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1

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

NASA Astrophysics Data System (ADS)

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).

Liang, Song-Mao; Schmid-Fetzer, Rainer

2014-11-01

2

Wear properties of thixoformed AlSiCuFe alloys  

Microsoft Academic Search

High-performance compressors which use low-viscosity lubricants face heavier wear problems and thus require a material more\\u000a resistant to wear than the current high pressure die cast AlSi8Cu3Fe alloy in connecting rod applications. While hypereutectic\\u000a versions of this alloy are expected to offer superior wear resistance, their processing via die casting is not straightforward.\\u000a Semisolid processing of hypereutectic AlSiCuFe alloys offers

Y. Birol; F. Birol

2008-01-01

3

On the thermodynamic stability and solid solution behavior of the phases ? 5Fe 2Al 7.4Si and ? 6Fe 2Al 9Si 2  

Microsoft Academic Search

The existence of the ternary compounds ?5-Fe2Al74Si and ?6-Fe2Al9Si2 has been confirmed at 550°C. The solid solution behavior of these compounds with respect to possible atom site exchanges of Fe, Si atoms by copper or manganese has been determined at 550°C. The limits of the solid solution with respect to site exchange have been plutted in a magnified Gibb's triangle.

M. Vybornov; P. Rogl; F. Sommer

1997-01-01

4

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

PubMed

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

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

5

Solidification behavior of Al-Si-Fe alloys and phase transformation of metastable intermetallic compound by heat treatment  

Microsoft Academic Search

Solidification behavior of Al-20 wt% Si-8 wt% Fe and Al-30 wt% Si-5 wt% Fe alloys during cooling with a cooling rate of 10 K\\/min has been studied using optical microscopy, X-ray diffractometry, differential thermal analysis, scanning electron microscopy and energy dispersive X-ray spectroscopy. In Al-20Si-8Fe alloy, metastable d-Al4FeSi2 phase with tetragonal structure formed first from melt, followed by primary Si

Y. S. Choi; J. S. Lee; W. T. Kim; H. Y. Ra

1999-01-01

6

Neutron diffraction study of Fe substitutions in Nd2Fe17- deltaXdelta (X = Al, Si, Ga, Mo, W)  

Microsoft Academic Search

In Nd2Fe17-deltaXdelta (X = Al, Si, Ga, Mo, W and delta = 0 to 1.5, depending on the concentration), the X elements substitute for Fe atoms without changing the crystal structure. Neutron diffraction measurements show that Al, Si, and Ga elements tend to substitute for Fe with a strong preference for the 18h site while Mo, and W tend to

Z. Altounian; Er. Girt; M. Mao; I. P. Swainson; R. L. Donaberger

1996-01-01

7

Thermoelectric Properties of Si2Ti-Type Al-(Mn,Cr,Fe)-Si Alloys  

NASA Astrophysics Data System (ADS)

To optimize the thermoelectric properties of Si2Ti-type Al32Mn34Si34 ( C54-phase), which possesses a large absolute Seebeck coefficient | S| exceeding 300 ?V/K with negative sign, we partially substituted Cr and Fe for Mn, and succeeded in decreasing the number of valence electrons (in the case of Cr) without observing precipitation of secondary phases. A large, positive Seebeck coefficient exceeding 200 ?V/K was observed for Al32Cr x Mn34- x Si34 (1 ? x ? 2.5), which consists almost solely of the C54-phase. The increase of hole concentration caused by Cr substitution for Mn was confirmed by both the reduction in electrical resistivity and the sign reversal of the Seebeck coefficient. The largest ZT-value for positive Seebeck coefficient ( p-type behavior) was obtained for Al32Cr2.5Mn31.5Si34, with the resulting ZT-value reaching a magnitude twice as large as the largest ZT-value of the ternary compound Al33Mn34Si33 possessing p-type behavior.

Toyama, Yasuhiro; Hazama, Hirofumi; Asahi, Ryoji; Takeuchi, Tsunehiro

2011-05-01

8

EBSD study of crystallographic identification of Fe-Al-Si intermetallic phases in Al-Si coating on Cr-Mo steel  

NASA Astrophysics Data System (ADS)

5Cr-0.5Mo steel was coated by hot-dipping in a molten Al-10 wt.% Si bath at 700 °C for 10, 60, 120 or 180 s. The identification of the phases in the Fe-Al-Si intermetallic phases formed in the aluminide layers during hot-dipping was carried out by using a combination of scanning electron microscope (SEM) with energy dispersive X-ray spectroscopy (EDS), X-ray diffraction (XRD) and electron backscatter diffraction (EBSD). The EDS results show a ?5(H)-Al7Fe2Si phase, which exhibited 2 distinct morphologies, small particles widely dispersed and a continuous layer. Also revealed by EDS were ?6-Al4FeSi and ?4-Al3FeSi2 phases, which showed plate-shaped morphology, in an Al-Si topcoat. However, the XRD results show the intermetallic phases in the aluminide layer were composed of outer cubic ?5(C)-Al7(Fe,Cr)2Si and inner hexagonal ?5(H)-Al7Fe2Si. EBSPs and mapping functions in EBSD helped to clarify the confused phase identifications yielded by EDS and XRD. In this way, the small intermetallic particles and the continuous intermetallic layer were identified as cubic ?5(C)-Al7(Fe,Cr)2Si and hexagonal ?5(H)-Al7Fe2Si, respectively, and the plate-shaped intermetallic phase was identified as monoclinic ?6-Al4FeSi and tetragonal ?4-Al3FeSi2 with the same metallographic morphology. EBSD proved to be a very effective technique for local phase identification of aluminide layers with complicated multiphase morphologies.

Cheng, Wei-Jen; Wang, Chaur-Jeng

2011-03-01

9

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

NASA Astrophysics Data System (ADS)

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

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

2015-02-01

10

Preparation of Al-Cu-Fe-(Sn,Si) quasicrystalline bulks by laser multilayer cladding  

NASA Astrophysics Data System (ADS)

(Al65Cu20Fe15)100- x Sn x ( x=0, 12, 20, 30) and Al57Si10Cu18Fe15 powders were cladded on a medium carbon steel (45# steel) substrate by laser multilayer cladding, respectively. The phases and properties of the produced quasicrystalline bulks were investigated. It was found that the main phases in the Al65Cu20Fe15 sample were crystalline ?-Al13Fe4 and icosahedral quasicrystal together with a small volume fraction of ?-Al2Cu phase. The volume fraction of icosahedral phase decreased as the Sn content in the (Al65Cu20Fe15)100- x Sn x samples increased owing to the formation of ?-CuSn phase. The increase of Sn content improved the brittleness of the quasicrystal samples. The morphology of the solidification microstructure in the Al57Si10Cu18Fe15 sample changed from elongated shape to spherical shape due to the addition of Si. The nanohardness of the laser multilayer cladded quasicrystal samples was equal to that of the as-cast sample prepared by vacuum quenching. In terms of hardness, the laser cladded Al57Si10Cu18Fe15 quasicrystalline alloy has the highest value among all the investigated samples.

Feng, Li-ping; Fleury, Eric; Zhang, Guo-sheng

2012-05-01

11

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

E-print Network

transforms to a more rounded -Al(FeMn)Si phase which are more favourable for the extrusion process: Phase transformation; Intermetallics; Aluminium alloy; Diffusion; Stefan problem 1. Introduction-cast AA 6xxx aluminium alloys. During this homogenisation pro- cess, at temperatures between 530 and 600 C

Vuik, Kees

2005-01-01

12

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

SciTech Connect

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

Yamada, S., E-mail: yamada@ee.es.osaka-u.ac.jp [Graduate School of Engineering Science, Osaka University, Toyonaka 560-8531 (Japan); Tanikawa, K.; Oki, S.; Kawano, M.; Miyao, M. [Department of Electronics, Kyushu University, 744 Motooka, Fukuoka 819-0395 (Japan); Hamaya, K. [Graduate School of Engineering Science, Osaka University, Toyonaka 560-8531 (Japan); CREST, Japan Science and Technology Agency, Gobancho, Tokyo 102-0075 (Japan)

2014-08-18

13

Valence electron structure analysis of the cubic silicide intermetallics in rapidly solidified Al-Fe-V-Si alloy  

Microsoft Academic Search

The application of rapid solidification for the development of elevated temperature aluminum alloys has resulted in the emergence of several alloys based on the Al-Fe alloy system. Of particular interest are Al-Fe-V-Si alloys which have excellent room temperature and high temperature mechanical properties. In a pioneering study, Skinner et al. showed the stabilization of the cubic phase in ternary Al-Fe-Si

J. Q. Wang; C. F. Qian; B. J. Zhang; M. K. Tseng; S. W. Xiong

1996-01-01

14

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

NASA Astrophysics Data System (ADS)

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

Jain, Syadwad

15

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

NASA Astrophysics Data System (ADS)

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.

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

2014-08-01

16

Spin pumping at the Co2FeAl0.5Si0.5/Pt interface  

NASA Astrophysics Data System (ADS)

Spin pumping at the Co2FeAl0.5Si0.5/Pt and Pt/Co2FeAl0.5Si0.5 interfaces has been studied by ferromagnetic resonance technology (FMR). The spin mixing conductance of the Co2FeAl0.5Si0.5/Pt and Pt/Co2FeAl0.5Si0.5 interfaces was determined to be 3.7×1019 m-2 and 2.1×1019 m-2 by comparing the Gilbert damping in a Co2FeAl0.5Si0.5 single film, Co2FeAl0.5Si0.5/Pt bilayer film and a Pt/Co2FeAl0.5Si0.5/Pt trilayer film. Spin pumping is more efficient in the Co2FeAl0.5Si0.5/Pt bilayer film than in permalloy/Pt bilayer film.

Wu, Yong; Zhao, Yue-Lei; Xiong, Qiang; Xu, Xiao-Guang; Sun, Young; Zhang, Shi-Qing; Jiang, Yong

2014-01-01

17

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

SciTech Connect

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

Prichard, P.D.

1998-02-23

18

Tunnel magnetoresistance in textured Co2FeAl/MgO/CoFe magnetic tunnel junctions on a Si/SiO2 amorphous substrate  

NASA Astrophysics Data System (ADS)

Magnetic tunnel junctions with B2-ordered Co2FeAl full Heusler alloy as a ferromagnetic electrode were fabricated by sputtering on thermally oxidized Si/SiO2 amorphous substrates. A Co2FeAl/MgO/Co50Fe50 structure showed a highly (001)-textured structure and the tunneling magnetoresistance (TMR) ratio of 166% at room temperature and 252% at 48 K were achieved. The temperature dependence of TMR can be fitted with spin wave excitation model, and the bias voltage dependence of differential conductance demonstrated that the high TMR was mainly contributed by coherent tunneling. This work suggests the B2-Co2FeAl is one of the promising candidates for practical spintronic applications.

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

2011-05-01

19

Optical properties of heusler alloys Co2FeSi, Co2FeAl, Co2CrAl, and Co2CrGa  

NASA Astrophysics Data System (ADS)

The results of an investigation of optical properties and the calculations of the electronic structure of Co2FeSi, Co2FeAl, Co2CrAl, and Co2CrGa Heusler alloys are presented. The main focus of our attention is the study of the spectral dependence of the real part (?1) and imaginary part (?2) of the dielectric constant in the range of wavelengths ? = 0.3-13 ?m using the ellipsometric method. An anomalous behavior of the optical conductivity ?(?) has been found in the infrared range in the Co2CrAl and Co2CrGa alloys, which differs substantially from that in the Co2FeSi and Co2FeAl alloys. The results obtained are discussed based on the calculations of the electronic structure.

Shreder, E. I.; Svyazhin, A. D.; Belozerova, K. A.

2013-11-01

20

Electronic Structure and Thermoelectric Properties of Al-Mn-Fe-Si Alloys  

NASA Astrophysics Data System (ADS)

In order to develop practical thermoelectric materials consisting solely of environmentally friendly elements, we investigated the thermoelectric properties of the Al10Mn3-type ( P63/ mmc, hp26) Al77- x Mn23Si x alloys and the Al102Mn24Si12-type ( Pm-3, cP138) Al82- x Mn5.5Fe12.5Si x alloys, both of which possess a pseudogap at the Fermi level. The formation range in which the single phase is obtained was determined for these two phases. The electrical resistivity, Seebeck coefficient, and thermal conductivity of the samples involving no secondary phase were measured over the temperature range of 2 K to 300 K. It is found that the thermoelectric properties of these phases are qualitatively accounted for in terms of the pseudogap at the Fermi level in the electronic density of states and the disordering in local atomic arrangements.

Takeuchi, T.; Toyama, Y.; Hazama, H.; Asahi, R.

2010-09-01

21

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

NASA Astrophysics Data System (ADS)

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.

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

2015-03-01

22

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

NASA Technical Reports Server (NTRS)

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.

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

1988-01-01

23

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

NASA Astrophysics Data System (ADS)

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

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

2012-04-01

24

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

NASA Astrophysics Data System (ADS)

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.

Zhang, Zehai

2015-03-01

25

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

SciTech Connect

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

Roger, J., E-mail: jerome.roger@univ-lyon1.f [Laboratoire des Multimateriaux et Interfaces, UMR CNRS no. 5615, Universite Claude Bernard Lyon 1, F-69622 Villeurbanne Cedex (France); Bosselet, F.; Viala, J.C. [Laboratoire des Multimateriaux et Interfaces, UMR CNRS no. 5615, Universite Claude Bernard Lyon 1, F-69622 Villeurbanne Cedex (France)

2011-05-15

26

Valence electron structure analysis of the cubic silicide intermetallics in rapidly solidified Al-Fe-V-Si alloy  

SciTech Connect

The application of rapid solidification for the development of elevated temperature aluminum alloys has resulted in the emergence of several alloys based on the Al-Fe alloy system. Of particular interest are Al-Fe-V-Si alloys which have excellent room temperature and high temperature mechanical properties. In a pioneering study, Skinner et al. showed the stabilization of the cubic phase in ternary Al-Fe-Si alloy by the addition of a quaternary element, vanadium. The evolution of the microstructure in these alloys both during rapid solidification and subsequent processing is of crucial importance. Kim has demonstrated that the composition of the silicide phase in rapidly solidified Al-Fe-V-Si alloy is very close to Al{sub 12}(Fe,V){sub 3}Si with the body centered cubic (bcc) structure. The structure is closely related to that of quasicrystals.In view of the structural features and the relationship between the {alpha}{sub 12} and {alpha}{sub 13} phases, the researching emphasis should firstly be put on the {alpha}{sub 12} phase. In this paper the authors analyzed the {alpha} {minus}(AlFeSi)({alpha}{sub 12}-type) phase from the angle of atomic valence electron structure other than the traditional methods of obtaining the diffraction spots of the phase. Several pieces of information were obtained about the hybrid levels and bond natures of every kind of atom in the {alpha} {minus}(AlFeSi) phase. Finally the authors explained the phenomenon which V atom can substitute for Fe atom in the {alpha}{sub 12} phase and improve the thermal stability of the phase in Al-Fe-V-Si alloy.

Wang, J.Q.; Qian, C.F.; Zhang, B.J.; Tseng, M.K.; Xiong, S.W. [Northeastern Univ., Shenyang (China)] [Northeastern Univ., Shenyang (China)

1996-05-15

27

Fabrication and characterization of nanocrystalline Al/Al12(Fe,V)3Si alloys by consolidation of mechanically alloyed powders  

NASA Astrophysics Data System (ADS)

The aim of this study was to produce bulk nanocrystalline Al/Al12(Fe,V)3Si alloys by mechanical alloying (MA) and subsequent hot pressing (HP) of elemental powders. A nanostructured Al-based solid solution was formed by MA of elemental powders for 60 h. After HP of the as-milled powders at 550°C for 20 min, the Al12(Fe,V)3Si phase was precipitated in a nanocrystalline Al matrix. Scanning electron microscopy (SEM) images of the bulk samples represented a homogeneous and uniform microstructure that was superior to those previously obtained by rapid solidification-powder metallurgy (RS-PM). Nanostructured Al-8.5Fe-1.3V-1.7Si and Al-11.6Fe-1.3V-2.3Si alloys exhibited high HV hardness values of ˜205 and ˜254, respectively, which are significantly higher than those reported for the RS-PM counterparts.

Ashrafi, Hamid; Emadi, Rahmatollah; Enayati, Mohammad Hosein

2014-07-01

28

X-rays structural analysis and thermal stability studies of the ternary compound ?-AlFeSi  

NASA Astrophysics Data System (ADS)

From literature data presently available, the decomposition temperature and the nature of the decomposition reaction of the ternary compound ?-AlFeSi (also designated as ?H or ?5) are not clearly identified. Moreover, some uncertainties remain concerning its crystal structure. The crystallographic structure and thermochemical behaviour of the ternary compound ?-AlFeSi were meticulously studied. The crystal structure of ?-AlFeSi was examined at room temperature from X-ray single crystal intensity data. It presents hexagonal symmetry, space group P6 3/mmc with unit cell parameters (293 K) a=12.345(2) Å and c=26.210(3) Å ( V=3459 Å 3). The average chemical formula obtained from refinement is Al 7.1Fe 2Si. From isothermal reaction-diffusion experiments and Differential Thermal Analysis, the title compound decomposes peritectically upon heating into ?-Fe 4Al 13(Si), ?-Al 3FeSi and a ternary Al-rich liquid. Under atmospheric pressure, the temperature of this reversible transformation has been determined to be 772±12 °C.

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

2011-05-01

29

Unified approach to electronic, thermodynamical, and transport properties of Fe3Si and Fe3Al alloys  

NASA Astrophysics Data System (ADS)

The electronic, thermodynamical, and transport properties of ordered Fe3X (X =Al,Si) alloys are studied from first principles. We present here a unified approach to the phase stability, the estimate of the Curie temperature, the temperature dependence of sublattice magnetizations, magnon spectra, the spin-stiffnesses, and residual resistivities. An important feature of the present study is that all calculated physical properties are determined in the framework of the same first-principles electronic structure model combined with the effective Ising and Heisenberg Hamiltonians used for study of the thermodynamical properties of alloys. Curie temperatures, spin-stiffnesses, and magnon spectra are determined using the same calculated exchange integrals. Finally, the transport properties are calculated using the linear-response theory. Our theoretical estimates compare well with available experimental data. In particular, calculations predict (in agreement with experiment) the ordered D03 phase as the ground-state alloy structure, demonstrate that a correct relation of Curie temperatures of Fe3Al/Fe3Si alloys can be obtained only by going beyond a simple mean-field approximation, provide reasonable estimates of spin-stiffnesses, and give resistivities compatible with structural disorder observed in the experiment. Although the calculated temperature dependences of the Fe magnetization on different sublattices are similar, they nevertheless deviate more than in the experiment, and we discuss a possible origin.

Kudrnovský, J.; Drchal, V.; Bergqvist, L.; Rusz, J.; Turek, I.; Újfalussy, B.; Vincze, I.

2014-10-01

30

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

NASA Astrophysics Data System (ADS)

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

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

2013-11-01

31

Equation of State of Lower Mantle (Al,Fe)-MgSiO3 Perovskite  

NASA Astrophysics Data System (ADS)

The compression behavior of various (Al,Fe)-MgSiO3 perovskites was investigated by powder X-ray diffraction up to 70 GPa on the ID30 beamline of ESRF (Grenoble). We used diamond anvil cell coupled with CO2 laser-heating, a most powerful technique to relax stresses and perform reliable equation of state up to typical lower mantle pressures. In contrast to Fe which essentially increases the room pressure unit cell volume [1], the effect of Al is to increase the bulk modulus of silicate perovskite. This result contrast with previous determinations performed at pressures below 10 GPa on samples synthesized in the multi-anvil press [2, 3]. Such a difference can be explained by a change in the substitution mechanism of Al in MgSiO3 with increasing pressure and temperature, in agreement with recent ab-initio calculations [4]. Our results confirm that the Earth's lower mantle (Mg+Fe)/Si ratio is greater than unity, because of the high stiffness of silicate perovskite. 1- H.K. Mao, R.J. Hemley, Y. Fei, J.F. Shu, L.C. Chen, A.P. Jephcoat, Y. Wu and W.A. Basset, Journal of Geophysical Research 96(B5), 8069-8079, 1991. 2- A. Kubo, T. Yagi, S. Ono and M. Akaogi, in: Proceeding of the Japan Academy 76, pp. 103-107, 2000. 3- J. Zhang and D.J. Weidner, Science 284, 782-784, 1999. 4- J.P. Brodholt, Nature 407, 620-622, 2000.

Prewitt, C. T.; Andrault, D.; Bolfan-Casanova, N.; Guignot, N.

2001-12-01

32

Critical Experiments with Highly Enriched Uranium and Matrix Elements (Si, Mg, Al, Gd, and Fe)  

SciTech Connect

Scientists at the Los Alamos National Laboratory measured the critical masses of square prisms of highly enriched uranium diluted in various X/{sup 235}U with matrix material and polyethylene. The configuration cores were 22.86 and 45.72 cm square and were reflected with 8.13-cm-thick and 10.16-cm-thick side polyethylene reflectors, respectively. The configurations had 10.16-cm-thick top and bottom polyethylene reflectors. For some configurations, the Rossi-{alpha}, which is an eigenvalue characteristic for a particular configuration, was measured to establish a reactivity scale based on the degree of subcriticality. These experiments provided critical mass data in the thermal energy range for systems containing Si, Mg, Al, Gd, and Fe. The measured k{sub eff} from these experiments was compared with the calculated k{sub eff} from MCNP using ENDF/B-V and ENDF/B-VI cross-section data. The observed biases were +0.005 {delta}k and +0.008 {delta}k for Si, +0.0006 {delta}k and +0.008 {delta}k for Al, +0.0023 {delta}k for Mg, +0.004 {delta}k and +0.01304 {delta}k for Gd, and +0.0123 {delta}k and -0.00106 {delta}k for Fe.

Sanchez, Rene; Loaiza, David; Brunson, Glenn; Kimpland, Robert [Los Alamos National Laboratory (United States)

2004-07-15

33

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

NASA Astrophysics Data System (ADS)

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.

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

2011-08-01

34

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

SciTech Connect

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

Jain, Vivek Kumar, E-mail: vivek.jain129@gmail.com; Jain, Vishal, E-mail: vivek.jain129@gmail.com; Lakshmi, N., E-mail: vivek.jain129@gmail.com; Venugopalan, K., E-mail: vivek.jain129@gmail.com [Department of Physics, Mohanlal Sukhadia University, Udaipur-313001 (India)

2014-04-24

35

Microstructural development during consolidation of rapidly solidified Al-Fe-V-Si powder by VHP, extrusion and rolling  

SciTech Connect

The rapid solidification of powder results in a high cooling rate which leads to microstructural refinement and extended solid solubility of alloying elements and thereby precipitation of fine dispersive phases during powder solidification and consolidation. During the last decade considerable research work has been done in the development of high temperature powder metallurgy aluminum alloys capable of competing with titanium alloys on a specific strength basis with the use of rapid solidification processes. The Al-Fe-V-Si family of alloys are one of the most promising on a basis of elevated temperature strength, stiffness and thermal stability. In previous studies, the Al-Fe-V-Si alloys were usually produced by melt spinning (both jet casting and planar flow casting) followed by consolidation of the resulting ribbons. The aim of the present study was to investigate the microstructural development of atomized Al-Fe-V-Si alloy powder during consolidation by vacuum hot pressing (VHP), extrusion and rolling.

Wang, Y.; Lorimer, G.W.; Sale, F.R. (Univ. of Manchester (United Kingdom). Manchester Materials Science Centre)

1994-11-15

36

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

NASA Astrophysics Data System (ADS)

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.

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

2010-01-01

37

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

NASA Astrophysics Data System (ADS)

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

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

2014-07-01

38

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

NASA Astrophysics Data System (ADS)

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

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

2013-12-01

39

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

NASA Astrophysics Data System (ADS)

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.

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

2005-09-01

40

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

NASA Astrophysics Data System (ADS)

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

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

2015-01-01

41

Structural dependence of the tunnel magnetoresistance for magnetic tunnel junctions with a full-Heusler Co2Fe(Al,Si) electrode  

NASA Astrophysics Data System (ADS)

We have investigated the crystal structure and magnetic moment of the Co2FeAl and Co2FeSi films deposited onto thermally oxidized Si and MgO(100) single-crystal substrates, and the structural effect on the tunnel magnetoresistance (TMR) of the magnetic tunnel junctions (MTJs) using a Co2FeZ (Z=Al or Si). The structure was changed by the substrate and postannealing temperatures, in which the fully epitaxial and polycrystalline Co2FeAl and Co2FeSi films were obtained with the different disorder structure. The magnetic moment of Co2FeAl films was found to be uninfluenced by the crystal structure. Spin-valve-type MTJs consisting of Co2FeZ(100 nm)/Al(1.2 nm)-oxide/Co75Fe25(2 nm)/IrMn(10 nm)/Ta(60 nm) were fabricated (Z=Al or Si) on thermally oxidized Si and MgO(100) single-crystal substrates. The maximum TMR obtained is about 50% at room temperature for MTJs with Co2FeAl films, regardless of the crystal structure of Co2FeAl.

Tezuka, N.; Okamura, S.; Miyazaki, A.; Kikuchi, M.; Inomata, K.

2006-04-01

42

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

NASA Technical Reports Server (NTRS)

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.

O'Neill, Bridget; Jeanloz, Raymond

1994-01-01

43

Optimization of exchange bias in Co2FeAl0.5Si0.5 Heusler alloy layers  

NASA Astrophysics Data System (ADS)

We have fabricated and investigated IrMn3/Co2FeAl0.5Si0.5 stacks to meet the criteria for future spintronic device applications which requires low-temperature crystallisation (<250 °C) and a large exchange bias Hex (>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 Co2FeAl0.5Si0.5 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.

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

2014-05-01

44

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

NASA Astrophysics Data System (ADS)

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.

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

2015-02-01

45

Pyroxene-garnet solid-solution equilibria in the systems Mg4Si4O12Mg3Al2Si3O12 and Fe4Si4O12Fe3Al2Si3O12 at high pressures and temperatures  

Microsoft Academic Search

Pyroxene-garnet solid-solution equilibria have been studied in the pressure range 41-200 kbar and over the temperature range 850-1,450°C for the system Mg4Si4O12-Mg3Al2Si3O12, and in the pressure range 30-105 kbar and over the temperature range 1,000-1,300°C for the system Fe4Si4O12-Fe3Al2Si3O12. At 1,000°C, the solid solubility of enstatite (MgSiO3) in pyrope (Mg3Al2Si3O12) increases gradually to 140 kbar and then increases suddenly in

M. Akaogi; S. Akimoto

1977-01-01

46

The effect of a ferromagnetic Gd marker on the effective work function of Fe in contact with Al2O3/Si  

NASA Astrophysics Data System (ADS)

The effect of a ferromagnetic Gd marker layer on the effective work function (WFeffFe) of Fe in a Fe/ Gd/Al2O3/Si stack has been systematically investigated by hard X-ray photoelectron spectroscopy (HAXPES) and capacitance-voltage measurements. A pronounced change in the band alignment at the buried Fe/Al2O3 interface WFeffFe=4.5/3.7eV is revealed by HAXPES as a function of the Gd marker thickness in the range 0/2.7 nm, in agreement with capacitance-voltage (C-V) data. Interface-sensitive 57Fe conversion-electron Mößbauer spectroscopy performed on Fe/Gd/Al2O3/Si stacks reveals major structural and magnetic changes at the Fe/Gd interface for different Gd thickness, which are correlated with the changes of the Fe/Al2O3 band alignment.

Zenkevich, A. V.; Matveyev, Yu. A.; Lebedinskii, Yu. Yu.; Mantovan, R.; Fanciulli, M.; Thiess, S.; Drube, W.

2012-04-01

47

The Effect of an Fe-doped GaN Buffer on off-State Breakdown Characteristics in AlGaN\\/GaN HEMTs on Si Substrate  

Microsoft Academic Search

An Fe-doped GaN buffer layer was employed in the growth of AlGaN\\/GaN high-electron mobility transistors (HEMTs) on Si substrates. In order to investigate the effects of an Fe-doped GaN buffer on OFF-state breakdown characteristics, HEMT devices with an Fe-doped GaN buffer on Si substrates were fabricated along with conventional devices utilizing an unintentionally doped GaN buffer on Si substrates. The

Young Chul Choi; Milan Pophristic; Ho-Young Cha; Boris Peres; Michael G. Spencer; Lester F. Eastman

2006-01-01

48

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

NASA Astrophysics Data System (ADS)

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

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

2008-04-01

49

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

NASA Technical Reports Server (NTRS)

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.

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

2004-01-01

50

An overview on phase equilibria and thermodynamic modeling in multicomponent Al alloys: Focusing on the Al–Cu–Fe–Mg–Mn–Ni–Si–Zn system  

Microsoft Academic Search

Knowledge of thermodynamics and phase diagram is a prerequisite for understanding many scientific and technological disciplines. To establish a reliable thermodynamic database, an integrated approach of key experiments and thermodynamic modeling, supplemented with first-principles calculations, can be utilized. In this paper, first investigations of phase diagram and thermodynamics of technologically important Al alloys (focusing on the Al–Cu–Fe–Mg–Mn–Ni–Si–Zn system, which covers

Yong Du; Shuhong Liu; Lijun Zhang; Honghui Xu; Dongdong Zhao; Aijun Wang; Liangcai Zhou

2011-01-01

51

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

NASA Astrophysics Data System (ADS)

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

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

2013-10-01

52

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

NASA Astrophysics Data System (ADS)

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

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

2013-02-01

53

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

PubMed

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

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

1995-07-01

54

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

NASA Astrophysics Data System (ADS)

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

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

2013-04-01

55

Theoretical phase relations involving cordierite and garnet in the system MgO-FeO-Al 2 O 3 SiO 2  

Microsoft Academic Search

Theoretical stability relations have been derived between the phases cordierite (Cd), garnet (Ga), hypersthene (Hy), olivine (Ol), sapphirine (Sa), spinel (Sp), sillimanite (Si) and quartz (Qz) in the system MgO-FeO-Al2O3-SiO2. Natural rock data and experimental evidence suggest that the Mg\\/Mg+Fe2+ ratio (X) of coexisting ferromagnesian phases decreases as follows: XCd>XSa>XHy>XOl>XSp>XGa. By use of this information four stable invariant points are

B. J. Hensen

1971-01-01

56

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

NASA Astrophysics Data System (ADS)

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.

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

2010-12-01

57

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

NASA Astrophysics Data System (ADS)

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.

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

2015-02-01

58

Nuclear magnetic resonance study of thin Co2FeAl0.5Si0.5 Heusler films with varying thickness  

NASA Astrophysics Data System (ADS)

Type, degree, and evolution of structural order are important aspects for understanding and controlling the properties of highly spin-polarized Heusler compounds, in particular, with respect to the optimal film growth procedure. In this work, we compare the structural order and the local magnetic properties revealed by nuclear magnetic resonance (NMR) spectroscopy with the macroscopic properties of thin Co2FeAl 0.5Si 0.5 Heusler films with varying thickness. A detailed analysis of the measured NMR spectra presented in this paper enables us to find a very high degree of L 21 -type ordering up to 81% concomitantly with excess Fe of 8%-13% at the expense of Al and Si. We show that the formation of certain types of order depends not only on the thermodynamic phase diagrams as in bulk samples, but also that the kinetic control may contribute to the phase formation in thin films. It is an exciting finding that Co2FeAl 0.5Si 0.5 can form an almost ideal L 21 structure in films, though with a considerable amount of Fe-Al/Si off stoichiometry. Moreover, the very good quality of the films as demonstrated by our NMR study suggests that the technique of off-axis sputtering used to grow the films sets the stage for the optimized performance of Co2FeAl 0.5Si 0.5 in spintronic devices.

Alfonsov, A.; Peters, B.; Yang, F. Y.; Büchner, B.; Wurmehl, S.

2015-02-01

59

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

PubMed

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 Hückel 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

Fredrickson, Rie T; Fredrickson, Daniel C

2012-10-01

60

59Co nuclear magnetic resonance study of the local distribution of atoms in the Heusler compound Co2FeAl0.5Si0.5  

NASA Astrophysics Data System (ADS)

In this work, the spin-echo nuclear magnetic resonance (NMR) technique is used to probe the local structure of Co2FeAl0.5Si0.5 bulk samples. The 59Co NMR spectrum of the Heusler compound Co2FeAl0.5Si0.5 consists of four main resonance lines with an underlying sub-structure. The splitting into the main resonance lines is explained by contributions of the B2 type structure. The sub-lines are attributed to a random distribution of Al and Si. By comparing the experimental results with an appropriate multinomial distribution, the fraction of the Al/Si intermixing and the ratio between the contributing structure types is assigned. The main structural contribution of as-cast bulk samples is of B2 type with 38% of L21 contributions. The L21 contribution can be enhanced to 59% by an appropriate annealing process. However, B2 contributions are still present after annealing. Additional foreign phases such as fcc-Co and Co-Al, with relative contributions of less than one percent, are also found in both as-cast and annealed samples. Resonance lines related to slight amounts of the ternary, parental Heusler compounds Co2FeAl and Co2FeSi are also observed.

Wurmehl, Sabine; Kohlhepp, Jürgen T.; Swagten, Henk J. M.; Koopmans, Bert

2012-02-01

61

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

NASA Astrophysics Data System (ADS)

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.

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

2013-02-01

62

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

NASA Astrophysics Data System (ADS)

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

Mikolajczak, Piotr; Ratke, Lorenz

2015-03-01

63

Determination of the crystal structure of the pi-AlFeMgSi phase using symmetry- and site-sensitive electron microscope techniques.  

PubMed

The crystal structure of the complex pi-AlFeMgSi phase, which was previously thought to have the composition Al(8)FeMg(3)Si(6), has been investigated. Microprobe analysis revealed that the phase has a different composition, Al(9)FeMg(3)Si(5). The space group was determined and confirmed to be P62m with the use of parallel-beam electron diffraction (SAD) and convergent-beam electron diffraction (CBED). Owing to symmetry considerations the elements within the unit cell had to be rearranged. The rearrangement was confirmed using electron channelling. The z parameters of the elements were refined by examining the intensities from high-angle convergent-beam electron diffraction. Finally, the x parameters were adjusted slightly to arrive at acceptable interatomic distances. PMID:12554970

Foss, S; Olsen, A; Simensen, C J; Taftø, J

2003-02-01

64

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)

Synthetic melilites on the join Ca2MgSi2O7 (åkermanite: Ak)-Ca2Fe3+AlSiO7 (ferrialuminium gehlenite: FAGeh) were studied using X-ray powder diffraction and 57Fe Mössbauer 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 Mössbauer 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 Mössbauer 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.

Hamada, Maki; Akasaka, Masahide

2013-03-01

65

Study of the [(Co 45Fe 45Zr 10) x(Al 2O 3) 100- x/a-Si:H] m multilayer nanostructure by polarized neutron reflectometry  

NASA Astrophysics Data System (ADS)

Polarized neutron reflectometry was used to investigate the amorphous multilayer nanostructures [(Co 45Fe 45Zr 10) x(Al 2O 3) 100- x/a-Si:H] m, whose magnetic properties are dependent on the concentration of the magnetic constituent ( x=34, 47 and 60 at%) as well as on the thicknesses of the metal-dielectric (Co 45Fe 45Zr 10) x(Al 2O 3) 100- x and semiconductor a-Si:H layers. The average magnetization of the individual magnetic layer is found to be inhomogeneous with the magnetically active central part and two magnetically dead parts at the interfaces.

Dyadkina, E. A.; Grigoriev, S. V.; Lott, D.; Sitnikov, A. V.; Kalinin, Y. E.

2011-06-01

66

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

NASA Astrophysics Data System (ADS)

10 nm and 50 nm Co2FeAl (CFA) thin films have been deposited on MgO(001) and Si(001) substrates by magnetron sputtering and annealed at different temperatures. X-rays diffraction revealed polycrystalline or epitaxial growth (according to CFA(001)[110]//MgO(001)[100] epitaxial relation) for CFA films grown on a Si and on a MgO substrate, respectively. For these later, the chemical order varies from the A2 phase to the B2 phase when increasing the annealing temperature (Ta), while only the A2 disorder type has been observed for CFA grown on Si. Microstrip ferromagnetic resonance (MS-FMR) measurements revealed that the in-plane anisotropy results from the superposition of a uniaxial and a fourfold symmetry term for CFA grown on MgO substrates. This fourfold anisotropy, which disappears completely for samples grown on Si, is in accord with the crystal structure of the samples. The fourfold anisotropy field decreases when increasing Ta, while the uniaxial anisotropy field is nearly unaffected by Ta within the investigated range. The MS-FMR data also allow for concluding that the gyromagnetic factor remains constant and that the exchange stiffness constant increases with Ta. Finally, the FMR linewidth decreases when increasing Ta, due to the enhancement of the chemical order. We derive a very low intrinsic damping parameter (1.1×10-3 and 1.3×10-3 for films of 50 nm thickness annealed at 615 °C grown on MgO and on Si, respectively).

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

2014-01-01

67

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)

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).

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

2009-01-01

68

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

NASA Astrophysics Data System (ADS)

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.

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

2015-01-01

69

Relative effectiveness of short-range ordered Mn(IV), Fe(III), Al, and Si oxides in the synthesis of humic acids from phenolic compounds  

Microsoft Academic Search

The relative effectiveness of short-range ordered Mn(IV), Fe(III), Al, and Si oxides in the catalytic synthesis of humic acids from phenolic compounds was investigated. The Mn(IV) oxide markedly accelerated the synthesis of humic acids from hydroquinone, resorcinol, and phloroglucinol. The catalytic effect of the Fe(III) oxide was remarkable on the synthesis of humic acids from catechol, pyrogallol, protocatechuic acid, and

Haruo Shindo

1992-01-01

70

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

NASA Astrophysics Data System (ADS)

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

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

2015-02-01

71

The Presence of Nanophase Al-Si-Fe Components at Mawrth Vallis Indicate Varying Environmental Conditions  

NASA Astrophysics Data System (ADS)

The presence of nanophase allophane, opal and Fe-rich material at Mawrth Vallis together with multiple phyllosilicates indicate varying environmental conditions over time and also suggests regionally different aqueous environments.

Bishop, J. L.; Rampe, E. B.

2014-07-01

72

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

E-print Network

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

Paris-Sud XI, Université de

73

High adsorptive ?-AlOOH(boehmite)@SiO2/Fe3O4 porous magnetic microspheres for detection of toxic metal ions in drinking water.  

PubMed

?-AlOOH(boehmite)@SiO(2)/Fe(3)O(4) porous magnetic microspheres with high adsorption capacity toward heavy metal ions were found to be useful for the simultaneous and selective electrochemical detection of five metal ions, such as ultratrace zinc(II), cadmium(II), lead(II), copper(II), and mercury(II), in drinking water. PMID:21897953

Wei, Yan; Yang, Ran; Zhang, Yong-Xing; Wang, Lun; Liu, Jin-Huai; Huang, Xing-Jiu

2011-10-21

74

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

NASA Astrophysics Data System (ADS)

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.

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

2014-09-01

75

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

SciTech Connect

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.

Soh, Wee Tee; Ong, C. K. [Department of Physics, Center for Superconducting and Magnetic Materials, National University of Singapore, 2 Science Drive 3, Singapore 117551 (Singapore); Zhong, Xiaoxi, E-mail: xiaoxi.zhong@gmail.com [Department of Physics, Center for Superconducting and Magnetic Materials, National University of Singapore, 2 Science Drive 3, Singapore 117551 (Singapore); School of Materials Science and Engineering, Sichuan University, Chengdu 610065 (China)

2014-09-15

76

The Anomalous Hall Effect of Co2FeAl0.5Si0.5/Pt Multilayers with Perpendicular Magnetic Anisotropy  

NASA Astrophysics Data System (ADS)

We investigate the anomalous Hall effect in Co2FeAl0.5Si0.5/Pt multilayers with perpendicular magnetic anisotropy. The anomalous Hall effect of the Co2FeAl0.5Si0.5/Pt multilayers mainly originates from the side jump contribution, which is similar to that of conventional perpendicular Co/Pt multilayers but different from that of CoFeB/Pt ones. The thickness of the Pt layer has a strong influence on the scaling relationship between the anomalous Hall coefficient Rs and longitudinal resistivity ?xx. For tPt = 18 Å, the traditional scaling relationship is invalid, and a large exponent ?˜2.8 has been observed by scaling analysis with Rs??xx? due to spin-dependent interface scattering.

Wu, Yong; Zhang, Jie; Xiong, Qiang; Gao, Shan; Xu, Xiaoguang; Miao, Jun; He, Zhanbin; Jiang, Yong

2013-11-01

77

Electronic structure and magnetism of Fe3-xVxX (X=Si, Ga, and Al) alloys by the KKR-CPA method  

NASA Astrophysics Data System (ADS)

We present first-principles charge- and spin-self-consistent electronic structure computations on the Heusler-type disordered alloys Fe3-xVxX for three different metalloids X=(Si, Ga, and Al). In these calculations we use the methodology based on the Korringa-Kohn-Rostoker formalism and the coherent-potential approximation generalized to treat disorder in multicomponent complex alloys. Exchange correlation effects are incorporated within the local spin density approximation. Total energy calculations for Fe3-xVxSi show that V substitutes preferentially on the Fe(B) site, not on the Fe(A,C) site, in agreement with experiment. Furthermore, calculations have been carried out for Fe3-xVxX alloys (with x=0.25, 0.50, and 0.75), together with the end compounds Fe3X and Fe2VX, and the limiting cases of a single V impurity in Fe3X and a single Fe(B) impurity in Fe2VX. We delineate clearly how the electronic states and magnetic moments at various sites in Fe3-xVxX evolve as a function of the V content and the metalloid valence. Notably, the spectrum of Fe3-xVxX (X=Al and Ga) develops a pseudogap for the majority as well as minority spin states around the Fermi energy in the V-rich regime, which, together with local moments of Fe(B) impurities, may play a role in the anomalous behavior of the transport properties. The total magnetic moment in Fe3-xVxSi is found to decrease nonlinearly, and the Fe(B) moment to increase with increasing x; this is in contrast to expectations of the ``local environment'' model, which holds that the total moment should vary linearly while the Fe(B) moment should remain constant. The common-band model, which describes the formation of bonding and antibonding states with different weights on the different atoms, however, provides insight into the electronic structure of this class of compounds.

Bansil, A.; Kaprzyk, S.; Mijnarends, P. E.; Tobo?a, J.

1999-11-01

78

Experimental kerma coefficients and dose distributions of C, N, O, Mg, Al, Si, Fe, Zr, A-150 plastic, Al2O3, AlN, SiO2 and ZrO2 for neutron energies up to 66 MeV  

Microsoft Academic Search

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, Al2 O3 , 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

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

2000-01-01

79

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

NASA Technical Reports Server (NTRS)

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.

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

1984-01-01

80

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

NASA Astrophysics Data System (ADS)

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

Kumar, Arvind; Srivastava, P. C.

2014-02-01

81

Heat capacity measurements for cryolite (Na 3AlF 6) and reactions in the system Na?Fe?Al?Si?O?F  

NASA Astrophysics Data System (ADS)

The heat capacity of cryolite (Na 3AlF 6) has been measured from 7 to 1000 K by low-temperature adiabatic and high-temperature differential scanning calorimetry. Low-temperature data were obtained on material from the same hand specimen in the calorimetric laboratories of the University of Michigan and U.S. Geological Survey. The results obtained are in good agreement, and yield average values for the entropy of cryolite of: S0298 = 238.5 J/ mol KS0T- S0298 = 145.114 ln T+ 193.009?10 -3T- 10.366? 10 5/T 2- 872.89 J/ mol K (273-836.5 K) ? STrans = 9.9 J/ mol KS0T- S0298 =198.414 ln T+73.203? 10 -3T-63.814? 10 5/T 2-1113.11 J/ mol K (836.5-1153 K) with the transition temperature between ?- and ?-cryolite taken at 836.5 K. These data have been combined with data in the literature to calculate phase equilibria for the system Na?Fe?Al?Si?O?F. The resultant phase diagrams allow constraints to be placed on the fO 2, fF 2, aSiO 2 and T conditions of formation for assemblages in alkalic rocks. A sample application suggests that log fO 2 is approximately -19.2, logfF 2 is -31.9 to -33.2, and aSiO 2 is -1.06 at assumed P/T conditions of 1000 K, 1 bar for the villiaumite-bearing Ilimaussaq intrusion in southwestern Greenland.

Anovitz, Lawrence M.; Hemingway, Bruce S.; Westrum, Edgar F., Jr.; Metz, Guy W.; Essene, Eric J.

1987-12-01

82

Ladle and Continuous Casting Process Models for Reduction of SiO2 in SiO2-Al2O3-CaO Slags by Al in Fe-Al(-Si) Melts  

NASA Astrophysics Data System (ADS)

Based on a mixed control or two-phase mass transfer model considering mass transport in the metal and the slag phases, process models for ladle and continuous castor mold were developed to predict the changes in the metal and the slag chemistry and viscosity. In the ladle process model, the rate of reaction is primarily determined by stirring gas flow rate, which greatly alters the mass transports of the metal and the slag phases. In the continuous casting process model, the effects of the Al, Si, and SiO2 contents in the incoming flow of the fluid phases, casting speed, mold flux consumption rate, and depth of the liquid mold flux pool on the steady-state compositions of the metal and the mold flux were assessed.

Park, Jiwon; Sridhar, S.; Fruehan, Richard J.

2015-02-01

83

Tensile deformation of 2618 and Al-Fe-Si-V aluminum alloys at elevated temperatures  

NASA Technical Reports Server (NTRS)

The present study experimentally characterizes the effects of elevated temperature on the uniaxial tensile behavior of ingot metallurgy 2618 Al alloy and the rapidly solidified FVS 0812 P/M alloy by means of two constitutive formulations: the Ramberg/Osgood equation and the Bodner-Partom (1975) incremental formulation for uniaxial tensile loading. The elastoplastic strain-hardening behavior of the ingot metallurgy alloy is equally well represented by either formulation. Both alloys deform similarly under decreasing load after only 1-5 percent uniform tensile strain, a response which is not described by either constitutive relation.

Leng, Y.; Porr, W. C., Jr.; Gangloff, R. P.

1990-01-01

84

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

NASA Astrophysics Data System (ADS)

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

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

2014-12-01

85

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)

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.

Bérubé, G.; Yandouzi, M.; Zúñiga, A.; Ajdelsztajn, L.; Villafuerte, J.; Jodoin, B.

2012-03-01

86

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)

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.

Schuon, S. R.

1982-01-01

87

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)

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.

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

2012-08-01

88

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

PubMed

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

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

2014-06-01

89

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)

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.

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

2014-05-01

90

Analysis of size distributions of primary oxide inclusions in Fe10 mass Pct Ni M ( M =Si, Ti, Al, Zr, and Ce) alloy  

Microsoft Academic Search

The planar and spatial size distributions of primary oxide inclusions were measured in an Fe-10 mass pct Ni alloy on deoxidation\\u000a with 0.2 mass pct M (M=Si, Ti, Al, Zr, and Ce). It was found that the size distribution of inclusions obtained at a certain magnification in microanalysis\\u000a was accurate only in a limited range of particle size, due to

Andrey Karasev; Hideaki Suito

1999-01-01

91

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

NASA Astrophysics Data System (ADS)

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

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

2014-04-01

92

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

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,

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

2009-01-01

93

/Al-Si Composite  

NASA Astrophysics Data System (ADS)

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

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

2014-08-01

94

Demonstration of half-metallicity in fermi-level-tuned Heusler alloy Co2FeAl0.5Si0.5 at room temperature.  

PubMed

Fermi level tuning has been successfully demonstrated in Co-based full-Heusler alloy Co(2)FeAl(0.5)Si(0.5) (CFAS). The half-metallic band gap of CFAS was proved by the behavior of differential conductance of CFAS/(MgAl(2))O(x)/CoFe magnetic tunneling junctions with an unexplored crystalline (MgAl(2))O(x) barrier. CFAS exhibits the highest effective spin polarization (P_{eff}) at 300 K and the weakest temperature dependence of P_{eff} among all known half metals. Further study shows that P_{eff} of CFAS decays with increasing temperature (T) following T;{3/2} law perfectly, which indicates that the depolarization of CFAS is determined by spin wave excitation only. PMID:19659034

Shan, R; Sukegawa, H; Wang, W H; Kodzuka, M; Furubayashi, T; Ohkubo, T; Mitani, S; Inomata, K; Hono, K

2009-06-19

95

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

NASA Astrophysics Data System (ADS)

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.

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

2012-12-01

96

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

NASA Astrophysics Data System (ADS)

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) Å, V = 786.40(3) Å3, Z = 2. The strongest lines in the X-ray powder diffraction pattern [ d, Å ( I, %) ( hkl)] are: 8.59 (100) (100), 4.094 (27) (102), 3.390 (35) (112), 3.147 (19) (202), 3.055 (31) (211), 2.657 (12) (212), 1.695 (9) (224). The type specimen of ferroindialite is deposited in the Fersman Mineralogical Museum, Russian Academy of Sciences, Moscow, registration number 4400/1.

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

2014-12-01

97

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

NASA Astrophysics Data System (ADS)

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.

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

2013-05-01

98

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

NASA Astrophysics Data System (ADS)

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

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

2012-12-01

99

Spectrophotometric determination of chloride in PtAl(2)O(3)/SiO(2) catalysts with Hg(SCN)(2)Fe(3+) reagent.  

PubMed

A method is described for the determination of chloride in PtAl(2)O(3)/SiO(2) catalysts, based on its extraction with alkali followed by reaction with Hg(SCN)(2)Fe(3+) reagent and spectrophotometric measurement at 460 nm. Beer's law is obeyed in the concentration range 5-75 mug of chloride in 25 ml of aqueous solution. The molar absorptivity is 1.99 x 10(3) l.mole(-1).cm(-1). The rapid colour development, excellent reproducibility and absence of interference from the species most often present in the catalysts are the advantages of the method. PMID:18964430

Koshy, V J; Garg, V N

1987-11-01

100

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

SciTech Connect

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

Vahidi, M.; Zhang, S. K.; Yu, L.; Huang, M.; Newman, N., E-mail: Nathan.Newman@asu.edu [School of Materials, Arizona State University, Tempe, Arizona 85287-8706 (United States); Gifford, J. A.; Chen, T. Y. [Department of Physics, Arizona State University, Tempe, Arizona 85287 (United States); Krishnamurthy, S.; Yu, Z. G. [SRI International, 301-64, Menlo Park, California 94025 (United States); Youngbull, C. [The Biodesign Institute, Arizona State University, Tempe, Arizona 85287 (United States)

2014-04-01

101

Investigation of the temperature-dependence of ferromagnetic resonance and spin waves in Co2FeAl0.5Si0.5  

NASA Astrophysics Data System (ADS)

Co2FeAl0.5Si0.5 (CFAS) is a Heusler compound that is of interest for spintronics applications, due to its high spin polarization and relatively low Gilbert damping constant. In this study, the behavior of ferromagnetic resonance as a function of temperature was investigated in CFAS, yielding a decreasing trend of damping constant as the temperature was increased from 13 to 300 K. Furthermore, we studied spin waves in CFAS using both frequency domain and time domain techniques, obtaining group velocities and attenuation lengths as high as 26 km/s and 23.3 ?m, respectively, at room temperature.

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

2014-06-01

102

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)

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.

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

2015-03-01

103

Activities of Fe t O in CaO-Al 2 O 3 SiO 2 Fe t O (<5 pct) slags saturated with liquid iron  

Microsoft Academic Search

The activity coefficients of FetO in CaO-Al2O3 and CaO-Al2O3-SiO2 slags with 0.01 to 5 mass pct FetO were determined at 1873 K from the data obtained in the present and previous slag-metal experiments, using an alumina or\\u000a lime crucible. It was found that the activity coefficients of FetO obeyed a dilute solution law and increased with increasing the content of

Kwang Ro Lee; Hideaki Suito

1994-01-01

104

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

NASA Astrophysics Data System (ADS)

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.

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

2012-12-01

105

Tunnel magnetoresistance effect in magnetic tunnel junctions with epitaxial Co2FeAl0.5Si0.5 Heusler electrodes on MgO (110) single substrates  

NASA Astrophysics Data System (ADS)

Tunnel magnetoresistance effect has been investigated for magnetic tunnel junctions with Co2FeAl0.5Si0.5 Heusler electrodes on a Cr-bufferd MgO (110) substrate. The grown Co2FeAl0.5Si0.5 has L21 structure for annealing above 500 °C. The TMR ratio of 73% at room temperature and 103% at 5 K were obtained for a junction consists of MgO(110) substrate/Cr/Co2FeAl0.5Si0.5/Al-oxide/Co75Fe25/IrMn/Ta. The tunnel magnetoresistance ratio obtained in this study is almost the same as that estimated by using magnetic tunnel junction with the same kind of Co2FeAl0.5Si0.5 electrode on a Cr-bufferd MgO (001) substrate. Smaller temperature dependence of magnetoresistance ratio was also found for the junctions on Cr-bufferd MgO(110) substrates.

Tezuka, N.; Mitsuhashi, F.; Sugimoto, S.

2012-04-01

106

Kanonaite, (Mn 0.76 3+ Al 0.23 Fe 0.02 3+ ) [6] Al [5] [O¦SiO 4 ], a new mineral isotypic with andalusite  

Microsoft Academic Search

Kanonaite forms rare porphyroblasts up to 12mm long in a gahnite— Mg-chlorite — coronadite — quartz schist occurring near Kanona, Zambia. The composition is (microprobe analysis): SiO2 32.2, Al2O3 33.9, Mn as Mn2O3 32.2, Fe2O3 0.66, ZnO 0.13, MgO 0.04, BaO 0.04, TiO2 0.01, CaO 0.01, PbO 0.01, CuO 0.01, total 99.21, corresponding to \\u000a$$\\\\left( {{\\\\text{Mn}}_{{\\\\text{0}}{\\\\text{.76}}}^{{\\\\text{3 + }}} {\\\\text{Al}}_{{\\\\text{0}}{\\\\text{.23}}} {\\\\text{Fe}}_{{\\\\text{0}}{\\\\text{.015}}}^{{\\\\text{3

S. Vrána; M. Rieder; J. Podlaha

1978-01-01

107

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

SciTech Connect

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 (1.1×10{sup ?3} and 1.3×10{sup ?3} for films of 50?nm thickness annealed at 615?°C grown on MgO and on Si, respectively)

Belmeguenai, M., E-mail: belmeguenai.mohamed@univ-paris13.fr; Tuzcuoglu, H.; Zighem, F.; Chérif, S. M.; Moch, P. [LSPM (CNRS-UPR 3407), 99 avenue Jean-Baptiste Clément, Université 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, Université de Nancy, BP 70239, F–54506 Vandoeuvre (France)

2014-01-28

108

The effect of foreign ions on the reactivity of the CaO–SiO 2–Al 2O 3–Fe 2O 3 system  

Microsoft Academic Search

The subject of this paper is the effect of foreign cations on the reactivity of the CaO–SiO2–Al2O3–Fe2O3 system. One reference mixture and eighteen modified mixtures, prepared by mixing the reference sample with 1% w\\/w of chemical grade MnO2, CuO, V2O5, PbO, CdO, ZrO2, Li2O, MoO3, Co2O3, NiO, WO3, ZnO, Nb2O5, CrO3, Ta2O5, TiO2, BaO2 and H3BO3 were studied. The effect

K Kolovos; S Tsivilis; G Kakali

2002-01-01

109

On a Fast and Accurate In Situ Measuring Strategy for Recrystallization Kinetics and Its Application to an Al-Fe-Si Alloy  

NASA Astrophysics Data System (ADS)

In the current study, we detail a novel in situ X-ray diffraction-based bulk measurement technique, which allows for the continuous tracking of primary recrystallization kinetics. The approach is based on measuring the diffracted intensity that is correlated with the evolution of the volume fraction of particular texture components during annealing of a sample within a texture goniometer. The method is applied in an experimental study on a cold-rolled industrial Al-Fe-Si alloy. For comparison purposes, the macrotexture and the hardness evolution were monitored ex situ along isothermal and nonisothermal annealing. These measurements were then contrasted to the in situ obtained growth kinetics of recrystallizing grains in beta-fiber deformation and cube orientation. The results showed clearly that this method can be reliably utilized for the characterization of recrystallization kinetics in an industrial context.

Kühbach, Markus; Brüggemann, Thiemo; Molodov, Konstantin D.; Gottstein, Günter

2015-03-01

110

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

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 MgO–CaO. The onset temperature for the formation of free Al, Be, Si, Ti, Mg, Hf, and Zr

M. Halmann; A. Frei; A. Steinfeld

2011-01-01

111

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

SciTech Connect

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

Anovitz, L.M. (Univ. of Arizona, Tucson, AZ (United States)); Essene, E.J.; Metz, G.W.; Westrum, E.F. Jr. (Univ. of Michigan, Ann Arbor, MI (United States)); Bohlen, S.R. (Geological Survey, Menlo Park, CA (United States)); Hemingway, B.S. (Geological Survey, Reston, VA (United States))

1993-09-01

112

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

NASA Astrophysics Data System (ADS)

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

Timelli, Giulio; Fabrizi, Alberto

2014-11-01

113

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

NASA Astrophysics Data System (ADS)

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 Sesták-Berggren combined kinetic model. The kinetic study evinces that in addition to the expected reactions, other reactions, necessary for good experimental adjustment, appear. An isoconversional study is undertaken to numerically evaluate the kinetic triplet of every process.

Luiggi Agreda, Ney José

2015-02-01

114

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)

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) Å, ? = 113.64(1)°; V = 832.2(2) Å3, Z = 2. The strong reflections in the X-ray powder diffraction pattern are [ d, Å ( I, %) ( hkl)]: 5.19 (40) (110), 3.53 (40) (overline 3 11), 2.96 (100) (overline 3 13, 311), 2.80 (50) (020), 2.14 (50) (overline 4 22, overline 3 15, 313), 1.947 (50) (024, 223), 1.657 (40) (overline 4 07, overline 4 33, 331). The holotype specimen of perrierite-(La) is deposited at the Fersman Mineralogical Museum, Russian Academy of Sciences, Moscow, Russia, with the registration number 4059/1.

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

2012-12-01

115

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

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.

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

2011-12-31

116

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

NASA Astrophysics Data System (ADS)

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

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

2014-05-01

117

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

NASA Astrophysics Data System (ADS)

We study polycrystalline B2-type Co2FeAl (CFA) full-Heusler-alloy-based magnetic tunnel junctions (MTJs) fabricated on a Si /SiO2 amorphous substrate. Polycrystalline CFA films with a (001) orientation, a high B2 ordering, and a flat surface are achieved by using a MgO buffer layer. A tunnel magnetoresistance ratio up to 175% is obtained for a MTJ with a CFA /MgO/CoFe structure on a 7.5-nm-thick MgO buffer. Spin-transfer-torque-induced magnetization switching is achieved in the MTJs with a 2-nm-thick polycrystalline CFA film as a switching layer. By using a thermal activation model, the intrinsic critical current density (Jc0) is determined to be 8.2×106 A /cm2, which is lower than 2.9×107 A /cm2, the value for epitaxial CFA MTJs [Appl. Phys. Lett. 100, 182403 (2012), 10.1063/1.4710521]. We find that the Gilbert damping constant (?) evaluated by using ferromagnetic resonance measurements for the polycrystalline CFA film is approximately 0.015 and is almost independent of the CFA thickness (2-18 nm). The low Jc0 for the polycrystalline MTJ is mainly attributed to the low ? of the CFA layer compared with the value in the epitaxial one (approximately 0.04).

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

2014-08-01

118

Kanonaite, (Mn{0.76\\/3+}Al0.23Fe{0.02\\/3+})[6]Al[5][O¦SiO4], a new mineral isotypic with andalusite  

Microsoft Academic Search

Kanonaite forms rare porphyroblasts up to 12mm long in a gahnite--- Mg-chlorite --- coronadite --- quartz schist occurring near Kanona, Zambia. The composition is (microprobe analysis): SiO2 32.2, Al2O3 33.9, Mn as Mn2O3 32.2, Fe2O3 0.66, ZnO 0.13, MgO 0.04, BaO 0.04, TiO2 0.01, CaO 0.01, PbO 0.01, CuO 0.01, total 99.21, corresponding to 410_2004_Article_BF00373417_TeX2GIFE1.gif left( {{text{Mn}}_{{text{0}}{text{.76}}}^{{text{3 + }}} {text{Al}}_{{text{0}}{text{.23}}}

S. Vrána; M. Rieder; J. Podlaha

1978-01-01

119

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

Microsoft Academic Search

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 100 GPa and at 300 K, using diamond cells and synchrotron Mssbauer spectroscopy techniques. At pressures below 12 GPa, our Mssbauer spectra can be sufficiently fitted by a “two-doublet” model, which assumes one ferrous Fe2+-like site and one

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

2006-01-01

120

Magnetic and optical investigation of 40SiO2·30Na2O·1Al2O3·(29 - x)B2O3·xFe2O3 glass matrix  

NASA Astrophysics Data System (ADS)

Samples of 40SiO2·30Na2O·1Al2O3·(29 - x)B2O3·xFe2O3 (mol%), with 0.0 ? x ? 17.5, were prepared by the fusion method and investigated by electron paramagnetic resonance (EPR), optical absorption (OA) and Mössbauer 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, Mössbauer 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).

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

121

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

NASA Astrophysics Data System (ADS)

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

Ramos, J.; Piamba, J. F.; Sánchez, H.; Alcazar, G. A. Pérez

2015-01-01

122

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

NASA Technical Reports Server (NTRS)

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

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

1991-01-01

123

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)

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.

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

2012-01-01

124

The effect of nitrogen on the microstructure, stress, and magnetic properties of RF-sputtered FeSiAl(N) thin films  

NASA Astrophysics Data System (ADS)

In a series of RF-sputtered soft FeSiAl(N) films, the partial pressure (pp) of N in the plasma was observed to have a profound effect on the magnetic properties, stress, and microstructure. 1% (pp) N caused the coercivity ( Hc) to more than double. Hc peaked for 3% (pp) N, then decreased steeply for N>4% (pp). Stress appears to have a major influence on the magnetic properties. Film stress correlated quite closely with Hc. Hysteresis loops appear to indicate a stripe domain structure in which the magnetization has in-plane components which are aligned parallel, but perpendicular components which alternate up and down. Stripe domains were observed directly by magnetic force microscopy. The microstructure also changed significantly with added N. 1% (pp) N caused the strong (1 1 0) texture to become very weak. For >4% (pp) N, there was a transition from textured columnar 100 nm diameter BCC grains to a mixture of randomly-oriented, equiaxed BCC nanograins (10 nm or less) in an amorphous matrix. Transmission electron microscopy observations appear to indicate that the grain refinement and phase separation take place by a decomposition process. Saturation magnetization also decreased with added N for >4% (pp) N, indicating that one of the two phases has a lower Ms value.

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

2001-05-01

125

Micromagnetic Simulation of Spin Transfer Torque Switching of Full-Heusler Co2FeAl0.5Si0.5 Alloy Thin Elliptical Disc  

NASA Astrophysics Data System (ADS)

We report micromagnetic simulation of spin transfer torque (STT) switching of a thin elliptical disc made of full-Heusler Co2FeAl0.5Si0.5 alloy. The STT results in switching the direction of initial magnetization of the disc to a new state based on the spin-polarization factor (?) of the material and magnitude of current density (J) applied. The value of J required for magnetization switching need to be reduced in the order of 106 A/cm2. In our simulation we obtained 3 × 105 A/cm2 as the critical current density (Jc) required for complete magnetization switching of the disc. We analyzed the effect of ? on magnetization switching time by reducing the value of ? by 0.10 from the actual value of 0.76. The decrement in ? results in the increment of time taken to switch the direction of magnetization. The change in switching time for variable disc thickness was also studied. This simulation result holds a key factor in the study of STT switching in spin-valve nanopillar.

Babu, R. Vignesh; Malathi, M.

126

Growth and characterization of high crystalline quality Co2FeAlxSi1-x Heusler alloy films on MgAl2O4(001) substrates  

NASA Astrophysics Data System (ADS)

A number of Heusler alloys have been predicted to be half-metallic and are thus ideal candidates for use in spintronics. Co2FeAlxSi1-x has been predicted and shown to have some of the highest Tc, saturation magnetization and lowest magnetic damping constant among Heusler half-metals. Here we outline the growth and characterization of the highest crystalline quality epitaxial Heusler films using a novel off-axis UHV sputtering technique. We grow these films onto a closely lattice matched MgAl2O4(001) substrate, without the need for a Cr-buffer layer or post annealing, as has been done previously. This eliminates the diffusion of Cr across the interface, thus improving the purity and crystallinity of the films at the interface. X-ray diffraction results demonstrate epitaxial films with distinct Laue oscillations and rocking curves of FWHM as low as 0.0035^o, which demonstrates the highest crystalline quality for Heusler films reported to date. Magnetic measurements show highly square hysteresis loops with a remanence of 95-98%, near ideal saturation magnetization, very small coercivities - between 3-8 Oe, pronounced magnetocrystalline anisotropy.

Peters, Brian; Blum, Christian; Woodward, Patrick; Wurmehl, Sabine; Yang, Fengyuan

2013-03-01

127

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

NASA Astrophysics Data System (ADS)

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

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

2014-08-01

128

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

NASA Astrophysics Data System (ADS)

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.

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

1994-11-01

129

Effect of Al content on the order of phase transition and magnetic entropy change in LaFe11Co0.8(Si1-xAlx)1.2 alloys  

NASA Astrophysics Data System (ADS)

The comparative studies of the effect of partial substitution of Al by Si on the structure and magnetic entropy change in LaFe11Co0.8(Si1-xAlx)1.2 alloys produced by arc-melting followed by long time annealing at 1323 K were performed. The X-ray diffraction analysis revealed almost single phase composition of annealed samples. The high intensity synchrotron radiation was used for studying the thermal evolution of lattice constant of the La(Fe,Co,Si)13 phase. Furthermore, calculations of temperature dependences of Landau coefficients were used to reveal changes in the character of phase transformation at around the Curie temperature.

G?bara, P.; Pawlik, P.; Škorvánek, I.; Bednarcik, J.; Marcin, J.; Michalik, Š.; Donges, J.; Wys?ocki, J. J.; Michalski, B.

2014-12-01

130

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

Microsoft Academic Search

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.

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

2008-01-01

131

Correlation between magnetic softness, sample surface and magnetoimpedance in Co69Fe4.5X1.5Si10B15 (X = Ni, Al, Cr) amorphous ribbons  

Microsoft Academic Search

In this work we have studied the giant magnetoimpedance (GMI) effect and its field sensitivity (eta) in Co69Fe4.5X1.5Si10B15 (X = Ni, Al, Cr) amorphous ribbons in the frequency (f) range of 0.1 to 10 MHz. We find that at f 5 MHz. Magnetization and atomic force microscopy (AFM) experiments reveal that the largest values of the low-frequency GMI effect and

A. Chaturvedi; T. Dhakal; S. Witanachchi; M. H. Phan; H. Srikanth; A. T. Le

2011-01-01

132

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

SciTech Connect

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

Bogard, James S [ORNL; Espinosa Garcia, Guillermo [ORNL

2007-01-01

133

Rapidly solidified NiAl and FeAl  

NASA Technical Reports Server (NTRS)

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 clevage fracture.

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

1985-01-01

134

Rapidly solidified NiAl and FeAl  

NASA Technical Reports Server (NTRS)

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.

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

1984-01-01

135

AlN/Fe/AlN nanostructures for magnetooptic magnetometry  

SciTech Connect

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.

Lišková-Jakubisová, E., E-mail: liskova@karlov.mff.cuni.cz; Viš?ovský, Š. [Faculty of Mathematics and Physics, Charles University in Prague, Ke Karlovu 5, 12116 Prague 2 (Czech Republic); Široký, P.; Hrabovský, D.; Pištora, 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

136

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

NASA Astrophysics Data System (ADS)

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

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

2013-07-01

137

Morphology and the magnetic and conducting properties of heterogeneous layered magnetic structures [(Co45Fe45Zr10)35(Al2O3)65/ a-Si:H]36  

NASA Astrophysics Data System (ADS)

The morphology and the magnetic and conducting properties of an amorphous multilayer nanosystem [(Co45Fe45Zr10)35(Al2O3)65/ a-Si:H]36 consisting of (Co45Fe45Zr10)35(Al2O3)65 magnetic layers and semiconducting hydrogenated amorphous silicon ( a-Si:H) layers of various thicknesses have been studied. Using a combination of methods (including polarized neutron reflectometry and grazing incidence small-angle X-ray scattering), it is shown that the magnetic and electrical properties of these multilayer structures are determined by their morphology. It is established that the magnetization and electric resistance of a sample is a nonmonotonic function of the a-Si:H layer thickness. Both characteristics are at a minimum for a structure with a semiconductor layer thickness of 0.4 nm. Samples with silicon layer thicknesses below 0.4 nm represent a three-dimensional structure of Co45Fe45Zr10 grains weakly ordered in space, while in samples with silicon layer thicknesses above 0.4 nm, these grains are packed in layers alternating in the vertical direction. The average lateral distance between nanoparticles in the layer plane has been determined, from which the dimensions of metal grains in each sample have been estimated.

Dyadkina, E. A.; Vorobiev, A. A.; Ukleev, V. A.; Lott, D.; Sitnikov, A. V.; Kalinin, Yu. E.; Gerashchenko, O. V.; Grigoriev, S. V.

2014-03-01

138

High-frequency permeability spectra of FeCoSiN/Al{sub 2}O{sub 3} laminated films: Tuning of damping by magnetic couplings dependent on the thickness of each ferromagnetic layer  

SciTech Connect

In this work, we investigate the high-frequency permeability spectra of as-sputtered FeCoSiN/Al{sub 2}O{sub 3} laminated films, and discuss their dependence on the thickness of each FeCoSiN layer, based on the phenomenological Landau-Lifshitz-Gilbert equation. The damping factor and coercivity show their minima with lamination, deviating from the expectation based on the grain size confinement effect. Such dependences on the layer thickness indicate the influence of magnetic coupling. The decreases in the damping factor and the coercivities with lamination can be partially attributed to the decrease in the magnetostatic coupling induced by ripple structures. The enhanced damping and enlarged coercivity values obtained with further lamination are ascribed to the enhanced Neel couplings. The dependences show that the lamination can be effective in tuning the magnetization dynamics by changing the magnetic couplings.

Xu Feng; Zhang Xiaoyu; Nguyen Nguyen Phuoc; Ma Yungui; Ong, C. K. [Department of Physics, Center for Superconducting and Magnetic Materials, National University of Singapore, Singapore 117542 (Singapore)

2009-02-15

139

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

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.

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

2011-11-15

140

Spin Injection, Transport, and Detection at Room Temperature in a Lateral Spin Transport Device with Co2FeAl0.5Si0.5/n-GaAs Schottky Tunnel Junctions  

NASA Astrophysics Data System (ADS)

We observed spin-valve signals and Hanle signals in four-terminal nonlocal measurements on a lateral spin transport device with Co2FeAl0.5Si0.5(CFAS)/n-GaAs Schottky tunnel junctions. The estimated spin injection/detection efficiency was 0.06 at 4.2 K, which is larger than those of the devices with Fe and CoFe electrodes [Nature Physics 3 (2007) 197 and Appl. Phys. Lett. 99 (2011) 082108]. The spin diffusion length estimated from Hanle signals was consistent with the gap length dependency of the spin-valve signals. Furthermore, the spin-valve signals were observed at up to 290 K. This is the first demonstration of detecting spin accumulation in semiconductor with full-Heusler alloys electrodes at room temperature.

Saito, Tatsuya; Tezuka, Nobuki; Matsuura, Masashi; Sugimoto, Satoshi

2013-10-01

141

STABILITY OF METALLIC Si-, Fe-RICH ALLOYS, SiC AND GRAPHITE IN MIXED SUPERNOVA EJECTA.  

E-print Network

STABILITY OF METALLIC Si-, Fe-RICH ALLOYS, SiC AND GRAPHITE IN MIXED SUPERNOVA EJECTA. L. Grossman1 supernova has the same C, N and O isotopic compositions, 48 Ti/44 Ti and inferred initial 26 Al/27 AlC is found as inclusions in some supernova graphite grains but not in others. Elemental Abundances

Grossman, Lawrence

142

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

SciTech Connect

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

Shieh, Sean R.; Dorfman, Susannah M.; Kubo, Atsushi; Prakapenka, Vitali B.; Duffy, Thomas S. (Princeton); (UWO); (UC)

2012-02-06

143

Fe/Al2O3 C2H4 Hata mm/10 min  

E-print Network

Fe/Al2O3 C2H4 () () () () () () () * () 1. (SWNT) SWNT (CVD) (CNT)[1] Hata mm/10 min SWNT (Super Growth)[2]Al2O3 Fe C2H4 SWNT Fe/Al2O3 C2H4 CVD SWNT CNT CNT 2 SiO2 Al2O3 20 (RBM) 1350 cm-1 (D-Band)Fe G/D RBM Fe SWNT Al 15 nm Fe 0.6 nm CVD TEM Fig. 3 3 nm SWNT

Maruyama, Shigeo

144

Improvement of magnetic and structural stabilities in high-quality Co2FeSi1-xAlx/Si heterointerfaces  

NASA Astrophysics Data System (ADS)

We study high-quality Co2FeSi1-xAlx Heusler compound/Si (0 ? x ? 1) heterointerfaces for silicon (Si)-based spintronic applications. In thermal treatment conditions, the magnetic and structural stabilities of the Co2FeSi1-xAlx/Si heterointerfaces are improved with increasing x in Co2FeSi1-xAlx. Compared with L21-ordered Co2FeSi/Si, B2-ordered Co2FeAl/Si can suppress the diffusion of Si atoms into the Heusler-compound structure. This experimental study will provide an important knowledge for applications in Si-based spin transistors with metallic source/drain contacts.

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

2014-08-01

145

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

NASA Astrophysics Data System (ADS)

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

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

2010-12-01

146

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

SciTech Connect

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

Loong, Li Ming; Kwon, Jae Hyun; Deorani, Praveen; Yang, Hyunsoo, E-mail: eleyang@nus.edu.sg [Department of Electrical and Computer Engineering, National University of Singapore, 117576 Singapore (Singapore); Tung Yu, Chris Nga [Department of Physics, The University of York, York YO10 5DD (United Kingdom); Hirohata, Atsufumi, E-mail: atsufumi.hirohata@york.ac.uk [Department of Electronics, The University of York, York YO10 5DD (United Kingdom)

2014-06-09

147

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

SciTech Connect

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.

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

2012-02-15

148

Al nanocluster growth on Si(111) and Si(100) surfaces  

Microsoft Academic Search

The structure of Al films on Si in the submonolayer range has been extensively studied, but at coverages above one monolayer (ML), the structural behaviour is not elucidated as yet. The growth of nanoclusters out of Al films with 4ML thickness, deposited on Si(111) and Si(100) surfaces by molecular beam epitaxy was studied with reflection high-energy electron diffraction, spot profile

R. Gröger; M. Barczewski; P. von Blanckenhagen

2000-01-01

149

Magnetic Properties of Disordered Fe3Al  

NASA Astrophysics Data System (ADS)

The magnetic properties of Fe3Al powders prepared by filing the ingot in both as-filed and annealed form are studied. Results of Mössbauer, X-ray diffraction and DC magnetization studies show that the magnetic properties are modified due to formation of non-magnetic Fe3AlC0.5 phase due to C intercalated on filing. The hyperfine fields obtained are explained in terms of nearest and next nearest neighbor configurations of 57Fe.

Nehra, J.; Kabra, K.; Jani, S.; Ranjith, P. M.; Lakshmi, N.; Venugopalan, K.

2011-07-01

150

Experimental investigation of zoisite-clinozoisite phase equilibria in the system CaO-Fe2O3-Al2O3-SiO2-H2O  

NASA Astrophysics Data System (ADS)

The system Ca2Al3Si3O11(O/OH)-Ca2Al2FeSi3O11(O/OH), with emphasis on the Al-rich portion, was investigated by synthesis experiments at 0.5 and 2.0 GPa, 500-800 °C, using the technique of producing overgrowths on natural seed crystals. Electron microprobe analyses of overgrowths up to >100 µm wide have located the phase transition from clinozoisite to zoisite as a function of P-T-Xps and a miscibility gap in the clinozoisite solid solution. The experiments confirm a narrow, steep zoisite-clinozoisite two-phase loop in T-Xps section. Maximum and minimum iron contents in coexisting zoisite and clinozoisite are given by $X{ ps}{ zo} (max) = 1.9*10{ - 4} T+ 3.1*10{ - 2} P - 5.36*10{ - 2} and X{ ps}{ czo} (min) = (4.6 * 10{ - 4} - 4 * 10{ - 5} P)T + 3.82 * 10{ - 2} P - 8.76 * 10{ - 2} $ (P in GPa, T in °C). The iron-free end member reaction clinozoisite = zoisite has equilibrium temperatures of 185+/-50 °C at 0.5 GPa and 0+/-50 °C at 2.0 GPa, with ?Hr0=2.8+/-1.3 kJ/mol and ?Sr0=4.5+/-1.4 J/mol×K. At 0.5 GPa, two clinozoisite modifications exist, which have compositions of clinozoisite I 0.15 to 0.25 Xps and clinozoisite II >0.55 Xps. The upper thermal stability of clinozoisite I at 0.5 GPa lies slightly above 600 °C, whereas Fe-rich clinozoisite II is stable at 650 °C. The schematic phase relations between epidote minerals, grossular-andradite solid solutions and other phases in the system CaO-Al2O3-Fe2O3-SiO2-H2O are shown.

Brunsmann, A.; Franz, G.; Heinrich, W.

2002-01-01

151

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

SciTech Connect

The microporous framework structure of (Mg{sub 1-x}Fe{sub x}){sub 2}Al{sub 4}Si{sub 5}O{sub 18} (=cordierite) has been subject to a comparative study on the effect of structural alterations originating from exposure to high-energy heavy ions. Oriented samples (with x=0.061, 0.122, and 0.170) were irradiated with swift {sup 124}Xe, {sup 197}Au and {sup 96}Ru ions with 11.1 MeV per nucleon energy and fluences of 1x10{sup 12} and 1x10{sup 13} ions/cm{sup 2}. Irradiated and non-irradiated samples were investigated by means of X-ray diffraction, Moessbauer spectroscopy and optical absorption spectroscopy. Structural investigations reveal an essentially unchanged Al,Si ordering, which appears to be unaffected by irradiation. The most remarkable macroscopic change is the ion-beam induced colouration, which could be assigned to electronic charge transfer transitions involving the Fe cations. Moessbauer spectra indicate an increased amount of {sup [4]}Fe{sup 3+} for the irradiated sample. The most noticeable structural alteration concerns irradiation-induced dehydration of extra-framework H{sub 2}O, which is accompanied by a reduction in the molar volume by {approx}0.2 vol%. - Graphical abstract: Cordierite single-crystal specimen showing the color change from pale blue (unirradiated) to a yellowish brown layer (irradiated) after exposure to relativistic {sup 124}Xe ions at a fluence of 1x10{sup 12} ions per cm{sup 2}.

Miletich, Ronald, E-mail: ronald.miletich@geow.uni-heidelberg.d [Institut fuer Geowissenschaften, Universitaet Heidelberg, Im Neuenheimer Feld 234-236, D-69120 Heidelberg (Germany); Diego Gatta, G. [Dipartimento di Scienze della Terra, Universita degli Studi di Milano, Via Botticelli 23, I-20133 Milano (Italy); Redhammer, Guenther J. [Fachbereich Materialforschung und Physik, Abteilung Mineralogie, Universitaet Salzburg, Hellbrunnerstrasse 34, A-5020 Salzburg (Austria); Burchard, Michael; Meyer, Hans-Peter [Institut fuer Geowissenschaften, Universitaet Heidelberg, Im Neuenheimer Feld 234-236, D-69120 Heidelberg (Germany); Weikusat, Christian [Institut fuer Geowissenschaften, Universitaet Heidelberg, Im Neuenheimer Feld 234-236, D-69120 Heidelberg (Germany); GSI Helmholtzzentrum fuer Schwerionenforschung, Materials Research, Planckstrasse 1, D-64291 Darmstadt (Germany); Rotiroti, Nicola [Dipartimento di Scienze della Terra, Universita degli Studi di Milano, Via Botticelli 23, I-20133 Milano (Italy); Glasmacher, Ulrich A. [Institut fuer Geowissenschaften, Universitaet Heidelberg, Im Neuenheimer Feld 234-236, D-69120 Heidelberg (Germany); Trautmann, Christina; Neumann, Reinhard [GSI Helmholtzzentrum fuer Schwerionenforschung, Materials Research, Planckstrasse 1, D-64291 Darmstadt (Germany)

2010-10-15

152

26Al and 60Fe yields from AGB stars  

NASA Astrophysics Data System (ADS)

We present yields for 26Al and 60Fe from asymptotic giant branch (AGB) stars. For AGB stars of masses lower than ?4 M ? yields are of the order of only 10 -7 M ?, while for AGB stars of higher masses yields are up to 10 -5 M ?. In these massive AGB stars 26Al is produced via 25Mg( p, ?) 26Al reactions when proton captures occur at the base of the convective envelope (hot bottom burning), while 60Fe is produced via the operation of the 59Fe( n, ?) 60Fe reaction when high neutron densities result from the activation of the 22Ne( ?, n) 25Mg neutron source during thermal pulses. Large nuclear and stellar uncertainties are associated with these predictions, ranging from the rate of the 26Al + p reaction to the amount of material carried from the He-rich shell to the convective envelope via the third dredge-up. When compared to the contribution from core-collapse supernovae, the overall contribution of AGB stars to the Galactic inventory of 26Al and 60Fe is insignificant. On the other hand, a massive AGB star may have polluted the early solar system with short lived radioactive nuclei since we obtain a self-consistent match for the abundances of 41Ca, 26Al, 60Fe, and 107Pd using our 6.5 M ? model. Finally, the interpretation of the 26Al/ 27Al ratios in the majority of meteoritic stellar grains from low-mass AGB stars is hindered by the three orders of magnitude error bar of the 26Al( p, ?) 27Si reaction. Grains with very high 26Al/ 27Al ratios may represent evidence for extra-mixing phenomena in AGB stars or for a post-AGB origin.

Lugaro, Maria; Karakas, Amanda I.

2008-10-01

153

Influence of mixing the low-valent transition metal atoms (Y, Y*=Cr, Mn, Fe) on the properties of the quaternary Co2[Y1-xYx*]Z (Z=Al, Ga, Si, Ge, or Sn) Heusler compounds  

NASA Astrophysics Data System (ADS)

We complement our study on the doping and disorder in Co2MnZ compounds [I. Galanakis, K. Özdo?an, B. Akta?, and E. ?a??o?lu, Appl. Phys. Lett. 89, 042502 (2006) and K. Özdo?an, E. ?a??o?lu, B. Akta?, and I. Galanakis, Phys. Rev. B 74, 172412 (2006)] to cover also the quaternary Co2[Y1-xYx?]Z compounds with the lower-valent transition metals Y, Y? being Cr, Mn, or Fe and the sp atom Z being one of Al, Ga, Si, Ge, and Sn. This study gives a global overview of the magnetic and electronic properties of these compounds since we vary both Y and Z elements. Our results suggest that for realistic applications the most appropriate compounds are the ones belonging to the families Co2[Mn1-xCrx]Z with x >0.5 irrespectively of the nature of the sp atoms since they combine high values of majority density of states at the Fermi level due to the presence of Cr, and half-metallicity with large band gaps. On the other hand, the presence of Fe considerably lowers the majority density of states at the Fermi level and when combined with an element belonging to the Si column, it can even destroy half-metallicity.

Özdo?an, K.; Akta?, B.; Galanakis, I.; ?a??o?lu, E.

2007-04-01

154

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

NASA Astrophysics Data System (ADS)

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

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

2012-01-01

155

Enhancing Photovoltaic Characteristics of Iron Doped Amphous Carbon\\/Al2O3\\/Si Solar Cell by Al2O3 Interface Passivation  

Microsoft Academic Search

This letter reports the enhanced photovoltaic (PV) performance of Fe doped amorphous carbon (a-C) film\\/n-Si heterojunctions by depositing a thin Al2O3 layer at the interface of a-C:Fe and Si substrate. We demonstrate that a thin Al2O3 film at the interface of Fe-doped a-C\\/Si heterojunction allows significantly improving the devices' PV performances up to one order of magnitude under AM1.5 illumination.

Xinyu Tan; Xiaozhong Zhang; Caihua Wan; Xili Gao; Hong Lin; Jing Zhang

2011-01-01

156

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

PubMed Central

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

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

2014-01-01

157

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

PubMed

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

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

2014-01-01

158

Development of SiAlON materials  

NASA Technical Reports Server (NTRS)

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.

Layden, G. K.

1979-01-01

159

Theoretical investigations of an influence of Ti on electronic structure and magnetic properties of half-metallic Fe2Mn1-xTixSi0.5Al0.5 alloys  

NASA Astrophysics Data System (ADS)

Ab-initio electronic structure calculations are carried out for quinternary Fe2Mn1-xTixSi0.5Al0.5 alloys basing on the density functional theory. When x=0, the alloy is a half-metallic ferromagnet with magnetic moment following the Slater-Pauling rule. Main carrier of magnetism of the alloy is manganese with the magnetic moment of about 2.5 ?B. Replacement of Mn by Ti, changes its electronic and magnetic structure. Half-metallicity is present up to Ti concentration x=0.375. However, the further increase of Ti content leads to a strong decrease of electronic spin polarization. When the concentration of Ti increases, total magnetic moment strongly decreases. Fe magnetic moment, in the presence of titanium, changes its orientation into antiparallel in respect to the total magnetic moment and its absolute value increases with increasing Ti content. However, absolute value of Fe magnetic moment does not exceed 0.17 ?B. Ti exhibits very weak spin polarization with magnetic moment not higher than 0.05 ?B.

Go, Anna

2015-02-01

160

Four-terminal nonlocal signals in lateral spin transport devices with variously ordered Co2FeAl0.5Si0.5 full-Heusler alloy electrodes  

NASA Astrophysics Data System (ADS)

The structural ordering of the Co2FeAl0.5Si0.5 (CFAS) full-Heusler alloy, the electrical transport properties, and the four-terminal (4T) nonlocal signals were investigated in lateral spin transport devices with CFAS/n-GaAs Schottky tunnel junctions as a function of the deposition temperature of CFAS (TCFAS). The 4T nonlocal signals increased with increasing TCFAS, in contrast to the trend in three-terminal Hanle measurements [Jpn. J. Appl. Phys., Part 1 52, 063001 (2013)]. No relationship between interface resistance and 4T nonlocal signal was confirmed, indicating that conductance mismatch problems did not affect the tendency of signal values.

Saito, Tatsuya; Tezuka, Nobuki; Matsuura, Masashi; Sugimoto, Satoshi

2013-09-01

161

Magneto-optical characterization of single crystalline Co2FeAl0.4Si0.6 thin films on MgO(1?0?0) substrates with Cr and MgO seed layers  

NASA Astrophysics Data System (ADS)

We report on the experimental investigation of the influence of a seed layer on the magnetic properties of the full-Heusler alloy Co2FeAl0.4Si0.6 (CFAS). The studied magnetic films are grown epitaxially on MgO (1?0?0) substrates with Cr and/or MgO seed layers. By employing magneto-optical Kerr effect magnetometry we show that magnetic anisotropy can be tuned by choosing the proper seed layer. The results on CFAS show an overall uniaxial anisotropy plus a biaxial contribution which depends on the seed layer. In addition, if grown on MgO, a sharp increase in the coercive field HC at a series of angles symmetric with respect to the easy axis is present. Scanning Kerr-microscope imaging is performed during the magnetization reversal process in order to reveal the type of magnetic domain formation taking place at these angles.

Ruiz-Calaforra, A.; Conca, A.; Graf, T.; Casper, F.; Leven, B.; Felser, C.; Hillebrands, B.

2013-11-01

162

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

NASA Astrophysics Data System (ADS)

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

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

2013-03-01

163

Three-Terminal Hanle Signals in Schottky Tunnel Junctions with Co2FeAl0.5Si0.5 Full-Heusler Alloy Electrodes Deposited at Various Temperatures  

NASA Astrophysics Data System (ADS)

We investigated the crystal structures, electrical transport properties, and three-terminal (3T) Hanle signals of Co2FeAl0.5Si0.5 (CFAS)/n-GaAs Schottky tunnel junctions fabricated with different deposition temperature of the CFAS (TCFAS). CFAS thin films were deposited on the n-GaAs at TCFAS ranging from room temperature to 300 °C, and 3T-Hanle signals were observed for all CFAS/n-GaAs junctions. Although the degree of structural ordering in the CFAS electrodes decreased and the rectifying characteristic disappeared as TCFAS decreased, the spin resistance area products (?RA) increased and the estimated spin relaxation time (?) decreased monotonically with decreasing TCFAS. Moreover, the bias voltage dependence of ?RA and ? became larger and smaller with decreasing TCFAS, respectively.

Saito, Tatsuya; Tezuka, Nobuki; Matsuura, Masashi; Sugimoto, Satoshi

2013-06-01

164

A First Result of Isothermal Annealing of an Fe-SiO Smoke  

NASA Astrophysics Data System (ADS)

Laboratory studies of thermally annealed smokes will advance the understanding of silicate dust evolution in O-rich protostellar environments. Previous condensation experiments on (Mg,Fe)-SiO vapors yielded amorphous solids of approximately olivine and pyroxene compositions. Condensation in refractory AlSiO, Fe-Al-SiO, and Fe-SiO vapors similarily produced amorphous solids but with cation proportions fixed at discrete values of existing Al, Fe-silicates. Thermal annealing of an MgSiO smoke at 1000 K for up to 30 hrs. showed increased crystallinity and coarsening of forsterite and tridymite grains prior to the formation of thermodynamically stable enstatite. In a related isothermal annealing study of an Fe-bearing MgSiO smoke, fayalite and ferrosilite formed at 1000 K from thier Mg-counterparts. After 167 hrs., this study documented partial evaporation of the smoke and recondensation of a metallic-Mg vapor. These studies showed that thermal metamorphism of smokes produced metastable high-temperature end members of the appropriate solid solution. This study represents the first data from a thermally annealed FeSiO condensate at 1000 K for 4 hrs. first studied in 1991.

Karner, J. M.; Rietmeijer, F. J. M.

1996-03-01

165

A thermodynamic model for di-trioctahedral chlorite from experimental and natural data in the system MgO-FeO-Al2O3-SiO2-H2O: applications to P- T sections and geothermometry  

NASA Astrophysics Data System (ADS)

We present a new thermodynamic activity-composition model for di-trioctahedral chlorite in the system FeO-MgO-Al2O3-SiO2-H2O that is based on the Holland-Powell internally consistent thermodynamic data set. The model is formulated in terms of four linearly independent end-members, which are amesite, clinochlore, daphnite and sudoite. These account for the most important crystal-chemical substitutions in chlorite, the Fe-Mg, Tschermak and di-trioctahedral substitution. The ideal part of end-member activities is modeled with a mixing-on-site formalism, and non-ideality is described by a macroscopic symmetric (regular) formalism. The symmetric interaction parameters were calibrated using a set of 271 published chlorite analyses for which robust independent temperature estimates are available. In addition, adjustment of the standard state thermodynamic properties of sudoite was required to accurately reproduce experimental brackets involving sudoite. This new model was tested by calculating representative P- T sections for metasediments at low temperatures (<400 °C), in particular sudoite and chlorite bearing metapelites from Crete. Comparison between the calculated mineral assemblages and field data shows that the new model is able to predict the coexistence of chlorite and sudoite at low metamorphic temperatures. The predicted lower limit of the chloritoid stability field is also in better agreement with petrological observations. For practical applications to metamorphic and hydrothermal environments, two new semi-empirical chlorite geothermometers named Chl(1) and Chl(2) were calibrated based on the chlorite + quartz + water equilibrium (2 clinochlore + 3 sudoite = 4 amesite + 4 H2O + 7 quartz). The Chl(1) thermometer requires knowledge of the (Fe3+/?Fe) ratio in chlorite and predicts correct temperatures for a range of redox conditions. The Chl(2) geothermometer which assumes that all iron in chlorite is ferrous has been applied to partially recrystallized detrital chlorite from the Zone houillère in the French Western Alps.

Lanari, Pierre; Wagner, Thomas; Vidal, Olivier

2014-02-01

166

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

NASA Astrophysics Data System (ADS)

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

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

2013-12-01

167

Effect of Al-Si-Al and Al-Si-Si-Al Pairs in the ZSM-5 Zeolite Framework on the 27 NMR Spectra. A Combined High-Resolution 27  

E-print Network

Effect of Al-Si-Al and Al-Si-Si-Al Pairs in the ZSM-5 Zeolite Framework on the 27 Al NMR Spectra. A Combined High-Resolution 27 Al NMR and DFT/MM Study Jiri´ Dedecek, Stepan Sklenak,*, Chengbin Li, Blanka of the presence of Al-O-Si-O-Al and Al-O-Si-O-Si-O-Al sequences in the ZSM-5 zeolite framework on the local

Sklenak, Stepan

168

Raman probe of the Si/silicide interface of Fe^+ ion implanted FeSi_2  

NASA Astrophysics Data System (ADS)

The formation of iron silicide by ion beam synthesis has attracted considerable recent attention. ?-FeSi2 is a semiconductor with a direct band gap of 0.87 eV and has recently been fabricated as an IR LED.(D. N. Leong, M. Harry, K. J. Reeson & K. P. Homewood, Nature) 387, 686 (1997). In order to help optimize the device we have used Raman spectroscopy to investigate the effect of ion dosage and annealing temperature on implanted silicon substrates. Here we report on implantation with 200 keV Fe^+ ions. In comparison to electron spectroscopy methods, Raman is advantageous for the non-destructive investigation of buried interfaces, since the information depth of visible light clearly exceeds that of electrons. We find that over a dosage range from 2 to 6x10^17 Fe^+ ions cm-2, the Raman peak at 247 cm-1 shifts to the red by about 2 cm-1. We correlate the results with the development of a continous silicide layer from the precipitates and concomitant developments at the Si/FeSi2 interface.

Birdwell, A. G.; Glosser, R.; Leong, D. N.; Homewood, K. P.

1998-03-01

169

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

SciTech Connect

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.

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

170

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

NASA Astrophysics Data System (ADS)

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].

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

2013-12-01

171

The mechanical properties of FeAl  

SciTech Connect

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

Baker, I. [Dartmouth Coll., Hanover, NH (United States); George, E.P. [Oak Ridge National Lab., TN (United States)

1996-12-31

172

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

NASA Astrophysics Data System (ADS)

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.

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

2014-09-01

173

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

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,

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

174

Fe-Mg Interdiffusion in (Mg,Fe)SiO3 Perovskite and Lower Mantle Reequilibration  

Microsoft Academic Search

Fe-Mg interdiffusion coefficients for (Mg,Fe)SiO3 perovskite have been measured at pressures of 22 to 26 gigapascals and temperatures between 1973 and 2273 kelvin. Perovskite Fe-Mg interdiffusion is as slow as Si self-diffusion and is orders of magnitude slower than Fe-Mg diffusion in other mantle minerals. Length scales over which chemical heterogeneities can homogenize, throughout the depth range of the lower

Christian Holzapfel; David C. Rubie; Daniel J. Frost; Falko Langenhorst

2005-01-01

175

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

NASA Astrophysics Data System (ADS)

Fe-Si-Mn-oxyhydroxide encrustations at the East Pacific Rise (EPR) near 13°N 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.

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

2014-12-01

176

Magnetization of Ni-Si, Co-Si, and Fe-Si layered systems  

SciTech Connect

Magnetization measurements have been performed, using a SQUID magnetometer, on multilayered X-Si films where X is Fe, Co, or Ni. The samples were produced by dc sputtering with the thickness of the Si layers fixed at a value between 30 and 70 A and the thickness of the X layers varying from 8 to 30 A. These nominal preparation thicknesses were verified by x-ray diffraction studies. We find that at 5 K the saturation magnetization decreases rapidly with decreasing thickness with a loss of ferromagnetism by layer thicknesses 8 and 14 A for Fe and Co, respectively. A Ni-Si sample with a Ni thickness of 30 A was not ferromagnetic. Comparison of measurements made with the applied field parallel and perpendicular to the layers indicates no magnetic aniostropy other than the expected shape anisotropy. Our data are compared with data by Wong and co-workers for Fe-V and data by Kazama and co-workers for amorphous Fe(C)-Si.

Foiles, C.L.; Slaughter, J.M.

1988-04-15

177

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

NASA Astrophysics Data System (ADS)

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

Dolejš, David; Wagner, Thomas

2008-01-01

178

Local Atomic and Electronic Structure of the Fe dopants in AlN:Fe Nanorods  

NASA Astrophysics Data System (ADS)

Fe-doped AlN nanorods were studied by means of x-ray absorption spectroscopy above the Fe K- and L2,3- edges. Theoretical simulations of the x-ray absorption spectra show that Fe atoms mainly substitute Al. A minor fraction of Fe interstitials or Fe-Al-N ternary alloy can be identified as well. Bader's AIM analysis predicts that neutral substitutional FeAl defect is in 2+ charge state, though Al in pure AlN is in 3+ charge state. Fe L2,3 absorption spectra and photoluminescence data indicate the coexistence of Fe2+/Fe3+ in AlN:Fe nanorods so different charge states of substitutional FeAl should co-exist.

Mazalova, V. L.; Zubavichus, Y. V.; Chub, D. S.; Guda, A. A.; Ji, X. H.; Lau, S. P.; Soldatov, A. V.

2013-04-01

179

Thermal cycling and stress relaxation response of SiAl and SiAl-SiO 2 layered thin films  

Microsoft Academic Search

The deformation of Si-Al and Si-Al-SiO2 multi-layered thin films in response to controlled sequences of constant- and variable-amplitude thermal cycling and isothermal exposures has been studied experimentally by recourse toin situ measurements of curvature changes which made use of the laser scanning technique. In an attempt to systematically isolate salient mechanistic features, a select set of companion experiments have also

Y.-L. Shen; S. Suresh

1995-01-01

180

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

NASA Astrophysics Data System (ADS)

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.

Bösch, Dominik; Pogatscher, Stefan; Hummel, Marc; Fragner, Werner; Uggowitzer, Peter J.; Göken, Mathias; Höppel, Heinz Werner

2015-03-01

181

4. Growth and Photoluminescence of Strained SiGe on Si 58 (a~___Al./'"  

E-print Network

4. Growth and Photoluminescence of Strained SiGe on Si 58 NP Si TOts .a. (a~___Al./'" ~ . :J,PL. #12;Growth and Photoluminescence of Strained SiGe on Si 594. .8= o. The electron confinementaswell asthe bandgapof strained #12;Growth and Photoluminescence of Strained SiGe on Si4. 60 I I I

182

Electron impact excitation of Si II and Fe XIV  

NASA Astrophysics Data System (ADS)

Energy levels, radiative rates, lifetimes, collision strengths and effective collision strengths are calculated for two important Al-like ions, namely Si II and Fe XIV. For Si II, the lowest 56 levels of the 3s23p, 3s3p2 3p3 3s23d, 3s3p3d, 3s24l and 3s25l configurations are included, whereas for Fe XIV additional 80 levels of 3p23d, 3s3d2 and 3p3d2 are considered, but not of 3s2 5l. For the determination of atomic structure GRASP has been adopted and radiative rates are calculated for all E1, E2, Ml and M2 transitions. Electron impact excitation collision strengths are calculated with the DARC code, over a wide energy range, and resonances are resolved in a fine energy mesh to determine effective collision strengths over a wide range of temperatures. Extensive comparisons are made for all atomic parameters with available theoretical and experimental data, and the accuracy of the present results is assessed. Energy levels are estimated to be accurate to ~1% and all other parameters to be better than 20%.

Aggarwal, K. M.; Keenan, F. P.

2015-01-01

183

Development of Fe-Mn-Al-X-C alloys  

NASA Technical Reports Server (NTRS)

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.

Schuon, S. R.

1982-01-01

184

Electronic and magnetic properties of AlFe 3 and AlFe 3N nitride  

Microsoft Academic Search

Self-consistent band structure calculations were performed for the metal aluminide AlFe3 (in the fcc structure) and the nitride AlFe3N (perovskite-like nitride) at several lattice parameters in order to obtain the electronic structure and magnetic properties of these compounds. In this study we have employed the full potential linear augmented plane wave (FPLAPW) and the linear muffin-tin orbital (LMTO-ASA) methods. Our

C. A. Kuhnen; A. V. dos Santos

2004-01-01

185

Sliding wear behavior of some Al-Si alloys: Role of shape and size of Si particles and test conditions  

Microsoft Academic Search

In this investigation, effects of the shape and size of silicon particles have been studied on the sliding wear response of\\u000a two Al-Si alloys, namely, LM13 and LM29. The LM13 alloy comprised 11.70 pct Si, 1.02 pct Cu, 1.50 pct Ni, 1.08 pct Mg, 0.70\\u000a pct Fe, 0.80 pct Mn, and remainder Al. The LM29 alloy contained 23.25 pct Si,

B. K. Prasad; K. Venkateswarlu; O. P. Modi; A. K. Jha; S. Das; R. Dasgupta; A. H. Yegneswaran

1998-01-01

186

X-Ray Videomicroscopy Studies of Eutectic Al-Si Solidification in Al-Si-Cu  

NASA Astrophysics Data System (ADS)

Al-Si eutectic growth has been studied in-situ for the first time using X-ray video microscopy during directional solidification (DS) in unmodified and Sr-modified Al-Si-Cu alloys. In the unmodified alloys, Si is found to grow predominantly with needle-like tip morphologies, leading a highly irregular progressing eutectic interface with subsequent nucleation and growth of Al from the Si surfaces. In the Sr-modified alloys, the eutectic reaction is strongly suppressed, occurring with low nucleation frequency at undercoolings in the range 10 K to 18 K. In order to transport Cu rejected at the eutectic front back into the melt, the modified eutectic colonies attain meso-scale interface perturbations that eventually evolve into equiaxed composite-structure cells. The eutectic front also attains short-range microscale interface perturbations consistent with the characteristics of a fibrous Si growth. Evidence was found in support of Si nucleation occurring on potent particles suspended in the melt. Yet, both with Sr-modified and unmodified alloys, Si precipitation alone was not sufficient to facilitate the eutectic reaction, which apparently required additional undercooling for Al to form at the Si-particle interfaces.

Mathiesen, R. H.; Arnberg, L.; Li, Y.; Meier, V.; Schaffer, P. L.; Snigireva, I.; Snigirev, A.; Dahle, A. K.

2011-01-01

187

Roll Casting of Al-25%Si  

SciTech Connect

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

Haga, Toshio [Osaka Institute of Technology, Omiya Asahiku Osaka city 535-8585 (Japan); Harada, Hideto [Graduate School of Osaka Institute of Technology, Omiya Asahiku Osaka city 535-8585 (Japan); Watari, Hisaki [Gunma University, Kiryu city, 376-8515 (Japan)

2011-05-04

188

Roll Casting of Al-25%Si  

NASA Astrophysics Data System (ADS)

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

Haga, Toshio; Harada, Hideto; Watari, Hisaki

2011-05-01

189

The erosion–corrosion behavior of some Fe 3Al-based alloys at high temperatures  

Microsoft Academic Search

The erosion–corrosion tests of some Fe3Al-based alloys were carried out in an elevated temperature erosion tester. In this facility, solid particle (SiO2) and corrosive gas (SO2) were fed into oil-fired gas by the feed subsystems, respectively. The test specimens were impacted in the temperature range of 600–800°C. Erosion–corrosion behavior of Fe3Al-based alloys was compared with that of Ni and Co

X. Q Yu; M Fan; Y. S Sun

2002-01-01

190

Magnetic and structural properties of Co2FeAl1-xSix thin films  

Microsoft Academic Search

We investigate different types of disorder which are predicted to influence the spin polarization by x-ray and electron diffraction (RHEED). We observe that the compound Co2FeAl grows in the B2 ordered structure. However, for Co2FeAl0.3Si0.7 the analysis revealed with increasing annealing temperature a crossover from B2 to L21 order. The magnetization of the samples is investigated by SQUID magnetometry and

E. Arbelo Jorge; M. Jourdan; M. Kallmayer; P. Klaer; H.-J. Elmers

2010-01-01

191

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

SciTech Connect

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

Turgut, Zafer; Attenweiler, Thomas; Huang, Meiqing; Horwath, John C.; Fingers, Richard T. [UES Inc., 4401 Dayton-Xenia Road, Dayton, Ohio 45432 (United States); AFRL, Wright-Patterson AFB, Ohio 45433-7251 (United States); UES Inc., 4401 Dayton-Xenia Road, Dayton, Ohio 45432 (United States); AFRL, Wright-Patterson AFB, Ohio 45433-7251 (United States)

2006-04-15

192

Disorder-induced reversal of spin polarization in the Heusler alloy Co{sub 2}FeSi  

SciTech Connect

We study the spin polarization in the conduction band of Co{sub 2}FeSi layers with a different degree of structural order. The injected spin polarization in Co{sub 2}FeSi/(Al,Ga)As spin light-emitting diodes as well as the planar Hall effect measured for the Co{sub 2}FeSi injectors exhibit a sign reversal between injectors crystallized in the ordered L2{sub 1} phase and the Fe-Si disordered B2 phase. These results are explained by a disorder-induced change in the spin polarization at the Fermi energy of Co{sub 2}FeSi. Support for the occurrence of such a striking change in the electronic band structure is obtained by first principles calculations.

Bruski, P.; Ramsteiner, M.; Brandt, O.; Friedland, K.-J.; Farshchi, R.; Herfort, J.; Riechert, H. [Paul-Drude Institut fuer Festkoerperelektronik, Hausvogteiplatz 5-7, D-10117 Berlin (Germany); Erwin, S. C. [Center for Computational Materials Science, Naval Research Laboratory, Washington, DC 20375 (United States)

2011-04-01

193

Roll Casting of Al25%Si  

Microsoft Academic Search

Strip casting of Al-25%Si strip was tried using an unequal diameter twin roll caster. The diameter of the lower roll (large roll) was 1000 mm and the diameter of the upper roll (small roll) was 250 mm. Roll material was mild steel. The sound strip could be cast at the speeds ranging from 8 m\\/min to 12 m\\/min. The strip

Toshio Haga; Hideto Harada; Hisaki Watari

2011-01-01

194

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

NASA Astrophysics Data System (ADS)

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

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

1995-09-01

195

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

NASA Astrophysics Data System (ADS)

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

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

2014-08-01

196

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)

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

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

2012-12-01

197

Hard boride coating on iron aluminide (FeAl)  

Microsoft Academic Search

The mechanical properties of borided iron aluminide (FeAl) were investigated. Boronizing was carried out in a solid medium consisting of Ekabor powders at 940 °C for 2, 4 and 8 h. The formation of FeB on the surface of FeAl was confirmed by XRD analysis. Metallographic studies revealed an almost saw-tooth-like and compact boride layer on the FeAl. The thickness of boride

Erdinç Ekmekçiler; Aytekin Polat; Metin Usta

2008-01-01

198

Günterblassite, (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)

A new mineral, günterblassite, 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, åkermanite, magnetite, perovskite, a lamprophyllite-group mineral, götzenite, chabazite-K, chabazite-Ca, phillipsite-K, and calcite. Günterblassite 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. Günterblassite is orthorhombic, space group Pnm21; the unit-cell dimensions are a = 6.528(1), b = 6.970(1), c = 37.216(5) Å, V = 1693.3(4) Å3, Z = 2. Günterblassite 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 Å ( 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 Günter Blass (born in 1943), a well-known amateur mineralogist and specialist in electron microprobe and X-ray diffraction. The type specimen of günterblassite is deposited in the collections of the Fersman Mineralogical Museum of the Russian Academy of Sciences, Moscow, Russia, with the registration number 4107/1.

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

2012-12-01

199

Mössbauer analysis of silicate Li2FeSiO4 and delithiated Li2-xFeSiO4 (x = 0.66) compounds  

NASA Astrophysics Data System (ADS)

Lithium iron silicate compounds of Li2FeSiO4 and partially delithiated Li2-xFeSiO4 (x = 0.66) were synthesized by vacuum-sealed solid-state and chemical delithiation reactions, and their magnetic properties were characterized based on Mössbauer analysis. Crystal structures of both Li2FeSiO4 and Li2-xFeSiO4 (x = 0.66) compounds are found to be ?s-type (P21/n) monoclinic structures with difference in the lattice parameters due to lithium delithiation. Mössbauer spectrum of Li2FeSiO4 below TN1 = 20 K exhibits eight Lorentzians of Fe2+ with antiferromagnetic ordering. However, the spectrum of intermediate Li2-xFeSiO4 (x = 0.66) compound shows the appearance of magnetically ordered Fe3+ sextet below TN2 = 28 K. The temperature-dependent isomer shift of Li2-xFeSiO4 indicates the coexistence of nonequivalent Fe2+/Fe3+ valence states with the partial oxidation of FeO4, enhanced by the lithium ion deficiency. Also, we have observed a considerable change in electric quadrupole interaction between Fe2+/Fe3+ ions in Li2-xFeSiO4, when compared to that of Li2FeSiO4, due to the different lattice and valence electron contributions, being originated from crystalline and valence transitions caused by the lithiation/delithiation process.

Lee, In Kyu; Kim, Sam Jin; Kouh, Taejoon; Kim, Chul Sung

2013-05-01

200

Thermodynamic evaluation of the C-Cr-Si, C-Ti-Si, and C-Fe-Si systems for rapid solution growth of SiC  

NASA Astrophysics Data System (ADS)

Solution growth of SiC is currently regarded as a promising process to produce high-quality SiC crystals. To date, Si-Cr, Si-Ti, and Fe-Si solvents have been used for rapid solution growth of SiC. However, optimization of the solvent system and composition is still needed to maximize the growth rate of high-quality SiC crystals. In this paper, to clarify the features of respective solvents from the viewpoint of the solubility of carbon, the C-Cr-Si, C-Ti-Si, and C-Fe-Si systems were evaluated by thermodynamic analysis. Phase relations in the respective ternary systems were investigated by the calculation of phase diagrams method. In addition, the solubility of carbon in Si-Cr, Si-Ti, and Fe-Si alloys at saturation with SiC was measured and its consistency with the estimated results was examined. Correlation of the experimental growth rate of SiC using Si-Cr, Si-Ti, and Fe-Si solvents was analyzed in terms of the supersaturation of carbon in each solution evaluated from the estimated temperature dependence of carbon solubility. Rate determining step for solution growth was presumed to be mass transfer in the liquid phase.

Narumi, Taka; Kawanishi, Sakiko; Yoshikawa, Takeshi; Kusunoki, Kazuhiko; Kamei, Kazuhito; Daikoku, Hironori; Sakamoto, Hidemitsu

2014-12-01

201

Fe-Mg interdiffusion in (Mg,Fe)SiO3 Perovskite and lower mantle reequilibration.  

PubMed

Fe-Mg interdiffusion coefficients for (Mg,Fe)SiO3 perovskite have been measured at pressures of 22 to 26 gigapascals and temperatures between 1973 and 2273 kelvin. Perovskite Fe-Mg interdiffusion is as slow as Si self-diffusion and is orders of magnitude slower than Fe-Mg diffusion in other mantle minerals. Length scales over which chemical heterogeneities can homogenize, throughout the depth range of the lower mantle, are limited to a few meters even on time scales equivalent to the age of Earth. Heterogeneities can therefore only equilibrate chemically when they are stretched and thinned by intense deformation. PMID:16051751

Holzapfel, Christian; Rubie, David C; Frost, Daniel J; Langenhorst, Falko

2005-09-01

202

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

PubMed

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

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

2010-03-01

203

Sound velocities of Fe and Fe-Si alloy in the Earth’s core  

PubMed Central

Compressional wave velocity-density (VP - ?) relations of candidate Fe alloys at relevant pressure-temperature conditions of the Earth’s core are critically needed to evaluate the composition, seismic signatures, and geodynamics of the planet’s remotest region. Specifically, comparison between seismic VP - ? profiles of the core and candidate Fe alloys provides first-order information on the amount and type of potential light elements—including H, C, O, Si, and/or S—needed to compensate the density deficit of the core. To address this issue, here we have surveyed and analyzed the literature results in conjunction with newly measured 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 8 wt?% Si at 6,000 K matches well with the Preliminary Reference Earth Model of the inner core. PMID:22689958

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

2012-01-01

204

Development of SiAlON materials  

NASA Technical Reports Server (NTRS)

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

Layden, G. K.

1977-01-01

205

Confirmation of a thin sheet toughening mechanism and anisotropic fracture in Al-Fe-X alloys  

NASA Astrophysics Data System (ADS)

The fracture toughness, K c, of two rapid-solidification powder-metallurgy Al-Fe-X alloys, Al-8Fe-1.4V-1. 7Si and Al-8Fe-2Mo-1V, has been measured as a function of specimen thickness. The former alloy has been found to exhibit crack-divider delamination and a K IC value independent of specimen thickness, while an opposite behavior is found in the latter alloy. The results confirm the presence of a thin sheet toughening mechanism in the Al-Fe-V-Si alloy. The orientation dependence of K IC and an unusual anisotropy fracture behavior observed in some, but not all, Al-Fe-X alloys have also been studied and their origins identified. It is shown that both thin sheet toughening and anisotropic fracture in Al-Fe-X alloys arise from interface delamination and void nucleation at oxide fragments aligned along prior powder-particle bound-aries (PPB’s).

Chan, Kwai S.

1989-11-01

206

Overview of the development of FeAl intermetallic alloys  

SciTech Connect

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

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

1995-09-01

207

Room-temperature magnetocurrent in antiferromagnetically coupled Fe\\/Si\\/Fe  

Microsoft Academic Search

Epitaxial Si-based ferromagnet\\/semiconductor structures demonstrate strong antiferromagnetic coupling (AFC) as well as resonant-type tunneling magnetoresistance, which vanishes at temperatures above T˜50K [1]. Magnetoresistance effects in Fe\\/Si\\/Fe close to room temperature (RT) were not established yet. By using the ballistic electron magnetomicroscopy (BEMM) techniques, with its nanometer-scaled locality [2] we observed for the first time a spin-dependent ballistic magnetotransport in AFC

Rashid Gareev; Maximilian Schmid; Johann Vancea; Christian Back; Reinert Schreiber; Daniel Buergler; Claus Schneider; Frank Stromberg; Heiko Wende

2011-01-01

208

Oxidation characteristics of artificially layered Fe\\/Al and Fe\\/Mg thin films  

Microsoft Academic Search

Investigations were carried out on the oxidation characteristics of artificially layered Fe\\/Al and Fe\\/Mg thin films using X-ray diffraction and Raman spectroscopy at 303, 473, 673 and 773 K in the laboratory atmosphere. X-ray diffractograms and Raman spectra reveal diffusion phenomena occurring in Fe\\/Al thin films. Individual oxides and a spinel-phase MgFe2O4, were the oxidation products in Fe\\/Mg multilayers while

S. Veena Kumari; V. K. Vaidyan; K. G. Sathyanarayana

1992-01-01

209

Moessbauer study in thin films of FeSi2 and FeSe systems  

NASA Technical Reports Server (NTRS)

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.

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

1978-01-01

210

Copper solubility in FeO?Fe 2 O 3 ?SiO 2 ?Al 2 O 3 slag and distribution equilibria of Pb, Bi, Sb and As between slag and metallic copper  

Microsoft Academic Search

The solubility of copper in silica-unsaturated fayalite slags containing an average of about 8 pct Al2O3 was measured by equilibrating the slag with metallic copper at 1200 and 1300°C under CO?CO2 atmospheres with oxygen potentials in the rangep\\u000a O\\u000a 2=10?6 to 10?11 at. The copper solubility, which was found to be dependent upon the oxygen potential, was expressed in terms

M. Nagamori; P. J. Mackey; P. Tarassoff

1975-01-01

211

Thermomagnetic properties of nanocrystalline Fe-Si alloys with high Si content  

NASA Astrophysics Data System (ADS)

We report the structural and temperature dependent magnetic properties of Fe100-xSix (0?x?40) alloy powders synthesized by a mechanical alloying process over a wide composition range. We have observed from X-ray diffraction (XRD) that non-equilibrium solid solution could be obtained up to 35 at% Si within 100 h of milling. As-milled powders have fine crystallites with size around 9 nm and dislocation density in the order of 1017 m-2. The variations of saturation magnetization and lattice constant with Si substitution show a good correlation between the structural and magnetic properties. Thermomagnetic studies reveal the presence of different magnetic phases in the milled Fe-Si powders with high Si content, which depends on both composition and milling time. Curie temperature of Fe-Si solid solution decreases gradually at a rate of 1.45 K/at% Si with increasing Si content. These results are in close agreement with the XRD data obtained for presently investigated nanocrystalline Fe-Si alloys.

Shyni, P. C.; Alagarsamy, Perumal

2014-09-01

212

Measurements of Al concentration in the primary Si crystals from the rheocast Al-15.5 wt% Si alloy  

SciTech Connect

The purpose of the present study is to investigate the distribution of Al in the primary crystal of Si in rheocast hypereutectic Al-Si alloy. Lattice parameters of primary Si crystals were determined using relative positions of the higher order Laue zone (HOLZ) lines recorded from the CBED patterns. The measured lattice parameters were then converted to the Al concentrations to compare with EPMA measurements for the accurate determination of solute concentration profile in the primary Si and to understand the role of solute redistribution on the microstructural change in hypereutectic Al-Si alloy during rheocasting.

Kim, G.H.; Lee, J.C.; Lee, H.I. [Korea Inst. of Science and Technology, Seoul (Korea, Republic of)] [Korea Inst. of Science and Technology, Seoul (Korea, Republic of); Lee, J.I. [Chungju National Univ. (Korea, Republic of). Dept. of Materials Science and Engineering] [Chungju National Univ. (Korea, Republic of). Dept. of Materials Science and Engineering

1997-10-01

213

Spray cast Al-Si base alloys for stiffness and fatigue strength requirements  

Microsoft Academic Search

SUMMARY Hypereutectic AlSiFe spray-cast alloys exhibit properties similar to those of metal-matrix composite (MMC's) : high Young's modulus and a low coefficient of thermal expansion. These physical properties can be adjusted by changing the Si content of the alloy. The refinement of the microstructure is produced by formation of a large amount of nuclei in the spray. Consolidation done by

M. COURBIERE; A. MOCELLIN

1993-01-01

214

Overview of the development of FeAl intermetallic alloys  

Microsoft Academic Search

B2-phase FeAl ordered intermetallic alloys based on an Fe-36 at.% Al composition are being developed to optimize a combination of properties that includes high-temperature strength, room-temperature ductility, and weldability. Microalloying with boron and proper processing are very important for FeAl properties optimization. These alloys also have the good to outstanding resistance to oxidation, sulfidation, and corrosion in molten salts or

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

1995-01-01

215

Modelling phase-assemblage diagrams for magnesian metapelites in the system K2O-FeO-MgO-Al2O3-SiO2-H2O: geodynamic consequences for the Monte Rosa nappe, Western Alps  

NASA Astrophysics Data System (ADS)

Magnesian metamorphic rocks with metapelitic mineral assemblage and composition are of great interest in metamorphic petrology for their ability to constrain P- T conditions in terranes where metamorphism is not easily visible. Phase-assemblage diagrams for natural and model magnesian metapelites in the system KFMASH are presented to document how phase relationships respond to water activity, bulk composition, pressure and temperature. The phase assemblages displayed on these phase diagrams are consistent with natural mineral assemblages occurring in magnesian metapelites. It is shown that the equilibrium assemblages at high pressure conditions are very sensitive to a(H2O). Specifically, the appearance of the characteristic HP assemblage chloritoid-talc-phengite-quartz (with excess H2O) in the magnesian metapelites of the Monte Rosa nappe (Western Alps) is due to the reduction of a(H2O). Furthermore, the mineral assemblages are determined by the whole-rock FeO/(FeO+MgO) ratio and effective Al content X A as well as P and T. The predicted mineral associations for the low- and high- X A model bulk compositions of magnesian metapelites at high pressure are not dependent on the X A variations as they show a similar sequence of mineral assemblages. Above 20 kbar, the prograde sequence of assemblages associated with phengite (with excess SiO2 and H2O) for low- and high- X A bulk compositions of magnesian metapelites is: carpholite-chlorite ? chlorite-chloritoid ? chloritoid-talc ? chloritoid-talc-kyanite ? talc-garnet-kyanite ? garnet-kyanite ± biotite. At low to medium P- T conditions, a low- X A stabilises the phengite-bearing assemblages associated with chlorite, chlorite + K-feldspar and chlorite + biotite while a high- X A results in the chlorite-phengite bearing assemblages associated with pyrophyllite, andalusite, kyanite and carpholite. A high- X A magnesian metapelite with nearly iron-free content stabilises the talc-kyanite-phengite assemblage at moderate to high P- T conditions. Taking into account the effective bulk composition and a(H2O) involved in the metamorphic history, the phase-assemblage diagrams presented here may be applied to all magnesian metapelites that have compositions within the system KFMASH and therefore may contribute to gaining insights into the metamorphic evolution of terranes. As an example, the magnesian metapelites of the Monte Rosa nappe have been investigated, and an exhumation path with P- T conditions for the western roof of the Monte Rosa nappe has been derived for the first time. The exhumation shows first a near-isothermal decompression from the Alpine eclogite peak conditions around 24 kbar and 505°C down to approximately 8 kbar and 475°C followed by a second decompression with concomitant cooling.

Le Bayon, R.; de Capitani, C.; Frey, M.

2006-04-01

216

Interlayer exchange coupling, crystalline and magnetic structure in Fe\\/CsCl–FeSi multilayers grown by molecular beam epitaxy  

Microsoft Academic Search

Crystalline and magnetic structure as well as the interlayer exchange coupling in MBE grown Fe\\/FeSi multilayers are investigated.\\u000a From conversion electron Mssbauer spectroscopy and ion beam channeling measurements the spacer FeSi material is found to\\u000a be stabilized in a crystalline metastable metallic FeSi phase with the CsCl structure. Strong non-oscillatory interlayer exchange\\u000a coupling is identified with magnetometry and synchrotron Mssbauer

J. Dekoster; S. Degroote; J. Meersschaut; R. Moons; A. Vantomme; L. Bottyán; L. Deák; E. Szilágyi; D. L. Nagy; A. Q. R. Baron; G. Langouche

1999-01-01

217

Large tunnel magnetoresistance at room temperature with a Co2FeAl full-Heusler alloy electrode  

NASA Astrophysics Data System (ADS)

Magnetic tunnel junctions (MTJs) with a Co2FeAl Heusler alloy electrode are fabricated by the deposition of the film using an ultrahigh vacuum sputtering system followed by photolithography and Ar ion etching. A tunnel magnetoresistance (TMR) of 47% at room temperature (RT) are obtained in a stack of Co2FeAl/Al-Ox/Co75Fe25 magnetic tunnel junction (MTJ) fabricated on a thermally oxidized Si substrate despite the A2 type atomic site disorder for Co2FeAl. There is no increase of TMR in MTJs with the B2 type Co2FeAl, which is prepared by the deposition on a heated substrate. X-ray photoelectron spectroscopy (XPS) depth profiles in Co2FeAl single layer films reveal that Al atoms in Co2FeAl are oxidized preferentially at the surfaces. On the other hand, at the interfaces in Co2FeAl/Al-Ox/Co75Fe25 MTJs, the ferromagnetic layers are hardly oxidized during plasma oxidation for a formation of Al oxide barriers.

Okamura, S.; Miyazaki, A.; Sugimoto, S.; Tezuka, N.; Inomata, K.

2005-06-01

218

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

NASA Astrophysics Data System (ADS)

?-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%.

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

2006-04-01

219

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

PubMed

We report the first comprehensive study of the high temperature form (?-phase) of iron disilicide. Measurements of the magnetic susceptibility, magnetization, heat capacity and resistivity were performed on well characterized single crystals. With a nominal iron d(6) configuration and a quasi-two-dimensional crystal structure that strongly resembles that of LiFeAs, ?-FeSi2 is a potential candidate for unconventional superconductivity. Akin to LiFeAs, ?-FeSi2 does not develop any magnetic order and we confirm its metallic state down to the lowest temperatures (T = 1.8 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. PMID:25837013

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

2015-05-01

220

Spark plasma sintering of SiAlON nanopowders  

NASA Astrophysics Data System (ADS)

The spark plasma sintering (SPS) method was used for sintering of different SiAlON nanopowders obtained by the method of plasma synthesis. Almost entirely dense samples were obtained at 1450-1500 °C (the range of ?-SiAlONs) and under 1600 °C (the range of ?-/?-SiAlONs). Results of research were compared wit that obtained by the method of pressureless sintering. Samples obtained at 1700 °C have similar characteristics, differing only with the time of processing: by the SPS method the sample was obtained during 23 minutes (100 °C/min 5 min.), but by the pressure-less sintering - during 290 minutes (10 °C/min 120 min.). Material obtained by the pressure-less sintering contains the phase of ?- SiAlON, but samples obtained by the SPS process contain almost only the phase of ?- SiAlON and the reason of this effect is a specific crystallization process of nanopowders: firstly at temperatures over 1400 - 1450 °C ?- SiAlON is formed and only after this the formation of ?- SiAlON occurs over 1500-1550 °C. In the case of SPS process a rapid increase of temperature (100 °C/min) and short dwelling time at high temperatures (5 min.) is the reason, why the transition of ?- SiAlON into ?- SiAlON does not occur.

Zalite, I.; Zilinska, N.; Steins, I.; Krastins, J.

2011-12-01

221

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

NASA Technical Reports Server (NTRS)

Several potential reinforcement materials were assessed for their chemical, coefficient of thermal expansion (CTE), and mechanical compatibility with the intermetallic matrices based on NiAl and FeAl. Among the ceramic reinforcement materials, Al2O3, TiC, and TiB2, appear to be the optimum choices for NiAl and FeAl matrices. However, the problem of CTE mismatch with the matrix needs to be solved for these three reinforcement materials. Beryllium-rich intermetallic compounds can be considered as potential reinforcement materials provided suitable reaction barrier coatings can be developed for these. Based on preliminary thermodynamic calculations, Sc2O3 and TiC appear to be suitable as reaction barrier coatings for the beryllides. Several reaction barrier coatings are also suggested for the currently available SiC fibers.

Misra, Ajay K.

1989-01-01

222

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

NASA Technical Reports Server (NTRS)

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

Dutta, S.

1982-01-01

223

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

SciTech Connect

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.

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

224

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

NASA Astrophysics Data System (ADS)

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

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

2000-09-01

225

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

E-print Network

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.

K. Aoki; M. Yoshida

1998-12-19

226

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

NASA Astrophysics Data System (ADS)

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.

Harada, Noriyuki; Takai, Hiroshi

2003-05-01

227

Influence of Electric Field on Magnetic Dynamic Properties of Multiferroic Co2FeAl0.5Si0.5/Pb(Mg1/3Nb2/3)0.7Ti0.3O3 Heterostructure  

NASA Astrophysics Data System (ADS)

Spin wave resonance with an applied electric field has been used to investigate the magnetoelectric (ME) effect in a Co2FeAl0.5Si0.5/Pb(Mg1/3Nb2/3)0.7Ti0.3O3 multiferroic heterostructure. The surface spin wave resonance peaks disappear along with the destruction of the initial spin orientation by the switch of ferroelectric domains. Meanwhile, the degree of symmetry for the uniform ferromagnetic resonance mode can also be modulated by the E field. These results are interpreted in terms of the voltage-driven spin reorientation.

Zhao, Yuelei; Wu, Yong; Jiang, Yong; Pan, Liqing; Sun, Young

2013-07-01

228

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

PubMed Central

Pyrosmalite-(Fe), ideally FeII 8Si6O15(OH,Cl)10 [refined composition in this study: Fe8Si6O15(OH0.814Cl0.186)10·0.45H2O, 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

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

2012-01-01

229

Pyrosmalite-(Fe), Fe(8)Si(6)O(15)(OH,Cl)(10).  

PubMed

Pyrosmalite-(Fe), ideally Fe(II) (8)Si(6)O(15)(OH,Cl)(10) [refined composition in this study: Fe(8)Si(6)O(15)(OH(0.814)Cl(0.186))(10)·0.45H(2)O, octa-iron(II) hexa-silicate deca-(chloride/hydroxide) 0.45-hydrate], is a phyllosilicate mineral and a member of the pyrosmalite series (Fe,Mn)(8)Si(6)O(15)(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 FeO(6)-octa-hedra alternating with sheets of SiO(4) tetra-hedra along [001]. These sheets consist of 12-, six- and four-membered rings of tetra-hedra 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

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

2012-01-01

230

A New Type Hysteresis Loop in SiN/GdFeCoSi/SiN Sandwich Structure  

NASA Astrophysics Data System (ADS)

A new type of inverted hysteresis loop was observed in an amorphous SiN/GdFeCoSi/SiN film, in which a magnetic GdFeCoSi layer with a thickness of 40 nm was sandwiched by SiN capping and buffer layers 5 nm thick. An inverted hysteresis loop with negative remanence appeared, when an applied field was perpendicular to the film plane, with remanance ratio of 0.4 and HC=120 Oe. An FMR experiment study showed that two magnetic phases existed in the system. A major magnetic phase had an easy-plane anisotropy and the other minor magnetic phase had an easy-normal anisotropy. By assuming an antiferromagnetic exchange coupling between them, the inverted loops can be explained.

Zhao, Yanling; Wang, Shiqi; Shono, Keiji; Yu, Xiangyou; Lu, Mu; Zhai, Hongru

231

Elastic Properties of Fe, Na, Ca - Bearing Majoritic Garnet (Mg1.875Ca0.75Fe0.375Na0.5Al0.5Si4O12) to 9.5 GPa and 1000 K  

NASA Astrophysics Data System (ADS)

Extensive knowledge of the elastic properties of majoritic garnet with compositions pertinent to the transition zone of the mantle is necessary for interpreting the region's seismic behavior and therefore critical to understanding the mantle's constituents. A polycrystalline garnet sample of a suitable composition (Mg1.875Ca0.75Fe0.375Na0.5Al0.5Si4O12) was fabricated using hot-pressing techniques, and subsequently characterized by density measurements, microprobe analysis, and synchrotron X-ray diffraction. The compressional and shear wave velocities were measured at simultaneous high pressures (to 9.5 GPa) and high temperatures (to 1000 K) using ultrasonic interferometry in conjunction with in-situ synchrotron X-ray diffraction and imaging techniques. These data were fit using both linear and Eulerian finite-strain equations to obtain the adiabatic bulk modulus, shear modulus, and their pressure and temperature derivatives. The data were also fit to a modified Birch-Murnaghan equation of state to obtain the isothermal bulk modulus, its pressure and temperature derivatives, and associated variables of interest. We will present these results, compare them to those for garnets with other compositions, and discuss their implications for deep-earth modeling.

Triplett, R.; Gwanmesia, G. D.; Wang, L.

2013-05-01

232

Structural evolution in mechanically alloyed Al-Fe powders  

SciTech Connect

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

Mukhopadhyay, D.K.; Suryanarayana, C.; Froes, F.H. [Univ. of Idaho, Moscow, ID (United States)

1995-08-01

233

Microstructural and mechanical characterization of Al–Zn–Si nanocomposites  

SciTech Connect

In this paper the addition of silicon nanoparticles into Al–Zn 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 Al–Zn 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 (TEM–EDXS) and the mechanical properties were measured by nanoindentation and micro-hardness tests. The results showed that during mechanical milling Si is added to the Al–Zn 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 Al–Zn matrix, which adversely affects the mechanical properties. Thus, it is important to tune the milling time and concentration of Si added to the Al–Zn 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 Al–Zn liquid alloy is reported. • Good dispersion and homogeneity of Si in the Al–Zn matrix are obtained. • Increasing Si content above 1.2 wt.% decreases the mechanical properties of Al–Zn alloy. • The saturation point of Si in 1.2 wt.% differs from Galvalume® composition. • The Al–Zn–1.5Si alloy with addition of nanocomposite shows 5.7 GPa of hardness.

García-Villarreal, S. [Centro de Investigación en Materiales Avanzados S.C. Monterrey, 66600, Alianza Nte. 202, Parque PIIT, Apodaca, N.L. (Mexico); Chávez-Valdez, A. [Katcon Institute for Innovation and Technology KIIT, 66629, Alianza Sur 200, Apodaca, N.L. (Mexico); Moreno, K.J. [Instituto Tecnológico de Celaya, Apartado Postal 57, 38010 Celaya, Guanajuato (Mexico); Leyva, C.; Aguilar-Martínez, J.A. [Centro de Investigación en Materiales Avanzados S.C. Monterrey, 66600, Alianza Nte. 202, Parque PIIT, Apodaca, N.L. (Mexico); Hurtado, A. [Centro de Investigación 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 Investigación en Materiales Avanzados S.C. Monterrey, 66600, Alianza Nte. 202, Parque PIIT, Apodaca, N.L. (Mexico)

2013-09-15

234

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

NASA Astrophysics Data System (ADS)

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.

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

2010-03-01

235

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

NASA Astrophysics Data System (ADS)

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

Duman, Songül; Ozcelik, Fikriye Seyma; Gürbulak, Bekir; Gülnahar, Murat; Turut, Abdulmecit

2015-01-01

236

Thermal equation of state of Al and Fe-bearing phase D  

Microsoft Academic Search

Pressure-volume-temperature relations have been measured to 20.6 GPa and 1273 K for Fe- and Al-bearing phase D (Mg0.99Fe0.12Al0.09Si1.75H2.51O6) using synchrotron X-ray diffraction with SPEED-MkII multianvil press at SPring-8 facility. The analysis of room temperature data fitted to a third-order Birch-Murnaghan equation of state (EOS) yields V0 = 85.32 ± 0.02 Å3; K0 = 141.5 ± 3 GPa and K' =

Konstantin D. Litasov; Eiji Ohtani; Yu Nishihara; Akio Suzuki; Kenichi Funakoshi

2008-01-01

237

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

PubMed Central

The three-dimensional (3-D) architecture of rigid multiphase networks present in AlSi10Cu5Ni1 and AlSi10Cu5Ni2 piston alloys in as-cast condition and after 4 h spheroidization treatment is characterized by synchrotron tomography in terms of the volume fraction of rigid phases, interconnectivity, contiguity and morphology. The architecture of both alloys consists of ?-Al matrix and a rigid long-range 3-D network of Al7Cu4Ni, Al4Cu2Mg8Si7, Al2Cu, Al15Si2(FeMn)3 and AlSiFeNiCu aluminides and Si. The investigated architectural parameters of both alloys studied are correlated with room-temperature and high-temperature (300 °C) strengths as a function of solution treatment time. The AlSi10Cu5Ni1 and AlSi10Cu5Ni2 alloys behave like metal matrix composites with 16 and 20 vol.% 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 4 h 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

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

2011-01-01

238

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

NASA Astrophysics Data System (ADS)

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

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

2015-01-01

239

Temperature dependence of the Si, Al distribution in ultramarines  

NASA Astrophysics Data System (ADS)

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.

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

1992-12-01

240

Electronic structure and transport properties of Fe–Al alloys  

Microsoft Academic Search

Electronic structure of iron-aluminides (Fe1?xAlx) has been calculated for a range of aluminum concentration (0?x?0.5) by using first principles density functional theory to explain the variation of electrical resistivity with increasing Al content. The Fe–Al intermetallics are modeled by a cluster of 15 atoms confined to their bulk geometry. The location of Al atoms as a function of concentration, x

B. V. Reddy; P. Jena; S. C. Deevi

2000-01-01

241

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

NASA Astrophysics Data System (ADS)

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 .

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

242

Electronic structure of substoichiometric Fe-Al intermetallics  

NASA Astrophysics Data System (ADS)

The formation energy, nature of bonding, electron density of states, and magnetic properties of Fe1-xAlx intermetallics have been calculated in the concentration range 0<=x<=0.5 using the tight-binding linearized muffin-tin orbital method and a super unit cell containing 16 atoms. The various concentration ranges are simulated by successively replacing Fe atoms by Al atoms and studying the electronic structure within the density-functional theory and generalized gradient approximation for exchange and correlation. The stability of the Fe1-xAlx alloys increases monotonically with increasing Al concentration, while the magnetic moment variation reveals exactly the opposite behavior. Stoichiometric FeAl is found to exhibit two nearly degenerate magnetic structures: a nonmagnetic state with zero moment on Fe and a ferromagnetic state with a moment of 0.75?B per Fe atom. Fe3Al, on the other hand, is ferromagnetic with a calculated moment of 2.45?B at the Fe-I site and 1.95?B at the Fe-II site. The coupling between Fe and Al atoms is antiferromagnetic, although the moment at the Al site is much smaller (-0.17?B) than that at the Fe sites. The bonding between Fe and Al atoms is primarily due to the hybridization between the 3d electrons of the former and the sp electrons of the latter. The bonding has a strong local character in that the coupling is between the nearest neighbor atoms. This is further verified by a calculation using small clusters as models of the bulk structure. The density of states at the Fermi energy is dominated by contributions from the Fe 3d state although its variation with Al is modulated by subtle interaction with Al 3p electrons. The total densities of states at the Fermi energy of Fe1-xAlx alloys show the same variation as the electrical resistivity, suggesting that the increase and then decrease in resistivity with Al concentration with a peak at 33% Al is purely of electronic origin.

Das, G. P.; Rao, B. K.; Jena, P.; Deevi, S. C.

2002-11-01

243

Cast AlSi9Cu4 alloy with hybride strenghtened by FexAly-Al2O3 composite powder  

NASA Astrophysics Data System (ADS)

The main objective of the study was to develop a technology of dispersion strenghtened hypoeutectic Al-Si alloy. The article presented the materials and technology conception for producing aluminium matrix composite AlSi9Cu4Fe alloy with hybride reinforcement of AlxFey intermetallic and aluminium oxide powders. Composite powder obtained in mechanical agllomerisation mixture of elemental powders. Changes in the structure were confirmed by TA and ATD thermal analyses plotting the solidification curves, which showed a decrease in temperature Tliq compared to the unmodified alloy and an exothermic effect originating from the crystallisation of eutectics with alloying elements. The examinations carried out by SEM and BSE as well as the determination of local chemical composition by EDX technique have characterised the structure of the alloy as containing some binary Al-Si-Al-Cu and Al-Fe eutectics and multicomponent eutectics.

Pi?tkowski, J.; Formanek, B.

2011-05-01

244

Strength anomaly in B2 FeAl single crystals  

SciTech Connect

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.

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

1994-12-31

245

MBE growth of ?-FeSi 2 epitaxial film on hydrogen terminated Si (1 1 1) substrate  

NASA Astrophysics Data System (ADS)

?-FeSi 2 single crystal epitaxial films were successfully grown on hydrogen terminated Si (1 1 1) substrates by using solid source molecular beam epitaxy (SS-MBE). The ?-FeSi 2 epitaxial film with thickness of 180 nm was grown without template-layer or post-growth annealing. By analyzing X-ray diffraction (XRD) patterns and the corresponding scanning electron microscopy (SEM) images, the optimal growth temperature was established to be 580 °C. To study the effect of Fe/Si ratio on the film quality, a series of epilayers were grown at 580 °C with various Fe/Si ratios from 2 to 0.4. The stoichiometric Fe/Si flux ratio of 0.5 was confirmed to be an essential condition to grow single crystalline ?-FeSi 2 epitaxial films at 580 °C, while the metallic ?-FeSi phase grew predominantly at 480 °C. The observations of transmission electron microscope (TEM) and reflective high-energy electron diffraction (RHEED) verified the epitaxial growth of ?-FeSi 2 films on Si (1 1 1).

Ji, S. Y.; Lalev, G. M.; Wang, J. F.; Lim, J. W.; Yoo, J. H.; Shindo, D.; Isshiki, M.

2005-11-01

246

New quarternary half metallic material CoFeMnSi  

Microsoft Academic Search

A good field to develop new materials with half metallicity is the quaternary Heusler alloys. The preferred route is to combine the compounds that have been already grown in Heusler structure. As a typical example, the quaternary LiMgPdSb-type CoFeMnSi have been investigated in detail. For the quaternary LiMgPdSb-type compounds, three nonequivalent structures exist. From the calculated density of state (DOS)

Xuefang Dai; Guodong Liu; Gerhard H. Fecher; Claudia Felser; Yangxian Li; Heyan Liu

2009-01-01

247

Oxidation behavior of FeAl+Hf,Zr,B  

NASA Technical Reports Server (NTRS)

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

Smialek, James L.; Doychak, Joseph

1988-01-01

248

Oxidation behavior of FeAl+Hf,Zr,B  

NASA Technical Reports Server (NTRS)

The oxidation behavior of Fe-40Al-1Hf, Fe-40Al-1Hf-0.4B, and Fe-40Al-0.1Zr-0.4B (at. percent) alloys was characterized after 900, 1000, and 100 C exposures. Isothermal tests revealed parabolic kinetics after a period of transitional theta-alumina scale growth. The parabolic growth rates for the subsequent alpha-alumina scales were about five times higher than those for NiAl+0.1Zr alloys. The isothermally grown scales showed a propensity toward massive scale spallation due to both extensive rumpling from growth stresses and to an inner layer of Hf02. Cyclic oxidation for 200 1-hr cycles produced little degradation at 900 or 1000 C, but caused significant spallation at 1100 C in the form of small segments of the outer scale. The major difference in the cyclic oxidation of the three FeAl alloys was increased initial spallation for FeAl+Zr,B. Although these FeAl alloys showed many similarities to NiAl alloys, they were generally less oxidation resistant. It is believed that this resulted from nonoptimal levels of dopants and larger thermal expansion mismatch stresses.

Smialek, James L.; Doychak, Joseph; Gaydosh, Darrell J.

1989-01-01

249

Thermal stability of Al-Cu-Fe icosahedral alloys  

NASA Astrophysics Data System (ADS)

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 idéalement quasipériodique 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 quantités de cuivre par de l'aluminium, conduisent à des alliages icosaédriques qui subissent vers 650 ^{circ}C des transformations structurales dont la nature n'est pas clairement identifiée: 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 localisés à des positions clairement en dehors de celles correspondant à la symétrie icosaédrique idéale. De faibles écarts à ce domaine de compositions conduisent à des diagrammes de rayons X où les pics de Bragg sont épaulés quel que soit le traitement thermique ; l'ordre icosaédrique 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}).

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

1991-12-01

250

Epoxy-bonded La-Fe-Co-Si magnetocaloric plates  

NASA Astrophysics Data System (ADS)

We report the processing, analysis and testing of magnetocaloric composite materials consisting of La-Fe-Co-Si particles of various size fractions and a polymer matrix. All of the composites have working temperatures close to room temperature. The composites were pressed into thin plates, a geometry favorable for testing the composites in an active magnetic regenerator (AMR). In order to investigate the influence of particle size and binder type (epoxy), eight different epoxy-bonded La-Fe-Co-Si plates were made and analyzed. We found that the higher filling factor that can be achieved by using a mixture of several particle size fractions has beneficial influence on the thermal conductivity. Tests in the AMR revealed that a maximum temperature span of approximately ?T=10 K under magnetic field change of ?0H=1.15 T can be obtained at no cooling load conditions. The stability of the measured ?T values and the mechanical integrity of sample after cyclic application of a magnetic field have been monitored for 90,000 cycles and showed no significant changes. We therefore conclude that epoxy-bonded La-Fe-Co-Si magnetocaloric composites have good magnetocaloric properties at low material-processing costs and hence represent a competitive way to produce magnetocaloric materials to be used in AMR.

Pulko, Barbara; Tušek, Jaka; Moore, James D.; Weise, Bruno; Skokov, Konstantin; Mityashkin, Oleg; Kitanovski, Andrej; Favero, Chiara; Fajfar, Peter; Gutfleisch, Oliver; Waske, Anja; Poredoš, Alojz

2015-02-01

251

Charge storage in ?-FeSi2 nanoparticles  

NASA Astrophysics Data System (ADS)

We report on the observation of a surprisingly high specific capacitance of ?-FeSi2 nanoparticle layers. Lateral, interdigitated capacitor structures were fabricated on thermally grown silicon dioxide and covered with ?-FeSi2 particles by drop or spin casting. The ?-FeSi2-nanoparticles, with crystallite sizes in the range of 10-30 nm, were fabricated by gas phase synthesis in a hot wall reactor. Compared to the bare electrodes, the nanoparticle-coated samples exhibit a 3-4 orders of magnitude increased capacitance. Time-resolved current voltage measurements show that for short times (seconds to minutes), the material is capable of storing up to 1 As/g at voltages of around 1 V. The devices are robust and exhibit long-term stability under ambient conditions. The specific capacitance is highest for a saturated relative humidity, while for a relative humidity below 40% the capacitance is almost indistinguishable from a nanoparticle-free reference sample. The devices work without the need of a fluid phase, the charge storing material is abundant and cost effective, and the sample design is easy to fabricate.

Theis, Jens; Bywalez, Robert; Küpper, Sebastian; Lorke, Axel; Wiggers, Hartmut

2015-02-01

252

Magnetic properties of Fe and Fe-Si alloys with {100}<0vw> texture  

NASA Astrophysics Data System (ADS)

When iron and its alloy sheets with clean metal surfaces undergo the ? to ? phase transformation, they develop strong {100}<0vw> texture with grain size being larger than the sheet thickness. For example, when Fe or Fe-1%Si sheets were subjected to the ? to ? phase transformation in a reducing gas atmosphere (hydrogen gas having the dew point below -50 °C), strong {100}<0vw> texture developed. Magnetic properties of Fe and Fe-Si alloys show that, by developing the {100}<0vw> texture, the core loss can be reduced by more than 25% and the permeability can be increased by 2-5 times. With 0.35 mm-thick Fe-1%Si with the {100}<0vw> texture, the magnetic properties are W15/50 (core loss at 1.5 T, 50 Hz) = 2.7 W/kg and B50 (magnetic flux density at 5000 A/m) = 1.80 T. The improvement of permeability together with reducing iron loss by texture control will make a significant contribution to improving power density as well as reducing copper losses in induction motors.

Kyung Sung, Jin; Mo Koo, Yang

2013-05-01

253

Si segregation at Fe grain boundaries analyzed by ab initio local energy and local stress.  

PubMed

Using density-functional theory calculations combined with recent local-energy and local-stress schemes, we studied the effects of Si segregation on the structural, mechanical and magnetic properties of the ?3(1 1 1) and ?11(3 3 2) Fe GBs formed by rotation around the [1 1 0] axis. The segregation mechanism was analyzed by the local-energy decomposition of the segregation energy, where the segregation energy is expressed as a sum of the following four terms: the local-energy change of Si atoms from the isolated state in bulk Fe to the GB segregated state, the stabilization of replaced Fe atoms from the GB to the bulk, the local-energy change of neighboring Fe atoms from the pure GB to the segregated GB and the local-energy change of neighboring Fe atoms from the system of an isolated Si atom in the bulk Fe to the pure bulk Fe. The segregation energy and value of each term greatly depends on the segregation site and Si concentration. The segregation at interface Fe sites with higher local energies in the original GB configurations naturally leads to higher segregation-energy gains, while interface sites with lower local energies can lead to larger energy gains if stronger Si-Fe interactions occur locally in the final segregated configurations. The high Si concentration reduces the segregation-energy gain per Si atom due to the local-energy increases of Si atoms neighboring to each other or through the reduction in the number of stabilized Fe atoms per Si atom as observed in a Si dimer in bulk Fe. In the Si-segregated GBs, Si-Fe bonds enhance local Young's moduli and tend to suppress the interface weakening, while the GB adhesion is slightly reduced. And Fe atoms contacting Si atoms have reduced magnetic moments, due to Si-Fe sp-d hybridization interactions. PMID:25077891

Bhattacharya, Somesh Kr; Kohyama, Masanori; Tanaka, Shingo; Shiihara, Yoshinori

2014-09-01

254

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

NASA Astrophysics Data System (ADS)

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

Ahmad, Zaki; Aleem, B. J. Abdul

2009-03-01

255

Electronic structure and bonding of β-SiAlON  

Microsoft Academic Search

The α- and β-SiAlONs are ceramic solid solutions with charge-neutral substitutions in α- and β-SiâNâ. They have high potential for applications as structural materials. The authors have calculated the electronic structure and bonding of β-Si{sub 6-z}Al{sub z}O{sub z}N{sub 8-z} decreases as z increases, in general agreement with experimental trends. Simultaneous substitution of the (Si,N) pair by (Al,O) results in impurity-like

W. Y. Ching; M. Z. Huang; S. D. Mo

2000-01-01

256

Potentiodynamic Polarization Aspects of the As-cast and Sprayed Al-Si, Al-Sn and Al-Sn-Si Alloys in a Sodium Chloride Solution  

NASA Astrophysics Data System (ADS)

The present study compares the corrosion behavior of Al-Sn, Al-Si and Al-Sn-Si alloys processed by spray forming with that of the conventional chill cast ones in aqueous 0.1 N NaCl solution. Spray forming resulted in finer microstructural features with uniform distribution of second-phase particles. The spray formed Al-Si samples showed improved corrosion resistance as compared to the chill cast ones. The Sn containing alloys showed inferior corrosion resistance in the neutral electrolyte. The addition of 12.5 wt.% Si to Al-Sn alloys improves the corrosion resistance.

Anil, M.; Balaji, S.; Upadhyaya, A.; Ghosh, M. K.; Ojha, S. N.

2010-12-01

257

Texture development in SiC-seeded AlN  

SciTech Connect

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.

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

258

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

SciTech Connect

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

Aparicio, Claudia, E-mail: claudia.aparicio@upol.cz; Filip, Jan, E-mail: claudia.aparicio@upol.cz; Mashlan, Miroslav, E-mail: claudia.aparicio@upol.cz; Zboril, Radek, E-mail: claudia.aparicio@upol.cz [Regional Centre of Advanced Technologies and Materials, Departments of Experimental Physics and Physical Chemistry, Faculty of Science, Palacky University, 17. listopadu 1192/12, 77146 Olomouc (Czech Republic)

2014-10-27

259

Ground state of stoichiometric B2 FeAl  

NASA Astrophysics Data System (ADS)

The ground state of stoichiometric B2 FeAl has been controversial for decades in the literature, and the present first principles calculation is dedicated to have a systematic study of B2 FeAl with nonmagnetic (NM), ferromagnetic (FM), antiferromagnetic (AFM), and paramagnetic (PM) states. It is found that the energetic, mechanical, and electronic properties of FeAl are not sufficient to determine the ground state, and that it is lattice dynamics which fundamentally decides the ground state of NM for FeAl. In addition, it is also revealed that the electron-phonon interaction induces the negative phonon branches of AFM and PM states, and brings about much deeper phonon dips of FM than those of NM and experiments.

Ren, Q. Q.; Gong, H. R.

2013-09-01

260

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

NASA Astrophysics Data System (ADS)

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

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

2015-03-01

261

The cavitation erosion of Fe?Mn?Al alloys  

Microsoft Academic Search

The cavitation erosion of Fe?Mn?Al alloys and 304 stainless steel in both distilled water and 3.5% NaCl solution was studied by an ultrasonic vibration system. In distilled water, the cavitation erosion resistance of solution heat treated Fe?Mn?Al alloys are superior to that of 304 stainless steel. The solution heat treated alloys with higher hardness shows better cavitation resistance. But, cavitation

S. C. Chang; W. H. Weng; H. C. Chen; S. J. Lin; P. C. K. Chung

1995-01-01

262

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

NASA Technical Reports Server (NTRS)

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

Bida, Thomas A.; Killen, Rosemary M.

2011-01-01

263

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

NASA Astrophysics Data System (ADS)

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

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

2013-12-01

264

Current-induced magnetization switching at low current densities in current-perpendicular-to-plane structural Fe3Si/FeSi2 artificial lattices  

NASA Astrophysics Data System (ADS)

Current-perpendicular-to-plane (CPP) junctions of Fe3Si/FeSi2 were fabricated from Fe3Si/FeSi2 artificial lattice films, which were prepared by facing-target direct-current sputtering, by employing a focused ion beam (FIB) technique. CPP structurization was confirmed by scanning electron microscopy. The CPP junctions, in which antiferromagnetic interlayer coupling is induced between the Fe3Si layers, exhibited a clear hysteresis loop in the electrical resistance for current injection, which is probably due to current-induced magnetization switching. The critical current density for it is approximately 3.3 × 101 A/cm2, which is at least four orders smaller than the values that have ever been reported.

Sakai, Ken-ichiro; Noda, Y?ta; Daio, Takeshi; Tsumagari, Daiki; Tominaga, Aki; Takeda, Kaoru; Yoshitake, Tsuyoshi

2014-02-01

265

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

E-print Network

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

Schmidt, Volker

266

High-energy Si implantation into InP:Fe  

NASA Astrophysics Data System (ADS)

The statistical moments of the Si-depth distribution are determined after implanting Si into InP:Fe, and the values are compared to calculations from TRIM-89. The energy ranges and implantation doses are given, and secondary-ion mass spectroscopy (SIMS) is used to calculate the experimental values of range, longitudinal straggle, skewness, and kurtosis. The implantations are repeated at energies ranging from 0.5 to 10 MeV, and the Si implants are activated with rapid-thermal-annealing (RTA) cycles and furnace annealing. At 2-10 MeV almost 100 percent of the 3 x 10 to the 14th/sq cm Si implants are activated, and low activation results for high-dose Si implants are discussed in terms of transport equation calculations. The range and straggle values are found to be lower in the experimental study, and the implant distribution profile tends to be skewed toward the surface and more sharply peaked than the corresponding Gaussian distribution.

Nadella, Ravi K.; Rao, Mulpuri V.; Simons, David S.; Chi, Peter H.; Fatemi, M.; Dietrich, H. B.

1991-08-01

267

SiAlON ceramic compositions and methods of fabrication  

Microsoft Academic Search

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

M. H. OBrien; B. H. Park

1994-01-01

268

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

E-print Network

. To study the variety of magnetic properties, we use NMR, magnetic susceptibility, specific heat and other methods in this work. The microscopic electronic and magnetic properties of the Al-rich Fe-Al system and Al20V2Eu have been studied via 27Al NMR...

Chi, Ji

2009-05-15

269

SiAlON ceramic compositions and methods of fabrication  

DOEpatents

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.

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

1994-05-31

270

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

NASA Technical Reports Server (NTRS)

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.

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

1996-01-01

271

The effect of Fe-coverage on the structure, morphology and magnetic properties of ?-FeSi2 nanoislands.  

PubMed

Self-assembled ?-FeSi(2) nanoislands were formed using solid-phase epitaxy of low (~1.2 ML) and high (~21 ML) Fe coverages onto vicinal Si(111) surfaces followed by thermal annealing. At a resulting low Fe-covered Si(111) surface, we observed in situ, by real-time scanning tunneling microscopy and surface electron diffraction, the entire sequence of Fe-silicide formation and transformation from the initially two-dimensional (2 × 2)-reconstructed layer at 300?°C into (2 × 2)-reconstructed nanoislands decorating the vicinal step-bunch edges in a self-ordered fashion at higher temperatures. In contrast, the silicide nanoislands at a high Fe-covered surface were noticeably larger, more three-dimensional, and randomly distributed all over the surface. Ex situ x-ray photoelectron spectroscopy and high-resolution transmission electron microscopy indicated the formation of an ?-FeSi(2) island phase, in an ?-FeSi(2){112} // Si{111} orientation. Superconducting quantum interference device magnetometry showed considerable superparamagnetism, with ~1.9 ?(B)/Fe atom at 4 K for the low Fe-coverage, indicating stronger ferromagnetic coupling of individual magnetic moments, as compared to high Fe-coverage, where the calculated moments were only ~0.8 ?(B)/Fe atom. Such anomalous magnetic behavior, particularly for the low Fe-coverage case, is radically different from the non-magnetic bulk ?-FeSi(2) phase, and may open new pathways to high-density magnetic memory storage devices. PMID:23154191

Tripathi, J K; Garbrecht, M; Kaplan, W D; Markovich, G; Goldfarb, I

2012-12-14

272

GaN on Si Substrate with AlGaN\\/AlN Intermediate Layer  

Microsoft Academic Search

A single crystal GaN thin film was successfully grown on a Si (111) substrate by means of atmospheric pressure metalorganic chemical vapor deposition. Though there is a large difference in thermal expansion coefficients between GaN and Si, an intermediate layer consisting of AlN and AlGaN improved the quality of GaN on Si and reduced meltback etching during growth. Pits and

Hiroyasu Ishikawa; Guang-Yuan Zhao; Naoyuki Nakada; Takashi Egawa; Takashi Jimbo; Masayoshi Umeno

1999-01-01

273

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

PubMed

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)+magnesiowüstite (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

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

2011-04-12

274

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

PubMed Central

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 (Fa34-41) 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)SiO3 perovskite (Pv)+magnesiowüstite (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)SiO3 Pv and Mw have 50–100 nm in diameter, and lamellar (Mg,Fe)SiO3 Pv and Mw have approximately 20 and approximately 10 nm in thickness, respectively. Partitioning coefficient, KPv/Mw = [FeO/MgO]/[FeO/MgO]Mw, between (Mg,Fe)SiO3 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

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

2011-01-01

275

Fabrication of magnetic nanosized ?-Fe- and Al 2O 3–Fe-coated cenospheres  

Microsoft Academic Search

The precursors for nanosized ?-Fe- and Al2O3–Fe-coated cenospheres were synthesized by the aqueous heterogeneous precipitation using ferrous(II) sulfate, ammonium bicarbonate, ammonium aluminum sulfate and cenospheres as main raw materials. Subsequently, the composite microspheres with magnetic coatings of ?-Fe in grain sizes of about 50 nm were successfully obtained by reduction of the as-prepared precursors in an H2\\/N2 atmosphere at 720 °C for

Wei Liu; Xiang-qian Shen; Dong-hong Li

2008-01-01

276

Fe-Mg interdiffusion in (Mg,Fe)SiO3 perovskite  

Microsoft Academic Search

(Mg,Fe)SiO3 perovskite is the dominant mineral in the lower mantle. Understanding the chemical and physical properties of this phase is therefore essential for understanding processes such as metal-silicate separation during core formation and mantle convection. An important parameter in describing the kinetics of such processes is the diffusion coefficient as function of P, T and fO2. Although there is a

C. Holzapfel; D. C. Rubie; D. J. Frost; F. Langenhorst

2001-01-01

277

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

Microsoft Academic Search

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

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

2000-01-01

278

/Al-Si Composites Fabricated by Reaction Hot Pressing  

NASA Astrophysics Data System (ADS)

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 µm) along with an increase of Al2O3 (~2 µm) 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.

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

2014-12-01

279

Electron-ion recombination rate coefficients and photoionization cross-sections for Al XI, Al XII, Si XII, Si XIII for UV and X-ray modeling  

E-print Network

Electron-ion recombination rate coefficients and photoionization cross-sections for Al XI, Al XII-ion recombination UV and X-rays Al XI, Al XII, Si XII, Si XIII a b s t r a c t Results are presented from detailed study of inverse processes of photoionization and electron-ion recombination of (hm + Al XI Al XII + e

Nahar, Sultana Nurun

280

Hysteresis and anisotropy in ultrathin Fe/Si(001) films  

NASA Astrophysics Data System (ADS)

It is challenging to investigate the magnetic anisotropy of Fe/Si(001) film in the case a limited magnetic field strength, when both coherent rotation and domain wall displacement coexist in the magnetization reversal process. Owing to the domain wall displacement, the magnetization reversal switching field is far lower than the magnetic anisotropy field, and, consequently, only the magnetization reversal process near easy axis can be treated as coherent rotation. Here, we record the slope of the magnetic torque curve of an iron film grown on a Si(001) substrate measured near the easy axis by anisotropic magnetoresistance (AMR) to separate the coherent rotation of magnetization reversal process from domain wall displacement. Furthermore, the magnitudes of various magnetic anisotropy constants were derived from the magnetic torque curves. Our work suggests that the AMR at low fields can clearly separate the detailed contributions of various magnetic anisotropies when domain wall displacement existed in Fe(001) ultrathin film. We also report on the hysteresis behavior of such films as measured by magneto-optic Kerr effect.

Ye, Jun; He, Wei; Wu, Qiong; Hu, Bo; Tang, Jin; Zhang, Xiang-Qun; Chen, Zi-Yu; Cheng, Zhao-Hua

2014-09-01

281

Microstructure of as-fabricated UMo/Al(Si) plates prepared with ground and atomized powder  

NASA Astrophysics Data System (ADS)

UMo-Al based fuel plates prepared with ground U8wt%Mo, ground U8wt%MoX (X = 1 wt%Pt, 1 wt%Ti, 1.5 wt%Nb or 3 wt%Nb) and atomized U7wt%Mo have been examined. The first finding is that that during the fuel plate production the metastable ?-UMo phases partly decomposed into two different ?-UMo phases, U2Mo and ?'-U in ground powder or ??-U in atomized powder. Alloying small amounts of a third element to the UMo had no measurable effect on the stability of the ?-UMo phase. Second, the addition of some Si inside the Al matrix and the presence of oxide layers in ground and atomized samples is studied. In the case with at least 2 wt%Si inside the matrix a Silicon rich layer (SiRL) forms at the interface between the UMo and the Al during the fuel plate production. The SiRL forms more easily when an Al-Si alloy matrix - which is characterized by Si precipitates with a diameter ?1 ?m - is used than when an Al-Si mixed powder matrix - which is characterized by Si particles with some ?m diameter - is used. The presence of an oxide layer on the surface of the UMo particles hinders the formation of the SiRL. Addition of some Si into the Al matrix [7-11]. Application of a protective barrier at the UMo/Al interface by oxidizing the UMo powder [7,12]. Increase of the Mo content or use of UMo alloys with ternary element addition X (e.g. X = Nb, Ti, Pt) to stabilize the ?-UMo with respect to ?-U or to control the UMo-Al interaction layer kinetics [9,12-24]. Use of ground UMo powder instead of atomized UMo powder [10,25] The points 1-3 are to limit the formation of the undesired UMo/Al layer. Especially the addition of Si into the matrix has been suggested [3,7,8,10,11,26,27]. It has been often mentioned that Silicon is efficient in reducing the Uranium-Aluminum diffusion kinetics since Si shows a higher chemical affinity to U than Al to U. Si suppresses the formation of brittle UAl4 which causes a huge swelling during the irradiation. Furthermore it enhances the formation of more stable UAl3 within the diffusion layer [14]. In addition, Si will not notably influence the reactor neutronics due to its low absorption cross section for thermal neutrons of ?abs = 0.24 barn. Aluminum has ?abs = 0.23 barn.Williams [28], Bierlein [29], Green [30] and de Luca [31] showed the first time in the 1950s that alloying Aluminum with some Silicon reduces the Uranium-Aluminum diffusion kinetics in can-type fuel elements. However, up to now uncertainties remained about the most promising Si concentration and the involved mechanisms.Ground powder - possibility 4 - introduces a high density of defects like dislocations, oxide layers and impurities into UMo grains. Fuel prepared with this kind of powder exhibits a larger porosity. It may also be combined with an AlSi matrix. As a consequence, the degree of swelling due to high-burn up is reduced compared to fuel with atomized powder [5,6,25].This study focuses on the metallurgical characterization of as-fabricated samples prepared with ground UMo and UMoX (X = Ti, Nb, Pt) powders and atomized UMo powder. The influence of some Si into the Al matrix and the presence of oxide layers on the UMo is discussed. Details of the differences of samples with ground UMo from atomized UMo will be discussed.The examined samples originate from non-irradiated spare fuel plates from the IRIS-TUM irradiation campaign [5,6]. The samples containing ground UMoX powders and atomized UMo powders with Si addition into the matrix have been produced for this study [32]. Powder mixing: The UMo powder is mixed with Al powder. Compact production: UMo-Al powder is poured into a mould and undergoes compaction under large force. Plate-processing: An AlFeNi frame is placed on an AlFeNi plate and the UMo-Al compact is placed into the frame. Afterwards it is covered with a second AlFeNi plate. This assembly is hot-rolled to reduce the total thickness to 1.4 mm. Subsequently, a blister test (1-2 h at 400-450 °C) ensures that the fuelplate is sealed. After this step, the UMo particles are tightly covered with Al as shown in Fig. 1.

Jungwirth, R.; Palancher, H.; Bonnin, A.; Bertrand-Drira, C.; Borca, C.; Honkimäki, V.; Jarousse, C.; Stepnik, B.; Park, S.-H.; Iltis, X.; Schmahl, W. W.; Petry, W.

2013-07-01

282

Iron silicide formation at different layers of (Fe/Si){sub 3} multilayered structures determined by conversion electron Mössbauer spectroscopy  

SciTech Connect

The morphology and the quantitative composition of the Fe-Si interface layer forming at each Fe layer of a (Fe/Si){sub 3} multilayer have been determined by means of conversion electron Mössbauer spectroscopy (CEMS) and high-resolution transmission electron microscopy (HRTEM). For the CEMS measurements, each layer was selected by depositing the Mössbauer active {sup 57}Fe isotope with 95% enrichment. Samples with Fe layers of nominal thickness d{sub Fe}?=?2.6?nm and Si spacers of d{sub Si}?=?1.5?nm were prepared by thermal evaporation onto a GaAs(001) substrate with an intermediate Ag(001) buffer layer. HRTEM images showed that Si layers grow amorphous and the epitaxial growth of the Fe is good only for the first deposited layer. The CEMS spectra show that at all Fe/Si and Si/Fe interfaces a paramagnetic c-Fe{sub 1?x}Si phase is formed, which contains 16% of the nominal Fe deposited in the Fe layer. The bottom Fe layer, which is in contact with the Ag buffer, also contains ?-Fe and an Fe{sub 1?x}Si{sub x} alloy that cannot be attributed to a single phase. In contrast, the other two layers only comprise an Fe{sub 1?x}Si{sub x} alloy with a Si concentration of ?0.15, but no ?-Fe.

Badía-Romano, L., E-mail: lbadia@unizar.es; Bartolomé, J. [Departamento de Física de la Materia Condensada, Instituto de Ciencia de Materiales de Aragón, CSIC-Universidad de Zaragoza, E-50009 Zaragoza (Spain); Rubín, J. [Departamento de Ciencia y Tecnología de Materiales y Fluidos, Instituto de Ciencia de Materiales de Aragón, CSIC-Universidad de Zaragoza, E-50018 Zaragoza (Spain); Magén, C. [Laboratorio de Microscopías Avanzadas (LMA), Instituto de Nanociencia de Aragón (INA), Universidad de Zaragoza, E-50018 Zaragoza (Spain); Bürgler, D. E. [Peter Grünberg Institut (PGI-6), Forschungszentrum Jülich GmbH, D-52425 Jülich (Germany)

2014-07-14

283

Pulsed laser ablation of Al Cu Fe quasicrystals  

NASA Astrophysics Data System (ADS)

Quasicrystalline Al65-Cu23-Fe12 targets have been ablated by a doubled Nd:YAG laser and deposited on silicon substrates. The results show evidence of distinct ablation mechanisms, which lead to different gas phase composition, as a function of the laser fluence. Films containing the quasicrystalline phase can be deposited only at fluences higher than about 6.5 J/cm2 while at lower fluences the aluminium content exceeds the stoichiometric value. The films obtained by laser ablation of quasicrystalline Al65-Cu23-Fe12 were compared with those obtained from the metallic alloy Al70-Cu20-Fe10. The differences between the two systems could be explained on the basis of the low thermal conductivity of the quasicrystalline phase.

Teghil, R.; D'Alessio, L.; Simone, M. A.; Zaccagnino, M.; Ferro, D.; Sordelet, D. J.

2000-12-01

284

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

NASA Astrophysics Data System (ADS)

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

Lázár, Károly; Tomaševi?, Andjelka; Boškovi?, Goran; Kiss, Ern?

2009-07-01

285

Dissolution of Si in Molten Al with Gas Injection  

NASA Astrophysics Data System (ADS)

Silicon is an essential component of many aluminum alloys, as it imparts a range of desirable characteristics. However, there are considerable practical difficulties in dissolving solid Si in molten Al, because the dissolution process is slow, resulting in material and energy losses. It is thus essential to examine Si dissolution in molten Al, to identify means of accelerating the process. This thesis presents an experimental study of the effect of Si purity, bath temperature, fluid flow conditions, and gas stirring on the dissolution of Si in molten Al, plus the results of physical and numerical modeling of the flow to corroborate the experimental results. The dissolution experiments were conducted in a revolving liquid metal tank to generate a bulk velocity, and gas was introduced into the melt using top lance injection. Cylindrical Si specimens were immersed into molten Al for fixed durations, and upon removal the dissolved Si was measured. The shape and trajectory of injected bubbles were examined by means of auxiliary water experiments and video recordings of the molten Al free surface. The gas-agitated liquid was simulated using the commercial software FLOW-3D. The simulation results provide insights into bubble dynamics and offer estimates of the fluctuating velocities within the Al bath. The experimental results indicate that the dissolution rate of Si increases in tandem with the melt temperature and bulk velocity. A higher bath temperature increases the solubility of Si at the solid/liquid interface, resulting in a greater driving force for mass transfer, and a higher liquid velocity decreases the resistance to mass transfer via a thinner mass boundary layer. Impurities (with lower diffusion coefficients) in the form of inclusions obstruct the dissolution of the Si main matrix. Finally, dissolution rate enhancement was observed by gas agitation. It is postulated that the bubble-induced fluctuating velocities disturb the mass boundary layer, which increases the mass transfer rate. Correlations derived for mass transfer from solids in liquids under various operating conditions were applied to the Al--Si system. A new correlation for combined natural and forced convection mass transfer from vertical cylinders in cross flow is presented, and a modification is proposed to take into account free stream turbulence in a correlation for forced convection mass transfer from vertical cylinders in cross flow.

Seyed Ahmadi, Mehran

286

Study of microstructure and magnetic properties of L10 FePt/SiO2 thin films  

NASA Astrophysics Data System (ADS)

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.

Giannopoulos, G.; Speliotis, Th.; Niarchos, D.

2014-07-01

287

Surface morphology evolution of amorphous Fe Si layers upon thermal annealing  

NASA Astrophysics Data System (ADS)

Changes in the surface morphology of ion-beam-synthesized amorphous Fe-Si layers after rapid thermal annealing (RTA) and furnace annealing (FA) were investigated using atomic force microscopy and transmission electron microscopy. Completely amorphous Fe-Si layers were formed by Fe implantation at a dosage of 5 × 1015 cm-2 using a metal vapour vacuum arc ion source under 80 kV extraction voltage and cryogenic temperature. After RTA at 850 °C, ?-FeSi2 precipitates in Si are completely aggregated from this amorphous Fe-Si layer and the surface of the implanted layer remains flat. To date, no obvious photoluminescence (PL) spectrum has been reported from RTA treated ?-FeSi2 precipitates. However, after annealing at 850 °C for 40 s, high-quality ?-FeSi2 precipitates in Si are obtained which clearly show 1.5 µm PL at 80 K for the first time. Even though additional long-term FA at 850 °C can enhance PL intensity to a limited extent, the longer thermal treatment induces the outdiffusion of ?-FeSi2 precipitates and degrades the surface flatness.

Sun, C. M.; Tsang, H. K.; Wong, S. P.; Ke, N.; Hark, S. K.

2008-04-01

288

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

SciTech Connect

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.

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

289

Fracture toughness of SiC\\/Al metal matrix composite  

Microsoft Academic Search

An experimental study was conducted to evaluate fracture toughness of SiC\\/Al metal matrix composite (MMC). The material was a 12.7 mm thick extrusion of 6061-T6 aluminum alloy with 40 v\\/o SiC particulates. Specimen configuration and test procedure conformed to ASTM E399 Standard for compact specimens. It was found that special procedures were necessary to obtain fatigue cracks of controlled lengths

Y. Flom; B. H. Parker; H. P. Chu

1989-01-01

290

Electronic structure and optical properties of ?-FeSi2(100)/Si(001) interface at high pressure  

NASA Astrophysics Data System (ADS)

The electronic structure and optical absorption properties of the ?-FeSi2(100)/Si(001) interface are investigated by first-principle calculation at high pressure. As the pressure increases, the optical gap decreases sharply, reaches a minimum, and then increases slowly. Structural analysis reveals that the Si(001) slab partially offsets the pressure exerted on the ?-FeSi2 (100) interface, thus downshifting the lowest unoccupied electronic states of the interface and decreasing the optical gap. As the pressure increases further, this offsetting effect weakens and the optical gap increases again gradually. Hence, a high pressure plays an important role in the optical behavior.

Liu, L. Z.; Wu, X. L.; Liu, X. X.; Shen, J. C.; Li, T. H.; Chu, Paul K.

2012-09-01

291

Dry (Mg,Fe)SiO3 perovskite in the Earth's lower mantle  

NASA Astrophysics Data System (ADS)

Combined synthesis experiments and first-principles calculations show that MgSiO3-perovskite with minor Al or Fe does not incorporate significant OH under lower mantle conditions. Perovskite, stishovite, and residual melt were synthesized from natural Bamble enstatite samples (Mg/(Fe + Mg) = 0.89 and 0.93; Al2O3 < 0.1 wt % with 35 and 2065 ppm weight H2O, respectively) in the laser-heated diamond anvil cell at 1600-2000 K and 25-65 GPa. Combined Fourier transform infrared spectroscopy, X-ray diffraction, and ex situ transmission electron microscopy analysis demonstrates little difference in the resulting perovskite as a function of initial water content. Four distinct OH vibrational stretching bands are evident upon cooling below 100 K (3576, 3378, 3274, and 3078 cm-1), suggesting four potential bonding sites for OH in perovskite with a maximum water content of 220 ppm weight H2O, and likely no more than 10 ppm weight H2O. Complementary, Fe-free, first-principles calculations predict multiple potential bonding sites for hydrogen in perovskite, each with significant solution enthalpy (0.2 eV/defect). We calculate that perovskite can dissolve less than 37 ppm weight H2O (400 ppm H/Si) at the top of the lower mantle, decreasing to 31 ppm weight H2O (340 ppm H/Si) at 125 GPa and 3000 K in the absence of a melt or fluid phase. We propose that these results resolve a long-standing debate of the perovskite melting curve and explain the order-of-magnitude increase in viscosity from upper to lower mantle.

Panero, Wendy R.; Pigott, Jeffrey S.; Reaman, Daniel M.; Kabbes, Jason E.; Liu, Zhenxian

2015-02-01

292

Ion Beam Mixing at Crystalline and Amorphous Fe/Si Interfaces  

SciTech Connect

Ion beam irradiation of a-Si/Fe/c-Si trilayers with 350-MeV Au ions and of Fe/a-Si bilayers with 250-keV Xe ions were carried out in order to measure the interface mixing rates and microstructure, phase formation, and magnetic polarization in the regimes of electronic and nuclear stopping. For Fe/a-Si and nuclear stopping, an enhancement of the interface mixing rate of 1.75{+-}0.15 was observed relative to Fe/c-Si. For electronic stopping, the enhancement is 3.21 {+-}0.34. A plausible explanation of this enhancement lies in the much smaller thermal conductivity in a-Si relative to c-Si, which prolongates the relaxation phase of the ion-induced thermal spikes.

Milinovic, V.; Zhang, K.; Lieb, K. P.; Sahoo, P. K. [II. Physikalisches Institut, Universitaet Goettingen, 37077 Goettingen (Germany); Bibic, N. [II. Physikalisches Institut, Universitaet Goettingen, 37077 Goettingen (Germany); VINCA Institute of Nuclear Sciences, Belgrade (Serbia); Milosavljevic, M. [VINCA Institute of Nuclear Sciences, Belgrade (Serbia)

2006-12-01

293

Microstructure and mechanical properties of Al-3Fe alloy processed by equal channel angular extrusion  

NASA Astrophysics Data System (ADS)

Al-Fe alloys are attractive for applications at temperatures beyond those normally associated with the conventional aluminum alloys. Under proper solidification condition, a full eutectic microstructure can be generated in Al-Fe alloys at Fe concentration well in excess of the eutectic composition of 1.8 wt.% Fe. The microstructure in this case is characterized by the metastable regular eutectic Al-Al6Fe fibers of nano-scale in diameter, instead of the equilibrium eutectic Al-Al3Fe phase. In this study, the microstructure and mechanical properties of the Al-3Fe alloy with metastable Al6Fe particles deformed by equal channel angular extrusion were investigated. Severe plastic deformation results in a microstructure consisting of submicron equiaxed Al grains with a uniform distribution of submicron Al6Fe particles on the grain boundaries. The room temperature tensile properties of the alloy with this microstructure will be presented.

Fuxiao, Yu; Fang, Liu; Dazhi, Zhao; Toth, Laszlo S.

2014-08-01

294

Room-temperature magnetocurrent in antiferromagnetically coupled Fe/Si/Fe  

NASA Astrophysics Data System (ADS)

Epitaxial Si-based ferromagnet/semiconductor structures demonstrate strong antiferromagnetic coupling (AFC) as well as resonant-type tunneling magnetoresistance, which vanishes at temperatures above T˜50K [1]. Magnetoresistance effects in Fe/Si/Fe close to room temperature (RT) were not established yet. By using the ballistic electron magnetomicroscopy (BEMM) techniques, with its nanometer-scaled locality [2] we observed for the first time a spin-dependent ballistic magnetotransport in AFC structures. We found that the hot-electron collector current with energies above the Fe/GaAsP Schottky barrier reflects magnetization alignment and changes from IcAP˜50fA for antiparallel alignment to IcP˜150fA for the parallel one. Thus, the magnetocurrent [(IcP-IcAP)/ IcAP]*100% is near 200 % at RT. The measured BEMM hysteresis loops match nicely with the magnetic MOKE data.[0pt] [1]. R.R. Gareev, M.Weides, R. Schreiber, U. Poppe, Appl. Phys. Letts 88, 172105 (2006); [2]. E. Heindl, J. Vancea, C.H. Back, Phys. Rev.B75, 073307 (2007).

Gareev, Rashid; Schmid, Maximilian; Vancea, Johann; Back, Christian; Schreiber, Reinert; Buergler, Daniel; Schneider, Claus; Stromberg, Frank; Wende, Heiko

2011-03-01

295

A Reaction Between High Mn-High Al Steel and CaO-SiO2-Type Molten Mold Flux: Part I. Composition Evolution in Molten Mold Flux  

NASA Astrophysics Data System (ADS)

In order to elucidate the reaction mechanism between high Mn-high Al steel such as twin-induced plasticity steel and molten mold flux composed mainly of CaO-SiO2 during continuous casting process, a series of laboratory-scale experiments were carried out in the present study. Molten steel and molten flux were brought to react in a refractory crucible in a temperature range between 1713 K to 1823 K (1440 °C to 1550 °C) and composition evolution in the steel and the flux was analyzed using inductively coupled plasma atomic emission spectroscopy, X-ray fluorescence, and electron probe microanalysis. The amount of SiO2 in the flux was significantly reduced by Al in the steel; thus, Al2O3 was accumulated in the flux as a result of a chemical reaction, 4[Al] + 3(SiO2) = 3[Si] + 2(Al2O3). In order to find a major factor which governs the reaction, a number of factors ((pct CaO/pct SiO2), (pct Al2O3), [pct Al], [pct Si], and temperature) were varied in the experiments. It was found that the above chemical reaction was mostly governed by [pct Al] in the molten steel. Temperature had a mild effect on the reaction. On the other hand, (pct CaO/pct SiO2), (pct Al2O3), and [pct Si] did not show any noticeable effect on the reaction. Apart from the above reaction, the following reactions are also thought to happen simultaneously: 2[Mn] + (SiO2) = [Si] + 2(MnO) and 2[Fe] + (SiO2) = [Si] + 2(FeO). These oxide components were subsequently reduced by Al in the molten steel. Na2O in the molten flux was gradually decreased and the decrease was accelerated by increasing [pct Al] and temperature. Possible reactions affecting the Al2O3 accumulation are summarized.

Kim, Min-Su; Lee, Su-Wan; Cho, Jung-Wook; Park, Min-Seok; Lee, Hae-Geon; Kang, Youn-Bae

2013-04-01

296

Redetermination of iron dialuminide, FeAl(2).  

PubMed

The crystal structure of iron dialuminide [Corby & Black (1973). Acta Cryst. B29, 2669-2677] has been redetermined on a single crystal synthesized from the elements by arc melting. The compound crystallizes in the triclinic space group P-1 with 19 atoms per unit cell, one Fe site being on an inversion centre. The crystal structure can be described as an inclusion-plus-deformation derivative of the orthorhombic YPd(2)Si structure type. PMID:20814091

Chumak, Ihor; Richter, Klaus W; Ehrenberg, Helmut

2010-09-01

297

Anisotropic magnetic properties of EuAl2Si2  

NASA Astrophysics Data System (ADS)

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 Mössbauer 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 Mössbauer spectroscopy are in conformity with a bulk transition at 33.3 K.

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

2015-03-01

298

Trapping of BTX compounds by SiO2, Ag-SiO2, Cu-SiO2, and Fe-SiO2 porous substrates.  

PubMed

Adsorption isotherms of BTX aromatic hydrocarbons (benzene, toluene, and p-xylene) on pristine (SiO2) and metal-doped (Ag-SiO2, Cu-SiO2 and Fe-SiO2) mesoporous and microporous substrates were measured and interpreted. These adsorbents were synthesized by the sol-gel procedure and their BTX sorption isotherms were obtained by the gas chromatographic technique (GC) at several temperatures in the range 423-593 K. The uptake amount of these hydrocarbon adsorptives on SiO2, Ag-SiO2, Cu-SiO2 and Fe-SiO2 mesoporous and microporous substrates was temperature-dependent. Additionally, the interaction of BTX molecules with the pore walls was evaluated by means of the corresponding isosteric heat of adsorption (qst), which was found to follow the next increasing sequence: qst (benzene)SiO2 structure leads to an increased adsorbed amount of BTX molecules on the solid surface if compared with the Cu-SiO2 adsorbent. The adsorption of benzene, but not of toluene and p-xylene, molecules on pristine SiO2 is facilitated by the pore size of this substrate since this is the highest of all materials. PMID:20817219

Hernández, M A; Asomoza, M; Rojas, F; Solís, S; Portillo, R; Salgado, M A; Felipe, C; Portillo, Y; Hernández, F

2010-11-01

299

Quaternary aluminum silicides grown in Al flux: RE5Mn4Al(23-x)Si(x) (RE = Ho, Er, Yb) and Er44Mn55(AlSi)237.  

PubMed

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) Å and c = 4.0297(2)-4.0575(4) Å with volumes ranging from 522.41(5) to 528.90(8) Å(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) Å. 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

Calta, Nicholas P; Kanatzidis, Mercouri G

2013-09-01

300

Correlation induced paramagnetic ground state in FeAl.  

PubMed

Experimentally the intermetallic compound FeAl is known to be nonmagnetic, whereas conventional density functional theory calculations within the local density approximation always yield a ferromagnetic ground state with a magnetic moment at the Fe site of about 0.7 mu(B). We show that a correlation correction within the LDA+U scheme yields a nonmagnetic ground state for U>or=3.7 eV using two different implementations. The disappearance of the magnetic ground state occurs since Fe-t(2g) and Fe-e(g) manifolds are affected differently by a common U. For large values of U a magnetic solution reappears as expected for strong correlation. PMID:11690436

Mohn, P; Persson, C; Blaha, P; Schwarz, K; Novák, P; Eschrig, H

2001-11-01

301

Crystal structure of the NaCa(Fe{sup 2+}, Al, Mn){sub 5}[Si{sub 8}O{sub 19}(OH)](OH){sub 7} {center_dot} 5H{sub 2}O mineral: A new representative of the palygorskite group  

SciTech Connect

A specimen of a new representative of the palygorskite-sepiolite family from Aris phonolite (Namibia) is studied by single-crystal X-ray diffraction. The parameters of the triclinic (pseudomonoclinic) unit cell are as follows: a = 5.2527(2) Angstrom-Sign , b = 17.901(1) Angstrom-Sign , c = 13.727(1) Angstrom-Sign , {alpha} = 90.018(3) Degree-Sign , {beta} = 97.278(4) Degree-Sign , and {gamma} = 89.952(3) Degree-Sign . The structure is solved by the direct methods in space group P1-bar and refined to R = 5.5% for 4168 |F| > 7{sigma}(F) with consideration for twinning by the plane perpendicular to y (the ratio of the twin components is 0.52: 0.48). The crystal chemical formula (Z = 1) is (Na{sub 1.6}K{sub 0.2}Ca{sub 0.2})[Ca{sub 2}(Fe{sub 3.6}{sup 2+}Al{sub 1.6}Mn{sub 0.8})(OH){sub 9}(H{sub 2}O){sub 2}][(Fe{sub 3.9}{sup 2+}Ti{sub 0.1})(OH){sub 5} (H{sub 2}O){sub 2}][Si{sub 16}O{sub 38}(OH){sub 2}] {center_dot} 6H{sub 2}O, where the compositions of two ribbons of octahedra and a layer of Si tetrahedra are enclosed in brackets. A number of specific chemical, symmetrical, and structural features distinguish this mineral from other minerals of this family, in particular, from tuperssuatsiaite and kalifersite, which are iron-containing representatives with close unit cell parameters.

Rastsvetaeva, R. K., E-mail: rast@ns.crys.ras.ru; Aksenov, S. M.; Verin, I. A. [Russian Academy of Sciences, Shubnikov Institute of Crystallography (Russian Federation)

2012-01-15

302

Correlation of the structural properties of a Pt seed layer with the perpendicular magnetic anisotropy features of full Heusler-based Co2FeAl/MgO/Co2Fe6B2 junctions via a 12-inch scale Si wafer process  

NASA Astrophysics Data System (ADS)

We elucidated the interfacial-perpendicular magnetic anisotropy (i-PMA) features of full Heusler-based Co2FeAl/MgO/Co2Fe6B2 magnetic-tunnel-junctions as functions of the structural properties of the Pt seed layer including its thickness and ex situ annealing temperature. All of the samples were prepared in a 12-inch silicon wafer process for real industry applications. The observations of the M-H loops emphasize that a thinner Pt seed layer and a high ex situ annealing temperature enhance the surface roughness of the seed layer, providing better i-PMA characteristics. HR-TEM images of the samples were evaluated to understand the structural effects of thin and thick Pt seed layers.

Chae, Kyo-Suk; Lee, Du-Yeong; Shim, Tae-Hun; Hong, Jin-Pyo; Park, Jea-Gun

2013-10-01

303

Itinerant magnetism in doped semiconducting ?-FeSi2 and CrSi2  

PubMed Central

Novel or unusual magnetism is a subject of considerable interest, particularly in metals and degenerate semiconductors. In such materials the interplay of magnetism, transport and other Fermi liquid properties can lead to fascinating physical behavior. One example is in magnetic semiconductors, where spin polarized currents may be controlled and used. We report density functional calculations predicting magnetism in doped semiconducting ?-FeSi2 and CrSi2 at relatively low doping levels particularly for n-type. In this case, there is a rapid cross-over to a half-metallic state as a function of doping level. The results are discussed in relation to the electronic structure and other properties of these compounds. PMID:24343332

Singh, David J.; Parker, David

2013-01-01

304

Itinerant magnetism in doped semiconducting ?-FeSi2 and CrSi2  

NASA Astrophysics Data System (ADS)

Novel or unusual magnetism is a subject of considerable interest, particularly in metals and degenerate semiconductors. In such materials the interplay of magnetism, transport and other Fermi liquid properties can lead to fascinating physical behavior. One example is in magnetic semiconductors, where spin polarized currents may be controlled and used. We report density functional calculations predicting magnetism in doped semiconducting ?-FeSi2 and CrSi2 at relatively low doping levels particularly for n-type. In this case, there is a rapid cross-over to a half-metallic state as a function of doping level. The results are discussed in relation to the electronic structure and other properties of these compounds.

Singh, David J.; Parker, David

2013-12-01

305

Magnetic damping constant of Co2FeSi Heusler alloy thin film  

NASA Astrophysics Data System (ADS)

Co2FeSi 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 (Ms and Hc), surface roughness, and magnetic damping constants (?) of the prepared Co2FeSi 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 Co2FeSi film exhibited an amorphous and disordered structure; the ? value was 0.008. In contrast, the Co2FeSi films annealed over 300°C showed epitaxial growth and had a (001)-oriented and L21 ordered structure. Both disordered and L21 ordered Co2FeSi films showed similar ? values.

Oogane, Mikihiko; Yilgin, Resul; Shinano, Masatsugu; Yakata, Satoshi; Sakuraba, Yuya; Ando, Yasuo; Miyazaki, Terunobu

2007-05-01

306

X-ray reflectivity and photoelectron spectroscopy study of interdiffusion at the Si /Fe interface  

NASA Astrophysics Data System (ADS)

We have investigated the nature of silicon on iron interface in electron beam deposited Fe /Si bilayers, with various iron and silicon thicknesses. The Fe and Si layer thicknesses are varied from 30to330Å and 20to86Å, respectively. Grazing incidence x-ray reflectivity and photoelectron spectroscopy measurements were carried out on these samples to determine interface characteristics. Si on Fe (Si&barbelow;Fe) interlayer thickness, roughness, and composition do not depend on the thickness of Fe and Si. The thickness of the interlayer is around 13Å. A systematic variation in silicide concentration across this interface is observed by x-ray photoelectron spectroscopy measurement. Change in the density of states in valence band across this interface is also observed by ultraviolet photoelectron measurement.

Naik, S. R.; Rai, S.; Lodha, G. S.; Brajpuriya, R.

2006-07-01

307

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

NASA Astrophysics Data System (ADS)

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.

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

2014-03-01

308

Refinement of primary Si in hypereutectic Al-Si alloys by intensive melt shearing  

NASA Astrophysics Data System (ADS)

Hypereutectic Al-Si based alloys are gaining popularity for applications where a combination of light weight and high wear resistance is required. The high wear resistance arising from the hard primary Si particles comes at the price of extremely poor machine tool life. To minimize machining problems while exploiting outstanding wear resistance, the primary Si particles must be controlled to a uniform small size and uniform spatial distribution. The current industrial means of refining primary Si chemically by the addition of phosphorous suffers from a number of problems. In the present paper an alternative, physical means of refining primary Si by intensive shearing of the melt prior to casting is investigated. Al-15wt%Si alloy has been solidified under varying casting conditions (cooling rate) and the resulting microstructures have been studied using microscopy and quantitative image analysis. Primary Si particles were finer, more compact in shape and more numerous with increasing cooling rate. Intensive melt shearing led to greater refinement and more enhanced nucleation of primary Si than was achieved by adding phosphorous. The mechanism of enhanced nucleation is discussed.

Zhang, Z.; Li, H.-T.; Stone, I. C.; Fan, Z.

2012-01-01

309

Effect of Fe- and Si-induced flaws on fracture of Si{sub 3}N{sub 4}  

SciTech Connect

Fracture studies were performed to detect and assess the effect of flaws on the fracture behavior of hot-pressed Si{sub 3}N{sub 4} with Fe or Si inclusions. The addition of 5 and 0.5 wt.% Fe inclusions of 88--250 {micro}m size reduced the strength of Si{sub 3}N{sub 4} specimens by {approx} 40 and 15%, respectively. Similarly, addition of 1 and 0.5 wt.% Si inclusions of < 149 {micro}m size reduced the strength of Si{sub 3}N{sub 4} specimens by {approx} 50 and 39%, respectively. Fractography indicated that failure occurred primarily from internal flaws which included Fe- and Si-rich inclusions and/or regions of Si{sub 3}N{sub 4} matrix that were degraded as a result of reaction between Si{sub 3}N{sub 4} and molten Fe or Si. For inclusion-induced internal flaws, the critical flaw sizes calculated by fracture mechanics were always larger than the fractographically measured flaw sizes. This observation suggested local degradation in fracture toughness of the Si{sub 3}N{sub 4} matrix. A ratio, K, of {approx} 3.5--4.2 appeared to exist between the calculated and measured values of the critical internal flaw sizes of specimens that contained Fe inclusions. A similar ratio of 1.7--3.1 was observed for specimens that contained Si inclusions. The ratio K has important implications for strength predictions that are based on observed flaw size.

Singh, J.P. [Argonne National Lab., IL (United States). Energy Technology Div.

1997-10-01

310

Effects of magnetic fields on Fe-Si composite electrodeposition  

NASA Astrophysics Data System (ADS)

Coatings containing Fe-Si particles were electrodeposited on 3.0wt% Si steel sheets under magnetic fields. The effects of magnetic flux density (MFD), electrode arrangement and current density on the surface morphology, the silicon content in the coatings and the cathode current efficiency were investigated. When a magnetic field was applied parallel to the current and when the MFD was less than 0.5 T, numerous needle-like structures appeared on the coating surface. With increasing MFD, the needle-like structures weakened and were transformed into dome-shaped structures. Meanwhile, compared to results obtained in the absence of a magnetic field, the silicon content in the coatings significantly increased as the MFD was increased for all of the samples obtained using a vertical electrode system. However, in the case of an aclinic electrode system, the silicon content decreased. Furthermore, the cathode current efficiency was considerably diminished when a magnetic field was applied. A possible mechanism for these phenomena was discussed.

Long, Qiong; Zhong, Yun-bo; Wang, Huai; Zheng, Tian-xiang; Zhou, Jun-feng; Ren, Zhong-ming

2014-12-01

311

Effect of Al2O3 on the Viscosity and Structure of CaO-SiO2-MgO-Al2O3-FetO Slags  

NASA Astrophysics Data System (ADS)

The present paper provided a fundamental investigation on the effect of Al2O3 on the viscosity and structure of CaO-SiO2-MgO-Al2O3-FetO slags for the purpose of efficiently recycling the valuable elements from the steelmaking slags. The results show that the viscosity of CaO-SiO2-Al2O3-MgO-FetO slags slightly increases with increasing Al2O3 content. The degree of the polymerization (DOP) of quenched slags, determined from Raman spectra and magic angle spinning-nuclear magnetic resonance, is also found to increase with increasing Al2O3 content. It can be deduced that the increasing DOP can promote the formation of gehlenite phase (Ca2Al2SiO7), thus facilitating the formation of higher phosphorous (or vanadium) contained solid solution (n'Ca2SiO4·Ca3((P or V)O4)2). As Al2O3 content increases up to a specific value, the charge compensating ions which present near [AlO4]-tetrahedra and [FeO4]-tetrahedra are not fully supplied due to the scarcity of Ca2+. In this case, the existing Fe3+ in the melt cannot completely form [FeO4]-tetrahedra and part of Fe3+ would form [FeO6]-octahedra to substitute Ca2+ to modify the slags.

Wang, Zhanjun; Sun, Yongqi; Sridhar, Seetharaman; Zhang, Mei; Guo, Min; Zhang, Zuotai

2015-02-01

312

The effect of Mg on the microstructure and mechanical behavior of Al-Si-Mg casting alloys  

SciTech Connect

The microstructure and tensile behavior of two Al-7 pct Si-Mg casting alloys, with magnesium contents of 0.4 and 0.7 pct, have been studied. Different microstructures were produced by varying the solidification rate and by modification with strontium. An extraction technique was used to determine the maximum size of the eutectic silicon flakes and particles. The eutectic Si particles in the unmodified alloys and, to a lesser extent, in the Sr-modified alloys are larger in the alloys with higher Mg content. Large Fe-rich {pi}-phase (Al{sub 9}FeMg{sub 3}Si{sub 5}) particles are formed in the 0.7 pct Mg alloys together with some smaller {beta}-phase (Al{sub 5}FeSi) plates; in contrast, only {beta}-phase plates are observed in the 0.4 pct Mg alloys. The yield stress increases with the Mg content, although, at 0.7 pct Mg, it is less than expected, possibly because some of the Mg is lost to {pi}-phase intermetallics. The tensile ductility is less in the higher Mg alloys, especially in the Sr-modified alloys, compared with the lower Mg alloys. The loss of ductility of the unmodified alloy seems to be caused by the larger Si particles, while the presence of large {pi}-phase intermetallic particles accounts for the loss in ductility of the Sr-modified alloy.

Caceres, C.H.; Davidson, C.J.; Griffiths, J.R.; Wang, Q.G.

1999-10-01

313

Thermal behavior of Al and Al3 at. % Ge thin films on Si wafers  

Microsoft Academic Search

The mechanical stresses of a pure Al film and a low-thermal-expansion Al-3 at. % Ge thin film on (100) Si wafers are measured and compared in the temperature range of room temperature to 400 °C by the vibrating membrane method. The results are discussed including the comparison with those obtained by the popular wafer bending method. It was found that

B. S. Lim; W. C. Pritchet; K. P. Rodbell; K. N. Tu

1993-01-01

314

Phase-separated Al-Si thin films  

SciTech Connect

Phase-separated Al-Si films composed of Al nanocylinders embedded in an amorphous-Si matrix have been prepared by a sputtering method. By controlling the deposition rate, substrate temperature, and film composition, the average diameter of the Al cylinders can be varied systematically from less than 5 to 13 nm with a cylinder density ranging from 10{sup 15} to in excess of 10{sup 16} cylinders m{sup -2}. A three-dimensional simulation of phase separation in binary thin films was performed using a modified Cahn-Hilliard [J. Chem. Phys. 28, 258 (1958)] equation to understand the growth mechanism. The simulation studies indicate that the surface diffusion length and film composition are important factors which determine film morphology. Experimental and simulation studies are compared and discussed.

Fukutani, Kazuhiko; Tanji, Koichi; Saito, Tatsuya; Den, Tohru [Leading-Edge Technology Development Headquarters, Canon Inc. 5-1, Morinosato-Wakamiya, Atsugi-shi, Kanagawa 243-0193 (Japan)

2005-08-01

315

Interesting magnetic behavior of Fe:Al disordered alloys  

NASA Astrophysics Data System (ADS)

The low temperature magnetic properties of FeAl alloys, near equiatomic composition, are a matter of contention from both theoretical perspectives and experimental measurements. There does not seem to be any consensus regarding these. In an attempt to find the source of contradictory behavior, we made a detailed study by both bulk magnetization and local probe by Mössbauer effect on a well characterized sample. It was interesting to find that while the former showed distinct magnetic phases, the local probe failed to resolve any magnetization on Fe atom down to very low temperature. This contradictory behavior suggested non-local moment formation in the system.

Mukhopadhyay, P. K.; Ghosh, Tanmoy; Mookerjee, Abhijit

2014-09-01

316

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  

Microsoft Academic Search

The theoreticalP-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

B. J. Hensen

1986-01-01

317

Core-shell Fe3O4@SiO2 nanoparticles synthesized with well-dispersed hydrophilic Fe3O4 seeds  

E-print Network

magnetite (Fe3O4@SiO2) core-shell nanoparticles (NPs) with controlled silica shell thicknesses were prepared in the control of silica shell thickness. These well-dispersed core-shell Fe3O4@SiO2 NPs show superparamagneticCore-shell Fe3O4@SiO2 nanoparticles synthesized with well-dispersed hydrophilic Fe3O4 seeds Chao

Gao, Hongjun

318

Current Transport in Al-Diffused ZnO/Si Heterostructures  

NASA Astrophysics Data System (ADS)

The current-voltage-temperature (I-V-T) characteristics of transparent Al-doped ZnO (AZO) on n-Si heterojunction structures were analyzed with respect to two different Al diffusion temperatures, 200°C and 600°C. Thin films of Al were deposited on top of the ZnO/Si structures, followed by introducing the Al atoms into the ZnO to form AZO through a process of thermal diffusion. Measurements at temperatures of 150-400 K were carried out in order to understand the temperature dependence of the heterostructure diode characteristics for photovoltaic applications. The results indicated the difference in current mechanisms observed in the two diodes with different Al-diffusion temperatures and Al thicknesses. The charge transport mechanism in the 200°C diodes indicated thermionic field emission (TFE) as the dominating mechanism, whereas the 600°C diodes resulted in field emission (FE) as the dominating current transport. The differences in conduction mechanisms explain the better solar cell performance using the 200°C process.

Chen, Yen-Jen; Tong, Chong; Yun, Juhyung; Anderson, Wayne A.

2015-01-01

319

Melting relationships of the Fe-S-Si system up to 60 GPa: Implications for the thermal structure of the Earth's core  

NASA Astrophysics Data System (ADS)

The Earth's core is mainly composed of iron alloy, however the lighter elements are required in the core to account for the core density deficit (Birch, 1964). The potential light elements have been considered to be S, Si, O, C, and H (Poirier, 1994). Alloying light elements significantly affects the physical properties of iron and depresses its melting temperature(e.g., Boehler, 1996b). Sulfur and silicon are considered as major light element components based on cosmochemical study (McDonough, 2003) and high pressure partitioning experiments (e.g., Sakai et al., 2006), therefore the melting relationship of the Fe-S-Si system is the key information to clarify the thermal and compositional structure of the Earth's core. Many melting experiments of Fe-light elements alloys have been performed under high pressure corresponding Earth's core using diamond anvil cell. However in the case of the Fe-S-Si ternary system, there are no experimental data at high pressure and the phase and melting relations have not been clarified in detail under core conditions. In this study, the phase relationships and the solidus temperature of the Fe-S-Si system were determined up to 60 GPa using a laser-heated diamond anvil cell combined with in situ X-ray diffraction technique. The sample composition used for this study were Fe80.1S12.7Si7.2(Fe-8wt.%S-4wt.%Si) and Fe74.4S18.5Si7.1(Fe-12wt.%S-4wt.%Si), which are in the range of the amounts of the light elements to explain the density deficit in the Earth's core (Chen et al., 2007). In situ X-ray diffraction experiments were conducted at the BL10XU beamline at the SPring-8 facility (Ohishi et al., 2008). On the basis of diffraction patterns, Fe(hcp/fcc) which contains silicon and Fe3S are stable phases under subsolidus conditions. First Fe3S phase melts at the solidus temperature, and Fe-Si alloy coexists with partial melts above the eutectic temperature in this system. This melting sequence is consistent with the study of the Fe-Fe3S system observed earlier by Kamada et al. (2010). The solidus temperature is significantly lower than the melting temperature of pure Fe (Ma et al., 2004) and close to the eutectic point of the Fe-Fe3S system (Morard et al., 2008), suggesting that the effect of 7.2 at.% silicon on the eutectic temperature in the Fe-Fe3S system is minor. In order to draw the solidus curve as a function of pressure, we fitted the present results using the Simon's law. The obtained fitting parameters are a=104(16) and c=0.88(1). Based on our results of the melting relationship, the temperature at the core-mantle boundary should be greater than 2900(200) K and the temperature at the boundary of the inner and outer cores is estimated to be 5680(350) K, assuming that sulfur and silicon are the light elements in the Earth's core. The results in this study provide important constraints on the thermal structure of the Earth's core.

Sakairi, T.; Ohtani, E.; Sakai, T.; Kamada, S.; Miyahara, M.; Hirao, N.; Ohishi, Y.

2012-12-01

320

Endotaxially stabilized B2-FeSi nanodots in Si (100) via ion beam co-sputtering  

SciTech Connect

We report on the formation of embedded B2-FeSi nanodots in [100]-oriented Si substrates, and investigate the crystallographic mechanism underlying the stabilization of this uncommon, bulk-unstable, phase. The nanodots were approximately 10?nm in size, and were formed by iron thin film deposition and subsequent annealing. Cross-sectional transmission electron microscopy, energy loss spectroscopy mapping, and quantitative image simulation and analysis were utilized to identify the phase, strain, and orientational relationship of the nanodots to the host silicon lattice. X-ray photoelectron spectroscopy was utilized to analyze the surface composition and local bonding. Elasticity calculations yielded a nanodot residual strain value of ?18%. Geometrical phase analysis graphically pinpointed the positions of misfit dislocations, and clearly showed the presence of pinned (11{sup ¯}1{sup ¯}){sub Si}//(100){sub FeSi}, and unpinned (2{sup ¯}42){sub Si}//(010){sub FeSi}, interfaces. This partial endotaxy in the host silicon lattice was the mechanism that stabilized the B2-FeSi phase.

Cassidy, Cathal, E-mail: c.cassidy@oist.jp; Singh, Vidyadhar; Grammatikopoulos, Panagiotis [Nanoparticles by Design Unit, Okinawa Institute of Science and Technology (OIST) Graduate University, 1919-1 Onna-Son, Okinawa 904-0495 (Japan); Kioseoglou, Joseph [Department of Physics, Aristotle University of Thessaloniki, GR-54124 Thessaloniki (Greece); Lal, Chhagan [Department of Physics, University of Rajasthan, Jaipur, Rajasthan 302005 (India); Sowwan, Mukhles, E-mail: mukhles@oist.jp [Nanoparticles by Design Unit, Okinawa Institute of Science and Technology (OIST) Graduate University, 1919-1 Onna-Son, Okinawa 904-0495 (Japan); Nanotechnology Research Laboratory, Al-Quds University, East Jerusalem, P.O. Box 51000, Palestine (Country Unknown)

2014-04-21

321

Synthesis and characterization of AlTiSiN/CrSiN multilayer coatings by cathodic arc ion-plating  

NASA Astrophysics Data System (ADS)

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.

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

322

Wear resistant Al-Si\\/TiC coatings prepared by high power laser cladding  

Microsoft Academic Search

High wear resistance Al-based composite coatings were prepared by laser cladding using powder mixtures of Al-12 wt. % Si+40 wt. % TiC and Al-40 wt. % Si+40 wt. % TiC. In the case of the coatings containing 12 % Si, the microstructure consists essentially of TiC particles dispersed in a matrix of primary alpha-Al dendrites and interdendritic alpha-Al+Si eutectic, whereas

Anandkumar Ramasamy; Amelia Almeida; Rui Vilar

2008-01-01

323

Effect of heat treatment on microstructure and interface of SiC particle reinforced 2124 Al matrix composite  

SciTech Connect

The microstructure and interface between metal matrix and ceramic reinforcement of a composite play an important role in improving its properties. In the present investigation, the interface and intermetallic compound present in the samples were characterized to understand structural stability at an elevated temperature. Aluminum based 2124 alloy with 10 wt.% silicon carbide (SiC) particle reinforced composite was prepared through vortex method and the solid ingot was deformed by hot rolling for better particle distribution. Heat treatment of the composite was carried out at 575 °C with varying holding time from 1 to 48 h followed by water quenching. In this study, the microstructure and interface of the SiC particle reinforced Al based composites have been studied using optical microscopy, scanning electron microscopy (SEM) coupled with energy dispersive X-ray spectroscopy (EDS), electron probe micro-analyzer (EPMA) associated with wavelength dispersive spectroscopy (WDS) and transmission electron microscopy (TEM) to identify the precipitate and intermetallic phases that are formed during heat treatment. The SiC particles are uniformly distributed in the aluminum matrix. The microstructure analyses of Al–SiC composite after heat treatment reveal that a wide range of dispersed phases are formed at grain boundary and surrounding the SiC particles. The energy dispersive X-ray spectroscopy and wavelength dispersive spectroscopy analyses confirm that finely dispersed phases are CuAl{sub 2} and CuMgAl{sub 2} intermetallic and large spherical phases are Fe{sub 2}SiAl{sub 8} or Al{sub 15}(Fe,Mn){sub 3}Si. It is also observed that a continuous layer enriched with Cu and Mg of thickness 50–80 nm is formed at the interface in between Al and SiC particles. EDS analysis also confirms that Cu and Mg are segregated at the interface of the composite while no carbide is identified at the interface. - Highlights: • The composite was successfully heat treated at 575°C for 1-48 hrs. • A layer of 50-75 nm is formed at interface after heat treatment. • No Carbide formation and SiC dissolution is observed at this temperature. • MgAl{sub 2}O{sub 4}, CuMgAl{sub 2} phases are segregated at interface of Al-SiC composite. • Mg and Cu are also segregated at near to the grain boundary.

Mandal, Durbadal, E-mail: durbadal73@yahoo.co.in [MEF Division, CSIR-National Metallurgical Laboratory, Jamshedpur 831007 (India); Viswanathan, Srinath [Dept of Metallurgical and Materials Engineering, University of Alabama, Tuscaloosa, AL (United States)

2013-11-15

324

Novel Fe@C-TiO2 and Fe@C-SiO2 water-dispersible magnetic nanocomposites  

NASA Astrophysics Data System (ADS)

We report the synthesis of novel nanocomposites based on Fe@C nanoparticles obtained from Fe(CO)5 and C2H4/H2 by laser pyrolysis technique using a three nozzles injector. The ?Fe-FexCy@C particles (below 24 nm diameter) were first functionalized with hydrophilic groups using Na carboxymethylcellulose. Oxidic precursors (Si(OC2H5)4 or Ti(OC2H5)4) dissolved in ethanol were mixed with ethanolic suspensions of hydrophilized Fe@C nanoparticles using strong ultrasonication, then with water (at different pH values) and finally the Fe-containing composites were recovered by magnetic separation. The SiO2 and TiO2-coated powders were characterized by XRD, FT-IR and TEM techniques and their magnetic hysteresis curves were recorded at different temperatures. Both composites contain submicron aggregates of Fe@C nanoparticles embedded in/surrounded by a disordered porous oxidic matrix/shell. Near superparamagnetic behavior and room temperature and 26 A m2/kg (for Fe@C/SiO2) or 57 A m2/kg (for Fe@C/TiO2) saturation magnetization values were recorded and a blocking temperature around 500 K was extrapolated.

Fleaca, Claudiu Teodor; Dumitrache, Florian; Morjan, Ion; Alexandrescu, Rodica; Luculescu, Catalin; Niculescu, Ana; Vasile, Eugeniu; Kuncser, Victor

2013-08-01

325

Perpendicular magnetic anisotropy in Ta/Co2FeAl/MgO multilayers  

NASA Astrophysics Data System (ADS)

In this paper, we demonstrate the stabilization of perpendicular magnetic anisotropy (PMA) in Ta/Co2FeAl/MgO multilayers sputtered on thermally oxidized Si(100) substrates. The magnetic analysis points out that these films show significant interfacial anisotropy even in the as-deposited state, KS=0.67 erg/cm2, enough to provide PMA for the as-deposited films with thicknesses below 1.5 nm. Moreover, the interfacial anisotropy is enhanced by thermal annealing up to 300 °C. The presence of a magnetic dead layer, whose thickness increases with annealing temperature, was also identified.

Gabor, M. S.; Petrisor, T.; Tiusan, C.; Petrisor, T.

2013-08-01

326

Investigation of Fe-Si-N films as magnetic overcoat for high density recording disk drives  

SciTech Connect

A 50-nm-thick Fe-Si-N films were deposited via reactive magnetron cosputtering of independent Fe and Si targets, in Ar/N{sub 2} gas mixture, under different dc Fe target power conditions. Magnetic properties, mechanical hardness and tribological properties were characterized as a function of the Fe target power by magnetometry, nanoindentation, and nanoscratch testing, respectively. Deposited samples were found to be ferromagnetic with a coercivity of approximately 20 Oe and a saturation magnetization increasing from 200 to 1100 emu/cm{sup 3} as a function of Fe sputter power, i.e., values typical of soft magnetic materials. The mechanical hardness was found to be between 50% and 70% of the hardness of a pure SiN{sub x} film. Nanotribological properties of films deposited with a Fe target power {>=}80 W degraded rapidly.

Gauvin, M.; Talke, F. E. [Department of Mechanical and Aerospace Engineering, Center for Magnetic Recording Research, University of California, San Diego, California 92093 (United States); Fullerton, E. E. [Department of Electrical and Computer Engineering, Center for Magnetic Recording Research, University of California, San Diego, California 92093 (United States)

2010-09-15

327

Phase relation of C-Mg-Fe-Si-O system under various oxygen fugacity conditions at high pressure and high temperature  

NASA Astrophysics Data System (ADS)

Many exoplanets have been found recently based on the spectroscopic observation. A carbon-rich circumstellar gas was reported to exist around “beta-Pictoris”, which has an exoplanet (Roberge et al., 2006). In such gas, carbon-enriched planet, “carbon-planet” may be formed. Carbon-bearing phase, such as carbide, carbonate, graphite and diamond are likely to compose the carbon-planet interior. Therefore, it is important to investigate phase relations of carbon-rich systems under high pressure conditions. In this study, C-enriched Mg-Si-Fe-O-C system was investigated at high pressure and temperature in order to understand the internal structure of the carbon-planet. Phase relations were studied based on 2 series of experiments; (I)textural observation and chemical analysis of the recovered sample from 4 GPa and 1873K and (II)in situ X-ray diffraction experiments under high pressure and temperature. For the starting materials, we used several different mineral assemblages, as shown below: (i) MgCO3 + Fe + Si + C, (ii) (Mg1.8,Fe0.2)SiO4 + Fe + SiO2 + C, (iii) (Mg1.8,Fe0.2)SiO4 + Fe + Si + C, (iv) MgO + Fe + SiO2 + C, (v) MgO + Fe + Si + C. Oxygen fugacity (fO2) of the sample vaies dependign on these assembleges due to different O amount in the starting materials. The sample was enclosed in graphite or MgO capsule. MgO capsule enables us to estimate fO2 in the sample based on the FeO content of the capsule contacting with the samples. Chemical analyses of the recovered samples were performed using electron microprobe. In situ X-ray diffraction experiments were conducted at 4 GPa and up to 1873 K at BL04B1 beamline, SPring-8 synchrotron facility. Different mineral assemblages and their compositions were observed in the recovered samples depending on the redox condition of the sample. The compositions of metallic melt phases changes from Fe-C composition (C = 6.9~8.2 wt.%) in oxidizing conditions (?IW = -2.4 ~ -1.7) to Fe-Si composition (Si = 18 wt.%) in the more reducing condition (?IW < -4.8). SiC grains were also found in the most reducing condition. The solubility of C into the Fe-melt phase increases with fO2, whereas the solubility of Si decreases with increasing fO2. Based on in situ X-ray diffraction experiments, Fe3C was formed at 1073 K in the all samples. Fe3C peak disappeared and FeSi and SiC peaks appeared at 1373 K in the most reducing sample (v), whereas Fe3C remained in the other samples. Metallic phases in all samples were melted at 1673 K. Any carbonates was not observed under the present experimental conditions. Therefore, carbon-bearing phases are graphite, SiC and Fe-C alloy or Fe-Si-C alloy in the present redox conditions at 4 GPa. These results may suggest existence of carbon in the mantle and/or core in some carbon-planets.

Takahashi, S.; Ohtani, E.; Terasaki, H.; Ito, Y.; Shibazaki, Y.; Ishii, M.; Funakoshi, K.; Higo, Y.

2010-12-01

328

Precipitation of Si particles in a super-rapidly solidified Al–Si hypereutectic alloy  

Microsoft Academic Search

Fine silicon particles of approximately 20nm in average diameter were dispersed in the Al matrix of a hypereutectic Al–Si alloy powder produced by the spinning water atomization process. This powder was sintered at a temperature between 623 and 773K for a maximum period of time of 20.4ks. The silicon particles grew during sintering but the size remained at a sub-micron

K. Matsuura; M. Kudoh; H. Kinoshita; H. Takahashi

2003-01-01

329

Near surface silicide formation after off-normal Fe-implantation of Si(001) surfaces  

SciTech Connect

We report on formation of non-crystalline Fe-silicides of various stoichiometries below the amorphized surface of crystalline Si(001) after irradiation with 5?keV Fe{sup +} ions under off-normal incidence. We examined samples prepared with ion fluences of 0.1?×?10{sup 17} and 5?×?10{sup 17} ions cm{sup ?2} exhibiting a flat and patterned surface morphology, respectively. Whereas the iron silicides are found across the whole surface of the flat sample, they are concentrated at the top of ridges at the rippled surface. A depth resolved analysis of the chemical states of Si and Fe atoms in the near surface region was performed by combining X-ray photoelectron spectroscopy and X-ray absorption spectroscopy (XAS) using synchrotron radiation. The chemical shift and the line shape of the Si 2p core levels and valence bands were measured and associated with the formation of silicide bonds of different stoichiometric composition changing from an Fe-rich silicides (Fe{sub 3}Si) close to the surface into a Si-rich silicide (FeSi{sub 2}) towards the inner interface to the Si(001) substrate. This finding is supported by XAS analysis at the Fe K-edge which shows changes of the chemical environment and the near order atomic coordination of the Fe atoms in the region close to surface. Because a similar Fe depth profile has been found for samples co-sputtered with Fe during Kr{sup +} ion irradiation, our results suggest the importance of chemically bonded Fe in the surface region for the process of ripple formation.

Khanbabaee, B., E-mail: khanbabaee@physik.uni-siegen.de; Pietsch, U. [Solid State Physics, University of Siegen, D-57068 Siegen (Germany); Lützenkirchen-Hecht, D. [Fachbereich C - Physik, Bergische Universität Wuppertal, D-42097 Wuppertal (Germany); Hübner, R.; Grenzer, J.; Facsko, S. [Helmholtz-Zentrum Dresden-Rossendorf, 01314 Dresden (Germany)

2014-07-14

330

Weldability of Fe[sub 3]Al-type Aluminide  

Microsoft Academic Search

An investigation was carried out to determine the weldability of a series of Fe[sub 3]Al-type alloys. Autogenous welds were made on thin sheets of iron aluminide alloys using gas tungsten arc (GTA) and electron beam (EB) welding processes at different travel speeds and power levels. The results indicate that although these alloys can be successfully welded using the EB welding

S. A. David; T. Zacharia

1993-01-01

331

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

NASA Astrophysics Data System (ADS)

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

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

2013-12-01

332

Elasticity and inelasticity of the SiC/Al-13Si-9Mg biomorphic metal ceramics  

NASA Astrophysics Data System (ADS)

The acoustic investigations of the elastic (Young’s modulus) and microplastic properties of a composite material, the SiC/Al-13Si-9Mg biomorphic metal ceramic, were performed. The ceramic was prepared by infiltration of the Al-13Si-9Mg melt into porous silicon carbide derived from wood of two species of trees, beech and sapele. The measurements were performed with a composite piezoelectric vibrator under resonance conditions, with rod-shaped samples vibrated longitudinally at about 100 kHz over a wide range of vibrational strain amplitudes, which included both the linear (amplitude-independent) and nonlinear (microplastic) regions. It was shown that the Young’s modulus and the microplastic properties of the composite are anisotropic and depend substantially on the tree species, particularly when longitudinal vibrations are excited in samples cut along the tree fibers.

Kardashev, B. K.; Orlova, T. S.; Smirnov, B. I.; Wilkes, T. E.; Faber, K. T.

2008-10-01

333

Viscosity Measurements of SiO2-"FeO"-CaO System in Equilibrium with Metallic Fe  

NASA Astrophysics Data System (ADS)

Viscosities of the synthetic slags have been measured at the temperature range of 1423 K to 1773 K (1150 °C to 1500 °C) in the SiO2-"FeO"-CaO system in equilibrium with Fe. The rotational spindle technique was employed in the measurements using molybdenum crucibles and spindles. Analysis of the quenched sample by electron probe X-ray microanalysis after the viscosity measurement enables the composition and microstructure of the slag to be directly linked with the viscosity. Effects of CaO and "FeO" on viscosity have been compared at different SiO2 concentrations. It was found that at low SiO2 concentration, the viscosities increase with the increasing CaO/"FeO" ratio. At high SiO2 concentration, the viscosities first decrease and then increase with the increasing CaO/"FeO" ratio. The activation energies increase with the increasing CaO/"FeO" ratio. The modified Quasi-chemical viscosity model has been further optimized in this system using the new viscosity measurements.

Chen, Mao; Zhao, Baojun

2014-11-01

334

Cohesive, electronic and magnetic properties of the transition metal aluminides FeAl CoAl and NiAl  

Microsoft Academic Search

Electronic structure calculations using the tight-binding linear muffin tin orbital (TB-LMTO) method have been performed for three transition metal aluminides, viz. FeAl, CoAl and NiAl. The band structures and density of states (DOS), valence electron charge density contours and Fermi surfaces have been obtained and compared with the available experimental results as well as with existing theoretical calculations. The lattice

V. Sundararajan; B. R. Sahu; D. G. Kanhere; P. V. Panat; G. P. Das

1995-01-01

335

Fabrication of High-Quality Co2FeSi/SiO x N y /Si(100) Tunnel Contacts Using Radical-Oxynitridation-Formed SiO x N y Barrier for Si-Based Spin Transistors  

NASA Astrophysics Data System (ADS)

A high-quality Co2FeSi (CFS)/SiO x N y /Si tunnel junction was fabricated, in which the SiO x N y barrier layer was formed by radical oxynitridation of an Si(100) substrate and the CFS electrode was formed by silicidation of an Fe/Co/amorphous-Si multilayer deposited on the barrier layer. The ultrathin SiO x N y barrier layer completely blocked diffusion of Co and Fe atoms into the Si substrate during rapid thermal annealing (RTA) for the silicidation. X-ray diffraction investigations clarified that the CFS film on the ultrathin SiO x N y barrier layer exhibited a highly (110)-oriented texture structure and that the film had the L21 structure with a high degree of L21 order. High resolution cross-sectional transmission electron microscopy investigations revealed that the CFS/SiO x N y interface was atomically flat and that the crystal lattice of the CFS film was directly grown on the SiO x N y surface without degradation of the crystallinity at the interface.

Takamura, Yota; Hayashi, Kengo; Shuto, Yusuke; Sugahara, Satoshi

2012-05-01

336

Electrical properties of p-type ?-FeSi 2 single crystals grown from Ga and Zn solvents  

Microsoft Academic Search

The electrical properties of ?-FeSi2 single crystals grown from solutions were investigated by the Hall effect measurements. The crystals grown from Ga solvent (Ga-?-FeSi2) and Zn solvent (Zn-?-FeSi2) showed p-type conduction. The resistivities at RT of Ga-?-FeSi2 and Zn-?-FeSi2 were 0.02–0.03 ? cm (Ga) and 0.4–2 ? cm (Zn), respectively. The hole concentration and Hall mobility at RT were (1–2)×1019

H. Udono; I Kikuma

2004-01-01

337

Tuning magnetization dynamic properties of Fe-SiO{sub 2} multilayers by oblique deposition  

SciTech Connect

The static and dynamic magnetic properties of Fe-SiO{sub 2} multilayers fabricated onto Si(100) substrates by a radio frequency sputter-deposition system are investigated as functions of deposition angle and Fe thickness. By changing the oblique deposition angle, one can effectively tune the ferromagnetic resonance frequency from 1.7 to 3.5 GHz. In addition, the frequency linewidth is significantly changed with the oblique deposition angle when the Fe layer is thick, but it is almost constant in the case of small Fe thickness.

Phuoc, Nguyen N.; Xu Feng [Temasek Laboratories, National University of Singapore, 5A Engineering Drive 2, Singapore 117411 (Singapore); Ong, C. K. [Department of Physics, Center for Superconducting and Magnetic Materials, National University of Singapore, 2 Science Drive 3, Singapore 117542 (Singapore)

2009-06-01

338

Melting and casting of FeAl-based cast alloy  

SciTech Connect

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.

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

339

Solid-state reactions upon mechanical alloying of an Fe32Al68 binary mixture  

NASA Astrophysics Data System (ADS)

The sequence of solid-state reactions that occur upon mechanical alloying of powder mixtures of Al and Fe taken in an atomic ratio of 68: 32 has been studied by the methods of X-ray diffraction analysis, Mössbauer spectrometry, and Auger spectrometry. Upon the formation of a nanocrystalline state (<10 nm), there takes place a mutual penetration of Al atoms into Fe and Fe atoms into Al particles. The rate of consumption of the fcc Al is substantially higher than that of the bcc Fe. The process of the mechanical alloying (MA) was found to be two-stage. At the first stage, up to 2 at % Fe is dissolved in the fcc Al, and an amorphous Fe25Al75 phase is formed in the interfaces, whose amount reaches 70 at % at the finish of the initial stage. In the interfaces of the ?-Fe phase, a disordered bcc phase of composition Fe66Al34 is formed, which contains up to 12 at % Al segregates. At the second stage, the amorphous phase crystallizes into an orthorhombic intermetallic compound Fe2Al5. The residual ?-Fe, bcc Fe66Al34, and segregated Al form a bcc phase of composition Fe35Al65.

Yelsukov, E. P.; Ul'yanov, A. L.; Protasov, A. V.; Kolodkin, D. A.

2012-06-01

340

High temperature properties of equiatomic FeAl with ternary additions  

NASA Technical Reports Server (NTRS)

The aluminide intermetallic compounds are considered potential structural materials for aerospace applications. The B2 binary aluminide FeAl has a melting point in excess of 1500 K, is of simple cubic structure, exists over a wide range of composition with solubility for third elements and is potentially self-protecting in extreme environments. The B2 FeAl compound has been alloyed with 1 to 5 at. pct ternary additions of Si, Ti, Zr, Hf, Cr, Ni, Co, Nb, Ta, Mo, W, and Re. The alloys were prepared by blending a third elemental powder with pre-alloyed binary FeAl powder. Consolidation was by hot extrusion at 1250 K. Annealing studies on the extruded rods showed that the third element addition can be classified into three categories based upon the amount of homogenization and the extent of solid solutioning. Constant strain rate compression tests were performed to determine the flow stress as a function of temperature and composition. The mechanical strength behavior was dependent upon the third element homogenization classification.

Titran, R. H.; Vedula, K. M.; Anderson, G. G.

1985-01-01

341

High temperature properties of equiatomic FeAl with ternary additions  

NASA Technical Reports Server (NTRS)

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.

Titran, R. H.; Vedula, K. M.; Anderson, G. G.

1984-01-01

342

Iron Oxidation State and Compressional Behaviors of Al,Fe-rich Mantle Silicate Perovskite up to 90 GPa  

NASA Astrophysics Data System (ADS)

Magnesium silicate perovskite, the dominant lower-mantle phase, may contain much more Al and Fe in the subducting oceanic crust than in the normal mantle. Therefore, it is important to understand the physical properties of Al,Fe-rich mantle silicate perovskite. We have synthesized Fe,Al-rich mantle silicate perovskites from two different starting materials [Mg2FeAl2Si3O12 (Alm33) and Mg2.5Fe0.5Al2Si3O12 (Alm17)] and conducted in-situ synchrotron X-ray diffraction (GSECARS and HPCAT) and Mössbauer spectroscopy (Sector 3) in the laser heated diamond-anvil cell at Advanced Photon Source. The garnet starting materials were synthesized in the multi-anvil press at Arizona State University. The starting materials were mixed with 10 wt% Au powder (internal pressure standard) and loaded with an Ar or Ne pressure medium in the diamond-anvil cell for X-ray diffraction measurements. Pure starting materials are loaded in the diamond-anvil cell with an Ne or KCl pressure medium for synchrotron Mössbauer measurements. In synchrotron Mössbauer spectroscopy, we obtained pressure from the unit-cell volumes of pressure media combined with their equations of state. During the laser heating of the Alm33 starting material at ~66 GPa and ~2300 K, perovskite was synthesized with a small amount of stishovite. For the same starting material, pure perovskite was synthesized at 90 GPa and ~2300 K. For the Alm17 starting material, perovskite was synthesized with a small amount of stishovite at 65-92 GPa and ~2200K. Between 60 and 90 GPa, the unit-cell volumes of the Alm33 and Alm17 perovskites are only slightly higher (0.3-0.6%) than that of Mg-end member perovskite and are comparable to that of (Mg0.85Fe0.15)SiO3 perovskite, indicating higher density of the Al,Fe-rich perovskite in subducting oceanic crust than surrounding mantle. Both Al,Fe-rich perovskites show a steep increase in unit-cell volume during decompression between 60 and 40 GPa, suggesting either spin transition or metastability at the pressure range. We successfully quenched both Al,Fe-rich perovskites and measured the unit-cell volumes at 1 bar: 166.3×0.1 Å3 for Alm17 perovskite, and 165.0×0.2 Å3 for Alm33 perovskite. Our direct measurements indicate that the combined effects of Fe and Al on the unit-cell volume is much greater at lower pressures (~2%) than those observed at higher pressure (0.3-0.6%). The preliminary spectral fitting of synchrotron Mössbauer data indicates that 50~80% of iron is Fe3+ in both Al,Fe-rich pervoskites, suggesting that similar degree of charge disproportionation reaction occurs in Al-rich mantle silicate perovskite. This result is in disagreement with a recent thermodynamic prediction by Nakajima et al. (2012, JGR) that Fe3+ concentration may be very low (near zero) in Al-rich perovskite.

Zhang, Q.; Shim, S.; Meng, Y.; Prakapenka, V.; Alp, E. E.

2013-12-01

343

Structural influence on the magnetic and electronic properties of annealed Fe/Al multilayers.  

PubMed

Temperature dependent magnetic and electronic properties of electron beam evaporated Fe/Al multilayer samples (MLS) with an average composition of Fe0.70A1(0.30) (MLS-A) and Fe0.50Al0.50 (MLS-B) have been investigated. A ferromagnetic behaviour in MLS-A and nonmagnetic behaviour in MLS-B is obtained after annealing the multilayers at 400 degrees C. The different magnetic behaviours can be interpreted in terms of constant increase of Fe-3d and Al-3sp hybridization accompanied by an increased de-localization of the d-electrons participating in the strong bonding of Fe with Al leading to formation of different Fe-Al phases (Fe3Al in MLS-A) and (FeAl in MLS-B) as suggested from valence band photoemission and X-ray diffraction measurements. PMID:19049186

Brajpuriya, R; Tripathi, S; Sharma, A; Chaudhari, S M; Shripathi, T

2008-08-01

344

Permanent magnetic properties of nano-composite Sm2Fe15Si2C/?-Fe with Cu additive  

NASA Astrophysics Data System (ADS)

The ribbons of nano-composite Sm2Fe15Si2C/?-Fe with Cu additive were prepared by melt spinning at substrate velocity v=20 m/s. The analysis of x-ray diffraction patterns shows that the relative content of ?-Fe phase increases with increasing Fe percent in samples, and the average grain size of 2:17 carbides and ?-Fe in the ribbons determined by the Scherrer method is about 50 and 30 nm, respectively. The ribbons exhibit a single hard magnetic phase behavior and remanence enhancement, due to inter-grain exchange coupling between hard and soft magnetic phases. The remanence increases with the increase of iron content in samples, while the coercivity decreases rapidly. The highest maximum energy product around 10.7 MGOe was obtained for Sm8Fe76Cu4Si8C4 ribbons. The reversible and irreversible magnetization portions were analyzed from the recoil loops, and an irreversible nucleation field around 4.8 kOe for hard magnetic phase was observed in Sm8Fe76Cu4Si8C4 ribbons.

Zhang, Hong-wei; Zhang, Shao-ying; Shen, Bao-gen; Lin, Chin

1999-04-01

345

Non-oscillatory antiferromagnetic coupling in sputtered Fe/Si superlattices  

SciTech Connect

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.

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

346

Effect of Al on the sharpness of the MgSiO3 perovskite to post-perovskite phase transition  

E-print Network

Effect of Al on the sharpness of the MgSiO3 perovskite to post-perovskite phase transition S. Akber the influence of Al on the recently discovered perovskite to post-perovskite phase transition in MgSiO3. We examine three substitution mechanisms for Al in the two structures: MgSi ! AlAl; SiSiO ! AlAl5; and Si

Steinle-Neumann, Gerd

347

Wettability of AlSi5Mg on Spodumene  

NASA Astrophysics Data System (ADS)

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.

Fankhänel, Beate; Stelter, Michael; Voigt, Claudia; Aneziris, Christos G.

2015-02-01

348

Properties of Si-doped GaN and AlGaN/GaN heterostructures grown by RF-MBE on high resistivity Fe-doped GaN  

NASA Astrophysics Data System (ADS)

Silicon-doped GaN epilayers and AlGaN/GaN heterostructures were developed by nitrogen plasma-assisted molecular beam epitaxy on high resistivity iron-doped GaN (0001) templates and their properties were investigated by atomic force microscopy, x-ray diffraction and Hall effect measurements. In the case of high electron mobility transistors heterostructures, the AlN mole fraction and the thickness of the AlGaN barrier employed were in the range of from 0.17 to 0.36 and from 7.5 to 30 nm, respectively. All structures were capped with a 2 nm GaN layer. Despite the absence of Ga droplets formation on the surface, growth of both GaN and AlGaN by RF-MBE on the GaN (0001) surfaces followed a step-flow growth mode resulting in low surface roughness and very abrupt heterointerfaces, as revealed by XRD. Reciprocal space maps around the (101¯5) reciprocal space point reveal that the AlGaN barriers are fully coherent with the GaN layer. GaN layers, n-doped with silicon in the range from 10 15 to 10 19 cm -3 exhibited state of the art electrical properties, consistent with a low unintentional background doping level and low compensation ratio. The carrier concentration versus silicon cell temperatures followed an Arhenius behaviour in the whole investigated doping range. The degenerate 2DEG, at the AlGaN/GaN heteroiterfaces, exhibited high Hall mobilities reaching 1860 cm 2/V s at 300 K and 10 220 cm 2/V s at 77 K for a sheet carrier density of 9.6E12 cm -2. The two dimensional degenerate electron gas concentration in the GaN capped AlGaN/GaN structures was also calculated by self-consistent solving the Schrödinger-Poisson equations. Comparison with the experimental measured values reveals a Fermi level pinning of the GaN (0001) surface at about 0.8 eV below the GaN conduction band.

Iliopoulos, E.; Zervos, M.; Adikimenakis, A.; Tsagaraki, K.; Georgakilas, A.

2006-10-01

349

FeMn Metal Droplet Behavior in the MnO-SiO2-CaO Slag System  

NASA Astrophysics Data System (ADS)

Optimization of the MnO-SiO2-CaO-based slag composition in the FeMn decarburization refining process to minimize metal droplet entrainment has been studied. FeMn spherical droplets with average diameter of 2.5 mm were dispersed within the refining slag of the medium carbon grade ferro-manganese alloy process. Approximately 4.2 pct of the slag existed as FeMn droplets contributing to the overall metal yield loss in the current process. Sedimentation tests of slags with various SiO2 content ranging from 26 to 47 pct using Al2O3 crucibles held at 1773 K (1500 °C) for 30 minutes showed an improvement of the metal/slag separation. Estimated and measured viscosity of the slags showed SiO2 at 32 pct to be optimal for metal/slag separation. Changes in the SiO2 content to 32 pct in actual plant trials allowed significant decrease in the amount of metal droplet entrainment resulting in a decrease of metal in slag to 1.3 pct. Refining times for this optimized slag composition required at least 20 minutes holding for increased separation according to Stokes' law.

Jang, Hyoung-Soon; Ryu, Jae Wook; Sohn, Il

2014-11-01

350

Local moments and suppression of antiferromagnetism in correlated Zr4Fe4Si7  

NASA Astrophysics Data System (ADS)

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=98±1 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.

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

351

Local moments and suppression of antiferromagnetism in correlated Zr4Fe4Si7  

SciTech Connect

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 = 98 1 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.

Simonson, Jack [Stony Brook University (SUNY); Pezzoli, M [Stony Brook University (SUNY); Garlea, Vasile O [ORNL; Aronson, M. [Department of Physics and Astronomy, Stony Brook University

2013-01-01

352

Surface modification of Fe3O4@SiO2 microsphere by silane coupling agent  

NASA Astrophysics Data System (ADS)

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.

Ahangaran, Fatemeh; Hassanzadeh, Ali; Nouri, Sirous

2013-04-01

353

Spin injection studies on thin film Fe/MgO/Si tunneling devices  

NASA Astrophysics Data System (ADS)

We report progress on the injection of spin polarized electrons into 35 nm thick Si films, using Fe/MgO injector/tunnel barrier structures grown by molecular beam epitaxy on SIMOX silicon-on-insulator substrates. The device requires heavy top-surface n-type doping of the Si film to produce a suitable tunnel barrier, accomplished by diffusion from a spin-on phosphorous-doped glass. Measurements indicate a roughly exponential doping profile with 7E20 per cubic cm at the top surface and a 2 nm decay length. Three terminal measurements showed evidence of spin injection similar to reports of Jansen et al. [1], while injection with a thinner MgO barrier shows more complicated behavior. On-going measurements and modeling will be discussed.[4pt] [1] R. Jansen et al.; Nature 462; 491 (2009) Funding for this research was provided by the Center for Emergent Materials at the Ohio State University, an NSF MRSEC (Award Number DMR-0820414).

Beardsley, Jonas; Pu, Yong; Swartz, Adrian; Bhallamudi, Vidya; Kawakami, Roland; Johnston-Halperin, Ezekiel; Hammel, Chris; Pelz, Jon

2011-03-01

354

First principles study of Al-Si nanosized clusters on Si (1 0 0) -2×1  

NASA Astrophysics Data System (ADS)

Ab initio local density approximation calculations were performed to investigate the energetics and atomic structures of Al-Si nanosized clusters on Si(1 0 0)-2×1. The transition from the Al-2×2 surface phase to Al-Si nanosized clusters has been found energetically favorable. Three different cluster models were considered. The first one was proposed by Kotlyar et al. The second model was proposed by Bunk et al. for the Si(1 0 0)-In system and was adopted by Cocoletzi and Takeuchi for Si(1 0 0)-Al(3×4) reconstruction. Third model is the mixture of the first and second. It has a pyramidal form like the Bunk-Cocoletzi cluster, but eight Al atoms like Kotlyar's cluster. The Bunk-Cocoletzi model has been found the most favorable.

Zavodinsky, V. G.

2002-09-01

355

Mechanism of Catalytic Ozonation in Fe2O3/Al2O3@SBA-15 Aqueous Suspension for Destruction of Ibuprofen.  

PubMed

Fe2O3 and/or Al2O3 were supported on mesoporous SBA-15 by wet impregnation and calcinations with AlCl3 and FeCl3 as the metal precursor and were characterized by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and Fourier transform infrared spectra (FTIR) of adsorbed pyridine. Fe2O3/Al2O3@SBA-15 was found to be highly effective for the mineralization of ibuprofen aqueous solution with ozone. The characterization studies showed that Al-O-Si was formed by the substitution of Al(3+) for the hydrogen of surface Si-OH groups, not only resulting in high dispersion of Al2O3 and Fe2O3 on SBA-15, but also inducing the greatest amount of surface Lewis acid sites. By studies of in situ attenuated total reflection FTIR (ATR-FTIR), in situ Raman, and electron spin resonance (ESR) spectra, the chemisorbed ozone was decomposed into surface atomic oxygen species at the Lewis acid sites of Al(3+) while it was converted into surface adsorbed (•)OHads and O2(•-) radicals at the Lewis acid sites of Fe(3+). The combination of both Lewis acid sites of iron and aluminum onto Fe2O3/Al2O3@SBA-15 enhanced the formation of (•)OHads and O2(•-) radicals, leading to highest reactivity. Mechanisms of catalytic ozonation were proposed for the tested catalysts on the basis of all the experimental information. PMID:25564945

Bing, Jishuai; Hu, Chun; Nie, Yulun; Yang, Min; Qu, Jiuhui

2015-02-01

356

Templated fabrication and characterization of SiO2 nanotube covered Fe nanowires  

NASA Astrophysics Data System (ADS)

In this study, Fe nanowires coated with SiO2 nanotubes have been synthesized by electrodeposition method using anodic alumina oxide template. Before growing Fe nanowires, 6-8 nm thick SiO2 nanotubes are grown inside the template using a "surface sol-gel" technique. The nanotube structures were characterized by field emission scanning electron microscopy and energy dispersive x-ray spectroscopy. Magnetic properties of the SiO2 insulated Fe nanowires inside the membrane are characterized by superconducting quantum interference device. Coercivities of around 120 Oe with field parallel to the nanowire axis and 240 Oe with field perpendicular the nanowire axis are observed at room temperature. These values are comparable to Fe nanowires without insulating layer in membrane. The magnetic hysteresis loop suggests that the SiO2 insulated nanowires have uniaxial magnetic anisotropy with the easy axis magnetization direction along the nanowire arrays due to their large shape anisotropy.

Dastagir, Tawab; Yu, Hongbin

2014-05-01

357

Templated fabrication and characterization of SiO{sub 2} nanotube covered Fe nanowires  

SciTech Connect

In this study, Fe nanowires coated with SiO{sub 2} nanotubes have been synthesized by electrodeposition method using anodic alumina oxide template. Before growing Fe nanowires, 6–8?nm thick SiO{sub 2} nanotubes are grown inside the template using a “surface sol-gel” technique. The nanotube structures were characterized by field emission scanning electron microscopy and energy dispersive x-ray spectroscopy. Magnetic properties of the SiO{sub 2} insulated Fe nanowires inside the membrane are characterized by superconducting quantum interference device. Coercivities of around 120?Oe with field parallel to the nanowire axis and 240?Oe with field perpendicular the nanowire axis are observed at room temperature. These values are comparable to Fe nanowires without insulating layer in membrane. The magnetic hysteresis loop suggests that the SiO{sub 2} insulated nanowires have uniaxial magnetic anisotropy with the easy axis magnetization direction along the nanowire arrays due to their large shape anisotropy.

Dastagir, Tawab; Yu, Hongbin, E-mail: yuhb@asu.edu [Ira A. Fulton Schools of Engineering, School of Electrical, Computer and Energy Engineering, Arizona State University, Tempe, Arizona, 85287 (United States)

2014-05-07

358

Al-Si/SiC nanoparticles composites synthesized by double stir casting.  

PubMed

The present invention provides Al-Si/SiC nanoparticles composites with the composition of 7%Si, 15%SiC with average particle size (APS) of SiC, 20, 30, 40 nm and 65?m using a novel double stir casting method. The inventive nano-composites by double stir casting show a nearly uniform distribution and good dispersion of the nano-particles within the Al matrix, although small agglomeration was found in the matrix of the micro-composite. The enhancement in values of impact strength and tensile strength observed in this study is due to small particle size and good distribution of the nano particles, which were confirmed by SEM spectrum. Patents WO 2010135848 and WO2011/011601 have some relevant information about the topic developed in this study, because the principle in both cases relies on the interactions between metal matrix and the nano-particles. Hence, novel double stir casting method can be used to improve the properties of nano-composites. PMID:21428904

Aigbodion, V S

2011-11-01

359

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

NASA Technical Reports Server (NTRS)

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.

Whittenberger, J. Daniel

2004-01-01

360

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

SciTech Connect

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

Baddorf, A.P. [Oak Ridge National Lab., TN (United States); Chandavarkar, S.S. [Tennessee Univ., Knoxville, TN (United States). Dept. of Physics and Astronomy

1995-06-30

361

Structural evolution and grain growth kinetics of the mechanically alloyed Fe50Al50 during heat treatment.  

PubMed

Nanocrystalline FeAl powder is synthesized by subsequent heat treating the Fe50Al50 (at.%) alloy prepared by mechanical alloying. During annealing the milled FeAl powder, the grain growth of B2-FeAl occurs with the order transformation from Fe(Al) to B2-FeAl. The activation energy for the nanocrystalline FeAl growth is calculated to be 534.9 kJ/mol, according to the kinetics theory of nanocrystalline growth. The grain growth of FeAl is significantly inhibited especially at elevated temperature. PMID:21125910

Ren, Rong; Wu, Yucheng; Tang, Wenming; Wang, Fengtao; Zheng, Zhixiang

2010-08-01

362

Magnetic and structural properties of epitaxial c-FeSi films grown on MgO(100)  

Microsoft Academic Search

Conversion electron Mössbauer spectroscopy (CEMS) and superconducting quantum interference device (SQUID) magnetometry have been applied to study the metastable iron monosilicide phase (c-FeSi) with the B2 (or CsCl ) lattice structure synthesized by molecular beam epitaxy (MBE). Thin films of nominal composition of c-FeSi0.85 were grown by codeposition of Fe57 and Si onto MgO(100) carrying a thin Fe or Cr

M. Walterfang; W. Keune; K. Trounov; R. Peters; U. Rücker; K. Westerholt

2006-01-01

363

Group-IV-diluted magnetic semiconductor Fe x Si 1? x thin films grown by molecular beam epitaxy  

Microsoft Academic Search

FexSi1?x-diluted magnetic semiconductor films with thickness 40nm but different Fe concentrations of 4% and 7% were grown on Si(100) substrates at 200 or 250°C by molecular beam epitaxy. Cross-sectional transmission electron microscopy observation confirms the epitaxial growth of the FexSi1?x films on Si substrate, and no Fe-related clusters are found in the films. Uniform distributions of Fe are observed along

W. F. Su; L. Gong; J. L. Wang; S. Chen; Y. L. Fan; Z. M. Jiang

2009-01-01

364

Wear and Friction Behavior of the Spray-Deposited SiCp/Al-20Si-3Cu Functionally Graded Material  

NASA Astrophysics Data System (ADS)

The spray-deposited SiCp/Al-20Si-3Cu functionally graded material (FGM) can meet the structure design requirements of brake disk. The effects of rotational speed and load on the wear and friction behaviors of the SiCp/Al-20Si-3Cu FGM sliding against the resin matrix friction material were investigated. For comparison, the wear and friction behaviors of a commercially used cast iron (HT250) brake rotor were also studied. The results indicate that the friction coefficient of the SiCp/Al-20Si-3Cu FGM decreases constantly with the increase of load or rotational speed and is affected by the gradient distribution of SiC particles. The wear rate of the SiCp/Al-20Si-3Cu FGM firstly increases, then decreases and finally increases again with increasing load or speed, and is about 1/10 of that of HT250. Based on observations and analyses on the morphology and substructure of the worn surface, the mechanical mixing layer acts as a protective coating and lubricant, and its thickness reduces with the SiC content increasing. Furthermore, it is proposed that the dominant wear mechanism of SiCp/Al-20Si-3Cu FGM changes from the abrasive wear to the oxidative wear and further to the delamination wear with increasing load or speed.

Su, B.; Yan, H. G.; Chen, J. H.; Zeng, P. L.; Chen, G.; Chen, C. C.

2013-05-01

365

Characterization of Fe–Mn–Si–Cr shape memory alloys containing VN precipitates  

Microsoft Academic Search

An Fe–28Mn–6Si–5Cr shape memory alloy containing VN coherent precipitates has been developed so that mechanical properties and shape recovery are high enough to be applied to pipe joining of steel pipes. The proof stress over 400MPa and 3.4% of recovery strain are obtained on aging, where VN compounds are formed homogeneously in the parent Fe–28Mn–6Si–5Cr material.Electron microscopic observation has indicated

Hiroshi Kubo; Kimio Nakamura; Susan Farjami; Tadakatsu Maruyama

2004-01-01

366

Solid-liquid phase equilibria at 727 °C in the ternary system Fe-Mg-Si  

Microsoft Academic Search

The solid-liquid phase equilibria in the Fe-Mg-Si ternary system were experimentally investigated at 727 °C by two complementary\\u000a approaches: reaction to equilibrium of Fe-Mg-Si powder mixtures and growth of reaction zones at the interface of diffusion\\u000a couples. X-ray powder diffraction, optical metallography (OM), scanning electron microscopy (SEM), and electron probe microanalysis\\u000a (EPMA) were used to characterize the phases formed in

D. Pierre; M. Peronnet; F. Bosselet; J. C. Viala; J. Bouix

2000-01-01

367

Soft magnetic properties of nanocrystalline Fe 100- xSi x (15< x<34) alloys  

NASA Astrophysics Data System (ADS)

Nanocrystalline Fe 100- xSi x (15< x<34) alloys have been prepared by melt spinning with high cooling rate. We have found by X-ray diffraction that the basic cubic symmetry could be extended up to 34 at% Si. Around the composition of Fe 2Si, a single-phase metastable B2 structure was found. If the quenching is not properly conducted, traces of hexagonal Fe 5Si 3 appear, which is detrimental to the soft magnetic properties. Our MS, TC, K, Dsp and ? results complement the existing (up to 25 at%) data and their soft magnetic properties are herein presented for the first time. The frequency dependence of the complex permeability in this high Si content region is comparable with that of NiZn ferrite.

Varga, L. K.; Mazaleyrat, F.; Kovac, J.; Kákay, A.

2000-06-01

368

Diffusion in single crystal of melilite: interdiffusion of Al + Al vs. Mg + Si  

Microsoft Academic Search

Interdiffusion coefficients of Al + Al vs. Mg + Si in the gehlenite–åkermanite system of melilite were determined by coupled\\u000a annealing of synthesized end-member single crystals. The observed diffusion coefficients for a couple-annealed sample vary\\u000a for about 2 orders of magnitude, showing strong dependence on the gehlenite–åkermanite composition: diffusion coefficient\\u000a observed at 1350 °C, for example, is 3 × 10?13

H. Nagasawa; T. Suzuki; M. Ito; M. Morioka

2001-01-01

369

Defect Band Characteristics in Mg-Al and Al-Si High-Pressure Die Castings  

Microsoft Academic Search

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

C. M. Gourlay; H. I. Laukli; A. K. Dahle

2007-01-01

370

Defect Band Characteristics in Mg-Al and Al-Si High-Pressure Die Castings  

Microsoft Academic Search

Bands of positive macrosegregation and porosity commonly follow the surface contour of components produced by high-pressure die casting (HPDC). In this article, Al alloy AlSi7Mg and Mg alloys AZ91 and AM60 were cast into tensile test bars using cold-chamber (cc) HPDC. Microstructural characterization revealed that externally solidified crystals (ESCs) are not necessary for defect band formation, and that defect bands

C. M. Gourlay; H. I. Laukli; A. K. Dahle

2007-01-01

371

Drilling of Al—Mg—Cu alloys and Al—Mg—Cu\\/SiC composites  

Microsoft Academic Search

Metal matrix composites are widely used in engineering applications including automotive, aircraft, and military industries. In this study, different Al—4 wt%Mg—Cu alloys, and Al—4 wt%Mg—Cu\\/SiC composites were drilled on a vertical drilling machine using moderate speed and general purpose high-speed steel tools. The machinability parameters studied in this research were drilling forces (torque and thrust force) and surface roughness of

Abdalla Alrashdan; Ahmad T. Mayyas; Adel Mahamood Hassan; Mohammed T. Hayajneh

2011-01-01

372

The optical properties of ?-FeSi 2 fabricated by ion beam assisted sputtering  

NASA Astrophysics Data System (ADS)

?-FeSi 2 has been shown to have a minimum direct band gap of 0.87 eV [T.D. Hunt, K.J. Reeson, K.P. Homewood, S.W. Teon, R.M. Gwilliam, B.J. Sealy, Nucl. Instr. and Meth. B 84 (1994) 168-171] which leads to the opportunity for Si based opto-electronics, optical communications and optical interconnects. Electroluminescence has been reported from structures containing ?-FeSi 2, which were produced by high dose ion implantation and annealing [D. Leong, M.A. Harry, K.J. Reeson, K.P. Homewood, Nature 387 (12 June 1987) 686]. In this paper we report the formation of ?-FeSi 2 by ion beam assisted co-sputtering of Fe and Si in varying percentages. The layers were deposited with a varying Fe/Si ratio, with a Si capping layer applied to prevent oxidation. Separate regions of the sample were investigated at room temperature using optical absorption, to measure the band gap values. Absorption under the fundamental edge was also analysed at room temperature. Further investigations looked at the temperature dependence of the band gap and the absorption under the fundamental edge. The results showed that a variety of Fe/Si ratios produced ?-FeSi 2, the formation of which was ascertained by the presence of a suitable band gap value [0.83-0.88 eV]. Absorption under the fundamental edge was shown to follow an exponential Urbach tail [C.H. Grein, S. John, Phys. Rev. B 39 (1989) 1140]. The temperature measurements are in good agreement with the Einstein model.

McKinty, C. N.; Kewell, A. K.; Sharpe, J. S.; Lourenço, M. A.; Butler, T. M.; Valizadeh, R.; Colligon, J. S.; Reeson Kirkby, K. J.; Homewood, K. P.

2000-03-01

373

Impact of SiO2 on Al–Al thermocompression wafer bonding  

NASA Astrophysics Data System (ADS)

Al–Al thermocompression bonding suitable for wafer level sealing of MEMS devices has been investigated. This paper presents a comparison of thermocompression bonding of Al films deposited on Si with and without a thermal oxide (SiO2 film). Laminates of diameter 150?mm containing device sealing frames of width 200?µm were realized. The wafers were bonded by applying a bond force of 36 or 60?kN at bonding temperatures ranging from 300–550?°C for bonding times of 15, 30 or 60?min. The effects of these process variations on the quality of the bonded laminates have been studied. The bond quality was estimated by measurements of dicing yield, tensile strength, amount of cohesive fracture in Si and interfacial characterization. The mean bond strength of the tested structures ranged from 18–61?MPa. The laminates with an SiO2 film had higher dicing yield and bond strength than the laminates without SiO2 for a 400?°C bonding temperature. The bond strength increased with increasing bonding temperature and bond force. The laminates bonded for 30 and 60?min at 400?°C and 60?kN had similar bond strength and amount of cohesive fracture in the bulk silicon, while the laminates bonded for 15?min had significantly lower bond strength and amount of cohesive fracture in the bulk silicon.

Malik, Nishant; Schjølberg-Henriksen, Kari; Poppe, Erik U.; Taklo, Maaike M. V.; Finstad, Terje G.

2015-03-01

374

Uniaxial magnetic anisotropy of quasi-one-dimensional Fe chains on Pb /Si  

NASA Astrophysics Data System (ADS)

We fabricated quasi-one-dimensional Fe chains on a 4° miscut Si (111) substrate with a Pb film as a buffer layer. The magnetic properties and morphology of Fe chains were investigated by means of scanning tunneling microscope (STM) and surface magneto-optical Kerr effect (SMOKE). STM images show that Fe chains are formed by Fe random islands along the steps of the Pb film due to step decoration. SMOKE data indicate that the Fe chains exhibit in-plane uniaxial magnetic anisotropy along the step direction. The effective in-plane uniaxial anisotropy constant at room temperature was determined by means of electron spin resonance.

Sun, Da-Li; Wang, De-Yong; Du, Hai-Feng; Ning, Wei; Gao, Jian-Hua; Fang, Ya-Peng; Zhang, Xiang-Qun; Sun, Young; Cheng, Zhao-Hua; Shen, Jian

2009-01-01

375

Development of dispersion U(Mo)/Al-Si miniplates fabricated at 500 °C with Al 6061 as cladding  

NASA Astrophysics Data System (ADS)

In the frame of U(Mo) dispersion fuel elements qualification, Si additions to Al matrix arose as a promising solution to the unacceptable failures found when pure Al is used. Analysis of as-fabricated fuel plates made with Al-Si matrices demonstrated that good irradiation behavior is correlated with the formation during fabrication of a Si-containing interaction layer around the U(Mo) particles. Thus, the analysis of the influence of fabrication parameters becomes important. Studies on Al-Si dispersion miniplates fabricated in CNEA, Argentina, have been initiated to determine how to obtain the better interaction layer characteristics with the lesser modifications to the fabrication process and the smaller amount of Si in the matrix. In this work results for miniplates made of atomized U-7 wt%Mo particles dispersed in Al-2 wt%Si and Al-4 wt%Si matrices, obtained by mixing pure Al and Si powders, and Al 6061 as cladding are presented. Interaction layer grown during fabrication process (500 °C) consists of Si-containing phases being U(Al, Si)3 its principal component. Its uniformity is not satisfactory due to the formation of an oxide layer.

Mirandou, M. I.; Aricó, S. F.; Balart, S. N.; Fabro, J. O.

2015-02-01

376

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

SciTech Connect

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

Kim, Hyong June

2011-12-01

377

Prediction of a potential high-pressure structure of FeSiO3  

NASA Astrophysics Data System (ADS)

We predict a candidate high-temperature, high-pressure structure of FeSiO3 with space-group symmetry Cmmm by applying an evolutionary algorithm within density functional theory (DFT)+U that we call post-perovskite II (PPv-II). An exhaustive search found no other competitive candidate structures with ABO3 composition. We compared the x-ray diffraction pattern of FeSiO3 PPv-II with experimental results of the recently reported "H phase" of (Fe,Mg)SiO3. The intensities and positions of two main x-ray diffraction peaks of PPv-II FeSiO3 compare well with those of the H phase. We also calculated the static equation of state, the enthalpy, and the bulk modulus of the PPv-II phase and compared it with those of the perovskite (Pv) and post-perovskite (PPv) phases of FeSiO3. According to the static DFT+U computations, the PPv-II phase of FeSiO3 is less stable than the Pv and PPv phases under lower mantle pressure conditions at T =0 K and has a higher volume. PPv-II may be entropically stabilized, and may be a stable phase in Earth's lower mantle, coexisting with -PbO2 (columbite-structure) silica and perovskite, or with magnesiowustite and/or ferropericlase, depending on the bulk composition.

Cohen, R. E.; Lin, Yangzheng

2014-10-01

378

A comparative wear study on Al-Li and Al-Li/SiC composite  

SciTech Connect

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.

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

379

A comparative wear study on Al-Li and Al-Li/SiC composite  

NASA Astrophysics Data System (ADS)

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 Al2O3 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-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.

Okumus, S. Cem; Karslioglu, Ramazan; Akbulut, Hatem

2013-12-01

380

Structural, Optical, and Electrical Characterization of Al/ n-ZnO/ p-Si/Al Heterostructures  

NASA Astrophysics Data System (ADS)

For heterojunction fabrication, zinc oxide thin films were grown on p-Si by pulsed laser deposition. X-ray diffraction patterns were used to study the grain size and morphology of the films. The optical properties of the films were studied by UV-visible and photoluminescence spectroscopy. Experimental observations confirmed that the deposited films have potential for sharp emission in the visible region. High-purity (99.999%) vacuum evaporated aluminium metal was used to make contacts to the n-ZnO and p-Si. The current-voltage characteristics of the Al/ n-ZnO/ p-Si(100)/Al heterostructure measured over the temperature range 60-300 K were studied on the basis of the thermionic emission diffusion mechanism. The equivalent Schottky barrier height and the diode ideality factor were determined by fitting measured current-voltage data to the thermionic emission diffusion equation. It was observed that the barrier height decreased and the ideality factor increased with decreasing temperature, and that the activation energy plot was non-linear at low temperature. These characteristics are attributed to the Gaussian distribution of barrier heights. The capacitance-voltage characteristics of the Al/ n-ZnO/ p-Si(100)/Al heterostructure diode were studied over a wide temperature range. The impurity concentration in deposited n-type ZnO films was estimated from measured capacitance-voltage data.

Kumar, Rajender; Chand, Subhash

2015-01-01

381

Effect of Ni on eutectic structural evolution in hypereutectic Al–Mg 2Si cast alloys  

Microsoft Academic Search

The aim of this work is to investigate the eutectic structural evolution of hypereutectic Al–20% Mg2Si with Ni addition under a gravity casting process. Three-dimensional morphologies of eutectic phases were observed in detail using field emission scanning electron microscopy, after Al matrix was removed by deep etching or extraction. The results show that Al–Mg2Si binary eutectic gradually evolves into Al–Mg2Si–NiAl3

Chong Li; Yaping Wu; Hui Li; Yuying Wu; Xiangfa Liu

2010-01-01

382

Si and Fe depletion in Galactic star-forming regions observed by the Spitzer Space Telescope  

NASA Astrophysics Data System (ADS)

We report the results of the mid-infrared spectroscopy of 14 Galactic star-forming regions with the high-resolution modules of the Infrared Spectrograph (IRS) on board the Spitzer Space Telescope. We detected Si II 35 micron, Fe II 26 micron, and Fe III 23 micron as well as S III 33 micron and H_2 S(0) 28 um emission lines. Based on photodissociation and H II region models the gas-phase Si and Fe abundance are suggested to be 3-100% and <22% of the solar abundance, respectively. Since the Fe II 26 micron, and Fe III 23 micron emissions are weak, the high sensitivity of the IRS enables to derive the gas-phase Fe abundance widely in star-forming regions. The derived gas-phase Si abundance is much larger than that in cool interstellar clouds and that of Fe. The present study indicates that 3-100% of Si atoms and <22% of Fe atoms are included in dust grains which are destroyed easily in H II regions, probably by the UV radiation. We discuss possible mechanisms to account for the observed trend: mantles which are photodesorbed by UV photons, organometallic complexes, or small grains.

Okada, Y.; Onaka, T.; Miyata, T.; Okamoto, Y. K.; Sakon, I.; Shibai, H.; Takahashi, H.

2009-01-01

383

Wear resistance of TiAlSiN thin coatings.  

PubMed

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

Silva, F J G; Martinho, R P; Alexandre, R J D; Baptista, A P M

2012-12-01

384

Large-scale synthesis of ear-like Si{sub 3}N{sub 4} dendrites from SiO{sub 2}/Fe composites and Si powders  

SciTech Connect

Large-scale ear-like Si{sub 3}N{sub 4} dendrites were prepared by the reaction of SiO{sub 2}/Fe composites and Si powders in N{sub 2} atmosphere. The product was characterized by field emission scanning electron microscopy, X-ray diffraction, and transmission electron microscopy. The results reveal that the product mainly consists of ear-like Si{sub 3}N{sub 4} dendrites with crystal structures, which have a length of several microns and a diameter of 100-200 nm. Nanosized ladder-like Si{sub 3}N{sub 4} was also obtained when changing the Fe content in the SiO{sub 2}/Fe composites. The Si{sub 3}N{sub 4} nanoladders have a length of hundreds nanometers to several microns and a width of 100-300 nm. The ear-like Si{sub 3}N{sub 4} dendrites are formed from a two-step growth process, the formation of inner stem structures followed by the epitaxial growth of secondary branches.

Wang Feng [State Key Laboratory of Coal Conversion, Institute of Coal Chemistry, CAS, Taiyuan 030001 (China); Graduate School of the Chinese Academy of Sciences, Beijing 100039 (China); Jin Guoqiang; Wang Yingyong [State Key Laboratory of Coal Conversion, Institute of Coal Chemistry, CAS, Taiyuan 030001 (China); Guo Xiangyun [State Key Laboratory of Coal Conversion, Institute of Coal Chemistry, CAS, Taiyuan 030001 (China)], E-mail: xyguo@sxicc.ac.cn

2008-07-01

385

Viscosities of melts in the Na 2O?FeO?Fe 2O 3?SiO 2 system and factors controlling relative viscosities of fully polymerized silicate melts  

NASA Astrophysics Data System (ADS)

The viscosity-temperature relationships of nine melts in the Na 2O?FeO?Fe 2O 3?SiO 2 system (in equilibrium with air) have been measured in the temperature range of 1450-800°C, using the concentric cylinder method. 57Fe Mössbauer spectra were obtained on quenched samples and show that all melts with ? 20 mole% ferrite component contain ? 95% Fe as tetrahedrally-coordinated ferric ions. The compositions investigated lie along the SiO 2?NaFeO 2 and Na 2Si 4O 9?Na 6Fe 4O 9 joins. The viscosities of m decrease strongly with decreasing silicate content along these joins. In contrast, the temperature dependence of viscosity does not vary significantly along these joins. Comparison with equivalent melt compositions (related by the trivalent cation exchange operators AlFe -1, BFe -1 and GaFe -1) in the Na 2O?Al 2O 3?SiO 2, Na 2O?B 2O 3?SiO 2 and Na 2O-Ga 2O 3 viscosities decrease in the order aluminosilicate > ferrosilicate, (galliosilicate ?) > borosilicate. Thp electronegativities of the trivalent cations are inversely correlated with the relative viscosities of melts in these systems. Similarly, the electronegativities of network-stabilizing cations are inversely correlated with melt viscosity for alkali and alkaline-earth aluminosilicate melt systems. The variation in the viscosity of tectosilicate melts is correlated with estimated average T-O-T bond angles, and exothermic heats of solution of quench glasses. Structural controls of viscosity discussed are tetrahedral ordering and relative bond strengths. The acmite component in natural, peralkaline, silicic volcanics will not contribute directly to high melt viscosities for these lavas.

Dingwell, Donald B.; Virgo, David

1988-02-01

386

Behavior of insoluble particles during parabolic flight solidification processing of Fe-C-Si and Fe-C-V alloys  

NASA Technical Reports Server (NTRS)

In a high-g rapid solidification environment, Fe-base alloy insoluble particles at the solidification interface may be pushed ahead of the interface or may be trapped in the solid, depending on the correlation of various interface energies, the solidification rates, and the Stokes force; particle agglomeration due to buoyancy-driven convection further complicates the problem. Attention is presently given to results obtained for directionally solidified Fe-C-Si and Fe-C-V alloys during parabolic low-g flight and ground experiments. In these systems, graphite and vanadium carbide can be considered to be the insoluble particles.

Stefanescu, D. M.; Fiske, M. R.; Curreri, P. A.

1986-01-01

387

Effect of (Mn + Cr) addition on the microstructure and thermal stability of spray-formed hypereutectic Al–Si alloys  

Microsoft Academic Search

Microstructures and thermal stability of hypereutectic Al–Si alloys with or without (Mn+Cr) addition, prepared via Spray Forming technique, are studied and compared with traditional cast alloys with same composition, using scanning electron microscopy with energy diffraction spectrum, X-ray diffraction, transmission electron microscopy and differential scanning calorimeter. The results show that the Fe-bearing and primary silicon phases in SF-3C alloy can

L. G. Hou; H. Cui; Y. H. Cai; J. S. Zhang

2009-01-01

388

Ab-initio calculation of (101) and (100) surface for ? - FeSi 2  

Microsoft Academic Search

We study the atomic and electric structure on the (101) and (100) surface of ?- FeSi2 by ab-initio calculation using the projector augmented wave method (PAW). The cohesive energy calculated with the slab model show that the structure Si layer biased in the surface is stable. The simulated STM image indicate that the charge in the neighborhood of Fermi level

Satoru Tanimoto; Takatoshi Nagano

2011-01-01

389

On the entropy of glaucophane Na2Mg3Al2Si8O22(OH)2  

USGS Publications Warehouse

The heat capacity of glaucophane from the Sesia-Lanza region of Italy having the approximate composition (Na1.93Ca0.05Fe0.02) (Mg2.60Fe0.41) (Al1.83Fe0.15Cr0.01) (Si7.92Al0.08)O22(OH)2 was measured by adiabatic calorimetry between 4.6 and 359.4 K. After correcting the Cp0data to values for ideal glaucophane, Na2Mg3Al2Si8O22(OH)2 the third-law entropy S2980-S00was calculated to be 541.2??3.0 J??mol-1??K-1. Our value for S2980-S00is 12.0 J??mol-1??K-1 (2.2%) smaller than the value of Likhoydov et al. (1982), 553.2??3.0, is within 6.2 J??mol-1??K-1 of the value estimated by Holland (1988), and agrees remarkably well with the value calculated by Gillet et al. (1989) from spectroscopic data, 539 J??mol-1??K-1. ?? 1991 Springer-Verlag.

Robie, R.A.; Hemingway, B.S.; Gillet, P.; Reynard, B.

1991-01-01

390

Phase relation of C-Mg-Fe-Si-O system under various oxygen fugacity conditions by in situ X-ray diffraction experiments: Implication for planetary interior  

NASA Astrophysics Data System (ADS)

Carbon is one of the major volatile elements and very important in the Earth, primitive meteorites and some achondrites, such as ureilites. The abundance of carbon has been estimated to be 100 times higher than that in the CI chondrite, in some of the stars with exoplanets, such as the circumstellar gas around Beta Pictoris (Roberge et al., 2006). In such a gas, carbon-enriched planets, "carbon-planet", may be formed. Carbon-planet interior is likely to be composed mainly of Carbon-bearing phase, such as carbide, carbonate, graphite and diamond. Therefore, it is important to investigate phase relations of carbon-rich systems under high pressure conditions. In this study, C-enriched Mg-Si-Fe-O system was investigated at high pressure and temperature in order to understand the internal structure of the carbon-planets. Phase relations were studied based on 2 series of experiments; (I) textural observation and chemical analysis of the sample recovered from high pressure and temperature and (II) in situ X-ray diffraction experiments. We used several different mineral assemblages for the starting materials, as shown below: (i) (Mg1.8,Fe0.2)SiO4 + Fe + SiO2 + C, (ii) (Mg1.8,Fe0.2)SiO4 + Fe + Si + C, (iii) MgO + Fe + SiO2 + C, (iv) MgO + Fe + Si + C. Oxygen fugacity (fO2) of the sample varies depending on these assembleges due to different O amounts in the starting materials. Chemical analyses of the recovered samples were performed using an electron microprobe. In situ X-ray diffraction experiments were conducted at 4 and 15 GPa, and up to 1873 K at BL04B1 beamline, SPring-8 synchrotron facility. Different mineral assemblages were observed depending on the redox condition of the sample. The compositions of metallic melts changes from Fe-C compositions in oxidizing conditions to Fe-Si compositions in the reducing conditions. Based on in situ X-ray diffraction experiments at 4 GPa, FeSi and SiC peaks appeared at 1373 K in the most reducing sample (iv), whereas Fe3C appeared in the other samples. Metallic phases in all samples were melted at 1673 K. In the experiments about the starting materials (i), (ii) and (iv) at 15 GPa, Fe3C was formed at about 1073 K and Fe7C3 was formed at 1273 K. In the samples (ii) and (iv), FeSi was formed with Fe7C3 at 1273 K. This indicates that carbon reacts with metallic iron and any carbonates were not observed under the present experimental conditions. Therefore, these results may suggest that carbon exists in the mantle and/or core in some carbon-planets and carbon-bearing phases could be graphite/diamond, SiC and Fe-C alloy or Fe-Si-C alloy depending on the redox conditions at high pressure.

Takahashi, S.; Ohtani, E.; Terasaki, H.; Ito, Y.; Funakoshi, K.; Higo, Y.

2011-12-01

391

MOKE Study of Fe/Co/Al Multilayers  

SciTech Connect

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.

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

392

Investigation of the {Fe}/{Si} interface and its phase transformations  

NASA Astrophysics Data System (ADS)

Thin 57Fe films (3-10 Å) 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 Mössbauer 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.

Fanciulli, M.; Degroote, S.; Weyer, G.; Langouche, G.

1997-04-01

393

Size Effect of SiC Particle on Microstructures and Mechanical Properties of SiCp/Al Composites  

E-print Network

matrix composites reinforced with ceramic particles have some attractive properties such as high strengthCp/Al composites were fabricated using aluminum alloy ZL101 as the matrix material, and SiC particles a composite is stretched, most of external load transfers from soft Al matrix to hard SiCp reinforcement

Qin, Qinghua

394

Local formation of a Heusler structure in CoFe-Al alloys  

NASA Astrophysics Data System (ADS)

We systematically study the changes in the local atomic environments of Co in CoFe-Al alloys as a function of Al content by means of nuclear magnetic resonance. We find that a Co2FeAl Heusler type structure is formed on a local scale. The observed formation of a highly spin-polarized Heusler compound may explain the improved magnetotransport properties in CoFe-Al based current-perpendicular-to-the-plane spin-valves.

Wurmehl, S.; Jacobs, P. J.; Kohlhepp, J. T.; Swagten, H. J. M.; Koopmans, B.; Maat, S.; Carey, M. J.; Childress, J. R.

2011-01-01

395

Angle-dependent photovoltaic effect in Al-Si multilayers  

SciTech Connect

Al-Si multilayer stacks have been prepared by an alloying process from aluminum and silicon platelets. Irradiation of a stack with infrared to visible laser radiation generates photovoltaic signals depending on the angle of incidence of the laser beam with respect to the layer planes, with zero signal and a polarity reversal for beam and layers in parallel. Results are explained in terms of photoactive layers connected in series and symmetrically aligned along the stack axis. For light beams inclined with respect to the layer planes, asymmetry is introduced by fractional shadowing of photoactive regions due to the intransparent metallic layers.

Kyarad, A.; Lengfellner, H. [Institut fuer Experimentelle und Angewandte Physik, Universitaet Regensburg, 93040 Regensburg (Germany)

2005-10-31

396

Low Voltage EPMA of Lunar, Terrestrial, and Synthetic Fe-Si Compounds  

NASA Astrophysics Data System (ADS)

Iron silicides have been reported in lunar regolith, fulgarites, and Stardust samples. They are important because of the extreme reducing conditions required for formation. However, their small size (< 1 ?m) precludes quantitative measurements using conventional electron probe microanalysis (EPMA). Conventional EPMA uses high electron beam energies (15-20 keV) to eject inner shell electrons, and measures the characteristic photon energy emitted when an outer shell electron transitions into a vacant inner shell electron state. It is therefore not suited for analyses of most features under 2 ?m width, as the electron beam causes primary excitation of electrons in atoms outside of the feature of interest. To properly analyze samples under 1?m, one must use low (<5) keV electron beams. Newer field emission electron probes are able to focus low voltage beams to sizes required for down to 100 nanometer features. A recent study by Llovet et al. (2012) attempted to analyze bulk stainless steels using soft X-ray emissions, and demonstrated the problems (ie incorrect compositions) associated with soft X-ray EPMA. Problems include changes in peak position/shape of the available X-ray lines, increased sensitivity to surface contamination, and limited understanding of the mass absorption coefficients (MAC) for low energy (soft) X-rays. Our research focuses on obtaining a better understanding of soft X-ray EPMA, by studying the iron-silicon system. This system is particularly well suited for this aim as it involves only two elements, Si K? yields good results at low keV allowing us to focus on the problem of the Fe L lines, and a relatively large suite of possible Fe-Si phases exists to conduct analyses on. Prior soft X-ray analysis of iron has involved Fe L? and L?. Experimental values using Fe L? yield extremely high iron concentrations (e.g. 125 wt% totals). These lines lie on the cusp of a large spike in the MAC (the L3 absorption edge). If there is a slight shift in the peak position, the MAC could be wrong by up to an order of magnitude. It is difficult if not impossible to obtain accurate quantitative data using Fe L? or L?, due to peak shifts and related drastic change in MAC. There does, however, appear to be a soft X-ray line of iron (Fe Ll, the L3-M1 transition) which lies far enough away from the L3 absorption edge that is it unaffected by the drastic increase in the MAC. The Fe Ll peak generates low count rates, but with proper selection of crystals, long count times, and sufficient beam current, more accurate analysis is possible. Synthetic layered diffractors (45-60Å 2d spacing) must be used in order to be have enough counts on the Fe Ll peak. Low keV EPMA increases the sensitivity to surface effects (ie carbon contamination). The current/accelerating voltage used has a large effect on the rate of carbon accumulation/removal of carbon from the sample. With carbon coated samples it has been noted that with enough current, the carbon coating is removed in the first few minutes, until it reaches a baseline and builds back up, leading to large fluctuations in the X-ray counts of low keV lines of interest.

Gopon, P.; Fournelle, J.; Llovet, X.; Sobol, P.

2012-12-01

397

Bonding of WC with an iron aluminide (FeAl) intermetallic  

SciTech Connect

FeAl, which has high oxidation and sulfidation resistance, was shown to be thermodynamically compatible with WC. Calculations indicate that soly. of WC in liq. Fe-40at.%Al at 1450 C is about 2 at.%. Since liquid FeAl wets WC very well, the WC/FeAl system lends itself to liquid-phase sintering, resulting in close to theoretical densities. Almost fully dense cermets with 20.6 wt% FeAl binder were produced. With one-step infiltration, 98% dense cermets with only 7 wt% FeAl binder were fabricated. RT bend strengths and fracture toughness for WC-20.6 wt% FeAl reached 1680 MPa and 22 MPa{center_dot}m{sup 1/2}. Ductile binder fracture was observed on the fracture surfaces. Pores containing oxide inclusions were found, suggesting that improvements in processing are likely to further improve the mechanical properties. Insufficient process control may explain why WC/FeAlNi cermets did not show improved mechanical properties, although Ni strengthens FeAl. For WC bonded with FeAl, mechanical properties were measured at RT and 800 C. Bend strengths at 800 C in air increased with WC volume fraction, and fracture toughness were higher than at RT.

Schneibel, J.H.; Subramanian, R.

1996-08-01

398

Préparation et étude d'un oxysilicate de fer de valence mixte Fe 7(SiO 4)O 6 (iscorite)  

NASA Astrophysics Data System (ADS)

Un cristal de Fe 7SiO 10 a été isolé par J. Smuts, J. Steyn, et J. Boeyens ( Acta Crystallogr. B25, 1251 (1969) ), dans un réfractaire sidérurgique usagé, et appelé iscorite. Selon ces auteurs, la maille est monoclinique et la structure basée sur un empilement de blocs FeO et Fe 3SiO 6; mais le facteur d'accord est médiocre ( R = 0,165) et les distances interatomiques très incorrectes. Nous avons donc préparé, pour la première fois, cette phase, et montré en combinant l'analyse chimique, la densité, l'étude aux rayons X du système Fe?Si?O, et l'analyse d'un cristal à la microsonde, que la composition la plus correcte est Fe 7(Si 0.94Fe 0.06)O 10. L'étude d'un cristal confirme et précise la maille de Smuts et al.: monoclinique, avec a = 21,336(2), b = 3,0679(3), c = 5,8744(8)Å, ? = 98°,06(1), {P2}/{m} ou {P2 1}/{m}. Cependant les diagrammes de Weissenberg présentent des lignes continues de diffusion pour certaines strates qui indiquent un désordre microstructural intense. Il en va de même pour la diffraction des électrons. Il n'est donc pas étonnant que l'affinement, sur la base du modèle de Smuts et al., ait donné R = 0,09 dans l'un ou l'autre groupe d'espace. Les mesures magnétiques conduisent à un paramagnétisme avec forte contribution orbitale pour Fe 2+, et mise en ordre vers 250 K avec, en-dessous, un comportement de ferromagnétique faible. Contrairement à la wüstite, l'iscorite ne se dismute pas facilement; elle donne avec Fe 9PO 12 des solutions solides limitées. A crystal of Fe 7SiO 10 has been isolated by J. Smuts, J. Steyn, and J. Boeyens ( Acta Crystallogr. B25, 1251 (1969) ), from a furnace refractory brick, and has been called iscorite. According to these authors, the cell is monoclinic and the structure based upon a stacking of FeO and Fe 3SiO 6 blocks; however the reliability factor is poor ( R = 0.165) and the interatomic calculated distances are not correct. Therefore, we have prepared this phase for the first time; combining chemical analysis, density measurements, X-ray investigation of the Fe?Si?O system, and electron probe microanalysis of a crystal, we have shown that the correct composition is Fe 7(Si 0.94Fe 0.06)O 10. The crystal study confirms, with a higher accuracy, the parameters for the cell proposed by Smuts et al.: a = 21.336(2), b = 3.0679(3), c = 5.8744(8)Å, ? = 98°.06(1), {P2}/{m} or {P2 1}/{m}. However, the Weissenberg patterns display continuous diffusion lines, indicating an intense microstructural disorder, in agreement with the electron diffraction patterns. Hence it is not surprising to obtain, on the basis of the Smuts et al. model, a value R = 0.09 with both space groups. The magnetic measurements indicate a paramagnetism with strong orbital Fe 2+ contribution and a transition at ˜250 K to an ordered magnetic state, with a weak ferromagnetism below 250 K. In contrast to the case of wustite, iscorite does not easily disporportionate; it forms limited solid solutions with Fe 9PO 12.

Modaressi, Ali; Malaman, Bernard; Gleitzer, C.; Tilley, R. J. D.

1985-11-01

399

Preparation of surface plasmon resonance biosensor based on magnetic core/shell Fe3O4/SiO2 and Fe3O4/Ag/SiO2 nanoparticles.  

PubMed

In this paper, surface plasmon resonance biosensors based on magnetic core/shell Fe(3)O(4)/SiO(2) and Fe(3)O(4)/Ag/SiO(2) nanoparticles were developed for immunoassay. With Fe(3)O(4) and Fe(3)O(4)/Ag nanoparticles being used as seeding materials, Fe(3)O(4)/SiO(2) and Fe(3)O(4)/Ag/SiO(2) 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), transmission electronic microscopy (TEM), FTIR and UV-vis absorption spectrometry. The magnetic nanoparticles possess the unique superparamagnetism property, exceptional optical properties and good compatibilities, and could be used as immobilization matrix for goat anti-rabbit IgG. The magnetic nanoparticles can be easily immobilized on the surface of SPR biosensor chip by a magnetic pillar. The effects of Fe(3)O(4)/SiO(2) and Fe(3)O(4)/Ag/SiO(2) nanoparticles on the sensitivity of SPR biosensors were also investigated. As a result, the SPR biosensors based on Fe(3)O(4)/SiO(2) nanoparticles and Fe(3)O(4)/Ag/SiO(2) nanoparticles exhibit a response for rabbit IgG in the concentration range of 1.25-20.00 ?g ml(-1) and 0.30-20.00 ?g ml(-1), respectively. PMID:21353500

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

2011-06-01

400

Structural and magnetic stability of Fe{sub 2}NiSi  

SciTech Connect

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.

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