Sample records for al fe si

  1. The formation of (Al8Fe2Si, Al13Fe4) phases from Al-Fe-Si system by TE mode

    NASA Astrophysics Data System (ADS)

    Boulouma, A.; Drici, A.; Benaldjia, A.; Guerioune, M.; Vrel, D.

    2015-03-01

    This work prepared Al8Fe2Si, Al13Fe4 mixed sample by ball milling and thermal explosion techniques applying Al, Fe and Si powders as precursors. Thermal combustion of powder mixes of composition 24, 37 Al+ 50, 36 Fe + 25, 27 Si in mass reveals production of several binary and ternary intermetallic phases such: A113Fe4 and Al8Fe2Si.. Synthesis conditions were optimized to fabricate these phases having many potential applications.

  2. Nucleants of Eutectic Silicon in Al-Si Hypoeutectic Alloys: ?-(Al, Fe, Si) or AlP Phase

    NASA Astrophysics Data System (ADS)

    Liang, Song-Mao; Schmid-Fetzer, Rainer

    2014-11-01

    A thermodynamic description of the Al-Si-P-Fe quaternary system focused on Al-(Si)-rich alloys is developed. The solidification sequence in typical Al-7Si cast alloys is derived using thermodynamic calculations of the phase diagrams and solidification simulation under Scheil and constrained Scheil conditions. The previously claimed nucleation of eutectic silicon by ?-(Al,Fe,Si) particles is not possible because under all conditions, ?-(Al,Fe,Si) precipitates after (Si) in pertinent alloys. Variation of P in the ppm range is crucial because it changes the solidification sequence of AlP and (Si).

  3. The dependence of the ?-AlFeSi to ?-Al(FeMn)Si transformation kinetics in AlMgSi alloys on the alloying elements

    Microsoft Academic Search

    N. C. W. Kuijpers; F. J. Vermolen; C. Vuik; P. T. G. Koenis; K. E. Nilsen; S. van der Zwaag

    2005-01-01

    An homogenisation process is applied to as cast billets AlMgSi alloys in order to improve the extrudability. During this homogenisation, plate-like ?-AlFeSi phase transforms to a more rounded ?-Al(FeMn)Si phase which are more favourable for the extrusion process. In this paper, the influence of the alloying elements on the rate of the intermetallic ?-to-? transformation is studied. A Finite Element

  4. Materials Science and Engineering A 394 (2005) 919 The dependence of the -AlFeSi to -Al(FeMn)Si transformation

    E-print Network

    Vuik, Kees

    2005-01-01

    Materials Science and Engineering A 394 (2005) 919 The dependence of the -AlFeSi to -Al(FeMn transforms to a more rounded -Al(FeMn)Si phase which are more favourable for the extrusion process The phase transformation of -AlFeSi to -Al(FeMn)Si is an important process during the homogenisation of as

  5. Kinetics of the ?-AlFeSi to ?-Al(FeMn)Si transformation in Al-Mg-Si alloys

    Microsoft Academic Search

    N. C. W. Kuijpers

    2004-01-01

    Among all the process steps of the production of aluminium extrusion products, the homogenisation of Al-Mg-Si aluminium billets\\u000ais a very important one, since it gives significant changes in the microstructure of the alloy, leading to an improved extrudability\\u000aof the material and improved properties of the final extruded product. During this homogenisation process the aluminium billets\\u000aare annealed in

  6. ICEMS study of isothermal oxidation of Fe Mn Al C Cr Si Mo, Fe Mn Al C Cr Si and Fe 9Cr 1Mo alloys

    Microsoft Academic Search

    J. D. Betancur-Rios; K. Nomura; C. J. Wang; G. A. Prez Alcazar; J. A. Tabares

    2008-01-01

    The purpose of this paper is to investigate the isothermal behavior of Fe 27.3Mn 7.6Al C 6.5Cr 0.25Si 0.88Mo (Mo(0)) and Fe 27.3Mn 7.6Al 1.0C 6.5Cr 0.25Si (Mo(1)) alloys and compare it against Fe 9Cr 1Mo (FCR) commercial alloy. The experiments were carried out at 600C, 700C, 750C and 850C, each one during 72 h in static air. The oxidation

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

    Microsoft Academic Search

    Syadwad Jain

    2006-01-01

    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,

  8. Impact of Al passivation and cosputter on the structural property of ?-FeSi2 for Al-doped ?-FeSi2/n-Si(100) based solar cells application.

    PubMed

    Dalapati, Goutam Kumar; Kumar, Avishek; Tan, Cheng Cheh; Liew, Siao Li; Sonar, Prashant; Seng, Hwee Leng; Hui, Hui Kim; Tripathy, Sudhiranjan; Chi, Dongzhi

    2013-06-26

    The aluminum (Al) doped polycrystalline p-type ?-phase iron disilicide (p-?-FeSi2) is grown by thermal diffusion of Al from Al-passivated n-type Si(100) surface into FeSi2 during crystallization of amorphous FeSi2 to form a p-type ?-FeSi2/n-Si(100) heterostructure solar cell. The structural and photovoltaic properties of p-type ?-FeSi2/n-type c-Si structures is then investigated in detail by using X-ray diffraction, Raman spectroscopy, transmission electron microscopy analysis, and electrical characterization. The results are compared with Al-doped p-?-FeSi2 prepared by using cosputtering of Al and FeSi2 layers on Al-passivated n-Si(100) substrates. A significant improvement in the maximum open-circuit voltage (Voc) from 120 to 320 mV is achieved upon the introduction of Al doping through cosputtering of Al and amorphous FeSi2 layer. The improvement in Voc is attributed to better structural quality of Al-doped FeSi2 film through Al doping and to the formation of high quality crystalline interface between Al-doped ?-FeSi2 and n-type c-Si. The effects of Al-out diffusion on the performance of heterostructure solar cells have been investigated and discussed in detail. PMID:23734756

  9. A Model of the -AlFeSi to -Al(FeMn)Si Transformation During Homogenization in 6xxx Alloys

    E-print Network

    Vuik, Kees

    the homogenization of cast AA 6xxx aluminum alloys. During this homogenization process, at temperatures between 530 treatment of 6xxx aluminum alloys is the transformation of plate-like -Al5FeSi particles to more rounded(FeMn)Si Transformation During Homogenization in 6xxx Alloys Prepared by -- F. J. Vermolen, C. Vuik, and S. van der Zwaag

  10. Magnetocrystalline anisotropy and magnetostriction of Fe-Si-Al (Sendust) single crystals

    Microsoft Academic Search

    M. Takahashi; S. Nishimaki; T. Wakiyama

    1987-01-01

    The magnetocrystalline anisotropy constant, K1 and the magnetostriction constants, lambda100 and lambda111 for the Sendust alloys were determined at 300 K in the composition region, 7.5-11.0 wt%Si, 4.0-7.0 wt%Al, bal. Fe. The line of K1 = 0 in the Fe-Si-Al alloy system was found to lie around 7.0-9.5 wt%Si, 5.5 wt%Al, bal.Fe and 9.5 wt%Si, 5.5-7.0 wt%Al bal.Fe compositions. The

  11. ICEMS study of isothermal oxidation of FeMnAlCCrSiMo, FeMnAlCCrSi and Fe9Cr1Mo alloys

    Microsoft Academic Search

    J. D. Betancur-Rios; K. Nomura; C. J. Wang; G. A. Prez Alcazar; J. A. Tabares

    2008-01-01

    The purpose of this paper is to investigate the isothermal behavior of Fe27.3Mn7.6AlC6.5Cr0.25Si0.88Mo (Mo(0)) and Fe27.3Mn7.6Al1.0C6.5Cr0.25Si\\u000a (Mo(1)) alloys and compare it against Fe9Cr1Mo (FCR) commercial alloy. The experiments were carried out at 600C, 700C,\\u000a 750C and 850C, each one during 72h in static air. The oxidation kinetics was measured as a function of time using a Thermogravimetry\\u000a analyzer (TGA). The

  12. ICEMS study of isothermal oxidation of FeMnAlCCrSiMo, FeMnAlCCrSi and Fe9Cr1Mo alloys

    Microsoft Academic Search

    J. D. Betancur-Rios; K. Nomura; C. J. Wang; G. A. Prez Alcazar; J. A. Tabares

    The purpose of this paper is to investigate the isothermal behavior of Fe27.3Mn7.6AlC6.5Cr0.25Si0.88Mo (Mo(0)) and Fe27.3Mn7.6Al1.0C6.5Cr0.25Si\\u000a (Mo(1)) alloys and compare it against Fe9Cr1Mo (FCR) commercial alloy. The experiments were carried out at 600C, 700C,\\u000a 750C and 850C, each one during 72h in static air. The oxidation kinetics was measured as a function of time using a Thermogravimetry\\u000a analyzer (TGA). The

  13. Chinese Script vs Plate-Like Precipitation of Beta-Al9Fe2Si2 Phase in an Al-6.5Si-1Fe Alloy

    NASA Astrophysics Data System (ADS)

    Ferdian, Deni; Josse, Claudie; Nguyen, Patrick; Gey, Nathalie; Ratel-Ramond, Nicolas; de Parseval, Philippe; Thebault, Yannick; Malard, Benoit; Lacaze, Jacques; Salvo, Luc

    2015-07-01

    The microstructure of a high-purity Al-6.5Si-1Fe (wt pct) alloy after solidification at various cooling rates was investigated. In most of the cases, the monoclinic beta-Al9Fe2Si2 phase was observed as long and thin lamellae. However, at a very slow cooling rate, Fe-bearing precipitates with Chinese script morphology appeared together with lamellae. Further analysis showed all these Chinese script precipitates correspond also to the monoclinic beta phase. This finding stresses that differentiating second phases according to their shape may be misleading.

  14. Laser Cladding of Quasi-Crystal-Forming Al-Cu-Fe-Bi on an Al-Si Alloy Substrate

    E-print Network

    Srivastava, Kumar Vaibhav

    to several distinctive properties, such as very high hardness,[2] low friction coefficient,[3] low thermal of aluminum. The for- mation of phases such as blocky hexagonal Al-Fe-Si and a ternary eutectic (Al CuAl2 Si a strong effect on the size and distribution of Bi particles. The dry-sliding wear properties

  15. 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.

  16. Effects of Mn on the crystal structure of ?-Al(Mn,Fe)Si particles in A356 alloys

    NASA Astrophysics Data System (ADS)

    Kim, Hyun You; Park, Tea Young; Han, Sang Won; Lee, Hyuck Mo

    2006-05-01

    In a commercial Al-7.0Si-0.38Mg cast alloy (A356) with 0.20 wt% Fe, added Mn modifies acicular ?-Al 5FeSi particles to less acicular ?-Al(Mn,Fe)Si in both crystallization and precipitation conditions. The crystal structure of ?-Al(Mn,Fe)Si changes from body-centered cubic (bcc)/ simple cubic (sc) to Pm3 structures in response to an increase in the bulk Mn content of the alloy. The ?-Al(Mn,Fe)Si particles (50-200 nm) precipitate during solution treatment and their precipitation temperature is about 485 C in the as-cast condition.

  17. Microstructure and magnetic properties of FeSiBNbCu-Al cold spray coatings

    Microsoft Academic Search

    M. Cherigui; W. Li; R. Hamzaoui; V. Ji; N. Fenineche; C. Coddet

    2008-01-01

    In this paper, the FeSiBNbCu and FeSiBNbCu-Al coatings were synthesized using cold spray technique in order to produce ferromagnetic materials. Ultra-fine grain coatings are obtained using FINEMET nanostructured powders mixed with Aluminum. Various percentages of Aluminum characterized by its low hardness were taken in account. The obtaining coatings were formed of Aluminum matrix and randomly distribution of FINEMET particles. Indeed,

  18. Effect of Si on the magnetic properties of the Fe70Al30 alloy

    Microsoft Academic Search

    G. A. Prez Alczar; Ligia. E. Zamora; J. D. Betancur-Ros; J. A. Tabares; J. M. Greneche; J. M. Gonzlez

    2006-01-01

    (Fe70Al30)100-xSix (x=0, 5, 10 and 20) alloys were obtained by mechanical milling for durations of 12, 24 and 36 h. They were studied by X-ray diffraction (XRD), Mssbauer spectrometry and magnetic measurements at room temperature. The XRD experiments show that all the samples have the Fe-BCC phase and for x=20 an additional Fe0.34Si0.66 phase appears. The obtained Mssbauer spectra show

  19. Effect of Si on the magnetic properties of the Fe 70Al 30 alloy

    Microsoft Academic Search

    G. A. Prez Alczar; Ligia. E. Zamora; J. D. Betancur-Ros; J. A. Tabares; J. M. Greneche; J. M. Gonzlez

    2006-01-01

    (Fe70Al30)100?xSix (x=0, 5, 10 and 20) alloys were obtained by mechanical milling for durations of 12, 24 and 36h. They were studied by X-ray diffraction (XRD), Mssbauer spectrometry and magnetic measurements at room temperature. The XRD experiments show that all the samples have the Fe-BCC phase and for x=20 an additional Fe0.34Si0.66 phase appears. The obtained Mssbauer spectra show a

  20. 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.

  1. Mssbauer study of mechanical deformation induced order-disorder transition in Fe75AlSi alloys

    NASA Astrophysics Data System (ADS)

    Legarra, Estibaliz; Plazaola, Fernando; Apianiz, Estibaliz; Garcia, Jose Angel; Garitaonandia, Jose Javier Saiz

    2012-03-01

    We study the influence of different Al/Si ratios on the magnetic and structural properties of mechanically disordered powder Fe75Al25 - xSix alloys. The results indicate that addition of Si to binary Fe-Al alloys makes the disordering more difficult. The study of the hyperfine fields indicates that there is an inversion of the behavior of the hyperfine field of the Fe atoms surrounded by 8 Fe atoms with disordering. The magnetic and hyperfine measurements indicate that the influence of Si is opposite to the one of Al in the magnetism of Fe atoms.

  2. Refinement of the crystal structure ?-Al 9FeMg 3Si 5

    Microsoft Academic Search

    R Krendelsberger; P Rogl; A Leithe-Jasper; C. J Simensen

    1998-01-01

    The crystal structure of the quaternary so-called ?-phase, which was originally solved from photographic single crystal data, has been refined from single crystal automatic four circle counter data. Single crystals were obtained from the residue of a slowly cooled melt of nominal composition (in at%) Al74.1Fe0.5Mg8.4Si17.0, which was dissolved in butanol. The composition of the ?-phase crystal was Al9Fe1Mg3.5Si5.0. The

  3. Influence of Ce and Mn addition on ?-Fe morphology in recycled Al-Si alloy ingots

    NASA Astrophysics Data System (ADS)

    Fan, Chao; Long, Si-yuan; Yang, Huai-de; Wang, Xiang-jie; Zhang, Jun-cheng

    2013-09-01

    The influence of Ce or Ce and Mn combined additions on the morphology of ?-Fe phases in recycled Al-Si alloys was experimentally investigated by microstructure observation and room temperature tensile testing. It is found that Ce modifies the morphology of ?-Fe phase from the large Chinese script-like into the individual and fine nodular shape. A combined addition of Ce and Mn results in the promotion of primary ?-Fe formation, and their size increases considerably with the increase in Ce content. The mechanism of the above morphological changes was discussed in accordance with the nucleation and growth of ?-Fe phase during solidification.

  4. Heterogeneous Nucleation of ?-Al Grain on Primary ?-AlFeMnSi Intermetallic Investigated Using 3D SEM Ultramicrotomy and HRTEM

    NASA Astrophysics Data System (ADS)

    Yang, Wenchao; Ji, Shouxun; Zhou, Xiaorong; Stone, Ian; Scamans, Geoff; Thompson, George E.; Fan, Zhongyun

    2014-08-01

    Microstructural examination of the Al-5.3Mg-2.4Si-0.6Mn-1.0Fe alloy in the die-cast condition revealed that a significant number of the primary ?-AlFeMnSi intermetallic particles were found inside both the coarse ?-Al dendrite fragments formed in the shot sleeve and the fine ?-Al grains formed in the die cavity. The heterogeneous nucleation of ?-Al phase on primary ?-AlFeMnSi intermetallic particle was further investigated experimentally. 3-Dimension (3D) scanning electron microscopy ultramicrotomy revealed that the probability of finding at least one primary ?-AlFeMnSi intermetallic particle inside each ?-Al grain was almost 90 pct. The detailed microstructural analysis identified the primary ?-AlFeMnSi intermetallic particle as the ?-Al12(Fe,Mn)3Si composition with a body-centered cubic structure and a lattice parameter of a = 1.265 nm. It was found that the primary ?-Al12(Fe,Mn)3Si intermetallic particle had a faceted morphology with {110} planes exposed as its natural surfaces. High resolution transmission electron microscopy further confirmed that the crystallographic orientation relationship between ?-Al12(Fe,Mn)3Si intermetallic particle and ?-Al phase was: [111]?-AlFeMnSi//[110]Al and (10)?-AlFeMnSi 6 deg from (11)?-Al, and the corresponding interface between two phases could be confirmed as a semi-coherent interface with a lattice misfit of 2.67 pct at 933 K (660 C), which was considerably smaller than the theoretical limit (5.7 pct) for epitaxial nucleation. Finally, based on these experimental evidences and the epitaxial nucleation model, we concluded that the primary ?-Al12(Fe,Mn)3Si intermetallic particles were both potent and effective nucleating substrates for the ?-Al phase.

  5. Skin solidification during high pressure die casting of Al11Si2Cu1Fe alloy

    Microsoft Academic Search

    Z. W. Chen

    2003-01-01

    Surface regions of Al11Si2Cu1Fe alloy castings produced by high pressure die casting (HPDC) were examined and three microstructural features were observed. In locations of direct melt impingement, there was not an ?-Al rich layer. In most surface locations, a porosity-free ?-Al rich layer was observed. However, in surface locations of low impact of melt, a porosity-free layer being a mixture

  6. FeAl and Mo-Si-B Intermetallic Coatings Prepared by Thermal Spraying

    SciTech Connect

    Totemeier, T.C.; Wright, R.N.; Swank, W.D.

    2003-04-22

    FeAl and Mo-Si-B intermetallic coatings for elevated temperature environmental resistance were prepared using high-velocity oxy-fuel (HVOF) and air plasma spray (APS) techniques. For both coating types, the effect of coating parameters (spray particle velocity and temperature) on the microstructure and physical properties of the coatings was assessed. Fe-24Al (wt.%) coatings were prepared using HVOF thermal spraying at spray particle velocities varying from 540 m/s to 700 m/s. Mo-13.4Si-2.6B coatings were prepared using APS at particle velocities of 180 and 350 m/s. Residual stresses in the HVOF FeAl coatings were compressive, while stresses in the APS Mo-Si-B coatings were tensile. In both cases, residual stresses became more compressive with increasing spray particle velocity due to increased peening imparted by the spray particles. The hardness and elastic moduli of FeAl coatings also increased with increasing particle velocity, again due to an increased peening effect. For Mo-Si-B coatings, plasma spraying at 180 m/s resulted in significant oxidation of the spray particles and conversion of the T1 phase into amorphous silica and {alpha}-Mo. The T1 phase was retained after spraying at 350 m/s.

  7. Nucleation of the Al6(Fe,?Mn)-to-?-Al(Fe,?Mn)Si transformation in 3XXX aluminium alloys. II. Transformation in cast aluminium alloys

    Microsoft Academic Search

    D. T. L. Alexander; A. L. Greer

    2004-01-01

    The nucleation behaviour of the homogenization-induced Al6(Fe,?Mn)-to-?-Al(Fe,?Mn)Si transformation is investigated in a companion paper to part I (a study with roll-bonded diffusion couples). Diffusion experiments using silicon-coated Al0.53?wt%?Fe1.02?wt%?Mn alloy blocks allow control of the thermodynamic driving force for transformation within a microstructure typical of a cast ingot. As expected, this microstructure appears to give ready and yet stochastic nucleation as

  8. 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.

  9. Effect of iron and manganese contents on convection-free precipitation and sedimentation of primary ?-Al(FeMn)Si phase in liquid Al11.5Si0.4Mg alloy

    Microsoft Academic Search

    X. Cao; N. Saunders; J. Campbell

    2004-01-01

    The effect of Fe and Mn contents on precipitation and sedimentation of primary a-Al(FeMn)Si phase in liquid Al-11.5Si-0.4Mg (wt%) alloy has been investigated at 600C in convection-free conditions. Almost all primary a-Al(FeMn)Si particles and some oxide films seem to completely settle to the base of the melts. With the increase of original iron equivalent values (IEV) or Mn\\/Fe ratio at

  10. 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.

  11. Orientation-dependent ion beam sputtering at normal incidence conditions in FeSiAl alloy

    SciTech Connect

    Batic, Barbara Setina; Jenko, Monika [Institute of Metals and Technology, Lepi pot 11, Ljubljana 1000 (Slovenia)

    2010-07-15

    The authors have performed Ar+ broad ion beam sputtering of a polycrystalline Fe-Si-Al alloy at normal incidence at energies varying from 6 to 10 keV. Sputtering results in the formation of etch pits, which can be classified in three shapes: triangular, rectangular, and square. As each grain of individual orientation exhibits a certain type of pattern, the etch pits were correlated with the crystal orientations by electron backscattered diffraction technique.

  12. 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

  13. 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.

  14. 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.

    2015-03-01

    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.

  15. 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.

  16. Thermal expansion along the NaAlSi2O6-NaFe3+Si2O6 and NaAlSi2O6-CaFe2+Si2O6 solid solutions

    NASA Astrophysics Data System (ADS)

    Tribaudino, Mario; Nestola, Fabrizio; Bruno, Marco; Ballaran, Tiziana Boffa; Liebske, Christian

    2008-06-01

    The high temperature volume and axial parameters for six C2/ c clinopyroxenes along the NaAlSi2O6-NaFe3+Si2O6 and NaAlSi2O6-CaFe2+Si2O6 joins were determined from room T up to 800C, using integrated diffraction profiles from in situ high temperature single crystal data collections. The thermal expansion coefficient was determined by fitting the experimental data according to the relation: ln( V/ V 0) = ?( T - T 0). The thermal expansion coefficient increases by about 15% along the jadeite-hedenbergite join, whereas it is almost constant between jadeite and aegirine. The increase is related to the Ca for Na substitution into the M2 site; the same behaviour was observed along the jadeite-diopside solid solution, which presents the same substitution at the M2 site. Strain tensor analysis shows that the major deformation with temperature occurs in all samples along the b axis; on the (010) plane the higher deformation occurs in jadeite and aegirine at a direction almost normal to the tetrahedral-octahedral planes, and in hedenbergite along the projection of the longer M2-O bonds. The orientation of the strain ellipsoid with temperature in hedenbergite is close to that observed with pressure in pyroxenes. Along the jadeite-aegirine join instead the high-temperature and high-pressure strain are differently oriented.

  17. Fe3+ and Al solubilities in MgSiO3 perovskite: implication of the Fe3+AlO3 substitution in MgSiO3 perovskite at the lower mantle condition

    NASA Astrophysics Data System (ADS)

    Nishio-Hamane, Daisuke; Nagai, Takaya; Fujino, Kiyoshi; Seto, Yusuke; Takafuji, Naoto

    2005-08-01

    Perovskite in the starting composition of Mg3Fe3+AlSi3O12 was investigated at 24 and 51 GPa and 2100 K using a laser-heated diamond anvil cell (LHDAC) and an analytical transmission electron microscopy (ATEM) to understand the solubilities of Fe3+ and Al into MgSiO3-dominated perovskite. A single phase of orthorhombic perovskite was formed at 51 GPa and 2100 K and the Fe3+AlO3 bearing perovskite showed no structural change during decompression. The samples synthesized at 24 GPa and 2100 K showed minor amounts of magnesioferrite and stishovite phases in spaces along the perovskite grain boundaries. These results indicate that the solubility of ferric iron incorporated as the Fe3+AlO3 component in MgSiO3-based perovskite is higher and slightly lower than 25 mole % at 51 and 24 GPa, respectively.

  18. Study of fretting wear of Al-Fe-Ce-SiC composites

    SciTech Connect

    Bai, M.; Xue, Q. [Lanzhou Inst. of Chemical Physics (China). Lab. of Solid Lubrication] [Lanzhou Inst. of Chemical Physics (China). Lab. of Solid Lubrication

    1996-07-15

    Due to adoption of rapid solidification technology (RST) in conjunction with powder metallurgy processing, aluminum matrix composites (AMC) offer significant improvements in density, strength, stiffness, fracture resistance, and/or higher use temperature which translates into improved aerospace vehicle performance. Fretting wear is a wear phenomena occurring between two surfaces having oscillatory relative motion of small amplitude. The objective of this paper was to investigate the effects of SiC reinforcement and fretting parameters on the fretting wear resistance of Al-7.8Fe-6.1Ce (AFC) alloys and to clarify the mechanism of material removal.

  19. Fe2?Mg2 and TiAl2?MgSi2 exchange reactions between clinopyroxenes and silicate melts

    NASA Astrophysics Data System (ADS)

    Sack, R. O.; Carmichael, I. S. E.

    1984-02-01

    The interdependence of the Fe(Mg)-1 (e.g., FeO-MgO in silicate melt; CaFeSi2O6-CaMgSi2O6 in pyroxene) and TiAl2(MgSi2)-1 exchange reactions between silicate melts and coexisting Ca-pyroxene has been examined. High-calcium clinopyroxenes were grown in 1 atmosphere melting and crystallization experiments on rock powders spanning the composition range tholeiite to melilitite (1,092Fe2+?Mg2+ exchange and (X_{{text{Ti}}^{{text{4 + }}} }^{M1} )^{{text{CPX}}} suggest that at given values of ? _{{text{Fe(Mg)}}_{ - {text{1}}} } extent of Fe(Mg)-1 substitution is strongly coupled with the TiAl2(MgSi2)-1 substitution in pyroxenes near the five-component space CaMg(Si2O6-CaFe(Si)2O6-CaTi(Al)2O6-CaFe?(Al,Si)2O6-CaAl(Al,Si)2O6. The inferred stabilization of Ti in iron-rich relative to magnesium pyroxene is consistent with the operation of Fe2+?Ti4+ intervalence charge transfer interactions (e.g., Rossman 1980) and observations on zoning in natural titanaugites (e.g., Tracy and Robinson 1977). Although the rims of some pyroxenes grown in some melting experiments exhibit prominent zoning in TiAl2(MgSi2)-1, the average values of (X_{{text{Ti}}^{{text{4 + }}} }^{M1} /X_{{text{Mg}}^{{text{2 + }}} }^{M1} ) inferred from the compositions of these pyroxenes, together with those of the relatively homogeneous pyroxenes produced in crystallization experiments, exhibit a 1?1 correlation with values of ? _{{text{TiAl}}_{text{2}} ({text{MgSi}}_{text{2}} )_{ - 1} } derived from the solution model of Ghiorso et al. (1983) with a standard error of 750 calories. The Ti contents of Ca-rich pyroxenes crystallizing from a wide range of natural silicate liquids can therefore be predicted.

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

    Microsoft Academic Search

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

    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 80wt% Fe. From these systems the following conclusions are obvious. Manganese acts as a strong stabilizer for the cementite carbide. Chromium and silicon, when present together prefer

  1. Spin transitions in (Mg,Fe)(Si,Al)O3 perovskite and the electrical conductivity of the lower mantle

    NASA Astrophysics Data System (ADS)

    McCammon, C. A.; Potapkin, V.; Glazyrin, K.; Kantor, A.; Kupenko, I.; Prescher, C.; Sinmyo, R.; Pesce, G.; Smirnov, G. V.; Chumakov, A. I.; Rffer, R.; Dubrovinsky, L. S.

    2012-12-01

    Iron has the ability to adopt different spin states in the dominant lower mantle phase, (Mg,Fe)(Si,Al)O3 perovskite, where the spin states of iron atoms can significantly influence mantle properties and dynamics. Most studies have observed a transition involving Fe2+ that starts above approximately 30 GPa, although there is disagreement as to whether it involves a high-spin (HS) to intermediate-spin (IS) transition or simply a structural modification of the local atomic environment. Previous studies have also suggested that Fe3+ (which constitutes at least half of the iron in lower mantle silicate perovskite) undergoes a HS to low-spin (LS) transition when Fe3+ occupies the octahedral site in the structure. Previous electrical conductivity measurements of (Mg,Fe)(Si,Al)O3 perovskite have shown that conductivity drops significantly above 50 GPa, which has been attributed to the HS-LS transition of Fe3+. In view of many existing controversies concerning the spin state of iron in the lower mantle and suggestions that spin transitions may cause seismic velocity anomalies, we made a new investigation of carefully characterised samples of (Mg,Fe)(Si,Al)O3 perovskite with a range of Fe3+/?Fe values. We applied a new synchrotron-based method of Mssbauer spectroscopy (which enables individual spin and valence states to be identified) combined with electrical conductivity measurements on one of the samples, in order to construct a clear picture of iron spin transitions in (Mg,Fe)(Si,Al)O3 perovskite at lower mantle pressures and temperatures. We studied four different samples using a laser heated diamond anvil cell (DAC) with a Synchrotron Mssbauer Source (SMS) at the Nuclear Resonance beamline ID18 at the European Synchrotron Radiation Facility. Our data demonstrate unambiguously that Fe3+ remains in the HS state at conditions throughout the lower mantle, and show evidence for a HS-IS transition in Fe2+. High-pressure high-temperature electrical conductivity measurements of (Mg,Fe)(Si,Al)O3 perovskite with high Fe3+/?Fe show a continuous increase in conductivity with pressure, strongly advocating that the conductivity drop in previous experiments with low Fe3+/?Fe is due to a HS-IS transition of Fe2+. Our results provide improved constraints for forward modelling of electromagnetic data as well as for joint inversion of electromagnetic and seismic data, providing a new probe of heterogeneity in the lower mantle.

  2. Giant magnetoimpedance effect in ultrasoft FeAlSiBCuNb nanocomposites for sensor applications

    SciTech Connect

    Phan, M.-H.; Peng, H.-X.; Wisnom, Michael R.; Yu, S.-C. [Advanced Composites Group, Department of Aerospace Engineering, Bristol University, Bristol, BS8 1TR (United Kingdom); Department of Physics, Chungbuk National University, Cheongju 361-763 (Korea, Republic of)

    2005-07-01

    Fe{sub 73-x}Al{sub x}Si{sub 14}B{sub 8.5}Cu{sub 1}Nb{sub 3.5} (x=0,2) nanocomposite materials consisting of a nanocrystalline phase in an amorphous matrix were obtained by annealing their precursor amorphous ribbons, which were prepared by the melt-spinning technique, at different temperatures ranging between 350 and 650 deg. C for 45 min in vacuum. Investigation on their magnetic and magnetoimpedance properties indicates that the Al-containing sample (x=2) possesses superior magnetic softness and giant magnetoimpedance (GMI) effect over the Al-free counterpart. This can be likely ascribed to the increased magnetic permeability, decreased coercive force, and decreased resistivity. The increased magnetic permeability results from a reduction in magnetocrystalline anisotropy and saturation magnetostriction. The correlations between magnetic softness, electrical properties, and GMI behavior are discussed in the light of the skin effect model. These results indicate that the Al-containing Fe-based nanocomposite material can be ideally used for high-performance GMI sensor applications.

  3. Electronic Specific Heat of Dilute Alloys: Fe(Ti), Fe(V), Fe(Cr), Fe(Mn), Fe(Co), Fe(Ni), Fe(Al), Fe(Si), Fe(Mo), Fe(W), and Ag(Au)

    Microsoft Academic Search

    Samuel S. Shinozaki; Anthony Arrott

    1966-01-01

    A method of measuring simultaneously the low-temperature specific heat of three samples, typically one pure-metal sample and two alloys with 1 and 2% solute, is described. The procedure is used to determine the variation of the electronic-specific-heat coefficient gamma (the coefficient of the term linear in temperature) with concentration c for various solutes (Al, Si, Ti, V, Cr, Mn, Co,

  4. 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.

  5. Epitaxially grown L1 0-FePt/(C, SiO 2, and Al 2O 3) granular films

    NASA Astrophysics Data System (ADS)

    Okamoto, Satoshi; Kitakami, Osamu

    2007-03-01

    Additive effects of C, SiO 2, and Al 2O 3 on L1 0-FePt epitaxial thin film were studied. Samples were fabricated by co-sputtering of FePt and (C, SiO 2, and Al 2O 3) on MgO (1 0 0) substrate at 973 K. These additives effectively reduce the particle size of FePt. C additive deteriorates the crystal orientation, while Al 2O 3 additive gradually degrades the L1 0 ordering. On the other hand, SiO 2 additive can reduce the particle size while keeping the high c-axis orientation and higher degree of L1 0 ordering.

  6. Phase transformations in an Fe-7. 8Al-29. 5Mn-1. 5Si-1. 05C alloy

    SciTech Connect

    Chao, C.Y. (National Chiao Tung Univ., Hsinchu (Taiwan, Province of China). Inst. of Mechanical Engineering); Liu, T.F. (National Chiao Tung Univ., Hsinchu (Taiwan, Province of China). Inst. of Materials Science and Engineering)

    1993-09-01

    Phase transformations in an Fe-7.8Al-29.5Mn-1.5Si-1.05C alloy have been investigated by means of optical microscopy and transmission electron microscopy. In the as-quenched condition, a high density of fine (Fe,Mn)[sub 3]AlC carbides could be observed within the austenite matrix. When the as-quenched alloy was aged at temperatures ranging from 550 C to 825 C, a [gamma] [r arrow] coarse (Fe,Mn)[sub 3]AlC carbide + DO[sub 3] reaction occurred by a cellular precipitation on the [gamma]/[gamma] grain boundaries and twin boundaries. Both of the observations are quite different from those observed by other workers in Fe-Al-Mn-C alloys. In their studies, it was found that the as-quenched microstructure was austenite phase ([gamma]), and (Fe,Mn)[sub 3]AlC carbides could only be observed within the austenite matrix in the aged alloys. In addition, a [gamma] [r arrow] [alpha] (ferrite) + coarse (Fe,Mn)[sub 3]AlC carbide reaction or a [gamma][r arrow] [alpha] + coarse (Fe,Mn)[sub 3]AlC carbide + [beta]-Mn reaction was found to occur on the [gamma]/[gamma] grain boundary in the aged Fe-Al-Mn-C alloys.

  7. Enhancement in soft magnetic and ferromagnetic ordering behaviour through nanocrystallisation in Al substituted CoFeSiBNb alloys

    NASA Astrophysics Data System (ADS)

    Mohanta, Ojaswini; Basumallick, A.; Mitra, A.; Panda, A. K.

    2010-01-01

    The effect of substituting Al for Si in Co 36Fe 36Si 4-xAl xB 20Nb 4, ( X=0, 0.5, 1.0, 1.5, 2.0 at%) alloys prepared in the form of melt-spun ribbons have been investigated. All the alloys were amorphous in their as-cast state. The onset of crystallization as observed using differential scanning calorimetry (DSC) was found to rise at low Al content up to X=1 at% beyond which there was a decreasing trend. The alloys also exhibited glass transition at ' Tg'. Microstructural studies of optimally annealed samples indicated finer dispersions of nanoparticles in amorphous matrix which were identified as bcc-(FeCo)Si and bcc-(FeCo)SiAl nanophases by X-ray diffraction technique. Alloy with optimum content of Al around X=1 at% exhibited stability in coercivity at elevated temperatures. Though Al addition is known to lower magnetostriction, such consistency in coercivity may also be attributed towards lowering in the nanoparticle size compared to X=0 alloy. In the nanostructured state, the alloy containing optimum Al content ( X=1) exhibited further enhancement in ferromagnetic ordering or the Curie temperature by 100 K compared to alloy without Al. Such addition also attributed to better frequency response of coercivity and low core losses.

  8. The solidification characteristics of Fe-rich intermetallics in Al11.5Si0.4Mg cast alloys

    Microsoft Academic Search

    X. Cao; J. Campbell

    2004-01-01

    After the nucleation and sedimentation of primary Fe-rich phases, the microstructures of Al-11.5Si-0.4Mg cast alloys with\\u000a 0.351.03Fe and 0.180.59Mn have been studied to investigate the solidification characteristics of Fe-rich phases. Depending\\u000a on the iron and manganese contents as well as cooling rates, Fe-rich phases may solidify as predendritic (primary), pre-eutectic,\\u000a coeutectic, and posteutectic intermetallics at the different stages of solidification

  9. Effect of rapid solidification on the microstructure and mechanical properties of hot-pressed Al-20Si-5Fe alloys

    SciTech Connect

    Rajabi, M.; Vahidi, M. [Department of Materials Science and Engineering, Sharif University of Technology, P.O. Box 11365-9466, Azadi Avenue, 14588 Tehran (Iran, Islamic Republic of); Simchi, A., E-mail: simchi@sharif.edu [Department of Materials Science and Engineering, Sharif University of Technology, P.O. Box 11365-9466, Azadi Avenue, 14588 Tehran (Iran, Islamic Republic of); Institute for Nanoscience and Nanotechnology (INST), Sharif University of Technology, P.O. Box 11365-9466, Azadi Avenue, 14588 Tehran (Iran, Islamic Republic of); Davami, P. [Department of Materials Science and Engineering, Sharif University of Technology, P.O. Box 11365-9466, Azadi Avenue, 14588 Tehran (Iran, Islamic Republic of)

    2009-11-15

    The aim of this work is to study the effect of cooling rate and subsequent hot consolidation on the microstructural features and mechanical strength of Al-20Si-5Fe-2X (X = Cu, Ni and Cr) alloys. Powder and ribbons were produced by gas atomization and melt spinning processes at two different cooling rates of 1 x 10{sup 5} K/s and 5 x 10{sup 7} K/s. The microstructure of the products was examined using optical microscopy, scanning electron microscopy, transmission electron microscopy, and X-ray diffraction. The particles were consolidated by hot pressing at 400 deg. C/250 MPa/1 h under a high purity argon atmosphere and the microstructure, hardness and compressive strength of the compacts were evaluated. Results showed a profound effect of the cooling rate, consolidation stage, and transition metals on the microstructure and mechanical strength of Al-20Si-5Fe alloys. While microstructural refining was obtained at both cooling rates, the microstructure of the atomized powder exhibited the formation of fine primary silicon ({approx} 1 {mu}m), eutectic Al-Si phase with eutectic spacing of {approx} 300 nm, and {delta}-iron intermetallic. Supersaturated Al matrix containing 5-7 at.% silicon and nanometric Si precipitates (20-40 nm) were determined in the microstructure of the melt-spun ribbons. The hot consolidation resulted in coarsening of Si particles in the atomized particles, and precipitation of Si and Fe-containing intermetallics from the supersaturated Al matrix in the ribbons. The consolidated ribbons exhibited higher mechanical strength compared to the atomized powders, particularly at elevated temperatures. The positive influence of the transition metals on the thermal stability of the Al-20Si-5Fe alloy was noticed, particularly in the Ni-containing alloy.

  10. Low-temperature electrical transport in Heusler-type Fe2V (AlSi) alloys

    NASA Astrophysics Data System (ADS)

    Vasundhara, M.; Srinivas, V.; Rao, V. V.

    2005-09-01

    The temperature variation of the electrical resistivity ? and the Seebeck coefficient S of Heusler-type Fe2VAl1-xSix (0<=x<=1) alloys has been investigated. We have shown that the transport parameters are very sensitive to doping. For the x = 0 sample, high values of ? and negative temperature coefficient of resistivity (TCR) have been observed. As the Si concentration increases, ? decreases and the TCR changes its sign, while S shows significant changes in magnitude as well as sign when Al is replaced with Si. These changes appear to be reminiscent of a metal to semiconductor transition. It has been shown that the conventional transport theories proposed for intermetallic alloys or semiconductors cannot explain the transport behaviour in the whole temperature range of the present study. Low-temperature resistivity data of x = 0-0.02 samples could be described with a gapless semiconductor model. The strong composition dependence of S and ? is attributed to the sharp variations in electronic density of states at the Fermi energy. It is also shown that by optimum doping one can achieve very large values of power factor (P). The estimated power factor at room temperature is observed to be highest (2.23 10-3 W mK-2) for x = 0.06 and comparable to that of conventional thermoelectric material. At lower temperatures P is found to be even higher than that of conventional thermoelectric material.

  11. 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.

  12. 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.

  13. 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.

  14. Effect of Fe and Si on the Structure and Mechanical Properties of Complex Al-Zn-Mg-Cu Alloys Produced by P\\/M and Casting Techniques

    Microsoft Academic Search

    Yu. Milman; D. Lotsko; A. Sirko; O. Neikov; N. Zakharova; V. Goncharuk; A. Koval; V. Voropaiev; A. Sharovski; O. Senkov; D. Miracle

    In order to establish the possibility of using recycled aluminum, which usually has an increased content of Fe and Si, the structure and mechanical properties of high-strength Al-Zn-Mg-Cu alloys additionally alloyed with only Fe and Si as well as additionally alloyed with Mn, Zr, Sc, Fe and Si were studied. Rods were manufactured from ingots cast into water-cooled copper molds

  15. Spin accumulation in Si channels using CoFe/MgO/Si and CoFe/AlOx/Si tunnel contacts with high quality tunnel barriers prepared by radical-oxygen annealing

    NASA Astrophysics Data System (ADS)

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

    2015-05-01

    We investigate spin injection into Si channels using three-terminal spin-accumulation (3T-SA) devices with high-quality CoFe/MgO/n-Si and CoFe/AlOx/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 AlOx 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.

  16. Magnetic force microscopy study of magnetization reversal in sputtered FeSiAl(N) films

    SciTech Connect

    Lo, C. C. H.; Snyder, J. E.; Leib, J.; Chen, R.; Kriegermeier-Sutton, B.; Kramer, M. J.; Jiles, D. C.; Kief, M. T.

    2001-03-01

    The magnetization reversal in a series of rf-sputtered FeSiAl(N) films has been studied using magnetic force microscopy. A system has been developed which has the capability to image domain structure while an in-plane magnetic field is applied in situ. All films exhibited a stripe domain structure in zero applied field which was indicative of a perpendicular component of domain magnetization which alternates in sign. All films showed a similar sequence of magnetization processes: on reducing the applied field from saturation a fine stripe domain structure nucleated and then coarsened as the field was decreased to zero. Local switching of domain contrast was observed along the steepest part of the hysteresis loop as the perpendicular component reversed. As the reverse field was increased toward saturation, the stripe domains disintegrated into smaller regions. This observation is consistent with an interpretation that the domain magnetization rotated locally into the sample plane. The saturation field and the film stress exhibited similar trends with nitrogen partial pressure. The results suggest that the perpendicular anisotropy that caused the formation of the stripe domain structure could be induced by the film stress via magnetoelastic coupling.

  17. Fabrication of MgAl2O4 Thin Films on Ferromagnetic Heusler Alloy Fe2CrSi by Reactive Magnetron Sputtering

    NASA Astrophysics Data System (ADS)

    Fukatani, Naoto; Inagaki, Keima; Mari, Kenichiro; Fujita, Hirohito; Miyawaki, Tetsuta; Ueda, Kenji; Asano, Hidefumi

    2012-02-01

    Epitaxial MgAl2O4 thin films were grown on Heusler alloy Fe2CrSi by reactive magnetron sputtering of a MgAl2 target in an O2+Ar atmosphere. To grow MgAl2O4 on Fe2CrSi, we inserted a protective layer of MgAl2 between Fe2CrSi and MgAl2O4 to prevent Fe2CrSi from being oxidized. Growth of MgAl2O4 was found to be very sensitive to the MgAl2 thickness and PO2 during deposition of MgAl2O4. A strong XRD peak of MgAl2O4 (004) was observed with an ultrathin (0.2 nm) MgAl2 layer. The saturation magnetic moment of Fe2CrSi was measured to be 370 emu/cm3 (1.84 B/f.u.) at room temperature and it is expected to have a high spin polarization. The Fe2CrSi/MgAl2O4 heterostructure is promising for use in future spintronic devices.

  18. Electronic state of Fe2+ in (Mg,Fe)(Si,Al)O3 perovskite and (Mg,Fe)SiO3 majorite at pressures up to 81 GPa and temperatures up to 800 K

    NASA Astrophysics Data System (ADS)

    Narygina, Olga V.; Kantor, I. Yu.; McCammon, C. A.; Dubrovinsky, L. S.

    2010-06-01

    Despite a large number of studies of iron spin state in silicate perovskite at high pressure and high temperature, there is still disagreement regarding the type and P- T conditions of the transition, and whether Fe2+ or Fe3+ or both iron cations are involved. Recently, our group published results of a Mssbauer spectroscopy study of the iron behaviour in (Mg,Fe)(Si,Al)O3 perovskite at pressures up to 110 GPa (McCammon et al. 2008), where we suggested stabilization of the intermediate spin state for 8- to 12-fold coordinated ferrous iron ([8-12]Fe2+) in silicate perovskite above 30 GPa. In order to explore the behaviour in related systems, we performed a comparative Mssbauer spectroscopic study of silicate perovskite (Fe0.12Mg0.88SiO3) and majorite (with two compositionsFe0.18Mg0.82SiO3 and Fe0.11Mg0.88SiO3) at pressures up to 81 GPa in the temperature range 296-800 K, which was mainly motivated by the fact that the oxygen environment of ferrous iron in majorite is quite similar to that in silicate perovskite. The [8-12]Fe2+ component, dominating the Mssbauer spectra of majorites, shows high quadrupole splitting (QS) values, about 3.6 mm s-1, in the entire studied P- T region (pressures to 58 GPa and 296-800 K). Decrease of the QS of this component with temperature at constant pressure can be described by the Huggins model with the energy splitting between low-energy e g levels of [8-12]Fe2+ equal to 1,500 (50) cm-1 for Fe0.18Mg0.82SiO3 and to 1,680 (70) cm-1 for Fe0.11Mg0.88SiO3. In contrast, for the silicate perovskite dominating Mssbauer component associated with [8-12]Fe2+ suggests the gradual change of the electronic properties. Namely, an additional spectral component with central shift close to that for high-spin [8-12]Fe2+ and QS about 3.7 mm s-1 appeared at ~35 (2) GPa, and the amount of the component increases with both pressure and temperature. The temperature dependence of QS of the component cannot be described in the framework of the Huggins model. Observed differences in the high-pressure high-temperature behaviour of [8-12]Fe2+ in the silicate perovskite and majorite phases provide additional arguments in favour of the gradual high-spinintermediate-spin crossover in lower mantle perovskite, previously reported by McCammon et al. (2008) and Lin et al. (2008).

  19. 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 (SCKCEN) 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 SCKCEN. 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.

  20. 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.

  1. The join CaMgSi2O6-CaFeAlSiO6-CaTiAl2O6 and its bearing on the Ti-rich fassaitic pyroxenes

    NASA Astrophysics Data System (ADS)

    Akasaka, Masahide; Onuma, Kosuke

    1980-01-01

    Phase equilibria in the join CaMgSi2O6-CaFeAlSiO6-CaTiAl2O6 have been determined in air at 1 atm by the ordinary quenching method. Clinopyroxeness, forsterite, perovskite, magnetitess, spinelss, hibonite and an unknown phase X are present at liquidus temperatures (ss: solid solution). At subsolidus temperatures the following phase assemblages were encountered; clinopyroxeness+perovskite, clinopyroxeness +perovskite+spinelss, clinopyroxeness +perovskite+melilite (+anorthite), clinopyroxeness +perovskite+melilite+spinelss+anorthite, clinopyroxeness +perovskite+anorthite+spinelss, and clinopyroxeness +perovskite+anorthite+hibonite. At subsolidus temperatures the single phase field of clinopyroxeness extends up to 19 wt.% CaTiAl2O6. Even in the field of clinopyroxeness+perovskite, the TiO2 content in clinopyroxeness continues to increase and attains 9.2 wt.% TiO2 with 24.8 wt.% Al2O3. An interesting fact is that unusual clinopyroxenes which contain more AlIV than SiIV are present in the CaFe-AlSiO6-rich region. The liquid coexisting with pyroxene is richer in Ti, Al, and Fe3+ than the coexisting pyroxene. The clinopyroxenesss coexisting with liquid contain less TiO2, Al2O3 and Fe2O3 than those crystallized at subsolidus temperatures. The petrological significance of the join and the crystallization of Ti- and Al-rich clinopyroxenes are discussed on the basis of the experimental results of the join.

  2. Simulation of a directional solidification of a binary Al-7wt%Si and a ternary alloy Al-7wt%Si-1wt%Fe under the action of a rotating magnetic field

    NASA Astrophysics Data System (ADS)

    Budenkova, O.; Baltaretu, F.; Kovcs, J.; Rosz, A.; Rnafldi, A.; Bianchi, A.-M.; Fautrelle, Y.

    2012-07-01

    We propose an approach for the solidification of metallic alloys taking into account the turbulence in the liquid phase. For modeling of the turbulent flow a k-? model is used. This model is applied for solidification of AlSi-based alloys under the action of rotating electromagnetic field of intensity up to 65mT. Two cases have been considered, namely solidification of a binary Al-7wt%Si and a ternary alloy Al-7wt%Si-1wt%Fe. It is shown that increase of the electromagnetic field leads to the formations of various types of channels.

  3. Physics of the Earth and Planetary Interiors 155 (2006) 96103 Al, Fe substitution in the MgSiO3 perovskite structure

    E-print Network

    Jacobsen, Steven D.

    2006-01-01

    perovskite structure: A single-crystal X-ray diffraction study C.B. Vanpeteghema,, R.J. Angela, N.L. Rossa, S substitution of Al and Fe into the perovskite structure are: (i) MgA 2+ + SiB 4+ FeA 3+ + AlB 3+ , where and experimental work and solves the long-debated issue of Fe3+ occupancy in the perovskite structure. 2005

  4. Structure and magnetic properties of Fe2NiZ (Z=Al, Ga, Si and Ge) Heusler alloys

    NASA Astrophysics Data System (ADS)

    Zhang, Y. J.; Wang, W. H.; Zhang, H. G.; Liu, E. K.; Ma, R. S.; Wu, G. H.

    2013-07-01

    Fe2NiZ (Z=Al, Ga, Si and Ge) Heusler alloys have been synthesized and investigated focusing on the phase stability and the magnetic properties. The experimental and theoretical results demonstrate that covalent bonding originating from p-d hybridization plays an important role in these alloys, which dominates the stability of the ordered structure but leads to a decrease of the band splitting. The electronic structure shows that the IV group main-group elements (Si and Ge) provide a stronger covalent effect than the III group elements (Al and Ga). The variations of the physical parameters, like lattice constants, atomic-ordering temperatures, magnetic moments and Curie temperature, can be attributed differences in covalent bonding in these alloy systems.

  5. Oscillatory antiferromagnetic interlayer exchange coupling in Co2Fe(Al0.5Si0.5)/Ag/Co2Fe(Al0.5Si0.5) films and its application to trilayer magnetoresistive sensor

    NASA Astrophysics Data System (ADS)

    Nakatani, T. M.; Mitani, S.; Furubayashi, T.; Hono, K.

    2011-10-01

    We report oscillatory antiferromagnetic (AFM) interlayer exchange coupling (IEC) in a trilayer film with Co2Fe(Al0.5Si0.5) (CFAS) Heusler alloy ferromagnetic layers and a Ag spacer layer. The AFM-IEC was observed only in the films annealed at >400 C, suggesting the enhancement of the interfacial spin-dependent scattering by improved B2 order in the CFAS film is its origin. Using the AFM coupled trilayer, we demonstrated a scissors-type trilayer CPP-GMR device with relatively large ?RA of 4.5 m? ?m2 and MR ratio of 24%.

  6. Electrochemical and microstructural study of oxide films formed electrochemically at microcrystalline Al-Fe-V-Si alloys.

    PubMed

    Thomas, S C; Birss, V I; Steele, D; Tessier, D

    1995-07-01

    A recent advance in metallurgical technology has been the application of rapid solidification techniques to Al alloy production. FVS0812 is the designation given to a microcrystalline Al-based alloy consisting of 8 wt% Fe, 1 wt% V and 2 wt% Si. It is a two-phase alloy, consisting of ca. 27 vol percent of approximately spherical Fe-V-Si-rich dispersoids in an essentially pure Al matrix. The high strength, low density properties of this advanced material, and other related alloys, have not yet been realized, however, due, in part, to the inability of the alloy to form a thick, adherent, abrasion-resistant outer surface oxide film, a feature readily achieved at conventional Al alloys by normal anodizing methods. The present research has involved an electro-chemical study of oxide film growth at the 812 alloy, with the specific goals being to seek an understanding of the origin of the oxide film growth problem and ultimately to propose alternative approaches to the formation of a thick, stable oxide film at this material. The techniques used in this research have included electrochemical methodologies such as cyclic voltammetry and electrochemical impedance spectroscopy. Crucial information has been obtained through transmission electron microscopy (TEM) of ultramicrotomed specimens. Experiments were carried out initially in neutral borate solutions to characterize the compact barrier oxide film formed in this environment and expected to be present beneath the porous oxide film formed in the normal sulfuric acid anodizing medium.(ABSTRACT TRUNCATED AT 250 WORDS) PMID:7549001

  7. DISCOVERY OF AHRENSITE -Fe2SiO4 AND TISSINTITE (Ca,Na,)AlSi2O6: TWO NEW HIGH PRESSURE MINERALS FROM THE TISSINT MARTIAN METEORITE. Chi Ma1

    E-print Network

    Rossman. George R.

    a nanomineralogy investigation of this meteorite by analytical scanning electron micro- scope, electron probeDISCOVERY OF AHRENSITE -Fe2SiO4 AND TISSINTITE (Ca,Na,)AlSi2O6: TWO NEW HIGH PRESSURE MINERALS FROM, micro-Raman, and synchrotron diffraction, we identified two new shock-induced min- erals ahrensite, -Fe2

  8. The effect of external magnetic field on the remagnetization process in FeCuNbSiB/Al/FeCuNbSiB films induced by an alternating current

    NASA Astrophysics Data System (ADS)

    Buznikov, N. A.; Antonov, A. S.; D'yachkov, A. L.; Rakhmanov, A. A.

    2004-02-01

    The alternating current induced remagnetization process in FeCuNbSiB/Al/FeCuNbSiB films is studied. The frequency spectra of the voltage arising in the pick-up coil wound around the sample are measured as a function of an external dc magnetic field. It is shown that the frequency spectra differ substantially for the transverse and longitudinal external magnetic field directions. For the transverse field, several harmonics have high amplitudes, whereas for the longitudinal field, even harmonics dominate in the frequency spectrum. A high field sensitivity of the voltage response is demonstrated. The experimental results are interpreted within the framework of a simple rotational model.

  9. Properties of a reaction-bonded ?-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 ?-SiAlON (FeMo/?-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 700C and after oxidization at 700C 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/?-SiAlON composite exhibits strong potential for application to molten aluminum environments.

  10. Interfacial exchange coupling in cubic Heusler Co2FeZ (Z = Al and Si)/tetragonal Mn3Ga bilayers

    NASA Astrophysics Data System (ADS)

    Ranjbar, R.; Suzuki, K.; Sugihara, A.; Ma, Q. L.; Zhang, X. M.; Miyazaki, T.; Ando, Y.; Mizukami, S.

    2015-05-01

    We have fabricated bilayer films of tetragonal Heusler-like D022 Mn3Ga and cubic Heusler Co2FeZ (Z = Si and Al) on (100) single-crystalline MgO substrates and investigated their structural and interfacial exchange coupling. The coupling in the Mn3Ga/Co2FeAl bilayer was either ferromagnetic or antiferromagnetic, depending on annealing temperature, whereas only antiferromagnetic exchange coupling was observed in the Mn3Ga/Co2FeSi bilayers. The effects of annealing on the structure and coupling strength in the bilayers are discussed.

  11. Low temperature magnetization behavior in Co 36Fe 36Si 3Al 1Nb 4B 20 (at%) nanostructured alloy

    NASA Astrophysics Data System (ADS)

    Panda, A. K.; Mohanta, Ojaswini; Basumallick, A.; Mitra, A.

    2010-12-01

    The investigation addresses low temperature magnetization behavior in Co 36Fe 36Si 3Al 1Nb 4B 20 alloy ribbons in their as-spun as well as annealed state. Optimum heat treatment at 875 K led to nanocrystallization whereby bcc-(FeCo)SiAl nanoparticles were dispersed in an amorphous matrix as evidenced from transmission electron microscopy. Low temperature magnetization studies were carried out in the range 77-300 K. Using the method of mathematical fittings, magnetization extrapolated to 0 K was obtained. The dependence of the magnetization with respect to temperature of BT 3/2 was used to determine the Bloch coefficient " B" and spin wave stiffness constant " D". Magnetic softening revealed by lowering in the coercivity in the optimum nanostructured state was also the cause of a drop in the stiffness constant. The range of exchange interaction given by D/ TC was higher in the nanostructured state compared to the as-spun amorphous state. The effect of nanocrystallization and the resulting ferromagnetic coupling was further evidenced by low temperature magnetization studies.

  12. Microstructural and Hardness Changes during Isothermal Annealing of Nanostructured Al-11.6Fe-1.3V-2.3Si Alloy

    NASA Astrophysics Data System (ADS)

    Ashrafi, H.; Emadi, R.; Enayati, M. H.

    2015-02-01

    Microstructural evolution and hardness change during isothermal annealing (300-550 C, 30 min) of nanostructured Al-11.6Fe-1.3V-2.3Si alloy, prepared by mechanical alloying (MA) of elemental powders, were investigated using x-ray diffraction, transmission electron microscopy, and Vickers microhardness test. The results showed that the microstructure of the alloy after 60 h of MA consisted of a nanostructured Al-based solid solution with embedded Si. Annealing of the as-milled powders led to grain growth, internal strain release, and precipitation of the Al12(Fe,V)3Si compound above 400 C. The grain growth of Al enhanced above the onset temperature for the precipitation of Al12(Fe,V)3Si phase. The grain size of Al after 30 min of annealing at 550 C reached ~50 nm. Solute drag was responsible for retarding the grain growth below 400 C, and above that temperature the grain growth was mainly limited by second-phase drag. The hardness (219 HV) of as-milled Al-11.6Fe-1.3V-2.3Si alloy decreased after annealing at 300 C, but above that temperature the hardness increased with increasing the annealing temperature and reached ~250 HV after annealing at 550 C for 30 min.

  13. 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.

  14. Fragmentation of the fluorite type in Fe8Al(17.4)Si(7.6): structural complexity in intermetallics dictated by the 18 electron rule.

    PubMed

    Fredrickson, Rie T; Fredrickson, Daniel C

    2012-10-01

    This Article presents the synthesis, structure determination, and bonding analysis of Fe(8)Al(17.4)Si(7.6). Fe(8)Al(17.4)Si(7.6) crystallizes in a new monoclinic structure type based on columns of the fluorite (CaF(2)) structure type. As such, the compound can be seen as part of a structural series in which the fluorite structure-adopted by several transition metal disilicides (TMSi(2))-is fragmented by the incorporation of Al. Electronic structure analysis using density functional theory (DFT) and DFT-calibrated Hckel calculations indicates that the fluorite-type TMSi(2) phases (TM = Co, Ni) exhibit density of states (DOS) pseudogaps near their Fermi energies. An analogous pseudogap occurs for Fe(8)Al(17.4)Si(7.6), revealing that its complex structure serves to preserve this stabilizing feature of the electronic structure. Pursuing the origins of these pseudogaps leads to a simple picture: the DOS minimum in the TMSi(2) structures arises via a bonding scheme analogous to those of 18 electron transition metal complexes. Replacement of Si with Al leads to the necessity of increasing the (Si/Al):TM ratio to maintain this valence electron concentration. The excess Si/Al atoms are accommodated through the fragmentation of the fluorite type. The resulting picture highlights how the elucidating power of bonding concepts from transition metal complexes can extend into the intermetallic realm. PMID:22984870

  15. Compositional dependence of the Nel transition, structural stability, magnetic properties and electrical resistivity in FeMnAlCrSi alloys

    Microsoft Academic Search

    Yan Sheng Zhang; Xing Lu; Xing Tian; Zuoxiang Qin

    2002-01-01

    Compositional dependence of the Nel transition temperature, TN, structural stability, magnetic properties, and anomaly of resistivity, ?, have been investigated in ?-FeMnAlCrSiC alloys. In the Fe(2032.5 at.%)Mn-based alloys, an increase in Mn, Al, Cr or C content will inhibit the ?????? martensitic transformation and lower the ? martensitic transformation temperature Ms or deformation-induced martensitic transformation temperature Md, while an increase

  16. Phase transformations in an Fe7.8Al29.5Mn1.5Si1.05C alloy

    Microsoft Academic Search

    C. Y. Chao; T. F. Liu

    1993-01-01

    Phase transformations in an Fe-7.8Al-29.5Mn-l.5Si-1.05C alloy have been investigated by means of optical microscopy and transmission electron microscopy. In the as-quenched condition, a high density of fine (Fe,Mn)3AlC carbides could be observed within the austenite matrix. When the as-quenched alloy was aged at temperatures ranging from 550 C to 825 C, a gamma --> coarse (Fe,Mn)3AlC carbide + DO3 reaction

  17. Phase transformations in an Fe7.8Al29.5Mn1.5Si1.05C alloy

    Microsoft Academic Search

    C. Y. Chao; T. F. Liu

    1993-01-01

    Phase transformations in an Fe-7.8Al-29.5Mn-l.5Si-1.05C alloy have been investigated by means of optical microscopy and transmission\\u000a electron microscopy. In the as-quenched condition, a high density of fine (Fe,Mn)3AlC carbides could be observed within the austenite matrix. When the as-quenched alloy was aged at temperatures ranging from\\u000a 550 ?C to 825 ?C, a? ? coarse (Fe,Mn)3AlC carbide + DO3 reaction occurred

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

    E-print Network

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

    2015-01-01

    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, MgSiO_3 bridgmanite, MgSiO_3 post-perovskite and MgO periclase, alters their elastic properties. However, knowledge on the thermoelasticity of Fe- and Al-bearing MgSiO_3 bridgmanite, and post-perovskite is scarce. In this study, we perform ab initio molecular dynamics to calculate the elastic and seismic properties of pure, Fe^{3+}- and Fe^{2+}-, and Al^{3+}-bearing MgSiO_3 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 ...

  19. Oxidation Studies of SiAlON/MgAlON Ceramics with Fe2O3 and CaO Impurities, Part II: Phase Evolution

    NASA Astrophysics Data System (ADS)

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

    2013-02-01

    The oxidation behavior of composite SiAlON/MgAlON phases, synthesized from the leaching residue after the aqueous treatment of salt cake from aluminum remelting, is compared with the oxidation of corresponding synthetic samples. The samples were subjected to oxidation under air as the oxidant atmosphere in the temperature range of 1373 K to 1773 K (1100 C to 1500 C). The phases present were analyzed by scanning electron microscopy (SEM)-electron-dispersive spectroscopy (EDS) and X-ray diffraction (XRD) to arrive at the evolution of the various phases formed during oxidation. From the experimental results, especially by the characterization of the oxidation products, the mechanism of the oxidation reaction was deduced as follows: With the progress of oxidation, the composition of the material being oxidized moved toward the Al2O3-rich corner of MgO-Al2O3-SiO2 and CaO-MgO-Al2O3-SiO2 phase diagrams relevant to the SiAlON/MgAlON composite. At lower temperatures, the addition of Fe2O3 and CaO facilitated the formation of cordierite and anorthite, respectively. With increasing temperature, islands of silicate melt were formed dissolving these oxides, with the liquidus temperature getting lowered as a consequence. The liquid phase formed engulfed the adjacent solid phases providing strong mobility for the cations and enabling the crystal growth. As a result, intermediate products, i.e., cordierite, anorthite, and spinel, which were formed earlier during oxidation, are found to get dissolved in the liquid phase.

  20. Role of the Fe-substitution in dielectric behavior of the glass-ceramic cordierite Mg2Al4Si5O18 system

    NASA Astrophysics Data System (ADS)

    Kirat, G.; Aksan, M. A.

    2014-12-01

    In this study, Mg2-xMxAl4Si5O18, where M=Fe and x=0.0, 0.20, 0.50, 1.0 and 1.5, have been synthesized using an arc-melter system. As a result of Fe-substitution, complex, deformed and multiphase samples were obtained. Microstructural analysis indicated that crystals of ?-cordierite disappeared in the x=1.5 Fe-substituted sample. However, more densified samples than the unsubstituted sample were obtained. Dielectric constant increased gradually and capacitive resistance decreased with increasing the Fe-content in the system. The results suggested that the Mg2Al4Si5O18 materials obtained by the Fe-substitution are not suitable for high frequency applications.

  1. Phase transformations in an Fe-7.8Al-29.5Mn-1.5Si-1.05C alloy

    NASA Astrophysics Data System (ADS)

    Chao, C. Y.; Liu, T. F.

    1993-09-01

    Phase transformations in an Fe-7.8Al-29.5Mn-l.5Si-1.05C alloy have been investigated by means of optical microscopy and transmission electron microscopy. In the as-quenched condition, a high density of fine (Fe,Mn)3AlC carbides could be observed within the austenite matrix. When the as-quenched alloy was aged at temperatures ranging from 550 C to 825 C, a ? ? coarse (Fe,Mn)3AlC carbide + DO3 reaction occurred by a cellular precipitation on the ?/? grain boundaries and twin boundaries. Both of the observations are quite different from those observed by other workers in Fe-Al-Mn-C alloys. In their studies, it was found that the as-quenched microstructure was austenite phase (?), and (Fe,Mn)3AlC carbides could only be observed within the austenite matrix in the aged alloys. In addition, a ? ? ? (ferrite) + coarse (Fe,Mn)3AlC carbide reaction or a ? ? ? + coarse (Fe,Mn)3AlC carbide + ?-Mn reaction was found to occur on the ?/? grain boundary in the aged Fe-Al-Mn-C alloys.

  2. Temperature dependence of the optimum particle size for the dislocation detachment controlled creep of Al-Fe-V-Si/SiC{sub p} composite

    SciTech Connect

    Kim, I.S.; Nam, S.W. [Korea Advanced Inst. of Science and Technology, Taejon (Korea, Republic of). Dept. of Materials Science and Engineering] [Korea Advanced Inst. of Science and Technology, Taejon (Korea, Republic of). Dept. of Materials Science and Engineering; Kim, N.J. [Pohang Univ. of Science and Technology (Korea, Republic of). Center for Advanced Aerospace Materials] [Pohang Univ. of Science and Technology (Korea, Republic of). Center for Advanced Aerospace Materials

    1995-06-01

    In order to improve the models for the dislocation detachment controlled creep in the dispersion strengthened alloys, the authors analyzed the creep behavior of Al-Fe-V-Si/SiC{sub p} composite based on the attractive dislocation-particle interaction with the assumption that the optimum particle radius is not a constant value but increases with increasing temperature. And in order to verify their suggestion, the creep behavior of the rapidly solidified aluminum alloys such as FVS1212 alloy and Al-8.4wt.%Fe-3.6wt.%Ce alloy is analyzed by the suggested method and they propose a good interpretation of the dislocation detachment process during creep. The unified model has been suggested to properly explain the creep behavior of dispersion strengthened aluminum alloys. This model assumes that the optimum particle radius related to the detachment process increases with increasing temperature. Using the modified creep equation, the normalized creep rate can be shown on a single line when plotted against the stress normalized by the detachment stress.

  3. Investigation of the Effects of Ni, Fe, and Mn on the Formation of Complex Intermetallic Compounds in Al-Si-Cu-Mg-Ni Alloys

    NASA Astrophysics Data System (ADS)

    Gholizadeh, R.; Shabestari, S. G.

    2011-11-01

    The aim of this work is to partially substitute Fe and Mn for Ni in the 3HA piston alloy and to study the consequences through microstructural evaluation and the thermal analysis technique. Three types of near-eutectic alloys containing (2.6 wt pct Ni-0.2 wt pct Fe-0.1 wt pct Mn), (1.8 wt pct Ni-0.75 wt pct Fe-0.3 wt pct Mn), and (1 wt pct Ni-1.15 wt pct Fe-0.6 wt pct Mn) were produced, and their solidification was studied at the cooling rate of 0.9 K/s (C/s) using the computer-aided thermal analysis technique. Optical microscopy and scanning electron microscopy were used to study the microstructure of the samples, and energy dispersive X-ray (EDX) analysis was used to identify the composition of the phases. Also, the quantity of the phases was measured using the image analysis technique. The results show that Ni mainly participates as Al3Ni, Al9FeNi, and Al3CuNi phases in the high Ni-containing alloy (2.6 wt pct Ni). In addition, substitution of Ni by Fe and Mn makes Al9FeNi the only Ni-rich phase, and Al12(Fe,Mn)3Si2 appears as an important Fe-rich intermetallic compound in the alloys with the higher Fe and Mn contents.

  4. 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.

  5. 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).

  6. 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.

  7. Diode-like behavior of I-V curves of CoFe-(Al-O)/Si(100) granular thin films

    NASA Astrophysics Data System (ADS)

    Tuan Anh, Nguyen; Van Cuong, Giap; Anh Tuan, Nguyen

    2015-01-01

    In this study, the electrical performance of (Co70Fe30)x(Al-O)1-x (where x=0.1 and 0.3) granular thin films sputtered on Si(1 0 0) substrates, which were subsequently annealing at 350 C for 1 h in vacuum, was investigated. The millimeter-sized samples were installed in an in-plane lateral Ag electrode configuration on the surface. The current-voltage (I-V) characteristics were measured in bias voltages of approximately 7 V. The I-V curves demonstrated the so-called large Coulomb gaps and diode-like asymmetric behavior similar to a Zener diode-type rectification. This remarkable behavior was evaluated using the most suitable transport models. Results suggest that an effective magnetic diode could be fabricated from millimeter-sized magnetic granular thin films.

  8. Shear modulus, heat capacity, viscosity and structural relaxation time of Na 2 OAl 2 O 3 SiO 2 and Na 2 OFe 2 O 3 Al 2 O 3 SiO 2 melts

    Microsoft Academic Search

    Katarzyna Falenty; Sharon L. Webb

    2010-01-01

    The configurational heat capacity, shear modulus and shear viscosity of a series of Na2OFe2O3Al2O3SiO2 melts have been determined as a function of composition. A change in composition dependence of each of the physical properties\\u000a is observed as Na2O\\/(Na2O+Al2O3) is decreased, and the peralkaline melts become peraluminous and a new charge-balanced Al-structure appears in the melts.\\u000a Of special interest are the

  9. The nucleation of Fe-Rich phases on oxide films in Al11.5Si0.4Mg cast alloys

    Microsoft Academic Search

    X. Cao; J. Campbell

    2003-01-01

    The microstructures of Al-11.5Si-0.4Mg alloys with various Fe and Mn contents have been studied to investigate the potential\\u000a influence of oxide films on the precipitation of Fe-rich phases from the liquid metal. Oxide films are incorporated into melts\\u000a by an entrainment process. This is an enfolding mechanism of incorporation. Folded oxide films in melts have two sides: the\\u000a dry unbonded

  10. Microstructure, Mechanical Properties, and Age-Hardening Behavior of an Al-Si-Fe-Mn-Cu-Mg Alloy Produced by Spray Deposition

    NASA Astrophysics Data System (ADS)

    Feng, Wang; Jishan, Zhang; Baiqing, Xiong; Yongan, Zhang

    2011-02-01

    It has been recognized generally that the spray-deposited process is an innovative technique of rapid solidification. In this paper, Al-20Si-5Fe-3Mn-3Cu-1Mg alloy was synthesized by the spray atomization and deposition technique. The microstructure and mechanical properties of the spray-deposited alloy were studied using x-ray diffraction, scanning electron microscopy, transmission electron microscopy (TEM), and tensile tests. It is observed that the microstructure of spray-deposited Al-20Si-5Fe-3Mn-3Cu-1Mg alloy is composed of the ?-Al,Si and the particle-like Al15(FeMn)3Si2 compounds. The aging process of the alloy was investigated by microhardness measurement, differential scanning calorimetry analysis, and TEM observations. The results indicate that the two types of precipitates, S-Al2CuMg and ?-Al5Cu6Mg2 precipitate from matrix and improve the tensile strength of the alloy efficiently at both the ambient and elevated temperatures (300 C).

  11. NUCLEAR THERMODYNAMIC DATABASE O-U-Zr-Fe-Cr-Ni-Ag-In-B-C-Ba-La-Ru-Sr-Al-Ca-Mg-Si

    E-print Network

    Paris-Sud XI, Universit de

    NUCLEAR THERMODYNAMIC DATABASE NUCLEA O-U-Zr-Fe-Cr-Ni-Ag-In-B-C-Ba-La-Ru-Sr-Al-Ca-Mg-Si + Ar - TVA : FR 91 304 441 090 #12;NUCLEA Nuclear Thermodynamic Database Version 2007-01 developed March 1996 on the legal protection of databases. Extraction and/or re-utilization of the whole

  12. High strength FeMn(Al, Si) TRIP\\/TWIP steels development properties application

    Microsoft Academic Search

    O Grssel; L Krger; G Frommeyer; L. W Meyer

    2000-01-01

    Deformation twinning, martensitic phase transformation and mechanical properties of austenitic Fe-(1530) wt.%Mn steels with additions of aluminium and silicon have been investigated. It is known that additions of aluminium increase the stacking fault energy ?fcc and therefore strongly suppress the ??? transformation while silicon decrease ?fcc and sustains the ??? transformation. The ??? phase transformation takes place in steels with

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

    NASA Astrophysics Data System (ADS)

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

    2014-09-01

    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.

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

    SciTech Connect

    Hirohata, Atsufumi, E-mail: ah566@ohm.york.ac.uk [Department of Electronics, University of York, Heslington, York YO10 5DD (United Kingdom); PRESTO, Japan Science and Technology Agency, Kawaguchi 332-0012 (Japan); Izumida, Keisuke; Ishizawa, Satoshi; Nakayama, Tadachika [Department of Electrical Engineering, Nagaoka University of Technology, Nagaoka 940-2188 (Japan); Sagar, James [Department of Physics, University of York, Heslington, York YO10 5DD (United Kingdom)

    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.

  15. 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.

  16. Study of deformation behavior, structure and mechanical properties of the AlSiMnFe alloy during ECAP-PBP.

    PubMed

    Naizabekov, A B; Andreyachshenko, V A; Kocich, Radim

    2013-01-01

    The presented article deals with the effects of equal channel angular pressing (ECAP) with a newly adjusted die geometry on the microstructure and mechanical properties of the Al-Si-Mn-Fe alloy. This alloy was subjected to two modes of heat treatment followed by the ECAP process, which led to partial back pressure (ECAP-PBP). Ultra-fine grained (UFG) structure formed through ECAP-PBP process has been studied by methods of optical as well as electron microscopy. The obtained results indicate that quenched alloys, in comparison to slowly cooled alloys, do not contain large brittle particles which subsequently initiate a premature creation of cracks. It was shown that the mechanical properties of these alloys after such processing depend first and foremost on the selected type of heat treatment and on the number of performed passes. The maximum of ultimate tensile strength (417 MPa) was obtained for quenched alloy after 3 passes. On the other hand, maximum ductility was found in slowly cooled alloy after second pass. Further passes reduced strength due to the brittle behavior of excluded particles. One of the partial findings is that there is only a small dependency of the resulting size of grains on previously applied thermal processing. The minimum grain sizes were obtained after 3 passages, where their size ranged between 0.4 and 0.8 ?m. The application of quick cooling after heat processing due to the occurrence of finer precipitates in the matrix seems to produce better results. PMID:22796374

  17. Anomalous Hall effect and current spin polarization in Co2Fe X Heusler compounds (X =Al , Ga , In , Si , Ge , and Sn ): A systematic ab initio study

    NASA Astrophysics Data System (ADS)

    Huang, Hung-Lung; Tung, Jen-Chuan; Guo, Guang-Yu

    2015-04-01

    Co-based Heusler compounds are ferromagnetic with a high Curie temperature and a large magnetization density, and thus are promising for spintronic applications. In this paper, we perform a systematic ab initio study of two principal spin-related phenomena, namely, anomalous Hall effect and current spin polarization, in Co2-based Heusler compounds Co2Fe X (X =Al , Ga , In , Si , Ge , Sn ) in the cubic L2 1 structure within the density functional theory with the generalized gradient approximation (GGA). The accurate all-electron full-potential linearized augmented plane-wave method is used. First, we find that the spin polarization of the longitudinal current (PL) in Co2Fe X (X =Al , Ga , In , Al0.5Si0.5 , and Sn ) is 100 % even though that of the electronic states at the Fermi level (PD) is not. Further, the other compounds also have a high current spin polarization with PL>85 %. This indicates that all the Co2Fe X compounds considered are promising for spin-transport devices. Interestingly, PD is negative in Co2Fe X (X =Si , Ge , and Sn ), differing in sign from the PL as well as that from the transport experiments. Second, the calculated anomalous Hall conductivities (AHCs) are moderate, being within 200 S/cm, and agree well with the available experiments on a highly L2 1 ordered Co2FeSi specimen although they differ significantly from the reported experiments on other compounds where the B2 antisite disorders were present. Surprisingly, the AHC in Co2FeSi decreases and then changes sign when Si is replaced by Ge and finally by Sn. Third, the calculated total magnetic moments agree well with the corresponding experimental ones in all the studied compounds except Co2FeSi where a difference of 0.3 ?B/f .u . exists. We also perform the GGA plus on-site Coulomb interaction U calculations in the GGA + U scheme. We find that including the U affects the calculated total magnetic moment, spin polarization and AHC significantly, and in most cases, unfortunately, results in a disagreement with the available experimental results. All these interesting findings are discussed in terms of the underlying band structures.

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

    NASA Astrophysics Data System (ADS)

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

    2011-12-01

    The formation and properties of the post-perovskite (CaIrO 3-type) phase were studied in Fe-rich compositions along the pyrope-almandine ((Mg,Fe) 3Al 2Si 3O 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 2O 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 3 system. The presence of Al 2O 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 2O 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 (~ 135 GPa).

  19. 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 ? 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 ? 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 ? phase and the microstructure coarsening.

  20. Phase Stability of Al-5Fe-V-Si Coatings Produced by Cold Gas Dynamic Spray Process Using Rapidly Solidified Feedstock Materials

    NASA Astrophysics Data System (ADS)

    Brub, G.; Yandouzi, M.; Ziga, A.; Ajdelsztajn, L.; Villafuerte, J.; Jodoin, B.

    2012-03-01

    In this study, aluminum alloy Al-5Fe-V-Si (in wt.%) feedstock powder, produced by rapid solidification (RS) using the gas atomization process, was selected to produce high-temperature resistant Al-alloy coatings using the cold gas dynamic spraying process (CGDS). The alloy composition was chosen for its mechanical properties at elevated temperature for potential applications in internal-combustion (IC) engines. The CGDS spray process was selected due to its relatively low operating temperature, thus preventing significant heating of the particles during spraying and as such allowing the original phases of the feedstock powder to be preserved within the coatings. The microstructure and phases stability was investigated by means of Scanning Electron Microscopy, transmission electron microscopy, X-ray diffraction and differential scanning calorimetery techniques. The coatings mechanical properties were evaluated through bond strength and microhardness testing. The study revealed the conservation of the complex microstructure of the rapid solidified powder during the spray process. Four distinct microstructures were observed as well as two different phases, namely a Al13(Fe,V)3Si silicide phase and a metastable (Al,Si) x (Fe,V) Micro-quasicrystalline Icosahedral (MI) phase. Aging of the coating samples was performed and confirmed that the phase transformation of the metastable phases and coarsening of the nanosized precipitates will occurs at around 400 C. The metastable MI phase was determined to be thermally stable up to 390 C, after which a phase transformation to silicide starts to occur.

  1. 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.

  2. Neutron diffraction structural analysis of Y{sub 2}Fe{sub 15}T{sub 2}C (T = Al, Ga, Si) alloys

    SciTech Connect

    Yelon, W.B.; Hu, Z. [Univ. of Missouri, Columbia, MO (United States). Research Reactor Center] [Univ. of Missouri, Columbia, MO (United States). Research Reactor Center; Chang, W.C.; Lu, S.L. [National Chung Cheng Univ., Chia-Yi (Taiwan, Province of China)] [National Chung Cheng Univ., Chia-Yi (Taiwan, Province of China)

    1996-09-01

    Y{sub 2}Fe{sub 15}T{sub 2}C (T = Al, Ga, Si) crystallize in the rhombohedral Th{sub 2}Zn{sub 17}-type structure. The refined compositions are in excellent agreement with that of the nominal ones. The site occupancies of the substitutional atoms, (Al, Ga and Si) are found to be similar to those of the corresponding uncarbided compounds and not changed by the C atoms. That is, Al, Ga and Si all prefer the 18h site at the present substituent content, which appears to be determined by the site environments since the 18h site has the highest number (3) of rare earth neighbors in the structure. C atoms are found to occupy the octahedral interstitial 9e site (1/2, 0, 0) which has two rare earth neighbors and four Fe/T neighbors, in all three samples. The Curie temperatures have been measured to be 588 K, 515 K, and 535 K for the Ga, Al, and Si samples respectively.

  3. Combinatorial investigation of the effects of the incorporation of Ti, Si, and Al on the performance of ?-Fe2O3 photoanodes.

    PubMed

    He, Jianghua; Parkinson, B A

    2011-07-11

    The effect of adding small amounts of Ti, Si, and Al on the photoelectrochemical activity of ?-Fe(2)O(3) is investigated using a high-throughput combinatorial method. Quantitative ink jet printing is used to pattern iron oxide and dopant precursors onto conductive glass substrates. Subsequent pyrolysis yields a library of doped iron oxide electrodes that are screened for photoelectrolysis activity by immersing in an electrolyte and scanning a laser over the electrodes to map the photocurrent response. When Si and Al are individually added to iron oxide at the levels we studied, the photoelectrolysis activity decreased whereas low levels of Ti addition enhanced the photocurrents. Synergistic effects were observed resulting in enhanced photocurrents when multiple impurities were added to ?-Fe(2)O(3). PMID:21627308

  4. The ferriannite KFe(3)(2+)(Al(0.26)Fe(0.76)(3+)Si(3))O(10)(OH)(2) at 100 and 270 K.

    PubMed

    Redhammer, Gnther J; Roth, G

    2004-04-01

    Unusually large and good-quality single crystals of the synthetic trioctahedral mica KFe(3)(2+)(Al(0.26)Fe(0.76)(3+)Si(3))O(10)(OH)(2) [potassium triiron(II) aluminasilaferrate(III) decaoxide dihydroxide] have been grown hydrothermally. X-ray diffraction data measured at 270 and 100 K have been used to refine the crystal structure, including the positions of the H atoms. This synthetic mica is similar to annite, KFe(3)AlSi(3)O(10)(OH)(2), and crystallizes with the same monoclinic C2/m symmetry. No phase transition has been observed down to 100 K. At low temperature, the ditrigonal distortion of the mica structure increases markedly, while the octahedral and tetrahedral bond lengths tend to decrease and increase, respectively. A detailed comparison of structural parameters in various Fe-rich micas is presented. PMID:15071193

  5. Al, Fe, and Si compounds in Tamm and Mehra-Jackson extracts from mucky-peaty-podzolic gley soil: Contents, reserves, and profile and particle-size distributions

    NASA Astrophysics Data System (ADS)

    Sokolova, T. A.; Tolpeshta, I. I.; Maksimova, Yu. G.

    2014-05-01

    Equal or comparable contents of Fe and Al extractable by Tamm and Mehra-Jackson solutions have been revealed in all the horizons of a loamy mucky-peaty-podzolic gley soil on binary deposits. The content of Si extractable by the Mehra-Jackson solution has exceeded that of oxalate-soluble Si by an order of magnitude. The distributions of Al in the Tamm solutions from the entire soil and its fractions of 1-5 and >5 ?m are of accumulative type with a maximum in the mucky H horizon and a gradual decrease of the content with depth in relation with the analogous distribution of Al-organic complexes. The maximum content of oxalate-soluble Al in the clay fraction has been found in the eluvial ELg horizon, which can be due to the partial dissolution of Al hydroxide interlayers in soil chlorites. The distribution of Fe in the entire soil has two maximums, in the H horizon due to the accumulation of Fe-organic complexes and in the concretion-rich ELnn,g horizon due to the accumulation of Fe hydroxides. Depletion of oxalate-soluble Fe in the eluvial ELg horizon has been observed in all the fractions, which can be related to its mobilization and removal under strongly acidic conditions and the development of reductive processes, as well as the enrichment of the concretion-rich horizon with these compounds because of an increase in pH and the development of conditions favorable for water stagnation and Fe segregation.

  6. 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.

  7. Undercooling and supersaturation of alloying elements in rapidly solidified Al8.5% Fe1.2% V-1.7% Si alloy

    Microsoft Academic Search

    S. Hariprasad; S. M. L. Sastry; K. L. Jerina

    1996-01-01

    Dispersion-strengthened Al-8.5% Fe-1.2% V-1.7% Si alloy was produced by inert gas atomization and atomized melt deposition processes. Differential scanning calorimetry was used to estimate the extent of undercooling in the alloy powders as a function of powder size and in the atomized melt-deposited alloy as a function of process parameters. The estimated undercooling was found to be a strong function

  8. Effect of Si doping on the magnetic properties and magnetic entropy changes in the LaFe11.4Al1.6 intermetallic compound

    Microsoft Academic Search

    Q Y Dong; H W Zhang; J R Sun; B G Shen

    2008-01-01

    For NaZn13-type LaFe11.4Al1.6?xSix (x = 01.6) compounds, the lattice parameter linearly reduces with the increase of Si concentration. A mixture of antiferromagnetic phase and ferromagnetic clusters has been observed in the compound with x = 0.22. The magnetic phase diagram obtained from the isofield magnetization curves shows that the antiferromagnetic phase changes into the ferromagnetic phase at low temperature with

  9. Thermodynamic Database for the Al-Ca-Co-Cr-Fe-Mg-Mn-Ni-Si-O-P-S System and Applications in Ferrous Process Metallurgy

    Microsoft Academic Search

    Sergei A. Decterov; Youn-Bae Kang; In-Ho Jung

    2009-01-01

    Computerized thermodynamic databases for solid and liquid metals, slag, and solid oxide phases in the Al2O3-CaO-CoO-CrO-Cr2O3-FeO-Fe2O3-MgO-MnO-NiO-SiO2 system (with dissolved S and P) have been developed by critical evaluation\\/optimization of various available phase equilibrium\\u000a and thermodynamic data. The databases contain parameters of models specifically developed for molten slags, liquid steel,\\u000a and solid oxide solutions such as spinel, pyroxenes, olivine, monoxide (wustite,

  10. Synthesis and equation of state of perovskites in the (Mg, Fe)3Al2Si3O12 system to 177 GPa

    NASA Astrophysics Data System (ADS)

    Dorfman, Susannah M.; Shieh, Sean R.; Meng, Yue; Prakapenka, Vitali B.; Duffy, Thomas S.

    2012-12-01

    Natural and synthetic pyrope-almandine compositions from 38 to 100 mol% almandine (Alm38-Alm100) were studied by synchrotron X-ray diffraction in the laser-heated diamond anvil cell to 177 GPa. Single-phase orthorhombic GdFeO3-type perovskites were synthesized across the entire examined compositional range at deep lower mantle pressures, with higher Fe-contents requiring higher synthesis pressures. The formation of perovskite with Alm100 (Fe3Al2Si3O12) composition at 80 GPa marks the first observation of a silicate perovskite in a Fe end-member. Fe-enrichment broadens and lowers the pressure range of the post-perovskite transition for intermediate compositions such as Alm54, but the more Fe-rich Alm100-composition perovskite remains stable to pressures as high as 149 GPa. Volume compression data for the Alm54 and Alm100 compositions were fit to the Birch-Murnaghan equation of state. The compressibility of perovskites synthesized from compositions along the pyrope-almandine join is not strongly sensitive to Fe-content. The compression curves were smooth over the entire measured range, and no evidence for a volume anomaly associated with a spin transition was observed.

  11. 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. [Department of Materials, Imperial College London, South Kensington Campus, Prince Consort Road, London SW7 2AZ (United Kingdom); Li Mei; Allison, John [Materials Research and Advanced Engineering Department, Ford Research Laboratory, Dearborn, Michigan 48121-2053 (United States)

    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.

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

    E-print Network

    Chen, Long-Qing

    -Heusler Co2FeAl0.5Si0.5 alloy spin valve nanopillar H.B. Huang a,c , X.Q. Ma a,n , Z.H. Liu a , F.Y. Meng simulation Critical current density Spin transfer torque switching Heusler alloy Spin valve nanopillar a b-Heusler Co2FeAl0.5Si0.5 alloy spin-valve nanopillar through micromagnetic simulations. The simulations

  13. 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.; Schller, 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 (-), ? = 1.539(2), ? = 1.552(2), ? = 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)?2.00(Al3.79Fe{0.21/3+})?4.00Si4.98O18. 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) , V = 786.40(3) 3, Z = 2. The strongest lines in the X-ray powder diffraction pattern [ d, ( 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.

  14. Transport properties of ?-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 ?-FeSi2. The ?-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 ?-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.

  15. Strong perpendicular magnetic anisotropy in Co2FeAl0.5Si0.5 film sandwiched by MgO layers

    NASA Astrophysics Data System (ADS)

    Wang, Sheng; Li, Xiao-Qi; Bai, Li-Juan; Xu, Xiao-Guang; Miao, Jun; Jiang, Yong

    2013-05-01

    Co2FeAl0.5Si0.5 (CFAS)-based multilayers sandwiched by MgO layers have been deposited and annealed at different temperatures. Perpendicular magnetic anisotropy (PMA) with the magnetic anisotropy energy density Ku ? 2.5 106 erg/cm3 (1 erg = 10-7 J) and the coercivity Hc = 363 Oe (1 Oe = 79.9775 A m-1) has been achieved in the Si/SiO2/MgO (1.5 nm)/CFAS (2.5 nm)/MgO (0.8 nm)/Pt (5 nm) film annealed at 300 C. The strong PMA is mainly due to the top MgO layer. The structure can be used as top magnetic electrodes in half-metallic perpendicular magnetic tunnel junctions.

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

    E-print Network

    Chen, Long-Qing

    Micromagnetic simulation of spin-transfer switching in a full-Heusler Co2FeAl0.5Si0.5 alloy spin-valve nanopillar H. B. Huang, X. Q. Ma, Z. H. Liu, F. Y. Meng, Z. H. Xiao et al. Citation: J. Appl. Phys. 110. Related Articles Bi-quadratic interlayer exchange coupling in Co2MnSi/Ag/Co2MnSi pseudo spin-valve J. Appl

  17. 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.

  18. Structure and spin polarization of outermost surface of the Co2FeAl0.5Si0.5 full-Heusler alloy studied by spin-polarized ion-scattering spectroscopy

    NASA Astrophysics Data System (ADS)

    Suzuki, T. T.; Sukegawa, H.; Inomata, K.

    2009-01-01

    The outermost surfaces of epitaxial full-Heusler Co2FeAl0.5Si0.5 (CFAS) films on MgO (001) substrates were investigated using spin-polarized ion-scattering spectroscopy. It was found that the CFAS surface was terminated by an Fe-Al-Si layer with substitution of Fe with Al and/or Si. The spin polarization of the outermost surface was detected for the first time among Heusler alloys. It was found that the spin polarization of Al and/or Si atoms in the topmost layer was significantly lower than that of Co atoms in the second layer. It was also found that the polarity of the spin polarization at the Fermi level on the outermost surface was opposite to majority spins. A possible application of SP-ISS in the development of magnetoresistance materials is suggested.

  19. Combinatorial Optimization of Ba\\/Fe-cordierite Solid Solution (Ba0.05Fe0.1Mg)2Al4Si5O18 for High Infrared Radiance Materials

    Microsoft Academic Search

    Fu-han Tang; Jian-dong Zhuang; Fan Fei; Qian Liu

    2012-01-01

    A combinatorial chemistry method was employed to screen the Ba2+ and Fe3+ incorporated into cordierite structure (Ba0.05Fe0.1Mg)2Al4Si5O18 for exploring of high infrared radiance materials. A series of square-type sample array that consists of 77 compositions was synthesized by ink-jetting nitrate solutions into micro-reactor wells in a ceramic plate and then heat-treated at high temperatures. X-ray diffraction and infrared thermograph were

  20. High-temperature creep in an Al8.5Fe1.3V-1.7Si alloy processed by rapid solidification

    Microsoft Academic Search

    S. J. Zhu; K. Kucha?ov; J. ?adek

    2000-01-01

    The creep behavior of an Al-8.5Fe-1.3V-1.7Si alloy processed by rapid solidification is investigated at three temperatures\\u000a ranging from 623 to 723 K. The measured minimum creep strain rates cover seven orders of magnitude. The creep behavior is\\u000a associated with the true threshold stress, decreasing with increasing temperature more strongly than the shear modulus of\\u000a aluminum. The minimum creep strain rate

  1. 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, Grgory; 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: 275C, 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.

  2. 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.

  3. 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 Mssbauer 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. Mssbauer 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.

  4. Study of structural and magnetic properties of Fe73.5Si3.8C14Mn0.7B4Al4 alloy

    NASA Astrophysics Data System (ADS)

    Tapkir, P.; Satalkar, M.; Shah, M.; Ghodke, N.; Varga, L. K.; Araujo, J. P.; Kane, S. N.

    2014-09-01

    Present work, reports the influence of thermal annealing on magnetic and structural properties of Ci92B4Al4 (Fe73.5Si3.8C14Mn0.7= Ci Cast iron) alloy using, magnetic measurements, differential scanning calorimetry (DSC) and x-ray diffraction (XRD) to obtain information on structure, formed nano-crystalline phases and their influence on soft magnetic properties. Structural changes were achieved by annealing of the samples performed at 350, 370, 400, 425 and 450 C for one hour. Studied specimen shows two-step crystallization, and the activation energy of crystallization, obtained using Kissinger's method, was 3.79 0.6 eV (for main peak) and 3.02 0.3 eV (for pre peak). Coercive field Hc of the studied samples varies between 22.06 838.67 A/m. Best coercivity (Hc) value of 22.06 A/m was obtained for the as cast sample. The measured saturation induction (B2000) values range between 0.89 and 1.31 Tesla. Best saturation induction (B2000) value of 1.31 Tesla was obtained for the as cast sample. XRD data shows that apart from ?-Fe, phase (lattice parameter ~ 0.2859 nm) an additional Fe-Al phase is also formed, with Al ranging between 53 64 %, responsible for the reduction of magnetic induction as well as the increase of coercivity.

  5. Planar Flow Casting of Fe71Si13.5B9Nb3Cu1Al1.5Ge1 Ribbons

    NASA Astrophysics Data System (ADS)

    Sohrabi, S.; Arabi, H.; Beitollahi, A.; Gholamipour, R.

    2013-08-01

    In this study, the planar flow casting (PFC) technique for producing wide amorphous ribbons of Fe71Si13.5B9Nb3Cu1Al1.5Ge1 alloy is investigated. Various ribbons of the mentioned alloy were produced through applying different values of wheel speed and ejection pressure. In addition, effects of wheel speed (13, 23, and 33 m/s) on the structure, degree of amorphicity, and surface quality of the ribbons were examined. The results showed that the trends of thickness variation with increasing wheel speed and ejection pressure for Fe71Si13.5B9Nb3Cu1Al1.5Ge1 ribbons are in good agreement with what the Bernoulli equation in fluid dynamics predicts for the PFC process. Further, based on x-ray diffraction and differential scanning calorimeter results, it was shown that the degree of amorphicity increases by increasing the wheel speed. Besides, surface roughness measurements and scanning electron microscope micrographs of the ribbons revealed that the surface quality of the prepared ribbons improved by increasing the wheel speed.

  6. Microstructural evolution and intermetallic formation in Al-8wt% Si-0.8wt% Fe alloy due to grain refiner and modifier additions

    NASA Astrophysics Data System (ADS)

    Hassani, Amir; Ranjbar, Khalil; Sami, Sattar

    2012-08-01

    An alloy of Al-8wt% Si-0.8wt% Fe was cast in a metallic die, and its microstructural changes due to Ti-B refiner and Sr modifier additions were studied. Apart from usual refinement and modification of the microstructure, some mutual influences of the additives took place, and no mutual poisoning effects by these additives, in combined form, were observed. It was noticed that the dimensions of the iron-rich intermetallics were influenced by the additives causing them to become larger. The needle-shaped intermetallics that were obtained from refiner addition became thicker and longer when adding the modifier. It was also found that ?-Al and eutectic silicon phases preferentially nucleate on different types of intermetallic compounds. The more iron content of the intermetallic compounds and the more changes in their dimensions occurred. Formation of the shrinkage porosities was also observed.

  7. Fabrication and characterization of spin injector using a high-quality B2-ordered-Co2FeSi0.5Al0.5/MgO/Si(100) tunnel contact

    NASA Astrophysics Data System (ADS)

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

    2015-05-01

    We successfully fabricate a (100)-orientated B2-type-Co2FeSi0.5Al0.5 (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.

  8. Spin state of iron and elastic properties of (MgFe)(SiAl)O3 under conditions of the lower mantle

    NASA Astrophysics Data System (ADS)

    Glazyrin, K.; Boffa Ballaran, T.; Frost, D. J.; McCammon, C. A.; Kantor, A.; Merlini, M.; Hanfland, M.; Dubrovinsky, L. S.

    2012-12-01

    Iron is incorporated into crystal structures of the dominant lower mantle phases, namely, magnesium silicate perovskite (Pv) and ferropericlase (Fp). There is no doubt that iron is the most abundant transition element of the lower mantle. Depending on conditions imposed by the latter, charge distribution between different electronic orbitals of iron may change, giving rise to spin state transitions (SST) which, in turn, may modify bulk elastic and transport properties of the material. Critical conditions promoting SST vary depending on iron cation charge and crystallographic environment. In the case of Pv, it was shown that Fe2+ will occupy exclusively the distorted dodecahedral (A) site, while Fe3+ can substitute in both the A and the B (octahedral) sites. However, the problem becomes more complicated if we consider Fe/Al coupled substitution in Pv and realistic compositions of the lower mantle. Although SST in Pv is a current and highly debated topic, there is clearly a lack of experimental data, and the literature shows strong controversies between theoretical calculations and experiment. The problem of iron SST in Pv is one of the most challenging and important for our understanding of mantle processes and dynamics. We conducted a single crystal diffraction experiment on Mg0.6Fe0.4Si0.63Al0.37O3 Pv at the ID09 beamline, ESRF, Grenoble. Comprehensive characterization of this sample synthesized in a multianvil apparatus revealed that almost all iron in this material is ferric and occupies exclusively the A site (Fe3+A). We studied the combined effect of compression and temperature on the crystal structure and elastic properties of the material, and we observed that (a) below 77 GPa, 1800K there is no SST for Fe3+A and (b) high pressure-high temperature treatment has no effect on Fe/Al cation distribution between different crystallographic sites. These observations are in good agreement with recent theoretical work. Based on a thermal equation of state derived from our experiments and data from the literature, we present a unified model capable of predicting elastic properties for a wide range of realistic lower mantle Pv compositions. Additionally we discuss the effect of iron spin state and iron oxidation state on one of the most important variables - bulk sound velocity of Pv at conditions of the lower mantle.

  9. Combinatorial Optimization of Ba/Fe-cordierite Solid Solution (Ba0.05Fe0.1Mg)2Al4Si5O18 for High Infrared Radiance Materials

    NASA Astrophysics Data System (ADS)

    Tang, Fu-han; Zhuang, Jian-dong; Fei, Fan; Liu, Qian

    2012-06-01

    A combinatorial chemistry method was employed to screen the Ba2+ and Fe3+ incorporated into cordierite structure (Ba0.05Fe0.1Mg)2Al4Si5O18 for exploring of high infrared radiance materials. A series of square-type sample array that consists of 77 compositions was synthesized by ink-jetting nitrate solutions into micro-reactor wells in a ceramic plate and then heat-treated at high temperatures. X-ray diffraction and infrared thermograph were used to analyze the effects of Ba2+/Fe3+ incorporating on the lattice distortion of cordierite and resultant changes in infrared radiance properties. Based on the results of X-ray phase analysis and radiance measurement of the scale-up prepared samples, the optimal Ba2+ and Fe3+ co-adding amount was determined to be 5%Ba2+ plus 10%Fe3+. Moreover, the infrared emissivity of the optimal composition at 100 C was found to be higher than 0.8 in a wide wavelength range of 5-24 ?m. The research work demonstrates a promising application of Ba2+/Fe3+ cordierite solid solution as a kind of infrared heating materials for energy saving.

  10. Half-metallic Fe2CrSi and non-magnetic Cu2CrAl Heusler alloys for current-perpendicular-to-plane giant magneto-resistance: First principle and experimental study

    NASA Astrophysics Data System (ADS)

    Ko, V.; Qiu, J.; Luo, P.; Han, G. C.; Feng, Y. P.

    2011-04-01

    We present results of our first principle and experimental study on new Heusler alloys candidates for half-metallic electrode and nonmagnetic spacer in current-perpendicular-to-plane giant magneto-resistance devices. The electronic structures of Fe2CrSi and Cu2CrAl are characterized by high density of states at the Fermi level in the majority spin band with a good match in their majority band structures near the Fermi level. The calculated interfacial spin polarization in Fe2CrSi/Cu2CrAl (100) superlattice is 80%. We have also epitaxially grown ferromagnetic A2 Fe-Cr-Si and nonmagnetic L21 Cu-Cr-Al (100) films on Cr-buffered MgO(100) substrates.

  11. 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 [School of Materials Science and Engineering, Jinan University, 106 Jiwei Road, Jinan 250022 (China); Zhang Zhonghua [Key Laboratory of Liquid Structure and Heredity of Materials, Ministry of Education, Shandong University, 73 Jingshi Road, Jinan 250061 (China)]. E-mail: zh_zhang@sdu.edu.cn; Geng Haoran [School of Materials Science and Engineering, Jinan University, 106 Jiwei Road, Jinan 250022 (China); Yang Zhongxi [School of Materials Science and Engineering, Jinan University, 106 Jiwei Road, Jinan 250022 (China)

    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}.

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

    SciTech Connect

    Belmeguenai, M., E-mail: belmeguenai.mohamed@univ-paris13.fr; Tuzcuoglu, H.; Zighem, F.; Chrif, S. M.; Moch, P. [LSPM (CNRS-UPR 3407), 99 avenue Jean-Baptiste Clment, Universit Paris 13, 93430 Villetaneuse (France); Gabor, M. S., E-mail: mihai.gabor@phys.utcluj.ro; Petrisor, T. [Center for Superconductivity, Spintronics and Surface Science, Technical University of Cluj-Napoca, Str. Memorandumului No. 28 RO-400114 Cluj-Napoca (Romania); Tiusan, C. [Center for Superconductivity, Spintronics and Surface Science, Technical University of Cluj-Napoca, Str. Memorandumului No. 28 RO-400114 Cluj-Napoca (Romania); Institut Jean Lamour, CNRS, Universit de Nancy, BP 70239, F54506 Vandoeuvre (France)

    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)

  13. Modelling Equilibrium and Fractional Crystallization in the System MgO-FeO-CaO-Al2O3-SiO2

    NASA Technical Reports Server (NTRS)

    Herbert, F.

    1985-01-01

    A mathematical modelling technique for use in petrogenesis calculations in the system MgO-FeO-CaO-Al2O3-SiO2 is reported. Semiempirical phase boundary and elemental distribution information was combined with mass balance to compute approximate equilibrium crystallization paths for arbitrary system compositions. The calculation is applicable to a range of system compositions and fractionation calculations are possible. The goal of the calculation is the computation of the composition and quantity of each phase present as a function of the degree of solidification. The degree of solidification is parameterized by the heat released by the solidifying phases. The mathematical requirement for the solution of this problem is: (1) An equation constraining the composition of the magma for each solid phase in equilibrium with the liquidus phase, and (2) an equation for each solid phase and each component giving the distribution of that element between that phase and the magma.

  14. 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) , b = 18.0457(3) ; c = 9.8684(2) , ? = 90.016(2), ? = 105.543(4), ? = 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| > 3?( 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.

  15. Vacuum Carbothermic Reduction of Al2O3, BeO, MgO-CaO, TiO2, ZrO2, HfO2+ZrO2, SiO2, SiO2+Fe2O3, and GeO2 to the Metals. A Thermodynamic Study

    Microsoft Academic Search

    M. Halmann; A. Frei; A. Steinfeld

    2011-01-01

    Thermochemical equilibrium calculations are carried out to elucidate improved conditions for the production of Al, Si, FeSi, Ti, Mg, Hf, Zr, Be, and Ge by the high-temperature carbothermic reduction of their oxides, and for the production of Mg by the silicothermic reduction of MgOCaO. The onset temperature for the formation of free Al, Be, Si, Ti, Mg, Hf, and Zr

  16. Mineral contents of some southern Italian wines I. Determination of B, Al, Si, Ti, V, Cr, Mn, Fe, Ni, Cu, Zn, Mo, Sn, Pb by inductively coupled plasma atomic emission spectrometry (ICP-AES)

    Microsoft Academic Search

    Francesco S. Interesse; Francesco Lamparelli; Vincenzo Alloggio

    1984-01-01

    Zusammeufassung Unter Anwendung emer neuen analytischen Methode, ICP Atomemissions-Spektrometrie, wurden in 51 Rot- und Ros-D.O.C.-Weinen aus Sditalien, die folgenden 14 Elemente bestimmt: B, Al, Si, Ti, V, Cr, Mn, Fe, Ni, Cu, Zn, Mo, Sn, Pb.

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

    NASA Astrophysics Data System (ADS)

    Luiggi Agreda, Ney Jos

    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 ?-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 ? 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 Sestk-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.

  18. 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.

  19. 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 (-), ? = 1.94(1), ? = 2.020(15), ? = 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)?4.06(Fe{0.53/2+}Mn0.38Mg0.08)?0.99(Ti2.44Fe{0.80/3+}Al0.62Nb0.07)?3.93Si4.04O22. 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) , ? = 113.64(1); V = 832.2(2) 3, Z = 2. The strong reflections in the X-ray powder diffraction pattern are [ d, ( 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.

  20. Menzerite-(Y) a New Species {(Y REE)(Ca Fe2plus)2}[(Mg Fe2plus)(Fe3plus Al)](Si3)O12 from a Felsic Granulite Parry Sound Ontario and a New Garnet End-member (Y2Ca)Mg2(SiO4)3

    SciTech Connect

    E Grew; J Marsh; M Yates; B Lazic; T Armbruster; A Locock; S Bell; M Dyar; H Bernhardt; O Medenbach

    2011-12-31

    Menzerite-(Y), a new mineral species, forms reddish brown cores, n = 1.844 (20), up to 70 {micro}m across, rimmed successively by euhedral almandine containing up to 2.7 wt% Y{sub 2}O{sub 3} and by K-feldspar in a felsic granulite on Bonnet Island in the interior Parry Sound domain, Grenville Orogenic Province, Canada. It is named after Georg Menzer (1897-1989), the German crystallographer who solved the crystal structure of garnet. Single-crystal X-ray-diffraction results yielded space group Ia3d, a = 11.9947(6) {angstrom}. An electron-microprobe analysis of the grain richest in Y (16.93 wt% Y{sub 2}O{sub 3}) gave the following formula, normalized to eight cations and 12 oxygen atoms: {l_brace}Y{sub 0.83}Gd{sub 0.01}Dy{sub 0.05}Ho{sub 0.02}Er{sub 0.07}Tm{sub 0.01}Yb{sub 0.06}Lu{sub 0.02}Ca{sub 1.37}Fe{sub 0.49}{sup 2+}Mn{sub 0.07}{r_brace} [Mg{sub 0.55}Fe{sub 0.42}{sup 2+}Fe{sub 0.58}{sup 3+}Al{sub 0.35} V{sub 0.01}Sc{sub 0.01}Ti{sub 0.08}](Si{sub 2.82}Al{sub 0.18})O{sub 12}, or {l_brace}(Y,REE)(Ca,Fe{sup 2+}){sub 2}{r_brace}[(Mg,Fe{sup 2+})(Fe{sup 3+},Al)](Si{sub 3})O{sub 12}. Synchrotron micro-XANES data gave Fe{sup 3+}/{Sigma}Fe = 0.56(10) versus 0.39(2) calculated from stoichiometry. The scattering power refined at the octahedral Y site, 17.68 epfu, indicates that a relatively light element contributes to its occupancy. Magnesium, as determined by electron-microprobe analyses, would be a proper candidate. In addition, considering the complex occupancy of this site, the average Y-O bond length of 2.0244(16) {angstrom} is in accord with a partial occupancy by Mg. The dominance of divalent cations with Mg > Fe{sup 2+} and the absence of Si at the octahedral Y site (in square brackets) are the primary criteria for distinguishing menzerite-(Y) from other silicate garnet species; the menzerite-(Y) end-member is {l_brace}Y{sub 2}Ca{r_brace}[Mg{sub 2}](Si{sub 3})O{sub 12}. The contacts of menzerite-(Y) with almandine are generally sharp and, in places, cuspate. It is interpreted to have equilibrated with ferrosilite, augite, quartz, oligoclase, allanite-(Ce), magnetite, ilmenite and fluorapatite, in the absence of almandine, on the prograde path at 7-8.5 kbar and T {approx} 700-800 C, and subsequently dissolved incongruently in an anatectic melt to form almandine, most likely, at P {approx} 8.5-9.5 kbar and T {approx} 800-850 C.

  1. Magnetic and optical investigation of 40SiO230Na2O1Al2O3(29 - x)B2O3xFe2O3 glass matrix

    NASA Astrophysics Data System (ADS)

    Dantas, Noelio O.; Ayta, Walter E. F.; Silva, Anielle C. A.; Cano, Nilo F.; Rodriguez, Anselmo F. R.; Oliveira, Aderbal C.; Garg, Vijayendra K.; Morais, Paulo C.

    2012-08-01

    Samples of 40SiO230Na2O1Al2O3(29 - x)B2O3xFe2O3 (mol%), with 0.0 ? x ? 17.5, were prepared by the fusion method and investigated by electron paramagnetic resonance (EPR), optical absorption (OA) and Mssbauer spectroscopy (MS). The EPR spectra of the as-synthesized samples exhibit two well-defined EPR signals around g = 4.27 and g = 2.01 and a visible EPR shoulder around g = 6.4, assigned to isolated Fe3+ ion complexes (g = 4.27 and g = 6.4) and Fe3+-based clusters (g = 2.01). Analyses of both EPR line intensity and line width support the model picture of Fe3+-based clusters built in from two sources of isolated ions, namely Fe2+ and Fe3+; the ferrous ion being used to build in iron-based clusters at lower x-content (below about x = 2.5%) whereas the ferric ion is used to build in iron-based clusters at higher x-content (above about x = 2.5%). The presence of Fe2+ ions incorporated within the glass template is supported by OA data with a strong band around 1100 nm due to the spin-allowed 5Eg-5T2g transition in an octahedral coordination with oxygen. Additionally, Mssbauer data (isomer shift and quadrupole splitting) confirm incorporation of both Fe2+ and Fe3+ ions within the template, more likely in tetrahedral-like environments. We hypothesize that ferrous ions are incorporated within the glass template as FeO4 complex resulting from replacing silicon in non-bridging oxygen (SiO3O-) sites whereas ferric ions are incorporated as FeO4 complex resulting from replacing silicon in bridging-like oxygen silicate groups (SiO4).

  2. 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.

  3. Pressure effect on the electronic structure of iron in (Mg,Fe)(Si,Al)O 3 perovskite: a combined synchrotron Mssbauer and X-ray emission spectroscopy study up to 100GPa

    Microsoft Academic Search

    J. Li; W. Sturhahn; J. M. Jackson; V. V. Struzhkin; J. F. Lin; J. Zhao; H. K. Mao; G. Shen

    2006-01-01

    We investigated the valence state and spin state of iron in an Al-bearing ferromagnesian silicate perovskite sample with the composition (Mg0.88Fe0.09)(Si0.94Al0.10)O3 between 1 bar and 100GPa and at 300K, using diamond cells and synchrotron Mssbauer spectroscopy techniques. At pressures below 12GPa, our Mssbauer spectra can be sufficiently fitted by a two-doublet model, which assumes one ferrous Fe2+-like site and one

  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. Neutron activation cross-section measurements from 16 to 20 MeV for isotopes of F, Na, Mg, Al, Si, P, Cl, Ti, V, Mn, Fe, Nb, Sn, and Ba

    Microsoft Academic Search

    A. Fessler; A. J. M. Plompen; D. L. Smith; J. W. Meadows; Y. Ikeda

    2000-01-01

    Cross sections have been measured with the activation technique at various neutron energies in the range of 16.0 to 20.5 MeV for the following 22 reactions: ¹⁹F(n,p)¹⁹O, ²³Na(n,p)²³Ne, ²³Na(n,α)²°F, ²⁵Mg(n,p)²⁵Na, ²⁷Al(n,p)²⁷Mg, ²⁸Si(n,p)²⁸Al, ²⁹Si(n,p)²⁹Al, ²⁹Si(n,np + pn + d)²⁸Al, ³¹P(n,α)²⁸Al, ³⁵Cl(n,2n){sup 34m}Cl, ³⁷Cl(n,p)³⁷S, ⁴⁶Ti(n,p){sup 46m}Sc, ⁵°Ti(n,p){sup 50g+m}Sc, ⁵¹V(n,p)⁵¹Ti, ⁵⁵Mn(n,α)⁵²V, ⁵⁶Fe(n,p)⁵⁶Mn, ⁵⁷Fe(n,np + pm + d)⁵⁶Mn, ⁵⁷Fe(n,p)⁵⁷Mn, ⁹³Nb(n,α){sup 90m}Y, ⁹³Nb(n,2n){sup 92m}Nb, ¹¹⁹Sn(n,p){sup

  6. Effects of intercritical annealing temperature on mechanical properties of Fe-7.9Mn-0.14Si-0.05Al-0.07C steel

    SciTech Connect

    Zhao, Xianming [Northeastern Univ., Shenyang (China); Shen, Yongfeng [Northeastern Univ., Shenyang (China); Qiu, Lina [Northeastern Univ., Shenyang (China); Liu, Yandong [Northeastern Univ., Shenyang (China); Sun, Xin [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Zuo, Liang [Northeastern Univ., Shenyang (China)

    2014-12-01

    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?/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 (50200 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.

  7. 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.

  8. The influence of SiC particulates on fatigue crack propagation in a rapidly solidified Al-Fe-V-Si alloy

    SciTech Connect

    Sutherland, T.J. (Chevron USA Products Co., Richmond, CA (United States)); Hoffman, P.B.; Gibeling, J.C. (Univ. of California, Davis, CA (United States). Division of Materials Science and Engineering)

    1994-11-01

    The fatigue crack propagation properties of a rapidly solidified aluminum alloy are compared with those of a metal matrix composite (MMC) made of the same base alloy with the addition of 11.5 vol pct SiC particulate. The high-temperature base material, alloy 8009 produced by Allied-Signal, Inc. (Morristown, NJ), is solidified and processed using powder metallurgy techniques; these techniques yield a fine-grained, nonequilibrium microstructure. A direct comparison between the fatigue crack propagation properties of the reinforced and unreinforced materials is possible, because alloy 8009 requires no postprocessing heat treatment. As a consequence, this comparison reflects the influence of the SiC particulate and not differences in microstructure that could arise during processing and aging. The experimental data demonstrate that the SiC-reinforced material exhibits modestly superior fatigue crack propagation properties: slower crack growth rates for a given [Delta]K, a near-threshold crack growth rates. Even when the data are corrected for crack closure using an effective stress intensity factor, [Delta]K[sub eff], the composite exhibits lower crack propagation rates than the unreinforced matrix alloy. Microscopic evidence shows a rougher fracture surface and a more tortuous crack path in the composite than in the base alloy. It is argued that the lower crack growth rates and higher intrinsic threshold stress intensity factor observed in the composite are associated with crack deflection around SiC particles.

  9. The influence of SiC particulates on fatigue crack propagation in a rapidly solidified Al-Fe-V-Si alloy

    NASA Astrophysics Data System (ADS)

    Sutherland, T. J.; Hoffman, P. B.; Gibeling, J. C.

    1994-11-01

    The fatigue crack propagation properties of a rapidly solidified aluminum alloy are compared with those of a metal matrix composite (MMC) made of the same base alloy with the addition of 11.5 vol pct SiC particulate. The high-temperature base material, alloy 8009 produced by Allied-Signal, Inc. (Morristown, NJ), is solidified and processed using powder metallurgy techniques; these techniques yield a fine-grained, nonequilibrium microstructure. A direct comparison between the fatigue crack propagation properties of the reinforced and unreinforced materials is possible, because alloy 8009 requires no postprocessing heat treatment. As a consequence, this comparison reflects the influence of the SiC particulate and not differences in microstructure that could arise during processing and aging. The experimental data demonstrate that the SiC-reinforced material exhibits modestly superior fatigue crack propagation properties: slower crack growth rates for a given ?K, at near-threshold crack growth rates. Even when the data are corrected for crack closure using an effective stress intensity factor, ?Keff, the composite exhibits lower crack propagation rates than the unreinforced matrix alloy. Microscopic evidence shows a rougher fracture surface and a more tortuous crack path in the composite than in the base alloy. It is argued that the lower crack growth rates and higher intrinsic threshold stress intensity factor observed in the composite are associated with crack deflection around SiC particles.

  10. The influence of SiC particulates on fatigue crack propagation in a rapidly solidified Al-Fe-V-Si alloy

    Microsoft Academic Search

    T. J. Sutherland; P. B. Hoffman; J. C. Gibeling

    1994-01-01

    The fatigue crack propagation properties of a rapidly solidified aluminum alloy are compared with those of a metal matrix\\u000a composite (MMC) made of the same base alloy with the addition of 11.5 vol pct SiC particulate. The high-temperature base material,\\u000a alloy 8009 produced by Allied-Signal, Inc. (Morristown, NJ), is solidified and processed using powder metallurgy techniques;\\u000a these techniques yield a

  11. 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. [Department of Physics, University of Science and Technology Beijing, Beijing, 100083 (China); Shi, S. Q. [Department of Mechanical Engineering, Hong Kong Polytechnic University, Hung Hom, Kowloon (Hong Kong); Chen, L. Q. [Department of Materials Science and Engineering, Pennsylvania State University, University Park, Pennsylvania 16802 (United States)

    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.

  12. Microstructures and mechanical properties of dispersion-strengthened high-temperature Al8.5Fe1.2V-1.7Si alloys produced by atomized melt deposition process

    Microsoft Academic Search

    S. Hariprasad; S. M. L. Sastry; K. L. Jerina; R. J. Lederich

    1993-01-01

    Dispersion-strengthened high-temperature Al-8.5 pct Fe-pct Si-pct V alloys were produced by atomized melt deposition (AMD) process. The effects of process parameters on the evolution of microstructures were determined using optical metallography and scanning and transmission electron microscopy. The extent of undercooling and the rate of droplet solidification were correlated with process parameters, such as melt superheat, metal\\/gas flow rates, and

  13. Spin-Dependent Transport For Magnetite (Fe3O4) Thin Films On SiO2Glass, MgO And MgAl2O4 Substrates

    Microsoft Academic Search

    H. Kobori; D. Shimizu; A. Yamasaki; A. Sugimura; T. Taniguchi; H. Kawanaka; A. Ando; T. Shimizu

    2008-01-01

    Spin-dependent-transport was studied for magnetite (Fe3O4) thin films on SiO2-glass, MgO (100) and MgAl2O4 (100) single crystal substrates prepared by RF-magnetron sputtering. The magnetite thin film was found to be composed of nano-sized grains. The magnetoresistance is mainly dominated by the crystallinity of the thin film rather than the grain-size.

  14. Spin-Dependent Transport For Magnetite (Fe3O4) Thin Films On SiO2-Glass, MgO And MgAl2O4 Substrates

    NASA Astrophysics Data System (ADS)

    Kobori, H.; Shimizu, D.; Yamasaki, A.; Sugimura, A.; Taniguchi, T.; Kawanaka, H.; Ando, A.; Shimizu, T.

    2008-04-01

    Spin-dependent-transport was studied for magnetite (Fe3O4) thin films on SiO2-glass, MgO (100) and MgAl2O4 (100) single crystal substrates prepared by RF-magnetron sputtering. The magnetite thin film was found to be composed of nano-sized grains. The magnetoresistance is mainly dominated by the crystallinity of the thin film rather than the grain-size.

  15. Fatigue crack growth rates and fracture toughness of rapidly solidified Al-8.5 pct Fe-1.2 pct V-1.7 pct Si alloys

    NASA Astrophysics Data System (ADS)

    Hariprasad, S.; Sastry, S. M. L.; Jerina, K. L.; Lederich, R. J.

    1994-05-01

    The room-temperature fatigue crack growth rates (FCGR) and fracture toughness were evaluated for different crack plane orientations of an Al-8.5 Pct Fe-1.2 Pct V-1.7 Pct Si alloy produced by planar flow casting (PFC) and atomized melt deposition (AMD) processes. For the alloy produced by the PFC process, properties were determined in six different orientations, including the short transverse directions S-T and S-L. Diffusion bonding and adhesive bonding methods were used to prepare specimens for determining FCGR and fracture toughness in the short transverse direction. Interparticle boundaries control fracture properties in the alloy produced by PFC. Fracture toughness of the PFC alloy varies from 13.4 MPa?m to 30.8 MPa?m, depending on the orientation of the crack plane relative to the interparticle boundaries. Fatigue crack growth resistance and fracture toughness are greater in the L-T, L-S, and T-S directions than in the T-L, S-T, and S-L orientations. The alloy produced by AMD does not exhibit anisotropy in fracture toughness and fatigue crack growth resistance in the as-deposited condition or in the extruded condition. The fracture toughness varies from 17.2 MPa?m to 18.5 MPa?m for the as-deposited condition and from 19.8 MPa?m to 21.0 MPa?m for the extruded condition. Fracture properties are controlled by intrinsic factors in the alloy produced by AMD. Fatigue crack growth rates of the AMD alloy are comparable to those of the PFC alloy in the L-T orientation. The crack propagation modes were studied by optical metallographic examination of crack-microstructure interactions and scanning electron microscopy of the fracture surfaces.

  16. Rapidly solidified NiAl and FeAl

    NASA Technical Reports Server (NTRS)

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

    1984-01-01

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

  17. AlN/Fe/AlN nanostructures for magnetooptic magnetometry

    SciTech Connect

    Likov-Jakubisov, E., E-mail: liskova@karlov.mff.cuni.cz; Vi?ovsk, . [Faculty of Mathematics and Physics, Charles University in Prague, Ke Karlovu 5, 12116 Prague 2 (Czech Republic); irok, P.; Hrabovsk, D.; Pitora, J. [Nanotechnology Center, Technical University of Ostrava, 17. listopadu 15/2172, 70833 Ostrava Poruba (Czech Republic); Harward, I.; Celinski, Z. [Center for Magnetism and Magnetic Nanostructures, University of Colorado at Colorado Springs, 1420 Austin Bluffs Pkwy., Colorado Springs, Colorado 80918 (United States)

    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.

  18. 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).

  19. Association in ternary metallic melts FeMnSi, FeCrP and FeMnP

    Microsoft Academic Search

    A. I. Zaitsev; A. D. Litvina; N. E. Shelkova; B. M. Mogutnov

    1998-01-01

    Knudsen-cell mass-spectrometry was used to investigate the thermodynamic properties of liquid alloys FeMnSi (14351809K), FeCrP (14031821K) and FeMnP (13021701K). Niobium or molybdenum double effusion cells with inner surfaces covered with ZrO2 or Al2O3 were used in the experiments. Nickel, copper, chromium or strontium fluoride served as a reference substance. The saturated vapor was found to consist mainly of atoms Fe,

  20. 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, Flvio de Andrade; Williams, Jason J.; Mller, 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.

  1. Tailoring of the structure of Fe-cationic species in Fe-ZSM-5 by distribution of Al atoms in the framework for N2O decomposition

    E-print Network

    Sklenak, Stepan

    at comparable condi- tions in high population of Fe(III)-oxo species. Fe(III)-oxo species of low nuclearity decomposition NH3-SCR-NO a b s t r a c t The heterogeneity and redox behavior of Fe-cationic species in Fe-ZSM-5 populations of close (AlSiSiAl sequences in one ring Al pairs) and far distant (single Al in different

  2. Partitioning of Si and platinum group elements between liquid and solid Fe-Si alloys

    NASA Astrophysics Data System (ADS)

    Morard, G.; Siebert, J.; Badro, J.

    2014-05-01

    Crystallization of the Earth's inner core fractionates major and minor elements between the solid and liquid metal, leaving physical and geochemical imprints on the Earth's core. For example, the density jump observed at the Inner Core Boundary (ICB) is related to the preferential partitioning of lighter elements in the liquid outer core. The fractionation of Os, Re and Pt between liquid and solid during inner core crystallization has been invoked as a process that explains the observed Os isotopic signature of mantle plume-derived lavas (Brandon et al., 1998; Brandon and Walker, 2005) in terms of core-mantle interaction. In this article we measured partitioning of Si, Os, Re and Pt between liquid and solid metal. Isobaric (2 GPa) experiments were conducted in a piston-cylinder press at temperatures between 1250 C and 1600 C in which an imposed thermal gradient through the sample provided solid-liquid coexistence in the Fe-Si system. We determined the narrow melting loop in the Fe-Si system using Si partitioning values and showed that order-disorder transition in the Fe-Si solid phases can have a large effect on Si partitioning. We also found constant partition coefficients (DOs, DPt, DRe) between liquid and solid metal, for Si concentrations ranging from 2 to 12 wt%. The compact structure of Fe-Si liquid alloys is compatible with incorporation of Si and platinum group elements (PGEs) elements precluding solid-liquid fractionation. Such phase diagram properties are relevant for other light elements such as S and C at high pressure and is not consistent with inter-elemental fractionation of PGEs during metal crystallization at Earth's inner core conditions. We therefore propose that the peculiar Os isotopic signature observed in plume-derived lavas is more likely explained by mantle source heterogeneity (Meibom et al., 2002; Baker and Krogh Jensen, 2004; Luguet et al., 2008).

  3. Thermoelectric properties of -FeSi2

    SciTech Connect

    Parker, David S [ORNL] [ORNL; Singh, David J [ORNL] [ORNL; Pandey, Tribhuwan [ORNL] [ORNL; Singh, Abhishek [Indian Institute of Science] [Indian Institute of Science

    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.

  4. Microstructures and mechanical properties of dispersion-strengthened high-temperature Al8.5Fe1.2V-1.7Si alloys produced by atomized melt deposition process

    Microsoft Academic Search

    S. Hariprasad; S. M. L. Sastry; K. L. Jerina; R. J. Lederich

    1993-01-01

    Dispersion-strengthened high-temperature Al-8.5 pct Fe-pct Si-pct V alloys were produced by atomized melt deposition (AMD)\\u000a process. The effects of process parameters on the evolution of microstructures were determined using optical metallography\\u000a and scanning and transmission electron microscopy. The extent of undercooling and the rate of droplet solidification were\\u000a correlated with process parameters, such as melt superheat, metal\\/gas flow rates, and

  5. Formation and ferromagnetic properties of FeSi thin films

    SciTech Connect

    Shin, Yooleemi; Anh Tuan, Duong; Hwang, Younghun; Viet Cuong, Tran; Cho, Sunglae [Department of Physics, University of Ulsan, Ulsan 680-749 (Korea, Republic of)

    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.

  6. 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.

    2015-05-01

    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.

  7. Tunneling magnetoresistance in Fe3Si/MgO/Fe3Si(001) magnetic tunnel junctions

    NASA Astrophysics Data System (ADS)

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

    2014-04-01

    We present a theoretical study of the tunneling magnetoresistance (TMR) and spin-polarized transport in Fe3Si/MgO/Fe3Si(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 Fe3Si electrode. From the symmetry analysis of the band structures, we found that there is no spin-polarized ?1 symmetry bands crossing the Fermi level for the cubic Fe3Si. In contrast, the tetragonal Fe3Si driven by in-plane strain reveals half-metal nature in terms of ?1 state. The giant TMR ratios are predicted for both MTJs with cubic and tetragonal Fe3Si 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 ?1 channel.

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

    SciTech Connect

    Cheng, Wei-Jen, E-mail: d9603505@mail.ntust.edu.tw; 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.

  9. Room temperature magnetoresistance in Fe3Si/CaF2/Fe3Si MTJ epitaxially grown on Si(111)

    NASA Astrophysics Data System (ADS)

    Harada, K.; Makabe, K. S.; Akinaga, H.; Suemasu, T.

    2011-01-01

    A tunnel magnetoresistance has been investigated for Fe3Si/CaF2/Fe3Si magnetic tunnel junctions (MTJs). We fabricated Fe3Si(20 nm)/CaF2(2 nm)/Fe3Si(15 nm) heterostructures on a CaF2(2 nm)/Si(111) substrate by molecular beam epitaxy (MBE) and processed them into 30015 mm2-area MTJs using selective wet chemical etching and conventional photolithography. The current-voltage (J-V) characteristics for the MTJs measured at room temperature (RT) were well fitted to Simmons' equation. The fitting yields the barrier height phi = 2.5 eV and the barrier thickness d = 1.26 nm. The magnetoresistance curve for the MTJs reaches a maximum in the range of 100-200 Oe and the magnetoresistance ratio is approximately 0.28% under a bias voltage of 20 mV at RT.

  10. Anomalous exchange bias of the bottom NiFe layer in NiFe\\/FeMn\\/Al\\/NiFe

    Microsoft Academic Search

    S. M. Yoon; J. J. Lim; Y. W. Lee; V. K. Sankaranarayanan; C. G. Kim; C. O. Kim

    2004-01-01

    The exchange bias of the bottom NiFe layer in NiFe(3 nm)\\/FeMn(8 nm)\\/Al(t)\\/NiFe(t) prepared by rf magnetron sputtering has been investigated as a function of the thickness of the top NiFe and Al layers, where the NiFe and Al thicknesses were varied from 3 to 24 nm and from 0.3 to 2 nm, respectively. The exchange bias of the top NiFe

  11. Elasticity of AlFeO3 and FeAlO3 perovskite and postperovskite from firstprinciples calculations

    E-print Network

    Paris-Sud XI, Universit de

    Elasticity of AlFeO3 and FeAlO3 perovskite and postperovskite from firstprinciples calculations R constants tensor of perovskite and postperovskite with formulas AlFeO3 and FeAlO3 in which Fe or Al perovskite and postperovskite is associated with a site exchange, during which Fe from the interoctahedral

  12. The nature of the FeAl3 liquid-(FeMn)Al6

    Microsoft Academic Search

    W. T. Denholm; J. D. Esdaile; N. G. Siviour; B. W. Wilson

    1987-01-01

    Crystallization studies using an inverted L pattern of liquid aluminum alloys of compositions just to the right of the ternary point, and the application of a theoretical analysis of the behavior of a hypothetical system, show that the FeAl3-(FeMn)Al6-liquid reaction is peritectic close to the ternary point, and that the invariant reaction is eutectic, i.e., L = FeAl3 + (FeMn)Al6

  13. The melting and phase relations of Fe-Ni and Fe-Ni-Si alloys up to 100 GPa

    NASA Astrophysics Data System (ADS)

    Takahata, A.; Ohtani, E.; Kamada, S.; Sakamaki, T.; Hirao, N.

    2013-12-01

    The existence of density deficit in the Earth's core has been proposed based on comparison of seismic data with the density of FeNi alloys, and Si is considered to be one of the major candidates for the light elements in the core (e.g., Birch, 1952). The phase relations in the Fe-Si system have been studied by some authors, and several polymorphs such as hcp phase, fcc phase, B2 phase, and bcc phase have been reported to date in the Fe-Si alloy system (e.g., Lin et al., 2002; Kuwayama and Hirose, 2004; Asanuma et al., 2008; Kuwayama et al., 2009). However the stability fields of these phases are not consistent among these studies. Kuwayama et al. (2009) reported that the stable phases changed with compositions from hcp + fcc phases for Fe-6.4 wt% Si to hcp + B2 phases for Fe-9.9 wt% Si at 65 GPa. On the other hand, Asanuma et al. (2008) reported that the stability field of hcp and fcc phases extended up to about 115 GPa for Fe-3.4 wt% Si. In this study we determined the phase and melting relations in Ni bearing Fe-4.0 wt% Si alloys. The melting and phase relations of Fe-Ni and Fe-Ni-Si alloys were studied using a double sided laser-heated diamond anvil cell up to about 100 GPa. The starting alloys are Fe-4.8 wt% Ni-4.0 wt% Si and Fe-5.2 wt% Ni alloys. The melting temperatures of Fe-4.8 wt% Ni-4.0 wt% Si and Fe-5.2 wt% Ni alloys were determined up to 70 GPa and 100 GPa respectively based on a discontinuity in a laser power and temperature relations during heating. Observation of the quenched texture was also conducted to determine melting in some runs. Both melting curves of Fe-Ni-Si and Fe-Ni alloys are very close with each other up to about 100 GPa and can be fitted to Simon's equation TM = T0 ((PM - P0)/a + 1)1/c, where P0 = 0, T0 = 1741 K, a = 67 39 GPa, and c = 1.2 0.5 for Fe-Ni-Si alloys, and P0 = 0, T0 = 1791 K, a = 85 22 GPa, and c = 1.1 0.2 for Fe-Ni alloys. The phase relations of Fe-4.8 wt% Ni-4.0 wt% Si alloys were studied by in situ X-ray diffraction in the pressure and temperature ranges of 50-100 GPa and 1500-3200 K. The hcp phase was observed in all pressure and temperature conditions studied. Coexistence of hcp and fcc phases were observed in some P-T conditions and the stability field of the coexistence was narrower than that of the Fe-Si system reported by Asanuma et al. (2008).

  14. A Thermodynamic Model of Phosphorus Distribution Ratio between CaO-SiO 2 -MgO-FeO-Fe 2 O 3 -MnO-Al 2 O 3 -P 2 O 5 Slags and Molten Steel during a TopBottom Combined Blown Converter Steelmaking Process Based on the Ion and Molecule Coexistence Theory

    Microsoft Academic Search

    Xue-Min Yang; Jian-Ping Duan; Cheng-Bin Shi; Meng Zhang; Yong-Liang Zhang; Jian-Chang Wang

    2011-01-01

    A thermodynamic model for calculating the phosphorus distribution ratio between topbottom combined blown converter steelmaking\\u000a slags and molten steel has been developed by coupling with a developed thermodynamic model for calculating mass action concentrations\\u000a of structural units in the slags, i.e., CaO-SiO2-MgO-FeO-Fe2O3-MnO-Al2O3-P2O5 slags, based on the ion and molecule coexistence theory (IMCT). Not only the total phosphorus distribution ratio but

  15. Experimental kerma coefficients and dose distributions of C, N, O, Mg, Al, Si, Fe, Zr, A-150 plastic, Al203, AlN, SiO2 and ZrO2 for neutron energies up to 66 MeV.

    PubMed

    Schrewe, U J; Newhauser, W D; Brede, H J; DeLuca, P M

    2000-03-01

    Low-pressure proportional counters (LPPCs) with walls made from the elements C, Mg, Al, Si, Fe and Zr and from the chemical compounds A-150 plastic, AlN, Al2O3, SiO2 and ZrO2 were used to measure neutron fluence-to-kerma conversion coefficients at energies up to 66 MeV. The LPPCs served to measure the absorbed dose deposited in the gas of a cavity surrounded by the counter walls that could be converted to the absorbed dose to the wall on the basis of the Bragg-Gray cavity theory. Numerically the absorbed doses to the walls were almost equal to the corresponding kerma values of the wall materials. The neutron fluence was determined by various experimental methods based on the reference cross sections of the 1H(n, p) scattering and/or the 238U(n, f) reactions. The measurements were performed in monoenergetic neutron fields of energies of 5 MeV, 8 MeV, 15 MeV and 17 MeV and in polyenergetic neutron beams with prominent peaks of energies of 34 MeV, 44 MeV and 66 MeV. For the measurements in the polyenergetic neutron beams, significant corrections for the contributions of the non peak energy neutrons were applied. The fluence-to kerma conversion coefficients of N and O were determined using the difference technique applied with matched pairs of LPPCs made from a chemical compound and a pure element. This paper reports experimental fluence-to-kerma conversion coefficient values of eight elements and four compounds measured for seven neutron energies, and presents a comparison with data from previous measurements and theoretical predictions. The distributions of the absorbed dose as a function of the lineal energy were measured for monoenergetic neutrons or, for polyenergetic neutron fields, deduced by applying iterative unfolding procedures in order to subtract the contributions from non-peak energy neutrons. The dose distributions provide insight into the neutron interaction processes. PMID:10730963

  16. The welding characteristics of Fe30Mn6Si and Fe30Mn6Si5Cr shape memory alloys

    Microsoft Academic Search

    H. C. Lin; K. M. Lin; Y. C. Chuang; T. S. Chou

    2000-01-01

    After tungsten-inert gas (TIG) and laser welding, the microstructure, shape memory effect and chemical corrosion resistance of Fe30Mn6Si and Fe30Mn6Si5Cr shape memory alloys have been investigated. Experimental results show that the dendrite structures in the laser-welded zones are finer than in the TIG-welded zones for both Fe30Mn6Si and Fe30Mn6Si5Cr specimens. The Mn content in the TIG-welded zone of Fe30Mn6Si specimen

  17. Iron low-temperature self-diffusion in Fe-1. 82 wt. % Si bicrystal

    SciTech Connect

    Cermak, J.; Pavlovsky, J. (Academy of Sciences of the Czech Republic, Brno (Czech Republic). Inst. of Physics of Materials); Lejcek, P. (Academy of Sciences of the Czech Republic, Prague (Czech Republic). Inst. of Physics)

    1994-10-01

    Structural and chemical characteristics of grain boundaries (GB's) have been studied very intensely in recent years. Due to variations of these characteristics with GB orientation and with the misorientation of adjoining grains, it is desirable to investigate individual GB's with known orientation in well-characterized bicrystals. In this way, various GB properties of Fe-Si alloys were studied in a series of papers devoted to GB structure, segregation and intergranular corrosion. Another one of the phenomena that may contribute to the general understanding of GB structure is GB diffusion. Data on GB diffusion in Fe-Si model alloys were reported in several papers. For example, Teheux et al. measured the diffusivity of iron in polycrystals with varying Si content whereas Haynes and Smoluchowski studied an orientation dependence of Fe penetration depth in Fe-Si bicrystals and Shvindlerman et al. investigated Zn heterodiffusion in Fe-2.58 wt% Si bicrystal. The diffusion of iron in monocrystalline Fe-Si alloys has been studied. In the present work, the diffusion of iron isotope [sup 59]Fe was studied in a bicrystal of an Fe-1.82 wt.% Si alloy.

  18. Dry sliding wear behaviour of Al12Si and Al12Si3Cu cast alloys

    Microsoft Academic Search

    K. G. Basavakumar; P. G. Mukunda; M. Chakraborty

    2009-01-01

    This paper attempts to investigate the influence of the microstructural changes on the dry sliding wear behaviour of Al12Si and Al12Si3Cu cast alloys by grain refinement (Al1Ti3B), modification (Al10Sr) and combined action of both (Al1Ti3B+Al10Sr). Results indicate that combined grain refined and modified Al12Si3Cu cast alloys have microstructures consisting of uniformly distributed ?-Al grains, eutectic Alsilicon and fine CuAl2 particles

  19. Structure and electronic properties of FeSi2

    NASA Astrophysics Data System (ADS)

    Clark, S. J.; Al-Allak, H. M.; Brand, S.; Abram, R. A.

    1998-10-01

    The nature of the band gap in the semiconducting material ?-FeSi2 is still under some dispute. Although most experimental results indicate the band gap to be direct, ab initio work generally reports the material to be an indirect semiconductor with the direct transition a few tens of millielectron volts higher than the indirect gap. However, ?-FeSi2 is commonly grown epitaxially on a diamond-structure Si substrate, and as a consequence, the ?-FeSi2 unit cell is strained. Here we report the results of ab initio density-functional calculations, which we have performed on ?-FeSi2 where its lattice parameters are constrained according to the heteroepitaxial system ?-FeSi2(100)/Si(001). This forms two types of lattice matching: (A) ?-FeSi2[010]\\|\\|Si<110> and (B) ?-FeSi2[010]\\|\\|Si<001>. We find that the ?-FeSi2 band gap is highly sensitive to its lattice parameters and therefore to the orientation at which the material is grown on silicon. We find that type A favors a more direct band gap, while type B has an indirect gap.

  20. 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

  1. New approximant phases in AlCrFe

    Microsoft Academic Search

    V Demange; J. S Wu; V Brien; F Machizaud; J. M Dubois

    2000-01-01

    Recently, new approximant phases were pointed out in the AlCrFe system, namely orthorhombic O-AlCrFe, hexagonal H-AlCrFe and monoclinic M-AlCrFe. In the corresponding analysed samples, the new approximant phases were always coexisting with metallic aluminium. We have studied the AlCrFe system within a broad composition range. In one alloy with composition Al81Cr11Fe8, two new crystalline approximants of the decagonal phase were

  2. 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.

  3. The nature of the FeAl 3 liquid-(FeMn)Al 6

    Microsoft Academic Search

    W. T. Denholm; J. D. Esdaile; N. G. Siviour; B. W. Wilson

    1987-01-01

    Crystallization studies using an invertedL pattern of liquid aluminum alloys of compositions just to the right of the ternary point, and the application of a theoretical\\u000a analysis of the behavior of a hypothetical system, show that the FeAl3-(FeMn)Al6-liquid reaction is peritectic close to the ternary point, and that the invariant reaction is eutectic,i.e., L = FeAl3 + (FeMn)Al6 + Al(C).

  4. Anomalous exchange bias of the bottom NiFe layer in NiFe/FeMn/Al/NiFe

    NASA Astrophysics Data System (ADS)

    Yoon, S. M.; Lim, J. J.; Lee, Y. W.; Sankaranarayanan, V. K.; Kim, C. G.; Kim, C. O.

    2004-06-01

    The exchange bias of the bottom NiFe layer in NiFe(3 nm)/FeMn(8 nm)/Al(t)/NiFe(t) prepared by rf magnetron sputtering has been investigated as a function of the thickness of the top NiFe and Al layers, where the NiFe and Al thicknesses were varied from 3 to 24 nm and from 0.3 to 2 nm, respectively. The exchange bias of the top NiFe layer is negligible when the Al thickness is larger than 0.3 nm. As the top NiFe thickness increases for a constant Al thickness of 1 nm, the exchange bias of the bottom layer increases from 21.2 to 228.8 Oe for a NiFe thickness of 12 nm, and then decreases with NiFe thickness. An exchange bias of 69.8 Oe for an Al thickness of 0.3 nm increases to 228 Oe on increasing the Al thickness up to 1 nm, and decreases with a further increase of Al thickness. The exchange bias of the bottom NiFe layer could be induced by the interfacial coupling between the bottom NiFe and FeMn layers, but this coupling is strongly dependent on the Al and top NiFe thicknesses, also revealing an anomalous character in the exchange bias of the bottom NiFe layer.

  5. ?-FeSi2 films prepared on 6H-SiC substrates by magnetron sputtering

    NASA Astrophysics Data System (ADS)

    Hong, Li; Hongbin, Pu; Chunlei, Zheng; Zhiming, Chen

    2015-06-01

    ?-FeSi2 thin films have been successfully prepared by magnetron sputtering and post rapid thermal annealing method on 6H-SiC (0001) substrates using a FeSi2 target and a Si target. X-ray diffraction (XRD) and Raman spectroscopy are applied to analyze the formation of ?-FeSi2 films. XRD spectra reveal that the amorphous FeSi2 films are transformed to ?-FeSi2 phase as the annealing temperature is increased from 500 to 900 C for 5 min and the optimal annealing temperature is 900 C. The formation of ?-FeSi2 is also confirmed by Raman spectroscopy. Scanning electron microscope (SEM) observations indicate that the film is flat, relatively compact and the interface between ?-FeSi2 and 6H-SiC is clear. Atomic force microscope (AFM) measurements demonstrate that the surface roughness confirmed by the root mean square (RMS) of the ?-FeSi2 film is 0.87 nm. Near-infrared spectrophotometer observation shows that the absorption coefficient is of the order of 105 cm?1 and the optical band-gap of the ?-FeSi2 film is 0.88 eV. The ?-FeSi2 film with high crystal quality is fabricated by co-sputtering a FeSi2 target and a Si target for 60 min and annealing at 900 C for 5 min. Project supported by the National Natural Science Foundation of China (No. 51177134) and the Natural Science Basic Research Plan in Shaanxi Province of China (No. 2015JM6286).

  6. Luminescence properties of Si-capped ?-FeSi{sub 2} nanodots epitaxially grown on Si(001) and (111) substrates

    SciTech Connect

    Amari, Shogo; Ichikawa, Masakazu [Department of Applied Physics, Graduate School of Engineering, The University of Tokyo, Bunkyo-ku, Tokyo 113-8656 (Japan); Nakamura, Yoshiaki, E-mail: nakamura@ee.es.osaka-u.ac.jp [Graduate School of Engineering Science, Osaka University, 1-3 Machikaneyama-cho, Toyonaka, Osaka 560-8531 (Japan); PRESTO, JST, 4-1-8 Honcho Kawaguchi, Saitama 332-0012 (Japan)

    2014-02-28

    We studied the luminescence properties of Si-capped ?-FeSi{sub 2} nanodots (NDs) epitaxially grown on Si substrates by using photoluminescence (PL) and electroluminescence (EL) spectroscopies. Codepositing Fe and Si on ultrathin SiO{sub 2} films induced the self-assembly of epitaxial ?-FeSi{sub 2} NDs. The PL spectra of the Si/?-FeSi{sub 2} NDs/Si structure depended on the crystal orientation of the Si substrate. These structures exhibited a broad PL peak near 0.8?eV on both Si(001) and (111) substrates. The PL intensity depended on the shape of the ?-FeSi{sub 2} NDs. For the flat NDs, which exhibited higher PL intensity, we also recorded EL spectra. We explained the luminescence properties of these structures by the presence of nanostructured Si offering radiative electronic states in the Si cap layers, generated by nano-stressors for upper Si layer: the strain-relaxed ?-FeSi{sub 2} NDs.

  7. Luminescence properties of Si-capped ?-FeSi2 nanodots epitaxially grown on Si(001) and (111) substrates

    NASA Astrophysics Data System (ADS)

    Amari, Shogo; Nakamura, Yoshiaki; Ichikawa, Masakazu

    2014-02-01

    We studied the luminescence properties of Si-capped ?-FeSi2 nanodots (NDs) epitaxially grown on Si substrates by using photoluminescence (PL) and electroluminescence (EL) spectroscopies. Codepositing Fe and Si on ultrathin SiO2 films induced the self-assembly of epitaxial ?-FeSi2 NDs. The PL spectra of the Si/?-FeSi2 NDs/Si structure depended on the crystal orientation of the Si substrate. These structures exhibited a broad PL peak near 0.8 eV on both Si(001) and (111) substrates. The PL intensity depended on the shape of the ?-FeSi2 NDs. For the flat NDs, which exhibited higher PL intensity, we also recorded EL spectra. We explained the luminescence properties of these structures by the presence of nanostructured Si offering radiative electronic states in the Si cap layers, generated by nano-stressors for upper Si layer: the strain-relaxed ?-FeSi2 NDs.

  8. 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].

  9. The nature of the FeAl3 liquid-(FeMn)Al6 reaction in the Al-Fe-Mn system

    NASA Astrophysics Data System (ADS)

    Denholm, W. T.; Esdaile, J. D.; Siviour, N. G.; Wilson, B. W.

    1987-03-01

    Crystallization studies using an inverted L pattern of liquid aluminum alloys of compositions just to the right of the ternary point, and the application of a theoretical analysis of the behavior of a hypothetical system, show that the FeAl3-(FeMn)Al6-liquid reaction is peritectic close to the ternary point, and that the invariant reaction is eutectic, i.e., L = FeAl3 + (FeMn)Al6 + Al( C).

  10. Glassy ferromagnetism in Al-doped 4H-SiC: AlSi-V complexes

    NASA Astrophysics Data System (ADS)

    Yang, Mao; Shi, Jun-jie

    2010-07-01

    The recent observed glassy ferromagnetism in Al-doped 4 H-SiC is investigated using first principles calculations. We find that the formation energy of V is significantly reduced by Al atoms doped in SiC. The Al Si- V complex induces a half-filled narrow a level in the band gap and contributes a net local moment of 1 ?. The exchange parameter J can be either positive or negative along different directions. Both the strong anisotropy of J and the correlation effects of the a level can lead to a glassy ferromagnetism in Al-doped 4 H-SiC.

  11. A Sulfide Capacity Prediction Model of CaO-SiO2-MgO-FeO-MnO-Al2O3 Slags during the LF Refining Process Based on the Ion and Molecule Coexistence Theory

    NASA Astrophysics Data System (ADS)

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

    2012-04-01

    A sulfide capacity prediction model of CaO-SiO2-MgO-FeO-MnO-Al2O3 ladle furnace (LF) refining slags has been developed based on the ion and molecule coexistence theory (IMCT). The predicted sulfide capacity of the LF refining slags has better accuracy than the measured sulfide capacity of the slags at the middle and final stages during the LF refining process. Increasing slag binary basicity, optical basicity, and the Mannesmann index can lead to an increase of the predicted sulfide capacity for the LF refining slags as well as to an increase of the sulfur distribution ratio between the slags and molten steel at the middle and final stages during the LF refining process. The calculated equilibrium mole numbers, mass action concentrations of structural units or ion couples, rather than mass percentages of components, are recommended to represent the slag composition for correlating with the sulfide capacity of the slags. The developed sulfide capacity IMCT model can calculate not only the total sulfide capacity of the slags but also the respective sulfide capacity of free CaO, MgO, FeO, and MnO in the slags. The comprehensive contribution of the combined ion couples (Ca2+ + O2-) and (Mn2+ + O2-) on the desulfurization reactions accounts for 96.23 pct; meanwhile, the average contribution of the ion couple (Fe2+ + O2-) and (Mg2+ + O2-) only has a negligible contribution as 3.13 pct and 0.25 pct during the LF refining process, respectively. The oxygen activity of bulk molten steel in LF is controlled by the [Al]-[O] equilibrium, and the oxygen activity of molten steel at the slag-metal interface is controlled by the (FeO)-[O] equilibrium. The ratio of the oxygen activity of molten steel at the slag-metal interface to the oxygen activity of bulk molten steel will decrease from 37 to 5 at the initial stage, and further decrease from 28 to 4 at the middle stage, but will maintain at a reliable constant as 5 to 14 at the final stage during the LF refining process. The proposed high-oxygen potential layer of molten steel beneath the slag-metal interface can be quantitatively verified.

  12. Inverse TMR in a nominally symmetric CoFe/AlOx/CoFe junction induced by interfacial Fe3O4 investigated by STEM-EELS

    NASA Astrophysics Data System (ADS)

    Shi, Fengyuan; Xiang, Hua; Yang, J. Joshua; Rzchowski, M. S.; Chang, Y. A.; Voyles, P. M.

    2012-05-01

    We have found inverse tunneling magnetoresistance (TMR) with a non-symmetric bias voltage dependence in a nominally symmetric Si (001)/Ag/CoFe/AlOx/CoFe/IrMn/Ag magnetic tunnel junction after field cooling. The O K edge fine structure extracted from electron energy loss spectroscopy spectrum images taken at the interfaces of junctions with inverse TMR shows a thin, discontinuous Fe3O4 layer at the CoFe/AlOx interfaces. The Fe L2,3 edge core level shifts are also consistent with those of Fe3O4. We find no Fe3O4 layer in junctions with normal TMR. We believe this Fe3O4 layer is responsible for the inverse TMR.

  13. Mechanosynthesis of nanocrystalline fayalite, Fe2SiO4.

    PubMed

    epelk, Vladimir; Myndyk, Maxym; Fabin, Martin; Da Silva, Klebson L; Feldhoff, Armin; Menzel, Dirk; Ghafari, Mohammad; Hahn, Horst; Heitjans, Paul; Becker, Klaus D

    2012-11-21

    Nanostructured fayalite (?-Fe(2)SiO(4)) with a large volume fraction of interfaces is synthesized for the first time via single-step mechanosynthesis, starting from a 2?-Fe(2)O(3) + 2Fe + 3SiO(2) mixture. The nonequilibrium state of the as-prepared silicate is characterized by the presence of deformed polyhedra in the interface/surface regions of nanoparticles. PMID:23042410

  14. A nuclear magnetic resonance probe of Fe-Al and Al20V2Eu intermetallics

    E-print Network

    Chi, Ji

    2009-05-15

    Al-rich Fe-Al systems (FeAl2, Fe2 Al5 and Fe4Al13) and Al20V2Eu have complicated structures with quasicrystal-like features making these materials potentially of interest for magnetic behavior. However, there is not much work on these materials...

  15. Electrochemical measurement of the free energy of almandine (Fe sub 3 Al sub 2 Si sub 3 O sub 12 ) garnet

    SciTech Connect

    Woodland, A.B.; Wood, B.J. (Northwestern Univ., Evanston, IL (USA))

    1989-09-01

    The free energy of the reaction which creates almandine has been measured electrochemically between 1,073 and 1,173 K at 1 atmosphere pressure. In the experimental temperature range this result is in excellent agreement with data obtained from studies of garnet-rutile-sillimanite-ilmenite-quartz (GRAIL) equilibrium and for Fe-Mg partitioning between garnet and olivine. It is also in good agreement with recently published estimates based on other phase equilibrium data. The measured f{sub O{sub 2}} for GISQ equilibrium was found to increase with increasing cell edge of the synthetic almandine. The above value is for almandine with a{sub 0} = 11.527 ({plus minus}0.001) {angstrom}. Almandine with a cell edge of 11.534 {angstrom} gave f{sub O{sub 2}} values about 0.3 log units more oxidized. This increase in f{sub O{sub 2}} correlates with increasing Fe{sup +3} of the synthetic garnet. {sup 57}Fe Moessbauer spectroscopy indicates that between 3 and 6 percent of the iron is Fe{sup +3} in the high cell-edge material, whereas almandine with a{sub 0} = 11.527 {angstrom} is essentially ferric-free.

  16. Fe-Si-Mn-oxyhydroxide encrustations on basalts at east pacific rise near 13N: An SEM-EDS study

    NASA Astrophysics Data System (ADS)

    Wang, Xiaoyuan; Zeng, Zhigang; Qi, Haiyan; Chen, Shuai; Yin, Xuebo; Yang, Baoju

    2014-12-01

    Fe-Si-Mn-oxyhydroxide encrustations at the East Pacific Rise (EPR) near 13N were analyzed using the scanning electron microscope (SEM) with an energy dispersive spectrometer (EDS). These encrustations are mainly composed of amorphous Fe-Si-Mn-oxyhydroxides forming laminated, spherical, porous aggregates with some biodetritus, anhydrite, nontronite, and feldspar particles. Anhydrite particles and nontronite crystals in the Fe-Si-Mn-oxyhydroxide encrustations imply that the Fe-Si-Mn-oxyhydroxide may have formed under relatively low- to high-temperature hydrothermal conditions. The Fe-Si-Mn-oxyhydroxide encrustations on pillow basalts are 1-2 mm thick. The growth rate of ferromanganese crusts in the survey area suggests that these encrustations are an unlikely result of hydrogenic deposition alone having a hydrothermal and (Fe/Mn ratio up to 7.7 and Fe/(Fe+Mn+Al) ratio exceeding 0.78) hydrogenic origin (0.22 Fe/Mn ratio close to the mean value of 0.7 for open-ocean seamount crusts). The varying Fe/Mn ratios indicate that the Fe-Si-Mn-oxyhydroxide encrustations have formed through several stages of seafloor hydrothermalism. It is suggested that, at the initial formation stage, dense Fe-Si-oxyhydroxides with low Mn content deposit from a relatively reducing hydrothermal fluid, and then the loose Fe-Si-Mn-oxyhydroxides deposit on the Fe-Si-oxyhydroxides. As the oxidation degree of hydrothermal fluid increases and Si-oxide is inhibited, Mn-oxide will precipitate with Fe-oxyhydroxides.

  17. 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.

  18. Formation of ferromagnetic interface between {beta}-FeSi{sub 2} and Si(111) substrate

    SciTech Connect

    Hattori, Azusa N.; Hattori, Ken; Kodama, Kenji; Hosoito, Nobuyoshi; Daimon, Hiroshi [Graduate School of Materials Science, Nara Institute of Science and Technology, Takayama 8916-5, Ikoma, Nara 630-0192 (Japan); Graduate School of Materials Science, Nara Institute of Science and Technology, Takayama 8916-5, Ikoma, Nara 630-0192 (Japan) and CREST-JST, Honcho 4-1-8, Kawaguchi, Saitama 332-0012 (Japan); Graduate School of Materials Science, Nara Institute of Science and Technology, Takayama 8916-5, Ikoma, Nara 630-0192 (Japan); Graduate School of Materials Science, Nara Institute of Science and Technology, Takayama 8916-5, Ikoma, Nara 630-0192 (Japan) and CREST-JST, Honcho 4-1-8, Kawaguchi, Saitama 332-0012 (Japan)

    2007-11-12

    Epitaxial {beta}-FeSi{sub 2} thin films were grown on Si(111)7x7 clean surfaces by solid phase epitaxy in ultrahigh vacuum: iron deposition at low temperature and subsequent annealing. We found that a ferromagnetic interface layer of iron-rich silicides forms between a {beta}-FeSi{sub 2} surface layer and a Si(111) substrate spontaneously from transmission electron microscopy observations and magnetization measurements.

  19. Interrelationship of TOC, As, Fe, Mn, Al and Si in shallow alluvial aquifers in Chapai-Nawabganj, Northwestern Bangladesh: implication for potential source of organic carbon

    Microsoft Academic Search

    A. H. M. Selim Reza; Jiin-Shuh Jean; Ming-Kuo Lee; Shang-De Luo; Jochen Bundschuh; Hong-Chun Li; Huai-Jen Yang; Chia-Chuan Liu

    2011-01-01

    Two boreholes and ten piezometers in the Ganges flood plain were drilled and installed for collecting As-rich sediments and\\u000a groundwater. Groundwater samples from the Ganges flood plain were collected for the analysis of cations (Ca2+, Mg2+, K+, Na+), anions (Cl?, NO3\\u000a ?, SO4\\u000a 2?), total organic carbon (TOC), and trace elements (As, Mn, Fe, Sr, Se, Ni, Co, Cu, Mo,

  20. Fe-implanted 6H-SiC: Direct evidence of Fe3Si nanoparticles observed by atom probe tomography and 57Fe Mssbauer spectroscopy

    NASA Astrophysics Data System (ADS)

    Diallo, M. L.; Lechevallier, L.; Fnidiki, A.; Lard, R.; Debelle, A.; Thom, L.; Viret, M.; Marteau, M.; Eyidi, D.; Declmy, A.; Cuvilly, F.; Blum, I.

    2015-05-01

    In order to understand ferromagnetic ordering in SiC-based diluted magnetic semiconductors, Fe-implanted 6H-SiC subsequently annealed was studied by Atom Probe Tomography, 57Fe Mssbauer spectroscopy and SQUID magnetometry. Thanks to its 3D imaging capabilities at the atomic scale, Atom Probe Tomography appears as the most suitable technique to investigate the Fe distribution in the 6H-SiC host semiconductor and to evidence secondary phases. This study definitely evidences the formation of Fe3Si nano-sized clusters after annealing. These clusters are unambiguously responsible for the main part of the magnetic properties observed in the annealed samples.

  1. Magnetoresistance effect in Ag-Fe3O4 and Al-Fe3O4 composite films

    Microsoft Academic Search

    Jen-Hwa Hsu; Shang-Yi Chen; Wen-Ming Chang; T. S. Jian; Ching-Ray Chang; Shan-Fan Lee

    2003-01-01

    The Agx-(Fe3O4)1-x and Agx-(Fe3O4)1-x composite films were prepared by dc sputtering on Si(100) substrates. The x-ray diffraction results show that the films contain essentially only the cubic inverse spinal phase from Fe3O4 and face-centered cubic phase from Ag or Al. The transmission electron microscopy images indicate that the metal granules are randomly distributed with Fe3O4 grains. The resistivity determined from

  2. Calculation of phase diagrams for the metastable Al-Fe phases forming in direct-chill (DC)-cast aluminum alloy ingots

    Microsoft Academic Search

    Celil A. Aliravci; Mihriban . Pekgleryz

    1998-01-01

    In direct-chill (DC)-cast 1xxx-and 5xxx-series Al sheet-ingots, the presence of mainly Fe and some Si, and cooling rates increasing from ?1 C\\/s in the ingot center to ~20 C\\/s near the surface cause the formation of metastable intermetallic Al6Fe and AlmFe compounds in addition to the stable Al3Fe, and hence the fir-tree defect. Since the Al-Fe and Al-Fe-Si phase diagrams

  3. Cross sections for the production of residual nuclides by low- and medium-energy protons from the target elements C, N, O, Mg, Al, Si, Ca, Ti, V, Mn, Fe, Co, Ni, Cu, Sr, Y, Zr, Nb, Ba and Au

    NASA Astrophysics Data System (ADS)

    Michel, R.; Bodemann, R.; Busemann, H.; Daunke, R.; Gloris, M.; Lange, H.-J.; Klug, B.; Krins, A.; Leya, I.; Lpke, M.; Neumann, S.; Reinhardt, H.; Schnatz-Bttgen, M.; Herpers, U.; Schiekel, Th.; Sudbrock, F.; Holmqvist, B.; Cond, H.; Malmborg, P.; Suter, M.; Dittrich-Hannen, B.; Kubik, P.-W.; Synal, H.-A.; Filges, D.

    1997-07-01

    Cross sections for residual nuclide production by p-induced reactions were measured from thresholds up to 2.6 GeV using accelerators at CERN/Geneve, IPN/Orsay, KFA/Jlich, LANL/Los Alamos, LNS/Saclay, PSI/Villigen, TSL/Uppsala, LUC/Louvain La Neuve. The target elements C, N, O, Mg, Al, Si, Ca, Ti, V, Mn, Fe, Co, Ni, Cu, Sr, Y, Zr, Nb, Ba and Au were investigated. Residual nuclides were measured by X- and ?-spectrometry and by Accelerator Mass Spectrometry (AMS). The measured cross sections were corrected for interfering secondary particles in experiments with primary proton energies above 200 MeV. Our consistent database covers presently ca 550 nuclear reactions and contains nearly 15000 individual cross sections of which about 10000 are reported here for the first time. They provide a basis for model calculations of the production of cosmogenic nuclides in extraterrestrial matter by solar and galactic cosmic ray protons. They are of importance for many other applications in which medium energy nuclear reactions have to be considered ranging from astrophysics over space and environmental sciences to accelerator technology and accelerator-based nuclear waste transmutation and energy amplification. The experimental data are compared with theoretical ones based on calculations using an INC/E model in form of the HETC/KFA2 code and on the hybrid model of preequilibrium reactions in form of the AREL code.>

  4. Bonding and adhesion at the SiC/Fe interface.

    PubMed

    Johnson, Donald F; Carter, Emily A

    2009-04-23

    Ceramics such as SiC have the potential to act as protective coatings, primarily due to their high melting points and wear resistance. We use periodic density functional theory (DFT) within the generalized gradient approximation (GGA) to calculate the adhesion strength between SiC and Fe, for Si- and C-terminations of SiC(100) and two surfaces of Fe: (100) and (110). We predict a maximum ideal work of adhesion of 6.51 J/m(2) at the SiC(100)/Fe(110) interface for C-Fe interfacial bonding, which is stronger than the traditional chrome coating's adherence to Fe. We characterize the interfacial bonding via local densities of states and electron density difference analysis and find strong covalent bonding and some evidence of metallic bonding between Si (C) and Fe. Our results suggest that SiC might prove useful as a thin adhesion layer in a multilayer protective coating for steel. PMID:19284747

  5. Boron strengthening in FeAl

    SciTech Connect

    Baker, I.; Li, X.; Xiao, H.; Klein, O.; Nelson, C. [Dartmouth Coll., Hanover, NH (United States). Thayer School of Engineering; Carleton, R.L.; George, E.P. [Oak Ridge National Lab., TN (United States). Metals and Ceramics Div.

    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.

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

    PubMed Central

    2013-01-01

    The possibility of a new technique for fabricating nanoparticles from thin films using selective oxidation in an atmosphere mixture of water vapor and hydrogen was investigated. Fe-5wt.%Al films were RF-sputtered and annealed in the atmosphere mixture at 900C for up to 200 min, in order to oxidize aluminum selectively. Thermodynamics simulation showed that temperatures exceeding 800C are necessary to prevent iron from being oxidized, as confirmed by the depth profile of XPS. As the annealing time increased, the morphology of the 200-nm Fe-Al films changed from the continuous to the discontinuous type; thus, particulate Fe-Al films formed after 100 min. The particulate 10- to 100-nm Fe-Al films showed super-paramagnetic behavior after the oxidation. Thus, a new technique for fabricating nanoparticles was successfully introduced using selective oxidation. PMID:23547781

  7. 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.

  8. 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.

  9. Interdiffusion in U 3Si-Al, U 3Si 2-Al, and USi-Al dispersion fuels during irradiation

    NASA Astrophysics Data System (ADS)

    Kim, Yeon Soo; Hofman, Gerard L.

    2011-03-01

    Uranium-silicide compound fuel dispersion in an Al matrix is used in research and test reactors worldwide. Interaction layer (IL) growth between fuel particles and the matrix is one of performance issues. The interaction layer growth data for U 3Si, U 3Si 2 and USi dispersions in Al were obtained from both out-of-pile and in-pile tests. The IL is dominantly U(AlSi) 3 from out-of-pile tests, but its (Al + Si)/U ratio from in-pile tests is higher than the out-of-pile data, because of amorphous behavior of the ILs. IL growth correlations were developed for U 3Si-Al and U 3Si 2-Al. The IL growth rates were dependent on the U/Si ratio of the fuel compounds. During irradiation, however, the IL growth rates did not decrease with the decreasing U/Si ratio by fission. It is reasoned that transition metal fission products in the IL compensate the loss of U atoms by providing chemical potential for Al diffusion and volume expansion by solid swelling and gas bubble swelling. The addition of Mo in U 3Si 2 reduces the IL growth rate, which is similar to that of UMo alloy dispersion in a silicon-added Al matrix.

  10. Dissimilar metal joining of aluminum alloy to galvanized steel with AlSi, AlCu, AlSiCu and ZnAl filler wires

    Microsoft Academic Search

    Honggang Dong; Wenjin Hu; Yuping Duan; Xudong Wang; Chuang Dong

    Aluminum alloy sheets were lap joined to galvanized steel sheets by gas tungsten arc welding (GTAW) with Al5% Si, Al12% Si, Al6% Cu, Al10% Si4% Cu and Zn15% Al filler wires. Different amounts of Si, Cu and Zn were introduced into the weld through different filler wires. The effects of alloying elements on the microstructure in the weld and tensile

  11. 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.

  12. The post-spinel transition in Fe3O4-Fe2SiO4 and Fe3O4- FeCr2O4 solid solutions

    NASA Astrophysics Data System (ADS)

    Woodland, Alan; Schollenbruch, Klaus; Frost, Daniel; Langenhorst, Falko

    2010-05-01

    Minerals with spinel structure are important phases in the Earth's mantle. Both magnetite (mt, Fe3O4) and chromite (chr, FeCr2O4) are known to transform to denser orthorhombic post-spinel phases at pressures?10 GPa and ?12.5 GPa, respectively (Schollenbruch et al. 2009a; Chen et al. 2003). On the other hand, Fe2SiO4 decomposes to its constituent oxides, FeO and SiO2 at high P and no post-spinel polymorph appears to be stable (e.g. Ito & Takahashi 1989). An important question is how spinel solid solutions behave at high pressures and temperatures since such compositions are arguably more petrologically relevant. In addition, since h-Fe3O4 is apparently not quenchable, it is difficult to investigate its structure. In contrast, two high-P polymorphs of FeCr2O4-rich compositions have been found in a meteorite (Chen et al. 2003), suggesting that the addition of Cr might allow us to recover the post-spinel phase of Fe3O4-bearing compositions from experiments. Building on recent results for the Fe3O4 end member (Schollenbruch et al. 2009a, 2009b), we have begun a study of the high-pressure behaviour of solid solutions along the Fe3O4 -Fe2SiO4 and Fe3O4- FeCr2O4 joins. Multianvil experiments were performed at 10 and 13 GPa and 1200-1300C on pre-synthesised spinels with compositions 85mt-15 Fe2SiO4, 50mt-50chr and 80mt-20chr. For the Si-bearing experiments, stishovite was present in the run products. This occurrence, along with observed twinning in the Fe-oxide phase (Schollenbruch et al. 2009a) allows us to conclude that the original spinel had transformed to a high-P polymorph at a pressure and that Si is essentially excluded from this new structure. However, the powder XRD data from the run products could not be indexed either to magnetite (spinel structure) or to any other expected phase, including the known post-spinel structures. Interestingly, these are the same reflections reported by Koch et al. (2004) for an unidentified phase in their high-P (> 9 GPa) syntheses in the system Fe3O4-Fe2SiO4-Mg2SiO4. In the Cr-bearing experiments, the 80mt-20chr composition produced a single phase, while the 50mt-50chr composition yielded several phases. In all samples, the same set of diffraction peaks found in the Si-bearing experiments were present even though microprobe analysis revealed that all phases present contained significant Cr. A first look at the 80mt-20chr sample with TEM suggests a hexagonal structure, however, it is inconsistent with an eskolaite-hematite solid solution. Positive identification of this phase awaits further analysis. In addition to this "mystery" phase, the 50mt-50chr samples either contained a spinel or an eskolaite-hematite solid solution. Thus, Si- and Cr-bearing spinels have also been demonstrated to undergo a phase transition at essentially the same pressure as that observed for the magnetite end member (Schollenbruch et al. 2009b), however, the resulting phase appears to be different. References Chen et al. (2003) Proc Nat Acad Sci, DOI 10.1073/pnas.2136599100 Ito & Takahashi (1989) J Geophys Res, 94, 10637-10646 Koch et al. (2004) Phys Earth Planet Interiors, 143, 171-183 Schollenbruch et al. (2009a) High Pressure Research, 29, 520-524 Schollenbruch et al. (2009b) AGU abstract MR31B-1649, Fall meeting, Dec. 2009

  13. FeAI and Mo-Si-B Intermetallic Coatings Prepared by Thermal Spraying

    SciTech Connect

    Terry C. Totemeier; Richard N. Wright; W. David Swank

    2004-12-01

    FeAl and MoSiB intermetallic coatings for elevated temperature environmental resistance were prepared using high-velocity oxy-fuel (HVOF) and air plasma spray (APS) techniques. For both coating types, the effect of coating parameters (spray particle velocity and temperature) on the microstructure and physical properties of the coatings was assessed. Fe24Al (wt%) coatings were prepared using HVOF thermal spraying at spray particle velocities varying from 540 to 700 m/s. Mo13.4Si2.6B coatings were prepared using APS at particle velocities of 180 and 350 m/s. Residual stresses in the HVOF FeAl coatings were compressive, while stresses in the APS MoSiB coatings were tensile. In both cases, residual stresses became more compressive with increasing spray particle velocity due to increased peening imparted by the spray particles. The hardness and elastic moduli of FeAl coatings also increased with increasing particle velocity. For MoSiB coatings, plasma spraying at 180 m/s resulted in significant oxidation of the spray particles and conversion of the T1 phase into amorphous silica and a-Mo. The T1 phase was retained after spraying at 350 m/s.

  14. High Pressure Melting, Phase Diagrams, and Equations of State in the Fe-FeSi System with Application to Earth's Core

    NASA Astrophysics Data System (ADS)

    Fischer, R. A.; Campbell, A. J.; Reaman, D. M.; Heinz, D. L.; Dera, P. K.; Prakapenka, V.

    2012-12-01

    The Earth's core is comprised mostly of iron, with some nickel and several weight percent of one or more light elements. The light element(s) dictate phase relations, structure, and dynamic behaviour, so it is crucial to evaluate various candidates at conditions of planetary interiors. We present results on high P-T phase diagrams and equations of state in the Fe-FeSi system with application to the structure and composition of Earth's core. X-ray diffraction measurements were performed on stoichiometric FeSi and on Fe-Si alloys containing 9 and 16 wt% silicon in a laser-heated diamond anvil cell at the APS, NSLS, and ALS. Pressures were determined from the lattice parameter of KBr. We have investigated the phase diagram of Fe-9Si to 100 GPa and over 3000 K. Our melting curve agrees with previous results on similar alloys [1,2], as demonstrated using multiple methods of detecting melting. Our subsolidus results are similar to those of Lin et al. [3], though we find the B2 structure instead of bcc, and a shallower slope for the hcp+B2 to fcc+B2 boundary. We studied phase relations of Fe-16Si to over 135 GPa, finding agreement with previous melting curves [2,4]. Below 45 GPa, this alloy has the D0_3 structure. At high pressures, Fe-16Si breaks down into a mixture of B2 and hcp phases, with this mixture stable to pressures of the Earth's outer core. This is the first study on the B2 phase of FeSi with in situ X-ray diffraction at high pressures and temperatures. We report a wide B2+B20 two-phase field in FeSi, with complete conversion to the B2 structure by ~42 GPa. A melting experiment on FeSi agrees with the results of Lord et al. [5]. We have synthesized our results with previous studies to construct T-X and P-X phase diagrams, and we have determined thermal equations of state of each alloy. Our measured densities can be used to constrain the maximum amount of silicon in the Earth's outer core by comparison to the equation of state of hcp-Fe [6] and the seismologically-determined density. Assuming a core-mantle boundary (CMB) temperature of 4000 +/- 500 K and a 1-2% density decrease upon melting, the amount of silicon in the outer core required to match PREM at the CMB is 11.3 +/- 1.5 weight percent, under the simplifying assumption of a purely Fe-Ni-Si outer core. The minimum temperature of an Fe-Si outer core is 4380 K, based on the eutectic melting point of Fe-FeSi alloys, and silicon is shown not to significantly depress the melting point of iron at core conditions. 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% Si 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] Kuwayama and Hirose (2004) Am Mineral 89, 273-276 [2] Morard et al. (2011) PCM 38, 767-776 [3] Lin et al (2002) Science 295, 313-315 [4] Asanuma et al. (2010) PCM 37, 353-359 [5] Lord et al. (2010) JGR 115, B06208 [6] Dewaele et al. (2006) PRL 97, 215504

  15. Sliding wear behavior of plasma sprayed Fe 3AlAl 2O 3 graded coatings

    Microsoft Academic Search

    Jingde Zhang; Kangning Sun; Jiangting Wang; Baoyan Tian; Hongsheng Wang; Yansheng Yin

    2008-01-01

    Fe3AlAl2O3 double-layer coatings (DC), Fe3AlFe3Al\\/50%Al2O3Al2O3 triple-layer coatings (TC) and Fe3AlAl2O3 graded coatings (GC) were produced from a series of Fe3Al\\/Al2O3 composite powders with different compositions on low carbon steel substrate using PLAXAIR plasma spraying equipment. Friction behaviors and wear resistance of the three kinds of coatings have been investigated under different loads. Tests were carried out using an MRH-3 standard

  16. 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

    2015-05-01

    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.

  17. Magnetic and corrosion properties comparison of FeSi-based, FeZr-based and FeCo-based alloys

    Microsoft Academic Search

    J. E. May; C. A. C. Souza; C. L. Morelli; N. A. Mariano; S. E. Kuri

    2005-01-01

    The main reason for the study of Fe-based (FINEMET and NANOPERM) alloys was their magnetic properties. The nanocrystalline phases ?-FeSi and ?-Fe are responsible for the soft magnetic properties of FINEMET and NANOPERM alloys, respectively. A new type of amorphous and nanocrystalline FeCo-based alloy (HITPERM) has recently been produced. Its soft magnetic properties, which are attributed to the formation of

  18. 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.

  19. 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 (?30Si), 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 ?30Si values of Fe-Si co-precipitates are ~2 lower than the initial AAS (?30Siprecip-AAS = -2.13 0.18 (2?)). 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.

  20. Ultrathin Si buffer layers to improve the exchange bias between NiFe and FeMn layers

    Microsoft Academic Search

    S. Nakagawa; K. Nishimura; Y. Shimizu; M. Naoe

    1999-01-01

    Ni-Fe\\/FeMn bilayers were deposited by using dual ion beam sputtering apparatus. In order to promote (111) orientation in gamma-FeMn layers and to exhibit exchange bias field Hex, Si and\\/or silicon nitride (Si3N4) layers were deposited as buffer layers. Although silicon nitride (Si3N4) buffer layers did not improve (111) orientation in FeMn layers, as well as in Ni-Fe layers, an amorphous

  1. Improvement of crystallinity and exchange bias field in reverse type NiFe\\/FeMn bilayers using Si\\/NiFe composite type of underlayers

    Microsoft Academic Search

    S. Nakagawa; K. Nishimura; Y. Shimizu; M. Naoe

    1999-01-01

    Composite-type Si\\/Ni-Fe underlayers were examined to improve crystallinity and exchange bias characteristics of the reverse-type exchange coupled layers, such as [FeMn\\/Ni-Fe] bilayers. A Si underlayer promoted (111) texture of fcc crystallites in the initial growth region of Ni-Fe layer deposited on it. FeMn layers deposited on the Si\\/Ni-Fe bilayered underlayer exhibited excellent (111) texture of fcc crystallites. The multilayer film

  2. High-resolution nitrogen and argon adsorption on ZSM-5 zeolites: effects of cation exchange and Si Al ratio

    Microsoft Academic Search

    Akira Saito; Henry C. Foley

    1995-01-01

    ZSM-5 zeolites with SiAl ratios of 23, 72 and >400 were synthesized in the laboratory as Na+ and cation (H+, Co2+, Cu2+, Fe2+ and Zn2+)-exchanged forms and were examined by nitrogen and argon porosimetry. Na-ZSM-5 of any SiAl ratio and high-alumina ZSM-5 (SiAl=23) zeolites of any exchanged cation display single transition adsorption isotherms (type I isotherm) for both nitrogen and

  3. Effects of temperature and pressure on phonons in FeSi1xAlx

    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.

    2013-05-01

    The effects of temperature and pressure on phonons in B20 compounds FeSi1xAlx 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 Fe??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 narrowmoreband 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

  4. 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

  5. Gnterblassite, (K,Ca)3 - x Fe[(Si,Al)13O25(OH,O)4] 7H2O, a new mineral: the first phyllosilicate with triple tetrahedral layer

    NASA Astrophysics Data System (ADS)

    Chukanov, N. V.; Rastsvetaeva, R. K.; Aksenov, S. M.; Pekov, I. V.; Zubkova, N. V.; Britvin, S. N.; Belakovskiy, D. I.; Schller, W.; Ternes, B.

    2012-12-01

    A new mineral, gnterblassite, has been found in the basaltic quarry at Mount Rother Kopf near Gerolstein, Rheinland-Pfalz, Germany as a constituent of the late assemblage of nepheline, leucite, augite, phlogopite, kermanite, magnetite, perovskite, a lamprophyllite-group mineral, gtzenite, chabazite-K, chabazite-Ca, phillipsite-K, and calcite. Gnterblassite occurs as colorless lamellar crystals up to 0.2 1 1.5 mm in size and their clusters. The mineral is brittle, with perfect cleavage parallel to (001) and less perfect cleavage parallel to (100) and (010). The Mohs hardness is 4. The calculated and measured density is 2.17 and 2.18(1) g/cm3, respectively. The IR spectrum is given. The new mineral is optically biaxial and positive as follows: ? = 1.488(2), ? = 1.490(2), ? = 1.493(2), 2 V meas = 80(5). The chemical composition (electron microprobe, average of seven point analyses, H2O is determined by gas chromatography, wt %) is as follows: 0.40 Na2O, 5.18 K2O, 0.58 MgO, 3.58 CaO, 4.08 BaO, 3.06 FeO, 13.98 Al2O3, 52.94 SiO2, 15.2 H2O, and the total is 98.99. The empirical formula is Na0.15K1.24Ba0.30Ca0.72Mg0.16F{0.48/2+}[Si9.91Al3.09O25.25(OH)3.75] 7.29H2O. The crystal structure has been determined from a single crystal, R = 0.049. Gnterblassite is orthorhombic, space group Pnm21; the unit-cell dimensions are a = 6.528(1), b = 6.970(1), c = 37.216(5) , V = 1693.3(4) 3, Z = 2. Gnterblassite is a member of a new structural type; its structure is based on three-layer block [Si13O25(OH,O)4]. The strong reflections in the X-ray powder diffraction pattern [ d ( I, %) are as follows: 6.532 (100), 6.263 (67), 3.244 (49), 3.062 (91), 2.996 (66), 2.955 (63), and 2.763 (60). The mineral was named in honor of Gnter Blass (born in 1943), a well-known amateur mineralogist and specialist in electron microprobe and X-ray diffraction. The type specimen of gnterblassite is deposited in the collections of the Fersman Mineralogical Museum of the Russian Academy of Sciences, Moscow, Russia, with the registration number 4107/1.

  6. [Analysis of reaction process between Si and Fe in poly-silicic-ferric sulfate (PSF) coagulant].

    PubMed

    Fu, Ying; Yu, Shui-Li; Yang, Yuan-Jing; Lu, Yan

    2007-03-01

    A new inorganic polymer coagulant, poly-silic-ferric sulfate (PSF) with various Si/Fe ratios (PSF0.5, PSF1 and PSF denote Si/Fe molar ratios of 0.5, 1 and 3, respectively), was prepared using water glass, ferrous sulfate and sodium chlorate by co-polymerization, and pH value was measured during the preparation process. The influence of both Si/Fe ratio and reaction time (polymerization time) on the complexation process (bonding mode) between Si and Fe was explored with many analytical methods (such as X-ray diffraction (XRD), ultraviolet/visible absorption (UVA) scanning, transmission electron microscope (TEM), photon correlation spectra (PCS) and infrared spectrum (IR) using PSF samples taken from different reaction time at different Si/Fe ratios. The results show that the characteristics of PSF are largely influenced by both reaction time and Si/Fe ratios. PSF is found to be a complexation compound of Si, Fe and many other ions, instead of a simple mixture of raw materials. The complexation process between Si and Fe may be different from various Si/Fe ratios, namely, the bonding rate, bonding mode and the stability of the bond between Si and Fe are different from various Si/Fe ratios: the polymer based on Si-O-Fe-O-Fe-O-Si bond may be formed at low Si/Fe ratio, in comparison with that based on Si-O-Fe-O-Si-O-Si bond at high Si/Fe ratio; the formation rate of Fe-O-Fe bond is rapid and there may be a mutual acceleration between Fe-O-Fe bond and Si-O-Fe bond, while the formation rate of Si-O-Si is slow and maybe there is a mutual retardation between Si-O-Fe bond and Si-O-Si bond; the stability of Fe-O-Fe bond is weaker than that of Si-O-Fe or Si-O-Si bond. PMID:17633635

  7. Microstructure and properties of Al{sub 2}O{sub 3}-Al(Si) and Al{sub 2}O{sub 3}-Al(Si)-Si composites formed by in situ reaction of Al with aluminosilicate ceramics

    SciTech Connect

    Ewsuk, K.G.; Glass, S.J.; Loehman, R.E. [Sandia National Labs., Albuquerque, NM (United States); Tomsia, A.P. [Lawrence Berkeley Lab., CA (United States); Fahrenholtz, W.G. [Univ. of New Mexico, Albuquerque, NM (United States). Dept. of Chemical and Nuclear Engineering

    1996-08-01

    Al{sub 2}O{sub 3}-Al(Si) and Al{sub 2}O{sub 3}-Al(Si)-Si composites have been formed by in situ reaction of molten Al with aluminosilicate ceramics. This reactive metal penetration (RMP) process is driven by a strongly negative Gibbs energy for reaction. In the Al/mullite system, Al reduces mullite to produce {alpha}-Al{sub 2}O{sub 3} and elemental Si. With excess Al (i.e., x > 0), a composite of {alpha}-Al{sub 2}O{sub 3}, Al(Si) alloy, and Si can be formed. Ceramic-metal composites containing up to 30 vol pct Al(Si) were prepared by reacting molten Al with dense, aluminosilicate ceramic preforms or by reactively hot pressing Al and mullite powder mixtures. Both reactive metal-forming techniques produce ceramic composite bodies consisting of a fine-grained alumina skeleton with an interpenetrating Al(Si) metal phase. The rigid alumina ceramic skeletal structure dominates composite physical properties such as the Young`s modulus, hardness, and the coefficient of thermal expansion, while the interpenetrating ductile Al(Si) metal phase contributes to composite fracture toughness. Microstructural analysis of composite fracture surfaces shows evidence of ductile metal failure of Al(Si) ligaments. Al{sub 2}O{sub 3}-Al(Si) and Al{sub 2}O{sub 3}-Al(Si)-Si composites produced by in situ reaction of aluminum with mullite have improved mechanical properties and increased stiffness relative to dense mullite, and composite fracture toughness increases with increasing Al(Si) content.

  8. Systematic study of surface magnetism in Si(111)-Fe system grown by solid phase epitaxy: In situ schematic magnetic phase diagram of Si(111)-Fe

    NASA Astrophysics Data System (ADS)

    Hattori, Azusa N.; Hattori, Ken; Kataoka, Keita; Takematsu, Emi; Ishii, Akira; Komori, Fumio; Daimon, Hiroshi

    2014-08-01

    We have studied in situ structures and magnetic properties for several iron silicides grown on Si(111)77 clean surfaces by the solid phase epitaxy (SPE) method: deposition of Fe at 40 K and subsequently annealing, and summarized almost all silicide phases depending on the deposition thickness and the annealing temperature as a schematic magnetic phase diagram. In the SPE growth, bcc-Fe(111)11, c-FeSi(111)11, 22, and c(48), ?-FeSi2(112)22, ?-FeSi(111)?3 ? 3-R30, ?-FeSi2(101)/(110) and polycrystalline phases are formed on Si(111)77 surfaces depending on Fe coverage (0.15-10.0 nm) and annealing temperature (470-1070 K). The structures and magnetic properties of all the above Fe silicide phases have been characterized by using in situ reflection high-energy electron diffraction, scanning tunneling microscopy, and surface magneto-optical Kerr effect. Bulk-unstable c-FeSi phases showed ferromagnetic property at 40 K and this ferromagnetism remained even after air exposure. For the c-FeSi(111)/Si(111) system, the large spin polarization was proposed at the Fe interface atoms in the B5-type interface structure between the c-FeSi(111) ultra-thin film and the Si(111) substrate by first-principle calculations.

  9. Magnetoresistance characteristics of Fe3 Si/CaF2/Fe3 Si heterostructures grown on Si(111) by molecular beam epitaxy

    NASA Astrophysics Data System (ADS)

    Harada, K.; Makabe, K. S.; Akinaga, H.; Suemasu, T.

    Fe3 Si/CaF2/Fe3 Si magnetic tunnel junctions (MTJs) have been investigated to demonstrate the tunnel magnetoresistance effects. We fabricated Fe3 Si(20 nm)/CaF2(2 nm)/Fe3 Si(15 nm) heterostructures epitaxially on a Si(111) substrate by molecular beam epitaxy. The current-voltage characteristics for the MTJs measured at room temperature (RT) were well fitted to Simmons' equation. The fitting yields the barrier height ? = 2.5eV and the barrier thickness d = 1.26nm. The magnetoresistance ratio for the MTJs were approximately 0.28% under a bias voltage of 20mV at RT.

  10. Magnetoresistance Effect in Co2MnSi/semimetallic-Fe2VAl/CoFe Junctions

    NASA Astrophysics Data System (ADS)

    Kubota, T.; Oogane, M.; Mizukami, S.; Naganuma, H.; Ando, Y.; Miyazaki, T.

    2011-01-01

    Epitaxially grown semimetallic-Fe2VAl Heusler thin films were fabricated on single crystalline MgO (100) substrate. Crystalline structure, magnetic property, and electrical transport property of the films were investigated. Non-magnetic and bulk-like resistivity was achieved in a B2-ordred Fe2VAl film annealed at 700C. Curret-perpendicular-to-plane (CPP-) Magnetoresistance effect in Co2MnSi/Fe2VAl/CoFe junctions was also investigated. Maximum value of MR ratio was 1.1% at room temperature, which is an evidence of spin-dependent transport through Fe2VAl Heusler alloy.

  11. 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.

  12. Erosion resistance of FeAl-TiB[sub 2] and FeAl-WC at room and elevated temperatures

    SciTech Connect

    David E. Alman; Joseph H. Tylczak; Jeffrey A. Hawk

    2000-01-01

    The resistance of FeAl-40%TiB[sub 2] and FeAl-80%WC cermets to solid particle erosion at 25, 180, 500 and 700 C was evaluated and compared to the behavior of WC-6%Co (Co-90%WC) cemented carbides. Even though the WC-Co contained a higher volume fraction of the hard phase, the erosion rates of the FeAl-cermets were similar in magnitude to the erosion rates of the WC-Co. However, the erosion rates of the FeAl-cermets either were constant (FeAl-TiB[sub 2]) or decreased (FeAl-WC) with increasing test temperature; whereas, the erosion rates of the WC-Co cemented carbides increased with increasing test temperature. This indicated that once the microstructures of the FeAl-cermets are optimized for wear resistance, these materials might make promising candidates for high-temperature wear applicati2048

  13. Erosion resistance of FeAl-TiB{sub 2} and FeAl-WC at room and elevated temperatures

    SciTech Connect

    Alman, D.E.; Tylczak, J.H.; Hawk, J.A.

    2000-01-01

    The resistance of FeAl-40%TiB{sub 2} and FeAl-80%WC cermets to solid particle erosion at 25, 180, 500 and 700 C was evaluated and compared to the behavior of WC-6%Co (Co-90%WC) cemented carbides. Even though the WC-Co contained a higher volume fraction of the hard phase, the erosion rates of the FeAl-cermets were similar in magnitude to the erosion rates of the WC-Co. However, the erosion rates of the FeAl-cermets either were constant (FeAl-TiB{sub 2}) or decreased (FeAl-WC) with increasing test temperature; whereas, the erosion rates of the WC-Co cemented carbides increased with increasing test temperature. This indicated that once the microstructures of the FeAl-cermets are optimized for wear resistance, these materials might make promising candidates for high-temperature wear applications.

  14. The chemical phenol extraction of intermetallic particles from casting AlSi5Cu1Mg alloy.

    PubMed

    Mrwka-Nowotnik, G; Sieniawski, J; Nowotnik, A

    2010-03-01

    This paper presents a chemical extraction technique for determination of intermetallic phases formed in the casting AlSi5Cu1Mg aluminium alloy. Commercial aluminium alloys contain a wide range of intermetallic particles that are formed during casting, homogenization and thermomechanical processing. During solidification, particles of intermetallics are dispersed in interdendritic spaces as fine primary phases. Coarse intermetallic compounds that are formed in this aluminium alloy are characterized by unique atomic arrangement (crystallographic structure), morphology, stability, physical and mechanical properties. The volume fraction, chemistry and morphology of the intermetallics significantly affect properties and material behaviour during thermomechanical processing. Therefore, accurate determination of intermetallics is essential to understand and control microstructural evolution in Al alloys. Thus, in this paper it is shown that chemical phenol extraction method can be applied for precise qualitative evaluation. The results of optical light microscopy LOM, scanning electron microscopy SEM and X-ray diffraction XRD analysis reveal that as-cast AlSi5Cu1Mg alloy contains a wide range of intermetallic phases such as Al(4)Fe, gamma- Al(3)FeSi, alpha-Al(8)Fe(2)Si, beta-Al(5)FeSi, Al(12)FeMnSi. PMID:20500407

  15. Heteroepitaxy of ?-FeSi2 on Si by gas-source MBE

    NASA Astrophysics Data System (ADS)

    Rizzi, A.; Rsen, B. N. E.; Freundt, D.; Dieker, Ch.; Lth, H.; Gerthsen, D.

    1995-06-01

    The gas-source molecular-beam epitaxy (GSMBE) of ?-FeSi2 layers on Si(111) and Si(001) has been studied. Results from two different growth processes, depending on the choice of either SiH4 or Si2H6 as the silicon gas source, are discussed. Fe(CO)5 acts as the Fe source for the silicide growth in both processes. Concerning surface roughness, thickness uniformity, and substrate/overlayer interface sharpness, best growth temperatures are found to be from 450 to 550 C for both the SiH4 and Si2H6 GSMBE processes. In situ electron spectroscopy combined with transmission-electron-microscopy structural analysis allows the identification of the grown silicide phases; furthermore, a heavily p-type doped accumulation layer is found to form at the surface, as revealed by high-resolution electron-energy-loss spectroscopy. High defect optical absorption is measured below the edge region (Eg~0.87) and compared with common semiconductor materials. The RT electrical properties as measured by Hall effect are shown to be masked by a contribution from the substrate. At 77 K the mobility and carrier concentration of the grown ?-FeSi2 layers are ?~2 cm2/V s and p~21018 cm-3, respectively.

  16. Fe adatoms along Bi nanolines on H\\/Si(001)

    Microsoft Academic Search

    W. Orellana; R. H. Miwa

    2006-01-01

    The stability and electronic and magnetic properties of Fe atoms adsorbed on the self-assembled Bi-line nanostructure on the H\\/Si(001) surface are addressed by spin-density functional calculations. Our results show that Fe adatoms are much more stable on sites closer to the Bi nanolines suggesting that they form one-dimensional atomic arrays. The most stable structure occurs on a missing dimer line

  17. Magnetic order in DyFe 2Si 2 compound

    NASA Astrophysics Data System (ADS)

    Boure-Vigneron, F.; Pinot, M.; Go??b; , M.; Szytu?a, A.; Ole?, A.

    1990-05-01

    Neutron diffraction measurements performed on polycrystalline DyFe 2Si 2 sample (body-centered tetragonal ThCr 2Si 2 type crystal structure) indicate that the compound becomes antiferromagnetic below the Nel temperature (3.8 K). The magnetic moment alignment of Dy 3+ ions is described as a modulated structures with a wave vector k = (0.335, 0, 0.136) with ? = 7.52(5)? B at T = 1.3 K.

  18. Thin-cell technology for Li(Si)/FeS/sub 2/ thermal batteries

    SciTech Connect

    Searcy, J.Q.; Armijo, J.R.

    1982-01-01

    Sandia National Laboratories (SNL) has been developing Li(Si)/FeS/sub 2/ thermal batteries for several years as an alternative to the older Ca/CaCrO/sub 4/ system. Batteries made with Li(Si)/FeS/sub 2/ have proven to be more predictable, more reliable, more capable, and more forgiving than those using the older system. Since the voltage per cell for Ca/CaCrO/sub 4/ is about 0.5 V higher than that for Li(Si)/FeS/sub 2/, the new system requires more cells to obtain a specified voltage. Furthermore, unlike the Ca/CaCrO/sub 4/ technology, a cell in the new technology must incorporate a separator layer. Consequently, it has become necessary to develop a thin-cell technology for Li(Si)/FeS/sub 2/ thermal batteries in order to replace Ca/CaCrO/sub 4/ in applications that require small batteries. A current program to develop such a technology is summarized and battery-discharge data representative of the most recent advances are given. Although the major effort has involved Li(Si) alloy as the anode, some preliminary work has been done with Li(Al). (WHK)

  19. Time-resolved photoluminescence properties of ion-beam-synthesized ?-FeSi2 and Si-implanted Si

    NASA Astrophysics Data System (ADS)

    Terai, Yoshikazu; Maeda, Yoshihito

    2015-07-01

    Temporal decay characteristics of 1.54 m photoluminescence (PL) were investigated in ?-FeSi2 and Si-implanted Si samples grown by ion-beam-synthesis (IBS). In the samples, the band-edge PL of ?-FeSi2 (A-band) and the dislocation-related PL (D1-band) of Si were both observed at ?0.8 eV. Regarding the dependence of the PL decay curves on excitation power density (P), PL decay curves without extrinsic effects were obtained at a low P of P ? 4.3 mW/cm2. The PL decay times obtained at a low P showed clear differences between the A-band and the D1-line. The result showed that the band-edge PL of ?-FeSi2 was distinguished from the dislocation-related PL of Si by the PL decay times. The intrinsic PL decay times of ?-FeSi2 were determined to be ?1 = 70100 ns and ?2 = 550670 ns at 5 K.

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

    NASA Astrophysics Data System (ADS)

    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 d6 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 = 1.8 K). 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.

  1. 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%.

  2. Ultrasonic nanowelding of SiC microparticles on Al surface

    NASA Astrophysics Data System (ADS)

    Zhao, Bo; Wang, Yanfang; Liu, Chang; Zhang, Liying; Liu, Xuan; Zhang, Yafei

    2012-05-01

    Ultrasonic nanowelding technique was used to coat silicon carbide (SiC) particles on aluminium (Al) substrate. Both sparse SiC particles and dense particle coating layers were fabricated on Al surface. Detailed analysis shows that SiC particles are bonded and compacted well with the Al surface after the ultrasonic nanowelding process, but no structural transformation and chemical combination at the interface between SiC and Al were observed. The samples of the SiC coatings nanowelded on Al surface possess high hardness, and bigger SiC particle size results in higher hardness values. Corrosion tests reveal that the corrosion resistant properties of Al are improved with the nanowelded SiC coatings.

  3. Tribological properties of FeAl intermetallics under dry sliding

    Microsoft Academic Search

    Jun Yang; Peiqing La; Weimin Liu; Qunji Xue

    2004-01-01

    The tribological properties of FeAl intermetallics under dry sliding against AISI52100 steel at ambient conditions were studied on an Optimol SRV oscillating friction and wear tester in a ball-on-disc contact configuration. Effects of load and sliding speed on tribological properties of the FeAl intermetallics were investigated. The worn surfaces of the FeAl intermetallics were examined with a scanning electron microscopy

  4. Fe Isotopic Composition of Presolar SiC Mainstream Grains

    NASA Technical Reports Server (NTRS)

    Tripa, C. E.; Pellin, M. J.; Savina, M. R.; Davis, A. M.; Lewis, R. S.; Clayton, R. N.

    2002-01-01

    Iron isotopic distribution was measured in SiC mainstream grains from the Murchison meteorite by time-of-flight resonance ionization mass spectrometry. All grains exhibit 54Fe depletions of 50 to 200, lower than what are predicted by calculations of s-process nucleosynthesis in AGB stars. Additional information is contained in the original extended abstract.

  5. 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.

  6. 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.

  7. Growth of AlN/SiC/AlN quantum wells on Si(111) by molecular beam epitaxy

    SciTech Connect

    Cheng Yana [Department of Physics, Brown University, Providence, Rhode Island 02912 (United States); Beresford, Roderic [School of Engineering, Brown University, Providence, Rhode Island 02912 (United States)

    2012-06-04

    AlN/SiC/AlN quantum well structures have been grown on Si(111) by molecular beam epitaxy at 700 deg. C. The microstructure is single-crystal wurtzite AlN and cubic SiC with stacking sequence disorder. Depth profiles taken by Auger electron spectroscopy indicate that the ratio of Si to C is about 5:4. Layers with lower carbon content exhibit regions with five-fold superstructures. Fourier transform infrared spectroscopy confirms the presence of Al-N and Si-C bonds. Our work demonstrates the feasibility of a low-temperature synthesis route for epitaxial SiC and AlN/SiC heterostructures on Si.

  8. Effect of Introducing ?-FeSi2 Template Layers on Defect Density and Minority Carrier Diffusion Length in Si Region near p-?-FeSi2/n-Si Heterointerface

    NASA Astrophysics Data System (ADS)

    Kawakami, Hideki; Suzuno, Mitsushi; Akutsu, Keiichi; Chen, Jun; Jiptner, Karolin; Sekiguchi, Takashi; Suemasu, Takashi

    2011-04-01

    The electrical properties of defects in a p-?-FeSi2/n-Si heterostructures were investigated by deep level transient spectroscopy (DLTS) and the electron-beam-induced current (EBIC) technique. DLTS revealed the presence of trap levels for holes, caused by defects in the n-Si layer near the interface during the ?-FeSi2 film fabrication. The defect density became small when a 20-nm-thick ?-FeSi2 template layer was grown on the n-Si prior to molecular beam epitaxy (MBE) of a 700-nm-thick ?-FeSi2 layer. The diffusion length of minority carriers in the n-Si was found to be approximately 15 m by EBIC. This is much larger than the value of approximately 3 m for the n-Si obtained when the template layer was not inserted.

  9. Rectifying property and giant positive magnetoresistance of Fe3O4\\/SiO2\\/Si heterojunction

    Microsoft Academic Search

    T. L. Qu; Y. G. Zhao; H. F. Tian; C. M. Xiong; S. M. Guo; J. Q. Li

    2007-01-01

    Fe3O4\\/SiO2\\/Si heterojunction was fabricated by growing Fe3O4 film on an n-typed Si wafer with the native SiO2 buffer layer using the pulsed laser deposition. Transmission electron microcopic study shows the high quality of the heterojunction interfaces and the SiO2 layer is 2.5 nm thick. This junction shows a backward diodelike rectifying behavior and an anomalously giant positive magnetoresistance (MR) for

  10. The Correlation between Si III] 1892/ C III] 1909 and Fe II 4500/ H beta in low redshift QSOs

    E-print Network

    K. Aoki; M. Yoshida

    1998-12-19

    HST archival FOS spectra of 40 QSOs with z <= 0.5 in the Bright Quasar Survey have been analyzed. The spectra cover the region 1800-2000 A in the QSOs' rest frames, including the Al III 1859, Si III] 1892, C III] 1909, and Fe III UV34 emission-lines. We measured the flux of these UV emission-lines, and analyzed the correlations among UV and optical (H beta, Fe II, and [O III]) emission-line properties as well as soft X-ray photon indices. We found a significant correlation between Si III]/C III] and Fe II/H beta. Si III and C III have similar ionization potentials, but Si III] has one order magnitude larger critical density than C III]. Si III]/C III] is thus a density indicator and becomes larger when density is higher. The correlation between Si III]/C III] and Fe II/H beta indicates that optical Fe II becomes strong when the density of the broad line region becomes high. Our correlation analysis shows that large Si III]/C III] associates with weak [O III] 5007, large soft X-ray photon index, and narrow H beta width as well as with large Fe II/H beta. Our results support the previous suggestions that the density of the broad line region gas and the mass accretion rate govern this correlation.

  11. Pyrosmalite-(Fe), Fe8Si6O15(OH,Cl)10

    PubMed Central

    Yang, Hexiong; Downs, Robert T.; Yang, Yongbo W.; Allen, Warren H.

    2012-01-01

    Pyrosmalite-(Fe), ideally FeII 8Si6O15(OH,Cl)10 [refined composition in this study: Fe8Si6O15(OH0.814Cl0.186)100.45H2O, octairon(II) hexasilicate deca(chloride/hydroxide) 0.45-hydrate], is a phyllosilicate mineral and a member of the pyrosmalite series (Fe,Mn)8Si6O15(OH,Cl)10, which includes pyrosmalite-(Mn), as well as friedelite and mcgillite, two polytypes of pyrosmalite-(Mn). This study presents the first structure determination of pyrosmalite-(Fe) based on single-crystal X-ray diffraction data from a natural sample from Burguillos del Cerro, Badajos, Spain. Pyrosmalite-(Fe) is isotypic with pyrosmalite-(Mn) and its structure is characterized by a stacking of brucite-type layers of FeO6-octahedra alternating with sheets of SiO4 tetrahedra along [001]. These sheets consist of 12-, six- and four-membered rings of tetrahedra in a 1:2:3 ratio. In contrast to previous studies on pyrosmalite-(Mn), which all assumed that Cl and one of the four OH-groups occupy the same site, our data on pyrosmalite-(Fe) revealed a split-site structure model with Cl and OH occupying distinct sites. Furthermore, our study appears to suggest the presence of disordered structural water in pyrosmalite-(Fe), consistent with infrared spectroscopic data measured from the same sample. Weak hydrogen bonding between the ordered OH-groups that are part of the brucite-type layers and the terminal silicate O atoms is present. PMID:22259315

  12. Spin-polarized ion scattering spectroscopy study on Si/Fe(100) surfaces

    NASA Astrophysics Data System (ADS)

    Suzuki, Taku; Hishita, Shunichi

    2013-03-01

    We investigated surface magnetic structure in the initial stage of Si deposition on an Fe(100) surface by spin-polarized ion scattering spectroscopy (SP-ISS). We found silicidation at the Si/Fe interface after Si deposition followed by annealing at 823 K. The silicidation occurs by the incorporation of silicon into the Fe substrate via the substitutional site of bcc Fe. After annealing, the incorporated Si atoms are distributed in surface layers several nanometers thick. The SP-ISS analysis revealed that the average magnetic moment of Fe in the silicide surface layer is about 70% of that of Fe in the Fe(100) surface layer, whereas that of Si is almost zero. These surface magnetic moments are discussed in terms of the local magnetic environment. It is likely that the outermost surface of the silicide layer has an atomic arrangement similar to that of Fe3Si(100) with surface termination by the Fe-Si plane. We investigated surface magnetic structure in the initial stage of Si deposition on an Fe(100) surface by spin-polarized ion scattering spectroscopy (SP-ISS). We found silicidation at the Si/Fe interface after Si deposition followed by annealing at 823 K. The silicidation occurs by the incorporation of silicon into the Fe substrate via the substitutional site of bcc Fe. After annealing, the incorporated Si atoms are distributed in surface layers several nanometers thick. The SP-ISS analysis revealed that the average magnetic moment of Fe in the silicide surface layer is about 70% of that of Fe in the Fe(100) surface layer, whereas that of Si is almost zero. These surface magnetic moments are discussed in terms of the local magnetic environment. It is likely that the outermost surface of the silicide layer has an atomic arrangement similar to that of Fe3Si(100) with surface termination by the Fe-Si plane. SENTAN-JST and JSPS KAKENHI Grant Number 22760032, 24560036

  13. Melting in the system CaO-MgO-Al2O3-SiO2-FeO-Cr2O3 spanning the plagioclase-spinel lherzolite transition at 7 to 10 kbar: experiments versus thermodynamics

    NASA Astrophysics Data System (ADS)

    Keshav, S.; Tirone, M.; Gudfinnsson, G.; Presnall, D.

    2008-12-01

    Voluminous basaltic magmas erupt at mid-oceanic ridges (mid-ocean ridge basalts, MORB) as a consequence of mantle upwelling and melting beneath spreading plates. However, because the geochemistry of MORB is distinct from OIB (ocean-island basalts), both have great petrogenetic significance and carry important information about the chemical and physical properties/dynamics of the mantle. In the context of MORB, a critical yet unresolved question is how phase transitions within a polybaric melting zone affect melt productivity and thereby, possibly exert control on major and trace element composition of erupted magmas. Currently, the disagreements on these issues are fundamental, with great consequences that extend beyond petrology to global issues of potential temperatures, mantle melting, mantle heterogeneity, and mantle dynamics. Thermodynamics show that melt productivity depends critically on the transition reaction, and melting can in principle increase, decrease, or even stop at a transition. Phase equilibrium work from both systems CaO-MgO-Al2O3-SiO2-Na2O (CMASN) and CMAS-FeO (CMASF) have been used to argue that melt productivity may increase at the plagioclase-spinel (pl-sp) transition because the univariant solidus transition reaction has a positive dT/dP slope in these systems, moving to higher pressure relative to the CMAS system. However, melting models derived on the basis of MELTS and pMELTS show that the solidus has a negative slope on the pl-sp transition. If correct, this would cause suppression of melting as the mantle decompresses along a pertinent adiabat. Owing to these vast discrepancies between experiments and thermodynamics and to further clarify MORB genesis, in this work we present melting phase relations in the system CMASFCr at the plagioclase-spinel lherzolite transition from 7 to 10 kbar. Cr was chosen since recent work has shown that the addition of Cr to CMAS has an unusually large effect on Ca/Al of melt compositions at 1.1 GPa. With six phases in the system CMASFCr, melting phase relations at a given P and T are invariant, and the solidus spans a divariant surface in P-T space. At all pressures, the experiments contain ol+opx+cpx+pl+sp+melt, and completely define the transition from pl- to sp-bearing lherzolite on the solidus. The solidus at 7, 8, 9, and 10 kbar is located at 1270, 1280, 1290, and 1300 C, respectively, and is linear in P-T space. In CMASFCr, the pl-sp transition moves to lower pressures, but the solidus curve in this system overlies that of pl-lherzolite in the system CMASN. Recently developed thermodynamic database optimized for peridotite melting in the system CMASNF has been modified by removing the Na component and adding the chromite component in the spinel phase (from MELTS) and picrochromite in the melt phase (from pMELTS). While the thermodynamic model in the system CMASNF produces a solidus with a slightly negative slope in the pl+sp stability field, in the system CMASFCr the slope becomes positive, in accordance with the experimental data of this work. Both the experimental and modeling results suggest that the effect of Cr is to increase the stability of sp at lower pressure. In addition, it seems that Na in the albite component plays a major role in controlling the slope of the computed solidus for a peridotite assemblage in the pl+sp field.

  14. 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.

  15. Direct conversion of cellulose into polyols over Ni/W/SiO2-Al2O3.

    PubMed

    Baek, In Gu; You, Su Jin; Park, Eun Duck

    2012-06-01

    The direct conversion of cellulose into polyols over Ni/W/SiO(2)-Al(2)O(3) catalysts with different Al molar fractions was examined. For comparison, Cu/W/SiO(2)-Al(2)O(3), Fe/W/SiO(2)-Al(2)O(3), and Co/W/SiO(2)-Al(2)O(3) were also evaluated. The bulk crystalline structure was determined using X-ray diffraction (XRD). The surface acidity was probed via temperature-programmed desorption of ammonia (NH(3)-TPD). The textural properties were investigated using N(2) physisorption. The metal contents were confirmed via inductively coupled plasma-atomic emission spectroscopy (ICP-AES). Among the various metal catalysts, Ni/W/SiO(2)-Al(2)O(3) was confirmed to be the most favorable for hydrogenolysis of cellulose into polyols. The effect of the Al molar fraction in SiO(2)-Al(2)O(3) on this reaction over Ni/W/SiO(2)-Al(2)O(3) was also investigated. It was found that the polyol yield was closely related to the total acidity of the support. Compared to Ni/W/SBA-15, Ni/W/SiO(2)-Al(2)O(3) (Al/(Al+Si)=0.6) showed better stability during the recycling test. The catalyst deactivation was confirmed to be caused by metal leaching. PMID:22497706

  16. Theoretical and experimental analysis of Al2O3/Al-Si composites processed from Al-Si-Zn and Al-Si-Mg by direct metal oxidation

    SciTech Connect

    Khatri, S.C.; Koczak, M.J.; Chou, Tongshik; Kagawa, Yutaka

    1992-08-01

    Directed oxidation is an innovative technique for the production of ceramic/metal composites via the exposure of melts to oxidizing atmospheres at elevated temperatures. The resulting material consists of a 3D-interconnected, interpenetrating network of the oxide and metal-alloy microchannels. Experimental and theoretical attention is presently given to the case of alumina/Al-Si alloy composites of this type, where the Si content of the Al alloy varied (2, 5, and 10 wt pct). The composite's growth rates increased with increasing oxygen partial pressure for alloys with lower Si content. The higher growth rates and/or processing times led to higher porosity due to the coalescence of alumina grains. 9 refs.

  17. Crystal and quasicrystal structures in Al-Mn-Si alloys

    Microsoft Academic Search

    Veit Elser; C. L. Henley

    1985-01-01

    It is shown that the alpha-(AlMnSi) crystal structure is closely (and systematically) related to that of the icosahedral Al-Mn-Si alloys. Using a modification of the 'projection' method of generating icosahedral structures from six-dimensional lattices, a simple description of the alpha-(AlMnSi) structure is found. This structure, and (it is conjectured) the icosahedral one, can also be described as a packing of

  18. Solidification of Iron-Rich Intermetallic Phases in Al-4.5Cu-0.3Fe Cast Alloy

    NASA Astrophysics Data System (ADS)

    Liu, K.; Cao, X.; Chen, X.-G.

    2011-07-01

    The iron-rich intermetallics in A206 type cast aluminum alloy (Al-4.5Cu-0.3Fe) were investigated using thermal analysis, interrupted quenching testing, and differential scanning calorimetry (DSC). An optical microscope with image analysis and scanning electron microscopy were used to identify and quantify the iron-rich intermetallics. Basically, two kinds of iron-rich intermetallics, Chinese script Al15(FeMn)3(SiCu)2 ( ?-Fe) and platelet Al7Cu2(FeMn) or Al7Cu2Fe ( ?-Fe), are found in the final microstructures of the A206 cast alloys. All the possible solidification reactions, precipitation temperatures, and nucleation mechanisms for the iron-rich phases were investigated systematically. It is found that both ?-Fe and ?-Fe phases can precipitate on the oxide films. The ?-Fe can also nucleate on Al6(FeMnCu) and Al3Ti particles. In addition, the previously formed ?-Fe phase is also favorable for the nucleation of the ?-Fe phase formed subsequently. These nucleation events were not only observed metallographically but also supported by the calculated planar disregistries. A possible nucleation hierarchy has been suggested.

  19. Phase relations in the greenschist-blueschist-amphibolite-eclogite facies in the system Na 2 O-CaO-FeO-MgO-Al 2 O 3 SiO 2 -H 2 O (NCFMASH), with application to metamorphic rocks from Samos, Greece

    Microsoft Academic Search

    Thomas Will; Martin Okrusch; Esther Schmdicke; Guoli Chen

    1998-01-01

    Calculated phase equilibria among the minerals sodic amphibole, calcic amphibole, garnet, chloritoid, talc, chlorite, paragonite,\\u000a margarite, omphacite, plagioclase, carpholite, zoisite\\/clinozoisite, lawsonite, pyrophyllite, kyanite, sillimanite, quartz\\u000a and H2O are presented for the model system Na2O-CaO-FeO-MgO-Al2O3-SiO2-H2O (NCFMASH), which is relevant for many greenschist, blueschist, amphibolite and eclogite facies rocks. Using the activity-composition\\u000a relationships for multicomponent amphiboles constrained by Will and Powell (1992),

  20. A Thermodynamic Model of Sulfur Distribution Ratio between CaOSiO 2 MgOFeOMnOAl 2 O 3 Slags and Molten Steel during LF Refining Process Based on the Ion and Molecule Coexistence Theory

    Microsoft Academic Search

    Xue-Min Yang; Cheng-Bin Shi; Meng Zhang; Guo-Ming Chai; Fei Wang

    A thermodynamic model for calculating the sulfur distribution ratio between ladle furnace (LF) refining slags and molten steel\\u000a has been developed by coupling with a developed thermodynamic model for calculating the mass action concentrations of structural\\u000a units in LF refining slags, i.e., CaOSiO2MgOFeOMnOAl2O3 hexabasic slags, based on the ion and molecule coexistence theory (IMCT). The calculated mass action concentrations of

  1. Noncollinear magnetic structures in an Fe\\/Si\\/Fe film with a ferromagnetic interlayer exchange interaction

    Microsoft Academic Search

    A. B. Chizhik; S. L. Gnatchenko; M. Baran; K. Fronc; R. Szymczak; R. Zuberek

    2002-01-01

    Results are presented from magnetic and magnetooptical studies of the magnetic configurations in a three-layer film Fe(30 )\\/Si(14 )\\/Fe(30 ) in which ferromagnetic and biquadratic exchange between iron layers is observed and which also possesses cubic and uniaxial anisotropy. These studies were done at temperatures of 300 and 10 K. It was found that in the absence of magnetic field

  2. Epitaxial growth and magnetic properties of Fe3O4 films on TiN buffered Si(001), Si(110), and Si(111) substrates

    Microsoft Academic Search

    Hua Xiang; Fengyuan Shi; Mark S. Rzchowski; Paul M. Voyles; Y. Austin Chang

    2010-01-01

    Epitaxial Fe3O4 thin films were grown on TiN buffered Si(001), Si(110), and Si(111) substrates by dc reactive sputtering deposition. Both Fe3O4 films and TiN buffer are fully epitaxial when grown at substrate temperatures above 150 C, with textured single phase Fe3O4 resulting from room temperature growth. The initial sputtered Fe3O4 formed nuclei islands and then coalesced to epitaxial columnar grains

  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. [AECL, Chalk River, Ontario (Canada). Chalk River Labs.] [AECL, Chalk River, Ontario (Canada). Chalk River Labs.; Morris, D.G. [Univ. of Neuchatel (Switzerland). Inst. of Structural Metallurgy] [Univ. of Neuchatel (Switzerland). Inst. of Structural Metallurgy

    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. Magnetoresistance effect in Ag-Fe3O4 and Al-Fe3O4 composite films

    NASA Astrophysics Data System (ADS)

    Hsu, Jen-Hwa; Chen, Shang-Yi; Chang, Wen-Ming; Jian, T. S.; Chang, Ching-Ray; Lee, Shan-Fan

    2003-05-01

    The Agx-(Fe3O4)1-x and Agx-(Fe3O4)1-x composite films were prepared by dc sputtering on Si(100) substrates. The x-ray diffraction results show that the films contain essentially only the cubic inverse spinal phase from Fe3O4 and face-centered cubic phase from Ag or Al. The transmission electron microscopy images indicate that the metal granules are randomly distributed with Fe3O4 grains. The resistivity determined from the four-probe method decreases rapidly with increasing metal content. At x?0.5, a percolation occurs. The conducting path is formed from metal granules in series with Fe3O4 grains. The magnetoresistance (MR) is defined to be {R(H=0.8 T)-R(H=0)}/R(H=0). It has been found that MR is isotropic and the appearance of Ag granules has significant impact on the MR effect. Furthermore, a positive MR region appears with 0.011Fe3O4)1-x. On the contrary, the incorporation of Al granules does not have the same effect on MR as in Agx-(Fe3O4)1-x. A slow increase of MR with Al content might be due to Coulomb blockade. The extra contribution to MR in Agx-(Fe3O4)1-x can be attributed to spin injection from Fe3O4 into Ag granules so that spin accumulation in Ag granules impedes the current causing a larger resistance under a field.

  5. Structural evolution in mechanically alloyed Al-Fe powders

    NASA Astrophysics Data System (ADS)

    Mukhopadhyay, D. K.; Suryanarayana, C.; Froes, F. H. (Sam)

    1995-08-01

    The structural evolution in mechanically alloyed binary aluminum-iron powder mixtures containing 1, 4, 7.3, 10.7, and 25 at. pct Fe was investigated using X-ray diffraction (XRD) and electron microscopic techniques. The constitution (number and identity of phases present), microstructure (crystal size, particle size), and transformation behavior of the powders on annealing were studied. The solid solubility of Fe in Al has been extended up to at least 4.5 at. pct, which is close to that observed using rapid solidification (RS) (4.4 at. pct), compared with the equilibrium value of 0.025 at. pct Fe at room temperature. Nanometer-sized grains were observed in as-milled crystalline powders in all compositions. Increasing the ball-to-powder weight ratio (BPR) resulted in a faster rate of decrease of crystal size. A fully amorphous phase was obtained in the Al-25 at. pct Fe composition, and a mixed amorphous phase plus solid solution of Fe in Al was developed in the Al-10.7 at. pct Fe alloy, agreeing well with the predictions made using the semiempirical Miedema model. Heat treatment of the mechanically alloyed powders containing the supersaturated solid solution or the amorphous phase resulted in the formation of the Al3Fe intermetallic in all but the Al-25 at. pct Fe powders. In the Al-25 at. pct Fe powder, formation of nanocrystalline Al5Fe2 was observed directly by milling. Electron microscope studies of the shock-consolidated mechanically alloyed Al-10.7 and 25 at. pct Fe powders indicated that nanometer-sized grains were retained after compaction.

  6. Ultrathin Si buffer layers to improve the exchange bias between Ni-Fe and FeMn layers

    NASA Astrophysics Data System (ADS)

    Nakagawa, S.; Nishimura, K.; Shimizu, Y.; Naoe, M.

    1999-04-01

    Ni-Fe/FeMn bilayers were deposited by using dual ion beam sputtering apparatus. In order to promote (111) orientation in ?-FeMn layers and to exhibit exchange bias field Hex, Si and/or silicon nitride (Si3N4) layers were deposited as buffer layers. Although silicon nitride (Si3N4) buffer layers did not improve (111) orientation in FeMn layers, as well as in Ni-Fe layers, an amorphous Si buffer layer only 1 nm thick improved (111) orientation in FeMn layers and increased Hex to above 100 Oe. FeMn/Ni-Fe bilayers deposited on Si(0.5 nm)/Si3N4(1 nm) bilayered buffer layer also exhibited high Hex of about 130 Oe. This result implies that the ultrathin a-Si buffer layer was effective in improving (111) orientation in Ni-Fe layers. Very thin Si/Si3N4 bilayers may be applicable as dielectric layers in tunneling magnetoresistive spin valve devices.

  7. Chemical pressure tuning of URu2Si2 via isoelectronic substitution of Ru with Fe

    NASA Astrophysics Data System (ADS)

    Das, Pinaki; Kanchanavatee, N.; Helton, J. S.; Huang, K.; Baumbach, R. E.; Bauer, E. D.; White, B. D.; Burnett, V. W.; Maple, M. B.; Lynn, J. W.; Janoschek, M.

    2015-02-01

    We have used specific heat and neutron diffraction measurements on single crystals of URu2 -xFexSi2 for Fe concentrations x ?0.7 to establish that chemical substitution of Ru with Fe acts as "chemical pressure" Pc h as previously proposed by Kanchanavatee et al. [Phys. Rev. B 84, 245122 (2011), 10.1103/PhysRevB.84.245122] based on bulk measurements on polycrystalline samples. Notably, neutron diffraction reveals a sharp increase of the uranium magnetic moment at x =0.1 , reminiscent of the behavior at the "hidden order" to large-moment-antiferromagnetic phase transition observed at a pressure Px?0.5 -0.7 GPa in URu2Si2 . Using the unit-cell volume determined from our measurements and an isothermal compressibility ?T=5.2 10-3 GPa-1 for URu2Si2 , we determine the chemical pressure Pc h in URu2 -xFexSi2 as a function of x . The resulting temperature (T )-chemical pressure (Pc h) phase diagram for URu2 -xFexSi2 is in agreement with the established temperature (T )-external pressure (P ) phase diagram of URu2Si2 .

  8. 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.

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

    SciTech Connect

    Chaiken, A.; Michel, R.P. [Lawrence Livermore National Lab., CA (United States); Wang, C.T. [Stanford Univ., Palo Alto, CA (United States)

    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.

  10. Reciprocating Sliding Friction and Wear Property of Fe 3 Si Based Alloys Containing Cu in Water Lubrication

    Microsoft Academic Search

    Jiangang Jia; Qin Ma; Jinjun Lu; Bo Wang

    2008-01-01

    Fe3Si, Fe3Si alloys containing Cu were fabricated by arc melting followed by hot-pressing. The friction and wear behaviors of Fe3Si based alloys with and without Cu addition against Si3N4 ball in water-lubrication were investigated. The friction coefficient and the wear rates of Fe3Si based alloys decreased as the load increased. The wear rate of Fe3Si was higher than that of

  11. Combustion of the Fe-Si alloy in nitrogen gas

    Microsoft Academic Search

    L. N. Chukhlomina; Yu. M. Maksimov

    2007-01-01

    Combustion of the Fe-Si alloy in nitrogen gas was explored. The combustion was found to proceed in an autooscillating mode.\\u000a Upon addition of nitrided ferrosilicon, magnesium fluoride, or ammonium chloride into a green mixture, the process becomes\\u000a steady-state, while the extent of nitriding attains its maximum value. The phase composition and morphology of the product\\u000a were found to depend on

  12. Fe adatoms along Bi nanolines on H /Si(001)

    NASA Astrophysics Data System (ADS)

    Orellana, W.; Miwa, R. H.

    2006-08-01

    The stability and electronic and magnetic properties of Fe atoms adsorbed on the self-assembled Bi-line nanostructure on the H /Si(001) surface are addressed by spin-density functional calculations. Our results show that Fe adatoms are much more stable on sites closer to the Bi nanolines suggesting that they form one-dimensional atomic arrays. The most stable structure occurs on a missing dimer line beside the Bi dimers, which corresponds to an array with distances between Fe adatoms of about 8. In this array the irons are coupled antiferromagnetically with spin magnetic moment of about 1.5?B per Fe atom, whereas the coupling exchange interactions is found to be of about 14.4meV. We also estimate a large magnetic anisotropy energy of 3meV/at. originated on the structural anisotropy of the Fe-adatom site. In addition, the electronic band structure of the Fe array at the most stable structure shows a magnetic half-metal behavior.

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

    SciTech Connect

    Zhang Wenda, E-mail: zwdno@139.com [School of Materials Science and Engineering, North University of China, Taiyuan 030051 (China); Liu Yun, E-mail: liuyun@nuc.edu.cn [School of Materials Science and Engineering, North University of China, Taiyuan 030051 (China); Yang Jing; Dang Jinzhi; Xu Hong [School of Materials Science and Engineering, North University of China, Taiyuan 030051 (China); Du Zhenmin [School of Materials Science and Engineering, University of Science and Technology Beijing, Beijing 100083 (China)

    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.

  14. Si adatoms as catalyst for the growth of monolayer Al film on Si(111)

    NASA Astrophysics Data System (ADS)

    Teng, Jing; Zhang, Lixin; Wu, Kehui; Jiang, Ying; Guo, Jiandong; Guo, Qinlin; Ebert, Philipp; Sakurai, Toshio; Wang, Enge

    2010-03-01

    Recently, we reported the growth of atomically smooth Al(111) films on Si(111) with continuously controllable thickness down to the extreme level of 1 ML. Here, we study the underlying unexpected Si adatom-mediated clustering-melting mechanism by scanning tunneling microscopy and by the first-principles calculations. The Si adatoms in the initial Si(111)3x3-Al surface act as seeds to form SiAl2 clusters. The clusters are then transformed into Al(111)1x1 by incorporating further incoming Al atoms and spontaneously releasing the Si atoms, which then participate in the next cycle of the process. As a result, a two-dimensional growth of monolayer Al(111) is achieved.

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

    E-print Network

    Lin, Jung-Fu "Afu"

    -solution case to better understand the light- element alloying effects. Our results show that high temperature - models of Fe alloys in order to deter- mine the chemical composition of the core. Our models show), silicon (Si), sulfur (S), carbon (C), and hydrogen (H), have been suggested via cosmochemical, geo

  16. Microstructural and mechanical characterization of AlZnSi nanocomposites

    SciTech Connect

    Garca-Villarreal, S. [Centro de Investigacin en Materiales Avanzados S.C. Monterrey, 66600, Alianza Nte. 202, Parque PIIT, Apodaca, N.L. (Mexico); Chvez-Valdez, A. [Katcon Institute for Innovation and Technology KIIT, 66629, Alianza Sur 200, Apodaca, N.L. (Mexico); Moreno, K.J. [Instituto Tecnolgico de Celaya, Apartado Postal 57, 38010 Celaya, Guanajuato (Mexico); Leyva, C.; Aguilar-Martnez, J.A. [Centro de Investigacin en Materiales Avanzados S.C. Monterrey, 66600, Alianza Nte. 202, Parque PIIT, Apodaca, N.L. (Mexico); Hurtado, A. [Centro de Investigacin en Materiales Avanzados S.C., 31109, Miguel de Cervantes 120, Chih., Chih. (Mexico); Arizmendi-Morquecho, A., E-mail: ana.arizmendi@cimav.edu.mx [Centro de Investigacin en Materiales Avanzados S.C. Monterrey, 66600, Alianza Nte. 202, Parque PIIT, Apodaca, N.L. (Mexico)

    2013-09-15

    In this paper the addition of silicon nanoparticles into AlZn alloys to form metallic matrix nanocomposites by mechanical alloying process was investigated. The influence of various process parameters such as milling time and Si concentration in the AlZn matrix has an interesting effect on the microstructure and mechanical properties of the synthesized nanocomposites. The microstructural characterization of the nanocomposites was evaluated by transmission electron microscopy and energy dispersive X-ray spectroscopy (TEMEDXS) and the mechanical properties were measured by nanoindentation and micro-hardness tests. The results showed that during mechanical milling Si is added to the AlZn matrix achieving a uniform and homogeneous dispersion. After solidification, it forms small particles of AlZnSi with blocky morphology in interdendritic regions. The nanoindentation profiles showed that the elastic modulus and hardness properties increase with increasing milling time. However, a high concentration of Si (> 1.2 wt.%) results in a saturation of Si in the AlZn matrix, which adversely affects the mechanical properties. Thus, it is important to tune the milling time and concentration of Si added to the AlZn alloys to control the growth of brittle phases that result in reduction of the mechanical properties of the material. - Highlights: A novel technique for addition of Si nanocomposites into AlZn liquid alloy is reported. Good dispersion and homogeneity of Si in the AlZn matrix are obtained. Increasing Si content above 1.2 wt.% decreases the mechanical properties of AlZn alloy. The saturation point of Si in 1.2 wt.% differs from Galvalume composition. The AlZn1.5Si alloy with addition of nanocomposite shows 5.7 GPa of hardness.

  17. Anomalous antiferromagnetic coupling in Fe/Si/Fe structures with Co ``dusting''

    NASA Astrophysics Data System (ADS)

    Gareev, R. R.; Buchmeier, M.; Kiessling, M.; Woltersdorf, G.; Back, C. H.

    2011-12-01

    We report on anomalous antiferromagnetic coupling in Fe/Si/Fe epitaxial structures with interfacial cobalt "dusting". Antiferromagnetic coupling exceeds 75 ?J/m2 for a 2.0 nm-thick Si spacer and is still detectable for a 2.3 nm-thick spacer at room temperature. From room temperature to T**150K the magnetization follows Bloch's law and the coupling shows metallic-type behaviour; for lower temperatures the coupling is of insulating type. Below T*50K an additional magnetic signal arises and the coupling becomes metallic-type again. We relate the observed features to the formation of inter-diffused magnetic FeCo-silicides with a Curie temperature close to 50 K.

  18. A Thermodynamic Model of Sulfur Distribution Ratio between CaO-SiO2-MgO-FeO-MnO-Al2O3 Slags and Molten Steel during LF Refining Process Based on the Ion and Molecule Coexistence Theory

    NASA Astrophysics Data System (ADS)

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

    2011-12-01

    A thermodynamic model for calculating the sulfur distribution ratio between ladle furnace (LF) refining slags and molten steel has been developed by coupling with a developed thermodynamic model for calculating the mass action concentrations of structural units in LF refining slags, i.e., CaO-SiO2-MgO-FeO-MnO-Al2O3 hexabasic slags, based on the ion and molecule coexistence theory (IMCT). The calculated mass action concentrations of structural units in CaO-SiO2-MgO-FeO-Al2O3-MnO slags equilibrated or reacted with molten steel show that the calculated equilibrium mole numbers or mass action concentrations of structural units or ion couples, rather than mass percentage of components, in the slags can represent their reaction abilities. The calculated total sulfur distribution ratio shows a reliable agreement with the measured or the calculated sulfur distribution ratio between the slags and molten steel by other models under the condition of choosing oxygen activity based on (FeO)-[O] equilibrium. Meanwhile, the developed thermodynamic model for calculating sulfur distribution ratio can quantitatively determine the respective contribution of free CaO, MgO, FeO, and MnO in the LF refining slags. A significant difference of desulfurization ability among free component as CaO, MgO, FeO, and MnO has been found with approximately 87-93 pct, 11.43-5.85 pct, 0.81-0.60 pct and 0.30-0.27 pct at both middle and final stages during LF refining process, respectively. A large difference of oxygen activity is found in molten steel at the slag-metal interface and in bulk molten steel. The oxygen activity in molten steel at the slag-metal interface is controlled by (FeO)-[O] equilibrium, whereas the oxygen activity in bulk molten steel is controlled by [Al]-[O] equilibrium. Decreasing the high-oxygen-activity boundary layer beneath the slag-metal interface can promote the desulfurization reaction rate effectively or shorten the refining period during the LF refining process.

  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. Effect of ternary alloying elements addition on atomic ordering characteristics of Fe-Al intermetallics

    SciTech Connect

    Mekhrabov, A.O.; Akdeniz, M.V. [Middle East Technical Univ., Ankara (Turkey). Dept. of Metallurgical and Materials Engineering] [Middle East Technical Univ., Ankara (Turkey). Dept. of Metallurgical and Materials Engineering

    1999-05-28

    The energetic and structural characteristics of atomic ordering processes in Fe{sub 0.5}(Al{sub 1{minus}n}X{sub n}){sub 0.5} intermetallics have been qualitatively analyzed based on the statistico-thermodynamical theory of ordering by means of a quasi-chemical method combined with electronic theory in the pseudopotential approximation. The effects of ternary impurities on order-disorder phase transformation temperature and the characteristics of atomic short-range order in Fe-Al type intermetallics have been calculated. Impurity elements in Fe{sub 0.5}(Al{sub 1{minus}n}X{sub n}){sub 0.5} where X = Ni, Co, Mn, Cr, Ti, Si, Zr, Hf, Nb, Ta, Re, Mo or W, are considered up to 1 at.% concentration. The results of the calculation indicate that the impurity elements, X, with regard to their lattice site occupancy characteristics (SRO) can be divided into two groups: X{sub I} = Ni, Co, Mn or Cr element atoms substitute mainly for Al sublattice sites, whereas X{sub II} = Ti, Si, Zr, Hf, Nb, Ta, Re, Mo or W element atoms substitute preferentially for Fe sublattice sites in Fe{sub 0.5}(Al{sub 1{minus}n}X{sub n}){sub 0.5} intermetallics. It has been found that the absolute values of partial ordering energies of the W{sup Al-X}(R{sub 1}) and W{sup Fe-X}(R{sub 1}) have a profound effect on the order-disorder transition temperature of Fe{sub 0.5}(Al{sub 1{minus}n}X{sub n}){sub 0.5} alloys that would either increase or remain unchanged depending on the type and content of the ternary substitutional alloying elements. The impurities X = Zr, Hf, Nb, Ta, Re, Mo or W which are preferentially distributed Fe sublattice sites are more effective in increasing order-disorder transition temperature in Fe-Al(B2) intermetallics. The results of the present calculation are in good qualitative agreement with experimental observation for most of the third component impurity elements X in Fe{sub 0.5}(Al{sub 1{minus}n}X{sub n}){sub 0.5} intermetallics.

  1. Temperature dependence of the Si, Al distribution in ultramarines

    NASA Astrophysics Data System (ADS)

    Gordillo, M. C.; Herrero, C. P.

    1992-12-01

    The Si, Al ordering pattern for blue ultramarine (aluminosilicate with a ratio Si/Al ? 1) is analyzed by a Monte Carlo method. The influence of the synthesis temperature and the large extraframework anions on the Si, Al distribution is studied. It is found that a combination of both factors (especially the first) can explain the reported violation of Loewenstein's rule in this compound. A long-range disordered Si, Al distribution was observed for temperatures above 800 K, which correspond to the pyrolytic synthesis of ultramarine. For lower temperatures, corresponding to the regime of hydrothermal synthesis, strict alternation of Si and Al was found, in agreement with experimental results for lazurite, the natural counterpart of ultramarine.

  2. Strength anomaly in B2 FeAl single crystals

    SciTech Connect

    Yoshimi, K.; Hanada, S.; Yoo, M.H. [Oak Ridge National Lab., TN (United States); Matsumoto, N. [Tohoku Univ. (Japan). Graduate School

    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. Simulation of near-infrared photodiode detectors based on ?-FeSi2/4H-SiC heterojunctions

    NASA Astrophysics Data System (ADS)

    Pu, Hong-Bin; He, Xin; Quan, Ru-Dai; Cao, Lin; Chen, Zhi-Ming

    2013-03-01

    In this paper, we propose a near-infrared p-type ?-FeSi2/n-type 4H-SiC heterojunction photodetector with semiconducting silicide (?-FeSi2) as the active region for the first time. The optoelectronic characteristics of the photodetector are simulated using a commercial simulator at room temperature. The results show that the photodetector has a good rectifying character and a good response to near-infrared light. Interface states should be minimized to obtain a lower reverse leakage current. The response spectrum of the ?-FeSi2/4H-SiC detector, which consists of a p-type ?-FeSi2 absorption layer with a doping concentration of 1 1015 cm-3 and a thickness of 2.5 ?m, has a peak of 755 mA/W at 1.42 ?m. The illumination of the SiC side obtains a higher responsivity than that of the ?-FeSi2 side. The results illustrate that the ?-FeSi2/4H-SiC heterojunction can be used as a near-infrared photodetector compatible with near-infrared optically-activated SiC-based power switching devices.

  4. Epitaxial growth and magnetic properties of Fe3O4 films on TiN buffered Si(001), Si(110), and Si(111) substrates

    NASA Astrophysics Data System (ADS)

    Xiang, Hua; Shi, Fengyuan; Rzchowski, Mark S.; Voyles, Paul M.; Chang, Y. Austin

    2010-08-01

    Epitaxial Fe3O4 thin films were grown on TiN buffered Si(001), Si(110), and Si(111) substrates by dc reactive sputtering deposition. Both Fe3O4 films and TiN buffer are fully epitaxial when grown at substrate temperatures above 150 C, with textured single phase Fe3O4 resulting from room temperature growth. The initial sputtered Fe3O4 formed nuclei islands and then coalesced to epitaxial columnar grains with increasing film thickness. The magnetization decreases and the coercive field increases with decreasing film thickness. There is no in-plane magnetic anisotropy of epitaxial Fe3O4(001) on Si(001) but Fe3O4 films grown on Si(110) and Si(111) substrates show uniaxial in-plane magnetic anisotropy.

  5. Thermal stability of Al-Cu-Fe icosahedral alloys

    NASA Astrophysics Data System (ADS)

    Bessire, M.; Quivy, A.; Lefebvre, S.; Devaud-Rzepski, J.; Calvayrac, Y.

    1991-12-01

    A stable ideally quasiperiodic phase exists in a small range of concentration, close to the composition Al{62}Cu{25.5}Fe{12.5}. Reducing the iron content, or replacing small amounts of copper by aluminium, lead to icosahedral alloys which exhibit around 650 ^{circ}C structural transformations of unclear nature: in the X-ray powder diffraction pattern, the peak profiles become purely Lorentzian (Al{62.3}Cu{25.3}Fe{12.4}) or diffuse side-bands appear in the tails of the Bragg peaks (Al{63}Cu{24.5}Fe{12.5}). In the last case long annealing treatments eventually transform the Bragg peaks into diffuse peaks located at positions clearly off the ideal icosahedral symmetry. Small deviations from this composition range lead to Bragg peaks with shoulders whatever the heat-treatment may be; perfect icosahedral order is never obtained for these compositions (Al{63,25}Cu{24,5}Fe{12,25}, Al{64}Cu{24}Fe{12}, Al{63}Cu{25}Fe{12}). Une phase stable idalement quasipriodique existe dans un petit domaine de concentration, au voisinage de la composition Al{62}Cu{25,5}Fe{12,5}. La diminution de la teneur en fer, ou le remplacement de faibles quantits de cuivre par de l'aluminium, conduisent des alliages icosadriques qui subissent vers 650 ^{circ}C des transformations structurales dont la nature n'est pas clairement identifie: dans le diagramme de diffraction des rayons X sur poudre, les profils de raies deviennent purement Lorentziens (Al{62,3}Cu{25,3}Fe{12,4}) ou bien des raies diffuses apparaissent dans le pied des pics de Bragg (Al{63}Cu{24,5}Fe{12,5}). Dans ce dernier cas un long traitement de recuit transforme finalement les pics de Bragg en des pics diffus localiss des positions clairement en dehors de celles correspondant la symtrie icosadrique idale. De faibles carts ce domaine de compositions conduisent des diagrammes de rayons X o les pics de Bragg sont pauls quel que soit le traitement thermique ; l'ordre icosadrique parfait n'est jamais obtenu pour ces compositions (Al{63,25}Cu{24,5}Fe{12,25}, Al{64}Cu{24}Fe{12}, Al{63}Cu{25}Fe{12}).

  6. Dielectric properties of spark plasma sintered AlN/SiC composite ceramics

    NASA Astrophysics Data System (ADS)

    Gao, Peng; Jia, Cheng-chang; Cao, Wen-bin; Wang, Cong-cong; Liang, Dong; Xu, Guo-liang

    2014-06-01

    In this study, we have investigated how the dielectric loss tangent and permittivity of AlN ceramics are affected by factors such as powder mixing methods, milling time, sintering temperature, and the addition of a second conductive phase. All ceramic samples were prepared by spark plasma sintering (SPS) under a pressure of 30 MPa. AlN composite ceramics sintered with 30wt%-40wt% SiC at 1600C for 5 min exhibited the best dielectric loss tangent, which is greater than 0.3. In addition to AlN and ?-SiC, the samples also contained 2H-SiC and Fe5Si3, as detected by X-ray difraction (XRD). The relative densities of the sintered ceramics were higher than 93%. Experimental results indicate that nano-SiC has a strong capability of absorbing electromagnetic waves. The dielectric constant and dielectric loss of AlN-SiC ceramics with the same content of SiC decreased as the frequency of electromagnetic waves increased from 1 kHz to 1 MHz.

  7. Room Temperature Mechanical Properties of Fe3Al Intermetallic Alloys with Li and Ni Additions

    NASA Astrophysics Data System (ADS)

    Rosas, G.; Esparza, R.; Bedolla-Jacuinde, A.; Prez, R.

    2009-02-01

    This work analyzes the effect of very small additions of Li and Ni on the mechanical properties of the Fe72Al28 intermetallic alloy, close to the Fe3Al ratio. Hardness and tensile strength at room temperature were analyzed for the cast Fe3Al intermetallic alloys as a function of Li and Ni additions. For this purpose, high-purity raw materials were melted in an open induction furnace into a SiC crucible and the liquid alloys were poured into sand moulds to directly get tensile test-shaped specimens to minimize machining. Mechanical tests were carried out in the as-cast condition as well as after a homogenization heat treatment at 400 C for 120 h. The obtained microstructure was characterized by XRD and SEM. Results show an increase in ductility, particularly when Li was added.

  8. Electronic Structures of CaAlSi with Different Stacking AlSi Layers by First-Principles Calculations

    NASA Astrophysics Data System (ADS)

    Kuroiwa, Sogo; Nakashima, Akiyoshi; Miyahara, Shin; Furukawa, Nobuo; Akimitsu, Jun

    2007-11-01

    The full-potential linear augmented plane-wave calculations have been applied to investigate the systematic change of electronic structures in CaAlSi due to different stacking sequences of AlSi layers. The present ab-initio calculations have revealed that the multistacking, buckling and 60 rotation of AlSi layer affect the electronic band structure in this system. In particular, such a structural perturbation gives rise to the disconnected and cylindrical Fermi surface along the M-L lines of the hexagonal Brillouin zone. This means that multistacked CaAlSi with the buckling AlSi layers increases degree of two-dimensional electronic characters, and it gives us qualitative understanding for the quite different upper critical field anisotropy between specimens with and without superstructure as reported previously.

  9. Nucleation mechanism of nano-sized NaZn13-type and ?-(Fe,Si) phases in La-Fe-Si alloys during rapid solidification

    NASA Astrophysics Data System (ADS)

    Hou, Xue-Ling; Xue, Yun; Liu, Chun-Yu; Xu, Hui; Han, Ning; Ma, Chun-Wei; Phan, Manh-Huong

    2015-03-01

    The nucleation mechanism involving rapid solidification of undercooled La-Fe-Si melts has been studied experimentally and theoretically. The classical nucleation theory-based simulations show a competitive nucleation process between the ?-(Fe,Si) phase (size approximately 10 to 30 nm) and the cubic NaZn13-type phase (hereinafter 1:13 phase, size approximately 200 to 400 nm) during rapid solidification, and that the undercooled temperature change ? T plays an important factor in this process. The simulated results about the nucleation rates of the ?-(Fe,Si) and 1:13 phases in La-Fe-Si ribbons fabricated by a melt-spinner using a copper wheel with a surface speed of 35 m/s agree well with the XRD, SEM, and TEM studies of the phase structure and microstructure of the ribbons. Our study paves the way for designing novel La-Fe-Si materials for a wide range of technological applications.

  10. Impact of firing on surface passivation of p-Si by SiO2/Al and SiO2/SiNx/Al stacks

    NASA Astrophysics Data System (ADS)

    Chen, J.; Cornagliotti, E.; Loozen, X.; Simoen, E.; Vanhellemont, J.; Lauwaert, J.; Vrielinck, H.; Poortmans, J.

    2011-12-01

    Firing impacts on surface passivation provided by a SiO2 and SiO2/SiNx stack with evaporated Al films are studied by capacitance-based techniques on MIS capacitors. For devices with insulator layers consisting solely of as-deposited SiO2, the densities of either interface states (Dit) or fixed charges (Qfc) are hardly influenced by firing. Capping the SiO2 layer with a SiNx layer results in a shift of the peak activation energy of Dit toward the valence band (Ev) of Si. Firing this SiO2/SiNx stack leads to an increase of Qfc, a reduction of Dit, and a moderate shift of peak activation energy of Dit toward Ev. Co-firing with the Al film on top significantly reduces the Qfc, Dit, and Dit peak activation energy, which is resulting from the atomic hydrogen passivation. These results are of particular interest for the development of solar cells with rear surface passivation and local contacts.

  11. 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 ?-Al5FeSi particles, V concentrations of 600 ppm were too low to have any influence on the phase's morphology.

  12. Nanostructure and related mechanical properties of an Al-Mg-Si alloy processed by severe plastic deformation.

    E-print Network

    Paris-Sud XI, Universit de

    .15-0.4, Cr 0.15-0.35, Mn 0.15, Fe 0.7, Zn 0.25, Ti 0.15 (wt.%)), 20 mm in diameter and 150 mm in length1 Nanostructure and related mechanical properties of an Al-Mg-Si alloy processed by severe plastic and mechanical properties of an Al-Mg-Si alloy processed by high-pressure torsion have been investigated using

  13. Al-Cu-Fe-Pd-Mn and Al-Cr-Pd-Mn quasicrystalline alloys

    SciTech Connect

    Chen Zhenhua (Univ. of Technology, Hunan (China). Powder Metallurgy Research Inst.); Inoue, Akihisa; Masumoto, Tsuyoshi (Tohoku Univ. (Japan). Metal Research Inst.)

    1993-12-15

    While searching for new multicomponent quasicrystalline alloys, the authors have suggested a principle of composition activity in the quasicrystal constitution. This means that some new quasicrystals can be constituted by adding several quasicrystalline alloy compositions, and these alloys can be obtained by means of rapid solidification or ingot processing. Guided by this principle, Al-Mn-Cr, Al-Cu-Fe-Mn, Al-Cu-Fe-Cr, Al-Cu-Fe-Cr-Mn, Al-Mn-Ni-Ti, Al-Mn-Fe-Ti, Al-Cu-Fe-Ni-Ti and other multicomponent quasicrystalline alloys have been found. A recent study used Al[sub 70]Pd[sub 20]Mn[sub 10], Al[sub 65]Cu[sub 20]Fe[sub 15] and Al[sub 85]Cr[sub 15] quasicrystalline alloys to formulate new alloys. Both Al-Cu-Fe-Pd-Mn and Al-Cr-Pd-Mn alloys are quasicrystalline. In this paper, they discuss these two quasicrystals, their formation, electronic diffraction and composition scope and thermal stability in detail.

  14. Effects of Fe-enrichment on the equation of state and stability of (Mg,Fe)SiO3 perovskite

    E-print Network

    Duffy, Thomas S.

    Effects of Fe-enrichment on the equation of state and stability of (Mg,Fe)SiO3 perovskite Susannah 2012 Editor: L. Stixrude Available online 8 December 2012 Keywords: perovskite post-perovskite lower and temperatures up to 3000 K. Single- phase orthorhombic GdFeO3-type perovskite was synthesized by heating

  15. Epitaxial growth of high quality ?-FeSi 2 layers on Si(1 1 1) under the presence of an Sb flux

    Microsoft Academic Search

    Tsutomu Koga; Hirokazu Tatsuoka; Hiroshi Kuwabara

    2001-01-01

    ?-FeSi2 layers were grown on Si(111) substrates by Fe deposition and simultaneous reaction with Si under the presence of an Sb flux. High quality epitaxial layers were obtained at the substrate temperature of 650C with smooth interface between the reactive resultant ?-FeSi2 layers and Si substrates, in comparison to the layers grown by conventional reactive deposition epitaxy (RDE). Sb\\/Fe flux

  16. Melting and casting of FeAl-based cast alloy

    Microsoft Academic Search

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

    1998-01-01

    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

  17. Millimetre-size single quasicrystals in Al - Cu - Fe alloy

    Microsoft Academic Search

    T. Ishimasa; M. Mori

    1990-01-01

    Millimetre-sized grains of F-type icosahedral phase are formed in ingots of AlCuFe alloy, for which the nominal composition is Al20.41 at.% Cu13.27 at.% Fe. These grains are located in the upper half part of the ingots. The lower half does not include the icosahedral phase but ordinary crystalline phases. In order to form these grains, the following heat treatment was

  18. Amplification of magnetoresistance of magnetite in an Fe3O4SiO2Si structure

    Microsoft Academic Search

    Xianjie Wang; Yu Sui; Jinke Tang; Cong Wang; Xingquan Zhang; Zhe Lu; Zhiguo Liu; Wenhui Su; Xiankui Wei; Richeng Yu

    2008-01-01

    Film of Fe3O4 was prepared with laser molecular beam epitaxy deposition on a Si substrate with a native SiO2 layer. When the temperature is increased above 250 K, the resistance drops rapidly because the conduction path starts to switch from the Fe3O4 film to the inversion layer underneath the SiO2 via thermally assisted tunneling. A greatly magnified low field negative

  19. Temperature dependence of electroluminescence from Si-based light emitting diodes with ?-FeSi 2 particles active region

    Microsoft Academic Search

    Cheng Li; T. Suemasu; F. Hasegawa

    2006-01-01

    Electroluminescence (EL) properties of Si-based light emitting diodes with ?-FeSi2 particles active region grown by reactive deposition epitaxy are investigated. EL intensity of ?-FeSi2 particles versus excitation current densities has different behaviors at 8, 77K and room temperature, respectively. The EL peak energy shifted from 0.81 to 0.83eV at 77K with the increase of current density from 1 to 70A\\/cm2.

  20. Structure Sensitive Properties of Liquid Al-Si Alloys

    NASA Astrophysics Data System (ADS)

    Sklyarchuk, V.; Plevachuk, Yu.; Yakymovych, A.; Eckert, S.; Gerbeth, G.; Eigenfeld, K.

    2009-05-01

    Development and application of new expedient aluminum-based light alloys are a key issue in current material science. In this study measurements are presented for the thermophysical properties of liquid Al-7Si, AlSi7Mg, and AlSi8Cu3 (mass%) alloys, which are the most utilized casting alloys in the aluminum industry. Experimental data with respect to the density, viscosity, and the electrical and thermal conductivities have been determined in a wide temperature range, and corresponding fit relations have been derived. Comparisons with already published data and scaling relations available in the literature are given.

  1. Synthesis of ternary Si clathrates in the AAlSi (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.

  2. Texture development in SiC-seeded AlN

    SciTech Connect

    Sandlin, M.S.; Bowman, K.J. [Purdue Univ., West Lafayette, IN (United States). School of Materials Engineering] [Purdue Univ., West Lafayette, IN (United States). School of Materials Engineering; Root, J. [AECL Research, Chalk River, Ontario (Canada). Chalk River Labs.] [AECL Research, Chalk River, Ontario (Canada). Chalk River Labs.

    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.

  3. Investigation of primary Li-Si/FeS2 cells

    NASA Astrophysics Data System (ADS)

    Redey, L.; Smaga, J. A.; Battles, J. E.; Guidotti, R.

    1987-04-01

    The factors that limit the performance of thermally activated Li-Si/FeS2 batteries were defined through the use of electrochemical characterization tests and post-test examinations. For the characterization tests, 82 individual cells were instrumented with multiple voltage sensors and discharged under isothermal and isobaric conditions. The voltage data for the sensors were recorded to determine the ohmic and electrochemical impedances of each cell component at different levels of discharge. The data analysis completed to date has demonstrated that this approach can successfully differentiate the influence of various operating parameters (e.g., temperature, current density), electrode structures (e.g., FeS2 particle size), and additives on cell capacity, specific energy, and power capability. Thirty cells selected from these tests and additional tests at SNL were examined using optical and scanning electron microscopy, energy dispersive spectroscopy, and X-ray diffraction. These analyses documented microstructural and compositional changes in the active materials and electrolyte. In general, the electrochemical impedance of the FeS electrode limited cell performance. Several methods (including use of fine FeS2 particle size, graphite additions, and higher operating temperatures) produced measurable reductions in this impedance and yielded significant improvements in specific energy and power.

  4. Formation and Magnetic Properties of Ultrahigh Density Fe3Si Nanodots Epitaxially Grown on Si(111) Substrates Covered with Ultrathin SiO2 Films

    NASA Astrophysics Data System (ADS)

    Nakamura, Yoshiaki; Amari, Shogo; Cho, Sung-Pyo; Tanaka, Nobuo; Ichikawa, Masakazu

    2011-01-01

    The epitaxial growth technique of ultrahigh density (>1012 cm-2) Fe3Si nanodots (NDs) on Si(111) substrates was developed using an ultrathin SiO2 film technique. Low temperature (<300 C) growth of the Fe3Si NDs was needed to suppress the interdiffusion between Fe atoms deposited on the sample surface and Si atoms in the substrate. The ND shape changed drastically from sphere to discontinuous films as the Fe content was increased slightly from a stoichiometric ratio of Fe:Si of 3:1. For almost-spherical NDs with the ultrahigh density, a transition from superparamagnetism to ferromagnetism was observed at specific temperatures, the ferromagnetism of which included the magnetic dipole interactions in ultrahigh density ND system. These ND structures with ND size dependence of the coercive force were expected to be selectively used as both magnetically fixed and free layers in magnetic tunneling junction structures only by changing the ND size.

  5. 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.

  6. Understanding the magnetic anisotropy in Fe-Si amorphous alloys

    SciTech Connect

    Diaz, J.; Hamdan, N.M.; Jalil, P.; Hussain, Z.; Valvidares, S.M.; Alameda, J.M.

    2002-08-01

    The origin of the magnetic anisotropy in a very disordered Fe-Si alloy has been investigated. The alloy containing 40 percent at. Si was prepared in the form of a thin film in a DC magnetron sputtering chamber. Structural disorder was obtained from Extended X-ray Absorption Fine Structure spectroscopy. The uniformity and lack of inhomogeneities at a microscopic level was checked by measuring their transverse magnetic susceptibility and hysteresis loops. The orbital component of the magnetic moment was measured by X-ray Magnetic Circular Dichroism spectroscopy. The orbital moment was extraordinary high, 0.4mB. Such a high value contrasted with the relatively small uniaxial anisotropy energy of the thin film (2kJ/m3). This suggests that the cause of the magnetic anisotropy in this alloy was a small degree of correlation in the orientation of the local orbital moments along a preferential direction.

  7. Etching Selectivity of Cr, Fe and Ni Masks on Si & SiO2 Wafers

    NASA Astrophysics Data System (ADS)

    Garcia, Jorge; Lowndes, Douglas H.

    2000-10-01

    During this Summer 2000 I joined the Semiconductors and Thin Films group led by Dr. Douglas H. Lowndes at Oak Ridge National Laboratorys Solid State Division. Our objective was to evaluate the selectivity that Trifluoromethane (CHF3), and Sulfur Hexafluoride (SF6) plasmas have for Si, SiO2 wafers and the Ni, Cr, and Fe masks; being this etching selectivity the ratio of the etching rates of the plasmas for each of the materials. We made use of Silicon and Silicon Dioxide-coated wafers that have Fe, Cr or Ni masks. In the semiconductor field, metal layers are often used as masks to protect layers underneath during processing steps; when these wafers are taken to the dry etching process, both the wafer and the mask layers thickness are reduced.

  8. Thermal stability of TiAlN and nanocomposite TiAlSiN thin films.

    PubMed

    Yang, Sheng-Min; Chang, Yin-Yu; Lin, Dong-Yih; Wang, Da-Yung; Wu, Weite

    2009-02-01

    TiAlN and TiAlSiN coatings were synthesized by a cathodic arc deposition process. Titanium, Ti50Al50 alloy and AlSi (88 at.% of Al and 12 at.% of Si) alloy targets were adopted as the cathode materials. X-ray diffraction analyses revealed that Ti0.5Al0.5N and Ti49Al0.44Si0.07N possess a B1-NaCl crystal structure. The lattice constants of the Ti0.5Al0.5N and Ti0.49Al0.44Si0.07N calculated from XRD pattern were 0.418 nm and 0.422 nm, respectively. For the high temperature oxidation test, the coated samples were annealed at 900 degrees C in air atmosphere for 2 hours. In this study, the deposited Ti0.5Al0.5N had completely transformed to TiO2 and Al2O3, and Ti0.49Al0.44Si0.07N remained the as-deposited structure after oxidation treatment. It indicated that Ti0.49Al0.44Si0.07N possesses superior oxidation resistance than Ti0.5Al0.5N, due to the amorphous SiNx phase existed in the nanocomposite structure. The different oxidation mechanisms of Ti50Al50N and Ti0.49Al0.44Si0.07N at high temperature of 900 degrees C are developed in this study. PMID:19441466

  9. Natural dissociation of olivine to (Mg,Fe)SiO3 perovskite and magnesiowustite in a shocked Martian meteorite.

    PubMed

    Miyahara, Masaaki; Ohtani, Eiji; Ozawa, Shin; Kimura, Makoto; El Goresy, Ahmed; Sakai, Takeshi; Nagase, Toshiro; Hiraga, Kenji; Hirao, Naohisa; Ohishi, Yasuo

    2011-04-12

    We report evidence for the natural dissociation of olivine in a shergottite at high-pressure and high-temperature conditions induced by a dynamic event on Mars. Olivine (Fa(34-41)) adjacent to or entrained in the shock melt vein and melt pockets of Martian meteorite olivine-phyric shergottite Dar al Gani 735 dissociated into (Mg,Fe)SiO(3) perovskite (Pv)+magnesiowstite (Mw), whereby perovskite partially vitrified during decompression. Transmission electron microscopy observations reveal that microtexture of olivine dissociation products evolves from lamellar to equigranular with increasing temperature at the same pressure condition. This is in accord with the observations of synthetic samples recovered from high-pressure and high-temperature experiments. Equigranular (Mg,Fe)SiO(3) Pv and Mw have 50-100 nm in diameter, and lamellar (Mg,Fe)SiO(3) Pv and Mw have approximately 20 and approximately 10 nm in thickness, respectively. Partitioning coefficient, K(Pv/Mw) = [FeO/MgO]/[FeO/MgO](Mw), between (Mg,Fe)SiO(3) Pv and Mw in equigranular and lamellar textures are approximately 0.15 and approximately 0.78, respectively. The dissociation of olivine implies that the pressure and temperature conditions recorded in the shock melt vein and melt pockets during the dynamic event were approximately 25 GPa but 700?C at least. PMID:21444781

  10. Magnetoresistance in tunnel junctions using Co2(Cr,Fe)Al full Heusler alloys

    Microsoft Academic Search

    K. Inomata; N. Tezuka; S. Okamura; H. Kurebayashi; A. Hirohata

    2004-01-01

    We grew Co2(Cr1-xFex)Al Heusler alloy films using a magnetron sputtering system on thermally oxidized Si substrates at room temperature without any buffer layers. The x-ray diffraction patterns did not show the L21 structure as expected for the bulk but revealed the B2 and A2 structures, depending on the Fe concentration x, in which the structure tends to become the A2

  11. Metastable phase formation in FeSi system using non-equilibrium techniques

    Microsoft Academic Search

    Ajay Gupta; Pratima Dhuri

    2001-01-01

    Metastable alloy phase formation in Fe\\/Si system with nominal composition Fe50Si50 using the techniques of mechanical alloying (MA), solid state interdiffusion (SSI) and swift heavy ion (SHI) irradiation has been compared. The products of SSI depend upon the structure of the iron layers. In the multilayer with amorphous iron layer, the product of SSI is crystalline FeSi phase, while in

  12. Soft magnetic properties of nanocrystalline Fe 100? x Si x (15< x<34) alloys

    Microsoft Academic Search

    L. K Varga; F Mazaleyrat; J Kovac; A Kkay

    2000-01-01

    Nanocrystalline Fe100?xSix (15Si. Around the composition of Fe2Si, a single-phase metastable B2 structure was found. If the quenching is not properly conducted, traces of hexagonal Fe5Si3 appear, which is detrimental to

  13. Stresses related to the shape memory effect in FeMnSi-based shape memory alloys

    Microsoft Academic Search

    N. Van Caenegem; L. Duprez; K. Verbeken; D. Segers; Y. Houbaert

    2008-01-01

    The shape memory behaviour of two FeMnSi-based alloys has been investigated. Two compositions were studied, i.e. Fe29Mn7Si and Fe29Mn7Si5Cr (numbers indicate mass%). Characterizations of the martensitic transformation and the different structural constituents were performed using optical microscopy and X-ray diffraction methods. Transformation temperatures were determined by thermodilatometry on undeformed and deformed samples. The shape recovery was quantified by means of

  14. Effect of thermomechanical cycling in an Fe-Mn-Si-Cr-Ni shape memory alloy

    Microsoft Academic Search

    M. M. Reyhani; P. G. McCormick

    1994-01-01

    Previous studies on the effect of cycling in Fe-Mn-Si alloys have shown an increase in reversibility with increasing number of thermal cycles. In Fe-Mn-Si-Cr-Ni and Fe-Mn-Si-Co-Ni alloys, the shape recovery strain during thermomechanical cycling increased when the strain amplitude for each successive cycle is kept constant. Where the total strain (i.e., the sum of the transformation and permanent strain) is

  15. Tribological properties of Fe 3AlFe 3AlC 0.5 composites under dry sliding

    Microsoft Academic Search

    Jun Yang; Peiqing La; Weimin Liu; Jiqiang Ma; Qunji Xue

    2005-01-01

    The tribological properties of Fe3Al composites with 40, 60 and 80wt.% Fe3AlC0.5 under dry sliding against AISI52100 steel at ambient conditions were studied. Effects of load and sliding speed on the tribological properties were investigated. Worn surfaces of the composites were analyzed by scanning electron microscopy. It was found that wear rate of the composites were in the magnitude of

  16. Competitive stochastic growth model for the 3D morphology of eutectic Si in Al-Si alloys

    E-print Network

    Schmidt, Volker

    Competitive stochastic growth model for the 3D morphology of eutectic Si in Al-Si alloys Gerd for the simulation of the 3D morphology of eutectic silicon in Al-Si alloys, which represents the colonies-Si alloys, coral-like eutectic Si, stochastic growth model, multivariate time series, FIB-SEM tomography

  17. 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.

  18. Constraints on Al, Fe and Li Abundances in Mercury's Exosphere

    NASA Astrophysics Data System (ADS)

    Doressoundiram, Alain; Leblanc, F.

    2009-09-01

    Before the arrival of Messenger and Bepi Colombo at Mercury, the only source of information available on Mercury's environment is observations done from ground based observatories. We performed high spectral resolution observations of the Mercury's exosphere on the 30th and 31st October 2005 using the ESO-NTT telescope, La Silla, Chile. The large spectral range, 385-855 nm of the spectrograph EMMI provides a unique opportunity to search for non-identified species in the Hermian's environment. In this paper, we report a tentative detection of atomic aluminium in the exosphere of Mercury. This detection should be confirmed by further observations and can be used as an upper limit for this element in Mercury's exosphere. We also estimate upper limit for the column densities of Fe and Si exospheric atoms. Detection of Al, a refractory element, if confirmed, as well as its high exospheric abundance (between 2 to 18) with respect to Ca would suggest either an unexpected surface composition or a relation between exosphere and surface composition that is not well understood.

  19. Electrical transport properties and magnetoresistance of polycrystalline Fe3O4\\/pSi heterostructures

    Microsoft Academic Search

    W. B. Mi; E. Y. Jiang; H. L. Bai

    2010-01-01

    Polycrystalline Fe3O4 films were deposited on the p-Si wafers using reactive sputtering to form the polycrystalline Fe3O4\\/p-Si heterostructures. A rectifying behavior was observed in the polycrystalline Fe3O4\\/p-Si heterostructures due to the formation of p-n junction between Fe3O4 and p-Si. The metal-insulator transition was observed, and the transition temperature decreases from 250 K at 100 mA to 110 K at 1

  20. Thermal Properties of Amorphous Al-Ni-Si Alloy

    SciTech Connect

    Goegebakan, Musa; Okumus, Mustafa [Department of Physics, Faculty of Art and Science, Kahramanmaras Sutcu Imam University, Kahramanmaras, 46000 (Turkey)

    2007-04-23

    Thermal properties of the amorphous phases in rapidly solidified Al70Ni13Si17 alloy has been investigated by a combination of differential scanning calorimetry DSC. During continuous heating, three exothermic crystallization peaks were observed. Activation energies for the three crystallization peaks were calculated by the Kissinger and Ozawa methods give good agreement. This study describes the thermal properties of rapidly solidified Al70Ni13Si17 amorphous alloy.

  1. Multifunctional SiC\\/Al Composites for Aerospace Applications

    Microsoft Academic Search

    Cui Yan; Wang Lifeng; Ren Jianyue

    2008-01-01

    Multi-functional Al-matrix composites with high volume fraction (55%-57%) of SiC particles are produced with the new pres-sureless infiltration fabrication technology. X-ray detection and microscopic observation display the composites which are macroscopi-cally homogeneous without porosity. The investigation further reveals that the SiC\\/Al composites possess low density (2.94 g\\/cm3), high elastic modulus (220 GPa), prominent thermal management function as a result of

  2. Phase Diagram and Electrostatic Levitation Undercooling Studies of Polytetrahedral Phases in Ti-Fe-Si-O and Ti-Zr-Ni Alloys

    E-print Network

    Phase Diagram and Electrostatic Levitation Undercooling Studies of Polytetrahedral Phases in Ti-Fe-Si-O and Ti-Zr-Ni Alloys T.K. Croat, J.P. Davis, A.K. Gangopadhyay, K.F. Kelton, G.W. Lee, J. Simmons, Dept, Huntsville, AL. ABSTRACT New information on the phase diagrams of Ti-Fe-Si-O and Ti-Zr-Ni alloys near

  3. Directional alignment of FeCo crystallites in Si/NiFe/Ru/FeCoB multilayer with high anisotropy field above 500 Oe.

    PubMed

    Hirata, Ken-Ichiro; Gomi, Shunsuke; Nakagawa, Shigeki

    2011-03-01

    In-plane magnetic anisotropy and crystal structure of FeCoB layer on Si/NiFe/Ru underlayer were investigated by using X-Ray Diffraction (XRD) measurement. A pole-figure measurement of XRD showed directionally tilted alignment of FeCo crystallites in Si/NiFe/Ru/FeCoB multilayered film with high in-plane anisotropy field H(k) but no directional alignment was found in FeCoB single layered film. The higher H(k) appeared in the Si/NiFe/Ru/FeCoB multilayered configuration with the thicker FeCoB layer. Since Ru crystallites in a multiunderlayer configuration exhibited no directional alignment, the surface structure of underlayer should be no main reason for the directional alignment of FeCo crystallites deposited on it. The dependence of hickness of FeCoB layer in Si/NiFe/Ru/FeCoB film on H(k) indicated that the in-plane magnetic anisotropy is caused by not only the structure of Ru underlayer but also oblique incidence effect of sputtered particles, which is attained in configuration of Facing Targets Sputtering (FTS) system. From these experimental results, remarkably high H(k) of 540 Oe was obtained. PMID:21449466

  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. Precipitation In Al-Mg-Si Alloys with Cu Additions and the Role of the Q' and Related Phases

    E-print Network

    Laughlin, David E.

    Precipitation In Al-Mg-Si Alloys with Cu Additions and the Role of the Q' and Related Phases D Keywords: Al-Mg-Si, Al-Mg-Si-Cu, Balanced alloy, Excess-Si, Precipitation, Q, Metastable phase, Q of Al-Mg-Si and Al-Mg-Si-Cu alloys. Ternary Al-Mg-Si alloys have been reported to go through

  6. Investigation of the Electrochemical Corrosion Behavior and Passive Film for Fe-Mn, Fe-Mn-Al, and Fe-Mn-Al-Cr Alloys in Aqueous Solutions

    Microsoft Academic Search

    X. M. Zhu; Y. S. Zhang

    1998-01-01

    The corrosion behavior of austenitic Fe-(17 wt% to 31 wt%) Mn-(1 wt% to 9 wt%) Al-(1 wt% to 7 wt%) Cr alloys in different aqueous solutions and the corrosion protection mechanism induced by adding Al or Al and Cr, were studied by anodic polarization and Auger electron spectroscopic\\/x-ray photoelectron spectroscopic (AES\\/XPS) analysis. Binary Fe-(17 wt% to 31 wt%) Mn-0.15 wt%

  7. 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.

  8. Nonmagnetostrictive glassy Co-Fe-Ni-Mo-B-Si alloys

    NASA Astrophysics Data System (ADS)

    Hasegawa, Ryusuke

    1982-11-01

    Magnetic properties of glassy (Co1-x-yFex-Niy)100-a-b-cMoaBbSic are presented where 0.03?x?0.10, 0?y?0.10, 0?a?6, 11?b?18, 0?c?14, and 18?(b+c)?26 atomic percent. Many of these alloys are nearly zero-magnetostrictive and exhibit properties comparable with or superior to crystalline zero magnetostrictive supermalloys. For example, heat-treated glassy Co67.4Fe4.1Ni3Mo1.5B12.5Si11.5 ribbon (25 ?m thick) exhibits core loss (L) of 4 W/kg and permeability (?) of 23 000 at f=50 kHz and Bm=0.1 T, which are superior to those (L=8 W/kg and ?=19 000) of a corresponding supermalloy. In these materials, high B-H squareness ratio close to 1 and low coercivity of 20 A/m at 50 kHz have been observed, which are useful in such devices as switch-mode power supplies. Furthermore, the glassy alloys with Si/B ratio close to 1 have been found to be relatively stable magnetically. For example, the activation energy for the kinetics at magnetization reorientation increases from 110-19 J to about 210-19 J when Si/B ratio changes from 0 to about 1.

  9. The role of fluid flow and intermetallic phases in the formation of the primary Al-phase in AlSi alloys

    NASA Astrophysics Data System (ADS)

    Miko?ajczak, P.; Ratke, L.

    2012-01-01

    In secondary AlSi alloys, the presence of small amounts of Fe causes the formation of intermetallic phases, which have a negative effect on mechanical and physical properties of castings. To understand the effect of fluid flow on the microstructure and intermetallic phases, Al-5/7/9 wt pet Si 0.2/0.5/1.0 wt pet Fe alloys have been directionally solidified under defined thermal (gradient 3 K/mm, solidification velocity 0.04 mm/s) and fluid flow (rotating magnetic field 6 mT) conditions. The primary ?-Al phase and intermetallic phases were studied using light microscopy and SEM with EDX. The influence of fluid flow and intermetallic phases (?-Al5FeSi) on microstructure was characterized by changes of primary and secondary dendrite arm spacing and specific surface area of the dendrites. We observe a pronounced effect of flow on the length of the intermetallic precipitates, a macro-segregation Fe and Si and even small amounts of iron and thus intermetallics reduce possible effects of flow on microstructural parameters.

  10. 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.

  11. Fluctuations of chemical composition of austenite and their consequence on shape memory effect in Fe-Mn-(Si, Cr, Ni, C, N) alloys

    SciTech Connect

    Bliznuk, V.V. [G.V. Kurdyumov Institute for Metal Physics, National Academy of Sciences, Vernadsky Blvd., 36, UA-03680, Kiev 142 (Ukraine); Gavriljuk, V.G. [G.V. Kurdyumov Institute for Metal Physics, National Academy of Sciences, Vernadsky Blvd., 36, UA-03680, Kiev 142 (Ukraine)]. E-mail: gavr@imp.kiev.ua; Kopitsa, G.P. [Petersburg Nuclear Physics Institute, Russian Academy of Sciences, Gatchina 188300 (Russian Federation); Grigoriev, S.V. [Petersburg Nuclear Physics Institute, Russian Academy of Sciences, Gatchina 188300 (Russian Federation); Runov, V.V. [Petersburg Nuclear Physics Institute, Russian Academy of Sciences, Gatchina 188300 (Russian Federation)

    2004-09-20

    Polycrystalline samples of shape memory iron-based alloys containing 17, and 30 mass% Mn and alloyed with Si, Cr, Ni, C, N were studied by means of small angle scattering of polarized neutrons (SAPNS). A direct correlation between chemical homogeneity of the Fe-Mn, Fe-Mn-Si, Fe-Mn-Si-Cr, Fe-Mn-Si-Cr-Ni solid solutions and the values of reversible strain caused by the {gamma} {yields} {epsilon} {yields} {gamma} martensitic transformation was found. The addition of silicon to the Fe-Mn alloys significantly improves chemical homogeneity of the fcc solid solution on the scale of larger than several nm, which correlates with the essential increase of reversible strain. A similar to silicon but weaker effect was observed in the case of nitrogen addition to the Fe-Mn-Si-Cr, Fe-Mn-Si-Cr-Ni alloys. Based on the obtained experimental data and in consistency with the previously expressed idea by Sade et al., the positive effect of silicon and nitrogen on chemical homogeneity and SME in Fe-Mn alloys is attributed to the short-range atomic ordering induced by these elements.

  12. Electrical spin injection and detection in Fe/MgO/Si: influence of interface states

    NASA Astrophysics Data System (ADS)

    Pu, Yong; Beardsley, Jonas; Swartz, Adrain; Odenthal, Patrick; Berger, Andrew; Ko, Dongkyun; Bhallamudi, Vydia; Hammel, Chris; Kawakami, Roland; Johnston-Halperin, Ezekiel; Pelz, Jon

    2012-02-01

    We report electrical spin injection and detection in Fe/MgO/Si tunnel diodes using a 3-terminal (3T) geometry. Analysis of our Hanle curves yields an effective spin life-time of 0.1 ns and a spin-RA product 1 M?*?m^2, both of which are in rough agreement with previous 3T studies. However, according to our analysis the spin-RA is 6 orders of magnitude larger than expectations for bulk Si, and the 0.1 ns effective spin life-time is much smaller than reported value in Si by ESR or non-local methods. Here we provide a detailed analysis of electrical injection and detection in the 3T geometry. We present an alternative expression for the 3T spin signal than is usually used, and we propose that spin is accumulating in localized states (LS) at the MgO/Si interface rather than just in bulk Si. Incorporating a theory of spin accumulation in LS developed by M. Tran et al (PRL 102, 036601), we propose an energy distribution for the density of localized states, and introduce a model that agrees well with our anomalously large spin-RA and can explain the strong bias dependence of both spin and charge transport.

  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. Structural evolution in mechanically alloyed Al-Fe powders

    Microsoft Academic Search

    D. K. Mukhopadhyay; C. Suryanarayana

    1995-01-01

    The structural evolution in mechanically alloyed binary aluminum-iron powder mixtures containing 1, 4, 7.3, 10.7, and 25 at. pct Fe was investigated using X-ray diffraction (XRD) and electron microscopic techniques. The constitution (number and identity of phases present), microstructure (crystal size, particle size), and transformation behavior of the powders on annealing were studied. The solid solubility of Fe in Al

  15. Structural evolution in mechanically alloyed Al-Fe powders

    Microsoft Academic Search

    D. K. Mukhopadhyay; C. Suryanarayana

    1995-01-01

    The structural evolution in mechanically alloyed binary aluminum-iron powder mixtures containing 1, 4, 7.3, 10.7, and 25 at.\\u000a pct Fe was investigated using X-ray diffraction (XRD) and electron microscopic techniques. The constitution (number and identity\\u000a of phases present), microstructure (crystal size, particle size), and transformation behavior of the powders on annealing\\u000a were studied. The solid solubility of Fe in Al

  16. Observation of triatomic species with conflicting aromaticity: AlSi2- and AlGe2-.

    PubMed

    Zubarev, Dmitry Yu; Boldyrev, Alexander I; Li, Xi; Wang, Lai-Sheng

    2006-05-25

    We created mixed triatomic clusters, AlCGe(-), AlSi(2)(-), and AlGe(2)(-), and studied their electronic structure and chemical bonding using photoelectron spectroscopy and ab initio calculations. Excellent agreement between theoretical and experimental photoelectron spectra confirmed the predicted global minimum structures for these species. Chemical bonding analysis revealed that the AlSi(2)(-) and AlGe(2)(-) anions can be described as species with conflicting (sigma-antiaromatic and pi-aromatic) aromaticity. The AlCGe(-) anion represents an interesting example of chemical species which is between classical and aromatic. PMID:16706418

  17. /Al-Si Composites Fabricated by Reaction Hot Pressing

    NASA Astrophysics Data System (ADS)

    Mokhnache, El Oualid; Wang, G. S.; Geng, L.; Huang, L. J.

    2014-12-01

    Three in situ formed Al2O3/Al-Si composites with a different volume fraction of 10, 20, and 30 vol pct were fabricated using low energy ball milling and reaction hot pressing. The effect of reinforcement volume fraction on the microstructure and mechanical properties were studied. When the volume fraction was 30 vol pct, a massive primary Si (~130 m) along with an increase of Al2O3 (~2 m) was observed. The YS, UTS, and Brinell hardness of the composites were significantly higher than the aluminum matrix. Mechanisms governing the tensile fracture process are discussed.

  18. 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.

  19. Host Atom Diffusion in Ternary Fe-Cr-Al Alloys

    NASA Astrophysics Data System (ADS)

    Rohrberg, Diana; Spitzer, Karl-Heinz; Drrer, Lars; Kuli?ska, Anna J.; Borchardt, Gnter; 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.

  20. Band diagram of the AlF3/SiO2/Si system

    NASA Astrophysics Data System (ADS)

    Knig, D.; Scholz, R.; Zahn, D. R. T.; Ebest, G.

    2005-05-01

    The material system aluminum fluoride-silicon oxide-silicon (AlF3/SiO2/Si) can localize a high density of fixed negative charges in fluorine (F) vacancies within AlF3, serving as a source for a strong drift field. This assignment is corroborated by a determination of the stoichiometry with Rutherford backscattering techniques and the transient response of the negatively charged defects with deep level transient spectroscopy. From the density-functional calculations of stoichiometric and understoichiometric AlF3, we deduce a microscopic picture where the energetic eigenstates of the the singly and doubly occupied F vacancies surround the Fermi energy. The lineup of the band edges of the system AlF3/SiO2/Si is determined by self-consistent electrostatic calculations including local charges, resulting in excellent agreement with the energetics deduced from the transient response of the charged defects.

  1. Electrical, optical and materials properties of ion beam synthesised (IBS) FeSi 2

    NASA Astrophysics Data System (ADS)

    Reeson, K. J.; Finney, M. S.; Harry, M. A.; Hutchinson, S. V.; Tan, Y. S.; Leong, D.; Bearda, T. R.; Yang, Z.; Curello, G.; Homewood, K. P.; Gwilliam, R. M.; Sealy, B. J.

    1995-12-01

    The electrical and optical properties of FeSi 2 structures produced by ion beam synthesis (IBS) are investigated. Above 150 K both ? and {? FeSi2}/{n-Si} structures display good Schottky diode characteristics. {? FeSi2}/{n-Si} exhibits a low reverse leakage current up to -20 V after which abrupt avalanche breakdown occurs. As expected, the reverse leakage current of {? FeSi2}/{n-Si} for the same diode area, is an order to magnitude higher than that for the {? FeSi2}/{n-Si} diodes and the breakdown is less abrupt. The characteristics of both types of diode suggest that thermionic emission is the main conduction mechanism across the barrier. For samples implanted with higher doses of Fe, where a continuous layer of ?FeSi 2, is produced, the photoluminescence (PL) signal is indistinguishable from the background noise at 80 K. However, for lower dose samples (in the dose range 5 10 15-1 10 17 Fe cm -2) although the peak position remains the same the signal intensity is significantly increased and is visible at 80 K. Cross-sectional transmission electron microscopy (XTEM) results from these samples show precipitates with diameters of 400-600 at the surface and smaller precipitates <50 in diameter around the projected range of the implant. For even lower dose samples (1 10 14 Fe cm -2) no PL signal is observed which correlates to the lack of ?FeSi 2 precipitates in the XTEM micrographs.

  2. Magnetic anisotropy in Fe-25Cr-12Co-1Si alloy induced by external magnetic field

    E-print Network

    Qin, Lu-Chang

    Magnetic anisotropy in Fe-25Cr-12Co-1Si alloy induced by external magnetic field ZHEN Liang( )1 properties of Fe-25Cr-12Co-1Si alloy thermo-magnetically treated under different external magnetic field of external magnetic field during isothermal magnetic ageing. Approximately 28% of the total coercivity can

  3. Reactive Ion Etching of ?-FeSi2 with Inductively Coupled Plasma

    NASA Astrophysics Data System (ADS)

    Wakayama, Takayuki; Suemasu, Takashi; Kanazawa, Tomomi; Akinaga, Hiroyuki

    2006-06-01

    A dry etching technique for a ?-FeSi2 film on Si(111) was successfully developed. The technique is reactive ion etching (RIE) with inductively coupled plasma using CH4/O2/NH3/CHF3 discharge at a low pressure. It was found that CHF3 gas is indispensable in this etching technique, since CH4/O2/NH3 did not etch the film, and neither did SF6/O2, which is widely used for Si etching. Almost no further etching of the bottom Si substrate was observed and a carbon residual appeared on the surface, when the present RIE process using CH4/O2/NH3/CHF3 discharge was used to etch the entire ?-FeSi2 film such that the Si substrate emerged. This experimental result shows a possibility of highly selective RIE for ?-FeSi2/Si heterostructures.

  4. Amplification of magnetoresistance and Hall effect of Fe3O4SiO2Si structure

    Microsoft Academic Search

    Xianjie Wang; Yu Sui; Jinke Tang; Yao Li; Xingquan Zhang; Cong Wang; Zhiguo Liu; Wenhui Su

    2009-01-01

    In this paper, we report the magnetoresistance and the Hall effect in the Fe3O4-SiO2-Si structure. Single phase magnetite films were deposited on n-type silicon substrates using laser molecular beam epitaxy. When the temperature is increased beyond 230 K, the resistance drops rapidly because the conduction path starts to switch from the Fe3O4 film to the inversion layer underneath the native

  5. Oxidation behavior of TiAl protected by Si+Nb combined ion implantation

    Microsoft Academic Search

    X. Y Li; S Taniguchi; Y.-C Zhu; K Fujita; N Iwamoto; Y Matsunaga; K Nakagawa

    2001-01-01

    The combined ion implantation of Si+Nb at room temperature and at 1173 K with C contamination was employed to improve the oxidation resistance of a ?-TiAl based alloy [Ti48Al1.3Fe1.1V0.3B (at%)]. The implantation was conducted with a dose of 3.01021 ions\\/m2 and at an accelerate voltage of 50 kV for each element. The isothermal oxidation behavior of above treated alloys was

  6. (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. [Department of Chemistry and Biochemistry, Arizona State University, Tempe, Arizona 85287-1604 (United States); Jiang, L.; Xu, C.; Smith, D. J.; Menendez, J. [Department of Physics, Arizona State University, Tempe, Arizona 85287-1504 (United States)

    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.

  7. Effect of high temperature heat treatment on intergranular corrosion of AlMgSi(Cu) model alloy

    Microsoft Academic Search

    Gaute Svenningsen; Magnus Hurlen Larsen; Jan Halvor Nordlien; Kemal Nisancioglu

    2006-01-01

    Copper containing 6000-series aluminium alloys may become susceptible to intergranular corrosion (IGC) as a result of improper thermomechanical processing. Effect of cooling rate after solution heat treatment on the corrosion behaviour of a model AlMgSi(Cu) alloy of nominal composition (wt%) 0.6 Mg, 0.6 Si, 0.2 Fe, 0.2 Mn and 0.1 Cu was investigated. Slow cooling rates were simulated by isothermal

  8. Amplification of magnetoresistance and Hall effect of Fe3O4-SiO2-Si structure

    NASA Astrophysics Data System (ADS)

    Wang, Xianjie; Sui, Yu; Tang, Jinke; Li, Yao; Zhang, Xingquan; Wang, Cong; Liu, Zhiguo; Su, Wenhui

    2009-04-01

    In this paper, we report the magnetoresistance and the Hall effect in the Fe3O4-SiO2-Si structure. Single phase magnetite films were deposited on n-type silicon substrates using laser molecular beam epitaxy. When the temperature is increased beyond 230 K, the resistance drops rapidly because the conduction path starts to switch from the Fe3O4 film to the inversion layer underneath the native SiO2 via thermally assisted tunneling. A large negative magnetoresistance is observed at about 230 K, and this maximum shifts to higher temperature with increasing film thickness. Hall effect data of the structure show that the carriers are holes above the channel switching temperature. Our results confirm that the large magnetoresistance at 230 K originates from the amplification of the magnetoresistance of the magnetite in the Fe3O4-SiO2-Si structure.

  9. Surface morphology and magnetic properties of evaporated Fe/Si and Fe/glass thin films

    NASA Astrophysics Data System (ADS)

    Mebarki, M.; Layadi, A.; Kerkache, L.; Tiercelin, N.; Preobrazhensky, V.; Pernod, P.

    2015-07-01

    A series of Fe thin films have been deposited by thermal evaporation onto glass and Si substrates. The Fe thicknesses, t, are in the 76-431 nm range. We report experimental results on the surface morphology and the magnetic properties of these samples. The surface morphology has been studied by means of the atomic force microscopy technique. Hysteresis curves were obtained by means of the vibrating sample magnetometer (VSM) setup. The VSM experiments were done at two temperatures (room temperature and -130 C). We investigated the effect of thickness t, substrates and deposition rate v (0.3-13.7 /s) on the surface roughness, the coercive field and the squareness. A correlation between the structural and the magnetic properties is established.

  10. Synthesis and Characterization of Si-Al, Si-Ti, Si-Zr, Al-Zr, Al-Ti, and Al-Ti-Zr Nanocomposites of Lamellar or Hexagonal Structure

    SciTech Connect

    de Farias, Robson F.; Airoldi, Claudio

    2001-05-01

    By using tetraethylortosilicate, titanium and zirconium tetrabutoxide, and aluminum sec-butoxide, as well as neutral 1,10 and 1,12 alkyldiamines or dodecyltrimethylammonium bromide as precursors, a series of six oxides, Si-Al, Si-Ti, Si-Zr, Al-Zr, Al-Ti, and Al-Ti-Zr, were obtained. These materials were characterized by infrared spectroscopy, thermogravimetry, X-ray diffraction patterns, and scanning electron microscopy. Si-Ti, Si-Zr, and Al-Ti matrices exhibit a lamellar structure, whereas the others have a hexagonal nature. With the exception of the Al-Ti matrix for which grains with spheric morphology are observed, all the other matrices exhibited grains with amorphous nature, as observed by SEM micrographs.

  11. Nonmagnetostrictive glassy Co-Fe-Ni-Mo-B-Si alloys

    Microsoft Academic Search

    Ryusuke Hasegawa

    1982-01-01

    Magnetic properties of glassy (Co1?x?yFexNiy)100?a?b?cMoaBbSic are presented where 0.03?x?0.10, 0?y?0.10, 0?a?6, 11?b?18, 0?c?14, and 18?(b+c)?26 atomic percent. Many of these alloys are nearly zero-magnetostrictive and exhibit properties comparable with or superior to crystalline zero magnetostrictive supermalloys. For example, heat-treated glassy Co67.4Fe4.1Ni3Mo1.5B12.5Si11.5 ribbon (25 ?m thick) exhibits core loss (L) of 4 W\\/kg and permeability (?) of 23 000 at f=50

  12. 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; a?lar, 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.

  13. ?-FeSi2 as the bottom absorber of triple-junction thin-film solar cells: A numerical study

    NASA Astrophysics Data System (ADS)

    Yuan, Ji-Ren; Shen, Hong-Lie; Zhou, Lang; Huang, Hai-Bin; Zhou, Nai-Gen; Deng, Xin-Hua; Yu, Qi-Ming

    2014-03-01

    Using ?-FeSi2 as the bottom absorber of triple-junction thin-film solar cells is investigated by a numerical method for widening the long-wave spectral response. The presented results show that the ?-FeSi2 subcell can contribute 0.273 V of open-circuit voltage to the a-Si/?c-Si/?-FeSi2 triple-junction thin-film solar cell. The optimized absorber thicknesses for a-Si, ?c-Si, and ?-FeSi2 subcells are 260 nm, 900 nm, and 40 nm, respectively. In addition, the temperature coefficient of the conversion efficiency of the a-Si/?c-Si/?-FeSi2 cell is -0.308%/K, whose absolute value is only greater than that of the a-Si subcell. This result indicates that the a-Si/?c-Si/?-FeSi2 triple-junction solar cell has a good temperature coefficient. As a result, using ?-FeSi2 as the bottom absorber can improve the thin-film solar cell performance, and the a-Si/?c-Si/?-FeSi2 triple-junction solar cell is a promising structure configuration for improving the solar cell efficiency.

  14. Charge exchange of Si ions with clean and I-covered Al(100)

    NASA Astrophysics Data System (ADS)

    Chen, Xiaojian

    2005-03-01

    Ion-surface charge exchange is a central process in many surface analysis and processing methods. Charge exchange of alkali, halogen and noble gas ions with surfaces has been investigated in previous ion scattering studies, while the interaction between a semiconductor atom and a metal surface has not been measured despite its importance. Si^+ ions were incident on an atomically clean Al (100) surface in ultra-high vacuum. The absolute ionization probability of scattered Si and recoiled Al were measured with time-of-flight, and detailed spectra of the ion yield were collected with an electrostatic analyzer. All of the scattered Si was neutralized, as expected for resonant charge transfer (RCT) of Si, which has a large ionization potential. Multi-charged recoiled Al ions were emitted, however. Surprisingly, Si scattered from iodine adatoms is partially ionized and the ionization changes little with respect to the coverage, energy and exit angle. This is in direct contrast to Li scattering from I/Fe*, and cannot be explained by RCT. * J.A. Yarmoff, Y. Yang and Z. Sroubek, Phys. Rev. Lett. 91, 086104/1-4 (2003).

  15. Prediction and identification of calcium-rich phases in Al-Si alloys by electron backscatter diffraction EBSD/SEM

    SciTech Connect

    Zaldivar-Cadena, A.A. [Department of Metallurgical Engineering, Centro de Investigacion y de Estudios Avanzados del IPN, Unidad Saltillo, Carr. Saltillo-Monterrey Km.13, Ramos Arizpe, Coahuila, 25900 (Mexico)]. E-mail: antonio.zaldivar@cinvestav.edu.mx; Flores-Valdes, A. [Department of Metallurgical Engineering, Centro de Investigacion y de Estudios Avanzados del IPN, Unidad Saltillo, Carr. Saltillo-Monterrey Km.13, Ramos Arizpe, Coahuila, 25900 (Mexico)]. E-mail: alfredo.flores@cinvestav.edu.mx

    2007-08-15

    Al-7Si-3Cu-Fe, Al-7Si-3Cu-Fe-0.5Mn, Al-12Si-Mg-Ni-Cu, A319 and A380 alloys containing 0.0020, 0.0040, 0.0080, 0.1 and 0.2 wt.% Ca were used in this research to study the effects of Ca additions on their microstructures and hardness. Samples from the molten alloys were taken and characterized by SEM, EDS and EBSD analysis. Electron backscatter diffraction patterns (EBSDPs) were used to assess the crystallographic characteristics of calcium compounds, thus identifying their stoichiometry. On the other hand, microstructural formation was predicted using an adapted version of Thermo-Calc{sup TM} software. Compounds which contain calcium-rich particles with 'needle-like' or 'plate-like' morphologies were consistent with that of the hexagonal CaAl{sub 2}Si{sub 2} intermetallic phase in all of the alloys used. Moreover, it was found that Ca additions of 40 ppm and higher, refined the eutectic Si particles and coarsened the iron-rich intermetallics as well. Brinell hardness was evaluated to determine the effect of calcium concentration on the hardness of the Al-Si alloys used in this study.

  16. 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.

  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. 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.

  19. Fe_2Si (Hapkeite) from the Subsoil in the Alpine Foreland (Southeast Germany): Is it Associated with an Impact?

    NASA Astrophysics Data System (ADS)

    Bauer, F.; Hiltl, M.; Rappenglck, M. A.; Neumair, A.; Ernstson, K.

    2013-09-01

    We report on particles containing hapkeite Fe_2Si in conjunction with xifengite and gupeiite, and inclusions of cubic SiC (moissanite) and (Ti,V,Fe)C (khambraevite) and suggest a cosmic origin related with a meteorite impact.

  20. 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.

  1. Spin-state transitions in CaFeSi2O6 and NaFeSi2O6 under pressure

    NASA Astrophysics Data System (ADS)

    Streltsov, S. V.; Skorikov, N. A.

    2011-06-01

    The spin-state transitions in Fe-based clinopyroxenes are predicted and investigated with the use of the band structure calculations within GGA + U approach. The transitions were found to be of first order with critical pressures Pc~40 GPa for CaFeSi2O6 and Pc~60 GPa for NaFeSi2O6. The spin-state transitions are accompanied by 4% change in the lattice volume for both compounds. The present study will motivate further experimental and theoretical investigations of the spin-state transitions in pyroxenes.

  2. Phase stability and fcc\\/hcp martensitic transformation in FeMnSi alloys

    Microsoft Academic Search

    S Cotes; A. Fernndez Guillermet; M Sade

    1998-01-01

    This paper presents the first part of an experimental and thermodynamic study of the fcc\\/hcp relative phase stability and the fcc?hcp Martensitic Transformation (MT) in the FeMnSi system. In the present work, the building up of an extensive experimental database is described in detail. FeMnSi alloys with 15 to 35 wt.% Mn and up to 6.5 wt.% Si are investigated.

  3. Improvement of shape memory effect in Fe-Mn-Si alloy by Cr and Ni addition

    Microsoft Academic Search

    L. J. Rong; D. H. Ping; Y. Y. Li; C. X. Shi

    1995-01-01

    It has been reported that Fe-Mn-Si alloys containing 28-34wt%Mn and 4-6.5wt%Si exhibit a good shape memory behavior with the γε martensite transformation, when the shape deformation is applied at room temperature. Although the theoretical shear for fcchcp transformation implies a possible recoverable shape of 20%, usually in Fe-Mn-Si polycrystalline alloy it is limited to about 2%. The poor corrosion resistance

  4. Soft Magnetic Properties of Carbide-Dispersed Nanocrystalline Fe-Si-Hf-C Films

    Microsoft Academic Search

    N. Hasegawa; N. Kataoka; H. Fujimori

    1992-01-01

    The structural and soft magnetic properties of (Fe1-xSix)-Hf-C films (0x0.27) crystallized from the amorphous state were investigated as functions of the Si concentration. The samples crystallized with a nanocrystalline microstructure including dispersed ultrafine HfC particles. Most of the Si in the films was dissolved in bec Fe after crystallization. By increasing the Si concentration to x=0.13, the upper limit to

  5. Magnetostriction and tunneling magnetoresistance of CoFeB /AlOx/Co/IrMn junctions

    NASA Astrophysics Data System (ADS)

    Chen, Yuan-Tsung; Jen, S. U.; Tsai, T. L.; Huang, C. Y.; Yao, Y. D.

    2008-04-01

    Cross-strip magnetic tunnel junctions (MTJs) were fabricated following this sequence: Si(100)/Ta(30 )/CoFeB(80)/AlOx(to)/Co(70)/IrMn(90)/Ta(100), under an in-plane deposition field (h)=500Oe, where to=12, 17, 22, and 26 is the thickness of the AlOx layer. From the resistance (Ro) versus to plot, Ro increases from 255to1138? exponentially, as to increases from 12to26. This indicates that the quantum tunneling mechanism is valid in our case. Furthermore, the tunneling magnetoresistance (TMR) increases initially from 49% to 63% and then decreases to 33%, as to increases monotonically. This shows that with the increase of the barrier thickness, to?17, the spin polarization in the current after tunneling is weakened eventually. The microstructure of the to=17 MTJ observed under high-resolution cross-sectional transmission electron microscope shows that the interfaces between CoFeB /AlOx and AlOx/Co are smooth, resulting in the high TMR ratio observed. Saturation magnetostriction (?s) of this series of CoFeB /AlOx/Co MTJs ranges from -5to-2ppm. The ?s versus to plot also shows the concave-up feature. Finally, we find that the optimal MTJ has the following properties: TMR =63% and ?s=-5ppm.

  6. Segregation effects in Fe microalloyed NiAl single crystals

    SciTech Connect

    Vaerst, G.; Loeser, W.; Leonhardt, M.; Oswald, S. [Inst. fur Festkoerper- und Werkstofforschung Dresden (Germany)] [Inst. fur Festkoerper- und Werkstofforschung Dresden (Germany)

    1995-10-15

    The low density, excellent oxidation resistance and high thermal conductivity of the intermetallic phase NiAl compared to conventional nickel-based superalloys make NiAl based materials suitable for gas turbine applications. The lack of room-temperature ductility has been one of the barriers which hamper the technical use of the new material. Recently, a significant enhancement of room temperature tensile ductility up to 6% of soft <110> oriented NiAl single crystalline samples by microalloying with Fe, Ga or Mo was reported, compared with {approximately} 1 to 2% of binary stoichiometric NiAl. Dopant elements can display a rather inhomogeneous distribution along the crystal due to the redistribution of solute during directional solidification. Furthermore, the solute pile-up ahead of the smooth solidification front may lead to a morphological instability and to a transition from the single crystalline to a cellular/dendritic solidification mode. The scope of this paper is, therefore, to investigate the Fe distribution along the directionally solidified NiAl(Fe) crystals and possible transitions in microstructure, in order to reveal limitations for microalloying and to find out appropriate levels of dopant concentration and process parameters for homogeneously microalloyed NiAl single crystals.

  7. Processing and properties of FeAl-bonded composites

    SciTech Connect

    Schneibel, J.H.; Subramanian, R.; Alexander, K.B.; Becher, P.F. [Oak Ridge National Lab., TN (United States). Metals and Ceramics Div.

    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.

  8. Spin glass behavior in FeAl2

    E-print Network

    Lue, CS; Oner, Y.; Naugle, Donald G.; Ross, JH.

    2001-01-01

    Magnetic and transport measurements indicate FeAl2 to be an ordered intermetallic spin glass, with canonical behavior including a susceptibility cusp at T-f = 35 K and frequency-dependent susceptibility below T-f. The field-cooled and zero...

  9. Double-layer oxidation protective SiC\\/CrAlSi coating for carboncarbon composites

    Microsoft Academic Search

    Min Huang; Ke-Zhi Li; He-Jun Li; Qian-Gang Fu; Guo-Dong Sun

    2007-01-01

    Double-layer oxidation resistant SiC\\/CrAlSi coating for carboncarbon composites was prepared by a two-step method of pack cementation and slurry. The phase composition, micro-structure and oxidation resistance of mono-layer SiC coating and double-layer SiC\\/CrAlSi coating were studied by XRD, SEM, and isothermal oxidation test at 1773K in air, respectively. Mono-layer SiC coating consists of SiC and Si, which can protect carboncarbon

  10. Anisotropic magnetic properties of EuAl2Si2

    NASA Astrophysics Data System (ADS)

    Maurya, Arvind; Kulkarni, Ruta; Thamizhavel, A.; Bonville, P.; Dhar, S. K.

    2015-03-01

    EuAl2Si2 is known to crystallize in the CaAl2Si2-type trigonal structure. We have grown single crystals of EuAl2Si2 by flux method, using Al-Si eutectic (87.8% Al) as self-flux, and investigated their anisotropic magnetic properties by means of magnetization, electrical resistivity and heat capacity in zero and applied magnetic fields, and 151Eu Mssbauer spectroscopy. Magnetic susceptibility data show an antiferromagnetic transition at TN = 33.3 K in agreement with the previously reported value on polycrystalline sample. The isothermal magnetization at 2 K measured along and perpendicular to the c-axis shows anisotropic behaviour, which is rather unexpected as Eu2+ is an S-state ion. The spin flip fields along the two directions are 2.8 and 4.8 T, respectively, while two closely spaced spin-flop transitions in the ab-plane are observed near 1.4 and 1.6 T. The electrical resistivity shows an upturn between TN and 60 K as the temperature is lowered below ~ 60 K, suggesting the presence of antiferromagnetic correlations in the paramagnetic state. Magnetoresistivity at 2 K in 14 T is nearly 1070 % for H // [0001]. The results of heat capacity and 151Eu Mssbauer spectroscopy are in conformity with a bulk transition at 33.3 K.

  11. X-ray powder diffraction and 57Fe Mssbauer spectroscopy of synthetic trioctahedral micas {K}[Me3]Fe2+; T = Al3+, Fe3+

    NASA Astrophysics Data System (ADS)

    Redhammer, G. J.; Amthauer, G.; Lottermoser, W.; Bernroider, M.; Tippelt, G.; Roth, G.

    2005-11-01

    Trioctahedral 1 M micas have been synthesized along (pseudo)binary joins using hydrothermal techniques and controlled oxygen fugacities. Octahedrally coordinated iron in annite {K}[Fe3]<AlSi3rangleO10(OH)2 was successively replaced by Co2+, Mg2+ and Ni2+ and tetrahedrally coordinated aluminum by Fe3+. Unit cell parameters decrease almost linearly with decreasing average radius of the octahedral cation/average M O bond length within the octahedral sheet. With increasing substitution of Fe2+ the octahedral sheet becomes more flattened, the ditrigonal distortion of the tetrahedral sheet increases up to a maximum value of ?10 for micas with tetrahedral sheet compositions close to <AlSi3rangle and up to ?14 for those containing a <FeSi3rangle tetrahedral sheet. All iron-bearing samples were studied by 57Fe Mssbauer spectroscopy. With increasing substitution of iron by smaller divalent cations the quadrupole splitting distribution (QSD) evolves from a broad bimodal distribution in annite to a smaller unimodal distribution in Mg2+ and Ni2+-rich samples so that for high substitution rates more regular local environments are dominating. These results, however, can not be interpreted in terms of an octahedral cation ordering scheme. For none of the micas investigated reliable Fe2+ M2/M1 area ratios can be extracted. fMoreover, the complete QSD is shifted towards higher quadrupole splitting values. Similar observations were obtained for substituting Fe2+ by Mg2+ and Ni2+ in tetra-ferri-annite free of octahedral coordinated trivalent cations. Unlike in the Al3+ bearing micas a third QSD component is missing which supports the claim that the appearance of this third QSD component is closely related to the presence of trivalent cations (Al3+, Fe3+) in octahedra coordination.

  12. 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. [Institut fuer Festkoerperfoschung, Forschungszentrum Juelich GmbH, D-52425 Juelich (Germany) and Center of Nanoelectronic Systems for Information Technology (CNI), Forschungszentrum Juelich GmbH, D-52425 Juelich (Germany)

    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.

  13. 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

  14. Theoretical phase relations involving cordierite and garnet revisited: the influence of oxygen fugacity on the stability of sapphirine and spinel in the system Mg-Fe-Al-Si-O

    NASA Astrophysics Data System (ADS)

    Hensen, B. J.

    1986-09-01

    The theoretical P-T grid for stability relations of the phases cordierite (Cd), sapphirine (Sa), hypersthene (Hy), garnet (Ga), spinel (Sp), sillimanite (Si), and quartz (Qz) of Hensen (1971), has proved useful in the interpretation of metamorphic mineral assemblages formed at low oxygen fugacity. Both experimental data and evidence from natural rocks indicate that at high oxygen fugacity compatability relations change as a result of the enlargement of the stability field of spinel, which causes a topological inversion and the stabilisation of the invariant points [Sa], [Ga], and [Cd]. This implies the stable existence of the univariant equilibria (forf_{{text{O}}_{text{2}} } buffered conditions): Sp+Qz=Ga+Hy+Si+O2 (Sa, Cd), Cd+Sp+Qz=Hy+Si+O2 (Sa, Ga) and Sa+Sp+Qz=Hy+Si+O2 (Ga, Cd) and the divariant reaction: Sp+Qz=Hy+Si+O2 (Sa, Ga, Cd). These redox equilibria are restricted to conditions of high oxygen fugacity. The proposed theoretical P-T grids, for both low and high oxygen fugacity, satisfactorily explain all experimental data and metamorphic mineral assemblages so far found in granulites.

  15. Study on contact angles of Au, Ag, Cu, Sn, Al and Al alloys to SiC

    Microsoft Academic Search

    Sennosuke Takahashi; Osamu Kuboi

    1996-01-01

    Contact angles of Au, Ag, Cu, Sn, Al and Al alloys to SiC were measured by use of sessile drops heated by a high frequency induction coil designed to be convex against the SiC plate. Three crystal configurations of a-SiC, polycrystalline plane of sintered SiC, SiC (1 1 1) plane, and SiC (1 0 0 0) plane were used as

  16. New superlattice ordering in AlPdMn and AlPdMnSi icosahedral quasicrystals

    Microsoft Academic Search

    T. Ishimasa; M. Mori

    1992-01-01

    AlPdMnSi alloys with nominal compositions (AlPdMn) Si and 0 ? x ?; 0.03 were annealed at various temperatures between 1075 and 779 K. The existence of the following five structures has been recognized in these alloys by electron microscopy observations: traditional Ftype icosahedral phase, an Ftype icosahedral phase with a new superlattice ordering, a third Ftype icosahedral phase with a

  17. Electrical transport properties and magnetoresistance of polycrystalline Fe3O4/p-Si heterostructures

    NASA Astrophysics Data System (ADS)

    Mi, W. B.; Jiang, E. Y.; Bai, H. L.

    2010-05-01

    Polycrystalline Fe3O4 films were deposited on the p-Si wafers using reactive sputtering to form the polycrystalline Fe3O4/p-Si heterostructures. A rectifying behavior was observed in the polycrystalline Fe3O4/p-Si heterostructures due to the formation of p-n junction between Fe3O4 and p-Si. The metal-insulator transition was observed, and the transition temperature decreases from 250 K at 100 mA to 110 K at 1 mA in the reverse range, but it keeps at 100 K in the forward range. The current-dependent magnetoresistance (MR) crossovers from negative to positive with different manners for the forward and reverse currents. The characteristic MR is thought to be caused by the rectifying effect and band structure of the Fe3O4 near the interface of the heterostructures.

  18. Mechanical properties of {beta}-SiAlON ceramics joined using composite {beta}-SiAlON-glass adhesives

    SciTech Connect

    Walls, P.A.; Ueki, Masanori [Nippon Steel Corp., Kawasaki (Japan). Advanced Technology Research Labs.

    1995-04-01

    The mechanical properties of {beta}-SiAlON ceramics joined using {beta}-SiAlON-glass-forming adhesives consisting of mixed Si{sub 3}N{sub 4}, Y{sub 2}O{sub 3}, Al{sub 2}O{sub 3}, and SiO{sub 2} powders are described. Use of adhesives with a {beta}-SiAlON:glass ratio of 60:40 gave an optimum joint strength of 650 MPa in four-point bending mode, i.e., 85% of that of unbonded material, when joining was carried out at 1,600-C for 10 min, under an applied uniaxial pressure of 2 MPa. Bonding pressures in excess of 2 MPa caused excessive compressive creep distortion during the joining operation. The strengths of postjoined HIPed material and HIPed, unbonded material, differed by only 4%, i.e., 975 and 1,010 MPa, respectively, which indicates that HIPing reduces the size of critical defects in the joint. Fracture toughness of the joint also improved upon HIPing.

  19. Performance of LiAl\\/LiI(Al2O3)\\/FeS2 thermal batteries

    Microsoft Academic Search

    Yung-Hsin Lin; Kuo-Tung Yu; Pei-Chin Yao; Shu-En Hsu

    1986-01-01

    Performances of the LiAl\\/LiI(Al2O3)\\/FeS2 systems with different percentages of Al2O3 in the electrolyte were tested from 460 C to 580 C at various current densities and were compared with the performance of the LiAl\\/LiCl-KCl\\/FeS2 system. The results of single-cell and battery tests indicate that the LiAl\\/LiI(Al2O3)\\/FeS2 system has a feasibility for thermal potential applications. Compared to the LiAl\\/LiCl-KCl\\/FeS2 system, the

  20. Calibration of Al\\/Si order variations in anorthite

    Microsoft Academic Search

    M. A. Carpenter; R. J. Angel; L. W. Finger

    1990-01-01

    New single crystal diffraction data for natural and heat-treated anorthite crystals (Angel et al. 1990) allow the determination of their states of Al\\/Si order in terms of a macroscopic order parameter,QOD, for the transition. Numerical values ofQOD obtained from estimates of site occupancies are shown to vary with the scalar spontaneous strain, es, as es?QOD2, and with the ratio of

  1. Carburisation of FeX (X=Si, Mo, V) diffusion couples

    Microsoft Academic Search

    R. Bernst; G. Inden; A. Schneider

    2008-01-01

    Experimental studies of carburisation of diffusion couples Fe\\/Fe4at.% Si, Fe\\/Fe7.5at.% Mo and Fe\\/Fe20at.% V are reported. The diffusion couples were carburised at 700?C for 10 h in a strongly carburising COH2H2OH2S gas mixture imposing a carbon activity aC=100. The growth of cementite at the surface of the couples was found to depend on the concentration of the alloying element X

  2. Preparation of surface plasmon resonance biosensor based on magnetic core\\/shell Fe 3O 4\\/SiO 2 and Fe 3O 4\\/Ag\\/SiO 2 nanoparticles

    Microsoft Academic Search

    Liying Wang; Ying Sun; Jing Wang; Jian Wang; Aimin Yu; Hanqi Zhang; Daqian Song

    2011-01-01

    In this paper, surface plasmon resonance biosensors based on magnetic core\\/shell Fe3O4\\/SiO2 and Fe3O4\\/Ag\\/SiO2 nanoparticles were developed for immunoassay. With Fe3O4 and Fe3O4\\/Ag nanoparticles being used as seeding materials, Fe3O4\\/SiO2 and Fe3O4\\/Ag\\/SiO2 nanoparticles were formed by hydrolysis of tetraethyl orthosilicate. The aldehyde group functionalized magnetic nanoparticles provide organic functionality for bioconjugation. The products were characterized by scanning electronic microscopy (SEM),

  3. Influence of grain refinement and modification on microstructure and mechanical properties of Al7Si and Al7Si2.5Cu cast alloys

    Microsoft Academic Search

    K. G. Basavakumar; P. G. Mukunda; M. Chakraborty

    2008-01-01

    The microstructures and mechanical properties (impact toughness, tensile and hardness) of Al7Si and Al7Si2.5Cu cast alloys were studied after various melt treatments like grain refinement and modification. Results indicate that combined grain refined and modified Al7Si2.5Cu alloys have microstructures consisting of uniformly distributed ?-Al grains, interdendritic network of fine eutectic silicon and fine CuAl2 particles in the interdendritic region. These

  4. Optical investigations of AlSi-SiC composites subjected to laser CO 2 annealing

    NASA Astrophysics Data System (ADS)

    Jaglarz, Janusz; Grabowski, Andrzej

    2010-10-01

    The optical study of the AlSi/SiC composite materials before and after laser annealing has been performed. They concerned total and diffuse reflectance measurements obtained by the means of integrating sphere in the spectral range 250-2500 nm, measurements of intensity of scattered light as a function of scattering angle ( BRDF method) and ellipsometric measurements performed in the range 190-1700 nm. For determination of optical constants, the Kramers-Krnig dispersion relation has been applied. Obtained results had great differences of optical properties alloys before and after laser annealing. For investigated composites roughness and correlation lengths of studied surfaces have been determined. Moreover, optical measurements allowed concluding the light scattering being a result of interaction of light with surface topography and material scattering appeared due to variation of optical constants on surfaces of AlSi/SiC composites.

  5. 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.

  6. Laser welding of Al-Si coated hot stamping steel

    Microsoft Academic Search

    C. Kim; M. J. Kang; Y. D. Park

    2011-01-01

    Advanced high strength steel (AHSS) is being increasingly used in automotive industries for weight reduction purposes. Hot stamping steel, which is a boron alloyed steel, has a strength greater than 1500MPa after hot forming and successive quenching. Because the heating temperature is normally greater than 900C, a thin Al-Si based coating layer is applied to the steel surface to prevent

  7. 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.

  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. Coercivity and remanence of amorphous and nanocrystalline Fe(Cu,Ta)SiB ribbons

    Microsoft Academic Search

    N. Murillo; J. Gonzalez; J. M. Blanco

    1996-01-01

    We report on the evolution, with the thermal treatment parameters, of the remanence and coercive force of amorphous melt spun ribbons having compositions of Fe77.5Si13.5B9, Fe76.5Cu1Si13.5B9, and Fe74.5Ta3Si13.5B9. The thermal treatments were carried out by using the current annealing technique with and without the simultaneous application of a tensile stress along the axis of the samples. Our results show that

  10. 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.

  11. Fabrication and characterization of L10-ordered FePt\\/AlO\\/FeCo magnetic tunnel junctions

    Microsoft Academic Search

    S. Mitani; K. Tsukamoto; T. Seki; T. Shima; K. Takanashi; K. Taka

    2005-01-01

    Magnetic tunnel junctions (MTJs) with an L10-ordered FePt alloy were fabricated and characterized. As a bottom electrode, an in-plane magnetized L10 FePt(110) layer was grown epitaxially on an Au buffer layer. A multiple oxidation process was used for the formation of Al oxide barriers. The L10-FePt\\/AlO\\/FeCo MTJ prepared shows tunnel magnetoresistance of 18% and 40% at room temperature (RT) and

  12. High noise suppression using magnetically isotropic (CoFe-AlN)/(AlN) multilayer films

    NASA Astrophysics Data System (ADS)

    Kijima, Hanae; Ohnuma, Shigehiro; Masumoto, Hiroshi; Shimada, Yutaka; Endo, Yasushi; Yamaguchi, Masahiro

    2015-05-01

    Magnetically isotropic (CoFe-AlN)n/(AlN)n+1 multilayer films, in which the number of CoFe-AlN magnetic layers n ranged from 1 to 27, were prepared by radio frequency sputtering to achieve noise suppression at gigahertz frequencies. The soft CoFe-AlN magnetic layers consisted of nanometer-sized CoFe ferromagnetic grains embedded in an insulating AlN amorphous matrix, while the insulating AlN layers comprised AlN columnar crystals. All films showed a similar frequency dependence of permeability and ferromagnetic resonance of 1.7 GHz. Noise suppression was evaluated using a microstrip line as a noise source by determining the in-line conductive loss and the near-field intensity picked up by magnetic field detective probes. High noise suppression effects were observed in every direction in the film plane. Maximum noise suppression values amounted to 60% for the in-line conductive loss and -20 dB for the magnetic near-field intensity at around 1.7 GHz in the 27-layer film. These high-frequency noise suppression levels may be attributed to eddy current losses and ferromagnetic resonance.

  13. Laser cutting of AlSi-alloy/SiC p composite: modelling of the cut kerf geometry

    NASA Astrophysics Data System (ADS)

    Grabowski, Andrzej; Sleziona, Jzef; Nowak, Marian

    2007-02-01

    This paper presents a physical model characterizing the geometry of gas-assisted laser cutting of the AlSi-alloy/SiCp composite. In the model, a lot of relevant parameters that describe the inhomogeneous optical and thermophysical properties of AlSi-alloy/SiC p have been used. Numerical evaluations of this model give some explanations of "double slope" formation mechanism during laser cutting of the AlSi-alloy/SiC p. The theoretical results are compared with experimental data. It is found that increasing laser beam scanning speed increases the slope of cutting front.

  14. 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. [Argonne National Lab., IL (United States); Parker, F.T. [California Univ., San Diego, La Jolla, CA (United States). Center for Magnetic Recording Research

    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.

  15. Synthesis and characterization of AlTiSiN/CrSiN multilayer coatings by cathodic arc ion-plating

    NASA Astrophysics Data System (ADS)

    Yang, B.; Tian, C. X.; Wan, Q.; Yan, S. J.; Liu, H. D.; Wang, R. Y.; Li, Z. G.; Chen, Y. M.; Fu, D. J.

    2014-09-01

    AlTiSiN/CrSiN multilayer coatings were deposited on Si (1 0 0) and cemented carbide substrates using Cr, AlTi cathodes and SiH4 gases by cathodic arc ion plating system. The influences of SiH4 gases flowrate on the structural and mechanical properties of the coatings were investigated, systematically. AlTiSiN/CrSiN coatings exhibit a B1 NaCl-type nano-multilayered structure in which the CrSiN nano-layers alternate with AlTiSiN nano-layers with multiple orientations of crystal planes indicated by XRD patterns and TEM. Si contents of the coatings increase with increasing SiH4 flowrate. The hardness of the coatings increases to the maximum value of 3500 Hv0.05 with increasing SiH4 flowrate from 20 to 40 sccm and then decreases with further addition of SiH4 gases. A higher adhesive force of 73 N is obtained at the flowrate of 48 sccm. The coatings exhibit different tribological performance when the mating materials were varied from Si3N4 to cemented carbide balls and the variation of friction coefficients of the coatings against Si3N4 influenced by SiH4 flowrate are not obvious as against cemented carbide balls.

  16. Refinement performance and mechanism of an Al-50Si alloy

    SciTech Connect

    Dai, H.S. [Key Laboratory of Liquid Structure and Heredity of Materials, Ministry of Education, Shandong University, 73 Jingshi Road, Jinan 250061 (China); Liu, X.F. [Key Laboratory of Liquid Structure and Heredity of Materials, Ministry of Education, Shandong University, 73 Jingshi Road, Jinan 250061 (China)], E-mail: xfliu@sdu.edu.cn

    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.

  17. Surface modification of Fe3O4@SiO2 microsphere by silane coupling agent

    NASA Astrophysics Data System (ADS)

    Ahangaran, Fatemeh; Hassanzadeh, Ali; Nouri, Sirous

    2013-04-01

    In the present study, Fe3O4@SiO2 core-shell microspheres were prepared via two steps. First, Fe3O4 nanoparticles were synthesized by co-precipitation of Fe+3 and Fe+2 as reaction substrates and NaOH as precipitant. Second, the surface of Fe3O4 was coated with silica by hydrolysis of tetraethylorthosilicate as the silica source. Subsequently, in order to reduce the amount of interaction and the agglomeration of Fe3O4@SiO2 microspheres, the silica shell of these particles was modified by vinyltriethoxysilane as the silane coupling agent. The structural properties of the samples were characterized by X-ray diffraction, scanning electron microscopy, transmission electron microscopy, and Fourier transform infrared spectroscopy analyses. The results indicated that the average sizes of Fe3O4 and Fe3O4@SiO2 particles were about 50 and 500 nm, respectively. Also, the surface characterization of Fe3O4@SiO2 microspheres showed that the silane coupling agent was covalently coupled with the silica surface.

  18. 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.

  19. Incorporation of Cu and Al in thin layer silicon grown from Cu-Al-Si

    SciTech Connect

    Wang, T.H.; Ciszek, T.F. [National Renewable Energy Laboratory, 1617 Cole Blvd., Golden, Colorado 80401 (United States of America)

    1997-02-01

    Cu and Al concentrations in silicon thin layers grown from Cu-Al-Si are determined by segregation at the solid-liquid interface, and for the fast diffusing Cu, also at the free silicon surface. Using the multicomponent regular solution model and experimental results, we found that Si-Al and Si-Cu interactions in the liquid solution are repulsive, and Al-Cu interaction is attractive. As a result, Al incorporation as a function of Cu and Al compositions in the growth solution is determined at about 900{degree}C. Up to 0.2{Omega}{center_dot}cm P-type resistivities caused by Al doping are achieved because of suppression of Al incorporation by Cu, yet with a substantial amount of Al still present in the liquid for substrate surface-oxide removal. On the other hand, Cu concentration in the grown layers is reduced by Al in the liquid during growth and by surface segregation after growth. The surface segregation phenomenon can be conveniently used to getter Cu from the bulk of silicon layers so that its concentration ({approximately}10{sup 16}cm{sup {minus}3}) is much lower than its solubility (2.5{times}10{sup 17}cm{sup {minus}3}) at the layer growth temperature and the reported 10{sup 17}cm{sup {minus}3} degradation onset for solar-cell performance. {copyright} {ital 1997 American Institute of Physics.}

  20. Amplification of magnetoresistance of magnetite in an Fe3O4-SiO2-Si structure

    NASA Astrophysics Data System (ADS)

    Wang, Xianjie; Sui, Yu; Tang, Jinke; Wang, Cong; Zhang, Xingquan; Lu, Zhe; Liu, Zhiguo; Su, Wenhui; Wei, Xiankui; Yu, Richeng

    2008-01-01

    Film of Fe3O4 was prepared with laser molecular beam epitaxy deposition on a Si substrate with a native SiO2 layer. When the temperature is increased above 250K, the resistance drops rapidly because the conduction path starts to switch from the Fe3O4 film to the inversion layer underneath the SiO2 via thermally assisted tunneling. A greatly magnified low field negative magnetoresistance of Fe3O4 is observed at 280K. The effect is similar to a metal-oxide-semiconductor field-effect transistor. The magnetoresistance becomes positive with further increase in the magnetic field due to the Lorentz force and other effects on the carriers in the inversion layer.

  1. 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).

  2. Fe and Al Abundances in the Globular Cluster NGC 6171

    NASA Astrophysics Data System (ADS)

    O'Connell, Julia; Johnson, C.; Pilachowski, C.; Burks, G.

    2009-01-01

    We have performed chemical analyses for eleven stars in the metal-rich globular cluster NGC 6171 using spectra obtained with the WIYN 3.5m telescope and Hydra multifiber spectrograph. The observed wavelength range covers 6460-6860 A with an average S/N ratio 75. Effective temperatures, surface gravities, and microturbulent velocities were estimated using V-K photometry and bolometric magnitudes, but further refined using spectroscopic analyses based on equivalent width measurements. All abundances were determined using the LTE line analysis code MOOG and ATLAS9 model atmospheres. We find <[Fe/H]>= -1.17 0.13, which is consistent with previous photometric and small sample spectroscopic estimates. Al appears enhanced with <[Al/Fe]>= +0.62 0.09, but the modest star-to-star dispersion differs from the trend seen in more metal-poor globular clusters.

  3. High frequency magnetic properties of FeCoBSi\\/SiO2 and (FeCo\\/CoB)\\/SiO2 multilayer thin films

    Microsoft Academic Search

    M. Frommberger; A. Ludwig; C. Zanke; A. Sehrbrock; E. Quandt

    2003-01-01

    Soft magnetic, magnetostrictive (Fe90Co10)78Si12B10 thin films and Fe50Co50\\/Co80B20 multilayers are used in high frequency applications like stress sensors or transmission-line structures. The devices are based on strip-lines with incorporated magnetic thin films, in order to increase the inductance of the strip. However, relatively thick (?1 ?m) magnetic layers are necessary to reach a high inductance. In both investigated applications high

  4. Ferromagnetism and Nonmetallic Transport of Thin-Film ? - FeSi 2 : A Stabilized Metastable Material

    DOE PAGESBeta

    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

    2015-04-01

    A metastable phase ?-FeSi? was epitaxially stabilized on a silicon substrate using pulsed laser deposition. Nonmetallic and ferromagnetic behaviors are tailored on ?-FeSi? (111) thin films, while the bulk material of ?-FeSi? is metallic and nonmagnetic. The transport property of the films renders two different conducting states with a strong crossover at 50 K, 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? 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.

  5. Ferromagnetism and Nonmetallic Transport of Thin-Film ? -FeSi2 : A Stabilized Metastable Material

    NASA Astrophysics Data System (ADS)

    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

    2015-04-01

    A metastable phase ? -FeSi2 was epitaxially stabilized on a silicon substrate using pulsed laser deposition. Nonmetallic and ferromagnetic behaviors are tailored on ? -FeSi2 (111) thin films, while the bulk material of ? -FeSi2 is metallic and nonmagnetic. The transport property of the films renders two different conducting states with a strong crossover at 50 K, 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 ? -FeSi2 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.

  6. Ferromagnetism and Nonmetallic Transport of Thin-Film ? - FeSi 2 : A Stabilized Metastable Material

    DOE PAGESBeta

    Cao, Guixin; Singh, D.?J.; Zhang, X.-G.; Samolyuk, German; Qiao, Liang; Parish, Chad; Jin, Ke; Zhang, Yanwen; Guo, Hangwen; Tang, Siwei; et al

    2015-04-01

    A metastable phase ?-FeSi? was epitaxially stabilized on a silicon substrate using pulsed laser deposition. Nonmetallic and ferromagnetic behaviors are tailored on ?-FeSi? (111) thin films, while the bulk material of ?-FeSi? is metallic and nonmagnetic. The transport property of the films renders two different conducting states with a strong crossover at 50 K, 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? obtained within density functional calculations and Boltzmann transport calculations with and without strain. Our finding shedsmorelight 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.less

  7. Crystallization behavior and high temperature magnetic phase transitions of Nb-substituted FeCoSiBCu nanocomposites

    E-print Network

    McHenry, Michael E.

    Crystallization behavior and high temperature magnetic phase transitions of Nb-substituted FeCo temperature magnetic properties of FeCoSiBCu nanocomposites is reported. Magnetization changes accompany the primary crystallization of a-Fe(Co) nanocrystals and the secondary crystallization of (FeCo)23B6 and (FeCo

  8. A Stable Quasicrystal in Al-Cu-Fe System

    Microsoft Academic Search

    An-Pang Tsai; Akihisa Inoue; Tsuyoshi Masumoto

    1987-01-01

    A thermodynamically stable quasicrystalline single phase with an icosahedral structure was found to be formed at an atomic composition of Al65Cu20Fe15 in a fully annealed state as well as in a conventionally solidified state. The stable quasicrystal consisted of large grains with an average size of 0.2 mm after annealing for 48 h at 1118 K (0.98 Tm).

  9. Photoemission study of an Al-Cu-Fe icosahedral phase

    Microsoft Academic Search

    M. Mori; S. Matsuo; T. Ishimasa; T. Matsuura; K. Kamiya; H. Inokuchi; T. Matsukawa

    1991-01-01

    Photoemission spectra of the Al-Cu-Fe quasicrystal with the icosahedral phase were studied at room temperature. The line shape of the overall observed spectrum is like a large peak on a plateau cut-off at EF. The large peak observed at about 4 eV below EF seems to originate mainly from the 3d state of Cu atoms. The bump was observed at

  10. Quasicrystal structure in Al-Cu-Fe annealed alloy

    Microsoft Academic Search

    T. Ishimasa; Y. Fukano; M. Tsuchimori

    1988-01-01

    Powder X-ray diffraction, electron diffraction and electron microscopic experiments, including high-resolution electron microscopy, have revealed that the Al?Cu?Fe icosahedral phase has a higher degree of structural perfection than other known icosahedral phases. This icosahedral phase exhibits clear equal thickness fringes in bright and dark-field images and also sharp diffraction spots with small Bragg angles, both of which have not been

  11. Nonequilibrium phase diagram of Fe-Mn-Al system

    Microsoft Academic Search

    Xing Tian; Zhang Yansheng

    1993-01-01

    The development of a new austenitic steel system with manganese and aluminum replacing nickel and chromium has been an important subject in the field of metallic materials. In, 1958, Ham and Cairns reported on the development of the Fe-Mn-Al alloy and called it a poor man's stainless steel'. Since 1960's, Zhang Yansheng and co-workers have systematically investigated austenitic steels of

  12. Stress corrosion cracking of Fe-Co-B-Si metallic glasses in HCl solutions

    SciTech Connect

    Habib, K. [KISR, Safat (Kuwait). Materials Application Dept.

    1994-12-31

    A study on the susceptibility of various iron-cobalt-boron-silicon metallic glasses to stress-corrosion cracking has been conducted. Testing was carried out on thin metallic ribbons of Fe{sub 78}B{sub 13}Si{sub 9}, Fe{sub 66}Co{sub 18}B{sub 15}Si{sub 1}, Co{sub 66}Fe{sub 4}Ni{sub 1}B{sub 14}Si{sub 15}, Co{sub 76}Fe{sub 2}Mn{sub 4}B{sub 12}Si{sub 6}, and Co{sub 69}Fe{sub 4}Ni{sub 1}MO{sub 2}B{sub 12} Si{sub 12} in 0%, 25%, 50%, 75%, and 100% hydrochloric acids solutions at room temperature. The tests were performed under constant-strain conditions in the various solutions until complete separation of the ribbons occurred. Typical fractographic techniques were used for analyzing the failure of the glasses. The results indicated that the susceptibility of the glasses Fe{sub 78}B{sub 13}Si{sub 9}, Fe{sub 66}Co{sub 18}B{sub 15}Si{sub 1}, Co{sub 76}Fe{sub 2}Mn{sub 4}B{sub 12}Si{sub 6} and samples of Co{sub 66}Fe{sub 4} NiB{sub 14}Si{sub 15} glass to stress-corrosion cracking varies only as a function of the amplitude of the strain, Susceptibility is independent of the solution concentration. It is found that the additions of Ni, Mn, Mo and high content of Co into the Fe-Co-B-Si glass enhance the resistance of the alloy against stress-corrosion cracking in HCl solution. On contrary, the results showed that Co{sub 69}Fe{sub 4}Ni{sub 1}Mo{sub 2}B{sub 12}Si{sub 12} glass is not susceptible to stress-corrosion cracking in HCl solutions.

  13. Effect of Si and Fe doping on calcium phosphate glass fibre reinforced polycaprolactone bone analogous composites.

    PubMed

    Mohammadi, M Shah; Ahmed, I; Muja, N; Almeida, S; Rudd, C D; Bureau, M N; Nazhat, S N

    2012-04-01

    Reinforcing biodegradable polymers with phosphate-based glass fibres (PGF) is of interest for bone repair and regeneration. In addition to increasing the mechanical properties, PGF can also release bioinorganics, as they are water soluble, a property that may be controllably translated into a fully degradable composite. Herein, the effect of Si and Fe on the solubility of calcium-containing phosphate-based glasses (PG) in the system (50P(2)O(5)-40CaO-(10-x)SiO(2)-xFe(2)O(3), where x=0, 5 and 10 mol.%) were investigated. On replacing SiO(2) with Fe(2)O(3), there was an increase in the glass transition temperature and density of the PG, suggesting greater crosslinking of the phosphate chains. This significantly reduced the dissolution rates of degradation and ion release. Two PG formulations, 50P(2)O(5)-40CaO-10Fe(2)O(3) (Fe10) and 50P(2)O(5)-40CaO-5Fe(2)O(3)-5SiO(2) (Fe5Si5), were melt drawn into fibres and randomly incorporated into polycaprolactone (PCL). Initially, the flexural strength and modulus significantly increased with PGF incorporation. In deionized water, PCL-Fe(5)Si(5) displayed a significantly greater weight loss and ion release compared with PCL-Fe10. In simulated body fluid, brushite was formed only on the surface of PCL-Fe(5)Si(5). Dynamic mechanical analysis in phosphate buffered saline (PBS) at 37C revealed that the PCL-Fe10 storage modulus (E') was unchanged up to day 7, whereas the onset of PCL-Fe(5)Si(5)E' decrease occurred at day 4. At longer-term ageing in PBS, PCL-Fe(5)Si(5) flexural strength and modulus decreased significantly. MC3T3-E1 preosteoblasts seeded onto PCL-PGF grew up to day 7 in culture. PGF can be used to control the properties of biodegradable composites for potential application as bone fracture fixation devices. PMID:22248526

  14. Electronic and Magnetic Structure of Fe Nanoparticle Embedded in FeAl

    NASA Astrophysics Data System (ADS)

    Wang, Yang; Stocks, G. Malcolm; Rusanu, Aurelian; Nicholson, Don M. C.; Eisenbach, Markus; Faulkner, J. S.

    2006-03-01

    Magnetic nanostructures are of great scientific interest because of their potential applications in a wide range of technologies - data storage, magneto-electronics, permanent magnets, smart drug delivery, etc. Unfortunately magnetic nanostructures present substantial theoretical challenges due to the need to treat the electronic interactions quantum mechanically whilst dealing with a, still, large number of atoms. In this presentation, we discuss our recent studies of magnetic nanoparticles using the Locally Self-consistent Multiple Scattering (LSMS) method, an order-N ab initio method capable of treating tens of thousands of atoms. In particular, we show results for a Fe nanoparticle embedded in a stoichiometric B2-FeAl binary alloy. The Fe nanoparticle, has the shape of a BCC Wigner-Seitz cell, contains 4,409 Fe atoms, and measures about 5 nm across the diagonal corners. Including the surrounding matrix the calculation involves 16,000 atoms. We show results for the moment and charge distribution within nanoparticle, on the facets, and in the FeAl matrix.

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

    SciTech Connect

    Guanabara, Paulo Jr. [Lab. of Manufacturing Eng.-Dept. Mechatronics and Mechanical Systems Eng-Escola Politecnica-Universidade de Sao Paulo-Av. Prof. Mello Moraes, 2231 CEP05508-970-Sao Paulo (Brazil); Bueno, Levi de O. [Federal University of Sao Carlos-(UFSCar)-Dept. of Materials Engineering-Rod. Washington Luiz, km 235-CEP 13565.905-Sao Carlos (Brazil); 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.

  16. Melting and casting of FeAl-based cast alloy

    SciTech Connect

    Sikka, V.K. [Oak Ridge National Lab., TN (United States); Wilkening, D. [Columbia Falls Aluminum Co., Columbia Falls, MT (United States); Liebetrau, J.; Mackey, B. [AFFCO, L.L.C., Anaconda, MT (United States)

    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.

  17. Soft magnetic properties of a high temperature CoFeSiBNb nanocrystalline alloy

    Microsoft Academic Search

    A. K. Panda; O. Mohanta; A. Mitra; D. C. Jiles; C. C. H. Lo; Y. Melikhov

    2007-01-01

    We have investigated the magnetic properties of a Co36Fe36Si4B20Nb4 alloy developed for high temperature soft magnetic applications. Studies of the crystallization of the alloy, prepared in the form of amorphous ribbons by melt-spinning, were performed using differential scanning calorimetry and X-ray diffraction. These studies, and further validation by transmission electron microscopy, suggested the formation of (CoFe)2Si nanoparticles dispersed in an

  18. 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.

  19. Cavitation erosion of FeMnSiCr shape memory alloys

    Microsoft Academic Search

    Zaiyou Wang; Jinhua Zhu

    2004-01-01

    Cavitation erosion tests of three FeMnSiCr shape memory alloys were carried out at speed 34 and 45m\\/s using a rotating disc rig, and their cavitation damage has been investigated by comparison with a referring 13Cr5NiMo stainless steel used for hydraulic turbine vanes. The research results proved that the cavitation erosion of the FeMnSiCr shape memory alloys is a failure of

  20. Assisted self-sustaining combustion reaction in the FeSi system: Mechanical and chemical activation

    Microsoft Academic Search

    Ch. Gras; N. Zink; F. Bernard; E. Gaffet

    2007-01-01

    This work presents original investigations carried out to improve the activated self-propagating high-temperature synthesis (SHS) process in the FeSi system: different ignition modes are tested (volume heating as opposed to a local ignition source), and the use of additive is considered in order to enhance the SHS type reactivity in the FeSi system. When 20wt.% of KNO3 is added to

  1. Compatibility and accelerated aging study for Li(Si)\\/FeS\\/sub 2 thermally activated batteries

    Microsoft Academic Search

    J. W. Mead; J. Q. Searcy; P. N. Neiswander; R. L. Poole

    1983-01-01

    Thermally activated batteries using the lithium (silicon) iron disulfide (Li(Si)\\/FeS2) electrochemical system are used in weapons having a required storage life of 25 years and high reliability. A review of known data revealed no information on the compatibility of Li(Si)\\/FeS2 with the organic materials used in the system. The compatibility question is studied. Accelerated-aging data on pairs of materials were

  2. EVOLUTION OF OXIDE SCALES ON FeAl GRADE 3 INTERMETALLIC F. Pedraza1

    E-print Network

    Boyer, Edmond

    on either the binary FeAl or its yttrium oxide dispersion strengthened (ODS) counterpart have indicatedEVOLUTION OF OXIDE SCALES ON FeAl GRADE 3 INTERMETALLIC ALLOY F. Pedraza1 , J.L. Grosseau-Poussard2@univ-lr.fr Abstract The ODS FeAl Grade 3 intermetallic alloy have been shown to develop a structured oxide scale upon

  3. Optical properties and electronic structure of the intermetallic phases NiAl, CoAl, and FeAl

    Microsoft Academic Search

    K. Schlemper; L. K. Thomas

    1994-01-01

    The dielectric functions of the intermetallic B2 phases NiAl, CoAl, and FeAl have been determined by differential reflectometry and the Kramers-Kronig analysis in the energy range of 1.2-5 eV for various compositions near stoichiometry. The experimental absorption maxima are correlated to the band structure of these alloys taken from the literature. All transitions could be assigned to the band structure.

  4. Corrosion behaviour and biocompatibility of a novel Ni-free intermetallic coating growth on austenitic steel by hot dipping in an Al12.6%Si alloy

    Microsoft Academic Search

    M. A. Arenas; E. Frutos; L. Saldaa; A. Conde; L. Labajos-Broncano; M. L. Gonzlez-Martn; J. L. Gonzlez-Carrasco; N. Vilaboa

    2011-01-01

    Commercial 316 LVM austenitic stainless steel samples have been coated by immersion in a bath of molten Al12.6%Si alloy for\\u000a 120s. The coating consists of the Al12(Fe,Cr)3Si2 intermetallic. In vitro corrosion behaviour has been evaluated in the Ringers solution by means of potentiodynamic curves\\u000a and electrochemical impedance spectroscopy. The results reveal that the coated specimens exhibit lower susceptibility to localised

  5. 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.

  6. Characterization of Ni-Fe/Si3N4 Nanocomposite Coatings Deposited by Electroplating

    NASA Astrophysics Data System (ADS)

    Marita, Yusrini; Yaacob, Iskandar Idris

    2009-05-01

    Ni-Fe/Si3N4 nanocomposite coatings with various amount of Si3N4 were prepared by electrodeposition technique. The effect of Si3N4 nanoparticulates in the Ni-Fe nanocomposite coatings was investigated in relation to the ratio of Si3N4 to Na-saccharine in the plating bath. X-ray diffraction analysis showed that the Ni-Fe nanocomposite coating has face-centered cubic structure (FCC). However, a mixture of body-centered cubic (BCC) and face-centered cubic (FCC) phases was observed when the ratio of Si3N4 to Na-saccharine was around 8.3. The crystallite size of the Ni-Fe nanocomposite coating decreased when the ratio of Si3N4 to Na-saccharine was increased. From the results of the elemental mapping procedure, it was found that inclusions of silicon were uniformly distributed in Ni-Fe composite coating, indicating good dispersion of Si3N4 and this contributed in increasing the microhardness of coating.

  7. Large Barkhausen and Matteucci effects in FeCoSiB, FeCrSiB, and FeNiSiB amorphous wires

    SciTech Connect

    Mohri, K.; Kimura, K.; Mizutani, M. (Dept. of Electrical Engineering, Nagoya Univ., Nagoya 464-01 (JP)); Humphrey, F.B. (Dept. of EC and SE, Boston Univ., Boston, MA (US)); Kawashima, K. (Unitika Ltd., R and D, Uji, Kyoto 611 (JP))

    1990-09-01

    This paper reports the mechanism of sensitive and stable large Barkhausen effect of as-cast amorphous magnetostrictive wires having three composition systems investigated using measured values of stress induced anisotropy constant K{sub u}, saturation magnetostriction {lambda}, residual internal stress {sigma}{sub r}, and MH hysteresis loop squareness Mr/M{sub s}. The entire composition range of FeCo is compared to FeCr with up to 10 at. % and FeNi with Ni up to 12 at. %. Matteucci effects are also investigated in magnetostrictive and non-magnetostrictive amorphous wires magnetized with a longitudinal AC field, AC wire current, or AC field perpendicular to the wire axis.

  8. Effect of Si interlayers on the magnetic and mechanical properties of Fe/Ge neutron polarizing multilayer mirrors

    SciTech Connect

    Maruyama, R.; Yamazaki, D.; Hayashida, H.; Soyama, K. [J-PARC Center, Japan Atomic Energy Agency, Tokai, Ibaraki 319-1195 (Japan); Okayasu, S. [Advanced Science Research Center, Japan Atomic Energy Agency, Tokai, Ibaraki 319-1195 (Japan); Takeda, M. [J-PARC Center, Japan Atomic Energy Agency, Tokai, Ibaraki 319-1195 (Japan); Quantum Beam Science Directorate, Japan Atomic Energy Agency, Tokai, Ibaraki 319-1195 (Japan); Zettsu, N.; Nagano, M.; Yamamura, K. [Research Center for Ultra-precision Science and Technology, Graduate School of Engineering, Osaka University, Yamadaoka 2-1, Suita, Osaka 565-0871 (Japan)

    2012-03-15

    The neutron polarizing supermirror is one of the most important optical devices for polarizing neutron beams. To meet a variety of research demands, neutron polarizing supermirrors need to display high polarization efficiencies at low external magnetic fields. Fe/Si and Fe/Ge multilayers are typically used in neutron polarizing supermirrors because the contrast in scattering length densities almost vanishes for spin-down neutrons. The Fe/Si/Ge/Si multilayer, obtained by adding thin interlayers of Si to an Fe/Ge multilayer, is effective in reducing the external field strength necessary to achieve efficient neutron polarization. To gain insight into the mechanism that controls the required external field strength for a neutron polarizing supermirror, we investigated the magnetic and mechanical properties of Fe/Si, Fe/Ge, and Fe/Si/Ge/Si multilayers. The external field strength required to achieve efficient neutron polarization was found to be proportional to the compressive film stress. The compressive stress of the Fe/Si/Ge/Si multilayer was smaller by a factor of 4.4 and 2.7 than that of Fe/Si and Fe/Ge multilayers, respectively. These measurements and analyses showed that a reduction in the compressive film stress in the Fe/Si/Ge/Si multilayer permits the use of lower external field strength to achieve efficient neutron polarization. X-ray photoelectron spectroscopic studies showed that the formation of a Ge-Si solid solution in the Ge layer may explain the marked reduction in compressive stress in the case of the Fe/Si/Ge/Si multilayer. This study confirmed that a reduction in compressive film stress is very important for a high-performance neutron polarizing supermirror.

  9. Microstructure analysis of Al-Si-Cu alloys prepared by gradient solidification technique

    NASA Astrophysics Data System (ADS)

    Borkar, Hemant; Seifeddine, Salem; Jarfors, Anders E. W.

    2015-03-01

    Al-Si-Cu alloys were cast with the unique gradient solidification technique to produce alloys with two cooling rates corresponding to secondary dendrite arm spacing (SDAS) of 9 and 27 ?m covering the microstructural fineness of common die cast components. The microstructure was studied with optical microscopy and scanning electron microscopy (SEM) equipped with energy dispersive spectroscopy (EDS) and electron backscattered diffraction (EBSD). The alloy with higher cooling rate, lower SDAS, has a more homogeneous microstructure with well distributed network of eutectic and intermetallic phases. The results indicate the presence of Al-Fe-Si phases, Al-Cu phases and eutectic Si particles but their type, distribution and amount varies in the two alloys with different SDAS. EBSD analysis was also performed to study the crystallographic orientation relationships in the microstructure. One of the major highlights of this study is the understanding of the eutectic formation mechanism achieved by studying the orientation relationships of the aluminum in the eutectic to the surrounding primary aluminum dendrites.

  10. Magnetic properties of Nd\\/Fe double layers grown on Si(111) by electron beam evaporation

    Microsoft Academic Search

    Jos R. Fermin; Antonio Azevedo; Sergio M. Rezende; Luiz G. Pereira; Sergio Teixeira

    1998-01-01

    In-plane ferromagnetic resonance (FMR) has been used to study the room-temperature magnetic and crystalline properties of Nd\\/Fe bilayers. Several samples were grown by electron beam evaporation onto Si(111) substrates, for various Fe and Nd thicknesses. The symmetry of the resonance field as a function of the azimuthal angle departs from the sixfold one expected for a (111)Fe film. The FMR

  11. Equilibrium thermodynamics of Al\\/Si ordering in anorthite

    Microsoft Academic Search

    M. A. Carpenter

    1992-01-01

    Variations in the equilibrium degree of Al\\/Si order in anorthite have been investigated experimentally over the temperature range 800-1535 C. Spontaneous strain measurements give the temperature dependence of the macroscopic order parameter, Q, defined with respect to the \\u000a$$C\\\\bar 1 \\\\rightleftharpoons I\\\\bar 1$$\\u000a phase transition, while high temperature solution calorimetric data allow the relationship between Q and excess enthalpy, H,

  12. 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.

  13. The effect of alloy grain size on the transient oxidation behavior of an alumina-forming alloy. [Ni-16. 2%Cr-4. 7%Al-2. 5%Fe-0. 01%Si-0. 02%Y

    SciTech Connect

    Goedjen, J.G.; Shores, D.A. (Univ. of Minnesota, Minneapolis (United States))

    1992-04-01

    In the early stages of alloy oxidation, diffusion of solute through the metal to the surface is important in determining the composition of the oxide scale that forms during the transient stage. Rapid solute diffusion to the interface will promote the formation of a protective scale, thereby suppressing the formation of base-metal oxide. The effect of alloy grain size on the formation of the transient oxide scale has been studied using a very fine grained NiCrAlY alloy produced by plasma spraying. The long-term oxidation behavior of this alloy was found to be independent of the grain size of the underlying alloy. However, the short-term, transient oxidation rate was found to decrease with decreasing alloy grain size. This is attributed to the rapid grain boundary transport of Al and Cr to the oxide/metal interface which promoted the formation of Cr{sub 2}O{sub 3} and Al{sub 2}O{sub 3}.

  14. Effect of eutectic Si on surface nanocrystallization of AlSi alloys by surface mechanical attrition treatment

    Microsoft Academic Search

    H.-W. Chang; P. M. Kelly; Y.-N. Shi; M.-X. Zhang

    Pure Al (AA196) and AlSi (A356) alloy were subjected to surface nanocrystallization through surface mechanical attrition treatment (SMAT). Strain induced microstructure evolution, including grain refinement of Al matrix and Si particles, was examined using transmission electron microscopy. Nanocrystallization of Al matrix in both pure Al and A356 alloy occurs through formation of dislocation cells separated by dense dislocation walls and

  15. Magnetic properties of stoichiometric NpFe4Al8

    NASA Astrophysics Data System (ADS)

    Gonalves, A. P.; Almeida, M.; Cardoso, C.; Gasche, T.; Godinho, M.; Boulet, P.; Colineau, E.; Wastin, F.; Rebizant, J.

    2005-02-01

    The compound NpFe4Al8 was prepared by direct arc melting of the constituent elements, followed by annealing. It crystallizes in the ThMn12-type structure (space group I4/mmm, a = 8.7480(5) , c = 5.0372(4) ), with the iron atoms completely and only occupying the 8f positions. Magnetization measurements (T = 2-300 K, B = 0-7 T) show a ferromagnetic-type transition at TC = 135(2) K and a second anomaly at 118(3) K. The low temperature magnetization cycle is characterized by a hysteresis with a step similar to that previously observed for UFe4Al8 single crystals. First-principles density functional theory calculations of the NpFe4Al8 band structure point to a magnetic structure similar to that of UFe4Al8, in agreement with the observed magnetization cycle. The calculations indicate that the neptunium moment is aligned along one of the a or b axes, and the iron moments form a noncollinear structure in the a-b plane, with the antiferromagnetic and ferromagnetic contributions perpendicular and antiparallel to the neptunium spin moment, respectively.

  16. Microstructure and degradation behavior of forged Fe-Mn-Si alloys

    NASA Astrophysics Data System (ADS)

    Xu, Zhigang; Hodgson, Michael A.; Cao, Peng

    2015-03-01

    This work presents a comparative study of a series of Fe-Mn-Si alloys proposed as degradable biomaterials for medical applications. Five Fe-28wt.%Mn-xSi (where x = 0 to 8 wt.%) alloys were fabricated by an arc-melting method. All the as-cast alloys were subsequently subjected to homogenization treatment and hot forging. The microstructure and phase constituents were investigated. It is found that the grain size of the as-forged alloys ranged approximately from 30 to 50 ?m. The as-forged Fe-Mn-Si alloys containing Si from 2 to 6 wt.% was comprised of duplex martensitic ? and austenitic ? phases; however, the Si-free and 8 wt.% Si alloys only consisted of a single ? phase. After 30 days of static immersion test in a simulated body fluid (SBF) medium, it is found that pitting and general corrosion occur on the sample surfaces. Potentiodynamic analysis reveals that the degradation rate of the Fe-Mn-Si alloys increased gradually with Si content up to 6 wt.%, beyond which the degradation slows down.

  17. Electromagnetic and Microwave Absorption Properties of Fe Coating on SiC with Metal Organic Chemical Vapor Reaction

    NASA Astrophysics Data System (ADS)

    Liu, Yuan; Liu, Xiang-Xuan; Wang, Xuan-Jun; Wen, Wu

    2014-04-01

    SiC-Fe composites are prepared by metal organic chemical vapor deposition (MOCVD) using silicon carbide (SiC) and iron pentacarbonyl (Fe(CO)5) as the precursors. The structure and morphology analyses demonstrate that the Fe nanoparticles have been deposited on the surface of the SiC particles. In terms of reflection loss (RL), the absorbing frequency band (AFB, the value of RL < -10 dB), and the matching thickness (tm), SiC-Fe composites show the best performances: minimum RL of -31.6 dB with tm = 2.0 mm at 15.1 GHz, AFB of 12.9-17.3 GHz, indicating that Fe-doped SiC by MOCVD can significantly improve the electromagnetic properties of SiC and that SiC-Fe composites could be used as an effective microwave absorption material.

  18. Magnetic and thermodynamic properties of DyFe 2Si 2 further investigated with crystal-field theory and two-ion model

    Microsoft Academic Search

    Z.-S. Liu; M. Divis; V. Sechovsk

    2010-01-01

    We report our theoretical studies on the magnetic and thermodynamic properties of DyFe2Si2 using the crystal-field parameters (CFPs) proposed by Chatterji et al. recently [1]. Our calculated magnetization and magnetic specific heat curves obtained with the above CFPs based on the two-ion model we developed recently show reasonable agreement with the experimental data.

  19. THz Magneto-electric atomic rotations in the chiral compound Ba3NbFe3Si2O14. L. Chaix, S. de Brion,

    E-print Network

    Paris-Sud XI, Universit de

    and electric properties often appear encouraging the search for novel multiferroic and magnetoelectric phe fundamental research on multiferroics and magnetoelectric materi- als [1]. These magnetoelectric couplingsTHz Magneto-electric atomic rotations in the chiral compound Ba3NbFe3Si2O14. L. Chaix, S. de Brion

  20. 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.

  1. Galvanic Deposition of Nanoporous Si onto 6061 Al Alloy from Aqueous HF

    E-print Network

    Suni, Ian Ivar

    Galvanic Deposition of Nanoporous Si onto 6061 Al Alloy from Aqueous HF Aarti Krishnamurthy,a Don H University, Potsdam, New York 13699-5705, USA We report galvanic deposition of Si onto 6061 Al alloy from is currently dominated by thick film Si solar cells, thin film crystalline, polycrystalline, and amorphous Si

  2. [Relationship between Fe, Al oxides and stable organic carbon, nitrogen in the yellow-brown soils].

    PubMed

    Heng, Li-Sha; Wang, Dai-Zhang; Jiang, Xin; Rao, Wei; Zhang, Wen-Hao; Guo, Chun-Yan; Li, Teng

    2010-11-01

    The stable organic carbon and nitrogen of the different particles were gained by oxidation of 6% NaOCl in the yellow-brown soils. The relationships between the contents of selective extractable Fe/Al and the stable organic carbon/nitrogen were investigated. It shown that amounts of dithionite-citrate-(Fe(d)) and oxalate-(Fe(o)) and pyrophosphate extractable (Fe(p)) were 6-60.8 g x kg(-1) and 0.13-4.8 g x kg(-1) and 0.03-0.47 g x kg(-1) in 2-250 microm particles, respectively; 43.1-170 g x kg(-1) and 5.9-14.0 g x kg(-1) and 0.28-0.78 g x kg(-1) in < 2 microm particles, respectively. The contents of oxalate-(Al(o)) and pyrophosphate extractable (Al(p)) were 0.08-1.34 g x kg(-10 and 0.11-0.47 g x kg(-1) in 2-250 microm particles, respectively; 2.96-6.20 g x kg(-1) and 0.38-0.78 g x kg(-1) in < 2 microm particles, respectively. And amounts of selective extractable Fe are generally higher in paddy yellow-brown soils than in arid yellow-brown soils, and that of selective extractable Al are lower in the former than in the latter. Amounts of the stable organic carbon and nitrogen, higher in paddy yellow-brown soils than in arid yellow-brown soils, were 0.93-6.0 g x kg(-1) and 0.05-0.36 g x kg(-1) in 2-250 microm particles, respectively; 6.05-19.3 g x kg(-1) and 0.61-2.1 g x kg(-1) in < 2 microm particles, respectively. The ratio of the stable organic carbon and nitrogen (C(stable)/N(stable)) were 9.50-22.0 in 2-250 microm particles and 7.43-11.54 in < 2 microm particles, respectively. The stabilization index (SI(C) and SI(N)) of the organic carbon and nitrogen were 14.3-50.0 and 11.9-55.6 in 2-250 microm particles, respectively; 53.72-88.80 and 40.64-70.0 in < 2 microm particles, respectively. According to SI, it is lower in arid yellow-brown soils than in paddy yellow-brown soils. The organic carbon and nitrogen are advantageously conserved in paddy yellow-brown soil. An extremely significant positive correlation of the stable organic carbon and nitrogen with selective extractable Fe/Al is observed. The most amounts between the stable organic carbon and nitrogen and selective extractable Fe/Al appear in clay particles, namely the clay particles could protect the soil organic carbon and nitrogen. PMID:21250461

  3. Investigation of the {Fe}/{Si} interface and its phase transformations

    NASA Astrophysics Data System (ADS)

    Fanciulli, M.; Degroote, S.; Weyer, G.; Langouche, G.

    1997-04-01

    Thin 57Fe films (3-10 ) have been grown by molecular beam epitaxy (MBE) on (7 7) reconstructed Si(111) and (2 1) reconstructed Si(001) surfaces and by e-gun evaporation on an H-terminated Si(111) surface. Conversion electron Mssbauer spectroscopy (CEMS) with high statistical accuracy and resolution allowed a detailed microscopic investigation of the silicide formation mechanism and of the structural phase transformations upon annealing.

  4. 29 Si MAS-NMR spectroscopy of mica-type silicates: Observed and predicted distribution of tetrahedral Al-Si

    Microsoft Academic Search

    C. P. Herrero; M. Gregorkiewitz; J. Sanz; J. M. Serratosa

    1987-01-01

    29Si MAS-NMR spectra were obtained for vermiculite with tetrahedral composition x=Al\\/(Al+Si)=0.28, a synthetic mica with x=0.43, and margarite with x=0.5. Comparison between the observed and Monte-Carlo simulated spectra was used to test different Al-Si distribution schemes in the tetrahedral sheet. The results of this analysis are interpreted including earlier data corresponding to lower Al for Si substitutions (0.12=x=0.28), and it

  5. 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.

  6. Crystallization kinetics and magnetic properties of FeSiCr amorphous alloy powder cores

    NASA Astrophysics Data System (ADS)

    Xu, Hu-ping; Wang, Ru-wu; Wei, Ding; Zeng, Chun

    2015-07-01

    The crystallization kinetics of FeSiCr amorphous alloy, characterized by the crystallization activation energy, Avrami exponent and frequency factor, was studied by non-isothermal differential scanning calorimetric (DSC) measurements. The crystallization activation energy and frequency factor of amorphous alloy calculated from Augis-Bennett model were 476 kJ/mol and 5.51018 s-1, respectively. The Avrami exponent n was calculated to be 2.2 from the Johnson-Mehl-Avrami (JMA) equation. Toroid-shaped Fe-base amorphous powder cores were prepared from the commercial FeSiCr amorphous alloy powder and subsequent cold pressing using binder and insulation. The characteristics of FeSiCr amorphous alloy powder and the effects of compaction pressure and insulation content on the magnetic properties, i.e., effective permeability ?e, quality factor Q and DC-bias properties of FeSiCr amorphous alloy powder cores, were investigated. The FeSiCr amorphous alloy powder cores exhibit a high value of quality factor and a stable permeability in the frequency range up to 1 MHz, showing superior DC-bias properties with a "percent permeability" of more than 82% at H=100 Oe.

  7. Anomalous microstructure and magnetocaloric properties in off-stoichiometric LaFeSi and its hydride

    NASA Astrophysics Data System (ADS)

    He, Chun; Zhang, Ming-Xiao; Shao, Yan-Yan; Dong, Jing-Du; Yan, A.-Ru; Liu, Jian

    2015-07-01

    In the present work we reported the phase formation, microstructure, magnetocaloric effect and hydrogenation behavior of La-rich La1.7Fe11.6Si1.4 alloy. In this off-stoichiometric La(Fe,Si)13 alloy, the NaZn13-type La(Fe,Si)13 matrix phase shows faceted grains, with the Cr5B3-type La5Si3 used as the secondary phase distributed intergranularly. Such a peculiar morphology quickly forms upon one day annealing. In La1.7Fe11.6Si1.4 alloy, we have observed a significant field dependence of magnetostructural transition temperature (? 6.3 K/T), resulting in a large and table-like entropy change (?S ? 18 J/kgK in 2 T) over a broad temperature range (? 10 K). Upon hydrogenation, the maximum value of ?S keeps almost unchanged, while the Curie temperature increases up to 350 K. These results indicate that the investigated off-stoichiometric La(Fe,Si)13 alloy is a promising magnetic material for magnetic refrigerators. Project supported by the National Natural Science Foundation of China (Grant No. 51371184) and the Outstanding Youth Fund of Zhejiang Province, China (Grant No. LR14E010001).

  8. Si-based magnetic tunnel transistor with single CoFe base layer

    NASA Astrophysics Data System (ADS)

    Jang, S. H.; Kim, Y. W.; Lee, J. H.; Kim, K. Y.

    2005-11-01

    Magnetic tunnel transistors were prepared on Si(100) substrates by magnetron sputter deposition. By means of spin filtering through a single Co90Fe10 base layer, magnetocurrent ratios of 53%-55% and high transfer ratios of (1-2)10-4 for emitter-base bias of 1.5-2 V were obtained at 77 K. The bias dependence of the collector current showed the square-law behavior. From the modified Bell-Kaiser model, attenuation lengths of majority and minority spins of hot electrons are expected as 40+/-5 and 16+/-1 A? in the single Co90Fe10 layer, respectively. The decrease of transfer ratio was observed with decreasing base thickness from 80 to 30 A?, which may be related to the extension of the (Co2Si and Fe) intermediate region formed at Co90Fe10/Si interface in the thinner base layer.

  9. Influence of melt treatments on sliding wear behavior of Al7Si and Al7Si2.5Cu cast alloys

    Microsoft Academic Search

    K. G. Basavakumar; P. G. Mukunda; M. Chakraborty

    2007-01-01

    The microstructures and dry sliding wear behavior of Al7Si and Al7Si2.5Cu cast alloys were studied after various melt treatments\\u000a like grain refinement and modification. Results indicate that combined grain refined and modified Al7Si2.5Cu cast alloys\\u000a have microstructures consisting of uniformly distributed ?-Al grains, eutectic Al silicon and fine CuAl2 particles in the interdendritic region. These alloys exhibited better wear resistance

  10. 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 (DMMCs) 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.

  11. Solute redistribution during phase separation of ternary Fe-Cu-Si alloy

    NASA Astrophysics Data System (ADS)

    Luo, S. B.; Wang, W. L.; Xia, Z. C.; Wu, Y. H.; Wei, B.

    2015-06-01

    Ternary Fe48Cu48Si4 immiscible alloy was rapidly solidified under the containerless microgravity condition inside a drop tube. Liquid phase separation took place in the alloy melt and led to the formation of various segregated structures. The core-shell structure consisting of Fe-rich and Cu-rich zones and the homogenously dispersed structure were the major structural morphologies. Phase field simulation results revealed that the two-layer core-shell was the final structure of liquid phase separation. The solute redistribution of liquid Fe48Cu48Si4 alloy experienced the macroscopic solute distribution induced by liquid phase separation, the secondary phase separation within the separated liquid phases and the solute trapping during rapid solidification. Energy dispersive spectroscopy analysis showed that the solute Si was enriched in the Fe-rich zone whereas depleted in the Cu-rich zone. In addition, both ?Fe and (Cu) phases in the Fe-rich zone exhibited a conspicuous solute trapping effect. As compared with (Cu) phase, ?Fe phase had a stronger affinity with solute Si.

  12. Tailoring of a metastable material: alfa-FeSi2 thin film

    SciTech Connect

    Cao, Guixin [ORNL; Singh, David J [ORNL; Zhang, Xiaoguang [ORNL; Samolyuk, German D [ORNL; Qiao, Liang [ORNL; Parish, Chad M [ORNL; Ke, Jin [The University of Tennessee; Zhang, Yanwen [University of Tennessee (UTK) and Oak Ridge National Laboratory (ORNL); Guo, Hangwen [ORNL; Tang, Siwei [ORNL; Wang, Wenbin [ORNL; Yi, Jieyu [University of Tennessee (UTK) and Oak Ridge National Laboratory (ORNL); Cantoni, Claudia [ORNL; Siemons, Wolter [ORNL; Payzant, E Andrew [ORNL; Biegalski, Michael D [ORNL; Ward, Thomas Zac [ORNL; Sales, Brian C [ORNL; Mandrus, D. [University of Tennessee (UTK) and Oak Ridge National Laboratory (ORNL); Stocks, George Malcolm [ORNL; Gai, Zheng [ORNL

    2015-01-01

    The epitaxially stabilized metallic -FeSi2 thin films on Si(001) were grown using pulsed laser deposition. While the bulk material of -FeSi2 is a high temperature metastable phase and nonmagnetic, the thin film is stabilized at room temperature and shows unusual electronic transport and magnetic properties due to strain modification. The transport renders two different conducting states with a strong crossover at 50 K accompanied by an onset of ferromagnetism as well as a substantial magnetocaloric effect and magnetoresistance. These experimental results are discussed in terms of the unusual electronic structure of -FeSi2 obtained within density functional calculations and Boltzmann transport calculations with and without strain. Our findings provide an example of a tailored material with interesting physics properties for practical applications.

  13. Acetic Acid (H3COOH): GaAs; Pb; Ti Hydrochloric Acid (HCl): Al; Cr; Cu; Fe2O3; Ga; GaAs; GaN; In; Fe; Pb; Ni; NiO, Ni2O3; Sn;

    E-print Network

    Garmestani, Hamid

    Acetic Acid (H3COOH): GaAs; Pb; Ti Hydrochloric Acid (HCl): Al; Cr; Cu; Fe2O3; Ga; GaAs; GaN; In; Fe; Pb; Ni; NiO, Ni2O3; Sn; SnO2; Ti; Zn Hydrofluoric Acid (HF): GaAs; Ni; SiO2; Ti Nitric Acid (HNO3): C; Cu; GaAs; In; Fe; Pb; Ni; Ag; Pd; Pt; Sn; Ti; Zn; ZnO Phosphoric Acid (H3PO4): Al; Cu; GaAs; Ga

  14. Temperature Dependence of Tunnel Magnetoresistance in Co-Mn-Al/Al-Oxide/Co-Fe Junctions

    NASA Astrophysics Data System (ADS)

    Oogane, Mikihiko; Nakata, Jun; Kubota, Hitoshi; Ando, Yasuo; Sakuma, Akimasa; Miyazaki, Terunobu

    2005-06-01

    We investigated the temperature dependence of the tunnel magnetoresistance (TMR) effect in Co-Mn-Al/Al-oxide/Co-Fe tunnel junctions. The junction prepared without exposure to air during deposition showed very large TMR ratios of 65% at 10 K and 40% at room temperature. In contrast, the junction prepared with air exposure before and after Al-oxide layer fabrication showed a maximum TMR ratio of only 40% at a low temperature. Temperature dependences of tunnel conductance of these junctions were analyzed using a simple model that incorporates two contributions: elastic tunneling with decreasing spin polarization as temperature increases and spin-independent hopping tunneling through trap states in Al-oxide tunnel barriers. Results of analyses indicated that air exposure drastically reduced spin polarization and Curie temperature. It also created an inferior insulating layer at the Co-Mn-Al/Al-oxide interface.

  15. Performance of LiAl/LiI(Al2O3)/FeS2 thermal batteries

    NASA Astrophysics Data System (ADS)

    Lin, Yung-Hsin; Yu, Kuo-Tung; Yao, Pei-Chin; Hsu, Shu-En

    Performances of the LiAl/LiI(Al2O3)/FeS2 systems with different percentages of Al2O3 in the electrolyte were tested from 460 C to 580 C at various current densities and were compared with the performance of the LiAl/LiCl-KCl/FeS2 system. The results of single-cell and battery tests indicate that the LiAl/LiI(Al2O3)/FeS2 system has a feasibility for thermal potential applications. Compared to the LiAl/LiCl-KCl/FeS2 system, the LiI(Al2O3)-based system has poorer specific conductance and lower cell potential, but longer discharge life and greater capacity. A salient feature of the LiI(Al2O3)-based system, important for reliability considerations, is its apparent greater flexibility in battery internal heat control.

  16. Size dependent structural, vibrational and magnetic properties of BiFeO3 and core-shell structured BiFeO3@SiO2 nanoparticles

    NASA Astrophysics Data System (ADS)

    Chauhan, Sunil; Kumar, Manoj; Chhoker, Sandeep; Katyal, S. C.

    2014-04-01

    Bulk BiFeO3, BiFeO3 nanoparticles and core-shell structured BiFeO3@SiO2 nanoparticles were synthesized by solid state reaction method, sol-gel and Stber process (SiO2 shell) respectively. Transmission electron microscopy image confirmed the core-shell structure of BiFeO3@SiO2 nanoparticles with BiFeO3 core 50-90 nm and SiO2 shell 16 nm. X-ray diffraction and FTIR spectroscopy results showed the presence of distorted rhombohedral structure with R3c space group in all three samples. The magnetic measurement indicated the existence of room-temperature weak ferromagnetism in core-shell BiFeO3@SiO2 nanoparticles and BiFeO3 nanoparticles, whereas bulk BiFeO3 showed antiferromagnteic nature. Electron Spin Resonance results confirmed the enhancement in magnetic properties of coreshell structured BiFeO3@SiO2 nanoparticles in comparison with BiFeO3 nanoparticles and bulk BiFeO3.

  17. Near-infrared photodetection in n-type nanocrystalline FeSi2/p-type Si heterojunctions.

    PubMed

    Promros, Nathaporn; Chen, Li; Yoshitake, Tsuyoshi

    2013-05-01

    n-Type nanocrystalline (NC) FeSi2/p-type Si heterojunctions, which were prepared by pulsed laser deposition, were evaluated as a near infrared photodiode. The built-in potential was estimated to be approximately 1.1 eV from the capacitance-voltage measurement. These junctions showed a rectifying behavior accompanied by a large leakage current. The near infrared light detection performance was evaluated using a 1.33 microm laser in the temperature range of 77-300 K. At a reverse bias of -5 V, the detectivity was 5.5 x 10(7) cm Hz1/2 W(-1) at 300 K and it was dramatically enhanced to be 8.0 x 10(10) cm Hz1/2 W(-1) at 77 K. It was demonstrated that NC-FeSi2 is a new potential material applicable to NIR photodetectors operating at low temperatures. PMID:23858906

  18. Defect Band Characteristics in Mg-Al and Al-Si High-Pressure Die Castings

    Microsoft Academic Search

    C. M. Gourlay; H. I. Laukli; A. K. Dahle

    2007-01-01

    Bands of positive macrosegregation and porosity commonly follow the surface contour of components produced by high-pressure\\u000a die casting (HPDC). In this article, Al alloy AlSi7Mg and Mg alloys AZ91 and AM60 were cast into tensile test bars using cold-chamber\\u000a (cc) HPDC. Microstructural characterization revealed that externally solidified crystals (ESCs) are not necessary for defect\\u000a band formation, and that defect bands

  19. Tridymite and maghemite formation in an Fe-SiO smoke

    NASA Astrophysics Data System (ADS)

    Rietmeijer, F. J. M.; Nuth, J. A., III

    Grains produced in porous Fe-SiO smoke are analyzed by means of electron microscopy to determine their crystallographical, morphological, and chemical properties. The nucleation of metal oxide condensates takes place as the vapor evolves in a condensation-flow apparatus, initially producing simple crystalline phases. Fe nucleation follows, and the subsequent heterogeneous nucleation of quenched mixed high-Fe silica grains exhibits associated Fe-depletion, eventually producing pure silica grains. The coalescence exhibited by the pure silica grains is compatible with the higher surface energy found in the pure silica phase. During coagulation the grains melt and anneal to a chemically pure mixture of alpha- and beta-tridymite, and the precipitation of amorphous silica material is observed. The settling of grains in evolving solar nebula is theorized to be related to the stickiness of this material, and maghemite is suggested to contribute to the Fe/Si fractionation in solar nebula.

  20. Site location of Co in {beta}-FeSi{sub 2}

    SciTech Connect

    Dezsi, I.; Fetzer, Cs.; Kiss, M.; Degroote, S.; Vantomme, A. [KFKI Research Institute for Particle and Nuclear Physics, 114 P.O. Box 49, H-1525 Budapest (Hungary); Instituut voor Kern- en Stralingsfysika, Katholieke Universiteit Leuven, Celestijnenlaan 200D, B-3001 Leuven (Belgium)

    2005-10-01

    In order to reveal cationic site preference in {beta}-FeSi{sub 2}, Co-substituted samples synthesized by various techniques such as molecular beam epitaxy, ion implantation, and chemical vapor transport were investigated by {sup 57}Fe conversion electron Moessbauer (CEM) as well as {sup 57}Co Moessbauer emission (ME) spectroscopy. Literature on the structure of {beta}-FeSi{sub 2} is somewhat contradictory, especially on the point of the population of the two iron sites in the orthorhombic structure. {sup 57}Co ME and {sup 57}Fe CEM spectra both showed two quadrupole split spectral components in the crystalline phase. Hyperfine parameters indicate that Co atoms substitute Fe in both Fe positions in the orthorhombic lattice. The aim of the present study was to get reliable results on the relative population of the two iron sites and determine the substitution of the iron sites by Co atoms in the {beta}-FeSi{sub 2} lattice. The relative intensities of the two components in the absorption and emission Moessbauer spectra were found to be very similar for the samples prepared by different techniques, indicating a homogeneous distribution of Co on both Fe sites.

  1. PHYSICAL REVIEW B 85, 014113 (2012) Structure and stability of Al2Fe and Al5Fe2: First-principles total energy and phonon calculations

    E-print Network

    Widom, Michael

    2012-01-01

    is the prototype binary magnetic alloy based on a bcc structure.1 The specific phase Al5Fe2 is important Al-Fe phase diagram, is distinguished by an unusually low triclinic symmetry. The initial phase diagram determination is difficult because many phases often exist within small composition ranges

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

    NASA Astrophysics Data System (ADS)

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

    2015-05-01

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

  3. 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

  4. MOKE Study of Fe/Co/Al Multilayers

    SciTech Connect

    Jani, Snehal; Lakshmi, N.; Venugopalan, K. [Department of Physics, Mohanlal Sukhadia University, Udaipur 313 001 (India); Rajput, Parasmani; Zajaoc, M.; Rueffer, R. [European Synchrotron Radiation Facility, 6 rue Jules Horowitz, BP 220 F-38043 Grenoble Cedex (France); Reddy, V. R.; Gupta, Ajay [UGC-DAE Consortium for Scientific Research, Khandwa Road, Indore 452 001 (India)

    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.

  5. A comparative wear study on Al-Li and Al-Li/SiC composite

    SciTech Connect

    Okumus, S. Cem, E-mail: cokumus@sakarya.edu.tr; Karslioglu, Ramazan, E-mail: cokumus@sakarya.edu.tr; Akbulut, Hatem, E-mail: cokumus@sakarya.edu.tr [Sakarya University Engineering Faculty, Department of Metallurgical and Materials Engineering, Esentepe Campus, 54187, Sakarya (Turkey)

    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.

  6. Core-shell Fe3O4@SiO2 nanoparticles synthesized with well-dispersed hydrophilic Fe3O4 seeds

    E-print Network

    Gao, Hongjun

    Core-shell Fe3O4@SiO2 nanoparticles synthesized with well-dispersed hydrophilic Fe3O4 seeds Chao by a modified Stober method using 20 nm hydrophilic Fe3O4 NPs as seeds. The core-shell NPs were characterized, the ratio of TEOS/Fe3O4, and the concentration of hydrophilic Fe3O4 seeds were found to be very influential

  7. The effects of Mn additions on the microstructure and mechanical properties of AlSiCu casting alloys

    Microsoft Academic Search

    J. Y. Hwang; H. W. Doty; M. J. Kaufman

    2008-01-01

    The effects of Mn on the microstructure and mechanical properties of Type 319 aluminum casting alloys have been examined. It is shown that, as the Mn content is increased up to 0.65wt.pct (corresponding to an Fe\\/Mn ratio of ?1.2) in the baseline alloy (Al7wt.%Si3.8wt.%Cu0.5wt.%Fe), the plate-like ? intermetallic phase is completely converted to the Chinese script ? phase resulting in

  8. Electrolyte effects in Li(Si)/FeS{sub 2} thermal batteries

    SciTech Connect

    Guidotti, R.A.; Reinhardt, F.W.

    1994-10-01

    The most common electrochemical couple for thermally activated (``thermal``) batteries is the Li-alloy/FeS{sub 2} system. The most common Li-alloys used for anodes are 20% Li-80% Al and 44% Li-56% Si (by weight); liquid Li immobilized with iron powder has also been used. The standard electrolyte that has been used in thermal batteries over the years is the LiCl-KCl eutectic that melts at 352{degrees}C. The LiCl-LiBr-LiF eutectic had the best rate and power characteristics. This electrolyte melts at 436{degrees}C and shows very low polarization because of the absence of Li+ gradients common with the LiCl-KCl eutectic. The low-melting electrolytes examined included a KBr-LiBr-LiCl eutectic (melting at 321{degrees}C), a LiBr-KBr-LiF eutectic (melting at 313{degrees}C), and a CsBr-LiBr-KBr eutectic (melting at 238{degrees}C). The CsBr-based salt had poor conductivity and was not studied further. The LiBr-KBr-LiF eutectic outperformed the KBr-LiBr-LiCl eutectic and was selected for more extensive testing. Because of their lower melting points and larger liquidi relative to the LiCl-KCl eutectic, the low-melting electrolytes are prime candidates for long-life applications (i.e., for activated lives of one hour or more). This paper will detail the relative performance of the Li(Si)/FeS{sub 2} couple using primarily the LiCl-KCl (standard) eutectic, the LiCl-LiBr-LiF (all-Li) eutectic, and the LiBr-KBr-LiF (low-melting) eutectic electrolytes. Most of the tests were conducted with 5-cell batteries; validation tests were also carried out with appropriate full-sized batteries.

  9. Electrolyte effects in Li(Si)/FeS2 thermal batteries

    NASA Astrophysics Data System (ADS)

    Guidotti, Ronald A.; Reinhardt, Frederick W.

    The most common electrochemical couple for thermally activated ('thermal') batteries is the Li-alloy/FeS2 system. The most common Li-alloys used for anodes are 20% Li-80% Al and 44% Li-56% Si (by weight); liquid Li immobilized with iron powder has also been used. The standard electrolyte that has been used in thermal batteries over the years is the LiCl-KCl eutectic that melts at 352 C. The LiCl-LiBr-LiF eutectic had the best rate and power characteristics. This electrolyte melts at 436(degrees)C and shows very low polarization because of the absence of Li(+) gradients common with the LiCl-KCl eutectic. The low-melting electrolytes examined included a KBr-LiBr-LiCl eutectic (melting at 321 C), a LiBr-KBr-LiF eutectic (melting at 313 C), and a CsBr-LiBr-KBr eutectic (melting at 238 C). The CsBr-based salt had poor conductivity and was not studied further. The LiBr-KBr-LiF eutectic outperformed the KBr-LiBr-LiCl eutectic and was selected for more extensive testing. Because of their lower melting points and larger liquidi relative to the LiCl-KCl eutectic, the low-melting electrolytes are prime candidates for long-life applications (i.e., for activated lives of one hour or more). This paper will detail the relative performance of the Li(Si)/FeS2 couple using primarily the LiCl-KCl (standard) eutectic, the LiCl-LiBr-LiF (all-Li) eutectic, and the LiBr-KBr-LiF (low-melting) eutectic electrolytes. Most of the tests were conducted with 5-cell batteries; validation tests were also carried out with appropriate full-sized batteries.

  10. Structural and magnetic stability of Fe{sub 2}NiSi

    SciTech Connect

    Gupta, Dinesh C., E-mail: idu.idris@gmail.com; Bhat, Idris Hamid, E-mail: idu.idris@gmail.com; Chauhan, Mamta, E-mail: idu.idris@gmail.com [Condensed Matter Theory Group, School of Studies in Physics, Jiwaji University, Gwalior - 474011 (India)

    2014-04-24

    Full-potential ab-initio calculations in the stable F-43m phase have been performed to investigate the structural and magnetic properties of Fe{sub 2}NiSi inverse Heusler alloys. The spin magnetic moment distributions show that present material is ferromagnetic in stable F-43m phase. Further, spin resolved electronic structure calculations show that the discrepancy in magnetic moments of Fe-I and Fe-II depend upon the hybridization of Fe with the main group element. It is found that the main group electron concentration is predominantly responsible in establishing the magnetic properties, formation of magnetic moments and the magnetic order for present alloy.

  11. Speciation and crystal chemistry of Iron(III) chloride hydrolyzed in the presence of SiO{sub 4} ligands. 1. An Fe K-edge EXAFS study

    SciTech Connect

    Doelsch, E.; Rose, J.; Masion, A.; Bottero, J.Y.; Nahon, D.; Bertsch, P.M.

    2000-05-16

    The hydrolysis of Fe-Si systems with Si/Fe ratios between 0 and 4 leads to the formation of poorly crystalline or, more frequently, of long-range disorganized precipitates. The increase of Si/Fe molar ratios results in a dramatic change of Fe polymerization. The formation of double and single corner-sharing Fe linkages is reduced compared to pure Fe hydrolysis products. The growth regime depends on the Si concentration in the system. Three-dimensional and two-dimensional growth of Fe colloids occurs at low and high Si/Fe ratios, respectively, systems with Si/Fe ratios around 1 representing a crossover between these two regimes. Though Si neighbors cannot be detected unequivocally by Fe K-edge EXAFS, their presence in the close environment of Fe atoms is evident from the change in Fe speciation.

  12. Importance of Doping and Frustration in Itinerant Fe-doped Cr2Al

    SciTech Connect

    Susner, Michael A [ORNL; Parker, David S [ORNL; Safa-Sefat, Athena [ORNL

    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.

  13. Studies of spectra for gas-phase prepared Sm 2Fe 17 - xSi xC y

    NASA Astrophysics Data System (ADS)

    Li, Z. W.; Morrish, A. H.

    1996-10-01

    Mssbauer spectra of the carbides Sm 2Fe 17 - xSi xC y with x = 1, 2 and 3, made by heating powders of their parents in CH 4 at 700C, have been studied at room temperature and above the Curie temperature. Only 5-8% of an ?-Fe phase coexists with the carbides when the Si concentration is x ? 1. This shows that Si is effective in stabilizing the 2:17-type structure of the carbides. For Sm 2Fe 17 - xSi xC y, the isomer shifts increase with Si concentration and the quadrupole splittings have a significant increase in magnitude but a different sign as compared to their parents. The hyperfine fields as well as the Fe moments for Sm 2Fe 17 - xSi xC y decrease with Si substitution. This may be responsible for the smaller saturation magnetization observed for the carbides.

  14. Thermodynamic calculations of Fe-Mg interdiffusion in (Mg,Fe)2SiO4 polymorphs and perovskite

    NASA Astrophysics Data System (ADS)

    Zhang, Baohua; Shan, Shuangming

    2015-02-01

    In this study, we show that the temperature and pressure dependence of Fe-Mg interdiffusion in (Fe,Mg)2SiO4 polymorphs (olivine, wadsleyite, and ringwoodite) and perovskite can be successfully reproduced in terms of bulk elastic and expansivity data through a thermodynamic model (so-called cB? model) that interconnects point defect parameters with bulk properties. Under dry and wet conditions, our calculated Fe-Mg interdiffusion coefficients DcalcFe-Mg (particularly for anisotropic diffusivity in olivine), activation enthalpy hact, and activation volume ?act over a wide range of geologically relevant temperatures (1000-2400 K) and pressures (0-100 GPa) are consistent with the experimental ones when the uncertainties are considered.

  15. High frequency properties of Fe-Si nano-powder/epoxy films.

    PubMed

    Kim, Hyun-Bin; Jeun, Joon-Pyo; Hong, Seong-Min; Kang, Phil-Hyun

    2010-01-01

    Composites of Fe93.5Si6.5 powder and epoxy (diglycidyl ether of bisphenol A type) were prepared using an electron beam irradiation process. Scanning electron microscope (SEM), vibrating sample magnetometer (VSM) and network analyzer were used to analyze the structure, electromagnetic properties and micro wave absorption of the composites. Results show that the saturation magnetization depends on the fraction of the Fe93.5Si6.5 powder in the composite, which affects initial permeability. It is believed that the eddy current loss is a dominant factor over 1 GHz and that the resonance frequency of the composite decreases with increasing fractions of Fe93.5Si6.5 powder. Finally, reflection loss was calculated from the permeability and permittivity of these composites. Composite with 50 wt% Fe93.5Si6.5 powder fractions and 5 mm thickness showed reflection loss below -20 dB from 3.66 GHz to 4.16 GHz. Therefore, it is believed that thin Fe-Si/epoxy composites may be a good candidate for microwave absorption application. PMID:20352813

  16. Electromagnetic properties of flake-shaped Fe-Si alloy particles prepared by ball milling

    NASA Astrophysics Data System (ADS)

    Cao, Lei; Jiang, Jian-Tang; Wang, Zeng-Quan; Gong, Yuan-Xun; Liu, Chao; Zhen, Liang

    2014-11-01

    Flake-shaped Fe-Si alloy particles with high aspect ratios were fabricated by ball milling commercially available Fe-Si powder, aiming to fabricate high-performance microwave absorbing fillers for coatings applied in 1-4 GHz range. To compare with spherical particles, higher permittivity and permeability was observed by using flaky particles as fillers. High aspect ratios contributed to an enhanced dielectric relaxation in the 1-4 GHz band, resulting in an increased permittivity. The thin thickness together with the high resistivity of Fe-Si flakes was believed to be helpful for suppressing the effect of eddy current and thus lead to an increase in the permeability. The electromagnetic wave absorbing (EMA) performances were observed to be enhanced. With a thin thickness of 2 mm, a wide absorption band with a minimum reflection loss of -12 dB was achieved in 1-4 GHz range, when using 75 wt% of flaky Fe-Si particles as fillers. The study indicated that flake-shaped Fe-Si particles were a promising candidate for EMA materials in L and S bands.

  17. Magnetic damping constant of Co{sub 2}FeSi Heusler alloy thin film

    SciTech Connect

    Oogane, Mikihiko; Yilgin, Resul; Shinano, Masatsugu; Yakata, Satoshi; Sakuraba, Yuya; Ando, Yasuo; Miyazaki, Terunobu [Department of Applied Physics, Graduate School of Engineering, Tohoku University, Aoba-yama 05, Sendai 980-8579 (Japan)

    2007-05-01

    Co{sub 2}FeSi films were prepared using magnetron sputtering technique on Cr buffer layers and MgO(001) substrates at various annealing temperatures. We investigated the crystal structures, magnetic properties (M{sub s} and H{sub c}), surface roughness, and magnetic damping constants ({alpha}) of the prepared Co{sub 2}FeSi films. Out-of-plane angular dependences of the resonance field and the linewidth of the ferromagnetic resonance spectra were measured and fitted using the Landau-Lifshitz-Gilbert equation to determine the damping constant. The as-deposited Co{sub 2}FeSi film exhibited an amorphous and disordered structure; the {alpha} value was 0.008. In contrast, the Co{sub 2}FeSi films annealed over 300 degree sign C showed epitaxial growth and had a (001)-oriented and L2{sub 1} ordered structure. Both disordered and L2{sub 1} ordered Co{sub 2}FeSi films showed similar {alpha} values.

  18. Nitriding thermochemical treatment and niobium dual effect on nanocrystallization of FeSiBCu ribbons

    SciTech Connect

    Atmani, H.; Grognet, S.; Teillet, J.

    1999-12-31

    In recent years, nanocrystalline magnetic materials have been widely investigated in order to manufacture a material with high saturation magnetic flux density, and good soft magnetic properties compatible with thermal stability. These materials have been achieved by the granular structure crystallized from an amorphous phase as is the case for Fe{sub 73{center_dot}5}Cu{sub 1}Nb{sub 3}Si{sub 13{center_dot}5}B{sub 9} melt spun ribbon. This material exhibits excellent soft magnetic properties due to the formation of bcc Fe(Si) nanocrystallites immersed in a remaining amorphous phase. Such a material has a magnetostriction close to zero. The factors contributing to such nanophased structures are the additive elements to the basic FeSiB system, and the method of treatment. Copper addition is known to increase the nucleation centers in crystals while niobium is known to hinder their growth process. Conventional thermal treatment (CTT) is commonly used as annealing method. In this study, starting from the FeSiBCu system, the authors have added Nb. For the annealing, they have used a nitriding thermochemical treatment (NTT). The authors show the nitriding treatment effect on the structural behavior of FeSiBCu({+-}Nb) ribbons and they propose a nitriding mechanism.

  19. Prediction of potential high-pressure structures of FeSiO3

    NASA Astrophysics Data System (ADS)

    Cohen, R. E.; Lin, Yangzheng; Floris, Andrea

    2015-03-01

    We predict candidate high-temperature, high-pressure structures of FeSiO3 that we call post-perovskite II (PPv-II) by applying an evolutionary algorithm within density functional theory (DFT)+U using PWSCF and XTALOPT. Using density functional perturbation theory (DFPT) we compute the phonons and found some more stable versions of this phase for the ground state. We compared the x-ray diffraction pattern of FeSiO3 PPv-II with experimental results of the recently reported ``H phase'' of (Fe,Mg)SiO3. We also calculated the static equation of state, the enthalpy, and the bulk modulus of the PPv-II phases and compared them 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. We explore the different predictions of DFT and DFT+U. This work is supported by NSF.

  20. Effect of melt treatment on microstructure and impact properties of Al7Si and Al7Si2.5Cu cast alloys

    Microsoft Academic Search

    K. G. Basavakumar; P. G. Mukunda; M. Chakraborty

    2007-01-01

    The microstructures and impact toughness of Al-7Si and Al-7Si-2.5Cu cast alloys were studied after various melt treatments\\u000a like grain refinement and modification. The results indicate that combined grain refined and modified Al-7Si-2.5Cu alloys\\u000a have microstructures consisting of uniformly distributed ?-Al grains, interdendritic network of fine eutectic silicon and fine CuAl2 particles in the interdendritic region. These alloys exhibited improved impact

  1. On Core Structure Properties and Peierls Stress of Dissociated Superdislocations in Aluminides: NiAl and FeAl

    Microsoft Academic Search

    Xiaozhi Wu; Shaofeng Wang; Congbo Li

    2010-01-01

    The study of dislocation properties in B2 structure intermetallics NiAl and FeAl is crucial to understand their mechanical behaviors. In this paper, the core structure and Peierls stress of collinear dissociated (111}{110} edge superdislocations in NiAl and FeAl are investigated with the modified P-N dislocation equation. The generalized stacking fault energy curve along (111) direction in {110} slip plane contains

  2. Structure of Ti-Al-Si-N gradient coatings

    NASA Astrophysics Data System (ADS)

    Ovchinnikov, S. V.; Korotaev, A. D.; Pinzhin, Yu. P.

    2015-05-01

    The microstructure, the stresses, and the elemental composition of Ti-Al-Si-N gradient coatings are studied by transmission electron microscopy and electron-probe microanalysis of thin foils prepared in the cross section of the coatings. As the concentration of the elements that alloy titanium nitride increases across the coating thickness, the structure of the coating changes from submicrocrystalline columnar grains to nanocrystalline grains. In these structural states, the structural characteristics (lattice parameter, lattice bending-torsion, crystal size, type of intragranular defect structure) and the residual stresses change. The magnitude and the sign of residual stresses change when the type of structural state changes.

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

    SciTech Connect

    Gao, Tenghua, E-mail: gao.t.ab@m.titech.ac.jp; Zhang, Cong; Sannomiya, Takumi; Muraishi, Shinji; Nakamura, Yoshio; Shi, Ji [Department of Metallurgy and Ceramics Science, Tokyo Institute of Technology, 2-12-1 Oh-okayama, Meguro-ku, Tokyo 152-8552 (Japan)

    2014-09-01

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

  4. Magnetic and optical properties of Fe2VAl and Fe3Al

    NASA Astrophysics Data System (ADS)

    Xu, B.; Liu, J.; Yi, L.

    2007-04-01

    Full-potential linearized augmented plane wave plus local orbital method (FPLAPW + lo) calculations were performed for Fe2VAl and Fe3Al in order to investigate magnetic and optical properties and to show the origin of various optical transitions. It was found that the lattice constant and spin magnetic moments with the GGA method differ more from the respective experimental values than those calculated with the LSDA method. Furthermore, our calculated lattice constant and spin magnetic moments with the LSDA method were in overall better agreement with experiment. Our predictions agreed well with recent experimental reflectivity spectra. Meanwhile, the spectral peaks at the transitions were analyzed from the imaginary part of the dielectric function.

  5. Dopant species with AlSi and NSi 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 AlSi bonding such as (CH3)2AlSiH3 and NSi 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 AlN bonding. By reflecting on experimental evidence in the MOCVD of various doped semiconductor materials, it is anticipated that the availability of dopant species with AlSi, and alternatively NSi bonding near the hot deposition surface, can govern the incorporation of Si atoms, as well as other point defects, at the AlN surface.

  6. Adhesion of Escherichia coli to nano-Fe/Al oxides and its effect on the surface chemical properties of Fe/Al oxides.

    PubMed

    Liu, Zhao-Dong; Li, Jiu-Yu; Jiang, Jun; Hong, Zhi-Neng; Xu, Ren-Kou

    2013-10-01

    We investigated the adhesion of Escherichia coli to ?-Fe2O3 and ?-Al2O3 and the effects of adhesion on the surface properties of the oxides in batch experiments, where we conducted potentiometric titration, zeta potential measurements, and FTIR spectroscopy. The adhesion isotherms fitted a Langmuir equation well. ?-Al2O3 had a higher adhesion capacity than ?-Fe2O3 because of the higher positive charge on ?-Al2O3. The adhesion of E. coli to Fe/Al oxides decreased with increasing pH. Adhesion increased with increasing NaCl concentration, reaching its maximum at 0.05M for ?-Fe2O3 and at 0.1M for ?-Al2O3, after which it decreased with further increases in NaCl concentration. Therefore, the electrostatic force plays an important role in the adhesion of E. coli to Fe/Al oxides. The zeta potential-pH curves of the binary-system fell between that for bacteria and those for Fe/Al oxides. Thus, overlapping of the diffuse layers of the electric double layers on the negatively-charged E. coli and positively-charged Fe/Al oxides reduced the effective surface charge density of the minerals and bacteria. E. coli adhesion decreased the point of zero salt effect and the isoelectric point of the Fe/Al oxides. The FTIR spectra indicated that non-electrostatic force also contributed to the interaction between E. coli and Fe/Al oxides, in addition to the electrostatic force between them. PMID:23732807

  7. Spin crossover in Fe2SiO4 liquid at high pressure

    NASA Astrophysics Data System (ADS)

    Ramo, David Muoz; Stixrude, Lars

    2014-07-01

    We combine spin-polarized density functional theory with first principle molecular dynamics (FPMD) to study the spin crossover in liquid Fe2SiO4, up to 300 GPa and 6000 K. In contrast to the much sharper transition seen in crystals, we find that the high- to low-spin transition occurs over a very broad pressure interval (>200 GPa) due to structural disorder in the liquid. We find excellent agreement with the experimental Hugoniot. We combine our results with previous FPMD calculations to derive the partial molar volumes of the oxide components MgO, FeO, and SiO2. We find that eutectic melts in the MgO-FeO-SiO2 system are denser than coexisting solids in the bottom 600 km of Earth's mantle.

  8. Hydriding and dehydriding kinetics in magnetocaloric La(Fe,Si)13 compounds

    NASA Astrophysics Data System (ADS)

    Wang, G. F.; Mu, L. J.; Zhang, X. F.; Zhao, Z. R.; Huang, J. H.

    2014-04-01

    We report on the kinetics of hydrogen absorption and desorption in magnetocaloric La(Fe,Si)13 materials based on experimental results and model calculations. In the model, the diffusion process is considered to take place dominantly in a hydriding or dehydriding reaction. An important parameter "characteristic absorption/desorption time" is introduced to predict the kinetics of hydriding/dehydriding reaction in a simple way. The application of the model on the La0.9Ce0.1Fe11.44Si1.56 compound gives coincident kinetic results with those determined from experiments. It indicates that the model provides an efficient guidance for measuring and comparing the kinetic property of the magnetocaloric La(Fe,Si)13Hy materials.

  9. Formation and Phase Selection of Iron-Rich Intermetallics in Al-4.6Cu-0.5Fe Cast Alloys

    NASA Astrophysics Data System (ADS)

    Liu, K.; Cao, X.; Chen, X.-G.

    2013-02-01

    The solidification structures of Al-Cu 206 cast alloys at a high iron level of 0.5 pct were systematically studied by means of differential scanning calorimetry, electron backscattered diffraction, and transmission electron microscopy. The full solidification sequences of the 206 cast alloys at 0.5 pct Fe were established. The influences of both alloy composition ( i.e., Si and Mn contents) and cooling rate on the formation and phase selection of the iron-rich intermetallics have been systematically explored. At a cooling rate of 12 K/min, it was found that one of the three iron-rich phases, i.e., Chinese script Alm(FeMn) and ?-Fe, or platelet Al3(FeMn), may precipitate as the dominant iron-rich intermetallic, depending on Si and Mn contents. However, the dominant Chinese script iron-rich intermetallics, Alm(FeMn) and/or ?-Fe, can be fully obtained for the 206 Al-Cu cast alloys at 0.5 pct Fe above a threshold cooling rate that can easily be obtained in normal industrial casting conditions, indicating that there is a significant potential of designing and developing new 206 Al-Cu cast alloys with a high tolerant iron content.

  10. In situ structural investigation of Fe-S-Si immiscible liquid system and evolution of Fe-S bond properties with pressure

    Microsoft Academic Search

    G. Morard; C. Sanloup; B. Guillot; G. Fiquet; M. Mezouar; J. P. Perrillat; G. Garbarino; K. Mibe; T. Komabayashi; K. Funakoshi

    2008-01-01

    Fe-S-Si immiscibility has been investigated using in situ X-ray methods at high pressure and high temperature. An in situ X-ray diffraction study of immiscible liquids for P?5 GPa and T\\/Tm?1.1 has been performed, showing differences in structural properties between S-rich and Si-rich coexisting liquid phases. Moreover, the respective role of S and Si on Fe alloys has been quantitatively investigated

  11. Solid solubility of Ge, Si, and Mg in Fe 2O 3 and photoelectric behavior

    NASA Astrophysics Data System (ADS)

    Sanchez, H. L.; Steinfink, H.; White, H. S.

    1982-01-01

    Solid solutions of GeO 2 in Fe 2O 3 were prepared by mechanically mixing the solids and firing at 1000C in air, and from a gel obtained by the addition of an alcohol solution of germanium ethoxide to iron dissolved in HNO 3. The dried gel was then heated at 1000C. The solubility limit is 5 mole% GeO 2, Fe 1.95Ge 0.05O 3. Similar procedures were used to prepare solid solutions with Si and the solubility limit is greater than 4 mole% SiO 2. Firing of mixtures or gels of Fe 2O 3 containing Mg produces a spinel phase even at the lowest detectable concentrations. The resistivity of pressed pellets of Fe 2- xGe xO 3 varies from about 10 6 ohm-cm for x = 0 to about 10 -1 ohm-cm for x = 0.05. The photoassisted electrolysis of water at Ge-doped Fe 2O 3 electrodes is demonstrated. The {Fe 2O 3(Ge) }/{0.7 M Fe(CN)4-6}, {0.05 M Fe(CN) 3-6}/{Pt} photoelectrochemical cell showed a 0.29-V open-circuit voltage, 1.2-mA/cm 2 short-circuit current, 0.31 fill factor, and 0.06% power efficiency.

  12. Thermal Conductivity of the Molten CaO-SiO2-FeO x System

    NASA Astrophysics Data System (ADS)

    Kang, Youngjo; Nomura, Kiyoshi; Tokumitsu, Kazuto; Tobo, Hiroyuki; Morita, Kazuki

    2012-12-01

    Thermal conductivity measurements were carried out on synthetic steelmaking slag using the hot-wire method. Furthermore, local structure analysis in the melts was carried out in order to investigate the relationship with the composition dependence. The thermal conductivity of the CaO-SiO2-FeO x melts significantly decreased as the content of FeO x increases, particularly at lower basicity. Both chemical analysis and the observation show that the amount of Fe2+ increases when CaO/SiO2 is smaller, implying more basic behavior of FeO than FeO1.5. According to further analyses by Mssbauer spectroscopy, the degree of basicity of FeO1.5 remains virtually unchanged in the composition range of interest. From the experimental results, it could be concluded that the thermal conductivity of the silicate melt containing iron oxide is highly dependent on the valence of the Fe ion and comparatively independent of the amphoteric behavior of FeO1.5.

  13. High-quality epitaxial CoFe/Si(111) heterostructures fabricated by low-temperature molecular beam epitaxy

    SciTech Connect

    Maeda, Y.; Yamada, S.; Ando, Y.; Yamane, K.; Miyao, M. [Department of Electronics, Kyushu University, 744 Motooka, Fukuoka 819-0395 (Japan); Hamaya, K. [Department of Electronics, Kyushu University, 744 Motooka, Fukuoka 819-0395 (Japan); PRESTO, Japan Science and Technology Agency, Sanbancho, Tokyo 102-0075 (Japan)

    2010-11-08

    We demonstrate atomically controlled heterojunctions consisting of ferromagnetic CoFe alloys and silicon (Si) using low-temperature molecular beam epitaxy with a good atomic matching at the (111) plane. The saturation magnetization of the CoFe layers grown reaches {approx}85% of the value of bulk samples reported so far, and can be systematically controlled by tuning the ratio of Co to Fe, indicating that the silicidation reactions between CoFe and Si are suppressed and the heterojunctions are very high quality. We find that the Schottky barrier height of the high-quality CoFe/Si(111) junctions is unexpectedly low compared to the previous data for other metal/Si ones, implying the reduction in the Fermi-level-pinning effect. We can expand the available high-quality ferromagnet/Si heterostructures in the field of Si-based spintronics.

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

    PubMed

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

    2013-02-15

    We have investigated the structure of the Al(13)Fe(4)(010) surface using both experimental and ab initio computational methods. The results indicate that the topmost surface layers correspond to incomplete puckered (P) planes present in the bulk crystal structure. The main building block of the corrugated termination consists of two adjacent pentagons of Al atoms, each centered by a protruding Fe atom. These motifs are interconnected via additional Al atoms referred to as "glue" atoms which partially desorb above 873 K. The surface structure of lower atomic density compared to the bulk P plane is explained by a strong Fe-Al-Fe covalent polar interaction that preserves intact clusters at the surface. The proposed surface model with identified Fe-containing atomic ensembles could explain the Al(13)Fe(4) catalytic properties recently reported in line with the site-isolation concept [M. Armbrster et al., Nat. Mater. 11, 690 (2012)]. PMID:25166385

  15. Field-emission properties of diamond grains grown on textured Fe/Si substrates

    NASA Astrophysics Data System (ADS)

    Hirakuri, K. K.; Kurata, T.; Mutsukura, N.; Friedbacher, G.; Ohuchi, M.

    2000-02-01

    Diamond grains were produced by the hot-filament chemical-vapor deposition technique using a mixture of CH4/H2 as the synthesis gas. The Si substrates were textured (random pyramids) by chemical etching before growth of diamond grains, because emission of electrons is facilitated at the top of the pyramids. In order to increase the diamond nucleation density, an iron thin film (Fe) was deposited on the textured Si substrate by a radio-frequency plasma sputtering technique. Moreover, partial iron thin films (20% surface coverage) were fabricated for application as field emitter displays using a metal mask. The relationship between the nucleation density and the thickness of the iron films has been investigated by scanning electron microscopy (SEM). The samples were placed in a high-vacuum chamber with a pumping system and the emission current was measured as a function of the applied voltage. The voltage-current (V-I) characteristics were estimated for the field emitter. In order to etch nondiamond components, these samples were etched by O2 and CF4 plasmas. SEM observation revealed that diamond growth is concentrated at the textured Fe/Si area. The nucleation density was 107cm-2 on the textured Fe/Si area. On the plain textured Si substrate diamond growth could not be observed. Numberless tips were observed on the Fe/Si area after etching. The V-I characteristics revealed a current 10-8 at an applied voltage of 1.8 kV. The V-I characteristics could be enhanced by using the textured Fe/Si substrate.

  16. Novel electrostatically tunable FeGaB\\/(Si)\\/PMN-PT multiferroic heterostructures for microwave application

    Microsoft Academic Search

    Jing Lou; David Reed; Ming Liu; Carl Pettiford; Nian X. Sun

    2009-01-01

    Strong magnetoelectric (ME) coupling can be realized in multiferroic heterostructures, which have led to a variety of devices. However, it has been challenging in achieving strong ME coupling at microwave frequencies. Here, we report on novel FeGaB\\/Si\\/PMN-PT and FeGaB\\/PMN-PT microwave multiferroic heterostructures, which show strong ME coupling at both DC and microwave frequencies. A high microwave frequency tunability of Deltaf

  17. Magnetic properties of GdFe 11? x Si x Ti

    Microsoft Academic Search

    C. B Cizmas; C Djega-Mariadassou; L Bessais

    2002-01-01

    Induction melted GdFe11?xSixTi alloys (x?2) with ThMn12-type structure have been investigated by X-ray diffraction, weak field thermomagnetometry from 300 to 850 K and isotherm magnetization measurements in magnetic fields up to 5.5 T from 4.5 to 300 K. The unit-cell volume decreases with increasing Si content. The reduction of the Curie temperature is correlated to the decrease of the Fe

  18. Electromagnetic wave absorbing properties and hyperfine interactions of FeCuNbSiB nanocomposites

    NASA Astrophysics Data System (ADS)

    Han, Man-Gui; Guo, Wei; Wu, Yan-Hui; Liu, Min; Magundappa, L. Hadimani

    2014-08-01

    The FeCuNbSiB alloy nanocomposite containing two ferromagnetic phases (amorphous phase and nanophase phase) is obtained by properly annealing the as-prepared alloys. High resolution transmission electron microscopy (HR-TEM) images show the coexistence of these two phases. It is found that FeSi nanograins are surrounded by the retained amorphous ferromagnetic phase. Mssbauer spectroscopy measurements show that the nanophase is the D03-type FeSi phase, which is employed to find the atomic fractions of resonant 57Fe atoms in these two phases. The microwave permittivity and permeability spectra of FeCuNbSiB nanocomposite are measured in the frequency range of 0.5 GHz-10 GHz. Large relative microwave permeability values are obtained. The results show that the absorber containing the nanocomposite flakes with a volume fraction of 28.59% exhibits good microwave absorption properties. The reflection loss of the absorber is less than -10 dB in a frequency band of 1.93 GHz-3.20 GHz.

  19. Tribological behavior of AlSiSiC p composites\\/automobile brake pad system under dry sliding conditions

    Microsoft Academic Search

    R. K. Uyyuru; M. K. Surappa; S. Brusethaug

    2007-01-01

    Tribological behavior of stir-cast AlSi\\/SiCp composites against automobile brake pad material was studied using Pin-on-Disc tribo-tester. The Al-metal matrix composite (Al-MMC) material was used as disc, whereas the brake pad material forms the pin. It has been found that both wear rate and friction coefficient vary with both applied normal load and sliding speed. With increase in the applied normal

  20. Letter Report Documenting Progress of Second Generation ATF FeCrAl Alloy Fabrication

    SciTech Connect

    Yamamoto,, Y. [ORNL] [ORNL; Yang, Y. [ORNL] [ORNL; Field, K. G. [ORNL] [ORNL; Terrani, K. [ORNL] [ORNL; Pint, B. A. [ORNL] [ORNL; Snead, L. L. [ORNL] [ORNL

    2014-06-10

    Development of the 2nd generation ATF FeCrAl alloy has been initiated, and a candidate alloy was selected for trial tube fabrication through hot-extrusion and gun-drilling processes. Four alloys based on Fe-13Cr-4.5Al-0.15Y in weight percent were newly cast with minor alloying additions of Mo, Si, Nb, and C to promote solid-solution and second-phase precipitate strengthening. The alloy compositions were selected with guidance from computational thermodynamic tools. The lab-scale heats of ~ 600g were arc-melted and drop-cast, homogenized, hot-forged and -rolled, and then annealed producing plate shape samples. An alloy with Mo and Nb additions (C35MN) processed at 800C exhibits very fine sub-grain structure with the sub-grain size of 1-3?m which exhibited more than 25% better yield and tensile strengths together with decent ductility compared to the other FeCrAl alloys at room temperature. It was found that the Nb addition was key to improving thermal stability of the fine sub-grain structure. Optimally, grains of less than 30 microns are desired, with grains up to and order of magnitude in desired produced through Nb addition. Scale-up effort of the C35MN alloy was made in collaboration with a commercial cast company who has a capability of vacuum induction melting. A 39lb columnar ingot with ~81mm diameter and ~305mm height (with hot-top) was commercially cast, homogenized, hot-extruded, and annealed providing 10mm-diameter bar-shape samples with the fine sub-grain structure. This commercial heat proved consistent with materials produced at ORNL at the lab-scale. Tubes and end caps were machined from the bar sample and provided to another work package for the ATF-1 irradiation campaign in the milestone M3FT-14OR0202251.