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Sample records for al fe si

  1. 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.

  2. Structure of Fe3Si/Al/Fe3Si thin film stacks on GaAs(001)

    NASA Astrophysics Data System (ADS)

    Jenichen, B.; Jahn, U.; Nikulin, A.; Herfort, J.; Kirmse, H.

    2015-11-01

    Fe3Si/Al/Fe3Si/GaAs(001) structures were deposited by molecular-beam epitaxy and characterized by transmission and scanning electron microscopy, and x-ray diffraction. The first Fe3Si film on GaAs(001) grew epitaxially as a (001) oriented single crystal. The subsequent Al film grew almost {111} oriented in a fibrous texture although the underlying Fe3Si is exactly (001) oriented. The growth in this orientation is triggered by a thin transition region which is formed at the Fe3Si/Al interface. In the end, after the growth of the second Fe3Si layer on top of the Al, the final properties of the whole stack depended on the substrate temperature T s during deposition of the last film. The upper Fe3Si films are mainly {110} oriented although they are poly-crystalline. At lower T s, around room temperature, all the films retain their original structural properties.

  3. Electron Diffraction Study of ?- and ? T -AlFeSi

    NASA Astrophysics Data System (ADS)

    Jensen, C. L.; Wyss, R. K.

    1988-04-01

    Electron diffraction patterns from a-AIFeSi and ? T -AlFeSi are compared. Unusual Kikuchi band patterns are found in both a and ? T . Structure factor calculations can be used to explain these patterns. Additional higher order Laue zone (HOLZ) rings are seen in ? T . Reflections located at n/9[521] are seen in some zero order Laue zones (ZOLZ) in ? T . These additional reflections are responsible for the additional HOLZ rings found in ? T . Most atomic positions in a and ? T are similar. The specific structural feature which causes the additional reflections in ? T is not known. Lattice imaging and image calculation will be necessary to determine the exact structure of ? T .

  4. 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.

  5. Synthesis, microstructure and magnetic properties of Fe3Si0.7Al0.3@SiO2 core-shell particles and Fe3Si/Al2O3 soft magnetic composite core

    NASA Astrophysics Data System (ADS)

    Wang, Jian; Fan, Xi'an; Wu, Zhaoyang; Li, Guangqiang

    2015-11-01

    Fe3Si0.7Al0.3@SiO2 core-shell particles and Fe3Si/Al2O3 soft magnetic composite core have been synthesized via a modified stber method combined with following high temperature sintering process. Most of conductive Fe3Si0.7Al0.3 particles could be uniformly coated by insulating SiO2 using the modified stber method. The Fe3Si0.7Al0.3@SiO2 core-shell particles exhibited good soft magnetic properties with low coercivity and high saturation magnetization. The reaction 4Al+3SiO2=2?-Al2O3+3Si took place during the sintering process. As a result the new Fe3Si/Al2O3 composite was formed. The Fe3Si/Al2O3 composite core displayed more excellent soft magnetic properties, better frequency stability at high frequencies, much higher electrical resistivity and lower core loss than the pure Fe3Si0.7Al0.3 core. The method of introducing insulating layers surrounding magnetic particles provides a promising route to develop new and high compact soft magnetic materials with good magnetic and electric properties.

  6. 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.

  7. SDAS, Si and Cu Content, and the Size of Intermetallics in Al-Si-Cu-Mg-Fe Alloys

    NASA Astrophysics Data System (ADS)

    Sivarupan, Tharmalingam; Taylor, John Andrew; Cceres, Carlos Horacio

    2015-05-01

    Plates of Al-(a)Si-(b)Cu-Mg-(c)Fe alloys with varying content of (mass pct) Si ( a = 3, 4.5, 7.5, 9, 10, or 11), Cu ( b = 0, 1, or 4), and Fe ( c = 0.2, 0.5 or 0.8) were cast in sand molds with a heavy chill at one end to ensure quasi-directional solidification over a wide range of Secondary Dendrite Arm Spacing (SDAS). Statistical analysis on the size of the ?-Al5FeSi, ?-Al8Fe2Si, or Al2Cu intermetallics on Backscattered Electron images showed that a high Si content reduced the size of the ? platelets in alloys with up to 0.5 Fe content regardless of the SDAS, whereas at small SDAS the refining effect extended up to 0.8 Fe, and involved ?-phase intermetallics which replaced the beta platelets at those concentrations. At low Si contents, a high Cu level appeared to have similar refining effects as increased Si, through the formation of ?-phase particles in the post-eutectic stage which agglomerated with the Al2Cu intermetallics. A high content of Si appears to make the overall refining process less critical in terms of SDAS/cooling rate.

  8. Electronic structure and magnetism on FeSiAl alloy: A DFT study

    NASA Astrophysics Data System (ADS)

    Cardoso Schwindt, V.; Sandoval, M.; Ardenghi, J. S.; Bechthold, P.; González, E. A.; Jasen, P. V.

    2015-09-01

    Density functional theory (DFT) calculation has been performed to study the electronic structure and chemical bonding in FeSiAl alloy. These calculations are useful to understand the magnetic properties of this alloy. Our results show that the mean magnetic moment of Fe atoms decreases due to the crystal structure and the effect of Si and Al. Depending on the environment, the magnetic moment of one Fe site (Fe1) increases to about 14.3% while of the other site (Fe2) decreases to about 25.9% (compared with pure bcc Fe). All metal-metal overlap interactions are bonding and slightly weaker than those found in the bcc Fe structure. The electronic structure (DOS) shows an important hybridization among Fe, Si and Al atoms, thus making asymmetric the PDOS with a very slight polarization of Al and Si atoms. Our study explains the importance of crystal structure in determining the magnetic properties of the alloys. FeSiAl is a good candidate for electromagnetic interference shielding combining low price and good mechanical and magnetic properties.

  9. CEMS Study on Fe-Si-Al Alloy Flakes-Polymer Composites

    NASA Astrophysics Data System (ADS)

    Nomura, K.; Suzuki, K.; Sawada, T.; Ujihira, Y.; Yoshida, S.

    2003-06-01

    The composites of Fe-Si-Al alloy flakes and dielectric polymer fabricated for a new noise suppression filter in high-frequency bands were characterized by transmission and conversion electron Mssbauer spectrometry (TMS and CEMS). The Fe-Si-Al flakes were prepared by sand milling the atomized sendust powder (9.7 wt.% Si, 5.4 wt.% Al, and balance Fe) in n-hexane for several hours and days. The deformed structures were estimated by magnetic hyperfine field (Hin) distributions, and the annealing effects were investigated. The composites of Fe-Si-Al alloy forged for less than 100 hours recovered the high permeability with production of D03 structure after annealing at 650C for 2 hours in Ar atmosphere. However, the Fe-Si-Al alloy flakes forged for 180 hours gave the broad Hin with high magnetic fields, and were decomposed into ?-Fe in the bulk and Fe species dispersed in the interface beneath the Si and Al oxides surface.

  10. 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.

  11. High-temperature oxidation of Fe-Cr-Al-Si alloys extruded into honeycomb structures

    SciTech Connect

    Ohashi, Tsuneaki; Harada, Takashi

    1996-10-01

    The oxidation behavior of Fe-20Cr-5Al-(0.5-5)Si and Fe-(12-20)Cr-(5-7)Al-(1-2)Si alloys extruded into honeycomb structures has been investigated at 1150{degrees}C in air for up to 500 hr. The oxidation weight gains decrease with increasing Si and Cr contents in the 5-Al alloys. Si additions are more efficient than Cr additions to reduce the weight gain. Increasing Si content in the 5-Al alloys suppresses the formation of an iron-chromium complex oxide, forming mullite and vitreous silica in the scale, although the location is not clearly indicated. The 5-Si alloy shows anisotropy in elongation of the honeycomb specimen during oxidation in the Fe-20Cr-5Al-xSi alloys, whereas alloying with Si and Cr does not improve the oxidation resistance of the 7-Al alloys significantly. These results are explained by Wagner`s theory of a secondary getter. However, the authors point out additionally that the difference between Si and Cr in the Pilling-Bedworth ratio and the solubility of their oxides in the Al{sub 2}O{sub 3} scale may contribute to the significant effect of Si additions. Finally, this paper demonstrates that the selected Fe-Cr-Al-Si honeycombs having walls 200 {mu}m thick show excellent oxidation resistance over 500 hr at 1150{degrees}C in air. The time to catastrophic oxidation is roughly proportional to the wall thickness in extruded honeycombs.

  12. Precipitation of β-Al5FeSi Phase Platelets in Al-Si Based Casting Alloys

    NASA Astrophysics Data System (ADS)

    Liu, L.; Mohamed, A. M. A.; Samuel, A. M.; Samuel, F. H.; Doty, H. W.; Valtierra, S.

    2009-10-01

    The aim of the present work has been to investigate the factors affecting the precipitation of the β-Al5FeSi iron intermetallic phase of directionally solidified A356- and 319-type alloys as a function of the iron content, a Sr addition of ~250 ppm, and superheating or cooling rates. The iron levels selected varied from 0.12 to 0.8 wt pct and cover the range of Fe levels in commercial casting alloys. The use of an end-chill mold provided different cooling rates along the height of the same casting, with dendritic arm spacing values that varied from ~15 to 85 μm, corresponding to levels of 5, 10, 30, 50, and 100 mm above the chill end. The microstructure and phase identification were monitored using optical microscopy, scanning electron microscopy (SEM), thermal analysis, and electron probe microanalysis (EPMA) techniques. An image analyzer was used in conjunction with the optical microscope for quantification purposes. The results showed that, for the range of cooling rates covered in the present study, the highest cooling rate (at a 5-mm distance from the chill) is the more significant parameter in controlling the size and distribution of the β-Al2FeSi intermetallic phase in the nonmodified 319 and 356 alloys. The addition of strontium leads to fragmentation of coeutectic or posteutectic β platelets. This effect diminishes with an increase in the iron concentration, and further strontium addition leads to the precipitation of Al2Si2Sr phase particles, instead.

  13. Solidification Sequence and Evolution of Microstructure During Rheocasting of Four Al-Si-Mg-Fe Alloys with Low Si Content

    NASA Astrophysics Data System (ADS)

    Payandeh, Mostafa; Jarfors, Anders E. W.; Wessén, Magnus

    2016-03-01

    Four Al-Si-Mg-Fe alloys with Si contents varying from 1.6 to 4.5 wt pct were rheocast, using the RheoMetal™ process to prepare slurry and cast in a vertical high-pressure die casting machine. Particle size and Si concentration in the α-Al particles in the slurry and in the as-rheocast component were investigated. A uniform distribution of Si in the globular α 1-Al particles was achieved in the slurry. In the rheocast samples, measurement of the α 1-Al particles showed that these particles did not increase significantly in size during pouring and secondary solidification. The two additional α-Al particles types, α 2-Al particles and α 3-Al particles, were identified as being a result of two discrete nucleation events taking place after slurry production. The Si concentration in the α 2-Al and α 3-Al particles indicated that the larger α 2-Al particles precipitated before the α 3-Al particles. In addition, in the as-rheocast condition, the Si distribution inside the α 1-Al particles showed three distinct zones; an unaffected zone, a transition zone, and in some cases the start of a dendritic/cellular zone. The phenomenon of dendritic growth of globular α 1-Al particles during secondary solidification occurred concomitantly with the final eutectic reaction and increased with increasing amount of the Al-Si eutectic phase.

  14. Solidification Sequence and Evolution of Microstructure During Rheocasting of Four Al-Si-Mg-Fe Alloys with Low Si Content

    NASA Astrophysics Data System (ADS)

    Payandeh, Mostafa; Jarfors, Anders E. W.; Wessn, Magnus

    2015-12-01

    Four Al-Si-Mg-Fe alloys with Si contents varying from 1.6 to 4.5 wt pct were rheocast, using the RheoMetal process to prepare slurry and cast in a vertical high-pressure die casting machine. Particle size and Si concentration in the ?-Al particles in the slurry and in the as-rheocast component were investigated. A uniform distribution of Si in the globular ? 1-Al particles was achieved in the slurry. In the rheocast samples, measurement of the ? 1-Al particles showed that these particles did not increase significantly in size during pouring and secondary solidification. The two additional ?-Al particles types, ? 2-Al particles and ? 3-Al particles, were identified as being a result of two discrete nucleation events taking place after slurry production. The Si concentration in the ? 2-Al and ? 3-Al particles indicated that the larger ? 2-Al particles precipitated before the ? 3-Al particles. In addition, in the as-rheocast condition, the Si distribution inside the ? 1-Al particles showed three distinct zones; an unaffected zone, a transition zone, and in some cases the start of a dendritic/cellular zone. The phenomenon of dendritic growth of globular ? 1-Al particles during secondary solidification occurred concomitantly with the final eutectic reaction and increased with increasing amount of the Al-Si eutectic phase.

  15. 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.

  16. Compaction behavior of rapidly solidified Al-Si-Fe-Cr alloy powders

    SciTech Connect

    Kin, H.S.; Lee, H.R.; Won, C.W.; Cho, S.S.; Chun, B.S.; Kim, S.J.

    1997-12-01

    Recently, the powder forging process of rapidly solidified Al alloys was investigated in order to develop an inexpensive alternative process to produce high strength parts with complex shapes. It has been shown that the mechanical properties of powder-forged parts are as good as those produced by extrusion. In this study, the consolidation behaviors of rapidly solidified Al-Si-Fe-Cr alloy powders with different shapes and sizes have been investigated using the Al-Si-Fe-Cr alloy powders made by three different rapid solidification processes: gas atomization, centrifugal atomization, and twin roll quenching.

  17. Improvement of magnetic and structural stabilities in high-quality Co{sub 2}FeSi{sub 1?x}Al{sub x}/Si heterointerfaces

    SciTech Connect

    Yamada, S.; Tanikawa, K.; Oki, S.; Kawano, M.; Miyao, M.; Hamaya, K.

    2014-08-18

    We study high-quality Co{sub 2}FeSi{sub 1?x}Al{sub x} Heusler compound/Si (0 ? x ? 1) heterointerfaces for silicon (Si)-based spintronic applications. In thermal treatment conditions, the magnetic and structural stabilities of the Co{sub 2}FeSi{sub 1?x}Al{sub x}/Si heterointerfaces are improved with increasing x in Co{sub 2}FeSi{sub 1?x}Al{sub x}. Compared with L2{sub 1}-ordered Co{sub 2}FeSi/Si, B2-ordered Co{sub 2}FeAl/Si can suppress the diffusion of Si atoms into the Heusler-compound structure. This experimental study will provide an important knowledge for applications in Si-based spin transistors with metallic source/drain contacts.

  18. Thermoelectric properties of Fe and Al double substituted MnSi? (?~1.73)

    NASA Astrophysics Data System (ADS)

    Barczak, S. A.; Downie, R. A.; Popuri, S. R.; Decourt, R.; Pollet, M.; Bos, J. W. G.

    2015-07-01

    Two series of Fe and Al double substituted MnSi? chimney ladders with a nominal valence electron count, VEC=14 per transition metal were prepared (?=1.75). Simultaneous replacement of Mn with Fe and Si with Al yielded the Mn1-xFexSi1.75-xAlx series while the second Mn1-xFexSi1.75-1.75xAl2x series follows the pseudo-binary between MnSi1.75 and FeAl2. Scanning electron microscopy and elemental mapping revealed that ~60% of the nominal Al content ends up in the product with the remainder lost to sublimation, and that up to 7% Al can be substituted in the main group sublattice. Profile analysis of X-ray powder diffraction data revealed gradual changes in the cell metrics, consistent with the simultaneous substitution of Fe and Al in a fixed ratio. All samples are p-type with VEC?13.95 from the structural data and ~11021 holes cm-3 from variable temperature Seebeck measurements. The substituted samples have lower electrical resistivities (?300 K=2-5 m? cm) due to an improved microstructure. This leads to increased thermoelectric power factors (largest S2/?=1.95 mW m-1 K-2) compared to MnSi?. The thermal conductivity for the Mn0.95Fe0.05Si1.66Al0.1 sample is 2.7 W m-1 K-1 between 300 and 800 K, and is comparable to literature data for the parent material.

  19. The precipitation in annealing and its effect on permittivity of Fe-Si-Al powders

    NASA Astrophysics Data System (ADS)

    Li, Gang; Cui, Yin; Zhang, Nan; Wang, Xin; Xie, Jian Liang

    2016-01-01

    SEM images show that some precipitates distributed on the surface of as-annealed Fe-Si-Al powders. Subsequent experimental results indicate that both morphology and microstructure of as-annealed Fe-Si-Al powders change with increasing annealing temperature. Meanwhile, dielectric properties analysis suggesting that both real part ε‧ and imaginary part ε″ of the Fe-Si-Al powders decrease significantly after annealed at 450 °C or higher temperature. We assume that it's the precipitates with low electrical conductivity developed on the surface of powders that increase the surface resistivity of as-annealed powders and leading to a lower imagine part of permittivity. The drop of real part ε‧ ascribed to the weakened interfacial polarization which resulted from the decrease of structural defects such as grain boundaries and interfaces during annealing process.

  20. Corrosion and protection of heterogeneous cast Al-Si (356) and Al-Si-Cu-Fe (380) alloys by chromate adn cerium inhibitors

    NASA Astrophysics Data System (ADS)

    Jain, Syadwad

    In this study, the localized corrosion and conversion coating on cast alloys 356 (Al-7.0Si-0.3Mg) and 380 (Al-8.5Si-3.5Cu-1.6Fe) were characterized. The intermetallic phases presence in the permanent mold cast alloy 356 are primary-Si, Al5FeSi, Al8Si6Mg3Fe and Mg2Si. The die cast alloy 380 is rich in Cu and Fe elements. These alloying elements result in formation of the intermetallic phases Al 5FeSi, Al2Cu and Al(FeCuCr) along with primary-Si. The Cu- and Fe-rich IMPS are cathodic with respect to the matrix phase and strongly govern the corrosion behavior of the two cast alloys in an aggressive environment due to formation of local electrochemical cell in their vicinity. Results have shown that corrosion behavior of permanent mould cast alloy 356 is significantly better than the die cast aluminum alloy 380, primarily due to high content of Cu- and Fe-rich phases such as Al2Cu and Al 5FeSi in the latter. The IMPS also alter the protection mechanism of the cast alloys in the presence of inhibitors in an environment. The presence of chromate in the solution results in reduced cathodic activity on all the phases. Chromate provides some anodic inhibition by increasing pitting potentials and altering corrosion potentials for the phases. Results have shown that performance of CCC was much better on 356 than on 380, primarily due to inhomogeneous and incomplete coating deposition on Cu- and Fe- phases present in alloy 380. XPS and Raman were used to characterize coating deposition on intermetallics. Results show evidence of cyanide complex formation on the intermetallic phases. The presence of this complex is speculated to locally suppress CCC formation. Formation and breakdown of cerium conversion coatings on 356 and 380 was also analyzed. Results showed that deposition of cerium hydroxide started with heavy precipitation on intermetallic particles with the coatings growing outwards onto the matrix. Electrochemical analysis of synthesized intermetallics compounds in the presence of soluble cerium cations showed that of anodic and cathodic activity was not as strongly inhibited as was observed for chromate ions. Overall cerium conversion coating showed good performance on Al-Si (356) ally, but poor performance on Fe- and Cu-rich alloy (380).

  1. The structure-property relationships of powder processed Fe-Al-Si alloys

    SciTech Connect

    Prichard, P.D.

    1998-02-23

    Iron-aluminum alloys have been extensively evaluated as semi-continuous product such as sheet and bar, but have not been evaluated by net shape P/M processing techniques such as metal injection molding. The alloy compositions of iron-aluminum alloys have been optimized for room temperature ductility, but have limited high temperature strength. Hot extruded powder alloys in the Fe-Al-Si system have developed impressive mechanical properties, but the effects of sintering on mechanical properties have not been explored. This investigation evaluated three powder processed Fe-Al-Si alloys: Fe-15Al, Fe-15Al-2.8Si, Fe-15Al-5Si (atomic %). The powder alloys were produced with a high pressure gas atomization (HPGA) process to obtain a high fraction of metal injection molding (MIM) quality powder (D{sub 84} < 32 {micro}m). The powders were consolidated either by P/M hot extrusion or by vacuum sintering. The extruded materials were near full density with grain sizes ranging from 30 to 50 {micro}m. The vacuum sintering conditions produced samples with density ranging from 87% to 99% of theoretical density, with an average grain size ranging from 26 {micro}m to 104 {micro}m. Mechanical property testing was conducted on both extruded and sintered material using a small punch test. Tensile tests were conducted on extruded bar for comparison with the punch test data. Punch tests were conducted from 25 to 550 C to determine the yield strength, and fracture energy for each alloy as a function of processing condition. The ductile to brittle transition temperature (DBTT) was observed to increase with an increasing silicon content. The Fe-15Al-2.8Si alloy was selected for more extensive testing due to the combination of high temperature strength and low temperature toughness due to the two phase {alpha} + DO{sub 3} structure. This investigation provided a framework for understanding the effects of silicon in powder processing and mechanical property behavior of Fe-Al-Si alloys.

  2. Atomic dynamics of the ?-(Al,Si)CuFe alloy: A crystalline approximant of a quasicrystal...

    NASA Astrophysics Data System (ADS)

    Parshin, P. P.; Zemlyanov, M. G.; Brand, R. A.; Pavlyuchkov, D.; Ollivier, J.

    2010-07-01

    The atomic dynamics of the Al0.550Si0.070Cu0.255Fe0.125 alloy with the structure that approximates the structure of an icosahedral quasicrystal with a similar chemical composition has been investigated using inelastic neutron scattering. The partial vibrational spectra of copper, iron, and aluminum atoms and the total spectrum of thermal vibrations of the compound have been directly reconstructed from the experimental data for the first time. A combined analysis of the results obtained and the data on the atomic dynamics of the i-AlCuFe icosahedral quasicrystal has been performed.

  3. First-principles study of the electronic and magnetic properties of Fe2MnAl, Fe2MnSi and Fe2MnSi0.5Al0.5

    NASA Astrophysics Data System (ADS)

    Belkhouane, M.; Amari, S.; Yakoubi, A.; Tadjer, A.; Mabih, S.; Murtaza, G.; Bin Omran, S.; Khenata, R.

    2015-03-01

    In this work, first-principles calculations of the structural, electronic and magnetic properties of Heusler compounds Fe2MnAl, Fe2MnSi and alloy Fe2MnSi0.5Al0.5 are presented. We have applied the full-potential linearized augmented plane waves plus local orbitals (FP-L/APW+lo) method based on the density functional theory (DFT). For the exchange and correlation potential the generalized-gradient approximation (GGA) is used. It is shown that the calculated lattice constants and spin magnetic moments are in good agreement with the available theoretical and experimental data. The calculated atomic resolved densities of states of Fe2MnAl, Fe2MnSi indicate half-metallic behavior with vanishing electronic density of states for minority spin at the Fermi level, which yields perfect spin polarization while for Fe2MnSi0.5Al0.5 shows nearly half-metallic behavior with small spin-down electronic density of states at the Fermi level.

  4. Iron-base superalloys - A phase analysis of the multicomponent system (Fe-Mn-Cr-Mo-Nb-Al-Si-C)

    NASA Technical Reports Server (NTRS)

    Gupta, H.; Nowotny, H.; Lemkey, F. D.

    1988-01-01

    In the course of studies on the iron-rich multicomponent system Fe-Mn-Cr-Mo-Nb-Al-Si-C, work was concentrated on pertinent quinary and six-component combinations namely Fe-Mn-Al-Si-C, Fe-Cr-Al-Si-C and Fe-Mn-Cr-Al-Si-C which had been elaborated at 65, 72, and 80 wt pct Fe. Manganese acts as a strong stabilizer for the cementite carbide. Chromium seems to stabilize the iron aluminide Fe2Al5 which forms in a considerable amount within an alloy of nominal composition Fe(65)Mn(15)Cr(12)Al(5)Si(2)C(1) (percent by weight). Although the Mn3AlC carbide is, like Fe3AlC, a perovskite carbide, manganese does not appear to favor the formation of the perovskite carbide. Because of the relatively low sintering temperature (700 C), for al large portion of the samples equilibria conditions are not always reached.

  5. Effect of Al and Si substitutions on the magnetic properties of SmTbFe17

    NASA Astrophysics Data System (ADS)

    Ingersoll, J. C.; Markandeyulu, G.; Murty, V. S.; Rama Rao, K. V. S.

    2005-11-01

    The structural and magnetic properties of SmTbFe17-xAlx (x=0-8) and SmTbFe17-xSix (x=0-3.5) were investigated by x-ray-diffraction and magnetization studies. All the compounds stabilize in rhombohedral structure. The lattice parameters are found to increase with Al substitution whereas they are found to decrease with Si substitution. The rates of the decrease of saturation magnetization (Ms) value with the substitution of Al and Si are almost the same. The easy direction of magnetization (EMD) is in the ab plane up to an Al concentration of x=7 and has a tendency to shift towards the c axis at x=8. All the compounds with Si are seen to have the EMD in the ab plane. Electron-magnon scattering is seen to contribute to the electrical resistivity in both Al- and Si-substituted compounds; in the temperature range of 30-60 K and at higher temperatures, scattering due to phonons is observed.

  6. Mechanical behaviour of ultrafine grained aluminium containing Al8Fe2Si precipitates

    NASA Astrophysics Data System (ADS)

    Korchef, A.; Kolsi, A. W.; Njah, N.

    2006-06-01

    A 99.1% aluminium was deformed by Equal Channel Angular (ECA) pressing. The material contains a low volume fraction of Al8Fe2Si precipitates located essentially at the grain boundaries. An important increase of the X-ray diffraction peak broadening was observed after ECA pressings. This is due to grain refinement and enhanced lattice distortions. This was accompanied by a lattice decrease due to compressive stresses and partial dissolution of the Al8Fe2Si precipitates. The grain refinement leads to a significant improvement of the mechanical properties in compression and tension after the first pass through the die. Thereafter, the increase was less significant. The strengthening of the material was accompanied by decreased strain hardening, due to enhanced activities in grain boundaries.

  7. Effect of Wavelike Sloping Plate Rheocasting on Microstructures of Hypereutectic Al-18 pct Si-5 pct Fe Alloys

    NASA Astrophysics Data System (ADS)

    Guan, Ren-Guo; Zhao, Zhan-Yong; Lee, Chong Soo; Zhang, Qiu-Sheng; Liu, Chun-Ming

    2012-04-01

    To refine and spheroidize the microstructures of hypereutectic Al-Si-Fe alloys, a novel method of wavelike sloping plate (WSP) rheocasting was proposed, and the effect of the WSP rheocasting on the microstructures of hypereutectic Al-18 pct Si-5 pct Fe alloys was investigated. The results reveal that the morphologies of the primary Si crystal, the Al18Si10Fe5, and the Al8Si2Fe phases can be improved by the WSP rheocasting, and various phases tend to be refined and spheroidized with the decrease of the casting temperature. The alloy ingots with excellent microstructures can be obtained when the casting temperature is between 943 K and 953 K (670 C and 680 C). During the WSP rheocasting, the crystal nucleus multiplication, inhibited grain growth, and dendrite break-up take place simultaneously, which leads to grain refinement of the alloys.

  8. Experimental study on parasitic mode suppression using FeSiAl in relativistic klystron amplifier

    SciTech Connect

    Zhang, Zehai

    2015-03-15

    Experimental study of parasitic mode suppression using electromagnetic attenuate material FeSiAl in an S-band Relativistic Klystron Amplifier (RKA) is presented in this paper. The FeSiAl powder is coated and sintered onto the inner surface of a drift tube which locates between the input and the middle cavity of the RKA. Cold tests show that the attenuate rate of the tube against parasitic mode TE{sub 11} is about 50%. Experiments carried out on the Torch-01 accelerator present that the tube is effective in suppressing the parasitic mode. Two typical outputs are obtained. When the diode voltage is on a moderate level, the RKA operates well and the parasitic mode is totally suppressed. The pulse length of the High Power Microwave (HPM) almost equals the electron beam pulse length and the HPM average output power is about 300 MW, with a power efficiency of 10%. When the diode voltage is on a higher level, the output power and efficiency rise but the parasitic mode oscillation occurred and the pulse length is shortened. By contrast, the parasitic mode oscillation is too strong for the RKA to operate normally with un-sintered drift tube. The experimental study implies that FeSiAl is effective in suppressing the parasitic mode oscillation in a certain extent. However, total suppression needs a deeper attenuate rate and further investigation.

  9. Experimental study on parasitic mode suppression using FeSiAl in relativistic klystron amplifier

    NASA Astrophysics Data System (ADS)

    Zhang, Zehai

    2015-03-01

    Experimental study of parasitic mode suppression using electromagnetic attenuate material FeSiAl in an S-band Relativistic Klystron Amplifier (RKA) is presented in this paper. The FeSiAl powder is coated and sintered onto the inner surface of a drift tube which locates between the input and the middle cavity of the RKA. Cold tests show that the attenuate rate of the tube against parasitic mode TE11 is about 50%. Experiments carried out on the Torch-01 accelerator present that the tube is effective in suppressing the parasitic mode. Two typical outputs are obtained. When the diode voltage is on a moderate level, the RKA operates well and the parasitic mode is totally suppressed. The pulse length of the High Power Microwave (HPM) almost equals the electron beam pulse length and the HPM average output power is about 300 MW, with a power efficiency of 10%. When the diode voltage is on a higher level, the output power and efficiency rise but the parasitic mode oscillation occurred and the pulse length is shortened. By contrast, the parasitic mode oscillation is too strong for the RKA to operate normally with un-sintered drift tube. The experimental study implies that FeSiAl is effective in suppressing the parasitic mode oscillation in a certain extent. However, total suppression needs a deeper attenuate rate and further investigation.

  10. Experimental study on parasitic mode suppression using FeSiAl in Relativistic Klystron Amplifier.

    PubMed

    Zhang, Zehai

    2015-03-01

    Experimental study of parasitic mode suppression using electromagnetic attenuate material FeSiAl in an S-band Relativistic Klystron Amplifier (RKA) is presented in this paper. The FeSiAl powder is coated and sintered onto the inner surface of a drift tube which locates between the input and the middle cavity of the RKA. Cold tests show that the attenuate rate of the tube against parasitic mode TE11 is about 50%. Experiments carried out on the Torch-01 accelerator present that the tube is effective in suppressing the parasitic mode. Two typical outputs are obtained. When the diode voltage is on a moderate level, the RKA operates well and the parasitic mode is totally suppressed. The pulse length of the High Power Microwave (HPM) almost equals the electron beam pulse length and the HPM average output power is about 300 MW, with a power efficiency of 10%. When the diode voltage is on a higher level, the output power and efficiency rise but the parasitic mode oscillation occurred and the pulse length is shortened. By contrast, the parasitic mode oscillation is too strong for the RKA to operate normally with un-sintered drift tube. The experimental study implies that FeSiAl is effective in suppressing the parasitic mode oscillation in a certain extent. However, total suppression needs a deeper attenuate rate and further investigation. PMID:25832258

  11. Assessment of Post-eutectic Reactions in Multicomponent Al-Si Foundry Alloys Containing Cu, Mg, and Fe

    NASA Astrophysics Data System (ADS)

    Javidani, Mousa; Larouche, Daniel; Grant Chen, X.

    2015-07-01

    Post-eutectic reactions occurring in Al-Si hypoeutectic alloys containing different proportions of Cu, Mg, and Fe were thoroughly investigated in the current study. As-cast microstructures were initially studied by optical and electron microscopy to investigate the microconstituents of each alloy. Differential scanning calorimetry (DSC) was then used to examine the phase transformations occurring during the heating and cooling processes. Thermodynamic calculations were carried out to assess the phase formation under equilibrium and in nonequilibrium conditions. The Q-Al5Cu2Mg8Si6 phase was predicted to precipitate from the liquid phase, either at the same temperature or earlier than the ?-Al2Cu phase depending on the Cu content of the alloy. The AlCuFe-intermetallic, which was hardly observed in the as-cast microstructure, significantly increased after the solution heat treatment in the alloys containing high Cu and Fe contents following a solid-state transformation of the ?-Al5FeSi phase. After the solution heat treatment, the AlCuFe-intermetallics were mostly identified with the stoichiometry of the Al7Cu2Fe phase. Thermodynamic calculations and microstructure analysis helped in determining the DSC peak corresponding to the melting temperature of the N-Al7Cu2Fe phase. The effect of Cu content on the formation temperature of ?-Al8Mg3FeSi6 is also discussed.

  12. Effect of Iron and Silicon Content on the Hot Compressive Deformation Behavior of Dilute Al-Fe-Si Alloys

    NASA Astrophysics Data System (ADS)

    Shakiba, M.; Parson, N.; Chen, X.-G.

    2015-01-01

    The hot deformation behavior of dilute Al-Fe-Si alloys (1xxx) containing various amounts of Fe (0.1 to 0.7 wt.%) and Si (0.1 to 0.25 wt.%) was studied by uniaxial compression tests conducted at various temperatures (350-550 C) and strain rates (0.01-10 s-1). The flow stress of the 1xxx alloys increased with increasing Fe and Si content. Increasing the Fe content from 0.1 to 0.7% raised the flow stress by 11-32% in Al-Fe-0.1Si alloys, whereas the flow stress increased 5-14% when the Si content increased from 0.1 to 0.25% in Al-0.1Fe-Si alloys. The influence of the temperature and the strain rate on the hot deformation behavior was analyzed using the Zener-Holloman parameter, and the effect of the chemical composition was considered in materials constants in the constitutive analysis. The proposed constitutive equations yielded an excellent prediction of the flow stress over wide ranges of temperature and strain rate with various Fe and Si contents. The microstructural analysis results revealed that the dynamic recovery (DRV) is the sole softening mechanism of the 1xxx alloys during hot deformation. Increasing the Fe and Si content retarded the DRV and resulted in a decrease in the subgrain size and mean misorientation angle of the boundaries.

  13. X-rays structural analysis and thermal stability studies of the ternary compound {alpha}-AlFeSi

    SciTech Connect

    Roger, J.; Bosselet, F.; Viala, J.C.

    2011-05-15

    From literature data presently available, the decomposition temperature and the nature of the decomposition reaction of the ternary compound {alpha}-AlFeSi (also designated as {alpha}{sub H} or {tau}{sub 5}) are not clearly identified. Moreover, some uncertainties remain concerning its crystal structure. The crystallographic structure and thermochemical behaviour of the ternary compound {alpha}-AlFeSi were meticulously studied. The crystal structure of {alpha}-AlFeSi was examined at room temperature from X-ray single crystal intensity data. It presents hexagonal symmetry, space group P6{sub 3}/mmc with unit cell parameters (293 K) a=12.345(2) A and c=26.210(3) A (V=3459 A{sup 3}). The average chemical formula obtained from refinement is Al{sub 7.1}Fe{sub 2}Si. From isothermal reaction-diffusion experiments and Differential Thermal Analysis, the title compound decomposes peritectically upon heating into {theta}-Fe{sub 4}Al{sub 13}(Si), {gamma}-Al{sub 3}FeSi and a ternary Al-rich liquid. Under atmospheric pressure, the temperature of this reversible transformation has been determined to be 772{+-}12 {sup o}C. -- Graphical abstract: Partial representation of the crystal structure of the {alpha}-Al{sub 7.1}Fe{sub 2}Si compound. Display Omitted Highlights: The main findings of our work are: {yields} a detailed X-rays crystal structure determination of the ternary compound {alpha}-AlFeSi. {yields} The precision of the silicon atoms positions in the crystal structure. {yields} A precised determination of the decomposition temperature of this compound.

  14. X-rays structural analysis and thermal stability studies of the ternary compound α-AlFeSi

    NASA Astrophysics Data System (ADS)

    Roger, J.; Bosselet, F.; Viala, J. C.

    2011-05-01

    From literature data presently available, the decomposition temperature and the nature of the decomposition reaction of the ternary compound α-AlFeSi (also designated as αH or τ5) are not clearly identified. Moreover, some uncertainties remain concerning its crystal structure. The crystallographic structure and thermochemical behaviour of the ternary compound α-AlFeSi were meticulously studied. The crystal structure of α-AlFeSi was examined at room temperature from X-ray single crystal intensity data. It presents hexagonal symmetry, space group P6 3/mmc with unit cell parameters (293 K) a=12.345(2) Å and c=26.210(3) Å ( V=3459 Å 3). The average chemical formula obtained from refinement is Al 7.1Fe 2Si. From isothermal reaction-diffusion experiments and Differential Thermal Analysis, the title compound decomposes peritectically upon heating into θ-Fe 4Al 13(Si), γ-Al 3FeSi and a ternary Al-rich liquid. Under atmospheric pressure, the temperature of this reversible transformation has been determined to be 772±12 °C.

  15. Effects of Melt Thermal-Rate Treatment on Fe-Containing Phases in Hypereutectic Al-Si Alloy

    NASA Astrophysics Data System (ADS)

    Wang, Qinglei; Geng, Haoran; Zhang, Shuo; Jiang, Huawei; Zuo, Min

    2013-11-01

    In this paper, effects of melt thermal-rate treatment (MTRT) on Fe-containing phases in hypereutectic Al-Si alloy were investigated. Results show that MTRT can refine microstructures and improve castability, mechanical properties, wear characteristics, and corrosion resistance of Fe-containing Al-Si alloy. When Al-15Si-2.7Fe alloy is treated with MTRT by 1203 K (930 C) melt: coarse primary Si and plate-like Fe-containing phase both can be refined to small blocky morphology, and the long needle-like Fe-containing phase disappears almost entirely; ultimate tensile strength and elongation are 195 MPa and 1.8 pct, and increase by 12.7 and 50 pct, respectively; and the wear loss and coefficient of friction decrease 7 to 17 and 24 to 30 pct, respectively, compared with that obtained with conventional casting technique. Corrosion resistance of the alloy treated with MTRT by 1203 K (930 C) melt is the best, that is it has the lowest i corr value and the highest E corr value. Besides, effects of MTRT on Al-15Si-xFe (x = 0.2, 0.7, 1.7, 3.7, 4.7) alloys were also studied, MTRT can only refine microstructure and improve mechanical properties of Al-15Si alloy with 0.7 to 3.7 pct Fe content greatly in the present work.

  16. New type of Al-based decagonal quasicrystal in Al60Cr20Fe10Si10 alloy.

    PubMed

    He, Zhanbing; Ma, Haikun; Li, Hua; Li, Xingzhong; Ma, Xiuliang

    2016-01-01

    A new kind of decagonal quasicrystal (DQC) with a periodicity of 1.23?nm was observed in the as-cast quaternary Al60Cr20Fe10Si10 alloy. The intensity distribution of some spots in the selected-area electron diffraction pattern along the tenfold zone axis was found to be different from other Al-based DQCs. High-angle annular dark-field scanning transmission electron microscopy was adopted to reveal the structural features at an atomic level. Both the tenfold symmetry and symmetry-broken decagonal (D) clusters of 1.91?nm in diameter were found, but with structural characteristics different from the corresponding D clusters in the other Al-based DQCs. The neighboring D clusters are connected by sharing one edge rather than covering, suggesting the tiling model is better than the covering model for structural description. PMID:26928759

  17. New type of Al-based decagonal quasicrystal in Al60Cr20Fe10Si10 alloy

    PubMed Central

    He, Zhanbing; Ma, Haikun; Li, Hua; Li, Xingzhong; Ma, Xiuliang

    2016-01-01

    A new kind of decagonal quasicrystal (DQC) with a periodicity of 1.23 nm was observed in the as-cast quaternary Al60Cr20Fe10Si10 alloy. The intensity distribution of some spots in the selected-area electron diffraction pattern along the tenfold zone axis was found to be different from other Al-based DQCs. High-angle annular dark-field scanning transmission electron microscopy was adopted to reveal the structural features at an atomic level. Both the tenfold symmetry and symmetry-broken decagonal (D) clusters of 1.91 nm in diameter were found, but with structural characteristics different from the corresponding D clusters in the other Al-based DQCs. The neighboring D clusters are connected by sharing one edge rather than covering, suggesting the tiling model is better than the covering model for structural description. PMID:26928759

  18. New type of Al-based decagonal quasicrystal in Al60Cr20Fe10Si10 alloy

    NASA Astrophysics Data System (ADS)

    He, Zhanbing; Ma, Haikun; Li, Hua; Li, Xingzhong; Ma, Xiuliang

    2016-03-01

    A new kind of decagonal quasicrystal (DQC) with a periodicity of 1.23 nm was observed in the as-cast quaternary Al60Cr20Fe10Si10 alloy. The intensity distribution of some spots in the selected-area electron diffraction pattern along the tenfold zone axis was found to be different from other Al-based DQCs. High-angle annular dark-field scanning transmission electron microscopy was adopted to reveal the structural features at an atomic level. Both the tenfold symmetry and symmetry-broken decagonal (D) clusters of 1.91 nm in diameter were found, but with structural characteristics different from the corresponding D clusters in the other Al-based DQCs. The neighboring D clusters are connected by sharing one edge rather than covering, suggesting the tiling model is better than the covering model for structural description.

  19. The Viscous Behavior of FeOt-Al2O3-SiO2 Copper Smelting Slags

    NASA Astrophysics Data System (ADS)

    Park, Hyun-Shik; Park, Su Sang; Sohn, Il

    2011-08-01

    Understanding the viscous behavior of copper smelting slags is essential in increasing the process efficiency and obtaining the discrete separation between the matte and the slag. The viscosity of the FeOt-SiO2-Al2O3 copper smelting slags was measured in the current study using the rotating spindle method. The viscosity at a fixed Al2O3 concentration decreased with increasing Fe/SiO2 ratio because of the depolymerization of the molten slag by the network-modifying free oxygen ions (O2-) supplied by FeO. The Fourier transform infrared (FTIR) analyses of the slag samples with increasing Fe/SiO2 ratio revealed that the amount of large silicate sheets decreased, whereas the amount of simpler silicate structures increased. Al2O3 additions to the ternary FeOt-SiO2-Al2O3 slag system at a fixed Fe/SiO2 ratio showed a characteristic V-shaped pattern, where initial additions decreased the viscosity, reached a minimum, and increased subsequently with higher Al2O3 content. The effect of Al2O3 was considered to be related to the amphoteric behavior of Al2O3, where Al2O3 initially behaves as a basic oxide and changes to an acidic oxide with variation in slag composition. Furthermore, Al2O3 additions also resulted in the high temperature phase change between fayalite/hercynite and the modification of the liquidus temperature with Al2O3 additions affecting the viscosity of the copper smelting slag.

  20. Ab initio study of Fe{sub 2}MnZ (Al, Si, Ge) Heusler alloy using GGA approximation

    SciTech Connect

    Jain, Vivek Kumar Jain, Vishal Lakshmi, N. Venugopalan, K.

    2014-04-24

    Density functional theory based on FP-LAPW method used to investigate the electronic structure of Fe{sub 2}MnZ, shows that the total spin magnetic moment shows a trend consistent with the Slater–Pauling curve. The Fe and Mn magnetic moment depend on choice of Z element although the magnetic moment of Z element is negative and less than 0.1 μ{sub B}. Spin polarization calculations evidence 100% spin polarization for Fe{sub 2}MnSi. Fe{sub 2}MnAl and Fe{sub 2}MnGe show metallic behavior with 93%, 98% spin polarization.

  1. Effects of Al and Si addition on the structure and properties of CoFeNi equal atomic ratio alloy

    NASA Astrophysics Data System (ADS)

    Zuo, T. T.; Li, R. B.; Ren, X. J.; Zhang, Y.

    2014-12-01

    In this work, a series of AlxCoFeNi and CoFeNiSix high-entropy alloys (HEAs) of different Al and Si molar ratio (x=0, 0.25, 0.5, 0.75 and 1)were designed and, the effects of Al and Si addition on the structure and properties of the materials was investigated by a systematic study on the phase, microstructure, mechanical behavior, electrical and magnetic properties. It was found that the amounts of Al and Si additions strongly influence the phase structures of the alloys; high molar ratio of Al element can change the FCC structure to BCC structure, while more Si addition can lead to new compounds. Both Al and Si addition can increase the yield strength and hardness with the sacrifice of plasticity and, the effect of adding Si on the mechanical properties is more significant than that of adding Al. Characterization of the magnetic properties and hysteresis loops revealed that, all these alloys show typical ferromagnetic behavior. The saturation magnetization decreases from 151.3 emu/g (x=0) to 101.8 emu/g (x=1) when changing the Al content; and decreases from 151.3 emu/g (x=0) to 80.5 emu/g (x=0.75) with changing the Si content. Si addition can decrease the saturation magnetization more significantly than Al addition. The opposite trend can be found in the effects of the alloying element on the electrical resistivity with varying Al or Si content, adding Si can increase the electrical resistivity from 16.7 ?? cm to 82.89 ?? cm. It was also found that, the alloys also undergo very small magnetostriction, which is essential to ensure that the materials are not stressed when an external magnetic field is applied (or conversely, that external stresses do not disrupt the magnetic properties).

  2. Galvanomagnetic properties of Fe2YZ (Y = Ti, V, Cr, Mn, Fe, Ni; Z = Al, Si) heusler alloys

    NASA Astrophysics Data System (ADS)

    Kourov, N. I.; Marchenkov, V. V.; Belozerova, K. A.; Weber, H. W.

    2015-11-01

    The Hall effect and the magnetoresistance of Fe2YZ Heusler alloys, where Y = Ti, V, Cr, Mn, Fe, and Ni, are the 3 d transition metals and Z = Al and Si are the s, p elements of the third period of the periodic table, are studied at T = 4.2 K in magnetic fields H ≤ 100 kOe. It is shown that, in the high-field limit ( H > 10 kOe), the value and the sign of the normal ( R 0) and anomalous ( R s ) Hall coefficients change anomalously during transition from paramagnetic (Y = Ti, V) to ferromagnetic (Y = Cr, Mn, Fe, Ni) alloys. These coefficients have different signs for all alloys. Constant R s in the ferromagnetic alloys is positive, proportional to the residual resistivity ratio ( R s ∝ ρ 0 3.1 ), and inversely proportional to spontaneous magnetization. The magnetoresistance of the alloys is a few percent and has a negative sign. A positive addition to transverse magnetoresistance is only detected in high magnetic fields, H > 10 kOe.

  3. Specific features of the properties of half-metallic ferromagnetic Heusler alloys Fe2MnAl, Fe2MnSi, and Co2MnAl

    NASA Astrophysics Data System (ADS)

    Kourov, N. I.; Marchenkov, V. V.; Korolev, A. V.; Stashkova, L. A.; Emel'yanova, S. M.; Weber, H. W.

    2015-04-01

    The structural, magnetic, and electrical properties of half-metallic Heusler alloys Fe2MnAl, Fe2MnSi, and Co2MnAl have been investigated in the temperature range of 4-900 K. According to the X-ray diffraction analysis, these alloys have the B2 and L21 structures with different degrees of atomic order. The magnetic state of the alloys is considered as a two-sublattice ferrimagnet. The electrical resistivity and thermoelectric power have been discussed in the framework of the two-current conduction model taking into account the existence of an energy gap in the electronic spectrum of the alloys near the Fermi level for the subband with spin-down (minority) electrons.

  4. Crystallographic Orientation of the ? ? ?' Martensitic (Athermal) Transformation in a FeMnAlSi Steel

    NASA Astrophysics Data System (ADS)

    Pisarik, S. T.; Van Aken, D. C.

    2014-07-01

    The presence of athermal ?- and ?-martensite ( ?') in the as-cast structure of a Fe-0.08C-1.95Si-15.1Mn-1.4Al-0.017N alloy has been revealed by electron backscattered diffraction analysis. The alloy exhibited two athermal martensitic transformations described by ? ? ?' and ? ? ? ? ?'. The Shoji-Nishiyama orientation relationship was observed between ?-austenite and ?-martensite, while ?-martensite nucleated from ?-austenite exhibited a Kurdjumov-Sachs orientation relationship. Six crystallographic variants of ?-martensite consisting of three twin-related variant pairs were observed in ?-bands. A planar parallelism of {0001} ? || {110} ?' and a directional relation of lying within 1 deg of existed for these variants.

  5. Effects of metallurgical parameters on the decomposition of pi-AlFeMgSi phase in Al-Si-Mg alloys and its influence on the mechanical properties

    NASA Astrophysics Data System (ADS)

    Elsharkawi, Ehab A.

    2011-12-01

    The formation of the pi-AlFeMgSi iron intermetallic phase in Al-Si-Mg alloys is known for its detrimental effect on ductility and strength, in that it is controlled by the Fe and Mg content of the alloy, as well as by the cooling rate. The current study was carried out with a view to investigating all the metallurgical parameters affecting the formation of the pi-phase iron intermetallic and, in turn, the role of the pi-phase as it relates to the tensile and impact properties of Al-Si-Mg alloys. Microstructural assessment was carried out by means of quantitative metallography using electron probe microanalysis (EPMA) and scanning electron microscopy (SEM). The results indicate that increasing the Mg and Fe content increases the amount of the pi-AlMgFeSi phase formed. All the alloys containing low levels of iron regardless of the amount of Mg-content show low amounts of pi-phase iron intermetallic. The addition of trace amounts of Be has an observable effect in reducing the amount of the pi-phase formed in all the alloys studied. The pi-phase iron intermetallic particles appear to be segregated away from the modified Si in the Sr-modified alloys, particularly those solidified at a low cooling rate. The effects of different solution treatment times on the decomposition of the pi-phase were investigated in order to examine how this type of decomposition affected the chemistry of the matrix itself. After 8 hours of solution heat treatment and at Mg content of 0.4wt%, the pi-phase showed complete decomposition into fine beta-phase needles. The a-phase, however, showed only partial decomposition into beta-AlFeSi phase needles at Mg levels of over 0.4%wt. This type of decomposition was examined for the purposes of this study over extended periods of solution heat treatment time in Al-7Si-0.55Mg-0.1Fe alloy samples obtained at different cooling rates in order to evaluate the mechanism of pi to beta-phase decomposition. The results obtained show that the volume fraction of pi-AlFeMgSi phase decreases significantly at prolonged solution treatment times. The highest amount of the newly-formed beta-phase was observed in the solution treatment time range of 60 to 80 hours. An analysis of the chemical composition of the matrix using wavelength-dispersive spectroscopy (WDS) at different stages of solution heat treatment revealed that the pi to beta-phase decomposition during solution heat treatment results in a distinct increase in the Mg content of the matrix. Furthermore, no changes were observed in the calculated stoichiometries of the pi-phase or the beta-phase intermetallics during solution treatment in all the alloy samples studied. The study also investigated the decomposition of pi-AlFeMgSi into beta-phase needles during extended periods of solution heat treatment and its effects on the mechanical properties of Al-7Si-0.55Mg-0.1Fe alloys. The results obtained from the calculated quality index values show that the optimum solution treatment time for Sr-modified alloys is of the order of 12 hours. Using prolonged solution treatment time leads to the decomposition of a large amount of pi-phase into beta-phase needles, approximately 85%, thereby providing a slight improvement in the tensile properties at 80 hrs compared to standard heat treatment times; this improvement may be attributed to the increased amount of Mg in the matrix resulting from the decomposition of the pi-phase, and which is then available for precipitation as Mg2Si upon subsequent aging. An analysis of the results obtained from the Charpy impact test using unnotched samples shows that the greatest improvement in the initiation and propagation energies is obtained for the as-cast and heat-treated alloys when these alloys are solidified at a low cooling rate and modified with strontium. An increase in the solution treatment time improves the impact properties of the alloys compared to the as-cast condition. In accordance with this finding, the recommended solution treatment time at which the maximum initiation and propagation energy values can be obtained is 20 hou

  6. Microstructure Evolution and Rheological Behavior of Cooling Slope Processed Al-Si-Cu-Fe Alloy Slurry

    NASA Astrophysics Data System (ADS)

    Das, Prosenjit; Samanta, Sudip K.; Bera, Supriya; Dutta, Pradip

    2016-02-01

    In the present work, microstructure evolution during semi-solid slurry generation of Al-Si-Cu-Fe alloy, using a cooling slope, was studied and the effect of microstructural morphology of the slurry on its rheological behavior was investigated. Microstructure evolution during melt flow along the slope was studied by extracting samples from various locations of the slope and performing rapid oil quenching experiments. Quantitative investigation was performed to evaluate primary phase shape and size for different process conditions of the semi-solid slurry, and subsequently rheological investigations were performed to correlate slurry morphology with its flow behavior. Three different types of rheological experiments were performed: isothermal test, shear jump test, and shear time test, in order to investigate rheological behavior of the semi-solid slurry. In addition, effect of melt treatment, by adding modifier (0.1 wt pct of Al-10Sr) and grain refiner (0.15 wt pct of Al-5Ti-1B), on the microstructure evolution during slurry generation, flow behavior of the slurry, and intermetallics formation was studied.

  7. Magnetic and structural properties of Co2FeAl thin films grown on Si substrate

    NASA Astrophysics Data System (ADS)

    Belmeguenai, Mohamed; Tuzcuoglu, Hanife; Gabor, Mihai; Petrisor, Traian; Tiusan, Coriolan; Berling, Dominique; Zighem, Fatih; Mourad Chrif, Salim

    2015-01-01

    The correlation between magnetic and structural properties of Co2FeAl (CFA) thin films of different thicknesses (10 nmSi/SiO2 substrates and annealed at 600 C has been studied. x-ray diffraction (XRD) measurements revealed an (011) out-of-plane textured growth of the films. The deduced lattice parameter increases with the film thickness. Moreover, pole figures showed no in-plane preferential growth orientation. The magneto-optical Kerr effect hysteresis loops showed the presence of a weak in-plane uniaxial anisotropy with a random easy axis direction. The coercive field, measured with the applied field along the easy axis direction, and the uniaxial anisotropy field increase linearly with the inverse of the CFA thickness. The microstrip line ferromagnetic resonance measurements for in-plane and perpendicular applied magnetic fields revealed that the effective magnetization and the uniaxial in-plane anisotropy field follow a linear variation versus the inverse CFA thickness. This allows deriving a perpendicular surface anisotropy coefficient of -1.86 erg/cm2.

  8. Effect of Heat Treatment on Morphology of Fe-Rich Intermetallics in Hypereutectic Al-Si-Cu-Ni Alloy with 1.26 pct Fe

    NASA Astrophysics Data System (ADS)

    Sha, Meng; Wu, Shusen; Wan, Li; Lü, Shulin

    2013-12-01

    Cobalt is generally considered as the element that can neutralize the negative effects of iron in Al alloys, such as inducing fracture and failure for stress concentration. Nevertheless, Fe-rich intermetallics would be inclined to form coarse plate-like δ-Al4(Fe, Co, Ni)Si2 particles when the content of Fe was high, which could also cause inferior mechanical properties. The dissolution and transformation of δ-Al4(Fe, Co, Ni)Si2 phase in solution heat-treated samples of Al-20Si-1.85Cu-1.05Ni-1.26Fe-1.35Co alloy were studied using optical microscopy, image analysis, and scanning electron microscopy. The effects of solution heat treatment time ranging from 0 to 9 hours at 783.15 K (510 °C) on mechanical properties were also investigated. The coarse plate-like δ-Al4(Fe, Co, Ni)Si2 particles varied slowly through concurrent dissolution along widths and at the plate tips as solution treatment time increased, which could be explained from diffusion-induced grain boundary migration. Solution heat treatment also has an important influence on mechanical properties. The maximum ultimate tensile strength and yield strength after T6 treatment were 258 and 132 MPa, respectively, while the maximum hardness was 131 HB. Compared with those of the samples in the as-cast state, they increased by 53, 42, and 28 pct, respectively. Moreover, δ-Al4(Fe, Co, Ni)Si2 phase, which appears as a coarse plate-like particle in two dimensions, is actually a cuboid in three dimensions. The length of this cuboid is close to the width, while the height is much smaller.

  9. MgSiO3-FeSiO3-Al2O3 in the Earth's lower mantle: Perovskite and garnet at 1200 km depth

    NASA Technical Reports Server (NTRS)

    O'Neill, Bridget; Jeanloz, Raymond

    1994-01-01

    Natural pyroxene and garnet starting material are used to study the effects of joint Fe and Al substitution into MgSiO3 perovskite at approxmiately 50 GPa. Garnet is found to coexist with perovskite in samples containing both Fe and Al to pressures occurring deep into the lower mantel (approximately 1200 km depth). The volume of the perovskite unit cell is V(sub o(Angstrom(exp 3)) = 162.59 + 5.95x(sub FeSiO3) + 10.80x(sub Al2O3) with aluminum causing a significant increase in the distortion from the ideal cubic cell. On the basis of a proposed extension of the MgSiO3-Al2O3 high-pressure phase diagram toward FeSiO3, Fe is shown to partition preferentially into the garnet phase. The stability of garnet deep into the lower mantel may hinder the penetration of subducted slabs below the transition zone.

  10. Local Structure of Transition Elements (V, Cr, Mn, Fe and Zn) in Al2SiO5 Polymorphs

    SciTech Connect

    Furukawa, Yuki; Yoshiasa, Akira; Nishiyama, Tadao; Arima, Hiroshi; Okube, Maki; Murai, Kei-ichiro

    2007-02-02

    We measured XAFS spectra near the Ti, V, Cr, Mn, Fe, Co, Ni, Cu and Zn K-edges in Al2SiO5 polymorphs to reveal the local structure around these elements in the minerals. XANES spectra show that the valence of Fe and Cr is different depending on the crystal structure and formation environments. The spectra of kyanite, a high pressure mineral, shift to high energy side. The Fe-O bond length of kyanite determined by EXAFS data analyses is the shortest of all samples.

  11. Electromagnetic properties of Fe-Si-Al/BaTiO3/Nd2Fe14B particulate composites at microwave frequencies

    NASA Astrophysics Data System (ADS)

    Wang, Xian; Xu, Xiaojun; Gong, Wei; Feng, Zekun; Gong, Rongzhou

    2014-05-01

    Ferroelectric/ferromagnetic (soft and hard) three-phase microwave absorption composites, consisting of Fe-Si-Al/BaTiO3/Nd2Fe14B, are presented, which were fabricated by mechanical ball milling. The microstructure, magnetic, and microwave properties were measured, demonstrating significant improvement in magnetization and coercivity, compared to those single phase materials. In particular, either ferroelectric or hard magnetic phase presents a strong tunability of permeability and permittivity with frequency, which can tailor a frequency band of microwave absorption. The experiments indicate that an optimal reflection loss of the Fe-Si-Al/BaTiO3/Nd2Fe14B was tuned from 2 to 9.52 GHz, whereas the peak value was remarkably enhanced by 62.8%. Therefore, the three-phase microwave absorption composites may remain thin but have great potential to be used at high frequency range.

  12. High damping Al-Fe-Mo-Si/Zn-Al composites produced by rapidly solidified powder metallurgy process

    SciTech Connect

    Li, P.Y.; Dai, S.L.; Chai, S.C.; Li, Y.R.

    2000-05-10

    The metallic materials commonly used in aircraft and aerospace fields, such as aluminum and titanium alloys, steels, etc., show extremely low damping capacity (usually of the order of or less than 10{sup {minus}3}). Thus, some problems related to vibration may emerge and influence the reliability, safety and life of airplanes, satellites, etc. It has been reported that almost two thirds of errors for rockets and satellites are related to vibration and noise. One effective way to solve these vibration-related problems is to adopt high damping metallic materials. Conventional high damping alloys exhibit damping capacity above 10{sup {minus}2}, however, their densities are usually great than 5 x 10{sup 3} kg m{sup {minus}3}, or their strengths are less than 200 MPa (for alloys based on dislocation damping), making them impossible to be applied to aircraft and aerospace areas. Recently, some low-density high-damping metal/metal composites based on aluminum and high damping alloys have been developed in Beijing Institute of Aeronautical Materials (BIAM) by the rapidly solidified power metallurgy process. This paper aims to report the properties of the composites based on a high temperature Al-Fe-Mo-Si alloy and a high damping Zn-Al alloy, and compare them with that of 2618-T61 alloy produced by the ingot metallurgy process.

  13. High-field magnetization of heusler alloys Fe2 XY ( X = Ti, V, Cr, Mn, Fe, Co, Ni; Y = Al, Si)

    NASA Astrophysics Data System (ADS)

    Kourov, N. I.; Marchenkov, V. V.; Korolev, A. V.; Belozerova, K. A.; Weber, H. W.

    2015-10-01

    The magnetization curves of ferromagnetic Heusler alloys Fe2 XY (where X = Ti, V, Cr, Mn, Fe, Co, Ni are transition 3 d elements and Y = Al, Si are the s and p elements of the third period of the Periodic Table) have been measured at T = 4.2 K in the field range H ? 70 kOe. It has been shown that the high-field ( H ? 20 kOe) magnetization is described within the Stoner model.

  14. Corrosion resistance of the NdFeB coated with AlN/SiC bilayer thin films by magnetron sputtering under different environments

    NASA Astrophysics Data System (ADS)

    Tao, Lei; Li, Heqin; Shen, Jiong; Qiao, Kai; Wang, Wei; Zhou, Chu; Zhang, Jing; Tang, Qiong

    2015-02-01

    The AlN/SiC bilayer and SiC monolayer thin films were deposited on sintered NdFeB by RF magnetron sputtering to improve the corrosion resistance. Their structures and morphologies were studied by XRD and AFM and SEM. The corrosion behaviors of AlN/SiC and SiC-coated NdFeB in 3.5 wt% NaCl, 20 wt% NaOH and 0.1 mol/L H2SO4 solutions were characterized with potentiodynamic polarization curves. The results show that AlN/SiC and SiC thin films can evidently improve the corrosion resistance of NdFeB, and the AlN/SiC films have the better resistance than the SiC film.

  15. The role of tree uprooting dynamics on the dynamics of Fe (Mn, Al and Si) forms in different forest soils

    NASA Astrophysics Data System (ADS)

    Tejneck, V.; Samonil, P.; Boruvka, L.; Nikodem, A.; Drabek, O.; Valtera, M.

    2013-12-01

    Tree uprooting dynamics plays an important role in the development of forest ecosystems. This process causes bioturbation of soils and creates new microenvironments which consist of pits and mounds. These microtopographical forms could persist for some thousands of years. Pits and mounds undergo different pedogenesis in comparison to adjacent undisturbed soils. The stage of pedogenesis can be assessed according to the results of fractionation of Fe and also partially Mn, Al and Si. The main aim of this contribution is to assess the fractionation of Fe, Mn, Al and Si for three different soil regions. Soil samples were collected at three localities occurred along hypothetical gradient of soil weathering and leaching processes: The first was a (spruce)-fir-beech natural forest in the Razula region. The second location is the same type of natural forest in Zofin; however it has contrasting lithology. Both these natural forests are located in the Czech Republic (CZ). The third forest was a northern hardwood forest in Upper Peninsula, Michigan, USA. The prevailing soil types - Haplic Cambisols have formed on flysch parent materials in the Razula reserve; Entic Podzols have developed on granite residuum at the Zofin reserve, and Albic Podzols occurred in outwash parent materials at the Michigan sites (amonil et al., in press). In total 790 soil samples were analysed. These samples were collected from 5 depths (0-10, 15, 30, 50 and 100 cm) within the pit, mound and control, currently undisturbed position. For each sample, content of Fe (and Mn, Al, Si) forms: exchangeable, crystalline, and amorphous together with organically complexed Fe were determined. We generally observed an increased content of Fe soil forms in the pits of studied treethrows. The content of Fe forms increased along depth gradient at the disturbed sites. However, exchangeable Fe was most abundant in the 0-10cm layer which corresponds to the A horizon. Naturally, if present, the E horizon exhibited the lowest content of exchangeable Fe forms. The content of crystalline Fe forms also increased with the age of the windthrow. Differences in the amounts of Fe, Mn, Al and Si forms were observed between all studied localities. Research was supported by the Czech Science Foundation (project No. P504/11/2135). amonil P., Schaetzl R. J., Valtera M., Goli V., Baldrian P., Va?kov I., Adam D., Jank D., Hort L. (in press). Crossdating of disturbances by tree uprooting: Can treethrow microtopography persist for 6,000 years? Forest Ecology and Management.

  16. Elevated temperature deformation behavior of a dispersion-strengthened Al-Fe,V,Si alloy

    NASA Astrophysics Data System (ADS)

    Mitra, Shantanu

    1996-12-01

    The deformation behavior of a rapidly solidified, dispersion-strengthened Al alloy containing 11.7 pct Fe, 1.2 pct V, and 2.4 pct Si was studied at test temperatures up to 450 C using constantstress creep and constnt strain-rate tensile tests. Apparent stress exponents ( n) up to 24 and an activation energy of 360 kJ/mol were obtained with the standard Arrhenius type power-law creep equation, which also suggested a change in behavior at 300 C. Substructure-invariant and dislocation/dispersoid interaction models were found to be inadequate for explaining the behavior. When the data were replotted asdot \\varepsilon ^{1/n} vs ?, two regimes were found between 350 C and 450 C. A model with a pseudothreshold stress ( ? Th' ) for the higher stress regime resulted in n 3, indicating solute drag in this regime. Transmission electron microscopy (TEM) showed departureside pinning of dislocations at higher stresses. In the lower stress regime, TEM showed dislocation subgrain structures. Here, the model resulted in a stress exponent of 4.5 indicating the dislocation climb mechanism. At temperatures below 300 C, a single regime was found along with lower activation energies and a stress dependence of 3. Dislocation pipe diffusion is proposed to explain the lower activation energy. The origin of ? Th' has been tied to dislocation generation at the grain boundaries.

  17. Spin accumulation in Si channels using CoFe/MgO/Si and CoFe/AlO{sub x}/Si tunnel contacts with high quality tunnel barriers prepared by radical-oxygen annealing

    SciTech Connect

    Akushichi, T. Shuto, Y.; Sugahara, S.; Takamura, Y.

    2015-05-07

    We investigate spin injection into Si channels using three-terminal spin-accumulation (3T-SA) devices with high-quality CoFe/MgO/n-Si and CoFe/AlO{sub x}/n-Si tunnel spin-injectors whose tunnel barriers are formed by radical oxidation of Mg and Al thin films deposited on Si(100) substrates and successive annealing under radical-oxygen exposure. When the MgO and AlO{sub x} barriers are not treated by the radical-oxygen annealing, the Hanle-effect signals obtained from the 3T-SA devices are closely fitted by a single Lorentz function representing a signal due to trap spins. On the other hand, when the tunnel barriers are annealed under radical-oxygen exposure, the Hanle-effect signals can be accurately fitted by the superposition of a Lorentz function and a non-Lorentz function representing a signal due to accumulated spins in the Si channel. These results suggest that the quality improvement of tunnel barriers treated by radical-oxygen annealing is highly effective for spin-injection into Si channels.

  18. Post-irradiation examination of AlFeNi cladded U 3Si 2 fuel plates irradiated under severe conditions

    NASA Astrophysics Data System (ADS)

    Leenaers, A.; Koonen, E.; Parthoens, Y.; Lemoine, P.; Van den Berghe, S.

    2008-04-01

    Three full size AlFeNi cladded U 3Si 2 fuel plates were irradiated in the BR2 reactor of the Belgian Nuclear Research Centre (SCK·CEN) under relatively severe, but well defined conditions. The irradiation was part of the qualification campaign for the fuel to be used in the future Jules Horowitz reactor in Cadarache, France. After the irradiation, the fuel plates were submitted to an extensive post-irradiation campaign in the hot cell laboratory of SCK·CEN. The PIE shows that the fuel plates withstood the irradiation successfully, as no detrimental defects have been found. At the cladding surface, a multilayered corrosion oxide film has formed. The U-Al-Si layer resulting from the interaction between the U 3Si 2 fuel and the Al matrix, has been quantified as U(Al,Si) 4.6. It is found that the composition of the fuel particles is not homogenous; zones of USi and U 3Si 2 are observed and measured. The fission gas-related bubbles generated in both phases show a different morphology. In the USi fuel, the bubbles are small and numerous while in U 3Si 2 the bubbles are larger but there are fewer.

  19. Magnetic Fe, Si, Al-Rich Impact Spherules from the P-T Boundary Layer at Graphite Peak, Antarctica

    NASA Technical Reports Server (NTRS)

    Petaev, M. I.; Jacobsen, S. B.; Basu, A. R.; Becker, L.

    2004-01-01

    The geological boundary between Triassic and Permian strata coincides with the greatest life extinction in the Earth's history. Although the cause of the extinction is still the subject of intense debates, recent discoveries in the P-T boundary layer of shocked quartz grains, fullerenes with the extraterrestrial noble gases, Fe metal nuggets, and chondritic meteorite fragments all point to a powerful collision of Earth with a celestial body in the late Permian. Here we report the discovery of magnetic Fe, Si, Al-rich impact spherules which accompany the chondritic meteorite fragments in some samples from the P-T boundary layer at Graphite Peak, Antarctica.

  20. Heat capacity and phase equilibria of almandine, Fe3Al2Si3O12

    USGS Publications Warehouse

    Anovitz, Lawrence M.; Essene, E.J.; Metz, G.W.; Bohlen, S.R.; Westrum, E.F., Jr.; Hemingway, B.S.

    1993-01-01

    The heat capacity of a synthetic almandine, Fe3Al2Si3O12, was measured from 6 to 350 K using equilibrium, intermittent-heating quasi-adiabatic calorimetry and from 420 to 1000 K using differential scanning calorimetry. These measurements yield Cp298 = 342.80 ?? 1.4 J/mol ?? K and S298o = 342.60 J/mol ?? K. Mo??ssbauer characterizations show the almandine to contain less than 2 ?? 1% of the total iron as Fe3+. X-ray diffraction studies of this synthetic almandine yield a = 11.521 ?? 0.001 A?? and V298o = 115.11 +- 0.01 cm3/mol, somewhat smaller than previously reported. The low-temperature Cp data indicate a lambda transition at 8.7 K related to an antiferromagnetic-paramagnetic transition with TN = 7.5 K. Modeling of the lattice contribution to the total entropy suggests the presence of entropy in excess of that attributable to the effects of lattice vibrations and the magnetic transition. This probably arises from a low-temperature electronic transition (Schottky contribution). Combination of the Cp data with existing thermodynamic and phase equilibrium data on almandine yields ??Gf,298o = -4938.3 kJ/mol and ??Hf,298o= -5261.3 kJ/mol for almandine when calculated from the elements. The equilibrium almandine = hercynite + fayalite + quartz limits the upper T P for almandine and is metastably located at ca. 570??C at P = 1 bar, with a dP dT of +17 bars/??C. This agrees well with reversed experiments on almandine stability when they are corrected for magnetite and hercynite solid-solutions. In {norm of matrix}O2-T space, almandine oxidizes near QFM by the reactions almandine + O2 = magnetite + sillimanite + quartz and almandine + 02 = hercynite + magnetite + quartz. With suitable correction for reduced activities of solid phases, these equilibria provide useful oxygen barometers for medium- to high-grade metamorphic rocks. ?? 1993.

  1. Heat capacity and phase equilibria of almandine, Fe 3Al 2Si 3O 12

    NASA Astrophysics Data System (ADS)

    Anovitz, L. M.; Essene, E. J.; Metz, G. W.; Bohlen, S. R.; Westrum, E. F., Jr.; Hemingway, B. S.

    1993-09-01

    The heat capacity of a synthetic almandine, Fe 3Al 2Si 3O 12, was measured from 6 to 350 K using equilibrium, intermittent-heating quasi-adiabatic calorimetry and from 420 to 1000 K using differential scanning calorimetry. These measurements yield Cp298 = 342.80 1.4 J/mol K and S298o = 342.60 J/mol K. Mssbauer characterizations show the almandine to contain less than 2 1% of the total iron as Fe 3+. X-ray diffraction studies of this synthetic almandine yield a = 11.521 0.001 and V298o = 115.11 +- 0.01 cm 3/mol, somewhat smaller than previously reported. The low-temperature Cp data indicate a lambda transition at 8.7 K related to an antiferromagnetic-paramagnetic transition with TN = 7.5 K. Modeling of the lattice contribution to the total entropy suggests the presence of entropy in excess of that attributable to the effects of lattice vibrations and the magnetic transition. This probably arises from a low-temperature electronic transition (Schottky contribution). Combination of the Cp data with existing thermodynamic and phase equilibrium data on almandine yields ?Gf,298 o = -4938.3 kJ/mol and ?Hf,298 o= - 5261.3 kJ/mol for almandine when calculated from the elements. The equilibrium almandine = hercynite + fayalite + quartz limits the upper T/P for almandine and is metastably located at ca. 570C at P = 1 bar, with a dP/dT of +17 bars/C. This agrees well with reversed experiments on almandine stability when they are corrected for magnetite and hercynite solid-solutions. In ? O2- T space, almandine oxidizes near QFM by the reactions almandine + O2 = magnetite + sillimanite + quartzandalmandine + 02 = hercynite + magnetite + quartz. With suitable correction for reduced activities of solid phases, these equilibria provide useful oxygen barometers for medium- to high-grade metamorphic rocks.

  2. Epitaxial films of Heusler compound Co2FeAl0.5Si0.5 with high crystalline quality grown by off-axis sputtering

    NASA Astrophysics Data System (ADS)

    Peters, B.; Alfonsov, A.; Blum, C. G. F.; Hageman, Stephen J.; Woodward, P. M.; Wurmehl, S.; Bchner, B.; Yang, F. Y.

    2013-10-01

    Co2FeAl0.5Si0.5 films with a surface roughness of 0.12 nm have been grown epitaxially on lattice-matched MgAl2O4 (001) substrates by off-axis sputtering. X-ray diffraction shows pronounced Laue oscillations, rocking curves as narrow as 0.0043, and clear Co2FeAl0.5Si0.5 (111) peaks indicating L21 ordering. Magnetic characterizations show a clear magnetocrystalline anisotropy comprising cubic and epitaxy-induced uniaxial terms. Nuclear magnetic resonance measurements reveal L21 order of 81% in the Co2FeAl0.5Si0.5 films. Magnetotransport measurements show a distinct separation of anisotropic magnetoresistance and ordinary magnetoresistance. These results demonstrate the state-of-the-art crystalline quality and magnetic uniformity of the Co2FeAl0.5Si0.5 films.

  3. Oxidation Studies of SiAlON/MgAlON Ceramics with Fe2O3 and CaO Impurities, Part I: Kinetics

    NASA Astrophysics Data System (ADS)

    Li, Peng; Zhang, Mei; Teng, Lidong; Seetharaman, Seshadri

    2013-02-01

    T he oxidation behaviors of composites SiAlON/MgAlON phases (?-SiAlON, 15R-SiAlON and MgAlON) synthesized from the residue during the leaching treatment of salt cake and corresponding synthetic samples were investigated in air by thermogravimetric measurements. Combined kinetics, viz. linear law + arctan law + parabolic law, are used to describe the kinetics of oxidation in isothermal mode. The oxidation studies reveal the effects of impurities, namely, Fe2O3 and CaO, present in the salt cake residue. The addition of Fe2O3 results in a lower activation energy and more aggressive oxidation. The addition of CaO caused the shrinkage during the synthesis and liquid formation during the oxidation above 1673 K (1400 C). The impurities of CaO and Fe2O3 in the leaching residue can result in an aggressive oxidation at low temperature and a protective oxidation at temperatures above the eutectic point.

  4. High-Temperature Oxidation Behavior of Al-Co-Cr-Ni-(Fe or Si) Multicomponent High-Entropy Alloys

    NASA Astrophysics Data System (ADS)

    Butler, T. M.; Alfano, J. P.; Martens, R. L.; Weaver, M. L.

    2015-01-01

    High-entropy alloys (HEAs) are a class of alloys that are being considered for a number of applications. In the present study, the microstructures and 1050°C oxidation behaviors of two HEAs, Al10Cr22.5Co22.5Ni22.5Fe22.5 (at.%) and Al20Cr25Co25Ni25Si5 have been investigated along with Al15Cr10Co35Ni35Si5, which is a high-temperature shape-memory alloy. Oxide formation occurred via selective oxidation in a manner that was consistent with the oxide formation model devised by Giggins and Pettit for model Ni-Cr-Al alloys. The lower Al content alloy formed an external Cr2O3 scale and an internal subscale consisting of Al2O3 and AlN precipitates. The higher Al content alloys exhibited smaller mass gains and formed external Al2O3 scales without any internal oxidation of the alloys.

  5. Electromagnetic and microwave absorbing properties of the composites containing flaky FeSiAl powders mixed with MnO2 in 1-18 GHz

    NASA Astrophysics Data System (ADS)

    Xu, Haibing; Bie, Shaowei; Jiang, Jianjun; Yuan, Wei; Chen, Qian; Xu, Yongshun

    2016-03-01

    The flaky FeSiAl/ irregular shaped MnO2 composite with the different mass ratios were prepared by using a two-roll mixer and a vulcanizing machine. The morphologies of the composite absorbers were characterized by a scanning electron microscope. The microwave electromagnetic properties of the composites were measured using a vector network analyzer in the range of 1-18 GHz. The effect of the mass ratio of FeSiAl/MnO2 on the microwave loss properties of the composites was investigated. The results show that the reflection loss (RL) values exceeding -20 dB from 3.5 to 16.5 GHz can be obtained for the flaky FeSiAl/MnO2 mass ratio of 1:1 from 1.5 mm to 5 mm. In addition, the FeSiAl/MnO2 composite with the FeSiAl/MnO2 mass ratio of 7:3 has -10 dB bandwidth of 6.6 GHz (from 11.4-18 GHz) with a thickness of 1.5 mm. It is found that the flaky FeSiAl/MnO2 composites can be potential microwave absorption materials.

  6. Extrusion, Properties, and Failure of Spray-Formed Hypereutectic Al-Si Alloys Based on the Optimization of Fe-Bearing Phase

    NASA Astrophysics Data System (ADS)

    Hou, L. G.; Yu, H.; Cui, H.; Cai, Y. H.; Zhuang, L. Z.; Zhang, J. S.

    2013-04-01

    Based on the densification of the spray-formed hypereutectic Al-Si (hyper-AS) alloys, the microstructural evolution, mechanical properties, as well as the failure are studied in this investigation. The appropriate process and parameters for the densification of the deposits are gained from the thermomechanical simulation. Besides of the spray-formed Al-25Si-5Fe-3Cu (3C) alloy, the microstructures of other spray-formed alloys with Mn/Cr addition are stable without coarsening of the refined ?-Al(Fe,TM)Si (TM = Mn/Cr/(Mn+Cr)) particles, which can improve the heat resistance. Especially, a great number of the submicrosized ?-Al(Fe,TM)Si phases are observed in the hot-extruded TM-containing alloys. The critical ranges of the major parameter TM/Fe mass ratios that can affect the formation of the ?-Al(Fe,TM)Si phases in the cast or spray-formed hyper-AS alloys are severally determined. The structure and lattice constant of the refined ?-Al(Fe,TM)Si phases also are characterized. The mechanical properties of the current extruded hyper-AS alloys at room or elevated temperatures are close to or higher than some commercial alloys or other published results. Therefore, the hyper-AS alloys can be proposed as new lightweight, heat-resistant, and high-strength alloys, which can be used in the complex working conditions, such as advanced engine systems. The main reason for the enhanced properties would be the formation of a large quantity of microsized/submicrosized ?-Al(Fe,TM)Si phases and abundant dislocations, which can greatly reinforce the matrix and transform the brittle fracture of the needle-like Fe-bearing phases into ductile fracture.

  7. Crystal-induced anisotropy of spin accumulation in Si/MgO/Fe and Si/Al2O3/ferromagnet tunnel devices

    NASA Astrophysics Data System (ADS)

    Sharma, S.; Spiesser, A.; Saito, H.; Yuasa, S.; van Wees, B. J.; Jansen, R.

    2013-02-01

    The effect of crystalline order on the anisotropy of spin accumulation in Si/oxide/ferromagnet tunnel devices has been investigated. The spin accumulation induced electrically in the silicon changes when the magnetization of the ferromagnet is rotated either from in-plane to perpendicular to the tunnel interface or when it is rotated within the plane of the magnetic layer. A fourfold in-plane anisotropy, which reflects the crystalline nature of the tunnel contact, is observed not only for crystalline MgO/Fe contacts, but also for devices with amorphous Al2O3 tunnel barrier and polycrystalline ferromagnetic electrode. The in-plane anisotropy is attributed to the direct coupling of states from the ferromagnet to those in the Si, as in coherent tunneling, causing anisotropy in devices in which only the nonmagnetic (Si) electrode is crystalline.

  8. Properties of a reaction-bonded β-SiAlON ceramic doped with an FeMo alloy for application to molten aluminum environments

    NASA Astrophysics Data System (ADS)

    Li, Yan-jun; Yu, Hai-liang; Jin, Hai-yun; Shi, Zhong-qi; Qiao, Guan-jun; Jin, Zhi-hao

    2015-05-01

    An FeMo-alloy-doped β-SiAlON (FeMo/β-SiAlON) composite was fabricated via a reaction-bonding method using raw materials of Si, Al2O3, AlN, FeMo, and Sm2O3. The effects of FeMo on the microstructure and mechanical properties of the composite were investigated. Some properties of the composite, including its bending strength at 700°C and after oxidization at 700°C for 24 h in air, thermal shock resistance and corrosion resistance to molten aluminum, were also evaluated. The results show that the density, toughness, bending strength, and thermal shock resistance of the composite are obviously improved with the addition of an FeMo alloy. In addition, other properties of the composite such as its high-temperature strength and oxidized strength are also improved by the addition of FeMo alloy, and its corrosion resistance to molten aluminum is maintained. These findings indicate that the developed FeMo/β-SiAlON composite exhibits strong potential for application to molten aluminum environments.

  9. Soft magnetic properties and structures of nanocrystalline Fe-Al-Si-B-Cu-Nb alloy ribbons

    NASA Astrophysics Data System (ADS)

    Tate, B. J.; Parmar, B. S.; Todd, I.; Davies, H. A.; Gibbs, M. R. J.; Major, R. V.

    1998-06-01

    The effects of Al on the magnetic properties of nanocrystalline Fe73.5-XAlXSi13.5B9Cu1Nb3 alloy ribbons, where 0?X?10, are reported for the first time. The evolution of the structure and magnetic properties of the ribbons, which were initially cast into the amorphous state in an inert gas environment at subatmospheric pressure, were studied as a function of annealing temperature Tann. The minimum dc coercivity developed during annealing, Hcmin, was found to decrease significantly with increasing Al content from 0.5 A/m at X=0 to 0.3 A/m at X=2 and to remain at approximately this level over the range 2Al.

  10. Magnetocaloric effects in RTX intermetallic compounds (R = GdTm, T = FeCu and Pd, X = Al and Si)

    NASA Astrophysics Data System (ADS)

    Zhang, Hu; Shen, Bao-Gen

    2015-12-01

    The magnetocaloric effect (MCE) of RTSi and RT Al systems with R = GdTm, T = FeCu and Pd, which have been widely investigated in recent years, is reviewed. It is found that these RTX compounds exhibit various crystal structures and magnetic properties, which then result in different MCE. Large MCE has been observed not only in the typical ferromagnetic materials but also in the antiferromagnetic materials. The magnetic properties have been studied in detail to discuss the physical mechanism of large MCE in RTX compounds. Particularly, some RTX compounds such as ErFeSi, HoCuSi, HoCuAl exhibit large reversible MCE under low magnetic field change, which suggests that these compounds could be promising materials for magnetic refrigeration in a low temperature range. Project supported by the National Natural Science Foundation of China (Grant Nos.51371026, 11274357, and 51327806) and the Fundamental Research Funds for the Central Universities (Grant Nos.FRF-TP-14-011A2 and FRF-TP-15-002A3).

  11. Effect of on-site Coulomb interaction (U) on the electronic and magnetic properties of Fe2MnSi, Fe2MnAl and Co2MnGe

    NASA Astrophysics Data System (ADS)

    Sharma, Sonu; Pandey, Sudhir K.

    2016-04-01

    The electronic band structures, density of states' plots and magnetic moments of Fe2MnSi, Fe2MnAl, and Co2MnGe are studied by using the first principles calculation. The FM solutions using LSDA without U show the presence of half-metallic ferromagnetic (HFM) ground state in Fe2MnSi, whereas the ground state of Fe2MnAl is found to be metallic. In both compounds the maximum contribution to the total magnetic moment is from the Mn atom, while the Fe atom contributes very less. The electronic structures and magnetic moments of Fe-based compounds are affected significantly by U under around-the-mean-field (AMF) double counting scheme, whereas its effect is very less on Co2MnGe. The magnetic moment of Fe atom in Fe2MnSi (Fe2MnAl) increased by ∼70% (∼75%) and in Mn atom it decreases by ∼50% (∼70%) when the value of U is increased from 1 to 5 eV. Hund's like exchange interactions are increasing in Fe atom while decreasing in Mn atom with increase in U. The Fe and Mn moments are ferromagnetically coupled in Fe2MnSi for all values of U, whereas in Fe2MnAl they are coupled antiferromagnetically below U=2 eV and ferromagnetically above it. Above U=2 eV the metallic ground state of Fe2MnAl changes to semiconducting ground state and the ferromagnetic coupling between Fe and Mn atoms appears to be responsible for this. This shows that the validity of AFM double counting scheme is not robust for the entire range of U in the Fe2MnAl compound.

  12. Perpendicular magnetic anisotropy in Ta/Pd/Co2FeAl0.5Si0.5/MgO/Ta structured films

    NASA Astrophysics Data System (ADS)

    Fu, H. R.; You, C. Y.; Zhang, X.; Tian, N.

    2015-07-01

    In this work, the perpendicular magnetic anisotropy (PMA) was realized in Ta/Pd/Co2FeAl0.5Si0.5/MgO/Ta films, but not observed in Ta/Pd/Co2FeAl0.5Si0.5/Ta films without MgO cap layer. A strong PMA had been achieved for a thick Co2FeAl0.5Si0.5 layer about 4.8 nm at the annealing temperature of 300 C. Inserted Pd layer between Ta and Co2FeAl0.5Si0.5 layers was crucial to obtain PMA in Ta/Pd/Co2FeAl0.5Si0.5/MgO/Ta structured films. However, the thickness of inserted Pd layer has no significant effect on the value (Keff) of PMA. The films annealed at 300 C remain a similar Keff of around 1.23106 erg/cm3 while the inserted Pd layer is beyond a critical thickness.

  13. Search for half-metallic magnets with large half-metallic gaps in the quaternary Heusler alloys CoFeTiZ and CoFeVZ (Z=Al, Ga, Si, Ge, As, Sb)

    NASA Astrophysics Data System (ADS)

    Xiong, Lun; Yi, Lin; Gao, G. Y.

    2014-06-01

    We investigate the electronic structure and magnetic properties of the twelve quaternary Heusler alloys CoFeTiZ and CoFeVZ (Z=Al, Ga, Si, Ge, As, Sb) by using the first-principles calculations. It is shown that only CoFeTiSi, CoFeTiAs and CoFeVSb are half-metallic ferromagnets with considerable half-metallic gaps of 0.31, 0.18 and 0.17 eV, respectively. CoFeTiAl and CoFeTiGa are conventional semiconductors, and other alloys exhibit nearly half-metallicity or their half-metallic gaps are almost zero eV. We also find that the half-metallicities of CoFeTiSi, CoFeTiAs and CoFeVSb can be preserved under appropriate uniform and in-plane strains. The considerable half-metallic gaps and the robust half-metallicities under uniform and in-plane strains make CoFeTiSi, CoFeTiAs and CoFeVSb promising candidates for spintronic applications.

  14. Interplay Between Melt Flow and the 3D Distribution and Morphology of Fe-Rich Phases in AlSi Alloys

    NASA Astrophysics Data System (ADS)

    Mikolajczak, Piotr; Ratke, Lorenz

    2015-03-01

    The presence of Fe aids in establishing the mechanical and physical properties of AlSi alloys and is also one of the main impurities leading to formation of ?-Al5FeSi intermetallics. This study aims to understand the effect of fluid flow on the dendritic microstructure with intermetallics in Al-5/7/9 wt pct Si-0.2/0.5/1.0 wt pct Fe alloys that are directionally solidified under defined thermal and fluid flow conditions. We made extensive use of 3D X-ray tomography to obtain a better insight into the morphology and formation of the intermetallics. Three-dimensional (3-D) distribution of intermetallics presented here shows that the growth of large ?-Al5FeSi due to forced flow occurs in the eutectic specimen center and together with an increase in the number density of ? precipitates. The 3D reconstructions have verified the ? shaped to be curved, bent with twining, branched, and to have imprints, holes, and propeller-shaped platelets. The 3D views showed that hole-shaped ? arose from the lateral growth around ?-Al dendrites. These views also confirmed the phenomenon of shortening of ? as an effect of flow in the dendritic region, where ? could be fragmented or completely remelted, and ultimately resulting in microstructures with shorter ?-Al5FeSi and increases in number density. The analysis revealed an interaction between melt flow, 3D distribution, and the morphology of ?-Al5FeSi. The growth of a large and complex group of ? intermetallics can reduce the melt flow between dendrites and strengthen pore nucleation and eutectic colonies nucleation, leading to lower permeability of the mushy zone and increased porosity in the castings.

  15. Effects of Al2O3 and CaO/SiO2 Ratio on Phase Equilbria in the ZnO-"FeO"-Al2O3-CaO-SiO2 System in Equilibrium with Metallic Iron

    NASA Astrophysics Data System (ADS)

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

    2011-02-01

    The phase equilibria and liquidus temperatures in the ZnO-"FeO"-Al2O3-CaO-SiO2 system in equilibrium with metallic iron have been determined experimentally in the temperature range 1383 K to 1573 K (1150 C to 1300 C). The experimental conditions were selected to characterize lead blast furnace and imperial smelting furnace slags. The results are presented in a form of pseudoternary sections ZnO-"FeO"-(Al2O3 + CaO + SiO2) with fixed CaO/SiO2 and (CaO + SiO2)/Al2O3 ratios. It was found that wustite and spinel are the major primary phases in the composition range investigated. Effects of Al2O3 concentration as well as the CaO/SiO2 ratio on the primary phase field, the liquidus temperature, and the partitioning of ZnO between liquid and solid phases have been discussed for zinc-containing slags.

  16. High-pressure, temperature elasticity of Fe- and Al-bearing MgSiO3: Implications for the Earth's lower mantle

    NASA Astrophysics Data System (ADS)

    Zhang, Shuai; Cottaar, Sanne; Liu, Tao; Stackhouse, Stephen; Militzer, Burkhard

    2016-01-01

    Fe and Al are two of the most important rock-forming elements other than Mg, Si, and O. Their presence in the lower mantle's most abundant minerals, MgSiO3 bridgmanite, MgSiO3 post-perovskite and MgO periclase, alters their elastic properties. However, knowledge on the thermoelasticity of Fe- and Al-bearing MgSiO3 bridgmanite, and post-perovskite is scarce. In this study, we perform ab initio molecular dynamics to calculate the elastic and seismic properties of pure, Fe3+- and Fe2+-, and Al3+-bearing MgSiO3 perovskite and post-perovskite, over a wide range of pressures, temperatures, and Fe/Al compositions. Our results show that a mineral assemblage resembling pyrolite fits a 1D seismological model well, down to, at least, a few hundred kilometers above the core-mantle boundary, i.e. the top of the D″ region. In D″, a similar composition is still an excellent fit to the average velocities and fairly approximate to the density. We also implement polycrystal plasticity with a geodynamic model to predict resulting seismic anisotropy, and find post-perovskite with predominant (001) slip across all compositions agrees best with seismic observations in the D″.

  17. Co2FeAl Heusler thin films grown on Si and MgO substrates: Annealing temperature effect

    NASA Astrophysics Data System (ADS)

    Belmeguenai, M.; Tuzcuoglu, H.; Gabor, M. S.; Petrisor, T.; Tiusan, C.; Zighem, F.; Chrif, S. M.; Moch, P.

    2014-01-01

    10 nm and 50 nm Co2FeAl (CFA) thin films have been deposited on MgO(001) and Si(001) substrates by magnetron sputtering and annealed at different temperatures. X-rays diffraction revealed polycrystalline or epitaxial growth (according to CFA(001)[110]//MgO(001)[100] epitaxial relation) for CFA films grown on a Si and on a MgO substrate, respectively. For these later, the chemical order varies from the A2 phase to the B2 phase when increasing the annealing temperature (Ta), while only the A2 disorder type has been observed for CFA grown on Si. Microstrip ferromagnetic resonance (MS-FMR) measurements revealed that the in-plane anisotropy results from the superposition of a uniaxial and a fourfold symmetry term for CFA grown on MgO substrates. This fourfold anisotropy, which disappears completely for samples grown on Si, is in accord with the crystal structure of the samples. The fourfold anisotropy field decreases when increasing Ta, while the uniaxial anisotropy field is nearly unaffected by Ta within the investigated range. The MS-FMR data also allow for concluding that the gyromagnetic factor remains constant and that the exchange stiffness constant increases with Ta. Finally, the FMR linewidth decreases when increasing Ta, due to the enhancement of the chemical order. We derive a very low intrinsic damping parameter (1.110-3 and 1.310-3 for films of 50 nm thickness annealed at 615 C grown on MgO and on Si, respectively).

  18. Distribution of cations at two tetrahedral sites in Ca2MgSi2O7-Ca2Fe3+AlSiO7 series synthetic melilite and its relation to incommensurate structure

    NASA Astrophysics Data System (ADS)

    Hamada, Maki; Akasaka, Masahide

    2013-03-01

    Synthetic melilites on the join Ca2MgSi2O7 (kermanite: Ak)-Ca2Fe3+AlSiO7 (ferrialuminium gehlenite: FAGeh) were studied using X-ray powder diffraction and 57Fe Mssbauer spectroscopic methods to determine the distribution of Fe3+ between two different tetrahedral sites (T1 and T2), and the relationship between ionic substitution and incommensurate (IC) structure. Melilites were synthesized from starting materials with compositions of Ak100, Ak80FAGeh20, Ak70FAGeh30 and Ak50FAGeh50 by sintering at 1,170-1,350 C and 1 atm. The average chemical compositions and end-member components, Ak, FAGeh and Geh (Ca2Al2SiO7), of the synthetic melilites were Ca2.015Mg1.023Si1.981O7 (Ak100), Ca2.017Mg0.788Fe{0.187/3+}Al0.221Si1.791O7 (Ak78FAGeh19Geh3), Ca1.995Mg0.695Fe{0.258/3+}Al0.318Si1.723O7 (Ak69FAGeh25Geh6) and Ca1.982Mg0.495Fe{0.449/3+}Al0.519Si1.535O7 (Ak49FAGeh44Geh7), respectively. Rietveld refinements using X-ray powder diffraction data measured using Cu K ? -radiation at room temperature converged successfully with goodness-of-fits of 1.15-1.26. The refined Fe occupancies at the T1 and T2 sites and the Mg and Si contents determined by electron microprobe analysis gave the site populations of [0.788Mg + 0.082Fe3+ + 0.130Al]T1[0.104Fe3+ + 0.104Al + 1.792Si]T2 for Ak78FAGeh19Geh3, [0.695Mg + 0.127Fe3+ + 0.178Al]T1[0.132Fe3+ + 0.144Al + 1.724Si]T2 for Ak69FAGeh25Geh6 and [0.495Mg + 0.202Fe3+ + 0.303Al]T1[0.248Fe3+ + 0.216Al + 1.536Si]T2 for Ak49FAGeh44Geh7 (apfu: atoms per formula unit), respectively. The results indicate that Fe3+ is distributed at both the T1 and the T2 sites. The mean T1-O distance decreases with the substitution of Fe3+ + Al3+ for Mg2+ at the T1 site, whereas the mean T2-O distance increases with substitution of Fe3+ + Al3+ for Si4+ at the T2 site, causing decrease in the a dimension and increase in the c dimension. However, in spite of the successful Rietveld refinements for the X-ray powder diffraction data measured using Cu K ?-radiation at room temperature, each Bragg reflection measured using Cu K ?1-radiation at room temperature showed weak shoulders, which were not observed in those measured at 200 C. The Mssbauer spectra of the melilites measured at room temperature consist of two doublets assigned to Fe3+ at the T1 site and two or three doublets to Fe3+ at the T2 site, implying the existence of multiple T1 and T2 sites with different site distortions. These facts can be interpreted in terms of the IC structure in all synthetic melilites at room temperature, respectively. The results of Mssbauer analysis indicate that the IC structure in melilite is caused by not only known multiple T1 site, but also multiple T2 site at room temperature.

  19. Crystal Structure and Magnetic Properties of (Fe,Si,Al)-Based Nanocomposite Magnets Designed for Cryogenic Applications

    NASA Astrophysics Data System (ADS)

    Daniil, Maria; Fonda, Helen M.; Willard, Matthew A.

    2015-06-01

    In this work, we performed a detailed study of the crystallization, crystal structure, and magnetic properties of Fe87- z Si z- x Al x Nb3B9Cu1 nanocrystalline alloys that were designed primarily for low-temperature applications. In addition, their interesting low-temperature [77 K to 300 K (-196 C to 27 C)] magnetic properties ( H c and M s) were also investigated. These alloys were produced by annealing their amorphous precursors at 823 K (550 C). Si and Al substitution do not seem to alter the crystallization procedure and crystal structure of the parent alloy but reduces the lattice parameter, the Curie temperature, and the saturation magnetization. On the other hand, it improves the room temperature coercivity at small amounts ( H c = 0.35 A/m for x = 3.5, z = 19) and changes its temperature dependence. As a result, a remarkably low H c value at 77 K (-196 C) of 0.45 A/m was observed for x = 6 and z = 23.5.

  20. Steam Oxidation of FeCrAl and SiC in the Severe Accident Test Station (SATS)

    SciTech Connect

    Pint, Bruce A.; Unocic, Kinga A.; Terrani, Kurt A.

    2015-08-01

    Numerous research projects are directed towards developing accident tolerant fuel (ATF) concepts that will enhance safety margins in light water reactors (LWR) during severe accident scenarios. In the U.S. program, the high temperature steam oxidation performance of ATF solutions has been evaluated in the Severe Accident Test Station (SATS) at Oak Ridge National Laboratory (ORNL) since 2012 [1-3] and this facility continues to support those efforts in the ATF community. Compared to the current UO2/Zr-based alloy fuel system, alternative cladding materials can offer slower oxidation kinetics and a smaller enthalpy of oxidation that can significantly reduce the rate of heat and hydrogen generation in the core during a coolant-limited severe accident [4-5]. Thus, steam oxidation behavior is a key aspect of the evaluation of ATF concepts. This report summarizes recent work to measure steam oxidation kinetics of FeCrAl and SiC specimens in the SATS.

  1. Effect of the addition of Mn on the tensile properties of a spray-formed and extruded Al-9Si-4Cu-1Fe alloy

    NASA Astrophysics Data System (ADS)

    Benetti, G. D.; Jorge, A. M., Jr.; Kiminami, C. S.; Botta, W. J.; Bolfarini, C.

    2009-01-01

    The microstructure and the tensile properties of a spray-formed and extruded Al- 9Si-4Cu-1Fe alloy were investigated. Manganese (0.3, 1, 2 in wt%) was added to the alloy to avoid the formation of the needle-like ?-AlFeSi intermetallic phases that are highly detrimental to the alloy's ductility. The deposits were extruded at 623K with a n area reduction of 5 to 1. Small faceted dispersoids surrounding the equiaxial ?-Al matrix, mainly in the form of silicon particles, were identified by SEM-EDS, as well as the Mn-containing ?-Al15(Fe,Mn)3Si2 phase. The presence of the needle-like ?-Al(Fe,Mn)Si was scanty, even with the lowest Mn content. The room temperature tensile tests of all the extruded alloys showed a significant increase in elongation to fracture when compared with the values observed fo r the as-spray formed deposits.This result can be ascribed to the elimination of porosity promoted by the extrusion process and to the smaller grain size of the extruded samples. PUBLISHER'S NOTE This article by Benetti et al was published in error, it was a duplicate of article 012114 which appears later in this volume, the duplicate PDF and references have been deleted. The missing article by S Jayalakshmi, E Fleury and D J Sordelet, which forms part of the section HYDROGEN IN METASTABLE ALLOYS, now appears at the end of the volume (012120).

  2. Effects of NaBF4 + NaF on the Tensile and Impact Properties of Al-Si-Mg-Fe Alloys

    NASA Astrophysics Data System (ADS)

    Chen, Zongning; Wang, Tongmin; Zhao, Yufei; Zheng, Yuanping; Kang, Huijun

    2015-05-01

    NaBF4 + NaF were found to play three roles, i.e., Fe-eliminator, grain refiner, and eutectic modifier, in treating A356 alloy with a high Fe content. The joint effects led to significant improvement in both tensile and impact properties of thus treated alloy. The multiple reactions between the NaBF4 + NaF and Al-Si-Mg-Fe system are suggested to form Fe2B, AlB2, and Na in the melt, as per thermodynamic analysis. The three are responsible for Fe removal, grain refinement, and eutectic modification, respectively. When NaBF4 and NaF are mixed in weight ratio of 1:1, an optimum addition rate is in the range between 1.0 and 2.0 wt pct for treating AlSi7Mg0.3Fe0.65 alloy, based on the results of tensile and impact tests. Excessive addition of the salt may deteriorate the mechanical properties of the alloy, basically owing to overmodification of Si and contamination of salt inclusions.

  3. Magnetic properties of AlFe2B2 and CeMn2Si2 synthesized by melt spinning of stoichiometric compositions

    NASA Astrophysics Data System (ADS)

    Du, Qianheng; Chen, Guofu; Yang, Wenyun; Song, Zhigang; Hua, Muxin; Du, Honglin; Wang, Changsheng; Liu, Shunquan; Han, Jingzhi; Zhang, Yan; Yang, Jinbo

    2015-05-01

    By suppressing the growth of impurities, a melt spinning method was successfully applied to the synthesis of typical 1:2:2 layered CeMn2Si2 and AlFe2B2 compounds. X-ray diffraction analysis showed that CeMn2Si2 and AlFe2B2 had good purity and crystallized in ThCr2Si2- and AlFe2B2-type structures, respectively. The differences among three 1:2:2-type structures were also analyzed. The magnetic properties were investigated by magnetic measurements and electronic structure calculations. It was found that the Fe moment of AlFe2B2 reaches 1.32 ?B at 5 K, which fits well with the calculated result of 1.44 ?B at 0 K, and that the isothermal magnetic entropy change reaches 7.2 J kg-1 K-1 at 5 T, which shows great potential for room-temperature refrigeration applications.

  4. Sound velocities of Fe3Al2Si3O12 almandine up to 19 GPa and 1700 K

    NASA Astrophysics Data System (ADS)

    Arimoto, Takeshi; Graux, Steeve; Irifune, Tetsuo; Zhou, Chunyin; Higo, Yuji

    2015-09-01

    Elastic wave velocities of synthetic Fe3Al2Si3O12 almandine have been determined at simultaneous high pressure and temperature up to 19 GPa and 1700 K by the ultrasonic technique in conjunction with in situ synchrotron X-ray diffraction in a multi-anvil apparatus. Velocities of almandine are found substantially lower than those of other major end-member garnets such as pyrope, grossular, and MgSiO3 majorite, while their pressure and temperature derivatives are comparable to those of the latter garnets. The observed density, and compressional (VP) and shear (VS) velocities were combined and fitted to functions of the Eulerian strain EoS, yielding a adiabatic bulk modulus KS0 = 174.2 (12) GPa and a shear modulus G0 = 94.9 (7) GPa, and their pressure and temperature derivatives ?KS/?P = 4.61 (14), ?G/?P = 1.06 (6), ?KS/?T = -2.67 (7) 10-2 GPa K-1, and ?G/?T = -1.31 (8) 10-2 GPa K-1. The pressure derivative of the bulk modulus of almandine is similar to those of other garnet end-members, which is in contrast to the substantially higher value (?KS/?P = 6.2 (5)) reported for pure almandine in an earlier study based on experiments up to 3 GPa. The present new results combined with those of pyrope, grossular, and MgSiO3 majorite are successfully used to reproduce the sound velocities of majoritic garnet in the pyrolite composition.

  5. Transport properties and Moessbauer spectra of Fe-substituted La{sub 10-x}(Si,Al){sub 6}O{sub 26} apatites

    SciTech Connect

    Shaula, A.L.; Kharton, V.V.; Waerenborgh, J.C.; Rojas, D.P.; Tsipis, E.V.; Vyshatko, N.P.; Patrakeev, M.V.; Marques, F.M.B

    2004-05-05

    Increasing iron content in apatite-type La{sub 9.83}Si{sub 4.5}Al{sub 1.5-y}Fe{sub y}O{sub 26+{delta}} (y=0.5-1.5) leads to increasing unit cell volume, fraction of Fe{sup 4+}, partial oxygen ionic and p-type electronic conductivities, and ceramics sinterability. The oxygen ion transference numbers, determined by Faradaic efficiency (FE) measurements at 973-1223 K in air, are in the range 0.986-0.994. Data on total conductivity and Seebeck coefficient as functions of the oxygen partial pressure, varying in the range 10{sup -2} Pa to 70 kPa, confirm that under oxidizing conditions the ionic conduction in Fe-substituted La{sub 9.83}(Si,Al){sub 6}O{sub 26+{delta}} apatites is dominant. Due to stabilization of Fe{sup 3+}, substantially worse transport properties are observed for A-site stoichiometric La{sub 10}Si{sub 4}Fe{sub 2}O{sub 26}, having activation energy for ionic conductivity of 107 kJ/mol and electron transference numbers close to 0.03. The correlation between partial ionic and electron-hole conductivities suggests a significant role of Fe{sup 4+} formation compensated by extra oxygen incorporation into the vacant sites, which are formed due to Frenkel-type disorder induced by La vacancies. The average thermal expansion coefficients of Fe-doped La{sub 10-x}(Si,Al){sub 6}O{sub 26+{delta}} ceramics, calculated from dilatometric data in air, are 8.9x10{sup -6} to 9.9x10{sup -6} K{sup -1} at 300-1250 K.

  6. Analysis of interface states of FeO-Al2O3 spinel composite film/p-Si diode by conductance technique

    NASA Astrophysics Data System (ADS)

    Tataroğlu, Adem; Al-Ghamdi, Ahmed A.; El-Tantawy, Farid; Farooq, W. A.; Yakuphanoğlu, F.

    2016-03-01

    The interface states and series resistance properties of the Al/FeO-Al2O3/p-Si diode were investigated by the capacitance ( C) and conductance ( G) measurements. The measured capacitance and conductance values were corrected to eliminate the effect of series resistance to obtain the real capacitance and conductance values of the diode. The C and G characteristics indicate the presence of interface states at the interface of the diode. The interface states density, N ss, was determined using Hill-Coleman method, and it was found that the density of interface states is decreased with the frequency. The obtained results suggest that the series resistance and interface states affect significantly the electronic parameters of the Al/FeO-Al2O3/p-Si diode.

  7. Effects of temperature and pressure on phonons in FeSi1–xAlx

    SciTech Connect

    Delaire, O.; Al-Qasir, I. I.; Ma, J.; dos Santos, A. M.; Sales, B. C.; Mauger, L.; Stone, M. B.; Abernathy, D. L.; Xiao, Y.; Somayazulu, M.

    2013-05-31

    The effects of temperature and pressure on phonons in B20 compounds FeSi1–xAlx were measured using inelastic neutron scattering and nuclear-resonant inelastic x-ray scattering. The effect of hole doping through Al substitution is compared to results of alloying with Co (electron doping) in Fe₁₋xCoxSi. While the temperature dependence of phonons in FeSi is highly anomalous, doping with either type of carriers leads to a recovery of the normal quasiharmonic behavior. Density functional theory (DFT) computations of the electronic band structure and phonons were performed. The anomaly in the temperature dependence of the phonons in undoped FeSi was related to the narrow band gap, and its sensitivity to the effect of thermal disordering by phonons. On the other hand, the pressure dependence of phonons at room temperature in undoped FeSi follows the quasiharmonic behavior and is well reproduced by the DFT calculations.

  8. Dependence of dynamic magnetization and magneto-transport properties of FeAlSi films with oblique sputtering studied via spin rectification effect

    SciTech Connect

    Soh, Wee Tee; Ong, C. K.; Zhong, Xiaoxi

    2014-09-15

    FeAlSi (Sendust) is known to possess excellent soft magnetic properties comparable to traditional soft magnetic alloys such as NiFe (Permalloy), while having a relatively higher resistance for lower eddy current losses. However, their dynamic magnetic and magneto-transport properties are not well-studied. Via the spin rectification effect, we electrically characterize a series of obliquely sputtered FeAlSi films at ferromagnetic resonance. The variations of the anisotropy fields and damping with oblique angle are extracted and discussed. In particular, two-magnon scattering is found to dominate the damping behavior at high oblique angles. An analysis of the results shows large anomalous Hall effect and anisotropic magneto-resistance across all samples, which decreases sharply with increasing oblique incidence.

  9. Optimization of exchange bias in Co{sub 2}FeAl{sub 0.5}Si{sub 0.5} Heusler alloy layers

    SciTech Connect

    Hirohata, Atsufumi; Izumida, Keisuke; Ishizawa, Satoshi; Nakayama, Tadachika; Sagar, James

    2014-05-07

    We have fabricated and investigated IrMn{sub 3}/Co{sub 2}FeAl{sub 0.5}Si{sub 0.5} stacks to meet the criteria for future spintronic device applications which requires low-temperature crystallisation (<250?C) and a large exchange bias H{sub ex} (>500?Oe). Such a system would form the pinned layer in spin-valve or tunnel junction applications. We have demonstrated that annealing at 300?C which can achieve crystalline ordering in the Co{sub 2}FeAl{sub 0.5}Si{sub 0.5} layer giving ?80% of the predicted saturation magnetisation. We have also induced an exchange bias of ?240?Oe at the interface. These values are close to the above criteria and confirm the potential of using antiferromagnet/Heusler-alloy stacks in current Si-based processes.

  10. Carbides in iron-rich Fe-Mn-Cr-Mo-Al-Si-C systems

    NASA Technical Reports Server (NTRS)

    Lemkey, F. D.; Gupta, H.; Nowotny, H.; Wayne, S. F.

    1984-01-01

    The optimization of high carbon iron-base superalloy properties with duplex microstructure gamma + M7C3 carbide requires analysis in the context of a seven-component system. Data are first provided here for the Fe-Mn-Cr-Mo-C quinary system, at 30 at. pct carbon. A characterization of competing carbides, according to a pseudoternary phase diagram at 35 wt pct iron, is made from isothermal sections. It is noted that while M7C3 and M3C carbides' occurrences are respectively favored at the Cr and Mn corners, the M2C carbide and molybdenum cementite are predominant with increasing amounts of Mo. Lattice parameters are reported for the various carbides.

  11. Heat capacity measurements for cryolite (Na3AlF6) and reactions in the system NaFeAlSiOF

    USGS Publications Warehouse

    Anovitz, Lawrence M.; Hemingway, B.S.; Westrum, E.F., Jr.; Metz, G.W.; Essene, E.J.

    1987-01-01

    The heat capacity of cryolite (Na3AlF6) has been measured from 7 to 1000 K by low-temperature adiabatic and high-temperature differential scanning calorimetry. Low-temperature data were obtained on material from the same hand specimen in the calorimetric laboratories of the University of Michigan and U.S. Geological Survey. The results obtained are in good agreement, and yield average values for the entropy of cryolite of: S0298 = 238.5 J/mol KS0T-S0298 = 145.114 ln T+ 193.009*10-3T- 10.366* 105 T2- 872.89 J/mol K (273-836.5 K)??STrans = 9.9J/mol KS0T-S0298 =198.414 ln T+73.203* 10-3T-63.814* 105 T2-1113.11 J/mol K (836.5-1153 K) with the transition temperature between ??- and ??-cryolite taken at 836.5 K. These data have been combined with data in the literature to calculate phase equilibria for the system NaFeAlSiOF. The resultant phase diagrams allow constraints to be placed on the fO2, fF2, aSiO2 and T conditions of formation for assemblages in alkalic rocks. A sample application suggests that log fO2 is approximately -19.2, log fF2 is -31.9 to -33.2, and aSiO2 is -1.06 at assumed P T conditions of 1000 K, 1 bar for the villiaumite-bearing Ilimaussaq intrusion in southwestern Greenland. ?? 1987.

  12. The influence of microchemistry on the recrystallization texture of cold-rolled Al-Mn-Fe-Si alloys

    NASA Astrophysics Data System (ADS)

    Huang, K.; Li, Y. J.; Marthinsen, K.

    2015-04-01

    The recrystallization textures of a cold-rolled Al-Mn-Fe-Si model alloy with three different microchemistry states after non-isothermal annealing were studied. The microstructure and texture evolution have been characterized by EBSD. It is clearly demonstrated that the actual microchemistry state as determined by the homogenization procedure strongly influence the recrystallized grain size and recrystallization texture after nonisothermal annealing. High Mn content in solid solution promotes stronger concurrent precipitation and retards recrystallization, which finally leads to a coarse grain structure, accompanied by strong P {011}<566> and/or M {113}<110> texture components and a ND- rotated cube {001}<310> component. A refined grain structure with Cube {001}<100> and/or a weak P component as the main texture components were obtained when the pre-existing dispersoids are coarser and fewer, and concurrent precipitation is limited. The different recrystallization textures are discussed with respect to the effect of second-phase particles using two different heating rates.

  13. Electronic and Magneto-Transport Across the Heusler Alloy (Co2FeAl)/ p-Si Interfacial Structure

    NASA Astrophysics Data System (ADS)

    Kumar, Arvind; Srivastava, P. C.

    2014-02-01

    Electronic and magneto-transport across the Heusler alloy Co2FeAl (CFA)/ p-Si structure have been studied. The morphology of the Heusler alloy film surface has also been characterized by atomic force microscopy and magnetic force microscopy (MFM). X-ray diffraction data revealed formation of the CFA alloy phase with the L21 structure. MFM results revealed formation of a fine domain structure of average size 10 nm and magnetic signal strength 0.23. The I- V characteristics are strongly temperature-dependent between 80 K and 300 K for forward bias, compared with weak temperature dependence on reversing the polarity. At low temperature the I- V characteristics have the features of a backward diode. The observed strong temperature dependence is because of thermionic emission of carriers across the interface. The weak temperature dependence is because of dominant field-emission tunnelling of carriers across the interface. Large magnetic field sensitivity of the reverse current has also been observed. The observed magnetic field sensitivity for the reverse current shows the involvement of electronic spin in transport across the interface, from the Heusler alloy to the silicon. An MR of 35% in the presence of a magnetic field was estimated from the I- V data. The study has shown that spin-dependent tunnel transport from the CFA alloy to silicon across the interface results in the observed value of MR, which seems to be because of spin scattering.

  14. Preparation of high-strength Al-Mg-Si-Cu-Fe alloy via heat treatment and rolling

    NASA Astrophysics Data System (ADS)

    Liu, Chong-yu; Yu, Peng-fei; Wang, Xiao-ying; Ma, Ming-zhen; Liu, Ri-ping

    2014-07-01

    An Al-Mg-Si-Cu-Fe alloy was solid-solution treated at 560C for 3 h and then cooled by water quenching or furnace cooling. The alloy samples which underwent cooling by these two methods were rolled at different temperatures. The microstructure and mechanical properties of the rolled alloys were investigated by optical microscopy, scanning electron microscopy, transmission electron microscopy, X-ray diffraction analysis, and tensile testing. For the water-quenched alloys, the peak tensile strength and elongation occurred at a rolling temperature of 180C. For the furnace-cooled alloys, the tensile strength decreased initially, until the rolling temperature of 420C, and then increased; the elongation increased consistently with increasing rolling temperature. The effects of grain boundary hardening and dislocation hardening on the mechanical properties of these rolled alloys decreased with increases in rolling temperature. The mechanical properties of the 180C rolling water-quenched alloy were also improved by the presence of ?? phase. Above 420C, the effect of solid-solution hardening on the mechanical properties of the rolled alloys increased with increases in rolling temperature.

  15. The influence of Si addition on the glass forming ability, magnetic and magnetocaloric properties of the Gd-Fe-Al glassy ribbons

    NASA Astrophysics Data System (ADS)

    Zhao, X. G.; Lai, J. H.; Hsieh, C. C.; Fang, Y. K.; Chang, W. C.; Zhang, Z. D.

    2011-04-01

    The effects of Si substitution for Al on the glass forming ability, Curie temperature TC, magnetocaloric effect, and refrigeration capacity (RC) of melt-spun Gd-based Gd65Fe20Al15-xSix (x = 0-7) glassy ribbons have been investigated. The small amounts of Si substitution for Al in the Gd65Fe20Al15-xSix glassy ribbons with high Tx/Tm (> 0.70) and small ΔTm (ΔTm = Tm-Tx) promote the formation of high thermal stability of these alloys. The Si addition leads to an increase of Curie temperature TC of glassy ribbons from 181 K for x = 0 to 227 K for x = 7. The maximal magnetic entropy changes -ΔSM and RC values for magnetic field change of 50 kOe are about 4.70-5.20 J/kg K and 710-760 J/kg, respectively. The large RC values are due to the broad temperature range of the half maximum of ΔSM peak (˜ 200 K), which is caused by the change of the amorphous disorder structure. The moderate ΔSM and large RC values jointly make the Gd65Fe20Al15-xSix glassy ribbons promising candidates for magnetic refrigeration materials working at temperature range of 100-300 K.

  16. /Al-Si Composite

    NASA Astrophysics Data System (ADS)

    Li, Wei; Chen, Jian; Hu, Yongle; Cong, Li; Sun, YouPing; Yang, JiMing

    2014-08-01

    The cyclic fatigue characteristics of spray-deposited SiCp/Al-Si composite were investigated in comparison with the unreinforced Al-Si alloy. The as-extruded specimens were cyclically deformed with fully reversed loading under a range of total strain amplitudes. The results show that the cyclic response characteristics for the reinforced and unreinforced materials are similar to each other. Both the composite and matrix alloys display cyclic hardening under total strain amplitude of 0.35-0.5%. Otherwise, the composite exhibits higher degree of strain hardening than that of the matrix alloy. Dislocation substructure developed during cyclic deformation was analyzed using transmission electron microscopy. The discrepancy between dislocation substructures obtained from processing compared to its development during cyclic strain loading is thought to give rise to the observed cyclic stress response behavior. Fractographic analysis shows that particle/matrix debonding and particle cracking are the main mechanisms of failure in the SiC particle-reinforced composite.

  17. Phase Transformation and Aging Behavior of Al0.5CoCrFeNiSi0.2 High-Entropy Alloy

    NASA Astrophysics Data System (ADS)

    Zhang, C.; Wu, G. F.; Dai, P. Q.

    2015-05-01

    An Al0.5CoCrFeNiSi0.2 high-entropy alloy was prepared by vacuum arc melting. The alloy was aged from 700 to 1100 °C. The effects of aging on the phase transformation and mechanical performances were explored. The as-cast alloy showed a dendritic (DR) microstructure. The DR region was an Fe,Cr-rich FCC phase, while the interdendritic (ID) region was a spinodal structure composed of Fe,Cr-rich BCC (A2) and Ni,Al-rich BCC (B2) phases. At aging temperatures between 700 and 900 °C, the Fe,Cr-rich BCC (A2) phase in the ID region transformed into σ and Fe,Cr-rich FCC phases. Meanwhile, some Ni,Al-rich FCC phase particles precipitated from the DR region. During aging at 1100 °C, the DR microstructure disappeared, and a microstructure composed of Fe,Cr-rich FCC and Ni,Al-rich BCC (B2) phases both possessing a lamellar shape was developed. The alloy exhibited evident hardening and lower tensile strain when the aging temperature was lower than 1000 °C, which was mainly attributed to the generation of the σ phase in the ID region. However, a contrasting behavior was observed when the aging temperature was higher than 1000 °C, which was attributed to the redissolution of the σ phase and the microstructure coarsening.

  18. Structure and magnetic properties of FeSiAl-based soft magnetic composite with AlN and Al2O3 insulating layer prepared by selective nitridation and oxidation

    NASA Astrophysics Data System (ADS)

    Zhong, Xiaoxi; Liu, Ying; Li, Jun; Wang, Yiwei

    2012-08-01

    FeSiAl is widely used in switching power supply, filter inductors and pulse transformers. But when used under higher frequencies in some particular condition, it is required to reduce its high-frequency loss. Preparing a homogeneous insulating coating with good heat resistance and high resistivity, such as AlN and Al2O3, is supposed to be an effective way to reduce eddy current loss, which is less focused on. In this project, mixed AlN and Al2O3 insulating layers were prepared on the surface of FeSiAl powders after 30 min exposure at 1100 C in high purity nitrogen atmosphere, by means of surface nitridation and oxidation. The results revealed that the insulating layers increase the electrical resistivity, and hence decrease the loss factor, improve the frequency stability and increase the quality factor, especially in the high-frequency range. The morphologies, microstructure and compositions of the oxidized and nitrided products on the surface were characterized by Scanning Electron Microscopy/Energy Disperse Spectroscopy, X-Ray Diffraction, Transmission Electron Microscopy, Selected Area Electron Diffraction and X-ray Photoelectron Spectroscopy.

  19. 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 group F23; a = 14.9346(4) Å; V = 3331.07(15) Å3, Z = 4. The strongest lines of the X-ray powder-diffraction pattern [ d, Å - ( I obs )] are: 2.874(57), 2.640 (100), 2.524(42), 2.278(41), 1.760(54), 1.725(25), 1.524(33), 1.500(33). The crystal structure was solved from single-crystal X-ray diffraction data and refined to wR2 = 0.0672 on the basis of 913 unique reflections with I 0 > 2σ( I). Tululite belongs to a group of compounds with the general formula Ca14 MT 15O35+ x (0 ≤ x ≤ 1), and is a new structure type. The tetrahedral framework of tululite structure is formed by T7O13 secondary building units (SBU), which consist of four corner-linked tetrahedra sharing a common oxygen atom and three tetrahedra sharing two O atoms with the neighbor SBU. Ca2+ cations occupy three positions; two of them also contain a minor amount of Cd2+. The Ca sites surround an island (Fe3+,Al)O6 octahedron and a (Si,P)O4 tetrahedron in the centers of framework cages at the junction of eight SBUs. The (Fe3+,Al)O6 octahedron is coordinated by fourteen Ca positions into a 6-capped cube, whereas the (Si,P)O4 tetrahedron is coordinated by six Ca positions into a regular octahedron. The structural formula of tululite is Ca14{Fe3+O6}M1[(Si,P)O4]T1[(Al,Zn)7O13]2 T2-T4. The mineral is yellow with greenish tint, transparent with vitreous luster, non-fluorescent under ultraviolet light, and showing neither parting nor cleavage; Mohs hardness is 6.5. The density calculated on the basis of the empirical formula is 3.826 g/cm3. Its Raman spectrum shows strong bands at 522, 550 and 636 cm-1 and weak bands at 199, 260, 295, 456, and 754 cm-1.

  20. 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.

    2015-11-01

    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 group F23; a = 14.9346(4) Å; V = 3331.07(15) Å3, Z = 4. The strongest lines of the X-ray powder-diffraction pattern [d, Å - (I obs )] are: 2.874(57), 2.640 (100), 2.524(42), 2.278(41), 1.760(54), 1.725(25), 1.524(33), 1.500(33). The crystal structure was solved from single-crystal X-ray diffraction data and refined to wR2 = 0.0672 on the basis of 913 unique reflections with I 0 > 2σ(I). Tululite belongs to a group of compounds with the general formula Ca14 MT 15O35+x (0 ≤ x ≤ 1), and is a new structure type. The tetrahedral framework of tululite structure is formed by T7O13 secondary building units (SBU), which consist of four corner-linked tetrahedra sharing a common oxygen atom and three tetrahedra sharing two O atoms with the neighbor SBU. Ca2+ cations occupy three positions; two of them also contain a minor amount of Cd2+. The Ca sites surround an island (Fe3+,Al)O6 octahedron and a (Si,P)O4 tetrahedron in the centers of framework cages at the junction of eight SBUs. The (Fe3+,Al)O6 octahedron is coordinated by fourteen Ca positions into a 6-capped cube, whereas the (Si,P)O4 tetrahedron is coordinated by six Ca positions into a regular octahedron. The structural formula of tululite is Ca14{Fe3+O6}M1[(Si,P)O4]T1[(Al,Zn)7O13]2 T2-T4. The mineral is yellow with greenish tint, transparent with vitreous luster, non-fluorescent under ultraviolet light, and showing neither parting nor cleavage; Mohs hardness is 6.5. The density calculated on the basis of the empirical formula is 3.826 g/cm3. Its Raman spectrum shows strong bands at 522, 550 and 636 cm-1 and weak bands at 199, 260, 295, 456, and 754 cm-1.

  1. Tuning Fermi level of Cr2CoZ (Z=Al and Si) inverse Heusler alloys via Fe-doping for maximum spin polarization

    NASA Astrophysics Data System (ADS)

    Singh, Mukhtiyar; Saini, Hardev S.; Thakur, Jyoti; Reshak, Ali H.; Kashyap, Manish K.

    2014-12-01

    We report full potential treatment of electronic and magnetic properties of Cr2-xFexCoZ (Z=Al, Si) Heusler alloys where x=0.0, 0.25, 0.5, 0.75 and 1.0, based on density functional theory (DFT). Both parent alloys (Cr2CoAl and Cr2CoSi) are not half-metallic frromagnets. The gradual replacement of one Cr sublattice with Fe induces the half-metallicity in these systems, resulting maximum spin polarization. The half-metallicity starts to appear in Cr2-xFexCoAl and Cr2-xFexCoSi with x=0.50 and x=0.25, respectively, and the values of minority-spin gap and half-metallic gap or spin-flip gap increase with further increase of x. These gaps are found to be maximum for x=1.0 for both cases. An excellent agreement between the structural properties of CoFeCrAl with available experimental study is obtained. The Fermi level tuning by Fe-doping makes these alloys highly spin polarized and thus these can be used as promising candidates for spin valves and magnetic tunnelling junction applications.

  2. The effects of Ni, Mo, Ti and Si on the mechanical properties of Cr free Mn steel (Fe-25Mn-5Al-2C)

    NASA Technical Reports Server (NTRS)

    Schuon, S. R.

    1982-01-01

    The FeMnAlC alloys may hold potential as Cr-free replacements for high strategic material iron base superalloys, but little is known about their intermediate temperature (650 C to 870 C) mechanical properties. The effects of alloying elements on the mechanical properties of model FeMnAlC alloys were studied. Results showed that modified FeMnAlC alloys had promising short term, intermediate temperature properties but had relatively poor stress rupture lives at 172 MPa and 788 C. Room temperature and 788 C tensile strength of FeMnAlC alloys were better than common cast stainless steels. Changes in room temperature tensile and 788 C tensile strength and ductility, and 788 C stress rupture life were correlated with changes in Ni, Mo, Ti, and Si levels due to alloying effects on interstitial carbon levels and carbide morphology. Fe-25Mn-5Al-2C had a very poor stress rupture life at 172 MPa and 788 C. Addition of carbide-forming elements improved the stress rupture life.

  3. Modeling of viscosities of the partly crystallized slags in the Al2O3-CaO-``FeO''-SiO2 system

    NASA Astrophysics Data System (ADS)

    Kondratiev, Alex; Jak, Evgueni

    2001-12-01

    A viscosity model of the partly crystallized slag in the Al2O3-CaO-FeO-SiO2 system has been developed in conjunction with the thermodynamic computer package F*A*C*T. Proportions of solids crystallized out of the liquid phase and compositions of the remaining liquid phase predicted by F*A*C*T are used in the viscosity model. Various heterogeneous viscosity models have been tested using large experimental dataset in the Al2O3-CaO-FeO-SiO2 system in reducing conditions close to the equilibrium with metallic iron. The Roscoe equation with new empirical parameters was found to provide reasonable agreement with experimental data. Examples of model application to industrial nonferrous smelting slag systems are presented. This model can also be applied to coal ash slags.

  4. Fabrication of highly spin-polarized Co2FeAl0.5Si0.5 thin-films

    NASA Astrophysics Data System (ADS)

    Vahidi, M.; Gifford, J. A.; Zhang, S. K.; Krishnamurthy, S.; Yu, Z. G.; Yu, L.; Huang, M.; Youngbull, C.; Chen, T. Y.; Newman, N.

    2014-04-01

    Ferromagnetic Heusler Co2FeAl0.5Si0.5 epitaxial thin-films have been fabricated in the L21 structure with saturation magnetizations over 1200 emu/cm3. Andreev reflection measurements show that the spin polarization is as high as 80% in samples sputtered on unheated MgO (100) substrates and annealed at high temperatures. However, the spin polarization is considerably smaller in samples deposited on heated substrates.

  5. Impact of a long term fire retardant (Fire Trol 931) on the leaching of Na, Al, Fe, Mn, Cu and Si from a Mediterranean forest soil: a short-term, lab-scale study.

    PubMed

    Koufopoulou, Sofia; Michalopoulos, Charalampos; Tzamtzis, Nikolaos; Pappa, Athina

    2014-06-01

    Long term fire retardant (LTR) application for forest fire prevention purposes as well as wildland fires can result in chemical leaching from forest soils. Large quantities of sodium (Na), aluminium (Al), iron (Fe), manganese (Mn), copper (Cu) and silicon (Si) in leachates, mainly due to ammonium (one of the major LTR components) soil deposition, could affect the groundwater quality. The leaching of Na, Al, Fe, Mn, Cu and Si due to nitrogen based LTR application (Fire Trol 931) was studied at laboratory scale. The concentrations of Na(+), Al(3+), Fe(3+)/Fe(2+), Mn(2+), Cu(2+) and Si(4+) were measured in the resulting leachates from pots with forest soil and pine trees alone and in combination with fire. The leaching of Na, Fe and Si from treated pots was significantly greater than that from control pots. The leaching of Al, Mn and Cu was extremely low. PMID:24687225

  6. Photoluminescence study of interfaces between heavily doped Al0.48In0.52As:Si layers and InP (Fe) substrates

    NASA Astrophysics Data System (ADS)

    Poas, L. C.; Duarte, J. L.; Dias, I. F. L.; Laureto, E.; Loureno, S. A.; Filho, D. O. Toginho; Meneses, E. A.; Mazzaro, I.; Harmand, J. C.

    2002-06-01

    Properties of the interface between the epitaxial layer of heavily doped Al0.48In0.52As:Si and the InP(Fe) substrate are investigated by photoluminescence in AlInAs:Si/InP(Fe) heteroestructures grown by molecular beam epitaxy. The effect on heterostructure optical properties of including a thin Al0.22Ga0.26In0.52As:Si layer at the interface is investigated as well. To explain the different interface emission energies observed, the results are analyzed by using the mixed-type I-II interface model, which considers in the type II interface a narrow InAs well, with variable width, between AlInAs and InP. The observation of the interface emission at energies as high as 1.36 eV, at low excitation intensity, is explained taking into account the high doping level of the samples. The observed interface transition luminescence thermal quenching is tentatively explained by analyzing the spatial distribution of electrons in the triangular quantum well formed at the type II interface (or at the mixed I-II interface) as a function of the temperature.

  7. Significance of Elevated Contents of Si4O8 and AlAl3SiO8 End Members in Black Clouded Plagioclase From Anorthosite: Evidence for Oxidation-Induced Postmagmatic Exsolution of Fe-Ti Oxide Inclusions From Plagioclase

    NASA Astrophysics Data System (ADS)

    Murakami, H.; Lalonde, A. E.

    2004-12-01

    Plagioclase phenocrysts from large Proterozoic massif anorthosites that have escaped metamorphic recrystallization commonly have a distinctive black color that is attributed to myriads of minute Fe-Ti oxide inclusions. These inclusions are responsible for the black color of the feldspar. The orientation of these inclusions along specific crystallographic directions in the plagioclase is strong evidence that these formed by exsolution from the plagioclase. Plagioclase from the Proterozoic Lac Saint-Jean anorthosite in Qubec is a good example of such clouded feldspar. In this plagioclase we recognize four types of Fe-Ti oxide inclusions: 1) Myriads of fine, submicroscopic and unidentifiable dust-like inclusions, presumably Fe-Ti oxides, and responsible in great part for the black color. 2) Small 1 ? m sized crystals of hemo-ilmenite that occur in regions of the plagioclase that are free of type 1 dust, suggesting that these originated by Ostwald ripening from the dusty material. 3) Larger aligned and acicular crystals of hematite, 10 ? m in diameter and with good rhombohedral sections. These occur, like type 2 inclusions, in zones free of type 1 dust suggesting again that they result from Ostwald ripening. 4) Millimetric inclusions of ilmenite or magnetite of magmatic origin, often rimmed by amphibole or biotite, signs of late hydration. As part of our study, EPMA analyses of plagioclase from Lac Saint-Jean were done. In addition, a large single crystal, 30 cm in diameter was analyzed by bulk XRF. Our results show that plagioclase contains significant amounts of the Si4O8 (up to 6.6 mole %) and AlAl3SiO8 (up to 2.2 mole %) endmembers. A positive relationship is observed between the content of these two endmembers. Furthermore, the ratio of Si4O8 to AlAl3SiO8 is approximately 3:4. We believe that the high content of Si4O8 and AlAl3SiO8 in plagioclase, and the presence of minute Fe-Ti oxide inclusions are both products of a late postmagmatic oxidation via the following chemical reactions: 1) 4Fe2+Al2Si2O8 + 4CaFe2+Si3O8 + 2O2 -> 4Fe2O3 + 4CaAl2Si2O8 + 3 Si4O8 2) 8Fe2+Al2Si2O8 + 2O2 -> 4Fe2O3 + 3 Si4O8 + 4 AlAl3SiO8 3) 8CaAl2SiTiO8 + 8Fe2+Al2Si2O8 -> 8CaAl2Si2O8 + 8FeTiO3 + Si4O8 + 4 AlAl3SiO8 These reactions indicate that significant amounts of Fe2+ were originally present in the tetrahedral and cavity sites of the plagioclase and that Ti4+ was also present in the tetrahedral sites. We conclude that plagioclase in the Lac Saint-Jean anorthosite crystallized under fairly reducing conditions and later underwent postmagmatic oxidation when the plutonic mass was uplifted and came into contact with crustally-derived oxygenated fluids. These findings have important implications for studies of magnetic remanence and anisotropy fabrics in anorthositic rocks.

  8. Multiscale modeling of the influence of Fe content in a Al-Si-Cu alloy on the size distribution of intermetallic phases and micropores

    SciTech Connect

    Wang Junsheng; Lee, Peter D.; Li Mei; Allison, John

    2010-03-15

    A multiscale model was developed to simulate the formation of Fe-rich intermetallics and pores in quaternary Al-Si-Cu-Fe alloys. At the microscale, the multicomponent diffusion equations were solved for multiphase (liquid-solid-gas) materials via a finite difference framework to predict microstructure formation. A fast and robust decentered plate algorithm was developed to simulate the strong anisotropy of the solid/liquid interfacial energy for the Fe-rich intermetallic phase. The growth of porosity was controlled by local pressure drop due to solidification and interactions with surrounding solid phases, in addition to hydrogen diffusion. The microscale model was implemented as a subroutine in a commercial finite element package, producing a coupled multiscale model. This allows the influence of varying casting conditions on the Fe-rich intermetallics, the pores, and their interactions to be predicted. Synchrotron x-ray tomography experiments were performed to validate the model by comparing the three-dimensional morphology and size distribution of Fe-rich intermetallics as a function of Fe content. Large platelike Fe-rich {beta} intermetallics were successfully simulated by the multiscale model and their influence on pore size distribution in shape castings was predicted as a function of casting conditions.

  9. Ferroindialite (Fe2+,Mg)2Al4Si5O18, a new beryl-group mineral from the Eifel volcanic region, Germany

    NASA Astrophysics Data System (ADS)

    Chukanov, N. V.; Aksenov, S. M.; Pekov, I. V.; Ternes, B.; Schüller, W.; Belakovskiy, D. I.; Van, K. V.; Blass, G.

    2014-12-01

    A new mineral, ferroindialite, a Fe2+-dominant analog of indialite, has been found in a pyrometamorphosed xenolith of pelitic rock hosted in alkaline basalts. Associated minerals are phlogopite, sanidine, sillimanite, pyroxenes of the enstatite-ferrosilite series, wagnerite, fluorapatite, tridymite, zircon and almandine. Ferroindialite forms brown-purple to gray with a violet-blue tint short prismatic or thick tabular hexagonal crystals up to 1.5 mm in size. The new mineral is brittle, with a Mohs' hardness of 7. Cleavage is not observed. D meas = 2.66(1), D calc = 2.667 g/cm3. IR spectrum shows neither H2O nor OH groups. Ferroindialite is anomalously biaxial (-), α = 1.539(2), β = 1.552(2), γ = 1.554(2), 2 V meas = 30(10)°. The mineral is weakly pleochroic, ranging from colorless on X to pale violet on Z. Dispersion is weak, r < v. The chemical composition (electron microprobe, mean of five point analyses, wt %) is as follows: 0.14 Na2O, 0.46 K2O, 4.95 MgO, 1.13 MnO, 12.66 FeO, 2.64 Fe2O3, 30.45 Al2O3, 47.22 SiO2, total is 99.65. The distribution of total iron content between Fe2+ and Fe3+ was carried out according to structural data. The empirical formula of ferroindialite is: (K0.06Na0.03)(Fe{1.12/2+}Mg0.78Mn0.10)Σ2.00(Al3.79Fe{0.21/3+})Σ4.00Si4.98O18. The simplified formula is: (Fe2+,Mg)2Al4Si5O18. The crystal structure has been refined on a single crystal, R = 0.049. Ferroindialite is hexagonal, space group P6/ mcc; a = 9.8759(3), c = 9.3102(3) Å, V = 786.40(3) Å3, Z = 2. The strongest lines in the X-ray powder diffraction pattern [ d, Å ( I, %) ( hkl)] are: 8.59 (100) (100), 4.094 (27) (102), 3.390 (35) (112), 3.147 (19) (202), 3.055 (31) (211), 2.657 (12) (212), 1.695 (9) (224). The type specimen of ferroindialite is deposited in the Fersman Mineralogical Museum, Russian Academy of Sciences, Moscow, registration number 4400/1.

  10. Thermal-cycling-dependent magnetostructural transitions in a Ge-free system Mn0.5Fe0.5Ni(Si,Al)

    NASA Astrophysics Data System (ADS)

    Zhang, C. L.; Shi, H. F.; Nie, Y. G.; Ye, E. J.; Han, Z. D.; Wang, D. H.

    2014-12-01

    Magnetostructural transitions from low-temperature TiNiSi-type phases to high-temperature Ni2In-type phases had been observed in some MnCoGe-based and MnNiGe-based intermetallic systems. In this work, the TiNiSi-to-Ni2In-type magnetostructural transitions, which are associated with large changes in magnetization and large anisotropy lattice distortion, were obtained in a Ge-free system Mn0.5Fe0.5Ni(Si,Al) in the vicinity of room temperature. Thermal-cycling-dependent properties were observed in the as-prepared bulk polycrystalline samples. This phenomenon could be attributed to the presence of anisotropy internal stress and its release by spontaneously cracking across the thermally activated magnetostructural transitions.

  11. Production of Na-22 and Other Radionuclides by Neutrons in Al, SiO2, Si, Ti, Fe and Ni Targets: Implications for Cosmic Ray Studies

    NASA Technical Reports Server (NTRS)

    Sisterson, J. M.; Jones, D. T. L.; Binns, P. J.; Langen, K.; Schroeder, I.; Buthelezi, Z.; Latti, E.; Brooks, F. D.; Buffler, A.; Allie, M. S.; Herbert, M. S.; Nchodu, M. R.; Makupula, S.; Ullmann, J.; Reedy, R. C.

    2001-01-01

    Cross section measurements for neutron-induced reactions are summarized. Measured cross sections for 22 Na produced by neutrons in Al and Si are used to calculate the production rate for 22 Na in lunar rock 12002 by galactic cosmic ray particles. Additional information is contained in the original extended abstract.

  12. First-principles study of the Hume-Rothery electron concentration rule in Al-Cu-(Fe,Ru)-Si 1/1-cubic approximants

    NASA Astrophysics Data System (ADS)

    Asahi, Ryoji; Kontsevoi, O. Y.; Mizutani, U.; Takeuchi, T.; Freeman, A. J.

    2006-03-01

    To elucidate the Hume-Rothery electron concentration rule, we determined the self-consistent electronic structures of the Al108Ru24Cu6Si6 and Al108Fe24Cu6Si6 1/1-1/1-1/1 approximants containing 144 atoms in each Pm-3 cubic unit cell using the full-potential linearized augmented plane wave (FLAPW) method [1], now running on massively parallel computer platforms. A significant pseudogap was found around the Fermi level for both alloys in the calculated densities of states, which should contribute to stabilization of the system. The FLAPW wave functions provide a direct observation of the Brillouin zone resonance in the Fermi surface [2]: a Fourier analysis of the wave functions confirms the Hume-Rothery matching rule 2kF=K where the reciprocal lattice vectors K consist of 543, 550, and 710 planes highly degenerate at the N point. Consequently, an effective electron concentration per atom (e/a) was evaluated to be 0.8 for both Ru and Fe in these structures making a sharp contrast with the previously assumed empirical value of -2.7 proposed by Raynor [3]. [1] Wimmer et al., Phys. Rev. B 24, 864 (1981). [2] Asahi et al., Phys. Rev. B 72, 125102 (2005). [3] Raynor, Prog. Metal Phys. 1, 1 (1949).

  13. Melts in the Deep Earth: Calculating the Densities of CaO-FeO-MgO-Al2O3-SiO2 Liquids

    NASA Astrophysics Data System (ADS)

    Thomas, C.; Guo, X.; Agee, C. B.; Asimow, P. D.; Lange, R. A.

    2012-12-01

    We present new equation of state (EOS) measurements for hedenbergite (Hd, CaFeSi2O6) and forsterite (Fo, Mg2SiO4) liquids. These liquid EOS add to the basis set in the CaO-FeO-MgO-Al2O3-SiO2 (CMASF) oxide space at elevated temperatures and pressures; other liquids include: enstatite (En, MgSiO3), anorthite (An, CaAl2Si2O8), diopside (Di, CaMgSi2O6), and fayalite (Fa, Fe2SiO4). The Hd EOS measurement was a multi-technique collaboration using 1-atm double-bob Archimedean, ultrasonic, sink/float, and shock wave techniques. Un-weighted linear fitting of the shock data in shock velocity (US)-particle velocity (up) space defines a pre-heated (1400 °C) Hugoniot US = 2.628(0.024) + 1.54(0.01)up km/s. The slope corresponds to a K' of 5.16(0.04), consistent with piston-cylinder and multi-anvil sink/float experiments. The intercept is fixed at the ultrasonic sound speed (Co) since the unconstrained intercept is within the stated error. This behavior demonstrates consistency across methods and that the liquid is relaxed during shock compression. Shock compression of pre-heated (2000°C) single crystal Fo gives an un-weighted linear Hugoniot of US = 2.674(0.188) + 1.64(0.06)up km/s. The unconstrained Co falls below estimates based on extrapolation in both temperature and composition from two published partial molar sound speed models, 3.195m/s [1] and 3.126 m/s [2]. The shock-derived Co indicates that dC/dT is negative for Fo liquid, contrary to the positive [1] and zero [2] temperature dependences derived over relatively narrow temperature intervals. CMASF liquid isentropes were calculated using five end-members (En, Fo, Fa, An, Di). For modeling crystallization of a fictive magma ocean, we examined two liquids: peridotite [3] (P=.33En+.56Fo+.07Fa+.03An+.007Di) and simplified chondrite [4] (Ch=.62En+.24Fo+.08Fa+.04An+.02Di). Each end-member is defined by a 3rd or 4th order Birch-Murnaghan isentrope, Mie-Grüneisen thermal pressure and a constant heat capacity. The volumes are assumed to ideally mix allowing for interpolation between end-member compositions. Results show the chondrite critical isentrope intersecting its liquidus at the core-mantle boundary with a potential temperature (TP) of 2400 K, whereas the peridotite critical isentrope has a TP of 2800 K and first crystallizes at 85 GPa. An identical calculation fails to recover the Hd isentrope (Hd = Di+0.5Fa-0.5Fo). This failure is likely due to the very different partial molar volumes of FeO in Hd and Fa, which have average Fe2+ coordination states of ~4.5 and ~6, respectively [5]. Consequently the simple ideal model is likely to only support mixing among like-coordinated Fe2+ liquids. We hope to further investigate this hypothesis for linear-mixing by constraining the EOS of An-Hd (50:50), and An-Di-Hd (33:33:33) melts using pre-heated shock wave techniques. [1] Ghiorso & Kress (2004) AJS 304, 679-751.[2] Ai & Lange(2008) JGR 113,B04203.[3] Fiquet et al. (2010) Science 329, 1516-1518.[4]Andrault et al. (2011) EPSL 304, 251-259.[5]Lange et al. (2012) Goldschmidt meeting, abstract.

  14. Structure alterations in microporous (Mg,Fe) 2Al 4Si 5O 18 crystals induced by energetic heavy-ion irradiation

    NASA Astrophysics Data System (ADS)

    Miletich, Ronald; Diego Gatta, G.; Redhammer, Gnther J.; Burchard, Michael; Meyer, Hans-Peter; Weikusat, Christian; Rotiroti, Nicola; Glasmacher, Ulrich A.; Trautmann, Christina; Neumann, Reinhard

    2010-10-01

    The microporous framework structure of (Mg 1- xFe x) 2Al 4Si 5O 18 (=cordierite) has been subject to a comparative study on the effect of structural alterations originating from exposure to high-energy heavy ions. Oriented samples (with x=0.061, 0.122, and 0.170) were irradiated with swift 124Xe, 197Au and 96Ru ions with 11.1 MeV per nucleon energy and fluences of 110 12 and 110 13 ions/cm 2. Irradiated and non-irradiated samples were investigated by means of X-ray diffraction, Mssbauer spectroscopy and optical absorption spectroscopy. Structural investigations reveal an essentially unchanged Al,Si ordering, which appears to be unaffected by irradiation. The most remarkable macroscopic change is the ion-beam induced colouration, which could be assigned to electronic charge transfer transitions involving the Fe cations. Mssbauer spectra indicate an increased amount of [4]Fe 3+ for the irradiated sample. The most noticeable structural alteration concerns irradiation-induced dehydration of extra-framework H 2O, which is accompanied by a reduction in the molar volume by 0.2 vol%.

  15. Study of Projectile Fragmentation for Fe and Si Nuclei in Collisions with H, C, Al, Cu, Ag and Pb

    NASA Astrophysics Data System (ADS)

    Flesch, Frank

    We have used stacks containing CR-39 track detectors and targets C, CH2 , Al, Cu, Ag and Pb to measure 6 elemental fragmentation cross sections of fragments with charges Z . Cross sections of iron projectiles at 700 A MeV, for different targets, have been presented at the last cosmic ray conference. For the fragments produced in these interactions we have measured the transverse momenta. Furthermore, simultaneously emitted light fragments produced in multifragmentation of iron projectiles were studied. Recently a set of stacks has been exposed to a Si beam with 490 A MeV at the HIMAC (Chiba, Japan). In this paper we present first results for fragmentation cross sections of Si projectiles in collisions with carbon target nuclei. These results are compared to our earlier data measured at higher beam energy and to the results of Webber, Kish & Schrier.

  16. Fabrication of highly spin-polarized Co{sub 2}FeAl{sub 0.5}Si{sub 0.5} thin-films

    SciTech Connect

    Vahidi, M.; Zhang, S. K.; Yu, L.; Huang, M.; Newman, N.; Gifford, J. A.; Chen, T. Y.; Krishnamurthy, S.; Yu, Z. G.; Youngbull, C.

    2014-04-01

    Ferromagnetic Heusler Co{sub 2}FeAl{sub 0.5}Si{sub 0.5} epitaxial thin-films have been fabricated in the L2{sub 1} structure with saturation magnetizations over 1200 emu/cm{sup 3}. Andreev reflection measurements show that the spin polarization is as high as 80% in samples sputtered on unheated MgO (100) substrates and annealed at high temperatures. However, the spin polarization is considerably smaller in samples deposited on heated substrates.

  17. Direct band-gap measurement on epitaxial Co2FeAl0.5Si0.5 Heusler-alloy films

    NASA Astrophysics Data System (ADS)

    Alhuwaymel, Tariq F.; Carpenter, Robert; Yu, Chris Nga Tung; Kuerbanjiang, Balati; Abdullah, Ranjdar M.; Lazarov, Vlado K.; El-Gomati, Mohamed; Hirohata, Atsufumi

    2015-05-01

    In this study, a newly developed band-gap measurement technique has been used to characterise epitaxial Co2FeAl0.5Si0.5 (CFAS) films. The CFAS films were deposited on MgO(001) substrate by ultra high vacuum molecular beam epitaxy. The band-gap for the as deposited films was found to be 110 meV when measured at room temperature. This simple technique provides a macroscopic analysis of the half-metallic properties of a thin film. This allows for simple optimisation of growth and annealing conditions.

  18. Direct band-gap measurement on epitaxial Co{sub 2}FeAl{sub 0.5}Si{sub 0.5} Heusler-alloy films

    SciTech Connect

    Alhuwaymel, Tariq F.; Carpenter, Robert; Yu, Chris Nga Tung; Kuerbanjiang, Balati; Lazarov, Vlado K.; Abdullah, Ranjdar M.; El-Gomati, Mohamed; Hirohata, Atsufumi

    2015-05-07

    In this study, a newly developed band-gap measurement technique has been used to characterise epitaxial Co{sub 2}FeAl{sub 0.5}Si{sub 0.5} (CFAS) films. The CFAS films were deposited on MgO(001) substrate by ultra high vacuum molecular beam epitaxy. The band-gap for the as deposited films was found to be ∼110 meV when measured at room temperature. This simple technique provides a macroscopic analysis of the half-metallic properties of a thin film. This allows for simple optimisation of growth and annealing conditions.

  19. Review of experimental data and modeling of the viscosities of fully liquid slags in the Al2O3-CaO-`FeO'-SiO2 system

    NASA Astrophysics Data System (ADS)

    Kondratiev, Alex; Jak, Evgueni

    2001-12-01

    A general model based on the Urbain formalism has been developed, which enables the viscosities of liquid slags to be predicted for all compositions in the Al2O3-CaO-FeO-SiO2 system in equilibrium with metallic iron. Available experimental viscosity data have been analyzed and critically reviewed. The Urbain formalism has been modified to include compositional dependent model parameters. Experimental data in unaries, binaries, ternaries, and the quaternary system have been described by the model over the whole compositional and temperature ranges using one set of model parameters. This viscosity model can now be applied to various industrial slag systems.

  20. Constraints on silicates formation in the Si-Al-Fe system: Application to hard deposits in steam generators of PWR nuclear reactors

    NASA Astrophysics Data System (ADS)

    Berger, Gilles; Million-Picallion, Lisa; Lefevre, Grégory; Delaunay, Sophie

    2015-04-01

    Introduction: The hydrothermal crystallization of silicates phases in the Si-Al-Fe system may lead to industrial constraints that can be encountered in the nuclear industry in at least two contexts: the geological repository for nuclear wastes and the formation of hard sludges in the steam generator of the PWR nuclear plants. In the first situation, the chemical reactions between the Fe-canister and the surrounding clays have been extensively studied in laboratory [1-7] and pilot experiments [8]. These studies demonstrated that the high reactivity of metallic iron leads to the formation of Fe-silicates, berthierine like, in a wide range of temperature. By contrast, the formation of deposits in the steam generators of PWR plants, called hard sludges, is a newer and less studied issue which can affect the reactor performance. Experiments: We present here a preliminary set of experiments reproducing the formation of hard sludges under conditions representative of the steam generator of PWR power plant: 275°C, diluted solutions maintained at low potential by hydrazine addition and at alkaline pH by low concentrations of amines and ammoniac. Magnetite, a corrosion by-product of the secondary circuit, is the source of iron while aqueous Si and Al, the major impurities in this system, are supplied either as trace elements in the circulating solution or by addition of amorphous silica and alumina when considering confined zones. The fluid chemistry is monitored by sampling aliquots of the solution. Eh and pH are continuously measured by hydrothermal Cormet© electrodes implanted in a titanium hydrothermal reactor. The transformation, or not, of the solid fraction was examined post-mortem. These experiments evidenced the role of Al colloids as precursor of cements composed of kaolinite and boehmite, and the passivation of amorphous silica (becoming unreactive) likely by sorption of aqueous iron. But no Fe-bearing was formed by contrast to many published studies on the Fe-clay interactions in the nuclear waste storage, and by contrast with basic thermodynamic predictions. Conclusion: The Fe-clays and steam generators contexts imply relatively close aqueous environments: hydrothermal, reduced, diluted, neutral to slightly alkaline. The main difference is the status of iron: ferric/ferrous (magnetite) in the steam generators, metallic in the Fe-clay experiments. The concentration of aqueous iron when supplied by magnetite is low and does not allow its incorporation in secondary phases. By contrast, aqueous ferrous iron released by the corrosion of steel is not limited by the source, rather by the sink, and produces Fe-rich silicates. This example illustrates the discrepancy between complex mineral reactions and oversimplified predictions when sorption/passivation and nucleation/growth constraints are ignored. Reference: [1] Lanson et al. (2012) Amer. Min. 97, 864-871. [2] Lantenois et al. (2005) Clays & Clay Min. 53, 597-612. [3] Mosser-Ruck et al. (2010) Clays & Clay Min. 58, 280-291. [4] Perronnet et al. (2008) App. Clay Sci. 38, 187-202. [5] Osacky et al. (2010) App. Clay Sci. 50, 237-244. [6] Guillaume et al. (2003) Clay Min. 38, 281-302. [7] Rivard et al. (2013) Amer. Mineral. 98, 163-180. [8] Svensson and Hansen (2013) Clays & Clay Min. 61, 566-579.

  1. 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.

  2. Effects of annealing temperature on structure and magnetic properties of CoAl0.2Fe1.8O4/SiO2 nanocomposites

    NASA Astrophysics Data System (ADS)

    Wang, L.; Li, J.; Liu, M.; Zhang, Y. M.; Lu, J. B.; Li, H. B.

    2012-12-01

    CoAl0.2Fe1.8O4/SiO2 nanocomposites were prepared by sol-gel method. The effects of annealing temperature on the structure and magnetic properties of the samples were studied by X-ray diffraction, transmission electron microscopy, vibrating sample magnetometer and Mössbauer spectroscopy. The results show that the CoAl0.2Fe1.8O4 in the samples exhibits a spinel structure after being annealed. As annealing temperature increases from 800 to 1200 °C, the average grain size of CoAl0.2Fe1.8O4 in the nanocomposites increases from 5 to 41 nm while the lattice constant decreases from 0.8397 to 0.8391 nm, the saturation magnetization increases from 21.96 to 41.53 emu/g. Coercivity reaches a maximum of 1082 Oe for the sample annealed at 1100 °C, and thereafter decreases with further increasing annealing temperature. Mössbauer spectra show that the isomer shift decreases, hyperfine field increases and the samples transfer from mixed state of superparamagnetic and magnetic order to the completely magnetic order with annealing temperature increasing from 800 to 1200 °C.

  3. Phase Equilibria Study of the ZnO-"FeO"-SiO2-Al2O3 System at Po2 10-8 atm

    NASA Astrophysics Data System (ADS)

    Liu, Hongquan; Cui, Zhixiang; Chen, Mao; Zhao, Baojun

    2016-04-01

    Phase equilibria studies on ZnO-"FeO"-SiO2-Al2O3 system have been carried out in the temperature range between 1523 K and 1573 K (1250 °C and 1300 °C) at Po2 10-8 atm. Experimental techniques applied in the present study include high temperature equilibration, quenching, and electron probe X-ray microanalysis (EPMA). The compositions of the phases present in the quenched samples were measured by EPMA and used to construct phase diagrams of the pseudo-ternary sections at fixed Al2O3 content. The experimental results show that, spinel, SiO2, and willemite are the major primary phase fields in the composition range investigated. With 2 wt pct Al2O3 content in the liquid phase, the liquidus temperature can be increased by 35 K in the spinel primary phase in comparison with Al2O3-free system. The partitioning of ZnO and Al2O3 between the spinel and liquid phases is also discussed in the paper.

  4. Interaction of Ta-O and perpendicular magnetic anisotropy of Ta/Pd (0-2.4 nm)/Co2FeAl0.5Si0.5/MgO/Ta structured films

    NASA Astrophysics Data System (ADS)

    You, C. Y.; Fu, H. R.; Zhang, X.; Tian, N.; Wang, P. W.

    2015-03-01

    Perpendicular magnetic anisotropy (PMA) was realized by inserting Pd layer into the stack of Ta/Pd (0-2.4 nm)/Co2FeAl0.5Si0.5/MgO/Ta. The realization of PMA is accompanied by the (Co, Fe)-O reduction at Co2FeAl0.5Si0.5/MgO interface under annealing. Without inserting Pd layer, the annealed Ta/Co2FeAl0.5Si0.5/MgO/Ta film presents an in-plane magnetization. Through X-ray photoelectron spectrometry analyzes, it was found that the oxygen was enriched at the interface of Ta/Co2FeAl0.5Si0.5. This work clarifies that the inserted Pd layer effectively blocks the diffusion of interfacial oxygen to Ta layer, achieving the beneficial redox reaction at Co2FeAl0.5Si0.5/MgO interface to realize PMA.

  5. Full potential results on the magneto-optical properties of the Heuslercompounds Co(2)FeX (X = Al, Ga, Si and Ge).

    PubMed

    Kumar, Manish; Nautiyal, Tashi; Auluck, Sushil

    2009-05-13

    We have calculated the magneto-optical (MO) properties of Co(2)FeX (X = Al, Ga, Si and Ge) Heusler compounds using the full potential linearized augmented plane wave (FPLAPW) method as implemented in the WIEN2K code using the local spin density approximation (LSDA) and also by using the generalized gradient approximation (GGA) for the electronic exchange and correlation. In all the compounds, Kerr rotation ?(K) has a strong minimum near 2eV, the value of |?(K)| corresponding to this minimum being almost as large as in pure Co-Fe compounds. The calculated MO spectra help to identify the features of the experimental spectra. A comparison of the results shows that the Kerr spectrum is quite similar from both LSDA and GGA but the latter gives better agreement with experiment. Moreover, we find that inclusion of correlation effects using GGA+U removes the discrepancy in magnetic moment of Co(2)FeX (X = Si, Ge) though it has an insignificant effect on the Kerr spectra. PMID:21825501

  6. The Effect of Chlorine on the Rheology of Na2O-Fe2O3-Al2O3-SiO2 Melts

    NASA Astrophysics Data System (ADS)

    Zimova, M.; Webb, S.

    2004-12-01

    Because of the high fluid mobility of chlorine, the mantle wedge in subduction zone settings may be enriched in chlorine by the fluids released by the subducted altered oceanic crust plus sediments. The presence of chlorine (and other halogens) will affect the solidus temperature and the rheology of melts, thus influencing the magma evolution, eruption and degassing. Very little is known about the solubility mechanism and diffusivity of Cl in silicate melts and even less is known about the effect of Cl on viscosity. The present study addresses the effect of the halogen chlorine on the viscosity of silicate melts. The shear viscosities of Cl-bearing melts in the system Na2O-Fe2O3-Al2O3-SiO2 were determined over the temperature range 550-950C at room pressure in air. Viscosities were determined using the micropenetration technique in the range of 108.5 to 1012.0 Pa s. The compositions are based on addition of Fe2O3 or FeCl3 to aluminosilicate glasses with a fixed amount of SiO2 (67 mol %). Although there was loss of Cl- during the glass syntheses, no loss occurred during the viscometry experiments. It is to be expected that Cl- takes the structural position of an oxygen, and thus reduces the polymerization of the melt structure, and therefore the viscosity of the melt; as F- does. Our measurements show that, depending upon the melt composition, the addition of Cl- will either increase or decrease the viscosity of the melt. In the present melts at least 20% of the iron exists as network modifying, viscosity reducing Fe2+; while the rest exists as network forming Fe3+. It is proposed here that the different effects of chlorine on viscosity are due to the preferred Cl--Fe2+NBO bonding together with the different structure of peralkaline and peraluminous melts. In peralkaline aluminosilicate melts, the addition of Cl2O-1 will destroy 2 NBOs and create one BO if Cl- bonds primarily to the Fe2+ creating non-bridging oxygens. This would result in an increase in viscosity. In peraluminous melts, the addition of Cl2O-1 may result in Cl- bonds to the charge-balancing Fe2+, creating 2 new tri-clusters (assuming (Al3+, Fe3+)Si2O5 tri-clusters exist). The viscosity should then decrease due to the weaker bonds of the charge balancing Fe2+-Cl- units. The preference of Cl- to form bonds to the NBO-forming Fe2+ is indicated by the small amount of Cl- soluble in the peraluminous melt structure in comparison to that soluble in the peralkaline structure.

  7. Effect of annealing on Co2FeAl0.5Si0.5 thin films: A magneto-optical and x-ray absorption study

    NASA Astrophysics Data System (ADS)

    Trudel, Simon; Wolf, Georg; Hamrle, Jaroslav; Hillebrands, Burkard; Klaer, Peter; Kallmayer, Michael; Elmers, Hans-Joachim; Sukegawa, Hiroaki; Wang, Wenhong; Inomata, Koichiro

    2011-03-01

    A series of Al and MgO-capped Co2FeAl0.5Si0.5 epitaxial thin films grown on MgO with various levels of L21 ordering was obtained by in situ annealing. The films were studied by means of x-ray absorption spectroscopy, x-ray magnetic circular dichroism (XMCD), magneto-optical Kerr effect magnetometry, and Brillouin light scattering. We find the anisotropy constants decrease, while the spin wave stiffness increases as the samples are annealed to higher temperatures. The magnetization as determined by Brillouin light scattering reveals a maximum value at intermediate annealing temperatures. Surprisingly, the orbital-to-spin-moment ratio (as seen from XMCD) is essentially stable through the sample series and does not change upon annealing, despite the observed changes in anisotropy and exchange.

  8. Fabrication and characterization of spin injector using a high-quality B2-ordered-Co{sub 2}FeSi{sub 0.5}Al{sub 0.5}/MgO/Si(100) tunnel contact

    SciTech Connect

    Kawame, Yu Akushichi, Taiju; Shuto, Yusuke; Sugahara, Satoshi; Takamura, Yota

    2015-05-07

    We successfully fabricate a (100)-orientated B2-type-Co{sub 2}FeSi{sub 0.5}Al{sub 0.5} (CFSA)/MgO/Si(100) tunnel contact that is promising for an efficient spin injector for Si channels. The MgO barrier is formed by radical oxidation of an Mg thin film deposited on a Si(100) surface at room temperature and successive radical oxygen annealing at 400?C. The CFSA electrode is grown on the MgO barrier at 400?C by ultrahigh-vacuum molecular beam deposition, and it exhibits a (100)-orientated columnar polycrystalline structure with a high degree (63%) of B2-order. The MgO barrier near the interface of the CFSA/MgO junction is crystallized with the (100) orientation, i.e., the spin filter effect due to the MgO barrier could be expected for this junction. A three-terminal Si-channel spin-accumulation device with a CFSA/MgO/Si(100) spin injector is fabricated, and the Hanle effect of accumulated spin polarized electrons injected from this contact to the Si channel is observed.

  9. Formation of the icosahedral quasicrystalline phase in a rapidly solidified Al{sub 52}Cu{sub 25.5}Fe{sub 12.5}Si{sub 1} alloy

    SciTech Connect

    Wang Yan; Zhang Zhonghua . E-mail: zh_zhang@sdu.edu.cn; Geng Haoran; Yang Zhongxi

    2006-04-15

    In the present work, the effect of wheel speed (quenching rate) on the formation of the quasicrystalline phase in a rapidly solidified Al{sub 52}Cu{sub 25.5}Fe{sub 12.5}Si{sub 1} alloy has been investigated using X-ray diffraction (XRD), differential thermal analysis (DTA), differential scanning calorimetry (DSC) and transmission electron microscopy (TEM). The results show that rapid solidification has no effect on the phase constitution of the Al{sub 52}Cu{sub 25.5}Fe{sub 12.5}Si{sub 1} alloy. The addition of Si decreases the stability of the quasicrystalline phase in the conventionally cast Al{sub 52}Cu{sub 25.5}Fe{sub 12.5}Si{sub 1} alloy. The thermal stability of the quasicrystalline phase in the melt-spun alloy depends upon the quenching rate. Moderate-rate rapid solidification can improve the thermal stability of the quasicrystalline phase in the melt-spun alloy. Higher quenching rate instigates the transformation of the quasicrystalline phase into the cubic approximant phase and decreases the stability of the quasicrystalline phase. Furthermore, the transformation temperature decreases with increasing Si addition into the Al{sub (62-x)}Cu{sub 25.5}Fe{sub 12.5}Si{sub x}.

  10. Effect of Mg and Sr additions on the formation of intermetallics in Al-6 wt pct Si-3.5 wt pct Cu-(0.45) to (0.8) wt pct Fe 319-type alloys

    SciTech Connect

    Samuel, F.H.; Ouellet, P.; Samuel, A.M.; Doty, H.W.

    1998-12-01

    Al-Si alloys are materials that have been developed over the years to meet the increasing demands of the automotive industry for smaller, lighter-weight, high-performance components. An important alloy in this respect is the 319 alloy, wherein silicon and copper are the main alloying elements, and magnesium is often added in automotive versions of the alloy for strengthening purposes. the mechanical properties are also ameliorated by modifying the eutectic silicon structure (strontium being commonly employed) and by reducing the harmful effect of the {beta}-Al{sub 5}FeSi iron intermetallic present in the cast structure. Magnesium is also found to refine the silicon structure. The present study was undertaken to investigate the individual and combined roles of Mg and Sr on the morphologies of Si, Mg{sub 2}Si, and the iron and copper intermetallics likely to form during the solidification of 319-type alloys at very slow (close to equilibrium) cooling rates. The results show that magnesium leads to the precipitation of Al{sub 8}Mg{sub 3}FeSi{sub 6}, Mg{sub 2}Si, and Al{sub 5}Mg{sub 8}Cu{sub 2}Si{sub 6} intermetallics. With a strontium addition, dissolution of a large proportion of the needle-like {beta}-Al{sub 5}FeSi intermetallic in the aluminum matrix takes place; no transformation of this phase into any other intermetallics (including the Al{sub 15}(Fe,Mn){sub 3}Si{sub 2} phase) is observed. When both Mg and Sr are added, the diminution of the {beta}-Al{sub 5}FeSi phase is enhanced, through both its dissolution in the aluminum matrix as well as its transformation into Al{sub 8}Mg{sub 3}FeSi{sub 6}. The reactions and phases obtained have been analyzed using thermal analysis, optical microscopy, image analysis, and electron microprobe analysis (EMPA) coupled with energy-dispersive X-ray (EDX) analysis.

  11. Co{sub 2}FeAl Heusler thin films grown on Si and MgO substrates: Annealing temperature effect

    SciTech Connect

    Belmeguenai, M. Tuzcuoglu, H.; Zighem, F.; Chrif, S. M.; Moch, P.; Gabor, M. S. Petrisor, T.; Tiusan, C.

    2014-01-28

    10?nm and 50?nm Co{sub 2}FeAl (CFA) thin films have been deposited on MgO(001) and Si(001) substrates by magnetron sputtering and annealed at different temperatures. X-rays diffraction revealed polycrystalline or epitaxial growth (according to CFA(001)[110]//MgO(001)[100] epitaxial relation) for CFA films grown on a Si and on a MgO substrate, respectively. For these later, the chemical order varies from the A2 phase to the B2 phase when increasing the annealing temperature (T{sub a}), while only the A2 disorder type has been observed for CFA grown on Si. Microstrip ferromagnetic resonance (MS-FMR) measurements revealed that the in-plane anisotropy results from the superposition of a uniaxial and a fourfold symmetry term for CFA grown on MgO substrates. This fourfold anisotropy, which disappears completely for samples grown on Si, is in accord with the crystal structure of the samples. The fourfold anisotropy field decreases when increasing T{sub a}, while the uniaxial anisotropy field is nearly unaffected by T{sub a} within the investigated range. The MS-FMR data also allow for concluding that the gyromagnetic factor remains constant and that the exchange stiffness constant increases with T{sub a}. Finally, the FMR linewidth decreases when increasing T{sub a}, due to the enhancement of the chemical order. We derive a very low intrinsic damping parameter (1.110{sup ?3} and 1.310{sup ?3} for films of 50?nm thickness annealed at 615?C grown on MgO and on Si, respectively)

  12. Phase Equilibria Studies of Cu-O-Si Systems in Equilibrium with Air and Metallic Copper and Cu-Me-O-Si Systems (Me = Ca, Mg, Al, and Fe) in Equilibrium with Metallic Copper

    NASA Astrophysics Data System (ADS)

    Hidayat, Taufiq; Henao, Hector M.; Hayes, Peter C.; Jak, Evgueni

    2012-12-01

    The pseudo-binary phase diagrams in the Cu-O-Si system in equilibrium with air and metallic copper have been constructed. Equilibration at high temperature in an appropriate containment material, followed by rapid quenching and measurement of phase compositions using an electron probe x-ray microanalysis (EPMA) technique, was carried out to obtain the phase equilibria data. The investigation has been extended to characterize the effects of CaO, MgO, Al2O3, and "Fe2O3" on the liquidus isotherms of tridymite in equilibrium with metallic copper at temperatures of 1473 K and 1573 K (1200 C and 1300 C).

  13. Influence of Bridgman solidification on microstructures and magnetic behaviors of a non-equiatomic FeCoNiAlSi high-entropy alloy

    SciTech Connect

    Zuo, Tingting; Yang, Xiao; Liaw, Peter K.; Zhang, Yong

    2015-09-07

    The non-equiatomic FeCoNiAlSi alloy is prepared by the Bridgman solidification (BS) technique at different withdrawal velocities (V = 30, 100, and 200 μm/s). Various characterization techniques have been used to study the microstructure and crystal orientation. The morphological evolutions accompanying the crystal growth of the alloy prepared at different withdrawal velocities are nearly the same, from equiaxed grains to columnar crystals. The transition of coercivity is closely related to the local microstructure, while the saturation magnetization changes little at different sites. The coercivity can be significantly reduced from the equiaxed grain area to the columnar crystal area when the applied magnetic field direction is parallel to the crystal growth direction, no matter what is the withdrawal velocity. As a result, the alloy possesses magnetic anisotropy when the applied magnetic field is in different directions.

  14. Influence of Bridgman solidification on microstructures and magnetic behaviors of a non-equiatomic FeCoNiAlSi high-entropy alloy

    DOE PAGESBeta

    Zuo, Tingting; Yang, Xiao; Liaw, Peter K.; Zhang, Yong

    2015-09-07

    The non-equiatomic FeCoNiAlSi alloy is prepared by the Bridgman solidification (BS) technique at different withdrawal velocities (V = 30, 100, and 200 μm/s). Various characterization techniques have been used to study the microstructure and crystal orientation. The morphological evolutions accompanying the crystal growth of the alloy prepared at different withdrawal velocities are nearly the same, from equiaxed grains to columnar crystals. The transition of coercivity is closely related to the local microstructure, while the saturation magnetization changes little at different sites. The coercivity can be significantly reduced from the equiaxed grain area to the columnar crystal area when the appliedmore » magnetic field direction is parallel to the crystal growth direction, no matter what is the withdrawal velocity. As a result, the alloy possesses magnetic anisotropy when the applied magnetic field is in different directions.« less

  15. Solution behavior of reduced N-H-O volatiles in FeO-Na2O-SiO2-Al2O3 melt equilibrated with molten Fe alloy at high pressure and temperature

    NASA Astrophysics Data System (ADS)

    Kadik, Arnold A.; Litvin, Yuri A.; Koltashev, Vasily V.; Kryukova, Elena B.; Plotnichenko, Victor G.; Tsekhonya, Tatiana I.; Kononkova, Nataliya N.

    2013-01-01

    Solubility and speciation of NOH volatiles in a model silicate melt (FeO-Na2O-Al2O3-SiO2) equilibrated with molten Fe alloy have been examined via nitrogen and hydrogen analyses and vibrational spectroscopy (Raman and FTIR). Experiments were performed in an anvil-with-hole apparatus conducted at 4 GPa, 1550 C, and oxygen fugacity (fO2) from 2.1 to 3.3 log units below IW buffer. The technique of hydrogen fugacity (fH2) buffering via the dissociation of H2O employed here relies upon the diffusion of H2 through Pt to achieve equal chemical potentials of H2 in the Pt capsule and outer assemblage elements. The nitrogen source was Si3N4. The fO2 imposed on the charge was controlled by redox reactions between H2 buffered externally, Si3N4 and components of the Fe-bearing melt that was reduced with O2 liberation and metallic Fe formation. The initial Si3N4 was unstable under the experimental conditions and completely consumed according to the reaction of oxidation: Si3N4 (initial) + 3O2 ? 3SiO2 (melt) + 2N2 (melt) with a subsequent participation of nitrogen in the reactions with H2, the components of silicate and metallic melts. The nitrogen and hydrogen solubility, calculated as N and H, ranges from 0.4 to 1.9 wt.% and from 0.2 to 0.3 wt.%, accordingly. The nitrogen content in iron globules at ?log fO2(IW) = -3.3 was measured as 4.4 wt.%. Characterization by Raman and IR spectroscopy indicates that at fO2, where a metallic Fe phase is stable, the silicate melt would contain species with N-H bonds (NH3, NH4+, NH2-, NH2+) as well as N2, oxidized H species (OH- and H2O) and H2. Experimental studies have shown that the fO2 evolution during metal segregation would have strongly influenced the nature of nitrogen and hydrogen species in reduced magmas of the early Earth.

  16. Interfacial tension between immiscible melts in the system K2O - FeO - Fe2O3 - Al2O3 - SiO2

    NASA Astrophysics Data System (ADS)

    Kaehn, J.; Veksler, I. V.; Franz, G.; Dingwell, D. B.

    2009-12-01

    Interfacial tension is a very important parameter of the kinetics of phase nucleation, dissolution and growth. Excess surface energy contributes to the energy barrier for phase nucleation, and works as the main driving force for minimization of phase contact surfaces in heterogeneous systems. Immiscible silicate melts have been found to form in a broad range of basaltic, dacitic and rhyolitic magmas (Philpotts, 1982). However, liquid-liquid interfaces remain poorly studied in comparison with crystal-melt and vapor-melt interfaces. Here we present first experimental measurements of interfacial tension between synthetic Fe-rich and silica-rich immiscible melts composed of Fe oxides, K2O, alumina and silica. According to Naslund (1983), the miscibility gap in the 5-oxide system expands with increasing fO2 and becomes widest in air (fO2 = 0.2). Our goal was to estimate the maximal liquid-liquid interfacial tension for the immiscible liquids composed of silica and Fe oxides. Therefore, we have chosen the most contrasting liquid compositions that coexist in air at and above 1465 C. Silica-rich and Fe-rich conjugate liquids at these conditions contain 73 and 17 wt. % SiO2, and 14 and 80 wt. % FeOt, respectively. These starting compositions were synthesized by fusion of reagent-grade oxides and K2CO3 at 1600 C. In addition to interfacial tension, we have measured density and surface tension of individual coexisting liquids. All the measurements were done at 1500, 1527 and 1550 C. Density was measured by the Archimedean method; surface and interfacial tensions were calculated from the maximal pool on a vertical cylinder (a 3-mm Pt rod attached to a high precision balance). We found interfacial tension between the immiscible liquids to decrease with increasing temperature from 16.42 mN/m at 1500 C to 8.20.8 mN/m at 1550 C. These values are approximately 2 orders of magnitude lower than typical interfacial tensions between silicate melts and crystals (Wanamaker and Kohlstedt, 1991), or 20-40 times lower than the surface tension of natural lavas in air (Walker and Mullins, 1981). Interfacial tension between natural, less compositionally contrasting ferrobasaltic and rhyolitic melts should be even lower by a factor of 2 or 3. Very low interfacial tension implies easy nucleation of immiscible liquid droplets, and very slow coarsening of silicate emulsions. The results of interfacial tension measurements corroborate protracted stability of sub-micron immiscible silicate emulsions that we observed in our previous immiscibility experiments. References Naslund H.R. (1983) Am. J. Sci. 283, 1034-1059. Philpotts A.R. (1982) Contrib. Mineral. Petrol. 80, 201-218. Walker D. and Mullins Jr. O. (1981) Contrib. Mineral. Petrol. 76, 455-462. Wanamaker B.J. and Kohlstedt D.L. (1991) Phys. Chem. Minerals, 18, 26-36.

  17. Crystal structure of the mineral (Na,Ca,K)2(Ca,Na)4(Mg,Fe)5(Mg,Fe,Ti)5[Si12Al4O44](F,O)4: a triclinic representative of the amphibole family

    NASA Astrophysics Data System (ADS)

    Rastsvetaeva, R. K.; Aksenov, S. M.

    2012-05-01

    A mineral belonging to the amphibole family found at the Rothenberg paleovolcano (Eifel, Germany) was studied by single-crystal X-ray diffraction. The triclinic pseudomonoclinic unit-cell parameters are a = 5.3113(1) Å, b = 18.0457(3) Å; c = 9.8684(2) Å, α = 90.016(2)°, β = 105.543(4)°, γ = 89.985(2)°. The structure was solved by direct methods in sp. gr. P1 and refined to the R factor of 2.7% based on 6432 reflections with | F| > 3σ( F) taking into account twinning. The mineral with the idealized formula (Na,Ca,K)2(Ca,Na)4(Mg,Fe)5(Mg,Fe,Ti)5[Si12Al4O44](F,O)4 has some symmetry and structural features that distinguish it from other minerals of this family.

  18. Heat capacity and phase equilibria of almandine, Fe[sub 3]Al[sub 2]Si[sub 3]O[sub 12

    SciTech Connect

    Anovitz, L.M. ); Essene, E.J.; Metz, G.W.; Westrum, E.F. Jr. ); Bohlen, S.R. ); Hemingway, B.S. )

    1993-09-01

    The heat capacity of a synthetic almandine, Fe[sub 3]Al[sub 2]Si[sub 3]O[sub 12], was measured from 6 to 350 K using equilibrium, intermittent-heating quasi-adiabatic calorimetry and from 420 to 1000 K using differential scanning calorimetry. These measurements yield Cp[sub 298] = 342.80 [+-] 1.4 J/mol[center dot]K and S[degrees][sub 298] = 342.60 J/mol[center dot]K. Moessbauer characterizations show the almandine to contain less than 2 [+-] 1% of the total iron as Fe[sup 3+]. X-ray diffraction studies of this synthetic almandine yield a = 11.521 [+-] 0.001 [angstrom] and V[degrees][sub 298] = 115.11 [+-] 0.01 cm[sup 3]/mol, somewhat smaller than previously reported. The low-temperature Cp data indicate a lambda transition at 8.7 K related to an antiferromagnetic-paramagnetic transition with T[sub N] = 7.5 K. Modeling of the lattice contribution to the total entropy suggests the presence of entropy in excess of that attributable to the effects of lattice vibrations and the magnetic transition. This probably arises from a low-temperature electronic transition (Schottky contribution).

  19. The Effects of Microstructure Heterogeneities and Casting Defects on the Mechanical Properties of High-Pressure Die-Cast AlSi9Cu3(Fe) Alloys

    NASA Astrophysics Data System (ADS)

    Timelli, Giulio; Fabrizi, Alberto

    2014-11-01

    Detailed investigations of the salient microstructural features and casting defects of the high-pressure die-cast (HPDC) AlSi9Cu3(Fe) alloy are reported. These characteristics are addressed to the mechanical properties and reliability of separate HPDC tensile bars. Metallographic and image analysis techniques have been used to quantitatively examine the microstructural changes throughout the tensile specimen. The results indicate that the die-cast microstructure consists of several microstructural heterogeneities such as positive eutectic segregation bands, externally solidified crystals (ESCs), cold flakes, primary Fe-rich intermetallics (sludge), and porosities. In addition, it results that sludge particles, gas porosity, as well as ESCs, and cold flakes are concentrated toward the casting center while low porosity and fine-grained structure is observed on the surface layer of the castings bars. The local variation of the hardness along the cross section as well as the change of tensile test results as a function of gage diameter of the tensile bars seem to be ascribed to the change of porosity content, eutectic fraction, and amount of sludge. Further, this behavior reflects upon the reliability of the die-cast alloy, as evidenced by the Weibull statistics.

  20. Thermoelasticity of Al3+- and Fe3+-bearing bridgemanite

    NASA Astrophysics Data System (ADS)

    Shukla, G.; Wentzcovitch, R. M.

    2014-12-01

    We present quasi-harmonic LDA+U calculations of thermoelastic properties of Fe3+- and Al3+-bearing bridgemanite (MgSiO3), the main phase of the Earth's lower mantle, at relevant P,T conditions and compositions. Four charge-coupled substitutions, namely, Al3+-Al3+, Fe3+-Fe3+, Fe3+-Al3+, and Al3+-Fe3+have been studied. Aggregate elastic moduli and sound velocities are compared with available experimental measurements. In the case of the Fe3+-Fe3+ substitution, the effect of pressure induced high-spin (HS) to low-spin (LS) crossover in the B-site iron has been investigated in great detail. Using these results, we analyze the possible influence of Al and Fe on lower mantle velocity heterogeneities.

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

    NASA Astrophysics Data System (ADS)

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

    2010-04-01

    The phase equilibria and liquidus temperatures in the system ZnO-FeO-Al2O3-CaO-SiO2 in equilibrium with metallic iron have been determined experimentally in the temperature range of 1423 K to 1553 K. The experimental conditions were focused on the composition range relevant to Imperial Smelting Furnace slags. The results are presented in the form of a pseudo-ternary section ZnO-FeO-(CaO + SiO2 + Al2O3) in which CaO/SiO2 = 0.93 and (CaO + SiO2)/Al2O3 = 7.0. It was found that wustite and spinel are the major primary phases and that zincite and melilite are also present in the composition range investigated. Wustite (Fe2+,Zn)O and spinel (Fe2+,Zn)O (A1,Fe3+)2O3 solid solutions are formed in this system, and the ZnO concentration in the spinel phase is found to be much greater than in the liquid phase.

  2. Kinetic Analysis of Recovery, Recrystallization, and Phase Precipitation in an Al-Fe-Si Alloy Using JMAEK and Sesták-Berggren Models

    NASA Astrophysics Data System (ADS)

    Luiggi Agreda, Ney José

    2015-02-01

    When studying the phase changes process in a rolled AA8011 alloy using DSC, we find that the peaks associated with phase precipitation under this microstructural condition are different from those obtained in homogenized microstructures. The differences observed are attributable, first, to the recovery process occurring at temperatures below 423 K (150 °C), which interacts with the precipitation of Si-rich precipitates or with Guinier-Preston zones both coexistent in that temperature range; and second, to the recrystallization above 473 K (200 °C), which coexists with precipitation of the α-AlFeSi phase. In this work, the precipitation and recovery-recrystallization kinetics are experimentally obtained and deconvoluted in peaks characteristic for each of the mechanisms involved; i.e., precipitation of GP zones, recovery, precipitation of α phase, and recrystallization. The deconvolution is achieved using functions of Gauss, Weibull, and Fraser-Suzuki; and the characterization of each reaction deconvoluted is realized through both Jhonson-Melh-Avrami-Erofeev-Kolmorokov kinetic models and Sesták-Berggren combined kinetic model. The kinetic study evinces that in addition to the expected reactions, other reactions, necessary for good experimental adjustment, appear. An isoconversional study is undertaken to numerically evaluate the kinetic triplet of every process.

  3. Sound Velocities of Fe-C and Fe-Si alloying liquids at high pressures

    NASA Astrophysics Data System (ADS)

    Jing, Z.; Han, J.; Yu, T.; Wang, Y.

    2014-12-01

    Geophysical and geochemical observations suggest light elements such as S, Si, C, O, H, etc., are likely present in the Earth's outer core and the molten cores of other terrestrial planets and moons including Mercury, Mars, Earth's Moon, and Ganymede. In order to constrain the abundances of light elements in planetary cores, it is crucial to determine the density and sound velocity of Fe-light element alloying liquids under core conditions. In this study, sound velocities of Fe-rich liquids were determined by combining the ultrasonic measurements with synchrotron X-ray radiography and diffraction techniques under high-pressure and temperature conditions from 1 to 6 GPa and 1573 to 1973 K. An Fe-C composition (Fe-5wt%C) and four Fe-Si compositions (Fe-10wt%Si, Fe-17wt%Si, Fe-25wt%Si, and FeSi) were studied. Compared to our previous results on the velocity of Fe and Fe-S liquids at high pressures (Jing et al., 2014, Earth Planet. Sci. Lett. 396, 78-87), the presence of both C and Si increases the velocity of liquid Fe, in contrast to the effect of S. The measured velocities of Fe-C and Fe-Si liquids increase with compression and decrease slightly with increasing temperature. Combined with 1-atm density data in the literature, the high-pressure velocity data provide tight constraints on the equations of state and thermodynamic properties such as the adiabatic temperature gradient for Fe-C and Fe-Si liquids. We will discuss these results with implications to planetary cores.

  4. Processing effects on the magnetic and mechanical properties of FeCoNiAl0.2Si0.2 high entropy alloy

    NASA Astrophysics Data System (ADS)

    Zuo, Ting-ting; Ren, Song-bo; Liaw, Peter K.; Zhang, Yong

    2013-06-01

    High entropy alloys with the composition of FeCoNiAl0.2Si0.2 were prepared by arc melting and induction melting, denoted by A1 and A2, respectively. The samples prepared by these two techniques have a face-centered cubic (FCC) phase structure and a typical dendrite morphology. The tensile yield strength and maximum strength of A2 samples are about 280 and 632 MPa, respectively. Moreover, the elongation can reach 41.7%. These two alloys prepared by the different methods possess the similar magnetic properties. The saturation magnetization and coercivity can reach 1.151 T and 1400 A/m for Al samples and 1.015 T and 1431 A/m for A2 samples, respectively. Phases in A2 samples do not change, which are heat treated at different temperatures, then quenched in water. Only the sample, which is heat treated at 600°C for 3 h and then furnace cooled, has a new phase precipitated. Besides, the coercivity decreases obviously at this temperature. Cold rolling and the subsequent heat treatment cannot improve the magnetic properties effectively. However, cold rolling plays an important role in improving the strength.

  5. Blended elemental P/M synthesis of Ti-6Al-1.7Fe-0.1Si alloy with improved high cycle fatigue strength

    SciTech Connect

    Hagiwara, M.; Emura, S.; Kim, S.J.

    1998-10-05

    Titanium alloys are attractive materials for aircraft and automobile application due to their high strength to weight ratio and excellent corrosion resistance. However, the use of titanium alloys in these industrial area is still limited due to the high manufacturing cost associated with the expensiveness of raw materials and processing difficulty. The production of titanium alloys using a blended elemental (BE) powder metallurgy (P/M) method has potential to overcome this cost problem. However, conventionally processed BE P/M titanium alloys show inferior high cycle fatigue strength due to the microstructural formation of {alpha}-platelet colony and a massive grain boundary alpha (GB{alpha}) phase. In the present study, the new processing method was applied to an {alpha}-{beta} type Ti-6Al-1.7Fe-0.1Si (Ti-62S) alloy in order to investigate the effect of microstructural modification on the high cycle fatigue strength. Ti-62S alloy is a new low cost {alpha}-{beta} type alloy developed by Timet which is expected to replace with the Ti-6Al-4V alloy in the areas of automobile parts.

  6. Local effects of interstitial versus substitutional atoms in Y{sub 2}Fe{sub 17{minus}x}M{sub x}A{sub y} compounds, with M=Al or Si and A=C or N

    SciTech Connect

    Plugaru, N.; Morariu, M.; Galatanu, A.; Lazar, D.P.; Barb, D.

    1997-12-01

    Interstitial Y{sub 2}Fe{sub 17{minus}x}M{sub x}C{sub y} compounds, with M=Al or Si and x{le}2, y{le}1, were investigated by {sup 57}Fe M{umlt o}ssbauer spectroscopy at room temperature. In the analysis of the spectra, the preferential occupation by Al or Si of the Fe (12k) sites in the hexagonal R{sub 2}Fe{sub 17} phase was taken into account. The hyperfine parameters variations are discussed on the grounds of local crystallographic details at the inequivalent iron sites, altered by the composition modifications. The low values of the isomer shifts and quadrupole interactions suggest small electronic charge redistribution in Y{sub 2}Fe{sub 17{minus}x}M{sub x}A{sub y} as compared to Y{sub 2}Fe{sub 17}. However, the isomer shift variations upon Wigner{endash}Seitz cell volume changes evidence for screening and electron transfer effects. In order to provide a more consistent picture of the local effects of interstitial versus substitutional atoms in R{sub 2}(Fe,M){sub 17}A{sub y} compounds, the discussion of the present results is extended to {sup 57}Fe M{umlt o}ssbauer data obtained on the parent compounds and their nitrides. {copyright} {ital 1997 American Institute of Physics.}

  7. Solubility of iron among plagioclase, clinopyroxene and silicate liquid in the system CaO-MgO-Al/sub 2/O/sub 3/ - SiO/sub 2/-Fe-O

    SciTech Connect

    Virgo, D.; Mysen, B.O.

    1985-01-01

    The 1-atm liquidus of the system diopside-anorthite + 10wt% ferric iron is lower (approx. 30/sup 0/C) for end-member compositions but the temperature and projected (Fe-free) composition of the minimum melt are unchanged. The effect of fO/sub 2/ on the liquidus curve is minimal. The major element compositions, the structural state of iron and the ferrous/ferric ratio of existing crystal-liquid pairs have been determined using electron microprobe analyses and /sup 57/Fe Mossbauer spectroscopy. For anorthite-liquid pairs, the partition coefficient, D(Fe) (equal to (Fe in xtal)/(Fe in liquid)) decreases with increasing temperature and with increasing anorthite/diopside ratio, at fixed fO/sub 2/. The effect of bulk composition on D(Fe) predominates over the relatively weak temperature dependence (Longhi et al. 1976). Significantly, at fixed temperature and anorthite/diopside ratio, D(Fe) decreases linearly with fO/sub 2/ from 0.25 (log fO/sub 2/=-0.68) to 0.05 (log fO/sub 2/=-6.0). The increase in D(Fe) with increasing fO/sub 2/ is accompanied by an increase in the ferric iron content of the feldspar lattice. The mechanisms for incorporation of iron in synthetic anorthite are Fe(3+)-Al under oxidizing conditions and Fe(2+), Si-2Al under reducing conditions. The use of D(Fe) as an oxygen barometer is considered. D(Fe) for the system diopside-Fe/sub 2/O/sub 3/ is not strongly fO/sub 2/-dependent at constant temperature. The incorporation of iron in liquidus pyroxene is via the Fe(2+)-Ca substitution. Ferric iron acts as an inert diluent in these melts. Tschermak's substitution is discussed for igneous, ferric-bearing clinopyroxenes.

  8. Perrierite-(La), (La,Ce,Ca)4(Fe2+,Mn)(Ti,Fe3+,Al)4(Si2O7)2O8, a new mineral species from the Eifel volcanic district, Germany

    NASA Astrophysics Data System (ADS)

    Chukanov, N. V.; Blass, G.; Pekov, I. V.; Belakovskiy, D. I.; Van, K. V.; Rastsvetaeva, R. K.; Aksenov, S. M.

    2012-12-01

    Non-metamict perrierite-(La) discovered in the Dellen pumice quarry, near Mendig, in the Eifel volcanic district, Rheinland-Pfalz, Germany has been approved as a new mineral species (IMA no. 2010-089). The mineral was found in the late assemblage of sanidine, phlogopite, pyrophanite, zirconolite, members of the jacobsite-magnetite series, fluorcalciopyrochlore, and zircon. Perrierite-(La) occurs as isolated prismatic crystals up to 0.5 × 1 mm in size within cavities in sanidinite. The new mineral is black with brown streak; it is brittle, with the Mohs hardness of 6 and distinct cleavage parallel to (001). The calculated density is 4.791 g/cm3. The IR spectrum does not contain absorption bands that correspond to H2O and OH groups. Perrierite-(La) is biaxial (-), α = 1.94(1), β = 2.020(15), γ = 2.040(15), 2 V meas = 50(10)°, 2 V calc = 51°. The chemical composition (electron microprobe, average of seven point analyses, the Fe2+/Fe3+ ratio determined from the X-ray structural data, wt %) is as follows: 3.26 CaO, 22.92 La2O3, 19.64 Ce2O3, 0.83 Pr2O2, 2.09 Nd2O3, 0.25 MgO, 2.25 MnO, 3.16 FeO, 5.28 Fe2O3, 2.59 Al2O3, 16.13 TiO2, 0.75 Nb2O5, and 20.06 SiO2, total is 99.21. The empirical formula is (La1.70Ce1.45Nd0.15Pr0.06Ca0.70)Σ4.06(Fe{0.53/2+}Mn0.38Mg0.08)Σ0.99(Ti2.44Fe{0.80/3+}Al0.62Nb0.07)Σ3.93Si4.04O22. The simplified formula is (La,Ce,Ca)4(Fe2+,Mn)(Ti,Fe3+,Al)4(Si2O7)2O8. The crystal structure was determined by a single crystal. Perrierite-(La) is monoclinic, space group P21/ a, and the unit-cell dimensions are as follows: a =13.668(1), b = 5.6601(6), c = 11.743(1) Å, β = 113.64(1)°; V = 832.2(2) Å3, Z = 2. The strong reflections in the X-ray powder diffraction pattern are [ d, Å ( I, %) ( hkl)]: 5.19 (40) (110), 3.53 (40) (overline 3 11), 2.96 (100) (overline 3 13, 311), 2.80 (50) (020), 2.14 (50) (overline 4 22, overline 3 15, 313), 1.947 (50) (024, 223), 1.657 (40) (overline 4 07, overline 4 33, 331). The holotype specimen of perrierite-(La) is deposited at the Fersman Mineralogical Museum, Russian Academy of Sciences, Moscow, Russia, with the registration number 4059/1.

  9. Tunnel Magnetoresistance and Spin-Transfer-Torque Switching in Polycrystalline Co2FeAl Full-Heusler-Alloy Magnetic Tunnel Junctions on Amorphous Si /SiO2 Substrates

    NASA Astrophysics Data System (ADS)

    Wen, Zhenchao; Sukegawa, Hiroaki; Kasai, Shinya; Inomata, Koichiro; Mitani, Seiji

    2014-08-01

    We study polycrystalline B2-type Co2FeAl (CFA) full-Heusler-alloy-based magnetic tunnel junctions (MTJs) fabricated on a Si /SiO2 amorphous substrate. Polycrystalline CFA films with a (001) orientation, a high B2 ordering, and a flat surface are achieved by using a MgO buffer layer. A tunnel magnetoresistance ratio up to 175% is obtained for a MTJ with a CFA /MgO/CoFe structure on a 7.5-nm-thick MgO buffer. Spin-transfer-torque-induced magnetization switching is achieved in the MTJs with a 2-nm-thick polycrystalline CFA film as a switching layer. By using a thermal activation model, the intrinsic critical current density (Jc0) is determined to be 8.2106 A /cm2, which is lower than 2.9107 A /cm2, the value for epitaxial CFA MTJs [Appl. Phys. Lett. 100, 182403 (2012), 10.1063/1.4710521]. We find that the Gilbert damping constant (?) evaluated by using ferromagnetic resonance measurements for the polycrystalline CFA film is approximately 0.015 and is almost independent of the CFA thickness (2-18 nm). The low Jc0 for the polycrystalline MTJ is mainly attributed to the low ? of the CFA layer compared with the value in the epitaxial one (approximately 0.04).

  10. Structure and transport properties of current-perpendicular-to-plane spin valves using Co2FeAl0.5Si0.5 and Co2MnSi Heusler alloy electrodes

    NASA Astrophysics Data System (ADS)

    Furubayashi, T.; Kodama, K.; Nakatani, T. M.; Sukegawa, H.; Takahashi, Y. K.; Inomata, K.; Hono, K.

    2010-06-01

    We report the structure and transport properties of current-perpendicular-to-plane spin valves (CPP SVs) with Co2FeAl0.5Si0.5 (CFAS) or Co2MnSi (CMS) Heusler alloy magnetic layers and an Ag or Cu spacer layer. A multilayer stack of sub/Cr/Ag/Heusler/(Ag or Cu)/ Heusler/Co75Fe25/Ir22Mn78/Ru was deposited on a MgO(001) single crystalline substrate by magnetron sputtering. Transmission electron microscopy observations showed epitaxial growth from the substrate to the top Heusler layer. The CPP SV with a CFAS/Ag/CFAS trilayer showed relatively large magnetoresistance (MR) ratios of 12% at room temperature and 31% at 12 K, with monotonous temperature dependence. However, the MR values of the SV with the CMS/Ag/CMS trilayer showed a different temperature dependence with a maximum value of 22% at 100 K. This might be related to the 90 couplings between the two CMS layers.

  11. Synthesis of quenchable high-pressure form of magnetite (h-Fe3O4) with composition [4](Fe0.732+ Mg0.26)[6](Fe0.713+ Cr0.14Al0.10 Si0.04)2O4

    NASA Astrophysics Data System (ADS)

    Koch-Mller, Monika; Mugnaioli, Enrico; Rhede, Dieter; Speziale, Sergio; Kolb, Ute; Wirth, Richard

    2014-05-01

    Cubic inverse-spinel magnetite transforms under pressure to orthorhombic normal-spinel magnetite, h-Fe3O4 ( e.g. Fei et al. 1999; Bengtson et al. 2013). The pressure at which the transition takes place is still controversial. The high-pressure form is reported to be not quenchable to ambient conditions. We report the synthesis of h-magnetite which incorporates considerable amounts of additional cations (Cr, Mg, Al, Si) and is quenchable to ambient conditions. Two experiments were performed at 18 GPa and 1800 C in a multi-anvil press. The run products were investigated by electron microprobe, transmission electron microscopy and electron diffraction tomography. We observed the formation of h-magnetite in both experiments. In experiment MA-367 we used an oxide mixture with a majoritic stoichiometry Mg1.8Fe1.2(Al1.4 Cr0.2Si0.2Mg0.2)Si3O12 as starting material, with Si and Mg in excess. The Fe-oxide phase forms elongated aggregates 10-30 ?m in length, mutually intergrown with majorite, the latter being the main phase of the run products coexisting with small amounts of stishovite. The formula for h-magnetite in run MA-367 was calculated as [4](Fe0.732+ Mg0.26)[6](Fe0.713+ Cr0.14Al0.10 Si0.04)2O4. In the second experiment (MA-376) we used an oxide mixture corresponding to the composition of h-magnetite obtained in MA-367. In this experiment the main phase was h-magnetite with composition [4](Fe0.982+)[6](Fe0.683+ Cr0.17Al0.13 Si0.02)2O4coexisting with very small amounts of wadsleyite. Interestingly no magnesium was incorporated into the Fe-oxide in this experiment compared to MA-367 and no iron was found in the coexisting wadsleyite. For the first time it was possible to perform electron diffraction on recovered h-magnetite of both experiments and we observed that -at least in our case- the h-magnetite structure can better be described in space group Amam than in space group Bbmm as previously proposed. The substitution of Fe by Cr, Mg, Al and Si, all smaller in atomic size, may have favored the survival of the high pressure form to ambient conditions. We prove that the h-magnetite phase is also stable in chemical systems more complex than the simple Fe-O. Based on our results obtained at 18 GPa and 1800 oC in a system that is closely related to Fe-enriched oceanic lithospheric material, we suggest that h-magnetite may be present in environments connected to deeply subducted slabs. The strong enrichment of Cr in this oxide phase implies that coexisting silicates may be depleted in Cr compared to Fe3O4-free assemblages. This would significantly affect the chemical signature of melts produced in the deep mantle. References: Fei et al. (1999) American Mineralogist, 84, 203 - 206 Bengtson et al. (2013) Physical Review B87, 155141

  12. Soft magnetic powder-core composites of Fe90Zr7B3 and Fe49Co21Al5Ga2P9.65C5.75B4.6Si3 alloys

    NASA Astrophysics Data System (ADS)

    Turgut, Zafer; Attenweiler, Thomas; Huang, Meiqing; Horwath, John C.; Fingers, Richard T.

    2006-04-01

    Amorphous and nanocrystalline alloys in ribbon form exhibit excellent soft magnetic properties, but their forms are limited to tape wound cores. Complex shapes require the implementation of a powder metallurgical approach resulting in reduced permeabilities. The present study investigates Fe-based Fe90Zr7B3 (C1) and Fe49Co21Al5Ga2P9.65C5.75B4.6Si3 (C2) melt-spun ribbons as precursors for compacted powder cores. Single-roller melt spinning of C1 produced partially crystallized structures while C2 resulted in amorphous ribbons. Annealing studies were carried out based on the crystallization temperatures of various phases extracted from M(T) measurements. In ribbon form and under optimum annealing conditions, C1 revealed a 1.88 T saturation flux density (Bs) and 44 A/m coercivity (Hc), while C2 exhibited a Bs of 0.78 T and Hc of 2.4 A/m.

  13. Mossbauer and XRD characterization of the phase transformations in a Fe-Mn-Al-C-Mo-Si-Cu as cast alloy during tribology test

    NASA Astrophysics Data System (ADS)

    Ramos, J.; Piamba, J. F.; Snchez, H.; Alcazar, G. A. Prez

    2015-06-01

    In present study Fe-29.0Mn-6Al-0.9C-1.8Mo-1.6Si-0.4Cu (%w) alloy was obtained after melted in an induction furnace, and then molded as an ingot. From the as cast ingot it were cut samples for the different characterization measurements. The microstructure of the as-cast sample is of dendritic type and its XRD pattern was refined with the lines of the austenite, with a big volumetric fraction, and the lines of the martensite, with small volumetric fraction. The Mssbauer spectrum of the sample was fitted with a broad singlet which corresponds to disordered austenite. After the tribology test, its XRD pattern was refined with the lines of two austenite phases, one similar to the previous one and other with bigger lattice parameter. The total volumetric fraction of the austenite is smaller than that obtained for sample without wear. It was added the lines of the martensite phase with bigger volumetric fraction than that of the previous sample. The Mssbauer spectrum of the weared sample was fitted with two paramagnetic sites which correspond to the two Fe austenite phases and a hyperfine magnetic field distribution which is associated to the disordered original martensite and the new one which appears in the surface as a consequence of the wear process. These results show that during wear process the original austenite phase is transformed in martensite and in a new austenite phase. The increases of the martensitic phase improves mechanical properties and wear behavior.

  14. Discovery of Ahrensite ?-Fe2SiO4 and Tissintite (Ca,Na,[])AlSi2O6, Two New Shock-induced Minerals from the Tissint Martian Meteorite: a Nanomineralogy Investigation

    NASA Astrophysics Data System (ADS)

    Ma, C.; Tschauner, O. D.; Liu, Y.; Sinogeikin, S. V.; Zhuravlev, K. K.; Prakapenka, V.; Dera, P. K.; Taylor, L. A.

    2013-12-01

    The recent Martian meteorite fall, Tissint, is a fresh olivine-phyric shergottite, with strong shock features. During our nano-mineralogy investigation of the Tissint meteorite with a combined analytical scanning electron microscope and synchrotron diffraction approach, two new shock-induced minerals have been discovered; these provide new insights into understanding shock conditions and impact processes on Mars. Ahrensite (IMA 2013-028), the Fe-analogue (?-Fe2SiO4) of ringwoodite, is a new high-pressure mineral identified in Tissint. Both ahrensite and ringwoodite occur in Tissint as fine-grained polycrystalline aggregates in the rims of olivines around some shock-melt pockets. The morphology and texture of these silicate-spinels suggest formation by a solid-state transformation from Fe-rich olivine. Associated with the ahrensite and ringwoodite, inside melt pockets, often resides a thin layer of vitrified silicate-perovskite and magnesio-wstite or wstite. Such transitions represent a unique pressure and temperature gradient. Tissintite (IMA 2013-027), (Ca,Na,[])AlSi2O6 with the C2/c clinopyroxene structure, is a new jadeite-like mineral in Tissint. It appears as fine-grained aggregates within plagioclase glass, inside many shock-melt pockets. Both ahrensite and tissintite are high-pressure minerals formed by shock during the impact event(s) on Mars that excavated and ejected the rock off Mars. We will discuss the path of structure analysis for both new-mineral cases. Such novel methodology be utilized for many cases of mineralogical phase identification or structure analysis; this demonstrates how nano-mineralogy can be addressed and how it may play a unique role in meteorite and Mars rock research, in general.

  15. Effects of breadfruit seed hull ash on the microstructures and properties of Al-Si-Fe alloy/breadfruit seed hull ash particulate composites

    NASA Astrophysics Data System (ADS)

    Atuanya, C. U.; Ibhadode, A. O. A.; Dagwa, I. M.

    2012-01-01

    The microstructures and properties of Al-Si-Fe alloy matrix composites reinforced with different weight fractions of breadfruit seed hull (husk) ash particles of size 500 nm were investigated. Six (6) different weight fractions of breadfruit seed hull ash particles were added to aluminium alloy matrix using a double stir-casting method. Microstructural analysis shows that with the increase of the reinforcement weight fraction, the matrix grain size decreases. The mechanical properties of the composites are improved over the matrix materials, except for the slightly decrease of the impact energy. Fracture surface examination indicates that there is a good interfacial bonding between the aluminium alloy matrix and the breadfruit seed hull ash particles and that fracture initiation does not occur at the particle-matrix interface. Hence, incorporation of breadfruit seed hull ash particles in aluminium matrix can lead to the production of low cost aluminium composites with improved hardness and strength. These composites can find applications in automotive components where light weight materials are required with good stiffness and strength.

  16. Effects of Intercritical Annealing Temperature on Mechanical Properties of Fe-7.9Mn-0.14Si-0.05Al-0.07C Steel

    SciTech Connect

    Zhao, Xianming; Shen, Yongfeng; Qiu, Lina; Liu, Yandong; Sun, Xin; Zuo, Liang

    2014-12-09

    A medium Mn steel has been designed to achieve an excellent combination of strength and ductility based on the TRIP (Transformation Induced Plasticity) concept for automotive applications. Following six passes of hot rolling at 850 °C, the Fe-7.9Mn-0.14Si-0.05Al-0.07C (wt.%) steel was warm-rolled at 630 °C for seven passes and subsequently air cooled to room temperature. The sample was subsequently intercritically annealed at various temperatures for 30 min to promote the reverse transformation of martensite into austenite. The obtained results show that the highest volume fraction of austenite is 39% for the sample annealed at 600 °C. This specimen exhibits a yield stress of 910 MPa and a high ultimate tensile stress of 1600 MPa, with an elongation-to-failure of 0.29 at a strain rate of 1 × 10⁻³/s. The enhanced work-hardening ability of the investigated steel is closely related to martensitic transformation and the interaction of dislocations. Especially, the alternate arrangement of acicular ferrite (soft phase) and ultrafine austenite lamellae (50–200 nm, strong and ductile phase) is the key factor contributing to the excellent combination of strength and ductility. On the other hand, the as-warm-rolled sample also exhibits the excellent combination of strength and ductility, with elongation-to-failure much higher than those annealed at temperatures above 630 °C.

  17. Correlations between structural, electronic transport, and magnetic properties of Co2FeAl0.5Si0.5 Heusler alloy epitaxial thin films

    NASA Astrophysics Data System (ADS)

    Gabor, M. S.; Belmeguenai, M.; Petrisor, T.; Ulhaq-Bouillet, C.; Colis, S.; Tiusan, C.

    2015-08-01

    The structural and chemical order are the most important parameters governing the physical properties of the Heusler compounds. Here, we give a comprehensive overview of the correlations between structural and chemical order, electronic transport (longitudinal and transverse) and magnetic (static and dynamic) properties of Co2FeAl0.5Si0.5 Heusler alloy epitaxial thin films grown on MgO(001) single-crystal substrates. X-ray diffraction measurements indicated that depending on the annealing temperature the films show B 2 or L 21 chemical ordering. Longitudinal magnetoresistivity experiments revealed that for the best L 21 ordered film, at temperatures bellow 125 K , the magnon assisted electronic scattering is quenched indicating the appearance of half-metallicity. The presence of quantum correction in resistivity, whose strength is dependent on the structural ordering, was evidenced at low temperatures. Anomalous Hall experiments indicated that the intrinsic band structure contribution has an opposite sign and that is dominant over the extrinsic skew scattering mechanism. The presence of a small uniaxial magnetic anisotropy contribution superimposed on a larger biaxial one was evidenced via ferromagnetic resonance microstrip line measurements. The biaxial term is well correlated with chemical ordering, having a minimum value for the optimum L 21 ordered film. The damping parameter was evaluated from ferromagnetic resonance linewidth measurements, and a coefficient as low as 1.9 10-3 was found for the L 21 phase.

  18. Effect of thermal exposure, forming, and welding on high-temperature, dispersion-strengthened aluminum alloy: Al-8Fe-1V-2Si

    NASA Technical Reports Server (NTRS)

    Kennedy, J. R.; Gilman, P. S.; Zedalis, M. S.; Skinner, D. J.; Peltier, J. M.

    1991-01-01

    The feasibility of applying conventional hot forming and welding methods to high temperature aluminum alloy, Al-8Fe-1V-2Si (FVS812), for structural applications and the effect of thermal exposure on mechanical properties were determined. FVS812 (AA8009) sheet exhibited good hot forming and resistance welding characteristics. It was brake formed to 90 deg bends (0.5T bend radius) at temperatures greater than or equal to 390 C (730 F), indicating the feasibility of fabricating basic shapes, such as angles and zees. Hot forming of simple contoured-flanged parts was demonstrated. Resistance spot welds with good static and fatigue strength at room and elevated temperatures were readily produced. Extended vacuum degassing during billet fabrication reduced porosity in fusion and resistance welds. However, electron beam welding was not possible because of extreme degassing during welding, and gas-tungsten-arc welds were not acceptable because of severely degraded mechanical properties. The FVS812 alloy exhibited excellent high temperature strength stability after thermal exposures up to 315 C (600 F) for 1000 h. Extended billet degassing appeared to generally improve tensile ductility, fatigue strength, and notch toughness. But the effects of billet degassing and thermal exposure on properties need to be further clarified. The manufacture of zee-stiffened, riveted, and resistance-spot-welded compression panels was demonstrated.

  19. Perpendicular magnetic anisotropy and thermal stability in Co2FeAl0.5Si0.5/Pt multilayers

    NASA Astrophysics Data System (ADS)

    Wu, Y.; Zhang, J.; Wang, Z. C.; Wang, J.; Xu, X. G.; Miao, J.; Zhang, J. X.; Jiang, Y.

    2014-08-01

    Perpendicular magnetic anisotropy (PMA) and thermal stability of Co2FeAl0.5Si0.5 (CFAS)/Pt multilayer structure prepared by dc magnetron sputtering have been studied. It is found that the strength of PMA depends on the thickness of CFAS layer, and the maximum effective thickness of CFAS with PMA is demonstrated to be about 1.5 nm. The interfacial anisotropy energy K s is estimated to be 0.45 erg/cm2, which is larger than those of Co/Pd and Co/Ni multilayers and responsible for the strong PMA of the CFAS/Pt multilayer. The annealing treatments will give rise to the loss of PMA of CFAS/Pt multilayer and has the relatively less influence with large period number N. With the increasing of the period number N, the CFAS/Pt multilayers tend to have wasp-waist-shaped easy-axis hysteresis loops and multidomain structures.

  20. Microstructure Evolution Associated with a Superior Low-Cycle Fatigue Resistance of the Fe-30Mn-4Si-2Al Alloy

    NASA Astrophysics Data System (ADS)

    Nikulin, Ilya; Sawaguchi, Takahiro; Ogawa, Kazuyuki; Tsuzaki, Kaneaki

    2015-11-01

    The microstructure evolution responsible for the superior low-cycle fatigue (LCF) resistance ( N f > 8000 cycles at a total strain range of 2 pct) was studied in the Fe-30Mn-4Si-2Al alloy susceptible to strain-induced martensitic transformation. To investigate the microstructure effect on the LCF behaviors of the alloy, a series of interrupted fatigue tests at total strain range of 2 pct were carried out. A characteristic softening stage followed by the secondary hardening was observed during cyclic loading of the studied alloy. This softening is associated with the strain localization caused by persistent Lders bands formation and the transformation of Lders bands into strain-induced ?-martensite is found to have a key role in the delayed fatigue fracture of the alloy being studied. Therefore, the continuous transformation process involving Lders bands and ?-martensite formation associated with intermediate stacking fault energy (SFE) ( ? SF of 14 mJ/m2) is necessary to prevent the rearrangement of dislocations into walls/channels and substructures inherent to high-SFE ( ? SF higher 20 mJ/m2) alloys capable to accelerated fatigue damage. However, sluggish martensite transformation kinetics is necessary to delay the formation of the ?-martensite associated with the development and propagation of fatigue crack in alloys with very low SFE.

  1. Microstructural stability and creep response of a new Al-Fe-W-Si alloy. Final report, Sep 89-Dec 90

    SciTech Connect

    Benci, J.; Frazier, W.

    1991-04-01

    The microstructural stability and creep properties of a new aluminum alloy for potential aerospace applications at service temperatures up to 700 F (371 C) were evaluated. The Al alloy composition is 11.50% iron, 3.75% tungsten and 2.25% silicon by weight. The material was rapidly solidified via planar flow casting, vacuum hot-pressed, and then extruded into bar form. The room temperature yield strength and ultimate tensile strength are 603 MPa and 626 MPa, respectively, with an 11.3% elongation and a 33.0% reduction of area at fracture. A series of creep experiments were performed on this alloy at 700 F (371 C), and the results were compared to alloys FVS0812 (8009) and FVS1212. A change in creep deformation mechanism was discovered at a stress level of approximately 85 MPa defining the maximum allowable stress for components made from this material. The microstructural stability was evaluated by aging samples at either 700 F (371 C) or 900 F (482 C) and measuring the average grain and dispersoid sizes as a function of aging time with transmission electron microscopy. Upon aging at 371 C, the room temperature hardness did not change even after times greater than 1000 hrs., indicating the microstructure is stable at this temperature. The hardness decreased slightly during 482 C aging over a period of 670 hrs. indicating minor microstructural changes (e.g., dispersoid coarsening) were occurring over long periods of time.

  2. Stable isotope studies of metasomatic Ca-Fe-Al-Si skarns and associated metamorphic and igneous rocks, Osgood Mountains, Nevada

    USGS Publications Warehouse

    Taylor, B.E.; O'Neil, J.R.

    1977-01-01

    Garnet-pyroxene skarns were formed 90 m.y. B.P. in the Osgood Mountains at or near contacts of grandiorite with calcareous rocks of the Cambrian Preble Formation. The metasomatic replacement followed contact metamorphic recrystallization of the Preble. The sources, temperature, and variation in H2O/CO2 ratios of the metasomatic fluid are interpreted from 269 analyses of oxygen, carbon, hydrogen, and sulfur isotopes in whole rocks, minerals and inclusion fluids. Skarns formed in three mineralogical stages. Oxygen isotope data indicate that temperatures during the crystallization of garnet, pyroxene and wollastonite (Stage I) were least 550 ?? C, and that the metasomatic fluid had an {Mathematical expression} ??? 0.035 in the massive skarns, and ??? 0.12 in vein skarns up to 3 cm thick. Pore fluids in isotopic equilibrium with garnet in calc-silicate metamorphic rocks, on the other hand, had {Mathematical expression} ??? 0.15. The metasomatic fluids of Stage I were derived primarily from the crystallizing magma. The isotopic composition of magmatic water was ??18O =+9.0, ??D= -30 to -45. Oxygen isotope temperatures of greater than 620 ?? C were determined for the granodiorite. Isotopic and chemical equilibria between mineral surfaces and the metasomatic fluid were approached simultaneously in parts of the skarn several meters or more apart, while isotopic and chemical disequilibria (i.e. zoning) have been preserved between 20 to 40 ??m-thick zones in grandite garnet. More Fe-, or andradite-rich garnet crystallized in more H2O-rich C-O-H fluids ( {Mathematical expression} ??? 0.01) than present with grossularite-rich garnet ( {Mathematical expression}??? 0.035). Stage II was marked by the replacement of garnet and pyroxene by quartz, amphibole, plagioclase, epidote, magnetite, and calcite. Many of the replacement reactions took place over a relatively narrow range in temperature (480-550 ?? C), as indicated by 18O fractionations between quartz and amphibole. Meteoric water comprised 20 to 50% of the metasomatic fluid during Stage II. Calcite was formed along with pyrite, minor pyrrhotite, and chalcopyrite during Stage III, although the crystallization of pyrite and calcite had begun earlier, during Stages I and II, respectively. Carbon and sulfur isotope compositions of calcite and pyrite indicate a magmatic source for most of the C and S in the metasomatic fluids of Stage III. By the end of Stage III, meteoric water constituted as much as 100% of the metasomatic fluid. Minerals from grandiorite and skarn do not show large depletions in 18O because the oxygen isotope composition of the metasomatic fluid was buffered by the calcareous wall rocks and the grandiorite. Meteoric water in the vicinity of the Osgood Mountains during the Late Crectaceous (??18Ocale. ??? -14.0, ??D = - 107) was slightly enriched in 18O and D relative to present-day meteoric water (??18O = 15.9, ??D = - 117) ?? 1977 Springer-Verlag.

  3. Micromagnetic simulation of spin-transfer switching in a full-Heusler Co{sub 2}FeAl{sub 0.5}Si{sub 0.5} alloy spin-valve nanopillar

    SciTech Connect

    Huang, H. B.; Ma, X. Q.; Liu, Z. H.; Meng, F. Y.; Xiao, Z. H.; Wu, P. P.; Shi, S. Q.; Chen, L. Q.

    2011-08-01

    We investigated the spin-transfer switching in a full-Heusler Co{sub 2}FeAl{sub 0.5}Si{sub 0.5} alloy spin-valve nanopillar through micromagnetic simulation. A two-step switching hysteresis loop due to the fourfold in-plane magnetocrystalline anisotropy of Co{sub 2}FeAl{sub 0.5}Si{sub 0.5} layers was obtained. The simulation explains the experimental result of the resistance versus current hysteresis loop and yields good agreement with the measured critical current. Furthermore, the magnetization trajectory and magnetization distribution were shown and analyzed to elucidate the different characters of two-step switching.

  4. Phase separation in Fe2CrSi thin films

    NASA Astrophysics Data System (ADS)

    Meinert, Markus; Hbner, Torsten; Schmalhorst, Jan; Reiss, Gnter; Arenholz, Elke

    2013-09-01

    Thin films of a nominal Fe2CrSi alloy have been deposited by magnetron co-sputtering with various heat treatments on MgO and MgAl2O4 substrates. After heat treatment, the films were found to decompose into a nearly epitaxial Fe3Si film with the D03 structure and Cr3Si precipitates with the A15 structure. We explain the experimental results on the basis of ab initio calculations, which reveal that this decomposition is energetically highly favorable.

  5. X-ray-absorption spectral study of the R2Fe17-xMx solid solutions (R=Ce, Nd and M=Al, Si)

    NASA Astrophysics Data System (ADS)

    Vandormael, D.; Grandjean, F.; Briois, V.; Middleton, D. P.; Buschow, K. H. J.; Long, Gary J.

    1997-09-01

    The x-ray-absorption near-edge structure (XANES) spectra obtained at the cerium LIII edge of the Ce2Fe17-xAlx solid solutions and Ce2Fe14Si3 show two absorption peaks characteristic of the 4f1 and 4f0 configurations of cerium, peaks which indicate that cerium is in a mixed valent state in these compounds. All the XANES spectra have been consistently and excellently fit with one sigmoidal function and two Gaussian-broadened Lorentzian functions. The cerium spectroscopic valence obtained from the relative areas of the two peaks decreases from 3.64 to 3.43 between x=0 and 9 in Ce2Fe17-xAlx, and correlates linearly with the cerium site volume. This correlation confirms that the cerium valence is strongly dependent upon steric effects. In contrast, the cerium valence obtained from the XANES spectrum of Ce2Fe14Si3 is not determined by steric effects and indicates, in agreement with other measurements and calculations, that silicon is more covalently bonded with its near-neighbor cerium atoms than is aluminum. The neodymium LIII-edge XANES spectra of the Nd2Fe17-xAlx solid solutions, where x is 0, 3, and 8, reveal the presence of only trivalent neodymium and an increase of the empty 5d state density when aluminum is substituted in place of iron. XANES measurements at the iron K edge of the Ce2Fe17-xAlx and Nd2Fe17-xAlx solid solutions show changes in the relative intensity of the multiple scattering peaks, changes which are related to the changing composition of the first three neighbor shells with increasing aluminum content.

  6. U-Mo/Al-Si interaction: Influence of Si concentration

    NASA Astrophysics Data System (ADS)

    Allenou, J.; Palancher, H.; Iltis, X.; Cornen, M.; Tougait, O.; Tucoulou, R.; Welcomme, E.; Martin, Ph.; Valot, C.; Charollais, F.; Anselmet, M. C.; Lemoine, P.

    2010-04-01

    Within the framework of the development of low enriched nuclear fuels for research reactors, U-Mo/Al is the most promising option that has however to be optimised. Indeed at the U-Mo/Al interfaces between U-Mo particles and the Al matrix, an interaction layer grows under irradiation inducing an unacceptable fuel swelling. Adding silicon in limited content into the Al matrix has clearly improved the in-pile fuel behaviour. This breakthrough is attributed to an U-Mo/Al-Si protective layer around U-Mo particles appeared during fuel manufacturing. In this work, the evolution of the microstructure and composition of this protective layer with increasing Si concentrations in the Al matrix has been investigated. Conclusions are based on the characterization at the micrometer scale (X-ray diffraction and energy dispersive spectroscopy) of U-Mo7/Al-Si diffusion couples obtained by thermal annealing at 450 C. Two types of interaction layers have been evidenced depending on the Si content in the Al-Si alloy: the threshold value is found at about 5 wt.% but obviously evolves with temperature. It has been shown that for Si concentrations ranging from 2 to 10 wt.%, the U-Mo7/Al-Si interaction is bi-layered and the Si-rich part is located close to the Al-Si for low Si concentrations (below 5 wt.%) and close to the U-Mo for higher Si concentrations. For Si weight fraction in the Al alloy lower than 5 wt.%, the Si-rich sub-layer (close to Al-Si) consists of U(Al, Si) 3 + UMo 2Al 20, when the other sub-layer (close to U-Mo) is silicon free and made of UAl 3 and U 6Mo 4Al 43. For Si weight concentrations above 5 wt.%, the Si-rich part becomes U 3(Si, Al) 5 + U(Al, Si) 3 (close to U-Mo) and the other sub-layer (close to Al-Si) consists of U(Al, Si) 3 + UMo 2Al 20. On the basis of these results and of a literature survey, a scheme is proposed to explain the formation of different types of ILs between U-Mo and Al-Si alloys (i.e. different protective layers).

  7. Effects of Intercritical Annealing Temperature on Mechanical Properties of Fe-7.9Mn-0.14Si-0.05Al-0.07C Steel

    DOE PAGESBeta

    Zhao, Xianming; Shen, Yongfeng; Qiu, Lina; Liu, Yandong; Sun, Xin; Zuo, Liang

    2014-12-09

    A medium Mn steel has been designed to achieve an excellent combination of strength and ductility based on the TRIP (Transformation Induced Plasticity) concept for automotive applications. Following six passes of hot rolling at 850 °C, the Fe-7.9Mn-0.14Si-0.05Al-0.07C (wt.%) steel was warm-rolled at 630 °C for seven passes and subsequently air cooled to room temperature. The sample was subsequently intercritically annealed at various temperatures for 30 min to promote the reverse transformation of martensite into austenite. The obtained results show that the highest volume fraction of austenite is 39% for the sample annealed at 600 °C. This specimen exhibits amore » yield stress of 910 MPa and a high ultimate tensile stress of 1600 MPa, with an elongation-to-failure of 0.29 at a strain rate of 1 × 10⁻³/s. The enhanced work-hardening ability of the investigated steel is closely related to martensitic transformation and the interaction of dislocations. Especially, the alternate arrangement of acicular ferrite (soft phase) and ultrafine austenite lamellae (50–200 nm, strong and ductile phase) is the key factor contributing to the excellent combination of strength and ductility. On the other hand, the as-warm-rolled sample also exhibits the excellent combination of strength and ductility, with elongation-to-failure much higher than those annealed at temperatures above 630 °C.« less

  8. Optically Stimulated Luminescence Response to Ionizing Radiation of Red Bricks (SiO2, Al2O3, and Fe2O3) Used as Building Materials

    SciTech Connect

    Bogard, James S; Espinosa Garcia, Guillermo

    2007-01-01

    Quartz is the most common mineral in our environment. It is found in granite, hydrothermal veins and volcanic rocks, as well as in sedimentary deposits derived from such solid materials. These sediments are also made into building materials, such as bricks and pottery. Thus the potential use of a dose reconstruction technique based on quartz grains is enormous, whether as a dating tool in archaeology and quaternary geology, or in nuclear accident dosimetry. This work describes the Optically Stimulated Luminescence (OSL) response of red brick to ionizing radiation. The bricks, from the state of Puebla, Mexico, represent another class of materials that can be used in retrospective dosimetry following nuclear or radiological incidents. The chemical composition of fifteen bricks (three samples from five different brick factories) was determined, using energy dispersive spectroscopy (EDS), be primarily SiO{sub 2}, Al{sub 2}O{sub 3} and Fe{sub 2}O{sub 3} and is believed to be representative for this common building material. Individual aliquots from these bricks were powdered in agate mortars and thermally annealed. Replicate samples of the aliquots were then irradiated with beta particles from a sealed source of {sup 90}Sr/{sup 90}Y. The OSL response was measured with a Daybreak Model 2200 High-Capacity OSL Reader System. We present here for this material the characteristic OSL response to beta particles; the reproducibility of the OSL response; the linearity of the response in the dose range 0.47 Gy to 47 Gy; and the fading characteristics.

  9. AFM surface morphology and magnetic properties of nanocrystalline Fe 71Nb 3.7Cu 1Al 3Mn 0.8Si 13.5B 7 ribbons

    NASA Astrophysics Data System (ADS)

    Panda, A. K.; Manimaran, M.; Mitra, A.; Basu, S.

    2004-08-01

    The effect of structural and surface morphological developments on the soft magnetic properties of Fe 71Nb 3.7Cu 1Al 3Mn 0.8Si 13.5B 7 alloy was investigated. AFM studies showed that the material, which was amorphous in the as-cast state indicated segregates in the form of Cu atoms seated within the holes in the surface topography. With an increase in annealing temperature, nucleation and subsequent growth of ?-Fe phase from the adjoining matrix on these nucleating Cu atoms was manifested in the form of magnetic softening. At optimum temperature Si and Al dissolved from adjoining matrix on these ?-Fe phase indicating relatively low surface roughness and ultrasoft magnetic properties. The correlation between the surface morphology and magnetic properties were explained by nucleation and growth model. At elevated temperatures formation of strongly magneto-crystalline anisotropic crystalline phases like Fe-borides and Fe 7Nb 6 deteriorated the soft magnetic properties. The occurrence of these phases in the form of multiple protrusions increased surface roughness.

  10. AlN/Fe/AlN nanostructures for magnetooptic magnetometry

    SciTech Connect

    Likov-Jakubisov, E. Vi?ovsk, .; irok, P.; Hrabovsk, D.; Pitora, J.

    2014-05-07

    AlN/Fe/AlN/Cu nanostructures with ultrathin Fe grown by sputtering on Si substrates are evaluated as probes for magnetooptical (MO) mapping of weak currents. They are considered for a laser wavelength of ??=?410?nm (3.02?eV) and operate at oblique light incidence angles, ?{sup (0)}, to enable detection of both in-plane and out-of-plane magnetization. Their performance is evaluated in terms of MO reflected wave electric field amplitudes. The maximal MO amplitudes in AlN/Fe/AlN/Cu are achieved by a proper choice of layer thicknesses. The nanostructures were characterized by MO polar Kerr effect at ?{sup (0)}???5 and longitudinal Kerr effect spectra (?{sup (0)}?=?45) at photon energies between 1 and 5?eV. The nominal profiles were refined using a model-based analysis of the spectra. Closed form analytical expressions are provided, which are useful in the search for maximal MO amplitudes.

  11. 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 ?/?-AlFeSi white intermetallics, and Chinese script-like ?-AlFeSi compounds. During high temperature homogenization treatment, only harmful needle-like ?-AlFeSi phase undergoes fragmentation and spheroidizing at its tips, and the destructive needle-like ?-phase does not show any morphological and size changes. Phase transitions from ?-AlFeSi to ?-AlFeSi and from ?-AlFeSi to ?-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.

  12. Magnetic properties of the U{sub 2}Fe{sub 17-x}M{sub x}C{sub y} intermetallic compounds with M = Al, Si, and Ge

    SciTech Connect

    Chevalier, B.; Rogl, P.; Etourneau, J.

    1995-02-15

    {open_quotes}U{sub 2}Fe{sub 17}{close_quotes} does not exist in thermodynamic equilibrium; however, alloying uranium with electron donor elements such as Al, Si, or Ge yields compound formation with crystal structures isotypic with the Th{sub 2}Ni{sub 17}-type or derivative structures such as U{sub 2}Fe{sub 12.8}Si{sub 4.2}. The octahedral voids can be partially filled with carbon atoms without exceeding one carbon atom per formula unit. Powder X-ray diffraction of the carbon-containing compounds in all cases revealed the Th{sub 2}Ni{sub 17}-type of structure with a small increase in volume by {approximately}0.0075 nm{sup 3} per interstitial carbon atom per formula unit. There is only a small influence of the carbon-induced volume increase on the ferromagnetic ordering temperature of the alloys.

  13. Evaluation of Methods of Soldering AlSi and AlSi-SiC Particle Composite Al Foams

    NASA Astrophysics Data System (ADS)

    Nowacki, Jerzy; Moraniec, Kacper

    2015-01-01

    The cellular structure and unique properties of aluminum foams are the reason of their numerous applications and interests in respect of their joining. The paper includes the characterization of the essence of properties and application of aluminum and aluminum composite foams, the limitations, and possibilities of their soldering. The aim of the research is the consideration of methods of soldering AlSi foams and AlSi-SiC composite foams, and the joint structure. EDS and XRD investigations of the AlSi-SiC composite foams' joints were done. The possibility of soldering AlSi9 foams and AlSi9-SiC composite foams using S-Bond 220 solder was confirmed, and higher tensile strength of the joint than the parent material was also ascertained

  14. Three-Dimensional Microstructure Visualization of Porosity and Fe-Rich Inclusions in SiC Particle-Reinforced Al Alloy Matrix Composites by X-Ray Synchrotron Tomography

    SciTech Connect

    Silva, Flávio de Andrade; Williams, Jason J.; Müller, Bernd R.; Hentschel, Manfred P.; Portella, Pedro D.; Chawla, Nikhilesh

    2011-11-15

    Microstructural aspects of composites such as reinforcement particle size, shape, and distribution play important roles in deformation behavior. In addition, Fe-rich inclusions and porosity also influence the behavior of these composites, particularly under fatigue loading. Three-dimensional (3-D) visualization of porosity and Fe-rich inclusions in three dimensions is critical to a thorough understanding of fatigue resistance of metal matrix composites (MMCs), because cracks often initiate at these defects. In this article, we have used X-ray synchrotron tomography to visualize and quantify the morphology and size distribution of pores and Fe-rich inclusions in a SiC particle-reinforced 2080 Al alloy composite. The 3-D data sets were also used to predict and understand the influence of defects on the deformation behavior by 3-D finite element modeling.

  15. Thermoelasticity of Al3+- and Fe3+-bearing bridgemanite

    NASA Astrophysics Data System (ADS)

    Valencia-Cardona, Juan; Shukla, Gaurav; Cococcioni, Matteo; Wentzcovitch, Renata

    2015-03-01

    We present quasi-harmonic LDA+U calculations of thermoelastic properties of Fe3+- and Al3+-bearing bridgemanite (MgSiO3), the main Earth forming phase, at relevant P,T conditions and compositions. Three charge-coupled substitutions, namely, Al3+-Al3+, Fe3+-Fe3+, and Fe3+-Al3+ have been investigated. Aggregate elastic moduli and sound velocities are successfully compared with limited experimental measurements available. The effect of the pressure induced high-spin to low-spin state change in Fe3+ in the B-site has been investigated in great detail since it has potentially dramatic effects on seismic velocities in the Earth's lower mantle. Research supported by NSF/EAR and NSF/CAREER.

  16. Transport properties of β-FeSi2

    NASA Astrophysics Data System (ADS)

    Arushanov, Ernest; Lisunov, Konstantin G.

    2015-07-01

    The aim of this paper is to summarize considerable experimental efforts undertaken within the last decades in the investigations of transport properties of β-FeSi2. The β-FeSi2 compound is the most investigated among a family of semiconducting silicides. This material has received considerable attention as an attractive material for optoelectronic, photonics, photovoltaics and thermoelectric applications. Previous reviews of the transport properties of β-FeSi2 have been given by Lange and Ivanenko et al. about 15 years ago. The Hall effect, the conductivity, the mobility and the magnetoresistance data are presented. Main attention is paid to the discussion of the impurity (defect) band conductivity, the anomalous Hall effect, the scattering mechanisms of charge carriers, as well as to the hopping conduction and the magnetoresistance.

  17. Synthesis and equation of state of post-perovskites in the (Mg,Fe)[subscript 3]Al[subscript 2]Si[subscript 3]O[subscript 12] system

    SciTech Connect

    Shieh, Sean R.; Dorfman, Susannah M.; Kubo, Atsushi; Prakapenka, Vitali B.; Duffy, Thomas S.

    2012-02-06

    The formation and properties of the post-perovskite (CaIrO{sub 3}-type) phase were studied in Fe-rich compositions along the pyrope-almandine ((Mg,Fe){sub 3}Al{sub 2}Si{sub 3}O{sub 12}) join. Natural and synthetic garnet starting materials with almandine fractions from 38 to 90 mol% were studied using synchrotron X-ray diffraction in the laser-heated diamond anvil cell. Single-phase post-perovskite could be successfully synthesized from garnet compositions at pressures above 148 GPa and temperatures higher than 1600 K. In some cases, evidence for a minor amount of Al{sub 2}O{sub 3} post-perovskite was observed for Alm38 and Alm54 compositions in the perovskite + post-perovskite two-phase region. Pressure-volume data for the post-perovskite phases collected during decompression show that incorporation of Fe leads to a systematic increase of unit cell volume broadly similar to the variation observed in the (Mg,Fe)SiO{sub 3} system. The presence of Al{sub 2}O{sub 3} increases the stability of perovskite relative to post-perovskite, requiring higher pressures (> 148 GPa) for synthesis of pure post-perovskites. Our data together with those of Tateno et al. (2005) also suggest that in the Al-rich system the presence of Fe has no strong effect on the pressure required to synthesize the pure post-perovskite phase, but the two-phase perovskite and post-perovskite region may be broad and its width dependent on Fe content. Our results suggest that any regions highly enriched in Al{sub 2}O{sub 3} may consist of either the perovskite phase or a mixture of perovskite and post-perovskite phases throughout the entire thickness of the D* region. The observed synthesis pressures (> 148 GPa) for a pure post-perovskite phase are beyond that at the Earth's core-mantle boundary ({approx} 135 GPa).

  18. Microstructural and Fracture Behavior of Phosphorus-Containing Fe-30Mn-9Al-1Si-0.9C-0.5Mo Alloy Steel

    NASA Astrophysics Data System (ADS)

    Howell, Ryan A.; Van Aken, David C.

    2015-08-01

    Five different phosphorus (P)-containing heat-treated Fe-Mn-Al-C alloys were tested in accordance with ASTM E 23 Charpy V-notch Energy (CVNE) standards. Room temperature CVNE of solution treated and quenched specimens revealed ductile fracture for 0.001 and 0.006 wt pct (pct P-containing alloys). Brittle cleavage fracture dominated the 0.043 and 0.07 pct P-containing alloys. A hard brittle P eutectic phase was observed in the 0.07 pct P-containing alloy.

  19. Investigation of the temperature-dependence of ferromagnetic resonance and spin waves in Co{sub 2}FeAl{sub 0.5}Si{sub 0.5}

    SciTech Connect

    Loong, Li Ming; Kwon, Jae Hyun; Deorani, Praveen; Yang, Hyunsoo; Tung Yu, Chris Nga; Hirohata, Atsufumi

    2014-06-09

    Co{sub 2}FeAl{sub 0.5}Si{sub 0.5} (CFAS) is a Heusler compound that is of interest for spintronics applications, due to its high spin polarization and relatively low Gilbert damping constant. In this study, the behavior of ferromagnetic resonance as a function of temperature was investigated in CFAS, yielding a decreasing trend of damping constant as the temperature was increased from 13 to 300?K. Furthermore, we studied spin waves in CFAS using both frequency domain and time domain techniques, obtaining group velocities and attenuation lengths as high as 26?km/s and 23.3??m, respectively, at room temperature.

  20. An experimental study of the Fe oxidation states in garnet and clinopyroxene as a function of temperature in the system CaO-FeO-Fe2O3-MgO-Al2O3-SiO2: implications for garnet-clinopyroxene geothermometry

    NASA Astrophysics Data System (ADS)

    Purwin, Horst; Lauterbach, Stefan; Brey, Gerhard P.; Woodland, Alan B.; Kleebe, Hans-Joachim

    2013-04-01

    Samples with eclogitic composition in the system CaO-FeO-Fe2O3-MgO-Al2O3-SiO2 were produced from various kinds of starting materials held in graphite-lined Pt capsules at a pressure of 2.5-3.0 GPa and temperatures of 800-1,300 C using a piston-cylinder or Belt apparatus. Garnets and clinopyroxenes were characterized by analytical transmission electron microscopy and electron probe micro-analysis (EPMA). Fe3+/?Fe ratios determined by electron energy-loss spectroscopy (EELS) decrease in clinopyroxene from 22.2 3.4 % at 800 C to 13.3 5.4 % at 1,300 C, while in garnet, they vary between 10.8 1.5 and 15.4 4.7 %, respectively. Temperature estimates according to Krogh (Contrib Mineral Petrol 99:44-48, 1988) reproduce the experimental temperature to 60 C without systematic deviations if total iron is used in the calculation. If only the Fe2+ content is used, which was obtained by combining EPMA and EELS results, the experimental temperature is underestimated by 33 C on average at 800-1,200 C and overestimated by 77 C on average at 1,300 C. These systematic deviations can be explained by the temperature-dependent ratio of Fe2+/?Fe in garnet divided by that in clinopyroxene. Since the difference between the calculated and experimental temperature is relatively small, a Fe2+-based recalibration of the thermometer appears not to be necessary for the investigated system in the range of pressure, temperature and composition covered by the experiments of this study.

  1. Thermoelectric properties of -FeSi2

    SciTech Connect

    Parker, David S; Singh, David J; Pandey, Tribhuwan; Singh, Abhishek

    2013-01-01

    We investigate the thermoelectric properties of -FeSi2 using first principles electronic structure and Boltzmann trans- port calculations. We report a high thermopower for both p- and n-type -FeSi2 over a wide range of carrier concentra- tion and in addition find the performance for n-type to be higher than for the p-type. Our results indicate that, depending upon temperature, a doping level of 3 1020 - 2 1021 cm 3 may optimize the thermoelectric performance.

  2. EBSD characterization of high-temperature phase transformations in an Al-Si coating on Cr-Mo steel

    SciTech Connect

    Cheng, Wei-Jen Wang, Chaur-Jeng

    2012-02-15

    5Cr-0.5Mo steel was coated by hot-dipping in a molten bath containing Al-10 wt.% Si. The phase transformation in the aluminide layer during diffusion at 750 Degree-Sign C in static air was analyzed by electron backscatter diffraction. The results show the aluminide layer of the as-coated specimen consisted of an outer Al-Si topcoat, a middle layer formed of scattered {tau}{sub 5(C)}-Al{sub 7}(Fe,Cr){sub 2}Si particles and minor plate-shaped {tau}{sub 4}-Al{sub 4}FeSi{sub 2} and {tau}{sub 6}-Al{sub 4}FeSi phases in the Al-Si matrix and an inner continuous {tau}{sub 5(H)}-Al{sub 7}Fe{sub 2}Si layer, respectively from the coating surface to the steel substrate. The formation of FeAl{sub 3} and Fe{sub 2}Al{sub 5} with {tau}{sub 1}-(Al,Si){sub 5}Fe{sub 3} precipitates can be observed with increasing exposure time at 750 Degree-Sign C. After 5 h of exposure, the Al-Si topcoat has been consumed, and the aluminide layer consisted of Fe{sub 2}Al{sub 5} and a few {tau}{sub 1}-(Al,Si){sub 5}Fe{sub 3} precipitates. The FeAl phase not only formed at the interface between Fe{sub 2}Al{sub 5} and the steel substrate, but also transformed from {tau}{sub 1}-(Al,Si){sub 5}Fe{sub 3} after diffusion for 10 h. With prolonged exposure, the aluminide layer comprised only FeAl{sub 2} and FeAl. - Highlights: Black-Right-Pointing-Pointer EBSD can differentiate phases in aluminide layer with similar chemical compositions. Black-Right-Pointing-Pointer Mapping and EBSPs functions in EBSD provide a reliable phase identification. Black-Right-Pointing-Pointer A phase transformation in the aluminide layer has been described in detail. Black-Right-Pointing-Pointer 5 Fe-Al-Si and 4 Fe-Al intermetallic phases are performed during the diffusion. Black-Right-Pointing-Pointer Cubic {tau}{sub 5(C)}-Al{sub 7} (Fe,Cr){sub 2}Si and hexagonal {tau}{sub 5(H)}-Al{sub 7}(Fe,Cr){sub 2}Si are identified.

  3. Fe stable isotope fractionation in modern and ancient hydrothermal Fe-Si deposits

    NASA Astrophysics Data System (ADS)

    Moeller, K.; Schoenberg, R.; Thorseth, I. H.; vres, L.; Pedersen, R.

    2010-12-01

    Modern iron-silica deposits of small yellow to rust coloured mounds and chimney-like structures were found in a low-temperature venting area distal to a white smoker type hydrothermal vent site at the south-western part of the Mohns Ridge, North Atlantic. Individual stratified mm to cm thick laminated layers within these structures are largely composed of branching, twisted filaments resembling encrusted stalks of Fe-oxidising bacteria. DNA analyses have confirmed the presence of both Fe-oxidising (Mariprofundus ferrooxidans and other ?-Proteobacteria) and Fe-reducing bacteria (Shewanellaceae). Similar morphologic features, such as several mm thick red hematite-rich laminae and micron-scale filamentous structures concentrated in discrete laminae, have also been found in Early Ordovician volcanogenic massive sulphide (VMS) hosted jasper deposits in the Lkken-Hydal area, Norway [1]. These filamentous structures are believed to be formed by Fe-oxidising bacteria similar to Mariprofundus ferrooxidans [2]. Here, we compare the Fe isotope composition of these two different types of Fe-Si deposits with the aim to gain further information about deposition mechanisms and the role of microorganisms in Fe redox cycling of deep-sea hydrothermal systems. Fe isotope compositions of the modern biogenic Fe-Si deposit vary between -2.09 and -0.66 in ?56Fe values, a range that is comparable to late Archaean to early Proterozoic banded iron formations. The ~490 Ma old Lkken jaspers show a similar variation, but with significantly higher ?56Fe values ranging from -0.39 to +0.89 . The Fe isotopic composition of the Lkken jaspers clearly correlates with morphological features with the lowest ?56Fe values in layered and the highest ones in brecciform jaspers. Our data demonstrate that variations in Fe isotope compositions of the modern Fe-Si deposit cannot be explained by a single process, but rather reflect the full complexity of Fe redox cycling within deep-sea sediments and the deposit itself, including abiogenic partial oxidation of hydrothermal Fe(II)aq through mixing with oxygenated seawater, reduction of Fe(III) precipitates by dissimilatory iron reduction (DIR) and re-oxidation by Fe-oxidising bacteria. The Lkken jaspers were postulated to be a combination of Fe-oxyhydroxide precipitation within buoyant and non-buoyant hydrothermal plumes and Si flocculation in a silica-saturated ocean [1]. Observations from a modern basalt-hosted hydrothermal system indicate that Fe(II)aq in a buoyant plume gets fractionated towards heavier isotopic compositions due to precipitation of low-?56Fe iron sulphides [3]. However, mass balance calculations of plume particles revealed that Fe-oxyhydroxides have ?56Fe values of around -0.2 , thus significantly lighter than the heaviest Lkken signatures of 0.89 . Possible scenarios to explain the Fe isotope compositions of Lkken jaspers and the modern Mohns Ridge Fe-Si deposits will be discussed. [1] Grenne, T. & Slack, J. (2003) Miner Deposita, 38, 625ff. [2] Little, C. et al. (2004) Geomicrobiol J, 21, 415ff. [3] Bennett, S. et al. (2009) Geochim. Cosmochim. Acta., 73, 5619ff.

  4. Growth of ?-FeSi2 Layers on Si(100) Substrates by Exchange Reaction between Si and Molten Salts

    NASA Astrophysics Data System (ADS)

    Yoneyama, Tsuyoshi; Yoshikawa, Takeshi; Morita, Kazuki

    2007-08-01

    The growth of ?-FeSi2 layers on Si(100) substrates by a cation exchange reaction between Si and molten NaCl-KCl-FeCl2 salts, namely, 5Si(s)+2FeCl2(l)=2?-FeSi2(s)+SiCl4(g), has been investigated. A single-crystal Si(100) substrate was reacted with the molten salt at 1173 K for 1-64 h in Ar or He atmosphere. The grown layers were characterized by X-ray diffraction (XRD) measurement, scanning electron microscopy (SEM), and transmission electron microscopy (TEM). When the FeCl2 concentration in molten salt was as low as 0.02 mol %, a ?-FeSi2 single layer was obtained, although the double layer of FeSi/?-FeSi2 formed with a higher FeCl2 concentration of 0.1-1.0 mol %. The ?-FeSi2 single layer grown at low FeCl2 concentration had a rough surface structure due to the decrease in driving force caused by the consumption of FeCl2 during the reaction. By annealing a flat double layer of FeSi/?-FeSi2 formed with a higher FeCl2 concentration where the driving force could be kept constant, a flat ?-FeSi2 single layer was obtained on the Si(100) substrate.

  5. Magnetoelasticity of Fe-Si single crystals

    SciTech Connect

    Xing, Q; Wu, D.; Lograsso, T. A.

    2010-04-20

    The tetragonal magnetostriction constant, (3/2){lambda}{sub 100}, of Fe-Si single crystals was measured and was found to be structure dependent. Similar to that of Fe-Ge single crystals, (3/2){lambda}{sub 100} is positive in the single phase A2 regime, becomes negative in the single phase D0{sub 3} regime, and changes from positive to negative between the two regimes. Short-range order in the A2 regime decreases the magnetostriction prior to the onset of long range order. In the single phase regions of both A2 and D0{sub 3}, thermal history does not show any obvious effect on the magnetostriction, contrary to that found for Fe-Ga alloys. However, in the regions of phase mixture involving A2, B2, and D0{sub 3} phases, quenching pushes the change in magnetostriction from positive to negative to higher Si contents.

  6. Investigation of Liquidus Temperatures and Phase Equilibria of Copper Smelting Slags in the FeO-Fe2O3-SiO2-CaO-MgO-Al2O3 System at PO2 10-8 atm

    NASA Astrophysics Data System (ADS)

    Henao, Hector M.; Nexhip, Colin; George-Kennedy, David P.; Hayes, P. C.; Jak, E.

    2010-08-01

    Copper concentrates and fluxes can contain variable levels of SiO2, CaO, and MgO in addition to main components Cu, Fe, and S. Metal recovery, slag tapping, and furnace wall integrity all are dependent on phase equilibria and other properties of the phases and are functions of slag composition and operational temperature. Optimal control of the slag chemistry in the copper smelting, therefore, is essential for high recovery and productivity; this, in turn, requires detailed knowledge of the slag phase equilibria. The present work provides new phase equilibrium experimental data in the FeO-Fe2O3-SiO2-CaO-MgO-Al2O3 system at oxygen partial pressure of 10-8 atm within the range of temperatures and compositions directly relevant to copper smelting. For the range of conditions relevant to the Kennecott Utah Copper (South Magna, UT) smelting furnace, it was confirmed experimentally that increasing concentrations of MgO or CaO resulted in significant decreases of the tridymite liquidus temperature and in changes in the position of the tridymite liquidus in the direction of higher silica concentration; in contrast, the spinel liquidus temperatures increase significantly with the increase of MgO or CaO. Olivine and clinopyroxene precipitates appeared at high MgO concentrations in the liquid slag. The liquidus temperature in the spinel primary phase field was expressed as a linear function of 1/(wt pctFe/wt pctSiO2), wt pctCaO, wt pctMgO, and wt pctAl2O3. The positions of each of the liquidus points (wt pctFe)/(wt pctSiO2) at a fixed temperatures in the tridymite primary phase field were expressed as linear functions of wt pctCaO, wt pctMgO, and wt pctAl2O3.

  7. Formation and ferromagnetic properties of FeSi thin films

    SciTech Connect

    Shin, Yooleemi; Anh Tuan, Duong; Hwang, Younghun; Viet Cuong, Tran; Cho, Sunglae

    2013-05-07

    In this work, the growth and ferromagnetic properties of {epsilon}-FeSi thin film on Si(100) substrate prepared by molecular beam epitaxy are reported. The inter-diffusion of Fe layer on Si(100) substrate at 600 Degree-Sign C results in polycrystalline {epsilon}-FeSi layer. The determined activation energy was 0.044 eV. The modified magnetism from paramagnetic in bulk to ferromagnetic states in {epsilon}-FeSi thin films was observed. The saturated magnetization and coercive field of {epsilon}-FeSi film are 4.6 emu/cm{sup 3} and 29 Oe at 300 K, respectively.

  8. Development of SiAlON materials

    NASA Technical Reports Server (NTRS)

    Layden, G. K.

    1979-01-01

    Cold pressing and sintering techniques were used to produce ceramic test specimens in which the major phase was either Si3N4 or a solid solution having the beta Si3N4 structure. Additional components were incorporated to promote liquid phase sintering. Glass and/or crystalline phase were consequently retained in boundaries between Si3N4 grains which largely determined the physical properties of the bodies. Systems investigated most extensively included R-Si-Al-O-N (R = rare earth element) Zr-Si-Al-O-N, Y-Si-Be-O-N, and R1-R2-Si-O-N. Room temperature and 1370 C modulus of ruptured, 1370 C creep, and oxidation behavior are discussed in terms of phase relationships in a parent quinery, and relavent oxide systems.

  9. Investigation of various phases of Fe-Si structures formed in Si by low energy Fe ion implantation

    NASA Astrophysics Data System (ADS)

    Lakshantha, Wickramaarachchige J.; Dhoubhadel, Mangal S.; Reinert, Tilo; McDaniel, Floyd D.; Rout, Bibhudutta

    2015-12-01

    The compositional phases of ion beam synthesized Fe-Si structures at two high fluences (0.50 1017 atoms/cm2 and 2.16 1017 atoms/cm2) were analyzed using X-ray photoelectron spectroscopy (XPS) and X-ray diffraction (XRD). The distribution of Fe implanted in Si was simulated using a dynamic simulation code (TRIDYN) incorporating target sputtering effects. The Fe depth profiles in the Si matrix were confirmed with Rutherford backscattering spectrometry (RBS) and XPS depth profiling using Ar-ion etching. Based on XPS binding energy shift and spectral asymmetry, the distribution of stable Fe-Si phases in the substrate was analyzed as a function of depth. Results indicate Fe implantation with a fluence of 0.50 1017 atoms/cm2 and subsequent thermal annealing produce mainly the ?-FeSi2 phase in the whole thickness of the implanted region. But for the samples with a higher fluence Fe implantation, multiple phases are formed. Significant amount of Fe3Si phase are found at depth intervals of 14 nm and 28 nm from the surface. Initially, as-implanted samples show amorphous Fe3Si formation and further thermal annealing at 500 C for 60 min formed crystalline Fe3Si structures at the same depth intervals. In addition, thermal annealing at 800 C for 60 min restructures the Fe3Si clusters to form FeSi2 and FeSi phases.

  10. Crystal structure of the NaCa(Fe2+, Al, Mn)5[Si8O19(OH)](OH)7 5H2O mineral: A new representative of the palygorskite group

    NASA Astrophysics Data System (ADS)

    Rastsvetaeva, R. K.; Aksenov, S. M.; Verin, I. A.

    2012-01-01

    A specimen of a new representative of the palygorskite-sepiolite family from Aris phonolite (Namibia) is studied by single-crystal X-ray diffraction. The parameters of the triclinic (pseudomonoclinic) unit cell are as follows: a = 5.2527(2) , b = 17.901(1) , c = 13.727(1) , ? = 90.018(3), ? = 97.278(4), and ? = 89.952(3). The structure is solved by the direct methods in space group P bar 1 and refined to R = 5.5% for 4168 | F| > 7?( F) with consideration for twinning by the plane perpendicular to y (the ratio of the twin components is 0.52: 0.48). The crystal chemical formula ( Z = 1) is (Na1.6K0.2Ca0.2)[Ca2(Fe{3.6/2+}Al1.6Mn0.8)(OH)9(H2O)2][(Fe{3.9/2+}Ti0.1)(OH)5(H2O)2][Si16O38(OH)2] 6H2O, where the compositions of two ribbons of octahedra and a layer of Si tetrahedra are enclosed in brackets. A number of specific chemical, symmetrical, and structural features distinguish this mineral from other minerals of this family, in particular, from tuperssuatsiaite and kalifersite, which are iron-containing representatives with close unit cell parameters.

  11. Al-Co-Fe (Aluminium - Cobalt - Iron)

    NASA Astrophysics Data System (ADS)

    Materials Science International Team MSIT

    This document is part of Subvolume A1 'Light Metal Systems. Part 1: Selected Systems from Ag-Al-Cu to Al-Cu-Er' of Volume 11 'Ternary Alloy Systems - Phase Diagrams, Crystallographic and Thermodynamic Data critically evaluated by MSIT' of Landolt-Brnstein - Group IV Physical Chemistry. It provides the data for the ternary system Al-Co-Fe (Aluminium - Cobalt - Iron).

  12. Interfacial Reaction Between CaO-SiO2-MgO-Al2O3 Flux and Fe- xMn- yAl ( x = 10 and 20 mass pct, y = 1, 3, and 6 mass pct) Steel at 1873 K (1600 °C)

    NASA Astrophysics Data System (ADS)

    Kim, Dong Jin; Park, Joo Hyun

    2012-08-01

    This study investigated the interfacial reaction kinetics and related phenomena between CaO-SiO2-MgO-Al2O3 flux and Fe- xMn- yAl ( x = 10 and 20 mass pct, y = 1, 3, and 6 mass pct) steel, which simulates transformation-induced plasticity (TRIP) and twinning-induced plasticity (TWIP) steels at 1873 K (1600 °C). It also examines the effect of changes in the composition of the steel and slag phases on the interfacial reaction rate and the reaction mechanisms. The content of Al and Si in the 1 mass pct Al-containing steel was found to change rapidly within the first 15 minutes of the reaction, but then it remained relatively constant. The content of Al and Si in the 3 to 6 mass pct Al-containing steels, in contrast, changed continuously throughout the entire reaction time. In addition, the content of Mn in the 1 mass pct Al-containing steels initially decreased with increasing time, but the content did not change in the 3 to 6 mass pct Al-containing steels. Furthermore, the mass transfer coefficient of Al, k Al, in the 1 mass pct Al-containing systems was significantly higher than that in other systems; i.e., the k Al can be arranged such that 1 mass pct Al systems >> 3 mass pct Al systems ≥ 6 mass pct Al systems. The compositions of the final slags were close to the saturation lines of the [Mg,Mn]Al2O4 and MgAl2O4 spinels when the slags reacted with 1 mass pct Al and 3 to 6 mass pct Al-containing steels, respectively. These results, which show the effect of Al content on the reaction phenomena, can be explained by the significant increase in the apparent viscosity of the slags that reacted with the 3 to 6 mass pct Al-containing steels. This reaction was likely caused by the precipitation of solid compounds such as MgAl2O4 spinel and CaAl4O7 grossite at locally alumina-enriched areas in the slag phase. This analysis is in good accordance with the combination of Higbie's surface renewal model and the Eyring equation.

  13. Dynamic and static measurements on epitaxial Fe/Si/Fe

    NASA Astrophysics Data System (ADS)

    Kuanr, Bijoy K.; Buchmeier, M.; Buergler, D. E.; Gruenberg, P.; Camley, R.; Celinski, Z.

    2003-07-01

    Strong antiferromagnetic interlayer exchange coupling across an insulating spacer is in increasing demand for high-density magnetic recording. We report here on the interlayer exchange coupling of epitaxial Fe(8 nm)/Si(t)/Fe(10 nm) trilayers as a function of Si thickness studied by ferromagnetic resonance (FMR), Brillouin light scattering, and magneto optic Kerr effect (MOKE) measurement techniques. A very strong antiferromagnetic (AFM) interlayer exchange coupling (>6 erg/cm2) was observed at a spacer Si thickness of 0.7 nm. The bilinear J1 and biquadratic J2 coupling constants were determined from (i) the fitting of the angular variation of the resonance field (Hres) in FMR experiments, (ii) the field variation of the frequencies of the Damon-Eshbach surface modes (both optic and acoustic) in BLS measurements, and (iii) the fitting of longitudinal MOKE hysteresis loops. We obtain a higher Hres along the easy axis than along the hard axis and the magnetizations of the two Fe films are canted. The eightfold-like symmetry of Hres as a function of the angle observed at room temperature is due to the competition between the Fe fourfold anisotropy and AFM interfacial coupling energy. This behavior vanishes at low temperatures due to a strong increase of AFM coupling (especially J2) in comparison to fourfold in-plane anisotropy. From the fitting of the temperature dependent FMR data, we obtain the temperature variation of the bilinear and biquadratic exchange coupling constants. We distinguish the existence of canted magnetization states at resonance by fitting the experimental Hres versus ?H data to the model calculation.

  14. Investigating and engineering spin-orbit torques in heavy metal/Co2FeAl0.5Si0.5/MgO thin film structures

    NASA Astrophysics Data System (ADS)

    Loong, Li Ming; Deorani, Praveen; Qiu, Xuepeng; Yang, Hyunsoo

    2015-07-01

    Current-induced spin-orbit torques (SOTs) have the potential to revolutionize magnetization switching technology. Here, we investigate SOT in a heavy metal (HM)/Co2FeAl0.5Si0.5 (CFAS)/MgO thin film structure with perpendicular magnetic anisotropy (PMA), where the HM is either Pt or Ta. Our results suggest that both the spin Hall effect and the Rashba effect contribute significantly to the effective fields in the Pt underlayer samples. Moreover, after taking the PMA energies into account, current-induced SOT-based switching studies of both the Pt and Ta underlayer samples suggest that the two HM underlayers yield comparable switching efficiency in the HM/CFAS/MgO material system.

  15. Preparation and characterization of highly L2{sub 1}-ordered full-Heusler alloy Co{sub 2}FeAl{sub 0.5}Si{sub 0.5} thin films for spintronics device applications

    SciTech Connect

    Wang Wenhong; Sukegawa, Hiroaki; Shan Rong; Furubayashi, Takao; Inomata, Koichiro

    2008-06-02

    We report the investigation of structure and magnetic properties of full-Heusler alloy Co{sub 2}FeAl{sub 0.5}Si{sub 0.5} (CFAS) thin films grown on MgO-buffered MgO (001) substrates through magnetron sputtering. It was found that single-crystal CFAS thin films with high degree of L2{sub 1} ordering and sufficiently flat surface could be obtained after postdeposition annealing. All the films show a distinct uniaxial magnetic anisotropy with the easy axis of magnetization along the in-plane [110] direction. These results indicate that the use of the MgO buffer for CFAS is a promising approach for achieving a higher tunnel magnetoresistance ratio, and thus for spintronics device applications.

  16. Micromagnetic simulation of critical current density of spin transfer torque switching in a full-Heusler Co2FeAl0.5Si0.5 alloy spin valve nanopillar

    NASA Astrophysics Data System (ADS)

    Huang, H. B.; Ma, X. Q.; Liu, Z. H.; Meng, F. Y.; Shi, S. Q.; Chen, L. Q.

    2013-03-01

    We investigated the critical current density of spin transfer torque switching in a full-Heusler Co2FeAl0.5Si0.5 alloy spin-valve nanopillar through micromagnetic simulations. The simulations explain the experimental results on the resistance versus external magnetic field and yield good agreement with the measured switching behavior. It is shown that different magnitudes of current densities and directions of external magnetic fields give rise to a shift of resistance hysteretic loop and a variable range of switching. We demonstrated that three critical current densities have different slopes with Gilbert damping constant α and spin polarization constant η, indicating that α and η have different contributions to the critical current densities. Furthermore, we found that the area of resistance-current hysteretic loop decreases as the nanopillar size decreases. The domain structures indicated that the magnetization reversals have different switching processes between small and large sizes of pillars.

  17. Structure and stability of Al2Fe and Al5Fe2: First-principles total energy and phonon calculations

    NASA Astrophysics Data System (ADS)

    Mihalkovi?, M.; Widom, M.

    2012-01-01

    We employ first-principles total energy and phonon calculations to address the structure and stability of Al2Fe and Al5Fe2. The observed structure of Al2Fe, which is reported as stable in the assessed Al-Fe phase diagram, is distinguished by an unusually low triclinic symmetry. The initial crystallographic structure determination additionally featured an unusual hole large enough to accommodate an additional atom. Our calculations indicate that the hole must be filled, but predict that the triclinic structure is unstable relative to a simpler tetragonal structure based on the prototype MoSi2. This tetragonal structure is interesting because it is predicted to be nonmagnetic, electrically insulating, and high density, while the triclinic structure is magnetic, metallic, and low density. We reconcile this seeming contradiction by demonstrating a high vibrational entropy that explains why the triclinic structure is stable at high temperatures. Finally, we note that orthorhombic Al5Fe2 is also destabilized by the tetragonal structure but may be stabilized at high temperatures, again by vibrational entropy and partial occupancy associated with the diffusion of Al atoms along channels.

  18. Release of Si from silicon, a ferrosilicon (FeSi) alloy and a synthetic silicate mineral in simulated biological media.

    PubMed

    Herting, Gunilla; Jiang, Tao; Sjstedt, Carin; Odnevall Wallinder, Inger

    2014-01-01

    Unique quantitative bioaccessibility data has been generated, and the influence of surface/material and test media characteristics on the elemental release process were assessed for silicon containing materials in specific synthetic body fluids at certain time periods at a fixed loading. The metal release test protocol, elaborated by the KTH team, has previously been used for classification, ranking, and screening of different alloys and metals. Time resolved elemental release of Si, Fe and Al from particles, sized less than 50 m, of two grades of metallurgical silicon (high purity silicon, SiHG, low purity silicon, SiLG), an alloy (ferrosilicon, FeSi) and a mineral (aluminium silicate, AlSi) has been investigated in synthetic body fluids of varying pH, composition and complexation capacity, simple models of for example dermal contact and digestion scenarios. Individual methods for analysis of released Si (as silicic acid, Si(OH)4) in synthetic body fluids using GF-AAS were developed for each fluid including optimisation of solution pH and graphite furnace parameters. The release of Si from the two metallurgical silicon grades was strongly dependent on both pH and media composition with the highest release in pH neutral media. No similar effect was observed for the FeSi alloy or the aluminium silicate mineral. Surface adsorption of phosphate and lactic acid were believed to hinder the release of Si whereas the presence of citric acid enhanced the release as a result of surface complexation. An increased presence of Al and Fe in the material (low purity metalloid, alloy or mineral) resulted in a reduced release of Si in pH neutral media. The release of Si was enhanced for all materials with Al at their outermost surface in acetic media. PMID:25225879

  19. Release of Si from Silicon, a Ferrosilicon (FeSi) Alloy and a Synthetic Silicate Mineral in Simulated Biological Media

    PubMed Central

    Herting, Gunilla; Jiang, Tao; Sjstedt, Carin; Odnevall Wallinder, Inger

    2014-01-01

    Unique quantitative bioaccessibility data has been generated, and the influence of surface/material and test media characteristics on the elemental release process were assessed for silicon containing materials in specific synthetic body fluids at certain time periods at a fixed loading. The metal release test protocol, elaborated by the KTH team, has previously been used for classification, ranking, and screening of different alloys and metals. Time resolved elemental release of Si, Fe and Al from particles, sized less than 50 m, of two grades of metallurgical silicon (high purity silicon, SiHG, low purity silicon, SiLG), an alloy (ferrosilicon, FeSi) and a mineral (aluminium silicate, AlSi) has been investigated in synthetic body fluids of varying pH, composition and complexation capacity, simple models of for example dermal contact and digestion scenarios. Individual methods for analysis of released Si (as silicic acid, Si(OH)4) in synthetic body fluids using GF-AAS were developed for each fluid including optimisation of solution pH and graphite furnace parameters. The release of Si from the two metallurgical silicon grades was strongly dependent on both pH and media composition with the highest release in pH neutral media. No similar effect was observed for the FeSi alloy or the aluminium silicate mineral. Surface adsorption of phosphate and lactic acid were believed to hinder the release of Si whereas the presence of citric acid enhanced the release as a result of surface complexation. An increased presence of Al and Fe in the material (low purity metalloid, alloy or mineral) resulted in a reduced release of Si in pH neutral media. The release of Si was enhanced for all materials with Al at their outermost surface in acetic media. PMID:25225879

  20. Fabrication and Analysis of the Wear Properties of Hot-Pressed Al-Si/SiCp + Al-Si-Cu-Mg Metal Matrix Composite

    NASA Astrophysics Data System (ADS)

    Bang, Jeongil; Oak, Jeong-Jung; Park, Yong Ho

    2015-12-01

    The aim of this study was to characterize microstructures and mechanical properties of aluminum metal matrix composites (MMC's) prepared by powder metallurgy method. Consolidation of mixed powder with gas atomized Al-Si/SiCp powder and Al-14Si-2.5Cu-0.5Mg powder by hot pressing was classified according to sintering temperature and sintering time. Sintering condition was optimized using tensile properties of sintered specimens. Ultimate tensile strength of the optimized sintered specimen was 228 MPa with an elongation of 5.3% in longitudinal direction. In addition, wear properties and behaviors of the sintered aluminum-based MMC's were analyzed in accordance with vertical load and linear speed. As the linear speed and vertical load of the wear increased, change of the wear behavior occurred in order of oxidation of Al-Si matrix, formation of C-rich layer, Fe-alloying to matrix, and melting of the specimen

  1. Fabrication and Analysis of the Wear Properties of Hot-Pressed Al-Si/SiCp + Al-Si-Cu-Mg Metal Matrix Composite

    NASA Astrophysics Data System (ADS)

    Bang, Jeongil; Oak, Jeong-Jung; Park, Yong Ho

    2016-01-01

    The aim of this study was to characterize microstructures and mechanical properties of aluminum metal matrix composites (MMC's) prepared by powder metallurgy method. Consolidation of mixed powder with gas atomized Al-Si/SiCp powder and Al-14Si-2.5Cu-0.5Mg powder by hot pressing was classified according to sintering temperature and sintering time. Sintering condition was optimized using tensile properties of sintered specimens. Ultimate tensile strength of the optimized sintered specimen was 228 MPa with an elongation of 5.3% in longitudinal direction. In addition, wear properties and behaviors of the sintered aluminum-based MMC's were analyzed in accordance with vertical load and linear speed. As the linear speed and vertical load of the wear increased, change of the wear behavior occurred in order of oxidation of Al-Si matrix, formation of C-rich layer, Fe-alloying to matrix, and melting of the specimen

  2. Geometry controls the stability of FeSi14.

    PubMed

    Chauhan, Vikas; Abreu, Marissa Baddick; Reber, Arthur C; Khanna, Shiv N

    2015-06-28

    First-principles theoretical studies have been carried out to investigate the stability of Sin cages impregnated with a Fe atom. It is shown that FeSi9, FeSi11, and FeSi14 clusters exhibit enhanced local stability as seen through an increase in Si binding energy, Fe embedding energy, the gap between the Highest Occupied Molecular Orbital (HOMO) and the Lowest Unoccupied Molecular Orbital (LUMO), and the Ionization Potential (IP). The conventional picture for the stability of such species combines an assumption of electron precise bonding with the 18-electron rule; however, we find this to be inadequate to explain the enhanced stability in FeSi11 and FeSi14 because the d-band is filled for all FeSin clusters for n? 9. FeSi14 is shown to be the most stable due to a compact and highly symmetric Si14 cage with octahedral symmetry that allows better mixing between Fe 3d- and Si 3p-electronic states. PMID:26013325

  3. Current-induced magnetization switching in Fe 3Si/FeSi 2 superlattices

    NASA Astrophysics Data System (ADS)

    Hirakawa, Shin-ichi; Sakai, Ken-ichiro; Sonoda, Takayuki; Takeda, Kaoru; Yoshitake, Tsuyoshi

    Fe3Si/FeSi2 superlattices were prepared on Si(111) by facing targets direct-current sputtering, and current-induced magnetization switching in current-perpendicular-to-plane (CPP) geometry was studied for the antiferromagnetically coupled films. The electrical resistance was alternatively changed for the injected current. The large and small vales were in agreement with those of the films with antiferromagnetic and ferromagnetic interlayer-couplings. The change in the electrical conductivity for the injected current should be due to the change in the interlayer coupling. Under a magnetic field, the electrical resistivity was hardly changed for the injected current since the interlayer-coupling is fixed to be ferromagnetic.

  4. The mechanical properties of FeAl

    SciTech Connect

    Baker, I.; George, E.P.

    1996-12-31

    Only in the last few years has progress been made in obtaining reproducible mechanical properties data for FeAl. Two sets of observations are the foundation of this progress. The first is that the large vacancy concentrations that exist in FeAl at high temperature are easily retained at low temperature and that these strongly affect the low-temperature mechanical properties. The second is that RT ductility is adversely affected by water vapor. Purpose of this paper is not to present a comprehensive overview of the mechanical properties of FeAl but rather to highlight our understanding of key phenomena and to show how an understanding of the factors which control the yield strength and fracture behavior has followed the discovery of the above two effects. 87 refs, 9 figs.

  5. Nanocrystalline FeAl intermetallics obtained in mechanically alloyed Fe 50Al 40Ni 10 powder

    NASA Astrophysics Data System (ADS)

    Hadef, F.; Otmani, A.; Djekoun, A.; Grenche, J. M.

    2011-06-01

    B2-Fe 47Al 53 intermetallics has been produced by mechanical alloying in a planetary ball mill, using elemental Fe, Al and Ni powder mixture. The microstructural and magnetic properties of the mechanically alloyed Fe 50Al 40Ni 10 powdered samples were investigated by X-ray diffraction and 57Fe Mssbauer spectrometry at 300 and 77 K. As resulted from the X-ray diffraction studies, the ordered B2 structure was formed in the Fe 50Al 40Ni 10 powder, together with the bcc ? i-Fe(Al, Ni) ( i = 1, 2) solid solutions. Further milling led to a partial disordering of B2-Fe 47Al 53; it has undergone an order-disorder transition which is characterized by an expansion of the volume ? a0 (lattice disorder) and a magnetic transition from the paramagnetic to ferromagnetic state which is characterized by strong ferromagnetic interactions in the alloy. The nanocrystalline bcc ? i-Fe(Al, Ni) solid solution was ferromagnetic with a mean crystallite size of 6 nm.

  6. Melting, Processing, and Properties of Disordered Fe-Al and Fe-Al-C Based Alloys

    NASA Astrophysics Data System (ADS)

    Satya Prasad, V. V.; Khaple, Shivkumar; Baligidad, R. G.

    2014-09-01

    This article presents a part of the research work conducted in our laboratory to develop lightweight steels based on Fe-Al alloys containing 7 wt.% and 9 wt.% aluminum for construction of advanced lightweight ground transportation systems, such as automotive vehicles and heavy-haul truck, and for civil engineering construction, such as bridges, tunnels, and buildings. The melting and casting of sound, porosity-free ingots of Fe-Al-based alloys was accomplished by a newly developed cost-effective technique. The technique consists of using a special flux cover and proprietary charging schedule during air induction melting. These alloys were also produced using a vacuum induction melting (VIM) process for comparison purposes. The effect of aluminum (7 wt.% and 9 wt.%) on melting, processing, and properties of disordered solid solution Fe-Al alloys has been studied in detail. Fe-7 wt.% Al alloy could be produced using air induction melting with a flux cover with the properties comparable to the alloy produced through the VIM route. This material could be further processed through hot and cold working to produce sheets and thin foils. The cold-rolled and annealed sheet exhibited excellent room-temperature ductility. The role of carbon in Fe-7 wt.% Al alloys has also been examined. The results indicate that Fe-Al and Fe-Al-C alloys containing about 7 wt.% Al are potential lightweight steels.

  7. On the crack growth resistance and strength of the B2 iron aluminides Fe-40Al, Fe-45Al, and Fe-10Ni-40Al (at. %)

    SciTech Connect

    Schneibel, J.H.; Maziasz, P.J.

    1994-09-01

    The crack growth resistance and yield strength of the B2 iron aluminides Fe-40Al, Fe-45Al, are Fe-10Ni-40Al (at. %) have been investigated at room temperature laboratory air. After fast cooling from 1273 K, Fe-45Al and Fe-10Ni-40Al are much stronger than Fe-40Al, and exhibit considerably lower crack growth resistance. The crack growth resistance decreases with decreasing crack propagation velocity. Low crack propagation velocities favor intergranular fracture, whereas high velocities can lead to significant contributions from transgranular fracture. Boron additions to Fe-40Al and Fe-10Ni-40Al improve the crack growth resistance, reduce its dependence on the crack propagation velocity, and cause the path to be predominantly transgranular. In a plot of fracture toughness versus yield strength, the properties of the iron aluminides are similar to those of typical aluminum alloys.

  8. The molar volume of cubic garnets in the system SiO2-Al2O3-TiO2-Fe2O3-Cr2O3-FeO-MnO-MgO-CaO-Na2O

    NASA Astrophysics Data System (ADS)

    Hamecher, E. A.; Antoshechkina, P. M.; Ghiorso, M. S.; Asimow, P. D.

    2012-12-01

    Garnet is a critical phase that controls major and trace element partitioning at pressures above ~3 GPa during partial melting of the Earth's upper mantle. A molar volume model is calibrated for cubic garnets (space group Ia3d) in the oxide system listed in the title. This model and a recent calibration of spinel molar volume (Hamecher et al., in press, CMP) will be used in calibration of thermodynamic activity-composition models of garnet and pyroxene solid solutions. The activity and molar volume models will be incorporated into the next generation MELTS (Ghiorso & Sack, 1995, CMP) model, xMELTS. A new garnet volume model calibrated with recent in situ high-P, T diffraction data is crucial for accurately modeling key mineralogical transitions in the mantle, e.g., the spinel-garnet transition and the mantle transition zone. Above 5 GPa a majorite component is an essential part of any thermodynamic model of mantle garnets, which to be useful must accurately predict garnet stability with respect to spinel, pyroxene, perovskites, and melt. Our model system contains nine independent end members: Ca3Al2Si3O12, Mg3Al2Si3O12, Fe2+3Al2Si3O12, Mg3Cr2Si3O12, Mg3Fe3+2Si3O12, Mn3Al2Si3O12, Na2(MgSi2)Si3O12, Mg3(TiMg)Si3O12, and cubic majorite component Mg3(MgSi)Si3O12. An inclusive set of end-member components is formed by linear combinations of these explicit end members. Approximately 950 published X-ray diffraction experiments performed on garnets at ambient and in situ high-P, T conditions are used to calibrate end-member equations of state and an excess volume model for this system. Optimal values of the bulk modulus and its pressure derivative are obtained by analyzing published compression and/or ultrasonic data for the end members for which such studies exist; for other end members, density functional theory results are used. For any cubic garnet in this chemical system, the model molar volume is obtained by adding excess volume terms to a linear combination of the nine independent end-member volumes. In the first step of our least squares fitting procedure we calculate volumes of the explicit end members as a function of P and T using the high-T Vinet equation of state. We allow standard state volumes and coefficients of thermal expansion to vary for those independent end members where pure compositional data exist, either for the phase itself or for an appropriate dependent end member. For each dependent end member for which there are data, we calculate the volume of reaction for formation of the phase from the independent end members, ?V. We then fit the binary and mixed composition data, using the singular value analysis method of Lawson & Hanson (1974) to ensure that the calibrated combinations of excess parameters obey the nine ?V constraints from the first step. A key plausibility check on the model results from comparing the predicted T-dependence of the bulk modulus to high-T ultrasonic results that were not used in the calibration. The calculated pressure of the spinel-garnet transition using the new volume models is compared to that obtained with the previous models. The implications our model has for the density of the lithospheric mantle are explored.

  9. Thermodynamic constraints on Fe and Si carbide stabilities in the Earth's mantle

    NASA Astrophysics Data System (ADS)

    Golubkova, A.; Schmidt, M. W.; Connolly, J. A.

    2013-12-01

    The ambient Earth mantle is metal saturated at ? 250 km, its redox state is buffered close to iron-wustite (IW). At such oxygen fugacity (fO2), oxidized forms of carbon are not stable; thus, the presence of oxidized carbon, as represented by CO2-rich fluid inclusions in diamonds and volatile-rich deep-seated magmas (e.g. kimberlites), indicates a local increase in fO2. Major forms of C within sublithospheric or deep mantle are diamond/graphite or carbides (mostly cementite, Fe3C and moissanite, SiC). Such carbides are reported from mantle-derived rocks and inclusions in diamonds. Furthermore, SiC and associated metallic Fe and Fe-silicides are found in podiform chromitites in ophiolites [Trumbull et al. 2009, Lithos]. Previous experiments on the redox stability of SiC have demonstrated that moissanite becomes stable at fO2 below IW to at least 9 GPa [Ulmer et al. 1998, Neues Jahrb Min]. Since Fe- and C-speciation is strongly fO2 dependent, we calculated ranges of redox conditions allowing for Fe and Si carbides within typical mantle assemblages. We thus added thermodynamic parameters and solution models for alloys (Fe-Si-C and Fe-Cr), stoichiometric compounds (Fe-silicides) and carbides to a thermodynamic database for silicates and oxides [Holland & Powell 2011, J. metamorphic Geol.]. Calculated T-fO2 diagrams indicate that cementite coexists with ol, opx, and gph/diam at ?logfO2[IW] ? -1 at 2 GPa and ? IW at 10 GPa. With decreasing fO2, Fe2+ in mantle silicates is progressively reduced while the XMg of silicates increases, the latter reaching unity at the conditions for SiC stability. Reduced Fe-bearing species occur in the sequence Fe3C ? ?-FeSiC alloy ? ?-FeSiC alloy ? ?-FeSi. For the dominant ?-alloy, Si content increases with decreasing fO2 to XSi ~ 0.3 (molar), thereafter stoichiometric FeSi becomes stable. SiC appears at ?logfO2[IW] ? -7.5 at 2 GPa and 1300oC and -7.0 at 10 GPa and 1500oC. Chromite solid solution is reduced to ?-Fe-Cr alloy at lower fO2 than IW, but is, nonetheless, stable at conditions that are ~ 4 log units more oxidizing than SiC. Based on these phase relations, the variety of Fe-, Si- and C-bearing phases in mantle-derived inclusions can only be explained by extraordinary mantle heterogeneity in terms of redox conditions. Subducted organic sediments are a possible source for such ultra-reducing environments, a hypothesis that is consistent with the light C isotopic composition of moissanite [Trumbull et al., 2009]. The temperature of interaction between mantle minerals and recycled material must be low (<800-1000oC) to prevent the homogenization of ultra-reduced regions by diffusion. Moissanite is reported in podiform chromitites, but our analysis indicates that chromite and SiC do not stably coexist. Therefore, we attribute natural SiC + chromite assemblages to kinetic inhibition. The involvement of recycled components transported by fluids into the source region of deeply generated magmas has been proposed based on isotopic and trace-element chemistry. Evidently, the interaction between mantle peridotites and subducted material at different P-T-fO2 results in the formation of mantle regions with highly contrasting redox environments. The change of Fe and C redox states in such regions is one of important mechanisms initiating melting or freezing within the mantle [Rohrbach & Schmidt 2011, Nature].

  10. Thermodynamic modeling of non-ideal mineral-fluid equilibria in the system Si-Al-Fe-Mg-Ca-Na-K-H-O-Cl at elevated temperatures and pressures: Implications for hydrothermal mass transfer in granitic rocks

    NASA Astrophysics Data System (ADS)

    Dolej, David; Wagner, Thomas

    2008-01-01

    We present the results of thermodynamic modeling of fluid-rock interaction in the system Si-Al-Fe-Mg-Ca-Na-H-O-Cl using the GEM-Selektor Gibbs free energy minimization code. Combination of non-ideal mixing properties in solids with multicomponent aqueous fluids represents a substantial improvement and it provides increased accuracy over existing modeling strategies. Application to the 10-component system allows us to link fluid composition and speciation with whole-rock mineralogy, mass and volume changes. We have simulated granite-fluid interaction over a wide range of conditions (200-600 C, 100 MPa, 0-5 m Cl and fluid/rock ratios of 10-2-104) in order to explore composition of magmatic fluids of variable salinity, temperature effects on fluid composition and speciation and to simulate several paths of alteration zoning. At low fluid/rock ratios (f/r) the fluid composition is buffered by the silicate-oxide assemblage and remains close to invariant. This behavior extends to a f/r of 0.1 which exceeds the amount of exsolved magmatic fluids controlled by water solubility in silicate melts. With increasing peraluminosity of the parental granite, the Na-, K- and Fe-bearing fluids become more acidic and the oxidation state increases as a consequence of hydrogen and ferrous iron transfer to the fluid. With decreasing temperature, saline fluids become more Ca- and Na-rich, change from weakly acidic to alkaline, and become significantly more oxidizing. Large variations in Ca/Fe and Ca/Mg ratios in the fluid are a potential geothermometer. The mineral assemblage changes from cordierite-biotite granites through two-mica granites to chlorite-, epidote- and zeolite-bearing rocks. We have carried out three rock-titration simulations: (1) reaction with the 2 m NaCl fluid leads to albitization, chloritization and desilication, reproducing essential features observed in episyenites, (2) infiltration of a high-temperature fluid into the granite at 400 C leads to hydrolytic alteration commencing with alkali-feldspar breakdown and leading to potassic, phyllic and argillic assemblages; this is associated with reduction and iron metasomatism as observed in nature and (3) interaction with a multicomponent fluid at 600 C produces sodic-calcic metasomatism. Na, Ca and Fe are the most mobile elements whereas immobility of Al is limited by f/r ? 400. All simulations predict a volume decrease by 3.4-5.4%, i.e., porosity formation at f/r < 30. At higher fluid/rock ratios simulation (2) produces a substantial volume increase (59%) due to mineral precipitation, whereas simulation (3) predicts a volume decrease by 49% at the advanced albitization-desilication stage. Volume changes closely correlate with mass changes of SiO2 and are related to silica solubility in fluids. The combined effects of oxygen fugacity, fluid acidity and pH for breakdown of aqueous metal complexes and precipitation of ore minerals were evaluated by means of reduced activity products. Sharp increases in saturation indexes for oxidative breakdown occur at each alteration zone whereas reductive breakdown or involvement of other chloride complexes favor precipitation at high fluid/rock ratios only. Calculations of multicomponent aqueous-solid equilibria at high temperatures and pressures are able to accurately predict rock mineralogy and fluid chemistry and are applicable to diverse reactive flow processes in the Earth's crust.

  11. Boron strengthening in FeAl

    SciTech Connect

    Baker, I.; Li, X.; Xiao, H.; Klein, O.; Nelson, C.; Carleton, R.L.; George, E.P.

    1998-11-01

    The effect of boron on the strength of B2-structured FeAl is considered as a function of composition, grain size and temperature. Boron does not affect the concentrations of antisite atoms or vacancies present, with the former increasing and the latter decreasing with increasing deviation from the stoichiometric composition. When vacancies are absent, the strength increase per at. % B per unit lattice strain, {Delta}{sigma}/({Delta}c x {epsilon}) increases with increasing aluminum concentration, but when vacancies are present (>45 at. % Al), {Delta}{sigma}/({Delta}c x {epsilon}) decreases again. Boron increases grain size strengthening in FeAl. B strengthening is roughly independent of temperature up to the yield strength peak but above the point, when diffusion-assisted deformation occurs, boron strengthening increases dramatically.

  12. Roll Casting of Al-25%Si

    NASA Astrophysics Data System (ADS)

    Haga, Toshio; Harada, Hideto; Watari, Hisaki

    2011-05-01

    Strip casting of Al-25%Si strip was tried using an unequal diameter twin roll caster. The diameter of the lower roll (large roll) was 1000 mm and the diameter of the upper roll (small roll) was 250 mm. Roll material was mild steel. The sound strip could be cast at the speeds ranging from 8 m/min to 12 m/min. The strip did not stick to the roll without the parting material. The primary Si, which existed at centre area of the thickness direction, was larger than that which existed at other area. The size of the primary Si was smaller than 0.2 mm. Eutectic Si was smaller 5 ?m. The as-cast strip was ranging from 2 mm to 3 mm thick and its width was 100 mm. The as-cast strip could be hot rolled down to 1 mm. The hot rolled strip was cold rolled. The primary Si became smaller and the pore occurred around the primary Si after the rolling.

  13. Hillesheimite, (K,Ca,□)2(Mg,Fe,Ca,□)2[(Si,Al)13O23(OH)6](OH) · 8H2O, a new phyllosilicate mineral of the Günterblassite group

    NASA Astrophysics Data System (ADS)

    Chukanov, N. V.; Zubkova, N. V.; Pekov, I. V.; Belakovskiy, D. I.; Schüller, W.; Ternes, B.; Blass, G.; Pushcharovsky, D. Yu.

    2013-12-01

    A new mineral, hillesheimite, has been found in the Graulai basaltic quarry, near the town of Hillesheim, the Eifel Mountains, Rhineland-Palatinate (Rheinland-Pfalz), Germany. It occurs in the late assemblage comprising nepheline, augite, fluorapatite, magnetite, perovskite, priderite, götzenite, lamprophyllite-group minerals, and åkermanite. Colorless flattened crystals of hillesheimite reaching 0.2 × 1 × 1.5 mm in size and aggregates of the crystals occur in miarolitic cavities in alkali basalt. The mineral is brittle, with Mohs' hard-ness 4. Cleavage is perfect parallel to (010) and distinct on (100) and (001). D calc = 2.174 g/cm3, D meas = 2.16(1) g/cm3. IR spectrum is given. Hillesheimite is biaxial (-), α = 1.496(2), β = 1.498(2), γ = 1.499(2), 2 V meas = 80°. The chemical composition (electron microprobe, mean of 4 point analyses, H2O determined from structural data, wt %) is as follows: 0.24 Na2O, 4.15 K2O, 2.14 MgO, 2.90 CaO, 2.20 BaO, 2.41 FeO, 15.54 Al2O3, 52.94 SiO2, 19.14 H2O, total is 101.65. The empirical formula is: K0.96Na0.08Ba0.16Ca0.56Mg0.58Fe{0.37/2+}[Si9.62Al3.32O23(OH)6][(OH)0.82(H2O)0.18] · 8H2O. The crystal structure has been determined from X-ray single-crystal diffraction data, R = 0.1735. Hillesheimite is orthorhombic, space group Pmmn, the unit-cell dimensions are: a = 6.979(11), b = 37.1815(18), c = 6.5296(15) Å; V=1694(3) Å3, Z = 2. The crystal structure is based on the block [(Si,Al)13O25(OH)4] consisting of three single tetrahedral layers linked via common vertices and is topologically identical to the triple layers in günterblassite and umbrianite. The strong reflections [ d Å ( I %)] in the X-ray powder diffraction pattern are: 6.857(58), 6.545(100), 6.284(53), 4.787(96), 4.499(59), 3.065(86), 2.958(62), 2.767(62). The mineral was named after its type locality. Type specimens are deposited in the Fersman Mineralogical Museum, Russian Academy of Sciences, Moscow, registration number 4174/1.

  14. Magnetic phase transitions in Y1-xTbxMn6Sn6, La1-xSmxMn2Si2, Lu2(Fe1-xMnx)17, and La(Fe0.88SixAl0.12-x)13 intermetallic compounds

    NASA Astrophysics Data System (ADS)

    Mushnikov, N. V.; Kuchin, A. G.; Gerasimov, E. G.; Terentev, P. B.; Gaviko, V. S.; Serikov, V. V.; Kleinerman, N. M.; Vershinin, A. V.

    2015-06-01

    Magnetic properties have been measured for the Y1-xTbxMn6Sn6, La1-xSmxMn2Si2, Lu2(Fe1-xMnx)17, and La(Fe0.88SixAl0.12-x)13 systems which show up transitions from antiferromagnetic to ferromagnetic state upon changing concentration of the constituents or application of magnetic field. We determined the concentrations and temperatures of the magnetic phase transitions and plotted magnetic phase diagrams. Near a critical concentration, the AF-F transition can be realized in low magnetic fields, which makes these compounds attractive for magnetothermal applications. Using the data of the magnetization measurement, we determined the isothermal magnetic entropy change in a wide temperature range. All the studied systems have a layered magnetic structure with the positive intralayer exchange interaction and the interlayer exchange integrals of different signs depending on the composition and temperature. For the compounds La(Fe0.88SixAl0.12-x)13 with the cubic crystal structure, the origin of formation of a layered magnetic structure is discussed based on the data of Mssbauer studies which revealed a difference in the local surrounding of resonant atoms in the compounds with different magnetic orders.

  15. Constitution of the Moon: 1. Assessment of thermodynamic properties and reliability of phase relation calculations in the FeO-MgO-Al2O3-SiO2 system

    NASA Astrophysics Data System (ADS)

    Fabrichnaya, O. B.; Kuskov, O. L.

    1994-06-01

    The thermodynamic functions of minerals in the FeO-MgO-Al2O3-SiO2 (FMAS) system have been assessed using phase equilibria, equations of state and calorimetric data. Phase equilibria in this system have been calculated using ideal, symmetric and asymmetric models of solid solution for minerals to obtain KD of exchange reactions consistent with experimental data. A symmetric model for olivine (Wol = 10 800 J mol-1), spinel (Wsp = 1300 J mol-1) and pyroxene (WFeAlopx = WAlFeopx = -3383 - 2.35T - 0.4723P) and an asymmetric model for garnet (WFeMggr = 230 + 0.01P, WMgFegr = 3720 + 0.06P) were recommended, as these mixing parameters provide a better agreement for the calculated phase equilibria with the totality of experimental data. The THERMOSEISM database which includes experimental and assessed data on thermodynamic and thermoelastic properties (bulk modulus and its pressure derivative, thermal expansion, heat capacity, volume, Debye temperature, enthalpy of formation, entropy and mixing parameters of solid solutions), has been obtained for calculation of mineral assemblages at high pressure and temperature and for the further application to the modelling of the mineral composition of the lunar mantle.

  16. Secondary Al-Si-Mg High-pressure Die Casting Alloys with Enhanced Ductility

    NASA Astrophysics Data System (ADS)

    Bsch, Dominik; Pogatscher, Stefan; Hummel, Marc; Fragner, Werner; Uggowitzer, Peter J.; Gken, Mathias; Hppel, Heinz Werner

    2015-03-01

    Al-Si-Mg-based secondary cast alloys are attractive candidates for thin-walled high-pressure die castings for applications in the transport industry. The present study investigates the effect of manganese additions at high cooling rates on microstructure, mechanical properties, and on the dominating fracture mechanisms of alloy AlSi10Mg with an elevated iron concentration. Systematic variations of the Mn content from 0.20 to 0.85 wt pct at a constant Fe content of 0.55 wt pct illustrate the key changes in type, phase fraction, and shape of the Fe-containing intermetallic phases, and the corresponding influence on the alloy's ductility. For high-pressure die casting (HPDC), an optimal range of the Mn content between 0.40 and 0.60 wt pct, equivalent to a Mn/Fe ratio of approximately 1, has been identified. At these Mn and Fe contents, the high cooling rates obtained in HPDC result in the formation of fine and homogeneously distributed ?-Al15(Fe,Mn)3Si2 phase, and crack initiation is transferred from AlFeSi intermetallics to eutectic silicon. The study interprets the microstructure-property relationship in the light of thermodynamic calculations which reveal a significant increase in undercooling of the ?-Al15(Fe,Mn)3Si2 phase with increased Mn content. It concludes that the interdependence of the well-defined Mn/Fe ratio and the high cooling rate in HPDC can generate superior ductility in secondary AlSi10Mg cast alloys.

  17. 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.

  18. Characterization of Dendritic Microstructure, Intermetallic Phases, and Hardness of Directionally Solidified Al-Mg and Al-Mg-Si Alloys

    NASA Astrophysics Data System (ADS)

    Brito, Crystopher; Costa, Thiago A.; Vida, Talita A.; Bertelli, Felipe; Cheung, No; Spinelli, Jos Eduardo; Garcia, Amauri

    2015-08-01

    Despite the widespread application of Al-Mg-Si alloys, especially in the automotive industry, interrelations of solidification thermal parameters (cooling rate and growth rate), microstructure, and hardness are not properly established. For instance, the control of the scale of the microstructure on both Al-Mg and Al-Mg-Si alloys by adequate pre-programming of the solidification thermal parameters remains a task to be accomplished. In the present study, the directional solidification (DS) of these alloys under unsteady-state solidification conditions is investigated in an attempt to characterize the evolution of microstructural features, macrosegregation, and hardness as a function of local solidification thermal parameters along the DS castings length. Silicon addition to the Al-Mg alloy was found not to affect the sizes of primary and secondary dendrite arm spacings, but induced the onset of tertiary dendritic branches and affected also the size and distribution of intermetallic particles within the interdendritic regions. The Al-Mg-Si alloy is characterized by a more complex arrangement of phases, including binary ( ?-Al + Mg2Si) and refined ternary ( ?-Al + Mg2Si + AlFe(Si) eutectic mixtures. As a consequence, a higher Vickers hardness profile is shown to be associated with the ternary Al-Mg-Si alloy DS casting. For both alloys examined, hardness is shown to increase with the increase in the microstructural spacing according to Hall-Petch type equations.

  19. Thermal transformations in mechanically alloyed Fe-Zn-Si materials

    NASA Astrophysics Data System (ADS)

    Uwakweh, O.; Jordan, A.; Maziasz, P.

    2000-11-01

    The ball milling of elemental powders corresponding to ? (Fe3Zn10)+0.12 wt pct Si; ?1 (Fe5Zn21) + 0.12 wt pct Si; ? (FeZn7)+0.12 wt pct Si; and ? (FeZn13)+0.12 wt pct Si composition ratios yields crystalline, mechanically alloyed phases. Differential scanning calorimetry (DSC) measurements of these materials show that they evolve differently, with well-defined characteristic stages. The activation energies for processes corresponding to these stages, based on kinetic analyses, are determined and correlated to microstructural evolvements. The processes occurring during the first stage below 250 C, for all of the materials studied using X-ray diffraction (XRD) analysis, are associated with release of strain, recovery, and limited atomic diffusion. The activation energies for recovery processes are 120 kJ/mole for the ?+0.12 wt pct Si, 131 kJ/mole for ?+0.12 wt pct Si, and 96 kJ/mole for ?+0.12 wt pct Si alloys. At higher temperatures, recrystallization and other structural transformations occur with activation energies of 130 and 278 kJ/mole for ?+0.12 wt % Si; of 161 kJ/mole for ?1+0.12 wt pct Si; of 167 and 244 kJ/mole for ?+0.12 wt pct Si; and of 641 kJ/mole for the ?+0.12 wt pct Si. In addition, a eutectic reaction at 420 C3 C, corresponding to the Zn-Si system, and a melting of Zn in Fe-Zn systems are observed for the ?+0.12 wt pct Si material. The relation of FeSi formation in the Sandelin process is discussed.

  20. The mechanical properties of FeAl

    SciTech Connect

    Baker, I.; George, E.P.

    1999-07-01

    In the last few years, considerable progress has been made in obtaining reproducible mechanical properties data for binary FeAl alloys. Two sets of observations are the foundation of this progress. The first is that the large equilibrium vacancy concentrations that exist in FeAl at high temperature are easily retained during cooling, and that these strongly affect the low-temperature mechanical properties. The second is that room-temperature ductility is adversely affected by water vapor. The purpose of this paper is to highlight their understanding of key phenomena and to show how an understanding of the factors which control the yield strength and fracture behavior has followed from the discovery of the above two effects. 94 refs., 8 figs.

  1. (Fe,Al)-bearing post-perovskite in the Earth's lower mantle

    NASA Astrophysics Data System (ADS)

    Mao, Zhu; Lin, Jung-Fu; Yang, Jing; Bian, Hui; Liu, Jin; Watson, Heather C.; Huang, Shu; Chen, Jiuhua; Prakapenka, Vitali B.; Xiao, Yuming; Chow, Paul

    2014-10-01

    The combined effects of Fe and Al on the electronic spin and valence states as well as the equation of state (EoS) of post-perovskite have been investigated using synchrotron X-ray diffraction and Mössbauer spectroscopy in high-pressure diamond anvil cells. Two post-perovskite samples (Mg0.6Fe0.15Al0.5Si0.75O3 and Mg0.66Fe0.13Al0.28Si0.86O3) were synthesized at approximately 165 GPa and 2200-2500 K, and were subsequently investigated for these properties at 114-170 GPa and 300 K. Analyses of the high-pressure Mössbauer spectra show that Fe2+ and Fe3+ occupy the large bipolar prismatic sites in both of our samples and remain in the high-spin state at ˜165-168 GPa and 300 K. Combining the Mössbauer results with the obtained pressure-volume relationship from X-ray diffraction, we have found that the unit cell volume of post-perovskite can be significantly affected by the spin and valence states of Fe and the Al substitution. Mg0.6Fe0.15Al0.5Si0.75O3-PPv with the predominantly high-spin Fe2+ (˜95%) and a greater amount of Al has a unit cell volume similar to that of Mg0.66Fe0.13Al0.28Si0.86O3-PPv in which ˜65% of Fe is in the high-spin Fe3+ state. Our results are used together with previous results regarding the EoS parameters in Fe-bearing perovskite and post-perovskite to model the density and bulk sound velocity variation between perovskite and post-perovskite in the D layer, in which the enrichment of Fe and Al can produce an increase in density but substantially reduce the bulk sound velocity across the phase transition. That is, the combined effect of Fe and Al leads to an anti-correlation between the enhanced density and the reduced bulk sound velocity at the pressure condition of the lowermost mantle. Our results indicate that (Fe,Al)-rich silicate post-perovskite existing in the D region would be shown as a relatively high-density and low-velocity region in deep-mantle seismic observations.

  2. Measurement and Modeling of the Production of He, Ne, and AR from Mg, Al, Si, Fe, and NI in an Artificial Iron Meteoroid Irradiated Isotropically with 1.6 GeV Protons

    NASA Astrophysics Data System (ADS)

    Busemann, H.; Wieler, R.; Leya, I.; Lange, H.-J.; Michel, R.; Meltzow, B.; Herpers, U.

    1995-09-01

    The production by GCR protons of He, Ne and Ar isotopes from their main target elements was investigated in a simulation experiment [1] by irradiating a 20-cm diameter iron sphere isotropically with 1.6 GeV protons. The model-meteoroid contained, among other targets, pure Mg, Al, Si, Fe, and Ni foils at various depths in central bores. Radionuclide production in these targets was measured by gamma-spectrometry. Stable He, Ne, and Ar isotopes were measured by mass spectrometry. These latter results and the ^22Na data are reported here. As in our earlier simulation with a 50-cm diameter gabbro sphere irradiated with 1.6 GeV protons [2], the present experiment simulates the exposure of meteoroids to galactic protons in space within about 20%, if normalized to the same number of particles. Some systematic deviations are attributed to differences between the monoenergetic irradiation and the exposure to the GCR spectrum and to resulting differences between the secondary particle fields. A comparison of the new production rates with those obtained in the gabbro sphere [2] clearly exhibits the influence of bulk chemical composition on production rates which was discovered earlier by Begemann and Schultz [3] in stony irons. Model calculations of the production of He, Ne, Ar, and ^22Na were performed for all artificial iron and stony meteoroids irradiated by our collaboration [2, 4, 5, this work]. Production rates were calculated from depth-dependent p- and n-spectra derived by Monte Carlo techniques using the HERMES code system [6] and from cross sections for the relevant nuclear reactions. For p-induced reactions all available experimental thin-target cross sections were used [2]. Cross sections for n-induced reactions were calculated by the new AREL code [7] which is a relativistic version of the hybrid model of preequilibrium reactions [8]. In addition to these a priori calculations a posteriori model calculations were performed. Theoretical cross sections for n-induced reactions were improved by a least square fitting procedure adjusting the calculated production rates to all experimental ones from the simulation experiments. The simultanous interpretation of rare gas production rates measured in artificial meteoroids of different radii and bulk chemical composition irradiated by 600 MeV and 1.6 GeV protons results in an improved set of neutron cross sections. The new experimental production rates provide a basis for validation of model calculations of rare gas production in all types of extraterrestrial matter. In particular, they allow to validate model calculations of the matrix effect [9, 10] on the basis of laboratory data obtained under controlled conditions. Production rates in stony and iron meteoroids are consistently described by a physical model without free parameters. Acknowledgments: This work was supported by the Swiss National Science Foundation. References: [1] Michel R. et al. (1993) Meteoritics, 28, 399-400. [2] Wieler R. et al. (1992) Meteoritics, 27, 315-316. [3] Begemann F. and Schultz L. (1988) LPS XIX, 51-52. [4] Michel R. et al. (1986) Nucl. Instr. Meth. Phys. Res., B16, 61-82. [5] Michel R. et al. (1989) Nucl. Instr. Meth. Phys. Res., B42, 76-100. [6] Cloth P. et al. (1988) Juel 2203. [7] Blann M. (1994) personal communication. [8] Blann M. (1972) Phys. Rev. Lett., 28, 757-759. [9] Michel et al. (1990) Meteoritics, 25, 386-387. [10] Masarik J. et al. (1994) GCA, 58, 5307-5317.

  3. Separation and purification of Si from solidification of hypereutectic Al-Si melt under rotating magnetic field

    NASA Astrophysics Data System (ADS)

    Jie, J. C.; Zou, Q. C.; Wang, H. W.; Sun, J. L.; Lu, Y. P.; Wang, T. M.; Li, T. J.

    2014-08-01

    A low-cost and high-efficiency method to purify Si directly from cheap MG-Si at low temperature was proposed and demonstrated in this paper, which used power frequency rotating magnetic field (RMF) to separate the primary Si from a hypereutectic Al-Si alloy and was followed by the acid peeling. The separation mechanism was based on the flow characteristic of melt under RMF and the cooling condition of the liquid metal. A Si-rich layer with Si content of 65-59 wt% was formed in the periphery of alloy, while the inner microstructure of the alloy was mainly the Al-Si eutectic structure. The refined silicon was collected after aqua regia leaching, and had much fewer typical impurities (Fe, Ti, Ca, B, P) than those in MG-Si, and the metallic impurities besides Al had removal fraction higher than 98%, which is mainly ascribed to the segregation effect of Al-30Si alloy during solidification under RMF.

  4. Effect of intensive melt shearing on the formation of Fe-containing intermetallics in LM24 Al-alloy

    NASA Astrophysics Data System (ADS)

    Li, H. T.; Ji, S.; Wang, Y.; Xia, M.; Fan, Z.

    2012-01-01

    Fe is one of the inevitable and detrimental impurities in aluminium alloys that degrade the mechanical performance of castings. In the present work, intensive melt shearing has been demonstrated to modify the morphology of Fe-containing intermetallic compounds by promoting the formation of compact ?-Al(Fe,Mn)Si at the expense of needle-shaped ?-AlFeSi, leading to an improved mechanical properties of LM24 alloy processed by MC-HPDC process. The promotion of the formation of ? -Al(Fe, Mn)Si phase is resulted from the enhanced nucleation on the well dispersed MgAl2O4 particles in the melt. The Fe tolerance of LM24 alloy can be effectively improved by combining Mn alloying and intensive melt shearing.

  5. Soft magnetic powder-core composites of Fe{sub 90}Zr{sub 7}B{sub 3} and Fe{sub 49}Co{sub 21}Al{sub 5}Ga{sub 2}P{sub 9.65}C{sub 5.75}B{sub 4.6}Si{sub 3} alloys

    SciTech Connect

    Turgut, Zafer; Attenweiler, Thomas; Huang, Meiqing; Horwath, John C.; Fingers, Richard T.

    2006-04-15

    Amorphous and nanocrystalline alloys in ribbon form exhibit excellent soft magnetic properties, but their forms are limited to tape wound cores. Complex shapes require the implementation of a powder metallurgical approach resulting in reduced permeabilities. The present study investigates Fe-based Fe{sub 90}Zr{sub 7}B{sub 3} (C1) and Fe{sub 49}Co{sub 21}Al{sub 5}Ga{sub 2}P{sub 9.65}C{sub 5.75}B{sub 4.6}Si{sub 3} (C2) melt-spun ribbons as precursors for compacted powder cores. Single-roller melt spinning of C1 produced partially crystallized structures while C2 resulted in amorphous ribbons. Annealing studies were carried out based on the crystallization temperatures of various phases extracted from M(T) measurements. In ribbon form and under optimum annealing conditions, C1 revealed a 1.88 T saturation flux density (B{sub s}) and 44 A/m coercivity (H{sub c}), while C2 exhibited a B{sub s} of 0.78 T and H{sub c} of 2.4 A/m.

  6. Localized Corrosion Behavior of Al-Si-Mg Alloys Used for Fabrication of Aluminum Matrix Composites

    NASA Astrophysics Data System (ADS)

    Pech-Canul, M. A.; Giridharagopal, R.; Pech-Canul, M. I.; Coral-Escobar, E. E.

    2013-12-01

    The relationship between microstructure and localized corrosion behavior in neutral aerated chloride solutions was investigated with SEM/EDAX, conventional electrochemical techniques, and with scanning Kelvin probe force microscopy (SKPFM) for two custom-made alloys with Si/Mg molar ratios of 0.12 and 0.49. In this order, Al3Fe, Al3Mg2, and Mg2Si intermetallics were identified in the first alloy and Al(FeMn)Si and Mg2Si particles in the second one. Anodic polarization curves and corrosion morphology showed that the alloy with higher Si/Mg molar ratio exhibited a better corrosion performance and evidence was shown that it had a more corrosion-resistant passive film. The corrosion process for both alloys in aerated 0.1 M NaCl solutions was localized around the Fe-rich intermetallics. They acted as local cathodes and produced dissolution of the aluminum matrix surrounding such particles. Mg2Si and Al3Mg2 exhibited anodic behavior. SKPFM was successfully used to map the Volta potential distribution of main intermetallics. The localized corrosion behavior was correlated with a large Volta potential difference between the Fe-rich intermetallics and the matrix. After immersion in the chloride solution, such Volta potential difference decreased.

  7. Atomic data from the iron project. 3: Rate coefficients for electron impact excitation of boron-like ions: Ne VI, Mg VIII, Al IX, Si X, S XII, Ar XIV, Ca XVI and Fe XXII

    NASA Technical Reports Server (NTRS)

    Zhang, Hong Lin; Graziani, Mark; Pradhan, Anil K.

    1994-01-01

    Collison strengths and maxwellian averaged rate coefficients have been calculated for the 105 transitions among all 15 fine structure levels of the 8 LS terms 2s(sup 2) 2 P(P-2(sup 0 sub 1/, 3/2)), 2s2p(sup 2)(P-4(sub 1/2,3/2,5/2), D-2(sub 3/2, 5/2), S-2(sub 1/2), P-2(sub 1/2, 3/2)), 2p(sup 3)(S-4(sup 0)(sub 3/2), D-2(sup 0 sub 3/2, 5/2), P-2(sup 0 sub 1/2, 3/2)) in highly- charged B-like Ne, Mg, Al, Si, S, Ar, Ca and Fe. Rate coefficients have been tabulated at a wide range of temperatures, depending on the ion charge and abundance in plasma sources. Earlier work for O IV has also been extended to include the high temperature range. A brief discussion of the calculations, sample results, and comparison with earlier works is also given. While much of the new data should be applicable to UV spectral diagnostics, the new rates for the important ground state fine structure transition P-2(sup 0 sub 1/2)-P-2(sup 0 sub 3/2) should result in significant revision of the IR cooling rates in plasmas where B-like ions are prominent constituents, since the new rate coefficients are generally higher by several factors compared with the older data.

  8. Development of SiAlON materials

    NASA Technical Reports Server (NTRS)

    Layden, G. K.

    1977-01-01

    Cold pressing and sintering techniques were used to produce ceramic bodies in which the major phase was beta prime Si3-Al-O-N4 solid solution. A variety of foreign oxides were used to promote liquid phase sintering, and this resulted in the incorporation of additional solid phases in the ceramic bodies which controlled elevated temperature properties. None of the bodies studied to date exhibited both adequate high temperature mechanical properties and oxidation resistance. Criteria are suggested to guide the formulation of bodies with improved high temperature properties.

  9. Density measurements of liquid Fe-Si alloys at high pressure using the sink-float method

    NASA Astrophysics Data System (ADS)

    Tateyama, Ryuji; Ohtani, Eiji; Terasaki, Hidenori; Nishida, Keisuke; Shibazaki, Yuki; Suzuki, Akio; Kikegawa, Takumi

    2011-12-01

    The compositional dependence on the density of liquid Fe alloys under high pressure is important for estimating the amount of light elements in the Earth's outer core. Here, we report on the density of liquid Fe-Si at 4 GPa and 1,923 K measured using the sink-float method and our investigation on the effect of the Si content on the density of the liquid. Our experiments show that the density of liquid Fe-Si decreases from 7.43 to 2.71 g/cm3 non-linearly with increasing Si content (0-100 at%). The molar volume of liquid Fe-Si calculated from the measured density gradually decreases in the compositional range 0-50 at% Si, and increases in the range 50-100 at% Si. It should be noted that the estimated molar volume of the alloys shows a negative volume of mixing between Fe and Si. This behaviour is similar to Fe-S liquid (Nishida et al. in Phys Chem Miner 35:417-423, 2008). However, the excess molar volume of mixing for the liquid Fe-Si is smaller than that of liquid Fe-S. The light element contents in the outer core estimated previously may be an underestimation if we take into account the possible negative value of the excess mixing volume of iron-light element alloys in the outer core.

  10. Structural stability in the Al-Li-Si system

    NASA Astrophysics Data System (ADS)

    Pisch, A.; Jakse, N.; Pasturel, A.; Harvey, J. P.; Chartrand, P.

    2007-06-01

    Density functional theory calculations are performed to theoretically interpret the structural stability of different ternary phases in the Al-Li-Si system. The stability of the already well-known AlLiSi compound is determined and found to be in excellent agreement with calorimetric measurements. The authors also study the stability of different phases reported in the literature. It is found that the ternary Al3Li7Si4, AlLi5Si2, and AlLi9Si3 compounds display much higher negative formation energies than that of the Al3Li8Si5 compound, giving new insights in understanding phase stabilities of compounds in the ternary Al-Li-Si system.

  11. Optical properties of isostructural ?-FeSi 2,OsSi 2,Fe 0.5Os 0.5Si 2 and Os 0.5Fe 0.5Si 2

    NASA Astrophysics Data System (ADS)

    Migas, D. B.; Henrion, W.; Rebien, M.; Shaposhnikov, V. L.; Borisenko, V. E.; Miglio, Leo

    2001-06-01

    We have performed a comparative study of optical properties of isostructural ?-FeSi 2,OsSi 2, and two ternary configurations of (FeOs)Si 2 by first-principle calculations of band structure and the imaginary part of the dielectric function. The latter for ?-FeSi 2 and OsSi 2 were compared to those deduced from ellipsometric measurements, indicating an excellent agreement. From theoretical calculations both binaries are found to be indirect gap semiconductors, whereas one ternary is characterised by a direct transition with high oscillator strength.

  12. Magnetic ordering in Ho2Fe2Si2C

    NASA Astrophysics Data System (ADS)

    Susilo, R. A.; Cadogan, J. M.; Cobas, R.; Hutchison, W. D.; Avdeev, M.; Campbell, S. J.

    2015-05-01

    We have used neutron diffraction and 57Fe Mssbauer spectroscopy, complemented by magnetisation and specific heat measurements, to examine the magnetic ordering of Ho2Fe2Si2C. We have established that Ho2Fe2Si2C orders antiferromagnetically below TN = 16(1) K with a magnetic structure involving ordering of the Ho sublattice along the b-axis with a propagation vector k =[0 0 1/2 ] . 57Fe Mssbauer spectra collected below TN show no evidence of a magnetic splitting, demonstrating the absence of long range magnetic ordering of the Fe sublattice. A small line broadening is observed in the 57Fe spectra below TN, which is due to a transferred hyperfine fieldestimated to be around 0.3 T at 10 Kfrom the Ho sublattice.

  13. Fabrication and Current-Voltage Characteristics of Fe3Si/CaF2/Fe3Si Magnetic Tunnel Junction

    NASA Astrophysics Data System (ADS)

    Harianto, Teddy; Sadakuni, Kenji; Akinaga, Hiro; Suemasu, Takashi

    2008-08-01

    The possibility of selective wet chemical etching and the current-voltage characteristics (I-V) of Fe3Si (9 nm)/CaF2 (2 nm)/Fe3Si (13 nm) magnetic-tunnel-junctions structures have been investigated. It was found that the Fe3Si and CaF2 layers were selectively etched using a mixture of hydrofluoric and nitric acids (HF:HNO3:H2O = 1:2:400) and a sulfuric solution (H2SO4:H2O = 1:20), respectively. The etch rates were 120 and 45 nm/min at 0 C for Fe3Si and CaF2, respectively. The I-V characteristics measured at room temperature were well fitted to Simmons' equation within the bias voltages of 0.3 V using the barrier height ?= 2.5 eV and barrier thickness d = 2.0 nm.

  14. Realization of small intrinsic hysteresis with large magnetic entropy change in La{sub 0.8}Pr{sub 0.2}(Fe{sub 0.88}Si{sub 0.10}Al{sub 0.02}){sub 13} by controlling itinerant-electron characteristics

    SciTech Connect

    Fujita, A.; Matsunami, D.; Yako, H.

    2014-03-24

    Tuning of phase-transition characteristics in La(Fe{sub x}Si{sub 1−x}){sub 13} was conducted in view of the correlation between microscopic itinerant electron natures and macroscopic thermodynamic (magnetocaloric) quantities. To realize a small hysteresis loss Q{sub H} accompanied by a large magnetic entropy change ΔS{sub M} in La(Fe{sub x}Si{sub 1−x}){sub 13}, two types of modulation based on itinerant electron characteristics, namely, the Fermi-level shift and the magnetovolume effect were combined by complex partial substitution of Al and Pr. Ab-initio calculations predict the reduction of a transition hysteresis owing to the Fermi-level shift after partial substitution of Al. On the other hand, the chemical pressure arisen from partial substitution of Pr enhances ΔS{sub M} through magnetovolume effect. The selective enhancement of ΔS{sub M} apart from Q{sub H} by the magnetovolume effect is well explained by the phenomenological Landau model. Consequently, ΔS{sub M} of La{sub 0.8}Pr{sub 0.2}(Fe{sub 0.88}Si{sub 0.10}Al{sub 0.02}){sub 13} is −18 J/kg K under a magnetic field change of 0–1.2 T, while the maximum value of Q{sub H} becomes 1/6 of that for La(Fe{sub 0.88}Si{sub 0.12}){sub 13}.

  15. AlN/Al dual protective coatings on NdFeB by DC magnetron sputtering

    NASA Astrophysics Data System (ADS)

    Li, Jinlong; Mao, Shoudong; Sun, Kefei; Li, Xiaomin; Song, Zhenlun

    2009-11-01

    AlN/Al dual protective coatings were prepared on NdFeB by DC magnetron sputtering in a home-made industrial apparatus. Comparing with Al coating, AlN/Al coatings have a denser structure of an outmost AlN amorphous layer following an inner Al columnar crystal layer. The coatings and NdFeB substrate combine well, and moreover, there is occurrence of metallurgy bonding in the interface layer. Both Al and AlN/Al coatings have a good protective ability to NdFeB. Especially, the corrosion resistance of AlN/Al coated NdFeB is improved largely. AlN/Al and Al protective coatings not only do not deteriorate the magnetic properties of NdFeB, but contribute to their slight increase.

  16. Tunneling magnetoresistance in Fe{sub 3}Si/MgO/Fe{sub 3}Si(001) magnetic tunnel junctions

    SciTech Connect

    Tao, L. L.; Liang, S. H.; Liu, D. P.; Wei, H. X.; Han, X. F.; Wang, Jian

    2014-04-28

    We present a theoretical study of the tunneling magnetoresistance (TMR) and spin-polarized transport in Fe{sub 3}Si/MgO/Fe{sub 3}Si(001) magnetic tunnel junction (MTJ). It is found that the spin-polarized conductance and bias-dependent TMR ratios are rather sensitive to the structure of Fe{sub 3}Si electrode. From the symmetry analysis of the band structures, we found that there is no spin-polarized ?{sub 1} symmetry bands crossing the Fermi level for the cubic Fe{sub 3}Si. In contrast, the tetragonal Fe{sub 3}Si driven by in-plane strain reveals half-metal nature in terms of ?{sub 1} state. The giant TMR ratios are predicted for both MTJs with cubic and tetragonal Fe{sub 3}Si electrodes under zero bias. However, the giant TMR ratio resulting from interface resonant transmission for the former decreases rapidly with the bias. For the latter, the giant TMR ratio can maintain up to larger bias due to coherent transmission through the majority-spin ?{sub 1} channel.

  17. Magnetic anisotropy in Fe films deposited on SiO2/Si(001) and Si(001) substrates

    NASA Astrophysics Data System (ADS)

    Komogortsev, S. V.; Varnakov, S. N.; Satsuk, S. A.; Yakovlev, I. A.; Ovchinnikov, S. G.

    2014-02-01

    The magnetic anisotropy of 10 nm iron films deposited in an ultra high vacuum on the Si(001) surface and on the Si(001) over caped by 1.5 nm layer of SiO2 was investigated. There is in-plane uniaxial magnetic anisotropy caused by oblique sputtering in the Fe films on a SiO2 buffer layer. The easy magnetization axis is always normal to the atomic flux direction but the value of the anisotropy field is different depending on the axial angle among sputtering direction and the substrate crystallographic axes. It is argued that the uniaxial magnetic anisotropy results from elongated surface roughness formation during film deposition. Several easy magnetization axes are found in Fe/Si(001) film without the SiO2 buffer layer. The mutual orientation of the main easy axes and Si crystallographic axes indicates that there is epitaxial growth of Fe/Si(001) film with the following orientation relative to the substrate: Fe[100] ?Si[110]. The anisotropy energy of Fe/Si(001) film is estimated by simulation of angle dependence of remnant magnetization mr as the sum of the mr angle plot from uniaxial anisotropy (induced by oblique deposition) and the polar plot from biaxial magnetocrystalline anisotropy.

  18. Structural and transport properties of ferromagnetically coupled Fe/Si/Fe trilayers

    SciTech Connect

    Naik, S. R.; Rai, S.; Lodha, G. S.; Chattopadhyay, M. K.; Sharma, V. K.; Majumdar, S.

    2008-09-15

    We report structural, transport, and magnetic studies on ion beam deposited Fe(30,50 A)/Si(15,20,25,30,40 A)/Fe(30,50 A) trilayers. Grazing incidence x-ray reflectivity, grazing incidence x-ray diffraction, and x-ray photoelectron spectroscopy techniques are used to characterize the trilayers. From these studies we infer the formation of silicide interlayers at both Fe/Si and Si/Fe interfaces. Above 25 A nominal thickness of the Si layer, a uniform density layer of pure Si is formed. But below 25 A nominal thickness of Si layer, a nonuniform density layer of Si and silicide is found. The electrical resistance of trilayers depends on both Fe and Si layer thicknesses. Resistance decreases with the increase in temperature between 30 and 300 K. Attempts are made to analyze the temperature dependence of resistance with the help of semiconducting and electron hopping mechanisms. Magneto-optical Kerr effect results suggest that ferromagnetic correlations are established between the Fe layers of the trilayers.

  19. The protective coatings of NdFeB magnets by Al and Al(Fe)

    SciTech Connect

    Qin, C.; Li, A.S.; Ng, D.H.

    1996-04-01

    NdFeB permanent magnets are coated by two different methods, dip coating and evaporation coating, with Al. It is found that an intermetallic reaction has occurred and formed a dominant phase of FeAl{sub 2.5}B{sub {ital x}} at the interface between the Al coating and the magnet material. Such reaction enhances strong bonding between the coating and the magnet. When Al(Fe) is used for the coating, no detectable intermetallic phase is observed, and therefore the amount of magnet material is conserved. We have studied the effect of the intermetallic phase on corrosion protection of the magnet. It is found that this phase is less resistive towards HNO{sub 3} solution than pure Al; but it is more resistive towards NaOH and NaCl. The investigation of the changes of microstructures of the coatings under different tempering conditions have also been carried out. The results show that the heat treatment at 500{degree}C for 10 min for a {approximately} 2 {mu}m thick Al coating by evaporation can produce an optimal layer of intermetallics. If the temperature is too low, the coating will not adhere to the magnet or if too high, it will fully react with the magnet and produce a rough coating surface. {copyright} {ital 1996 American Institute of Physics.}

  20. Phase relations in the Fe-FeSi system at high pressures and temperatures

    NASA Astrophysics Data System (ADS)

    Fischer, Rebecca A.; Campbell, Andrew J.; Reaman, Daniel M.; Miller, Noah A.; Heinz, Dion L.; Dera, Przymyslaw; Prakapenka, Vitali B.

    2013-07-01

    The Earth's core is comprised mostly of iron and nickel, but it also contains several weight percent of one or more unknown light elements, which may include silicon. Therefore it is important to understand the high pressure, high temperature properties and behavior of alloys in the Fe-FeSi system, such as their phase diagrams. We determined melting temperatures and subsolidus phase relations of Fe-9 wt% Si and stoichiometric FeSi using synchrotron X-ray diffraction at high pressures and temperatures, up to ~200 GPa and ~145 GPa, respectively. Combining this data with that of previous studies, we generated phase diagrams in pressure-temperature, temperature-composition, and pressure-composition space. We find the B2 crystal structure in Fe-9Si where previous studies reported the less ordered bcc structure, and a shallower slope for the hcp+B2 to fcc+B2 boundary than previously reported. In stoichiometric FeSi, we report a wide B2+B20 two-phase field, with complete conversion to the B2 structure at ~42 GPa. The minimum temperature of an Fe-Si outer core is 4380 K, based on the eutectic melting point of Fe-9Si, and silicon is shown to be less efficient at depressing the melting point of iron at core conditions than oxygen or sulfur. At the highest pressures reached, only the hcp and B2 structures are seen in the Fe-FeSi system. We predict that alloys containing more than ~4-8 wt% silicon will convert to an hcp+B2 mixture and later to the hcp structure with increasing pressure, and that an iron-silicon alloy in the Earth's inner core would most likely be a mixture of hcp and B2 phases.

  1. 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.

  2. Crystal structure of the mineral (Na,Ca,K){sub 2}(Ca,Na){sub 4}(Mg,Fe){sub 5}(Mg,Fe,Ti){sub 5}[Si{sub 12}Al{sub 4}O{sub 44}](F,O){sub 4}: a triclinic representative of the amphibole family

    SciTech Connect

    Rastsvetaeva, R. K. Aksenov, S. M.

    2012-05-15

    A mineral belonging to the amphibole family found at the Rothenberg paleovolcano (Eifel, Germany) was studied by single-crystal X-ray diffraction. The triclinic pseudomonoclinic unit-cell parameters are a = 5.3113(1) Angstrom-Sign , b = 18.0457(3) Angstrom-Sign ; c = 9.8684(2) Angstrom-Sign , {alpha} = 90.016(2) Degree-Sign , {beta} = 105.543(4) Degree-Sign , {gamma} = 89.985(2) Degree-Sign . The structure was solved by direct methods in sp. gr. P1 and refined to the R factor of 2.7% based on 6432 reflections with |F| > 3{sigma}(F) taking into account twinning. The mineral with the idealized formula (Na,Ca,K){sub 2}(Ca,Na){sub 4}(Mg,Fe){sub 5}(Mg,Fe,Ti){sub 5}[Si{sub 12}Al{sub 4}O{sub 44}](F,O){sub 4} has some symmetry and structural features that distinguish it from other minerals of this family.

  3. Swift heavy ion irradiation of a-Si/Fe/c-Si trilayers

    SciTech Connect

    Zhang, K.; Lieb, K. P.; Milinovic, V.; Sahoo, P. K.

    2006-09-01

    Si/Fe/Si trilayers, with 12 nm amorphous Si and 45 nm polycrystalline Fe films deposited on Si(100) wafers, were irradiated with 350 MeV Au{sup 26+} ions at fluences of (0.6-11.3)x10{sup 14} ions/cm{sup 2}. The ion-induced modifications of their structural and magnetic properties were characterized by means of Rutherford backscattering, glancing angle x-ray diffractometry, and the magneto-optical Kerr effect. The mixing rate at the upper a-Si/Fe interface was three times as high as that at the lower Fe/c-Si interface. A simple formula is proposed, which on the basis of (nuclear) thermal-spike mixing reproduces the observed (electronic) mixing rates. Ion irradiation at a moderate fluence (6.7x10{sup 14}/cm{sup 2}) induced a magnetic anisotropy in the sample, which was magnetically isotropic after deposition. At the highest fluence, full interface mixing occurred and the magnetic anisotropy almost disappeared. The results are compared with those obtained in Fe/Si and Ni/Si bilayers ion irradiated in the regimes of nuclear and electronic stopping.

  4. Sound velocities of Fe and Fe-Si alloy in the Earth's core.

    PubMed

    Mao, Zhu; Lin, Jung-Fu; Liu, Jin; Alatas, Ahmet; Gao, Lili; Zhao, Jiyong; Mao, Ho-Kwang

    2012-06-26

    Compressional wave velocity-density (V(P)--?) relations of candidate Fe alloys at relevant pressure-temperature conditions of the Earth's core are critically needed to evaluate the composition, seismic signatures, and geodynamics of the planet's remotest region. Specifically, comparison between seismic V(P)--? profiles of the core and candidate Fe alloys provides first-order information on the amount and type of potential light elements--including H, C, O, Si, and/or S-needed to compensate the density deficit of the core. To address this issue, here we have surveyed and analyzed the literature results in conjunction with newly measured V(P)--? results of hexagonal closest-packed (hcp) Fe and hcp-Fe(0.85)Si(0.15) alloy using in situ high-energy resolution inelastic X-ray scattering and X-ray diffraction. The nature of the Fe-Si alloy where Si is readily soluble in Fe represents an ideal solid-solution case to better understand the light-element alloying effects. Our results show that high temperature significantly decreases the V(P) of hcp-Fe at high pressures, and the Fe-Si alloy exhibits similar high-pressure V(P)--? behavior to hcp-Fe via a constant density offset. These V(P)--? data at a given temperature can be better described by an empirical power-law function with a concave behavior at higher densities than with a linear approximation. Our new datasets, together with literature results, allow us to build new V(P)--? models of Fe alloys in order to determine the chemical composition of the core. Our models show that the V(P)--? profile of Fe with 8 wt % Si at 6,000 K matches well with the Preliminary Reference Earth Model of the inner core. PMID:22689958

  5. Sound velocities of Fe and Fe-Si alloy in the Earths core

    PubMed Central

    Mao, Zhu; Lin, Jung-Fu; Liu, Jin; Alatas, Ahmet; Gao, Lili; Zhao, Jiyong; Mao, Ho-Kwang

    2012-01-01

    Compressional wave velocity-density (VP-?) relations of candidate Fe alloys at relevant pressure-temperature conditions of the Earths core are critically needed to evaluate the composition, seismic signatures, and geodynamics of the planets remotest region. Specifically, comparison between seismic VP-? profiles of the core and candidate Fe alloys provides first-order information on the amount and type of potential light elementsincluding H, C, O, Si, and/or Sneeded to compensate the density deficit of the core. To address this issue, here we have surveyed and analyzed the literature results in conjunction with newly measured VP-? results of hexagonal closest-packed (hcp) Fe and hcp-Fe0.85Si0.15 alloy using in situ high-energy resolution inelastic X-ray scattering and X-ray diffraction. The nature of the Fe-Si alloy where Si is readily soluble in Fe represents an ideal solid-solution case to better understand the light-element alloying effects. Our results show that high temperature significantly decreases the VP of hcp-Fe at high pressures, and the Fe-Si alloy exhibits similar high-pressure VP-? behavior to hcp-Fe via a constant density offset. These VP-? data at a given temperature can be better described by an empirical power-law function with a concave behavior at higher densities than with a linear approximation. Our new datasets, together with literature results, allow us to build new VP-? models of Fe alloys in order to determine the chemical composition of the core. Our models show that the VP-? profile of Fe with 8wt?% Si at 6,000K matches well with the Preliminary Reference Earth Model of the inner core. PMID:22689958

  6. Fracture toughness in SiC/Al composite material

    NASA Technical Reports Server (NTRS)

    Flom, Y.; Wu, S. B.; Arsenault, R. J.

    1989-01-01

    Crack initiation fracture toughness does not depend on SiC particle size. Crack growth fracture toughness increases as the size of the SiC particle increases. The fracture process is confined to a very narrow band and takes place within the matrix. In the case of composite reinforced with SiC particles of 20 microns and above, fracture of SiC begins to dominate. The matrix is influenced by a triaxial tension in the matrix and a high density of dislocations generated at SiC/Al interfaces due to the difference in coefficient of thermal expansion between SiC and the Al matrix.

  7. Effect of Cooling Rate on Boron Removal and Solidification Behavior of Al-Si Alloy

    NASA Astrophysics Data System (ADS)

    Li, Yanlei; Chen, Jian; Ban, Boyuan; Zhang, Taotao; Dai, Songyuan

    2015-02-01

    The effect of cooling rate on boron removal and solidification behavior of Al-Si alloy with different silicon contents were studied during solar grade silicon purification. It is found that the boron removal rate is controlled by kinetic factor. A method is proposed to calculate apparent segregation coefficient of solidification process that spans over a temperature range. This apparent segregation coefficient is used to evaluate purification effect in alloy system with changing segregation coefficients. When average solidification temperature decreases, the apparent segregation coefficient of boron decreases. The average width and mass of primary silicon flakes decrease with increasing cooling rate. Impurity elements form intermetallic compound phases such as α-Al8SiFe2 and π-Al8Si6Mg3Fe in eutectic matrix.

  8. Partitioning of Si in a Fe87Zr7Si4B2 nanocrystalline soft magnetic alloy

    NASA Astrophysics Data System (ADS)

    Zhang, Y.; Hono, K.; Inoue, A.; Sakurai, T.

    1996-09-01

    We have studied partitioning of Si in nanocrystalline Fe-Zr-Si-B soft magnetic alloy by atom probe field ion microscopy (APFIM). Unlike our expectation from our previous results in nanocrystalline Fe-Si-B-Nb-Cu alloy, we have found that Si atoms are rejected from ?-Fe primary crystals and partitioned into the residual amorphous phase. This result suggests that Si addition does not cause reduction in inherent magnetostriction of ?-Fe nanoparticles, but it brings the volume fraction of the ?-Fe particles to an optimum value so that the average magnetostriction becomes zero. This conclusion has been strengthened by comparing the changes in magnetostriction constants as a function of Si content in Fe-Zr-Si-B and Fe-Si-B-Nb-Cu alloys.

  9. Removal of phosphate from water using six Al-, Fe-, and Al-Fe-modified bentonite adsorbents.

    PubMed

    Shanableh, Abdallah M; Elsergany, Moetaz M

    2013-01-01

    This study was part of a larger effort that involves evaluating alternatives to upgrading secondary treatment systems in the United Arab Emirates for the removal of nutrients. In this study, six modified bentonite (BNT) phosphate adsorbents were prepared using solutions that contained hydroxy-polycations of aluminum (Al-BNT), iron (Fe-BNT), and mixtures of aluminum and iron (Al-Fe-BNT). The adsorption kinetics and capacities of the six adsorbents were evaluated, and the adsorbents were used to remove phosphorus from synthetic phosphate solutions and from treated wastewater. The experimental adsorption kinetics results were well represented by the pseudo-second-order kinetic model, with R(2) values ranging from 0.99 to 1.00. Similarly, the experimental equilibrium adsorption results were well represented by the Freundlich and Langmuir isotherms, with R(2) values ranging from 0.98 to 1.00. The adsorption capacities of the adsorbents were dependent on the BNT preparation conditions; the types, quantities and combination of metals used; BNT particle size; and adsorption pH. The Langmuir maximum adsorption capacities of the six adsorbents ranged from 8.9-14.5mg P/g-BNT. The results suggested that the BNT preparations containing Fe alone or in combination with Al achieved higher adsorption capacities than the preparations containing only Al. However, the Al-BNT preparations exhibited higher adsorption rates than the Fe-BNT preparation. Three of the six adsorbents were used to remove phosphate from secondarily treated wastewater samples, and the removal results were comparable to those obtained using synthetic phosphate solutions. The BNT adsorbents also exhibited adequate settling characteristics and significant regeneration potential. PMID:23043345

  10. Electronic and magnetic properties of Si substituted Fe3Ge

    NASA Astrophysics Data System (ADS)

    Shanavas, K. V.; McGuire, Michael A.; Parker, David S.

    2015-09-01

    Using first principles calculations, we studied the effect of Si substitution in the hexagonal Fe3Ge. We find the low temperature magnetic anisotropy in this system to be planar and originating mostly from the spin-orbit coupling in Fe-d states. Reduction of the unitcell volume reduces the magnitude of in-plane magnetic anisotropy, eventually turning it positive which reorients the magnetic moments to the axial direction. Substituting Ge with the smaller Si ions also increases the anisotropy, potentially enhancing the region of stability of the axial magnetization, which is beneficial for magnetic applications such as permanent magnets. Our experimental measurements on samples of Fe3Ge1-xSix confirm these predictions and show that substitution of about 6% of the Ge with Si increases by approximately 35 K the temperature range over which anisotropy is uniaxial.

  11. Electronic and magnetic properties of Si substituted Fe3Ge

    DOE PAGESBeta

    Shanavas, Kavungal Veedu; McGuire, Michael A.; Parker, David S.

    2015-09-23

    Using first principles calculations we studied the effect of Si substitution in the hexagonal Fe3Ge. We find the low temperature magnetic anisotropy in this system to be planar and originating mostly from the spin-orbit coupling in Fe-d states. Reduction of the unitcell volume reduces the in-plane magnetic anisotropy, eventually turning it positive which reorients the magnetic moments to the axial direction. We find that substituting Ge with the smaller Si ions also reduces the anisotropy, potentially enhancing the region of stability of the axial magnetization, which is beneficial for magnetic applications. Thus our experimental measurements on samples of Fe3Ge1–xSix confirmmore » these predictions and show that substitution of about 6% of the Ge with Si increases by approximately 35 K the temperature range over which anisotropy is uniaxial.« less

  12. Thermal annealing and magnetic anisotropy of NiFe thin films on n+-Si for spintronic device applications

    NASA Astrophysics Data System (ADS)

    Lu, Q. H.; Huang, R.; Wang, L. S.; Wu, Z. G.; Li, C.; Luo, Q.; Zuo, S. Y.; Li, J.; Peng, D. L.; Han, G. L.; Yan, P. X.

    2015-11-01

    To ensure that the magnetic metal electrodes can meet the requirements of the spin injection, NiFe films prepared both on HfO2 dielectric layer and n+-Si directly by sputtering deposition, and treated by conventional furnace annealing and/or high vacuum magnetic field annealing were investigated. It was found that thermal annealing at 250 C improved the crystalline quality and reduced surface roughness of the NiFe films, thus enhancing its saturation magnetization intensity. The 100 nm thick NiFe films had too large coercive force and saturation magnetization intensity in vertical direction to meet the requirements of Hanle curve detection. While, 30 nm thick NiFe films showed paramagnetic hysteresis loops in vertical direction, and the magnetization intensity of the sample after annealing at 250 C for 30 min was less than 2% to the parallel when the external magnetic field was given between 10 Oe. This was preferred to Hanle curve detection. The thin HfO2 dielectric layer between metal and Si partially suppressed the diffusion of Ni in NiFe into Si substrate and formation of NiSi, greatly enhancing the saturation magnetization intensity of the Al/NiFe/HfO2/Si sample by thermal annealing. Those results suggest that Al/NiFe/HfO2/Si structure, from the point view of magnetic electrodes, would be suitable for spin injection and detection applications.

  13. Solidification and Microstructural Evolution of Hypereutectic Al-15Si-4Cu-Mg Alloys with High Magnesium Contents

    NASA Astrophysics Data System (ADS)

    Tebib, M.; Ajersch, F.; Samuel, A. M.; Chen, X.-G.

    2013-09-01

    The low coefficient of thermal expansion and good wear resistance of hypereutectic Al-Si-Mg alloys with high Mg contents, together with the increasing demand for lightweight materials in engine applications have generated an increasing interest in these materials in the automotive industry. In the interests of pursuing the development of new wear-resistant alloys, the current study was undertaken to investigate the effects of Mg additions ranging from 6 to 15 pct on the solidification behavior of hypereutectic Al-15Si-4Cu-Mg alloy using thermodynamic calculations, thermal analysis, and extensive microstructural examination. The Mg level strongly influenced the microstructural evolution of the primary Mg2Si phase as well as the solidification behavior. Thermodynamic predictions using ThermoCalc software reported the occurrence of six reactions, comprising the formation of primary Mg2Si; two pre-eutectic binary reactions, forming either Mg2Si + Si or Mg2Si + ?-Al phases; the main ternary eutectic reaction forming Mg2Si + Si + ?-Al; and two post-eutectic reactions resulting in the precipitation of the Q-Al5Mg8Cu2Si6 and ?-Al2Cu phases, respectively. Microstructures of the four alloys studied confirmed the presence of these phases, in addition to that of the ?-Al8Mg3FeSi6 (?-Fe) phase. The presence of the ?-Fe phase was also confirmed by thermal analysis. The morphology of the primary Mg2Si phase changed from an octahedral to a dendrite form at 12.52 pct Mg. Any further Mg addition only coarsened the dendrites. Image analysis measurements revealed a close correlation between the measured and calculated phase fractions of the primary Mg2Si and Si phases. ThermoCalc and Scheil calculations show good agreement with the experimental results obtained from microstructural and thermal analyses.

  14. Microstructure and property characterization of sintered Si3N4, SiC, and SiAlON

    NASA Technical Reports Server (NTRS)

    Dutta, S.

    1982-01-01

    Commercially-produced, pressureless sintered Si3N4, SiC, and SiAlON were characterized with respect to density, phases present, bend strength, and oxidation resistance. The room-temperature bend strengths of sintered Si3N4, SiC, and SiAlON are comparable. However, the room-temperature strengths are much lower (approximately 40 to 50%) than the room-temperature strength of hot-pressed Si3N4 (NC-132). The strength loss in Si3N4 and SiAlON materials at high temperature was attributed to a viscous grain-boundary phase, retained during cooling from the sintering temperature. The oxidation resistance of sintered alpha-SiC was the best of any materials tested.

  15. Moessbauer study in thin films of FeSi2 and FeSe systems

    NASA Technical Reports Server (NTRS)

    Escue, W. J.; Aggarwal, K.; Mendiratta, R. G.

    1978-01-01

    Thin films of FeSi2 and FeSe were studied using Moessbauer spectroscopy information regarding dangling bond configuration and nature of crystal structure in thin films was derived. A significant influence of crystalline aluminum substrate on film structure was observed.

  16. The influence of ternary alloying elements on the Al-Si eutectic microstructure and the Si morphology

    NASA Astrophysics Data System (ADS)

    Darlapudi, A.; McDonald, S. D.; Terzi, S.; Prasad, A.; Felberbaum, M.; StJohn, D. H.

    2016-01-01

    The influence of the ternary alloying elements Cu, Mg and Fe on the Al-Si eutectic microstructure is investigated using a commercial purity Al-10 wt%Si alloy in unmodified and Sr-modified conditions. A change in the Al-Si eutectic microstructure was associated with a change in the nucleation density of the eutectic grains caused by the addition of ternary alloying elements. When the ternary alloying element addition resulted in an increase in the eutectic nucleation frequency, a fibrous to flake-like transition was observed within the eutectic grain. When the ternary alloying element addition decreased the eutectic nucleation frequency significantly, a change in the eutectic morphology from flake-like to a mixture of flake-like and fibrous morphologies was observed. The mechanism of Al-Si eutectic modification is discussed. The growth velocity of the eutectic grain - liquid interface and the constitutional driving force available for growth are proposed as important parameters that influence the degree of eutectic modification in Al-Si alloys.

  17. CaAl 12Si 4O 27, a New High-Pressure Phase Containing Al 6O 19 Clusters

    NASA Astrophysics Data System (ADS)

    Grey, I. E.; Madsen, I. C.; Hibberson, W. O.; O'Neill, H. St. C.

    2000-09-01

    CaAl12Si4O27, a new high-pressure phase in the CaO-Al2O3-SiO2 system, was prepared at 1550C and 14 GPa. It has trigonal symmetry, P-3, with a=7.223(1) and c=8.614(3) . Its structure was solved using crystal chemistry principles and refined using the Rietveld method applied to powder X-ray diffraction data, Rwp=6.1%, RB=2.7%. The structure is a new type based on a close-packed anion lattice with a mixed layer stacking sequence ABACA?(hc)2 and with Ca atoms ordered in one-seventh of the anion sites in alternate c-stacked layers. The Si atoms are ordered in both octahedral and tetrahedral sites while the Al atoms are ordered in two independent octahedral sites. Octahedral edge-shared clusters, Al6O19, occur in the structure, interconnected within the close-packed layers by corner-linking to SiO4 tetrahedra. The clusters are also connected by corner-sharing to nine-member rings of edge-shared Al- and Si-centered octahedra in adjacent layers. The new phase has structural features in common with the barium titanium ferrite of similar composition, BaFe11Ti3O23, as well as with the mineral simpsonite, Al4Ta3O13(OH), and alkali metal niobates which contain Nb6O19 clusters.

  18. (Fe, Al)-bearing post-perovskite in the Earth's lower mantle

    NASA Astrophysics Data System (ADS)

    Bian, H.; Mao, Z.; Lin, J. F.; Yang, J.; Liu, J.; Watson, H. C.; Chen, J.; Prakapenka, V.; Xiao, Y.; Chow, P.

    2014-12-01

    In the past two decades, a number of seismic velocity anomalies have been identified in the bottom 200-300 km of the lower mantle above the core-mantle boundary (CMB). Deciphering the observed seismic anomalies in the region has attracted extensive research interests. Of particular importance is the discovery of Mg-silicate perovskite (Pv) to post-perovskite (PPv) phase transition, which has shed light on understanding the abnormal behavior above the CMB. In this study, we have investigated the combined effect of Fe and Al on the electronic spin and valence states as well as the equation of state of PPv using synchrotron X-ray diffraction and Mssbauer spectroscopy in high-pressure diamond anvil cells. We have synthesized two PPv samples, Mg0.6Fe0.15Al0.5Si0.75O3 and Mg0.66Fe0.13Al0.28Si0.86O3, at ~165 GPa and 2200-2500 K. By analyzing the collected Mssbauer spectra, we found that most Fe2+ and Fe3+ occupy the large bipolar prismatic sites in both of our samples. All of the Fe remains in the high-spin state at ~165-168 GPa and 300 K, which is consistent with theoretical predications. Together with the X-ray diffraction results, we have noted that the unit cell volume and density of PPv are significantly affected by the spin and valence states of Fe and the Al substitution. Using these results, we have further modeled the density and velocity change across the perovskite and PPv phase transition. The combined effect of Fe and Al will cause an increase in density but a decrease in the bulk sound velocity. As a result, the Fe and Al rich PPv existing above the CMB would be shown as relatively high-density and low-velocity regions.

  19. Anomalous metal-to-insulator transition in FeSi films deposited on SiO2/Si substrates

    NASA Astrophysics Data System (ADS)

    Witanachchi, S.; Abou Mourad, H.; Mukherjee, P.

    2006-04-01

    In-plane conductivity measurements of FeSi films deposited on boron-doped silicon substrates exhibited an anomalous metal-to-insulator transition near 250 K. In the temperature range of 250-215 K the resistance of the films increased by more than three orders of magnitude. For temperatures >250 K, metallic conductivity consistent with the conductivity of the doped silicon substrate was observed. This indicates an ohmic contact between the film and the silicon substrate across the native SiO2 layer. Below the transition temperature (<250 K), the temperature dependence of the resistance implies hopping conduction between localized states that is observed in disordered FeSi films. This metal-to-insulator transition observed in these films suggests switching of the current percolation path from substrate to the film due to a rapid increase in the interfacial resistance. The experimental results agree well with a three-layer model that incorporates an exponentially increasing interfacial resistance with decreasing temperature. The presence of a thin native oxide layer between the deposited film and the silicon substrate is essential for manifestation of the transition. Cross-sectional transmission electron microscopy analysis indicated diffusion of Fe through the oxide barrier and accumulation of Fe at the SiO2/Si interface. The band bending at the interface resulting from Fermi level pinning due to interface states and the formation of (Fe+/++B-)0/+ pairs at the SiO2/Si interface may be responsible for the observed transition.

  20. Theoretical analysis of compatibility of several reinforcement materials with NiAl and FeAl matrices

    SciTech Connect

    Misra, A.K.

    1989-05-01

    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.

  1. 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.

  2. Effects of temperature and pressure on phonons in FeSi1–xAlx

    DOE PAGESBeta

    Delaire, O.; Al-Qasir, I. I.; Ma, J.; dos Santos, A. M.; Sales, B. C.; Mauger, L.; Stone, M. B.; Abernathy, D. L.; Xiao, Y.; Somayazulu, M.

    2013-05-31

    The effects of temperature and pressure on phonons in B20 compounds FeSi1–xAlx were measured using inelastic neutron scattering and nuclear-resonant inelastic x-ray scattering. The effect of hole doping through Al substitution is compared to results of alloying with Co (electron doping) in Fe₁₋xCoxSi. While the temperature dependence of phonons in FeSi is highly anomalous, doping with either type of carriers leads to a recovery of the normal quasiharmonic behavior. Density functional theory (DFT) computations of the electronic band structure and phonons were performed. The anomaly in the temperature dependence of the phonons in undoped FeSi was related to the narrowmore » band gap, and its sensitivity to the effect of thermal disordering by phonons. On the other hand, the pressure dependence of phonons at room temperature in undoped FeSi follows the quasiharmonic behavior and is well reproduced by the DFT calculations.« less

  3. Long range order and vacancy properties in Al-rich Fe{sub 3}Al and Fe{sub 3}Al(Cr) alloys

    SciTech Connect

    Kim, S.M.; Morris, D.G.

    1998-05-01

    Neutron powder diffraction measurements have been carried out in situ from room temperature to about 100 C in Fe28Al (28 at.% Al), Fe32.5Al (32.5 at.% Al) and Fe28Al15Cr (28 at.% Al, 5 at.% Cr) alloys. X-ray diffraction and TEM studies provided supporting information. The data were analyzed to obtain information about the temperature dependence of the DO{sub 3} and B2 long range order parameters, the location of the Cr atoms and their effect on the ordering energies, and on the vacancy formation and migration properties in Fe28Al and Fe32.5Al alloys. The location of the ternary alloying addition in DO{sub 3} and B2 ordered Al-rich Fe{sub 3}Al is shown to be consistent with considerations of interatomic bond energies.

  4. Current-Voltage and Capacitance-Conductance-Voltage Characteristics of Al/SiO2/p-Si and Al/Methyl Green (MG)/p-Si Structures

    NASA Astrophysics Data System (ADS)

    Duman, Songl; Ozcelik, Fikriye Seyma; Grbulak, Bekir; Glnahar, Murat; Turut, Abdulmecit

    2015-01-01

    The organic methyl green (MG) has been investigated for the first time for its electronic applications. In order to see the effect of organic MG layer on electrical characteristics of Al/p-Si diode, Al/MG/p-Si structure has been fabricated by inexpensive and simple "drop coating" method. The current-voltage ( I- V) and capacitance-conductance-voltage ( C- G- V) characteristics of Al/SiO2/p-Si and Al/MG/p-Si structures have been investigated. The parameters such as ideality factor ( n), barrier height (), series and shunt resistance, and the density of interface states have been investigated using current-voltage measurements, in dark and under illumination conditions at room temperature. The n and values of 1.56 and 0.81 eV for Al/SiO2/p-Si and 1.36 and 0.80 eV for Al/MG/p-Si are calculated from the forward bias I- V characteristics. The value of the Al/SiO2/p-Si structure at room temperature is larger than that of conventional Al/p-Si diode. It is seen that the n value of 1.36 calculated for the Al/MG/p-Si structure is lower than most of the metal/organic compound/inorganic semiconductor devices.

  5. Protected Fe valence in quasi-two-dimensional ?-FeSi2.

    PubMed

    Miiller, W; Tomczak, J M; Simonson, J W; Smith, G; Kotliar, G; Aronson, M C

    2015-05-01

    We report the first comprehensive study of the high temperature form (?-phase) of iron disilicide. Measurements of the magnetic susceptibility, magnetization, heat capacity and resistivity were performed on well characterized single crystals. With a nominal iron d(6) configuration and a quasi-two-dimensional crystal structure that strongly resembles that of LiFeAs, ?-FeSi2 is a potential candidate for unconventional superconductivity. Akin to LiFeAs, ?-FeSi2 does not develop any magnetic order and we confirm its metallic state down to the lowest temperatures (T=1.8K). However, our experiments reveal that paramagnetism and electronic correlation effects in ?-FeSi2 are considerably weaker than in the pnictides. Band theory calculations yield small Sommerfeld coefficients of the electronic specific heat ?=Ce/T that are in excellent agreement with experiment. Additionally, realistic many-body calculations further corroborate that quasi-particle mass enhancements are only modest in ?-FeSi2. Remarkably, we find that the natural tendency to vacancy formation in the iron sublattice has little influence on the iron valence and the density of states at the Fermi level. Moreover, Mn doping does not significantly change the electronic state of the Fe ion. This suggests that the iron valence is protected against hole doping and indeed the substitution of Co for Fe causes a rigid-band like response of the electronic properties. As a key difference from the pnictides, we identify the smaller inter-iron layer spacing, which causes the active orbitals near the Fermi level to be of a different symmetry in ?-FeSi2. This change in orbital character might be responsible for the lack of superconductivity in this system, providing constraints on pairing theories in the iron based pnictides and chalcogenides. PMID:25837013

  6. Photonic crystals composed of ?-FeSi2 with amorphous Si cladding layers

    NASA Astrophysics Data System (ADS)

    Tokushige, Hiroki; Endo, Takashi; Hiidome, Keita; Saiki, Kenta; Kitamura, Shigehiro; Katsuyama, Toshio; Ikeda, Naoki; Sugimoto, Yoshimasa; Maeda, Yoshihito

    2015-07-01

    Photonic crystals (PhCs) composed of ?-FeSi2 with amorphous Si (a-Si) cladding layers are systematically studied to realize silicon photonics devices incorporating Si-based light-emitting layers. The bandgap characteristics of two types of triangular-lattice-type PhC in the telecommunication wavelength region of approximately 1.55 m are calculated. They are composed of a-Si circular holes surrounded by ?-FeSi2 (hole type) and ?-FeSi2 circular columns surrounded by a-Si (column type). As a result, the bandgap for the hole-type PhC is obtained for TE polarization, while that for the column-type PhC is obtained for TM polarization. Furthermore, the PhC lattice constant range giving a bandgap for the column-type PhC is much wider than that for the hole-type PhC. The column-type PhC can be easily fabricated compared with the hole-type PhC. Thus, the column-type PhC is useful for actual applications from the viewpoint of fabrication and the bandgap characteristics themselves.

  7. First-principles electronic structure of ?-FeSi2 and FeS2 surfaces

    NASA Astrophysics Data System (ADS)

    Xu, Pengxiang; Schena, Timo; Bl&Gel, Stefan; Bihlmayer, Gustav

    2013-03-01

    Applying density functional theory in the framework of the full-potential linearized augmented plane-wave (FLAPW) method, we investigated electronic structure of potential future photovoltaic materials, ?-FeSi2 and FeS2, for selected surface orientations and terminations. The most stable orientations are determined by comparing their surface energy. Detailed electronic structure calculations show that surface states originating from Fe play an important role and might determine photovoltaic properties. Our results show that anti-ferrimagnetic ordering exists for Fe-terminated surface. Furthermore, we also studied how electronic structure and photovoltaic efficiency are affected by the recently observed structural defects such as stacking fault in ?-FeSi2. This work is supported by BMBF under project Nr. 03SF0402A (NADNuM).

  8. Effects of Sc content on the microstructure of As-Cast Al-7 wt.% Si alloys

    SciTech Connect

    Zhang Wenda; Liu Yun; Yang Jing; Dang Jinzhi; Xu Hong; Du Zhenmin

    2012-04-15

    The effects of Sc content on the microstructure of as-cast Al-Si alloys were investigated by adding 0.05, 0.1, 0.15, 0.2, 0.25, 0.3, and 0.4 wt.% Sc to hypoeutectic Al-7 wt.% Si alloys. The results show that there are significant changes in the microstructure when the Sc content is increased to 0.15%. The volume fraction of the primary {alpha}-Al phase increased nearly monotonically with increasing Sc content in the as-cast state. As the Sc content increased, the average length of the eutectic Si in the as-cast Al-7Si-xSc alloy decreased sharply from 150 {mu}m (without Sc content) to 20 {mu}m (0.4 wt.% Sc content). The Sc atoms are concentrated in the interdendritic regions. A fish-bone structure composed of Al, Si, Sc, and Fe, which might be the Fe-rich phase precipitated on the AlSc{sub 2}Si{sub 2} (V-phase) was detected adjacent to the grain boundary by scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS). - Highlights: Black-Right-Pointing-Pointer Significant changes in the microstructure when the Sc content is increased to 0.15%. Black-Right-Pointing-Pointer Volume fraction of the primary a-Al phase increased with increasing Sc content. Black-Right-Pointing-Pointer Average length of Si decreased sharply from 150 to 20 {mu}m with increasing Sc content. Black-Right-Pointing-Pointer The Sc atoms are concentrated in the interdendritic regions.

  9. Characterization of ?-FeSi II films as a novel solar cell semiconductor

    NASA Astrophysics Data System (ADS)

    Fukuzawa, Yasuhiro; Ootsuka, Teruhisa; Otogawa, Naotaka; Abe, Hironori; Nakayama, Yasuhiko; Makita, Yunosuke

    2006-04-01

    ?-FeSi II is an attractive semiconductor owing to its extremely high optical absorption coefficient (?>10 5 cm -1), and is expected to be an ideal semiconductor as a thin film solar cell. For solar cell use, to prepare high quality ?-FeSi II films holding a desired Fe/Si ratio, we chose two methods; one is a molecular beam epitaxy (MBE) method in which Fe and Si were evaporated by using normal Knudsen cells, and occasionally by e-gun for Si. Another one is the facing-target sputtering (FTS) method in which deposition of ?-FeSi II films is made on Si substrate that is placed out of gas plasma cloud. In both methods to obtain ?-FeSi II films with a tuned Fe/Si ratio, Fe/Si super lattice was fabricated by varying Fe and Si deposition thickness. Results showed significant in- and out-diffusion of host Fe and Si atoms at the interface of Si substrates into ?-FeSi II layers. It was experimentally demonstrated that this diffusion can be suppressed by the formation of template layer between the epitaxial ?-FeSi II layer and the substrate. The template layer was prepared by reactive deposition epitaxy (RDE) method. By fixing the Fe/Si ratio as precisely as possible at 1/2, systematic doping experiments of acceptor (Ga and B) and donor (As) impurities into ?-FeSi II were carried out. Systematical changes of electron and hole carrier concentration in these samples along variation of incorporated impurities were observed through Hall effect measurements. Residual carrier concentrations can be ascribed to not only the remaining undesired impurities contained in source materials but also to a variety of point defects mainly produced by the uncontrolled stoichiometry. A preliminary structure of n-?-FeSi II/p-Si used as a solar cell indicated a conversion efficiency of 3.7%.

  10. Magnetic moments induce strong phonon renormalization in FeSi.

    PubMed

    Krannich, S; Sidis, Y; Lamago, D; Heid, R; Mignot, J-M; Löhneysen, H v; Ivanov, A; Steffens, P; Keller, T; Wang, L; Goering, E; Weber, F

    2015-01-01

    The interactions of electronic, spin and lattice degrees of freedom in solids result in complex phase diagrams, new emergent phenomena and technical applications. While electron-phonon coupling is well understood, and interactions between spin and electronic excitations are intensely investigated, only little is known about the dynamic interactions between spin and lattice excitations. Noncentrosymmetric FeSi is known to undergo with increasing temperature a crossover from insulating to metallic behaviour with concomitant magnetic fluctuations, and exhibits strongly temperature-dependent phonon energies. Here we show by detailed inelastic neutron-scattering measurements and ab initio calculations that the phonon renormalization in FeSi is linked to its unconventional magnetic properties. Electronic states mediating conventional electron-phonon coupling are only activated in the presence of strong magnetic fluctuations. Furthermore, phonons entailing strongly varying Fe-Fe distances are damped via dynamic coupling to the temperature-induced magnetic moments, highlighting FeSi as a material with direct spin-phonon coupling and multiple interaction paths. PMID:26611619

  11. Magnetic moments induce strong phonon renormalization in FeSi

    NASA Astrophysics Data System (ADS)

    Krannich, S.; Sidis, Y.; Lamago, D.; Heid, R.; Mignot, J.-M.; Lhneysen, H. V.; Ivanov, A.; Steffens, P.; Keller, T.; Wang, L.; Goering, E.; Weber, F.

    2015-11-01

    The interactions of electronic, spin and lattice degrees of freedom in solids result in complex phase diagrams, new emergent phenomena and technical applications. While electron-phonon coupling is well understood, and interactions between spin and electronic excitations are intensely investigated, only little is known about the dynamic interactions between spin and lattice excitations. Noncentrosymmetric FeSi is known to undergo with increasing temperature a crossover from insulating to metallic behaviour with concomitant magnetic fluctuations, and exhibits strongly temperature-dependent phonon energies. Here we show by detailed inelastic neutron-scattering measurements and ab initio calculations that the phonon renormalization in FeSi is linked to its unconventional magnetic properties. Electronic states mediating conventional electron-phonon coupling are only activated in the presence of strong magnetic fluctuations. Furthermore, phonons entailing strongly varying Fe-Fe distances are damped via dynamic coupling to the temperature-induced magnetic moments, highlighting FeSi as a material with direct spin-phonon coupling and multiple interaction paths.

  12. Hot-electron transport properties of CoFe/n-Si and CoFe/Cu/n-Si junctions

    NASA Astrophysics Data System (ADS)

    Tang, Xiao-Li; Zhang, Huai-Wu; Su, Hua; Zhong, Zhi-Yong; Jing, Yu-Lan

    2008-08-01

    The hot-electron transport properties of different thickness of CoFe films deposited on n-Si substrate with and without Cu layer were investigated. Diode characteristics were tested to obtain the heights of Schottky barrier for different samples. The dependences of Schottky heights on CoFe thickness were studied. The research shows that the height of the Schottky barrier can be adjusted and a good Schottky diode can be obtained by controlling the thickness of CoFe film accurately. The results are very important for the application of spintronic devices, such as spin valve transistor (SVT) and magnetic tunnel transistor (MTT).

  13. Structure determination of Fe-Al-Ge alloys

    NASA Astrophysics Data System (ADS)

    Gargicevich, D.; Galván Josa, V. M.; Blanco, C.; Lambri, A.; Cuello, G. J.

    2015-11-01

    We studied the crystalline structure of Fe - 8at.%Al - 4at.%Ge alloy between 300 and 1300 K and its relation to the mechanical response by means of neutron diffraction and mechanical spectroscopy. At room temperature we observe a Fe3Al-type ordered structure with a deficiency of Al in the 8c sites. The Ge atoms are distributed in the 4a and Al atoms in 8c sites. At high temperature we observe an order-disorder transformation when the crystal structure becomes Fe-α type. This loss of order gives rise to the hysteresis behavior of damping between the heating and cooling runs.

  14. Ab initio studies on the adsorption and implantation of Al and Fe to nitride materials

    NASA Astrophysics Data System (ADS)

    Riedl, H.; Zlek, J.; Arndt, M.; Polcik, P.; Holec, D.; Mayrhofer, P. H.

    2015-09-01

    The formation of transfer material products on coated cutting and forming tools is a major failure mechanism leading to various sorts of wear. To describe the atomistic processes behind the formation of transfer materials, we use ab initio to study the adsorption energy as well as the implantation barrier of Al and Fe atoms for (001)-oriented surfaces of TiN, Ti0.50Al0.50N, Ti0.90Si0.10N, CrN, and Cr0.90Si0.10N. The interactions between additional atoms and nitride-surfaces are described for pure adhesion, considering no additional stresses, and for the implantation barrier. The latter, we simplified to the stress required to implant Al and Fe into sub-surface regions of the nitride material. The adsorption energies exhibit pronounced extrema at high-symmetry positions and are generally highest at nitrogen sites. Here, the binary nitrides are comparable to their ternary counterparts and the average adhesive energy is higher (more negative) on CrN than TiN based systems. Contrary, the implantation barrier for Al and Fe atoms is higher for the ternary systems Ti0.50Al0.50N, Ti0.90Si0.10N, and Cr0.90Si0.10N than for their binary counterparts TiN and CrN. Based on our results, we can conclude that TiN based systems outperform CrN based systems with respect to pure adhesion, while the Si-containing ternaries exhibit higher implantation barriers for Al and Fe atoms. The data obtained are important to understand the atomistic interaction of metal atoms with nitride-based materials, which is valid not just for machining operations but also for any combination such as interfaces between coatings and substrates or multilayer and phase arrangements themselves.

  15. Wetting behavior in the Al-Si/SiC system: Interface reactions and solubility effects

    SciTech Connect

    Ferro, A.C.; Derby, B.

    1995-08-01

    The sessile drop technique was used to study the wetting behavior of Al-Si alloys on SiC sintered ceramic substrates under vacuum in the 700--1,100 C temperature interval. Al-Si alloys with Si concentrations up to 50% were tested. An expected non-wetting/wetting transition was observed at 900--1,000 C due to the presence of an alumina film surrounding the molten alloy. At higher temperatures wetting was observed and the Si concentration of the alloy has a marked effect on the measured contact angles, {theta}. At 1,100 C {theta} decreases from 55 to 25{degree} when instead of pure Al an Al12.3%Si or an Al16.6%Si alloy is used. The suppression of the formation of a continuous Al{sub 4}C{sub 3} layer at the interface and a process of dissolution and reconstruction of the SiC surface, due to the increased Si concentration of the Al-Si alloys, are the key factors to explain the observed behavior.

  16. Fabrication of novel double-hetero-epitaxial SOI structure Si/?-Al 2O 3/Si

    NASA Astrophysics Data System (ADS)

    Tan, Liwen; Wang, Qiyuan; Wang, Jun; Yu, Yuanhuan; Liu, Zhongli; Lin, Lanying

    2003-01-01

    In this paper, we report the fabrication of Si-based double-hetero-epitaxial silicon on insulator (SOI) structure Si/?-Al 2O 3/Si. Firstly, single crystalline ?-Al 2O 3(1 0 0) insulator films were grown epitaxially on Si(1 0 0) using the sources of TMA (Al(CH 3) 3) and O 2 by very low-pressure chemical vapor deposition. Afterwards, Si(1 0 0) epitaxial films were grown on ?-Al 2O 3 (1 0 0)/Si(1 0 0) epi-substrates using a chemical vapor deposition method similar to the silicon on sapphire epitaxial growth. The Si/?-Al 2O 3/Si SOI materials are characterized in detail by reflect high-energy electron diffraction, X-ray diffraction and Auger energy spectrum (AES) techniques. The insulator layer of ?-Al 2O 3 has an excellent dielectric property. The leakage current is less than 110 -10 A/cm 2 when the electric field is below 1.3 MV/cm. The Si film grown on ?-Al 2O 3/Si epi-substrates was single crystalline. Meanwhile, the AES depth profile of the SOI structure shows that the composition of ?-Al 2O 3 film is uniform, and the carbon contamination is not observed. Additionally, the ?-Al 2O 3/Si epi-substrates are suitable candidates as a platform for a variety of active layers such as GaN, SiC and GeSi. It shows a bright future for microelectronic and optical electronics applications.

  17. Magnetic properties, morphology and interfaces of (Fe/Si)n nanostructures

    NASA Astrophysics Data System (ADS)

    Bartolom, J.; Bada-Romano, L.; Rubn, J.; Bartolom, F.; Varnakov, S. N.; Ovchinnikov, S. G.; Brgler, D. E.

    2016-02-01

    A systematic study of the iron-silicon interfaces formed upon preparation of (Fe/Si) multilayers has been performed by the combination of modern and powerful techniques. Samples were prepared by molecular beam epitaxy under ultrahigh vacuum onto Si wafers or single crystalline Ag(100) buffer layers grown on GaAs(100). The morphology of these films and their interfaces was studied by a combination of scanning transmission electron microscopy, X-ray reflectivity, angle resolved X-ray photoelectron spectroscopy and hard X-ray photoelectron spectroscopy. The Si-on-Fe interface thickness and roughness were determined to be 1.4(1) nm and 0.6(1) nm, respectively. Moreover, determination of the stable phases formed at both Fe-on-Si and Si-on-Fe interfaces was performed using conversion electron Mssbauer spectroscopy on multilayers with well separated Si-on-Fe and Fe-on-Si interfaces. It is shown that while a fraction of Fe remains as ?-Fe, the rest has reacted with Si, forming the paramagnetic FeSi phase and a ferromagnetic Fe rich silicide. We conclude that there is an identical paramagnetic c-Fe1-xSi silicide sublayer in both Si-on-Fe and Fe-on-Si interfaces, whereas an asymmetry is revealed in the composition of the ferromagnetic silicide sublayer.

  18. Formation of ?-FeSi 2 thin films by partially ionized vapor deposition

    NASA Astrophysics Data System (ADS)

    Harada, Noriyuki; Takai, Hiroshi

    2003-05-01

    The partially ionized vapor deposition (PIVD) is proposed as a new method to realize low temperature formation of ?-FeSi 2 thin films. In this method, Fe is evaporated by E-gun and a few percents of Fe atoms are ionized. We have investigated influences of the ion content and the accelerating voltage of Fe ions on the structural properties of ?-FeSi 2 films deposited on Si substrates. It was confirmed that ?-FeSi 2 can be formed on Si(1 0 0) substrate by PIVD even at substrate temperature as low as 350, while FeSi by the conventional vacuum deposition. It was concluded that the influence of Fe ions on preferential orientation of ?-FeSi 2 depends strongly on the content and the acceleration energy of ions.

  19. Three-dimensional rigid multiphase networks providing high-temperature strength to cast AlSi10Cu5Ni1-2 piston alloys.

    PubMed

    Asghar, Z; Requena, G; Boller, E

    2011-09-01

    The three-dimensional (3-D) architecture of rigid multiphase networks present in AlSi10Cu5Ni1 and AlSi10Cu5Ni2 piston alloys in as-cast condition and after 4h spheroidization treatment is characterized by synchrotron tomography in terms of the volume fraction of rigid phases, interconnectivity, contiguity and morphology. The architecture of both alloys consists of ?-Al matrix and a rigid long-range 3-D network of Al(7)Cu(4)Ni, Al(4)Cu(2)Mg(8)Si(7), Al(2)Cu, Al(15)Si(2)(FeMn)(3) and AlSiFeNiCu aluminides and Si. The investigated architectural parameters of both alloys studied are correlated with room-temperature and high-temperature (300C) strengths as a function of solution treatment time. The AlSi10Cu5Ni1 and AlSi10Cu5Ni2 alloys behave like metal matrix composites with 16 and 20vol.% reinforcement, respectively. Both alloys have similar strengths in the as-cast condition, but the AlSi10Cu5Ni2 is able to retain ?15% higher high temperature strength than the AlSi10Cu5Ni1 alloy after more than 4h of spheroidization treatment. This is due to the preservation of the 3-D interconnectivity and the morphology of the rigid network, which is governed by the higher degree of contiguity between aluminides and Si. PMID:21977004

  20. Three-dimensional rigid multiphase networks providing high-temperature strength to cast AlSi10Cu5Ni1-2 piston alloys

    PubMed Central

    Asghar, Z.; Requena, G.; Boller, E.

    2011-01-01

    The three-dimensional (3-D) architecture of rigid multiphase networks present in AlSi10Cu5Ni1 and AlSi10Cu5Ni2 piston alloys in as-cast condition and after 4h spheroidization treatment is characterized by synchrotron tomography in terms of the volume fraction of rigid phases, interconnectivity, contiguity and morphology. The architecture of both alloys consists of ?-Al matrix and a rigid long-range 3-D network of Al7Cu4Ni, Al4Cu2Mg8Si7, Al2Cu, Al15Si2(FeMn)3 and AlSiFeNiCu aluminides and Si. The investigated architectural parameters of both alloys studied are correlated with room-temperature and high-temperature (300C) strengths as a function of solution treatment time. The AlSi10Cu5Ni1 and AlSi10Cu5Ni2 alloys behave like metal matrix composites with 16 and 20vol.% reinforcement, respectively. Both alloys have similar strengths in the as-cast condition, but the AlSi10Cu5Ni2 is able to retain ?15% higher high temperature strength than the AlSi10Cu5Ni1 alloy after more than 4h of spheroidization treatment. This is due to the preservation of the 3-D interconnectivity and the morphology of the rigid network, which is governed by the higher degree of contiguity between aluminides and Si. PMID:21977004

  1. Origin of Fe3+ in Fe-containing, Al-free mantle silicate perovskite

    NASA Astrophysics Data System (ADS)

    Xu, Shenzhen; Shim, Sang-Heon; Morgan, Dane

    2015-01-01

    We have studied the ferrous (Fe2+) and ferric (Fe3+) iron concentrations in Al-free Fe containing Mg-silicate perovskite (Mg-Pv) at pressure (P), temperature (T), and oxygen fugacity (fO2) conditions related to the lower mantle using a thermodynamic model based on ab initio calculations. We consider the oxidation reaction and the charge disproportionation reaction, both of which can produce Fe3+ in Mg-Pv. The model shows qualitatively good agreement with available experimental data on Fe3+/ΣFeFe = total Fe in system), spin transitions, and equations of state. We predict that under lower-mantle conditions Fe3+/ΣFe determined by the charge disproportionation is estimated to be 0.01-0.07 in Al-free Mg-Pv, suggesting that low Al Mg-Pv in the uppermost pyrolitic mantle (where majoritic garnet contains most of the Al) and in the harzburgitic heterogeneities throughout the lower mantle contains very little Fe3+. We find that the volume reduction by the spin transition of the B-site Fe3+ leads to a minimum Fe3+/ΣFe in Mg-Pv at mid-mantle pressures. The model shows that configurational entropy is a key driving force to create Fe3+ and therefore Fe3+ content is highly temperature sensitive. The temperature sensitivity may lead to a maximum Fe3+/ΣFe in Mg-Pv in warm regions at the core-mantle boundary region, such as Large Low Shear Velocity Provinces (LLSVPs), potentially altering the physical (e.g., bulk modulus) and transport (e.g., thermal and electrical conductivities) properties of the heterogeneities.

  2. 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.

  3. Magnetic moments induce strong phonon renormalization in FeSi

    PubMed Central

    Krannich, S.; Sidis, Y.; Lamago, D.; Heid, R.; Mignot, J.-M.; Löhneysen, H. v.; Ivanov, A.; Steffens, P.; Keller, T.; Wang, L.; Goering, E.; Weber, F.

    2015-01-01

    The interactions of electronic, spin and lattice degrees of freedom in solids result in complex phase diagrams, new emergent phenomena and technical applications. While electron–phonon coupling is well understood, and interactions between spin and electronic excitations are intensely investigated, only little is known about the dynamic interactions between spin and lattice excitations. Noncentrosymmetric FeSi is known to undergo with increasing temperature a crossover from insulating to metallic behaviour with concomitant magnetic fluctuations, and exhibits strongly temperature-dependent phonon energies. Here we show by detailed inelastic neutron-scattering measurements and ab initio calculations that the phonon renormalization in FeSi is linked to its unconventional magnetic properties. Electronic states mediating conventional electron–phonon coupling are only activated in the presence of strong magnetic fluctuations. Furthermore, phonons entailing strongly varying Fe–Fe distances are damped via dynamic coupling to the temperature-induced magnetic moments, highlighting FeSi as a material with direct spin–phonon coupling and multiple interaction paths. PMID:26611619

  4. Influence of Some Trace Elements on Solidification Path and Microstructure of Al-Si Foundry Alloys

    NASA Astrophysics Data System (ADS)

    Ludwig, Thomas Hartmut; Schaffer, Paul Louis; Arnberg, Lars

    2013-08-01

    In the present study, Ca, Ni, V, and Zn were added to a high purity binary Al-7wt pct Si and commercial purity A356 foundry alloy in the nominal range of 50 to 600 ppm in order to study their effect on the solidification path and the resultant microstructure. Thermal analysis was used to assess nucleation and growth of the various phases. It was found that Ca and Ni additions suppress characteristic temperatures associated with nucleation and growth of the eutectic by up to 4 and 1.5 K, respectively. Additionally, Ca was observed to modify the eutectic Si and a concentration as low as 39 ppm Ca was sufficient to precipitate the geometrically unfavored polyhedral Al2Si2Ca phase. Furthermore, Ni addition resulted in the formation of two intermetallic phases when the Ni concentration exceeded 300 ppm. These phases have been quantified as Al3Ni and Al9FeNi by SEM-EDS. V and Zn had no apparent effect on the cooling curve and the microstructure. Even though it could be shown that V accumulates preferably in β-Al5FeSi particles, V concentrations of 600 ppm were too low to have any influence on the phase's morphology.

  5. On electronic structure and pressure response of FeSi 1- xGe x

    NASA Astrophysics Data System (ADS)

    Reichl, Ch.; Wiesinger, G.; Zaussinger, G.; Bauer, E.; Galli, M.; Marabelli, F.

    1999-01-01

    57Fe Mssbauer measurements performed on FeSi 1- xGe x reveal a reduction of the band gap ? E with increasing x together with a band broadening. Resistivity studies of FeSi and on various Si-rich alloys up to 93kbar, in turn, unveil a continuous growth of ? E.

  6. 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.

  7. Texture development in SiC-seeded AlN

    SciTech Connect

    Sandlin, M.S.; Bowman, K.J.; Root, J.

    1997-01-01

    Polycrystalline AlN specimens containing 15 volume percent SiC seed particles were slip-cast then hot-pressed at 1,800 C. These processing steps resulted in oriented SiC platelets in a nearly random AlN matrix. Samples were then annealed for up to 18 hours at 2,150 C under nitrogen. Quantitative texture measurements of the AlN and SiC basal poles, and powder diffraction measurements were performed using neutron and X-ray diffraction. The results indicate that SiC platelets effectively seed AlN-SiC alloy textures by a coalescence and growth mechanism during annealing. Texture intensification does not occur in AlN specimens without SiC platelet additions, or in specimens containing non-oriented SiC powder. The most effective seeing was observed in specimens containing 15 volume percent SiC platelets. Optical microscopy and electron microscopy were used in conjunction with texture analysis to elucidate texture development mechanisms.

  8. All-epitaxial Co2FeSi/Ge/Co2FeSi trilayers fabricated by Sn-induced low-temperature epitaxy

    NASA Astrophysics Data System (ADS)

    Kawano, M.; Ikawa, M.; Arima, K.; Yamada, S.; Kanashima, T.; Hamaya, K.

    2016-01-01

    We demonstrate low-temperature growth of all-epitaxial Co2FeSi/Ge/Co2FeSi trilayer structures by developing Sn-induced surfactant-mediated molecular beam epitaxy (SMBE) of Ge on Co2FeSi. Despite the growth of a semiconductor on a metal, we verify that the inserted Sn monolayers between Ge and Co2FeSi enable to promote the 2D epitaxial growth of Ge up to 5 nm at a TG of 250 C. An understanding of the mechanism of the Sn-induced SMBE leads to the achievement of all-epitaxial Co2FeSi/Ge/Co2FeSi trilayer structures with spin-valve-like magnetization reversals. This study will open a way for vertical-type and high-performance Ge-based spintronics devices.

  9. Reversibility and coercivity of Fe-alloy/Fe:SiO2 multilayers

    NASA Astrophysics Data System (ADS)

    Zhang, Rui; Skomski, Ralph; Yin, Xiaolu; Liou, Sy-Hwang; Sellmyer, D. J.

    2010-05-01

    Soft bilayer alloys were produced by depositing granular Fe:SiO2 onto transition-metal thin films. We have prepared series of samples using different soft-magnetic materials including permalloy (Ni80Fe20), hcp Co90Fe10, and amorphous Co60Fe20B20, all covered by a layer of superparamagnetic Fe particles in a silicon-oxide matrix. The thickness of transition-metal layer was fixed and the magnetic properties of the bilayer system were studied by varying the Fe:SiO2 layers thicknesses from 0 to 70 nm. The bilayer yields a moderate improvement of the soft-magnetic performance. The hysteresis loops show a pronounced twofold anisotropy in the film plane for permalloy and amorphous CoFeB, which is consistent with the presence of external magnetic field during processing. This indicates that the coercivity is controlled by the pinning of 180 domain walls and that the effect of the Fe particles on the hysteresis is mediated by the interaction with the domain-wall stray fields.

  10. Electronic structure of Fe{sub 3}Si on Si(100) substrates

    SciTech Connect

    Lal, Chhagan; Di Santo, G.; Caputo, M.; Panighel, M.; Goldoni, A.; Taleatu, B. A.; Jain, I. P.

    2014-04-24

    The improved performance of large-scale integrated circuits (LSIs) by the shrinking of devices is becoming difficult due to physical limitations. Here we report, the growth and formation of Fe{sub 3}Si on Si(100) and characterized by x-ray photoemission, UV photoemission and low energy electron diffraction to study the electronic structure. The results revealed that the DO{sub 3} phase formation is exist and photoemission results also support the electron diffraction outcome.

  11. 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.

  12. Phonon-Drag Effect of Ultra-Thin FeSi2 and MnSi1.7/FeSi2 Films

    NASA Astrophysics Data System (ADS)

    Hou, Q. R.; Gu, B. F.; Chen, Y. B.; He, Y. J.

    Phonon-drag effect usually occurs in single crystals at very low temperatures (10-200 K). Strong phonon-drag effect is observed in ultra-thin ?-FeSi2 films at around room temperature. The Seebeck coefficient of a 23 nm-thick ?-FeSi2 film can reach -1.375 mV/K at 343 K. However, the thermoelectric power factor of the film is still small, only 0.4210-3 W/m-K2, due to its large electrical resistivity. When a 27 nm-thick MnSi1.7 film with low electrical resistivity is grown on it, the thermoelectric power factor of the MnSi1.7 film can reach 1.510-3 W/m-K2 at around room temperature. This value is larger than that of bulk MnSi1.7 material in the same temperature range.

  13. Synthesis of ternary Si clathrates in the A-Al-Si (A = Na and K) system

    NASA Astrophysics Data System (ADS)

    Imai, Motoharu; Singh, Shiva Kumar; Nishio, Mitsuaki; Yamada, Takahiro; Yamane, Hisanori

    2015-07-01

    With the aim of producing functional materials based on earth-abundant elements, we examined the synthesis of the ternary type-I clathrates A8AlxSi46-x (A = Na and K). The type-I Si clathrate K7.9(1)Al7.1(1)Si38.9(4), having a lattice parameter of 10.434(1) , was successfully synthesized via the direct reaction of K, Al, and Si by optimization of both the synthesis temperature and the molar ratios among the raw ingredients. K8Al7Si39 exhibited metallic conduction: its electrical resistivity increased with increasing temperature. The high pressure synthesis of Na8AlxSi46-x was also examined, using a belt-type apparatus and employing a mixture of NaSi, Al, and Si as the reagents. In this manner, the type-I Si clathrate Na8.7(9)Al0.5(1)Si45(2), having a lattice parameter of 10.211(1) , was synthesized at 5.5 GPa and 1570 K.

  14. Phase relations in the Fe-FeSi system at high pressures and temperatures

    SciTech Connect

    Fischer, Rebecca A.; Campbell, Andrew J.; Reaman, Daniel M.; Miller, Noah A.; Heinz, Dion L.; Dera, Przymyslaw; Prakapenka, Vitali B.

    2013-06-12

    The Earth's core is comprised mostly of iron and nickel, but it also contains several weight percent of one or more unknown light elements, which may include silicon. Therefore it is important to understand the high pressure, high temperature properties and behavior of alloys in the Fe–FeSi system, such as their phase diagrams. We determined melting temperatures and subsolidus phase relations of Fe–9 wt% Si and stoichiometric FeSi using synchrotron X-ray diffraction at high pressures and temperatures, up to ~200 GPa and ~145 GPa, respectively. Combining this data with that of previous studies, we generated phase diagrams in pressure–temperature, temperature–composition, and pressure–composition space. We find the B2 crystal structure in Fe–9Si where previous studies reported the less ordered bcc structure, and a shallower slope for the hcp+B2 to fcc+B2 boundary than previously reported. In stoichiometric FeSi, we report a wide B2+B20 two-phase field, with complete conversion to the B2 structure at ~42 GPa. The minimum temperature of an Fe–Si outer core is 4380 K, based on the eutectic melting point of Fe–9Si, and silicon is shown to be less efficient at depressing the melting point of iron at core conditions than oxygen or sulfur. At the highest pressures reached, only the hcp and B2 structures are seen in the Fe–FeSi system. We predict that alloys containing more than ~4–8 wt% silicon will convert to an hcp+B2 mixture and later to the hcp structure with increasing pressure, and that an iron–silicon alloy in the Earth's inner core would most likely be a mixture of hcp and B2 phases.

  15. Growth of ?-FeSi 2 thin film on textured silicon substrate for solar cell application

    NASA Astrophysics Data System (ADS)

    Xu, Jiaxiong; Yao, Ruohe; Liu, Yurong

    2011-09-01

    (2 0 2)/(2 2 0)-oriented epitaxial ?-FeSi2 thin films were deposited on textured Si (1 0 0) substrate by magnetron sputtering. The influences of thickness and annealing temperature on the ?-FeSi2 crystallization were studied to find the optimal condition. The results of surface morphology and optical property measurements showed that the inverted pyramid array in the surface of ?-FeSi2 thin films could reduce the surface reflection of ?-FeSi2. In dark condition, the ?-FeSi2/textured-Si heterojunction showed diode property with rectifying ratio of 2.89 105 and built-in potential of 0.58 V. These results indicated the potential application of textured Si substrate in ?-FeSi2 solar cells.

  16. Experimental investigations of Si-isotope fractionation associated with Fe-Si co-precipitates in simulated Precambrian seawater

    NASA Astrophysics Data System (ADS)

    Zheng, X.; Beard, B. L.; Reddy, T. R.; Johnson, C.

    2014-12-01

    The Si cycle was dramatically different in the Precambrian ocean due to the absence of marine Si-secreting organisms. Precambrian Si isotopic compositions were largely controlled by chemical precipitation of Si, input of Si with different isotopic compositions (e.g., continental versus hydrothermal sources) and later alteration and diagenetic processes associated with silicification. In Precambrian banded iron formations (BIFs) and chert deposits there is an over 4‰ spread of Si isotopes (δ30Si), which stands in marked contrast to the narrow range (<0.5) measured in igneous rocks, highlighting the potential of using Si isotopes to reconstruct those processes that controlled the Precambrian marine Si cycle. However, unequivocal interpretations of Si isotope compositions measured in Precambrian Fe-Si rich sediments is hampered by a lack of understanding of Si-isotope fractionation factors associated with formation of these sediments and subsequent diagenetic processes. This study experimentally investigates Si isotope fractionation during the formation of Fe-Si co-precipitates, and between aqueous Si and Fe-Si co-precipitates. All experiments are conducted in an artificially prepared medium that mimics Archean seawater (e.g. Si: ~60 ppm), rather than in a simple Fe-Si solution, because previous studies have revealed distinct Fe isotope fractionation behaviors in artificial Archean seawater (AAS) compared to simple solutions. One set of experiments investigated oxidation of Fe2+ in the AAS at room temperature, which produced amorphous Fe-Si precipitates. Preliminary results show that δ30Si values of Fe-Si co-precipitates are ~2‰ lower than the initial AAS (Δ30Siprecip-AAS = -2.13 ± 0.18‰ (2σ)). A second set of experiments trace Si-isotope exchange between aqueous Si (AAS) and Fe-Si co-precipitates in an anaerobic chamber, using a 29Si spike (i.e. three-isotope method). The results of these experiments will form a basis for reliable interpretations of Si isotopes recorded in Precambrian sediments.

  17. Nucleation and Growth of Eutectic Si in Al-Si Alloys with Na Addition

    NASA Astrophysics Data System (ADS)

    Li, J. H.; Barrirero, J.; Engstler, M.; Aboulfadl, H.; Mücklich, F.; Schumacher, P.

    2015-03-01

    Al-5 wt pct Si-based alloys with Na additions (19 and 160 ppm) have been produced by controlled sand casting and melt spinning. Entrained droplet technique and differential scanning calorimetry were employed to investigate the nucleation behavior of eutectic Si. High-resolution transmission electron microscopy and atom probe tomography were used to investigate the distribution of Na atoms within eutectic Si and at the interfaces between eutectic Si and eutectic Al. It was found that (i) only 19 ppm Na addition results into a high undercooling (49 K (49 °C)) of the entrained eutectic droplet. However, further increasing Na addition up to 160 ppm exerts no positive effect on the nucleation of eutectic Si, instead a decreased undercooling (29 K (29 °C)) was observed. (ii) Na addition suppresses the growth of eutectic Si due to the Na segregation at the interface between eutectic Si and eutectic Al, and (iii) Na addition promotes significant multiple Si twins, which can be attributed to the proposed adsorption of Na atoms at the intersection of Si twins and along the <112>Si growth direction of Si. The present investigation demonstrates, for the first time, a direct observation on the distribution of Na atoms within eutectic Si and thereby provides strong experimental supports to the well-accepted impurity-induced twinning growth mechanism and poisoning of the twin plane re-entrant edge growth mechanism.

  18. The Effect of Inhibitors on the Susceptibility of Al 6013/SiC Interface to Localized Corrosion

    NASA Astrophysics Data System (ADS)

    Ahmad, Zaki; Aleem, B. J. Abdul

    2009-03-01

    Al 6013-20 SiC (p) in tempers T4, O, and F is sensitive to localized corrosion in 3.5 wt.% NaCl because of the preponderance of the secondary phase particles of Cu, Fe, and Cr at the Al/SiC interface. Treatment with cerium chloride effectively inhibited the localized corrosion of the alloy by suppressing the cathodic reactions at Al 6013/SiC interface as shown by electrochemical investigations. Morphological studies showed the formation of a protective cerium oxide/hydroxide films, which suppresses the corrosion of the alloy.

  19. {beta}-SiAlON-silicon nitride multilayered composites

    SciTech Connect

    Shigegaki, Yasuhiro; Brito, M.E.; Hirao, Kiyoshi; Toriyama, Motohiro; Kanzaki, Shuzo

    1997-10-01

    Layered composites with alternating {beta}-SiAlON and silicon nitride layers were fabricated using a tape-casting and laminating technique. A distinct layered structure was obtained by hot pressing, where compositions of yttrium and aluminum at the layer interface were functionally graded in a thickness of {approximately} 10 {micro}m. A solid-solution reaction prior to densification in the {beta}-SiAlON layer contributed to the coexistence, in equilibrium, of these two layers. Density and Young`s modulus depended on the volume fraction of silicon nitride layers according to the rule of mixtures. The strength of the {beta}-SiAlON layer, estimated by an equivalent strain model, increased when compared to that of the monolithic material, although the fracture origin always was observed within the {beta}-SiAlON layer. The layer thickness in an alternating layered configuration affected the strength of discrete layers.

  20. The Effect of Plasma Spraying on the Microstructure and Aging Kinetics of the Al-Si Matrix Alloy and Al-Si/SiC Composites

    NASA Astrophysics Data System (ADS)

    Altunpak, Yahya; Akbulut, Hatem; stel, Fatih

    2010-02-01

    The Al-Si (LM 13)-based matrix alloy reinforced with SiC particles containing 10, 20, and 30 vol.% SiC particles were spray-formed onto Al-Si substrates. The sprayed samples were directly subjected to a standard aging treatment (T551). From the experiments, it was observed that the high rate of solidification resulted in very fine silicon particles which were observed as continuous islands in the matrix and each island exhibited several very fine silicon crystals. Analysis showed that plasma-spraying caused an increased solid solubility of the silicon in the aluminum matrix. DSC measurements in the permanent mold-cast Al-Si matrix alloy and plasma-sprayed Al-Si matrix alloy showed that plasma-spraying causes an increase in the amount of GP-zone formation owing to the very high rate solidification after plasma-spraying. In the plasma-sprayed Al-Si/SiC composites GP zones were suppressed, since particle-matrix interfaces act as a sink for vacancies during quenching from high plasma process temperature. Introduction of SiC particles to the Al-Si age-hardenable alloy resulted in a decrease in the time required to reach plateau matrix hardness owing to acceleration of aging kinetics by ceramic SiC particles.

  1. Magnetic properties of epitaxial and polycrystalline Fe/Si multilayers

    SciTech Connect

    Chaiken, A.; Michel, R.P.; Wang, C.T.

    1995-08-01

    Fe/Si multilayers with antiferromagnetic interlayer coupling have been grown via ion-beam sputtering on both glass and single-crystal substrates. X-ray diffraction measurements show that both sets of films have crystalline iron silicide spacer layers and a periodic composition modulation. Films grown on glass have smaller crystallite sizes than those grown on single-crystal substrates and have a significant remanent magnetization. Films grown on single-crystal substrates have a smaller remanence. The observation of magnetocrystalline anisotropy in hysteresis loops and (hkl) peaks in x-ray diffraction demonstrates that the films grown on MgO and Ge are epitaxial. The smaller remanent magnetization in Fe/Si multilayers with better crystallinity suggests that the remanence is not intrinsic.

  2. Structural investigations of laser-deposited Fe/Al multilayers

    NASA Astrophysics Data System (ADS)

    Noetzel, J.; Brand, K.; Geisler, H.; Gorbunov, A.; Tselev, A.; Wieser, E.; Mller, W.

    Fe/Al multilayers are prepared by crossed-beam pulsed laser deposition and investigated by Rutherford backscattering, conversion electron Mssbauer spectroscopy, and transmission electron microscopy. The results are compared to purely ballistic simulations of the deposition process using the TRIDYN4.0 code. It is found that the intermixing of adjacent layers must be described in terms of ballistic mixing followed by chemical mixing. The phase formation in the transition layer between adjacent layers follows the non-equilibrium behavior of Fe/Al in analogy to investigations on mechanically alloyed and ion-beam-mixed Fe/Al. In Fe-rich areas a bcc solid solution is formed. In Al-rich environment an amorphous phase is observed.

  3. 57Fe Mössbauer study of Lu2Fe3Si5 iron silicide superconductor

    DOE PAGESBeta

    Ma, Xiaoming; Ran, Sheng; Pang, Hua; Li, Fashen; Canfield, Paul C.; Bud'ko, Sergey L.

    2015-08-01

    With the advent of Fe–As based superconductivity it has become important to study how superconductivity manifests itself in details of 57Fe Mössbauer spectroscopy of conventional, Fe-bearing superconductors. The iron-based superconductor Lu2Fe3Si5 has been studied by 57Fe Mössbauer spectroscopy over the temperature range from 4.4 K to room temperature with particular attention to the region close to the superconducting transition temperature (Tc=6.1 K). Consistent with the two crystallographic sites for Fe in this structure, the observed spectra appear to have a pattern consisting of two doublets over the whole temperature range. Furthermore, the value of Debye temperature was estimated from temperaturemore » dependence of the isomer shift and the total spectral area and compared with the specific heat capacity data. Neither abnormal behavior of the hyperfine parameters at or near Tc, nor phonon softening were observed.« less

  4. SiAlON ceramic compositions and methods of fabrication

    DOEpatents

    O'Brien, M.H.; Park, B.H.

    1994-05-31

    A method of fabricating a SiAlON ceramic body includes: (a) combining quantities of Si[sub 3]N[sub 4], Al[sub 2]O[sub 3] and CeO[sub 2] to produce a mixture; (b) forming the mixture into a desired body shape; (c) heating the body to a densification temperature of from about 1,550 C to about 1,850 C; (d) maintaining the body at the densification temperature for a period of time effective to densify the body; (e) cooling the densified body to a devitrification temperature of from about 1,200 C to about 1,400 C; and (f) maintaining the densified body at the devitrification temperature for a period of time effective to produce a [beta][prime]-SiAlON crystalline phase in the body having elemental or compound form Ce incorporated in the [beta][prime]-SiAlON crystalline phase. Further, a SiAlON ceramic body comprises: (a) an amorphous phase; and (b) a crystalline phase, the crystalline phase comprising [beta][prime]-SiAlON having lattice substituted elemental or compound form Ce.

  5. The influence of the iron content on the reductive decomposition of A{sub 3?x}Fe{sub x}Al{sub 2}Si{sub 3}O{sub 12} garnets (A = Mg, Mn; 0.47 ? x ? 2.85)

    SciTech Connect

    Aparicio, Claudia Filip, Jan Mashlan, Miroslav Zboril, Radek

    2014-10-27

    Thermally-induced reductive decomposition of natural iron-bearing garnets of the almandine-pyrope and almandine-spessartine series were studied at temperatures up to 1200 C (heating rate of 10 C/min) under atmosphere of forming gas (10% of H{sub 2} in N{sub 2}). Crystallochemical formula of the studied garnet was calculated as {sup VIII}(A{sub 3?x}Fe{sub x}{sup 2+}){sup VI}(Al,Fe{sup 3+}){sub 2}Si{sub 3}O{sub 12}, where the amount of Fe{sup 3+} in the octahedral sites is negligible with the exception of pyrope, A = Mg, Mn, and 0.47 ? x ? 2.85. The observed decomposition temperature, determined from differential scanning calorimetry and thermogravimetry, is greater than 1000 C in all cases and showed almost linear dependence on the iron content in the dodecahedral sites of the studied garnets, with the exception of garnet with a near-pyrope composition (Prp{sub 80}Alm{sub 20}). The initial garnet samples and decomposition products were characterized in details by means of X-ray powder diffraction and {sup 57}Fe Mssbauer spectroscopy. We found that all studied garnets have common decomposition products such as metallic iron (in general, rounded particles below 4 ?m) and Fe-spinel; the other identified decomposition products depend on starting chemical composition of the garnet: Fe-cordierite, olivine (fayalite or tephroite), cristobalite, pyroxene (enstatite or pigeonite), and anorthite. Anorthite and pigeonite were only present in garnets with Ca in the dodecahedral site. All the identified phases were usually well crystallized.

  6. Microstructure and Wear Behavior of Solidification Sonoprocessed B390 Hypereutectic Al-Si Alloy

    NASA Astrophysics Data System (ADS)

    Khalifa, Waleed; El-Hadad, Shimaa; Tsunekawa, Yoshiki

    2013-12-01

    The hypereutectic Al-Si alloys constitute an important family of alloys because of their excellent wear resistance and low thermal expansion. However, the optimal microstructure and hence the optimal service performance of these alloys cannot be achieved by the conventional melt treatments used in industry today, because of the chemical incompatibility between the primary-Si refiners and the eutectic-Si modifiers used in microstructure control. The current study aimed at using ultrasonic vibrations to improve the microstructure and the properties of these alloys. The results of the current study showed that for the B390 Al-Si alloy (i) the ultrasonic treatment has potential refining effect on the primary Si and Fe intermetallic phases, (ii) the primary Si particles become finer as the pouring temperature decreases from 1033 K (760 C) to 938 K (665 C), (iii) pouring and ultrasonic treatment at temperatures below the start of primary Si precipitation result in the coexistence of large and fine Si particles in microstructure, (iv) phosphorous additions of 50 ppm did not show any substantial effect in the ultrasonically treated ingots, (v) ultrasonic-treated samples have uniform hardness over the surface while the untreated samples show large scattering (high standard deviation) in hardness levels and (vi) ultrasonic-treated samples showed better wear resistance in the absence of phosphorous.

  7. The Sintering, Sintered Microstructure and Mechanical Properties of Ti-Fe-Si Alloys

    NASA Astrophysics Data System (ADS)

    Yang, Y. F.; Luo, S. D.; Schaffer, G. B.; Qian, M.

    2012-12-01

    A systematic study has been conducted of the sintering, sintered microstructure and tensile properties of a range of lower cost Ti-Fe-Si alloys, including Ti-3Fe-(0-4)Si, Ti-(3-6)Fe-0.5Si, and Ti-(3-6)Fe-1Si (in wt pct throughout). Small additions of Si (?1 pct) noticeably improve the as-sintered tensile properties of Ti-3Fe alloy, including the ductility, with fine titanium silicides (Ti5Si3) being dispersed in both the ? and ? phases. Conversely, additions of >1 pct Si produce coarse and/or networked Ti5Si3 silicides along the grain boundaries leading to predominantly intergranular fracture and, hence, poor ductility, although the tensile strength continues to increase because of the reinforcement by Ti5Si3. Increasing the Fe content in the Ti- xFe-0.5/1.0Si alloys above 3 pct markedly increases the average grain size and changes the morphology of the ?-phase phase to much thinner and more acicular laths. Consequently, the ductility drops to <1 pct. Si reacts exothermically with Fe to form Fe-Si compounds prior to the complete diffusion of the Fe into the Ti matrix during heating. The heat thus released in conjunction with the continuous external heat input melts the silicides leading to transient liquid formation, which improves the densification during heating. No Ti-TiFe eutectoid was observed in the as-sintered Ti-Fe-Si alloys. The optimum PM Ti-Fe-Si compositions are determined to be Ti-3Fe-(0.5-1.0)Si.

  8. 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.

  9. Charge storage in β-FeSi{sub 2} nanoparticles

    SciTech Connect

    Theis, Jens; Küpper, Sebastian; Lorke, Axel; Bywalez, Robert; Wiggers, Hartmut

    2015-02-07

    We report on the observation of a surprisingly high specific capacitance of β-FeSi{sub 2} nanoparticle layers. Lateral, interdigitated capacitor structures were fabricated on thermally grown silicon dioxide and covered with β-FeSi{sub 2} particles by drop or spin casting. The β-FeSi{sub 2}-nanoparticles, with crystallite sizes in the range of 10–30 nm, were fabricated by gas phase synthesis in a hot wall reactor. Compared to the bare electrodes, the nanoparticle-coated samples exhibit a 3–4 orders of magnitude increased capacitance. Time-resolved current voltage measurements show that for short times (seconds to minutes), the material is capable of storing up to 1 As/g at voltages of around 1 V. The devices are robust and exhibit long-term stability under ambient conditions. The specific capacitance is highest for a saturated relative humidity, while for a relative humidity below 40% the capacitance is almost indistinguishable from a nanoparticle-free reference sample. The devices work without the need of a fluid phase, the charge storing material is abundant and cost effective, and the sample design is easy to fabricate.

  10. Epoxy-bonded La-Fe-Co-Si magnetocaloric plates

    NASA Astrophysics Data System (ADS)

    Pulko, Barbara; Tuek, Jaka; Moore, James D.; Weise, Bruno; Skokov, Konstantin; Mityashkin, Oleg; Kitanovski, Andrej; Favero, Chiara; Fajfar, Peter; Gutfleisch, Oliver; Waske, Anja; Poredo, Alojz

    2015-02-01

    We report the processing, analysis and testing of magnetocaloric composite materials consisting of La-Fe-Co-Si particles of various size fractions and a polymer matrix. All of the composites have working temperatures close to room temperature. The composites were pressed into thin plates, a geometry favorable for testing the composites in an active magnetic regenerator (AMR). In order to investigate the influence of particle size and binder type (epoxy), eight different epoxy-bonded La-Fe-Co-Si plates were made and analyzed. We found that the higher filling factor that can be achieved by using a mixture of several particle size fractions has beneficial influence on the thermal conductivity. Tests in the AMR revealed that a maximum temperature span of approximately ?T=10 K under magnetic field change of ?0H=1.15 T can be obtained at no cooling load conditions. The stability of the measured ?T values and the mechanical integrity of sample after cyclic application of a magnetic field have been monitored for 90,000 cycles and showed no significant changes. We therefore conclude that epoxy-bonded La-Fe-Co-Si magnetocaloric composites have good magnetocaloric properties at low material-processing costs and hence represent a competitive way to produce magnetocaloric materials to be used in AMR.

  11. Charge storage in ?-FeSi2 nanoparticles

    NASA Astrophysics Data System (ADS)

    Theis, Jens; Bywalez, Robert; Kpper, Sebastian; Lorke, Axel; Wiggers, Hartmut

    2015-02-01

    We report on the observation of a surprisingly high specific capacitance of ?-FeSi2 nanoparticle layers. Lateral, interdigitated capacitor structures were fabricated on thermally grown silicon dioxide and covered with ?-FeSi2 particles by drop or spin casting. The ?-FeSi2-nanoparticles, with crystallite sizes in the range of 10-30 nm, were fabricated by gas phase synthesis in a hot wall reactor. Compared to the bare electrodes, the nanoparticle-coated samples exhibit a 3-4 orders of magnitude increased capacitance. Time-resolved current voltage measurements show that for short times (seconds to minutes), the material is capable of storing up to 1 As/g at voltages of around 1 V. The devices are robust and exhibit long-term stability under ambient conditions. The specific capacitance is highest for a saturated relative humidity, while for a relative humidity below 40% the capacitance is almost indistinguishable from a nanoparticle-free reference sample. The devices work without the need of a fluid phase, the charge storing material is abundant and cost effective, and the sample design is easy to fabricate.

  12. Electromagnetic and microwave absorbing properties of raw and milled FeSiCr particles

    NASA Astrophysics Data System (ADS)

    Yang, R. B.; Liang, W. F.; Chen, C. C.; Choi, S. T.

    2014-05-01

    FeSiCr alloy (Fe: 90%, Si: 7.9%, and Cr: 2.1%) with pre-milled flaky shape was re-milled in a planetary ball-mill for 30 h. The complex permittivity (?'-j??) and permeability (?'-j??) are measured by using the transmission/reflection method for two different aspect ratios of flake-shaped FeSiCr/epoxy composites for 30%, 40%, and 50% weight ratios. Dielectric loss tangent and magnetic loss tangent of re-milled FeSiCr powder show larger electromagnetic wave energy dissipation than those of the raw flaky FeSiCr powder. For 30 wt. % of FeSiCr/epoxy absorbers with 2 mm thickness, the calculated reflection loss reaches -25 dB at 13.0 GHz for raw flaky powder, -40 dB at 11.4 GHz for the re-milled FeSiCr powder with higher aspect ratios.

  13. 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.

  14. Magnetic properties of Fe and Fe-Si alloys with {100}<0vw> texture

    NASA Astrophysics Data System (ADS)

    Kyung Sung, Jin; Mo Koo, Yang

    2013-05-01

    When iron and its alloy sheets with clean metal surfaces undergo the γ to α phase transformation, they develop strong {100}<0vw> texture with grain size being larger than the sheet thickness. For example, when Fe or Fe-1%Si sheets were subjected to the γ to α phase transformation in a reducing gas atmosphere (hydrogen gas having the dew point below -50 °C), strong {100}<0vw> texture developed. Magnetic properties of Fe and Fe-Si alloys show that, by developing the {100}<0vw> texture, the core loss can be reduced by more than 25% and the permeability can be increased by 2-5 times. With 0.35 mm-thick Fe-1%Si with the {100}<0vw> texture, the magnetic properties are W15/50 (core loss at 1.5 T, 50 Hz) = 2.7 W/kg and B50 (magnetic flux density at 5000 A/m) = 1.80 T. The improvement of permeability together with reducing iron loss by texture control will make a significant contribution to improving power density as well as reducing copper losses in induction motors.

  15. A polarized neutron study of the magnetization distribution in Co?FeSi.

    PubMed

    Brown, P J; Kainuma, R; Kanomata, T; Neumann, K-U; Okubo, A; Umetsu, R Y; Ziebeck, K R A

    2013-05-22

    The magnetization distribution in Co2FeSi which has the largest moment per formula unit ?6 ?B of all Heusler alloys, has been determined using polarized neutron diffraction. The experimentally determined magnetization has been integrated over spheres centred on the three sites of the L12 structure giving ? Fe = 3.10(3) ?B and ? Co = 1.43(2) ?B, results which are slightly lower than the moments in atomic spheres of similar radii obtained in recent LDA + U band structure calculations (Li et al 2010 Chin. Phys. B 19 097102). Approximately 50% of the magnetic carriers at the Fe sites were found to be in orbitals with eg symmetry. This was higher, ?65%, at the Co sites. Both Fe and Co were found to have orbital moments that are larger than those predicted. Comparison with similar results obtained for related alloys suggests that there must be a finite density of states in both spin bands at the Fermi energy indicating that Co2FeSi is not a perfect half-metallic ferromagnet. PMID:23612471

  16. Electron energy loss spectroscopy characterization of TANOS (TaN/Al?O?/Si?N?/SiO?/Si) stacks.

    PubMed

    Park, Jucheol; Heo, Sung; Chung, JaeGwan; Park, Gyeong-Su

    2013-08-01

    The interfacial layer between the Al?O? layer and the Si?N? layer formed after postdeposition annealing (PDA) of TaN/Al?O?/Si?N?/SiO?/Si (TANOS) stacks was investigated using transmission electron microscopy (TEM), scanning transmission electron microscopy, and electron energy loss spectroscopy (EELS). From the result of the TEM analysis, it was found that the 2-nm-thick interface layer between Al?O? and Si?N? layers was amorphous. The high-loss EELS analysis showed that the phases of the interfacial layer weakly bound together instead of the substoichiometric silicon oxide and amorphous Al?O? near the bottom interface of the crystalline Al?O?. The low-loss EELS analysis showed that aluminum existed in metallic state at the interface. Therefore, we speculated that SiO(x)N(y) could be formed by oxidation of Si?N? during PDA and that metallic aluminum could be formed by the decomposition of weakly bound amorphous Al?O? during electron irradiation. These complicated reactions near the interface could induce oxygen deficiency in the Al?O? layer and finally degrade the retention properties of TANOS stacks. PMID:23920186

  17. Interdiffusion in Diffusion Couples: U-Mo v. Al and Al-Si

    SciTech Connect

    D. D. Keiser, Jr.; E. Perez; B. Yao; Y. H. Sohn

    2009-11-01

    Interdiffusion and microstructural development in the U-Mo-Al system was examined using solid-tosolid diffusion couples consisting of U-7wt.%Mo, U-10wt.%Mo and U-12wt.%Mo vs. pure Al, annealed at 600C for 24 hours. The influence of Si alloying addition (up to 5 wt.%) in Al on the interdiffusion microstructural development was also examined using solid-to-solid diffusion couples consisting of U-7wt.%Mo, U-10wt.%Mo and U-12wt.%Mo vs. pure Al, Al-2wt.%Si, and Al-5wt.%Si annealed at 550C up to 20 hours. Scanning electron microscopy (SEM), transmission electron microscopy (TEM) and electron probe microanalysis (EPMA) were employed to examine the development of a very fine multiphase intermetallic layer. In ternary U-Mo-Al diffusion couples annealed at 600C for 24 hours, interdiffusion microstructure varied of finely dispersed UAl3, UAl4, U6Mo4Al43, and UMo2Al20 phases while the average composition throughout the interdiffusion zone remained constant at approximately 80 at.% Al. Interdiffusion microstructure observed by SEM/TEM analyses and diffusion paths drawn from concentration profiles determined by EPMA appear to deviate from the assumption of local thermodynamic equilibrium, and suggest that interdiffusion occurs via supersaturated UAl4 followed by equilibrium transformation into UAl3, U6Mo4Al43, UAl4 and UMo2Al20 phases. Similar observation was made for U-Mo vs. Al diffusion couples annealed at 550C. The addition of Si (up to 5 wt.%) in Al significantly reduced the thickness of the intermetallic layer by changing the constituent phases of the interdiffusion zone developed in U-Mo vs. Al-Si diffusion couples. Specifically, the formation of (U,Mo)(Al,Si)3 with relatively large solubility for Mo and Si, along with UMo2Al20 phases was observed along with disappearance of U6Mo4Al43 and UAl4 phases. Simplified understanding based on U-Al, U-Si, and Mo-Si binary phase diagrams is discussed in the light of the beneficial effect of Si alloying addition.

  18. 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.

  19. Influence of FeCrAl Content on Microstructure and Bonding Strength of Plasma-Sprayed FeCrAl/Al2O3 Coatings

    NASA Astrophysics Data System (ADS)

    Zhou, Liang; Luo, Fa; Zhou, Wancheng; Zhu, Dongmei

    2016-02-01

    Low-power plasma-sprayed FeCrAl/Al2O3 composite coatings with 1.5 mm thickness have been fabricated for radar absorption applications. The effects of FeCrAl content on the coating properties were studied. The FeCrAl presents in the form of a few thin lamellae and numerous particles, demonstrating relatively even distribution in all the coatings. Results show that the micro-hardness and porosity decrease with the increase in FeCrAl content. With FeCrAl content increasing from 28 to 47 wt.%, the bonding strength of the coatings with 1.5 mm thickness increases from 10.5 to 27 MPa, and the failure modes are composed of cohesive and adhesive failure, which are ascribed to the coating microstructure and the residual stress, respectively.

  20. Influence of FeCrAl Content on Microstructure and Bonding Strength of Plasma-Sprayed FeCrAl/Al2O3 Coatings

    NASA Astrophysics Data System (ADS)

    Zhou, Liang; Luo, Fa; Zhou, Wancheng; Zhu, Dongmei

    2015-12-01

    Low-power plasma-sprayed FeCrAl/Al2O3 composite coatings with 1.5 mm thickness have been fabricated for radar absorption applications. The effects of FeCrAl content on the coating properties were studied. The FeCrAl presents in the form of a few thin lamellae and numerous particles, demonstrating relatively even distribution in all the coatings. Results show that the micro-hardness and porosity decrease with the increase in FeCrAl content. With FeCrAl content increasing from 28 to 47 wt.%, the bonding strength of the coatings with 1.5 mm thickness increases from 10.5 to 27 MPa, and the failure modes are composed of cohesive and adhesive failure, which are ascribed to the coating microstructure and the residual stress, respectively.

  1. Investigation of mechanosynthesized Fe50Ni40Al10 powders

    NASA Astrophysics Data System (ADS)

    Hadef, F.; Otmani, A.; Djekoun, A.; Grenèche, J. M.

    2013-10-01

    The synthesis of Fe50Ni40Al10 powder mixture has been performed in a high-energy planetary ball mill. The phase transformations and structural changes occurring during mechanical alloying were investigated by X-ray diffraction (XRD) and Mössbauer spectroscopy. XRD analysis and Rietveld method revealed the formation of a single nanocrystalline fcc γ-Ni(Fe,Al) solid solution with a lattice parameter close to aγ-Ni(Fe,Al)=0.3612 nm, after 4 h of milling. The final powder is characterized by an average crystallite size of 14 nm accompanied by the introduction of a lattice strain of order of 1.37%. These values are markedly higher than those reported for mechanically alloyed Fe50Ni50 powders. It was found that the formation of the bcc phase, which coexisted with the fcc structure in the Fe-Ni phase diagram, was inhibited. However, mechanical alloying process gives rise to the Ni3Al intermetallic phase, at the early stages of milling. Mössbauer spectroscopy showed that all powders exhibited a ferromagnetic behavior and no paramagnetic phase was detected. The addition of low aluminium content caused more broadening of hyperfine field distributions and lower magnetic field due to the diffusion of Al atoms into γ-FeNi lattice.

  2. Preparation of Fe-doped colloidal SiO(2) abrasives and their chemical mechanical polishing behavior on sapphire substrates.

    PubMed

    Lei, Hong; Gu, Qian; Chen, Ruling; Wang, Zhanyong

    2015-08-20

    Abrasives are one of key influencing factors on surface quality during chemical mechanical polishing (CMP). Silica sol, a widely used abrasive in CMP slurries for sapphire substrates, often causes lower material removal rate (MRRs). In the present paper, Fe-doped colloidal SiO2 composite abrasives were prepared by a seed-induced growth method in order to improve the MRR of sapphire substrates. The CMP performance of Fe-doped colloidal SiO2 abrasives on sapphire substrates was investigated using UNIPOL-1502 CMP equipment. Experimental results indicate that the Fe-doped colloidal SiO2 composite abrasives exhibit lower surface roughness and higher MRR than pure colloidal SiO2 abrasives for sapphire substrates under the same testing conditions. Furthermore, the acting mechanism of Fe-doped colloidal SiO2 composite abrasives in sapphire CMP was analyzed by x-ray photoelectron spectroscopy. Analytical results show that the Fe in the composite abrasives can react with the sapphire substrates to form aluminum ferrite (AlFeO3) during CMP, which promotes the chemical effect in CMP and leads to improvement of MRR. PMID:26368752

  3. Scandium iridium boride Sc{sub 3}Ir{sub 5}B{sub 2} and the quaternary derivatives Sc{sub 2}MIr{sub 5}B{sub 2} with M = Be, Al, Si, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Ga, or Ge: Preparation, crystal structure, and physical properties

    SciTech Connect

    Nagelschmitz, E.A.; Jung, W.

    1998-10-01

    The new compounds Sc{sub 3}Ir{sub 5}B{sub 2} and Sc{sub 2}MIr{sub 5}B{sub 2} with M = Be, Al, Si, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Ga, or Ge were prepared by arc-melting appropriate compressed mixtures of the elemental components in an argon atmosphere. They crystallize tetragonally with Z = 2 in the space group P4/mbm. According to powder diagrams, all compounds are isotypic. Structure determinations based on single-crystal X-ray data were performed for Sc{sub 2}SiIr{sub 5}B{sub 2}, Sc{sub 2}VIr{sub 5}B{sub 2}, and Sc{sub 2}FeIr{sub 5}B{sub 2}. Sc{sub 3}Ir{sub 5}B{sub 2} crystallizes with the Ti{sub 3}Co{sub 5}B{sub 2}-type compounds, while the quaternary compounds form an ordered substitutional variant of this structure. The M atoms are arranged in rows along [001] with M-M distances of {approximately}300 pm in the rows and {approximately}660 pm between the rows. For the compounds with M = Mn, Fe, or Co, this results in highly anisotropic magnetic properties. Susceptibility measurements with a Faraday balance in the range 7--770 K suggest ferromagnetic coupling in the rows at low temperatures. Between the rows, the coupling was antiferromagnetic for Sc{sub 2}FeIr{sub 5}B{sub 2} (T{sub N} {approx} 190 K) and ferromagnetic for Sc{sub 2}MnIr{sub 5}B{sub 2} (T{sub C} {approx} 115 K, {mu}{sub s} {approx} 1.2 {mu}{sub B}) and for Sc{sub 2}CoIr{sub 5}B{sub 2} (T{sub C} {approx} 135 K, {mu}{sub s} {approx} 1.2 {mu}{sub B}). The temperature dependence of the resistivity was measured for the compounds with M = Si, Mn, Fe, and Co.

  4. Broad Negative Thermal Expansion Operation-Temperature Window Achieved by Adjusting Fe-Fe Magnetic Exchange Coupling in La(Fe,Si)13 Compounds.

    PubMed

    Li, Shaopeng; Huang, Rongjin; Zhao, Yuqiang; Li, Wen; Wang, Wei; Huang, Chuanjun; Gong, Pifu; Lin, Zheshuai; Li, Laifeng

    2015-08-17

    Cubic La(Fe,Si)13-based compounds have been recently developed as promising negative thermal expansion(NTE) materials, but the narrow NTE operation-temperature window(?110 K) restricts their actual applications. In this work, we demonstrate that the NTE operation-temperature window of LaFe(13-x)Si(x) can be significantly broadened by adjusting Fe-Fe magnetic exchange coupling as x ranges from 2.8 to 3.1. In particular, the NTE operation-temperature window of LaFe10.1Si2.9 is extended to 220 K. More attractively, the coefficients of thermal expansion of LaFe10.0Si3.0 and LaFe9.9Si3.1 are homogeneous in the NTE operation-temperature range of about 200 K, which is much valuable for the stability of fabricating devices. The further experimental characterizations combined with first-principles studies reveal that the tetragonal phase is gradually introduced into the cubic phase as the Si content increases, hence modifies the Fe-Fe interatomic distance. The reduction of the overall Fe-Fe magnetic exchange interactions contributes to the broadness of NTE operation-temperature window for LaFe(13-x)Si(x). PMID:26196377

  5. Removal of arsenite by Fe(VI), Fe(VI)/Fe(III), and Fe(VI)/Al(III) salts: effect of pH and anions.

    PubMed

    Jain, Amita; Sharma, Virender K; Mbuya, Odemari S

    2009-09-30

    The removal of arsenate and arsenite from drinking water poses challenges, especially when arsenite is present in a significant amount. The removal of arsenite by K(2)FeO(4), K(2)FeO(4)/FeCl(3), and K(2)FeO(4)/AlCl(3) salts was studied at pH 6.5 and at an initial As concentration of 500 microg As(III)L(-1). The arsenite removal in Fe(VI)/Fe(III) and Fe(VI)/Al(III) systems was also examined as a function of pH (6.0-8.0). Arsenite was first oxidized by Fe(VI) to arsenate, which was subsequently removed through adsorption by Fe(III) or mixed Fe(III)-Al(III) oxy/hydroxide phases. Fe(VI)/Al(III) salts had higher removal efficiency of arsenite than Fe(VI) and Fe(VI)/Fe(III) salts. A molar ratio of 6(3/3):1 for Fe(VI)/Al(III) to As(III) decreased arsenite concentration from 500 to 1.4 microg L(-1) at pH 6.5. Arsenite removal increased with a decrease in pH from 8.0 to 6.0 and exhibited less pH dependence in the Fe(VI)/Al(III) system than in the Fe(VI)/Fe(III) system. Aluminum chloride salts performed better than FeCl(3) and FeCl(3)/AlCl(3) salts (Fe:Al=1:1) in removing As(V) from water. Effect of anions (phosphate, silicate, bicarbonate, nitrate, and sulfate) on the arsenite removal by Fe(VI)/Al(III) salts at pH 6.5 was examined. Phosphate, silicate, and bicarbonate ions interfered with the removal of arsenite in water. Nitrate and sulfate had none to minimal effect on arsenite removal. Fe(VI)/Al(III) salts showed a potential for removing arsenite below the current drinking water standard (10 microg L(-1)). PMID:19409704

  6. Growth of β-FeSi2 films via noble-gas ion-beam mixing of Fe/Si bilayers

    NASA Astrophysics Data System (ADS)

    Milosavljević, M.; Dhar, S.; Schaaf, P.; Bibić, N.; Huang, Y.-L.; Seibt, M.; Lieb, K. P.

    2001-11-01

    A detailed study of the formation of β-FeSi2 films by ion-beam mixing of Fe/Si bilayers with noble gas ions is presented. Fe films of 35-50 nm deposited on Si (100) were irradiated with 80-700 keV Ar, Kr, or Xe ions in a wide temperature interval, from room temperature to 600 °C. The structures were analyzed by Rutherford backscattering spectroscopy, x-ray diffraction, conversion electron Mössbauer spectroscopy, elastic recoil detection analysis, cross-section high resolution transmission electron microscopy, and energy dispersive x-ray spectroscopy. Already after Xe irradiation at 300 °C the whole Fe layer is transformed to a mixture of Fe3Si, ɛ-FeSi, and β-FeSi2 phases. At 400-450 °C, a unique, layer by layer growth of β-FeSi2 starting from the surface was found. A full transformation of 35 nm Fe on Si to a 105 nm β-FeSi2 layer was achieved by irradiation with 205 keV Xe to 2×1016 ions/cm2, at a temperature of 600 °C. The fully ion-beam grown layers exhibit a pronounced surface roughness, but a sharp interface to Si. This structure is assigned to a growth of β-FeSi2 grains in a local surrounding of interdiffused silicon. Rapid diffusion of silicon to the surface was observed during all ion irradiations. Single-phase β-FeSi2 layers were also synthesized by vacuum annealing for 2 h at 600 °C of 35 nm Fe/Si bilayers premixed with Xe at 450 °C. In this case, the layers form with a smoother surface topography. It is concluded that ion-beam mixing can be used successfully for growth of β-FeSi2 layers at moderate temperatures, either directly or combined with postirradiation annealing.

  7. Effect of Cr, Ti, V, and Zr Micro-additions on Microstructure and Mechanical Properties of the Al-Si-Cu-Mg Cast Alloy

    NASA Astrophysics Data System (ADS)

    Shaha, S. K.; Czerwinski, F.; Kasprzak, W.; Friedman, J.; Chen, D. L.

    2016-02-01

    Uniaxial static and cyclic tests were used to assess the role of Cr, Ti, V, and Zr additions on properties of the Al-7Si-1Cu-0.5Mg (wt pct) alloy in as-cast and T6 heat-treated conditions. The microstructure of the as-cast alloy consisted of α-Al, eutectic Si, and Cu-, Mg-, and Fe-rich phases Al2.1Cu, Al8.5Si2.4Cu, Al5.2CuMg4Si5.1, and Al14Si7.1FeMg3.3. In addition, the micro-sized Cr/Zr/Ti/V-rich phases Al10.7SiTi3.6, Al6.7Si1.2TiZr1.8, Al21.4Si3.4Ti4.7VZr1.8, Al18.5Si7.3Cr2.6V, Al7.9Si8.5Cr6.8V4.1Ti, Al6.3Si23.2FeCr9.2V1.6Ti1.3, Al92.2Si16.7Fe7.6Cr8.3V1.8, and Al8.2Si30.1Fe1.6Cr18.8V3.3Ti2.9Zr were present. During solution treatment, Cu-rich phases were completely dissolved, while the eutectic silicon, Fe-, and Cr/Zr/Ti/V-rich intermetallics experienced only partial dissolution. Micro-additions of Cr, Zr, Ti, and V positively affected the alloy strength. The modified alloy in the T6 temper during uniaxial tensile tests exhibited yield strength of 289 MPa and ultimate tensile strength of 342 MPa, being significantly higher than that for the Al-Si-Cu-Mg base. Besides, the cyclic yield stress of the modified alloy in the T6 state increased by 23 pct over that of the base alloy. The fatigue life of the modified alloy was substantially longer than that of the base alloy tested using the same parameters. The role of Cr, Ti, V, and Zr containing phases in controlling the alloy fracture during static and cyclic loading is discussed.

  8. Nucleation mechanism of nano-sized NaZn13-type and ?-(Fe,Si) phases in La-Fe-Si alloys during rapid solidification.

    PubMed

    Hou, Xue-Ling; Xue, Yun; Liu, Chun-Yu; Xu, Hui; Han, Ning; Ma, Chun-Wei; Phan, Manh-Huong

    2015-01-01

    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 ?-(Fe,Si) phase (size approximately 10 to 30nm) and the cubic NaZn13-type phase (hereinafter 1:13 phase, size approximately 200 to 400nm) 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 ?-(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 35m/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. PMID:25852432

  9. B Removal by Zr Addition in Electromagnetic Solidification Refinement of Si with Si-Al Melt

    NASA Astrophysics Data System (ADS)

    Lei, Yun; Ma, Wenhui; Sun, Luen; Dai, Yongnian; Morita, Kazuki

    2016-02-01

    This study investigated a new process of enhancing B removal by adding small amounts of Zr in the electromagnetic solidification refinement of Si with Si-Al melt. B in Si was removed by as much as 97.2 pct by adding less than 1057 ppma Zr, and the added Zr was removed by as much as 99.7 pct. In addition, Zr is more effective in enhancing B removal than Ti in the same electromagnetic solidification refining process.

  10. B Removal by Zr Addition in Electromagnetic Solidification Refinement of Si with Si-Al Melt

    NASA Astrophysics Data System (ADS)

    Lei, Yun; Ma, Wenhui; Sun, Luen; Dai, Yongnian; Morita, Kazuki

    2015-11-01

    This study investigated a new process of enhancing B removal by adding small amounts of Zr in the electromagnetic solidification refinement of Si with Si-Al melt. B in Si was removed by as much as 97.2 pct by adding less than 1057 ppma Zr, and the added Zr was removed by as much as 99.7 pct. In addition, Zr is more effective in enhancing B removal than Ti in the same electromagnetic solidification refining process.

  11. Sound velocity and density of liquid Fe-Ni-Si under pressure: Application to the composition of planetary molten core

    NASA Astrophysics Data System (ADS)

    Terasaki, H. G.; Kuwabara, S.; Shimoyama, Y.; Takubo, Y.; Urakawa, S.; Nishida, K.; Takeuchi, A.; Suzuki, Y.; Uesugi, K.; Watanuki, T.; Katayama, Y.; Kondo, T.; Higo, Y.

    2014-12-01

    The cores of Mercury, Mars and Moon are reported to be partially/totally molten (e.g., Margot et al. 2007, Yoder et al. 2003, Williams et al. 2001). In order to constrain the core compositions of those bodies from observed and future-planned seismic data, sound velocity and density of the core material, i.e., liquid Fe-alloy, are necessary. In this study, we have performed simultaneous measurements on these physical properties of liquid Fe-Ni-Si alloys, which is one of the major candidates for the core constituent. The effects of pressure and Si content on these properties were studied. High pressure experiments were performed using 80-ton uniaxial press designed for CT measurement or 180-ton cubic type multi-anvil press installed at BL20XU and BL22XU beamlines of SPring-8 synchrotron facility, respectively. Used samples were Fe-Ni-Si with Si content of 10-30 at%. The sample pellet was sandwiched by the single crystal sapphire buffer rod for sound velocity measurement. P-wave sound velocity was measured using pulse-echo overlapping ultrasonic method. LiNbO3 transducer was attached to the backside of the anvil to generate and receive elastic wave signals. Density was determined based on 3D volume data obtained from CT measurement or X-ray absorption profile. The P-wave velocity (VP) and density of liquid Fe-Ni-Si were successfully measured up to 2.5 GPa and 1773 K. Obtained VP of the Fe-Ni-Si is found to increase rapidly with pressure below 1 GPa and increase gradually above 1 GPa. It is also found that VP increases slightly with Si content on the density-VP plot. These trends provide a constraint on the core composition of the planets and moon by comparing with observed data.

  12. Assessment of Mn-Fe-Si-C Melt in Unified Interaction Parameter Formalism

    NASA Astrophysics Data System (ADS)

    Shin, Jung Pil; Lee, Young E.

    2016-02-01

    The solubility of C in Mn-Fe-Si-C melt decreases with increasing Si content, and its decrease becomes greater when the phase in equilibrium with Mn-Fe-Si-C melt changes from carbon to SiC. Such behavior has an industrial implication for low carbon products and processes of steels and Mn alloys. Li and Morris assessed the solution properties of Mn-Fe-Si-C system in the UIP formalism, but the effectiveness of their assessment was limited in applicable ranges of composition to Mn-rich solution and of temperature to around 1673 K (1400 °C). This study develops the information of activity coefficients of C and Si of Mn-Fe-Si-C system from the consistent experimental solubility of C and assesses them in the UIP formalism. This assessment of Mn-Fe-Si-C system describes confidently the behavior of solution properties in a wide range of composition and temperature.

  13. (Si){sub 5-2y}(AlP){sub y} alloys assembled on Si(100) from Al-P-Si{sub 3} building units

    SciTech Connect

    Watkins, T.; Chizmeshya, A. V. G.; Kouvetakis, J.; Jiang, L.; Xu, C.; Smith, D. J.; Menendez, J.

    2012-01-09

    An original class of IV/III-V hybrid (Si){sub 5-2y}(AlP){sub y}/Si(100) semiconductors have been produced via tailored interactions of molecular P(SiH{sub 3}){sub 3} and atomic Al yielding tetrahedral ''Al-P-Si{sub 3}'' building blocks. Extensive structural, optical, and vibrational characterization corroborates that these units condense to assemble single-phase, monocrystalline alloys containing 60%-90% Si (y = 0.3-1.0) as nearly defect-free layers lattice-matched to Si. Spectroscopic ellipsometry and density functional theory band structure calculations indicate mild compositional bowing of the band gaps, suggesting that the tuning needed for optoelectronic applications should be feasible.

  14. Iron spin state and site distribution in FeAlO3-bearing bridgmanite

    NASA Astrophysics Data System (ADS)

    Mohn, Chris E.; Trønnes, Reidar G.

    2016-04-01

    DFT at the GGA, GGA + U and hybrid functional levels were used to investigate thousands of different Al and Fe3+ configurations of MgSiO3-FeAlO3 (MS-FA) and MgSiO3-FeAlO3-Al2O3 bridgmanite at deep mantle conditions. Comparison of the different functionals and atomic charge analysis suggests that GGA, frequently used to explain high to low spin transitions observed in several Mössbauer and X-ray emission spectroscopy experiments, is hampered by spurious self-interaction errors in the exchange-correlation energy. Configurational Boltzmann averaging shows that the B site is thermally inaccessible to Fe3+ at the GGA + U and hybrid levels, and we find no evidence for a spin-pairing transition in fully (thermodynamically) equilibrated samples of bridgmanite, even at the lowermost mantle conditions. The comparison of the cation radii of Fe3+ and Mg supports a spin transition accompanied by a site exchange, but the flexibility of Fesbnd O bonds to locally adapt promotes the incorporation of iron in the irregularly coordinated A-site. The concept of ionic radii is therefore unsuitable for analysis of spin state and site exchange in bridgmanite at these conditions. Consistent with previous computational work and experimental studies with glass and gel as starting material, we find that ferric iron kinetically trapped at the B site undergoes a spin transition under lowermost mantle conditions. In bridgmanite with mole fraction of Fe3+ >Al a charge-balancing amount of low spin Fe3+ will be thermodynamically stable at the B site, but because bridgmanite in peridotitic and basaltic lithologies mostly has Al/Fetotal above unity, FA with high spin Fe3+ in the A-site will be the dominant iron component. The lack of a Fe3+ spin transition in the FA-component has important implications for bridgmanite-ferropericlase partitioning of iron and magnesium and the mineral physics of the lowermost mantle.

  15. Dissolution of Si in Molten Al with Gas Injection

    NASA Astrophysics Data System (ADS)

    Seyed Ahmadi, Mehran

    Silicon is an essential component of many aluminum alloys, as it imparts a range of desirable characteristics. However, there are considerable practical difficulties in dissolving solid Si in molten Al, because the dissolution process is slow, resulting in material and energy losses. It is thus essential to examine Si dissolution in molten Al, to identify means of accelerating the process. This thesis presents an experimental study of the effect of Si purity, bath temperature, fluid flow conditions, and gas stirring on the dissolution of Si in molten Al, plus the results of physical and numerical modeling of the flow to corroborate the experimental results. The dissolution experiments were conducted in a revolving liquid metal tank to generate a bulk velocity, and gas was introduced into the melt using top lance injection. Cylindrical Si specimens were immersed into molten Al for fixed durations, and upon removal the dissolved Si was measured. The shape and trajectory of injected bubbles were examined by means of auxiliary water experiments and video recordings of the molten Al free surface. The gas-agitated liquid was simulated using the commercial software FLOW-3D. The simulation results provide insights into bubble dynamics and offer estimates of the fluctuating velocities within the Al bath. The experimental results indicate that the dissolution rate of Si increases in tandem with the melt temperature and bulk velocity. A higher bath temperature increases the solubility of Si at the solid/liquid interface, resulting in a greater driving force for mass transfer, and a higher liquid velocity decreases the resistance to mass transfer via a thinner mass boundary layer. Impurities (with lower diffusion coefficients) in the form of inclusions obstruct the dissolution of the Si main matrix. Finally, dissolution rate enhancement was observed by gas agitation. It is postulated that the bubble-induced fluctuating velocities disturb the mass boundary layer, which increases the mass transfer rate. Correlations derived for mass transfer from solids in liquids under various operating conditions were applied to the Al--Si system. A new correlation for combined natural and forced convection mass transfer from vertical cylinders in cross flow is presented, and a modification is proposed to take into account free stream turbulence in a correlation for forced convection mass transfer from vertical cylinders in cross flow.

  16. The roles of Eu during the growth of eutectic Si in Al-Si alloys

    NASA Astrophysics Data System (ADS)

    Li, Jiehua; Hage, Fredrik; Wiessner, Manfred; Romaner, Lorenz; Scheiber, Daniel; Sartory, Bernhard; Ramasse, Quentin; Schumacher, Peter

    2015-09-01

    Controlling the growth of eutectic Si and thereby modifying the eutectic Si from flake-like to fibrous is a key factor in improving the properties of Al-Si alloys. To date, it is generally accepted that the impurity-induced twinning (IIT) mechanism and the twin plane re-entrant edge (TPRE) mechanism as well as poisoning of the TPRE mechanism are valid under certain conditions. However, IIT, TPRE or poisoning of the TPRE mechanism cannot be used to interpret all observations. Here, we report an atomic-scale experimental and theoretical investigation on the roles of Eu during the growth of eutectic Si in Al-Si alloys. Both experimental and theoretical investigations reveal three different roles: (i) the adsorption at the intersection of Si facets, inducing IIT mechanism, (ii) the adsorption at the twin plane re-entrant edge, inducing TPRE mechanism or poisoning of the TPRE mechanism, and (iii) the segregation ahead of the growing Si twins, inducing a solute entrainment within eutectic Si. This investigation not only demonstrates a direct experimental support to the well-accepted poisoning of the TPRE and IIT mechanisms, but also provides a full picture about the roles of Eu atoms during the growth of eutectic Si, including the solute entrainment within eutectic Si.

  17. The roles of Eu during the growth of eutectic Si in Al-Si alloys.

    PubMed

    Li, Jiehua; Hage, Fredrik; Wiessner, Manfred; Romaner, Lorenz; Scheiber, Daniel; Sartory, Bernhard; Ramasse, Quentin; Schumacher, Peter

    2015-01-01

    Controlling the growth of eutectic Si and thereby modifying the eutectic Si from flake-like to fibrous is a key factor in improving the properties of Al-Si alloys. To date, it is generally accepted that the impurity-induced twinning (IIT) mechanism and the twin plane re-entrant edge (TPRE) mechanism as well as poisoning of the TPRE mechanism are valid under certain conditions. However, IIT, TPRE or poisoning of the TPRE mechanism cannot be used to interpret all observations. Here, we report an atomic-scale experimental and theoretical investigation on the roles of Eu during the growth of eutectic Si in Al-Si alloys. Both experimental and theoretical investigations reveal three different roles: (i) the adsorption at the intersection of Si facets, inducing IIT mechanism, (ii) the adsorption at the twin plane re-entrant edge, inducing TPRE mechanism or poisoning of the TPRE mechanism, and (iii) the segregation ahead of the growing Si twins, inducing a solute entrainment within eutectic Si. This investigation not only demonstrates a direct experimental support to the well-accepted poisoning of the TPRE and IIT mechanisms, but also provides a full picture about the roles of Eu atoms during the growth of eutectic Si, including the solute entrainment within eutectic Si. PMID:26328541

  18. The roles of Eu during the growth of eutectic Si in Al-Si alloys

    PubMed Central

    Li, Jiehua; Hage, Fredrik; Wiessner, Manfred; Romaner, Lorenz; Scheiber, Daniel; Sartory, Bernhard; Ramasse, Quentin; Schumacher, Peter

    2015-01-01

    Controlling the growth of eutectic Si and thereby modifying the eutectic Si from flake-like to fibrous is a key factor in improving the properties of Al-Si alloys. To date, it is generally accepted that the impurity-induced twinning (IIT) mechanism and the twin plane re-entrant edge (TPRE) mechanism as well as poisoning of the TPRE mechanism are valid under certain conditions. However, IIT, TPRE or poisoning of the TPRE mechanism cannot be used to interpret all observations. Here, we report an atomic-scale experimental and theoretical investigation on the roles of Eu during the growth of eutectic Si in Al-Si alloys. Both experimental and theoretical investigations reveal three different roles: (i) the adsorption at the intersection of Si facets, inducing IIT mechanism, (ii) the adsorption at the twin plane re-entrant edge, inducing TPRE mechanism or poisoning of the TPRE mechanism, and (iii) the segregation ahead of the growing Si twins, inducing a solute entrainment within eutectic Si. This investigation not only demonstrates a direct experimental support to the well-accepted poisoning of the TPRE and IIT mechanisms, but also provides a full picture about the roles of Eu atoms during the growth of eutectic Si, including the solute entrainment within eutectic Si. PMID:26328541

  19. Phase Identification and Microstructure Analysis of Interface Al-Si/SiC Composites

    NASA Astrophysics Data System (ADS)

    Abdullah, Yusof; Daud, Abdul Razak; Harun, Mohd B.; Shamsudin, Roslinda

    2010-01-01

    Phase composition determined by X-ray diffraction (XRD) and microstructure analysis using scanning electron microscopy (SEM) have been performed on Al-Si/15% SiC composites prepared by stir casting method to investigate interface properties. Energy-dispersive X-ray spectroscopy (EDS) was also used to examine the product at interface where crystallisation was prominent. The interface reaction between particles and matrix was indicated that the nucleation of MgAl2O4, Mg2Si and MgO phases growth in the composites. These Interface reaction products play an important role to ensure good physical and mechanical properties of composites.

  20. The Bauschinger effect in a SiC/Al composite

    SciTech Connect

    Shi, N.; Pillai, U.T.S.; Arsenault, R.J.

    1995-09-01

    SiC/Al composites have interesting mechanical properties, the tensile yield stress, whereas, the apparent modulus in tension is greater than that in compression. The Bauschinger effect of SiC/Al composites is also asymmetric with regard to loading directions. Quantitative measurements of the asymmetry of composite Bauschinger Effect was made in this research . An investigation was undertaken to determine the origin of the asymmetrical Bauschinger effect. We have successfully reconstructed the observed asymmetry using an internal stress model based on the development of internal stresses, conveniently referred to as the ``black stress``, and work hardening.

  1. Hysteresis and Domain Behaviors Analysis of High Purity Fe-(5, 6) wt% Si Alloys

    NASA Astrophysics Data System (ADS)

    Lei, Zhe; Horiuchi, Takuro; Sasaki, Iwao; Kaido, Chikara; Yochi, Horibe; Hata, Satoshi; Ogawa, Toshifumi; Era, Hidenori

    We investigated the improvement in magnetic properties of high-purity Fe-(5, 6) wt% Si formed by cold crucible levitation melting. The results showed that Fe-6 wt% Si alloy has a smaller coercivity than Fe-5 wt% Si. The hysteresis loss of both alloys increases linearly and slightly with maximum magnetization, and increases significantly after a certain maximum magnetization. Additionally, demagnetized domain structure and domain wall motion in both samples was studied by means of Lorentz microscopy. The results indicated that the domain wall motion of Fe-6 wt% Si can be activated in lower external fields and displaces more rapidly than Fe-5 wt% Si. Moreover, the displacement of domain walls that penetrate symmetrical grain boundaries and dislocations in Fe-6 wt% Si was analyzed. The boundaries and dislocations have no pinning effect on domain wall motion.

  2. Host Atom Diffusion in Ternary Fe-Cr-Al Alloys

    NASA Astrophysics Data System (ADS)

    Rohrberg, Diana; Spitzer, Karl-Heinz; Dörrer, Lars; Kulińska, Anna J.; Borchardt, Günter; Fraczkiewicz, Anna; Markus, Torsten; Jacobs, Michael H. G.; Schmid-Fetzer, Rainer

    2014-01-01

    In the Fe-rich corner of the Fe-Cr-Al ternary phase diagram, both interdiffusion experiments [1048 K to 1573 K (775 °C to 1300 °C)] and 58Fe tracer diffusion experiments [873 K to 1123 K (600 °C to 850 °C)] were performed along the Fe50Cr50-Fe50Al50 section. For the evaluation of the interdiffusion data, a theoretical model was used which directly yields the individual self-diffusion coefficients of the three constituents and the shift of the original interface of the diffusion couple through inverse modeling. The driving chemical potential gradients were derived using a phenomenological Gibbs energy function which was based on thoroughly assessed thermodynamic data. From the comparison of the individual self-diffusivities of Fe as obtained from interdiffusion profiles and independent 58Fe tracer diffusivities, the influence of the B2-A2 order-disorder transition becomes obvious, resulting in a slightly higher activation enthalpy for the bcc-B2 phase and a significantly lower activation entropy for this phase.

  3. Newly developed Ti-Nb-Zr-Ta-Si-Fe biomedical beta titanium alloys with increased strength and enhanced biocompatibility.

    PubMed

    Kopova, Ivana; Stráský, Josef; Harcuba, Petr; Landa, Michal; Janeček, Miloš; Bačákova, Lucie

    2016-03-01

    Beta titanium alloys are promising materials for load-bearing orthopaedic implants due to their excellent corrosion resistance and biocompatibility, low elastic modulus and moderate strength. Metastable beta-Ti alloys can be hardened via precipitation of the alpha phase; however, this has an adverse effect on the elastic modulus. Small amounts of Fe (0-2wt.%) and Si (0-1wt.%) were added to Ti-35Nb-7Zr-6Ta (TNZT) biocompatible alloy to increase its strength in beta solution treated condition. Fe and Si additions were shown to cause a significant increase in tensile strength and also in the elastic modulus (from 65GPa to 85GPa). However, the elastic modulus of TNZT alloy with Fe and Si additions is still much lower than that of widely used Ti-6Al-4V alloy (115GPa), and thus closer to that of the bone (10-30GPa). Si decreases the elongation to failure, whereas Fe increases the uniform elongation thanks to increased work hardening. Primary human osteoblasts cultivated for 21days on TNZT with 0.5Si+2Fe (wt.%) reached a significantly higher cell population density and significantly higher collagen I production than cells cultured on the standard Ti-6Al-4V alloy. In conclusion, the Ti-35Nb-7Zr-6Ta-2Fe-0.5Si alloy proves to be the best combination of elastic modulus, strength and also biological properties, which makes it a viable candidate for use in load-bearing implants. PMID:26706526

  4. Melting phase relations in MgO-FeO-SiO2 ternary system at high pressure

    NASA Astrophysics Data System (ADS)

    Morishita, A.; Nomura, R.; Hirose, K.

    2014-12-01

    Seismological observations show that the presence of a small fraction of partial melt at the base of the mantle. The knowledge of chemical composition of such partial melt is key to understand its buoyancy and stability in the lowermost mantle. Recent melting experiments performed in the deep lower mantle conditions demonstrated that 1) MgSiO3-rich perovskite (bridgemanite) is the first phase to crystallize from melts with a wide range of (Mg + Fe)/ Si ratios in the middle to deep lower mantle and 2) iron is preferentially partitioned into melt rather than solid [Nomura et al., 2011 Nature; Tateno et al., 2014 JGR], suggesting that melts evolves towards a FeO-rich / SiO2-poor composition upon crystallization. Here we carried out melting experiments under both shallow and deep lower mantle pressures using a laser-heated diamond-anvil cell (DAC), in order to determine melting phase equilibria in the MgO-FeO-SiO2 ternary system. Several different starting materials were used. After heating at high pressure, sample was recovered from a DAC, and then examined with dual beam scanning microprobe (FIB + FE-SEM) (Versa 3DTM, FEI) and field-emission-type electron probe microanalyzer (FE-EPMA) (JXA-8530F, JEOL). On the basis of X-ray maps and quantitative point-analyses, quenched partial melt with non-stoichiometric composition was found at the center of the sample (the hottest part) and surrounded by a liquidus phase. The partial melts were sometimes in direct contact with more than one solid phases such as bridgemanite + ferropericlase or bridgemanite + stishovite, which can tightly constrain the locations of cotectic lines. These results imply that eutectic melt is strongly enriched in FeO in the MgO-FeO-SiO2 ternary system in a wide range of lower mantle pressures.

  5. The corrosion behavior of Fe-Mn-Al weld metals

    NASA Astrophysics Data System (ADS)

    Aidun, Daryush K.

    2001-02-01

    The corrosion resistance of a newly developed iron-base, Fe-Mn-Al austenitic, and duplex weld metal has been examined in the NACE solution consisting of 5 wt.% NaCl, 0.5 wt.% acetic acid, and the balance distilled water. The electrochemical techniques such as potentiodynamic polarization, Tafel plots, linear polarization, cyclic polarization, and open-circuit potential versus time were employed. The Fe-Mn-Al weld metals did not passivate and exhibited high corrosion rates. Fe-Cr-Ni (310 and 316) weld and base metals were also examined in the NACE solution at room temperature. The 310 and 316 base metals were more resistant to corrosion than the as-welded 310 and 316 weld metals. Postweld heat treatment (PWHT) improved the corrosion performance of the Fe-Mn-Al weld metals. The corrosion resistance of Fe-Mn-Al weld metals after PWHT was still inferior to that of the 310 and 316 weld and base metals.

  6. Theoretical investigation of structural stability and lattice vibrations of U 6Fe 16Si 7 and its interstitial carbide U 6Fe 16Si 7C

    NASA Astrophysics Data System (ADS)

    Qian, Ping; Hu, Qing-Yu; Shen, Jiang

    2009-12-01

    A series of lattice inversion pair potentials are used to evaluate the phase stability and site preference for uranium intermetallics U 6Fe 16Si 7 and its interstitial carbide U 6Fe 16Si 7C. The calculated preferentially occupation site of the Si atom is found to be the 4 a site. Interstitial C atom can only be located on the 4 b site. Calculated lattice constants are found to agree with a report in the literature. It is noted that the total and partial phonon densities of states are first evaluated for the U 6Fe 16Si 7 and U 6Fe 16Si 7C compounds. The analysis for the inverted potentials explains qualitatively the contributions of different atoms to the vibrational modes.

  7. Effect of Different Production Methods on the Mechanical and Microstructural Properties of Hypereutectic Al-Si Alloys

    NASA Astrophysics Data System (ADS)

    Fatih Kilicaslan, M.; Uzun, Orhan; Yilmaz, Fikret; Çağlar, Seyit

    2014-10-01

    In this study, the effects of different production methods like melt spinning, high-energy ball milling, and combined melt spinning and high-energy ball milling on the mechanical and microstructural properties of hypereutectic Al-20Si-5Fe alloys were investigated. While microstructural and spectroscopic analyses were performed using scanning electron microscopy and X-ray diffractometry, mechanical properties were measured using a depth-sensing indentation instrument with a Berkovich tip. Microstructural and spectroscopic analyses demonstrate that high-energy ball milling process applied on the melt-spun Al-20-Si-5Fe alloy for 10 minutes brings about a reduction in the size of silicon particles and intermetallic compounds. However, further increase in milling time does not yield any significant reduction in size. High-energy ball milling for 10 minutes on the starting powders is not enough to form any intermetallic phase. According to the depth-sensing indentation experiments, high-energy milling of melt-spun Al-20Si-5Fe alloys shows an incremental behavior in terms of hardness values. For the Al-20Si-5Fe alloys investigated in this study, the production technique remarkably influences their elastic-plastic response to the indentation process in terms of both magnitude and shape of P- h curves.

  8. Effect of Ga Addition on Morphology and Recovery of Primary Si During Al-Si Alloy Solidification Refining

    NASA Astrophysics Data System (ADS)

    Li, Jingwei; Bai, Xiaolong; Li, Yanlei; Ban, Boyuan; Chen, Jian

    2015-12-01

    The effect of Ga addition on alloy macrostructure, morphology and recovery rate of primary Si during the Al-Si-Ga alloy solvent refining process of silicon was studied in this work. The addition of Ga to Al-Si alloy could change the morphology of the primary Si. The average plate thickness of the primary Si increases with increase of Ga content. With the increase of Ga content, the average plate length of the primary Si crystals becomes larger when the Ga content is less than 5% in the Al-30%Si-xGa alloy, but becomes smaller when the Ga content exceeds 5%. Al-Si-Ga alloys consist of three types, primary Si, GaxAl1-x, (?-Al+Si+?-Ga) eutectic. (111) is the preferred growth surface of the plate-like primary Si. The recovery rate of the primary Si increases with the increase of Ga content. When the Ga content increased to 20% in Al-30%Si-xGa alloy, the relative recovery rate of the primary Si increased to 50.41% than that in Al-30%Si alloy.

  9. Spin transport and accumulation in n+-Si using Heusler compound Co2FeSi/MgO tunnel contacts

    NASA Astrophysics Data System (ADS)

    Ishikawa, Mizue; Sugiyama, Hideyuki; Inokuchi, Tomoaki; Hamaya, Kohei; Saito, Yoshiaki

    2015-08-01

    We investigate spin transport and accumulation in n+-Si using Heusler compound Co2FeSi/MgO/Si on insulator (SOI) devices. The magnitudes of the non-local four- and three-terminal Hanle effect signals when using Heusler compound Co2FeSi/MgO/SOI devices are larger than when using CoFe/MgO/SOI devices, whereas the preparation methods of MgO layers on SOI are exactly same in both devices. Different bias voltage dependencies on the magnitude of spin accumulation signals are also observed between these devices. Especially, Co2FeSi/MgO/SOI devices show large spin accumulation signals compared with CoFe/MgO/SOI devices in the low bias voltage region less than 1000 mV in which the increase of the spin polarization is expected from the estimation of the density of states in Heusler compound Co2FeSi and CoFe under spin extraction conditions. These results indicate that the species of ferromagnetic material definitely affects the magnitude and behavior of the spin signals. The use of highly polarized ferromagnets such as Heusler compounds would be important for improving the spin polarization and the magnitude of spin signals through Si channels.

  10. Charge storage in ?-FeSi2 nanoparticle layers

    NASA Astrophysics Data System (ADS)

    Lorke, Axel; Theis, Jens; Kpper, Sebastian; Bywalez, Robert; Wiggers, Hartmut

    2014-03-01

    We report on the observation of a surprisingly high specific capacitance of ?-FeSi2 nanoparticle layers. Lateral, interdigitated capacitor structures were fabricated on silicon dioxide and covered by FeSi2 particles in the size range 10-30 nm. Compared to the bare electrodes, the nanoparticle-coated samples exhibit a 3-4 orders of magnitude increased capacitance. Time-resolved current-voltage measurements show that for short times (seconds to minutes), the material is capable of storing up to 1 As/g at voltages of around 1 V. The devices are rugged and exhibit long-term stability under ambient conditions. The specific capacitance is the highest for a relative humidity of ~ 95%, while for a relative humidity below 40% the capacitance is almost indistinguishable from the bare electrodes. This strongly suggests that the storage mechanism is not purely geometric and that a -yet unexplored- electrochemical process may be responsible for the observed high specific capacitance. Our findings may also be of technological interest: The devices work without the need of a fluid phase, the charge storing material is earth abundant and cost-effective, and the sample design is easy to fabricate.

  11. Quaternary aluminum silicides grown in Al flux: RE5Mn4Al(23-x)Si(x) (RE = Ho, Er, Yb) and Er44Mn55(AlSi)237.

    PubMed

    Calta, Nicholas P; Kanatzidis, Mercouri G

    2013-09-01

    Four novel intermetallic silicides, RE5Mn4Al(23-x)Si(x) (x = 7.9(9), RE = Ho, Er, Yb) and Er44Mn55(AlSi)237, have been prepared by reaction in aluminum flux. Three RE5Mn4Al(23-x)Si(x) compounds crystallize in the tetragonal space group P4/mmm with the relatively rare Gd5Mg5Fe4Al(18-x)Si(x) structure type. Refinement of single-crystal X-ray diffraction data yielded unit cell parameters of a = 11.3834(9)-11.4171(10) and c = 4.0297(2)-4.0575(4) with volumes ranging from 522.41(5) to 528.90(8) (3). Structure refinements on single-crystal diffraction data show that Er44Mn55(AlSi)237 adopts a new cubic structure type in the space group Pm3n with a very large unit cell edge of a = 21.815(3) . This new structure is best understood when viewed as two sets of nested polyhedra centered on a main group atom and a manganese atom. These polyhedral clusters describe the majority of the atomic positions in the structure and form a perovskite-type network. We also report the electrical and magnetic properties of the title compounds. All compounds except the Ho analogue behave as normal paramagnetic metals without any observed magnetic transitions above 5 K and exhibit antiferromagnetic correlations deduced from the value of their Curie constants. Ho5Mn4Al(23-x)Si(x) exhibits a ferromagnetic transition at 20 K and an additional metamagnetic transition at 10 K, suggesting independent ordering temperatures for two distinct magnetic sublattices. PMID:23931551

  12. Hydrogen effects on an amorphous Fe-Si-B alloy

    NASA Astrophysics Data System (ADS)

    Eliaz, N.; Eliezer, D.

    2000-10-01

    Hydrogen absorption in and desorption from an amorphous Fe80B11Si9 alloy, hydrogen effects on the microstructure of this alloy, and the possible mechanism of hydrogen embrittlement (HE) in this alloy have been studied. Ribbons were electrochemically charged with hydrogen at room temperature. The interaction of hydrogen with structural defects and the characteristics of hydrogen desorption were studied by means of thermal desorption spectroscopy (TDS). The effects of hydrogen on the microstructure and thermal stability were studied using X-ray diffraction (XRD), transmission electron microscopy (TEM), electrical resistivity measurements, and differential scanning calorimetry (DSC). The phenomenon of HE was investigated using scanning electron microscopy (SEM) and various mechanical testing techniques. The absence of hydride-forming elements resulted in low hydrogen solubility and low desorption temperatures. Hydrogenation at room temperature is reported for the first time to lead to either local nanocrystallization of the amorphous phase or transformation of nanocrystalline phases such as Fe3.5B, originally present in the uncharged material, to a new nanocrystalline Fe23B6 phase. The susceptibility of this alloy to HE is explained in terms of high-pressure bubble formation.

  13. 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.

  14. Refinement of primary Si in hypereutectic Al-Si alloys by intensive melt shearing

    NASA Astrophysics Data System (ADS)

    Zhang, Z.; Li, H.-T.; Stone, I. C.; Fan, Z.

    2012-01-01

    Hypereutectic Al-Si based alloys are gaining popularity for applications where a combination of light weight and high wear resistance is required. The high wear resistance arising from the hard primary Si particles comes at the price of extremely poor machine tool life. To minimize machining problems while exploiting outstanding wear resistance, the primary Si particles must be controlled to a uniform small size and uniform spatial distribution. The current industrial means of refining primary Si chemically by the addition of phosphorous suffers from a number of problems. In the present paper an alternative, physical means of refining primary Si by intensive shearing of the melt prior to casting is investigated. Al-15wt%Si alloy has been solidified under varying casting conditions (cooling rate) and the resulting microstructures have been studied using microscopy and quantitative image analysis. Primary Si particles were finer, more compact in shape and more numerous with increasing cooling rate. Intensive melt shearing led to greater refinement and more enhanced nucleation of primary Si than was achieved by adding phosphorous. The mechanism of enhanced nucleation is discussed.

  15. Microstructure and mechanical properties of Al-3Fe alloy processed by equal channel angular extrusion

    NASA Astrophysics Data System (ADS)

    Fuxiao, Yu; Fang, Liu; Dazhi, Zhao; Toth, Laszlo S.

    2014-08-01

    Al-Fe alloys are attractive for applications at temperatures beyond those normally associated with the conventional aluminum alloys. Under proper solidification condition, a full eutectic microstructure can be generated in Al-Fe alloys at Fe concentration well in excess of the eutectic composition of 1.8 wt.% Fe. The microstructure in this case is characterized by the metastable regular eutectic Al-Al6Fe fibers of nano-scale in diameter, instead of the equilibrium eutectic Al-Al3Fe phase. In this study, the microstructure and mechanical properties of the Al-3Fe alloy with metastable Al6Fe particles deformed by equal channel angular extrusion were investigated. Severe plastic deformation results in a microstructure consisting of submicron equiaxed Al grains with a uniform distribution of submicron Al6Fe particles on the grain boundaries. The room temperature tensile properties of the alloy with this microstructure will be presented.

  16. Crystal structure of the compound Lu/sub 3/FeSi/sub 6/

    SciTech Connect

    Krivulya, L.V.; Bodak, O.I.; Gorelenko, Yu.K.

    1987-04-01

    The crystal structure of Lu/sub 3/FeSi/sub 6/ was determined by the powder method. The filling coefficient and thermal and atomic parameters are given for the title structure. The results of calculation and experimental diffraction pattern of the title structure are given. Also shown are the atomic parameters of structural types CeNiSi/sub 2/ and ZrSi/sub 2/ and compound Lu/sub 3/FeSi/sub 6/. The parameters and volume of the unit cell of R/sub 3/FeSi/sub 6/ (R = Y, Tb, Ho, Er, Tm, Lu) are listed.

  17. A Reaction Between High Mn-High Al Steel and CaO-SiO2-Type Molten Mold Flux: Part I. Composition Evolution in Molten Mold Flux

    NASA Astrophysics Data System (ADS)

    Kim, Min-Su; Lee, Su-Wan; Cho, Jung-Wook; Park, Min-Seok; Lee, Hae-Geon; Kang, Youn-Bae

    2013-04-01

    In order to elucidate the reaction mechanism between high Mn-high Al steel such as twin-induced plasticity steel and molten mold flux composed mainly of CaO-SiO2 during continuous casting process, a series of laboratory-scale experiments were carried out in the present study. Molten steel and molten flux were brought to react in a refractory crucible in a temperature range between 1713 K to 1823 K (1440 C to 1550 C) and composition evolution in the steel and the flux was analyzed using inductively coupled plasma atomic emission spectroscopy, X-ray fluorescence, and electron probe microanalysis. The amount of SiO2 in the flux was significantly reduced by Al in the steel; thus, Al2O3 was accumulated in the flux as a result of a chemical reaction, 4[Al] + 3(SiO2) = 3[Si] + 2(Al2O3). In order to find a major factor which governs the reaction, a number of factors ((pct CaO/pct SiO2), (pct Al2O3), [pct Al], [pct Si], and temperature) were varied in the experiments. It was found that the above chemical reaction was mostly governed by [pct Al] in the molten steel. Temperature had a mild effect on the reaction. On the other hand, (pct CaO/pct SiO2), (pct Al2O3), and [pct Si] did not show any noticeable effect on the reaction. Apart from the above reaction, the following reactions are also thought to happen simultaneously: 2[Mn] + (SiO2) = [Si] + 2(MnO) and 2[Fe] + (SiO2) = [Si] + 2(FeO). These oxide components were subsequently reduced by Al in the molten steel. Na2O in the molten flux was gradually decreased and the decrease was accelerated by increasing [pct Al] and temperature. Possible reactions affecting the Al2O3 accumulation are summarized.

  18. Abnormal acoustic wave velocities in basaltic and (Fe,Al)-bearing silicate glasses at high pressures

    NASA Astrophysics Data System (ADS)

    Liu, Jin; Lin, Jung-Fu

    2014-12-01

    We have measured acoustic VP and VS velocities of (Fe,Al)-bearing MgSiO3 silicate glasses and an Icelandic basalt glass up to 25 GPa. The velocity profiles of the (Fe,Al)-bearing and basaltic silicate glasses display decreased VP and VS with minima at approximately 5 and 2 GPa, respectively, which could be explained by the mode softening in the aluminosilicate networks. Our results represent the first observation of such velocity softening extending into the chemically complex basaltic glass at a relatively low transition pressure, which is likely due to its degree of polymerization, while the Fe and Al substitutions reduce sound velocities in MgSiO3 glass. If the velocity softening in the basaltic and silicate glasses can be used as analogs for understanding melts in Earth's interior, these observations suggest that the melt fraction needed to account for the velocity reduction in the upper mantle low-velocity zone may be smaller than previously thought.

  19. 57Fe Mössbauer study of Lu2Fe3Si5 iron silicide superconductor

    DOE PAGESBeta

    Ma, Xiaoming; Ran, Sheng; Pang, Hua; Li, Fashen; Canfield, Paul C.; Bud'ko, Sergey L.

    2015-03-28

    With the advent of Fe–As based superconductivity it has become important to study how superconductivity manifests itself in details of 57Fe Mössbauer spectroscopy of conventional, Fe-bearing superconductors. The iron-based superconductor Lu2Fe3Si5 has been studied by 57Fe Mössbauer spectroscopy over the temperature range from 4.4 K to room temperature with particular attention to the region close to the superconducting transition temperature (Tc=6.1 K). Furthermore, consistent with the two crystallographic sites for Fe in this structure, the observed spectra appear to have a pattern consisting of two doublets over the whole temperature range. The value of Debye temperature was estimated from temperaturemore » dependence of the isomer shift and the total spectral area and compared with the specific heat capacity data. As a result, neither abnormal behavior of the hyperfine parameters at or near Tc, nor phonon softening were observed.« less

  20. Enhancement of the Si p-n diode NIR photoresponse by embedding ?-FeSi2 nanocrystallites.

    PubMed

    Shevlyagin, A V; Goroshko, D L; Chusovitin, E A; Galkin, K N; Galkin, N G; Gutakovskii, A K

    2015-01-01

    By using solid phase epitaxy of thin Fe films and molecular beam epitaxy of Si, a p(+)-Si/p-Si/?-FeSi2 nanocrystallites/n-Si(111) diode structure was fabricated. Transmission electron microscopy data confirmed a well-defined multilayered structure with embedded nanocrystallites of two typical sizes: 3-4 and 15-20 nm, and almost coherent epitaxy of the nanocrystallites with the Si matrix. The diode at zero bias conditions exhibited a current responsivity of 1.7 mA/W, an external quantum efficiency of about 0.2%, and a specific detectivity of 1.2 10(9) cm Hz(1/2)/W at a wavelength of 1300 nm at room temperature. In the avalanche mode, the responsivity reached up to 20 mA/W (2% in terms of efficiency) with a value of avalanche gain equal to 5. The data obtained indicate that embedding of ?-FeSi2 nanocrystallites into the depletion region of the Si p-n junction results in expansion of the spectral sensitivity up to 1600 nm and an increase of the photoresponse by more than two orders of magnitude in comparison with a conventional Si p-n junction. Thereby, fabricated structure combines advantage of the silicon photodiode functionality and simplicity with near infrared light detection capability of ?-FeSi2. PMID:26434582

  1. Enhancement of the Si p-n diode NIR photoresponse by embedding ?-FeSi2 nanocrystallites

    NASA Astrophysics Data System (ADS)

    Shevlyagin, A. V.; Goroshko, D. L.; Chusovitin, E. A.; Galkin, K. N.; Galkin, N. G.; Gutakovskii, A. K.

    2015-10-01

    By using solid phase epitaxy of thin Fe films and molecular beam epitaxy of Si, a p+-Si/p-Si/?-FeSi2 nanocrystallites/n-Si(111) diode structure was fabricated. Transmission electron microscopy data confirmed a well-defined multilayered structure with embedded nanocrystallites of two typical sizes: 3-4 and 15-20?nm, and almost coherent epitaxy of the nanocrystallites with the Si matrix. The diode at zero bias conditions exhibited a current responsivity of 1.7?mA/W, an external quantum efficiency of about 0.2%, and a specific detectivity of 1.2??109?cm??Hz1/2/W at a wavelength of 1300?nm at room temperature. In the avalanche mode, the responsivity reached up to 20?mA/W (2% in terms of efficiency) with a value of avalanche gain equal to 5. The data obtained indicate that embedding of ?-FeSi2 nanocrystallites into the depletion region of the Si p-n junction results in expansion of the spectral sensitivity up to 1600?nm and an increase of the photoresponse by more than two orders of magnitude in comparison with a conventional Si p-n junction. Thereby, fabricated structure combines advantage of the silicon photodiode functionality and simplicity with near infrared light detection capability of ?-FeSi2.

  2. Enhancement of the Si p-n diode NIR photoresponse by embedding β-FeSi2 nanocrystallites

    PubMed Central

    Shevlyagin, A. V.; Goroshko, D. L.; Chusovitin, E. A.; Galkin, K. N.; Galkin, N. G.; Gutakovskii, A. K.

    2015-01-01

    By using solid phase epitaxy of thin Fe films and molecular beam epitaxy of Si, a p+-Si/p-Si/β-FeSi2 nanocrystallites/n-Si(111) diode structure was fabricated. Transmission electron microscopy data confirmed a well-defined multilayered structure with embedded nanocrystallites of two typical sizes: 3–4 and 15–20 nm, and almost coherent epitaxy of the nanocrystallites with the Si matrix. The diode at zero bias conditions exhibited a current responsivity of 1.7 mA/W, an external quantum efficiency of about 0.2%, and a specific detectivity of 1.2 × 109 cm × Hz1/2/W at a wavelength of 1300 nm at room temperature. In the avalanche mode, the responsivity reached up to 20 mA/W (2% in terms of efficiency) with a value of avalanche gain equal to 5. The data obtained indicate that embedding of β-FeSi2 nanocrystallites into the depletion region of the Si p-n junction results in expansion of the spectral sensitivity up to 1600 nm and an increase of the photoresponse by more than two orders of magnitude in comparison with a conventional Si p-n junction. Thereby, fabricated structure combines advantage of the silicon photodiode functionality and simplicity with near infrared light detection capability of β-FeSi2. PMID:26434582

  3. Comparison of the Crystallization Behavior of Fe-Si-B-Cu and Fe-Si-B-Cu-Nb-Based Amorphous Soft Magnetic Alloys

    NASA Astrophysics Data System (ADS)

    Smith, Casey; Katakam, Shravana; Nag, Soumya; Zhang, Y. R.; Law, J. Y.; Ramanujan, Raju V.; Dahotre, Narendra B.; Banerjee, Rajarshi

    2014-06-01

    The role of the solute elements, copper, and niobium, on the different stages of de-vitrification or crystallization of two amorphous soft magnetic alloys, Fe73.5Si13.5B9Nb3Cu1, also referred to as FINEMET, and a Fe76.5Si13.5B9Cu1 alloy, a model composition without Nb, has been investigated in detail by coupling atom probe tomography and transmission electron microscopy. The effects of copper clustering and niobium pile-up at the propagating interface between the ?-Fe3Si nanocrystals and the amorphous matrix, on the nucleation and growth kinetics have been addressed. The results demonstrate that while Cu clustering takes place in both alloys in the early stages, the added presence of Nb in FINEMET severely restricts the diffusivity of solute elements such as Cu, Si, and B. Therefore, the kinetics of solute partitioning and mobility of the nanocrystal/amorphous matrix interface is substantially slower in FINEMET as compared to the Fe76.5Si13.5B9Cu1 alloy. Consequently, the presence of Nb limits the growth rate of the ?-Fe3Si nanocrystals in FINEMET and results in the activation of a larger no. of nucleation sites, leading to a substantially more refined microstructure as compared to the Fe76.5Si13.5B9Cu1 alloy.

  4. Simulation models of defects in MgAl2O4:Fe2 , Fe3 spinels

    NASA Astrophysics Data System (ADS)

    de Souza, S. S.; Ayres, F.; Blak, A. R.

    A static computer simulation using the GULP code has been used to study dipole defects in iron doped spinels in normal and inverse structures. The occupation of tetrahedral (Mg2+) and octahedral (Al3+) sites in the normal structure was simulated and the results indicate a preferential replacement of Mg2- by an Al3+ justified by the observed stoichiometric deviation in synthetic spinels. Besides this, Al2O3 excess produces Mg2+ vacancies and favours the hole centre production. Antisite disorder of the form [Mg2+]Al3+ and [Al3+]Mg2+ is one of the possible mechanisms responsible for the existence of dipole defects in these materials. The obtained energy for the interchange between Al3+ and Mg2+ was 0.52eV. The calculated energies indicate that Fe2+ replaces Mg2+ and Fe3+ replaces Al3+. The presence of Fe3+ in octahedral sites takes into account the oxidation process of Fe2+ in these sites. Computer simulation has also been carried out on the inverse structure where the stability of the lattice was obtained for the Imma space group.

  5. Development of a Cast Al-Mg2Si-Si In Situ Composite: Microstructure, Heat Treatment, and Mechanical Properties

    NASA Astrophysics Data System (ADS)

    Georgatis, E.; Lekatou, A.; Karantzalis, A. E.; Petropoulos, H.; Katsamakis, S.; Poulia, A.

    2013-03-01

    An Al-11Mg2Si-Si in situ composite was prepared by a modified investment casting technique that employs sub-pressure for castability improvement and immersion of ceramic shell molds in fluidized beds of silica sand and iron particles for heat extraction improvement. The microstructure of the as-cast composite is explained according to the pseudoeutectic Al-Mg2Si phase diagram. The positive effect of a decreased number of mold investment layers and cooling assisted by immersion of the mold in a metallic bed on the tensile strength and hardness of the heat treated composite is noted. A minor presence of Fe in the master alloys constitutes an essential factor for the brittleness of the composite. Solution treatment notably improves the tensile strength of the composite; however, prolonged treatment deteriorates its ductility. The effect of time and temperature of the aging treatment on the hardness of the composite is investigated. The positive influence of cooling assisted by a metallic fluidized bed on the effectiveness of the aging treatment is noticed.

  6. 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.

  7. Effect of electron correlations on the Fe3Si and α -FeSi2 band structure and optical properties

    NASA Astrophysics Data System (ADS)

    Sandalov, Igor; Zamkova, Natalia; Zhandun, Vyacheslav; Tarasov, Ivan; Varnakov, Sergey; Yakovlev, Ivan; Solovyov, Leonid; Ovchinnikov, Sergey

    2015-11-01

    We use the Vienna ab initio simulation package (vasp) for evaluation of the quasiparticle spectra and their spectral weights within Hedin's GW approximation (GWA) for Fe3Si and α -FeSi2 within the non-self-consistent one-shot approximation G0W0 and self-consistent scGWA with the vertex corrections in the particle-hole channel, taken in the form of two-point kernel. As input for G0W0 , the band structure and wave functions evaluated within the generalized gradient corrected local-density approximation to density functional theory (GGA) have been used. The spectral weights of quasiparticles in these compounds deviate from unity everywhere and show nonmonotonic behavior in those parts of bands where the delocalized states contribute to their formation. The G0W0 and scGWA spectral weights are the same within 2%-5%. The scGWA shows a general tendency to return G0W0 bands to their GGA positions for the delocalized states, while in the flat bands it flattens even more. Variable angle spectroscopic ellipsometry measurements at T =296 K on grown single-crystalline ˜50 -nm-thick films of Fe3Si on n -Si(111) wafer have been performed in the interval of energies ω ˜(1.3 -5 ) eV. The comparison of G0W0 and scGW theory with experimental real and imaginary parts of permittivity, refractive index, extinction and absorption coefficients, reflectivity, and electron energy loss function shows that both G0W0 and scGW qualitatively describe experiment correctly, the position of the low-energy peaks is described better by the scGW theory, however, its detailed structure is not observed in the experimental curves. We suggest that the angle-resolved photoemission spectroscopy experiments, which can reveal the fine details of the quasiparticle band structure and spectral weights, could help to understand (i) if the scGWA with this type of vertex correction is sufficiently good for description of these iron silicides and, possibly, (ii) why some features of calculated permittivity are not seen in optical experiments.

  8. Study of microstructure and magnetic properties of L10 FePt/SiO2 thin films

    NASA Astrophysics Data System (ADS)

    Giannopoulos, G.; Speliotis, Th.; Niarchos, D.

    2014-07-01

    Achieving magnetic recording densities in excess of 1Tbit/in2 requires not only perpendicular media with anisotropies larger than 7 MJ/m3, making FePt alloys an ideal choice, but also a narrow distribution below 10 nm for a reduced S/N ratio. Such grain size reduction and shape control are crucial parameters for high density magnetic recording, along with high thermal stability. Previous work has shown that the L10 FePt grain size can be controlled by alloying FePt with materials such as C, Ag, and insulators such as AlOx, MgO. Au and Al2O3 also act to segregate and magnetically decouple the FePt grains. Better results were obtained with C with respect to the uniformity of grains and SiO2 with respect to the shape. We present our results on co-sputtering FePt with C or SiO2 (up to 30 vol %) on MgO (001) single crystal substrates at 350 and 500 oC. With C or SiO2 addition we achieved grain size reduction, shape control and isolated structure formation, producing continuous films with high uniformity and a narrow grain size distribution. These additions thus allow us to simultaneously control the coercivity and the S/N ratio. We also will report structural and microstructural properties.

  9. Correlation between microstructure evolution and high temperature properties of TiAlSiN hard coatings with different Si and Al content

    NASA Astrophysics Data System (ADS)

    Chen, Tian; Xie, Zhiwen; Gong, Feng; Luo, Zhuangzhu; Yang, Zhi

    2014-09-01

    TiAlSiN coatings with different Si and Al content are synthesized by multi-plasma immersion ion implantation and deposition (MPIIID). The microstructure, oxidation resistance and wear resistance of as-deposited coatings are characterized by x-ray diffraction (XRD), scanning electron microscopy (SEM), x-ray photoelectron spectroscopy (XPS), transmission electron microscopy (TEM), nano-indentation, thermo gravimetric analysis (TGA) and friction tests. Studies show that TiAlSiN coating has nc-TiAlN/a-Si3N4 structure. The grain size of nc-TiAlN decreases gradually and the volume fraction of the interfacial a-Si3N4 increases with the increased Si level. The obvious reduction in grain size together with the increase in interfacial a-Si3N4 eventually leads to the superior oxidation resistance of TiAlSiN coating. In addition, TiAlSiN coating with low Si and Al content exhibits poor oxidation stability and thermal stability, which results in its unsatisfied wear resistance at 800 ?C. However, TiAlSiN coating with higher Si and Al content possesses better oxidation stability and thermal stability, and this coating shows excellent wear resistance both at RT and 800 ?C. The correlation between microstructure evolution and oxidation resistance and wear resistance of as-deposited coatings are systematically discussed.

  10. In situ resistivity of endotaxial FeSi2 nanowires on Si(110)

    NASA Astrophysics Data System (ADS)

    Tobler, S. K.; Bennett, P. A.

    2015-09-01

    We present in situ ultra-high vacuum measurements of the resistivity ρ of self-assembled endotaxial FeSi2 nanowires (NWs) on Si(110) using a variable-spacing two-point method with a moveable scanning tunneling microscope tip and fixed contact pad. The resistivity at room temperature was found to be nearly constant down to NW width W = 4 nm, but rose sharply to nearly double the bulk value at W = 3 nm. These data are not well-fit by a simple Fuch-Sondheimer model for boundary scattering, suggesting that other factors, possibly quantum effects, may be significant at the smallest dimensions. For a NW width of 4 nm, partial oxidation increased ρ by approximately 50%, while cooling from 300 K to 150 K decreased ρ by approximately 10%. The relative insensitivity of ρ to NW size or oxidation or cooling is attributed to a high concentration of vacancies in the FeSi2 structure, with a correspondingly short length for inelastic electron scattering, which obscures boundary scattering except in the smallest NWs. It is remarkable that the vacancy concentration persists in very small structures.

  11. Microstructure of as-fabricated UMo/Al(Si) plates prepared with ground and atomized powder

    NASA Astrophysics Data System (ADS)

    Jungwirth, R.; Palancher, H.; Bonnin, A.; Bertrand-Drira, C.; Borca, C.; Honkimäki, V.; Jarousse, C.; Stepnik, B.; Park, S.-H.; Iltis, X.; Schmahl, W. W.; Petry, W.

    2013-07-01

    UMo-Al based fuel plates prepared with ground U8wt%Mo, ground U8wt%MoX (X = 1 wt%Pt, 1 wt%Ti, 1.5 wt%Nb or 3 wt%Nb) and atomized U7wt%Mo have been examined. The first finding is that that during the fuel plate production the metastable γ-UMo phases partly decomposed into two different γ-UMo phases, U2Mo and α'-U in ground powder or α″-U in atomized powder. Alloying small amounts of a third element to the UMo had no measurable effect on the stability of the γ-UMo phase. Second, the addition of some Si inside the Al matrix and the presence of oxide layers in ground and atomized samples is studied. In the case with at least 2 wt%Si inside the matrix a Silicon rich layer (SiRL) forms at the interface between the UMo and the Al during the fuel plate production. The SiRL forms more easily when an Al-Si alloy matrix - which is characterized by Si precipitates with a diameter ⩽1 μm - is used than when an Al-Si mixed powder matrix - which is characterized by Si particles with some μm diameter - is used. The presence of an oxide layer on the surface of the UMo particles hinders the formation of the SiRL. Addition of some Si into the Al matrix [7-11]. Application of a protective barrier at the UMo/Al interface by oxidizing the UMo powder [7,12]. Increase of the Mo content or use of UMo alloys with ternary element addition X (e.g. X = Nb, Ti, Pt) to stabilize the γ-UMo with respect to α-U or to control the UMo-Al interaction layer kinetics [9,12-24]. Use of ground UMo powder instead of atomized UMo powder [10,25] The points 1-3 are to limit the formation of the undesired UMo/Al layer. Especially the addition of Si into the matrix has been suggested [3,7,8,10,11,26,27]. It has been often mentioned that Silicon is efficient in reducing the Uranium-Aluminum diffusion kinetics since Si shows a higher chemical affinity to U than Al to U. Si suppresses the formation of brittle UAl4 which causes a huge swelling during the irradiation. Furthermore it enhances the formation of more stable UAl3 within the diffusion layer [14]. In addition, Si will not notably influence the reactor neutronics due to its low absorption cross section for thermal neutrons of σabs = 0.24 barn. Aluminum has σabs = 0.23 barn.Williams [28], Bierlein [29], Green [30] and de Luca [31] showed the first time in the 1950s that alloying Aluminum with some Silicon reduces the Uranium-Aluminum diffusion kinetics in can-type fuel elements. However, up to now uncertainties remained about the most promising Si concentration and the involved mechanisms.Ground powder - possibility 4 - introduces a high density of defects like dislocations, oxide layers and impurities into UMo grains. Fuel prepared with this kind of powder exhibits a larger porosity. It may also be combined with an AlSi matrix. As a consequence, the degree of swelling due to high-burn up is reduced compared to fuel with atomized powder [5,6,25].This study focuses on the metallurgical characterization of as-fabricated samples prepared with ground UMo and UMoX (X = Ti, Nb, Pt) powders and atomized UMo powder. The influence of some Si into the Al matrix and the presence of oxide layers on the UMo is discussed. Details of the differences of samples with ground UMo from atomized UMo will be discussed.The examined samples originate from non-irradiated spare fuel plates from the IRIS-TUM irradiation campaign [5,6]. The samples containing ground UMoX powders and atomized UMo powders with Si addition into the matrix have been produced for this study [32]. Powder mixing: The UMo powder is mixed with Al powder. Compact production: UMo-Al powder is poured into a mould and undergoes compaction under large force. Plate-processing: An AlFeNi frame is placed on an AlFeNi plate and the UMo-Al compact is placed into the frame. Afterwards it is covered with a second AlFeNi plate. This assembly is hot-rolled to reduce the total thickness to 1.4 mm. Subsequently, a blister test (1-2 h at 400-450 °C) ensures that the fuelplate is sealed. After this step, the UMo particles are tightly covered with Al as shown in Fig. 1. To access the meat layer, small samples have been cut from the fuel plates. The AlFeNi cladding has been removed using abrasive paper and diamond polishing paste. Cross sections were prepared from each sample and examined using SEM/EDX and XRD. Laboratory scale XRD Laboratory sealed-tube XRD on a STOE-STADIP diffractometer equipped with an incident beam focusing monochromator and used in reflection geometry with respect to the sample. MoK-α radiation has been used. Details on the systems used can be found in [39]. mu;-XRD using micro-focused synchrotron radiation at the Swiss Light Source μ-XAS beamline (PSI, Switzerland). At SLS, the beam size was 3 × 3 μm2, the energy was 19.7 keV. Further details on the experimental procedure can be found in [40]. Only very small sample volumes are probed with this technique, therefore the results may not be representative for the whole miniplate. The standard deviation of the lattice parameters obtained with this method is ±0.01 Å in case not different given. High-energy XRD (HE-XRD) in transmission mode using synchrotron radiation at the "High Energy Diffraction and Scattering Beamline ID15B" of ESRF. An X-ray energy of 87 keV has been used, the beam size was 0.3 × 0.3 mm2. Details on the experimental procedure are presented in [41,42]. It was possible to determine the average mass fractions of the phases present inside the sample using this technique. The standard deviation of the lattice parameters obtained with this method is ±0.001 Å in case not different given. laser granulometry to determine the size distribution of the particles, XRD for phase identification. Granulometry measurements showed that a significant amount of very fine particles of a few μm to 10 μm size are present in the first class of powder.In both cases, laboratory XRD analyses evidenced only two phases: γ-UMo and UO2. In contrast to observations on the final fuel plates, there are no signs of α-U. Comparing XRD data of atomized UMo powder (taken form the IRIS4 experiment) and ground UMo powder with almost the same Mo content, the peaks are broader in XRD patterns of ground UMo and there is a higher background [44]. This points that the lattice structure of the UMo inside the ground powder is strongly disordered during the grinding process.Complementary investigations were performed in these ground UMo powder samples using HE-XRD. The obtained data can therefore directly be compared to those measured on pre-oxidized atomized UMo powders [45] and IRIS-TUM fuel plates [41]. For both powder samples the γ-UMo lattice constant has been estimated to 3.433 ± 0.002 Å which corresponds to about 7.2 wt% for Mo in the alloy according to Dwight's law [46]. The existence of two UMo phases inside these ground particles (as in atomized case) could not be investigated because of the huge peak broadening (presence of micro distortions). Whatever the sample granulometry, the analysis of the HE-XRD data showed a non-negligible nitride contamination in ground powders (see Fig. 2). Two uranium nitride phases are indeed found in these samples: UN and U2N3+x[47]. Note that the presence of UN has also been found in the as-fabricated plates. These results confirm the high reactivity of UMo with both Oxygen and Nitrogen in the grinding conditions. As a comparison for temperatures in the 200-250 °C range, it seems that UNx phases are more difficult to grow: they were not present in outer layers obtained by heat treatment under air on atomized particles [45]. Finally it can be seen in Table 3 that the weight fractions of UO2 and U2N3+x phases are lower in the sample with larger UMo particles. This suggests the existence of an oxide, nitride outer shell around UMo ground particle with thickness that does not strongly evolve with particle size. This constant outer shell thickness has also been found in pre-oxidized atomized powders [45].The UMoX powder used for the samples MAFIA-I-18 - MAFIA-I-21 has not been investigated prior to plate fabrication. However, since the grinding process is essentially the same as for the pure UMo powder, similar characteristics are assumed. Thin oxide layers with a thickness ⩽1 μm on some of the particles that were not intentionally oxidized. Although the UMo powder was stored and handled under an inert atmosphere over the whole production process, some residual oxygen has reacted with the UMo. Already this thin oxide layers exhibits cracks (Fig. 5). Thicker oxide layers with a thickness up to 5 μm on the UMo particles that were oxidized purposely. This kind of oxide layer is very brittle and shows large cracks (Fig. 6). The oxidized UMo particles tend to detach with the matrix as gaps between the UMo particles and the oxide layer could be observed (Fig. 6). This is most obvious at spots where a UMo particle has been pulled out during polishing. A part of the oxide layer remained inside the resulting hole (Fig. 7). Atomized UMo powder 2 wt%Si in Al matrix, alloyed AlSi 2 wt%Si in Al matrix, mixed AlSi 5 wt%Si in Al matrix, mixed AlSi 7 wt%Si in Al matrix, mixed AlSi Ground UMo powder 2 wt%Si in Al matrix, alloyed AlSi The influence of an oxide layer around the UMo particles on the formation of the SiRL during fuel plate production is further discussed. The growth of a Si rich layer surrounding the UMo particles in the 2 wt%Si alloyed powder (oxidized UMo), as well as the 5 wt% and 7 wt%Si mixed powder (non-oxidized UMo) during production of the miniplates. The presence of Si precipitates in the Al-matrix (large precipitates in case of mixture, small si particles in alloy). No oxide layer: If no oxide layer is present around the UMo particles a homogeneous SiRL grows at the interface UMo-Al (Fig. 15a). Brittle oxide layer: An oxide layer is present around the UMo particles, the SiRL grows always between the UMo particle and the oxide layer (Fig. 15b). In this case the the SiRL is thin and not homogeneous. As presumed by Ripert et al. [7] it is essential that the oxide layer reveals cracks perpendicular the UMo particle surface to make path for the Si diffusion. Dense oxide layer: In case of a thin (≈1 μm) but compact oxide layer no SiRL is formed even at high Si concentrations inside the matrix (Fig. 15c). The observed effects are pronounced when the thickness of the oxide layer is increased, as shown in Fig. 16: UMo particles covered with a thicker oxide layer (>1 μm) inside an Aluminum matrix with 5 wt%Si (mixed Al-Si powder). The oxide layer is dense at the left side of the particle, no Si can be found there (Fig. 16a). In contrast, the brittle and cracked oxide layer on the right side made path for a Si diffusion but the SiRL is thinner than in the sites where the UMo particle is not covered with an oxide layer. EDX maps at different positions of the sample showed that in general no SiRL forms around UMo particles covered by oxide layers with a thickness greater than 1 μm (Fig. 16b). This behavior is identical for the samples with 5 wt%Si and 7 wt%Si added to the Aluminum matrix (mixed Al-Si powder). Obviously the presence of a (dense) oxide layer hampers the formation of a SiRL. different UXSiY phases with strongly overlapping peaks can be found in the SiRL, these phases are characterized by small sizes of the crystallites (a few tens of nanometers) and/or cell parameter gradients. Two different crystallographic phases have been usually identified: U(Al,Si)3 displaying a small lattice parameter of a0 = 4.16 Å. This indicates that about 40% of the Al lattice sites are occupied by Si atoms. The second phase is isostructural to U3Si54 with a different lattice parameter [59-61]. Although the U-Si-Al phase diagram contains a variety of phases, none of the phases reported in literature [62] could be used to fully refine the measured diagram. Therefore, three different hypotheses are suggested to explain the occurence of this unknown phase: The observed compound consists of two phases: Conventional U3Si5 and USi2, as has been suggested by the authors before [58]. However, only one literature source (Brown et al.) describing the occurrence of USi2 below 450 °C could be found [63,64]. Furthermore, it has not been possible to reproduce the experiments described by Brown et al. Therefore, this hypothesis remains doubtful [59]. The observed phase may be a new unknown phase. For example, a cubic phase with lattice constant a0 = 3.96 Å can be used to refine the observed peaks. This hypothesis can neither be confirmed nor refused based on the existing data. The observed phase can be a U3Si5 variant containing Mo and/or Al atoms. This hypothesis is supported by the authors. Hence in the following sections this structure will be denoted as U3Si5. No traces of SiRL phases are found inside the sample with 2 wt%Si mixed-powder matrix (MAFIA-I-3), all the Si remained inside the matrix. A SiRL is present inside the samples with 2.1 wt%Si alloyed powder matrix (MAFIA-I-4) and 5 wt%Si (MAFIA-I-5) and 7 wt%Si (MAFIA-I-7) mixed powder matrix. However, between 76% and 96% of the Si remained inside the matrix in form of precipitates or Si particles. The SiRL is formed readily when the Si is present inside the matrix in form of precipitates (i.e. Al-Si alloy matrix, MAFIA-I-4 and IRIS-TUM 8502) compared to particles (i.e. Al-Si mixed powder matrix, MAFIA-I-3, MAFIA-I-5 and MAFIA-I-7). This behavior can best be observed on the sample prepared with ground powder and with 2.1 wt%Si alloyed powder matrix (IRIS-TUM-8502): The matrix contains no Si, only SiRL phases are found. Since the sample with 5 wt%Si mixed powder matrix (MAFIA-I-5) has the lowest SiRL fraction but by far the highest UO2 content, it is concluded that the presence of UO2 around the UMo kernels tends to hamper the formation of a SiRL. UMo/Al samples prepared with ground powder contain irregularly shaped UMo kernels. They are in general oxidized and also contain oxide stringers. These samples have a high porosity content of around 8 vol%. In contrast, UMo/Al samples prepared with atomized powder contain spherical UMo kernels. Only the surface of the UMo kernels is oxidized in some cases. Thick oxide layers must be grown intentionally while thinner layers are the result of oxidation during the whole process. The oxide layer is in general brittle and exhibits cracks. The Uranium-oxide content of all examined samples (atomized and ground) varies between 2 and 13 wt%. gamma;-UMo present in the fresh UMo powder destabilizes to transform to an α-U-like phase, U2Mo, and two γ-UMo phases with different Mo content during the fuel plate production. For ground powder, α-U content varies in 28-38 wt%, for atomized powder in 11-14 wt%. The degree of γ-phase destabilization is therefore higher for ground powder. Ternary addition of Nb, Ti or Pt to the UMo did not impact the extent of decomposition. The γ-phase decomposition in the atomized and ground powder does not follow the expected in the U8wt%Mo TTT diagram between 400 and 450 °C [41]. According to Repas et al. [65], the route is γ-UMoa → γ-UMob + α-U → γ-UMoc+α-U + U2Mo . γ-UMoa,b,c differ in the Mo content where γ-UMoa has the lowest and γ-UMoc has the highest Mo content. We observe a new route of decomposition of ground powder into two different γ-UMo phases. One of them has approximately the original Mo content and the other has a higher Mo content. Further U2Mo and a phase with deformed lattice parameters compared to pure α-U have been observed. The latter is known as α' in literature.For atomized powder, also two different γ-UMo phases and traces of U2Mo have been found. However, a different α-U like phase has been identified: α″ [41,53-55].Repas et al. used as cast samples that have been examined with conventional XRD and different metallographic methods [65]. The difference to our data can be explained by the superior resolution of the here used HE-XRD diffraction. Most probably, conventional lab X-ray sourcces could not resolve fine differences in the lattice parameters of α-U and may not enable to separate two γ-UMo phase. To overcome this uncertainty it is highly desirable to examine the TTT diagram of UMo with high resolution. When Si is added into the matrix - by using alloyed Al-Si powder as a matrix or blending Al and Si powder - in general a SiRL is formed at the interface between the UMo and the Al matrix. An exception can be found in MAFIA-I-3 in which the overall Si content was to low to form a SiRL. The SiRL consists of U(Al,Si)3 and U3Si5. The SiRL forms less readily in case of mixed Al-Si than in case of alloyed Al-Si powder. In the latter case (MAFIA-I-4), a Si depleted zone has been observed around the UMo particles. For ground powder in combination with an Al-Si alloyed matrix, the entire Si from the matrix has reacted with the UMo forming SiRL phases. The presence of a dense oxide layer around the UMo kernels can prevent the formation of a SiRL. However, as soon as the oxide layer is cracked a SiRL forms between the UMo and the oxide layer. A dense oxide layer isolates the UMo from the Si inside the matrix and occurring cracks make path for the diffusion of Si towards the UMo. U3Si 5 is also called USi2-x or USi1.66 in literature.

  12. Crystal structure of the NaCa(Fe{sup 2+}, Al, Mn){sub 5}[Si{sub 8}O{sub 19}(OH)](OH){sub 7} {center_dot} 5H{sub 2}O mineral: A new representative of the palygorskite group

    SciTech Connect

    Rastsvetaeva, R. K. Aksenov, S. M.; Verin, I. A.

    2012-01-15

    A specimen of a new representative of the palygorskite-sepiolite family from Aris phonolite (Namibia) is studied by single-crystal X-ray diffraction. The parameters of the triclinic (pseudomonoclinic) unit cell are as follows: a = 5.2527(2) Angstrom-Sign , b = 17.901(1) Angstrom-Sign , c = 13.727(1) Angstrom-Sign , {alpha} = 90.018(3) Degree-Sign , {beta} = 97.278(4) Degree-Sign , and {gamma} = 89.952(3) Degree-Sign . The structure is solved by the direct methods in space group P1-bar and refined to R = 5.5% for 4168 |F| > 7{sigma}(F) with consideration for twinning by the plane perpendicular to y (the ratio of the twin components is 0.52: 0.48). The crystal chemical formula (Z = 1) is (Na{sub 1.6}K{sub 0.2}Ca{sub 0.2})[Ca{sub 2}(Fe{sub 3.6}{sup 2+}Al{sub 1.6}Mn{sub 0.8})(OH){sub 9}(H{sub 2}O){sub 2}][(Fe{sub 3.9}{sup 2+}Ti{sub 0.1})(OH){sub 5} (H{sub 2}O){sub 2}][Si{sub 16}O{sub 38}(OH){sub 2}] {center_dot} 6H{sub 2}O, where the compositions of two ribbons of octahedra and a layer of Si tetrahedra are enclosed in brackets. A number of specific chemical, symmetrical, and structural features distinguish this mineral from other minerals of this family, in particular, from tuperssuatsiaite and kalifersite, which are iron-containing representatives with close unit cell parameters.

  13. Sound velocities and melting of Fe-Ni-Si system at high pressures under shock loading

    NASA Astrophysics Data System (ADS)

    Zhang, Y.; Sekine, T.; He, H.; Yu, Y.; Liu, F.; Zhang, M.

    2014-12-01

    The Earth's liquid outer core is dominantly composed of iron and nickel (~5-10%), with a density lower by ~8% than that of the liquid iron at the core conditions [e.g., 1], requiring the presence of light element(s) [e.g., 2]. Silicon, geochemically abundant, has long been considered as a major potential light element in the Earth's outer core because of its high solubility in iron, iron-silicate interactions at core-mantle boundary, the Si isotope data, and core formation modeling [3]. To examine effects of Si on physical properties of Fe-Ni system, we directly measured densities, sound velocities, and melting of Fe-9Ni-10Si (in weight percent) system up to ~280 GPa by shock experiments using a two-stage light-gas gun. The sound velocities were determined by the optical analyzer technique [4]. The results, compared with the seismic observations, show that silicon-rich liquid Fe-Ni system can satisfy the observed density deficit and seismological data simultaneously at the physical conditions of the outer core. Analyses of the melting temperatures of Fe-9Ni-10Si system imply the Fe-Ni-Si core will be at lower temperatures by ~600-1000 K than the pure iron core at ~330 GPa of the inner-core boundary. [1]. Anderson, O. and D. Isaak, Another look at the core density deficit of Earth's outer core. Physics of the Earth and Planetary Interiors, 2002. 131(1): p. 19-27.[2]. Poirier, J.-P., Light elements in the Earth's outer core: A critical review. Physics of the Earth and Planetary Interiors, 1994. 85(3): p. 319-337.[3]. Hirose, K., S. Labrosse, and J. Hernlund, Composition and State of the Core. Annual Review of Earth and Planetary Sciences, 2013. 41: p. 657-691.[4]. Huang, H., et al., Evidence for an oxygen-depleted liquid outer core of the Earth. Nature, 2011. 479(7374): p. 513-516.

  14. Stability of FeAl(110) alloy surface structures: a first-principles study

    NASA Astrophysics Data System (ADS)

    Pan, J. L.; Ni, J.; Yang, B.

    2010-02-01

    We have studied the stability of FeAl(110) alloy surface structures by first-principles calculations. A general method is employed to determine the allowed chemical potential range for the surface structures of alloys with several bulk ground state structures. We show that there are three stable surface structures, the Fe:Al=1:1, Fe:Al=1:2 and Fe:Al=1:3 surface structures, within the allowed chemical potential range for FeAl bulk. In the three stable surface structures, surface buckling extends deep into the bulk layers. For the Fe:Al=1:1 surface structure, the surface Al atoms displace outwards and surface Fe atoms move inwards relative to their bulk positions. The Fe:Al=1:2 and Fe:Al=1:3 surfaces show large surface rippling due to composition reconstruction of the surface.

  15. Ritz wavelengths of Fe I, Si II and Ni II for quasar absorption spectroscopy

    NASA Astrophysics Data System (ADS)

    Nave, Gillian

    2016-01-01

    The study of absorption lines in the spectra of galaxies along the line of sight to distant quasars can give important information about the abundances, ionization and kinematics of atoms within these galaxies. They have also been used to study the variability of the fine structure constant at high redshifts. However, the laboratory wavelengths need to be known to better than 6 parts in 108 (20 ms-1). A paper by M. Murphy and J. C. Berengut (2014, MNRAS 438,388) includes a table of spectral lines for which the laboratory wavelength uncertainties are greater than this, including 13 resonance lines of Fe I, 11 lines of Ni II, and 4 lines of Si II.Improved wavelengths for these lines were derived by re-analyzing archival spectra of iron hollow cathode lamps and a silicon carbide Penning discharge lamp. These spectra have previously been used in a comprehensive analysis of the spectrum of Fe I (Nave et al. 1994, ApJS 94, 221) and in a study of Si II, Si IV, and C IV for quasar spectroscopy (Griesmann & Kling, 2000, ApJ 536, L113). By re-optimizing the energy levels of Fe I, the absolute uncertainty of the resonance lines has been reduced by over a factor of 2 and the relative uncertainty by an order of magnitude. A similar analysis for Si II gives a improved values for the resonance lines with wavelength uncertainties of around 4 parts in 108. Analysis of new spectra of Ni II is in progress.

  16. Lower mantle electrical conductivity based on measurements of Al,?Fe-bearing perovskite under lower mantle conditions

    NASA Astrophysics Data System (ADS)

    Sinmyo, R.; Pesce, G.; Greenberg, E.; McCammon, C.; Dubrovinsky, L.

    2014-05-01

    Laboratory measurements of the electrical conductivities of minerals provide important constraints on the chemistry and structure of the Earth's interior. We have measured the electrical conductivity of Al, Fe-bearing perovskite (Pv), the most abundant lower mantle phase, using a laser-heated diamond-anvil cell (LHDAC). The sample with composition Mg0.83Fe0.21Al0.06Si0.91O3 (Fe3+/?Fe ratio ? 0.4) was synthesized at 26 GPa and 2073 K using a multianvil press. Sample resistance was measured in situ at high pressure and high temperature up to 82 GPa and 2000 K, respectively. Results show a continuous increase in electrical conductivity with increasing pressure, in contrast to some previous studies of (Mg, Fe)SiO3 perovskite and a pyrolite assemblage where a decrease in conductivity was observed at higher pressure. Our results suggest that (1) incorporation of aluminum in Pv has a strong effect on its electrical conductivity and evolution with pressure; (2) spin crossover of Fe3+ does not occur or its effect on the conductivity is small in Al, Fe-bearing Pv, and (3) the contribution of ferropericlase to the electrical conductivity of pyrolite may be significant. The electrical conductivity profile of the Earth's lower mantle derived from geomagnetic data can be better explained by a pyrolitic bulk chemical composition rather than a non-pyrolitic model such as one based solely on perovskite.

  17. Lower Mantle Electrical Conductivity Based on Measurements of Al, Fe-Bearing Perovskite Under Lower Mantle Conditions

    NASA Astrophysics Data System (ADS)

    Sinmyo, R.; Pesce, G.; Greenberg, E.; McCammon, C. A.; Dubrovinsky, L. S.

    2014-12-01

    Laboratory measurements of the electrical conductivities of minerals provide important constraints on the chemistry and structure of the Earth's interior. We have measured the electrical conductivity of Al, Fe-bearing perovskite (Pv), the most abundant lower mantle phase, using a laser-heated diamond-anvil cell (LHDAC). The sample with composition Mg0.83Fe0.21Al0.06Si0.91O3 (Fe3+/?Fe ratio ~ 0.4) was synthesized at 26 GPa and 2073 K using a multianvil press. Sample resistance was measured in situ at high pressure and high temperature up to 82 GPa and 2000 K. Results show a continuous increase in electrical conductivity with increasing pressure, in contrast to some previous studies of (Mg,Fe)SiO3 perovskite and a pyrolite assemblage where a decrease in conductivity was observed at higher pressure. Our results suggest that (1) incorporation of aluminum in Pv has a strong effect on its electrical conductivity and evolution with pressure; (2) spin crossover of Fe3+ does not occur or its effect on the conductivity is small in Al, Fe-bearing Pv, and (3) the contribution of ferropericlase to the electrical conductivity of pyrolite may be significant. The electrical conductivity profile of the Earth's lower mantle derived from geomagnetic data can be better explained by a pyrolitic bulk chemical composition rather than a non-pyrolitic model such as one based solely on perovskite.

  18. Ultra high vacuum growth of CrSi2 and ?-FeSi2 nanoislands and Si top layers on the plasma modified monocrystalline silicon surfaces

    NASA Astrophysics Data System (ADS)

    Galkin, Nikolay G.; Astashynski, Valiantsin M.; Chusovitin, Evgenii A.; Galkin, Konstantin N.; Dergacheva, Tatyana A.; Kuzmitski, Anton M.; Kostyukevich, Evgenii A.

    A set of silicon substrates processed by compression plasma was studied by means of atomic force microscopy (AFM). AFM data revealed a threshold nature (in terms of plasma flow energy) of the formation of tube-like surface structures (SS) observed as "waves" regardless of the conductivity type, resistivity, and the substrate orientation ((111) or (100)). For the first time nanoheterostructures Si(111)/NC CrSi2/Si and Si(100)/NC ?-FeSi2 / Si have been formed on silicon substrates processed by compression plasma flow. Avery high density of CrSi2 nanoislands - (2-3)1011 cm-2 was obtained for Cr-Si system but in the case of Fe-Si system the ?-FeSi2 nanoislands density was only about 2109 cm-2. According to the optical spectroscopy data during the process of silicon capping layer formation the CrSi2 and ?-FeSi2 nanocrystals move up to the surface.

  19. Al flux synthesis of the oxidation-resistant quaternary phase REFe{sub 4}Al{sub 9}Si{sub 6} (RE = Tb, Er).

    SciTech Connect

    Sieve, B.; Gray, D. L.; Henning, R.; Bakas, T.; Schultz, A. J.; Kanatzidis, M. G.; Intense Pulsed Neutron Source; Northern Kentucky Univ.; Northwestern Univ.; Univ. of Ioannina

    2008-01-01

    Two rare earth iron aluminum silicides, REFe{sub 4}Al{sub 9}Si{sub 6} (RE = Tb, Er), were synthesized in liquid Al at temperatures below 850 C. They crystallize in the tetragonal space group P4{sub 2}/nmc (no. 137) with cell dimensions of a = 8.718(1) {angstrom} and c = 15.171(3) {angstrom} for the Tb analogue. The structure, which is highly intricate and represents a rare structural arrangement, is based on that of NdRh{sub 4}Al{sub 15.4}. It can be understood in terms of highly corrugated layers of merged Al{sub 6} rings stacking to form a three-dimensional framework. The Fe and Si atoms are situated in various sites in the framework. The RE atoms have a very high coordination number (20) and sit in remaining pockets formed by the bonding arrangements in the structure. Magnetic measurements show that the rare earth ions are in a 3+ state, whereas Moessbauer measurements show that the Fe atoms do not exhibit a magnetic moment and are more reduced than in elemental Fe. The possible insights gained from these results into the metallurgical processing of advanced aluminum matrix alloys are discussed. Thermal gravimetric analysis experiments in air show that REFe{sub 4}Al{sub 9}Si{sub 6} is resistant to oxidation up to 900 C, which is attributable to an alumina/silica surface scale.

  20. Anomalous Hall effect in the Co-based Heusler compounds Co2FeSi and Co2FeAI

    NASA Astrophysics Data System (ADS)

    Imort, I.-M.; Thomas, P.; Reiss, G.; Thomas, A.

    2012-04-01

    The anomalous Hall effect (AHE) in the Heusler compounds Co2FeSi and Co2FeAl is studied in dependence of the annealing temperature to achieve a general comprehension of its origin. We have demonstrated that the crystal quality affected by annealing processes is a significant control parameter to tune the electrical resistivity ?xx as well as the anomalous Hall resistivity ?ahe. Analyzing the scaling behavior of ?ahe in terms of ?xx points to a temperature-dependent skew scattering as the dominant mechanism in both Heusler compounds.

  1. Precipitation hardening in ternary alloys of the Al-Sc-Cu and Al-Sc-Si systems

    SciTech Connect

    Kharakterova, M.L.; Eskin, D.G.; Toropova, L.S. . A.A. Baikov Inst. of Metallurgy)

    1994-07-01

    The processes of precipitation hardening in cast ternary alloys of the Al-Sc-Cu and Al-Sc-Si systems were studied in the temperature range of aging from 100 to 450 C and at exposures to 200 h. It was shown that the CuAl[sub 2] and ScAl[sub 3] phases were involved in the process of aging in ternary Al-Sc-Cu alloys, and the Si and V (AlSiSc) phases, in ternary Al-Sc-Si alloys with excess silicon in a supersaturated solid solution. The V phase was for the first time revealed as the hardening phase in aluminum alloys.

  2. 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.

  3. Refinement performance and mechanism of an Al-50Si alloy

    SciTech Connect

    Dai, H.S.; Liu, X.F.

    2008-11-15

    The microstructure and melt structure of primary silicon particles in an Al-50%Si (wt.%) alloy have been investigated by optical microscopy, scanning electron microscopy, electron probe micro-analysis and a high temperature X-ray diffractometer. The results show that the Al-50Si alloy can be effectively refined by a newly developed Si-20P master alloy, and the melting temperature is crucial to the refinement process. The minimal overheating degree {delta}T{sub min} ({delta}T{sub min} is the difference between the minimal overheating temperature T{sub min} and the liquidus temperature T{sub L}) for good refinement is about 260 deg. C. Primary silicon particles can be refined after adding 0.2 wt.% phosphorus amount at sufficient temperature, and their average size transforms from 2-4 mm to about 30 {mu}m. The X-ray diffraction data of the Al-50Si melt demonstrate that structural change occurs when the melting temperature varies from 1100 deg. C to 1300 deg. C. Additionally, the relationship between the refinement mechanism and the melt structure is discussed.

  4. Crystallization of Fe82Si2B16 and Fe82Si4B14 metallic glasses upon isothermal and non-isothermal annealing

    NASA Astrophysics Data System (ADS)

    Shpak, A. P.; Il'Inskii, A. G.; Marunyak, A. V.; Slukhovskyy, O. I.; Lepeeva, Yu. V.; Dekhtyar, A.; Kaban, I.; Mattern, N.; Eckert, J.

    2011-05-01

    Crystallization of Fe82Si2B16 and Fe82Si4B14 metallic glasses upon heat treatment has been studied. The amorphous ribbons have been isothermally annealed at different temperatures (673, 693, 733 and 743 K) and for various times (from 15 min to 78 hours). Phase compositions and the sequence of their appearance in dependence on the annealing temperature and time have been established.

  5. Densification and mechanical properties of nanocrystalline FeAl

    NASA Astrophysics Data System (ADS)

    Arnett, Michael D.

    The densification and mechanical properties of nanocrystalline FeAl was studied using sinterforging and impression creep measurements. Powders of nanocrystalline FeAl were prepared by mechanical alloying mixtures of Fe and Al powders; the as-milled powder was a disordered solid-solution of Al and Fe with a BCC lattice structure. Sinterforging was performed on partially dense compacts produced from this powder. An unexpected decrease in total deformation was observed when the temperature was raised from 500C to 525C. This is attributed to a combination of grain growth and reordering of the lattice to the equilibrium B2 structure. The apparent stress exponent deduced from the results of step-load tests was 5.5, which is indicative of deformation by a dislocation mechanism. Bulging of the specimen during the sinterforging tests prevented calculation of the density in-situ; the bulging is attributed to dead zones resulting from friction at the specimen/platen interface. Full densification of FeAl was achieved while retaining a grain size far below 100 nm. Impression creep measurements were performed on nanocrystalline FeAl specimens sinterforged to full density. The tests were conducted over the temperature range of 500--600C, and using punches with diameters of 0.5 and 0.2 mm. For specimens sinterforged at 500C, a decrease in creep rate was observed between 500C and 525C, similar to the decrease in deformation rate observed in sinterforging experiments. The stress exponent was calculated from the steady-state impression velocities at punching stresses of 400, 600 and 800 MPa, which are equivalent to conventional stresses of 130, 195 and 260MPa. The stress exponent was 2 at all temperatures; its value is attributed to a deformation mechanism of grain boundary sliding. The discrepancy between the stress exponent in sinterforging and impression creep tests is attributed to the lower stresses employed in the impression creep experiments, suggesting different mechanisms are presumably in operation in the two regimes. The activation energy for impression creep was 1.6 eV, which is explained by accommodation by grain boundary diffusion. Impression creep tests on nanocrystalline Fe produced similar results; the stress exponent was 2 and the activation energy, 0.8 eV, was indicative of grain boundary diffusion.

  6. Tape cast MoSi{sub 2}/{beta}{prime}-SiAlON composite reinforced with SiC monofilaments

    SciTech Connect

    Huang, C.M.; Ho, W.T.Y.; Yuh, C.Y.

    1996-12-31

    A composite of MoSi{sub 2}/{beta}{prime}-SiAlON (Si{sub 3}Al{sub 3}O{sub 3}N{sub 5}) reinforced with SiC monofilaments (AVCO SCS-6) was fabricated using a tape casting technique. The composite was hot-pressed at a temperature of 1600{degrees}C for 2 h under a pressure of 34 MPa in a N{sub 2} environment. The fiber reinforced composite exhibited significant improvement in work of fracture (WOF) as well as in ultimate strength, in comparison to the MoSi{sub 2}/{beta}{prime}-SiAlON composite. Ultimate flexure strength values measured using four-point bending were 690 {+-} 127 MPa and 490 {+-} 31 MPa for the materials with and without fiber reinforcement, respectively. A work of fracture of 23.6 kJ m{sup {minus}2} was obtained for composite with fiber reinforcement, compared to 1.9 kJ m{sup {minus}2} for the composite without fiber reinforcement. Filament push-out tests revealed a moderate interfacial bonding strength of 46 MPa and a frictional sliding stress of 40 MPa. SEM observation of fractured specimens showed that the enhanced WOF was attributed to a significant amount of fiber pull-out during fracture.

  7. Effect of Al2O3 on the Viscosity and Structure of CaO-SiO2-MgO-Al2O3-FetO Slags

    NASA Astrophysics Data System (ADS)

    Wang, Zhanjun; Sun, Yongqi; Sridhar, Seetharaman; Zhang, Mei; Guo, Min; Zhang, Zuotai

    2015-04-01

    The present paper provided a fundamental investigation on the effect of Al2O3 on the viscosity and structure of CaO-SiO2-MgO-Al2O3-FetO slags for the purpose of efficiently recycling the valuable elements from the steelmaking slags. The results show that the viscosity of CaO-SiO2-Al2O3-MgO-FetO slags slightly increases with increasing Al2O3 content. The degree of the polymerization (DOP) of quenched slags, determined from Raman spectra and magic angle spinning-nuclear magnetic resonance, is also found to increase with increasing Al2O3 content. It can be deduced that the increasing DOP can promote the formation of gehlenite phase (Ca2Al2SiO7), thus facilitating the formation of higher phosphorous (or vanadium) contained solid solution ( n'Ca2SiO4Ca3((P or V)O4)2). As Al2O3 content increases up to a specific value, the charge compensating ions which present near [AlO4]-tetrahedra and [FeO4]-tetrahedra are not fully supplied due to the scarcity of Ca2+. In this case, the existing Fe3+ in the melt cannot completely form [FeO4]-tetrahedra and part of Fe3+ would form [FeO6]-octahedra to substitute Ca2+ to modify the slags.

  8. Phonons and the electronic gap in FeSi

    NASA Astrophysics Data System (ADS)

    Parshin, P. P.; Alekseev, P. A.; Nemkovskii, K. S.; Peron, J.; Chumakov, A. I.; Rffer, R.

    2014-02-01

    The partial phonon densities of states of iron atoms in the intermetallic compound FeSi have been measured in the temperature range 46-297 K using nuclear resonant inelastic scattering of synchrotron radiation. A significant phonon softening with increasing temperature has been established. The greatest phonon softening for iron atoms is shown to occur in the region of long-wavelength acoustic phonons, for the acoustic branches near the boundary of the Brillouin zone, and for the low-lying weakly dispersive optical branches. The results obtained are analyzed in terms of the views that relate the change in the phonon density of states of iron atoms to the temperature evolution of the electronic density of state for the compound.

  9. Electron microscopy of Co/Fe/B/Si amorphous alloys

    SciTech Connect

    Rabenberg, L.; Mishra, R.K.; Thomas, G.; Kohmoto, O.; Ojima, T.

    1980-09-01

    Changes in magnetic structures with annealing are studied using Lorentz electron microscopy and are correlated with changes in magnetic properties for the Co/sub 71/ /sub 4/Fe/sub 4/ /sub 6/Si/sub 9/ /sub 6/B/sub 14/ /sub 4/ amorphous alloy. Domain wall stablization is shown to be the dominant factor resulting in decreasing ..mu.. and increasing H/sub c/ and K during low temperature annealing. Annealing near T/sub c/ results in an isotropic magnetic structure due to domain wall relaxation, and annealing above T/sub cry/ results in magnetically hard crystalline particles. It is concluded that treatments capable of producing a magnetically isotropic structure can produce the best soft magnetic materials.

  10. Electron microscopy of Co/Fe/B/Si amorphous alloys

    SciTech Connect

    Rabenberg, L.; Mishra, R.K.; Thomas, G.; Kohmoto, O.; Ojima, T.

    1980-09-01

    Changes in magnetic structures with annealing are studied using Lorentz electron microscopy and are correlated with changes in magnetic properties for the Co/sub 71/./sub 4/Fe/sub 4/./sub 6/Si/sub 9/./sub 6/B/sub 14/./sub 4/ amorphous alloy. Domain wall stabilization is shown to be the dominant factor resulting in decreasing ..mu.. and increasing H/sub c/ and K during low temperature annealing. Annealing near T/sub c/ results in an isotropic magnetic structure due to domain wall relaxation, and annealing above T/sub cry/ results in magnetically hard crystalline particles. It is concluded that treatments capable of producing a magnetically isotropic structure can produce the best soft magnetic materials.

  11. Microindentation of Al-Cu-Fe icosahedral quasicrystal

    SciTech Connect

    Giacometti, E.; Baluc, N.; Bonneville, J.; Rabier, J.

    1999-10-08

    Many different microindentation experiments have been performed at ambient temperature on icosahedral quasicrystals (QCs). They have shown that icosahedral QCs, such as Al-Cu-Fe, Al-Pd-Mn, Al-Li-Cu, Al-Ru-Cu and Mg-Zn-Y are rather hard and exhibit a low fracture toughness. In other respects, compression experiments have shown that these materials exhibit a brittle-to-ductile transition temperature (BDTT) at about 0.7 T{sub m} where T{sub m} is the melting temperature. Few results have been reported concerning microindentation experiments performed at high temperatures, either in the brittle or in the ductile regime. The hardness behavior of icosahedral QCs as a function of temperature has been presented in two cases, however: Al-Li-Cu and Al-Pd-Mn. This paper is aimed at providing information about microindentation measurements performed on an icosahedral Al-Cu-Fe alloy over an extended temperature range. The results are analyzed within the frame used for previous results obtained in the same alloy by means of compression experiments.

  12. Transmission electron microscopy characterization of laser-clad iron-based alloy on Al-Si alloy

    SciTech Connect

    Mei, Z. . E-mail: mikemei_99@yahoo.com; Wang, W.Y.; Wang, A.H.

    2006-04-15

    Microstructure characterization is important for controlling the quality of laser cladding. In the present work, a detailed microstructure characterization by transmission electron microscopy was carried out on the iron-based alloy laser-clad on Al-Si alloy and an unambiguous identification of phases in the coating was accomplished. It was found that there is austenite, Cr{sub 7}C{sub 3} and Cr{sub 23}C{sub 6} in the clad region; {alpha}-Al, NiAl{sub 3}, Fe{sub 2}Al{sub 5} and FeAl{sub 2} in the interface region; and {alpha}-Al and silicon in the heat-affected region. A brief discussion was given for their existence based on both kinetic and thermodynamic principles.

  13. Itinerant magnetism in doped semiconducting ?-FeSi2 and CrSi2

    PubMed Central

    Singh, David J.; Parker, David

    2013-01-01

    Novel or unusual magnetism is a subject of considerable interest, particularly in metals and degenerate semiconductors. In such materials the interplay of magnetism, transport and other Fermi liquid properties can lead to fascinating physical behavior. One example is in magnetic semiconductors, where spin polarized currents may be controlled and used. We report density functional calculations predicting magnetism in doped semiconducting ?-FeSi2 and CrSi2 at relatively low doping levels particularly for n-type. In this case, there is a rapid cross-over to a half-metallic state as a function of doping level. The results are discussed in relation to the electronic structure and other properties of these compounds. PMID:24343332

  14. Change in the magnetization of multilayer Fe/Si nanostructures during synthesis and subsequent heating

    NASA Astrophysics Data System (ADS)

    Varnakov, S. N.; Komogortsev, S. V.; Bartolom, J.; Ses, J.; Ovchinnikov, S. G.; Parshin, A. S.; Kosyrev, N. N.

    2008-07-01

    The magnetization of multilayer Fe/Si films made of nanolayers and fabricated by thermal evaporation in an ultrahigh vacuum is studied. The magnetization of (Fe/Si) n films and its temperature gradient are found to depend on the Fe layer thickness. This dependence is shown to result from the formation of a chemical compound (nonmagnetic phase) at the Fe-Si interface during synthesis. The fraction of this phase accounts for up to 50% of the Fe layer thickness. The irreversible change in the magnetization of these nanostructures is analyzed, and a procedure is proposed for the estimation of the kinetic coefficients of the synthesis of the nonmagnetic phase (silicide) in the multilayer Fe/Si nanostructures at high temperatures. An Fe(1.2 nm)/Si(1.5 nm)/Fe(1.2 nm)/Si(1.5 nm)/Fe(1.2 nm)/Si(10 nm) film is used as an example in order to determine the activation energy E a and the diffusion coefficient D 0 of this process with this procedure.

  15. Screened moments and absence of ferromagnetism in FeAl

    NASA Astrophysics Data System (ADS)

    Galler, A.; Taranto, C.; Wallerberger, M.; Kaltak, M.; Kresse, G.; Sangiovanni, G.; Toschi, A.; Held, K.

    2015-11-01

    While the stoichiometric intermetallic compound FeAl is found to be paramagnetic in experiment, standard band-theory approaches predict the material to be ferromagnetic. We show that this discrepancy can be overcome by a better treatment of electronic correlations with density-functional plus dynamical mean-field theory. Our results show no ferromagnetism down to 100 K and since the susceptibility is decreasing at the lowest temperatures studied we also do not expect ferromagnetism at even lower temperatures. This behavior is found to originate from temporal quantum fluctuations that screen short-lived local magnetic moments of 1.6 ?B on Fe.

  16. Missing superconductivity in BaAlSi with the AlB 2 type structure

    NASA Astrophysics Data System (ADS)

    Yamanaka, Shoji; Otsuki, Teruyoshi; Ide, Takayuki; Fukuoka, Hiroshi; Kumashiro, Ryotaro; Rachi, Takeshi; Tanigaki, Katsumi; Guo, FangZhun; Kobayashi, Keisuke

    2007-01-01

    The solid solutions BaAl 1- xSi 1+ x (0 ? x ? 0.5) were prepared. The compound with the stoichiometric composition ( x = 0) did not show superconductivity as reported by other investigators, but the solid solutions with x > 0 became superconductors with a transition temperature Tc = 2.8 K. The comparison of the lattice parameters with those of the other isotypic ternary superconductors MAlSi (M = Ca, Sr) suggested that the superconductivity could be related to the lattice parameter within the (AlSi) plane rather than the interlayer spacing. The band structures near the Fermi level of MAlSi (M = Ca, Sr, Ba) were measured using soft X-ray photoelectron spectroscopy, which were in good agreement with the calculated ones, confirming that the contribution of the d orbitals of the alkaline-earth metals were predominant in the conduction bands.

  17. Thermoelasticity of (Mg,Fe)SiO3 perovskite

    NASA Astrophysics Data System (ADS)

    Shukla, Gaurav; Wu, Zhongqing; Hsu, Han; Cococcioni, Matteo; Wentzcovitch, Renata

    2015-03-01

    We present LDA+U calculations of high temperature elastic properties of (Mg(1 - x)Fex2+)SiO3 bridgemanite (0 <= x <= 0 . 125), the most abundant constituent of Earth's lower mantle. Calculations of aggregate elastic moduli and acoustic velocities for the Mg-end member (x=0) are in excellent agreement with the latest high pressure and high temperature experimental measurements. In the iron bearing system, we particularly focus on the change in thermoelastic parameters across the state change that occurs in ferrous iron above ~30 GPa, often attributed to a high-spin (HS) to intermediate spin (IS) crossover but explained by calculations as a lateral displacement of substitutional iron in the perovskite cage. We show that the measured effect on the equation of state of this change in the state of iron can be explained by the lateral displacement of substitutional iron, not by the HS to IS crossover. Calculated elastic properties of (Mg0.875 Fe0.125 2 +)SiO3 along an adiabatic mantle geotherm, somewhat overestimate longitudinal velocities but produce densities and shear velocities consistent with Preliminary Reference Earth Model data throughout most of the lower mantle. Research supported by NSF/EAR and NSF/CAREER.

  18. Ab initio study of 59Co NMR spectra in Co2FeAl1-xSix Heusler alloys

    NASA Astrophysics Data System (ADS)

    Nishihara, H.; Sato, K.; Akai, H.; Takiguchi, C.; Geshi, M.; Kanomata, T.; Sakon, T.; Wada, T.

    2015-05-01

    Ab initio electronic structure calculation of a series of Co2FeAl1-xSix Heusler alloys has been performed, using the Korringa-Kohn-Rostoker-coherent potential approximation method to explain experimental 59Co NMR spectra. Two prominent features are explained semi-quantitatively-a global shift of the 59Co resonance line due to alloying with Al and Si atoms in Co2FeAl1-xSix, and the effect of local disorder in creating distinct satellite lines of 59Co NMR in Co2FeAl. The importance is stressed of the positive contribution to the 59Co hyperfine field from valence electron polarization, which emerges from the half-metallic band structure inherent in Co-based Heusler alloys.

  19. Fabrication and characterization of novel Fe(Os)Si 2 semiconductor

    NASA Astrophysics Data System (ADS)

    Gao, Y.; Liu, H. W.; Lin, Y.; Shao, G.

    Ternary Fe(Os)Si2 alloys, a novel semiconducting opto-electronic material with a tuneable direct band gap property, was designed by energy-band engineering. The electronic structures of FeSi2,OsSi2 and (FeOs)Si2 were theoretically calculated using the density functional theory (DFT) method. The thin films were fabricated by magnetic co-sputtering deposition, so as to substitute the Fe sublattice sites by Os. X-ray diffraction, energy dispersion X-ray spectrometry and optical absorption spectroscopy were used to characterize the structural properties of the thin films. Experimental results showed that all the Fe1-xOsxSi2 films have a direct band gap property. The strongest optical absorption was obtained when x is equal to 0.5, which is consistent with the theoretical prediction.

  20. The Origin of the Galactic 26Al and 60Fe

    NASA Astrophysics Data System (ADS)

    Suades, Moiss; Hernanz, Margarita; de Srville, Nicolas

    The radioactive nucleus 26Al (1Myr lifetime) was the first cosmic radioactivity ever detected, through its gamma ray emission line at 1.809MeV, with the HEAO-3 satellite in the 80's. More recently, COMPEL instrument onboard CGRO made the first all-sky map of its diffuse emission in the Galaxy, which revealed that 1.8MeV photons trace the massive star population, but with room to other potential important producers like AGB stars and novae. The SPI instrument of the current ESA mission INTEGRAL has corroborated the detection of the 26Al line with excellent spectroscopic resolution, and has also detected the two lines at 1.173 and 1.333MeV of 60Fe (2Myr lifetime), yielding an observed 60Fe/26Al gamma ray flux ratio which can not be reproduced with current theoretical determinations based solely on massive stars. We will discuss the contribution of the different stellar scenarios to the global 26Al and 60Fe content of the Milky Way and give an interpretation of the recent INTEGRAL observations.

  1. Synthesis of Li2FeSiO4/carbon nano-composites by impregnation method

    NASA Astrophysics Data System (ADS)

    Sun, Shijiao; Matei Ghimbeu, Camelia; Vix-Guterl, Cathie; Sougrati, Moulay-Tahar; Masquelier, Christian; Janot, Raphal

    2015-06-01

    Nanocrystalline lithium iron silicate/carbon (Li2FeSiO4/C) composites were successfully prepared by impregnation of a commercial porous carbon using ethanolic solutions of the different metallic precursors, followed by thermal annealing at 600 C. The effects of Li2FeSiO4 loading content on the structure and organization of the Li2FeSiO4/C composites at the nanoscale were investigated. Through optimization of the synthesis conditions, small Li2FeSiO4 nanocrystals (4-12 nm) are formed and well dispersed in the porous conductive carbon. The electrochemical performances of these composites were tested as positive electrodes for lithium-ion batteries. The Li2FeSiO4/C composite with the lowest Li2FeSiO4 loading exhibits the best rate capability with a significant capacity contribution from carbon. It was found that the presence of carbon delays the lowering of the Fe3+/Fe2+ redox voltage usually reported for Li2FeSiO4 (from 3.1/3.0 to 2.8/2.7 V vs. Li+/Li), due to a stabilization effect of the initial Li2FeSiO4 crystal structure. For the Li2FeSiO4/C composite (81/19 weight ratio), a discharge capacity of 81 mAh g-1 can be achieved at 55 C for a charge/discharge rate of 2C, with 86% capacity retention after 500 cycles, showing the positive effect of the porous carbon addition for long term cycling stability.

  2. Elasticity and inelasticity of the SiC/Al-13Si-9Mg biomorphic metal ceramics

    NASA Astrophysics Data System (ADS)

    Kardashev, B. K.; Orlova, T. S.; Smirnov, B. I.; Wilkes, T. E.; Faber, K. T.

    2008-10-01

    The acoustic investigations of the elastic (Youngs modulus) and microplastic properties of a composite material, the SiC/Al-13Si-9Mg biomorphic metal ceramic, were performed. The ceramic was prepared by infiltration of the Al-13Si-9Mg melt into porous silicon carbide derived from wood of two species of trees, beech and sapele. The measurements were performed with a composite piezoelectric vibrator under resonance conditions, with rod-shaped samples vibrated longitudinally at about 100 kHz over a wide range of vibrational strain amplitudes, which included both the linear (amplitude-independent) and nonlinear (microplastic) regions. It was shown that the Youngs modulus and the microplastic properties of the composite are anisotropic and depend substantially on the tree species, particularly when longitudinal vibrations are excited in samples cut along the tree fibers.

  3. Effect of heat treatment on microstructure and interface of SiC particle reinforced 2124 Al matrix composite

    SciTech Connect

    Mandal, Durbadal; Viswanathan, Srinath

    2013-11-15

    The microstructure and interface between metal matrix and ceramic reinforcement of a composite play an important role in improving its properties. In the present investigation, the interface and intermetallic compound present in the samples were characterized to understand structural stability at an elevated temperature. Aluminum based 2124 alloy with 10 wt.% silicon carbide (SiC) particle reinforced composite was prepared through vortex method and the solid ingot was deformed by hot rolling for better particle distribution. Heat treatment of the composite was carried out at 575 C with varying holding time from 1 to 48 h followed by water quenching. In this study, the microstructure and interface of the SiC particle reinforced Al based composites have been studied using optical microscopy, scanning electron microscopy (SEM) coupled with energy dispersive X-ray spectroscopy (EDS), electron probe micro-analyzer (EPMA) associated with wavelength dispersive spectroscopy (WDS) and transmission electron microscopy (TEM) to identify the precipitate and intermetallic phases that are formed during heat treatment. The SiC particles are uniformly distributed in the aluminum matrix. The microstructure analyses of AlSiC composite after heat treatment reveal that a wide range of dispersed phases are formed at grain boundary and surrounding the SiC particles. The energy dispersive X-ray spectroscopy and wavelength dispersive spectroscopy analyses confirm that finely dispersed phases are CuAl{sub 2} and CuMgAl{sub 2} intermetallic and large spherical phases are Fe{sub 2}SiAl{sub 8} or Al{sub 15}(Fe,Mn){sub 3}Si. It is also observed that a continuous layer enriched with Cu and Mg of thickness 5080 nm is formed at the interface in between Al and SiC particles. EDS analysis also confirms that Cu and Mg are segregated at the interface of the composite while no carbide is identified at the interface. - Highlights: The composite was successfully heat treated at 575C for 1-48 hrs. A layer of 50-75 nm is formed at interface after heat treatment. No Carbide formation and SiC dissolution is observed at this temperature. MgAl{sub 2}O{sub 4}, CuMgAl{sub 2} phases are segregated at interface of Al-SiC composite. Mg and Cu are also segregated at near to the grain boundary.

  4. Properties of Intruder States in 34Al and 34Si

    NASA Astrophysics Data System (ADS)

    Rotaru, F.; Lica, R.; Negoita, F.; Grvy, S.; Marginean, N.; Dessagne, Ph.; Stora, T.; Borcea, C.; Borcea, R.; Calinescu, S.; Daugas, J. M.; Filipescu, D.; Kuti, I.; Fraille, L. M.; Franchoo, S.; Gheorghe, I.; Marginean, R.; Mihai, C.; Morfouace, P.; Mrazek, J.; Morel, P.; Negret, A.; Pietreanu, D.; Sava, T.; Sohler, D.; Stanoiu, M.; Stefan, I.; Suvaila, R.; Toma, S.

    We report on two experimental results for nuclei located in the region of the N = 20 island of inversion. In the first experiment, performed at GANIL, we have discovered and studied the 02 + state in 34Si and made the hypothesis that it was fed by the beta-decay of a predicted isomeric 1+ state in 34Al. In the second experiment, performed at ISOLDE, we have studied the beta-decay of 34Mg in order to obtain information on the structure of 34Al and in particular the position of the isomeric 1+ state.

  5. First-principles study of tunneling magnetoresistance in Fe/MgAl2O4/Fe(001) magnetic tunnel junctions

    NASA Astrophysics Data System (ADS)

    Miura, Yoshio; Muramoto, Shingo; Abe, Kazutaka; Shirai, Masafumi

    2012-07-01

    We investigated the spin-dependent transport properties of Fe/MgAl2O4/Fe(001) magnetic tunneling junctions (MTJs) on the basis of first-principles calculations of the electronic structures and the ballistic conductance. The calculated tunneling magnetoresistance (TMR) ratio of a Fe/MgAl2O4/Fe(001) MTJ was about 160%, which was much smaller than that of a Fe/MgO/Fe(001) MTJ (1600%) for the same barrier thickness. However, there was an evanescent state with ?1 symmetry in the energy gap around the Fermi level of normal spinel MgAl2O4, indicating the possibility of a large TMR in Fe/MgAl2O4/Fe(001) MTJs. The small TMR ratio of the Fe/MgAl2O4/Fe(001) MTJ was due to new conductive channels in the minority spin states resulting from a band-folding effect in the two-dimensional Brillouin zone of the in-plane wave vector (k?) of the Fe electrode. Since the in-plane cell size of MgAl2O4 is twice that of the primitive in-plane cell size of bcc Fe, the bands in the boundary edges are folded, and minority-spin states coupled with the ?1 evanescent state in the MgAl2O4 barrier appear at k?=0, which reduces the TMR ratio of the MTJs significantly.

  6. Spray Casting Aluminum and Al/SiC Composites

    NASA Astrophysics Data System (ADS)

    Buhrmaster, C. L.; Clark, D. E.; Smartt, H. B.

    1988-11-01

    The gas metal arc welding process has been modified to deposit aluminum, aluminum alloys and Al/SiC composites on a substrate or in a mold. Density is close to theoretical and mechanical properties are comparable to those of wrought or cast materials. The thermal characteristics of the deposit vary with controllable parameters. This new process can be adapted to produce a variety of pure metals or metal-matrix composite materials.

  7. Wettability of AlSi5Mg on Spodumene

    NASA Astrophysics Data System (ADS)

    Fankhnel, Beate; Stelter, Michael; Voigt, Claudia; Aneziris, Christos G.

    2015-02-01

    The development of new filters for the aluminum industry requires investigations on the wettability of aluminum and its alloys on novel filter materials. The requested filter effects require not only an adequate wetting but also information about the interaction between the filter material and the metal. In the present work the wettability of an AlSi5Mg alloy on spodumene (LiAl[Si2O6]) containing substrates is investigated using the sessile drop technique. These measurements were carried out at 1223 K (950 C) under vacuum. The spodumene-based substrates showed a completely different wetting behavior compared with an alumina substrate. The contact angel reduced more quickly and leveled out at a lower value (75 2 deg) than in case of a pure alumina substrate (90 1 deg). The reason for this behavior is a reaction between the LiAl(Si2O6) and the alloy droplet which supported deoxidation and formed a silica-rich reaction layer at the droplet/substrate interface.

  8. Evolution of Intermetallics, Dispersoids, and Elevated Temperature Properties at Various Fe Contents in Al-Mn-Mg 3004 Alloys

    NASA Astrophysics Data System (ADS)

    Liu, K.; Chen, X.-G.

    2015-12-01

    Nowadays, great interests are rising on aluminum alloys for the applications at elevated temperature, driven by the automotive and aerospace industries requiring high strength, light weight, and low-cost engineering materials. As one of the most promising candidates, Al-Mn-Mg 3004 alloys have been found to possess considerably high mechanical properties and creep resistance at elevated temperature resulted from the precipitation of a large number of thermally stable dispersoids during heat treatment. In present work, the effect of Fe contents on the evolution of microstructure as well as high-temperature properties of 3004 alloys has been investigated. Results show that the dominant intermetallic changes from α-Al(MnFe)Si at 0.1 wt pct Fe to Al6(MnFe) at both 0.3 and 0.6 wt pct Fe. In the Fe range of 0.1-0.6 wt pct studied, a significant improvement on mechanical properties at elevated temperature has been observed due to the precipitation of dispersoids, and the best combination of yield strength and creep resistance at 573 K (300 °C) is obtained in the 0.3 wt pct Fe alloy with the finest size and highest volume fraction of dispersoids. The superior properties obtained at 573 K (300 °C) make 3004 alloys more promising for high-temperature applications. The relationship between the Fe content and the dispersoid precipitation as well as the materials properties has been discussed.

  9. Microstructure selection maps for Al-Fe alloys

    SciTech Connect

    Gilgien, P.; Zryd, A.; Kurz, W.

    1995-09-01

    The solidification microstructures for Al-0.5-4 at.% Fe alloys under constrained growth conditions have been calculated using analytical models of the growth kinetics of dendritic, eutectic and plane front interface morphologies of stable and metastable phases. Laser remelting experiments are carried out on an Al-4 at.% Fe alloy with low beam velocity (10 mm/s) in order to complete previous experimental results on the solidification microstructures obtained at intermediate growth rates by Bridgman experiments and at a high growth rates by rapid laser resolidification. Comparison of predicted with experimentally determined solidification microstructure maps shows satisfactory agreement in view of the limited knowledge of the thermophysical properties of this system. These maps are useful for the interpretation of microstructures and phases forming under medium to high solidification rates and for the understanding and development of rapid solidification processing. Further the modeling is useful for improving available phase diagram information.

  10. Surface carbon films on Al-Cu-Fe quasicrystalline powders

    SciTech Connect

    Bloomer, T.E.; Flumerfelt, J.; Kramer, M.J.

    1996-12-31

    In order to study the unique properties of quasicrystals, it is necessary to form dense, homogeneous monoliths of these alloys. Unfortunately, Al-Cu-Fe quasicrystalline alloy ingots prepared by conventional casting techniques result in large scale chemical inhomogeneities which contain numerous cracks due to differential thermal contraction between the various phases during cooling. Thus a powder metallurgical approach using gas atomized (GA) powders is being pursued in order to form large samples of phase pure Al-Cu-Fe quasicrystal. A samples of specific compositions and sizes are hot isostatic pressed (HIPed) to form dense monoliths. The effects of surface contamination of GA powders, which may inhibit particle-to-particle sintering and may also increase second phase contamination in the HIPed piece, is being studied by scanning Auger microprobe (SAM), scanning electron microscopy (SEM), and transmission electron microscopy (TEM).

  11. Magnetic properties and switching volumes of nanocrystalline SmFeSiC films

    SciTech Connect

    Zhang, S.Y.; Shan, Z.S.; Liu, Y.; Zhao, T.Y.; Zhao, J.G.; Shen, B.G.; Zhan, W.S.; Sellmyer, D.J.

    1997-04-01

    Systematic studies of the effects of Si addition on the magnetic and magnetization reversal properties of SmFeSiC films are presented. The magnetic switching volume and other magnetic parameters (e.g., coercivity) are strongly dependent upon the Si content. Correlations between switching volume, coercivity, and the intergrain interactions are discussed. {copyright} {ital 1997 American Institute of Physics.}

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

    NASA Astrophysics Data System (ADS)

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

    2011-01-01

    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 C to 1000 C and strain-rates varying from 10-6 to 1 s-1. The strain rate sensitivity parameter (m) and observed maximum elongation until rupture (?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 C to 900 C with grain size around 3 ?m (ASTM grain size 12) and average strain rate sensitivity of m 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 C.

  13. 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.

  14. 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.

  15. 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.

  16. Endotaxially stabilized B2-FeSi nanodots in Si (100) via ion beam co-sputtering

    SciTech Connect

    Cassidy, Cathal Singh, Vidyadhar; Grammatikopoulos, Panagiotis; Kioseoglou, Joseph; Lal, Chhagan; Sowwan, Mukhles

    2014-04-21

    We report on the formation of embedded B2-FeSi nanodots in [100]-oriented Si substrates, and investigate the crystallographic mechanism underlying the stabilization of this uncommon, bulk-unstable, phase. The nanodots were approximately 10 nm in size, and were formed by iron thin film deposition and subsequent annealing. Cross-sectional transmission electron microscopy, energy loss spectroscopy mapping, and quantitative image simulation and analysis were utilized to identify the phase, strain, and orientational relationship of the nanodots to the host silicon lattice. X-ray photoelectron spectroscopy was utilized to analyze the surface composition and local bonding. Elasticity calculations yielded a nanodot residual strain value of −18%. Geometrical phase analysis graphically pinpointed the positions of misfit dislocations, and clearly showed the presence of pinned (11{sup ¯}1{sup ¯}){sub Si}//(100){sub FeSi}, and unpinned (2{sup ¯}42){sub Si}//(010){sub FeSi}, interfaces. This partial endotaxy in the host silicon lattice was the mechanism that stabilized the B2-FeSi phase.

  17. Endotaxially stabilized B2-FeSi nanodots in Si (100) via ion beam co-sputtering

    NASA Astrophysics Data System (ADS)

    Cassidy, Cathal; Kioseoglou, Joseph; Singh, Vidyadhar; Grammatikopoulos, Panagiotis; Lal, Chhagan; Sowwan, Mukhles

    2014-04-01

    We report on the formation of embedded B2-FeSi nanodots in [100]-oriented Si substrates, and investigate the crystallographic mechanism underlying the stabilization of this uncommon, bulk-unstable, phase. The nanodots were approximately 10 nm in size, and were formed by iron thin film deposition and subsequent annealing. Cross-sectional transmission electron microscopy, energy loss spectroscopy mapping, and quantitative image simulation and analysis were utilized to identify the phase, strain, and orientational relationship of the nanodots to the host silicon lattice. X-ray photoelectron spectroscopy was utilized to analyze the surface composition and local bonding. Elasticity calculations yielded a nanodot residual strain value of -18%. Geometrical phase analysis graphically pinpointed the positions of misfit dislocations, and clearly showed the presence of pinned (11¯1¯)Si//(100)FeSi, and unpinned (2¯42)Si//(010)FeSi, interfaces. This partial endotaxy in the host silicon lattice was the mechanism that stabilized the B2-FeSi phase.

  18. High-pressure synthesis and superconductivity of the Laves phase compound Ca(Al,Si)2 composed of truncated tetrahedral cages Ca@(Al,Si))12.

    PubMed

    Tanaka, Masashi; Zhang, Shuai; Inumaru, Kei; Yamanaka, Shoji

    2013-05-20

    The Zintl compound CaAl2Si2 peritectically decomposes to a new ternary cubic Laves phase Ca(Al,Si)2 and an Al-Si eutectic at temperatures above 750 C under a pressure of 13 GPa. The ternary Laves phase compound can also be prepared as solid solutions Ca(Al(1-x)Si(x))2 (0.35 ? x ? 0.75) directly from the ternary mixtures under high-pressure and high-temperature conditions. The cubic Laves phase structure can be regarded as a type of clathrate compound composed of face-sharing truncated tetrahedral cages with Ca atoms at the center, Ca@(Al,Si)12. The compound with a stoichiometric composition CaAlSi exhibits superconductivity with a transition temperature of 2.6 K. This is the first superconducting Laves phase compound composed solely of commonly found elements. PMID:23654286

  19. Site preference of ternary alloying addition (Ti, Fe, Co and Ni) in DO3 Fe3Al, Co3Al and Ni3Al - basic compound for alnico-8 magnetic materials

    NASA Astrophysics Data System (ADS)

    Samolyuk, German; jfalussy, Balazs; Stocks, Malcolm

    2014-03-01

    We performed first-principles calculations to investigate the site preference of ternary alloying additions in DO3 Fe3Al, Co3Al and Ni3Al alloys. In Fe3Al the discussed ternary elements are found to occupy the Fe sublattice. For both Fe-rich and Al-rich compounds, the ternary elements with fewer 3 d electrons than Fe (Ti) prefer to occupy ?-sites of Fe sublattice and elements with larger number of 3 d electrons - the ?-sites. In Fe-rich regions, the small enthalpy difference of Ti occupying ?-sites of Fe and Al sublattices, the site distribution of Ti varies with concentration and temperature. A similar dependency was obtained for Ni distribution between Co and Al sublattice in Co3Al. Similar to the Fe3Al alloy, the ternary element prefer to occupy Co sublattice with a change of preferred sites from ? for Ti and Fe to ? for Ni. In the Ni-rich Ni3Al the ternary elements prefer to occupy the Al sublattice, while, in the Al-rich alloy the ternary elements prefer to occupy Ni sublattice in a similar fashion. The magnetic moments of transition metals in Fe3Al and Co3Al are ordered ferromagnetically, whereas the Ni3Al is nonmagnetic unless the Fe or Co are added as a ternary element. This work was supported by U.S. Department of Energy (DOE), Energy Efficiency and Renewable Energy.

  20. Impact of SiO2 on Al-Al thermocompression wafer bonding

    NASA Astrophysics Data System (ADS)

    Malik, Nishant; Schjlberg-Henriksen, Kari; Poppe, Erik U.; Taklo, Maaike M. V.; Finstad, Terje G.

    2015-03-01

    Al-Al thermocompression bonding suitable for wafer level sealing of MEMS devices has been investigated. This paper presents a comparison of thermocompression bonding of Al films deposited on Si with and without a thermal oxide (SiO2 film). Laminates of diameter 150?mm containing device sealing frames of width 200?m were realized. The wafers were bonded by applying a bond force of 36 or 60?kN at bonding temperatures ranging from 300-550?C for bonding times of 15, 30 or 60?min. The effects of these process variations on the quality of the bonded laminates have been studied. The bond quality was estimated by measurements of dicing yield, tensile strength, amount of cohesive fracture in Si and interfacial characterization. The mean bond strength of the tested structures ranged from 18-61?MPa. The laminates with an SiO2 film had higher dicing yield and bond strength than the laminates without SiO2 for a 400?C bonding temperature. The bond strength increased with increasing bonding temperature and bond force. The laminates bonded for 30 and 60?min at 400?C and 60?kN had similar bond strength and amount of cohesive fracture in the bulk silicon, while the laminates bonded for 15?min had significantly lower bond strength and amount of cohesive fracture in the bulk silicon.

  1. A comparative wear study on Al-Li and Al-Li/SiC composite

    SciTech Connect

    Okumus, S. Cem Karslioglu, Ramazan Akbulut, Hatem

    2013-12-16

    Aluminum-lithium based unreinforced (Al-8090) alloy and Al-8090/SiCp/17 vol.% metal matrix composite produced by extrusion after spray co-deposition. A dry ball-on disk wear test was carried out for both alloy and composite. The tests were performed against an Al{sub 2}O{sub 3} ball, 10 mm in diameter, at room temperature and in laboratory air conditions with a relative humidity of 40-60%. Sliding speed was chosen as 1.0 ms{sup ?1} and normal loads of 1.0, 3.0 and 5.0 N were employed at a constant sliding distance of 1000 m. The wear damage on the specimens was evaluated via measurement of wear depth and diameter. Microstructural and wear characterization was carried out via scanning electron microscopy (SEM). The results showed that wear loss of the Al-8090/SiC composite was less than that of the Al-8090 matrix alloy. Plastic deformation observed on the wear surface of the composite and the matrix alloy, and the higher the applied load the greater the plastic deformation. Scanning electron microscopy examinations of wear tracks also reveal that delamination fracture was the dominant wear mechanism during the wear progression. Friction coefficient was maximum at the low applied load in the case of the Al-8090/SiC composite while a gradual increase was observed with applied load for the matrix alloy.

  2. Effect of Mg and Si on infiltration behavior of Al alloys pressureless infiltration into porous SiCp preforms

    NASA Astrophysics Data System (ADS)

    Ren, Shu-Bin; Shen, Xiao-Yu; Qu, Xuan-Hui; He, Xin-Bo

    2011-12-01

    The effect of Mg and Si additon to Al matrix on infiltration kinetics and rates of Al alloys pressureless infiltration into porous SiCp preform was investigated by observing the change of infiltration distance with time as the Al alloys infiltrate into SiCp preforms at different temperatures. The results show that infiltration of SiCp preforms by Al melt is a thermal activation process and there is an incubation period before the infiltration becomes stable. With the increase of Mg content in the Al alloys from 0wt% to 8wt%, the infiltration will become much easier, the incubation period becomes shorter and the infiltration rate is faster, but these effects are not obvious when the Mg content is higher than 8wt%. As for Si addition to the Al alloys, it has no obvious effect on the incubation period, but the infiltration rate increases markedly with the increase of Si content from 0wt% to 12wt% and the rate has no obvious change when the content is bigger than 12wt%. The effect of Mg and Si on the incubation period is related to the infiltration mechanism of Al pressureless infiltration into SiCp preforms and their impact on the infiltration rate is a combined result from viscosity and surface tension of Al melt and SiC-Al wetting ability.

  3. In Situ Al Based Composites Fabricated in Al-SiO2-C System by Reaction Sintering

    NASA Astrophysics Data System (ADS)

    Mokhnache, El Oualid; Wang, Guisong; Geng, Lin; Kaveendran, Balasubramaniam; Henniche, Abdelkhalek; Ramdani, Noureddine

    2015-07-01

    In situ Al-based composites with different SiO2/C/Al molar ratios were fabricated by reaction hot pressing. Differential scanning calorimetry (DSC) was used to investigate the reaction mechanisms in the Al-SiO2-C system. X-ray diffraction results revealed that no new resultant phase was observed below the melting temperature of aluminum except the SiO2, C and Al phases. Heating at different synthesis temperatures showed that, up to 1000C with a holding time of 1 h, the reactions in the Al-SiO2-C system took place completely, where the final products were Al2O3, SiC, Al4C3 and Si. Microstructural observation showed that the in situ synthesized Al2O3, SiC, Al4C3, and Si were dispersed uniformly and had fine sizes less than 2 m. The formed interfaces between the reinforcements and Al matrix are clean and free from any interfacial phase. During cooling, the synthesized Si formed a multilayer growth in the (111) direction. When the SiO2/C/Al molar ratio was (6/3/9), more Al2O3 and Si were produced along with the complete prevention of Al4C3 in the Al-SiO2-C system. The yield strength, ultimate tensile strength and Brinell hardness of the in situ fabricated composites are significantly higher than those of pure aluminum matrix, with a decrease of ductility. Mechanisms governing the tensile fracture process are also discussed.

  4. Structure of AlSi-SiC composite foams surface formed by mechanical and thermal cutting

    NASA Astrophysics Data System (ADS)

    Krajewski, S?awomir; Nowacki, Jerzy

    2015-02-01

    The article presents the geometric structure of AlSi-SiC composite foam surface after thermal, mechanical and erosive cutting with regards to its subsequent practical applications. In stereometric measurements of foam surfaces, confocal microscopy was suggested as a method fit for measuring surfaces of high discontinuity ratio that results from porosity. Basic quality parameters of cutting plane were characterised, and technical as well as methodological problems deriving from atypical porous structure of metallic foams were identified. On the basis of the results obtained, the influence of cutting methods on the geometric parameters of foam plane was established, and most favourable cutting conditions were determined.

  5. Magnetic properties of Fe films and Fe/Si/Fe trilayers grown on GaAs(001) and MgO(001) by ion-beam sputter epitaxy

    SciTech Connect

    Damm, Thorsten; Buchmeier, Matthias; Schindler, Alexandra; Buergler, Daniel E.; Gruenberg, Peter; Schneider, Claus M.

    2006-05-01

    We grow monocrystalline Fe(001) films and Fe/Si/Fe(001) trilayers by ion-beam sputter epitaxy on GaAs(001) and MgO(001) substrates. Ion-beam sputtering parameters such as substrate presputtering time, substrate temperature, beam voltage, and target angle are optimized for 10-nm-thick Fe(001) films with respect to epitaxial growth and magnetic properties. In situ low-energy electron diffraction patterns confirm the epitaxial and monocrystalline nature of the sputtered films, surprisingly even on untreated and thus oxidized substrates. The magneto-optical Kerr effect and ferromagnetic resonance are employed to investigate the magnetic properties, and the structural properties are characterized by atomic force microscopy and x-ray reflectivity measurements. Using the optimized set of parameters that yields the best magnetic properties for single Fe films on GaAs, we deposit epitaxial Fe/Si/Fe(001) structures and observe antiferromagnetic interlayer exchange coupling for epitaxially sputtered Fe/Si/Fe(001) trilayers on GaAs(001). The total coupling strength reaches values of up to 2 mJ/m{sup 2} at a Si thickness of 15 A.

  6. High temperature properties of equiatomic FeAl with ternary additions

    NASA Technical Reports Server (NTRS)

    Titran, R. H.; Vedula, K. M.; Anderson, G. G.

    1985-01-01

    The aluminide intermetallic compounds are considered potential structural materials for aerospace applications. The B2 binary aluminide FeAl has a melting point in excess of 1500 K, is of simple cubic structure, exists over a wide range of composition with solubility for third elements and is potentially self-protecting in extreme environments. The B2 FeAl compound has been alloyed with 1 to 5 at. pct ternary additions of Si, Ti, Zr, Hf, Cr, Ni, Co, Nb, Ta, Mo, W, and Re. The alloys were prepared by blending a third elemental powder with pre-alloyed binary FeAl powder. Consolidation was by hot extrusion at 1250 K. Annealing studies on the extruded rods showed that the third element addition can be classified into three categories based upon the amount of homogenization and the extent of solid solutioning. Constant strain rate compression tests were performed to determine the flow stress as a function of temperature and composition. The mechanical strength behavior was dependent upon the third element homogenization classification.

  7. High temperature properties of equiatomic FeAl with ternary additions

    NASA Technical Reports Server (NTRS)

    Titran, R. H.; Vedula, K. M.; Anderson, G. G.

    1984-01-01

    The aluminide intermetallic compounds are considered potential structural materials for aerospace applications. The B2 binary aluminide FeAl has a melting point in excess of 1500 K, is of simple cubic structure, exits over a wide range of composition with solubility for third elements and is potentially self-protecting in extreme environments. The B2 FeAl compound has been alloyed with 1 to 5 at % ternary additions of Si, Ti, Zr, Hf, Cr, Ni, Co, Nb, Ta, Mo, W, and Re. The alloys were prepared by blending a third elemental powder with prealloyed binary FeAl powder. Consolidation was by hot extrusion at 1250 K. Annealing studies on the extruded rods showed that the third element addition can be classified into three categories based upon the amount of homogenization and the extent of solid solutioning. Constant strain rate compression tests were performed to determine the flow stress as a function of temperature and composition. The mechanical strength behavior was dependent upon the third element homogenization classification.

  8. Photoelectric properties of p-?-FeSi2/n-4H-SiC heterojunction near-infrared photodiode

    NASA Astrophysics Data System (ADS)

    Chunlei, Zheng; Hongbin, Pu; Hong, Li; Zhiming, Chen

    2015-05-01

    We give the first report on the experimental investigation of a p-?-FeSi2/n-4H-SiC heterojunction. A p-?-FeSi2/n-4H-SiC heterojunction near-infrared photodiode was fabricated on 4H-SiC substrate by magnetron sputtering and rapid thermal annealing (RTA). Sharp filmsubstrate interfaces were confirmed by scanning electron microscopy (SEM). The current densityvoltage and photoresponse characteristics were measured. The measurements showed that the device exhibited good rectifying properties. The photocurrent density was about 1.82 mA/cm2 at a bias voltage of -1 V under illumination by a 5 mW, 1.31 ?m laser, and the dark current density was approximately 0.537 mA/cm2. The detectivity was estimated to be 8.8 109 cmHz1/2/W at 1.31 ?m. All of the measurements were made at room temperature. The results suggest that the p-?-FeSi2/n-4H-SiC heterojunctions can be used as near-infrared photodiodes that are applicable to optically-activated SiC-based devices. Project supported by the National Natural Science Foundation of China (No. 51177134).

  9. Structural, Optical, and Electrical Characterization of Al/ n-ZnO/ p-Si/Al Heterostructures

    NASA Astrophysics Data System (ADS)

    Kumar, Rajender; Chand, Subhash

    2015-01-01

    For heterojunction fabrication, zinc oxide thin films were grown on p-Si by pulsed laser deposition. X-ray diffraction patterns were used to study the grain size and morphology of the films. The optical properties of the films were studied by UV-visible and photoluminescence spectroscopy. Experimental observations confirmed that the deposited films have potential for sharp emission in the visible region. High-purity (99.999%) vacuum evaporated aluminium metal was used to make contacts to the n-ZnO and p-Si. The current-voltage characteristics of the Al/ n-ZnO/ p-Si(100)/Al heterostructure measured over the temperature range 60-300 K were studied on the basis of the thermionic emission diffusion mechanism. The equivalent Schottky barrier height and the diode ideality factor were determined by fitting measured current-voltage data to the thermionic emission diffusion equation. It was observed that the barrier height decreased and the ideality factor increased with decreasing temperature, and that the activation energy plot was non-linear at low temperature. These characteristics are attributed to the Gaussian distribution of barrier heights. The capacitance-voltage characteristics of the Al/ n-ZnO/ p-Si(100)/Al heterostructure diode were studied over a wide temperature range. The impurity concentration in deposited n-type ZnO films was estimated from measured capacitance-voltage data.

  10. Quench strengthening mechanism of Al-SiC composites

    SciTech Connect

    Ma, Z.Y.; Bi, J.; Lu, Y.X.; Luo, M.; Gao, Y.X. )

    1993-07-15

    Incorporation of silicon carbide particulate or whisker into the aluminum matrix increases the strength and stiffness of the material. The composites also exhibit excellent elevated temperature properties and size stability, as well as good resistance to fatigue and wear. There are various theories and models about the strengthening mechanism of the composites, which is attributed to many factors. When the composites are rapidly cooled down from elevated temperature, the high density dislocation generates in the aluminum matrix adjacent to SiC particulates due to the great difference in the coefficients of thermal expansion (CTE) of SiC and Al. Volgelsang et al conducted in-situ observations on the generation process of the dislocation using HVEM. It is indicated that the dislocation density in the discontinuous SiC reinforced aluminum matrix composites is an order of magnitude greater than that of the aluminum matrix. On the basis of the experimental observations, Arsenault suggested the theory of dislocation strengthening and suggested that the high dislocation density was one of main factors for composite strengthening. A theoretical model was established, and the dislocation density which was calculated using the model was in fair agreement with the measured values. However, systematic experimental verification about the dislocation strengthening mechanism of the composites is lacking. In this paper the silicon carbide particulate and whisker reinforced pure aluminum composites were employed as model materials to understand the precipitation strengthening due to the existence of alloy elements.

  11. Fracture toughness of SiC/Al metal matrix composite

    NASA Technical Reports Server (NTRS)

    Flom, Yury; Parker, B. H.; Chu, H. P.

    1989-01-01

    An experimental study was conducted to evaluate fracture toughness of SiC/Al metal matrix composite (MMC). The material was a 12.7 mm thick extrusion of 6061-T6 aluminum alloy with 40 v/o SiC particulates. Specimen configuration and test procedure conformed to ASTM E399 Standard for compact specimens. It was found that special procedures were necessary to obtain fatigue cracks of controlled lengths in the preparation of precracked specimens for the MMC material. Fatigue loading with both minimum and maximum loads in compression was used to start the precrack. The initial precracking would stop by self-arrest. Afterwards, the precrack could be safely extended to the desired length by additional cyclic tensile loading. Test results met practically all the E399 criteria for the calculation of plane strain fracture toughness of the material. A valid K sub IC value of the SiC/Al composite was established as K sub IC = 8.9 MPa square root of m. The threshold stress intensity under which crack would cease to grow in the material was estimated as delta K sub th = 2MPa square root of m for R = 0.09 using the fatigue precracking data. Fractographic examinations show that failure occurred by the micromechanism involved with plastic deformation although the specimens broke by brittle fracture. The effect of precracking by cyclic loading in compression on fracture toughness is included in the discussion.

  12. XPS study of the Al/SiO2 interface viewed from the SiO2 side

    NASA Technical Reports Server (NTRS)

    Hecht, M. H.; Grunthaner, F. J.; Maserjian, J.

    1984-01-01

    The first nondestructive measurement of the chemical and physical characteristics of the interface between bulk SiO2 and thick aluminum films is presented. Both X-ray photoelectron spectroscopy (XPS) and electrical measurements of unannealed resistively evaporated Al films on thermal SiO2 indicate an atomically abrupt interface. Postmetallization annealing (PMA) at 450 C induces reduction of the SiO2 by the aluminum, resulting in the layer ordering SiO2/Al2O3/Si/Al. The XPS measurement is performed from the SiO2 side after removal of the Si substrate after etching with XeF2 gas and thinning of the SiO2 layer with HF:ETOH. This represents a powerful new approach to the study of metal-insulator and other interfaces.

  13. FeAl and NbAl3 Intermetallic-HVOF Coatings: Structure and Properties

    NASA Astrophysics Data System (ADS)

    Guilemany, J. M.; Cinca, N.; Dosta, S.; Cano, I. G.

    2009-12-01

    Transition metal aluminides in their coating form are currently being explored in terms of resistance to oxidation and mechanical behavior. This interest in transition metal aluminides is mainly due to the fact that their high Al content makes them attractive for high-temperature applications. This is also a reason to study their resistance to wear; they may be suitable for use in applications that produce a lot of wear in aggressive environments, thus replacing established coating materials. In this study, the microstructure, microhardness, and wear and oxidation performance of FeAl and NbAl3 coatings produced by high-velocity oxy-fuel spraying are evaluated with two main aims: (i) to compare these two coating systemsa commonly studied aluminide (FeAl) and, NbAl3, an aluminide whose deposition by thermal spraying has not been attempted to dateand (ii) to analyze the relationship between their microstructure, composition and properties, and so clarify their wear and oxidation mechanisms. In the present study, the higher hardness of niobium aluminide coatings did not correlate with a higher wear resistance and, finally, although pesting phenomena (disintegration in oxidizing environments) were already known of in bulk niobium aluminides, here their behavior in the coating form is examined. It was shown that such accelerated oxidation was inevitable with respect to the better resistance of FeAl, but further improvements are foreseen by addition of alloying elements in that alloy.

  14. Investigation of Fe-Si-N films as magnetic overcoat for high density recording disk drives

    SciTech Connect

    Gauvin, M.; Talke, F. E.; Fullerton, E. E.

    2010-09-15

    A 50-nm-thick Fe-Si-N films were deposited via reactive magnetron cosputtering of independent Fe and Si targets, in Ar/N{sub 2} gas mixture, under different dc Fe target power conditions. Magnetic properties, mechanical hardness and tribological properties were characterized as a function of the Fe target power by magnetometry, nanoindentation, and nanoscratch testing, respectively. Deposited samples were found to be ferromagnetic with a coercivity of approximately 20 Oe and a saturation magnetization increasing from 200 to 1100 emu/cm{sup 3} as a function of Fe sputter power, i.e., values typical of soft magnetic materials. The mechanical hardness was found to be between 50% and 70% of the hardness of a pure SiN{sub x} film. Nanotribological properties of films deposited with a Fe target power {>=}80 W degraded rapidly.

  15. The nature of hydroxyl groups in aluminosilicate glasses: Quantifying Si-OH and Al-OH abundances along the SiO 2-NaAlSiO 4 join by 1H, 27Al- 1H and 29Si- 1H NMR spectroscopy

    NASA Astrophysics Data System (ADS)

    Malfait, Wim J.; Xue, Xianyu

    2010-01-01

    The combined results of 27Al- 1H and 1H- 29Si- 1H cross polarization NMR experiments for hydrous glasses (containing 0.5-2 wt% water) along the SiO 2-NaAlSiO 4 join confirm that the dissolution mechanism of water in aluminosilicate glasses is fundamentally the same as for Al-free systems, i.e. the dissolved water ruptures oxygen bridges and creates Si-OH and Al-OH groups, in addition to forming molecular water (H 2O mol). The fraction of Al-OH increases non-linearly as the Al content increases with up to half of the OH groups as Al-OH for compositions close to NaAlSiO 4. The relative abundances of the different species are controlled by the degree of Al-avoidance and the relative tendency of hydrolysis of the different types of oxygen bridges, Si-O-Si, Si-O-Al and Al-O-Al. A set of homogeneous reactions is derived to model the measured Al-OH/Si-OH speciation, and the obtained equilibrium constants are in agreement with literature data on the degree of Al-avoidance. With these equilibrium constants, the abundance of the different oxygen species, i.e. Si-O-Si, Si-O-Al, Al-O-Al, Si-OH, Al-OH and H 2O mol, can be predicted for the entire range of water and Al contents.

  16. Wear resistance of TiAlSiN thin coatings.

    PubMed

    Silva, F J G; Martinho, R P; Alexandre, R J D; Baptista, A P M

    2012-12-01

    In the last decades TiAIN coatings deposited by PVD techniques have been extensively investigated but, nowadays, their potential development for tribological applications is relatively low. However, new coatings are emerging based on them, trying to improve wear behavior. TiAlSiN thin coatings are now investigated, analyzing if Si introduction increases the wear resistance of PVD films. Attending to the application, several wear test configurations has been recently used by some researchers. In this work, TiAISiN thin coatings were produced by PVD Unbalanced Magnetron Sputtering technique and they were conveniently characterized using Scanning Electron Microscopy (SEM) provided with Energy Dispersive Spectroscopy (EDS), Atomic Force Microscopy (AFM), Electron Probe Micro-Analyzer (EPMA), Micro Hardness (MH) and Scratch Test Analysis. Properties as morphology, thickness, roughness, chemical composition and structure, hardness and film adhesion to the substrate were investigated. Concerning to wear characterization, two very different ways were chosen: micro-abrasion with ball-on-flat configuration and industrial non-standardized tests based on samples inserted in a feed channel of a selected plastic injection mould working with 30% (wt.) glass fiber reinforced polypropylene. TiAISiN coatings with a small amount of about 5% (wt.) Si showed a similar wear behavior when compared with TiAIN reported performances, denoting that Si addition does not improve the wear performance of the TiAIN coatings in these wear test conditions. PMID:23447962

  17. 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.

  18. Near surface silicide formation after off-normal Fe-implantation of Si(001) surfaces

    SciTech Connect

    Khanbabaee, B. Pietsch, U.; Lützenkirchen-Hecht, D.; Hübner, R.; Grenzer, J.; Facsko, S.

    2014-07-14

    We report on formation of non-crystalline Fe-silicides of various stoichiometries below the amorphized surface of crystalline Si(001) after irradiation with 5 keV Fe{sup +} ions under off-normal incidence. We examined samples prepared with ion fluences of 0.1 × 10{sup 17} and 5 × 10{sup 17} ions cm{sup −2} exhibiting a flat and patterned surface morphology, respectively. Whereas the iron silicides are found across the whole surface of the flat sample, they are concentrated at the top of ridges at the rippled surface. A depth resolved analysis of the chemical states of Si and Fe atoms in the near surface region was performed by combining X-ray photoelectron spectroscopy and X-ray absorption spectroscopy (XAS) using synchrotron radiation. The chemical shift and the line shape of the Si 2p core levels and valence bands were measured and associated with the formation of silicide bonds of different stoichiometric composition changing from an Fe-rich silicides (Fe{sub 3}Si) close to the surface into a Si-rich silicide (FeSi{sub 2}) towards the inner interface to the Si(001) substrate. This finding is supported by XAS analysis at the Fe K-edge which shows changes of the chemical environment and the near order atomic coordination of the Fe atoms in the region close to surface. Because a similar Fe depth profile has been found for samples co-sputtered with Fe during Kr{sup +} ion irradiation, our results suggest the importance of chemically bonded Fe in the surface region for the process of ripple formation.

  19. Iron Oxidation State and Compressional Behaviors of Al,Fe-rich Mantle Silicate Perovskite up to 90 GPa

    NASA Astrophysics Data System (ADS)

    Zhang, Q.; Shim, S.; Meng, Y.; Prakapenka, V.; Alp, E. E.

    2013-12-01

    Magnesium silicate perovskite, the dominant lower-mantle phase, may contain much more Al and Fe in the subducting oceanic crust than in the normal mantle. Therefore, it is important to understand the physical properties of Al,Fe-rich mantle silicate perovskite. We have synthesized Fe,Al-rich mantle silicate perovskites from two different starting materials [Mg2FeAl2Si3O12 (Alm33) and Mg2.5Fe0.5Al2Si3O12 (Alm17)] and conducted in-situ synchrotron X-ray diffraction (GSECARS and HPCAT) and Mssbauer spectroscopy (Sector 3) in the laser heated diamond-anvil cell at Advanced Photon Source. The garnet starting materials were synthesized in the multi-anvil press at Arizona State University. The starting materials were mixed with 10 wt% Au powder (internal pressure standard) and loaded with an Ar or Ne pressure medium in the diamond-anvil cell for X-ray diffraction measurements. Pure starting materials are loaded in the diamond-anvil cell with an Ne or KCl pressure medium for synchrotron Mssbauer measurements. In synchrotron Mssbauer spectroscopy, we obtained pressure from the unit-cell volumes of pressure media combined with their equations of state. During the laser heating of the Alm33 starting material at ~66 GPa and ~2300 K, perovskite was synthesized with a small amount of stishovite. For the same starting material, pure perovskite was synthesized at 90 GPa and ~2300 K. For the Alm17 starting material, perovskite was synthesized with a small amount of stishovite at 65-92 GPa and ~2200K. Between 60 and 90 GPa, the unit-cell volumes of the Alm33 and Alm17 perovskites are only slightly higher (0.3-0.6%) than that of Mg-end member perovskite and are comparable to that of (Mg0.85Fe0.15)SiO3 perovskite, indicating higher density of the Al,Fe-rich perovskite in subducting oceanic crust than surrounding mantle. Both Al,Fe-rich perovskites show a steep increase in unit-cell volume during decompression between 60 and 40 GPa, suggesting either spin transition or metastability at the pressure range. We successfully quenched both Al,Fe-rich perovskites and measured the unit-cell volumes at 1 bar: 166.30.1 3 for Alm17 perovskite, and 165.00.2 3 for Alm33 perovskite. Our direct measurements indicate that the combined effects of Fe and Al on the unit-cell volume is much greater at lower pressures (~2%) than those observed at higher pressure (0.3-0.6%). The preliminary spectral fitting of synchrotron Mssbauer data indicates that 50~80% of iron is Fe3+ in both Al,Fe-rich pervoskites, suggesting that similar degree of charge disproportionation reaction occurs in Al-rich mantle silicate perovskite. This result is in disagreement with a recent thermodynamic prediction by Nakajima et al. (2012, JGR) that Fe3+ concentration may be very low (near zero) in Al-rich perovskite.

  20. Preliminary Results on FeCrAl Alloys in the As-received and Welded State Designed to Have Enhanced Weldability and Radiation Tolerance

    SciTech Connect

    Field, Kevin G.; Gussev, Maxim N.; Hu, Xunxiang; Yamamoto, Yukinori

    2015-09-30

    The present report summarizes and discusses the recent results on developing a modern, nuclear grade FeCrAl alloy designed to have enhanced radiation tolerance and weldability. The alloys used for these investigations are modern FeCrAl alloys based on a Fe-13Cr-5Al-2Mo-0.2Si-0.05Y alloy (in wt.%, designated C35M). Development efforts have focused on assessing the influence of chemistry and microstructure on the fabricability and performance of these newly developed alloys. Specific focus was made to assess the weldability, thermal stability, and radiation tolerance.

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

    SciTech Connect

    Kim, Hyong June

    2011-12-01

    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.

  2. Hydrogen permeation characteristics of some Fe-Cr-Al alloys

    NASA Astrophysics Data System (ADS)

    Van Deventer, E. H.; Maroni, V. A.

    1983-01-01

    Hydrogen permeation data are reported for two Fe-Cr-Al alloys, Type-405 SS (Cr 14-A1 0.2) and a member of the Fecralloy family of alloys (Cr 16-A1 5). The hydrogen permeability of each alloy (in a partially oxidized condition) was measured over a period of several weeks at randomly selected temperatures (between 150 and 850°C) and upstream H 2 pressures (between 2 and 1.5 × 10 4 Pa). The permeabilities showed considerable scatter with both time and temperature and were 10 2 to 10 3 times lower than those of pure iron, even in strongly reducing environments. The exponent, n, for the relationship between upstream H 2 pressure, P, and permeability, φ, ( φ ~ Pn) was closer to 0.7 than to the expected 0.5, indicating a process limited by surface effects (e.g., surface oxide films) as opposed to bulk material effects. Comparison of these results with prior permeation measurements on other Fe-Cr-Al alloys, on Fe-Cr alloys, and on pure iron shows that the presence of a few weight percent aluminum offers the best prospects for achieving low tritium permeabilities with martensitic and ferritic steels used in fusion-reactor first wall and blanket applications.

  3. Chemical behavior of indigenous impurities (Al, Fe, Si, Mg, F, K, Na, NH{sub 3}, Ca, and SO{sub 4}) during the production of filter-grade wet-process phosphoric acid

    SciTech Connect

    Sullivan, J.M.; Frazier, A.W.; Griffin, C.L.; Grinstead, J.H. Jr.; Kim, Y.K.; Kohler, J.J.

    1992-12-01

    The conventional (dihydrate process) extraction of phosphate rocks with sulfuric acid and subsequent filtration results in a dilute ``filter-grade`` wet-process phosphoric acid (WPA) containing many cationic and anionic impurities which can cause problems during fertilizer production. Most of these problems result because many of the impurities are present in amounts above saturation. This factorial study was designed to define the nature and amounts of components precipitating from simulated filter-grade (28% P{sub 2}O{sub 5}) phosphoric acid at 85, 68, and 25 C, with 2-day retention times. Results show that the precipitation of the iron ammonium and iron potassium phosphates generally provide the largest source of solids in filter-grade phosphoric acid; Mg and Ca fluoroaluminates and alkali fluorosilicates also provide a significant proportion of solids. The distribution of solids between these 3 groups is governed by the F/Si ratio in the acid. The study also delineates the deleterious effect of ammonia contamination (such as from ammonia leakage to gypsum ponds).

  4. Chemical behavior of indigenous impurities (Al, Fe, Si, Mg, F, K, Na, NH[sub 3], Ca, and SO[sub 4]) during the production of filter-grade wet-process phosphoric acid

    SciTech Connect

    Sullivan, J.M.; Frazier, A.W.; Griffin, C.L.; Grinstead, J.H. Jr.; Kim, Y.K.; Kohler, J.J.

    1992-01-01

    The conventional (dihydrate process) extraction of phosphate rocks with sulfuric acid and subsequent filtration results in a dilute ''filter-grade'' wet-process phosphoric acid (WPA) containing many cationic and anionic impurities which can cause problems during fertilizer production. Most of these problems result because many of the impurities are present in amounts above saturation. This factorial study was designed to define the nature and amounts of components precipitating from simulated filter-grade (28% P[sub 2]O[sub 5]) phosphoric acid at 85, 68, and 25 C, with 2-day retention times. Results show that the precipitation of the iron ammonium and iron potassium phosphates generally provide the largest source of solids in filter-grade phosphoric acid; Mg and Ca fluoroaluminates and alkali fluorosilicates also provide a significant proportion of solids. The distribution of solids between these 3 groups is governed by the F/Si ratio in the acid. The study also delineates the deleterious effect of ammonia contamination (such as from ammonia leakage to gypsum ponds).

  5. Y-Si-Al-O-N glass fibers. Final report

    SciTech Connect

    Messier, D.R.; Gleisner, R.P.; Rich, R.E.

    1989-05-01

    The excellent mechanical properties and outstanding water corrosion resistance of Y-Si-Al-O-N glasses indicate that they are attractive candidate materials for forming into high-performance glass fibers. Fibers of glasses containing, respectively, 3.2 and 6.6 wt% N were drawn freehand in air, and from glass rods in N2. Continuous fibers (100-m long) of the former glass were melt-drawn in N2 while being wound in air outside of the glass-melting furnace. Some fibers had diameters as small as 10 um, and characterization data show that the fibers retain all of the desirable properties of the bulk glass.

  6. Non-oscillatory antiferromagnetic coupling in sputtered Fe/Si superlattices

    SciTech Connect

    Fullerton, E.E.; Mattson, J.E.; Lee, S.R.; Sowers, C.H.; Huang, Y.Y.; Felcher, G.; Bader, S.D.; Parker, F.T.

    1992-06-01

    A series of sputtered Fe(30{Angstrom})/Si(x) superlattices were grown for x=10--40{Angstrom}. Magnetization and Kerr hysteresis loops, and neutron-reflectively measurements identify antiferromagnetic (AF) coupling of the Fe layers at room temperature for x=15{Angstrom} nominal thickness, with switching fields of 6kOe. X-ray structural analysis indicate that the spacer medium is crystalline for x<20{Angstrom}, while sputtered Si is amorphous (a). Failure to detect oscillations in the AF coupling for thicker Si layers is due to the formation of a-Si, as opposed to the crystalline silicide responsible for the coupling.

  7. Piezomagnetic behavior of Fe-Al-B alloys

    NASA Astrophysics Data System (ADS)

    Bormio-Nunes, Cristina; Hubert, Olivier

    2015-11-01

    For the first time, the piezomagnetic behavior of polycrystalline Fe-Al-B alloys is accessed. Piezomagnetic factors of up to 4.0 kA m-1/MPa were reached for an interval of applied compressive stresses between 0 and -140 MPa. The experimental results together with a powerful multiscale and biphasic modeling allowed the general understanding of the magnetostrictive and piezomagnetic behaviors of these materials. The magnetic and mechanical localizations as well as homogeneous stresses were considered in the modeling and are associated to the intrinsic presence of the Fe2B phase. The interplay of the magnetocrystalline anisotropy, initial susceptibility, saturation magnetostriction and texture were quantified by the model and compared to the experimental results. An improvement of the piezomagnetic factor to 15 kA m-1/MPa is predicted, for an alloy containing 20% of aluminum, by getting an adequate texture near < 100 > directions.

  8. A declaration of independence for Mg/Si. [Al/Si intensity ratio predictive usefulness for Mg/Si intensity ratio in lunar X-ray fluorescence

    NASA Technical Reports Server (NTRS)

    Hubbard, N.; Keith, J. E.

    1978-01-01

    The weak covariation that exists between Al/Si and Mg/Si for large areas of the lunar surface is little, if any, stronger than that forced on a random set of numbers that are subject to closure. The Mg and Al variations implied by the Mg/Si and Al/Si intensity ratio data are qualitatively like those seen in lunar soil sample data. Two petrogenetic provinces are suggested for terra materials; one appears to have 50% higher Mg values than the other. Using the improved data, Mg/Si variations can be studied at a signal-to-noise ratio greater than 5/1.

  9. Properties of AlN film grown on Si (111)

    NASA Astrophysics Data System (ADS)

    Dai, Yiquan; Li, Shuiming; Sun, Qian; Peng, Qing; Gui, Chengqun; Zhou, Yu; Liu, Sheng

    2016-02-01

    Stress and strain in an AlN film grown on Si (111) substrate have been evaluated by measuring Raman frequency shifts. Mechanical properties and phonon deformation potentials of AlN are evaluated by first principles calculations. The calculation model is verified by comparing the calculated Raman frequencies and frequencies detected from a bulk single crystal. Results show that the two sets of frequencies agree very well with each other. Thus, with the same verified model and parameters, elastic constants and phonon deformation potentials are calculated. Additionally, we successfully develop a numerical model to verify the calculation above and the model itself is also useful to predict properties of crystal films. Finally, the stress, strain, and piezoelectric properties are analyzed and compared for films on different substrates.

  10. Structural Evolution of Fe Particles in Fe-Al2O3 Granular Films by Ar Ion Irradiations

    NASA Astrophysics Data System (ADS)

    Nakayama, Hiro; Ishida, Tomoya; Kinoshita, Ryosuke; Purwanto, Setyo; Sakamoto, Isao; Honda, Shigeo; Koike, Masaki; Yasumoto, Masato; Hayashi, Nobuyuki; Toriyama, Tamotsu

    2013-01-01

    Fe-Al2O3 granular films were prepared by helicon plasma sputtering. Fe64(Al2O3)36 in volume percent of as-prepared films was irradiated with 400 keV Ar ions in the fluence range of 11015-51016 ions/cm2. The growth of Fe particles with increasing ion fluence was observed from X-ray diffraction (XRD) patterns, magnetization curves, and conversion electron Mssbauer (CEM) spectra. The magnetization curves and CEM spectra of as-prepared Fe-Al2O3 films indicated the superparamagnetic nature and the ferromagnetic nature with increasing ion fluence. In addition, the reduction of Fe3+ component to the Fe2+ and metallic Fe components by ion irradiation was observed from CEM spectra.

  11. Local moments and suppression of antiferromagnetism in correlated Zr4Fe4Si7

    NASA Astrophysics Data System (ADS)

    Simonson, J. W.; Pezzoli, M. E.; Garlea, V. O.; Smith, G. J.; Grose, J. E.; Misuraca, J. C.; Kotliar, G.; Aronson, M. C.

    2013-08-01

    We report magnetic, transport, and neutron diffraction measurements as well as a doping study of the V-phase compound Zr4Fe4Si7. This compound exhibits collinear antiferromagnetic order below TN=981 K with a staggered moment of 0.57(3)?B/Fe as T? 0. The magnetic order can be quenched with Co substitution to the Fe site, but even then a 1.5?B/Fe paramagnetic moment remains. The resistivity and heat capacity of Zr4Fe4Si7 are Fermi-liquid-like below 16 and 7 K, respectively, and reveal correlations on the scale of those observed in superconducting Fe pnictides and chalcogenides. Electronic structure calculations overestimate the ordered moment, suggesting the importance of dynamical effects. The existence of magnetic order, electronic correlations, and spin fluctuations make Zr4Fe4Si7 distinct from the majority of Fe-Si compounds, fostering comparison instead with the parent compounds of Fe-based superconductors.

  12. Analysis Si/Al ratio in zeolites type FAU by laser induced breakdown spectroscopy (LIBS)

    NASA Astrophysics Data System (ADS)

    Contreras, W. A.; Cabanzo, R.; Mejía-Ospino, E.

    2011-01-01

    In this work, Laser Induced Breakdown Spectroscopy (LIBS) is used to determine the Si/Al ratio of Zeolite type Y. The catalytic activity of zeolite is strongly dependent of the Si/Al ratio. We have used Si lines in the spectral region between 245-265 nm to determine temperature of the plasma generated on pelletized sample of zeolite, and stoichiometry relation between Si and Al.

  13. On the entropy of glaucophane Na2Mg3Al2Si8O22(OH)2

    USGS Publications Warehouse

    Robie, R.A.; Hemingway, B.S.; Gillet, P.; Reynard, B.

    1991-01-01

    The heat capacity of glaucophane from the Sesia-Lanza region of Italy having the approximate composition (Na1.93Ca0.05Fe0.02) (Mg2.60Fe0.41) (Al1.83Fe0.15Cr0.01) (Si7.92Al0.08)O22(OH)2 was measured by adiabatic calorimetry between 4.6 and 359.4 K. After correcting the Cp0data to values for ideal glaucophane, Na2Mg3Al2Si8O22(OH)2 the third-law entropy S2980-S00was calculated to be 541.2??3.0 J??mol-1??K-1. Our value for S2980-S00is 12.0 J??mol-1??K-1 (2.2%) smaller than the value of Likhoydov et al. (1982), 553.2??3.0, is within 6.2 J??mol-1??K-1 of the value estimated by Holland (1988), and agrees remarkably well with the value calculated by Gillet et al. (1989) from spectroscopic data, 539 J??mol-1??K-1. ?? 1991 Springer-Verlag.

  14. Influence of extra La and annealing temperature on microstructure and magnetocaloric properties of La-Fe-Co-Si alloys

    NASA Astrophysics Data System (ADS)

    Zhang, Zhongtian; He, Chun; Zhang, Mingxiao; Liu, Jian

    2015-11-01

    The microstructure, phase constitution and magnetocaloric properties of non-stoichiometric La1.7Fe11Co0.8Si1.2 alloys were investigated. Compared with stoichiometric La(Fe,Co,Si)13 alloys, a complex phase, including La(Fe,Co,Si)13 phase, La5Si3 phase, La(Fe,Co)Si phase, ?-Fe phase and La oxide, can rapidly form upon annealing at 1323 K for 24 h in the present alloy. The resulting alloy exhibits a large magnetic entropy change of 7.5 J kg-1 K-1 at 271 K in a magnetic field change of 2 T. In addition, the annealed La1.7Fe11Co0.8Si1.2 alloy shows a reversible magnetic phase transition with zero hysteresis. These characteristics indicate that the present La-rich La-Fe-Co-Si compounds have potential for the applications as ambient magnetic refrigeration materials.

  15. FeMn Metal Droplet Behavior in the MnO-SiO2-CaO Slag System

    NASA Astrophysics Data System (ADS)

    Jang, Hyoung-Soon; Ryu, Jae Wook; Sohn, Il

    2015-04-01

    Optimization of the MnO-SiO2-CaO-based slag composition in the FeMn decarburization refining process to minimize metal droplet entrainment has been studied. FeMn spherical droplets with average diameter of 2.5 mm were dispersed within the refining slag of the medium carbon grade ferro-manganese alloy process. Approximately 4.2 pct of the slag existed as FeMn droplets contributing to the overall metal yield loss in the current process. Sedimentation tests of slags with various SiO2 content ranging from 26 to 47 pct using Al2O3 crucibles held at 1773 K (1500 C) for 30 minutes showed an improvement of the metal/slag separation. Estimated and measured viscosity of the slags showed SiO2 at 32 pct to be optimal for metal/slag separation. Changes in the SiO2 content to 32 pct in actual plant trials allowed significant decrease in the amount of metal droplet entrainment resulting in a decrease of metal in slag to 1.3 pct. Refining times for this optimized slag composition required at least 20 minutes holding for increased separation according to Stokes' law.

  16. Room-temperature fabrication of ?-FeSi2 microprecipitates by pulsed laser deposition

    NASA Astrophysics Data System (ADS)

    Narazaki, Aiko; Sato, Tadatake; Kawaguchi, Yoshizo; Niino, Hiroyuki

    2004-10-01

    We have developed a room-temperature fabrication process for ?-FeSi2 microprecipitates through the active use of droplets generated by pulsed laser deposition. The droplets generated by KrF excimer laser ablation of an ?-FeSi2 metallic target were characterized by micro-Raman spectroscopy with a spatial resolution of 1 ?m and X-ray diffraction measurements. As a result, it was confirmed that the micron-sized droplets precipitated as the ?-FeSi2 semiconducting phase on silicon and silica glass substrates maintained even at room temperature, whereas the rest of the deposited film was amorphous. It was also found that films containing a high density of ?-FeSi2 microprecipitates exhibited 1.55 ?m photoluminescence at low temperature after annealing at 800C for 6 h in an argon atmosphere.

  17. Ferromagnetism and nonmetallic transport of thin-film ?-FeSi(2): a stabilized metastable material.

    PubMed

    Cao, Guixin; Singh, D J; Zhang, X-G; Samolyuk, German; Qiao, Liang; Parish, Chad; Jin, Ke; Zhang, Yanwen; Guo, Hangwen; Tang, Siwei; Wang, Wenbin; Yi, Jieyu; Cantoni, Claudia; Siemons, Wolter; Payzant, E Andrew; Biegalski, Michael; Ward, T Z; Mandrus, David; Stocks, G M; Gai, Zheng

    2015-04-10

    A metastable phase ?-FeSi_{2} was epitaxially stabilized on a silicon substrate using pulsed laser deposition. Nonmetallic and ferromagnetic behaviors are tailored on ?-FeSi_{2} (111) thin films, while the bulk material of ?-FeSi_{2} is metallic and nonmagnetic. The transport property of the films renders two different conducting states with a strong crossover at 50K, which is accompanied by the onset of a ferromagnetic transition as well as a substantial magnetoresistance. These experimental results are discussed in terms of the unusual electronic structure of ?-FeSi_{2} obtained within density functional calculations and Boltzmann transport calculations with and without strain. Our finding sheds light on achieving ferromagnetic semiconductors through both their structure and doping tailoring, and provides an example of a tailored material with rich functionalities for both basic research and practical applications. PMID:25910157

  18. Comparison of the effects of particle shape on thin FeSiCr electromagnetic wave absorber

    NASA Astrophysics Data System (ADS)

    Kim, Moon Suk; Min, Eui Hong; Koh, Jae Gui

    2009-03-01

    The raw materials of FeSiCr were processed in the ball mill for 30 h and the shape of the FeSiCr particles was changed from sphere to flake type, which was observed using a scanning electron microscope. And FeSiCr composite microwave absorbers were mixed with silicone for mobile phones and the effects of the thickness of the samples on the absorption were measured using a network analyzer in order to investigate the relationship between the microwave absorption and the material constants. The flake-type FeSiCr-rubber composite showed high reflection loss, which was due to the high complex permittivity and permeability. Also, the matching frequency shifted toward lower frequency range with microwave absorber thickness, and the maximum reflection loss of -8.7 dB was observed in 1.85 GHz for a 1.6 mm thickness.

  19. Welding of Very Dissimilar Materials (Fe-Al)

    NASA Astrophysics Data System (ADS)

    Schneider, Judy; Radzilowski, Ron

    2014-09-01

    Designers of transportation vehicles (air, land, or sea) continually seek ways to reduce vehicle weight in response to increasing fuel economy mandates, mission requirements, or other competitive pressures. One way to do this is by the selection of material types and their properties based on functional and structural requirements. While these material changes can help meet performance mandates, their implementation in a production environment relies on retaining economic competitiveness. This article traces the history of the various joining processes relevant to the current challenge in joining the very dissimilar families of steel (Fe) and aluminum (Al) alloys.

  20. Welding of Very Dissimilar Materials (Fe-Al)

    NASA Astrophysics Data System (ADS)

    Schneider, Judy; Radzilowski, Ron

    2014-10-01

    Designers of transportation vehicles (air, land, or sea) continually seek ways to reduce vehicle weight in response to increasing fuel economy mandates, mission requirements, or other competitive pressures. One way to do this is by the selection of material types and their properties based on functional and structural requirements. While these material changes can help meet performance mandates, their implementation in a production environment relies on retaining economic competitiveness. This article traces the history of the various joining processes relevant to the current challenge in joining the very dissimilar families of steel (Fe) and aluminum (Al) alloys.

  1. 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.

  2. MOKE Study of Fe/Co/Al Multilayers

    NASA Astrophysics Data System (ADS)

    Jani, Snehal; Rajput, Parasmani; Zaj?c, M.; Rffer, R.; Lakshmi, N.; Reddy, V. R.; Venugopalan, K.; Gupta, Ajay

    2011-07-01

    The multilayer system (MLS)-[57Fe25/Co11 /Al17 ]20 has been deposited by Ion beam sputtering (IBS) technique. The MLS has been annealed at 700 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.

  3. Electronic and optical properties of isostructural {beta}-FeSi{sub 2} and OsSi{sub 2}

    SciTech Connect

    Migas, D. B.; Miglio, Leo; Henrion, W.; Rebien, M.; Marabelli, F.; Cook, B. A.; Shaposhnikov, V. L.; Borisenko, V. E.

    2001-08-15

    We present both theoretical and experimental investigations of electronic and optical properties of isostructural {beta}-FeSi{sub 2} and OsSi{sub 2} by means of a full-potential linear augmented plane wave method and optical measurements. We report also ellipsometric and reflectance measurements on samples of polycrystalline osmium disilicide prepared by mechanical alloying. From ab initio calculations these compounds are found to be indirect band-gap semiconductors with the fundamental gap of OsSi{sub 2} larger some 0.3--0.4 eV than the one of {beta}-FeSi{sub 2}. In addition to that, a low value of the oscillator strength is predicted for the first direct transitions in both cases. Computed optical functions for these materials were compared to the ones deduced from optical measurements, indicating very good agreement and the presence of some anisotropic effects.

  4. Influence of Fe and Cu seed layers on the magnetoresistance in Fe/Cu superlattices grown on Si(111) and CaF 2(111) /Si(111)

    NASA Astrophysics Data System (ADS)

    Mosca, D. H.; Mattoso, N.; Kakuno, E. M.; Schreiner, W. H.; Mazzaro, I.; Teixeira, S. R.

    1996-04-01

    The structural characterization of superlattices was carried out by X-ray diffraction, reflectivity measurements and TEM. Our results indicate that the superlattices are very different from the structural point of view, whereas the magnetoresistance values are rather similar with respect to the magnitude and field dependence at room temperature, independently of the Cu and Fe 50 seed layers grown on Si(111) or Si(111)/CaF 2(111).

  5. Dopant species with Al-Si and N-Si bonding in the MOCVD of AlN implementing trimethylaluminum, ammonia and silane

    NASA Astrophysics Data System (ADS)

    dos Santos, R. B.; Rivelino, R.; de Brito Mota, F.; Gueorguiev, G. K.; Kakanakova-Georgieva, A.

    2015-07-01

    We have investigated gas-phase reactions driven by silane (SiH4), which is the dopant precursor in the metalorganic chemical vapor deposition (MOCVD) of aluminum nitride (AlN) doped by silicon, with prime focus on determination of the associated energy barriers. Our theoretical strategy is based on combining density-functional methods with minimum energy path calculations. The outcome of these calculations is suggestive for kinetically plausible and chemically stable reaction species with Al-Si bonding such as (CH3)2AlSiH3 and N-Si bonding such as H2NSiH3. Within this theoretical perspective, we propose a view of these reaction species as relevant for the actual MOCVD of Si-doped AlN, which is otherwise known to be contributed by the reaction species (CH3)2AlNH2 with Al-N bonding. By reflecting on experimental evidence in the MOCVD of various doped semiconductor materials, it is anticipated that the availability of dopant species with Al-Si, and alternatively N-Si bonding near the hot deposition surface, can govern the incorporation of Si atoms, as well as other point defects, at the AlN surface.

  6. 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.

  7. Amorphization of Fe/Al: bulk and thin-film effects

    NASA Astrophysics Data System (ADS)

    Noetzel, J.; Meyer, D. C.; Tselev, A.; Mcklich, A.; Paufler, P.; Prokert, F.; Wieser, E.; Mller, W.

    The amorphous non-equilibrium state of the system Fe/Al is studied in bulk and thin-film systems. For bulk samples prepared by ion-beam mixing of laser-deposited multilayers, a bcc solid solution is found for alloys with up to 70 at.% Al. Around 75 at.% Al a Fe2Al5-like crystalline phase is found. An amorphous state with Fe2Al5-like short-range order is found for 80 at.% Al. In thin films, for example the amorphous Al-rich transition layer of a laser-deposited Fe/Al multilayer, the amorphous state can exist for up to 30 at.% Fe due to the high interfacial energy. By ion-beam mixing at low temperatures (about 140 K) an oversaturation with 40 at.% Fe can be achieved.

  8. Microstructure Evolution of Cold-Sprayed Al-Si Alloy Coatings on ?-TiAl During Heat Treatment

    NASA Astrophysics Data System (ADS)

    Wang, Jiqiang; Kong, Lingyan; Li, Tiefan; Xiong, Tianying

    2015-08-01

    This paper investigated the influence of heat treatment on the microstructure of Al-Si alloy coatings on ?-TiAl alloy. The coatings were prepared by cold spraying with Al-12Si and Al-20Si alloy powders as the feedstock, and then the as-sprayed coatings were subjected to heat treatment. The microstructure, chemical composition, and phase transformation of the coatings were studied by SEM, XRD, and EPMA. The diffusing behavior of Al and Si during heat treatment was investigated. The results showed that a silicon-aluminizing coating was formed through the inward diffusion of Al/Si elements into the substrate. The obtained kinetics curve of the formation of silicon-aluminizing coating at 580 C similarly followed parabolic law.

  9. The optical properties of ?-FeSi 2 fabricated by ion beam assisted sputtering

    NASA Astrophysics Data System (ADS)

    McKinty, C. N.; Kewell, A. K.; Sharpe, J. S.; Loureno, M. A.; Butler, T. M.; Valizadeh, R.; Colligon, J. S.; Reeson Kirkby, K. J.; Homewood, K. P.

    2000-03-01

    ?-FeSi 2 has been shown to have a minimum direct band gap of 0.87 eV [T.D. Hunt, K.J. Reeson, K.P. Homewood, S.W. Teon, R.M. Gwilliam, B.J. Sealy, Nucl. Instr. and Meth. B 84 (1994) 168-171] which leads to the opportunity for Si based opto-electronics, optical communications and optical interconnects. Electroluminescence has been reported from structures containing ?-FeSi 2, which were produced by high dose ion implantation and annealing [D. Leong, M.A. Harry, K.J. Reeson, K.P. Homewood, Nature 387 (12 June 1987) 686]. In this paper we report the formation of ?-FeSi 2 by ion beam assisted co-sputtering of Fe and Si in varying percentages. The layers were deposited with a varying Fe/Si ratio, with a Si capping layer applied to prevent oxidation. Separate regions of the sample were investigated at room temperature using optical absorption, to measure the band gap values. Absorption under the fundamental edge was also analysed at room temperature. Further investigations looked at the temperature dependence of the band gap and the absorption under the fundamental edge. The results showed that a variety of Fe/Si ratios produced ?-FeSi 2, the formation of which was ascertained by the presence of a suitable band gap value [0.83-0.88 eV]. Absorption under the fundamental edge was shown to follow an exponential Urbach tail [C.H. Grein, S. John, Phys. Rev. B 39 (1989) 1140]. The temperature measurements are in good agreement with the Einstein model.

  10. 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.

  11. Multi-technique equation of state for Fe2SiO4 melt and the density of Fe-bearing silicate melts from 0 to 161 GPa

    NASA Astrophysics Data System (ADS)

    Thomas, Claire W.; Liu, Qiong; Agee, Carl B.; Asimow, Paul D.; Lange, Rebecca A.

    2012-10-01

    We have conducted new equation of state measurements on liquid Fe2SiO4in a collaborative, multi-technique study. The liquid density (?), the bulk modulus (K), and its pressure derivative (K') were measured from 1 atm to 161 GPa using 1-atm double-bob Archimedean, multi-anvil sink/float, and shock wave techniques. Shock compression results on initially molten Fe2SiO4 (1573 K) fitted with previous work and the ultrasonically measured bulk sound speed (Co) in shock velocity (US)-particle velocity (up) space yields the Hugoniot: US = 1.58(0.03) up + 2.438(0.005) km/s. Sink/float results are in agreement with shock wave and ultrasonic data, consistent with an isothermal KT = 19.4 GPa and K' = 5.33 at 1500C. Shock melting of initially solid Fe2SiO4 (300 K) confirms that the Grneisen parameter (?) of this liquid increases upon compression where ? = ?o(?o/?)q yields a qvalue of -1.45. Constraints on the liquid fayalite EOS permit the calculation of isentropes for silicate liquids of general composition in the multicomponent system CaO-MgO-Al2O3-SiO2-FeO at elevated temperatures and pressures. In our model a whole mantle magma ocean would first crystallize in the mid-lower mantle or at the base of the mantle were it composed of either peridotite or simplified "chondrite" liquid, respectively. In regards to the partial melt hypothesis to explain the occurrence and characteristics of ultra-low velocity zones, neither of these candidate liquids would be dense enough to remain at the core mantle boundary on geologic timescales, but our model defines a compositional range of liquids that would be gravitationally stable.

  12. Metastable-stable phase transformation behavior of Al2O3 scale formed on Fe-Ni-Al alloys

    NASA Astrophysics Data System (ADS)

    Hayashi, Shigenari; Takada, Yuto; Yoneda, S.; Ukai, Shigeharu

    2016-02-01

    The oxidation behavior of Ni-Fe-41.5Al alloy with different Fe/Ni ratio was investigated in air at 1000°C using in-situ high-temperature X-ray diffraction study by means of Synchrotron radiation. The oxidation mass gain of alloys decreased with increasing Fe content, particularly initial oxidation mass gain significantly decreased with increasing alloy Fe content. In-situ X-ray diffraction study indicated that the stable α-Al2O3 formed from beginning of oxidation on the alloy with higher Fe ratio, but metastable Al2O3 formed on the alloy with lower Fe ratio, and it remained longer when alloy Fe ratio was decreased. The effect of Fe on promoting α-Al2O3 formation is explained due to initial formation of α-Fe2O3, which has isomorphous structure with α-Al2O3. The additional effect of Fe on the growth rate of α-Al2O3 was also discussed.

  13. Uniaxial magnetic anisotropy of quasi-one-dimensional Fe chains on Pb/Si

    SciTech Connect

    Sun, Da-li; Wang, De-yong; Du, Hai-Feng; Ning, Wei; Gao, Jian-Hua; Fang, Ya-Peng; Zhang, Xiang-Qun; Sun, Young; Cheng, Zhao-Hua; Shen, Jian

    2009-01-01

    We fabricated quasi-one-dimensional Fe chains on a 4{sup o} miscut Si (111) substrate with a Pb film as a buffer layer. The magnetic properties and morphology of Fe chains were investigated by means of scanning tunneling microscope (STM) and surface magneto-optical Kerr effect (SMOKE). STM images show that Fe chains are formed by Fe random islands along the steps of the Pb film due to step decoration. SMOKE data indicate that the Fe chains exhibit in-plane uniaxial magnetic anisotropy along the step direction. The effective in-plane uniaxial anisotropy constant at room temperature was determined by means of electron spin resonance.

  14. Prediction of a potential high-pressure structure of FeSiO3

    NASA Astrophysics Data System (ADS)

    Cohen, R. E.; Lin, Yangzheng

    2014-10-01

    We predict a candidate high-temperature, high-pressure structure of FeSiO3 with space-group symmetry Cmmm by applying an evolutionary algorithm within density functional theory (DFT)+U that we call post-perovskite II (PPv-II). An exhaustive search found no other competitive candidate structures with ABO3 composition. We compared the x-ray diffraction pattern of FeSiO3 PPv-II with experimental results of the recently reported "H phase" of (Fe,Mg)SiO3. The intensities and positions of two main x-ray diffraction peaks of PPv-II FeSiO3 compare well with those of the H phase. We also calculated the static equation of state, the enthalpy, and the bulk modulus of the PPv-II phase and compared it with those of the perovskite (Pv) and post-perovskite (PPv) phases of FeSiO3. According to the static DFT+U computations, the PPv-II phase of FeSiO3 is less stable than the Pv and PPv phases under lower mantle pressure conditions at T =0 K and has a higher volume. PPv-II may be entropically stabilized, and may be a stable phase in Earth's lower mantle, coexisting with -PbO2 (columbite-structure) silica and perovskite, or with magnesiowustite and/or ferropericlase, depending on the bulk composition.

  15. Thermodynamic Phase Relations in the MgO-FeO-SiO2 System in the Lower Mantle

    NASA Astrophysics Data System (ADS)

    Wolf, A. S.; Caracas, R.; Asimow, P. D.

    2008-12-01

    The perovskite (Pv) to post-perovskite (PPv) phase transition at pressures near the Earth's core-mantle boundary (CMB) is currently the favored candidate for explaining most, if not all, of the peculiarities of the D" layer (~200 km region above core) [1, 2]. Additionally, the pressure- and temperature-dependence of this phase boundary in the Earth provides the possibility of an important new thermo-barometer at the bottom of the convecting mantle. The post-perovskite phase boundary in pure MgSiO3 is fairly well known, but the experimental and calculated results on the partitioning of Fe among the stable coexisting phases and its influence on the transition pressure are currently contradictory [3, 4, 5, 6]. Using density functional theory (DFT), we investigate the MgO-FeO-SiO2 ternary system over the temperatures and pressures relevant to the core-mantle boundary. We use DFT to calculate the energies of the relevant stable phases (Pv, PPv, (Mg,Fe)O magnesio-wustite, and SiO2 stishovite) for a range of Fe compositions along the Mg-Fe binary. These results are fit with a Vinet equation of state, allowing us to parameterize the effect of both pressure and Fe composition. The effect of temperature is modeled using a Grneisen thermal correction, where the vibrational heat capacities are determined using DFT perturbation calculations and the quasi-harmonic approximation. These pressure-, temperature-, and composition-dependent equations of state are then used to explore the predicted phase relations. The results of this investigation are a complete thermodynamic description of the stable phases for this simplified chemistry and a theoretical prediction for iron partioning in the lower mantle. In particular, we find that there may be a coincidence point (azeotrope) on the Pv-PPv phase loop, across which the sense of Fe-partitioning changes sign, as well as significant immiscibility between Mg-rich and Fe-rich post-perovskite. These findings help explain many of the seemingly incongruent experimental results on the effect of iron and are also useful in the planning of future experiments. [1] Murakami et al. (2004) Science 304, 855-858. [2] Oganov & Ono (2004) Nature 430, 445-448. [3] Caracas & Cohen (2005) GRL 32, L16310. [4] Kobayashi et al. (2005) GRL 32, L19301. [5] Auzende et al. (2007) Goldschmidt Abstract. [6] Caracas and Cohen (2008) PEPI 168, 147.

  16. 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. PMID:22409244

  17. Large-scale synthesis of ear-like Si{sub 3}N{sub 4} dendrites from SiO{sub 2}/Fe composites and Si powders

    SciTech Connect

    Wang Feng; Jin Guoqiang; Wang Yingyong; Guo Xiangyun

    2008-07-01

    Large-scale ear-like Si{sub 3}N{sub 4} dendrites were prepared by the reaction of SiO{sub 2}/Fe composites and Si powders in N{sub 2} atmosphere. The product was characterized by field emission scanning electron microscopy, X-ray diffraction, and transmission electron microscopy. The results reveal that the product mainly consists of ear-like Si{sub 3}N{sub 4} dendrites with crystal structures, which have a length of several microns and a diameter of 100-200 nm. Nanosized ladder-like Si{sub 3}N{sub 4} was also obtained when changing the Fe content in the SiO{sub 2}/Fe composites. The Si{sub 3}N{sub 4} nanoladders have a length of hundreds nanometers to several microns and a width of 100-300 nm. The ear-like Si{sub 3}N{sub 4} dendrites are formed from a two-step growth process, the formation of inner stem structures followed by the epitaxial growth of secondary branches.

  18. Al/SiOx/Al single and multiband metamaterial absorbers for terahertz sensor applications

    NASA Astrophysics Data System (ADS)

    Kearney, Brian; Alves, Fabio; Grbovic, Dragoslav; Karunasiri, Gamani

    2013-01-01

    To increase the sensitivity of uncooled thermal sensors in the terahertz (THz) spectral range (1 to 10 THz), we investigated thin metamaterial layers exhibiting resonant absorption in this region. These metamaterial films are comprised of periodic arrays of aluminum (Al) squares and an Al ground plane separated by a thin silicon-rich silicon oxide (SiOx) dielectric film. These standard MEMS materials are also suitable for fabrication of bi-material and microbolometer thermal sensors. Using SiOx instead of SiO2 reduced the residual stress of the metamaterial film. Finite element simulations were performed to establish the design criteria for very thin films with high absorption and spectral tunability. Single-band structures with varying SiOx thicknesses, square size, and periodicity were fabricated and found to absorb nearly 100% at the designed frequencies between three and eight THz. Multiband absorbing structures were fabricated with two or three distinct peaks or a single-broad absorption band. Experimental results indicate that is possible to design very efficient thin THz absorbing films to match specific applications.

  19. Importance of Doping and Frustration in Itinerant Fe-doped Cr2Al

    SciTech Connect

    Susner, Michael A; Parker, David S; Safa-Sefat, Athena

    2015-01-01

    We have 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. 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 explain 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.

  20. Importance of Doping and Frustration in Itinerant Fe-doped Cr2Al

    DOE PAGESBeta

    Susner, Michael A; Parker, David S; Safa-Sefat, Athena

    2015-01-01

    We have 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. 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 calculationsmore » explain 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

  1. Development of FePt-Si-N nanocomposite thin films for magnetic recording

    NASA Astrophysics Data System (ADS)

    Liu, Jing; Zeng, Y. P.; Yu, H. Y.; Jiao, D. L.; Zheng, Z. G.; Liu, Z. W.; Zhang, G. Q.

    2014-05-01

    Nanocomposite FePt-Si-N thin films consisting of magnetic L10 FePt nanograins and non-magnetic Si-N matrix for high density recording medium are developed in this work. The (FexPt100-x)100-ySiy-N films (x = 50-65 and y = 0-10) were fabricated on Si (100) substrates by dc reactive magnetron sputtering followed by vacuum annealing. The maximum value of coercivity around 15.3 kOe was obtained in the film with atom ratio Fe:Pt = 55:45. To achieve a high coercivity, the concentrations of Si and N also have to be properly controlled. Doping Si-N improves the coercivity of FePt film through weakening the exchange coupling interaction. Si and N also play an important role in reducing average grain size of the magnetic particles and smoothing the surface of the films. Transmission electron microscopy demonstrated the nanogranular structure consisting of FePt nanoparticles embedded in the amorphous Si-N matrix.

  2. Crystallization and structural relaxation of Fe78-xPtxB10Si12 metallic glasses

    NASA Astrophysics Data System (ADS)

    Hwang, Suk-Won; Kim, Suk J.; Yoon, C. S.; Kim, C. K.

    2004-06-01

    Fe78-xPtxB10Si12 (x = 0, 5, 15, 25) metallic glasses were produced to investigate the effects of Pt on the thermally annealed microstructure and ensuing magnetic properties of the alloy. The Pt addition progressively lowered the glass stability and accelerated the onset of devitrification. Final crystallization products contained either Fe3Pt or FePt, depending on the Pt content together with Fe-borides. A maximum coercivity of 1140 Oe was obtained with the Fe63Pt15B10Si12 alloy annealed at 500 C due to the precipitation of elongated FePt crystals. Measurements of the saturation magnetization of the annealed alloys gave an indication that the amorphous structure may have undergone structural relaxation prior to devitrification.

  3. Magnetic ordering in Ho{sub 2}Fe{sub 2}Si{sub 2}C

    SciTech Connect

    Susilo, R. A. Cadogan, J. M.; Cobas, R.; Hutchison, W. D.; Campbell, S. J.; Avdeev, M.

    2015-05-07

    We have used neutron diffraction and {sup 57}Fe Mssbauer spectroscopy, complemented by magnetisation and specific heat measurements, to examine the magnetic ordering of Ho{sub 2}Fe{sub 2}Si{sub 2}C. We have established that Ho{sub 2}Fe{sub 2}Si{sub 2}C orders antiferromagnetically below T{sub N}?=?16(1) K with a magnetic structure involving ordering of the Ho sublattice along the b-axis with a propagation vector k=[0?0?1/2 ]. {sup 57}Fe Mssbauer spectra collected below T{sub N} show no evidence of a magnetic splitting, demonstrating the absence of long range magnetic ordering of the Fe sublattice. A small line broadening is observed in the {sup 57}Fe spectra below T{sub N}, which is due to a transferred hyperfine fieldestimated to be around 0.3?T at 10?Kfrom the Ho sublattice.

  4. Swift heavy ion irradiation and annealing effects in Fe/Si multilayers

    NASA Astrophysics Data System (ADS)

    Dhuri, Pratima; Gupta, Ajay; Chaudhari, S. M.; Phase, D. M.; Avasthi, D. K.

    Effects of 200 MeV silver ion irradiation and thermal annealing in Fe/Si multilayers with overall composition Fe 50Si 50 have been studied. Two multilayers with Fe layer thickness of 19 and 62 have been studied. While in the first case Fe layer is amorphous in structure, in the second case it has a crystalline bcc structure. X-ray reflectivity study shows that, at this composition both thermal annealing and heavy ion irradiation result in significant interdiffusion between the Fe and Si layers. However, while the products of thermal annealing depend upon the initial structure of the Fe layer, in the case of swift heavy ion irradiation the final phases formed are similar in the two multilayers. The results of heavy ion irradiation can be understood in