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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

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

2014-09-01

3

Al-Fe-Si (Aluminum-Iron-Silicon)  

SciTech Connect

[88Ray] reviewed the experimental results on the phase equilibria of this system. The reviewed data were presented as: (1) a liquidus surface for the entire composition range with isotherms at 50{degrees}C intervals; (2) a table of the invariant reactions on this liquidus surface; (3) liquidus and solidus projections near the Al-corner; (4) a table of selected crystallographic data on the ternary phases of the systems; (5) a pseudobinary section along the Fe{sub 3}Al-Fe{sub 3}Si line; (6) an isothermal section at 1000{degrees}C covering the entire composition range; (7) isothermal sections near the Al-corner at 560, 550, and 450{degrees}C; and (8) solubility limits of Si and Fe in Al at 577, 500, and 420{degrees}C.

Raghavan, V.

1994-08-01

4

Liquid metal corrosion of 316L, Fe 3 Al, and FeCrSi in molten Zn-Al baths  

Microsoft Academic Search

Corrosion tests of 316L and two intermetallic compounds Fe3Al and FeCrSi in industrial Galvanizing (Zn-0.18Al), GALFAN (Zn-5Al), GALVALUME (Zn-55Al), and Aluminizing (Al-8Si) baths\\u000a and lab-scale static baths were conducted. In on-line tests in industrial hot-dip baths, 316L steel shows better corrosion\\u000a resistance than Fe3Al in Galvanizing, GALFAN, and GALVALUME baths. The corrosion resistance of 316L and Fe3Al is similar in

Xingbo Liu; Ever Barbero; Jing Xu; Matthew Burris; Keh-Minn Chang; Vinod Sikka

2005-01-01

5

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

NASA Astrophysics Data System (ADS)

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

Ghosh, S. K.

2012-04-01

6

First-principles study of Fe and FeAl defects in SiGe alloys  

SciTech Connect

First-principles, spin-polarized local-density-functional calculations are used to model interstitial iron (Fe{sub i}) and its complexes with substitutional aluminum in dilute Si{sub x}Ge{sub 1-x} alloys (x<8%). We considered both the effect of direct bonding between Fe{sub i} or Fe{sub i}Al with Ge atoms in the x{yields}0 limit and the evolution of the defect properties with the alloy composition. It is found that Fe{sub i} prefers Si-rich regions, but when placed near a Ge atom, its (0/+) level is shifted toward the conduction band. However, the ionization energy of Fe{sup (+/+2)}-Al{sup -} is only slightly changed by the presence of neighboring Ge atoms in the proximity. It is also found that indirect alloying effects shift the donor levels of Fe{sub i} and FeAl at a fast rate toward the valence band. The acceptor levels, however, remain approximately at the same distance from E{sub v}.

Carvalho, A. [School of Physics, University of Exeter, Exeter EX4 4QL (United Kingdom); Ceramics Laboratory, Swiss Federal Institute of Technology (EPFL), CH-1015 Lausanne (Switzerland); Coutinho, J.; Barroso, M. [I3N and Department of Physics, University of Aveiro, Campus Santiago, 3810-193 Aveiro (Portugal); Jones, R. [School of Physics, University of Exeter, Exeter EX4 4QL (United Kingdom); Goss, J.; Briddon, P. R. [School of Natural Sciences, University of Newcastle upon Tyne, Newcastle upon Tyne, NE1 7RU (United Kingdom)

2008-09-15

7

Comparative analysis of mechanisms and kinetics of mechanical alloying in Fe-Al and Fe-Si systems  

SciTech Connect

A detailed study of the mechanical alloying processes in the Fe-32 at.% Al system was carried out using X-ray diffraction, Moessbauer spectroscopy, Auger spectroscopy, magnetic and chemical composition measurements. The results are compared with those for the Fe-32 at.% Si system obtained under the same milling conditions. Differences in the kinetics of solid state reactions are found, which do not depend on the differences in the individual properties (structure, melting temperature, mechanical properties, etc.) of Al and Si.

Yelsukov, E.P.; Ulyanov, A.L.; Dorofeev, G.A

2004-08-16

8

High temperature deformation behavior and mechanism of spray deposited Al-Fe-V-Si alloy  

Microsoft Academic Search

Al-8.5Fe-1.3V-1.7Si alloy was prepared by spray deposition and hot extrusion. The high temperature plastic deformation behavior of the spray deposited Al-8.5Fe-1.3V-1.7Si alloy was investigated in the strain rate range of 2.77 × 10?4?2.77 × 10?2s?1 and temperature range of 350–550 °C by Gleebe-1500 thermomechanical simulator. The mechanism of the high temperature plastic deformation of the alloys was studied by TEM

Yu-de XIAO; Wei WANG; Wen-xian LI

2007-01-01

9

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

NASA Astrophysics Data System (ADS)

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

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

2013-09-01

10

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

11

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

12

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

SciTech Connect

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

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

2003-04-22

13

Multi-channel magnetotransport in Co 2FeSi/(Al,Ga)As spin-LEDs  

NASA Astrophysics Data System (ADS)

We have performed Hall effect measurements on Co2FeSi/(Al,Ga)As spin light emitting diodes and have found unique field dependencies that differ strongly from the expected behaviors for both the ferromagnetic Co2FeSi layer and the underlying semiconductor structure. To understand such unique field dependencies, we have developed a multi-channel transport model for parallel transport through a ferromagnet and a semiconductor. By applying this model to our data for the Hall and sheet resistance, we extract values for the carrier density and mobility in the semiconductor layer. We find that these values decrease with increasing growth temperature of the Co2FeSi layer, presumably due to stronger in-diffusion of Co and Fe impurities, which compensate the n-type dopants in the underlying n-(Al, Ga) As layer. Despite such compensation, spin-LEDs with the Co2FeSi layer grown at the relatively high temperature of 280 °C exhibit the highest spin injection efficiencies of more than 50%, hence calling into question the requirement of electron tunneling through the ferromagnet/semiconductor Schottky barrier for efficient spin injection.

Farshchi, R.; Bruski, P.; Ramsteiner, M.; Herfort, J.; Brandt, O.; Manzke, Y.; Friedland, K.-J.; Grahn, H. T.

2011-03-01

14

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

15

Photovoltaic characteristics of p-beta-FeSi2(Al)\\/n-Si(100) heterojunction solar cells and the effects of interfacial engineering  

Microsoft Academic Search

Heterojunction solar cells with Al-alloyed polycrystalline p-type beta-phase iron disilicide [p-beta-FeSi2(Al)] on n-Si(100) were investigated. The p-beta-FeSi2(Al) was grown by sputter deposition and rapid-thermal annealing. Photocurrent of ~1.8 mA\\/cm2 and open-circuit voltage of ~63 mV were obtained for p-beta-FeSi2(Al)\\/n-Si(100)\\/Ti\\/Al control cells with indium-tin-oxide (ITO) top electrode. Open-circuit voltage increased considerably once thin Al layer was deposited before amorphous-FeSi2(Al) deposition. Furthermore,

G. K. Dalapati; S. L. Liew; A. S. W. Wong; Y. Chai; S. Y. Chiam; D. Z. Chi

2011-01-01

16

Laser processed TiC-Al13Fe4 composite layer formation on Al-Si alloy  

NASA Astrophysics Data System (ADS)

TiC reinforced with Al13Fe4 matrix composite layer is produced on Al-Si alloy using 5 kW CO2 laser. This attempt was made to identify the suitable coating compositions and laser processing parameters needed to form a TiC-Al13Fe4 composite layer. The study intended to form a composite layer which is having uniform TiC distribution, high hardness, high wear resistance and good adherence with substrate of Al-Si alloy. The results confirmed that the expected good quality composite layer has formed for the coating compositions of 75TiC-25Fe (wt%) and laser processing parameters of 2.5 kW laser power and 1.5 m min-1 scanning speed. TiC particles size varies from 10 to 20 ?m are reinforced with in-situ formed Al13Fe4 matrix in the composite layer. The good quality composite layer is exhibited an average hardness of about 750 HV and hardness distributions show very minimum fluctuations. The effect of TiC reinforcement with Al13Fe4 matrix in the composite layer displayed very less wear rate (3.98×10-7 mg m-1) than the substrate (3.85×10-6 mg m-1).

Viswanathan, A.; Sastikumar, D.; Kumar, Harish; Nath, A. K.

2012-09-01

17

Anomalous Hall effects in Co2FeSi Heusler compound films and Co2FeSi-Al2O3 granular films  

NASA Astrophysics Data System (ADS)

We fabricated three Co2FeSi Heusler compound films at different temperatures (room temperature, 673, and 873 K) by rf sputtering deposition method and a series of (Co2FeSi)x(Al2O3)1-x (0.4 ?x?1) granular films at room temperature by co-sputtering method. The structures as well as the temperature behaviors of anomalous Hall resistivities, low-field Hall sensitivities, and longitudinal resistivities of those films were investigated experimentally. We found that the Co2FeSi Heusler compound film deposited at room temperature is poorly crystallized, the film deposited at 673 K is crystallized in the disordered A2 type structure, and L21 and B2 structures are present in the film deposited at 873 K. For the Co2FeSi films deposited at 673 and 873 K, the saturated anomalous Hall resistivity ?As scales with the longitudinal resistivity ?xx as ?As??xxn, with n much larger than 2. There is no scaling relation between ?As and ?xx for the (Co2FeSi)x(Al2O3)1-x (0.58?x ?1, x =1 represents the Co2FeSi film deposited at room temperature) granular films. For the granular films, as x decreases from 1 to 0.67, the magnitude of ?xx increases by a factor of ˜25, whereas the magnitude enhancement in ?As is less than 50%, which strongly suggests that the longitudinal and anomalous Hall transports in ferromagnetic granular films are governed by different mechanisms. The low-field Hall sensitivities of (Co2FeSi)x(Al2O3)1-x films with x values of 0.6 and 0.65 are large and temperature insensitivity from 300 down to ˜75 K, which might make them be good candidate materials for low-field Hall sensors.

Qin, Zhu; Liu, Xin-Dian; Li, Zhi-Qing

2012-04-01

18

Alloy Composition and Dendrite Arm Spacing in Al-Si-Cu-Mg-Fe Alloys  

NASA Astrophysics Data System (ADS)

Six Al-Si-Cu-Mg-(Fe/Mn) alloys with two levels of each of Cu, Si, and Fe/Mn were cast in the form of quasi-directionally solidified plates. The secondary dendrite arm spacing (SDAS) was measured as a function of the distance from the chill end for each composition and related to the local cooling rate as determined by thermocouples embedded in one of the cast plates. For a given cooling rate, Si has a strong, consistently refining effect on the SDAS per unit of solute content. Cu showed its strongest refining effect at low-Si and high-Fe contents. It is argued that the scale of the SDAS is determined by a combination of five main factors: constitutional undercooling; the fraction of Al-Si eutectic; and the amount, morphology, and distribution of the various intermetallic phases. The first two factors affect the early stages of the dendrite structure and SDAS formation, whereas the ones involving intermetallics affect the dendrite-coarsening mechanisms in the post-eutectic stage. The latter ones are more sensitive to cooling rate than the ones involving solute in solution. The scales of both, SDAS and intermetallics, can be predetermined to a measurable extent through the solute content to best suit particular casting conditions.

Sivarupan, Tharmalingam; Caceres, Carlos H.; Taylor, John A.

2013-09-01

19

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

20

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

SciTech Connect

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

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

2010-07-15

21

The effects of Se in AlN-inhibited permeability 3% SiFe  

Microsoft Academic Search

One of the techniques for producing highly textured 3% SiFe involves the use of AlN precipitates for the stabilization of primary grains during the process of secondary recrystallization; however, the presence of S (presumably as MnS) was also found necessary. Because of the chemical similarity between S and Se, an investigation was made to determine if Se could be used

J. A. Salsgiver; D. J. McMahon

1976-01-01

22

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

23

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

24

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

25

Fe 2 ?Mg 2 and TiAl 2 ?MgSi 2 exchange reactions between clinopyroxenes and silicate melts  

Microsoft Academic Search

The interdependence of the Fe(Mg)?1 (e.g., FeO-MgO in silicate melt; CaFeSi2O6-CaMgSi2O6 in pyroxene) and TiAl2(MgSi2)?1 exchange reactions between silicate melts and coexisting Ca-pyroxene has been examined. High-calcium clinopyroxenes were grown in 1 atmosphere melting and crystallization experiments on rock powders spanning the composition range tholeiite to melilitite (1,092

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

1984-01-01

26

Crystal chemistry of ferric iron in (Mg,Fe)(Si,Al)O 3 majorite with implications for the transition zone  

Microsoft Academic Search

Fifteen samples of (Mg,Fe)SiO3 majorite with varying Fe\\/Mg composition and one sample of (Mg,Fe)(Si,Al)O3 majorite were synthesized at high pressure and temperature under different conditions of oxygen fugacity using a multianvil\\u000a press, and examined ex situ using X-ray diffraction and Mössbauer and optical absorption spectroscopy. The relative concentration\\u000a of Fe3+ increases both with total iron content and increasing oxygen fugacity,

C. A. McCammon; N. L. Ross

2003-01-01

27

Giant magnetoimpedance effect in ultrasoft FeAlSiBCuNb nanocomposites for sensor applications  

SciTech Connect

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

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

2005-07-01

28

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

29

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

NASA Astrophysics Data System (ADS)

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

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

2014-12-01

30

The Study of an Al-Fe-Si Alloy After Equal-Channel Angular Pressing (ECAP) and Subsequent Semisolid Heating  

NASA Astrophysics Data System (ADS)

The effects of coupling equal-channel angular pressing (ECAP) and heating at semisolid temperature on the microstructure of an Al-Fe-Si alloy were investigated. The microstructure of the equal-channel, angular-pressed samples after semisolid heating was found to be globular, fine, and uniform. Both the globularity and the grain size of the semisolid samples increased by increasing the holding temperature and holding time. The kinetics of grain coarsening was studied and the apparent activation energy was calculated on the basis of Lifshitz, Slyozov, and Wagner theory. Coupling ECAP and semisolid heating resulted in an enhanced microstructure and mechanical properties in the Al-Fe-Si alloy.

Aghaie-Khafri, M.; Azimi-Yancheshme, D.

2012-05-01

31

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

32

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

NASA Astrophysics Data System (ADS)

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

Elsharkawi, Ehab A.

33

Electronic spin state of Fe,Al-containing MgSiO3 perovskite at lower mantle conditions  

NASA Astrophysics Data System (ADS)

We have investigated silicate perovskite with composition Mg0.83Fe0.21Al0.06Si0.91O3 relevant for the lower mantle at pressures up to 81 GPa and temperatures up to 2000 K using conventional Mössbauer spectroscopy and synchrotron Nuclear Forward Scattering (NFS) combined with double-sided laser heating in a diamond anvil cell. Room temperature Mössbauer and NFS spectra at low pressure are dominated by high-spin Fe2 +, with minor amounts of Fe3 + and a component assigned to a metastable position of high-spin Fe2 + in the A-site predicted by computational studies. NFS data show a sharp transition (< 20 GPa) from high-spin Fe2 + to a new component with extremely high quadrupole splitting, similar to previous studies. Mössbauer data show the same transition, but over a broader pressure range likely due to the higher pressure gradient. The new Fe2 + component is assigned to intermediate-spin Fe2 +, consistent with previous X-ray emission studies. NFS data at high temperatures and high pressures comparable to those in the lower mantle are consistent with the presence of Fe2 + only in the intermediate-spin state and Fe3 + only in the high-spin state. Our results are therefore consistent with the occurrence of spin crossover only in Fe2 + in Fe-, Al-containing perovskite within the lower mantle.

Kupenko, I.; McCammon, C.; Sinmyo, R.; Prescher, C.; Chumakov, A. I.; Kantor, A.; Rüffer, R.; Dubrovinsky, L.

2014-02-01

34

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

35

Modified embedded atom method potential for Al, Si, Mg, Cu, and Fe alloys  

NASA Astrophysics Data System (ADS)

A set of modified embedded-atom method (MEAM) potentials for the interactions between Al, Si, Mg, Cu, and Fe was developed from a combination of each element's MEAM potential in order to study metal alloying. Previously published MEAM parameters of single elements have been improved for better agreement to the generalized stacking fault energy (GSFE) curves when compared with ab initio generated GSFE curves. The MEAM parameters for element pairs were constructed based on the structural and elastic properties of element pairs in the NaCl reference structure garnered from ab initio calculations, with adjustment to reproduce the ab initio heat of formation of the most stable binary compounds. The new MEAM potentials were validated by comparing the formation energies of defects, equilibrium volumes, elastic moduli, and heat of formation for several binary compounds with ab initio simulations and experiments. Single elements in their ground-state crystal structure were subjected to heating to test the potentials at elevated temperatures. An Al potential was modified to avoid formation of an unphysical solid structure at high temperatures. The thermal expansion coefficient of a compound with the composition of AA 6061 alloy was evaluated and compared with experimental values. MEAM potential tests performed in this work, utilizing the universal atomistic simulation environment (ASE), are distributed to facilitate reproducibility of the results.

Jelinek, B.; Groh, S.; Horstemeyer, M. F.; Houze, J.; Kim, S. G.; Wagner, G. J.; Moitra, A.; Baskes, M. I.

2012-06-01

36

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

NASA Astrophysics Data System (ADS)

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

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

2014-05-01

37

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

38

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

SciTech Connect

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

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

2000-05-10

39

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

NASA Astrophysics Data System (ADS)

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

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

2014-11-01

40

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

41

Electrical memory features of ferromagnetic CoFeAlSi nano-particles embedded in metal-oxide-semiconductor matrix  

Microsoft Academic Search

Half-metallic Heusler material Co2FeAl0.5Si0.5 (CFAS) nano-particles (NPs) embedded in metal-oxide-semiconductor (MOS) structures with thin HfO2 tunneling and MgO control oxides were investigated. The CFAS NPs were prepared by rapid thermal annealing. The formation of well-controlled CFAS NPs on thin HfO2 tunneling oxide was confirmed by atomic force microscopy (AFM). Memory characteristics of CFAS NPs in MOS devices exhibited a large

Jabin Lee; Kiwoong Kim; Junseok Lee; Gwangguk An; Jinpyo Hong

2011-01-01

42

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

43

Phase relations associated with the aluminum blast furnace: Aluminum oxycarbide melts and Al-C-X (X=Fe, Si) liquid alloys  

Microsoft Academic Search

The thermodynamic properties and the phase relations were evaluated and estimated for the Al-O-C, Al-Si-C, and Al-Fe-C systems\\u000a which are important to understand the chemical behavior in an aluminum blast furnace. The mixing properties of binary liquid\\u000a alloys, including metal-carbon systems, were represented by the Redlich-Kister equation. The properties of liquid Al?C and\\u000a Si?C alloys were estimated so as to

Harumi Yokokawa; Masao Fujishige; Seiichi Ujiie; Masayuki Dokiya

1987-01-01

44

The effect of Sr and Fe additions on the microstructure and mechanical properties of a direct squeeze cast Al-7Si-0.3Mg alloy  

SciTech Connect

This article describes the results of an investigation into the microstructure and mechanical properties of a gravity die cast and direct squeeze cast LM25 alloy (Al-7Si-0.3Mg-0.3Fe). The direct squeeze cast LM25 alloy has superior mechanical properties compared to the gravity die cast LM25 alloy, especially with regard to ductility, which is increased from {approximately}1.7 pct for the gravity die cast LM25 alloy to {approximately}8.0 pct for the direct squeeze cast LM25 alloy in the T6 heat-treated conditions. This increase in ductility is due to (1) the removal of porosity, (2) a decrease in Si particle size, and (3) a refinement of the Fe-Si-aluminide particles. High cooling rates in direct squeeze casting result in quench modification of the Si particles, such that chemical modification with Sr or Na may not be required. In addition, direct squeeze casting is more tolerant of Fe impurities in the alloy, due to the formation of smaller Fe-Si-aluminide particles than those in gravity die cast material. The direct squeeze cast LM25 + Fe alloy (Al-7Si-0.3Mg-1.0Fe) has a ductility of {approximately}6.5 pct, compared to that of {approximately}0.5 pct for the gravity die cast LM25 + Fe alloy in the T6 heat-treated condition. This increase in tolerance to Fe impurities can lead to a substantial reduction in manufacturing costs due to (1) reduced raw-material costs, (2) reduced die sticking, and (3) improved die life.

Dong, J.X.; Karnezis, P.A.; Durrant, G.; Cantor, B. [Univ. of Oxford (United Kingdom). Dept. of Materials

1999-05-01

45

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

46

Mössbauer studies on the shape effect of Fe84.94Si9.68Al5.38 particles on their microwave permeability  

NASA Astrophysics Data System (ADS)

Ball milling for long time (such as 10, 20, and 30 h) can transform Fe84.94Si9.68Al5.38 alloy powders with irregular shapes into flakes. X-ray diffraction (XRD) and Mössbauer measurements have proven that the unmilled particles and the flakes obtained by milling for 10 h have the same D03-type superlattice structure. The flakes obtained by milling for 20 h and 30 h have the same disorder ?-Fe(Si, Al) structure. There are more than 6 absorption peaks in the transmission Mössbauer spectra (TMSs) for the particles with D03-type superlattice structure, which can be fitted with 5 sextets representing 5 different Fe-site environments. However, only 6 TMS absorption peaks have been found for particles with a disorder ?-Fe(Si, Al) structure, which can be fitted with the distributions of Mössbauer parameters (Bhf, isomer shift). The TMS results show that the flaky particles have a stronger tendency to possess the planar magnetic anisotropy. As the result, the flakes have larger microwave permeability values than particles with irregular shapes. The conversion electron Mössbauer spectra (CEMSs) also show the significantly different Fe-sites environments between the alloy surface and the inside.

Han, Man-Gui; Deng, Long-Jiang

2013-08-01

47

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

48

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

49

Effects of Fe intermetallics on the machinability of heat-treated Al–(7–11)% Si alloys  

Microsoft Academic Search

The need for bridging the divide between the casting process and the machining process provides a strong motivation for examining the various aspects affecting the machinability of Al–Si casting alloys, given that these alloys constitute about 85% of all aluminum castings produced. Strontium-modified, grain-refined, T6 heat-treated 396 alloys (containing ?11% Si), and B319.2 and A356.2 alloys (containing ?7% Si) were

Y. Zedan; F. H. Samuel; A. M. Samuel; H. W. Doty

2010-01-01

50

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

PubMed

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

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

2013-01-01

51

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

52

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

53

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

54

/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

55

Thermodynamics of (Fe 2+ , Mn 2+ , Mg, Ca) 3? Al 2 Si 3 O 12 garnet: a review and analysis  

Microsoft Academic Search

Summary The thermodynamic properties of garnets in the system (Fe2+, Mn2+, Mg, Ca)3A12Si3O12 are reviewed. The thermodynamic properties of the three end-member garnets pyrope, almandine and grossular, including their volume, enthalpy of formation, entropy, compressibility and thermal expansion have been well determined. For spessartine enthalpy of formation and heat capacity at low temperatures are needed. Pyrope's unusual behavior in some

C. A. Geiger

1999-01-01

56

Magnetoelectric response of AlN/[(Fe90Co10)78Si12B10 + Terfenol-D] composite films  

NASA Astrophysics Data System (ADS)

The magnetoelectric (ME) composite films composed of piezoelectric layer AlN film and new magnetostrictive layer [(Fe90Co10)78Si12B10 + Terfenol-D] films were successfully prepared by RF magnetron sputtering. The influence of bias magnetic field Hdc on ME response, as well as, the ac magnetic field sensitivity were investigated in detail. The results demonstrated that the respective magnetic properties of (Fe90Co10)78Si12B10 and Terfenol-D films are coupled in this new magnetostrictive layer, resulting in the fact that ME voltage coefficient ?ME reaches the maximum of 78.1 V/cm Oe and 77.5 V/cm Oe at the bias field of 11 Oe and 96 Oe, respectively. Meanwhile, the composite films display ac magnetic field sensitivity of 0.45 nT/?Hz and 0.47 nT/?Hz at Hdc of 11 Oe and 96 Oe, respectively. The results above indicate that the AlN/[(Fe90Co10)78Si12B10 + Terfenol-D] composite films exhibit a promising potential application in diverse range of magnetic field detection.

Tong, Bei; Yang, Xiaofei; Ouyang, Jun; Lin, Gengqi; Zhang, Yue; Chen, Shi

2014-05-01

57

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

SciTech Connect

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

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

2010-03-15

58

A new garnet, {(Y, REE)(Ca, Fe2+)2}[(Mg,Fe2+)(Fe3+,Al)](Si3)O12, and its role in the yttrium and rare-earth element budget in a granulite  

NASA Astrophysics Data System (ADS)

A pyroxene-plagioclase granulite on Bonnet Island in the interior Parry Sound domain, Central Gneiss Belt, Grenville Orogenic Province, Canada contains 4 minerals with essential Y and rare-earth elements (REE): monazite(Ce), xenotime-(Y), allanite-(Ce) and a new Y garnet. There are only a few grains of Y-REE phosphate. Monazite grains (to 20 µm) are contiguous to or enclosed in apatite. Xenotime grains (to 7 µm) are enclosed in apatite or sandwiched between it and zircon. Allanite is coarser (to 400 µm), more abundant and not restricted in association. Fresh allanite (ThO2 < 0.4 wt%) has 18-30 mol% epidote, 29-10 mol% ferriallanite; Fe3+/Fe ~ 0.36. The new garnet (IMA 2009-050, submitted) forms cores to 75 µm rimmed along sharp, irregular contacts by euhedral almandine-grossular (Alm59Grs18Prp9Adr5Sps4other5; <2 wt% Y2O3). Locally the new garnet contacts K-feldspar, apatite and allanite - the last where both phases are enclosed in euhedral Alm-Grs. The formula for the new garnet is {Y0.83Gd0.01Dy0.05Ho0.02Er0.07Tm0.01Yb0.06Lu0.02Ca1.37Fe2+0.49Mn0.07}[Mg0.55Fe2+0.42Fe3+0.58Al0.35V0.01Sc0.01Ti0.08](Si2.82Al0.18)O12. Incorporation of Y + REE is largely through the components {Y2Ca}[Mg2](Si3)O12 = YMg and {Y2Ca}[Fe2+2](Si3)O12 = YFe instead of {Y3}[Al2](Al3)O12 (YAG) and {Y3}[Fe3+2](Fe3+3)O12 (YIG) as reported in many Y + REE enriched garnets. Equations such as 3YMg + 5Al2O3 = 2YAG + 3Di + 3En relate YMg and YFe to YAG and YIG, that is, YMg and YFe incorporation would be expected in rocks with pyroxene. Prior to growth of Alm-Grs the new garnet and allanite presumably equilibrated with ferrosilite (Fs56-60En41-37Wo~1 and ~1%MnSiO3), oligoclase (An27), quartz, magnetite, ilmenite and possibly coarse-grained augite during the first stage of metamorphism estimated to be at T > 830 °C, P ~ 11 kbar. The second stage assemblage included biotite, ferropargasite, fined-grained augite and Alm-Grs + Qtz ± augite symplectite; the later augite has less Na, Al and higher Mg/(Mg+Fe). The Y-REE phosphates could be later phases formed by reaction of apatite with Y + REE released by the breakdown of the new garnet and allanite. The host granulite is silica saturated and poor in K (66.06 wt% SiO2; 0.85 wt% K2O) and meta-aluminous (ASI 0.90). Selected trace elements in ppm: Cr, Ni < 20, Zr 668, Nb 15.5, Y 80.4, La 42.4, Ce 95.9, Pr 12, Nd 46.5, Sm 10.6, Eu 3.21, Gd 12, Tb 2, Dy 12.7, Ho 2.92, Er 9.85, Tm 1.62, Yb 11, Lu 1.65 ppm, which gives Eu/Eu* 0.87, LaN/YbN 2.62, Y + HREE 51-68*chondrite. The appearance of a Y + HREE silicate is most likely due to (1) the major constituents (Pl, Opx, Qz, Mgt, Ilm) and allanite being unable to accommodate the relatively high bulk Y + HREE content at the peak of metamorphism and (2) the instability of xenotime and titanite in this bulk composition. Two other granulites have similar bulk composition and nearly identical Y + REE contents, but more hornblende, less allanite and none of the new garnet. If hornblende had been stable at the metamorphic peak in these rocks, it could have incorporated more of the Y + REE. There would have been less LREE available for allanite, and insufficient Y + HREE to form the new garnet.

Grew, E. S.; Marsh, J. H.; Yates, M. G.; Locock, A.

2009-12-01

59

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

NASA Astrophysics Data System (ADS)

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

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

2014-09-01

60

Enthalpy of formation of Fe 3Al 2Si 3O 12 (almandine) by high temperature alkali borate solution calorimetry  

NASA Astrophysics Data System (ADS)

A high-temperature solution calorimetric method suitable for thermochemical studies of anhydrous minerals containing Fe 2+ ions has been developed. The method is based on an oxide melt solvent with 52 wt% LiBO 2 and 48 wt% NaBO 2 maintained at a temperature of 750°C. In a first application of this method the enthalpies of solution of synthetic almandine, fayalite, a mixture of fayalite plus quartz on FeSiO 3 composition, and natural quartz were measured. For the reaction: ? the enthalpy change at 1023 K is -3.82 ± 0.87 kcal, based on fayalite, quartz, corundum and almandine, and -5.96 ± 0.90 kcal based on the fayalite plus quartz mixture, corundum, and almandine. These values lead to standard molar enthalpies of formation of almandine from the oxides at 1023 K of -14.10 ± 1.22 kcal and -16.24 ± 1.74 kcal, respectively. The measured enthalpy of formation of almandine is less negative by several kilocalories than values derived from analysis of the phase equilibrium work of HSU (1968), but in closer agreement with the phase equilibrium study of O'NEILL and WOOD (1979) and similar to the phase equilibrium deduction of FROESE (1973). The agreement of the present almandine enthalpy of formation with O'NEILL and WOOD (1979) and FROESE (1973) suggests that almandine entropies at 298 K to be obtained from their studies, in the range 79-81 cal/K, are more nearly correct than the several estimates based on oxide sum and volume-entropy systematics, most of which are much lower.

Chatillon-Colinet, C.; Kleppa, O. J.; Newton, R. C.; Perkins, D., III

1983-03-01

61

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

NASA Astrophysics Data System (ADS)

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

Hassani, Amir; Ranjbar, Khalil; Sami, Sattar

2012-08-01

62

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

NASA Astrophysics Data System (ADS)

A combinatorial chemistry method was employed to screen the Ba2+ and Fe3+ incorporated into cordierite structure (Ba0.05Fe0.1Mg)2Al4Si5O18 for exploring of high infrared radiance materials. A series of square-type sample array that consists of 7×7 compositions was synthesized by ink-jetting nitrate solutions into micro-reactor wells in a ceramic plate and then heat-treated at high temperatures. X-ray diffraction and infrared thermograph were used to analyze the effects of Ba2+/Fe3+ incorporating on the lattice distortion of cordierite and resultant changes in infrared radiance properties. Based on the results of X-ray phase analysis and radiance measurement of the scale-up prepared samples, the optimal Ba2+ and Fe3+ co-adding amount was determined to be 5%Ba2+ plus 10%Fe3+. Moreover, the infrared emissivity of the optimal composition at 100 °C was found to be higher than 0.8 in a wide wavelength range of 5-24 ?m. The research work demonstrates a promising application of Ba2+/Fe3+ cordierite solid solution as a kind of infrared heating materials for energy saving.

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

2012-06-01

63

Biogeochemistry of Mariana Islands coastal sediments: terrestrial influence on /gd13, Ash, CaCO3, Al, Fe, Si and P  

NASA Astrophysics Data System (ADS)

Stable C isotope ratios (?13C-PDB), percentages of organic matter, and HCl insoluble ash and soluble carbonates, extractable Fe, Al, Si and P were used to determine the distribution and accumulation of terrestrial material in reef-flat moats and lagoons of two high islands (Guam and Saipan) in the western tropical Pacific. Carbonate sediments of a reef-flat moat infiltrated by seepage of aquifer waters (but without surface runoff) were depleted in both P (by 38%) and 13C (by 41%) and enriched in Si (by 100%) relative to offshore lagoon sediments. Iron and ash accumulated in depositional regimes regardless of the occurrence of runoff but was depleted from coarse-grained carbonates in turbulent regimes. Aluminum (>ca. 10 to 20 ?mol g-1), Fe (>ca. 1 to 3 ?mol g-1) and ash (>0.5%) indicated terrigenous influence which was corroborated by depletions in both 13C and P. Low-salinity geochemical segregation, natural biochemical accumulation, as well as long-shore currents and eddies help sequester these materials nearshore.

Matson, Ernest A.

1989-01-01

64

Contact and non-contact magnetoimpedance in amorphous and nanocrystalline Fe 73.5Si 13.5B 8CuV 3Al ribbons  

NASA Astrophysics Data System (ADS)

The giant magnetoimpedance ( GMI) effect in amorphous and nanocrystalline Fe 73.5Si 13.5B 8CuV 3Al ribbons has been studied as a function of a dc magnetic field, by contact and non-contact methods. In the contact method, an MI of 19% was obtained in the nanocrystalline ribbon while it is of the order of 10 4 in the non-contact method. The huge sensitivity of the non-contact method is promising with regard to the increase of the sensitivity of the MI sensors. Field dependence of MI has shown double peak behavior in contact method and single peak profile in non-contact method. The domains were found to lie normal to the plane of the ribbon, through MFM studies. All the experimental results were discussed using the Polivanov model.

Dwevedi, Sandhya; Sreenivasulu, G.; Markandeyulu, G.

2010-02-01

65

Epitaxial films of Heusler compound Co{sub 2}FeAl{sub 0.5}Si{sub 0.5} with high crystalline quality grown by off-axis sputtering  

SciTech Connect

Co{sub 2}FeAl{sub 0.5}Si{sub 0.5} films with a surface roughness of 0.12 nm have been grown epitaxially on lattice-matched MgAl{sub 2}O{sub 4} (001) substrates by off-axis sputtering. X-ray diffraction shows pronounced Laue oscillations, rocking curves as narrow as 0.0043°, and clear Co{sub 2}FeAl{sub 0.5}Si{sub 0.5} (111) peaks indicating L2{sub 1} ordering. Magnetic characterizations show a clear magnetocrystalline anisotropy comprising cubic and epitaxy-induced uniaxial terms. Nuclear magnetic resonance measurements reveal L2{sub 1} order of 81% in the Co{sub 2}FeAl{sub 0.5}Si{sub 0.5} 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 Co{sub 2}FeAl{sub 0.5}Si{sub 0.5} films.

Peters, B.; Hageman, Stephen J.; Yang, F. Y. [Department of Physics, The Ohio State University, Columbus, Ohio 43210 (United States)] [Department of Physics, The Ohio State University, Columbus, Ohio 43210 (United States); Alfonsov, A.; Blum, C. G. F. [Leibniz Institute for Solid State and Materials Research Dresden, IFW, D-01171 Dresden (Germany)] [Leibniz Institute for Solid State and Materials Research Dresden, IFW, D-01171 Dresden (Germany); Woodward, P. M. [Department of Chemistry and Biochemistry, The Ohio State University, Columbus, Ohio 43210 (United States)] [Department of Chemistry and Biochemistry, The Ohio State University, Columbus, Ohio 43210 (United States); Wurmehl, S.; Büchner, B. [Leibniz Institute for Solid State and Materials Research Dresden, IFW, D-01171 Dresden (Germany) [Leibniz Institute for Solid State and Materials Research Dresden, IFW, D-01171 Dresden (Germany); Institute for Solid State Physics, Technische Universität Dresden, D-01062 Dresden (Germany)

2013-10-14

66

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

67

Melting Experiments in the Fe-FeSi System at High Pressure  

NASA Astrophysics Data System (ADS)

The principal light element in the Earth's core must reproduce the density jump at the inner core boundary (ICB). Silicon is thought to be a plausible light element in the core, and the melting phase relations in Fe-FeSi binary system at the ICB pressure are of great importance. Theoretical calculations on the Fe-FeSi binary system suggested that the difference in Si content between the outer core and the inner core would be too small to satisfy the observed density jump at the ICB [Alfè et al., 2002 EPSL], which requires other light elements in addition to silicon. Here we experimentally examined partitioning of silicon between liquid and solid iron up to 97 GPa. High pressure and temperature conditions were generated in a laser-heated diamond-anvil cell. Chemical compositions of co-existing quenched liquid and solid Fe-Si alloys were determined with a field-emission-type electron probe micro-analyzer. We used Fe-Si alloy containing 9 wt% Si as a starting material. Chemical analyses on the recovered samples from 39 and 49 GPa demonstrated the coexistence of quenched Si-depleted liquid and Si-enriched solid. In contrast, silicon partitions preferentially into liquid metal at 97 GPa, suggesting the starting composition (Fe-9wt% Si) lies on the iron-rich part of the eutectic. These results indicate the eutectic composition shifts toward FeSi between 49 and 97 GPa.

Ozawa, H.; Hirose, K.

2013-12-01

68

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

NASA Astrophysics Data System (ADS)

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

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

2013-06-01

69

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

70

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

71

Simulation of a directional solidification of a binary Al7wt%Si and a ternary alloy Al7wt%Si1wt%Fe under the action of a rotating magnetic field  

Microsoft Academic Search

We propose an approach for the solidification of metallic alloys taking into account the turbulence in the liquid phase. For modeling of the turbulent flow a k-? model is used. This model is applied for solidification of AlSi-based alloys under the action of rotating electromagnetic field of intensity up to 65mT. Two cases have been considered, namely solidification of a

O Budenkova; F Baltaretu; J Kovács; A Roósz; A Rónaföldi; A-M Bianchi; Y Fautrelle

2012-01-01

72

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

NASA Astrophysics Data System (ADS)

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

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

2013-12-01

73

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

74

Electronic structure and magnetism of Fe_3-xV_xX (X = Si, Ga and Al) alloys by the KKR-CPA method  

NASA Astrophysics Data System (ADS)

We present highly accurate, first principles, charge- and spin-selfconsistent electronic structures of the Heusler-type disordered alloys Fe_3-xV_xX for three metalloids. By assuming V to substitute randomly at the Fe(B) site, specific calculations are reported for x = 0.25, 0.50, and 0.75, the end compounds Fe_3X and Fe_2VX, and the limiting single impurity cases. KKR-CPA methodology, generalized to treat multi-component complex alloys, was used to treat disorder effects within the LSD framework. We delineate clearly how the electronic states and magnetic moments at various sites in Fe_3-xV_xX evolve as a function of x and metalloid valence. The total magnetic moment in Fe_3-xV_xSi is found to decrease non-linearly, and the Fe(B) moment to increase with increasing x, in sharp contrast to expectations of the `local environment' model. We discuss the type, spin, and number of carriers in Fe_3-xV_xX relevant for various transport phenomena. Hyperfine fields and spherical spin form factors at various sites were computed for all alloys. Theoretical predictions are compared with available measurements as far as possible, and some areas where further experiments should prove interesting are noted. Work supported by the DOE.

Bansil, A.; Tobola, J.; Kaprzyk, S.

1997-03-01

75

Electrical Spin injection into Silicon: a comparison between Fe/Schottky and Fe/Al2O3 tunnel contacts  

NASA Astrophysics Data System (ADS)

We have recently demonstrated successful electrical injection of spin-polarized electrons from an Fe film through an Al2O3 tunnel barrier into Si [1]. The spin polarization in the Si is ˜30% at 5K, with significant polarization sustained to at least 125K. In this study we compare electrical spin injection from Fe into MBE grown Si n-i-p heterostructures using different tunnel barriers- a reversed biased Fe/Si Schottky contact and an Fe/Al2O3 barrier. For both types of structures the electroluminescence (EL) spectra are dominated by transverse acoustic and optical phonon emissions in the Si. The surface emitted circular polarization of the EL due to radiative recombination in the Si tracks the Fe magnetization, confirming that the spin-polarized electrons originate from the Fe for both types of samples. However, the polarization is lower for the Fe/Si contact than that of the Fe/Al2O3/Si system. Systematic TEM analysis has been performed to correlate the interface structure with the observed optical polarization, and reveals some Fe/Si intermixing which is absent in the Fe/ Al2O3/Si structure. [1] B.T. Jonker et al., Nature Physics 3, 542 (2007). This work was supported by ONR and core programs at NRL.

Kioseoglou, G.; Hanbicki, A. T.; Li, C. H.; Thompson, P. E.; Goswami, R.; Spanos, G.; Jonker, B. T.

2008-03-01

76

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

77

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

78

The sulfide capacities of CaO-SiO2 melts containing MgO, FeO, TiO2, and Al2O3  

NASA Astrophysics Data System (ADS)

The sulfide capacities of CaO-SiO2 melts containing MgO, FeO, TiO2, and A12O3 have been measured by simultaneous equilibration within quartz capsules at 1776 K (1503 °C). The compositions of the melt samples and static gas phase within each capsule adjusted to establish a mutual equilibrium. The sulfide capacities, Cs, of all equilibrated samples must satisfy the following equation: 11663_2007_Article_BF02654142_TeX2GIFE1.gif C_{{text{S(}}j{text{)}}} = {{text{pctS}}_j }/{pctS_i } bullet C_{S(i)} The inclusion of several reference slags for which values of Cs are known from previous measurements enabled the calculation of the sulfide capacities of unknown samples. The influences of basic oxide substitutions (FeO and MgO) for CaO and acidic oxide substitutions (TiO2 and A12O3) for SiO2 on the sulfide capacities of CaO-SiO2 melts have been measured. When a basic oxide/acidic oxide ratio of 1.21 is maintained, MgO additions decrease sulfide capacity, while FeO, TiO2 and A12O3 additions increase sulfide capacity. The results are compared with earlier measurements on the influences of CaF2 and B2O3, and the relative effects are discussed in terms of the activity of free oxide ions.

Bronson, Arturo; Pierre, George R. St.

1981-12-01

79

Room-Temperature 1.56 ?m Electroluminescence of Highly Oriented ?-FeSi2/Si Single Heterojunction Prepared by Magnetron-Sputtering Deposition  

NASA Astrophysics Data System (ADS)

?-FeSi2/Si light-emitting devices were prepared by growing continuous and highly oriented ?-FeSi2 films on Si (111) substrates using RF magnetron-sputtering deposition with a Fe target. In-plane X-ray diffraction reveals that the epitaxial relationship is such that < 001>?-FeSi2//< 110>Si, indicating a (110) orientation in the growth direction. Post annealing was performed at 830°C and Al electrodes were deposited on both p-?-FeSi2 and n-Si sides. Room-temperature 1.56 ?m electroluminescence was clearly observed from such a simple structure for the first time. Compared with the previously reported results for ?-FeSi2 balls or ?-FeSi2 precipitates buried in Si, the injection current density is more than one order of magnitude lower, indicating that the nonradiative recombination was effectively suppressed for the junction consisting of a continuous film.

Chu, Shucheng; Hirohada, Toru; Nakajima, Kazutoshi; Kan, Hirofumi; Hiruma, Teruo

2002-11-01

80

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

81

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

Microsoft Academic Search

A tunnel magnetoresistance has been investigated for Fe3Si\\/CaF2\\/Fe3Si magnetic tunnel junctions (MTJs). We fabricated Fe3Si(20 nm)\\/CaF2(2 nm)\\/Fe3Si(15 nm) heterostructures on a CaF2(2 nm)\\/Si(111) substrate by molecular beam epitaxy (MBE) and processed them into 300×15 mm2-area MTJs using selective wet chemical etching and conventional photolithography. The current-voltage (J-V) characteristics for the MTJs measured at room temperature (RT) were well fitted to

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

2011-01-01

82

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

83

An electrical resistivity study of Ce{sub 2}Fe{sub 16.8} and the Ce{sub 2}Fe{sub 17{minus}x}Al{sub x} and Ce{sub 2}Fe{sub 17{minus}x}Si{sub x} solid solutions  

SciTech Connect

Electrical resistivity measurements have been carried out between 20 and 300 K on Ce{sub 2}Fe{sub 16.8}, on the Ce{sub 2}Fe{sub 17{minus}x}Al{sub x} solid solutions, with x=0.4, 1, 2, 5, 6, 8, and 9, and on the Ce{sub 2}Fe{sub 17{minus}x}Si{sub x} solid solutions, with x=0.2, 0.4, 1, and 2, with the four probe method. The temperature dependence of the resistivity of Ce{sub 2}Fe{sub 16.8} shows an inflection at 110 K, a feature which is also observed in the temperature dependence of the magnetization and is related to a magnetic phase transition from a helical structure, above 110 K, to a fan structure, below 110 K. The temperature dependence of the resistivity of Ce{sub 2}Fe{sub 16.8} is characteristic over the investigated temperature range of weak antiferromagnetic behavior with incommensurate periodicity as has been observed in the earlier neutron diffraction study. The resistivity of Ce{sub 2}Fe{sub 17{minus}x}Al{sub x} increases with temperature in agreement with a density of states at the Fermi level dominated by the {ital d} band. For a given temperature, the resistivity increases substantially and regularly with {ital x} for both series of solid solutions because of an increase in the number of conduction electron scattering potentials. This increase in resistivity also corresponds to a decrease in the number of conduction electrons due to their increasing transfer into the localized cerium {ital 4f} orbitals as the cerium valence state changes from a mixture of trivalent and tetravalent in Ce{sub 2}Fe{sub 17} to predominantly trivalent in Ce{sub 2}Fe{sub 17{minus}x}Al{sub x} and Ce{sub 2}Fe{sub 17{minus}x}Si{sub x} with increasing {ital x}. {copyright} {ital 1997 American Institute of Physics.}

Vandormael, D.; Grandjean, F. [Group MAGNET, Institute of Physics, B5, University of Liege, B-4000 Sart-Tilman (Belgium)] [Group MAGNET, Institute of Physics, B5, University of Liege, B-4000 Sart-Tilman (Belgium); Bougrine, H.; Ausloos, M. [S.U.P.R.A.S., Institute of Physics, B5, University of Liege, B-4000 Sart-Tilman (Belgium)] [S.U.P.R.A.S., Institute of Physics, B5, University of Liege, B-4000 Sart-Tilman (Belgium); Middleton, D.P. [Philips Research Laboratories, NL-5600 JA Eindhoven (the Netherlands)] [Philips Research Laboratories, NL-5600 JA Eindhoven (the Netherlands); Buschow, K.H. [Van der Waals-Zeeman Institute, University of Amsterdam, NL-1018 XE Amsterdam (the Netherlands)] [Van der Waals-Zeeman Institute, University of Amsterdam, NL-1018 XE Amsterdam (the Netherlands); Long, G.J. [Department of Chemistry, University of Missouri-Rolla, Rolla, Missouri 65409-0010 (United States)] [Department of Chemistry, University of Missouri-Rolla, Rolla, Missouri 65409-0010 (United States)

1997-03-01

84

Anisotropic layered high-temperature thermoelectric materials based on the two-phase CrSi2-?-FeSi2 system  

NASA Astrophysics Data System (ADS)

The feasibility of synthesizing a wide spectrum of multiphase microstructurally ordered high-temperature thermoelectrics with highly anisotropic thermoelectric parameters is demonstrated with an aluminum-doped CrSi2-?-FeSi2 system the composition of which varies from Cr0.1Fe0.9Si2- x Al x to Cr0.9Fe0.1Si2- x Al x ( x = 0.0-0.4). Doping of either phase (CrSi2 and ?-FeSi2) is viewed as a promising way for synthesizing n- and p-type domains inside the same sample.

Solomkin, F. Yu.; Zaitsev, V. K.; Novikov, S. V.; Samunin, A. Yu.; Pshenai-Severin, D. A.; Isachenko, G. N.

2014-08-01

85

X-ray-absorption spectral study of the R{sub 2}Fe{sub 17{minus}x}M{sub x} solid solutions (R=Ce,Nd and M=Al,Si)  

SciTech Connect

The x-ray-absorption near-edge structure (XANES) spectra obtained at the cerium L{sub III} edge of the Ce{sub 2}Fe{sub 17{minus}x}Al{sub x} solid solutions and Ce{sub 2}Fe{sub 14}Si{sub 3} show two absorption peaks characteristic of the 4f{sup 1} and 4f{sup 0} configurations of cerium, peaks which indicate that cerium is in a mixed valent state in these compounds. All the XANES spectra have been consistently and excellently fit with one sigmoidal function and two Gaussian-broadened Lorentzian functions. The cerium spectroscopic valence obtained from the relative areas of the two peaks decreases from 3.64 to 3.43 between x=0 and 9 in Ce{sub 2}Fe{sub 17{minus}x}Al{sub x}, and correlates linearly with the cerium site volume. This correlation confirms that the cerium valence is strongly dependent upon steric effects. In contrast, the cerium valence obtained from the XANES spectrum of Ce{sub 2}Fe{sub 14}Si{sub 3} is not determined by steric effects and indicates, in agreement with other measurements and calculations, that silicon is more covalently bonded with its near-neighbor cerium atoms than is aluminum. The neodymium L{sub III}-edge XANES spectra of the Nd{sub 2}Fe{sub 17{minus}x}Al{sub x} solid solutions, where x is 0, 3, and 8, reveal the presence of only trivalent neodymium and an increase of the empty 5d state density when aluminum is substituted in place of iron. XANES measurements at the iron K edge of the Ce{sub 2}Fe{sub 17{minus}x}Al{sub x} and Nd{sub 2}Fe{sub 17{minus}x}Al{sub x} solid solutions show changes in the relative intensity of the multiple scattering peaks, changes which are related to the changing composition of the first three neighbor shells with increasing aluminum content. {copyright} {ital 1997} {ital The American Physical Society}

Vandormael, D.; Grandjean, F. [Institute of Physics, B5, University of Liege, B-4000 Sart-Tilman (Belgium)] [Institute of Physics, B5, University of Liege, B-4000 Sart-Tilman (Belgium); Briois, V. [Laboratoire pour lUtilisation du Rayonnement Electromagnetique, Batiment 209D, Universite Paris-Sud, F-91405 Orsay (France)] [Laboratoire pour lUtilisation du Rayonnement Electromagnetique, Batiment 209D, Universite Paris-Sud, F-91405 Orsay (France); Middleton, D.P. [Philips Research Laboratories, NL-5600 JA Eindhoven (the Netherlands)] [Philips Research Laboratories, NL-5600 JA Eindhoven (the Netherlands); Buschow, K.H. [Van der Waals-Zeeman Institute, University of Amsterdam, NL-1018 XE Amsterdam (the Netherlands)] [Van der Waals-Zeeman Institute, University of Amsterdam, NL-1018 XE Amsterdam (the Netherlands); Long, G.J. [Department of Chemistry, University of Missouri-Rolla, Rolla, Missouri 65409-0010 (United States)] [Department of Chemistry, University of Missouri-Rolla, Rolla, Missouri 65409-0010 (United States)

1997-09-01

86

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

NASA Astrophysics Data System (ADS)

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

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

2014-05-01

87

Thermoelectric properties of -FeSi2  

SciTech Connect

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

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

2013-01-01

88

Ab-initio study of electronic structure and magnetic properties of half-metallic Fe2Mn1-xVxSi0.5Al0.5 alloys  

NASA Astrophysics Data System (ADS)

Ab-initio electronic structure calculations are carried out for quinternary Fe2Mn1-xVxSi0.5Al0.5 alloys. When x=0 the alloy is half-metallic ferromagnet, with magnetic moment following the Slater-Pauling rule. Replacement of Mn by V, changes its electronic and magnetic structure. V-doped alloys exhibit half-metallic behavior for x?0.25. However, even for higher V concentrations, electronic spin polarization is still very high, what makes the alloys interesting for spintronic applications.

Go, Anna

2014-11-01

89

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

90

Effect of silicon alloying additions on growth temperature and primary spacing of Al 3Fe in Al8wt%Fe alloy  

Microsoft Academic Search

Alloys of Al-8.4Fe-1.7Si, Al-8.5Fe-3.4Si and Al-8.5Fe-5.6Si (wt%) designated A, B and C, respectively, were prepared from high purity (99.99%) aluminum, Japanese electrolytic iron (99.9%) and superpure silicon (99.99%). Melting was carried out in a recrystallized alumina crucible by using a Radyne induction furnace and was followed by chill casting under flowing argon into steel molds of cavity dimension 15 mm

D. Liang; P Gilgien; H Jones

1995-01-01

91

Formation and ferromagnetic properties of FeSi thin films  

SciTech Connect

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

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

2013-05-07

92

Wetting of polycrystalline SiC by molten Al and Al-Si alloys  

NASA Astrophysics Data System (ADS)

The wetting of ?-SiC by molten Al and Al-Si alloys was investigated using a dispensed sessile drop method in a high vacuum. In the Al-SiC system, representative wetting stages were identified. The liquid spreading was initially controlled by the deoxidation of the SiC surface and then by the formation of Al4C3 at the interface. The intrinsic contact angle for molten Al on the polycrystalline ?-SiC surface was suggested to be lower than 90? provided that the oxide films covering the Al and SiC surfaces were removed, i.e., the system is partial wetting in nature. An increase in the Si concentration in liquid Al weakened the interfacial reaction but improved the final wettability. The role of the Si addition on the wetting was presumably attributed to its segregation at the interface and the formation of strong chemical bonds with the SiC surface.

Cong, Xiao-Shuang; Shen, Ping; Wang, Yi; Jiang, Qichuan

2014-10-01

93

Energetic ion bombarded Fe/Al multilayers  

SciTech Connect

The utility of ion-assisted deposition is investigated to explore the possibility of counteracting the deficiency of back-reflected current of Ar neutrals in the case of lighter elements such as Al. A range of energetically ion bombarded Fe/Al multilayers sputtered with applied surface bias of 0, -200, or -400 V were deposited onto Si(111) substrates in an argon atmosphere of 4 mTorr using a computer controlled dc magnetron sputtering system. Grazing incidence reflectivity and rocking curve scans by synchrotron x rays of wavelength of 1.38 A were used to investigate the structures of the interfaces produced. Substantial evidence has been gathered to suggest the gradual suppression of interfacial mixing and reduction in interfacial roughness with increases of applied bias. The densification of the Al microstructure was noticeable and may be a consequence of resputtering attributable to the induced ion bombardment. The average interfacial roughnesses were calculated for the 0, -200, and -400 V samples to be 7{+-}0.5, 6{+-}0.5, and 5{+-}0.5 A respectfully demonstrating a 30% improvement in interface quality. Data from rocking curve scans point to improved long-range correlated roughness in energetically deposited samples. The computational code based on the recursive algorithm developed by Parratt [Phys. Rev. 95, 359 (1954)] was successful in the simulation of the specular reflectivity curves.

Al-Busaidy, M.S.; Crapper, M.D. [College Science, Physics Department, Sultan Qaboos University, P.O. Box 36, Al-Khod 123 (Oman); Department of Physics, Loughborough University, Loughborough (United Kingdom)

2006-05-15

94

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

NASA Astrophysics Data System (ADS)

A tunnel magnetoresistance has been investigated for Fe3Si/CaF2/Fe3Si magnetic tunnel junctions (MTJs). We fabricated Fe3Si(20 nm)/CaF2(2 nm)/Fe3Si(15 nm) heterostructures on a CaF2(2 nm)/Si(111) substrate by molecular beam epitaxy (MBE) and processed them into 300×15 mm2-area MTJs using selective wet chemical etching and conventional photolithography. The current-voltage (J-V) characteristics for the MTJs measured at room temperature (RT) were well fitted to Simmons' equation. The fitting yields the barrier height phi = 2.5 eV and the barrier thickness d = 1.26 nm. The magnetoresistance curve for the MTJs reaches a maximum in the range of 100-200 Oe and the magnetoresistance ratio is approximately 0.28% under a bias voltage of 20 mV at RT.

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

2011-01-01

95

High-performance batteries for off-peak energy storage and electric-vehicle propulsion. Progress report, January--March 1976. [Li--Al\\/LiCl--KCl\\/FeS or FeS; some work on CaAl, CaSi, and Mg anodes and FeS, FeO and FeS cathodes; ANL  

Microsoft Academic Search

The research and management efforts of Argonne National Laboratory's program on lithium\\/metal sulfide batteries during the period January--March 1976 are described. These batteries are being developed for energy storage on utility networks and for electric-vehicle propulsion. The present cells are vertically oriented, prismatic cells with a central positive electrode of FeS or FeS and two facing negative electrodes of lithium--aluminum

P. A. Nelson; R. O. Ivins; N. P. Yao; J. E. Battles; A. A. Chilenskas; E. C. Gay; R. K. Steunenberg; W. J. Walsh

1976-01-01

96

Elastic properties of FeSi  

SciTech Connect

Measurements of the sound velocities in a single crystal of FeSi were performed in the temperature range 4-300 K. Elastic constants C{sub 11} and C{sub 44} deviate from a quasiharmonic behavior at high temperature; on the other hand, elastic constants C{sub 12} increases anomalously in the entire temperature range, indicating a change in the electron structure of this material.

Petrova, A. E.; Krasnorussky, V. N.; Stishov, S. M., E-mail: sergei@hppi.troitsk.r [Russian Academy of Sciences, Institute for High Pressure Physics (Russian Federation)

2010-09-15

97

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

NASA Astrophysics Data System (ADS)

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

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

2013-12-01

98

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 nm Fe Fe - [3] CNT25 mmCVD 820 500 sccmC2H4 60 Torr, H2 200 Torr, H2O 100 ppmv, Ar 500 Torr 0 min

Maruyama, Shigeo

99

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

100

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

101

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

102

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

103

Correlation between magnetic softness, sample surface and magnetoimpedance in Co 69Fe 4.5X 1.5Si 10B 15 (X=Ni, Al, Cr) amorphous ribbons  

NASA Astrophysics Data System (ADS)

The giant magnetoimpedance (GMI) effect and its field sensitivity ( ?) have been studied in Co 69Fe 4.5X 1.5Si 10B 15 (X=Ni, Al, Cr) amorphous ribbons in the frequency ( f) range of 0.1-10 MHz. It is found that at f<5 MHz, the GMI effect and ? reach the largest values for the Al-containing sample and the smallest values for the Ni-containing sample, while an opposite trend is observed at f>5 MHz. Magnetization and atomic force microscopy (AFM) experiments reveal that the largest values of the low-frequency GMI effect and ? for the Al-containing sample result from the largest value of magnetic permeability, while the largest values of the high-frequency GMI effect and ? for the Ni-containing sample are attributed to the smallest surface roughness of this sample. These results point to the importance of the sample surface in determining high-frequency GMI behavior. A correlation between the sample surface and high-frequency GMI is established in the investigated ribbons.

Chaturvedi, Anurag; Dhakal, Tara; Witanachchi, Sarath; Le, Anh-Tuan; Phan, Manh-Huong; Srikanth, Hariharan

2010-07-01

104

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

NASA Astrophysics Data System (ADS)

In this work we have studied the giant magnetoimpedance (GMI) effect and its field sensitivity (?) 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, the GMI effect and ? reach the largest values for the Al-containing sample and the smallest values for the Ni-containing sample, while an opposite trend is observed at f > 5 MHz. Magnetization and atomic force microscopy (AFM) experiments reveal that the largest values of the low-frequency GMI effect and ? for the Al-containing sample result from the largest value of magnetic permeability, while the largest values of the high-frequency GMI effect and ? for the Ni-containing sample are attributed to the smallest surface roughness of this sample. These results point to the importance of the sample surface in determining high-frequency GMI behavior. A correlation between the sample surface and high-frequency GMI is established in the investigated ribbons.

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

2011-03-01

105

Creep-rupture behavior of a developmental cast-iron-base alloy for use up to 800/sup 0/C. [NASAUT 4G-Al: Fe-15Mn-15Cr-2Mo-1. 5C-1Nb-1Si  

SciTech Connect

As part of the DOE/NASA Stirling Engine Systems Project, an iron-base cast alloy was developed, designated NASAUT 4G-Al. Its nominal composition, in percent by weight, is Fe-15Mn-15Cr-2Mo-1.5C-1Nb-1Si. This report presents the results of a study of this alloy, 4G-Al, performed to determine its creep-rupture properties. The alloy was studied in the directionally solidified (DS) form with a 650/sup 0/C/100 h anneal recommended by UTRC to optimize properties and in the investment-cast (IC) form with either a 760/sup 0/C/20 h anneal recommended by UTRC to optimize properties, or a solution anneal of 790/sup 0/C/20 h followed by a simulated brazing cycle of 1065/sup 0/C/15 min + a heat treatment of 760/sup 0/C/16 h + 650/sup 0/C/16 h. Alloy 4G-Al exhibited typical 3-stage creep response under all conditions tested. The most creep resistant condition was the DS material. This condition compares very favorably to the prototype (HS-31) and prime candidate (XF-818) alloys for the automotive Stirling engine cylinder/regenerator housing. 14 refs., 7 figs., 6 tabs.

Titran, R.H.; Scheuermann, C.M.

1987-08-01

106

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

E-print Network

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

Chi, Ji

2009-05-15

107

Bonding in MgSi and Al-Mg-Si compounds relevant to Al-Mg-Si alloys  

NASA Astrophysics Data System (ADS)

The bonding and stability of MgSi and Al-Mg-Si compounds relevant to Al-Mg-Si alloys is investigated with the use of (linearized) augmented plane-wave + (local-orbitals) density-functional theory calculations. We show that the ? and ?? phases found in the precipitation sequence are characterized by the presence of covalent bonds between Si-Si nearest-neighbor pairs and covalent/ionic bonds between Mg-Si nearest-neighbor pairs. We then investigate the stability of two recently discovered precipitate phases, U1 and U2, both containing Al in addition to Mg and Si. We show that both phases are characterized by tightly bound Al-Si networks, made possible by a transfer of charge from the Mg atoms.

Frøseth, Anders G.; Høier, Ragnvald; Derlet, Peter M.; Andersen, Sigmund J.; Marioara, Calin D.

2003-06-01

108

Electronic properties of Co2FeSi investigated by X-ray magnetic linear dichroism  

NASA Astrophysics Data System (ADS)

We present experimental XMLD spectra measured on epitaxial (001)-oriented thin Co2FeSi films, which are rich in features and depend sensitively on the degree of atomic order and interdiffusion from capping layers. Al- and Cr-capped films with different degrees of atomic order were prepared by DC magnetron sputtering by varying the deposition temperatures. The local structural properties of the film samples were additionally investigated by nuclear magnetic resonance (NMR) measurements. The XMLD spectra of the different samples show clear and uniform trends at the L3,2 edges. The Al-capped samples show similar behavior as previous measured XMLD spectra of Co2FeSi0.6Al0.4. Thus, we assume that during deposition Al atoms are being implanted into the subsurface of Co2FeSi. Such an interdiffusion is not observed for the corresponding Cr-capped films, which makes Cr the material of choice for capping Co2FeSi films. We report stronger XMLD intensities at the L3,2 Co and Fe egdes for films with a higher saturation magnetization. Additionally, we compare the spectra with ab initio predictions and obtain a reasonably good agreement. Furthermore, we were able to detect an XMCD signal at the Si L-edge, indicating the presence of a magnetic moment at the Si atoms.

Emmel, M.; Alfonsov, A.; Legut, D.; Kehlberger, A.; Vilanova, E.; Krug, I. P.; Gottlob, D. M.; Belesi, M.; Büchner, B.; Kläui, M.; Oppeneer, P. M.; Wurmehl, S.; Elmers, H. J.; Jakob, G.

2014-11-01

109

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

110

Relations of the Al, B, Ba, Br, Ca, Cl, Cu, Fe, K, Li, Mg, Mn, Na, P, S, Si, Sr, and Zn mass fractions to morphometric parameters in pediatric and nonhyperplastic young adult prostate glands.  

PubMed

The variation with age of the 18 trace element mass fractions and some histological characteristics of intact prostate glands of 50 subjects aged 0-30 years was investigated by instrumental neutron activation analysis, inductively coupled plasma atomic emission spectrometry, and a quantitative morphometric analysis. Mean values ± standard error of the mean (M ± S??) for the mass fractions (in milligrams per kilogram wet tissue) of these trace elements in pre-puberty were: Al 28.5 ± 9.0, B 0.40 ± 0.11, Ba 1.48 ± 0.44, Br 10.5 ± 1.5, Ca 241 ± 30, Cl 3,203 ± 278, Cu 3.51 ± 0.89, Fe 33.7 ± 4.1, K 2,364 ± 145, Li 0.020 ± 0.004, Mg 153 ± 23, Mn 0.46 ± 0.06, Na 2,286 ± 130, P 1,391 ± 100, S 1,698 ± 132, Si 62 ± 11, Sr 0.38 ± 0.08, and Zn 27.6 ± 2.3. During puberty and postpuberty, when there is a significant increase in circulating androgens, the mean values were: Al 7.2 ± 1.4, B 0.21 ± 0.05, Ba 0.25 ± 0.06, Br 5.8 ± 1.0, Ca 433 ± 81, Cl 2,314 ± 201, Cu 1.77 ± 0.13, Fe 20.9 ± 1.6, K 2,585 ± 118, Li 0.0088 ± 0.0014, Mg 232 ± 27, Mn 0.34 ± 0.04, Na 1,875 ± 107, P 1,403 ± 98, S 1,673 ± 73, Si 22.2 ± 3.1, Sr 0.22 ± 0.03, and Zn 93.3 ± 8.9. Mean values (M ± S??) of percent volumes (%) of the stroma, epithelium and lumen in the prostate before puberty were 73.4 ± 2.6, 20.4 ± 1.7, and 4.45 ± 0.94, respectively, versus 46.5 ± 2.5, 38.5 ± 1.9, and 14.9 ± 1.2 during puberty and postpuberty. This work's results confirm that the Zn mass fraction in prostate tissue is an androgen-dependent parameter. For the first time it has been demonstrated that the glandular lumen is a main pool of Ca, Mg, and Zn accumulation and that the stroma is a main pool of Al, B, Ba, Br, Cl, Cu, Fe, Mn, Na, and Si accumulation in the normal human prostate, for the age range 0-30 years. It was concluded that the Ca, Mg, and Zn binds tightly within the prostatic fluid, because the volume of glandular lumen reflects the volume of prostatic fluid. PMID:24554283

Zaichick, Vladimir; Zaichick, Sofia

2014-04-01

111

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

NASA Astrophysics Data System (ADS)

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

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

2012-12-01

112

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

113

Electronic properties of ?-FeSi2 -- single crystal study  

NASA Astrophysics Data System (ADS)

The discovery of high temperature superconductivity (HTS) in Fe pnictides has simulated a lot of work in field of Fe-based materials. We focus on the tetragonal (high-temperature) form of the iron disilicide, which crystal structure resembles one of the HTS, LiFeAs (Tsc=18 K). Single crystals of ?-FeSi2 with Fe0.83Si2 composition were grown and magnetic, transport and heat capacity studies were performed in consistent way. Magnetic susceptibility of ?-FeSi2 increases in a linear fashion with increasing temperature, as was commonly observed among Fe HTS. In a contrast to superconducting pnictides, where ?(T) ˜ T is associated to antiferromagnetic fluctuations, in ?-FeSi2 this behavior is rather related to the electronic structure of this metal. In Fe-based HTS proximity of the SDW instability seems to be crucial for the emergence of superconducting state -- in ?-FeSi2 the experimental data do not find evidence for any strong electronic correlations. Our LDA and DMFT calculations results find low density of states, supporting weakness of correlations and suggest electronic configuration of Fe close to d^6.

Miiller, Wojciech; Tomczak, Jan; Simonson, Jack; Smith, Greg; Aronson, Meigan

2013-03-01

114

Acetic Acid (H3COOH): GaAs; Pb; Ti Hydrochloric Acid (HCl): Al; Cr; Cu; Fe2O3; Ga; GaAs; GaN; In; Fe; Pb; Ni; NiO, Ni2O3; Sn;  

E-print Network

Gold (Au) 1 I2 : 2 KI : 10 H2O Fe SiO2, SiN, Si, M, PR KCN Ag, Cu Al2O3, SiO2, SiN, Si, M, PR Iron (Fe) KI : potassium iodide (s) I2 : iodine (s) Br2 : bromine (l) CrO3 : chromic oxide (s) SiO2 : silicon

Garmestani, Hamid

115

Site location of Co in ?-FeSi2  

Microsoft Academic Search

In order to reveal cationic site preference in ?-FeSi2, Co-substituted samples synthesized by various techniques such as molecular beam epitaxy, ion implantation, and chemical vapor transport were investigated by 57Fe conversion electron Mo¨ssbauer (CEM) as well as 57Co Mo¨ssbauer emission (ME) spectroscopy. Literature on the structure of ?-FeSi2 is somewhat contradictory, especially on the point of the population of the

I. De´zsi; Cs. Fetzer; M. Kiss; S. Degroote; A. Vantomme

2005-01-01

116

Magnetron-sputter epitaxy of {beta}-FeSi{sub 2}(220)/Si(111) and {beta}-FeSi{sub 2}(431)/Si(001) thin films at elevated temperatures  

SciTech Connect

{beta}-FeSi{sub 2} thin films have been grown on Si(111) and Si(001) substrates by magnetron-sputter epitaxy at 700 Degree-Sign C. On Si(111), the growth is consistent with the commonly observed orientation of [001]{beta}-FeSi{sub 2}(220)//[1-10]Si(111) having three variants, in-plane rotated 120 Degree-Sign with respect to one another. However, on Si(001), under the same growth conditions, the growth is dominated by [-111]{beta}-FeSi{sub 2}(431)//[110]Si(001) with four variants, which is hitherto unknown for growing {beta}-FeSi{sub 2}. Photoelectron spectra reveal negligible differences in the valance-band and Fe2p core-level between {beta}-FeSi{sub 2} grown on Si(111) and Si(001) but an apparent increased Si-oxidization on the surface of {beta}-FeSi{sub 2}/Si(001). This phenomenon is discussed and attributed to the Si-surface termination effect, which also suggests that the Si/Fe ratio on the surface of {beta}-FeSi{sub 2}(431)/Si(001) is larger than that on the surface of {beta}-FeSi{sub 2}(220)/Si(111).

Liu Hongfei; Tan Chengcheh; Chi Dongzhi [Institute of Materials Research and Engineering (IMRE), A-STAR (Agency for Science, Technology and Research), 3 Research Link, Singapore 117602 (Singapore)

2012-07-15

117

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

118

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

119

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

PubMed Central

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

2013-01-01

120

Structural characterization of glass-ceramics made from fly ash containing SiO2-Al2O3-Fe2O3-CaO and analysis by FT-IR-XRD-SEM methods  

NASA Astrophysics Data System (ADS)

The glass-ceramics has been proposed as a useful recycling fly ash from thermal power plants. In this study, C type fly ash containing SiO2-Al2O3-Fe2O3-CaO has been sintered to form glass-ceramic materials at different temperatures between 850 °C and 1050 °C after using powder processing based on milling and powder compaction without inorganic additives. The effect of firing temperatures between 850 °C and 1050 °C on mineralogy and microstructure of sintered samples is reported. The Fourier Transform Infrared Spectra (FT-IR), Differential Thermal Analysis (DTA), X-ray Diffraction (XRD) and Scanning Electron Microscopy (SEM) techniques were applied on the sintered powder form. From the XRD results, the amount of quartz decreases on sintering, when the sintering temperature increases. On the basis of SEM observations, new crystallites structure developed in the microstructures of the C type of fly ash samples and the glassy region decreased at the crystallization temperature.

Yilmaz, G.

2012-07-01

121

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

122

Epitaxial ferromagnetic Fe{sub 3}Si/Si(111) structures with high-quality heterointerfaces  

SciTech Connect

To develop silicon-based spintronic devices, we have explored high-quality ferromagnetic Fe{sub 3}Si/silicon (Si) structures. Using low-temperature molecular beam epitaxy at 130 deg. C, we realize the epitaxial growth of ferromagnetic Fe{sub 3}Si layers on Si(111) with an abrupt interface, and the grown Fe{sub 3}Si layer has the ordered DO{sub 3} phase. Measurements of magnetic and electrical properties for the Fe{sub 3}Si/Si(111) yield a magnetic moment of {approx}3.16{mu}{sub B}/f.u. at room temperature and a rectifying Schottky-diode behavior with the ideality factor of {approx}1.08, respectively.

Hamaya, K.; Ueda, K.; Kishi, Y.; Ando, Y.; Sadoh, T.; Miyao, M. [Department of Electronics, Kyushu University, 744 Motooka, Fukuoka 819-0395 (Japan)

2008-09-29

123

Machining performance of Ti–Al–Si–N coated inserts  

Microsoft Academic Search

Ti–Al–Si–N quaternary coating has recently been developed for industrial applications due to its excellent machining performance. Here, we present a comparative research on Ti–Al–N single layer, Ti–Al–Si–N single layer, TiAlN–TiAlSiN bilayer and TiAlN\\/TiAlSiN multilayer coatings deposited onto cemented carbide substrates by cathodic arc evaporation. The incorporation of Si into the Ti–Al–N coating results in an increase in hardness and thermal

Li Chen; She Q. Wang; Yong Du; Shu Z. Zhou; Tie Gang; Ji C. Fen; Ke K. Chang; Yi W. Li; Xiang Xiong

2010-01-01

124

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

125

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

NASA Astrophysics Data System (ADS)

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

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

2014-10-01

126

?-FeSi2 in (111)Si and in (001) Si formed by ion-beam synthesis  

NASA Astrophysics Data System (ADS)

Ion-beam synthesis of ?-FeSi2 is demonstrated both in (111) Si and (001) Si substrates by 450 keV Fe ion implantation at elevated temperatures using a dose of 6×1017 Fe/cm2 and subsequent annealing at 900 °C. The structure of the buried layers has been analyzed using Rutherford backscattering spectrometry, x-ray diffraction, and (cross-section) transmission electron microscopy. In (111) Si an epitaxial layer is formed consisting of grains with lateral dimensions of approximately 5 ?m. Epitaxy of ?-FeSi2 (110) and/or (101) planes parallel to the (111) Si substrate plane is observed. In (001) Si a layer is formed consisting of grains with lateral dimensions of typically 0.5 ?m. Several grain orientations have been observed in this material, among others ?-FeSi2 {320}, {103}, and {13,7,0} parallel to (001) Si. Selected (111) Si samples were investigated optically using spectroscopic ellipsometry, and near-infrared transmittance and reflectance spectroscopy. The results confirm that the ?-FeSi2 layer has an optical band gap of 0.87 eV. The ellipsometry results indicate that the layers formed by ion-beam synthesis are more dense than those formed by surface growth techniques. Hall measurements show that the ?-FeSi2 layers obtained are p type. Mobilities observed are 1-4 cm2/V s at room temperature and approximately 25 cm2/V s at liquid-nitrogen temperature. These results show that the electrical properties of ion-beam-synthesized ?-FeSi2 is comparable with those of surface-grown material. The results confirm that optoelectronic applications of ?-FeSi2 are limited.

Oostra, D. J.; Bulle-Lieuwma, C. W. T.; Vandenhoudt, D. E. W.; Felten, F.; Jans, J. C.

1993-10-01

127

Electronic and magnetic properties of Fe2SiC  

NASA Astrophysics Data System (ADS)

The electronic structure and magnetic properties of Fe2SiC compound have been studied using the framework of an all-electron full-potential linearized augmented-plane wave (FP-LAPW) method within the local density (LSDA) and + U corrected (LSDA + U) approximations. An antiferromagnetic spin ordering of Fe atoms is shown to be the ground state for this compound. From the electronic band structures and density of states (DOS), Fe2SiC has a metallic character and from the analysis of the site and momentum projected densities, it is deduced that the bonding is achieved through hybridization of Fe-3d with C-2p states and Fe-3d with Si-3p states. It is also pointed out that the Fe-C bonding is more covalent than Fe-Si. In the FM phase, the spin polarized calculations indicate that the total magnetic moment of Fe2SiC increases from 0.41 to 4.33?B when the Hubbard U parameter for iron is considered.

Metadjer, Nadjet; Beldi, Lilia; Bouhafs, Bachir; Ruterana, Pierre

2014-10-01

128

Mesoporous FeAlMCM-41: an improved catalyst for the vapor phase tert-butylation of phenol  

Microsoft Academic Search

A range of iron and aluminum-containing mesoporous molecular sieves FeAlMCM-41 with different nSi\\/(nFe+nAl) ratios have been synthesized hydrothermally and characterized in detail by physicochemical methods, viz. X-ray diffraction (XRD), N2 adsorption, elementary analysis, UV-Vis, ESR and 27Al MAS NMR spectroscopy. UV-Vis and ESR spectroscopy suggest that iron is present in tetrahedral coordination and imparts Brønsted acidity. The catalyst FeAlMCM-41 (nSi\\/nAl=40;

A. Vinu; K. Usha Nandhini; V. Murugesan; Winfried Böhlmann; V. Umamaheswari; Andreas Pöppl; Martin Hartmann

2004-01-01

129

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

130

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

131

Iron disilicide formed in a-Si> thin films by magnetron co-sputtering  

NASA Astrophysics Data System (ADS)

The formation of ?-FeSi 2 precipitates was observed for the first time in microcrystalline Si films. The Fe-doped amorphous Si films (a-Si:Fe) were obtained using magnetron sputtering. Subsequent short-time thermal treatment led to the transition of amorphous Si to microcrystalline Si and to the formation of ?-FeSi 2 precipitates. The synthesized samples emitted at a wavelength of ??1.54 ?m at 100 K.

Kudoyarova, V. Kh.; Terukov, E. I.; Kon'kov, O. I.; Gusev, O. B.; Davydov, V. Yu.; Mosina, G. N.

2003-12-01

132

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

Microsoft Academic Search

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

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

2005-01-01

133

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

134

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

135

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

SciTech Connect

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

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

2004-12-01

136

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

137

Temperature compensating Elinvar character in Fe–Mn–Si alloys  

Microsoft Academic Search

Young's modulus–temperature and thermal expansion curves were measured in ?-Fe–31Mn–(0.25–8.67) Si–0.77C (at%) alloys by dynamic audio resonance method and in a light dilatometer. The results show that the anomalies in Young's modulus and thermal expansion appear near the Néel temperature. The temperature coefficient of Young's modulus, (1\\/Ep)(dEp\\/dT), is controlled by Si content below the Néel temperature. When Si content increases

Yansheng Zhang; Xing Tian; Zuoxiang Qin; Haichang Jiang

138

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

SciTech Connect

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

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

2000-01-01

139

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

SciTech Connect

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

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

2000-01-01

140

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

141

High temperature stability of multicomponent TiAlSiN and CrAlSiN coatings.  

PubMed

The high temperature oxidation behavior of TiAlSiN and CrAlSiN coatings was studied. These coatings were deposited on silicon substrates by using a cathodic-arc deposition system with lateral rotating arc cathodes. Titanium, chromium and Al88Si12 cathodes were used for the deposition of TiAlSiN and CrAlSiN coatings. All the deposited Ti(0.49)Al(0.44)Si(0.07)N, Ti(0.41)Al(0.51)Si(0.08)N and Cr(0.50)Al(0.440Si(0.06)N coatings showed B1-NaCl crystal structure and possessed nano-grain sizes of 6-8 nm. For the high temperature oxidation test, the coated samples were annealed at 900 degrees C in air for 2 hours. The Ti(0.41)Al(0.51)Si(0.08)N with higher Al and Si contents possessed lower oxidation rate than that of Ti(0.49)Al(0.44)Si(0.07)N. The oxide layer formed on the Ti(0.49)Al(0.44)Si(0.07)N coatings consisted of large TiO2 and TiAlSiN grains at the oxide-coating interface, followed by a layer of Al2O3 in the near-surface region. The oxidation rate of the Cr(0.50)Al(0.44)Si(0.06)N coated sample was much lower than that of the Ti(0.49)Al(0.44)Si(0.07)N and Ti(0.41)Al(0.51)Si(0.08)N. The dense Al2O3 with amorphous top layer at the oxide-coating interface retarded the diffusion of oxygen into the Cr(0.50)Al(0.44)Si(0.06)N. The deposited Cr(0.50)Al(0.44)Si(0.06)N showed a high temperature performance superior to those of the Ti(0.49)Al(0.44)Si(0.07)N and Ti(0.41)Al(0.51)Si(0.08)N. PMID:21128495

Chang, Yin-Yu; Chang, Chi-Pang

2010-07-01

142

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

SciTech Connect

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

Qin, C.; Li, A.S.; Ng, D.H. [Department of Physics, The Chinese University of Hong Kong, Shatin (Hong Kong)] [Department of Physics, The Chinese University of Hong Kong, Shatin (Hong Kong)

1996-04-01

143

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

144

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

145

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

SciTech Connect

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

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

2012-05-15

146

Characterization of the evaluation of the solid solubility of Si in sintered Fe-Si alloys using DSC technique  

SciTech Connect

Differential scanning calorimeter (DSC) is used to quantify the solid solubility of Si in sintered Fe-Si alloys. The calorimetry tests are run on Fe-Si alloys by arc melting and sintering. The relationship between the Curie temperature and the solid solubility of Si in Fe-Si alloys was determined using DSC. The solid solubility of Si in sintered Fe-Si alloys evaluated according to the relationship between magnetic transition and compositions can be compared with the results from a related quantitative electron probe microanalysis (EPMA)

Yuan, W.J. [State Key Laboratory of Advanced Technology for Materials Synthesis and Processing, Wuhan University of Technology, Wuhan 430070 (China)]. E-mail: wjyuanwut@yahoo.com.cn; Li, R. [State Key Laboratory of Advanced Technology for Materials Synthesis and Processing, Wuhan University of Technology, Wuhan 430070 (China); School of Materials Science and Engineering, Beijing University of Aeronautics and Astronautics, Beijing 100083 (China); Shen, Q. [State Key Laboratory of Advanced Technology for Materials Synthesis and Processing, Wuhan University of Technology, Wuhan 430070 (China); Zhang, L.M. [State Key Laboratory of Advanced Technology for Materials Synthesis and Processing, Wuhan University of Technology, Wuhan 430070 (China)

2007-04-15

147

Ion implantation and diffusion of Al in a {SiO 2}/{Si} system  

NASA Astrophysics Data System (ADS)

The diffusion and segregation of ion implanted Al in SiO 2 and Si layers were studied for several experimental conditions. Al ions were implanted into SiO 2, Si and through a SiO 2 layer into Si substrates at several energies (80, 300, 650 and 6000 keV) and doses (3.4 × 10 14-1 × 10 15 cm -2). The Al diffusion coefficient in SiO 2 was measured at 1200°C for times up to 5 days, and it results five orders of magnitude lower than in Si. The experiments show that the Al atoms implanted into Si do not out-diffuse during thermal treatments from the SiO 2 capping layer, but segregate at the {SiO 2}/{Si} interface. The high segregation coefficient gives rise to a trapping of Al into the oxide layer comparable to the out-diffusion of Al from uncapped Si substrates. The determined parameters for Al diffusion and segregation in the {SiO 2}/{Si} system were introduced in a simulation code to calculate the Al diffusion profiles which result in agreement with the experimental data.

La Ferla, A.; Galvagno, G.; Rinaudo, S.; Raineri, V.; Franco, G.; Camalleri, M.; Gasparotto, A.; Carnera, A.; Rimini, E.

148

Study of the structural and magnetic characteristics of epitaxial Fe3Si/Si(111) films  

NASA Astrophysics Data System (ADS)

The results of the structural and magnetic studies of the epitaxial structure prepared during the simultaneous evaporation from two iron and silicon sources on an atomically pure Si(111)7 × 7 surface at a substrate temperature of 150°C have been presented. The epitaxial structure has been identified as a single-crystal Fe3Si silicide film with the orientation Si[111]?Fe3Si[111] using methods of the X-ray structural analysis, transmission electron microscopy, and reflection high-energy electron diffraction. It has been established that the epitaxial Fe3Si film at room temperature has magnetic uniaxial anisotropy ( H a = 26 Oe) and a relatively narrow uniform ferromagnetic resonance line (? H = 11.57 Oe) measured at a pump frequency of 2.274 GHz.

Yakovlev, I. A.; Varnakov, S. N.; Belyaev, B. A.; Zharkov, S. M.; Molokeev, M. S.; Tarasov, I. A.; Ovchinnikov, S. G.

2014-07-01

149

Temperature compensating Elinvar character in Fe-Mn-Si alloys  

NASA Astrophysics Data System (ADS)

Young's modulus-temperature and thermal expansion curves were measured in ?-Fe-31Mn-(0.25-8.67) Si-0.77C (at%) alloys by dynamic audio resonance method and in a light dilatometer. The results show that the anomalies in Young's modulus and thermal expansion appear near the Néel temperature. The temperature coefficient of Young's modulus, (1/ Ep)( dEp/ dT), is controlled by Si content below the Néel temperature. When Si content increases to 5.31 at%, ( 1/ Ep)( dEp/ dT) is close to zero in temperature range from 260 to 335 K, i.e. the Fe-31Mn-5.31Si-0.67C (at%) alloy shows Elinvar character. The temperature range in which the Elinvar character appears is wider than that of ?-Fe-Mn Elinvar alloys. The change in exchange energy and the ? E effect result from the effect of Si on the antiferromagnetic behavior in ?-Fe-Mn alloys since it induces or enhances localized magnetic moment. When the increase in normal Young's modulus due to lowering temperature is compensated by the ? E effect caused by the antiferromagnetic ordering, Elinvar character appears.

Zhang, Yansheng; Tian, Xing; Qin, Zuoxiang; Jiang, Haichang

2012-03-01

150

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

NASA Astrophysics Data System (ADS)

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

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

2008-12-01

151

Sr-Al-Si co-segregated regions in eutectic Si phase of Sr-modified Al-10Si alloy.  

PubMed

The addition of 200 ppm strontium to an Al-10 wt% Si casting alloy changes the morphology of the eutectic silicon phase from coarse plate-like to fine fibrous networks. In order to clarify this modification mechanism the location of Sr within the eutectic Si phase has been investigated by a combination of high-resolution methods. Whereas three-dimensional atom probe tomography allows us to visualise the distribution of Sr on the atomic scale and to analyse its local enrichment, transmission electron microscopy yields information about the crystallographic nature of segregated regions. Segregations with two kinds of morphologies were found at the intersections of Si twin lamellae: Sr-Al-Si co-segregations of rod-like morphology and Al-rich regions of spherical morphology. Both are responsible for the formation of a high density of multiple twins and promote the anisotropic growth of the eutectic Si phase in specific crystallographic directions during solidification. The experimental findings are related to the previously postulated mechanism of "impurity induced twinning". PMID:23298536

Timpel, M; Wanderka, N; Schlesiger, R; Yamamoto, T; Isheim, D; Schmitz, G; Matsumura, S; Banhart, J

2013-09-01

152

In situ and ex situ structural characterization of beta-FeSi2 films epitaxially grown on Si(111)  

Microsoft Academic Search

The structural properties of ?-FeSi2 films grown on Si(111) are studied by means of several techniques. The films were grown in ultrahigh vacuum by solid phase epitaxy. The as-deposited Fe films were studied in situ by low energy electron diffraction (LEED) and Auger spectroscopy. Fe thicknesses were calibrated by Rutherford backscattering. The behavior of the FeMVV\\/SiLVV Auger peaks ratio intensity

S. Lagomarsino; F. Scarinci; G. Savelli; C. Giannini; P. Castrucci; M. G. Grimaldi

1992-01-01

153

Al-Fe-Ni (Aluminum-Iron-Nickel)  

SciTech Connect

[88Ray] reviewed the experimental results on the phase equilibria of this system. The reviewed results were presented as: (1) liquidus and solidus projections for Al-poor Fe-Ni alloys and for compositions near the Al-corner; (2) a reaction sequence for the solidification reactions; (3) isothermal sections at 1250, 950, 850, and 750{degrees}C for Al-poor Fe-Ni compositions; and (4) an isothermal section at 600{degrees}C near the Al-corner.

Raghavan, V.

1994-08-01

154

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

155

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

156

Vacancy formation and effects in FeAl  

Microsoft Academic Search

Iron aluminide, FeAl, has been widely studied because of its excellent high temperature oxidation and corrosion properties. At high temperatures, FeAl generates a large number of thermal vacancies, and the vacancy concentration increases with increasing aluminum content. The mechanical properties depend on the vacancy concentration, so a thorough understanding of the generation and annihilation of vacancies is necessary. Heat treatment,

J. L. Jordan; S. C. Deevi

2003-01-01

157

Mössbauer study of ultrathin Fe\\/Al multilayer films  

Microsoft Academic Search

Multilayers of Fe (between 0.3 and 2.0nm thickness) separated by a 3.0nm thick Al spacer were prepared by vacuum evaporation and were then investigated by Fe57 Mössbauer spectroscopy measurements between 4.2 and 300K and in various external magnetic fields. Mixing of the components at the interface was studied by transmission electron microscopy. The formation of a nonmagnetic Al-Fe interface alloy

D. Kaptás; J. Balogh; T. Kemény; L. F. Kiss; L. Bujdosó; A. Kovács; A. Hirata; I. Vincze

2007-01-01

158

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

Microsoft Academic Search

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

Thomas Will; Martin Okrusch; Esther Schmädicke; Guoli Chen

1998-01-01

159

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

NASA Astrophysics Data System (ADS)

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

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

2011-04-01

160

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

161

Optical characteristics of an epitaxial Fe3Si/Si(111) iron silicide film  

NASA Astrophysics Data System (ADS)

The dispersion of the relative permittivity ? of a 27-nm-thick epitaxial Fe3Si iron silicide film has been measured within the E = 1.16-4.96 eV energy range using the spectroscopic ellipsometry technique. The experimental data are compared to the relative permittivity calculated in the framework of the density functional theory using the GGA-PBE approximation. For Fe3Si, the electronic structure and the electronic density of states (DOS) are calculated. The analysis of the frequencies corresponding to the transitions between the DOS peaks demonstrates qualitative agreement with the measured absorption peaks. The analysis of the single wavelength laser ellipsometry data obtained in the course of the film growth demonstrates that a continuous layer of Fe3Si iron silicide film is formed if the film thickness achieves 5 nm.

Tarasov, I. A.; Popov, Z. I.; Varnakov, S. N.; Molokeev, M. S.; Fedorov, A. S.; Yakovlev, I. A.; Fedorov, D. A.; Ovchinnikov, S. G.

2014-07-01

162

Eutectic nucleation in hypoeutectic Al-Si alloys  

SciTech Connect

The nucleation mechanism of eutectic grains in hypoeutectic Al-Si foundry alloys has been investigated by examining deep etched specimens in high-resolution field emission gun scanning electron microscope (FEG-SEM) and by using in-situ Focused Ion Beam (FIB) milling and microscopy. Both unmodified and Sr-modified alloys were studied to characterize the nucleation mechanism of eutectic silicon flakes and fibers. It is proposed that following nucleation of eutectic Al on the primary {alpha}-Al dendrites, fine Si particles form at the solidification front upon which the eutectic Si flakes and fibers could develop. The formation of small Si particles is attributed to Si enrichment of the remaining melt due to the formation of eutectic Al (aluminum spikes) at the eutectic temperature. A hypothesis is then proposed to explain the mechanism of eutectic grains formation with main emphasis on the eutectic Si phase.

Nafisi, S. [Facility for Electron Microscopy Research, McGill University, 3640 University St., Montreal, QC, H3A 2B2 (Canada)], E-mail: snafisi@ipsco.com; Ghomashchi, R. [Advanced Materials and Processing Research Institute, Suite 122, A7-1390 Major MacKenzie, ON, L4S 0A1 (Canada); Vali, H. [Facility for Electron Microscopy Research, McGill University, 3640 University St., Montreal, QC, H3A 2B2 (Canada)

2008-10-15

163

Solid-state 27Al and 29Si NMR investigations on Si-substituted hydrogarnets  

Microsoft Academic Search

Partially deuterated Ca3Al2(SiO4)3?x(OH)4x hydrates prepared by a reaction in the presence of D2O of synthetic tricalcium aluminate with different amounts of amorphous silica were characterized by 29Si and 27Al magic-angle spinning nuclear magnetic resonance (NMR) spectroscopy. The 29Si NMR spectroscopy was used for quantifying the non-reacted silica and the resulting hydrated products. The incorporation of Si into Ca3Al2(SiO4)3?x(OH)4x was followed

J. M. Rivas Mercury; P. Pena; A. H. De Aza; X. Turrillas; I. Sobrados; J. Sanz

2007-01-01

164

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

SciTech Connect

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

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

2012-04-15

165

Growth in ultrahigh vacuum and structural characterization of FeSi sub 2 on Si(111)  

Microsoft Academic Search

FeSiâ films grown in ultrahigh vacuum on Si (111) substrates by solid phase epitaxy (SPE) have been characterized by several in situ and ex situ structural techniques: reflection high-energy electron diffraction (RHEED), x-ray diffraction (XRD), and Rutherford backscattering (RBS). The results on a film a few hundred angstroms thick confirm that the FeSiâ which forms in these conditions is the

Lagomarsino; C. Giannini; P. Castrucci; G. Savelli; J. Derrien; J. Chevrier; V. le Thanh; M. G. Grimaldi

2008-01-01

166

Characterization of a-FeSi2/c-Si heterojunctions for photovoltaic applications  

NASA Astrophysics Data System (ADS)

Amorphous iron disilicide (a-FeSi2) shows potential as a photovoltaic material due to its bandgap of ˜0.9 eV and high absorption coefficient. We present a detailed characterization of a-FeSi2, with particular emphasis on the electrical properties of a-FeSi2/c-Si heterostructures, under both dark and illuminated conditions. The samples were prepared on quartz and silicon substrates using RF co-sputtering of an iron/silicon target. Optical transmission spectroscopy was used to confirm the bandgap of the samples. Van der Pauw measurements and current-voltage analysis techniques were used to determine the carrier type and conduction mechanisms of the samples. The results show that a-FeSi2 forms a rectifying p-n heterojunction on p-type crystalline silicon. The silicide is characterized by very high carrier concentrations, resulting in the depletion region being almost entirely formed within the silicon substrate. Initial J-V results suggest carrier recombination within the silicide to be the dominant contribution to the conduction across the junction, with photovoltaic effects having been observed under AM1.5 conditions.

Antwis, L.; Gwilliam, R.; Smith, A.; Homewood, K.; Jeynes, C.

2012-03-01

167

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

168

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

169

Electrical and optical properties of Fe doped AlGaN grown by molecular beam epitaxy  

NASA Astrophysics Data System (ADS)

Electrical and optical properties of AlGaN grown by molecular beam epitaxy were studied in the Al composition range 15%-45%. Undoped films were semi-insulating, with the Fermi level pinned near Ec-0.6-0.7 eV. Si doping to (5-7)×1017 cm-3 rendered the 15% Al films conducting n-type, but a large portion of the donors were relatively deep (activation energy 95 meV), with a 0.15 eV barrier for capture of electrons giving rise to strong persistent photoconductivity (PPC) effects. The optical threshold of this effect was ˜1 eV. Doping with Fe to a concentration of ˜1017 cm-3 led to decrease in concentration of uncompensated donors, suggesting compensation by Fe acceptors. Addition of Fe strongly suppressed the formation of PPC-active centers in favor of ordinary shallow donors. For higher Al compositions, Si doping of (5-7)×1017 cm-3 did not lead to n-type conductivity. Fe doping shifted the bandedge luminescence by 25-50 meV depending on Al composition. The dominant defect band in microcathodoluminescence spectra was the blue band near 3 eV, with the energy weakly dependent on composition.

Polyakov, A. Y.; Smirnov, N. B.; Govorkov, A. V.; Kozhukhova, E. A.; Dabiran, A. M.; Chow, P. P.; Wowchak, A. M.; Pearton, S. J.

2010-01-01

170

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

NASA Astrophysics Data System (ADS)

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

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

2009-02-01

171

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

NASA Astrophysics Data System (ADS)

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

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

2013-08-01

172

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

173

Electromagnetic and microwave absorbing properties of raw and milled FeSiCr particles  

NASA Astrophysics Data System (ADS)

FeSiCr alloy (Fe: 90%, Si: 7.9%, and Cr: 2.1%) with pre-milled flaky shape was re-milled in a planetary ball-mill for 30 h. The complex permittivity (?'-j??) and permeability (?'-j??) are measured by using the transmission/reflection method for two different aspect ratios of flake-shaped FeSiCr/epoxy composites for 30%, 40%, and 50% weight ratios. Dielectric loss tangent and magnetic loss tangent of re-milled FeSiCr powder show larger electromagnetic wave energy dissipation than those of the raw flaky FeSiCr powder. For 30 wt. % of FeSiCr/epoxy absorbers with 2 mm thickness, the calculated reflection loss reaches -25 dB at 13.0 GHz for raw flaky powder, -40 dB at 11.4 GHz for the re-milled FeSiCr powder with higher aspect ratios.

Yang, R. B.; Liang, W. F.; Chen, C. C.; Choi, S. T.

2014-05-01

174

Spin transition and substitution of Fe3+ in Al-bearing post-Mg-perovskite  

NASA Astrophysics Data System (ADS)

The spin transition and substitution of Fe3+ in Mg0.85Fe3+0.15Al0.15Si0.85O3 post-Mg-perovskite (PPv) synthesized at 165-170 GPa, 2100 K were examined by X-ray emission spectroscopy (XES) and X-ray diffraction (XRD) during decompression to 37 GPa without annealing. XRD showed that samples were single phase PPv down to 49 GPa, although the samples may have partly become amorphous. The result of XES measurement indicates that Fe3+ is fully low spin (LS) for 165-100 GPa and Fe3+ largely changes from LS to high spin (HS) between 80 and ˜40 GPa. These results combined with previous reports indicate that Al and LS Fe3+ may occupy the A-(dodecahedral) and B-(octahedral) sites, respectively, as the favorable cation sites for 165-100 GPa in Al-bearing PPv. Based on the present results on Fe3+ and recent theoretical reports on Fe2+, the spin states of iron in lower mantle PPv are discussed.

Fujino, Kiyoshi; Nishio-Hamane, Daisuke; Kuwayama, Yasuhiro; Sata, Nagayoshi; Murakami, Sayaka; Whitaker, Matthew; Shinozaki, Ayako; Ohfuji, Hiroaki; Kojima, Yohei; Irifune, Tetsuo; Hiraoka, Nozomu; Ishii, Hirofumi; Tsuei, Ku-Ding

2013-04-01

175

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

176

Alloy development and processing of FeAl: An overview  

SciTech Connect

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

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

1997-03-01

177

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

NASA Astrophysics Data System (ADS)

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

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

2013-03-01

178

Role of Si on the Al behavior in the reaction layer of Al/UMo diffusion couples  

SciTech Connect

The basic experimental features characterizing the Al-Si/U-Mo interface are identified in this atomistic modeling effort, such as the formation of interfacial compounds, Si depletion in the Al matrix near the interface, reduced Al diffusion in the UMo solid solution, and the interaction between Mo and Si which inhibits Al and Si diffusion to the UMo bulk.

Garces, Jorge E.; Bozzolo, Guillermo; Hofman, Gerard; Rest, Jeffrey [Centro Atomico Bariloche, Comision Nacional de Energia Atomica, 8400 Bariloche (Argentina); Ohio Aerospace Institute, Cleveland, Ohio 44142 and NASA Glenn Research Center, Cleveland, Ohio 44135 (United States); Argonne National Laboratory, 9700 South Cass Ave., Argonne, Illinois 60439 (United States)

2007-02-12

179

FeAl–TiC and FeAl–WC composites—melt infiltration processing, microstructure and mechanical properties  

Microsoft Academic Search

TiC-based and WC-based cermets were processed with iron aluminide, an intermetallic, as a binder by pressureless melt infiltration to near full density (>97% TD). Phase equilibria calculations in the quaternary Fe–Al–Ti–C and Fe–Al–W–C systems at 1450°C were performed to determine the solubility of the carbide phases in liquid iron aluminide. This was done by using Thermocalc™ and the results show

R Subramanian; J. H Schneibel

1998-01-01

180

Corrosion resistance study of Fe Mn Al C alloys using immersion and potentiostatic tests  

NASA Astrophysics Data System (ADS)

The interaction of the Fe-32.7Mn-6.59Al-1.26Si-0.25C (wt.%) and Fe-32.3Mn-8.54Al-1.31Si-0.54C (wt.%) alloys with the environment was evaluated. Potentiostatic and total immersion tests, planned and analyzed by the statistic model of fixed effects were used for the evaluation of corrosion in gasoline, alcohol fuel, lactic acid solution (40 wt.%), sodium chloride solution (3 wt.%), and boiler water. Potentiostatic tests in 1N H 2SO 4 medium presented that the alloys showed a tendency towards passivation. The role that aluminum and silicon play in alloy corrosion mechanism was discussed.

Lins, Vanessa F. C.; Freitas, Marta Afonso; Silva, Evando M. Paula e.

2005-08-01

181

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

SciTech Connect

In this investigation, effects of the shape and size of silicon particles have been studied on the sliding wear response of two Al-Si alloys, namely, LM13 and LM29. The LM13 alloy comprised 11.70% Si, 1.02% Cu, 1.50% Ni, 1.08% Mg, 0.70% Fe, 0.80% Mn, and remainder Al. The LM29 alloy contained 23.25% Si, 0.80% Cu, 1.10% Ni, 1.21% Mg, 0.71% Fe, 0.61% Mn, and remainder Al. Wear tests were conducted under the conditions of varying sliding speed and applied pressure. The alloys were also characterized for their microstructural features and mechanical properties. The presence of primary silicon particles in the alloy led to a higher hardness but lower tensile properties. Further, refinement in the size of the primary particles improved the mechanical properties of the alloy system. The wear behavior of the alloys was influenced by the presence of primary Si particles and was a function of their size. Samples with refined but identical microconstituents (e.g., pressure cast vs gravity cast LM29 in terms of the size of primary Si particles and dendritic arm spacing) exhibited better wear characteristics. Their overall effect was further controlled by the test conditions. The study suggests that shape, size, microcracking tendency, and thermal stability of different microconstituents greatly control the mechanical and tribological properties of these alloys. The extent of effective load transfer between the phases plays an important role in this regard. Further, The overall effect of these factors is significantly governed by the test conditions.

Prasad, B.K.; Modi, O.P.; Jha, A.K.; Das, S.; Dasgupta, R.; Yegneswaran, A.H. [Regional Research Lab., Bhopal (India); Venkateswarlu, K. [National Metallurgical Lab., Jamshedpur (India)

1998-11-01

182

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

183

Thermal Properties of Amorphous Al-Ni-Si Alloy  

SciTech Connect

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

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

2007-04-23

184

Domain wall resistance in AlFe nanocontact  

NASA Astrophysics Data System (ADS)

In spin electronic devices, passing a spin-polarized current through the device is a better way to switch the magnetic configuration than applying an external magnetic field with an external current line, because there are several drawbacks associated with the use of external magnetic fields in terms of energy consumption and the risk of crosstalk. One good method is using a current to induce domain wall motion from a constriction in a spin-valve structure, which generates much interest in the case of spin-dependent electron transport across a nanocontact or a nanoconstriction. The samples are fabricated on a SiO II/Si substrate using electron beam lithography and a lift-off technique. Electron beam lithography was used to define the nanocontact structure and radio frequency magnetic sputtering with pure Ar was used to deposit an Al 50Fe 50 alloy layer about 30 nm thick and an Au cap-layer about 2 nm thick. Ultrasonic assisted lift-off in acetone is used to obtain the wire and the constriction. The I-V measurement is performed at room temperature without applied magnetic field. A sharp drop in resistance was observed in the 50-nm-wide nanocontact, which is attributed to the removal of the domain wall from the contact by the reflection of spin polarized electron. In the low resistance state, no domain wall is pinned at the contact, while in the high resistance state the presence of a domain wall must be responsible for the additional resistance, which is the domain wall resistance.

Xu, Peng; San, Haisheng; Chen, Xuyuan

2008-04-01

185

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

186

A contact electromigration study of Al-Si-Cu alloys  

Microsoft Academic Search

With the advent of VLSI device density, new materials and technologies are being developed to ensure that interconnects and interlevel contacts are reliable. In addition to the use of Si-doped Al, barrier metallization has been introduced to prevent electromigration-induced junction spiking. To permit increased current densities, Cu has also been added to the Al alloy. It could be argued that

M. Repeta; J. Kolk; M. Saran; V. Q. Ho

1990-01-01

187

Ionic radius-bond strength systematics, ionic compressibilities, and an application to (Mg, Fe)SiO3 perovskites  

NASA Astrophysics Data System (ADS)

Ionic radius-bond strength systematics have been developed from ionic radii inferred from crystal structures. These relationships, which differ for each type of ion, have been used to calculate the effective ionic radius corresponding to the bond strengths of the A and B sites of silicate perovskite. From these quantities, the substitution of Mg, rather than Fe, for Si in the B site of (Mg5Fe)SiO3 can be explained in terms of minimum strain. The model also yields linear compressibility coefficients for some metal-oxygen bonds, such as Si, Cr, Al, Fe, Mg, and Ca, that are in better agreement with observations than those predicted from bulk modulus-volume systematics.

Kudoh, Y.; Prewitt, C. T.; Finger, L. W.; Ito, E.

188

Nonequilibrium phase diagram of Fe-Mn-Al system  

SciTech Connect

The development of a new austenitic steel system with manganese and aluminum replacing nickel and chromium has been an important subject in the field of metallic materials. In, 1958, Ham and Cairns reported on the development of the Fe-Mn-Al alloy and called it a poor man's stainless steel'. Since 1960's, Zhang Yansheng and co-workers have systematically investigated austenitic steels of the Fe-Mn-Al and Fe-Mn-Al-Cr systems. These investigations include the kinetics and mechanisms of [beta]-Mn transformation, the [gamma][r arrow][epsilon][r arrow][alpha][prime] martensite transformation, the effects of alloying elements on the mechanical and physical properties and on the resistance to oxidation and to corrosion, and the formation of different alloy phases as well as their effects on the properties. The suitable range of composition for non-magnetic, cryogenic and high temperature-high strength steels based on the Fe-Mn-Al system have developed. In this paper, the nonequilibrium phase diagram of the Fe-Mn-Al system in solid solution condition and after tensile deformation at room temperature and 77 K will be presented.

Xing Tian; Zhang Yansheng (Dalian Railway Inst., Liaoning (China))

1993-05-15

189

Electrical properties of Co-doped and Ni-doped ?-FeSi2  

NASA Astrophysics Data System (ADS)

The Hall effect and electrical resistivity of iron disilicide, Fe1-xCoxSi2(0.01?x?0.03) and Fe1-yNiySi2 (0.01?y?0.03) have been measured in the temperature range between 80 and 300 K. The solid solution Fe1-xCoxSi2 is n type over the measured temperature range, while the solid solution Fe1-yNiySi2 is p type below 160 K and n type above 160 K. The carrier concentration of Fe1-xCoxSi2 at 300 K, which is in good agreement with the Co atom concentration, is one order of magnitude higher than that of Fe1-yNiySi2. The electron conduction at high temperatures for these solid solutions is explained by the small polaron mechanism.

Tani, Jun-ichi; Kido, Hiroyasu

1998-08-01

190

Mechanochemical Behavior of NiO-Al-Fe Powder Mixtures to Produce (Ni, Fe)3Al-Al2O3 Nanocomposite Powder  

NASA Astrophysics Data System (ADS)

(Ni, Fe)3Al-30 vol pct Al2O3 nanocomposite powder was synthesized by mechanochemical reaction of Fe-NiO-Al powder mixtures. Structural evolution during mechanical alloying was studied by employing X-ray diffractometry (XRD), differential thermal analysis (DTA), and transmission electron microscopy (TEM). After 78 minutes of milling, the (Ni, Fe)3Al-30 vol pct Al2O3 nanocomposite can be synthesized by reaction 3Fe + 7Al + 6NiO with a combustion mode. DTA results revealed that milling for 60 minutes decreases the temperature of reaction from 1040 K to 898 K (767 °C to 625 °C). TEM images corroborate a homogenous dispersion of reinforcements in the matrix of the nanocomposite proving that the reduction in the crystallite size of both reinforcements and matrix is within the nanometer range.

Adabavazeh, Z.; Karimzadeh, F.; Enayati, M. H.

2012-09-01

191

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

192

Phase separation in Fe-Si and Co-Si sputtered ferromagnetic alloys and the origin of their magnetic anisotropy  

SciTech Connect

Fe-Si and Co-Si thin films were studied with different Si concentrations by x-ray absorption spectroscopy (XAFS), and the analysis was confronted to their magnetic properties of coercivity and anisotropy. The analysis of the XAFS spectra showed a higher disorder in the amorphous Fe-Si films than in the Co-Si films and a larger degree of clustering of Co atoms, consistent with the higher heat of alloying of Fe-Si with respect to Co-Si alloys. Both kinds of amorphous films contained a strongly disordered silicide phase that was hardly detected by extended XAFS spectroscopy (EXAFS). EXAFS spectra were dominated by the nonmagnetic (Fe,Co)Si{sub 2} environments. The orientation of the magnetic easy axis of the films was correlated with the expected anisotropic spatial distribution of Si concentration, which was defined by the oblique angle of incidence of Si atoms during film deposition. This indicates that such a detected nonmagnetic Si rich environments were anisotropically distributed and possibly segregated, influencing in a significant way the magnetic anisotropy of these films.

Diaz, J.; Morales, R.; Valvidares, S.M.; Alameda, J.M. [Departamento de Fisica, Universidad de Oviedo, Avenida de Calvo Sotelo s/n, Oviedo-33007 (Spain)

2005-10-01

193

(Si){sub 5-2y}(AlP){sub y} alloys assembled on Si(100) from Al-P-Si{sub 3} building units  

SciTech Connect

An original class of IV/III-V hybrid (Si){sub 5-2y}(AlP){sub y}/Si(100) semiconductors have been produced via tailored interactions of molecular P(SiH{sub 3}){sub 3} and atomic Al yielding tetrahedral ''Al-P-Si{sub 3}'' building blocks. Extensive structural, optical, and vibrational characterization corroborates that these units condense to assemble single-phase, monocrystalline alloys containing 60%-90% Si (y = 0.3-1.0) as nearly defect-free layers lattice-matched to Si. Spectroscopic ellipsometry and density functional theory band structure calculations indicate mild compositional bowing of the band gaps, suggesting that the tuning needed for optoelectronic applications should be feasible.

Watkins, T.; Chizmeshya, A. V. G.; Kouvetakis, J. [Department of Chemistry and Biochemistry, Arizona State University, Tempe, Arizona 85287-1604 (United States); Jiang, L.; Xu, C.; Smith, D. J.; Menendez, J. [Department of Physics, Arizona State University, Tempe, Arizona 85287-1504 (United States)

2012-01-09

194

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

Microsoft Academic Search

Catalytic performances of Fe-AlPILC (14 wt.% Fe) and Fe-ZSM-5 (5 wt.% Fe) catalysts are compared in the wet oxidative degradation\\u000a of methomyl. Fe-ZSM-5 exhibits outstanding whereas Fe-AlPILC shows only mediocre activity. Positions of iron are analysed\\u000a in the two catalysts by Mössbauer spectroscopy. Iron is in highly dispersed state in Fe-AlPILC whereas in the other case a\\u000a hematite\\/ZSM-5 composite is formed. The

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

195

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

Microsoft Academic Search

Catalytic performances of Fe-AlPILC (14 wt.% Fe) and Fe-ZSM-5 (5 wt.% Fe) catalysts are compared in the wet oxidative degradation\\u000a of methomyl. Fe-ZSM-5 exhibits outstanding whereas Fe-AlPILC shows only mediocre activity. Positions of iron are analysed\\u000a in the two catalysts by Mössbauer spectroscopy. Iron is in highly dispersed state in Fe-AlPILC whereas in the other case a\\u000a hematite\\/ZSM-5 composite is formed. The

Károly Lázár; Andjelka Tomasevic; Goran Boskovic; Erno Kiss

2009-01-01

196

Investigation of H+ implanted Fe-Al alloys  

NASA Astrophysics Data System (ADS)

In the present work hydrogen interaction with vacancies was investigated in Fe-Al alloys with various concentration of vacancies. The Fe-Al samples were implanted with low energy H+ ions (100 keV). This procedure introduced high hydrogen concentration into relatively narrow sub-surface region in the depth of ~500 nm. Variable energy positron annihilation spectroscopy (VEPAS) was employed for investigation of hydrogen interaction with vacancies in the sub-surface region. This study revealed formation of vacancy hydrogen complexes in the sub-surface region. Thermal stability of vacancy-hydrogen complexes was investigated as well.

Luká?, F.; ?ížek, J.; Procházka, I.; Jirásková, Y.; Jani?kovi?, D.; Šimeg Veterníková, J.; Anwand, W.; Butterling, M.

2014-04-01

197

Study on electroforming Ni-Fe-SiC alloy for micro fabrication  

Microsoft Academic Search

Ni-Fe-SiC alloy is a promising material in the fabrication of micro actuator. Electrolytic codeposition technique was adopted in the deposition of Ni-Fe-SiC composite coating on stainless steel substrate, using nickel alloyed with iron as the binder phase and SiC as dispersed particles. The morphology analysis indicated that the deposit with SiC nanoparticles is level and compact and the crystal-planes of

Zheng Xiaohu; Liu Yuanwei; Gu Feng

2010-01-01

198

Evidence of intermixing at the Fe/Al interface in multilayers produced by metal vapor deposition at room temperature  

NASA Astrophysics Data System (ADS)

[Al/Fe] n multilayers have been produced by metal vapor deposition on an SiO 2 substrate. X-ray absorption spectroscopy at the Fe K-edge has been used as a local probe capable of describing the first stages of interface formation. Absorption data clearly indicate the formation of an iron aluminide at the interface below a deposited iron thickness of 0.9 nm.

Fonda, E.; Traverse, A.

2004-01-01

199

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

200

Molecular beam epitaxy of ?- FeSi films on Si(111) substrates and its influence on minority-carrier diffusion length of Si measured by EBIC  

NASA Astrophysics Data System (ADS)

We have studied the influence of molecular beam epitaxy (MBE) of ?- FeSi films on minority-carrier diffusion length of an n-type Si(111) substrate. It was found from electron beam induced current technique that the diffusion length was less influenced in sample formed with a ?- FeSi template prior to the MBE growth than that in sample grown without the template. The size of ?- FeSi grains measured by electron back-scatter diffraction was also discussed.

Kawakami, H.; Suzuno, M.; Akutsu, K.; Chen, J.; Fuxing, Y.; Sekiguchi, T.; Suemasu, T.

201

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

202

Al-Cr-Fe (Aluminum-Chromium-Iron)  

SciTech Connect

[88Ray] reviewed the experimental data on this system and presented the reviewed results as: (1) a liquidus projection for alloys near the Al-corner; (2) liquidus and solidus projections for the other regions; (3) isothermal sections for alloys with less than 50 wt.% Al at 1150, 900, 750, 700, 650, and 600{degrees}C; (4) an isothermal section at 600{degrees}C near the Al-corner; (5) a partial reaction sequence; and (6) vertical sections depicting the ordering reactions in Fe{sub 3}Al as a function of Cr content.

Raghavan, V.

1994-08-01

203

Irradiation mixing of Al into U{sub 3}Si  

SciTech Connect

Thermal and irradiation induced intermixing of uranium silicide reactor fuels with the aluminum cladding is an important consideration in understanding their fission gas and fuel swelling behavior. The authors have used Rutherford backscattering to follow the behavior of an Al thin film on U{sub 3}Si and U{sub 3}Si{sub 2} during 1.5 MeV Kr ion irradiation at temperatures of 30 and 350 C. After an initial dose during which no intermixing occurs, the Al mixes quickly into U{sub 3}Si. The threshold dose is believed to be associated with an oxide layer between the Al and the uranium silicide. At 300 C and doses greater than threshold, rates of mixing and aluminide phase growth are extracted.

Birtcher, R.C.; Ding, F.R.; Kestel, B.J.; Baldo, P.M.; Zaluzec, N.J. [Argonne National Lab., IL (United States). Materials Science Div.

1995-11-01

204

Comparison of the Crystallization Behavior of Fe-Si-B-Cu and Fe-Si-B-Cu-Nb-Based Amorphous Soft Magnetic Alloys  

NASA Astrophysics Data System (ADS)

The role of the solute elements, copper, and niobium, on the different stages of de-vitrification or crystallization of two amorphous soft magnetic alloys, Fe73.5Si13.5B9Nb3Cu1, also referred to as FINEMET, and a Fe76.5Si13.5B9Cu1 alloy, a model composition without Nb, has been investigated in detail by coupling atom probe tomography and transmission electron microscopy. The effects of copper clustering and niobium pile-up at the propagating interface between the ?-Fe3Si nanocrystals and the amorphous matrix, on the nucleation and growth kinetics have been addressed. The results demonstrate that while Cu clustering takes place in both alloys in the early stages, the added presence of Nb in FINEMET severely restricts the diffusivity of solute elements such as Cu, Si, and B. Therefore, the kinetics of solute partitioning and mobility of the nanocrystal/amorphous matrix interface is substantially slower in FINEMET as compared to the Fe76.5Si13.5B9Cu1 alloy. Consequently, the presence of Nb limits the growth rate of the ?-Fe3Si nanocrystals in FINEMET and results in the activation of a larger no. of nucleation sites, leading to a substantially more refined microstructure as compared to the Fe76.5Si13.5B9Cu1 alloy.

Smith, Casey; Katakam, Shravana; Nag, Soumya; Zhang, Y. R.; Law, J. Y.; Ramanujan, Raju V.; Dahotre, Narendra B.; Banerjee, Rajarshi

2014-06-01

205

Narrow-gap signature of Fe xCo 1- xSi single crystals  

NASA Astrophysics Data System (ADS)

Heat capacity, resistance, and magnetic susceptibility have been measured on FeSi, Fe 0.90Co 0.10Si, Fe 0.10Co 0.10Si, and CoSi single crystals. From resistance experiments, the activation energy (?) shows a small variation from ??310 K in FeSi to ??325 K for the Fe 0.90Co 0.10Si compound. For the 90% Co compound the gap signature disappears completely. Heat capacity experiments performed in the temperature range 1.5 K< T<20 K reveal an increasing Sommerfeld coefficient (?) with increasing Co content. A comparison is made with the hybridization gapped material Ce 3Bi 4Pt 3.

Lacerda, A.; Zhang, H.; Canfield, P. C.; Hundley, M. F.; Fisk, Z.; Thompson, J. D.; Seaman, C. L.; Maple, M. B.; Aeppli, G.

1993-05-01

206

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

SciTech Connect

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

Subramanian, R.; Schneibel, J.H.

1997-04-01

207

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

208

27Al-NQR\\/NMR Study of Kondo Semiconductor CeFe2Al10  

Microsoft Academic Search

27Al-NQR\\/NMR measurements have been performed on CeFe2Al10 in relevance to the novel phase below T0=27 K of isostructural CeRu2Al10. NQR peaks are assigned to five crystallographically inequivalent Al sites. No splitting of the NQR spectra down to 1.5 K confirms the lack of phase transition in this compound. The gaplike decrease in the spin-lattice relaxation rate 1\\/T1 above about 20

Yukihiro Kawamura; Shingo Edamoto; Tomoaki Takesaka; Takashi Nishioka; Harukazu Kato; Masahiro Matsumura; Yo Tokunaga; Shinsaku Kambe; Hiroshi Yasuoka

2010-01-01

209

Effect of Different Production Methods on the Mechanical and Microstructural Properties of Hypereutectic Al-Si Alloys  

NASA Astrophysics Data System (ADS)

In this study, the effects of different production methods like melt spinning, high-energy ball milling, and combined melt spinning and high-energy ball milling on the mechanical and microstructural properties of hypereutectic Al-20Si-5Fe alloys were investigated. While microstructural and spectroscopic analyses were performed using scanning electron microscopy and X-ray diffractometry, mechanical properties were measured using a depth-sensing indentation instrument with a Berkovich tip. Microstructural and spectroscopic analyses demonstrate that high-energy ball milling process applied on the melt-spun Al-20-Si-5Fe alloy for 10 minutes brings about a reduction in the size of silicon particles and intermetallic compounds. However, further increase in milling time does not yield any significant reduction in size. High-energy ball milling for 10 minutes on the starting powders is not enough to form any intermetallic phase. According to the depth-sensing indentation experiments, high-energy milling of melt-spun Al-20Si-5Fe alloys shows an incremental behavior in terms of hardness values. For the Al-20Si-5Fe alloys investigated in this study, the production technique remarkably influences their elastic-plastic response to the indentation process in terms of both magnitude and shape of P- h curves.

Fatih Kilicaslan, M.; Uzun, Orhan; Yilmaz, Fikret; Ça?lar, Seyit

2014-10-01

210

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

211

Segregation effects in Fe microalloyed NiAl single crystals  

SciTech Connect

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

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

1995-10-15

212

Processing and properties of FeAl-bonded composites  

SciTech Connect

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

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

1996-12-31

213

Al-Fe-Mn (Aluminum-Iron-Manganese)  

SciTech Connect

[88Ray] reviewed the experimental data on this system. The reviewed results were presented as: (1) liquidus and solidus projections for Fe-rich alloys and for compositions near the Al-corner; and (2) partial isothermal sections at 1200, 1000, 760, and 600{degrees}C.

Raghavan, V.

1994-08-01

214

Spin glass behavior in FeAl 2  

E-print Network

Magnetic and transport measurements indicate FeAl 2 to be an ordered intermetallic spin glass, with canonical behavior including a susceptibility cusp at T-f = 35 K and frequency-dependent susceptibility below T-f. The field-cooled and zero...

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

2001-01-01

215

Lower mantle electrical conductivity based on measurements of Al,?Fe-bearing perovskite under lower mantle conditions  

NASA Astrophysics Data System (ADS)

Laboratory measurements of the electrical conductivities of minerals provide important constraints on the chemistry and structure of the Earth's interior. We have measured the electrical conductivity of Al, Fe-bearing perovskite (Pv), the most abundant lower mantle phase, using a laser-heated diamond-anvil cell (LHDAC). The sample with composition Mg0.83Fe0.21Al0.06Si0.91O3 (Fe3+/?Fe ratio ? 0.4) was synthesized at 26 GPa and 2073 K using a multianvil press. Sample resistance was measured in situ at high pressure and high temperature up to 82 GPa and 2000 K, respectively. Results show a continuous increase in electrical conductivity with increasing pressure, in contrast to some previous studies of (Mg, Fe)SiO3 perovskite and a pyrolite assemblage where a decrease in conductivity was observed at higher pressure. Our results suggest that (1) incorporation of aluminum in Pv has a strong effect on its electrical conductivity and evolution with pressure; (2) spin crossover of Fe3+ does not occur or its effect on the conductivity is small in Al, Fe-bearing Pv, and (3) the contribution of ferropericlase to the electrical conductivity of pyrolite may be significant. The electrical conductivity profile of the Earth's lower mantle derived from geomagnetic data can be better explained by a pyrolitic bulk chemical composition rather than a non-pyrolitic model such as one based solely on perovskite.

Sinmyo, R.; Pesce, G.; Greenberg, E.; McCammon, C.; Dubrovinsky, L.

2014-05-01

216

Influence of acid-base equilibrium in the Na/sub 2/O-CaO-FeO-Al/sub 2/O/sub 3/-SiO/sub 2/-H/sub 2/O system on the structure and characteristics of man-made rock  

SciTech Connect

The influence of acid-base equilibrium on the Na/sub 2/O-CaO-FeO-Al/sub 2/O/sub 3/-SiO/sub 2/-H/sub 2/O system was investigated in this work. Granulated slag from smelted nickel, copper, and lead was used as the silicate component; and aqueous solutions of Na/sub 2/CO/sub 3/ and Na/sub 2/O x SiO/sub 2/ were used in the alkaline component. The use of this raw material in alkaline slag binders is made possible by the high activity of the alkali metal compounds which interact with nonferrous metal slags to form low based calcium hydrosilicates of the tobermorite group, sodium-calcium zeolites of gmelinite composition, calcite, and hydrated iron-containing neogenics in the solidification products that serve as auxiliary structure forming elements. These conclusions are based on a nuclear gamma resonance (Moessbauer effect) study of the iron ions during the hydration of alkaline slag binders. The study showed that there is an acid-base equilibrium which accelerates the transformation of iron II into iron III oxide, making amphoteric properties possible in this system.

Krivenko, P.V.; Skurchinskaya, Zh. V.; Sulmanov, A.A.; Pol'shin, E.V.

1987-08-20

217

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

218

Phase Diagram and Equation of State of Fe-Si Alloy  

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. While geophysical and cosmochemical models have identified several candidates (e.g. Si, O, S, C), the nature of the light element(s) remains ambiguous. The light-element component may dictate phase relations, structure and dynamic behaviour; thus, it is crucial to constrain the plausibility of various light-element candidates and their phase relations and equations of state at conditions of deep planetary interiors. Here, we present results on the high-temperature, high-pressure equation of state and phase diagram of an Fe73Si27 alloy in application to the structure and composition of Earth's core. X-ray diffraction measurements on this alloy were performed in a diamond anvil cell at high pressures. Room temperature compression experiments were conducted at beamlines 12.2.2 of the Advanced Light Source and X17C of the National Synchrotron Light Source, and laser-heating experiments were performed at beamline 13-ID-D of the Advanced Photon Source. Pressures were determined from the lattice parameter of KBr, which also acted as the thermal insulator and pressure medium in the high temperature experiments. Temperatures were determined by spectroradiometry. To benchmark our temperature measurements, we replicated the location of the hcp-fcc transition in Fe [1]. Room temperature experiments were performed in a neon pressure medium to achieve quasi-hydrostatic conditions. We have investigated the phase diagram of Fe73Si27 to pressures of over 135 GPa and temperatures up to 2800 K. In experiments up to 45 GPa at high temperatures, we find that this alloy is stable in the BiF3-type crystal structure, which is a more ordered version of the B2 crystal structure previously reported for this alloy at 300 K [2]. At pressures above 65 GPa at high temperatures, Fe73Si27 breaks down into a mixture of B2 and hcp phases, with this mixture stable to pressures of the Earth's outer core. We have determined the thermal equation of state of BiF3-type Fe73Si27 to 45 GPa, using a Mie-Gruneisen equation of state with a Burch-Murnaghan isothermal pressure term and a Debye thermal pressure contribution. We obtain an isothermal bulk modulus K = 213 GPa, its pressure derivative K' = 3.78, Gruneisen parameter 2.01, and volume 6.764 cc/mol (all at one bar) with q fixed at one. Our measured densities of the B2+hcp mixture can be used to constrain the maximum amount of silicon in the Earth's outer core by comparing them to the equation of state of hcp-Fe [3] and the seismologically-determined density. Assuming a core-mantle boundary 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 core-mantle boundary is 12.2 +/- 1.3 weight percent, under the simplifying assumption of a purely Fe-Ni-Si outer core. [1] Komabayashi & Fei (2010) JGR 115, B03202. [2] Lin et al. (2003) JGR 108, 11. [3] Dewaele et al. (2006) PRL 97, 215504.

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

2011-12-01

219

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

E-print Network

Magnetic anisotropy in Fe-25Cr-12Co-1Si alloy induced by external magnetic field ZHEN Liang( )1 27599-3255, USA Received 29 June 2006; accepted 15 January 2007 Abstract: Structural and magnetic properties of Fe-25Cr-12Co-1Si alloy thermo-magnetically treated under different external magnetic field

Qin, Lu-Chang

220

Large spin-accumulation signal in Si for epitaxial CoFe/highly (100)-textured MgO/Si devices  

NASA Astrophysics Data System (ADS)

Spin-accumulation in Si for epitaxial CoFe/highly (100)-textured MgO/Si devices is investigated and compared to that for CoFe/polycrystalline or (110)-textured MgO/Si devices. We find that magnesium (Mg) insertion between MgO and Si leads to highly (100)-textured MgO and epitaxial CoFe films. Interface resistance dependence on magnitude of spin-accumulation signal by the three-terminal Hanle measurement is quantitatively evaluated. Devices with highly (100)-textured MgO show larger magnitude of spin-accumulation signal in the low-interface-resistance region, than that with polycrystalline or (110)-textured MgO. These results indicate that magnitude of spin-accumulation signal depends on the crystallinity or the texture of ferromagnet/tunnel barrier layers on Si.

Sugiyama, H.; Ishikawa, M.; Inokuchi, T.; Tanamoto, T.; Saito, Y.; Tezuka, N.

2014-07-01

221

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

222

Double-layer oxidation protective SiC\\/Cr–Al–Si coating for carbon–carbon composites  

Microsoft Academic Search

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

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

2007-01-01

223

Limb-brightening observations from the OSO-7 satellite. III - Comparison of EUV line intensities of Fe XII, Fe XI, Fe XV, Si X and S XII, Si IX and S XI with predictions  

NASA Technical Reports Server (NTRS)

Continuing a study of heliocentric dependence of EUV emission line intensities observed by the Goddard OSO-7 spectroheliograph in 1972, the variation of lines of the ions Fe XII, Fe XI, Fe XV, Si X and S XII, Si IX and S XI is compared with the results of individual calculations for these ions, including theoretical intensities presented for Fe XII and Fe XI. Agreement is found to be good for Fe XII and reasonable for some of the lines of the other ions which in general are weaker in intensity. Several apparent anomalies are found however which may be due to unknown line components near the wavelengths observed.

Kastner, S. O.; Mason, H. E.

1978-01-01

224

Thermal expansion, Debye temperature and Grüneisen parameter of synthetic (Fe, Mg)SiO 3 orthopyroxenes  

Microsoft Academic Search

Thermal expansion properties of synthetic orthopyroxenes (Fe0.20Mg0.80)SiO3, (Fe0.40Mg0.60)SiO3, (Fe0.50Mg0.50)SiO3, (Fe0.75Mg0.25)SiO3 and (Fe0.83Mg0.17)SiO3 were systematically studied by means of single-crystal x-ray diffraction in the temperature range from 296 to 1300 K. The measurements of unit cell dimensions as a function of temperature reveal that the a and c dimensions and the unit cell volume V increase nonlinearly with a positive curvature

Hexiong Yang; Subrata Ghose

1994-01-01

225

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

NASA Astrophysics Data System (ADS)

The morphology and the quantitative composition of the Fe-Si interface layer forming at each Fe layer of a (Fe/Si)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 57Fe isotope with 95% enrichment. Samples with Fe layers of nominal thickness dFe = 2.6 nm and Si spacers of dSi = 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-Fe1-xSi 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 Fe1-xSix alloy that cannot be attributed to a single phase. In contrast, the other two layers only comprise an Fe1-xSix alloy with a Si concentration of ?0.15, but no ?-Fe.

Badía-Romano, L.; Rubín, J.; Magén, C.; Bürgler, D. E.; Bartolomé, J.

2014-07-01

226

Properties of Si-doped GaN and AlGaN\\/GaN heterostructures grown by RF-MBE on high resistivity Fe-doped GaN  

Microsoft Academic Search

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

E. Iliopoulos; M. Zervos; A. Adikimenakis; K. Tsagaraki; A. Georgakilas

2006-01-01

227

Moss bioconcentration of trace elements around a FeSi smelter: modelling and cellular distribution  

NASA Astrophysics Data System (ADS)

This article describes an evaluation of contamination by Al, As, Cd, Co, Cr, Cu, Fe, Hg, Mn, Ni, Pb, Se and Zn in the surroundings of a FeSi smelter, by measurement of tissue levels of the elements in terrestrial mosses growing in the area. The total concentrations of As, Cu and Fe were modelled by surface response fitting. Use of the sequential elution technique (using EDTA as the extracellular displacing agent) enabled determination of the concentrations of Cu and Fe in the extra- and intracellular and insoluble particulate fractions. A gradient of exponentially decreasing contamination with increasing distance from the factory was found with all fractions except for the extracellular fraction of Zn. The advantages of using of the intracellular rather than the total fraction is discussed, i.e. the former clearly shows the dose-effect relationship and reveals the concentration-distance gradients as clearly as the latter, and the difficulties associated with toxicological risk evaluation are reduced (because of different bioavailabilities of the contaminants it is not possible to infer their concentrations from total fractions).

Fernández, J. A.; Aboal, J. R.; Couto, J. A.; Carballeira, A.

228

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

229

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

230

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

231

Magnetic and transport properties of annealed Fe(SiO) alloys  

NASA Astrophysics Data System (ADS)

Previous experiments performed with co-evaporated Fe c(SiO) 1-c alloys have shown that this composite is superparamagnetic for an atomic concentration c between 0.3 and 0.5 and that it exhibits a tunnel magnetoresistance (TMR) effect for 0.4?c?0.5. We present here a further study of annealed alloys in the superparamagnetic phase performed by transmission electron microscopy, infrared absorption spectroscopy, magnetic and transport measurements. Infrared absorption spectroscopy shows that the SiO matrix decomposes in SiO x and Si, even for as-deposited alloys. The TMR observed in as-deposited alloys is thus attributed to tunneling between amorphous FeSi granules. The decomposition of the insulating matrix is activated by annealing and enhanced compared to pure SiO by the presence of Fe, as if Fe attracts Si to form an FeSi amorphous alloy. The TMR is almost unchanged until an annealing temperature of 300 °C. Above 300 °C and before reaching the crystallization temperature, the TMR steeply decreases. These results are readily attributed to the presence of amorphous FeSi.

Anas, M.; Bellouard, C.; Moreau, L.; Vergnat, M.

2004-12-01

232

Effect of Al additive in Si slurry coating on liquid Si infiltration into carbon–carbon composites  

Microsoft Academic Search

Two-dimensional carbon–carbon composites (2D-C\\/C) applied with a pure Si pre-coating or a Si–6 wt.%Al pre-coating by dipping slurry method were heated above Si melting point to perform liquid Si infiltration. For pure Si slurry pre-coating, liquid Si excessively infiltrated into the C\\/C composite and many cracks were formed inside resulting in serious degradation of the flexural strength of the C\\/C

Hai-Tao Fang; Zhong-Da Yin; Jing-Chuan Zhu; Jae-Ho Jeon; Yoo-Dong Hahn

2001-01-01

233

Transmission electron microscopy characterization of laser-clad iron-based alloy on Al-Si alloy  

SciTech Connect

Microstructure characterization is important for controlling the quality of laser cladding. In the present work, a detailed microstructure characterization by transmission electron microscopy was carried out on the iron-based alloy laser-clad on Al-Si alloy and an unambiguous identification of phases in the coating was accomplished. It was found that there is austenite, Cr{sub 7}C{sub 3} and Cr{sub 23}C{sub 6} in the clad region; {alpha}-Al, NiAl{sub 3}, Fe{sub 2}Al{sub 5} and FeAl{sub 2} in the interface region; and {alpha}-Al and silicon in the heat-affected region. A brief discussion was given for their existence based on both kinetic and thermodynamic principles.

Mei, Z. [State Key Lab of Die and Mould Technology, Huazhong University of Science and Technology, Wuhan 430074 (China)]. E-mail: mikemei_99@yahoo.com; Wang, W.Y. [Institute of Materials Science and Engineering, Henan University of Science and Technology, Luoyang 471003 (China); Wang, A.H. [State Key Lab of Die and Mould Technology, Huazhong University of Science and Technology, Wuhan 430074 (China)

2006-04-15

234

Earth mineralogical model: Gibbs free energy minimization computation in the system MgO?FeO?SiO 2  

Microsoft Academic Search

A thermodynamic database which is consistent with most available phase equilibrium experiments and calorimetric and physical measurements on the solids in the system MgO?FeO?SiO2 is established for the phases with the compositions (Mg, Fe)SiO3 (garnet, perovskite, pyroxene, and ilmenite), (Mg, Fe)2SiO4 (olivine, ?, and ? phases), SiO2 (stishovite and coesite), and (Mg, Fe)O (periclase and wustite). The data are systematized

S. K. Saxena

1996-01-01

235

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.

2014-10-01

236

The Effect of Cu Additions on the Precipitation Kinetics in an Al-Mg-Si Alloy with Excess Si  

E-print Network

The Effect of Cu Additions on the Precipitation Kinetics in an Al-Mg-Si Alloy with Excess Si M-bearing Al-Mg-Si alloy has been investi- gated by the three-dimensional atom probe (3DAP) and transmission-hardening response. After 30 minutes of artificial aging at 175 C, the alloy shows a significant increase in hardness

Laughlin, David E.

237

Creep behaviour of icosahedral Al–Cu–Fe  

Microsoft Academic Search

Transient creep experiments have been performed on poly-quasicrystalline specimens of the icosahedral Al–Cu–Fe phase. Three temperatures (870, 960 and 1000K) have been selected in the ductile regime for creep stresses that range between 30 and 320MPa. In these experiments, the specimens are first loaded in constant strain-rate conditions, then the testing machine is switched to load control and the specimens

E Giacometti; N Baluc; J Bonneville

2000-01-01

238

Deformation of FeAl single crystals at high temperatures  

Microsoft Academic Search

Single crystals of the intermetallic compound FeAl with the CsCl structure have been deformed in compression at temperatures between 470 and 1000 K to study the slip geometry and the dislocation arrangements in this material at high temperatures. At temperatures below 0·44 of the melting temperature, Tm, slip occurs on the {110}?111? systems, while at 0·44Tm, the transitions in the

Y. Umakoshi; M. Yamaguchi

1980-01-01

239

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

240

Influence of Si\\/Ga and Si\\/Al ratios on propane aromatization over highly active H-GaAlMFI  

Microsoft Academic Search

Conversion of propane to aromatics has been investigated at 550°C and space velocity range of 3000–12000cc\\/g\\/h over galloaluminosilicate zeolites (GaAlMFI) containing similar bulk Si\\/(Al+Ga) ratio but markedly different individual Si\\/Al and Si\\/Ga ratios. While Al showed a propensity to be distributed predominantly in the zeolite framework, a large fraction of total Ga was present as non-FW Ga species; due to

T. V. Choudhary; A. Kinage; S. Banerjee; V. R. Choudhary

2006-01-01

241

Evaluation of minority-carrier diffusion length in n-type ?-FeSi2 single crystals by electron-beam-induced current  

NASA Astrophysics Data System (ADS)

We have evaluated the diffusion length of minority carriers (holes) in single-crystalline n-type ?-FeSi2 bulk grown by chemical vapor transport by means of electron-beam-induced current (EBIC) technique in the edge-scan configuration. The EBIC line-scan data showed a clear exponential dependence of distance from the Al electrode. The diffusion length was estimated to be 20?m at room temperature, and increased upon high-temperature annealing, reaching approximately 30?m after annealing at 800°C for 8h. This result explained the improvement of photoresponsivity in the Al /n-?-FeSi2 Schottky diodes by high-temperature annealing.

Ootsuka, Teruhisa; Suemasu, Takashi; Chen, Jun; Sekiguchi, Takashi

2008-01-01

242

Microstructure and magnetic properties of mechanically alloyed FeSiBAlNi (Nb) high entropy alloys  

NASA Astrophysics Data System (ADS)

In this paper, the effects of milling duration and composition on the microstructure and magnetic properties of equi-atomic FeSiBAlNi and FeSiBAlNiNb high entropy alloys during mechanical alloying have been investigated using X-ray diffraction, differential scanning calorimetry, scanning electron microscopy, transmission electron microscopy and alternating gradient magnetometry. The amorphous high entropy alloys have been successfully fabricated using the mechanical alloying method. The results show that the Nb addition prolongs the milling time for the formation of the fully FeSiBAlNi amorphous phase and decreases the glass forming ability. However, FeSiBAlNiNb amorphous high entropy alloy has the higher thermal stability and heat resisting properties. Moreover, the as-milled FeSiBAlNi(Nb) powders are soft-magnetic materials indicated by their low coercivity. The saturation magnetization of the as-milled FeSiBAlNi(Nb) powders decreases with prolonging of the milling time and shows the lowest value when the amorphous high entropy alloys are formed. It suggests that the as-milled products with solid solution phases show the better soft-magnetic properties than those with fully amorphous phases. The Nb addition does not improve the soft-magnetic properties of the FeSiBAlNi high entropy alloys. Rather, both amorphous high entropy alloys have similar soft-magnetic properties after a long milling time.

Wang, Jian; Zheng, Zhou; Xu, Jing; Wang, Yan

2014-04-01

243

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

244

Towards a Superplastic Forming of Fe-Mn-Al Alloys  

SciTech Connect

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

Guanabara, Paulo Jr. [Lab. of Manufacturing Eng.-Dept. Mechatronics and Mechanical Systems Eng-Escola Politecnica-Universidade de Sao Paulo-Av. Prof. Mello Moraes, 2231 CEP05508-970-Sao Paulo (Brazil); Bueno, Levi de O. [Federal University of Sao Carlos-(UFSCar)-Dept. of Materials Engineering-Rod. Washington Luiz, km 235-CEP 13565.905-Sao Carlos (Brazil); Ferreira Batalha, Gilmar

2011-01-17

245

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

SciTech Connect

It has been reported that Fe-Mn-Si alloys containing 28-34wt%Mn and 4-6.5wt%Si exhibit a good shape memory behavior with the {gamma}{r_arrow}{epsilon} martensite transformation, when the shape deformation is applied at room temperature. Although the theoretical shear for fcc{r_arrow}hcp transformation implies a possible recoverable shape of 20%, usually in Fe-Mn-Si polycrystalline alloy it is limited to about 2%. The poor corrosion resistance and small shape memory effect (SME) in these alloys are two critical problems for their practical applications. In the present study, Fe-20.0Mn-5.1Si-8.1Cr-4.7Ni (wt%) alloy, which has better SME according to the results reported by Otsuka, is chosen to understand the mechanism of improvement of SME in Fe-Mn-Si alloy by addition of Cr and Ni.

Rong, L.J.; Ping, D.H.; Li, Y.Y.; Shi, C.X. [Academia Sinica, Shenyang (China)] [Academia Sinica, Shenyang (China)

1995-06-15

246

Structural characteristics and high-temperature oxidation behavior of porous Fe–40 at.%Al alloy  

Microsoft Academic Search

Porous FeAl alloy was prepared by Fe and Al elemental reaction synthesis. The cyclic oxidation evolutions of porous Fe–40 at.%Al\\u000a alloy at the elevated temperatures of 600 and 800 °C in air were studied and compared to porous materials of Ti, Ni, and 316L\\u000a stainless steel. It has been shown that the oxidation of porous Fe–40 at.%Al alloy fitted a power law and

P. Z. Shen; M. Song; H. Y. Gao; Y. H. He; J. Zou; N. P. Xu; B. Y. Huang; C. T. Liu

2009-01-01

247

KARAKTERISASI SIFAT MEKANIK DAN MIKROSTRUKTUR PADUAN INTERMETALIK AlFeNi SEBAGAI BAHAN KELONGSONG BAHAN BAKAR  

Microsoft Academic Search

CHARACTERIZATION OF THE MECHANICAL PROPERTIES AND MICROSTRUCTURE OF AlFeNi INTERMETALLIC ALLOY AS FUEL CLADDING MATERIAL. The AlFeNi alloy for cladding material was used to contain research reactor fuel. The alloying of AlFeNi was performed employing fusion method in arc furnace. The analysis of the mechanical properties of AlFeNi was carried out using Vickers method. The microstructure observation was performed by

M. Husna Al Hasa

2007-01-01

248

XAFS studies on a modified Al-Si hypoeutectic alloy  

NASA Astrophysics Data System (ADS)

To understand the role of Sr in doped aluminium-silicon alloys, we have conducted for the first time, Sr- K edge XAFS measurements on Al-3%Si-0.04%Sr. Aluminium-Silicon alloys are widely used in automobile and aerospace applications. Modification of these alloys with addition of trace levels of Sr (200-400 ppm) results in changing the morphology of Si eutectic from "plate" like structure to "fibrous" structure. Several theories have been proposed to understand the mechanism of modification of eutectic phases with Sr addition in these alloys, but there is no conclusive evidence in support of these theories. From our XAFS analysis, we suggest Sr-Si bonds and Sr-Sr correlations may be responsible for the morphological transformation observed in the alloy.

Srirangam, V. S. Prakash; Chattopadhyay, S.; Shibata, T.; Kaduk, J. A.; Miller, J. T.; Segre, C. U.; Shankar, S.

2009-11-01

249

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

250

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

NASA Astrophysics Data System (ADS)

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+ ions under off-normal incidence. We examined samples prepared with ion fluences of 0.1 × 1017 and 5 × 1017 ions cm-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 (Fe3Si) close to the surface into a Si-rich silicide (FeSi2) 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+ ion irradiation, our results suggest the importance of chemically bonded Fe in the surface region for the process of ripple formation.

Khanbabaee, B.; Lützenkirchen-Hecht, D.; Hübner, R.; Grenzer, J.; Facsko, S.; Pietsch, U.

2014-07-01

251

Stable Structures and Magnetic Properties of the Fe Adatom on Si(001)  

NASA Astrophysics Data System (ADS)

We determine the stable structures of Fe adatoms on Si(001) and investigate their magnetic properties, based on the density functional theory. For the Si(001) surface, we consider the clean surface and the H-terminated surface. We find that the structure of the clean Si surface is reconstructed, but the structure of the H-terminated surface is hardly reconstructed and that the magnetic moment of the Fe adatom on the H-terminated surface is larger than that of the Fe adatom on the clean surface.

Suzuki, Kenji; Kishi, Tomoya; Matsunaka, Daisuke; Diño, Wilson Agerico; Nakanishi, Hiroshi; Kasai, Hideaki

252

Effects of 2 mass % Si admixture in a laser-produced Fe plasma  

SciTech Connect

Emission of multiply charged ions and soft x-rays from the plasmas produced by laser pulses focused on (111) surface of Fe and Fe-2 mass % Si single crystals is investigated for wavelengths of 1064 and 248 nm and intensities up to {approx_equal}1x10{sup 10} W/cm{sup 2}. It is demonstrated that the Si admixture in the Fe plasma results in a higher emission of Fe{sup q+} ions (1{<=}q{<=}4) but in a markedly lower x-ray emission. The relation of wavelengths and pulse durations of laser beams used is figured in the fluence dependence of the ion emission.

Krasa, Josef; Laska, Leos; Rohlena, Karel; Velyhan, Andriy [Institute of Physics, ASCR, v.v.i., 182 21 Prague 8 (Czech Republic); Lorusso, Antonella; Nassisi, Vincenzo [Department of Physics of Lecce, Laboratorio di Elettronica Applicata e Strumentazione (LEAS), INFN of Lecce, 73100 Lecce (Italy); Czarnecka, Agata; Parys, Piotr; Ryc, Leszek; Wolowski, Jerzy [Institute of Plasma Physics and Laser Microfusion, EURATOM Association, 00-908 Warsaw (Poland)

2008-11-10

253

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

254

FeAl and NbAl3 Intermetallic-HVOF Coatings: Structure and Properties  

NASA Astrophysics Data System (ADS)

Transition metal aluminides in their coating form are currently being explored in terms of resistance to oxidation and mechanical behavior. This interest in transition metal aluminides is mainly due to the fact that their high Al content makes them attractive for high-temperature applications. This is also a reason to study their resistance to wear; they may be suitable for use in applications that produce a lot of wear in aggressive environments, thus replacing established coating materials. In this study, the microstructure, microhardness, and wear and oxidation performance of FeAl and NbAl3 coatings produced by high-velocity oxy-fuel spraying are evaluated with two main aims: (i) to compare these two coating systems—a commonly studied aluminide (FeAl) and, NbAl3, an aluminide whose deposition by thermal spraying has not been attempted to date—and (ii) to analyze the relationship between their microstructure, composition and properties, and so clarify their wear and oxidation mechanisms. In the present study, the higher hardness of niobium aluminide coatings did not correlate with a higher wear resistance and, finally, although pesting phenomena (disintegration in oxidizing environments) were already known of in bulk niobium aluminides, here their behavior in the coating form is examined. It was shown that such accelerated oxidation was inevitable with respect to the better resistance of FeAl, but further improvements are foreseen by addition of alloying elements in that alloy.

Guilemany, J. M.; Cinca, N.; Dosta, S.; Cano, I. G.

2009-12-01

255

A thermochemical data base for phase equilibria in the system Fe-Mg-Si-O at high pressure and temperature  

Microsoft Academic Search

A thermochemical data base for phases in the system Fe-Mg-Si-O at high pressures up to 300 kbar is established by supplementing the available calorimetric data with data calculated from experimental high pressure synthesis studies. Phases included in the data base are the SiO2 polymorphs, rock salt solid solutions (Fe-Mg-O), Fe2O3, Fe3O4, (Mg, Fe)2SiO4 olivine, spinel, modified spinel and (Mg, Fe)SiO3

Yingwei Fei; Surendra K. Saxena

1986-01-01

256

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

257

Phonon- and phason-dynamics in Al Cu Fe quasicrystals  

NASA Astrophysics Data System (ADS)

The lattice dynamics of quasicrystals includes local phason jumps as well as phonons. Phason dynamics is important for the understanding of both the structure and atomic motion in quasicrystals, leading to short-ranged atomic motion not involving vacancies in addition to diffusion. We have studied the phason and phonon dynamics of icosahedral i-Al62Cu25.5Fe12.5. Quasielastic Mössbauer spectroscopy (QMS) was used to probe the iron phason dynamics. Inelastic nuclear-resonant absorption (INA) of synchrotron radiation and inelastic neutron scattering (INS) were used to study the iron-partial as well as the total vibrational DOS (VDOS). We find from preliminary QMS studies that iron atoms jump on a time scale about two orders of magnitude slower than that found for copper. The EFG shows an abrupt change in slope at ca. 825 K which may be related to a transition from simple (isolated) to more complicated (co-operative) phason jumps. From INA we find that the iron-partial VDOS differs radically from that of the total (neutron-weighted) generalised VDOS measured by INS. Both these properties are related to the specific local environments of Fe and Cu in i-AlCuFe.

Brand, R. A.; Voss, J.; Calvayrac, Y.

2000-07-01

258

Determination of Al-Si connectivities in zeolites with 2D Al-Si RAPT-CPMG-HETCOR NMR  

SciTech Connect

The recently introduced concept of the combined use of rotor assisted population transfer (RAPT) and Carr-Purcell-Meiboom-Gill (CPMG) techniques to boost the sensitivity of cross polarization (CP) based NMR experiments is applied to a synthetic zeolite (ZSM-4). The sensitivity was increased by a factor of 4, which enabled acquisition of a high quality two-dimensional {sup 27}Al-{sup 29}Si HETCOR (heteronuclear correlation) spectrum. By separating the resonances in two dimensions, through-space connectivities between spins were revealed and the effective resolution was improved in both dimensions, which allowed determination of the existing ambiguities in spectral assignments in this material. The spectra provided clear indication of random distribution of aluminum and silicon within the ZSM-4 network. Additionally, unexpected correlations were observed between different components of inhomogeneously broadened {sup 29}Si and {sup 27}Al lines, which are most likely due to differences in the second coordination sphere environments.

Kennedy, G.; Wiench, J.; Pruski, M.

2008-04-11

259

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

260

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

261

Joining 6061 aluminum alloy with Al–Si–Cu filler metals  

Microsoft Academic Search

In this study, brazing of 6061 aluminum alloy was carried out with Al–10.8Si–10Cu and Al–9.6Si–20Cu filler metals at 560°C. The addition of 10wt.% copper into the Al–12Si filler metal lowered the solidus temperature from 586°C to 522°C, and the liquidus temperature from 592°C to 570°C. With the addition of 20wt.% copper into the Al–12Si filler metal, the liquidus temperature of

S. Y. Chang; L. C. Tsao; T. Y. Li; T. H. Chuang

2009-01-01

262

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

263

Al–Si Thin Films Assisted Anodic Bonding of R2O–Al2O3–SiO2 Glass–Ceramics to Stainless Steel  

Microsoft Academic Search

In this work the anodic bonding of R2O–Al2O3–SiO2 glass–ceramic to stainless steel (No. 430), together with Al–Si thin films, was investigated for the first time. Relatively smooth and dense non-crystalline Al–Si thin films with a thickness of about 60 nm, were deposited on stainless steel surfaces by DC magnetron sputtering. The anodic bonding process was performed at 350°C and between

Jinshu Cheng; Dehua Xiong; Hong Li; Hongcheng Wang

2011-01-01

264

Comparison of the effects of particle shape on thin FeSiCr electromagnetic wave absorber  

NASA Astrophysics Data System (ADS)

The raw materials of FeSiCr were processed in the ball mill for 30 h and the shape of the FeSiCr particles was changed from sphere to flake type, which was observed using a scanning electron microscope. And FeSiCr composite microwave absorbers were mixed with silicone for mobile phones and the effects of the thickness of the samples on the absorption were measured using a network analyzer in order to investigate the relationship between the microwave absorption and the material constants. The flake-type FeSiCr-rubber composite showed high reflection loss, which was due to the high complex permittivity and permeability. Also, the matching frequency shifted toward lower frequency range with microwave absorber thickness, and the maximum reflection loss of -8.7 dB was observed in 1.85 GHz for a 1.6 mm thickness.

Kim, Moon Suk; Min, Eui Hong; Koh, Jae Gui

2009-03-01

265

XPS study of the Al/SiO2 interface viewed from the SiO2 side  

NASA Technical Reports Server (NTRS)

The first nondestructive measurement of the chemical and physical characteristics of the interface between bulk SiO2 and thick aluminum films is presented. Both X-ray photoelectron spectroscopy (XPS) and electrical measurements of unannealed resistively evaporated Al films on thermal SiO2 indicate an atomically abrupt interface. Postmetallization annealing (PMA) at 450 C induces reduction of the SiO2 by the aluminum, resulting in the layer ordering SiO2/Al2O3/Si/Al. The XPS measurement is performed from the SiO2 side after removal of the Si substrate after etching with XeF2 gas and thinning of the SiO2 layer with HF:ETOH. This represents a powerful new approach to the study of metal-insulator and other interfaces.

Hecht, M. H.; Grunthaner, F. J.; Maserjian, J.

1984-01-01

266

Formation of a single ?-Fe nanophase during mechanically driven crystallization of an FeMoSiB metallic glass  

Microsoft Academic Search

In this paper we report an investigation of the mechanically driven nanocrystallization of a Fe77.2Mo0.8Si9B13 metallic glass during ball milling. TEM, XRD and DSC measurements indicated that after milling for 135 h, the amorphous sample crystallizes completely into a single ?-Fe supersaturated solid solution with a mean grain size of about 6 nm, which is fundamentally different from the thermally

F. Q. Guo; K. Lu

1996-01-01

267

Doping Effect of Transition Metal Ions on Magnetic and Optical Properties of EuO-Al2O3-SiO2 Glass  

NASA Astrophysics Data System (ADS)

We previously reported Faraday rotation of EuO-Al2O3-SiO2 glass operating in the visible region. At that time, magnetic/magnetooptic improvement of EuO-Al2O3-SiO2 glasses could be expected by incorporating divalent transition metal ions M2+ such as Co2+ and Fe2+ ions. In this paper, we report magnetic and optical properties of 70EuAl2O4-30SiO2 glasses doped with Co2+ or Fe2+ ions. Faraday rotation effects of these glasses are also presented. Conclusively, it is revealed that the ferromagnetic couplings of the dimmer Eu2+ ? -Fe2+ ? and the trimer Eu2+ ? -Co2+ ? -Eu2+ ? formed in the glasses enhance Faraday Rotation effects.

Yasuoka, Yuta; Hayakawa, Tomokatsu; Nogami, Masayuki

2011-10-01

268

Performance of LiAl/LiI(Al2O3)/FeS2 thermal batteries  

NASA Astrophysics Data System (ADS)

Performances of the LiAl/LiI(Al2O3)/FeS2 systems with different percentages of Al2O3 in the electrolyte were tested from 460 C to 580 C at various current densities and were compared with the performance of the LiAl/LiCl-KCl/FeS2 system. The results of single-cell and battery tests indicate that the LiAl/LiI(Al2O3)/FeS2 system has a feasibility for thermal potential applications. Compared to the LiAl/LiCl-KCl/FeS2 system, the LiI(Al2O3)-based system has poorer specific conductance and lower cell potential, but longer discharge life and greater capacity. A salient feature of the LiI(Al2O3)-based system, important for reliability considerations, is its apparent greater flexibility in battery internal heat control.

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

269

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

270

Electronic and optical properties of isostructural {beta}-FeSi{sub 2} and OsSi{sub 2}  

SciTech Connect

We present both theoretical and experimental investigations of electronic and optical properties of isostructural {beta}-FeSi{sub 2} and OsSi{sub 2} by means of a full-potential linear augmented plane wave method and optical measurements. We report also ellipsometric and reflectance measurements on samples of polycrystalline osmium disilicide prepared by mechanical alloying. From ab initio calculations these compounds are found to be indirect band-gap semiconductors with the fundamental gap of OsSi{sub 2} larger some 0.3--0.4 eV than the one of {beta}-FeSi{sub 2}. In addition to that, a low value of the oscillator strength is predicted for the first direct transitions in both cases. Computed optical functions for these materials were compared to the ones deduced from optical measurements, indicating very good agreement and the presence of some anisotropic effects.

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

2001-08-15

271

High strain-rate plastic flow in Al and Fe  

NASA Astrophysics Data System (ADS)

Thin Fe and Al foils were ramp-compressed over several to tens of ns timescales to study the time-dependence associated with the onset of plastic flow. Peak stress states of 15-200 GPa were achieved through laser ramp-compression where the strain rate was varied, shot-to-shot, between 106 to 108 s-1. Our data combined with data from other dynamic compression platforms reveals a strong correlation between the peak elastic precursor stress, ?E, and the strain rate at the onset of plastic flow, ?.p. In fcc Al, phonon drag dislocation flow dominates above ?.p~103s-1 and ?E ˜ 0.03 GPa where ?E scales as ?.p0.43. By contrast, the Al alloy 6061-T6 exhibits a relatively weak dependency of ?E with ?.p up to strain rates of ˜107 s-1. Our Fe data, reveals a sharp increase in ?E at ?.p>5×106s-1. This is consistent with a transition in plastic flow to a phonon drag regime.

Smith, R. F.; Eggert, J. H.; Rudd, R. E.; Swift, D. C.; Bolme, C. A.; Collins, G. W.

2011-12-01

272

Substrates influence on the structure and static electromagnetic properties of FeCoB-SiO2 thin films  

Microsoft Academic Search

The microstructure and electromagnetic properties of FeCoB-SiO2 thin films which were deposited on different substrates (silicon, glass and Mylar) by using magnetron sputtering were studied. X-Ray Diffraction revealed that FeCo nanocrystalline only precipitated in FeCoB-SiO2 thin films on silicon and glass substrates, and the FeCoB-SiO2 films on Mylar substrate were amorphous. The surface images obtained by atomic microscopy (AFM) indicated

L. Zhang; Z. W. Zhu; L. J. Deng

2009-01-01

273

Fracture toughness of SiC/Al metal matrix composite  

NASA Technical Reports Server (NTRS)

An experimental study was conducted to evaluate fracture toughness of SiC/Al metal matrix composite (MMC). The material was a 12.7 mm thick extrusion of 6061-T6 aluminum alloy with 40 v/o SiC particulates. Specimen configuration and test procedure conformed to ASTM E399 Standard for compact specimens. It was found that special procedures were necessary to obtain fatigue cracks of controlled lengths in the preparation of precracked specimens for the MMC material. Fatigue loading with both minimum and maximum loads in compression was used to start the precrack. The initial precracking would stop by self-arrest. Afterwards, the precrack could be safely extended to the desired length by additional cyclic tensile loading. Test results met practically all the E399 criteria for the calculation of plane strain fracture toughness of the material. A valid K sub IC value of the SiC/Al composite was established as K sub IC = 8.9 MPa square root of m. The threshold stress intensity under which crack would cease to grow in the material was estimated as delta K sub th = 2MPa square root of m for R = 0.09 using the fatigue precracking data. Fractographic examinations show that failure occurred by the micromechanism involved with plastic deformation although the specimens broke by brittle fracture. The effect of precracking by cyclic loading in compression on fracture toughness is included in the discussion.

Flom, Yury; Parker, B. H.; Chu, H. P.

1989-01-01

274

Phase constitution and microstructure of the Fe–Si–Cr ternary ferritic alloys  

Microsoft Academic Search

Phase constitution and microstructure of Fe-corner of the ternary Fe–Si–Cr system are investigated particularly on the multiphase fields involving bcc disordered phase, A2 phase, and bcc ordered phases, B2 and D03 phases. The (A2+D03) two-phase region is found to exist in compositions between 12 and 15 at.% Si at 10% Cr at 873 K.

Keisuke Yamamoto; Yoshisato Kimura; Yoshinao Mishima

2004-01-01

275

Characteristics of magnetic tunnel junctions comprising ferromagnetic amorphous NiFeSiB layers  

Microsoft Academic Search

In this study, we investigated that both magnetic switching and tunneling magnetoresistance (TMR) ratio of MTJs with the NiFeSiB free layer. The junctions were fabricated by a photolithographic patterning procedure and ion beam etching. A magnetic field of 100 Oe was applied during deposition to induce the uniaxial magnetic anisotropy in ferromagnetic layer.The NiFeSiB layers were used to substitute for

J. Rhee; B. Chun; J. Hwang; H. Yim; T. Kim; Y. Kim

2006-01-01

276

Al 2O 3–mullite–SiC–Al 4SiC 4 multi-composition coating for carbon\\/carbon composites  

Microsoft Academic Search

A new type of oxidation-protective multi-composition coating for carbon\\/carbon (C\\/C) composites has been produced by a pack cementation technique in an argon atmosphere. XRD analyses shows that the phases of the composite coating are composed of Al2O3, mullite, SiC and Al4SiC4, and the bonding layer between the coating and C\\/C composites are composed of Al4C3, SiC and Al4SiC4. It is

Huang Jian-feng; Zeng Xie-rong; Li He-jun; Xiong Xin-bo; Huang Min

2004-01-01

277

Liquid phase epitaxy of cubic FeSi2 on (111) Si induced by pulsed laser irradiation  

Microsoft Academic Search

Epitaxial ?FeSi2 layers thermally grown on (111) Si substrates have been irradiated by 25 ns ruby laser pulses in the energy density range 0.3–0.7 J\\/cm2. Rutherford backscattering analyses in combination with the channeling effect have shown that the silicide stoichiometry does not change for irradiations up to an energy density of 0.5 J\\/cm2, while alignment of the irradiated silicide along

M. G. Grimaldi; P. Baeri; C. Spinella; S. Lagomarsino

1992-01-01

278

The influence of rare earth element on shape memory effect in Fe-Mn-Si alloys  

SciTech Connect

Recently Fe-Mn-Si based shape memory alloys have been studied intensely. Unlike Ni-Ti and Cu-based alloys, the shape memory effect(SME) in Fe-Mn-Si based alloys is often associated with the stress induced martensite by the movement of preferred partial dislocation and its reverse motion during heating. In general, there are two effective ways to improve SME in Fe-Mn-Si alloys: (1) increasing the strength of matrix to inhibit the permanent slip of perfect dislocations to austenite during a shape change and (2) reducing the stacking fault energy to enhance the movement of partial dislocations. For Fe-Mn-Si-Re (rare earth element), Hsu suggested that Re may diminish the stacking fault energy, increase the amount of thermal or stress-induced martensite, lower the T{sub N} temperature of austenite and strengthen austenite. Consequently, the addition of rare earth element in Fe-Mn-Si may significantly improve the SME. In the present study rare earth elements were added to the Fe-Mn-Si alloy in order to investigate their effect on the shape memory effect.

Zhou, W.; Jiang, B.; Qi, X.; Hsu, T.Y.

1998-10-13

279

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

280

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

SciTech Connect

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

Amils, X.; Nogues, J.; Surinach, S.; Baro, M.D.; Munoz, J.S. [Univ. Autonoma Barcelona (Spain)] [Univ. Autonoma Barcelona (Spain)

1998-07-01

281

Welding of Very Dissimilar Materials (Fe-Al)  

NASA Astrophysics Data System (ADS)

Designers of transportation vehicles (air, land, or sea) continually seek ways to reduce vehicle weight in response to increasing fuel economy mandates, mission requirements, or other competitive pressures. One way to do this is by the selection of material types and their properties based on functional and structural requirements. While these material changes can help meet performance mandates, their implementation in a production environment relies on retaining economic competitiveness. This article traces the history of the various joining processes relevant to the current challenge in joining the very dissimilar families of steel (Fe) and aluminum (Al) alloys.

Schneider, Judy; Radzilowski, Ron

2014-09-01

282

Welding of Very Dissimilar Materials (Fe-Al)  

NASA Astrophysics Data System (ADS)

Designers of transportation vehicles (air, land, or sea) continually seek ways to reduce vehicle weight in response to increasing fuel economy mandates, mission requirements, or other competitive pressures. One way to do this is by the selection of material types and their properties based on functional and structural requirements. While these material changes can help meet performance mandates, their implementation in a production environment relies on retaining economic competitiveness. This article traces the history of the various joining processes relevant to the current challenge in joining the very dissimilar families of steel (Fe) and aluminum (Al) alloys.

Schneider, Judy; Radzilowski, Ron

2014-10-01

283

Thermodynamic Phase Relations in the MgO-FeO-SiO2 System in the Lower Mantle  

NASA Astrophysics Data System (ADS)

The perovskite (Pv) to post-perovskite (PPv) phase transition at pressures near the Earth's core-mantle boundary (CMB) is currently the favored candidate for explaining most, if not all, of the peculiarities of the D" layer (~200 km region above core) [1, 2]. Additionally, the pressure- and temperature-dependence of this phase boundary in the Earth provides the possibility of an important new thermo-barometer at the bottom of the convecting mantle. The post-perovskite phase boundary in pure MgSiO3 is fairly well known, but the experimental and calculated results on the partitioning of Fe among the stable coexisting phases and its influence on the transition pressure are currently contradictory [3, 4, 5, 6]. Using density functional theory (DFT), we investigate the MgO-FeO-SiO2 ternary system over the temperatures and pressures relevant to the core-mantle boundary. We use DFT to calculate the energies of the relevant stable phases (Pv, PPv, (Mg,Fe)O magnesio-wustite, and SiO2 stishovite) for a range of Fe compositions along the Mg-Fe binary. These results are fit with a Vinet equation of state, allowing us to parameterize the effect of both pressure and Fe composition. The effect of temperature is modeled using a Grüneisen thermal correction, where the vibrational heat capacities are determined using DFT perturbation calculations and the quasi-harmonic approximation. These pressure-, temperature-, and composition-dependent equations of state are then used to explore the predicted phase relations. The results of this investigation are a complete thermodynamic description of the stable phases for this simplified chemistry and a theoretical prediction for iron partioning in the lower mantle. In particular, we find that there may be a coincidence point (azeotrope) on the Pv-PPv phase loop, across which the sense of Fe-partitioning changes sign, as well as significant immiscibility between Mg-rich and Fe-rich post-perovskite. These findings help explain many of the seemingly incongruent experimental results on the effect of iron and are also useful in the planning of future experiments. [1] Murakami et al. (2004) Science 304, 855-858. [2] Oganov & Ono (2004) Nature 430, 445-448. [3] Caracas & Cohen (2005) GRL 32, L16310. [4] Kobayashi et al. (2005) GRL 32, L19301. [5] Auzende et al. (2007) Goldschmidt Abstract. [6] Caracas and Cohen (2008) PEPI 168, 147.

Wolf, A. S.; Caracas, R.; Asimow, P. D.

2008-12-01

284

Phase relations of Fe-Si alloy in Earth?s core  

SciTech Connect

Phase relations of an Fe{sub 0.85}Si{sub 0.15} alloy were investigated up to 240 GPa and 3000 K using in situ X-ray diffraction in a laser-heated diamond anvil cell. An alloy of this composition as starting material is found to result in a stabilized mixture of Si-rich bcc and Si-poor hcp Fe-Si phases up to at least 150 GPa and 3000 K, whereas only hcp-Fe{sub 0.85}Si{sub 0.15} is found to be stable between approximately 170 GPa and 240 GPa at high temperatures. Our extended results indicate that Fe{sub 0.85}Si{sub 0.15} alloy is likely to have the hcp structure in the inner core, instead of the previously proposed mixture of hcp and bcc phases. Due to the volumetric dominance of the hcp phase in the hcp + bcc coexistence region close to the outer-core conditions, the dense closest-packed Fe-Si liquid is more relevant to understanding the properties of the outer core.

Lin, J.-F.; Scott, H.P.; Fischer, R.A.; Chang, Y.-Y.; Kantor, I.; Prakapenka, V.B.; (NWU); (UC); (Texas); (Indiana)

2009-04-01

285

Development of FePt-Si-N nanocomposite thin films for magnetic recording  

NASA Astrophysics Data System (ADS)

Nanocomposite FePt-Si-N thin films consisting of magnetic L10 FePt nanograins and non-magnetic Si-N matrix for high density recording medium are developed in this work. The (FexPt100-x)100-ySiy-N films (x = 50-65 and y = 0-10) were fabricated on Si (100) substrates by dc reactive magnetron sputtering followed by vacuum annealing. The maximum value of coercivity around 15.3 kOe was obtained in the film with atom ratio Fe:Pt = 55:45. To achieve a high coercivity, the concentrations of Si and N also have to be properly controlled. Doping Si-N improves the coercivity of FePt film through weakening the exchange coupling interaction. Si and N also play an important role in reducing average grain size of the magnetic particles and smoothing the surface of the films. Transmission electron microscopy demonstrated the nanogranular structure consisting of FePt nanoparticles embedded in the amorphous Si-N matrix.

Liu, Jing; Zeng, Y. P.; Yu, H. Y.; Jiao, D. L.; Zheng, Z. G.; Liu, Z. W.; Zhang, G. Q.

2014-05-01

286

In situ synthesis of flexible magnetic ?-Fe2O3@SiO2 nanofibrous membranes.  

PubMed

Novel flexible, mesoporous, and magnetic ?-Fe2O3@SiO2 nanofibrous membranes with high ?-Fe2O3 content and uniform distribution were prepared by a facile in situ growth method, which exhibit prominent mechanical strength and magnetic responsive performance, as well as efficient adsorption for organics in water. PMID:24424296

Si, Yang; Tang, Xiaomin; Ge, Jianlong; Yang, Shan; El-Newehy, Mohamed; Al-Deyab, Salem S; Yu, Jianyong; Ding, Bin

2014-02-21

287

XPS study of 2H-TPP at Fe/Si(111) system  

NASA Astrophysics Data System (ADS)

Metalloporphyrins control the decisive steps in various natural and technological processes, which often involve the reversible attachment of a molecular ligand to the central metal ion. Here we studied the metalation of 2HTetraphenyl Porphyrin (2H-TPP) on Fe metal films on well reconstructed Si(111)-7×7 surface. XPS results give evidence for the Fe-TPP coordination.

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

2013-02-01

288

Growth Kinetics of Fe Films Electrodeposited on n-Si(111)  

NASA Astrophysics Data System (ADS)

Iron thin films were grown directly on n-Si(111) substrates by pulsed electrodeposition in a non-aqueous 0.1 M FeCl2 electrolyte solution. In this solution, Fe2+/Si interface showed a good diode behavior by forming a Schottky barrier. From single-step potential experiment in the potential ranges from 1.0 to 1.4 V, the formation of Fe nuclei in the early deposition stages was proceeded according to the three dimensional (3D) instantaneous nucleation followed by diffusion-limited growth rather than a progressive one. When depositing Fe using pulse potentials with the maximum voltage of 1.0 and 1.5 V, it was found that nucleation mechanism of Fe is similar with the results for the case of single-step potential experiment. However, nucleation during depositing Fe at 2.0 V initiated according to the progressive mechanism. Fe thin films, which obtains from pulse potential of 1.4 V with a frequency of 300 Hz, revealed a highly oriented columnar structures perpendicular to the surface of Si(111) and that only the single phase ?-Fe(110) was grown on Si(111) substrate.

Lee, Jong Duk; Kim, Kun Ho; Lee, Jeoung Ju; Jeong, Soon Young; Ahn, Byeong Yeol; Kim, Hyeon Soo; Shin, Yong Woon

2006-04-01

289

Charge offset stability in Si single electron devices with Al gates  

NASA Astrophysics Data System (ADS)

We report on the charge offset drift (time stability) in Si single electron devices (SEDs) defined with aluminum (Al) gates. The size of the charge offset drift (0.15 e) is intermediate between that of Al/AlO x /Al tunnel junctions (greater than 1 e) and Si SEDs defined with Si gates (0.01 e). This range of values suggests that defects in the AlO x are the main cause of the charge offset drift instability.

Zimmerman, Neil M.; Yang, Chih-Hwan; Shyan Lai, Nai; Lim, Wee Han; Dzurak, Andrew S.

2014-10-01

290

Effect of Si interlayers on the magnetic and mechanical properties of Fe/Ge neutron polarizing multilayer mirrors  

SciTech Connect

The neutron polarizing supermirror is one of the most important optical devices for polarizing neutron beams. To meet a variety of research demands, neutron polarizing supermirrors need to display high polarization efficiencies at low external magnetic fields. Fe/Si and Fe/Ge multilayers are typically used in neutron polarizing supermirrors because the contrast in scattering length densities almost vanishes for spin-down neutrons. The Fe/Si/Ge/Si multilayer, obtained by adding thin interlayers of Si to an Fe/Ge multilayer, is effective in reducing the external field strength necessary to achieve efficient neutron polarization. To gain insight into the mechanism that controls the required external field strength for a neutron polarizing supermirror, we investigated the magnetic and mechanical properties of Fe/Si, Fe/Ge, and Fe/Si/Ge/Si multilayers. The external field strength required to achieve efficient neutron polarization was found to be proportional to the compressive film stress. The compressive stress of the Fe/Si/Ge/Si multilayer was smaller by a factor of 4.4 and 2.7 than that of Fe/Si and Fe/Ge multilayers, respectively. These measurements and analyses showed that a reduction in the compressive film stress in the Fe/Si/Ge/Si multilayer permits the use of lower external field strength to achieve efficient neutron polarization. X-ray photoelectron spectroscopic studies showed that the formation of a Ge-Si solid solution in the Ge layer may explain the marked reduction in compressive stress in the case of the Fe/Si/Ge/Si multilayer. This study confirmed that a reduction in compressive film stress is very important for a high-performance neutron polarizing supermirror.

Maruyama, R.; Yamazaki, D.; Hayashida, H.; Soyama, K. [J-PARC Center, Japan Atomic Energy Agency, Tokai, Ibaraki 319-1195 (Japan); Okayasu, S. [Advanced Science Research Center, Japan Atomic Energy Agency, Tokai, Ibaraki 319-1195 (Japan); Takeda, M. [J-PARC Center, Japan Atomic Energy Agency, Tokai, Ibaraki 319-1195 (Japan); Quantum Beam Science Directorate, Japan Atomic Energy Agency, Tokai, Ibaraki 319-1195 (Japan); Zettsu, N.; Nagano, M.; Yamamura, K. [Research Center for Ultra-precision Science and Technology, Graduate School of Engineering, Osaka University, Yamadaoka 2-1, Suita, Osaka 565-0871 (Japan)

2012-03-15

291

Coherent inelastic scattering in Si and TiAl.  

PubMed

An image filter has been used to test a simple model describing the dynamical scattering of electrons that have suffered multiple interactions with plasmons. Semi-quantitative agreement is observed in both Si and TiAl under quasi two-beam conditions. In the latter material it is shown that the classical Hirsch, Howie, Whelan analysis of contrast due to dislocations can be carried out in images produced by electrons that have suffered as many as five interactions with plasmons and at thicknesses at which the unfiltered and zero loss images show no contrast. PMID:15450670

Moodie, Alexander F; Colson, Tobias A; Whitfield, Harold J

2004-11-01

292

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

293

Electromagnetic and Microwave Absorption Properties of Fe Coating on SiC with Metal Organic Chemical Vapor Reaction  

NASA Astrophysics Data System (ADS)

SiC-Fe composites are prepared by metal organic chemical vapor deposition (MOCVD) using silicon carbide (SiC) and iron pentacarbonyl (Fe(CO)5) as the precursors. The structure and morphology analyses demonstrate that the Fe nanoparticles have been deposited on the surface of the SiC particles. In terms of reflection loss (RL), the absorbing frequency band (AFB, the value of RL < -10 dB), and the matching thickness (tm), SiC-Fe composites show the best performances: minimum RL of -31.6 dB with tm = 2.0 mm at 15.1 GHz, AFB of 12.9-17.3 GHz, indicating that Fe-doped SiC by MOCVD can significantly improve the electromagnetic properties of SiC and that SiC-Fe composites could be used as an effective microwave absorption material.

Liu, Yuan; Liu, Xiang-Xuan; Wang, Xuan-Jun; Wen, Wu

2014-04-01

294

Sintering, microstructure and properties of WC-FeAlB and WC-Ni3AlB composite materials  

Microsoft Academic Search

The effect of boron on microstructure and mechanical properties of the intermetallic matrix composites (WC-FeAl-B and WC-Ni3Al-B) were investigated. The results were compared with those obtained from WC-Co composite which had same binder volume fraction and fabricated under identical sintering conditions. Boron doped FeAl (FeooA14o) and NhAl alloys were selected as potential new alternative binders in place of cobalt for

Mehdi Ahmadian-Najafabadi

2005-01-01

295

Weldability of Fe[sub 3]Al-type Aluminide  

SciTech Connect

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

David, S.A.; Zacharia, T. (Oak Ridge National Lab., TN (United States))

1993-05-01

296

Chemical synthesis of iron aluminide [FeAl] and iron aluminum carbide [Fe 3AlC 0.5] nanopowders  

Microsoft Academic Search

Nanopowders of iron aluminide [FeAl] and iron aluminum carbide [Fe3AlC0.5] are prepared by a two-step process involving the reduction of iron chloride [FeCl3] with lithium aluminum hydride [LiAlH4]. LiAlH4 serves both as a reducing agent and as a source of aluminum atoms required for the formation of the aluminides. The two-step process involves a solution phase reduction step resulting in

Yezdi B. Pithawalla; Sarojini Deevi

2004-01-01

297

Rust formation and corrosion performance of Si and Al-bearing ultrafine grained weathering steel  

Microsoft Academic Search

A high Si, Al type ultrafine-grained (UFG) weathering steel was produced by the multi-pass warm rolling method, and its corrosion resistance was estimated by a cyclic wet\\/dry corrosion test using chloride ions. The Si- and Al-bearing UFG steel exhibited excellent corrosion resistance in comparison with Si–Mn carbon steel (SM).EPMA and TEM analyses showed that Si and Al mainly exist in

T. Nishimura

2008-01-01

298

A microwave method for the preparation and sintering of {beta}'-SiAlON  

SciTech Connect

A microwave-assisted carbothermal reduction and nitridation (CTR/N) method has been used for successful preparation of monophasic {beta}'-SiAlON starting from kaolinite and carbon black. Phase pure {beta}'-SiAlON has been obtained in under 60 min in microwave field. The z value of microwave prepared {beta}'-SiAlON is found to be 2.95, which is very close to the expected value from kaolinite composition. Formation of {beta}'-SiAlON has been monitored with XRD and MASNMR of {sup 29}Si and {sup 27}Al; the possible reaction mechanism has been discussed. Kaolinite to {beta}'-SiAlON conversion appears to be a very rapid single-step reaction under microwave irradiation. {beta}'-SiAlON powders have been microwave sintered to 98.7% of theoretical density in 30 min.

Panneerselvam, M.; Rao, K.J

2003-03-24

299

A new etching method for single-crystal Al 2O 3 film on Si using Si ion implantation  

Microsoft Academic Search

A new etching method for a single-crystalline Al2O3 (100) film grown on Si (100) by chemical-vapour deposition (CVD) and a sapphire wafer is proposed for the first time using Si ion implantation and HF chemical etchant to develop potential applications of the silicon on insulator (SOI) structure. Line and space patterns of resist are transferred to sharp Al2O3 and Si

Makoto Ishida; Hoon Kim; Takayuki Kimura; Tetsuro Nakamura

1996-01-01

300

Low-cycle fatigue behavior of SiC p\\/Al–Si composites produced by spray deposition  

Microsoft Academic Search

In this research, the low-cycle fatigue life and cyclic stress response of SiCp\\/Al–Si composites produced by spray deposition were investigated in comparison to the unreinforced alloy. Both the composite and matrix alloy display cyclic hardening under total-strain amplitude 0.35–0.5%. However, under low strain amplitude (0.3%), the Al–Si alloy shows cyclic stable after the initial hardening for 200 cycles. In contrast,

W. Li; Z. H. Chen; D. Chen; J. Teng; C. Fan

2010-01-01

301

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

302

Structural and electronic properties of ?-FeSi2 nanoparticles: The role of stacking fault domains  

NASA Astrophysics Data System (ADS)

We use conventional and aberration-corrected transmission electron microscopy (TEM) and ab initio calculations to investigate the structural and electronic properties of ?-FeSi2 nanoparticles, which are a promising material for photovoltaic applications due to a band gap of <1 eV and a high absorption coefficient. The nanoparticles have average sizes of ˜20 nm, form aggregates, and are prepared by gas-phase synthesis. Amorphous SiOx shells with thicknesses of ˜1.7 nm around ?-FeSi2 cores are identified on individual nanoparticles using electron energy-loss spectroscopy, while stacking fault domains in the nanoparticles are observed using high-resolution TEM, nanobeam electron diffraction, and automated diffraction tomography. Ab initio calculations indicate only minor changes in band structure in the faulted structure when compared to perfect ?-FeSi2. The optical properties of imperfect ?-FeSi2 nanoparticles are therefore expected to be the same as those of the perfect structure, suggesting that ?-FeSi2 nanoparticles are suitable candidates for use in optical absorber layers in thin film solar cells.

Imlau, Robert; Kovács, András; Mehmedovic, Ervin; Xu, Pengxiang; Stewart, Andrew A.; Leidinger, Christine; Dunin-Borkowski, Rafal E.; Bihlmayer, Gustav; Wiggers, Hartmut; Carius, Reinhard; Kolb, Ute; Luysberg, Martina

2014-02-01

303

The Fracture Characteristics of a Near Eutectic Al-Si Based Alloy Under Compression  

NASA Astrophysics Data System (ADS)

The fracture of eutectic Si particles dictates the fracture characteristics of Al-Si based cast alloys. The morphology of these particles is found to play an important role in fracture initiation. In the current study, the effects of strain rate, temperature, strain, and heat treatment on Si particle fracture under compression were investigated. Strain rates ranging from 3 × 10-4/s to 102/s and three temperatures RT, 373 K, and 473 K (100 °C and 200 °C) are considered in this study. It is found that the Si particle fracture shows a small increase with increase in strain rate and decreases with increase in temperature at 10 pct strain. The flow stress at 10 pct strain exhibits the trend similar to particle fracture with strain rate and temperature. Particle fracture also increases with increase in strain. Large and elongated particles show a greater tendency for cracking. Most fracture occurs on particles oriented nearly perpendicular to the loading axis, and the cracks are found to occur almost parallel to the loading axis. At any strain rate, temperature, and strain, the Si particle fracture is greater for the heat-treated condition than for the non-heat-treated condition because of higher flow stress in the heat-treated condition. In addition to Si particle fracture, elongated Fe-rich intermetallic particles are also seen to fracture. These particles have specific crystallographic orientations and fracture along their major axis with the cleavage planes for their fracture being (100). Fracture of these particles might also play a role in the overall fracture behavior of this alloy since these particles cleave along their major axis leading to cracks longer than 200 ?m.

Joseph, Sudha; Tewari, Asim; Kumar, S.

2013-05-01

304

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

305

27Al-NQR/NMR Study of Kondo Semiconductor CeFe2Al10  

NASA Astrophysics Data System (ADS)

27Al-NQR/NMR measurements have been performed on CeFe2Al10 in relevance to the novel phase below T0=27 K of isostructural CeRu2Al10. NQR peaks are assigned to five crystallographically inequivalent Al sites. No splitting of the NQR spectra down to 1.5 K confirms the lack of phase transition in this compound. The gaplike decrease in the spin-lattice relaxation rate 1/T1 above about 20 K, following the Korringa law (T1T = const.) below 20 K, indicates a pseudogap opening near the Fermi level. The gap magnitude of 70 K with a mid-gap state of 42% is estimated based on a rectangular density of states. The gap magnitude is much larger than the gap of 15 K evaluated previously from the electrical resistivity, which suggests CeFe2Al10 to be a Kondo semiconductor with a Kondo temperature much higher than 300 K.

Kawamura, Yukihiro; Edamoto, Shingo; Takesaka, Tomoaki; Nishioka, Takashi; Kato, Harukazu; Matsumura, Masahiro; Tokunaga, Yo; Kambe, Shinsaku; Yasuoka, Hiroshi

2010-10-01

306

Magnetic properties and thermal stability of Fe-Zr-N/Si-N and Fe-Ta-N/Si-N multilayer film (abstract)  

SciTech Connect

It has been shown that Fe-N/Si-N multilayer films has excellent soft magnetic properties, but their properties are deteriorated easily by increasing the temperature above 400 {degree}C.{sup 1} In this study, we added a small amount of Zr and Ta to the Fe-N layer to improve their thermal stability of the soft magnetic properties. Multilayer films about 3000 A thick were deposited by an opposed target sputtering apparatus on glass slide substrates. Thickness of the Si-N layer was fixed at 50 A, while those of the Fe-Zr-N (or Fe-Ta-N) layer {ital T}{sub Fe-N} was changed in the range from 200 to 1000 A. For control of the film composition, a composite target was used. The area ratio of the Zr (or Ta) plate to total target area was changed in the range 0{similar to}4.8%. Figure 1 shows the changes in coercivity {ital H}{sub {ital c}} and saturation magnetization {ital M}{sub {ital s}} of the Fe-Zr-N/Si-N film with annealing temperature. The changes in x-ray diffraction patterns of these films are shown in Fig. 2. It is evident from these figures that the crystal growth in the films obtained by the sputtering of 4.8%: Zr-Fe target is significantly suppressed, though the film obtained by the sputtering of 3.2%: Zr is crystallized at a temperature below 400 {degree}C. Soft magnetic properties of the 4.8%: Zr film are not deteriorated by the annealing at the temperature up to 550 {degree}C. Saturation magnetization has a tendency to increase as the annealing temperature increases. Similar results are obtained in the addition of Ta.

Hoshi, Y. (Tokyo Institute of Polytechnics, Atsugi-shi, Kanagawaken 243-02 (Japan)); Naoe, M. (Tokyo Institute of Technology, Meguro-ku, Tokyo 152 (Japan))

1991-11-15

307

Disproportionation of (Mg,Fe)SiO? perovskite in Earth's deep lower mantle.  

PubMed

The mineralogical constitution of the Earth's mantle dictates the geophysical and geochemical properties of this region. Previous models of a perovskite-dominant lower mantle have been built on the assumption that the entire lower mantle down to the top of the D? layer contains ferromagnesian silicate [(Mg,Fe)SiO3] with nominally 10 mole percent Fe. On the basis of experiments in laser-heated diamond anvil cells, at pressures of 95 to 101 gigapascals and temperatures of 2200 to 2400 kelvin, we found that such perovskite is unstable; it loses its Fe and disproportionates to a nearly Fe-free MgSiO3 perovskite phase and an Fe-rich phase with a hexagonal structure. This observation has implications for enigmatic seismic features beyond ~2000 kilometers depth and suggests that the lower mantle may contain previously unidentified major phases. PMID:24855264

Zhang, Li; Meng, Yue; Yang, Wenge; Wang, Lin; Mao, Wendy L; Zeng, Qiao-Shi; Jeong, Jong Seok; Wagner, Andrew J; Mkhoyan, K Andre; Liu, Wenjun; Xu, Ruqing; Mao, Ho-kwang

2014-05-23

308

Interlayer exchange coupling of epitaxial Fe/Al/Fe trilayer films: Dynamic and static measurements  

NASA Astrophysics Data System (ADS)

This report deals with the interlayer exchange coupling of epitaxial Fe(3 nm)/Al(tAl=0.4-0.9 nm)/Fe(2 nm) trilayers studied by using ferromagnetic resonance (FMR), Brillouin light scattering (BLS) and magneto-optic Kerr effect (MOKE) measurement techniques. A very strong antiferromagnetic (AFM) interlayer exchange coupling (>3 erg/cm2) was observed at a spacer Al thickness of 0.7 nm. The bilinear (J1) and the biquadratic (J2) coupling constants were determined from (i) the fitting of angular variation (?H) of resonance field (Hres) from FMR, (ii) field variation of acoustic and optic surface mode frequencies from BLS and (iii) by fitting of longitudinal MOKE hysteresis loops. The samples with strong antiferromagnetic (AFM) coupling have a higher Hres along the easy axis than that along hard axis and their magnetizations are canted. The eightfold-like symmetry, of the acoustic Hres as a function of in-plane field angle at room temperature, is due to the strong competition between the fourfold anisotropy energy (HK) and the AFM interfacial coupling energy. This behavior vanished at low temperatures due to a strong increase of AFM coupling in comparison to HK. We distinguish the existence of canted magnetization states at resonance by fitting the experimental Hres(?H) data to the model calculation.

Kuanr, Bijoy K.

2003-05-01

309

Vacuum Carbothermic Production of Aluminum and Al-Si Alloys From Kaolin Clay: A Thermodynamic Study  

Microsoft Academic Search

Examination of the thermodynamic constraints for the carbothermic reduction of iron-free kaolinite, Al2Si2O5(OH)4, or of its calcination product mullite, Al6Si2O13, either at atmospheric pressure, or under vacuum of 10 to 10 bar, indicates the conditions required at equilibrium to produce either elementary Al or Al-Si alloys. At atmospheric pressure, a very high temperature of 3200 K would be required to obtain from

M. Halmann

2012-01-01

310

Dislocation mechanism of high-temperature plastic deformation of Al–Cu–Fe and Al–Pd–Mn icosahedral quasicrystals  

Microsoft Academic Search

Microstructures in hot-impacted Al62.5Cu25Fe12.5 and Al70.4Pd21.2Mn8.4 icosahedral quasicrystals (IQCs) were studied by transmission electron microscopy (TEM). Densely distributed dislocations and stacking fault (SF) type contrast were observed for the first time in Al–Cu–Fe IQC. This result confirms that dislocation motion is an important deformation mechanism for Al–Cu–Fe IQC. Moving dislocations in quasicrystalline materials leave phason-type SFs behind. In situ TEM

Renhui Wang; Wenge Yang; Jianian Gui; Knut Urban

2000-01-01

311

Positron annihilation study on the effect of Si-content on the recovery of deformed cast Al-Si alloys  

NASA Astrophysics Data System (ADS)

Isochronal annealing of Al-1100 and cast Al-Si alloys (Si-content 2, 4, 6 and 8 wt%) after deformation of 66% thickness reduction was investigated between room temperature (RT) and 500 °C. The annealing of defects was studied using Doppler Broadening Spectroscopy (DBS), Total Strain (?T) and Scanning Electron Microscope (SEM). It was found that; (i) three annealing stages of microstructure have been identified for Al-1100 and Al-Si alloys which are related to recovery, partial recrystallization and complete recrystallization (ii) the interaction between Si-precipitates and dislocations in Al-Si alloys leads to higher values of normalized line shape parameter (Snor) and lower values of ?T than those for Al-1100 alloy also, it retarded the recovery and recrystallization with temperature (iii) the S-W plot revealed the presence of one type of defects in Al-1100 alloy but in Al-Si alloys the slope of the trajectory changes, which may indicate the occurrence of another defect type (Si-dislocation interaction) (iv) a negative correlation is observed between ?T and Snor while a positive correlation between ?T and normalized wing parameter (Wnor) is obvious.

El-Gamal, S.

2013-09-01

312

Tetrakis[tris(trimethylsilyl)silylaluminium(I)] Al 4[Si(SiMe 3) 3] 4—eine siliziumreicheVerbindung mit zentralem tetraedrischem Al 4Kern  

Microsoft Academic Search

The first neutral aluminium(I) compound Al4Cp*4 [Angew. Chem. 103 (1991) 594; Angew. Chem. Int. Ed. Engl. 30 (1991) 564] was published in 1991. Until now other neutral aluminum polyhedra, e.g. Al4[Si(t-Bu)3]4 [Organometallics 17 (1998) 1894], Al4[C(SiMe3)3]4 [Angew. Chem. 110 (1998) 2059; Angew. Chem. Int. Ed. Engl. 37 (1998) 1952] and Al4Cp*3[N(SiMe3)2] [J. Organomet. Chem. 561 (1998) 203], could be synthesized

Andreas Purath; Hansgeorg Schnöckel

1999-01-01

313

Galvanic Deposition of Nanoporous Si onto 6061 Al Alloy from Aqueous HF  

E-print Network

Galvanic Deposition of Nanoporous Si onto 6061 Al Alloy from Aqueous HF Aarti Krishnamurthy,a Don H University, Potsdam, New York 13699-5705, USA We report galvanic deposition of Si onto 6061 Al alloy from,4 and for corrosion-resistant coatings.5 Si thin films are typically deposited by expensive vacuum meth- ods

Suni, Ian Ivar

314

Oxidation Control of Atmospheric Plasma Sprayed FeAl Intermetallic Coatings Using Dry-Ice Blasting  

NASA Astrophysics Data System (ADS)

The performance of atmospheric plasma sprayed FeAl coatings has been remarkably limited because of oxidation and phase transformation during the high-temperature process of preparation. In the present work, FeAl intermetallic coatings were prepared by atmospheric plasma spraying combined with dry-ice blasting. The microstructure, oxidation, porosity, and surface roughness of FeAl intermetallic coatings were investigated. The results show that a denser FeAl coating with a lower content of oxide and lower degree of phase transformation can be achieved because of the cryogenic, the cleaning, and the mechanical effects of dry-ice blasting. The surface roughness value decreased, and the adhesive strength of FeAl coating increased after the application of dry-ice blasting during the atmospheric plasma spraying process. Moreover, the microhardness of the FeAl coating increased by 72%, due to the lower porosity and higher dislocation density.

Song, Bo; Dong, Shujuan; Coddet, Pierre; Hansz, Bernard; Grosdidier, Thierry; Liao, Hanlin; Coddet, Christian

2013-03-01

315

On the improvement of shape memory effect in Fe-16Mn-5Si-9Cr-4Ni alloys by thermomechanical treatment  

SciTech Connect

The shape memory effect in Fe-Mn-Si alloys was discovered in the early 80's. Since then many efforts have been made in improving the shape memory effect in this alloy. Obtaining a shape memory strain up to 5% in order to get practical use is still an endeavor. Complete shape memory effect has been found both in single crystalline and in polycrystalline Fe-Mn-Si alloys, but as the prestrains in those investigations were quite small, the recoverable strain is limited to about 2%. Recently, Yang et al. obtained in Fe-29Mn-5.5Si-4.5Cr-2Ni-3.5Co (wt%) and Fe-13.7Mn-6Si-8.3Cr-4.9Ni (wt%) alloys over 5% reversible strain by applying 8% prestrain in a bending test. But till now a full recoverable strain is only obtained for a prestrain less than 2%. In the present study, the shape memory effect of an Fe-16Mn-5Si-9Cr-4Ni (wt%) alloy was tested. By applying the training treatment of 3--5% prestrain and 600 C annealing, a 3.5% recoverable strain can be reached in this alloy. Reasons for the improvement of the shape memory effect are proposed.

Gu, Q.; Humbeeck, J. Van; Delaey, L. (K.U. Leuven (Belgium.). Dept. of Metallurgy and Materials Engineering)

1994-06-15

316

Mechanical alloying of FeAl intermetallics in the DO3 composition range  

Microsoft Academic Search

Binary Fe-Al intermetallics with compositions ranging between 10 and 30 at% have been produced by mechanical alloying. The elemental powders were milled together resulting in the dissolution of the Al atoms into the Fe lattice. Subsequent heat treatment of the compacted powder resulted in the formation of the intermetallic. However, complete suppression of the DO3 (Fe3Al) structure in favour of

G. H. Fair; J. V. Wood

1994-01-01

317

Semiconducting behaviour in CeT2Al10 (T=Fe and Ru)  

Microsoft Academic Search

We present results of the magnetic susceptibility, electrical resistivity and thermopower for CeT2Al10 (T=Fe and Ru) crystallizing in the orthorhombic YbFe2Al10-type structure. The magnetic susceptibility for CeFe2Al10 shows a maximum at 70 K which is a characteristic of a valence fluctuation system. The electrical resistivity below 20 K exhibits semiconducting behaviour with an energy gap of 15 K. On the

Yuji Muro; Kiyoichiro Motoya; Yuta Saiga; Toshiro Takabatake

2010-01-01

318

Electromagnetic properties of flake-shaped Fe-Si alloy particles prepared by ball milling  

NASA Astrophysics Data System (ADS)

Flake-shaped Fe-Si alloy particles with high aspect ratios were fabricated by ball milling commercially available Fe-Si powder, aiming to fabricate high-performance microwave absorbing fillers for coatings applied in 1-4 GHz range. To compare with spherical particles, higher permittivity and permeability was observed by using flaky particles as fillers. High aspect ratios contributed to an enhanced dielectric relaxation in the 1-4 GHz band, resulting in an increased permittivity. The thin thickness together with the high resistivity of Fe-Si flakes was believed to be helpful for suppressing the effect of eddy current and thus lead to an increase in the permeability. The electromagnetic wave absorbing (EMA) performances were observed to be enhanced. With a thin thickness of 2 mm, a wide absorption band with a minimum reflection loss of -12 dB was achieved in 1-4 GHz range, when using 75 wt% of flaky Fe-Si particles as fillers. The study indicated that flake-shaped Fe-Si particles were a promising candidate for EMA materials in L and S bands.

Cao, Lei; Jiang, Jian-Tang; Wang, Zeng-Quan; Gong, Yuan-Xun; Liu, Chao; Zhen, Liang

2014-11-01

319

First-principles investigation of mechanical behavior of B2 type aluminides: FeAl and NiAl  

SciTech Connect

First-principles calculations of the elastic constants, shear fault energies, and cleavage strength of NiAl and FeAl are presented. For NiAl, we find that the dissociation of {l angle}111{r angle} superdislocation into partial dislocations is unlikely, due to a high antiphase boundary energy and a weak repulsive elastic force between partial dislocations. FeAl has a high ideal cleavage strength as a result of the directional d-bond formation at the Fe sites. The strong ordering behavior of NiAl is explained in terms of the Al-to-Ni charge transfer and the repulsive interaction between Al atoms. The spontaneous glide decomposition of the {l angle}111{r angle} superdislocation in NiAl is also discussed. 8 refs., 2 figs., 2 tabs.

Fu, C.L.; Yoo, M.H.

1990-01-01

320

Negative stiffness of the FeAl intermetallic nanofilm  

NASA Astrophysics Data System (ADS)

Uniaxial tension of the nanofilm of the FeAl intermetallic alloy has been simulated by the molecular dynamics method. It has been found that the nanofilm is elastically deformed by 37%. There is a region in the stress-strain curve, where the strain increases with a decrease in the tensile stress, which indicates the negative stiffness of the nanofilm in this region. The uniform strain with a decrease in the tensile stress is unstable thermodynamically, which leads to the appearance domains with different elastic strains in the nanofilm. The deformation in the unstable region develops due to the domain-wall motion; as a result, the domains with a higher strain grow at the expense of the domains with a lower strain. A similar deformation mechanism was recently described by Savin with coworkers for the DNA molecule.

Bukreeva, K. A.; Babicheva, R. I.; Dmitriev, S. V.; Zhou, K.; Mulyukov, R. R.

2013-09-01

321

Effect of Multi-Scale Thermoelectric Magnetic Convection on Solidification Microstructure in Directionally Solidified Al-Si Alloys Under a Transverse Magnetic Field  

NASA Astrophysics Data System (ADS)

The influence of a transverse magnetic field (B < 1 T) on the solidification structure in directionally solidified Al-Si alloys was investigated. Experimental results indicate that the magnetic field caused macrosegregation, dendrite refinement, and a decrease in the length of the mushy zone in both Al-7 wt pct Si alloy and Al-7 wt pct Si-1 wt pct Fe alloys. Moreover, the application of the magnetic field is capable of separating the Fe-rich intermetallic phases from Al-7 wt pct Si-1 wt pct Fe alloy. Thermoelectric magnetic convection (TEMC) was numerically simulated during the directional solidification of Al-Si alloys. The results reveal that the TEMC increases to a maximum ( u_{{max} } ) when the magnetic field reaches a critical magnetic field strength ( B_{{max} } ), and then decreases as the magnetic field strength increases further. The TEMC exhibits the multi-scales effects: the u_{{max} } and B_{{max} } values are different at various scales, with u_{{max} } decreasing and B_{{max} } increasing as the scale decreases. The modification of the solidification structure under the magnetic field should be attributed to the TEMC on the sample and dendrite scales.

Li, Xi; Du, Dafan; Gagnoud, Annie; Ren, Zhongming; Fautrelle, Yves; Moreau, Rene

2014-08-01

322

Effect of Multi-Scale Thermoelectric Magnetic Convection on Solidification Microstructure in Directionally Solidified Al-Si Alloys Under a Transverse Magnetic Field  

NASA Astrophysics Data System (ADS)

The influence of a transverse magnetic field ( B < 1 T) on the solidification structure in directionally solidified Al-Si alloys was investigated. Experimental results indicate that the magnetic field caused macrosegregation, dendrite refinement, and a decrease in the length of the mushy zone in both Al-7 wt pct Si alloy and Al-7 wt pct Si-1 wt pct Fe alloys. Moreover, the application of the magnetic field is capable of separating the Fe-rich intermetallic phases from Al-7 wt pct Si-1 wt pct Fe alloy. Thermoelectric magnetic convection (TEMC) was numerically simulated during the directional solidification of Al-Si alloys. The results reveal that the TEMC increases to a maximum () when the magnetic field reaches a critical magnetic field strength (), and then decreases as the magnetic field strength increases further. The TEMC exhibits the multi-scales effects: the and values are different at various scales, with decreasing and increasing as the scale decreases. The modification of the solidification structure under the magnetic field should be attributed to the TEMC on the sample and dendrite scales.

Li, Xi; Du, Dafan; Gagnoud, Annie; Ren, Zhongming; Fautrelle, Yves; Moreau, Rene

2014-11-01

323

Influence of Si on the particle growth of AlN ceramics  

NASA Astrophysics Data System (ADS)

Aluminum nitride (AlN) powders doped with various concentrations of Si were investigated to understand the effects of Si on the growth and luminescence of AlN. Certain Si-doping concentrations enhanced the particle growth of AlN and affected the UV emission bands at 280 and 350 nm. Cross-sectional cathodoluminescence images showed that SiNx coated AlN particles on the surface and formed grain boundaries. These grain boundaries may play a critical role in the solid-state reaction and crystal growth of AlN.

Cho, Yujin; Dierre, Benjamin; Takeda, Takashi; Takahashi, Kohsei; Hirosaki, Naoto; Sekiguchi, Takashi

2014-11-01

324

Infiltration of Saffil alumina fiber with AlCu and AlSi alloys  

SciTech Connect

Currently there is a considerable scientific and technological interest in the composite materials, which a strong ceramic reinforcement is incorporated into a metal matrix (MMC) to tailor its properties for specific applications. Among the various techniques for fabricating MMC, the liquid metal infiltration process by means of a pressurized gas is an attractive fabrication route for near net shaped metal matrix composite and has been successfully used to fabricate Al, Mg and more recently, Ni and Ni aluminide matrix composites, which can be reinforced by SiC or Al[sub 2]O[sub 3] particles, whiskers, or short fibers. This paper describes the experimental technique used and presents an experimental investigation of the effects of the process parameters employed, such as the preform and melt temperatures, the volume fraction of fibers in the preform and the applied pressure upon the infiltration length of a chopped preform during a unidirectional infiltration aided by gas pressure casting. The experiments of the present work were conducted to provide kinetic data with a view to optimizing the selection of the process initial conditions for infiltration which have an effect on the infiltration length of the molten matrix alloy into a preform and it is a first step in investigating the correlation between the infiltration length (fluidity) of AlCuSi matrix alloys and the microstructure of the composites fabricated by pressure casting. For this purpose, this paper focuses on AlCu and AlSi matrix alloys reinforced by short-fibers [delta]-alumina SAFFIL. The experiments reported here were performed with the fibers initially at a temperature significantly below the metal melting point. This is the case of practical interest for the fabrication of many fiber-reinforced metal components.

Garbellini, O.; Morando, C.; Biloni, H.; Palacio, H. (Comision de Investigaciones Cientificas de la Provincia de Buenos Aires, Tandil (Argentina). Inst. de Fisica de Materiales)

1999-06-18

325

Porosity formation in Al-9 wt pct Si-3 wt pct Cu alloy systems: Metallographic observations  

SciTech Connect

The formation of porosity in Al-9 wt pct Si-3 wt pct Cu-X alloys was studied as a function of (1) the hydrogen content of the melt; (2) the melt treatment additives, namely, modifier (Sr), grain refiner (TiB{sub 2}), and primary silicon refiner (P); (3) alloying elements for precipitation hardening such as Mg and Zn; (4) intermetallics ({alpha}-iron, {beta}-iron, sludge, and Al{sub 2}Cu); and (5) solidification conditions (solidification time and solidus velocity). The results were statistically analyzed, based on the quantitative image analysis data of the porosity observed in samples obtained from a set of 72 solidification experiments. Metallographic aspects of pore size and pore morphology related to the preceding parameters and the possible mechanisms of porosity formation are highlighted in this article. The results show that a melt hydrogen content of 0.1 mL/100 g Al has the same effect on percentage porosity as that obtained with an addition of 185 ppm strontium to the melt. Grain refiner particles, phosphorus, and magnesium reduce percentage porosity, although in different magnitudes. A Mg-Sr or Mg-GR combination further reduces the percentage porosity observed in the casting. The {beta} needles of the Al{sub 5}FeSi intermetallic phase are very active as pore nucleation sites. All intermetallics, viz. {beta} needles, {alpha}-Chinese script phase, Al{sub 2}Cu phase, and sludge restrict pore growth and expansion. Increasing the local solidification time or the solidus velocity increases the pore parameters. Pore growth in the two cases is attributed, respectively, to a diffusion-controlled growth process and to the formation of hot spots.

Roy, N.; Samuel, A.M.; Samuel, F.H. [Univ. of Quebec, Chicoutimi, Quebec (Canada). Dept. of Applied Sciences

1996-02-01

326

High strain rate superplasticity of an ultrafine grained Al-Ti-Fe alloy  

SciTech Connect

Transition metals have limited solubility in aluminum, and alloying content higher than the solubility limit results in high melting point aluminides. When Fe is added into a hyper peritectic Al-Ti alloy, Al{sub x}Fe(X = 3 or 6) aluminide forms by an eutectic reaction at 655 C, and thus the Al{sub x}Fe phase could be an additional reinforcement to the Al-Ti system. The presence of the secondary Al{sub x}Fe particles is expected to enhance superplasticity by promoting finer grain size during PM processing and by retarding grain growth during deformation at elevated temperatures. The purpose of this study is to investigate HSRS behavior of an Fe-added Al-10wt%Ti alloy prepared by powder metallurgy and to compare it with that of similarly processed Al-10wt%Ti alloy.

Kum, D.W. [Korea Inst. of Science and Technology, Seoul (Korea, Republic of)] [Korea Inst. of Science and Technology, Seoul (Korea, Republic of); Kim, W.J. [Hong-ik Univ., Seoul (Korea, Republic of)] [Hong-ik Univ., Seoul (Korea, Republic of); Frommeyer, G. [Max-Plank-Inst. fuer Eisenforschung GmbH, Dusseldorf (Germany)] [Max-Plank-Inst. fuer Eisenforschung GmbH, Dusseldorf (Germany)

1998-12-18

327

Superferromagnetism in chain-like Fe@SiO2 nanoparticle ensembles  

NASA Astrophysics Data System (ADS)

One-dimensional (1D) chain-like nanocomposites, created by ensembles of nanoparticles of with diameter ˜ 13 nm, which are composed of an iron core (˜4 nm) and a silica protective layer, were prepared by a self-assembly process. Chain-like Fe@SiO2 ensembles were formed due to strong magnetic dipole-dipole interactions between individual Fe nanoparticles and the subsequent fixation of the Fe particles by the SiO2 layers. X-ray near edge absorption spectra measurements at the Fe K absorption edge confirm that the presence of a silica layer prevents the oxidation of the magnetic Fe core. Strong magnetic interactions between Fe cores lead to long-range ordering of magnetic moments, and the nanoparticle ensembles exhibit superferromagnetic characteristics demonstrated by a broad blocking Zero-field cooling (ZFC)/field-cooling distribution, nearly constant temperature dependence of ZFC magnetization, and non-zero coercivity at room temperature. Low room-temperature coercivity and the presence of electrically insulating SiO2 shells surrounding the Fe core make the studied samples suitable candidates for microelectronic applications.

ZeleÅáková, A.; ZeleÅák, V.; Mat'ko, I.; Stre?ková, M.; Hrubov?ák, P.; Ková?, J.

2014-07-01

328

Surface structure and electronic states of epitaxial ?-FeSi2(100)/Si(001) thin films: Combined quantitative LEED, ab initio DFT, and STM study  

NASA Astrophysics Data System (ADS)

The surface structure of epitaxial ?-FeSi2(100) thin film grown on Si(001) was analyzed using the quantitative low-energy electron diffraction intensity-voltage (LEED I-V) method, ab initio density functional theory (DFT) calculations, and scanning tunneling microscopy (STM). LEED patterns measured on the ?-FeSi2(100) surface reveal two domains of a p (2×2) reconstruction with p2gg diffraction symmetry. The iron-silicide film truncation and atomic surface structure were determined by LEED I-V method: The smallest Pendry's reliability factor RP=0.22±0.02 was achieved for the bare ?-FeSi2 film truncated by an Si layer, whereas Si and Fe ad-atom structures were excluded. Significant atomic relaxations within the topmost surface layers were revealed by the LEED I-V method and confirmed by DFT. The simulated STM patterns from the best-fit model agree well with the measured STM images on the ?-FeSi2(100)/Si(001)-p(2×2) surface: Four Si atoms on a surface form one bright protrusion on STM patterns. Electronic band structure analysis of the bulk and epitaxial ?-FeSi2(100) was carried out. A bare truncated epitaxial film was found to be metallic. Surface electronic states were identified by a partial k-resolved atomic-orbital based local density-of-state analysis.

Romanyuk, O.; Hattori, K.; Someta, M.; Daimon, H.

2014-10-01

329

Pulse TIG Welding of Two Al-Mg-Si Alloys  

NASA Astrophysics Data System (ADS)

This article reports the influence of pulse tungsten inert gas (TIG) welding parameters on the microstructure, hardness and tensile strength of weld joints of two Al-(0.5-0.8%)Si-(0.5-0.6%)Mg alloy (T4) produced by using three pulse frequencies (25, 33, and 50 Hz) and two duty cycles (40 and 50%). It has been observed that the mechanical properties (hardness and tensile strength) are sensitive to microstructure of weld metal, which is appreciably affected by the pulse parameters. Low frequency produced higher strength and hardness than high pulse frequency under identical welding conditions. Weld metal and HAZ were found stronger than the base metal. SEM study showed that the fracture of weldment was mostly brittle type.

Manti, Rajesh; Dwivedi, D. K.; Agarwal, A.

2008-10-01

330

Microstructural development of rapid solidification in Al-Si powder  

SciTech Connect

The microstructure and the gradient of microstructure that forms in rapidly solidificated powder were investigated for different sized particles. High pressure gas atomization solidification process has been used to produce a series of Al-Si alloys powders between 0.2 {mu}m to 150 {mu}m diameter at the eutectic composition (12.6 wt pct Si). This processing technique provides powders of different sizes which solidify under different conditions (i.e. interface velocity and interface undercooling), and thus give different microstructures inside the powders. The large size powder shows dendritic and eutectic microstructures. As the powder size becomes smaller, the predominant morphology changes from eutectic to dendritic to cellular. Microstructures were quantitatively characterized by using optical microscope and SEM techniques. The variation in eutectic spacing within the powders were measured and compared with the theoretical model to obtain interface undercooling, and growth rate during the solidification of a given droplet. Also, nucleation temperature, which controls microstructures in rapidly solidified fine powders, was estimated. A microstructural map which correlates the microstructure with particle size and processing parameters is developed.

Jin, F.

1995-11-01

331

FEM simulation of Rayleigh waves for CMOS compatible SAW devices based on AlN/SiO?/Si(100).  

PubMed

A simulation study of Rayleigh wave devices based on a stacked AlN/SiO?/Si(100) device was carried out. Dispersion curves with respect to acoustic phase velocity, reflectivity and electromechanical coupling efficiency for tungsten W and aluminium Al electrodes and different layer thicknesses were quantified by 2D FEM COMSOL simulations. Simulated acoustic mode shapes are presented. The impact of these parameters on the observed Rayleigh wave modes was discussed. High coupling factors of 2% and high velocities up to 5000 m/s were obtained by optimizing the AlN/SiO? thickness ratio. PMID:23684473

Kaletta, Udo Christian; Wenger, Christian

2014-01-01

332

High Performance Polycrystalline SiGe Thin Film Transistors Using Al2O3 Gate Insulator  

E-print Network

1 High Performance Polycrystalline SiGe Thin Film Transistors Using Al2O3 Gate Insulator Zhonghe TFTs [6], its applicability in poly-SiGe is investigated in this work. Experimental The Al2O3 thin was used to generate the plasma. Al2O3 was sputtered reactively using an N2O plasma, with the wafer

333

The abrasive wear behaviour of Al-SiCp composites for automotive parts  

Microsoft Academic Search

The present work reports on the continuous abrasives wear behaviour of Al-SiCp composites with 5 to 30 wt. % of SiC particulates. A pin-on-drum wear-testing machine was designed and fabricated to study the effects of wt. % of SiCp, load, relative velocity and abrasive particle characteristics on abrasive wear behaviour of Al-SiCp composite with 5 to 30 wt. % of

G. Hemath Kumar; B. R. Ramesh Bapu; R. Sagar; H. Mohit

2010-01-01

334

Experimental and Theoretical Investigations of the Solidification of Eutectic Al-Si Alloy  

NASA Technical Reports Server (NTRS)

The eutectic alloys have a wide spectrum of applications due to their good castability and physical and mechanical properties. The interphase spacing resulting during solidification is an important microstructural feature that significantly influences the mechanical behavior of the material. Thus, knowledge of the evolution of the interphase spacing during solidification is necessary in order to properly design the solidification process and optimize the material properties. While the growth of regular eutectics is rather well understood, the irregular eutectics such as Al-Si or Fe-graphite exhibit undercoolings and lamellar spacings much larger than those theoretically predicted. Despite of a considerable amount of experimental and theoretical work a clear understanding of the true mechanism underlying the spacing selection in irregular eutectics is yet to be achieved. A new experimental study of the solidification of the eutectic Al-Si alloy will be reported in this paper. The measured interface undercoolings and lamellar spacing will be compared to those found in the literature in order to get more general information regarding the growth mechanism of irregular eutectics. A modification of the present theory of the eutectic growth is also proposed. The results of the modified mathematical model, accounting for a non-isothermal solid/liquid interface, will be compared to the experimental measurements.

Sen, S.; Catalina, A. V.; Rose, M. Franklin (Technical Monitor)

2001-01-01

335

Magnetic and transport properties of evaporated Fe/SiO multilayers  

NASA Astrophysics Data System (ADS)

Fe/SiO discontinuous multilayers consisting of layers of Fe particles embedded in an insulating SiO matrix have been prepared by evaporation. Their structural, magnetic, and transport properties have been studied as a function of Fe and SiO thickness. For small iron thicknesses, magnetic measurements show a superparamagnetic behavior above a blocking temperature determined by field-cooled and zero-field-cooled magnetization curves. Negative magnetoresistance due to spin-dependent tunneling has been observed in both current-in-plane and current-perpendicular-to-the-plane geometries. For the smaller iron thickness (5 Å), a Coulomb blockade effect is observed at low temperature together with an increase of the magnetoresistance.

Anas, M.; Bellouard, C.; Vergnat, M.

2004-07-01

336

Magneto-elastic and magnetic domain properties of Fe81Ga19/Si(100) films  

NASA Astrophysics Data System (ADS)

Fe81Ga19 films were deposited on Si(100) substrates at room temperature by the dc magnetron sputtering method. Each film sample was rectangular: the length (L) and the width (w). From the curvature measurement on the film surface, we found that the principal stresses in the film are compressive and anisotropic. Based on the magneto-elastic theory, the true easy axis of the Fe81Ga19/Si(100) film should be parallel to the minimum stress axis. In addition, we discovered that the Fe81Ga19/Si(100) film is an inverted film (i.e., its HC is larger than HK, where HC is the coercive force and HK is the anisotropy field). The magnetic domain (MD) structures were examined with a magnetic force microscope. After the external field HE (parallel to L) was increased to saturation and then decreased to zero, the MD pattern showed the labyrinth structure.

Jen, S. U.; Liu, C. C.

2014-01-01

337

Observation of strongly enhanced inverse spin Hall voltage in Fe3Si/GaAs structures  

NASA Astrophysics Data System (ADS)

We performed spin pumping experiment on high quality, epitaxial Fe3Si/GaAs structures grown by molecular beam epitaxy. By tailoring the thickness and doping (n, p) level of the conducting GaAs epi-layer, thermal heating common of ferromagnetic metal/semiconductor heterostructure was removed effectively. A large inverse spin Hall Effect (ISHE) voltage up to 49.2 ?V was observed for Fe3Si/p-GaAs. Smaller ISHE voltage (VISHE) by a factor of ˜0.4 was obtained for Fe3Si/n-GaAs, as scaled with its resistivity. By taking into account of the "self-induced" ISHE apparently observed in our samples, the minimum value of spin Hall angle ?ISHE for n-GaAs and p-GaAs was estimated to be 1.9 × 10-4 and 2.8 × 10-5, respectively.

Hung, H. Y.; Chiang, T. H.; Syu, B. Z.; Fanchiang, Y. T.; Lin, J. G.; Lee, S. F.; Hong, M.; Kwo, J.

2014-10-01

338

Magnetic entropy change in LaMn 2-xFe xSi 2 compounds  

NASA Astrophysics Data System (ADS)

LaMn 2-xFe xSi 2 ( x=0, 0.05, 0.10, 0.15, 0.20) compounds were prepared by arc melting. The crystal structure and magnetic properties have been investigated by X-ray diffraction and by using a vibrating sample magnetometer, respectively. The compounds crystallize in the ThCr 2Si 2-type structure with the space group I4/mmm. The Curie temperature decreases gradually with the increase of Fe content. The magnetic entropy changes of the compounds, with a field change from 0 to 1.8 T, are derived from the magnetization isotherms at different temperatures. The maximal magnetic entropy change of LaMn 1.9Fe 0.1Si 2 reaches 1.72 J/kg K (0-1.8 T) around the Curie temperature near room temperature.

Zhang, Tiebang; Chen, Yungui; Tang, Yongbai; Tu, Mingjing

2006-05-01

339

Vacancy Behavior and Solute Cluster Growth During Natural Aging of an Al-Mg-Si Alloy  

NASA Astrophysics Data System (ADS)

The natural aging behavior of an Al-0.46Mg-1.05Si-0.14Fe (wt pct) alloy was studied with positron annihilation lifetime spectroscopy at four temperatures and with 25Mg solid-state nuclear magnetic resonance. The evolution of positron lifetime is shown to consist of three distinct stages. In an effort to understand the physical processes occurring during natural aging, a phenomenological model was developed for the first two stages and is shown to describe the experimental observations well. The description accounts for the decay in positron lifetime due to diffusion of vacancies to sinks and an increase in positron lifetime attributed to growing solute clusters. NMR measurements of 25Mg solute partitioning during natural aging support the model.

Lay, M. D. H.; Zurob, H. S.; Hutchinson, C. R.; Bastow, T. J.; Hill, A. J.

2012-12-01

340

Fabrication and electrical properties of p-CuAlO2/(n-, p-)Si heterojunctions  

NASA Astrophysics Data System (ADS)

CuAlO2 thin films have been prepared by the chemical solution deposition method on both n-Si and p-Si substrates. X-ray diffraction analysis indicates that the obtained CuAlO2 films have a single delafossite structure. The current transport properties of the resultant p-CuAlO2/n-Si and p-CuAlO2/p-Si heterojunctions are investigated by current-voltage measurements. The p-CuAlO2/n-Si has a rectifying ratio of ~35 within the applied voltages of -3.0 to +3.0 V, while the p-CuAlO2/p-Si shows Schottky diode-like characteristics, dominated in forward bias by the flow of space-charge-limited current.

Suzhen, Wu; Zanhong, Deng; Weiwei, Dong; Jingzhen, Shao; Xiaodong, Fang

2014-04-01

341

Magnetoresistance Variation of Magnetic Tunnel Junctions with NiFeSiB\\/CoFeB Free Layers Depending on MgO Tunnel Barrier Thickness  

Microsoft Academic Search

We developed NiFeSiB\\/CoFeB hybrid free-layers for magnetic tunnel junctions (MTJs) with MgO tunnel barrier layers. These junctions show tunneling magnetoresistance (TMR) ratios and resistance-area (RA) values ranging from 118-209% and 36-2380 Omega mum2 , respectively, obtained at room temperature. Compared to the CoFeB single free-layer case, the NiFeSiB\\/CoFeB hybrid free-layer approach has the advantage of lowering saturation magnetization. The low

Ji Ung Cho; Do Kyun Kim; Tian Xing Wang; Shinji Isogami; Masakiyo Tsunoda; Migaku Takahashi; Young Keun Kim

2008-01-01

342

Characterization of Al/Si junctions on Si(100) wafers with chemical vapor deposition-based sulfur passivation  

NASA Astrophysics Data System (ADS)

Chemical vapor deposition-based sulfur passivation using hydrogen sulfide is carried out on both n-type and p-type Si(100) wafers. Al contacts are fabricated on sulfur-passivated Si(100) wafers and the resultant Schottky barriers are characterized with current-voltage ( I- V), capacitance-voltage ( C- V) and activation-energy methods. Al/S-passivated n-type Si(100) junctions exhibit ohmic behavior with a barrier height of <0.078 eV by the I- V method and significantly lower than 0.08 eV by the activation-energy method. For Al/S-passivated p-type Si(100) junctions, the barrier height is ~0.77 eV by I- V and activation-energy methods and 1.14 eV by the C- V method. The discrepancy between C- V and other methods is explained by image force-induced barrier lowering and edge-leakage current. The I- V behavior of an Al/S-passivated p-type Si(100) junction remains largely unchanged after 300 °C annealing in air. It is also discovered that heating the S-passivated Si(100) wafer before Al deposition significantly improves the thermal stability of an Al/S-passivated n-type Si(100) junction to 500 °C.

Zhang, Hai-feng; Saha, Arunodoy; Sun, Wen-cheng; Tao, Meng

2014-09-01

343

In situ synthesis of flexible magnetic ?-Fe2O3@SiO2 nanofibrous membranes  

NASA Astrophysics Data System (ADS)

Novel flexible, mesoporous, and magnetic ?-Fe2O3@SiO2 nanofibrous membranes with high ?-Fe2O3 content and uniform distribution were prepared by a facile in situ growth method, which exhibit prominent mechanical strength and magnetic responsive performance, as well as efficient adsorption for organics in water.Novel flexible, mesoporous, and magnetic ?-Fe2O3@SiO2 nanofibrous membranes with high ?-Fe2O3 content and uniform distribution were prepared by a facile in situ growth method, which exhibit prominent mechanical strength and magnetic responsive performance, as well as efficient adsorption for organics in water. Electronic supplementary information (ESI) available: Detailed synthesis and structural confirmation of BA-a; TEM and flexibility results; Movies S1 and S2. See DOI: 10.1039/c3nr05879d

Si, Yang; Tang, Xiaomin; Ge, Jianlong; Yang, Shan; El-Newehy, Mohamed; Al-Deyab, Salem S.; Yu, Jianyong; Ding, Bin

2014-01-01

344

Strain state in bcc Fe films grown on Si(1 1 1)  

NASA Astrophysics Data System (ADS)

The strain state of Fe films grown on Si(1 1 1) has been investigated by X-ray diffraction (XRD) in the thickness range between 11 and 304 monolayers. Fe grows tetragonally distorted with the orientation relationship Fe(1 1 1) <1 2¯ 1> // Si(1 1 1) <1¯ 2 1¯>. At low coverage, the films grow pseudomorphic. Above 15 monolayers the films are characterized by the coexistence of a pseudomorphic phase with another one which relaxes with the Fe thickness. This relaxation proceeds rapidly in the earlier stages then slowly with the film thickness. The XRD characterization allows one to obtain quantitative information on the in-plane and out-of-plane strains.

Stephan, R.; Zabrocki, S.; Wetzel, P.; Berling, D.; Mehdaoui, A.; Bubendorff, J.-L.; Garreau, G.; Pirri, C.; Gewinner, G.; Boudet, N.; Berar, J. F.

2006-08-01

345

Thermal Conductivity of the Molten CaO-SiO2-FeO x System  

NASA Astrophysics Data System (ADS)

Thermal conductivity measurements were carried out on synthetic steelmaking slag using the hot-wire method. Furthermore, local structure analysis in the melts was carried out in order to investigate the relationship with the composition dependence. The thermal conductivity of the CaO-SiO2-FeO x melts significantly decreased as the content of FeO x increases, particularly at lower basicity. Both chemical analysis and the observation show that the amount of Fe2+ increases when CaO/SiO2 is smaller, implying more basic behavior of FeO than FeO1.5. According to further analyses by Mössbauer spectroscopy, the degree of basicity of FeO1.5 remains virtually unchanged in the composition range of interest. From the experimental results, it could be concluded that the thermal conductivity of the silicate melt containing iron oxide is highly dependent on the valence of the Fe ion and comparatively independent of the amphoteric behavior of FeO1.5.

Kang, Youngjo; Nomura, Kiyoshi; Tokumitsu, Kazuto; Tobo, Hiroyuki; Morita, Kazuki

2012-12-01

346

In situ structural investigation of Fe-S-Si immiscible liquid system and evolution of Fe-S bond properties with pressure  

Microsoft Academic Search

Fe-S-Si immiscibility has been investigated using in situ X-ray methods at high pressure and high temperature. An in situ X-ray diffraction study of immiscible liquids for P?5 GPa and T\\/Tm?1.1 has been performed, showing differences in structural properties between S-rich and Si-rich coexisting liquid phases. Moreover, the respective role of S and Si on Fe alloys has been quantitatively investigated

G. Morard; C. Sanloup; B. Guillot; G. Fiquet; M. Mezouar; J. P. Perrillat; G. Garbarino; K. Mibe; T. Komabayashi; K. Funakoshi

2008-01-01

347

Melting of Au and Al in nanometer Fe/Au and Fe/Al multilayers under swift heavy ions: A thermal spike study  

NASA Astrophysics Data System (ADS)

Knowing that Fe is sensitive to swift heavy ion irradiations whereas Au and Al are not, the behavior of nanometric metallic multilayer systems, like [Fe(3 nm)/Au( x)] y and [Fe(3 nm)/Al( x)] y with x ranging between 1 and 10 nm, were studied within the inelastic thermal spike model. In addition to the usual cylindrical geometry of energy dissipation perpendicular to the ion projectile direction, the heat transport along the ion path was implemented in the electronic and atomic sub-systems. The simulations were performed using three different values of linear energy transfer corresponding to 3 MeV/u of 208Pb, 132Xe and 84Kr ions. For the Fe/Au system, evidence of appearance of a molten phase was found in the entire Au layer, provided the Au thickness is less than 7 nm and 3 nm for Pb and Xe ions, respectively. For the Fe/Al( x) system irradiated with Pb ions, the Al layers with a thickness less than 4 nm melt along the entire ion track. Surprisingly, the Fe layer does not melt if the Al thickness is larger than 2 nm, although the deposited energy surpasses the electronic stopping power threshold of track formation in Fe. For Kr ions melting does not occur in any of the multilayer systems.

Chettah, A.; Wang, Z. G.; Kac, M.; Kucal, H.; Meftah, A.; Toulemonde, M.

2006-04-01

348

Copper matrix SiC and Al 2O 3 particulate composites by powder metallurgy technique  

Microsoft Academic Search

Copper matrix reinforced with either Ni-coated or uncoated SiC and Al2O3 particulate composites were made by means of the powder metallurgy route. The reinforcement particles of SiC and Al2O3 were coated with a thin layer of nickel by electroless method. The coated or uncoated reinforcement particles of either SiC or Al2O3 were added to copper metal powders with nominal loading

S. F Moustafa; Z Abdel-Hamid; A. M Abd-Elhay

2002-01-01

349

Densification mechanism and microstructural evolution in selective laser sintering of Al–12Si powders  

Microsoft Academic Search

The role of processing parameters on the densification mechanism and microstructural evolution in laser sintered Al–12Si powder has been explored. It was established that both the densification mechanism and microstructural evolution in laser sintered Al–12Si powder were controlled by the specific laser energy input. Analysis of the cross-section of laser sintered microstructures of Al–12Si powders indicated that the tops of

E. O. Olakanmi; R. F. Cochrane; K. W. Dalgarno

2011-01-01

350

Anisotropic physical properties of the Al13Fe4 complex intermetallic and its ternary derivative Al13(Fe,Ni)4  

NASA Astrophysics Data System (ADS)

We have investigated the magnetic susceptibility, the electrical resistivity, the specific heat, the thermoelectric power, the Hall coefficient, and the thermal conductivity of the Al13Fe4 and Al13(Fe,Ni)4 monoclinic approximants to the decagonal quasicrystal. While the Al13Fe4 crystals are structurally well ordered, the ternary derivative Al13(Fe,Ni)4 contains substitutional disorder and is considered as a disordered version of the Al13Fe4 . The crystallographic-direction-dependent measurements were performed along the a? , b , and c directions of the monoclinic unit cell, where the (a?,c) atomic planes are stacked along the b direction. The electronic transport and the magnetic properties exhibit significant anisotropy. The stacking b direction is the most conducting direction for the electricity and heat. The effect of substitutional disorder in Al13(Fe,Ni)4 is manifested in the large residual resistivity ?(T?0) and significantly reduced thermal conductivity of this compound, as compared to the ordered Al13Fe4 . Specific-heat measurements reveal that the electronic density of states at the Fermi level of both compounds is high. The anisotropic Hall coefficient RH reflects complex structure of the anisotropic Fermi surface that contains electronlike and holelike contributions. Depending on the combination of directions of the current and the magnetic field, electronlike (RH<0) or holelike (RH>0) contributions may dominate, or the two contributions compensate each other (RH?0) . Similar complicated anisotropic behavior was observed also in the thermopower. The anisotropic Fermi surface was calculated ab initio using the atomic parameters of the refined Al13Fe4 structural model that is also presented in this work.

Pop?evi?, P.; Smontara, A.; Ivkov, J.; Wencka, M.; Komelj, M.; Jegli?, P.; Vrtnik, S.; Bobnar, M.; Jagli?i?, Z.; Bauer, B.; Gille, P.; Borrmann, H.; Burkhardt, U.; Grin, Yu.; Dolinšek, J.

2010-05-01

351

Synthesis of pillared clays with Al 13Fe and Al 13Fe-Ce polymers in solid state assisted by microwave and ultrasound: Characterization and catalytic activity  

Microsoft Academic Search

A new methodology for the synthesis of pillared clays with the Al13-Fe and Al13-Fe-Ce polymers in solid state was developed by using microwaves and ultrasound in the aging of the olygomeric solution, in the precipitation of the corresponding sulphates, and in the intercalation of the polymer with the powdered clay. This methodology reduces significantly the water consumption in the intercalation

A. Olaya; S. Moreno; R. Molina

2009-01-01

352

Optical and electrical characterizations of Mn doped p-type ?-FeSi 2  

NASA Astrophysics Data System (ADS)

?-FeSi 2 has attracted increasing attention as a promising material for optoelectronic and thermoelectronic devices due to a high optical absorption coefficient (?) of about 10 5 cm -1 near 1.0 eV and its chemical stability at higher temperatures. For the future practical use of this material in devices, the control of each electrical conductivity type and the improvement of the material quality are highly required. Although unintentionally doped ?-FeSi 2 layers formed on n-type Si(1 0 0) by the conventional electron-beam deposition (EBD) have typically shown n-type conductivity, the p-type ?-FeSi 2 layers were formed by the introduction of Mn impurity using ion-implantation at room temperature (RT) and subsequent annealing procedures. In this study, we aimed to make p-type ?-FeSi 2 by implantation of 55Mn + ions into EBD-grown n-type ?-FeSi 2 layers/n-Si, where 55Mn + ions were implanted at two different temperatures ( Tsub) of RT and 250°C using an energy and a dose of 300 keV and 2.68 × 10 15 cm -2, respectively. Their optical and electrical properties, which ought to be affected by implantation and annealing temperatures ( Ta2), were investigated by Raman scattering, optical transmittance, reflectance and van der Pauw measurements. The results showed that the 55Mn + doping with Tsub=RT and higher thermal annealing at Ta2=900°C produced p-type layers of good quality with maximum hole mobility of 454.5 cm 2/Vs at about 65 K.

Takada, T.; Makita, Y.; Shima, T.; Banba, T.; Shikama, K.; Sanpei, H.; Hasegawa, M.; Sandhu, A.; Hoshino, Y.; Katsumata, H.; Uekusa, S.

1999-01-01

353

Erosion-corrosion behavior of SiC particle-reinforced Al-Si alloy in NaOH slurry  

NASA Astrophysics Data System (ADS)

The erosion-corrsosion behavior of SiC particle-reinforced Al-Si alloy has been studied in NaOH slurry simulating the mining atmosphere. The study was performed at two different sand concentrations, namely, 20 and 30 wt pct, and at a speed of 900 rpm. It is depicted that the wear rates decreased with increasing sand content, indicating that corrosion is the dominating mode of material removal. Further composite exhibited lower wear resistance than the laloys irrespective of the sand concentration. Scanning electron microscope (SEM) observations indicated the dissolution of dendrites of Al due to severe corrosion, leaving behind the network of Si. This ultimately results in the falling of Si particles from the matrix, leaving behind voids. This also results in the formation of voids around the SiC particles and leads to pullout of SiC particles from the matrix during the wear process.

Saraswathi, Y. L.; Das, S.; Mondal, D. P.

2005-08-01

354

High-quality epitaxial CoFe/Si(111) heterostructures fabricated by low-temperature molecular beam epitaxy  

NASA Astrophysics Data System (ADS)

We demonstrate atomically controlled heterojunctions consisting of ferromagnetic CoFe alloys and silicon (Si) using low-temperature molecular beam epitaxy with a good atomic matching at the (111) plane. The saturation magnetization of the CoFe layers grown reaches ˜85% of the value of bulk samples reported so far, and can be systematically controlled by tuning the ratio of Co to Fe, indicating that the silicidation reactions between CoFe and Si are suppressed and the heterojunctions are very high quality. We find that the Schottky barrier height of the high-quality CoFe/Si(111) junctions is unexpectedly low compared to the previous data for other metal/Si ones, implying the reduction in the Fermi-level-pinning effect. We can expand the available high-quality ferromagnet/Si heterostructures in the field of Si-based spintronics.

Maeda, Y.; Hamaya, K.; Yamada, S.; Ando, Y.; Yamane, K.; Miyao, M.

2010-11-01

355

Microstructural Evolution and Solidification Behavior of Al-Mg-Si Alloy in High-Pressure Die Casting  

NASA Astrophysics Data System (ADS)

Microstructural evolution and solidification behavior of Al-5 wt pct Mg-1.5 wt pct Si-0.6 wt pct Mn-0.2 wt pct Ti alloy have been investigated using high-pressure die casting. Solidification commences with the formation of primary ?-Al phase in the shot sleeve and is completed in the die cavity. The average size of dendrites and fragmented dendrites of the primary ?-Al phase formed in the shot sleeve is 43 ?m, and the globular primary ?-Al grains formed inside the die cavity is at a size of 7.5 ?m. Solidification inside the die cavity also forms the lamellar Al-Mg2Si eutectic phase and the Fe-rich intermetallics. The size of the eutectic cells is about 10 ?m, in which the lamellar ?-Al phase is 0.41 ?m thick. The Fe-rich intermetallic compound exhibits a compact morphology and is less than 2 ?m with a composition of 1.62 at. pct Si, 3.94 at. pct Fe, and 2.31 at. pct Mn. A solute-enriched circular band is always observed parallel to the surface of the casting. The band zone separates the outer skin region from the central region of the casting. The solute concentration is consistent in the skin region and shows a general drop toward the center inside the band for Mg and Si. The peak of the solute enrichment in the band zone is much higher than the nominal composition of the alloy. The die casting exhibits a combination of brittle and ductile fracture. There is no significant difference on the fracture morphology in the three regions. The band zone is not significantly detrimental in terms of the fracture mechanism in the die casting. Calculations using the Mullins and Sekerka stability criterion reveal that the solidification of the primary ?-Al phase inside the die cavity has been completed before the spherical ?-Al globules begin to lose their stability, but the ?-Al grains formed in the shot sleeve exceed the limit of spherical growth and therefore exhibit a dendritic morphology.

Ji, Shouxun; Wang, Yun; Watson, D.; Fan, Z.

2013-07-01

356

Infrared Brazing Fe3Al Using Ag-Based Filler Metals  

NASA Astrophysics Data System (ADS)

The microstructural evolution and bonding shear strength of infrared brazed Fe3Al using Ag and BAg-8 (72Ag-28Cu in wt pct) braze alloys have been studied. The Ag-rich phase alloyed with Al dominates the entire Ag brazed joints, and the shear strength is independent of the brazing time. The BAg-8 brazed joint contains Ag-Cu eutectic for all brazing conditions, and its shear strength increases slightly with increasing brazing time. The highest shear strength of 181 MPa is acquired from the joint infrared brazed at 1073 K (800 °C) for 600 seconds. A thin layer of Fe3Al is identified at the interface between the brazed zone and the substrate for both braze alloys. An Al depletion zone in the Fe3Al substrate next to the interfacial Fe3Al is identified as the ?-Fe phase. The dissolution of Al from the Fe3Al substrate into the molten braze causes the formation of ?-Fe in the Fe3Al substrate.

Shiue, Ren-Kae; Li, Yao; Wu, Shyi-Kaan; Wu, Ling-Mei

2010-11-01

357

A significant reduction of hysteresis in MnFe(P,Si) compounds  

NASA Astrophysics Data System (ADS)

The magnetocaloric effects in Mn1.3Fe0.7- x Co x P0.46Si0.54 compounds ( x = 0, 0.025, 0.05 and 0.1) were investigated systematically. X-ray diffraction shows that the compounds crystallize in the Fe2P-type hexagonal structure with space group P-62m symmetry. Magnetic measurements show that the paramagnetic-ferromagnetic transition temperatures range from 247 to 298 K. The maximal magnetic entropy changes in the Mn1.3Fe0.7P0.46Si0.54 compound reaches 8.3 J/kgK for a field change from 0 to 1.5 T. The thermal hysteresis of these compounds is less than 3 K. The maximum adiabatic temperature change is 2.2 K in Mn1.3Fe0.7P0.46Si0.54 and Mn1.3Fe0.65Co0.05P0.46Si0.54 compounds for a field change from 0 to 1.48 T, indicating this material system has potential for room-temperature magnetic refrigeration applications.

Huliyageqi, B.; Geng, Yao-xiang; Li, Ying-jie; Tegus, O.

2013-08-01

358

An investigation of martensitic transformation in an Fe-30Mn-6Si shape memory alloy  

SciTech Connect

Fe-Mn-Si compositions represent newly developed shape memory alloys which are attracting attention due to their low cost and excellent workability. To obtain a shape memory effect, one must precisely control the Ms temperature and the Neel temperature (T{sub N}). In this study, the authors examine differential scanning calorimetry (DSC), magnetic susceptibility, internal friction, and electrical resistivity measurements as ways of determining Ms and T{sub N} in an Fe-30Mn-6Si alloy. The efficiency of these experiments are also discussed and compared.

Lin, H.C.; Lin, K.M. [Feng Chia Univ., Taichung (Taiwan, Province of China). Dept. of Materials Science] [Feng Chia Univ., Taichung (Taiwan, Province of China). Dept. of Materials Science

1996-02-01

359

Strain sensors for civil engineering application based on CoFeCrSiB amorphous ribbons  

NASA Astrophysics Data System (ADS)

Appropriate amorphous material composition and annealing conditions providing the magneto-elastic efficiency and linearity of the transfer characteristics in a wide interval of strain were found. A prototype of the two-coil strain sensor based on these materials was tested at different magnetizing conditions. The obtained results show a possibility to use the stress annealed·amorphous ribbons of the composition Co69Fe2Cr7Si8B14 (?s<0) and Co67Fe4Si8B14 (?s>0) for sensors in civil engineering applications.

Bydžovský, Jan; Kollár, Mojmír; Jan?árik, Vladimír; Švec, Peter; Kraus, Lud?k

2002-01-01

360

Strain sensors for civil engineering application based on CoFeCrSiB amorphous ribbons  

Microsoft Academic Search

Appropriate amorphous material composition and annealing conditions providing the magneto-elastic efficiency and linearity\\u000a of the transfer characteristics in a wide interval of strain were found. A prototype of the two-coil strain sensor based on\\u000a these materials was tested at different magnetizing conditions. The obtained results show a possibility to use the stress\\u000a annealed·amorphous ribbons of the composition Co69Fe2Cr7Si8B14 (?s67Fe4Si8B14 (?s>0)

Jan Bydzovský; Mojmír Kollár; Vladimír Jancárik; Peter Švec; Ludek Kraus

2002-01-01

361

Experimental realization of a semiconducting full-Heusler compound: Fe2TiSi  

NASA Astrophysics Data System (ADS)

Single-phase films of the full-Heusler compound Fe2TiSi have been prepared by magnetron sputtering. The compound is found to be a semiconductor with a gap of 0.4 eV. The electrical resistivity has a logarithmic temperature dependence up to room temperature due to Kondo scattering of a dilute free electron gas off superparamagnetic impurities. The origin of the electron gas is extrinsic due to residual off-stoichiometry. Density functional theory calculations of the electronic structure are in excellent agreement with electron energy loss, optical, and x-ray absorption experiments. Fe2TiSi may find applications as a thermoelectric material.

Meinert, Markus; Geisler, Manuel P.; Schmalhorst, Jan; Heinzmann, Ulrich; Arenholz, Elke; Hetaba, Walid; Stöger-Pollach, Michael; Hütten, Andreas; Reiss, Günter

2014-08-01

362

Analysis of the stress-strain curves of a Fe-Mn-Si shape memory alloy  

SciTech Connect

The stress-induced martensitic transformation of an Fe-30(wt.%)Mn-6(wt.%)Si shape memory alloy has been studied through the tensile deformation and the recovery processes. The results show that the deformation process of Fe-Mn-Si shape memory alloys can be divided into three stages with different mechanisms. The first stage is the elastic stage, the second one is related to the {gamma} {r_arrow} {epsilon} phase transformation, and the third one can be described as plastic deformation. An appropriate thermomechanical training procedure can markedly increase the recovery rate to close to 100%.

Zhang, J.; Chen, S.; Li, L.; Hsu, T.Y. [Shanghai Jiao Tong Univ., Shanghai (China). Dept. of Materials Science] [Shanghai Jiao Tong Univ., Shanghai (China). Dept. of Materials Science

1998-01-01

363

Texture and Magnetic Properties of Rolled Fe-6.5 wt.%Si Thin Sheets  

NASA Astrophysics Data System (ADS)

Thin (0.20 mm) Fe-6.5 wt.%Si sheets have been successfully fabricated by the continuous rolling method. The designed rolling process parameters, including the initial hot-band grain size, grain size after intermediate annealing, cold rolling reduction, and cold rolling temperature, were selected to control the texture development. Dominant recrystallization ? fiber [rolling direction (RD)//] was achieved after high-temperature annealing. The produced Fe-6.5 wt.%Si thin sheets are promising alternatives for use in power electronics because of their magnetic properties from 400 Hz to 40 kHz.

Yao, Y. C.; Sha, Y. H.; Liu, J. L.; Zhang, F.; Zuo, L.

2014-01-01

364

Current transport and thermoelectric properties of very high power factor Fe3O4/SiO2/p-type Si(001) devices  

NASA Astrophysics Data System (ADS)

The current transport and thermoelectric properties of Fe3O4/SiO2/p-type Si(001) heterostructures with Fe3O4 thicknesses of 150, 200, and 350 nm have been investigated between 100 and 300 K. We observe a sharp drop of the in-plane resistivity at 200 K due to the onset of conduction along the Si/SiO2 interface related to tunneling of electrons from the Fe3O4 into the accumulation layer of holes at the Si/SiO2 interface, whose existence was confirmed by capacitance-voltage measurements and a two band analysis of the Hall effect. This is accompanied by a large increase of the Seebeck coefficient reaching +1000 ?V/K at 300 K that is related to holes in the p-type Si(001) and gives a power factor of 70 mW/K2m when the Fe3O4 layer thickness is reduced down to 150 nm. We show that most of the current flows in the Fe3O4 layer at 300 K, while the Fe3O4/SiO2/p-type Si(001) heterostructures behave like tunneling p-n junctions in the transverse direction.

Zervos, M.; Viskadourakis, Z.; Athanasopoulos, G.; Flores, R.; Conde, O.; Giapintzakis, J.

2014-01-01

365

Microstructure of the Rust Formed on Si-Al Bearing Ultrafine-Grained Weathering Steel  

NASA Astrophysics Data System (ADS)

In the Ultra-steel project in NIMS, high-Si and Al type ultrafinegrained (UFG) weathering steel was created by the multi-pass warm rolling method, and the corrosion resistance and microstructure of the rust were estimated. The Si and Al-bearing UFG steels exhibited excellent corrosion resistance than carbon steel (SM). The EPMA and TEM analyses showed that Si and Al were mainly existing as nano-oxides in the inner rust layer formed on the UFG steels. The Al K? X-ray spectrum of the test sample exhibited the peak at the same position as that of Al2O3, which suggests that Al is present in the inner rust in Al3+ state. In the same way, Si was identified as Si2+ in the complex Iron oxides of inner rust using EPMA.

Raman, V.; Nishimura, T.

366

Effects of strontium impurity on the structure and dynamics of Al88Si12 liquid.  

PubMed

The effects of strontium modification on the structure and dynamics of Al88Si12 liquid are studied by means of ab initio molecular dynamics simulations. By replacing 0.5% and 4.0% of Al with Sr, we show that the addition of Sr lowers the self-diffusion of Al and Si of the liquid and reduces the nearest-neighbor correlation between Si atoms. The simulation provides an explanation for the change in morphology of the eutectic phases observed in rapidly solidified Al-Si alloys modified with Sr. PMID:23685677

Yue, G Q; Wu, S; Shen, B; Wang, S Y; Wang, C Z; Ho, K M; Kramer, M J; Chen, L Y

2013-06-19

367

Effects of strontium impurity on the structure and dynamics of Al88Si12 liquid  

NASA Astrophysics Data System (ADS)

The effects of strontium modification on the structure and dynamics of Al88Si12 liquid are studied by means of ab initio molecular dynamics simulations. By replacing 0.5% and 4.0% of Al with Sr, we show that the addition of Sr lowers the self-diffusion of Al and Si of the liquid and reduces the nearest-neighbor correlation between Si atoms. The simulation provides an explanation for the change in morphology of the eutectic phases observed in rapidly solidified Al-Si alloys modified with Sr.

Yue, G. Q.; Wu, S.; Shen, B.; Y Wang, S.; Wang, C. Z.; Ho, K. M.; Kramer, M. J.; Y Chen, L.

2013-06-01

368

Monolithic integration of AlGaInP laser diodes on SiGe\\/Si substrates by molecular beam epitaxy  

Microsoft Academic Search

Room temperature operation of visible AlGaInP laser diodes epitaxially integrated on Si was demonstrated. Compressively strained laser heterostructures were grown by molecular beam epitaxy (MBE) on low dislocation density SiGe\\/Si substrates, where the threading dislocation density of the top relaxed Ge layers was measured in the range of 2×106 cm-2. A threshold current density of Jth~1.65 kA\\/cm2 for the as-cleaved,

O. Kwon; J. J. Boeckl; M. L. Lee; A. J. Pitera; E. A. Fitzgerald; S. A. Ringel

2006-01-01

369

Monolithic integration of AlGaInP laser diodes on SiGe?Si substrates by molecular beam epitaxy  

Microsoft Academic Search

Room temperature operation of visible AlGaInP laser diodes epitaxially integrated on Si was demonstrated. Compressively strained laser heterostructures were grown by molecular beam epitaxy (MBE) on low dislocation density SiGe?Si substrates, where the threading dislocation density of the top relaxed Ge layers was measured in the range of 2×106 cm?2. A threshold current density of Jth?1.65 kA?cm2 for the as-cleaved,

O. Kwon; J. J. Boeckl; M. L. Lee; A. J. Pitera; E. A. Fitzgerald; S. A. Ringel

2006-01-01

370

Influence of Si and Ge on the magnetic phase transition and magnetocaloric properties of MnFe(P, Si, Ge)  

Microsoft Academic Search

Recently, we found a large magnetocaloric effect (MCE) and favourable magnetic properties in low cost and nontoxic MnFe(P,Si,Ge) compounds [D.T. Cam Thanh, E. Brück, O. Tegus, J.C.P. Klaasse, T.J. Gortenmulder, K.H.J. Buschow, J. Appl. Phys. 99 (2006) 08Q107]. These compounds are promising for magnetic refrigeration applications. One of the interesting points in these compounds is a nonlinear dependence of the

D. T. Cam Thanh; E. H. Brück; O. Tegus; J. C. P. Klaasse; K. H. J. Buschow

2007-01-01

371

Influence of pressure on crystallization kinetics in an Al–Ni–Ce–Fe amorphous alloy  

Microsoft Academic Search

The influence of pressure on crystallization kinetics in an Al–Ni–Ce–Fe amorphous alloy was studied by means of piston-cylinder measurements over a pressure range up to 1.07 GPa. It was found that an applied pressure enhances the primary crystallization of the fcc-Al phase from the amorphous phase, i.e., the growth process of quenched-in Al nuclei in the amorphous Al–Ni–Ce–Fe alloy. The

X. J Gu; J. Q Wang; F Ye; K Lu

2001-01-01

372

Nanocrystalline Al–Fe intermetallics – light weight alloys with high hardness  

Microsoft Academic Search

Nanocrystalline Al–Fe alloys containing 60–85at.% Al were produced by consolidation of mechanically alloyed nanocrystalline or amorphous (Al85Fe15 composition) powders at 1000°C under a pressure of 7.7GPa. The hardness of the alloys varied between 5.8 and 9.5GPa, depending on the Al content. The specific strength, calculated using an approximation of the yield strength according to the Tabor relation, was between 544

M. Krasnowski; T. Kulik

2010-01-01

373

Structure of molten Al and eutectic Al-Si alloy studied by neutron diffraction  

SciTech Connect

The structure of molten eutectic Al87.8Si12.2 alloy has been studied by neutron diffraction during a temperature cycle. For comparison measurements were performed on pure molten Al. The measurements show that the alloy after heating above the liquidus contains particles of two kinds, aluminum-rich and silicon-rich. The silicon-rich particles are partly dissolved after a further heating. Earlier published data obtained by the ?-ray absorption technique of the density of the molten eutectic Al–Si alloy had demonstrated the existence of two temperatures above the liquidus temperature: A dissolution temperature Td, at which the microstructure of the melt inherited from the ingot starts to dissolve and a branching temperature, Tb, at which the melt reaches a fully mixed state. The highest temperature that was possible to reach during the neutron experiments lies between Td and Tb. The obtained results support these conclusions that molten alloys after melting are inhomogeneous up to a temperature well above the liquidus. Moreover, the difference in shape between the static structure factors measured by neutron and X-ray diffraction on molten aluminum is observed and is found to be more accentuated and to extend to larger wavevectors than in earlier works.

Dahlborg, U. [University of Rouen; Kramer, Matthew J. [Ames Laboratory; Besser, M. [Ames Laboratory; Morris, J. R. [Oak Ridge National Laboratory; Calvo-Dahlborg, M. [University of Rouen

2012-11-24

374

Segregation of Si to the surface of Fe-29Ni-17Co alloy  

SciTech Connect

The segregation of Si impurities from the bulk to the surface of a low Cr Lot of Kovar{sup TM} (Fe-29Ni-17Co) has been investigated in order to determine the effects on the quality of the braze of Cu to these altered surfaces. It is found that oxides of Si are formed on the surface during wet hydrogen firing. Kinetics of this segregation process have been measured.

Nelson, G.C.; Buttry, R.W.

1993-09-01

375

Magnetic phase transition and magnetocaloric effect in Mn 5? x Fe x Si 3  

Microsoft Academic Search

The magnetic phase transitions and the magnetocaloric properties of the pseudo binary system Mn5?xFexSi3 with x=0, 1, 2, 3, 4, 5 have been investigated by measuring the magnetisation as a function of temperature and magnetic field. With increasing Fe content, the antiferromagnetic ordering temperature shifts to higher temperatures. The compound Mn5Si3 is an antiferromagnet with a field-induced transition. At 4.2

O Songlin; W. Dagula; O. Tegus; E. H. Bruck; J. C. P. Klaasse; F. R de Boer; K. H. J. Buschow

2002-01-01

376

Monolithic integration of AlGaInP laser diodes on SiGe /Si substrates by molecular beam epitaxy  

NASA Astrophysics Data System (ADS)

Room temperature operation of visible AlGaInP laser diodes epitaxially integrated on Si was demonstrated. Compressively strained laser heterostructures were grown by molecular beam epitaxy (MBE) on low dislocation density SiGe /Si substrates, where the threading dislocation density of the top relaxed Ge layers was measured in the range of 2×106cm-2. A threshold current density of Jth˜1.65kA/cm2 for the as-cleaved, gain-guided AlGaInP laser grown on SiGe /Si was obtained at the peak emission wavelength of 680nm under pulsed mode current injection. These results show that not only can high quality AlGaInP materials grown by MBE be achieved on Si via relaxed SiGe interlayers, but the prototype demonstration of laser diode operation on Si illustrates that very defect sensitive optoelectronics in the III-P system can indeed be integrated with Si substrates by heteroepitaxial methods.

Kwon, O.; Boeckl, J. J.; Lee, M. L.; Pitera, A. J.; Fitzgerald, E. A.; Ringel, S. A.

2006-07-01

377

Monolithic integration of AlGaInP laser diodes on SiGe/Si substrates by molecular beam epitaxy  

SciTech Connect

Room temperature operation of visible AlGaInP laser diodes epitaxially integrated on Si was demonstrated. Compressively strained laser heterostructures were grown by molecular beam epitaxy (MBE) on low dislocation density SiGe/Si substrates, where the threading dislocation density of the top relaxed Ge layers was measured in the range of 2x10{sup 6} cm{sup -2}. A threshold current density of J{sub th}{approx}1.65 kA/cm{sup 2} for the as-cleaved, gain-guided AlGaInP laser grown on SiGe/Si was obtained at the peak emission wavelength of 680 nm under pulsed mode current injection. These results show that not only can high quality AlGaInP materials grown by MBE be achieved on Si via relaxed SiGe interlayers, but the prototype demonstration of laser diode operation on Si illustrates that very defect sensitive optoelectronics in the III-P system can indeed be integrated with Si substrates by heteroepitaxial methods.

Kwon, O.; Boeckl, J. J.; Lee, M. L.; Pitera, A. J.; Fitzgerald, E. A.; Ringel, S. A. [Department of Electrical and Computer Engineering, Ohio State University, Columbus, Ohio 43210 (United States); Department of Materials Science and Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139 (United States); Department of Electrical and Computer Engineering, Ohio State University, Columbus, Ohio 43210 (United States)

2006-07-01

378

Finite element analysis of the stress distributions near damaged Si particle clusters in cast Al–Si alloys  

Microsoft Academic Search

The finite element method is used to study the effects of particle cluster morphology on the fracture and debonding of silicon particles embedded in an Al–1%Si matrix subjected to tensile-compressive cyclic loading conditions. Representative of an actual cast Al–Si alloy, clusters of silicon inclusions (4–8 particles) are considered rather than a single isolated inclusion or an infinite periodic array of

Ken Gall; Mark Horstemeyer; David L. McDowell; Jinghong Fan

2000-01-01

379

Impulse plasma deposition of aluminum oxide layers for Al 2O 3\\/Si, SiC, GaN systems  

Microsoft Academic Search

Nanocrystalline Al2O3 layers were produced by means of impulse plasma deposition (IPD) technique on Si and SiC substrates. Morphology, microstructure and chemical composition of films and film\\/substrate interfaces were investigated using SEM and SIMS methods. After depositing on top of the layers metal (Al) dot contacts also C–V and I–V measurements of so produced metal-insulator–semiconductor structures were performed in order

A. Werbowy; K. Zdunek; E. Dusi?ski; J. Szmidt; M. Elert

2003-01-01

380

Spin transition of Fe3+ in Al-bearing phase D: An alternative explanation for small-scale seismic scatterers in the mid-lower mantle  

NASA Astrophysics Data System (ADS)

Among dense-hydrous magnesium silicates potentially transporting H2O into Earth's deep interior, phase D (MgSi2H2O6) exhibits the highest P-T stability range, extending into the lower mantle along cold slab geotherms. We have studied the compressibility and spin state of Fe in Al-bearing phase D up to 90 GPa using synchrotron X-ray diffraction and X-ray emission spectroscopy. Fe-Al-bearing phase D was synthesized at 25 GPa and 1400 °C with approximate composition MgSi1.5Fe0.15Al0.32H2.6O6, where nearly all of the Fe is ferric (Fe3+). Analysis of Fe-K? emission spectra reveals a gradual, pressure-induced high-spin (HS) to low-spin (LS) transition of Fe3+ extending from 40 to 65 GPa. The fitted equation of state for high-spin Fe-Al-bearing phase D results in a bulk modulus KT0=147(2) GPa with pressure derivative K?=6.3(3). An equation of state over the entire pressure range was calculated using the observed variation in low-spin fraction with pressure and a low-spin bulk modulus of KT0=253(30) GPa, derived from the data above 65 GPa. Pronounced softening in the bulk modulus occurs during the spin transition, reaching a minimum at 50 GPa (?1500 km) where the bulk modulus of Fe-Al phase D is about 35% lower than Fe-Al-bearing silicate perovskite. Recovery of the bulk modulus at 50-65 GPa results in a structure that has a similar incompressibility as silicate perovskite above 65 GPa. Similarly, the bulk sound velocity of Fe-Al phase D reaches a minimum at ?50 GPa, being about 10% slower than silicate perovskite. The potential association of Fe-Al phase D with subducted slabs entering the lower mantle, along with its elastic properties through the Fe3+ spin transition predicted at 1200-1800 km, suggests that phase D may provide an alternative explanation for small-scale mid-lower mantle seismic scatterers and supports the presence of deeply recycled sediments in the lower mantle.

Chang, Yun-Yuan; Jacobsen, Steven D.; Lin, Jung-Fu; Bina, Craig R.; Thomas, Sylvia-Monique; Wu, Junjie; Shen, Guoyin; Xiao, Yuming; Chow, Paul; Frost, Daniel J.; McCammon, Catherine A.; Dera, Przemyslaw

2013-11-01

381

Reactive sintering of TiAl–Ti5Si3 in situ composites  

SciTech Connect

TiAl with between 0 and 20 vol%Ti5Si3 was produced by reactive sintering (700 °C for 15 min in vacuum) of cold pressed compacts of elemental Ti, Al and Si powder. The results show that adding Si to Ti and Al reduces the swelling associated with reactive sintering of TiAl, as composites containing more than 5 vol%Ti5Si3 densified during reactive sintering. However, composites containing more than 10 vol%Ti5Si3 did not retain their shape and the TiAl+20 vol%Ti5Si3 composite completely melted during the sintering process. A thermodynamic analysis indicated that the simultaneous formation of TiAl and Ti5Si3 increases the adiabatic flame temperature during the reaction between the powders. In fact, the analysis predicted that the maximum temperature of the reaction associated with the formation TiAl+20 vol%Ti5Si3 should exceed the melting point of TiAl, and this was observed experimentally. Differential thermal analysis (DTA) revealed that an Al–Si eutectic reaction occurred in mixtures of Ti, Al and Si powders prior to the formation of the TiAl and Ti5Si3 phases. There was no such pre-reaction formation of a eutectic liquid in Ti and Al powder mixtures. The formation of the pre-reaction liquid and the increase in adiabatic flame temperature resulted in the melting that occurred and the enhanced densification (minimization of swelling) during reactive sintering of the in situ composites.

Alman, David E.

2005-06-01

382

Control of silicon solidification and the impurities from an Al-Si melt  

NASA Astrophysics Data System (ADS)

The investigation on purification of metallurgical grade silicon by solidification of hypereutectic Al-Si melt under the temperature gradient as an intensified separation way was carried out. Based on the available thermodynamic parameters and experimental data, the thermodynamic behavior and chemical composition of metallic impurities was studied in the solidification process. The principle for the silicon growth in the Al-Si melts was investigated. The results indicated that the refined silicon grains were successfully enriched at the top of the Al-Si alloy. Then the top part refined silicon was collected by aqua regia leaching. Electrorefining of the bottom part (Al-22%Si) was investigated effectively in view of recovering pure Si and Al. Additionally, according to previous investigation, the optimized technical process for SOG-Si production was proposed.

Wang, Panpan; Lu, Huimin; Lai, Yuanshi

2014-03-01

383

Influence of Si on the microstructure of reactive sintered TiAl  

SciTech Connect

TiAl with between 0 and 20 volume percent (v%)Ti5Si3 was produced by reactive sintering of cold pressed compacts of elemental Ti, Al and Si powder mixtures at 700C for 15 minutes in vacuum. The results show that adding Si to Ti and Al reduces the swelling associated with reactive sintering of TiAl, as composites containing more than 5 v%Ti5Si3 densified during reactive sintering. However, composites containing more than 10v% Ti5Si3 did not retain their shape during processing, and the TiAl+20v% Ti5Si3 composite completely melted during the sintering process. The formation of pre-reaction liquid phase and the increase in adiabatic flame temperature with simultaneous compound formation resulted in the melting that occurred and the enhanced densification (minimization of swelling) during reactive sintering of the insitu composites.

Alman, David E.

2005-02-01

384

Moessbauer spectroscopy of Mg(0.9)Fe(0.1)SiO3 perovskite  

NASA Technical Reports Server (NTRS)

Ambient pressure Moessbauer spectra of Mg(0.9)Fe-57(0.1)SiO3 perovskite synthesized at pressure-temperature conditions of about 50 GPa and 1700 K show that the iron is entirely high-spin Fe(2+) and appears to be primarily located in the octahedral site within the crystal structure. We observe broad Moessbauer lines, suggesting a distribution of electric-field gradients caused by disorder associated with the Fe ions. Also, the perovskite exhibits magnetic ordering at temperatures lower than 5 K, implying that there is a magnetic contribution to the absolute ('third-law') entropy of this phase.

Jeanloz, Raymond; O'Neill, Bridget; Pasternak, Moshe P.; Taylor, R. D.; Bohlen, Steven R.

1992-01-01

385

THE DETERMINATION OF SOME CHEMICAL POLLUTION PARAMETERS (Cd, Al, Fe) IN TUZLA BALIK LAKE  

Microsoft Academic Search

This study aims to search the some chemical (Cd, Al, Fe) pollution parameters in the Tuzla Balik Lake. For this purpose 50 water samples were taken and analysed from 5 stations in the lake, during a year period. For detecting the chemical pollution, dithizone, aluminon and 1.10 phenanthroline methods were used for analysing Cd, Al and Fe amounts respectively. APHA

F. E. Kayhan; E. Özhatay

386

On the half-metallicity of Co2FeSi Heusler alloy: Point-contact Andreev reflection spectroscopy and ab initio study  

Co2FeSi, a Heusler alloy with the highest magnetic moment per unit cell and the highest Curie temperature, has largely been described theoretically as a half-metal. This conclusion, however, disagrees with point contact Andreev reflection (PCAR) spectroscopy measurements, which give much lower values of spin polarization, P. Here, we present the spin polarization measurements of Co2FeSi by the PCAR technique, along with a thorough computational exploration, within the DFT and a GGA+U approach, of the Coulomb exchange U parameters for Co and Fe atoms, taking into account spin-orbit coupling. We find that the orbital contribution (mo) to the total magnetic moment (mT) is significant, since it is at least 3 times greater than the experimental uncertainty of mT. The account of mo radically affects the acceptable values of U. Specifically, we find no values of U that would simultaneously satisfy the experimental values of the magnetic moment and result in the half-metallicity of Co2FeSi. On the other hand, the ranges of U that we report as acceptable are compatible with spin polarization measurements (ours and the ones found in the literature), which all are within approximately the 40–60 % range. Thus, based on reconciling experimental and computational results, we conclude that (a) spin-orbit coupling cannot be neglected in calculating Co2FeSi magnetic properties, and (b) Co2FeSi Heusler alloy is not half-metallic. We believe that our approach can be applied to other Heusler alloys such as Co2FeAl.

Makinistian, L.; Faiz, Muhammad M.; Panguluri, Raghava P.; Balke, B.; Wurmehl, S.; Felser, C.; Albanesi, E. A.; Petukhov, A. G.; Nadgorny, B.

2013-06-01

387

Brazing 6061 aluminum alloy with Al-Si-Zn filler metals containing Sr  

NASA Astrophysics Data System (ADS)

Al-6.5Si-42Zn and Al-6.5Si-42Zn-0.09Sr filler metals were used for brazing 6061 aluminum alloy. Air cooling and water cooling were applied after brazing. Si phase morphologies in the brazing alloy and the brazed joints were investigated. It was found that zinc in the Al-Si filler metals could reduce the formation of eutectic Al-Si phase and lower the brazing temperature at about 520°C. Adding 0.09wt% Sr element into the Al-6.5Si-42Zn alloy caused ?-Al phase refinement and transformed acicular Si phase into the finely fiber-like. After water cooling, Zn element dissolved into the Al-Si eutectic area, and ?-Zn phase disappeared in the brazed joints. Tensile strength testing results showed that the Sr-modified filler metal could enhance the strength of the brazed joints by 13% than Al-12Si, while water-cooling further improved the strength at 144 MPa.

Dai, Wei; Xue, Song-bai; Ji, Feng; Lou, Jiang; Sun, Bo; Wang, Shui-qing

2013-04-01

388

Chemical synthesis of iron aluminide [FeAl] and iron aluminum carbide [Fe{sub 3}AlC{sub 0.5}] nanopowders  

SciTech Connect

Nanopowders of iron aluminide [FeAl] and iron aluminum carbide [Fe{sub 3}AlC{sub 0.5}] are prepared by a two-step process involving the reduction of iron chloride [FeCl{sub 3}] with lithium aluminum hydride [LiAlH{sub 4}]. LiAlH{sub 4} serves both as a reducing agent and as a source of aluminum atoms required for the formation of the aluminides. The two-step process involves a solution phase reduction step resulting in the formation of colloidal mixtures, which when heat treated at temperatures above 550 deg. C undergo solid state reactions to form the aluminides. Presence of ethereal solvents [tetrahydrofuran (THF) and diethyl ether] during the solution phase reduction step predominantly favors the formation of the carbide phase while reduction in a largely aromatic [75/25 volume percent toluene/THF] solvent mixture promotes the formation of the intermetallic FeAl phase in the heat-treated product. In the presence of ethereal solvents, the use of slower heating rates and performing a solvent removal step enhance the formation of the aluminide phase over the carbide phase. When the largely aromatic mixture is used as the solvent the treatments have no effect on the product distribution. Microstructure analysis using SEM and TEM imaging show that both FeAl and Fe{sub 3}AlC{sub 0.5} nanoparticles formed are embedded within aluminum oxide matrices. The average particle size of the FeAl nanoparticles is 4-8 nm.

Pithawalla, Yezdi B. [Research, Development and Engineering Center, Philip Morris USA, Richmond, VA 23261 (United States); Deevi, Sarojini [Research, Development and Engineering Center, Philip Morris USA, Richmond, VA 23261 (United States)]. E-mail: Sarojini.Deevi@pmusa.com

2004-12-02

389

Thermodynamic aspects of TiAl and TiSi 2 oxidation: The Al-Ti-O and Si-Ti-O Phase diagrams  

Microsoft Academic Search

Thermodynamic data from the literature were used to calculate the activity variations of Ti and Al in the Ti-Al system at 700, 900, and 1100°C and of Ti and Si in the Ti-Si system at 800, 1000, and 1300°C. The activity data were then applied to estimate the stable oxide phase in equilibrium with the metal phase, assuming that the

A. Rahmel; P. J. Spencert

1991-01-01

390

In situ observations of phase transitions in CaGeO3 and Fe2SiO4  

NASA Astrophysics Data System (ADS)

Some ABO3 and A2BO4 compounds are excellent analogues of MgSiO3 or Mg2SiO4, which are major constituents of the Earth's mantle. Calcium germinate (CaGeO3) exhibits a sequence of phase transitions from a pyroxenoid (wollastonite structure) to a tetragonal garnet phase, and subsequently to an orthorhombic perovskite phase. This indicates that CaGeO3 is an excellent analogue of MgSiO3. Iron olivine (Fe2SiO4) is an end-member of magnesium-iron silicate, which is also the major constituent in the Earth's mantle. The phase transitions of these minerals have been used as pressure calibration points at high temperatures in static high-pressure experiments, such as for SiO2, MgSiO3, and Mg2SiO4. Therefore, the precise phase boundaries of CaGeO3 and Fe2SiO4 need to be determined. In our study, the use of a multi-anvil high-pressure system combined with a synchrotron radiation source made it possible to acquire precise data from samples under high-pressure and high-temperature conditions. In our experiments, pressure was applied to the sample by generating an anvil load from the desired oil pressure in the press. The sample was then heated until it reached the desired temperature for a given oil pressure. After reaching the required temperature, we performed in situ measurements using the synchrotron X-rays. The duration of heating was 0.5-3.0 hours. Determination of the stable phase in each experimental run was carried out by observing the X-ray diffraction pattern of the sample. At the end of the experimental runs, the sample was quenched by cutting off the electrical power, resulting in a temperature drop to <400 K within a period of 2-5 s. This heating procedure was the same as that used in conventional quench experiments. To check the identification of each phase in the in situ experiments, the recovered samples were also examined using micro-Raman spectroscopy. In the CaGeO3 study, we performed approximately 30 experimental runs to investigate the phase boundary between the garnet and perovskite structures. The gradient of dP/dT of the phase boundary was negative [1]. The boundary determined in this study is in general agreement with that reported in previous in situ experiments. However, the value of our dP/dT slope was 2-3 times more negative than that in previous in situ study. The calculated value of the dP/dT slope using calorimetry data reported in previous study is consistent with our value of dP/dT. In the case of Fe2SiO4 experiments [2], the phase boundary between olivine and gamma structures observed in our study was in general agreement with that reported by previous in situ study. However, the discrepancy between our and previous experiments was confirmed at the low temperatures. This indicated that the value of our dP/dT slope was more positive than that in previous in situ experiments. The transition kinetics at low temperatures may influence the discrepancies for the dP/dT slopes in CaGeO3 and Fe2SiO4. [1] Ono et al., Phys. Chem. Minerals, 38, 735-740 (2011). [2] Ono et al., Phys. Chem. Minerals, (in press).

Ono, S.

2013-12-01

391

One-step synthesis and characterization of core-shell Fe@SiO2 nanocomposite for Cr (VI) reduction.  

PubMed

A facile one-step method was developed to fabricate mono-dispersed Fe nanoparticles (Fe NPs) coated with SiO(2) shell by aqueous reduction method combined with modified Stöber method. Borohydride was acted not only as a reductant for iron salt but also as a catalyst for hydrolysis and polycondensation reaction of tetraethylorthosilicate (TEOS), and more importantly, there was no need to use surface primer for the generation of Fe NPs and catalyst NH(4)OH for SiO(2). Both the Fe NPs agglomeration and SiO(2) shell thickness can be controlled through the synthetic conditions. Lower potassium borohydride (KBH(4)) injection speed was preferable to assemble Fe NPs. The SiO(2) shell thickness increased gradually with the increase of TEOS amount. Under the condition of TEOS amount of 0.1mL and KBH(4) injection speed of 5mL/min, 25nm single Fe NP was coated with SiO(2) shell with thickness of about 9nm. The resulting nanoporous SiO(2) shell was proved to allow reactant to reach the Fe NPs while at the same time protect them from aggregation. The reactivity characterization of the SiO(2)-coated Fe nanoparticles (Fe@SiO(2)) showed that both TEOS concentration and KBH(4) injection speed had effect on Cr (VI) degradation ability. The highest removal capacity of Fe@SiO(2) can reach 467mgCr/gFe at an initial Cr (VI) concentration of 70mg/L under pH 6.0±0.1. XPS and TEM results showed that Cr (VI) was converted to nontoxic Cr (III) and the reaction product was completely adsorbed to SiO(2) shell. PMID:22381028

Li, Yongchao; Jin, Zhaohui; Li, Tielong; Xiu, Zongming

2012-04-01

392

Modeling the Dynamic Damage Process of the SiC3d/Al Interpenetrating Phase Composites  

NASA Astrophysics Data System (ADS)

In the current study, a 3D mesoscopic structure FE-Model of interpenetrating SiC3d/Al composite is built based on the digital image-based modeling technique together with optimized methods of three-dimensional mesh generation. Subsequently, the finite element method is proposed to simulate the dynamic damage process of the interpenetrating phase composites SiC3d/Al under dynamic axial crushing. The cracking process in micro 3D space is clearly presented in the current study. It is shown that the cracks initialization and propagation mainly appear in the region of interface between ceramic and metallic phase. Moreover, the ceramic phase attributes to the model's damage predominantly. The method proposed in this paper would be of help in the microstructure design of Interpenetrating Phase Composites.

Guoju, Li; Qunbo, Fan; Zheng, Wu; Xu, Zhang; Yangwei, Wang; Fuchi, Wang

2013-03-01

393

Radioactive Al26 and Fe60 in the Milky Way: implications of the RHESSI detection of Fe60  

E-print Network

The recent detection of gamma-ray lines from radioactive Al26 and Fe60 in the Milky Way by the RHESSI satellite calls for a reassessment of the production sites of those nuclides. The observed gamma-ray line flux ratio is in agreement with calculations of nucleosynthesis in massive stars, exploding as SNII (Woosley and Weaver 1995); in the light of those results, this observation would suggest then that SNII are the major sources of Al26 in the Milky Way, since no other conceivable source produces substantial amounts of Fe60. However, more recent theoretical studies find that SNII produce much higher Fe60/Al26 ratios than previously thought and, therefore, they cannot be the major Al26 sources in the Galaxy (otherwise Fe60 would be detected long ago, with a line flux similar to the one of Al26). Wolf-Rayet stars, ejecting Al26 (but not Fe60) in their stellar winds, appear then as a most natural candidate. We point out, however, that this scenario faces also an important difficulty. Forthcoming results of ESA's INTEGRAL satellite, as well as consistent calculations of nucleosynthesis in massive stars (including stars of initial masses as high as 100 M_sun and metallicities up to 3 Z_sun), are required to settle the issue.

N. Prantzos

2004-02-09

394

Dry Sliding Wear Behavior of a Novel 6351 Al-(Al4SiC4 + SiC) Hybrid Composite  

NASA Astrophysics Data System (ADS)

In this research study, the dry sliding wear behaviors of 6351 Al alloy and its composites with single and hybrid reinforcements (ex situ SiC and in situ Al4SiC4) were investigated at low sliding speed (1 ms-1) against a hardened EN 31 disk at different loads. In general, the wear mechanism involved adhesion (coupled with subsurface cracking) and microcutting-abrasion at lower loads. With higher loads, abrasive wear involving microcutting and microplowing along with adherent oxide formation was observed. At higher loads, the abrasive wear mechanism caused rapid wear loss initially up to a certain sliding distance beyond which, by virtue of frictional heat generation and associated temperature rise, an adherent oxide layer was developed at the pin surface, which drastically reduced the wear loss. Moreover, the overall wear rates of all the composites (either single or hybrid reinforcement) were found to be lower than that of the 6351 Al alloy at all applied loads. The ex situ SiC particles were found to resist abrasive wear; while, in situ Al4SiC4 particles offered resistance to adhesive wear. Accordingly, the 6351 Al-(SiC + Al4SiC4) hybrid composite exhibited the best wear resistance among all composites.

Show, Bijay Kumar; Mondal, Dipak Kumar; Maity, Joydeep

2014-03-01

395

Nonisothermal and Cyclic Oxidation Behavior of Mo-Si-B and Mo-Si-B-Al Alloys  

Microsoft Academic Search

A study on nonisothermal and cyclic oxidation behavior of the reaction-hot-pressed 76Mo-14Si-10B, 77Mo-12Si-8B-3Al, and 73.4Mo-11.2Si-8.1B-7.3Al\\u000a alloys has been carried out in dry air, and the results have been compared with those of isothermal tests. Nonisothermal studies\\u000a by thermogravimetric (TG) analysis up to 1300 °C have shown a transient mass gain between 700 °C and 860 °C, followed by a\\u000a sharp mass loss with

Sharma Paswan; R. Mitra; S. K. Roy

2009-01-01

396

Ferrite Effects in Fe-Mn-Al-C Triplex Steels  

NASA Astrophysics Data System (ADS)

In order to determine the ferrite effect on tensile properties of Fe-28.8Mn-9.4Al-C Triplex steels, four Triplex steel sheets with different carbon contents were solution treated under various conditions leading to different ferrite fractions ranging from 0 to 39 pct. This approach was used as it was very difficult to prepare samples with a wide range of ferrite contents from only one grade. However, in order to isolate the ferrite effect from this approach, it was necessary to precisely know the effect of the austenite carbon content and that of the austenite grain size on tensile properties of fully austenitic samples. This is why, a preliminary study was performed to assess these two effects, which required a thorough analysis of the microstructures of the investigated samples combining electron backscattered diffraction experiments and transmission electron microscopy observations. The study of fully austenitic samples led us to the conclusion that a decrease in the austenite grain size leads to higher strength and lower elongation and that the austenite carbon content has a greatly significant influence on tensile properties. However, this influence was difficult to estimate with a very good accuracy. Finally, the study of samples with different ferrite contents showed that ferrite had a positive effect on strength when its content was lower than 5 pct. In contrast, a higher content of ferrite (more than 30 pct) has a deleterious effect on mechanical properties.

Etienne, Auriane; Massardier-Jourdan, Véronique; Cazottes, Sophie; Garat, Xavier; Soler, Michel; Zuazo, Ian; Kleber, Xavier

2014-01-01

397

Melting of Fe and Fe120Si8 at the Earth's Core Pressures by ab Initio Molecular Dynamics  

NASA Astrophysics Data System (ADS)

The solid Earth's inner core (IC) consists mainly of iron likely alloyed with some light elements. At low temperature iron is stable in hexagonal close packed (hcp) phase up to very high pressures. However, there is an accumulating evidence that under pressures (~ 364 GPa) and temperatures (above 6000 K) in the Earth's IC iron, either pure or alloyed with light elements (e.g. Si), might be stable in the body-centred cubic (bcc) phase1,2. The melting temperature of this phase in the IC is unknown. Conditions of the IC are not achieved in experiment. Previous theoretical studies concentrated mostly on the melting of the hcp phase3. We show, by combination of ab initio molecular dynamics and Z-method4 that pure bcc Fe melts at at the pressure in the center of IC at ~7000 K. Iron, alloyed with 6.25% of Si, melts at a temperature of ~7200 K. While light elements depress hcp Fe melting temperatures5, we show that Si addition has opposite effect on bcc Fe. Melting temperatures of bcc and hcp 2,3 are within mutual error bars, even though bcc melts at a higher temperature. However, the melting temperature of Si-alloyed bcc iron is clearly above that of Si-alloyed hcp phase5. This is because of different bonding of Si-Fe within the bcc as compared to the hcp structure. Therefore, the existing estimates of core temperatures have to be corrected upwards. 1. Brown, J.M. & McQueen, R.G. J. Geophys. Res. 91, 7485(1986). 2. Belonoshko, A.B., Ahuja, R. & Johansson, B. Nature 424, 1032(2003); Belonoshko, A.B., Skorodumova, N.V., Rosengren, A. & Johansson, B. Science 319, 797(2008). 3. Belonoshko, A.B., Ahuja, R. & Johansson, B. Phys. Rev. Lett. 84, 3638(2000); Alfé, D., Gillan, M.J. & Price, G.D. Nature 401, 462(1999). 4. Kresse, G. & Furthmüller, J. J. Phys. Rev. B 54, 11169(1996); Belonoshko, A.B., Skorodumova, N.V., Rosengren, A. & Johansson, B. Phys. Rev. B 73, 012201(2006). 5. Alfé, D., Price, G.D. & Gillan, M.J. Cont. Phys. 48, 63 (2007).

Belonoshko, A. B.; Rosengren, A.; Burakovsky, L.; Preston, D. L.; Johansson, B.

2008-12-01

398

Deposition and characterization of Si xC 1 ? x \\/Al 2O 3 coatings by magnetron sputtering for nuclear fusion applications  

Microsoft Academic Search

Al2O3 coatings were fabricated on CLAM steel substrates at 300°C by RF magnetron sputtering, and SixC1?x coatings with different Si concentrations were then fabricated on the Al2O3 coatings by pulse magnetron sputtering. The coating composition, topography, structure and mechanical properties were investigated by X-ray photoelectron spectroscopy (XPS), atomic force microscopy (AFM), field emission scanning electron microscopy (FE-SEM), X-ray diffractometry (XRD),

Binbin Song; Ping Wu; Sen Chen; Murad Ali Khaskheli; Liang Liang

2011-01-01

399

18.5% efficient AlOx/SiNy rear passivated industrial multicrystalline silicon solar cells  

NASA Astrophysics Data System (ADS)

Due to the trend toward thinner and higher efficient crystalline silicon solar cells, excellent rear surface passivation and internal optical reflectance have become more and more important. Aluminum oxide (AlOx) capped with silicon nitride (SiNy), which is considered as one of the most promising candidates to achieve superior rear passivation and internal reflectance, has to date been mostly used for the rear side of p-type monocrystalline silicon (mono-Si) solar cells. In this paper, we have optimized rear AlOx/SiNy stacks deposited by industrial plasma enhanced chemical vapor deposition (PECVD) for multicrystalline silicon (mc-Si) passivated emitter and rear cells (PERC). Sufficient passivation activation effect from industrial fast-firing process and SiNy deposition process have been demonstrated, so the samples were not subjected to additional thermal treatment process in the cell fabrication flow. For rear AlOx/SiNy stack, it is shown that when PECVD AlOx is thicker than 40 nm, apparent blisters in fired AlOx deteriorate the cell performance, and the appropriate SiNy capping is N-rich SiNy with thickness of at least 180 nm. After process optimization with the least additional process steps, independently confirmed efficiency of 18.5% for Pluto-PERC with PECVD AlOx/SiNy rear passivation on standard 156 mm × 156 mm p-type mc-Si wafers has been achieved.

Qiao, Qi; Lu, Hongyan; Ge, Jian; Xi, Xi; Chen, Rulong; Yang, Jian; Zhu, Jingbing; Shi, Zhengrong; Chu, Junhao

2014-06-01

400

Thermodynamic analysis of compatibility of several reinforcement materials with FeAl alloys  

NASA Technical Reports Server (NTRS)

Chemical compatibility of several reinforcement materials with FeAl alloys within the concentration range 40 to 50 at pct Al have been analyzed from thermodynamic considerations at 1173 and 1273 K. The reinforcement materials considered in this study include carbides, borides, oxides, nitrides, and silicides. Although several chemically compatible reinforcement materials are identified, the coefficients of thermal expansion for none of these materials match closely with that of FeAl alloys and this might pose serious problems in the design of composite systems based on FeAl alloys.

Misra, Ajay K.

1988-01-01

401

Magnetic properties and domain structure in grain-oriented 3% Si-Fe  

Microsoft Academic Search

Magnetic domain observations have been used to clarify the relationship between metallurgical structure and the core loss, permeability, and magnetostriction of grain-oriented 3% Si-Fe. Both the prediction of domain structures based on anisotropy, magnetostatics, stress, etc., and the various methods of making domain observations are reviewed. Both static and dynamic domain structures are shown and used to illustrate the relationships

J. W. SHILLING

1974-01-01

402

Characterization of near-infrared n-type {beta}-FeSi{sub 2}/p-type Si heterojunction photodiodes at room temperature  

SciTech Connect

n-type {beta}-FeSi{sub 2}/p-type Si heterojunctions were fabricated from {beta}-FeSi{sub 2} films epitaxially grown on Si(111) by facing-target direct-current sputtering. Sharp film-substrate interfaces were confirmed by scanning electron microscopy. The current-voltage and photoresponse characteristics were measured at room temperature. They exhibited good rectifying properties and a change of approximately one order of magnitude in the current at a bias voltage of -1 V under illumination by a 6 mW, 1.31 {mu}m laser. The estimated detectivity was 1.5x10{sup 9} cm {radical}Hz W at 1.31 {mu}m. The results suggest that the {beta}-FeSi{sub 2}/Si heterojunctions can be used as near-infrared photodetectors that are compatible with silicon integrated circuits.

Shaban, Mahmoud [Department of Applied Science for Electronics and Materials, Kyushu University, Kasuga, Fukuoka 816-85