited by Ion beam sputtering (IBS) technique. The MLS has been annealed at 700 deg. C for 1 h. Overall composition of as deposited and annealed MLS have been characterized by EDX and magnetic properties have been studied through angular dependent magneto optic Kerr effect (MOKE) hysteresis curves. The study shows that the as-deposited MLS has excellent soft magnetic properties coupled with perpendicular magnetic isotropy which is destroyed on annealing.

  12. Al and Zn Impurity Diffusion in Binary and Ternary Magnesium Solid-Solutions

    SciTech Connect

    Kammerer, Catherine; Kulkarni, Nagraj S; Warmack, Robert J Bruce; Sohn, Yong Ho

    2014-01-01

    Magnesium alloys are considered for implementation into structural components where energy-efficiency and light-weighting are important. Two of the most common alloying elements in magnesium alloys are Aluminum and Zinc. The present work examines impurity diffusion coefficients of Al and Zn in Mg(Zn) and Mg(Al) binary solid solutions, respectively. Experimental investigation is carried out with ternary diffusion couples with polycrystalline alloys. Concentration profiles were measured by electron microprobe micro-analysis and the impurity diffusion coefficients were determined by the Hall Method. Results of Al and Zn impurity diffusion in Mg solid solutions are reported, and examined as a function of composition of Mg solid solution.

  13. Visible light photo-degradation of methylene blue over Fe or Cu promoted ZnO nanoparticles.

    PubMed

    Mardani, Hamid Reza; Forouzani, Mehdi; Ziari, Mitra; Biparva, Pourya

    2015-04-15

    CuxZn(1-x)O, FexZn(1-x)O (x=0.01) and ZnO nanoparticles were and were characterized by X-ray diffraction, ultraviolet and visible spectroscopy, FTIR spectroscopy and SEM. The photodegradation of an aqueous solution of methylene blue (as an organic pollutant) by nanoparticles with H2O2 (30%) under visible light and the progress of the reaction were monitored by UV-Vis spectroscopy absorption. The photocatalytic oxidation efficiency of all nanoparticles was 100% at the appropriate time. The degradation time was 90 min for FeZnO, 120 min for CuZnO and 210 min for ZnO. This indicates that the photocatalytic activity of the doped nanoparticles was better than that of ZnO alone. ZnO doped with a small amount of Fe or Cu decreased the size of the nanoparticles and the band gap and increased photocatalytic efficiency.

  14. Cyclic Oxidation of FeCrAlY/Al2O3 Composites

    NASA Technical Reports Server (NTRS)

    Nesbitt, James A.; Draper, Susan L.; Barrett, Charles A.

    1999-01-01

    Three-ply FeCrAlY/Al2O3 composites and FeCrAlY matrix-only samples were cyclically oxidized at 1000 C and 1100 C for up to 1000 1-hr cycles. Fiber ends were exposed at the ends of the composite samples. Following cyclic oxidation, cracks running parallel to and perpendicular to the fibers were observed on the large surface of the composite. In addition, there was evidence of increased scale damage and spallation around the exposed fiber ends, particularly around the middle ply fibers. This damage was more pronounced at the higher temperature. The exposed fiber ends showed cracking between fibers in the outer plies, occasionally with Fe and Cr-rich oxides growing out of the cracks. Large gaps developed at the fiber/matrix interface around many of the fibers, especially those in the outer plies. Oxygen penetrated many of these gaps resulting in significant oxide formation at the fiber/matrix interface far within the composite sample. Around several fibers, the matrix was also internally oxidized showing Al2O3 precipitates in a radial band around the fibers. The results show that these composites have poor cyclic oxidation resistance due to the CTE mismatch and inadequate fiber/matrix bond strength at temperatures of 1000 C and above.

  15. Preparation of iron aluminate (FeAl2O4) nanoparticles from FeAl2O4 hollow particles fabricated by using a spray pyrolysis process

    NASA Astrophysics Data System (ADS)

    Yun, Jaecheol; Kim, Yangdo; Park, Dahee; Yun, Jung-Yeul

    2015-05-01

    Iron aluminate (FeAl2O4) hollow particles with a spinel structure were synthesized by using a spray pyrolysis process. FeAl2O4 hollow particles were formed at a reaction temperature of 900 °C at a flow rate of 40 L/min as a result of the rapid solvent evaporation and decomposition gases from the droplets in the spray solution prepared from metal salts and organic reagents. FeAl2O4 hollow particles were fabricated at a reaction temperature of 900 °C with a flow rate of 40 L/min. The FeAl2O4 hollow particles were heat treated for 3 hours at 600 °C in a 5% H2/Ar atmosphere to form the crystal particles. Subsequently, FeAl2O4 nanoparticles were fabricated from the FeAl2O4 hollow particles by using the wet milling process. After milling for 60 minutes, transmission electron microscopy revealed the FeAl2O4 particles to have a mean size of approximately 50 nm. The FeAl2O4 nanoparticles were fabricated successfully by using a two-step process, spray pyrolysis and wet milling.

  16. Application of Fe(VI) in the treatment of Zn(II)-NTA complexes in aqueous solutions.

    PubMed

    Yang, J; Tiwari, D; Yu, M; Pachuau, L; Kim, W; Lee, S

    2010-06-01

    The higher oxidation state of iron, i.e. Fe(VI), was exploited to treat the synthetic wastewater containing Zn(II)-NTA. The decomposition of Zn(II)-NTA by Fe(VI) was investigated with the help of analytical data obtained for the change in Fe(VI) concentration, dissolved organic carbon (DOC) and total soluble Zn(II) concentration as a function of time at various concentrations of Zn(II)-NTA and at constant Fe(VI) concentration. The UV-Visible data was used to explain the reaction kinetics for redox reactions between Fe(VI) and Zn(II)-NTA. The pseudo-first-order rate constant was calculated keeping the Zn(II)-NTA concentration in excess and hence the overall second-order-rate constant was obtained. Fe(VI) reduction was almost unaffected with the 1000 times increase in ionic strength (NaNO3), as well as in the presence of completely oxidized background electrolytes. However, Fe(VI) reduction was greatly affected in the presence of both SO3(2-) and NO2(-) especially at higher concentrations, indicating a competitive reduction took place between Zn(II)-NTA and Na2SO3 or NaNO2 in the Fe(VI) treatment. These results were again supported by the dissolved organic carbon observations since relatively very low removal of the dissolved organic carbon occurred in the presence of Na2SO3 and NaNO2.

  17. Room-temperature 1.2-J Fe{sup 2+}:ZnSe laser

    SciTech Connect

    Velikanov, S D; Zaretsky, N A; Zotov, E A; Maneshkin, A A; Yutkin, I M; Kazantsev, S Yu; Kononov, I G; Firsov, K N; Korostelin, Yu V; Frolov, M P

    2016-01-31

    The characteristics of a laser based on a Fe{sup 2+}:ZnSe single crystal pumped by an electric-discharge HF laser at room temperature are studied. The HF laser beam diameter on the crystal surface was 17 mm. The achieved laser energy was 1.2 J with an efficiency of ∼ 25% with respect to the pump energy. (letters)

  18. Mn, Fe, Zn and As speciation in a fast-growing ferromanganese marine nodule

    SciTech Connect

    Marcus, Matthew A.; Manceau, Alain; Kersten, Michael

    2004-04-01

    The speciation of Mn, Fe, As and Zn in a fast-growing (0.02mm/yr), shallow-marine ferromanganese nodule has been examined by micro X-ray fluorescence, micro X-ray diffraction, and micro X-ray absorption spectroscopy. This nodule exhibits alternating Fe-rich and Mn-rich layers reflecting redox variations in water chemistry. Fe occurs as two-line ferrihydrite. The As is strictly associated with Fe and is mostly pentavalent, with an environment similar to that of As sorbed on or coprecipitated with synthetic ferrihydrite. The Mn is in the form of turbostratic birnessite with {approx} 10 percent trivalent manganese in the layers and probably {approx} 8 percent corner-sharing metal octahedra in the interlayers. The Zn is enriched on the rim of the nodule, associated with Mn. The Zn is completely (>90 percent) tetrahedrally coordinated and sorbed in the interlayers of birnessite on vacant layer Mn sites. The Zn and Mn species are similar to ones found in soils, suggesting common structural principles, despite the differing formation conditions in these systems.

  19. Structural and Mossbauer Studies of Fe Doped ZnO Nanocrystals

    NASA Astrophysics Data System (ADS)

    Dhiman, Pooja; Kumar, S.; Gautam, Ashish; Singh, M.

    2011-12-01

    Zn1-xFexO (x = 0.01, 0.02, 0.03, 0.04, 0.1) nanoparticles synthesized by a solution combustion method were characterized by different techniques. The structural characterization by XRD confirmed the phase purity of the samples. The optical characterization of the nanoparticles by FTIR revealed the formation of wurtzite structure. Local environment around Fe atoms has been probed by 57Fe Mossbauer spectroscopy and measured isomer shifts confirmed the charge state of iron is Fe3+.

  20. A CEMS search for precipitate formation in 57Fe implanted ZnO

    NASA Astrophysics Data System (ADS)

    Bharuth-Ram, Krishanlal; Masenda, Hilary; Doyle, Terence B.; Geburt, Sebastian; Ronning, Carsten; Gunnlaugsson, Harald Palle

    2012-03-01

    Conversion electron Mössbauer Spectroscopy measurements have been made on ZnO single crystals implanted with 60 keV 57Fe to 4 and 8 at.% peak concentrations, and annealed up to 800°C. The spectra show quite strong changes with annealing, but no evidence of magnetic components, thus precluding the formation of large sized precipitates or secondary phases. Above an annealing temperature of 650°C, the dominant spectral component is a doublet with hyperfine parameters typical of Fe3 + , which is attributed to Fe3 + ions in nano-precipitates ˜5 nm in size.

  1. Fe3O4/CuO/ZnO/Nano graphene platelets (Fe3O4/CuO/ZnO/NGP) composites prepared by sol-gel method with enhanced sonocatalytic activity for the removal of dye

    NASA Astrophysics Data System (ADS)

    Hendry, Tju; Taufik, Ardiansyah; Saleh, Rosari

    2016-04-01

    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.

  2. Phase Separation kinetics in an Fe-Cr-Al alloy

    SciTech Connect

    Capdevila, C.; Miller, Michael K; Chao, J.

    2012-01-01

    The {alpha}-{alpha}{prime} phase separation kinetics in a commercial Fe-20 wt.% Cr-6 wt.% Al oxide dispersion-strengthened PM 2000{trademark} steel have been characterized with the complementary techniques atom probe tomography and thermoelectric power measurements during isothermal aging at 673, 708, and 748 K for times up to 3600 h. A progressive decrease in the Al content of the Cr-rich {alpha}{prime} phase was observed at 708 and 748 K with increasing time, but no partitioning was observed at 673 K. The variation in the volume fraction of the {alpha}{prime} phase well inside the coarsening regime, along with the Avrami exponent 1.2 and activation energy 264 kJ mol{sup -1}, obtained after fitting the experimental results to an Austin-Rickett type equation, indicates that phase separation in PM 2000{trademark} is a transient coarsening process with overlapping nucleation, growth, and coarsening stages.

  3. Nuclear excitation functions of proton-induced reactions (Ep = 35-90 MeV) from Fe, Cu, and Al

    NASA Astrophysics Data System (ADS)

    Graves, Stephen A.; Ellison, Paul A.; Barnhart, Todd E.; Valdovinos, Hector F.; Birnbaum, Eva R.; Nortier, Francois M.; Nickles, Robert J.; Engle, Jonathan W.

    2016-11-01

    Fe, Cu, and Al stacked foils were irradiated by 90 MeV protons at the Los Alamos Neutron Science Center's Isotope Production Facility to measure nuclear cross sections for the production of medically relevant isotopes, such as 52gMn, 54Mn, 48Cr, 55Co, 58mCo and 57Ni. The decay of radioactive isotopes produced during irradiation was monitored using high-purity germanium gamma spectroscopy over the months following irradiation. Proton fluence was determined using the natAl(p,x)22Na, natCu(p,x)62Zn natCu(p,x)65Zn, and natCu(p,x)56Co monitor reactions. Calculated cross sections were compared against literature values and theoretical TALYS predictions. Notably this work includes the first reported independent cross section measurements of natCu(p,x)58mCo and natCu(p,x)58gCo.

  4. Magnetic properties of CoFe2O4 and ZnFe2O4 nanoparticles synthesized by novel chemical route

    NASA Astrophysics Data System (ADS)

    Kharat, S. P.; Darvade, T. C.; Gaikwad, S. K.; Baraskar, B. G.; Kakade, S. G.; Kambale, R. C.; Kolekar, Y. D.

    2016-05-01

    CoFe2O4 and ZnFe2O4 nanoparticles were synthesized by modified and cost effective sol-gel autocombustion method. X-ray diffraction study confirms the spinel phase formation of face centered cubic lattice with space group Fd3m and without any impurity. Magnetic measurements demonstrate that the CoFe2O4 shows saturation magnetization of 2.73 µB/f.u. where as ZnFe2O4 shows paramagnetic behavior. Magnetic behavior of CoFe2O4 and ZnFe2O4 is confirmed from Mössbauer studies. Effect of sintering on structural, magnetic and cation occupancy of substituted cobalt ferrite is discussed in this paper.

  5. Importance of doping and frustration in itinerant Fe-doped Cr2Al

    DOE PAGES

    Susner, M. A.; Parker, D. S.; Sefat, A. S.

    2015-05-12

    We performed an experimental and theoretical study comparing the effects of Fe-doping of Cr2Al, an antiferromagnet with a N el temperature of 670 K, with known results on Fe-doping of antiferromagnetic bcc Cr. (Cr1-xFex)2Al materials are found to exhibit a rapid suppression of antiferromagnetic order with the presence of Fe, decreasing TN to 170 K for x=0.10. Antiferromagnetic behavior disappears entirely at x≈0.125 after which point increasing paramagnetic behavior is exhibited. Moreover, this is unlike the effects of Fe doping of bcc antiferromagnetic Cr, in which TN gradually decreases followed by the appearance of a ferromagnetic state. Theoretical calculations explainmore » that the Cr2Al-Fe suppression of magnetic order originates from two effects: the first is band narrowing caused by doping of additional electrons from Fe substitution that weakens itinerant magnetism; the second is magnetic frustration of the Cr itinerant moments in Fe-substituted Cr2Al. In pure-phase Cr2Al, the Cr moments have an antiparallel alignment; however, these are destroyed through Fe substitution and the preference of Fe for parallel alignment with Cr. This is unlike bulk Fe-doped Cr alloys in which the Fe anti-aligns with the Cr atoms, and speaks to the importance of the Al atoms in the magnetic structure of Cr2Al and Fe-doped Cr2Al.« less

  6. Influence Al doped ZnO nanostructure on structural and optical properties

    NASA Astrophysics Data System (ADS)

    Ramelan, Ari Handono; Wahyuningsih, Sayekti; Chasanah, Uswatul; Munawaroh, Hanik

    2016-04-01

    The preparation of Al-doped ZnO (AZO) thin films prepared by the spin-coating method was reported. Preparation of AZO was conducted by annealing treatment at a temperature of 700°C. While the spin-coating process of AZO thin films were done at 2000 and 3000 rpm respectively. The structural properties of ZnO were determined by X- ray diffraction (XRD) analysis. ZnOnanostructure was formed after annealed at atemperature of 400°C.The morphology of ZnO was determined by Scanning Electron Microscopy (SEM) showed the irregular morphology about 30-50µm in size. Al doped on ZnO influenced the optical properties of those material. Increasing Al contain on ZnO cause of shifting to the lower wavelength. The optical properties of the ZnO as well as AZO films showed that higher reflectance on the ultraviolet region so those materials were used as anti-reflecting agent.Al addition significantly enhance the optical transparency and induce the blue-shift in optical bandgap of ZnO films.

  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.

  8. Thermoelectric properties of Al-doped ZnO: experiment and simulation

    NASA Astrophysics Data System (ADS)

    Jantrasee, S.; Moontragoon, P.; Pinitsoontorn, S.

    2016-09-01

    Advancement in doping other elements, such as Ce, Dy, Ni, Sb, In and Ga in ZnO[1], have stimulated great interest for high-temperature thermoelectric application. In this work, the effects of Al-doping in a ZnO system on the electronic structure and thermoelectric properties are presented, by experiment and calculation. Nanosized powders of Zn1-x Al x O (x = 0,0.01, 0.02, 0.03 and 0.06) were synthesized by hydrothermal method. From XRD results, all samples contain ZnO as the main phase and ZnAl2O4 (spinel phase) peaks were visible when Al additive concentrations were just 6 at%. The shape of the samples changed and the particle size decreased with increasing Al concentration. Seebeck coefficients, on the other hand, did not vary significantly. They were negative and the absolute values increased with temperature. However, the electrical resistivity decreased significantly for higher Al content. The electronic structure calculations were carried out using the open-source software package ABINIT[2], which is based on DFT. The energy band gap, density of states of Al-doped ZnO were investigated using PAW pseudopotential method within the LDA + U. The calculated density of states was then used in combination with the Boltzmann transport equation[3] to calculate the thermoelectric parameters of Al-doped ZnO. The electronic band structures showed that the position of the Fermi level of the doped sample was shifted upwards in comparison to the undoped one. After doping Al in ZnO, the energy band gap was decreased, Seebeck coefficient and electrical conductivity were increased. Finally, the calculated results were compared with the experimental results. The good agreement of thermoelectric properties between the calculation and the experimental results were obtained.

  9. Weldability of Fe[sub 3]Al-type Aluminide

    SciTech Connect

    David, S.A.; Zacharia, T. )

    1993-05-01

    An investigation was carried out to determine the weldability of a series of Fe[sub 3]Al-type alloys. Autogenous welds were made on thin sheets of iron aluminide alloys using gas tungsten arc (GTA) and electron beam (EB) welding processes at different travel speeds and power levels. The results indicate that although these alloys can be successfully welded using the EB welding process, some compositions may hot crack during GTA welding. Boron and zirconium additions have been found to promote hot cracking in these alloys. Among the alloys investigated, Fe[sub 3]Al modified with chromium, niobium and carbon (FA-129) showed the most promise for good weldability. Hot-cracking severity of this alloy was further investigated using the Sigmajig test. The minimum threshold stress of 25 ksi measured is within the material range of other aluminides and some commercial stainless steels. Also, some of these alloys exhibited a tendency for cold cracking. This is related to severe hydrogen embrittlement associated with this class of alloys.

  10. Interfacial Reactions Between ZnAl(Ge) Solders on Cu and Ni Substrates

    NASA Astrophysics Data System (ADS)

    Rautiainen, Antti; Vuorinen, Vesa; Paulasto-Kröckel, Mervi

    2017-04-01

    Reactions between zinc-aluminum-germanium solder and copper/nickel substrates were investigated after 30 min of soldering at 420°C that simulates a wafer-level bonding process, and the results were compared to a eutectic zinc-aluminum solder. The ZnAlGe system (81.4 at.% Zn, 13.1 at.% Al, 5.5 at.% Ge) was selected in order to decrease the eutectic temperature of the ZnAleut (88.7 at.% Zn, 11.3 at.% Al) for high-temperature lead-free solder applications. In addition, a standard high temperature storage test at 150°C was performed up to 3000 h in order to investigate the evolution of the interconnection microstructures. Extensive copper dissolution was discovered during the soldering process. Germanium did not participate in any of the interfacial reactions on a copper substrate. On a nickel substrate, rapid formation of intermetallic compounds was discovered with both solders, and all the aluminum from the 500 μm thick solder was consumed by the formation of the Al3Ni2 phase during bonding. Germanium was observed to dissolve in the Al3Ni2 phase, but the addition of germanium to the solder was not found to affect markedly the interfacial microstructure. Based on the results, isothermal sections at 150°C of Al-Cu-Zn and Al-Ni-Zn systems are presented with superimposed diffusion paths.

  11. Properties of Al-doped ZnS Films Grown by Chemical Bath Deposition

    NASA Astrophysics Data System (ADS)

    Nagamani, K.; Prathap, P.; Lingappa, Y.; Miles, R. W.; Reddy, K. T. R.

    Zinc sulphide (ZnS) buffer layers are a cadmium free, wider energy band gap, alternative to the cadmium sulphide (CdS) buffer layers commonly used in copper indium gallium diselenide (CuInGaSe2)-based solar cells. However extrinsic doping of the ZnS is important to lower the resistivity of the layers and to improve flexibility of device design. In this work, Al-doped ZnS nanocrystalline films have been produced on glass substrates using a chemical bath deposition (CBD) method. The Al- concentration was varied from 0 at. % to 10 at. %, keeping other deposition parameters constant. The elemental composition of a typical sample with 6 at. % 'Al' in ZnS was Zn=44.9 at. %, S=49.8 at. % and Al=5.3 at.%. The X-ray diffraction data taken on these samples showed a broad peak corresponding to the (111) plane of ZnS while the crystallite size varied in the range, 8 - 15 nm, depending on the concentration of Al in the layers. The films with a Al-doping content of 6 at. % had an optical transmittance of 75% in the visible range and the energy band gap evaluated from the data was 3.66 eV. The films n-type electrical conductivities and the electrical resistivity varied in the range, 107-103 Ωcm, it decreasing with an increase of the Al-concentration in the solution.

  12. Lattice location and thermal stability of implanted Fe in ZnO

    SciTech Connect

    Rita, E.; Wahl, U.; Correia, J.G.; Alves, E.; Soares, J.C.

    2004-11-22

    The emission channeling technique was applied to evaluate the lattice location of implanted {sup 59}Fe in single-crystalline ZnO. The angular distribution of {beta}{sup -} particles emitted by {sup 59}Fe was monitored with a position-sensitive electron detector, following 60 keV low dose (2.0x10{sup 13} cm{sup -2}) room-temperature implantation of the precursor isotope {sup 59}Mn. The emission patterns around the [0001], [1102],[1101], and [2113] directions revealed that following annealing at 800 deg. C, 95(8)% of the Fe atoms occupy ideal substitutional Zn sites with rms displacements of 0.06-0.09 A.

  13. Evaluation of ZnO:Al as a contact material to CdZnTe for radiation detector applications (Conference Presentation)

    NASA Astrophysics Data System (ADS)

    Roy, Utpal N.; Camarda, Giuseppe S.; Cui, Yonggang; Gul, Rubi; Hossain, Anwar; Yang, Ge; James, Ralph B.; Pradhan, Aswini K.; Mundle, Rajeh

    2016-09-01

    Aluminum (Al) doped ZnO with very high Al concentration acts as metal regarding its electrical conductivity. ZnO offers many advantages over the commonly-known metals being used today as electrode materials for nuclear detector fabrication. Often, the common metals show poor adhesion to CdZnTe or CdTe surfaces and have a tendency to peel off. In addition, there is a large mismatch of the coefficients of thermal expansion (CTE) between the metals and underlying CdZnTe, which is one of the reasons for mechanical degradation of the contact. In contrast ZnO has a close match of the CTE with CdZnTe and possesses 8-20 times higher hardness than the commonly-used metals. In this presentation, we will explore and discuss the properties of CdZnTe detectors with ZnO:Al contacts.

  14. Development and evaluation of ZnO-Fe2O3 based nanocomposite sensors for butanol detection.

    PubMed

    Sankaran, Sindhuja; Panigrahi, Suranjan

    2012-03-01

    Olfactory sensing of specific volatile organic compounds released by bacterial pathogens is one of the unique ways for determining microbial contamination in packaged food products. This study reports the development and evaluation of zinc oxide-iron oxide (ZnO-Fe2O3) nanocomposite sensors to detect low concentrations of butanol, one of the VOCs specific to Salmonella contamination in packaged beef, at low operating temperature (100 degrees C). The ZnO-Fe2O3 sensor was developed using modified Sol-gel method on an interdigitated alumina substrate. The sensor thin film characterization confirmed a uniform layer of ZnO-Fe2O3 thin film formation with ZnO nanorods of 100 nm height. Also, ZnO-Fe2O3 nanocomposite sensor demonstrated repeatable responses and good sensitivity to butanol with an estimated lower detection limit of about 26 ppm at 100 degrees C.

  15. Annealing effect of double dip coated ZnAl2O4 thin films

    NASA Astrophysics Data System (ADS)

    Chandramohan, R.; Dhanasekaran, V.; Sundaram, K.; Mahalingam, T.

    2013-02-01

    Thin films of ZnAl2O4 were prepared by dip technique involving chemical solutions. Investigations on the effect of post heat treatment on the structural, optical properties of ZnAl2O4 thin films were studied and reported. Xray diffraction patterns revealed that the thin films are polycrystalline cubic structure of ZnAl2O4. The microstructural properties of ZnAl2O4 thin films were calculated and crystallite size tends to increase with increase of annealing temperatures. The texture coefficients have been evaluated and found to be greater than unity revealing high texturing of the architecture of the film. The optical band gap values were found to be in the range of 3.48 - 3.62 eV. The n and k were found to decrease with increase of post annealing temperature. The SEM revealed the uniform distribution of spherical grains.

  16. Fe dopant in ZnO: 2+ versus 3+ valency and ion-carrier s ,p -d exchange interaction

    NASA Astrophysics Data System (ADS)

    Papierska, J.; Ciechan, A.; Bogusławski, P.; Boshta, M.; Gomaa, M. M.; Chikoidze, E.; Dumont, Y.; Drabińska, A.; Przybylińska, H.; Gardias, A.; Szczytko, J.; Twardowski, A.; Tokarczyk, M.; Kowalski, G.; Witkowski, B.; Sawicki, K.; Pacuski, W.; Nawrocki, M.; Suffczyński, J.

    2016-12-01

    Dopants of transition metal ions in II-VI semiconductors exhibit native 2+ valency. Despite this, 3+ or mixed 3+/2+ valency of iron ions in ZnO was reported previously. Several contradictory mechanisms have been put forward for explanation of this fact so far. Here we analyze Fe valency in ZnO by complementary theoretical and experimental studies. Our calculations within the generalized gradient approximation (GGA+U ) indicate that the Fe ion is a relatively shallow donor. Its stable charge state is Fe2 + in ideal ZnO, however, the high energy of the (+/0) transition level enhances the compensation of Fe2 + to Fe3 + by nonintentional acceptors in real samples. Using several experimental methods like electron paramagnetic resonance, magnetometry, conductivity, excitonic magnetic circular dichroism, and magnetophotoluminescence we confirm the 3+ valency of the iron ions in polycrystalline (Zn,Fe)O films with the Fe content attaining 0.2%. We find a predicted increase of n -type conductivity upon the Fe doping with the Fe donor ionization energy of 0.25 ±0.02 eV consistent with the results of theoretical considerations. Moreover, our magneto-optical measurements confirm the calculated nonvanishing s,p-d exchange interaction between band carriers and localized magnetic moments of the Fe3 + ions in the ZnO, being so far an unsettled issue.

  17. Degradability Enhancement of Poly(Lactic Acid) by Stearate-Zn3Al LDH Nanolayers

    PubMed Central

    Eili, Mahboobeh; Shameli, Kamyar; Ibrahim, Nor Azowa; Yunus, Wan Md Zin Wan

    2012-01-01

    Recent environmental problems and societal concerns associated with the disposal of petroleum based plastics throughout the world have triggered renewed efforts to develop new biodegradable products compatible with our environment. This article describes the preparation, characterization and biodegradation study of poly(lactic acid)/layered double hydroxide (PLA/LDH) nanocomposites from PLA and stearate-Zn3Al LDH. A solution casting method was used to prepare PLA/stearate-Zn3Al LDH nanocomposites. The anionic clay Zn3Al LDH was firstly prepared by co-precipitation method from a nitrate salt solution at pH 7.0 and then modified by stearate anions through an ion exchange reaction. This modification increased the basal spacing of the synthetic clay from 8.83 Å to 40.10 Å. The morphology and properties of the prepared PLA/stearate-Zn3Al LDH nanocomposites were studied by X-ray diffraction (XRD), transmission electron microscope (TEM), scanning electron microscope (SEM), thermogravimetric analysis (TGA), tensile tests as well as biodegradation studies. From the XRD analysis and TEM observation, the stearate-Zn3Al LDH lost its ordered stacking-structure and was greatly exfoliated in the PLA matrix. Tensile test results of PLA/stearate-Zn3Al LDH nanocomposites showed that the presence of around 1.0–3.0 wt % of the stearate-Zn3Al LDH in the PLA drastically improved its elongation at break. The biodegradation studies demonstrated a significant biodegradation rate improvement of PLA in the presence of stearate-Zn3Al LDH nanolayers. This effect can be caused by the catalytic role of the stearate groups in the biodegradation mechanism leading to much faster disintegration of nanocomposites than pure PLA. PMID:22942682

  18. Synthesis and conductivity enhancement of Al-doped ZnO nanorod array thin films.

    PubMed

    Hsu, Chih-Hsiung; Chen, Dong-Hwang

    2010-07-16

    Al-doped ZnO (AZO) nanorod array thin films with various Al/Zn molar ratios were synthesized by chemical bath deposition. The resultant AZO nanorods were well-aligned at the glass substrate, growing vertically along the c-axis [001] direction. In addition, they had an average diameter of 64.7 +/- 16.8 nm and an average length of about 1.0 microm with the structure of wurtzite-type ZnO. Analyses of energy dispersive x-ray spectra and x-ray photoelectron spectra indicated that Al atoms had been doped into the ZnO crystal lattice. The doping of Al atoms did not result in significant changes in the structure and crystal orientation, but the electrical resistivity was found to increase first and then decrease with increasing Al content owing to the increase of carrier concentration and the decrease of mobility. In addition, the transmission in the visible region increased but the increase was reduced at higher Al doping levels. After hydrogen treatment, the morphology of the AZO nanorod array thin films remained unchanged. However, the electrical resistivity decreased significantly due to the formation of oxygen vacancies and interstitial hydrogen atoms. When the real Al/Zn molar ratio was about 3.7%, the conductivity was enhanced about 1000 times and a minimum electrical resistivity of 6.4 x 10( - 4) Omega cm was obtained. In addition, the transmission of the ZnO nanorod array thin film in the visible region was significantly increased but the increase was less significant for the AZO nanorod array thin film, particularly at higher Al doping levels. In addition, the current-voltage curves of the thin film devices with ZnO or AZO nanorod arrays revealed that AZO had a higher current response than ZnO and hydrogen treatment led to a more significant enhancement of current responses (about 100-fold).

  19. Degradability enhancement of poly(lactic acid) by stearate-Zn(3)Al LDH nanolayers.

    PubMed

    Eili, Mahboobeh; Shameli, Kamyar; Ibrahim, Nor Azowa; Yunus, Wan Md Zin Wan

    2012-01-01

    Recent environmental problems and societal concerns associated with the disposal of petroleum based plastics throughout the world have triggered renewed efforts to develop new biodegradable products compatible with our environment. This article describes the preparation, characterization and biodegradation study of poly(lactic acid)/layered double hydroxide (PLA/LDH) nanocomposites from PLA and stearate-Zn(3)Al LDH. A solution casting method was used to prepare PLA/stearate-Zn(3)Al LDH nanocomposites. The anionic clay Zn(3)Al LDH was firstly prepared by co-precipitation method from a nitrate salt solution at pH 7.0 and then modified by stearate anions through an ion exchange reaction. This modification increased the basal spacing of the synthetic clay from 8.83 Å to 40.10 Å. The morphology and properties of the prepared PLA/stearate-Zn(3)Al LDH nanocomposites were studied by X-ray diffraction (XRD), transmission electron microscope (TEM), scanning electron microscope (SEM), thermogravimetric analysis (TGA), tensile tests as well as biodegradation studies. From the XRD analysis and TEM observation, the stearate-Zn(3)Al LDH lost its ordered stacking-structure and was greatly exfoliated in the PLA matrix. Tensile test results of PLA/stearate-Zn(3)Al LDH nanocomposites showed that the presence of around 1.0-3.0 wt % of the stearate-Zn(3)Al LDH in the PLA drastically improved its elongation at break. The biodegradation studies demonstrated a significant biodegradation rate improvement of PLA in the presence of stearate-Zn(3)Al LDH nanolayers. This effect can be caused by the catalytic role of the stearate groups in the biodegradation mechanism leading to much faster disintegration of nanocomposites than pure PLA.

  20. Structural, morphological, ferromagnetic and photoluminescence properties of Fe-doped ZnO, prepared by hydrothermal route

    NASA Astrophysics Data System (ADS)

    Cernea, Marin; Mihalache, Valentina; Secu, Elisabeta Corina; Trusca, Roxana; Bercu, Vasile; Diamandescu, Lucian

    2017-04-01

    Fe doped ZnO particles of flower-like shape, hexagonal prisms and hybrid structures flower-prisms have been synthesized by hydrothermal technique, and their luminescence and magnetic properties have been investigated as a function of the morphology changes due to iron dopant (0-0.03 at.% Fe3+). The X-ray diffractograms of Zn1-xFexO powders indicated a hexagonal wurtzite polycrystalline structure. SEM images reveal the change of Zn1-xFexO grains shape from flower-like to hexagonal prisms as the Fe concentration (x) increases from 0 to 3 at.% Fe. Undoped ZnO shown weak room temperatures ferromagnetism, with high coercivity (Hc = 107 Oe) and saturation magnetization Ms of 1.5·10-3 emu/g. ZnO doped with 1 and 3 at.% Fe presented a significant increase of the magnetization in comparison with the undoped ZnO. For ZnO doped with 3 at.% Fe, Ms = 32.5·10-3 emu/g and Mrem = 0.78·10-3 emu/g. Compared with other reports on magnetic properties of undoped and Fe doped ZnO, these results indicated higher coercivity and smaller magnetizations. The drop in the intensity of characteristic green-yellow photoluminescence band of ZnO at about 550-600 nm was attributed to the decrease of the number of oxygen vacancies and interstitial oxygen. By increasing the Fe concentration, the electron paramagnetic resonance (EPR) signal of undoped ZnO decreases due to the decrease of defects concentration.

  1. Structural and electronic properties of CuI doped with Zn, Ga and Al

    NASA Astrophysics Data System (ADS)

    Zhu, Jiajie; Gu, Mu; Pandey, Ravindra

    2013-08-01

    The structural and electronic properties of CuI doped with Zn, Ga and Al are investigated using density functional theory. The calculated results find that the solubility of the cation dopants considered is primarily determined by the difference in the electronic configurations between host and dopants. The order of the formation energy of the dopants is predicted to be E(ZnCu)>E(AlCu)>E(GaCu) in CuI. Furthermore, dopants at the octahedral interstitial sites have lower formation energies as compared to dopants located at the tetrahedral interstitial sites in the lattice. The defect complex consisting of ZnCu and the copper vacancy (ZnCu+VCu) is predicted to be preferred in the lattice, suggesting that incorporation of Zn is expected to enhance the concentration of copper vacancies in CuI.

  2. 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.

  3. Photoluminescence enhancement of ZnO via coupling with surface plasmons on Al thin films

    NASA Astrophysics Data System (ADS)

    Dellis, S.; Kalfagiannis, N.; Kassavetis, S.; Bazioti, C.; Dimitrakopulos, G. P.; Koutsogeorgis, D. C.; Patsalas, P.

    2017-03-01

    We present that the ultra-violet emission of ZnO can be enhanced, as much as six-times its integral intensity, using an Al thin interlayer film between the Si substrate and ZnO thin film and a post-fabrication laser annealing process. The laser annealing is a cold process that preserves the chemical state and integrity of the underlying aluminum layer, while it is essential for the improvement of the ZnO performance as a light emitter and leads to enhanced emission in the visible and in the ultraviolet spectral ranges. In all cases, the metal interlayer enhances the intensity of the emitted light, either through coupling of the surface plasmon that is excited at the Al/ZnO interface, in the case of light-emitting ZnO in the ultraviolet region, or by the increased back reflection from the Al layer, in the case of the visible emission. In order to evaluate the process and develop a solid understanding of the relevant physical phenomena, we investigated the effects of various metals as interlayers (Al, Ag, and Au), the metal interlayer thickness, and the incorporation of a dielectric spacer layer between Al and ZnO. Based on these experiments, Al emerged as the undisputable best choice of metal interlayers because of its compatibility with the laser annealing process, as well as due to its high optical reflectivity at 380 and 248 nm, which leads to the effective coupling with surface plasmons at the Al/ZnO interfaces at 380 nm and the secondary annealing of ZnO by the back-reflected 248 nm laser beam.

  4. Microstructural characterization of the dispersed phases in Al-Ce-Fe system

    NASA Astrophysics Data System (ADS)

    Ayer, Raghavan; Angers, L. M.; Mueller, R. R.; Scanlon, J. C.; Klein, C. F.

    1988-07-01

    Analytical electron microscopy studies were conducted on a rapidly solidified Al-8.8Fe-3.7Ce alloy and arc melted buttons of aluminum rich Al-Fe-Ce alloys to determine the characteristics of the metastable and equilibrium phases. The rapidly solidified alloy consisted of binary and ternary metastable phases in the as-extruded condition. The binary metastable phase was identified to be Al6Fe, while the ternary metastable phases were identified to be Al10Fe2Ce and Al20Fe5Ce. The Al20Fe5Ce was a decagonal quasicrystal while the Al10Fe2Ce phase was determined to have an orthorhombic crystal structure belonging to space group Cmmm, Cmm2, or C222. Microscopy studies of RS alloy and cast buttons annealed at 700 K established the equilibrium phases to be Al13Fe4, Al4Ce, and an Al13Fe3Ce ternary phase which was first identified in the present study. The crystal structure of the equilibrium ternary phase was determined to be orthorhombic with a Cmcm or Cmc2 space group. The details of X-ray microanalysis and convergent beam electron diffraction analysis are described.

  5. Structural investigation of the (010) surface of the Al13 Fe4 catalyst.

    PubMed

    Ledieu, J; Gaudry, É; Loli, L N Serkovic; Villaseca, S Alarcón; de Weerd, M-C; Hahne, M; Gille, P; Grin, Y; Dubois, J-M; Fournée, V

    2013-02-15

    We have investigated the structure of the Al(13)Fe(4)(010) surface using both experimental and ab initio computational methods. The results indicate that the topmost surface layers correspond to incomplete puckered (P) planes present in the bulk crystal structure. The main building block of the corrugated termination consists of two adjacent pentagons of Al atoms, each centered by a protruding Fe atom. These motifs are interconnected via additional Al atoms referred to as "glue" atoms which partially desorb above 873 K. The surface structure of lower atomic density compared to the bulk P plane is explained by a strong Fe-Al-Fe covalent polar interaction that preserves intact clusters at the surface. The proposed surface model with identified Fe-containing atomic ensembles could explain the Al(13)Fe(4) catalytic properties recently reported in line with the site-isolation concept [M. Armbrüster et al., Nat. Mater. 11, 690 (2012)].

  6. Effect of nitrogen upon structural and magnetic properties of FePt in FePt/AlN multilayer structures

    SciTech Connect

    Gao, Tenghua Zhang, Cong; Sannomiya, Takumi; Muraishi, Shinji; Nakamura, Yoshio; Shi, Ji

    2014-09-01

    This paper investigates the effect of the addition of nitrogen in FePt layers for ultrathin FePt/AlN multilayer structures. X-ray diffraction results reveal that a compressive stress relaxation occurs after annealing owing to the release of interstitial nitrogen atoms in the FePt layers. The introduction of nitrogen also induces a large in-plane compressive strain during grain growth not seen in FePt deposited without nitrogen. This strain is considered to decrease the driving force for (111) grain growth and FePt ordering.

  7. Al-doped ZnO seed layer-dependent crystallographic control of ZnO nanorods by using electrochemical deposition

    SciTech Connect

    Son, Hyo-Soo; Choi, Nak-Jung; Kim, Kyoung-Bo; Kim, Moojin; Lee, Sung-Nam

    2016-10-15

    Highlights: • Polar and semipolar ZnO NRs were successfully achieved by hydrothermal synthesis. • Semipolar and polar ZnO NRs were grown on ZnO and AZO/m-sapphire, respectively. • Al % of AZO/m-sapphire enhanced the lateral growth rate of polar ZnO NRs. - Abstract: We investigated the effect of an Al-doped ZnO film on the crystallographic direction of ZnO nanorods (NRs) using electrochemical deposition. From high-solution X-ray diffraction measurements, the crystallographic plane of ZnO NRs grown on (1 0 0) ZnO/m-plane sapphire was (1 0 1). The surface grain size of the (100) Al-doped ZnO (AZO) film decreased with increasing Al content in the ZnO seed layer, implying that the Al dopant accelerated the three-dimensional (3D) growth of the AZO film. In addition, it was found that with increasing Al doping concentration of the AZO seed layer, the crystal orientation of the ZnO NRs grown on the AZO seed layer changed from [1 0 1] to [0 0 1]. With increasing Al content of the nonpolar (1 0 0) AZO seed layer, the small surface grains with a few crystallographic planes of the AZO film changed from semipolar (1 0 1) ZnO NRs to polar (0 0 1) ZnO NRs due to the increase of the vertical [0 0 1] growth rate of the ZnO NRs owing to excellent electrical properties.

  8. Origins of low resistivity in Al ion-implanted ZnO bulk single crystals

    SciTech Connect

    Oga, T.; Izawa, Y.; Kuriyama, K.; Kushida, K.; Kinomura, A.

    2011-06-15

    The origins of low resistivity in Al ion-implanted ZnO bulk single crystals are studied by combining Rutherford backscattering spectroscopy (RBS), nuclear reaction analysis (NRA), photoluminescence (PL), and Van der Pauw methods. The Al-ion implantation (peak concentration: 2.6 x 10{sup 20}cm{sup -3}) into ZnO is performed using a multiple-step energy. The resistivity decreases from {approx}10{sup 4{Omega}} cm for un-implanted ZnO to 1.4 x 10{sup -1{Omega}} cm for as-implanted, and reaches 6.0 x 10{sup -4{Omega}} cm for samples annealed at 1000 deg. C. RBS and NRA measurements for as-implanted ZnO suggest the existence of the lattice displacement of Zn (Zn{sub i}) and O (O{sub i}), respectively. After annealing at 1000 deg. C, the Zn{sub i} related defects remain and the O{sub i} related defects disappear. The origin of the low resistivity in the as-implanted sample is attributed to the Zn{sub i} ({approx}30 meV [Look et al., Phys. Rev. Lett. 82, 2552 (1999)]). In contrast, the origin of the low resistivity in the sample annealed at 1000 deg. C is assigned to both of the Zn{sub i} related defects and the electrically activated Al donor. A new PL emission appears at around 3.32 eV after annealing at 1000 deg. C, suggesting electrically activated Al donors.

  9. Origin of Ferromagnetism in Al and Ni Co-doped ZnO Based DMS Materials

    NASA Astrophysics Data System (ADS)

    Murtaza, Saleem; Saadat, A. Siddiqi; Shahid, M. Ramay; Shahid, Atiq; Shahzad, Naseem

    2012-10-01

    Zn0.95Ni0.05O and Zn0.90Ni0.05Al0.05O compositions of nanocrystallites are synthesised using the well recognised auto-combustion technique. The x-ray diffraction patterns demonstrate the phase pure characteristic wurtzite-type crystal structure with space group P63mc in both the compositions. The elemental incorporation of Ni and Al contents into the ZnO structure is confirmed by energy dispersive x-ray analysis. The micrographs of scanning electron microscopy show an approximate ordered morphology. The electrical resistivity is observed to decrease with the rising temperature, depicting the characteristic semiconductor behaviour of the samples. The lower values of resistivity and ferromagnetic interactions in the Al-doped sample correspond to an increase of carrier's density. It is observed that the carrier mediated mechanism is mainly responsible for ferromagnetism in ZnO-based diluted magnetic semiconductors.

  10. Luminescence Spectra of ZnAl 2 O 4 {:}Cr 3+ Spinel Nanopowders

    NASA Astrophysics Data System (ADS)

    Luc, H. H.; Nguyen, T. K.; Nguyen, V. M.; Suchocki, A.; Kamiñska, A.; Le, V. K.; Nguyen, V. H.; Luong, T. T.

    2002-12-01

    The synthetic ZnAl 2 O 4 spinels doped with Cr 3+ ions are prepared from ZnSO,dwi{4}>, Al 2 (SO 4 ) 3 , and Cr 2 (SO 4 ) 3 . The spinel single phase is detected from X-ray diffraction. Luminescence properties of Cr 3+ in ZnAl 2 O 4 were studied by low temperature luminescence and decay measurements. Four luminescence lines at 14570, 14520, 14460, and 14330 cm -1 were found to originate from structure distortion and the line at 14175 cm -1 - from chromium pairs. The broad emission band at about 13540 cm -1 is considered to arise from a new Cr 3+ center in ZnCr 2 O 4 .

  11. Characterization and study of antibacterial activity of spray pyrolysed ZnO:Al thin films

    NASA Astrophysics Data System (ADS)

    Manoharan, C.; Pavithra, G.; Bououdina, M.; Dhanapandian, S.; Dhamodharan, P.

    2016-08-01

    Aluminum-doped zinc oxide (ZnO:Al) thin films were deposited onto glass substrates using spray pyrolysis technique with the substrate temperature of 400 °C. X-ray diffraction analysis indicated that the films were polycrystalline with hexagonal wurtzite structure preferentially oriented along (002) direction. Surface morphology of the films obtained by scanning electron microscopy showed that the grains were of nanoscale size with porous nature for 6 at.% of Al. Atomic force microscopy observations revealed that the particles size and surface roughness of the films decreased with Al-doping. Optical measurements indicated that ZnO:Al (6 at.%) exhibited a band gap of 3.11 eV, which is lower than that of pure ZnO film, i.e. 3.42 eV. Photoluminescence analysis showed weak NBE emission at 396 nm for Al-doped films. The low resistivity, high hall mobility and carrier concentration values were obtained at a doping ratio of 6 at.% of Al. The effective incorporation of 6 at.% of Al into ZnO lattice by occupying Zn sites yielded a well-pronounced antibacterial activity against Staphylococcus aureus.

  12. Anomalous Dilatometric Response in Fe-Mn-Al-Si Steel

    NASA Astrophysics Data System (ADS)

    Ghosh, S. K.

    2012-04-01

    The present study deals with the transformation of an aggregate consisting of ferrite and pearlite into austenite in a Fe-0.36C-1.98Mn-1.97Al-0.30Si (wt%) steel. The transformation phenomenon has been studied using dilatometry which confirms that austenite starts to nucleate due to dissolution of ferrite and pearlite and subsequently it commences to grow when the appropriate elevated temperature is reached. The austenite formation has been accompanied with the formation of a hump in the dilatation curve which is different with respect to the results reported earlier. The non-conventional behaviour associated with the austenite formation has been explained using the X-ray diffraction data, microstructural investigation and also with MT-DATA theoretical calculations.

  13. Novel ZnO:Al contacts to CdZnTe for X- and gamma-ray detectors

    NASA Astrophysics Data System (ADS)

    Roy, U. N.; Mundle, R. M.; Camarda, G. S.; Cui, Y.; Gul, R.; Hossain, A.; Yang, G.; Pradhan, A. K.; James, R. B.

    2016-05-01

    CdZnTe (CZT) has made a significant impact as a material for room-temperature nuclear-radiation detectors due to its potential impact in applications related to nonproliferation, homeland security, medical imaging, and gamma-ray telescopes. In all such applications, common metals, such as gold, platinum and indium, have been used as electrodes for fabricating the detectors. Because of the large mismatch in the thermal-expansion coefficient between the metal contacts and CZT, the contacts can undergo stress and mechanical degradation, which is the main cause for device instability over the long term. Here, we report for the first time on our use of Al-doped ZnO as the preferred electrode for such detectors. The material was selected because of its better contact properties compared to those of the metals commonly used today. Comparisons were conducted for the detector properties using different contacts, and improvements in the performances of ZnO:Al-coated detectors are described in this paper. These studies show that Al:ZnO contacts to CZT radiation detectors offer the potential of becoming a transformative replacement for the common metallic contacts due to the dramatic improvements in the performance of detectors and improved long-term stability.

  14. Novel ZnO:Al contacts to CdZnTe for X- and gamma-ray detectors

    PubMed Central

    Roy, U. N.; Mundle, R. M.; Camarda, G. S.; Cui, Y.; Gul, R.; Hossain, A.; Yang, G.; Pradhan, A. K.; James, R. B.

    2016-01-01

    CdZnTe (CZT) has made a significant impact as a material for room-temperature nuclear-radiation detectors due to its potential impact in applications related to nonproliferation, homeland security, medical imaging, and gamma-ray telescopes. In all such applications, common metals, such as gold, platinum and indium, have been used as electrodes for fabricating the detectors. Because of the large mismatch in the thermal-expansion coefficient between the metal contacts and CZT, the contacts can undergo stress and mechanical degradation, which is the main cause for device instability over the long term. Here, we report for the first time on our use of Al-doped ZnO as the preferred electrode for such detectors. The material was selected because of its better contact properties compared to those of the metals commonly used today. Comparisons were conducted for the detector properties using different contacts, and improvements in the performances of ZnO:Al-coated detectors are described in this paper. These studies show that Al:ZnO contacts to CZT radiation detectors offer the potential of becoming a transformative replacement for the common metallic contacts due to the dramatic improvements in the performance of detectors and improved long-term stability. PMID:27216387

  15. Plasmonic enhancement of UV emission from ZnO thin films induced by Al nano-concave arrays

    NASA Astrophysics Data System (ADS)

    Norek, Małgorzata; Łuka, Grzegorz; Włodarski, Maksymilian

    2016-10-01

    Surface plasmons (SPs) supported by Al nano-concave arrays with increasing interpore distance (Dc) were used to enhance the ultraviolet light emission from ZnO thin films. Two sets of samples were prepared: in the first set the thin ZnO films were deposited directly on Al nanoconcaves (the Al/ZnO samples) and in the second set a 10 nm - Al2O3 spacer was placed between the textured Al and the ZnO films (the Al/Al2O3-ALD/ZnO samples). In the Al/ZnO samples the enhancement was limited by a nonradiative energy dissipation due to the Ohmic loss in the Al metal. However, for the ZnO layer deposited directly on Al nanopits synthesized at 150 V (Dc = 333 ± 18 nm), the largest 9-fold enhancement was obtained by achieving the best energy fit between the near band-edge (NBE) emission from ZnO and the λ(0,1) SPP resonance mode. In the Al/Al2O3-ALD/ZnO samples the amplification of the UV emission was smaller than in the Al/ZnO samples due to a big energy mismatch between the NBE emission and the λ(0,1) plasmonic mode. The results obtained in this work indicate that better tuning of the NBE - λ(0,1) SPP resonance mode coupling is possible through a proper modification of geometrical parameters in the Al/Al2O3-ALD/ZnO system such as Al nano-concave spacing and the thickness of the corresponding layer. This approach will reduce the negative influence of the non-radiative plasmonic modes and most likely will lead to further enhancement of the SP-modulated UV emission from ZnO thin films.

  16. Pseudo-one-dimensional Zn-Fe-O Nanostructure Arrays: Controlled Fabrication, Magnetic Properties and Photocatalytic Applications

    NASA Astrophysics Data System (ADS)

    Guo, Xuan

    In the present thesis, several kinds of pseudo-one-dimensional Zn-Fe-O nanostructure arrays with tunable chemical compositions, crystal structures and morphologies are successfully synthesized via a simple wet-chemical ZnO-nanowire-array templating method. Vertically-aligned ZnO nanowire arrays are firstly fabricated on several different substrates and then serve as templates for other nanostructured arrays growth. The ZnO nanowires not only act as morphology-defining skeleton but also contribute chemically to the final composition of the nanostructures. By controlling the reaction time between ZnO and FeCl3 solution, ZnO/ZnFe2O4 nanocable arrays, stoichiometric ZnFe 2O4 nanotube arrays, nonstoichiometric ZnFe2O 4 nanotube arrays, ZnFe2O4/alpha-Fe2O 3 nanotube arrays and alpha-Fe2O3 nanotube arrays can be synthesized in a controlled manner after calcination. Both ZnFe 2O4 and alpha-Fe2O3 nanotube arrays exhibit visible light absorption and their bandgap are estimated to be ˜2.3 eV and ˜1.7 eV, respectively. The detailed structural information of the ZnFe2O4 nanotube arrays are obtained by electron energy loss spectroscopy (EELS). In particular, EELS are carried out for two different series (i.e., temperature and stoichiometric series). The magnetic properties of these samples are found to closely correlate to their structural characteristics. Firstly, with the decrease of the calcination temperature from 600 °C to 400 °C, more Fe3+ ions occupy A sites (tetrahedral sites in spinel structure) rather than their equilibrium B sites (octahedral sites in spinel structure). The deviation from the normal spinel structure leads to the enhancement of superexchange interactions between Fe3+ ions in A and B sites, and thus results in an increase in blocking temperature (T B), magnetic anisotropic constant (K), saturation magnetization (MS, at 3 K and 300 K), coercivity (H C, at 3 K) and a decrease in MS (3K)/MS(300 K) ratios. Secondly, by comparing stoichiometric and

  17. Nanostructure evolution in joining of Al and Fe nanoparticles with femtosecond laser irradiation

    SciTech Connect

    Jiao, Z.; Huang, H.; Zhou, Y. E-mail: nzhou@uwaterloo.ca; Liu, L.; Hu, A.; Duley, W.; He, P. E-mail: nzhou@uwaterloo.ca

    2014-04-07

    The joining of Al-Fe nanoparticles (NPs) by femtosecond (fs) laser irradiation is reported in this paper. Fe and Al NPs were deposited on a carbon film in vacuum via fs laser ablation. Particles were then exposed to multiple fs laser pulses at fluences between 0.5 and 1.3 mJ/cm{sup 2}. Transmission Electron Microscopy (TEM) and Electron Diffraction X-ray observations indicate that Al and Fe NPs bond to each other under these conditions. For comparison, bonding of Al to Al and Fe to Fe NPs was also investigated. The nanostructure, as observed using TEM, showed that individual Al NPs were monocrystalline while individual Fe NPs were polycrystalline prior to joining and that these structures are retained after the formation of Al-Al and Fe-Fe NPs. Al-Fe NPs produced by fs laser joining exhibited a mixed amorphous and crystalline phase at the interface. Bonding is suggested to originate from intermixing within a region of high field intensity between particles.

  18. Inhibition of trace element release during Fe(II)-activated recrystallization of Al-, Cr-, and Sn-substituted goethite and hematite.

    PubMed

    Frierdich, Andrew J; Scherer, Michelle M; Bachman, Jonathan E; Engelhard, Mark H; Rapponotti, Brett W; Catalano, Jeffrey G

    2012-09-18

    Aqueous Fe(II) reacts with Fe(III) oxides by coupled electron transfer and atom exchange (ETAE) resulting in mineral recrystallization, contaminant reduction, and trace element cycling. Previous studies of Fe(II)-Fe(III) ETAE have explored the reactivity of either pure iron oxide phases or those containing small quantities of soluble trace elements. Naturally occurring iron oxides, however, contain substantial quantities of insoluble impurities (e.g., Al) which are known to affect the chemical properties of such minerals. Here we explore the effect of Al(III), Cr(III), and Sn(IV) substitution (1-8 mol %) on trace element release from Ni(II)-substituted goethite and Zn(II)-substituted hematite during reaction with aqueous Fe(II). Fe(II)-activated trace element release is substantially inhibited from both minerals when an insoluble element is cosubstituted into the structure, and the total amount of release decreases exponentially with increasing cosubstituent. The limited changes in surface composition that occur following reaction with Fe(II) indicate that Al, Cr, and Sn do not exsolve from the structure and that Ni and Zn released to solution originate primarily from the bulk rather than the particle exterior (upper ~3 nm). Incorporation of Al into goethite substantially decreases the amount of iron atom exchange with aqueous Fe(II) and, consequently, the amount of Ni release from the structure. This implies that trace element release inhibition caused by substituting insoluble elements results from a decrease in the amount of mineral recrystallization. These results suggest that naturally occurring iron oxides containing insoluble elements are less susceptible to Fe(II)-activated recrystallization and exhibit a greater retention of trace elements and contaminants than pure mineral phases.

  19. Inhibition of trace element release during Fe(II)-activated recrystallization of Al-, Cr-, and Sn-substituted goethite and hematite

    SciTech Connect

    Frierdich, Andrew J.; Scherer, M.; Bachman, Jonathan E.; Engelhard, Mark H.; Rapponotti, Brett W.; Catalano, Jeffrey G.

    2012-09-18

    Aqueous Fe(II) reacts with Fe(III) oxides by coupled electron transfer and atom exchange (ETAE) resulting in mineral recrystallization, contaminant reduction, and trace element cycling. Previous studies of Fe(II)-Fe(III) ETAE have explored the reactivity of either pure iron oxide phases or those containing small quantities of soluble trace elements. Naturally occurring iron oxides, however, contain substantial quantities of insoluble impurities (e.g., Al) which are known to affect the chemical properties of such minerals. Here we explore the effect of Al(III), Cr(III), and Sn(IV) substitution on trace element release from Ni(II)-substituted goethite and Zn(II)-substituted hematite during reaction with aqueous Fe(II). Fe(II)-activated trace element release is substantially inhibited from both minerals when an insoluble element is co-substituted into the structure, and the total amount of release decreases exponentially with increasing co substituent. The limited changes in surface composition that occur following reaction with Fe(II) indicate that Al, Cr, and Sn do not exsolve from the structure and that Ni and Zn released to solution originate primarily from the bulk rather than the particle exterior (upper ~3 nm). Incorporation of Al into goethite substantially decreases the amount of iron atom exchange with aqueous Fe(II) and, consequently, the amount of Ni release from the structure. This implies that trace element release inhibition caused by substituting insoluble elements results from a decrease in the amount of mineral recrystallization. These results suggest that naturally occurring iron oxides containing insoluble elements are less susceptible to Fe(II)-activated recrystallization and exhibit a greater retention of trace elements and contaminants than pure mineral phases.

  20. Interpretation of the Hume-Rothery electron concentration rule in the T2 Zn11 ( T=Ni , Pd, Co, and Fe) γ brasses based on first-principles FLAPW calculations

    NASA Astrophysics Data System (ADS)

    Asahi, R.; Sato, H.; Takeuchi, T.; Mizutani, U.

    2005-09-01

    The first-principles full-potential augmented plane wave (FLAPW) band calculations were performed for a series of T2Zn11 ( T=Ni , Pd, Co, and Fe) γ brasses to elucidate the Hume-Rothery electron concentration rule. The pseudogap is found immediately below the Fermi level EF in the Ni2Zn11 and Pd2Zn11γ brasses. A resulting gain in the electronic energy is attributed to their stabilization in the same way as in Cu5Zn8 and Cu9Al4 previously studied. However, the pseudogap is essentially shifted above EF in both Co2Zn11 and Fe2Zn11 . The Fourier analysis of the FLAPW wave function was made at the symmetry point N of the reduced Brillouin zone in the energy range involving the pseudogap. It is found that the plane wave giving rise to the largest Fourier component always resonates with the {330} and {411} zone planes to produce the pseudogap near EF . Moreover, a single-branch energy dispersion relation was constructed in the extended zone scheme by averaging the wave vector 2(k+G) having the largest Fourier component of the FLAPW wave function over selected electronic states in the Brillouin zone. The e/a value thus deduced is found to be close to 21/13=1.615 for Cu5Zn8 , Cu9Al4 , Ni2Zn11 , and Pd2Zn11γ brasses but to be only 1.4 and 1.3 for Co2Zn11 and Fe2Zn11 , respectively.

  1. Photovoltaic effect in an indium-tin-oxide/ZnO/BiFeO3/Pt heterostructure

    NASA Astrophysics Data System (ADS)

    Fan, Zhen; Yao, Kui; Wang, John

    2014-10-01

    We have studied the photovoltaic effect in a metal/semiconductor/ferroelectric/metal heterostructure of In2O3-SnO2/ZnO/BiFeO3/Pt (ITO/ZnO/BFO/Pt) multilayer thin films. The heterolayered structure shows a short-circuit current density (Jsc) of 340 μA/cm2 and an energy conversion efficiency of up to 0.33% under blue monochromatic illumination. The photovoltaic mechanism, specifically in terms of the major generation site of photo-excited electron-hole (e-h) pairs and the driving forces for the separation of e-h pairs, is clarified. The significant increase in photocurrent of the ITO/ZnO/BFO/Pt compared to that of ITO/BFO/Pt is attributed to the abundant e-h pairs generated from ZnO. Ultraviolet photoelectron spectroscopy reveals the energy band alignment of ITO/ZnO/BFO/Pt, where a Schottky barrier and an n+-n junction are formed at the BFO/Pt and ZnO/BFO interfaces, respectively. Therefore, two built-in fields developed at the two interfaces are constructively responsible for the separation and transport of photo-excited e-h pairs.

  2. Formation of a paramagnetic Al complex and extrusion of Fe during the reaction of (diiminepyridine)Fe with AlR3 (R = Me, Et).

    PubMed

    Scott, Jennifer; Gambarotta, Sandro; Korobkov, Ilia; Knijnenburg, Quinten; de Bruin, Bas; Budzelaar, Peter H M

    2005-12-14

    The reaction of the {2,6-[2,6-(iPr)2PhN=C(CH3)]2(C5H3N)}FeCl2 catalyst precursor with R3Al [R = Me, Et] afforded {2,6-[2,6-(iPr)2PhN=C(CH3)]2(C5H3N)}AlMe2 (1) and [eta4-LAl2Et3(mu-Cl)]Fe-(eta6-C7H8) (2), respectively. These paramagnetic species arises from both transmetalation, during which the strong terdentate ligand loses the Fe center, and reduction. The extent of reduction depends on the nature of the Al alkylating agent. The electrons necessary for the reduction are likely to be provided by cleavage of Fe-C bond of transient low-valent organo-Fe species.

  3. 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

    SciTech Connect

    Xu, Xunling; Liu, Weifang E-mail: shouyu.wang@yahoo.com; Wu, Ping; Zhang, Hong; Guo, Minchen; Han, Yuling; Zhang, Chuang; Gao, Ju; Rao, Guanghui; Wang, Shouyu E-mail: shouyu.wang@yahoo.com

    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.

  4. Predicting a ferrimagnetic phase of Zn(2)FeOsO(6) with strong magnetoelectric coupling.

    PubMed

    Wang, P S; Ren, W; Bellaiche, L; Xiang, H J

    2015-04-10

    Multiferroic materials, in which ferroelectric and magnetic ordering coexist, are of practical interest for the development of novel memory devices that allow for electrical writing and nondestructive magnetic readout operation. The great challenge is to create room temperature multiferroic materials with strongly coupled ferroelectric and ferromagnetic (or ferrimagnetic) orderings. BiFeO_{3} is the most heavily investigated single-phase multiferroic to date due to the coexistence of its magnetic order and ferroelectric order at room temperature. However, there is no net magnetic moment in the cycloidal (antiferromagneticlike) magnetic state of bulk BiFeO_{3}, which severely limits its realistic applications in electric field controlled memory devices. Here, we predict that LiNbO_{3}-type Zn_{2}FeOsO_{6} is a new multiferroic with properties superior to BiFeO_{3}. First, there are strong ferroelectricity and strong ferrimagnetism at room temperature in Zn_{2}FeOsO_{6}. Second, the easy plane of the spontaneous magnetization can be switched by an external electric field, evidencing the strong magnetoelectric coupling existing in this system. Our results suggest that ferrimagnetic 3d-5d LiNbO_{3}-type material may therefore be used to achieve voltage control of magnetism in future memory devices.

  5. Predicting a Ferrimagnetic Phase of Zn2FeOsO6 with Strong Magnetoelectric Coupling

    NASA Astrophysics Data System (ADS)

    Wang, P. S.; Ren, W.; Bellaiche, L.; Xiang, H. J.

    2015-04-01

    Multiferroic materials, in which ferroelectric and magnetic ordering coexist, are of practical interest for the development of novel memory devices that allow for electrical writing and nondestructive magnetic readout operation. The great challenge is to create room temperature multiferroic materials with strongly coupled ferroelectric and ferromagnetic (or ferrimagnetic) orderings. BiFeO3 is the most heavily investigated single-phase multiferroic to date due to the coexistence of its magnetic order and ferroelectric order at room temperature. However, there is no net magnetic moment in the cycloidal (antiferromagneticlike) magnetic state of bulk BiFeO3 , which severely limits its realistic applications in electric field controlled memory devices. Here, we predict that LiNbO3 -type Zn2FeOsO6 is a new multiferroic with properties superior to BiFeO3 . First, there are strong ferroelectricity and strong ferrimagnetism at room temperature in Zn2FeOsO6 . Second, the easy plane of the spontaneous magnetization can be switched by an external electric field, evidencing the strong magnetoelectric coupling existing in this system. Our results suggest that ferrimagnetic 3 d -5 d LiNbO3 -type material may therefore be used to achieve voltage control of magnetism in future memory devices.

  6. Facile synthesis and characterization of ZnFe{sub 2}O{sub 4}/{alpha}-Fe{sub 2}O{sub 3} composite hollow nanospheres

    SciTech Connect

    Shen, Yu; Li, Xinyong; Zhao, Qidong; Hou, Yang; Tade, Moses; Liu, Shaomin

    2011-12-15

    Highlights: Black-Right-Pointing-Pointer ZnFe{sub 2}O{sub 4}/{alpha}-Fe{sub 2}O{sub 3} composite hollow nanospheres were successfully synthesized via a facile method. Black-Right-Pointing-Pointer Detailed structural, morphology and the phase composition were studied. Black-Right-Pointing-Pointer The incorporation of ZnFe{sub 2}O{sub 4} and {alpha}-Fe{sub 2}O{sub 3} gives an appropriate band gap value to utilize solar energy. -- Abstract: ZnFe{sub 2}O{sub 4}/{alpha}-Fe{sub 2}O{sub 3} composite hollow nanospheres were successfully fabricated via a facile one-pot solvothermal method, utilizing polyethylene glycol as soft template. X-ray diffraction and scanning electron microscopy analysis revealed that the prepared nanospheres with cubic spinel and rhombohedra composite structure had a uniform diameter of about 370 nm, and the hollow structure could be further confirmed by transmission electron microscopy. Energy dispersive X-ray, X-ray photoelectron spectroscopy and Fourier transform infrared techniques were also applied to characterize the elemental composition and chemical bonds in the hollow nanospheres. The ZnFe{sub 2}O{sub 4}/{alpha}-Fe{sub 2}O{sub 3} composite hollow nanospheres show attractive light absorption property for potential applications in electronics, optics, and catalysis.

  7. Investigation of the ɛ phase in the Fe-Al system by high-temperature neutron diffraction

    NASA Astrophysics Data System (ADS)

    Vogel, Sven C.; Stein, Frank; Palm, Martin

    2010-06-01

    In the central part of the Fe-Al system between about 58 and 65 at.% Al, a high-temperature phase denoted as ɛ occurs with a hitherto unknown crystallographic structure. The phase is stable between 1231°C and 1095°C. In order to study the crystallographic structure of the ɛ phase, in situ high-temperature neutron time-of-flight diffraction experiments have been performed at the HIPPO instrument at the Los Alamos Neutron Science Center (LANSCE). The ɛ phase was found to have the formula Fe5Al8 with a body-centred cubic structure of the Hume-Rothery Cu5Zn8 type (Ibar{4}3m (No. 217), Z=4, cI52) and 52 atoms in the unit cell. Its lattice parameter is a=8.9756(2) Å at 1120°C, which is 3.02 times that of cubic FeAl (B2) at the same temperature. We report here the evolution of the crystallographic parameters over the temperature range between 1080°C and 1120°C.

  8. Enhanced Performance in Al-Doped ZnO Based Transparent Flexible Transparent Thin-Film Transistors Due to Oxygen Vacancy in ZnO Film with Zn-Al-O Interfaces Fabricated by Atomic Layer Deposition.

    PubMed

    Li, Yang; Yao, Rui; Wang, Huanhuan; Wu, Xiaoming; Wu, Jinzhu; Wu, Xiaohong; Qin, Wei

    2017-04-05

    Highly conductive and optical transparent Al-doped ZnO (AZO) thin film composed of ZnO with a Zn-Al-O interface was fabricated by thermal atomic layer deposition (ALD) method. The as-prepared AZO thin film exhibits excellent electrical and optical properties with high stability and compatibility with temperature-sensitive flexible photoelectronic devices; film resistivity is as low as 5.7 × 10(-4) Ω·cm, the carrier concentration is high up to 2.2 × 10(21) cm(-3). optical transparency is greater than 80% in a visible range, and the growth temperature is below 150 °C on the PEN substrate. Compared with the conventional AZO film containing by a ZnO-Al2O3 interface, we propose that the underlying mechanism of the enhanced electrical conductivity for the current AZO thin film is attributed to the oxygen vacancies deficiency derived from the free competitive growth mode of Zn-O and Al-O bonds in the Zn-Al-O interface. The flexible transparent transistor based on this AZO electrode exhibits a favorable threshold voltage and Ion/Ioff ratio, showing promising for use in high-resolution, fully transparent, and flexible display applications.

  9. High stability of magnetic parameters in Fe-Al nanocomposite powders

    NASA Astrophysics Data System (ADS)

    Jani, S.; Sebastian, V.; Sudheesh, V.; Nehra, J.; Lakshmi, N.; Venugopalan, K.

    2016-09-01

    The structural and magnetic properties of Fe75Al25 nanosystem prepared by high energy ball milling for 15 h milling time have been studied. Structural analysis shows the formation of distinct Fe-Al portions with Al at grain boundaries, indicating that Fe-Al nanocomposite formation is favored over alloying due to the formation of diffusion hindering Fe-Al phase at grain boundaries. The saturation magnetization (Ms) of the nanocomposite at 8 nm grain size is 117 emu/g (i.e. 55 % that of pure Fe). The Curie temperature (TC) 1053 K matches the value of pure bcc α-Fe. M-H curves recorded after M-T studies are the same as before indicating the extreme stability of this system against high temperatures. Low temperature M-T measurements and room temperature remanence measurements show that interparticle interactions are demagnetizing kind and dipolar in nature.

  10. Magnetism in the magnetoelectric hexaferrite system (Ba1-xSrx)2Zn2Fe12O22

    NASA Astrophysics Data System (ADS)

    Novák, P.; Knížek, K.; Rusz, J.

    2007-07-01

    The hexaferrite system (Ba1-xSrx)2Zn2Fe12O22 possesses a rich magnetic phase diagram and for strontium content x=0.75 exhibits a magnetoelectricity, the existence of which is intimately connected to the noncollinear arrangement of the iron spins. The system comprises seven cation sublattices, two of which have tetrahedral coordination. The tetrahedral sublattices are partly occupied by Fe and partly by Zn. Using ab initio-calculated exchange interactions we show that the magnetism in the (Ba1-xSrx)2Zn2Fe12O22 system is sensitive to the Fe and Zn distributions. The region of existence of the noncollinear spin structure and hence of ferroelectricity is determined and found to be rather narrow. The critical temperature of magnetic ordering is calculated using molecular field and random phase approximations. The results are in good agreement with the experiment.

  11. The Structural, optical and electrical properties of nanocrystalline ZnO:Al thin films

    NASA Astrophysics Data System (ADS)

    Benhaoua, Boubaker; Rahal, Achour; Benramache, Said

    2014-04-01

    The Al doped ZnO thin films were deposited by ultrasonic spray technique. The influence of Al doping on structural, optical and electrical properties of the ZnO thin films was studied. A set of Al doped ZnO (0-3.5 wt.%) were deposited at 350 °C. Nanocrystalline films with a hexagonal wurtzite structure with a strong (0 0 2) preferred orientation were observed after Al doping. The maximum value of grain size (33.28 nm) is attained with Al doped ZnO at 3 wt.%. Texture coefficient TC(h k l) of the four major peaks where evaluated. Optically, in visible region the transmissions spectra T(λ) show that the whole doped films exhibit lower values than the non doped one which has as transmittance more than 80%; whereas in the same region the optical transmissions of the doped films are affected by the doping ration. The band gap (Eg) increased after doping from 3.267 to 3.325 eV with increasing concentration of doping from 0 to 2.75 wt.%, respectively, according to the Burstein-Moss effect (blue shift of Eg) then beyond 3 wt.% in doping the band gap exhibit a slight decreasing due to the coexistence of Roth and Burstein-Moss effect. The electrical resistivity of the films decreased from 20 to 5.26 (Ω cm). The best results are achieved with 2.75 wt.% Al doped ZnO film.

  12. Magnetic properties of (Zn,Cd,Cu) Co Fe Ti spinel oxides

    NASA Astrophysics Data System (ADS)

    Moyo, T.; Giordanengo, B.; de Melo, M. A. C.; Takeuchi, A. Y.; Silva, P. R. J.; Saitovitch, H.; Baggio-Saitovitch, E.

    1999-09-01

    AC susceptibility, magnetization and Mössbauer spectra have been measured for (Zn,Cd,Cu)0.5Co0.9Fe1.2Ti0.4O4 and Zn0.3Co0.9Fe1.4Ti0.4O4 spinel oxides. The variation of coercive field below the spin glass transition temperature Tsg is found to fit a double exponential function of the form H_c left( T right) = H_{1e} ^{ - β _1 T} + H_{2e} ^{ - β _2 T} , where Hi and βi are constants. Mössbauer spectra and analysis show superparamagnetic fluctuations associated with magnetic clusters. Symmetric doublets above Tsg are decomposed into quadrupole doublets associated with tetrahedral (A) and octahedral (B) sites.

  13. The electric properties of low-magnetic-loss magnetic composites containing Zn-Ni-Fe particles

    NASA Astrophysics Data System (ADS)

    Hidaka, Nobuhiro; Ishitsuka, Masayuki; Shirakata, Yasushi; Teramoto, Akinobu; Ohmi, Tadahiro

    2009-10-01

    Recently, magnetic composites consisting of magnetic particles dispersed in a polymer matrix have been widely discussed for miniaturizing high-frequency electronic components such as antennae. Previously, we investigated the influence of the manufacturing process on the homogeneous dispersion of magnetic particles in the polymer and on the magnetic properties of the magnetic composites. In order to miniaturize electronic components, it is crucial to be able to independently control the permeability and permittivity in magnetic composites. This paper investigates the anisotropy and frequency dependence of the dielectric properties of magnetic composites fabricated from 20 vol% Zn5Ni75Fe20 flaked particles. The permittivity of magnetic composites fabricated from Zn5Ni75Fe20 flaked particles is anisotropic: at 1 GHz, the relative permittivities parallel and perpendicular to the plane of the specimens are 27.2 and 16.9, respectively. The permittivity varied little between frequencies of 50 MHz and 10 GHz.

  14. [Determination of Cu, Zn and Fe in Huaiyao by suspension sampling-flame atomic absorption spectrometry].

    PubMed

    Wei, Wei; Qu, Ling-bo; Li, Jian-jun; Li, Yan-hong

    2002-10-01

    A new method--suspension sampling technique was applied to flame atomic absorption spectrometry and was successfully used to determine Cu, Zn, Fe in Huaiyao. Then studied the choice of suspension agent and elimination of chemical interference. The huaiyao sample was suspended in agar sol, and injected into air-acetylene flame by using standard addition method to determine Cu, Zn, Fe. Determined results were consistent with those obtained by HNO3 + H2SO4 + HClO4 method. The t-test showed that no obvious difference was found between the two methods. Displacement of HNO3 + H2SO4 + HClO4 method by suspension sampling method for the sample pretreatment is possible. This method is convenient, rapid and accurate.

  15. Zero thermal expansion in NaZn13-type La(Fe,Si)13 compounds.

    PubMed

    Wang, Wei; Huang, Rongjin; Li, Wen; Tan, Jie; Zhao, Yuqiang; Li, Shaopeng; Huang, Chuanjun; Li, Laifeng

    2015-01-28

    A zero thermal expansion material in a pure form of NaZn13-type La(Fe,Si)13 was fabricated. Through optimizing the chemical composition, an isotropic zero thermal expansion material is achieved. The obtained materials exhibit a low expansion of |α| < 1.0 × 10(-6) K(-1) (α is the coefficient of linear thermal expansion) over a broad temperature range (15-150 K). The present study indicates that the thermal expansion behavior of the NaZn13-type La(Fe,Si)13 compounds depends mainly on the content of Si element. This new material is desirable in many fields of industry as a reliable and low-cost zero thermal expansion material.

  16. 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.

  17. Growth of Polarity-Controlled ZnO Films on (0001) Al2O3

    NASA Astrophysics Data System (ADS)

    Park, J. S.; Chang, J. H.; Minegishi, T.; Lee, H. J.; Park, S. H.; Im, I. H.; Hanada, T.; Hong, S. K.; Cho, M. W.; Yao, T.

    2008-05-01

    The polarity control of ZnO films grown on (0001) Al2O3 substrates by plasma-assisted molecular-beam epitaxy (P-MBE) was achieved by using a novel CrN buffer layer. Zn-polar ZnO films were obtained by using a Zn-terminated CrN buffer layer, while O-polar ZnO films were achieved by using a Cr2O3 layer formed by O-plasma exposure of a CrN layer. The mechanism of polarity control was proposed. Optical and structural quality of ZnO films was characterized by high-resolution X-ray diffraction and photoluminescence (PL) spectroscopy. Low-temperature PL spectra of Zn-polar and O-polar samples show dominant bound exciton (I8) and strong free exciton emissions. Finally, one-dimensional periodic structures consisting of Zn-polar and O-polar ZnO films were simultaneously grown on the same substrate. The periodic inversion of polarity was confirmed in terms of growth rate, surface morphology, and piezo response microscopy (PRM) measurement.

  18. Enhanced Homogenization of Vanadium in Spark Plasma Sintering of Ti-10V-2Fe-3Al Alloy from Titanium and V-Fe-Al Master Alloy Powder Blends

    NASA Astrophysics Data System (ADS)

    Yang, Y. F.; Imai, H.; Kondoh, K.; Qian, M.

    2017-02-01

    Strong and ductile powder metallurgy (PM) Ti-10V-2Fe-3Al alloy has been fabricated by spark plasma sintering (SPS) of titanium and V-Fe-Al master alloy powder blends at 1100°C for 30 min under 30 MPa. The homogenization of vanadium, which dictates the realization of a uniform microstructure of the Ti-10V-2Fe-3Al alloy, was markedly accelerated by SPS. The mechanism is attributed to the intensive Joule heating effect produced by the direct current passing through the electric conducting powder blends, rather than through spark plasma discharge, because homogenization occurred mainly after near full identification had been achieved. The chemical and microstructural homogeneity ensured the achievement of excellent tensile properties of PM Ti-10V-2Fe-3Al in the as-sintered state, with tensile strength >1250 MPa and elongation >10%.

  19. Brillouin light scattering study of Co2Cr0.6Fe0.4Al and Co2FeAl Heusler compounds

    NASA Astrophysics Data System (ADS)

    Gaier, O.; Hamrle, J.; Trudel, S.; Conca Parra, A.; Hillebrands, B.; Arbelo, E.; Herbort, C.; Jourdan, M.

    2009-04-01

    The thermal magnonic spectra of Co2Cr0.6Fe0.4Al (CCFA) and Co2FeAl were investigated using Brillouin light scattering (BLS) spectroscopy. For CCFA, the exchange constant A (exchange stiffness D) is found to be 0.48 ± 0.04 µerg cm-1 (203 ± 16 meV Å2), while for Co2FeAl the corresponding values of 1.55 ± 0.05 µerg cm-1 (370 ± 10 meV Å2) were found. The observed asymmetry in the BLS spectra between the Stokes and anti-Stokes frequencies was assigned to an interplay between the asymmetrical profiles of hybridized Damon-Esbach and perpendicular standing spin-wave modes, combined with the optical sensitivity of the BLS signal to the upper side of the CCFA or Co2FeAl film.

  20. Deposition and Characterization of Al:ZnO Thin Films for Optoelectronic Applications

    NASA Astrophysics Data System (ADS)

    Pandey, R. K.; Mishra, Swati; Bajpai, P. K.

    2016-11-01

    Transparent aluminum-doped zinc oxide (Al:ZnO) thin films have been successfully synthesized on silicon substrates at room temperature using a sol-gel spin-coating method. The structural and optical properties and surface morphology of the synthesized films were characterized using x-ray diffraction (XRD) analysis, ultraviolet-visible (UV-Vis) spectroscopy, Fourier-transform infrared (FTIR) spectroscopy, micro-Raman spectroscopy, and atomic force microscopy (AFM). The prepared Al:ZnO retained the hexagonal wurtzite structure of ZnO. FTIR and Raman spectra clearly revealed a major peak at 437 cm-1, associated with the ZnO bond. UV-Vis spectra showed that the Al:ZnO films were transparent from the near-ultraviolet to near-infrared region. The effect of film thickness on the physical and optical properties of the Al:ZnO thin films for 2.0 at.% aluminum concentration was investigated. Measurements revealed that the film transparency, optical energy bandgap, Urbach energy, extinction coefficient, and porosity varied with the film thickness. The energy bandgap values for the prepared thin films increased in the range of 3.18 eV to 3.2 eV with increasing film thickness.

  1. ZnFe2O4 Nanotapers: Slag Assistant-Growth and Enhanced Photoelectrochemical Efficiency.

    PubMed

    She, Xuefeng; Zhang, Zhuo

    2017-12-01

    In this study, ZnFe2O4 (ZFO) nanotapers are fabricated on the ZnO nanorods (NRs) by recycling rare-earth oxide (REO) slag as the iron source, which thereby exhibits dramatically enhanced photoelectrochemical (PEC) efficiency. Our studies demonstrate that the electron-hole separation and charge migration can be facilitated by the cascade band alignment of ZFO and ZnO and the branched nanotaper structures. Not only the iron source, the slag particles can also act as the passivation layers, leading to improved electron lifetime and significant PEC enhancement. The current study presents a novel REO-slag-modified PEC anode for high-efficiency PEC devices and offers a possibility of recycling industrial waste for renewable energy generation.

  2. Evaluating Fe and Zn Isotopes as Tracers in the Marine System

    NASA Astrophysics Data System (ADS)

    Boyle, E. A.; Bergquist, B. A.; John, S.

    2005-12-01

    Early work on Fe and Zn isotopes showed that these isotope systems show significant fractionations under earth-surface conditions and that earth-surface samples are significantly fractionated from one another. Because both of these elements are essential to marine life, they may limit the growth of marine organisms in certain circumstances (Fe has been demonstrated to be limiting in parts of the modern ocean; Zn has not yet been shown limiting in the modern ocean, but may have been limiting under different environmental conditions). Hence we need tools to understand their chemistry in the ocean and to evaluate past changes they have undergone. By (very rough) analogy to the carbon and nitrogen isotope system, it seems that the stable isotopes of these elements might be useful in understanding the present and past chemistry of these elements in the ocean. Information is scarce on these isotope systems in the marine environment; most published work concerns samples from sedimentary rocks, ferromanganese nodules, sediment traps, and laboratory experiments. There is no published information on these isotope systems in marine plankton or ocean waters, mainly because these elements occur at very low levels in the ocean and marine samples are difficult to process without contamination. Armed with experience in oceanic trace element sampling and analysis, we have undertaken Fe and Zn isotope analyses of samples of plankton tows and seawater from the marine environment in the North Atlantic and North Pacific Oceans, as well as samples from laboratory cultures and a few other types of marine materials. These samples show significant Fe and Zn isotope fractionations. Although we do not yet have enough information to confidently describe the mechanisms driving these fractionations, this data provide support for the hope that these isotope systems may prove useful in evaluating the marine environmental chemistry of these elements.

  3. ZnFe2O4 nanoparticles as radiosensitizers in radiotherapy of human prostate cancer cells.

    PubMed

    Meidanchi, Alireza; Akhavan, Omid; Khoei, Samideh; Shokri, Ali A; Hajikarimi, Zahra; Khansari, Nakisa

    2015-01-01

    Nanoparticles of high-Z elements exhibit stronger photoelectric effects than soft tissues under gamma irradiation. Hence, they can be used as effective radiosensitizers for increasing the efficiency of current radiotherapy. In this work, superparamagnetic zinc ferrite spinel (ZnFe2O4) nanoparticles were synthesized by a hydrothermal reaction method and used as radiosensitizers in cancer therapy. The magnetic nanoparticles showed fast separation from solutions (e.g., ~1 min for 2 mg mL(-1) of the nanoparticles in ethanol) by applying an external magnetic field (~1T). The ZnFe2O4 nanoparticles were applied in an in vitro radiotherapy of lymph node carcinoma of prostate cells (as high radioresistant cells) under gamma irradiation of (60)Co source. The nanoparticles exhibited no significant effects on the cancer cells up to the high concentration of 100 μg mL(-1), in the absence of gamma irradiation. The gamma irradiation alone (2Gy dose) also showed no significant effects on the cells. However, gamma irradiation in the presence of 100 μg mL(-1) ZnFe2O4 nanoparticles resulted in ~53% inactivation of the cells (~17 times higher than the inactivation that occurred under gamma irradiation alone) after 24h. The higher cell inactivation was assigned to interaction of gamma radiation with nanoparticles (photoelectric effect), resulting in a high level electron release in the media of the radioresistant cells. Our results indicated that ZnFe2O4 nanoparticles not only can be applied in increasing the efficiency of radiotherapy, but also can be easily separated from the cell environment by using an external magnetic field after the radiotherapy.

  4. Transitions in Fe-, Co-, Cu-, and Zn-like ions of W and Re

    NASA Technical Reports Server (NTRS)

    Seely, J. F.; Brown, C. M.; Behring, W. E.

    1989-01-01

    The spectra of highly ionized W and Re were observed by using laser-produced plasmas and a 3-m grazing-incidence spectrograph. Transitions in Fe- through Zn-like ions were identified. Wavelengths in the range 7-75 A were measured with an uncertainty of + or - 0.015 A, and energy levels were derived from the measured wavelengths. The ionization limits of Cu-like W and Re were determined.

  5. Fe nanoparticles on ZnSe: Reversible temperature dependence of the surface barrier potential

    NASA Astrophysics Data System (ADS)

    Cantoni, M.; Bertacco, R.; Brambilla, A.; Finazzi, M.; Duò, L.; Ciccacci, F.; Verdini, A.; Floreano, L.; Morgante, A.; Passoni, M.; Casari, C. S.; Li Bassi, A.

    2012-04-01

    The Fe growth on ZnSe(001) takes place via the initial formation of superparamagnetic nano-islands that subsequently coalesce, giving rise to a continuous film for a nominal thickness of 8 Fe monolayers. For a very low Fe coverage (2 Fe monolayers), we show that the surface barrier potential (i.e. the barrier potential seen by electrons incident on the surface), measured by absorbed current spectroscopy, attains very large values (6.9 eV at room temperature) and dramatically changes as a function of temperature, with an increase of ˜1.5 eV from room temperature down to 130 K, largely exceeding similar changes observed in both thin films and nanoparticles. This phenomenon disappears as the thickness increases and is fully reversible with temperature. Nonequilibrium phenomena due to the experimental conditions are present, but are not able to explain the observed data. Inverse photoemission, core level photoemission, x-ray photoemission diffraction, and scanning tunneling microscopy are employed in order to find temperature-dependent properties of the Fe islands: while only minor changes as a function of temperature are present in the electronic band structure, the Fe crystal structure, and the morphology of the islands, a noticeable temperature dependence of the Se segregation through the Fe islands is found.

  6. Microanalytical method development for Fe, Cu and Zn determination in colorectal cancer cells.

    PubMed

    Polgári, Zsófia; Ajtony, Zsolt; Kregsamer, Peter; Streli, Christina; Mihucz, Victor G; Réti, Andrea; Budai, Barna; Kralovánszky, Judit; Szoboszlai, Norbert; Záray, Gyula

    2011-09-30

    Microanalytical methods suitable for the determination of Fe, Cu in HT-29 (human colon adenocarcinoma) cells treated with different iron compounds (Fe(II) sulfate, Fe(III) chloride, Fe(III) citrate and Fe(III) transferrin) and cultured in medium supplemented or not with 10% (v/v) fetal calf serum (FCS) by total reflection X-ray fluorescence spectrometry (TXRF) and simultaneous graphite furnace atomic absorption spectrometry (GF-AAS) were developed. The developed TXRF method was also suitable for Zn determination in the samples. The main advantage of the proposed methods is the execution of all sample preparation steps following incubation and prior to the elemental analysis in the same Eppendorf tubes. Sample preparation was performed at microscale (115 μL sample volume) with 65% nitric acid and 30% hydrogen peroxide. According to scanning electron microscopic measurements, the organic matrix of the cell samples could be eliminated to the extent that accurate results were obtained for Cu and Fe by analyzing the same samples by TXRF and GF-AAS. Concerning the iron uptake, HT-29 cells incubated in FCS-free medium contained Fe in cca. 5-50 times higher amounts compared to cells cultured in FCS supplemented medium. Pronounced differences in the iron uptake compared to the iron supply (inorganic vs. organic chelated as well as iron(II) vs. iron(III)) were observed in the case of cell lines incubated in FCS-free medium.

  7. 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.

  8. Mesocrystalline Zn-Doped Fe3O4 Hollow Submicrospheres: Formation Mechanism and Enhanced Photo-Fenton Catalytic Performance.

    PubMed

    Nguyen, Xuan Sang; Zhang, Gaoke; Yang, Xianfeng

    2017-03-15

    Uniform and magnetic recyclable mesocrystalline Zn-doped Fe3O4 hollow submicrospheres (HSMSs) were successfully synthesized via a simple one-pot solvothermal route and were used for efficient heterogeneous photo-Fenton catalyst. XRD, XPS, Raman spectroscopy, Mössbauer spectroscopy, SEM, HRTEM, and EDX analyses revealed that the shell of HSMSs is highly porous and assembled by oriented attachment of magnetite nanocrystal building blocks with Zn-rich surfaces. Furthermore, a possible formation mechanism of mesocrystalline hollow materials was proposed. First, Fe3O4 mesocrystals were assembled by oriented nanocrystals, and a Zn-rich amorphous shell grew on the surfaces. Then, Zn gradually diffused into Fe3O4 crystals to form Zn-doped Fe3O4 due to the Kirkendall effect with increasing the reaction time. Meanwhile, the inner nanocrystals would be dissolved, and outer particles would grow larger owing to the Ostwald ripening process, leading to the formation of a hollow structure with porous shell. The Zn-doped Fe3O4 HSMSs exhibited high and stable photo-Fenton activity for degradation of rhodamine B (RhB) and cephalexin under visible-light irradiation in the presence of H2O2, which results from their hollow mesocrystal structure and Zn doping. It could be easily separated and reused by an external magnetic field. The results suggested that the as-obtained magnetite hollow mesocrystals could be a promising catalyst in the photo-Fenton process.

  9. Fe-Zn Alloy Coating on Galvannealed (GA) Steel Sheet to Improve Product Qualities

    NASA Astrophysics Data System (ADS)

    Pradhan, Debabrata; Guin, Akshya Kumar; Raju, Pankaj; Manna, Manindra; Dutta, Monojit; Venugopalan, T.

    2014-09-01

    Galvannealed steel sheets (GA) have become the mainstream steel sheet for automobile applications because of their superior corrosion resistance, paintability, and weldability. To impart specific properties, different coatings on GA steel sheet were reported to improve properties further. In this context, we have developed an electroplating process (flash coating) for bright and adherent Fe-Zn alloy coating on GA steel sheet to enhance performances such as weldability, frictional behavior, phosphatability, and defect coverage. A comparative study with bare GA steel sheet was carried out for better elastration. The electroplating time was reduced below 10 s for practical applicability in an industrial coating line by modulating the bath composition. Electroplating was performed at current density of 200-500 A/m2 which yielded with higher cathode current efficiency of 85-95%. The performance results show that Fe-10 wt.% Zn-coated GA steel sheet (coating time 7 s) has better spot weldability, lower dynamic coefficient of friction (0.06-0.07 in lubrication), and better corrosion resistance compared to bare GA steel sheet. Uniform phosphate coating with globular crystal size of 2-5 µm was obtained on Fe-Zn flash-coated GA steel sheet. Hopeite was the main phosphate compound (77.9 wt.%) identified along with spencerite (13.6 wt.%) and phosphophyllite (8.5 wt.%).

  10. Infrared Brazing Fe3Al Using Ag-Based Filler Metals

    NASA Astrophysics Data System (ADS)

    Shiue, Ren-Kae; Li, Yao; Wu, Shyi-Kaan; Wu, Ling-Mei

    2010-11-01

    The microstructural evolution and bonding shear strength of infrared brazed Fe3Al using Ag and BAg-8 (72Ag-28Cu in wt pct) braze alloys have been studied. The Ag-rich phase alloyed with Al dominates the entire Ag brazed joints, and the shear strength is independent of the brazing time. The BAg-8 brazed joint contains Ag-Cu eutectic for all brazing conditions, and its shear strength increases slightly with increasing brazing time. The highest shear strength of 181 MPa is acquired from the joint infrared brazed at 1073 K (800 °C) for 600 seconds. A thin layer of Fe3Al is identified at the interface between the brazed zone and the substrate for both braze alloys. An Al depletion zone in the Fe3Al substrate next to the interfacial Fe3Al is identified as the α-Fe phase. The dissolution of Al from the Fe3Al substrate into the molten braze causes the formation of α-Fe in the Fe3Al substrate.

  11. 840 mW Continuous-Wave Fe:ZnSe Laser Operating at 4140 nm (Postprint)

    DTIC Science & Technology

    2012-11-30

    lasing has been demonstrated in the 2–3 μm region from Cr2 ions doped into various II–VI crystal hosts [1], most notably ZnSe [2] and ZnS [3]. These...beam waist diameters of 220 μm. The Fe:ZnSe sample measured 2 mm × 6 mm × 8 mm and was wrapped in indium foil and clamped to a copper mount cooled to

  12. Influence of Fe doping on the structural, optical and magnetic properties of ZnS diluted magnetic semiconductor

    NASA Astrophysics Data System (ADS)

    Saikia, D.; Raland, RD.; Borah, J. P.

    2016-09-01

    Fe doped ZnS nanoparticles with different concentrations of Fe, synthesized by microwave assisted co-precipitation method have been reported. The incorporation of Fe2+ and Fe3+ ions into ZnS lattice are confirmed by X-ray diffraction (XRD) and Electron Paramagnetic resonance (EPR) study. XRD and High Resolution Transmission electron Microscope (HRTEM) results confirm the phase purity of the samples and indicate a reduction of the particle size with increase in Fe concentration. EDAX analysis confirms the presence of Zn, S and Fe in the samples. A yellow-orange emission peak is observed in Photoluminescence (PL) spectra which exhibits the Characteristic 4T2 (4G)-6A1 (6S) transition of Fe3+ ion. The room temperature magnetic studies as analyzed from M-H curves were investigated from vibrating samples magnetometer (VSM) which shows a weak ferro and superparamagnetic like behavior in 1% and 3% Fe-doped ZnS nanocrystals, whereas; at 10% Fe-doping concentrations, antiferromagnetism behavior is achieved. The ZFC-FC measurement reveals that the blocking temperature of the nanoparticle is above the room temperature.

  13. Preparation and photocatalytic properties of magnetically reusable Fe3O4@ZnO core/shell nanoparticles

    NASA Astrophysics Data System (ADS)

    Wang, Jian; Yang, Jinghai; Li, Xiuyan; Wang, Dandan; Wei, Bing; Song, Hang; Li, Xuefei; Fu, Siwei

    2016-01-01

    Fe3O4@ZnO binary nanoparticles were synthesized by a simple two-step chemical method and characterized using various analytical instruments. TEM result proved the binary nanoparticles have core/shell structures and average particle size is 60 nm. Photocatalytic investigation of Fe3O4@ZnO core/shell nanoparticles was carried out using rhodamine B (RhB) solution under UV light. Fe3O4@ZnO core/shell nanoparticles showed enhanced photocatalytic performance in comparison with the as prepared ZnO nanoparticles. The enhanced photocatalytic activity for Fe3O4@ZnO might be resulting from the higher concentration of surface oxygen vacancies and the suppressing effect of the Fe3+ ions on the recombination of photoinduced electron-hole pairs. Magnetization saturation value (5.96 emu/g) of Fe3O4@ZnO core/shell nanoparticles is high enough to be magnetically removed by applying a magnetic field. The core/shell photocatalyst can be easily separated by using a commercial magnet and almost no decrease in photocatalytic efficiency was observed even after recycling six times.

  14. Growth mechanism of ZnO nanorod/Fe3O4 nanoparticle composites and their photocatalytic properties

    NASA Astrophysics Data System (ADS)

    Wang, Wenda; Yu, Leiming; Yang, Hanjia; Hong, Kunquan; Qiao, Zhenfang; Wang, Hai

    2015-11-01

    ZnO nanorods/Fe3O4 nanocomposites as the recyclable photocatalyst were synthesized by a co-precipitation method, with microwave assistant by dropping alkaline solution with Fe3O4 nanoparticles into the aqueous of zinc salt. These Fe3O4 nanoparticles were the nucleated centers for the ZnO nanorods growth so that these nanorods ended with aggregated Fe3O4 nanoparticles. The growth processes and mechanism are explained as those insoluble zinc hydroxides prefer to nucleate on the surface of Fe3O4 nanoparticles (heterogeneous nucleation) rather than nucleated as isolated ZnO nanostructures (homogeneous nucleation). These nanocomposites have strong photocatalytic ability to reduce RhB and moderate magnetization, which make them being good recyclable photocatalysts.

  15. Interdiffusion and impurity diffusion in polycrystalline Mg solid solution with Al or Zn

    SciTech Connect

    Kammerer, Catherine; Kulkarni, Nagraj S; Warmack, Robert J Bruce; Sohn, Yong Ho

    2014-01-01

    Interdiffusion and impurity diffusion in Mg binary solid solutions, Mg(Al) and Mg(Zn) were investigated at temperatures ranging from 623 to 723 K. Interdiffusion coef cients were determined via the Boltzmann Matano Method using solid-to-solid diffusion couples assembled with polycrystalline Mg and Mg(Al) or Mg(Zn) solid solutions. In addition, the Hall method was employed to extrapolate the impurity diffusion coef cients of Al and Zn in pure polycrystalline Mg. For all diffusion couples, electron micro-probe analysis was utilized for the measurement of concentration pro les. The interdiffusion coef cient in Mg(Zn) was higher than that of Mg(Al) by an order of magnitude. Additionally, the interdiffusion coef cient increased signi cantly as a function of Al content in Mg(Al) solid solution, but very little with Zn content in Mg(Zn) solid solution. The activation energy and pre-exponential factor for the average effective interdiffusion coef cient in Mg(Al) solid solution were determined to be 186.8 ( 0.9) kJ/mol and 7.69 x 10-1 ( 1.80 x 10-1) m2/s, respectively, while those determined for Mg(Zn) solid solution were 139.5 ( 4.0) kJ/mol and 1.48 x 10-3 ( 1.13 x 10-3) m2/s. In Mg, the Zn impurity diffusion coef cient was an order of magnitude higher than the Al impurity diffusion coef cient. The activation energy and pre-exponential factor for diffusion of Al impurity in Mg were determined to be 139.3 ( 14.8) kJ/mol and 6.25 x 10-5 ( 5.37 x 10-4) m2/s, respectively, while those for diffusion of Zn impurity in Mg were determined to be 118.6 ( 6.3) kJ/mol and 2.90 x 10-5 ( 4.41 x 10-5) m2/s.

  16. Electrospinning direct synthesis of magnetic ZnFe2O4/ZnO multi-porous nanotubes with enhanced photocatalytic activity

    NASA Astrophysics Data System (ADS)

    Wang, Chunlei; Tan, Xing; Yan, Juntao; Chai, Bo; Li, Jianfen; Chen, Shizhong

    2017-02-01

    Magnetic ZnFe2O4/ZnO (ZFO/ZnO) multi-porous nanotubes have been first fabricated via a facile electrospinning and subsequent calcination process. A series of ZFO/ZnO photocatalysts with different ZFO molar content and morphologies are also obtained by varying the molar ratio of Zn/Fe metal salt and its dosage. The morphology, composition, crystal structure and specific surface area of achieved photocatalysts are systematically examined. TEM images demonstrate ZFO/ZnO-3 multi-porous nanotubes possess perfect 1D nanotube profile with hierarchical pores. HRTEM images confirm the formation of ZFO/ZnO heterojunctions. DRS spectra show that ZFO/ZnO-3 multi-porous nanotubes exhibit an enhanced absorption both in UV and visible-light region. PL spectra and photocurrent responses of ZFO/ZnO-3 multi-porous nanotube demonstrated that the photogenerated electrons and holes are effectively separated. Above all, ZFO/ZnO-3 multi-porous nanotubes photocatalysts with a larger specific surface area of 57.79 m2 g-1 exhibit the best photocatalytic efficiency of 99% after 150 min under the solar irradiation for the decolorization of RhB. Moreover, ZFO/ZnO photocatalysts not only possess magnetic separation property, but also keep a relatively high photocatalytic efficiency even after four cycles, which is beneficial for practical application. In addition, both the formation and potential photocatalytic mechanisms of ZFO/ZnO-3 multi-porous nanotubes are proposed in detail.

  17. Corrosion Protection of Al/Au/ZnO Anode for Hybrid Cell Application

    PubMed Central

    Slaughter, Gymama; Stevens, Brian

    2015-01-01

    Effective protection of power sources from corrosion is critical in the development of abiotic fuel cells, biofuel cells, hybrid cells and biobateries for implantable bioelectronics. Corrosion of these bioelectronic devices result in device inability to generate bioelectricity. In this paper Al/Au/ZnO was considered as a possible anodic substrate for the development of a hybrid cell. The protective abilities of corrosive resistant aluminum hydroxide and zinc phosphite composite films formed on the surface of Al/Au/ZnO anode in various electrolyte environments were examined by electrochemical methods. The presence of phosphate buffer and physiological saline (NaCl) buffer allows for the formation of aluminum hyrdroxide and zinc phosphite composite films on the surface of the Al/Au/ZnO anode that prevent further corrosion of the anode. The highly protective films formed on the Al/Au/ZnO anode during energy harvesting in a physiological saline environment resulted in 98.5% corrosion protective efficiency, thereby demonstrating that the formation of aluminum hydroxide and zinc phosphite composite films are effective in the prevention of anode corrosion during energy harvesting. A cell assembly consisting of the Al/Au/ZnO anode and platinum cathode resulted in an open circuit voltage of 1.03 V. A maximum power density of 955.3 μW/ cm2 in physiological saline buffer at a cell voltage and current density of 345 mV and 2.89 mA/ cm2, respectively. PMID:26580661

  18. Synthesis, spectral and electrochemical properties of Al(III) and Zn(II) complexes with flavonoids

    NASA Astrophysics Data System (ADS)

    Souza, Rubens F. V. de; De Giovani, Wagner F.

    2005-07-01

    The synthesis, electrochemical and spectral (UV-vis, 1H NMR, IR, fluorescence) properties as well as thermal behaviors of Al(III) and Zn(II) complexes with the flavonoids quercetin (H 2L 1), rutin (H 2L 2) and galangin (HL 3) are presented. The complexes may be formulated as [Al 2(L 1)(H 2O) 8]Cl 4, [Al 3(L 2) 2(H 2O) 12]Cl 5, [Al(L 3)(H 2O) 4]Cl 2, [Zn 2(L 1)(H 2O) 4]Cl 2, [Zn 3(L 2) 2(H 2O) 6]Cl 2 and [Zn(L 3)(H 2O) 2]Cl. The higher fluorescence intensities of the complexes related to the free flavonoids, are attributed to the coordination of the ligands to the small, highly charged Al(III) and Zn(II) ions. The coordination effectively increases the rigidity of the ligand structure and increases the fluorescence quantum yield by reducing the probability of non-radiative energy dissipation process. Antioxidant activities of the compounds were also investigated under an electrochemical point of view. The cyclic voltammetric data show a considerable decrease of the oxidation potentials of the complexes related to that of the free flavonoids. Thus, the flavonoid-metal complexes are more effective antioxidants than the free flavonoids.

  19. Preparation, characterization and dye adsorption of Au nanoparticles/ZnAl layered double oxides nanocomposites

    NASA Astrophysics Data System (ADS)

    Zhang, Yu Xin; Hao, Xiao Dong; Kuang, Min; Zhao, Han; Wen, Zhong Quan

    2013-10-01

    In this work, Au/ZnAl-layer double oxides (LDO) nanocomposties were prepared through a facile calcination process of AuCl4- intercalated ZnAl-layered double hydroxides (LDHs) nanocomposites. The morphology and crystal structure of these nanocomposites were characterized by Scanning electron microscopy (SEM), transmission electron microscopy (TEM), powder X-ray diffraction (XRD), and N2 sorption analysis. By tailoring the process parameter, such as calcination temperature, heating time and the component composition, the adsorption properties of methyl orange (MO) on the Au/ZnAl-LDO nanocomposites were investigated in this work. In a typical adsorption process, it was found that 0.985 mg of MO (0.01 g L-1, 100 mL, 1 mg of MO in total) can be removed in 60 min by utilizing only 2.5 mg of Au/ZnAl-LDO (Au content, 1%) as adsorbents. Our adsorption data obtained from the Langmuir model also gave good values of the determination coefficient, and the saturated adsorption capacity of Au/ZnAl-LDO nanocomposites for MO was found to be 627.51 mg/g under ambient condition (e.g., room temperature, 1 atm). In principle, these hybrid nanostructures with higher adsorption abilities could be very promising adsorbents for wastewater treatment.

  20. Enhancement of photoluminescence properties in ZnO/AlN bilayer heterostructures grown by atomic layer deposition

    SciTech Connect

    Zhu, Shang-Bin; Lu, Hong-Liang Zhang, Yuan; Sun, Qing-Qing; Zhou, Peng; Ding, Shi-Jin; Zhang, David Wei; Zhang, Qiu-Xiang

    2015-01-15

    The AlN/ZnO bilayer heterostructures were deposited on Si (100) substrate by thermal atomic layer deposition. X-ray diffraction results show that the crystallinity of polycrystalline ZnO layer is enhanced by amorphous AlN capping layer. Compared with ZnO thin film, ZnO/AlN bilayer with 10.7 nm AlN capping layer exhibits three times enhanced near band edge (NBE) emission from the photoluminescence measurements. In addition, the near band edge emission from the ZnO can be further increased by ∼10 times through rapid thermal annealing at 600 °C. The underlying mechanisms for the enhancement of the NBE emission after coating AlN capping layer and thermal treatment are discussed. These results suggest that coating of a thin AlN layer and sequential thermal treatments can effectively tailor the luminescence properties of ZnO film.

  1. Synthesis, characterization and superparamagnetic resonance studies of ZnFe2O4 nanoparticles.

    PubMed

    Köseoğlu, Yüksel; Yildiz, Hayrettin; Yilgin, Resul

    2012-03-01

    Superparamagnetic nanoparticles of zinc ferrite (ZnFe2O4) were produced by a microwave induced combustion synthesis method. XRD, FT-IR, SEM, VSM and ESR were used for the structural, morphological, and magnetic investigation of the product, respectively. Average particle size of the nanoparticles was estimated by the Schérrer equation using the full-width at half maximum (FWHM) of the most intense XRD peak and found as 41 nm. Magnetization measurements have shown that the samples have a blocking temperature of 72 K which indicates a superparamagnetic behavior. Superparamagnetic resonance (SPR) spectra at room temperature show a broad line with a Landé g-factor, g(eff) approximately 2. We used a theoretical formalism based on a distribution of diameters of the nanoparticles following lognormal proposed by Berger et al. The nanoparticles behave as single magnetic domains with random orientations of magnetic moments which are subject to thermal fluctuations. A Landau-Lifshitz line shape function presents adequate results which are in good agreement with the experimental ones. At high temperatures, the SPR line shape is governed by the core anisotropy and the thermal fluctuations. By decreasing the temperature, the magnetic susceptibility of shell spins increases. As a result of this, the surface spins produce an effective field on the core leading to a decrease of resonance field, B(r). Also, the effective anisotropy increases as the shell spins begin to order. So, the results are interpreted by a simple model, in which each single-domain nanoparticle is considered as a core-shell system, with magneto-crystalline anisotropy on the core and surface anisotropy on the shell.

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

    NASA Astrophysics Data System (ADS)

    Naeem, Haider T.; Mohammad, Kahtan S.; Hussin, Kamarudin; Tan, T. Qing; Idris, M. Sobri

    2015-05-01

    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 30 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 (Mg2Zn11) phases during matrix of aluminum-alloy.

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

    SciTech Connect

    Naeem, Haider T.; Mohammad, Kahtan S.; Hussin, Kamarudin; Tan, T. Qing; Idris, M. Sobri

    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 30 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.

  4. Synthesis and characterization of lawsone-lntercalated Zn-Al-layered double hydroxides.

    PubMed

    Yasin, Yamin; Ismail, Nur Mushirah; Hussein, Mohd Zobir; Aminudin, Norhaniza

    2011-06-01

    A drug-inorganic nanostructured material involving pharmaceutically active compound lawsone intercalated Zn-Al layered double hydroxides (Law-LDHs) with Zn/AI = 4 has been assembled by co-precipitation and ion exchange methods. Powder X-ray diffraction (XRD) and Fourier transform infrared spectra (FTIR) analysis indicate a successful intercalation of lawsone between the layers of layered double hydroxides. It suggests that layered double hydroxides may have application as the basis of a drug delivery system.

  5. The effects of doping and shell thickness on the optical and magnetic properties of Mn/Cu/Fe-doped and Co-doped ZnS nanowires/ZnO quantum dots/SiO2 heterostructures

    NASA Astrophysics Data System (ADS)

    Cao, Jian; Yang, Jinghai; Yang, Lili; Wei, Maobin; Feng, Bo; Han, Donglai; Fan, Lin; Wang, Bingji; Fu, Hao

    2012-07-01

    In this paper, we demonstrated the encapsulation of Mn/Cu/Fe-doped and co-doped ZnS nanowires (NWs) and ZnO quantum dots (QDs) with a layer of mesoporous SiO2 shell for the purpose of integrating dual emission and ferromagnetism property into one common nanostructure at room temperature. Within the ZnS:Mn2+Cu2+Fe2+/ZnO@SiO2 nanocomposites, ZnS:Mn2+Cu2+Fe2+ NWs and ZnO QDs provided color-tunable visible emission and UV emission, respectively. The color-tunable visible emission in the ZnS:Mn2+Cu2+Fe2+ NWs can be obtained by adjusting the concentrations of Mn2+, Cu2+, and Fe2+ ions. The ferromagnetism of the ZnS:Mn2+Cu2+Fe2+ NWs was observed around room temperature, the mechanism of which was explained by the super-exchange mechanism. The results of the effect of the ZnO QDs shell thickness on the optical properties of the ZnS:Mn2+/ZnO@SiO2 nanocomposites showed that the luminescence intensity of the yellow-orange emission and UV emission reached the highest value when the ratio of ZnS:Mn2+/ZnO equaled 1:5.

  6. CEMS study of defect annealing in Fe implanted AlN

    NASA Astrophysics Data System (ADS)

    Bharuth-Ram, K.; Geburt, S.; Ronning, C.; Masenda, H.; Naidoo, D.

    2016-12-01

    An AlN thin film grown on sapphire substrate was implanted with 45 keV 57Fe and 56Fe ions at several energies to achieve a homogeneous concentration profile of approximately 2.6 at.%. in the AlN film. Conversion electron Mössbauer Spectroscopy data were collected after annealing the sample up to 900 °C. The spectra were fitted with three components, a single line attributed to small Fe clusters, and two quadrupole split doublets attributed to Fe substituting Al in the wurtzite AlN lattice and to Fe located in implantation induced lattice damage. The damage component shows significant decrease on annealing up to 900 °C, accompanied by corresponding increases in the singlet component and the substitutional Fe.

  7. Structural and Magnetic Studies of Zn0.95Co0.05O and Zn0.90Co0.05Al0.05O

    NASA Astrophysics Data System (ADS)

    Murtaza, Saleem; Saadat, A. Siddiqi; Shahid, Atiq; M. Sabieh, Anwar

    2011-11-01

    Single-phase Zn0.95Co0.05O and Zn0.90Co0.05Al0.05O samples were prepared by a novel combustion method. X-ray diffraction studies exhibit the pure phase wurtzite structure of doped ZnO. Energy dispersive x-ray analysis confirms the incorporation of dopants into the host material. Scanning electron microscopy shows the ordered morphology in both of the samples. Temperature-dependent resistivity analysis describes the expected semiconducting behavior that is similar to the parent ZnO materials. Room-temperature magnetic measurements reveal the absence of ferromagnetism in Co-doped ZnO, while the Co and Al co-doped sample displays apparent room-temperature ferromagnetic behavior. The decrease of resistivity and presence of ferromagnetic behavior in Al-doped ZnCoO system corroborate the significant role of free carriers.

  8. Defect assisted saturable absorption characteristics in Al and Li doped ZnO thin films

    NASA Astrophysics Data System (ADS)

    K. M., Sandeep; Bhat, Shreesha; S. M., Dharmaprakash; P. S., Patil; Byrappa, K.

    2016-09-01

    The influence of different doping ratios of Al and Li on the nonlinear optical properties, namely, a two-photon absorption and a nonlinear refraction using single beam Z-scan technique, of nano-crystalline ZnO thin films has been investigated in the present study. A sol-gel spin-coated pure ZnO, Al-doped ZnO (AZO), and Li-doped ZnO (LZO) thin films have been prepared. The stoichiometric deviations induced by the occupancy of Al3+ and Li+ ions at the interstitial sites injects the compressive stress in the AZO and LZO thin films, respectively, while the extended defect states below the conduction band leads to a redshift of energy band gap in the corresponding films as compared to pure ZnO thin film. Switching from an induced absorption in ZnO and 1 at. wt. % doped AZO and LZO films to a saturable absorption (SA) in 2 at. wt. % doped AZO and LZO films has been observed, and it is attributed to the saturation of a linear absorption of the defect states. The closed aperture Z-scan technique revealed the self-focusing (a positive nonlinear refractive index) in all the films, which emerge out of the thermo-optical effects due to the continuous illumination of laser pulses. A higher third-order nonlinear optical susceptibility χ(3) of the order 10-3 esu has been observed in all the films.

  9. Synthesis of Glycerol Carbonate by Transesterification of Glycerol with Urea Over Zn/Al Mixed Oxide.

    PubMed

    Ryu, Young Bok; Baek, Jae Ho; Kim, Yangdo; Lee, Man Sig

    2015-01-01

    Reactions of glycerol carbonate using glycerol and urea have been carried out previously using ZnSO4 and ZnO catalysts, and high yields have been reported using ZnSO4 as catalyst. However, this salt is soluble in glycerol, and recycling of catalyst is difficult after the reaction. In this study, we prepared a mixed metal oxide catalyst using Zn and Al, and this catalyst consisted of a mixture of ZnO and ZnAl2O4. We confirmed the conversion of glycerol and the yield of glycerol carbonate of the amount of Al. As a result, we obtained a yield of 82.3% and a conversion of 82.7%. In addition we obtained high yield in recycling of catalyst. The yield of the glycerol carbonate increases with an increase of acid and base site of catalysts and the highest catalytic activity was obtained when acid/base ratio was approx. 1. From this result, we may conclude that the acid and base site density and ratio of catalysts were very important parameters in the synthesis of glycerol carbonate from urea and glycerol.

  10. 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.

  11. Characterization of nanocrystalline ZnO:Al films by sol-gel spin coating method

    SciTech Connect

    Gareso, P. L. Rauf, N. Juarlin, E.; Sugianto,; Maddu, A.

    2014-09-25

    Nanocrystalline ZnO films doped with aluminium by sol-gel spin coating method have been investigated using optical transmittance UV-Vis and X-ray diffraction (X-RD) measurements. ZnO films were prepared using zinc acetate dehydrate (Zn(CH{sub 3}COO){sub 2}@@‡2H{sub 2}O), ethanol, and diethanolamine (DEA) as a starting material, solvent, and stabilizer, respectively. For doped films, AlCl{sub 3} was added to the mixture. The ZnO:Al films were deposited on a transparent conductive oxide (TCO) substrate using spin coating technique at room temperature with a rate of 3000 rpm in 30 sec. The deposited films were annealed at various temperatures from 400°C to 600°C during 60 minutes. The transmittance UV-Vis measurement results showed that after annealing at 400°C, the energy band gap profile of nanocrystalline ZnO:Al film was a blue shift. This indicated that the band gap of ZnO:Al increased after annealing due to the increase of crystalline size. As the annealing temperature increased the bandgap energy was a constant. In addition to this, there was a small oscillation occurring after annealing compared to the as–grown samples. In the case of X-RD measurements, the crystalinity of the films were amorphous before annealing, and after annealing the crystalinity became enhance. Also, X-RD results showed that structure of nanocrystalline ZnO:Al films were hexagonal polycrystalline with lattice parameters are a = 3.290 Å and c = 5.2531 Å.

  12. 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.

  13. 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

  14. Fe electron transfer and atom exchange in goethite: influence of Al-substitution and anion sorption.

    PubMed

    Latta, Drew E; Bachman, Jonathan E; Scherer, Michelle M

    2012-10-02

    The reaction of Fe(II) with Fe(III) oxides and hydroxides is complex and includes sorption of Fe(II) to the oxide, electron transfer between sorbed Fe(II) and structural Fe(III), reductive dissolution coupled to Fe atom exchange, and, in some cases mineral phase transformation. Much of the work investigating electron transfer and atom exchange between aqueous Fe(II) and Fe(III) oxides has been done under relatively simple aqueous conditions in organic buffers to control pH and background electrolytes to control ionic strength. Here, we investigate whether electron transfer is influenced by cation substitution of Al(III) in goethite and the presence of anions such as phosphate, carbonate, silicate, and natural organic matter. Results from (57)Fe Mössbauer spectroscopy indicate that both Al-substitution (up to 9%) and the presence of common anions (PO(4)(3-), CO(3)(2-), SiO(4)(4-), and humic acid) does not inhibit electron transfer between aqueous Fe(II) and Fe(III) in goethite under the conditions we studied. In contrast, sorption of a long-chain phospholipid completely shuts down electron transfer. Using an enriched isotope tracer method, we found that Al-substitution in goethite (10%), does, however, significantly decrease the extent of atom exchange between Fe(II) and goethite (from 43 to 12%) over a month's time. Phosphate, somewhat surprisingly, appears to have little effect on the rate and extent of atom exchange between aqueous Fe(II) and goethite. Our results show that electron transfer between aqueous Fe(II) and solid Fe(III) in goethite can occur under wide range of geochemical conditions, but that the extent of redox-driven Fe atom exchange may be dependent on the presence of substituting cations such as Al.

  15. UV light photocatalytic degradation of organic dyes with Fe-doped ZnO nanoparticles

    NASA Astrophysics Data System (ADS)

    Saleh, Rosari; Djaja, Nadia Febiana

    2014-10-01

    Iron doped wurtzite ZnO nanoparticles were synthesized and characterized by X-ray diffraction, energy dispersive X-ray spectroscopy, scanning electron microscopy, UV-Vis diffuse reflectance spectroscopy, electron spin resonance and vibrating sample magnetometer techniques. The photocatalytic activities were also evaluated for the degradation of methyl orange and methylene blue under UV irradiation. The effects of various parameters, such as pH, dopant concentrations and photocatalytic dosage, were studied. The ESR results indicate the presence of Fe in both the Fe2+ and Fe3+ valence states. As the dopant concentrations increased, the number of spins due to Fe2+ ions increased and the number of spins due to Fe3+ ions decreased resulting in an increase in magnetization. The catalysts with the highest number of spins due to Fe2+ ions exhibited the optimum photocatalytic activity for the degradation of methyl orange and methylene blue. In addition, the role of photoactive species was investigated using a radical scavenger technique. The results indicated that the doping concentration is the most important factor in photocatalytic performance.

  16. Identification of Fe3+-Li+ complexes in ZnO by means of high-frequency EPR/ENDOR spectroscopy

    NASA Astrophysics Data System (ADS)

    Kutin, Yu. S.; Mamin, G. V.; Orlinskii, S. B.

    2013-12-01

    Theoretical prediction of a high Curie temperature in ZnO doped with Mn, Fe, and other transition metals has stimulated the investigation of these materials by many research groups. Although charge-compensated Fe3+ centers in ZnO:Fe have been observed by means of EPR and have been known for decades, conclusions on the chemical nature of these defects are still contradictory. Originally, these centers were treated as Fe3+-Li+ complexes with both ions occupying adjacent cationic sites. Recently, however, the centers were interpreted as a substitutional Fe3+ ion with a vacancy at an adjacent zinc or oxygen site (Fe-VZn or Fe-VO). In order to determine the chemical nature of the impurity associated with Fe3+, electron-nuclear double resonance (ENDOR) spectroscopy was used. ENDOR measurements reveal NMR transitions corresponding to nuclei with g-factor gN = 2.171 and spin I = 3/2. This unambiguously shows presence of Li as a charge compensator and also resolves contradictions with the theoretical prediction of the Fe-VO formation energy. The electric field gradients at the 7Li nuclei (within the Fe3+-Li+ complexes) were estimated to be significantly lower than the gradient at undistorted Zn sites.

  17. Identification of Fe3+-Li+ complexes in ZnO by means of high-frequency EPR/ENDOR spectroscopy.

    PubMed

    Kutin, Yu S; Mamin, G V; Orlinskii, S B

    2013-12-01

    Theoretical prediction of a high Curie temperature in ZnO doped with Mn, Fe, and other transition metals has stimulated the investigation of these materials by many research groups. Although charge-compensated Fe(3+) centers in ZnO:Fe have been observed by means of EPR and have been known for decades, conclusions on the chemical nature of these defects are still contradictory. Originally, these centers were treated as Fe(3+)-Li(+) complexes with both ions occupying adjacent cationic sites. Recently, however, the centers were interpreted as a substitutional Fe(3+) ion with a vacancy at an adjacent zinc or oxygen site (Fe-VZn or Fe-VO). In order to determine the chemical nature of the impurity associated with Fe(3+), electron-nuclear double resonance (ENDOR) spectroscopy was used. ENDOR measurements reveal NMR transitions corresponding to nuclei with g-factor gN=2.171 and spin I=3/2. This unambiguously shows presence of Li as a charge compensator and also resolves contradictions with the theoretical prediction of the Fe-VO formation energy. The electric field gradients at the (7)Li nuclei (within the Fe(3+)-Li(+) complexes) were estimated to be significantly lower than the gradient at undistorted Zn sites.

  18. Photoluminescence lifetime of Al-doped ZnO films in visible region

    NASA Astrophysics Data System (ADS)

    Sharma, Bhupendra K.; Khare, Neeraj; Haranath, D.

    2010-12-01

    ZnO and Al-doped ZnO films have been deposited on quartz substrates by ultrasonically assisted chemical vapor deposition technique. Photoluminescence (PL) spectra of the films reveal that Al doping leads to suppression of defect related visible band. Time resolved photoluminescence studies have been carried out for the measurement of lifetime of deep level luminescence. The decay of PL intensity with time has been found to follow biexponential behavior. The relative contributions of fast decay component (τ1) and slow decay component (τ2) in total decay process are found to be ˜99% and ˜1% respectively. The values of τ1 and τ2 are found to decrease with Al doping in ZnO film. The decrease of both τ1 and τ2 is attributed to increase in non-radiative recombination due to reduction in grain sizes and the decrease in radiative recombination due to suppression of defects.

  19. Gas sensing properties of Al-doped ZnO for UV-activated CO detection

    NASA Astrophysics Data System (ADS)

    Dhahri, R.; Hjiri, M.; El Mir, L.; Bonavita, A.; Iannazzo, D.; Latino, M.; Donato, N.; Leonardi, S. G.; Neri, G.

    2016-04-01

    Al-doped ZnO (AZO) samples were prepared using a modified sol-gel route and charaterized by means of trasmission electron microscopy, x-ray diffraction and photoluminescence analysis. Resistive planar devices based on thick films of AZO deposited on interdigitated alumina substrates were fabricated and investigated as UV light activated CO sensors. CO sensing tests were performed in both dark and illumination condition by exposing the samples to UV radiation (λ  =  400 nm).Under UV light, Al-doped ZnO gas sensors operated at lower temperature than in dark. Furthermore, by photoactivation we also promoted CO sensitivity and made signal recovery of AZO sensors faster. Results demonstrate that Al-doped ZnO might be a promising sensing material for the detection of CO under UV illumination.

  20. Structural properties of ZnO:Al films produced by the sol–gel technique

    SciTech Connect

    Zaretskaya, E. P. Gremenok, V. F.; Semchenko, A. V.; Sidsky, V. V.; Juskenas, R. L.

    2015-10-15

    ZnO:Al films are produced by sol–gel deposition at temperatures of 350–550°C, using different types of reagents. Atomic-force microscopy, X-ray diffraction analysis, Raman spectroscopy, and optical transmittance measurements are used to study the dependence of the structural, morphological, and optical properties of the ZnO:Al coatings on the conditions of deposition. The optical conditions for the production of ZnO:Al layers with preferred orientation in the [001] direction and distinguished by small surface roughness are established. The layers produced in the study possess optical transmittance at a level of up to 95% in a wide spectral range and can be used in optoelectronic devices.

  1. [Adsorption of perchlorate by calcined Mg/Zn/Al layered double hydroxides].

    PubMed

    Wang, Hong-Yu; Liu, Yan

    2014-07-01

    The adsorption capacity of perchlorate by Mg/Zn/Al layered double hydroxides was investigated. The samples were characterized by X-ray diffraction (XRD) and the adsorption isothermal model and dynamic model were discussed. The effect of calcination temperature, Mg/Zn/Al molar ratio, pH value of solution, adsorption time and dosage on the adsorption capacity of samples were studied. The experiment results showed that the removal ratio and adsorption capacity reached the highest and the pH value had good applicability when the molar ratio was Mg/Zn/Al = 2: 1 : 1. The adsorption of perchlorate basically conformed to the pseudo-second kinetics and Langmuir, Freundlich isotherm model.

  2. Intercalation of diclofenac in modified Zn/Al hydrotalcite-like preparation

    NASA Astrophysics Data System (ADS)

    Heraldy, E.; Suprihatin, R. W.; Pranoto

    2016-02-01

    The intercalation of a pharmaceutically active material diclofenac into modified Zn/Al Hydrotalcite-like (Zn/Al HTlc) preparation has been investigated by the coprecipitation and ion exchange method, respectively. The synthetic materials were characterized using X- Ray Diffraction (XRD); Fourier transforms infrared spectroscopy (FTIR); Scanning Electron Microscope (SEM); X-Ray Fluorescence (XRF) and surface area analyzer. The results show that the basal spacing of the product was expanded to 11.03 A for direct synthesis and 10.68 A for indirect synthesis, suggesting that diclofenac anion was intercalated into Zn/Al HTlc and arranged in a tilted bilayer fashion and the specific surface area of material increased after the intercalation of diclofenac.

  3. Structural and optical properties of pure and Al doped ZnO nanocrystals

    NASA Astrophysics Data System (ADS)

    Ghosh, A.; Kumari, N.; Tewari, S.; Bhattacharjee, A.

    2013-11-01

    Pure and Al doped zinc oxide (ZnO) were prepared by co-precipitation method. The dopant concentration [Al/Zn in atomic percentage (wt%)] was varied from 0 to 3 wt%. Structural characterisation of the samples performed with XRD and SEM-EDAX confirmed that polycrystalline nature of samples containing ZnO nanoparticles of size in the range of 97-47 nm. UV-Vis studies showed that the absorbance peaks, observed in the wavelength range of 800-250 nm, decreased with the increase in dopant concentration indicating widening of the band gap. The calculations of band gap (analyzed in terms of Burstein-Moss shift) from the reflectance showed an increase from 3.37 to 3.49 eV with increasing Al concentration.

  4. Multiple diffraction in an icosahedral Al-Cu-Fe quasicrystal

    NASA Astrophysics Data System (ADS)

    Fan, C. Z.; Weber, Th.; Deloudi, S.; Steurer, W.

    2011-07-01

    In order to reveal its influence on quasicrystal structure analysis, multiple diffraction (MD) effects in an icosahedral Al-Cu-Fe quasicrystal have been investigated in-house on an Oxford Diffraction four-circle diffractometer equipped with an Onyx™ CCD area detector and MoKα radiation. For that purpose, an automated approach for Renninger scans (ψ-scans) has been developed. Two weak reflections were chosen as the main reflections (called P) in the present measurements. As is well known for periodic crystals, it is also observed for this quasicrystal that the intensity of the main reflection may significantly increase if the simultaneous (H) and the coupling (P-H) reflections are both strong, while there is no obvious MD effect if one of them is weak. The occurrence of MD events during ψ-scans has been studied based on an ideal structure model and the kinematical MD theory. The reliability of the approach is revealed by the good agreement between simulation and experiment. It shows that the multiple diffraction effect is quite significant.

  5. Photoluminescence and EPR studies on Fe³⁺ doped ZnAl₂O₄: an evidence for local site swapping of Fe³⁺ and formation of inverse and normal phase.

    PubMed

    Pathak, Nimai; Gupta, Santosh K; Sanyal, Kaushik; Kumar, Mithlesh; Kadam, R M; Natarajan, V

    2014-06-28

    Considering that ZnAl2O4 spinel has two different sites (octahedral and tetrahedral) and its properties change with dopant ion distribution among these two sites; ZnAl2O4 doped with varied concentrations of Fe(3+) was synthesized by a low temperature sol-gel combustion method. Phase purity and structural investigations were carried out using Rietveld refined X-ray diffraction which shows a decrease in the value of cell parameters at higher doping levels. Photoluminescence (PL) and electron paramagnetic resonance (EPR) studies have shown that on doping, Fe(3+) ions were distributed in both tetrahedral and octahedral sites. At octahedral sites, Fe(3+) exhibited a broad red emission around 745 nm while at tetrahedral sites it exhibited well-defined vibronic sidebands at 665, 674, 684 and 693 nm along with a broad blue band with a maxima at 445 nm at room temperature. EPR studies have shown a broad spectrum at g ≈ 2.2 which corresponds to the Fe(3+) in octahedral sites, while the broad signal at g ≈ 4.2 belongs to Fe(3+) in tetrahedral sites. It was also inferred from these studies that Fe(3+) prefers to occupy octahedral sites at higher concentrations and at higher annealing temperatures. The PL decay behavior of Fe(3+) in ZnAl2O4 has also shown that two different types of Fe(3+) ions were present in this matrix. The first type was a long lived species (τ ≈ 170 μs) present at octahedral sites and the other was a short lived species (τ ≈ 40 μs) present at the tetrahedral sites; the fraction of the long lived species predominate at higher concentrations. Thus the present work is mainly focused on understanding the tuning of local site occupancy of the dopant ion among those sites with varying concentration and annealing temperature, using the dopant ion itself as a spectroscopic probe, which further helps in understanding the phase (inverse and normal) of the spinel.

  6. Pathways of phosphate uptake from aqueous solution by ZnAl layered double hydroxides.

    PubMed

    Cheng, X; Wang, Y; Sun, Z; Sun, D; Wang, A

    2013-01-01

    ZnAl layered double hydroxides (LDHs) were prepared by urea hydrolysis-based coprecipitation for removing phosphate from aqueous solutions. The chemical formula of the product was determined as Zn5.54Al3.02(OH)8.73(CO3)0.57Cl5.66·7.84H2O. Chloride ion was the major interlayer anion of the ZnAl LDHs. Adsorption of phosphate onto the ZnAl sorbent over the entire study period was not in close agreement with pseudo-first-order or pseudo-second-order models. The adsorption can be divided into two steps. A fast adsorption was observed during the first 10 h with a marked increase in the concentration of Cl(-) in the bulk solution. This indicated that the adsorption of phosphate was largely attributed to the ion exchange between phosphate and the interlayer Cl(-). A second fast adsorption of phosphate occurred after 10 h. During this period, the pH increased slowly, whereas the Cl(-) concentration was stable. The uptake of phosphate was likely attributed to OH(-)-H2PO4(-)/HPO4(2-) ion exchange as well as surface adsorption/complexation. Acidic conditions favored adsorption of phosphate by ZnAl LDHs, which is consistent with the pH increases during the adsorption. Coexisting anions, e.g., SO4(2-) and CO3(2-), are competitive ions for the adsorption of phosphate. The results verify the contribution of ion exchange and surface adsorption/complexation in the removal of phosphate by ZnAl LDHs.

  7. Enhanced nonvolatile holographic properties in Zn, Ru and Fe co-doped LiNbO3 crystals

    NASA Astrophysics Data System (ADS)

    Xu, Chao; Leng, Xuesong; Xu, Lei; Wen, Aihua; Xu, Yuheng

    2012-08-01

    A series of LiNbO3 crystals doped with various concentrations of ZnO and fixed concentrations of RuO2 and Fe2O3 have been grown by the Czochralski method from the congruent melts. The type of charge carriers was determined by Kr+ laser (476 nm) and He-Ne laser (633 nm). The results revealed that the holes were the dominant charge carriers at blue light irradiation. Dual-wavelength and two-color techniques were employed to investigate the nonvolatile holographic storage properties of Ru:Fe:LiNbO3 and Zn doped Ru:Fe:LiNbO3 crystals. The essential parameters of blue nonvolatile holographic storage in Zn:Ru:Fe:LiNbO3 crystals were enhanced greatly with the increase of Zn concentration. This indicates that the damage resistant dopants Zn2+ ions enhance the photorefractive properties at 476 nm wavelength instead of suppressing the photorefraction. The different mechanisms of blue photorefractive and nonvolatile holographic storage properties by dual wavelength recording in Zn:Ru:Fe:LiNbO3 crystals were discussed.

  8. Thermodynamic analysis of compatibility of several reinforcement materials with FeAl alloys

    NASA Technical Reports Server (NTRS)

    Misra, Ajay K.

    1988-01-01

    Chemical compatibility of several reinforcement materials with FeAl alloys within the concentration range 40 to 50 at pct Al have been analyzed from thermodynamic considerations at 1173 and 1273 K. The reinforcement materials considered in this study include carbides, borides, oxides, nitrides, and silicides. Although several chemically compatible reinforcement materials are identified, the coefficients of thermal expansion for none of these materials match closely with that of FeAl alloys and this might pose serious problems in the design of composite systems based on FeAl alloys.

  9. Highly transparent and conductive ZnO:Al thin films prepared by vacuum arc plasma evaporation

    NASA Astrophysics Data System (ADS)

    Miyata, Toshihiro; Minamino, Youhei; Ida, Satoshi; Minami, Tadatsugu

    2004-07-01

    A vacuum arc plasma evaporation (VAPE) method using both oxide fragments and gas sources as the source materials is demonstrated to be very effective for the preparation of multicomponent oxide thin films. Highly transparent and conductive Al-doped ZnO (AZO) thin films were prepared by the VAPE method using a ZnO fragment target and a gas source Al dopant, aluminum acethylacetonate (Al(C5H7O2)3) contained in a stainless steel vessel. The Al content in the AZO films was altered by controlling the partial pressure (or flow rate) of the Al dopant gas. High deposition rates as well as uniform distributions of resistivity and thickness on the substrate surface were obtained on large area glass substrates. A low resistivity on the order of 10-4 Ω cm and an average transmittance above 80% in the visible range were obtained in AZO thin films deposited on glass substrates. .

  10. A facile method for the preparation of bifunctional Mn:ZnS/ZnS/Fe3O4 magnetic and fluorescent nanocrystals

    PubMed Central

    Labiadh, Houcine; Ben Chaabane, Tahar; Sibille, Romain; Balan, Lavinia

    2015-01-01

    Summary Bifunctional magnetic and fluorescent core/shell/shell Mn:ZnS/ZnS/Fe3O4 nanocrystals were synthesized in a basic aqueous solution using 3-mercaptopropionic acid (MPA) as a capping ligand. The structural and optical properties of the heterostructures were characterized by X-ray diffraction (XRD), dynamic light scattering (DLS), transmission electron microscopy (TEM), UV–vis spectroscopy and photoluminescence (PL) spectroscopy. The PL spectra of Mn:ZnS/ZnS/Fe3O4 quantum dots (QDs) showed marked visible emission around 584 nm related to the 4T1 → 6A1 Mn2+ transition. The PL quantum yield (QY) and the remnant magnetization can be regulated by varying the thickness of the magnetic shell. The results showed that an increase in the thickness of the Fe3O4 magnetite layer around the Mn:ZnS/ZnS core reduced the PL QY but improved the magnetic properties of the composites. Nevertheless, a good compromise was achieved in order to maintain the dual modality of the nanocrystals, which may be promising candidates for various biological applications. PMID:26425426

  11. Investigation on thermo physical characteristics of ethylene glycol based Al:ZnO nanofluids

    NASA Astrophysics Data System (ADS)

    R, Kiruba.; George, Ritty; M, Gopalakrishnan.; A, Kingson Solomon Jeevaraj.

    2015-06-01

    The present work describes the experimental aspects of viscosity and thermal conductivity characteristics of nanofluids. Aluminium doped zinc oxide nanostructures were synthesized by chemical precipitation method. Ultrasonic technique is used to disperse the nanostructures in ethylene glycol. Structural and morphological properties of Al doped ZnO nanostructures are characterized using X-ray diffractometer and scanning electron microscopic technique. The effect of concentration and temperature on thermo-physical properties of Al/ZnO nanofluids is also investigated. The experimental results showed there is enhancement in thermal conductivity with rise in temperature which can be utilized for coolant application.

  12. Synthesis and optical properties of ZnAl2O4:Cr3+, Tb3+ powders

    NASA Astrophysics Data System (ADS)

    Thi Loan, Trinh; Thi Thuy, Nguyen; Long, Nguyen Ngoc

    2013-10-01

    ZnAl2O4:Cr3+, Tb3+ powders with different dopant contents have been synthesized by sol-gel method using the following precursors: zinc nitrate (Zn(NO3)2), aluminum nitrate (Al(NO3)3), terbium nitrate (Tb(NO3)3), chrome nitrate (Cr(NO3)3), and citric acid. The effect of the Cr3+, Tb3+ concentration and heat-treating temperature on structural and optical properties of the synthesized samples has been studied. International Workshop on Advanced Materials and Nanotechnology 2012 (IWAMN 2012).

  13. Investigation on thermo physical characteristics of ethylene glycol based Al:ZnO nanofluids

    SciTech Connect

    Kiruba, R. E-mail: drkingson@karunya.edu; George, Ritty; Gopalakrishnan, M.; Kingson Solomon Jeevaraj, A.

    2015-06-24

    The present work describes the experimental aspects of viscosity and thermal conductivity characteristics of nanofluids. Aluminium doped zinc oxide nanostructures were synthesized by chemical precipitation method. Ultrasonic technique is used to disperse the nanostructures in ethylene glycol. Structural and morphological properties of Al doped ZnO nanostructures are characterized using X-ray diffractometer and scanning electron microscopic technique. The effect of concentration and temperature on thermo-physical properties of Al/ZnO nanofluids is also investigated. The experimental results showed there is enhancement in thermal conductivity with rise in temperature which can be utilized for coolant application.

  14. Donnan membrane speciation of Al, Fe, trace metals and REEs in coastal lowland acid sulfate soil-impacted drainage waters.

    PubMed

    Jones, Adele M; Xue, Youjia; Kinsela, Andrew S; Wilcken, Klaus M; Collins, Richard N

    2016-03-15

    Donnan dialysis has been applied to forty filtered drainage waters collected from five coastal lowland acid sulfate soil (CLASS) catchments across north-eastern NSW, Australia. Despite having average pH values<3.9, 78 and 58% of Al and total Fe, respectively, were present as neutral or negatively-charged species. Complementary isotope dilution experiments with (55)Fe and (26)Al demonstrated that only soluble (i.e. no colloidal) species were present. Trivalent rare earth elements (REEs) were also mainly present (>70%) as negatively-charged complexes. In contrast, the speciation of the divalent trace metals Co, Mn, Ni and Zn was dominated by positively-charged complexes and was strongly correlated with the alkaline earth metals Ca and Mg. Thermodynamic equilibrium speciation calculations indicated that natural organic matter (NOM) complexes dominated Fe(III) speciation in agreement with that obtained by Donnan dialysis. In the case of Fe(II), however, the free cation was predicted to dominate under thermodynamic equilibrium, whilst our results indicated that Fe(II) was mainly present as neutral or negatively-charged complexes (most likely with sulfate). For all other divalent metals thermodynamic equilibrium speciation calculations agreed well with the Donnan dialysis results. The proportion of Al and REEs predicted to be negatively-charged was also grossly underestimated, relative to the experimental results, highlighting possible inaccuracies in the stability constants developed for these trivalent Me(SO4)2(-) and/or Me-NOM complexes and difficulties in modeling complex environmental samples. These results will help improve metal mobility and toxicity models developed for CLASS-affected environments, and also demonstrate that Australian CLASS environments can discharge REEs at concentrations an order of magnitude greater than previously reported.

  15. Half-metallic ferromagnetism in Fe-doped Zn3P2 from first-principles calculations

    NASA Astrophysics Data System (ADS)

    Jaiganesh, G.; Jaya, S. Mathi

    2014-04-01

    Using the first-principles calculations based on the density functional theory, we have studied the magnetism and electronic structure of Fe-doped Zinc Phosphide (Zn3P2). Our results show that the half-metallic ground state and ferromagnetic stability for the small Fe concentrations considered in our study. The stability of the doped material has been studied by calculating the heat of formation and analyzing the minimum total energies in nonmagnetic and ferromagnetic phases. A large value of the magnetic moment is obtained from our calculations and our calculation suggests that the Fe-doped Zn3P2 may be a useful material in semiconductor spintronics.

  16. Ferromagnetism and suppression of metallic clusters in Fe implanted ZnO -- a phenomenon related to defects?

    SciTech Connect

    Arenholz, Elke; Zhou, S.; Potzger, K.; Talut, G.; Reuther, H.; Kuepper, K.; Grenzer, J.; Xu, Q.; Mucklich, A.; Helm, M.; Fassbender, J.; Arenholz, E.

    2008-03-12

    We investigated ZnO(0001) single crystals annealed in high vacuum with respect to their magnetic properties and cluster formation tendency after implant-doping with Fe. While metallic Fe cluster formation is suppressed, no evidence for the relevance of the Fe magnetic moment to the observed ferromagnetism was found. The latter along with the cluster suppression is discussed with respect to defects in the ZnO host matrix, since the crystalline quality of the substrates was lowered due to the preparation as observed by x-ray diffraction.

  17. 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, Fe2C (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

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

    SciTech Connect

    Lu, Yongwu; Yu, Fei; Hu, Jin; Liu, Jian

    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. Cu (111) was the active site for mixed alcohols synthesis, Fe2C (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.

  19. Al-doped ZnO contact to CdZnTe for x- and gamma-ray detector applications

    NASA Astrophysics Data System (ADS)

    Roy, U. N.; Camarda, G. S.; Cui, Y.; Gul, R.; Hossain, A.; Yang, G.; Mundle, R. M.; Pradhan, A. K.; James, R. B.

    2016-06-01

    The poor adhesion of common metals to CdZnTe (CZT)/CdTe surfaces has been a long-standing challenge for radiation detector applications. In this present work, we explored the use of an alternative electrode, viz., Al-doped ZnO (AZO) as a replacement to common metallic contacts. ZnO offers several advantages over the latter, such as having a higher hardness, a close match of the coefficients of thermal expansion for CZT and ZnO, and better adhesion to the surface of CZT due to the contact layer being an oxide. The AZO/CZT contact was investigated via high spatial-resolution X-ray response mapping for a planar detector at the micron level. The durability of the device was investigated by acquiring I-V measurements over an 18-month period, and good long-term stability was observed. We have demonstrated that the AZO/CZT/AZO virtual-Frisch-grid device performs fairly well, with comparable or better characteristics than that for the same detector fabricated with gold contacts.

  20. Enhanced density control of Al:ZnO nanowires via one-by-one coupling of nanowires and pyramids.

    PubMed

    Kuo, Chien-Lin; Liang, Yu-Han; Huang, Jun-Hang; Wang, Ruey-Chi; Huang, Jow-Lay; Chang, Hong-Ren; Liu, Chuan-Pu

    2010-02-01

    Al doped ZnO nanowire arrays with controlled growth densities were fabricated on silicon without using catalysts via sputtering followed by thermal chemical vapor deposition (CVD). Scanning electron microscopy and high-resolution transmission electron microscopy results show that the Al:ZnO single-crystalline nanowires synthesized by CVD prefer growing epitaxially on the tips of the ZnO pyramids pre-synthesized by sputtering with the c-axis perpendicular to the substrate. Consequently, the densities of the as-grown Al:ZnO nanowires were controllable by changing the particle densities of the pre-grown ZnO seed layers. The Al concentration of the Al:ZnO nanowires were measured to be around 2.63 at.% by electron energy loss spectrum. Field-emission measurements show the turn-on fields of the Al:ZnO nanowire arrays with controllable area densities are tunable. Room-temperature cathodoluminescence spectra of the Al:ZnO nanowires show relatively strong and sharp ultraviolet emissions centered at 383 nm and broad green emissions at around 497 nm. This work provides a simple method to control the field emission and luminescence densities of Al doped ZnO nanowire arrays, which also shows good potential for developing nano-pixel optical devices.

  1. Preparation of Al-Cu-Fe-(Sn,Si) quasicrystalline bulks by laser multilayer cladding

    NASA Astrophysics Data System (ADS)

    Feng, Li-ping; Fleury, Eric; Zhang, Guo-sheng

    2012-05-01

    (Al65Cu20Fe15)100- x Sn x ( x=0, 12, 20, 30) and Al57Si10Cu18Fe15 powders were cladded on a medium carbon steel (45# steel) substrate by laser multilayer cladding, respectively. The phases and properties of the produced quasicrystalline bulks were investigated. It was found that the main phases in the Al65Cu20Fe15 sample were crystalline λ-Al13Fe4 and icosahedral quasicrystal together with a small volume fraction of θ-Al2Cu phase. The volume fraction of icosahedral phase decreased as the Sn content in the (Al65Cu20Fe15)100- x Sn x samples increased owing to the formation of β-CuSn phase. The increase of Sn content improved the brittleness of the quasicrystal samples. The morphology of the solidification microstructure in the Al57Si10Cu18Fe15 sample changed from elongated shape to spherical shape due to the addition of Si. The nanohardness of the laser multilayer cladded quasicrystal samples was equal to that of the as-cast sample prepared by vacuum quenching. In terms of hardness, the laser cladded Al57Si10Cu18Fe15 quasicrystalline alloy has the highest value among all the investigated samples.

  2. Determination of Serum Trace Elements (Zn, Cu, and Fe) in Pakistani Patients with Rheumatoid Arthritis.

    PubMed

    Ullah, Zia; Ullah, Muhammad Ikram; Hussain, Shabbir; Kaul, Haiba; Lone, Khalid P

    2017-01-01

    Rheumatoid arthritis (RA) is a chronic autoimmune inflammatory disease, which mainly involves the joints. RA is prevalent worldwide with increasing prevalence in elderly people. The mechanism of RA pathogenesis is still undefined, and it is interplaying between genetic susceptibility and environmental factors. Although risk factors for RA are not fully established, various studies have focused on the role of trace elements in association with RA. Trace elements act as co-factors for most of the enzymes, and their deficiency is associated with many untoward effects on human health. The homeostatic alterations in the metabolism of trace elements may partly be due to inflammatory response in RA. The objective of the present study was to determine the serum concentrations and correlation of zinc, copper, and iron in RA patients and healthy controls. The study comprised of 61 RA patients and 61 age- and sex-related healthy individuals of Pakistani population. Serum levels of Zn, Cu, and Fe were measured in all the participants by atomic absorption spectrophotometer. Serum Zn and Fe were significantly reduced in the RA patients than those in the healthy controls. Serum Cu concentrations were found elevated in the RA patients. Correlation studies of trace elements determine that there was negative correlation between Zn and Cu in the RA patients and no correlation in the control group. It is very important to explore the deficiency of essential trace metals in biological samples of the RA patients in different populations which may be helpful for diagnosis and supplementary management of rheumatoid arthritis patients.

  3. Activities of the components in a spinel solid solution of the Fe-Al-O system

    NASA Astrophysics Data System (ADS)

    Lykasov, A. A.; Kimyashev, A. A.

    2011-09-01

    The conditions of the equilibrium between the Fe3O4-FeAl2O4 solution and wustite are determined by measuring the EMF of galvanic cells containing a solid electrolyte, and the activities of the components in the Fe3O4-FeAl2O4 solution are calculated by treating the results of the experiment on the equilibrium between the spinel solution and wustite. Their properties are found to be different from those of ideal solutions at temperatures of 1000-1300 K. A significant positive deviation from the Raoult's law is believed to indicate the tendency of the solution to decompose. The experimental data are treated in terms of the theory of regular solutions, assuming the energy of mixing to be a function of temperature only. The critical temperature of decomposition for the Fe3O4-FeAl2O4 solution is found to be 1084 K.

  4. Experiments of eliminating the destructive effects of excessive Fe inclusions for Al secondary products

    NASA Astrophysics Data System (ADS)

    Sun, D. Q.; Dai, G. H.; Geng, F.; Yang, K.

    2017-02-01

    Excessive Fe content in Al alloys caused the serious decline of mechanical properties, such as the ductility and impact toughness. Carried out the experiments of eliminating the destructive effects of excessive Fe content by flux-adding technology, which including removing a part of Fe content from Al scrap melt and modifying the morphology of Fe rich precipitates. The experimental results showed that, the ratio of removing Fe element was above 20%, and the morphology of Fe rich precipitates changed from Lamellar to bulk or lath precipitations under the process parameters: the fluxing-agents composed of borax, and MnCl2 (mixed by mass ratio of 1:1), and the adding amount of fluxing-agents was about 1.5%; thrown the fluxing-agents into the Al scrap melt by powder injection process and kept for 30 min.

  5. Influence of Be and Al on the magnetostrictive behavior of FeGa alloys

    SciTech Connect

    Mungsantisuk, Pinai; Corson, Robert P.; Guruswamy, Sivaraman

    2005-12-15

    The rare-earth-free body-centered-cubic FeGa-based alloys have an attractive combination of large low-field magnetostriction at room temperature, good mechanical properties, low hysteresis, and relatively low cost for use in sensor and actuator devices. This paper examines the influence of partially substituting Ga in FeGa alloys with Be and Al on their magnetostrictive behavior. Magnetic and magnetostrictive properties of the various ternary FeGaAl and FeGaBe alloys prepared by directional growth process are presented. It is shown that substitution of Ga with Al and Be can be made in FeGa alloys in certain composition ranges without a significant reduction in magnetostriction. Minimal reductions in magnetostriction when Ga is partially substituted by smaller Be or larger Al atoms in certain composition ranges indicate that local electronic environments are more important and that the effects of Ga and Be are additive.

  6. Point defect concentrations and solid solution hardening in NiAl with Fe additions

    SciTech Connect

    Pike, L.M.; Chang, Y.A.; Liu, C.T.

    1997-08-01

    The solid solution hardening behavior exhibited when Fe is added to NiAl is investigated. This is an interesting problem to consider since the ternary Fe additions may choose to occupy either the Ni or the Al sublattice, affecting the hardness at differing rates. Moreover, the addition of Fe may affect the concentrations of other point defects such as vacancies and Ni anti-sites. As a result, unusual effects ranging from rapid hardening to solid solution softening are observed. Alloys with varying amounts of Fe were prepared in Ni-rich (40 at. % Al) and stoichiometric (50 at. % Al) compositions. Vacancy concentrations were measured using lattice parameter and density measurements. The site occupancy of Fe was determined using ALCHEMI. Using these two techniques the site occupancies of all species could be uniquely determined. Significant differences in the defect concentrations as well as the hardening behavior were encountered between the Ni-rich and stoichiometric regimes.

  7. Influence of Be and Al on the magnetostrictive behavior of FeGa alloys

    NASA Astrophysics Data System (ADS)

    Mungsantisuk, Pinai; Corson, Robert P.; Guruswamy, Sivaraman

    2005-12-01

    The rare-earth-free body-centered-cubic FeGa-based alloys have an attractive combination of large low-field magnetostriction at room temperature, good mechanical properties, low hysteresis, and relatively low cost for use in sensor and actuator devices. This paper examines the influence of partially substituting Ga in FeGa alloys with Be and Al on their magnetostrictive behavior. Magnetic and magnetostrictive properties of the various ternary FeGaAl and FeGaBe alloys prepared by directional growth process are presented. It is shown that substitution of Ga with Al and Be can be made in FeGa alloys in certain composition ranges without a significant reduction in magnetostriction. Minimal reductions in magnetostriction when Ga is partially substituted by smaller Be or larger Al atoms in certain composition ranges indicate that local electronic environments are more important and that the effects of Ga and Be are additive.

  8. Slow-release formulations of the herbicide picloram by using Fe-Al pillared montmorillonite.

    PubMed

    Marco-Brown, Jose L; Undabeytia, Tomás; Torres Sánchez, Rosa M; Dos Santos Afonso, María

    2017-04-01

    Slow-release formulations of the herbicide picloram (PCM, 4-amino-3,5,6-trichloropyridine-2-carboxylic acid) were designed based on its adsorption on pillared clays (pillared clays (PILCs)) for reducing the water-polluting risk derived from its use in conventional formulations. Fe-Al PILCs were synthesized by the reaction of Na(+)-montmorillonite (SWy-2) with base-hydrolyzed solutions of Fe and Al. The Fe/(Fe + Al) ratios used were 0.15 and 0.50. The PCM adsorption isotherms on Fe-Al PILCs were well fitted to Langmuir and Freundlich models. The PCM adsorption capacity depended on the Fe content in the PILCs. Slow-release formulations were prepared by enhanced adsorption of the herbicide from PCM-cyclodextrin (CD) complexes in solution. CDs were able to enhance up to 2.5-fold the solubility of PCM by the formation of inclusion complexes where the ring moiety of the herbicide was partially trapped within the CD cavity. Competitive adsorption of anions such as sulfate, phosphate, and chloride as well as the FTIR analysis of PCM-PILC complexes provided evidence of formation of inner sphere complexes of PCM-CD on Fe-Al PILCs. Release of the herbicide in a sandy soil was lower from Fe-Al PILC formulations relative to a PCM commercial formulation.

  9. Structural defects and photoluminescence studies of sol-gel prepared ZnO and Al-doped ZnO films

    NASA Astrophysics Data System (ADS)

    Sandeep, K. M.; Bhat, Shreesha; Dharmaprakash, S. M.

    2016-11-01

    ZnO and Al-doped ZnO (AZO) films were synthesized using sol-gel spin-coating method. The powder XRD analysis revealed the stress relaxation mechanism upon Al doping in ZnO film. The reduction in the imaginary part of the dielectric constant and suppression of deep level acceptor type octahedral oxygen interstitial defects account for the reduction in carrier concentration in AZO with respect to ZnO. Electrical conductivity measurements and grain boundary conduction model are used to quantify the carrier concentration. From the Commission Internationale d'Eclairge diagram of ZnO and AZO, color parameters like dominant wavelength, color purity and luminosity are determined and reported for the first time. The prepared ZnO and AZO films show considerable blue emission. These films can be used for white light generation.

  10. Transparent conductive Al-doped ZnO thin films grown at room temperature

    SciTech Connect

    Wang Yuping; Lu Jianguo; Bie Xun; Gong Li; Li Xiang; Song Da; Zhao Xuyang; Ye Wenyi; Ye Zhizhen

    2011-05-15

    Aluminum-doped ZnO (ZnO:Al, AZO) thin films were prepared on glass substrates by dc reactive magnetron sputtering from a Zn-Al alloy target at room temperature. The effects of the Ar-to-O{sub 2} partial pressure ratios on the structural, electrical, and optical properties of AZO films were studied in detail. AZO films grown using 100:4 to 100:8 Ar-to-O{sub 2} ratio result in acceptable quality films with c-axis orientated crystals, uniform grains, 10{sup -3} {Omega} cm resistivity, greater than 10{sup 20} cm{sup -3} electron concentration, and high transmittance, 90%, in the visible region. The lowest resistivity of 4.11x10{sup -3} {Omega} cm was obtained under the Ar-to-O{sub 2} partial pressure ratio of 100:4. A relatively strong UV emission at {approx}3.26 eV was observed in the room-temperature photoluminescence spectrum. X-ray photoelectron spectroscopy analysis confirmed that Al was introduced into ZnO and substitutes for Zn and doped the film n-type.

  11. A Pyrolitic Lower Mantle with (Mg,Fe3+)(Si,Al3+)O3 Bridgmanite

    NASA Astrophysics Data System (ADS)

    Wang, X.; Tsuchiya, T.

    2014-12-01

    To better understand the Earth's lower mantle (LM), thermodynamic properties (TDPs) of LM minerals should be illustrated clearly. We have so far reported the TDPs of Fe (and Al)-bearing MgO, MgSiO3 bridgmanite (Br) and post bridgmanite [1-5] by using the internally consistent LSDA+U method and the lattice dynamics method. In this work, two spin states, the high (HS) and low spin (LS) state, and several possible distribution configurations are considered in the LM pressure range. For Fe incorporated in Br, only Fe3+ at the Si site undergoes a HS to LS transition. However, this is suppressed by Al incorporation, because Al3+ prefers the Si site and attracts HS Fe3+ at the adjacent Mg site forming Fe3+-Al3+ pair. Br with geophysically relevant 6.25 mol% Fe2+ or Fe3+-Al3+ pair is found vibrationally stable. Incorporation of these elements increases the Br volume a little but gives marginal effects on the TDPs. Simulated densities, adiabatic bulk moduli, and bulk sound velocities of possible LM mineral aggregations show that a composition close to pyrolite with (Mg,Fe3+)(Si,Al3+)O3 Br is accountable for the reference Earth model, while Fe2+-bearing Br instead gives unignorable disagreements in deeper part. Neither Si-richer nor Si-poorer composition improves the disagreements. This indicates that Fe in LM bridgmanite should predominantly be ferric acquiring the HS state, and pyrolitic composition with (Mg,Fe3+)(Si,Al3+)O3 Br is a reasonable LM model. References:[1] A. Metsue, and T. Tsuchiya, J. Geophys. Res. 116, B08207 (2011). [2] A. Metsue, and T. Tsuchiya, Geophys. J. Int. 190, 310 (2012). [3] H. Fukui, T. Tsuchiya, and A. Q. R. Baron, J. Geophys. Res. 117, B12202 (2012). [4] T. Tsuchiya, and X. Wang, J. Geophys. 118, 83 (2013). [5] X. Wang, and T. Tsuchiya, under reviewing.

  12. Synthesis of nanosized (Li0.5xFe0.5xZn1-x)Fe2O4 particles and magnetic properties

    NASA Astrophysics Data System (ADS)

    Gee, S. H.; Hong, Y. K.; Park, M. H.; Erickson, D. W.; Lamb, P. J.; Sur, J. C.

    2002-05-01

    In an attempt to synthesize nanosized (Li0.5xFe0.5xZn1-x)Fe2O4 (0⩽x⩽1) particles with high magnetic saturation and low coercivity, the energetic ball milling technique was employed. LiCO3, α-Fe2O3, and ZnO powders were used as starting materials. The ball milled, partially crystallized lithium zinc ferrite starts to crystallize at about 600 °C. This is much lower than the temperature of 1000 °C, which is used in conventional methods. Particle size of lithium zinc ferrite was in the range of 20 to 50 nm. Regardless of the annealing temperature, the saturation magnetization increases with increasing x and reaches the maximum (about 80 emu/g) at x=0.7 [(Li0.35Fe0.35Zn0.3)Fe2O4], followed by a decrease to 60 emu/g for x=1 [(Li0.5Fe0.5)Fe2O4]. On the other hand, the coercivity of x=0.7 composition decreases with increasing annealing temperatures. Saturation magnetization and low coercivity for x=0.7 annealed at various temperatures are discussed in terms of site occupation.

  13. Development of ODS FeCrAl alloys for accident-tolerant fuel cladding

    SciTech Connect

    Dryepondt, Sebastien N.; Hoelzer, David T.; Pint, Bruce A.; Unocic, Kinga A.

    2015-09-18

    FeCrAl alloys are prime candidates for accident-tolerant fuel cladding due to their excellent oxidation resistance up to 1400 C and good mechanical properties at intermediate temperature. Former commercial oxide dispersion strengthened (ODS) FeCrAl alloys such as PM2000 exhibit significantly better tensile strength than wrought FeCrAl alloys, which would alloy for the fabrication of a very thin (~250 m) ODS FeCrAl cladding and limit the neutronic penalty from the replacement of Zr-based alloys by Fe-based alloys. Several Fe-12-Cr-5Al ODS alloys where therefore fabricated by ball milling FeCrAl powders with Y2O3 and additional oxides such as TiO2 or ZrO2. The new Fe-12Cr-5Al ODS alloys showed excellent tensile strength up to 800 C but limited ductility. Good oxidation resistance in steam at 1200 and 1400 C was observed except for one ODS FeCrAl alloy containing Ti. Rolling trials were conducted at 300, 600 C and 800 C to simulate the fabrication of thin tube cladding and a plate thickness of ~0.6mm was reached before the formation of multiple edge cracks. Hardness measurements at different stages of the rolling process, before and after annealing for 1h at 1000 C, showed that a thinner plate thickness could likely be achieved by using a multi-step approach combining warm rolling and high temperature annealing. Finally, new Fe-10-12Cr-5.5-6Al-Z gas atomized powders have been purchased to fabricate the second generation of low-Cr ODS FeCrAl alloys. The main goals are to assess the effect of O, C, N and Zr contents on the ODS FeCrAl microstructure and mechanical properties, and to optimize the fabrication process to improve the ductility of the 2nd gen ODS FeCrAl while maintaining good mechanical strength and oxidation resistance.

  14. Electronic structure and soft magnetic properties of Se/FeSiAl (110) films

    NASA Astrophysics Data System (ADS)

    Schwindt, V. Cardoso; Ardenghi, J. S.; Bechthold, P.; Juan, A.; Batic, B. Setina; Jenko, M.; González, E. A.; Jasen, P. V.

    2015-11-01

    The Se adsorption at different coverages on DO3 FeSiAl(110) surface is studied using density functional theory (DFT). Se adsorption is favorable in almost all surface high-symmetry sites, except for the bridge site formed by Fe-Si atoms. The most stable is a hollow site formed by four Fe atoms with adsorption energy of -5.30 eV. When the coverages increase, the energies decrease in the case of hollow sites. The surface present a reconstruction after Se adsorption, being the most important at 1/2 ML. The local magnetic moment for Fe atoms increase for the type A (all nearst neighbours (nn) are Fe atoms) and decrease for the type B (nn are Fe, Si and Al atoms). The most affected metal orbitals are Fe 4s and 4p. In the case of the hollow site the surface Fe-Fe bond is weakened after Se adsorption. A Fe-Se bond is developed at all coverages in both sites being the most important on top (dFe-Se = 2.23 Å, OP: 0.774 at 1/4 ML). The first and second layer Fe-Fe bond increase at 1/4 ML and decrease at 1/2 and 1 ML. Small Se-Se bonding interaction appear at 1/2 ML and increase noticeable for 1 ML. For the top site, the Se-Se bond appears at all coverage. The Fe-Fe surface bonds also decrease its strength with respect to the clean surface at all coverage. The first and second layer Fe-Fe bond increase at all coverage.

  15. 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.

  16. Structural, Optical, and Magnetic Properties of Zn-Doped CoFe2O4 Nanoparticles

    NASA Astrophysics Data System (ADS)

    Tatarchuk, Tetiana; Bououdina, Mohamed; Macyk, Wojciech; Shyichuk, Olexander; Paliychuk, Natalia; Yaremiy, Ivan; Al-Najar, Basma; Pacia, Michał

    2017-02-01

    The effect of Zn-doping in CoFe2O4 nanoparticles (NPs) through chemical co-precipitation route was investigated in term of structural, optical, and magnetic properties. Both XRD and FTIR analyses confirm the formation of cubic spinel phase, where the crystallite size changes with Zn content from 46 to 77 nm. The Scherrer method, Williamson-Hall (W-H) analysis, and size-strain plot method (SSPM) were used to study of crystallite sizes. The TEM results were in good agreement with the results of the SSP method. SEM observations reveal agglomeration of fine spherical-like particles. The optical band gap energy determined from diffuse reflectance spectroscopy (DRS) varies increases from 1.17 to 1.3 eV. Magnetization field loops reveal a ferromagnetic behavior with lower hysteresis loop for higher Zn content. The magnetic properties are remarkably influenced with Zn doping; saturation magnetization (Ms) increases then decreases while both coercivity (HC) and remanent magnetization (Mr) decrease continuously, which was associated with preferential site occupancy and the change in particle size.

  17. Composition dependence of the electronic properties of Al-Cu-Fe and Al-Cu-Ru-Si semimetallic quasicrystals

    NASA Astrophysics Data System (ADS)

    Pierce, F. S.; Bancel, P. A.; Biggs, B. D.; Guo, Q.; Poon, S. J.

    1993-03-01

    Electronic transport properties and specific heats of ordered icosahedral phase alloys in the Al-Cu-Ru-Si and Al-Cu-Fe systems are examined, and comparison with high-quality rhombohedral (3/2) approximant phase samples of Al-Cu-Fe is made. Strong temperature dependence and sensitivity to composition changes of these properties are observed. The similarity of transport properties between the icosahedral (i) and rhombohedral (r) phases of Al62.5Cu26.5Fe11 is noted. The results can be qualitatively interpreted in terms of band structure. There appears to be sufficient evidence for a rapidly varying conductivity spectrum σ(E) in the ordered i phases. However, important questions concerning the physics of these semimetallic quasicrystals remain to be answered.

  18. Quantum many-body intermetallics: Phase stability of Fe3Al and small-gap formation in Fe2VAl

    NASA Astrophysics Data System (ADS)

    Kristanovski, Oleg; Richter, Raphael; Krivenko, Igor; Lichtenstein, Alexander I.; Lechermann, Frank

    2017-01-01

    Various intermetallic compounds harbor subtle electronic correlation effects. To elucidate this fact for the Fe-Al system, we perform a realistic many-body investigation based on a combination of density functional theory with dynamical mean-field theory in a charge self-consistent manner. A better characterization and understanding of the phase stability of bcc-based D 03-Fe3Al through an improved description of the correlated charge density and the magnetic energy is achieved. Upon replacement of one Fe sublattice with V, the Heusler compound Fe2VAl is realized, known to display bad-metal behavior and increased specific heat. Here we document a charge-gap opening at low temperatures in line with previous experimental work. The gap structure does not match conventional band theory and is reminiscent of (pseudo)gap characteristics in correlated oxides.

  19. Phase equilibria and structural investigations in the system Al-Fe-Si.

    PubMed

    Marker, Martin C J; Skolyszewska-Kühberger, Barbara; Effenberger, Herta S; Schmetterer, Clemens; Richter, Klaus W

    2011-12-01

    The Al-Fe-Si system was studied for an isothermal section at 800 °C in the Al-rich part and at 900 °C in the Fe-rich part, and for half a dozen vertical sections at 27, 35, 40, 50 and 60 at.% Fe and 5 at.% Al. Optical microscopy and powder X-ray diffraction (XRD) was used for initial sample characterization, and Electron Probe Microanalysis (EPMA) and Scanning Electron Microscopy (SEM) of the annealed samples was used to determine the exact phase compositions. Thermal reactions were studied by Differential Thermal Analysis (DTA). Our experimental results are generally in good agreement with the most recent phase diagram versions of the system Al-Fe-Si. A new ternary high-temperature phase τ12 (cF96, NiTi2-type) with the composition Al48Fe36Si16 was discovered and was structurally characterized by means of single-crystal and powder XRD. The variation of the lattice parameters of the triclinic phase τ1 with the composition Al2+x Fe3Si3-x (-0.3 < x < 1.3) was studied in detail. For the binary phase FeSi2 only small solubility of Al was found in the low-temperature modification LT-FeSi2 (ζβ ) but significant solubility in the high-temperature modification HT-FeSi2 (ζα ) (8.5 at.% Al). It was found that the high-temperature modification of FeSi2 is stabilized down to much lower temperature in the ternary, confirming earlier literature suggestions on this issue. DTA results in four selected vertical sections were compared with calculated sections based on a recent CALPHAD assessment. The deviations of liquidus values are significant suggesting the need for improvement of the thermodynamic models.

  20. Phase separation in equiatomic AlCoCrFeNi high-entropy alloy.

    PubMed

    Manzoni, A; Daoud, H; Völkl, R; Glatzel, U; Wanderka, N

    2013-09-01

    The microstructure of the as-cast AlCoCrFeNi high entropy alloy has been investigated by transmission electron microscopy and atom probe tomography. The alloy shows a very pronounced microstructure with clearly distinguishable dendrites and interdendrites. In both regions a separation into an Al-Ni rich matrix and Cr-Fe-rich precipitates can be observed. Moreover, fluctuations of single elements within the Cr-Fe rich phase have been singled out by three dimensional atom probe measurements. The results of investigations are discussed in terms of spinodal decomposition of the alloying elements inside the Cr-Fe-rich precipitates.

  1. Light emission from an m-plane n-ZnO/p-Si heterojunction with an AlN interlayer

    NASA Astrophysics Data System (ADS)

    Chen, Chao; Wang, Ti; Xu, Yang; Ai, Zhiwei

    2017-01-01

    Nonpolar m-plane n-ZnO/p-Si heterojunction light-emitting devices with and without an AlN intermediate layer were fabricated by atomic layer deposition. The energy band alignment of the ZnO/AlN/Si heterostructure was studied using X-ray photoelectron spectroscopy, and the result confirmed the electron-blocking ability of the AlN interlayer. Electroluminescence results revealed that the devices with the AlN intermediate layer emit a quasi-white light. This work indicates that the AlN intermediate layer can effectively improve the performance of n-ZnO/p-Si heterojunction light-emitting devices.

  2. Fabrication of highly transparent Al-ion-implanted ZnO thin films by metal vapor vacuum arc method

    NASA Astrophysics Data System (ADS)

    Lee, Han; Sivashanmugan, Kundan; Kao, Chi-Yuan; Liao, Jiunn-Der

    2017-03-01

    In this study, we utilized the metal vapor vacuum arc technique to implant vaporized aluminum (Al) ions in zinc oxide (ZnO) thin films. By adjusting the ion implantation dose and operational parameters, the conductivity and optical properties of the ZnO thin film can be controlled. The electrical sheet resistance of Al-ion-implanted ZnO decreased from 3.02 × 107 to 3.03 × 104 Ω/sq, while the transparency of the film was mostly preserved (91.5% at a wavelength of 550 nm). The ZnO thin-film Young’s modulus significantly increased with increasing Al ion dose.

  3. Evidence for a Fe3+-rich pyrolitic lower mantle from (Al,Fe)-bearing bridgmanite elasticity data

    NASA Astrophysics Data System (ADS)

    Kurnosov, A.; Marquardt, H.; Frost, D. J.; Ballaran, T. Boffa; Ziberna, L.

    2017-03-01

    The chemical composition of Earth’s lower mantle can be constrained by combining seismological observations with mineral physics elasticity measurements. However, the lack of laboratory data for Earth’s most abundant mineral, (Mg,Fe,Al)(Al,Fe,Si)O3 bridgmanite (also known as silicate perovskite), has hampered any conclusive result. Here we report single-crystal elasticity data on (Al,Fe)-bearing bridgmanite (Mg0.9Fe0.1Si0.9Al0.1)O3 measured using high-pressure Brillouin spectroscopy and X-ray diffraction. Our measurements show that the elastic behaviour of (Al,Fe)-bearing bridgmanite is markedly different from the behaviour of the MgSiO3 endmember. We use our data to model seismic wave velocities in the top portion of the lower mantle, assuming a pyrolitic mantle composition and accounting for depth-dependent changes in iron partitioning between bridgmanite and ferropericlase. We find excellent agreement between our mineral physics predictions and the seismic Preliminary Reference Earth Model down to at least 1,200 kilometres depth, indicating chemical homogeneity of the upper and shallow lower mantle. A high Fe3+/Fe2+ ratio of about two in shallow-lower-mantle bridgmanite is required to match seismic data, implying the presence of metallic iron in an isochemical mantle. Our calculated velocities are in increasingly poor agreement with those of the lower mantle at depths greater than 1,200 kilometres, indicating either a change in bridgmanite cation ordering or a decrease in the ferric iron content of the lower mantle.

  4. First observation of sol-gel derived Al:CsZnO/CsZnO bilayer thin film for solar cells application

    NASA Astrophysics Data System (ADS)

    Ahmadi, Mehdi; Rashidi Dafeh, Sajjad; Alinazmabadi, Saeid

    2016-10-01

    In this research, we fabricated CsZnO and Al:CsZnO/CsZnO bilayer thin films grown by the spin-coating-assisted sol-gel method on ITO substrate. The influence of diverse velocity of spin-coating (500, 1000, 1500, 2000, 2500 and 3000RPM) and also annealing times (30, 60, 90, 120, 150 and 180min) on the characteristics of the ZnO thin film was examined. The samples were examined by X-ray diffraction, scanning electron microscopy, Uv-Vis spectrometer and conductivity measurement. With the optimization of the velocity of spin-coating (2500RPM) and annealing times (60min), we fabricated Al:CsZnO/CsZnO bilayer thin films with diverse dopant concentration. By comparing the effect of dopant concentration with different dopant ratio (0, 0.5, 1.0 and 2%), 0.5% of CsZnO and Al:CsZnO/CsZnO bilayer was found as the most effective doping level with the best conductivity properties among the selected doping concentrations.

  5. Magnetic and Magnetocaloric Properties of Zn1-x Co x Fe2O4 Nanoparticles

    NASA Astrophysics Data System (ADS)

    Phan, T. L.; Tran, N.; Kim, D. H.; Dang, N. T.; Manh, D. H.; Bach, T. N.; Liu, C. L.; Lee, B. W.

    2017-02-01

    We have prepared Zn1-x Co x Fe2O4 nanoparticles (NPs) by using a hydrothermal method, and then studied their structural and magnetic properties. The analyses of x-ray diffraction (XRD) patterns and Raman scattering spectra reveal that the samples crystallized mainly in a cubic-spinel structure with the lattice parameter a ≈ 8.4 Å. Averaged crystallite sizes determined from the XRD linewidth are about 16-22 nm, close to the particle sizes of 19-28 nm determined from scanning electron microscopy images. Magnetization measurements versus temperature, M(T), in the field H = 100 Oe indicate that the ferromagnetic-paramagnetic (FM-PM) phase transition temperature (T C) of Zn1-x Co x Fe2O4 NPs increases from 606 K for x = 0 to 823 K for x = 1. The features of the M(T) curves also indicate magnetic inhomogeneity in the samples, and their magnetic property is unstable versus temperature. This is ascribed to the changes in the structural characterization and/or concentration of magnetic ions situated at the A and B sites in the spinel lattice. At room temperature, we found that both the saturation magnetization (M s) and coercivity (H c) increase with increasing Co content, with M s = 59-70 emu/g and H c = 100-1100 Oe. These results reflect that the Co doping into ZnFe2O4 NPs greatly improves their magnetic property, making them more useful for practical applications. Additionally, we also assess magnetic interactions and the magnetocaloric effect in the samples based on analyzing initial magnetization data, M(H), recorded at temperatures around T C.

  6. Tailoring Energy Bandgap of Al Doped ZnO Thin Films Grown by Vacuum Thermal Evaporation Method.

    PubMed

    Vyas, Sumit; Singh, Shaivalini; Chakrabarti, P

    2015-12-01

    The paper presents the results of our experimental investigation pertaining to tailoring of energy bandgap and other associated characteristics of undoped and Al doped ZnO (AZO) thin film by varying the atomic concentration of Al in ZnO. Thin films of ZnO and ZnO doped with Al (1, 3, and 5 atomic percent (at.%)) were deposited on silicon substrate for structural characterization and on glass substrate for optical characterization. The dependence of structural and optical properties of Al doped ZnO on the atomic concentration of Al added to ZnO has been reported. On the basis of the experimental results an empirical formula has been proposed to calculate the energy bandgap of AZO theoretically in the range of 1 to 5 at.% of Al. The study revealed that AZO films are composed of smaller and larger number of grains as compared to pure ZnO counterpart and density of the grains was found to increase as the Al concentration increased (from 1 to 5 at.%). The transmittance in the visible region was greater than 90% and found to increase with increasing Al concentration up to 5 at.%. The optical bandgap was found to increase initially with increase in atomic concentration of Al concentration up to 3 at.% and decrease thereafter with increasing concentration of Al.

  7. Comparative X-ray diffraction and infrared spectroscopy study of Zn-Al layered double hydroxides: Vanadate vs nitrate

    NASA Astrophysics Data System (ADS)

    Salak, Andrei N.; Tedim, João; Kuznetsova, Alena I.; Ribeiro, José L.; Vieira, Luís G.; Zheludkevich, Mikhail L.; Ferreira, Mário G. S.

    2012-03-01

    Zn-Al layered double hydroxides (LDH) are promising as nanocontainers of corrosion inhibitors in self-healing corrosion protection coatings. Zn(2)Al-vanadate (Zn/Al = 2:1) is prepared by anion exchange from the parent composition Zn(2)Al-nitrate at pH ˜ 8. Crystal structure and vibrational spectra of both LDHs have been studied in comparison. Their interlayer distances are rather larger than those corresponding to the most compact arrangement of the intercalated anions. Nevertheless, no sign of a turbostratic disorder has been detected in these LDH. Based on the analysis of the spectroscopic data in combination with the XRD results, it has been shown that vanadate anion, which substitutes nitrate at the anion exchange, is pyrovanadate, VO74-. The observed disorder in the hydroxide layers in Zn(2)Al-V2O7 is likely to result from strong interactions between V5+ and Zn2+/Al3. Although Zn(2)Al-NO3 is less disordered than Zn(2)Al-V2O7, it exhibits no long-range order in arrangement of cations in the hydroxide layers.

  8. Effects of Fe3+ and Zn2+ on the structural and thermodynamic properties of a soybean ASR protein.

    PubMed

    Li, Ran-Hui; Liu, Guo-Bao; Wang, Hui; Zheng, Yi-Zhi

    2013-01-01

    Abscisic acid-, stress-, and ripening-induced (ASR) protein play important roles in protecting plants from abiotic stress. The functions of some ASR proteins are known to be modulated by binding to metal ions. In this study, we demonstrated that the non-tagged full-length soybean (Glycine max) ASR protein (GmASR) can bind Fe(3+), Ni(2+), Cu(2+), and Zn(2+). The direct binding properties of GmASR to Fe(3+) and Zn(2+) were further confirmed by intrinsic fluorescence assays. The GmASR protein was found to have three Fe(3+) binding sites but only two Zn(2+) binding sites. Natively disordered in aqueous solution, GmASR remained disordered in the presence of Fe(3+), but was found to aggregate in the presence of Zn(2+). The aggregated GmASR protein was partially resolubilized after Zn(2+) was chelated by EDTA. GmASR exhibited Fe(3+)-binding-dependent antioxidant activity in vitro. We speculate that GmASR thus protects against oxidation damage by buffering metal ions, thus alleviating metal toxicity in plant cells under stressed conditions.

  9. [Study on the chemical form and extraction rate of Cr, Cu, Fe, Mn, Ni and Zn in tea].

    PubMed

    Gao, G; Tao, R

    2000-07-01

    The content of Cr, Cu, Fe, Mn, Ni and Zn in the tea commonly available in China market were measured by inductivity coupled plasma-optical emission spectrometry (ICP-OES). The extraction rates of the six elements in tea leachate were measured. The solubilitied were 39.8% for Cr, 42.5% for Cu, 8.6% for Fe, 45.5% for Mn, 87.1% for Ni and 71.0% for Zn. The process of making tea leachate affects the elements extraction rates. The content of the microelements in tea leave extracts decreases gradually with the processing. About 80% of Cr, Cu, Mn, Ni and Zn and 60% of Fe were in the first infusion of tea. Moreover, the chemical forms of six elements were determined. The ratios of organic to inorganic forms were 0.33 for Cr, 0.022 for Cu, 0.18 for Fe, 0.002 for Mn, 0.01 for Ni and 0.18 for Zn. It is concluded that the six elements from the tea infusion extracted from 5 g tea are too little to meet the recommend dietary allowance (RDA). Therefore, tea is not a rich food source of Cr, Cu, Fe, Mn, Ni and Zn.

  10. Preparation of Modified Semi-Coke–Supported ZnFe2O4 Sorbent with the Assistance of Ultrasonic Irradiation

    PubMed Central

    Mi, Jie; Ren, Jun; Zhang, Yongyan

    2012-01-01

    Abstract Modified semi-coke (MSC) supported ZnFe2O4 was prepared under the condition of ultrasonic irradiation. Performance of the sorbents was tested using a fixed-bed reactor as a hot gas desulfurizer. The MSC support, the mass ratio of zinc ferrites to the support, calcination temperature, and the ultrasonic conditions of power and time all had influences on the structure and the breakthrough behavior of the sorbent. Ultrasonic irradiation can help to make ZnFe2O4 highly dispersed on MSC. ZnFe2O4/MSC had increased porosity and a larger specific surface area compared to unsupported ZnFe2O4. The sorbent exhibited a higher sulfur capacity at the optimum preparing conditions, where the mass ratio of ZnFe2O4 to MSC was 8:10, calcinated at 500°C, and the ultrasonic power and time was 900 W and 1.5 h, respectively. PMID:23133310

  11. Correlation between former alpha boundary growth kinetics and superplastic flow in Zn-22 pct Al

    SciTech Connect

    Yousefiani, A.; Mohamed, F.A.

    2000-01-01

    Former {alpha} boundaries (F{alpha}Bs) are residual grain boundaries that develop in Zn-22 pct Al during a heat treatment, which is normally applied to produce the fine structure necessary for micrograin superplasticity. They represent domains consisting of fine elongated {alpha} grains, which encompass groups of fine {alpha} (Al-rich) and {beta} (Zn-rich) phases (the superplastic microstructure). The results of a detailed investigation conducted on F{alpha}B growth kinetics in five grades of Zn-22 pct Al with various impurity contents reveal a direct correspondence between the level of impurities in the alloy and the characteristics associated with F{alpha}Bs (average size of F{alpha}Bs and the value of the F{alpha} B growth exponent). This correspondence, which, according to available evidence, is the result of impurity segregation at F{alpha}Bs, lends strong support to the interpretation of superplastic behavior at low stresses in terms of phenomena arising from boundary segregation. It is suggested that information on F{alpha}B growth kinetics in Zn-22 pct Al can be utilized to predict the low-stress superplastic characteristics of the alloy, such as the existence of region 1 or the occurrence of extensive cavitation.

  12. Electron capture processes in ZnS: The role of Al related and other donors

    NASA Astrophysics Data System (ADS)

    Przybylińska, H.; Godlewski, M.

    1986-12-01

    A transient electron spin resonance experiment shows that the Al-related donor in ZnS plays an insignificant role in electron-capture processes, which are dominated by a 35-meV native donor of unknown nature. The methods of determining effective capture cross sections of these donors are discussed.

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

    PubMed

    Çakar, Soner; Özacar, Mahmut

    2016-06-15

    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.

  14. 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.

  15. Thermodynamic analysis of chemical compatibility of several compounds with Fe-Cr-Al alloys

    NASA Technical Reports Server (NTRS)

    Misra, Ajay K.

    1993-01-01

    Chemical compatibility between Fe-19.8Cr-4.8Al (weight percent), which is the base composition for the commercial superalloy MA956, and several carbides, borides, nitrides, oxides, and silicides was analyzed from thermodynamic considerations. The effect of addition of minor alloying elements, such as Ti, Y, and Y2O3, to the Fe-Cr-Al alloy on chemical compatibility between the alloy and various compounds was also analyzed. Several chemically compatible compounds that can be potential reinforcement materials and/or interface coating materials for Fe-Cr-Al based composites were identified.

  16. Structural Disorder and Magnetism in the Spin-Gapless Semiconductor CoFeCrAl

    DTIC Science & Technology

    2016-08-24

    semiconductor CoFeCrAl into a half- metallic ferrimagnet and increases the half- metallic band gap by 0.12 eV. Compared CoFeCrAl, the moment of...magnets. However, Si addition improves the degree of Heusler ordering and changes the electronic structure from a SGS to a half- metal with increased...total moment per relaxed unit cell are 1.71 µB (I), –0.60 µB (II), and 1.05 µB (III). None of the disordered CoFeCrAl structures is energetically

  17. Emission Mössbauer spectroscopy study of fluence dependence of paramagnetic relaxation in Mn/Fe implanted ZnO

    NASA Astrophysics Data System (ADS)

    Masenda, H.; Geburt, S.; Bharuth-Ram, K.; Naidoo, D.; Gunnlaugsson, H. P.; Johnston, K.; Mantovan, R.; Mølholt, T. E.; Ncube, M.; Shayestehaminzadeh, S.; Gislason, H. P.; Langouche, G.; Ólafsson, S.; Ronning, C.

    2016-12-01

    Emission Mössbauer Spectroscopy following the implantation of radioactive precursor isotope 57Mn+ ( T 1/2= 1.5 min) into ZnO single crystals at ISOLDE/CERN shows that a large fraction of 57Fe atoms produced in the 57Mn beta decay is created as paramagnetic Fe3+ with relatively long spin-lattice relaxation times. Here we report on ZnO pre-implanted with 56Fe to fluences of 2×1013, 5×10 13 and 8 × 1013 ions/cm2 in order to investigate the dependence of the paramagnetic relaxation rate of Fe3+ on fluence. The spectra are dominated by magnetic features displaying paramagnetic relaxation effects. The extracted spin-lattice relaxation rates show a slight increase with increasing ion fluence at corresponding temperatures and the area fraction of Fe3+ at room temperature reaches a maximum contribution of 80(3)% in the studied fluence range.

  18. Microwave properties of RF- sputtered ZnFe{sub 2}O{sub 4} thin films

    SciTech Connect

    Garg, T. Kulkarni, A. R.; Venkataramani, N.; Sahu, B. N.; Prasad, Shiva

    2014-04-24

    In this work, RF- magnetron sputtering technique has been employed to deposit nanocrystalline ZnFe{sub 2}O{sub 4} thin films at room temperature. The as grown films were ex-situ annealed in air for 2 h at temperatures from 150°C to 650°C. X-ray diffraction, vibrating sample magnetometer and ferromagnetic resonance were used to analyze the phase formation, magnetic properties and microwave properties respectively. From the hysteresis loops and ferromagnetic resonance spectra taken at room temperature, a systematic study on the effect of O{sub 2} plasma on microwave properties with respect to processing temperature has been carried out.

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

    DTIC Science & Technology

    2014-03-01

    minimum pulsewidth of 64 ns Full- Width Half-Maximum. The pulse energy and peak power were >600 nJ and 8.3 W, respectively. The average output power was...switched Fe:ZnSe laser with PRFs as high as 867 k H z with pulse widths as small as 56 ns. II. APPARATUS Thermally-activated non-radiative processes...a corresponding minimum pulsewidth of 64 ns Full- Width Half-Maximum. The pulse energy and peak power were >600 nJ and 8.3 W, respectively. The

  20. Electron transport in Al-Cu co-doped ZnO thin films

    NASA Astrophysics Data System (ADS)

    Serin, T.; Atilgan, A.; Kara, I.; Yildiz, A.

    2017-03-01

    To investigate the influence of varying Al content on structural, optical, and electrical properties of ZnO thin films, Al-Cu co-doped ZnO thin films with fixed Cu content at 1 wt. % and different Al contents (1, 3, and 5 wt. %) were successfully synthesized on glass substrates using a sol-gel process. The results indicated that the varying Al content affects not only the grain size and band gap but also the electrical conductivity of the films, and a linear relationship was found between the band gap and strain values of the films. The temperature-dependent electrical conductivity data of the films demonstrated that electron transport was mainly controlled by the grain boundaries at intermediate and high temperatures, whereas it was governed by Mott-variable range hopping at low temperatures. Additionally, 3 wt. % Al content improved the electrical conductivity of Al-Cu co-doped ZnO by lowering the trap density and enhancing the hopping probability.

  1. Field dependence of the dynamic properties of colloidal suspensions of Mn 0.66Zn 0.34Fe 2O 4 and Ni 0.5Zn 0.5Fe 2O 4 particles

    NASA Astrophysics Data System (ADS)

    Fannin, P. C.; Charles, S. W.; Dormann, J. L.

    1999-07-01

    Results of the magnetic field dependence of the complex susceptibility, of colloidal suspensions of Mn 0.66Zn 0.34Fe 2O 4 and Ni 0.5Zn 0.5Fe 2O 4 particles in a polarising magnetic field, H, covering the range 0-116 kA m -1 are presented. Ferromagnetic resonance is observed for both samples and from plots of the dependence of the resonant frequency fres on polarising field, average values of anisotropy field, H¯A, and anisotropy constant, K¯, are determined. In the case of the Ni 0.5Zn 0.5Fe 20 4 sample the variation in the ferromagnetic linewidth as a function of increasing polarising field shows a steady monotonic increase in contrast to that of the manganese zinc ferrite sample. This effect is attributed to the influence of the polarising field on the local canted structure.

  2. Magnetic properties of Zn-substituted Co-Ge-Fe-O ferrites near the dilution limit

    NASA Astrophysics Data System (ADS)

    Nogués, J.; Puig, T.; Jotania, R. B.; Upadhyay, R. V.; Kulkarni, R. G.; Rao, K. V.

    1991-09-01

    The magnetic properties of Co-doped spinel system Co 1.4- xZn xGe 0.4Fe 1.2O 4 ( x = 0.4, 0.5, 0.6) have been investigated through Mössbauer spectroscopy, ac susceptibility and dc-magnetization measurements. In these alloys the A-sublattice has been diluted to below the percolation threshold and hence ferrimagnetic long range order cannot be retained. The observation of the (i) 57Fe Mössbauer data, (ii) broad peaks in the real component of the ac-susceptibility χ( T), (iii) similar temperature dependencies for χ' and χ″ and (iv) irreversibility of magnetization during field cooling leads to a picture of local spin canting structure in this system. At high magnetic fields these systems behave as highly anisotropic ferrimagnets.

  3. Directional solidification of Al-8 wt. %Fe alloy under high magnetic field gradient

    NASA Astrophysics Data System (ADS)

    Wu, Mingxu; Liu, Tie; Dong, Meng; Sun, Jinmei; Dong, Shulin; Wang, Qiang

    2017-02-01

    We investigated applying a magnetic field (up to 6 T) during directional solidification of a hypereutectic Al-8 wt. %Fe alloy, finding that it dramatically affected the final microstructure. A eutectic area appeared at the top of the samples, and as the magnetic flux density increased, the eutectic area clearly enlarged. In addition, the Al3Fe phase was twisted and fractured, and some phases aggregated and distributed randomly in the samples. We also investigated the volume fraction distribution of the Al3Fe phase, revealing that applying the magnetic field during solidification caused dramatic disorder in the solute and phase distributions. The magnetic force induced by the interaction between the magnetic field gradient and the magnetic materials appeared to be the main reason not only for the occurrence and enlargement of the eutectic area but also for the movement of Fe-enriched zones during directional solidification. Otherwise, the deformation and fracture of the Al3Fe phase, the morphological instability in the interface between the eutectic area and the Al3Fe phase, and the random distribution of the aggregated Al3Fe phase appeared to come from the thermoelectric magnetic force/thermoelectric magnetic convection under the magnetic field.

  4. Tribological Properties of the Fe-Al-Cr Alloyed Layer by Double Glow Plasma Surface Metallurgy

    NASA Astrophysics Data System (ADS)

    Luo, Xixi; Yao, Zhengjun; Zhang, Pingze; Zhou, Keyin; Wang, Zhangzhong

    2016-09-01

    A Fe-Al-Cr alloyed layer was deposited onto the surface of Q235 low-carbon steel via double glow plasma surface metallurgy (DGPSM) to improve the steel's wear resistance. After the DGPSM treatment, the Fe-Al-Cr alloyed layer grown on the Q235 low-carbon steel was homogeneous and compact and had a thickness of 25 µm. The layer was found to be metallurgically adhered to the substrate. The frictional coefficient and specific wear rate of the sample with a Fe-Al-Cr alloyed layer (treated sample) were both lower than those of the bare substrate (untreated sample) at the measured temperatures (25, 250 and 450 °C). The results indicated that the substrate and the alloyed layer suffered oxidative wear and abrasive wear, respectively, and that the treated samples exhibited much better tribological properties than did the substrate. The formation of Fe2AlCr, Fe3Al(Cr), FeAl(Cr), Fe(Cr) sosoloid and Cr23C6 phases in the alloyed layer dramatically enhanced the wear resistance of the treated sample. In addition, the alloyed layer's oxidation film exhibited a self-healing capacity with lubrication action that also contributed to the improvement of the wear resistance at high temperature. In particular, at 450 °C, the specific wear rate of treated sample was 2.524 × 10-4 mm3/N m, which was only 45.2% of the untreated sample.

  5. Development of weldable, corrosion-resistant iron-aluminide (FeAl) alloys

    SciTech Connect

    Maziasz, P.J.; Goodwin, G.M.; Wang, X.L.; Alexander, D.J.

    1997-04-01

    A boron-microalloyed FeAl alloy (Fe-36Al-0.2Mo-0.05Zr-0.13C, at.%, with 100-400 appm B) with improved weldability and mechanical properties was developed in FY 1994. A new scale-up and industry technology development phase for this work began in FY 1995, pursuing two parallel paths. One path was developing monolithic FeAl component and application technology, and the other was developing coating/cladding technology for alloy steels, stainless steels and other Fe-Cr-Ni alloys. In FY 1995, it was found that cast FeAl alloys had good strength at 700-750{degrees}C, and some (2.5%) ductility in air at room-temperature. Hot-extruded FeAl with refined grain size was found to have ductility and to also have good impact-toughness at room-temperature. Further, it was discovered that powder-metallurgy (P/M) FeAl, consolidated by direct hot-extrusion at 950-1000{degrees}C to have an ultra fine-grained microstructure, had the highest ductility, strength and impact-toughness ever seen in such intermetallic alloys.

  6. Using Atom-Probe Tomography to Understand Zn O ∶Al /SiO 2/Si Schottky Diodes

    NASA Astrophysics Data System (ADS)

    Jaramillo, R.; Youssef, Amanda; Akey, Austin; Schoofs, Frank; Ramanathan, Shriram; Buonassisi, Tonio

    2016-09-01

    We use electronic transport and atom-probe tomography to study Zn O ∶Al /SiO 2/Si Schottky diodes on lightly doped n - and p -type Si. We vary the carrier concentration in the ZnO ∶Al films by 2 orders of magnitude, but the Schottky barrier height remains nearly constant. Atom-probe tomography shows that Al segregates to the interface, so that the ZnO ∶Al at the junction is likely to be metallic even when the bulk of the ZnO ∶Al film is semiconducting. We hypothesize that the observed Fermi-level pinning is connected to the insulator-metal transition in doped ZnO. This implies that tuning the band alignment at oxide/Si interfaces may be achieved by controlling the transition between localized and extended states in the oxide, thereby changing the orbital hybridization across the interface.

  7. Impurity Diffusion Coefficients of Al and Zn in Mg Determined from Solid-to-Solid Diffusion Couples

    SciTech Connect

    Kammerer, Catherine; Kulkarni, Nagraj S; Warmack, Robert J Bruce; Perry, Kelly A; Belova, Irina; Murch, Prof. Graeme; Sohn, Yong Ho

    2013-08-01

    Increasing use and development of lightweight Mgalloys have led to the desire for more fundamental research in and understanding of Mg-based systems. As property enhancing components, Al and Zn are two of the most important and common alloying elements for Mg-alloys. We have investigated the concentration dependent interdiffusion of Al and Zn in Mg using diffusion couples of pure polycrystalline Mg mated to Mg solid solutions containing either <9 at.% Al or <3 at.% Zn. Concentration profiles were determined by electron micro-probe microanalysis of the diffusion zone. The interdiffusion coefficients were determined by the classical Boltzmann-Matano method within the Mg solid solution. As the concentration of Al or Zn approaches the dilute ends, we employ an analytical approach based on the Hall method to estimate the impurity diffusion coefficients. Results of Al and Zn impurity diffusion in Mg are reported and compared to published impurity diffusion coefficients typically determined by thin film techniques.

  8. CdS/CdSe-sensitized solar cell based on Al-doped ZnO nanoparticles prepared by the decomposition of zinc acetate solid solution

    NASA Astrophysics Data System (ADS)

    Deng, Jianping; Wang, Minqiang; Ye, Wei; Fang, Junfei; Zhang, Pengchao; Yang, Yongping; Yang, Zhi

    2017-01-01

    In the study, Al-doped ZnO nanoparticles (Al-ZnO NPs) were prepared by the decomposition of zinc acetate solid solution. The X-ray diffraction results showed that Al3+ was successfully doped without the formation of Al and Al2O3 impurity phases. The less Al-doping did not change the hexagonal wurtzite crystal structure of ZnO. The ratio of Al to Al + Zn (9.05%) measured by the energy dispersive X-ray also confirmed the formation of Al-ZnO. The Al-ZnO NPs were used as the photoanode material to prepare CdS/CdSe-sensitized solar cell. Compared with the cell based on commercial ZnO NPs (C-ZnO), the short-circuit current density and the fill factor of the cell were increased from 5.8 mA/cm2 and 34.1% (C-ZnO) to 7.78 mA/cm2 and 48.7% (Al-ZnO), respectively. The cell efficiency was increased from 1.01% (C-ZnO) to (1.9%) (Al-ZnO) and the increase percentage reached 88.1%. The results of electrochemical impedance spectroscopy and open-circuit voltage-decay suggested the lower carrier transport resistance and the longer electron lifetime of Al-ZnO-based cell.

  9. Preparation and magnetic properties of BaFe12O19/Ni0.8Zn0.2Fe2O4 nanocomposite ferrite

    NASA Astrophysics Data System (ADS)

    Wang, Yan; Huang, Ying; Wang, Qiufen

    2012-09-01

    Nanocomposite of hard (BaFe12O19)/soft ferrite (Ni0.8Zn0.2Fe2O4) have been prepared by the sol-gel process. The nanocomposite ferrite are formed when the calcining temperature is above 800 °C. It is found that the magnetic properties strongly depend on the presintering treatment and calcining temperature. The “bee waist” type hysteresis loops for samples disappear when the presintering temperature is 400 °C and the calcination temperature reaches 1100 °C owing to the exchange-coupling interaction. The remanence of BaFe12O19/Ni0.8Zn0.2Fe2O4 nanocomposite ferrite with the mass ratio of 5:1 is higher than a single phase ferrite. The specific saturation magnetization, remanence magnetization and coercivity are 63 emu/g, 36 emu/g and 2750 G, respectively. The exchange-coupling interaction in the BaFe12O19/Ni0.8Zn0.2Fe2O4 nanocomposite ferrite is discussed.

  10. Synthesis and magnetic properties of hard/soft SrFe12O19/Ni0.7Zn0.3Fe2O4 nanocomposite magnets

    NASA Astrophysics Data System (ADS)

    Radmanesh, M. A.; Seyyed Ebrahimi, S. A.

    2012-09-01

    Magnetic nanocomposite SrFe12O19/Ni0.7Zn0.3Fe2O4 powders with different weight fractions of the Ni0.7Zn0.3Fe2O4 soft ferrite were synthesized by a combination of the sol-gel self-propagation and glyoxilate precursor methods. The results of magnetic measurements revealed the higher Mr/Ms ratio for the nanocomposites than that for the single phase SrFe12O19 which proves the existence of the intergrain exchange coupling between hard and soft magnetic phases with the exchange spring behavior. The highest Mr/Ms ratio of 0.63 was obtained in the composite consisting of 80 wt% of SrFe12O19 and 20 wt% Ni0.7Zn0.3Fe2O4. The microstructural studies of this sample exhibited the average dimensions of hard and soft phases about 20 nm and 15 nm, respectively which are small enough for strong exchange coupling according to the theoretical studies. The variations of the reduced remanence (Mr/Ms) with increasing the weight fraction of the soft phase could be also explained by the role of the exchange and dipolar interactions in tuning the magnetic properties of the nanocomposites.

  11. Constitutive expression of the ZmZIP7 in Arabidopsis alters metal homeostasis and increases Fe and Zn content.

    PubMed

    Li, Suzhen; Zhou, Xiaojin; Zhao, Yongfeng; Li, Hongbo; Liu, Yuanfeng; Zhu, Liying; Guo, Jinjie; Huang, Yaqun; Yang, Wenzhu; Fan, Yunliu; Chen, Jingtang; Chen, Rumei

    2016-09-01

    Iron (Fe) and zinc (Zn) are important micronutrients for plant growth and development. Zinc-regulated transporters and the iron-regulated transporter-like protein (ZIP) are necessary for the homeostatic regulation of these metal micronutrients. In this study, the physiological function of ZmZIP7 which encodes a ZIP family transporter was characterized. We detected the expression profiles of ZmZIP7 in maize, and found that the accumulation of ZmZIP7 in root, stem, leaf, and seed was relatively higher than tassel and young ear. ZmZIP7 overexpression transgenic Arabidopsis lines were generated and the metal contents in transgenic and wild-type (WT) plants were examined using inductively coupled plasma atomic emission spectroscopy (ICP-OES) and Zinpyr-1 staining. Fe and Zn concentrations were elevated in the roots and shoots of ZmZIP7-overexpressing plants, while only Fe content was elevated in the seeds. We also analyzed the expression profiles of endogenous genes associated with metal homeostasis. Both endogenic Fe-deficiency inducible genes and the genes responsible for Zn and Fe transport and storage were stimulated in ZmZIP7 transgenic plants. In conclusion, ZmZIP7 encodes a functional Zn and Fe transporter, and ectopic overexpression of ZmZIP7 in Arabidopsis stimulate endogenous Fe and Zn uptake mechanisms, thereby facilitating both metal uptake and homeostasis. Our results contribute to improved understanding of ZIP family transporter functions and suggest that ZmZIP7 could be used to enhance Fe levels in grains.

  12. Durability of PEM fuel cell cathode in the presence of Fe 3+ and Al 3+

    NASA Astrophysics Data System (ADS)

    Li, Hui; Tsay, Ken; Wang, Haijiang; Shen, Jun; Wu, Shaohong; Zhang, Jiujun; Jia, Nengyou; Wessel, Silvia; Abouatallah, Rami; Joos, Nathan; Schrooten, Jeremy

    The contamination effects of Fe 3+ and Al 3+ on the performance of polymer electrolyte membrane fuel cells were investigated by continuously injecting Fe 3+ or Al 3+ salt solution into the air stream of an operating fuel cell. Both metal ions individually caused significant cell performance degradation at a level of only 5 ppm mol in air. In addition, elevated temperature accelerated fuel cell performance degradation in the presence of Fe 3+. Moreover, the presence of Fe 3+ in an operating fuel cell resulted in the cell's sudden death, due to the formation of membrane pinholes that may have been promoted by the enhanced production of peroxy radicals catalyzed by Fe species. Half-cell tests in liquid electrolyte revealed that the presence of Al 3+ in the electrolyte changed the kinetics and mechanisms of the oxygen reduction reaction by reducing the kinetic current densities and the electron transfer number.

  13. 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

  14. Synthesis and Characterization of In Situ Dendritic/Particulate α-Al(Fe,TM)Si Phase Reinforced Al Matrix Composites

    NASA Astrophysics Data System (ADS)

    Hou, L. G.; Wang, Shuai; He, Z. B.; Zhang, D.; Wang, X. D.; Zhuang, L. Z.; Zhang, J. S.

    2016-12-01

    The strength and ductility of transition metallic element alloyed Al alloys could be inevitably and severely weakened if these elements appeared as coarse intermetallics. Present studies aimed to optimize the morphologies and sizes of these intermetallics via composition design and process selection so as to decrease their detrimental effects to the properties. It is shown that the dendritic α-Al(Fe,TM)Si phase solidified as primary phase can be refined into small dendrites or micro- and submicro-sized particles via controlling the cooling rate and alloy composition, and this phase exhibits better heat resistance. After spark plasma sintering (SPS) the atomized alloy powders, the bulk aluminum matrix composites (AMCs) were successfully prepared and well strengthened by the uniformly distributed particulate α-Al(Fe,TM)Si phase. These sintered bulk composites also possess good heat resistance that might facilitate their application for some heat-resistant parts. The transmission electron microscope (TEM) and high-resolution TEM (HRTEM) results indicate these α-Al(Fe,TM)Si phases possesses body-centered-cubic structure with a lattice constant of 1.25 to 1.27 nm. The solidification or phase formation of these alloys is discussed as well as the densification process for the SPS of powders. The present studies indicate a possibility to prepare in situ small dendritic/particulate α-Al(Fe,TM)Si phase reinforced AMCs by using the casting process and controlling the normal impurity elements in Al alloys.

  15. Theoretical analysis of compatibility of several reinforcement materials with NiAl and FeAl matrices

    NASA Technical Reports Server (NTRS)

    Misra, Ajay K.

    1989-01-01

    Several potential reinforcement materials were assessed for their chemical, coefficient of thermal expansion (CTE), and mechanical compatibility with the intermetallic matrices based on NiAl and FeAl. Among the ceramic reinforcement materials, Al2O3, TiC, and TiB2, appear to be the optimum choices for NiAl and FeAl matrices. However, the problem of CTE mismatch with the matrix needs to be solved for these three reinforcement materials. Beryllium-rich intermetallic compounds can be considered as potential reinforcement materials provided suitable reaction barrier coatings can be developed for these. Based on preliminary thermodynamic calculations, Sc2O3 and TiC appear to be suitable as reaction barrier coatings for the beryllides. Several reaction barrier coatings are also suggested for the currently available SiC fibers.

  16. Characterization of novel microstructures in Al-Fe-V-Si and Al-Fe-V-Si-Y alloys processed at intermediate cooling rates

    NASA Astrophysics Data System (ADS)

    Marshall, Ryan

    Samples of an Al-Fe-V-Si alloy with and without small Y additions were prepared by copper wedge-mold casting. Analysis of the microstructures developed at intermediate cooling rates revealed the formation of an atypical morphology of the cubic alpha-Al12(Fe/V)3Si phase (Im 3 space group with a = 1.26 nm) in the form of a microeutectic with alpha-Al that forms in relatively thick sections. This structure was determined to exhibit promising hardness and thermal stability when compared to the commercial rapidly solidified and processed Al-Fe-V-Si (RS8009) alloy. In addition, convergent beam electron diffraction (CBED) and selected area electron diffraction (SAD) were used to characterize a competing intermetallic phase, namely, a hexagonal phase identified as h-AlFeSi (P6/mmm space group with a = 2.45 nm c = 1.25 nm) with evidence of a structural relationship to the icosahedral quasicrystalline (QC) phase (it is a QC approximant) and a further relationship to the more desirable alpha-Al12(Fe/V) 3Si phase, which is also a QC approximant. The analysis confirmed the findings of earlier studies in this system, which suggested the same structural relationships using different methods. As will be shown, both phases form across a range of cooling rates and appear to have good thermal stabilities. Additions of Y to the alloy were also studied and found to cause the formation of primary YV2Al20 particles on the order of 1 microm in diameter distributed throughout the microstructure, which otherwise appeared essentially identical to that of the Y-free 8009 alloy. The implications of these results on the possible development of these structures will be discussed in some detail.

  17. The distribution alloying elements in alnico 8 and 9 magnets: Site preference of ternary Ti, Fe, Co, and Ni additions in DO3 Fe3Al, Co3Al, and Ni3Al based intermetallic phases

    NASA Astrophysics Data System (ADS)

    Samolyuk, G. D.; Újfalussy, B.; Stocks, G. M.

    2014-11-01

    Recently, interest in alnico magnetic alloys has been rekindled due to their potential to substitute for rare-earth based permanent magnets provided modest improvements in their coercivity can be achieved without loss of saturation magnetization. Recent experimental studies have indicated that atomic and magnetic structure of the two phases (one AlNi-based, the other FeCo-based) that comprise these spinodally decomposed alloy is not as simple as previously thought. A key issue that arises is the distribution of Fe, Co, and Ti within the AlNi-based matrix phase. In this paper, we report the results of first-principles calculations of the site preference of ternary alloying additions in DO3 Fe3Al, Co3Al, and Ni3Al alloys, as models for the aluminide phase. For compound compositions that are Al rich, which correspond to experimental situation, Ti and Fe are found to occupy the α sites, while Co and Ni prefer the γ sites of the DO3 lattice. An important finding is that the magnetic moments of transition metals in Fe3Al and Co3Al are ordered ferromagnetically, whereas the Ni3Al were found to be nonmagnetic unless the Fe or Co is added as a ternary element.

  18. The distribution alloying elements in alnico 8 and 9 magnets: Site preference of ternary Ti, Fe, Co, and Ni additions in DO3 Fe3Al, Co3Al, and Ni3Al based intermetallic phases

    DOE PAGES

    Samolyuk, G. D.; Újfalussy, B.; Stocks, G. M.

    2014-11-07

    Recently, interest in alnico magnetic alloys has been rekindled due to their potential to substitute for rare-earth based permanent magnets provided modest improvements in their coercivity can be achieved without loss of saturation magnetization. Recent experimental studies have indicated that atomic and magnetic structure of the two phases (one AlNi-based, the other FeCo-based) that comprise these spinodally decomposed alloy is not as simple as previously thought. A key issue that arises is the distribution of Fe, Co and Ti within the AlNi-based matrix phase. In our paper we report the results of first-principles calculations of the site preference of ternarymore » alloying additions in DO3 Fe3Al, Co3Al and Ni3Al alloys, as models for the aluminide phase. For compound compositions that are Al rich, which corresponds to experimental situation, Ti and Fe are found to occupy the sites, while Co and Ni prefer the sites of the DO3 lattice. Finally, an important finding is that the magnetic moments of transition metals in Fe3Al and Co3Al are ordered ferromagnetically, whereas the Ni3Al were found to be nonmagnetic unless the Fe or Co are added as a ternary element.« less

  19. Room Temperature Ferromagnetism of FeCo-Codoped ZnO Nanorods Prepared by Chemical Vapor Deposition

    SciTech Connect

    Chen, J.; Liu, J.; West, A.; Yan, Y.; Yu, M.; Zhou, W.

    2008-11-01

    FeCo-codoped ZnO nanorods with room temperature ferromagnetic ordering have been synthesized by chemical vapor deposition. Detailed nanostructures were investigated by field emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM) and nanoprobe X-ray energy dispersive spectroscopy (EDS). The ZnO nanorods were grown along c-axis of a single crystalline wurtzite structure and no second phase was observed by high resolution TEM. EDS analysis along the nanowires indicated that Co and Fe were successfully doped into the ZnO lattice with concentrations about 0.6-1.0 at.%. Magnetic measurement demonstrates a ferromagnetic ordering with Curie temperature higher than 300 K presents in the ZnO nanorods.

  20. Structural, electrical, and optomagnetic tweaking of Zn doped CoFe2-xZnxO4-δ nanoparticles

    NASA Astrophysics Data System (ADS)

    Agrawal, Shraddha; Parveen, Azra; Azam, Ameer

    2016-09-01

    Nanoparticles of pure and Zn doped CoFe2O4 of the composition CoFe2-xZnxO4-δ (x=0, 0.05, 0.10, 0.15) have been successfully synthesized by microwave gel combustion. The microstructural and compositional analyses were carried out by X-ray diffraction, Scanning Electron Microscopy. The crystallite size was found to increase with the increase in the Zn content. The dielectric constant (ε) and A.C. conductivity were studied as a function of frequency and temperature and were explained on the basis of Maxwell-Wagner model and electron hopping respectively. The energy band gap was found to decrease gradually with Zn doping. The magnetic measurements, depicts an increase in magnetization with the increase in Zn concentration, which in turn shows a strong dependency on the particle size. The magnetic hysteresis loop confirms the ferromagnetic nature.

  1. Synthesis and characterization of core∕shell Fe3O4∕ZnSe fluorescent magnetic nanoparticles

    PubMed Central

    Vargas, José M.; McBride, Amber A.; Plumley, John B.; Fichou, Yann; Memon, Tosifa A.; Shah, Vichiksha; Cook, Nathaniel C.; Akins, Brian A.; Rivera, Antonio C.; Smolyakov, Gennady A.; O’Brien, James R.; Adolphi, Natalie L.; Smyth, Hugh D. C.; Osiński, Marek

    2011-01-01

    We report on the successful preparation and characterization of fluorescent magnetic core∕shell Fe3O4∕ZnSe nanoparticles (NPs) with a spherical shape by organometallic synthesis. The 7 nm core∕3 nm shell NPs show good magnetic and photoluminescence (PL) responses. The observed PL emission∕excitation spectra are shifted to shorter wavelengths, compared to a reference ZnSe NP sample. A dramatic reduction of PL quantum yield is also observed. The temperature dependence of the magnetization for the core∕shell NPs shows the characteristic features of two coexisting and interacting magnetic (Fe3O4) and nonmagnetic (ZnSe) phases. Compared to a reference Fe3O4 NP sample, the room-temperature Néel relaxation time in core∕shell NPs is three times longer. PMID:21559088

  2. High-frequency permeability and permittivity of Ni xZn (1-x)Fe 2O 4 thick film

    NASA Astrophysics Data System (ADS)

    Kulkarni, D. C.; Lonkar, U. B.; Puri, Vijaya

    Magnetic materials such as Ni xZn (1-x)Fe 2O 4 have resonant frequency in high frequency; therefore, they are more useful especially in microwaves. The Ni xZn (1-x)Fe 2O 4 was prepared by the chemical coprecipitation method using citrate precursors, and the fritless thick film was screen printed on alumina substrates. The composition-dependent permeability and permittivity in the high frequency 8-12 GHz are investigated. Using the overlay technique on Ag-thick-film patch antenna, the change in reflectance and transmittance has been measured. The Ni xZn (1-x)Fe 2O 4 thick film, when used as overlay on Ag-thick-film patch antenna, changes the resonance characteristics. The changes in resonance frequency, reflectance and transmittance have been used to calculate the permeability and permittivity of the thick film. Zinc-concentration-dependent changes are obtained.

  3. Structural, electrical, and optical properties of atomic layer deposition Al-doped ZnO films

    SciTech Connect

    Banerjee, P; Lee, W. J.; Bae, K. R.; Lee, Sang Bok; Rubloff, Gary W

    2010-01-01

    Al-doped ZnO (AZO) films of ~100nm thickness with various Aldoping were prepared at 150°C by atomic layer deposition on quartz substrates. At low Aldoping, the films were strongly textured along the [100] direction, while at higher Aldoping the films remained amorphous. Atomic force microscopy results showed that Al–O cycles when inserted in a ZnOfilm, corresponding to a few atomic percent Al, could remarkably reduce the surface roughness of the films. Hall measurements revealed a maximum mobility of 17.7cm{sup 2} /Vs . Film resistivity reached a minima of 4.4×10{sup -3} Ωcm whereas the carrier concentration reached a maxima of 1.7×10{sup 20} cm{sup -3} , at 3 at.% Al. The band gap of AZO films varied from 3.23 eV for undoped ZnOfilms to 3.73 eV for AZO films with 24.6 at.% Al. Optical transmittance over 80% was obtained in the visible region. The detrimental impact of increased Al resulting in decreased conductivity due to doping past 3.0 at.% is evident in the x-ray diffraction data, as an abrupt increase in the optical band gap and as a deviation from the Burstein–Moss effect.

  4. 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.

  5. Understanding phase stability of Al-Co-Cr-Fe-Ni high entropy alloys

    SciTech Connect

    Zhang, Chuan; Zhang, Fan; Diao, Haoyan; Gao, Michael C.; Tang, Zhi; Poplawsky, Jonathan D.; Liaw, Peter K.

    2016-07-19

    The concept of high entropy alloy (HEA) opens a vast unexplored composition range for alloy design. As a well-studied system, Al-Co-Cr-Fe-Ni has attracted tremendous amount of attention to develop new-generation low-density structural materials for automobile and aerospace applications. In spite of intensive investigations in the past few years, the phase stability within this HEA system is still poorly understood and needs to be clarified, which poses obstacles to the discovery of promising Al-Co-Cr-Fe-Ni HEAs. In the present work, the CALPHAD approach is employed to understand the phase stability and explore the phase transformation within the Al-Co-Cr-Fe-Ni system. As a result, the phase-stability mapping coupled with density contours is then constructed within the composition - temperature space, which provides useful guidelines for the design of low-density Al-Co-Cr-Fe-Ni HEAs with desirable properties.

  6. Characterization and Fabrication of ZnO Nanowires Grown on AlN Thin Film

    SciTech Connect

    Yousefi, Ramin; Kamaluddin, Burhanuddin; Ghoranneviss, Mahmood; Hajakbari, Fatemeh

    2009-07-07

    In this paper, we report ZnO nanowires grown on AlN thin film deposited on glass as substrate by physical vapour deposition. The temperature of substrates was kept between 600 deg. C and 500 deg. C during the growth. The typical average diameters of the obtained nanowires on substrate at 600 deg. C and 500 deg. C was about 57 nm and 22 nm, respectively with several micrometers in lengths. X-ray diffraction and Auger spectroscopy results showed Al diffused from AlN thin film into ZnO nanowires for sample at high temperature zone. In the photoluminescence spectra two emission bands appeared, one related to ultraviolet emission with a strong peak at 380-382 nm, and another related to deep level emission with a weak peak at 510 nm.

  7. Strikingly dissimilar effect of Mn and Zn dopants imposed on local structural distortion of Ba0.5K0.5Fe2As2 superconductor.

    PubMed

    Cheng, Jie; Dong, Peng; Chu, Wangsheng; Xu, Wei; Wen, Haihu; Marcelli, Augusto; Wu, Ziyu

    2013-05-01

    To clarify the contrasting impurity effects of Mn and Zn dopants on the critical temperature of optimally doped Ba0.5K0.5Fe2As2 superconductors, extended X-ray absorption fine-structure spectroscopy was implemented at the Fe and As K-edge. In Mn-doped compounds a gradual deviation of the symmetric FeAs4 tetrahedron and weakening of the Fe-As bond was observed. Conversely, in Zn-doped compounds the perfect FeAs4 tetrahedron is maintained and the Fe-As bond is rigid. The local structural details are consistent with the development of superconductivity in these two systems, suggesting a significant role played by the topology of the FeAs4 tetrahedron and rigidness of the Fe-As bond in Mn/Zn-doped Ba0.5K0.5Fe2As2 superconductors.

  8. Filled and empty states of Zn-TPP films deposited on Fe(001)-p(1×1)O

    PubMed Central

    Calloni, Alberto; Yivlialin, Rossella; Picone, Andrea; Bottegoni, Federico; Finazzi, Marco

    2016-01-01

    Zn-tetraphenylporphyrin (Zn-TPP) was deposited on a single layer of metal oxide, namely an Fe(001)-p(1×1)O surface. The filled and empty electronic states were measured by means of UV photoemission and inverse photoemission spectroscopy on a single monolayer and a 20 monolayer thick film. The ionization energy and the electron affinity of the organic film were deduced and the interface dipole was determined and compared with data available in the literature. PMID:28144503

  9. Using the hydrothermal method to grow p-type ZnO nanowires on Al-doped ZnO thin film to fabricate a homojunction diode.

    PubMed

    Tseng, Yung-Kuan; Hung, Meng-Chun; Su, Shun-Lung; Li, Sheng-Kai

    2014-10-01

    In this study, the hydrothermal method is used to grow phosphorus-doped ZnO nanowires on Si/SiO2 substrates deposited with Al-doped ZnO thin film. This structure forms a homogeneous p-n junction. In this study, we are the pioneers to use ammonium hypophosphite (NH4H2PO2) as a source of phosphorus to prepare the precursor solution. Ammonium hypophosphite of different concentration levels is used to observe its effects on the growth of nanowires. The results show that the precursor solution prepared from ammonium hypophosphite can produce good crystalline ZnO nanowires while there is no linear relationship between the amounts and concentration levels of phosphorus doped into the nanowires. Whether the phosphorus-doped ZnO nanowires have the characteristics of a p-type semiconductor is indirectly verified by measuring whether the p-n junction made up of Al-doped ZnO thin film and phosphorus-doped ZnO nanowires shows rectifying behavior. I-V measurements are made on the specimens. The results show good rectifying behavior, proving that the phosphorus-doped ZnO nanowires and Al-doped AZO films have p-type and n-type semiconductor properties, constituting a good p-n junction. This result also proves that ammonium hypophosphite is a better source of phosphorus in the hydrothermal method to synthesize phosphorus-doped ZnO nanowires.

  10. Preparation and property of magnetic photocatalyst BiOCl/Mn x Zn1- x Fe2O4

    NASA Astrophysics Data System (ADS)

    Feng, Shan; Xu, Longjun; Liu, Chenglun; Du, Haigang; Xie, Taiping; Zhu, Qianqian

    2017-02-01

    The magnetic photocatalyst BiOCl/Mn x Zn1- x Fe2O4 was prepared by impregnation-calcination method. The structure and properties of the prepared photocatalyst were characterized by FTIR, XRD, SEM, TEM, UV-vis DRS, and VSM. Mn x Zn1- x Fe2O4 inhibited the growth along (001) crystal face and promoted (110) crystal surface exposure of BiOCl. The as-prepared magnetic composite appeared flower-like microspheres assembled with nanosheets. The average crystallite size and the nanosheet thickness range of BiOCl/Mn x Zn1- x Fe2O4 were 57.6 and 75.7-112.2 nm, respectively. The band gap energy ( E g) of BiOCl/Mn x Zn1- x Fe2O4 was 2.48 eV, which was lower than that of BiOCl. The saturation magnetization ( Ms), coercive force ( Hc), and remanent magnetization ( Mr) of BiOCl/Mn x Zn1- x Fe2O4 were respectively 4.64 emu g-1, 50.12 G and 0.09 emu g-1, indicating a good resistance to demagnetization and paramagnetism. The optimum synthesis condition of BiOCl/Mn x Zn1- x Fe2O4 was obtained by orthogonal experiments, and the degradation ratio of RhB with the photocatalyst was 99.6% at 30 min. After four cycles, the degradation ratio of RhB with the recovered photocatalyst was still above 83%.

  11. Electron paramagnetic resonance study of ZnAl(2)S(4) spinel.

    PubMed

    Güner, S; Yıldız, F; Rameev, B; Aktaş, B

    2005-06-29

    Single crystals of ZnAl(2)S(4) spinel doped by paramagnetic Cr(3+) and Mn(2+) ions have been studied by the electron paramagnetic resonance (EPR) technique. The crystal field symmetry around the impurity ions has been determined from the angular behaviour of X-band EPR spectra. The anisotropic EPR signal of the Cr(3+) ions shows splitting into 31 narrow lines due to the super-hyperfine interaction between unpaired electron spins of the chromium centres and nuclear spins of six neighbouring Al(27) (I = 5/2) ions. It has been established that the Cr(3+) ions are located at the octahedral sites in the spinel structure, and the super-hyperfine interaction results from a weak covalent bounding with the Al atoms. The EPR signals of the Cr(3+) paramagnetic centres show no fine-structure splitting due to a perfectly cubic symmetry of the local crystal field in the octahedral sites of the ZnAl(2)S(4) spinel structure. A weak EPR signal consisting of six components has been ascribed to the transitions between hyperfine levels of the Mn(2+) (I = 5/2,S = 5/2) ions located at tetrahedral sites, while the fine-structure splitting of each component could be resolved only for special orientations of the sample in the external magnetic field. The parameters of the EPR signal of both chromium and manganese centres indicate that there is an essential covalence in the ZnAl(2)S(4) spinel crystal. Very narrow linewidths (∼2 Oe) of the Cr(3+) EPR signal components point to very high homogeneity and quality of the ZnAl(2)S(4) crystals.

  12. Impact of biogenic nanoscale metals Fe, Cu, Zn and Se on reproductive LV chickens

    NASA Astrophysics Data System (ADS)

    Khiem Nguyen, Quy; Dieu Nguyen, Duy; Kien Nguyen, Van; Thinh Nguyen, Khac; Chau Nguyen, Hoai; Tin Tran, Xuan; Nguyen, Huu Cuong; Tien Phung, Duc

    2015-09-01

    Using biogenic nanoscale metals (Fe, Cu, ZnO, Se) to supplement into diet premix of reproductive LV (a Vietnamese Luong Phuong chicken breed) chickens resulted in certain improvement of poultry farming. The experimental data obtained showed that the farming indices depend mainly on the quantity of nanocrystalline metals which replaced the inorganic mineral component in the feed premix. All four experimental groups with different quantities of the replacement nano component grew and developed normally with livability reaching 91 to 94%, hen’s bodyweight at 38 weeks of age and egg weight ranged from 2.53-2.60 kg/hen and 50.86-51.55 g/egg, respectively. All these farming indices together with laying rate, egg productivity and chick hatchability peaked at group 5 with 25% of nanoscale metals compared to the standard inorganic mineral supplement, while feed consumption was lowest. The results also confirmed that nanocrystalline metals Fe, Cu, ZnO and Se supplemented to chicken feed were able to decrease inorganic minerals in the diet premixes at least four times, allowing animals to more effectively absorb feed minerals, consequently decreasing environmental pollution risks.

  13. Radiochemical neutron activation analysis of Fe, Co, Zn, Sb and Se in biomedical and environmental samples.

    PubMed

    Garg, A N; Weginwar, R G; Chutke, N L

    1993-11-01

    A radiochemical neutron activation method has been developed for the simultaneous determination of Fe, Co, Zn, Sb and Se levels in cancerous breast tissue, milk samples and fugitive cement dust particulates. Various Standard Reference Materials from NIST, USA (Bovine Liver 1577a, Milk Powder 1549, Coal Fly Ash 1633a and Urban Particulate Matter 1648), IAEA Vienna (Animal Muscle H-4, Milk powder A-11 and Soil-5) and NIES Japan (Pond Sediment) were also analysed for quality control. Samples together with standards were irradiated at a thermal neutron fluence of 10(13) ncm-2s-1 for 2 weeks. After dissolution/fusion together with carriers, the Fe was first separated by extracting with diethyl ether followed by extraction with cupferron in chloroform. From the aqueous phase Co and Zn were extracted using alpha-nitroso-beta-naphthol in chloroform and 2-thenoyltrifluoroacetone in isobutylmethyl ketone, respectively. From another aliquot, Se was first complexed with o-phenylenediamine and extracted in benzene. Later Sb was extracted using KI and 4-(2-pyridylazo)-resorcinol (PAR) in benzene. The method yields reasonably accurate data for monitoring of trace elements in biomedical and environmental specimens.

  14. Synthesis, characterization and surface modification of ZnCrFeO4 nanoparticles.

    PubMed

    Hamed, Amal; Fitzgerald, Alexander G; Wang, Lijun; Gueorguieva, Mariana; Malik, Ritu; Melzer, Andreas

    2013-04-01

    The aim of this research was to investigate zinc chromium ferrite (ZnCrFeO4) nanoparticles, synthesized using the sol gel technique with nanoparticle size controlled through a two-stage annealing process. Stage one was a low temperature firing which produced low quality nanocrystals with an average size of 15 nm. This was followed by a second firing stage at high temperature which enhanced the crystal quality. The nanoparticles were then coated with a bio-compatible shell to form a stable suspension in the ferrofluid carrier. The resulting nanoparticles were found by electron microscopy, atomic force microscopy and X-ray diffraction studies to have excellent crystal quality. The average size was 8.5 nm. Preliminary cell culture studies indicated the ZnCrFeO4 nanoparticles were non-toxic. The relatively high measured value of the relaxivity r2 showed that the nanoparticle coating was effective in substantially reducing aggregation and enhancing the properties of the nanoparticles associated with contrast enhancement in MRI.

  15. Plasma Nitriding Behavior of Fe-C-M (M = Al, Cr, Mn, Si) Ternary Martensitic Steels

    NASA Astrophysics Data System (ADS)

    Tomio, Yusaku; Kitsuya, Shigeki; Oh-ishi, Keilchiro; Hono, Kazuhiro; Miyamoto, Goro; Furuhara, Tadashi

    2014-01-01

    Change in surface hardness and nitrides precipitated in Fe-0.6C binary and Fe-0.6 mass pct C-1 mass pct M (M = Al, Cr, Mn, Si) ternary martensitic alloys during plasma nitriding were investigated. Surface hardness was hardly increased in the Fe-0.6C binary alloy and slightly increased in Fe-0.6C-1Mn and Fe-0.6C-1Si alloys. On the other hand, it was largely increased in Fe-0.6C-1Al and Fe-0.6C-1Cr alloys. In all the Fe-0.6C-1M alloys except for the Si-added alloy, fine platelet alloy nitrides precipitated inside martensite laths. In the Fe-0.6C-1Si alloy, Si-enriched film was observed mainly at a grain boundary and an interface between cementite and matrix. Crystal structure of nitrides observed in the martensitic alloys was similar to those in Fe-M binary ferritic alloys reported previously. However, there was a difference in hardening behavior between ferrite and martensite due to a high density of dislocations acting as a nucleation site of the nitrides and partitioning of an alloying element between martensite and cementite changing the driving force of precipitation of the nitrides.

  16. Structure and magnetism of granular Fe-Al 2O 3

    NASA Astrophysics Data System (ADS)

    Santos, A.; Ardisson, J. D.; Viegas, A. D. C.; Schmidt, J. E.; Persiano, A. I. C.; Macedo, W. A. A.

    2001-05-01

    The structural and magnetic properties of granular Fe-Al 2O 3 nanocomposite obtained starting from sol-gel processing are presented. Samples with nominal Fe content ranging from 20% to 62% in volume were prepared. The conversion of Fe oxides into metallic Fe was obtained by calcination at 800°C followed by reduction at 600°C for 2 h in H 2 atmosphere. After reduction, our results indicated up to 78% α-Fe, preserving the mean diameter of the metallic nanoparticles between 50 and 80 nm, ˜16% Fe oxides and ˜7% interstitial Fe 2+ and substitutional Fe 3+ cations in the Al 2O 3 lattice. Vibrating sample magnetometry at 300 K resulted in coercivity between 400 and 630 Oe and saturation magnetization between 40 and 134 emu/g. From transport measurements, the highest magnetoresistance, close to 2% at room temperature, was observed for samples with 25% α-Fe and 51 vol% total Fe.

  17. 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.

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

    SciTech Connect

    Lin, Yin-Chih 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 for 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.

  19. Growth and characterization of insulating ferromagnetic semiconductor (Al,Fe)Sb

    SciTech Connect

    Anh, Le Duc Kaneko, Daiki; Tanaka, Masaaki; Hai, Pham Nam

    2015-12-07

    We investigate the crystal structure, transport, and magnetic properties of Fe-doped ferromagnetic semiconductor (Al{sub 1−x},Fe{sub x})Sb thin films up to x = 14% grown by molecular beam epitaxy. All the samples show p-type conduction at room temperature and insulating behavior at low temperature. The (Al{sub 1−x},Fe{sub x})Sb thin films with x ≤ 10% maintain the zinc blende crystal structure of the host material AlSb. The (Al{sub 1−x},Fe{sub x})Sb thin film with x = 10% shows intrinsic ferromagnetism with a Curie temperature (T{sub C}) of 40 K. In the (Al{sub 1−x},Fe{sub x})Sb thin film with x = 14%, a sudden drop of the hole mobility and T{sub C} was observed, which may be due to the microscopic phase separation. The observation of ferromagnetism in (Al,Fe)Sb paves the way to realize a spin-filtering tunnel barrier that is compatible with well-established III-V semiconductor devices.

  20. Hydrogen permeation in FeCrAl alloys for LWR cladding application

    DOE PAGES

    Hu, Xunxiang; Terrani, Kurt A.; Wirth, Brian D.; ...

    2015-03-19

    FeCrAl is an advanced oxidation-resistant iron-based alloy class, is a highly prevalent candidate as an accident-tolerant fuel cladding material. Compared with traditional zirconium alloy fuel cladding, increased tritium permeation through FeCrAl fuel cladding to the primary coolant is expected, raising potential safety concerns. In our study, the hydrogen permeability of several FeCrAl alloys was obtained using a static permeation test station, which was calibrated and validated using 304 stainless steel. The high hydrogen permeability of FeCrAl alloys leads to concerns with respect to potentially significant tritium release when used for fuel cladding in LWRs. Also, the total tritium inventory insidemore » the primary coolant of a light water reactor was quantified by applying a 1-dimensional steady state tritium diffusion model to demonstrate the dependence of tritium inventory on fuel cladding type. Furthermore, potential mitigation strategies for tritium release from FeCrAl fuel cladding were discussed and indicate the potential for application of an alumina layer on the inner clad surface to serve as a tritium barrier. More effort is required to develop a robust, economical mitigation strategy for tritium permeation in reactors using FeCrAl clad fuel assemblies.« less

  1. Viability of thin wall tube forming of ATF FeCrAl

    SciTech Connect

    Maloy, Stuart Andrew; Aydogan, Eda; Anderoglu, Osman; Lavender, Curt; Yamamoto, Yukinori

    2016-09-16

    Fabrication of thin walled tubing of FeCrAl alloys is critical to its success as a candidate enhanced accident-tolerant fuel cladding material. Alloys that are being investigated are Generation I and Generation II FeCrAl alloys produced at ORNL and an ODS FeCrAl alloy, MA-956 produced by Special Metals. Gen I and Gen II FeCrAl alloys were provided by ORNL and MA-956 was provided by LANL (initially produced by Special Metals). Three tube development efforts were undertaken. ORNL led the FeCrAl Gen I and Gen II alloy development and tube processing studies through drawing tubes at Rhenium Corporation. LANL received alloys from ORNL and led tube processing studies through drawing tubes at Century Tubing. PNNL led the development of tube processing studies on MA-956 through pilger processing working with Sandvik Corporation. A summary of the recent progress on tube development is provided in the following report and a separate ORNL report: ORNL/TM-2015/478, “Development and Quality Assessments of Commercial Heat Production of ATF FeCrAl Tubes”.

  2. Hydrogen permeation in FeCrAl alloys for LWR cladding application

    SciTech Connect

    Hu, Xunxiang; Terrani, Kurt A.; Wirth, Brian D.; Snead, Lance L.

    2015-03-19

    FeCrAl is an advanced oxidation-resistant iron-based alloy class, is a highly prevalent candidate as an accident-tolerant fuel cladding material. Compared with traditional zirconium alloy fuel cladding, increased tritium permeation through FeCrAl fuel cladding to the primary coolant is expected, raising potential safety concerns. In our study, the hydrogen permeability of several FeCrAl alloys was obtained using a static permeation test station, which was calibrated and validated using 304 stainless steel. The high hydrogen permeability of FeCrAl alloys leads to concerns with respect to potentially significant tritium release when used for fuel cladding in LWRs. Also, the total tritium inventory inside the primary coolant of a light water reactor was quantified by applying a 1-dimensional steady state tritium diffusion model to demonstrate the dependence of tritium inventory on fuel cladding type. Furthermore, potential mitigation strategies for tritium release from FeCrAl fuel cladding were discussed and indicate the potential for application of an alumina layer on the inner clad surface to serve as a tritium barrier. More effort is required to develop a robust, economical mitigation strategy for tritium permeation in reactors using FeCrAl clad fuel assemblies.

  3. Orientation Dependence of Cracking in Hot-Dip Zn-Al-Mg Alloy Coatings on a Sheet Steel

    NASA Astrophysics Data System (ADS)

    Park, Y. B.; Kim, I. G.; Kim, S. G.; Kim, W. T.; Kim, T. C.; Oh, M. S.; Kim, J. S.

    2017-01-01

    The present study was aimed at investigating a basic cause of cracking in hot-dip Zn-Al-Mg alloy coatings on an extra deep drawing quality sheet steel. The electron backscattering diffraction technique was employed to examine the crystallographic planes of the cracks generated before and after bending deformation of the coated steel sheets. It was clarified that the occurrence of cracking in the Zn-Al-Mg alloy coatings absolutely depends on the orientation of the primary Zn and eutectic Zn alloy phases. Finally, a cracking mechanism was proposed on the basis of the anisotropy of thermal expansion and the Young's modulus in the phases constituting the coatings.

  4. Orientation Dependence of Cracking in Hot-Dip Zn-Al-Mg Alloy Coatings on a Sheet Steel

    NASA Astrophysics Data System (ADS)

    Park, Y. B.; Kim, I. G.; Kim, S. G.; Kim, W. T.; Kim, T. C.; Oh, M. S.; Kim, J. S.

    2017-03-01

    The present study was aimed at investigating a basic cause of cracking in hot-dip Zn-Al-Mg alloy coatings on an extra deep drawing quality sheet steel. The electron backscattering diffraction technique was employed to examine the crystallographic planes of the cracks generated before and after bending deformation of the coated steel sheets. It was clarified that the occurrence of cracking in the Zn-Al-Mg alloy coatings absolutely depends on the orientation of the primary Zn and eutectic Zn alloy phases. Finally, a cracking mechanism was proposed on the basis of the anisotropy of thermal expansion and the Young's modulus in the phases constituting the coatings.

  5. Synthesis of Cd/(Al+Fe) layered double hydroxides and characterization of the calcination products

    SciTech Connect

    Perez, M.R.; Barriga, C.; Fernandez, J.M.; Rives, V.; Ulibarri, M.A.

    2007-12-15

    Layered double hydroxides (LDHs) containing Cd(II), Al(III), and Fe(III) in the brucite-like layers with different starting Fe/Al atomic ratios and with nitrate as counteranion have been prepared following the coprecipitation method at a constant pH value of 8. An additional Cd(II),Al(III)-LDH sample interlayered with hexacyanoferrate(III) ions has been prepared by ionic exchange at pH 9. The samples have been characterized by elemental chemical analysis, powder X-ray diffraction (PXRD), and FT-IR spectroscopy. Their thermal stability has been assessed by thermogravimetric and differential thermal analyses (TG-DTA) and mass spectrometric analysis of the evolved gases. The PXRD patterns of the solids calcined at 800 deg. C show diffraction lines corresponding to Cd(Al)O and spinel-type materials, which precise nature (CdAl{sub 2}O{sub 4}, Cd{sub 1-x}Fe{sub 2+x}O{sub 4}, or Cd{sub x}Fe{sub 2.66}O{sub 4}) depends on location and concentration of iron in the parent material or precursor. - Graphical abstract: Layered double hydroxides (LDHs) containing Cd(II), Al(III), and Fe(III) in the brucite-like layers with different starting Fe/Al atomic ratios and with nitrate as counteranion have been prepared following the coprecipitation method. An additional Cd(II),Al(III)-LDH sample interlayered with hexacyanoferrate(III) ions has been prepared by ionic exchange. Calcination at 800 deg. C shows diffraction lines corresponding to CdO and to spinel-type materials. SEM micrograph of sample CdAlFe-N-0.

  6. Magnetic and microstructural properties of nanocrystalline Fe-25 at% Al and Fe-25 at% Al +0.2 at%B alloys prepared by mechanical alloying process

    NASA Astrophysics Data System (ADS)

    Ibn Gharsallah, H.; Makhlouf, T.; Escoda, L.; Suñol, J. J.; Khitouni, M.

    2016-04-01

    In the present work, structural and magnetic properties of nanocrystalline Fe-25at%Al and Fe-25at%Al+0.02at%B alloys produced by mechanical alloying were studied. Their microstructural properties were investigated by X-ray diffraction, scanning electron microscopy and vibrating sample magnetometer. A BCC-nanostructured Fe(Al,B) solid solution with an average crystallite size of about 18nm has been produced by milling for 4h. Whereas in Fe-25at%Al the alloying process has been accomplished after 16h of milling. It is found that B speeds up the formation of a bcc phase with finer microstructure (around 5nm) after 40h of milling. When increasing the milling time, the crystallite size decreases for all powders. An increase in microstrain was observed with increasing the milling time and also with addition of boron. Coercivity and the saturation magnetization of alloyed powders were measured at room temperature by a vibration sample magnetization. The magnetic measurements show a contrasting saturation magnetization and coercivity ( Hc) in both alloys. These variations are explained by crystallite size and strain variations in the samples during milling.

  7. A method for Ca, Fe, Ga, Na, Si and Zn determination in alumina by inductively coupled plasma optical emission spectrometry after aluminum precipitation

    NASA Astrophysics Data System (ADS)

    Souza, Alexandre L.; Lemos, Sherlan G.; Oliveira, Pedro V.

    2011-05-01

    In this present work a method for the determination of Ca, Fe, Ga, Na, Si and Zn in alumina (Al 2O 3) by inductively coupled plasma optical emission spectrometry (ICP OES) with axial viewing is presented. Preliminary studies revealed intense aluminum spectral interference over the majority of elements and reaction between aluminum and quartz to form aluminosilicate, reducing drastically the lifetime of the torch. To overcome these problems alumina samples (250 mg) were dissolved with 5 mL HCl + 1.5 mL H 2SO 4 + 1.5 mL H 2O in a microwave oven. After complete dissolution the volume was completed to 20 mL and aluminum was precipitated as Al(OH) 3 with NH 3 (by bubbling NH 3 into the solution up to a pH ~ 8, for 10 min). The use of internal standards (Fe/Be, Ga/Dy, Zn/In and Na/Sc) was essential to obtain precise and accurate results. The reliability of the proposed method was checked by analysis of alumina certified reference material (Alumina Reduction Grade-699, NIST). The found concentrations (0.037% w w -1 CaO, 0.013% w w -1 Fe 2O 3, 0.012% w w -1 Ga 2O 3, 0.49% w w -1 Na 2O, 0.014% w w -1 SiO 2 and 0.013% w w -1 ZnO) presented no statistical differences compared to the certified values at a 95% confidence level.

  8. Coexistence of Cu, Fe, Pb, and Zn oxides and chlorides as a determinant of chlorinated aromatics generation in municipal solid waste incinerator fly ash.

    PubMed

    Fujimori, Takashi; Tanino, Yuta; Takaoka, Masaki

    2014-01-01

    We investigated chemical determinants of the generation of chlorinated aromatic compounds (aromatic-Cls), such as polychlorinated biphenyls (PCBs) and chlorobenzenes (CBzs), in fly ash from municipal solid waste incineration. The influences of the following on aromatic-Cls formation in model fly ash (MFA) were systematically examined quantitatively and statistically: (i) inorganic chlorides (KCl, NaCl, CaCl2), (ii) base materials (SiO2, Al2O3, CaCO3), (iii) metal oxides (CuO, Fe2O3, PbO, ZnO), (iv) metal chlorides (CuCl2, FeCl3, PbCl2, ZnCl2), and (v) "coexisting multi-models." On the basis of aromatic-Cls concentrations, the ∑CBzs/∑PCBs ratio, and the similarity between distribution patterns, MFAs were categorized into six groups. The results and analysis indicated that the formation of aromatic-Cls depended strongly on the "coexistence condition", namely multimodels composed of not only metal chlorides, but also of metal oxides. The precise replication of metal chloride to oxide ratios, such as the precise ratios of Cu-, Fe-, Pb-, and Zn-chlorides and oxides, may be an essential factor in changing the thermochemical formation patterns of aromatic-Cls. Although CuCl2 acted as a promoter of aromatic-Cls generation, statistical analyses implied that FeCl3 also largely influenced the generation of aromatic-Cls under mixture conditions. Various additional components of fly ash were also comprehensively analyzed.

  9. Growth of ZnO:Al thin films onto different substrates

    SciTech Connect

    Prepelita, Petronela; Medianu, R.; Garoi, F.; Moldovan, A.

    2010-11-01

    In this paper we present some results regarding undoped and doped ZnO thin films deposited on various substrates like glass, silicon and kapton by rf magnetron sputtering. The influence of the amount of aluminum as well as the usage of different substrates on the final photovoltaic properties of the thin films is studied. For this, structural-morphological and optical investigations on the thin films are conducted. It was found that three important factors must be taken into account for adjusting the final desired application intended for the deposited thin films. These factors are: deposition conditions, the nature of both the dopant material and the substrate. A comparison study between undoped and doped case is also realized. Smooth Al doped ZnO thin films with a polycrystalline structure and a lower roughness than undoped ZnO are obtained.

  10. Microstructured Al/Fe2O3/Nitrocellulose Energetic Fibers Realized by Electrospinning

    NASA Astrophysics Data System (ADS)

    Li, Rui; Xu, Hongmei; Hu, Hailong; Yang, Guangcheng; Wang, Jun; Shen, Jinpeng

    2014-01-01

    At present, metastable intermolecular composites (MICs) have been widely studied for their potential in high-density energetic materials and nanotechnology, but the relatively low-pressure discharge in a short period of time and the oxidation of Al powders have seriously impeded their applications in rocket solid fuels and explosives. In this work, the authors successfully fabricated microstructured Al/Fe2O3/nitrocellulose (Al/Fe2O3/NC) fibers via simple electrospinning, introducing nitrocellulose (NC), a gas generator to MICs. In view of previous reports, wrapping nAl in NC fibers might reduce their further oxidation during storage. In addition, the thermal properties and elastic modulus of NC fibers were measured before and after adding Al/Fe2O3.

  11. Microstructure properties and microhardness of rapidly solidified Al64Cu20Fe12Si4 quasicrystal alloy

    NASA Astrophysics Data System (ADS)

    Karaköse, Ercan; Keskin, Mustafa

    2012-04-01

    This paper presents differences in the microstructure and microhardness properties of conventional casting (ingot) and rapidly solidified Al64Cu20Fe12Si4 quasicrystal (QC) alloys. The phases present in the Al64Cu20Fe12Si4 ingot alloy were determined to be icosahedral quasicrystalline (IQC) Ψ-Al65Cu20Fe15, cubic β-AlFe, tetragonal θ-Al2Cu, and monoclinic λ-A13Fe4 phases, whereas only IQC Ψ-Al65Cu20Fe15 and cubic β-AlFe phases were identified in the rapidly solidified alloy. The microhardness value of the melt spun alloy was measured to be approximately 790 kg/mm2. Microhardness increases with increasing solidification rates.

  12. A systematic ALCHEMI study of Fe-doped NiAl alloys

    SciTech Connect

    Anderson, I.M.; Bentley, J.; Duncan, A.J.

    1995-06-01

    ALCHEMI site-occupation studies of alloying additions to ordered aluminide intermetallic alloys have been performed with varying degrees of success, depending on the ionization delocalization correction. This study examines the variation in the site-occupancy of Fe in B2-ordered NiAl vs solute concentration and alloy stoichiometry. The fraction of Fe on the `Ni` site is plotted vs Fe concentration. The good separation among the data from alloys of the three stoichiometries shows that the site occupancy of iron depends on the relative concentrations of the Ni and Al host elements; however a preference for the `Ni` site is clearly indicated.

  13. Comparative study using MS and XRD of Fe80Al20 alloy produced by mechanical alloying

    NASA Astrophysics Data System (ADS)

    Hadef, F.; Otmani, A.; Grenèche, J. M.

    2013-08-01

    An X-ray diffraction and 57Fe Mössbauer effect study of mechanically alloyed Fe80Al20 is presented. X-ray measurements indicate that the disordered bcc α-Fe(Al) solid solution was formed after 2 h of milling, while the analysis of Mössbauer spectra suggested that total dissolution of aluminium is achieved after 10 h of milling. These differences can be attributed to: (i) rapid nanocrystallization of aluminium and/or (ii) small particles with small amounts of aluminium cannot be detected by the X-ray diffraction technique.

  14. Incommensurate modulated structure study of a Cu-Zn-Al-Zr phase

    SciTech Connect

    Chung, C.Y.; Zou, W.H.; Han, X.D.; Lam, C.W.H.; Lai, J.K.L.; Gao, M.; Duan, X.F.

    1998-09-18

    Zr was added to Cu-Zn-Al shape memory alloy as a grain refinement element. There are two new phases, Cu{sub 50.2}Zr{sub 24.6}Al{sub 17.3}Zn{sub 7.9} (at%) (Z{sub 1} phase) and Cu{sub 57.4}Zr{sub 20.4}Zn{sub 10.3}Al{sub 11.9} (at%) (Z{sub 2}) phase is studied in detail in the present paper. The results of electron diffraction and high-resolution electron microscopy (HREM) investigations indicated a one-dimensional incommensurate modulated structure in the Z{sub 2} phase. The average structure of the phase is base-centered orthorhombic. The systematic reflection conditions associated with the main and satellite reflections demonstrate that the Bravais class of the Z{sub 2} phases is P{sub 11{bar 1}}{sup Cmmm} type in a (3 + 1) dimensional space for the incommensurate modulated structure. The substitution modulation effects of the Al and Zr elements are revealed by energy-filtered transmission electron microscopy (EFTEM), {l_brace}1{bar 3}{bar 2}{r_brace} compound-type twins are observed in the Z{sub 2} phase. The relationship between the Z{sub 1} and Z{sub 2} phases in the alloy is discussed.

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

    NASA Astrophysics Data System (ADS)

    Tao, B. S.; Li, D. L.; Yuan, Z. H.; Liu, H. F.; Ali, S. S.; Feng, J. F.; Wei, H. X.; Han, X. F.; Liu, Y.; Zhao, Y. G.; Zhang, Q.; Guo, Z. B.; Zhang, X. X.

    2014-09-01

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

  16. Nucleation mechanism of nano-sized NaZn13-type and α-(Fe,Si) phases in La-Fe-Si alloys during rapid solidification

    NASA Astrophysics Data System (ADS)

    Hou, Xue-Ling; Xue, Yun; Liu, Chun-Yu; Xu, Hui; Han, Ning; Ma, Chun-Wei; Phan, Manh-Huong

    2015-03-01

    The nucleation mechanism involving rapid solidification of undercooled La-Fe-Si melts has been studied experimentally and theoretically. The classical nucleation theory-based simulations show a competitive nucleation process between the α-(Fe,Si) phase (size approximately 10 to 30 nm) and the cubic NaZn13-type phase (hereinafter 1:13 phase, size approximately 200 to 400 nm) during rapid solidification, and that the undercooled temperature change ∆ T plays an important factor in this process. The simulated results about the nucleation rates of the α-(Fe,Si) and 1:13 phases in La-Fe-Si ribbons fabricated by a melt-spinner using a copper wheel with a surface speed of 35 m/s agree well with the XRD, SEM, and TEM studies of the phase structure and microstructure of the ribbons. Our study paves the way for designing novel La-Fe-Si materials for a wide range of technological applications.

  17. Thermal Stability of the Dynamic Magnetic Properties of FeSiAl-Al2O3 and FeSiAl-SiO2 Films Grown by Gradient-Composition Sputtering Technique

    NASA Astrophysics Data System (ADS)

    Zhong, Xiaoxi; Phuoc, Nguyen N.; Soh, Wee Tee; Ong, C. K.; Peng, Long; Li, Lezhong

    2017-01-01

    We carry out a systematic investigation of the dynamic magnetic properties of FeSiAl-Al2O3 and FeSiAl-SiO2 thin films prepared by gradient-composition deposition technique with respect to temperature in the range of 300 K to 420 K. It was found that the magnetic anisotropy field ( H K) and ferromagnetic resonance frequency ( f FMR) are increased with increasing deposition angle ( β) due to the enhancement of stress ( σ) when concentrations of Al and O or Si and O are increased. The thermal stability of FeSiAl-Al2O3 films show a very interesting behavior with the magnetic anisotropy increasing with temperature when the deposition angle is increased. In contrast, when the deposition angle is lower, the usual trend of decreasing magnetic anisotropy with increasing temperature is observed. Moreover, the temperature-dependent behaviors of the dynamic permeability and effective Gilbert damping coefficient ( α eff) for FeSiAl-Al2O3 and FeSiAl-SiO2 films at different deposition angles are discussed in detail.

  18. Influence of addition of Si in FeAl alloys: Theory

    NASA Astrophysics Data System (ADS)

    Apiñaniz, E.; Legarra, E.; Plazaola, F.; Garitaonandia, J. S.

    The magnetic behaviour of Fe-based magnetic systems has been studied theoretically and experimentally for many years [E.P. Wohlfath, K.H.J. Buschow, Handbook of Ferromagnetic Materials, vol. 4, North-Holland Elsevier Science Publishers, Amsterdam, New York, Oxford, Tokyo, 1988 (Chapter 1)]. Starting with Al dissolved in Fe, the first stable structure is the D03 cubic structure and it exists over the range 23-37 at% Al. In this range these alloys present interesting magnetic properties. The other stable compound existing over a wide range of composition is FeAl which is also cubic, with the B2 structure (CsCl), and it exists over the range 37-50 at% Al. On the other hand, the FeAlSi alloys show the D03 structure, but do not show the B2 structure. The effect of Si in these alloys is double; on the one hand, it contributes to the decrease of the lattice parameter which, as reported by Nogues et al. [Phys. Rev. B 74 (2006) 024407], has a major influence on the magnetism and, on the other hand, having one more p electron than the Al atom, it promotes the charge transfer from Si to Fe atoms, as reported by Legarra et al. [Hyperfine Interact. 169 (2006) 1217-1222]. In this work, we perform ab-initio electronic calculations by means of tight binding linear muffin-tin orbital (TBLMTO) and Vienna Ab-initio Simulation Package (VASP) in order to study the magnetic contribution of Si/Al substitution in the FeAl alloys.

  19. High-pressure modifications of CaZn{sub 2}, SrZn{sub 2}, SrAl{sub 2}, and BaAl{sub 2}: Implications for Laves phase structural trends

    SciTech Connect

    Kal, Subhadeep; Stoyanov, Emil; Belieres, Jean-Philippe; Groy, Thomas L.; Norrestam, Rolf; Haeussermann, Ulrich

    2008-11-15

    High-pressure forms of intermetallic compounds with the composition CaZn{sub 2}, SrZn{sub 2}, SrAl{sub 2}, and BaAl{sub 2} were synthesized from CeCu{sub 2}-type precursors (CaZn{sub 2}, SrZn{sub 2}, SrAl{sub 2}) and Ba{sub 21}Al{sub 40} by multi-anvil techniques and investigated by X-ray powder diffraction (SrAl{sub 2} and BaAl{sub 2}), X-ray single-crystal diffraction (CaZn{sub 2}), and electron microscopy (SrZn{sub 2}). Their structures correspond to that of Laves phases. Whereas the dialuminides crystallize in the cubic MgCu{sub 2} (C15) structure, the dizincides adopt the hexagonal MgZn{sub 2} (C14) structure. This trend is in agreement with the structural relationship displayed by sp bonded Laves phase systems at ambient conditions. - Graphical abstract: CeCu{sub 2}-type polar intermetallics can be transformed to Laves phases upon simultaneous application of pressure and temperature. The observed structures are controlled by the valence electron concentration.

  20. Photovoltaic study of dye sensitized solar cells based on TiO2, ZnO:Al3+ nanoparticles

    NASA Astrophysics Data System (ADS)

    Sánchez Godoy, H. E.; Rodríguez-Rojas, R. A.; Castañeda-Contreras, J.; Marañón-Ruiz, V. F.; Pérez-Ladrón de Guevara, H.; López-Luke, T.; De la Rosa-Cruz

    2015-10-01

    A technique to fabricate dye (rhodamine B) sensitized solar cells based on Titanium Oxide (TiO2) and Zinc Oxide (ZnO) nanoparticles are reported. The TiO2 was synthesized using the sol-gel method and the ZnO was synthesized by hydrolysis method to obtain nanoparticles of ~ 5 nm and 150 nm respectively. ZnO was doped with Al3+ in order to enhance the photovoltaic efficiency to promote the electrons mobility. The photovoltaic conversion characterization of films of TiO2, ZnO and ZnO:Al3+ nanoparticles is also reported. The generated photocurrent was measured by two methods; one of those uses a three electrode electrochemical cell and the other use an electronic array where the cells were exposed to UV lamp and the sun light. The role of the TiO2, ZnO and Al3+ doped ZnO nanoparticles is discussed to obtain a better efficiency in the generation of photocurrent (PC). The results exhibited by the electrochemical cell method, efficiencies of 0.55 (PC=187 μA/cm2) and 0.22 (PC=149 μA/cm2) for TiO2 and undoped ZnO respectively. However, when ZnO is doped with Al3+ at the higher concentration the efficiency was 0.44. While using the electronic array the results exhibited efficiencies of 0.31 (PC=45 μA/cm2) and 0.09 (PC=16 μA/cm2) for TiO2 and undoped ZnO respectively. However, when ZnO is doped with Al3+ at the higher concentration the efficiency was 0.44 and 0.48 for electrochemical cell and electronic array respectively. This shows that Al3+ enhances the photogenerated charge carriers increasing the mobility of electrons.

  1. 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.

  2. Amplified spontaneous emission from ZnO in n-ZnO/ZnO nanodots-SiO(2) composite/p-AlGaN heterojunction light-emitting diodes.

    PubMed

    Shih, Ying Tsang; Wu, Mong Kai; Li, Wei Chih; Kuan, Hon; Yang, Jer Ren; Shiojiri, Makoto; Chen, Miin Jang

    2009-04-22

    This study demonstrates amplified spontaneous emission (ASE) of the ultraviolet (UV) electroluminescence (EL) from ZnO at lambda~380 nm in the n-ZnO/ZnO nanodots-SiO(2) composite/p- Al(0.12)Ga(0.88)N heterojunction light-emitting diode. A SiO(2) layer embedded with ZnO nanodots was prepared on the p-type Al(0.12)Ga(0.88)N using spin-on coating of SiO(2) nanoparticles followed by atomic layer deposition (ALD) of ZnO. An n-type Al-doped ZnO layer was deposited upon the ZnO nanodots-SiO(2) composite layer also by the ALD technique. High-resolution transmission electron microscopy (HRTEM) reveals that the ZnO nanodots embedded in the SiO(2) matrix have diameters of 3-8 nm and the wurtzite crystal structure, which allows the transport of carriers through the thick ZnO nanodots-SiO(2) composite layer. The high quality of the n-ZnO layer was manifested by the well crystallized lattice image in the HRTEM picture and the low-threshold optically pumped stimulated emission. The low refractive index of the ZnO nanodots-SiO(2) composite layer results in the increase in the light extraction efficiency from n-ZnO and the internal optical feedback of UV EL into n-ZnO layer. Consequently, significant enhancement of the UV EL intensity and super-linear increase in the EL intensity, as well as the spectral narrowing, with injection current were observed owing to ASE in the n-ZnO layer.

  3. Magnetic Origin of Giant Magnetoelectricity in Doped Y-type Hexaferrite Ba0.5Sr1.5Zn2(Fe1 -xAlx)12O22

    NASA Astrophysics Data System (ADS)

    Noh, Woo-Suk; Ko, Kyung-Tae; Chun, Sae Hwan; Kim, Kee Hoon; Park, Byeong-Gyu; Kim, Jae-Young; Park, Jae-Hoon

    2015-03-01

    We investigated site-specific magnetic behaviors of multiferroic Ba0.5Sr1.5Zn2(Fe1 -xAlx)12O22 using Fe L2 ,3-edge x-ray magnetic circular dichroism. The Al dopants mostly replace the Fe3 + ions at octahedral (Oh) sites, which contribute unquenched angular momenta through off-centering displacements. This replacement greatly reduces the magnetic anisotropy energy to change the magnetic order from a helical to a heliconical type with enhanced magnetoelectric susceptibility (αME). The tetrahedral (Td) Fe sites exhibit magnetic hysteresis distinguishable from that of the Oh sites, especially at low magnetic fields. These results provide essential clues for the heliconical order with a giant αME and multibit memory effects in the Al-doped Y-type hexaferrite.

  4. Dendritic Growth Morphologies in Al-Zn Alloys—Part II: Phase-Field Computations

    NASA Astrophysics Data System (ADS)

    Dantzig, J. A.; Di Napoli, Paolo; Friedli, J.; Rappaz, M.

    2013-12-01

    In Part I of this article, the role of the Zn content in the development of solidification microstructures in Al-Zn alloys was investigated experimentally using X-ray tomographic microscopy. The transition region between dendrites found at low Zn content and dendrites found at high Zn content was characterized by textured seaweed-type structures. This Dendrite Orientation Transition (DOT) was explained by the effect of the Zn content on the weak anisotropy of the solid-liquid interfacial energy of Al. In order to further support this interpretation and to elucidate the growth mechanisms of the complex structures that form in the DOT region, a detailed phase-field study exploring anisotropy parameters' space is presented in this paper. For equiaxed growth, our results essentially recapitulate those of Haxhimali et al.[1] in simulations for pure materials. We find distinct regions of the parameter space associated with and dendrites, separated by a region where hyperbranched dendrites are observed. In simulations of directional solidification, we find similar behavior at the extrema, but in this case, the anisotropy parameters corresponding to the hyperbranched region produce textured seaweeds. As noted in the experimental work reported in Part I, these structures are actually dendrites that prefer to grow misaligned with respect to the thermal gradient direction. We also show that in this region, the dendrites grow with a blunted tip that oscillates and splits, resulting in an oriented trunk that continuously emits side branches in other directions. We conclude by making a correlation between the alloy composition and surface energy anisotropy parameters.

  5. Structure and thermoelectric properties of Al-doped ZnO films prepared by thermal oxidization under high magnetic field

    NASA Astrophysics Data System (ADS)

    Liu, Shiying; Peng, Sunjuan; Ma, Jun; Li, Guojian; Qin, Xuesi; Li, Mengmeng; Wang, Qiang

    2017-04-01

    This paper studies the effects of high magnetic field (HMF) on the structure, optical and thermoelectric properties of the doped ZnO thin films. The results show that both Al dopant and application of HMF can affect the crystal structure, surface morphology, elemental distribution and so on. The particles of the thin films become small and regular by doping Al. The ZnO films oxidized from the Au/Zn bilayer have needle structure. The ZnO films oxidized from the Au/Zn-Al bilayer transform to spherical from hexagonal due to the application of HMF. The transmittance decreases with doping Al because of the opaque of Al element and decreases with the application of HMF due to the dense structure obtained under HMF. Electrical resistivity (ρ) of the ZnO films without Al decreases with increasing measurement temperature (T) and is about 1.5 × 10-3 Ω·m at 210 °C. However, the ρ of the Al-doped ZnO films is less than 10-5 Ω·m. The Seebeck coefficient (S) of the films oxidized from the Au/Zn-Al films reduces with increasing T. The S values oxidized under 0 T and 12 T conditions are 2.439 μV/K and -3.415 μV/K at 210 °C, respectively. Power factor reaches the maximum value (3.198 × 10-4 W/m·K2) at 210 °C for the film oxidized under 12 T condition. These results indicate that the Al dopant and the application of HMF can be used to control structure and thermoelectric properties of doped ZnO films.

  6. Synthesis of monodispersed ZnAl{sub 2}O{sub 4} nanoparticles and their tribology properties as lubricant additives

    SciTech Connect

    Song, Xiaoyun; Zheng, Shaohua; Zhang, Jun; Li, Wei; Chen, Qiang; Cao, Bingqiang

    2012-12-15

    Graphical abstract: Display Omitted Highlights: ► The preparation of ZnAl{sub 2}O{sub 4} nanoparticles was realized by hydrothermal method. ► After surface modification, ZnAl{sub 2}O{sub 4} nanoparticles of narrow size distribution can disperse in lubricating oil stably. ► The modified ZnAl{sub 2}O{sub 4} nanoparticles as lubricating oil additives exhibit good tribology properties. -- Abstract: Monodispersed spherical zinc aluminate spinel (ZnAl{sub 2}O{sub 4}) nanoparticles were synthesized via a solvothermal method and modified by oleic acid in cyclohexanol solution. The nanoparticles were characterized by X-ray diffraction (XRD), scanning electron microscope (SEM) and infrared spectrum (IR). The dispersion ability of nanoparticles in lubricant oil was measured with optical absorbance spectrum. The results show that the modified nanoparticles are nearly monodispersed and can stably disperse in lubricant oil. The tribological properties of the ZnAl{sub 2}O{sub 4} nanoparticles as an additive in lubricant oil were evaluated with four-ball test and thrust-ring test. For comparison, ZnO and Al{sub 2}O{sub 3} nanoparticles as additive in lubricant oil were also tested respectively. The results show that ZnAl{sub 2}O{sub 4} nanoparticles exhibit better tribology properties in terms of anti-wear and anti-friction than ZnO or Al{sub 2}O{sub 3} nanoparticles. The anti-friction and anti-wear mechanisms were discussed and the lubricating effect of ZnAl{sub 2}O{sub 4} nanoparticles can be attributed to nano-bearings effect and tribo-sintering mechanism.

  7. An overview of the welding of Ni{sub 3}Al and Fe{sub 3}Al alloys

    SciTech Connect

    Santella, M.L.

    1996-12-31

    Weldability (degree to which defect formation is resisted when an alloy is welded) is an issue in fabrication of Ni{sub 3}Al and Fe{sub 3}Al. Work to define and improve welding of Ni{sub 3}Al and Fe{sub 3}Al alloys is reviewed and progress illustrated by examples of current activities. The cast Ni{sub 3}Al alloys currently under development, IC221M and IC396M, have low resistance to solidification cracking and hence difficult to weld. Modifications to the composition of both base alloys and weld deposits,however, increase their resistance to cracking. Crack-free, full-penetration welds were made in centrifugally cast tubes of IC221M. Tensile and stress- rupture properties of the weldments compare favorably with base metal properties. Weldability issues have limited the use of Fe{sub 3}Al alloys to weld overlay applications. Filler metal compositions suitable for weld overlay cladding were developed, and the preheat and postweld heat treatment needed to avoid cracking, were determined experimentally.

  8. Search for the origin of giant Tc suppression in YBa 2Cu 3O 7- d doped simultaneously with Fe and Zn

    NASA Astrophysics Data System (ADS)

    Ogale, S. B.; Gapchup, K. M.; Lele, Pramada; Choughule, D. D.; Chikate, R. C.; Marest, G.

    1996-02-01

    In a recent paper [S.B. Ogale et al., Solid State Commun 89 (1994) 1] we reported that the superconducting transition temperature ( Tc) is suppressed drastically in YBa 2Cu 3O 7- d (YBCO) doped simultaneously with Fe and Zn as compared to an equivalent total doping of Zn or Fe, on the higher side of dopant concentration (approximately 3% or more substitution at Cu sites). In this paper, we report the results of our studies on this co-doped system, performed using the techniques of Mössbauer spectroscopy, X-ray diffraction, X-ray photoelectron spectroscopy, and iodometry, to explore the origin of the reported observation. The Tc suppression appears to be caused by a drop in the concentration of mobile holes in the CuO 2 planes as well as to be due to a reduced dimensionality of the system resulting from the suppression of the order parameter between the CuO 2 planes by the Fe atoms.

  9. 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.

  10. Interfacial perpendicular magnetic anisotropy and damping parameter in ultra thin Co2FeAl films

    NASA Astrophysics Data System (ADS)

    Cui, Yishen; Khodadadi, Behrouz; Schäfer, Sebastian; Mewes, Tim; Lu, Jiwei; Wolf, Stuart A.

    2013-04-01

    B2-ordered Co2FeAl films were synthesized using an ion beam deposition tool. A high degree of chemical ordering ˜81.2% with a low damping parameter (α) less than 0.004 was obtained in a 50 nm thick film via rapid thermal annealing at 600 °C. The perpendicular magnetic anisotropy (PMA) was optimized in ultra thin Co2FeAl films annealed at 350 °C without an external magnetic field. The reduced thickness and annealing temperature to achieve PMA introduced extrinsic factors thus increasing α significantly. However, the observed damping of Co2FeAl films was still lower than that of Co60Fe20B20 films prepared at the same thickness and annealing temperature.

  11. Magnetic properties and microstructure of L10-FePt/AlN perpendicular nanocomposite films

    NASA Astrophysics Data System (ADS)

    Feng, C.; Zhang, E.; Xu, C. C.; Li, N.; Jiang, Y.; Yu, G. H.; Li, B. H.

    2011-09-01

    Based on interfacial manipulation of a MgO (100) substrate and non-magnetic AlN compound, L10-FePt/AlN perpendicular nanocomposite films were designed and prepared. Systematic studies on magnetic properties and microstructure of the films show that the MgO substrate controls crystal orientation of the FePt lattice and induces perpendicular magnetic anisotropy (PMA). The AlN compound helps to control the island growth mode and acts as isolators of FePt islands to pin the sites of FePt domains, resulting in manipulation of coercivity and magnetic exchange interaction of the films. Moreover, PMA of the film was optimized by appropriately decreasing film thickness or increasing substrate temperature.

  12. Status of FeCrAl ODS Irradiations in the High Flux Isotope Reactor

    SciTech Connect

    Field, Kevin G.; Howard, Richard H.

    2016-08-19

    FeCrAl oxide-dispersion strengthened (ODS) alloys are an attractive sub-set alloy class of the more global FeCrAl material class for nuclear applications due to their high-temperature steam oxidation resistance and hypothesized enhanced radiation tolerance. A need currently exists to determine the radiation tolerance of these newly developed alloys. To address this need, a preliminary study was conducted using the High Flux Isotope Reactor (HFIR) to irradiate an early generation FeCrAl ODS alloy, 125YF. Preliminary post-irradiation examination (PIE) on these irradiated specimens have shown good radiation tolerance at elevated temperatures (≥330°C) but possible radiation-induced hardening and embrittlement at irradiations of 200°C to a damage level of 1.9 displacement per atom (dpa). Building on this experience, a new series of irradiations are currently being conceptualized. This irradiation series called the FCAD irradiation program will irradiate the latest generation FeCrAl ODS and FeCr ODS alloys to significantly higher doses. These experiments will provide the necessary information to determine the mechanical performance of irradiated FeCrAl ODS alloys at light water reactor and fast reactor conditions.

  13. Observations of the Minor Species Al, Fe and Ca(+) in Mercury's Exosphere

    NASA Technical Reports Server (NTRS)

    Bida, Thomas A.; Killen, Rosemary M.

    2011-01-01

    We report the first detections of Al and Fe, and strict upper limits for Ca(+) in the exosphere of Mercury, using the HIRES spectrometer at the Keck I telescope. We report observed 4-sigma tangent columns of 1.5x10(exp 7) Al atoms per square centimeter at an altitude of 1220 km (1.5 Mercury radii (R(sub M)) from planet center), and that for Fe of 1.6 x 10 per square centimeter at an altitude of 950 km (1.4 R(sub M)). The observed 3-sigma Ca(+) column was 3.9x10(exp 6) ions per square centimeter at an altitude of 1630 km (1.67 R(sub M). A simple model for zenith column abundances of the neutral species were 9.5 x 10(exp 7) Al per square centimeter, and 3.0 x 10(exp 8) Fe per square centimeter. The observations appear to be consistent with production of these species by impact vaporization with a large fraction of the ejecta in molecular form. The scale height of the Al gas is consistent with a kinetic temperature of 3000 - 9000 K while that of Fe is 10500 K. The apparent high temperature of the Fe gas would suggest that it may be produced by dissociation of molecules. A large traction of both Al and Fe appear to condense in a vapor cloud at low altitudes.

  14. Large magnetization and high Curie temperature in highly disordered nanoscale Fe2CrAl thin films

    NASA Astrophysics Data System (ADS)

    Dulal, Rajendra P.; Dahal, Bishnu R.; Forbes, Andrew; Pegg, Ian L.; Philip, John

    2017-02-01

    We have successfully grown nanoscale Fe2CrAl thin films on polished Si/SiO2 substrates using an ultra-high vacuum deposition with a base pressure of 9×10-10 Torr. The thickness of thin films ranges from 30 to 100 nm. These films exhibit cubic crystal structure with lattice disorder and display ferromagnetic behavior. The Curie temperature is greater than 400 K, which is much higher than that reported for bulk Fe2CrAl. The magnetic moments of the films varies from 2.5 to 2.8 μB per formula unit, which is larger than the reported bulk values. Thus, the disordered nanoscale Fe2CrAl films exhibit strong Fe-Fe exchange interactions through Fe-Cr-Fe and Fe-Al-Fe layers, resulting in both a large magnetization and a high Curie temperature.

  15. Atomic origin of the spin-polarization of the Co2FeAl Heusler compound

    NASA Astrophysics Data System (ADS)

    Liang, Jaw-Yeu; Lam, Tu-Ngoc; Lin, Yan-Cheng; Chang, Shu-Jui; Lin, Hong-Ji; Tseng, Yuan-Chieh

    2016-02-01

    Using synchrotron x-ray techniques, we studied the Co2FeAl spin-polarization state that generates the half-metallicity of the compound during an A2 (low-spin)  →  B2 (high-spin) phase transition. Given the advantage of element specificity of x-ray techniques, we could fingerprint the structural and magnetic cross-reactions between Co and Fe within a complex Co2FeAl structure deposited on a MgO (0 0 1) substrate. X-ray diffraction and extended x-ray absorption fine structure investigations determined that the Co atoms preferably populate the (1/4,1/4,1/4) and (3/4,3/4,3/4) sites during the development of the B2 phase. X-ray magnetic spectroscopy showed that although the two magnetic elements were ferromagnetically coupled, they interacted in a competing manner via a charge-transfer effect, which enhanced Co spin polarization at the expense of Fe spin polarization during the phase transition. This means that the spin-polarization of Co2FeAl was electronically dominated by Fe in A2 whereas the charge transfer turned the dominance to Co upon B2 formation. Helicity-dependent x-ray absorption spectra also revealed that only the minority state of Co/Fe was involved in the charge-transfer effect whereas the majority state was independent of it. Despite an overall increase of Co2FeAl magnetization, the charge-transfer effect created an undesired trade-off during the Co-Fe exchange interactions, because of the presence of twice as many X sites (Co) as Y sites (Fe) in the Heusler X 2 YZ formula. This suggests that the spin-polarization of Co2FeAl is unfortunately regulated by compromising the enhanced X (Co) sites and the suppressed Y (Fe) sites, irrespective of the development of the previously known high-spin-polarization phase of B2. This finding provides a possible cause for the limited half-metallicity of Co2FeAl discovered recently. Electronic tuning between the X and Y sites is necessary to further increase the spin-polarization, and likely the half

  16. Atomic scattering spectroscopy for determination of the polarity of semipolar AlN grown on ZnO

    SciTech Connect

    Kobayashi, Atsushi; Ohta, Jitsuo; Ueno, Kohei; Oshima, Masaharu; Fujioka, Hiroshi

    2013-11-04

    Determination of the polarity of insulating semipolar AlN layers was achieved via atomic scattering spectroscopy. The back scattering of neutralized He atoms on AlN surfaces revealed the atomic alignment of the topmost layers of semipolar AlN and the ZnO substrate. Pole figures of the scattering intensity were used to readily determine the polarity of these wurtzite-type semipolar materials. In addition, we found that +R-plane AlN epitaxially grows on −R-plane ZnO, indicating that the polarity flips at the semipolar AlN/ZnO interface. This polarity flipping is possibly explained by the appearance of −c and m-faces on the −R ZnO surfaces, which was also revealed by atomic scattering spectroscopy.

  17. The influence of cooling rate and Fe/Cr content on the evolution of Fe-rich compounds in a secondary Al-Si-Cu diecasting alloy

    NASA Astrophysics Data System (ADS)

    Fabrizi, A.; Timelli, G.

    2016-03-01

    This study investigates the morphological evolution of primary α-Al(Fe,Mn,Cr)Si phase in a secondary Al-Si-Cu alloy with respect to the initial Fe and Cr contents as well as to the cooling rate. The solidification experiments have been designed in order to cover a wide range of cooling rates, and the Fe and Cr contents have been varied over two levels. Metallographic and image analysis techniques have been used to quantitatively examine the microstructural changes occurring at different experimental conditions. The morphological evolution of the α-Fe phase has been also analysed by observing deep etched samples. By changing the cooling rate, α-Al15(Fe,Mn,Cr)3Si2 dodecahedron crystals, as well as Chinese- script, branched structures and dendrites form, while primary coarse β-Al5(Fe,Mn)Si needles appear in the alloy with the highest Fe content at low cooling rates.

  18. Transformation of α-Al(Fe,Mn)Si in Al-7Si-0.4Mg cast alloys after solution heat treatment

    NASA Astrophysics Data System (ADS)

    Han, Sang Won

    2013-01-01

    The α-Al(Fe,Mn)Si compound in an Al-7Si-0.35Mg-0.2Fe-xMn cast alloy has two shapes, a needle-like shape and a Chinese script shape. These two kinds of compounds are tinged with either white or gray tones irrespective of their shape. Unlike compounds with a white tone, during solution heat treatment, all α-Al (Fe,Mn)Si compounds with a gray tone experience severe dissolution. Concerning white-tinged α-Al (Fe,Mn)Si compounds, unlike the needle-like α-Al(Fe,Mn)Si, α-Al(Fe,Mn)Si that resembles Chinese script is rarely transformed.

  19. Facile synthesis of ZnFe{sub 2}O{sub 4}/reduced graphene oxide nanohybrids for enhanced microwave absorption properties

    SciTech Connect

    Yang, Zhiwei; Wan, Yizao; Xiong, Guangyao; Li, Deying; Li, Qiuping; Ma, Chunying; Guo, Ruisong; Luo, Honglin

    2015-01-15

    Highlights: • ZnFe{sub 2}O{sub 4} nanoparticles with a small diameter are uniformly anchored on RGO surface. • A strong interfacial bonding was formed between ZnFe{sub 2}O{sub 4} nanoparticles and RGO. • The minimum RL of ZnFe{sub 2}O{sub 4}/RGO nanohybrids is −29.3 dB at 16.7 GHz and 1.6 mm. • ZnFe{sub 2}O{sub 4}/RGO nanohybrids show great promise as a microwave absorption material. - Abstract: The nanohybrids composed of ZnFe{sub 2}O{sub 4} and reduced graphene oxide (RGO) have been synthesized by a facile one-step hydrothermal strategy. The morphology and structure of ZnFe{sub 2}O{sub 4}/RGO nanohybrids were characterized by transmission electron microscopy, X-ray diffraction and Raman spectra. RGO content was also determined by thermogravimetric analysis. The results confirm the formation of nanohybrids with a content of 20.4 wt% RGO and extensive interfaces between small-diameter ZnFe{sub 2}O{sub 4} nanoparticles and RGO sheets. The magnetic properties and electromagnetic parameters of ZnFe{sub 2}O{sub 4}/RGO nanohybrids were measured and the microwave absorption properties were investigated. ZnFe{sub 2}O{sub 4}/RGO nanohybrids exhibit the advantages of thin matching thickness and strong absorption at high frequency bands. It is demonstrated that ZnFe{sub 2}O{sub 4}/RGO nanohybrids can be a powerful candidate in the field of microwave absorption.

  20. Magnetic properties of Nd-Fe-Co(Cu)-Al-B amorphous alloys prepared by nonequilibrium techniques

    NASA Astrophysics Data System (ADS)

    Kumar, G.; Eckert, J.; Roth, S.; Löser, W.; Ram, S.; Schultz, L.

    2002-03-01

    The amorphous alloys Nd40Fe40Co5Al8B7, Nd57Fe20Co5Al10B8, and Nd57Fe20Cu5Al10B8 were prepared by copper mold casting, melt spinning, and mechanical alloying. Despite their similar x-ray diffraction patterns, samples display different magnetic and thermal behavior correlated with the method of preparation. The fully amorphous melt-spun ribbons exhibit relatively soft magnetic properties with coercivities ≈40 kA/m at room temperature and a Curie temperature (TC)≈474 K. Apparently only the mold-cast cylinders of 3 mm diameter show hard magnetic behavior with a coercivity in the range of 258-270 kA/m (depending on composition) and have approximately the same TC as that of the melt-spun ribbons. An additional magnetic transition at 585 K due to the presence of Nd2Fe14B phase in the case of Nd40Fe40Co5Al8B7 cast rod has been observed. Heat treatment above crystallization temperature in as-cast Nd57Fe20Co5Al10B8 and Nd57Fe20Cu5Al10B8 samples destroys the hard magnetic properties. In contrast, mechanically alloyed amorphous samples are soft magnetic with maximum coercivity up to 11 kA/m but show an entirely different TC≈680-740 K, which is rather characteristic of an Fe solid solution. The magnetic properties are discussed in terms of different local atomic environment and cluster sizes in amorphous samples prepared by different methods.